Predictive model for local scour downstream of hydrokinetic turbines in erodible channels

NASA Astrophysics Data System (ADS)

Musa, Mirko; Heisel, Michael; Guala, Michele

2018-02-01

A modeling framework is derived to predict the scour induced by marine hydrokinetic turbines installed on fluvial or tidal erodible bed surfaces. Following recent advances in bridge scour formulation, the phenomenological theory of turbulence is applied to describe the flow structures that dictate the equilibrium scour depth condition at the turbine base. Using scaling arguments, we link the turbine operating conditions to the flow structures and scour depth through the drag force exerted by the device on the flow. The resulting theoretical model predicts scour depth using dimensionless parameters and considers two potential scenarios depending on the proximity of the turbine rotor to the erodible bed. The model is validated at the laboratory scale with experimental data comprising the two sediment mobility regimes (clear water and live bed), different turbine configurations, hydraulic settings, bed material compositions, and migrating bedform types. The present work provides future developers of flow energy conversion technologies with a physics-based predictive formula for local scour depth beneficial to feasibility studies and anchoring system design. A potential prototype-scale deployment in a large sandy river is also considered with our model to quantify how the expected scour depth varies as a function of the flow discharge and rotor diameter.

Application of subsurface vertical flow constructed wetlands to reject water treatment in dairy wastewater treatment plant.

PubMed

Dąbrowski, Wojciech; Karolinczak, Beata; Gajewska, Magdalena; Wojciechowska, Ewa

2017-01-01

The paper presents the effects of applying subsurface vertical flow constructed wetlands (SS VF) for the treatment of reject water generated in the process of aerobic sewage sludge stabilization in the biggest dairy wastewater treatment plant (WWTP) in Poland. Two SS VF beds were built: bed (A) with 0.65 m depth and bed (B) with 1.0 m depth, planted with reeds. Beds were fed with reject water with hydraulic load of 0.1 m d -1 in order to establish the differences in treatment efficiency. During an eight-months research period, a high removal efficiency of predominant pollutants was shown: BOD 5 88.1% (A) and 90.5% (B); COD 84.5% (A) and 87.5% (B); TSS 87.6% (A) and 91.9% (B); TKN 82.4% (A) and 76.5% (B); N-NH 4 + 89.2% (A) and 85.7% (B); TP 30.2% (A) and 40.6% (B). There were not statistically significant differences in the removal efficiencies between bed (B) with 1.0 m depth and bed (A) with 0.65 m depth. The research indicated that SS VF beds could be successfully applied to reject water treatment in dairy WWTPs. The study proved that the use of SS VF beds in full scale in dairy WWTPs would result in a significant decrease in pollutants' load in reject water. In the analyzed case, decreasing the load of ammonia nitrogen was of greatest importance, as it constituted 58% of the total load treated in dairy WWTP and posed a hazard to the stability of the treatment process.

Temporal and spatial variability in thalweg profiles of a gravel-bed river

USGS Publications Warehouse

Madej, Mary Ann

1999-01-01

This study used successive longitudinal thalweg profiles in gravel-bed rivers to monitor changes in bed topography following floods and associated large sediment inputs. Variations in channel bed elevations, distributions of residual water depths, percentage of channel length occupied by riffles, and a spatial autocorrelation coefficient (Moran's I) were used to quantify changes in morphological diversity and spatial structure in Redwood Creek basin, northwestern California. Bed topography in Redwood Creek and its major tributaries consists primarily of a series of pools and riffles. The size, frequency and spatial distribution of the pools and riffles have changed significantly during the past 20 years. Following large floods and high sediment input in Redwood Creek and its tributaries in 1975, variation in channel bed elevations was low and the percentage of the channel length occupied by riffles was high. Over the next 20 years, variation in bed elevations increased while the length of channel occupied by riffles decreased. An index [(standard deviation of residual water depth/bankfull depth) × 100] was developed to compare variations in bed elevation over a range of stream sizes, with a higher index being indicative of greater morphological diversity. Spatial autocorrelation in the bed elevation data was apparent at both fine and coarse scales in many of the thalweg profiles and the observed spatial pattern of bed elevations was found to be related to the dominant channel material and the time since disturbance. River reaches in which forced pools dominated, and in which large woody debris and bed particles could not be easily mobilized, exhibited a random distribution of bed elevations. In contrast, in reaches where alternate bars dominated, and both wood and gravel were readily transported, regularly spaced bed topography developed at a spacing that increased with time since disturbance. This pattern of regularly spaced bed features was reversed following a 12-year flood when bed elevations became more randomly arranged.

Investigation of pier scour in coarse-bed streams in Montana, 2001 through 2007

USGS Publications Warehouse

Holnbeck, Stephen R.

2011-01-01

A primary goal of ongoing field research of bridge scour is improvement of scour-prediction equations so that pier-scour depth is predicted accurately-an important element of hydraulic analysis and design of highway bridges that cross streams, rivers, and other waterways. Scour depth for piers in streambeds with a mixture of sand, gravel, cobbles, and boulders (coarse-bed streams, which are common in Montana) generally is less than the scour depth in finer-grained (sandy) streambeds under similar conditions. That difference is attributed to an armor layer of coarser material. Pier-scour data from the U.S. Geological Survey were used in this study to develop a bed-material correction factor, which was incorporated into the Federal Highway Administration's recommended equation for computing pier scour. This report describes results of a study of pier scour in coarse-bed streams at 59 bridge sites during 2001-2007 in the mountain and foothill regions of western Montana. Respective drainage areas ranged from about 3 square miles (mi2) to almost 20,000 mi2. Data collected and analyzed for this study included 103 pier-scour measurements; the report further describes data collection, shows expansion of the national coarse pier-scour database, discusses use of the new data in evaluation of relative accuracy of various predictive equations, and demonstrates how differences in size and gradation between surface bed material and shallow-subsurface bed material might relate to pier scour. Nearly all measurements were made under clear-water conditions with no incoming sediment supply to the bridge opening. Half of the measurements showed approach velocities that equaled or surpassed the critical velocity for incipient motion of bed material, possibly indicating that measurements were made very near the threshold between clear-water and live-bed scour, where maximum scour was shown in laboratory studies. Data collected in this study were compared to selected pier-scour data from the nationwide Bridge Scour Data Management System (BSDMS), to show the effect of bed-material size and gradation on scour depth. Unsteady field flow conditions and armoring by coarser material reduced scour relative to the clear-water/sandy-bed laboratory results at steady flow. The new correction factor and the standard scour equation produced the most accurate estimates of scour depth in armored, coarse-bed conditions. Maximum relative scour occurred at similar velocity across variations in bed material and gradation. Pier scour decreased with increased variation in particle size and gradation.

Evaluating the potential for remote bathymetric mapping of a turbid, sand-bed river: 1. Field spectroscopy and radiative transfer modeling

USGS Publications Warehouse

Legleiter, C.J.; Kinzel, P.J.; Overstreet, B.T.

2011-01-01

Remote sensing offers an efficient means of mapping bathymetry in river systems, but this approach has been applied primarily to clear-flowing, gravel bed streams. This study used field spectroscopy and radiative transfer modeling to assess the feasibility of spectrally based depth retrieval in a sand-bed river with a higher suspended sediment concentration (SSC) and greater water turbidity. Attenuation of light within the water column was characterized by measuring the amount of downwelling radiant energy at different depths and calculating a diffuse attenuation coefficient, Kd. Attenuation was strongest in blue and near-infrared bands due to scattering by suspended sediment and absorption by water, respectively. Even for red wavelengths with the lowest values of Kd, only a small fraction of the incident light propagated to the bed, restricting the range of depths amenable to remote sensing. Spectra recorded above the water surface were used to establish a strong, linear relationship (R2 = 0.949) between flow depth and a simple band ratio; even under moderately turbid conditions, depth remained the primary control on reflectance. Constraints on depth retrieval were examined via numerical modeling of radiative transfer within the atmosphere and water column. SSC and sensor radiometric resolution limited both the maximum detectable depth and the precision of image-derived depth estimates. Thus, although field spectra indicated that the bathymetry of turbid channels could be remotely mapped, model results implied that depth retrieval in sediment-laden rivers would be limited to shallow depths (on the order of 0.5 m) and subject to a significant degree of uncertainty. ?? 2011 by the American Geophysical Union.

Estimating maximum depth distribution of seagrass using underwater videography

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

Norris, J.G.; Wyllie-Echeverria, S.

1997-06-01

The maximum depth distribution of eelgrass (Zostera marina) beds in Willapa Bay, Washington appears to be limited by light penetration which is likely related to water turbidity. Using underwater videographic techniques we estimated that the maximum depth penetration in the less turbid outer bay was -5.85 ft (MILW) and in the more turbid inner bay was only -1.59 ft (MLLW). Eelgrass beds had well defined deepwater edges and no eelgrass was observed in the deep channels of the bay. The results from this study suggest that aerial photographs taken during low tide periods are capable of recording the majority ofmore » eelgrass beds in Willapa Bay.« less

Development of channel organization and roughness following sediment pulses in single‐thread, gravel bed rivers

USGS Publications Warehouse

Madej, Mary Ann

2001-01-01

Large, episodic inputs of coarse sediment (sediment pulses) in forested, mountain streams may result in changes in the size and arrangement of bed forms and in channel roughness. A conceptual model of channel organization delineates trajectories of response to sediment pulses for many types of gravel bed channels. Channels exhibited self‐organizing behavior to various degrees based on channel gradient, presence of large in‐channel wood or other forcing elements, the size of the sediment pulse, and the number of bed‐mobilizing flows since disturbance. Typical channel changes following a sediment pulse were initial decreases in water depth, in variability of bed elevations, and in the regularity of bed form spacing. Trajectories of change subsequently showed increased average water depth, more variable and complex bed topography, and increased uniformity of bed form spacing. Bed form spacing in streams with abundant forcing elements developed at a shorter spatial scale (two to five channel widths) than in streams without such forcing mechanisms (five to 10 channel widths). Channel roughness increased as bed forms developed.

Evaluation of pier-scour equations for coarse-bed streams

USGS Publications Warehouse

Chase, Katherine J.; Holnbeck, Stephen R.

2004-01-01

Streambed scour at bridge piers is among the leading causes of bridge failure in the United States. Several pier-scour equations have been developed to calculate potential scour depths at existing and proposed bridges. Because many pier-scour equations are based on data from laboratory flumes and from cohesionless silt- and sand-bottomed streams, they tend to overestimate scour for piers in coarse-bed materials. Several equations have been developed to incorporate the mitigating effects of large particle sizes on pier scour, but further investigations are needed to evaluate how accurately pier-scour depths calculated by these equations match measured field data. This report, prepared in cooperation with the Montana Department of Transportation, describes the evaluation of five pier-scour equations for coarse-bed streams. Pier-scour and associated bridge-geometry, bed-material, and streamflow-measurement data at bridges over coarse-bed streams in Montana, Alaska, Maryland, Ohio, and Virginia were selected from the Bridge Scour Data Management System. Pier scour calculated using the Simplified Chinese equation, the Froehlich equation, the Froehlich design equation, the HEC-18/Jones equation and the HEC-18/Mueller equation for flood events with approximate recurrence intervals of less than 2 to 100 years were compared to 42 pier-scour measurements. Comparison of results showed that pier-scour depths calculated with the HEC-18/Mueller equation were seldom smaller than measured pier-scour depths. In addition, pier-scour depths calculated using the HEC-18/Mueller equation were closer to measured scour than for the other equations that did not underestimate pier scour. However, more data are needed from coarse-bed streams and from less frequent flood events to further evaluate pier-scour equations.

Bed topography and sand transport responses to a step change in discharge and water depth

USDA-ARS?s Scientific Manuscript database

Ephemeral streams with sand and gravel beds may inherit bed topography caused by previous flow events, resulting in bed topography that is not in equilibrium with flow conditions, complicating the modeling of flow and sediment transport. Major flow events, resulting from rainfall with high intensity...

Application of a Line Laser Scanner for Bed Form Tracking in a Laboratory Flume

NASA Astrophysics Data System (ADS)

de Ruijsscher, T. V.; Hoitink, A. J. F.; Dinnissen, S.; Vermeulen, B.; Hazenberg, P.

2018-03-01

A new measurement method for continuous detection of bed forms in movable bed laboratory experiments is presented and tested. The device consists of a line laser coupled to a 3-D camera, which makes use of triangulation. This allows to measure bed forms during morphodynamic experiments, without removing the water from the flume. A correction is applied for the effect of laser refraction at the air-water interface. We conclude that the absolute measurement error increases with increasing flow velocity, its standard deviation increases with water depth and flow velocity, and the percentage of missing values increases with water depth. Although 71% of the data is lost in a pilot moving bed experiment with sand, still high agreement between flowing water and dry bed measurements is found when a robust LOcally weighted regrESSion (LOESS) procedure is applied. This is promising for bed form tracking applications in laboratory experiments, especially when lightweight sediments like polystyrene are used, which require smaller flow velocities to achieve dynamic similarity to the prototype. This is confirmed in a moving bed experiment with polystyrene.

A comparison of measures of riverbed form for evaluating distributions of benthic fishes

USGS Publications Warehouse

Wildhaber, Mark L.; Lamberson, Peter J.; Galat, David L.

2003-01-01

A method to quantitatively characterize the bed forms of a large river and a preliminary test of the relationship between bed-form characteristics and catch per unit area of benthic fishes is presented. We used analog paper recordings of bathymetric data from the Missouri River and fish data collected from 1996 to 1998 at both the segment (???101-102-km) and macrohabitat (???10-1-100-km) spatial scales. Bed-form traces were transformed to digital data with image analysis software. The slope, mean residual, and SD of the residuals of the regression of depth versus distance along the bottom, as well as mean depth, were estimated for each trace. These four metrics were compared with sinuosity, fractal dimension, critical scale, and maximum mean angle for the same traces. Mean depth and sinuosity differed among segments and macrohabitats. Fractal-based measures of the relative depth of bottom troughs (critical scale) and smoothness (maximum mean angle) differed among segments. Statistics-based measures of the relative depth of bottom troughs (mean residual) and smoothness (SD of the residuals) differed among macrohabitats. Sites with shovelnose sturgeon Scaphirhynchus platorynchus were shallower and smoother than sites without shovelnose sturgeon. When compared with sites without sicklefin chub Macrhybopsis meeki, sites with sicklefin chub were shallower, had shallower troughs, and sloped more out of the flow of the river. Sites with sturgeon chub M. gelida were shallower, had shallower troughs, and were smoother than sites without sturgeon chub. Sites with and without channel catfish Ictalurus punctatus did not differ for any bed-form variables measured. Nonzero shovelnose sturgeon density increased with depth, whereas nonzero sturgeon chub density decreased with depth. Indices of bed-form structure demonstrated potential for describing the distribution and abundance of Missouri River benthic fishes. The observed fish patterns, though limited, provide valuable direction for future research into the habitat preferences of these fishes.

Dune migration in a steep, coarse-bedded stream

USGS Publications Warehouse

Dinehart, Randy L.

1989-01-01

During 1986 and 1987, migrating bed forms composed of coarse sand and fine gravel (d50=1.8 to 9.1 mm) were documented in the North Fork Toutle River at Kid Valley, Washington, at flow velocities ranging from 1.6 to 3.4 m s−1 and depths of 0.8 to 2.2 m. The bed forms (predominantly lower regime dunes) were studied with a sonic depth sounder transducer suspended in the river at a stationary point. Twelve temporal depth-sounding records were collected during storm runoff and nearly steady, average streamflow, with record durations ranging from 37 to 261 min. Waveform height was defined by dune front heights, which ranged from 12 to 70 cm. A weak correlation between flow depth and the standard deviation of bed elevation was noted. Dune front counts and spectral analyses of the temporal records showed that dune crests passed the observation point every 2 to 5 min. Dunes were often superposed on larger bed forms with wave periods between 10 and 30 min. Gradual changes in waveform height and periodicity occurred over several hours during storm runoff. The processes of dune growth and decay were both time-dependent and affected by changes in streamflow. Rates of migration for typical dunes were estimated to be 3 cm s−1, and dune wavelengths were estimated to be 6 to 7 m.

Study and Control of Scour below Pipelines under unidirectional flow

NASA Astrophysics Data System (ADS)

Kabiri, Shima; Hoseinzadeh Dalir, Ali

2016-04-01

Water and other fluids pipelines laid on sandy rivers and sea bed change flow pattern around pipelines. These changes increase the bed shear stress and the degree of confusion around the pipes and cause to create scour hole below the pipes. In this situation, the occurrence of scour below the pipelines may lead to instability, fracture and bending and even breakage where cause very severe economic and environmental harms eventually. In this research as well as studying of scour under the pipelines, the bed sill had been used as a new mechanism in order to reduce and control of scour. For this purpose, 3 pipes (smooth) with different diameters (D) were modelled in flow condition of PIC U/Uc=0.8-0.9 in the channel with 11m length, 25cm width and depth of 50 cm. Experiment has been performed in below 2 modes: 1) Scour below a smooth pipe without bed sill 2) Scour below a smooth pipe with bed sill. In the 2nd modes bed sill was located at 4 different distances (L=0,D/4,D/2,D) of downstream Of the pipe central axis. In the experiments bed sill was a barrier for spreading wake vortices and it controlled erosions of downstream. Results of this research indicated that whatever the distance of bed sill from central axis of pipe is less, there is the most influence in reducing the scour depth below pipe. In the case that bed sill had been located exactly under central axis of pipe, scour depth under pipe decreased about 100% Also in this situation with passing a long time from the beginning of examination, the pipe self-burial process occurred due to vortex creation in pipe downstream and relocation of particles toward pipe.

Supply-Limited Bedforms in a Gravel-Sand Transition

NASA Astrophysics Data System (ADS)

Venditti, J. G.; Nittrouer, J. A.; Humphries, R. P.; Allison, M. A.

2009-12-01

Rivers often exhibit an abrupt transition from gravel to sand-bedded conditions as river channel slopes decrease. A distinct suite of bedforms has been observed through these reaches where sand supply to the bed is limited. The suite of bedforms includes a sequence of sand ribbons, barchans, and channel spanning dunes as sediment supply increases in the downstream direction. While these bedforms have been extensively documented in laboratory channels, there are relatively few observations of this sequence of supply-limited bedforms from large natural channels. Here we examine the sequence through the gravel-sand transition of the Fraser River in Southwestern British Columbia. We mapped the bed using multi-beam swath-bathymetry (Reson 8101 Seabat) at high flow (~9,000 m3s-1) immediately following a high peak flow of 11,800 m3s-1 in June 2007 The bed material grades from >70% gravel to entirely sand through the reach. The bedforms follow the expected sequence where sand ribbons and barchanoid forms cover the bed where it is primarily gravel. Channel spanning dunes form as the sand bed coverage increases. Bedform dimensions (height and length) increase moving downstream as the sand moving on the bed increases. Supply-unlimited bedforms typically scale with the flow depth where the height is 1/5 the flow depth. The bedforms developed over the gravel are undersized by this criterion. Downstream, where the bed is dominantly sand, bedforms do scale with flow depth. These data highlight the dominant role sediment supply can play in bedform morphology and scaling, confirming patterns observed in laboratory data.

Semiochemicals of the common bed bug, Cimex lectularius L. (Hemiptera: Cimicidae), and their potential for use in monitoring and control.

PubMed

Weeks, Emma N I; Birkett, Mike A; Cameron, Mary M; Pickett, John A; Logan, James G

2011-01-01

The recent resurgence of the common bed bug, Cimex lectularius L., has driven an increase in research into the biology and behaviour of this pest. Current control is reliant on the application of insecticides, but, owing to the development of insecticide resistance, there is a need for new tools and techniques. Semiochemicals (behaviour- and physiology-modifying chemicals) could be exploited for management of bed bugs. The aim of this review was to evaluate studies undertaken in bed bug chemical ecology to date, with particular reference to how the research could be exploited for monitoring and control. Bed bugs, like many other insects, have a complex olfactory system. Recent studies have characterised the olfactory sensilla, located on the terminal segment of the antennae, to functional classes by electrophysiological screening. Behavioural studies have revealed the presence of an alarm pheromone and potential airborne aggregation semiochemicals, but it is not yet understood if bed bugs use a sex pheromone during mating. Host location cues have been investigated, and carbon dioxide has been found to be highly attractive both in laboratory and in field studies. Recent field trials have tested blends of other potential kairomones, which have been shown to have an additive effect when used in a heated bed bug trap with carbon dioxide. The trap, which combines heat and kairomones, is the only trap currently available with proven efficacy in the field. In order for semiochemicals to be useful for bed bug management, an increased knowledge and understanding of the biology, behaviour and chemical ecology of this insect is essential. Copyright © 2010 Society of Chemical Industry.

Evaluation of Sleeping Comfort of Bed Mattresses using Physiological and Psychological Response Measurements

NASA Astrophysics Data System (ADS)

Aoi, Masataka; Kamijo, Masayoshi; Yoshida, Hiroaki

The purpose of this study is to create a method of evaluating the quality of sleep based on the elastic properties of bed mattresses through measurement of physiological and psychological responses while sleeping. We gathered Profile of Mood States (POMS) results before and after sleep, and investigated changes in subjects' moods according to sleep. A total of 4 bed mattresses with different degrees of elasticity were prepared. They were all pocket coil mattresses. We conducted polysomnography (PSG) testing on subjects with a bioamplifier while they slept in each bed mattress, so that sleeping depth indicating the quality of sleep could be estimated. PSG is a comprehensive recording of the biophysiological changes that occur during sleep. As a result, the sleep depth of bed mattress with a high degree of elasticity increased in the PSG evaluation. Because the hip sinks in deeply from the waist, it is not easy to turn over on mattresses with a low degree of elasticity. We have therefore considered that the sleep depth of the subjects became shallow as a result. We have concluded that it is possible to estimate the quality of sleep through analysis of PSG and POMS results.

Sonic depth sounder for laboratory and field use

USGS Publications Warehouse

Richardson, E.V.; Simons, Daryl B.; Posakony, G.J.

1961-01-01

The laboratory investigation of roughness in alluvial channels has led to the development of a special electronic device capable of mapping the streambed configuration under dynamic conditions. This electronic device employs an ultrasonic pulse-echo principle, similar to that of a fathometer, that utilizes microsecond techniques to give high accuracy in shallow depths. This instrument is known as the sonic depth sounder and was designed to cover a depth range of 0 to 4 feet with an accuracy of ? 0.5 percent. The sonic depth sounder is capable of operation at frequencies of 500, 1,000 and 2,000 kilocycles. The ultrasonic beam generated at the transducer is designed to give a minimum-diameter interrogating signal over the extended depth range. The information obtained from a sonic depth sounder is recorded on a strip-chart recorder. This permanent record allows an analysis to be made of the streambed configuration under different dynamic conditions. The model 1024 sonic depth sounder was designed principally as a research instrument to meet laboratory needs. As such, it is somewhat limited in its application as a field instrument on large streams and rivers. The principles employed in this instrument, however, have many potentials for field applications such as the indirect measurement of bed load when the bed roughness is ripples and (or) dunes, depth measurement, determination of bed configuration, and determination of depth of scour around bridge piers and abutments. For field application a modification of the present system into a battery-operated lightweight instrument designed to operate at a depth range of 0 to 30 feet is possible and desirable.

Sampling interval analysis and CDF generation for grain-scale gravel bed topography

USDA-ARS?s Scientific Manuscript database

In river hydraulics, there is a continuing need for characterizing bed elevations to arrive at quantitative roughness measures that can be used in predicting flow depth and for improved prediction of fine-sediment transport over and through coarse beds. Recently published prediction methods require...

21. Overflow pipe in filtration bed. Located at each corner ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

21. Overflow pipe in filtration bed. Located at each corner of the bed, the pipes drain off any excess water and maintain a limit on water depth. - Lake Whitney Water Filtration Plant, Filtration Plant, South side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

Field Calibration of the Saltation-Abrasion Model Using Measurements of the Energy Delivered to the Channel Bed

NASA Astrophysics Data System (ADS)

Turowski, J. M.; Wyss, C. R.; Beer, A. R.

2014-12-01

The saltation-abrasion model (SAM) is one of the highest-developed process models for fluvial bedrock erosion, describing bedrock erosion due to the impact of saltating bedload particles. The fundamental assumption in the model is a proportionality of the erosion rate and the energy delivered to the channel bed by these impacts. So far, the SAM has been calibrated on laboratory data, but field tests are rare. Here, we exploit the availability of high-quality field data at the Erlenbach bedload observatory to test and calibrate the SAM. The Erlenbach is a small, steep stream in the Swiss Prealps that hosts a well-instrumented observatory for bedload transport and erosion. Bedload samples can be taken during floods with automatic basket samplers and bedload transport rates are measured continuously with Swiss plate geophones, a surrogate method for bedload monitoring. The geophone plates can also be used to measure the energy transferred to the bed by passingbedload. Thus, we can calibrate the SAM by exploiting independent data on particle impacts, the energy they transfer to the bed, and bedload samples including grain size distributions. We find that the dimensionless pre-factor to the model is dependent on grain size. Predictions of bedrock erosion can be compared to spatial erosion data obtained from successive scans of bedrock slabs installed in the channel bed immediately upstream of the plate geophones.

Atmospheric volatilization and distribution of (Z)- and (E)-1,3-dichloropropene in field beds with and without plastic covers.

PubMed

Thomas, John E; Allen, L Hartwell; McCormack, Leslie A; Vu, Joseph C; Dickson, Donald W; Ou, Li-Tse

2004-01-01

The fumigant 1,3-dichloropropene (1,3-D) is considered to be a potential replacement for methyl bromide when methyl bromide is phased out in 2005. This study on surface emissions and subsurface diffusion of 1,3-D in a Florida sandy soil was conducted in field beds with or without plastic covers. After injection of the commercial fumigant Telone II by conventional chisels to field beds at 30cm depth which were covered with polyethylene film (PE), virtually impermeable film, or no cover (bare), (Z)- and (E)-1,3-D rapidly diffused upward. Twenty hours after injection, majority of (Z)- and (E)-1,3-D had moved upward from 30 cm depth to the layer of 5-20 cm depth. Downward movement of the two isomers in the beds with or without a plastic cover was not significant. (Z)-1,3-D diffused more rapidly than (E)-1,3-D. Virtually impermeable films (VIF) had a good capacity to retain (Z)- and (E)-1,3-D in soil pore air space. Vapor concentrations of the two isomers in the shallow subsurface of the field bed covered with VIF were greater than that in the two beds covered with polyethylene film (PE) or no cover (bare). In addition, VIF cover provided more uniform distribution of (Z)- and (E)-1,3-D in shallow subsurface than PE cover or no cover. Virtually impermeable film also had a better capability to retard surface emissions of the two isomers from soil in field beds than PE cover or no cover.

SPH modelling of depth-limited turbulent open channel flows over rough boundaries.

PubMed

Kazemi, Ehsan; Nichols, Andrew; Tait, Simon; Shao, Songdong

2017-01-10

A numerical model based on the smoothed particle hydrodynamics method is developed to simulate depth-limited turbulent open channel flows over hydraulically rough beds. The 2D Lagrangian form of the Navier-Stokes equations is solved, in which a drag-based formulation is used based on an effective roughness zone near the bed to account for the roughness effect of bed spheres and an improved sub-particle-scale model is applied to account for the effect of turbulence. The sub-particle-scale model is constructed based on the mixing-length assumption rather than the standard Smagorinsky approach to compute the eddy-viscosity. A robust in/out-flow boundary technique is also proposed to achieve stable uniform flow conditions at the inlet and outlet boundaries where the flow characteristics are unknown. The model is applied to simulate uniform open channel flows over a rough bed composed of regular spheres and validated by experimental velocity data. To investigate the influence of the bed roughness on different flow conditions, data from 12 experimental tests with different bed slopes and uniform water depths are simulated, and a good agreement has been observed between the model and experimental results of the streamwise velocity and turbulent shear stress. This shows that both the roughness effect and flow turbulence should be addressed in order to simulate the correct mechanisms of turbulent flow over a rough bed boundary and that the presented smoothed particle hydrodynamics model accomplishes this successfully. © 2016 The Authors International Journal for Numerical Methods in Fluids Published by John Wiley & Sons Ltd.

Tectonic significance of porosity and permeability regimes in the red beds formations of the South Georgia Rift Basin

NASA Astrophysics Data System (ADS)

Akintunde, Olusoga M.; Knapp, Camelia C.; Knapp, James H.

