Heat and mass transfer analogy for condensation of humid air in a vertical channel

NASA Astrophysics Data System (ADS)

Desrayaud, G.; Lauriat, G.

This study examines energy transport associated with liquid film condensation in natural convection flows driven by differences in density due to temperature and concentration gradients. The condensation problem is based on the thin-film assumptions. The most common compositional gradient, which is encountered in humid air at ambient temperature is considered. A steady laminar Boussinesq flow of an ideal gas-vapor mixture is studied for the case of a vertical parallel plate channel. New correlations for the latent and sensible Nusselt numbers are established, and the heat and mass transfer analogy between the sensible Nusselt number and Sherwood number is demonstrated.

A passive microwave snow depth algorithm with a proxy for snow metamorphism

USGS Publications Warehouse

Josberger, E.G.; Mognard, N.M.

2002-01-01

Passive microwave brightness temperatures of snowpacks depend not only on the snow depth, but also on the internal snowpack properties, particularly the grain size, which changes through the winter. Algorithms that assume a constant grain size can yield erroneous estimates of snow depth or water equivalent. For snowpacks that are subject to temperatures well below freezing, the bulk temperature gradient through the snowpack controls the metamorphosis of the snow grains. This study used National Weather Service (NWS) station measurements of snow depth and air temperature from the Northern US Great Plains to determine temporal and spatial variability of the snow depth and bulk snowpack temperature gradient. This region is well suited for this study because it consists primarily of open farmland or prairie, has little relief, is subject to very cold temperatures, and has more than 280 reporting stations. A geostatistical technique called Kriging was used to grid the randomly spaced snow depth measurements. The resulting snow depth maps were then compared with the passive microwave observations from the Special Sensor Microwave Imager (SSM/I). Two snow seasons were examined: 1988-89, a typical snow year, and 1996-97, a record year for snow that was responsible for extensive flooding in the Red River Basin. Inspection of the time series of snow depth and microwave spectral gradient (the difference between the 19 and 37 GHz bands) showed that while the snowpack was constant, the spectral gradient continued to increase. However, there was a strong correlation (0.6 < R2 < 0.9) between the spectral gradient and the cumulative bulk temperature gradient through the snowpack (TGI). Hence, TGI is an index of grain size metamorphism that has occurred within the snowpack. TGI time series from 21 representative sites across the region and the corresponding SSM/I observations were used to develop an algorithm for snow depth that requires daily air temperatures. Copyright ?? 2002 John Wiley & Sons, Ltd.

Quantification of the effect of temperature gradients in soils on subsurface radon signal

NASA Astrophysics Data System (ADS)

Haquin, Gustavo; Ilzycer, Danielle; Kamai, Tamir; Zafrir, Hovav; Weisbrod, Noam

2017-04-01

Temperature gradients that develop in soils due to atmospheric temperature cycles are factors of primary importance in determining the rates and directions of subsurface gas flow. Models including mechanisms of thermal convection and thermal diffusion partially explain the impact of temperature gradients on subsurface radon transport. However, the overall impact of temperature gradients on subsurface radon transport is still not well understood. A laboratory setup was designed and built to experimentally investigate the influence of temperature gradients on radon transport under well controlled conditions. A 60 cm diameter and 120 cm tall column was thermally insulated except from the atmosphere-soil interface, such that it was constructed to simulate field conditions where temperature gradients in soils are developed following atmospheric temperature cycles. The column was filled with fine grinded phosphate rock which provided the porous media with radon source. Radon in soil-air was continuously monitored using NaI gamma detectors positioned at different heights along the column. Soil temperature, differential pressure, and relative humidity were monitored along the column. Experiments based on steep and gradual stepwise changes in ambient temperature were conducted. Absolute changes on radon levels in the order of 10-30% were measured at temperature gradients of up to ±20oC/m. Results showed a non-linear correlation between the temperature gradient and the subsurface radon concentration. An asymmetric relationship between the radon concentration and the temperature gradients for ΔT>0 and ΔT<0 was also observed. Laboratory simulations of the time- and depth-dependent temperature wave functions with frequencies ranged from a daily cycle to few days were performed. In response to the harmonic temperature behaviour radon oscillations at similar frequencies were detected correspondingly. In this work a quantitative relationship between radon and temperature gradients will be presented for cases beyond the classical conditions for thermal convection and thermal diffusion.

Temperature of ground water at Philadelphia, Pennsylvania, 1979- 1981

USGS Publications Warehouse

Paulachok, Gary N.

1986-01-01

Anthropogenic heat production has undoubtedly caused increased ground-water temperatures in many parts of Philadelphia, Pennsylvania, as shown by temperatures of 98 samples and logs of 40 wells measured during 1979-81. Most sample temperatures were higher than 12.6 degrees Celsius (the local mean annual air temperature), and many logs depict cooling trends with depth (anomalous gradients). Heating of surface and shallow-subsurface materials has likely caused the elevated temperatures and anomalous gradients. Solar radiation on widespread concrete and asphalt surfaces, fossil-fuel combustion, and radiant losses from buried pipelines containing steam and process chemicals are believed to be the chief sources of heat. Some heat from these and other sources is transferred to deeper zones, mainly by conduction. Temperatures in densely urbanized areas are commonly highest directly beneath the land surface and decrease progressively with depth. Temperatures in sparsely urbanized areas generally follow the natural geothermal gradient and increase downward at about that same rate.

The impact of summer rainfall on the temperature gradient along the United States-Mexico border

NASA Technical Reports Server (NTRS)

Balling, Robert C., Jr.

1989-01-01

The international border running through the Sonoran Desert in southern Arizona and northern Sonora is marked by a sharp discontinuity in albedo and grass cover. The observed differences in surface properties are a result of long-term, severe overgrazing of the Mexican lands. Recently, investigators have shown the Mexican side of the border to have higher surface and air temperatures when compared to adjacent areas in the United State. The differences in temperatures appear to be more associated with differential evapotranspiration rates than with albedo changes along the border. In this study, the impact of summer rainfall on the observed seasonal and daily gradient in maximum temperature is examined. On a seasonal time scale, the temperature gradient increases with higher moisture levels, probably due to a vegetative response on the United States' side of the border; at the daily level, the gradient in maximum temperature decreases after a rain event as evaporation rates equalize between the countries. The results suggest that temperature differences between vegetated and overgrazed landscapes in arid areas are highly dependent upon the amount of moisture available for evapotranspiration.

Repeatability of gradient ultrahigh pressure liquid chromatography-tandem mass spectrometry methods in instrument-controlled thermal environments.

PubMed

Grinias, James P; Wong, Jenny-Marie T; Kennedy, Robert T

2016-08-26

The impact of viscous friction on eluent temperature and column efficiency in liquid chromatography is of renewed interest as the need for pressures exceeding 1000bar to use with columns packed with sub-2μm particles has grown. One way the development of axial and radial temperature gradients that arise due to viscous friction can be affected is by the thermal environment the column is placed in. In this study, a new column oven integrated into an ultrahigh pressure liquid chromatograph that enables both still-air and forced-air operating modes is investigated to find the magnitude of the effect of the axial thermal gradient that forms in 2.1×100mm columns packed with sub-2μm particles in these modes. Temperature increases of nearly 30K were observed when the generated power of the column exceeded 25W/m. The impact of the heating due to viscous friction on the repeatability of peak capacity, elution time, and peak area ratio to an internal standard for a gradient UHPLC-MS/MS method to analyze neurotransmitters was found to be limited. This result indicates that high speed UHPLC-MS/MS gradient methods under conditions of high viscous friction may be possible without the negative effects typically observed with isocratic separations under similar conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

The relationship of meteorological patterns with changes in floristic richness along a large elevational gradient in a seasonally dry region of southern Mexico.

PubMed

Salas-Morales, Silvia H; Meave, Jorge A; Trejo, Irma

2015-12-01

Globally, climate is a fundamental driver of plant species' geographical distributions, yet we still lack a good understanding of climatic variation on tropical mountains and its consequences for elevational floristic patterns. In a seasonally dry region of southern Mexico, we analysed meteorological patterns along a large elevational gradient (0-3670 m a.s.l.) and examined their relationship with changes in floristic richness. Meteorological patterns were characterised using two data sources. First, climatic information was extracted from cartography and records from a few existing meteorological stations. Additionally, air temperature and humidity were recorded hourly during 1 year with data loggers, at sites representing 200-m elevation increments. Floristic information was extracted from a database containing 10,124 records of plant collections, and organized in 200-m elevational belts. Climatic charts distinguished three climate types along the gradient, all with marked rainfall seasonality, but these bore little correspondence with the information obtained with the data loggers. Mean annual air temperature decreased with increasing elevation (lapse rate of 0.542 °C 100 m(-1)). Thermal oscillation was minimum around 1400 m and increased towards both extremes of the gradient. Relative humidity opposed this pattern, with maxima between 800 and 1800 m, decreasing towards the highest elevations. An analysis of temperature frequency distributions revealed meteorological features undetectable from the annual or monthly means of this variable; despite an overall gradual transition of the proportions of time recorded at different temperatures, some changes did not conform to this pattern. The first discontinuity occurred between 1000-1200 m, where dominant temperatures shifted abruptly; also noticeable was an abrupt increase of the proportion of time elapsed at 0.1-10 °C between 2400 and 2600 m. Air temperature appears to be the most influential climatic factor driving elevational variation of plant species richness in this region.

Mangrove expansion and contraction at a poleward range limit: Climate extremes and land-ocean temperature gradients

USGS Publications Warehouse

Osland, Michael J.; Day, Richard H.; Hall, Courtney T.; Brumfield, Marisa D; Dugas, Jason; Jones, William R.

2017-01-01

Within the context of climate change, there is a pressing need to better understand the ecological implications of changes in the frequency and intensity of climate extremes. Along subtropical coasts, less frequent and warmer freeze events are expected to permit freeze-sensitive mangrove forests to expand poleward and displace freeze-tolerant salt marshes. Here, our aim was to better understand the drivers of poleward mangrove migration by quantifying spatiotemporal patterns in mangrove range expansion and contraction across land-ocean temperature gradients. Our work was conducted in a freeze-sensitive mangrove-marsh transition zone that spans a land-ocean temperature gradient in one of the world's most wetland-rich regions (Mississippi River Deltaic Plain; Louisiana, USA). We used historical air temperature data (1893-2014), alternative future climate scenarios, and coastal wetland coverage data (1978-2011) to investigate spatiotemporal fluctuations and climate-wetland linkages. Our analyses indicate that changes in mangrove coverage have been controlled primarily by extreme freeze events (i.e., air temperatures below a threshold zone of -6.3 to -7.6 °C). We expect that in the past 121 years, mangrove range expansion and contraction has occurred across land-ocean temperature gradients. Mangrove resistance, resilience, and dominance were all highest in areas closer to the ocean where temperature extremes were buffered by large expanses of water and saturated soil. Under climate change, these areas will likely serve as local hotspots for mangrove dispersal, growth, range expansion, and displacement of salt marsh. Collectively, our results show that the frequency and intensity of freeze events across land-ocean temperature gradients greatly influences spatiotemporal patterns of range expansion and contraction of freeze-sensitive mangroves. We expect that, along subtropical coasts, similar processes govern the distribution and abundance of other freeze-sensitive organisms. In broad terms, our findings can be used to better understand and anticipate the ecological effects of changing winter climate extremes, especially within the transition zone between tropical and temperate climates.

Response of sugarcane to carbon dioxide enrichment and elevated temperature

USDA-ARS?s Scientific Manuscript database

Four sugarcane cultivars (CP72-2086, CP73-1547, CP88-1508, and CP80-1827) were grown in elongated temperature-gradient greenhouses (TGG) at ambient or elevated carbon dioxide (CO2) of 360 or 720 µmol CO2 mol-1 air, respectively. Each TGG maintained temperatures in four zones at Base temperature wit...

A Preliminary Study of Streamside Air Temperatures Within the Coast Redwood Zone 2001 to 2003

Treesearch

Tracie Nelson; Richard Macedo; Bradley E. Valentine

2007-01-01

Timber harvest practices must address potential impacts to aquatic and riparian habitats. Stream shading and cool water temperature regimes are important to protect stream-dwelling organisms. We are examining riparian temperature regimes within the coastal redwood area of Mendocino County. Summer temperature gradients are being characterized along fifteen transects set...

Temperature cycling vapor deposition HgI.sub.2 crystal growth

DOEpatents

Schieber, Michael M.; Beinglass, Israel; Dishon, Giora

1977-01-01

A method and horizontal furnace for vapor phase growth of HgI.sub.2 crystals which utilizes controlled axial and radial airflow to maintain the desired temperature gradients. The ampoule containing the source material is rotated while axial and radial air tubes are moved in opposite directions during crystal growth to maintain a desired distance and associated temperature gradient with respect to the growing crystal, whereby the crystal interface can advance in all directions, i.e., radial and axial according to the crystallographic structure of the crystal. Crystals grown by this method are particularly applicable for use as room-temperature nuclear radiation detectors.

Geothermal as a heat sink application for raising air conditioning efficency

NASA Astrophysics Data System (ADS)

Ibrahim, Hesham Safwat Osman Mohamed

2016-04-01

Objective: Geothermal applications in heating, ventilation, air-conditioning is a US technology for more than 30 years old ,which saves more than 30% average energy cost than the traditional air-conditioning systems systems. Applying this technology in Middle East and African countries would be very feasible specially in Egypt specially as it suffers Electric crisis --The temperature of the condensers and the heat rejecting equipment is much higher than the Egyptian land at different depth which is a great advantages, and must be measured, recorded, and studied accurately -The Far goal of the proposal is to construct from soil analysis a temperature gradient map for Egypt and , African countries on different depth till 100 m which is still unclear nowadays and must be measured and recorded in databases through researches - The main model of the research is to study the heat transfer gradient through the ground earth borehole,grout,high density polyethylene pipes , and water inlet temperature which affect the electric efficiency of the ground source heat pump air conditioning unit Impact on the Region: Such research result will contribute widely in Energy saving sector specially the air conditioning sector in Egypt and the African countries which consumes more than 30% of the electric consumption of the total consumption . and encouraging Green systems such Geothermal to be applied

Numerical Simulation of Atmospheric Response to Pacific Tropical Instability Waves(.

NASA Astrophysics Data System (ADS)

Small, R. Justin; Xie, Shang-Ping; Wang, Yuqing

2003-11-01

Tropical instability waves (TIWs) are 1000-km-long waves that appear along the sea surface temperature (SST) front of the equatorial cold tongue in the eastern Pacific. The study investigates the atmospheric planetary boundary layer (PBL) response to TIW-induced SST variations using a high-resolution regional climate model. An investigation is made of the importance of pressure gradients induced by changes in air temperature and moisture, and vertical mixing, which is parameterized in the model by a 1.5-level turbulence closure scheme. Significant turbulent flux anomalies of sensible and latent heat are caused by changes in the air sea temperature and moisture differences induced by the TIWs. Horizontal advection leads to the occurrence of the air temperature and moisture extrema downwind of the SST extrema. High and low hydrostatic surface pressures are then located downwind of the cold and warm SST patches, respectively. The maximum and minimum wind speeds occur in phase with SST, and a thermally direct circulation is created. The momentum budget indicates that pressure gradient, vertical mixing, and horizontal advection dominate. In the PBL the vertical mixing acts as a frictional drag on the pressure-gradient-driven winds. Over warm SST the mixed layer deepens relative to over cold SST. The model simulations of the phase and amplitude of wind velocity, wind convergence, and column-integrated water vapor perturbations due to TIWs are similar to those observed from satellite and in situ data.

Morning Martian Atmospheric Temperature Gradients and Fluctuations Observed by Mars Pathfinder

NASA Technical Reports Server (NTRS)

Mihalov, John D.; Haberle, R. M.; Murphy, J. R.; Seiff, A.; Wilson, G. R.

1999-01-01

We have studied the most prominent atmospheric temperature fluctuations observed during Martian mornings by Mars Pathfinder and have concluded, based on comparisons with wind directions, that they appear to be a result of atmospheric heating associated with the Lander spacecraft. Also, we have examined the morning surface layer temperature lapse rates, which are found to decrease as autumn approaches at the Pathfinder location, and which have mean (and median) values as large as 7.3 K/m in the earlier portions of the Pathfinder landed mission. It is plausible that brief isolated periods with gradients twice as steep are associated with atmospheric heating adjacent to Lander air bag material. In addition, we have calculated the gradient with height of the structure function obtained with Mars Pathfinder, for Mars' atmospheric temperatures measured within about 1.3 m from the surface, assuming a power law dependence, and have found that these gradients superficially resemble those reported for the upper region of the terrestrial stable boundary layer.

Exact solutions of laminar-boundary-layer equations with constant property values for porous wall with variable temperature

NASA Technical Reports Server (NTRS)

Donoughe, Patrick L; Livingood, John N B

1955-01-01

Exact solution of the laminar-boundary-layer equations for wedge-type flow with constant property values are presented for transpiration-cooled surfaces with variable wall temperatures. The difference between wall and stream temperature is assumed proportional to a power of the distance from the leading edge. Solutions are given for a Prandtl number of 0.7 and ranges of pressure-gradient, cooling-air-flow, and wall-temperature-gradient parameters. Boundary-layer profiles, dimensionless boundary-layer thicknesses, and convective heat-transfer coefficients are given in both tabular and graphical form. Corresponding results for constant wall temperature and for impermeable surfaces are included for comparison purposes.

Full-field measurement of surface topographies and thin film stresses at elevated temperatures by digital gradient sensing method.

PubMed

Zhang, Changxing; Qu, Zhe; Fang, Xufei; Feng, Xue; Hwang, Keh-Chih

2015-02-01

Thin film stresses in thin film/substrate systems at elevated temperatures affect the reliability and safety of such structures in microelectronic devices. The stresses result from the thermal mismatch strain between the film and substrate. The reflection mode digital gradient sensing (DGS) method, a real-time, full-field optical technique, measures deformations of reflective surface topographies. In this paper, we developed this method to measure topographies and thin film stresses of thin film/substrate systems at elevated temperatures. We calibrated and compensated for the air convection at elevated temperatures, which is a serious problem for optical techniques. We covered the principles for surface topography measurements by the reflection mode DGS method at elevated temperatures and the governing equations to remove the air convection effects. The proposed method is applied to successfully measure the full-field topography and deformation of a NiTi thin film on a silicon substrate at elevated temperatures. The evolution of thin film stresses obtained by extending Stoney's formula implies the "nonuniform" effect the experimental results have shown.

Apparatus for growing HgI.sub.2 crystals

DOEpatents

Schieber, Michael M.; Beinglass, Israel; Dishon, Giora

1978-01-01

A method and horizontal furnace for vapor phase growth of HgI.sub.2 crystals which utilizes controlled axial and radial airflow to maintain the desired temperature gradients. The ampoule containing the source material is rotated while axial and radial air tubes are moved in opposite directions during crystal growth to maintain a desired distance and associated temperature gradient with respect to the growing crystal, whereby the crystal interface can advance in all directions, i.e., radial and axial according to the crystallographic structure of the crystal. Crystals grown by this method are particularly applicable for use as room-temperature nuclear radiation detectors.

Seasonal mapping of NICU temperature.

PubMed

Thomas, Karen A; Magbalot, Almita; Shinabarger, Kelley; Mokhnach, Larisa; Anderson, Marilyn; Diercks, Kristi; Millar, April; Thorngate, Lauren; Walker, Wendy; Dilback, Nancy; Berkan, Maureen

2010-04-01

To create a thermal map of ambient air, radiant, and evaporative temperatures and humidity throughout the NICU nursery by season across a calendar year. Each cubicle of the 32-bed NICU, distributed across 5 rooms, in a level III nursery was measured. Temperatures were recorded at a consistent time on one day during January, April, July, and October. An electronic monitor (QUESTemp degrees 34; Quest Technologies, Oconomowoc, Wisconsin) was used to measure dry bulb, wet bulb, and globe thermometer temperatures. Analysis of variance revealed statistically significant (P < .000) differences in season, room, and season by room interaction. Room ambient air temperatures differed by less than 2 degrees F across season. Radiant temperature paralleled air temperature. Humidity, the predominant difference across season, produced evaporative temperatures considerably lower than room air temperature, and the gradient between mean nursery dry bulb temperature and wet bulb temperature was 9.3 degrees F in summer and 16.8 degrees F in winter. The thermal map revealed seasonal thermal differences, particularly in humidity level and evaporative temperature. Room temperature alone does not reflect the total thermal environment. Recommendations include periodic assessment of nurseries along with air, evaporative, and radiant temperatures as well as humidity to fully appreciate the impact of the thermal environment on infants.

Seasonal mapping of NICU temperature.

PubMed

Thomas, Karen A; Magbalot, Almita; Shinabarger, Kelley; Mokhnach, Larisa; Anderson, Marilyn; Diercks, Kristi; Millar, April; Thorngate, Lauren; Walker, Wendy; Dilback, Nancy; Berkan, Maureen

2010-10-01

To create a thermal map of ambient air, radiant, and evaporative temperatures and humidity throughout the NICU nursery by season across a calendar year. Each cubicle of the 32-bed NICU, distributed across 5 rooms, in a level III nursery was measured. Temperatures were recorded at a consistent time on one day during January, April, July, and October. : An electronic monitor (QUESTemp ° 34; Quest Technologies, Oconomowoc, Wisconsin) was used to measure dry bulb, wet bulb, and globe thermometer temperatures. Analysis of variance revealed statistically significant (P ≤ .000) differences in season, room, and season by room interaction. Room ambient air temperatures differed by less than 2 ° F across season. Radiant temperature paralleled air temperature. Humidity, the predominant difference across season, produced evaporative temperatures considerably lower than room air temperature, and the gradient between mean nursery dry bulb temperature and wet bulb temperature was 9.3 ° F in summer and 16.8 ° F in winter. The thermal map revealed seasonal thermal differences, particularly in humidity level and evaporative temperature. Room temperature alone does not reflect the total thermal environment. Recommendations include periodic assessment of nurseries along with air, evaporative, and radiant temperatures as well as humidity to fully appreciate the impact of the thermal environment on infants.

Full spatial-field visualization of gas temperature in an air micro-glow discharge by calibrated Schlieren photography

NASA Astrophysics Data System (ADS)

Xiong, Qing; Xu, Le; Wang, Xia; Xiong, Lin; Huang, Qinghua; Chen, Qiang; Wang, Jingang; Peng, Wenxiong; Li, Jiarui

2018-03-01

Gas temperature is an important basic parameter for both fundamental research and applications of plasmas. In this work, efforts were made to visualize the full spatial field of gas temperature (T g) in a microdischarge with sharp T g gradients by a method of calibrated Schlieren (CS) photography. Compared to other two typical diagnostic approaches, optical emission spectroscopy (OES) and Rayleigh scattering, the proposed CS method exhibits the ability to capture the whole field of gas temperature using a single Schlieren image, even the discharge is of non-luminous zones like Faraday dark space (FDS). The image shows that the T g field in the studied micro-glow air discharge expands quickly with the increase of discharge currents, especially in the cathode region. The two-dimensional maps of gas temperature display a ‘W-shape’ with sharp gradients in both areas of negative and positive glows, slightly arched distributions in the positive column, and cooling zones in the FDS. The obtained T g fields show similar patterns to that of the discharge luminance. With an increase in discharge currents, more electric energy is dissipated by heating air gas and inducing constriction of the low-temperature FDS. Except in the vicinities of electrode boundaries, due to the interference from optical diffraction, the estimated gas temperature distributions are of acceptable accuracy, confirmed by the approaches of OES and UV Rayleigh scattering.

Effects of a Circulating-water Garment and Forced-air Warming on Body Heat Content and Core Temperature

PubMed Central

Taguchi, Akiko; Ratnaraj, Jebadurai; Kabon, Barbara; Sharma, Neeru; Lenhardt, Rainer; Sessler, Daniel I.

2005-01-01

Background: Forced-air warming is sometimes unable to maintain perioperative normothermia. We therefore compared heat transfer, regional heat distribution, and core rewarming of forced-air warming with a novel circulating-water garment. Methods: Nine volunteers were each evaluated on two randomly ordered study days. They were anesthetized and cooled to a core temperature near 34°C. The volunteers were subsequently warmed for 2.5 hours with either a circulating-water garment or forced-air cover. Overall, heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Average arm and leg (peripheral) tissue temperatures were determined from 18 intramuscular needle thermocouples, 15 skin thermal flux transducers, and “deep” arm and foot thermometers. Results: Heat production (≈ 60 kcal/h) and loss (≈45 kcal/h) were similar with each treatment before warming. The increase in heat transfer across anterior portions of the skin surface was similar with each warming system (≈65 kcal/h). Forced-air warming had no effect on posterior heat transfer whereas circulating-water transferred 21 ± 9 kcal/h through the posterior skin surface after a half hour of warming. Over 2.5 h, circulating-water thus increased body heat content 56% more than forced air. Core temperatures thus increased faster than with circulating water than forced air, especially during the first hour, with the result that core temperature was 1.1 ± 0.7°C greater after 2.5 h (P < 0.001). Peripheral tissue heat content increased twice as much as core heat content with each device, but the core-to-peripheral tissue temperature gradient remained positive throughout the study. Conclusions: The circulating-water system transferred more heat than forced air, with the difference resulting largely from posterior heating. Circulating water rewarmed patients 0.4°C/h faster than forced air. A substantial peripheral-to-core tissue-temperature gradient with each device indicated that peripheral tissues insulated the core, thus slowing heat transfer. PMID:15114200

Evidence of latitudinal fractionation of polychlorinated biphenyl congeners along the Baltic Sea region

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

Agrell, C.; Okla, L.; Larsson, P.

Annual cycles of the atmospheric concentrations of PCBs were determined at 16 (mostly rural) stations around the Baltic Sea between 1990 and 1993. The concentration levels of individual congeners were found to be influenced by their physical-chemical properties, ambient temperature, and geographical location. Median levels of PCBs were similar at all stations except at one urban site near Riga. A latitudinal gradient with higher levels in the south was found for the sum of PCB as well as for individual congeners, and the gradient was more pronounced for the low volatility congeners. As a result, the high volatility congeners increasedmore » in relative importance with latitude. Generally, PCB concentrations increased with temperature, but slopes of the partial pressure in air versus reciprocal temperature were different between congeners and between stations. In general, the low volatility congeners were more temperature dependent than the high volatility PCB congeners. Steep slopes at a sampling location indicate that the concentration in air is largely determined by diffusive exchange with soils. Lack of a temperature dependence may be due to the influence of long-range transported air masses at remote sites and due to the episodic or random nature of PCB sources at urban sites.« less

The neotropical shrub Lupinus elegans, fromtemperate forests, may not adapt to climate change.

PubMed

Soto-Correa, J C; Sáenz-Romero, C; Lindig-Cisneros, R; de la Barrera, E

2013-05-01

Considering that their distribution is limited to altitudinal gradients along mountains that are likely to become warmer and drier, climate change poses an increased threat to temperate forest species from tropical regions. We studied whether the understorey shrub Lupinus elegans, endemic to temperate forests of west-central Mexico, will be able to withstand the projected temperature increase under seven climate change scenarios. Seeds were collected along an altitudinal gradient and grown in a shade-house over 7 months before determining their temperature tolerance as electrolyte leakage. The plants from colder sites tolerated lower temperatures, i.e. the temperature at which half of the maximum electrolyte leakage occurred (LT50), ranged from −6.4 ± 0.7 to −2.4 ± 0.3 °C. In contrast, no pattern was found for tolerance to high temperature (LT50 average 42.8 ± 0.3 °C). The climate change scenarios considered here consistently estimated an increase in air temperature during the present century that was higher for the maximum air temperature than for the mean or minimum. In particular, the anomaly from the normal maximum air temperature at the study region ranged from 2.8 °C by 2030 to 5.8 °C by 2090. In this respect, the inability of L. elegans to adapt to increasingly higher temperatures found here, in addition to a possible inhibition of reproduction caused by warmer winters, may limit its future distribution.

Daniel K. Inouye Solar Telescope: computational fluid dynamic analyses and evaluation of the air knife model

NASA Astrophysics Data System (ADS)

McQuillen, Isaac; Phelps, LeEllen; Warner, Mark; Hubbard, Robert

2016-08-01

Implementation of an air curtain at the thermal boundary between conditioned and ambient spaces allows for observation over wavelength ranges not practical when using optical glass as a window. The air knife model of the Daniel K. Inouye Solar Telescope (DKIST) project, a 4-meter solar observatory that will be built on Haleakalā, Hawai'i, deploys such an air curtain while also supplying ventilation through the ceiling of the coudé laboratory. The findings of computational fluid dynamics (CFD) analysis and subsequent changes to the air knife model are presented. Major design constraints include adherence to the Interface Control Document (ICD), separation of ambient and conditioned air, unidirectional outflow into the coudé laboratory, integration of a deployable glass window, and maintenance and accessibility requirements. Optimized design of the air knife successfully holds full 12 Pa backpressure under temperature gradients of up to 20°C while maintaining unidirectional outflow. This is a significant improvement upon the .25 Pa pressure differential that the initial configuration, tested by Linden and Phelps, indicated the curtain could hold. CFD post- processing, developed by Vogiatzis, is validated against interferometry results of initial air knife seeing evaluation, performed by Hubbard and Schoening. This is done by developing a CFD simulation of the initial experiment and using Vogiatzis' method to calculate error introduced along the optical path. Seeing error, for both temperature differentials tested in the initial experiment, match well with seeing results obtained from the CFD analysis and thus validate the post-processing model. Application of this model to the realizable air knife assembly yields seeing errors that are well within the error budget under which the air knife interface falls, even with a temperature differential of 20°C between laboratory and ambient spaces. With ambient temperature set to 0°C and conditioned temperature set to 20°C, representing the worst-case temperature gradient, the spatial rms wavefront error in units of wavelength is 0.178 (88.69 nm at λ = 500 nm).

Mangrove expansion and contraction at a poleward range limit: climate extremes and land-ocean temperature gradients.

PubMed

Osland, Michael J; Day, Richard H; Hall, Courtney T; Brumfield, Marisa D; Dugas, Jason L; Jones, William R

2017-01-01

Within the context of climate change, there is a pressing need to better understand the ecological implications of changes in the frequency and intensity of climate extremes. Along subtropical coasts, less frequent and warmer freeze events are expected to permit freeze-sensitive mangrove forests to expand poleward and displace freeze-tolerant salt marshes. Here, our aim was to better understand the drivers of poleward mangrove migration by quantifying spatiotemporal patterns in mangrove range expansion and contraction across land-ocean temperature gradients. Our work was conducted in a freeze-sensitive mangrove-marsh transition zone that spans a land-ocean temperature gradient in one of the world's most wetland-rich regions (Mississippi River Deltaic Plain; Louisiana, USA). We used historical air temperature data (1893-2014), alternative future climate scenarios, and coastal wetland coverage data (1978-2011) to investigate spatiotemporal fluctuations and climate-wetland linkages. Our analyses indicate that changes in mangrove coverage have been controlled primarily by extreme freeze events (i.e., air temperatures below a threshold zone of -6.3 to -7.6°C). We expect that in the past 121 yr, mangrove range expansion and contraction has occurred across land-ocean temperature gradients. Mangrove resistance, resilience, and dominance were all highest in areas closer to the ocean where temperature extremes were buffered by large expanses of water and saturated soil. Under climate change, these areas will likely serve as local hotspots for mangrove dispersal, growth, range expansion, and displacement of salt marsh. Collectively, our results show that the frequency and intensity of freeze events across land-ocean temperature gradients greatly influences spatiotemporal patterns of range expansion and contraction of freeze-sensitive mangroves. We expect that, along subtropical coasts, similar processes govern the distribution and abundance of other freeze-sensitive organisms. In broad terms, our findings can be used to better understand and anticipate the ecological effects of changing winter climate extremes, especially within the transition zone between tropical and temperate climates. © 2016 by the Ecological Society of America.

AIRS Observations of DomeC in Antarctica and Comparison with Automated Weather Stations (AWS)

NASA Technical Reports Server (NTRS)

Aumann, Hartmut H.; Gregorich, Dave; Broberg, Steve

2006-01-01

We compare the surface temperatures at Dome Concordia (DomeC) deduced from AIRS data and two Automatic Weather Stations at Concordia Station: AWS8989 , which has been in operation since December 1996, and AWS.it, for which data are available between January and November 2005. The AWS8989 readings are on average 3 K warmer than the AWS.it readings, with a warmer bias in the Antarctic summer than in the winter season. Although AIRS measures the skin brightness temperature, while the AWS reports the temperature of the air at 3 meter above the surface, the AIRS measurements agree well with the AWS.it readings for all data and separately for the summer and winter seasons, if data taken in the presence of strong surface inversions are filtered out. This can be done by deducing the vertical temperature gradient above the surface directly from the AIRS temperature sounding channels or indirectly by noting that extreme vertical gradients near the surface are unlikely if the wind speed is more than a few meters per second. Since the AIRS measurements are very well calibrated, the agreement with AWS.it is very encouraging. The warmer readings of AWS8989 are likely due to thermal contamination of the AWS8989 site by the increasing activity at Concordia Station. Data from an AWS.it quality station could be used for the evaluation of radiometric accuracy and stability of polar orbiting sounders at low temperatures. Unfortunately, data from AWS.it was available only for a limited time. The thermal contamination of the AWS8989 data makes long-term trends deduced from AWS8989 and possibly results about the rapid Antarctic warming deduced from other research stations on Antarctica suspect. AIRS is the first hyperspectral infrared sounder designed in support of weather forecasting and climate research. It was launched in May 2002 on the EOS Aqua spacecraft into a 704 km altitude polar sun-synchronous orbit. The lifetime of AIRS, estimated before launch to be at least 5 years is, based on the latest evaluation, limited by the amount of attitude control gas on the EOS Aqua spacecraft, which is expected to last through 2015.

Thermochromatography and activation analysis

NASA Astrophysics Data System (ADS)

Stattarov, G. S.; Kist, A. A.

1999-01-01

Gas thermochromatography is a promising method in combination with neutron activation analysis. The procedure includes heating of irradiated samples in a stream of reacting gas carrier (air, chlorine, etc.) or heating in presence of compounds evolving gas at high temperatures. Gaseous products are passed through a tube with certain temperature gradient filled with various sorbents and the gases condense in different parts of the column. Studies of the processes of producing and trapping of volatile compounds allowed to work out various set-ups of apparatus with sorption tubes of various length and various temperature gradients, various filters, sorbents, etc. Sensitivity of these methods is sufficiently better then in INAA.

