Development of a New Rain Erosion Test Method

NASA Astrophysics Data System (ADS)

Chung, Dong-Teak; Kang, Hyung; Jin, Doo-Han

The nose of a missile, flying through raining region with a supersonic speed, is subjected to the rain erosion because the nose is made of a brittle ceramic material. Various test methods are used to address such a phenomenon. However, most of the methods are expensive and/or require complicated facilities. The simple yet very effective rain erosion test method is developed. It consists of (1) a low pressure air gun, (2) a sabot assembly for launching single rain drop, (3) a stopper, and (4) a specimen holder block. The sabot assembly similar to the hypodermic syringe carries specific amount of water toward the stopper launched by the low pressure air gun. When the impact occurs against the stopper which stops the sabot, the water and the steel plunger (at the back of the sabot) continues pushing the sabot to generate a high pressure in the chamber filled with resilient silicon rubber. The pressurized silicon rubber then is squeezed through the small opening in front of the sabot, thus, accelerates the water droplet to a much higher velocity. The velocity of the droplet is measured by the make-screen method, where there are two aluminum foils with an insulating layer in between. The droplet velocity up to 800 m/s is successfully attained using a low pressure air compressor. The specimen made of a ceramic material is placed in front of the high speed water droplet and the rain erosion damage on the surface of the specimen is observed.

Manufacturing issues which affect coating erosion performance in wind turbine blades

NASA Astrophysics Data System (ADS)

Cortés, E.; Sánchez, F.; Domenech, L.; Olivares, A.; Young, T. M.; O'Carroll, A.; Chinesta, F.

2017-10-01

Erosion damage, caused by repeated rain droplet impact on the leading edges of wind turbine blades, is a major cause for cost concern. Resin Infusion (RI) is used in wind energy blades where low weight and high mechanical performance materials are demanded. The surface coating plays a crucial role in the manufacturing and performance response. The Leading Edge coating is usually moulded, painted or sprayed onto the blade surface so adequate adhesion in the layers' characterization through the thickness is required for mechanical performance and durability reasons. In the current work, an investigation has been directed into the resulting rain erosion durability of the coating was undertaken through a combination of mass loss testing measurements with manufacturing processing parameter variations. The adhesion and erosion is affected by the shock wave caused by the collapsing water droplet on impact. The stress waves are transmitted to the substrate, so microestructural discontinuities in coating layers and interfaces play a key role on its degradation. Standard industrial systems are based on a multilayer system, with a high number of interfaces that tend to accelerate erosion by delamination. Analytical and numerical models are commonly used to relate lifetime prediction and to identify suitable coating and composite substrate combinations and their potential stress reduction on the interface. In this research, the input parameters for the appropriate definition of the Cohesive Zone Modelling (CZM) of the coating-substrate interface are outlined by means of Pull off testing and Peeling testing results. It allowed one to optimize manufacturing and coating process for blades into a knowledge-based guidance for leading edge coating material development. It was achieved by investigating the erosion degradation process using both numerical and laboratory techniques (Pull off, Peeling and Rain Erosion Testing in a whirling arm rain erosion test facility).

Final Evaluation of Rain Erosion Sled Test Results at Mach 3.7 to 5.0 for Slip-Cast Fused Silica Radome Structures

DTIC Science & Technology

1979-03-06

capable of testing radome materials in multiple impact simulated rain at Mach 5 is the monorail sled facility at the Holloman Air Force Base, New Mexico...existing 9-in. monorail sled at the Holloman test track, to be structurally adequate for the environment, and to carry samples of the desired shape...direction over a total length of 15,480 m(50,788 ft). For Mach 5 rain erosion tests, the sled operates on a monorail . Braking for these monorail

Water droplet erosion mechanisms of Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Kamkar Zahmatkesh, Niloofar

Water impingement erosion of materials can be a life-limiting phenomenon for the components in many erosive environments. For example, aircraft body exposed to rain, steam turbine blade, and recently in gas turbine coupled with inlet fogging system. The last is the focus of this study. Inlet fogging system is the most common method used to augment gas turbine output during hot days; high ambient temperature causes strong deterioration of the engine performance. Micro-scaled droplets introduced into the inlet airflow allow the cooling of entering air as well as intercooling the compressor (overspray) and thus optimizes the output power. However, erosion damage of the compressor blades in overspray stage is one of the major concerns associated with the inlet fogging system. The main objective of this research work (CRIAQ MANU419 project) is to understand the erosion induced by water droplets on Titanium alloy to eventually optimize the erosion resistance of the Ti-based compressor blade. Therefore, characterization of the water droplet erosion damage on Ti-6Al-4V receives the major importance. The influence of base material microstructure and impact parameters were considered in erosion evaluation in present study. This work covers the characterization of the erosion damage on Ti-6Al-4V alloy in two parts: - The water droplet erosion damage through a novel experimental approach. The collected data were processed both qualitatively and quantitatively for multi-aspects damage study. - The influence of impact velocity on erosion in an attempt to represent the in-service conditions.

Impact of erosion testing aspects on current and future flight conditions

NASA Astrophysics Data System (ADS)

Gohardani, Omid

2011-05-01

High speed of aero vehicles including commercial and military aircraft, missiles, unmanned air vehicles, as well as conceptual aircraft of the future are imposing larger restrictions on the materials of these vehicles and highlight the importance of adequate quantification of material behavior and performance during different flight conditions. Erosion due to weather conditions and other present particles such as hydrometeors; rain, hail and ice, as well as sand, volcanic ash and dust resulting from residues in the atmosphere are eminent as hazardous on the structure of a flying vehicle and may adversely influence the lifecycle of the structure. This study outlines an extensive review of research efforts on erosion in aviation and provides a basis for comparison between different apparatus simulating rain erosion and their usage within the aerospace industry. The significant aspects of erosion testing and future prospects for erosion impact are further addressed for forthcoming generations of flying vehicles.

Erosion of composite materials

NASA Technical Reports Server (NTRS)

Springer, G. S.

1980-01-01

A model for describing the response of uncoated and coated fiber reinforced composites subjected to repeated impingements of liquid (rain) droplets is presented. The model is based on the concept that fatigue is the dominant factor in the erosion process. Algebraic expressions are provided which give the incubation period, the rate of mass loss past the incubation period, and the total mass loss of the material during rain impact. The influence of material properties on erosion damage and the protection offered by different coatings are discussed and the use of the model in the design in the design of structures and components is illustrated.

Illuminating wildfire erosion and deposition patterns with repeat terrestrial lidar

USGS Publications Warehouse

Rengers, Francis K.; Tucker, G.E.; Moody, J.A.; Ebel, Brian

2016-01-01

Erosion following a wildfire is much greater than background erosion in forests because of wildfire-induced changes to soil erodibility and water infiltration. While many previous studies have documented post-wildfire erosion with point and small plot-scale measurements, the spatial distribution of post-fire erosion patterns at the watershed scale remains largely unexplored. In this study lidar surveys were collected periodically in a small, first-order drainage basin over a period of 2 years following a wildfire. The study site was relatively steep with slopes ranging from 17° to > 30°. During the study period, several different types of rain storms occurred on the site including low-intensity frontal storms (2.4 mm h−1) and high-intensity convective thunderstorms (79 mm h−1). These storms were the dominant drivers of erosion. Erosion resulting from dry ravel and debris flows was notably absent at the site. Successive lidar surveys were subtracted from one another to obtain digital maps of topographic change between surveys. The results show an evolution in geomorphic response, such that the erosional response after rain storms was strongly influenced by the previous erosional events and pre-fire site morphology. Hillslope and channel roughness increased over time, and the watershed armored as coarse cobbles and boulders were exposed. The erosional response was spatially nonuniform; shallow erosion from hillslopes (87% of the study area) contributed 3 times more sediment volume than erosion from convergent areas (13% of the study area). However, the total normalized erosion depth (volume/area) was highest in convergent areas. From a detailed understanding of the spatial locations of erosion, we made inferences regarding the processes driving erosion. It appears that hillslope erosion is controlled by rain splash (for detachment) and overland flow (for transport and quasi-channelized erosion), with the sites of highest erosion corresponding to locations with the lowest roughness. By contrast, in convergent areas we found erosion caused by overland flow. Soil erosion was locally interrupted by immobile objects such as boulders, bedrock, or tree trunks, resulting in a patchy erosion network with increasing roughness over time.

ERMiT: Estimating Post-Fire Erosion in Probabilistic Terms

NASA Astrophysics Data System (ADS)

Pierson, F. B.; Robichaud, P. R.; Elliot, W. J.; Hall, D. E.; Moffet, C. A.

2006-12-01

Mitigating the impact of post-wildfire runoff and erosion on life, property, and natural resources have cost the United States government tens of millions of dollars over the past decade. The decision of where, when, and how to apply the most effective mitigation treatments requires land managers to assess the risk of damaging runoff and erosion events occurring after a fire. The Erosion Risk Management Tool (ERMiT) is a web-based application that estimates erosion in probabilistic terms on burned and recovering forest, range, and chaparral lands. Unlike most erosion prediction models, ERMiT does not provide `average annual erosion rates;' rather, it provides a distribution of erosion rates with the likelihood of their occurrence. ERMiT combines rain event variability with spatial and temporal variabilities of hillslope burn severity, soil properties, and ground cover to estimate Water Erosion Prediction Project (WEPP) model input parameter values. Based on 20 to 40 individual WEPP runs, ERMiT produces a distribution of rain event erosion rates with a probability of occurrence for each of five post-fire years. Over the 5 years of modeled recovery, the occurrence probability of the less erodible soil parameters is increased and the occurrence probability of the more erodible soil parameters is decreased. In addition, the occurrence probabilities and the four spatial arrangements of burn severity (arrangements of overland flow elements (OFE's)), are shifted toward lower burn severity with each year of recovery. These yearly adjustments are based on field measurements made through post-fire recovery periods. ERMiT also provides rain event erosion rate distributions for hillslopes that have been treated with seeding, straw mulch, straw wattles and contour-felled log erosion barriers. Such output can help managers make erosion mitigation treatment decisions based on the probability of high sediment yields occurring, the value of resources at risk for damage, cost, and other management considerations.

Rain Garden Research at EPA's Urban Watershed Research Facility

EPA Science Inventory

I have been invited to give a presentation at the 2009 National Erosion Conference in Hartford, CT, on October 27-28, 2009. My presentation discusses the research on sizing of rain gardens that is being conducted using the large, parking lot rain gardens on-site. I discuss the ...

Modelling approach for the rainfall erosivity index in sub-humid urban areas in northern Algeria

NASA Astrophysics Data System (ADS)

Touaibia, I.; Abderrahmane Guenim, N.; Touaibia, B.

2014-09-01

This work presents an approach for storm water erosivity index modelling in the absence of measurement in an urban area, in a sub-humid climate. In torrential storms, floods, loaded with sediments, obstruct storm water drainage. With the aim of estimating the amount of sediment that can be deposited on a stretch of road, adjacent to the study area, the erosivity index is determined from a count of 744 rain showers recorded over a period of 19 years. The Universal Soil Loss Equation (USLE) of Wischmeier and Smith is applied, where only the index of erosivity is calculated; it is based on the intensity of the rain starting the process of erosion in the basin. Functional relations are required between this factor and the explanatory variables. A power type regression model is reached, making it possible to bring a decision-making aid in absences of measurements.

Modelling erosion on a daily basis, an adaptation of the MMF approach

NASA Astrophysics Data System (ADS)

Shrestha, Dhruba Pikha; Jetten, Victor G.

2018-02-01

Effect of soil erosion causing negative impact on ecosystem services and food security is well known. On the other hand there can be yearly variation of total precipitation received in an area, with the presence of extreme rains. To assess annual erosion rates various empirical models have been extensively used in all the climatic regions. While these models are simple to operate and do not require lot of input data, the effect of extreme rain is not taken into account. Although physically based models are available to simulate erosion processes including particle detachment, transportation and deposition of sediments during a storm they are not applicable for assessing annual soil loss rates. Moreover storm event data may not be available everywhere prohibiting their extensive use.

Recent and future rainfall erosivity on the territory of the Czech Republic

NASA Astrophysics Data System (ADS)

Krasa, Josef; Stredova, Hana; Stepanek, Petr; Hanel, Martin; Dostal, Tomas; Novotny, Ivan

2015-04-01

Water erosion is a main factor of degradation of soils used for agriculture in the Czech Republic. For landscape conservation purposes the soil erosion risk is defined here mostly by USLE (Wischmeier and Smith, 1978). Within USLE the precipitation impact on erosion is a function of rainfall kinetic energy and intensity represented by R-factor. In the Czech Republic historically and recently several research teams have analyzed rainfall data to assess R-factor. Till now not many European countries have performed detailed spatially distributed analyses of rain erosivities. Most studies use only simplified methods based on long-term rainfall averages or databases of only several station-datasets. The most recent study on rainfall erosivity spatial distribution over the Czech Republic was based on digital rain gauge data from automatic stations of the Czech Hydrometeorogical Institute. The erosive rains were derived from continuous 1 minute step 10-year rainfall data (2003-2012) from 245 stations. Based on the research recent annual R-factor values in the stations vary from 37 to 239 [N.h-1] (values over 100 are located in mountain regions with minimum of agricultural land). Average value is 69 [N.h-1.year-1]. For the Czech Republic the future prediction is based on 10km resolution ALADIN/CZ regional climate model. Within the EU FP6 project CECILIA it was coupled with GCM ARPEGE to provide a projection of future climate in two time slices, 2021-2050 and 2071-2100, according to the IPCC A1B emission scenario. Daily precipitation volumes and percentiles of maximal events allowed authors to develop R-factor maps of present and future scenarios. Based on the analyses we can conclude that average value for the whole territory of the Czech Republic will remain close to 70 [N.h-1.year-1] or even decrease for 2071-2100, but we can expect significant changes (30-40 % rise or decrease) for several large agricultural regions (eg. Southern Moravia). These changes will have impact on soil erosion dynamics of the specific areas. Details on the spatial distribution of recent and future rain erosivities over the Czech Republic and the consequences for the erosion risk will be presented. The paper was prepared within the projects NAZV QJ1230056 and BV VG 20122015092.

Monsoonal vs. glacial control on erosion and sediment storage in the Himalayan rain shadow, Zanskar River, northwest India

NASA Astrophysics Data System (ADS)

Jonell, Tara; Clift, Peter; Carter, Andrew; Böning, Philipp; Wittmann, Hella

2016-04-01

Summer monsoon precipitation strongly controls erosion and sediment storage in the frontal Himalaya but the relationship between monsoonal variability and erosion is less well-constrained beyond the High Himalayan topographic divide in the rain shadow. Here we establish a Quaternary erosional history for a rain shadow tributary of the upper Indus River system, the Zanskar River, by applying several sediment provenance techniques to modern and dated terrace river sediments. We evaluate if there are temporal links between sediment storage and moisture supply to the rain shadow and if regions like the Zanskar River basin play a significant role in controlling total sediment flux to the Indus River. We compile bulk sediment petrography and Sr and Nd isotope geochemistry, detrital U-Pb zircon and apatite fission track dating with in-situ 10Be cosmogenic radionuclide techniques to identify patterns of erosion and sediment production across Zanskar. Bulk petrography, Sr and Nd isotope geochemistry, and U-Pb detrital zircon spectra of modern and older terrace sediments indicate high rates of erosion along the Greater Himalaya in the Zanskar River basin. We find that the wettest and most glaciated subcatchment dominates the bulk sediment provenance signal, with only moderate input from other tributaries, and that other basin parameters cannot explain our observations. Catchment-averaged in-situ 10Be cosmogenic nuclide concentrations of modern sediments indicate erosion rates up to ˜1.2 mm y-1 but show strong dilution attributed to glacial sediment recycling into the modern river, suggesting rates nearer 0.4-0.6 mm•y-1. These rates are consistent with longer-term rates of incision (0.3-0.7 mm•y-1) calculated from detrital apatite fission track ages, and incision rates inferred from Late Glacial and Holocene terraces near the Zanskar-Indus confluence. Our findings suggest that sediment production in glaciated Himalayan rain shadow environments like Zanskar is largely controlled by internal glacial fluctuations coupled with periodic dissection and reworking of terrace material during strong monsoonal precipitation phases.

Advances in modeling soil erosion after disturbance on rangelands

USDA-ARS?s Scientific Manuscript database

Research has been undertaken to develop process based models that predict soil erosion rate after disturbance on rangelands. In these models soil detachment is predicted as a combination of multiple erosion processes, rain splash and thin sheet flow (splash and sheet) detachment and concentrated flo...

Silt fences: An economical technique for measuring hillslope soil erosion

Treesearch

Peter R. Robichaud; Robert E. Brown

2002-01-01

Measuring hillslope erosion has historically been a costly, time-consuming practice. An easy to install low-cost technique using silt fences (geotextile fabric) and tipping bucket rain gauges to measure onsite hillslope erosion was developed and tested. Equipment requirements, installation procedures, statistical design, and analysis methods for measuring hillslope...

Wind, rain and soil erosion rates on bare and plant covered agriculture plots at the experimental station of El Teularet -Sierra de Enguera, Eastern Spain

NASA Astrophysics Data System (ADS)

Cerdà, A.; Azorin-Molina, C.; Iserloh, Th.

2012-04-01

Soil erosion is being scientifically researched for more tan one century, but there is some knowledge lacks that should be researched. Within the factors of the soil erosion wind and rain were studied, but little is know about the impact of the combination of both. Soil erosion by wind was mainly studied on drylands and agriculture land (Sterk and Spaan, 1997; Bielders et al., 2002; Rajot et al., 2003; Zobeck et al., 2003). Soil erosion by water was studied in many ecosystems but it is especially active on agriculture land (Cerdà et al., 2009) and under Mediterranean climatic conditions (Cerdà et al., 2010). The importance of wind on soil erosion is base in the fact that rainstorms occurs with wind, adding a driving component to the falling raindrops. The influence of wind on raindrops is clear, but there is not measurements and there is no information of this influence under field conditions with natural rainfall events.This paper aims to determine the interaction between wind and rain as factors of the soil losses under Mediterranean climatic conditions and different agriculture managements and land uses. Since 2003, the El Teularet-Serra de Enguera Soil Erosion Experimental Station located in Eastern Spain is measuring the soil losses in plots under different land uses and land managements. The station is devoted to study the soil water erosion processes under rain-fed agriculture fields and the rangelands by means of simulated rainfall experiments and plots of different sizes. The soil erosion measure ments are done by means of 13 plots, each of them composed of 5 subplots of 1, 2, 4, 16 and 48 m2 under different land uses and managements. Two plots are covered by two different types of shrubs: Quercus coccifera and Ulex parviflorus, respectively. Three plots reproduce the use of herbicides, one is ploughed, and three plots follow conservation practices (oats and beans with no-tillage, with tillage, and with a vege- tation cover of weeds). Other plots are covered with straw, chipped branches of olive and with a geotextil developed specifically to control erosion on agricultural fields. The Soil Erosion Experimental Station of the El Teularet-Serra de Enguera is located in Eastern Spain. The station is devoted to study the soil water erosion processes under rain-fed agriculture fields and the rangelands. Agriculture is the main source of sedi ments on the mountainous areas of Spain due to the current management. The exper imental station of the El Teularet-Sierra de Enguera is composed also of a meteorological station with tipping-bucket raingauges (0.2 mm), and sensors that measure soil and air moisture and temperature, wind direction and speed and the sun radiation connected to a data-logger that record these data every five minutes. This paper will review the data collected during the period 2004 to 2011 in order to determine if the wind direction and wind speed determined the soil erosion rates. In this way it will be clarified the infliuence of wind on the soil erosion processes.The results will be compared to the measurement collected at the Montesa experimental station devoted to the study of soil erosion on citrus orchards. The experimental setup within the citrus plantation is being supported by the research project CGL2008- 02879/BTE.

Rain Erosion Studies of Sapphire, Aluminum Oxynitride, Spinel, Lanthana- Doped Yttria, and TAF Glass

DTIC Science & Technology

1990-07-01

small , there is little change in average scatter for any material in any test. CONCLUSIONS AND DISCUSSION The principal conclusions are 1. ALON...20 Sample broke erosion damage 10 Slight pitting, 20 No change erosion damage 15 Pitting, cratering, 20 Small surface pits erosion damage 15 Pitting...Sample broke 10 No damage 15 Sample pitted, small edge fracture 15 Slight pitting, 1 crater, 20 Sample pitted, erosion damage small edge fracture 15 SUght

Co-evolution of landforms and vegetation under the influence of orographic precipitation

NASA Astrophysics Data System (ADS)

Yetemen, Omer; Srivastava, Ankur; Saco, Patricia M.

2017-04-01

Landforms are controlled by the interaction between tectonics, climate, and vegetation. Orography induced precipitation not only has implications on erosion resistance through vegetation dynamics but also affects erosive forces through modifying runoff production. The implications of elevated precipitation due to orography on landscape morphology requires a numerical framework that integrates a range of ecohydrologic and geomorphic processes to explore the competition between erosive and resisting forces in catchments where pronounced orographic precipitation prevails. In this study, our aim was to realistically represent ecohydrology driven by orographic precipitation and explore its implications on landscape evolution through a numerical model. The model was used to investigate how ecohydro-geomorphic differences caused by differential precipitation patterns as a result of orographic influence and rain-shadow effect lead to differences in the organization of modelled topography, soil moisture, and plant biomass. We use the CHILD landscape evolution model equipped with a vegetation dynamics component that explicitly tracks above- and below-ground biomass, and a precipitation forcing component that simulates rainfall as a function of elevation and orientation. The preliminary results of the model have shown how the competition between an increased shear stress through runoff production and an enhanced resistance force due to denser canopy cover, shape the landscape. Hillslope asymmetry between polar- and equator-facing hillslopes are enhanced (diminished) when they coincide with windward (leeward) side of the mountain series. The mountain divide accommodates itself by migrating toward the windward direction to increase (decrease) hillslope gradients on windward (leeward) slopes. These results clearly demonstrate the strong coupling between landform evolution and climate processes.

Can salvage logging affect seed dispersal by birds into burned forests?

NASA Astrophysics Data System (ADS)

Rost, J.; Pons, P.; Bas, J. M.

2009-09-01

The recovery of vegetation in Mediterranean ecosystems after wildfire is mostly a result of direct regeneration, since the same species existing before the fire regenerate on-site by seeding or resprouting. However, the possibility of plant colonization by dispersal of seeds from unburned areas remains poorly studied. We addressed the role of the frugivorous, bird-dependent seed dispersal (seed rain) of fleshy-fruited plants in a burned and managed forest in the second winter after a fire, before on-site fruit production had begun. We also assessed the effect on seed rain of different microhabitats resulting from salvage logging (erosion barriers, standing snags, open areas), as well as the microhabitats of unlogged patches and an unburned control forest, taking account of the importance of perches as seed rain sites. We found considerable seed rain by birds in the burned area. Seeds, mostly from Olive trees Olea europaea and Evergreen pistaches Pistacia lentiscus, belonged to plants fruiting only in surrounding unburned areas. Seed rain was heterogeneous, and depended on microhabitat, with the highest seed density in the unburned control forest but closely followed by the wood piles of erosion barriers. In contrast, very low densities were found under perches of standing snags. Furthermore, frugivorous bird richness seemed to be higher in the erosion barriers than elsewhere. Our results highlight the importance of this specific post-fire management in bird-dependent seed rain and also may suggest a consequent heterogeneous distribution of fleshy-fruited plants in burned and managed areas. However, there needs to be more study of the establishment success of dispersed seeds before an accurate assessment can be made of the role of bird-mediated seed dispersal in post-fire regeneration.

Kinetic energy of rainfall simulation nozzles

USDA-ARS?s Scientific Manuscript database

Different spray nozzles are used frequently to simulate natural rain for soil erosion and chemical transport, particularly phosphorous (P), studies. Oscillating VeeJet nozzles are used mostly in soil erosion research while constant spray FullJet nozzles are commonly used for P transport. Several ch...

Feasibility for Application of Soil Bioengineering Techniques to Natural Wastewater Treatment Systems

DTIC Science & Technology

1992-12-01

surface erosion control technique, providing shallow soil protection against the impact of heavy rains and running water. As adventitious rooting... soil protection against the impact of heavy rains and running water (Schiechtl, 1980). Figure 13 shows a typical brushmattress used as streambank

Does thermophoresis reduce aggregate stability?

NASA Astrophysics Data System (ADS)

Sachs, Eyal; Sarah, Pariente

2017-04-01

Thermophoresis is mass flow driven by a thermal gradient. As a result of Seebeck effect and Soret effect, colloids can move from the hot to the cold region or vice versa, depending on the electrolyte composition and on the particle size. This migration of colloids can weaken aggregates. The effect of raindrop temperatures on runoff generation and erosion on clayey soil was investigated in sprinkling experiments with a laboratory rotating disk rain simulator. The experiments were applied to Rhodoxeralt (Terra Rossa) soil with two pre-prepared moisture contents: hygroscopic and field capacity. For each moisture content three rainfall temperatures were applied: 2, 20, and 35°C. Erosion was generally lower in the pre-wetted soil than in the dry soil (12.5 and 24.4 g m-2 per 40 mm of rain,respectively). Whereas there was no significant effect of raindrop temperature on the dry soil the soil that was pre-moistened to field capacity was affected by rainwater temperature: runoff and erosion were high when the temperature difference between rainfall and soil surface was high, sediment yields were 13.9, 5.2, and 18.3 g m-2 per 40 mm of rain, for rain temperature of 2, 20, and 35 °C, respectively. It is reasonable to conclude that thermophoresis caused by thermal gradients within the soil solution reduces the stability of aggregates and then increase the soil losses.

Soil erosion - a local and national problem

Treesearch

C.G. Bates; O.R. Zeasman

1930-01-01

The erosion of soils through the action of rain water and that from melting snow is almost universal in its occurrence. The gradual erosion and levelling of any country is inevitable, being a process which has gone on as long as there has been free water on the face of the earth. Nevertheless, this process is an extremely slow one where the landscape is naturally well...

Shoreline Erosion Processes: Orwell Lake, Minnesota.

DTIC Science & Technology

1984-12-01

1976) and Savat ( 1981 ) found such splash layer Will absorb much of the impact of the rain- erosion to increase with increasing slope angle, but...pp. 188-196. U.S. Army Corps of Engineers (1979) Flood control, Savat , J. ( 1981 ) Work done by splash: Laboratory Orwell Dam, Otter Tail River

Use of RHEM to assess runoff and erosion following disturbance on rangelands

USDA-ARS?s Scientific Manuscript database

Landscape disturbance such as fire or woody plant encroachment on rangelands can have major impacts on the hydrological and erosion responses. As canopy and ground cover are reduced, soil sediments become available and can be detached by rain splash and overland flow. Disturbance can also increase t...

The burrowing activity of scorpions ( Scorpio maurus palmatus) and their potential contribution to the erosion of Hamra soils in Karkur, central Israel

NASA Astrophysics Data System (ADS)

Rutin, J.

1996-03-01

The burrowing activity of the scorpion Scorpio maurus palmatus was studied on a 1200 m 2 slope of a so-called "Hamra" sandy soil in Karkur, Israel. The main results were (1) The scorpions excavate soil material after rain storms, preparing this material for erosion processes by rain splash and rainwash. (2) The burrowing activity stops in the dry summer and during cold days of the winter. This means that Scorpio Maurus Palmatus is preparing soil for erosion from one storm to the next, and not from one season to the next as was previously thought. Further, it was found that the amount of soil material excavated from the burrow is proportional to the size of the scorpion and that most of the mounds were deposited toward the upper part of the slope which means that part is washed back into the burrow itself.

Carbon and macronutrient loss during accelerated erosion under different tillage and residue management systems

USDA-ARS?s Scientific Manuscript database

The effects of tillage and crop residue removal on erosion and associated macronutrient fluxes on erodible soils subjected to a high intensity simulated rain event (70 mm/h) were investigated in an experimental watershed in Ohio, USA. A set of plots which constitute two experiments at this site were...

Postfire seeding for erosion control: Effectiveness and impacts on native plant communities

Treesearch

Jan L. Beyers

2004-01-01

Abstract: Large, high-severity wildfires remove vegetation cover and expose mineral soil, ofen causing erosion and runoff during postfire rain events to increase dramatically. Land-management agencies in the United States are required to assess site conditions after wildfire and, where necessary, implement emergency watershed rehabilitation measures to help...

Soil erosion and deposition before and after fire in oak savannas

Treesearch

Peter F. Ffolliott; Gerald J. Gottfried; Hui Chen; Aaron T. Kauffman; Cody L. Stropki; Daniel G. Neary

2013-01-01

Effects of low severity prescribed burning treatments and a wildfire on soil erosion and deposition in the oak savannas in the Southwestern Borderlands are reported. Measurements in the spring and fall, respectively, characterize soil movements following winter rains and high-intensity summer rainstorms. Annual values are also presented. Relationships between soil...

Design and evaluation of thin metal surface insulation for hypersonic flight

NASA Technical Reports Server (NTRS)

Miller, R. C.; Petach, A. M.

1976-01-01

An all-metal insulation was studied as a thermal protection system for hypersonic vehicles. Key program goals included fabricating the insulation in thin packages which are optimized for high temperature insulation of an actively cooled aluminum structure, and the use of state-of-the-art alloys. The insulation was fabricated from 300 series stainless steel in thicknesses of 0.8 to 12 mm. The outer, 0.127 mm thick, skin was textured to accommodate thermal expansion and oxidized to increase emittance. The thin insulating package was achieved using an insulation concept consisting of foil radiation shields spaced within the package, and conical foil supports to carry loads from the skin and maintain package dimensions. Samples of the metal-insulation were tested to evaluate thermal insulation capability, rain and sand erosion resistance, high temperature oxidation resistance, applied load capability, and high temperature emittance.

Statistical compilation of NAPAP chemical erosion observations

USGS Publications Warehouse

Mossotti, Victor G.; Eldeeb, A. Raouf; Reddy, Michael M.; Fries, Terry L.; Coombs, Mary Jane; Schmiermund, Ron L.; Sherwood, Susan I.

2001-01-01

In the mid 1980s, the National Acid Precipitation Assessment Program (NAPAP), in cooperation with the National Park Service (NPS) and the U.S. Geological Survey (USGS), initiated a Materials Research Program (MRP) that included a series of field and laboratory studies with the broad objective of providing scientific information on acid rain effects on calcareous building stone. Among the several effects investigated, the chemical dissolution of limestone and marble by rainfall was given particular attention because of the pervasive appearance of erosion effects on cultural materials situated outdoors. In order to track the chemical erosion of stone objects in the field and in the laboratory, the Ca 2+ ion concentration was monitored in the runoff solution from a variety of test objects located both outdoors and under more controlled conditions in the laboratory. This report provides a graphical and statistical overview of the Ca 2+ chemistry in the runoff solutions from (1) five urban and rural sites (DC, NY, NJ, NC, and OH) established by the MRP for materials studies over the period 1984 to 1989, (2) subevent study at the New York MRP site, (3) in situ study of limestone and marble monuments at Gettysburg, (4) laboratory experiments on calcite dissolution conducted by Baedecker, (5) laboratory simulations by Schmiermund, and (6) laboratory investigation of the surface reactivity of calcareous stone conducted by Fries and Mossotti. The graphical representations provided a means for identifying erroneous data that can randomly appear in a database when field operations are semi-automated; a purged database suitable for the evaluation of quantitative models of stone erosion is appended to this report. An analysis of the sources of statistical variability in the data revealed that the rate of stone erosion is weakly dependent on the type of calcareous stone, the ambient temperature, and the H + concentration delivered in the incident rain. The analysis also showed that the rate of stone erosion is strongly dependent on the rain-delivery conditions and on the surface morphology and orientation.

Seasonal change of WEPP erodibility parameters on a fallow plot

Treesearch

D. K. McCool; S. Dun; J. Q. Wu; W. J. Elliot

2011-01-01

In cold regions, frozen soil has a significant influence on runoff and water erosion. Frozen soil can reduce infiltration capacity, and the freeze-thaw processes degrade soil cohesive strength and increase soil erodibility. In the Inland Pacific Northwest of the USA, major erosion events typically occur during winter from low-intensity rain, snowmelt, or both as frozen...

Phosphorus loading to tropical rain forest streams after clear-felling and burning in Sabah, Malaysia

NASA Astrophysics Data System (ADS)

Malmer, Anders

1996-07-01

Most estimates of P export from natural or disturbed humid tropical ecosystems by streams have been based only on export of dissolved P, even though P often is limiting and can be expected to be strongly associated to particles. Therefore loss of ignition (LOI) and particulate P (Ppart) analyses were made on organic and inorganic detritus resulting from surface erosion and on stream-suspended sediments in an undisturbed rain forest (control), as well as during and after conversion of rain forest into forest plantation. Control forest surface erosion and stream sediments consisted mainly of organics, and dissolved P (Pdiss) dominated over Ppart in stream water. The same relation was found after conversion, with a maximum mean Pdiss/Ppart ratio of up to 10 after burning, compared with 2-2.5 for control forests. This larger difference was assumed to depend on PO4 dissolved from ashes to larger concentrations than could be adsorbed during the short time (<1 hour) to reach peak flow during rainstorms.

Calibration of three rainfall simulators with automatic measurement methods

NASA Astrophysics Data System (ADS)

Roldan, Margarita

2010-05-01

CALIBRATION OF THREE RAINFALL SIMULATORS WITH AUTOMATIC MEASUREMENT METHODS M. Roldán (1), I. Martín (2), F. Martín (2), S. de Alba(3), M. Alcázar(3), F.I. Cermeño(3) 1 Grupo de Investigación Ecología y Gestión Forestal Sostenible. ECOGESFOR-Universidad Politécnica de Madrid. E.U.I.T. Forestal. Avda. Ramiro de Maeztu s/n. Ciudad Universitaria. 28040 Madrid. margarita.roldan@upm.es 2 E.U.I.T. Forestal. Avda. Ramiro de Maeztu s/n. Ciudad Universitaria. 28040 Madrid. 3 Facultad de Ciencias Geológicas. Universidad Complutense de Madrid. Ciudad Universitaria s/n. 28040 Madrid The rainfall erosivity is the potential ability of rain to cause erosion. It is function of the physical characteristics of rainfall (Hudson, 1971). Most expressions describing erosivity are related to kinetic energy or momentum and so with drop mass or size and fall velocity. Therefore, research on factors determining erosivity leds to the necessity to study the relation between fall height and fall velocity for different drop sizes, generated in a rainfall simulator (Epema G.F.and Riezebos H.Th, 1983) Rainfall simulators are one of the most used tools for erosion studies and are used to determine fall velocity and drop size. Rainfall simulators allow repeated and multiple measurements The main reason for use of rainfall simulation as a research tool is to reproduce in a controlled way the behaviour expected in the natural environment. But in many occasions when simulated rain is used in order to compare it with natural rain, there is a lack of correspondence between natural and simulated rain and this can introduce some doubt about validity of data because the characteristics of natural rain are not adequately represented in rainfall simulation research (Dunkerley D., 2008). Many times the rainfall simulations have high rain rates and they do not resemble natural rain events and these measures are not comparables. And besides the intensity is related to the kinetic energy which determines the rainfall erosivity (Dunkerley D., 2008). A special attention must be paid to the experimental design and the understanding of the measurements obtained. The objective of this study is the calibration of simulated rain. In order to achieve this objective a rainfall simulator and disdrometer have been used. The first one is a nozzle type and its sprinkler system was located at different heights, three different spray nozzles supplied the water with known pressure. The simulated rainfall presented different intensities, drop diameters distribution and so different kinetic energy. The instrument of measurement for registering data is the disdrometer (Joss and Waldvogel, 1967) which provides the total number of impacts of raindrops, minute after minute, grouped in 20 classes according to their size which allows the real time measurements of the drop diameter distributions, kinetic energy per minute and intensity per minute. Disdrometer registers data in supposing drops fall down with terminal velocity but this velocity can reach up to 7-9 m of height in natural raindrop, depending on drop diameters. If the height of simulator is high enough the drops could recuperate their terminal velocities and their kinetic energies could be true. The nozzles were located to different heights in order to achieve these terminal velocities. These heights vary depending on the nozzles used, when the drops supplied by the nozzle are smaller the terminal velocity is reached sooner than when the drops are bigger. The physical characteristics of simulated rainfall in the three nozzles, intensity, drop diameter distributions and kinetic energy, are known and steady when the drops supplied by the nozzles reach terminal velocities.

Soil conservation in Central America and Panama: current problems.

PubMed

Popenoe, H

1976-06-01

Soil conservation measures in Central America go back to the Maya civilization, in which terracing was employed. After the Spanish conquest, plowing, livestock raising, and the succession of social and political changes all contributed to accelerate erosion. Through the past few decades, awareness of the need for soil conservation has again increased; El Salvador and Costa Rica began efforts in that direction in 1943. For sometime, the use of machinery and chemical fertilizers has masked the loss of topsoil, but under recent increases in population pressures, soil conservation measures are gaining in importance. Important agents of erosion in the tropics are heavy seasonal rains at high elevations, alternating with long dry seasons; wind erosion; and landslides after saturation of the soil during prolonged rains. Modern machinery often hastens soil removal, as do also overgrazing, deforestation and vertical crop rows. Under the present energy crisis, human labor is becoming again a significant element in crop production, and soil conservation becomes thereby more feasible and more important.

The erosion of carbonate stone by acid rain: Laboratory and field investigations

USGS Publications Warehouse

Baedecker, P.A.; Reddy, M.M.

1993-01-01

One of the goals of research on the effects of acidic deposition on carbonate stone surfaces is to define the incremental impact of acidic deposition relative to natural weathering processes on the rate of carbonate stone erosion. If rain that impacts carbonate stone surfaces is resident on the surface long enough to approach chemical equilibrium, the incremental effect of hydrogen ion is expected to be small (i.e., 6% for a rain of pH 4.0). Under nonequilibrium (i.e., high flow rate) conditions, kinetic considerations suggest that the incremental effect of hydrogen ion deposition could be quite significant. Field run-off experiments involving the chemical analysis of rain collected from inclined stone slabs have been used to evaluate stone dissolution processes under ambient conditions of wet and dry deposition of acidic species. The stoichiometry of the reaction of stone with hydrogen ion is difficult to define from the field data due to scatter in the data attributed to hydrodynamic effects. Laboratory run-off experiments show that the stoichiometry is best defined by a reaction with H+ in which CO2 is released from the system. The baseline effect caused by water in equilibrium with atmospheric CO2 is identical in the field and in laboratory simulation. The experiments show that the solutions are close enough to equilibrium for the incremental effect of hydrogen ion to be minor (i.e., 24% for marble for a rain of pH 4.0) relative to dissolution due to water and carbonic acid reactions. Stone erosion rates based on physical measurement are approximately double the recession rates that are due to dissolution (estimated from the observed calcium content of the run-off solutions). The difference may reflect the loss of granular material not included in recession estimates based on the run-off data. Neither the field nor the laboratory run-off experiments indicate a pH dependence for the grain-removal process.

Effects of land clearing techniques and tillage systems on runoff and soil erosion in a tropical rain forest in Nigeria.

PubMed

Ehigiator, O A; Anyata, B U

2011-11-01

This work reports runoff and soil loss from each of 14 sub-watersheds in a secondary rain forest in south-western Nigeria. The impact of methods of land clearing and post-clearing management on runoff and soil erosion under the secondary forest is evaluated. These data were acquired eighteen years after the deforestation of primary vegetation during the ' West bank' project of the International Institute for Tropical Agriculture (IITA). These data are presented separately for each season; however, statistical analyses for replicates were not conducted due to differences in their past management. Soil erosion was affected by land clearing and tillage methods. The maximum soil erosion was observed on sub-watersheds that were mechanically cleared with tree-pusher/root-rake attachments and tilled conventionally. A high rate of erosion was observed even when graded-channel terraces were constructed to minimize soil erosion. In general there was much less soil erosion on manually cleared than on mechanically cleared sub-watersheds (2.5 t ha(-1) yr(-1) versus 13.8 t ha(-1) yr(-1)) and from the application of no-tillage methods than from conventionally plowed areas (6.5 t ha(-1) yr(-1) versus 12.1 t ha(-1) yr(-1)). The data indicate that tillage methods and appropriate management of soils and crops play an important role in soil and water conservation and in decreasing the rate of decline of soil quality. Copyright © 2011 Elsevier Ltd. All rights reserved.

Post-wildfire landscape change and erosional processes from repeat terrestrial lidar in a steep headwater catchment, Chiricahua Mountains, Arizona, USA

NASA Astrophysics Data System (ADS)

DeLong, Stephen B.; Youberg, Ann M.; DeLong, Whitney M.; Murphy, Brendan P.

2018-01-01

Flooding and erosion after wildfires present increasing hazard as climate warms, semi-arid lands become drier, population increases, and the urban interface encroaches farther into wildlands. We quantify post-wildfire erosion in a steep, initially unchannelized, 7.5 ha headwater catchment following the 2011 Horseshoe 2 Fire in the Chiricahua Mountains of southeastern Arizona. Using time-lapse cameras, rain gauges, and repeat surveys by terrestrial laser scanner, we quantify the response of a burned landscape to subsequent precipitation events. Repeat surveys provide detailed pre-and post-rainfall measurements of landscape form associated with a range of weather events. The first post-fire precipitation led to sediment delivery equivalent to 0.017 m of erosion from hillslopes and 0.12 m of erosion from colluvial hollows. Volumetrically, 69% of sediment yield was generated from hillslope erosion and 31% was generated from gully channel establishment in colluvial hollows. Processes on hillslopes included erosion by extensive shallow overland flow, formation of rills and gullies, and generation of sediment-laden flows and possibly debris flows. Subsequent smaller rain events caused ongoing hillslope erosion and local deposition and erosion in gullies. Winter freeze-thaw led to soil expansion, likely related to frost-heaving, causing a net centimeter-scale elevation increase across soil-mantled slopes. By characterizing landscape form, the properties of near-surface materials, and measuring both precipitation and landscape change, we can improve our empirical understanding of landscape response to environmental forcing. This detailed approach to studying landscape response to wildfires may be useful in the improvement of predictive models of flood, debris flow and sedimentation hazards used in post-wildfire response assessments and land management, and may help improve process-based models of landscape evolution.

Post-wildfire landscape change and erosional processes from repeat terrestrial lidar in a steep headwater catchment, Chiricahua Mountains, Arizona, USA

USGS Publications Warehouse

DeLong, Stephen B.; Youberg, Ann M.; DeLong, Whitney M.; Murphy, Brendan P.

2018-01-01

Flooding and erosion after wildfires present increasing hazard as climate warms, semi-arid lands become drier, population increases, and the urban interface encroaches farther into wildlands. We quantify post-wildfire erosion in a steep, initially unchannelized, 7.5 ha headwater catchment following the 2011 Horseshoe 2 Fire in the Chiricahua Mountains of southeastern Arizona. Using time-lapse cameras, rain gauges, and repeat surveys by terrestrial laser scanner, we quantify the response of a burned landscape to subsequent precipitation events. Repeat surveys provide detailed pre-and post-rainfall measurements of landscape form associated with a range of weather events. The first post-fire precipitation led to sediment delivery equivalent to 0.017 m of erosion from hillslopes and 0.12 m of erosion from colluvial hollows. Volumetrically, 69% of sediment yield was generated from hillslope erosion and 31% was generated from gully channel establishment in colluvial hollows. Processes on hillslopes included erosion by extensive shallow overland flow, formation of rills and gullies, and generation of sediment-laden flows and possibly debris flows. Subsequent smaller rain events caused ongoing hillslope erosion and local deposition and erosion in gullies. Winter freeze-thaw led to soil expansion, likely related to frost-heaving, causing a net centimeter-scale elevation increase across soil-mantled slopes. By characterizing landscape form, the properties of near-surface materials, and measuring both precipitation and landscape change, we can improve our empirical understanding of landscape response to environmental forcing. This detailed approach to studying landscape response to wildfires may be useful in the improvement of predictive models of flood, debris flow and sedimentation hazards used in post-wildfire response assessments and land management, and may help improve process-based models of landscape evolution.

[Responses of biological soil crust to and its relief effect on raindrop kinetic energy].

PubMed

Qin, Ning-qiang; Zhao, Yun-ge

2011-09-01

Based on the field investigation and by the method of simulated single-drop rain, this paper studied the responses of different types of biological soil crusts (biocrusts) in the wind-water erosion interleaving region of Loess Plateau to and their relief effect on the kinetic energy of raindrops. The responses of the biocrusts to raindrop kinetic energy had close relations with their biological composition. The cyanobacteria-dominated biocrusts with a thickness of 1 cm and the moss-dominated biocrusts with the coverage of 80% could resist in 0.99 J and 75.56 J of cumulative rain drop kinetic energy, respectively, and the potential resistance of the biocrusts with the same biological compositions was relative to the biomass of the biological compositions, i.e., the larger the biomass, the higher the resistance. As the chlorophyll a content of cyanobacteria- dominated biocrusts (which characterizes the cyanobacterial biomass) increased from 3.32 to 3.73 microg x g(-1), the resistance of the biocrusts against the cumulative raindrop kinetic energy increased from 0.99 to 2.17 J; when the moss biomass in the moss- dominated biocrusts increased from 2.03 to 4.73 g x dm(-2), the resistance of the crusts increased from 6.08 to 75.56 J. During the succession of the biocrusts, their responses to the raindrop kinetic energy presented an "S" pattern. No significant differences in the resistance against raindrop cumulative kinetic energy were observed between the cyanobacteria-dominated biocrusts with variable biomass, but the resistance of moss-dominated biocrusts increased significantly as their biomass per unit area increased. The resistance of moss-dominated biocrusts increased linearly when their biomass increased from 2.03 g x dm(-2) to 4.73 g x dm(-2). The moss-dominated biocrusts could resist in 62.03 J of raindrop kinetic energy when their biomass was up to 3.70 g x dm(-2). Biocrusts had obvious effects in relieving raindrop kinetic energy, and the relief effect increased with their increasing biomass.

Hydrometeor Data and Analytical-Theoretical Investigations Pertaining to the SAMS Rain Erosion Program of the 1972-73 Season at Wallops Island, Virginia - AFGL/SAMS Report Number 5

DTIC Science & Technology

1977-07-05

Report No.5 1. INTRODUCTION The liquid-water-content values and other associated hydrometeorological information for the trajectories of the SAMS...Map Showin« Sitini; Locations of Rain ( Jauges and Oisdrometers Relative to the Missile Launch Pads 80 OltOftOMCTCR I |"fy/^n ^J^^^^^ 01 J I

Effects of acidic deposition on the erosion of carbonate stone — experimental results from the U.S. National Acid Precipitation Assessment Program (NAPAP)

NASA Astrophysics Data System (ADS)

Baedecker, Philip A.; Reddy, Michael M.; Reimann, Karl J.; Sciammarella, Cesar A.

One of the goals of NAPAP-sponsored research on the effects of acidic deposition on carbonate stone has been to quantify the incremental effects of wet and dry deposition of hydrogen ion, sulfur dioxide and nitrogen oxides on stone erosion. Test briquettes and slabs of freshly quarried Indiana limestone and Vermont marble have been exposed to ambient environmental conditions in a long-term exposure program. Physical measurements of the recession of test stones exposed to ambient conditions at an angle of 30° to horizontal at the five NAPAP materials exposure sites range from ˜ 15 to ˜ 30 μm yr -1 for marble, and from ˜ 25 to ˜ 45 μm yr -1 for limestone, and are approximately double the recession estimates based on the observed calcium content of run-off solutions from test slabs. The difference between the physical and chemical recession measurements is attributed to the loss of mineral grains from the stone surfaces that are not measured in the run-off experiments. The erosion due to grain loss does not appear to be influenced by rainfall acidity, however, preliminary evidence suggests that grain loss may be influenced by dry deposition of sulfur dioxide between rainfall events. Chemical analyses of the run-off solutions and associated rainfall blanks suggest that ˜ 30% of erosion by dissolution can be attributed to the wet deposition of hydrogen ion and the dry deposition of sulfur dioxide and nitric acid between rain events. The remaining ˜ 70% of erosion by dissolution is accounted for by the solubility of carbonate stone in rain that is in equilibrium with atmospheric carbon dioxide ("clean rain"). These results are for marble and limestone slabs exposed at an angle of 30° from horizontal. The relative contribution of sulfur dioxide to chemical erosion is significantly enhanced for stone slabs having an inclination of 60° or 85°. The dry deposition of alkaline particulate material has a mitigating effect at the two urban field exposure sites at Washington, DC, and Steubenville, OH.

Effects of acidic deposition on the erosion of carbonate stone - experimental results from the U.S. National Acid Precipitation Assessment Program (NAPAP)

USGS Publications Warehouse

Baedecker, P.A.; Reddy, M.M.; Reimann, K.J.; Sciammarella, C.A.

1992-01-01

One of the goals of NAPAP-sponsored research on the effects of acidic deposition on carbonate stone has been to quantify the incremental effects of wet and dry deposition of hydrogen ion, sulfur dioxide and nitrogen oxides on stone erosion. Test briquettes and slabs of freshly quarried Indiana limestone and Vermont marble have been exposed to ambient environmental conditions in a long-term exposure program. Physical measurements of the recession of test stones exposed to ambient conditions at an angle of 30?? to horizontal at the five NAPAP materials exposure sites range from ~15 to ~30?? ??m yr-1 for marble, and from ~25 to ~45 ??m yr -1 for limestone, and are approximately double the recession estimates based on the observed calcium content of run-off solutions from test slabs. The difference between the physical and chemical recession measurements is attributed to the loss of mineral grains from the stone surfaces that are not measured in the run-off experiments. The erosion due to grain loss does not appear to be influenced by rainfall acidity, however, preliminary evidence suggests that grain loss may be influenced by dry deposition of sulfur dioxide between rainfall events. Chemical analyses of the run-off solutions and associated rainfall blanks suggest that ~30% of erosion by dissolution can be attributed to the wet deposition of hydrogen ion and the dry deposition of sulfur dioxide and nitric acid between rain events. The remaining ~70% of erosion by dissolution is accounted for by the solubility of carbonate stone in rain that is in equilibrium with atmospheric carbon dioxide ('clean rain'). These results are for marble and limestone slabs exposed at an angle of 30?? from horizontal. The relative contribution of sulfur dioxide to chemical erosion is significantly enhanced for stone slabs having an inclination of 60?? or 85??. The dry deposition of alkaline particulate material has a mitigating effect at the two urban field exposure sites at Washington, DC, and Steubenville, OH.

Short-term soil loss by eolian erosion in response to different rain-fed agricultural practices

NASA Astrophysics Data System (ADS)

Tanner, Smadar; Katra, Itzhak; Zaady, Eli

2016-04-01

Eolian (wind) erosion is a widespread process and a major form of soil degradation in arid and semi-arid regions. The present study examined changes in soil properties and eolian soil loss at a field scale in response to different soil treatments in two rain-fed agricultural practices. Field experiments with a boundary-layer wind tunnel and soil analysis were used to obtain the data. Two practices with different soil treatments (after harvest), mechanical tillage and stubble grazing intensities, were applied in the fallow phase of the rotation (dry season). The mechanical tillage and the stubble grazing had an immediate and direct effects on soil aggregation but not on the soil texture, and the contents of soil water, organic matter, and CaCO3. Higher erosion rates, that was measured as fluxes of total eolian sediment and particulate matter <10 μm (PM10), were recorded under mechanical tillage and grazing intensities compared with the undisturbed topsoil of the control plots. The erosion rates were higher in grazing plots than in tillage plots. The calculated soil fluxes in this study indicate potentially rapid soil degradation due to loss of fine particles by wind. The finding may have implications for long-term management of agricultural soils in semi-arid areas.

Evaluation of Erosion Resistance of Advanced Turbine Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Kuczmarski, Maria A.; Miller, Robert A.; Cuy, Michael D.

2007-01-01

The erosion resistant turbine thermal barrier coating system is critical to aircraft engine performance and durability. By demonstrating advanced turbine material testing capabilities, we will be able to facilitate the critical turbine coating and subcomponent development and help establish advanced erosion-resistant turbine airfoil thermal barrier coatings design tools. The objective of this work is to determine erosion resistance of advanced thermal barrier coating systems under simulated engine erosion and/or thermal gradient environments, validating advanced turbine airfoil thermal barrier coating systems based on nano-tetragonal phase toughening design approaches.

Combined slurry and cavitation erosion resistance of surface modified SS410 stainless steel

NASA Astrophysics Data System (ADS)

Amarendra, H. J.; Pratap, M. S.; Karthik, S.; Punitha Kumara, M. S.; Rajath, H. C.; Ranjith, H.; Shubhatunga, S. V.

2018-03-01

Slurry erosion and combined slurry and cavitation erosion resistance of thermal spray coatings are studied and compared with the as-received martensitic stainless steel material. 70Ni-Cr coatings are deposited on SS 410 material through plasma thermal spray process. The synergy effect of the combined slurry and cavitation erosion resistance of plasma thermal spray coatings were investigated in a slurry pot tester in the presence of bluff bodies known as Cavitation Inducers. Results showed the combined slurry and cavitation erosion resistance of martensitic stainless steel - 410 can be improved by plasma thermal spray coating. It is observed that the plasma spray coated specimens are better erosion resistant than the as- received material, subjected to erosion test under similar conditions. As-received and the surface modified steels are mechanically characterized for its hardness, bending. Morphological studies are conducted through scanning electron microscope.

Pollen resistance to water in 80 angiosperm species: flower structures protect rain-susceptible pollen.

PubMed

Mao, Yun-Yun; Huang, Shuang-Quan

2009-08-01

Flowers exhibit adaptive responses to biotic and abiotic factors. It remains unclear whether pollen susceptibility to rain damage plays a role in the evolution of floral form. We investigated flower performance in rain and compared pollen longevity in dry conditions, pure water and solutions with different sucrose concentrations in 80 flowering species from 46 families with diverse floral shapes and pollination modes. A pollen viability test showed that pollen longevity in all studied species was greatly reduced by wetting. We found that pollen of species with complete protection by flower structures was susceptible to water damage and a high proportion of resistant pollen occurred in unprotected species. Flowers whose structures expose pollen to rain may also reduce rain damage through temporal patterns of pollen presentation. This prediction was supported by our direct measurement of pollen presentation duration on rainy days. Our observations showed that variation in pollen performance in water was associated with differences in floral forms. Water-resistant pollen and extended pollen presentation duration were favored by selection via rain contact in species in which pollen was not protected from rain. These findings support the functional hypothesis that flower structures protect susceptible pollen from rain, demonstrating that rain acts as a force shaping floral form.

Performance Evaluation and Modeling of Erosion Resistant Turbine Engine Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Miller, Robert A.; Zhu, Dongming; Kuczmarski, Maria

2008-01-01

The erosion resistant turbine thermal barrier coating system is critical to the rotorcraft engine performance and durability. The objective of this work was to determine erosion resistance of advanced thermal barrier coating systems under simulated engine erosion and thermal gradient environments, thus validating a new thermal barrier coating turbine blade technology for future rotorcraft applications. A high velocity burner rig based erosion test approach was established and a new series of rare earth oxide- and TiO2/Ta2O5- alloyed, ZrO2-based low conductivity thermal barrier coatings were designed and processed. The low conductivity thermal barrier coating systems demonstrated significant improvements in the erosion resistance. A comprehensive model based on accumulated strain damage low cycle fatigue is formulated for blade erosion life prediction. The work is currently aiming at the simulated engine erosion testing of advanced thermal barrier coated turbine blades to establish and validate the coating life prediction models.

Mini rainfall simulation for assessing soil erodibility

NASA Astrophysics Data System (ADS)

Peters, Piet; Palese, Dina; Baartman, Jantiene

2016-04-01

The mini rainfall simulator is a small portable rainfall simulator to determine erosion and water infiltration characteristics of soils. The advantages of the mini rainfall simulator are that it is suitable for soil conservation surveys and light and easy to handle in the field. Practical experience over the last decade has shown that the used 'standard' shower is a reliable method to assess differences in erodibility due to soil type and/or land use. The mini rainfall simulator was used recently in a study on soil erosion in olive groves (Ferrandina-Italy). The propensity to erosion of a steep rain-fed olive grove (mean slope ~10%) with a sandy loam soil was evaluated by measuring runoff and sediment load under extreme rain events. Two types of soil management were compared: spontaneous grass as a ground cover (GC) and tillage (1 day (T1) and 10 days after tillage (T2)). Results indicate that groundcover reduced surface runoff to approximately one-third and soil-losses to zero compared with T1. The runoff between the two tilled plots was similar, although runoff on T1 plots increased steadily over time whereas runoff on T2 plots remained stable.

Rainfall erosivity in Central Chile

NASA Astrophysics Data System (ADS)

Bonilla, Carlos A.; Vidal, Karim L.

2011-11-01

SummaryOne of the most widely used indicators of potential water erosion risk is the rainfall-runoff erosivity factor ( R) of the Revised Universal Soil Loss Equation (RUSLE). R is traditionally determined by calculating a long-term average of the annual sum of the product of a storm's kinetic energy ( E) and its maximum 30-min intensity ( I30), known as the EI30. The original method used to calculate EI30 requires pluviograph records for at most 30-min time intervals. Such high resolution data is difficult to obtain in many parts of the world, and processing it is laborious and time-consuming. In Chile, even though there is a well-distributed rain gauge network, there is no systematic characterization of the territory in terms of rainfall erosivity. This study presents a rainfall erosivity map for most of the cultivated land in the country. R values were calculated by the prescribed method for 16 stations with continuous graphical record rain gauges in Central Chile. The stations were distributed along 800 km (north-south), and spanned a precipitation gradient of 140-2200 mm yr -1. More than 270 years of data were used, and 5400 storms were analyzed. Additionally, 241 spatially distributed R values were generated by using an empirical procedure based on annual rainfall. Point estimates generated by both methods were interpolated by using kriging to create a map of rainfall erosivity for Central Chile. The results show that the empirical procedure used in this study predicted the annual rainfall erosivity well (model efficiency = 0.88). Also, an increment in the rainfall erosivities was found as a result of the rainfall depths, a regional feature determined by elevation and increasing with latitude from north to south. R values in the study area range from 90 MJ mm ha -1 h -1 yr -1 in the north up to 7375 MJ mm ha -1 h -1 yr -1 in the southern area, at the foothills of the Andes Mountains. Although the map and the estimates could be improved in the future by generating additional data points, the erosivity map should prove to be a good tool for land-use planners in Chile and other areas with similar rainfall characteristics.

Evaluation of Post Flooding Shoulder Reconditioning : final report.

DOT National Transportation Integrated Search

2017-02-01

The Ohio Department of Transportation (ODOT) Holmes County Garage has to frequently maintain the shoulders of the hilly and curvy highways, which are prone to shoulder erosion and material loss due to floods or heavy rain. Currently, the problematic ...

Reviews.

ERIC Educational Resources Information Center

Science Teacher, 1988

1988-01-01

Presents information and concerns regarding computer courseware, books, and audiovisual materials reviewed by teachers. Covers a variety of topics including dissection of common classroom specimens, medicine, acid rain projects, molecules, the water cycle, erosion, plankton, and evolution. Notes on availability, price, and needed equipment, where…

Biologically-initiated rock crust on sandstone: Mechanical and hydraulic properties and resistance to erosion

NASA Astrophysics Data System (ADS)

Slavík, Martin; Bruthans, Jiří; Filippi, Michal; Schweigstillová, Jana; Falteisek, Lukáš; Řihošek, Jaroslav

2017-02-01

Biocolonization on sandstone surfaces is known to play an important role in rock disintegration, yet it sometimes also aids in the protection of the underlying materials from rapid erosion. There have been few studies comparing the mechanical and/or hydraulic properties of the BIRC (Biologically-Initiated Rock Crust) with its subsurface. As a result, the overall effects of the BIRC are not yet well understood. The objective of the present study was to briefly characterize the BIRC from both the mineralogical and biological points of view, and especially to quantify the effect of the BIRC upon the mechanical and hydraulic properties of friable sandstone. The mineralogical investigation of a well-developed BIRC showed that its surface is enriched in kaolinite and clay- to silt-sized quartz particles. Total organic carbon increases with the age of the BIRC. Based on DNA sequencing and microscopy, the BIRC is formed by various fungi, including components of lichens and green algae. Using the method of drilling resistance, by measuring tensile strength, and based on water jet testing, it was determined that a BIRC is up to 12 times less erodible and has 3-35 times higher tensile strength than the subsurface friable sandstone. Saturated hydraulic conductivity of the studied BIRC is 15-300 times lower than the subsurface, and was measured to also decrease in capillary water absorption (2-33 times). Water-vapor diffusion is not significantly influenced by the presence of the BIRC. The BIRC thus forms a hardened surface which protects the underlying material from rain and flowing water erosion, and considerably modifies the sandstone's hydraulic properties. Exposing the material to calcination (550 °C), and experiments with the enzyme zymolyase indicated that a major contribution to the surface hardening is provided by organic matter. In firmer sandstones, the BIRC may still considerably decrease the rate of weathering, as it is capable of providing cohesion to strongly weathered (and disintegrated) sandstone surfaces. However, only a near-surface zone of the sandstone is stabilized by the BIRC, and additional sources of stabilization (gravity-induced stress, inorganic cement, etc.) contribute to the resistance of the subsurface zone of sandstone exposures.

Analysis of Navy radome failure problems

NASA Technical Reports Server (NTRS)

Tatnall, G. J.; Foulke, K.

1974-01-01

A survey of radome failure problems in military aircraft under actual operating conditions was conducted. The aircraft were operating from aircraft carriers in the Pacific Ocean. Critical problem areas were identified and a plan was developed for failure prevention. The development and application of repair kits for correcting the erosion damage are reported. It is stated that the rain erosion damage survey established a strong justification for qualification testing of all materials and designs which may have questionable life expectancy on the aircraft.

Effect of rainfall intensity and slope steepness on the development of soil erosion in the Southern Cis-Ural region (A model experiment)

NASA Astrophysics Data System (ADS)

Sobol, N. V.; Gabbasova, I. M.; Komissarov, M. A.

2017-09-01

The effect of rainfall intensity on the erosion of residual calcareous agrogray soils and clay-illuvial agrochernozems in the Southern Cis-Ural region on slopes of different inclination and vegetation type has been studied by simulating with a small-size sprinkler. It has been shown that soil loss linearly depends on rainfall intensity (2, 4, and 6 mm/min) and slope inclination (3° and 7°). When the rainfall intensity and duration, and the slope inclination increase, soil loss by erosion from agrogray soils increases higher than from agrochernozems. On the plowland with a slope of 3°, runoff begins 12, 10, and 5 min, on the average, after the beginning of rains at these intensities. When the slope increases to 7°, runoff begins earlier by 7, 6, and 4 min, respectively. After the beginning of runoff and with its increase by 1 mm, the soil loss from slopes of 3° and 7° reaches 4.2 and 25.7 t/ha on agrogray soils and 1.4 and 4.7 t/ha on agrochernozems, respectively. Fallow soils have higher erosion resistance, and the soil loss little depends on the slope gradient: it gradually increases to 0.3-1.0 t/ha per 1 mm of runoff with increasing rainfall intensity and duration. The content of physical clay in eroded material is higher than in the original soils. Fine fractions prevail in this material, which increases their humus content. The increase in rainfall intensity and duration to 4 and 6 mm/min results in the entrapment of coarse silt and sand by runoff.

Erosion of iron-chromium alloys by glass particles

NASA Technical Reports Server (NTRS)

Salik, J.; Buckley, D. H.

1984-01-01

The material loss upon erosion was measured for several iron-chromium alloys. Two types of erodent material were used: spherical glass beads and sharp particles of crushed glass. For erosion with glass beads the erosion resistance (defined as the reciprocal of material loss rate) was linearly dependent on hardness. This is in accordance with the erosion behavior of pure metals, but contrary to the erosion behavior of alloys of constant composition that were subjected to different heat treatments. For erosion with crushed glass, however, no correlation existed between hardness and erosion resistance. Instead, the erosion resistance depended on alloy composition rather than on hardness and increased with the chromium content of the alloy. The difference in erosion behavior for the two types of erodent particles suggested that two different material removal mechanisms were involved. This was confirmed by SEM micrographs of the eroded surfaces, which showed that for erosion with glass beads the mechanism of material removal was deformation-induced flaking of surface layers, or peening, whereas for erosion with crushed glass it was cutting or chopping.

Erosion resistant coatings

NASA Technical Reports Server (NTRS)

Falco, L.; Cushini, A.

1981-01-01

Apparatus for measuring the resistance of materials to erosion is examined and a scheme for standardization of the test parameters is described. Current materials being used for protecting aircraft parts from erosion are surveyed, their chief characteristics being given. The superior properties of urethane coatings are pointed out. The complete cycle for painting areas subject to erosion is described.

Design and Performance Optimizations of Advanced Erosion-Resistant Low Conductivity Thermal Barrier Coatings for Rotorcraft Engines

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

2012-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future rotorcraft engine higher fuel efficiency and lower emission goals. For thermal barrier coatings designed for rotorcraft turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability, because the rotorcraft are often operated in the most severe sand erosive environments. Advanced low thermal conductivity and erosion-resistant thermal barrier coatings are being developed, with the current emphasis being placed on thermal barrier coating toughness improvements using multicomponent alloying and processing optimization approaches. The performance of the advanced thermal barrier coatings has been evaluated in a high temperature erosion burner rig and a laser heat-flux rig to simulate engine erosion and thermal gradient environments. The results have shown that the coating composition and architecture optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic oxidation durability

The Development of Erosion and Impact Resistant Turbine Airfoil Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

2007-01-01

Thermal barrier coatings are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments and extend component lifetimes. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Advanced erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the doped thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion and impact damage mechanisms of the thermal barrier coatings will also be discussed.

Erosion-resistant coatings for gas turbine engine compressor blades

NASA Astrophysics Data System (ADS)

Kablov, E. N.; Muboyadzhyan, S. A.

2017-06-01

The erosion-resistant ZrN and Cr3C2 coatings intended for the protection of the titanium and steel blades in a GTE compressor are studied. The erosion resistance of the substrate-coating composition is shown to depend on the coating thickness, the deposition conditions, and the coating texture. Ion-assisted deposition changes the structure-phase state of a coating and substantially increases its erosion resistance. It is found that a nanolayer 2D TiN/CrN coating with an average nanolayer thickness of 60 nm is the best erosion- corrosion-resistant coating for titanium alloys and that a (NiCrTiAlHf)C + CrC coating formed by ionassisted deposition is the best coating for steels. The testing of alloy VT8 compressor blades in an engine supported high protective properties of the nanolayer TiN/CrN coating.

The Green Pages: Environmental Education Activities K-12.

ERIC Educational Resources Information Center

Clearing, 1991

1991-01-01

Presented are 38 environmental education activities for grades K-12. Topics include seed dispersal, food chains, plant identification, sizes and shapes, trees, common names, air pollution, recycling, temperature, litter, water conservation, photography, insects, urban areas, diversity, natural cycles, rain, erosion, phosphates, human population,…

Significance of connectivity and post-wildfire runoff

USDA-ARS?s Scientific Manuscript database

Amplified hillslope soil loss from rain storms following wildfire results from the evolution of runoff and erosion processes across spatial scales. At point to small-plot scales, soil is detached and transported a short distance by rainsplash and sheetflow. Soil transport by water over larger scales...

Promoting nitrate removal in rain gardens | Science Inventory ...

EPA Pesticide Factsheets

Rain gardens are vegetated surface depressions, often located at low points in landscapes, designed to receive stormwater runoff from roads, roofs, and parking lots. The gardens’ sandy soils allow stormwater to drain quickly to the native soils below and eventually to groundwater. The rain garden vegetation and soils remove pollutants and nutrients from stormwater runoff through biological and physical processes such as plant uptake and sorption to soil particles. In comparison with stormwater release to receiving waters through conventional storm drain systems, infiltrating stormwater through rain gardens reduces peak flows and loadings of both pollutants and nutrients. This reduction improves the physical and biological integrity of receiving streams by reducing stream bank erosion and negative effects on stream communities. While local governments and individual homeowners are building these systems, relatively few scientific studies have documented the ability of rain gardens to remove pollutants and nutrients. This U.S. EPA long-term research project investigates: 1) the performance of rain gardens in removing pollutants, and 2) whether currently-accepted design standards can be adjusted to improve nitrate removal capabilities. Typical rain garden designs provide large removals of pollutants of concern, including heavy metals, phosphorus, total nitrogen, and ammonium. The gardens have been less successful in removing nitrate, an importan

Application of Computer Simulation to Identify Erosion Resistance of Materials of Wet-steam Turbine Blades

NASA Astrophysics Data System (ADS)

Korostelyov, D. A.; Dergachyov, K. V.

2017-10-01

A problem of identifying the efficiency of using materials, coatings, linings and solderings of wet-steam turbine rotor blades by means of computer simulation is considered. Numerical experiments to define erosion resistance of materials of wet-steam turbine blades are described. Kinetic curves for erosion area and weight of the worn rotor blade material of turbines K-300-240 LMP and atomic icebreaker “Lenin” have been defined. The conclusion about the effectiveness of using different erosion-resistant materials and protection configuration of rotor blades is also made.

Biological soil crusts exhibit a dynamic response to seasonal rain and release from grazing with implications for soil stability

USGS Publications Warehouse

Jimenez, Aguilar A.; Huber-Sannwald, E.; Belnap, J.; Smart, D.R.; Arredondo, Moreno J.T.

2009-01-01

In Northern Mexico, long-term grazing has substantially degraded semiarid landscapes. In semiarid systems, ecological and hydrological processes are strongly coupled by patchy plant distribution and biological soil crust (BSC) cover in plant-free interspaces. In this study, we asked: 1) how responsive are BSC cover/composition to a drying/wetting cycle and two-year grazing removal, and 2) what are the implications for soil erosion? We characterized BSC morphotypes and their influence on soil stability under grazed/non-grazed conditions during a dry and wet season. Light- and dark-colored cyanobacteria were dominant at the plant tussock and community level. Cover changes in these two groups differed after a rainy season and in response to grazing removal. Lichens with continuous thalli were more vulnerable to grazing than those with semi-continuous/discontinuous thalli after the dry season. Microsites around tussocks facilitated BSC colonization compared to interspaces. Lichen and cyanobacteria morphotypes differentially enhanced resistance to soil erosion; consequently, surface soil stability depends on the spatial distribution of BSC morphotypes, suggesting soil stability may be as dynamic as changes in the type of BSC cover. Longer-term spatially detailed studies are necessary to elicit spatiotemporal dynamics of BSC communities and their functional role in biotically and abiotically variable environments. ?? 2009 Elsevier Ltd.

Splash erosion in recently-burnt area in North-West Spain

NASA Astrophysics Data System (ADS)

Fernández Raga, María

2013-04-01

Splash erosion is generally acknowledged as the main erosive agent, because it represents the first step in water erosion (Ellison, 1944, Sempere Torres et al., 1994). The impact of raindrops not only modifies the structure of the earth's surface, (Moss, 1991) but also breaks down and emits soil fragments which are later transported over long distances in the case of additional surface runoff processes (Moss and Green, 1983). In the whole process we need to take into account not only the specific kinetic energy associated to each rain event, but also the type of soil and the size of the particles released (Sharma et al 1991), as well as the characteristics of the layer of water formed on the surface (Moss and Green, 1983, Kinnell, 1991, Leguédois et al., 2005). The erosion process is more obvious when it affects vulnerable areas that have recently been devastated by a wildfire. This study has computed the raindrop size, its volume, the fall velocity, and its kinetic energy by means of an optical disdrometer. The data have subsequently been compared with the mass of soil that was splashed and collected in a particular area devastated by an important wildfire on the 17th of May 2012. The splash erosion produced in 6 months has been analyzed. 2. Study Site The data were gathered in the period between the 29th May and the 30th November 2012, in the area of Congosto, in the province of León, Spain. The study zone is part of a transition area between the plain and the mountainous regions. The dominant climate is the continentalized Mediterranean climate, although with more moderate temperatures. In general, in this area we find a wide temperature range (from 12 to 20°C), long and cold winters, short springs and autumns, and short and warm summers. Precipitation is irregularly scattered along the year, and may reach, depending on the area, up to 1,500 mm per year. Intense precipitation events may occur. The area presents a coarse-grained siliceous lithology, that is, quartzite with sandstone and slate, with a soil cover of inceptisol of franc-sandy texture. The vegetation, which is the first defense line against erosion in the area, is limited to holm oaks and pine trees, all of which were virtually eliminated by the virulence of the wildfire in May 2012. 3. Materials and Methods Precipitation was measured using a Thies optical disdrometer which registers raindrop size spectra every minute. This device is described in detail in Bloemink and Lanzinger (2005). The instruments used to carry out this study on splash erosion have been the funnels described in Fernández-Raga 2010. The area affected by the wildfire was divided into 2 sections, one former pine tree area, and another former scrubland area. Five sampling points were installed in each area. Similar control areas were established in the part of land not affected by the fire, with the same type of vegetation, and with another 5 sampling points in each case. In addition, control devices were installed to collect airborne soil. 4. The kinetic energy of rain The kinetic energy of rain was assessed using data obtained by the disdrometer: raindrop size distribution (DSD). This information enables us to compute the mass of the raindrop and its fall velocity (Ryzhkov et al 1999). To compute the mass, we need to know the shape of the drop. The shape of raindrops has been the object of many previous studies (Brandes, 2002, Sansom, 2004). The main conclusion is that drops smaller than 1 mm are spherical, but raindrops with diameters larger than 1 mm take on a shape that resembles more an ellipsoid. Considering that size, we adopt a polynomial equation of degree 12 (Fernández-Raga 2010). 5. Evolution of splash erosion The study has assessed the amount of splash erosion as well as its composition. In addition, the erosion caused has been compared with the regeneration of the vegetation in the area. The results reveal a very slow recovery of the vegetation in the study zone, and a halt in the amount of soil affected by splash erosion until now. 5. Results and Conclusions It was found that the precipitation in Congosto has a nearly exponential drop size distribution (DSD), except for large sizes. It can also be noted that drops between the sizes of 2 and 2.5 mm are the ones that contribute more to the kinetic energy hitting the ground. The comparison between the splash erosion registered and the total kinetic energy in each rain event has led to the following conclusions: • The DSD of precipitation in Congosto follows an exponential or gamma distribution. The energy distribution, on the other hand, is a gamma distribution. • Splash erosion has been found to be very important in the area devastated by the wildfire in the 2 months immediately after the fire. Later, splash erosion decreases, though it remains relatively high despite fewer rain events during the summer. • The vegetation has not recovered at all in the 6 months that followed the wildfire. • The soil analysis reveals a high degree of degradation caused by the wildfire. 6. References Angulo-Martínez, M., Beguería, S., Navas, A. Machín, J. 2012. Splash erosion under natural rainfall on three soil types in NE Spain Geomorphology, 175-176, 38-44. Bloemink, HI and Lanzinger, E., 2005.precipitation type from the thies disdrometer. Wmo technical conference on meteorological and environmental instruments and methods of observations (teco-2005) Bucharest, Romania, 4-7 may, 3. Brandes, e. A., g. Zhang, and j. Vivekanandan, 2002: experiments in rainfall estimation with a polarimetric radar in a subtropical environment. J. Appl. Meteor., 41, 674-685. Ellison, W.D. 1944. Studies of raindrop erosion. Agric. Eng. 25:131 136, 181-182. Fernandez-Raga, M., Fraile, R., Keizer, J.J., Teijeiro, M.E.V., Castro, A., Palencia, C., Calvo, A.I., Koenders, J. and Marques, R.L.D., 2010. The kinetic energy of rain measured with an optical disdrometer: An application to splash erosion. Atmos. Res. 96, 225-240. Kinnell, P.I.A. 1991. The effect of flow depth on sediment transport induced by raindrops impacting shallow flows. Trans. ASAE. 34: 161-168. Leguedois C., S., Malam-Issa O., and Bissonnais Y. Le. 2005. Splash distance and size distributions for various soils. Geoderma, 124, 3-4, 279-292 Moss, A.J., and Green, P.. 1983. Movement of solids in air and water- by raindrop impact. Effects of drop-size and water-depth variations. Austr. J. Soil Res. 21:257-269. Moss, Aj. 1991. Rain impact soil crust.I. Formation on a granite derived soil.Austr. J. Soil Res 29:271-289. Ryzhkov A., Schuur, T., Zrnic, D. and Schönhuber M. 1999, Comparison of radar polarimetric measurements of rainfall with 2D-video disdrometer observations. Preprints, National Radio Science Meeting, 1999, Boulder, CO, USA. Sansom, J. 2004 Rainfall as breakpoints: observations and physically based Markov models. International Precipitation Conference, Quantifying Uncertainties in Precipitation Measurements, Estimates, and Forecasts, Vancouver, Canada. Sempere Torres, D., Porrà, J.M., Creutin, J.D., 1994. A general formulation for raindrop size distribution. Journal of Applied Meteorology 33, 1494-1502. Sharma, P.P., Gupta, S.C. and Rawls. W.J. 1991. Soil detachment by single raindrops of varying kinetic energy. Soil Sci. Soc. Am. J. 55:301-307.

Soil erosion and effluent particle size distribution under different initial conditions and rock fragment coverage

NASA Astrophysics Data System (ADS)

Jomaa, S.; Barry, D. A.; Brovelli, A.; Heng, B. C. P.; Sander, G. C.; Parlange, J.-Y.

2012-04-01

It is well known that the presence of rock fragments on the soil surface and the soil's initial characteristics (moisture content, surface roughness, bulk density, etc.) are key factors influencing soil erosion dynamics and sediment delivery. In addition, the interaction of these factors increases the complexity of soil erosion patterns and makes predictions more difficult. The aim of this study was (i) to investigate the effect of soil initial conditions and rock fragment coverage on soil erosion yields and effluent particle size distribution and (ii) to evaluate to what extent the rock fragment coverage controls this relationship. Three laboratory flume experiments with constant precipitation rate of 74 mm/h on a loamy soil parcel with a 2% slope were performed. Experiments with duration of 2 h were conducted using the 6-m × 2-m EPFL erosion flume. During each experiment two conditions were considered, a bare soil and a rock fragment-protected (with 40% coverage) soil. The initial soil surface state was varied between the three experiments, from a freshly re-ploughed and almost dry condition to a compacted soil with a well-developed shield layer and high moisture content. Experiments were designed so that rain splash was the primary driver of soil erosion. Results showed that the amount of eroded mass was highly controlled by the initial soil conditions and whether the steady-state equilibrium was un-, partially- or fully- developed during the previous event. Additionally, results revealed that sediment yields and particle size composition in the initial part of an erosion event are more sensitive to the erosion history than the long-time behaviour. This latter appears to be mainly controlled by rainfall intensity. If steady-state was achieved for a previous event, then the next event consistently produced concentrations for each size class that peaked rapidly, and then declined gradually to steady-state equilibrium. If steady state was not obtained, then different and more complex behaviour was observed in the next event, with large differences found between fine, medium and coarse size classes. The presence of rock fragments on the topsoil reduced the time needed to reach steady state compared with the bare soil. This was attributed to the reduction of rain splash erosion caused by the rapid development of the overland flow, as a result of rock fragments reducing the flow cross-sectional area.

Quantifying the Spatial Distribution of Hill Slope Erosion Using a 3-D Laser Scanner

NASA Astrophysics Data System (ADS)

Scholl, B. N.; Bogonko, M.; He, Y.; Beighley, R. E.; Milberg, C. T.

2007-12-01

Soil erosion is a complicated process involving many interdependent variables including rainfall intensity and duration, drop size, soil characteristics, ground cover, and surface slope. The interplay of these variables produces differing spatial patterns of rill versus inter-rill erosion by changing the effective energy from rain drop impacts and the quantities and timing of sheet and shallow, concentrated flow. The objective of this research is to characterize the spatial patterns of rill and inter-rill erosion produced from simulated rainfall on different soil densities and surface slopes using a 3-D laser scanner. The soil used in this study is a sandy loam with bulk density due to compaction ranging from 1.25-1.65 g/cm3. The surface slopes selected for this study are 25, 33, and 50 percent and represent common slopes used for grading on construction sites. The spatial patterns of soil erosion are measured using a Trimble GX DR 200+ 3D Laser Scanner which employs a time of flight calculation averaged over 4 points using a class 2, pulsed, 532 nm, green laser at a distance of 2 to 11 m from the surface. The scanner measures point locations on an approximately 5 mm grid. The pre- and post-erosion scan surfaces are compared to calculate the change in volume and the dimensions of rills and inter-rill areas. The erosion experiments were performed in the Soil Erosion Research Laboratory (SERL), part of the Civil and Environmental Engineering department at San Diego State University. SERL experiments utilize a 3-m by 10-m tilting soil bed with a soil depth of 0.5 meters. Rainfall is applied to the soil surface using two overhead Norton ladder rainfall simulators, which produce realistic rain drop diameters (median = 2.25 mm) and impact velocities. Simulated storm events used in this study consist of rainfall intensities ranging from 5, 10 to 15 cm/hr for durations of 20 to 30 minutes. Preliminary results are presented that illustrate a change in runoff processes and erosion patterns as soil density increases and reduces infiltration characteristics. Total soil loss measured from the bottom of the erosion bed is compared to the volume of soil loss determined using the laser scanner. Due to soil consolidation during the experiment, the accuracy of measured soil loss from the laser scanner increases with increasing soil density. Ratios of rill and inter-rill erosions for each experiment are also presented. URL: http://spatialhydro.sdsu.edu

Vegetation effects on soil water erosion rates and nutrient losses at Santa Catarina highlands, south Brazil

NASA Astrophysics Data System (ADS)

Bertol, I.; Barbosa, F. T.; Vidal Vázquez, E.; Paz Ferreiro, J.