2014-09-01

A simple, new porosity/permeability-depth profile was developed from available laboratory measurements on Triassic sedimentary red beds (sandstone) from parts of the South Georgia Rift (SGR) basin in order to investigate the feasibility for long-term CO2 storage. The study locations were: Sumter, Berkeley, Dunbarton, Clubhouse Crossroad-3 (CC-3) and Norris Lightsey wells. As expected, both porosity and permeability show changes with depth at the regional scale that was much greater than at local scale. The significant changes in porosity and permeability with depth suggest a highly compacted, deformed basin, and potentially, a history of uplift and erosion. The permeability is generally low both at shallow (less than 1826 ft/556.56 m) and deeper depths (greater than 1826 ft/556.56 m). Both porosity and permeability follow the normal trend, decreasing linearly with depth for most parts of the study locations with the exception of the Norris Lightsey well. A petrophysical study on a suite of well logs penetrating the Norris Lightsey red beds at depths sampled by the core-derived laboratory measurements shows an abnormal shift (by 50%) in the acoustic travel time and/or in the sonic-derived P-wave velocity that indicates possible faulting or fracturing at depth. The departure of the Norris Lightsey's porosities and permeabilities from the normal compaction trend may be a consequence of the existence of a fault/fracture controlled abnormal pressure condition at depth. The linear and non-linear behaviors of the porosity/permeability distribution throughout the basin imply the composition of the SGR red beds, and by extension analog/similar Triassic-Jurassic formations within the Eastern North American Margin have been altered by compaction, uplift, erosion and possible faulting that have shaped the evolution of these Triassic formations following the major phase of rifting.

Chemical characteristics of beddings for swine: effects of bedding depths and of addition of inoculums in a pilot-scale.

PubMed

Corrêa, E K; Corezzolla, J L; Corrêa, M N; Bianchi, I; Gil-Turnes, C; Lucia, T

2012-11-01

The effect of depths and of addition of inoculums on the chemical content of swine beddings was evaluated. For beddings 0.25m (25D) and 0.50m (50D) deep, three treatments were tested in two repeats with the same beddings: control (no inoculums); T1 (250g of Bacillus cereus var. toyoii at 8.4×10(7)CFU/g); and T2 (250g of a pool of Bacillus sp. at 8.4×10(7)CFU/g) (250g for 25D and 500g for 50D). For 25D, the C:N ratio was lower, but N, K and C contents were greater than for 50D (P<0.05). The inoculums did not benefit any chemical parameter (P>0.05). In the second repeat, beddings presented lower C:N ratio and greater N, P and K contents than in the first repeat (P<0.05). Thus, the compost produced after using 25D twice had greater fertilizer value than that of 50D. Copyright © 2012 Elsevier Ltd. All rights reserved.

Fluvial processes and local lithology controlling abundance, structure, and composition of mussel beds.

PubMed

Vannote, R L; Minshall, G W

1982-07-01

In the Salmon River Canyon, Idaho, the fresh-water pearl mussel, Margaritifera falcata, attains maximum density and age in river reaches where large block-boulders structurally stabilize cobbles and interstitial gravels. We hypothesize that block-boulders prevent significant bed scour during major floods, and these boulder-sheltered mussel beds, although rare, may be critical for population recruitment elsewhere within the river, especially after periodic flood scour of less protected mussel habitat. Mussel shells in Indian middens adjacent to these boulder-stabilized areas suggest that prehistoric tribes selectively exploited the high-density old-aged mussel beds. Locally, canyon reaches are aggrading with sand and gravel, and M. falcata is being replaced by Gonidea angulata.

Research on the relationship between the structural properties of bedding layer in spring mattress and sleep quality.

PubMed

Shen, Liming; Chen, Yu-xia; Guo, Yong; Zhong, ShiLu; Fang, Fei; Zhao, Jing; Hu, Tian-Yi

2012-01-01

Mattress, as a sleep platform, its types and physical properties has an important effect on sleep quality and rest efficiency. In this paper, by subjective evaluations, analysis of sleeping behaviors and tests of depth of sleep, the relationship between characteristics of the bedding materials, the structure of mattress, sleep quality and sleep behaviors were studied. The results showed that: (1) Characteristics of the bedding materials and structure of spring mattress had a remarkable effect on sleep behaviors and sleep quality. An optimum combination of the bedding materials, the structure of mattress and its core could improve the overall comfort of mattress, thereby improving the depth of sleep and sleep quality. (2) Sleep behaviors had a close relationship with sleeping postures and sleep habits. The characteristics of sleep behaviors vary from person to person.

The Source Physics Experiments (SPE): A Physics-Based Approach to Discriminate Low-Yield Nuclear Events (Invited)

NASA Astrophysics Data System (ADS)

Snelson, C. M.; Chipman, V.; White, R. L.; Emmitt, R.; Townsend, M.

2013-12-01

Discriminating low-yield nuclear explosions is one of the current challenges in the field of monitoring and verification. Work is currently underway in Nevada to address this challenge by conducting a series of experiments using a physics-based approach. This has been accomplished by using a multifaceted, multi-disciplinary approach that includes a range of activities, from characterizing the shallow subsurface to acquiring new explosion data both in the near field (< 100 m from the source) to the far field (> 100 m to 10 s km from the source). The Source Physics Experiment (SPE) is a collaborative project between National Security Technologies, LLC, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, Sandia National Laboratories, the Defense Threat Reduction Agency, and the Air Force Technical Applications Center. The goal of the SPE is to understand the transition of seismic energy from the near field to the far field; to understand the development of S-waves in explosives sources; and to understand how anisotropy controls seismic energy transmission and partitioning. To fully explore these problems, the SPE test series includes tests in both simple and complex geology cases. The current series is being conducted in a highly fractured granite body. This location was chosen, in part, because it was the location of previous nuclear tests in the same rock body and because generally the geology has been well characterized. In addition to historic data, high-resolution seismic reflection, cross-hole tomography, core samples, LIDAR, hyperspectral, and fracture mapping data have been acquired to further characterize and detect changes after each of the shot across the test bed. The complex geology series includes 7 planned shots using conventional explosives in the same shot hole surrounded by Continuous Reflectometry for Radius vs. Time Experiment (CORRTEX), Time of Arrival, Velocity of Detonation, down-hole accelerometers, surface accelerometers, infrasound, and a suite of seismic sensors of various frequency bands from the near field to the far field. This allows for the use of a single test bed in the granite instead of multiple test beds to obtain the same results. The shots are planned at various depths to obtain a Green's function, scaled depth-of-burial data, nominal depth-of-burial data and damage-zone data. Three shots have been executed to date and the fourth is planned for August 2013 as a 220 lb (100 kg) TNT equivalent shot at a depth of 315 ft (96 m). Over 400 data channels have been recorded on the first series of shots with high fidelity. Once the complex geology site data have been exploited, a new test bed will be developed in a simpler geology to test these physics-based models. Ultimately, the results from this project will provide the next advances in the science of monitoring to enable a physics-based predicative capability. This work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy. DOE/NV/25946--1835.

Bed erosion control at 60 degree river confluence using vanes

NASA Astrophysics Data System (ADS)

Wuppukondur, Ananth; Chandra, Venu

2017-04-01

Confluences are common occurrences along natural rivers. Hydrodynamics at the confluence is complex due to merging of main and lateral flows with different characteristics. Bed erosion occurs at the confluence due to turbulence and also secondary circulation induced by centrifugal action of the lateral flow. The eroded sediment poses various problems in the river ecosystem including river bank failure. Reservoirs are majorly affected due to sediment deposition which reduces storage capacity. The bed erosion also endangers stability of pipeline crossings and bridge piers. The aim of this experimental study is to check the performance of vanes in controlling bed erosion at the confluence. Experiments are performed in a 600 confluence mobile bed model with a non-uniform sediment of mean particle size d50 = 0.28mm. Discharge ratio (q=ratio of lateral flow discharge to main flow discharge) is maintained as 0.5 and 0.75 with a constant average main flow depth (h) of 5cm. Vanes of width 0.3h (1.5cm) and thickness of 1 mm are placed along the mixing layer at an angle of 150, 300 and 600(with respect to main flow) to perform the experiments. Also, two different spacing of 2h and 3h (10cm and 15cm) between the vanes are used for conducting the experiments. A digital point gauge with an accuracy of ±0.1mm is used to measure bed levels and flow depths at the confluence. An Acoustic Doppler Velocitimeter (ADV) with a frequency of 25Hz and accuracy of ±1mm/s is used to measure flow velocities. Maximum scour depth ratio Rmax, which is ratio between maximum scour depth (Ds) and flow depth (h), is used to present the experimental results.From the experiments without vanes, it is observed that the velocities are increasing along the mixing layer and Rmax=0.82 and 1.06, for q=0.5 and 0.75, respectively. The velocities reduce with vanes since roughness increases along the mixing layer. For q=0.5 and 0.75, Rmax reduces to 0.62 and 0.7 with vanes at 2h spacing, respectively. Similarly, for the same discharge ratios (q), Rmax reduces to 0.64 and 0.72 with 3h spacing between the vanes, respectively. Obstruction to the flow increases with an increase of vane angle which leads to decrease of bed erosion. Also, the bed erosion increases with an increase of spacing between the vanes. Hence, vanes placed at 600 vane angle and 2h spacing exhibit better performance.

Resonant generation of internal waves on the soft sea bed by a surface water wave

NASA Astrophysics Data System (ADS)

Wen, Feng

1995-08-01

The nonlinear response of an initially flat sea bed to a monochromatic surface progressive wave was studied using the multiple scale perturbation method. Two opposite-traveling subliminal internal ``mud'' waves are selectively excited and form a resonant triad with the surface wave. The amplitudes of the internal waves grow on a time scale much longer than the period of the surface wave. It was found that the sea bed response is critically dependent on the density ratio of water and soil, depth of water, and depth and viscosity of the saturated soil. The result of instability analysis is in qualitative agreement with the result of a wave flume experiment.

Formulating the shear stress distribution in circular open channels based on the Renyi entropy

NASA Astrophysics Data System (ADS)

Khozani, Zohreh Sheikh; Bonakdari, Hossein

2018-01-01

The principle of maximum entropy is employed to derive the shear stress distribution by maximizing the Renyi entropy subject to some constraints and by assuming that dimensionless shear stress is a random variable. A Renyi entropy-based equation can be used to model the shear stress distribution along the entire wetted perimeter of circular channels and circular channels with flat beds and deposited sediments. A wide range of experimental results for 12 hydraulic conditions with different Froude numbers (0.375 to 1.71) and flow depths (20.3 to 201.5 mm) were used to validate the derived shear stress distribution. For circular channels, model performance enhanced with increasing flow depth (mean relative error (RE) of 0.0414) and only deteriorated slightly at the greatest flow depth (RE of 0.0573). For circular channels with flat beds, the Renyi entropy model predicted the shear stress distribution well at lower sediment depth. The Renyi entropy model results were also compared with Shannon entropy model results. Both models performed well for circular channels, but for circular channels with flat beds the Renyi entropy model displayed superior performance in estimating the shear stress distribution. The Renyi entropy model was highly precise and predicted the shear stress distribution in a circular channel with RE of 0.0480 and in a circular channel with a flat bed with RE of 0.0488.

Effect of Fumigation on Rotylenchulus reniformis Population Density Through Subsurface Drip Irrigation Located Every Other Furrow.

PubMed

Wheeler, T A; Porter, D O; Archer, D; Mullinix, B G

2008-09-01

Plots naturally infested with Rotylenchulus reniformis were sampled in the spring of 2006 and 2007 at depths of 15 and 30 cm in the bed, furrow over the drip tape, and "dry" furrow, and at approximately 40 to 45 cm depth in the bed and dry furrow. Then, 1,3-dichloropropene (Telone EC) was injected into the subsurface drip irrigation at 46 kg a.i./ha, and 3 to 4 weeks later the plots were resampled and assayed for nematodes. The transformed values for nematode population density (IvLRr) before fumigation were higher at 30 and 40 cm depths than at a 15 cm depth. IvLRr before fumigation was higher in the soil over the drip lines than in the bed or dry furrow and was higher in the bed than the dry furrow. IvLRr was higher in the plots to be fumigated than the plots that were not to be fumigated for all depths and locations except at a 15 cm depth over the drip lines, where the values were similar. However, after fumigation, IvLRr was lower over the drip lines at a 30 cm depth in plots that were fumigated compared to samples in a similar location and depth that were not fumigated. There were no other location/depth combinations where the fumigation reduced IvLRr below that in the nonfumigated plots. Yield in 2006, which was a very hot and dry year, was predicted adequately (R(2) = 0.67) by a linear model based on the preplant population density of R. reniformis, with a very steep slope (-2.8 kg lint/ha per R. reniformis/100 cm(3) soil). However, no relationship between nematode density and yield was seen in 2007, which had cooler weather for most of the season. Yield was not significantly improved by fumigation through the drip irrigation system in either year compared to plots treated only with aldicarb (0.84 kg a.i./ha), indicating that the level of control with fumigation did not kill enough R. reniformis to be successful.

Entrainment of bed material by Earth-surface mass flows: review and reformulation of depth-integrated theory

USGS Publications Warehouse

Iverson, Richard M.; Chaojun Ouyang,

2015-01-01

Earth-surface mass flows such as debris flows, rock avalanches, and dam-break floods can grow greatly in size and destructive potential by entraining bed material they encounter. Increasing use of depth-integrated mass- and momentum-conservation equations to model these erosive flows motivates a review of the underlying theory. Our review indicates that many existing models apply depth-integrated conservation principles incorrectly, leading to spurious inferences about the role of mass and momentum exchanges at flow-bed boundaries. Model discrepancies can be rectified by analyzing conservation of mass and momentum in a two-layer system consisting of a moving upper layer and static lower layer. Our analysis shows that erosion or deposition rates at the interface between layers must in general satisfy three jump conditions. These conditions impose constraints on valid erosion formulas, and they help determine the correct forms of depth-integrated conservation equations. Two of the three jump conditions are closely analogous to Rankine-Hugoniot conditions that describe the behavior of shocks in compressible gasses, and the third jump condition describes shear traction discontinuities that necessarily exist across eroding boundaries. Grain-fluid mixtures commonly behave as compressible materials as they undergo entrainment, because changes in bulk density occur as the mixtures mobilize and merge with an overriding flow. If no bulk density change occurs, then only the shear-traction jump condition applies. Even for this special case, however, accurate formulation of depth-integrated momentum equations requires a clear distinction between boundary shear tractions that exist in the presence or absence of bed erosion.

Organic petrology of subbituminous carbonaceous shale samples from Chalaw, Kabul Province, Afghanistan: Considerations for paleoenvironment and energy resource potential

USGS Publications Warehouse

Hackley, P.C.; SanFilipo, J.R.; Azizi, G.P.; Davis, P.A.; Starratt, S.W.

2010-01-01

Neogene (?) subbituminous carbonaceous shale deposits from Chalaw, Afghanistan, were investigated through organic petrology techniques and standard coal analyses to determine paleoenvironment and potential for resource utilization. The Chalaw deposit, approximately 30. km southeast of Kabul, currently is exploited for brick making and domestic heating and cooking. Three multiple-bench channel samples of the mined bed at Chalaw were collected and evaluated. The presence of significant huminite (ranging from 0.2 to 59.0. vol.%, mineral-inclusive basis) is suggestive of a terrestrial lignin-rich precursor plant material. Measured reflectance values of 0.38-0.55% indicate subbituminous rank. This rank suggests burial depths of approximately 1500. m and maximum temperatures of approximately 50. ??C. Structured liptinite macerals generally are absent except for some fluorescing morphologies interpreted to be poorly-preserved root cork suberinite. Sponge spicule bioliths including gemmoscleres and megascleres are common. These petrographic observations, in addition to high mineral matter content (33 to >95 vol%), medium to high sulfur content (2.1-11.5. wt.%, dry basis; db), and the presence of common gastropod? shell fragments and an aragonite-needle chalk bed are consistent with, but not directly indicative of, a marginal marine or estuarine mangrove depositional environment. However, additional data are necessary to confirm this hypothesis and deposition in a freshwater environment cannot be ruled out at this time.Commercial-scale development and utilization of the Chalaw deposit as a thermal fuel resource may be possible using a fluidized bed combustion system which could accept the low-quality mine product currently produced. Samples examined herein contain high-ash yield (45-90. wt.%, db), high total moisture content (17-39. wt.%), low calorific value (980-6860. Btu/lb, m,mmf), and have poor agglomerating properties (FSI=0), consistent with fuels utilized in fluidized bed combustors. However, delineation of the extent of the deposit through field investigation will be necessary to make a quantified resource estimate for mine planning. ?? 2009.

Sediment entrainment by debris flows: In situ measurements from the headwaters of a steep catchment

USGS Publications Warehouse

McCoy, S.W.; Kean, Jason W.; Coe, Jeffrey A.; Tucker, G.E.; Staley, Dennis M.; Wasklewicz, T.A.

2012-01-01

Debris flows can dramatically increase their volume, and hence their destructive potential, by entraining sediment. Yet quantitative constraints on rates and mechanics of sediment entrainment by debris flows are limited. Using an in situ sensor network in the headwaters of a natural catchment we measured flow and bed properties during six erosive debris-flow events. Despite similar flow properties and thicknesses of bed sediment entrained across all events, time-averaged entrainment rates were significantly faster for bed sediment that was saturated prior to flow arrival compared with rates for sediment that was dry. Bed sediment was entrained from the sediment-surface downward in a progressive fashion and occurred during passage of dense granular fronts as well as water-rich, inter-surge flow.En massefailure of bed sediment along the sediment-bedrock interface was never observed. Large-magnitude, high-frequency fluctuations in total normal basal stress were dissipated within the upper 5 cm of bed sediment. Within this near surface layer, concomitant fluctuations in Coulomb frictional resistance are expected, irrespective of the influence of pore fluid pressure or fluctuations in shear stress. If the near-surface sediment was wet as it was overridden by a flow, additional large-magnitude, high-frequency pore pressure fluctuations were measured in the near-surface bed sediment. These pore pressure fluctuations propagated to depth at subsonic rates and in a diffusive manner. The depth to which large excess pore pressures propagated was typically less than 10 cm, but scaled as (D/fi)0.5, in which D is the hydraulic diffusivity and fi is the frequency of a particular pore pressure fluctuation. Shallow penetration depths of granular-normal-stress fluctuations and excess pore pressures demonstrate that only near-surface bed sediment experiences the full dynamic range of effective-stress fluctuations, and as a result, can be more easily entrained than deeper sediment. These data provide robust tests for mechanical models of entrainment and demonstrate that a debris flow over wet bed sediment will be larger than the same flow over dry bed sediment.

[Use of low-grade potatoes in the production of whole flour for the preparation of foods for popular consumption].

PubMed

Beristain Guevara, C I; Vázquez Luna, A; Cortés García, R

1990-03-01

A whole flour potato obtention process was developed which could be used in semirural areas. The potato without peeling was previously washed and ground adding 100 p.p.m. of sodium bisulphite, then it was dehydrated in a cabinet tray dryer with an air flow circulation set at 70 degrees C using three different deep beds (10, 20 and 25 mm). Finally it was milled, sieved and packed in polyethylene Kraft bags and stored for 10 months at room temperature. Results showed that drying time increased less rapidly when the bed depth was increased, so that the overall dryer productivity increased when increasing bed depth. Nevertheless, a better-quality product was obtained, as well as a greater process efficiency when a 10 mm bed depth was used. The whole flour had a particle size of 80 mesh and a moisture and protein content of 7 and 6.7%, respectively. No brown color formation or mold growth occurred during storage. "Tamales de dulce" and chocolate cookies were made with the flour obtained. These were subjected to an acceptability test at community level, and the test revealed that for both products, such acceptability was higher than 90%.

Prediction and observation of munitions burial in energetic storms

NASA Astrophysics Data System (ADS)

Klammler, Harald; Sheremet, Alexandru; Calantoni, Joseph

2017-04-01

The fate of munitions or unexploded ordnance (UXO) resting on a submarine sediment bed is a critical safety concern. Munitions may be transported in uncontrolled ways to create potentially dangerous situations at places like beaches or ports. Alternatively, they may remain in place or completely disappear for significant but unknown periods, after becoming buried in the sediment bed. Clearly, burial of munitions drastically complicates the detection and removal of potential threats. Here, we present field data of wave height and (surrogate) munitions burial depths near the 8-m isobath at the U.S. Army Corps of Engineers, Field Research Facility, Duck, North Carolina, observed between January and March 2015. The experiment captured a remarkable sequence of storms that included at least 10 events, of which 6 were characterized by wave fields of significant heights exceeding 2 m and with peak periods of approximately 10 s. During the strongest storm, waves of 14 s period and heights exceeding 2 m were recorded for more than 3 days; significant wave height reached 5 m at the peak of activity. At the end of the experiment, divers measured munition burial depths of up to 60 cm below the seabed level. However, the local bathymetry showed less than 5 cm variation between the before and after-storm states, suggesting the local net sediment accumulation / loss was negligible. The lack of bathymetric variability excludes the possibility of burial by a migrating bed form or by sediment deposition, and strongly indicates that the munitions sank into the bed. The depth of burial also suggest an extreme state of sand agitation during the storm. For predicting munitions burial depths, we explore existing analytical solutions for the dynamic interaction between waves and sediment. Measured time series of wave pressure near the sediment bed were converted into wave-induced changes in pore pressures and the effective stress states of the sediment. Different sediment failure criteria based on minimum normal and maximum shear stresses are then applied to evaluate the appropriateness of individual failure criteria to predict observed burial depths. Results are subjected to a sensitivity analysis with respect to uncertain sediment parameters and summarized by representing cumulative failure times as a function of depth.

Column study of chromium(VI) adsorption from electroplating industry by coconut coir pith.

PubMed

Suksabye, Parinda; Thiravetyan, Paitip; Nakbanpote, Woranan

2008-12-15

The removal of Cr(VI) from electroplating wastewater by coir pith was investigated in a fixed-bed column. The experiments were conducted to study the effect of important parameters such as bed depth (40-60cm) and flow rate (10-30ml min(-1)). At 0.05 C(t)/C(0), the breakthrough volume increased as flow rate decreased or a bed depth increased due to an increase in empty bed contact time (EBCT). The bed depth service time model (BDST) fit well with the experimental data in the initial region of the breakthrough curve, while the simulation of the whole curve using non-linear regression analysis was effective using the Thomas model. The adsorption capacity estimated from the BDST model was reduced with increasing flow rate, which was 16.40mg cm(-3) or 137.91mg Cr(VI)g(-1) coir pith for the flow rates of 10ml min(-1) and 14.05mg cm(-3) or 118.20mg Cr(VI)g(-1) coir pith for the flow rates of 30ml min(-1). At the highest bed depth (60cm) and the lowest flow rate (10mlmin(-1)), the maximum adsorption reached 201.47mg Cr(VI)g(-1) adsorbent according to the Thomas model. The column was regenerated by eluting chromium using 2M HNO(3) after adsorption studies. The desorption of Cr(III) in each of three cycles was about 67-70%. The desorption of Cr(III) in each cycle did not reach 100% due to the fact that Cr(V) was present through the reduction of Cr(VI), and was still in coir pith, possibly bound to glucose in the cellulose part of coir pith. Therefore, the Cr(V) complex cannot be desorbed in solution. The evidence of Cr(V) signal was observed in coir pith, alpha-cellulose and holocellulose extracted from coir pith using electron spin resonance (ESR).

Coupling Solute and Fine Particle Transport with Sand Bed Morphodynamics within a Field Experiment

NASA Astrophysics Data System (ADS)

Phillips, C. B.; Ortiz, C. P.; Schumer, R.; Jerolmack, D. J.; Packman, A. I.

2017-12-01

Fine suspended particles are typically considered to pass through streams and rivers as wash load without interacting with the bed, however experiments have demonstrated that hyporheic flow causes advective exchange of fine particles with the stream bed, yielding accumulation of fine particle deposits within the bed. Ultimately, understanding river morphodynamics and ecosystem dynamics requires coupling both fine particle and solute transport with bed morphodynamics. To better understand the coupling between these processes we analyze a novel dataset from a controlled field experiment conducted on Clear Run, a 2nd order sand bed stream located within the North Carolina coastal plain. Data include concentrations of continuously injected conservative solutes and fine particulate tracers measured at various depths within the stream bed, overhead time lapse images of bed forms, stream discharge, and geomorphological surveys of the stream. We use image analysis of bed morphodynamics to assess exchange, retention, and remobilization of solutes and fine particles during constant discharge and a short duration experimental flood. From the images, we extract a time series of bedform elevations and scour depths for the duration of the experiment. The high-resolution timeseries of bed elevation enables us to assess coupling of bed morphodynamics with both the solute and fine particle flux during steady state mobile bedforms prior to the flood and to changing bedforms during the flood. These data allow the application of a stochastic modeling framework relating bed elevation fluctuations to fine particle residence times. This combined experimental and modeling approach ultimately informs our ability to predict not only the fate of fine particulate matter but also associated nutrient and carbon dynamics within streams and rivers.

Evaluating the use of side-scan sonar for detecting freshwater mussel beds in turbid river environments

USGS Publications Warehouse

Powers, Jarrod; Brewer, Shannon K.; Long, James M.; Campbell, Thomas

2015-01-01

Side-scan sonar is a valuable tool for mapping habitat features in many aquatic systems suggesting it may also be useful for locating sedentary biota. The objective of this study was to determine if side-scan sonar could be used to identify freshwater mussel (unionid) beds and the required environmental conditions. We used side-scan sonar to develop a series of mussel-bed reference images by placing mussel shells within homogenous areas of fine and coarse substrates. We then used side-scan sonar to map a 32-km river reach during spring and summer. Using our mussel-bed reference images, several river locations were identified where mussel beds appeared to exist in the scanned images and we chose a subset of sites (n = 17) for field validation. The validation confirmed that ~60% of the sites had mussel beds and ~80% had some mussels or shells present. Water depth was significantly related to our ability to predict mussel-bed locations: predictive ability was greatest at depths of 1–2 m, but decreased in water >2-m deep. We determined side-scan sonar is an effective tool for preliminary assessments of mussel presence during times when they are located at or above the substrate surface and in relatively fine substrates excluding fine silt.

Reduction of particulate carryover from a pressurized fluidized bed

NASA Technical Reports Server (NTRS)

Patch, R. W.

1979-01-01

A bench scale fluidized bed combustor was constructed with a conical shape so that the enlarged upper part of the combustor would also serve as a granular bed filter. The combustor was fed coal and limestone. Ninety-nine tests of about four hours each were conducted over a range of conditions. Coal-to-air ratio varied from 0.033 to 0.098 (all lean). Limestone-to-coal ratio varied from 0.06 to 0.36. Bed depth varied from 3.66 to 8.07 feet. Temperature varied from 1447 to 1905 F. Pressure varied from 40 to 82 psia. Heat transfer area had the range zero to 2.72 ft squared. Two cone angles were used. The average particulate carry over of 2.5 grains/SCF was appreciably less than cylindrical fluidized bed combustors. The carry over was correlated by multiple regression analysis to yield the dependence on bed depth and hence the collection efficiency, which was 20%. A comparison with a model indicated that the exhaust port may be below the transport disengaging height for most of the tests, indicating that further reduction in carry over and increase in collection efficiency could be affected by increasing the freeboard and height of the exhaust port above the bed.

Stream bed temperature profiles as indicators of percolation characteristics beneath arroyos in the middle Rio Grande Basin, USA

USGS Publications Warehouse

Constantz, J.; Thomas, C.L.

1997-01-01

Stream bed temperature profiles were monitored continuously during water year 1990 and 1991 (WY90 and 91) in two New Mexico arroyos, similar in their meteorological features and dissimilar in their hydrological features. Stream bed temperature profiles between depths of 30 and 300 cm were examined to determine whether temporal changes in temperature profiles represent accurate indicators of the timing, depth and duration of percolation in each stream bed. These results were compared with stream flow, air temperature, and precipitation records for WY90 and 91, to evaluate the effect of changing surface conditions on temperature profiles. Temperature profiles indicate a persistently high thermal gradient with depth beneath Grantline Arroyo, except during a semi-annual thermal reversal in spring and autumn. This typifies the thermal response of dry sediments with low thermal conductivities. High thermal gradients were disrupted only during infrequent stream flows, followed by rapid re-establishment of high gradients. The stream bed temperature at 300 cm was unresponsive to individual precipitation or stream flow during WY90 and 91. This thermal pattern provides strong evidence that most seepage into Grantline Arroyo failed to percolate at a sufficient rate to reach 300 cm before being returned to the atmosphere. A distinctly different thermal pattern was recorded beneath Tijeras Arroyo. Low thermal gradients between 30 and 300 cm and large diurnal variations in temperature, suggest that stream flow created continuous, advection-dominated heat transport for over 300 days, annually. Beneath Tijeras Arroyo, low thermal gradients were interrupted only briefly during periodic, dry summer conditions. Comparisons of stream flow records for WY90 and 91 with stream bed temperature profiles indicate that independent analysis of thermal patterns provides accurate estimates of the timing, depth and duration of percolation beneath both arroyos. Stream flow loss estimates indicate that seepage rates were 15 times greater for Tijeras Arroyo than for Grantline Arroyo, which supports qualitative conclusions derived from analysis of stream bed temperature responses to surface conditions. ?? 1997 John Wiley & Sons, Ltd.