Mechanisms of the intensification of the upwelling-favorable winds during El Niño 1997-1998 in the Peruvian upwelling system

NASA Astrophysics Data System (ADS)

Chamorro, Adolfo; Echevin, Vincent; Colas, François; Oerder, Vera; Tam, Jorge; Quispe-Ccalluari, Carlos

2018-01-01

The physical processes driving the wind intensification in a coastal band of 100 km off Peru during the intense 1997-1998 El Niño (EN) event were studied using a regional atmospheric model. A simulation performed for the period 1994-2000 reproduced the coastal wind response to local sea surface temperature (SST) forcing and large scale atmospheric conditions. The model, evaluated with satellite data, represented well the intensity, seasonal and interannual variability of alongshore (i.e. NW-SE) winds. An alongshore momentum budget showed that the pressure gradient was the dominant force driving the surface wind acceleration. The pressure gradient tended to accelerate the coastal wind, while turbulent vertical mixing decelerated it. A quasi-linear relation between surface wind and pressure gradient anomalies was found. Alongshore pressure gradient anomalies were caused by a greater increase in near-surface air temperature off the northern coast than off the southern coast, associated with the inhomogeneous SST warming. Vertical profiles of wind, mixing coefficient, and momentum trends showed that the surface wind intensification was not caused by the increase of turbulence in the planetary boundary layer. Moreover, the temperature inversion in the vertical mitigated the development of pressure gradient due to air convection during part of the event. Sensitivity experiments allowed to isolate the respective impacts of the local SST forcing and large scale condition on the coastal wind intensification. It was primarily driven by the local SST forcing whereas large scale variability associated with the South Pacific Anticyclone modulated its effects. Examination of other EN events using reanalysis data confirmed that intensifications of alongshore wind off Peru were associated with SST alongshore gradient anomalies, as during the 1997-1998 event.

Seasonal body size reductions with warming covary with major body size gradients in arthropod species.

PubMed

Horne, Curtis R; Hirst, Andrew G; Atkinson, David

2017-03-29

Major biological and biogeographical rules link body size variation with latitude or environmental temperature, and these rules are often studied in isolation. Within multivoltine species, seasonal temperature variation can cause substantial changes in adult body size, as subsequent generations experience different developmental conditions. Yet, unlike other size patterns, these common seasonal temperature-size gradients have never been collectively analysed. We undertake the largest analysis to date of seasonal temperature-size gradients in multivoltine arthropods, including 102 aquatic and terrestrial species from 71 global locations. Adult size declines in warmer seasons in 86% of the species examined. Aquatic species show approximately 2.5-fold greater reduction in size per °C of warming than terrestrial species, supporting the hypothesis that greater oxygen limitation in water than in air forces aquatic species to exhibit greater plasticity in body size with temperature. Total percentage change in size over the annual cycle appears relatively constant with annual temperature range but varies between environments, such that the overall size reduction in aquatic-developing species (approx. 31%) is almost threefold greater than in terrestrial species (approx. 11%). For the first time, we show that strong correlations exist between seasonal temperature-size gradients, laboratory responses and latitudinal-size clines, suggesting that these patterns share common drivers. © 2017 The Author(s).

Formation of anisotropic hollow-fiber membranes via thermally induced phase separation

NASA Astrophysics Data System (ADS)

Batarseh, Melanie Turkett

The goal of this research project was to study the formation of anisotropic hollow fiber membranes via thermally induced phase separation (TIPS). This objective included developing a fundamental knowledge of the factors that contribute to anisotropy and studying how anisotropy can be controlled via operational parameters in hollow fiber spinning. The objective was met by creating a model to simulate the mass and heat transfer in the fiber wall during spinning and by experimentally varying spinning parameters and observing the affect on the membrane microstructure. The TIPS membrane formation process consists of forming a homogeneous solution of polymer and diluent and extruding the solution through a spinneret to form a hollow fiber. The fiber is cooled in an air gap followed by a quench bath, which results in phase separation of the solution into a diluent-rich phase dispersed in a continuous polymer-rich liquid phase. The diluent-rich domains grow in size until the polymer-rich phase crystallizes. Then the diluent is removed, and the spaces left behind become the pores of the microporous membrane. Therefore, the size of the diluent-rich domains when the polymer solidifies is related to the size of the pores in the finished membrane. Increasing the polymer concentration of the homogeneous solution or increasing the cooling rate of the phase separated solution decreases the domain size, and thus decreases pore size. An anisotropic membrane, which has a gradation of pore size from small pores at the feed-side to large pores at the permeate-side, can be formed by creating a concentration gradient or a cooling rate gradient across the membrane. In hollow fiber spinning, a concentration gradient can be created by allowing diluent to evaporate from the outside wall of the fiber in the air gap, and a cooling rate gradient can be created by quenching the fiber in a liquid bath. The spinning model calculates concentration and temperature profiles across the hollow fiber wall over time. The model results indicate that spinning temperature, air velocity, and air gap length have a significant effect on the concentration profile in the wall, and spinning temperature and quench temperature have a significant effect on the cooling rate profile. Experimental results indicate that increasing the air gap length from 5 to 50 cm. or increasing the quench temperature from 298 to 323 K has a significant effect on the anisotropic structure of the hollow fiber.

Regional and local meteorology influences high-resolution tropospheric ozone concentration in the Los Angeles Basin

NASA Astrophysics Data System (ADS)

Koutzoukis, S.; Jenerette, D.; Chandler, M.; Wang, J.; Ge, C.; Ripplinger, J.

2017-12-01

Urban air quality and climate directly affect resident health. The Los Angeles (LA) Basin is a highly populated metropolitan area, with widespread point sources of ozone (O3) precursors (NOx , Volatile Organic Compounds, CO) from fossil fuel combustion. The LA basin exists on a coast-to-mountain gradient, with increasing temperatures towards the Transverse Ranges, which rise to 1700m. Frequently not compliant with 8-hour O3 standards, the LA and South Coast Air Basins are designated as severe and extreme non-attainment areas. Summer weather in the LA basin is characterized by a persistent high pressure system, creating an inversion that traps air pollutants, including O3 precursors, coupled with physical geography that blocks prevailing upper atmosphere air flow. These interactions make neighborhood-level O3 levels more variable than common regional models. Over the summer of 2017, we investigated the importance of local meteorology, wind patterns and air temperature, in transporting and mixing ozone precursors from point sources along the coast-to-mountain gradient. We deployed a network of six EPA federal equivalent method ozone and meteorological sensors in three campaigns in the LA basin along the coast-to-mountain transect. Each campaign, we collaborated with citizen scientists to deploy three sensor stations in two, 4 km2 quadrats, for a total of six high-resolution 4 km2 pixels. O3 concentrations vary greatly along the transect. At the coastal sites, daily O3 ranges from 0ppm to 60ppm and the range increases at the inland sites, to 100ppm. At all sites, there was a positive relationship between wind speed, air temperature, and O3 concentration, with increasing correlation inland. The Pearson correlation coefficient between wind speed and O3 concentration doubles from the coast to inland, and triples between air temperature and O3. The site-specific relationships between O3 and wind direction and temperature vary, suggesting neighborhood-effects from local point sources.

Particulate emissions from a beef cattle feedlot using the flux-gradient technique.

PubMed

Bonifacio, Henry F; Maghirang, Ronaldo G; Trabue, Steven L; McConnell, Laura L; Prueger, John H; Razote, Edna B

2013-09-01

Data on air emissions from open-lot beef cattle () feedlots are limited. This research was conducted to determine fluxes of particulate matter with an aerodynamic diameter ≤10 μm (PM) from a commercial beef cattle feedlot in Kansas using the flux-gradient technique, a widely used micrometeorological method for air emissions from open sources. Vertical PM concentration profiles and micrometeorological parameters were measured at the feedlot using tapered element oscillating microbalance PM samplers and eddy covariance instrumentations (i.e., sonic anemometer and infrared hygrometer), respectively, from May 2010 through September 2011, representing feedlot conditions with air temperatures ranging from -24 to 39°C. Calculated hourly PM fluxes varied diurnally and seasonally, ranging up to 272 mg m h, with an overall median of 36 mg m h. For warm conditions (air temperature of 21 ± 10°C), the highest hourly PM fluxes (range 116-146 mg m h) were observed during the early evening period, from 2000 to 2100 h. For cold conditions (air temperature of -2 ± 8°C), the highest PM fluxes (range 14-27 mg m h) were observed in the afternoon, from 1100 to 1500 h. Changes in the hourly trend of PM fluxes coincided with changes in friction velocity, air temperature, sensible heat flux, and surface roughness. The PM emission was also affected by the pen surface water content, where a water content of at least 20% (wet basis) would be sufficient to effectively reduce PM emissions from pens by as much as 60%. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

The numerical modeling the sensitivity of coastal wind and ozone concentration to different SST forcing

NASA Astrophysics Data System (ADS)

Choi, Hyun-Jung; Lee, Hwa Woon; Jeon, Won-Bae; Lee, Soon-Hwan

2012-01-01

This study evaluated an atmospheric and air quality model of the spatial variability in low-level coastal winds and ozone concentration, which are affected by sea surface temperature (SST) forcing with different thermal gradients. Several numerical experiments examined the effect of sea surface SST forcing on the coastal atmosphere and air quality. In this study, the RAMS-CAMx model was used to estimate the sensitivity to two different resolutions of SST forcing during the episode day as well as to simulate the low-level coastal winds and ozone concentration over a complex coastal area. The regional model reproduced the qualitative effect of SST forcing and thermal gradients on the coastal flow. The high-resolution SST derived from NGSST-O (New Generation Sea Surface Temperature Open Ocean) forcing to resolve the warm SST appeared to enhance the mean response of low-level winds to coastal regions. These wind variations have important implications for coastal air quality. A higher ozone concentration was forecasted when SST data with a high resolution was used with the appropriate limitation of temperature, regional wind circulation, vertical mixing height and nocturnal boundary layer (NBL) near coastal areas.

Comparison of forced-air warming systems with upper body blankets using a copper manikin of the human body.

PubMed

Bräuer, A; English, M J M; Steinmetz, N; Lorenz, N; Perl, T; Braun, U; Weyland, W

2002-09-01

Forced-air warming with upper body blankets has gained high acceptance as a measure for the prevention of intraoperative hypothermia. However, data on heat transfer with upper body blankets are not yet available. This study was conducted to determine the heat transfer efficacy of eight complete upper body warming systems and to gain more insight into the principles of forced-air warming. Heat transfer of forced-air warmers can be described as follows: Qdot;=h. DeltaT. A, where Qdot;= heat flux [W], h=heat exchange coefficient [W m-2 degrees C-1], DeltaT=temperature gradient between the blanket and surface [ degrees C], and A=covered area [m2]. We tested eight different forced-air warming systems: (1) Bair Hugger and upper body blanket (Augustine Medical Inc. Eden Prairie, MN); (2) Thermacare and upper body blanket (Gaymar Industries, Orchard Park, NY); (3) Thermacare (Gaymar Industries) with reusable Optisan upper body blanket (Willy Rüsch AG, Kernen, Germany); (4) WarmAir and upper body blanket (Cincinnati Sub-Zero Products, Cincinnati, OH); (5) Warm-Gard and single use upper body blanket (Luis Gibeck AB, Upplands Väsby, Sweden); (6) Warm-Gard and reusable upper body blanket (Luis Gibeck AB); (7) WarmTouch and CareDrape upper body blanket (Mallinckrodt Medical Inc., St. Luis, MO); and (8) WarmTouch and reusable MultiCover trade mark upper body blanket (Mallinckrodt Medical Inc.) on a previously validated copper manikin of the human body. Heat flux and surface temperature were measured with 11 calibrated heat flux transducers. Blanket temperature was measured using 11 thermocouples. The temperature gradient between the blanket and surface (DeltaT) was varied between -8 and +8 degrees C, and h was determined by linear regression analysis as the slope of DeltaT vs. heat flux. Mean DeltaT was determined for surface temperatures between 36 and 38 degrees C, as similar mean skin surface temperatures have been found in volunteers. The covered area was estimated to be 0.35 m2. Total heat flow from the blanket to the manikin was different for surface temperatures between 36 and 38 degrees C. At a surface temperature of 36 degrees C the heat flows were higher (4-26.6 W) than at surface temperatures of 38 degrees C (2.6-18.1 W). The highest total heat flow was delivered by the WarmTouch trade mark system with the CareDrape trade mark upper body blanket (18.1-26.6 W). The lowest total heat flow was delivered by the Warm-Gard system with the single use upper body blanket (2.6-4 W). The heat exchange coefficient varied between 15.1 and 36.2 W m-2 degrees C-1, and mean DeltaT varied between 0.5 and 3.3 degrees C. We found total heat flows of 2.6-26.6 W by forced-air warming systems with upper body blankets. However, the changes in heat balance by forced-air warming systems with upper body blankets are larger, as these systems are not only transferring heat to the body but are also reducing heat losses from the covered area to zero. Converting heat losses of approximately 37.8 W to heat gain, results in a 40.4-64.4 W change in heat balance. The differences between the systems result from different heat exchange coefficients and different mean temperature gradients. However, the combination of a high heat exchange coefficient with a high mean temperature gradient is rare. This fact offers some possibility to improve these systems.

Heating of metallic implants and instruments induced by gradient switching in a 1.5-Tesla whole-body unit.

PubMed

Graf, Hansjörg; Steidle, Günter; Schick, Fritz

2007-11-01

To examine gradient switching-induced heating of metallic parts. Copper and titanium frames and sheets ( approximately 50 x 50 mm(2), 1.5 mm thick, frame width = 3 mm) surrounded by air were positioned in the scanner perpendicular to the static field horizontally 20 cm off-center. During the execution of a sequence (three-dimensional [3D] true fast imaging with steady precession [True-FISP], TR = 6.4 msec) exploiting the gradient capabilities (maximum gradient = 40 mT/m, maximum slew rate = 200 T/m/second), heating was measured with an infrared camera. Radio frequency (RF) amplitude was set to zero volts. Heating of a copper frame with a narrowing to 1 mm over 20 mm at one side was examined in air and in addition surrounded by several liters of gelled saline using fiber-optic thermography. Further heating studies were performed using an artificial hip made of titanium, and an aluminum replica of the hip prosthesis with the same geometry. For the copper specimens, considerable heating (>10 degrees C) in air and in gelled saline (>1.2 degrees C) could be observed. Heating of the titanium specimens was markedly less ( approximately 1 degrees C in air). For the titanium artificial hip no heating could be detected, while the rise in temperature for the aluminum replica was approximately 2.2 degrees C. Heating of more than 10 degrees C solely due to gradient switching without any RF irradiation was demonstrated in isolated copper wire frames. Under specific conditions (high gradient duty cycle, metallic loop of sufficient inductance and low resistance, power matching) gradient switching-induced heating of conductive specimens must be considered.

Thermal-gradient migration of brine inclusions in salt crystals. [Synthetic single crystals of NaCl and KCl

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

Yagnik, S.K.

1982-09-01

It has been proposed that high-level nuclear waste be disposed in a geologic repository. Natural-salt deposits, which are being considered for this purpose, contain a small volume fraction of water in the form of brine inclusions distributed throughout the salt. Radioactive-decay heating of the nuclear wastes will impose a temperature gradient on the surrounding salt which mobilizes the brine inclusions. Inclusions filled completely with brine migrate up the temperature gradient and eventually accumulate brine near the buried waste forms. The brine may slowly corrode or degrade the waste forms which is undesirable. In this work, thermal gradient migration of bothmore » all-liquid and gas-liquid inclusions was experimentally studied in synthetic single crystals of NaCl and KCl using a hot-stage attachment to an optical microscope which was capable of imposing temperature gradients and axial compressive loads on the crystals. The migration velocities of the inclusions were found to be dependent on temperature, temperature gradient, and inclusion shape and size. The velocities were also dictated by the interfacial mass transfer resistance at brine/solid interface. This interfacial resistance depends on the dislocation density in the crystal, which in turn, depends on the axial compressive loading of the crystal. At low axial loads, the dependence between the velocity and temperature gradient is non-linear.At high axial loads, however, the interfacial resistance is reduced and the migration velocity depends linearly on the temperature gradient. All-liquid inclusions filled with mixed brines were also studied. For gas-liquid inclusions, three different gas phases (helium, air and argon) were compared. Migration studies were also conducted on single crystallites of natural salt as well as in polycrystalline natural salt samples. The behavior of the inclusions at large angle grain boundaries was observed. 35 figures, 3 tables.« less

Complete temperature profiles in ultra-high-pressure liquid chromatography columns.

PubMed

Gritti, Fabrice; Guiochon, Georges

2008-07-01

The temperature profiles were calculated along and across seven packed columns (lengths 30, 50, 100, and 150 mm, i.d., 1 and 2.1 mm, all packed with Acquity UPLC, BEH-C 18 particles, average d(p) approximately 1.7 microm) and their stainless steel tubes (o.d. 4.53 and 6.35 mm). These columns were kept horizontal and sheltered from forced air convection (i.e., under still air conditions), at room temperature. They were all percolated with pure acetonitrile, either under the maximum pressure drop (1034 bar) or at the maximum flow rate (2 mL/min) permitted by the chromatograph. The heat balance equation of chromatographic columns was discretized and solved numerically with minimum approximation. Both the compressibility and the thermal expansion of the eluent were taken into account. The boundary conditions were determined from the experimental measurements of the column inlet pressure and of the temperature profile along the column wall, which were made with a precision better than +/-0.1 K. These calculation results provide the 3-D temperature profiles along and across the columns. The axial and radial temperature gradients are discussed in relationship with the experimental conditions used. The temperature map obtained permits a prediction of the chromatographic data obtained under a very high pressure gradient.

Characterization of the thermal conductivity for Advanced Toughened Uni-piece Fibrous Insulations

NASA Technical Reports Server (NTRS)

Stewart, David A.; Leiser, Daniel B.

1993-01-01

Advanced Toughened Uni-piece Fibrous Insulations (TUFI) is discussed in terms of their thermal response to an arc-jet air stream. A modification of the existing Ames thermal conductivity program to predict the thermal response of these functionally gradient materials is described in the paper. The modified program was used to evaluate the effect of density, surface porosity, and density gradient through the TUFI materials on the thermal response of these insulations. Predictions using a finite-difference code and calculated thermal conductivity values from the modified program were compared with in-depth temperature measurements taken from TUFI insulations during short exposures to arc-jet hypersonic air streams.

Implications of climatic seasonality on activity patterns and resource use by sympatric peccaries in northern Pantanal.

PubMed

Hofmann, Gabriel Selbach; Coelho, Igor Pfeifer; Bastazini, Vinicius Augusto Galvão; Cordeiro, José Luís Passos; de Oliveira, Luiz Flamarion Barbosa

2016-03-01

We evaluated the effects of climate seasonality from a thermal and water availability perspective on the activity patterns and resource use of Pecari tajacu and Tayassu pecari during wet and dry seasons in the northeastern Brazilian Pantanal. We used camera traps and temperature sensors to record species activity patterns in relation to temperature, established five habitat categories based on flooding intensity and local vegetation characteristics, assessed the activity patterns of each species in dry and wet periods and in artificial water bodies using circular statistical metrics, and calculated niche amplitude and overlap on three axes (temperature, time, and habitat) in both periods. Peccaries shared a strong resemblance in resource use and in their responses to seasonal variations in the tested gradients. The activity patterns of both species exhibited a significant correlation with air temperature on all the evaluated measures, and both species strongly reduced their activity when the air temperature exceeded 35 °C. High temperatures associated with low water availability were most likely responsible for the changes in species activity patterns, which resulted in an increased temporal overlap in habitat use throughout the dry season. However, the peccaries avoided intensively flooded habitats; therefore, the habitat gradient overlap was greater during the wet period. Our results show that an increase in niche overlap on the environmental gradient as a result of climatic seasonality may be partially compensated by a reduction in other niche dimensions. In this case, temporal partitioning appears to be an important, viable mechanism to reduce competition by potentially competing species.

Experimental feasibility study of radial injection cooling of three-pad radial air foil bearings

NASA Astrophysics Data System (ADS)

Shrestha, Suman K.

Air foil bearings use ambient air as a lubricant allowing environment-friendly operation. When they are designed, installed, and operated properly, air foil bearings are very cost effective and reliable solution to oil-free turbomachinery. Because air is used as a lubricant, there are no mechanical contacts between the rotor and bearings and when the rotor is lifted off the bearing, near frictionless quiet operation is possible. However, due to the high speed operation, thermal management is one of the very important design factors to consider. Most widely accepted practice of the cooling method is axial cooling, which uses cooling air passing through heat exchange channels formed underneath the bearing pad. Advantage is no hardware modification to implement the axial cooling because elastic foundation structure of foil bearing serves as a heat exchange channels. Disadvantage is axial temperature gradient on the journal shaft and bearing. This work presents the experimental feasibility study of alternative cooling method using radial injection of cooling air directly on the rotor shaft. The injection speeds, number of nozzles, location of nozzles, total air flow rate are important factors determining the effectiveness of the radial injection cooling method. Effectiveness of the radial injection cooling was compared with traditional axial cooling method. A previously constructed test rig was modified to accommodate a new motor with higher torque and radial injection cooling. The radial injection cooling utilizes the direct air injection to the inlet region of air film from three locations at 120° from one another with each location having three axially separated holes. In axial cooling, a certain axial pressure gradient is applied across the bearing to induce axial cooling air through bump foil channels. For the comparison of the two methods, the same amount of cooling air flow rate was used for both axial cooling and radial injection. Cooling air flow rate was referenced to the rotor surface speed for radial injection cooling. The mass flow rates for the radial injection were 0.032, 0.0432, 0.054 and 0.068 Kg/min, which result in average injection speed of 150, 200, 250 and 300% of rotor surface speed. Several thermocouples were attached at various circumferential directions of the bearing sleeve, two plenums, bearing holder and ball bearing housings to collect the temperature data of the bearing at 30krpm under 10lb of load. Both axial cooling and radial injection are effective cooling mechanism and effectiveness of both cooling methods is directly proportional to the total mass flow rates. However, axial cooling is slightly more efficient in controlling the average temperature of the bearing sleeve, but results in higher thermal gradient of the shaft along the axial direction and also higher thermal gradient of the bearing sleeve along the circumferential direction compared to the radial injection cooling. The smaller thermal gradient of the radial injection cooling is due to the direct cooling effect of the shaft by impinging jets. While the axial cooling has an effect on only the bearing, the radial injection has a cooling effect on both the bearing sleeve and shaft. It is considered the radial injection cooling needs to be further optimized in terms of number of injection holes and their locations.

Improved Cloud Condensation Nucleus Spectrometer

NASA Technical Reports Server (NTRS)

Leu, Ming-Taun

2010-01-01

An improved thermal-gradient cloud condensation nucleus spectrometer (CCNS) has been designed to provide several enhancements over prior thermal- gradient counters, including fast response and high-sensitivity detection covering a wide range of supersaturations. CCNSs are used in laboratory research on the relationships among aerosols, supersaturation of air, and the formation of clouds. The operational characteristics of prior counters are such that it takes long times to determine aerosol critical supersaturations. Hence, there is a need for a CCNS capable of rapid scanning through a wide range of supersaturations. The present improved CCNS satisfies this need. The improved thermal-gradient CCNS (see Figure 1) incorporates the following notable features: a) The main chamber is bounded on the top and bottom by parallel thick copper plates, which are joined by a thermally conductive vertical wall on one side and a thermally nonconductive wall on the opposite side. b) To establish a temperature gradient needed to establish a supersaturation gradient, water at two different regulated temperatures is pumped through tubes along the edges of the copper plates at the thermally-nonconductive-wall side. Figure 2 presents an example of temperature and supersaturation gradients for one combination of regulated temperatures at the thermally-nonconductive-wall edges of the copper plates. c) To enable measurement of the temperature gradient, ten thermocouples are cemented to the external surfaces of the copper plates (five on the top plate and five on the bottom plate), spaced at equal intervals along the width axis of the main chamber near the outlet end. d) Pieces of filter paper or cotton felt are cemented onto the interior surfaces of the copper plates and, prior to each experimental run, are saturated with water to establish a supersaturation field inside the main chamber. e) A flow of monodisperse aerosol and a dilution flow of humid air are introduced into the main chamber at the inlet end. The inlet assembly is designed to offer improved (relative to prior such assemblies) laminar-flow performance within the main chamber. Dry aerosols are subjected to activation and growth in the supersaturation field. f) After aerosol activation, at the outlet end of the main chamber, a polished stainless-steel probe is used to sample droplets into a laser particle counter. The probe features an improved design for efficient sampling. The counter has six channels with size bins in the range of 0.5- to 5.0-micron diameter. g) To enable efficient sampling, the probe is scanned along the width axis of the main chamber (thereby effecting scanning along the temperature gradient and thereby, further, effecting scanning along the supersaturation gradient) by means of a computer-controlled translation stage.

Solid oxide fuel cell operable over wide temperature range

DOEpatents

Baozhen, Li; Ruka, Roswell J.; Singhal, Subhash C.

2001-01-01

Solid oxide fuel cells having improved low-temperature operation are disclosed. In one embodiment, an interfacial layer of terbia-stabilized zirconia is located between the air electrode and electrolyte of the solid oxide fuel cell. The interfacial layer provides a barrier which controls interaction between the air electrode and electrolyte. The interfacial layer also reduces polarization loss through the reduction of the air electrode/electrolyte interfacial electrical resistance. In another embodiment, the solid oxide fuel cell comprises a scandia-stabilized zirconia electrolyte having high electrical conductivity. The scandia-stabilized zirconia electrolyte may be provided as a very thin layer in order to reduce resistance. The scandia-stabilized electrolyte is preferably used in combination with the terbia-stabilized interfacial layer. The solid oxide fuel cells are operable over wider temperature ranges and wider temperature gradients in comparison with conventional fuel cells.

Influence of air humidity and the distance from the source on negative air ion concentration in indoor air.

PubMed

Wu, Chih Cheng; Lee, Grace W M; Yang, Shinhao; Yu, Kuo-Pin; Lou, Chia Ling

2006-10-15

Although negative air ionizer is commonly used for indoor air cleaning, few studies examine the concentration gradient of negative air ion (NAI) in indoor environments. This study investigated the concentration gradient of NAI at various relative humidities and distances form the source in indoor air. The NAI was generated by single-electrode negative electric discharge; the discharge was kept at dark discharge and 30.0 kV. The NAI concentrations were measured at various distances (10-900 cm) from the discharge electrode in order to identify the distribution of NAI in an indoor environment. The profile of NAI concentration was monitored at different relative humidities (38.1-73.6% RH) and room temperatures (25.2+/-1.4 degrees C). Experimental results indicate that the influence of relative humidity on the concentration gradient of NAI was complicated. There were four trends for the relationship between NAI concentration and relative humidity at different distances from the discharge electrode. The changes of NAI concentration with an increase in relative humidity at different distances were quite steady (10-30 cm), strongly declining (70-360 cm), approaching stability (420-450 cm) and moderately increasing (560-900 cm). Additionally, the regression analysis of NAI concentrations and distances from the discharge electrode indicated a logarithmic linear (log-linear) relationship; the distance of log-linear tendency (lambda) decreased with an increase in relative humidity such that the log-linear distance of 38.1% RH was 2.9 times that of 73.6% RH. Moreover, an empirical curve fit based on this study for the concentration gradient of NAI generated by negative electric discharge in indoor air was developed for estimating the NAI concentration at different relative humidities and distances from the source of electric discharge.

A Description of Methodologies Used in Estimation of A-Weighted Sound Levels for FAA Advisory Circular AC-36-3B.

DTIC Science & Technology

1982-01-01

second) Dia propeller diameter (expressed in inches) T°F air temperature in degrees Farenheit T°C air temperature in degrees Celsius T:dBA total dBA...eMpiriC31 function to the absolute noise level ordinate. The term 240 log ( MH is the most sensitive and important part of the equation. The constant (240...standard day, zero wind, dry, zero gradient runway, at a sea level airport. 2. All aircraft operate at maximum takeoff gross weight. 3. All aircraft climb

Observations of a stratospheric depletion and annual mean interhemispheric gradient in the atmospheric Ar/N2 ratio from the HIPPO Global campaign

NASA Astrophysics Data System (ADS)

Bent, J. D.; Keeling, R. F.; Stephens, B. B.; Wofsy, S. C.; Daube, B. C.; Kort, E. A.; Pittman, J. V.; Jimenez-Pizarro, R.; Santoni, G.

2014-12-01

The atmospheric Ar/N2 ratio varies on a seasonal basis due to temperature-dependent solubility changes in the surface ocean. Low signal:noise ratios, limited vertical coverage, and sampler-sampler offsets have historically hampered characterization of vertical and inter-hemispheric gradients. We present data from the HIPPO Global campaign (2009-11) showing that Ar/N2 and interannually-detrended N2O correlate well in the lower stratosphere, suggesting that, as stratospheric air ages and loses N2O to photolysis and photo-oxidation, it also gradually loses argon to gravity as the heavier atom preferentially "rains out" of the air parcel. The HIPPO Ar/N2 data from the lower troposphere also resolve seasonal cycles in each hemisphere, as well as a gradient in the annual mean between hemispheres, with higher values in the southern hemisphere. The HIPPO cycles and inter-hemispheric gradient are in good agreement with data from surface stations.

Cooling vests with phase change materials: the effects of melting temperature on heat strain alleviation in an extremely hot environment.

PubMed

Gao, Chuansi; Kuklane, Kalev; Holmér, Ingvar

2011-06-01

A previous study by the authors using a heated thermal manikin showed that the cooling rates of phase change material (PCM) are dependent on temperature gradient, mass, and covering area. The objective of this study was to investigate if the cooling effects of the temperature gradient observed on a thermal manikin could be validated on human subjects in extreme heat. The subjects wore cooling vests with PCMs at two melting temperatures (24 and 28°C) and fire-fighting clothing and equipment, thus forming three test groups (vest24, vest28 and control group without the vest). They walked on a treadmill at a speed of 5 km/h in a climatic chamber (air temperature = 55°C, relative humidity = 30%, vapour pressure = 4,725 Pa, and air velocity = 0.4 m/s). The results showed that the PCM vest with a lower melting temperature (24°C) has a stronger cooling effect on the torso and mean skin temperatures than that with a higher melting temperature (28°C). Both PCM vests mitigate peak core temperature increase during the resting recovery period. The two PCM vests tested, however, had no significant effect on the alleviation of core temperature increase during exercise in the heat. To study the possibility of effective cooling of core temperature, cooling garments with PCMs at even lower melting temperatures (e.g. 15°C) and a larger covering area should be investigated.

Limitations of using a thermal imager for snow pit temperatures

NASA Astrophysics Data System (ADS)

Schirmer, M.; Jamieson, B.

2014-03-01

Driven by temperature gradients, kinetic snow metamorphism plays an import role in avalanche formation. When gradients based on temperatures measured 10 cm apart appear to be insufficient for kinetic metamorphism, faceting close to a crust can be observed. Recent studies that visualised small-scale (< 10 cm) thermal structures in a profile of snow layers with an infrared (IR) camera produced interesting results. The studies found melt-freeze crusts to be warmer or cooler than the surrounding snow depending on the large-scale gradient direction. However, an important assumption within these studies was that a thermal photo of a freshly exposed snow pit was similar enough to the internal temperature of the snow. In this study, we tested this assumption by recording thermal videos during the exposure of the snow pit wall. In the first minute, the results showed increasing gradients with time, both at melt-freeze crusts and artificial surface structures such as shovel scours. Cutting through a crust with a cutting blade or shovel produced small concavities (holes) even when the objective was to cut a planar surface. Our findings suggest there is a surface structure dependency of the thermal image, which was only observed at times during a strong cooling/warming of the exposed pit wall. We were able to reproduce the hot-crust/cold-crust phenomenon and relate it entirely to surface structure in a temperature-controlled cold laboratory. Concave areas cooled or warmed more slowly compared with convex areas (bumps) when applying temperature differences between snow and air. This can be explained by increased radiative and/or turbulent energy transfer at convex areas. Thermal videos suggest that such processes influence the snow temperature within seconds. Our findings show the limitations of using a thermal camera for measuring pit-wall temperatures, particularly during windy conditions, clear skies and large temperature differences between air and snow. At crusts or other heterogeneities, we were unable to create a sufficiently planar snow pit surface and non-internal gradients appeared at the exposed surface. The immediate adjustment of snow pit temperature as it reacts with the atmosphere complicates the capture of the internal thermal structure of a snowpack with thermal videos. Instead, the shown structural dependency of the IR signal may be used to detect structural changes of snow caused by kinetic metamorphism. The IR signal can also be used to measure near surface temperatures in a homogenous new snow layer.

Comparison of Vertical Soundings and Sidewall Air Temperature Measurements in a Small Alpine Basin

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

Whiteman, Charles D.; Eisenbach, Stefan; Pospichal, Bernhard

2004-11-01

Tethered balloon soundings from two sites on the floor of a 1-km diameter limestone sinkhole in the Eastern Alps are compared with pseudo-vertical temperature ‘soundings’ from three lines of temperature data loggers on the basin’s northwest, southwest and southeast sidewalls. Under stable nighttime conditions with low background winds, the pseudo-vertical profiles from all three lines were good proxies for free air temperature soundings over the basin center, with a mean nighttime cold temperature bias of about 0.4°C and a standard deviation of 0.4°C. Cold biases were highest in the upper basin where relatively warm air subsides to replace air thatmore » spills out of the basin through the lowest altitude saddle. On a windy night, standard deviations increased to 1 - 2°C. After sunrise, the varying exposures of the data loggers to sunlight made the pseudo-vertical profiles less useful as proxies for free air soundings. The good correspondence between sidewall and free air temperatures during high static stability conditions suggests that sidewall soundings will prove useful in monitoring temperatures and vertical temperature gradients in the sinkhole. The sidewall soundings can produce more frequent profiles at less cost than tethersondes or rawinsondes, and provide valuable advantages for some types of meteorological analyses.« less

Geometric effects on bilayer convection in cylindrical containers

NASA Astrophysics Data System (ADS)

Johnson, Duane Thomas

The study of convection in two immiscible fluid layers is of interest for reasons both theoretical as well as applied. Recently, bilayer convection has been used as a model of convection in the earth's mantle. It is also an interesting system to use in the study of pattern formation. Bilayer convection also occurs in a process known as liquid encapsulated crystal growth, which is used to grow compound semiconductors. It is the last application which motivates this study. To analyze bilayer convection, theoretical models, numerical calculations and experiments were used. One theoretical model involves the derivation of the Navier- Stokes and energy equation for two immiscible fluid layers, using the Boussinesq approximation. A weakly nonlinear analysis was also performed to study the behavior of the system slightly beyond the onset of convection. Numerical calculations were necessary to solve both models. The experiments involved a single liquid layer of silicone oil, superposed by a layer of air. The radius and height of each fluid layer were changed to observe different flow patterns at the onset of convection. From the experiments and theory, two major discoveries were made as well as several interesting observations. The first discovery is the existence of codimension-two points-particular aspect ratios where two flow patterns coexist-in cylindrical containers. At these points, dynamic switching between different flow patterns was observed. The second discovery was the effect of air convection on the flow pattern in silicone oil. Historically, air has been considered a passive medium that has no effect on the lower fluid. However, experiments were done to show that for large air heights, convection in the air can cause radial temperature gradients at the liquid interface. These temperature gradients then cause surface tension gradient-driven flows. It was also shown that changing the radius of the container can change the driving force of convection from a surface tension gradient-driven to buoyancy-driven and back again. Finally, the weakly nonlinear analysis was able to give a qualitative description of codimension-two points as well as the change in flow patterns due to the convecting air layer.

Effect of Climate Change on Soil Temperature in Swedish Boreal Forests

PubMed Central

Jungqvist, Gunnar; Oni, Stephen K.; Teutschbein, Claudia; Futter, Martyn N.