2009-04-01

Water erosion involves three main processes: detachment, transport and deposition of soil particles. The main factors affecting water erosion are rainfall, soil, topography, soil management and land cover and use. Soil erosion potential is increased if the soil has no or very little vegetative cover of plants and/or crop residues, whereas plant and residue cover substantially decrease rates of soil erosion. Plant and residue cover protects the soil from raindrop impact and splash, tends to slow down the movement of surface runoff and allows excess surface water to infiltrate. Moreover, plant and residue cover improve soil physical, chemical and biological properties. Soils with improved structure have a greater resistance to erosion. By contrast, accelerated soil erosion is accentuated by deforestation, biomass burning, plowing and disking, cultivation of open-row crops, etc. The erosion-reducing effectiveness of plant and/or residue covers depends on the type, extent and quantity of cover. Vegetation and residue combinations that completely cover the soil are the most efficient in controlling soil. Partially incorporated residues and residual roots are also important, as these provide channels that allow surface water to move into the soil. The effectiveness of any crop, management system or protective cover also depends on how much protection is available at various periods during the year, relative to the amount of erosive rainfall that falls during these periods. Most of the erosion on annual row crop land can be reduced by leaving a residue cover greater after harvest and over the winter months, or by inter-seeding a forage crop. Soil erosion potential is also affected by tillage operations and tillage system. Conservation tillage reduces water erosion in relation to conventional tillage by increasing soil cover and soil surface roughness. Here, we review the effect of vegetation on soil erosion in the Santa Catarina highlands, south of Brazil, under subtropical climatic conditions. The area cropped under no tillage in Brazil has increased rapidly since 1990, especially in the southern region. This practice was first introduced in the 1970s as a strategy to control soil erosion and continuous declines in land productivity under conventional tillage systems. No tillage almost entirely keeps the previous crop residue on the surface. In the last 15 years soil and water losses by water erosion have been quantified for different soil tillage systems, diverse crop rotations and successive crop stages under simulated and natural rain conditions. Plot experiments showed that soil losses under no tillage systems with a vegetative cover were 98% lower when compared with conventionally tilled bare soil. Moreover water losses were 60% lower for these conditions. Conventional tillage (plowing + harrowing) in the presence of vegetative cover reduced soil losses and water losses by 80% and 50%, respectively, taken the uncultivated bare soil as a reference. The review includes the effect of vegetative cover on nutrient losses at the studied sites in the Santa Catarina highlands.

Environmental Detectives. Grades 5-8. Teacher's Guide.

ERIC Educational Resources Information Center

Beals, Kevin; Willard, Carolyn

This book uses a detective approach to teach about environmental issues. Student sleuths investigate many potential causes of fish dying including chlorine pollution, acid rain, erosion and sediment pollution, predator-prey relationships, phosphate pollution and algal blooms, and oil pollution. The text provides students the opportunity to grapple…

[Effects and mechanisms of plant roots on slope reinforcement and soil erosion resistance: a research review].

PubMed

Xiong, Yan-Mei; Xia, Han-Ping; Li, Zhi-An; Cai, Xi-An

2007-04-01

Plant roots play an important role in resisting the shallow landslip and topsoil erosion of slopes by raising soil shear strength. Among the models in interpreting the mechanisms of slope reinforcement by plant roots, Wu-Waldron model is a widely accepted one. In this model, the reinforced soil strength by plant roots is positively proportional to average root tensile strength and root area ratio, the two most important factors in evaluating slope reinforcement effect of plant roots. It was found that soil erosion resistance increased with the number of plant roots, though no consistent quantitative functional relationship was observed between them. The increase of soil erosion resistance by plant roots was mainly through the actions of fiber roots less than 1 mm in diameter, while fiber roots enhanced the soil stability to resist water dispersion via increasing the number and diameter of soil water-stable aggregates. Fine roots could also improve soil permeability effectively to decrease runoff and weaken soil erosion.

Pyrite oxidation under simulated acid rain weathering conditions.

PubMed

Zheng, Kai; Li, Heping; Wang, Luying; Wen, Xiaoying; Liu, Qingyou

2017-09-01

We investigated the electrochemical corrosion behavior of pyrite in simulated acid rain with different acidities and at different temperatures. The cyclic voltammetry, polarization curve, and electrochemical impedance spectroscopy results showed that pyrite has the same electrochemical interaction mechanism under different simulated acid rain conditions, regardless of acidity or environmental temperature. Either stronger acid rain acidity or higher environmental temperature can accelerate pyrite corrosion. Compared with acid rain having a pH of 5.6 at 25 °C, the prompt efficiency of pyrite weathering reached 104.29% as the acid rain pH decreased to 3.6, and it reached 125.31% as environmental temperature increased to 45 °C. Increasing acidity dramatically decreases the charge transfer resistance, and increasing temperature dramatically decreases the passivation film resistance, when other conditions are held constant. Acid rain always causes lower acidity mine drainage, and stronger acidity or high environmental temperatures cause serious acid drainage. The natural parameters of latitude, elevation, and season have considerable influence on pyrite weathering, because temperature is an important influencing factor. These experimental results are of direct significance for the assessment and management of sulfide mineral acid drainage in regions receiving acid rain.

Standardization of splash device

NASA Astrophysics Data System (ADS)

Fernández Raga, María; Peters, Piet

2017-04-01

The erosion is a complex process that has been studied extensively by numerous researchers, requiring a prolongued time effort and a large economic investment. To be effective, the measurements of erosion should be precise, controlled and replicable, and to assure efectiveness, measurement devices of erosion should be properly designed, constructed, well calibrated and also they should be operated by a trained person (Stroosnijder, 2005). Because researchers try to improve old devices, the equipment is constantly being redesigned, making the measurements not comparable and furthermore, producing a lack of available standarized device. The lack of standardization of erosion equipment is more obvious in the case of the local splash erosion, where the nature of the process makes very difficult to isolate its effects. In this article we compare the results obtained from five of the most common splash erosion devices (selected from more than 16 different currently types), under the same rain conditions, with the objective of facilitate the standardization of the method that will be more easy to build, minimizing the error. A set of six splash devices were setted in well known positions under simulated rain, to measured the differences, among devices and the accuracy of the data recovered after 10 minutes of rainfall simulation under different intensities (from 60 to 130 mm/h). The rainfall simulator of Wageningen was used, using sand as splash erosion source. Differences in the infiltration were also measured, and a calibration of sizes and speeds of the raindrops was done using the photography method (Hamidreza-Sadeghi et al., 2013). The splash devices selected for this study were unbounded splash devices (like the funnel, the cup (Fernandez-Raga et al., 2010) and the splash flume (Jomaa et al., 2010)), and bounded devices that allow the calculation of splash rate, (like the new cup (Scholten et al., 2011) and the Morgan tray). The behaviour of different splash devices with the changes of intensity will be explained and discussed, with a recommendation of use. References Fernandez-Raga, M, Fraile, R, Keizer, J, Teijeiro, MEV, Castro, A, Palencia, C, Koenders, J and Marques, RLD. 2010. The kinetic energy of rain measured with an optical disdrometer: An application to splash erosion. Atmospheric Research 96, 225-240. doi: 10.1016/j.atmosres.2009.07.013 Hamidreza-Sadeghi, S, Abdollahi, Z and Khaledi-Darvishan, A. 2013. Experimental comparison of some techniques for estimating natural raindrop size distribution on the south coast of the Caspian Sea, Iran. Hydrological sciences Journal 58, 1374-1382. doi: 10.1080/02626667.2013.814917 Jomaa, S, Barry, D, Brovelli, A, Sander, G, Parlange, J, Heng, B and Tromp-van Meerveld, H. 2010. Effect of raindrop splash and transversal width on soil erosion: Laboratory flume experiments and analysis with the Hairsine-Rose model. Journal of Hydrology 395, 117-132. doi: 10.1016/j.jhydrol.2010.10.021 Scholten, T, Geißler, C, Goc, J, Kühn, P and Wiegand, C. 2011. A new splash cup to measure the kinetic energy of rainfall. Journal of Plant Nutrition and Soil Science 174, 596-601. doi: 10.1002/jpln.201000349 Stroosnijder, L. 2005. Measurement of erosion: is it possible? Catena 64, 162-173. doi: 10.1016/j.catena.2005.08.004

The relevance of wind-driven rain for future soil erosion research

NASA Astrophysics Data System (ADS)

Fister, Wolfgang; Marzen, Miriam; Iserloh, Thomas; Seeger, Manuel; Heckrath, Goswin; Greenwood, Philip; Kuhn, Nikolaus J.; Ries, Johannes B.

2014-05-01

The influence of wind on falling raindrops and its potential to alter soil erosion rates was already proposed during the 1960s, but never really reached broad awareness in the soil erosion research community. Laboratory investigations over the last 15 years confirmed earlier findings and have proven that wind modifies the characteristics of falling raindrops in many ways. Most importantly, the impact angles and impact frequencies, as well as the drop velocities, drop sizes and hence the kinetic energy are modified. Consequently, the results of laboratory experiments on highly disturbed, loose, and mostly sandy substrates indicate that soil detachment and transport/splash distances of particles increase under the influence of wind. However, these experiments cannot reflect the complexity of naturally developed soils and a direct transfer of these findings to field conditions is therefore limited. So far, only a few field studies have reported increased erosion rates due to splash drift or increased runoff by wind-driven rain. Because of the lack of simultaneous reference measurements without the influence of wind, these studies were not able to discriminate between the different processes and thus couldn not clearly prove the relevance of wind-driven rainfall. Despite all these findings, the awareness of this phenomenon is, in our opinion, still limited. Almost all rainfall simulations exclude the factor of wind as a disturbance to reach more representative rainfall conditions on the plot. We think, that among other reasons, this underestimation of the influence of wind could be due to the absence of an adequate measurement device to simulate these processes and additionally, due to the fact that the relevance of wind-driven rain in a landscape context has not yet been proven. To overcome this lack of a useful device, and to take the research from the laboratory to the field on real soils again, the first portable wind and rainfall simulator was developed within this PhD-project. By measuring soil erosion rates on the same plot, both with and without wind application, the influence of wind on soil detachment and erosion rates can now clearly be determined. Field experiments with the Portable Wind and Rainfall Simulator, which were carried out in Andalusia (Spain), in Wageningen (The Netherlands), and in Foulum (Denmark) during and within 3 years after finishing the PhD-project, aimed to improve the knowledge of processes involved, and to show the relevance of wind-driven rainfall erosion. The results indicate that the influence of wind depends on the complexity of the landscape. In an environment with homogenous conditions (loose sand mixture) and only a few variable factors (i.e. no vegetation, no surface roughness, no slope), like the test site in Wageningen, the increase of erosion rates due to the influence of wind could be seen in almost every test run. This clear influence of wind decreased with the amount of involved factors from agricultural soils in Denmark with a homogenous sandy texture and steep slopes, to highly degraded abandoned/fallow land with thick soil crusts and a clay-silt texture in Andalusia. The results obtained by "simple" rainfall simulations, therefore, clearly underestimate soil erosion rates, depending on the environment. This could, in our opinion, have strong implications for future soil erosion research and modelling.

A new concept for stainless steels ranking upon the resistance to cavitation erosion

NASA Astrophysics Data System (ADS)

Bordeasu, I.; Popoviciu, M. O.; Salcianu, L. C.; Ghera, C.; Micu, L. M.; Badarau, R.; Iosif, A.; Pirvulescu, L. D.; Podoleanu, C. E.

2017-01-01

In present, the ranking of materials as their resistance to cavitation erosion is obtained by using laboratory tests finalized with the characteristic curves mean depth erosion against time MDE(t) and mean depth erosion rate against time MDER(t). In some previous papers, Bordeasu and co-workers give procedures to establish exponential equation representing the curves, with minimum scatter of the experimental obtained results. For a given material, both exponential equations MDE(t) and MDER(t) have the same values for the parameters of scale and for the shape one. For the ranking of materials is sometimes important to establish single figure. Till now in Timisoara Polytechnic University Cavitation Laboratory were used three such numbers: the stable value of the curve MDER(t), the resistance to cavitation erosion (Rcav ≡ 1/MDERstable) and the normalized cavitation resistance Rns which is the rate between vs = MDERstable for the analyzed material and vse= MDERse the mean depth erosion rate for the steel OH12NDL (Rns = vs/vse ). OH12NDL is a material used for manufacturing the blades of numerous Kaplan turbines in Romania for which both cavitation erosion laboratory tests and field measurements of cavitation erosions are available. In the present paper we recommend a new method for ranking the materials upon cavitation erosion resistance. This method uses the scale and shape parameters of the exponential equations which represents the characteristic cavitation erosion curves. Till now the method was applied only for stainless steels. The experimental results show that the scale parameter represents an excellent method for ranking the stainless steels. In the future this kind of ranking will be tested also for other materials especially for bronzes used for manufacturing ship propellers.

Aggregate stability as an indicator of soil erodibility and soil physical quality: review and perspectives

NASA Astrophysics Data System (ADS)

Le Bissonnais, Yves; Chenu, Claire; Darboux, Frédéric; Duval, Odile; Legout, Cédric; Leguédois, Sophie; Gumiere, Silvio

2010-05-01

Aggregate breakdown due to water and rain action may cause surface crusting, slumping, a reduction of infiltration and interrill erosion. Aggregate stability determines the capacity of aggregates to resist the effects of water and rainfall. In this paper, we evaluated and reviewed the relevance of an aggregate stability measurement to characterize soil physical properties as well as to analyse the processes involved in these properties. Stability measurement assesses the sensitivity of soil aggregates to various basic disaggregation mechanisms such as slaking, differential swelling, dispersion and mechanical breakdown. It has been showed that aggregate size distributions of structural stability tests matched the size distributions of eroded aggregates under rainfall simulations and that erosion amount was well predicted using aggregate stability indexes. It means stability tests could be used to estimate both the erodibility and the size fractions that are available for crust formation and erosion processes. Several studies showed that organic matter was one of the main soil properties affecting soil stability. However, it has also been showed that aggregate stability of a given soil could vary within a year or between years. The factors controlling such changes have still to be specified. Aggregate stability appears therefore as a complex property, depending both on permanent soil characteristics and on dynamic factors such as the crusting stage, the climate and the biological activity. Despite, and may be, because of this complexity, aggregate stability seems an integrative and powerful indicator of soil physical quality. Future research efforts should look at the causes of short-term changes of structural stability, in order to fully understand all its aspects.

Freeze-thaw processes and intense winter rainfall: The one-two punch for high streambank legacy sediment and nutrient loads from Mid-Atlantic watersheds

NASA Astrophysics Data System (ADS)

Inamdar, S. P.; Johnson, E. R.; Rowland, R. D.; Walter, R. C.; Merritts, D.

2017-12-01

Historic and contemporary anthropogenic soil erosion combined with early-American milldams resulted in large deposits of legacy sediments in the valley bottoms of Piedmont watersheds of the eastern US. Breaching of milldams subsequently yielded highly incised streams with exposed vertical streambanks that are vulnerable to erosion. Streambank erosion is attributed to fluvial scouring, freeze-thaw processes and mass wasting. While streambanks represent a large reservoir of fine sediments and nutrients, there is considerable uncertainty about the contribution of these sources to watershed nonpoint source pollution. Using high-frequency hydrologic, sediment, and turbidity data we show that freeze-thaw events followed by intense winter rainstorms can export unusually high concentrations of suspended sediment and particulate nutrients from watersheds. Data from a 12 ha forested, Piedmont, stream following an intense rain event (54 mm) on February 2016 yielded suspended sediment and particulate nutrient (organic carbon and nitrogen) concentrations and exports that exceeded those from tropical storms Irene, Lee, and Sandy that had much greater rainfall and discharge amounts, but which occurred later in the year. A similar response was also observed with regards to turbidity data for USGS stream monitoring locations at Brandywine Creek (813 km2) and White Clay Creek (153 km2). We hypothesize that much of the sediment export associated with winter storms is likely due to erosion of streambank sediments and was driven by the coupled occurrence of freeze-thaw conditions and intense rainfall events. We propose that freeze-thaw erosion represents an important and underappreciated mechanism in streams that "recharges" the sediment supply, which then is available for flushing by moderate to large storms. Future climate projections indicate increased intensification of storm events and increased variability of winter temperatures. Freeze-thaw cycles coupled with winter rain events could increase erosion and transport of streambank sediments with detrimental consequences for water quality and health of downstream aquatic ecosystems. This study underscores the need to better understand the mechanisms of legacy sediment erosion and transport along with appropriate restoration strategies.

Natural dust and acid rain

Treesearch

Erhard M. Winkler

1976-01-01

Atmospheric dust originates from three sources, terrestrial airborn matter, volcanic, and cosmic. Terrestrial natural dust makes up the main bulk reflecting the soil composition to 150 miles away. Soil erosion from flood plains, plowed fields and construction sites are the main source. Quartz, feldspar, the carbonates calcite and dolomite, and clay minerals are the...

Effects on wetting by spray on concentrated flow erosion and intake rate

USDA-ARS?s Scientific Manuscript database

When water flows in dry rills (or furrows), fast wetting and aggregate slaking occur. Conversely, when rain wets the surface of the soil before applying concentrated flow, slow wetting precedes the concentrated flow, and less aggregate disintegration occurs. It is hypothesized that slow wetting by t...

Building climate resilience in the Blue Nile/Abay Highlands: Part II-arole for earth system sciences

USDA-ARS?s Scientific Manuscript database

The Blue Nile (Abay) Highlands of Ethiopia are characterized by significant interannual climate variability, dissected topography and associated local climate contrasts, erosive rains and erodible soils, and intense land pressure due to an increasing population and an economy that is almost entirely...

Screening study of select cotton-based hydromulch blends produced using the cross-linked biofiber process

USDA-ARS?s Scientific Manuscript database

As global populations continue to expand, stresses placed on our renewable resources are increasing. Disturbance of native landscapes from agriculture, urbanization, or by natural evolution brings the potential for soil erosion caused by normal rain events. Increasing regulatory pressure has resulte...

Rain Check Application: Mobile tool to monitor rainfall in remote parts of Haiti

NASA Astrophysics Data System (ADS)

Huang, X.; Baird, J.; Chiu, M. T.; Morelli, R.; de Lanerolle, T. R.; Gourley, J. R.

2011-12-01

Rainfall observations performed uniformly and continuously over a period of time are valuable inputs in developing climate models and predicting events such as floods and droughts. Rain-Check is a mobile application developed in Google App Inventor Platform, for android based smart phones, to allow field researchers to monitor various rain gauges distributed though out remote regions of Haiti and send daily readings via SMS messages for further analysis and long term trending. Rainfall rate and quantity interact with many other factors to influence erosion, vegetative cover, groundwater recharge, stream water chemistry and runoff into streams impacting agriculture and livestock. Rainfall observation from various sites is especially significant in Haiti with over 80% of the country is mountainous terrain. Data sets from global models and limited number of ground stations do not capture the fine-scale rainfall patterns necessary to describe local climate. Placement and reading of rain gauges are critical to accurate measurement of rainfall.

A rain splash transport equation assimilating field and laboratory measurements

USGS Publications Warehouse

Dunne, T.; Malmon, D.V.; Mudd, S.M.

2010-01-01

Process-based models of hillslope evolution require transport equations relating sediment flux to its major controls. An equation for rain splash transport in the absence of overland flow was constructed by modifying an approach developed by Reeve (1982) and parameterizing it with measurements from single-drop laboratory experiments and simulated rainfall on a grassland in East Africa. The equation relates rain splash to hillslope gradient, the median raindrop diameter of a storm, and ground cover density; the effect of soil texture on detachability can be incorporated from other published results. The spatial and temporal applicability of such an equation for rain splash transport in the absence of overland flow on uncultivated hillslopes can be estimated from hydrological calculations. The predicted transport is lower than landscape-averaged geologic erosion rates from Kenya but is large enough to modify short, slowly eroding natural hillslopes as well as microtopographic interrill surfaces between which overland flow transports the mobilized sediment. Copyright 2010 by the American Geophysical Union. Copyright 2010 by the American Geophysical Union.

Effect of mechanical properties on erosion resistance of ductile materials

NASA Astrophysics Data System (ADS)

Levin, Boris Feliksovih

Solid particle erosion (SPE) resistance of ductile Fe, Ni, and Co-based alloys as well as commercially pure Ni and Cu was studied. A model for SPE behavior of ductile materials is presented. The model incorporates the mechanical properties of the materials at the deformation conditions associated with SPE process, as well as the evolution of these properties during the erosion induced deformation. An erosion parameter was formulated based on consideration of the energy loss during erosion, and incorporates the material's hardness and toughness at high strain rates. The erosion model predicts that materials combining high hardness and toughness can exhibit good erosion resistance. To measure mechanical properties of materials, high strain rate compression tests using Hopkinson bar technique were conducted at strain rates similar to those during erosion. From these tests, failure strength and strain during erosion were estimated and used to calculate toughness of the materials. The proposed erosion parameter shows good correlation with experimentally measured erosion rates for all tested materials. To analyze subsurface deformation during erosion, microhardness and nanoindentation tests were performed on the cross-sections of the eroded materials and the size of the plastically deformed zone and the increase in materials hardness due to erosion were determined. A nanoindentation method was developed to estimate the restitution coefficient within plastically deformed regions of the eroded samples which provides a measure of the rebounding ability of a material during particle impact. An increase in hardness near the eroded surface led to an increase in restitution coefficient. Also, the stress rates imposed below the eroded surface were comparable to those measured during high strain-rate compression tests (10sp3-10sp4 ssp{-1}). A new parameter, "area under the microhardness curve" was developed that represents the ability of a material to absorb impact energy. By incorporating this parameter into a new erosion model, good correlation was observed with experimentally measured erosion rates. An increase in area under the microhardness curve led to an increase in erosion resistance. It was shown that an increase in hardness below the eroded surface occurs mainly due to the strain-rate hardening effect. Strain-rate sensitivities of tested materials were estimated from the nanoindentation tests and showed a decrease with an increase in materials hardness. Also, materials combining high hardness and strain-rate sensitivity may offer good erosion resistance. A methodology is presented to determine the proper mechanical properties to incorporate into the erosion parameter based on the physical model of the erosion mechanism in ductile materials.

Ion implantation method for preparing polymers having oxygen erosion resistant surfaces

DOEpatents

Lee, Eal H.; Mansur, Louis K.; Heatherly, Jr., Lee

1995-01-01

Hard surfaced polymers and the method for making them are generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface, improved wear resistance, and improved oxygen erosion resistance.

Effects of Crop Canopies on Rain Splash Detachment

PubMed Central

Ma, Bo; Yu, Xiaoling; Ma, Fan; Li, Zhanbin; Wu, Faqi

2014-01-01

Crops are one of the main factors affecting soil erosion in sloping fields. To determine the characteristics of splash erosion under crop canopies, corn, soybean, millet, and winter wheat were collected, and the relationship among splash erosion, rainfall intensity, and throughfall intensity under different crop canopies was analyzed through artificial rainfall experiments. The results showed that, the mean splash detachment rate on the ground surface was 390.12 g/m2·h, which was lower by 67.81% than that on bare land. The inhibiting effects of crops on splash erosion increased as the crops grew, and the ability of the four crops to inhibit splash erosion was in the order of winter wheat>corn>soybeans>millet. An increase in rainfall intensity could significantly enhance the occurrence of splash erosion, but the ability of crops to inhibit splash erosion was 13% greater in cases of higher rainfall intensity. The throughfall intensity under crop canopies was positively related to the splash detachment rate, and this relationship was more significant when the rainfall intensity was 40 mm/h. Splash erosion tended to occur intensively in the central row of croplands as the crop grew, and the non-uniformity of splash erosion was substantial, with splash erosion occurring mainly between the rows and in the region directly under the leaf margin. This study has provided a theoretical basis for describing the erosion mechanisms of cropland and for assisting soil erosion prediction as well as irrigation and fertilizer management in cultivated fields. PMID:24992386

Effects of crop canopies on rain splash detachment.

PubMed

Ma, Bo; Yu, Xiaoling; Ma, Fan; Li, Zhanbin; Wu, Faqi

2014-01-01

Crops are one of the main factors affecting soil erosion in sloping fields. To determine the characteristics of splash erosion under crop canopies, corn, soybean, millet, and winter wheat were collected, and the relationship among splash erosion, rainfall intensity, and throughfall intensity under different crop canopies was analyzed through artificial rainfall experiments. The results showed that, the mean splash detachment rate on the ground surface was 390.12 g/m2 · h, which was lower by 67.81% than that on bare land. The inhibiting effects of crops on splash erosion increased as the crops grew, and the ability of the four crops to inhibit splash erosion was in the order of winter wheat>corn>soybeans>millet. An increase in rainfall intensity could significantly enhance the occurrence of splash erosion, but the ability of crops to inhibit splash erosion was 13% greater in cases of higher rainfall intensity. The throughfall intensity under crop canopies was positively related to the splash detachment rate, and this relationship was more significant when the rainfall intensity was 40 mm/h. Splash erosion tended to occur intensively in the central row of croplands as the crop grew, and the non-uniformity of splash erosion was substantial, with splash erosion occurring mainly between the rows and in the region directly under the leaf margin. This study has provided a theoretical basis for describing the erosion mechanisms of cropland and for assisting soil erosion prediction as well as irrigation and fertilizer management in cultivated fields.

Development and Life Prediction of Erosion Resistant Turbine Low Conductivity Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

2010-01-01

Future rotorcraft propulsion systems are required to operate under highly-loaded conditions and in harsh sand erosion environments, thereby imposing significant material design and durability issues. The incorporation of advanced thermal barrier coatings (TBC) in high pressure turbine systems enables engine designs with higher inlet temperatures, thus improving the engine efficiency, power density and reliability. The impact and erosion resistance of turbine thermal barrier coating systems are crucial to the turbine coating technology application, because a robust turbine blade TBC system is a prerequisite for fully utilizing the potential coating technology benefit in the rotorcraft propulsion. This paper describes the turbine blade TBC development in addressing the coating impact and erosion resistance. Advanced thermal barrier coating systems with improved performance have also been validated in laboratory simulated engine erosion and/or thermal gradient environments. A preliminary life prediction modeling approach to emphasize the turbine blade coating erosion is also presented.

Reduction of soil erosion and mercury losses in agroforestry systems compared to forests and cultivated fields in the Brazilian Amazon.

PubMed

Béliveau, Annie; Lucotte, Marc; Davidson, Robert; Paquet, Serge; Mertens, Frédéric; Passos, Carlos J; Romana, Christine A

2017-12-01

In addition to causing physical degradation and nutrient depletion, erosion of cultivated soils in the Amazon affects aquatic ecosystems through the release of natural soil mercury (Hg) towards lakes and rivers. While traditional agriculture is generally cited as being among the main causes of soil erosion, agroforestry practices are increasingly appreciated for soil conservation. This study was carried out in family farms of the rural Tapajós region (Brazil) and aimed at evaluating soil erosion and associated Hg release for three land uses. Soils, runoff water and eroded sediments were collected at three sites representing a land cover gradient: a recently burnt short-cycle cropping system (SCC), a 2-year-old agroforestry system (AFS) and a mature forest (F). At each site, two PVC soil erosion plots (each composed of three 2 × 5 m isolated subplots) were implemented on steep and moderate slopes respectively. Sampling was done after each of the 20 rain events that occurred during a 1-month study period, in the peak of the 2011 rain season. Runoff volume and rate, as well as eroded soil particles with their Hg and cation concentrations were determined. Total Hg and cation losses were then calculated for each subplot. Erosion processes were dominated by land use type over rainfall or soil slope. Eroded soil particles, as well as the amount of Hg and cations (CaMgK) mobilized at the AFS site were similar to those at the F site, but significantly lower than those at the SCC site (p < 0.0001). Erosion reduction at the AFS site was mainly attributed to the ground cover plants characterizing the recently established system. Moreover, edaphic change throughout AFS and F soil profiles differed from the SCC site. At the latter site, losses of fine particles and Hg were enhanced towards soil surface, while they were less pronounced at the other sites. This study shows that agroforestry systems, even in their early stages of implementation, are characterized by low erosion levels resembling those of local forest environments, thus contributing to the maintenance of soil integrity and to the reduction of Hg and nutrient mobility. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ion implantation method for preparing polymers having oxygen erosion resistant surfaces

DOEpatents

Lee, E.H.; Mansur, L.K.; Heatherly, L. Jr.

1995-04-18

Hard surfaced polymers and the method for making them are generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface, improved wear resistance, and improved oxygen erosion resistance. 8 figs.

Erosion-corrosion resistance properties of 316L austenitic stainless steels after low-temperature liquid nitriding

NASA Astrophysics Data System (ADS)

Zhang, Xiangfeng; Wang, Jun; Fan, Hongyuan; Pan, Dong

2018-05-01

The low-temperature liquid nitriding of stainless steels can result in the formation of a surface zone of so-called expanded austenite (S-phase) by the dissolution of large amounts of nitrogen in the solid solution and formation of a precipitate-free layer supersaturated with high hardness. Erosion-corrosion measurements were performed on low-temperature nitrided and non-nitrided 316L stainless steels. The total erosion-corrosion, erosion-only, and corrosion-only wastages were measured directly. As expected, it was shown that low-temperature nitriding dramatically reduces the degree of erosion-corrosion in stainless steels, caused by the impingement of particles in a corrosive medium. The nitrided 316L stainless steels exhibited an improvement of almost 84% in the erosion-corrosion resistance compared to their non-nitrided counterparts. The erosion-only rates and synergistic levels showed a general decline after low-temperature nitriding. Low-temperature liquid nitriding can not only reduce the weight loss due to erosion but also significantly reduce the weight loss rate of interactions, so that the total loss of material decreased evidently. Therefore, 316L stainless steels displayed excellent erosion-corrosion behaviors as a consequence of their highly favorable corrosion resistances and superior wear properties.

Erosion and corrosion resistance of laser cladded AISI 420 stainless steel reinforced with VC

NASA Astrophysics Data System (ADS)

Zhang, Zhe; Yu, Ting; Kovacevic, Radovan

2017-07-01

Metal Matrix Composites (MMC) fabricated by the laser cladding process have been widely applied as protective coatings in industries to improve the wear, erosion, and corrosion resistance of components and prolong their service life. In this study, the AISI 420/VC metal matrix composites with different weight percentage (0 wt.%-40 wt.%) of Vanadium Carbide (VC) were fabricated on a mild steel A36 by a high power direct diode laser. An induction heater was used to preheat the substrate in order to avoid cracks during the cladding process. The effect of carbide content on the microstructure, elements distribution, phases, and microhardness was investigated in detail. The erosion resistance of the coatings was tested by using the abrasive waterjet (AWJ) cutting machine. The corrosion resistance of the coatings was studied utilizing potentiodynamic polarization. The results showed that the surface roughness and crack susceptibility of the laser cladded layer were increased with the increase in VC fraction. The volume fraction of the precipitated carbides was increased with the increase in the VC content. The phases of the coating without VC consisted of martensite and austenite. New phases such as precipitated VC, V8C7, M7C3, and M23C6 were formed when the primary VC was added. The microhardness of the clads was increased with the increase in VC. The erosion resistance of the cladded layer was improved after the introduction of VC. The erosion resistance was increased with the increase in the VC content. No obvious improvement of erosion resistance was observed when the VC fraction was above 30 wt.%. The corrosion resistance of the clads was decreased with the increase in the VC content, demonstrating the negative effect of VC on the corrosion resistance of AISI 420 stainless steel

Angular particle impingement studies of thermoplastic materials at normal incidence

NASA Technical Reports Server (NTRS)

Rao, P. V.; Buckley, D. H.

1985-01-01

Scanning electron microscope studies were conducted to characterize the erosion resistance of polymethyl methacrylate (PMMA), polycarbonate (PC), polytetrafluorethylene (PTFE), and ultra-high-molecular-weight polyethylene (UHMWPE). Erosion was caused by a jet of angular microparticles of crushed glass at normal incidence. Material built up above the original surface on all of the materials. As erosion progressed, this buildup disappeared. UHMWPE was the most resistant material and PMMA the least. The most favorable properties for high erosion resistance were high values of ultimate elongation, maximum service temperature, and strain energy and a low value of the modulus of elasticity. Erosion-rate-versus-time curves of PC and PTFE exhibited incubation, acceleration, and steady-state periods. PMMA also exhibited a deceleration period, and an incubation period with deposition was observed for UHMWPE.

Erosion Resistance Index (ERI) to Assess Surface Stability in Desert Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamada, Yuki; Grippo, Mark A.

2015-11-01

A new spectral index—erosion resistance index (ERI)—was developed to assess erosion risks in desert landscapes. The index was developed by applying trigonometry to the combination of the green/red band-ratio and the red/near infrared band-ratio from very high spatial resolution imagery. The resultant ERI maps showed spatially cohesive distributions of high and low index values across the study areas. High index values were observed over areas that were resistant to erosion (such as desert pavement and dense vegetation), while low index values overlapped with areas likely dominated by loose sandy soils, such as stream beds and access roads. Although further investigationmore » is warranted, this new index, ERI, shows promise for the assessment of erosion risks in desert regions.« less

Slurry Erosion Performance of Ni-Al2O3 Based Thermal-Sprayed Coatings: Effect of Angle of Impingement

NASA Astrophysics Data System (ADS)

Grewal, H. S.; Agrawal, Anupam; Singh, H.; Shollock, B. A.

2014-02-01

In this paper, slurry erosion performance of high velocity flame-sprayed Ni-Al2O3 based coatings was evaluated. The coatings were deposited on a hydroturbine steel (CA6NM) by varying the content of Al2O3 in Ni. Using jet-type test rig, erosion behavior of coatings and bare steel was evaluated at different impingement angles. Detailed investigation of the surface morphology of the eroded specimens was undertaken using SEM/EDS to identify potential erosion mechanism. A parameter named "erosion mechanism identifier" (ξ) was used to predict the mode of erosion. It was observed that the coating prepared using 40 wt.% of Al2O3 showed a highest resistance to erosion. This coating enhanced the erosion resistance of the steel by 2 to 4 times. Spalling in the form of splats and chunks of material (formed by interlinking of cracks) along with fracture of Al2O3 splats were identified as primary mechanisms responsible for the loss of coating material. The erosion mechanism of coatings and bare steel predicted by ξ was in good agreement with that observed experimentally. Among different parameters,, a function of fracture toughness ( K IC) and hardness ( H) showed excellent correlation with erosion resistance of coatings at both the impingement angles.

Splash erosion. A bibliometric Review

NASA Astrophysics Data System (ADS)

Fernández Raga, M. B.

2012-04-01

Ellison (1944) developed the splash board as a system for measuring splash erosion that was both cheap and reliable. Bollinne (1975), Morgan (1978, 1981). Mutchler (1967) described another different type of splash detectors according to whether they were passive or could register data. In the study mentioned above these authors included bottles, funnels, glasses, photography, markers. After that several devices has been made up like the splash sampler (Leguedois et al., 2005), soil tray (Van Dijk et al., 2002), splash funnel (Terry, 1989) and several rain cups (Fernandez-Raga et al., 2010; Molina and Llinares, 1996; Torri et al., 1987). Splash erosion research has materialized in the form of a number of papers published in international journals. The database of bibliographic references employed has been one of the most prestigious ones: theWeb of Science (ISI). The search was carried out on January 27th 2012. Among the 3x10^8 scholarly documents included in the Science Citation Index Expanded (SCI-EXPANDED) 1899 to present , the searching engine located 439 containing the word "splash erosion*", where the asterisk acts as a wildcard for any letter or group of letters. Of these, 383 were classified as articles, 87 as proceeding papers, 5 as editorial material, 2 as notes and 1 as correction. These documents have been published in 163 different journals, although four are particularly recurrent: Earth surface processes and Landforms, Catena, Soil Science Society of America Journal and Hydrological processes, with 41, 35, 35 and 26 published documents respectively. A geographic analysis of these articles has been carried out in an attempt to determine in what parts of the world research projects were making use of splash erosion. The results are that anglo-saxon countries, as USA, England and Australia dominate, particularly USA, with 130 articles. China and Japan are large communities of researches too, and some Central European countries as Belgium, France Germany and Netherlands. It is interesting to analyze the evolution of research by means of splash erosion publications. Figure 6 shows the number of documents published every decade from 1961 (the first publication appears in 1967) . Various aspects need to be commented: • The decades show an exponential increase in the number of publications. • The line in the figure represents the rise in the number of publications, which have been larger in the last two decades (900s and 20000s). • The last decade included began in 2001 leads us to predict a strong boost in research in this particular field. It is also worthwhile to consider briefly the main concepts dealt with in the documents published: • There are only 3 publications with disdrometer + splash erosion as topic words. • After 1991 and 2000 we find that there are several lines of measurement of two main research lines today are already defined: the study of the splash produces with rain simulation processes or splash produces with natural rain (relationship with atmospheric variables and accuracy of the measurements). • The current decade is characterized by an increase in research using disdrometers for studying splash erosion. Summing up, the research that is being carried out using splash erosion is evolving towards an increasing number of projects, countries, and especially, papers published in prestigious scientific journals.

Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V

PubMed Central

Mahdipoor, M.S.; Kirols, H.S.; Kevorkov, D.; Jedrzejowski, P.; Medraj, M.

2015-01-01

Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ Vn, where the speed exponent is 7–9 for Ti6Al4V and 11–13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl. PMID:26391370

Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V.

PubMed

Mahdipoor, M S; Kirols, H S; Kevorkov, D; Jedrzejowski, P; Medraj, M

2015-09-22

Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ V(n), where the speed exponent is 7-9 for Ti6Al4V and 11-13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl.

Comparative Sand and Rain Erosion Studies of Spinel, Aluminum Oxynitride (ALON), Magnesium Fluoride, and Germanate Glass

DTIC Science & Technology

1993-08-01

A speed of 206 m/s (406 knots) was chosen for small particles (ព gim) to simulate aircraft cruising conditions. Seven samples (Table 3) were exposed...Infrared Optical Materials and Their Antireflection Coatings, Bristol, Adam Hilger, 1985. 3. S. Musikant . Optical Materials, New York, Marcel Dekker, 1985

Hybrid Ultra-Low VOC and Non-HAP Rain Erosion Coatings

DTIC Science & Technology

2018-01-12

cavitation test stand for running the modified ASTM G32 method...Objective Numerous military aircraft and shipboard surfaces, such as radomes, antennas, gun shields, wing leading edges, and helicopter blade leading edges... blades , and helicopter blade leading edges. The application market is extremely widespread. Luna will leverage existing internal contacts for

Watershed management for disaster mitigation and sustainable development in Taiwan

Treesearch

J. D. Cheng; H. K. Hsu; Way Jane Ho; T. C. Chen

2000-01-01

Heavy torrential rains during the typhoon season, steep topography, young and weak geologic formations, erodible soils and improper land uses are factors contributing to disasters associated with erosion, landslides, debris flows, and floods in Taiwan. With steady public and government support over the past 5 decades, Taiwan's watershed management program in which...

Oxygen plasma treatment and deposition of CN{sub x} on a fluorinated polymer matrix composite for improved erosion resistance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muratore, C.; Korenyi-Both, A.; Bultman, J. E.

2007-07-15

The use of polymer matrix composites in aerospace propulsion applications is currently limited by insufficient resistance to erosion by abrasive media. Erosion resistant coatings may provide necessary protection; however, adhesion to many high temperature polymer matrix composite (PMC) materials is poor. A low pressure oxygen plasma treatment process was developed to improve adhesion of CN{sub x} coatings to a carbon reinforced, fluorinated polymer matrix composite. Fullerene-like CN{sub x} was selected as an erosion resistant coating for its high hardness-to-elastic modulus ratio and elastic resilience which were expected to reduce erosion from media incident at different angles (normal or glancing) relativemore » to the surface. In situ x-ray photoelectron spectroscopy was used to evaluate the effect of the plasma treatment on surface chemistry, and electron microscopy was used to identify changes in the surface morphology of the PMC substrate after plasma exposure. The fluorine concentration at the surface was significantly reduced and the carbon fibers were exposed after plasma treatment. CN{sub x} coatings were then deposited on oxygen treated PMC substrates. Qualitative tests demonstrated that plasma treatment improved coating adhesion resulting in an erosion resistance improvement of a factor of 2 compared to untreated coated composite substrates. The combination of PMC pretreatment and coating with CN{sub x} reduced the erosion rate by an order of magnitude for normally incident particles.« less

Erosion-resistant composite material

DOEpatents

Finch, C.B.; Tennery, V.J.; Curlee, R.M.

A highly erosion-resistant composite material is formed of chemical vapor-deposited titanium diboride on a sintered titanium diboride-nickel substrate. This material may be suitable for use in cutting tools, coal liquefaction systems, etc.

Short-term transport of glyphosate with erosion in Chinese loess soil--a flume experiment.

PubMed

Yang, Xiaomei; Wang, Fei; Bento, Célia P M; Xue, Sha; Gai, Lingtong; van Dam, Ruud; Mol, Hans; Ritsema, Coen J; Geissen, Violette

2015-04-15

Repeated applications of glyphosate may contaminate the soil and water and threaten their quality both within the environmental system and beyond it through water erosion related processes and leaching. In this study, we focused on the transport of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) related to soil erosion at two slope gradients (10 and 20°), two rates of pesticide with a formulation of glyphosate (Roundup®) application (360 and 720 mg m(-2)), and a rain intensity of 1.0 mm min(-1) for 1 h on bare soil in hydraulic flumes. Runoff and erosion rate were significantly different within slope gradients (p<0.05) while suspended load concentration was relatively constant after 15 min of rainfall. The glyphosate and AMPA concentration in the runoff and suspended load gradually decreased. Significant power and exponent function relationship were observed between rainfall duration and the concentration of glyphosate and AMPA (p<0.01) in runoff and suspended load, respectively. Meanwhile, glyphosate and AMPA content in the eroded material depended more on the initial rate of application than on the slope gradients. The transport rate of glyphosate by runoff and suspended load was approximately 14% of the applied amount, and the chemicals were mainly transported in the suspended load. The glyphosate and AMPA content in the flume soil at the end of the experiment decreased significantly with depth (p<0.05), and approximately 72, 2, and 3% of the applied glyphosate (including AMPA) remained in the 0-2, 2-5, and 5-10 cm soil layers, respectively. The risk of contamination in deep soil and the groundwater was thus low, but 5% of the initial application did reach the 2-10 cm soil layer. The risk of contamination of surface water through runoff and sedimentation, however, can be considerable, especially in regions where rain-induced soil erosion is common. Copyright © 2015 Elsevier B.V. All rights reserved.

Developpement d'un montage simulant l'erosion par la pluie pour l'evaluation des revetements glaciophobes dans le domaine aerospatial

NASA Astrophysics Data System (ADS)

Tremblay, Sarah-Eve

Ce memoire presente le developpement d’un montage simulant l’erosion par la pluie afin d’effectuer l’evaluation de differents revetements glaciophobes dans le domaine aerospatial. Bien que plusieurs revetements presentent une bonne efficacite a reduire l’adherence et/ou l’accumulation de glace, ils ne repondent pas necessairement aux normes de resistance a l’erosion simulee par les gouttes de pluie les frappant a grande vitesse. Il n’existe qu’une installation en Amerique du Nord offrant un service d’essai qui evalue la resistance a l’erosion par la pluie suivant les normes aerospatiales. Etant l’unique institution pouvant faire la certification de peintures utilisees sur les avions en ce qui a trait a l’erosion par la pluie, ce service est donc difficile d’acces et couteux. Le laboratoire international des materiaux antigivre (LIMA) a developpe un essai plus rapide et moins couteux, facilitant ainsi le developpement de revetements glaciophobes devant resister a l’erosion par la pluie. Dans cette etude, le developpement du montage d’erosion par la pluie effectue au laboratoire des materiaux antigivre (LIMA) est presente. En particulier, des essais sur quatre (4) revetements dont la resistance a l’erosion est connue, et sur trois revetements industriels, ont ete effectues afin d’ajuster les differents parametres du montage comme la pression et la temperature de l’eau ainsi que la robustesse du montage. Ensuite, des essais de sensibilite et de reproductibilite des resultats ont egalement ete effectues pour fin de validation du montage et du protocole experimental. Pour ce faire, le montage de type jet d’eau developpe consiste principalement en une pompe a haute pression qui projette un jet d’eau continu passant par les orifices d’un disque tournant. Cette operation permet de generer une goutte de pluie simulee qui est projetee sur un echantillon de revetement statique. L’essai est base sur la norme standard ASTM (Liquid Impingement Erosion Testing, G73-82). La resistance a l’erosion du materiau est determinee a l’aide du nombre d’impacts subi par l’echantillon obtenu avant la production de dommages visibles. Donc, pour determiner le niveau d’erosion, quatre sites d’impacts doivent etre erodes sur cinq sur le meme rang pour le meme nombre d’impact. L’analyse des quatre revetements de resistance a l’erosion connus a ete completee par l’examen microscopique de chaque site d’impact et d’une photo. Le choix des quatre revetements de resistance a l’erosion connue, allant du plus resistant au moins resistant, a permis de verifier que le montage etait assez sensible pour evaluer les revetements souvent utilises dans le domaine aerospatial. De plus, l’evaluation des trois revetements industriels a permis, pour sa part, de confirmer les resultats obtenus precedemment. Finalement, pour evaluer la sensibilite et la reproductibilite des resultats, de deux a six repetitions pour chaque revetement a ete effectuees donnant des taux d’erosion allant de 100 a 100 000 impacts. L’intervalle des ecarts-types varie de ± 0% a ± 47% pour une moyenne de ± 17%. Le critere d’echec a ete determine a l’aide du nombre d’impacts avant l’apparition de dommage visible ainsi que de la repetabilite des resultats.

Mycophenolate mofetil in erosive genital lichen planus: a case and review of the literature.

PubMed

Deen, Kristyn; McMeniman, Erin

2015-03-01

Erosive genital lichen planus is a disabling, inflammatory mucocutaneous condition that can cause significant patient morbidity and loss of function. Treatment initially involves topical corticosteroids but some patients can have severe treatment-resistant courses requiring systemic immunosuppression. With potentially unfavorable adverse effect profiles and subsequent intolerance of these agents by patients, erosive lichen planus can ultimately be a challenging condition to treat effectively. We present a case of a 66-year-old woman with treatment-resistant erosive genital lichen planus who was successfully managed with mycophenolate mofetil. Although there is only weak evidence for this agent in this condition, its role in dermatology is growing due to its efficacy and advantageous adverse effect profile and should therefore be considered in patients with treatment-resistant erosive genital lichen planus. © 2015 Japanese Dermatological Association.

The role of mechanical properties in cavitation erosion resistance. [parameters affecting metal fatigue under cavitation flow conditions

NASA Technical Reports Server (NTRS)

Gould, G. C.

1974-01-01

Methods for determining the correlations of erosion resistance and mechanical properties of materials are discussed. The most common method of testing cavitation erosion resistance of materials is the vibratory cavitation probe. The instrument and its operation are described. The use of the whirling arm device is considered as a second method. Metallographic investigations of the earliest stages of cavitation erosion damage of metallic materials was conducted. The materials show plastic deformation occurring during the incubation period and increasing until cracks form and metal fragments are lost. The parameters of the work done to cause material fractures are identified. The reactions obtained with specific materials are reported.

How well does the Post-fire Erosion Risk Management Tool (ERMiT) really work?

NASA Astrophysics Data System (ADS)

Robichaud, Peter; Elliot, William; Lewis, Sarah; Miller, Mary Ellen

2016-04-01

The decision of where, when, and how to apply the most effective postfire erosion mitigation treatments requires land managers to assess the risk of damaging runoff and erosion events occurring after a fire. The Erosion Risk Management Tool (ERMiT) was developed to assist post fire assessment teams identify high erosion risk areas and effectiveness of various mitigation treatments to reduce that risk. ERMiT is a web-based application that uses the Water Erosion Prediction Project (WEPP) technology to estimate erosion, in probabilistic terms, on burned and recovering forest, range, and chaparral lands with and without the application of mitigation treatments. User inputs are processed by ERMiT to combine rain event variability with spatial and temporal variabilities of hillslope burn severity and soil properties which are then used as WEPP inputs. Since 2007, the model has been used in making hundreds of land management decisions in the US and elsewhere. We use eight published field study sites in the Western US to compare ERMiT predictions to observed hillslope erosion rates. Most sites experience only a few rainfall events that produced runoff and sediment except for a California site with a Mediterranean climate. When hillslope erosion occurred, significant correlations occurred between the observed hillslope erosion and those predicted by ERMiT. Significant correlation occurred for most mitigation treatments as well as the five recovery years. These model validation results suggest reasonable estimates of probabilistic post-fire hillslope sediment delivery when compared to observation.

Erosion resistance of arc-sprayed coatings to iron ore at 25 and 315 °C

NASA Astrophysics Data System (ADS)

Dallaire, S.; Levert, H.; Legoux, J.-G.

2001-06-01

Iron ore pellets are sintered and reduced in large continuous industrial oil-fired furnaces. From the furnace, powerful fans extract large volumes of hot gas. Being exposed to gas-borne iron ore particles and temperatures ranging between 125 and 328 °C, fan components are rapidly eroded. Extensive part repair or replacement is required for maintaining a profitable operation. The arc spraying technique has been suggested for repair provided it could produce erosion-resistant coatings. Conventional and cored wires (1.6 mm diameter) were arc sprayed using various spray parameters to produce 250 to 300 µm thick coatings. Arc-sprayed coatings and reference specimens were erosion tested at 25 and 315 °C and impact angles of 25 and 90° in a laboratory gas-blast erosion rig. This device was designed to impact materials with coarse (32 to 300 µm) iron ore particles at a speed of 100 m/s. The coating volume loss due to erosion was measured with a laser profilometer built by National Research Council Canada several years ago. Few arc-sprayed coatings exhibited erosion resistance comparable with structural steel at low impact angles. Erosion of arc-sprayed coatings and reference specimens dramatically increases at 315 °C for both 25° and 90° impact angles. Erosion-enhanced oxidation was found to be responsible for the increase in volume loss above room temperature. Though arc spraying can be appropriate for on-site repair, the development of more erosion-resistant coatings is required for intermediate temperatures.

Bioengineering Technology to Control River Soil Erosion using Vetiver (Vetiveria Zizaniodes)

NASA Astrophysics Data System (ADS)

Sriwati, M.; Pallu, S.; Selintung, M.; Lopa, R.

2018-04-01

Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock or dissolved material from one location on the earth’s crust, and then transport it away to another location. Bioengineering is an attempt to maximise the use of vegetation components along riverbanks to cope with landslides and erosion of river cliffs and another riverbank damage. This study aims to analyze the bioengineering of Vetiver as a surface layer for soil erosion control using slope of 100, 200, and 300. This study is conducted with 3 variations of rain intensity (I), at 103 mm/hour, 107 mm/hour, and 130 mm/hour by using rainfall simulator tool. In addition, the USLE (Universal Soil Loss Equation) method is used in order to measure the rate of soil erosion. In this study, there are few USLE model parameters were used such as rainfall erosivity factor, soil erodibility factor, length-loss slope and stepness factor, cover management factor, and support practise factor. The results demonstrated that average of reduction of erosion rate using Vetiver, under 3 various rainfalls, namely rainfall intensity 103 mm/hr had reduced 84.971%, rainfall intensity 107 mm/hr had reduced 86.583 %, rainfall intensity 130 mm/hr had reduced 65.851%.

Evaluation of soil erosion rates in the southern half of the Russian Plain: methodology and initial results

NASA Astrophysics Data System (ADS)

Golosov, Valentin; Gusarov, Artem; Litvin, Leonid; Yermolaev, Oleg; Chizhikova, Nelly; Safina, Guzel; Kiryukhina, Zoya

2017-03-01

The Russian Plain (RP) is divided into two principally different parts. The northern half of the RP is a predominantly forested area with a low proportion of arable fields. In contrast, the southern half of the RP has a very high proportion of arable land. During the last 30 years, this agricultural region of the RP has experienced considerable land use transformation and changes in precipitation due to climate change have altered soil erosion rates. This paper describes the use of erosion model calculations and GIS spatial analytical methods for the evaluation of trends in erosion rates in the RP. Climate change (RIHMI World Data Center, 2016), land use transformation and crop rotation modification (Rosstat, 2016; R Core Team, 2016) are the main factors governing erosion rates in the region during recent decades. It was determined that mean annual erosion rates have decreased from 7.3 to 4.1 t ha-1 yr-1 in the forest zone mostly because of the serious reduction in the surface runoff coefficient for periods of snowmelt. At the same time, the erosion rates have increased from 3.9 to 4.6 t ha-1 yr-1 in the steppe zone due to the increasing frequency of heavy rain-storms.

Enhancement of cavitation erosion resistance of 316 L stainless steel by adding molybdenum.

PubMed

Li, D G; Chen, D R; Liang, P

2017-03-01

The influence of Mo on ultrasonic cavitation erosion of 316 L stainless steel in 3.5% NaCl solution were investigated using an ultrasonic cavitation erosion (CE) facility. The morphologies of specimen after cavitation erosion were observed by scanning electron microscopy (SEM). The results showed that the addition of Mo can sharply decrease the mean depth of erosion (MDE) of 316 L SS, implying the increased resistance of cavitation erosion. In order to better understanding the influence of Mo on the cavitation erosion of 316 L SS, the semi-conductive property of passive films on 316 L SS containing different concentrations of Mo were studied by Mott-Schottky plot. Based on Mott-Schottky results and semiconductor physics, a physical model was proposed to explain the effect mechanism of Mo on cavitation erosion of 316 L SS. Copyright © 2016 Elsevier B.V. All rights reserved.

Feasibility of SiC composite structures for 1644 deg gas turbine seal applications

NASA Technical Reports Server (NTRS)

Darolia, R.

1979-01-01

The feasibility of silicon carbide composite structures was evaluated for 1644 K gas turbine seal applications. The silicon carbide composites evaluated consisted of Si/SiC Silcomp (Trademark) - and sintered silicon carbide as substrates, both with attached surface layers containing BN as an additive. A total of twenty-eight candidates with variations in substrate type and density, and layer chemistry, density, microstructure, and thickness were evaluated for abradability, cold particle erosion resistance, static oxidation resistance, ballistic impact resistance, and fabricability. The BN-free layers with variations in density and pore size were later added for evaluation. The most promising candidates were evaluated for Mach 1.0 gas oxidation/erosion resistance from 1477 K to 1644 K. The as-fabricated rub layers did not perform satisfactorily in the gas oxidation/erosion tests. However, preoxidation was found to be beneficial in improving the hot gas erosion resistance. Overall, the laboratory and rig test evaluations show that material properties are suitable for 1477 K gas turbine seal applications.

Assessment of Erosion Resistance of Coated Polymer Matrix Composites for Propulsion Applications

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Sutter, James K.; Horan, Richard A.; Naik, Subhash K.; Cupp, Randall J.

2004-01-01

The erosion behavior of tungsten carbide-cobalt (WC-Co) coated and uncoated polymer matrix composites (PMCs) was examined with solid particle impingement using air jets. Erosion tests were conducted with Arizona road dust impinging at 20 degrees, 60 degrees, and 90 degrees angles at a velocity of 229 meters per second at both 294 and 366 K. Noncontact optical profilometry was used to measure the wear volume loss. Results indicate that the WC-Co coating enhanced erosion resistance and reduced erosion wear volume loss by a factor of nearly 2. This should contribute to longer wear lives, reduced related breakdowns, decreased maintenance costs, and increased product reliability.

Use of USLE/GIS methodology for predicting soil loss in a semiarid agricultural watershed.

PubMed

Erdogan, Emrah H; Erpul, Günay; Bayramin, Ilhami

2007-08-01

The Universal Soil Loss Equation (USLE) is an erosion model to estimate average soil loss that would generally result from splash, sheet, and rill erosion from agricultural plots. Recently, use of USLE has been extended as a useful tool predicting soil losses and planning control practices in agricultural watersheds by the effective integration of the GIS-based procedures to estimate the factor values in a grid cell basis. This study was performed in the Kazan Watershed located in the central Anatolia, Turkey, to predict soil erosion risk by the USLE/GIS methodology for planning conservation measures in the site. Rain erosivity (R), soil erodibility (K), and cover management factor (C) values of the model were calculated from erosivity map, soil map, and land use map of Turkey, respectively. R values were site-specifically corrected using DEM and climatic data. The topographical and hydrological effects on the soil loss were characterized by LS factor evaluated by the flow accumulation tool using DEM and watershed delineation techniques. From resulting soil loss map of the watershed, the magnitude of the soil erosion was estimated in terms of the different soil units and land uses and the most erosion-prone areas where irreversible soil losses occurred were reasonably located in the Kazan watershed. This could be very useful for deciding restoration practices to control the soil erosion of the sites to be severely influenced.

77 FR 36871 - Endangered and Threatened Wildlife and Plants; Withdrawal of the Proposed Rule To List Dunes...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-19

... shinnery oak community. During the late Pleistocene era, wind erosion of the Blackwater Draw formation along with shinnery oak encroachment formed this unique dune system. The prevailing winds blow from the... spatially dynamic system that is altered by natural processes like wind and rain. Over time, these natural...

Rain and Solid Particle Erosion Damage Mechanisms and Materials Evaluations

DTIC Science & Technology

1986-08-01

intersectiog a laser light beanm just before impact. A schematic diagram of the apparatus is shown in figure 10. A description of the basic gas gun design can be...important, since the collapse of the liquid cavities near a solid boundary produce both shocks and microjets and this adds to the pressures already present

Erosion-Resistant Nanocoatings for Improved Energy Efficiency in Gas Turbine Engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2009-06-01

This factsheet describes a research project whose goal is to test and substantiate erosion-resistant (ER) nanocoatings for application on compressor airfoils for gas turbine engines in both industrial gas turbines and commercial aviation.

Materials for Advanced Turbine Engines (MATE). Project 4: Erosion resistant compressor airfoil coating

NASA Technical Reports Server (NTRS)

Rashid, J. M.; Freling, M.; Friedrich, L. A.

1987-01-01

The ability of coatings to provide at least a 2X improvement in particulate erosion resistance for steel, nickel and titanium compressor airfoils was identified and demonstrated. Coating materials evaluated included plasma sprayed cobalt tungsten carbide, nickel carbide and diffusion applied chromium plus boron. Several processing parameters for plasma spray processing and diffusion coating were evaluated to identify coating systems having the most potential for providing airfoil erosion resistance. Based on laboratory results and analytical evaluations, selected coating systems were applied to gas turbine blades and evaluated for surface finish, burner rig erosion resistance and effect on high cycle fatigue strength. Based on these tests, the following coatings were recommended for engine testing: Gator-Gard plasma spray 88WC-12Co on titanium alloy airfoils, plasma spray 83WC-17Co on steel and nickel alloy airfoils, and Cr+B on nickel alloy airfoils.

Researches upon the cavitation erosion behaviour of austenite steels

NASA Astrophysics Data System (ADS)

Bordeasu, I.; Popoviciu, M. O.; Mitelea, I.; Salcianu, L. C.; Bordeasu, D.; Duma, S. T.; Iosif, A.

2016-02-01

Paper analyzes the cavitation erosion behavior of two stainless steels with 100% austenitic structure but differing by the chemical composition and the values of mechanical properties. The research is based on the MDE(t) and MDER(t) characteristic curves. We studied supplementary the aspect of the eroded areas by other to different means: observations with performing optical microscopes and roughness measurements. The tests were done in the T2 vibratory facility in the Cavitation Laboratory of the Timisoara Polytechnic University. The principal purpose of the study is the identification of the elements influencing significantly the cavitation erosion resistance. It was established the effect of the principal chemical components (determining the proportion of the structural components in conformity the Schaffler diagram) upon the cavitation erosion resistance. The results of the researches present the influence of the proportion of unstable austenite upon cavitation erosion resistance. The stainless steel with the great proportion of unstable austenite has the best behavior. The obtained conclusion are important for the metallurgists which realizes the stainless steels used for manufacturing the runners of hydraulic machineries (turbines and pumps) with increased resistance to cavitation attack.

Vegetation and erosion: comments on the linking mechanisms from the perspective of the Australian drylands.

NASA Astrophysics Data System (ADS)

Dunkerley, D.

2009-04-01

John Thorne's wide-ranging research included an emphasis on the diverse roles of vegetation in modifying erosion processes under Mediterranean conditions, with primary field studies in Spain. Different global drylands reflect some differences in the nature or strength of the mechanisms linking vegetation and erosion. In Australia, low topographic gradients and plants adapted to water scarcity have facilitated the widespread development of contour-aligned vegetation groves. In these landscapes, the role of individual plants in modifying raindrop impact energy or overland flow erosivity is secondary to the community-level effects of the grove structures. Erosion in common rain events is limited to quite local redistribution of soil materials on metre scales. This highlights one of the unresolved issues that warrants more attention in drylands globally: under what range of rain events does the protective role of individual plants (or of groves) operate, and what is the threshold event size beyond which their effect is swamped by integrated overland flow arriving from upslope? In contrast with, for example, the well-understood role of bankfull flows in river architecture, general principles underlying dryland hillslope and channel responses to events of various magnitudes remain obscure. Clearly, however, there is no single role for plant cover; rather, that role varies with event magnitude and related properties such as the time since the last rain event. An important conclusion is therefore that context is important when evaluating the links between vegetation and erosion. The developing view of overland flow generally, but particularly relevant in drylands where plant cover is sparse, is that the connectedness of runoff flowpaths is a key parameter. It partly determines the extent to which the downslope movement of resources (soil, water, organic matter) is free or constrained, and this conception has the potential to support the formulation of some general models of overland flow behaviour. In such analyses, the role of vascular plants has to be seen as one component of the system that also includes organic litter and non-vascular plants. A gap in understanding here relates to splash dislodgement of soil materials. This is known to depend on the depth of water lying above the mineral soil, being reduced for both shallow and deep water layers, and maximised at depths of a few incident drop diameters. Resolving how vegetation modifies surface water depths, and how splash dislodgement responds, across the spectrum of event sizes, remains a significant research challenge. Australian dryland streams exhibit abundant channel-associated vegetation. This exhibits diverse roles, again depending on context. Trees growing in the channel, together with associated barriers formed from floating woody debris, reduce flow speeds. On the other hand, deflector jams can result in locally intensified erosion of the banks. But the mechanisms linking vegetation and erosion are again complex. For instance, by reducing flow speeds and creating backwater effects, debris barriers promote mud deposition over channel margin sediments. This in turn reduces transmission losses, and sustains peak flow and associated sediment transport capacity further downstream than would otherwise be the case. As for hillslope processes, much remains to be learned about how these various processes play out across the spectrum of event magnitudes. Clearly, therefore, in a time of ongoing environmental change, the informed management of the global drylands requires continued research effort of the kind so well championed by John Thornes.

[Mechanisms of grass in slope erosion control in Loess sandy soil region of Northwest China].

PubMed

Zhao, Chun-Hong; Gao, Jian-En; Xu, Zhen

2013-01-01

By adopting the method of simulated precipitation and from the viewpoint of slope hydrodynamics, in combining with the analysis of soil resistance to erosion, a quantitative study was made on the mechanisms of grass in controlling the slope erosion in the cross area of wind-water erosion in Loess Plateau of Northwest China under different combinations of rainfall intensity and slope gradient, aimed to provide basis to reveal the mechanisms of vegetation in controlling soil erosion and to select appropriate vegetation for the soil and water conservation in Loess Plateau. The grass Astragalus adsurgens with the coverage about 40% could effectively control the slope erosion. This grass had an efficiency of more than 70% in reducing sediment, and the grass root had a greater effect than grass canopy. On bare slope and on the slopes with the grass plant or only the grass root playing effect, there existed a functional relation between the flow velocity on the slopes and the rainfall intensity and slope gradient (V = DJ(0.33 i 0.5), where V is flow velocity, D is the comprehensive coefficient which varies with different underlying surfaces, i is rainfall intensity, and J is slope gradient). Both the grass root and the grass canopy could markedly decrease the flow velocity on the slopes, and increase the slope resistance, but the effect of grass root in decreasing flow velocity was greater while the effect in increasing resistance was smaller than that of grass canopy. The effect of grass root in increasing slope resistance was mainly achieved by increasing the sediment grain resistance, while the effect of canopy was mainly achieved by increasing the slope form resistance and wave resistance. The evaluation of the soil resistance to erosion by using a conceptual model of sediment generation by overland flow indicated that the critical shear stress value of bare slope and of the slopes with the grass plant or only the grass root playing effect was 0.533, 1.672 and 0.925 Pa, respectively.

Spherical microglass particle impingement studies of thermoplastic materials at normal incidence

NASA Technical Reports Server (NTRS)

Veerabhadra Rao, P.; Buckley, D. H.

1984-01-01

Light optical and scanning electron microscope studies were conducted to characterize the erosion resistance of polymethyl methacrylate (PMMA), polycarbonate (PC), polytetrafluoroethylene (PTFE) and ultra-high-molecular-weight-polyethylene (UHMWPE). Erosion was caused by a jet of spherical micro-glass beads at normal impact. During the initial stages of damage, the surfaces of these materials were studied using a profilometer. Material buildup above the original surface was observed on PC and PMMA. As erosion progressed, this buildup disappeared as the pit became deeper. Little or no buildup was observed on PTFE and on UHMWPE. UHMWPE and PTFE are the most resistant materials and PMMA the least. Favorable properties for high erosion resistance seem to be high values of ultimate elongation, and strain energy and a low value of the modulus of elasticity. Erosion-rate-versus-time curves of PC and PTFE exhibit incubation, acceleration and steady state periods. A continuously increasing erosion rate period was observed however for PMMA instead of a steady state period. At early stages of damage and at low impact pressure material removal mechanisms appear to be similar to those for metallic materials.

Spherical micro-glass particle impingement studies of thermoplastic materials at normal incidence

NASA Technical Reports Server (NTRS)

Rao, P. V.; Buckley, D. H.

1983-01-01

Light optical and scanning electron microscope studies were conducted to characterize the erosion resistance of polymethyl methacrylate (PMMA), polycarbonate (PC), polytetrafluoroethylene (PTFE) and ultra-high-molecular-weight-polyethylene (UHMWPE). Erosion was caused by a jet of spherical micro-glass beads at normal impact. During the initial stages of damage, the surfaces of these materials were studied using a profilometer. Material buildup above the original surface was observed on PC and PMMA. As erosion progressed, this buildup disappeared as the pit became deeper. Little or no buildup was observed on PTFE and on UHMWPE. UHMWPE and PTFE are the most resistant materials and PMMA the least. Favorable properties for high erosion resistance seem to be high values of ultimate elongation, and strain energy and a low value of the modulus of elasticity. Erosion-rate-versus-time curves of PC and PTFE exhibit incubation, acceleration and steady state periods. A continuously increasing erosion rate period was observed however for PMMA instead of a steady state period. At early stages of damage and at low impact pressure material removal mechanisms appear to be similar to those for metallic materials.

Cavitation Erosion of Cermet-Coated Aluminium Bronzes.

PubMed

Mitelea, Ion; Oancă, Octavian; Bordeaşu, Ilare; Crăciunescu, Corneliu M

2016-03-17

The cavitation erosion resistance of CuAl10Ni5Fe2.5Mn1 following plasma spraying with Al₂O₃·30(Ni 20 Al) powder and laser re-melting was analyzed in view of possible improvements of the lifetime of components used in hydraulic environments. The cavitation erosion resistance was substantially improved compared with the one of the base material. The thickness of the re-melted layer was in the range of several hundred micrometers, with a surface microhardness increasing from 250 to 420 HV 0.2. Compositional, structural, and microstructural explorations showed that the microstructure of the re-melted and homogenized layer, consisting of a cubic Al₂O₃ matrix with dispersed Ni-based solid solution is associated with the hardness increase and consequently with the improvement of the cavitation erosion resistance.

An Experimental Study on Slurry Erosion Resistance of Single and Multilayered Deposits of Ni-WC Produced by Laser-Based Powder Deposition Process

NASA Astrophysics Data System (ADS)

Balu, Prabu; Hamid, Syed; Kovacevic, Radovan

2013-11-01

Single and multilayered deposits containing different mass fractions of tungsten carbide (WC) in nickel (Ni)-matrix (NT-20, NT-60, NT-80) are deposited on a AISI 4140 steel substrate using a laser-based powder deposition process. The transverse cross section of the coupons reveals that the higher the mass fraction of WC in Ni-matrix leads to a more uniform distribution through Ni-matrix. The slurry erosion resistance of the fabricated coupons is tested at three different impingement angles using an abrasive water jet cutting machine, which is quantified based on the erosion rate. The top layer of a multilayered deposit (i.e., NT-60 in a two-layer NT-60 over NT-20 deposit) exhibits better erosion resistance at all three tested impingement angles when compared to a single-layer (NT-60) deposit. A definite increase in the erosion resistance is noted with an addition of nano-size WC particles. The relationship between the different mass fractions of reinforcement (WC) in the deposited composite material (Ni-WC) and their corresponding matrix (Ni) hardness on the erosion rate is studied. The eroded surface is analyzed in the light of a three-dimensional (3-D) profilometer and a scanning electron microscope (SEM). The results show that a volume fraction of approximately 62% of WC with a Ni-matrix hardness of 540 HV resulting in the gouging out of WC from the Ni-matrix by the action of slurry. It is concluded that the slurry erosion resistance of the AISI 4140 steel can be significantly enhanced by introducing single and multilayered deposits of Ni-WC composite material fabricated by the laser-based powder deposition process.

Manufacturing Techniques for Application of Erosion Resistant Coatings to Turbine Engine Compressor Components.

DTIC Science & Technology

means of increasing the life of aircraft gas turbine compressor rotor blades and stator vanes . Two proprietary erosion resistant coating systems... engine tests as the two most promising systems for doubling compressor airfoil lives. An Air Force Sponsored program to evaluate the applicability of...Helicopter engine erosion has become a severe problem in S. E. Asia because of extensive operations in sand and dust. Hard coatings offer a potential

Geomorphic aspects of post-fire soil erosion - Schultz Fire 2010

Treesearch

Ann Youberg; Karen A. Koestner; Daniel G. Neary; Peter E. Koestner

2011-01-01

The summer of 2010 brought wildfires and near record monsoon rains to northern Arizona, USA, which generated debris flows and floods that caused extensive damage. The human-caused Schultz Fire on the Coconino National Forest northeast of Flagstaff was the largest wildfire in Arizona during 2010, burning 6,100 ha between June 20th and 30th. Ignited by an abandoned...

Basal area growth for 15 tropical trees species in Puerto Rico. Forest

Treesearch

B. R. Parresol

1995-01-01

The tabonuco forest of Puerto Rico support a diverse population of tree species valued for timber, fuel, food, wildlife food and cover, and erosion control among other use. tree basal area growth data spanning 39 years are avaible on 15 species from eigth permanent plots in Luquillo Experimental Forest. The complexity of the rain forest challeges current forest...

Basal area growth for 15 tropical tree species in Puerto Rico

Treesearch

Bernard R. Parresol

1995-01-01

The tabonuco forests of Puerto Rico support a diverse population of tree species valued for timber, fuel, food, wildlife food and cover, and erosion control among other uses. Tree basal area growth data spanning 39 years are available on 15 species from eight permanent plots in the Luquillo Experimental Forest. The complexity of the rain forest challenges current...

Effect of vegetal cover on runoff and soil erosion under light intensity events. Rainfall simulation over USLE plots.

PubMed

Marques, María José; Bienes, Ramón; Jiménez, Luis; Pérez-Rodríguez, Raquel

2007-05-25

The erosive power of frequent light rainfalls is studied in this paper. Field experiments of simulated rainfall (Intensity, 21 mm h(-1) and kinetic energy, 13.5 J m(-2) mm(-1)) were conducted over 8 bounded USLE plots (80 m(2) each) with a slope of 10%. In 4 plots the soil was almost bare (<4% vegetation cover); the other 4 plots had almost full cover with natural vegetation in one year. Runoff and sediment yield was recorded. The results revealed the efficiency of vegetation cover reducing runoff and sediments. Runoff and sediments were negligible in covered plots. Therefore, in bare plots, although sediment yield was generally low, averaging 74+/-43 kg ha(-1), the mean of runoff achieved a coefficient of 35%, this magnitude has to be taken into consideration in this region verging on aridity. Rains around 13.5 J m(-2) mm(-1) of kinetic energy are quite frequent in the study area (34% of recorded rains en 12 years). If we would consider the usual lower limits from the literature, we would be ignoring an important percent of natural rainfall episodes.

A Biologically Informed, Mechanistic Model of Desert Shrub Population Dynamics Bearing on Arid Landscape Evolution

NASA Astrophysics Data System (ADS)

Worman, Stacey; Furbish, David; Fathel, Siobhan

2014-05-01

In arid landscapes, desert shrubs individually and collectively modify how sediment is transported (e.g by wind, overland-flow, and rain-splash). Addressing how desert shrubs modify landscapes on geomorphic timescales therefore necessitates spanning multiple shrub lifetimes and accounting for how processes affecting shrub dynamics on these longer timescales (e.g. fire, grazing, drought, and climate change) may in turn impact sediment transport. To fulfill this need, we present a mechanistic model of the spatiotemporal dynamics of a desert-shrub population that uses a simple accounting framework and tracks individual shrubs as they enter, age, and exit the population (via recruitment, growth, and mortality). Our model is novel insomuch as it (1) features a strong biophysical foundation, (2) mimics well-documented aspects of how shrub populations respond to changes in precipitation, and (3) possesses the process granularity appropriate for use in geomorphic simulations. In a complimentary abstract (Fathel et al. 2014), we demonstrate the potential of this biological model by coupling it to a physical model of rain-splash sediment transport: We mechanistically reproduce the empirical observation that the erosion rate of a hillslope decreases as its vegetation coverage increases and we predict erosion rates under different climate-change scenarios.

Conception de couches minces tribologiques pour augmenter la resistance a l'erosion par impacts de particules

NASA Astrophysics Data System (ADS)

Hassani, Salim

Solid particle erosion (SPE) is a serious problem in gas turbines, pumps, heat exchangers and piping systems in aircrafts and other applications. Sand and dust ingested by gas turbine engines may cause major damage to compressor gas path components, leading to severe performance degradation, excessive wear, increased maintenance and eventually premature failure of the engines. For the compressor section of aerospace gas turbine engines, in addition to the complex filtration systems used to screen the eroding particles, tribological coatings, such as TiN, Ti/TiN, CrN and TiAlN are used as protective layers of the base titanium alloy (Ti-6Al-4V) or stainless steels (17-4PH and 410) materials (substrates) against erosive wear. Such coatings can extend the service life of the components, but their performance still remains insufficient due to the complexity of failure mechanisms occurring upon SPE. Therefore, aerospace industry seeks to develop high performance coatings for the protection against erosion by solid particles. However, with many new materials used and tested for different applications and operation under different conditions, conducting experiments for each one of them is becoming increasingly difficult. Presently, coating selection criteria to prevent damage caused by erosion are based on trial and error experiments instead of prior design of coating's architecture and properties to maximize erosion resistance. The present work focuses on the use of advanced finite element (FE) methods to design erosion resistant (ER) coatings. It contributes a new methodology based on the analysis of transient stresses generated by a single impact event. Identification of coating architectures in which such stresses are minimized and crack propagation suppressed, allows one to predict and possibly minimize the erosion rate. Erosion mechanisms and governing erosion parameters are investigated to predict the coating behavior in simulated erosion conditions. The calculation variables include impact velocity (in the range of 50--300 m/s), particle size and the mechanical properties of both the target and the impacting particle. Specifically, we investigate the impact response of coatings fabricated by physical vapor deposition (PVD) and plasma enhanced chemical vapor deposition (PECVD). This includes single and multilayer TiN and nanocomposite nc-TiN/a-SiN1.3 and nc-TiCN/a-SiCN systems on titanium alloy and stainless steel substrates. In particular, we correlate the thickness and the coating macroscopic properties, such as hardness, Young's modulus, and toughness with the erosion. The calculations confirmed earlier findings that for a single layer coating, a combination of low modulus and a high thickness lead to local stress reduction and hence possible erosion resistance enhancement. The FE simulations have further shown that a tensile stress exceeding a critical stress sigmacrit = 3.95 GPa can be easily produced by a single particle impact. For each combination of particle velocity and size, a map of tensile stresses in the TiN coating, corresponding to the predicted erosion performance, was produced. The FE model has then been extended to multilayer coating systems containing superhard nanocomposite materials. These coatings configurations, when combined with tailored mechanical properties have shown to provide an improvement of the performance over comparable single layer configurations. The development of high performance erosion-resistant coatings also requires understanding of stress propagation upon particle impact. In the second part of this work, we apply a finite element methodology to enhance and optimize the resistance of protective coatings to erosion by solid particles with appropriate stress management. A controlled distribution of the initial residual stress in the coating was used to counteract impact stress, while a Young's modulus distribution was applied to optimize impact energy spreading throughout the coating system. Considering both tensile stress reduction and energy absorption, a multi-layer configuration with specific Young's modulus and residual stress distributions along the coating depth is suggested as an optimal coating architecture. In the third part of this work, we propose practical semi-empirical and numerical predictive methods to determine erosion resistance of tribological coatings. The study presents data obtained by FE calculations that can be compared with those obtained by classical theories developed for the erosion of materials. The simulation-based approach allows one to express the functional dependence of erosion on the coating properties, and to quantitatively predict the erosion rate. We determined a proportionality coefficient for a wide range of hard coatings. This coefficient was then used, in combination with the semi-empirical expression derived from FE simulations, to determine the erosion rate of different coatings. The existing erosion theories tend to emphasize hardness, H, and Young's modulus, E, as the main parameters defining erosion resistance. In this context, we specifically focus here on the role of the H/E and H3/E 2 ratios. We demonstrate that the latter characteristics allow one to rank coatings with respect to their erosion performance. Target values for these two ratios were determined for an optimal erosion resistance. We demonstrate that the FE design of the coating architecture, combined with the tailored mechanical properties of individual components of the coating systems, opens new opportunities as a predictive tool for high performance erosion coatings. The present thesis also includes a complementary experimental study of a new kind of ER coatings. We modify the surface profile of hard coatings such as diamond like carbon (DLC) and chrome silicon nitride CrSiN in attempt to correlate the surface characteristics to the functional performance. A specific surface texture (or pattern), designed to enhance erosion resistance, was obtained using a simple and cost effective method consisting of a masking operation, followed by conventional film fabrication techniques PVD or PECVD. Micro-patterned coatings (MPC) possessing specific 3D profiles were produced. In addition to a high potential for several tribological applications, MPC allowed to provide erosion resistance enhancement by a factor of 30 compared to the non-coated stainless steel and of 3--5 times compared to that of the same coating without micro pattern.

Integration of transport concepts for risk assessment of pesticide erosion.

PubMed

Yang, Xiaomei; Van Der Zee, Sjoerd E A T M; Gai, Lingtong; Wesseling, Jan G; Ritsema, Coen J; Geissen, Violette

2016-05-01

Environmental contamination by agrochemicals has been a large problem for decades. Pesticides are transported in runoff and remain attached to eroded soil particles, posing a risk to water and soil quality and human health. We have developed a parsimonious integrative model of pesticide displacement by runoff and erosion that explicitly accounts for water infiltration, erosion, runoff, and pesticide transport and degradation in soil. The conceptual framework was based on broadly accepted assumptions such as the convection-dispersion equation and lognormal distributions of soil properties associated with transport, sorption, degradation, and erosion. To illustrate the concept, a few assumptions are made with regard to runoff in relatively flat agricultural fields: dispersion is ignored and erosion is modelled by a functional relationship. A sensitivity analysis indicated that the total mass of pesticide associated with soil eroded by water scouring increased with slope, rain intensity, and water field capacity of the soil. The mass of transported pesticide decreased as the micro-topography of the soil surface became more distinct. The timing of pesticide spraying and rate of degradation before erosion negatively affected the total amount of transported pesticide. The mechanisms involved in pesticide displacement, such as runoff, infiltration, soil erosion, and pesticide transport and decay in the topsoil, were all explicitly accounted for, so the mathematical complexity of their description can be high, depending on the situation. Copyright © 2016 Elsevier B.V. All rights reserved.

The Monsoon Erosion Pump and the Indian Monsoon since Eocene

NASA Astrophysics Data System (ADS)

Giosan, L.

2017-12-01

Lack of consensus on the Neogene establishment and evolution of the Indian Monsoon is remarkable after half a century of research. Conflicting interpretations point toward the possibility of periodic decoupling between monsoon winds and monsoon precipitation. Here I introduce the concept of a monsoon erosion pump based on terrestrial and oceanic records reconstructed from recent NGHP and IODP drilling and spanning the last 34 million years in the Bay of Bengal, Arabian and Andaman Seas. From millennial to orbital to tectonic timescales, these records suggest that vegetation land cover interacts and modulates the regime of erosion and weathering under perennial but variable monsoonal rain conditions. Under this new proposed paradigm the Indian monsoon exhibits two distinct flavours during the Neogene that can be largely explained by its heartbeat, or astronomical forcing, mediated by the global glacial state and interacting with the paleogeography of South Asia.

Influence of Ultrasound Treatment on Cavitation Erosion Resistance of AlSi7 Alloy

PubMed Central

Pola, Annalisa; Montesano, Lorenzo; Tocci, Marialaura; La Vecchia, Giovina Marina

2017-01-01

Ultrasound treatment of liquid aluminum alloys is known to improve mechanical properties of castings. Aluminum foundry alloys are frequently used for production of parts that undergo severe cavitation erosion phenomena during service. In this paper, the effect of the ultrasound treatment on cavitation erosion resistance of AlSi7 alloy was assessed and compared to that of conventionally cast samples. Cavitation erosion tests were performed according to ASTM G32 standard on as-cast and heat treated castings. The response of the alloy in each condition was investigated by measuring the mass loss as a function of cavitation time and by analyzing the damaged surfaces by means of optical and scanning electron microscope. It was pointed out that the ultrasound treatment increases the cavitation erosion resistance of the alloy, as a consequence of the higher chemical and microstructural homogeneity, the finer grains and primary particles and the refined structure of the eutectic induced by the treatment itself. PMID:28772617

Influence of Ultrasound Treatment on Cavitation Erosion Resistance of AlSi7 Alloy.

PubMed

Pola, Annalisa; Montesano, Lorenzo; Tocci, Marialaura; La Vecchia, Giovina Marina

2017-03-03

Ultrasound treatment of liquid aluminum alloys is known to improve mechanical properties of castings. Aluminum foundry alloys are frequently used for production of parts that undergo severe cavitation erosion phenomena during service. In this paper, the effect of the ultrasound treatment on cavitation erosion resistance of AlSi7 alloy was assessed and compared to that of conventionally cast samples. Cavitation erosion tests were performed according to ASTM G32 standard on as-cast and heat treated castings. The response of the alloy in each condition was investigated by measuring the mass loss as a function of cavitation time and by analyzing the damaged surfaces by means of optical and scanning electron microscope. It was pointed out that the ultrasound treatment increases the cavitation erosion resistance of the alloy, as a consequence of the higher chemical and microstructural homogeneity, the finer grains and primary particles and the refined structure of the eutectic induced by the treatment itself.