SECURE MATHEMATICALLY- ASSURED COMPOSITION OF CONTROL MODELS

DTIC Science & Technology

2017-09-27

and in fact, often introduces new vulnerabilities that can be exploited. The situation is even worse for em - bedded software because it is often...fork- bomb is a program which continuously replicates itself, thus making it very hard to kill off all instances of the forkbomb. This causes the...binaries. In Eduardo Tovar, editor, IEEE Real-Time and Em - bedded Technology and Applications Symposium (RTAS), pages 97–106, Philadelphia, USA, April 2013

Scour at bridge sites in Delaware, Maryland, and Virginia

USGS Publications Warehouse

Hayes, Donald C.

1996-01-01

Scour data were obtained from discharge measure- ments to develop and evaluate the reliability of constriction-scour and local-scour equations for rivers in Delaware, Maryland, and Virginia. No independent constriction-scour or local-scour equations were developed from the data because no significant relation was deter-mined between measured scour and streamflow, streambed, and bridge characteristics. Two existing equations were evaluated for prediction of constriction scour and 14 existing equations were evaluated for prediction of local scour. Constriction-scour data were obtained from historical stream discharge measurements, field surveys, and bridge plans at nine bridge sites in the three-State area. Constriction scour was computed by subtracting the average-streambed elevation in the constricted reach from an uncontracted-channel reference elevation. Hydraulic conditions were estimated for the measurements with the greatest discharges by use of the Water-Surface Profile computation model. Measured and calculated constriction-scour data were used to evaluate the reliability of Laursen's clear-water constriction-scour equation and Laursen's live-bed constriction-scour equation. Laursen's clear-water constriction-scour equation underestimated 21 of 23 scour measure- ments made at three sites. A sensitivity analysis showed that the equation is extremely sensitive to estimates of the channel-bottom width. Reduction in estimates of bottom width by one-third resulted in predictions of constriction scour slightly greater than measured values for all scour measurements. Laursen's live-bed constriction- scour equation underestimated 10 of 14 scour measurements made at one site. The error between measured and predicted constriction scour was less than 1.0 ft (feet) for 12 measure-ments and less than 0.5 ft for 8 measurements. Local-scour data were obtained from stream discharge measurements, field surveys, and bridge plans at 15 bridge sites in the three-State area. The reliability of 14 local-scour equations were evaluated. From visual inspection of the plotted data, the Colorado State University, Froehlich design, Laursen, and Mississippi pier-scour equations appeared to be the best predictors of local scour. The Colorado State University equation underestimated 11 scour depths in clear-water scour conditions by a maximum of 2.4 ft, and underestimated 3 scour depth in live-bed scour conditions by a maximum of 1.3 ft. The Froehlich design equation under- estimated two scour depth in clear-water scour conditions by a maximum of 1.2 ft, and under- estimated one scour depth in live-bed scour conditions by a maximum of 0.4 ft. Laursen's equation overestimated the maximum scour depth in clear-water scour conditions by approximately one-half pier width or approximately 1.5 ft, and overestimated the maximum scour depth in live-bed scour conditions by approximately one-pier width or approximately 3 ft. The Mississippi equation underestimated six scour depths in clear-water scour conditions by a maximum of 1.2 ft, and underestimated one scour depth in live-bed scour conditions by 1.6 ft. In both clear-water and live-bed scour conditions, the upper limit for the depth of scour to pier-width ratio for all local scour measurements was 2.1. An accurate pier- approach velocity is necessary to use many local pier-scour equations for bridge design. Velocity data from all the discharge measurements reviewed for this investigation were used to develop a design curve to estimate pier-approach velocity from mean cross-sectional velocity. A least- squares regression and offset were used to envelop the velocity data.

Bed elevation of Jakobshavn Isbræ, West Greenland, from high-resolution airborne gravity and other data

NASA Astrophysics Data System (ADS)

An, L.; Rignot, E.; Elieff, S.; Morlighem, M.; Millan, R.; Mouginot, J.; Holland, D. M.; Holland, D.; Paden, J.

2017-04-01

Jakobshavn Isbræ, West Greenland, which holds a 0.6 m sea level volume equivalent, has been speeding up and retreating since the late 1990s. Interpretation of its retreat has been hindered by difficulties in measuring its ice thickness with airborne radar depth sounders. Here we employ high-resolution, helicopter-borne gravity data from 2012 to reconstruct its bed elevation within 50 km of the ocean margin using a three-dimensional inversion constrained by fjord bathymetry data offshore and a mass conservation algorithm inland. We find the glacier trough to be asymmetric and several 100 m deeper than estimated previously in the lower part. From 1996 to 2016, the grounding line migrated at 0.6 km/yr from 700 m to 1100 m depth. Upstream, the bed drops to 1600 m over 10 km then slowly climbs to 1200 m depth in 40 km. Jakobshavn Isbræ will continue to retreat along a retrograde slope for decades to come.

Evaluation of a numerical model's ability to predict bed load transport observed in braided river experiments

NASA Astrophysics Data System (ADS)

Javernick, Luke; Redolfi, Marco; Bertoldi, Walter

2018-05-01

New data collection techniques offer numerical modelers the ability to gather and utilize high quality data sets with high spatial and temporal resolution. Such data sets are currently needed for calibration, verification, and to fuel future model development, particularly morphological simulations. This study explores the use of high quality spatial and temporal data sets of observed bed load transport in braided river flume experiments to evaluate the ability of a two-dimensional model, Delft3D, to predict bed load transport. This study uses a fixed bed model configuration and examines the model's shear stress calculations, which are the foundation to predict the sediment fluxes necessary for morphological simulations. The evaluation is conducted for three flow rates, and model setup used highly accurate Structure-from-Motion (SfM) topography and discharge boundary conditions. The model was hydraulically calibrated using bed roughness, and performance was evaluated based on depth and inundation agreement. Model bed load performance was evaluated in terms of critical shear stress exceedance area compared to maps of observed bed mobility in a flume. Following the standard hydraulic calibration, bed load performance was tested for sensitivity to horizontal eddy viscosity parameterization and bed morphology updating. Simulations produced depth errors equal to the SfM inherent errors, inundation agreement of 77-85%, and critical shear stress exceedance in agreement with 49-68% of the observed active area. This study provides insight into the ability of physically based, two-dimensional simulations to accurately predict bed load as well as the effects of horizontal eddy viscosity and bed updating. Further, this study highlights how using high spatial and temporal data to capture the physical processes at work during flume experiments can help to improve morphological modeling.

Comparisons of Derived Metrics from Computed Tomography (CT) Scanned Images of Fluvial Sediment from Gravel-Bed Flume Experiments

NASA Astrophysics Data System (ADS)

Voepel, Hal; Ahmed, Sharif; Hodge, Rebecca; Leyland, Julian; Sear, David

2016-04-01

Uncertainty in bedload estimates for gravel bed rivers is largely driven by our inability to characterize arrangement, orientation and resultant forces of fluvial sediment in river beds. Water working of grains leads to structural differences between areas of the bed through particle sorting, packing, imbrication, mortaring and degree of bed armoring. In this study, non-destructive, micro-focus X-ray computed tomography (CT) imaging in 3D is used to visualize, quantify and assess the internal geometry of sections of a flume bed that have been extracted keeping their fabric intact. Flume experiments were conducted at 1:1 scaling of our prototype river. From the volume, center of mass, points of contact, and protrusion of individual grains derived from 3D scan data we estimate 3D static force properties at the grain-scale such as pivoting angles, buoyancy and gravity forces, and local grain exposure. Here metrics are derived for images from two flume experiments: one with a bed of coarse grains (>4mm) and the other where sand and clay were incorporated into the coarse flume bed. In addition to deriving force networks, comparison of metrics such as critical shear stress, pivot angles, grain distributions, principle axis orientation, and pore space over depth are made. This is the first time bed stability has been studied in 3D using CT scanned images of sediment from the bed surface to depths well into the subsurface. The derived metrics, inter-granular relationships and characterization of bed structures will lead to improved bedload estimates with reduced uncertainty, as well as improved understanding of relationships between sediment structure, grain size distribution and channel topography.

Late Consequential Surgical Bed Soft Tissue Necrosis in Advanced Oropharyngeal Squamous Cell Carcinomas Treated With Transoral Robotic Surgery and Postoperative Radiation Therapy

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

Lukens, J. Nicholas; Lin, Alexander, E-mail: alexander.lin@uphs.upenn.edu; Gamerman, Victoria

Purpose: A subset of patients with oropharyngeal squamous cell carcinoma (OP-SCC) managed with transoral robotic surgery (TORS) and postoperative radiation therapy (PORT) developed soft tissue necrosis (STN) in the surgical bed months after completion of PORT. We investigated the frequency and risk factors. Materials and Methods: This retrospective analysis included 170 consecutive OP-SCC patients treated with TORS and PORT between 2006 and 2012, with >6 months' of follow-up. STN was defined as ulceration of the surgical bed >6 weeks after completion of PORT, requiring opioids, biopsy, or hyperbaric oxygen therapy. Results: A total of 47 of 170 patients (28%) hadmore » a diagnosis of STN. Tonsillar patients were more susceptible than base-of-tongue (BOT) patients, 39% (41 of 104) versus 9% (6 of 66), respectively. For patients with STN, median tumor size was 3.0 cm (range 1.0-5.6 cm), and depth of resection was 2.2 cm (range 1.0-5.1 cm). Median radiation dose and dose of fraction to the surgical bed were 6600 cGy and 220 cGy, respectively. Thirty-one patients (66%) received concurrent chemotherapy. Median time to STN was 2.5 months after PORT. All patients had resolution of STN after a median of 3.7 months. Multivariate analysis identified tonsillar primary (odds ratio [OR] 4.73, P=.01), depth of resection (OR 3.12, P=.001), total radiation dose to the resection bed (OR 1.51 per Gy, P<.01), and grade 3 acute mucositis (OR 3.47, P=.02) as risk factors for STN. Beginning May 2011, after implementing aggressive avoidance of delivering >2 Gy/day to the resection bed mucosa, only 8% (2 of 26 patients) experienced STN (all grade 2). Conclusions: A subset of OP-SCC patients treated with TORS and PORT are at risk for developing late consequential surgical bed STN. Risk factors include tonsillar location, depth of resection, radiation dose to the surgical bed, and severe mucositis. STN risk is significantly decreased with carefully avoiding a radiation dosage of >2 Gy/day to the surgical bed.« less

Bed bug aggregation on dirty laundry: a mechanism for passive dispersal.

PubMed

Hentley, William T; Webster, Ben; Evison, Sophie E F; Siva-Jothy, Michael T

2017-09-28

Bed bugs have shown a recent and rapid global expansion that has been suggested to be caused by cheap air travel. How a small, flightless and anachoretic insect that hides within its host's sleeping area manages to travel long distances is not yet clear. Bed bugs are attracted to the odour of sleeping humans and we suggest that soiled clothing may present a similarly attractive cue, allowing bed bugs to 'hitch-hike' around the world after aggregating in the laundry bags of travellers. We show that (1) soiled clothing is significantly more attractive than clean clothing to active bed bugs moving within a bedroom sized arena and (2) elevation of CO 2 to a level that simulates human occupancy in the same arena appears to initiate search behaviour rather than direct it. Our results show, for the first time, how leaving worn clothing exposed in sleeping areas when travelling can be exploited by bed bugs to facilitate passive dispersal.

The Influence of Relative Submergence on the Near-bed Flow Field: Implications for Bed-load Transport

NASA Astrophysics Data System (ADS)

Cooper, J.; Tait, S.; Marion, A.

2005-12-01

Bed-load is governed by interdependent mechanisms, the most significant being the interaction between bed roughness, surface layer composition and near-bed flow. Despite this, practically all transport rate equations are described as a function of average bed shear stress. Some workers have examined the role of turbulence in sediment transport (Nelson et al. 1995) but have not explored the potential significance of spatial variations in the near-bed flow field. This is unfortunate considering evidence showing that transport is spatially heterogeneous and could be linked to the spatial nature of the near-bed flow (Drake et al., 1988). An understanding is needed of both the temporal and spatial variability in the near-bed flow field. This paper presents detailed spatial velocity measurements of the near-bed flow field over a gravel-bed, obtained using Particle Image Velocimetry. These data have been collected in a laboratory flume under two regimes: (i) tests with one bed slope and different flow depths; and (ii) tests with a combination of flow depths and slopes at the same average bed shear stress. Results indicate spatial variation in the streamwise velocities of up to 45 per cent from the double-averaged velocity (averaged in both time and space). Under both regimes, as the depth increased, spatial variability in the flow field increased. The probability distributions of near-bed streamwise velocities became progressively more skewed towards the higher velocities. This change was more noticeable under regime (i). This has been combined with data from earlier tests in which the near-bed velocity close to an entraining grain was measured using a PIV/image analysis system (Chegini et al, 2002). This along with data on the shape of the probability density function of velocities capable of entraining individual grains derived from a discrete-particle model (Heald et al., 2004) has been used to estimate the distribution of local velocities required for grain motion in the above tests. The overlap between this distribution and the measured velocities are used to estimate entrainment rates. Predicted entrainment rates increase with relative submergence, even for similar bed shear stress. Assuming bed-load rate is the product of entrainment rate and hop length, and that hop lengths are sensibly stable, suggests that transport rate has a dependence on relative submergence. This demonstrates that transport rate is not a direct function of average bed shear stress. The results describe a mechanism that will cause river channels with contrasting morphologies (and different relative submergence) but similar levels of average bed stress to experience different levels of sediment mobility. Chegini A. Tait S. Heald J. McEwan I. 2002 The development of an automated system for the measurement of near bed turbulence and grain motion. Proc. ASCE Conf. on Hydraulic Measurements and Experimental Methods, ISBN 0-7844-0655-3. Drake T.G. Shreve R.L. Dietrich W.E. Whiting P.J. Leopold L.B. 1988 Bedload transport of fine gravel observed by motion-picture photography, J. Fluid Mech., 192, 193-217. Heald J. McEwan I. Tait, S. 2004 Sediment transport over a flat bed in a unidirectional flow: simulations and validation, Phil. Trans. Roy. Soc. of London A, 362, 1973-1986. Nelson J.M. Shreve R.L. McLean S.R. Drake T.G. 1995 Role of near-bed turbulence structure in bed-load transport and bed form mechanics, Water. Res. Res., 31, 8, 2071-2086.

Indirect heating pyrolysis of oil shale

DOEpatents

Jones, Jr., John B.; Reeves, Adam A.

1978-09-26

Hot, non-oxygenous gas at carefully controlled quantities and at predetermined depths in a bed of lump oil shale provides pyrolysis of the contained kerogen of the oil shale, and cool non-oxygenous gas is passed up through the bed to conserve the heat

FY-2015 Methyl Iodide Deep-Bed Adsorption Test Report

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

Soelberg, Nicholas Ray; Watson, Tony Leroy

2015-09-30

Nuclear fission produces fission and activation products, including iodine-129, which could evolve into used fuel reprocessing facility off-gas systems, and could require off-gas control to limit air emissions to levels within acceptable emission limits. Deep-bed methyl iodide adsorption testing has continued in Fiscal Year 2015 according to a multi-laboratory methyl iodide adsorption test plan. Updates to the deep-bed test system have also been performed to enable the inclusion of evaporated HNO 3 and increased NO 2 concentrations in future tests. This report summarizes the result of those activities. Test results showed that iodine adsorption from gaseous methyl iodide using reducedmore » silver zeolite (AgZ) resulted in initial iodine decontamination factors (DFs, ratios of uncontrolled and controlled total iodine levels) under 1,000 for the conditions of the long-duration test performed this year (45 ppm CH3I, 1,000 ppm each NO and NO 2, very low H 2O levels [3 ppm] in balance air). The mass transfer zone depth exceeded the cumulative 5-inch depth of 4 bed segments, which is deeper than the 2-4 inch depth estimated for the mass transfer zone for adsorbing I 2 using AgZ in prior deep-bed tests. The maximum iodine adsorption capacity for the AgZ under the conditions of this test was 6.2% (6.2 g adsorbed I per 100 g sorbent). The maximum Ag utilization was 51%. Additional deep-bed testing and analyses are recommended to (a) expand the data base for methyl iodide adsorption and (b) provide more data for evaluating organic iodide reactions and reaction byproducts for different potential adsorption conditions.« less

Micro-tidal coastal reed beds: Hydro-morphological insights and observations on wave transformation from the southern Baltic Sea

NASA Astrophysics Data System (ADS)

I.; | J., Möller; | T., Mantilla-Contreras; | A., Spencer; Hayes

2011-05-01

This paper investigates the hydro-morphological controls on incident wind-generated waves at, and the transformation of such waves within, two Phragmites australis reed beds in the southern Baltic Sea. Meteorological conditions in combination with geomorphological controls result, over short (<2 km) distances, in significant differences in water level and wave climate to which fringing reed beds are exposed. Significant wave height attenuation reached a maximum of 2.6% m -1 and 11.8% m -1 at the transition from open water into the reed vegetation at the sheltered and exposed sites respectively. Wave attenuation through the emergent reed vegetation was significantly lower in greater water depths, suggesting (1) a reduced influence of bed friction by small shoots/roots and/or (2) drag reduction due to flexing of plants when the wave motion is impacting stems at a greater height above the bed. For a given water depth, wave dissipation increased with increasing incident wave height, however, suggesting that, despite their ability to flex, reed stems may be rigid enough to cause increased drag under greater wave forcing. The higher frequency part of the wave spectrum (>0.5 Hz) was preferentially reduced at the reed margin, confirming the theoretical wave frequency dependence of bottom friction. The possibility of physiological adaptation (differences in reed stem diameter) to water depth and wave exposure differences is discussed. The results have implications for the possible impact of environmental changes, both acute (e.g. storm surges) or chronic (e.g. sea level rise) in character, and for the appropriate management of reed bed sites and delivery of ecological goods and services.

Kansas coal distribution, resources, and potential for coalbed methane

USGS Publications Warehouse

Brady, L.L.

2000-01-01

100 ft (>30 m)] determined from 32 different coal beds. Strippable coal resources at a depth Kansas has large amounts of bituminous coal both at the surface and in the subsurface of eastern Kansas. Preliminary studies indicate at least 53 billion tons (48 billion MT) of deep coal [>100 ft (>30 m)] determined from 32 different coal beds. Strippable coal resources at a depth < 100 ft (<30 m) total 2.8 billion tons (2.6 billion MT), and this total is determined from 17 coals. Coal beds present in the Cherokee Group (Middle Pennsylvanian) represent most of these coal resource totals. Deep coal beds with the largest resource totals include the Bevier, Mineral, "Aw" (unnamed coal bed), Riverton, and Weir-Pittsburg coals, all within the Cherokee Group. Based on chemical analyses, coals in the southeastern part of the state are generally high volatile A bituminous, whereas coals in the east-central and northeastern part of the state are high-volatile B bituminous coals. The primary concern of coal beds in Kansas for deep mining or development of coalbed methane is the thin nature [<2 ft (0.6 m)] of most coal beds. Present production of coalbed methane is centered mainly in the southern Wilson/northern Montgomery County area of southeastern Kansas where methane is produced from the Mulky, Weir-Pittsburg, and Riverton coals.

Growth of Azotobacter vinelandii in a solid-state fermentation of technical lignin.

PubMed

Zhang, Xiaoyong; Zhao, Hua; Zhang, Jianan; Li, Zuohu

2004-10-01

Azotobacter vinelandii was cultured on technical lignin, derived from Kraft pulping processes, for biofertilizer production in solid-state fermentation. The effects of the ratio of technical lignin to corn straw, initial water content, and material bed depth on the microorganisms were studied in detail. At 30 degrees C, technical lignin to corn straw at the ratio of 1:0.75, the bed depth of 5 cm, and 67% moisture content, A. vinelandii was grown and reached 4.2 x 10(10) cfu g(-1) dry rot after 36 h.

Estimating Discharge, Depth and Bottom Friction in Sand Bed Rivers Using Surface Currents and Water Surface Elevation Observations

NASA Astrophysics Data System (ADS)

Simeonov, J.; Czapiga, M. J.; Holland, K. T.

2017-12-01

We developed an inversion model for river bathymetry estimation using measurements of surface currents, water surface elevation slope and shoreline position. The inversion scheme is based on explicit velocity-depth and velocity-slope relationships derived from the along-channel momentum balance and mass conservation. The velocity-depth relationship requires the discharge value to quantitatively relate the depth to the measured velocity field. The ratio of the discharge and the bottom friction enter as a coefficient in the velocity-slope relationship and is determined by minimizing the difference between the predicted and the measured streamwise variation of the total head. Completing the inversion requires an estimate of the bulk friction, which in the case of sand bed rivers is a strong function of the size of dune bedforms. We explored the accuracy of existing and new empirical closures that relate the bulk roughness to parameters such as the median grain size diameter, ratio of shear velocity to sediment fall velocity or the Froude number. For given roughness parameterization, the inversion solution is determined iteratively since the hydraulic roughness depends on the unknown depth. We first test the new hydraulic roughness parameterization using estimates of the Manning roughness in sand bed rivers based on field measurements. The coupled inversion and roughness model is then tested using in situ and remote sensing measurements of the Kootenai River east of Bonners Ferry, ID.

Non-energy resources, Connecticut and Rhode Island coastal waters

USGS Publications Warehouse

Neff, N.F.; Lewis, R.S.

1989-01-01

Cores collected from Long Island Sound, Connecticut, were used to establish control on the geologic framework of the area. Lithologic and stratigraphic analyses verified the presence of the following units: (1) Cretaceous coastal plain, (2) Pleistocene glacial till, (3) late Pleistocene glacial lake, (4) late Pleistocene glacial outwash, and (5) Holocene fluvial, estuarine and marine deposits. Cores collected in Block Island Sound, Rhode Island, were obtained from inferred, relict shoreline features and were analyzed for heavy mineral content. Concentrations ranged from 0.3 to 3.4%; no significant downcore changes were found. The results indicated that surficial sediments in areas of high-velocity tidal flow yield greater amounts of heavy minerals than do inferred placer deposits. During the second phase of the program of study, Connecticut and Rhode Island pooled resources to develop a study plan for the comprehensive quantification of all non-energy resources in the adjacent waters of the states. A literature and data survey was conducted to assess the occurrence, extent, and accessibility of these resources. Sand and gravel and heavy minerals were found in concentrations offering potential for resource exploitation. Constraints on exploitation include (1) water depth restrictions for the protection of shellfish beds and public beaches, (2) fishing activities, (3) military, commercial, and fishing vessel traffic, (4) seafloor cable routes and (5) dump sites. Deposits composed of Pleistocene glacial sediments and/or Holocene marine sediments in regions of little or no user conflict were identified as sites potentially suitable for resource exploitation. The study plan stated additional data needs (geophysical profiling and vibracore sampling) at these sites. Subsequent to these recommendations, high-resolution seismic profiles and sidescan sonographs were obtained from these sites. Seismic stratigraphic analyses confirm the presence of extensive deposits of potential economic value. ?? 1989.

Entrainment of bed sediment by debris flows: results from large-scale experiments

USGS Publications Warehouse

Reid, Mark E.; Iverson, Richard M.; Logan, Matthew; LaHusen, Richard G.; Godt, Jonathan W.; Griswold, Julie P.

2011-01-01

When debris flows grow by entraining sediment, they can become especially hazardous owing to increased volume, speed, and runout. To investigate the entrainment process, we conducted eight largescale experiments in the USGS debris-flow flume. In each experiment, we released a 6 m3 water-saturated debris flow across a 47-m long, ~12-cm thick bed of partially saturated sediment lining the 31º flume. Prior to release, we used low-intensity overhead sprinkling and real-time monitoring to control the bed-sediment wetness. As each debris flow descended the flume, we measured the evolution of flow thickness, basal total normal stress, basal pore-fluid pressure, and sediment scour depth. When debris flows traveled over relatively dry sediment, net scour was minimal, but when debris flows traveled over wetter sediment (volumetric water content > 0.22), debris-flow volume grew rapidly and flow speed and runout were enhanced. Data from scour sensors showed that entrainment occurred by rapid (5-10 cm/s), progressive scour rather than by mass failure at depth. Overriding debris flows rapidly generated high basal pore-fluid pressures when they loaded and deformed bed sediment, and in wetter beds these pressures approached lithostatic levels. Reduction of intergranular friction within the bed sediment thereby enhanced scour efficiency, entrainment, and runout.

Potential nitrification and denitrification and the corresponding composition of the bacterial communities in a compact constructed wetland treating landfill leachates.

PubMed

Sundberg, C; Tonderski, K; Lindgren, P E

2007-01-01

Constructed wetlands can be used to decrease the high ammonium concentrations in landfill leachates. We investigated nitrification/denitrification activity and the corresponding bacterial communities in landfill leachate that was treated in a compact constructed wetland, Tveta Recycling Facility, Sweden. Samples were collected at three depths in a filter bed and the sediment from a connected open pond in July, September and November 2004. Potential ammonia oxidation was measured by short-term incubation method and potential denitrification by the acetylene inhibition technique. The ammonia-oxidising and the denitrifying bacterial communities were investigated using group-specific PCR primers targeting 16S rRNA genes and the functional gene nosZ, respectively. PCR products were analysed by denaturing gradient gel electrophoresis and nucleotide sequencing. The same degree of nitrification activity was observed in the pond sediment and at all levels in the filter bed, whereas the denitrification activity decreased with filter bed depth. Denitrification rates were higher in the open pond, even though the denitrifying bacterial community was more diverse in the filter bed. The ammonia-oxidising community was also more varied in the filter bed. In the filter bed and the open pond, there was no obvious relationship between the nitrification/denitrification activities and the composition of the corresponding bacterial communities.

Unraveling hominin behavior at another anthropogenic site from Olduvai Gorge (Tanzania): new archaeological and taphonomic research at BK, Upper Bed II.

PubMed

Domínguez-Rodrigo, M; Mabulla, A; Bunn, H T; Barba, R; Diez-Martín, F; Egeland, C P; Espílez, E; Egeland, A; Yravedra, J; Sánchez, P

2009-09-01

New archaeological excavations and research at BK, Upper Bed II (Olduvai Gorge, Tanzania) have yielded a rich and unbiased collection of fossil bones. These new excavations show that BK is a stratified deposit formed in a riverine setting close to an alluvial plain. The present taphonomic study reveals the second-largest collection of hominin-modified bones from Olduvai, with abundant cut marks found on most of the anatomical areas preserved. Meat and marrow exploitation is reconstructed using the taphonomic signatures left on the bones by hominins. Highly cut-marked long limb shafts, especially those of upper limb bones, suggest that hominins at BK were actively engaged in acquiring small and middle-sized animals using strategies other than passive scavenging. The exploitation of large-sized game (Pelorovis) by Lower Pleistocene hominins, as suggested by previous researchers, is supported by the present study.

Dynamic controls on shallow clinoform geometry: Mekong Delta, Vietnam

NASA Astrophysics Data System (ADS)

Eidam, E. F.; Nittrouer, C. A.; Ogston, A. S.; DeMaster, D. J.; Liu, J. P.; Nguyen, T. T.; Nguyen, T. N.

2017-09-01

Compound deltas, composed of a subaerial delta plain and subaqueous clinoform, are common termini of large rivers. The transition between clinoform topset and foreset, or subaqueous rollover point, is located at 25-40-m water depth for many large tide-dominated deltas; this depth is controlled by removal of sediment from the topset by waves, currents, and gravity flows. However, the Mekong Delta, which has been classified as a mixed-energy system, has a relatively shallow subaqueous rollover at 4-6-m depth. This study evaluates dynamical measurements and seabed cores collected in Sep 2014 and Mar 2015 to understand processes of sediment transfer across the subaqueous delta, and evaluate possible linkages to geometry. During the southwest rainy monsoon (Sep 2014), high river discharge, landward return flow under the river plume, and regional circulation patterns facilitated limited sediment flux to the topset and foreset, and promoted alongshore flux to the northeast. Net observed sediment fluxes in Sep 2014 were landward, however, consistent with hypotheses about seasonal storage on the topset. During the northeast rainy monsoon, low river discharge and wind-driven currents facilitated intense landward and southwestward fluxes of sediment. In both seasons, bed shear velocities frequently exceeded the 0.01-0.02 m/s threshold of motion for sand, even in the absence of strong wave energy. Most sediment transport occurred at water depths <14 m, as expected from observed cross-shelf gradients of sedimentation. Sediment accumulation rates were highest on the upper and lower foreset beds (>4 cm/yr at <10 m depth, and 3-8 cm/yr at 10-20 m depth) and lowest on the bottomset beds. Physically laminated sediments transitioned into mottled sediments between the upper foreset and bottomset regions. Application of a simple wave-stress model to the Mekong and several other clinoforms illustrates that shallow systems are not necessarily energy-limited, and thus rollover depths cannot be predicted solely by bed-stress distributions. In systems like the subaqueous Mekong Delta, direction of transport may have a key impact on morphology.

Fine dust filtration using a metal fiber bed.