2014-01-01

Complex non-linear relationships exist between air and soil temperature responses to climate change. Despite its influence on hydrological and biogeochemical processes, soil temperature has received less attention in climate impact studies. Here we present and apply an empirical soil temperature model to four forest sites along a climatic gradient of Sweden. Future air and soil temperature were projected using an ensemble of regional climate models. Annual average air and soil temperatures were projected to increase, but complex dynamics were projected on a seasonal scale. Future changes in winter soil temperature were strongly dependent on projected snow cover. At the northernmost site, winter soil temperatures changed very little due to insulating effects of snow cover but southern sites with little or no snow cover showed the largest projected winter soil warming. Projected soil warming was greatest in the spring (up to 4°C) in the north, suggesting earlier snowmelt, extension of growing season length and possible northward shifts in the boreal biome. This showed that the projected effects of climate change on soil temperature in snow dominated regions are complex and general assumptions of future soil temperature responses to climate change based on air temperature alone are inadequate and should be avoided in boreal regions. PMID:24747938

Effect of climate change on soil temperature in Swedish boreal forests.

PubMed

Jungqvist, Gunnar; Oni, Stephen K; Teutschbein, Claudia; Futter, Martyn N

2014-01-01

Complex non-linear relationships exist between air and soil temperature responses to climate change. Despite its influence on hydrological and biogeochemical processes, soil temperature has received less attention in climate impact studies. Here we present and apply an empirical soil temperature model to four forest sites along a climatic gradient of Sweden. Future air and soil temperature were projected using an ensemble of regional climate models. Annual average air and soil temperatures were projected to increase, but complex dynamics were projected on a seasonal scale. Future changes in winter soil temperature were strongly dependent on projected snow cover. At the northernmost site, winter soil temperatures changed very little due to insulating effects of snow cover but southern sites with little or no snow cover showed the largest projected winter soil warming. Projected soil warming was greatest in the spring (up to 4°C) in the north, suggesting earlier snowmelt, extension of growing season length and possible northward shifts in the boreal biome. This showed that the projected effects of climate change on soil temperature in snow dominated regions are complex and general assumptions of future soil temperature responses to climate change based on air temperature alone are inadequate and should be avoided in boreal regions.

Insights on the High-Temperature Operational Limits of ZrO2-Y2O3 TBCs Manufactured via Air Plasma Spray

NASA Astrophysics Data System (ADS)

Lima, Rogerio S.; Marple, Basil R.

2017-03-01

The effective high-temperature operation limit of a ZrO2-7-8 wt.%Y2O3 (YSZ) thermal barrier coating (TBC) manufactured via air plasma spray (APS) is considered to be 1300 °C. This is related to the metastable tetragonal t'-phase formed during the rapid quenching of the YSZ particles during spraying. The t'-phase transforms into the equilibrium tetragonal and cubic phases at temperatures ≥ 1300 °C, which can lead to the formation of the monoclinic phase of YSZ upon cooling to room temperature. This formation of the monoclinic phase is accompanied by a volume expansion that leads to TBC failure due to extensive micro-cracking. To further investigate this limitation, an APS YSZ TBC was sprayed on a CMSX-4 substrate. By using a thermal (laser) gradient cyclic testing, a temperature gradient was generated across the TBC/substrate system. The YSZ T- front and substrate backside T- back temperature levels were 1500 and 1000 °C, respectively. In cycle conditions (5-min or 1-h hot and 2-min cool), no TBC failure has been observed. This behavior was partially attributed to the unexpected absence of the monoclinic phase of the YSZ in the cycled coatings. Although preliminary, these results are promising regarding increasing the effective high-temperature operational limits of APS YSZ TBCs.

Interfacial material for solid oxide fuel cell

DOEpatents

Baozhen, Li; Ruka, Roswell J.; Singhal, Subhash C.

1999-01-01

Solid oxide fuel cells having improved low-temperature operation are disclosed. In one embodiment, an interfacial layer of terbia-stabilized zirconia is located between the air electrode and electrolyte of the solid oxide fuel cell. The interfacial layer provides a barrier which controls interaction between the air electrode and electrolyte. The interfacial layer also reduces polarization loss through the reduction of the air electrode/electrolyte interfacial electrical resistance. In another embodiment, the solid oxide fuel cell comprises a scandia-stabilized zirconia electrolyte having high electrical conductivity. The scandia-stabilized zirconia electrolyte may be provided as a very thin layer in order to reduce resistance. The scandia-stabilized electrolyte is preferably used in combination with the terbia-stabilized interfacial layer. The solid oxide fuel cells are operable over wider temperature ranges and wider temperature gradients in comparison with conventional fuel cells.

Time-Lapse Micro-Tomography Measurements and Determination of Effective Transport Properties of Snow Metamorphism Under Advective Conditions

NASA Astrophysics Data System (ADS)

Ebner, P. P.; Grimm, S.; Steen-Larsen, H. C.; Schneebeli, M.; Steinfeld, A.

2014-12-01

The metamorphism of snow under advective air flow, with and without temperature gradient, was never experimentally investigated. We developed a new sample holder where metamorphism under advective conditions can be observed and measured using time-lapse micro-tomography [1]. Long-term experiments were performed and direct pore-level simulation (DPLS) [2,3] was directly applied on the extracted 3D digital geometry of the snow to calculate the effective transport properties by solving the governing fluid flow equations. The results showed no effect of isothermal advection, compared to rates typical for isothermal metamorphism. Appling a temperature gradient, the results showed increased snow metamorphism compared to rates typical for temperature gradient metamorphism. However, for both cases a change in the isotopic composition in the air as well as in the snow sample could be observed. These measurements could be influential to better understand snow-air exchange processes relevant for atmospheric chemistry and isotopic composition. REFERENCES[1] Ebner P. P., Grimm S., Schneebeli M., and Steinfeld A.: An instrumented sample holder for time-lapse micro-tomography measurements of snow under advective airflow. Geoscientific Instrumentation, Methods and Data Systems 4(2014), 353-373. [2] Zermatten E., Haussener S., Schneebeli M., and Steinfeld A.: Tomography-based determination of permeability and Dupuit-Forchheimer coefficient of characteristic snow samples. Journal of Glaciology 57(2011), 811-816. [3] Zermatten E., Schneebeli M., Arakawa H., and Steinfeld A.: Tomography-based determination of porosity, specific area and permeability of snow and comparison with measurements. Cold Regions Science and Technology 97 (2014), 33-40. Fig. 1: 3-D surface rendering of a refrozen wet snow sample with fluid flow streamline.

Seasonal variation in diffusive exchange of polycyclic aromatic hydrocarbons across the air-seawater interface in coastal urban area.

PubMed

Kim, Seung-Kyu; Chae, Doo Hyun

2016-08-15

Concentrations of 15 polycyclic aromatic hydrocarbons (PAHs) in air-seawater interface were measured over 1year in the coastal region of Incheon, South Korea. Most individual PAHs and total PAHs in air displayed statistically significant negative correlations with temperature, but not significant in seawater. Less hydrophobic compounds with three rings were at or near equilibrium in summer, while PAHs with four to six rings were in disequilibrium in all seasons, with higher fugacity gradients in colder seasons and for more hydrophobic compounds. Differently from fugacity gradients, the highest net fluxes occurred for some three- and four-ring PAHs showing the highest atmospheric concentrations. Net gaseous exchange, which was higher in winter, occurred from air to seawater with an annual cumulative flux of 2075μg/m(2)/year (for Σ15PAHs), indicating that atmospheric PAHs in this region, originating from coal/biomass combustion, can deteriorate the quality of seawater and sediment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Horizontal cryogenic bushing for the termination of a superconducting power-transmission line

DOEpatents

Minati, K.F.; Morgan, G.H.; McNerney, A.J.; Schauer, F.

1982-07-29

A termination for a superconducting power transmission line is disclosed which is comprised of a standard air entrance insulated vertical bushing with an elbow, a horizontal cryogenic bushing linking the pressurized cryogenic cable environment to the ambient temperature bushing and a stress cone which terminated the cable outer shield and transforms the large radial voltage gradient in the cable dielectric into a much lower radial voltage gradient in the high density helium coolant at the cold end of the cryogenic bushing.

Termination for a superconducting power transmission line including a horizontal cryogenic bushing

DOEpatents

Minati, Kurt F.; Morgan, Gerry H.; McNerney, Andrew J.; Schauer, Felix

1984-01-01

A termination for a superconducting power transmission line is disclosed which is comprised of a standard air entrance insulated vertical bushing with an elbow, a horizontal cryogenic bushing linking the pressurized cryogenic cable environment to the ambient temperature bushing and a stress cone which terminates the cable outer shield and transforms the large radial voltage gradient in the cable dielectric into a much lower radial voltage gradient in the high density helium coolant at the cold end of the cryogenic bushing.

Active Pattern Factor Control for Gas Turbine Engines

NASA Technical Reports Server (NTRS)

May, James E.

1998-01-01

Small variations in fuel/air mixture ratios within gas turbine combustors can result in measurable, and potentially detrimental, exit thermal gradients. Thermal gradients can increase emissions, as well as shorten the design life of downstream turbomachinery, particularly stator vanes. Uniform temperature profiles are usually sought through careful design and manufacturing of related combustor components. However, small componentto-component variations as well as numerous aging effects degrade system performance. To compensate for degraded thermal performance, researchers are investigating active, closed-loop control schemes.

Two dimensional, transient catalytic combustion of CO-air on platinum

NASA Technical Reports Server (NTRS)

Sinha, N.; Bruno, C.; Bracco, F. V.

1985-01-01

The light off transient of catalytic combustion of lean CO-air mixtures in a platinum coated channel of a honeycomb monolith is studied with a model that resolves transient radial and axial gradients in both the gas and the solid. For the conditions studied it is concluded that: the initial heat release occurs near the entrance at the gas-solid interface and is controlled by heterogeneous reactions; large spatial and temporal temperature gradients occur in the solid near the entrance controlled mostly by the availability of fuel; the temperature of the solid near the entrance achieves almost its steady state value before significant heating of the back; heterogeneous reactions and the gas heated up front and flowing downstream heat the back of the solid; the overall transient time is controlled by the thermal inertia of the solid and by forced convection; radiation significantly influences both transient and steady state particularly near the entrance; the oxidation of CO occurs mostly on the catalyst and becomes diffusion controlled soon into the transient.

Evolution of surface sensible heat over the Tibetan Plateau under the recent global warming hiatus

NASA Astrophysics Data System (ADS)

Zhu, Lihua; Huang, Gang; Fan, Guangzhou; Qu, Xia; Zhao, Guijie; Hua, Wei

2017-10-01

Based on regular surface meteorological observations and NCEP/DOE reanalysis data, this study investigates the evolution of surface sensible heat (SH) over the central and eastern Tibetan Plateau (CE-TP) under the recent global warming hiatus. The results reveal that the SH over the CE-TP presents a recovery since the slowdown of the global warming. The restored surface wind speed together with increased difference in ground-air temperature contribute to the recovery in SH. During the global warming hiatus, the persistent weakening wind speed is alleviated due to the variation of the meridional temperature gradient. Meanwhile, the ground surface temperature and the difference in ground-air temperature show a significant increasing trend in that period caused by the increased total cloud amount, especially at night. At nighttime, the increased total cloud cover reduces the surface effective radiation via a strengthening of atmospheric counter radiation and subsequently brings about a clear upward trend in ground surface temperature and the difference in ground-air temperature. Cloud-radiation feedback plays a significant role in the evolution of the surface temperature and even SH during the global warming hiatus. Consequently, besides the surface wind speed, the difference in ground-air temperature becomes another significant factor for the variation in SH since the slowdown of global warming, particularly at night.

Modeling of microclimatic characteristics of highland area

NASA Astrophysics Data System (ADS)

Sitdikova, Iuliia; Rusin, Igor

2013-04-01

Microclimatic characteristics of highlands may vary considerably over distances of a few meters depending on slope and aspect. There is a problem of estimation of components of surface energy balance based on observation of single stations for description of microclimate highlands. The aim of this paper is to develop a method that would restore microclimatic characteristics of terrain, based on observations of the single station, by physical extrapolation. The input parameters to obtain the microclimatic characteristics are as follows: air temperature, relative humidity, and wind speed on two vertical levels, air pressure, surface temperature, direct and diffused solar radiation and surface albedo. The recent version of the Meteorological Radiation Model (MRM) has been used to calculate a solar radiation over the area and to estimate an influence of cloudiness amounts. The height, slope and aspect were accounted at each point with using a digital elevation model. Have been supposed that air temperature and specific humidity vary with altitude only. Net radiation was calculated at all points of the area. Supposed that the difference between the surface temperature and the air temperature is a linear function of net radiation. The empirical coefficient, which depends on wind speed with adjustment of given area. Latent and sensible fluxes are calculated by using the modified Bowen ratio, which varies on the area. Method was tested on field research in Krasnodar region (RF). The meteorological observations were made every three hour on actinometric and gradient sites. The editional gradient site with different orientation of the slope was organized from 400 meters of the main site. Topographic survey of area was made 1x1,3 km in size for a digital elevation model constructing. At all points of the area of radiation and heat balance were calculated. The results of researches are the maps of surface temperature, net radiation, latent and sensible fluxes. The calculations showed that the average value of components of heat balance by area differ significantly from the data observed on meteorological station.

Design of a Helium Vapor Shroud for Liquid Hydrogen Fueling of an Unmanned Aerial Vehicle (UAV)

NASA Astrophysics Data System (ADS)

Cavender, K.; Evans, C.; Haney, J.; Leachman, J.

2017-12-01

Filling a vehicular liquid hydrogen fuel tank presents the potential for flammable mixtures due to oxygen concentration from liquid air condensation. Current liquid hydrogen tank designs utilize insulating paradigms such as aerogel/fiberglass materials, vacuum jackets, or inert gas purge systems to keep the outer surface from reaching the condensation temperature of air. This work examines the heat transfer at the refuelling connection of the tank to identify potential areas of condensation, as well as the surface temperature gradient. A shrouded inert gas purge was designed to minimize vehicle weight and refuelling time. The design of a shrouded inert gas purge system is presented to displace air preventing air condensation. The design investigates 3D printed materials for an inert gas shroud, as well as low-temperature sealing designs. Shroud designs and temperature profiles were measured and tested by running liquid nitrogen through the filling manifold. Materials for the inert gas shroud are discussed and experimental results are compared to analytical model predictions. Suggestions for future design improvements are made.

Can Nocturnal Cold Air Drainage be Used to Monitor Ecosystem Function?

NASA Astrophysics Data System (ADS)

Pypker, T. G.; Unsworth, M. H.; Sulzman, E. W.; Lamb, B.; Allwine, G.; Mix, A. C.; Bond, B. J.

2005-12-01

Ecosystem carbon dynamics in flat, uniform terrain are commonly studied using standard micrometeorological techniques such as eddy covariance or gradient methods. But many of the world's ecosystems are in complex topography that is inappropriate for these methods. Nocturnal cold air drainage commonly occurs in mountainous terrain. This drainage provides an opportunity to monitor ecosystem carbon dynamics because as air flows downhill through a watershed, it collects respired CO2 from the soil and vegetation. If the nocturnal drainage can be treated as a river of air flowing down a valley, sampling this air from a tower at the base of a watershed could provide an estimate of ecosystem respiration and the 12C/13C ratio. To interpret the measured CO2 and the 12C/13C ratio, the characteristics of the drainage and the footprint (source area) of air passing the tower must be understood. To explore the potential of using nocturnal cold air drainage we built a 37 m tower at the base of a deeply incised watershed of ~40 y-old Douglas-fir in the Oregon Cascades. At various heights on the tower we monitored air temperature, wind speed/direction, and the CO2 concentration and 12C/13C isotopic ratio with a combination of thermistors, sonic anemometers (2-D and 3-D) and a CO2 profile system. The temperature gradient along the axis of the watershed was monitored by 30 temperature sensors from the base to the top of the watershed. The maximum drainage windspeeds on the tower occurred near sunset and, unlike past reports of cold air drainage, this drainage was very deep (> 37 m). The drainage became well mixed when the vertical profile of potential temperature became isothermal. It remained well mixed through the night into the early morning. The drainage occurred on most summer nights and typically provided a range of CO2 (> 60 ppm) sufficient for "Keeling plot" analysis. In September 2005, we released a tracer in the watershed (SF6) to determine the varying footprint size of the tower. The footprint size and windspeed varied throughout the night, resulting in a change in the CO2 concentration at the tower. Further analysis will determine how the CO2 passing the tower is altered by entrainment of the air overlying the drainage and the change in the source area of the drainage.

[Thermal tolerance, diel variation of body temperature, and thermal dependence of locomotor performance of hatchling soft-shelled turtles, Trionyx sinensis].

PubMed

Sun, Pingyue; Xu, Xiaoyin; Chen, Huili; Ji, Xiang

2002-09-01

The thermal tolerance, body temperature, and influence of temperature on locomotor performance of hatchling soft-shelled turtles (Trionyx sinensis) were studied under dry and wet conditions, and the selected body temperature of hatchlings was 28.0 and 30.3 degrees C, respectively. Under wet condition, the critical thermal maximum and minimum averaged 40.9 and 7.8 degrees C, respectively. In the environments without thermal gradients, the diel variation of body temperature was highly consistent with the variation of both air and water temperatures, and the body temperature was more directly affected by water temperature than by air temperature, which implied that the physiological thermoregulation of hatchling T. sinensis was very weak. In the environments with thermal gradients, hatchling turtles could maintain relatively high and constant body temperatures, primarily through behavioral thermoregulation. The locomotor performance of hatchling turtles was highly dependent on their body temperature. Within a certain range, the locomotor performance increased with increasing body temperature. In our study, the optimal body temperature for locomotor performance was 31.5 degrees C, under which, the maximum continuous running distance, running distance per minute, and number of stops per minute averaged 1.87 m, 4.92 m.min-1, and 6.2 times.min-1, respectively. The correspondent values at 33.0 degrees C averaged 1.30 m, 4.28 m.min-1, and 7.7 times.min-1, respectively, which indicated that the locomotor performance of hatchling turtles was impaired at 33.0 degrees C. Therefore, extremely high body temperatures might have an adverse effect on locomotor performance of hatchling turtles.

Study of performance characteristics of noble metal thermocouple materials to 2000 C

NASA Technical Reports Server (NTRS)

Freeze, P. D.; Thomas, D.; Edelman, S.; Stern, J.

1972-01-01

Three performance characteristics of noble metal thermocouples in various environments are discussed. Catalytic effects cause significant errors when noble metal thermocouple materials are exposed to air containing unburned gases in temperature ranges from 25 C to 1500 C. The thermoelectric stability of the iridium 40 rhodium to iridium thermocouple system at 2000 C in an oxidizing medium is described. The effects of large and small temperature gradients on the accuracy and stability of temperature measurements are analyzed.

High-speed measurement of an air transect's temperature shift heated by laser beam

NASA Astrophysics Data System (ADS)

Li, WenYu; Jiang, ZongFu; Xi, Fengjie; Li, Qiang; Xie, Wenke

2005-02-01

Laser beam heat the air on the optic path, Beam-deflection optical tomography is a non-intrusive method to measure the 2-dimension temperature distribution in the transect. By means of linear Hartmann Sensor at the rate of 27kHz, the optic path was heated by a 2.7μm HF laser, continuous and high time resolution gradients of optic phase were obtained. the result of analysing and calculation showed the temperament shift in the heated beam path was not higher than 50K when the HF laser power was 9W. The experiment showed that it is a practical non-intrusive temperature shift measurement method for a small area aero-optical medium.

Dead wood biomass and turnover time, measured by radiocarbon, along a subalpine elevation gradient.

PubMed

Kueppers, Lara M; Southon, John; Baer, Paul; Harte, John

2004-12-01

Dead wood biomass can be a substantial fraction of stored carbon in forest ecosystems, and coarse woody debris (CWD) decay rates may be sensitive to climate warming. We used an elevation gradient in Colorado Rocky Mountain subalpine forest to examine climate and species effects on dead wood biomass, and on CWD decay rate. Using a new radiocarbon approach, we determined that the turnover time of lodgepole pine CWD (340+/-130 years) was roughly half as long in a site with 2.5-3 degrees C warmer air temperature, as that of pine (630+/-400 years) or Engelmann spruce CWD (800+/-960 and 650+/-410 years) in cooler sites. Across all sites and both species, CWD age ranged from 2 to 600 years, and turnover time was 580+/-180 years. Total standing and fallen dead wood biomass ranged from 4.7+/-0.2 to 54+/-1 Mg ha(-1), and from 2.8 to 60% of aboveground live tree biomass. Dead wood biomass increased 75 kg ha(-1) per meter gain in elevation and decreased 13 Mg ha(-1) for every degree C increase in mean air temperature. Differences in biomass and decay rates along the elevation gradient suggest that climate warming will lead to a loss of dead wood carbon from subalpine forest.

Hydrothermal extremes at the South-West Pribaikalie during the current climate changes

NASA Astrophysics Data System (ADS)

Voropay, Nadezhda

2017-04-01

Climatic extremes of air temperature and precipitation were analyzed for the Tunka Intermountain Depression (South-West Pribaikalie, Buryatia, Russian Federation). Intermountain depressions occupy a quarter of the territory of the Baikal region. The specific climatic conditions in the depressions are formed due to the geographic location and the influence of latitudinal zonation and altitudinal gradients. Air temperature and precipitation data records from at weather stations for the period 1940-2015 were analyzed. Long-term average annual temperature is negative and varies from -0.8 °C to -2.4 °C. Air temperature absolute minimum is -48 °C, absolute maximum is +36 °C. The long-term average annual precipitation is 370-480 mm, but in some years annual precipitation reach 760 mm. The summer months have about 70% of the total annual precipitation, in July and August the sum may reach 340 mm. Maximum daily sum of rainfalls is 80 mm. The contribution of the global and regional circulation characteristics into the variability of regional climatic characteristics was estimated.

Microfluidic liquid-air dual-gradient chip for synergic effect bio-evaluation of air pollutant.

PubMed

Liu, Xian-Jun; Hu, Shan-Wen; Xu, Bi-Yi; Zhao, Ge; Li, Xiang; Xie, Fu-Wei; Xu, Jing-Juan; Chen, Hong-Yuan

2018-05-15

In this paper, a novel prototype liquid-air dual gradient chip is introduced, which has paved the way for effective synergic effect bio-evaluation of air pollutant. The chip is composed of an array of the agarose liquid-air interfaces, top air gradient layer and bottom liquid gradient layer. The novel agarose liquid-air interface allows for non-biased exposure of cells to all the substances in the air and diffusive interactions with the liquid phase; while the dual liquid-air gradient provides powerful screening abilities, which well reduced errors, saved time and cost from repeated experiment. Coupling the two functions, the chip subsequently facilitates synergic effect evaluation of both liquid and air factors on cells. Here cigarette smoke was taken as the model air pollutant, and its strong synergic effects with inflammatory level of A549 lung cancer cells on their fate were successfully quantified for the first time. These results well testified that the proposed dual-gradient chip is powerful and indispensable for bio-evaluation of air pollutant. Copyright © 2018 Elsevier B.V. All rights reserved.

USSR and Eastern Europe Scientific Abstracts Geophysics, Astronomy and Space No. 409

DTIC Science & Technology

1977-11-15

flow, which is computed from the gradient of temperature and thermal conductivity of the rocks. Under such conditions thermometric sen- sors give...34Reaktsiya" instruments. The "Kristall" instrument is an air thermostat with three crystallizers in which aluminum -potassium sulfate was formed from

Characterizing Intra-Urban Air Quality Gradients with a Spatially-Distributed Network

NASA Astrophysics Data System (ADS)

Zimmerman, N.; Ellis, A.; Schurman, M. I.; Gu, P.; Li, H.; Snell, L.; Gu, J.; Subramanian, R.; Robinson, A. L.; Apte, J.; Presto, A. A.

2016-12-01

City-wide air pollution measurements have typically relied on regulatory or research monitoring sites with low spatial density to assess population-scale exposure. However, air pollutant concentrations exhibit significant spatial variability depending on local sources and features of the built environment, which may not be well captured by the existing monitoring regime. To better understand urban spatial and temporal pollution gradients at 1 km resolution, a network of 12 real-time air quality monitoring stations was deployed beginning July 2016 in Pittsburgh, PA. The stations were deployed at sites along an urban-rural transect and in urban locations with a range of traffic, restaurant, and tall building densities to examine the impact of various modifiable factors. Measurements from the stationary monitoring stations were further supported by mobile monitoring, which provided higher spatial resolution pollutant measurements on nearby roadways and enabled routine calibration checks. The stationary monitoring measurements comprise ultrafine particle number (Aerosol Dynamics "MAGIC" CPC), PM2.5 (Met One Neighborhood PM Monitor), black carbon (Met One BC 1050), and a new low-cost air quality monitor, the Real-time Affordable Multi-Pollutant (RAMP) sensor package for measuring CO, NO2, SO2, O3, CO2, temperature and relative humidity. High time-resolution (sub-minute) measurements across the distributed monitoring network enable insight into dynamic pollutant behaviour. Our preliminary findings show that our instruments are sensitive to PM2.5 gradients exceeding 2 micro-grams per cubic meter and ultrafine particle gradients exceeding 1000 particles per cubic centimeter. Additionally, we have developed rigorous calibration protocols to characterize the RAMP sensor response and drift, as well as multiple linear regression models to convert sensor response into pollutant concentrations that are comparable to reference instrumentation.

Using Distributed Temperature Sensing for evaporation measurements: background, verification, and future applications.

NASA Astrophysics Data System (ADS)

Schilperoort, Bart; Coenders-Gerrits, Miriam; van Iersel, Tara; Jiménez Rodríguez, Cesar; Luxemburg, Willem; Cisneros Vaca, Cesar; Ucer, Murat

2017-04-01

Distributed temperature sensing (DTS) is a relatively new method for measuring latent and sensible heat fluxes. The method has been successfully tested before on multiple sites (Euser, 2014). It uses a glass fibre optic cable of which the temperature can be measured every 12.5cm. By placing the cable vertically along a structure, the air temperature profile can be measured. If the cable is wrapped with cloth and kept wet (akin to a psychrometer), a vertical wet-bulb temperature gradient over height can be calculated. From these dry and wet-bulb temperatures over the height the Bowen ratio is determined and together with the energy balance the latent and sensible heat can be determined. To verify the measurements of the DTS based Bowen ratio method (BR-DTS) we assessed in detail; the accuracy of the air temperature and wet-bulb temperature measurements, the influence of solar radiation and wind on these temperatures, and a comparison to standard methods of evaporation measurement. We tested the performance of the BR-DTS on a 45m high tower in a tall mixed forest in the centre of the Netherlands in August. The average tree height is 30m, hence we measure temperature gradients above, in, and underneath the canopy. We found that solar radiation has a significant effect on the temperature measurements due to heating of the cable coating and leads to deviations up to 2° C. By using cables with different coating thickness we could theoretically correct for this effect, but this introduces too much uncertainty for calculating the temperature gradient. By installing screens the effect of direct sunlight on the cable is sufficiently reduced, and the correlation of the cable temperature with reference air temperature sensors is very high (R2=0.988 to 0.998). Wind speed seems to have a minimal effect on the measured wet-bulb temperature, both below and above the canopy. The latent heat fluxes of the BR-DTS were compared to an eddy covariance system using data from 10 days, with quality control applied to both methods. When comparing the daytime values, there is a high correlation (R2=0.75), a low bias (mean difference of ±15W/m2) and a good accuracy (standard deviation of the difference of 40W/m2) for both the latent and sensible heat flux. This can lead to a small error. Nonetheless, the results show that when the system is set up with care, and by eliminating sources of errors, the DTS based Bowen ratio is in agreement with an eddy covariance system, even above a tall forest canopy, which is notoriously hard to measure. Further applications of the DTS data in evaporation measurement studies are the flux-variance method (where the standard deviations of the air temperature and absolute humidity are used to estimate the sensible and latent heat fluxes), the surface-renewal method, and correcting the Bowen ratio for the non-unity of the eddy diffusivity ratios. These can all be used to gather additional data on the evaporation to increase the accuracy.

Global Climatic Controls On Leaf Size

NASA Astrophysics Data System (ADS)

Wright, I. J.; Prentice, I. C.; Dong, N.; Maire, V.

2015-12-01

Since the 1890s it's been known that the wet tropics harbour plants with exceptionally large leaves. Yet the observed latitudinal gradient of leaf size has never been fully explained: it is still unclear which aspects of climate are most important for understanding geographic trends in leaf size, a trait that varies many thousand-fold among species. The key is the leaf-to-air temperature difference, which depends on the balance of energy inputs (irradiance) and outputs (transpirational cooling, losses to the night sky). Smaller leaves track air temperatures more closely than larger leaves. Widely cited optimality-based theories predict an advantage for smaller leaves in dry environments, where transpiration is restricted, but are silent on the latitudinal gradient. We aimed to characterize and explain the worldwide pattern of leaf size. Across 7900 species from 651 sites, here we show that: large-leaved species predominate in wet, hot, sunny environments; smaller-leaved species typify hot, sunny environments only when arid; small leaves are required to avoid freezing in high latitudes and at high elevation, and to avoid overheating in dry environments. This simple pattern was unclear in earlier, more limited analyses. We present a simple but robust, fresh approach to energy-balance modelling for both day-time and night-time leaf-to-air temperature differences, and thus risk of overheating and of frost damage. Our analysis shows night-chilling is important as well as day-heating, and simplifies leaf temperature modelling. It provides both a framework for modelling leaf size constraints, and a solution to one of the oldest conundrums in ecology. Although the path forward is not yet fully clear, because of its role in controlling leaf temperatures we suggest that climate-related leaf size constraints could usefully feature in the next generation of land ecosystem models.

The incompressibility assumption in computational simulations of nasal airflow.

PubMed

Cal, Ismael R; Cercos-Pita, Jose Luis; Duque, Daniel

2017-06-01

Most of the computational works on nasal airflow up to date have assumed incompressibility, given the low Mach number of these flows. However, for high temperature gradients, the incompressibility assumption could lead to a loss of accuracy, due to the temperature dependence of air density and viscosity. In this article we aim to shed some light on the influence of this assumption in a model of calm breathing in an Asian nasal cavity, by solving the fluid flow equations in compressible and incompressible formulation for different ambient air temperatures using the OpenFOAM package. At low flow rates and warm climatological conditions, similar results were obtained from both approaches, showing that density variations need not be taken into account to obtain a good prediction of all flow features, at least for usual breathing conditions. This agrees with most of the simulations previously reported, at least as far as the incompressibility assumption is concerned. However, parameters like nasal resistance and wall shear stress distribution differ for air temperatures below [Formula: see text]C approximately. Therefore, density variations should be considered for simulations at such low temperatures.

Convective heat transfer studies at high temperatures with pressure gradient for inlet flow Mach number of 0.45

NASA Technical Reports Server (NTRS)

Pedrosa, A. C. F.; Nagamatsu, H. T.; Hinckel, J. A.

1984-01-01

Heat transfer measurements were determined for a flat plate with and without pressure gradient for various free stream temperatures, wall temperature ratios, and Reynolds numbers for an inlet flow Mach number of 0.45, which is a representative inlet Mach number for gas turbine rotor blades. A shock tube generated the high temperature and pressure air flow, and a variable geometry test section was used to produce inlet flow Mach number of 0.45 and accelerate the flow over the plate to sonic velocity. Thin-film platinum heat gages recorded the local heat flux for laminar, transition, and turbulent boundary layers. The free stream temperatures varied from 611 R (339 K) to 3840 R (2133 K) for a T(w)/T(r,g) temperature ratio of 0.87 to 0.14. The Reynolds number over the heat gages varied from 3000 to 690,000. The experimental heat transfer data were correlated with laminar and turbulent boundary layer theories for the range of temperatures and Reynolds numbers and the transition phenomenon was examined.

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.

Shadowgraph Study of Gradient Driven Fluctuations

NASA Technical Reports Server (NTRS)

Cannell, David; Nikolaenko, Gennady; Giglio, Marzio; Vailati, Alberto; Croccolo, Fabrizio; Meyer, William

2002-01-01

A fluid or fluid mixture, subjected to a vertical temperature and/or concentration gradient in a gravitational field, exhibits greatly enhanced light scattering at small angles. This effect is caused by coupling between the vertical velocity fluctuations due to thermal energy and the vertically varying refractive index. Physically, small upward or downward moving regions will be displaced into fluid having a refractive index different from that of the moving region, thus giving rise to the enhanced scattering. The scattered intensity is predicted to vary with scattering wave vector q, as q(sup -4), for sufficiently large q, but the divergence is quenched by gravity at small q. In the absence of gravity, the long wavelength fluctuations responsible for the enhanced scattering are predicted to grow until limited by the sample dimensions. It is thus of interest to measure the mean-squared amplitude of such fluctuations in the microgravity environment for comparison with existing theory and ground based measurements. The relevant wave vectors are extremely small, making traditional low-angle light scattering difficult or impossible because of stray elastically scattered light generated by optical surfaces. An alternative technique is offered by the shadowgraph method, which is normally used to visualize fluid flows, but which can also serve as a quantitative tool to measure fluctuations. A somewhat novel shadowgraph apparatus and the necessary data analysis methods will be described. The apparatus uses a spatially coherent, but temporally incoherent, light source consisting of a super-luminescent diode coupled to a single-mode optical fiber in order to achieve extremely high spatial resolution, while avoiding effects caused by interference of light reflected from the various optical surfaces that are present when using laser sources. Results obtained for a critical mixture of aniline and cyclohexane subjected to a vertical temperature gradient will be presented. The sample was confined between two horizontal parallel sapphire plates with a vertical spacing of 1 mm. The temperatures of the sapphire plates were controlled by independent circulating water loops that used Peltier devices to add or remove heat from the room air as required. For a mixture with a temperature gradient, two effects are involved in generating the vertical refractive index gradient, namely thermal expansion and the Soret effect, which generates a concentration gradient in response to the applied temperature gradient. For the aniline/cyclohexane system, the denser component (aniline) migrates toward the colder surface. Consequently, when heating from above, both effects result in the sample density decreasing with altitude and are stabilizing in the sense that no convective motion occurs regardless of the magnitude of the applied temperature gradient. The Soret effect is strong near a binary liquid critical point, and thus the dominant effect is due to the induced concentration gradient. The results clearly show the divergence at low q and the predicted gravitational quenching. Results obtained for different applied temperature gradients at varying temperature differences from the critical temperature, clearly demonstrate the predicted divergence of the thermal diffusion ratio. Thus, the more closely the critical point is approached, the smaller becomes the temperature gradient required to generate the same signal. Two different methods have been used to generate pure concentration gradients. In the first, a sample cell was filled with a single fluid, ethylene glycol, and a denser miscible fluid, water, was added from below thus establishing a sharp interface to begin the experiment. As time went on the two fluids diffused into each other, and large amplitude fluctuations were clearly observed at low q. The effects of gravitational quenching were also evident. In the second method, the aniline/cyclohexane sample was used, and after applying a vertical temperature gradient for several hours, the top and bottom temperatures were set equal and the thermal gradient died on a time scale of seconds, leaving the Soret induced concentration gradient in place. Again, large-scale fluctuations were observed and died away slowly in amplitude as diffusion destroyed the initial concentration gradient.

Geothermal studies at Kirtland Air Force Base, Albuquerque, New Mexico

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

Riddle, L.; Grant, B.