TEMPEST code modifications and testing for erosion-resisting sludge simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onishi, Y.; Trent, D.S.

The TEMPEST computer code has been used to address many waste retrieval operational and safety questions regarding waste mobilization, mixing, and gas retention. Because the amount of sludge retrieved from the tank is directly related to the sludge yield strength and the shear stress acting upon it, it is important to incorporate the sludge yield strength into simulations of erosion-resisting tank waste retrieval operations. This report describes current efforts to modify the TEMPEST code to simulate pump jet mixing of erosion-resisting tank wastes and the models used to test for erosion of waste sludge with yield strength. Test results formore » solid deposition and diluent/slurry jet injection into sludge layers in simplified tank conditions show that the modified TEMPEST code has a basic ability to simulate both the mobility and immobility of the sludges with yield strength. Further testing, modification, calibration, and verification of the sludge mobilization/immobilization model are planned using erosion data as they apply to waste tank sludges.« less

Estimation of Annual Average Soil Loss, Based on Rusle Model in Kallar Watershed, Bhavani Basin, Tamil Nadu, India

NASA Astrophysics Data System (ADS)

Rahaman, S. Abdul; Aruchamy, S.; Jegankumar, R.; Ajeez, S. Abdul

2015-10-01

Soil erosion is a widespread environmental challenge faced in Kallar watershed nowadays. Erosion is defined as the movement of soil by water and wind, and it occurs in Kallar watershed under a wide range of land uses. Erosion by water can be dramatic during storm events, resulting in wash-outs and gullies. It can also be insidious, occurring as sheet and rill erosion during heavy rains. Most of the soil lost by water erosion is by the processes of sheet and rill erosion. Land degradation and subsequent soil erosion and sedimentation play a significant role in impairing water resources within sub watersheds, watersheds and basins. Using conventional methods to assess soil erosion risk is expensive and time consuming. A comprehensive methodology that integrates Remote sensing and Geographic Information Systems (GIS), coupled with the use of an empirical model (Revised Universal Soil Loss Equation- RUSLE) to assess risk, can identify and assess soil erosion potential and estimate the value of soil loss. GIS data layers including, rainfall erosivity (R), soil erodability (K), slope length and steepness (LS), cover management (C) and conservation practice (P) factors were computed to determine their effects on average annual soil loss in the study area. The final map of annual soil erosion shows a maximum soil loss of 398.58 t/ h-1/ y-1. Based on the result soil erosion was classified in to soil erosion severity map with five classes, very low, low, moderate, high and critical respectively. Further RUSLE factors has been broken into two categories, soil erosion susceptibility (A=RKLS), and soil erosion hazard (A=RKLSCP) have been computed. It is understood that functions of C and P are factors that can be controlled and thus can greatly reduce soil loss through management and conservational measures.

A Study on Tribological Behavior of Glass-Epoxy Composite Filled with Granite Dust

NASA Astrophysics Data System (ADS)

Ray, Subhrajit; Rout, Arun Ku; KuSahoo, Ashok

2017-08-01

Granite powder is one of the solid wastes generated from stone processing industry used as organic filler replacing the conventional ceramic fillers in polymer matrix composite to increase the mechanical properties. The present work investigates the addition of granite powder on erosion wear properties of epoxy-glass fiber composite. The solid particle erosion wear rates of these hybrid composites are recorded considering various control parameters as impingement angles, erodent sizes and impact velocities following erosion resistance test in an air erosion test device at room temperatures. The test was conducted as per the Taguchi experimental design to minimize the erosion loss of material. The SEM views show the surface resistivity for the granite added specimens. The microscopic study also indicates various methods of material removal, crater wear and other subjective allocation during erosion experiment of the samples.

Slurry Erosive Wear Evaluation of HVOF-Spray Cr2O3 Coating on Some Turbine Steels

NASA Astrophysics Data System (ADS)

Goyal, Deepak Kumar; Singh, Harpreet; Kumar, Harmesh; Sahni, Varinder

2012-09-01

In this study, Cr2O3 coatings were deposited on CF8M and CA6NM turbine steels by high-velocity oxy-fuel (HVOF)-spray process and analyzed with regard to their performance under slurry erosion conditions. High Speed Erosion Test Rig was used for slurry erosion tests, and the effects of three parameters, namely, average particle size, speed (rpm), and slurry concentration on slurry erosion of these materials were investigated. SEM micrographs on the surface of samples, before and after slurry erosion tests, were taken to study the erosion mechanism. For the uncoated steels, CA6NM steel showed better erosion resistance in comparison with CF8M steel. The HVOF-sprayed Cr2O3-coated CF8M and CA6NM steels showed better slurry erosion resistance in comparison with their uncoated counterparts. It may be due to the higher hardness as a result of HVOF-sprayed Cr2O3 coating in comparison with the uncoated CF8M and CA6NM steels.

Surface biosolids application: effects on infiltration, erosion, and soil organic carbon in Chihuahuan Desert grasslands and shrublands.

PubMed

Moffet, C A; Zartman, R E; Wester, D B; Sosebee, R E

2005-01-01

Land application of biosolids is a beneficial-use practice whose ecological effects depend in part on hydrological effects. Biosolids were surface-applied to square 0.5-m2 plots at four rates (0, 7, 34, and 90 dry Mg ha(-1)) on each of three soil-cover combinations in Chihuahuan Desert grassland and shrubland. Infiltration and erosion were measured during two seasons for three biosolids post-application ages. Infiltration was measured during eight periods of a 30-min simulated rain. Biosolids application affected infiltration rate, cumulative infiltration, and erosion. Infiltration increased with increasing biosolids application rate. Application of biosolids at 90 dry Mg ha(-1) increased steady-state infiltration rate by 1.9 to 7.9 cm h(-1). Most of the measured differences in runoff among biosolids application rates were too large to be the result of interception losses and/or increased hydraulic gradient due to increased roughness. Soil erosion was reduced by the application of biosolids; however, the extent of reduction in erosion depended on the initial erodibility of the site. Typically, the greatest marginal reductions in erosion were achieved at the lower biosolids application rates (7 and 34 dry Mg ha(-1)); the difference in erosion between 34 and 90 dry Mg ha(-1) biosolids application rates was not significant. Surface application of biosolids has important hydrological consequences on runoff and soil erosion in desert grasslands that depend on the rate of biosolids applied, and the site and biosolids characteristics.

Erosion-Resistant Nanocoatings for Improved Energy Efficiency in Gas Turbines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alman, David; Marcio, Duffles

2014-02-05

The objective of this Stage Gate IV project was to test and substantiate the viability of an erosion-resistant nanocoating for application on compressor airfoils for gas turbines in both industrial power generation and commercial aviation applications. To effectively complete this project, the National Energy Technology Laboratory’s Office of Research & Development teamed with MDS Coating Technologies Inc. (MCT), Delta Air Lines - Technical Operations Division (Delta Tech Ops), and Calpine Corporation. The coating targeted for this application was MCT’s Next Generation Coating, version 4 (NGC-v4 - with the new registered trademark name of BlackGold®). The coating is an erosion andmore » corrosion resistant composite nanostructured coating. This coating is comprised of a proprietary ceramic-metallic nano-composite construction which provides enhanced erosion resistance and also retains the aerodynamic geometry of the airfoils. The objective of the commercial aviation portion of the project was to substantiate the coating properties to allow certification from the FAA to apply an erosion-resistant coating in a commercial aviation engine. The goal of the series of tests was to demonstrate that the durability of the airfoils is not affected negatively with the application of the NGC v4 coating. Tests included erosion, corrosion, vibration and fatigue. The results of the testing demonstrated that the application of the coating did not negatively impact the properties of the blades, especially fatigue performance – which is of importance in acceptance for commercial aviation applications. The objective of the industrial gas turbine element of the project was to evaluate the coating as an enabling technology for inlet fogging during the operation of industrial gas turbines. Fluid erosion laboratory scale tests were conducted to simulate inlet fogging conditions. Results of these tests indicated that the application of the erosion resistant NGC-v4 nanocoating improved the resistance to simulated inlet fogging conditions by a factor of 10 times. These results gave confidence for a field trial at Calpine’s power plant in Corpus Christi, TX, which commenced in April 2012. This test is still on-going as of November 2013, and the nanocoated blades have accumulated over 13,000 operational hours on this specific power plant in approximately 19 months of operation.« less

Erosion Coatings for High-Temperature Polymer Composites: A Collaborative Project With Allison Advanced Development Company

NASA Technical Reports Server (NTRS)

Sutter, James K.

2000-01-01

The advantages of replacing metals in aircraft turbine engines with high-temperature polymer matrix composites (PMC's) include weight savings accompanied by strength improvements, reduced part count, and lower manufacturing costs. Successfully integrating high-temperature PMC's into turbine engines requires several long-term characteristics. Resistance to surface erosion is one rarely reported property of PMC's in engine applications because PMC's are generally softer than metals and their erosion resistance suffers. Airflow rates in stationary turbine engine components typically exceed 2.3 kg/sec at elevated temperatures and pressures. In engine applications, as shown in the following photos, the survivability of PMC components is clearly a concern, especially when engine and component life-cycle requirements become longer. Although very few publications regarding the performance of erosion coatings on PMC's are available particularly in high-temperature applications the use of erosion-resistant coatings to significantly reduce wear on metallic substrates is well documented. In this study initiated by the NASA Glenn Research Center at Lewis Field, a low-cost (less than $140/kg) graphite-fiber-reinforced T650 35/PMR 15 sheet-molding compound was investigated with various coatings. This sheet-molding compound has been compression molded into many structurally complicated components, such as shrouds for gas turbine inlet housings and gearboxes. Erosion coatings developed for PMC s in this study consisted of a two-layered system: a bondcoat sprayed onto a cleaned PMC surface, followed by an erosion-resistant, hard topcoat sprayed onto the bondcoat as shown in following photomicrograph. Six erosion coating systems were evaluated for their ability to withstand harsh thermal cycles, erosion resistance (ASTM G76 83 "Standard Practice for Conducting Erosion Tests by Solid Particle Impingement Using Gas Jets") using Al2O3, and adhesion to the graphite fiber polyimide composite (ASTM D 4541 95 "Pull Off Strength of Coatings"). Glenn and Allison Advanced Development Company collaborated to optimize erosion coatings for gas turbine fan and compressor applications. All the coating systems survived aggressive thermal cycling without spalling. During erosion tests (see the final photo), the most promising coating systems tested had Cr3C2-NiCr and WC-Co as the hard topcoats. In all cases, these coating systems performed significantly better than that with a TiN hard topcoat. When material depth (thickness) loss is considered, the Cr3C2-NiCr and WC-Co coating systems provided, on average, an erosion resistance 8.5 times greater than that for the uncoated PMR 15/T650 35 composite. Similarly, Cr3C2-NiCr and WC-Co coating systems adhered to the PMC substrate during tensile tests significantly better than systems containing a TiN topcoat. Differences in topcoats of Cr3C2-NiCr and WC-Co were determined by considering issues such as cost and environmental impact. The preferred erosion-resistant coating system for PMR 15/T650 35 has WC-Co as the hard topcoat. This system provides the following benefits in comparison to the coating system with Cr3C2-NiCr topcoat: lower powder material cost (15 to 20 percent), environmentally friendly materials (Cr3C2-NiCr is hazardous), and higher deposition yield (10 to 15 percent), which results in less waste.

A durability test rig and methodology for erosion-resistant blade coatings in turbomachinery

NASA Astrophysics Data System (ADS)

Leithead, Sean Gregory

A durability test rig for erosion-resistant gas turbine engine compressor blade coatings was designed, completed and commissioned. Bare and coated 17-4PH steel V103-profile blades were rotated at up to 11500 rpm and impacted with Garnet sand for 5 hours at an average concentration of 2.51 gm3of air , at a blade leading edge Mach number of 0.50. The rig was determined to be an acceptable first stage axial compressor representation. Two types of 16 microm-thick coatings were tested: Titanium Nitride (TiN) and Chromium-Aluminum-Titanium Nitride (CrAlTiN), both applied using an Arc Physical Vapour Deposition technique at the National Research Council in Ottawa, Canada. A Leithead-Allan-Zhao (LAZ) score was created to compare the durability performance of uncoated and coated blades based on mass-loss and blade dimension changes. The bare blades' LAZ score was set as a benchmark of 1.00. The TiN-coated and CrAlTiN-coated blades obtained LAZ scores of 0.69 and 0.41, respectively. A lower score meant a more erosion-resistant coating. Major modes of blade wear included: trailing edge, leading edge and the rear suction surface. Trailing edge thickness was reduced, the leading edge became blunt, and the rear suction surface was scrubbed by overtip and recirculation zone vortices. It was found that the erosion effects of vortex flow were significant. Erosion damage due to reflected particles was not present due to the low blade solidity of 0.7. The rig is best suited for studying the performance of erosion-resistant coatings after they are proven effective in ASTM standardized testing. Keywords: erosion, compressor, coatings, turbomachinery, erosion rate, blade, experimental, gas turbine engine

NASA Glenn/AADC-Rolls Royce Collaborated to Measure Erosion Resistance on Coated Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Sutter, James K.; Mondry, Richard; Ma, Kong; Horan, Dick; Naik, Subhash; Cupp, Randall

2003-01-01

Polymer matrix composites (PMCs) are increasingly used in aerospace and automotive applications because of their light weight and high strength-to-weight ratio relative to metals. However, a major drawback of PMCs is poor abrasion resistance, which restricts their use, especially at high temperatures. Simply applying a hard coating on PMCs to improve abrasion and erosion resistance is not effective since coating durability is short lived (ref. 1). Generally, PMCs have higher coefficients of thermal expansion than metallic or ceramic coatings have, and coating adhesion suffers because of poor interfacial adhesion strength. One technique commonly used to improve coating adhesion or durability is the use of bond coats that are interleaved between a coating and a substrate with vastly different coefficients of thermal expansion. An example of this remedy is the use of bondcoats for ceramic thermal barrier coatings on metallic turbine components (ref. 2). Prior collaborative research between the NASA Glenn Research Center and the Allison Advanced Development Company (AADC) demonstrated that bond coats sandwiched between PMCs and high-quality plasma-sprayed, erosion-resistant coatings substantially improved the erosion resistance of PMCs (ref. 3). One unresolved problem in this earlier collaboration was that there was no easy, accurate way to measure the coating erosion wear scar. Coating wear was determined by both profilometry and optical microscopy. Both techniques are time consuming. Wear measurement by optical microscopy requires sample destruction and does not provide a comprehensive measure of the entire wear volume. An even more subtle, yet critical, problem is that these erosion coatings contain two or more materials with different densities. Therefore, simply measuring specimen mass loss before and after erosion will not provide an accurate gauge for coating and/or substrate volume loss. By using a noncontact technique called scanning optical interferometry, which was recently developed at Glenn, researchers can accurately determine the wear performance of erosion-coated PMCs while preserving the sample. An example of this interferometry technique is shown in the preceding figure for an erosion-coated inlet guide vane from a Rolls Royce AE3007 regional gas turbine jet engine. Erosion was conducted with coated and uncoated PMC vanes, with the abrasive material moving at a velocity of 229 m/s at impingement angles of 20 and 90 degrees. The coatings for PMCs remarkably reduced the erosion volume loss by a factor of approximately 10. Currently, several erosion coatings for PMCs are being compared and downselected for engine testing at Rolls Royce.

Thermal shock and erosion resistant tantalum carbide ceramic material

NASA Technical Reports Server (NTRS)

Honeycutt, L., III; Manning, C. R. (Inventor)

1978-01-01

Ceramic tantalum carbide artifacts with high thermal shock and mechanical erosion resistance are provided by incorporating tungsten-rhenium and carbon particles in a tantalum carbide matrix. The mix is sintered by hot pressing to form the ceramic article which has a high fracture strength relative to its elastic modulus and thus has an improved thermal shock and mechanical erosion resistance. The tantalum carbide is preferable less than minus 100 mesh, the carbon particles are preferable less than minus 100 mesh, and the tungsten-rhenium particles are preferable elongate, having a length to thickness ratio of at least 2/1. Tungsten-rhenium wire pieces are suitable as well as graphite particles.

Evaluation of air jet erosion profiles in metal mesh supported SCR plate catalyst based on glass fiber concentrations

NASA Astrophysics Data System (ADS)

Rajath, S.; Nandakishora, Y.; Siddaraju, C.; Roy, Sukumar

2018-04-01

This paper explains the evaluation of erosion profiles in metal mesh supported SCR plate catalyst structures in which the glass fibers concentration in the catalyst material is considered as prime factor for erosion resistance and mechanical strength. The samples are prepared and tested at the specified and constant conditions like velocity as 30m/s, sand flow rate as 2g/min, average particle diameter 300 µm and all these samples were tested at different angles at impact preferably 15°,30°,45°,60°,75°,and 90° as per ASTM G76 standards. Say, if 5% glass fibers are present in catalyst material, then erosion resistance increases, but the density of glass fibers is very less because each glass fiber is approximately 20 microns in diameter and weight of individual is negligible. The composition in which 2% fiber is present has slightly higher erosion comparatively, but 3% glass fibers or more foreign inclusion like excessive binders can be eliminated that contributes much for the conversion of NOx. So 2% -3% glass fibers are preferred and optimized based on NOx conversion and erosion resistance property.

Effect of substrate preheating treatment on the microstructure and ultrasonic cavitation erosion behavior of plasma-sprayed YSZ coatings.

PubMed

Deng, Wen; An, Yulong; Hou, Guoliang; Li, Shuangjian; Zhou, Huidi; Chen, Jianmin

2018-09-01

Inconel 718 was used as the substrate and preheated at different temperatures to deposit yttrium stabilized zirconia (denoted as YSZ) coatings by atmospheric plasma spraying. The microstructure of the as-deposited YSZ coatings and those after cavitation-erosion tests were characterized by field emission scanning electron microscopy, Raman spectroscopy, and their hardness and toughness as well as cavitation-erosion resistance were evaluated in relation to the effect of substrate preheating temperature. Results indicate that the as-deposited YSZ coatings exhibit typical layered structure and consist of columnar crystals. With the increase of the substrate preheating temperature, the compactness and cohesion strength of coatings are obviously enhanced, which result in the increases in the hardness, elastic modulus and toughness as well as cavitation-erosion resistance of the ceramic coatings therewith. Particularly, the YSZ coating deposited at a substrate preheating temperature of 800 °C exhibits the highest hardness and toughness as well as the strongest lamellar interfacial bonding and cavitation-erosion resistance (its cavitation-erosion life is as much as 8 times than that of deposited at room temperature). Copyright © 2018 Elsevier B.V. All rights reserved.

A Comparison of Splash Erosion Behavior between Wettable and Water Repellent 'Soil' Particles

NASA Astrophysics Data System (ADS)

Ahn, S.; Hamlett, C. A.; Doerr, S.; Bryant, R.; Shirtcliffe, N.; McHale, G.; Newton, M.

2011-12-01

Wildfires remove vegetation and litter cover and expose soil surfaces to particle detachment by rain splash. This can serve as an agent of initial soil modification and erosion in the post-fire period. Splash behavior is mainly determined by the kinetic energy delivered by impacting water drops (erosivity), and the detachability (erodibility) of surface particles, affected by their size, aggregate stability and shear strength. Soil detachability may also be affected by water repellency (hydrophobicity). This soil characteristic is influenced by wildfire and may affect splash behavior by reducing capillary forces between particles. Previous work on splash behavior using cumulative drop impact reported larger ejection droplets and lower and shorter trajectories of ejections for water repellent soil compared with wettable soil (Terry and Shakesby 1993). A water film generated by delayed infiltration on water repellent soil was suggested to account for the difference. This study compares the trajectories of ejected wettable and hydrophobic model soil particles from single water drop impacts in order to isolate the effect of soil particle wettability on splash erosion behavior. Acid-washed (wettable) and hydrophobized (water repellent) glass beads used as model soil particles were held in an array within a squat cylinder of 1.5 cm diameter in the centre of a 20 cm diameter disk covered with a viscous adhesive film. A distilled water drop (20μL) was released 40 cm above the centre of the array and the resultant impact was recorded at 976 frames per second using a high speed video camera. The populations of, and distances travelled by, the particles were measured for three arrays of bead sizes within the range (180-400 μm). Three to five replications were made for each test. The trajectory of each ejected particle was traced on video frames and corrected for the actual distance and direction of travel measured from the adhesive film. The initial velocity and ejecting angle of individual particles were calculated from the equation of motion, ignoring the air resistance and in-flight evaporation. In contrast to Terry and Shakesby (1993), we observed that a single drop impact resulted mainly in dispersion (splash saltation) with few ejections of particles entrained by a water droplet (splashing), and the trajectories of ejections from water repellent particle arrays were higher than those from the hydrophilic arrays. These higher trajectories were driven by higher initial velocity for the water repellent particles, despite lower ejecting angles. This result suggests that water repellent soil is more vulnerable to initial splash detachment before a water film is generated by accumulation of rain drops. The distributions of initial velocity and ejecting angle of all particles are compared between wettable and water repellent particles and discussed in detail in this contribution. Terry JP and Shakesby RA, 1993. Earth Surface Processes and Landforms 18: 519-525. Acknowledgement: This study has been funded by Engineering and Physical Sciences Research Council of United Kingdom.

Interactive effects of vegetation and sediment properties on erosion of salt marshes in the Northern Adriatic Sea.

PubMed

Lo, V B; Bouma, T J; van Belzen, J; Van Colen, C; Airoldi, L

2017-10-01

We investigated how lateral erosion control, measured by novel photogrammetry techniques, is modified by the presence of Spartina spp. vegetation, sediment grain size, and the nutrient status of salt marshes across 230 km of the Italian Northern Adriatic coastline. Spartina spp. vegetation reduced erosion across our study sites. The effect was more pronounced in sandy soils, where erosion was reduced by 80% compared to 17% in silty soils. Erosion resistance was also enhanced by Spartina spp. root biomass. In the absence of vegetation, erosion resistance was enhanced by silt content, with mean erosion 72% lower in silty vs. sandy soils. We found no relevant relationships with nutrient status, likely due to overall high nutrient concentrations and low C:N ratios across all sites. Our results contribute to quantifying coastal protection ecosystem services provided by salt marshes in both sandy and silty sediments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Erosivity, surface runoff, and soil erosion estimation using GIS-coupled runoff-erosion model in the Mamuaba catchment, Brazil.

PubMed

Marques da Silva, Richarde; Guimarães Santos, Celso Augusto; Carneiro de Lima Silva, Valeriano; Pereira e Silva, Leonardo

2013-11-01

This study evaluates erosivity, surface runoff generation, and soil erosion rates for Mamuaba catchment, sub-catchment of Gramame River basin (Brazil) by using the ArcView Soil and Water Assessment Tool (AvSWAT) model. Calibration and validation of the model was performed on monthly basis, and it could simulate surface runoff and soil erosion to a good level of accuracy. Daily rainfall data between 1969 and 1989 from six rain gauges were used, and the monthly rainfall erosivity of each station was computed for all the studied years. In order to evaluate the calibration and validation of the model, monthly runoff data between January 1978 and April 1982 from one runoff gauge were used as well. The estimated soil loss rates were also realistic when compared to what can be observed in the field and to results from previous studies around of catchment. The long-term average soil loss was estimated at 9.4 t ha(-1) year(-1); most of the area of the catchment (60%) was predicted to suffer from a low- to moderate-erosion risk (<6 t ha(-1) year(-1)) and, in 20% of the catchment, the soil erosion was estimated to exceed > 12 t ha(-1) year(-1). Expectedly, estimated soil loss was significantly correlated with measured rainfall and simulated surface runoff. Based on the estimated soil loss rates, the catchment was divided into four priority categories (low, moderate, high and very high) for conservation intervention. The study demonstrates that the AvSWAT model provides a useful tool for soil erosion assessment from catchments and facilitates the planning for a sustainable land management in northeastern Brazil.

Respiratory disease and particulate air pollution in Santiago Chile: Contribution of erosion particles from fine sediments

Treesearch

Pablo A. Garcia-Chevesich; Sergio Alvarado; Daniel G. Neary; Rodrigo Valdes; Juan Valdes; Juan Jose Aguirre; Marcelo Mena; Roberto Pizarro; Paolo Jofre; Mauricio Vera; Claudio Olivares

2014-01-01

Air pollution in Santiago is a serious problem every winter, causing thousands of cases of breathing problems within the population. With more than 6 million people and almost two million vehicles, this large city receives rainfall only during winters. Depending on the frequency of storms, statistics show that every time it rains, air quality improves for a couple of...

Capturing the Initiation and Spatial Variability of Runoff on Soils Affected by Wildfire

NASA Astrophysics Data System (ADS)

Martin, D. A.; Wickert, A. D.; Moody, J. A.

2011-12-01

Rainfall after wildfire often leads to intense runoff and erosion, since fire removes ground cover that impedes overland flow and water is unable to efficiently infiltrate into the fire-affected soils. In order to understand the relation between rainfall, infiltration, and runoff, we modified a camera to be triggered by a rain gage to take time-lapse photographs of the ground surface every 10 seconds until the rain stops. This camera allows us to observe directly the patterns of ground surface ponding, the initiation of overland flow, and erosion/deposition during single rainfall events. The camera was deployed on a hillslope (average slope = 23 degrees) that was severely burned by the 2010 Fourmile Canyon Fire near Boulder, Colorado. The camera's field of view is approximately 3 m2. We integrate the photographs with rainfall and overland flow measurements to determine thresholds for the initiation of overland flow and erosion. We have recorded the spatial variability of wetted patches of ground and the connection of these patches together to initiate overland flow. To date we have recorded images for rain storms with 30-minute maximum intensities ranging from 5 mm/h (our threshold to trigger continuous photographs) to 32 mm/h. In the near future we will update the camera's control system to 1) include a clock to enable time-lapse photographs at a lower frequency in addition to the event-triggered images, and 2) to add a radio to allow the camera to be triggered remotely. Radio communication will provide a means of starting the camera in response to non-local events, allowing us to capture images or video of flash flood surge fronts and debris flows, and to synchronize the operations of multiple cameras in the field. Schematics and instructions to build this camera station, which can be used to take either photos or video, are open-source licensed and are available online at http://instaar.colorado.edu/~wickert/atvis. It is our hope that this tool can be used by other researchers to better understand processes in burned watersheds and other sensitive areas that are likely to respond rapidly to rainfall.

Behavior of farmers in regard to erosion by water as reflected by their farming practices.

PubMed

Auerswald, Karl; Fischer, Franziska K; Kistler, Michael; Treisch, Melanie; Maier, Harald; Brandhuber, Robert

2018-02-01

The interplay between natural site conditions and farming raises erosion by water above geological background levels. We examined the hypothesis that farmers take erosion into account in their farming decisions and switch to farming practices with lower erosion risk the higher the site-specific hazard becomes. Erosion since the last tillage was observed from aerial orthorectified photographs for 8100 fields belonging to 1879 farmers distributed across Bavaria (South Germany) and it was modeled by the Universal Soil Loss Equation using highly detailed input data (e.g., digital terrain model with 5×5m 2 resolution, rain data with 1×1km 2 and 5min resolution, crop and cropping method from annual field-specific data from incentive schemes). Observed and predicted soil loss correlated closely, demonstrating the accuracy of this method. The close correlation also indicted that the farmers could easily observe the degree of recent erosion on their fields, even without modelling. Farmers clearly did not consider erosion in their decisions. When natural risk increased, e.g. due to steeper slopes, they neither grew crops with lower erosion potential, nor reduced field size, nor used contouring. In addition, they did not compensate for the cultivation of crops with higher erosion potential by using conservation techniques like mulch tillage or contouring, or by reducing field size. Only subsidized measures, like mulch tillage or organic farming, were applied but only at the absolute minimum that was necessary to obtain subsidies. However, this did not achieve the reduction in erosion that would be possible if these measures had been fully applied. We conclude that subsidies may be an appropriate method of reducing erosion but the present weak supervision, which assumes that farmers themselves will take erosion into account and that subsidies are only needed to compensate for any disadvantages caused by erosion-reducing measures, is clearly not justified. Copyright © 2017 Elsevier B.V. All rights reserved.

Erosion Resistant Coatings for Polymer Matrix Composites in Propulsion Applications

NASA Technical Reports Server (NTRS)

Sutter, James K.; Naik, Subhash K.; Horan, Richard; Miyoshi, Kazuhisa; Bowman, Cheryl; Ma, Kong; Leissler, George; Sinatra, Raymond; Cupp, Randall

2003-01-01

Polymer Matrix Composites (PMCs) offer lightweight and frequently low cost alternatives to other materials in many applications. High temperature PMCs are currently used in limited propulsion applications replacing metals. Yet in most cases, PMC propulsion applications are not in the direct engine flow path since particulate erosion degrades PMC component performance and therefore restricts their use in gas turbine engines. This paper compares two erosion resistant coatings (SANRES and SANPRES) on PMCs that are useful for both low and high temperature propulsion applications. Collaborating over a multi-year period, researchers at NASA Glenn Research Center, Allison Advanced Developed Company, and Rolls-Royce Corporation have optimized these coatings in terms of adhesion, surface roughness, and erosion resistance. Results are described for vigorous hot gas/particulate erosion rig and engine testing of uncoated and coated PMC fan bypass vanes from the AE 3007 regional jet gas turbine engine. Moreover, the structural durability of these coatings is described in long-term high cycle fatigue tests. Overall, both coatings performed well in all tests and will be considered for applications in both commercial and defense propulsion applications.

Use of multi-temporal SPOT-5 satellite images for land degradation assessment in Cameron Highlands, Malaysia using Geospatial techniques

NASA Astrophysics Data System (ADS)

Nampak, Haleh; Pradhan, Biswajeet

2016-07-01

Soil erosion is the common land degradation problem worldwide because of its economic and environmental impacts. Therefore, land-use change detection has become one of the major concern to geomorphologists, environmentalists, and land use planners due to its impact on natural ecosystems. The objective of this paper is to evaluate the relationship between land use/cover changes and land degradation in the Cameron highlands (Malaysia) through multi-temporal remotely sensed satellite images and ancillary data. Land clearing in the study area has resulted increased soil erosion due to rainfall events. Also unsustainable development and agriculture, mismanagement and lacking policies contribute to increasing soil erosion rates. The LULC distribution of the study area was mapped for 2005, 2010, and 2015 through SPOT-5 satellite imagery data which were classified based on object-based classification. A soil erosion model was also used within a GIS in order to study the susceptibility of the areas affected by changes to overland flow and rain splash erosion. The model consists of four parameters, namely soil erodibility, slope, vegetation cover and overland flow. The results of this research will be used in the selection of the areas that require mitigation processes which will reduce their degrading potential. Key words: Land degradation, Geospatial, LULC change, Soil erosion modelling, Cameron highlands.

The Rangeland Hydrology and Erosion Model

NASA Astrophysics Data System (ADS)

Nearing, M. A.

2016-12-01

The Rangeland Hydrology and Erosion Model (RHEM) is a process-based model that was designed to address rangelands conditions. RHEM is designed for government agencies, land managers and conservationists who need sound, science-based technology to model, assess, and predict runoff and erosion rates on rangelands and to assist in evaluating rangeland conservation practices effects. RHEM is an event-based model that estimates runoff, erosion, and sediment delivery rates and volumes at the spatial scale of the hillslope and the temporal scale of as single rainfall event. It represents erosion processes under normal and fire-impacted rangeland conditions. Moreover, it adopts a new splash erosion and thin sheet-flow transport equation developed from rangeland data, and it links the model hydrologic and erosion parameters with rangeland plant community by providing a new system of parameter estimation equations based on 204 plots at 49 rangeland sites distributed across 15 western U.S. states. A dynamic partial differential sediment continuity equation is used to model the total detachment rate of concentrated flow and rain splash and sheet flow. RHEM is also designed to be used as a calculator, or "engine", within other watershed scale models. From the research perspective RHEM acts as a vehicle for incorporating new scientific findings from rangeland infiltration, runoff, and erosion studies. Current applications of the model include: 1) a web site for general use (conservation planning, research, etc.), 2) National Resource Inventory reports to Congress, 3) as a computational engine within watershed scale models (e.g., KINEROS, HEC), 4) Ecological Site & State and Transition Descriptions, 5) proposed in 2015 to become part of the NRCS Desktop applications for field offices.

Sediment detachment and transport processes associated with internal erosion of soil pipes: Often overlooked processes of gully erosion

USDA-ARS?s Scientific Manuscript database

Subsurface flow can be an important process in gully erosion through its impact on decreasing soil cohesion and erosion resistance as soil water content or pressure increases and more directly by the effects of seepage forces on particle detachment and piping. The development of perched water tables...

Wind erodibility response of physical and biological crusts to rain and flooding

NASA Astrophysics Data System (ADS)

Aubault, H.; Bullard, J. E.; Strong, C. L.; Ghadiri, H.; McTainsh, G. H.

2015-12-01

Soil surface crusts are important controllers of the small-scale wind entrainment processes that occur across all dust source regions globally. The crust type influences water and wind erosion by impacting infiltration, runoff, threshold wind velocity and surface storage capacity of both water and loose erodible material. The spatial and temporal patterning of both physical and biological crusts is known to change with rainfall and flooding. However, little is known about the impact of differing water quantity (from light rainfall through to flooding) on soil crusting characteristics (strength, roughness, sediment loss). This study compares the response of two soil types (loamy sand - LS, sandy loam - SL) with and without BSCs to three different rainfall events (2mm, 8mm, 15mm). Two BSC treatments were used one that simulated a young cyanobacteria dominated crust and an older flood induced multi species biological crust. For both soil types, soil surface strength increased with increasing rainfall amount with LS having consistently higher resistance to rupture than SL. Regardless of texture, soils with BSCs were more resistant and strength did not change in response to rainfall impact. Soil loss due to wind erosion was substantially higher on bare LS (4 times higher) and SL (3 times higher) soils compared with those with BSCs. Our results also show that young biological crust (formed by the rainfall event) have reduced soil erodibility with notably greater strength, roughness and reduced sediment losses when compared to soils with physical crust. Interestingly though, the erodibility of the old BSC did not differ greatly from that of the young BSC with respect to strength, roughness and sediment loss. This raises questions regarding the rapid soil surface protection offered by young colonising cyanobacteria crusts. Further analyses exploring the role of biological soil crusts on surface response to rainfall and wind saltation impact are ongoing.

Soil coverage evolution and wind erosion risk on summer crops under contrasting tillage systems

NASA Astrophysics Data System (ADS)

Mendez, Mariano J.; Buschiazzo, Daniel E.

2015-03-01

The effectiveness of wind erosion control by soil surface conditions and crop and weed canopy has been well studied in wind tunnel experiments. The aim of this study is to assess the combined effects of these variables under field conditions. Soil surface conditions, crop and weed coverage, plant residue, and non-erodible aggregates (NEA) were measured in the field between the fallow start and the growth period of sunflower (Helianthus annuus) and corn (Zea mays). Both crops were planted on a sandy-loam Entic Haplustoll with conventional-(CT), vertical-(VT) and no-till (NT) tillage systems. Wind erosion was estimated by means of the spreadsheet version the Revised Wind Erosion Equation and the soil coverage was measured each 15 days. Results indicated that wind erosion was mostly negligible in NT, exceeding the tolerable levels (estimated between 300 and 1400 kg ha-1 year-1 by Verheijen et al. (2009)) only in an year with high climatic erosivity. Wind erosion exceeded the tolerable levels in most cases in CT and VT, reaching values of 17,400 kg ha-1. Wind erosion was 2-10 times higher after planting of both crops than during fallows. During the fallows, the soil was mostly well covered with plant residues and NEA in CT and VT and with residues and weeds in NT. High wind erosion amounts occurring 30 days after planting in all tillage systems were produced by the destruction of coarse aggregates and the burying of plant residues during planting operations and rains. Differences in soil protection after planting were given by residues of previous crops and growing weeds. The growth of weeds 2-4 weeks after crop planting contributed to reduce wind erosion without impacting in crops yields. An accurate weeds management in semiarid lands can contribute significantly to control wind erosion. More field studies are needed in order to develop management strategies to reduce wind erosion.

Evaluation of compost blankets for erosion control from disturbed lands.

PubMed

Bhattarai, Rabin; Kalita, Prasanta K; Yatsu, Shotaro; Howard, Heidi R; Svendsen, Niels G

2011-03-01

Soil erosion due to water and wind results in the loss of valuable top soil and causes land degradation and environmental quality problems. Site specific best management practices (BMP) are needed to curb erosion and sediment control and in turn, increase productivity of lands and sustain environmental quality. The aim of this study was to investigate the effectiveness of three different types of biodegradable erosion control blankets- fine compost, mulch, and 50-50 mixture of compost and mulch, for soil erosion control under field and laboratory-scale experiments. Quantitative analysis was conducted by comparing the sediment load in the runoff collected from sloped and tilled plots in the field and in the laboratory with the erosion control blankets. The field plots had an average slope of 3.5% and experiments were conducted under natural rainfall conditions, while the laboratory experiments were conducted at 4, 8 and 16% slopes under simulated rainfall conditions. Results obtained from the field experiments indicated that the 50-50 mixture of compost and mulch provides the best erosion control measures as compared to using either the compost or the mulch blanket alone. Laboratory results under simulated rains indicated that both mulch cover and the 50-50 mixture of mulch and compost cover provided better erosion control measures compared to using the compost alone. Although these results indicate that the 50-50 mixtures and the mulch in laboratory experiments are the best measures among the three erosion control blankets, all three types of blankets provide very effective erosion control measures from bare-soil surface. Results of this study can be used in controlling erosion and sediment from disturbed lands with compost mulch application. Testing different mixture ratios and types of mulch and composts, and their efficiencies in retaining various soil nutrients may provide more quantitative data for developing erosion control plans. Copyright © 2010 Elsevier Ltd. All rights reserved.

Rainfall and sheet power model for interrill erosion in steep slope

NASA Astrophysics Data System (ADS)

Shin, Seung Sook; Deog Park, Sand; Nam, Myeong Jun

2015-04-01

The two-phase process of interrill erosion consist of the splash and detachment of individual particles from soil mass by impact of raindrops and the transport by erosive running water. Most experimental results showed that the effect of interaction between rainfall impact and surface runoff increases soil erosion in low or gentle slope. Especially, the combination of rain splash and sheet flow is the dominant runoff and erosion mechanism occurring on most steep hillslopes. In this study, a rainfall simulation was conducted to evaluate interrill erosion in steep slope with cover or non-cover. The kinetic energy of raindrops of rainfall simulator was measured by disdrometer used to measure the drop size distribution and velocity of falling raindrops and showed about 0.563 rate of that calculated from empirical equation between rainfall kinetic energy and rainfall intensity. Surface and subsurface runoff and sediment yield depended on rainfall intensity, gradient of slope, and existence of cover. Sediment from steep plots under rainfall simulator is greatly reduced by existence of the strip cover that the kinetic energy of raindrop approximates to zero. Soil erosion in steep slope with non-cover was nearly 4.93 times of that measured in plots with strip cover although runoff was only 1.82 times. The equation of a rainfall and sheet power was used to evaluate sediment yields in steep slope with cover or non-cover. The power model successfully explained physical processes for interrill erosion that combination of raindrop impact and sheet flow increases greatly soil erosion in steep slope. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(No. 2013R1A1A3011962).

Investigating links between climate and orography in the central Andes: Coupling erosion and precipitation using a physical-statistical model

NASA Astrophysics Data System (ADS)

Lowman, Lauren E. L.; Barros, Ana P.

2014-06-01

Prior studies evaluated the interplay between climate and orography by investigating the sensitivity of relief to precipitation using the stream power erosion law (SPEL) for specified erosion rates. Here we address the inverse problem, inferring realistic spatial distributions of erosion rates for present-day topography and contemporaneous climate forcing. In the central Andes, similarities in the altitudinal distribution and density of first-order stream outlets and precipitation suggest a direct link between climate and fluvial erosion. Erosion rates are estimated with a Bayesian physical-statistical model based on the SPEL applied at spatial scales that capture joint hydrogeomorphic and hydrometeorological patterns within five river basins and one intermontane basin in Peru and Bolivia. Topographic slope and area data were generated from a high-resolution (˜90 m) digital elevation map, and mean annual precipitation was derived from 14 years of Tropical Rainfall Measuring Mission 3B42v.7 product and adjusted with rain gauge data. Estimated decadal-scale erosion rates vary between 0.68 and 11.59 mm/yr, with basin averages of 2.1-8.5 mm/yr. Even accounting for uncertainty in precipitation and simplifying assumptions, these values are 1-2 orders of magnitude larger than most millennial and million year timescale estimates in the central Andes, using various geological dating techniques (e.g., thermochronology and cosmogenic nuclides), but they are consistent with other decadal-scale estimates using landslide mapping and sediment flux observations. The results also reveal a pattern of spatially dependent erosion consistent with basin hypsometry. The modeling framework provides a means of remotely estimating erosion rates and associated uncertainties under current climate conditions over large regions. 2014. American Geophysical Union. All Rights Reserved.

Calibration and Validation of Nonpoint Source Pollution and Erosion Comparison Tool,N- SPECT, for Tropical Conditions

NASA Astrophysics Data System (ADS)

Fares, A.; Cheng, C. L.; Dogan, A.

2006-12-01

Impaired water quality caused by agriculture, urbanization, and spread of invasive species has been identified as a major factor in the degradation of coastal ecosystems in the tropics. Watershed-scale nonpoint source pollution models facilitate in evaluating effective management practices to alleviate the negative impacts of different land-use changes. The Non-Point Source Pollution and Erosion Comparison Tool (N-SPECT) is a newly released watershed model that was not previously tested under tropical conditions. The two objectives of this study were to: i) calibrate and validate N-SPECT for the Hanalei Watershed of the Hawai`ian island of Kaua`i; ii) evaluate the performance of N-SPECT under tropical conditions using the sensitivity analysis approach. Hanalei watershed has one of the wettest points on earth, Mt. Waialeale with an average annual rainfall of 11,000 mm. This rainfall decreases to 2,000 mm at the outlet of the watershed near the coast. Number of rain days is one of the major input parameters that influences N-SPECT's simulation results. This parameter was used to account for plant canopy interception losses. The watershed was divided into sub- basins to accurately distribute the number of rain days throughout the watershed. Total runoff volume predicted by the model compared well with measured data. The model underestimated measured runoff by 1% for calibration period and 5% for validation period due to higher intensity precipitation in the validation period. Sensitivity analysis revealed that the model was most sensitive to the number of rain days, followed by canopy interception, and least sensitive to the number of sub-basins. The sediment and water quality portion of the model is currently being evaluated.

Response of Main Maize Varieties to Water Stress and Comprehensive Evaluation in Hebei Province

NASA Astrophysics Data System (ADS)

Yue, Haiwang; Chen, Shuping; Bu, Junzhou; Wei, Jianwei; Peng, Haicheng; Li, Yuan; Li, Chunjie; Xie, Junliang

2018-01-01

Drought is a serious threat to maize production in Hebei province. Planting drought resistant maize varieties is an effective measure to solve drought in arid and less rain areas. Drought resistance in maize is controlled by many genes, and multiple indexes should be used for comprehensive evaluation (Campos H et al.2004). In the arid rain shed, using 34 maize varieties to promote crop production compared to the drought resistance test. The experiment was conducted with two treatments of drought stress (irrigation only at seedling stage) and normal irrigation, and 12 agronomic traits related to drought resistance of maize were determined. The results showed that drought had significant effects on maize yield and main agronomic characters. Under drought stress, plant height, ear length, bare tip, ear row number, row grains, 1000-kernel weight, ASI index can be used as identification index of drought resistance of maize in different period. The results indicated that the variety with strong drought resistance is Zhongdi175, the worst drought resistance is Woyu964.

Cavitation erosion resistance of diamond-like carbon coating on stainless steel

NASA Astrophysics Data System (ADS)

Cheng, Feng; Jiang, Shuyun

2014-02-01

Two diamond-like carbon (DLC) coatings are prepared on stainless steel 304 by cathodic arc plasma deposition technology at different substrate bias voltages and arc currents (-200 V/80 A, labeled DLC-1, and -100 V/60 A, labeled DLC-2). Cavitation tests are performed by using a rotating-disk test rig to explore the cavitation erosion resistance of the DLC coating. The mass losses, surface morphologies, chemical compositions and the phase constituents of the specimens after cavitation tests are examined by using digital balance, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The results indicate that the DLC-2 coatings can elongate the incubation period of stainless steel, leading to an excellent cavitation erosion resistance as compared to the untreated stainless steel specimens. After duration of 100 h cavitation test, serious damaged surfaces and plenty of scratches can be observed on the surfaces of the stainless steel specimens, while only a few grooves and tiny pits are observed on the DLC-2 coatings. It is concluded that, decreasing micro defects and increasing adhesion can reduce the delamination of DLC coating, and the erosion continues in the stainless steel substrate after DLC coating failure, and the eroded surface of the substrate is subjected to the combined action from cavitation erosion and slurry erosion.

Correlation between cavitation erosion resistance and cyclic mechanical properties of different metallic materials

NASA Astrophysics Data System (ADS)

Kaufhold, Corinna; Pöhl, Fabian; Theisen, Werner

2017-05-01

Machine components in contact with flowing fluids are especially prone to cavitation erosion, where plastic deformation and material loss occur due to the repeated implosion of cavitation bubbles in the vicinity of a solid surface. Identifying a correlation between experimentally derivable material properties and resistance against cavitation erosion could help improve the lifetime of cavitation-affected components. Cavitation erosion is a predominantly fatigue-driven phenomenon. In this investigation, we conducted nanoindentation experiments to examine cyclic micromechanical material properties in response to an increasing number of cycles. The experiments were performed on pure iron and different steel grades, i.e., austenitic stainless CrMnCN steels, interstitially alloyed with carbon and nitrogen. We confirmed the view, also proposed in literature, that indentation hardness is inappropriate for ordering the investigated materials by incubation period or maximum erosion rate. We found that the percentage increase of nanoindentation contact stiffness, after an increasing number of cycles, is a promising indicator in terms of the overall ranking of cavitation erosion resistance among the considered materials. Although a single cavitation impact is associated with a significantly higher strain rate than nanoindentation experiments, it is shown that the plastically deformed area around each indent exhibits indications of deformation, such as the formation of slip lines that are also observable after cavitation-induced impacts.

An evaluation of three wood shred blends for post-fire erosion control using indoor simulated rain events on small plots

Treesearch

R. B. Foltz; N. S. Wagenbrenner

2010-01-01

The assessment teams who make post-fire stabilization and treatment decisions are under pressure to employ more effective and economic post-fire treatments, as wild fire activity and severity has increased in recent years across the western United States. Use of forest-native wood-based materials for hillslope mulching has been on the rise due to potential...

Advances in spinel optical quality, size/shape capacity, and applications

NASA Astrophysics Data System (ADS)

Roy, Donald W.; Martin, Gay G., Jr.

1992-12-01

Polycrystalline MgAl2O4 Spinel, transparent from two hundred nanometers to six microns, offers a unique combination of optical and physical properties. A superior dome and window material with respect to rain and particle erosion, solar radiation, high temperatures and humidity, it is resistant to attack by strong acids, alkali solutions, sea water and jet fuels. Residual microporosity from the powder process used for fabricating Spinel which previously limited the use of Spinel to thin wall thicknesses and small sizes, has been significantly reduced by advanced hot press and hot isostatic press (HIP) technology. It is now possible to manufacture high quality shallow domes up to seven inches in diameter with a two tenths inch thick wall thickness. Eight inch diameter flat windows have been produced for an advanced missile system. Proof of process near hemispherical 8 inch dome blanks have been fabricated. Recent measurements of refractive index, homogeneity, scatter and surface roughness are available for design purposes. Improvement in the optical quality and in size/shape capability along with several successful prototype tests demonstrate that Spinel is ready for inclusion in appropriate production systems.

A GIS-based hillslope erosion and sediment delivery model and its application in the Cerro Grande burn area

NASA Astrophysics Data System (ADS)

Wilson, Cathy J.; Carey, J. William; Beeson, Peter C.; Gard, Marvin O.; Lane, Leonard J.

2001-10-01

An Erratum has been published for this article in Hydrological Processes 16(5) 2002, 1130-1130.A profile-based, analytical hillslope erosion model (HEM) is integrated into a geographical information system (GIS) framework to provide a tool to assess the impact of the Cerro Grande fire on erosion and sediment delivery to the many streams draining the burn area. The model, HEM-GIS, calculates rill and interrill erosion, transport and deposition along digital flow-pathways generated with GIS software. This new erosion and sediment yield technology accounts for complex terrain attributes and their impact on the connectivity of sediment transport pathways from source areas to streams. GIS digital spatial data, including elevation, vegetation cover, burn severity and soil type, are used as input to the model. Output includes spatially distributed predictions of total event-based sediment yield (tonnes or kilograms per square metre). Here the model is applied across an 800 km2 region of the Pajarito Plateau watershed to assess the sedimentation risks associated with a 100 year design rain event. Although unvalidated for the design storm, the model predicts that the fire may cause runoff to increase by three to six times, and sediment yield to increase by more than an order of magnitude. Published in 2001 John Wiley & Sons, Ltd.

Evaluation and selection of indicators for land degradation and desertification monitoring: types of degradation, causes, and implications for management.

PubMed

Kairis, Or; Kosmas, C; Karavitis, Ch; Ritsema, C; Salvati, L; Acikalin, S; Alcalá, M; Alfama, P; Atlhopheng, J; Barrera, J; Belgacem, A; Solé-Benet, A; Brito, J; Chaker, M; Chanda, R; Coelho, C; Darkoh, M; Diamantis, I; Ermolaeva, O; Fassouli, V; Fei, W; Feng, J; Fernandez, F; Ferreira, A; Gokceoglu, C; Gonzalez, D; Gungor, H; Hessel, R; Juying, J; Khatteli, H; Khitrov, N; Kounalaki, A; Laouina, A; Lollino, P; Lopes, M; Magole, L; Medina, L; Mendoza, M; Morais, P; Mulale, K; Ocakoglu, F; Ouessar, M; Ovalle, C; Perez, C; Perkins, J; Pliakas, F; Polemio, M; Pozo, A; Prat, C; Qinke, Y; Ramos, A; Ramos, J; Riquelme, J; Romanenkov, V; Rui, L; Santaloia, F; Sebego, R; Sghaier, M; Silva, N; Sizemskaya, M; Soares, J; Sonmez, H; Taamallah, H; Tezcan, L; Torri, D; Ungaro, F; Valente, S; de Vente, J; Zagal, E; Zeiliguer, A; Zhonging, W; Ziogas, A

2014-11-01

Indicator-based approaches are often used to monitor land degradation and desertification from the global to the very local scale. However, there is still little agreement on which indicators may best reflect both status and trends of these phenomena. In this study, various processes of land degradation and desertification have been analyzed in 17 study sites around the world using a wide set of biophysical and socioeconomic indicators. The database described earlier in this issue by Kosmas and others (Environ Manage, 2013) for defining desertification risk was further analyzed to define the most important indicators related to the following degradation processes: water erosion in various land uses, tillage erosion, soil salinization, water stress, forest fires, and overgrazing. A correlation analysis was applied to the selected indicators in order to identify the most important variables contributing to each land degradation process. The analysis indicates that the most important indicators are: (i) rain seasonality affecting water erosion, water stress, and forest fires, (ii) slope gradient affecting water erosion, tillage erosion and water stress, and (iii) water scarcity soil salinization, water stress, and forest fires. Implementation of existing regulations or policies concerned with resources development and environmental sustainability was identified as the most important indicator of land protection.

Spatial variability of polycyclic aromatic hydrocarbon load of urban wet weather pollution in combined sewers.

PubMed

Gasperi, J; Moilleron, R; Chebbo, G

2006-01-01

In Paris, the OPUR research programme created an experimental on-site observatory of urban pollutant loads in combined sewer systems in order to characterise the dry and wet weather flows at different spatial scales. This article presents the first results on the spatial variability of the polycyclic aromatic hydrocarbon (PAH) load during wet weather flow (WWF). At the scale of a rain event, investigations revealed that (i) PAH concentrations were relatively homogenous whatever the spatial scale and were greater than those of the dry weather flow (DWF), (ii) PAH distributions between dissolved and particulate phases were constant, and (iii) PAH fingerprints exhibited a similar pattern for all catchments. Moreover, an evaluation of the contribution of DWF, runoff and erosion of sewer deposits to WWF load was established. According to the hypothesis on the runoff concentration, the contributions were evaluated at 14, 8 and 78%, respectively, at the scale of the Marais catchment. For all the catchments, the runoff contribution was found quite constant and evaluated at approximately 10%. The DWF contribution seems to increase with the catchment area, contrary to the sewer erosion contribution, which seems to decrease. However, this latter still remains an important source of pollution. These first trends should be confirmed and completed by more investigations of rain events.

Map of debris flows caused by rainfall during 1996 in parts of the Reedsport and Deer Head Point quadrangles, Douglas County, southern Coast Range, Oregon

USGS Publications Warehouse

Coe, Jeffrey A.; Michael, John A.; Burgos, Marianela Mercado

2011-01-01

This 1:12,000-scale map shows an inventory of debris flows caused by rainfall during 1996 in a 94.4 km2 area in the southern Coast Range of Oregon. This map and associated digital data are part of a larger U.S. Geological Survey study of debris flows in the southern Coast Range. Available evidence indicates that the flows were triggered by a rain storm that occurred between November 17 and 19. The closest rain gage in the Coast Range (Goodwin Peak) recorded 245 mm during the storm. Maximum rainfall intensity during the storm was 13.2 mm/hr on November 18. Debris flows were photogrammetrically mapped from 1:12,000-scale aerial photographs flown in May, 1997. The inventory is presented on imagery derived from LiDAR data acquired in 2008. We classified mapped debris flows into four categories based on the type of debris-flow activity: (1) discrete slide source areas, (2) predominantly erosion, (3) predominantly transport or mixed erosion and deposition, and (4) predominantly deposition. Locations of woody-debris jams are also shown on the map. The area encompassed by debris flows is 2.1 percent of the 94.4 km2 map area.

The Effect of Grain Refinement on Solid Particle Erosion of Grade 5 Ti Alloy

NASA Astrophysics Data System (ADS)

Kazarinov, N. A.; Evstifeev, A. D.; Petrov, Y. V.; Atroshenko, S. A.; Valiev, R. R.

2018-04-01

In this work, the results on solid particle erosion of an ultrafine-grained Grade 5 titanium alloy, which was produced using high-pressure torsion (HPT) technique, are presented. In order to assess influence of the HPT treatment on material's behavior in erosive conditions, special experimental procedures were developed. The ultrafine-grained (UFG) alloy was tested alongside with a conventional coarse-grained (CG) Grade 5 titanium alloy in equal conditions. The experiments were conducted in a small-scale wind tunnel with corundum particles as an abrasive material. Both particle dimensions and particle velocities were varied in course of the experiments. Erosion resistance of the samples was evaluated in two ways—mass reduction measurements with subsequent gravimetric erosion rate calculations and investigation of samples' surface roughness after erosion tests. The UFG titanium alloy demonstrated considerable improvement of static mechanical properties (ultimate tensile strength, microhardness), whereas its CG counterpart appeared to be slightly more resistant to solid particle erosion, which might indicate the drop of dynamic strength properties for the HPT-processed material.

Methods for monitoring erosion using optical coherence tomography

NASA Astrophysics Data System (ADS)

Chan, Kenneth H.; Chan, Andrew C.; Darling, Cynthia L.; Fried, Daniel

Since optical coherence tomography is well suited for measuring small dimensional changes on tooth surfaces it has great potential for monitoring tooth erosion. The purpose of this study was to explore different approaches for monitoring the erosion of enamel. Application of an acid resistant varnish to protect the tooth surface from erosion has proven effective for providing a reference surface for in vitro studies but has limited potential for in vivo studies. Two approaches which can potentially be used in vivo were investigated. The first approach is to measure the remaining enamel thickness, namely the distance from the tooth surface to the dentinal-enamel junction (DEJ). The second more novel approach is to irradiate the surface with a carbon dioxide laser to create a reference layer which resists erosion. Measuring the remaining enamel thickness proved challenging since the surface roughening and subsurface demineralization that commonly occurs during the erosion process can prevent resolution of the underlying DEJ. The areas irradiated by the laser manifested lower rates of erosion compared to the non-irradiated areas and this method appears promising but it is highly dependent on the severity of the acid challenge.

A Transition from Depressed to Inverted Channels in Gorgonum Basin

NASA Image and Video Library

2016-10-05

This image shows a transition from depressed to inverted channels in the Gorgonum Basin. In the darker terrain, there are two channels that display depressed topography. As these two channels cross into the underlying brighter terrain, the channels now stand above the surrounding area, indicating they are inverted in topography. This change from depressed to inverted topography is the result of what is called "differential erosion." The channel may contain hardened sediments or have cements that make it more resistant to erosion relative to the darker terrain that once flowed through it. As a result, erosion has removed the less resistant upper darker terrain, leaving behind the more resistant channel standing above the underlying bright terrain. http://photojournal.jpl.nasa.gov/catalog/PIA21103

Plant biodiversity effects in reducing fluvial erosion are limited to low species richness.

PubMed

Allen, Daniel C; Cardinale, Bradley J; Wynn-Thompson, Theresa

2016-01-01

It has been proposed that plant biodiversity may increase the erosion resistance of soils, yet direct evidence for any such relationship is lacking. We conducted a mesocosm experiment with eight species of riparian herbaceous plants, and found evidence that plant biodiversity significantly reduced fluvial erosion rates, with the eight-species polyculture decreasing erosion by 23% relative to monocultures. Species richness effects were largest at low levels of species richness, with little increase between four and eight species. Our results suggest that plant biodiversity reduced erosion rates indirectly through positive effects on root length and number of root tips, and that interactions between legumes and non-legumes were particularly important in producing biodiversity effects. Presumably, legumes increased root production of non-legumes by increasing soil nitrogen availability due to their ability to fix atmospheric nitrogen. Our data suggest that a restoration project using species from different functional groups might provide the best insurance to maintain long-term erosion resistance.

Different erosion characteristics of sediment deposits in combined and storm sewers.

PubMed

Xu, Zuxin; Wu, Jun; Li, Huaizheng; Liu, Zhenghua; Chen, Keli; Chen, Hao; Xiong, Lijun

2017-04-01

To investigate the different erosion patterns of sediments in combined and storm sewers, sediments from three separate sewer systems and two combined sewer systems in urban Shanghai were collected for the flushing experiments. These experiments were conducted with different consolidation periods and shear velocities. As the consolidation period increases, dissolved oxygen exhibits a positive effect on the microbial transformations of organic substrates. Potential structural changes and separations of the surface and bottom layers of sediments are observed. The results also reveal that the organic matter, particle size and moisture have different effects on the erosion resistance of sediments. Furthermore, illicit connections behaved as an important factor affecting the viscosity and static friction force of particles, which directly alter the erosion resistance of sewer sediments.

Improvement of the cavitation erosion resistance for Cr3Si film on stainless steel by double cathode glow discharge

NASA Astrophysics Data System (ADS)

Ding, Hongqin; Qiu, Yujiang

2017-04-01

In this study, sputter-deposited Cr3Si film was prepared by double cathode glow discharge (DCGD) technique onto 304 stainless steel. The phase constituents, surface microstructure and chemical compositions of the film were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After the DCGD process, the hardness of Cr3Si film was 26 GPa, about 10 times of the stainless steel, 2.5 GPa. The cavitation erosion resistance of Cr3Si film and stainless steel were investigated by using an ultrasonic vibration cavitation erosion system. After 30 hours of cavitation tests, the cumulative mass loss of Cr3Si film was only 60% of the stainless steel. Compared with the untreated stainless steel, the cavitation erosion resistance of Cr3Si film was improved. The cavitation mechanism of Cr3Si film is due to the delamination and spalling of local surface layer derived from its inherent brittleness.

Upgraded flowing liquid lithium limiter for improving Li coverage uniformity and erosion resistance in EAST device

NASA Astrophysics Data System (ADS)

Zuo, G. Z.; Hu, J. S.; Maingi, R.; Yang, Q. X.; Sun, Z.; Huang, M.; Chen, Y.; Yuan, X. L.; Meng, X. C.; Xu, W.; Gentile, C.; Carpe, A.; Diallo, A.; Lunsford, R.; Mansfield, D.; Osborne, T.; Tritz, K.; Li, J. G.

2017-12-01

We report on design and technology improvements for a flowing liquid lithium (FLiLi) limiter inserted into auxiliary heated discharges in the experimental advanced superconducting tokamak device. In order to enhance Li coverage uniformity and erosion resistance, a new liquid Li distributor with homogenous channels was implemented. In addition, two independent electromagnetic pumps and a new horizontal capillary structure contributed to an improvement in the observed Li flow uniformity (from 30% in the previous FLiLi design to >80% in this FLiLi design). To improve limiter surface erosion resistance, hot isostatic press technology was applied, which improved the thermal contact between thin stainless steel protective layers covering the Cu heat sink. The thickness of the stainless steel layer was increased from 0.1 mm to 0.5 mm, which also helped macroscopic erosion resilience. Despite the high auxiliary heating power up to 4.5 MW, no Li bursts were recorded from FLiLi, underscoring the improved performance of this new design.

Elevated Temperature Solid Particle Erosion Performance of Plasma-Sprayed Co-based Composite Coatings with Additions of Al2O3 and CeO2

NASA Astrophysics Data System (ADS)

Nithin, H. S.; Desai, Vijay; Ramesh, M. R.

2017-11-01

In this paper, investigation into solid particle erosion behavior of atmospheric plasma-sprayed composite coating of CoCrAlY reinforced with Al2O3 and CeO2 oxides on Superni 76 at elevated temperature of 600 °C is presented. Alumina particles are used as erodent at two impact angles of 30° and 90°. The microstructure, porosity, hardness, toughness and adhesion properties of the as-sprayed coatings are studied. The effects of temperature and phase transformation in the coatings during erosion process are analyzed using XRD and EDS techniques. Optical profilometer is used for accurate elucidation of erosion volume loss. CoCrAlY/CeO2 coating showed better erosion resistance with a volume loss of about 50% of what was observed in case of CoCrAlY/Al2O3/YSZ coating. Lower erosion loss is observed at 90° as compared to 30° impact angle. The erosion mechanism evaluated using SEM micrograph revealed that the coatings experienced ductile fracture exhibiting severe deformation with unusual oxide cracks. Reinforced metal oxides provide shielding effect for erodent impact, enabling better erosion resistance. The oxidation of the coating due to high-temperature exposure reforms erosion process into oxidation-modified erosion process.

Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions (Invited paper)

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

2008-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

2008-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

Laser surface alloying of FeCoCrAlNi high-entropy alloy on 304 stainless steel to enhance corrosion and cavitation erosion resistance

NASA Astrophysics Data System (ADS)

Zhang, S.; Wu, C. L.; Zhang, C. H.; Guan, M.; Tan, J. Z.

2016-10-01

FeCoCrAlNi high-entropy alloy coating was synthesized with premixed high-purity Co, Cr, Al and Ni powders on 304 stainless steel by laser surface alloying, aiming at improving corrosion and cavitation erosion resistance. Phase constituents, microstructure and microhardness were investigated using XRD, SEM, and microhardness tester, respectively. The cavitation erosion and electrochemical corrosion behavior of FeCoCrAlNi coating in 3.5% NaCl solution were also evaluated using an ultrasonic vibrator and potentiodynamic polarization measurement. Experimental results showed that with appropriate laser processing parameters, FeCoCrAlNi coating with good metallurgical bonding to the substrate could be achieved. FeCoCrAlNi coating was composed of a single BCC solid solution. The formation of simple solid solutions in HEAs was the combined effect of mixing entropy (ΔSmix), mixing enthalpy (ΔHmix), atom-size difference (δ) and valence electron concentration (VEC), and the effect of ΔSmix was much larger than that of the other factors. The microhardness of the FeCoCrAlNi coating was ~3 times that of the 304 stainless steel. Both the corrosion and cavitation erosion resistance of the coating were improved. The cavitation erosion resistance for FeCoCrAlNi HEA coating was ~7.6 times that of 304 stainless steel. The corrosion resistance was also improved as reflected by a reduction in the current density of one order of magnitude as compared with 304 stainless steel.

Estimating eroded soil and predicting further erosion in Daisetsuzan National Park in Hokkaido, Japan

NASA Astrophysics Data System (ADS)

Kobayashi, Yusuke; Watanabe, Teiji

2017-04-01

This study has three objectives: (1) to estimate changes of the eroded volume of mountain trails from 2014 to 2016 by making DSMs, (2) to understand a relationship between the trail erosion and micro-topography, and (3) to predict the volume of soil that can be eroded in future. Trail erosion has been investigated near Mt. Hokkai-dake in Daisetzuzan National Park, Hokkaido, northern Japan, with a drone (UAV) from 2014 to 2016. Seven segments with the soil erosion from starting sites to ending sites were selected to make DSMs and Orthophotographs by Agisoft, which is one of the Structure from Motion (SfM) software. Then, at fourteen points in each of the seven segments were selected to estimate the volume of soil that can be eroded in the future by PANDA2, a soil compaction penetrometer. The eroded volume in the segment with the largest eroded value attained 274.67 m3 for the two-year period although extremely heavy rain hit this area in the 2016 summer. The result obtained by PANDA2 shows that soil more than 100 cm in depth will be potentially eroded at four points in three years to one hundred years.

Investigations of Martian history

NASA Technical Reports Server (NTRS)

Hartmann, W. K.

1976-01-01

Geologic and stratigraphic analyses of Martian channels were accomplished using Mariner frames of high resolution. Crater counts were made to determine which forms had the least relative age. Results indicate that major channel and chaotic systems were relatively young, and that Mars experienced periods of enhanced erosive activity during a period of early dense atmospheric activity with rain. The problem of absolute age determination is discussed and geomorphological studies of selected Local Martian Regions are presented.

A new perspective on soil erosion: exploring a thermodynamic approach in a small area of the River Inn catchment

NASA Astrophysics Data System (ADS)

Reid, Lucas; Scherer, Ulrike; Zehe, Erwin

2016-04-01

Soil erosion modeling has always struggled with compensating for the difference in time and spatial scale between model, data and the actual processes involved. This is especially the case with non-event based long-term models based on the Universal Soil Loss Equation (USLE), yet USLE based soil erosion models are among the most common and widely used for they have rather low data requirements and can be applied to large areas. But the majority of mass from soil erosion is eroded within short periods of times during heavy rain events, often within minutes or hours. Advancements of the USLE (eg. the Modified Universal Soil Loss Equation, MUSLE) allow for a daily time step, but still apply the same empirical methods derived from the USLE. And to improve the actual quantification of sediment input into rivers soil erosion models are often combined with a Sediment Delivery Ratio (SDR) to get results within the range of measurements. This is still a viable approach for many applications, yet it leaves much to be desired in terms of understanding and reproducing the processes behind soil erosion and sediment input into rivers. That's why, instead of refining and retuning the existing methods, we explore a more comprehensive, physically consistent description on soil erosion. The idea is to describe soil erosion as a dissipative process (Kleidon et al., 2013) and test it in a small sub-basin of the River Inn catchment area in the pre-Alpine foothills. We then compare the results to sediment load measurements from the sub-basin and discuss the advantages and issues with the application of such an approach.

Evaluating uncertainty in 7Be-based soil erosion estimates: an experimental plot approach

NASA Astrophysics Data System (ADS)

Blake, Will; Taylor, Alex; Abdelli, Wahid; Gaspar, Leticia; Barri, Bashar Al; Ryken, Nick; Mabit, Lionel

2014-05-01

Soil erosion remains a major concern for the international community and there is a growing need to improve the sustainability of agriculture to support future food security. High resolution soil erosion data are a fundamental requirement for underpinning soil conservation and management strategies but representative data on soil erosion rates are difficult to achieve by conventional means without interfering with farming practice and hence compromising the representativeness of results. Fallout radionuclide (FRN) tracer technology offers a solution since FRN tracers are delivered to the soil surface by natural processes and, where irreversible binding can be demonstrated, redistributed in association with soil particles. While much work has demonstrated the potential of short-lived 7Be (half-life 53 days), particularly in quantification of short-term inter-rill erosion, less attention has focussed on sources of uncertainty in derived erosion measurements and sampling strategies to minimise these. This poster outlines and discusses potential sources of uncertainty in 7Be-based soil erosion estimates and the experimental design considerations taken to quantify these in the context of a plot-scale validation experiment. Traditionally, gamma counting statistics have been the main element of uncertainty propagated and reported but recent work has shown that other factors may be more important such as: (i) spatial variability in the relaxation mass depth that describes the shape of the 7Be depth distribution for an uneroded point; (ii) spatial variability in fallout (linked to rainfall patterns and shadowing) over both reference site and plot; (iii) particle size sorting effects; (iv) preferential mobility of fallout over active runoff contributing areas. To explore these aspects in more detail, a plot of 4 x 35 m was ploughed and tilled to create a bare, sloped soil surface at the beginning of winter 2013/2014 in southwest UK. The lower edge of the plot was bounded by a perforated pipe which fed into a collection bin for overland flow and associated sediment capture. At the same time, a flat area at the top of the slope was ploughed and tilled to create a reference site with same inventory baseline as the slope. Rain gauges were set up at the reference and slope site. The tilled surface had a low bulk density and high permeability at the start of the experiment (ksat > 100 mm hr-1). Hence, despite high rainfall in December 2013 (200 mm), notable runoff was observed only after intense rain storms during late 2013 and early January 2014 when the soil profile was saturated. Captured eroded sediment was analysed for 7Be and particle size. Subsequently, the plot soil surface was intensively sampled to quantify 7Be inventory patterns and develop a tracer budget. Preliminary results are discussed in the context of the above potential sources of uncertainty.

Modeling sediment transport after ditch network maintenance of a forested peatland

NASA Astrophysics Data System (ADS)

Haahti, K.; Marttila, H.; Warsta, L.; Kokkonen, T.; Finér, L.; Koivusalo, H.

2016-11-01

Elevated suspended sediment (SS) loads released from peatlands after drainage operations and the resulting negative effect on the ecological status of the receiving water bodies have been widely recognized. Understanding the processes controlling erosion and sediment transport within the ditch network forms a prerequisite for adequate sediment control. While numerous experimental studies have been reported in this field, model based assessments are rare. This study presents a modeling approach to investigate sediment transport in a peatland ditch network. The transport model describes bed erosion, rain-induced bank erosion, floc deposition, and consolidation of the bed. Coupled to a distributed hydrological model, sediment transport was simulated in a 5.2 ha forestry-drained peatland catchment for 2 years after ditch cleaning. Comparing simulation results to measured SS concentrations suggested that the loose peat material, produced during excavation, contributed markedly to elevated SS concentrations immediately after ditch cleaning. Both snowmelt and summer rainstorms contributed critically to annual loads. Springtime peat erosion during snowmelt was driven by ditch flow whereas during summer rainfalls, bank erosion by raindrop impact was identified as an important process. Relating modeling results to observed spatial topographic changes in the ditch network was challenging and the results were difficult to verify. Nevertheless, the model has potential to identify risk areas for erosion. The results demonstrate that modeling is effective in separating the importance of different processes and complements pure experimental approaches. Modeling results can aid planning and designing efficient sediment control measures and guide the focus of experimental studies.

Cavitation Erosion of Electro Spark Deposited Nitinol vs. Stellite Alloy on Stainless Steel Substrate

DTIC Science & Technology

2015-07-15

EROSION OF ELECTRO SPARK DEPOSITED NITINOL VS. STELLITE® ALLOY ON STAINLESS STEEL SUBSTRATE Theresa A. Hoffard Lean-Miguel San Pedro Mikhail...SUBTITLE 5a. CONTRACT NUMBER CAVITATION EROSION TESTING OF ELECTRO SPARK DEPOSITED NITINOL VS STELLITE® ALLOY ON STAINLESS STEEL SUBTRATE 5b. GRANT...of combining Nitinol (NiTi) superelastic metal alloy with ElectroSpark Deposition (ESD) technology to increase the cavitation erosion resistance of

Improving Erosion Resistance of Plasma-Sprayed Ceramic Coatings by Elevating the Deposition Temperature Based on the Critical Bonding Temperature

NASA Astrophysics Data System (ADS)

Yao, Shu-Wei; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

2018-01-01

Interlamellar bonding within plasma-sprayed coatings is one of the most important factors dominating the properties and performance of coatings. The interface bonding between lamellae significantly influences the erosion behavior of plasma-sprayed ceramic coatings. In this study, TiO2 and Al2O3 coatings with different microstructures were deposited at different deposition temperatures based on the critical bonding temperature concept. The erosion behavior of ceramic coatings was investigated. It was revealed that the coatings prepared at room temperature exhibit a typical lamellar structure with numerous unbonded interfaces, whereas the coatings deposited at the temperature above the critical bonding temperature present a dense structure with well-bonded interfaces. The erosion rate decreases sharply with the improvement of interlamellar bonding when the deposition temperature increases to the critical bonding temperature. In addition, the erosion mechanisms of ceramic coatings were examined. The unbonded interfaces in the conventional coatings act as pre-cracks accelerating the erosion of coatings. Thus, controlling interlamellar bonding formation based on the critical bonding temperature is an effective approach to improve the erosion resistance of plasma-sprayed ceramic coatings.

Watershed rehabilitation: a process view

Treesearch

Robert R. Ziemer

1981-01-01

Abstract - The most effective control of erosion, in both physical and economic terms, is through prevention because once natural erosion is accelerated, corrective action is not only expensive but seldom entirely successful. To control erosion it is important to understand the forces that cause material to move or resist movement. Once the forces and processes of...

Cavitation Erosion in Hydraulic Turbine Components and Mitigation by Coatings: Current Status and Future Needs

NASA Astrophysics Data System (ADS)

Singh, Raghuvir; Tiwari, S. K.; Mishra, Suman K.

2012-07-01

Cavitation erosion is a frequently observed phenomenon in underwater engineering materials and is the primary reason for component failure. The damage due to cavitation erosion is not yet fully understood, as it is influenced by several parameters, such as hydrodynamics, component design, environment, and material chemistry. This article gives an overview of the current state of understanding of cavitation erosion of materials used in hydroturbines, coatings and coating methodologies for combating cavitation erosion, and methods to characterize cavitation erosion. No single material property fully characterizes the resistance to cavitation erosion. The combination of ultimate resilience, hardness, and toughness rather may be useful to estimate the cavitation erosion resistance of material. Improved hydrodynamic design and appropriate surface engineering practices reduce damage due to cavitation erosion. The coatings suggested for combating the cavitation erosion encompasses carbides (WC Cr2C3, Cr3C2, 20CrC-80WC), cermets of different compositions (e.g., 56W2C/Ni/Cr, 41WC/Ni/Cr/Co), intermetallic composites, intermetallic matrix composites with TiC reinforcement, composite nitrides such as TiAlN and elastomers. A few of them have also been used commercially. Thermal spraying, arc plasma spraying, and high velocity oxy-fuel (HVOF) processes have been used commercially to apply the coatings. Boronizing, laser surface hardening and cladding, chemical vapor deposition, physical vapor deposition, and plasma nitriding have been tried for surface treatments at laboratory levels and have shown promise to be used on actual components.

Soil-geomorphology and “wet” cycles in the Holocene record of North-Central Mexico

NASA Astrophysics Data System (ADS)

Butzer, Karl W.; Abbott, James T.; Frederick, Charles D.; Lehman, Paul H.; Cordova, Carlos E.; Oswald, John F.

2008-10-01

The distinction between the impact of climatic periodicities or land-use practices on soil erosion is an important issue for Pre-Hispanic and Colonial Mexico. That question can best be addressed by first documenting the dynamics of changing "wet" cycles during the Holocene in the central Mexican region between the northern limits of Pre-Hispanic agriculture and its southern margins in northwestern Chihuahua. Consequently the Laguna Project targeted a 125,000 km 2 sector of North-Central Mexico, 250 km from north to south and 500 km from east to west, from Saltillo to Durango. Some 40 sedimentary profiles with multiple cumulic soils were studied in the field and laboratory, supported by 163 conventional 14C and AMS dates on charcoal and soil humates. We distinguish: (1) wet floodplains (with humic paleosols, redox phenomena reflecting high water tables, channel-ponding sequences, and interbedded tufas) that imply aquifer recharge, sustained base flow, and mainly low-energy conditions; and (2) high-energy pulses of discharge that mobilized cobble gravels or forced channel entrenchment ("gullying") and were tied to episodic, excessive rains that promoted valley and slope instability. In between such "wet" cycles and recurrent disequilibrium events, climate was similar to today, probably less humid, with limited geomorphologic change or slow soil formation. "Wet" cycles were rare at the end of the Pleistocene, but prominent during the Holocene. Disequilibrium proxies became common and dramatic after 2500 BP. The drainages from the Eastern and Western Sierra Madres responded in phase, but varied in detail. Around AD 1050-1200 "natural" erosion led to loss of soil organic carbon, as alternating severe droughts and heavy rains destroyed the ground cover and led to ecological aridification, well before arrival of Spanish miners and settlers. The evidence that human activity triggered Pre-Hispanic or Colonial erosion in Central Mexico should therefore be re-evaluated. Global comparisons and interpretations are discussed, but with caution, since no single theory can explain the whole of the record. The soil-geomorphology geoarchive of North-Central Mexico primarily is an environmental history of alternating "wet" cycles, rather than of sustained wet or dry climates. The critical differences between "soaking" and "excessive" rains, with their respective impacts, may be due to switching between winter and summer storm categories.

Estimating Erosion Rates using Caesium-137 Tracers in the Ethiopian Highlands

NASA Astrophysics Data System (ADS)

Guzman, C. D.; Tilahun, S. A.; Zegeye, A. D.; Yitaferu, B.; Kay, R. W.; Steenhuis, T. S.

2016-12-01

The effects and seriousness of soil erosion have been gaining more attention recently, especially with respect to shortening the life of reservoirs for hydroelectric power generation and diminished agricultural productivity. A central aim of this study on soil erosion and conservation is to compare and contrast estimates and identification of eroding areas and patterns in the Ethiopian highlands. In Debre Mawi, Ethiopia, we examined spatial variations in erosion from an agricultural watershed using the soil-adsorbed radionuclide caesium-137(Cs-137) as a sediment tracer. Sixteen sites were monitored in this small watershed 30 km south of Lake Tana, with characteristic semi-monsoonal rains, during the long (kremt) rainy season for topsoil depth change, groundwater table height, and ceasium-137 inventory. These sixteen sites are divided among cropped and fallow land and are spread out among upslope, midslope, and downslope areas within the watershed. The Cs-137 tracer method mapped the upland mildly sloping areas to be eroding at a greater average rate than any of the mid-slope or toe-slope areas. From comparisons with the sediment concentration in the downstream weir and groundwater table measurements, we draw information helpful in understanding why and how sediment concentration and erosion decreases or increases at certain times during the rainy season. By combining these different detection methods we hope to enable the development of more effective and sustainable conservation practices.

Mapping of Rill Erosion of Arable Soils Based on Unmanned Aerial Vehicles Survey

NASA Astrophysics Data System (ADS)

Kashtanov, A. N.; Vernyuk, Yu. I.; Savin, I. Yu.; Shchepot'ev, V. V.; Dokukin, P. A.; Sharychev, D. V.; Li, K. A.

2018-04-01

Possibilities of using data obtained from unmanned aerial vehicles for detection and mapping of rill erosion on arable lands are analyzed. Identification and mapping of rill erosion was performed on a key plot with a predominance of arable gray forest soils (Greyzemic Phaeozems) under winter wheat in Tula oblast. This plot was surveyed from different heights and in different periods to determine the reliability of identification of rill erosion on the basis of automated procedures in a GIS. It was found that, despite changes in the pattern of rills during the warm season, only one survey during this season is sufficient for adequate assessment of the area of eroded soils. According to our data, the most reliable identification of rill erosion is based on the aerial survey from the height of 50 m above the soil surface. When the height of the flight is more than 200 m, erosional rills virtually escape identification. The efficiency of identification depends on the type of crops, their status, and time of the survey. The surveys of bare soil surface in periods with maximum possible interval from the previous rain or snowmelt season are most efficient. The results of our study can be used in the systems of remote sensing monitoring of erosional processes on arable fields. Application of multiand hyperspectral cameras can improve the efficiency of monitoring.

A method to estimate wind turbine blade damage and to design damage-resilient blades

NASA Astrophysics Data System (ADS)

Fiore, Giovanni

Wind turbine blades are affected by continuous impacts with airborne particles that deteriorate the blade surface and yield to a drop in output power. Based on the climatic conditions and geographic locations of a given wind farm, multiple types of particles are observed in air. The present study focuses on simulating the impact of four types of particles, namely insects, sand grains, hailstones, and rain drops with the blade surface. A numerical inviscid flowfield code, coupled with a particle position predictor code was used. Upon impact, the damaging effect to the blade surface was evaluated. Each type of particle was associated with a damage mode, which depends on the mass, size, and hardness of the particle. It was found that insects strike and adhere to the blade in a region close to the leading edge. On the other hand, it was seen that sand grains promote erosion just downstream of the leading edge, where local velocity reaches a maximum and the impact angle is shallow. Moreover, particles such as rain drops are associated with fatigue and erosion at the very leading edge and on the upper side of the blade section. Finally, hailstones promote delamination and fatigue in the composite panels of the blade surface. Photographic evidence of damaged blade surfaces was used in the present research as a comparison with the simulations performed for various types of particle and different initial conditions. Based on such observations, a theorization of the damage pattern and evolution was proposed. Finally, given a set of well-established blade section geometries, such as the Delft University and NREL S airfoil families, a comparison of airfoil damage fitness was proposed and possible means of shape optimization were discussed. The investigation of blade geometry features to mitigate damage was performed. Based on previous results, it was argued that a viable blade section optimization may be performed for the lightest and smallest particles considered in the study, the sand grains. A pool of airfoils was analyzed regarding the sand erosion rate. It was shown that a bulbous leading edge coupled with airfoil aft camber is beneficial toward the erosion rate due to sand grains. An optimization algorithm was written to improve the damage resilience toward sand erosion of wind turbine airfoils. A direct and inverse approach were integrated in a genetic algorithm code, and it was confirmed that bulbous leading edges, coupled with aft cambers allowed for a reduction in blade erosion rates. Lastly, a time-stepping code was developed to predict the blade section geometry when sand erosion is present. It was found that three main phases occur during the erosive life of a blade. A parametric study allowed to find the most relevant drivers to the blade lifespan with respect to erosion. Beneficial effects come from an increase in turbine hub height, turbine rated power, increase in lift coefficient, and a reduction in average particle diameter. A parametric study was also performed by investigating different airfoil geometries. Again, it was found that bulbous leading edges coupled with aft cambered geometries allow for longer blade lifespan.