PubMed

Lee, Kyung Mi; Lee, Young Sup; Jo, Young Min

2006-08-01

A bed-type filter composed of thin metal alloy fiber was closely examined with dust capturing in cold and hot runs. The investigation of an individual mechanism across the filter bed indicated that the aerated dust could be initially collected by depth filtration, and after a while, surface filtration dominated the overall dust collection. The present metal fiber bed was comparable to the conventional ceramic filters because of its good collection efficiency with low pressure drop. It also showed potential to be used as a prefilter in a diesel exhaust trapping system.

Sorting Out Effects of Active Stream Restoration: Channel Morphology, Channel Change Processes and Potential Controls

NASA Astrophysics Data System (ADS)

McDowell, P. F.

2017-12-01

In many active restoration projects, instream structures or modifications are designed to produce specific change in channel form, such as reduced W:D or increased pool depth, yet there is little monitoring to evaluate effectiveness. Active restoration often takes place within a context of other land management changes that can have an effect on channel form. Thus, the effects of active restoration are difficult to separate from the effects of other management actions. We measured morphologic response to restoration designs on sections of the Middle Fork John Day River, a gravel-cobble bed river under a cattle grazing regime in the Blue Mountain of Oregon. Since 2000, restoration actions have included elimination of cattle grazing in the riparian zone (passive restoration), riparian planting of woody vegetation, instream log structures for fish habitat and pool maintenance, and elimination of a major flow diversion. We listed the hypothetical effects of each of these management changes, showing overlap among effects of active and passive restoration. Repeat cross-section and longitudinal profile surveys over eight years, and repeat aerial imagery, documented changes in channel width, depth and bed morphology, and processes of change (bank erosion or aggradation, point bar erosion or aggradation, bed incision or aggradation), in two restored reaches and two adjacent control (unrestored) reaches. Morphologic changes were modest. Bankfull cross-section area, width, and W:D all decreased slightly in both restored reaches. Control reaches were unchanged or increased slightly. Processes of change were markedly different among the four reaches, with different reaches dominated by different processes. One restored reach was dominated by slight bed aggradation, increased pool depth and deep pools/km, while the other restored reach was dominated by bank erosion, bar aggradation and slight bed incision, along with increased deep pools/km. The longitudinal profile showed significant re-arrangement of bed morphology. The spatial context of processes and controls allows some separation of the effectiveness of different management actions. Active restoration directly increased pool depth, but passive restoration apparently had more impact on aggradation/degradation and width.

Observations of Morphodynamics During a Winter Storm at the Mouth of the Misa River

NASA Astrophysics Data System (ADS)

Calantoni, J.; Sheremet, A.; Brocchini, M.; Postacchini, M.

2016-02-01

The shallow mouth of the Misa River, Senigallia, Italy is exposed to wind and waves from the Adriatic Sea and is vulnerable to morphodynamic activity during even moderate storm events. Sediment loads and transport patterns may be strongly influenced by the confluence of fine cohesive suspended sediment contained in the discharge from the river mixing with coarser sandy material stirred up by waves impinging on the river mouth. Observations of rapid changes in bed elevation along a transect extending offshore of the river mouth were made using a combination of instruments deployed from 23-27 January 2014 at two locations in roughly 5 m water depth and 6 m water depth. Additionally, an up looking ADCP was located farther offshore in approximately 7 m water depth. The deposited sediment quickly consolidated into a hardened mixture of sand, mud, and venerids over the base of our instrument frames. At the 5 m water depth location over 0.4 m of deposition was observed roughly during a 6-hour period. Similarly, at the 6 m water depth location nearly 0.2 m of deposition was observed roughly over a 6-hour period with approximately a two-hour time lag. The onset of deposition was concurrent with a change in direction of the mean currents at both locations and a change in direction of wave skewness observed at the 5 m water depth location. We hypothesize that sandbar migration was responsible for the observed changes in bed elevation at both locations. Our analysis will focus on sediment transport modeling to explain rates of deposition and time lag of the observed changes in bed elevation at the 5 m and 6 m water depth locations.

Vertical variation of mixing within porous sediment beds below turbulent flows

PubMed Central

Chandler, I. D.; Pearson, J. M.; van Egmond, R.

2016-01-01

Abstract River ecosystems are influenced by contaminants in the water column, in the pore water and adsorbed to sediment particles. When exchange across the sediment‐water interface (hyporheic exchange) is included in modeling, the mixing coefficient is often assumed to be constant with depth below the interface. Novel fiber‐optic fluorometers have been developed and combined with a modified EROSIMESS system to quantify the vertical variation in mixing coefficient with depth below the sediment‐water interface. The study considered a range of particle diameters and bed shear velocities, with the permeability Péclet number, PeK between 1000 and 77,000 and the shear Reynolds number, Re*, between 5 and 600. Different parameterization of both an interface exchange coefficient and a spatially variable in‐sediment mixing coefficient are explored. The variation of in‐sediment mixing is described by an exponential function applicable over the full range of parameter combinations tested. The empirical relationship enables estimates of the depth to which concentrations of pollutants will penetrate into the bed sediment, allowing the region where exchange will occur faster than molecular diffusion to be determined. PMID:27635104

Starting procedure for internal combustion vessels

DOEpatents

Harris, Harry A.

1978-09-26

A vertical vessel, having a low bed of broken material, having included combustible material, is initially ignited by a plurality of ignitors spaced over the surface of the bed, by adding fresh, broken material onto the bed to buildup the bed to its operating depth and then passing a combustible mixture of gas upwardly through the material, at a rate to prevent back-firing of the gas, while air and recycled gas is passed through the bed to thereby heat the material and commence the desired laterally uniform combustion in the bed. The procedure permits precise control of the air and gaseous fuel mixtures and material rates, and permits the use of the process equipment designed for continuous operation of the vessel.

Evaluation of Sensor Technology to Detect Fall Risk and Prevent Falls in Acute Care.

PubMed

Potter, Patricia; Allen, Kelly; Costantinou, Eileen; Klinkenberg, William Dean; Malen, Jill; Norris, Traci; O'Connor, Elizabeth; Roney, Wilhemina; Tymkew, Heidi Hahn; Wolf, Laurie

2017-08-01

Sensor technology that dynamically identifies hospitalized patients' fall risk and detects and alerts nurses of high-risk patients' early exits out of bed has potential for reducing fall rates and preventing patient harm. During Phase 1 (August 2014-January 2015) of a previously reported performance improvement project, an innovative depth sensor was evaluated on two inpatient medical units to study fall characteristics. In Phase 2 (April 2015-January 2016), a combined depth and bed sensor system designed to assign patient fall probability, detect patient bed exits, and subsequently prevent falls was evaluated. Fall detection depth sensors remained in place on two medicine units; bed sensors used to detect patient bed exits were added on only one of the medicine units. Fall rates and fall with injury rates were evaluated on both units. During Phase 2, the designated evaluation unit had 14 falls, for a fall rate of 2.22 per 1,000 patient-days-a 54.1% reduction compared with the Phase 1 fall rate. The difference in rates from Phase 1 to Phase 2 was statistically significant (z = 2.20; p = 0.0297). The comparison medicine unit had 30 falls-a fall rate of 4.69 per 1,000 patient-days, representing a 57.9% increase as compared with Phase 1. A fall detection sensor system affords a level of surveillance that standard fall alert systems do not have. Fall prevention remains a complex issue, but sensor technology is a viable fall prevention option. Copyright © 2017 The Joint Commission. Published by Elsevier Inc. All rights reserved.

Elementary theory of bed-sediment entrainment by debris flows and avalanches

USGS Publications Warehouse

Iverson, Richard M.

2012-01-01

Analyses of mass and momentum exchange between a debris flow or avalanche and an underlying sediment layer aid interpretations and predictions of bed-sediment entrainment rates. A preliminary analysis assesses the behavior of a Coulomb slide block that entrains bed material as it descends a uniform slope. The analysis demonstrates that the block's momentum can grow unstably, even in the presence of limited entrainment efficiency. A more-detailed, depth-integrated continuum analysis of interacting, deformable bodies identifies mechanical controls on entrainment efficiency, and shows that entrainment rates satisfy a jump condition that involves shear-traction and velocity discontinuities at the flow-bed boundary. Explicit predictions of the entrainment rateEresult from making reasonable assumptions about flow velocity profiles and boundary shear tractions. For Coulomb-friction tractions, predicted entrainment rates are sensitive to pore fluid pressures that develop in bed sediment as it is overridden. In the simplest scenario the bed sediment liquefies completely, and the entrainment-rate equation reduces toE = 2μ1gh1 cos θ(1 − λ1)/ , where θ is the slope angle, μ1 is the flow's Coulomb friction coefficient, h1 is its thickness, λ1 is its degree of liquefaction, and is its depth-averaged velocity. For values ofλ1ranging from 0.5 to 0.8, this equation predicts entrainment rates consistent with rates of 0.05 to 0.1 m/s measured in large-scale debris-flow experiments in which wet sediment beds liquefied almost completely. The propensity for bed liquefaction depends on several factors, including sediment porosity, permeability, and thickness, and rates of compression and shear deformation that occur when beds are overridden.

Large-wave simulation of spilling breaking and undertow current over constant slope beach

NASA Astrophysics Data System (ADS)

Dimas, Athanassios; Kolokythas, Gerasimos; Dimakopoulos, Aggelos

2011-11-01

The three-dimensional, free-surface flow, developing by the propagation of nonlinear breaking waves over a constant slope bed, is numerically simulated. The main objective is to investigate the effect of spilling breaking on the characteristics of the induced undertow current by performing large-wave simulations (LWS) based on the numerical solution of the Navier-Stokes equations subject to the fully nonlinear free-surface boundary conditions and the appropriate bottom, inflow and outflow boundary conditions. The equations are properly transformed so that the computational domain becomes time-independent. In the present study, the case of incoming waves with wavelength to inflow depth ratio λ/ d ~ 6.6 and wave steepness H/ λ ~0.025, over bed of slope tan β = 1/35, is investigated. The LWS predicts satisfactorily breaking parameters - height and depth - and wave dissipation in the surf zone, in comparison to experimental data. In the corresponding LES, breaking height and depth are smaller and wave dissipation in the surf zone is weaker. For the undertow current, it is found that it is induced by the breaking process at the free surface, while its strength is controlled by the bed shear stress. Finally, the amplitude of the bed shear stress increases substantially in the breaking zone, becoming up to six times larger than the respective amplitude at the outer region.

Species coexistence and the superior ability of an invasive species to exploit a facilitation cascade habitat.

PubMed

Altieri, Andrew H; Irving, Andrew D

2017-01-01

Facilitation cascades generated by co-occurring foundation species can enhance the abundance and diversity of associated organisms. However, it remains poorly understood how differences among native and invasive species in their ability to exploit these positive interactions contribute to emergent patterns of community structure and biotic acceptance. On intertidal shorelines in New England, we examined the patterns of coexistence between the native mud crabs and the invasive Asian shore crab in and out of a facilitation cascade habitat generated by mid intertidal cordgrass and ribbed mussels. These crab species co-occurred in low intertidal cobbles adjacent to the cordgrass-mussel beds, despite experimental findings that the dominant mud crabs can kill and displace Asian shore crabs and thereby limit their successful recruitment to their shared habitat. A difference between the native and invasive species in their utilization of the facilitation cascade likely contributes to this pattern. Only the Asian shore crabs inhabit the cordgrass-mussel beds, despite experimental evidence that both species can similarly benefit from stress amelioration in the beds. Moreover, only Asian shore crabs settle in the beds, which function as a nursery habitat free of lethal mud crabs, and where their recruitment rates are particularly high (nearly an order of magnitude higher than outside beds). Persistence of invasive adult Asian shore crabs among the dominant native mud crabs in the low cobble zone is likely enhanced by a spillover effect of the facilitation cascade in which recruitment-limited Asian shore crabs settle in the mid intertidal cordgrass-mussel beds and subsidize their vulnerable populations in the adjacent low cobble zone. This would explain why the abundances of Asian shore crabs in cobbles are doubled when adjacent to facilitation cascade habitats. The propensity for this exotic species to utilize habitats created by facilitation cascades, despite the lack of a shared evolutionary history, contributes to species coexistence and the acceptance of invasives into a diverse community.

Species coexistence and the superior ability of an invasive species to exploit a facilitation cascade habitat

PubMed Central

Irving, Andrew D.

2017-01-01

Facilitation cascades generated by co-occurring foundation species can enhance the abundance and diversity of associated organisms. However, it remains poorly understood how differences among native and invasive species in their ability to exploit these positive interactions contribute to emergent patterns of community structure and biotic acceptance. On intertidal shorelines in New England, we examined the patterns of coexistence between the native mud crabs and the invasive Asian shore crab in and out of a facilitation cascade habitat generated by mid intertidal cordgrass and ribbed mussels. These crab species co-occurred in low intertidal cobbles adjacent to the cordgrass–mussel beds, despite experimental findings that the dominant mud crabs can kill and displace Asian shore crabs and thereby limit their successful recruitment to their shared habitat. A difference between the native and invasive species in their utilization of the facilitation cascade likely contributes to this pattern. Only the Asian shore crabs inhabit the cordgrass–mussel beds, despite experimental evidence that both species can similarly benefit from stress amelioration in the beds. Moreover, only Asian shore crabs settle in the beds, which function as a nursery habitat free of lethal mud crabs, and where their recruitment rates are particularly high (nearly an order of magnitude higher than outside beds). Persistence of invasive adult Asian shore crabs among the dominant native mud crabs in the low cobble zone is likely enhanced by a spillover effect of the facilitation cascade in which recruitment-limited Asian shore crabs settle in the mid intertidal cordgrass–mussel beds and subsidize their vulnerable populations in the adjacent low cobble zone. This would explain why the abundances of Asian shore crabs in cobbles are doubled when adjacent to facilitation cascade habitats. The propensity for this exotic species to utilize habitats created by facilitation cascades, despite the lack of a shared evolutionary history, contributes to species coexistence and the acceptance of invasives into a diverse community. PMID:28243523

Depth resolved granular transport driven by shearing fluid flow

NASA Astrophysics Data System (ADS)

Allen, Benjamin; Kudrolli, Arshad

2017-02-01

We investigate granular transport by a fluid flow under steady-state driving conditions, from the bed-load regime to the suspension regime, with an experimental system based on a conical rheometer. The mean granular volume fraction ϕg, the mean granular velocity ug, and the fluid velocity uf are obtained as a function of depth inside the bed using refractive index matching and particle-tracking techniques. A torque sensor is utilized to measure the applied shear stress to complement estimates obtained from measured strain rates high above the bed where ϕg≈0 . The flow is found to be transitional at the onset of transport and the shear stress required to transport grains rises sharply as grains are increasingly entrained by the fluid flow. A significant slip velocity between the fluid and the granular phases is observed at the bed surface before the onset of transport as well as in the bed-load transport regime. We show that ug decays exponentially deep into the bed for ϕg>0.45 with a decay constant which is described by a nonlocal rheology model of granular flow that neglects fluid stress. Further, we show that uf and ug can be described using the applied shear stress and the Krieger-Dougherty model for the effective viscosity in the suspension regime, where 0 <ϕg<0.45 and where ug≈uf .

Soft-bed experiments beneath Engabreen, Norway: Regelation, infiltration, basal slip and bed deformation

USGS Publications Warehouse

Iverson, N.R.; Hooyer, T.S.; Fischer, U.H.; Cohen, D.; Moore, P.L.; Jackson, M.; Lappegard, G.; Kohler, J.

2007-01-01

To avoid some of the limitations of studying soft-bed processes through boreholes, a prism of simulated till (1.8 m ?? 1.6 m ?? 0.45 m) with extensive instrumentation was constructed in a trough blasted in the rock bed of Engabreen, a temperate glacier in Norway. Tunnels there provide access to the bed beneath 213 m of ice. Pore-water pressure was regulated in the prism by pumping water to it. During experiments lasting 7-12 days, the glacier regelated downward into the prism to depths of 50-80 mm, accreting ice-infiltrated till at rates predicted by theory. During periods of sustained high pore-water pressure (70-100% of overburden), ice commonly slipped over the prism, due to a water layer at the prism surface. Deformation of the prism was activated when this layer thinned to a sub-millimeter thickness. Shear strain in the till was pervasive and decreased with depth. A model of slip by ploughing of ice-infiltrated till across the prism surface accounts for the slip that occurred when effective pressure was sufficiently low or high. Slip at low effective pressures resulted from water-layer thickening that increased non-linearly with decreasing effective pressure. If sufficiently widespread, such slip over soft glacier beds, which involves no viscous deformation resistance, may instigate abrupt increases in glacier velocity.

Mounted Smartphones as Measurement and Control Platforms for Motor-Based Laboratory Test-Beds †

PubMed Central

Frank, Jared A.; Brill, Anthony; Kapila, Vikram

2016-01-01

Laboratory education in science and engineering often entails the use of test-beds equipped with costly peripherals for sensing, acquisition, storage, processing, and control of physical behavior. However, costly peripherals are no longer necessary to obtain precise measurements and achieve stable feedback control of test-beds. With smartphones performing diverse sensing and processing tasks, this study examines the feasibility of mounting smartphones directly to test-beds to exploit their embedded hardware and software in the measurement and control of the test-beds. This approach is a first step towards replacing laboratory-grade peripherals with more compact and affordable smartphone-based platforms, whose interactive user interfaces can engender wider participation and engagement from learners. Demonstrative cases are presented in which the sensing, computation, control, and user interaction with three motor-based test-beds are handled by a mounted smartphone. Results of experiments and simulations are used to validate the feasibility of mounted smartphones as measurement and feedback control platforms for motor-based laboratory test-beds, report the measurement precision and closed-loop performance achieved with such platforms, and address challenges in the development of platforms to maintain system stability. PMID:27556464

Mounted Smartphones as Measurement and Control Platforms for Motor-Based Laboratory Test-Beds.

PubMed

Frank, Jared A; Brill, Anthony; Kapila, Vikram

2016-08-20

Laboratory education in science and engineering often entails the use of test-beds equipped with costly peripherals for sensing, acquisition, storage, processing, and control of physical behavior. However, costly peripherals are no longer necessary to obtain precise measurements and achieve stable feedback control of test-beds. With smartphones performing diverse sensing and processing tasks, this study examines the feasibility of mounting smartphones directly to test-beds to exploit their embedded hardware and software in the measurement and control of the test-beds. This approach is a first step towards replacing laboratory-grade peripherals with more compact and affordable smartphone-based platforms, whose interactive user interfaces can engender wider participation and engagement from learners. Demonstrative cases are presented in which the sensing, computation, control, and user interaction with three motor-based test-beds are handled by a mounted smartphone. Results of experiments and simulations are used to validate the feasibility of mounted smartphones as measurement and feedback control platforms for motor-based laboratory test-beds, report the measurement precision and closed-loop performance achieved with such platforms, and address challenges in the development of platforms to maintain system stability.

Predictions and Observations of Munitions Burial Under Intense Storm Waves at Duck, NC

NASA Astrophysics Data System (ADS)

Calantoni, J.; Klammer, H.; Sheremet, A.

2017-12-01

The fate of munitions or unexploded ordnance (UXO) resting on a submarine sediment bed is a critical safety concern. Munitions may remain in place or completely disappear for significant but unknown periods, after becoming buried in the sediment bed. Clearly, burial of munitions drastically complicates the detection and removal of potential threats. Here, we present field data of wave height and surrogate munitions burial depths near the 8-m isobath at the U.S. Army Corps of Engineers, Field Research Facility, Duck, North Carolina, observed between January and March 2015. The experiment captured a remarkable sequence of storms that included at least 10 events, of which 6 were characterized by wave fields of significant heights exceeding 2 m and with peak periods of approximately 10 s. During the strongest storm, waves of 14 s period and heights exceeding 2 m were recorded for more than 3 days; significant wave height reached 5 m at the peak of activity. At the end of the experiment, divers measured munition burial depths of up to 60 cm below the seabed level. However, the local bathymetry showed less than 5 cm variation between the before and after-storm states, suggesting the local net sediment accumulation / loss was negligible. The lack of bathymetric variability strongly suggests that the munitions sank into the bed, which would suggest an extreme state of sand agitation during the storm. We explore existing analytical solutions for the dynamic interaction between waves and sediment to predict munitions burial depths. Measured time series of wave pressure near the sediment bed were converted into wave-induced changes in pore pressures and the effective stress states of the sediment. Different sediment failure criteria based on minimum normal and maximum shear stresses were then applied to evaluate the appropriateness of individual failure criteria to predict observed burial depths. Results are subjected to a sensitivity analysis with respect to uncertain sediment parameters and summarized by representing cumulative failure times as a function of depth.

Estimating Fuel Bed Loadings in Masticated Areas

Treesearch

Sharon Hood; Ros Wu

2006-01-01

Masticated fuel treatments that chop small trees, shrubs, and dead woody material into smaller pieces to reduce fuel bed depth are used increasingly as a mechanical means to treat fuels. Fuel loading information is important to monitor changes in fuels. The commonly used planar intercept method however, may not correctly estimate fuel loadings because masticated fuels...

ANALYSIS OF BACTERIAL COMMUNITIES IN SEAGRASS BED SEDIMENTS BY DOUBLE-GRADIENT DENATURING GRADIENT GEL ELECTROPHORESIS OF PCR-AMPLIFIED 16SRRNA GENES

EPA Science Inventory

Bacterial communities associated with seagrass bed sediments are not well studied. The work presented here investigated several factors, including the presence or absence of vegetation, depth into sediment, and season, and their impact on bacterial community diversity. Double gra...

Breakthrough curves for toluene adsorption on different types of activated carbon fibers: application in respiratory protection.

PubMed

Balanay, Jo Anne G; Floyd, Evan L; Lungu, Claudiu T

2015-05-01

Activated carbon fibers (ACF) are considered viable alternative adsorbent materials in respirators because of their larger surface area, lighter weight, and fabric form. The purpose of this study was to characterize the breakthrough curves of toluene for different types of commercially available ACFs to understand their potential service lives in respirators. Two forms of ACF, cloth (AC) and felt (AF), with three surface areas each were tested. ACFs were challenged with six toluene concentrations (50-500 p.p.m.) at constant air temperature (23°C), relative humidity (50%), and air flow (16 l min-1) at different bed depths. Breakthrough data were obtained using continuous monitoring by gas chromatography using a gas sampling valve. The ACF specific surface areas were measured by an automatic physisorption analyzer. Results showed unique shapes of breakthrough curves for each ACF form: AC demonstrated a gradual increase in breakthrough concentration, whereas AF showed abrupt increase in concentration from the breakpoint, which was attributed to the difference in fiber density between the forms. AF has steeper breakthrough curves compared with AC with similar specific surface area. AC exhibits higher 10% breakthrough times for a given bed depth due to higher mass per bed depth compared with AF, indicating more adsorption per bed depth with AC. ACF in respirators may be appropriate for use as protection in environments with toluene concentration at the Occupational Safety and Health Administration Permissible Exposure Limit, or during emergency escape for higher toluene concentrations. ACF has shown great potential for application in respiratory protection against toluene and in the development of thinner, lighter, and more efficient respirators. © The Author 2014. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

SU-F-T-124: Radiation Biological Equivalent Presentations OfLEM-1 and MKM Approaches in the Carbon-Ion Radiotherapy

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

Hsi, W; Jiang, G; Sheng, Y

Purpose: To study the correlations of the radiation biological equivalent doses (BED) along depth and lateral distance between LEM-1 and MKM approaches. Methods: In NIRS-MKM (Microdosimetric Kinetic Model) approach, the prescribed BED, referred as C-Eq, doses aims to present the relative biological effectiveness (RBE) for different energies of carbon-ions on a fixed 10% survival value of HCG cell with respect to convention X-ray. Instead of a fixed 10% survival, the BED doses of LEM-1 (Local Effect Model) approach, referred as X-Eq, aims to present the RBE over the whole survival curve of chordoma-like cell with alpha/beta ratio of 2.0. Themore » relationship of physical doses as a function of C-Eq and X-Eq doses were investigated along depth and lateral distance for various sizes of cubic targets in water irradiated by carbon-ions. Results: At the center of each cubic target, the trends between physical and C-Eq or X-Eq doses can be described by a linear and 2nd order polynomial functions, respectively. Using fit functions can then calculate a scaling factor between C-Eq and X-Eq doses to have similar physical doses. With equalized C-Eq and X-Eq doses at the depth of target center, over- and under-estimated X-Eq to C-Eq are seen for depths before and after the target center, respectively. Near the distal edge along depth, sharp rising of RBE value is observed for X-Eq, but sharp dropping of RBE value is observed for C-Eq. For lateral locations near and just outside 50% dose level, sharp raising of RBE value is also seen for X-Eq, while only minor increasing with fast dropping for C-Eq. Conclusion: An analytical function to model the differences between the CEq and X-Eq doses along depth and lateral distance need to further investigated to explain varied clinic outcome of specific cancers using two different approaches to calculated BED doses.« less

A bioassay for studying behavioural responses of the common bed bug, Cimex lectularius (Hemiptera: Cimicidae) to bed bug-derived volatiles.

PubMed

Weeks, E N I; Logan, J G; Gezan, S A; Woodcock, C M; Birkett, M A; Pickett, J A; Cameron, M M

2011-02-01

The common bed bug, Cimex lectularius (Hemiptera: Cimicidae), has recently re-emerged in increasing numbers, distribution and intensity of infestation in many countries. Current control relies on the application of residual pesticides; but, due to the development of insecticide resistance, there is a need for new tools and techniques. Semiochemicals (behaviour and physiology modifying chemicals) could be exploited for management of bed bugs. However, in order to identify semiochemicals that can be utilised in monitoring or control, a suitable olfactometer is needed that enables the study of the responses of bed bugs to volatile chemicals. Previous studies have used olfactometers that do not separate olfactory responses from responses to physical contact. In this study, a still-air olfactometer was used to measure behavioural responses to different bed bug-derived volatiles presented in an odour pot. Bed bugs were significantly more likely to visit the area above the odour pot first, and more frequently, in the presence of volatiles from bed bug-exposed paper but not in the presence of volatiles from conspecific bed bugs. Bed bug activity was found to be dependent on the presence of the volatiles from bed bug-exposed paper, the time during the scotophase and the sex of the insect being tested. The still-air olfactometer could be used to test putative semiochemicals, which would allow an understanding of their behavioural role in bed bug ecology. Ultimately, this could lead to the identification of new semiochemical tools for bed bug monitoring and control.

Factors controlling the size and shape of stream channels in coarse noncohesive sands

USGS Publications Warehouse

Wolman, M. Gordon; Brush, Lucien M.

1961-01-01

The size and shape of equilibrium channels in uniform, noncohesive sands, 0.67 mm and 2.0 mm in diameter, were studied experimentally in a laboratory flume 52 feet long in which discharge, slope, sediment load, and bed and bank material could be varied independently. For each run a straight trapezoidal channel was molded in the sand and the flume set at a predetermined slope. Introduction of the discharge was accompanied by widening and aggradation until a stable channel was established. By definition a stable equilibrium existed when channel width, water surface slope, and rate of transport became constant. The duration of individual runs ranged from 2 to 52 hours depending upon the time required for establishing equilibrium. Stability of the banks determined channel shape. In the 2.0 mm sand at a given slope and discharge, only one depth was stable. At this depth the flow was just competent to move particles along the bed of the channel. An increase in discharge produced a wider channel of the same depth and thus transport per unit width remained at a minimum. Channels in the 0.67 mm sand were somewhat more stable and permitted a 1.5 fold increase in depth above that required to start movement of the bed material. An increased transport was associated with the increase in depth. The rate of transport is adequately described in terms of the total shear or in terms of the difference between the total shear and the critical shear required to begin movement. In these experiments the finer, or 0.67 mm, sand, began to move along the bed of the channel at a constant shear stress. Incipient movement of the coarser, or 2.0 mm, sand, varied with the shear stress as well as the mean velocity. At the initiation of movement a lower shear was associated with a higher velocity and vice versa. Anabranches of braided rivers and some natural river channels formed in relatively noncohesive materials resemble the essential characteristics of the flume channels. For a given slope and size of bed material the discharge per unit width in the laboratory channels was similar to that computed for anabranches and river channels measured in the field. Unlike most natural channels, despite impressive bank erosion, the channels in the laboratory only meandered at supercritical flows associated with very steep slopes. These conditions involving shallow depths, high velocity, and steep slopes are uncommon in most natural rivers.

Effects of ablation depth and repair time on the corneal elastic modulus after laser in situ keratomileusis.