Due to an effort by government installations to discontinue use of natural gas, alternative energy sources are being investigated at Kirtland Air Force Base, Albuquerque, New Mexico. New Mexico has geologic characteristics favorable for geothermal energy utilization. Local heat flow and geochemical studies indicate a normal subsurface temperature regime. The alluvial deposits, however, extend to great depths where hot fluids, heated by the normal geothermal gradient, could be encountered. Two potential models for tapping geothermal energy are presented: the basin model and the fault model.

Structure of the microclimate at a woodland/parking-lot interface

Treesearch

David R. Miller

1977-01-01

Radiation balances and vertical and horizontal profiles of air temperature, vapor pressure and wind speed were measured across the interface of a large asphalt parking lot and an 18-m-tall Quercus velutina forest. The partitioning of available energy over the adjacent areas shows steep gradients between the parking lot and forest microclimates....

Statistical analysis of environmental variability within the CELSS breadboard project's biomass production chamber

NASA Technical Reports Server (NTRS)

Stutte, G. W.; Chetirkin, P. V.; Mackowiak, C. L.; Fortson, R. E.

1993-01-01

Variability in the aerial and root environments of NASA's Breadboard Project's Biomass Production Chamber (BPC) was determined. Data from two lettuce and two potato growouts were utilized. One growout of each crop was conducted prior to separating the upper and lower chambers; the other was subsequent to separation. There were little or no differences in pH, EC, or solution temperature between the upper and lower chamber or within a chamber. Variation in the aerial environment within a chamber was two to three times greater than variation between chambers for air temperature, relative humidity, and PPF. High variability in air velocity, relative to tray position, was observed. Separating the BPC had no effect on PPF, air velocity, solution temperature, pH, or EC. Separation reduced the gradient in air temperature and relative humidity between the upper and lower chambers, but increased the variability within a chamber. Variation between upper and lower chambers was within 5 percent of environmental set-points and of little or no physiological significance. In contrast, the variability within a chamber limits the capability of the BPC to generate statistically reliable data from individual tray treatments at this time.

Enhanced thermal shock resistance of ceramics through biomimetically inspired nanofins.

PubMed

Song, Fan; Meng, Songhe; Xu, Xianghong; Shao, Yingfeng

2010-03-26

We propose here a new method to make ceramics insensitive to thermal shock up to their melting temperature. In this method the surface of ceramics was biomimetically roughened into nanofinned surface that creates a thin air layer enveloping the surface of the ceramics during quenching. This air layer increases the heat transfer resistance of the surface of the ceramics by about 10,000 times so that the strong thermal gradient and stresses produced by the steep temperature difference in thermal shock did not occur both on the actual surface and in the interior of the ceramics. This method effectively extends the applications of existing ceramics in the extreme thermal environments.

Advances in thermal control and performance of the MMT M1 mirror

NASA Astrophysics Data System (ADS)

Gibson, J. D.; Williams, G. G.; Callahan, S.; Comisso, B.; Ortiz, R.; Williams, J. T.

2010-07-01

Strategies for thermal control of the 6.5-meter diameter borosilicate honeycomb primary (M1) mirror at the MMT Observatory have included: 1) direct control of ventilation system chiller setpoints by the telescope operator, 2) semiautomated control of chiller setpoints, using a fixed offset from the ambient temperature, and 3) most recently, an automated temperature controller for conditioned air. Details of this automated controller, including the integration of multiple chillers, heat exchangers, and temperature/dew point sensors, are presented here. Constraints and sanity checks for thermal control are also discussed, including: 1) mirror and hardware safety, 2) aluminum coating preservation, and 3) optimization of M1 thermal conditions for science acquisition by minimizing both air-to-glass temperature differences, which cause mirror seeing, and internal glass temperature gradients, which cause wavefront errors. Consideration is given to special operating conditions, such as high dew and frost points. Precise temperature control of conditioned ventilation air as delivered to the M1 mirror cell is also discussed. The performance of the new automated controller is assessed and compared to previous control strategies. Finally, suggestions are made for further refinement of the M1 mirror thermal control system and related algorithms.

Foliar Temperature Gradients as Drivers of Budburst in Douglas-fir: New Applications of Thermal Infrared Imagery

NASA Astrophysics Data System (ADS)

Miller, R.; Lintz, H. E.; Thomas, C. K.; Salino-Hugg, M. J.; Niemeier, J. J.; Kruger, A.

2014-12-01

Budburst, the initiation of annual growth in plants, is sensitive to climate and is used to monitor physiological responses to climate change. Accurately forecasting budburst response to these changes demands an understanding of the drivers of budburst. Current research and predictive models focus on population or landscape-level drivers, yet fundamental questions regarding drivers of budburst diversity within an individual tree remain unanswered. We hypothesize that foliar temperature, an important physiological property, may be a dominant driver of differences in the timing of budburst within a single tree. Studying these differences facilitates development of high throughput phenotyping technology used to improve predictive budburst models. We present spatial and temporal variation in foliar temperature as a function of physical drivers culminating in a single-tree budburst model based on foliar temperature. We use a novel remote sensing approach, combined with on-site meteorological measurements, to demonstrate important intra-canopy differences between air and foliar temperature. We mounted a thermal infrared camera within an old-growth canopy at the H.J. Andrews LTER forest and imaged an 8m by 10.6m section of a Douglas-fir crown. Sampling one image per minute, approximately 30,000 thermal infrared images were collected over a one-month period to approximate foliar temperature before, during and after budburst. Using time-lapse photography in the visible spectrum, we documented budburst at fifteen-minute intervals with eight cameras stratified across the thermal infrared camera's field of view. Within the imaged tree's crown, we installed a pyranometer, 2D sonic anemometer and fan-aspirated thermohygrometer and collected 3,000 measurements of net shortwave radiation, wind speed, air temperature and relative humidity. We documented a difference of several days in the timing of budburst across both vertical and horizontal gradients. We also observed clear spatial and temporal foliar temperature gradients. In addition to exploring physical drivers of budburst, this remote sensing approach provides insight into intra-canopy structural complexity and opportunities to advance our understanding of vegetation-­atmospheric interactions.

Estimation of tropical forest canopy temperatures, thermal response numbers, and evapotranspiration using an aircraft-based thermal sensor

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Lieberman, Diana; Lieberman, Milton; Hartshorn, Gary S.; Peralta, Rodolfo

1990-01-01

Thermal infrared Multispectral Scanner (TIMS) data were collected at a resolution of 5 to 10 m from a tropical rain forest over an elevation gradient from 35 to 2700 m in the Braulio Carrillo National Park in Costa Rica. Flight lines were repeated with a 15 to 30 minute time difference for measurement of forest canopy thermal response over time. Concurrent radiosonde measurements of atmospheric profiles of air temperature and moisture provided inputs to LOWTRAN6 for atmospheric radiance corrections of the TIMS data. Techniques for using calibrated aircraft-based thermal scanner data to examine tropical forest canopy thermal properties are described. Forest canopy temperature changes over time assessed between repeated, duplicated flight lines were combined with estimates of surface radiative energy measurements from towers above the forest canopy to determine temperature spatial variability, calculate Thermal Response Numbers (TRN), and estimate evapotranspiration along the elevation gradient from selected one hectare forest inventory plots.

Flame imaging using planar laser induced fluorescence of sulfur dioxide

NASA Astrophysics Data System (ADS)

Honza, Rene; Ding, Carl-Philipp; Dreizler, Andreas; Böhm, Benjamin

2017-09-01

Laser induced fluorescence of sulfur dioxide (SO2-PLIF) has been demonstrated as a useful tool for flame imaging. Advantage was taken from the strong temperature dependence of the SO2 fluorescence signal. SO2 fluorescence intensity increases by more than one order of magnitude if the temperature changes from ambient conditions to adiabatic flame temperatures of stoichiometric methane-air flames. This results in a steep gradient of SO2-PLIF intensities at the reaction zone and therefore can be used as a reliable flame marker. SO2 can be excited electronically using the fourth-harmonic of an Nd:YAG laser at 266 nm. This is an attractive alternative to OH-LIF, a well-recognized flame front marker, because no frequency-doubled dye lasers are needed. This simplifies the experimental setup and is advantageous for measurements at high repetition rates where dye bleaching can become an issue. To prove the performance of this approach, SO2-PLIF measurements were performed simultaneously with OH-PLIF on laminar premixed methane-air Bunsen flames for equivalence ratios between 0.9 and 1.25. These measurements were compared to 1D laminar flamelet simulations. The SO2 fluorescence signal was found to follow the temperature rise of the flame and is located closer to the steep temperature gradient than OH. Finally, the combined SO2- and OH-PLIF setup was applied to a spark ignition IC-engine to visualize the development of the early flame kernel.

Role of a single shield in thermocouple measurements in hot air flow

NASA Astrophysics Data System (ADS)

Ma, Hongwei; Shi, Lei; Tian, Yangtao

2017-12-01

To investigate the role of a single shield on steady temperature measurement using thermocouples in hot air flow, a methodology for solving convection, conduction, and radiation in one single model is provided. In order to compare with the experimental results, a cylindrical computational domain is established, which is the same size with the hot calibration wind-tunnel. In the computational domain, two kinds of thermocouples, the bare-bead and the single-shielded thermocouples, are simulated respectively. Surface temperature distribution and the temperature measurement bias of the two typical thermocouples are compared. The simulation results indicate that: 1) The existence of the shield reduces bead surface heat flux and changes the direction of wires inner heat conduction in a colder surrounding; 2) The existence of the shield reduces the temperature measurement bias both by improving bead surface temperature and by reducing surface temperature gradient; 3) The shield effectively reduces the effect of the ambient temperature on the temperature measurement bias; 4) The shield effectively reduces the influence of airflow velocity on the temperature measurement bias.

Thermal Cyclic Behavior of Thermal and Environmental Barrier Coatings Investigated Under High-Heat-Flux Conditions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

2002-01-01

Environmental barrier coatings (EBC's) have been developed to protect silicon-carbide- (SiC) based ceramic components in gas turbine engines from high-temperature environmental attack. With continuously increasing demands for significantly higher engine operating temperature, future EBC systems must be designed for both thermal and environmental protection of the engine components in combustion gases. In particular, the thermal barrier functions of EBC's become a necessity for reducing the engine-component thermal loads and chemical reaction rates, thus maintaining the required mechanical properties and durability of these components. Advances in the development of thermal and environmental barrier coatings (TBC's and EBC's, respectively) will directly impact the successful use of ceramic components in advanced engines. To develop high-performance coating systems, researchers must establish advanced test approaches. In this study, a laser high-heat-flux technique was employed to investigate the thermal cyclic behavior of TBC's and EBC's on SiC-reinforced SiC ceramic matrix composite substrates (SiC/SiC) under high thermal gradient and thermal cycling conditions. Because the laser heat flux test approach can monitor the coating's real-time thermal conductivity variations at high temperature, the coating thermal insulation performance, sintering, and delamination can all be obtained during thermal cycling tests. Plasma-sprayed yttria-stabilized zirconia (ZrO2-8 wt% Y2O3) thermal barrier and barium strontium aluminosilicate-based environmental barrier coatings (BSAS/BSAS+mullite/Si) on SiC/SiC ceramic matrix composites were investigated in this study. These coatings were laser tested in air under thermal gradients (the surface and interface temperatures were approximately 1482 and 1300 C, respectively). Some coating specimens were also subject to alternating furnace cycling (in a 90-percent water vapor environment at 1300 C) and laser thermal gradient cycling tests (in air), to investigate the water vapor effect. All cyclic tests were conducted using a 60-min hot-time temperature.

Using Distributed Temperature Sensing for measuring vertical temperature profiles and air temperature variance in the roughness sublayer above a forest canopy

NASA Astrophysics Data System (ADS)

Schilperoort, B.; Coenders, M.; Savenije, H. H. G.

2017-12-01

In recent years, the accuracy and resolution of Distributed Temperature Sensing (DTS) machines has increased enough to expand its use in atmospheric sciences. With DTS the temperature of a fiber optic (FO) cable can be measured with a high frequency (1 Hz) and high resolution (0.30 m), for cable lengths up to kilometers. At our measurement site, a patch of 26 to 30 m tall Douglas Fir in mixed forest, we placed FO cables vertically along a 48 m tall flux tower. This gives a high resolution vertical temperature profile above, through, and below the canopy. By using a `bare' FO cable, with a diameter of 0.25 mm, we are able to measure variations in air temperature at a very small timescale, and are able to measure a vertical profile of the air temperature variance. The vertical temperature profiles can be used to study the formation of the stable boundary layer above and in the canopy at a high resolution. It also shows that a stable layer can develop below the canopy, which is not limited to night time conditions but also occurs during daytime. The high frequency measurements can be used to study the gradient of the variance of air temperature over the height. To study how the flux tower itself affects temperature variance measurements, the `bare' FO cable can be placed horizontally under a support structure away from the flux tower. Lastly, by using the hot-wire anemometer principle with DTS, the measurements can be expanded to also include vertical wind profile.

Apparatus for investigating the reactions of soft-bodied invertebrates to controlled humidity gradients

PubMed Central

Russell, Joshua; Pierce-Shimomura, Jonathan T.

2015-01-01

Background While many studies have assayed behavioral responses of animals to chemical, temperature and light gradients, fewer studies have assayed how animals respond to humidity gradients. Our novel humidity chamber has allowed us to study the neuromolecular basis of humidity sensation in the nematode Caenorhabditis elegans (Russell et al. 2014). New Method We describe an easy-to-construct, low-cost humidity chamber to assay the behavior of small animals, including soft-bodied invertebrates, in controlled humidity gradients. Results We show that our humidity-chamber design is amenable to soft-bodied invertebrates and can produce reliable gradients ranging 0.3–8% RH/cm across a 9-cm long x 7.5-cm wide gel-covered arena. Comparison with Existing Method(s) Previous humidity chambers relied on circulating dry and moist air to produce a steep humidity gradient in a small arena (e.g. Sayeed & Benzer, 1996). To remove the confound of moving air that may elicit mechanical responses independent of humidity responses, our chamber controlled the humidity gradient using reservoirs of hygroscopic materials. Additionally, to better observe the behavioral mechanisms for humidity responses, our chamber provided a larger arena. Although similar chambers have been described previously, these approaches were not suitable for soft-bodied invertebrates or for easy imaging of behavior because they required that animals move across wire or fabric mesh. Conclusion The general applicability of our humidity chamber overcomes limitations of previous designs and opens the door to observe the behavioral responses of soft-bodied invertebrates, including genetically powerful C. elegans and Drosophila larvae. PMID:25176025

Understanding Climate Variability of Urban Ecosystems Through the Lens of Citizen Science

NASA Astrophysics Data System (ADS)

Ripplinger, J.; Jenerette, D.; Wang, J.; Chandler, M.; Ge, C.; Koutzoukis, S.

2017-12-01

The Los Angeles megacity is vulnerable to climate warming - a process that locally exacerbates the urban heat island effect as it intensifies with size and density of the built-up area. We know that large-scale drivers play a role, but in order to understand local-scale climate variation, more research is needed on the biophysical and sociocultural processes driving the urban climate system. In this study, we work with citizen scientists to deploy a high-density network of microsensors across a climate gradient to characterize geographic variation in neighborhood meso- and micro-climates. This research asks: How do urbanization, global climate, and vegetation interact across multiple scales to affect local-scale experiences of temperature? Additionally, citizen scientist-led efforts generated research questions focused on examining microclimatic differences among yard groundcover types (rock mulch vs. lawn vs. artificial turf) and also on variation in temperature related to tree cover. Combining sensor measurements with Weather Research and Forecasting (WRF) spatial models and satellite-based temperature, we estimate spatially-explicit maps of land surface temperature and air temperature to illustrate the substantial difference between surface and air urban heat island intensities and the variable degree of coupling between land surface and air temperature in urban areas. Our results show a strong coupling between air temperature variation and landcover for neighborhoods, with significant detectable signatures from tree cover and impervious surface. Temperature covaried most strongly with urbanization intensity at nighttime during peak summer season, when daily mean air temperature ranged from 12.8C to 30.4C across all groundcover types. The combined effects of neighborhood geography and vegetation determine where and how temperature and tree canopy vary within a city. This citizen science-enabled research shows how large-scale climate drivers and urbanization intensity jointly influence the nature and magnitude of coupling between air temperature and tree cover, and demonstrate how urban vegetation provides an important ecosystem service in cities by decreasing the intensity of local urban heat islands.

The mid-cretaceous water bearer: Isotope mass balance quantification of the Albian hydrologic cycle

USGS Publications Warehouse

Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.

2002-01-01

A latitudinal gradient in meteoric ??18O compositions compiled from paleosol sphaerosiderites throughout the Cretaceous Western Interior Basin (KWIB) (34-75??N paleolatitude) exhibits a steeper, more depleted trend than modern (predicted) values (3.0??? [34??N latitude] to 9.7??? [75??N] lighter). Furthermore, the sphaerosiderite meteoric ??18O latitudinal gradient is significantly steeper and more depleted (5.8??? [34??N] to 13.8??? [75??N] lighter) than a predicted gradient for the warm mid-Cretaceous using modern empirical temperature-??18O precipitation relationships. We have suggested that the steeper and more depleted (relative to the modern theoretical gradient) meteoric sphaerosiderite ??18O latitudinal gradient resulted from increased air mass rainout effects in coastal areas of the KWIB during the mid-Cretaceous. The sphaerosiderite isotopic data have been used to constrain a mass balance model of the hydrologic cycle in the northern hemisphere and to quantify precipitation rates of the equable 'greenhouse' Albian Stage in the KWIB. The mass balance model tracks the evolving isotopic composition of an air mass and its precipitation, and is driven by latitudinal temperature gradients. Our simulations indicate that significant increases in Albian precipitation (34-52%) and evaporation fluxes (76-96%) are required to reproduce the difference between modern and Albian meteoric siderite ??18O latitudinal gradients. Calculations of precipitation rates from model outputs suggest mid-high latitude precipitation rates greatly exceeded modern rates (156-220% greater in mid latitudes [2600-3300 mm/yr], 99% greater at high latitudes [550 mm/yr]). The calculated precipitation rates are significantly different from the precipitation rates predicted by some recent general circulation models (GCMs) for the warm Cretaceous, particularly in the mid to high latitudes. Our mass balance model by no means replaces GCMs. However, it is a simple and effective means of obtaining quantitative data regarding the mid-Cretaceous hydrologic cycle in the KWIB. Our goal is to encourage the incorporation of isotopic tracers into GCM simulations of the mid-Cretaceous, and to show how our empirical data and mass balance model estimates help constrain the boundary conditions. ?? 2002 Elsevier Science B.V. All rights reserved.

Wall temperature measurements at elevated pressures and high temperatures in sooting flames in a gas turbine model combustor

NASA Astrophysics Data System (ADS)

Nau, Patrick; Yin, Zhiyao; Geigle, Klaus Peter; Meier, Wolfgang

2017-12-01

Wall temperatures were measured with thermographic phosphors on the quartz walls of a model combustor in ethylene/air swirl flames at 3 bar. Three operating conditions were investigated with different stoichiometries and with or without additional injection of oxidation air downstream of the primary combustion zone. YAG:Eu and YAG:Dy were used to cover a total temperature range of 1000-1800 K. Measurements were challenging due to the high thermal background from soot and window degradation at high temperatures. The heat flux through the windows was estimated from the temperature gradient between the in- and outside of the windows. Differences in temperature and heat flux density profiles for the investigated cases can be explained very well with the previously measured differences in flame temperatures and flame shapes. The heat loss relative to thermal load is quite similar for all investigated flames (15-16%). The results complement previous measurements in these flames to investigate soot formation and oxidation. It is expected, that the data set is a valuable input for numerical simulations of these flames.

Linking rainforest ecophysiology and microclimate through fusion of airborne LiDAR and hyperspectral imagery

Treesearch

Eben N. Broadbent; Angélica M. Almeyda Zambrano; Gregory P. Asner; Christopher B. Field; Brad E. Rosenheim; Ty Kennedy-Bowdoin; David E. Knapp; David Burke; Christian Giardina; Susan Cordell

2014-01-01

We develop and validate a high-resolution three-dimensional model of light and air temperature for a tropical forest interior in Hawaii along an elevation gradient varying greatly in structure but maintaining a consistent species composition. Our microclimate models integrate high-resolution airborne waveform light detection and ranging data (LiDAR) and hyperspectral...

Air-Cooled Turbine Blades with Tip Cap For Improved Leading-Edge Cooling

NASA Technical Reports Server (NTRS)

Calvert, Howard F.; Meyer, Andre J., Jr.; Morgan, William C.

1959-01-01

An investigation was conducted in a modified turbojet engine to determine the cooling characteristics of the semistrut corrugated air- cooled turbine blade and to compare and evaluate a leading-edge tip cap as a means for improving the leading-edge cooling characteristics of cooled turbine blades. Temperature data were obtained from uncapped air-cooled blades (blade A), cooled blades with the leading-edge tip area capped (blade B), and blades with slanted corrugations in addition to leading-edge tip caps (blade C). All data are for rated engine speed and turbine-inlet temperature (1660 F). A comparison of temperature data from blades A and B showed a leading-edge temperature reduction of about 130 F that could be attributed to the use of tip caps. Even better leading-edge cooling was obtained with blade C. Blade C also operated with the smallest chordwise temperature gradients of the blades tested, but tip-capped blade B operated with the lowest average chordwise temperature. According to a correlation of the experimental data, all three blade types 0 could operate satisfactorily with a turbine-inlet temperature of 2000 F and a coolant flow of 3 percent of engine mass flow or less, with an average chordwise temperature limit of 1400 F. Within the range of coolant flows investigated, however, only blade C could maintain a leading-edge temperature of 1400 F for a turbine-inlet temperature of 2000 F.

Comparison of heat dissipation response between Malaysian and Japanese males during exercise in humid heat stress.

PubMed

Wakabayashi, Hitoshi; Wijayanto, Titis; Lee, Joo-Young; Hashiguchi, Nobuko; Saat, Mohamed; Tochihara, Yutaka

2011-07-01

This study investigated the differences in heat dissipation response to intense heat stress during exercise in hot and humid environments between tropical and temperate indigenes with matched physical characteristics. Ten Japanese (JP) and ten Malaysian (MY) males participated in this study. Subjects performed exercise for 60 min at 55% peak oxygen uptake in 32°C air with 70% relative humidity, followed by 30 min recovery. The increase in rectal temperature (T(re)) was smaller in MY during exercise compared to JP. The local sweat rate and total body mass loss were similar in both groups. Both skin blood flow and mean skin temperature was lower in MY compared to JP. A significantly greater increase in hand skin temperature was observed in MY during exercise, which is attributable to heat loss due to the greater surface area to mass ratio and large number of arteriovenous anastomoses. Also, the smaller increase in T(re) in MY may be explained by the presence of a significantly greater core-skin temperature gradient in MY than JP. The thermal gradient is also a major factor in increasing the convective heat transfer from core to skin as well as skin blood flow. It is concluded that the greater core-skin temperature gradient observed in MY is responsible for the smaller increase in T(re).

High-temperature microphone system. [for measuring pressure fluctuations in gases at high temperature

NASA Technical Reports Server (NTRS)

Zuckerwar, A. J. (Inventor)

1979-01-01

Pressure fluctuations in air or other gases in an area of elevated temperature are measured using a condenser microphone located in the area of elevated temperature and electronics for processing changes in the microphone capacitance located outside the area the area and connected to the microphone by means of high-temperature cable assembly. The microphone includes apparatus for decreasing the undesirable change in microphone sensitivity at high temperatures. The high temperature cable assembly operates as a half-wavelength transmission line in an AM carrier system and maintains a large temperature gradient between the two ends of the cable assembly. The processing electronics utilizes a voltage controlled oscillator for automatic tuning thereby increasing the sensitivity of the measuring apparatus.

Effect of canopy structure and open-top chamber techniques on micrometeorological parameters and the gradients and transport of water vapor, carbon dioxide and ozone in the canopies of plum trees (`prunus salicina`) in the San Joaquin valley. Final report

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

Grantz, D.A.; Vaughn, D.L.; Metheny, P.A.

1995-03-15

Plum trees (Prunus salicina cv. Casselman) were exposed to ozone in open-top chambers (OTC) or chamberless plots, and trace gas concentrations and microenvironmental conditions were monitored within tree canopies inside the outside the OTC. Concentrations of ozone, carbon dioxide and water vapor, leaf and air temperature, light intensity, and wind speed were measured at nine positions in the tree canopies. The objectives were to: (1) map the distribution of microenvironmental parameters within the canopies inside and outside the OTC; (2) determine transport parameters for gas exchange, and (3) calculate ozone flux. Significant vertical and horizontal gradients were observed; gradients weremore » diminished and often inverted inside relative to outside the OTC due to air distribution at the bottom of the OCT. Ozone flux was readily modeled from measures of stomatal conductance, nonstomatal conductance and ozone concentration at the leaf surface.« less

The influence of pressure relaxation on the structure of an axial vortex

NASA Astrophysics Data System (ADS)

Ash, Robert L.; Zardadkhan, Irfan; Zuckerwar, Allan J.

2011-07-01

Governing equations including the effects of pressure relaxation have been utilized to study an incompressible, steady-state viscous axial vortex with specified far-field circulation. When sound generation is attributed to a velocity gradient tensor-pressure gradient product, the modified conservation of momentum equations that result yield an exact solution for a steady, incompressible axial vortex. The vortex velocity profile has been shown to closely approximate experimental vortex measurements in air and water over a wide range of circulation-based Reynolds numbers. The influence of temperature and humidity on the pressure relaxation coefficient in air has been examined using theoretical and empirical approaches, and published axial vortex experiments have been employed to estimate the pressure relaxation coefficient in water. Non-equilibrium pressure gradient forces have been shown to balance the viscous stresses in the vortex core region, and the predicted pressure deficits that result from this non-equilibrium balance can be substantially larger than the pressure deficits predicted using a Bernoulli equation approach. Previously reported pressure deficit distributions for dust devils and tornados have been employed to validate the non-equilibrium pressure deficit predictions.

Isoscapes of δ18O and δ2H reveal climatic forcings on Alaska and Yukon precipitation

NASA Astrophysics Data System (ADS)

Lachniet, Matthew S.; Lawson, Daniel E.; Stephen, Haroon; Sloat, Alison R.; Patterson, William P.

2016-08-01

Spatially extensive Arctic stable isotope data are sparse, inhibiting the climatic understanding required to interpret paleoclimate proxy records. To fill this need, we constrained the climatic and physiographic controls on δ18O and δD values of stream waters across Alaska and the Yukon to derive interpolated isoscape maps. δ18O is strongly correlated to winter temperature parameters and similarity of the surface water line (δ2H = 8.0 × δ18O + 6.4) to the Global Meteoric Water Line suggests stream waters are a proxy for meteoric precipitation. We observe extreme orographic δ18O decreases and a trans-Alaskan continental gradient of -8.3‰ 1000 km-1. Continental gradients are high in coastal zones and low in the interior. Localized δ18O increases indicate inland air mass penetration via topographic lows. Using observed δ18O/temperature gradients, we show that δ18O decreases in a ˜24 ka permafrost ice wedge relative to the late Holocene indicate mean annual and coldest quarter temperature reductions of 8.9 ± 1.7°C and 17.2 ± 3.2°C, respectively.

The energetic and carbon economic origins of leaf thermoregulation.

PubMed

Michaletz, Sean T; Weiser, Michael D; McDowell, Nate G; Zhou, Jizhong; Kaspari, Michael; Helliker, Brent R; Enquist, Brian J

2016-08-22

Leaf thermoregulation has been documented in a handful of studies, but the generality and origins of this pattern are unclear. We suggest that leaf thermoregulation is widespread in both space and time, and originates from the optimization of leaf traits to maximize leaf carbon gain across and within variable environments. Here we use global data for leaf temperatures, traits and photosynthesis to evaluate predictions from a novel theory of thermoregulation that synthesizes energy budget and carbon economics theories. Our results reveal that variation in leaf temperatures and physiological performance are tightly linked to leaf traits and carbon economics. The theory, parameterized with global averaged leaf traits and microclimate, predicts a moderate level of leaf thermoregulation across a broad air temperature gradient. These predictions are supported by independent data for diverse taxa spanning a global air temperature range of ∼60 °C. Moreover, our theory predicts that net carbon assimilation can be maximized by means of a trade-off between leaf thermal stability and photosynthetic stability. This prediction is supported by globally distributed data for leaf thermal and photosynthetic traits. Our results demonstrate that the temperatures of plant tissues, and not just air, are vital to developing more accurate Earth system models.

High-temperature synthesis of silica particles by the chloride method in the regime of counter flow jet quenching

NASA Astrophysics Data System (ADS)

Kartaev, E. V.; Emel'kin, V. A.; Aul'chenko, S. M.

2017-10-01

The experimental and numerical investigations of synthesis of silica (SiO2) nanoparticles from premixed gaseous silicon tetrachloride (SiCl4) and oxygen of dry air in the high-temperature nitrogen flow of plasma-chemical reactor have been carried out. The regime of counter flow jet quenching of high-temperature heterogeneous flow has been utilized. The latter provided a rapid cooling of silica particles under nonequilibrium conditions with substantial temperature gradients. Synthesized silica particles were amorphous, with surface-average size being about 28 nm. The results of numerical calculations are found to agree qualitatively with experimental data.

Daily spectral energy conversions of the global circulation during 10-27 January 1979

NASA Technical Reports Server (NTRS)

Huang, Huo-Jin; Vincent, Dayton G.

1988-01-01

A modified version of ECMWF Level III-b analyses is used to examine the energetics of the daily low and middle latitude wave activity that occurred over the globe during part of FGGE. The results indicate that the eddy available potential is increased by sensible heat transport down the temperature gradient at all wavenumbers; it is immediately converted to eddy kinetic energy through warmer air rising and/or colder air sinking. In the present study, particular attention is given to Southern Hemispheric energetics.

Numerical simulation of a mini PEMFC stack

NASA Astrophysics Data System (ADS)

Liu, Zhixiang; Mao, Zongqiang; Wang, Cheng; Zhuge, Weilin; Zhang, Yangjun

Fuel cell modeling and simulation has aroused much attention recently because it can probe transport and reaction mechanism. In this paper, a computational fuel cell dynamics (CFCD) method was applied to simulate a proton exchange membrane fuel cell (PEMFC) stack for the first time. The air cooling mini fuel cell stack consisted of six cells, in which the active area was 8 cm 2 (2 cm × 4 cm). With reasonable simplification, the computational elements were effectively reduced and allowed a simulation which could be conducted on a personal computer without large-scale parallel computation. The results indicated that the temperature gradient inside the fuel cell stack was determined by the flow rate of the cooling air. If the air flow rate is too low, the stack could not be effectively cooled and the temperature will rise to a range that might cause unstable stack operation.

Contrasting responses of the extended Gulf Stream to severe winter forcing

NASA Astrophysics Data System (ADS)

Jacobs, Z.; Grist, J. P.; Marsh, R.; Josey, S. A.; Sinha, B.

2015-12-01

Changes in the path and strength of the extended Gulf Stream, downstream of Cape Hatteras, and the North Atlantic Current (GSNAC), are associated with strong wintertime air-sea interactions that can further influence the atmospheric storm track. The GSNAC response to anomalous air-sea heat fluxes in particular is dependent on the location of excess heat loss, in turn related to meteorological circumstances. Outbreaks of cold continental air may lead to excess cooling over the Sargasso Sea, as in 1976-77. Under these circumstances, the Gulf Stream may intensify through a steepening of cross-stream density gradients. An alternative scenario prevailed during the cold outbreak of 2013-14 where excess cooling occurred over the central subpolar gyre and may have influenced the extreme storminess experienced in western Europe. An objectively-analysed temperature and salinity product (EN4) is used to investigate the variability of the GSNAC. Temperature and salinity profiles are used to obtain geostrophic transport at selected GSNAC transects, confirming strong horizontal temperature gradients and a positive geostrophic velocity anomaly at 70oW in spring 1977, the strongest spring transport seen in the 1970s at this location. In addition to observations, an eddy-resolving model hindcast spanning 1970-2013, is used to further characterise GSNAC transport variability, allowing a fuller assessment of the relationship between the winter surface heat flux, end-of-winter mixed layer depth, subtropical mode water volume and GSNAC transports. Preliminary results reveal a significant negative correlation between the winter surface heat flux over the Sargasso Sea and the GSNAC transport in the following spring.

Thermal modelling of cooling tool cutting when milling by electrical analogy

NASA Astrophysics Data System (ADS)

Benabid, F.; Arrouf, M.; Assas, M.; Benmoussa, H.

2010-06-01

Measurement temperatures by (some devises) are applied immediately after shut-down and may be corrected for the temperature drop that occurs in the interval between shut-down and measurement. This paper presents a new procedure for thermal modelling of the tool cutting used just after machining; when the tool is out off the chip in order to extrapolate the cutting temperature from the temperature measured when the tool is at stand still. A fin approximation is made in enhancing heat loss (by conduction and convection) to air stream is used. In the modelling we introduce an equivalent thermal network to estimate the cutting temperature as a function of specific energy. In another hand, a local modified element lumped conduction equation is used to predict the temperature gradient with time when the tool is being cooled, with initial and boundary conditions. These predictions provide a detailed view of the global heat transfer coefficient as a function of cutting speed because the heat loss for the tool in air stream is an order of magnitude larger than in normal environment. Finally we deduct the cutting temperature by inverse method.

Test of Monin-Obukhov similarity theory using distributed temperature sensing

NASA Astrophysics Data System (ADS)

Cheng, Y.; Sayde, C.; Li, Q.; Gentine, P.

2017-12-01

Monin-Obukhov similarity theory [Monin and Obukhov, 1954] (MOST) has been widely used to calculate atmospheric surface fluxes applying the structure correction functions [Stull, 1988]. The exact forms of the structure correction functions for momentum and heat, which depend on the vertical gradient velocity and temperature, have been determined empirically mostly from the Kansas experiment [Kaimal et al., 1972]. However, due to the limitation of point measurement, the vertical gradient of temperature and horizontal wind speed are not well captured. Here we propose a way to measure the vertical gradient of temperature and horizontal wind speed with high resolution in space (every 12.7 cm) and time (every second) using the Distributed Temperature Sensing [Selker et al., 2006] (DTS), thus determining the exact form of the structure correction functions of MOST under various stability conditions. Two parallel vertical fiber optics will be placed on a tower at the central facility of ARM SGP site. Vertical air temperature will be measured every 12.7 cm by the fiber optics and horizontal wind speed along fiber will be measured. Then vertical gradient of temperature and horizontal wind speed will be calculated and stability correction functions for momentum and heat will be determined. ReferencesKaimal, J. C., Wyngaard, J. C., Izumi, Y., and Cote, O. R. (1972), Spectral characteristics of surface-layer turbulence, Quarterly Journal of the Royal Meteorological Society, 98(417), 563-589, doi: 10.1002/qj.49709841707. Monin, A., and Obukhov, A. (1954), Basic laws of turbulent mixing in the surface layer of the atmosphere, Contrib. Geophys. Inst. Acad. Sci. USSR, 24(151), 163-187. Selker, J., Thévenaz, L., Huwald, H., Mallet, A., Luxemburg, W., van de Giesen, N., Stejskal, M., Zeman, J., Westhoff, M., and Parlange, M. B. (2006), Distributed fiber-optic temperature sensing for hydrologic systems, Water Resources Research, 42, W12202, doi: 10.1029/2006wr005326. Stull, R. (1988), An Introduction to Boundary Layer Meteorology, pp. 666, Kluwer Academic Publishers, Dordrecht.