Multiple antibiotic resistant Escherichia coli from a tropical rain forest stream

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carrasco, C.E.; Alvarez, H.J.; Ortiz, N.

1988-12-31

High densities of fecal coliforms were obtained from a pristine site and sewage contaminated site in a tropical rain forest watershed in Puerto Rico. Confirmation of fecal coliform isolates as Escherichia coli was significantly lower than for temperate waters. Antibiotic resistance and multiple antibiotic resistance were common for isolates at both sites; however, the site receiving sewage effluent had a greater proportion of multiple antibiotic resistant isolates. R. plasmids were recovered from 4 MAR isolates, 2 from each site. All recovered plasmids were approximately 1 kilobase. The recovered plasmid were also capable of transforming E. coli HB101 in vitro. Themore » high concentrations of enterobacteriaceae, small R-plasmid size, R-plasmid transformability, and long term survival of fecal origin bacteria in tropical freshwater environments give increasing importance to adequate sewage treatment, and better indicator monitoring methods for tropical areas.« less

A comparison among root soil-conservation effects for nine herbs at the cold region highway in north-eastern China

NASA Astrophysics Data System (ADS)

Xu, W.; Wang, X.; Zhang, Y.; Liu, Y.

2014-12-01

High soil-conservation herbs are very important for slope vegetation restoration of a highway in serious sandstorm regions. In this study, nine common herbs in northeast China were selected and compared to study soil-conservation effects by using an undisturbed-soil trough scouring method for soil anti-scourability enhancement and hydrostatic collapse method for soil anti-erodibility. Further, principal components analysis was used to identify significant root features that affected soil erosion resistance. Results indicated that different herbs had distinct enhancement effects on soil erosion resistance. Soil anti-scourability enhancement index decreased with increases of soil depth, slope gradient and rainfall amount. Relationship between soil anti-erodibility enhancement index ( S) and immersion time ( t) is a cubic spline in each different herb type ( R 2 ≥ 0.88). Herb root features such as micro-aggregates, organic matter, net leaf weight, thick root length, fine root length and biomass contributed a leading role in soil erosion resistance enhancement effect, and all their common factor variances were more than 0.81. Descending order of soil erosion resistance enhancement effect in soil anti-scourability for nine herbs is Poa pratensis, Medicago sativa, Viola philippica, Rudbeckia hirta, Clematis heracleifolia, Kalimeris indica, Cosmos bipinnata, Hemerocallis fulva and Sedum elatinoides, while the sequence of soil anti-erodibility is M. sativa, S. elatinoides, P. pratensis, R. hirta, H. fulva, V. philippica, C. heracleifolia, C. bipinnata and K. indica. Therefore, we concluded that P. pratensis and M. sativa were the most suitable herbs for resisting soil erosion and recommended to be widely planted for road vegetation recovery in this region.

Upgraded flowing liquid lithium limiter for improving Li coverage uniformity and erosion resistance in EAST device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zuo, G. Z.; Hu, J. S.; Maingi, R.

In this paper, we report on design and technology improvements for a flowing liquid lithium (FLiLi) limiter inserted into auxiliary heated discharges in the experimental advanced superconducting tokamak device. In order to enhance Li coverage uniformity and erosion resistance, a new liquid Li distributor with homogenous channels was implemented. In addition, two independent electromagnetic pumps and a new horizontal capillary structure contributed to an improvement in the observed Li flow uniformity (from 30% in the previous FLiLi design to >80% in this FLiLi design). To improve limiter surface erosion resistance, hot isostatic press technology was applied, which improved the thermalmore » contact between thin stainless steel protective layers covering the Cu heat sink. The thickness of the stainless steel layer was increased from 0.1 mm to 0.5 mm, which also helped macroscopic erosion resilience. Finally, despite the high auxiliary heating power up to 4.5 MW, no Li bursts were recorded from FLiLi, underscoring the improved performance of this new design.« less

Upgraded flowing liquid lithium limiter for improving Li coverage uniformity and erosion resistance in EAST device

DOE PAGES

Zuo, G. Z.; Hu, J. S.; Maingi, R.; ...

2017-12-14

In this paper, we report on design and technology improvements for a flowing liquid lithium (FLiLi) limiter inserted into auxiliary heated discharges in the experimental advanced superconducting tokamak device. In order to enhance Li coverage uniformity and erosion resistance, a new liquid Li distributor with homogenous channels was implemented. In addition, two independent electromagnetic pumps and a new horizontal capillary structure contributed to an improvement in the observed Li flow uniformity (from 30% in the previous FLiLi design to >80% in this FLiLi design). To improve limiter surface erosion resistance, hot isostatic press technology was applied, which improved the thermalmore » contact between thin stainless steel protective layers covering the Cu heat sink. The thickness of the stainless steel layer was increased from 0.1 mm to 0.5 mm, which also helped macroscopic erosion resilience. Finally, despite the high auxiliary heating power up to 4.5 MW, no Li bursts were recorded from FLiLi, underscoring the improved performance of this new design.« less

Test method for assessing resistance of pine lumber and waferboard to mold

Treesearch

Carol A. Clausen; Michael West

2005-01-01

Methods are needed to evaluate the ability of framing lumber and composite construction materials to withstand mold growth when they are exposed to rain between manufacture and installation. A laboratory-controlled rain chamber was developed to expose biocide-treated specimens of pine lumber and waferboard to bi-weekly wetting followed by re-inoculation with test fungi...

Exceptionally high cavitation erosion and corrosion resistance of a high entropy alloy.

PubMed

Nair, R B; Arora, H S; Mukherjee, Sundeep; Singh, S; Singh, H; Grewal, H S

2018-03-01

Cavitation erosion and corrosion of structural materials are serious concerns for marine and offshore industries. Durability and performance of marine components are severely impaired due to degradation from erosion and corrosion. Utilization of advanced structural materials can play a vital role in limiting such degradation. High entropy alloys (HEAs) are a relatively new class of advanced structural materials with exceptional properties. In the present work, we report on the cavitation erosion behavior of Al 0.1 CoCrFeNi HEA in two different media: distilled water with and without 3.5wt% NaCl. For comparison, conventionally used stainless steel SS316L was also evaluated in identical test conditions. Despite lower hardness and yield strength, the HEA showed significantly longer incubation period and lower erosion-corrosion rate (nearly 1/4th) compared to SS316L steel. Enhanced erosion resistance of HEA was attributed to its high work-hardening behavior and stable passivation film on the surface. The Al 0.1 CoCrFeNi HEA showed lower corrosion current density, high pitting resistance and protection potential compared to SS316L steel. Further, HEA showed no evidence of intergranular corrosion likely due to the absence of secondary precipitates. Although, the degradation mechanisms (formation of pits and fatigue cracks) were similar for both the materials, the damage severity was found to be much higher for SS316L steel compared to HEA. Copyright © 2017 Elsevier B.V. All rights reserved.

Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray

NASA Astrophysics Data System (ADS)

Mahade, Satyapal; Curry, Nicholas; Björklund, Stefan; Markocsan, Nicolaie; Nylén, Per; Vaßen, Robert

2017-01-01

7-8 wt.% Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used by the gas turbines industry due to its excellent thermal and thermo-mechanical properties up to 1200 °C. The need for improvement in gas turbine efficiency has led to an increase in the turbine inlet gas temperature. However, above 1200 °C, YSZ has issues such as poor sintering resistance, poor phase stability and susceptibility to calcium magnesium alumino silicates (CMAS) degradation. Gadolinium zirconate (GZ) is considered as one of the promising top coat candidates for TBC applications at high temperatures (>1200 °C) due to its low thermal conductivity, good sintering resistance and CMAS attack resistance. Single-layer 8YSZ, double-layer GZ/YSZ and triple-layer GZdense/GZ/YSZ TBCs were deposited by suspension plasma spray (SPS) process. Microstructural analysis was carried out by scanning electron microscopy (SEM). A columnar microstructure was observed in the single-, double- and triple-layer TBCs. Phase analysis of the as-sprayed TBCs was carried out using XRD (x-ray diffraction) where a tetragonal prime phase of zirconia in the single-layer YSZ TBC and a cubic defect fluorite phase of GZ in the double and triple-layer TBCs was observed. Porosity measurements of the as-sprayed TBCs were made by water intrusion method and image analysis method. The as-sprayed GZ-based multi-layered TBCs were subjected to erosion test at room temperature, and their erosion resistance was compared with single-layer 8YSZ. It was shown that the erosion resistance of 8YSZ single-layer TBC was higher than GZ-based multi-layered TBCs. Among the multi-layered TBCs, triple-layer TBC was slightly better than double layer in terms of erosion resistance. The eroded TBCs were cold-mounted and analyzed by SEM.

Tackling soil degradation and environmental changes in Lake Manyara Basin, Tanzania to support sustainable landscape/ecosystem management.

NASA Astrophysics Data System (ADS)

Munishi, Linus; Mtei, Kelvin; Bode, Samuel; Dume, Bayu; Navas, Ana; Nebiyu, Amsalu; Semmens, Brice; Smith, Hugh; Stock, Brian; Boeckx, Pascal; Blake, Will

2017-04-01

The Lake Manyara Basin (LMB), which encompasses Lake Manyara National Park a world ranking World Biosphere Reserve, is of great ecological and socio-economic value because it hosts a small-holder rain fed and extensive irrigation agriculture, grazing grounds for pastoralists, terrestrial and aquatic habitat for wildlife and tourism business contributing to poverty alleviation. Despite these multiple ecosystem services that support the local communities, the LMB is threatened by; (a) siltation from eroded soil fed from the wider catchment and rift escarpment of the basin and (b) declining water levels due to water capture by agriculture and possibly climate change. These threats to the ecosystem and its services are augmented by increasing human population, pollution by agricultural pesticides, poaching, human encroachment and infrastructure development, and illegal fisheries. Despite these challenges, here is a dearth of information on erosion hotspots and to date soil erosion and siltation problems in LMB have been interpreted largely in qualitative terms, and no coherent interpretative framework of these records exists. Despite concerns that modern sediment fluxes to the Lake may exceed long-term fluxes, little is known about erosion sources, how erosion rates and processes vary across the landscape and how erosion rates are influenced by the strong climate gradients in the basin. This contribution describes a soil erosion and sediment management project that aims to deliver a demonstration dataset generated from inter-disciplinary sediment-source tracing technologies and approaches to assess erosion hotspots, processes and spatial patterns of erosion in the area. The work focuses on a sub basin, the Monduli Sub catchment, located within the greater LMB. This is part of efforts to establish an understanding of soil erosion and landscape degradation in the basin as a pathway for generating and developing knowledge, building capacity to assist conservationists, farmers and pastoralists, agro-entrepreneurs, and their support agents to address the problems while feeding the information into the national development policies in Tanzania and the entire East African region.

The dominant erosion processes supplying fine sediment to three major rivers in tropical Australia, the Daly (NT), Mitchell (Qld) and Flinders (Qld) Rivers

NASA Astrophysics Data System (ADS)

Caitcheon, Gary G.; Olley, Jon M.; Pantus, Francis; Hancock, Gary; Leslie, Christopher

2012-05-01

The tropics of northern Australia have received relatively little attention with regard to the impact of soil erosion on the many large river systems that are an important part of Australia's water resource, especially given the high potential for erosion when long dry seasons are followed by intense wet season rain. Here we use 137Cs concentrations to determine the erosion processes supplying sediment to two major northern Australian Rivers; the Daly River (Northern Territory), and the Mitchell River (Queensland). We also present data from five sediment samples collected from a 100 km reach of the Cloncurry River, a major tributary of the Flinders River (Queensland). Concentrations of 137Cs in the surface soil and subsurface (channel banks and gully) samples were used to derive 'best fit' probability density functions describing their distributions. These modelled distributions are then used to estimate the relative contribution of these two components to the river sediments. Our results are consistent with channel and gully erosion being the dominant source of sediment, with more than 90% of sediment transported along the main stem of these rivers originating from subsoil. We summarize the findings of similar studies on tropical Australian rivers and conclude that the primary source of sediment delivered to these systems is gully and channel bank erosion. Previously, as a result of catchment scale modelling, sheet-wash and rill erosion was considered to be the major sediment source in these rivers. Identifying the relative importance of sediment sources, as shown in this paper, will provide valuable information for land management planning in the region. This study also reinforces the importance of testing model predictions before they are used to target investment in remedial action.

Ouragans et diversité biologique dans les forêts tropicales. L'exemple de la Guadeloupe

NASA Astrophysics Data System (ADS)

Imbert, Daniel; Roustéau, Alain; Labbé, Patrick

1998-06-01

In this work, we consider the role played by hurricanes in the maintenance of high biodiversity, ,and we look at how biodiversity may influence the response of tropical forest ecosystems to hurricane disturbances. After hurricane Hugo struck Guadeloupe in 1989, we started a comparative study on the resistance and the resilience of the rain forest, the semi-deciduous forest and the mangrove forest. It appeared that the resistance of these forests was positively linked to their diversity, which was assessed both through flora richness and structure complexity (resultin from the variety of life forms). Examples of species specific resistance or vulnerability occur in the three forests; however, the higher the ecosystem diversity, the fewer and the weaker they are. Abundant species tend to be less vulnerable than others — at least in the rain forest and in the semi-deciduous forest. Forest recovery operates mainly through pre-existing individuals (surviving trees, coppicing stumps, saplings or seedlings). Pioneer species may slightly and temporarily benefit from large openings, especially in the rain forest. Strong recurrence of hurricanes may lead to the extinction of some rare, vulnerable, short-range disseminating, non pioneer species.

A high space-time resolution dataset linking meteorological forcing and hydro-sedimentary response in a mesoscale Mediterranean catchment (Auzon) of the Ardèche region, France

NASA Astrophysics Data System (ADS)

Nord, Guillaume; Boudevillain, Brice; Berne, Alexis; Branger, Flora; Braud, Isabelle; Dramais, Guillaume; Gérard, Simon; Le Coz, Jérôme; Legoût, Cédric; Molinié, Gilles; Van Baelen, Joel; Vandervaere, Jean-Pierre; Andrieu, Julien; Aubert, Coralie; Calianno, Martin; Delrieu, Guy; Grazioli, Jacopo; Hachani, Sahar; Horner, Ivan; Huza, Jessica; Le Boursicaud, Raphaël; Raupach, Timothy H.; Teuling, Adriaan J.; Uber, Magdalena; Vincendon, Béatrice; Wijbrans, Annette

2017-03-01

A comprehensive hydrometeorological dataset is presented spanning the period 1 January 2011-31 December 2014 to improve the understanding of the hydrological processes leading to flash floods and the relation between rainfall, runoff, erosion and sediment transport in a mesoscale catchment (Auzon, 116 km2) of the Mediterranean region. Badlands are present in the Auzon catchment and well connected to high-gradient channels of bedrock rivers which promotes the transfer of suspended solids downstream. The number of observed variables, the various sensors involved (both in situ and remote) and the space-time resolution ( ˜ km2, ˜ min) of this comprehensive dataset make it a unique contribution to research communities focused on hydrometeorology, surface hydrology and erosion. Given that rainfall is highly variable in space and time in this region, the observation system enables assessment of the hydrological response to rainfall fields. Indeed, (i) rainfall data are provided by rain gauges (both a research network of 21 rain gauges with a 5 min time step and an operational network of 10 rain gauges with a 5 min or 1 h time step), S-band Doppler dual-polarization radars (1 km2, 5 min resolution), disdrometers (16 sensors working at 30 s or 1 min time step) and Micro Rain Radars (5 sensors, 100 m height resolution). Additionally, during the special observation period (SOP-1) of the HyMeX (Hydrological Cycle in the Mediterranean Experiment) project, two X-band radars provided precipitation measurements at very fine spatial and temporal scales (1 ha, 5 min). (ii) Other meteorological data are taken from the operational surface weather observation stations of Météo-France (including 2 m air temperature, atmospheric pressure, 2 m relative humidity, 10 m wind speed and direction, global radiation) at the hourly time resolution (six stations in the region of interest). (iii) The monitoring of surface hydrology and suspended sediment is multi-scale and based on nested catchments. Three hydrometric stations estimate water discharge at a 2-10 min time resolution. Two of these stations also measure additional physico-chemical variables (turbidity, temperature, conductivity) and water samples are collected automatically during floods, allowing further geochemical characterization of water and suspended solids. Two experimental plots monitor overland flow and erosion at 1 min time resolution on a hillslope with vineyard. A network of 11 sensors installed in the intermittent hydrographic network continuously measures water level and water temperature in headwater subcatchments (from 0.17 to 116 km2) at a time resolution of 2-5 min. A network of soil moisture sensors enables the continuous measurement of soil volumetric water content at 20 min time resolution at 9 sites. Additionally, concomitant observations (soil moisture measurements and stream gauging) were performed during floods between 2012 and 2014. Finally, this dataset is considered appropriate for understanding the rainfall variability in time and space at fine scales, improving areal rainfall estimations and progressing in distributed hydrological and erosion modelling. DOI of the referenced dataset: doi:10.6096/MISTRALS-HyMeX.1438.

Preliminary Evaluation of Cavitation-Erosion Resistance of Ti-Alloys in Mercury for the Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawel, Steven J; Mansur, Louis K

2010-01-01

A number of Ti-based alloys in both the mill-annealed and 20% cold-worked conditions were subjected to sonication conditions in Hg using a vibratory horn to assess relative cavitation-erosion resistance. Weight loss as a function of exposure time was roughly proportional to hardness for all alloys/conditions examined, with Ti-6Al-4V (Ti-Grade 5) and Ti-6Al-2Sn-4Zr-2Mo yielding the best resistance to cavitation-erosion as evidenced by low weight losses and little or no tendency to form pits on the exposed surface. Unalloyed Ti (Ti-Grade 4) and Ti-0.12Pd (Ti-Grade 7) exhibited greater weight losses by a factor or about two and about five, respectively, with Ti-0.12Pdmore » particularly prone to pitting development. The mean erosion rates of the best two Ti-alloys examined here were about a factor of three higher than identically tested 316LN stainless steel following a low temperature carburizing treatment, but this difference is considered minor given that the rate for both materials is very low/manageable and represents a through-thickness property for the Ti-alloys. A nitriding surface treatment was also evaluated as a potential method to further increase the cavitation-erosion resistance of these alloys in Hg, but the selected treatment proved largely ineffective. Recommendations for further work to evaluate the efficacy of Ti-based alloys for use in high-powered targets for the Spallation Neutron Source are given.« less

Erosion assessment at the Petroglyph National Monument area, Albuquerque, New Mexico

USGS Publications Warehouse

Gellis, A.C.

1995-01-01

Areas of the Petroglyph National Monument, specifically those located along the West Mesa escarpment, are being affected by erosion and gullying. A reconnaissance along the 17-mile-long escarpment identified 50 gullies. The gullies were given a qualitative ranking of Class I, least erosion, to Class IV, highest erosion. Of the 50 gullies identified, 21 were assigned Class I, 22 to Class II, 6 to Class III, and 1 to Class IV. Although the gullies may not be a direct threat to petroglyphs, the effects of gullying may have a greater effect on the aesthetics of the monument and the residences located downgradient from a gully. Most of the gullies were found along the northern part of the escarpment. This area, which is more developed than the southern areas of the escarpment, contains many dirt roads and nonpaved foot and bicycle paths. These features channel surface runoff and increase erosion. Thirty of the 50 gullies were noted as being connected to the runoff from dirt roads. High-intensity storms during the summer of 1991 may have caused or increased gullying. Analyses of these storms indicate recurrence intervals of rainfall of no more than 2 years. Indirect measurements of peak discharge in La Boca Negra Arroyo after the August 22, 1991, storm indicate that this runoff event may have a frequency of no more than 10 years. Regional frequency reports on rainfall and data collected at the rain gages indicate that gullying and erosion that occurred during the summer of 1991 were not a result of infrequent rainfall or runoff events.

4 years of high-resolution LiDAR erosion monitoring of an elementary gully in the badlands of SE France (Draix)

NASA Astrophysics Data System (ADS)

Rudaz, Benjamin; Carrea, Dario; Antonio, Abellan; Jaboyedoff, Michel; Klotz, Sébastien

2016-04-01

The black marls outcrops of Draix (SE France) are an ideal site to study multiple erosional processes such as rain splashing, sheet erosion, concentrated flow erosion and micro-landslides. Their erosion constitute an important contribution to the bedload and suspended load of the Durance river basin, which can affect human infrastructure such as hydroelectric dams, irrigation systems and in general river maintenance. The badlands response to climatic events is thus crucial for long term management of those human endeavours. The topographical changes resulting from those different processes can be quantified and localized in both space and time, with repeated LiDAR acquisitions of high-resolution topography (up to 10 pts per cm2). To avoid shadowing induced vy vegetation or topography's curvature, an instrumented individual gully (named Roubinette) is equipped with a 4 m high scanning tower. It is small enough (400 m2) that the LiDAR can acquire it with no shadowing and in one scan, reducing merging and alignment errors. Seasonal acquisitions have been carried out since 2011, constituting a comprehensive dataset of the gully's evolution. The aligned scans are then converted to square grids and compared vertically to obtain DEMs of differences (DoD). Concentrated flow erosion, volume remobilization inside the secondary gullies and micro-landslides are easily detected by the DoD. Diffuse erosion is detected using a space-time filter to improve detection level accuracy. Combined with local meteorological data, photographic monitoring and sediment trap content data, a sequence of events can be reconstituted between each acquisition.

Surface erosion at disturbed alpine sites: effects of vegetation cover and plant diversity

NASA Astrophysics Data System (ADS)

Martin, C.; Pohl, M.; Alewell, C.; Körner, C.; Buttler, A.; Rixen, C.

2009-04-01

The relationship between plant diversity and soil stability in disturbed alpine terrain is poorly studied. In this paper, we investigated the influence of plant cover and diversity on water run-off and sediment yield on ski slopes. Rainfall simulations were conducted on a micro-scale (25 x 25 cm) to be able to replicate plots with different degrees of vegetation cover. We selected plots with 10%, 30% and 60% of vegetation cover containing different combinations of plant diversities: (i) grass, (ii) herb, (iii) moss/ lichen, and all combinations of these plant groups. Each combination was replicated five times with an applied rain intensity of 375 ml min-1 for about 5 minutes. As could be expected, percent vegetation cover had a large effect on surface erosion: sediment yield decreased with increasing vegetation cover. However, within the plots with 60% cover, sediment yield was lower at higher plant diversity and functional group diversity. The findings of this study support the view that beside the re-establishment of a closed vegetation cover, plant diversity is a relevant factor to reduce surface erosion at disturbed sites in alpine ecosystems.

Defense Small Business Innovation Research Program (SBIR). Program Solicitation Number 89.1. FY-1989

DTIC Science & Technology

1989-01-06

scale testing, such as plasma-arc and oxyacetylene torch test are performed. However, correlations to relate ablation rate from these test data to...helicopter rotor. In phase II, the contractor should construct and demonstrate a working model. 36 A89-010 TITLE: Smooth, Erosion Resistant Coatings ...for Organic Matrix Composites OBJECTIVE: Erosion Resistant Coatings for Organic Matrix Composites for use in Compressor Section of Future Gas Turbine

Continued development of abradable gas path seals. [for gas turbine engines

NASA Technical Reports Server (NTRS)

Shiembob, L. T.

1975-01-01

Major program objectives were the continued development of NiCrAlY feltmetal and honeycomb systems for knife edge seal applications in the 1144 to 1366 K temperature range, and to initiate abradable seal material evaluation for blade tip seal applications in the 1366 to 1589 K temperature range. Larger fiber size, higher density feltmetal showed greatly improved erosion resistance with a slight reduction in abradability compared to the baseline feltmetal. Pack aluminide coating of the honeycomb extended the oxidation resistance and slightly improved the abradability of this material. Evaluation through selected abradability, erosion and oxidation testing, and pertinent metallography led to selection of a plasma sprayed yttria stabilized zirconia (ZrO2)/CoCrAlY layered system as the system with the most potential to meet the 1589 K requirement for blade tip seals. This system demonstrated structural integrity, erosion resistance, and some degree of abradability.

Improved high pressure turbine shroud

NASA Technical Reports Server (NTRS)

Bessen, I. I.; Rigney, D. V.; Schwab, R. C.

1977-01-01

A new high pressure turbine shroud material has been developed from the consolidation of prealloyed powders of Ni, Cr, Al and Y. The new material, a filler for cast turbine shroud body segments, is called Genaseal. The development followed the identification of oxidation resistance as the primary cause of prior shroud deterioration, since conversion to oxides reduces erosion resistance and increases spalling under thermal cycled engine conditions. The NICrAlY composition was selected in preference to NIAL and FeCRALY alloys, and was formulated to a prescribed density range that offers suitable erosion resistance, thermal conductivity and elastic modulus for improved behavior as a shroud.

Antisoiling Coatings for Solar-Energy Devices

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.; Willis, P.

1986-01-01

Fluorocarbons resist formation of adherent deposits. Promising coating materials reduce soiling of solar photovoltaic modules and possibly solar thermal collectors. Contaminating layers of various degrees of adherence form on surfaces of devices, partially blocking incident solar energy, reducing output power. Loose soil deposits during dry periods but washed off by rain. New coatings help prevent formation of more-adherent, chemically and physically bonded layers rain alone cannot wash away.

Evaluation of Upland Disposal of Oakland Harbor, California, Sediment. Volume 2: Inner and Outer Harbor Sediments

DTIC Science & Technology

1993-08-01

the drop size and terminal velocities of natural rain- fall, factors which are critical in erosion and infiltration studies ( Westerdahl and Skogerboe... Westerdahl and Skogerboe 1982; Lee and Skogerboe 1984; Skogerboe et al. 1987). The WES Rainfall Simulator/ Lysimeter System proved to be an effective...Waters (Phase IIIA of -42-Foot Project); Volume 2: Appendixes," iNL-83-2, Vol 2, Battelle/Marine Science Laboratory, Sequim, WA. Westerdahl , H. E., and

Hillslope-channel coupling in a steep Hawaiian catchment accelerates erosion rates over 100-fold

NASA Astrophysics Data System (ADS)

Stock, J. D.; Hanshaw, M. N.; Rosener, M.; Schmidt, K. M.; Brooks, B. A.; Tribble, G.; Jacobi, J.

2009-12-01

In tropical watersheds, hillslope changes are producing increasing amounts of fine sediment that can be quickly carried to reefs by channels. Suspended sediment concentrations off the reefs of Molokai, Hawaii, chronically exceed a toxic level of 10 mg/L, threatening reef ecosystems. We hypothesize that historic conversion of watersheds from soil creep to overland flow erosion increased both magnitude and frequency of sediment flooding adjacent reefs. We combined surficial and ecological mapping, hillslope and stream gages, and novel sensors to locate, quantify and model the generation of fine sediments polluting the Molokai reef. Ecological and geomorphic mapping from LiDAR and multi-spectral imagery located a subset of overland flow areas with vegetation cover below a threshold value preventing erosion. Here, feral goat grazing exposed cohesive volcanic soils whose low matrix hydraulic conductivities (1-20 mm/hour) promote Horton overland flow erosion. We instrumented steep, barren hillslopes with soil moisture sensors, overland flow meters, Parshall flumes, ISCO sediment samplers, and a rain gage and conducted repeat Tripod LiDAR and infiltration tests. To characterize soil resistance here and elsewhere to overland flow erosion, we deployed a Cohesive Strength Meter (CSM) to simulate the stresses of flowing water. At the 13.5 km 2 watershed mouth we used a USGS stream gage and ISCO sediment sampler to estimate total load. Over 2 years, storms triggered overland flow during rainfall intensities above 10-15 mm/hr. Overland flow meters indicate such flows can be up to 3 cm deep, with a tendency to deepen downslope. CSM tests indicate that these depths are insufficient to erode soils where vegetation is dense, but far above threshold values of 2-3 mm depth for bare soil erosion. Sediment ratings curves for both hillslope and downstream catchment gages show strong clock-wise hysteresis during the first intense storms in the Fall, becoming linear later in the rainy season. During Fall storms, sediment concentration is often 10X higher at a given stage. During intense Fall storms, we measured erosion rates using erosion pins (1.0 cm/a), suspended sediment flux (1.5 cm/a) and repeat tripod LiDAR (1.7 cm/a). These rates are at least 100-fold greater than the long-term lowering rate of 0.13 mm/a. A sediment budget constructed by extrapolating hillslope lowering rates to the portions of the catchments mapped as overland flow hotspots predicts a total yearly flux of ~ 6500 t, in agreement with the measured total of ~6200 t. A decadal record illustrates that rainfall intensities sufficient to generate overland flow occur for at least 8-10 hours every year, coincident with 1-3 large storm events. We hypothesize that high lowering rates reflect a combination of long-duration overland flow events, and availability of weathered soils that can be entrained by thin flows. It appears that the generation of loose, seasonally weathered silt is a 1st order control on the amount of sediment exported to the reef. If climate change increases storm frequency or duration, or decreases vegetation cover, sediment loading rates to the reef here could increase dramatically.

Characterizing soil erosion potential using electrical resistivity imaging : final report.

DOT National Transportation Integrated Search

2017-04-01

The erosion rate, or erodibility, of soil depends on many soil characteristics including: plasticity, : water content, grain size, percent clay, compaction, and shear strength. Many of these characteristics also : influence soil in situ bulk electric...

Characterizing soil erosion potential using electrical resistivity imaging : technical summary.

DOT National Transportation Integrated Search

2017-04-01

The erosion rate, or erodibility, of soil depends on many soil characteristics : including: plasticity, water content, grain size, percent clay, compaction, and shear : strength. Many of these characteristics also influence soil in situ bulk electric...

Spinel: where did it go?

NASA Astrophysics Data System (ADS)

Roy, Donald W.

1997-11-01

Polycrystalline magnesium aluminum oxide, transparent from 200 nanometers to 6 microns, offers a unique combination of optical and physical properties. A superior dome and window material in respect to rain and particle erosion, solar radiation, high temperatures and humidity; it is resistant to attack by strong acids, sea water, and jet fuels. Although it had been qualified for, and designed into several advanced UV/visible/IR optical systems, production of hot-pressed Spinel was stopped at Alpha Optical Systems in 1993 by the parent company Coors Ceramics. Development efforts on cold-pressed/sinter/HIP Spinel at RCS Technologies are reportedly stalemated at the present time. Therefore, there is no known significant effort directed toward the development of polycrystalline Spinel. however, the author is in contact with both domestic and foreign laboratories which have expressed a desire to develop the technology for transparent Spinel. Renewed development may begin during calendar year 1997. Because of the apparent continuing significant interest in Spinel this paper will review the properties of Spinel and will compare the most significant properties of Spinel with sapphire and aluminum oxynitride. The limitations of competing manufacturing processes, will be mentioned. Grinding and polishing considerations will be reviewed in respect to maximizing optical and structural properties.

Gibbsian segregating alloys driven by thermal and concentration gradients: A potential grazing collector optics used in EUV lithography

NASA Astrophysics Data System (ADS)

Qiu, Huatan

A critical issue for EUV lithography is the minimization of collector degradation from intense plasma erosion and debris deposition. Reflectivity and lifetime of the collector optics will be heavily dependent on surface chemistry interactions between fuels and various mirror materials, in addition to high-energy ion and neutral particle erosion effects. An innovative Gibbsian segregation (GS) concept has been developed for being a self-healing, erosion-resistant collector optics. A Mo-Au GS alloy is developed on silicon using a DC dual-magnetron co-sputtering system in order for enhanced surface roughness properties, erosion resistance, and self-healing characteristics to maintain reflectivity over a longer period of mirror lifetime. A thin Au segregating layer will be maintained through segregation during exposure, even though overall erosion is taking place. The reflective material, Mo, underneath the segregating layer will be protected by this sacrificial layer which is lost due to preferential sputtering. The two dominant driving forces, thermal (temperature) and surface concentration gradient (surface removal flux), are the focus of this work. Both theoretical and experimental efforts have been performed to prove the effectiveness of the GS alloy used as EUV collection optics, and to elucidate the underlying physics behind it. The segregation diffusion, surface balance, erosion, and in-situ reflectivity will be investigated both qualitatively and quantitatively. Results show strong enhancement effect of temperature on GS performance, while only a weak effect of surface removal rate on GS performance. When equilibrium between GS and erosion is reached, the surface smoothness could be self-healed and reflectivity could be maintained at an equilibrium level, instead of continuously dropping down to an unacceptable level as conventional optic mirrors behave. GS process also shows good erosion resistance. The effectiveness of GS alloy as EUV mirror is dependent on the temperature and surface removal rate. The Mo-Au GS alloy could be effective at elevated temperature as the potential grazing mirror as EUV collector optics.

Environmentally regulated aerospace coatings

NASA Technical Reports Server (NTRS)

Morris, Virginia L.

1995-01-01

Aerospace coatings represent a complex technology which must meet stringent performance requirements in the protection of aerospace vehicles. Topcoats and primers are used, primarily, to protect the structural elements of the air vehicle from exposure to and subsequent degradation by environmental elements. There are also many coatings which perform special functions, i.e., chafing resistance, rain erosion resistance, radiation and electric effects, fuel tank coatings, maskants, wire and fastener coatings. The scheduled promulgation of federal environmental regulations for aerospace manufacture and rework materials and processes will regulate the emissions of photochemically reactive precursors to smog and air toxics. Aerospace organizations will be required to identify, qualify and implement less polluting materials. The elimination of ozone depleting chemicals (ODC's) and implementation of pollution prevention requirements are added constraints which must be addressed concurrently. The broad categories of operations affected are the manufacture, operation, maintenance, and repair of military, commercial, general aviation, and space vehicles. The federal aerospace regulations were developed around the precept that technology had to be available to support the reduction of organic and air toxic emissions, i.e., the regulations cannot be technology forcing. In many cases, the regulations which are currently in effect in the South Coast Air Quality Management District (SCAQMD), located in Southern California, were used as the baseline for the federal regulations. This paper addresses strategies used by Southern California aerospace organizations to cope with these regulatory impacts on aerospace productions programs. All of these regulatory changes are scheduled for implementation in 1993 and 1994, with varying compliance dates established.

Study of Traverse Speed Effects on Residual Stress State and Cavitation Erosion Behavior of Arc-Sprayed Aluminum Bronze Coatings

NASA Astrophysics Data System (ADS)

Hauer, Michél; Henkel, Knuth Michael; Krebs, Sebastian; Kroemmer, Werner

2017-01-01

Within a research project regarding cavitation erosion-resistant coatings, arc spraying was used with different traverse speeds to influence heat transfer and the resulting residual stress state. The major reason for this study is the lack of knowledge concerning the influence of residual stress distribution on mechanical properties and coating adhesion, especially with respect to heterogeneous aluminum bronze alloys. The materials used for spray experiments were the highly cavitation erosion-resistant propeller alloys CuAl9Ni5Fe4Mn (Ni-Al-Bronze) and CuMn13Al8Fe3Ni2 (Mn-Al-Bronze). Analyses of cavitation erosion behavior were carried out to evaluate the suitability for use in marine environments. Further microstructural, chemical and mechanical analyses were realized to examine adhesive and cohesive coating properties. Residual stress distribution was measured by modified hole drilling method using electronic speckle pattern interferometry (ESPI). It was found that the highest traverse speed led to higher tensile residual stresses near the surface and less cavitation erosion resistance of the coatings. Moreover, high oxygen affinity of main alloying element aluminum was identified to severely influence the microstructures by the formation of large oxides and hence the coating properties. Overall, Mn-Al-Bronze coatings showed lower residual stresses, a more homogeneous pore and oxide distribution and less material loss by cavitation than Ni-Al-Bronze coatings.

Spatial and temporal heterogeneity of water soil erosion in a Mediterranean rain-fed crop

NASA Astrophysics Data System (ADS)

López-Vicente, M.; Quijano, L.; Gaspar, L.; Machín, J.; Navas, A.

2012-04-01

Fertile soil loss by raindrop impact and runoff processes in croplands presents significant variations at temporal and spatial scales. The combined use of advanced GIS techniques and detailed databases allows high resolution mapping of runoff and soil erosion processes. In this study the monthly values of soil loss are calculated in a medium size field of rain-fed winter barley and its drainage area located in the Central Spanish Pre-Pyrenees. The field is surrounded by narrow strips of dense Mediterranean vegetation (mainly holm oaks) and grass. Man-made infrastructures (paved trails and drainage ditches) modify the overland flow pathways and the study site appears hydrologically closed in its northern and western boundaries. This area has a continental Mediterranean climate with two humid periods, one in spring and a second in autumn and a dry summer with rainfall events of high intensity from July to October. The average annual rainfall is 495 mm and the average monthly rainfall intensity ranges from 1.1 mm / h in January to 7.4 mm / h in July. The predicted rates were obtained after running the RMMF model (Morgan, 2001) with the enhancements made to this model by Morgan and Duzant (2008) to the topographic module, and by López-Vicente and Navas (2010) to the hydrological module. A total of 613 soil samples were collected and all input and output maps were generated at high spatial resolution (1 x 1 m of cell size) with ArcMapTM 10.0. A map of effective cumulative runoff was calculated for each month of the year with a weighted multiple flow algorithm and four sub-catchments were distinguished within the field. The average soil erosion in the cultivated area is 1.32 Mg / ha yr and the corresponding map shows a high spatial variability (s.d. = 7.52 Mg / ha yr). The highest values of soil erosion appear in those areas where overland flow is concentrated and slope steepness is higher. The unpaved trail present the highest values of soil erosion with an average value of 72.23 Mg / ha yr, whereas the grass and forested areas have annual rates lower than 0.1 Mg / ha yr. The highest values of soil erosion appear in March, April, May, October and November showing a very good correlation with the depth of monthly rainfall (Pearson's r = 0.97) and a good correlation with the number of rainy days per month (Pearson's r = 0.76). However, no correlation was obtained with the values of monthly rainfall intensity. The availability of a detailed database of soil properties, weather values and a high resolution DEM allows mapping and calculating the spatial and temporal variations of the soil erosion processes within the cultivated area and the area surrounding the crop. Thus, the application of soil erosion models at high spatial and temporal resolution improves their predicting capability due to the complexity and large number of relevant interactions between the different sub-factors.

Reply to the comment on "Rainfall erosivity in Europe" by Auerswald et al.

PubMed

Panagos, Panos; Meusburger, Katrin; Ballabio, Cristiano; Borrelli, Pasquale; Beguería, Santiago; Klik, Andreas; Rymszewicz, Anna; Michaelides, Silas; Olsen, Preben; Tadić, Melita Perčec; Aalto, Juha; Lakatos, Mónika; Dumitrescu, Alexandru; Rousseva, Svetla; Montanarella, Luca; Alewell, Christine

2015-11-01

Recently, in the Auerswald et al. (2015) comment on "Rainfall erosivity in Europe", 5 criticisms were addressed: i) the neglect of seasonal erosion indices, ii) the neglect of published studies and data, iii) the low temporal resolution of the data, especially of the maximum rain intensity, iv) the use of precipitation data instead of rain data and the subsequent deviation of the R-factor in Germany and Austria compared with previous studies, and v) the differences in considered time periods between countries. We reply as follows: (i) An evaluation of the seasonal erosion index at the European scale is, to our knowledge, not achievable at present with the available data but would be a future goal. Synchronous publication of the seasonal erosion index is not mandatory, specifically because seasonal soil loss ratios are not available at this scale to date. We are looking forward to the appropriate study by the authors of the comment, who assert that they have access to the required data. (ii) We discuss and evaluate relevant studies in our original work and in this reply; however, we cannot consider what is not available to the scientific community. (iii) The third point of critique was based on a misunderstanding by Auerswald et al. (2015), as we did indeed calculate the maximum intensity with the highest resolution of data available. (iv) The low R-factor values in Germany and the higher values in Austria compared with previous studies are not due to the involvement of snow but are rather due to a Pan-European interpolation. We argue that an interpolation across the borders of Austria creates a more reliable data set. (v) We agree that the use of a short time series or time series from different periods is generally a problem in all large-scale studies and requires improvement in the future. However, because this affects countries with a rather low variability of the R-factor in our study, we are confident that the overall results of the map are not biased. In conclusion, the Pan-European rainfall data compilation (REDES) was a great success and yielded data from 1541 stations with an average length of 17.1years and a temporal resolution of <60min. However, a Pan-European data collection will never be complete without the help and supply of data from its users. Thus, we invite the authors of the comment to share their data in the open REDES to help build even better rainfall-erosivity maps at regional or European scales. Copyright © 2015 Elsevier B.V. All rights reserved.

An Establishment of Rainfall-induced Soil Erosion Index for the Slope Land in Watershed

NASA Astrophysics Data System (ADS)

Tsai, Kuang-Jung; Chen, Yie-Ruey; Hsieh, Shun-Chieh; Shu, Chia-Chun; Chen, Ying-Hui

2014-05-01

With more and more concentrated extreme rainfall events as a result of climate change, in Taiwan, mass cover soil erosion occurred frequently and led to sediment related disasters in high intensity precipiton region during typhoons or torrential rain storms. These disasters cause a severely lost to the property, public construction and even the casualty of the resident in the affected areas. Therefore, we collected soil losses by using field investigation data from the upstream of watershed where near speific rivers to explore the soil erosion caused by heavy rainfall under different natural environment. Soil losses induced by rainfall and runoff were obtained from the long-term soil depth measurement of erosion plots, which were established in the field, used to estimate the total volume of soil erosion. Furthermore, the soil erosion index was obtained by referring to natural environment of erosion test plots and the Universal Soil Loss Equation (USLE). All data collected from field were used to compare with the one obtained from laboratory test recommended by the Technical Regulation for Soil and Water Conservation in Taiwan. With MATLAB as a modeling platform, evaluation model for soil erodibility factors was obtained by golden section search method, considering factors contributing to the soil erosion; such as degree of slope, soil texture, slope aspect, the distance far away from water system, topography elevation, and normalized difference vegetation index (NDVI). The distribution map of soil erosion index was developed by this project and used to estimate the rainfall-induced soil losses from erosion plots have been established in the study area since 2008. All results indicated that soil erodibility increases with accumulated rainfall amount regardless of soil characteristics measured in the field. Under the same accumulated rainfall amount, the volume of soil erosion also increases with the degree of slope and soil permeability, but decreases with the shear strength of top soil within 30 cm and the coverage of vegetation. The slope plays more important role than the soil permeability on soil erosion. However, soil losses are not proportional to the hardness of top soil or subsurface soil. The empirical formula integrated with soil erosion index map for evaluating soil erodibility obtained from optimal numerical search method can be used to estimate the soil losses induced by rainfall and runoff erosion on slope land in Taiwan. Keywords: Erosion Test Plot, Soil Erosion, Optimal Numerical Search, Universal Soil Loss Equation.

Effect of biocrust: study of mechanical and hydraulic properties and erodibility

NASA Astrophysics Data System (ADS)

Slavík, Martin; Bruthans, Jiří; Schweigstillová, Jana

2016-04-01

It is well-known that lichens and other organisms forming crust on soil or rock surface play important role in weathering but may also protect underlying material from fast erosion. So far, there have been only few measurements comparing mechanical or hydraulic properties of biocrust with its subsurface on locked sand and friable sandstones, so the overall effect of the biocrust is not well-understood. Objective of our study is to quantify the effect of the biocrust on mechanical and hydraulic properties of friable sandstone and locked sand of Cretaceous age in six different localities with varying aspect and inclination and age of exposure in sandpit Strelec (Czech Rep.). On the artificial exposures, biocrust developed within last 10-30 years. Beside measurements of mechanical and hydraulic properties, SEM and mercury intrusion porosimetry in crust and subsurface was performed. Drilling resistance technique was found an excellent method to distinguish the biocrust from its subsurface (~3 mm thick biocrust has up to 12 times higher drilling resistance than underlying material). Surface zone with the biocrust has 3 - 25 times higher tensile strength than the subsurface material (1 - 25 kPa). In comparison with the subsurface, the biocrust is considerably less erodible (based on water jet testing). Biocrust saturated hydraulic conductivity is 15 - 240 times lower than the subsurface (6*10 -5 - 1*10 -4 m/s) and its permeability for water vapor is 4 - 9 times lower than subsurface. Presence of the biocrust slows down capillary absorption of water 4 - 25 times. The biocrust is thus forming firm surface which protects underlying material from rain and flowing water erosion and which considerably modifies its hydraulic properties. Material with crust exposed to calcination, leaching by concentrated peroxide and experiments with zymoliase enzyme strongly indicate that major contribution to crust hardening is provided by organic matter. Based on DNA sequencing the crust is formed by fungi including components of lichens which differ at individual localities. This research was funded by the Czech Science Foundation (GA CR No. 13-28040S) and Grant Agency of Charles University (No. 386815)

Magnetically triggered dual functional nanoparticles for resistance-free apoptotic hyperthermia.

PubMed

Yoo, Dongwon; Jeong, Heeyeong; Noh, Seung-Hyun; Lee, Jae-Hyun; Cheon, Jinwoo

2013-12-02

Overcoming resistance: Heat-treated cancer cells possess a protective mechanism for resistance and survival. Resistance-free apoptosis-inducing magnetic nanoparticles (RAINs) successfully promote hyperthermic apoptosis, obstructing cell survival by triggering two functional units of heat generation and the release of geldanamycin (GM) for heat shock protein (Hsp) inhibition under an alternating magnetic field (AMF). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A linear relationship between wave power and erosion determines salt-marsh resilience to violent storms and hurricanes

PubMed Central

Leonardi, Nicoletta; Ganju, Neil K.; Fagherazzi, Sergio

2016-01-01

Salt marsh losses have been documented worldwide because of land use change, wave erosion, and sea-level rise. It is still unclear how resistant salt marshes are to extreme storms and whether they can survive multiple events without collapsing. Based on a large dataset of salt marsh lateral erosion rates collected around the world, here, we determine the general response of salt marsh boundaries to wave action under normal and extreme weather conditions. As wave energy increases, salt marsh response to wind waves remains linear, and there is not a critical threshold in wave energy above which salt marsh erosion drastically accelerates. We apply our general formulation for salt marsh erosion to historical wave climates at eight salt marsh locations affected by hurricanes in the United States. Based on the analysis of two decades of data, we find that violent storms and hurricanes contribute less than 1% to long-term salt marsh erosion rates. In contrast, moderate storms with a return period of 2.5 mo are those causing the most salt marsh deterioration. Therefore, salt marshes seem more susceptible to variations in mean wave energy rather than changes in the extremes. The intrinsic resistance of salt marshes to violent storms and their predictable erosion rates during moderate events should be taken into account by coastal managers in restoration projects and risk management plans. PMID:26699461

A linear relationship between wave power and erosion determines salt-marsh resilience to violent storms and hurricanes

USGS Publications Warehouse

Leonardi, Nicoletta; Ganju, Neil K.; Fagherazzi, Sergio

2016-01-01

Salt marsh losses have been documented worldwide because of land use change, wave erosion, and sea-level rise. It is still unclear how resistant salt marshes are to extreme storms and whether they can survive multiple events without collapsing. Based on a large dataset of salt marsh lateral erosion rates collected around the world, here, we determine the general response of salt marsh boundaries to wave action under normal and extreme weather conditions. As wave energy increases, salt marsh response to wind waves remains linear, and there is not a critical threshold in wave energy above which salt marsh erosion drastically accelerates. We apply our general formulation for salt marsh erosion to historical wave climates at eight salt marsh locations affected by hurricanes in the United States. Based on the analysis of two decades of data, we find that violent storms and hurricanes contribute less than 1% to long-term salt marsh erosion rates. In contrast, moderate storms with a return period of 2.5 mo are those causing the most salt marsh deterioration. Therefore, salt marshes seem more susceptible to variations in mean wave energy rather than changes in the extremes. The intrinsic resistance of salt marshes to violent storms and their predictable erosion rates during moderate events should be taken into account by coastal managers in restoration projects and risk management plans.

A linear relationship between wave power and erosion determines salt-marsh resilience to violent storms and hurricanes.

PubMed

Leonardi, Nicoletta; Ganju, Neil K; Fagherazzi, Sergio

2016-01-05

Salt marsh losses have been documented worldwide because of land use change, wave erosion, and sea-level rise. It is still unclear how resistant salt marshes are to extreme storms and whether they can survive multiple events without collapsing. Based on a large dataset of salt marsh lateral erosion rates collected around the world, here, we determine the general response of salt marsh boundaries to wave action under normal and extreme weather conditions. As wave energy increases, salt marsh response to wind waves remains linear, and there is not a critical threshold in wave energy above which salt marsh erosion drastically accelerates. We apply our general formulation for salt marsh erosion to historical wave climates at eight salt marsh locations affected by hurricanes in the United States. Based on the analysis of two decades of data, we find that violent storms and hurricanes contribute less than 1% to long-term salt marsh erosion rates. In contrast, moderate storms with a return period of 2.5 mo are those causing the most salt marsh deterioration. Therefore, salt marshes seem more susceptible to variations in mean wave energy rather than changes in the extremes. The intrinsic resistance of salt marshes to violent storms and their predictable erosion rates during moderate events should be taken into account by coastal managers in restoration projects and risk management plans.

Diamondlike carbon protective coatings for optical windows

NASA Technical Reports Server (NTRS)

Swec, Diane M.; Mirtich, Michael J.

1989-01-01

Diamondlike carbon (DLC) films were deposited on infrared transmitting optical windows and were evaluated as protective coatings for these windows exposed to particle and rain erosion. The DLC films were deposited on zinc selenide (ZnSe) and zinc sulfide (ZnS) by three different ion beam methods: (1) sputter deposition from a carbon target using an 8-cm argon ion source; (2) direct deposition by a 30-cm hollow cathode ion source with hydrocarbon gas in argon; and (3) dual beam direct deposition by the 30-cm hollow cathode ion source and an 8-cm argon ion source. In an attempt to improve the adherence of the DLC films on ZnSc and ZnS, ion beam cleaning, ion implantation with helium and neon ions, or sputter deposition of a thin, ion beam intermediate coating was employed prior to deposition of the DLC film. The protection that the DLC films afforded the windows from particle and rain erosion was evaluated, along with the hydrogen content, adherence, intrinsic stress, and infrared transmittance of the films. Because of the elevated stress levels in the ion beam sputtered DLC films and in those ion beam deposited with butane, films thicker than 0.1 micron and with good adherence on ZnS and ZnSe could not be generated. An intermediate coating of germanium successfully allowed the DLC films to remain adherent to the optical windows and caused only negligible reduction in the specular transmittance of the ZnS and ZnSe at 10 microns.

Analysis and determination of susceptibility Risk from slope instability at Colima State Mexico due to the accelerators factors of rain and seismicity

NASA Astrophysics Data System (ADS)

Ramirez-Ruiz, J. J.

2016-12-01

Slope instability is presented each year in the mountain region of the Colima State, Mexico. It occurs due to the combination of different factors existing in this area as: Precipitation, topography contrast, type and mechanical properties of deposits that constitute the rocks and soils of the region and the erosion due to the elimination of vegetation deck to develop and grow urban areas. To these geological factors we can extend the tectonic activity of the Western part of Mexico that originate high seismicity by the interaction of Cocos plate and North America plate forming the region of Graben de Colima, were is located our study area. Here we will present a Zonification and determination of the Susceptibility maps of slope instability due to the rain and seismicity accelerators factors. The North part of the State Colima is covered by deposits of the Volcan de Colima with an elevation of 3860 masl. It is the area of major precipitation yearly with more than 1200 mm in comparison to the average precipitation of about 900 mm of the State of Colima. Using a SIG system and the mapping of more than 30 sites we realize a zonification and analysis of the Risk using a methodology developed by CENAPRED. The susceptibility map developed in this area in combination with erosion factors permit us to determine an approximation of the Risk considering some limitations that will be present in this study.

Prediction of Rainfall-Induced Landslides

NASA Astrophysics Data System (ADS)

Nadim, F.; Sandersen, F.

2009-12-01

Rainfall-induced landslides can be triggered by two main mechanisms: shear failure due to build-up of pore water pressure and erosion by surface water runoff when flow velocity exceeds a critical value. Field measurements indicate that, in the initial phase, the slip surface of a landslide often occurs along the top of a relatively impermeable layer located at some depth within the soil profile, e.g. at the contact with a shallow underlying bedrock or parent rock. The shear strength along this surface and hence the stability of the slope is governed by the pore water pressure. The pore pressure is in turn controlled by water seepage through the slope, either from infiltrated rain, or from groundwater that follows bedrock joints and soil layers with high permeability. When the infiltration rate of the underlying layer is too low for further downward penetration of water or when a wetting front is produced, pore water pressure builds up, reducing the soil shear strength. During high intensity rainfall, surface water runoff will exert shear stresses on the bed material. De-pending on the grain size distribution and specific gravity of the material, erosion might occur when the flow velocity exceeds a critical value. As erosion progresses and sediment concentration increases, the flow regime may become unstable with heavy erosion at high flow velocity locations triggering a debris flow. In many cases, previous landslides along steep gully walls have fed an abundance of loose soil material into the gullies. Landslides along gully walls that obstruct the water transport may also trigger debris flows when the landslide-dam collapses, creating a surge downstream. Both the long-duration (1 or more days) and short-duration precipitation (of the order of 1 hour) are significant in the triggering of shallow landslides, since the critical short-duration rainfall intensity reduces as the antecedent accumulated rainfall increases. Experiences in Norway indicate that the maxi-mum intensity of rain within a short period of time (1-3 hours) during a storm is most critical for triggering of debris flows. Therefore empirical methods developed for prediction of initiation of debris flows include both long-duration and short-duration rain-fall. More recent research has focused on the spatial distribution of unstable areas and on better spatial resolution of the occurrence of landslide-triggering precipitation events. Spatial distribution can be assessed by analyzing the stability conditions for shallow landslides if reasonable estimates of strength parameters are available. In general, two different approaches may be adopted for the assessment of threshold values for rainfall-induced landslides: empirical methods that are based on past observations and statistical analyses, and numerical analyses that are based on geo-mechanical modelling. The former approach together with very short-term weather forecasting (now-casting) are commonly used in the design of early warning systems for debris flows.

Field Jet Erosion Tests on the Mississippi River Collocated Demonstration Section, Plaquemines Parish, Louisiana

DTIC Science & Technology

2015-06-01

ash/bed-ash blend treatment, and the second segment was constructed of Bonnet Carré clay treated with lime . In addition, a section of untreated clay...on the original levee was also tested. The field JET data showed that the clay treated with lime was categorized as resistant to very resistant. The...treatments reduced the erodibility of the soil. However, the field JET results showed that lime treatment performed better at reducing erosion than the

Comparative proteomic analysis of differentially expressed proteins in β-aminobutyric acid enhanced Arabidopsis thaliana tolerance to simulated acid rain.

PubMed

Liu, Tingwu; Jiang, Xinwu; Shi, Wuliang; Chen, Juan; Pei, Zhenming; Zheng, Hailei

2011-05-01

Acid rain is a worldwide environmental issue that has seriously destroyed forest ecosystems. As a highly effective and broad-spectrum plant resistance-inducing agent, β-aminobutyric acid could elevate the tolerance of Arabidopsis when subjected to simulated acid rain. Using comparative proteomic strategies, we analyzed 203 significantly varied proteins of which 175 proteins were identified responding to β-aminobutyric acid in the absence and presence of simulated acid rain. They could be divided into ten groups according to their biological functions. Among them, the majority was cell rescue, development and defense-related proteins, followed by transcription, protein synthesis, folding, modification and destination-associated proteins. Our conclusion is β-aminobutyric acid can lead to a large-scale primary metabolism change and simultaneously activate antioxidant system and salicylic acid, jasmonic acid, abscisic acid signaling pathways. In addition, β-aminobutyric acid can reinforce physical barriers to defend simulated acid rain stress. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effectiveness Of Miraba an Indigenous Soil and Water Conservation Measures On Reducing Runoff And Soil Loss In Arable Land Of Western Usambara Mountains

NASA Astrophysics Data System (ADS)

Msita, H. B.; Kimaro, D. N.; Mtakwa, P. W.; Msanya, B. M.; Dondyene, S.; Poesen, J.; Deckers, J.

2012-04-01

Soil erosion by water is rampant mainly in mountainous areas of Tanzania leading to environmental hazards, low land productivity, low income and increased poverty. Despite the severity of the soil erosion problem, there is not much quantitative data on the erosion effects and effectiveness of indigenous soil and water conservation (SWC) measures. The consequence is that indigenous knowledge in SWC planning is ignored. The on-farm field experiment was conducted for three years in Migambo village, Lushoto district in Tanzania, to determine the effectiveness of improved Miraba (IM) an indigenous soil erosion control measure on reducing runoff and soil loss. Management practices were tested viz: control that is without any soil conservation measure (C), Miraba alone (M), Miraba with farmyard manure and mulching (MFM) replicated three times in CRD setting. Maize (Zea mays) and beans (Phaseolus vulgaris) were used as test crops, due to their importance as food crops and the high erosion rates on fields with these crops. The crops were planted in rotation, maize and beans in short and long rains respectively. Gerlach troughs and runoff plots were used to evaluate the physical effectiveness. Results show significant effects of IM against control on crop yields, soil loss, surface runoff and moisture retention. MFM is the most effective measure in reducing soil and water losses followed by MF and M. The results further showed that these management practices can be implemented to reduce soil erosion and nutrient losses in the study area and areas with similar ecological setting. To facilitate adoption of these practices further research works is recommended for identifying economically feasible indigenous SWC measures under different biophysical and socio-economic conditions.

Small scale rainfall simulators: Challenges for a future use in soil erosion research

NASA Astrophysics Data System (ADS)

Ries, Johannes B.; Iserloh, Thomas; Seeger, Manuel

2013-04-01

Rainfall simulation on micro-plot scale is a method used worldwide to assess the generation of overland flow, soil erosion, infiltration and interrelated processes such as soil sealing, crusting, splash and redistribution of solids and solutes. The produced data are of great significance not only for the analysis of the simulated processes, but also as a source of input-data for soil erosion modelling. The reliability of the data is therefore of paramount importance, and quality management of rainfall simulation procedure a general responsibility of the rainfall simulation community. This was an accepted outcome at the "International Rainfall Simulator Workshop 2011" at Trier University. The challenges of the present and near future use of small scale rainfall simulations concern the comparability of results and scales, the quality of the data for soil erosion modelling, and further technical developments to overcome physical limitations and constraints. Regarding the high number of research questions, different fields of application, and due to the great technical creativity of researchers, a large number of different types of rainfall simulators is available. But each of the devices produces a different rainfall, leading to different kinetic energy values influencing soil surface and erosion processes. Plot sizes are also variable, as well as the experimental simulation procedures. As a consequence, differing runoff and erosion results are produced. The presentation summarises the three important aspects of rainfall simulations, following a processual order: 1. Input-factor "rain" and its calibration 2. Surface-factor "plot" and its documentation 3. Output-factors "runoff" and "sediment concentration" Finally, general considerations about the limitations and challenges for further developments and applications of rainfall simulation data are presented.

Response of runoff and soil loss to reforestation and rainfall type in red soil region of southern China.

PubMed

Huang, Zhigang; Ouyang, Zhiyun; Li, Fengrui; Zheng, Hua; Wang, Xiaoke

2010-01-01

To evaluate the long-term effects of reforestation types on soil erosion on degraded land, vegetation and soil properties under conventional sloping farmland (CSF) and three different reforestation types including a Pinus massoniana secondary forest (PSF), an Eucommia ulmoides artificial economic forest (EEF) and a natural succession type forest (NST), were investigated at runoff plot scale over a six-year period in a red soil region of southern China. One hundred and thirty erosive rainfall events generating runoff in plots were grouped into four rainfall types by means of K-mean clustering method. Erosive rainfall type I is the dominant rainfall type. The amount of runoff and the soil loss under erosive rainfall type III were the most, followed by rain-fall type II, IV and I. Compared with CSF treatment, reforestation treatments decreased the average annual runoff depth and the soil loss by 25.5%-61.8% and 93.9%-96.2% during the study period respectively. Meanwhile, runoff depth at PSF and EEF treatments was significantly lower than that in NST treatment, but no significant difference existed in soil erosion modulus among the three reforestation treatments. This is mainly due to the improved vegetation properties (i.e., vegetation coverage, biomass of above- and below-ground and litter-fall mass) and soil properties (i.e., bulk density, total porosity, infiltration rate and organic carbon content) in the three reforestation treatments compared to CSF treatment. The PSF and EEF are recommended as the preferred reforestation types to control runoff and soil erosion in the red soil region of southern China, with the NST potentially being used as an important supplement.

Effects of hydrology, watershed size, and agricultural practices on sediment yields in two river basins in Iowa and Mississippi

USGS Publications Warehouse

Merten, Gustavo Henrique; Welch, Heather L.; Tomer, M.D.

2016-01-01

The specific sediment yield (SSY) from watersheds is the result of the balance between natural, scale-dependent erosion and deposition processes, but can be greatly altered by human activities. In general, the SSY decreases along the course of a river as sediments are trapped in alluvial plains and other sinks. However, this relation between SSY and basin area can actually be an increasing one when there is a predominance of channel erosion relative to hillslope erosion. The US Geological Survey (USGS) conducted a study of suspended sediment in the Iowa River basin (IRB), Iowa, and the Yazoo River basin (YRB), Mississippi, from 2006 through 2008. Within each river basin, the SSY from four largely agricultural watersheds of various sizes (2.3 to 35,000 km2 [0.9 to 13,513 mi2]) was investigated. In the smallest watersheds, YRB sites had greater SSY compared to IRB sites due to higher rain erosivity, more erodible soils, more overland flow, and fluvial geomorphological differences. Watersheds in the YRB showed a steady decrease in SSY with increasing drainage basin area, whereas in the IRB, the maximum SSY occurred at the 30 to 500 km2 (11.6 to 193 mi2) scale. Subsurface tile drainage and limits to channel downcutting restrict the upstream migration of sediment sources in the IRB. Nevertheless, by comparing the SSY-basin size scaling relationships with estimated rates of field erosion under conservation and conventional tillage treatments reported in previous literature, we show evidence that the SSY-basin size relationship in both the IRB and YRB remain impacted by historical erosion rates that occurred prior to conservation efforts.

A closer look at the Neogene erosion and accumulation rate increase

NASA Astrophysics Data System (ADS)

Willenbring, J.; von Blanckenburg, F.

2008-12-01

Glacial erosion and Quaternary cold-stage warm-stage climate cycling have been cited as mechanisms to explain observations of increased Neogene marine sedimentation rates. Quantification of long-term glacial erosion rates from cosmogenic radionuclides from large areas mostly covered by cold-based ice during the Quaternary show very low erosion rates over several glacial cycles. In addition, isotope ratio proxies of dissolved metals in seawater, measured in chemical ocean sediments, lack clear evidence for an increase in terrigenous denudation. In particular, the stable isotope 9Be, derived from continental erosion, shows no change in its ratio to meteoric cosmogenic nuclide 10Be, derived from rain over the past 10 My. Radiogenic Pb and Nd isotopes, mainly show a change in the style of denudation from more chemical to more physical processes in the Quaternary. These data are at odds with a suggested increase in marine sedimentation rates during the late Cenozoic. In order to resolve this contradiction we have scrutinized these sedimentation rate calculations from ocean cores to identify whether they might show only apparent increases in the Neogene sections. Potential explanations are that in some cases, measured sediment thicknesses for different time intervals lack corrections for sediment compaction. Compaction of the lower portions of the cores drastically increases the apparent thickness of the more recent (Quaternary) sediment. In addition, sedimentation rates often only appear higher for recent sections in cores due to an artifact of an averaging timescale that decreases up-core. Such an averaging time scale decrease arises from better chronological resolution in recent times (Sadler et al., 1999). Cannibalization of older sediment might add to this effect. Together, these data question a clear, global-scale Quaternary climate-erosion connection that would be unique in Earth's history.

The Effect of pH on Slurry Erosion-Corrosion of Tungsten Carbide Overlays Alloyed with Ru

NASA Astrophysics Data System (ADS)

Nelwalani, Ndivhuwo B.; van der Merwe, Josias W.

2018-02-01

The aim of the study was to determine the effect of Ru additions to WC-Fe overlays when exposed to low pH slurry erosion conditions. These overlays were applied through Plasma Transferred Arc, and the original bulk Ru powder concentrations varied from 0.5 to 5 wt.%. A slurry jet impingement erosion-corrosion test rig was used to evaluate wear, and electrochemical measurements were performed to characterize the corrosion properties. The slurry mixtures contained silica sand and synthetic mine water. The pH was varied between 3 and 6.5 for the slurry erosion tests and lowered further for the corrosion characterization. Samples were examined optically and with a scanning electron microscope using energy-dispersive x-ray spectroscopy. X-ray diffraction analysis was used to determine the phases present. For the slurry erosion-corrosion results at the pH of 6.5, addition of Ru did not show a decrease in erosion-corrosion rates. However, when the pH was decreased to 3, by the addition of HCl, Ru improved the resistance. From the electrochemistry, it was also clear that Ru additions improved the corrosion resistance, but more than 1 wt.% Ru was required. At very low pH levels, the presence of Ru was not able to prevent corrosion.

Correlating Inertial Acoustic Cavitation Emissions with Material Erosion Resistance

NASA Astrophysics Data System (ADS)

Ibanez, I.; Hodnett, M.; Zeqiri, B.; Frota, M. N.

The standard ASTM G32-10 concerns the hydrodynamic cavitation erosion resistance of materials by subjecting them to acoustic cavitation generated by a sonotrode. The work reported extends this technique by detecting and monitoring the ultrasonic cavitation, considered responsible for the erosion process, specifically for coupons of aluminium-bronze alloy. The study uses a 65 mm diameter variant of NPL's cavitation sensor, which detects broadband acoustic emissions, and logs acoustic signals generated in the MHz frequency range, using NPL's Cavimeter. Cavitation readings were made throughout the exposure duration, which was carried out at discrete intervals (900 to 3600 s), allowing periodic mass measurements to be made to assess erosion loss under a strict protocol. Cavitation measurements and erosion were compared for different separations of the sonotrode tip from the material under test. The maximum variation associated with measurement of cavitation level was between 2.2% and 3.3% when the separation (λ) between the transducer horn and the specimen increased from 0.5 to 1.0 mm, for a transducer (sonotrode) displacement amplitude of 43.5 μm. Experiments conducted at the same transducer displacement amplitude show that the mass loss of the specimen -a measure of erosion- was 67.0 mg (λ = 0.5 mm) and 66.0 mg (λ = 1.0 mm).

Effect of micro-particles on cavitation erosion of Ti6Al4V alloy in sulfuric acid solution.

PubMed

Li, D G; Long, Y; Liang, P; Chen, D R

2017-05-01

The influences of micro-particles on ultrasonic cavitation erosion of Ti6Al4V alloy in 0.1M H 2 SO 4 solution were investigated using mass loss weight, scanning electron microscopy (SEM) and white light interferometer. Mass loss results revealed that the cavitation erosion damage obviously decreased with increasing particle size and mass concentration. Open circuit potential recorded during cavitation erosion shifted to positive direction with the decreased mass loss. Meanwhile, the mass loss sharply decreased with applying a positive potential during the entire ultrasonic cavitation erosion, and the relationship between the open circuit potential and the cavitation erosion resistance was discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

Experimental and numerical studies on laser-based powder deposition of slurry erosion resistant materials

NASA Astrophysics Data System (ADS)

Balu, Prabu

Slurry erosion (the removal of material caused by the randomly moving high velocity liquid-solid particle mixture) is a serious issue in crude oil drilling, mining, turbines, rocket nozzles, pumps, and boiler tubes that causes excessive downtime and high operating costs as a result of premature part failure. The goal of this research is to enhance the service life of high-value components subjected to slurry erosion by utilizing the concept of functionally graded metal-ceramic composite material (FGMCCM) in which the favorable properties of metal (toughness, ductility, etc.) and ceramic (hardness) are tailored smoothly to improve erosion resistance. Among the potential manufacturing processes, such as the laser-based powder deposition (LBPD), the plasma transferred arc (PTA), and the thermal spray the LBPD process offers good composition and microstructure control with a high deposition rate in producing the FGMCCM. This research focuses on the development of nickel-tungsten carbide (Ni-WC) based FGMCCM using the LBPD process for applications the above mentioned. The LBPD of Ni-WC involves the introduction of Ni and WC powder particle by an inert gas into the laser-formed molten pool at the substrate via nozzles. The LBPD of Ni-WC includes complex multi-physical interactions between the laser beam, Ni-WC powder, substrate, and carrier and shielding gases that are governed by a number of process variables such as laser power, scanning speed, and powder flow rate. In order to develop the best Ni-WC based slurry erosion resistant material using the LBPD process, the following challenges associated with the fabrication and the performance evaluation need to be addressed: 1) flow behavior of the Ni-WC powder and its interaction with the laser, 2) the effect of the process variables, the material compositions, and the thermo-physical properties on thermal cycles, temperature gradient, cooling rate, and residual stress formation within the material and the subsequent cracking issue, and 3) the effect of composition and composition gradient of Ni and WC on the slurry erosion resistance over a wide range of erosion conditions. This thesis presents a set of numerical and experimental methods in order to address the challenges mentioned above. A three-dimensional (3-D) computational fluid dynamics (CFD) based powder flow model and three vision based techniques were developed in order to visualize the process of feeding the Ni-WC powder in the LBPD process. The results provide the guidelines for efficiently feeding the Ni-WC composite powder into the laser-formed molten pool. The finite element (FE) based experimentally verified 3-D thermal and thermo-mechanical models are developed in order to understand the thermal and stress evolutions in Ni-WC composite material during the LBPD process. The models address the effect of the process variables, preheating temperature, and different mass fractions of WC in Ni on thermal cycles and stress distributions within the deposited material. The slurry erosion behavior of the single and multilayered deposits of Ni-WC composite material produced by the LBPD process is investigated using an accelerated slurry erosion testing machine and a 3-D FE dynamic model. The verified model is used to identify the appropriate composition and composition gradient of Ni-WC composite material required to achieve erosion resistance over a wide range of erosion conditions.

Lithologic controls on valley width and strath terrace formation

NASA Astrophysics Data System (ADS)

Schanz, Sarah A.; Montgomery, David R.

2016-04-01

Valley width and the degree of bedrock river terrace development vary with lithology in the Willapa and Nehalem river basins, Pacific Northwest, USA. Here, we present field-based evidence for the mechanisms by which lithology controls floodplain width and bedrock terrace formation in erosion-resistant and easily friable lithologies. We mapped valley surfaces in both basins, dated straths using radiocarbon, compared valley width versus drainage area for basalt and sedimentary bedrock valleys, and constructed slope-area plots. In the friable sedimentary bedrock, valleys are 2 to 3 times wider, host flights of strath terraces, and have concavity values near 1; whereas the erosion-resistant basalt bedrock forms narrow valleys with poorly developed, localized, or no bedrock terraces and a channel steepness index half that of the friable bedrock and an average channel concavity of about 0.5. The oldest dated strath terrace on the Willapa River, T2, was active for nearly 10,000 years, from 11,265 to 2862 calibrated years before present (cal YBP), whereas the youngest terrace, T1, is Anthropocene in age and recently abandoned. Incision rates derived from terrace ages average 0.32 mm y- 1 for T2 and 11.47 mm y- 1 for T1. Our results indicate bedrock weathering properties influence valley width through the creation of a dense fracture network in the friable bedrock that results in high rates of lateral erosion of exposed bedrock banks. Conversely, the erosion-resistant bedrock has concavity values more typical of detachment-limited streams, exhibits a sparse fracture network, and displays evidence for infrequent episodic block erosion and plucking. Lithology thereby plays a direct role on the rates of lateral erosion, influencing valley width and the potential for strath terrace planation and preservation.

Study on erosion behaviour of hybrid aluminium composite

NASA Astrophysics Data System (ADS)

Vishwas, D. K.; Chandrappa, C. N.; Venkatesh, Shreyas

2018-04-01

The origin of the light metals, as compared to other metals in this century, is noticeable and an exciting area of expansion for innovation. Light metals, are need of the day in engineering, among them application of aluminium and its alloys is enormous. we observe that these metals tend to have a progressive loss of metal from having contact surface with other metals. Erosion is one such wear process, where damage occurs by the repeated application of high localised stresses. Erosion due to impact of solid particle, is a significant problem. In the present work, the erosion behaviour of hybrid aluminium composite is studied. AL 6061 is used as the base alloy. AL 6061 alloy has excellent corrosion resistance but poor wear resistance. So, in order to have improved properties, it is reinforced with Tungsten Chromium Nickel powder in varied proportions by the method of stir casting. The results are compared with the as-cast Al-alloy to determine the improvement in mechanical properties. The tests were conducted in ASTM G76 setup, to determine solid particle erosion behaviour and the results of the hybrid composite were compared with that of as-cast AL 6061 alloy. It was evident that mass loss was maximum at 300 inclinations, which is a characteristic of ductile materials. It was observed that upon increasing the percentages of reinforcement (wt.%), the wear resistance of the hybrid composite increased significantly. It was also observed that the inclusion of tungsten-chromium-nickel powder increased the hardness of the hybrid composite significantly.

Preparation of high-content hexagonal boron nitride composite film and characterization of atomic oxygen erosion resistance

NASA Astrophysics Data System (ADS)

Zhang, Yu; Li, Min; Gu, Yizhuo; Wang, Shaokai; Zhang, Zuoguang

2017-04-01

Space aircrafts circling in low earth orbit are suffered from highly reactive atomic oxygen (AO). To shield AO, a flexible thin film with 80 wt.% hexagonal boron nitride (h-BN) and h-BN/epoxy film were fabricated through vacuum filtration and adding nanofibrillated cellulose fibers. H-BN nanosheets were hydroxylated for enhancing interaction in the films. Mass loss and erosion yield at accumulated AO fluence about 3.04 × 1020 atoms/cm2 were adopted to evaluate the AO resistance properties of the films. A carpet-like rough surface, chemical oxidations and change in crystal structure of h-BN were found after AO treatment, and the degrading mechanism was proposed. The mass loss and erosion yield under AO attack were compared between h-BN film and h-BN/epoxy film, and the comparison was also done for various types of shielding AO materials. Excellent AO resistance property of h-BN film is shown, and the reasons are analyzed.

Effect of Spray Particle Velocity on Cavitation Erosion Resistance Characteristics of HVOF and HVAF Processed 86WC-10Co4Cr Hydro Turbine Coatings

NASA Astrophysics Data System (ADS)

Kumar, R. K.; Kamaraj, M.; Seetharamu, S.; Pramod, T.; Sampathkumaran, P.

2016-08-01

The hydro plants utilizing silt-laden water for power generation suffer from severe metal wastage due to particle-induced erosion and cavitation. High-velocity oxy-fuel process (HVOF)-based coatings is widely applied to improve the erosion life. The process parameters such as particle velocity, size, powder feed rate, temperature, affect their mechanical properties. The high-velocity air fuel (HVAF) technology, with higher particle velocities and lower spray temperatures, gives dense and substantially nonoxidized coating. In the present study, the cavitation resistance of 86WC-10Co4Cr-type HVOF coating processed at 680 m/s spray particle velocity was compared with HVAF coatings made at 895, 960, and 1010 m/s. The properties such as porosity, hardness, indentation toughness, and cavitation resistance were investigated. The surface damage morphology has been analyzed in SEM. The cohesion between different layers has been examined qualitatively through scratch depth measurements across the cross section. The HVAF coatings have shown a lower porosity, higher hardness, and superior cavitation resistance. Delamination, extensive cracking of the matrix interface, and detachment of the WC grains were observed in HVOF coating. The rate of metal loss is low in HVAF coatings implying that process parameters play a vital role in achieving improved cavitation resistance.

Formation of protective deposits by anti-erosive toothpastes-A microscopic study on enamel with artificial defects.

PubMed

Bradna, Pavel; Vrbova, Radka; Fialova, Vlasta; Housova, Devana; Gojisova, Eva

2016-09-01

This study investigated formation of protective deposits on the enamel surface after application of several anti-erosive toothpastes with different active ingredients. NaF-containing Sensodyne Pronamel, SnCl 2 /F-based Elmex Erosion Protection and calcium phosphate-based BioRepair Plus Sensitivity Control, SensiShield and Enamel Care toothpastes with claimed anti-erosive properties were tested. Artificial saliva and Elmex Erosion Protection mouth rinse served as control groups. The toothpastes were applied 30 times by a toothbrush for 2 min per day, mouth rinse for 30 s on polished enamel of thirty five human molars (n = 5) with series of five rhomboid-shaped indents of various length prepared by a Knoop indentor. After 15 and 30 applications, the shape of the indents and surface morphology was characterised using light and scanning electron microscopy. At the end of treatment, the samples were exposed to 0.2 wt. % citric acid (pH 3.30) to test resistance of the treated enamel to erosion. Pronounced differences were observed between protective properties of the toothpastes. While Sensodyne Pronamel and BioRepair Plus Sensitivity Control did not produce any protective deposits, Enamel Care formed a compact layer of deposits which protected the enamel surface against erosion. With Elmex Erosion Protection and SensiShield fractured indent edges and scratches on the treated enamel suggested that their abrasive properties prevailed over ability of active ingredients to form deposits. These results revealed that toothpastes with strong potential to form acid-resistant deposits on the enamel surface and of low abrasivity should be used for effective prevention of enamel erosion. SCANNING 38:380-388, 2016. © 2015 Wiley Periodicals, Inc. © Wiley Periodicals, Inc.

Efficacy of Natural Polymer Derivatives on Soil Physical Properties and Erosion on an Experimental Loess Hillslope.

PubMed

Liu, Jun'e; Wang, Zhanli; Li, Yuanyuan

2017-12-22

Raindrops disperse large soil aggregates into smaller particles, which can clog soil pores, cause soil crusting, reduce rainfall infiltration and increase soil loss. It was found that natural polymer derivatives were effective in improving soil physical properties and decreasing soil erosion on an experimental loess hillslope. This study investigated the effect of new natural polymer derivatives (Jag S and Jag C162) on soil properties, rainfall infiltration and sediment yield at four rates of sprayed polymers (0, 1, 3 and 5 g/m²), three rainfall intensities (1, 1.5 and 2 mm/min) and a slope gradient of 15° with a silt loam soil through simulated rain. The results showed that both Jag S and Jag C162 significantly increased the shear strength and improved the aggregates composition of the soil surface. The water-stable soil aggregates >0.25 mm increased from 9% to 50% with increasing rates of Jag S and Jag C162. Jag S and Jag C162 also effectively increased rainfall infiltration and final infiltration rate, and reduced erosion compared to controls without natural polymer derivatives added. However, higher rates of Jag S produced lower infiltration rates. Although both Jag S and Jag C162 effectively influenced soil physical properties and erosion, the effect of Jag C162 was more significant than that of Jag S.

Soil Erosion Study on the Chinese Loess Plateau

NASA Astrophysics Data System (ADS)

Hu, Yaxian; Guo, Shengli; Kuhn, Nikolaus

2017-04-01

The Chinese Loess Plateau, because of its highly erodible loess soils and hilly topography, has been extensively studied by soil scientists and geomorphologists. As a research hotspot, there are five national-level field stations across the Loess Plateau, with hundreds of erosion plots set up with various sizes, lengths, slope angles and vegetation covers. In addition, huge indoor rain simulation facilities exist in in different institutes which can provide rainfall simulations under a wide range of controlled conditions. Consequently, national-level restoration projects have achieved tremendous improvements in curbing soil erosion and improving regional agro-ecosystem, mostly by afforestation and soil rehabilitation. However, when implementing the advanced techniques and models that have been widely applied in the rest of the world, there are often regional considerations, which demand new approaches to overcome. One example are the unintentional impacts of restoration efforts, such as the establishment of apple orchards. Over 20 years, they have caused an increase in soil erodibility and lowered local ground water levels. Neither before the introduction of this landscape rehabilitation technique, nor now, has the impact of intensive fruit production been systematically studied, despite lending itself to systematic experiments. The lack of research is attributed to the general idea that trees protect soils and improve environmental services. This presentation identifies several such specific regional environmental issues associated with soil erosion on the Loess Plateau and discusses strategies to avoid missing important research questions.

Efficacy of Natural Polymer Derivatives on Soil Physical Properties and Erosion on an Experimental Loess Hillslope

PubMed Central

Liu, Jun’e; Wang, Zhanli; Li, Yuanyuan

2017-01-01

Raindrops disperse large soil aggregates into smaller particles, which can clog soil pores, cause soil crusting, reduce rainfall infiltration and increase soil loss. It was found that natural polymer derivatives were effective in improving soil physical properties and decreasing soil erosion on an experimental loess hillslope. This study investigated the effect of new natural polymer derivatives (Jag S and Jag C162) on soil properties, rainfall infiltration and sediment yield at four rates of sprayed polymers (0, 1, 3 and 5 g/m2), three rainfall intensities (1, 1.5 and 2 mm/min) and a slope gradient of 15° with a silt loam soil through simulated rain. The results showed that both Jag S and Jag C162 significantly increased the shear strength and improved the aggregates composition of the soil surface. The water-stable soil aggregates >0.25 mm increased from 9% to 50% with increasing rates of Jag S and Jag C162. Jag S and Jag C162 also effectively increased rainfall infiltration and final infiltration rate, and reduced erosion compared to controls without natural polymer derivatives added. However, higher rates of Jag S produced lower infiltration rates. Although both Jag S and Jag C162 effectively influenced soil physical properties and erosion, the effect of Jag C162 was more significant than that of Jag S. PMID:29271899

A lichen protected by a super-hydrophobic and breathable structure.

PubMed

Shirtcliffe, Neil J; Brian Pyatt, F; Newton, Michael I; McHale, Glen

2006-11-01

A species of lichen, Lecanora conizaeoides, is shown to be super-hydrophobic. It uses a combination of hydrophobic compounds and multi-layered roughness to shed water effectively. This is combined with gas channels to produce a biological analogue of a waterproof, breathable garment. The particular lichen grows mostly during wet seasons and is unusually resistant to acid rain [Hauck, M., 2003. The Bryologist 106(2), 257-269; Honegger, R., 1998. Lichenologist 30(3),193-212]. The waterproof, breathable surface allows this lichen to photosynthesise when other species are covered with a layer of water. In addition, rainwater runs off the surface of the organism, reducing its intake of water from above and probably contributing to its resistance to acid rain.