PubMed

Wang, Xiaojun; Li, Xiaona; Chen, Weiyi; He, Rui; Gao, Zhipeng; Feng, Pengfei

2017-01-17

The biomechanical properties of the cornea should be taken into account in the refractive procedure in order to perform refractive surgery more accurately. The effects of the ablation depth and repair time on the elastic modulus of the rabbit cornea after laser in situ keratomileusis (LASIK) are still unclear. In this study, LASIK was performed on New Zealand rabbits with different ablation depth (only typical LASIK flaps were created; residual stroma bed was 50 or 30% of the whole cornea thickness respectively). The animals without any treatment were served as normal controls. The corneal thickness was measured by ultrasonic pachymetry before animals were humanly killed after 7 or 28 days post-operatively. The corneal elastic modulus was measured by uniaxial tensile testing. A mathematical procedure considering the actual geometrics of the cornea was created to analyze the corneal elastic modulus. There were no obvious differences among all groups in the elastic modulus on after 7 days post-operatively. However, after 28th days post-operatively, there was a significant increase in the elastic modulus with 50 and 30% residual stroma bed; only the elastic modulus of the cornea with 30% residual stroma bed was significantly higher than that of 7 days. Changes in elastic modulus after LASIK suggest that this biomechanical effect may correlate with the ablation depth and repair time.

The Influence of Fuel Properties on Combustion Efficiency and the Partitioning of Pyrogenic Carbon

NASA Astrophysics Data System (ADS)

Urbanski, S. P.; Baker, S. P.; Lincoln, E.; Richardson, M.

2016-12-01

The partitioning of volatized pyrogenic carbon into CO2, CO, CH4, non-methane organic carbon, and particulate organic carbon (POC) and elemental carbon (PEC) depends on the combustion characteristics of biomass fires which are influenced by the moisture content, structure and arrangement of the fuels. Flaming combustion is characterized by efficient conversion of volatized carbon into CO2. In contrast, smoldering is less efficient and produces incomplete combustion products like CH4 and carbonaceous particles. This paper presents a laboratory study that has examined the relationship between the partitioning of volatized pyrogenic carbon and specific fuel properties. The study focused on fuel beds composed of simple fuel particles — ponderosa pine needles. Ponderosa pine was selected because it contains a common wildland fuel component, conifer needles, which can be easily arranged into fuel beds of variable structure (bulk density and depth) and moisture contents that are both representative of natural conditions and are easily replicated. Modified combustion efficiency (MCE, ΔCO2/[ΔCO2+ ΔCO]) and emission factors (EF) for CO2, CO, CH4, POC, and PEC were measured over a range of needle moisture content and fuel bed bulk density and depth representative of naturally occurring fuel beds. We found that, as expected, MCE decreases as the fuel bed bulk density increases and emissions of CO, CH4, PM2.5, and POC increased. However, fuel bed depth did not appear to have an effect on how effect on MCE or emission factors. Surprisingly, a consistent relationship between the needle moisture content and emissions was not identified. At the high bulk densities, moisture content had a strong influence on MCE which explained variability in EFCH4. However, moisture content appeared to have an influence EFPOC and EFPEC that was independent of MCE. These findings may have significant implications since many models of biomass burning assume that litter fuels, such as ponderosa pine needles, burn almost exclusively via flaming combustion with a high efficiency. Our results indicate that for fuel bed properties typical of many conifer forests, pollutants generated from fires will be higher than that predicted using standard biomass burning models.

Characterizing flow pathways in a sandstone aquifer at multiple depths

NASA Astrophysics Data System (ADS)

Medici, Giacomo; West, Jared; Mountney, Nigel

2017-04-01

Sandstone aquifers are commonly assumed to represent porous media characterized by a permeable matrix. However, such aquifers may be heavily fractured where rock properties and timing of deformation favour brittle failure and crack opening. In many aquifer types, fractures associated with faults, bedding planes and stratabound joints represent preferential pathways for fluids and contaminants. This presentation reports well-test results and outcrop-scale studies that reveal how strongly lithified siliciclastic rocks may be entirely dominated by fracture flow at shallow depths (≤ 150 m), similar to limestone and crystalline aquifers. The Triassic St Bees Sandstone Formation of the UK East Irish Sea Basin represents an optimum succession for study of the influence of both sedimentary and tectonic aquifer heterogeneities in a strongly lithified sandstone aquifer-type. This sedimentary succession of fluvial origin accumulated in rapidly subsiding basins, which typically favour preservation of complete depositional cycles, including fine-grained mudstone and silty sandstone layers of floodplain origin interbedded with sandstone-dominated fluvial channel deposits. Vertical joints in the St Bees Sandstone Formation form a pervasive stratabound system whereby joints terminate at bedding-parallel discontinuities. Additionally, normal faults are present through the succession and record development of open-fractures in their damage zones. Here, the shallow aquifer (depth ≤150 m BGL) was characterized in outcrop and well tests. Fluid temperature, conductivity and flow-velocity logs record inflows and outflows from normal faults, as well as from pervasive bed-parallel fractures. Quantitative flow logging analyses in boreholes that cut fault planes indicate that zones of fault-related open fractures typically represent ˜ 50% of well transmissivity. The remaining flow component is dominated by bed-parallel fractures. However, such sub-horizontal fractures become the principal flow conduits in wells that penetrate the exterior parts of fault damage zones, as well as in non-faulted areas. Optical televiewer logs show development of karst-like conduits in correspondence of bedding fractures and faults up to 150 m below the ground surface, where recharge water containing dissolved carbonic acid enlarges fractures; these features may be responsible for the relatively high field-scale permeability (K˜0.1-1 m/day) of the phreatic zone at these depths. Below this 'karstifed' zone, field-scale permeability progressively decreases from K˜10-2 to 10-4 m/day from 150 m to 1100 m depth. Notably, differences between plug and field-scale permeability, and frequency of well in-flows seen in temperature and conductivity logs, also decrease between intermediate (150 to 450 m) and elevated (450 to 1100 m) depths. This confirms how fracture closure leads to a progressively more important matrix contribution to flow with increasing lithostatic stress, leading to intergranular flow dominance at ˜ 1 km depth.

Tracking bed bugs (Cimex lectularius): a study of the effect of physiological and extrinsic factors on the response to bed bug-derived volatiles.

PubMed

Weeks, E N I; Logan, J G; Birkett, M A; Pickett, J A; Cameron, M M

2013-02-01

The common bed bug, Cimex lectularius, feeds on the blood of mammal and bird hosts, and is a pest of global importance. Semiochemicals are chemicals involved in animal communication that may affect behaviour and/or physiology. Attractive semiochemicals that play a role in mediating bed bug behaviour could be exploited for the development of a highly effective novel monitoring device. Tracking software was used to record the response of bed bugs to volatiles from paper previously exposed to conspecific bugs in a still-air olfactometer illuminated by infrared lights, through a variety of activity variables. The effect of time of day as an extrinsic factor, and sex, stage, mating status and nutritional status as physiological factors on the response of bed bugs to the volatiles was examined. Bed bugs of both sexes and all stages responded to the volatiles from bed bug-exposed papers, showing significant attraction and orientation towards the volatile source whether they were starved or engorged. Confirmation that the physiological factors examined do not affect the response of bed bugs to the volatiles from bed bug-exposed papers provides evidence that these bed bug-derived volatiles contain aggregation cues, as semiochemicals that promote aggregation should by definition be detected by both sexes and all life stages. A device baited with such semiochemicals could play a major role in limiting the impact of the current bed bug resurgence by enabling timely detection of infestations, along with quantitative evaluation of control and effective surveillance of the geographical distribution of the pest species.

Flow resistance and suspended load in sand-bed rivers: Simplified stratification model

USGS Publications Warehouse

Wright, S.; Parker, G.

2004-01-01

New methods are presented for the prediction of the flow depth, grain-size specific near-bed concentration, and bed-material suspended sediment transport rate in sand-bed rivers. The salient improvements delineated here all relate to the need to modify existing formulations in order to encompass the full range of sand-bed rivers, and in particular large, low-slope sand-bed rivers. They can be summarized as follows: (1) the inclusion of density stratification effects in a simplified manner, which have been shown in the companion paper to be particularly relevant for large, low-slope, sand-bed rivers; (2) a new predictor for near-bed entrainment rate into suspension which extends a previous relation to the range of large, low-slope sand-bed rivers; and (3) a new predictor for form drag which again extends a previous relation to include large, low-slope sand-bed rivers. Finally, every attempt has been made to cast the relations in the simplest form possible, including the development of software, so that practicing engineers may easily use the methods. ?? ASCE.

New technological developments provide deep-sea sediment density flow insights: the Monterey Coordinated Canyon Experiment

NASA Astrophysics Data System (ADS)

O'Reilly, T. C.; Kieft, B.; Chaffey, M. R.; Wolfson-Schwehr, M.; Herlien, R.; Bird, L.; Klimov, D.; Paull, C. K.; Gwiazda, R.; Lundsten, E. M.; Anderson, K.; Caress, D. W.; Sumner, E. J.; Simmons, S.; Parsons, D. R.; Talling, P.; Rosenberger, K. J.; Xu, J.; Maier, K. L.; Gales, J. A.

2017-12-01

The Monterey Coordinated Canyon Experiment (CCE) deployed an array of instruments along the Monterey Canyon floor to characterize the structure, velocity and frequency of sediment flows. CCE utilized novel technologies developed at MBARI to capture sediment flow data in unprecedented detail. 1. The Seafloor Instrument Node (SIN) at 1850 meters depth housed 3 ADCPs at 3 different frequencies, CTD, current meter, oxygen optode, fluorometer/backscatter sensor, and logged data at 10 second intervals or faster. The SIN included an acoustic modem for communication with shore through a Wave Glider relay, and provided high-resolution measurements of three flow events during three successive deployments over 1.5 years. 2. Beachball-sized Benthic Event Detectors (BEDs) were deployed on or under the seafloor to measure the characteristics of sediment density flows. Each BED recorded data from a pressure sensor and a 3-axis accelerometer and gyro to characterize motions during transport events (e.g. tumble vs rotation). An acoustic modem capable of operating through more than a meter of sediment enabled communications with a ship or autonomous surface vehicle. Multiple BEDs were deployed at various depths in the canyon during CCE, detecting and measuring many transport events; one BED moved 9 km down canyon in 50 minutes during one event. 3. Wave Glider Hot Spot (HS), equipped with acoustic and RF modems, acted as data relay between SIN, BEDs and shore, and acoustically located BEDs after sediment density flows.. In some cases HS relayed BED motion data to shore within a few hours of the event. HS provided an acoustic console to the SIN, allowing shore-based users to check SIN health and status, perform maintenance, etc. 4. Mapping operations were conducted 4 times at the SIN site to quantify depositional and erosional patterns, utilizing a prototype ultra-high-resolution mapping system on the ROV Doc Ricketts. The system consists of a 400-kHz Reson 7125 multibeam sonar, a 3DatDepth SL1 subsea LiIDAR, two stereo color cameras, and a Kearfott SeaDevil INS. At a survey altitude of 3 m above the bed, the mapping system provides 5-cm resolution multibeam bathymetry, 1-cm resolution lidar bathymetry, and 2-mm resolution photomosaics. We will describe the design and full capabilities of these novel systems.

Kinetics of bed fracturing around mine workings

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

Veksler, Yu.A.

1988-03-01

A failure of the bed near the walls of the workings of a mine away from the face occurs gradually over time and in this paper the authors take a kinetic approach to evaluating its development. The influence of certain mine engineering factors on the pattern of bed fracturing is discussed. The effect of the depth of mining is shown. Cracking occurs in the portion of the seam at the face near the ground at some distance from it on the interface between soft and hard coal. The density of the fractured rocks and their response affect the bed fracturingmore » near the stope face.« less

Dimensional Analysis on Forest Fuel Bed Fire Spread.

PubMed

Yang, Jiann C

2018-01-01

A dimensional analysis was performed to correlate the fuel bed fire rate of spread data previously reported in the literature. Under wind condition, six pertinent dimensionless groups were identified, namely dimensionless fire spread rate, dimensionless fuel particle size, fuel moisture content, dimensionless fuel bed depth or dimensionless fuel loading density, dimensionless wind speed, and angle of inclination of fuel bed. Under no-wind condition, five similar dimensionless groups resulted. Given the uncertainties associated with some of the parameters used to estimate the dimensionless groups, the dimensionless correlations using the resulting dimensionless groups correlate the fire rates of spread reasonably well under wind and no-wind conditions.

What controls channel form in steep mountain streams?

NASA Astrophysics Data System (ADS)

Palucis, M. C.; Lamb, M. P.

2017-07-01

Steep mountain streams have channel morphologies that transition from alternate bar to step-pool to cascade with increasing bed slope, which affect stream habitat, flow resistance, and sediment transport. Experimental and theoretical studies suggest that alternate bars form under large channel width-to-depth ratios, step-pools form in near supercritical flow or when channel width is narrow compared to bed grain size, and cascade morphology is related to debris flows. However, the connection between these process variables and bed slope—the apparent dominant variable for natural stream types—is unclear. Combining field data and theory, we find that certain bed slopes have unique channel morphologies because the process variables covary systematically with bed slope. Multiple stable states are predicted for other ranges in bed slope, suggesting that a competition of underlying processes leads to the emergence of the most stable channel form.

The influence of bed friction variability due to land cover on storm-driven barrier island morphodynamics

USGS Publications Warehouse

Passeri, Davina L.; Long, Joseph W.; Plant, Nathaniel G.; Bilskie, Matthew V.; Hagen, Scott C.

2018-01-01

Variations in bed friction due to land cover type have the potential to influence morphologic change during storm events; the importance of these variations can be studied through numerical simulation and experimentation at locations with sufficient observational data to initialize realistic scenarios, evaluate model accuracy and guide interpretations. Two-dimensional in the horizontal plane (2DH) morphodynamic (XBeach) simulations were conducted to assess morphodynamic sensitivity to spatially varying bed friction at Dauphin Island, AL using hurricanes Ivan (2004) and Katrina (2005) as experimental test cases. For each storm, three bed friction scenarios were simulated: (1) a constant Chezy coefficient across land and water, (2) a constant Chezy coefficient across land and depth-dependent Chezy coefficients across water, and (3) spatially varying Chezy coefficients across land based on land use/land cover (LULC) data and depth-dependent Chezy coefficients across water. Modeled post-storm bed elevations were compared qualitatively and quantitatively with post-storm lidar data. Results showed that implementing spatially varying bed friction influenced the ability of XBeach to accurately simulate morphologic change during both storms. Accounting for frictional effects due to large-scale variations in vegetation and development reduced cross-barrier sediment transport and captured overwash and breaching more accurately. Model output from the spatially varying friction scenarios was used to examine the need for an existing sediment transport limiter, the influence of pre-storm topography and the effects of water level gradients on storm-driven morphodynamics.

Flow over gravel beds with clusters

NASA Astrophysics Data System (ADS)

Little, M.; Venditti, J. G.

2014-12-01

The structure of a gravel bed has been shown to alter the entrainment threshold. Structures such as clusters, reticulate stone cells and other discrete structures lock grains together, making it more difficult for them to be mobilized. These structures also generate form drag, reducing the shear stress available for mobilization. Form drag over gravel beds is often assumed to be negligible, but this assumption is not well supported. Here, we explore how cluster density and arrangement affect flow resistance and the flow structure over a fixed gravel bed in a flume experiment. Cluster density was varied from 6 to 68.3 clusters per square meter which corresponds to areal bed coverages of 2 to 17%. We used regular, irregular and random arrangements of the clusters. Our results show that flow resistance over a planar gravel bed initially declines, then increases with flow depth. The addition of clusters increases flow resistance, but the effect is dependent on cluster density, flow depth and arrangement. At the highest density, clusters can increase flow resistance as by as much as 8 times when compared to flat planar bed with no grain-related form drag. Spatially resolved observations of flow over the clusters indicate that a well-defined wake forms in the lee of each cluster. At low cluster density, the wakes are isolated and weak. As cluster density increases, the wakes become stronger. At the highest density, the wakes interact and the within cluster flow field detaches from the overlying flow. This generates a distinct shear layer at the height of the clusters. In spite of this change in the flow field at high density, our results suggest that flow resistance simply increases with cluster density. Our results suggest that the form drag associated with a gravel bed can be substantial and that it depends on the arrangement of the grains on the bed.

Between two beds: inappropriately delayed discharges from hospitals.

PubMed

Holmås, Tor Helge; Islam, Mohammad Kamrul; Kjerstad, Egil

2013-12-01

Acknowledging the necessity of a division of labour between hospitals and social care services regarding treatment and care of patients with chronic and complex conditions, is to acknowledge the potential conflict of interests between health care providers. A potentially important conflict is that hospitals prefer comparatively short length of stay (LOS) at hospital, while social care services prefer longer LOS all else equal. Furthermore, inappropriately delayed discharges from hospital, i.e. bed blocking, is costly for society. Our aim is to discuss which factors that may influence bed blocking and to quantify bed blocking costs using individual Norwegian patient data, merged with social care and hospital data. The data allow us to divide hospital LOS into length of appropriate stay (LAS) and length of delay (LOD), the bed blocking period. We find that additional resources allocated to social care services contribute to shorten LOD indicating that social care services may exploit hospital resources as a buffer for insufficient capacity. LAS increases as medical complexity increases indicating hospitals incentives to reduce LOS are softened by considerations related to patients’ medical needs. Bed blocking costs constitute a relatively large share of the total costs of inpatient care.

Lateral Erosion Encourages Vertical Incision in a Bimodal Alluvial River

NASA Astrophysics Data System (ADS)

Gran, K. B.

2015-12-01

Sand can have a strong impact on gravel transport, increasing gravel transport rates by orders of magnitude as sand content increases. Recent experimental work by others indicates that adding sand to an armored bed can even cause armor to break-up and mobilize. These two elements together help explain observations from a bimodal sand and gravel-bedded river, where lateral migration into sand-rich alluvium breaks up the armor layer, encouraging further incision into the bed. Detailed bedload measurements were coupled with surface and subsurface grain size analyses and cross-sectional surveys in a seasonally-incised channel carved into the upper alluvial fan of the Pasig-Potrero River at Mount Pinatubo, Philippines. Pinatubo erupted in 1991, filling valleys draining the flanks of the volcano with primarily sand-sized pyroclastic flow debris. Twenty years after the eruption, sand-rich sediment inputs are strongly seasonal, with most sediment input to the channel during the rainy season. During the dry season, flow condenses from a wide braided planform to a single-thread channel in most of the upper basin, extending several km onto the alluvial fan. This change in planform creates similar unit discharge ranges in summer and winter. Lower sediment loads in the dry season drive vertical incision until the bed is sufficiently armored. Incision proceeds downstream in a wave, with increasing sediment transport rates and decreasing grain size with distance downstream, eventually reaching a gravel-sand transition and return to a braided planform. Incision depths in the gravel-bedded section exceeded 3 meters in parts of a 4 km-long study reach, a depth too great to be explained by predictions from simple winnowing during incision. Instead, lateral migration into sand-rich alluvium provides sufficient fine sediment to break up the armor surface, allowing incision to start anew and increasing the total depth of the seasonally-incised valley. Lateral migration is recorded in a series of inset terraces within the valley. The importance of sand on channel behavior thus extends beyond transport rates, affecting the depth of incision and volume of material excavated during a rainy to dry season transition.

Controlling thermal properties of dense gas fluidized beds for concentrated solar power by internal and external solids circulation

NASA Astrophysics Data System (ADS)

Ammendola, Paola; Bareschino, Piero; Chirone, Riccardo; Salatino, Piero; Solimene, Roberto

2017-06-01

Fluidization technology displays a long record of success stories, mostly related to applications to thermal and thermochemical processes, which are fostering extension to novel and relatively unexplored fields. Application of fluidized beds to collection and thermal storage of solar radiation in Concentrated Solar Power (CSP) is one of the most promising, a field which poses challenging issues and great opportunities to fluidization scientists and technologists. The potential of this growing field calls for reconsideration of some of the typical design and operation guidelines and criteria, with the goal of exploiting the inherently good thermal performances of gas-fluidized beds at their best. "Creative" and non-conventional design and operation of fluidized beds, like those based on internal and external solids circulation, may be beneficial to the enhancement of thermal diffusivity and surface-to-bed heat transfer, improving the potential for application in the very demanding context of CSP with thermal energy storage. This paper investigated: i) a fluidized bed configuration with an uneven distribution of the fluidizing gas to promote vortices in the scale of bed height (internal solids circulation); ii) a dual fluidized bed configuration characterized by an external solids circulation achieved by the operation of a riser and a bubbling fluidized bed. CFD simulations showed the hydrodynamics conditions under which the internal solids circulation was established. The hydrodynamic characterization of the external solids circulation was achieved by an experimental study carried out with different cold models. The dual fluidized bed system was optimized in terms of operating conditions and geometrical features of the connections between two fluidized beds.

Coastal Remote Sensing Investigations. Volume 1. Marine Environment.

DTIC Science & Technology

1980-04-01

and heavy growths of vegetation (mainly Thalassia ) in protected areas. The water is very clear, and extensive shallow areas exist with depths rangin...16.0 boundary of vegetated area A-2 3 5.0 Thalassia bed A-3 3 32.0 white carbonate sand B-I 5 16.5 hard, non-vegetated bottom B-2 4 30.0 white...carbonate sand B-3 3 12.5 boundary of vegetated area B-4 4 5.0 Thalassia bed C-I 3 35.0 white carbonate sand C-2 4 3.0 Thalassia bed 30 Figure

Pneumatic transportation of dispersed medium through a vertical tube immersed into a fluidized bed

NASA Astrophysics Data System (ADS)

Krasnykh, V. Yu.; Korolev, V. N.; Ostrovskaya, A. V.; Nagornov, S. A.

2013-11-01

We discuss the technical problem of how to transport granular material in a vertical direction from the underlying section of a multistage apparatus containing a fluidized bed to an upper section through tubes immersed into the fluidized bed without additional expenditures of energy. The intensity with which the dispersed medium (a mixture of gas and fuel particles) moves through the tube and the mass flowrate of particles are determined by the ratio between the hydraulic resistances of dispersed medium inside the tube and of the fluidized bed outside of it. In turn, this ratio depends on the fluidization number W (W = w s/ w 0, where w s is the seepage velocity and w 0 is the fluidization commencement velocity) and on the tube immersing depth into the bed.

Species removal from aqueous radioactive waste by deep-bed filtration.

PubMed

Dobre, Tănase; Zicman, Laura Ruxandra; Pârvulescu, Oana Cristina; Neacşu, Elena; Ciobanu, Cătălin; Drăgolici, Felicia Nicoleta

2018-05-26

Performances of aqueous suspension treatment by deep-bed sand filtration were experimentally studied and simulated. A semiempirical deterministic model and a stochastic model were used to predict the removal of clay particles (20 μm) from diluted suspensions. Model parameters, which were fitted based on experimental data, were linked by multiple linear correlations to the process factors, i.e., sand grain size (0.5 and 0.8 mm), bed depth (0.2 and 0.4 m), clay concentration in the feed suspension (1 and 2 kg p /m 3 ), suspension superficial velocity (0.015 and 0.020 m/s), and operating temperature (25 and 45 °C). These relationships were used to predict the bed radioactivity determined by the deposition of radioactive suspended particles (>50 nm) from low and medium level aqueous radioactive waste. A deterministic model based on mass balance, kinetic, and interface equilibrium equations was developed to predict the multicomponent sorption of 60 Co, 137 Cs, 241 Am, and 3 H radionuclides (0.1-0.3 nm). A removal of 98.7% of radioactive particles was attained by filtering a radioactive wastewater volume of 10 m 3 (0.5 mm sand grain size, 0.3 m bed depth, 0.223 kg p /m 3 suspended solid concentration in the feed suspension, 0.003 m/s suspension superficial velocity, and 25 °C operating temperature). Predicted results revealed that the bed radioactivity determined by the sorption of radionuclides (0.01 kBq/kg b ) was significantly lower than the bed radioactivities caused by the deposition of radioactive particles (0.5-1.8 kBq/kg b ). Copyright © 2018 Elsevier Ltd. All rights reserved.

Learning discriminative features from RGB-D images for gender and ethnicity identification

NASA Astrophysics Data System (ADS)

Azzakhnini, Safaa; Ballihi, Lahoucine; Aboutajdine, Driss

2016-11-01

The development of sophisticated sensor technologies gave rise to an interesting variety of data. With the appearance of affordable devices, such as the Microsoft Kinect, depth-maps and three-dimensional data became easily accessible. This attracted many computer vision researchers seeking to exploit this information in classification and recognition tasks. In this work, the problem of face classification in the context of RGB images and depth information (RGB-D images) is addressed. The purpose of this paper is to study and compare some popular techniques for gender recognition and ethnicity classification to understand how much depth data can improve the quality of recognition. Furthermore, we investigate which combination of face descriptors, feature selection methods, and learning techniques is best suited to better exploit RGB-D images. The experimental results show that depth data improve the recognition accuracy for gender and ethnicity classification applications in many use cases.

Predicting bed shear stress and its role in sediment dynamics and restoration potential of the Everglades and other vegetated flow systems

USGS Publications Warehouse

Larsen, Laurel G.; Harvey, Judson; Crimaldi, John P.

2009-01-01

Entrainment of sediment by flowing water affects topography, habitat suitability, and nutrient cycling in vegetated floodplains and wetlands, impacting ecosystem evolution and the success of restoration projects. Nonetheless, restoration managers lack simple decision-support tools for predicting shear stresses and sediment redistribution potential in different vegetation communities. Using a field-validated numerical model, we developed state-space diagrams that provide these predictions over a range of water-surface slopes, depths, and associated velocities in Everglades ridge and slough vegetation communities. Diminished bed shear stresses and a consequent decrease in bed sediment redistribution are hypothesized causes of a recent reduction in the topographic and vegetation heterogeneity of this ecosystem. Results confirmed the inability of present-day flows to entrain bed sediment. Further, our diagrams showed bed shear stresses to be highly sensitive to emergent vegetation density and water-surface slope but less sensitive to water depth and periphyton or floating vegetation abundance. These findings suggested that instituting a pulsing flow regime could be the most effective means to restore sediment redistribution to the Everglades. However, pulsing flows will not be sufficient to erode sediment from sloughs with abundant spikerush, unless spikerush density first decreases by natural or managed processes. Our methods provide a novel tool for identifying restoration parameters and performance measures in many types of vegetated aquatic environments where sediment erosion and deposition are involved.

A new approach to define surface/sub-surface transition in gravel beds

NASA Astrophysics Data System (ADS)

Haynes, Heather; Ockelford, Anne-Marie; Vignaga, Elisa; Holmes, William

2012-12-01

The vertical structure of river beds varies temporally and spatially in response to hydraulic regime, sediment mobility, grain size distribution and faunal interaction. Implicit are changes to the active layer depth and bed porosity, both critical in describing processes such as armour layer development, surface-subsurface exchange processes and siltation/ sealing. Whilst measurements of the bed surface are increasingly informed by quantitative and spatial measurement techniques (e.g., laser displacement scanning), material opacity has precluded the full 3D bed structure analysis required to accurately define the surface-subsurface transition. To overcome this problem, this paper provides magnetic resonance imaging (MRI) data of vertical bed porosity profiles. Uniform and bimodal (σ g = 2.1) sand-gravel beds are considered following restructuring under sub-threshold flow durations of 60 and 960 minutes. MRI data are compared to traditional 2.5D laser displacement scans and six robust definitions of the surface-subsurface transition are provided; these form the focus of discussion.

Scour around vertical wall abutment in cohesionless sediment bed

NASA Astrophysics Data System (ADS)

Pandey, M.; Sharma, P. K.; Ahmad, Z.

2017-12-01

At the time of floods, failure of bridges is the biggest disaster and mainly sub-structure (bridge abutments and piers) are responsible for this failure of bridges. It is very risky if these sub structures are not constructed after proper designing and analysis. Scour is a natural phenomenon in rivers or streams caused by the erosive action of the flowing water on the bed and banks. The abutment undermines due to river-bed erosion and scouring, which generally recognized as the main cause of abutment failure. Most of the previous studies conducted on scour around abutment have concerned with the prediction of the maximum scour depth (Lim, 1994; Melvill, 1992, 1997 and Dey and Barbhuiya, 2005). Dey and Barbhuiya (2005) proposed a relationship for computing maximum scour depth near an abutment, based on laboratory experiments, for computing maximum scour depth around vertical wall abutment, which was confined to their experimental data only. However, this relationship needs to be also verified by the other researchers data in order to support the reliability to the relationship and its wider applicability. In this study, controlled experimentations have been carried out on the scour near a vertical wall abutment. The collected data in this study along with data of the previous investigators have been carried out on the scour near vertical wall abutment. The collected data in this study along with data of the previous have been used to check the validity of the existing equation (Lim, 1994; Melvill, 1992, 1997 and Dey and Barbhuiya, 2005) of maximum scour depth around the vertical wall abutment. A new relationship is proposed to estimate the maximum scour depth around vertical wall abutment, it gives better results all relationships.