Successful experiments on an external MHD Accelerator: wall confinement of the plasma, annihilation of the electrothermal instability by magnetic gradient inversion, creation of a stable spiral current pattern

NASA Astrophysics Data System (ADS)

Petit, Jean-Pierre; Dore, Jean-Christophe

2013-09-01

MHD propulsion has been extensively studied since the fifties. To shift from propulsion to an MHD Aerodyne, one only needs to accelerate the air externally, along its outer skin, using Lorentz forces. We present a set of successful experiments, obtained around a model, placed in low density air. We successfully dealt with various problems: wall confinement of two-temperature plasma obtained by inversion of the magnetic pressure gradient, annihilation of the Velikhov electrothermal instability by magnetic confinement of the streamers, establishment of a stable spiral distribution of the current, obtained by an original method. Another direction of research is devoted to the study of an MHD-controlled inlet which, coupled with a turbofan engine and implying an MHD-bypass system, would extend the flight domain to hypersonic conditions. Research manager

Cryogenic Moisture Apparatus

NASA Technical Reports Server (NTRS)

Fesmire, James; Smith, Trent; Breakfield, Robert; Baughner, Kevin; Heckle, Kenneth; Meneghelli, Barry

2010-01-01

The Cryogenic Moisture Apparatus (CMA) is designed for quantifying the amount of moisture from the surrounding air that is taken up by cryogenic-tank-insulating material specimens while under typical conditions of use. More specifically, the CMA holds one face of the specimen at a desired low temperature (e.g., the typical liquid-nitrogen temperature of 77 K) while the opposite face remains exposed to humid air at ambient or near-ambient temperature. The specimen is weighed before and after exposure in the CMA. The difference between the "after" and "before" weights is determined to be the weight of moisture absorbed by the specimen. Notwithstanding the term "cryogenic," the CMA is not limited to cryogenic applications: the low test temperature can be any temperature below ambient, and the specimen can be made of any material affected by moisture in air. The CMA is especially well suited for testing a variety of foam insulating materials, including those on the space-shuttle external cryogenic tanks, on other cryogenic vessels, and in refrigerators used for transporting foods, medicines, and other perishables. Testing is important because absorbed moisture not only adds weight but also, in combination with thermal cycling, can contribute to damage that degrades insulating performance. Materials are changed internally when subjected to large sub-ambient temperature gradients.

Study on the temperature gradient evolution of large size nonlinear crystal based on the fluid-solid coupling theory

NASA Astrophysics Data System (ADS)

Sun, F. Z.; Zhang, P.; Liang, Y. C.; Lu, L. H.

2014-09-01

In the non-critical phase-matching (NCPM) along the Θ =90° direction, ADP and DKDP crystals which have many advantages, including a large effective nonlinear optical coefficient, a small PM angular sensitivity and non beam walk-off, at the non-critical phase-matching become the competitive candidates in the inertial confinement fusion(ICF) facility, so the reasonable temperature control of crystals has become more and more important .In this paper, the fluid-solid coupling models of ADP crystal and DKDP crystal which both have anisotropic thermal conductivity in the states of vacuum and non-vacuum were established firstly, and then simulated using the fluid analysis software Fluent. The results through the analysis show that the crystal surface temperature distribution is a ring shape, the temperature gradients in the direction of the optical axis both the crystals are 0.02°C and 0.01°C due to the air, the lowest temperature points of the crystals are both at the center of surface, and the temperatures are lower than 0.09°C and 0.05°C compared in the vacuum and non-vacuum environment, then propose two designs for heating apparatus.

Short-term effects of air quality and thermal stress on non-accidental morbidity-a multivariate meta-analysis comparing indices to single measures.

PubMed

Lokys, Hanna Leona; Junk, Jürgen; Krein, Andreas

2018-01-01

Air quality and thermal stress lead to increased morbidity and mortality. Studies on morbidity and the combined impact of air pollution and thermal stress are still rare. To analyse the correlations between air quality, thermal stress and morbidity, we used a two-stage meta-analysis approach, consisting of a Poisson regression model combined with distributed lag non-linear models (DLNMs) and a meta-analysis investigating whether latitude or the number of inhabitants significantly influence the correlations. We used air pollution, meteorological and hospital admission data from 28 administrative districts along a north-south gradient in western Germany from 2001 to 2011. We compared the performance of the single measure particulate matter (PM10) and air temperature to air quality indices (MPI and CAQI) and the biometeorological index UTCI. Based on the Akaike information criterion (AIC), it can be shown that using air quality indices instead of single measures increases the model strength. However, using the UTCI in the model does not give additional information compared to mean air temperature. Interaction between the 3-day average of air quality (max PM10, max CAQI and max MPI) and meteorology (mean air temperature and mean UTCI) did not improve the models. Using the mean air temperature, we found immediate effects of heat stress (RR 1.0013, 95% CI: 0.9983-1.0043) and by 3 days delayed effects of cold stress (RR: 1.0184, 95% CI: 1.0117-1.0252). The results for air quality differ between both air quality indices and PM10. CAQI and MPI show a delayed impact on morbidity with a maximum RR after 2 days (MPI 1.0058, 95% CI: 1.0013-1.0102; CAQI 1.0068, 95% CI: 1.0030-1.0107). Latitude was identified as a significant meta-variable, whereas the number of inhabitants was not significant in the model.

Short-term effects of air quality and thermal stress on non-accidental morbidity—a multivariate meta-analysis comparing indices to single measures

NASA Astrophysics Data System (ADS)

Lokys, Hanna Leona; Junk, Jürgen; Krein, Andreas

2018-01-01

Air quality and thermal stress lead to increased morbidity and mortality. Studies on morbidity and the combined impact of air pollution and thermal stress are still rare. To analyse the correlations between air quality, thermal stress and morbidity, we used a two-stage meta-analysis approach, consisting of a Poisson regression model combined with distributed lag non-linear models (DLNMs) and a meta-analysis investigating whether latitude or the number of inhabitants significantly influence the correlations. We used air pollution, meteorological and hospital admission data from 28 administrative districts along a north-south gradient in western Germany from 2001 to 2011. We compared the performance of the single measure particulate matter (PM10) and air temperature to air quality indices (MPI and CAQI) and the biometeorological index UTCI. Based on the Akaike information criterion (AIC), it can be shown that using air quality indices instead of single measures increases the model strength. However, using the UTCI in the model does not give additional information compared to mean air temperature. Interaction between the 3-day average of air quality (max PM10, max CAQI and max MPI) and meteorology (mean air temperature and mean UTCI) did not improve the models. Using the mean air temperature, we found immediate effects of heat stress (RR 1.0013, 95% CI: 0.9983-1.0043) and by 3 days delayed effects of cold stress (RR: 1.0184, 95% CI: 1.0117-1.0252). The results for air quality differ between both air quality indices and PM10. CAQI and MPI show a delayed impact on morbidity with a maximum RR after 2 days (MPI 1.0058, 95% CI: 1.0013-1.0102; CAQI 1.0068, 95% CI: 1.0030-1.0107). Latitude was identified as a significant meta-variable, whereas the number of inhabitants was not significant in the model.

Photosynthetic temperature adaptation of Pinus cembra within the timberline ecotone of the Central Austrian Alps

PubMed Central

Wieser, Gerhard; Oberhuber, Walter; Walder, Lisa; Spieler, Daniela; Gruber, Andreas

2011-01-01

Temperature is suggested to determine the upper limit of tree life. Therefore, future climate warming may be of importance for tree distribution within the European Alps, where low temperatures limit carbon metabolism. We focused on the effects of air and soil temperature on net photosynthesis (Pn) of Pinus cembra an evergreen climax species of the timberline ecotone of the Central Austrian Alps. Light response and temperature response curves were estimated along an altitudinal gradient ranging from the forest limit up to the krummholz limit in both summer and fall. In general, Pn was significantly lower in fall as compared to summer. Nevertheless, independent from season mean Pn values tended to increase with elevation and were positively correlated with root zone temperatures. The specific leaf area by contrast declined with increasing elevation. Furthermore, the temperature optimum of net photosynthesis declined with increasing elevation and was positively correlated with the mean maximum air temperature of the 10 days prior the date of measurement. Thus, our findings appear to reflect a long-term adaptation of the photosynthetic apparatus of Pinus cembra to the general temperature conditions with respect to elevation combined with a short term acclimation to the prevailing temperature regime. PMID:21379394

Large-scale effects on the regulation of tropical sea surface temperature

NASA Technical Reports Server (NTRS)

Hartmann, Dennis L.; Michelsen, Marc L.

1993-01-01

The dominant terms in the surface energy budget of the tropical oceans are absorption of solar radiation and evaporative cooling. If it is assumed that relative humidity in the boundary layer remains constant, evaporative cooling will increase rapidly with sea surface temperature (SST) because of the strong temperature dependence of saturation water vapor pressure. The resulting stabilization of SST provided by evaporative cooling is sufficient to overcome positive feedback contributed by the decrease of surface net longwave cooling with increasing SST. Evaporative cooling is sensitive to small changes in boundary-layer relative humidity. Large and negative shortwave cloud forcing in the regions of highest SST are supported by the moisture convergence associated with largescale circulations. In the descending portions of these circulations the shortwave cloud forcing is suppressed. When the effect of these circulations is taken into account by spatial averaging, the area-averaged cloud forcing shows no sensitivity to area-averaged SST changes associated with the 1987 warming event in the tropical Pacific. While the shortwave cloud forcing is large and important in the convective regions, the importance of its role in regulating the average temperature of the tropics and in modulating temperature gradients within the tropics is less clear. A heuristic model of SST is used to illustrate the possible role of large-scale atmospheric circulations on SST in the tropics and the coupling between SST gradients and mean tropical SST. The intensity of large-scale circulations responds sensitivity to SST gradients and affects the mean tropical SST by supplying dry air to the planetary boundary layer. Large SST gradients generate vigorous circulations that increase evaporation and reduce the mean SST.

Analytical Model for Diffusive Evaporation of Sessile Droplets Coupled with Interfacial Cooling Effect.

PubMed

Nguyen, Tuan A H; Biggs, Simon R; Nguyen, Anh V

2018-05-30

Current analytical models for sessile droplet evaporation do not consider the nonuniform temperature field within the droplet and can overpredict the evaporation by 20%. This deviation can be attributed to a significant temperature drop due to the release of the latent heat of evaporation along the air-liquid interface. We report, for the first time, an analytical solution of the sessile droplet evaporation coupled with this interfacial cooling effect. The two-way coupling model of the quasi-steady thermal diffusion within the droplet and the quasi-steady diffusion-controlled droplet evaporation is conveniently solved in the toroidal coordinate system by applying the method of separation of variables. Our new analytical model for the coupled vapor concentration and temperature fields is in the closed form and is applicable for a full range of spherical-cap shape droplets of different contact angles and types of fluids. Our analytical results are uniquely quantified by a dimensionless evaporative cooling number E o whose magnitude is determined only by the thermophysical properties of the liquid and the atmosphere. Accordingly, the larger the magnitude of E o , the more significant the effect of the evaporative cooling, which results in stronger suppression on the evaporation rate. The classical isothermal model is recovered if the temperature gradient along the air-liquid interface is negligible ( E o = 0). For substrates with very high thermal conductivities (isothermal substrates), our analytical model predicts a reversal of temperature gradient along the droplet-free surface at a contact angle of 119°. Our findings pose interesting challenges but also guidance for experimental investigations.

Impacts of land use and land cover on surface and air temperature in urban landscapes

NASA Astrophysics Data System (ADS)

Crum, S.; Jenerette, D.

2015-12-01

Accelerating urbanization affects regional climate as the result of changing land cover and land use (LCLU). Urban land cover composition may provide valuable insight into relationships among urbanization, air, and land-surface temperature (Ta and LST, respectively). Climate may alter these relationships, where hotter climates experience larger LULC effects. To address these hypotheses we examined links between Ta, LST, LCLU, and vegetation across an urban coastal to desert climate gradient in southern California, USA. Using surface temperature radiometers, continuously measuring LST on standardized asphalt, concrete, and turf grass surfaces across the climate gradient, we found a 7.2°C and 4.6°C temperature decrease from asphalt to vegetated cover in the coast and desert, respectively. There is 131% more temporal variation in asphalt than turf grass surfaces, but 37% less temporal variation in concrete than turf grass. For concrete and turf grass surfaces, temporal variation in temperature increased from coast to desert. Using ground-based thermal imagery, measuring LST for 24 h sequences over citrus orchard and industrial use locations, we found a 14.5°C temperature decrease from industrial to orchard land use types (38.4°C and 23.9°C, respectively). Additionally, industrial land use types have 209% more spatial variation than orchard (CV=0.20 and 0.09, respectively). Using a network of 300 Ta (iButton) sensors mounted in city street trees throughout the region and hyperspectral imagery data we found urban vegetation greenness, measured using the normalized difference vegetation index (NDVI), was negatively correlated to Ta at night across the climate gradient. Contrasting previous findings, the closest coupling between NDVI and Ta is at the coast from 0000 h to 0800 h (highest r2 = 0.6, P < 0.05) while relationships at the desert are weaker (highest r2 = 0.38, P < 0.05). These findings indicate that vegetation cover in urbanized regions of southern California, USA decrease Ta and LST and spatial variation in LST, while built surfaces and land uses have the opposite effect. Furthermore these relationships are regulated by regional climate patterns, with decreases in Ta and LST being strongest in the coastal sub-region.

Reanalysis of the Indian summer monsoon: four dimensional data assimilation of AIRS retrievals in a regional data assimilation and modeling framework

NASA Astrophysics Data System (ADS)

Attada, Raju; Parekh, Anant; Chowdary, J. S.; Gnanaseelan, C.

2018-04-01

This work is the first attempt to produce a multi-year downscaled regional reanalysis of the Indian summer monsoon (ISM) using the National Centers for Environmental Prediction (NCEP) operational analyses and Atmospheric Infrared Sounder (AIRS) version 5 temperature and moisture retrievals in a regional model. Reanalysis of nine monsoon seasons (2003-2011) are produced in two parallel setups. The first set of experiments simply downscale the original NCEP operational analyses, whilst the second one assimilates the AIRS temperature and moisture profiles. The results show better representation of the key monsoon features such as low level jet, tropical easterly jet, subtropical westerly jet, monsoon trough and the spatial pattern of precipitation when AIRS profiles are assimilated (compared to those without AIRS data assimilation). The distribution of temperature, moisture and meridional gradients of dynamical and thermodynamical fields over the monsoon region are better represented in the reanalysis that assimilates AIRS profiles. The change induced by AIRS data on the moist and thermodynamic conditions results in more realistic rendering of the vertical shear associated with the monsoon, which in turn leads to a proper moisture transport and the moist convective feedback. This feedback benefits the representation of the regional monsoon characteristics, the monsoon dynamics and the moist convective processes on the seasonal time scale. This study emphasizes the use of AIRS soundings for downscaling of ISM representation in a regional reanalysis.

TEMPERATURE DISTRIBUTION IN A DIFFUSION CLOUD CHAMBER

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

Slavic, I.; Szymakowski, J.; Stachorska, D.

1961-03-01

A diffusion cloud chamber with working conditions within a pressure range from 10 mm Hg to 2 atmospheres and at variable boundary surface temperatures in a wide interval is described. A simple procedure is described for cooling and thermoregulating the bottom of the chamber by means of vapor flow of liquid air which makes possible the achievement of temperature up to -120 deg C with stability better that plus or minus 1 deg C. A method for the measurement of temperature distribution by means of a thermistor is described, and a number of curves of the observed temperature gradient, dependentmore » on the boundary surface temperature is given. Analysis of other factors influencing the stable work of the diffusion cloud chamber was made. (auth)« less

The increase in September precipitation in the Mediterranean region as a result of changes in atmospheric circulation

NASA Astrophysics Data System (ADS)

Nojarov, Peter

2017-04-01

The study analyzes changes in September precipitation in the Mediterranean region and their possible causes. The research period is 1950-2014. The main finding is that the reduction in aerosol pollution over Europe in the late twentieth century has led to an upward shift of air temperatures in the region, which in turn has reduced the meridional temperature gradient, leading to weakening and shift to the north of the Azores High (the north end of Hadley circulation). This northward shift placed the Mediterranean region in an area with decreasing SLP, which results in an increase in the number or intensity of cyclones, increase in cloudiness and precipitation and a decrease in air temperatures. In the period 1995-2014 the region (especially its eastern part) lies within the boundaries of Inter Tropical Convergence Zone in September.

Air, telescope, and instrument temperature effects on the Gemini Planet Imager’s image quality

NASA Astrophysics Data System (ADS)

Tallis, Melisa; Bailey, Vanessa P.; Macintosh, Bruce; Hayward, Thomas L.; Chilcote, Jeffrey K.; Ruffio, Jean-Baptiste; Poyneer, Lisa A.; Savransky, Dmitry; Wang, Jason J.; GPIES Team

2018-01-01

We present results from an analysis of air, telescope, and instrument temperature effects on the Gemini Planet Imager’s (GPI) image quality. GPI is a near-infrared, adaptive optics-fed, high-contrast imaging instrument at the Gemini South telescope, designed to directly image and characterize exoplanets and circumstellar disks. One key metric for instrument performance is “contrast,” which quantifies the sensitivity of an image in terms of the flux ratio of the noise floor vs. the primary star. Very high contrast signifies that GPI could succeed at imaging a dim, close companion around the primary star. We examine relationships between multiple temperature sensors placed on the instrument and telescope vs. image contrast. These results show that there is a strong correlation between image contrast and the presence of temperature differentials between the instrument and the temperature outside the dome. We discuss potential causes such as strong induced dome seeing or optical misalignment due to thermal gradients. We then assess the impact of the current temperature control and ventilation strategy and discuss potential modifications.

Temperature And Wind Velocity Oscillations Along a Gentle Slope During Sea-Breeze Events

NASA Astrophysics Data System (ADS)

Bastin, Sophie; Drobinski, Philippe

2005-03-01

The flow structure on a gentle slope at Vallon d’Ol in the northern suburbs of Marseille in southern France has been documented by means of surface wind and temperature measurements collected from 7 June to 14 July 2001 during the ESCOMPTE experiment. The analysis of the time series reveals temperature and wind speed oscillations during several nights (about 60--90 min oscillation period) and several days (about 120-180 min oscillation period) during the whole observing period. Oscillating katabatic winds have been reported in the literature from theoretical, experimental and numerical studies. In the present study, the dynamics of the observed oscillating katabatic winds are in good agreement with the theory.In contrast to katabatic winds, no daytime observations of oscillating anabatic upslope flows have ever been published to our knowledge, probably because of temperature inversion break-up that inhibits upslope winds. The present paper shows that cold air advection by a sea breeze generates a mesoscale horizontal temperature gradient, and hence baroclinicity in the atmosphere, which then allows low-frequency oscillations, similar to a katabatic flow. An expression for the oscillation period is derived that accounts for the contribution of the sea-breeze induced mesoscale horizontal temperature gradient. The theoretical prediction of the oscillation period is compared to the measurements, and good agreement is found. The statistical analysis of the wind flow at Vallon d’Ol shows a dominant north-easterly to easterly flow pattern for nighttime oscillations and a dominant south-westerly flow pattern for daytime oscillations. These results are consistent with published numerical simulation results that show that the air drains off the mountain along the maximum slope direction, which in the studied case is oriented south-west to north-east.

Effect of the thermal environment on the efficiency of packed columns in supercritical fluid chromatography.

PubMed

Zauner, Jordan; Lusk, Ryan; Koski, Steven; Poe, Donald P

2012-11-30

When a packed column is operated at temperatures and pressures near the critical point in supercritical fluid chromatography, the thermal environment in which it is placed has a significant impact on retention and efficiency. We measured the retention factors, plate heights, and related parameters for elution of a test mixture of alkylbenzenes with 5% methanol/95% carbon dioxide mobile phase on a 250 mm × 4.6 mm i.d. column packed with 5-micron Luna-C18 particles. Separations were performed at outlet pressures from 100 to 150 bar and a column oven temperature of 323K. For a bare column thermostated with convective air, significant efficiency losses were observed for outlet pressures equal to or less than 120 bar. These large efficiency losses are attributed to radial temperature gradients. Addition of foam insulation resulted in significant improvements in efficiency. Operating the column in still air using a commercially available column heater provided the best overall performance, with no measurable efficiency loss over the entire range of pressures studied. A reduced plate height of 1.88 was obtained at an optimum flow rate of 3.0 mL/min at 100 bar outlet pressure and with the temperature of the incoming mobile phase set approximately 2.3K above the temperature of the column oven. Retention time repeatability for all three thermal conditions was equal to or less than 0.5% RSD. These results demonstrate that it is possible to perform fast, efficient separations with excellent repeatability using SFC under near-critical conditions if the thermal environment is optimized to minimize the generation of radial temperature gradients. Copyright © 2012 Elsevier B.V. All rights reserved.

Finite Volume Numerical Methods for Aeroheating Rate Calculations from Infrared Thermographic Data

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Berry, Scott A.; Horvath, Thomas J.; Nowak, Robert J.

2003-01-01

The use of multi-dimensional finite volume numerical techniques with finite thickness models for calculating aeroheating rates from measured global surface temperatures on hypersonic wind tunnel models was investigated. Both direct and inverse finite volume techniques were investigated and compared with the one-dimensional semi -infinite technique. Global transient surface temperatures were measured using an infrared thermographic technique on a 0.333-scale model of the Hyper-X forebody in the Langley Research Center 20-Inch Mach 6 Air tunnel. In these tests the effectiveness of vortices generated via gas injection for initiating hypersonic transition on the Hyper-X forebody were investigated. An array of streamwise orientated heating striations were generated and visualized downstream of the gas injection sites. In regions without significant spatial temperature gradients, one-dimensional techniques provided accurate aeroheating rates. In regions with sharp temperature gradients due to the striation patterns two-dimensional heat transfer techniques were necessary to obtain accurate heating rates. The use of the one-dimensional technique resulted in differences of 20% in the calculated heating rates because it did not account for lateral heat conduction in the model.

Sensitivity of Last Glacial Maximum climate to uncertainties in tropical and subtropical ocean temperatures

USGS Publications Warehouse

Hostetler, S.; Pisias, N.; Mix, A.

2006-01-01

The faunal and floral gradients that underlie the CLIMAP (1981) sea-surface temperature (SST) reconstructions for the Last Glacial Maximum (LGM) reflect ocean temperature gradients and frontal positions. The transfer functions used to reconstruct SSTs from biologic gradients are biased, however, because at the warmest sites they display inherently low sensitivity in translating fauna to SST and they underestimate SST within the euphotic zones where the pycnocline is strong. Here we assemble available data and apply a statistical approach to adjust for hypothetical biases in the faunal-based SST estimates of LGM temperature. The largest bias adjustments are distributed in the tropics (to address low sensitivity) and subtropics (to address underestimation in the euphotic zones). The resulting SSTs are generally in better agreement than CLIMAP with recent geochemical estimates of glacial-interglacial temperature changes. We conducted a series of model experiments using the GENESIS general atmospheric circulation model to assess the sensitivity of the climate system to our bias-adjusted SSTs. Globally, the new SST field results in a modeled LGM surface-air cooling relative to present of 6.4 ??C (1.9 ??C cooler than that of CLIMAP). Relative to the simulation with CLIMAP SSTs, modeled precipitation over the oceans is reduced by 0.4 mm d-1 (an anomaly -0.4 versus 0.0 mm d-1 for CLIMAP) and increased over land (an anomaly -0.2 versus -0.5 mm d-1 for CLIMAP). Regionally strong responses are induced by changes in SST gradients. Data-model comparisons indicate improvement in agreement relative to CLIMAP, but differences among terrestrial data inferences and simulated moisture and temperature remain. Our SSTs result in positive mass balance over the northern hemisphere ice sheets (primarily through reduced summer ablation), supporting the hypothesis that tropical and subtropical ocean temperatures may have played a role in triggering glacial changes at higher latitudes.

Numerical modelling of convective heat transport by air flow in permafrost talus slopes

NASA Astrophysics Data System (ADS)

Wicky, Jonas; Hauck, Christian

2017-06-01

Talus slopes are a widespread geomorphic feature in the Alps. Due to their high porosity a gravity-driven internal air circulation can be established which is forced by the gradient between external (air) and internal (talus) temperature. The thermal regime is different from the surrounding environment, leading to the occurrence of permafrost below the typical permafrost zone. This phenomenon has mainly been analysed by field studies and only few explicit numerical modelling studies exist. Numerical simulations of permafrost sometimes use parameterisations for the effects of convection but mostly neglect the influence of convective heat transfer in air on the thermal regime. In contrast, in civil engineering many studies have been carried out to investigate the thermal behaviour of blocky layers and to improve their passive cooling effect. The present study further develops and applies these concepts to model heat transfer in air flows in a natural-scale talus slope. Modelling results show that convective heat transfer has the potential to develop a significant temperature difference between the lower and the upper parts of the talus slope. A seasonally alternating chimney-effect type of circulation develops. Modelling results also show that this convective heat transfer leads to the formation of a cold reservoir in the lower part of the talus slope, which can be crucial for maintaining the frozen ground conditions despite increasing air temperatures caused by climate change.

Progress in Ion Transport Membranes for Gas Separation Applications

NASA Astrophysics Data System (ADS)

Bose, Arun C.; Stiegel, Gary J.; Armstrong, Phillip A.; Halper, Barry J.; (Ted) Foster, E. P.

This chapter describes the evolution and advances of ion transport membranes for gas separation applications, especially separation of oxygen from air. In partnership with the US Department of Energy (DOE), Air Products and Chemicals, Inc. (Air Products) successfully developed a novel class of mixed ion-electron conducting materials and membrane architecture. These novel materials are referred to as ion transport membranes (ITM). Generically, ITMs consist of modified perovskite and brownmillerite oxide solid electrolytes and provide high oxygen anion and electron conduction typically at high temperatures driven by an oxygen potential gradient without the need for external power. The partial pressure ratio across the ITM layer creates the driving force for oxygen separation.

Ocean Surface Temperature Response to Atmosphere-Ocean Interaction of the MJO: A Component of Coupled Air-Wave-Sea Processes in the Subtropics Department Research Initiative

DTIC Science & Technology

2012-09-30

Lamont-Doherty Earth Observatory of Columbia University Ocean and Climate Physics Division 61 Route 9W Palisades , NY 10964 Phone: (845) 365-8547...Route 9W Palisades , NY 10964 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S...convective cells in the region as seen in the S-Pol. The robust large-scale temperature gradient of nearly 1°C is real with window and atmosphere

Surface temperatures and temperature gradient features of the US Gulf Coast waters

NASA Technical Reports Server (NTRS)

Huh, O. K.; Rouse, L. J., Jr.; Smith, G. W.

1977-01-01

Satellite thermal infrared data on the Gulf of Mexico show that a seasonal cycle exists in the horizontal surface temperature structure. In the fall, the surface temperatures of both coastal and deep waters are nearly uniform. With the onset of winter, atmospheric cold fronts, which are accompanied by dry, low temperature air and strong winds, draw heat from the sea. A band of cooler water forming on the inner shelf expands, until a thermal front develops seaward along the shelf break between the cold shelf waters and the warmer deep waters of the Gulf. Digital analysis of the satellite data was carried out in an interactive mode using a minicomputer and software. A time series of temperature profiles illustrates the temporal and spatial changes in the sea-surface temperature field.

Subsurface temperature distribution in a tropical alluvial fan

NASA Astrophysics Data System (ADS)

Chen, Wenfu; Chang, Minhsiang; Chen, Juier; Lu, Wanchung; Huang, Chihc; Wang, Yunshuen

2017-04-01

As a groundwater intensive use country, Taiwan's 1/3 water supplies are derived from groundwater. The major aquifers consist of sand and gravel formed in alluvial fans which border the fronts of central mountains. Thanks to high density of monitoring wells which provide a window to see the details of the subsurface temperature distribution and the thermal regime in an alluvial fan system. Our study area, the Choshui Alluvial Fan, is the largest groundwater basin in Taiwan and, located within an area of 2,000 km2, has a population of over 1.5 million. For this work, we investigated temperature-depth profiles using 70 groundwater monitoring wells during 2000 to 2015. Our results show that the distribution of subsurface temperature is influenced by various factors such as groundwater recharge, groundwater flow field, air temperature and land use. The groundwater recharge zone, hills to the upper fan, contains disturbed and smaller geothermal gradients. The lack of clay layers within the upper fan aquifers and fractures that developed in the hills should cause the convection and mixing of cooler recharge water to groundwater, resulting in smaller geothermal gradients. The groundwater temperatures at a depth to 300 m within the upper fan and hill were approximately only 23-24 °C while the current mean ground surface temperature is approximately 26 °C.

Effects of cold front passage on turbulent fluxes over a large inland water

NASA Astrophysics Data System (ADS)

Zhang, Q.; Liu, H.

2011-12-01

Turbulent fluxes of sensible and latent heat over a large inland water in southern USA were measured using the eddy covariance method through the year of 2008. In addition, net radiation, air temperatures and relative humidity, and water temperature in different depths were also measured. The specific objective of this study is to examine effects of a cold front passage on the surface energy fluxes. For the typical cold front event selected from April 11 to 14, air temperature decreased by 16°C, while surface temperature only dropped 6°C. Atmospheric vapor pressure decreased by 1.6 kPa, while that in the water-air interface dropped 0.7 kPa. The behavior difference in the water-air interface was caused by the passage of cold, dry air masses immediately behind the cold front. During the cold front event, sensible heat and latent heat flux increased by 171 W m-2 and 284 W m-2, respectively. Linear aggression analysis showed that the sensible heat flux was proportional to the product of wind speed and the temperature gradient of water-air interface, with a correlation coefficient of 0.95. Latent heat flux was proportional to the product of wind speed and vapor pressure difference between the water surface and overlaying atmosphere, with a correlation coefficient of 0.81. Also, the correlations between both fluxes and the wind speed were weak. This result indicated that the strong wind associated with the cold front event contributed to the turbulent mixing, which indirectly enhanced surface energy exchange between the water surface and the atmosphere. The relationship between the water heat storage energy and turbulent fluxes was also examined.

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

Wereszczak, A.A.; Ferber, M.K.; Kirkland, T.P.

Several yttria-fluxed, hot-isostatically pressed (HIPed) silicon nitrides have been tensile creep tested at temperatures representative of gas turbine engines. Creep and oxidation assisted damage mechanisms concurrently evolve when these materials are tested at high temperatures and low stresses (i.e., long exposure times at temperature). Atmospheric creep testing results in creation of oxygen and yttrium gradients across the radial dimension. High concentrations of oxygen and yttrium coincide with dense populations of lenticular-shaped cavities near the surface of crept specimens. The center of the tensile specimens was devoid of oxygen or yttrium; in addition, lenticular cavities were rare. The gradient in lenticular-cavitymore » concentration is coincident with the oxygen and yttrium gradients. Stress corrosion cracking (SCC) also occurs in these HIPed silicon nitrides when they are subjected to stress at high temperatures in ambient air. The size of this damage zone increases when the temperature is higher and/or the applied stress is lower. Stress-corrosion cracking initiates at the surface of the tensile specimen and advances radially inwards. What nucleates SCC has not yet been identified, but it is believed to result from a stress-concentrator (e.g., machining damage) at the surface and its growth is a result of coalescence of microcracks and cavities. The higher concentration of oxygen and yttrium in the grain boundaries near the specimen`s surface lessens the local high temperature mechanical integrity; this is believed to be associated with the growth of the SCC zone. This SCC zone continues to grow in size during tensile loading until it reaches a critical size which causes fracture.« less

Evaluation of thermal X/5-detector Skylab S-192 data for estimating evapotranspiration and thermal properties of soils for irrigation management

NASA Technical Reports Server (NTRS)

Moore, D. G.; Horton, M. L.; Russell, M. J.; Myers, V. I.

1975-01-01

An energy budget approach to evaluating the SKYLAB X/5-detector S-192 data for prediction of soil moisture and evapotranspiration rate was pursued. A test site which included both irrigated and dryland agriculture in Southern Texas was selected for the SL-4 SKYLAB mission. Both vegetated and fallow fields were included. Data for a multistage analysis including ground, NC-130B aircraft, RB-57F aircraft, and SKYLAB altitudes were collected. The ground data included such measurements as gravimetric soil moisture, percent of the ground covered by green vegetation, soil texture, net radiation, soil temperature gradients, surface emittance, soil heat flux, air temperature and humidity gradients, and cultural practices. Ground data were used to characterize energy budgets and to evaluate the utility of an energy budget approach for determining soil moisture differences among twelve specific agricultural fields.

A heat budget for the Stratus mooring in the southeast Pacific

NASA Astrophysics Data System (ADS)

Holte, J.; Straneo, F.; Weller, R. A.; Farrar, J. T.

2012-12-01

The surface layer of the southeast Pacific Ocean (SEP) requires an input of fresh, cold water to balance evaporation and heat gain from incoming solar radiation. Numerous processes contribute to closing the SEP's upper-ocean heat budget, including gyre circulation, Ekman transport and pumping, vertical mixing, and horizontal eddy heat flux divergence. However, there is little consensus on which processes are most important, as many modeling and observational studies have reported conflicting results. To examine how the SEP maintains relatively cool surface temperatures despite such strong surface forcing, we calculate a heat budget for the upper 250 m of the Stratus mooring. The Stratus mooring, deployed at 85(^o)W 20(^o)S since 2000, is in the center of the stratus cloud region. The surface buoy measures meteorological conditions and air-sea fluxes; the mooring line is heavily instrumented, measuring temperature, salinity, and velocity at approximately 15 to 20 depth levels. Our heat budget covers 2004 - 2010. The net air-sea heat flux over this period is 32 W m(^{-2}), approximately 2/3 of the flux over earlier periods. We use Argo profiles, relatively abundant in the region since 2004, to calculate horizontal temperature gradients. These gradients, coupled with the mooring velocity record, are used to estimate the advective heat flux. We find that the cool advective heat flux largely compensates the air-sea heat flux at the mooring; in our calculation this term includes the mean gyre circulation, horizontal Ekman transport, and some contribution from eddies. The passage of numerous eddies is evident in the mooring velocity record, but with the available data we cannot separate the eddy heat flux divergence from the mean heat advection. Vertical mixing and Ekman pumping across the base of the layer are both small.