A laboratory rainfall simulator to study the soil erosion and runoff water

NASA Astrophysics Data System (ADS)

Cancelo González, Javier; Rial, M. E.; Díaz-Fierros, Francisco

2010-05-01

The soil erosion and the runoff water composition in some areas affected by forest fires or submitted to intensive agriculture are an important factor to keep an account, particularly in sensitive areas like estuary and rias that have a high importance in the socioeconomic development of some regions. An understanding of runoff production indicates the processes by which pollutants reach streams and also indicates the management techniques that might be uses to minimize the discharge of these materials into surface waters. One of the most methodology implemented in the soil erosion studies is a rainfall simulation. This method can reproduce the natural soil degradation processes in field or laboratory experiences. With the aim of improve the rainfall-runoff generation, a laboratory rainfall simulator which incorporates a fan-like intermittent water jet system for rainfall generation were modified. The major change made to the rainfall simulator consist in a system to coupling stainless steel boxes, whose dimensions are 12 x 20 x 45 centimeters, and it allows to place soil samples under the rainfall simulator. Previously these boxes were used to take soil samples in field with more of 20 centimeters of depth, causing the minimum disturbance in their properties and structure. These new implementations in the rainfall simulator also allow collect water samples of runoff in two ways: firstly, the rain water that constituted the overland flow or direct runoff and besides the rain water seeps into the soil by the process of infiltration and contributed to the subsurface runoff. Among main the variables controlled in the rainfall simulations were the soil slope and the intensity and duration of rainfall. With the aim of test the prototype, six soil samples were collected in the same sampling point and subjected to rainfall simulations in laboratory with the same intensity and duration. Two samples will constitute the control test, and they were fully undisturbed, and four samples were subjected to controlled burnings with different fire severity: two samples burnt to 250°C and the other two samples burnt to 450°C. Preliminary laboratory data of soil erosion and surface and subsurface runoff were obtained. The water parameters analysed were: pH, electrical conductivity, temperature (in the moment of sampling) and suspended sediments, ammonium, nitrates, total nitrogen (Kjeldahl method), within 24 hours after sampling.

The use of Rz roughness parameter for evaluation of materials behavior to cavitation erosion

NASA Astrophysics Data System (ADS)

Bordeasu, I.; Popoviciu, M. O.; Ghera, C.; Micu, L. M.; Pirvulescu, L. D.; Bena, T.

2018-01-01

It is well known that the cavitation eroded surfaces have a porous appearance with a pronounced roughness. The cause is the pitting resulted from the impact with the micro jets as well as the shock waves both determined by the implosion of cavitation bubbles. The height and the shape of roughness is undoubtedly an expression of the resistance of the surface to the cavitation stresses. The paper put into evidence the possibility of using the roughness parameter Rz for estimating the material resistance to cavitation phenomena. For this purpose, the mean depth erosion penetration (MDE-parameter, recommended by the ASTM G32-2010 Standard) was compared with the roughness of three different materials (an annealed bronze, the same bronze subjected to quenching and an annealed alloyed steel), both measured at four cavitation erosion exposure (30, 75, 120 and 165 minutes). The roughness measurements were made in 18 different zones, disposed after two perpendicular diameters, along a measuring lengths of 4 mm. The results confirm the possibility of using the parameter Rz for estimating the cavitation erosion resistance of a material. The differences between the measured values of Rz and those of the characteristic parameter MDE are of the same order of magnitude as those obtained for MDE determination, using more samples of the same material.

Suppression Effect and Mechanism of Platinum and Nitrogen-Containing Silane on the Tracking and Erosion of Silicone Rubber for High-Voltage Insulation.

PubMed

Chen, Wan Juan; Zeng, Xingrong; Lai, Xuejun; Li, Hongqiang; Fang, Wei Zhen; Hou, Fei

2016-08-17

How to effectively improve the tracking and erosion resistance of silicone rubber (SR) was an urgent topic in the field of high-voltage insulation. In this work, the tracking and erosion resistance of SR was significantly improved by incorporating platinum (Pt) catalyst and nitrogen-containing silane (NS). The suppression effect and mechanism of Pt/NS on tracking and erosion were studied by inclined plane (IP) test, thermogravimetry (TG), thermogravimetry-Fourier transform infrared spectrometry, laser Raman spectroscopy, and scanning electron microscopy. It revealed that when 1.4 phr of NS and 6.7 ppm of Pt were added, the tracking resistance of SR was improved from 2.5 to 4.5 kV level in the IP test, and the eroded mass was significantly reduced. This might be attributed to the synergistic effect of Pt/NS on silicone chains. At a high temperature produced by arc discharge, Pt/NS would catalyze radical cross-linking, meanwhile suppressing oxidation and depolymerization of silicone chains. Hence, a tightly cross-linked network was formed and protected inner materials from arc ablation. Moreover, carbon deposit during pyrolysis was suppressed by Pt/NS, which served as the secondary mechanism of tracking suppression.

Genetic erosion in wild populations makes resistance to a pathogen more costly.

PubMed

Luquet, Emilien; Garner, Trenton W J; Léna, Jean-Paul; Bruel, Christophe; Joly, Pierre; Lengagne, Thierry; Grolet, Odile; Plénet, Sandrine

2012-06-01

Populations that have suffered from genetic erosion are expected to exhibit reduced average trait values or decreased variation in adaptive traits when experiencing periodic or emergent stressors such as infectious disease. Genetic erosion may consequentially modify the ability of a potential host population to cope with infectious disease emergence. We experimentally investigate this relationship between genetic variability and host response to exposure to an infectious agent both in terms of susceptibility to infection and indirect parasite-mediated responses that also impact fitness. We hypothesized that the deleterious consequences of exposure to the pathogen (Batrachochytrium dendrobatidis) would be more severe for tadpoles descended from European treefrog (Hyla arborea) populations lacking genetic variability. Although all exposed tadpoles lacked detectable infection, we detected this relationship for some indirect host responses, predominantly in genetically depleted animals, as well as an interaction between genetic variability and pathogen dose on life span during the postmetamorphic period. Lack of infection and a decreased mass and postmetamorphic life span in low genetic diversity tadpoles lead us to conclude that genetic erosion, while not affecting the ability to mount effective resistance strategies, also erodes the capacity to invest in resistance, increased tadpole growth rate, and metamorphosis relatively simultaneously. © 2012 The Author(s). Evolution © 2012 The Society for the Study of Evolution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gordon, A.; Suzuki, D.

The authors of this book warn us of the transition we will need to make if we are to arrive safely in the next century. They have written a book about us as a species: our shortsightedness, our failure to read the warnings, our inability of grasp the significance of our actions. The power of the book lies in the consensus of the many voices, those of scientists and other scholars, that speak through it. The components of our predicament global warming, soil erosion, acid rain, species depletion, ozone damage, rainforest destruction, overpopulation are quantified with authority.

Advances in the application of holography for NDE

NASA Astrophysics Data System (ADS)

Sciammarella, C. A.

1985-01-01

The basic methodology of holographic interferometry in nondestructive testing (NDT) applications are described. Applications to crack detection in ceramic materials, including a crack 50 microns deep in a turbine blade, are discussed in detail. The theoretical principles of holographic interferometry are explained, and a general description of a holographic interferometric recording system is given. A nondestructive interferometric technique for measuring the gradual erosion of calcareous stones exposed to acid rain is also presented. Detailed line drawings illustrating the hologram recording and interferometric fringe pattern analysis elements in an interferometric holographic NDT device are provided.

Bayesian analysis for erosion modelling of sediments in combined sewer systems.

PubMed

Kanso, A; Chebbo, G; Tassin, B

2005-01-01

Previous research has confirmed that the sediments at the bed of combined sewer systems are the main source of particulate and organic pollution during rain events contributing to combined sewer overflows. However, existing urban stormwater models utilize inappropriate sediment transport formulas initially developed from alluvial hydrodynamics. Recently, a model has been formulated and profoundly assessed based on laboratory experiments to simulate the erosion of sediments in sewer pipes taking into account the increase in strength with depth in the weak layer of deposits. In order to objectively evaluate this model, this paper presents a Bayesian analysis of the model using field data collected in sewer pipes in Paris under known hydraulic conditions. The test has been performed using a MCMC sampling method for calibration and uncertainty assessment. Results demonstrate the capacity of the model to reproduce erosion as a direct response to the increase in bed shear stress. This is due to the model description of the erosional strength in the deposits and to the shape of the measured bed shear stress. However, large uncertainties in some of the model parameters suggest that the model could be over-parameterised and necessitates a large amount of informative data for its calibration.

Steady evolution of hillslopes in layered landscapes: self-organization of a numerical hogback

NASA Astrophysics Data System (ADS)

Glade, R.; Anderson, R. S.

2017-12-01

Landscapes developed in layered sedimentary or igneous rocks are common across Earth, as well as on other planets. Features such as hogbacks, exposed dikes, escarpments and mesas exhibit resistant rock layers in tilted, vertical, or horizontal orientation­s adjoining more erodible rock. Hillslopes developed in the erodible rock are typically characterized by steep, linear-to-concave slopes or "ramps" mantled with material derived from the resistant layers, often in the form of large blocks. Our previous work on hogbacks has shown that feedbacks between weathering and transport of the blocks and underlying soft rock are fundamental to their formation; our numerical model incorporating these feedbacks explain the development of commonly observed concave-up slope profiles in the absence of rilling processes. Here we employ an analytic approach to describe the steady behavior of our model, in which hillslope form and erosion rates remain constant in the reference frame of the retreating feature. We first revisit a simple geometric analysis that relates structural dip to erosion rates. We then explore the mechanisms by which our numerical model of hogback evolution self-organizes to meet these geometric expectations. Autogenic adjustment of soil depth, slope and erosion rates enables efficient transport of resistant blocks; this allows erosion of the resistant layer to keep up with base level fall rate, leading to steady evolution of the feature. Analytic solutions relate easily measurable field quantities such as ramp length, slope, block size and resistant layer dip angle to local incision rate, block velocity, and block weathering rate. These equations provide a framework for exploring the evolution of layered landscapes, and pinpoint the processes for which we require a more thorough understanding to predict the evolution of such signature landscapes over time.

Solid impingement erosion mechanisms and characterization of erosion resistance of ductile metals

NASA Technical Reports Server (NTRS)

Rao, V. P.; Buckley, D. H.

1982-01-01

Experimental results pertaining to spherical glass bead and angular crushed glass particle impingement are presented. A concept of energy adsorption to explain the failure of material is proposed. The erosion characteristics of several pure metals were correlated with the proposed energy parameters and with other properties. Correlations of erosion and material properties were also carried out with these materials to study the effect of the angle of impingement. Analyses of extensive erosion data indicate that surface energy, strain energy, melting point, bulk modulus, hardness, ultimate resilience, atomic volume and product of linear coefficient of thermal expansion, bulk modulus, and temperature rise required for melting, and ultimate resilience, and hardness exhibit the best correlations. It appears that both energy and thermal properties contribute to the total erosion.

Initial hydrologic and geomorphic response following a wildfire in the Colorado front range

USGS Publications Warehouse

Moody, J.A.; Martin, D.A.

2001-01-01

A wildfire in May 1996 burned 4690 hectares in two watersheds forested by ponderosa pine and Douglas fir in a steep, mountainous landscape with a summer, convective thunderstorm precipitation regime. The wildfire lowered the erosion threshold in the watersheds, and consequently amplified the subsequent erosional response to shorter time interval episodic rainfall and created both erosional and depositional features in a complex pattern throughout the watersheds. The initial response during the first four years was an increase in runoff and erosion rates followed by decreases toward pre-fire rates. The maximum unit-area peak discharge was 24 m3 s-1 km-2 for a rainstorm in 1996 with a rain intensity of 90 mm h-1. Recovery to pre-fire conditions seems to have occured by 2000 because for a maximum 30-min rainfall intensity of 50 mm h-1, the unit-area peak discharge in 1997 was 6.6 m3 s-1 km-2, while in 2000 a similar intensity produced only 0.11 m3 s-1 km-2. Rill erosion accounted for 6 per cent, interrill erosion for 14 per cent, and drainage erosion for 80 per cent of the initial erosion in 1996. This represents about a 200-fold increase in erosion rates on hillslopes which had a recovery or relaxation time of about three years. About 67 per cent of the initially eroded sediment is still stored in the watersheds after four years with an estimated residence time greater than 300 years. This residence time is much greater than the fire recurrence interval so erosional and depositional features may become legacies from the wildfire and may affect landscape evolution by acting as a new set of initial conditions for subsequent wildfire and flood sequences. Published in 2001 by John Wiley and Sons, Ltd.

Based on the rainfall system platform raindrops research and analysis of pressure loss

NASA Astrophysics Data System (ADS)

Cao, Gang; Sun, Jian

2018-01-01

With the rapid development of China’s military career, land, sea and air force all services and equipment of modern equipment need to be in the rain test, and verify its might suffer during transportation, storage or use a different environment temperature lower water or use underwater, the water is derived from the heavy rain, the wind and rain, sprinkler system, splash water, water wheel, a violent shock waves or use underwater, etcTest the product performance and quality, under the condition of rainfall system platform in the process of development, how to control the raindrops pressure loss becomes the key to whether the system can simulate the real rainfall [1], this paper is according to the rainfall intensity, nozzle flow resistance, meet water flow of rain pressure loss calculation and analysis, and system arrangement of the optimal solution of rainfall is obtained [2].

Erosion resistant nozzles for laser plasma extreme ultraviolet (EUV) sources

DOEpatents

Kubiak, Glenn D.; Bernardez, II, Luis J.

2000-01-04

A gas nozzle having an increased resistance to erosion from energetic plasma particles generated by laser plasma sources. By reducing the area of the plasma-facing portion of the nozzle below a critical dimension and fabricating the nozzle from a material that has a high EUV transmission as well as a low sputtering coefficient such as Be, C, or Si, it has been shown that a significant reduction in reflectance loss of nearby optical components can be achieved even after exposing the nozzle to at least 10.sup.7 Xe plasma pulses.

Weather resistance of CaSO4 ṡ 1/2H2O-based sand-fixation material

NASA Astrophysics Data System (ADS)

Liu, Xin; Tie, Shengnian

2017-07-01

Searching for an economical and effective sand-fixing material and technology is of great importance in Northwest China. This paper described the use of a semihydrated gypsum-(CaSO4 ṡ 1/2H2O-)based composite as a sand-fixing material. Its morphology and composition were characterized by SEM, and its water resistance, freezing-thawing resistance and wind erosion resistance were tested in the field. The results indicated that semihydrated gypsum-(CaSO4 ṡ 1/2H2O-)based sand-fixing composite has good water resistance and water-holding capacity. Its strength is maintained at 1.42 MPa after 50 freezing and thawing cycles, and its wind erosion increases with increasing wind speed and slope. Its compressive strength starts to decrease after nine months of field tests with no change in appearance, but it still satisfies the requirements of fixation technology. This sand-fixing material should have wide application owing to its good weather resistance.

Quaternary bedrock erosion and landscape evolution in the Sør Rondane Mountains, East Antarctica: Reevaluating rates and processes

NASA Astrophysics Data System (ADS)

Matsuoka, Norikazu; Thomachot, Céline E.; Oguchi, Chiaki T.; Hatta, Tamao; Abe, Masahiro; Matsuzaki, Hiroyuki

2006-11-01

Rates and processes of rock weathering, soil formation, and mountain erosion during the Quaternary were evaluated in an inland Antarctic cold desert. The fieldwork involved investigations of weathering features and soil profiles for different stages after deglaciation. Laboratory analyses addressed chemistry of rock coatings and soils, as well as 10Be and 26Al exposure ages of the bedrock. Less resistant gneiss bedrock exposed over 1 Ma shows stone pavements underlain by in situ produced silty soils thinner than 40 cm and rich in sulfates, which reflect the active layer thickness, the absence of cryoturbation, and the predominance of salt weathering. During the same exposure period, more resistant granite bedrock has undergone long-lasting cavernous weathering that produces rootless mushroom-like boulders with a strongly Fe-oxidized coating. The red coating protects the upper surface from weathering while very slow microcracking progresses by the growth of sulfates. Geomorphological evidence and cosmogenic exposure ages combine to provide contrasting average erosion rates. No erosion during the Quaternary is suggested by a striated roche moutonnée exposed more than 2 Ma ago. Differential erosion between granite and gneiss suggests a significant lowering rate of desert pavements in excess of 10 m Ma - 1 . The landscape has been (on the whole) stable, but the erosion rate varies spatially according to microclimate, geology, and surface composition.

Ultrasonic cavitation erosion-corrosion behavior of friction stir processed stainless steel.

PubMed

Selvam, Karthikeyan; Mandal, Priya; Grewal, Harpreet Singh; Arora, Harpreet Singh

2018-06-01

Cavitation erosion remains the primary cause of material degradation in fluid machinery components operating at high speed. Micro-jets/shock waves caused by implosion of bubbles on material surface results in significant material loss and premature failure of the components. The presence of corrosive medium further exuberates this effect, causing rapid degradation. Here, we demonstrate a novel pathway to control cavitation erosion-corrosion by tailoring the surface properties using submerged friction stir processing (FSP), a severe plastic deformation process. FSP parameters were varied over wide range of strain-rates to generate tailored microstructures. High strain-rate processing resulted in nearly single phase fine grained structure while low strain-rate processing resulted in phase transformation in addition to grain refinement. As-received and processed samples were subjected to ultrasonic cavitation in distilled water as well as in corrosive environment of 3.5% NaCl solution. Individual roles of cavitation erosion, corrosion and their synergistic effects were analyzed. Depending on the microstructure, processed samples showed nearly 4-6 times higher cavitation erosion resistance compared to as-received alloy. Superior cavitation erosion-corrosion resistance of processed samples was attributed to surface strengthening, higher strain-hardening ability and quick passivation kinetics. The results of current study could be potentially transformative in designing robust materials for hydro-dynamic applications. Copyright © 2018 Elsevier B.V. All rights reserved.

Ultrasonic cavitation erosion of 316L steel weld joint in liquid Pb-Bi eutectic alloy at 550°C.

PubMed

Lei, Yucheng; Chang, Hongxia; Guo, Xiaokai; Li, Tianqing; Xiao, Longren

2017-11-01

Liquid lead-bismuth eutectic alloy (LBE) is applied in the Accelerator Driven transmutation System (ADS) as the high-power spallation neutron targets and coolant. A 19.2kHz ultrasonic device was deployed in liquid LBE at 550°C to induce short and long period cavitation erosion damage on the surface of weld joint, SEM and Atomic force microscopy (AFM) were used to map out the surface properties, and Energy Dispersive Spectrometer (EDS) was applied to the qualitative and quantitative analysis of elements in the micro region of the surface. The erosion mechanism for how the cavitation erosion evolved by studying the element changes, their morphology evolution, the surface hardness and the roughness evolution, was proposed. The results showed that the pits, caters and cracks appeared gradually on the erode surface after a period of cavitation. The surface roughness increased along with exposure time. Work hardening by the bubbles impact in the incubation stage strengthened the cavitation resistance efficiently. The dissolution and oxidation corrosion and cavitation erosion that simultaneously happened in liquid LBE accelerated corrosion-erosion process, and these two processes combined to cause more serious damage on the material surface. Contrast to the performance of weld metal, base metal exhibited a much better cavitation resistance. Copyright © 2017. Published by Elsevier B.V.

Decision Theories used in Areas Planning around La Colacha Basin (Cordoba, Argentina) considering Natural and Human Hazards

NASA Astrophysics Data System (ADS)

Antón, Jose M.; Grau, Juan B.; Tarquis, A. M.; Cisneros, Jose M.; Andina, Diego

2010-05-01

The authors of U.P.M. have had relations with Argentine Universities and Administrations, in part with J.M.Cisneros that is Professor at Universidad Nacional de Rio Cuarto in Prov. de Córdoba Arg., and have applied Decision Theories with Mathematic tools for the planning of defences and uses of soils in these areas and especially of La Colacha bassin enlarged with larger areas around it as "Cuenca de los Arroyos Menores" at West and South of Rio Cuarto. These large flat lands have loess soils brought by winds from Los Andes that are much far at West, there is a very old line of not high mountains at West near the study area from which rivers flow with little slopes to somehow lower flat areas at West with some marshes. Rivers through loess get regressive erosions with rains forming kilometres long ditches in the loess called "cárcavas" some meters deep and quite large across otherwise flat agricultural lands, and J.M. Cisneros, that has numerous publications about local soil uses, has directed diverse genie rural works to halt the regression of some of them. Part of the study is about protection against floods and "cárcavas". There are famous experiences and records of higher inundations of large areas by rivers. Latitude of Rio Cuarto is 31°25' South, that area is temperate refreshed by south winds, Zonda föhn winds from West being hotter and drier, and there are monsoons and so winter in July is dry and summer and December has rains, that average 829mm per year. Wind erosion and fires occur frequently on these loess soils in winter. This is an excellent area for agriculture but some actual uses may be not sustainable in long term such as excesses with genetically engineered soy, and the authors have studied aided with mathematical models (ELECTRE I, PROMETHEE and Expert Choice) the preferences of various alternative systems of land use (Autochthonous forest, High value forest, Traditional farms, Erosion control Crop with agriculture use, and Erosion control Crop with industrial use (biomass) ) in view of diverse Criteria (Water erosion index, Eolian erosion index, Implementation facility, Water resources, Economical Benefits, Hand power, Environmental Impacts, social Acceptance), as contribution for territorial planning, in part in relation with local official agencies. There are numerous references in local Spanish Argentine literature about the region uses of soils, some of J.M.Cisneros, and many general references, let note about Decision Theory: (1) Grau, J. B., Antón, J.M., Tarquis A. M., Andina, D. Election of water Resources Management Entity using a Multi-criteria decision (MCD) Method in Salta Province (Argentine)". CITSA 2008, Orlando 29 June-2 July, 2008. (2) Roy, B., D. Bouyssou. Aidé Multicritère à la Décision: Méthodes et cas. Economica, Paris 1993. (3) Saaty, T. The Analytic Hierarchy Process, Mac Graw-Hill, New York, 1980.

Soil stabilization linked to plant diversity and environmental context in coastal wetlands.

PubMed

Ford, Hilary; Garbutt, Angus; Ladd, Cai; Malarkey, Jonathan; Skov, Martin W

2016-03-01

Plants play a pivotal role in soil stabilization, with above-ground vegetation and roots combining to physically protect soil against erosion. It is possible that diverse plant communities boost root biomass, with knock-on positive effects for soil stability, but these relationships are yet to be disentangled. We hypothesize that soil erosion rates fall with increased plant species richness, and test explicitly how closely root biomass is associated with plant diversity. We tested this hypothesis in salt marsh grasslands, dynamic ecosystems with a key role in flood protection. Using step-wise regression, the influences of biotic (e.g. plant diversity) and abiotic variables on root biomass and soil stability were determined for salt marshes with two contrasting soil types: erosion-resistant clay (Essex, southeast UK) and erosion-prone sand (Morecambe Bay, northwest UK). A total of 132 (30-cm depth) cores of natural marsh were extracted and exposed to lateral erosion by water in a re-circulating flume. Soil erosion rates fell with increased plant species richness ( R 2  = 0.55), when richness was modelled as a single explanatory variable, but was more important in erosion-prone ( R 2  = 0.44) than erosion-resistant ( R 2  = 0.18) regions. As plant species richness increased from two to nine species·m -2 , the coefficient of variation in soil erosion rate decreased significantly ( R 2  = 0.92). Plant species richness was a significant predictor of root biomass ( R 2  = 0.22). Step-wise regression showed that five key variables accounted for 80% of variation in soil erosion rate across regions. Clay-silt fraction and soil carbon stock were linked to lower rates, contributing 24% and 31%, respectively, to variation in erosion rate. In regional analysis, abiotic factors declined in importance, with root biomass explaining 25% of variation. Plant diversity explained 12% of variation in the erosion-prone sandy region. Our study indicates that soil stabilization and root biomass are positively associated with plant diversity. Diversity effects are more pronounced in biogeographical contexts where soils are erosion-prone (sandy, low organic content), suggesting that the pervasive influence of biodiversity on environmental processes also applies to the ecosystem service of erosion protection.

Mechanical Properties and Plasma Erosion Resistance of ZrO2p(3Y)/BN-SiO2 Ceramic Composites under Different Sintering Temperature

NASA Astrophysics Data System (ADS)

Zhou, Yu; Duan1, Xiaoming; Jia, Dechang; Yang, Zhihua; Meng, Qingchang; Yu, Yang; Yu, Daren; Ding, Yongjie

2011-10-01

ZrO2p(3Y)/BN-SiO2 ceramic composites were hot pressed under different sintering temperature. The ceramic composites were composed by BN, m-ZrO2, t-ZrO2 and SiO2. The relative density, bending strength, elastic modulus and fracture toughness increase with the sintering temperature increasing, the maximum value of which at the sintering temperature of 1800°C are 97.5%, 229.9MPa, 60.8GPa and 3.55MPam1/2, respectively. The erosion resistance ability of ZrO2p(3Y)/BN-SiO2 ceramic composites rise gradually with the sintering temperature increasing, and the erosion rate of the ceramic composite sintered at 1800°C is 8.03×10-3mm/h.

Phosphorus loss to runoff water twenty-four hours after application of liquid swine manure or fertilizer.

PubMed

Tabbara, Hadi

2003-01-01

Phosphorus (P) added to soil from fertilizer or manure application could pose a threat to water quality due to its role in eutrophication of fresh water resources. Incorporating such amendments into the soil is an established best management practice (BMP) for reducing soluble P losses in runoff water, but could also lead to higher erosion. The objective of this study was to test whether incorporation of manure or fertilizer 24 h before an intense rain could also reduce sediment-bound and total phosphorus (TP) losses in runoff. A rainfall simulation study was conducted on field plots (sandy loam with 6-7% slope, little surface residue, recently cultivated) that received two application rates of liquid swine manure or liquid ammonium polyphosphate fertilizer, using either surface-broadcast or incorporated methods of application. Incorporation increased the total suspended solids (TSS) concentrations in runoff but mass losses were not affected. Incorporation also reduced flow-weighted concentrations and losses of dissolved reactive phosphorus (DRP) and TP by as much as 30 to 60% depending on source (fertilizer vs. manure) and application rate. Phosphorus is moved below the mixing zone of interaction on incorporation, and thus the effect of the amount and availability of P in this zone is more important than cultivation on subsequent P losses in runoff. Incorporating manure or fertilizer in areas of intense erosive rain, recent extensive tillage, and with little or no surface residue is therefore a best management practice that should be adhered to in order to minimize contamination of surface water. Results also show comparatively lower P losses from manure than fertilizer.

Erosion of a grooved surface caused by impact of particle-laden flow

NASA Astrophysics Data System (ADS)

Jung, Sohyun; Yang, Eunjin; Kim, Ho-Young

2016-11-01

Solid erosion can be a life-limiting process for mechanical elements in erosive environments, thus it is of practical importance in many industries such as construction, mining, and coal conversion. Erosion caused by particle-laden flow occurs through diverse mechanisms, such as cutting, plastic deformation, brittle fracture, fatigue and melting, depending on particle velocity, total particle mass and impingement angle. Among a variety of attempts to lessen erosion, here we investigate the effectiveness of millimeter-sized grooves on the surface. By experimentally measuring the erosion rates of smooth and triangular-grooved surfaces under various impingement angles, we find that erosion can be significantly reduced within a finite range of impingement angles. We show that such erosion resistance is attributed to the swirls of air within grooves and the differences in erosive strength of normal and slanted impact. In particular, erosion is mitigated when we increase the effective area under normal impact causing plastic deformation and fracture while decreasing the area under slanted impact that cuts the surface to a large degree. Our quantitative model for the erosion rate of grooved surfaces considering the foregoing effects agrees with the measurement results.

Effects of Laser Shock Processing on Morphologies and Mechanical Properties of ANSI 304 Stainless Steel Weldments Subjected to Cavitation Erosion

PubMed Central

Zhang, Lei; Lu, Jin-Zhong; Zhang, Yong-Kang; Ma, Hai-Le; Luo, Kai-Yu; Dai, Feng-Ze

2017-01-01

Effects of laser shock processing (LSP) on the cavitation erosion resistance of laser weldments were investigated by optical microscope (OM), scanning electron microscope (SEM) observations, roughness tester, micro hardness tester, and X-ray diffraction (XRD) technology. The morphological microstructures were characterized. Cumulative mass loss, incubation period, erosion rate, and damaged surface areas were monitored during cavitation erosion. Surface roughness, micro-hardness, and residual stress were measured in different zones. Results showed that LSP could improve the damage of morphological microstructures and mechanical properties after cavitation erosion. The compressive residual stresses were generated during the process of LSP, which was an effective guarantee for the improvement of the above mentioned properties. PMID:28772652

Wear resistance and mechanisms of composite hardfacings at abrasive impact erosion wear

NASA Astrophysics Data System (ADS)

Surzhenkov, A.; Viljus, M.; Simson, T.; Tarbe, R.; Saarna, M.; Casesnoves, F.

2017-05-01

Tungsten carbide based hardmetal containing sprayed and melted composite hardfacings are prospective for protection against abrasive wear. For selection of abrasive wear resistant hardfacings under intensive impact wear conditions, both mechanical properties (hardness, fracture toughness, etc.) and abrasive wear conditions (type of abrasive, impact velocity, etc.) should be considered. This study focuses on the wear (wear rate and mechanisms) of thick metal-matrix composite hardfacings with hardmetal (WC-Co) reinforcement produced by powder metallurgy technology. The influence of the hardmetal reinforcement type on the wear resistance at different abrasive impact erosion wear (AIEW) conditions was studied. An optimal reinforcement for various wear conditions is described. Based on wear mechanism studies, a mathematical model for wear prediction was drafted.

Provision of wear resistance and fatigue strength of surfaces during electroerosive processing

NASA Astrophysics Data System (ADS)

Fedonin, O. N.; Syanov, S. Yu; Papikyan, A. M.

2018-03-01

This article is a generalization of the results of theoretical studies of the effect of erosion control regimes on the operational properties of mold-forming parts of molds. The main problem is the provision of wear resistance and fatigue strength in the electroerosion processing of these types of products. The analysis showed that the fatigue strength is affected by the processing regimes and the coefficient after the erosion treatment. The index of wear resistance is determined both by the treatment modes and by the physical-mechanical properties of the billet materials. To ensure the operational performance of products, it is necessary to establish the physical picture of the processing of complex profile parts by finding the optimum eroding regime.

[Study on surface modification and biocompatibility of NiTi alloy intravascular stents].

PubMed

Shen, Yang; Wang, Gui-xue; Quan, Xue-jun; Yu, Qing-song

2006-01-01

This paper introduces the surface modification of NiTi alloy intravascular stents for roughness by chemical erosion and plasma deposition technology. The stent which had been granulated with chemical erosion was treated with TiO2 film prepared with Gel-sol. The study on the biocompatibility of the modified stent by the above two ways shows that the modified stent is rougher, and its anticoagulation and hydrophilicity are improved. However, the capability of erosion resistance is not enhanced significantly.

Evaluation of rate of swelling and erosion of verapamil (VRP) sustained-release matrix tablets.

PubMed

Khamanga, Sandile M; Walker, Roderick B

2006-01-01

Tablets manufactured in-house were compared to a marketed sustained-release product of verapamil to investigate the rate of hydration, erosion, and drug-release mechanism by measuring the wet and subsequent dry weights of the products. Swelling and erosion rates depended on the polymer and granulating fluid used, which ultimately pointed to their permeability characteristics. Erosion rate of the marketed product was highest, which suggests that the gel layer that formed around these tablets was weak as opposed to the robust and resistant layers of test products. Anomalous and near zero-order transport mechanisms were dominant in tests and commercial product, respectively.

Erosion Characteristics of Nanoparticle-Reinforced Polyurethane Coatings on Stainless Steel Substrate

NASA Astrophysics Data System (ADS)

Syamsundar, C.; Chatterjee, Dhiman; Kamaraj, M.; Maiti, A. K.

2015-04-01

Hydropower generation from the Himalayan rivers in India faces challenge in the form of silt-laden water which can erode the turbine blades and reduce turbine life. To address this issue, polyurethane coatings reinforced with boron carbide (B4C) or silicon carbide (SiC) nanoparticles on 16Cr-5Ni martensitic stainless steel substrate were used in the present investigation to improve erosion wear resistance in silt erosion conditions. Slurry erosive wear tests were carried out based on ASTM G-73 protocol at various test conditions of impact velocity, impingement angle, and erodent particle size as well as slurry concentrations as determined by the implementation of Taguchi design of experiments. Analysis of variance studies of erosion rate indicated that nanoparticle content in PU material is the single most important parameter, and interaction of impact velocity and impingement angle was also proved to be significant. The coatings with B4C nanoparticles had higher wear resistances than those with SiC nanoparticles due to higher hardness of the former. An interesting finding from the results is that there is an optimum amount of nanoparticles at which mass removal is the minimum. This observation has been explained in terms of surface characteristics of coatings as brought out by a combination of measurements including SEM images as well as roughness measurement.

Human impact on the environment in the Ethiopian and Eritrean highlands—a state of the art

NASA Astrophysics Data System (ADS)

Nyssen, Jan; Poesen, Jean; Moeyersons, Jan; Deckers, Jozef; Haile, Mitiku; Lang, Andreas

2004-02-01

This review analyses the environmental evolution of the Ethiopian highlands in the late Quaternary. The late Pleistocene (20,000-12,000 14C years BP) was cold and dry, with (1) low lake levels in the Rift Valley, (2) large debris fans on the flanks of Lake Abhé basin, and (3) the Blue Nile transporting coarse bedload. Then, a period with abundant and less seasonal rains existed between 11,500 and 4800 14C years BP, as suggested by increased arboreal pollen, high river and lake levels, low river turbidities and soil formation. Around 5000-4800 14C years BP, there was a shift to more arid conditions and more soil erosion. Many phenomena that were previously interpreted as climate-driven might, however, well be of anthropic origin. Thick sediment deposits on pediments as well as an increase of secondary forest, scrub and ruderal species in pollen diagrams are witnesses of this human impact. One important aspect of the late Quaternary palaeoenvironment is unclear: changes in Nile flow discharges and Rift Valley lake levels have been linked to changes in precipitation depth. Most authors do not take into account changes in land use in the highlands, nor changes in the seasonality of rain, both of which can lead to a change in runoff coefficients. Tufa and speleothem deposition around 14,000 years ago tend to indicate that at the end of the Last Glacial Maximum (LGM), conditions might have been wetter than generally accepted. The most important present-day geomorphic processes are sheet and rill erosion throughout the country, gullying in the highlands, and wind erosion in the Rift Valley and the peripheral lowlands. Based on existing sediment yield data for catchments draining the central and northern Ethiopian highlands, an equation was developed allowing to assess area-specific sediment yields: SY=2595A -0.29 (n=20; r 2=0.59) where SY=area-specific sediment yield (t km -2 year -1), and A=drainage area (km 2). With respect to recent environmental changes, temporal rain patterns, apart from the catastrophic impact of dry years on the degraded environment, cannot explain the current desertification in the driest parts of the country and the accompanying land degradation elsewhere. Causes are changing land use and land cover, which are expressions of human impact on the environment. Deforestation over the last 2000-3000 years was probably not a linear process in Ethiopia. Studies on land use and land cover change show, however, a tendency over the last decades of increasing removal of remnant vegetation, which is slowed down or reversed in northern Ethiopia by a set-aside policy. Ongoing land degradation requires urgent action at different levels of society. Soil and water conservation (SWC) structures are now widely implemented. Local knowledge and farmer's initiatives are integrated with introduced SWC techniques at various degrees. Impact assessments show clear benefits of the soil conservation measures in controlling runoff and soil erosion. In high rain areas, runoff management requires greater emphasis during the design of soil conservation structures. In such areas, investment in SWC might not be profitable at farm level, although benefits for society are positive. This pleads in favour of public support. The present land degradation in the Ethiopian highlands has a particular origin, which includes poverty and lack of agricultural intensification. Causes of these are to be found in the nature of past and present regional social relations as well as in international unequal development. This review strengthens our belief that, under improved socio-economic conditions, land husbandry can be made sustainable, leading to a reversal of the present desertification and land degradation of the Ethiopian highlands.

Sea-cliff erosion at Pacifica, California caused by 1997/98 El Niño storms

USGS Publications Warehouse

Snell, Charles B.; Lajoie, Kenneth R.; Medley, Edward W.

2000-01-01

Twelve homes were constructed in 1949 at the top of a sea cliff along Esplanade Drive in the City of Pacifica, located on the northern coast of San Mateo County, California. The rear yards of those properties were bounded by an approximately 20-meter (70-foot) high cliff that has retreated episodically at an average rate of 0.5 to 0.6 meter (1.5 to 2 feet) per year over the past 146 years. During the heavy storms of the 1997/1998 El Niño winter, a severe episode of cliff retreat undermined seven homes and threatened three others. All ten homes were condemned and demolished by the City of Pacifica. In this study we analyze geologic, tide, wave, rainfall and wind data in an attempt to determine the causes of this most recent erosion event. We identify the following possible contributory causes of the cliff retreat: 1) wave-induced undercutting of the cliff landward of an old revetment, 2) reduction in beach width over time, 3) reduction in cliff-face stability owing to infiltration from heavy rains, 4) erosion of the cliff face by groundwater piping, and 5) wind-induced erosion of loose dune sand at the top of the cliff. While these factors may explain the retreat of the cliff below the twelve homes along Esplanade Drive, the question remains as to why other geologically similar sites in the region were not severely eroded during the 1997/1998 El Niño winter.

The Influence of Landslides on Channel Flood Response: A Case Study from the Colorado Front Range

NASA Astrophysics Data System (ADS)

Bennett, G. L.; Ryan, S. E.; Sholtes, J.; Rathburn, S. L.

2016-12-01

Studies have identified the role of thresholds and gradients in stream power in inducing geomorphic change during floods. At much longer time scales, empirical and modeling studies suggest the role of landslides in modifying channel response to external forcing (e.g. tectonic uplift); landslide-delivered sediment may behave as a tool, enhancing channel incision, or as cover, reducing channel incision. However, the influence of landslides on channel response to an individual flood event remains to be elucidated. Here we explore the influence of landslides on channel response to a 200-yr flood in Colorado, USA. From 9 - 15th September 2013 up to 450 mm of rain fell across a 100 km-wide swath of the Colorado Front Range, triggering >1000 landslides and inducing major flooding in several catchments. The flood caused extensive channel erosion, deposition and planform change, resulting in significant damage to property and infrastructure and even loss of life. We use a combination of pre and post flood LiDAR and field mapping to quantify geomorphic change in several catchments spanning the flooded region. We make a reach-by-reach analysis of channel geomorphic change metrics (e.g. volume of erosion) in relation to landslide sediment input and total stream power as calculated from radar-based rainfall measurements. Preliminary results suggest that landslide-sediment input may complicate the predictive relationship between channel erosion and stream power. Low volumes of landslide sediment input appear to enhance channel erosion (a tools effect), whilst very large volumes appear to reduce channel erosion (a cover effect). These results have implications for predicting channel response to floods and for flood planning and mitigation.

Development of a Sediment Transport Component for DHSVM

NASA Astrophysics Data System (ADS)

Doten, C. O.; Bowling, L. C.; Maurer, E. P.; Voisin, N.; Lettenmaier, D. P.

2003-12-01

The effect of forest management and disturbance on aquatic resources is a problem of considerable, contemporary, scientific and public concern in the West. Sediment generation is one of the factors linking land surface conditions with aquatic systems, with implications for fisheries protection and enhancement. Better predictive techniques that allow assessment of the effects of fire and logging, in particular, on sediment transport could help to provide a more scientific basis for the management of forests in the West. We describe the development of a sediment transport component for the Distributed Hydrology Soil Vegetation Model (DHSVM), a spatially distributed hydrologic model that was developed specifically for assessment of the hydrologic consequences of forest management. The sediment transport module extends the hydrologic dynamics of DHSVM to predict sediment generation in response to dynamic meteorological inputs and hydrologic conditions via mass wasting and surface erosion from forest roads and hillslopes. The mass wasting component builds on existing stochastic slope stability models, by incorporating distributed basin hydrology (from DHSVM), and post-failure, rule-based redistribution of sediment downslope. The stochastic nature of the mass wasting component allows specification of probability distributions that describe the spatial variability of soil and vegetation characteristics used in the infinite slope model. The forest roads and hillslope surface erosion algorithms account for erosion from rain drop impact and overland erosion. A simple routing scheme is used to transport eroded sediment from mass wasting and forest roads surface erosion that reaches the channel system to the basin outlet. A sensitivity analysis of the model input parameters and forest cover conditions is described for the Little Wenatchee River basin in the northeastern Washington Cascades.

Dispersal of Salmonella Typhimurium by rain splash onto tomato plants.

PubMed

Cevallos-Cevallos, Juan M; Danyluk, Michelle D; Gu, Ganyu; Vallad, Gary E; van Bruggen, Ariena H C

2012-03-01

Outbreaks of Salmonella enterica have increasingly been associated with tomatoes and traced back to production areas, but the spread of Salmonella from a point source onto plants has not been described. Splash dispersal by rain could be one means of dissemination. Green fluorescent protein-labeled, kanamycin-resistant Salmonella enterica sv. Typhimurium dispensed on the surface of plastic mulch, organic mulch, or soil at 10⁸ CFU/cm² was used as the point source in the center of a rain simulator. Tomato plants in soil with and without plastic or organic mulch were placed around the point source, and rain intensities of 60 and 110 mm/h were applied for 5, 10, 20, and 30 min. Dispersal of Salmonella followed a negative exponential model with a half distance of 3 cm at 110 mm/h. Dispersed Salmonella survived for 3 days on tomato leaflets, with a total decline of 5 log and an initial decimal reduction time of 10 h. Recovery of dispersed Salmonella from plants at the maximum observed distance ranged from 3 CFU/g of leaflet after a rain episode of 110 mm/h for 10 min on soil to 117 CFU/g of leaflet on plastic mulch. Dispersal of Salmonella on plants with and without mulch was significantly enhanced by increasing rain duration from 0 to 10 min, but dispersal was reduced when rainfall duration increased from 10 to 30 min. Salmonella may be dispersed by rain to contaminate tomato plants in the field, especially during rain events of 10 min and when plastic mulch is used.

Salmonella can reach tomato fruits on plants exposed to aerosols formed by rain.

PubMed

Cevallos-Cevallos, Juan M; Gu, Ganyu; Danyluk, Michelle D; Dufault, Nicholas S; van Bruggen, Ariena H C

2012-08-17

Outbreaks of Salmonella enterica have been associated with tomatoes and traced back to production areas but the spread of Salmonella in agricultural fields is still poorly understood. Post-rain Salmonella transfer from a point source to the air and then to tomato plants was evaluated. GFP-labeled kanamycin-resistant S. enterica serovar Typhimurium (10(8)CFU/mL) with and without expression of the rdar morphotype (rough colonies; cells with fimbriae and cellulose) was used as the point source in the center of a rain simulator. Rain intensities of 60 and 110 mm/h were applied for 5, 10, 20, and 30 min. Petri dishes with lactose broth and tomato plants with fruit (50-80 cm high) were placed in the simulator after the rain had ceased. Salmonella recovery from air was maximum (300 CFU/plate) after a rain episode of 60 mm/h for 10 min at distances of at least 85.5 cm above the source and when the rdar morphotype strain was used. Small scale experiments showed that the smooth-colony strain without fimbriae precipitated from the air in significantly higher numbers than the rdar strain. Transfer of aerial Salmonella with the rdar morphotype to tomato fruits on plants followed a beta distribution (2.5950, 4.7393) within the generalized range from 0 to 30 min of rain. Results show for the first time that Salmonella may transfer from rain to the air and contaminate tomato fruits at levels that could possibly be infectious to humans. Copyright © 2012 Elsevier B.V. All rights reserved.

Experimental research results of solid particle erosion resistance of blade steel with protective coating

NASA Astrophysics Data System (ADS)

Kachalin, G. V.; Mednikov, A. F.; Tkhabisimov, A. B.; Seleznev, L. I.

2017-11-01

The paper presents the results of metallographic studies and solid particle erosion tests of uncoated blade steel 20kH13 samples and samples with a protective coating based on chromium carbide (Cr-CrC) at a flow (air) velocity CA = 180 m/s, flow temperature tA = 25 °C, attack angle α = 30° and consumption of solid abrasive particles GP = 5·10-4 kg/s. It was found that the coating has a granular structure, a thickness is about 11 μm, the microhardness of the surface is 1520 ± 50 HV0.05. Processing of the obtained data by statistical analysis methods showed that the protective coating based on Cr-CrC increases the solid particle erosion resistance of the blade steel 20kH13 by the incubation-transitional period duration more than 2.5 times.

Ablative material testing for low-pressure, low-cost rocket engines

NASA Technical Reports Server (NTRS)

Richter, G. Paul; Smith, Timothy D.

1995-01-01

The results of an experimental evaluation of ablative materials suitable for the production of light weight, low cost rocket engine combustion chambers and nozzles are presented. Ten individual specimens of four different compositions of silica cloth-reinforced phenolic resin materials were evaluated for comparative erosion in a subscale rocket engine combustion chamber. Gaseous hydrogen and gaseous oxygen were used as propellants, operating at a nominal chamber pressure of 1138 kPa (165 psi) and a nominal mixture ratio (O/F) of 3.3. These conditions were used to thermally simulate operation with RP-1 and liquid oxygen, and achieved a specimen throat gas temperature of approximately 2456 K (4420 R). Two high-density composition materials exhibited high erosion resistance, while two low-density compositions exhibited approximately 6-75 times lower average erosion resistance. The results compare favorably with previous testing by NASA and provide adequate data for selection of ablatives for low pressure, low cost rocket engines.

Partitioning washoff of manure-borne fecal indicators (Escherichia coli and stanols) into splash and hydraulic components: field rainfall simulations in a tropical agro-ecosystem.

NASA Astrophysics Data System (ADS)

Ribolzi, Olivier; Rochelle-Newall, Emma J.; Janeau, Jean-Louis; Viguier, Marion; Jardé, Emilie; Latsachack, Keooudone; Henri-Des-Tureaux, Thierry; Thammahacksac, Chanthamousone; Mugler, Claude; Valentin, Christian; Sengtaheuanghoung, Oloth

2017-04-01

Overland flow from manured fields and pastures is known to be an important mechanism by which organisms of faecal origin are transferred to streams in rural watersheds. In the tropical montane areas of South-East Asia, recent changes in land use have induced increased runoff, soil erosion, in-stream suspended sediment loads resulting in increased microbial pathogen dissemination and contamination of stream waters. The majority of enteric and environmental bacteria in aquatic systems are associated with particles such as sediments which can strongly influence their survival and transport characteristics. Escherichia coli (E. coli) has emerged as one of the most appropriate microbial indicators of faecal contamination of natural waters, with the presence of E. coli indicating that faecal contamination is present. In association with E. coli, faecal stanols can also be used as microbial source tracking tool for the identification of the origin of the faecal contamination (e.g. livestock, human, etc). Field rain simulations were used to examine how E.coli and stanols are exported from the surface of upland, agricultural soils during overland flow events. The objectives were to characterize the loss dynamics of these indicators from agricultural soils contaminated with livestock waste, and to partition total detachment into the splash and hydraulic components. Nine 1m2 microplots were divided in triplicated treatment groups: (a) controls with no amendments, (b) amended with pig manure or (c) poultry manure. Each plot was divided into two 0.5m2 rectangular subplots. For each simulation, one subplot was designated as a rain splash treatment; the other was covered with 2-mm grid size wire screen 10 cm above the soil surface to break the raindrops into fine droplets, thus drastically reducing their kinetic energy. E. coli concentrations in overland flow were estimated for both the attached and free living fractions and stanols were measured on the particulate matter washed off each sub-plot. Rain splash reduced infiltration rate, enhanced overland flow generation and contributed greatly to sediment detachment and entrainment. It had a strong impact on the export of E. coli and stanols from the soil surface and particle bound, rather than free E. coli dominated, although some differences were observed between treatment. High stanol concentrations were measured in overland flow waters from amended plots and specific stanol fingerprints were found between plots amended with pig or poultry manure, suggesting that stanols can be used to determine the origin of the faecal matter at the catchment scale in tropical rural environments. This work underlines the importance of rain drop impacts on the washoff of manure-borne fecal indicator organisms and biomarkers; it also opens the door for the improvement of focused models on faecal bacteria and stanol export that take into account both hydraulic and splash effects of rain induced erosion.

Persistence of rock-derived nutrients in the wet tropical forests of La Selva, Costa Rica.

PubMed

Porder, Stephen; Clark, Deborah A; Vitousek, Peter M

2006-03-01

We used strontium isotopes and analysis of foliar and soil nutrients to test whether erosion can rejuvenate the supply of rock-derived nutrients in the lowland tropical rain forest of La Selva, Costa Rica. We expected that these nutrients would be depleted from soils on stable surfaces, a result of over one million years of weathering in situ. In fact, trees and palms in all landscape positions derive a relatively high percentage (> or =40%) of their strontium from bedrock, rather than atmospheric, sources. The fraction that is rock-derived increases on slopes, but with no detectable effect on plant macronutrient concentrations. These results differ from those in a similar ecosystem on Kauai, Hawaii, where plants on uneroded surfaces derive almost all of their foliar Sr from atmospheric, rather than bedrock, sources. The results from La Selva challenge the assumption that tropical Oxisols in general have low nutrient inputs from bedrock, and support the hypothesis that erosion can increase the supply of these nutrients in lower landscape positions.

Reducing insecticide and fungicide loads in runoff from plastic mulch with vegetative-covered furrows.

PubMed

Rice, Pamela J; Harman-Fetcho, Jennifer A; Sadeghi, Ali M; McConnell, Laura L; Coffman, C Benjamin; Teasdale, John R; Abdul-Baki, Aref; Starr, James L; McCarty, Gregory W; Herbert, Rachel R; Hapeman, Cathleen J

2007-02-21

A common management practice for the production of fresh-market vegetables utilizes polyethylene (plastic) mulch because it increases soil temperature, decreases weed pressure, maintains soil moisture, and minimizes soil contact with the product. However, rain events afford much more erosion and runoff because 50-75% of the field is covered with an impervious surface. A plot study was conducted to compare and to quantify the off-site movement of soil, insecticides, and fungicides associated with runoff from plots planted with Sunbeam tomatoes (Lycopersicon esculentum Mill) using the conventional polyethylene mulch management practice vs an alternative management practice-polyethylene mulch-covered beds with cereal rye (Secale cereale) planted in the furrows between the beds. The use of cereal rye-covered furrows with the conventional polyethylene system decreased runoff volume by more than 40%, soil erosion by more than 80%, and pesticide loads by 48-74%. Results indicate that vegetative furrows are critical to minimizing the negative aspects of this management practice.

Crew Earth Observations (CEO) taken during Expedition 8

NASA Image and Video Library

2004-03-25

ISS008-E-19233 (25 March 2004) --- This image featuring the Betsiboka estuary on the northwest coast of Madagascar was taken by an Expedition 8 crewmember on the International Space Station (ISS). The Betsiboka estuary is the mouth of Madagascar’s largest river and one of the world’s fast-changing coastlines. Nearly a century of extensive logging of Madagascar’s rainforests and coastal mangroves has resulted in nearly complete clearing of the land and fantastic rates of erosion. After every heavy rain, the bright red soils are washed from the hillsides into the streams and rivers to the coast. Astronauts describe their view of Madagascar as “bleeding into the ocean”. One impact of the extensive 20th century erosion is the filling and clogging of coastal waterways with sediment – a process that is well illustrated in the Betsiboka estuary. In fact, ocean-going ships were once able to travel up the Betsiboka estuary, but must now berth at the coast.

Crew Earth Observations (CEO) taken during Expedition 8

NASA Image and Video Library

2004-03-25

ISS008-E-19236 (25 March 2004) --- This image featuring the Betsiboka estuary on the northwest coast of Madagascar was taken by an Expedition 8 crewmember on the International Space Station (ISS). The Betsiboka estuary is the mouth of Madagascar’s largest river and one of the world’s fast-changing coastlines. Nearly a century of extensive logging of Madagascar’s rainforests and coastal mangroves has resulted in nearly complete clearing of the land and fantastic rates of erosion. After every heavy rain, the bright red soils are washed from the hillsides into the streams and rivers to the coast. Astronauts describe their view of Madagascar as “bleeding into the ocean”. One impact of the extensive 20th century erosion is the filling and clogging of coastal waterways with sediment – a process that is well illustrated in the Betsiboka estuary. In fact, ocean-going ships were once able to travel up the Betsiboka estuary, but must now berth at the coast.

Evaluating the influence of gully erosion on landslide hazard analysis triggered by heavy rainfall

NASA Astrophysics Data System (ADS)

Ruljigaljig, Tjuku; Tsai, Ching-Jun; Peng, Wen-Fei; Yu, Teng-To

2017-04-01

During the rainstorm period such as typhoon or heavy rain, the development of gully will induce a large-scale landslide. The purpose of this study is to assess and quantify the existence and development of gully for the purpose of triggering landslides by analyzing the landslides hazard. Firstly, based on multi-scale DEM data, this study uses wavelet transform to construct an automatic algorithm. The 1-meter DEM is used to evaluate the location and type of gully, and to establish an evaluation model for predicting erosion development.In this study, routes in the Chai-Yi were studied to clarify the damage potential of roadways from local gully. The local of gully is regarded as a parameter to reduce the strength parameter. The distribution of factor of safe (F.S.) is compared with the landslide inventory map. The result of this research could be used to increase the prediction accuracy of landslide hazard analysis due to heavy rainfalls.

Respiratory disease and particulate air pollution in Santiago Chile: contribution of erosion particles from fine sediments.

PubMed

Garcia-Chevesich, Pablo A; Alvarado, Sergio; Neary, Daniel G; Valdes, Rodrigo; Valdes, Juan; Aguirre, Juan José; Mena, Marcelo; Pizarro, Roberto; Jofré, Paola; Vera, Mauricio; Olivares, Claudio

2014-04-01

Air pollution in Santiago is a serious problem every winter, causing thousands of cases of breathing problems within the population. With more than 6 million people and almost two million vehicles, this large city receives rainfall only during winters. Depending on the frequency of storms, statistics show that every time it rains, air quality improves for a couple of days, followed by extreme levels of air pollution. Current regulations focus mostly on PM10 and PM2.5, due to its strong influence on respiratory diseases. Though more than 50% of the ambient PM10s in Santiago is represented by soil particles, most of the efforts have been focused on the remaining 50%, i.e. particulate material originating from fossil and wood fuel combustion, among others. This document emphasizes the need for the creation of erosion/sediment control regulations in Chile, to decrease respiratory diseases on Chilean polluted cities. Copyright © 2014 Elsevier Ltd. All rights reserved.

Monitoring the inhibition of erosion by a CO2 laser with OCT

NASA Astrophysics Data System (ADS)

Chan, Kenneth H.; Tom, Henry; Fried, Daniel

2014-02-01

Since optical coherence tomography (OCT) is well suited for measuring small dimensional changes on tooth surfaces, OCT has great potential for monitoring tooth erosion. Previous studies have shown that enamel areas ablated by a carbon dioxide laser manifested lower rates of erosion compared to the nonablated areas. The purpose of this study was to develop a model to monitor erosion in vitro that could potentially be used in vivo. Teeth surfaces were irradiated with a carbon dioxide laser at low sub-ablative fluence to create an acid-resistant reference layer without damaging the enamel. The laser treated areas were compared with the unprotected areas using OCT during exposure to a pH cycling model for up to 6 days. The laser treated areas markedly reduced the rate of erosion.

Sputtering Erosion Measurement on Boron Nitride as a Hall Thruster Material

NASA Technical Reports Server (NTRS)

Britton, Melissa; Waters, Deborah; Messer, Russell; Sechkar, Edward; Banks, Bruce

2002-01-01

The durability of a high-powered Hall thruster may be limited by the sputter erosion resistance of its components. During normal operation, a small fraction of the accelerated ions will impact the interior of the main discharge channel, causing its gradual erosion. A laboratory experiment was conducted to simulate the sputter erosion of a Hall thruster. Tests of sputter etch rate were carried out using 300 to 1000 eV Xenon ions impinging on boron nitride substrates with angles of attack ranging from 30 to 75 degrees from horizontal. The erosion rates varied from 3.41 to 14.37 Angstroms/[sec(mA/sq cm)] and were found to depend on the ion energy and angle of attack, which is consistent with the behavior of other materials.

Ash Leachate Can Reduce Surface Erosion

Treesearch

George J. Holcomb; Philip B. Durgin

1979-01-01

In laboratory analyses of the Larabee soil from north-western California, ash leachate flocculated the clay fractions. As a result, the soil quickly settled out of suspension. To test the hypothesis that field plots on disturbed areas treated with ash leachate would be more resistant to erosion than nontreated plots, a study was done in July and August 1978, on two...

Multitemporal analysis of estimated soil loss for the river Mourão watershed, Paraná - Brazil.

PubMed

Graça, C H; Passig, F H; Kelniar, A R; Piza, M A; Carvalho, K Q; Arantes, E J

2015-12-01

The multitemporal behavior of soil loss by surface water erosion in the hydrographic basin of the river Mourão in the center-western region of the Paraná state, Brazil, is analyzed. Forecast was based on the application of the Universal Soil Loss Equation (USLE) with the data integration and estimates within an Geography Information System (GIS) environment. Results had shown high mean annual rain erosivity (10,000 MJ.mm.ha(-1).h(-1).year(-1)), with great concentration in January and December. As a rule, soils have average erodibilities, exception of Dystroferric Red Latisol (low class) and Dystrophic Red Argisol (high class). Although the topographic factor was high (>20), rates lower than 1 were predominant. Main land uses comprise temporal crops and pasture throughout the years. The watershed showed a natural potential for low surface erosion. When related to usage types, yearly soil loss was also low (<50 ton.ha(-1).year(-1)), with more critical scores that reach rates higher than 150 ton.ha(-1).year(-1). Soil loss over the years did not provide great distinctions in distribution standards, although it becames rather intensified in some sectors, especially in the center-eastern and southwestern sections of the watershed.

Estimation of small-scale soil erosion in laboratory experiments with Structure from Motion photogrammetry

NASA Astrophysics Data System (ADS)

Balaguer-Puig, Matilde; Marqués-Mateu, Ángel; Lerma, José Luis; Ibáñez-Asensio, Sara

2017-10-01

The quantitative estimation of changes in terrain surfaces caused by water erosion can be carried out from precise descriptions of surfaces given by means of digital elevation models (DEMs). Some stages of water erosion research efforts are conducted in the laboratory using rainfall simulators and soil boxes with areas less than 1 m2. Under these conditions, erosive processes can lead to very small surface variations and high precision DEMs are needed to account for differences measured in millimetres. In this paper, we used a photogrammetric Structure from Motion (SfM) technique to build DEMs of a 0.5 m2 soil box to monitor several simulated rainfall episodes in the laboratory. The technique of DEM of difference (DoD) was then applied using GIS tools to compute estimates of volumetric changes between each pair of rainfall episodes. The aim was to classify the soil surface into three classes: erosion areas, deposition areas, and unchanged or neutral areas, and quantify the volume of soil that was eroded and deposited. We used a thresholding criterion of changes based on the estimated error of the difference of DEMs, which in turn was obtained from the root mean square error of the individual DEMs. Experimental tests showed that the choice of different threshold values in the DoD can lead to volume differences as large as 60% when compared to the direct volumetric difference. It turns out that the choice of that threshold was a key point in this method. In parallel to photogrammetric work, we collected sediments from each rain episode and obtained a series of corresponding measured sediment yields. The comparison between computed and measured sediment yields was significantly correlated, especially when considering the accumulated value of the five simulations. The computed sediment yield was 13% greater than the measured sediment yield. The procedure presented in this paper proved to be suitable for the determination of sediment yields in rainfall-driven soil erosion experiments conducted in the laboratory.

The erosion resistance of tool alloys in foundry melt the Zamak 4 - 1

NASA Astrophysics Data System (ADS)

Muhametzyanova, GF; Kolesnikov, M. S.; Muhametzyanov, I. R.

2016-06-01

The paper considers the resistance against erosion dissolution in the melt of foundry Zamak 4 - 1 die steels used for press machine parts manufacturing for injection molding, and hard alloys system WC - Co. It is established that the solubility in the melt Zamak - 4 - 1 steel of 4H5MFS and DI - 22 are promising for the parts fabrication of metal-wire casting machines of CLT and IDRA types. A significant reserve to increase the resistance of metal wires is the use of cast steel, as well as in electroslag and electro-beam remelting options. Metal-ceramic alloy doped with chromium VK25H may be recommended for reinforcement of heavily loaded parts of the press-nodes of hot casting machines under pressure.

Solid Particle Erosion Behaviors of Carbon-Fiber Epoxy Composite and Pure Titanium

NASA Astrophysics Data System (ADS)

Cai, Feng; Gao, Feng; Pant, Shashank; Huang, Xiao; Yang, Qi

2016-01-01

Rotor blades of Bell CH-146 Griffon helicopter experience excessive solid particle erosion at low altitudes in desert environment. The rotor blade is made of an advanced light-weight composite which, however, has a low resistance to solid particle erosion. Coatings have been developed and applied to protect the composite blade. However, due to the influence of coating process on composite material, the compatibility between coating and composite base, and the challenges of repairing damaged coatings as well as the inconsistency between the old and new coatings, replaceable thin metal shielding is an alternative approach; and titanium, due to its high-specific strength and better formability, is an ideal candidate. This work investigates solid particle erosion behaviors of carbon-fiber epoxy composite and titanium in order to assess the feasibility of titanium as a viable candidate for erosion shielding. Experiment results showed that carbon-fiber epoxy composite showed a brittle erosion behavior, whereas titanium showed a ductile erosion mode. The erosion rate on composite was 1.5 times of that on titanium at impingement angle 15° and increased to 5 times at impact angle 90°.

Contribution of different sources to the pollution of wet weather flows in combined sewers.

PubMed

Gromaire, M C; Garnaud, S; Saad, M; Chebbo, G

2001-02-01

Experiments performed on "Marais" catchment, in central Paris, aimed to follow up the quality of wet weather flows from the entry to the exit of a combined sewer network. SS, VSS, COD, BOD5, Cd, Cu, Pb, Zn concentrations were measured for an important number of rain events in roof, yard, street runoff, as well as in dry and wet weather flows at the catchment outlet. Mass entry-exit totals, at the scale of the catchment, were calculated over 31 rain events in order to evaluate the contribution of different types of runoff, of sanitary sewage and of sewer sediments to the total wet weather pollutant loads at the catchment outlet. The erosion of in-sewer pollutant stocks was found to be the main source of particles and of organic matter in wet weather flows, whereas heavy metal loads mainly originated from roof runoff, due to the corrosion of metallic roofs. Particles eroded inside the sewer during rain events were found to be quite different from the particles constituting the main part of sewer sediments: they are organic and biodegradable, with rather important settling velocities and seem to accumulate during dry weather periods. A change of the chemical form of heavy metals was noticed during the transport in the sewer and it is suspected that a fraction of the dissolved metals from the runoff is adsorbed on sewer sediments.

Pre-rain green-up is ubiquitous across southern tropical Africa: implications for temporal niche separation and model representation.

PubMed

Ryan, Casey M; Williams, Mathew; Grace, John; Woollen, Emily; Lehmann, Caroline E R

2017-01-01

Tree phenology mediates land-atmosphere mass and energy exchange and is a determinant of ecosystem structure and function. In the dry tropics, including African savannas, many trees grow new leaves during the dry season - weeks or months before the rains typically start. This syndrome of pre-rain green-up has long been recognized at small scales, but the high spatial and interspecific variability in leaf phenology has precluded regional generalizations. We used remote sensing data to show that this precocious phenology is ubiquitous across the woodlands and savannas of southern tropical Africa. In 70% of the study area, green-up preceded rain onset by > 20 d (42% > 40 d). All the main vegetation formations exhibited pre-rain green-up, by as much as 53 ± 18 d (in the wet miombo). Green-up showed low interannual variability (SD between years = 11 d), and high spatial variability (> 100 d). These results are consistent with a high degree of local phenological adaptation, and an insolation trigger of green-up. Tree-tree competition and niche separation may explain the ubiquity of this precocious phenology. The ubiquity of pre-rain green-up described here challenges existing model representations and suggests resistance (but not necessarily resilience) to the delay in rain onset predicted under climate change. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Influence of successive phases of volcanic construction and erosion on Mayotte Island's hydrogeological functioning as determined from a helicopter-borne resistivity survey correlated with borehole geological and permeability data

NASA Astrophysics Data System (ADS)

Vittecoq, B.; Deparis, J.; Violette, S.; Jaouën, T.; Lacquement, F.

2014-02-01

The purpose of this study is to show how a multidisciplinary approach that combines geophysics, geology and hydrogeology has made it possible to: (a) significantly improve our understanding of the hydrogeological regime of the volcanic island of Mayotte, and (b) provide a new set of geophysical measurement calibration data. In 2010 a helicopter-borne geophysical survey (SkyTEM) was flown over the entire island (374 km2) with a measurement density hitherto unheard of in a volcanic environment. In addition, a database was compiled containing the geological logs of 55 boreholes. 52 of these boreholes have hydrogeological information like aquifer position and piezometric level. 21 of the boreholes have transmissivity values. Correlations were made between the inverted resistivities as obtained from the helicopter-borne TDEM profiles and the nature, age and hydrodynamic properties of the formations as obtained from the borehole data. Five hydrogeological units were mapped. These are characterized by an alternation between phases of dominant volcanic construction, with the emplacement of basaltic lavas, phonolite massifs and pyroclastic deposits, and phases of dominant erosion with the deposition of volcaniclastic material (colluvium, breccias, basaltic lavas and phonolite blocks and all materials resulting from slope slides) along the slopes and in the topographic depressions. It has also been possible to assign resistivity and permeability ranges to four of these units. Ranges that are also dependent on the age of the deposits: the younger the formation is, the greater its resistivity and the higher its permeability. The hydrogeological regime is marked by the phases of volcanic construction and erosion that succeeded one another during the geological history of Mayotte over the last 10 Ma. A conceptual model adapted to the specific geological context of this island, and differing from the Canarian and Hawaiian models, is also put forward. This model is marked by the island's “fragmented” character resulting from its geological history (several volcanic edifices, several phases of construction and erosion), and is applicable to an old volcanic island in an advanced stage of erosion and weathering, with a volcanic history similar to that of Mayotte, i.e. with climate variations and erosion periods long enough to register volcaniclastic deposits.

Cultivar architecture modulates spore dispersal by rain splash: A new perspective to reduce disease progression in cultivar mixtures.

PubMed

Vidal, Tiphaine; Lusley, Pauline; Leconte, Marc; de Vallavieille-Pope, Claude; Huber, Laurent; Saint-Jean, Sébastien

2017-01-01

Cultivar mixtures can be used to improve the sustainability of disease management within farming systems by growing cultivars that differ in their disease resistance level in the same field. The impact of canopy aerial architecture on rain-splash dispersal could amplify disease reduction within mixtures. We designed a controlled conditions experiment to study single splash-dispersal events and their consequences for disease. We quantified this impact through the spore interception capacities of the component cultivars of a mixture. Two wheat cultivars, differing in their aerial architecture (mainly leaf area density) and resistance to Septoria tritici blotch, were used to constitute pure stands and mixtures with 75% of resistant plants that accounted for 80% of the canopy leaf area. Canopies composed of 3 rows of plants were exposed to standardized spore fluxes produced by splashing calibrated rain drops on a linear source of inoculum. Disease propagation was measured through spore fluxes and several disease indicators. Leaf susceptibility was higher for upper than for lower leaves. Dense canopies intercepted more spores and mainly limited horizontal spore transfer to the first two rows. The presence of the resistant and dense cultivar made the mixed canopy denser than the susceptible pure stand. No disease symptoms were observed on susceptible plants of the second and third rows in the cultivar mixture, suggesting that the number of spores intercepted by these plants was too low to cause disease symptoms. Both lesion area and disease conditional severity were significantly reduced on susceptible plants within mixtures on the first row beside the inoculum source. Those reductions on one single-splash dispersal event, should be amplified after several cycle over the full epidemic season. Control of splash-dispersed diseases within mixtures could therefore be improved by a careful choice of cultivars taking into consideration both resistance and architecture.

Cultivar architecture modulates spore dispersal by rain splash: A new perspective to reduce disease progression in cultivar mixtures

PubMed Central

Vidal, Tiphaine; Lusley, Pauline; Leconte, Marc; de Vallavieille-Pope, Claude; Huber, Laurent

2017-01-01

Cultivar mixtures can be used to improve the sustainability of disease management within farming systems by growing cultivars that differ in their disease resistance level in the same field. The impact of canopy aerial architecture on rain-splash dispersal could amplify disease reduction within mixtures. We designed a controlled conditions experiment to study single splash-dispersal events and their consequences for disease. We quantified this impact through the spore interception capacities of the component cultivars of a mixture. Two wheat cultivars, differing in their aerial architecture (mainly leaf area density) and resistance to Septoria tritici blotch, were used to constitute pure stands and mixtures with 75% of resistant plants that accounted for 80% of the canopy leaf area. Canopies composed of 3 rows of plants were exposed to standardized spore fluxes produced by splashing calibrated rain drops on a linear source of inoculum. Disease propagation was measured through spore fluxes and several disease indicators. Leaf susceptibility was higher for upper than for lower leaves. Dense canopies intercepted more spores and mainly limited horizontal spore transfer to the first two rows. The presence of the resistant and dense cultivar made the mixed canopy denser than the susceptible pure stand. No disease symptoms were observed on susceptible plants of the second and third rows in the cultivar mixture, suggesting that the number of spores intercepted by these plants was too low to cause disease symptoms. Both lesion area and disease conditional severity were significantly reduced on susceptible plants within mixtures on the first row beside the inoculum source. Those reductions on one single-splash dispersal event, should be amplified after several cycle over the full epidemic season. Control of splash-dispersed diseases within mixtures could therefore be improved by a careful choice of cultivars taking into consideration both resistance and architecture. PMID:29140990

Why Devil's town has Devil's water

NASA Astrophysics Data System (ADS)

Jovic, Sladjana; Mitriceski, Bojana

2015-04-01

Why Devil's town has Devil's water In the south of Serbia, lies a first-class natural landmark "Devil's Town" at an altitude of 660-700 m. Earthen figures or "towers" as the locals call them, are located in the watershed between two gullies, whose sources joined together create a unique erosive formation, tremendously demolished by the erosive processes. The gullies also have strange names: "Devil's Gully" and "Hell's Gully". There are two rare natural phenomena at the same spot: 202 earthen figures of different shape and dimension, from 2 m to 15 m in height, and from 0.5 m to 3 m in width, with stone caps on the top. They are an outcome of a specific erosive process that lasts for centuries. When figures are formed, they grow, change, shorten, gradually (very slowly) disappear and reappear. The loose soil is dissolved and washed away by the rain. However, the material under the stone caps is protected from the "bombardment" of the rain drops and washout, and remains in place in the form of the rising earthen pillars - figures. Another natural rarity in "Devil's Town" are two springs of extraordinary properties "Devil's Water", which is located in vicinity of these earthen figures, is a cold and extremely acid spring (pH 1.5) of high mineral concentration (15 g/l of water), springing out in "Devil's Gully". In comparison to drinking water, it is 10 to 1000 times richer in minerals (aluminium, iron, potassium, copper, nickel, sulphur, and alaun). "Red Well" is another spring located downstream, in the alluvial plain, 400 m away from the first spring. Its water (pH 3.5) is less acid and has a lower general mineral concentration (4.372 mg/l of water). Due to the oxidation of iron, which is contained in water in large amounts, an attractive red terrace in the form of a fan is created. The main assessment for students is to take some examples of water from Devils Gully and the others from Red Well . Second part is to find out content of minerals in water examples and this part should be done in laboratory while measured of PH with PH meters should be done on the spot. At the same time students can analyze erosion process which is developed in this place. This type of public classes is very popular and teaching and learning process are taking place at the same time.

Remote sensing for environmental protection of the eastern Mediterranean rugged mountainous areas, Lebanon

NASA Astrophysics Data System (ADS)

Khawlie, M.; Awad, M.; Shaban, A.; Bou Kheir, R.; Abdallah, C.

Lying along the eastern Mediterranean coast with elevated mountain chains higher than 2500 m straddling its terrain, Lebanon is a country of natural beauty and is thus attracting tourism. However, with a population density exceeding 800/km 2 and a rugged steep sloping land, problems abound in the country calling for holistic-approach studies. Only remote sensing, whose use is new in Lebanon can secure such needed studies within a scientific and pragmatic framework. The paper demonstrates for the concerned themes, the innovative use of remote sensing in such a difficult terrain, giving three examples of major environmental problems in the coastal mountains. Only few studies have so far focused on those mountains, notably application of remote sensing. The rugged mountainous terrain receives considerable rain, but the water is quickly lost running on the steep slopes, or infiltrating through fractures and the karstic conduits into the subsurface. Field investigations are difficult to achieve, therefore, remote sensing helps reveal various surface land features important in reflecting water feeding into the subsurface. Optical, radar and thermal infrared remotely sensed data cover a wide spectrum serving that purpose. A map of preferential groundwater accumulation potential is produced. It can serve for better water exploitation as well as protection. Because the terrain is karstic and rugged, the subsurface water flow is difficult to discern. Any pollution at a certain spot would certainly spread around. This constitutes the second example of environmental problems facing the mountainous areas in Lebanon. An integrated approach using remote sensing and geographic information systems (GIS) gives good results in finding out the likelihood of how pollution, or contaminants, can selectively move in the subsurface. A diagnostic analysis with a GIS-type software acts as a guide producing indicative maps for the above purpose. The third example given deals with the problem of losing soil, which is a very vital source in such mountainous land. With steep slopes, torrential rain and improper human interference, run-off is high and water-soil erosion is continuously deteriorating the land cover. Remote sensing can facilitate studying the factors enhancing the process, such as soil type, slope gradient, drainage, geology and land cover. Digital elevation models created from SAR imagery contribute significantly to assessing vulnerability of hydric-soil erosion over such a difficult terrain. GIS layers of the above factors are integrated with erosional criteria to produce a risk map of soil erosion. Results indicate that 36% of the Lebanese terrain is under threat of high-level erosion, and 52% of that is concentrated in the rugged mountainous regions.

Erosion resistant elbow for solids conveyance

DOEpatents

Everett, J.W.

1984-10-23

An elbow and process for fabrication for use in particulate material conveyancing comprises a curved outer pipe, a curved inner pipe having the same radius of curvature as the outer pipe, concentric with and internal to the outer pipe, comprising an outer layer comprised of a first material and an inner layer comprised of a second material wherein said first material is characterized by high erosion resistance when impinged by particulate material and wherein said second material is characterized by high tensile strength and flexibility, and an inner pipe supporting means for providing support to said inner pipe, disposed between said inner pipe and said outer pipe. 4 figs.

Erosion resistant elbow for solids conveyance

DOEpatents

Everett, James W.

1984-10-23

An elbow and process for fabrication for use in particulate material conveyancing comprising a curved outer pipe, a curved inner pipe having the same radius of curvature as the outer pipe, concentric with and internal to the outer pipe, comprising an outer layer comprised of a first material and an inner layer comprised of a second material wherein said first material is characterized by high erosion resistance when impinged by particulate material and wherein said second material is characterized by high tensile strength and flexibility, and an inner pipe supporting means for providing support to said inner pipe, disposed between said inner pipe and said outer pipe.

Erosion resistant elbow for solids conveyance

DOEpatents

Not Available

An elvow and process for fabrication for use in particulate material conveying comprising a curved outer pipe, a curved inner pipe having the same radius of curvature as the outer pipe, concentric with and internal to the outer pipe, comprising an outer layer comprised of a first material and an inner layer comprised of a second material wherein said first material is characterized by high erosion resistance when impinged by particulate material and wherein said second material is characterized by high tensile strength and flexibility, and an inner pipe supporting means for providing support to said inner pipe, disposed between said inner pipe and said outer pipe. 4 figures.

Quantifying Hillslope to Watershed Erosional Response Following Wildfire

NASA Astrophysics Data System (ADS)

Vega, S.; Pierson, F. B.; Williams, C. J.; Brooks, E. S.; Strand, E. K.; Seyfried, M. S.; Murdock, M.; Pierce, J. L.; Roehner, C.; Lindsay, K.; Robichaud, P. R.; Brown, R. E.

2017-12-01

Across the western US, wildfires in sagebrush vegetation are occurring at a more frequent rate and higher severity. This has resulted in a decline of sagebrush rangeland. The changing fire regime can be attributed to invasive plant species and warming climate conditions. As the result of wildfire, protective vegetation cover is removed leaving the soil bare and exposed to erosion. Erosion following wildfire is a main concern among land managers due to the threat it poses to resources, infrastructure, and human health. Numerous studies have used artificial rainfall to assess post-fire runoff and erosion and rehabilitation treatment effectiveness. These results have found that high intensity rain events typical of summer convective storms drive post-fire erosion. The purpose of this study is to improve scientific understanding of how site-specific physical and biological attributes affect hillslope to watershed scale sediment yield on a mountainous burned sagebrush landscape. This study uses natural rainfall and a network of silt fences to quantify hillslope to watershed scale erosion response. The erosional drivers over various spatial scales were evaluated in context with vegetation recovery for a 2 year post-fire period. A network of silt fences was installed over long and short hillslope distances and in swales within the 130 ha Murphy Creek catchment in the Reynolds Creek Experimental Watershed in southwestern Idaho. We evaluated: 1) vegetation, soils, and sediment delivery across multiple spatial scales associated with 30 silt fences spanning north and south facing aspects, 2) precipitation input at two meteorological stations, and 3) watershed streamflow and sediment discharge from an existing weir. During the first and second year post-fire, the swales on both aspects produced more sediment than the short and long hillslopes. The results suggest that significant amounts of sediment and organic matter were deposited in the swales creating drifts. Sediment delivery was mainly by wind in the first few months post-fire and from runoff during low intensity rainfall and snowmelt events during the first autumn and winter seasons. This study will aid land management agencies throughout the western US with predicting post-fire erosion responses and determining appropriate erosion mitigation strategies.

Persistence of Episodic Extreme Events: Sustained Colluvial Contributions of Fine Sediment to Vermont Rivers Post-Irene

NASA Astrophysics Data System (ADS)

Dethier, E.; Magilligan, F. J.; Renshaw, C. E.; Sinclair, D.

2014-12-01

Tropical Storm Irene generated devastating floods in New England in 2011, causing more than $500 million of damage. In intervening years, many geomorphic signs of disturbance have attenuated, suggesting that impacts may be ephemeral. Yet persistent impact continues: channel-proximal landslide scars linger as point sources of fine sediment 3 yrs post-Irene. We evaluate the legacy of this major disturbance while also testing conceptual models of hillslope-channel connectivity and subsequent downstream sediment routing. We measure sustained landslide erosion by comparing DEMs generated by a Terrestrial Laser Scanner and trace sediment mobility using in-channel measurements of embeddedness, sediment concentration, and fallout radionuclide activity. We augmented detailed temporal sampling of an 850 m2 landslide along a 2nd-order stream with a spatially robust summer 2014 field campaign, scanning an additional 12 landslides. The initially sampled landslide eroded 250 m3 of sediment between fall 2013 and May 2014, averaging 0.3 m of erosion with nearly all erosion occurring during a two-week spring snowmelt. Landslide sediments had high measured 7Be activity (t1/2=53.4 d), caused by subaerial exposure; sediment collected downstream of the landslide had higher 7Be activity than that collected upstream, suggesting landslide provenance. Channel sediment upstream of the landslide had remained in the channel long enough for 7Be to decay below detectable activity. Embeddedness, a measure of fine sediment on a channel bed, was higher downstream of the landslide than upstream. Remote sensing reveals >50 similar landslides within the White River alone, and hundreds more in Vermont. Thus, landslide scar inputs may continue to influence the regional fine sediment budget. Ongoing successive scans in multiple watersheds show erosion continues in summer, an observation corroborated by elevated suspended sediment concentrations downstream of landslides after rain events. Summertime erosion has generally been low, but one extreme storm triggered >4000 m3 of erosion on a 3500 m2 landslide along the 5th-order Williams River, averaging 1.3 m erosion across the landslide. Understanding the loci of affected reaches and the magnitude of the continued effect is critical in assessing the long-term legacy of extreme events.

Erosion processes in molassic cliffs: the role of the rock surface temperature and atmospheric conditions

NASA Astrophysics Data System (ADS)

Carrea, Dario; Abellán, Antonio; Guerin, Antoine; Jaboyedoff, Michel; Voumard, Jérémie

2014-05-01

The morphology of the Swiss Plateau is modeled by numerous steep cliffs of Molasse. These cliffs are mainly composed of sub-horizontal alternated layers of sandstone, shale and conglomerates deposed in the Alps foreland basin during the Tertiary period. These Molasse cliffs are affected by erosion processes inducing numerous rockfall events. Thus, it is relevant to understand how different external factors influence Molasse erosion rates. In this study, we focus on analyzing temperature variation during a winter season. As pilot study area we selected a cliff which is formed by a sub-horizontal alternation of outcropping sandstone and shale. The westward facing test site (La Cornalle, Vaud, Switzerland), which is a lateral scarp of a slow moving landslide area, is currently affected by intense erosion. Regarding data acquisition, we monitored both in-situ rock and air temperatures at 15 minutes time-step since October 2013: (1) on the one hand we measured Ground Surface Temperature (GST) at near-surface (0.1 meter depth) using a GST mini-datalogger M-Log5W-Rock model; (2) On the other hand we monitored atmospheric conditions using a weather station (Davis Vantage pro2 plus) collecting numerous parameters (i.e. temperature, irradiation, rain, wind speed, etc.). Furthermore, the area was also seasonally monitored by Ground-Based (GB) LiDAR since 2010 and monthly monitored since September 2013. In order to understand how atmospheric conditions (such as freeze and thaw effect) influence the erosion of the cliff, we modeled the temperature diffusion through the rock mass. To this end, we applied heat diffusion and radiation equation using a 1D temperature profile, obtaining as a result both temperature variations at different depths together with the location of the 0°C isotherm. Our model was calibrated during a given training set using both in-situ rock temperatures and atmospheric conditions. We then carried out a comparison with the rockfall events derived from the 3D GB-LiDAR datasets in order to quantify the erosion rates and to correlate it with atmospheric conditions, aiming to analyze which parameters influence Molasse erosion process.