Flow resistance under conditions of intense gravel transport

USGS Publications Warehouse

Pitlick, John

1992-01-01

A study of flow resistance was undertaken in a channelized reach of the North Fork Toutle River, downstream of Mount St. Helens, Washington. Hydraulic and sediment transport data were collected in flows with velocities up to 3 m/s and shear stresses up to 7 times the critical value needed for bed load transport. Details of the flow structure as revealed in vertical velocity profiles indicate that weak bed load transport over a plane gravel bed has little effect on flow resistance. The plane gravel bed persists up to stresses ∼3 times critical, at which point, irregular bed forms appear. Bed forms greatly increase flow resistance and cause velocity profiles to become distorted. The latter arises as an effect of flows becoming depth-limited as bed form amplitude increases. At very high rates of bed load transport, an upper stage plane bed appeared. Velocity profiles measured in these flows match the law of the wall closely, with the equivalent roughness being well represented by ks = 3D84 of the bed load. The effects noted here will be important in very large floods or in rivers that are not free to widen, such as those cut into bedrock.

Comparative analysis of several sediment transport formulations applied to dam-break flows over erodible beds

NASA Astrophysics Data System (ADS)

Cea, Luis; Bladé, Ernest; Corestein, Georgina; Fraga, Ignacio; Espinal, Marc; Puertas, Jerónimo

2014-05-01

Transitory flows generated by dam failures have a great sediment transport capacity, which induces important morphological changes on the river topography. Several studies have been published regarding the coupling between the sediment transport and hydrodynamic equations in dam-break applications, in order to correctly model their mutual interaction. Most of these models solve the depth-averaged shallow water equations to compute the water depth and velocity. On the other hand, a wide variety of sediment transport formulations have been arbitrarily used to compute the topography evolution. These are based on semi-empirical equations which have been calibrated under stationary and uniform conditions very different from those achieved in dam-break flows. Soares-Frazao et al. (2012) proposed a Benchmark test consisting of a dam-break over a mobile bed, in which several teams of modellers participated using different numerical models, and concluded that the key issue which still needs to be investigated in morphological modelling of dam-break flows is the link between the solid transport and the hydrodynamic variables. This paper presents a comparative analysis of different sediment transport formulations applied to dam-break flows over mobile beds. All the formulations analysed are commonly used in morphological studies in rivers, and include the formulas of Meyer-Peter & Müller (1948), Wong-Parker (2003), Einstein-Brown (1950), van Rijn (1984), Engelund-Hansen (1967), Ackers-White (1973), Yang (1973), and a Meyer-Peter & Müller type formula but with ad-hoc coefficients. The relevance of corrections on the sediment flux direction and magnitude due to the bed slope and the non-equilibrium hypothesis is also analysed. All the formulations have been implemented in the numerical model Iber (Bladé et al. (2014)), which solves the depth-averaged shallow water equations coupled to the Exner equation to evaluate the bed evolution. Two different test cases have been studied. The first one is the benchmark case presented in Soares-Frazao et al. (2012), and consists in an instanteneous dam-break flow over a sand bed. The second one corresponds to the experimental studies performed at the Engineering Faculty of the UNAM (Fuentes-Mariles et al. (2010)) and consists in the erosion of a volcanic sand dike by an overtopping flow. In both cases experimental measurements of water depth and bed evolution are available to evaluate the performance of different sediment transport formulations. A sensitivity analysis to the physical properties of the bed material (grain density and size) is also presented for each formulation, in order to analyse to which degree the properties of the bed material need to be defined in the numerical model. References Bladé, E., Cea, L., Corestein, G., Escolano, E., Puertas, J., Vázquez-Cendón, M.E., Dolz, J., Coll, A. (2014). Iber: herramienta de simulación numérica del flujo en ríos. Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería, Vol.30(1), pp.1-10 Fuentes-Mariles, Ó. A., Cruz-Gerón, J. A., Rivera-Díaz, C., Luna-Cruz, F., and González-Prado, J. (2010). "Caracterización Experimental de Ruptura de Diques." XXIV Congreso Latinoamericano de Hidráulica Soares-Frazão et al. (2012). Dambreak flows over mobile beds: experiments and benchmark tests for numerical models. Journal of Hydraulic Research, Vol.50(4), pp.364-375

Hydrogeologic controls imposed by mechanical stratigraphy in layered rocks of the Châteauguay River Basin, a U.S.-Canada transborder aquifer

NASA Astrophysics Data System (ADS)

Morin, Roger; Godin, RéJean; Nastev, Miroslav; Rouleau, Alain

2007-04-01

The Châteauguay River Basin delineates a transborder watershed with roughly half of its surface area located in northern New York State and half in southern Québec Province, Canada. As part of a multidisciplinary study designed to characterize the hydrogeologic properties of this basin, geophysical logs were obtained in 12 wells strategically located to penetrate the four major sedimentary rock formations that constitute the regional aquifers. The layered rocks were classified according to their elastic properties into three primary units: soft sandstone, hard sandstone, and dolostone. Downhole measurements were analyzed to identify fracture patterns associated with each unit and to evaluate their role in controlling groundwater flow. Fracture networks are composed of orthogonal sets of laterally extensive, subhorizontal bedding plane partings and bed-delimited, subvertical joints with spacings that are consistent with rock mechanics principles and stress models. The vertical distribution of transmissive zones is confined to a few select bedding plane fractures, with soft sandstone having the fewest (one per 70-m depth) and hard sandstone the most (five per 70-m depth). Bed-normal permeability is examined using a probabilistic model that considers the lengths of flow paths winding along joints and bedding plane fractures. Soft sandstone has the smallest bed-normal permeability primarily because of its wide, geomechanically undersaturated joint spacing. Results indicate that the three formations have similar values of bulk transmissivity, within roughly an order of magnitude, but that each rock unit has its own unique system of groundwater flow paths that constitute that transmissivity.

Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport

NASA Astrophysics Data System (ADS)

Lamb, Michael P.; Brun, Fanny; Fuller, Brian M.

2017-09-01

Steep mountain streams have higher resistance to flow and lower sediment transport rates than expected by comparison with low gradient rivers, and often these differences are attributed to reduced near-bed flow velocities and stresses associated with form drag on channel forms and immobile boulders. However, few studies have directly measured drag and lift forces acting on bed sediment for shallow flows over coarse sediment, which ultimately control sediment transport rates and grain-scale flow resistance. Here we report on particle lift and drag force measurements in flume experiments using a planar, fixed cobble bed over a wide range of channel slopes (0.004 < S < 0.3) and water discharges. Drag coefficients are similar to previous findings for submerged particles (CD ˜ 0.7) but increase significantly for partially submerged particles. In contrast, lift coefficients decrease from near unity to zero as the flow shallows and are strongly negative for partially submerged particles, indicating a downward force that pulls particles toward the bed. Fluctuating forces in lift and drag decrease with increasing relative roughness, and they scale with the depth-averaged velocity squared rather than the bed shear stress. We find that, even in the absence of complex bed topography, shallow flows over coarse sediment are characterized by high flow resistance because of grain drag within a roughness layer that occupies a significant fraction of the total flow depth, and by heightened critical Shields numbers and reduced sediment fluxes because of reduced lift forces and reduced turbulent fluctuations.

Hydrogeologic controls imposed by mechanical stratigraphy in layered rocks of the Chateauguay River Basin, a U.S.-Canada transborder aquifer

USGS Publications Warehouse

Morin, Roger H.; Godin, Rejean; Nastev, Miroslav; Rouleau, Alain

2007-01-01

[1] The Châteauguay River Basin delineates a transborder watershed with roughly half of its surface area located in northern New York State and half in southern Québec Province, Canada. As part of a multidisciplinary study designed to characterize the hydrogeologic properties of this basin, geophysical logs were obtained in 12 wells strategically located to penetrate the four major sedimentary rock formations that constitute the regional aquifers. The layered rocks were classified according to their elastic properties into three primary units: soft sandstone, hard sandstone, and dolostone. Downhole measurements were analyzed to identify fracture patterns associated with each unit and to evaluate their role in controlling groundwater flow. Fracture networks are composed of orthogonal sets of laterally extensive, subhorizontal bedding plane partings and bed-delimited, subvertical joints with spacings that are consistent with rock mechanics principles and stress models. The vertical distribution of transmissive zones is confined to a few select bedding plane fractures, with soft sandstone having the fewest (one per 70-m depth) and hard sandstone the most (five per 70-m depth). Bed-normal permeability is examined using a probabilistic model that considers the lengths of flow paths winding along joints and bedding plane fractures. Soft sandstone has the smallest bed-normal permeability primarily because of its wide, geomechanically undersaturated joint spacing. Results indicate that the three formations have similar values of bulk transmissivity, within roughly an order of magnitude, but that each rock unit has its own unique system of groundwater flow paths that constitute that transmissivity.

A numerical investigation of wave-breaking-induced turbulent coherent structure under a solitary wave

NASA Astrophysics Data System (ADS)

Zhou, Zheyu; Sangermano, Jacob; Hsu, Tian-Jian; Ting, Francis C. K.

2014-10-01

To better understand the effect of wave-breaking-induced turbulence on the bed, we report a 3-D large-eddy simulation (LES) study of a breaking solitary wave in spilling condition. Using a turbulence-resolving approach, we study the generation and the fate of wave-breaking-induced turbulent coherent structures, commonly known as obliquely descending eddies (ODEs). Specifically, we focus on how these eddies may impinge onto bed. The numerical model is implemented using an open-source CFD library of solvers, called OpenFOAM, where the incompressible 3-D filtered Navier-Stokes equations for the water and the air phases are solved with a finite volume scheme. The evolution of the water-air interfaces is approximated with a volume of fluid method. Using the dynamic Smagorinsky closure, the numerical model has been validated with wave flume experiments of solitary wave breaking over a 1/50 sloping beach. Simulation results show that during the initial overturning of the breaking wave, 2-D horizontal rollers are generated, accelerated, and further evolve into a couple of 3-D hairpin vortices. Some of these vortices are sufficiently intense to impinge onto the bed. These hairpin vortices possess counter-rotating and downburst features, which are key characteristics of ODEs observed by earlier laboratory studies using Particle Image Velocimetry. Model results also suggest that those ODEs that impinge onto bed can induce strong near-bed turbulence and bottom stress. The intensity and locations of these near-bed turbulent events could not be parameterized by near-surface (or depth integrated) turbulence unless in very shallow depth.

Estimated and measured bridge scour at selected sites in North Dakota, 1990-97

USGS Publications Warehouse

Williams-Sether, Tara

1999-01-01

A Level 2 bridge scour method was used to estimate scour depths at 36 selected bridge sites located on the primary road system throughout North Dakota. Of the 36 bridge sites analyzed, the North Dakota Department of Transportation rated 15 as scour critical. Flood and scour data were collected at 19 of the 36 selected bridge sites during 1990-97. Data collected were sufficient to estimate pier scour but not contraction or abutment scour. Estimated pier scour depths ranged from -10.6 to -1.2 feet, and measured bed-elevation changes at piers ranged from -2.31 to +2.37 feet. Comparisons between the estimated pier scour depths and the measured bed-elevation changes indicate that the pier scour equations overestimate scour at bridges in North Dakota.A Level 1.5 bridge scour method also was used to estimate scour depths at 495 bridge sites located on the secondary road system throughout North Dakota. The North Dakota Department of Transportation determined that 26 of the 495 bridge sites analyzed were potentially scour critical.

Adsorption characteristics of activated carbon fibers (ACFs) for toluene: application in respiratory protection.

PubMed

Balanay, Jo Anne G; Bartolucci, Alfred A; Lungu, Claudiu T

2014-01-01

Granular activated carbon (GAC) is currently the standard adsorbent in respirators against several gases and vapors because of its efficiency, low cost, and available technology. However, a drawback of GAC due to its granular form is its need for containment, adding weight and bulkiness to respirators. This makes respirators uncomfortable to wear, resulting in poor compliance in their use. Activated carbon fibers (ACF) are considered viable alternative adsorbent materials for developing thinner, light-weight, and efficient respirators because of their larger surface area, lighter weight, and fabric form. This study aims to determine the critical bed depth and adsorption capacity of different types of commercially available ACFs for toluene to understand how thin a respirator can be and the service life of the adsorbents, respectively. ACF in cloth (ACFC) and felt (ACFF) forms with three different surface areas per form were tested. Each ACF type was challenged with six concentrations of toluene (50, 100, 200, 300, 400, 500 ppm) at constant air temperature (23°C), relative humidity (50%), and airflow (16 LPM) at different adsorbent weights and bed depths. Breakthrough data were obtained for each adsorbent using gas chromatography with flame ionization detector. The ACFs' surface areas were measured by an automatic physisorption analyzer. The results showed that ACFC has a lower critical bed depth and higher adsorption capacity compared to ACFF with similar surface area for each toluene concentration. Among the ACF types, ACFC2000 (cloth with the highest measured surface area of 1614 ± 5 m(2)/g) has one of the lowest critical bed depths (ranging from 0.11-0.22 cm) and has the highest adsorption capacity (ranging from 595-878 mg/g). Based on these studied adsorption characteristics, it is concluded that ACF has great potential for application in respiratory protection against toluene, particularly the ACFC2000, which is the best candidate for developing thinner and efficient respirators.

Comparison of toluene adsorption among granular activated carbon and different types of activated carbon fibers (ACFs).

PubMed

Balanay, Jo Anne G; Crawford, Shaun A; Lungu, Claudiu T

2011-10-01

Activated carbon fiber (ACF) has been demonstrated to be a good adsorbent for the removal of organic vapors in air. Some ACF has a comparable or larger surface area and higher adsorption capacity when compared with granular activated carbon (GAC) commonly used in respiratory protection devices. ACF is an attractive alternative adsorbent to GAC because of its ease of handling, light weight, and decreasing cost. ACF may offer the potential for short-term respiratory protection for first responders and emergency personnel. This study compares the critical bed depths and adsorption capacities for toluene among GAC and ACF of different forms and surface areas. GAC and ACF in cloth (ACFC) and felt (ACFF) forms were challenged in stainless steel chambers with a constant concentration of 500 ppm toluene via conditioned air at 25°C, 50% RH, and constant airflow (7 L/min). Breakthrough data were obtained for each adsorbent using gas chromatography with flame ionization detector. Surface areas of each adsorbent were determined using a physisorption analyzer. Results showed that the critical bed depth of GAC is 275% higher than the average of ACFC but is 55% lower than the average of ACFF. Adsorption capacity of GAC (with a nominal surface area of 1800 m(2)/g) at 50% breakthrough is 25% higher than the average of ACF with surface area of 1000 m(2)/g, while the rest of ACF with surface area of 1500 m(2)/g and higher have 40% higher adsorption capacities than GAC. ACFC with higher surface area has the smallest critical bed depth and highest adsorption capacity, which makes it a good adsorbent for thinner and lighter respirators. We concluded that ACF has great potential for application in respiratory protection considering its higher adsorption capacity and lower critical bed depth in addition to its advantages over GAC, particularly for ACF with higher surface area.

Erosion Characteristics and Horizontal Variability for Small Erosion Depths in the Sacramento - San Joaquin River Delta, California, USA

NASA Astrophysics Data System (ADS)

Schoellhamer, D. H.; Manning, A. J.; Work, P. A.

2015-12-01

Cohesive sediment in the Sacramento-San Joaquin River Delta affects pelagic fish habitat, contaminant transport, and marsh accretion. Observations of suspended-sediment concentration in the delta indicate that about 0.05 to 0.20 kg/m2 are eroded from the bed during a tidal cycle. If erosion is horizontally uniform, the erosion depth is about 30 to 150 microns, the typical range in diameter of suspended flocs. Application of an erosion microcosm produces similarly small erosion depths. In addition, core erodibility in the microcosm calculated with a horizontally homogeneous model increases with depth, contrary to expectations for a consolidating bed, possibly because the eroding surface area increases as applied shear stress increases. Thus, field observations and microcosm experiments, combined with visual observation of horizontally varying biota and texture at the surface of sediment cores, indicate that a conceptual model of erosion that includes horizontally varying properties may be more appropriate than assuming horizontally homogeneous erosive properties. To test this hypothesis, we collected five cores and measured the horizontal variability of shear strength within each core in the top 5.08 cm with a shear vane. Small tubes built by a freshwater worm and macroalgae were observed on the surface of all cores. The shear vane was inserted into the sediment until the top of the vane was at the top of the sediment, torque was applied to the vane until the sediment failed and the vane rotated, and the corresponding dial reading in Nm was recorded. The dial reading was assumed to be proportional to the surface strength. The horizontal standard deviation of the critical shear stress was about 30% of the mean. Results of the shear vane test provide empirical evidence that surface strength of the bed varies horizontally. A numerical simulation of erosion with an areally heterogeneous bed reproduced erosion characteristics observed in the microcosm.

Geomorphology of the north flank of the Uinta Mountains

USGS Publications Warehouse

Bradley, W.H.

1936-01-01

beds now form hogbacks ranked along the sides of the fold. In places large faults, approximating the regional strike, cut these steeply inclined beds. Gently warped Tertiary sediments, mostly of Eocene age, fill the large Green River Basin, which lies north of the range, to a depth of several thousand feet and lap up on the flanks of the mountains, from which they were chiefly derived.

Using Remote-sensing to Survey Topography and Morphologic Change on Large Braided River Beds

NASA Astrophysics Data System (ADS)

Maurice, D.; Hicks, M.; Shankar, U.

2007-12-01

Since 1999 we have made extensive use of a variety of remote-sensing technologies to survey bed topography over reaches of large braided gravel-bed rivers on the east coast of New Zealand's South Island. The motivations have been (i) to collect input and validation data for 2-d hydrodynamic models for quantifying in-stream physical habitat and for predicting flood levels and (ii) to survey spatially-distributed riverbed erosion and deposition in order to estimate bedload fluxes by the 'morphological' method. Typical applications have been to river reaches 3-4 km long and 1 km wide, with grid cells from 1-5 m. We use different techniques to survey dry and wet areas of braided riverbed. For dry areas, we have used digital photogrammetry and infra-red airborne LiDAR. For wetted channels, we have generally used ortho-rectified colour imagery or multi-spectral scanning to map water depth, then we map bed topography by subtracting the water depth from a DEM of the water surface obtained from photogrammetry or LiDAR. The imagery is calibrated to water depth using field measurements on the day of imagery acquisition. Surveys are undertaken during low flows to maximise bed exposure. We use ground-based RTK-GPS and echo-sounding to collect calibration and validation data, and sometimes simply use these methods to survey the wetted areas. Orthoimagery at multiple river flows is used to validate 2-d model results. We have been able to achieve elevation accuracies at interpolated points of the order of 10-15 cm for dry areas. This accuracy typically degrades to 20-30 cm for wetted areas. Our experience has exposed a number of issues relating to survey accuracy and practicality at large river scales. These include: changing geoidal models between surveys; local systematic error with photogrammetric model mosaics; geospatial synchronisation of multi-platform data; time-synchronisation of LiDAR and imagery- collecting aeroplanes and suitable weather and river conditions; confusions in water depth mapping; and the critical importance of good data at key hydraulic controls for eco-hydrologic applications. We suggest that high resolution bathymetric LiDAR offers the best potential for future surveys in large river reaches. While the current bathymetry LiDAR systems do not appear to deliver a significantly better accuracy of submerged bed elevations than we have achieved with mixed-technology approaches for dry and wet areas, and their cost remains high, a one-stop package is hard to beat in terms of practicality and data synchronisation.

Some technical issues on utilizing borehole breakouts for in-situ stress estimation in deepwater sediments

NASA Astrophysics Data System (ADS)

Lee, H.; Chang, C.; Ong, S.; Song, I.

2013-12-01

Stress-induced borehole breakouts have long been used as a reliable indicator of both the orientation and magnitude of in-situ stresses on the basis of the systematic alignment with the minimum horizontal principal far-field stress (σh), and the well-defined correlation between the breakout dimensions and in-situ stress magnitudes. Although breakouts can serve as a reliable stress indicator, cautions must be exercised when using them to constrain the orientation and magnitude of in-situ stresses because the breakout geometry can be altered by some geological characteristics in addition to the usual geomechanical parameters. Two factors are discussed here. We observed alterations in breakout geometry from some of the boreholes drilled along a transection of the Nankai subduction zone. In the C0002A hole, breakouts formed along the depth interval where the beddings are horizontal or sub-horizontal were consistently oriented along the regional σh direction. In contrast, a gradual rotation in breakout orientation with depth and a significant breakout widening at the borehole wall were observed along the deeper section where the beddings are steep (>40o). A geomechanical modeling taking into account the bedding effect shows that such breakout rotation and widening result from strength anisotropy inherent within the thinly bedded formations, and the misalignment between in-situ stresses and bedding dip directions. The model also revealed that there is a considerable difference in the stress magnitudes estimated with and without considering the bedding effect particularly in the steeply bedding intervals. This observation suggests that bedding effects on breakout geometry must be taken into account when using breakouts developed in such formations to estimate the orientation and magnitude of in-situ stresses, failure which would likely to lead to erroneous results. The second factor to discuss is the time-dependent growth of breakouts. While it was straightforward to estimate the stress direction based on the breakout azimuth, an ambiguity occurred when the breakout width widened significantly with time. Two independent borehole wall images of the same depth interval, captured at the bottom and the top of a 30m long logging-while-drilling (LWD) bottom-hole-assembly, indicate that breakout widths grew from 42o immediately after bit run to 135o about an hour later. Triaxial compression tests in cores revealed that all the specimens failed in a brittle mode immediately when the stresses reach the condition required for failure, suggesting that for the purpose of stress estimation, the use of breakout width immediately after the drill-bit passes is appropriate.

Removal of hexavalent chromium by biosorption process in rotating packed bed.

PubMed

Panda, M; Bhowal, A; Datta, S

2011-10-01

Removal of hexavalent chromium ions from an aqueous solution by crude tamarind (Tamarindus indica) fruit shell was examined in a rotating packed bed contactor by continuously recirculating a given volume of solution through the bed. Reduction of Cr(VI) to Cr(III) within the biosorbent appeared to be the removal mechanism. Depletion rate of Cr(VI) from, and release of reduced Cr(III) ions into the aqueous phase, was influenced by mass transfer resistance besides pH and packing depth. A mathematical model considering the reduction reaction to be irreversible and incorporating intraparticle and external phase mass transfer resistances represented the experimental data adequately. The study indicated that the limitations of fixed bed contactor operating under terrestrial gravity in intensifying mass transfer rates for this system can be overcome with rotating packed bed due to liquid flow under centrifugal acceleration.

Preliminary report on the lignite resources of the Niobe area, Burke and Ward counties, North Dakota

USGS Publications Warehouse

Owen, Hal E.

1977-01-01

Two lignite beds, the Niobe and the Bonus, occur at strippable depths within the Niobe area. The Niobe bed averages 5 feet (1.5 meters) in thickness and the Bonus bed averages 8 feet (2.4 meters) in thickness. These beds lie in the lower part of the Sentinel Butte Member of the Fort Union Formation (Paleocene). The demonstrated resources of both beds combined is 122 million tons (110 million tonnes), all of which are under less than 120 feet (37 meters) of overburden. The overburden consists of glacial till and shale. The lateral continuity of the coal has been locally interrupted by faulting, glacial outwash channels, and erosion. Folding and/or faulting occurs parallel to the Missouri Coteau escarpment and faulting occurs roughly perpendicular to the escarpment.

Capacity and Utilization in Health Care: The Effect of Empty Beds on Neonatal Intensive Care Admission

PubMed Central

Freedman, Seth

2016-01-01

Because geographic variation in medical care utilization is jointly determined by both supply and demand, it is difficult to empirically estimate whether capacity itself has a causal impact on utilization in health care. In this paper, I exploit short-term variation in Neonatal Intensive Care Unit (NICU) capacity that is unlikely to be correlated with unobserved demand determinants. I find that available NICU beds have little to no effect on NICU utilization for the sickest infants, but do increase utilization for those in the range of birth weights where admission decisions are likely to be more discretionary. PMID:27942353

Morpho-structure and sedimentology of the Holocene Ebro prodelta mud belt (northwestern Mediterranean Sea)

USGS Publications Warehouse

Diaz, J.I.; Palanques, A.; Nelson, C.H.; Guillen, J.

1996-01-01

The Ebro "mud belt" is a Holocene prodeltaic deposit which has developed around, and southwestward from, the present Ebro Delta plain, covering most of the inner and middle Ebro continental shelf. Seismic-reflection profiles of this mud belt exhibit a complex sigmoid-oblique configuration. Top-set strata dip gently seaward to the 20 m isobath, and overly the fore-set beds which are exposed in up to 40-60 m water depth. Top-set and fore-set beds have mostly parallel and high continuity reflectors. Thin, acoustically transparent bottom-set beds are present at the base of the fore-set beds and extend to the distal edge of the prodelta (60-80 m water depth), where they overly relict transgressive sand deposits. There is no evidence of mass movement. The suspended load discharged by the river is mainly transported alongshelf by advective processes. This dynamics produces thin clinoform deposits that extend alongshelf for tens of kilometres. Mud belt deposition began about 10,000-11,000 years BP. Accumulation rate ranges from less than 0.5 mm y-1 on the seaward and southern edges of the deposit to about 2.5 mm y-1 near the present river mouth. Copyright ?? 1995 Elsevier Science Ltd. All rights reserved.

Taking movement data to new depths: Inferring prey availability and patch profitability from seabird foraging behavior.

PubMed

Chimienti, Marianna; Cornulier, Thomas; Owen, Ellie; Bolton, Mark; Davies, Ian M; Travis, Justin M J; Scott, Beth E

2017-12-01

Detailed information acquired using tracking technology has the potential to provide accurate pictures of the types of movements and behaviors performed by animals. To date, such data have not been widely exploited to provide inferred information about the foraging habitat. We collected data using multiple sensors (GPS, time depth recorders, and accelerometers) from two species of diving seabirds, razorbills ( Alca torda , N  = 5, from Fair Isle, UK) and common guillemots ( Uria aalge , N  = 2 from Fair Isle and N  = 2 from Colonsay, UK). We used a clustering algorithm to identify pursuit and catching events and the time spent pursuing and catching underwater, which we then used as indicators for inferring prey encounters throughout the water column and responses to changes in prey availability of the areas visited at two levels: individual dives and groups of dives. For each individual dive ( N  = 661 for guillemots, 6214 for razorbills), we modeled the number of pursuit and catching events, in relation to dive depth, duration, and type of dive performed (benthic vs. pelagic). For groups of dives ( N  = 58 for guillemots, 156 for razorbills), we modeled the total time spent pursuing and catching in relation to time spent underwater. Razorbills performed only pelagic dives, most likely exploiting prey available at shallow depths as indicated by the vertical distribution of pursuit and catching events. In contrast, guillemots were more flexible in their behavior, switching between benthic and pelagic dives. Capture attempt rates indicated that they were exploiting deep prey aggregations. The study highlights how novel analysis of movement data can give new insights into how animals exploit food patches, offering a unique opportunity to comprehend the behavioral ecology behind different movement patterns and understand how animals might respond to changes in prey distributions.

Sediment mobility in fish bearing streams: the influence of floods and spawning salmon

NASA Astrophysics Data System (ADS)

Hassan, M. A.; Gottesfeld, A. S.; Tunnicliffe, J. F.

2002-12-01

Magnetically tagged particles were used to investigate the effects of sockeye salmon (Oncorhynchus nerka) on the mobility of substrate in gravel bed streams in the Stuart-Takla region of north-central British Columbia. The study reaches in Forfar and O'Ne-ell Creeks have gradients of from 0.005 to 0.019 and have a forced pool-riffle morphology. The dominant annual sediment-transporting event in the channels is the snow-melt flood events in late May or June, with lesser work usually accomplished during summer and fall storm floods. In August every year, the channel beds material is reworked by the Early Stuart salmon spawning event, as the fish excavated the streambed to deposit and bury their eggs. At each of the 5 reaches within the 2 study creeks, 250 tracers (8.5mm - 180mm) were placed in a line on the bed before and after transport events. Results were highly variable, subject to the magnitude of floods, and the returning population of salmon. Overall, the depositional pattern from nival flood events usually demonstrated a high degree of clast mobilization, long travel distances (up to 150m) and mean depths of burial up to 18cm. Storm flood events showed somewhat lower rates of mobilization, distances of travel and depths of burial. Although the fish did not move the tracers very far, their effect on the bed was generally quite pervasive: up to 100% of the clasts were mobilized, and the depth of burial was considerable (mean burial depths up to 14cm). Repeat topographic surveys of the streambed before and after transport events revealed considerable disruption of the bed surface. The geomorphic effect of fish was enhanced in the lower reaches where the hydraulic transporting capacity is somewhat less (lower stream power), the sediment calibre is finer, and fish spawning density is higher. The amount of sediment mobilized by salmonids is often on the same order of magnitude as flood events. The significant vertical mixing of sediments by the fish has important implications for the mobility of sediment in the stream. Since any armouring layer formed during high flows throughout the year are subject to the bioturbation of salmonids, the transport threshold in the creeks remains relatively low. Salmonids thus play an integral role in the annual sediment budget of the lower reaches of these creeks.

Batch and fixed-bed biosorption of Cd(II) from aqueous solution using immobilized Pleurotus ostreatus spent substrate.