Effects of vernal equinox solar eclipse on temperature and wind direction in Switzerland

NASA Astrophysics Data System (ADS)

Eugster, Werner; Emmel, Carmen; Wolf, Sebastian; Buchmann, Nina; McFadden, Joseph P.; Whiteman, Charles David

2017-12-01

The vernal equinox total solar eclipse of 20 March 2015 produced a maximum occultation of 65.8-70.1 % over Switzerland during the morning hours (09:22 to 11:48 CET). Skies were generally clear over the Swiss Alps due to a persistent high-pressure band between the UK and Russia associated with a rather weak pressure gradient over the continent. To assess the effects of penumbral shading on near-surface meteorology across Switzerland, air temperature data measured at 10 min intervals at 184 MeteoSwiss weather stations were used. Wind speed and direction data were available from 165 of these stations. Additionally, six Swiss FluxNet eddy covariance flux (ECF) sites provided turbulent measurements at 20 Hz resolution. During maximum occultation, the temperature drop was up to 5.8 K at a mountain site where cold air can pool in a topographic depression. The bootstrapped average of the maximum temperature drops of all 184 MeteoSwiss sites during the solar eclipse was 1.51 ± 0.02 K (mean ± SE). A detailed comparison with literature values since 1834 showed a temperature decrease of 2.6 ± 1.7 K (average of all reports), with extreme values up to 11 K. On fair weather days under weak larger-scale pressure gradients, local thermo-topographic wind systems develop that are driven by small-scale pressure and temperature gradients. At one ECF site, the penumbral shading delayed the morning transition from down-valley to up-valley wind conditions. At another site, it prevented this transition from occurring at all. Data from the 165 MeteoSwiss sites measuring wind direction did not show a consistent pattern of wind direction response to the passing of the penumbral shadow. These results suggest that the local topographic setting had an important influence on the temperature drop and the wind flow patterns during the eclipse. A significant cyclonic effect of the passing penumbral shadow was found in the elevation range ≈ 1700-2700 m a. s. l., but not at lower elevations of the Swiss Plateau. This contrasts with an earlier theory that the anticyclonic outflow should reach as far as ≈ 2400 km from the center of the eclipse, which would have included all of Switzerland during the 2015 eclipse. Thus, measurable effects of penumbral shading on the local wind system could be even found at ≈ 2000 km from the path of the eclipse (that is, Switzerland during the 2015 eclipse), and our results tend to lend support to a newer theory that the anticyclonic cold-air outflow from the center of the eclipse only extends ≈ 1600 km outwards, with cyclonic flow beyond that distance.

Spatial interpolation of monthly mean air temperature data for Latvia

NASA Astrophysics Data System (ADS)

Aniskevich, Svetlana

2016-04-01

Temperature data with high spatial resolution are essential for appropriate and qualitative local characteristics analysis. Nowadays the surface observation station network in Latvia consists of 22 stations recording daily air temperature, thus in order to analyze very specific and local features in the spatial distribution of temperature values in the whole Latvia, a high quality spatial interpolation method is required. Until now inverse distance weighted interpolation was used for the interpolation of air temperature data at the meteorological and climatological service of the Latvian Environment, Geology and Meteorology Centre, and no additional topographical information was taken into account. This method made it almost impossible to reasonably assess the actual temperature gradient and distribution between the observation points. During this project a new interpolation method was applied and tested, considering auxiliary explanatory parameters. In order to spatially interpolate monthly mean temperature values, kriging with external drift was used over a grid of 1 km resolution, which contains parameters such as 5 km mean elevation, continentality, distance from the Gulf of Riga and the Baltic Sea, biggest lakes and rivers, population density. As the most appropriate of these parameters, based on a complex situation analysis, mean elevation and continentality was chosen. In order to validate interpolation results, several statistical indicators of the differences between predicted values and the values actually observed were used. Overall, the introduced model visually and statistically outperforms the previous interpolation method and provides a meteorologically reasonable result, taking into account factors that influence the spatial distribution of the monthly mean temperature.

Practical strategies for stable operation of HFF-QCM in continuous air flow.

PubMed

Wessels, Alexander; Klöckner, Bernhard; Siering, Carsten; Waldvogel, Siegfried R

2013-09-09

Currently there are a few fields of application using quartz crystal microbalances (QCM). Because of environmental conditions and insufficient resolution of the microbalance, chemical sensing of volatile organic compounds in an open system was as yet not possible. In this study we present strategies on how to use 195 MHz fundamental quartz resonators for a mobile sensor platform to detect airborne analytes. Commonly the use of devices with a resonant frequency of about 10 MHz is standard. By increasing the frequency to 195 MHz the frequency shift increases by a factor of almost 400. Unfortunately, such kinds of quartz crystals tend to exhibit some challenges to obtain a reasonable signal-to-noise ratio. It was possible to reduce the noise in frequency in a continuous air flow of 7.5 m/s to 0.4 Hz [i.e., σ(τ) = 2 × 10-9] by elucidating the major source of noise. The air flow in the vicinity of the quartz was analyzed to reduce turbulences. Furthermore, we found a dependency between the acceleration sensitivity and mechanical stress induced by an internal thermal gradient. By reducing this gradient, we achieved reduction of the sensitivity to acceleration by more than one decade. Hence, the resulting sensor is more robust to environmental conditions such as temperature, acceleration and air flow.

Photosynthetic temperature adaptation of Pinus cembra within the timberline ecotone of the Central Austrian Alps.

PubMed

Wieser, Gerhard; Oberhuber, Walter; Walder, Lisa; Spieler, Daniela; Gruber, Andreas

2010-04-01

Temperature is suggested to determine the upper limit of tree life. Therefore, future climate warming may be of importance for tree distribution within the European Alps, where low temperatures limit carbon metabolism.We focused on the effects of air and soil temperature on net photosynthesis (P(n)) of Pinus cembra an evergreen climax species of the timberline ecotone of the Central Austrian Alps. Light response and temperature response curves were estimated along an altitudinal gradient ranging from the forest limit up to the krummholz limit in both summer and fall.In general, P(n) was significantly lower in fall as compared to summer. Nevertheless, independent from season mean P(n) values tended to increase with elevation and were positively correlated with root zone temperatures. The specific leaf area by contrast declined with increasing elevation. Furthermore, the temperature optimum of net photosynthesis declined with increasing elevation and was positively correlated with the mean maximum air temperature of the 10 days prior the date of measurement.Thus, our findings appear to reflect a long-term adaptation of the photosynthetic apparatus of Pinus cembra to the general temperature conditions with respect to elevation combined with a short term acclimation to the prevailing temperature regime.

The Response of Human Thermal Sensation and Its Prediction to Temperature Step-Change (Cool-Neutral-Cool)

PubMed Central

Du, Xiuyuan; Li, Baizhan; Liu, Hong; Yang, Dong; Yu, Wei; Liao, Jianke; Huang, Zhichao; Xia, Kechao

2014-01-01

This paper reports on studies of the effect of temperature step-change (between a cool and a neutral environment) on human thermal sensation and skin temperature. Experiments with three temperature conditions were carried out in a climate chamber during the period in winter. Twelve subjects participated in the experiments simulating moving inside and outside of rooms or cabins with air conditioning. Skin temperatures and thermal sensation were recorded. Results showed overshoot and asymmetry of TSV due to the step-change. Skin temperature changed immediately when subjects entered a new environment. When moving into a neutral environment from cool, dynamic thermal sensation was in the thermal comfort zone and overshoot was not obvious. Air-conditioning in a transitional area should be considered to limit temperature difference to not more than 5°C to decrease the unacceptability of temperature step-change. The linear relationship between thermal sensation and skin temperature or gradient of skin temperature does not apply in a step-change environment. There is a significant linear correlation between TSV and Qloss in the transient environment. Heat loss from the human skin surface can be used to predict dynamic thermal sensation instead of the heat transfer of the whole human body. PMID:25136808

Fermentation and microbial population dynamics during the ensiling of native grass and subsequent exposure to air.

PubMed

Zhang, Qing; Wu, Baiyila; Nishino, Naoki; Wang, Xianguo; Yu, Zhu

2016-03-01

To study the microbial population and fermentation dynamics of large needlegrass (LN) and Chinese leymus (CL) during ensiling and subsequent exposure to air, silages were sampled and analyzed using culture-based techniques and denaturing gradient gel electrophoresis (DGGE). A total of 112 lactic acid bacteria (LAB) strains were isolated and identified using the 16S rRNA sequencing method. Lactic acid was not detected in the first 20 days in LN silage and the pH decreased to 6.13 after 45 days of ensiling. The temperature of the LN silage increased after approximately 30 h of air exposure and the CL silage showed a slight temperature variation. Enterococcus spp. were mainly present in LN silage. The proportion of Lactobacillus brevis in CL silage increased after exposure to air. LN silage with a higher proportion of Enterococcus spp. and propionic acid concentration did not show higher fermentation quality or aerobic stability than CL silage, which had a higher concentration of acetic acid, butyric acid and increased proportion of L. brevis after exposure to air. © 2015 Japanese Society of Animal Science.

Biology and air-sea gas exchange controls on the distribution of carbon isotope ratios (δ13C) in the ocean

NASA Astrophysics Data System (ADS)

Schmittner, A.; Gruber, N.; Mix, A. C.; Key, R. M.; Tagliabue, A.; Westberry, T. K.

2013-05-01

Analysis of observations and sensitivity experiments with a new three-dimensional global model of stable carbon isotope cycling elucidate the processes that control the distribution of δ13C in the contemporary and preindustrial ocean. Biological fractionation dominates the distribution of δ13CDIC of dissolved inorganic carbon (DIC) due to the sinking of isotopically light δ13C organic matter from the surface into the interior ocean. This process leads to low δ13CDIC values at dephs and in high latitude surface waters and high values in the upper ocean at low latitudes with maxima in the subtropics. Air-sea gas exchange provides an important secondary influence due to two effects. First, it acts to reduce the spatial gradients created by biology. Second, the associated temperature dependent fractionation tends to increase (decrease) δ13CDIC values of colder (warmer) water, which generates gradients that oppose those arising from biology. Our model results suggest that both effects are similarly important in influencing surface and interior δ13CDIC distributions. However, air-sea gas exchange is slow, so biological effect dominate spatial δ13CDIC gradients both in the interior and at the surface, in constrast to conclusions from some previous studies. Analysis of a new synthesis of δ13CDIC measurements from years 1990 to 2005 is used to quantify preformed (δ13Cpre) and remineralized (δ13Crem) contributions as well as the effects of biology (Δδ13Cbio) and air-sea gas exchange (δ13C*). The model reproduces major features of the observed large-scale distribution of δ13CDIC, δ13Cpre, δ13Crem, δ13C*, and Δδ13Cbio. Residual misfits are documented and analyzed. Simulated surface and subsurface δ13CDIC are influenced by details of the ecosystem model formulation. For example, inclusion of a simple parameterization of iron limitation of phytoplankton growth rates and temperature-dependent zooplankton grazing rates improves the agreement with δ13CDIC observations and satellite estimates of phytoplankton growth rates and biomass, suggesting that δ13C can also be a useful test of ecosystem models.

Minimum Temperatures, Diurnal Temperature Ranges and Temperature Inversions in Limestone Sinkholes of Different Sizes and Shapes

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

Whiteman, Charles D.; Haiden, Thomas S.; Pospichal, Bernhard

2004-08-01

Air temperature data from five enclosed limestone sinkholes of various sizes and shapes on the 1300 m MSL Duerrenstein Plateau near Lunz, Austria have been analyzed to determine the effect of sinkhole geometry on temperature minima, diurnal temperature ranges, temperature inversion strengths and vertical temperature gradients. Data were analyzed for a non-snow-covered October night and for a snow-covered December night when the temperature fell as low as -28.5°C. Surprisingly, temperatures were similar in two sinkholes with very different drainage areas and depths. A three-layer model was used to show that the sky-view factor is the most important topographic parameter controllingmore » cooling for basins in this size range and that the cooling slows when net longwave radiation at the floor of the sinkhole is nearly balanced by the ground heat flux.« less

Range-Wide Latitudinal and Elevational Temperature Gradients for the World's Terrestrial Birds: Implications under Global Climate Change

PubMed Central

La Sorte, Frank A.; Butchart, Stuart H. M.; Jetz, Walter; Böhning-Gaese, Katrin

2014-01-01

Species' geographical distributions are tracking latitudinal and elevational surface temperature gradients under global climate change. To evaluate the opportunities to track these gradients across space, we provide a first baseline assessment of the steepness of these gradients for the world's terrestrial birds. Within the breeding ranges of 9,014 bird species, we characterized the spatial gradients in temperature along latitude and elevation for all and a subset of bird species, respectively. We summarized these temperature gradients globally for threatened and non-threatened species and determined how their steepness varied based on species' geography (range size, shape, and orientation) and projected changes in temperature under climate change. Elevational temperature gradients were steepest for species in Africa, western North and South America, and central Asia and shallowest in Australasia, insular IndoMalaya, and the Neotropical lowlands. Latitudinal temperature gradients were steepest for extratropical species, especially in the Northern Hemisphere. Threatened species had shallower elevational gradients whereas latitudinal gradients differed little between threatened and non-threatened species. The strength of elevational gradients was positively correlated with projected changes in temperature. For latitudinal gradients, this relationship only held for extratropical species. The strength of latitudinal gradients was better predicted by species' geography, but primarily for extratropical species. Our findings suggest threatened species are associated with shallower elevational temperature gradients, whereas steep latitudinal gradients are most prevalent outside the tropics where fewer bird species occur year-round. Future modeling and mitigation efforts would benefit from the development of finer grain distributional data to ascertain how these gradients are structured within species' ranges, how and why these gradients vary among species, and the capacity of species to utilize these gradients under climate change. PMID:24852009

Evidence for Ventilation through Collective Respiratory Movements in Giant Honeybee (Apis dorsata) Nests.

PubMed

Kastberger, Gerald; Waddoup, Dominique; Weihmann, Frank; Hoetzl, Thomas

2016-01-01

The Asian giant honeybees (Apis dorsata) build single-comb nests in the open, which makes this species particularly susceptible to environmental strains. Long-term infrared (IR) records documented cool nest regions (CNR) at the bee curtain (nCNR = 207, nnests > 20) distinguished by marked negative gradients (ΔTCNR/d < -3°C / 5 cm) at their margins. CNRs develop and recede within minutes, predominantly at higher ambient temperatures in the early afternoon. The differential size (ΔACNR) and temperature (ΔTCNR) values per time unit correlated mostly positively (RAT > 0) displaying the Venturi effect, which evidences funnel properties of CNRs. The air flows inwards through CNRs, which is verified by the negative spatial gradient ΔTCNR/d, by the positive grading of TCNR with Tamb and lastly by fanners which have directed their abdomens towards CNRs. Rare cases of RAT < 0 (< 3%) document closing processes (for ΔACNR/Δt < -0.4 cm2/s) but also suggest ventilation of the bee curtain (for ΔACNR/Δt > +0.4 cm2/s) displaying "inhalation" and "exhalation" cycling. "Inhalation" could be boosted by bees at the inner curtain layers, which stretch their extremities against the comb enlarging the inner nest lumen and thus causing a pressure fall which drives ambient air inwards through CNR funnels. The relaxing of the formerly "activated" bees could then trigger the "exhalation" process, which brings the bee curtain, passively by gravity, close to the comb again. That way, warm, CO2-enriched nest-borne air is pressed outwards through the leaking mesh of the bee curtain. This ventilation hypothesis is supported by IR imaging and laser vibrometry depicting CNRs in at least four aspects as low-resistance convection funnels for maintaining thermoregulation and restoring fresh air in the nest.

Cyclic Fatigue Durability of Uncoated and EBC Coated 3D SiC/SiC Composites Under Thermal Gradient Conditions at 2700F in Air

NASA Technical Reports Server (NTRS)

Smith, Craig; Harder, Bryan; Zhu, Dongming; Bhatt, Ramakrishna; Kalluri, Sreeramesh

2017-01-01

Ceramic matrix composites (CMCs) such as SiC/SiC are currently being designed and implemented in high temperature sections of aerospace turbine engines. Such components will be subject to through-thickness thermal gradients, which may affect the durability. In this study, SiC/SiC CMCs with a hybrid chemical vapor infiltrated (CVI) and polymer infiltration and pyrolysis (PIP) matrix were loaded in tension while one surface was heated with a laser and the opposite surface was cooled. Issues associated with laser testing will be discussed, along with initial results for coated and uncoated samples.

Amazon rainforest exchange of carbon and subcanopy air flow: Manaus LBA site--a complex terrain condition.

PubMed

Tóta, Julio; Fitzjarrald, David Roy; da Silva Dias, Maria A F

2012-01-01

On the moderately complex terrain covered by dense tropical Amazon Rainforest (Reserva Biologica do Cuieiras--ZF2--02°36'17.1'' S, 60°12'24.4'' W), subcanopy horizontal and vertical gradients of the air temperature, CO(2) concentration and wind field were measured for the dry and wet periods in 2006. We tested the hypothesis that horizontal drainage flow over this study area is significant and can affect the interpretation of the high carbon uptake rates reported by previous works at this site. A similar experimental design as the one by Tóta et al. (2008) was used with a network of wind, air temperature, and CO(2) sensors above and below the forest canopy. A persistent and systematic subcanopy nighttime upslope (positive buoyancy) and daytime downslope (negative buoyancy) flow pattern on a moderately inclined slope (12%) was observed. The microcirculations observed above the canopy (38 m) over the sloping area during nighttime presents a downward motion indicating vertical convergence and correspondent horizontal divergence toward the valley area. During the daytime an inverse pattern was observed. The micro-circulations above the canopy were driven mainly by buoyancy balancing the pressure gradient forces. In the subcanopy space the microcirculations were also driven by the same physical mechanisms but probably with the stress forcing contribution. The results also indicated that the horizontal and vertical scalar gradients (e.g., CO(2)) were modulated by these micro-circulations above and below the canopy, suggesting that estimates of advection using previous experimental approaches are not appropriate due to the tridimensional nature of the vertical and horizontal transport locally. This work also indicates that carbon budget from tower-based measurement is not enough to close the system, and one needs to include horizontal and vertical advection transport of CO(2) into those estimates.

Amazon Rainforest Exchange of Carbon and Subcanopy Air Flow: Manaus LBA Site—A Complex Terrain Condition

PubMed Central

Tóta, Julio; Roy Fitzjarrald, David; da Silva Dias, Maria A. F.

2012-01-01

On the moderately complex terrain covered by dense tropical Amazon Rainforest (Reserva Biologica do Cuieiras—ZF2—02°36′17.1′′ S, 60°12′24.4′′ W), subcanopy horizontal and vertical gradients of the air temperature, CO2 concentration and wind field were measured for the dry and wet periods in 2006. We tested the hypothesis that horizontal drainage flow over this study area is significant and can affect the interpretation of the high carbon uptake rates reported by previous works at this site. A similar experimental design as the one by Tóta et al. (2008) was used with a network of wind, air temperature, and CO2 sensors above and below the forest canopy. A persistent and systematic subcanopy nighttime upslope (positive buoyancy) and daytime downslope (negative buoyancy) flow pattern on a moderately inclined slope (12%) was observed. The microcirculations observed above the canopy (38 m) over the sloping area during nighttime presents a downward motion indicating vertical convergence and correspondent horizontal divergence toward the valley area. During the daytime an inverse pattern was observed. The micro-circulations above the canopy were driven mainly by buoyancy balancing the pressure gradient forces. In the subcanopy space the microcirculations were also driven by the same physical mechanisms but probably with the stress forcing contribution. The results also indicated that the horizontal and vertical scalar gradients (e.g., CO2) were modulated by these micro-circulations above and below the canopy, suggesting that estimates of advection using previous experimental approaches are not appropriate due to the tridimensional nature of the vertical and horizontal transport locally. This work also indicates that carbon budget from tower-based measurement is not enough to close the system, and one needs to include horizontal and vertical advection transport of CO2 into those estimates. PMID:22619608

Current landscapes and legacies of land-use past: understanding the distribution of juvenile coho salmon (Oncorhynchus kisutch) and their habitats along the Oregon Coast, USA

Treesearch

E. Ashley Steel; Ariel Muldoon; Rebecca L. Flitcroft; Julie C. Firman; Kara J. Anlauf-Dunn; Kelly M. Burnett; Robert J. Danehy

2017-01-01

The Oregon Coast landscape displays strong spatial patterns in air temperature, precipitation, and geology, which can confound our ability to detect relationships among land management, instream conditions, and fish at broad spatial scales. Despite this structure, we found that a suite of immutable or intrinsic attributes (e.g., reach gradient, drainage area, elevation...

Mixing and unmixedness in plasma jets 1: Near-field analysis

NASA Technical Reports Server (NTRS)

Ilegbusi, Olusegun J.

1993-01-01

The flow characteristics in the near-field of a plasma jet are simulated with a two-fluid model. This model accounts for both gradient-diffusion mixing and uni-directional sifting motion resulting from pressure-gradient-body-force imbalance. This latter mechanism is believed to be responsible for the umixedness observed in plasma jets. The unmixedness is considered to be essentially a Rayleigh-Taylor kind instability. Transport equations are solved for the individual plasma and ambient gas velocities, temperatures and volume fractions. Empirical relations are employed for the interface transfers of mass, momentum and heat. The empirical coefficients are first established by comparison of predictions with available experimental data for shear flows. The model is then applied to an Argon plasma jet ejecting into stagnant air. The predicted results show the significant build-up of unmixed air within the plasma gas, even relatively far downstream of the torch. By adjusting the inlet condition, the model adequately reproduces the experimental data.

Biology and air-sea gas exchange controls on the distribution of carbon isotope ratios (δ13C) in the ocean

NASA Astrophysics Data System (ADS)

Schmittner, A.; Gruber, N.; Mix, A. C.; Key, R. M.; Tagliabue, A.; Westberry, T. K.

2013-09-01

Analysis of observations and sensitivity experiments with a new three-dimensional global model of stable carbon isotope cycling elucidate processes that control the distribution of δ13C of dissolved inorganic carbon (DIC) in the contemporary and preindustrial ocean. Biological fractionation and the sinking of isotopically light δ13C organic matter from the surface into the interior ocean leads to low δ13CDIC values at depths and in high latitude surface waters and high values in the upper ocean at low latitudes with maxima in the subtropics. Air-sea gas exchange has two effects. First, it acts to reduce the spatial gradients created by biology. Second, the associated temperature-dependent fractionation tends to increase (decrease) δ13CDIC values of colder (warmer) water, which generates gradients that oppose those arising from biology. Our model results suggest that both effects are similarly important in influencing surface and interior δ13CDIC distributions. However, since air-sea gas exchange is slow in the modern ocean, the biological effect dominates spatial δ13CDIC gradients both in the interior and at the surface, in contrast to conclusions from some previous studies. Calcium carbonate cycling, pH dependency of fractionation during air-sea gas exchange, and kinetic fractionation have minor effects on δ13CDIC. Accumulation of isotopically light carbon from anthropogenic fossil fuel burning has decreased the spatial variability of surface and deep δ13CDIC since the industrial revolution in our model simulations. Analysis of a new synthesis of δ13CDIC measurements from years 1990 to 2005 is used to quantify preformed and remineralized contributions as well as the effects of biology and air-sea gas exchange. The model reproduces major features of the observed large-scale distribution of δ13CDIC as well as the individual contributions and effects. Residual misfits are documented and analyzed. Simulated surface and subsurface δ13CDIC are influenced by details of the ecosystem model formulation. For example, inclusion of a simple parameterization of iron limitation of phytoplankton growth rates and temperature-dependent zooplankton grazing rates improves the agreement with δ13CDIC observations and satellite estimates of phytoplankton growth rates and biomass, suggesting that δ13C can also be a useful test of ecosystem models.

Recent Climate Changes in Northwestern Qaidam Basin Inferred from Geothermal Gradients

NASA Astrophysics Data System (ADS)

Liu, J.; Zhang, T.

2014-12-01

Temperature perturbations under the ground surface are direct thermal response to ground surface temperature changes. Thus ground surface temperature history can be reconstructed from borehole temperature measurements using borehole paleothermometry inversion method. In this study, we use seven borehole temperature profiles to reconstruct the ground surface temperature variation of the past 500 years of the Qaidam basin, northwestern China. Borehole transient temperature measurement from seven sites in northwestern Qaidam basin were separated from geothermal gradients and analyzed by functional space inversion method to determine past ground surface temperature variations in this region. All temperature profiles show the effects of recent climatic disturbances. Inversion shows an overall increase in ground surface temperature by an averaged 1.2℃ (-0.11~2.21℃) during the last 500 years. Clear signs of a cold period between 1500 and 1900 A.D., corresponding to the Little Ice Age, have been found. Its coldest period was between 1780~1790 A.D. with the ground surface temperature of 5.4℃. During the 19th and the 20th century, reconstructed ground surface temperature shows a rising trend, and in the late 20th century, the temperature started to decrease. However, the highest temperature in 1990s broke the record of the past 500 years. This reconstructed past ground surface temperature variation is verified by the simulated annual surface air temperature computed by EdGCM and the cooling trend is also confirmed by other reconstruction of winter half year minimum temperatures using tree rings on the northeastern Tibetan Plateau.

Comparison of infrared thermometer with thermocouple for monitoring skin temperature.

PubMed

Matsukawa, T; Ozaki, M; Nishiyama, T; Imamura, M; Kumazawa, T

2000-02-01

To test the hypothesis that the infrared thermometer (Genius) is comparably useful with thermocouples that are routinely used for skin temperature monitoring. Prospective, controlled, not blinded study. Operating room of a university hospital. Ten healthy male volunteers. Volunteers were minimally clothed and were initially warmed by a forced air warmer until they became vasodilated at the finger and the foot for approximately 30 mins. Subsequently, they were kept in the room with no blanket. Skin temperatures were measured continuously with the Mon-a-Therm thermocouple and were also measured with the Genius thermometer just before and after the warming and subsequently every 10 mins for 70 mins. Forearm and finger-tip skin temperatures and skin-surface temperature gradients (from arm to finger and from calf to toe) measured by the Genius thermometer were compared with those measured by the Mon-a-Therm thermocouple using linear regression and Bland and Altman statistics. Forearm temperature and finger-tip temperature ranged from approximately 31 degrees to approximately 36.5 degrees C (87.8-97.7 degrees F) and approximately 22.5 degrees to approximately 36 degrees C (72.5-96.8 degrees F), respectively. Gradients (from arm to finger and from calf to toe) ranged from approximately -3 degrees to approximately 10 degrees C (26.6-50.0 degrees F) and approximately -3 degrees to approximately 11 degrees C (26.6-51.8 degrees F), respectively. Correlations between the temperatures measured by the Genius thermometer and those by the Mon-a-Therm thermocouple were similar and reliable. The correlation coefficients were as follows: 0.78 at forearm, 0.97 at finger-tip, and 0.97 at skin-surface temperature gradients. The infrared thermometer with a special probe is useful to measure the change of skin-surface temperatures and to evaluate the severity of shock in patients.

Finite Volume Numerical Methods for Aeroheating Rate Calculations from Infrared Thermographic Data

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Berry, Scott A.; Horvath, Thomas J.; Nowak, Robert J.

2006-01-01

The use of multi-dimensional finite volume heat conduction techniques for calculating aeroheating rates from measured global surface temperatures on hypersonic wind tunnel models was investigated. Both direct and inverse finite volume techniques were investigated and compared with the standard one-dimensional semi-infinite technique. Global transient surface temperatures were measured using an infrared thermographic technique on a 0.333-scale model of the Hyper-X forebody in the NASA Langley Research Center 20-Inch Mach 6 Air tunnel. In these tests the effectiveness of vortices generated via gas injection for initiating hypersonic transition on the Hyper-X forebody was investigated. An array of streamwise-orientated heating striations was generated and visualized downstream of the gas injection sites. In regions without significant spatial temperature gradients, one-dimensional techniques provided accurate aeroheating rates. In regions with sharp temperature gradients caused by striation patterns multi-dimensional heat transfer techniques were necessary to obtain more accurate heating rates. The use of the one-dimensional technique resulted in differences of 20% in the calculated heating rates compared to 2-D analysis because it did not account for lateral heat conduction in the model.

Technical report: The design and evaluation of a basin-scale wireless sensor network for mountain hydrology

NASA Astrophysics Data System (ADS)

Zhang, Ziran; Glaser, Steven D.; Bales, Roger C.; Conklin, Martha; Rice, Robert; Marks, Danny G.

2017-05-01

A network of sensors for spatially representative water-balance measurements was developed and deployed across the 2000 km2 snow-dominated portion of the upper American River basin, primarily to measure changes in snowpack and soil-water storage, air temperature, and humidity. This wireless sensor network (WSN) consists of 14 sensor clusters, each with 10 measurement nodes that were strategically placed within a 1 km2 area, across different elevations, aspects, slopes, and canopy covers. Compared to existing operational sensor installations, the WSN reduces hydrologic uncertainty in at least three ways. First, redundant measurements improved estimation of lapse rates for air and dew-point temperature. Second, distributed measurements captured local variability and constrained uncertainty in air and dew-point temperature, snow accumulation, and derived hydrologic attributes important for modeling and prediction. Third, the distributed relative-humidity measurements offer a unique capability to monitor upper-basin patterns in dew-point temperature and characterize elevation gradient of water vapor-pressure deficit across steep, variable topography. Network statistics during the first year of operation demonstrated that the WSN was robust for cold, wet, and windy conditions in the basin. The electronic technology used in the WSN-reduced adverse effects, such as high current consumption, multipath signal fading, and clock drift, seen in previous remote WSNs.

BOREAS TGB-1/TGB-3 Water Table and Peat Temperature Data over the NSA

NASA Technical Reports Server (NTRS)

Bubier, Jill L.; Comer, Neil; Moore, Tim R.; Hall, Forrest G. (Editor); Conrad, Sara K. (Editor)

2000-01-01

The BOREAS TGB-1 and TGB-3 teams collected several data sets that contributed to understanding the measured trace gas fluxes over sites in the NSA. This data set contains continuous and manual measurements of water level and air and soil temperatures at the four subsites within the NSA Tower Fen site complex. The measurements were taken to understand the thermal and hydrological gradients associated with each plant community present in the fen. Measurements were taken from May to September 1994 and May to October 1996. The data are provided in tabular ASCII files.

Predicted optical performance of the high-altitude balloon experiment (HABE) telescope in an adverse thermal environment

NASA Astrophysics Data System (ADS)

Akau, Ronald L.; Givler, Richard C.; Eastman, Daniel R.

1994-07-01

The High-Altitude Balloon Experiment telescope was designed to operate at an ambient temperature of -55 degree(s)C and an altitude of 26 km, using a precooled primary mirror. Although at this altitude the air density is only 1.4 percent of the value at sea level, the temperature gradients within the telescope are high enough to deform the optical wavefront. This problem is considerably lessened by precooling the primary mirror to -35 degree(s)C. This paper describes the application of several codes to determine the range of wavefront deformation during a mission.

A field study of air flow and turbulent features of advection fog

NASA Technical Reports Server (NTRS)

Connell, J. D.

1979-01-01

The setup and initial operation of a set of specialized meteorological data collection hardware are described. To study the life cycle of advection fogs at a lake test site, turbulence levels in the fog are identified, and correlated with the temperature gradients and mean wind profiles. A meteorological tower was instrumented to allow multiple-level measurements of wind and temperature on a continuous basis. Additional instrumentation was: (1)hydrothermograph, (2)microbarograph, (3)transmissometers, and (4)a boundary layer profiler. Two types of fogs were identified, and important differences in the turbulence scales were noted.

Effect of temperature gradient on liquid-liquid phase separation in a polyolefin blend.

PubMed

Jiang, Hua; Dou, Nannan; Fan, Guoqiang; Yang, Zhaohui; Zhang, Xiaohua

2013-09-28

We have investigated experimentally the structure formation processes during phase separation via spinodal decomposition above and below the spinodal line in a binary polymer blend system exposed to in-plane stationary thermal gradients using phase contrast optical microscopy and temperature gradient hot stage. Below the spinodal line there is a coupling of concentration fluctuations and thermal gradient imposed by the temperature gradient hot stage. Also under the thermal gradient annealing phase-separated domains grow faster compared with the system under homogeneous temperature annealing on a zero-gradient or a conventional hot stage. We suggest that the in-plane thermal gradient accelerates phase separation through the enhancement in concentration fluctuations in the early and intermediate stages of spinodal decomposition. In a thermal gradient field, the strength of concentration fluctuation close to the critical point (above the spinodal line) is strong enough to induce phase separation even in one-phase regime of the phase diagram. In the presence of a temperature gradient the equilibrium phase diagrams are no longer valid, and the systems with an upper critical solution temperature can be quenched into phase separation by applying the stationary temperature gradient. The in-plane temperature gradient drives enhanced concentration fluctuations in a binary polymer blend system above and below the spinodal line.

Sea breezes and advective effects in southwest James Bay

NASA Technical Reports Server (NTRS)

Mckendry, Ian; Roulet, Nigel

1994-01-01

Observations from a transect extending 100 km inland during the Northern Wetlands Study (NOWES) in 1990 show that the sea breeze develops on approximately 25% of days during summer and may penetrate up to 100 km inland on occasions. The sea breeze exhibits a marked diurnal clockwise rotation as a result of the Coriolis effect along the unobstructed coastline. The marine advective effect is shown to depend on gradient wind direction. With northwesterly upper level flow the sea breeze tends to be northeasterly in direction and is associated with decreased temperatures and vapor pressure deficits (VPD). With southwesterly upper level flow the sea breeze tends to have a southeasterly direction and less effect on temperatures and VPD. This is attributed to shorter residence times of air parcels over water. For two cases, Colorado State University mesoscale model simulations show good agreement with surface wind observations and suggest that under northwesterly gradient flow, Bowen ratios are increased in the onshore flow along western James Bay, while during southwesterly gradient flow these effects are negligible. These results have implications for the interpretation of local climate, ecology, and hydrology as well as land-based and airborne turbulent flux measurements made during NOWES.

Analyzing the edge effects in a Brazilian seasonally dry tropical forest.

PubMed

Arruda, D M; Eisenlohr, P V

2016-02-01

Due to the deciduous nature of dry forests (widely known as seasonally dry tropical forests) they are subject to microclimatic conditions not experienced in other forest formations. Close examinations of the theory of edge effects in dry forests are still rare and a number of questions arise in terms of this topic. In light of this situation we examined a fragment of the dry forest to respond to the following questions: (I) Are there differences in canopy cover along the edge-interior gradient during the dry season? (II) How does the microclimate (air temperature, soil temperature, and relative humidity) vary along that gradient? (III) How does the microclimate influence tree species richness, evenness and abundance along that gradient? (IV) Are certain tree species more dominant closer to the forest edges? Regressions were performed to address these questions. Their coefficients did not significantly vary from zero. Apparently, the uniform openness of the forest canopy caused a homogeneous internal microclimate, without significant differentiation in habitats that would allow modifications in biotic variables tested. We conclude that the processes of edge effect commonly seen in humid forests, not was shared with the dry forest assessed.

Controls of air temperature variability over an Alpine Glacier

NASA Astrophysics Data System (ADS)

Shaw, Thomas; Brock, Ben; Ayala, Álvaro; Rutter, Nick

2016-04-01

Near surface air temperature (Ta) is one of the most important controls on energy exchange between a glacier surface and the overlying atmosphere. However, not enough detail is known about the controls on Ta across a glacier due to sparse data availability. Recent work has provided insights into variability of Ta along glacier centre-lines in different parts of the world, yet there is still a limited understanding of off-centreline variability in Ta and how best to estimate it from distant off-glacier locations. We present a new dataset of distributed 2m Ta records for the Tsanteleina Glacier in Northwest Italy from July-September, 2015. Data provide detailed information of lateral (across-glacier) and centre-line variations in Ta, with ~20,000 hourly observations from 17 locations. The suitability of different vertical temperature gradients (VTGs) in estimating air temperature is considered under a range of meteorological conditions and from different forcing locations. A key finding is that local VTGs account for a lot of Ta variability under a broad range of climatic conditions. However, across-glacier variability is found to be significant, particularly for high ambient temperatures and for localised topographic depressions. The relationship of spatial Ta patterns with regional-scale reanalysis data and alternative Ta estimation methodologies are also presented. This work improves the knowledge of local scale Ta variations and their importance to melt modelling.