Modeling winter hydrological processes under differing climatic conditions: Modifying WEPP

NASA Astrophysics Data System (ADS)

Dun, Shuhui

Water erosion is a serious and continuous environmental problem worldwide. In cold regions, soil freeze and thaw has great impacts on infiltration and erosion. Rain or snowmelt on a thawing soil can cause severe water erosion. Of equal importance is snow accumulation and snowmelt, which can be the predominant hydrological process in areas of mid- to high latitudes and forested watersheds. Modelers must properly simulate winter processes to adequately represent the overall hydrological outcome and sediment and chemical transport in these areas. Modeling winter hydrology is presently lacking in water erosion models. Most of these models are based on the functional Universal Soil Loss Equation (USLE) or its revised forms, e.g., Revised USLE (RUSLE). In RUSLE a seasonally variable soil erodibility factor (K) was used to account for the effects of frozen and thawing soil. Yet the use of this factor requires observation data for calibration, and such a simplified approach cannot represent the complicated transient freeze-thaw processes and their impacts on surface runoff and erosion. The Water Erosion Prediction Project (WEPP) watershed model, a physically-based erosion prediction software developed by the USDA-ARS, has seen numerous applications within and outside the US. WEPP simulates winter processes, including snow accumulation, snowmelt, and soil freeze-thaw, using an approach based on mass and energy conservation. However, previous studies showed the inadequacy of the winter routines in the WEPP model. Therefore, the objectives of this study were: (1) To adapt a modeling approach for winter hydrology based on mass and energy conservation, and to implement this approach into a physically-oriented hydrological model, such as WEPP; and (2) To assess this modeling approach through case applications to different geographic conditions. A new winter routine was developed and its performance was evaluated by incorporating it into WEPP (v2008.9) and then applying WEPP to four study sites at different spatial scales under different climatic conditions, including experimental plots in Pullman, WA and Morris, MN, two agricultural drainages in Pendleton, OR, and a forest watershed in Mica Creek, ID. The model applications showed promising results, indicating adequacy of the mass- and energy-balance-based approach for winter hydrology simulation.

Characterization of solid particle erosion resistance of ductile metals based on their properties

NASA Technical Reports Server (NTRS)

Rao, P. V.; Buckley, D. H.

1985-01-01

This paper presents experimental results pertaining to spherical glass bead and angular crushed glass particle impingement. A concept of energy absorption to explain the failure of material is proposed and is correlated with the erosion characteristics of several pure metals. Analyses of extensive erosion data indicate that the properties - surface energy, specific melting energy, strain energy, melting point, bulk modulus, hardness, atomic volume - and the product of the parameters - linear coefficient of thermal expansion x bulk modulus x temperature rise required for melting, and ultimate resilience x hardness - exhibit the best correlations. The properties of surface energy and atomic volume are suggested for the first time for correlation purposes and are found to correlate well with erosion rates at different angles of impingement. It further appears that both energy and thermal properties contribute to the total erosion.

[Research progress on wind erosion control with polyacrylamide (PAM).

PubMed

Li, Yuan Yuan; Wang, Zhan Li

2016-03-01

Soil wind erosion is one of the main reasons for soil degradation in the northwest region of China. Polyacrylamide (PAM), as an efficient soil amendment, has gained extensive attention in recent years since it is effective in improving the structure of surface soil due to its special physical and chemical properties. This paper introduced the physical and chemical properties of PAM, reviewed the effects of PAM on soil wind erosion amount and threshold wind velocity, as well as the effect differences of PAM in soil wind erosion control under conditions of various methods and doses. Its effect was proved by comparing with other materials in detail. Furthermore, we analyzed the mecha-nism of wind erosion control with PAM according to its influence on soil physical characteristics. Comprehensive analysis showed that, although some problems existed in wind erosion control with (PAM), PAM as a sand fixation agent, can not only enhance the capacity of the soil resis-tance to wind erosion, but also improve soil physical properties to form better soil conditions. Besides, we proposed that combination of PAM and plant growth would increase the survival rate of plants greatly, control soil wind erosion in wind-erosive areas, and improve the quality of the ecological environment construction. Thus, PAM has practically important significance and wide application prospect in controlling soil wind erosion.

Robotic weld overlay coatings for erosion control

NASA Astrophysics Data System (ADS)

The erosion of materials by the impact of solid particles has received increasing attention during the past twenty years. Recently, research has been initiated with the event of advanced coal conversion processes in which erosion plays an important role. The resulting damage, termed Solid Particle Erosion (SPE), is of concern primarily because of the significantly increased operating costs which result in material failures. Reduced power plant efficiency due to solid particle erosion of boiler tubes and waterfalls has led to various methods to combat SPE. One method is to apply coatings to the components subjected to erosive environments. Protective weld overlay coatings are particularly advantageous in terms of coating quality. The weld overlay coatings are essentially immune to spallation due to a strong metallurgical bond with the substrate material. By using powder mixtures, multiple alloys can be mixed in order to achieve the best performance in an erosive environment. However, a review of the literature revealed a lack of information on weld overlay coating performance in erosive environments which makes the selection of weld overlay alloys a difficult task. The objective of this project is to determine the effects of weld overlay coating composition and microstructure on erosion resistance. These results will lead to a better understanding of erosion mitigation in CFB's.

Desertification risk in Kakheti Region, East Georgia.

PubMed

Basialashvili, Tsisana; Matchavariani, Lia; Lagidze, Lamzira

2015-01-01

Desertification or land degradation in drylands is caused by various factors. The most important of these is climate change, a significant global ecological problem. Desertification, like erosion, as an environmental process of ecosystem degradation, is often caused by human activity. It is a common misconception that droughts cause desertification. Well-managed lands can recover from drought if the rains return. These practices help to control erosion and maintain productivity during periods when moisture is available. Traditionally, the most vulnerable territories considered under the threat of desertification in Georgia is Kakheti region (East Georgia), which has been selected as one of the priority investigation area. In Eastern Georgia, intervals of atmospheric precipitation do not coincide with the phases of water demand of plants. In recent decades as a result of more frequent droughts in Kakheti, the region has already lost hundreds, thousands of hectares of fertile land. Based on the contemporary climate warming projections, the temperature is expected to increase and precipitation to decrease. This will lead to an increase in evaporation and reduction of river flow. Under such conditions the danger of desertification is evident. To mitigate the negative effects of desertification, it is recommended to put forward set of adaptation activities through rehabilitation of water use systems, prevention of loss of water, reconstruction and expansion of irrigation canals, accumulation of unused autumn-winter river water and spring floods in reservoirs, developing an optimal scheme of distributing water resources among water users, device windbreaks and work on breeding of drought resistant varieties, preparation of water volume forecasts of rivers and their role in planning of water use; application of apply drip and sprinkler irrigation, using artificial precipitation following increase as a result of active influence on clouds. All these activities will provide means for suspending desertification process, create ecological safety for the environment and improve the economic well-being of population.

Surface modification of hydroturbine steel using friction stir processing

NASA Astrophysics Data System (ADS)

Grewal, H. S.; Arora, H. S.; Singh, H.; Agrawal, A.

2013-03-01

Friction stir processing (FSP) has proved to be a viable tool for enhancing the mechanical properties of materials, however, the major focus has been upon improving the bulk properties of light metals and their alloys. Hydroturbines are susceptible to damage owing to slurry and cavitation erosion. In this study, FSP of a commonly employed hydroturbine steel, 13Cr4Ni was undertaken. Microstructural characterization of the processed steel was conducted using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and electron back scatter diffraction (EBSD) techniques. Mechanical characterization of the steel was undertaken in terms of microhardness and resistance to cavitation erosion (CE). FSP resulted in the refinement of the microstructure with reduction in grain size by a factor of 10. EBSD results confirmed the existence of submicron and ultrafine grained microstructure. The microhardness of the steel was found to enhance by 2.6 times after processing. The processed steel also showed 2.4 times higher resistance against cavitation erosion in comparison to unprocessed steel. The primary erosion mechanism for both the steels was identical in nature, with plastic deformation responsible for the loss of material.

Effects of the Treating Time on Microstructure and Erosion Corrosion Behavior of Salt-Bath-Nitrided 17-4PH Stainless Steel

NASA Astrophysics Data System (ADS)

Wang, Jun; Lin, Yuanhua; Li, Mingxing; Fan, Hongyuan; Zeng, Dezhi; Xiong, Ji

2013-08-01

The effects of salt-bath nitriding time on the microstructure, microhardness, and erosion-corrosion behavior of nitrided 17-4PH stainless steel at 703 K (430 °C) were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and erosion-corrosion testing. The experimental results revealed that the microstructure and phase constituents of the nitrided surface alloy are highly process condition dependent. When 17-4PH stainless steel was subjected to complex salt-bathing nitriding, the main phase of the nitrided layer was expanded martensite ( α`), expanded austenite (S), CrN, Fe4N, and Fe2N. The thickness of nitrided layers increased with the treating time. The salt-bath nitriding improves effectively the surface hardness. The maximum values measured from the treated surface are observed to be 1100 HV0.1 for 40 hours approximately, which is about 3.5 times as hard as the untreated material (309 HV0.1). Low-temperature nitriding can improve the erosion-corrosion resistance against two-phase flow. The sample nitrided for 4 hours has the best corrosion resistance.

In situ measurements of erosion shear stress and geotechnical shear strength of the intertidal sediments of the experimental managed realignment scheme at Tollesbury, Essex, UK

NASA Astrophysics Data System (ADS)

Watts, C. W.; Tolhurst, T. J.; Black, K. S.; Whitmore, A. P.

2003-11-01

Managed realignment is one of several 'soft' engineering options which may reduce the costs of coastal defence, provide a more 'natural' response to the problem of rising sea levels and at the same time deliver environmental, specifically nature conservation, benefits. The success of this technique depends on the ability of the soils and sediments within the site to resist the erosive action of waves and tidal currents and allow sediment accretion to occur, at least at a rate equal to mean sea-level rise. Once a critical shear stress, τ0 crt exerted by the moving fluids over the bed, is exceeded erosion will occur. A cohesive strength meter (CSM) and the fall-cone method were used to gather data, in situ on the strength and stability of sediments from an experimental managed realignment site and an adjacent, established saltmarsh in south-east England. Following six years of regular tidal cover, the underlying agricultural soil appeared both very strong (mean surface shear strength, τ f=228 kPa) and highly resistant to erosion ( τ 0 crt=6.23 N m -2). During this period much of the site had been covered by sediment, and saltmarsh plants ( Salicornia europaea) had become established above the mean high water neap tide (MHWN) level. Above MHWN level (tidal cover time <15%) sediments had greater bulk densities and lower water contents which resulted in a moderate shear strength (τ f=11.6 kPa) and resistance to erosion (τ 0 crt=2.45 N m -2) . Below MHWN, where sediment accretion rates were greatest, poor consolidation resulted in very high water contents and low bulk densities. These areas were at the highest potential risk of erosion (τ 0 crt=1.5 N m -2) and had very low shear strengths (τ f=0.33 kPa) . Where sediment exceeded 25 cm depth, gullies formed allowing their banks and adjacent margins to drain faster than the surrounding sediment. This led to a significant increase in bed strength (τ f=10.8 kPa) and stability (τ 0 crt=4.3 N m -2) . These gullies were probably the early stages of the complex creek patterns characteristic of the adjacent, established saltmarsh. The established saltmarsh was rich in plants and had a well-developed (aggregated) soil structure. These soils had a moderate to high resistance to erosion (τ 0 crt=2.45 N m -2) and shear strength (τ f=25.6 kPa) . Undrained sediment shear strength, τf, obtained with the fall-cone apparatus can also provide a useful indication of critical erosion shear stress, τ0 crt . Values of τ0 crt , measured across this site were all relatively large compared with computed bed stresses arising from locally generated waves. Thus this experimental managed realignment site was found to be primarily depositional and was thus successfully achieving the twin aims of protecting the coast from erosion and extending a rich ecosystem.

Vulnerability, survival and shame in Nina Raine's Tiger Country.

PubMed

Bowman, Deborah

2017-12-01

Shame in healthcare remains relatively underexplored, yet it is commonplace and its impact is significant. This paper explores shame in healthcare using Nina Raine's 2011 play Tiger Country Three manifestations of shame are explored, namely (1) shame in relation to professional identity and survival in the clinical workplace; (2) shame and illness as experienced by both patients and doctors; and (3) the systemic and organisational influences on shame within healthcare systems. I suggest that the theatre is particularly well-placed to elucidate shame, and that Tiger Country demonstrates the prevalence and impact of shame on clinical work. Shame has a fundamental and overlooked relationship with damaging and well-documented phenomena in healthcare, including moral distress, ethical erosion, compassion fatigue, burnout, stress and ill health. Attention to shame is essential for those interested in medicine and healthcare and must, I propose, include the experiences and perceptions of those who provide care, as well as attending to those who receive care. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Karst characterization in a semi-arid region using gravity, seismic, and resistivity geophysical techniques.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnhart, Kevin Scott

2013-10-01

We proposed to customize emerging in situ geophysical monitoring technology to generate time-series data during sporadic rain events in a semi-arid region. Electrodes were to be connected to wireless \

Erosion and channel changes due to extreme flooding in the Fourmile Creek catchment, Colorado

NASA Astrophysics Data System (ADS)

Wicherski, Will; Dethier, David P.; Ouimet, William B.

2017-10-01

Infrequent, large magnitude geomorphic events generate quantifiable change on geologically short timescales and are crucial to understanding landscape evolution. Airborne lidar surveys and field measurements were used to investigate floodplain erosion and deposition along a 19.5 km reach of Fourmile Creek, Colorado that was devastated by severe flooding in 2013 that followed a 2010 wildfire. > 350 mm of rain fell on the Fourmile catchment from September 9-15, 2013, generating discharge that exceeded bankfull for > 120 h at the Orodell gage, with local unit stream power > 300 W m- 2 throughout the study reach. Debris flows occurred on steep hillslopes and tributary channels in the most intensely burned areas. Lidar difference measurements and field studies highlight zones of local deposition along the study reach, but demonstrate overall net erosion of 0.25 m for the 19.5 km reach of Fourmile floodplain, mainly by channel widening. Tributary junctions where debris-flow sediment entered the floodplain and local decreases in unit stream power controlled some zones of deposition. Overall, mass balance calculations show that a total sediment loss of 91,000-161,000 m3 from the Fourmile Creek floodplain and hillslopes, which is broadly consistent with channel sediment flux estimates of 71,000-111,000 m3. Measurements from the Fourmile catchment demonstrate that floodplain erosion was a major source of sediment in the 2013 flood and demonstrate that infrequent events marked by long-duration flooding and high total energy expenditure can account for a large fraction of total sediment transport in mountain streams.

Reduction in soil aggregate size distribution due to wind erosion

NASA Astrophysics Data System (ADS)

Swet, Nitzan; Katra, Itzhak

2017-04-01

Soil erosion process by wind causes emission of fine soil particles, and thus alters the topsoil's properties, fertility, and erodibility. Topsoil resistance to erosion depends on its physicochemical properties, especially on the soil aggregation. Although the key role of aggregates in soil erodibility, quantitative information on the relations between soil aggregate size distribution (ASD) and erosion is still lucking. This study focuses on ASD analyses before and after soil erosion by wind. Wind tunnel experiments and soil analyses were conducted on semiarid loess topsoils with different initial conditions of aggregation. The results show that in all initial soil conditions saltation of sand particles caused the breakdown of macro-aggregates > 500 µm, resulting in increase of micro-aggregates (63-250 µm). The micro-aggregate production increases with the wind shear velocity (up to 0.61 m s-1) for soils with available macro-aggregates. The findings highlight dynamics in soil aggregation in response to erosion process, and therefore the significance of ASD in quantifying soil degradation and soil loss potential.

Slurry Erosion Studies on Surface Modified 13Cr-4Ni Steels: Effect of Angle of Impingement and Particle Size

NASA Astrophysics Data System (ADS)

Manisekaran, T.; Kamaraj, M.; Sharrif, S. M.; Joshi, S. V.

2007-10-01

Hydroturbine steels, such as 13Cr-4Ni martensitic steels, are generally subjected to heavy-erosive wear and loss of efficiency due to solid particulate entrainment in the water. Surface-modified steels have proven to give better performance in terms of erosive wear resistance. In the present study, an attempt is made to investigate the effect of angle of impingement and particle size on slurry-jet erosion behavior of pulsed plasma nitrided and laser hardened 13Cr-4Ni steels. Laser hardening process has shown good performance at all angles of impingement due to martensitic transformation of retained austenite. Plastic deformation mode of material removal was also an evident feature of all laser-hardened surface damage locations. However, pulsed-plasma nitrided steels have exhibited chip formation and micro-cutting mode of erosive wear. Erosion with 150-300 μm size was twice compared to 150 μm size slurry particulates.

Erosion-corrosion and cavitation-erosion measurements on copper alloys utilizing thin layer activation technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, C.H.; Hsu, K.Y.; Kai, J.J.

1992-12-31

The surface layers of copper alloy specimens were made radioactive by bombarding with 5 MeV protons from a van de Graaff accelerator which converted Cu-65 into Zn-65 through (p,n) reaction. The amount of surface material loss could then be monitored by measuring the total remaining {gamma}-ray activity generated from Zn-65 decay. This technique, termed thin layer activation (TLA), has the advantage of in situ monitoring the rate of surface removal due to corrosion, erosion-corrosion, wearing, etc. In this work, the erosion-corrosion tests on aluminum brass and 90Cu-10Ni were conducted in circulating sea water and the erosion-corrosion rates measured using TLAmore » and conventional methods such as linear polarization resistance (LPR) method and weight loss coupons were compared. A vibrational cavitation-erosion test was also performed on aluminum bronze, in which the measurements by TLA were compared with those of weight loss measurements.« less

Environmental factors affecting corrosion of munitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bundy, K.; Bricka, M.; Morales, A.

1995-12-31

Spent small arms munitions have accumulated for years at outdoor firing ranges operated by the DoD and other groups. Used bullets are often subjected to moisture sources. There is increasing concern that accumulations of lead-based munitions represent potential sources of water and soil pollution. To understand both the severity of and solutions to this problem, it is necessary to measure how rapidly bullets corrode and to determine the soil variables affecting the process. In this study M16 bullets were buried in samples of soil taken from Louisiana army firing ranges. Four environmental conditions were simulated; rain water, acid rain, seamore » water, and 50% sea water/50% acid rain. The three electrode technique was used to measure the bullet corrosion. Graphite rods served as counter electrodes. A saturated calomel reference electrode was used along with a specially constructed salt bridge. Electrochemical measurements were conducted using a computer-controlled potentiostat to determine corrosion potential, soil resistance, and corrosion current. The rate of corrosion was found to markedly increase with decreasing soil pH and increasing chloride and moisture contents, with the chloride content being the most influential variable. High soil resistance and noble corrosion potential were found to be associated with low corrosion rates. This is important since both parameters can be readily measured in the field.« less

Does vegetation prevent wave erosion of salt marsh edges?

PubMed

Feagin, R A; Lozada-Bernard, S M; Ravens, T M; Möller, I; Yeager, K M; Baird, A H

2009-06-23

This study challenges the paradigm that salt marsh plants prevent lateral wave-induced erosion along wetland edges by binding soil with live roots and clarifies the role of vegetation in protecting the coast. In both laboratory flume studies and controlled field experiments, we show that common salt marsh plants do not significantly mitigate the total amount of erosion along a wetland edge. We found that the soil type is the primary variable that influences the lateral erosion rate and although plants do not directly reduce wetland edge erosion, they may do so indirectly via modification of soil parameters. We conclude that coastal vegetation is best-suited to modify and control sedimentary dynamics in response to gradual phenomena like sea-level rise or tidal forces, but is less well-suited to resist punctuated disturbances at the seaward margin of salt marshes, specifically breaking waves.

Absolute Density Calibration Cell for Laser Induced Fluorescence Erosion Rate Measurements

NASA Technical Reports Server (NTRS)

Domonkos, Matthew T.; Stevens, Richard E.

2001-01-01

Flight qualification of ion thrusters typically requires testing on the order of 10,000 hours. Extensive knowledge of wear mechanisms and rates is necessary to establish design confidence prior to long duration tests. Consequently, real-time erosion rate measurements offer the potential both to reduce development costs and to enhance knowledge of the dependency of component wear on operating conditions. Several previous studies have used laser-induced fluorescence (LIF) to measure real-time, in situ erosion rates of ion thruster accelerator grids. Those studies provided only relative measurements of the erosion rate. In the present investigation, a molybdenum tube was resistively heated such that the evaporation rate yielded densities within the tube on the order of those expected from accelerator grid erosion. This work examines the suitability of the density cell as an absolute calibration source for LIF measurements, and the intrinsic error was evaluated.

Does vegetation prevent wave erosion of salt marsh edges?

PubMed Central

Feagin, R. A.; Lozada-Bernard, S. M.; Ravens, T. M.; Möller, I.; Yeager, K. M.; Baird, A. H.

2009-01-01

This study challenges the paradigm that salt marsh plants prevent lateral wave-induced erosion along wetland edges by binding soil with live roots and clarifies the role of vegetation in protecting the coast. In both laboratory flume studies and controlled field experiments, we show that common salt marsh plants do not significantly mitigate the total amount of erosion along a wetland edge. We found that the soil type is the primary variable that influences the lateral erosion rate and although plants do not directly reduce wetland edge erosion, they may do so indirectly via modification of soil parameters. We conclude that coastal vegetation is best-suited to modify and control sedimentary dynamics in response to gradual phenomena like sea-level rise or tidal forces, but is less well-suited to resist punctuated disturbances at the seaward margin of salt marshes, specifically breaking waves. PMID:19509340

Distinguishing between tectonic and lithologic controls on bedrock channel longitudinal profiles using cosmogenic 10Be erosion rates and channel steepness index

USGS Publications Warehouse

Cyr, Andrew J.; Granger, Darryl E.; Olivetti, Valerio; Molin, Paola

2014-01-01

Knickpoints in fluvial channel longitudinal profiles and channel steepness index values derived from digital elevation data can be used to detect tectonic structures and infer spatial patterns of uplift. However, changes in lithologic resistance to channel incision can also influence the morphology of longitudinal profiles. We compare the spatial patterns of both channel steepness index and cosmogenic 10Be-determined erosion rates from four landscapes in Italy, where the geology and tectonics are well constrained, to four theoretical predictions of channel morphologies, which can be interpreted as the result of primarily tectonic or lithologic controls. These data indicate that longitudinal profile forms controlled by unsteady or nonuniform tectonics can be distinguished from those controlled by nonuniform lithologic resistance. In each landscape the distribution of channel steepness index and erosion rates is consistent with model predictions and demonstrates that cosmogenic nuclide methods can be applied to distinguish between these two controlling factors.

Reusable Metallic Thermal Protection Systems Development

NASA Technical Reports Server (NTRS)

Blosser, Max L.; Martin, Carl J.; Daryabeigi, Kamran; Poteet, Carl C.

1998-01-01

Metallic thermal protection systems (TPS) are being developed to help meet the ambitious goals of future reusable launch vehicles. Recent metallic TPS development efforts at NASA Langley Research Center are described. Foil-gage metallic honeycomb coupons, representative of the outer surface of metallic TPS were subjected to low speed impact, hypervelocity impact, rain erosion, and subsequent arcjet exposure. TPS panels were subjected to thermal vacuum, acoustic, and hot gas flow testing. Results of the coupon and panel tests are presented. Experimental and analytical tools are being developed to characterize and improve internal insulations. Masses of metallic TPS and advanced ceramic tile and blanket TPS concepts are compared for a wide range of parameters.

Development and implementation of a laboratory spray device and rainfall simulator for retention research using small amounts of agroformulations.

PubMed

Zwertvaegher, Ingrid Ka; Van Daele, Inge; Verheesen, Peter; Peferoen, Marnix; Nuyttens, David

2017-01-01

Rainfall greatly affects the retention of foliar-applied agroformulations. Improving their resistance to wash-off is therefore of great importance in spray applications. When developing such formulations, small-scale laboratory assays are generally required. A set-up for retention studies using only small amounts of agroformulations (<0.5 L) was developed. The set-up consists of a spray device and a rainfall simulator. The effect of rain quantity (1, 3, 6 mm) on the spray retention of agroformulations was evaluated using this set-up. The data showed that uniform and repeatable spraying was achieved with the small-scale spray device (coefficient of variation 23.4%) on potato pot plants (Solanum tuberosum L.). Rain quantity significantly affected the spray retention. Approximately 40% of the initial deposition was lost after 1 mm of rain at an intensity of 25 mm h -1 . Additional losses decreased with increasing volumes of rain (65 and 80% loss after 3 and 6 mm of rain respectively). Future studies could implement the set-up to evaluate the effect of different rainfall characteristics and formulations on spray retention in order to improve the rainfastness of agroformulations. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Biochemical responses of the mycorrhizae in Pinus massoniana to combined effects of Al, Ca and low pH.

PubMed

Kong, F X; Liu, Y; Hu, W; Shen, P P; Zhou, C L; Wang, L S

2000-02-01

Biochemical responses of Pinus massoniana, with and without the inoculation mycorrhizal fungus Pisolithus tinctorius at the root, to artificial acid rain (pH 2.0) and various Ca/Al ratios were investigated. Some enzymes associated with the nutritive metabolism, such as acid phosphatase, alkaline phosphatase, nitrate reductase, mannitol dehydrogenase and trehalase, in the roots, stems and leaves of plant were obviously inhibited by the artificial acid rain and Al. After treatment with pH 2.0 + Ca/Al (0/1 or 1/10) artificial acid rain, the protein content in the organs was decreased. However, the activities of superoxide dismutase (SOD) and peroxidase (POD) and glutathione (GSH) concentrations were induced. It demonstrated that acid rain and Al could induce oxygen radicals in plant. Compared with the treatments with lower pH or Al, respectively, the combination of lower pH and Al concentration was more toxic to P. massoniana. Al toxicity could be ameliorated by the addition of Ca and the amelioration was the most when the ratio was 1/1 among the various Ca/Al ratio. Infection with mycorrhizal fungus P. tinctorius at the root of P. massoniana increased the ability of the plant to resist the toxicity of artificial acid rain and Al stress.

Development and Optimization of Tailored Composite TBC Design Architectures for Improved Erosion Durability

NASA Astrophysics Data System (ADS)

Schmitt, Michael P.; Schreiber, Jeremy M.; Rai, Amarendra K.; Eden, Timothy J.; Wolfe, Douglas E.

2017-08-01

Rare-earth pyrochlores, RE2Zr2O7, have been identified as potential thermal barrier coating (TBC) materials due to their attractive thermal properties and CMAS resistance. However, they possess a low fracture toughness which results in poor erosion durability/foreign object damage resistance. This research focuses on the development of tailored composite air plasma spray (APS) TBC design architectures utilizing a t' Low-k secondary toughening phase (ZrO2-2Y2O3-1Gd2O3-1Yb2O3; mol.%) to enhance the erosion durability of a hyper-stoichiometric pyrochlore, NZO (ZrO2-25Nd2O3-5Y2O3-5Yb2O3; mol.%). In this study, composite coatings have been deposited with 30, 50, and 70% (wt.%) t' Low-k toughening phase in a horizontally aligned lamellar morphology which enhances the toughening response of the coating. The coatings were characterized via SEM and XRD and were tested for erosion durability before and after isothermal heat treatment at 1100 °C. Analysis with mixing laws indicated improved erosion performance; however, a lack of long-term thermal stability was shown via isothermal heat treatments at 1316 °C. An impact stress analysis was performed using finite element analysis of a coating cross section, representing the first microstructurally realistic study of mechanical properties of TBCs with the results correlating well with observed behavior.

Effects of the May 5-6, 1973, storm in the Greater Denver area, Colorado

USGS Publications Warehouse

Hansen, Wallace R.

1973-01-01

Rain began falling on the Greater Denver area the evening of Saturday, May 5, 1973, and continued through most of Sunday, May 6. Below about 7,000 feet altitude, the precipitation was mostly rain; above that altitude, it was mostly snow. Although the rate of fall was moderate, at least 4 inches of rain or as much as 4 feet of snow accumulated in some places. Sustained precipitation falling at a moderate rate thoroughly saturated the ground and by midday Sunday sent most of the smaller streams into flood stage. The South Platte River and its major tributaries began to flood by late Sunday evening and early Monday morning. Geologic and hydrologic processes activated by the May 5-6 storm caused extensive damage to lands and to manmade structures in the Greater Denver area. Damage was generally most intense in areas where man had modified the landscape--by channel constrictions, paving, stripping of vegetation and topsoil, and oversteepening of hillslopes. Roads, bridges, culverts, dams, canals, and the like were damaged or destroyed by erosion and sedimentation. Streambanks and structures along them were scoured. Thousands of acres of croplands, pasture, and developed urban lands were coated with mud and sand. Flooding was intensified by inadequate storm sewers, blocked drains, and obstructed drainage courses. Saturation of hillslopes along the Front Range caused rockfalls, landslides, and mudflows as far west as Berthoud Pass. Greater attention to geologic conditions in land-use planning, design, and construction would minimize storm damage in the future.

Investigating the Effect of Compaction Characteristics on the Erodibility of Cohesive Soils Using the JET Method

NASA Astrophysics Data System (ADS)

Asghari Tabrizi, A.; LaRocque, L. A.; Chaudhry, M.; Imran, J.

2013-12-01

Several flood disasters occur every year all over the world, mostly due to levee and dam failure which result in human fatalities as well as devastating economic damages. To model and predict earthen embankment failures for the preparation of emergency action plans and risk assessments, the soil erodibility by flowing water is an essential parameter. The determination of erodibility becomes even more complicated for cohesive soils because of the large number of parameters controlling their erosion behavior (e.g. clay content, plasticity, compaction effort, compaction water content) and the difficulty of estimating these parameters. In this study the effect of the compaction energy and compaction water content on the erodibility of a sandy loam soil was assessed. Soil samples were prepared in a standard diameter compaction mold, 101.6 mm, for three levels of compaction effort and water content (i.e. low, medium, and high) with two replications for each case (18 tests total) and examined using the jet erosion test (JET). Observations from qualitative and statistical analyses of the data are: 1) a wide range of erodibility, from very erodible to very resistant, was produced by changes in the compaction characteristics; 2) for a given compaction energy, the erosion resistance based on the detachment rate coefficient kd tends to become minimum near the optimum compaction water content. On the dry side of optimum compaction water content, kd decreases with steep gradients by increasing the water content, while it increases with a flatter gradient on the wet side; 3) At a given water content, the soil erosion resistance increases with compaction efforts; 4) compaction water content influences soil erosibility more than compaction energy, especially on the dry side of the optimum compaction water content; and 5) for a given compaction effort, the critical shear stress increases with water content up to an optimum water content and then it decreases which is in consistent with the kd trends.

Simulation of torrential rain as a means for assessment of surface runoff coefficients and calculation of recurrent design events in alpine catchments

NASA Astrophysics Data System (ADS)

Markart, Gerhard; Kohl, Bernhard; Sotier, Bernadette; Klebinder, Klaus; Schauer, Thomas; Bunza, Günther

2010-05-01

Simulation of heavy rain is an established method for studying infiltration characteristics, runoff and erosion behaviour in alpine catchments. Accordingly for characterization and differentiation of various runoff producing areas in alpine catchments transportable spray irrigation installations for large plots have been developed at the BFW, Department of Natural Hazards and Alpine Timberline, in Innsbruck, Austria. One installation has been designed for assessment of surface runoff coefficients under convective torrential rain with applicable precipitation intensities between 30 and 120 mm*h-1 and a plot size between 50 and 100 m2. The second device is used for simulation of persistent rain events (rain intensity about 10 mm*h-1, plot size: 400-1200 m2). Very reasonable results have been achieved during the comparison with spray irrigations from other institutions (e.g. Bavarian Environmental Agency in Munich) in the field. Rain simulations at BFW are mostly combined with comprehensive additional investigations on land-use, vegetation cover, soil physical characteristics, soil humidity, hydrogeology and other features of the test-sites. This allows proper interpretation of the achieved runoff data. At the moment results from more than 280 rain simulations are available from about 25 catchments / regions of the Eastern Alps at the BFW. Results show that the surface runoff coefficient, when runoff is constant at the test site (φconst) increases only slightly between rain intensities from 30 to 120 mm*h-1 (increment is 6%). Therefore φconst shall be used for assessment of runoff behaviour of runoff contributing areas, because it is less dependent form system conditions than φtot. BFW-data have been consolidated with results of the LfU (Bavarian Environmental Agency in Munich) in a data base and formed the basis for the development of a simple code of practice for assessment of surface runoff coefficients in torrential rain. The manual is freely available under: http://bfw.ac.at/rz/bfwcms.web?dok=4342 (in German language). The runoff contributing areas delineated by use of the manual in the field can be compiled in digital surface runoff coefficient maps and surface roughness maps. These maps in Austria form the basis for calculation of recurrent design events by use of precipitation/runoff models (P/R-models) like ZEMOKOST (optimized runtime method after Zeller = ZEller MOdified by KOhl and STepanek) or HEC-HMS. The result is substantial information on runoff disposition in each sub-catchment and hydrographs showing peak runoff and runoff freight. The code of practice for assessment of surface runoff coefficients has become the standard procedure in Austria to derive input parameters for P/R-models in practice. Recent investigations done at the Institute of Geography at the University of Berne show that the code of practice is suitable for application in catchments at the northern edge of the Swiss Alps too.

Queensland 2010-2011: A Summer of Extremes

NASA Astrophysics Data System (ADS)

Maroulis, J.

2012-04-01

"I love a sunburnt country, A land of sweeping plains, Of ragged mountain ranges, Of droughts and flooding rains. I love her far horizons, I love her jewel-sea, Her beauty and her terror, The wide brown land for me." (Dorothea Mackellar OBE, 1885-1968). This second stanza from Mackellar's famous poem "My Country", beautifully sums up the Australian environment. In late 2010-early 2011, the "droughts and flooding rains" were the perfect terms to describe the climatic variability and the resulting flooding impacts experienced in many parts of Queensland under an enhanced La Niña as part of the ENSO (El Niño-Southern Oscillation) climate pattern, with over 75% of Queensland being declared a disaster zone. This contrasts with the severe drought that had gripped many parts of Australia over the previous 8 years which saw water storage levels plummet, and resulted in 35% of Queensland being 'drought declared' as at April 2010. On the Darling Downs in southern Queensland, over 100,000 ha of land was inundated by the Condamine River due to flooding in early 2011. The river which is generally <100 m wide was seven kilometres wide at the widest point during the floods. However, the erosive impacts of the floods on largely tilled floodplains was relatively low with most erosion confined to the bed and banks of the river. In Grantham, where 13 lives were lost, flooding was especially hazardous because of the combined depth and velocity of floodwaters and the rapid rise of floodwaters across the floodplain. Floodwaters were ~2.0-2.5 m deep across the northern parts of the floodplain with a maximum velocity of ~2-3 m/s. The rate of rise was estimated at ~12 m/hour, indicating that it would have taken only 10-15 minutes to rise to full depth. However, despite detailed river and flood gauging in the more urbanised catchments such as the Brisbane River valley, this is by far the exception rather than the rule throughout mainland Australia. The Queensland floods highlight the pressing and urgent need for an accurate and more intensive network of river gauging and sediment monitoring. In a country of "droughts and flooding rains" and in the face of climate change, this need is now imperative.

Plasma-edge studies using carbon resistance probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wampler, W.R.

1984-01-01

Characterization of erosion and hydrogen-recycling processes occurring at the edge of magnetically confined plasmas requires knowledge of the energy and flux of hydrogen isotopes incident on the materials. A new plasma-edge probe technique, the carbon resistance probe, has been developed to obtain this information. This technique uti

Interrill Erodibility of P and C on conventially and organically farmed Devon soils

NASA Astrophysics Data System (ADS)

Kuhn, N. J.

2012-04-01

Soil erosion can have significant off-site effects on water quality and thus human and habitat health. Apart from sedimentation, the transfer of nutrients, both dissolved and particulate, is a major concern. The particulate transfer of nutrients from agricultural land can occur either by rill or interrill erosion. Rill erosion is non-selective and affects only a limited extent of agricultural land. Interrill processes such as crusting, splash and raindrop-impacted wash, on the other hand, act on all cropland and affect the quality of the water from all areas generating runoff. A significant amount of phosphorus (P) is contained in the surface soil layer transformed by interrill processes annually. In the EU, the P content of a crusted (2 mm) surface layer corresponds to 4 to 40 kg ha-1 of P on arable land (1.094 mil km2). Therefore, the role of interrill processes and erosion for regional nutrient cycling requires close attention. Interrill erosion is a complex phenomenon, involving the detachment, transport and deposition of soil particles by raindrop impacted flow. Resistance to interrill erosion varies between soils depending on their physical, chemical and mineralogical properties. In addition, significant changes in soil resistance to interrill erosion occur during storms as a result of changes in surface roughness, cohesion and particle size. As a consequence, erosion on interrill areas is selective, moving the most easily detached small and/or light soil particles which are often enriched in clay, P and organic C. Commonly, the risk of erosion associated with organically farmed soils is lower than those farmed in a conventional way. This is attributed to greater aggregate stability and thus greater infiltration and lower erodibility. Erosion of nutrients on organically farmed soils is therefore considered to be reduced by the same order of magnitude than the amount of eroded soil compared to conventionally farmed soils. However, the selective nature of interrill erosion potentially counteracts this effect by the preferential removal of fine particles enriched in nutrients and soil organic matter. In this study, an experiment comparing the erodibility of P and C on organically and conventially farmed soils from Devon is presented. The results show a disproportional increase of P in sediment from the organically farmed soil, reducing the perceived benefit of organic farming on nutrient erosion by 80%. The pronounced P enrichment in the organically farmed soil is attributed to the higher concentrations of C and P as well as lower densities of the small particle fraction. The results, while very preliminary, indicate that the impact of soil management on off-site effects of erosion such as water quality can only be fully assessed when we understand the relevant erosion processes. They also indicate that some less than expected positive effects of changing soil management to improve water quality might be caused by the preferential erosion of P-bearing soil particles.

A Simplified Analytic Investigation of the Riverside Effects of Sediment Diversions

DTIC Science & Technology

2013-09-01

demonstrated that the river bed consists of a sand layer of variable thickness, underlain by erosion resistant strata (either relict glacial deposits...following analysis. Simplifications and Initial Conditions. Consider a river modeled as a wide rectangular channel of constant width (Figure 1). The...CHETN-VII-13 September 2013 14  Short term effects include the redistribution of sediment by erosion upstream of the diversion to deposition

Arbuscular-Mycorrhizal Networks Inhibit Eucalyptus tetrodonta Seedlings in Rain Forest Soil Microcosms

PubMed Central

Janos, David P.; Scott, John; Aristizábal, Catalina; Bowman, David M. J. S.

2013-01-01

Eucalyptus tetrodonta, a co-dominant tree species of tropical, northern Australian savannas, does not invade adjacent monsoon rain forest unless the forest is burnt intensely. Such facilitation by fire of seedling establishment is known as the "ashbed effect." Because the ashbed effect might involve disruption of common mycorrhizal networks, we hypothesized that in the absence of fire, intact rain forest arbuscular mycorrhizal (AM) networks inhibit E. tetrodonta seedlings. Although arbuscular mycorrhizas predominate in the rain forest, common tree species of the northern Australian savannas (including adult E. tetrodonta) host ectomycorrhizas. To test our hypothesis, we grew E. tetrodonta and Ceiba pentandra (an AM-responsive species used to confirm treatments) separately in microcosms of ambient or methyl-bromide fumigated rain forest soil with or without severing potential mycorrhizal fungus connections to an AM nurse plant, Litsea glutinosa. As expected, C. pentandra formed mycorrhizas in all treatments but had the most root colonization and grew fastest in ambient soil. E. tetrodonta seedlings also formed AM in all treatments, but severing hyphae in fumigated soil produced the least colonization and the best growth. Three of ten E. tetrodonta seedlings in ambient soil with intact network hyphae died. Because foliar chlorosis was symptomatic of iron deficiency, after 130 days we began to fertilize half the E. tetrodonta seedlings in ambient soil with an iron solution. Iron fertilization completely remedied chlorosis and stimulated leaf growth. Our microcosm results suggest that in intact rain forest, common AM networks mediate belowground competition and AM fungi may exacerbate iron deficiency, thereby enhancing resistance to E. tetrodonta invasion. Common AM networks–previously unrecognized as contributors to the ashbed effect–probably help to maintain the rain forest–savanna boundary. PMID:23460899

Arbuscular-mycorrhizal networks inhibit Eucalyptus tetrodonta seedlings in rain forest soil microcosms.

PubMed

Janos, David P; Scott, John; Aristizábal, Catalina; Bowman, David M J S

2013-01-01

Eucalyptus tetrodonta, a co-dominant tree species of tropical, northern Australian savannas, does not invade adjacent monsoon rain forest unless the forest is burnt intensely. Such facilitation by fire of seedling establishment is known as the "ashbed effect." Because the ashbed effect might involve disruption of common mycorrhizal networks, we hypothesized that in the absence of fire, intact rain forest arbuscular mycorrhizal (AM) networks inhibit E. tetrodonta seedlings. Although arbuscular mycorrhizas predominate in the rain forest, common tree species of the northern Australian savannas (including adult E. tetrodonta) host ectomycorrhizas. To test our hypothesis, we grew E. tetrodonta and Ceiba pentandra (an AM-responsive species used to confirm treatments) separately in microcosms of ambient or methyl-bromide fumigated rain forest soil with or without severing potential mycorrhizal fungus connections to an AM nurse plant, Litsea glutinosa. As expected, C. pentandra formed mycorrhizas in all treatments but had the most root colonization and grew fastest in ambient soil. E. tetrodonta seedlings also formed AM in all treatments, but severing hyphae in fumigated soil produced the least colonization and the best growth. Three of ten E. tetrodonta seedlings in ambient soil with intact network hyphae died. Because foliar chlorosis was symptomatic of iron deficiency, after 130 days we began to fertilize half the E. tetrodonta seedlings in ambient soil with an iron solution. Iron fertilization completely remedied chlorosis and stimulated leaf growth. Our microcosm results suggest that in intact rain forest, common AM networks mediate belowground competition and AM fungi may exacerbate iron deficiency, thereby enhancing resistance to E. tetrodonta invasion. Common AM networks-previously unrecognized as contributors to the ashbed effect-probably help to maintain the rain forest-savanna boundary.

Seed population dynamics on abandoned slopes in the hill and gully Loess Plateau region of China

NASA Astrophysics Data System (ADS)

Yu, Weijie; Jiao, Juying

2017-04-01

Recovery of natural vegetation is an effective but slow approach to control the soil erosion in the Chinese hill and gully Loess Plateau region. As seed stage is particularly vulnerable to environmental conditions, characteristics of seed population should be needed to study for determining whether the recovery of natural vegetation is limited during this stage on the abandoned slopes in this region. The study was performed on three abandoned slopes in a watershed with an area of 8.27 km2in the Shaanxi province of China. The differences in soil seed banks were investigated in two different points in time, late March2011 and early April 2013. Main factors of seed population dynamics, such as seed yield of dominant species, seed inputs by seed rain as well as seed outputs through seed loss by overland flow and seedling emergence, were monitored from late March 2011 to early April 2013. In this study, seed rain densities of the main later successional species, i.e., Lespedeza davurica, Stipa bungeana and Artemisia gmelinii accounted for 51.5-71.6% of their own seed yields. The soil seed bank density in early April 2013 was larger than that in late March 2011. The density of seed inputs by seed rain was 10186 seeds•m-2, and the total seed bank, including seed rain and seeds present in the soil seed bank in late March 2011, reached a density of 15018 seeds•m-2 during the study period. Seed densities of loss due to overland flow and seedling emergence were 79 seeds•m-2 from 20 species and 938 seedlings•m-2 that belonged to 38 species during a study period, and the seed output through them accounted for 0.5% and 6.3% of the total seed bank, respectively. The study concluded that overland flow could not result in large numbers of seeds loss and seeds were accumulating in the soil seed bank due to seed rain, and vegetation succession might be limited by curbed spatial seed dispersal and seedling establishment.

The cavitation erosion of ultrasonic sonotrode during large-scale metallic casting: Experiment and simulation.

PubMed

Tian, Yang; Liu, Zhilin; Li, Xiaoqian; Zhang, Lihua; Li, Ruiqing; Jiang, Ripeng; Dong, Fang

2018-05-01

Ultrasonic sonotrodes play an essential role in transmitting power ultrasound into the large-scale metallic casting. However, cavitation erosion considerably impairs the in-service performance of ultrasonic sonotrodes, leading to marginal microstructural refinement. In this work, the cavitation erosion behaviour of ultrasonic sonotrodes in large-scale castings was explored using the industry-level experiments of Al alloy cylindrical ingots (i.e. 630 mm in diameter and 6000 mm in length). When introducing power ultrasound, severe cavitation erosion was found to reproducibly occur at some specific positions on ultrasonic sonotrodes. However, there is no cavitation erosion present on the ultrasonic sonotrodes that were not driven by electric generator. Vibratory examination showed cavitation erosion depended on the vibration state of ultrasonic sonotrodes. Moreover, a finite element (FE) model was developed to simulate the evolution and distribution of acoustic pressure in 3-D solidification volume. FE simulation results confirmed that significant dynamic interaction between sonotrodes and melts only happened at some specific positions corresponding to severe cavitation erosion. This work will allow for developing more advanced ultrasonic sonotrodes with better cavitation erosion-resistance, in particular for large-scale castings, from the perspectives of ultrasonic physics and mechanical design. Copyright © 2018 Elsevier B.V. All rights reserved.

Preliminary assessment of soil erosion impact during forest restoration process

NASA Astrophysics Data System (ADS)

Lai, Yen-Jen; Chang, Cheng-Sheng; Tsao, Tsung-Ming; Wey, Tsong-Huei; Chiang, Po-Neng; Wang, Ya-Nan

2014-05-01

Taiwan has a fragile geology and steep terrain. The 921 earthquake, Typhoon Toraji, Typhoon Morakot, and the exploitation and use of the woodland by local residents have severely damaged the landscape and posed more severe challenges to the montane ecosystem. A land conservation project has been implemented by the Experimental Forest of National Taiwan University which reclaimed approximately 1,500 hectares of leased woodland from 2008 to 2010, primarily used to grow bamboo, tea trees, betel nut, fruit, and vegetable and about 1,298 hectares have been reforested. The process of forest restoration involves clear cutting, soil preparation and a six-year weeding and tending period which may affect the amount of soil erosion dramatically. This study tried to assess the impact of forest restoration from the perspective of soil erosion through leased-land recovery periods and would like to benefit the practical implementation of reforestation in the future. A new plantation reforested in the early 2013 and a nearby 29-year-old mature forest were chosen as experimental and comparison sites. A self-designed weir was set up in a small watershed of each site for the runoff and sediment yield observation. According to the observed results from May to August 2013, a raining season in Taiwan, the runoff and erosion would not as high as we expected, because the in-situ soil texture of both sites is sandy loam to sandy with high percentage of coarse fragment which increased the infiltration. There were around 200 kg to 250 kg of wet sand/soil yielded in mature forest during the hit of Typhoon Soulik while the rest of the time only suspended material be yielded at both sites. To further investigate the influence of the six-year weeding and tending period, long term observations are needed for a more completed assessment of soil erosion impact.

Remote Sensing Application of the Geophysical Changes in the Coastlines and Rivers of Zambales, Philippines

NASA Astrophysics Data System (ADS)

Paz-Alberto, Annie Melinda; Sison, Melissa Joy M.; Bulaong, Edmark Pablo; Pakaigue, Marietta A.

2016-06-01

Geophysical changes in river outlet, river upstream and coastlines near the rivers of Bucao and Santo Tomas in Zambales, Philippines were analyzed using the Google Earth's historical satellite imageries from 2004 to 2013. Data in 2015 were gathered from in situ field measurements ground validation. The study aimed to measure and determine changes in the width of river outlet, width of river bank upstream and shifting of coastline. Results revealed that there was a decrease and increase in the width size of the Bucao and Santo Tomas river outlets, respectively during the study period. Geophysical changes occurred in the two rivers due to the continuous supply of lahar as an after effect of the Mount Pinatubo eruption in 1991. Coastline positions near the two rivers also changed. The highest rate of erosion along the coastal area was prevalently observed near the river outlet of both rivers. Moreover, accretion was observed in the coastline of Santo Tomas and erosion phenomenon was observed in the North and South coastlines of Bucao River. The shifting was caused by natural processes such as erosion, sedimentation and natural calamities as well as anthropogenic processes such as reclamation/quarrying. Occurrence of erosion and sedimentation played active roles in the changes of coastlines during the study period. Furthermore, the upstream of the Bucao river changed physically due to deposits of lahar present in the upstream which are being discharged directly and continuously going down to the river. Generally, the width of the Bucao River upstream decreased its size because of the accumulated sediment in the riverbank. On the other hand, the observed erosion is caused by high velocity of river during heavy rains and typhoons. The width of the Santo Tomas river bank upstream did not change due to the construction of concrete dikes which prevent the lahar-filled river from breaching the embankment and flooding the agricultural, residential and commercial areas near the river.

A 9700-hour durability test of a five centimeter diameter ion thruster

NASA Technical Reports Server (NTRS)

Nakanishi, S.; Finke, R. C.

1973-01-01

A modified Hughes SIT-5 thrustor has been life-tested at the Lewis Research Center. The final 2700 hours of the test are described with a charted history of thrustor operating parameters and off-normal events. Performance and operating characteristics were nearly constant throughout the test except for neutralizer heater power requirements and accelerator drain current. A post-shutdown inspection revealed sputter erosion of ion chamber components and component flaking of sputtered metal. Several flakes caused beamlet divergence and anomalous grid erosion, causing the test to be terminated. All sputter erosion sources have been identified and promising sputter resistant components are currently being evaluated.

Antecedent moisture content and soil texture effects on infiltration and erosion

NASA Astrophysics Data System (ADS)

Mamedov, A. I.; Huang, C.; Levy, G. J.

2006-12-01

Water infiltration, seal formation, runoff and erosion depend on the soil's inherent properties and surface conditions. Most erosion models consider only soil inherent properties (mainly texture) in assessing infiltration and erosion without consideration of spatial and temporary variation in the surface condition, particularly the antecedent moisture content. We studied the interaction of two different surface conditions, i.e. antecedent moisture content (AMC) and aging (timing after wetting) on infiltration (IR), seal formation (runoff generation) and erosion in four soils varying from loam to clay. Soil samples were packed in erosion box and wetted with different amounts of water (0, 1, 2, 3, 4, 6, 8, or 16 mm) to obtain a wide moisture range (i.e., pF 0-6.2, or from air dry to full saturation). The boxes were put in plastic bags and allowed to age for 0.01, 1, 3, or 7 days. Then the soil in the erosion box exposed to 60 mm of rain. At no aging final IR of soils did not change significantly, but runoff volume (a measure for seal development) and soil loss increased with an increase in AMC mainly because of aggregate breakdown. For any given aging, the highest IR and smallest runoff volume and soil loss were obtained at the intermediate AMC levels (pF 2.4-4.2, between wilting point and field capacity). For instance, in the clay soil to which 3 mm of water (pF~2.7) was added, as aging increased from one to seven days, final IR increased from 5.3 to 7.9 mm h-1, while runoff and soil loss decreased from 34 mm to 22 mm, and from 630 to 360 g m2 respectively. At this AMC range, increasing aging time resulted in up to 40% increase in IR and decrease in runoff or soil loss. This tendency significantly more pronounced for clay soils because water-filled pores in the clay fabric were considered active in the stabilization process and the development of cohesive bonds between and within particles during the aging period. The results of this study are important for soil erosion modeling. In order to improve the prediction capabilities of erosion models, temporal and spatial variation of soil moisture content (AMC, wetting and aging) prior to erosive rainstorms should be considered and or incorporated. In addition, management practices could be adapted to diminish the severe soil moisture variation, where ever possible, (minimum till or no-till with known residue) to maintain the soil surface at a desired AMC level prior to expected rainstorms in order to decrease soil susceptibility to seal formation, runoff and soil loss.

Investigating the effect of lignosulfonate on erosion rate of the embankments constructed with clayey sand.

PubMed

Koohpeyma, Hamid Reza; Vakili, Amir Hossein; Moayedi, Hossein; Panjsetooni, Alireza; Nazir, Ramli

2013-01-01

Internal erosion is known as the most important cause of dam failure after overtopping. It is important to improve the erosion resistance of the erodible soil by selecting an effective technique along with the reasonable costs. To prevent internal erosion of embankment dams the use of chemical stabilizers that reduce the soil erodibility potential is highly recommended. In the present study, a lignin-based chemical, known as lignosulfonate, is used to improve the erodibility of clayey sand specimen. The clayey sand was tested in various hydraulic heads in terms of internal erosion in its natural state as well as when it is mixed with the different percentages of lignosulfonate. The results show that erodibility of collected clayey sand is very high and is dramatically reduced by adding lignosulfonate. Adding 3% of lignosulfonate to clayey sand can reduce the coefficient of soil erosion from 0.01020 to 0.000017. It is also found that the qualitative erodibility of stabilized soil with 3% lignosulfonate is altered from the group of extremely rapid to the group of moderately slow.

Solid particle erosion of polymers and composites

NASA Astrophysics Data System (ADS)

Friedrich, K.; Almajid, A. A.

2014-05-01

After a general introduction to the subject of solid particle erosion of polymers and composites, the presentation focusses more specifically on the behavior of unidirectional carbon fiber (CF) reinforced polyetheretherketone (PEEK) composites under such loadings, using different impact conditions and erodents. The data were analyzed on the basis of a newly defined specific erosive wear rate, allowing a better comparison of erosion data achieved under various testing conditions. Characteristic wear mechanisms of the CF/PEEK composites consisted of fiber fracture, matrix cutting and plastic matrix deformation, the relative contribution of which depended on the impingement angles and the CF orientation. The highest wear rates were measured for impingement angles between 45 and 60°. Using abrasion resistant neat polymer films (in this case PEEK or thermoplastic polyurethane (TPU) ones) on the surface of a harder substrate (e.g. a CF/PEEK composite plate) resulted in much lower specific erosive wear rates. The use of such polymeric films can be considered as a possible method to protect composite surfaces from damage caused by minor impacts and erosion. In fact, they are nowadays already successfully applied as protections for wind energy rotor blades.

Investigating the Effect of Lignosulfonate on Erosion Rate of the Embankments Constructed with Clayey Sand

PubMed Central

Koohpeyma, Hamid Reza; Vakili, Amir Hossein; Panjsetooni, Alireza; Nazir, Ramli

2013-01-01

Internal erosion is known as the most important cause of dam failure after overtopping. It is important to improve the erosion resistance of the erodible soil by selecting an effective technique along with the reasonable costs. To prevent internal erosion of embankment dams the use of chemical stabilizers that reduce the soil erodibility potential is highly recommended. In the present study, a lignin-based chemical, known as lignosulfonate, is used to improve the erodibility of clayey sand specimen. The clayey sand was tested in various hydraulic heads in terms of internal erosion in its natural state as well as when it is mixed with the different percentages of lignosulfonate. The results show that erodibility of collected clayey sand is very high and is dramatically reduced by adding lignosulfonate. Adding 3% of lignosulfonate to clayey sand can reduce the coefficient of soil erosion from 0.01020 to 0.000017. It is also found that the qualitative erodibility of stabilized soil with 3% lignosulfonate is altered from the group of extremely rapid to the group of moderately slow. PMID:24459437

Dust and chemical erosion biases in cosmogenic nuclide studies: A factor-of-ten problem that could mask strong climatic effects on landscape evolution

NASA Astrophysics Data System (ADS)

Riebe, C. S.; Arvin, L.; Ferrier, K.; Aciego, S.

2017-12-01

Cosmogenic nuclides have been widely used to quantify erosion in mountain ranges around the world, creating a global database of erosion rates from climatically and lithologically diverse sites, and providing vital clues about how mountain landscape evolution is coupled to Earth's carbon cycle and thus global climate change over geologic timescales. Despite this wealth of data, few studies have observed the widely expected strong control of erosion rates by climatic factors such as precipitation and temperature. Here we show that cosmogenic nuclide studies are prone to biases due to dust deposition and chemical erosion, which together can obscure strong relationships between climate and erosion rates. Erosion rates of sites exposed to intense chemical weathering can be underestimated by two-fold due to chemical enrichment of the cosmogenic target mineral quartz — a result of its high chemical erosion resistance, which increases its residence time and thus reduces its apparent erosion rate compared to other soil minerals. Meanwhile, erosion rates of sites with rapid dust deposition can be overestimated by more than ten-fold, due to dust's contributions to soil mass and target mineral abundance. Compilations of dust fluxes and cosmogenic nuclide data suggest that steep climatic trends in erosion rates, ranging from slow erosion rates in dry settings to twenty-fold faster erosion rates in wet settings, could be largely masked by the combined effects of dust deposition and chemical erosion. We argue that these effects need to be quantified in many cosmogenic nuclide studies of erosion rates. Doing so will require dust input rates; soil depth and density; quartz-enrichment ratios in both saprolite relative to bedrock and soil relative to saprolite; and quartz concentrations in deposited dust. Failure to quantify these crucial parameters can lead to misinterpretation of the strength — and even the sign — of feedbacks between climate and erosion rates in mountain landscapes.

Effects of Rainfall-Induced Topsoil Structure Changes on Root-Zone Moisture Regime during the Dry Period

NASA Astrophysics Data System (ADS)

Wang, Feng; Chen, Jiazhou; Lin, Lirong

2018-01-01

Rainfall erosion and subsequent intermittent drought are serious barriers for agricultural production in the subtropical red soil region of China. Although it is widely recognized that rainfall-induced soil structure degradation reduced soil water storage and water-holding capacity, the effects of variation of the rainfall-induced topsoil structure on the subsequent soil water regime during the dry period is still rarely considered. The objective of this study was to ascertain the way of rainfall-induced topsoil structure changes on the subsequent soil water regime during the dry period. In a three-year-long experiment, six practices (CK, only crop; SM, straw mulching; PAM, polyacrylamide surface application; B, contour Bahia-grass strip; SPAM, straw mulching and polyacrylamide surface application; and BPAM, contour Bahia-grass strip and polyacrylamide surface application) were conducted at an 8° farmland with planting summer maize resulting in different topsoil structure and root-zone moisture, to establish and reveal the quantitatively relationship between the factors of topsoil structure and soil drought. Rainfall erosion significantly increased the soil crust coverage, and decreased the WSA 0.25, 0-30 mm soil porosity and mean pore size. There was no significant difference during the raining stage of root-zone water storage between CK and other practices. An index of soil drought intensity ( I) and degree ( D) was established using soil water loss rate and soil drought severity. The larger value of I means a higher rate of water loss. The larger value of D means more severe drought. During the dry period, I and D were significantly higher in CK than in other practices. I and D had significantly positively correlation with the crust size and crust coverage, and negatively with WSA 0.25, 15-30 mm soil porosity and mean pore size. Among of soil structure factors, the soil porosity had the largest effect on I and D. The rainfall-induced topsoil structure changes greatly deteriorated the root-zone regime during the dry period mainly due to significant increasing soil water loss but little improving the raining stage of soil water storage. Straw mulching had greater effects than other practices in alleviating rainfall-induced erosion and intermittent drought, and could be a better strategy applied for this region.

Bedrock river erosion measurements and modelling along a river of the Frontal Himalaya

NASA Astrophysics Data System (ADS)

Lave, Jerome; Dubille, Matthieu

2017-04-01

River incision is a key process in mountains denudation and therefore in landscape evolution models. Despite its importance, most incision models for mountain rivers rely on simplified, or quite empirical relations, and generally only consider annual average values for water discharge and sediment flux. In contrast, very few studies consider mechanistic models at the timescale of a flood, and try to bridge the gap between experimental or theoretical approaches and long term river incision studies. In this contribution, we present observations made during 7 monsoon seasons on fluvial bedrock erosion along the Bakeya river across the Frontal Himalaya in Central Nepal. Along its lower gorge, this river incises alternation of indurated sandstone and less resistant claystone, at Holocene rates larger than 10mm/yr. More importantly, its upper drainage mostly drains through non-cohesive conglomerate which allows, in this specific setting, estimating the bedload characteristics and instantaneous fluxes, i.e. a pre-requisite to test mechanistic models of fluvial erosion. During the study period, we monitored and documented the channel bank erosion in order to understand the amplitude of the erosion processes, their occurrence in relation with hydrology, in order to test time-integrated models of erosion. Besides hydrologic monitoring, erosion measurements were threefold: (1) at the scale of the whole monsoon, plucking and block removal by repeated photo surveys of a 400m long channel reach, (2) detailed microtopographic surveys of channel bedrock elevation along a few sandstone bars to document their abrasion, (3) real time measurement of fluvial bedrock wear to document erosion timing using a new erosion sensor. Results indicate that: 1. Erosion is highly dependent on rock resistance, but on average block detachment and removal is a more efficient process than bedrock attrition, and operates at a rate that permit channel banks downcutting to keep pace with Holocene uplift rate. 2. Both block detachment and attrition processes clearly increase with fluvial shear stress, but non-linearly, in particular through the existence of a minimum threshold. As a result of which bank erosion occur during only a few hours per year during short and very high flood events, which questions the use of average discharge (or drainage area) in many bedrock erosion models. We then propose a semi-physical model of sandstone bars abrasion based on discharge history (HEC-RAS modelling), Rouse suspension model, and experimental measurements on dependency of abrasion rate vs impacting particle size. This model predicts well the timing and the amplitude of both real-time and monsoon average abrasion along the surveyed sandstone bars. This first validation of a model for bank erosion opens large perspective for future work on channel bottom incision modelling using physical models of erosion and their time- and gravel-size-integration, with the objective to introduce more physical rules in landscape evolution models.

Physical erosion modelling of complex morphodynamics in the upper Val d'Orcia: a combination of EROSION 3D, UAV, SFM and CANUPO

NASA Astrophysics Data System (ADS)

Buchholz, Arno; Kaiser, Andreas; Neugirg, Fabian; Schindewolf, Marcus; Schmidt, Jürgen

2017-04-01

Throughout the Mediterranean Basin soil erosion is both a widely spread and a landscape shaping process. In order to increase the understanding of morphodynamics inside large Italian badland areas, so called Calanchi, the process based erosion model EROSION 3D was parameterized by artificial rainfall simulations, soil sampling and an UAV based high resolution digital elevation model. Vegetation structures were removed with the CANUPO-classifier in CloudCompare. The rainfall experiments proved to be a convenient but costly tool for deriving the model input parameters. While building up the model, different composition of the inhomogeneous soil surface was considered. A diverse behavior against erosion by water was observed. The results showed that the deposition surfaces of rotational or translational slides, besides calanco depth contour, tend to degrade. Although these deposits present a comparatively low bulk density, they reduce the infiltration due to soil surface clogging and cause less erosion resistances. The differential consideration of erosion sub-processes turns out as particularly challenging. The simulation of a reference year showed an annual soil export from the catchment of 43 t/ha, which corresponds to an average surface lowering of 3 mm. Sheet erosion represents an amount of about 5% of the total erosion of badlands. Furthermore, infiltration depth, amount of runoff, sediment concentration, and grain size composition of the deposits were calculated. This study makes a contribution to the understanding of denudation processes in Calanchi badlands. The presented process-based modeling of badlands is contributing a new aspect to erosion research.

Elevated nitrogen metabolism and nitric oxide production are involved in Arabidopsis resistance to acid rain.

PubMed

Qiao, Fang; Zhang, Xi-Min; Liu, Xiang; Chen, Juan; Hu, Wen-Jun; Liu, Ting-Wu; Liu, Ji-Yun; Zhu, Chun-Quan; Ghoto, Kabir; Zhu, Xue-Yi; Zheng, Hai-Lei

2018-06-01

Acid rain (AR) can induce great damages to plants and could be classified into different types according to the different SO 4 2- /NO 3 - ratio. However, the mechanism of plants' responding to different types of AR has not been elucidated clearly. Here, we found that nitric-rich simulated AR (N-SiAR) induced less leaves injury as lower necrosis percentage, better physiological parameters and reduced oxidative damage in the leaves of N-SiAR treated Arabidopsis thaliana compared with sulfate and nitrate mixed (SN-SiAR) or sulfuric-rich (S-SiAR) simulated AR treated ones. Of these three types of SiAR, N-SiAR treated Arabidopsis maintained the highest of nitrogen (N) content, nitrate reductase (NR) and nitrite reductase (NiR) activity as well as N metabolism related genes expression level. Nitric oxide (NO) content showed that N-SiAR treated seedlings had a higher NO level compared to SN-SiAR or S-SiAR treated ones. A series of NO production and elimination related reagents and three NO production-related mutants were used to further confirm the role of NO in regulating acid rain resistance in N-SiAR treated Arabidopsis seedlings. Taken together, we concluded that an elevated N metabolism and enhanced NO production are involved in the tolerance to different types of AR in Arabidopsis. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

[Effects of gravel mulch technology on soil erosion resistance and plant growth of river flinty slope].

PubMed

Zhu, Wei; Xie, San-Tao; Ruan, Ai-Dong; Bian, Xun-Wen

2008-03-01

Aiming at the technical difficulties such as the stability and water balance in the ecological rehabilitation of river flinty slope, a gravel mulch technology was proposed, with the effects of different gravel mulch treatments on the soil anti-erosion capacity, soil water retention property, and plant growth investigated by anti-erosion and pot experiments. The results showed that mulching with the gravels 1.5-2 cm in size could obviously enhance the soil anti-erosion capacity, soil water retention property and plant biomass, but no obvious differences were observed between the mulch thickness of 5 cm and 8 cm. It was indicated that mulching with the gravels 1.5-2 cm in size and 5 cm in thickness was an effective and economical technology for the ecological rehabilitation of river flinty slope.

How does slope form affect erosion in CATFLOW-SED?

NASA Astrophysics Data System (ADS)

Gabelmann, Petra; Wienhöfer, Jan; Zehe, Erwin

2016-04-01

Erosion is a severe environmental problem in agro-ecosystems with highly erodible loess soils. It is controlled by various factors, e.g. rainfall intensity, initial wetness conditions, soil type, land use and tillage practice. Furthermore slope form and gradient have been shown to influence erosion amounts to a large extent. Within the last fifty years, various erosion models have been developed to describe the erosion process, estimate erosion amounts and identify erosion-prone areas. These models differ in terms of complexity, the processes which are considered, and the data required for model calibration and they can be categorised into empirical or statistical, conceptual, and physically-based models. CATFLOW-SED is a process-based hydrology and erosion model that can operate on catchment and hillslope scales. Soil water dynamics are described by the Richards equation including effective approaches for preferential flow. Evapotranspiration is simulated using an approach based on the Penman-Monteith equation. The model simulates overland flow using the diffusion wave equation. Soil detachment is related to the attacking forces of rainfall and overland flow, and the erosion resistance of soil. Sediment transport capacity and sediment deposition are related to overland flow velocity using the equation of Engelund and Hansen and the sinking velocity of grain sizes respectively. We performed a study to analyse the erosion process on different virtual hillslopes, with varying slope gradient and slope form, using the CATFLOW-SED model. We explored the role of landform on erosion and sedimentation, particularly we look for forms that either maximise or minimise erosion. Results indicate the importance to performing the process implementation within physically meaningful limits and choose appropriate model parameters respectively.

Thresholds in marsh resilience to the Deepwater Horizon oil spill

PubMed Central

Silliman, Brian R.; Dixon, Philip M.; Wobus, Cameron; He, Qiang; Daleo, Pedro; Hughes, Brent B.; Rissing, Matthew; Willis, Jonathan M.; Hester, Mark W.

2016-01-01

Ecosystem boundary retreat due to human-induced pressure is a generally observed phenomenon. However, studies that document thresholds beyond which internal resistance mechanisms are overwhelmed are uncommon. Following the Deepwater Horizon (DWH) oil spill, field studies from a few sites suggested that oiling of salt marshes could lead to a biogeomorphic feedback where plant death resulted in increased marsh erosion. We tested for spatial generality of and thresholds in this effect across 103 salt marsh sites spanning ~430 kilometers of shoreline in coastal Louisiana, Alabama, and Mississippi, using data collected as part of the natural resource damage assessment (NRDA). Our analyses revealed a threshold for oil impacts on marsh edge erosion, with higher erosion rates occurring for ~1–2 years after the spill at sites with the highest amounts of plant stem oiling (90–100%). These results provide compelling evidence showing large-scale ecosystem loss following the Deepwater Horizon oil spill. More broadly, these findings provide rare empirical evidence identifying a geomorphologic threshold in the resistance of an ecosystem to increasing intensity of human-induced disturbance. PMID:27679956

Crustal Uplift In The Alps and Why The Drainage Pattern Matters: An Alternative Way To Interpret Geodetic Data

NASA Astrophysics Data System (ADS)

Schlunegger, F.; Hinderer, M.

The Alpine drainage system comprises two large orogen-parallel drainage basins in the core of the Alps (the Rhone and Rhein valleys), and smaller orogen-normal ori- ented systems. Discharge of the large rivers is ca. 5-10 higher than that of the small ones. Also, the courses of the Rhone and Rhein Rivers are trapped by faults and thrusts that display lower erosional resistance than the neighbouring lithologies. Enhanced discharge of these rivers and low erosional resistance of bedrocks potentially enhances surface erosion. Indeed, present-day and glacial sediment yields have been ca. 1.6-1.7 times higher in these valleys than in the orogen-normal systems. Interestingly, geode- tic measurements indicate that rates of crustal uplift are also enhanced in the Rhein and Rhone valleys, where rates of ca. 1.4-1.6 mm/yr are currently measured. We inter- pret the spatial coincidence between the location of enhanced erosion and maximum crustal uplift rates to reflect a positive feedback between surface erosion and tectonic forcing.

Notes on status and ecology of the endangered Hawaiian annual 'Āwiwi, Centaurium sebaeoides (Gentianaceae)

USGS Publications Warehouse

Medeiros, Arthur C.; Chimera, Charles G.; Loope, Lloyd L.; Joe, Stephanie M.; Krushelnycky, Paul D.

2000-01-01

The annual, endemic, coastal herb Centaurium sebaeoides is the only native Hawaiian species in the gentian family. The U.S. Fish and Wildlife Service listed it as Endangered under the Endangered Species Act on 29 October 1991. Before surveys reported here, the total population of this species statewide was estimated at 80-110 individuals in eight populations. During counts made in April and May 1997, following ample winter rains, 12 populations of C. sebaeoides with a total of 6300-6600 plants were noted on five islands (Kaua'i, O'ahu, Lana'i, Moloka'i, and Maui). Five populations were mapped with a global positioning system and counted; in the remaining seven populations, the numbers of individuals were estimated. More recent surveys in 1998-1999 estimated a total of only 60-80 individuals at all sites. Such dramatic population fluctuations are believed to be related to the sporadic occurrence of winter rains. Threats that further contribute to the rarity of the species include (1) displacement and overtopping by salt-tolerant nonnative woody species, especially Casuarina spp., (2) trampling and erosion of habitat by ungulates, and (3) damage caused by off-road vehicles.

Georeferenced measurement of soil EC as a tool to detect susceptible areas to water erosion.

NASA Astrophysics Data System (ADS)

Fabian Sallesses, Leonardo; Aparicio, Virginia Carolina; Costa, Jose Luis

2017-04-01

The Southeast region of Buenos Aires Province, Argentina, is one of the main region for the cultivation of potato (Solanum tuberosum L.) in that country. The implementation of complementary irrigation for potato cultivation meant an increase in yield of up to 60%. Therefore, all potato production in the region is under irrigation. In this way, the area under central pivot irrigation has increased to 150% in the last two decades. The water used for irrigation in that region is underground with a high concentration of sodium bicarbonate. The combination of irrigation and rain increases the sodium absorption ratio of soil (SARs), consequently raising the clay dispersion and reducing infiltration. A reduction in infiltration means greater partitioning of precipitation into runoff. The degree of slope of the terrain, added to its length, increases the erosive potential of runoff water. The content of dissolved salts, in combination with the water content, affect the apparent Electrical Conductivity of the soil (EC), which is directly related to the concentration of Na + 2 in the soil solution. In August 2016, severe rill erosion was detected in a productive plot of 300 ha. The predecessor crop was a potato under irrigation campaign. However the history of the lot consists of various winter and summer crops, always made in dry land and no till. Cumulative rainfall from harvest to erosion detection (four months) was 250 mm. A georeferenced EC measurement was performed using the Verys 3100® contact sensor. With the data obtained, a geostatistical analysis was performed using Kriging spatial interpolation. The maps obtained were processed, dividing them into 4 EC ranges. The values and amplitude of the CEa ranges for each lot were determined according to the distribution observed in the generated histograms. It was observed a distribution of elevated EC ranges and consequently of a higher concentration of Na+ 2 coincident with the irrigation areas of the pivots. These areas presented the highest occurrence of clay dispersion and rill erosion. This would indicate that with one campaign of cultivation of potato under supplementary irrigation are given the conditions that facilitate erosive events. The georeferenced measurement of EC by contact ground sensors and their visualization through digital cartography could be an interesting tool to detect areas susceptible to erosive events. This information would help in decision making for a soil management that tends to avoid or reduce soil losses due to deterioration of physical and chemical properties by the incorporation of sodium by irrigation. Key words: Irrigation, soil sodium, erosion.

Study on reinforcement of soil for suppressing fugitive dust by bio-cementitious material

NASA Astrophysics Data System (ADS)

Zhan, Qiwei; Qian, Chunxiang

2017-06-01

Microbial-induced reinforcement of soil, as a new green and environmental-friendly method, is being paid extensive attention to in that it has low cost, simple operation and rapid effects. In this research, reinforcement of soil for suppressing fugitive dust by bio-cementitious material was investigated. Soil cemented by bio-cementitious material had superior mechanical properties, such as hardness, compressive strength, microstructure, wind-erosion resistance, rainfall-erosion resistance and freeze-thaw resistance. The average hardness of sandy soil, floury soil and clay soil is 18.9 º, 25.2 º and 26.1 º, while average compressive strength of samples is 0.43 MPa, 0.54 MPa and 0.69 MPa, respectively; meanwhile, the average calcite content of samples is 6.85 %, 6.09 %, and 5.96 %, respectively. Compared with the original sandy soil, floury soil and clay soil, the porosity decreases by 38.5 %, 33.7 % and 29.2 %. When wind speed is 12 m/s, the mass loss of sandy soil, floury soil and clay soil cemented by bio-cementitious material are all less than 30 g/(m2·h). After three cycles of rainfall erosion of 2.5 mm/h, the mass loss are less than 25 g/(m2·h) and the compressive strength residual ratio are more than 98.0 %. Under 25 cycles of freeze-thaw, the mass loss ratio are less than 3.0 %.

Slow erosion of a quantitative apple resistance to Venturia inaequalis based on an isolate-specific Quantitative Trait Locus.

PubMed

Caffier, Valérie; Le Cam, Bruno; Al Rifaï, Mehdi; Bellanger, Marie-Noëlle; Comby, Morgane; Denancé, Caroline; Didelot, Frédérique; Expert, Pascale; Kerdraon, Tifenn; Lemarquand, Arnaud; Ravon, Elisa; Durel, Charles-Eric

2016-10-01

Quantitative plant resistance affects the aggressiveness of pathogens and is usually considered more durable than qualitative resistance. However, the efficiency of a quantitative resistance based on an isolate-specific Quantitative Trait Locus (QTL) is expected to decrease over time due to the selection of isolates with a high level of aggressiveness on resistant plants. To test this hypothesis, we surveyed scab incidence over an eight-year period in an orchard planted with susceptible and quantitatively resistant apple genotypes. We sampled 79 Venturia inaequalis isolates from this orchard at three dates and we tested their level of aggressiveness under controlled conditions. Isolates sampled on resistant genotypes triggered higher lesion density and exhibited a higher sporulation rate on apple carrying the resistance allele of the QTL T1 compared to isolates sampled on susceptible genotypes. Due to this ability to select aggressive isolates, we expected the QTL T1 to be non-durable. However, our results showed that the quantitative resistance based on the QTL T1 remained efficient in orchard over an eight-year period, with only a slow decrease in efficiency and no detectable increase of the aggressiveness of fungal isolates over time. We conclude that knowledge on the specificity of a QTL is not sufficient to evaluate its durability. Deciphering molecular mechanisms associated with resistance QTLs, genetic determinants of aggressiveness and putative trade-offs within pathogen populations is needed to help in understanding the erosion processes. Copyright © 2016 Elsevier B.V. All rights reserved.

Pristine and Surface-Modified Polymers in LEO: MISSE Results versus Predictive Models and Ground-Based Testing

NASA Astrophysics Data System (ADS)

Iskanderova, Zelina; Kleiman, Jacob I.; Tennyson, Rod C.

2009-01-01

Space flight data, collected and published by NASA Glenn Research Center (GRC) team for a set of pristine polymeric materials selected, compiled, and tested in two LEO flight experiments at the International Space Station, as part of the "Materials International Space Station Experiment" (MISSE), has been used for comparison with previously developed atomic oxygen erosion predictive models. The same set of materials was used for a ground-based fast atomic beam (FAO) experimental erosion study at ITL/UTIAS, where the FAO exposure was performed mostly at a standard fluence of 2×1020 cm-2, with the results collected in a database for the development of a prototype of predictive software. A comparison of MISSE-1 flight data with two predictive correlations has shown good agreement, confirming the developed approach to polymers erosion resistance forecast that might be used also for newly developed or untested in space polymeric materials. A number of surface-modified thin film space polymers, treated by two ITL-developed and patented surface modification technologies, Implantox™ [5] and Photosil™ [6], have been also included in MISSE flight experiment. The results from those MISSE samples have shown full protection of AO-sensitive main space-related hydrocarbon polymers, such as Kapton HN, back-metalized Kapton H and Kapton E, and Mylar, when treated by Implantox™ surface modification technology and significant erosion resistance enhancement up to full protection by Photosil™ treatment.

A new methodology to prepare ceramic-organic composite coatings with good cavitation erosion resistance.

PubMed

Deng, Wen; Hou, Guoliang; Li, Shuangjian; Han, Jiesheng; Zhao, Xiaoqin; Liu, Xia; An, Yulong; Zhou, Huidi; Chen, Jianmin

2018-06-01

A simple, scalable and economical method was proposed to obtain ceramic-organic composite coating with excellent comprehensive properties include hardness, toughness, elastic recovery, lamellar interfacial bonding and anti-cavitation erosion: introducing epoxy resin into the pores and micro-cracks of plasma sprayed ceramic coating. The results indicate that the epoxy resin was successfully penetrated into the whole ceramic coating and filled almost all defects by vacuum impregnation, which greatly enhanced its compactness and mechanical properties. The bonding strength between top coating and metal interlayer significantly increased from 17.3 MPa to 53.0 MPa, and the hardness (H) of top coating greatly increased from 11.07 GPa to 23.57 GPa. Besides, the value of H 3 /E 2 also increased from 0.06 GPa to 0.15 GPa, meaning the toughness of ceramic coating had been obviously improved. The pure ceramic coating had been punctured only after 4 h of cavitation test. However, the resin with high elasticity and toughness can effectively absorb impact energy, prevent cracks propagation and delay splats spallation during the cavitation erosion process. The novel composite coating displayed far better cavitation erosion resistance than pure ceramic coating, and it was still intact after 10 h of test. Copyright © 2018 Elsevier B.V. All rights reserved.

Experimental investigation on erosive wear behaviour of plasma spray coated stainless steel

NASA Astrophysics Data System (ADS)

Girisha, K. G.; Sreenivas Rao, K. V.; Anil, K. C.; Sanman, S.

2017-04-01

Slurry erosion is an implicit problem in many engineering industrial components such as ore carrying pipelines, slurry pumps and extruders. Even the water turbine blades are subjected to erosive wear when the water contains considerable amount of silt. In the present study, Al2O3-40%TiO2 powder particles of average particle size of 50 micrometer were deposited on EN56B martenistic stainless steel by atmospheric plasma spray technique. Ni/Cr was pre coated to work as bond coat for good adhesion between coating and the substrate material. A coating thickness of 200 micrometer was achieved. Coated and un-coated substrates were subjected to slurry erosion test as per ASTM G-119 standard. Slurry erosion test rig was used to evaluate the erosion properties at room temperature condition by varying the spindle speed. Scanning electron microphotographs were taken before and after the slurry erosion test. Microstructures reveal uniform distribution of coating materials. Eroded surface shows lip, groove, and crater formation and dense coating resulting in less porosity. Micro hardness test was evaluated and reported. EDX analysis confirms the presence of Al, Ti and O2 particles. It was observed that, Al2O3-40%TiO2 coated substrates exhibit superior erosion resistance as compared to un-coated substrates due to higher hardness and less coating porosity.

Time dependence of solid-particle impingement erosion of an aluminum alloy

NASA Technical Reports Server (NTRS)

Veerabhadrarao, P.; Buckley, D. H.

1983-01-01

Erosion studies were conducted on 6061-T6511 aluminum alloy by using jet impingement of glass beads and crushed glass particles to investigate the influence of exposure time on volume loss rate at different pressures. The results indicate a direct relationship between erosion-versus-time curves and pitmorphology (width, depth, and width-depth ratio)-versus-time curves for both glass forms. Extensive erosion data from the literature were analyzed to find the variations of erosion-rate-versus-time curves with respect to the type of device, the size and shape of erodent particles, the abrasive charge, the impact velocity, etc. Analysis of the experimental data, obtained with two forms of glass, resulted in three types of erosion-rate-versus-time curves: (1) curves with incubation, acceleration, and steadystate periods (type 1); (2) curves with incubation, acceleration, decleration, and steady-state periods (type 3); and (3) curves with incubation, acceleration, peak rate, and deceleration periods (type 4). The type 4 curve is a less frequently seen curve and was not reported in the literature. Analysis of extensive literature data generally indicated three types of erosion-rate-versus-time curves. Two types (types 1 and 3) were observed in the present study; the third type involves incubation (and deposition), acceleration, and steady-state periods (type 2). Examination of the extensive literature data indicated that it is absolutely necessary to consider the corresponding stages or periods of erosion in correlating and characterizing erosion resistance of a wide spectrum of ductile materials.