PubMed

Jin, Yu; Teng, Chunying; Yu, Sumei; Song, Tao; Dong, Liying; Liang, Jinsong; Bai, Xin; Liu, Xuesheng; Hu, Xiaojing; Qu, Juanjuan

2018-01-01

To prevent the blockage in a continuous fix-bed system, Pleurotus Ostreatus spent substrate (POSS), a composite agricultural waste, was immobilized into granular adsorbents (IPOSS) with polymeric matrix, and used to remove Cd(II) from synthetic wastewater in batch experiment as well as in continuous fixed-bed column system. In batch experiment, higher pH, temperature and Cd(II) initial concentration were conducive to a higher biosorption capacity, and the maximum biosorption capacity reached up to 87.2 mg/g at Cd(II) initial concentration of 200 mg/L, pH 6 and 25 °C. The biosorption of Cd(II) onto IPOSS followed the Langmuir isotherm model with the maximum adsorption capacity(q max ) of 100 mg/g. The biosorption was an endothermic reaction and a spontaneous process based on positive value of ΔH 0 and negative value of ΔG 0 . In fixed-bed column system, higher bed depth, lower flow rate and influent Cd(II) concentration led to a longer breakthrough and exhaustion time, and the best performance (equilibrium uptake (q e ) of 14.4 mg, breakthrough time at 31 h and exhaustion time at 78 h) was achieved at a bed depth of 110 cm, a flow rate of 1.2 L/h and an influent concentration of 100 mg/L. Furthermore, regeneration experiment revealed a good reusability of IPOSS with 0.1 M HNO 3 as eluting agent during three cycles of adsorption and desorption. Cd(II) biosorption onto IPOSS mainly relied on a chemical process including ion exchange and complexation or coordination revealed by SEM-EDX, FTIR and XRD analysis. Copyright © 2017. Published by Elsevier Ltd.

Functional relationships between vegetation, channel morphology, and flow efficiency in an alluvial (anabranching) river

NASA Astrophysics Data System (ADS)

Jansen, John D.; Nanson, Gerald C.

2010-12-01

Water and sediment flux interactions are examined in Magela Creek, an alluvial (anabranching) sand bed river in the northern Australian tropics. Dense riparian vegetation stabilizes the channels and floodplains thereby preventing erosional instability at flow depths up to 6.2 times bankfull and discharges up to 15 times bankfull. Narrow anabranching channels characterize >92% of the alluvial reach and transport bed load more efficiently than short reaches of wide single-channels, yet overall 29 ± 12% of the bed load is sequestered and the average vertical accretion rate is 0.41 ± 0.17 mm yr-1 along the 12 km study reach. The most effective discharge for transporting sediment (40-45 m3 s-1) is consistent at all 5 stations (10 channels) examined and is equivalent to the channel-forming discharge. It has an average recurrence interval of 1.01 years, occurs for an exceptionally long portion (13-15%) of the annual flow duration, and averages a remarkable 2.1 times bankfull. The high flow efficiency (i.e., bed load transport rate to stream power ratio) of the anabranches is facilitated by low width/depth channels with banks reinforced by vegetation. Colonnades of bank top trees confine high-velocity flows overbed (i.e., over the channel bed) at stages well above bankfull. At even larger overbank flows, momentum exchange between the channels and forested floodplains restrains overbed velocities, in some cases causing them to decline, thereby limiting erosion. Magela Creek exhibits a complicated set of planform, cross-sectional and vegetative adjustments that boost overbed velocities and enhance bed load yield in multiple channels while restraining velocities and erosion at the largest discharges.

Factors affecting cleanup of exhaust gases from a pressurized, fluidized-bed coal combustor

NASA Technical Reports Server (NTRS)

Rollbuhler, R. J.; Kobak, J. A.

1980-01-01

The cleanup of effluent gases from the fluidized-bed combustion of coal is examined. Testing conditions include the type and feed rate of the coal and the sulfur sorbent, the coal-sorbent ratio, the coal-combustion air ratio, the depth of the reactor fluidizing bed, and the technique used to physically remove fly ash from the reactor effluent gases. Tests reveal that the particulate loading matter in the effluent gases is a function not only of the reactor-bed surface gas velocity, but also of the type of coal being burnt and the time the bed is operating. At least 95 percent of the fly ash particules in the effluent gas are removed by using a gas-solids separator under controlled operating conditions. Gaseous pollutants in the effluent (nitrogen and sulfur oxides) are held within the proposed Federal limits by controlling the reactor operating conditions and the type and quantity of sorbent material.

CFD-DEM Onset of Motion Analysis for Application to Bed Scour Risk Assessment

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

Sitek, M. A.; Lottes, S. A.

This CFD study with DEM was done as a part of the Federal Highway Administration’s (FHWA’s) effort to improve scour design procedures. The Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model, available in CD-Adapco’s StarCCM+ software, was used to simulate multiphase systems, mainly those which combine fluids and solids. In this method the motion of discrete solids is accounted for by DEM, which applies Newton's laws of motion to every particle. The flow of the fluid is determined by the local averaged Navier–Stokes equations that can be solved using the traditional CFD approach. The interactions between the fluid phase and solidsmore » phase are modeled by use of Newton's third law. The inter-particle contact forces are included in the equations of motion. Soft-particle formulation is used, which allows particles to overlap. In this study DEM was used to model separate sediment grains and spherical particles laying on the bed with the aim to analyze their movement due to flow conditions. Critical shear stress causing the incipient movement of the sediment was established and compared to the available experimental data. An example of scour around a cylindrical pier is considered. Various depths of the scoured bed and flow conditions were taken into account to gain a better understanding of the erosion forces existing around bridge foundations. The decay of these forces with increasing scour depth was quantified with a ‘decay function’, which shows that particles become increasingly less likely to be set in motion by flow forces as a scour hole increases in depth. Computational and experimental examples of the scoured bed around a cylindrical pier are presented.« less

Depth measurements of drilled holes in bone by laser triangulation for the field of oral implantology

NASA Astrophysics Data System (ADS)

Quest, D.; Gayer, C.; Hering, P.

2012-01-01

Laser osteotomy is one possible method of preparing beds for dental implants in the human jaw. A major problem in using this contactless treatment modality is the lack of haptic feedback to control the depth while drilling the implant bed. A contactless measurement system called laser triangulation is presented as a new procedure to overcome this problem. Together with a tomographic picture the actual position of the laser ablation in the bone can be calculated. Furthermore, the laser response is sufficiently fast as to pose little risk to surrounding sensitive areas such as nerves and blood vessels. In the jaw two different bone structures exist, namely the cancellous bone and the compact bone. Samples of both bone structures were examined with test drillings performed either by laser osteotomy or by a conventional rotating drilling tool. The depth of these holes was measured using laser triangulation. The results and the setup are reported in this study.

Adsorption of hexavalent chromium from synthetic and electroplating effluent on chemically modified Swietenia mahagoni shell in a packed bed column.

PubMed

Rangabhashiyam, S; Nandagopal, M S Giri; Nakkeeran, E; Selvaraju, N

2016-07-01

Packed bed column studies were carried out to evaluate the performance of chemically modified adsorbents for the sequestration of hexavalent chromium from synthetic and electroplating industrial effluent. The effects of parameters such as bed height (3-9 cm), inlet flow rate (5-15 mL/min), and influent Cr(VI) concentration (50-200 mg/L) on the percentage removal of Cr(VI) and the adsorption capacity of the adsorbents in a packed bed column were investigated. The breakthrough time increased with increasing bed height and decreased with the increase of inlet flow rate and influent Cr(VI) concentration. The adsorption column models such as Thomas, Adams-Bohart, Yoon-Nelson, and bed depth service time (BDST) were successfully correlated with the experimental data. The Yoon-Nelson and BDST model showed good agreement with the experimental data for all the studied parameter conditions. Results of the present study indicated that the chemically modified Swietenia mahagoni shell can be used as an adsorbent for the removal of Cr(VI) from industrial wastewater in a packed bed column.

Enacting legislation to restrict youth access to tanning beds: a survey of advocates and sponsoring legislators.

PubMed

Obayan, Busayo; Geller, Alan C; Resnick, Elissa A; Demierre, Marie-France

2010-07-01

Passing tanning bed legislation restricting underage use has remained challenging. We sought to determine the resources required to pass tanning bed legislation restricting use to children and identify key barriers to its passage. A total of 15 states sought to pass tanning bed legislation in 2006; in-depth surveys were completed with advocates in 10 states and legislators in 5 states. Advocates sought advice from the sponsoring legislator or legislators (n = 9), held discussions with other organizations (n = 8), and used a lobbyist (n = 5). The 3 major barriers were strong lobbying efforts by the tanning bed industry (n = 10), proceedings after the bill was filed (n = 5), and obtaining support from other organizations (n = 4). For legislators, the most significant barrier was making colleagues aware of the health effects of tanning bed use. Five of 10 legislators and 10 of 15 advocates responded to the survey. Barriers to passage of tanning bed legislation can potentially be surmounted with advice to advocates and coordinated efforts by multiple organizations. Copyright (c) 2009 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.

Relationship Between Faults Oriented Parallel and Oblique to Bedding in Neogene Massive Siliceous Mudstones at The Horonobe Underground Research Laboratory, Japan

NASA Astrophysics Data System (ADS)

Hayano, Akira; Ishii, Eiichi

2016-10-01

This study investigates the mechanical relationship between bedding-parallel and bedding-oblique faults in a Neogene massive siliceous mudstone at the site of the Horonobe Underground Research Laboratory (URL) in Hokkaido, Japan, on the basis of observations of drill-core recovered from pilot boreholes and fracture mapping on shaft and gallery walls. Four bedding-parallel faults with visible fault gouge, named respectively the MM Fault, the Last MM Fault, the S1 Fault, and the S2 Fault (stratigraphically, from the highest to the lowest), were observed in two pilot boreholes (PB-V01 and SAB-1). The distribution of the bedding-parallel faults at 350 m depth in the Horonobe URL indicates that these faults are spread over at least several tens of meters in parallel along a bedding plane. The observation that the bedding-oblique fault displaces the Last MM fault is consistent with the previous interpretation that the bedding- oblique faults formed after the bedding-parallel faults. In addition, the bedding-parallel faults terminate near the MM and S1 faults, indicating that the bedding-parallel faults with visible fault gouge act to terminate the propagation of younger bedding-oblique faults. In particular, the MM and S1 faults, which have a relatively thick fault gouge, appear to have had a stronger control on the propagation of bedding-oblique faults than did the Last MM fault, which has a relatively thin fault gouge.

Ground-water geology of the Gonaives Plain, Haiti

USGS Publications Warehouse

Taylor, George C.; Lemoine, Rémy C.

1950-01-01

The Gonaives Plain lies in northern Haiti at the head of the Gulf of Gonaives. Ground water in the plain is used widely for domestic and stock purposes but only to limited extent for irrigation. The future agricultural development of the plain will depend in large measure on the proper utilization of available ground-water supplies for irrigation. The rocks in the region of the Gonaives Plain belong to the upper (?) Cretaceous series of the Cretaceous system, the Nocene and Oligovene series of the Tertiary system, and the Pleistocene and Recent series of the Quarternary system. The structural depression occupied by the Gonaives Plain was formed in post-Miocene time by the dislocation of Oligocene and older rocks along normal faults and by the tilting of the adjacent crustal blocks. The lower parts of the depression contain a Pleistocene and Recent alluvial fill deposited by streams tributary to the plain. The upper (?) Cretaceous rocks include aniesite and basalt lava flows locally intercalated with some beds of tuff and agglomerate. These rocks are generally dense and impervious but locally small springs rise from fractures and bedding planes or from weathered zones. The Nocene rocks are hard, thin-bedded, cherty limestones with some beds of massive chalky limestone. Considerable ground water circulates through joints, bedding planes, and solution passages in these rocks giving rise to important springs such as Sources Madame Charles. These springs discharge at the rate of about 110 liters per second. The Oligocene rocks include limestone, shely limestone, limy sandstone, marl, and shale. The limestone beds contain solution passages and other openings and these may afford capacity for the circulation of ground water. However, no wells or springs in Oligocene rocks were observed during the present study. The alluvial fill of the plain is composed of interbedded lenses of clay, silt, sand, and gravel. These deposits contain a zone of saturation whose upper limit is marked by a water table. The depth to the water table beneath the alluvial lowland of the plain ranges from less than one meter to about 20 meters. In most places in the plain the depth to water is less that 15 meters. Where present in the zone of saturation the coarse, well-sorted sand and gravel beds of the alluvium will probably yield moderate to large supplies of water to wells and infiltration galleries. The individual yields of existing wells range from a few liters to about 60 liters per second. The most favorable part of the plain for ground-water prospecting and development lies 5 to 10 kilometers northeast of Gonaives. In this area yields of 10 to 50 liters per second could be obtained from the alluvium in simple wells drilled to depths of about 35 to 45 meters. Additional information on the yield and physical character of aquifers in the alluvium would be provided by test wells drilled to depths of 40 to 60 meters.

Rapid change with depth in megabenthic structure-forming communities of the Makapu'u deep-sea coral bed

NASA Astrophysics Data System (ADS)

Long, Dustin J.; Baco, Amy R.

2014-01-01

Seamounts are largely unexplored undersea mountains rising abruptly from the ocean floor, which can support an increased abundance and diversity of organisms. Deep-sea corals are important benthic structure-formers on current-swept hard substrates in these habitats. While depth is emerging as a factor structuring the fauna of seamounts on a large spatial scale, most work addressing deep-sea coral and seamount community structure has not considered the role of small-scale variation in species distributions. Video from six ROV dives over a depth range of ~320-530 m were analyzed to assess the diversity and density of benthic megafaunal invertebrates across the Makapu'u deep-sea coral bed, offshore of Oahu, Hawaii. At the same time, the physical environment along the dive track was surveyed to relate biotic patterns with abiotic variables including depth, aspect, rugosity, substrate, slope and relief to test the factors structuring community assemblages. Despite the narrow range examined, depth was found to be the strongest structuring gradient, and six unique macrobenthic communities were found, with a 93% faunal dissimilarity over the depth surveyed. Relief, rugosity and slope were also factors in the final model. Alcyonacean octocorals were the dominant macrofaunal invertebrates at all but the deepest depth zone. The commercially harvested precious coral C. secundum was the dominant species at depths 370-470 m, with a distribution that is on average deeper than similar areas. This may be artificial due to the past harvesting of this species on the shallower portion of its range. Primnoid octocorals were the most abundant octocoral family overall. This work yields new insight on the spatial ecology of seamounts, pointing out that community changes can occur over narrow depth ranges and that communities can be structured by small-scale physiography.

Run-of-River Impoundments Can Remain Unfilled While Transporting Gravel Bedload: Numerical Modeling Results

NASA Astrophysics Data System (ADS)

Pearson, A.; Pizzuto, J. E.

2015-12-01

Previous work at run-of-river (ROR) dams in northern Delaware has shown that bedload supplied to ROR impoundments can be transported over the dam when impoundments remain unfilled. Transport is facilitated by high levels of sand in the impoundment that lowers the critical shear stresses for particle entrainment, and an inversely sloping sediment ramp connecting the impoundment bed (where the water depth is typically equal to the dam height) with the top of the dam (Pearson and Pizzuto, in press). We demonstrate with one-dimensional bed material transport modeling that bed material can move through impoundments and that equilibrium transport (i.e., a balance between supply to and export from the impoundment, with a constant bed elevation) is possible even when the bed elevation is below the top of the dam. Based on our field work and previous HEC-RAS modeling, we assess bed material transport capacity at the base of the sediment ramp (and ignore detailed processes carrying sediment up and ramp and over the dam). The hydraulics at the base of the ramp are computed using a weir equation, providing estimates of water depth, velocity, and friction, based on the discharge and sediment grain size distribution of the impoundment. Bedload transport rates are computed using the Wilcock-Crowe equation, and changes in the impoundment's bed elevation are determined by sediment continuity. Our results indicate that impoundments pass the gravel supplied from upstream with deep pools when gravel supply rate is low, gravel grain sizes are relatively small, sand supply is high, and discharge is high. Conversely, impoundments will tend to fill their pools when gravel supply rate is high, gravel grain sizes are relatively large, sand supply is low, and discharge is low. The rate of bedload supplied to an impoundment is the primary control on how fast equilibrium transport is reached, with discharge having almost no influence on the timing of equilibrium.

Coupling hydrodynamic modeling and empirical measures of bed mobility to assess the risk of redd scour on a large regulated river

Treesearch

Christine L. May; Bonnie S. Pryor; Thomas E. Lisle; Margaret M. Lang

2009-01-01

n order to assess the risk of scour and fill of spawning redds during floods, an understanding of the relations among river discharge, bed mobility, and scour and fill depths in areas of the streambed heavily utilized by spawning salmon is needed. Our approach coupled numerical flow modeling and empirical data from the Trinity River, California, to quantify spatially...

Lewis Pressurized, Fluidized-Bed Combustion Program. Data and Calculated Results

NASA Technical Reports Server (NTRS)

Rollbuhler, R. J.

1982-01-01

A 200 kilowatt (thermal), pressurized, fluidized bed (PFB) reactor and research test facility were designed, constructed, and operated. The facility was established to assess and evaluate the effect of PFB hot gas effluent on aircraft turbine engine materials that may have applications in stationary powerplant turbogenerators. The facility was intended for research and development work and was designed to operate over a wide range of conditions. These conditions included the type and rate of consumption of fuel (e.g., coal) and sulfur reacting sorbent material: the ratio of feed fuel to sorbent material; the ratio of feed fuel to combustion airflow; the depth of the fluidized reaction bed; the temperature and pressure in the reaction bed; and the type of test unit that was exposed to the combustion exhaust gases.

Lewis pressurized, fluidized-bed combustion program. Data and calculated results

NASA Astrophysics Data System (ADS)

Rollbuhler, R. J.

1982-03-01

A 200 kilowatt (thermal), pressurized, fluidized bed (PFB) reactor and research test facility were designed, constructed, and operated. The facility was established to assess and evaluate the effect of PFB hot gas effluent on aircraft turbine engine materials that may have applications in stationary powerplant turbogenerators. The facility was intended for research and development work and was designed to operate over a wide range of conditions. These conditions included the type and rate of consumption of fuel (e.g., coal) and sulfur reacting sorbent material: the ratio of feed fuel to sorbent material; the ratio of feed fuel to combustion airflow; the depth of the fluidized reaction bed; the temperature and pressure in the reaction bed; and the type of test unit that was exposed to the combustion exhaust gases.

Evaluation of a depth proportional intake device for automatic pumping samplers

Treesearch

Rand E. Eads; Robert B. Thomas

1983-01-01

Abstract - A depth proportional intake boom for portable pumping samplers was used to collect suspended sediment samples in two coastal streams for three winters. The boom pivots on the stream bed while a float on the downstream end allows debris to depress the boom and pass without becoming trapped. This equipment modifies point sampling by maintaining the intake...

A Comparison of the Effects of Depth Rotation on Visual and Haptic Three-Dimensional Object Recognition

ERIC Educational Resources Information Center

Lawson, Rebecca

2009-01-01

A sequential matching task was used to compare how the difficulty of shape discrimination influences the achievement of object constancy for depth rotations across haptic and visual object recognition. Stimuli were nameable, 3-dimensional plastic models of familiar objects (e.g., bed, chair) and morphs midway between these endpoint shapes (e.g., a…

Method of regulating the amount of underfire air for combustion of wood fuels in spreader-stroke boilers

DOEpatents

Tuttle, Kenneth L.

1980-01-01

A method of metering underfire air for increasing efficiency and reducing particulate emissions from wood-fire, spreader-stoker boilers is disclosed. A portion of the combustion air, approximately one pound of air per pound of wood, is fed through the grate into the fuel bed, while the remainder of the combustion air is distributed above the fuel in the furnace, and the fuel bed is maintained at a depth sufficient to consume all oxygen admitted under fire and to insure a continuous layer of fresh fuel thereover to entrap charred particles inside the fuel bed.

BRIDGER WILDERNESS AND GREEN-SWEETWATER ROADLESS AREA, WYOMING.

USGS Publications Warehouse

Worl, Ronald G.; Ryan, George S.

1984-01-01

A mineral-resource appraisal of the Bridger Wilderness and contiguous Green-Sweetwater Roadless Area in Wyoming was made. This rugged and remote region is mostly Precambrian crystalline granitic rocks that contain only small and discontinuous areas of mineralization. The area is considered to have little promise for metallic mineral deposits. Sedimentary rocks in the area have minor coal seams and beds of phosphate rock, but the coal beds are thin and of limited extent, and the phosphate rock is low-grade compared to similar rocks elsewhere in the region. A probable potential for oil and gas at depth, assigned to part of the area, is based on the assumption that oil- and gas-bearing rocks exist at depth below a low-angle thrust fault and a wedge of Precambrian crystalline rock.

Impaired Flexible Reward-Based Decision-Making in Binge Eating Disorder: Evidence from Computational Modeling and Functional Neuroimaging.

PubMed

Reiter, Andrea M F; Heinze, Hans-Jochen; Schlagenhauf, Florian; Deserno, Lorenz

2017-02-01

Despite its clinical relevance and the recent recognition as a diagnostic category in the DSM-5, binge eating disorder (BED) has rarely been investigated from a cognitive neuroscientific perspective targeting a more precise neurocognitive profiling of the disorder. BED patients suffer from a lack of behavioral control during recurrent binge eating episodes and thus fail to adapt their behavior in the face of negative consequences, eg, high risk for obesity. To examine impairments in flexible reward-based decision-making, we exposed BED patients (n=22) and matched healthy individuals (n=22) to a reward-guided decision-making task during functional resonance imaging (fMRI). Performing fMRI analysis informed via computational modeling of choice behavior, we were able to identify specific signatures of altered decision-making in BED. On the behavioral level, we observed impaired behavioral adaptation in BED, which was due to enhanced switching behavior, a putative deficit in striking a balance between exploration and exploitation appropriately. This was accompanied by diminished activation related to exploratory decisions in the anterior insula/ventro-lateral prefrontal cortex. Moreover, although so-called model-free reward prediction errors remained intact, representation of ventro-medial prefrontal learning signatures, incorporating inference on unchosen options, was reduced in BED, which was associated with successful decision-making in the task. On the basis of a computational psychiatry account, the presented findings contribute to defining a neurocognitive phenotype of BED.

Impaired Flexible Reward-Based Decision-Making in Binge Eating Disorder: Evidence from Computational Modeling and Functional Neuroimaging

PubMed Central

Reiter, Andrea M F; Heinze, Hans-Jochen; Schlagenhauf, Florian; Deserno, Lorenz

2017-01-01

Despite its clinical relevance and the recent recognition as a diagnostic category in the DSM-5, binge eating disorder (BED) has rarely been investigated from a cognitive neuroscientific perspective targeting a more precise neurocognitive profiling of the disorder. BED patients suffer from a lack of behavioral control during recurrent binge eating episodes and thus fail to adapt their behavior in the face of negative consequences, eg, high risk for obesity. To examine impairments in flexible reward-based decision-making, we exposed BED patients (n=22) and matched healthy individuals (n=22) to a reward-guided decision-making task during functional resonance imaging (fMRI). Performing fMRI analysis informed via computational modeling of choice behavior, we were able to identify specific signatures of altered decision-making in BED. On the behavioral level, we observed impaired behavioral adaptation in BED, which was due to enhanced switching behavior, a putative deficit in striking a balance between exploration and exploitation appropriately. This was accompanied by diminished activation related to exploratory decisions in the anterior insula/ventro-lateral prefrontal cortex. Moreover, although so-called model-free reward prediction errors remained intact, representation of ventro–medial prefrontal learning signatures, incorporating inference on unchosen options, was reduced in BED, which was associated with successful decision-making in the task. On the basis of a computational psychiatry account, the presented findings contribute to defining a neurocognitive phenotype of BED. PMID:27301429

Field evaluation of the error arising from inadequate time averaging in the standard use of depth-integrating suspended-sediment samplers

USGS Publications Warehouse

Topping, David J.; Rubin, David M.; Wright, Scott A.; Melis, Theodore S.

2011-01-01

Several common methods for measuring suspended-sediment concentration in rivers in the United States use depth-integrating samplers to collect a velocity-weighted suspended-sediment sample in a subsample of a river cross section. Because depth-integrating samplers are always moving through the water column as they collect a sample, and can collect only a limited volume of water and suspended sediment, they collect only minimally time-averaged data. Four sources of error exist in the field use of these samplers: (1) bed contamination, (2) pressure-driven inrush, (3) inadequate sampling of the cross-stream spatial structure in suspended-sediment concentration, and (4) inadequate time averaging. The first two of these errors arise from misuse of suspended-sediment samplers, and the third has been the subject of previous study using data collected in the sand-bedded Middle Loup River in Nebraska. Of these four sources of error, the least understood source of error arises from the fact that depth-integrating samplers collect only minimally time-averaged data. To evaluate this fourth source of error, we collected suspended-sediment data between 1995 and 2007 at four sites on the Colorado River in Utah and Arizona, using a P-61 suspended-sediment sampler deployed in both point- and one-way depth-integrating modes, and D-96-A1 and D-77 bag-type depth-integrating suspended-sediment samplers. These data indicate that the minimal duration of time averaging during standard field operation of depth-integrating samplers leads to an error that is comparable in magnitude to that arising from inadequate sampling of the cross-stream spatial structure in suspended-sediment concentration. This random error arising from inadequate time averaging is positively correlated with grain size and does not largely depend on flow conditions or, for a given size class of suspended sediment, on elevation above the bed. Averaging over time scales >1 minute is the likely minimum duration required to result in substantial decreases in this error. During standard two-way depth integration, a depth-integrating suspended-sediment sampler collects a sample of the water-sediment mixture during two transits at each vertical in a cross section: one transit while moving from the water surface to the bed, and another transit while moving from the bed to the water surface. As the number of transits is doubled at an individual vertical, this error is reduced by ~30 percent in each size class of suspended sediment. For a given size class of suspended sediment, the error arising from inadequate sampling of the cross-stream spatial structure in suspended-sediment concentration depends only on the number of verticals collected, whereas the error arising from inadequate time averaging depends on both the number of verticals collected and the number of transits collected at each vertical. Summing these two errors in quadrature yields a total uncertainty in an equal-discharge-increment (EDI) or equal-width-increment (EWI) measurement of the time-averaged velocity-weighted suspended-sediment concentration in a river cross section (exclusive of any laboratory-processing errors). By virtue of how the number of verticals and transits influences the two individual errors within this total uncertainty, the error arising from inadequate time averaging slightly dominates that arising from inadequate sampling of the cross-stream spatial structure in suspended-sediment concentration. Adding verticals to an EDI or EWI measurement is slightly more effective in reducing the total uncertainty than adding transits only at each vertical, because a new vertical contributes both temporal and spatial information. However, because collection of depth-integrated samples at more transits at each vertical is generally easier and faster than at more verticals, addition of a combination of verticals and transits is likely a more practical approach to reducing the total uncertainty in most field situatio

Unusual seismogenic soft-sediment deformation structures in Cambrian epicratonic carbonate deposits, western Colorado, U.S.A

NASA Astrophysics Data System (ADS)

Myrow, P.; Chen, J.

2013-12-01

A wide variety of unusual penecontemporaneous deformation structures exist in grainstone and flat-pebble conglomerate beds of the Upper Cambrian strata, western Colorado, including slide scarps, thrusted beds, irregular blocks and internally deformed beds. Slide scarps are characterized by concave-up, sharp surfaces that truncate one or more underlying beds. Thrusted beds record movement of a part of a bed onto itself along a moderate to steeply inclined (generally 25°-40°) ramp. The hanging wall lenses in cases show fault-bend geometries, with either intact or mildly deformed bedding. Irregular bedded to internally deformed blocks isolated on generally flat upper bedding surfaces are similar in composition to the underlying beds. These features represent parts of beds that were detached, moved up onto, and some distances across, the laterally adjacent undisturbed bed surfaces. The blocks moved either at the sediment-water interface or intrastratally at shallow depths within overlying muddy deposits. Finally, internally deformed beds have large blocks, fitted fabrics of highly irregular fragments, and contorted lamination, which represent heterogeneous deformation, such as brecciation and liquefaction. The various deformation structures were most probably triggered by earthquakes, considering the nature of deformation (regional distribution of liquefaction structures, and the brittle segmentation and subsequent transportation of semi-consolidated beds) and the reactivation of Mesoproterozoic, crustal-scale shear zones in the central Rockies during the Late Cambrian. Features produced by initial brittle deformation are unusual relative to most reported seismites, and may represent poorly recognized to unrecognized seismogenic structures in the rock record.