Experimental aspects of buoyancy correction in measuring reliable high-pressure excess adsorption isotherms using the gravimetric method

NASA Astrophysics Data System (ADS)

Nguyen, Huong Giang T.; Horn, Jarod C.; Thommes, Matthias; van Zee, Roger D.; Espinal, Laura

2017-12-01

Addressing reproducibility issues in adsorption measurements is critical to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Standards and Technology Reference Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asymmetric two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcritical CO2 and supercritical N2 adsorption isotherms at 293 K. It was observed that measuring a collective volume for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temperature partition when there is a temperature gradient (i.e. analysis temperature is not equal to instrument air bath temperature). We demonstrate that a blank subtraction is effective in mitigating the biases associated with temperature partitioning, instrument calibration, and the determined volumes of the balance components. In general, the manual and subtraction methods allow for better treatment of the temperature gradient during buoyancy correction. From the study, best practices specific to asymmetric two-beam balances and more general recommendations for measuring isotherms far from critical temperatures using gravimetric instruments are offered.

Experimental aspects of buoyancy correction in measuring reliable highpressure excess adsorption isotherms using the gravimetric method.

PubMed

Nguyen, Huong Giang T; Horn, Jarod C; Thommes, Matthias; van Zee, Roger D; Espinal, Laura

2017-12-01

Addressing reproducibility issues in adsorption measurements is critical to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Standards and Technology Reference Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asymmetric two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcritical CO 2 and supercritical N 2 adsorption isotherms at 293 K. It was observed that measuring a collective volume for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temperature partition when there is a temperature gradient (i.e. analysis temperature is not equal to instrument air bath temperature). We demonstrate that a blank subtraction is effective in mitigating the biases associated with temperature partitioning, instrument calibration, and the determined volumes of the balance components. In general, the manual and subtraction methods allow for better treatment of the temperature gradient during buoyancy correction. From the study, best practices specific to asymmetric two-beam balances and more general recommendations for measuring isotherms far from critical temperatures using gravimetric instruments are offered.

Urban climate modifies tree growth in Berlin

NASA Astrophysics Data System (ADS)

Dahlhausen, Jens; Rötzer, Thomas; Biber, Peter; Uhl, Enno; Pretzsch, Hans

2017-12-01

Climate, e.g., air temperature and precipitation, differs strongly between urban and peripheral areas, which causes diverse life conditions for trees. In order to compare tree growth, we sampled in total 252 small-leaved lime trees (Tilia cordata Mill) in the city of Berlin along a gradient from the city center to the surroundings. By means of increment cores, we are able to trace back their growth for the last 50 to 100 years. A general growth trend can be shown by comparing recent basal area growth with estimates from extrapolating a growth function that had been fitted with growth data from earlier years. Estimating a linear model, we show that air temperature and precipitation significantly influence tree growth within the last 20 years. Under consideration of housing density, the results reveal that higher air temperature and less precipitation led to higher growth rates in high-dense areas, but not in low-dense areas. In addition, our data reveal a significantly higher variance of the ring width index in areas with medium housing density compared to low housing density, but no temporal trend. Transferring the results to forest stands, climate change is expected to lead to higher tree growth rates.

Urban climate modifies tree growth in Berlin

NASA Astrophysics Data System (ADS)

Dahlhausen, Jens; Rötzer, Thomas; Biber, Peter; Uhl, Enno; Pretzsch, Hans

2018-05-01

Climate, e.g., air temperature and precipitation, differs strongly between urban and peripheral areas, which causes diverse life conditions for trees. In order to compare tree growth, we sampled in total 252 small-leaved lime trees ( Tilia cordata Mill) in the city of Berlin along a gradient from the city center to the surroundings. By means of increment cores, we are able to trace back their growth for the last 50 to 100 years. A general growth trend can be shown by comparing recent basal area growth with estimates from extrapolating a growth function that had been fitted with growth data from earlier years. Estimating a linear model, we show that air temperature and precipitation significantly influence tree growth within the last 20 years. Under consideration of housing density, the results reveal that higher air temperature and less precipitation led to higher growth rates in high-dense areas, but not in low-dense areas. In addition, our data reveal a significantly higher variance of the ring width index in areas with medium housing density compared to low housing density, but no temporal trend. Transferring the results to forest stands, climate change is expected to lead to higher tree growth rates.

Urban climate modifies tree growth in Berlin.

PubMed

Dahlhausen, Jens; Rötzer, Thomas; Biber, Peter; Uhl, Enno; Pretzsch, Hans

2018-05-01

Climate, e.g., air temperature and precipitation, differs strongly between urban and peripheral areas, which causes diverse life conditions for trees. In order to compare tree growth, we sampled in total 252 small-leaved lime trees (Tilia cordata Mill) in the city of Berlin along a gradient from the city center to the surroundings. By means of increment cores, we are able to trace back their growth for the last 50 to 100 years. A general growth trend can be shown by comparing recent basal area growth with estimates from extrapolating a growth function that had been fitted with growth data from earlier years. Estimating a linear model, we show that air temperature and precipitation significantly influence tree growth within the last 20 years. Under consideration of housing density, the results reveal that higher air temperature and less precipitation led to higher growth rates in high-dense areas, but not in low-dense areas. In addition, our data reveal a significantly higher variance of the ring width index in areas with medium housing density compared to low housing density, but no temporal trend. Transferring the results to forest stands, climate change is expected to lead to higher tree growth rates.

Boundary layer analysis in turbulent Rayleigh-Bénard convection in air: experiment versus simulation.

PubMed

Li, Ling; Shi, Nan; du Puits, Ronald; Resagk, Christian; Schumacher, Jörg; Thess, André

2012-08-01

We report measurements and numerical simulations of the three-dimensional velocity and temperature fields in turbulent Rayleigh-Bénard convection in air. Highly resolved velocity and temperature measurements inside and outside the boundary layers have been directly compared with equivalent data obtained in direct numerical simulations (DNSs). This comparison comprises a set of two Rayleigh numbers at Ra=3×10(9) and 3×10(10) and a fixed aspect ratio; this is the ratio between the diameter and the height of the Rayleigh-Bénard cell of Γ=1. We find that the measured velocity data are in excellent agreement with the DNS results while the temperature data slightly differ. In particular, the measured mean temperature profile does not show the linear trend as seen in the DNS data, and the measured gradients at the wall are significantly higher than those obtained from the DNS. Both viscous and thermal boundary layer thickness scale with respect to the Rayleigh number as δ(v)~Ra(-0.24) and δ(θ)~Ra(-0.24), respectively.

Winter Eurasian cooling linked with the Atlantic Multidecadal Oscillation

NASA Astrophysics Data System (ADS)

Luo, Dehai; Chen, Yanan; Dai, Aiguo; Mu, Mu; Zhang, Renhe; Ian, Simmonds

2017-12-01

In this paper, we analyze observational and reanalysis data to demonstrate that the Atlantic Multidecadal Oscillation (AMO) significantly modulates winter Eurasian surface air temperature through its impact on the shape, frequency and persistence of Ural blocking (UB) events that last for 10-20 d. This impact results from changes in mid-high latitude westerly winds over Eurasia associated with the warming in the Barents-Kara Seas (BKS) through the AMO-driven high sea surface temperature and sea-ice decline and resultant weakening in meridional temperature gradients. The BKS warming has a strongest positive correlation with the AMO at a time lag of about 14 years. During the recent positive AMO phase, more persistent northwest-southeast (NW-SE) oriented UB events are favored by weakened westerly winds in Eurasian mid-high latitudes. Through cold atmospheric advection and radiative cooling, such UB events produce a strong, persistent and widespread cooling over Eurasia and enhance BKS warming during 1999-2015. However, the positive AMO phase cannot directly produce the Eurasian cooling if the UB is absent. Thus, we conclude that the recent AMO phase change is a major cause of the recent winter cooling over Eurasia through its impact on BKS temperature and sea ice, which in turn affect the meridional temperature gradient, the westerly winds and the UB events.

Spatiotemporal analysis of air conditions as a tool for the environmental management of a show cave (Cueva del Agua, Spain)

NASA Astrophysics Data System (ADS)

Fernandez-Cortes, A.; Calaforra, J. M.; Sanchez-Martos, F.

We recorded the air temperature and carbon dioxide concentration within the Cueva del Agua, a cave in Spain, under natural conditions prior to the cave being opened to tourists. Geostatistical tools are useful techniques for characterizing microclimate parameters with the aim of adopting measures to ensure the conservation and sound environmental management of tourist caves. We modelled the spatial distribution of these microclimatic parameters over an annual cycle using iterative residual kriging, revealing the stratification of air related to the cave's topography. Replenishment of the cave air is activated by convective circulation that accompanies the development of inversions in the thermal gradient of the air. Comparison of the spatial distribution of each microclimatic parameter over time enables us to characterize the exchange of air between the cave interior and the outside, as well as identify potential areas that could be opened to tourists and determine suitable visiting schedules.

Meteorological drivers of hypolimnetic anoxia in a eutrophic, north temperate lake

USGS Publications Warehouse

Snortheim, Craig A.; Hanson, Paul C.; McMahon, Katherine D.; Read, Jordan S.; Carey, Cayelan C.; Dugan, Hilary

2017-01-01

Oxygen concentration is both an indicator and driver of water quality in lakes. Decreases in oxygen concentration leads to altered ecosystem function as well as harmful consequences for aquatic biota, such as fishes. The responses of oxygen dynamics in lakes to climate-related drivers, such as temperature and wind speed, are well documented for lake surface waters. However, much less is known about how the oxic environment of bottom waters, especially the timing and magnitude of anoxia in eutrophic lakes, responds to changes in climate drivers. Understanding how important ecosystem states, such as hypolimnetic anoxia, may respond to differing climate scenarios requires a model that couples physical-biological conditions and sufficiently captures the density stratification that leads to strong oxygen gradients. Here, we analyzed the effects of changes in three important meteorological drivers (air temperature, wind speed, and relative humidity) on hypolimnetic anoxia in a eutrophic, north temperate lake using the anoxic factor as an index that captures both the temporal and spatial extent of anoxia. Air temperature and relative humidity were found to have a positive correlation with anoxic factor, while wind speed had a negative correlation. Air temperature was found to have the greatest potential impact of the three drivers on the anoxic factor, followed by wind speed and then relative humidity. Across the scenarios of climate variability, variation in the simulated anoxic factor was primarily due to changes in the timing of onset and decay of stratification. Given the potential for future changes in climate, especially increases in air temperature, this study provides important insight into how these changes will alter lake water quality.

Preliminary map of temperature gradients in the conterminous United States

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

Guffanti, M.; Nathenson, M.

1980-09-01

Temperature gradients have been determined from temperature/depth measurements made in drill holes deeper than 600 m and used in the construction of a temperature-gradient map of the conterminous United States. The map displays temperature gradients (in /sup 0/C/km) that can be expected to exist regionally in a conductive thermal regime to a depth of 2 km. The major difference between this map and the AAPG-USGS temperature-gradient map is in the midcontinental region where the AAPG-USGS map does not demarcate a division between colder eastern and warmer western thermal regimes. A comparison with the heat-flow map of Sass et al. (1980)more » indicates that temperature gradients commonly reflect regional heat flow, and the gross east-west division of the United States on the basis of heat flow is also expressed by temperature gradient.« less

Combined solvent- and non-uniform temperature-programmed gradient liquid chromatography. I - A theoretical investigation.

PubMed

Gritti, Fabrice

2016-11-18

An new class of gradient liquid chromatography (GLC) is proposed and its performance is analyzed from a theoretical viewpoint. During the course of such gradients, both the solvent strength and the column temperature are simultaneously changed in time and space. The solvent and temperature gradients propagate along the chromatographic column at their own and independent linear velocity. This class of gradient is called combined solvent- and temperature-programmed gradient liquid chromatography (CST-GLC). The general expressions of the retention time, retention factor, and of the temporal peak width of the analytes at elution in CST-GLC are derived for linear solvent strength (LSS) retention models, modified van't Hoff retention behavior, linear and non-distorted solvent gradients, and for linear temperature gradients. In these conditions, the theory predicts that CST-GLC is equivalent to a unique and apparent dynamic solvent gradient. The apparent solvent gradient steepness is the sum of the solvent and temperature steepness. The apparent solvent linear velocity is the reciprocal of the steepness-averaged sum of the reciprocal of the actual solvent and temperature linear velocities. The advantage of CST-GLC over conventional GLC is demonstrated for the resolution of protein digests (peptide mapping) when applying smooth, retained, and linear acetonitrile gradients in combination with a linear temperature gradient (from 20°C to 90°C) using 300μm×150mm capillary columns packed with sub-2 μm particles. The benefit of CST-GLC is demonstrated when the temperature gradient propagates at the same velocity as the chromatographic speed. The experimental proof-of-concept for the realization of temperature ramps propagating at a finite and constant linear velocity is also briefly described. Copyright © 2016 Elsevier B.V. All rights reserved.

Thermal imaging for cold air flow visualisation and analysis

NASA Astrophysics Data System (ADS)

Grudzielanek, M.; Pflitsch, A.; Cermak, J.

2012-04-01

In this work we present first applications of a thermal imaging system for animated visualization and analysis of cold air flow in field studies. The development of mobile thermal imaging systems advanced very fast in the last decades. The surface temperature of objects, which is detected with long-wave infrared radiation, affords conclusions in different problems of research. Modern thermal imaging systems allow infrared picture-sequences and a following data analysis; the systems are not exclusive imaging methods like in the past. Thus, the monitoring and analysing of dynamic processes became possible. We measured the cold air flow on a sloping grassland area with standard methods (sonic anemometers and temperature loggers) plus a thermal imaging system measuring in the range from 7.5 to 14µm. To analyse the cold air with the thermal measurements, we collected the surface infrared temperatures at a projection screen, which was located in cold air flow direction, opposite the infrared (IR) camera. The intention of using a thermal imaging system for our work was: 1. to get a general idea of practicability in our problem, 2. to assess the value of the extensive and more detailed data sets and 3. to optimise visualisation. The results were very promising. Through the possibility of generating time-lapse movies of the image sequences in time scaling, processes of cold air flow, like flow waves, turbulence and general flow speed, can be directly identified. Vertical temperature gradients and near-ground inversions can be visualised very well. Time-lapse movies will be presented. The extensive data collection permits a higher spatial resolution of the data than standard methods, so that cold air flow attributes can be explored in much more detail. Time series are extracted from the IR data series, analysed statistically, and compared to data obtained using traditional systems. Finally, we assess the usefulness of the additional measurement of cold air flow with thermal imaging systems.

Structure of the marine atmospheric boundary layer over an oceanic thermal front: SEMAPHORE experiment

NASA Astrophysics Data System (ADS)

Kwon, B. H.; BéNech, B.; Lambert, D.; Durand, P.; Druilhet, A.; Giordani, H.; Planton, S.

1998-10-01

The Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experimentale (SEMAPHORE) experiment, the third phase of which took place between October 4 and November 17, 1993, was conducted over the oceanic Azores Current located in the Azores basin and mainly marked at the surface by a thermal front due to the gradient of the sea surface temperature (SST) of about 1° to 2°C per 100 km. The evolution of the marine atmospheric boundary layer (MABL) over the SST front was studied with two aircraft and a ship in different meteorological conditions. For each case, the influence of the incoming air direction with respect to the orientation of the oceanic front was taken into account. During the campaign, advanced very high resolution radiometer pictures did not show any relation between the SST field and the cloud cover. The MABL was systematically thicker on the warm side than on the cold side. The mean MABL structure described from aircraft data collected in a vertical plane crossing the oceanic front was characterized by (1) an atmospheric horizontal gradient of 1° to 2°C per 100 km in the whole depth of the mixed layer and (2) an increase of the wind intensity from the cold to the warm side when the synoptic wind blew from the cold side. The surface sensible heat (latent heat) flux always increased from the cold to the warm sector owing to the increase of the wind and of the temperature (specific humidity) difference between the surface and the air. Turbulence increased from the cold to the warm side in conjunction with the MABL thickening, but the normalized profiles presented the same structure, regardless of the position over the SST front. In agreement with the Action de Recherche Programme te Petite Echelle and Grande Echelle model, the mean temperature and momentum budgets were highly influenced by the horizontal temperature gradient. In particular, the strong ageostrophic influence in the MABL above the SST front seems linked with the secondary circulation due to the SST front.

Freezing avoidance mechanisms in juveniles of giant rosette plants of the genus Espeletia

NASA Astrophysics Data System (ADS)

García-Varela, Sonia; Rada, Fermín

2003-07-01

Along soil-air gradients in tropical high mountains, plants growing at soil level tolerate frost while those growing well above ground, including all species in the genus Espeletia, use freezing avoidance mechanisms to survive low nighttime temperatures. The question that arises and the objective of this work were: What are the low temperature resistance mechanisms in giant rosettes when they are within the juvenile stages, i.e. closer to the ground? Juveniles of Espeletia spicata and Espeletia timotensis, dominant plants of the high Venezuelan Andes, were chosen for this study. To determine resistance mechanisms for these species, air and leaf temperatures were recorded in the field in 24 h cycles, while thermal analysis and injury temperature were determined in the laboratory. Both E. spicata and E. timotensis juveniles depend on avoidance mechanisms through a high supercooling capacity, permitting leaves to resist low nighttime temperatures. Minimum leaf temperatures were -4.9 and -5.1 °C, for E. spicata and E. timotensis, respectively, occurring during the dry season. Ice formation occurred at -14.3 and -15.3 °C for E. spicata and E. timotensis, respectively. Injury occurred at approximately -15 °C in both species. Low temperature resistance mechanisms in juveniles are similar to those in adult plants.

The Capacity for Thermal Protection of Photosynthetic Electron Transport Varies for Different Monoterpenes in Quercus ilex1

PubMed Central

Copolovici, Lucian O.; Filella, Iolanda; Llusià, Joan; Niinemets, Ülo; Peñuelas, Josep

2005-01-01

Heat stress resistance of foliar photosynthetic apparatus was investigated in the Mediterranean monoterpene-emitting evergreen sclerophyll species Quercus ilex. Leaf feeding with fosmidomycin, which is a specific inhibitor of the chloroplastic isoprenoid synthesis pathway, essentially stopped monoterpene emission and resulted in the decrease of the optimum temperature of photosynthetic electron transport from approximately 38°C to approximately 30°C. The heat stress resistance was partly restored by fumigation with 4 to 5 nmol mol−1 air concentrations of monoterpene α-pinene but not with fumigations with monoterpene alcohol α-terpineol. Analyses of monoterpene physicochemical characteristics demonstrated that α-pinene was primarily distributed to leaf gas and lipid phases, while α-terpineol was primarily distributed to leaf aqueous phase. Thus, for a common monoterpene uptake rate, α-terpineol is less efficient in stabilizing membrane liquid-crystalline structure and as an antioxidant in plant membranes. Furthermore, α-terpineol uptake rate (U) strongly decreased with increasing temperature, while the uptake rates of α-pinene increased with increasing temperature, providing a further explanation of the lower efficiency of thermal protection by α-terpineol. The temperature-dependent decrease of α-terpineol uptake was both due to decreases in stomatal conductance, gw, and increased volatility of α-terpineol at higher temperature that decreased the monoterpene diffusion gradient between the ambient air (FA) and leaf (FI; U = gw[FA − FI]). Model analyses suggested that α-pinene reacted within the leaf at higher temperatures, possibly within the lipid phase, thereby avoiding the decrease in diffusion gradient, FA − FI. Thus, these data contribute to the hypothesis of the antioxidative protection of leaf membranes during heat stress by monoterpenes. These data further suggest that fumigation with the relatively low atmospheric concentrations of monoterpenes that are occasionally observed during warm windless days in the Mediterranean canopies may significantly improve the heat tolerance of nonemitting vegetation that grows intermixed with emitting species. PMID:16126854

Effect of a surface tension gradient on the slip flow along a superhydrophobic air-water interface

NASA Astrophysics Data System (ADS)

Song, Dong; Song, Baowei; Hu, Haibao; Du, Xiaosong; Du, Peng; Choi, Chang-Hwan; Rothstein, Jonathan P.

2018-03-01

Superhydrophobic surfaces have been shown to produce significant drag reduction in both laminar and turbulent flows by introducing an apparent slip velocity along an air-water interface trapped within the surface roughness. In the experiments presented within this study, we demonstrate the existence of a surface tension gradient associated with the resultant Marangoni flow along an air-water interface that causes the slip velocity and slip length to be significantly reduced. In this study, the slip velocity along a millimeter-sized air-water interface was investigated experimentally. This large-scale air-water interface facilitated a detailed investigation of the interfacial velocity profiles as the flow rate, interfacial curvature, and interface geometry were varied. For the air-water interfaces supported above continuous grooves (concentric rings within a torsional shear flow) where no surface tension gradient exists, a slip velocity as high as 30% of the bulk velocity was observed. However, for the air-water interfaces supported above discontinuous grooves (rectangular channels in a Poiseuille flow), the presence of a surface tension gradient reduced the slip velocity and in some cases resulted in an interfacial velocity that was opposite to the main flow direction. The curvature of the air-water interface in the spanwise direction was found to dictate the details of the interfacial flow profile with reverse flow in the center of the interface for concave surfaces and along the outside of the interface for convex surfaces. The deflection of the air-water interface was also found to greatly affect the magnitude of the slip. Numerical simulations imposed with a relatively small surface tension gradient along the air-water interface were able to predict both the reduced slip velocity and back flow along the air-water interface.

Experimental Investigation of A Twin Shaft Micro Gas-Turbine System

NASA Astrophysics Data System (ADS)

Sadig, Hussain; Sulaiman, Shaharin Anwar; Ibrahim, Idris

2013-06-01

Due to the fast depletion of fossil fuels and its negative impact on the environment, more attention has been concentrated to find new resources, policies and technologies, which meet the global needs with regard to fuel sustainability and emissions. In this paper, as a step to study the effect of burning low calorific value fuels on gas-turbine performance; a 50 kW slightly pressurized non-premixed tubular combustor along with turbocharger based twin shaft micro gas-turbine was designed and fabricated. A series of tests were conducted to characterize the system using LPG fuel. The tests include the analysis of the temperature profile, pressure and combustor efficiency as well as air fuel ratio and speed of the second turbine. The tests showed a stable operation with acceptable efficiency, air fuel ratio, and temperature gradient for the single and twin shaft turbines.

Design Evaluation Using Finite Element Analysis of Cooled Silicon Nitride Plates for a Turbine Blade Application

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Baaklini, George Y.; Bhatt, Ramakrishna T.

2001-01-01

Two- and three-dimensional finite element analyses were performed on uncoated and thermal barrier coated (TBC) silicon nitride plates with and without internal cooling by air. Steady-state heat-transfer analyses were done to optimize the size and the geometry of the cooling channels to reduce thermal stresses, and to evaluate the thermal environment experienced by the plate during burner rig testing. The limited experimental data available were used to model the thermal profile exerted by the flame on the plate. Thermal stress analyses were performed to assess the stress response due to thermal loading. Contours for the temperature and the representative stresses for the plates were generated and presented for different cooling hole sizes and shapes. Analysis indicates that the TBC experienced higher stresses, and the temperature gradient was much reduced when the plate was internally cooled by air. The advantages and disadvantages of several cooling channel layouts were evaluated.

Mirage is an image in a flat ground surface.

PubMed

Tavassoly, M Taghi; Osanloo, Soghra; Salehpour, Ali

2015-04-01

Mirage is a fascinating phenomenon that has attracted many scientists to report their observations and descriptions about it. There are two different approaches to mirage formation. The more popular one is attributed to total internal reflection that occurs in the near ground air layers on hot sunny days. According to the other approach, mirage is an image in a rough surface that is observed at grazing angles of incidence. Most of the existing descriptions are qualitative and some include calculations based on guessing temperature change with no concrete experiments. In this report, first we show that Fermat's principle also concerns the wave nature of light and covers the constructive and destructive interference that is essential for image formation. Then, we provide a brief review of the image formation theory in a rough plane and demonstrate by experiments in the lab and deserts that the temperature gradient in the near ground air layers does not lead to mirage formation.

Cyclic Fatigue Durability of Uncoated and EBC Coated 3D SiC/SiC Composites Under Thermal Gradient Conditions at 2700F in Air

NASA Technical Reports Server (NTRS)

Smith, Craig; Harder, Bryan; Zhu, Dongming; Bhatt, Ramakrishna; Kalluri, Sreeramesh

2017-01-01

Ceramic matrix composites (CMCs) such as SiCSiC are currently being designed and implemented in high temperature sections of aerospace turbine engines. Such components will be subject to through-thickness thermal gradients, which may affect the durability. In this study, SiCSiC CMCs with a hybrid chemical vapor infiltrated (CVI) and polymer infiltration and pyrolysis (PIP) matrix were loaded in tension while one surface was heated with a laser and the opposite surface was cooled. The samples were each coated with an environmental barrier coating (EBC), which was produced by electron beam physical deposition (EBPVD). Results for CMCs tested with and without the EBC be discussed.

The Impact of Gulf Stream-Induced Diabatic Forcing on Coastal Mid-Atlantic Surface Cyclogenesis

NASA Astrophysics Data System (ADS)

Cione, Joseph Jerome

In this dissertation, numerical experiments were conducted using a mesoscale atmospheric model developed at North Carolina State University. Three sets of numerical experiments were conducted and were designed to: quantify the impact Gulf Stream frontal distance, initial surface air temperature and cold air outbreak timing each have on the subsequent development of the marine atmospheric boundary layer during periods of offshore cold advection; investigate critical processes associated with Gulf Stream -induced mesocyclogenesis and; elucidate the role SST gradients and surface fluxes of heat and moisture have on the intensification and track of propagating mesocyclonic systems within the highly baroclinic Gulf Stream region. A major finding from the offshore cold advection simulations is that the initial air-sea contrast is the dominant forcing mechanism linked to the offshore circulation development and marine boundary layer modification. Results from the mesocyclogenesis experiments indicate that surface cyclogenesis was simulated to occur along a Gulf Stream meander in a region where the gradients in sea surface temperature (SST) were maximized. Results from sensitivity experiments illustrate that changes in the Gulf Stream SST gradient pattern can act to alter the timing and degree of cyclonic development simulated, while the inclusion of surface fluxes and moist convective processes during the development phase act to strongly enhance the intensity and/or occurrence of simulated mesocyclogenesis. Both observational and numerical results from studies investigating the impact strong Gulf Stream SST gradients have on the development of pre-existing, propagating cyclonic systems show that the baroclinic nature of the low level environment near the circulation center (as well as the degree of simulated/observed surface cyclonic intensification) appear to be highly dependent upon the mesoscale storm track within the Gulf Stream frontal zone. Furthermore, the numerical storm track experiments conducted in this research illustrate that surfaces fluxes can act to significantly alter the storm track of the surface mesocyclone (in addition to impacting the overall intensification of the simulated cyclonic system). This work also presents the technique development and operational utilization of the recently devised Atlantic Surface Cyclone Intensification Index (ASCII). The index continues to be implemented by the National Weather Service at the Raleigh-Durham and surrounding coastal forecast offices, and to date, has been successfully utilized for 11 coastal winter storm events over the February 1994-January 1996 period.

Practical Strategies for Stable Operation of HFF-QCM in Continuous Air Flow

PubMed Central

Wessels, Alexander; Klöckner, Bernhard; Siering, Carsten; Waldvogel, Siegfried R.

2013-01-01

Currently there are a few fields of application using quartz crystal microbalances (QCM). Because of environmental conditions and insufficient resolution of the microbalance, chemical sensing of volatile organic compounds in an open system was as yet not possible. In this study we present strategies on how to use 195 MHz fundamental quartz resonators for a mobile sensor platform to detect airborne analytes. Commonly the use of devices with a resonant frequency of about 10 MHz is standard. By increasing the frequency to 195 MHz the frequency shift increases by a factor of almost 400. Unfortunately, such kinds of quartz crystals tend to exhibit some challenges to obtain a reasonable signal-to-noise ratio. It was possible to reduce the noise in frequency in a continuous air flow of 7.5 m/s to 0.4 Hz [i.e., σ(τ) = 2 × 10−9] by elucidating the major source of noise. The air flow in the vicinity of the quartz was analyzed to reduce turbulences. Furthermore, we found a dependency between the acceleration sensitivity and mechanical stress induced by an internal thermal gradient. By reducing this gradient, we achieved reduction of the sensitivity to acceleration by more than one decade. Hence, the resulting sensor is more robust to environmental conditions such as temperature, acceleration and air flow. PMID:24021970

Geometry effects on cooling in a standing wave cylindrical thermoacousic resonator

NASA Astrophysics Data System (ADS)

Mohd-Ghazali, Normah; Ghazali, Ahmad Dairobi; Ali, Irwan Shah; Rahman, Muhammad Aminullah A.

2012-06-01

Numerous reports have established the refrigeration applications of thermoacoustic cooling without compressors and refrigerants. Significant cooling effects can be obtained in a thermoacoustic resonator fitted with a heat exchanging stack and operated at resonance frequency. Past studies, however, have hardly referred to the fundamental relationship between resonant frequency and the resonator geometry. This paper reports the thermoacoustic cooling effects at resonance obtained by changing the diameter of the resonator while holding the length constant and vice versa. Experiments were completed at atmospheric pressure with air as the working fluid using a number of pvc tubes having parallel plate stack from Mylar. The temperature difference measured across the stack showed that a volume increase in the working fluid in general increases the temperature gradient for the quarter-and half-wavelength resonators. Doubling the diameter from 30 mm to 60 mm produced the highest temperature difference due to the greater number of stack plates resulting in a higher overall thermoacaoustic cooling. Increasing the resonator length only produced a small increase in temperature gradient since the resonant frequency at operation is only slightly changed. Investigation on the aspect ratio exhibits no influence on the temperature difference across the stack. This study have shown that the resonator length and diameter do affect the temperature difference across the thermoacoustic stack, and further research should be done to consider the contribution of the stack mass on the overall desired thermoacoustic cooling.

Characteristics of fall chum salmon spawning habitat on a mainstem river in Interior Alaska

USGS Publications Warehouse

Burril, Sean E.; Zimmerman, Christian E.; Finn, James E.

2010-01-01

Chum salmon (Oncorhynchus keta) are the most abundant species of salmon spawning in the Yukon River drainage system, and they support important personal use, subsistence, and commercial fisheries. Chum salmon returning to the Tanana River in Interior Alaska are a significant contribution to the overall abundance of Yukon River chum salmon and an improved understanding of habitat use is needed to improve conservation of this important resource. We characterized spawning habitat of chum salmon using the mainstem Tanana River as part of a larger study to document spawning distributions and habitat use in this river. Areas of spawning activity were located using radiotelemetry and aerial helicopter surveys. At 11 spawning sites in the mainstem Tanana River, we recorded inter-gravel and surface-water temperatures and vertical hydraulic gradient (an indication of the direction of water flux) in substrate adjacent to salmon redds. At all locations, vertical hydraulic gradient adjacent to redds was positive, indicating that water was upwelling through the gravel. Inter-gravel temperatures adjacent to redds generally were warmer than surface water at most locations and were more stable than surface-water temperature. Inter-gravel water temperature adjacent to redds ranged from 2.6 to 5.8 degrees Celsius, whereas surface-water temperature ranged from greater than 0 to 5.5 degrees Celsius. Some sites were affected more by extremes in air temperature than others. At these sites, inter-gravel water temperature profiles were variable (with ranges similar to those observed in surface water), suggesting that even though upwelling habitats provide a stable thermal incubation environment, eggs and embryos still may be affected by extremes in air temperature. Fine sand and silt covered redds at multiple sites and were evidence of increased river flow during the winter months, which may be a potential source of increased mortality during egg-to-fry development. This study provides documentation of spawning by fall chum salmon and is the first study to continuously measure inter-gravel water temperature at sites in the mainstem Tanana River.

Mechanism of nonlinear flow pattern selection in moderately non-Boussinesq mixed convection.

PubMed

Suslov, Sergey A

2010-02-01

Nonlinear (non-Boussinesq) variations in fluid's density, viscosity, and thermal conductivity caused by a large temperature gradient in a flow domain lead to a wide variety of instability phenomena in mixed convection channel flow of a simple gas such as air. It is known that in strongly nonisothermal flows, the instabilities and the resulting flow patterns are caused by competing buoyancy and shear effects [see S. A. Suslov and S. Paolucci, J. Fluid Mech. 302, 91 (1995)]. However, as is the case in the Boussinesq limit of small temperature gradients, in moderately non-Boussinesq regimes, only a shear instability mechanism is active. Yet in contrast to Boussinesq flows, multiple instability modes are still detected. By reducing the system of full governing Navier-Stokes equations to a dynamical system of coupled Landau-type disturbance amplitude equations we compute a comprehensive parametric map of various shear-driven instabilities observed in a representative moderately non-Boussinesq regime. Subsequently, we analyze nonlinear interaction of unstable modes and reveal physical reasons for their appearance.

Direct coupling of microbore HPLC columns to MS systems

NASA Technical Reports Server (NTRS)

Mcnair, H. M.

1985-01-01

A detailed investigation using electron microscopy was conducted which examined the conditions of materials used in the construction of stable, high performance microbore liquid chromatography (LC) columns. Small details proved to be important. The effects of temperature on the elution of several homologous series used as probe compounds was examined in reverse phase systems. They showed that accessible temperature changes provide roughly half the increase in solvent strength that would be obtained going from a 100% aqueous to a 100% organic mobile phase, which is sufficient to warrant their use in many analyses requiring the use of gradients. Air circulation temperature control systems provide the easiest means of obtaining rapid, wide range changes in column temperature. However, slow heat transfer from the gas leads to thermal nonuniformity in the column and a decrease in resolution as the temperature program progresses.

43 CFR 3252.14 - How must I complete a temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration of...

43 CFR 3252.14 - How must I complete a temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration of...

43 CFR 3252.14 - How must I complete a temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration of...

43 CFR 3252.14 - How must I complete a temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How must I complete a temperature gradient... LEASING Conducting Exploration Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper abandonment, and to prevent interzonal migration of...

Designing gradient coils with reduced hot spot temperatures.

PubMed

While, Peter T; Forbes, Larry K; Crozier, Stuart

2010-03-01

Gradient coil temperature is an important concern in the design and construction of MRI scanners. Closely spaced gradient coil windings cause temperature hot spots within the system as a result of Ohmic heating associated with large current being driven through resistive material, and can strongly affect the performance of the coils. In this paper, a model is presented for predicting the spatial temperature distribution of a gradient coil, including the location and extent of temperature hot spots. Subsequently, a method is described for designing gradient coils with improved temperature distributions and reduced hot spot temperatures. Maximum temperature represents a non-linear constraint and a relaxed fixed point iteration routine is proposed to adjust coil windings iteratively to minimise this coil feature. Several examples are considered that assume different thermal material properties and cooling mechanisms for the gradient system. Coil winding solutions are obtained for all cases considered that display a considerable drop in hot spot temperature (>20%) when compared to standard minimum power gradient coils with equivalent gradient homogeneity, efficiency and inductance. The method is semi-analytical in nature and can be adapted easily to consider other non-linear constraints in the design of gradient coils or similar systems. Crown Copyright (c) 2009. Published by Elsevier Inc. All rights reserved.