Identification and characterization of natural pipe systems in forested tropical soils

NASA Astrophysics Data System (ADS)

Bovi, Renata Cristina; Moreira, Cesar Augusto; Stucchi Boschi, Raquel; Cooper, Miguel

2017-04-01

Erosive processes on soil surface have been well studied and comprehended by several researchers, however little is known about subsurface erosive processes (piping). Piping is a type of subsurface erosion caused by water flowing in the subsurface and is still considered one of the most difficult erosive processes to be studied. Several processes have been considered as resposible for subsurface erosion and their interaction is complex and difficult to be studied separately. Surface investigations on their own may underestimate the erosion processes, due to the possible occurrence of subsurface processes that are not yet exposed on the surface. The network of subsurface processes should also be understood to better control erosion. Conservation practices that focus on water runoff control may be inefficient if the subsurface flow is not considered. In this study, we aimed to identify and characterize subsurface cavities in the field, as well as understand the network of these cavities, by using geophysical methods (electrical tomography). The study area is situated at the Experimental Station of Tupi, state of São Paulo, Brazil. The soil of the area was classified as Hapludults. The area presents several erosive features, ranging from laminar to permanent gullies and subsurface erosions. The geophysical equipment used was the Terrameter LS resistivity meter, manufactured by ABEM Instruments. The method of electrical tomography was efficient to detect collapsed and non-collapsed pipes. The results presented valuable information to detect areas of risk.

Assessment of the performance of several roadway mixes under rain, snow, and winter maintenance activities.

DOT National Transportation Integrated Search

2004-01-01

The purpose of this study was to assess the relative functional performance, including skid resistance and splash and spray, of five hot-mix-asphalt (HMA) surfaces and a tinned portland cement concrete highway surface during controlled wet and wintry...

High Flux, Fouling Resistant Membranes for RO Pretreatment

DTIC Science & Technology

2012-05-31

formed by decomposition of dead organisms (often termed humus ) and carried to surface and seawater with rain water drainage. The most important...formulation, NOM components are introduced by Orchid Pro, which is a plant food formulation made from humus deposits. Blue-green algae is used as a

Vegetation, substrate, and eolian sediment transport at Teesto Wash, Navajo Nation, 2009-2012

USGS Publications Warehouse

Draut, Amy E.; Redsteer, Margaret Hiza; Amoroso, Lee

2012-01-01

On the Navajo Nation, southwestern United States, warming temperatures and recent drought have increased eolian (windblown) sediment mobility such that large, migrating sand dunes affect grazing lands, housing, and road access. We present an assessment of seasonal variations in sand transport, mobility, and ground cover (vegetation and substrate) within a 0.2-km2 study area near Teesto Wash, southern Navajo Nation, as part of a multiyear study measuring the effects of drought on landscape stability. Sand mobility in the study area decreased substantially as one year (2010) with near-normal monsoon rainfall somewhat abated a decade-long drought, temporarily doubling vegetation cover. The invasive annual plant Russian thistle (Salsola sp.), in particular, thrived after the monsoon rains of 2010. Vegetation that grew during that year with adequate rain died off rapidly during drier conditions in 2011 and 2012, and the proportion of bare, open sand area increased steadily after summer 2010. We infer that isolated seasonal increases in rainfall will not improve landscape stability in the long term because sustained increase in perennial plants, which are more effective than annual plants at stabilizing sand against wind erosion, requires multiple consecutive seasons of adequate rain. On the basis of climate projections, a warmer, drier climate and potentially enhanced sediment supply from ephemeral washes may further increase eolian sediment transport and dune activity, worsening the present challenges to people living in this region. Connections between climate, vegetation cover, and eolian sediment erodibility in this region also are highly relevant for studies in other regions worldwide with similar environmental characteristics.

Influence of Heat Treatment on Mercury Cavitation Resistance of Surface Hardened 316LN Stainless Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawel, Steven J; Hsu, Julia

2010-11-01

The cavitation-erosion resistance of carburized 316LN stainless steel was significantly degraded but not destroyed by heat treatment in the temperature range 500-800 C. The heat treatments caused rejection of some carbon from the carburized layer into an amorphous film that formed on each specimen surface. Further, the heat treatments encouraged carbide precipitation and reduced hardness within the carburized layer, but the overall change did not reduce surface hardness fully to the level of untreated material. Heat treatments as short as 10 min at 650 C substantially reduced cavitation-erosion resistance in mercury, while heat treatments at 500 and 800 C weremore » found to be somewhat less detrimental. Overall, the results suggest that modest thermal excursions perhaps the result of a weld made at some distance to the carburized material or a brief stress relief treatment will not render the hardened layer completely ineffective but should be avoided to the greatest extent possible.« less

Excellent mechanical properties and resistance to cavitation erosion for an ultra-low carbon CrMnN stainless steel through quenching and partitioning treatment

NASA Astrophysics Data System (ADS)

Zhou, Ze-an; Fu, Wan-tang; Zhu, Zhe; Li, Bin; Shi, Zhong-ping; Sun, Shu-hua

2018-05-01

The retained austenite content (RAC), the mechanical properties, and the resistance to cavitation erosion (CE) of the 00Cr13Mn8MoN steel after quenching and partitioning (Q&P) processing were investigated. The results show that the Q&P process affected the RAC, which reached the maximum value after partitioning at 400°C for 10 min. The tensile strength of the steel slightly decreased with increasing partitioning temperature and time. However, the elongation and product of strength and elongation first increased and then decreased. The sample partitioned at 400°C for 10 min exhibited the optimal property: a strength-ductility of 23.8 GPa·%. The resistance to CE for the 00Cr13Mn8MoN steel treated by the Q&P process was improved due to work hardening, spalling, and cavitation-induced martensitic transformation of the retained austenite.

An analysis of the daily precipitation variability in the Himalayan orogen using a statistical parameterisation and its potential in driving landscape evolution models with stochastic climatic forcing

NASA Astrophysics Data System (ADS)

Deal, Eric; Braun, Jean

2015-04-01

A current challenge in landscape evolution modelling is to integrate realistic precipitation patterns and behaviour into longterm fluvial erosion models. The effect of precipitation on fluvial erosion can be subtle as well as nonlinear, implying that changes in climate (e.g. precipitation magnitude or storminess) may have unexpected outcomes in terms of erosion rates. For example Tucker and Bras (2000) show theoretically that changes in the variability of precipitation (storminess) alone can influence erosion rate across a landscape. To complicate the situation further, topography, ultimately driven by tectonic uplift but shaped by erosion, has a major influence on the distribution and style of precipitation. Therefore, in order to untangle the coupling between climate, erosion and tectonics in an actively uplifting orogen where fluvial erosion is dominant it is important to understand how the 'rain dial' used in a landscape evolution model (LEM) corresponds to real precipitation patterns. One issue with the parameterisation of rainfall for use in an LEM is the difference between the timescales for precipitation (≤ 1 year) and landscape evolution (> 103 years). As a result, precipitation patterns must be upscaled before being integrated into a model. The relevant question then becomes: What is the most appropriate measure of precipitation on a millennial timescale? Previous work (Tucker and Bras, 2000; Lague, 2005) has shown that precipitation can be properly upscaled by taking into account its variable nature, along with its average magnitude. This captures the relative size and frequency of extreme events, ensuring a more accurate characterisation of the integrated effects of precipitation on erosion over long periods of time. In light of this work, we present a statistical parameterisation that accurately models the mean and daily variability of ground based (APHRODITE) and remotely sensed (TRMM) precipitation data in the Himalayan orogen with only a few parameters. We also demonstrate over what spatial and temporal scales this parameterisation applies and is stable. Applying the parameterisation over the Himalayan orogen reveals large-scale strike-perpendicular gradients in precipitation variability in addition to the long observed strike-perpendicular gradient in precipitation magnitude. This observation, combined with the theoretical work mentioned above, suggests that variability is an integral part of the interaction between climate and erosion. References Bras, R. L., & Tucker, G. E. (2000). A stochastic approach to modeling the role of rainfall variability in drainage basin evolution. Water Resources Research, 36(7), 1953-1964. doi:10.1029/2000WR900065 Lague, D. (2005). Discharge, discharge variability, and the bedrock channel profile. Journal of Geophysical Research, 110(F4), F04006. doi:10.1029/2004JF000259

Diamondlike carbon protective coatings for IR materials

NASA Technical Reports Server (NTRS)

Mirtich, M. J.; Nir, D.; Swec, D. M.; Banks, B. A.

1985-01-01

Diamondlike carbon (DLC) films have the potential to protect optical windows in applications where it is important to maintain the integrity of the specular transmittance of these films on ZnS and ZnSe infrared transmitting windows. The films must be adherent and durable such that they protect the windows from rain and particle erosion as well as chemical attack. In order to optimize the performance of these films, 0.1 micro m thick diamondlike carbon films were deposited on fused silica and silicon wafers, using three different methods of ion beam deposition. One method was sputter deposition from a carbon target using an 8 cm ion source. The merits of hydrogen addition were experimentally evaluated in conjunction with this method. The second method used a 30 cm hollow cathode ion source with hydrocarbon/Argon gases to deposit diamondlike carbon films from the primary beam at 90 to 250 eV. The third method used a dual beam system employing a hydrocarbon/Argon 30 cm ion source and an 8 cm ion source. Films were evaluated for adherence, intrinsic stress, infrared transmittance between 2.5 and 50 micro m, and protection from particle erosion. An erosion test using a sandblaster was used to give quantitative values of the protection afforded to the fused silica by the diamondlike carbon films. The fused silica surfaces protected by diamondlike carbon films were exposed to 100 micro m diameter SiO particles at 60 mi/hr (26.8/sec) in the sandblaster.

Sediment source apportionment in Laurel Hill Creek, PA, using Bayesian chemical mass balance and isotope fingerprinting

USGS Publications Warehouse

Stewart, Heather; Massoudieh, Arash; Gellis, Allen C.

2015-01-01

A Bayesian chemical mass balance (CMB) approach was used to assess the contribution of potential sources for fluvial samples from Laurel Hill Creek in southwest Pennsylvania. The Bayesian approach provides joint probability density functions of the sources' contributions considering the uncertainties due to source and fluvial sample heterogeneity and measurement error. Both elemental profiles of sources and fluvial samples and 13C and 15N isotopes were used for source apportionment. The sources considered include stream bank erosion, forest, roads and agriculture (pasture and cropland). Agriculture was found to have the largest contribution, followed by stream bank erosion. Also, road erosion was found to have a significant contribution in three of the samples collected during lower-intensity rain events. The source apportionment was performed with and without isotopes. The results were largely consistent; however, the use of isotopes was found to slightly increase the uncertainty in most of the cases. The correlation analysis between the contributions of sources shows strong correlations between stream bank and agriculture, whereas roads and forest seem to be less correlated to other sources. Thus, the method was better able to estimate road and forest contributions independently. The hypothesis that the contributions of sources are not seasonally changing was tested by assuming that all ten fluvial samples had the same source contributions. This hypothesis was rejected, demonstrating a significant seasonal variation in the sources of sediments in the stream.

Floods, landslides and erosion from severe meteorological events in the Benevento Province, southern Italy.

NASA Astrophysics Data System (ADS)

Mascellaro, Neri; Guerriero, Luigi; Revellino, Paola; Grelle, Gerardo; Guadagno, Francesco M.

2017-04-01

As effect of the ongoing climate change, heavy meteorological events are increasing in frequency all over the world. The Campania Region in southern Italy is among the areas mostly affected by severe rainstorms and is periodically hit by their effect like floods and landslides. In October 2015, two intense rainfall events hit the central and southern regions of Italy but the most destructive effects occurred in the Benevento province (Campania region). The first storm, a self-healing V-shaped storm, began around at 7 p.m. of 14th October and stopped around at 3:00 a.m. of 15th October and was originated by the development of a cyclogenesis. The rain gages recorded a maximum cumulative value of 415.6 mm of rain in Paupisi (BN) and a strong increase in temperature; the maxima for the Benevento province was 24°C. The second storm began around at 12 a.m. of 19th October and stopped around at 7 p.m. of 20th October with a maximum cumulative value of 146.8 mm of rain in Colle Sannita(BN). These storms triggered a set of different effects that devastated more than 60 municipalities of the Sannio Province and were responsible for two casualties, €700 million of damage to infrastructures (estimates from Campania region) and about €1 billion damages to agriculture (Italian farmer Confederation). The the Calore river of the Benevento province and some of its tributaries overflowed destroying the surrounding area; major damages were recorded in the industrial area of the Benevento town. In the central and in the eastern sectors of the Benevento Province characterized by the outcropping of flyschoid units, the heavy rain triggered shallow earth flows, debris flows induced by rilling and soil slides. Debris avalanches and runoff-initiated debris flows reshaped the creeks of the Taburno-Camposauro massif and damaged a lot of infrastructure of the surrounding area. Flood events from the Calore river in the Benevento district have significant historical precedents. The most important events recorded in the past are: 1) the flood of the 2nd of October, 1949, that caused 20 fatalities, and 2) the flooding of May 1729. As first step of our study we reconstructed the spatial pattern and the temporal evolution of the storms affecting the Sannio area using the rainfall data recorded by the meteorological stations distributed across the Benevento Province. Subsequently we mapped all the effects to the landscape caused by the storms as: earth flows, soil slides, flooded area, runoff initiated debris flows and debris avalanches, debris flows initiated by rilling and soil erosion (using mainly Google earth images and field survey). We compered the location of these phenomena with the geological and topographic characteristics to understand likely controls in promote the triggering and the development of this unusual combination of different hazardous effects.

Study of the wear resistance of ion-plasma coatings based on titanium and aluminum and obtained by magnetron sputtering

NASA Astrophysics Data System (ADS)

Kachalin, G. V.; Mednikov, A. F.; Tkhabisimov, A. B.; Sidorov, S. V.

2017-05-01

The paper presents the results of metallographic researches and erosion tests of ion-plasma coatings (based on titanium, aluminum and their nitrides), which were formed on samples of 12Kh13 and EI961 blade steels. Erosion tests and studies of characteristics of obtained by magnetron sputtering coatings were carried out by using a set of research equipment UNU “Erosion-M” NRU “MPEI”. It was found that the formed Ti/Al-TiN/AlN coatings increase the duration of blade steels erosion wear incubation period by at least in 1.5 times and have a layered structure with thicknesses of nitride layers 1.3-1.6 μm and intermediate metallic layers 0.3-0.5 μm, with a total thickness of coatings of 10-14 μm for 12Kh13steel samples and 19-21 μm for EI961 steel samples.

High-Temperature Erosive Behavior of Plasma Sprayed Cr3C2-NiCr/Cenosphere Coating

NASA Astrophysics Data System (ADS)

Mathapati, Mahantayya; Doddamani, Mrityunjay; Ramesh, M. R.

2018-02-01

This research examines the deposition of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings on MDN 321 steel through the process of plasma spray. In this process, the solid particle erosion test is established at 200, 400, 600 °C with 30° and 90° impact angles. Alumina erodent is adopted to investigate the erosive behavior of the coating at higher temperatures. The properties of the Cr3C2-NiCr/cenosphere coating are established based on the microhardness, the adhesive strength, the fracture toughness, and the ductility. To quantify volume loss as a result of erosion, an optical profilometer is used. At higher temperature, decrease in the erosion volume loss of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings is observed. The erosion-resistive property of Cr3C2-NiCr/cenosphere coating is higher than that of MDN 321 steel by 76%. This property is influenced by high-temperature stability of mullite, alumina, and protective oxide layer that is formed at elevated temperatures. The morphology of eroded coating discloses a brittle mode of material removal.

Erosion onset of a cohesionless granular medium by an immersed impinging round jet

NASA Astrophysics Data System (ADS)

Brunier-Coulin, Florian; Cuéllar, Pablo; Philippe, Pierre

2017-03-01

Among different devices developed quite recently to quantify the resistance to erosion of natural soil within the broader context of dyke safety, the most commonly used is probably the jet erosion test in which a scouring crater is induced by impingement of an immersed water jet. A comprehensive experimental investigation on the jet erosion in the specific situation of a cohesionless granular material is presented here. The tests were performed by combining special optical techniques allowing for an accurate measurement of the scouring onset and evolution inside an artificially translucent granular sample. The impinging jet hydrodynamics are also analyzed, empirically validating the use of a self-similar theoretical framework for the laminar round jet. The critical conditions at the onset of erosion appear to be best described by a dimensionless Shields number based on the inertial drag force created by the fluid flow on the eroded particles rather than on the pressure gradients around them. To conclude, a tentative empirical model for the maximal flow velocity initiating erosion at the bottom of the scoured crater is put forward and discussed in the light of some preliminary results.

Stormwater Pollution Prevention Plan (SWPPP) for Coal Storage Area Stabilization Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Project and Design Engineering

2011-03-01

The scope of this project is to stabilize the abandoned coal storage area and redirect the storm water runoff from sanitary sewer system to the storm drain system. Currently, the existing storm water runoff is directed to a perimeter concrete drainage swale and collected in a containment basin. The collected water is then pumped to a treatment facility and after treatment, is discharged to the Y-12 sanitary sewer system. The existing drainage swale and collection basin along with silt fencing will be used during aggregate placement and grading to provide erosion and sediment control. Inlet protection will also be installedmore » around existing structures during the storm water diversion construction. This project scope will include the installation of a non-woven geotextile fabric and compacted mineral aggregate base (paving optional) to stabilize the site. The geotextile specifications are provided on the vendor cut sheets in Appendix B. The installation of a storm water collection/retention area will also be installed on the southern side of the site in accordance with EPA Technical Guidance on Implementing the Stormwater Runoff Requirements for federal Projects under Section 438 of the Energy Independence and Security Act. The total area to be disturbed is approximately 2.5 acres. The order of activities for this Stormwater Pollution Prevention Plan (SWPPP) will be: (1) post notice of coverage (NOC) in a prominent display near entrance of the site; (2) install rain gauge on site or contact Y-12 Plant Shift Superintendent daily for Met tower rain gauge readings; (3) install stabilized construction exit on site; (4) install silt fencing along perimeter as indicated on the attached site plan; (5) regrade site; (6) install geotextile fabric and compacted mineral aggregate base; (7) install catch basin inlet protection where required; (8) excavate and lower existing catch basin tops, re-grade and asphalt to drain; and (9) when all disturbed areas are re-stabilized, remove silt fencing and any other temporary erosion control.« less

Flame-Resistant Composite Materials For Structural Members

NASA Technical Reports Server (NTRS)

Spears, Richard K.

1995-01-01

Matrix-fiber composite materials developed for structural members occasionally exposed to hot, corrosive gases. Integral ceramic fabric surface layer essential for resistance to flames and chemicals. Endures high temperature, impedes flame from penetrating to interior, inhibits diffusion of oxygen to interior where it degrades matrix resin, resists attack by chemicals, helps resist erosion, and provides additional strength. In original intended application, composite members replace steel structural members of rocket-launching structures that deteriorate under combined influences of atmosphere, spilled propellants, and rocket exhaust. Composites also attractive for other applications in which corrosion- and fire-resistant structural members needed.

Quantitative Relationships Linking Rock Strength to Channel Morphology: A Case Study in Central Arizona

NASA Astrophysics Data System (ADS)

Larimer, J. E.; Yanites, B.

2016-12-01

River morphology is a consequence of the erosive forces acting on the channel boundary and the resisting forces that limit erosion. For bedrock rivers, the erosive forces are generated by the stresses exerted by impacting sediment and flowing water, while the resisting forces are controlled by the internal strength regime of the local rock. We investigate the susceptibility of different rock types to different erosional processes (i.e. abrasion and plucking) and how changes in channel morphology reflect rock strength properties across lithologic boundaries. The bedrock rivers in the Prescott National Forest, AZ flow over a number of rock types with variable strength including sedimentary, igneous, and metamorphic lithologies providing a natural experiment to quantify the influence of rock strength on channel morphology. We collected bedrock samples and channel surveys from 12 different rock types. Rock-strength and rock-mass properties include compressive strength, tensile strength, fatigue strength, decimeter scale P-wave velocity (varies by 8-fold), Schmidt rebound value, fracture spacing, fracture aperture, and slake durability (as a proxy for weathering susceptibility. Morphological measurements include channel width, channel steepness (varies by 10-fold), and grain size distribution. To distinguish between the major mechanisms of erosion we measure bedrock surface roughness factor at the centimeter scale. Preliminary results show that channel steepness (ksn) increases with P-wave velocity while normalized channel width (kwn) decreases with P-wave velocity. We use these data to quantify scaling relationships of channel geometry with rock strength properties. We consider the results in the context of the driving mechanistic process to develop new quantitative understandings of how rock strength properties influence the efficiency of erosion processes and how rock strength is reflected in river morphology. By comparing the results among different rock types in a landscape subject to spatially consistent tectonic and climatic influence, our work seeks to advance process-based river erosion models through field and laboratory measurements.

Role of Vegetation and Mulch in Mitigating the Effects of Raindrop Impact on Runoff and Infiltration from Urban Vegetated Green Infrastructure

NASA Astrophysics Data System (ADS)

Alizadehtazi, B.; Montalto, F. A.

2013-12-01

Rain drop impact causes soil crust formation which, in turn, reduces infiltration rates and increases runoff, contributing to soil erosion, downstream flooding and non point source pollutant loads. Unprotected soil surfaces (e.g. without vegetation canopies, mulch, or other materials), are more susceptible to crust formation due to the higher kinetic energy associated with raindrop impact. This impulse breaks larger soil aggregates into smaller particles and disperses soil from its original position. The displaced soil particles self-stratify, with finer particles at the top forming the crust. By contrast, soil that is protected by vegetation canopies and mulch layers is less susceptible to crust formation, since these surfaces intercept raindrops, dissipating some of their kinetic energy prior to their impact with the soil. Very little research has sought to quantify the effect that canopies and mulch can have on this phenomenon. This presentation presents preliminary findings from ongoing study conducted using rainfall simulator to determine the ability of new urban vegetation and mulch to minimize soil crust formation. Three different scenarios are compared: a) bare soil, b) soil with mulch cover, and c) soil protected by vegetation canopies. Soil moisture, surface penetration resistance, and physical measurements of the volume of infiltrate and runoff are made on all three surface treatments after simulated rainfall events. The results are used to discuss green infrastructure facility maintenance and design strategies, namely whether heavily vegetated GI facilities require mulching to maintain infiltration capacity.

Landscape evolution on Mars - A model of aeolian denudation in Gale Crater

NASA Astrophysics Data System (ADS)

Day, M. D.; Kocurek, G.; Grotzinger, J. P.

2015-12-01

Aeolian erosion has been the dominant geomorphic agent to shape the surface of Mars for the past ~3.5 billion years. Although individual geomorphic features evidencing aeolian activity are well understood (e.g., yardangs, dune fields, and wind streaks), landscapes formed by aeolian erosion remain poorly characterized. Intra-crater sedimentary mounds are hypothesized to have formed by wind deflation of craters once filled with flat-lying strata, and, therefore, should be surrounded by landscapes formed by aeolian erosion. Here we present a landscape evolution model that provides both an initial characterization of aeolian landscapes, and a mechanism for large-scale excavation. Wind excavation of Gale Crater to form the 5 km high Mount Sharp would require removal of 6.4 x 104 km3 of sediment. Imagery in Gale Crater from satellites and the Mars Science Laboratory rover Curiosity shows a surface characterized by first-cycle aeolian erosion of bedrock. The overall landscape is interpreted to represent stages in a cycle of aeolian deflation and excavation, enhanced by physical weathering (e.g., thermal fracturing, cratering). Initial wind erosion of bedrock is enhanced along fractures, producing retreating scarps. Underlying less resistant layers then erode faster than the armoring cap rock, increasing relief in scarps to form retreating mesas. As scarp retreat continues, boulders from the armoring cap unit break away and cover the hillslopes of less resistant material below the scarps. Eventually all material from the capping unit is eroded away and a boulder-capped hill remains. Winnowing of fine material flattens hillslope topography, leaving behind a desert pavement. Over long enough time, this pavement is breached and the cycle begins anew. This cycle of landscape denudation by the wind is similar to that of water, but lacks characteristic subaqueous features such as dendritic drainage networks.

Numerical modeling of suspended sediment tansfers at the catchment scale with TELEMAC

NASA Astrophysics Data System (ADS)

Taccone, Florent; Antoine, Germain; Delestre, Olivier; Goutal, Nicole

2017-04-01

In the mountainous regions, the filling of reservoirs is an important issue in terms of efficiency and environmental acceptability for producing hydro-electricity. Thus, the modelling of the sediment transfers on highly erodible watershed is a key challenge from both economic and scientific points of view. The sediment transfers at the watershed scale involve different local flow regimes due to the complex topography of the field and the time and space variability of the meteorological conditions, as well as several physical processes, because of the heterogeneity of the soil composition and cover. A physically-based modelling approach, associated with a fine discretization of the domain, provides an explicit representation of the hydraulic and sedimentary variables, and gives the opportunity to river managers to simulate the global effects of local solutions for decreasing erosion. On the other hand, this approach is time consuming, and needs both detailed data set for validation and robust numerical schemes for simulating various hydraulic and sediment transport conditions. The erosion processes being heavily reliant on the flow characteristics, this paper focus on a robust and accurate numerical resolution of the Shallow Water equations using TELEMAC 2D (www.opentelemac.org). One of the main difficulties is to have a numerical scheme able to represent correctly the hydraulic transfers, preserving the positivity of the water depths, dealing with the wet/dry interface and being well-balanced. Few schemes verifying these properties exist, and their accuracy still needs to be evaluated in the case of rain induced runoff on steep slopes. First, a straight channel test case with a variable slope (Kirstetter et al., 2015) is used to qualify the properties of several Finite Volume numerical schemes. For this test case, a steady rain applied on a dry domain has been performed experimentally in laboratory, and this configuration gives an analytical solution of the Shallow Water equations. The numerical scheme developed by Chen and Noelle (2015) appears to be the best compromise between robustness and accuracy. The sediment transport module SISYPHE of TELEMAC-MASCARET is also used for simulating suspended sediment transport and erosion in this configuration. Then, an application to a real, well-documented watershed is performed. With a total area of 86.4 ha, the Laval watershed is located in the Southern French Alps. It takes part of the Draix-Bleone Observatory, on which 30 years of collected data are available. On this site, several rainfall events have been simulated using high performance clusters and parallelized computation methods. The results show a good robustness and accuracy of the chosen numerical schemes for hydraulic and sediment transport. Furthermore, a good agreement with measured data is obtain if an infiltration model is added to the Shallow Water equations. This study gives promising perspectives for simulating sediment transfers at the catchment scale with a physically based approach. G. Chen et S. Noelle: A new hydrostatic reconstruction scheme motivated by the wet-dry front. 2015. G. Kirstetter et al: Modeling rain-driven overland fow: empirical versus analytical friction terms in the shallow water approximation. Journal of Hydrology, 2015.

Sediment budget for a polluted Hawaiian reef using hillslope monitoring and process mapping (Invited)

NASA Astrophysics Data System (ADS)

Stock, J. D.; Rosener, M.; Schmidt, K. M.; Hanshaw, M. N.; Brooks, B. A.; Tribble, G.; Jacobi, J.

2010-12-01

Pollution from coastal watersheds threatens the ecology of the nearshore, including tropical reefs. Suspended sediment concentrations off the reefs of Molokai, Hawaii, chronically exceed a toxic 10 mg/L, threatening reef ecosystems. We hypothesize that historic conversion of hillslope processes from soil creep to overland flow increased both magnitude and frequency of erosion. To create a process sediment budget, we used surficial and ecological mapping, hillslope and stream gages, and novel sensors to locate, quantify and model the generation of fine sediments polluting the reef. Ecological and geomorphic mapping from LiDAR and multi-spectral imagery located overland flow areas with vegetation cover below a threshold preventing erosion. Here, feral goat grazing exposed volcanic soils whose low matrix hydraulic conductivities (1-25 mm/hour) promote Horton overland flow. We instrumented steep, barren hillslopes with soil moisture sensors, overland flow meters, Parshal flumes, ISCO sediment samplers, and a rain gage and conducted repeat Tripod LiDAR and infiltration tests. To characterize soil resistance to overland flow erosion, we used a Cohesive Strength Meter (CSM) to simulate water stress. At the 13.5 km 2 watershed mouth we used a USGS stream gage with an ISCO sediment sampler to estimate total load. Over 3 years, storms triggered overland flow during rainfall intensities above 10-15 mm/hr. Overland flow meters indicate such flows can be up to 3 cm deep, with a tendency to deepen downslope. CSM tests indicate that these depths are insufficient to erode soils where vegetation is dense, but far above threshold values of 2-3 mm for bare soils. Sediment ratings curves for both hillslope and downstream catchment gages show clock-wise hysteresis during the first intense storms in the fall, becoming linear later in the season. During fall storms, sediment concentration is often 10X higher at a given stage. Revised annual lowering rates from experimental hillslopes are 1.5 cm/a (erosion pins), 1.4 cm/a (suspended sediment) and 1.6 cm/a (repeat Tripod LiDAR). These rates are at least 100-fold greater than the long-term river lowering rate of 0.13 mm/a. A sediment budget constructed by extrapolating hillslope lowering rates to the portions of the catchments mapped as unvegetated overland flow predicts a total yearly flux of ~ 6500 t, in agreement with the measured total of ~6200 t. Decadal records illustrate that rainfall intensities sufficient to generate overland flow occur for at least 8-10 hours every year, coincident with 1-3 large storm events. We hypothesize that high lowering rates reflect a combination of long-duration overland flow events, and availability of weathered soils that can be entrained by thin flow. It appears that generation of loose, seasonally weathered silt is a 1st order control on the amount of sediment exported to the reef. If climate change increases storm frequency or duration, or decreases vegetation cover, sediment loading to reefs could increase dramatically.

Generalizing a complex model for gully threshold identification in the Mediterranean environment

NASA Astrophysics Data System (ADS)

Torri, D.; Borselli, L.; Iaquinta, P.; Iovine, G.; Poesen, J.; Terranova, O.

2012-04-01

Among the physical processes leading to land degradation, soil erosion by water is the most important and gully erosion may contribute, at places, to 70% of the total soil loss. Nevertheless, gully erosion has often been neglected in water soil erosion modeling, whilst more prominence has been given to rill and interrill erosion. Both to facilitate the processing by agricultural machinery and to take advantage of all the arable land, gullies are commonly removed at each crop cycle, with significant soil losses due to the repeated excavation of the channel by the successive rainstorm. When the erosive forces of overland flow exceed the strength of the soil particles to detachment and displacement, water erosion occurs and usually a channel is formed. As runoff is proportional to the local catchment area, a relationship between local slope, S, and contributing area, A, is supposed to exists. A "geomorphologic threshold" scheme is therefore suitable to interpret the physical process of gully initiation: accordingly, a gully is formed when a hydraulic threshold for incision exceeds the resistance of the soil particles to detachment and transport. Similarly, it appears reasonable that a gully ends when there is a reduction of slope, or the concentrated flow meets more resistant soil-vegetation complexes. This study aims to predict the location of the beginning of gullies in the Mediterranean environment, based on an evaluation of S and A by means of a mathematical model. For the identification of the areas prone to gully erosion, the model employs two empirical thresholds relevant to the head (Thead) and to the end (Tend) of the gullies (of the type SA^ b>Thead, SA^ b

Ultrasonic cavitation erosion of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC-10Co-4Cr coating in NaCl solution.

PubMed

Hong, Sheng; Wu, Yuping; Zhang, Jianfeng; Zheng, Yugui; Qin, Yujiao; Lin, Jinran

2015-09-01

The high-velocity oxygen-fuel (HVOF) spraying process was used to prepare near-nanostructured WC-10Co-4Cr coating. The cavitation erosion behavior and mechanism of the coating in 3.5 wt.% NaCl solution were analyzed in detail. The results showed that the amorphous phase and WC grain were present in the coating. The cavitation erosion resistance of the coating was about 1.27 times that of the stainless steel 1Cr18Ni9Ti under the same testing conditions. The effects of erosion time on the microstructural evolution were discussed. It was revealed that cracks initiated at the edge of pre-existing pores and propagated along the carbide-binder interface, leading to the pull-out of carbide particle and the formation of pits and craters on the surface. The main failure mechanism of the coating was erosion of the binder phases, brittle detachment of hard phases and formation of pitting corrosion products. Copyright © 2015 Elsevier B.V. All rights reserved.

Constraints on Water Reservoir Lifetimes From Catchment-Wide 10Be Erosion Rates—A Case Study From Western Turkey

NASA Astrophysics Data System (ADS)

Heineke, Caroline; Hetzel, Ralf; Akal, Cüneyt; Christl, Marcus

2017-11-01

The functionality and retention capacity of water reservoirs is generally impaired by upstream erosion and reservoir sedimentation, making a reliable assessment of erosion indispensable to estimate reservoir lifetimes. Widely used river gauging methods may underestimate sediment yield, because they do not record rare, high-magnitude events and may underestimate bed load transport. Hence, reservoir lifetimes calculated from short-term erosion rates should be regarded as maximum values. We propose that erosion rates from cosmogenic 10Be, which commonly integrate over hundreds to thousands of years, are useful to complement short-term sediment yield estimates and should be employed to estimate minimum reservoir lifetimes. Here we present 10Be erosion rates for the drainage basins of six water reservoirs in Western Turkey, which are located in a tectonically active region with easily erodible bedrock. Our 10Be erosion rates for these catchments are high, ranging from ˜170 to ˜1,040 t/km2/yr. When linked to reservoir volumes, they yield minimum reservoir lifetimes between 25 ± 5 and 1,650 ± 360 years until complete filling, with four reservoirs having minimum lifespans of ≤110 years. In a neighboring region with more resistant bedrock and less tectonic activity, we obtain much lower catchment-wide 10Be erosion rates of ˜33 to ˜95 t/km2/yr, illustrating that differences in lithology and tectonic boundary conditions can cause substantial variations in erosion even at a spatial scale of only ˜50 km. In conclusion, we suggest that both short-term sediment yield estimates and 10Be erosion rates should be employed to predict the lifetimes of reservoirs.

Review of SiCf/SiCm corrosion, erosion and erosion-corrosion in high temperature helium relevant to GFR conditions

NASA Astrophysics Data System (ADS)

Fitzgerald, Kerr; Shepherd, Daniel

2018-01-01

The good thermal, mechanical and nuclear properties of silicon carbide composites (SiCf/SiCm) has led to their proposal as a gas-cooled fast reactor (GFR) fuel cladding material. Accordingly, previous studies on the corrosion, erosion and erosion-corrosion of SiCf/SiCm have been reviewed. A significant amount of corrosion data was compared for various SiCf/SiCm types tested under different conditions, which suggested that it may be suitable for use in a GFR. However some issues remain, specifically the potential for removal by oxidation of the pyrolytic carbon (PyC) interphase below 900 °C and highly damaging active oxidation at temperatures above 1200 °C. Few relevant papers were found on the erosion and erosion-corrosion behaviour of SiCf/SiCm, though those that were did indicate improved erosion resistance compared to metals. However, most data concerned particulate rather than gas erosion, and at relatively low temperatures. Exacerbation of erosion by corrosion (and vice versa) is hypothesised due to both phenomena potentially causing and being worsened by increased composite porosity. The possibility for this to be further exacerbated mechanically was also identified e.g. by surface damage or by crack formation and growth. The potential impact of irradiation in fast reactor conditions also needs to be better understood. Overall, limited data was found that is representative of anticipated GFR conditions and only in the form of separate effect corrosion tests, thus highlighting the need for erosion and combined effect experiments to progress SiCf/SiCm towards qualification as GFR fuel cladding. Finally, some potential means for improving performance have been identified including environmental adjustment and/or alternative composite design.

Formation and evolution of a drainage network during the Pleistocene through a process of homoclinal shifting initiated by headward erosion.

NASA Astrophysics Data System (ADS)

Castelltort, F. Xavier; Carles Balasch, J.; Cirés, Jordi; Colombo, Ferran

2017-04-01

A homoclinal shifting process in NE of the Ebro basin, NE Iberian Peninsula, reorganized an old flow network into a new one. This process was initiated by the reactivation of a major normal fault (Amer Fault). An anaclinal stream, flowing to the hanging wall block, incised in the fault-line scarp, accessing by headward erosion the less resistant Paleogene units. The result was the formation of a sequence of strike valleys. The first valleys are situated in a more elevated topographical position than the valleys formed later. The last and the most important valley is La Plana de Vic, which is being emptied by differential erosion in front of the resistant base layer. The study of the lateral migration of a drainage basin since its initial stages has allowed the recognition of the layout of a drainage network and its model of evolution. The new drainage network includes three different subsystems. The main subsystem consists of stream courses flowing along the strike valley. While the other two subsystems flow into the main or can flow directly to the basin sink. These are the anaclinal subsystem, which drains the scarp face of the asymmetric valley, and the cataclinal subsystem, which drains the cuesta. The process of homoclinal shifting makes the strike streams migrate laterally and dip in the less resistant unit. This migration implies the reorganization of the other two tributary subsystems. The sequence of reorganizations may be preserved on the resistant bedrock of the cuesta. This allows the reconstruction of the route of the headward erosion of the initial anaclinal stream course through remnants of ancient strike streams flowing into former basin sinks, and its cataclinal tributaries draining the cuesta. In the case study of La Plana de Vic the migration route of the basin sink can be reconstructed from its initial position, Early Pleistocene, until present day. Besides, reorganization of the cataclinal network can also be recognized. During the lateral migration three incisions were made in a large anticlinal structure in the north (Bellmunt Anticline) and one incision was made in a crystalline massif (Montseny) in the south. The last of the incisions into the Bellmunt Anticline captured by headward erosion an older drainage network with headwaters in the axial Pyrenees. The result of the homoclinal shifting process was the capture of older drainage basins and the formation of the current drainage basin of the river Ter.

A new methodology for hydro-abrasive erosion tests simulating penstock erosive flow

NASA Astrophysics Data System (ADS)

Aumelas, V.; Maj, G.; Le Calvé, P.; Smith, M.; Gambiez, B.; Mourrat, X.

2016-11-01

Hydro-abrasive resistance is an important property requirement for hydroelectric power plant penstock coating systems used by EDF. The selection of durable coating systems requires an experimental characterization of coating performance. This can be achieved by performing accelerated and representative laboratory tests. In case of severe erosion induced by a penstock flow, there is no suitable method or standard representative of real erosive flow conditions. The presented study aims at developing a new methodology and an associated laboratory experimental device. The objective of the laboratory apparatus is to subject coated test specimens to wear conditions similar to the ones generated at the penstock lower generatrix in actual flow conditions. Thirteen preselected coating solutions were first been tested during a 45 hours erosion test. A ranking of the thirteen coating solutions was then determined after characterisation. To complete this first evaluation and to determine the wear kinetic of the four best coating solutions, additional erosion tests were conducted with a longer duration of 216 hours. A comparison of this new method with standardized tests and with real service operating flow conditions is also discussed. To complete the final ranking based on hydro-abrasive erosion tests, some trial tests were carried out on penstock samples to check the application method of selected coating systems. The paper gives some perspectives related to erosion test methodologies for materials and coating solutions for hydraulic applications. The developed test method can also be applied in other fields.

Erosion and strength degradation of biomorphic SiC.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez-Fernandez, J.; de Arellano-Lopez, A. R; Varela-Feria, F. M.

2004-05-01

Solid-particle-erosion studies were conducted on biomorphic SiC based on eucalyptus and pine, reaction-bonded (RB) SiC, and hot-pressed (HP) SiC. The erodents were angular SiC abrasives of average diameter 63, 143, or 390 {mu}m and the impact velocity was 100 m s{sup -1}. Impact occurred at normal incidence. Material loss in all targets occurred by brittle fracture. The biomorphic specimens eroded by formation of both lateral and radial cracks and their erosion rates were higher than both conventional SiCs. The RB SiC eroded as a classic brittle material, by formation and propagation of lateral cracks. The HP SiC, the hardest target,more » was the most erosion resistant. In erosion of the HP SiC, the abrasive particles, especially the largest ones, fragmented upon impact. The resulting dissipation of energy led to relatively low erosion rates. Flexural strength before and after erosion was measured for the biomorphic eucalyptus, RB SiC, and HP SiC. Erosion damage reduced the flexural strengths of all of the specimens. The relative strength reductions were lowest for the biomorphic eucalyptus and highest for the HP SiC. The hot-pressed SiC responded as predicted by accepted models of impact damage in brittle solids. The responses of the biomorphic and reaction-bonded SiC specimens were modeled as if they consisted of only SiC and porosity. This approximation agreed reasonably well with observed degradations of strength.« less

Simwe model application on susceptibility analysis to linear erosion: a case study in Alto Douro wine region.

NASA Astrophysics Data System (ADS)

Fernandes, Joana; Bateira, Carlos; Soares, Laura; Faria, Ana; Moura, Rui; Gonçalves, José

2016-04-01

The wine production in Alto Douro Wine Region - one of the world's oldest regulated and demarcated wine region - is based on a slope system organized in agricultural terraces once supported exclusively by dry stone walls. It has been undergoing the necessary changes for the introduction of technological innovations partially associated to the mechanization of vineyards work. In this sense, different forms of terrain framing have been implemented, namely the substitution of stone walls by earth embankments. This evolution raises a group of problems related to the hydric soil erosion and landscape preservation, since Alto Douro Wine Region is classified as UNESCO World Heritage Site since 2001. The study area is mostly occupied by vineyards planted in the agriculture terraces without continuous vegetation, the flow proceeds superficially influenced by the weak infiltration capacity and hydraulic conductivity. So, because of this conditioning factor the erosive features present non-significant depth, and the length thereof is limited essentially by the slope of the land, where was registered 64 gullies and 78 rills This paper focuses on the evaluation of susceptibility to linear erosion, through the application of SIMWE (SIMulated Water Erosion), (Mitas and Mitasova, 1998), using a digital elevation model, with pixel of one square meter of spatial resolution, created through detail aerial photographs, (side pixel of 50 cm), submitted to automatic stereo-correlation procedures in Agisoft PhotoScan software. The results provided by the model are compared with hydrological characteristics of the soil, (infiltration capacity, and hydraulic conductivity), soil texture, and soil structure parameters (identified by electrical resistivity measurement) where obtained from field monitoring. This approach demonstrates an association between the spatial distribution of erosive features with high values of soil saturation, and reduced water discharge (10-110 cm3/s), that are consistent with the lower values of electrical resistivity. The areas with the highest amount of erosive features are related to medium sediment flux values, (13.8-334.2 g/ms), medium or high transport capacity (250.3g/ms - 9.4 kg/ms), and sediment concentration with medium or very high classes where register more than 70% of gullies. These values, combined with low hydraulic conductivity with average Ks values 0.0004 cm3/s, and soil infiltration capacity with values from 0.11 to 0.36 cm/min, derives from the fine texture of soils - gravel (18.8 - 47.9%), sand (10.8 - 20.5%) and silt/clay (32.1 - 64.9%), induce an increased runoff and the development of linear erosion. The obtained results seem to indicate a good performance of the SIMWE model in the identification of the areas more susceptible to the hydric erosion of the soils, indeed, the most critical areas show the connection between the inventoried erosive forms. Keywords: Water Erosion, SIMWE, Agricultural Terraces, Alto Douro Wine Region References Mitas, H. e Mitasova, L. (1998). Distribuited Soil Erosion Simulation for effective erosion prevention. Water Resources Research, Vol. 34(3), pp. 505-516.

Vulnerability to xylem embolism as a major correlate of the environmental distribution of rain forest species on a tropical island.

PubMed

Trueba, Santiago; Pouteau, Robin; Lens, Frederic; Feild, Taylor S; Isnard, Sandrine; Olson, Mark E; Delzon, Sylvain

2017-02-01

Increases in drought-induced tree mortality are being observed in tropical rain forests worldwide and are also likely to affect the geographical distribution of tropical vegetation. However, the mechanisms underlying the drought vulnerability and environmental distribution of tropical species have been little studied. We measured vulnerability to xylem embolism (P 50 ) of 13 woody species endemic to New Caledonia and with different xylem conduit morphologies. We examined the relation between P 50 , along with other leaf and xylem functional traits, and a range of habitat variables. Selected species had P 50 values ranging between -4.03 and -2.00 MPa with most species falling in a narrow range of resistance to embolism above -2.7 MPa. Embolism vulnerability was significantly correlated with elevation, mean annual temperature and percentage of species occurrences located in rain forest habitats. Xylem conduit type did not explain variation in P 50 . Commonly used functional traits such as wood density and leaf traits were not related to embolism vulnerability. Xylem embolism vulnerability stands out among other commonly used functional traits as a major driver of species environmental distribution. Drought-induced xylem embolism vulnerability behaves as a physiological trait closely associated with the habitat occupation of rain forest woody species. © 2016 John Wiley & Sons Ltd.

Lattice Boltzmann method for rain-induced overland flow

NASA Astrophysics Data System (ADS)

Ding, Yu; Liu, Haifei; Peng, Yong; Xing, Liming

2018-07-01

Complex rainfall situations can generate overland flow with complex hydrodynamic characteristics, affecting the surface configuration (i.e. sheet erosion) and environment to varying degrees. Reliable numerical simulations can provide a scientific method for the optimization of environmental management. A mesoscopic numerical method, the lattice Boltzmann method, was employed to simulate overland flows. To deal with complex rainfall, two schemes were introduced to improve the lattice Boltzmann equation and the local equilibrium function, respectively. Four typical cases with differences in rainfall, bed roughness, and slopes were selected to test the accuracy and applicability of the proposed schemes. It was found that the simulated results were in good agreement with the experimental data, analytical values, and the results produced by other models.

Influence of surface microroughness by plasma deposition and chemical erosion followed by TiO2 coating upon anticoagulation, hydrophilicity, and corrosion resistance of NiTi alloy stent.

PubMed

Wang, Gui-Xue; Shen, Yang; Zhang, He; Quan, Xue-Jun; Yu, Qing-Song

2008-06-15

Two different surface modification techniques were used to change the surface morphology and roughness of stents at the micrometer level, and eventually improve their surface adhesion properties with respect to endothelial cells. One was chemical erosion followed by sol-gel TiO(2) coating, and the other was low temperature gas plasma deposition. After surface modification, the biocompatibility including the anticoagulation properties, hydrophilicity, and corrosion resistance of these stents was evaluated. It was found that both techniques could change the surface morphology of the stents with microroughness. In comparison with the control, the treated NiTi alloy intravascular stents showed increased surface hydrophilicity and enhanced anticoagulation properties. However, the corrosion properties of the stents were not improved significantly.

Impact of Changes in Land Use in Hydro-physical Properties of Argiudolls of the Center of Santa Fe, Argentina

NASA Astrophysics Data System (ADS)

Marano, R. P.; Imhoff, S.; Micheloud, H.; Carnevale, I.

2012-04-01

In Santa Fe province (Argentina) the substitution of agricultural-grass rotations for continuous crop under no-till has become very important because vegetal residues reduces soil degradation caused by rain-drop impact. However, in Santa Fe the sequence wheat-soya seems to produce insufficient quantity of straw to avoid that problem. The objective of this research was to evaluate some soil properties to verify the changes induced by the no-till system. Evaluations were carried out in four Argiudolls, each one under a special management condition and slope grade, i.e. Place 1: plane relief (0,08%), continuous agriculture of wheat-soya under no-till (CANT1) and traditional tillage (CAT1); Place 2 plane relief (0,08%), cattle production over natural grass (CNG2) and bare soil (CBS2); Place 3 smoothly wavy relief (0,55%), continuous agriculture of wheat-soya under no-till (CANT3); Place 4 wavy relief (1,2%), continuous agriculture of wheat-soya-corn under no-till (CANT4). Rain simulators of small (RSS) and medium (RSM) size were used to determine regional values of the curve number (CN), runoff (R) and infiltration (I) rates for steady state. Tension infiltrometers (TI) with four tensions (5, 3, 1.5 and 0 cm) and double-rings (DRI) were used to compare the infiltration. Soil samples were extracted with shovel to measure aggregates stability (AS) and with cylinders to determine the soil penetration resistance (PR) curve. Important deviations of the CN were found when they were corrected by the antecedent moisture (AMC) regarding to those indicated by the SCS; there was an overestimation of R when soil moisture was low and an underestimate with high water contents. The DRI does not represent the process of the rain infiltration for the central region of Santa Fe. On the contrary, with the use of RSM or RSS an appropriate characterization is achieved, especially with RSS that has as advantage its handling easiness and versatility of the intensities to apply. Alternatively the TI can also be used to characterize infiltration, linking I at steady state with conductivity hydraulic at tension 3 and 1, 5. Tillage decreased I in CAT1 and CBS2 regarding to no-till, although in small proportion in CBS2. The fitted curves of PR indicated the coefficient corresponding to the soil bulk density variable had the greater impact in PR in CNG2, probably due to animal trampling degrades soil structure. The AE values increased according to the order CANT1

Comparing and Linking Post-fire Hillslope Erosion and Channel Change for Different Storm Types

NASA Astrophysics Data System (ADS)

MacDonald, Lee; Kampf, Stephanie; Brogan, Dan; Schmeer, Sarah; Nelson, Peter

2016-04-01

Moderate and high severity wildfires can greatly reduce infiltration rates, leading to orders of magnitude increases in hillslope-scale runoff and erosion rates. These increases can cause dramatic downstream channel change, with post-fire deposition being most common, but this depends on the number, magnitude and timing of storm events. The objective of this study is to compare post-fire hillslope erosion rates and downstream channel change from two distinct rainfall events approximately one year after burning. The first was a set of relatively typical, higher-intensity convective storms in June-August 2013, and the second was a highly unusual, week-long ~270 mm rainstorm in September 2013. The study was conducted in two ~15 km2 watersheds that had two-thirds of their area burned at high or moderate severity by 2012 High Park Fire in northcentral Colorado, USA. Hillslope erosion was measured with sediment fences at 29 sites grouped into five clusters, with each cluster having an associated tipping bucket rain gage. Downstream channel change was monitored at approximately ten cross-sections in each of the two watersheds, Skin Gulch and Hill Gulch. Twelve summer storms produced an overall mean hillslope erosion of 6 Mg ha-1, with higher rainfall intensities at lower elevations and in Skin Gulch causing higher sediment yields. The higher sediment yields in Skin Gulch caused substantial downstream deposition of up to 0.8 m at most cross-sections. Generally lower rainfall in Hill Gulch resulted in less Horton overland flow and hence lower erosion rates and much less downstream deposition. The September storm had roughly twice as much rainfall as the summer thunderstorms, but there were much lower peak rainfall intensities and hillslope-scale sediment yields except where shallow bedrock induced saturation overland flow. The much longer duration of the September storm resulted in sustained high flows, and these flows plus the lower hillslope erosion caused most of the cross-sections to incise rather than aggrade. Maximum mean bed incision was nearly one meter and some cross-sections also exhibited considerable lateral migration, removing much of the aggraded sediment from the previous two summer storm seasons. The results indicate that: 1) sediment yields are best correlated with the amount of precipitation above a given intensity threshold; 2) this threshold tends to increase over time with increasing surface cover; and 3) the standard trajectory of post-fire channel change can be completely altered by extreme storm events.

49 CFR 192.355 - Customer meters and regulators: Protection from damage.

Code of Federal Regulations, 2010 CFR

2010-10-01

... SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Customer... terminal must— (1) Be rain and insect resistant; (2) Be located at a place where gas from the vent can... that houses a customer meter or regulator at a place where vehicular traffic is anticipated, must be...

Global transcriptome response to ionic liquid by a tropical rain forest soil bacterium, Enterobacter lignolyticus.

PubMed

Khudyakov, Jane I; D'haeseleer, Patrik; Borglin, Sharon E; Deangelis, Kristen M; Woo, Hannah; Lindquist, Erika A; Hazen, Terry C; Simmons, Blake A; Thelen, Michael P

2012-08-07

To process plant-based renewable biofuels, pretreatment of plant feedstock with ionic liquids has significant advantages over current methods for deconstruction of lignocellulosic feedstocks. However, ionic liquids are often toxic to the microorganisms used subsequently for biomass saccharification and fermentation. We previously isolated Enterobacter lignolyticus strain SCF1, a lignocellulolytic bacterium from tropical rain forest soil, and report here that it can grow in the presence of 0.5 M 1-ethyl-3-methylimidazolium chloride, a commonly used ionic liquid. We investigated molecular mechanisms of SCF1 ionic liquid tolerance using a combination of phenotypic growth assays, phospholipid fatty acid analysis, and RNA sequencing technologies. Potential modes of resistance to 1-ethyl-3-methylimidazolium chloride include an increase in cyclopropane fatty acids in the cell membrane, scavenging of compatible solutes, up-regulation of osmoprotectant transporters and drug efflux pumps, and down-regulation of membrane porins. These findings represent an important first step in understanding mechanisms of ionic liquid resistance in bacteria and provide a basis for engineering microbial tolerance.

Monitoring and Assessment of Water Retention Measures in Agricultural Land

NASA Astrophysics Data System (ADS)

Výleta, Roman; Danáčová, Michaela; Škrinár, Andrej; Fencík, Róbert; Hlavčová, Kamila

2017-12-01

One of the most interesting events, from the environmental impact point of view, is the huge storm rainfall at which soil degradation processes occur. In Slovakia, agricultural areas with a higher slope have been recently increasingly denudated by water erosion processes. Areas having regular problems with muddy floods and denudation of soil particles have been currently identified. This phenomenon has long-term adverse consequences in the agricultural landscape, especially the decline in soil fertility, the influence on soil type and the reduction of depth of the soil profile. In the case of storm rainfall or long-term precipitation, soil particles are being transported and deposited at the foot of the slope, but in many cases the large amounts of sediment are transported by water in the form of muddy floods, while putting settlements and industrial zones at risk, along with contamination and clogging of watercourses and water reservoirs. These unfavourable phenomena may be prevented by appropriate management and application of technical measures, such as water level ditches, erosion-control weirs, terraces and others. The study deals with determination of the soil loss and denudation of soil particles caused by water erosion, as well as with determination of the volume of the surface runoff created by the regional torrential rains in the area of the village of Sobotište. The research is based on the analysis of flood and erosion-control measures implemented in this area. Monitoring of these level ditches for protection against muddy floods has been carried out since 2015 using UAV technology and terrestrial laser scanning. Monitoring is aimed on determination of the volume of the ditch, changes in its capacity and shape in each year. The study evaluates both the effectiveness of these measures to reduce the surface runoff as well as the amount of eroded soil particles depending on climatological conditions. The results of the research point to the good efficiency of these measures; however, in conjunction with belt crops cultivation they could form a comprehensive flood and erosion-control protection to eliminate the muddy floods and protect the settlements from surrounding slopes.

Subsoil erosion dominates the supply of fine sediment to rivers draining into Princess Charlotte Bay, Australia.

PubMed

Olley, Jon; Brooks, Andrew; Spencer, John; Pietsch, Timothy; Borombovits, Daniel

2013-10-01

The Laura-Normanby River (catchment area: 24,350 km(2)), which drains into Princess Charlotte Bay, has been identified in previous studies as the third largest contributor of sediment to the Great Barrier Reef World Heritage Area. These catchment scale modelling studies also identified surface soil erosion as supplying >80% of the sediment. Here we use activity concentrations of the fallout radionuclides (137)Cs and (210)Pbex to test the hypothesis that surface soil erosion dominates the supply of fine (<10 μm) sediment in the river systems draining into Princess Charlotte Bay. Our results contradict these previous studies, and are consistent with channel and gully erosion being the dominant source of fine sediment in this catchment. The hypothesis that surface soil erosion dominates the supply of fine sediment to Princess Charlotte Bay is rejected. River sediment samples were collected using both time-integrated samplers and sediment drape deposits. We show that there is no detectable difference in (137)Cs and (210)Pbex activity concentrations between samples collected using these two methods. Two methods were also used to collect samples to characterise (137)Cs and (210)Pbex concentrations in sediment derived from surface soil erosion; sampling of surface-wash deposits and deployment of surface runoff traps that collected samples during rain events. While there was no difference in the (137)Cs activity concentrations for samples collected using these two methods, (210)Pbex activity concentrations were significantly higher in the samples collected using the runoff traps. The higher (210)Pbex concentrations are shown to be correlated with loss-on-ignition (r(2) = 0.79) and therefore are likely to be related to higher organic concentrations in the runoff trap samples. As a result of these differences we use a three end member mixing model (channel/gully, hillslope surface-wash and hillslope runoff traps) to determine the relative contribution from surface soil erosion. Probability distributions for (137)Cs and (210)Pbex concentrations were determined for each of the end members, with these distributions then used to estimate the surface soil contribution to each of the collected river sediment samples. The mean estimate of contribution of surface derived sediment for all river samples (n = 70) is 16 ± 2%. This study reinforces the importance of testing model predictions before they are used to target investment in remedial action and adds to the body of evidence that the primary source of sediment delivered to tropical river systems is derived from subsoil erosion. Copyright © 2013 Elsevier Ltd. All rights reserved.

Solar concentrator materials development

NASA Technical Reports Server (NTRS)

Morel, D. E.; Ayers, S. R.; Gulino, D. A.; Tennyson, R. C.; Egger, R. A.

1986-01-01

Materials with potential applications in reflective and refractive solar dynamic concentrators are tested for resistance to atomic oxygen degradation. It is found that inorganic coatings such as MgF2, SiO(x), and ITO provide excellent protection for reflective surfaces while organic materials are much more susceptible to erosion and mass loss. Of the organic polymers tested, the silicones have the highest intrinsic resistance to atomic oxygen degradation.

Black soiling of an architectural limestone during two-year term exposure to urban air in the city of Granada (S Spain).

PubMed

Urosevic, Maja; Yebra-Rodríguez, Africa; Sebastián-Pardo, Eduardo; Cardell, Carolina

2012-01-01

A two-year term aging test was carried out on a building limestone under different urban conditions in the city of Granada (Southern Spain) to assess its Cultural Heritage sustainability. For this purpose stone tablets were placed vertically at four sites with contrasting local pollution micro-environments and exposure conditions (rain-sheltered and unsheltered). The back (rain-sheltered) and the front (rain-unsheltered) faces of the stone tablets were studied for each site. The soiling process (surface blackening) was monitored through lightness (ΔL*) and chroma changes (ΔC*). Additionally atmospheric particles deposited on the stone surfaces and on PM10 filters during the exposure time were studied through a multianalytical approach including scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM) and micro-Raman spectroscopy. The identified atmospheric particles (responsible for stone soiling) were mainly soot and soil dust particles; also fly ash and aged salt particles were found. The soiling process was related to surface texture, exposure conditions and proximity to dense traffic streets. On the front faces of all stones, black soiling and surface roughness promoted by differential erosion between micritic and sparitic calcite were noticed. Moreover, it was found that surface roughness enhanced a feedback process that triggers further black soiling. The calculated effective area coverage (EAC) by light absorbing dust ranged from 10.2 to 20.4%, exceeding by far the established value of 2% EAC (limit perceptible to the human eye). Soiling coefficients (SC) were estimated based on square-root and bounded exponential fittings. Estimated black carbon (BC) concentration resulted in relatively similar SC for all studied sites and thus predicts the soiling process better than using particulate matter (PM10) concentration. Copyright © 2011 Elsevier B.V. All rights reserved.

Abrasion-Erosion Resistance of Concrete Made with Two Aggregates, Stonewall Jackson Dam, West Virginia.

DTIC Science & Technology

1983-09-01

the concrete mixtures; Mr. Dale Glass , Mr. Frank W. Dorsey, and Mr. Roger Buttner conducted the abrasion-erosion tests. Mr. Stuart Long served as the...PITT- 8 S-1, was from the Buffalo Slag Co., Franklinville, New York. This fine aggregate is classified as a glacial sand and is composed primarily of...MATERIAL Fine Aggregate ILZAI% Franklin, NY R:.rLcE- Buffalo Slag Co. sA--L.. BY ~ J2rhDst:r esne Kinzua Damn - . USED A PROCESSING BEFORE TESTING

Low pressure cold spraying on materials with low erosion resistance

NASA Astrophysics Data System (ADS)

Shikalov, V. S.; Klinkov, S. V.; Kosarev, V. F.

2017-10-01

In present work, the erosion-adhesion transition was investigated during cold spraying of aluminum particles on brittle ceramic substrates. Cold spraying was carried out with aid of sonic nozzle, which use allows significantly reducing the gas stagnation pressure without the effect of flow separation inside the nozzle and, accordingly, reducing the velocity of the spraying particles. Two stagnation pressures were chosen. The coating tracks were sprayed at different air temperatures in nozzle pre-chamber under each of regimes. Single sprayed tracks were obtained and their profiles were investigated by optical profilometry.

Assessment of Cavitation-Erosion Resistance of 316LN Stainless Steel Following a Nitro-Carburizing Surface Treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawel, Steven J

2009-11-01

A nitro-carburizing surface treatment known domestically as the Melonite process was applied to type 316LN stainless steel test pieces and exposed to sonication conditions in mercury using a vibratory horn technique. Cavitation-erosion damage was evaluated for extended exposures and compared to other surface treatments on the same substrate alloy. The results indicate that the Melonite process substantially retards weight loss and crater development for extended periods, but gradually is eroded/destroyed leading to exposure of the substrate and cavitation-erosion behavior similar to untreated specimens. Compared with other surface treatments, cavitation-erosion results indicate that specimens treated with Melonite perform similarly to specimensmore » treated with a simple nitriding process. Neither the simple nitriding nor the Melonite treatment is quite as effective as a previously evaluated low temperature carburizing treatment, the latter being about a factor of three better than Melonite in terms of weight loss during sonication in mercury.« less

Root characteristics of cover crops and their erosion-reducing potential during concentrated runoff

NASA Astrophysics Data System (ADS)

de Baets, S.; Poesen, J.

2009-04-01

In the loam region in central Belgium, a lot of research has been conducted on the effects of cover crops for preventing splash and interrill erosion and on their nutrient pumping effectiveness. As this is a very effective erosion and environment conservation technique, planting cover crops during the winter season is widely applied in the loess belt. Most of these cover crops freeze at the beginning of the winter period. Consequently, the above-ground biomass becomes less effective in protecting the soil from water erosion. Apart from the effects of the above-ground biomass in protecting the soil against raindrop impacts and reducing flow velocities by the retarding effects of their stems, plant roots also play an important role in improving soil strength. Previous research showed that roots contribute to a large extent to the resistance of topsoils against concentrated flow erosion. Unfortunately, information on root properties of common cover crops (e.g. Sinapis alba, Phacelia tanacetifoli, Lolium perenne, Avena sativa, Secale cereale, Raphanus sativus subsp. oleiferus) is very scarce. Therefore, root density distribution with depth and their erosion-reducing effects during concentrated flow erosion were assessed by conducting root auger measurements and concentrated flow experiments at the end of the growth period (December). The preliminary results indicate that the studied cover crops are not equally effective in preventing soil loss by concentrated flow erosion at the end of the growing season. Cover crops with thick roots, such as Sinapis alba and Raphanus sativus subsp. oleiferus are less effective than cover crops with fine-branched roots such as Phacelia tanacetifoli, Lolium perenne (Ryegrass), Avena sativa (Oats) and Secale cereale (Rye) in preventing soil losses by concentrated flow erosion. These results enable soil managers to select the most suitable crops and maximize soil protection.

A study of cathode erosion in high power arcjets

NASA Astrophysics Data System (ADS)

Harris, William Jackson, III

Cathode erosion continues to be one of the predominant technology concerns for high power arcjets. This study will show that cathode erosion in these devices is significantly affected by several mitigating factors, including propellant composition, propellant flowrate, current level, cathode material, and power supply current ripple. In a series of 50-hour and 100-hour long duration experiments, using a water-cooled 30 kilowatt laboratory arcjet, variations in the steady-state cathode erosion rate were characterized for each of these factors using nitrogen propellant at a fixed arc current of 250 Amperes. A complementary series of measurements was made using hydrogen propellant at an arc current of 100 Amperes. The cold cathode erosion rate was also differentiated from the steady-state cathode erosion rate in a series of multi-start cathode erosion experiments. Results of these measurements are presented, along with an analysis of the significant effects of current ripple on arcjet cathode erosion. As part of this study, over a dozen refractory cathode materials were evaluated to measure their resistance to arcjet cathode erosion. Among the materials tested were W-ThO2(1%, 2%, 4%), poly and mono-crystalline W, W-LaB6, W-La2O3, W-BaO2, W-BaCaAl2O4, W-Y2O3, and ZrB2. Based on these measurements, several critical material properties were identified, such work function, density, porosity, melting point, and evaporation rate. While the majority of the materials failed to outperform traditional W-ThO2, these experimental results are used to develop a parametric model of the arcjet cathode physics. The results of this model, and the results of a finite-element thermal analysis of the arcjet cathode, are presented to better explain the relative performance of the materials tested.

Asynchronous changes in vegetation, runoff and erosion in the nile river watershed during the holocene.

PubMed

Blanchet, Cécile L; Frank, Martin; Schouten, Stefan

2014-01-01

The termination of the African Humid Period in northeastern Africa during the early Holocene was marked by the southward migration of the rain belt and the disappearance of the Green Sahara. This interval of drastic environmental changes was also marked by the initiation of food production by North African hunter-gatherer populations and thus provides critical information on human-environment relationships. However, existing records of regional climatic and environmental changes exhibit large differences in timing and modes of the wet/dry transition at the end of the African Humid Period. Here we present independent records of changes in river runoff, vegetation and erosion in the Nile River watershed during the Holocene obtained from a unique sedimentary sequence on the Nile River fan using organic and inorganic proxy data. This high-resolution reconstruction allows to examine the phase relationship between the changes of these three parameters and provides a detailed picture of the environmental conditions during the Paleolithic/Neolithic transition. The data show that river runoff decreased gradually during the wet/arid transition at the end of the AHP whereas rapid shifts of vegetation and erosion occurred earlier between 8.7 and ∼6 ka BP. These asynchronous changes are compared to other regional records and provide new insights into the threshold responses of the environment to climatic changes. Our record demonstrates that the degradation of the environment in northeastern Africa was more abrupt and occurred earlier than previously thought and may have accelerated the process of domestication in order to secure sustainable food resources for the Neolithic African populations.

Origin and Evolution of the Layered Sulfate-Rich Rocks in Meridiani Planum, Mars

NASA Astrophysics Data System (ADS)

Arvidson, R. E.

2007-12-01

Opportunity rover observations show that Meridiani Planum has extensive exposures of sulfate-rich dirty sandstones partially covered by a mix of wind-blown basaltic sand, dust, and a lag deposit of 1 to 5 mm diameter hematitic concretions. The dirty sandstones are interpreted to have formed in an acid-sulfate evaporative lacustrine system that left behind sulfate-rich muds with a siliciclastic component. Erosion by wind and water produced sandstones that were then cemented and diagenetically altered by rising groundwater. Subsequent wind erosion of these deposits and associated advection of basaltic sand onto the outcrops produced the surfaces encountered during the rover's traverses. On a regional scale these sulfate-rich deposits are up to several kilometers in thickness, extend over several hundred thousand square kilometers, and unconformably overlie the fluvially dissected Noachian cratered terrain. Both OMEGA and CRISM hyperspectral data show clear evidence for the presence of phyllosilicate minerals in the cratered terrains adjacent to the sulfate deposits, but not within the sulfate section proper. The ensemble of evidence indicates a change in Meridiani Planum from fluvial erosion and formation of phyllosilicate minerals to deposition of evaporite deposits associated with an acid-sulfate aqueous system. This change is interpreted to be due to a major climatic shift in which a relatively vigorous hydrologic system with extensive neutral rain and snowfall changed to more arid conditions in which a regional-scale acid sulfate groundwater system emerged in Meridiani Planum with enough of a hydrostatic head to produce and retain 1 to 3 km of sulfate-rich deposits.

Erosion tests of materials by energetic particle beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schechter, D.E.; Tsai, C.C.; Sluss, F.

1985-01-01

The internal components of magnetic fusion devices must withstand erosion from and high heat flux of energetic plasma particles. The selection of materials for the construction of these components is important to minimize contamination of the plasma. In order to study various materials' comparative resistance to erosion by energetic particles and their ability to withstand high heat flux, water-cooled copper swirl tubes coated or armored with various materials were subjected to bombardment by hydrogen and helium particle beams. Materials tested were graphite, titanium carbide (TiC), chromium, nickel, copper, silver, gold, and aluminum. Details of the experimental arrangement and methods ofmore » application or attachment of the materials to the copper swirl tubes are presented. Results including survivability and mass losses are discussed.« less

Erosions on a prolapsed uterine in an old woman: an unusual manifestation of pemphigus vulgaris.

PubMed

Ramezani, Ali; Ghandi, Narges; Akhyani, Maryam; Daneshpazhooh, Maryam; Naraghi, Zahra S; Chams-Davatchi, Cheyda

2009-09-15

Vaginal involvement in pemphigus vulgaris has previously been described. In all those cases a pelvic examination was needed to explore the lesions. We describe a patient with pemphigus vulgaris who had pemphigus erosions on a prolapsed uterus (i.e., on the everted surface of vagina). The patient had widespread lesions of pemphigus in other mucosal and cutaneous sites. Biopsy, antibodies against desmoglein 1 and 3, and direct and indirect immunofluorescence were confirming. The erosions on the prolapsed uterus were resistant to treatment; other mucosal and cutaneous lesions responded rapidly to prednisolone and azathioprine. After lowering the dose of prednisolone the patient was referred to a gynecologist for a vaginal hysterectomy. This case was unique because her vaginal lesions could be easily examined and followed.

The cathode material for a plasma-arc heater

NASA Astrophysics Data System (ADS)

Yelyutin, A. V.; Berlin, I. K.; Averyanov, V. V.; Kadyshevskii, V. S.; Savchenko, A. A.; Putintseva, R. G.

1983-11-01

The cathode of a plasma arc heater experiences a large thermal load. The temperature of its working surface, which is in contact with the plasma, reaches high values, as a result of which the electrode material is subject to erosion. Refractory metals are usually employed for the cathode material, but because of the severe erosion do not usually have a long working life. The most important electrophysical characteristic of the electrode is the electron work function. The use of materials with a low electron work function allows a decrease in the heat flow to the cathode, and this leads to an increase in its erosion resistance and working life. The electroerosion of certain materials employed for the cathode in an electric arc plasma generator in the process of reduction smelting of refractory metals was studied.

Threshold Responses to Soil Moisture Deficit by Trees and Soil in Tropical Rain Forests: Insights from Field Experiments

PubMed Central

Meir, Patrick; Wood, Tana E.; Galbraith, David R.; Brando, Paulo M.; Da Costa, Antonio C. L.; Rowland, Lucy; Ferreira, Leandro V.

2015-01-01

Many tropical rain forest regions are at risk of increased future drought. The net effects of drought on forest ecosystem functioning will be substantial if important ecological thresholds are passed. However, understanding and predicting these effects is challenging using observational studies alone. Field-based rainfall exclusion (canopy throughfall exclusion; TFE) experiments can offer mechanistic insight into the response to extended or severe drought and can be used to help improve model-based simulations, which are currently inadequate. Only eight TFE experiments have been reported for tropical rain forests. We examine them, synthesizing key results and focusing on two processes that have shown threshold behavior in response to drought: (1) tree mortality and (2) the efflux of carbon dioxdie from soil, soil respiration. We show that: (a) where tested using large-scale field experiments, tropical rain forest tree mortality is resistant to long-term soil moisture deficit up to a threshold of 50% of the water that is extractable by vegetation from the soil, but high mortality occurs beyond this value, with evidence from one site of increased autotrophic respiration, and (b) soil respiration reaches its peak value in response to soil moisture at significantly higher soil moisture content for clay-rich soils than for clay-poor soils. This first synthesis of tropical TFE experiments offers the hypothesis that low soil moisture–related thresholds for key stress responses in soil and vegetation may prove to be widely applicable across tropical rain forests despite the diversity of these forests. PMID:26955085

Selection criteria for wear resistant powder coatings under extreme erosive wear conditions

NASA Astrophysics Data System (ADS)

Kulu, P.; Pihl, T.

2002-12-01

Wear-resistant thermal spray coatings for sliding wear are hard but brittle (such as carbide and oxide based coatings), which makes them useless under impact loading conditions and sensitive to fatigue. Under extreme conditions of erosive wear (impact loading, high hardness of abrasives, and high velocity of abradant particles), composite coatings ensure optimal properties of hardness and toughness. The article describes tungsten carbide-cobalt (WC-Co) systems and self-fluxing alloys, containing tungsten carbide based hardmetal particles [NiCrSiB-(WC-Co)] deposited by the detonation gun, continuous detonation spraying, and spray fusion processes. Different powder compositions and processes were studied, and the effect of the coating structure and wear parameters on the wear resistance of coatings are evaluated. The dependence of the wear resistance of sprayed and fused coatings on their hardness is discussed, and hardness criteria for coating selection are proposed. The so-called “double cemented” structure of WC-Co based hardmetal or metal matrix composite coatings, as compared with a simple cobalt matrix containing particles of WC, was found optimal. Structural criteria for coating selection are provided. To assist the end user in selecting an optimal deposition method and materials, coating selection diagrams of wear resistance versus hardness are given. This paper also discusses the cost-effectiveness of coatings in the application areas that are more sensitive to cost, and composite coatings based on recycled materials are offered.

Measurements of Erosion Wear Volume Loss on Bare and Coated Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Sutter, James K.; Mondry, Richard J.; Bowman, Cheryl; Ma, Kong; Horan, Richard A.; Naik, Subhash K.; Cupp, Randall J.

2003-01-01

An investigation was conducted to examine the erosion behavior of uncoated and coated polymer matrix composite (PMC) specimens subjected to solid particle impingement using air jets. The PMCs were carbon-Kevlar (DuPont, Wilmington, DE) fiber-epoxy resin composites with a temperature capability up to 393 K (248 F). Tungsten carbide-cobalt (WC-Co) was the primary topcoat constituent. Bondcoats were applied to the PMC substrates to improve coating adhesion; then, erosion testing was performed at the University of Cincinnati. All erosion tests were conducted with Arizona road-dust (ARD), impinging at angles of 20 and 90 on both uncoated and two-layer coated PMCs at a velocity of 229 m/s and at a temperature of 366 K (200 F). ARD contains primarily 10-m aluminum oxide powders. Vertically scanning interference microscopy (noncontact, optical profilometry) was used to evaluate surface characteristics, such as erosion wear volume loss and depth, surface topography, and surface roughness. The results indicate that noncontact, optical interferometry can be used to make an accurate determination of the erosion wear volume loss of PMCs with multilayered structures while preserving the specimens. The two-layered (WC-Co topcoat and metal bondcoat) coatings on PMCs remarkably reduced the erosion volume loss by a factor of approximately 10. The tenfold increase in erosion resistance will contribute to longer PMC component lives, lower air friction, reduced related breakdowns, decreased maintenance costs, and increased PMC reliability. The decrease in the surface roughness of the coated vanes will lead to lower air friction and will subsequently reduce energy consumption. Eventually, the coatings could lead to overall economic savings.

The ability of 1.23% acidulated phosphate fluoride gel to inhibit simulated endogenous erosion in tooth roots.

PubMed

Saunders, J G C; McIntyre, J M

2005-12-01

Endogenous dental erosion is that produced by contact of gastric acids with tooth structure. It may affect exposed root cementum/dentine as well as coronal enamel, causing marked loss of mineral. The aim of this study was to determine whether 1.23 per cent acidulated phosphate fluoride gel, if applied to the surface cementum at certain intervals during an erosive acid challenge, could provide any protection against demineralization. Roots of preserved extracted human teeth were painted with a water and acid resistant varnish, leaving two windows (3x1mm) of exposed dentine. These were placed in a solution containing 0.06MHCl and 2.2mMCaHPO4, which has been shown to simulate gastric acid when it meets the tooth surface. The roots were placed in the erosive solution unprotected (controls), or subject to APF application for four minutes prior to and every 10, 30 or 120 minutes during the erosive challenge. Roots were removed at either 6 or 12 hours, washed thoroughly and cut into 120microm thick sections. Depths of demineralization were measured using an optical graticule under polarized light microscopy. A high level of protection was provided when the roots were coated with APF gel every 10 or 30 minutes. APF gel will partially inhibit endogenous erosion of roots for up to 30 minutes if applied, for example, the night before a morning reflux episode. This should be considered along with other erosion control or reduction procedures for patients suffering from the effects of endogenous erosion.

High-Voltage Isolation Transformer

NASA Technical Reports Server (NTRS)

Clatterbuck, C. H.; Ruitberg, A. P.

1985-01-01

Arcing and field-included surface erosion reduced by electrostatic shields around windings and ferromagnetic core of 80-kilovolt isolation transformer. Fabricated from high-resistivity polyurethane-based material brushed on critical surfaces, shields maintained at approximately half potential difference of windings.

Development of Erosion-Corrosion-Resistant Cold-Spray Nanostructured Ni-20Cr Coating for Coal-Fired Boiler Applications

NASA Astrophysics Data System (ADS)

Kumar, M.; Singh, H.; Singh, N.; Chavan, N. M.; Kumar, S.; Joshi, S. V.

2015-12-01

The erosion-corrosion (E-C) behavior of a cold-spray nanostructured Ni-20Cr coating was studied under cyclic conditions in a coal-fired boiler. This study was done for 15 cycles (1500 h), in which each cycle comprised 100 h of heating in the boiler environment, followed by 1 h of cooling under ambient air conditions. The E-C extent was evaluated in terms of thickness loss data of the samples. The eroded-corroded samples were characterized using XRD, SEM/EDS, and x-ray mapping analyses. The nanostructured coating offered excellent E-C protection to boiler tube material (SA 516 steel) under harsh live conditions of the boiler. This E-C resistance offered by investigated coating may be attributed to the presence of protective NiO and Cr2O3 phases in its oxide scale and its superior as-sprayed microhardness.

Exploration of the Esophageal Mucosal Barrier in Non-Erosive Reflux Disease

PubMed Central

Rinsma, Nicolaas F.; Farré, Ricard; Troost, Fred J.; Elizalde, Montserrat; Keszthelyi, Daniel; Helyes, Zsuzsanna; Masclee, Ad A.; Conchillo, José M.

2017-01-01

In the absence of visible mucosal damage, it is hypothesized that the esophageal mucosal barrier is functionally impaired in patients with non-erosive reflux disease (NERD). The aim of the present study was to perform an exploratory analysis of the mucosal barrier in NERD compared to erosive esophagitis (EE) and controls. A second aim was to explore TRPV1 gene transcription in relation to the mucosal barrier function and heartburn symptoms. In this prospective study, 10 NERD patients, 11 patients with active erosive esophagitis and 10 healthy volunteers were included. Biopsies from non-eroded mucosa were obtained for (1) ex vivo analyses (Ussing chamber) of transepithelial electrical resistance (TEER) and permeability (2) gene transcription of tight-junction proteins and transient receptor potential vanilloid subfamily member 1 (TRPV1). No differences in TEER or permeability were found between NERD and healthy volunteers, whereas TEER was lower in patients with erosive esophagitis. TRPV1 gene transcription was not significantly different between EE, NERD and controls. Conclusions: esophageal mucosal barrier function and TRPV1 transcription is not significantly altered in NERD patients. Future research is needed to explore other potential mechanisms that may account for the high symptom burden in these patients. PMID:28534850

LIF Density Measurement Calibration Using a Reference Cell

NASA Technical Reports Server (NTRS)

Domonkos, Matthew T.; Williams, George J., Jr.; Lyons, Valerie J. (Technical Monitor)

2002-01-01

Flight qualification of ion thrusters typically requires testing on the order of 10,000 hours. Extensive knowledge of wear mechanisms and rates is necessary to establish design confidence prior to long duration tests. Consequently, real-time erosion rate measurements offer the potential both to reduce development costs and to enhance knowledge of the dependency of component wear on operating conditions. Several previous studies have used laser induced fluorescence (LIF) to measure real-time, in situ erosion rates of ion thruster accelerator grids. Those studies provided only relative measurements of the erosion rate. In the present investigation, a molybdenum tube was resistively heated such that the evaporation rate yielded densities within the tube on the order of those expected from accelerator grid erosion. A pulsed UV laser was used to pump the ground state molybdenum at 345.64nm, and the non-resonant fluorescence at 550-nm was collected using a bandpass filter and a photomultiplier tube or intensified CCD array. The sensitivity of the fluorescence was evaluated to determine the limitations of the calibration technique. The suitability of the diagnostic calibration technique was assessed for application to ion engine erosion rate measurements.

Adjuvant alternative treatment with chemical peeling and subsequent iontophoresis for postinflammatory hyperpigmentation, erosion with inflamed red papules and non-inflamed atrophic scars in acne vulgaris.

PubMed

Kurokawa, Ichiro; Oiso, Naoki; Kawada, Akira

2017-04-01

The standard management of acne vulgaris in Japan includes a combination of topical treatment with benzoyl peroxide (BPO) and BPO/clindamycin (CLDM), topical adapalene and systemic antimicrobials. However, the treatment of therapy-resistant complications such as postinflammatory hyperpigmentation (PIH), erosions with inflamed red papules and atrophic scars has not been established. We performed chemical peeling with glycolic acid and iontophoresis with ascorbyl 2-phosphate 6-palmitate and DL-α-tocopherol phosphate for the treatment of PIH, erosions with inflamed red papules and non-inflamed atrophic scars in 31 patients with acne vulgaris (mild to severe severity), and evaluated the efficacy and safety of these interventions. In most of cases, there was remarkable improvement in PIH and erosions with inflamed red papules after treatment. There was also some improvement in non-inflamed atrophic scars without erythema. Mild redness and irritation was observed in four cases as adverse reactions. Early initial treatment of PIH and erosions with red papules by chemical peeling and iontophoresis is an effective and safe method to prevent the formation of atrophic scars in patients with acne vulgaris. © 2016 Japanese Dermatological Association.

Erosion of ejecta at Meteor Crater, Arizona

NASA Technical Reports Server (NTRS)

Grant, John A.; Schultz, Peter H.