Influence of bed surface changes on snow avalanche simulation

NASA Astrophysics Data System (ADS)

Fischer, Jan-Thomas; Issler, Dieter

2014-05-01

Gravitational flows, such as snow avalanches, are often modeled employing the shallowness assumption. The driving gravitational force has a first order effect on the dynamics of the flow, especially in complex terrain. Under suitable conditions, erosion and deposition during passage of the flow may change the bed surface by a similar amount as the flow depth itself. The accompanying changes of local slope angle and curvature are particularly significant at the side margins of the flow, where they may induce self-channeling and levée formation. Generally, one ought to expect visible effects wherever the flow depth and velocity are small, e.g., in deposition zones. Most current numerical models in practical use neglect this effect. In order to study the importance of these effects in typical applications, we modified the quasi-3D (depth-averaged) code MoT-Voellmy, which implements the well-known Voellmy friction law that is traditionally used in hazard mapping: The bed shear stress is given by τiz(h,u) = -ui(μgh cosθ+ ku2), ||u|| (1) with μ = O(0.1...0.5) and k = O(10-3...10-2) the dimensionless friction and drag coefficients, respectively. The leading curvature effects, i.e., extra friction due to centrifugal normal forces, are taken into account. The mass and momentum balances are solved by the (simplified) method of transport on a grid whose cells are squares when projected onto the horizontal plane. The direction of depth-averaging is everywhere perpendicular to the topographic surface. A simple erosion model is used. The erosion formula is based on the assumption that the snow cover behaves as a perfectly brittle solid with shear strength τc, above which it instantaneously fails. The erosion rate is derived from the balance of momentum across the interface between bed and flow, where there is a discontinuity of the shear stress, which is given by equation 1 just above the interface and by τc just below it according to the assumptions. This immediately leads to the formula 2 qe = μgh-cosθ+-ku- τc/ρfΘ (μgh cosθ+ ku2 - τc/ρf). ||u|| (2) We present numerical simulations with static and dynamic beds in two different cases. First, an avalanche simulation on an inclined plane allows to study the occurring effects in their most immediate form. This allows to study the influence of spatial resolution of the computational grid. Second, we back-calculate a typical mid-size avalanche that was measured and documented in 1993 at the Norwegian test site Ryggfonn. This case study serves to test the relevance of including bed surface changes under conditions typical of real-world applications.

Prevention of Bridge Scour with Non-uniform Circular Piers Plane under Steady Flows

NASA Astrophysics Data System (ADS)

Chen, Hsing-Ting; Wang, Chuan-Yi

2017-04-01

River bed scour and deposit variation extremely severe because of most of rivers are steep and rapid flows, and river discharge extremely unstable and highly unsteady during different seasons in Taiwan. In addition to the obstruction of piers foundation, it causes local scour and threatens the safety of bridges. In the past, riprap, wire gabion or wrap pier works were adopted as the protections of piers foundation, but there were no effectual outcomes. The events of break off piers still happen sometimes. For example, typhoon Kalmaegi (2008) and Morakot (2009) caused heavy damages on Ho-Fon bridge in the Da-jia river and Shuang-Yuan bridge in the Kao-Ping river, respectively. Accordingly, to understand the piers scour system and propose an appropriate protection of piers foundation becomes an important topic for this study currently. This research improves the protection works of the existing uniform bridge pier (diameter D) to ensure the safety of the bridge. The non-uniform plane of circular piers (diameter D*) are placed on the top of a bridge pier foundation to reduce the down flow impacting energy and scour by its' surface roughness characteristics. This study utilize hydraulic models to simulate local scour depth and scour depth change with time for non-uniform pier diameter ratio D/D* of 0.3,0.4,0.5,0.6,0.7 and 0.8, and different type pier and initial bed level (Y) relative under the foundation top elevation under steady flows of V/Vc=0.95,0.80 and 0.65. The research results show that the scour depth increases with an increase of flow intensity (V/Vc) under different types of steady flow hydrographs. The scour depth decreases with increase of initial bed level (Y=+0.2D*,0D*and -0.2D*) relative under the foundation top elevation of the different type pier. The maximum scour depth occurred in the front of the pier for all conditions. Because of the scouring retardation by the non-uniform plane of foundation, the scour depth is reduced for the un-exposed bridge foundation (Y=+0.2D*) under any steady flows. Opposite results are found for the exposed (Y=-0.2D*) bridge foundation. For the condition non-uniform pier diameter ratio (D/D*=0.3 0.8) scours, when D/D* is equal to 0.4, because pier oncoming flow area is the smallest one so that down flow intensity is less; as non-uniform area is bigger and decrease more down flow energy so that bring smaller scour depth and effect area. Therefore, local scour depth for pier diameter ratio of 0.4 is less than other type of pier. Considering the safety of bridge structure, a non-uniform circular pier with D/D* which equals to 0.4 and initial bed level relative to Y=+0.2D* is the most ideal pier allocations.

Drainage of Southeast Greenland firn aquifer water through crevasses to the bed

NASA Astrophysics Data System (ADS)

Poinar, Kristin; Joughin, Ian; Lilien, David; Brucker, Ludovic; Kehrl, Laura; Nowicki, Sophie

2017-02-01

A firn aquifer in the Helheim Glacier catchment of Southeast Greenland lies directly upstream of a crevasse field. Previous measurements show that a 3.5-km long segment of the aquifer lost a large volume of water (26,000 - 65,000 m2 in cross section) between spring 2012 and spring 2013, compared to annual meltwater accumulation of 6000 - 15,000 m2. The water is thought to have entered the crevasses, but whether the water reached the bed or refroze within the ice sheet is unknown. We used a thermo-visco-elastic model for crevasse propagation to calculate the depths and volumes of these water-filled crevasses. We compared our model output to data from the Airborne Topographic Mapper (ATM), which reveals the near-surface geometry of specific crevasses, and WorldView images, which capture the surface expressions of crevasses across our 1.5-km study area. We found a best fit with a shear modulus between 0.2 and 1.5 GPa within our study area. We show that surface meltwater can drive crevasses to the top surface of the firn aquifer ( 20 m depth), whereupon it receives water at rates corresponding to the water flux through the aquifer. Our model shows that crevasses receiving firn-aquifer water hydrofracture through to the bed, 1000 m below, in 10-40 days. Englacial refreezing of firn-aquifer water raises the average local ice temperature by 4°C over a ten-year period, which enhances deformational ice motion by 50 m/yr, compared to the observed surface velocity of 200 m/yr. The effect of the basal water on the sliding velocity remains unknown. Were the firn aquifer not present to concentrate surface meltwater into crevasses, we find that no surface melt would reach the bed; instead, it would refreeze annually in crevasses at depths <500 m. The crevasse field downstream of the firn aquifer likely allows a large fraction of the aquifer water in our study area to reach the bed. Thus, future studies should consider the aquifer and crevasses as part of a common system. This system may uniquely affect ice-sheet dynamics by routing a large volume of water to the bed outside of the typical runoff period.

Quantifying the accuracy of snow water equivalent estimates using broadband radar signal phase

NASA Astrophysics Data System (ADS)

Deeb, E. J.; Marshall, H. P.; Lamie, N. J.; Arcone, S. A.

2014-12-01

Radar wave velocity in dry snow depends solely on density. Consequently, ground-based pulsed systems can be used to accurately measure snow depth and snow water equivalent (SWE) using signal travel-time, along with manual depth-probing for signal velocity calibration. Travel-time measurements require a large bandwidth pulse not possible in airborne/space-borne platforms. In addition, radar backscatter from snow cover is sensitive to grain size and to a lesser extent roughness of layers at current/proposed satellite-based frequencies (~ 8 - 18 GHz), complicating inversion for SWE. Therefore, accurate retrievals of SWE still require local calibration due to this sensitivity to microstructure and layering. Conversely, satellite radar interferometry, which senses the difference in signal phase between acquisitions, has shown a potential relationship with SWE at lower frequencies (~ 1 - 5 GHz) because the phase of the snow-refracted signal is sensitive to depth and dielectric properties of the snowpack, as opposed to its microstructure and stratigraphy. We have constructed a lab-based, experimental test bed to quantify the change in radar phase over a wide range of frequencies for varying depths of dry quartz sand, a material dielectrically similar to dry snow. We use a laboratory grade Vector Network Analyzer (0.01 - 25.6 GHz) and a pair of antennae mounted on a trolley over the test bed to measure amplitude and phase repeatedly/accurately at many frequencies. Using ground-based LiDAR instrumentation, we collect a coordinated high-resolution digital surface model (DSM) of the test bed and subsequent depth surfaces with which to compare the radar record of changes in phase. Our plans to transition this methodology to a field deployment during winter 2014-2015 using precision pan/tilt instrumentation will also be presented, as well as applications to airborne and space-borne platforms toward the estimation of SWE at high spatial resolution (on the order of meters) over large regions (> 100 square kilometers).

Polyethylene Based Materials for Biofilm Carriers Used in Wastewater Treatment

NASA Astrophysics Data System (ADS)

Moga, I. C.; Iordache, O. I.; Petrescu, G.; Pricop, F.; Dumitrescu, I.

2018-06-01

The moving bed biofilm technology is based on biofilm carriers on which consortia of microorganisms attach, develop and grow. Around the world are known many biofilm carrier variants made of varied materials. The most common materials are based on polyethylene since this material has a close to water density. The authors propose a novel biofilm carrier to be used in tertiary treatment for tannery and paper-mill wastewaters. The biological treatment is based on fungal activity. The selected fungal strains will be grown on innovative polyethylene carriers containing cellulose. The carrier will be designed to be exploited in a moving bed bioreactor and to favour fungal growth in the presence of competing bacteria.

Efficient Software Systems for Cardio Surgical Departments

NASA Astrophysics Data System (ADS)

Fountoukis, S. G.; Diomidous, M. J.

2009-08-01

Herein, the design implementation and deployment of an object oriented software system, suitable for the monitoring of cardio surgical departments, is investigated. Distributed design architectures are applied and the implemented software system can be deployed on distributed infrastructures. The software is flexible and adaptable to any cardio surgical environment regardless of the department resources used. The system exploits the relations and the interdependency of the successive bed positions that the patients occupy at the different health care units during their stay in a cardio surgical department, to determine bed availabilities and to perform patient scheduling and instant rescheduling whenever necessary. It also aims to successful monitoring of the workings of the cardio surgical departments in an efficient manner.

Vertical redox profiles in treatment wetlands as function of hydraulic regime and macrophytes presence: surveying the optimal scenario for microbial fuel cell implementation.

PubMed

Corbella, Clara; Garfí, Marianna; Puigagut, Jaume

2014-02-01

Sediment microbial fuel cell (sMFC) represents a variation of the typical configuration of a MFC in which energy can be harvested via naturally occurring electropotential differences. Moreover, constructed wetlands show marked redox gradients along the depth which could be exploited for energy production via sMFC. In spite of the potential application of sMFC to constructed wetlands, there is almost no published work on the topic. The main objective of the present work was to define the best operational and design conditions of sub-surface flow constructed wetlands (SSF CWs) under which energy production with microbial fuel cells (MFCs) would be maximized. To this aim, a pilot plant based on SSF CW treating domestic sewage was operated during six months. Redox gradients along the depth of SSF CWs were determined as function of hydraulic regime (continuous vs discontinuous) and the presence of macrophytes in two sampling campaigns (after three and six months of plant operation). Redox potential (EH) within the wetlands was analysed at 5, 15 and 25 cm. Results obtained indicated that the maximum redox gradient was between the surface and the bottom of the bed for continuous planted wetlands (407.7 ± 73.8 mV) and, to a lesser extent, between the surface and the middle part of the wetland (356.5 ± 76.7 mV). Finally, the maximum redox gradients obtained for planted wetlands operated under continuous flow regime would lead to a power production of about 16 mW/m(2). © 2013.

Mapping water surface roughness in a shallow, gravel-bed river using hyperspectral imagery

NASA Astrophysics Data System (ADS)

Overstreet, B. T.; Legleiter, C. J.

2014-12-01

Rapid advances in remote sensing are narrowing the gap between the data available for characterizing physical and biological processes in rivers and the information needed to guide river management decisions. The availability and quality of hyperspectral imagery have increased drastically over the past 20 years and hyperspectral data is now used in a number of different capacities that range from classifying riverine environments to measuring river bathymetry. A fundamental challenge in relating the spectral data from images to biophysical processes is the difficulty of isolating individual contributions to the at-sensor radiance, each associated with a different component of the fluvial environment. In this presentation we describe a method for isolating the contribution of light reflected from the water surface, or sun glint, from a hyperspectral image of a shallow gravel-bed river. We show that isolation and removal of sun glint can improve the accuracy of spectrally-based depth retrieval in cases where sun glint dominates the at-sensor radiance. Observed-vs.-predicted R2 values for depth retrieval improved from 0.56 to 0.68 following sun glint removal. In addition to clarifying the signal associated with the water column and bed, isolating sun glint could unlock important hydraulic information contained within the topography of the water surface. We present data from flume and field experiments suggesting that the intensity of sun glint is a function of water surface roughness. In rivers, water surface roughness depends on local flow hydraulics: depth, velocity, and bed material grain size. To explore this relationship, we coupled maps of image-derived sun glint with hydraulic measurements collected with a kayak-borne acoustic Doppler current profiler along 2 km of the Snake River in Grand Teton National Park. Spatial patterns of sun glint are spatially correlated with field observations of near-surface velocity and depth, suggesting that reach scale hydraulics could be mapped from hyperspectral images. These findings also suggest that aquatic habitats, which are often associated with specific hydraulic conditions and manifested as distinct surface textures, could be mapped quantitatively over large areas using hyperspectral imagery.

Erosion and Accretion on a Mudflat: The Importance of Very Shallow-Water Effects

NASA Astrophysics Data System (ADS)

Shi, Benwei; Cooper, James R.; Pratolongo, Paula D.; Gao, Shu; Bouma, T. J.; Li, Gaocong; Li, Chunyan; Yang, S. L.; Wang, Ya Ping

2017-12-01

Understanding erosion and accretion dynamics during an entire tidal cycle is important for assessing their impacts on the habitats of biological communities and the long-term morphological evolution of intertidal mudflats. However, previous studies often omitted erosion and accretion during very shallow-water stages (VSWS, water depths < 0.20 m). It is during these VSWS that bottom friction becomes relatively strong and thus erosion and accretion dynamics are likely to differ from those during deeper flows. In this study, we examine the contribution of very shallow-water effects to erosion and accretion of the entire tidal cycle, based on measured and modeled time-series of bed-level changes. Our field experiments revealed that the VSWS accounted for only 11% of the duration of the entire tidal cycle, but erosion and accretion during these stages accounted for 35% of the bed-level changes of the entire tidal cycle. Predicted cumulative bed-level changes agree much better with measured results when the entire tidal cycle is modeled than when only the conditions at water depths of >0.2 m (i.e., probe submerged) are considered. These findings suggest that the magnitude of bed-level changes during VSWS should not be neglected when modeling morphodynamic processes. Our results are useful in understanding the mechanisms of micro-topography formation and destruction that often occur at VSWS, and also improve our understanding and modeling ability of coastal morphological changes.

Deep trophoblast invasion and spiral artery remodelling in the placental bed of the lowland gorilla.

PubMed

Pijnenborg, R; Vercruysse, L; Carter, A M

2011-08-01

In contrast to baboon or rhesus macaque, trophoblast invasion in the human placental bed occurs by the interstitial as well as the endovascular route and reaches as deep as the inner myometrium. We here describe two rare specimens of gorilla placenta. In the light of recent findings in the chimpanzee, we postulated the occurrence of deep invasion in gorilla pregnancy. Tissues were processed for histology (PAS, orcein), lectin staining (Ulex europaeus agglutinin 1) and immunohistochemistry (cytokeratin 7/17, α-actin). A specimen of young but undetermined gestational age included deep placental bed tissue, showing interstitial and spiral artery invasion of the inner myometrium as well as the decidua. The cell density and depth of trophoblast invasion was equivalent to a human placental bed of 10-14 weeks. Intraluminal trophoblasts were not seen in any of the invaded vessels, allowing no definite conclusions about the origin of the intramural trophoblast and the time-course of spiral artery invasion. A different late second trimester placenta specimen showed scattered extravillous trophoblast in the basal plate and underlying decidua, as well as a remodelled spiral artery containing intramural trophoblast. Absence of inner myometrial tissue precluded assessment of invasion depth in this later specimen. Despite the limited material we can conclude that key aspects of trophoblast invasion are shared by the three hominid species: gorilla, chimpanzee and human. Copyright © 2011 Elsevier Ltd. All rights reserved.

Bed Surface Adjustments to Spatially Variable Flow in Low Relative Submergence Regimes

NASA Astrophysics Data System (ADS)

Monsalve, A.; Yager, E. M.

2017-11-01

In mountainous rivers, large relatively immobile grains partly control the local and reach-averaged flow hydraulics and sediment fluxes. When the flow depth is similar to the size of these grains (low relative submergence), heterogeneous flow structures and plunging flow cause spatial distributions of bed surface elevations, textures, and sedimentation rates. To explore how the bed surface responds to these flow variations we conducted a set of experiments in which we varied the relative submergence of staggered hemispheres (simulated large boulders) between runs. All experiments had the same average sediment transport capacity, upstream sediment supply, and initial bed thickness and grain size distribution. We combined our laboratory measurements with a 3-D flow model to obtain the detailed flow structure around the hemispheres. The local bed shear stress field displayed substantial variability and controlled the bed load transport rates and direction in which sediment moved. The divergence in bed shear stress caused by the hemispheres promoted size-selective bed load deposition, which formed patches of coarse sediment upstream of the hemisphere. Sediment deposition caused a decrease in local bed shear stress, which combined with the coarser grain size, enhanced the stability of this patch. The region downstream of the hemispheres was largely controlled by a recirculation zone and had little to no change in grain size, bed elevation, and bed shear stress. The formation, development, and stability of sediment patches in mountain streams is controlled by the bed shear stress divergence and magnitude and direction of the local bed shear stress field.

Scaling relationships between bed load volumes, transport distances, and stream power in steep mountain channels

NASA Astrophysics Data System (ADS)

Schneider, Johannes M.; Turowski, Jens M.; Rickenmann, Dieter; Hegglin, Ramon; Arrigo, Sabrina; Mao, Luca; Kirchner, James W.

2014-03-01

Bed load transport during storm events is both an agent of geomorphic change and a significant natural hazard in mountain regions. Thus, predicting bed load transport is a central challenge in fluvial geomorphology and natural hazard risk assessment. Bed load transport during storm events depends on the width and depth of bed scour, as well as the transport distances of individual sediment grains. We traced individual gravels in two steep mountain streams, the Erlenbach (Switzerland) and Rio Cordon (Italy), using magnetic and radio frequency identification tags, and measured their bed load transport rates using calibrated geophone bed load sensors in the Erlenbach and a bed load trap in the Rio Cordon. Tracer transport distances and bed load volumes exhibited approximate power law scaling with both the peak stream power and the cumulative stream energy of individual hydrologic events. Bed load volumes scaled much more steeply with peak stream power and cumulative stream energy than tracer transport distances did, and bed load volumes scaled as roughly the third power of transport distances. These observations imply that large bed load transport events become large primarily by scouring the bed deeper and wider, and only secondarily by transporting the mobilized sediment farther. Using the sediment continuity equation, we can estimate the mean effective thickness of the actively transported layer, averaged over the entire channel width and the duration of individual flow events. This active layer thickness also followed approximate power law scaling with peak stream power and cumulative stream energy and ranged up to 0.57 m in the Erlenbach, broadly consistent with independent measurements.

Aeromagnetic measurements in the Cascade Range and Modoc Plateau of northern California; report on work done from December 1, 1980, to May 31, 1981

USGS Publications Warehouse

Couch, Richard W.; Gemperle, Michael

1982-01-01

Spectral analysis of aeromagnetic data collected over 6orth-central California during the summer of 1980 aided in determining magnetic-source bottom depths beneath the survey area. Five regions of shallow magnetic source bottom depths were detected: 1) Secret Spring Mountain and National Lava Beds Monument area, 2) the Mount Shasta area, 3) the Eddys Mountain area, 4) the Big Valley Mountains area, and 5) an area northeast of Lassen Peak. Except for the Eddys Mountain area, all regions exhibiting shallow depths are suggested to be due to elevated Curie-point isotherms. The elevated Curie-point depth beneath Secret Spring Mountain and the National Lava Beds Monument area was found to be 4-7 km BSL (Below Sea Level) and is an extension of a zone mapped beneath an area immediately to the north in Oregon. A similar depth was detected for the Mount Shasta area and the area northeast of Lassen Peak. A depth of 4-6 km BSL was detected beneath the Big Valley Mountains area. The shallow Curie-point depths beneath Secret Spring Mountain, Mount Shasta, Big Valley Mountains, and the area northeast of Lassen Peak appear to form a segmented Zone of elevated Curie-point isotherm depths which underlies the High Cascade Mountains and Modoc Plateau in north-central California. A small area of shallow depths to magnetic-source bottoms, 4-5 km BSL, beneath the Eddys Mountain area is attributed to a lithologic boundary rather than an elevated Curie-point isotherm. Deeper magnetic source bottom depths were mapped throughout the remainder of the study area, with depths greater than 9 km BSL indicated beneath Lassen Peak and greater than ii km BSL indicated beneath the Western Cascades, Eastern Klamath Mountains, and Great Valley.

Applied technology for mine waste water decontamination in the uranium ores extraction from Romania

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

Bejenaru, C.; Filip, G.; Vacariu, V.T.

1996-12-31

The exploitation of uranium ores in Romania is carried out in underground mines. In all exploited uranium deposits, mine waste waters results and will still result after the closure of uranium ore extraction activity. The mine waters are radioactively contaminated with uranium and its decay products being a hazard both for underground waters as for the environment. This paper present the results of research work carried out by authors for uranium elimination from waste waters as the problems involved during the exploitation process of the existent equipment as its maintenance in good experimental conditions. The main waste water characteristics aremore » discussed: solids as suspension, uranium, radium, mineral salts, pH, etc. The moist suitable way to eliminate uranium from mine waste waters is the ion exchange process based on ion exchangers in fluidized bed. A flowsheet is given with main advantages resulted.« less

Fractured-aquifer hydrogeology from geophysical logs; the passaic formation, New Jersey

USGS Publications Warehouse

Morin, R.H.; Carleton, G.B.; Poirier, S.

1997-01-01

The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground-water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid-transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km2 area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was statistically reduced to two principal subsets corresponding to two distinct fracture types: (1) bedding-plane partings and (2) high-angle fractures. Bedding-plane partings are the most numerous and have an average strike of N84??W and dip of 20??N. The high-angle fractures are oriented subparallel to these features, with an average strike of N79??E and dip of 71??S, making the two fracture types roughly orthogonal. Their intersections form linear features that also retain this approximately east-west strike. Inspection of fluid temperature and conductance logs in conjunction with flowmeter measurements obtained during pumping allows the transmissive fractures to be distinguished from the general fracture population. These results show that, within the resolution capabilities of the logging tools, approximately 51 (or 18 percent) of the 280 total fractures are water producing. The bedding-plane partings exhibit transmissivities that average roughly 5 m2/day and that generally diminish in magnitude and frequency with depth. The high-angle fractures have average transmissivities that are about half those of the bedding-plane partings and show no apparent dependence upon depth. The geophysical logging results allow us to infer a distinct hydrogeologic structure within this aquifer that is defined by fracture type and orientation. Fluid flow near the surface is controlled primarily by the highly transmissive, subhorizontal bedding-plane partings. As depth increases, the high-angle fractures apparently become more dominant hydrologically.The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground-water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid-transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km2 area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was statistically reduced to two principal subsets corresponding to two distinct fracture types: (1) bedding-plane partings and (2) high-angle fractures. Bedding-plane partings are the most numerous and have an average strike of N84?? W and dip of 20?? N. The high-angle fractures are oriented subparallel to these features, with an average strike of N79?? E and dip of 71?? S, making the two fracture types roughly orthogonal. Their intersections form linear features that also retain this approximately east-west strike. Inspection of fluid temperature and conductance logs in conjunction with flowmeter measurements obtained during pumping allows the transmissive fractures to be distinguished from the general fracture population. These results show that, within the resolution capabilities of the logging tools, approximately 51 (or 18 percent) of the 280 total fractures are water producing. The bedding-plane partings exhibit transmissivities that average roughly 5 m2/day and that generally dimi

Integrated detoxification methodology of hazardous phenolic wastewaters in environmentally based trickle-bed reactors: Experimental investigation and CFD simulation.

PubMed

Lopes, Rodrigo J G; Almeida, Teresa S A; Quinta-Ferreira, Rosa M

2011-05-15

Centralized environmental regulations require the use of efficient detoxification technologies for the secure disposal of hazardous wastewaters. Guided by federal directives, existing plants need reengineering activities and careful analysis to improve their overall effectiveness and to become environmentally friendly. Here, we illustrate the application of an integrated methodology which encompasses the experimental investigation of catalytic wet air oxidation and CFD simulation of trickle-bed reactors. As long as trickle-bed reactors are determined by the flow environment coupled with chemical kinetics, first, on the optimization of prominent numerical solution parameters, the CFD model was validated with experimental data taken from a trickle bed pilot plant specifically designed for the catalytic wet oxidation of phenolic wastewaters. Second, several experimental and computational runs were carried out under unsteady-state operation to evaluate the dynamic performance addressing the TOC concentration and temperature profiles. CFD computations of total organic carbon conversion were found to agree better with experimental data at lower temperatures. Finally, the comparison of test data with simulation results demonstrated that this integrated framework was able to describe the mineralization of organic matter in trickle beds and the validated consequence model can be exploited to promote cleaner remediation technologies of contaminated waters. Copyright © 2011 Elsevier B.V. All rights reserved.

Stress orientations of Taiwan Chelungpu-Fault Drilling Project (TCDP) hole-A as observed from geophysical logs

USGS Publications Warehouse

Wu, H.-Y.; Ma, K.-F.; Zoback, M.; Boness, N.; Ito, H.; Hung, J.-H.; Hickman, S.

2007-01-01

The Taiwan Chelungpu-fault Drilling Project (TCDP) drilled a 2-km-deep research borehole to investigate the structure and mechanics of the Chelungpu Fault that ruptured in the 1999 Mw 7.6 Chi-Chi earthquake. Geophysical logs of the TCDP were carried out over depths of 500-1900 in, including Dipole Sonic Imager (DSI) logs and Formation Micro Imager (FMI) logs in order to identify bedding planes, fractures and shear zones. From the continuous core obtained from the borehole, a shear zone at a depth of 1110 meters is interpreted to be the Chelungpu fault, located within the Chinshui Shale, which extends from 1013 to 1300 meters depth. Stress-induced borehole breakouts were observed over nearly the entire length of the wellbore. These data show an overall stress direction (???N115??E) that is essentially parallel to the regional stress field and parallel to the convergence direction of the Philippine Sea plate with respect to the Eurasian plate. Variability in the average stress direction is seen at various depths. In particular there is a major stress orientation anomaly in the vicinity of the Chelungpu fault. Abrupt stress rotations at depths of 1000 in and 1310 in are close to the Chinshui Shale's upper and lower boundaries, suggesting the possibility that bedding plane slip occurred during the Chi-Chi earthquake. Copyright 2007 by the American Geophysical Union.

Performance and application of a fluidized bed limestone reactor designed for control of alkalinity, hardness and pH at the Warm Springs Regional Fisheries Center

USDA-ARS?s Scientific Manuscript database

Springs serving the Warm Springs Regional Fisheries Center, Warm Springs, Georgia, have pH, alkalinity, and hardness levels that lie under the range required for successful fish propagation while free CO2 is well above allowable targets. We evaluate a pretreatment process that exploits limestone's (...

Observations of wave-induced pore pressure gradients and bed level response on a surf zone sandbar

NASA Astrophysics Data System (ADS)

Anderson, Dylan; Cox, Dan; Mieras, Ryan; Puleo, Jack A.; Hsu, Tian-Jian

2017-06-01

Horizontal and vertical pressure gradients may be important physical mechanisms contributing to onshore sediment transport beneath steep, near-breaking waves in the surf zone. A barred beach was constructed in a large-scale laboratory wave flume with a fixed profile containing a mobile sediment layer on the crest of the sandbar. Horizontal and vertical pore pressure gradients were obtained by finite differences of measurements from an array of pressure transducers buried within the upper several centimeters of the bed. Colocated observations of erosion depth were made during asymmetric wave trials with wave heights between 0.10 and 0.98 m, consistently resulting in onshore sheet flow sediment transport. The pore pressure gradient vector within the bed exhibited temporal rotations during each wave cycle, directed predominantly upward under the trough and then rapidly rotating onshore and downward as the wavefront passed. The magnitude of the pore pressure gradient during each phase of rotation was correlated with local wave steepness and relative depth. Momentary bed failures as deep as 20 grain diameters were coincident with sharp increases in the onshore-directed pore pressure gradients, but occurred at horizontal pressure gradients less than theoretical critical values for initiation of the motion for compact beds. An expression combining the effects of both horizontal and vertical pore pressure gradients with bed shear stress and soil stability is used to determine that failure of the bed is initiated at nonnegligible values of both forces.