1993-01-01

New methods for estimating erosion at Meteor Crater, Arizona, indicate that continuous ejecta deposits beyond 1/4-1/2 crater radii from the rim have been lowered less than 1 m on the average. This conclusion is based on the results of two approaches: coarsening of unweathered ejecta into surface lag deposits and calculation of the sediment budget within a drainage basin on the ejecta. Preserved ejecta morphologies beneath thin alluvium revealed by ground-penetrating radar provide qualitative support for the derived estimates. Although slightly greater erosion of less resistant ejecta locally has occurred, such deposits were limited in extent, particularly beyond 0.25R-0.5R from the present rim. Subtle but preserved primary ejecta features further support our estimate of minimal erosion of ejecta since the crater formed about 50,000 years ago. Unconsolidated deposits formed during other sudden extreme events exhibit similarly low erosion over the same time frame; the common factor is the presence of large fragments or large fragments in a matrix of finer debris. At Meteor Crater, fluvial and eolian processes remove surrounding fines leaving behind a surface lag of coarse-grained ejecta fragments that armor surfaces and slow vertical lowering.

Interactive Effects of Moss-Dominated Crusts and Artemisia ordosica on Wind Erosion and Soil Moisture in Mu Us Sandland, China

PubMed Central

Yang, Yongsheng; Bu, Chongfeng; Mu, Xingmin; Shao, Hongbo; Zhang, Kankan

2014-01-01

To better understand the effects of biological soil crusts (BSCs) on soil moisture and wind erosion and study the necessity and feasibility of disturbance of BSCs in the Mu Us sandland, the effects of four treatments, including moss-dominated crusts alone, Artemisia ordosica alone, bare sand, and Artemisia ordosica combined with moss-dominated crusts, on rainwater infiltration, soil moisture, and annual wind erosion were observed. The major results are as follows. (1) The development of moss-dominated crusts exacerbated soil moisture consumption and had negative effects on soil moisture in the Mu Us sandland. (2) Moss-dominated crusts significantly increased soil resistance to wind erosion, and when combined with Artemisia ordosica, this effect became more significant. The contribution of moss-dominated crusts under Artemisia ordosica was significantly lower than that of moss-dominated crusts alone in sites where vegetative coverage > 50%. (3) Finally, an appropriate disturbance of moss-dominated crusts in the rainy season in sites with high vegetative coverage improved soil water environment and vegetation succession, but disturbance in sites with little or no vegetative cover should be prohibited to avoid the exacerbation of wind erosion. PMID:24982973

Interactive effects of moss-dominated crusts and Artemisia ordosica on wind erosion and soil moisture in Mu Us sandland, China.

PubMed

Yang, Yongsheng; Bu, Chongfeng; Mu, Xingmin; Shao, Hongbo; Zhang, Kankan

2014-01-01

To better understand the effects of biological soil crusts (BSCs) on soil moisture and wind erosion and study the necessity and feasibility of disturbance of BSCs in the Mu Us sandland, the effects of four treatments, including moss-dominated crusts alone, Artemisia ordosica alone, bare sand, and Artemisia ordosica combined with moss-dominated crusts, on rainwater infiltration, soil moisture, and annual wind erosion were observed. The major results are as follows. (1) The development of moss-dominated crusts exacerbated soil moisture consumption and had negative effects on soil moisture in the Mu Us sandland. (2) Moss-dominated crusts significantly increased soil resistance to wind erosion, and when combined with Artemisia ordosica, this effect became more significant. The contribution of moss-dominated crusts under Artemisia ordosica was significantly lower than that of moss-dominated crusts alone in sites where vegetative coverage > 50%. (3) Finally, an appropriate disturbance of moss-dominated crusts in the rainy season in sites with high vegetative coverage improved soil water environment and vegetation succession, but disturbance in sites with little or no vegetative cover should be prohibited to avoid the exacerbation of wind erosion.

Development of an Arduino-based electrical impedance tomography system with application to dam internal erosion detection

NASA Astrophysics Data System (ADS)

Masi, Matteo; Ferdos, Farzad; Losito, Gabriella; Solari, Luca

2016-04-01

Electrical Impedance Tomography (EIT) is a technique for the imaging of the electrical properties of conductive materials. In EIT, the spatial distribution of the electrical resistivity or electrical conductivity within a domain is reconstructed using measurements made with electrodes placed at the boundaries of the domain. Data acquisition is typically made by applying an electrical current to the object under investigation using a set of electrodes, and measuring the developed voltage between the other electrodes. The tomographic image is then obtained using an inversion algorithm. This work describes the implementation of a simple and low cost 3D EIT measurement system suitable for laboratory-scale studies. The system was specifically developed for the time-lapse imaging of soil samples subjected to erosion processes during laboratory tests. The tests reproduce the process of internal erosion of soil particles by water flow within a granular media; this process is one of the most common causes of failure of earthen levees and embankment dams. The measurements needed strict requirements of speed and accuracy due to the varying time scale and magnitude of these processes. The developed EIT system consists of a PC which controls I/O cards (multiplexers) through the Arduino micro-controller, an external current generator, a digital acquisition device (DAQ), a power supply and the electrodes. The ease of programming of the Arduino interface greatly helped the implementation of custom acquisition software, increasing the overall flexibility of the system and the creation of specific acquisition schemes and configurations. The system works with a multi-electrode configuration of up to 48 channels but it was designed to be upgraded to an arbitrary large number of electrodes by connecting additional multiplexer cards (> 96 electrodes). The acquisition was optimized for multi-channel measurements so that the overall time of acquisition is dramatically reduced compared to the single channel instrumentation. The accuracy and operation were tested under different conditions. The results from preliminary tests show that the system is able to clearly identify objects discriminated by different resistivity. Furthermore, measurements carried out during internal erosion simulations demonstrate that even small variations in the electrical resistivity can be captured and these changes can be related to the erosion processes.

Comprehensive study of the abrasive wear and slurry erosion behavior of an expanded system of high chromium cast iron and microstructural modification for enhanced wear resistance

NASA Astrophysics Data System (ADS)

Chung, Reinaldo Javier

High chromium cast irons (HCCIs) have been demonstrated to be an effective material for a wide range of applications in aggressive environments, where resistances to abrasion, erosion and erosion-corrosion are required. For instance, machinery and facilities used in mining and extraction in Alberta's oil sands suffer from erosion and erosion-corrosion caused by silica-containing slurries, which create challenges for the reliability and maintenance of slurry pumping systems as well as other processing and handling equipment. Considerable efforts have been made to determine and understand the relationship between microstructural features of the HCCIs and their wear performance, in order to guide the material selection and development for specific service conditions with optimal performance. The focus was previously put on a narrow group of compositions dictated by ASTM A532. However, with recent advances in casting technology, the HCCI compositional range can be significantly expanded, which potentially brings new alloys that can be superior to those which are currently employed. This work consists of three main aspects of study. The first one is the investigation of an expanded system of white irons with their composition ranging from 1 to 6 wt.% C and 5 to 45 wt.% Cr, covering 53 alloys. This work has generated wear and corrosion maps and established correlation between the performance and microstructural features for the alloys. The work was conducted in collaboration with the Materials Development Center of Weir Minerals in Australia, and the results have been collected in a database that is used by the company to guide materials selection for slurry pump components in Alberta oil sands and in other mining operations throughout the world. The second part consists of three case studies on effects of high chromium and high carbon, respectively, on the performance of the HCCIs. The third aspect is the development of an approach to enhance the wear resistance of HCCIs by microstructural modification through addition of strong carbide-forming elements to produce eutectic microstructures reinforced with in-situ formed foreign carbides. Very promising results have been obtained in lab, which demonstrates that the approach is feasible and effective in tailoring HCCIs for improved performance.

Breeding for disease resistance in Hevea spp. - status, potential threats, and possible strategies.

Treesearch

Chaendaekattu Narayanan; Kavitha K. Mydin

2012-01-01

Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg., a forest tree native to the tropical rain forests of Central and South America, has only been recently domesticated outside its natural range of distribution. Almost all of the commercially cultivated clones of H. brasiliensis represent a very narrow genetic base...

Hydrological behavior of a Vertisol under different soil management systems in a rain-fed olive orchard

NASA Astrophysics Data System (ADS)

Cabezas, Jose Manuel; Gómez, Jose Alfonso; Auxiliadora Soriano, María

2016-04-01

Soil water availability is a major subject in Mediterranean agricultural systems, mainly due to the limited and highly variable annual rainfall, high evaporative demand, and soil hydrological characteristics. The recent expansion of olive cultivation in the rolling-plains of the Guadalquivir valley, due to the higher profitability of new intensive olive orchards, expanded the presence of olive orchards on Vertisols, soils traditionally used for annual rain-fed crops. These soils have a high content of smectitic clays, which give them a high water storage capacity, and are characterized by vertical and deep shrinkage cracks in the dry season, associated to low soil moisture. Farmers make several tillage passes in these olive groves during the summer, in order to cover the cracks and thus reduce soil water loss by evaporation, which will impact especially in rain-fed in the next olive yield. This tillage practice involves removal of plant residues from the soil surface, as well as burying seeds produced by the plants, so this will remain bared at the beginning of the rainy season, when in the Mediterranean climate is frequent occurrence of high-intensity rainfall, which are ideal conditions for soil loss by water erosion, one of the most serious problems for the sustainability of olive cultivation in Andalusia. Although there are some studies showing that water loss by evaporation from deep horizons of a vertic soil might be elevated (eg. Ritchie and Adams, 1974), the presence of plant residues on the soil surface drastically reduced soil water loss (eg Adams et al., 1969). Thus the aim of this study was to assess of soil moisture dynamics in a rain-fed olive orchard growing on a Vertisol under different soil management practices, in Andalusia (southern Spain). Four different soil management treatments were applied, which combined a cover crop (Bromus rubens L.) or bare soil throughout the year by applying herbicides, with tillage in summer to cover the cracks or non tillage. Results from the first experimental year showed that although, in the treatments of bare soil, the elimination of soil cracks resulted in lower soil water evaporation in summer compared to non tillage, water loss from soil in summer was even lower when cover crop residues were left on the soil surface, compensating water consumption by the cover crop during spring. As a result, the establishment of the cover crop (B. rubens) did not result in a penalty for productivity of the olive orchard. These initial results support the use of cover crops in Vertisols (sown in autumn, and mowed at early spring leaving the residues on the soil surface) as an alternative to tillage during summer to cover the soil cracks. The use of cover crops in olive groves has a number of environmental benefits, such as reduce soil loss by erosion and enhance biodiversity. However, this study should be carried out for a longer period in order to generalize these first results. References Adams JE, et al., Soil Science Society of America Journal, 1969. 33:609-613. Ritchie JT, Adams JE., Soil Science Society of America Journal, 1974. 38:131-134.

Soil redistribution and nutrient delivery in a Mediterranean rain-fed agro-ecosystem with different crops and management: environmental and economic aspects

NASA Astrophysics Data System (ADS)

López-Vicente, Manuel; Álvarez, Sara

2017-04-01

Mediterranean agro-ecosystems are characterised by fragmented fields and patched vegetation. This shape governs the spatial patterns of water, soil and nutrient redistribution. Rainfall parameters, human infrastructures, crop management, support practices, and land use changes (set aside crops, land abandonment) control the magnitude of these processes. Under rain-fed water supply conditions, runoff generation and soil water content are two important factors in determining crop yield. Soil erosion and nutrient delivery are two of the factors which limit crop yield and thus, the gross earning of the landowner. In hilly landscapes, farmers usually supply extra soil to fill in the ephemeral gullies, and nutrient replenishment with fertilizers is a common practice. The aim of this study is to evaluate the environmental (runoff yield, soil erosion and nutrient delivery) and economic (replenishment of soil and nutrient losses with new soil and fertilizers) consequences of different conventional and conservative practices (fallow/crop rotation, cover crops, land abandonment, buffer strips) in a Mediterranean rain-fed agro-ecosystem (27 ha) with vineyards, cereal crops, cultivated and abandoned olive orchards, several trails and patches of natural vegetation. The five winter cereal fields (wheat and barley) follow fallow/crop rotation. The four vineyards are devoted to the Garnacha variety: one planted in 2007 with white wine grapes, and three planted in 2008 with red wine grapes. The inter-crop strips are managed with a mixture of plant species as cover crop (CC), including: i) spontaneous vegetation, and ii) plantation of common sainfoin (Onobrychis viciifolia). The maintenance of the CC includes one mowing pass at the end of spring, between May and June. The appearance and development of ephemeral gullies and the deposition of soil at the bottom of the hillslope are two of the main concerns of the landowners. In some places, the accumulation of soil complicates grape harvest operations with machinery, forcing manual labour. A total of 222 soil samples were collected in 74 points, and some physical (coarse fragments, effective volume, bulk density, texture, infiltration, etc.) and chemical (soil organic carbon - SOC, total nitrogen, phosphorous and potassium) parameters analysed. The highest values of SOC and TN were found in the forestry (4.64% and 0.198%) and abandoned soils (2.96% and 0.132%), whereas the highest values of TP appeared in the cereal, olive and vineyards (458.4, 458.0 and 440.3 mg / kg P). The highest content of TK appeared in the vineyards (1979.1 mg / kg K), especially in the grapevine strips (2188.3 mg / kg K), due to the fertilizer supply. In order to assess the water, soil and nutrient budgets, four buried sediment traps were installed near the bottom and before reaching the depositional-prone area. The upslope contributing areas of the traps are not nested. Monitoring the magnitude of runoff and sediment yield and the chemical composition of the collected samples allowed calculating the economic cost of water, soil and nutrient losses. The results of this study have implications for other rain-fed productive agro-ecosystems as well as where conservative practices may reduce the economic cost of farmland management.

The Effects of Different Tillage Systems on Soil Hydrology and Erosion in Southeastern Brazil

NASA Astrophysics Data System (ADS)

Bertolino, A. V. F. A.; Fernandes, N. F.; Souza, A. P.; Miranda, J. P.; Rocha, M. L.

2009-04-01

Conventional tillage usually imposes a variety of modifications on soil properties that can lead to important changes in the type and magnitude of the hydrological processes that take place at the upper portion of the soil profile. Plough pan formation, for example, is considered to be an important consequence of conventional tillage practices in southeastern Brazil, decreasing infiltration rates and contributing to soil erosion, especially in steep slopes. In order to characterize the changes in soil properties and soil hydrology due to the plough pan formation we carried out detailed investigations in two experimental plots in Paty do Alferes region, located in the hilly landscape of Serra do Mar in southeastern Brazil, close to Rio de Janeiro city. Farming activities are very important in this area, in particular the ones related to the tomato production. The local hilly topography with short and steep hillslopes, as well as an average annual rainfall of almost 2000 mm, favor surface runoff and the evolution of rill and gully erosion. The two runoff plots are 22m long by 4m wide and were installed side by side along a representative hillslope, both in terms of soil (Oxisol) and steepness. At the lower portion of each plot there is a collecting trough connected by a PVC pipe to a 500 and 1000 liters sediment storage boxes. Soil tillage treatments used in the two plots were: Conventional Tillage (CT), with one plowing using disc-type plow (about 18 cm depth) and one downhill tractor leveling, in addition to burning residues from previous planting; and Minimum Tillage (MT), which did not allow burning residues from previous planting and preserved a vegetative cover between plantation lines. Runoff and soil erosion measurements were carried out in both plots immediately after each rainfall event. In order to characterize soil water movements under the two tillage systems (CT and MT), 06 nests of tensiometers and 04 nests of Watermark sensors were installed in each plot. Based on previous studies in this area, suggesting that the plough pan develop at about 20cm depth, the soil water potential (SWP) sensors were installed, in each nest, at 15, 30 and 80 cm depths. Continuously readings in the 30 SWP sensors were made both at a daily and event basis (during some rainfall events) for 25 months. Rainfall was continuously measured in the area by an automatic rain-gauge (tipping bucket) installed close to the plots. In order to characterize changes is soil porosity, both total pore space and pore inter-connections, undisturbed soil blocks were collected for micromorphological analyses (0-10cm, 12-22cm and 25-35cm depths) at small trenches located at the upper parts of each plot. The results attested that soil under CT developed a plough pan layer at about 20 cm depth, showing a 44% decrease in total pore space from 0-10cm to 12-22cm depths, with a predominant network of isolated pores. In the MT plot, soil porosity is more homogeneous with depth, with a predominant network of larger and better connected pores. The results related to soil hydrology show that in many moments, both CT and MT, stay very close to saturation, both at 15 and 30 cm depth. Above the plough pan under CT, soils tend to saturate faster and to have a slower drainage rate than the ones under MT. Detailed SWP analyses made during rain events suggest that CT may favors lateral flows while soils under MT are draining. Soil erosion rates measured for individual events at CT are about four times greater than the ones observed at MT. The results observed in this study attest that conventional tillage (CT) in this area imposed important changes in soil structure, pore-size distribution and connectivity, as well as in soil infiltration, drainage and erosion.

Ontogenetic changes in size, allometry, and mechanical design of tropical rain forest trees.

PubMed

Sterck, F; Bongers, F

1998-02-01

Size, allometry, and mechanical design were measured for trees of three canopy species in a tropical rain forest in French Guiana. Mechanical design was expressed as the safety factor, using the elastic-stability model, and the wind resistance factor, using the constant-stress model. Changes with ontogeny were described as regressions using stem diameter as the independent variable, and they were compared between species. Height, crown size, and the wind resistance factor increased with ontogeny. The safety factor decreased to a minimum and then increased continuously in thicker trees. The crown width/height ratio did not change with ontogeny. Interspecific differences in allometry and mechanical design were related to the adult stature of the species, and not to shade tolerance. The short stature species (Vouacapoua americana) was less slender (height:DBH [stem diameter at 1.3 m] ratio) and had a higher crown width/height ratio than the tall stature species (Goupia glabra and Dicorynia guianensis). Vouacapoua had a higher safety factor, but a similar wind resistance factor. The safety factors of our study species were lower than those of two temperate tree species because of a higher slenderness. Differences in safety factors between tropical and temperate trees may result from unrealistic assumptions of the elastic-stability model, and may also be related to lower light levels and-or wind rates in the tropics.

Verification and completion of a soil data base for process based erosion model applications in Mato Grosso/Brazil

NASA Astrophysics Data System (ADS)

Schindewolf, Marcus; Schultze, Nico; Schönke, Daniela; Amorim, Ricardo S. S.; Schmidt, Jürgen

2014-05-01

The study area of central Mato Grosso is subjected to severe soil erosion. Continuous erosion leads to massive losses of top soil and related organic carbon. Consequently agricultural soil soils suffer a drop in soil fertility which only can be balanced by mineral fertilization. In order to control soil degradation and organic carbon losses of Mato Grosso cropland soils a process based soil loss and deposition model is used. Applying the model it will be possible to: - identify the main areas affected by soil erosion or deposition in different scales under present and future climate and socio-economic conditions - estimate the related nutrient and organic carbon losses/yields - figure out site-related causes of soil mobilization/deposition - locate sediment and sediment related nutrient and organic matter pass over points into surface water bodies - estimate the impacts of climate and land use changes on the losses of top soil, sediment bound nutrients and organic carbon. Model input parameters include digital elevation data, precipitation characteristics and standard soil properties as particle size distribution, total organic carbon (TOC) and bulk density. The effects of different types of land use and agricultural management practices are accounted for by varying site-specific parameters predominantly related to soil surface properties such as erosional resistance, hydraulic roughness and percentage ground cover. In this context the existing EROSION 3D soil parameter data base deducted from large scale rainfall simulations in Germany is verified for application in the study area, using small scale disc type rainfall simulator with an additional runoff reflux approach. Thus it's possible to enlarge virtual plot length up to at least 10 m. Experimental plots are located in Cuiabá region of central Mato Grosso in order to cover the most relevant land use variants and tillage practices in the region. Results show that derived model parameters are highly influenced by soil management. This indicates a high importance of tillage impact on resistance to erosion, mulch cover and TOC. The measured parameter ranges can generally be confirmed by the existing data base, which only need to be completed due to changed phenological stages in Mato Grosso compared to German conditions.

Soil Erosion as a stochastic process

NASA Astrophysics Data System (ADS)

Casper, Markus C.

2015-04-01

The main tools to provide estimations concerning risk and amount of erosion are different types of soil erosion models: on the one hand, there are empirically based model concepts on the other hand there are more physically based or process based models. However, both types of models have substantial weak points. All empirical model concepts are only capable of providing rough estimates over larger temporal and spatial scales, they do not account for many driving factors that are in the scope of scenario related analysis. In addition, the physically based models contain important empirical parts and hence, the demand for universality and transferability is not given. As a common feature, we find, that all models rely on parameters and input variables, which are to certain, extend spatially and temporally averaged. A central question is whether the apparent heterogeneity of soil properties or the random nature of driving forces needs to be better considered in our modelling concepts. Traditionally, researchers have attempted to remove spatial and temporal variability through homogenization. However, homogenization has been achieved through physical manipulation of the system, or by statistical averaging procedures. The price for obtaining this homogenized (average) model concepts of soils and soil related processes has often been a failure to recognize the profound importance of heterogeneity in many of the properties and processes that we study. Especially soil infiltrability and the resistance (also called "critical shear stress" or "critical stream power") are the most important empirical factors of physically based erosion models. The erosion resistance is theoretically a substrate specific parameter, but in reality, the threshold where soil erosion begins is determined experimentally. The soil infiltrability is often calculated with empirical relationships (e.g. based on grain size distribution). Consequently, to better fit reality, this value needs to be corrected experimentally. To overcome this disadvantage of our actual models, soil erosion models are needed that are able to use stochastic directly variables and parameter distributions. There are only some minor approaches in this direction. The most advanced is the model "STOSEM" proposed by Sidorchuk in 2005. In this model, only a small part of the soil erosion processes is described, the aggregate detachment and the aggregate transport by flowing water. The concept is highly simplified, for example, many parameters are temporally invariant. Nevertheless, the main problem is that our existing measurements and experiments are not geared to provide stochastic parameters (e.g. as probability density functions); in the best case they deliver a statistical validation of the mean values. Again, we get effective parameters, spatially and temporally averaged. There is an urgent need for laboratory and field experiments on overland flow structure, raindrop effects and erosion rate, which deliver information on spatial and temporal structure of soil and surface properties and processes.

Differential erosion and the formation of layered yardangs in the Loulan region (Lop Nur), eastern Tarim Basin

NASA Astrophysics Data System (ADS)

Lin, Yongchong; Xu, Lishuai; Mu, Guijin

2018-02-01

Yardangs are a type of wind-sculpted landform which generally form in hyper-arid regions. Several factors affect the development of yardangs, and the relative importance of these factors likely varies with differences in regional environmental factors. In the Loulan region of Lop Nur, wind dynamics are the principal factor affecting the development of yardangs. However, layered yardangs, which have undergone a unique form of differential erosion, are common in the region. These erosional landforms differ from typical yardangs which are eroded solely by abrasion and deflation. We conducted field and laboratory investigations of layered yardangs to determine their origin. The results indicate that there are two types of strata comprising the yardangs: uncompacted sand-silt layers, with a lower carbonate content; and compacted clay-silt layers, with a higher carbonate content. Both types of strata are horizontal and occur in alternating layers. This type of structure enables the wind to more easily erode the less resistant sand-silt layers at different heights, leaving the more resistant compacted clay-silt layers relatively intact. Eventually the undercut remnant clay-silt layers collapse once the weight of the suspended strata exceeds their elastic resistance (more than 90% of the fallen blocks have length/thickness ratios between 1.2 and 2.5). Therefore, in addition to wind dynamics, the lithology and structure of the strata are important factors affecting the development of the layered yardangs. This type of differential erosion accelerates the development of the yardangs in the Loulan region.

Wear and corrosion resistance of electroforming layer after WEDM for 7075 aluminum alloy

NASA Astrophysics Data System (ADS)

Xu, Jinkai; Qiu, Rongxian; Lian, Zhongxu; Yu, Zhanjiang; Yu, Peng; Ren, Wanfei; Yu, Huadong

2018-06-01

In order to investigate the influence of the recast layer obtained by wire electrical discharge machining (WEDM) for 7075 aluminum alloy on the mechanical physical properties of the workpiece, we carried out research on the geometry parameters, microstructure, adhesion, wear resistance and corrosion resistance of the recast layer. The results show that the unit thermal power density decreases, the surface roughness Ra value increases, and the amount of the electric erosion craters and the micro/nano pits decrease with the increase of current and voltage. In the meantime, the thickness and hardness of the recast layer are increased, so the wear resistance and corrosion resistance are significantly improved. In addition, the surface hardness plays a major role in increasing wear resistance.

Analysis of Chromobacterium sp. natural isolates from different Brazilian ecosystems

PubMed Central

Lima-Bittencourt, Cláudia I; Astolfi-Filho, Spartaco; Chartone-Souza, Edmar; Santos, Fabrício R; Nascimento, Andréa MA

2007-01-01

Background Chromobacterium violaceum is a free-living bacterium able to survive under diverse environmental conditions. In this study we evaluate the genetic and physiological diversity of Chromobacterium sp. isolates from three Brazilian ecosystems: Brazilian Savannah (Cerrado), Atlantic Rain Forest and Amazon Rain Forest. We have analyzed the diversity with molecular approaches (16S rRNA gene sequences and amplified ribosomal DNA restriction analysis) and phenotypic surveys of antibiotic resistance and biochemistry profiles. Results In general, the clusters based on physiological profiles included isolates from two or more geographical locations indicating that they are not restricted to a single ecosystem. The isolates from Brazilian Savannah presented greater physiologic diversity and their biochemical profile was the most variable of all groupings. The isolates recovered from Amazon and Atlantic Rain Forests presented the most similar biochemical characteristics to the Chromobacterium violaceum ATCC 12472 strain. Clusters based on biochemical profiles were congruent with clusters obtained by the 16S rRNA gene tree. According to the phylogenetic analyses, isolates from the Amazon Rain Forest and Savannah displayed a closer relationship to the Chromobacterium violaceum ATCC 12472. Furthermore, 16S rRNA gene tree revealed a good correlation between phylogenetic clustering and geographic origin. Conclusion The physiological analyses clearly demonstrate the high biochemical versatility found in the C. violaceum genome and molecular methods allowed to detect the intra and inter-population diversity of isolates from three Brazilian ecosystems. PMID:17584942

Bare soil erosion modelling with rainfall simulations: experiments on crop and recently burned areas

NASA Astrophysics Data System (ADS)

Catani, F.; Menci, S.; Moretti, S.; Keizer, J.

2006-12-01

The use of numerical models is of fundamental importance in the comprehension and prediction of soil erosion. At the very basis of the calibration process of the numerical models are the direct measurements of the governing parameters, carried out during field or laboratory tests. To measure and model soil erosion rainfall simulations can be used, that allow the reproduction of project rainfall having chosen characteristics of intensity and duration. The main parameters that rainfall simulators can measure are hydraulic conductivity, parameters of soil erodibility, rate and features of splash erosion, discharge coefficient and sediment yield. Other important parameters can be estimated during the rainfall simulations through the use of photogrammetric instruments able to memorize high definition stereographic models of the soil plot under analysis at different time steps. In this research rainfall simulator experiments (rse) were conducted to measure and quantify runoff and erosion processes on selected bare soil plots. The selected plots are located in some vineyards, olive groves and crops in central Italy and in some recently burned areas in north-central Portugal, affected by a wildfire during early July 2005 and, at the time, largely covered by commercial eucalypt plantations. On the Italian crops the choice of the rainfall intensities and durations were performed on the basis of the previous knowledge of the selected test areas. The procedure was based on an initial phase of soil wetting and a following phase of 3 erosion cycles. The first should reproduce the effects of a normal rainfall with a return time of 2 years (23 mm/h). The second should represent a serious episode with a return time of 10 years (34 mm/h). The third has the objective to reproduce and understand the effects of an intense precipitation event, with a return time of 50 years (41 mm/h). During vineyards experiments some photogrammetric surveys were carried out as well. In the Portugal burned areas, to measure the influence of rain intensities, two rainfall simulations have been carried out simultaneously, one with an intensity of 45 mm/h and one with 85 mm/h. In both cases, before the experiments, soil and vegetation cover description have been made and soil samples have been taken. During the simulations soil samples leaving the parcels were taken at suitable time intervals to measure the sediment yield and the runoff. The rse data have been thought to provide a sufficient basis for erosion modelling at the small-plot scale and, through upscaling, for predicting erosion rates at the slope scale. For this purpose two soil erosion models, WEPP and MEFIDIS, have been selected and then compared. The comparison has shown a certain degree of uncertainty in numeric erosion prediction, due to the non linearity of the overland erosion processes, and to technical and conceptual difficulties, including the data collection. In the following laboratory phase high resolution (2 by 2 mm) DEMs of the vineyards plot are being produced for each meaningful processing phase. The digital elevation models will then be analysed to asses calibration parameters such as soil roughness (expressed by standard deviation of elevations, fractal dimension and local relief energy), soil and sediment transfer (hypsometric curves, local elevation and volume differences) and rill network evolution (Horton ordering, stream lengths, contributing area, drainage density, Hack's law)

Ground-water sapping processes, Western Desert, Egypt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, W.; Arvidson, R.E.; Sultan, M.

1997-01-01

Depressions of the Western Desert of Egypt (specifically, Kharga, Farafra, and Kurkur regions) are mainly occupied by shales that are impermeable, but easily erodible by rainfall and runoff, whereas the surrounding plateaus are composed of limestones that are permeable and more resistant to fluvial erosion under semiarid to arid conditions. A computer simulation model was developed to quantify the ground-water sapping processes, using a cellular automata algorithm with coupled surface runoff and ground-water flow for a permeable, resistant layer over an impermeable, friable unit. Erosion, deposition, slumping, and generation of spring-derived tufas were parametrically modeled. Simulations using geologically reasonable parametersmore » demonstrate that relatively rapid erosion of the shales by surface runoff, ground-water sapping, and slumping of the limestones, and detailed control by hydraulic conductivity inhomogeneities associated with structures explain the depressions, escarpments, and associated landforms and deposits. Using episodic wet pulses, keyed by {delta}{sup 18}O deep-sea core record, the model produced tufa ages that are statistically consistent with the observed U/Th tufa ages. This result supports the hypothesis that northeastern African wet periods occurred during interglacial maxima. This {delta}{sup 18}O-forced model also replicates the decrease in fluvial and sapping activity over the past million years. 65 refs., 21 figs., 2 tabs.« less

Microstructure and elevated-temperature erosion-oxidation behaviour of aluminized 9Cr-1Mo Steel

NASA Astrophysics Data System (ADS)

Huttunen-Saarivirta, E.; Honkanen, M.; Tsipas, S. A.; Omar, H.; Tsipas, D.

2012-10-01

Degradation of materials by a combination of erosive wear and atmospheric oxidation at elevated temperatures constitutes a problem in some power generation processes, such as fluidized-bed combustion. In this work, 9Cr-1Mo steel, a common tube material in combustion chambers, is coated by a pack cementation method from an Al-containing pack in order to improve the resistance to erosion-oxidation at elevated temperatures. The resulting coating is studied in terms of microstructure and microhardness and tested for its resistance against impacts by sand particles in air at temperatures of 550-700 °C under several conditions, with thickness changes and appearance of the exposed surfaces being studied. The coating was found to contain several phases and layers, the outermost of which was essentially Al-rich and contained e.g., small AlN precipitates. The microhardness values for such coating ranged from 950 to 1100 HV20g. The coating provided the substrate with increased protection particularly against normal particle impacts, as manifested by smaller thickness losses for coated specimens as compared to uncoated counterparts. However, much of the coating was lost under all test conditions, despite the fact that particle debris formed a homogeneous layer on the surface. These results are described and discussed in this paper.

A review of the impact of the environment on aerogenerator materials

NASA Astrophysics Data System (ADS)

Mortimer, A. R.

Factors which contribute to the unreliability of windpowered generators are examined, with specific regard to the availability of materials, durability, cost, ease of production, and ease of repair. The effects of wind loading and methods for testing salt air contaminants are discussed, along with the effect of moisture, of salt air on lubricants, of microbiological attack, of UV radiation, rain erosion, and icing. The probability of bird strikes is statistically defined, and consideration is given to electrostatic charging, lightning strikes, temperature changes, the corrosion of rubber by ozone, the effects of guano, and wet dry pollution. The visual, EM, and acoustic effects of wind turbines are explored, and production processes which may affect the integrity of the structure are outlined. Finally, failure mechanisms due to salt-air environments are detailed.

High-Frequency Testing of Composite Fan Vanes With Erosion-Resistant Coating Conducted

NASA Technical Reports Server (NTRS)

Bowman, Cheryl L.; Sutter, James K.; Naik, Subhash; Otten, Kim D.; Perusek, Gail P.

2003-01-01

The mechanical integrity of hard, erosion-resistant coatings were tested using the Structural Dynamics Laboratory at the NASA Glenn Research Center. Under the guidance of Structural Mechanics and Dynamics Branch personnel, fixturing and test procedures were developed at Glenn to simulate engine vibratory conditions on coated polymer-matrix- composite bypass vanes using a slip table in the Structural Dynamics Laboratory. Results from the high-frequency mechanical bench testing, along with concurrent erosion testing of coupons and vanes, provided sufficient confidence to engine-endurance test similarly coated vane segments. The knowledge gained from this program will be applied to the development of oxidation- and erosion-resistant coatings for polymer matrix composite blades and vanes in future advanced turbine engines. Fan bypass vanes from the AE3007 (Rolls Royce America, Indianapolis, IN) gas turbine engine were coated by Engelhard (Windsor, CT) with compliant bond coatings and hard ceramic coatings. The coatings were developed collaboratively by Glenn and Allison Advanced Development Corporation (AADC)/Rolls Royce America through research sponsored by the High-Temperature Engine Materials Technology Project (HITEMP) and the Higher Operating Temperature Propulsion Components (HOTPC) project. High-cycle fatigue was performed through high-frequency vibratory testing on a shaker table. Vane resonant frequency modes were surveyed from 50 to 3000 Hz at input loads from 1g to 55g on both uncoated production vanes and vanes with the erosion-resistant coating. Vanes were instrumented with both lightweight accelerometers and strain gauges to establish resonance, mode shape, and strain amplitudes. Two high-frequency dwell conditions were chosen to excite two strain levels: one approaching the vane's maximum allowable design strain and another near the expected maximum strain during engine operation. Six specimens were tested per dwell condition. Pretest and posttest inspections were performed optically at up to 60 magnification and using a fluorescent-dye penetrant. Accumulation of 10 million cycles at a strain amplitude of two to three times that expected in the engine (approximately 670 Hz and 20g) led to the development of multiple cracks in the coating that were only detectable using fluorescent-dye penetrant inspection. Cracks were prevalent on the trailing edge and on the convex side of the midsection. No cracking or spalling was evident using standard optical inspection at up to 60 magnification. Further inspection may reveal whether these fine cracks penetrated the coating or were strictly on the surface. The dwell condition that simulated actual engine conditions produced no obvious surface flaws even after up to 80 million cycles had been accumulated at strain amplitudes produced at approximately 1500 Hz and 45g.

Gender differences in the association of non-alcoholic fatty liver disease and metabolic syndrome with erosive oesophagitis: a cross-sectional study in a Taiwanese population.

PubMed

Hung, Wei-Chieh; Wu, Jin-Shang; Sun, Zih-Jie; Lu, Feng-Hwa; Yang, Yi-Ching; Chang, Chih-Jen

2016-11-15

Although metabolic syndrome correlates with erosive oesophagitis, few studies have examined the association between non-alcoholic fatty liver disease (NAFLD), associated with obesity and insulin resistance as metabolic syndrome, and erosive oesophagitis. The possible gender differences in risk factors of erosive oesophagitis should be considered. This study aimed to determine the concomitant effects of NAFLD and metabolic syndrome on erosive oesophagitis with respect to gender. This cross-sectional study, conducted between January 2000 and August 2009, included 12 090 participants from the health examination center of a tertiary hospital. NAFLD was diagnosed according to ultrasonographic findings after excluding participants with excessive alcohol consumption or other liver diseases. Metabolic syndrome was determined using the revised National Cholesterol Education Program Adult Treatment Panel III criteria. Erosive oesophagitis was defined according to the Los Angeles classification by oesophagogastroduodenoscopy. On the basis of the oesophagogastroduodenoscopic findings, the prevalence of erosive oesophagitis was 20.1% (n=1427/7110) and 9.9% (n=477/4842) in males and females, respectively. After adjusting for other variables, metabolic syndrome (OR 1.26; 95% CI 1.09 to 1.45) but not NAFLD (OR 1.14; 95% CI 0.98 to 1.30) significantly correlated with erosive oesophagitis in males, while NAFLD (OR 1.50; 95% CI 1.21 to 1.86) but not metabolic syndrome (OR 1.24; 95% CI 0.94 to 1.63) positively correlated with erosive oesophagitis in females. The detrimental effect on erosive oesophagitis is greater by metabolic syndrome than by NAFLD in males but greater by NAFLD than by metabolic syndrome in females. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Sustainable agriculture, soil management and erosion from prehistoric times to 2100

NASA Astrophysics Data System (ADS)

Vanwalleghem, Tom; Gómez, Jose Alfonso; Infante Amate, Juan; González Molina, Manuel; Fernández, David Soto; Guzmán, Gema; Vanderlinden, Karl; Laguna, Ana; Giráldez, Juan Vicente

2015-04-01

The rational use of soil requires the selection of management practices to take profit of the beneficial functions of plant growth, water and nutrient storage, and pollutants removal by filtering and decomposition without altering its properties. However, the first evidence of important and widespread erosion peaks can generally be found with the arrival of the first farmers all over the world. In areas with a long land-use history such as the Mediterranean, clear signs indicating the advanced degradation status of the landscape, such as heavily truncated soils, are visible throughout. Soil conservation practices are then aimed at reducing erosion to geological rates, in equilibrium with long-term soil formation rates, while maximizing agricultural production. The adoption of such practices in most areas of the world are as old as the earliest soil erosion episodes themselves. This work firstly reviews historical evidence linking soil management and soil erosion intensity, with examples from N Europe and the Mediterranean. In particular, work by the authors in olive orchards will be presented that shows how significant variations in soil erosion rates between could be linked to the historical soil management. The potential of historical documents for calibrating a soil erosion model is shown as the model, in this case RUSLE-based and combining tillage and water erosion, adequately represents the measured erosion rate dynamics. Secondly, results from present-day, long-term farm experiments in the EU are reviewed to evaluate the effect of different soil management practices on physical soil properties, such as bulk density, penetration resistance, aggregate stability, runoff coefficient or sediment yield. Finally, we reflect upon model and field data that indicate how future global climate change is expected to affect soil management and erosion and how the examples used above hold clues about sustainable historical management practices that can be used successfully in the future.

Impacts of simulated acid rain on recalcitrance of two different soils.

PubMed

Dai, Zhongmin; Liu, Xingmei; Wu, Jianjun; Xu, Jianming

2013-06-01

Laboratory experiments were conducted to estimate the impacts of simulated acid rain (SAR) on recalcitrance in a Plinthudult and a Paleudalfs soil in south China, which were a variable and a permanent charge soil, respectively. Simulated acid rains were prepared at pH 2.0, 3.5, 5.0, and 6.0, by additions of different volumes of H2SO4 plus HNO3 at a ratio of 6 to 1. The leaching period was designed to represent 5 years of local annual rainfall (1,200 mm) with a 33 % surface runoff loss. Both soils underwent both acidification stages of (1) cation exchange and (2) mineral weathering at SAR pH 2.0, whereas only cation exchange occurred above SAR pH 3.5, i.e., weathering did not commence. The cation exchange stage was more easily changed into that of mineral weathering in the Plinthudult than in the Paleudalfs soil, and there were some K(+) and Mg(2+) ions released on the stages of mineral weathering in the Paleudalfs soil. During the leaching, the release of exchangeable base cations followed the order Ca(2+) >K(+) >Mg(2+) >Na(+) for the Plinthudult and Ca(2+) >Mg(2+) >Na(+) >K(+) for the Paleudalfs soil. The SARs above pH 3.5 did not decrease soil pH or pH buffering capacity, while the SAR at pH 2.0 decreased soil pH and the buffering capacity significantly. We conclude that acid rain, which always has a pH from 3.5 to 5.6, only makes a small contribution to the acidification of agricultural soils of south China in the short term of 5 years. Also, Paleudalfs soils are more resistant to acid rain than Plinthudult soils. The different abilities to prevent leaching by acid rain depend upon the parent materials, types of clay minerals, and soil development degrees.

Slurry Erosion Behavior of F6NM Stainless Steel and High-Velocity Oxygen Fuel-Sprayed WC-10Co-4Cr Coating

NASA Astrophysics Data System (ADS)

Cui, S. Y.; Miao, Q.; Liang, W. P.; Huang, B. Z.; Ding, Z.; Chen, B. W.

2017-02-01

WC-10Co-4Cr coating was applied to the surface of F6NM stainless steel by high-velocity oxygen-fuel spraying. The slurry erosion behavior of the matrix and coating was examined at different rotational speeds using a self-made machine. This experiment effectively simulates real slurry erosion in an environment with high silt load. At low velocity (<6 m/s), the main failure mechanism was cavitation. Small bubbles acted as an air cushion, obstructing direct contact between sand and the matrix surface. However, at velocity above 9 m/s, abrasive wear was the dominant failure mechanism. The results indicate that WC-10Co-4Cr coating significantly improved the slurry resistance at higher velocity, because it created a thin and dense WC coating on the surface.

Effects of acid rain on plant microbial associations in California. Research report (final)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, D.; Paul, E.A.

1984-04-13

The effects of simulated acid rain of pH 5.6 to 3.0, with ionic composition similar to that found in California, on Trifolium repens, Lupinus densiflorus and L. benthamii grown in two soils were tested. The interactions of treatment intensity, soil type, phosphorus uptake and mycorrhizal influences on growth, carbon fixation and allocation and nitrogen fixation were determined. Acidic treatments generally decreased plant growth, nodulation and nitrogenase activity. The exposure of plants to a large number of simulated rainfall conditions of shorter duration did not result in the negative growth effects. Plants adequately supplied with P, either as fertilizer or bymore » mycorrhizal fungi, were much more resistant to conditions caused by acidic precipitation and in some cases growth increases were found.« less

Warnings and Human Response in the Oroville Dam Crisis, February 2017

NASA Astrophysics Data System (ADS)

Sorensen, J. H.; Mileti, D. S.; Needham, J. T.

2017-12-01

On February 7, 2017, erosion was detected in the primary spillway for Oroville Dam in northern California, causing an elevated concern for the safety of downstream communities. The situation seemed stable until heavy rains on February 11 resulted in the flow of water over the emergency spillway. On February 12, erosion below the emergency spillway was observed. At 4:21 PM on February 12, the Butte County Sheriff issued an evacuation order for "low levels of Oroville and downstream areas". Counties downstream followed with evacuation warnings. The purpose of this paper is to present preliminary results of research, conducted for the U.S. Army Corp of Engineers, on the Oroville event. This investigation is part of a research program designed to collect and analyze data on: 1) The timing of the decisions to order public evacuation warnings including the flow of information between engineers and geologist monitoring the hazard and local officials. 2) The method and timing of the dissemination of those warnings including the diffusion or warning by various communication channels. 3) The interpretation and response of the public to those warnings, including the timing of protective action decisions. The findings from these studies will be incorporated into risk assessment models used in assessing the impacts of dam and levee failures on a national basis.

Temporal Dynamics of Gully Evolution in a Small, Ephemeral Channel in a Semiarid Watershed

NASA Astrophysics Data System (ADS)

Nichols, Mary; Nearing, Mark

2015-04-01

Incised channels that terminate at a vertical-wall gully heads are common features in semiarid watersheds. The geomorphic evolution of such channels is often dominated by migration of the headwall. The evolution of a headwall in a low order channel on the USDA-ARS Walnut Gulch Experimental Watershed (WGEW) in southeastern Arizona has been monitored since 2004, and since 2012, time-lapse photography has been employed to observe the temporal dynamics at high resolution. A Canon A1300 off the shelf point and shoot digital camera mounted inside a weatherproof Pelican case has been taking 15 mp photographs since 2012. The camera power supply was modified to run from a 12V car battery that was charged with a 25 Watt solar panel through a solar controller. During the runoff season from July through September, images were collected every 30 seconds and the time step was increase to 30 minutes during winter months. The field of view covers the headcut and the immediate surroundings. Runoff events were distinct flash floods in response to high intensity rain. The temporal sequencing of the dominant processes of erosion including mass wasting, plunge pool erosion, and piping are described. In addition, we present a description of the time-lapse camera system with suggestions for future improvements.

Erosion and physical transport via overland flow of arsenic and lead bound to silt-sized particles

PubMed Central

Cadwalader, G. Owen; Renshaw, Carl E.; Jackson, Brian P.; Magilligan, Francis J.; Landis, Joshua D.; Bostick, Benjamin C.

2011-01-01

Understanding of the transport mechanisms of contaminated soils and sediment is essential for the sustainable management of contaminated lands. In New England and elsewhere, vast areas of agricultural lands are contaminated by the historical application of lead-arsenate pesticides. Left undisturbed the physical and chemical mobility of As and Pb in these soils is limited due to their strong affinity for adsorption onto solid phases. However, soil disturbance promotes erosion and overland flow during intense rainstorms. Here we investigate the event-scale transport of disturbed As and Pb contaminated soils through measurement of concentrations of As and Pb in suspended sediment and changes in Pb isotopic ratios in overland flow. Investigation of several rain events shows that where land disturbance has occurred, physical transport of silt-sized particles and aggregates is the primary transport vector of As and Pb derived from pesticide-contaminated soil. Although both As and Pb are associated with similarly-sized particles, we find that solid-phase As is more effectively mobilized and transported than Pb. Our results demonstrate that anthropogenic land disturbance of historical lands contaminated with lead-arsenate pesticides may redistribute, through physical transport, significant amounts of As, and lesser amounts of Pb, to riparian and stream sediments, where they are potentially more bioavailable. PMID:21552357

Multi-walled carbon nanotubes/graphene oxide hybrid and nanohydroxyapatite composite: A novel coating to prevent dentin erosion.

PubMed

Nahorny, Sídnei; Zanin, Hudson; Christino, Vinie Abreu; Marciano, Fernanda Roberta; Lobo, Anderson Oliveira; Soares, Luís Eduardo Silva

2017-10-01

To date is emergent the development of novel coatings to protect erosion, especially to preventive dentistry and restorative dentistry. Here, for the first time we report the effectiveness of multi-walled carbon nanotube/graphene oxide hybrid carbon-base material (MWCNTO-GO) combined with nanohydroxyapatite (nHAp) as a protective coating for dentin erosion. Fourier transform Raman spectroscopy (FT-Raman), scanning electron (SEM), and transmission electron (TEM) microscopy were used to investigated the coatings and the effect of acidulated phosphate fluoride gel (APF) treatment on bovine teeth root dentin before and after erosion. The electrochemical corrosion performance of the coating was evaluated. Raman spectra identified that: (i) the phosphate (ν 1 PO 4 3- ) content of dentin was not significantly affected by the treatments and (ii) the carbonate (ν 1 CO 3 2- ) content in dentin increased when nHAp was used. However, the nHAp/MWCNTO-GO composite exposited lower levels of organic matrix (CH bonds) after erosion compared to other treatments. Interesting, SEM micrographs identified that the nHAp/MWCNTO-GO formed layers after erosive cycling when associate with APF treatment, indicating a possible chemical bond among them. Treatments of root dentin with nHAp, MWCNTO-GO, APF_MWCNTO-GO, and APF_nHAp/MWCNTO-GO increased the carbonate content, carbonate/phosphate ratio, and organic matrix band area after erosion. The potentiodynamic polarization curves and Nyquist plot showed that nHAp, MWCNT-GO and nHAp/MWCNT-GO composites acted as protective agents against corrosion process. Clearly, the nHAp/MWCNTO-GO composite was stable after erosive cycling and a thin and acid-resistant film was formed when associated to APF treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Water erosion and climate change in a small alpine catchment

NASA Astrophysics Data System (ADS)

Berteni, Francesca; Grossi, Giovanna

2017-04-01

WATER EROSION AND CLIMATE CHANGE IN A SMALL ALPINE CATCHMENT Francesca Berteni, Giovanna Grossi A change in the mean and variability of some variables of the climate system is expected to affect the sediment yield of mountainous areas in several ways: for example through soil temperature and precipitation peak intensity change, permafrost thawing, snow- and ice-melt time shifting. Water erosion, sediment transport and yield and the effects of climate change on these physical phenomena are the focus of this work. The study area is a small mountainous basin, the Guerna creek watershed, located in the Central Southern Alps. The sensitivity of sediment yield estimates to a change of condition of the climate system may be investigated through the application of different models, each characterized by its own features and limits. In this preliminary analysis two different empirical mathematical models are considered: RUSLE (Revised Universal Soil Loss Equation; Renard et al., 1991) and EPM (Erosion Potential Method; Gavrilovic, 1988). These models are implemented in a Geographical Information System (GIS) supporting the management of the territorial database used to estimate relevant geomorphological parameters and to create different thematic maps. From one side the geographical and geomorphological information is required (land use, slope and hydrogeological instability, resistance to erosion, lithological characterization and granulometric composition). On the other side the knowledge of the weather-climate parameters (precipitation and temperature data) is fundamental as well to evaluate the intensity and variability of the erosive processes and estimate the sediment yield at the basin outlet. Therefore different climate change scenarios were considered in order to tentatively assess the impact on the water erosion and sediment yield at the small basin scale. Keywords: water erosion, sediment yield, climate change, empirical mathematical models, EPM, RUSLE, GIS, Guerna

Geomorphic and hydrologic assessment of erosion hazards at the Norman municipal landfill, Canadian River floodplain, central Oklahoma

USGS Publications Warehouse

Curtis, Jennifer A.; Whitney, John W.

2003-01-01

The Norman, Oklahoma, municipal landfill closed in 1985 after 63 years of operation, because it was identified as a point source of hazardous leachate composed of organic and inorganic compounds. The landfill is located on the floodplain of the Canadian River, a sand-bed river characterized by erodible channel boundaries and by large variation in mean monthly discharges. In 1986, floodwaters eroded riprap protection at the southern end of the landfill and penetrated the landfill's clay cap, thereby exposing the landfill contents. The impact of this moderate-magnitude flood event (Q12) was the catalyst to investigate erosion hazards at the Norman landfill. This geomorphic investigation analyzed floodplain geomorphology and historical channel changes, flood-frequency distributions, an erosion threshold, the geomorphic effectiveness of discharge events, and other factors that influence erosion hazards at the landfill site. The erosion hazard at the Norman landfill is a function of the location of the landfill with respect to the channel thalweg, erosional resistance of the channel margins, magnitude and duration of discrete discharge events, channel form and hydraulic geometry, and cumulative effects related to a series of discharge events. Based on current climatic conditions and historical channel changes, a minimum erosion threshold is set at bankfull discharge (Q = 572 m3/s). The annual probability of exceeding this threshold is 0.53. In addition, this analysis indicates that peak stream power is less informative than total energy expenditures when estimating the erosion potential or geomorphic effectiveness of discrete discharge events. On the Canadian River, long-duration, moderate-magnitude floods can have larger total energy expenditures than shorter-duration, high-magnitude floods and therefore represent the most serious erosion hazard to floodplain structures.

Effects of erosion in the fate of soil organic carbon and soil aggregation in a burned Mediterranean hill-slope

NASA Astrophysics Data System (ADS)

Campo, Julian; Cammeraat, Erik; Gimeno-García, Eugenia; Andreu, Vicente

2016-04-01

The Intergovernmental Panel on Climate Change indicated a higher degree of confidence that meteorological conditions associated to climate change will be propitious to increasing extreme events manifested, among others, in bigger and more frequent wildfires (IPCC, 2014). Wildfires contribute to shaping the landscape, and also the geomorphological and hydrological processes that operate on soil are affected (Bento-Gonçalves et al., 2012). Whereas, it is well documented that wildfires produce significant changes on erosion processes, the associated fate of soil organic carbon (SOC) has received less attention. This research assesses this gap by studying the loss, redistribution, and stabilization of SOC in a Mediterranean forest hill-slope burned the 28-08-2014, with high severity fire, at the Natural Park of Sierra de Espadán, Spain (39°50'45.11"N, 0°22'20.52"W). To this end, soil was sampled (19-9-2014) in the foot's slope (depositional), middle part (transport) and top (eroding) at two depths (<2 cm, 2-5 cm), and in two environments (under canopy soil: UC; bare soil: BS). Sediments were collected from four sediment fences constructed at the foot's slope, and together with soil samples, analysed with regard to SOC content and aggregate stability (AS). The main objective is to increase the understanding on the fate of SOC in Mediterranean burned areas experiencing soil erosion, transport and deposition, with special attention to the role of aggregation and disaggregation in redistribution processes. Immediately after the fire, SOC content was high (≈50 gC kg-1) as well as the AS (water drop test>146 drops). Significant differences (ANOVA, p<0.05) in SOC contents were observed between environments (UC>BS) and soil depths (topsoil>subsoil). However, no significant differences were observed among eroding (58.8+20.8 gC kg-1), transport (67.3+34.4 gC kg-1), and depositional zones (62.0+31.3 gC kg-1), which is not in agreement with other SOC redistribution studies (Wang et al., 2014). Significant differences (Kruskal-Wallis, p<0.05) were also found in AS between environments (UC>BS) but not between soil depths or hill-slope positions. In the first post-fire erosive rains occurred in the area (29-11-14), closest pluviometer (Sot de Ferrer: 4.5 km) registered a total daily rain up to 64.2 l m-2. In this event a total of 12.7 kg of sediment were collected (contributing area ≈0.25 ha), with a content of 252.6 gC kg-1 the total SOC transported or stored in the depositional zone can reach up to 3.2 kg. In the second erosive event (23-3-15: 103.2 l m-2), total sediment in the fences was 143.6 kg, with content of 112.2 gC kg-1, made a total SOC eroded of up to 16.1 kg. It is hypothesized that fire caused the homogenization of SOC content and AS in the different hill-slope positions, and only when erosion expose unburned organic matter to mineralization processes, SOC losses will increase in eroding sites, likely decreasing in transport and depositional ones. Ongoing work is related to the analyses of organic C in different soil fractions (determined by sieving and density) in order to understand C stabilization in post-fire soil, and its role in disaggregation and SOC redistribution by sediment in different hill-slope positions. Acknowledgements: This work has been supported by the Generalitat Valenciana through the VALi+d postdoctoral contract (APOSTD/2014/010). References: Bento-Goncalves, A., Vieira, A., Ubeda, X., Martin, D., 2012. Fire and soils: Key concepts and recent advances. Geoderma 191, 3-13. IPCC, 2014. Fifth Assessment Report (AR5). Climate Change 2014: Impacts, Adaptation, and Vulnerability. Wang, X., Cammeraat, E.L.H., Cerli, C., Kalbitz, K., 2014. Soil aggregation and the stabilization of organic carbon as affected by erosion and deposition. Soil Biology & Biochemistry 72, 55-65.

HVOF Thermal Spray TiC/TiB 2 Coatings for AUSC Boiler/Turbine Components for Enhanced Corrosion Protection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mondal, Kanchan; Koc, Rasit; Fan, Chinbay

The high temperatures of operations still pose significant risk of degradation and fatigue from oxidizing, corroding and eroding environment. In addition to unused O 2, water from combustion and SO x from the coal sulfur oxidation that result in highly corrosive environment, acid gases such as HCl and other sulfur compounds may also be present. These adverse effects are further accelerated due to the elevated temperatures. In addition, ash particulates and unburnt carbon and pyritic sulfur can cause erosion of the surface and thus loss of material. Unburnt carbon and pyritic sulfur may also cause localized reduction sites. Thus, firesidemore » corrosion protection and steam oxidation protection alternatives to currently used Ni-Cr overlays need to be identified and evaluated. Titanium carbide (TiC) is a suitable alternative on account of the material features such as the high hardness, the high melting point, the high strength and the low density for the substitution or to be used in conjunction with NiCr for enhancing the fireside corrosion and erosion of the materials. Another alternative is the use of titanium boride as a coating for chemical stability required for long-term service and high erosion resistance over the state-of-the-art, high fracture toughness (K 1C ~12 MPam 1/2) and excellent corrosion resistance (kp~1.9X10 -11 g 2/cm 4/s at 800°C in air). The overarching aim of the research endeavor was to synthesize oxidation, corrosion and wear resistant TiC and TiB 2 coating powders, apply thermal spray coating on existing boiler materials and characterize the coated substrates for corrosion resistance for applications at high temperatures (500 -750 °C) and high pressures (~350 bars) using the HVOF process and to demonstrate the feasibility of these coating to be used in AUSC boilers and turbines.« less

Resistance of Silicon Nitride Turbine Components to Erosion and Hot Corrosion/oxidation Attack

NASA Technical Reports Server (NTRS)

Strangmen, Thomas E.; Fox, Dennis S.

1994-01-01

Silicon nitride turbine components are under intensive development by AlliedSignal to enable a new generation of higher power density auxiliary power systems. In order to be viable in the intended applications, silicon nitride turbine airfoils must be designed for survival in aggressive oxidizing combustion gas environments. Erosive and corrosive damage to ceramic airfoils from ingested sand and sea salt must be avoided. Recent engine test experience demonstrated that NT154 silicon nitride turbine vanes have exceptional resistance to sand erosion, relative to superalloys used in production engines. Similarly, NT154 silicon nitride has excellent resistance to oxidation in the temperature range of interest - up to 1400 C. Hot corrosion attack of superalloy gas turbine components is well documented. While hot corrosion from ingested sea salt will attack silicon nitride substantially less than the superalloys being replaced in initial engine applications, this degradation has the potential to limit component lives in advanced engine applications. Hot corrosion adversely affects the strength of silicon nitride in the 850 to 1300 C range. Since unacceptable reductions in strength must be rapidly identified and avoided, AlliedSignal and the NASA Lewis Research Center have pioneered the development of an environmental life prediction model for silicon nitride turbine components. Strength retention in flexure specimens following 1 to 3300 hour exposures to high temperature oxidation and hot corrosion has been measured and used to calibrate the life prediction model. Predicted component life is dependent upon engine design (stress, temperature, pressure, fuel/air ratio, gas velocity, and inlet air filtration), mission usage (fuel sulfur content, location (salt in air), and times at duty cycle power points), and material parameters. Preliminary analyses indicate that the hot corrosion resistance of NT154 silicon nitride is adequate for AlliedSignal's initial engine applications. Protective coatings and/or inlet air filtration may be required to achieve required ceramic component lives in more aggressive environments.

Sediment transport dynamics in steep, tropical volcanic catchments

NASA Astrophysics Data System (ADS)

Birkel, Christian; Solano Rivera, Vanessa; Granados Bolaños, Sebastian; Brenes Cambronero, Liz; Sánchez Murillo, Ricardo; Geris, Josie

2017-04-01

How volcanic landforms in tropical mountainous regions are eroded, and how eroded materials move through these mostly steep landscapes from the headwaters to affect sediment fluxes are critical to water resources management in their downstream rivers. Volcanic landscapes are of particular importance because of the short timescales (< years) over which they transform. Owing to volcanism and seismic activity, landslides and other mass movements frequently occur. These processes are amplified by high intensity precipitation inputs resulting in significant, but natural runoff, erosion and sediment fluxes. Sediment transport is also directly linked to carbon and solute export. However, knowledge on the sediment sources and transport dynamics in the humid tropics remains limited and their fluxes largely unquantified. In order to increase our understanding of the dominant erosion and sediment transport dynamics in humid tropical volcanic landscapes, we conducted an extensive monitoring effort in a pristine and protected (biological reserve Alberto Manuel Brenes, ReBAMB) tropical forest catchment (3.2 km2), located in the Central Volcanic Cordillera of Costa Rica (Figure 1A). Typical for tropical volcanic and montane regions, deeply incised V-form headwaters (Figure 1B) deliver the majority of water (>70%) and sediments to downstream rivers. At the catchment outlet (Figure 1C) of the San Lorencito stream, we established high temporal resolution (5min) water quantity and sediment monitoring (turbidity). We also surveyed the river network on various occasions to characterize fluvial geomorphology including material properties. We could show that the rainfall-runoff-sediment relationships and their characteristic hysteresis patterns are directly linked to variations in the climatic input (storm intensity and duration) and the size, form and mineralogy of the transported material. Such a relationship allowed us to gain the following insights: (i) periodic landslides contribute significant volumes of material (> 100m3 per year) to the stream network, (ii) rainfall events that exceed a threshold of around 30mm/h rain intensity activate superficial flow pathways with associated mobilization of sediments (laminar erosion). However, the erosion processes are spatially very heterogeneous and mostly linked to finer material properties of the soils that mostly developed on more highly weathered bedrock. (iii) extreme events (return period > 50 years) mainly erode the streambed and banks cutting deeper into the bedrock and re-distribute massive amounts of material in the form of removed old alluvial deposits and new deposits created elsewhere, (iv) recovery after such extreme events in the form of fine material transport even during low intensity rainfall towards pre-event rainfall intensity thresholds takes only about two to three months. We conclude that the study catchment geomorphologically represents a low-resistance, but highly resilient catchment that quickly recovers after the impact of extreme rainfall-runoff events. The latter was indicated by a different pre and post-event hysteretic pattern of sediment-runoff dynamics and associated different material properties. The combined use of high-temporal resolution monitoring with spatially distributed surveys provided new insights into the fluvial geomorphology of steep, volcanic headwater catchments with potential to establish more complete sediment budgets and time-scales of land-forming processes of such highly dynamic environments in the humid tropics.

Quantification of sediment export from two contrasted catchments of the Mayotte Island: a multi-scale observatory to fight against soil erosion and siltation of the lagoon in Mayotte Island

NASA Astrophysics Data System (ADS)

Landemaine, Valentin; Lidon, Bruno; Lopez, Jean-Marie; Dejean, Cyril; Bozza, Jean-Louis; Benard, Bhavani; Parizot, Manuel; Desprats, Jean-Francois; Cerdan, Olivier

2017-04-01

As a consequence of a dramatic increase of its population, the Mayotte Island is undergoing significant land use changes, mainly through an increase in agricultural areas as well as unplanned urban sprawl. Resulting soil erosion in natural degraded areas, in agricultural fields or from rural habitat threatens the sustainability of agriculture, as well as the balance of the lagoon ecosystem, one of the largest in the world, by siltation of the aquatic environment by sediments and adsorbed pollutants. In order to implement pertinent and sustainable remediation measure there is a need to quantify the sediment fluxes, identify the sources areas and raise awareness of population on land degradation. To this end, a multiscale hydro-sedimentary observatory was installed on two coastal watersheds representative of the morphology, geology and land use observed on the island of Mayotte: the Mtsamboro basin (19 ha) and the Dzoumogné basin (343 ha). On the Mtsamboro basin, rainfall, runoff and sediment monitoring is carried out by two stations in order to distinguish the urbanized downstream part (11 ha) from the upstream part under agro-forest cover (8 ha). A single hydro-sedimentary station was installed at the outlet of the Dzoumogné basin insofar land use is homogeneous and represented by agro-forest cover. The observatory is completed by a survey of runoff and erosion on experimental plots installed on the main types of land use of the island of Mayotte. The cumulative rainfall of this first year of monitoring is closed to the long term mean (1934-1997) with 1200 mm rained over the wet season (December - April). During this period, recorded rainfall events reached a maximum of 90 to 120 mm in 24 hours. The soil erosion rate over this year at the outlet of the Mtsamboro basin is 5.4 t.ha-1. On the upstream part of the watershed, the soil erosion rate decreases to about 1 t.ha-1, clearly lower than the tens of tons generally observed at the plot scale for this context. Therefore, despite very steep slopes (> 20%), the scale effect on soil erosion rates is extremely marked with massive deposits of sediments on hillslopes and on the streambed of the stream network. The soil erosion rate is 0.3 t.ha-1 for the Dzoumogné basin. This figure is explained by a larger drainage area and an agroforestry cover offering more possibilities for sediment deposits. These results provide initial insight into the dynamics of hydro-sediment transfers on these basins and will be enriched and deepened as part of the multi-year survey of this observatory.

Nanoscale coatings for erosion and corrosion protection of copper microchannel coolers for high powered laser diodes

NASA Astrophysics Data System (ADS)

Flannery, Matthew; Fan, Angie; Desai, Tapan G.

2014-03-01

High powered laser diodes are used in a wide variety of applications ranging from telecommunications to industrial applications. Copper microchannel coolers (MCCs) utilizing high velocity, de-ionized water coolant are used to maintain diode temperatures in the recommended range to produce stable optical power output and control output wavelength. However, aggressive erosion and corrosion attack from the coolant limits the lifetime of the cooler to only 6 months of operation. Currently, gold plating is the industry standard for corrosion and erosion protection in MCCs. However, this technique cannot perform a pin-hole free coating and furthermore cannot uniformly cover the complex geometries of current MCCs involving small diameter primary and secondary channels. Advanced Cooling Technologies, Inc., presents a corrosion and erosion resistant coating (ANCERTM) applied by a vapor phase deposition process for enhanced protection of MCCs. To optimize the coating formation and thickness, coated copper samples were tested in 0.125% NaCl solution and high purity de-ionized (DIW) flow loop. The effects of DIW flow rates and qualities on erosion and corrosion of the ANCERTM coated samples were evaluated in long-term erosion and corrosion testing. The robustness of the coating was also evaluated in thermal cycles between 30°C - 75°C. After 1000 hours flow testing and 30 thermal cycles, the ANCERTM coated copper MCCs showed a corrosion rate 100 times lower than the gold plated ones and furthermore were barely affected by flow rates or temperatures thus demonstrating superior corrosion and erosion protection and long term reliability.

Preliminary evaluation of cavitation resistance of type 316LN stainless steel in mercury using a vibratory horn

NASA Astrophysics Data System (ADS)

Pawel, S. J.; Manneschmidt, E. T.

2003-05-01

Type 316LN stainless steel in a variety of conditions (annealed, cold-worked, surface-modified) was exposed to cavitation conditions in stagnant mercury using a vibratory horn. The test conditions included peak-to-peak displacement of the specimen surface of 25 μm at a frequency of 20 kHz and a mercury temperature in the range -5 to 80 °C. Following a brief incubation period in which little or no damage was observed, specimens of annealed 316LN exhibited increasing weight loss and surface roughening with increasing exposure times. Examination of test surfaces with the scanning electron microscope revealed primarily general/uniform wastage in all cases but, for long exposure times, a few randomly oriented 'pits' were also observed. Type 316LN that was 50% cold-worked was considerably more resistant to cavitation erosion damage than annealed material, but the surface modifications (CrN coating, metallic glass coating, laser treatment to form a diamond-like surface) provided little or no protection for the substrate. In addition, the cavitation erosion resistance of other materials - Inconel 718, Nitronic 60, and Stellite 3 - was also compared with that of 316LN for identical screening test conditions.

Seasonal electrical resistivity surveys of a coastal bluff, Barter Island, North Slope Alaska

USGS Publications Warehouse

Swarzenski, Peter W.; Johnson, Cordell; Lorenson, Thomas; Conaway, Christopher H.; Gibbs, Ann E.; Erikson, Li; Richmond, Bruce M.; Waldrop, Mark P.

2016-01-01

Select coastal regions of the North Slope of Alaska are experiencing high erosion rates that can be attributed in part to recent warming trends and associated increased storm intensity and frequency. The upper sediment column of the coastal North Slope of Alaska can be described as continuous permafrost underlying a thin (typically less than 1–2 m) active layer that responds variably to seasonal thaw cycles. Assessing the temporal and spatial variability of the active layer and underlying permafrost is essential to better constrain how heightened erosion may impact material fluxes to the atmosphere and the coastal ocean, and how enhanced thaw cycles may impact the stability of the coastal bluffs. In this study, multi-channel electrical resistivity tomography (ERT) was used to image shallow subsurface features of a coastal bluff west of Kaktovik, on Barter Island, northeast Alaska. A comparison of a suite of paired resistivity surveys conducted in early and late summer 2014 provided detailed information on how the active layer and permafrost are impacted during the short Arctic summer. Such results are useful in the development of coastal resilience models that tie together fluvial, terrestrial, climatic, geologic, and oceanographic forcings on shoreline stability.

Non-destructive evaluation of specialty coating degradation using terahertz time-domain spectroscopy

NASA Astrophysics Data System (ADS)

Nicoletti, Carley R.; Cramer, Laura; Fletcher, Alan; Zimdars, David; Iqbal, Zafar; Federici, John F.

2017-05-01

The Terahertz Time Domain Reflection Spectroscopy (THz-TDS) method of paint layer diagnostics is a non-contact electromagnetic technique analogous to pulsed-ultrasound with the added capability of spectroscopic characterization. The THz-TDS sensor emits a near-single cycle electromagnetic pulse with a bandwidth from 0.1 to 3 THz. This wide bandwidth pulse is focused on the coating, and echo pulses are generated from each interface (air-coating, layer-layer, coating-substrate). In this paper, the THz-TDS method is applied to specialty aircraft coatings. The THz-TDS method is able to penetrate the whole coating stack and sample the properties of each layer. Because the reflected pulses from individual layers typically overlap in time, the complex permittivity function and thickness of each layer is determined by a best fit of the measured reflection (either in time or frequency domain) to a layered model of the paint. The THz- TDS method is applied to specialty coatings prior to and during accelerated aging on a series of test coupons. The coupons are also examined during aging using ATR (attenuated total reflectance)-FTIR spectroscopy, Raman scattering spectroscopy, and Scanning Electron Microscopy (SEM) to ascertain, quantify, and understand the breakdown mechanisms of the coatings. In addition, the same samples are characterized using THz-TDS techniques to determine if the THz-TDS method can be utilized as a non-destructive evaluation technique to sense degradation of the coatings. Our results suggest that the degradation mechanism begins in the top coat layer. In this layer, 254 nm UV illumination in combination with the presence of moisture works partially with oxides as catalysts to decompose the polymer matrix thereby creating porosity in the top coat layer. Since the catalytic effect is partial, loss of the oxides by chemical reaction can also occur. As the topcoat layer becomes more porous, it allows water vapor to permeate the topcoat layer and interact with the rain erosion layer via carbonization of the polymer matrix in the rain erosion layer. The presence of the salt accelerates the pitting degradation. The goal of this paper is to determine if THz-TDS can be used to sense degradation of the coating.

Evaluation of iron aluminide weld overlays for erosion - corrosion resistant boiler tube coatings in low NO{sub x} boilers

DOE Office of Scientific and Technical Information (OSTI.GOV)

DuPont, J.N.; Banovic, S.W.; Marder, A.R.

1996-08-01

Low NOx burners are being installed in many fossil fired power plants in order to comply with new Clean Air Regulations. Due to the operating characteristics of these burners, boiler tube sulfidation corrosion is often enhanced and premature tube failures can occur. Failures due to oxidation and solid particle erosion are also a concern. A program was initiated in early 1996 to evaluate the use of iron aluminide weld overlays for erosion/corrosion protection of boiler tubes in Low NOx boilers. Composite iron/aluminum wires will be used with the Gas Metal Arc Welding (GMAW) process to prepare overlays on boiler tubesmore » steels with aluminum contents from 8 to 16wt%. The weldability of the composite wires will be evaluated as a function of chemical composition and welding parameters. The effect of overlay composition on corrosion (oxidation and sulfidation) and solid particle erosion will also be evaluated. The laboratory studies will be complemented by field exposures of both iron aluminide weld overlays and co-extruded tubing under actual boiler conditions.« less

Tafoni - A Llink Between Mars and Earth

NASA Astrophysics Data System (ADS)

Iacob, R. H.; Iacob, C. E.

2013-12-01

Remarkable rock erosion structures on the planetary surface, tafoni represent an important instrument for investigating the specific environmental conditions causing such rock formations. From simple cavities to refined honeycomb or other intricate patterns, tafoni are a reflection of the complex interaction between the rock structure and the environmental factors. On the genesis of tafoni, there is no unique breakdown mechanism at work, but a multitude of physical and chemical processes developing over time. However, some of these formation mechanisms are typically predominant. Tafoni can be found on a variety of rock substrates, from sandstone and vesicular lava rocks to granite and basalt, and in a variety of environments, from wet coastal areas to the extreme dry zones of hot deserts, high plateaus or frozen lands of Antarctica. During various NASA missions, tafoni were also identified on rock formations on Mars. Comparative study of the environmental conditions leading to the formation of tafoni on Earth and Mars can help explain past and present surface erosion mechanisms on the Red Planet. The mechanisms responsible for tafoni formation on Earth include wind erosion, exfoliation, frost shattering, and, in the majority of cases, salt weathering. Microclimate variations of temperature, evaporation of salt water, disaggregation of mineral grains, as well as sandblasting, are among most common contributors that initiate the pitting of the rock surface, giving way to further development of tafoni alveoli, cavities and other erosion patterns. Dissolution of calcium carbonates and siliceous cements, or hydration of feldspars, are representative examples of tafoni erosion involving rain water, sea water or air moisture. Live organisms and biochemical processes are significant contributors to the formation and evolution of tafoni, especially in humid or water reach environments. In many instances, tafoni reflect erosion mechanism specific to environmental conditions that no longer exist. NASA's current Mars Science Laboratory mission offers exceptional opportunities to perform a comparative study between tafoni formations on Mars and those on Earth. The present mission of Curiosity at Gale Crater, benefiting not only from the most advanced technology for in-situ investigations but also from a terrain rich in rock breakdown features, was able to reveal new tafoni formations. Gale Crater's landscape presents a variety of surface erosion elements, witnesses of major planetary transformations suffered by Mars during the past 3 billion years. While the wind and sand-blasting erosion are the most recent causes of the surface erosion at Gale Crater, leading to the smoothing, thinning, exfoliation and piercing of various rock layers, other geological formations such as alluvial fans, moat areas, gravel sediments, round shaped mounds and toadstool formations demonstrate that liquid water was vigorously shaping the surface of Mars billions of years ago. In such a context, the study of tafoni formations revealed during Curiosity's trek from Bradbury Landing through the Glenelg area of Gale Crater, will help advance the understanding of the Martian past and present environment, providing scenarios for the evolution of the Red Planet. The presentation contains various images of tafoni samples from Mars and Earth, explaining by similitude presumptive weathering mechanisms on Mars.

[Impact of heavy snow storm and freezing rain disasters on soil fauna in Chinese fir plantation in southern China].

PubMed

Yan, Shao-kui; Zhang, Wei-dong; Liu, Yan-xin; Fu, Sheng-lei; Li, Yuan-liang; Wang, Si-long

2009-01-01

In January 2008, southern China suffered an unusual heavy snowstorm and freezing rain over a large area for almost a month long. This catastrophic event was the worst one in past 50 years, which brought the area a serious impact on the infrastructure, ecology, and environment. To understand the long-term impact of this catastrophic event on the forest ecosystems in this area, a field investigation was conducted on the soil fauna in a pure Chinese fir plantation and a mixed Chinese fir plantation-alder plantation in Huitong County of Hunan Province on March 23, 2008, the date 40 days after the heavy snowstorm and freezing rain. With the abundance and community composition as the main parameters and the monitoring data from the two plantations on March 23, 2007 as the reference, the flexibility and resistance of soil fauna to the disturbances of the catastrophic event was preliminarily evaluated. The results showed that there was a significant deviation of soil fauna communities in the two plantations from the reference. An outbreak increase in microfauna nematode abundance was found from 12216.9 ind x m(-2) to 118343.9 ind x m(-2) in pure Chinese fir plantation and from 25435.9 ind x m(-2) to 84573.0 ind x m(-2) in mixed Chinese fir plantation-alder plantation, while a 27.0% and 85.6% decrease of macrofauna abundance was found in the two plantations, respectively, compared with the reference. Mesofauna abundance also had a significant decrease in litter layer but not in soil. The abundance recovery displayed a trend from quick rate for microfauna to slow rate for macrofauna, which indicated that the soil fauna functional groups, in terms of body size, could be used as a vulnerable indicator in evaluating disturbance event and post-disturbance recovery. By using community ordinations, no shift in soil fauna community composition was detected 40 days after the catastrophic event, suggesting that the community composition of soil invertebrate had a high resistance to catastrophic snowstorm and freezing rain disturbances.

Mycorrhizal inoculation as a tool for sustainable bio-engineering measures in steep alpine environments? - Results of a three year field experiment

NASA Astrophysics Data System (ADS)

Bast, Alexander; Wilcke, Wolfgang; Lüscher, Peter; Graf, Frank; Gärtner, Holger

2013-04-01

Global warming is anticipated to result in an increase of heavy precipitation events. In vegetation-free, steep Alpine areas intense rain fall events have distinct influences on erosional processes on slopes. These processes and (shallow) mass movements are directly linked with torrential rain falls, and for this lead to high erosion rates in those regions, resulting in an increased natural and socio-economic damage potential. For restoring and managing erosion-prone sites, bioengineering measures as a tool for hazard prevention gain more importance. Due to the rough environmental conditions, and hence, reduced germination capability and sprout vigour, it is difficult to establish a dense cover of pioneer vegetation. Thus, the question is what can be done to give planted saplings within bioengineering projects maximum support, to develop their above- and belowground structures to promote slope stabilization. Green-house and laboratory experiments have shown that mycorrhizal inoculum has a positive impact on plant development and soil structure, e.g. the formation of (stable) aggregates within several months. Based on these promising results, we intended to apply mycorrhizal inoculation in a field-experiment. In May 2010, we established experimental plots at an erosion-prone talus slope (inclination: ~40 - 45 °; elevation 1220 - 1360 m a.s.l.), located in the Eastern Swiss Alps. The slope, consisting of moraine and denudation-derived substrate, shows high geomorphic activity (e.g. debris flows, rill erosion). Two slope areas, 10m wide and 32m long, were stabilized with 1200 plants each. Additionally, mycorrhiza inoculum (INOQ Forst, 40 ml/plant) was added to one of the two areas. Within the stabilized areas, a mixture of eight saplings was planted per running meter in 15 rows. The assortment included four saplings of green alder and two of purple willow, as well as one tree (maple, birch, ash) and shrub species (e.g. guelder rose, honeysuckle). Finally, both areas were hand-seeded with an Alpine seed-mixture. In addition, a third was selected but not treated, reflecting the natural conditions and serving as a control. Next to analysing aboveground whole-plant traits (e.g. plant height, crown diameter, stem thickness) and leaf traits (e.g. specific leaf area, leaf size, leaf dry matter content, nitrogen and potassium analyses), we also focused on belowground properties. Undisturbed soil cores (0-20cm in depth) allow a determination of a aggregate stability coefficient, the aggregate-size development, as well as root traits (e.g. root length density, fine(root)diameter). Linear mixed-effect models and testing a posteriori contrasts permit a comparison between the different treatments. Preliminary results indicate, that four months after stabilization plant mortality was high over the two treatments, but it was significantly less on the inoculated treatment. In general plant and leaf traits are showing, that plant vitality is higher at the mycorrhizal-treated plots. Examination of belowground properties yield surprising results; the non-inoculated treatment is showing higher aggregate stability coefficients and higher root length density, which is in contrast to laboratory results. Our contribution will highlight the results of the entire three year field experiment.

Turbidity on the Shallow Reef off Kaulana and Hakioawa Watersheds, North Coast of Kaho`olawe, Hawai`iMeasurements of Turbidity and Ancillary Data on Winds, Waves, Precipitation, and Stream flow Discharge, November 2005 to June 2008

USGS Publications Warehouse

Presto, M. Katherine; Storlazzi, Curt D.; Field, Michael E.; Abbott, Lyman L.

2010-01-01

The island of Kaho`olawe has particular cultural and religious significance for native Hawaiians. Once known as Kanaloa, the island was a center for native Hawaiian navigation. In the mid-20th century, the island was used as a bombing range by the U.S. Navy, and that practice, along with the foraging by feral goats, led to a near-complete decimation of vegetation. The loss of ground cover led to greatly increased erosion and run-off of sediment-laden water onto the island's adjacent coral reefs. Litigation in 1990 ended the U.S. Navy's use of the island as a bombing range, and in 1994 the island was transferred to the Kaho`olawe Island Reserve Commission (KIRC), http://kahoolawe.hawaii.gov/. As a result of the litigation, the U.S. Navy began a 10-year clean-up effort that was the foundation for the present restoration effort by KIRC (Slay, 2009). The restoration effort is centered on revegetating the island, reducing erosion, and limiting run-off onto adjacent reefs. Restoration efforts to mitigate sediment runoff to streams and gulches by restoring native vegetation and minimizing erosion have focused on two watersheds, Kaulana and Hakioawa, on the northeast and northwest sides of the island, respectively. Stream flow and sediment gages were installed by the U.S. Geological Survey Pacific Islands Water Science Center in each of the watersheds, and a weather station was established upland of the watersheds. For this study, turbidity monitors were installed on the insular shelf off the two watersheds to monitor the overall quality of reef waters and their changes in response to rain and stream flow discharge events.

Earth Observations taken by the Expedition 17 Crew

NASA Image and Video Library

2008-08-19

ISS017-E-013789 (19 Aug. 2008) --- Desert erosion in Libya is featured in this image photographed by an Expedition 17 crewmember on the International Space Station. This detailed view (covering 13 kilometers) shows the classic patterns of an erosional desert landscape located 300 kilometers south of Libya's Mediterranean coast. Widespread indented patterns are low escarpments and stream terraces generated by stream erosion -- on those few occasions in any decade when enough rain falls for streams to flow. The only areas with active sediment deposition are the stream beds which appear in this image as sinuous zones with a distinct component of black minerals, resulting in a darker coloration than adjacent low escarpments. Sediment is transported into the area from a volcanic landscape immediately upstream to the west. Other stream-generated features are several relict stream banks, one of which even shows both of the original parallel banks. According to scientists, the ancient stream banks are preserved from erosion by various hardening cements (mainly calcium carbonate and gypsum) introduced by the streams when they were active, probably during wetter climates in the past two million years. Relict stream courses show prior positions of streams, and also provide Earth analogs for similar features on Mars. The lack of vegetation is the first indication of the great aridity of the region, but sand dunes also appear as sinuous lines oriented perpendicular to the dominant northeasterly wind direction (transverse dunes). Assuming the dominant wind direction remains the same, these transverse dunes are expected to move further to the southwest over time. Some of the dunes cross the river courses, showing how seldom the river flows.