Characterization of thermotropism in primary roots of maize: dependence on temperature and temperature gradient, and interaction with gravitropism

NASA Technical Reports Server (NTRS)

Poff, K. L.

1991-01-01

Thermotropism in primary roots of Zea mays L. was studied with respect to gradient strength (degrees C cm-1), temperature of exposure within a gradient, pre-treatment temperature, and gravitropic stimulation. The magnitude of the response decreased with gradient strength. Maximum thermotropism was independent of gradient strength and pre-treatment temperature. The range of temperature for positive and negative thermotropism did not change with pre-treatment temperature. However, the exact range of temperatures for positive and negative thermotropism varied with gradient strengths. In general, temperatures of exposure lower than 25 degrees C resulted in positive tropic responses while temperatures of exposure of 39 degrees C or more resulted in negative tropic responses. Thermotropism was shown to modify and reverse the normal gravitropic curvature of a horizontal root when thermal gradients were applied opposite the 1 g vector. It is concluded that root thermotropism is a consequence of thermal sensing and that the curvature of the primary root results from the interaction of the thermal and gravitational sensing systems.

A general strategy for performing temperature-programming in high performance liquid chromatography--prediction of segmented temperature gradients.

PubMed

Wiese, Steffen; Teutenberg, Thorsten; Schmidt, Torsten C

2011-09-28

In the present work it is shown that the linear elution strength (LES) model which was adapted from temperature-programming gas chromatography (GC) can also be employed to predict retention times for segmented-temperature gradients based on temperature-gradient input data in liquid chromatography (LC) with high accuracy. The LES model assumes that retention times for isothermal separations can be predicted based on two temperature gradients and is employed to calculate the retention factor of an analyte when changing the start temperature of the temperature gradient. In this study it was investigated whether this approach can also be employed in LC. It was shown that this approximation cannot be transferred to temperature-programmed LC where a temperature range from 60°C up to 180°C is investigated. Major relative errors up to 169.6% were observed for isothermal retention factor predictions. In order to predict retention times for temperature gradients with different start temperatures in LC, another relationship is required to describe the influence of temperature on retention. Therefore, retention times for isothermal separations based on isothermal input runs were predicted using a plot of the natural logarithm of the retention factor vs. the inverse temperature and a plot of the natural logarithm of the retention factor vs. temperature. It could be shown that a plot of lnk vs. T yields more reliable isothermal/isocratic retention time predictions than a plot of lnk vs. 1/T which is usually employed. Hence, in order to predict retention times for temperature-gradients with different start temperatures in LC, two temperature gradient and two isothermal measurements have been employed. In this case, retention times can be predicted with a maximal relative error of 5.5% (average relative error: 2.9%). In comparison, if the start temperature of the simulated temperature gradient is equal to the start temperature of the input data, only two temperature-gradient measurements are required. Under these conditions, retention times can be predicted with a maximal relative error of 4.3% (average relative error: 2.2%). As an example, the systematic method development for an isothermal as well as a temperature gradient separation of selected sulfonamides by means of the adapted LES model is demonstrated using a pure water mobile phase. Both methods are compared and it is shown that the temperature-gradient separation provides some advantages over the isothermal separation in terms of limits of detection and analysis time. Copyright © 2011 Elsevier B.V. All rights reserved.

Sub-diurnal Variation of SST Gradients in Infrared Satellite Data

NASA Astrophysics Data System (ADS)

Salter, J. P.; Cornillon, P. C.; Clayson, C. A.

2016-02-01

Ocean fronts are known to influence many physical, biological, and chemical processes including ocean mixing, air-sea interaction, cloud and wind patterns, and marine productivity. Satellite-derived Sea Surface Temperature (SST) measurements are an invaluable tool in studying ocean fronts because of the large spatial and temporal coverage of satellite data, extending back as far as the early 1980s. One of the limitations to satellite-derived ocean fronts is that they provide no information about the underlying vertical structure; furthermore, the dynamics on sub-diurnal time scales for ocean fronts are poorly understood. In this poster we examine the daily signal of SST gradient magnitudes for the eastern Mediterranean sea as the first step in quantifying a subset of ocean fronts globally and how they vary on sub-diurnal time scales. We find that mean gradient magnitude in summer months increases and peaks around 2-4 PM Local Sun Time (LST). We find that the peak in summer months results from an increase in the magnitude of weaker gradients while the magnitude of the strongest gradients decrease; however, the weaker gradients contribute more strongly to the mean signal, resulting in the increase. The mid-afternoon peak in SST gradient magnitude disappears in winter with only a suggestion of a peak earlier in the day although the paucity of cloud free data in winter precludes making a statistically significant statement in this regard.

Extreme Maximum Land Surface Temperatures.

NASA Astrophysics Data System (ADS)

Garratt, J. R.

1992-09-01

There are numerous reports in the literature of observations of land surface temperatures. Some of these, almost all made in situ, reveal maximum values in the 50°-70°C range, with a few, made in desert regions, near 80°C. Consideration of a simplified form of the surface energy balance equation, utilizing likely upper values of absorbed shortwave flux (1000 W m2) and screen air temperature (55°C), that surface temperatures in the vicinity of 90°-100°C may occur for dry, darkish soils of low thermal conductivity (0.1-0.2 W m1 K1). Numerical simulations confirm this and suggest that temperature gradients in the first few centimeters of soil may reach 0.5°-1°C mm1 under these extreme conditions. The study bears upon the intrinsic interest of identifying extreme maximum temperatures and yields interesting information regarding the comfort zone of animals (including man).

Litter decomposition across an air-pollution gradient in the San Bernardino Mountains

Treesearch

Mark E. Fenn; Paul H. Dunn

1989-01-01

Air pollution may affect forest ecosystems by altering nutrient cycling rates. The objective of this study was to compare decomposition rates of L-layer litter of ponderosa pine (Pinus ponderosa Laws.) and Jeffrey pine (Pinus jeffreyi Grev. & Balf,) collected from across an air-pollution gradient in the San Bernardino Mountains...

Measuring Inhomogeneities In Thermocouple Wires

NASA Technical Reports Server (NTRS)

Burkett, Cecil G., Jr.; West, James W.; Crum, James R.

1993-01-01

Spools rotated to pull thermocouple wires through liquid nitrogen, while output voltage of thermocouple recorded on strip chart. Wires exposed to severe temperature gradients, amounting to overall change of 200 degrees C, where they enter and leave liquid nitrogen. If wires homogeneous, net output voltage zero. If inhomogeneity passes through liquid-nitrogen/air interface, resulting deviation of output voltage from zero seen immediately on strip chart. If inhomogeneity greater than allowable, reels stopped temporarily so inhomogeneity tagged before wound onto takeup reel.

Thermal niches are more conserved at cold than warm limits in arctic-alpine plant species

PubMed Central

Pellissier, Loïc; Bråthen, Kari Anne; Vittoz, Pascal; Yoccoz, Nigel G.; Dubuis, Anne; Meier, Eliane S.; Zimmermann, Niklaus E.; Randin, Christophe F.; Thuiller, Wilfried; Garraud, Luc; Van Es, Jérémie; Guisan, Antoine

2014-01-01

Aim Understanding the stability of realized niches is crucial for predicting the responses of species to climate change. One approach is to evaluate the niche differences of populations of the same species that occupy regions that are geographically disconnected. Here, we assess niche conservatism along thermal gradients for 26 plant species with a disjunct distribution between the Alps and the Arctic. Location European Alps and Norwegian Finnmark. Methods We collected a comprehensive dataset of 26 arctic-alpine plant occurrences in two regions. We assessed niche conservatism through a multispecies comparison and analysed species rankings at cold and warm thermal limits along two distinct gradients corresponding to (1) air temperatures at 2 m above ground level and (2) elevation distances to the tree line (TLD) for the two regions. We assessed whether observed relationships were close to those predicted under thermal limit conservatism. Results We found a weak similarity in species ranking at the warm thermal limits. The range of warm thermal limits for the 26 species was much larger in the Alps than in Finnmark. We found a stronger similarity in species ranking and correspondence at the cold thermal limit along the gradients of 2-m temperature and TLD. Yet along the 2-m temperature gradient the cold thermal limits of species in the Alps were lower on average than those in Finnmark. Main conclusion We found low conservatism of the warm thermal limits but a stronger conservatism of the cold thermal limits. We suggest that biotic interactions at the warm thermal limit are likely to modulate species responses more strongly than at the cold limit. The differing biotic context between the two regions is probably responsible for the observed differences in realized niches. PMID:24790524

[Male infertility. Current life style could be responsible for infertility].

PubMed

Jung, A; Schill, W B

2000-09-14

Optimal spermatogenesis requires the testicles to be at a lower temperature than the body core. This is achieved by the following factors:--Blood in the testicular artery is precooled by the surrounding veins of the plexus pampiniformis; nevertheless, high fever results in substantial warming of the testicles;--Heat loss via the scrotal skin, with tight-fitting, thermally insulating clothing or obesity having an unfavorable effect;--increased circulation of air around the genitals on physical activity;--High temperature gradient to the environment when ambient temperatures are low. If the combination of these factors is unfavorable, disturbed spermatogenesis and fertility may result, which, however, is usually reversible. Likewise, electromagnetic waves may impair spermatogenesis by heat induction in the testicles, but only when exposure is excessive.

A BAPTA employing rotary transformers, stepper motors and ceramic ball bearings

NASA Technical Reports Server (NTRS)

Auer, W.

1981-01-01

The utilization of rotary transformers as an alternative to slip rings for the power transfer from solar panels to a satellite's main body could be advantageous, especially if an ac bus system is taken into consideration. Different approaches with main emphasis on the electromagnetic design were investigated and showed efficiencies of up to 99% with a 3 kW power capability. A solidly preloaded pair of ball bearings with ceramic balls assures proper transformer air gaps and acceptable torque changes over temperature and temperature gradients. The bearing and power transfer assembly is driven by a direct drive stepper motor with inherent redundancy properties and needs no caging mechanism.

Numerical Model Studies of the Martian Mesoscale Circulations

NASA Technical Reports Server (NTRS)

Segal, M.; Arritt, R. W.

1996-01-01

Studies concerning mesoscale topographical effects on Martian flows examined low-level jets in the near equatorial latitudes and the dynamical intensification of flow by steep terrain. Continuation of work from previous years included evaluating the dissipation of cold air mass outbreaks due to enhanced sensible heat flux, further sensitivity and scaling evaluations for generalization of the characteristics of Martian mesoscale circulation caused by horizontal sensible heat-flux gradients, and evaluations of the significance that non-uniform surface would have on enhancing the polar CO2 ice sublimation during the spring. The sensitivity of maximum and minimum atmospheric temperatures to changes in wind speed, surface albedo, and deep soil temperature was investigated.

Extraction of espresso coffee by using gradient of temperature. Effect on physicochemical and sensorial characteristics of espresso.

PubMed

Salamanca, C Alejandra; Fiol, Núria; González, Carlos; Saez, Marc; Villaescusa, Isabel

2017-01-01

Espresso extraction is generally carried out at a fixed temperature within the range 85-95°C. In this work the extraction of the espressos was made in a new generation coffee machine that enables temperature profiling of the brewing water. The effect of using gradient of temperature to brew espressos on physicochemical and sensorial characteristics of the beverage has been investigated. Three different extraction temperature profiles were tested: updrawn gradient (88-93°C), downdrawn gradient (93-88°C) and fixed temperature (90°C). The coffee species investigated were Robusta, Arabica natural and Washed Arabica. Results proved that the use of gradient temperature for brewing espressos allows increasing or decreasing the extraction of some chemical compounds from coffee grounds. Moreover an appropriate gradient of temperature can highlight or hide some sensorial attributes. In conclusion, the possibility of programming gradient of temperature in the coffee machines recently introduced in the market opens new expectations in the field of espresso brewing. Copyright © 2016 Elsevier Ltd. All rights reserved.

Relevance of the correlation between precipitation and the 0 °C isothermal altitude for extreme flood estimation

NASA Astrophysics Data System (ADS)

Zeimetz, Fraenz; Schaefli, Bettina; Artigue, Guillaume; García Hernández, Javier; Schleiss, Anton J.

2017-08-01

Extreme floods are commonly estimated with the help of design storms and hydrological models. In this paper, we propose a new method to take into account the relationship between precipitation intensity (P) and air temperature (T) to account for potential snow accumulation and melt processes during the elaboration of design storms. The proposed method is based on a detailed analysis of this P-T relationship in the Swiss Alps. The region, no upper precipitation intensity limit is detectable for increasing temperature. However, a relationship between the highest measured temperature before a precipitation event and the duration of the subsequent event could be identified. An explanation for this relationship is proposed here based on the temperature gradient measured before the precipitation events. The relevance of these results is discussed for an example of Probable Maximum Precipitation-Probable Maximum Flood (PMP-PMF) estimation for the high mountainous Mattmark dam catchment in the Swiss Alps. The proposed method to associate a critical air temperature to a PMP is easily transposable to similar alpine settings where meteorological soundings as well as ground temperature and precipitation measurements are available. In the future, the analyses presented here might be further refined by distinguishing between precipitation event types (frontal versus orographic).

Characteristics of early winter high Arctic atmospheric boundary layer profiles

NASA Astrophysics Data System (ADS)

Wickström, Siiri; Vihma, Timo; Nygård, Tiina; Kramer, Daniel; Palo, Timo; Jonassen, Marius

2017-04-01

For a large part of the year, the Arctic climate system is characterised by a stably stratified atmospheric boundary layer, with strong temperature inversions isolating the surface from the air aloft. These nversions are typically driven by longwave radiative cooling, warm-air advection aloft, or subsidence. All these mechanisms are affected by the synoptic sate of the atmosphere in the high Arctic. In this study we present data from an intensive measurement campaign in Svalbard in October 2014, when atmospheric profiles were measured with a tethered balloon in Adventdalen and Hornsund. In addition radiosonde soundings from Ny-Ålesund were analysed. A total of 115 individual profiles were analysed, almost all of them showing a surface-based temperature inversion. Our preliminary results show that the strongest and deepest inversions are observed at the beginning of a warm-air advection event, but as the temperature, wind and cloudiness increase the inversion strength and depth decrease rapidly. The inversion curvature parameter seems to be strongly dependent on the longwave radiative balance with the highest curvatures (strongest vertical temperature gradient close to the surface) associated with strong longwave radiative heat loss from the surface. The different processes affecting the stable atmospheric boundary layer during a low-pressure passage are determined, and the effects of the synoptic scale changes are isolated from those caused by local topographic forcing.

Wintertime Boundary Layer Structure in the Grand Canyon.

NASA Astrophysics Data System (ADS)

Whiteman, C. David; Zhong, Shiyuan; Bian, Xindi

1999-08-01

Wintertime temperature profiles in the Grand Canyon exhibit a neutral to isothermal stratification during both daytime and nighttime, with only rare instances of actual temperature inversions. The canyon warms during daytime and cools during nighttime more or less uniformly through the canyon's entire depth. This weak stability and temperature structure evolution differ from other Rocky Mountain valleys, which develop strong nocturnal inversions and exhibit convective and stable boundary layers that grow upward from the valley floor. Mechanisms that may be responsible for the different behavior of the Grand Canyon are discussed, including the possibility that the canyon atmosphere is frequently mixed to near-neutral stratification when cold air drains into the top of the canyon from the nearby snow-covered Kaibab Plateau. Another feature of canyon temperature profiles is the sharp inversions that often form near the canyon rims. These are generally produced when warm air is advected over the canyon in advance of passing synoptic-scale ridges.Wintertime winds in the main canyon are not classical diurnal along-valley wind systems. Rather, they are driven along the canyon axis by the horizontal synoptic-scale pressure gradient that is superimposed along the canyon's axis by passing synoptic-scale weather disturbances. They may thus bring winds into the canyon from either end at any time of day.The implications of the observed canyon boundary layer structure for air pollution dispersion are discussed.

Spatiotemporal Variability and in Snow Phenology over Eurasian Continent druing 1966-2012

NASA Astrophysics Data System (ADS)

Zhong, X.; Zhang, T.; Wang, K.; Zheng, L.; Wang, H.

2016-12-01

Snow cover is a key part of the cryosphere, which is a critical component of the global climate system. Snow cover phenology critically effects on the surface energy budget, the surface albedo and hydrological processes. In this study, the climatology and spatiotemporal variability of snow cover phenology were investigated using the long-term (1966-2012) ground-based measurements of daily snow depth from 1103 stations across the Eurasian Continent. The results showed that the distributions of the first date, last date, snow cover duration and number of snow cover days generally represented the latitudinal zonality over the Eurasian Continent, and there were significant elevation gradient patterns in the Tibetan Plateau. The first date of snow cover delayed by about 1.2 day decade-1, the last date of snow cover advanced with the rate of -1.2 day decade-1, snow cover duration and number of snow cover days shortened by about 2.7and 0.6 day decade-1, respectively, from 1966 through 2012. Compared with precipitation, the correlation between snow cover phenology and air temperature was more significant. The changes in snow cover duration were mainly controlled by the changes of air temperature in autumn and spring. The shortened number of snow cover days was affected by rising temperature during the cold season except for the air temperature in autumn and spring.

Two-dimensional microclimate distribution within and above a crop canopy in an arid environment: Modeling and observational studies

NASA Astrophysics Data System (ADS)

Naot, O.; Mahrer, Y.

1991-08-01

A numerical two-dimensional model based on higher-order closure assumptions is developed to simulate the horizontal microclimate distribution over an irrigated field in arid surroundings. The model considers heat, mass, momentum, and radiative fluxes in the soil-plant-atmosphere system. Its vertical domain extends through the whole planetary boundary layer. The model requires temporal solar and atmospheric radiation data, as well as temporal boundary conditions for wind-speed, air temperature, and humidity. These boundary conditions are specified by an auxiliary mesoscale model and are incorporated in the microscale model by a nudging method. Vegetation parameters (canopy height, leaf-angle orientation distribution, leaf-area index, photometric properties, root-density distribution), soil texture, and soil-hydraulic and photometric properties are considered. The model is tested using meteorological data obtained in a drip-irrigated cotton field located in an extremely arid area, where strong fetch effects are expected. Four masts located 50 m before the leading edge of the field and 10, 30, and 100 m inward from the leading edge are used to measure various meteorological parameters and their horizontal and vertical gradients. Calculated values of air and soil temperatures, wind-speed, net radiation and soil, latent, and sensible heat fluxes agreed well with measurements. Large horizontal gradients of air temperature are both observed and measured within the canopy in the first 40 m of the leading edge. Rate of evapotranspiration at both the upwind and the downwind edges of the field are higher by more than 15% of the midfield value. Model calculations show that a stable thermal stratification is maintained above the whole field for 24 h. The aerodynamic and thermal internal boundary layer (IBL) growth is proportional to the square root of the fetch. This is also the observed rate of growth of the thermal IBL over a cool sea surface.

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as your...

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as your...

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as your...

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How long may I collect information from my temperature gradient well? 3252.13 Section 3252.13 Public Lands: Interior Regulations Relating to Public Lands... temperature gradient well? You may collect information from your temperature gradient well for as long as your...

TEMPERATURE-GRADIENT INCUBATOR FOR DETERMINING THE TEMPERATURE RANGE OF GROWTH OF MICROORGANISMS

PubMed Central

Elliott, R. Paul

1963-01-01

Elliott, R. Paul (U.S. Department of Agriculture, Albany, Calif.). Temperature-gradient incubator for determining the temperature range of growth of microorganisms. J. Bacteriol. 85:889–894. 1963.—The temperature-gradient incubator consists of an aluminum bar with troughs for media, with controlled temperatures at each end, and with insulation to prevent heat transfer. The resulting linear temperature gradient provides a means for determining minimal or maximal growth temperatures of microorganisms in any desired range and at any desired gradient. The operation of the incubator is unaffected by line-voltage variations or by ambient temperature. Media do not dehydrate seriously even during prolonged periods of operation. The incubator can be used to determine water activity of media by an adjustment to permit partial freezing. Either thermocouples or thermistors may be used to measure temperatures. Images PMID:14044959

Impacts of Realistic Urban Heating. Part II: Air Quality and City Breathability

NASA Astrophysics Data System (ADS)

Nazarian, Negin; Martilli, Alberto; Norford, Leslie; Kleissl, Jan

2018-03-01

Urban morphology and inter-building shadowing result in a non-uniform distribution of surface heating in urban areas, which can significantly modify the urban flow and thermal field. In Part I, we found that in an idealized three-dimensional urban array, the spatial distribution of the thermal field is correlated with the orientation of surface heating with respect to the wind direction (i.e. leeward or windward heating), while the dispersion field changes more strongly with the vertical temperature gradient in the street canyon. Here, we evaluate these results more closely and translate them into metrics of "city breathability," with large-eddy simulations coupled with an urban energy-balance model employed for this purpose. First, we quantify breathability by, (i) calculating the pollutant concentration at the pedestrian level (horizontal plane at z≈ 1.5 -2 m) and averaged over the canopy, and (ii) examining the air exchange rate at the horizontal and vertical ventilating faces of the canyon, such that the in-canopy pollutant advection is distinguished from the vertical removal of pollution. Next, we quantify the change in breathability metrics as a function of previously defined buoyancy parameters, horizontal and vertical Richardson numbers (Ri_h and Ri_v , respectively), which characterize realistic surface heating. We find that, unlike the analysis of airflow and thermal fields, consideration of the realistic heating distribution is not crucial in the analysis of city breathability, as the pollutant concentration is mainly correlated with the vertical temperature gradient (Ri_v ) as opposed to the horizontal (Ri_h ) or bulk (Ri_b ) thermal forcing. Additionally, we observe that, due to the formation of the primary vortex, the air exchange rate at the roof level (the horizontal ventilating faces of the building canyon) is dominated by the mean flow. Lastly, since Ri_h and Ri_v depend on the meteorological factors (ambient air temperature, wind speed, and wind direction) as well as urban design parameters (such as surface albedo), we propose a methodology for mapping overall outdoor ventilation and city breathability using this characterization method. This methodology helps identify the effects of design on urban microclimate, and ultimately informs urban designers and architects of the impact of their design on air quality, human health, and comfort.

Minimizing hot spot temperature in asymmetric gradient coil design.

PubMed

While, Peter T; Forbes, Larry K; Crozier, Stuart

2011-08-01

Heating caused by gradient coils is a considerable concern in the operation of magnetic resonance imaging (MRI) scanners. Hot spots can occur in regions where the gradient coil windings are closely spaced. These problem areas are particularly common in the design of gradient coils with asymmetrically located target regions. In this paper, an extension of an existing coil design method is described, to enable the design of asymmetric gradient coils with reduced hot spot temperatures. An improved model is presented for predicting steady-state spatial temperature distributions for gradient coils. A great amount of flexibility is afforded by this model to consider a wide range of geometries and system material properties. A feature of the temperature distribution related to the temperature gradient is used in a relaxed fixed point iteration routine for successively altering coil windings to have a lower hot spot temperature. Results show that significant reductions in peak temperature are possible at little or no cost to coil performance when compared to minimum power coils of equivalent field error.

Magnetoelectrets prepared by using temperature gradient method

NASA Astrophysics Data System (ADS)

Ojha, Pragya; Qureshi, M. S.; Malik, M. M.

2015-05-01

A novel Temperature Gradient method for preparation of magnetoelectret is proposed. Non uniform magnetic field and temperature gradient are expected to be the main cause for the formation of magnetoelectrets (MEs). Being bad conductors of heat, during their formation, there is a possibility for the existence of a temperature gradient along the dielectric electrode interface. In this condition, the motion of, molecules and charge carriers are dependent on Temperature Gradient in a preferred direction. To increase this temperature gradient on both sides of the sample novel method for the preparation of MEs is developed for the first time. For this method the special sample holders are designed in our laboratory. MEs are prepared in such a way that one surface is cooled and the other is heated, during the process. With the help of XRD analysis using Type-E orientation pattern and surface charge studies on magnetoelectrets, the two main causes Non uniform magnetic field and temperature gradient for the formation of magnetoelectrets (MEs), are authenticated experimentally.

Thermal adaptation of net ecosystem exchange

DOE PAGES

Yuan, W.; Luo, Y.; Liang, S.; ...

2011-06-06

Thermal adaptation of gross primary production and ecosystem respiration has been well documented over broad thermal gradients. However, no study has examined their interaction as a function of temperature, i.e. the thermal responses of net ecosystem exchange of carbon (NEE). Here in this study, we constructed temperature response curves of NEE against temperature using 380 site-years of eddy covariance data at 72 forest, grassland and shrubland ecosystems located at latitudes ranging from ~29° N to 64° N. The response curves were used to define two critical temperatures: transition temperature (T b) at which ecosystem transfer from carbon source to sinkmore » and optimal temperature (T o) at which carbon uptake is maximized. T b was strongly correlated with annual mean air temperature. T o was strongly correlated with mean temperature during the net carbon uptake period across the study ecosystems. Our results imply that the net ecosystem exchange of carbon adapts to the temperature across the geographical range due to intrinsic connections between vegetation primary production and ecosystem respiration.« less

Thermal adaptation of net ecosystem exchange

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

Yuan, W.; Luo, Y.; Liang, S.

Thermal adaptation of gross primary production and ecosystem respiration has been well documented over broad thermal gradients. However, no study has examined their interaction as a function of temperature, i.e. the thermal responses of net ecosystem exchange of carbon (NEE). Here in this study, we constructed temperature response curves of NEE against temperature using 380 site-years of eddy covariance data at 72 forest, grassland and shrubland ecosystems located at latitudes ranging from ~29° N to 64° N. The response curves were used to define two critical temperatures: transition temperature (T b) at which ecosystem transfer from carbon source to sinkmore » and optimal temperature (T o) at which carbon uptake is maximized. T b was strongly correlated with annual mean air temperature. T o was strongly correlated with mean temperature during the net carbon uptake period across the study ecosystems. Our results imply that the net ecosystem exchange of carbon adapts to the temperature across the geographical range due to intrinsic connections between vegetation primary production and ecosystem respiration.« less

Scalable Nernst thermoelectric power using a coiled galfenol wire

NASA Astrophysics Data System (ADS)

Yang, Zihao; Codecido, Emilio A.; Marquez, Jason; Zheng, Yuanhua; Heremans, Joseph P.; Myers, Roberto C.

2017-09-01

The Nernst thermopower usually is considered far too weak in most metals for waste heat recovery. However, its transverse orientation gives it an advantage over the Seebeck effect on non-flat surfaces. Here, we experimentally demonstrate the scalable generation of a Nernst voltage in an air-cooled metal wire coiled around a hot cylinder. In this geometry, a radial temperature gradient generates an azimuthal electric field in the coil. A Galfenol (Fe0.85Ga0.15) wire is wrapped around a cartridge heater, and the voltage drop across the wire is measured as a function of axial magnetic field. As expected, the Nernst voltage scales linearly with the length of the wire. Based on heat conduction and fluid dynamic equations, finite-element method is used to calculate the temperature gradient across the Galfenol wire and determine the Nernst coefficient. A giant Nernst coefficient of -2.6 μV/KT at room temperature is estimated, in agreement with measurements on bulk Galfenol. We expect that the giant Nernst effect in Galfenol arises from its magnetostriction, presumably through enhanced magnon-phonon coupling. Our results demonstrate the feasibility of a transverse thermoelectric generator capable of scalable output power from non-flat heat sources.

Modelling heat and mass transfer in a membrane-based air-to-air enthalpy exchanger

NASA Astrophysics Data System (ADS)

Dugaria, S.; Moro, L.; Del, D., Col

2015-11-01

The diffusion of total energy recovery systems could lead to a significant reduction in the energy demand for building air-conditioning. With these devices, sensible heat and humidity can be recovered in winter from the exhaust airstream, while, in summer, the incoming air stream can be cooled and dehumidified by transferring the excess heat and moisture to the exhaust air stream. Membrane based enthalpy exchangers are composed by different channels separated by semi-permeable membranes. The membrane allows moisture transfer under vapour pressure difference, or water concentration difference, between the two sides and, at the same time, it is ideally impermeable to air and other contaminants present in exhaust air. Heat transfer between the airstreams occurs through the membrane due to the temperature gradient. The aim of this work is to develop a detailed model of the coupled heat and mass transfer mechanisms through the membrane between the two airstreams. After a review of the most relevant models published in the scientific literature, the governing equations are presented and some simplifying assumptions are analysed and discussed. As a result, a steady-state, two-dimensional finite difference numerical model is setup. The developed model is able to predict temperature and humidity evolution inside the channels. Sensible and latent heat transfer rate, as well as moisture transfer rate, are determined. A sensitive analysis is conducted in order to determine the more influential parameters on the thermal and vapour transfer.

Thermoelectrically cooled temperature-gradient apparatus for comparative cell and virus temperature studies.

PubMed

Clark, H F; Kaminski, F; Karzon, D T

1970-05-01

Establishment of a near-linear temperature gradient in an incubator has been accomplished by the application of heat to one terminus of a conducting body, normally a metal bar, and the removal of heat from the other terminus of the conducting body. Such incubators have been complex and unwieldy because of the need for mechanical refrigeration. We have described a simplified temperature gradient incubator which uses thermoelectric module cooling coupled with electric heating. Along the gradient, 20 stations in two parallel rows of 10, each accommodating a 30-ml plastic cell culture flask, were continually monitored by an electronic thermometer, and the temperatures were recorded. By manipulation of two simple potentiometer controls, any temperature gradient between 0 and 50 C could be obtained. Minor deviations which occurred between theoretically perfect and obtained temperature gradients were reproducible and readily measured. The gradient incubator was particularly applicable to (i) simultaneously studying a given biological activity over the entire temperature range supporting the growth of a given cell, virus, or microorganism, or (ii) precisely defining the upper or lower temperature limits of a biological system by 10-point determinations. Preliminary experiments have demonstrated the usefulness of the apparatus in characterizing the temperature limits for growth in vitro of cells of reptilian cell lines. The gradient incubator was also successfully utilized for the characterization of the effect of temperature on the efficiency of plating of amphibian viruses and possible temperature variants of those viruses.

Electron temperature critical gradient and transport stiffness in DIII-D

DOE PAGES

Smith, Sterling P.; Petty, Clinton C.; White, Anne E.; ...

2015-07-06

The electron energy flux has been probed as a function of electron temperature gradient on the DIII-D tokamak, in a continuing effort to validate turbulent transport models. In the scan of gradient, a critical electron temperature gradient has been found in the electron heat fluxes and stiffness at various radii in L-mode plasmas. The TGLF reduced turbulent transport model [G.M. Staebler et al, Phys. Plasmas 14, 055909 (2007)] and full gyrokinetic GYRO model [J. Candy and R.E. Waltz, J. Comput. Phys. 186, 545 (2003)] recover the general trend of increasing electron energy flux with increasing electron temperature gradient scale length,more » but they do not predict the absolute level of transport at all radii and gradients. Comparing the experimental observations of incremental (heat pulse) diffusivity and stiffness to the models’ reveals that TGLF reproduces the trends in increasing diffusivity and stiffness with increasing electron temperature gradient scale length with a critical gradient behavior. Furthermore, the critical gradient of TGLF is found to have a dependence on q 95, contrary to the independence of the experimental critical gradient from q 95.« less

On the calculation of air-sea fluxes of CO2 in the presence of temperature and salinity gradients

NASA Astrophysics Data System (ADS)

Woolf, D. K.; Land, P. E.; Shutler, J. D.; Goddijn-Murphy, L. M.; Donlon, C. J.

2016-02-01

The presence of vertical temperature and salinity gradients in the upper ocean and the occurrence of variations in temperature and salinity on time scales from hours to many years complicate the calculation of the flux of carbon dioxide (CO2) across the sea surface. Temperature and salinity affect the interfacial concentration of aqueous CO2 primarily through their effect on solubility with lesser effects related to saturated vapor pressure and the relationship between fugacity and partial pressure. The effects of temperature and salinity profiles in the water column and changes in the aqueous concentration act primarily through the partitioning of the carbonate system. Climatological calculations of flux require attention to variability in the upper ocean and to the limited validity of assuming "constant chemistry" in transforming measurements to climatological values. Contrary to some recent analysis, it is shown that the effect on CO2 fluxes of a cool skin on the sea surface is large and ubiquitous. An opposing effect on calculated fluxes is related to the occurrence of warm layers near the surface; this effect can be locally large but will usually coincide with periods of low exchange. A salty skin and salinity anomalies in the upper ocean also affect CO2 flux calculations, though these haline effects are generally weaker than the thermal effects.

Directional Bleb Formation in Spherical Cells under Temperature Gradient

PubMed Central

Oyama, Kotaro; Arai, Tomomi; Isaka, Akira; Sekiguchi, Taku; Itoh, Hideki; Seto, Yusuke; Miyazaki, Makito; Itabashi, Takeshi; Ohki, Takashi; Suzuki, Madoka; Ishiwata, Shin'ichi

2015-01-01

Living cells sense absolute temperature and temporal changes in temperature using biological thermosensors such as ion channels. Here, we reveal, to our knowledge, a novel mechanism of sensing spatial temperature gradients within single cells. Spherical mitotic cells form directional membrane extensions (polar blebs) under sharp temperature gradients (≥∼0.065°C μm−1; 1.3°C temperature difference within a cell), which are created by local heating with a focused 1455-nm laser beam under an optical microscope. On the other hand, multiple nondirectional blebs are formed under gradual temperature gradients or uniform heating. During heating, the distribution of actomyosin complexes becomes inhomogeneous due to a break in the symmetry of its contractile force, highlighting the role of the actomyosin complex as a sensor of local temperature gradients. PMID:26200871

On buoyancy-driven natural ventilation of a room with a heated floor

NASA Astrophysics Data System (ADS)

Gladstone, Charlotte; Woods, Andrew W.

2001-08-01

The natural ventilation of a room, both with a heated floor and connected to a cold exterior through two openings, is investigated by combining quantitative models with analogue laboratory experiments. The heated floor generates an areal source of buoyancy while the openings allow displacement ventilation to operate. When combined, these produce a steady state in which the air in the room is well-mixed, and the heat provided by the floor equals the heat lost by displacement. We develop a quantitative model describing this process, in which the advective heat transfer through the openings is balanced with the heat flux supplied at the floor. This model is successfully tested with observations from small-scale analogue laboratory experiments. We compare our results with the steady-state flow associated with a point source of buoyancy: for a given applied heat flux, an areal source produces heated air of lower temperature but a greater volume flux of air circulates through the room. We generalize the model to account for the effects of (i) a cooled roof as well as a heated floor, and (ii) an external wind or temperature gradient. In the former case, the direction of the flow through the openings depends on the temperature of the exterior air relative to an averaged roof and floor temperature. In the latter case, the flow is either buoyancy dominated or wind dominated depending on the strength of the pressure associated with the wind. Furthermore, there is an intermediate multiple-solution regime in which either flow regime may develop.

Thermal equilibrium of Nellore cattle in tropical conditions: an investigation of circadian pattern.

PubMed

de Melo Costa, Cíntia Carol; Campos Maia, Alex Sandro; Brown-Brandl, Tami M; Chiquitelli Neto, Marcos; de França Carvalho Fonsêca, Vinicius

2018-05-01

The aim of this work was to evaluate the diurnal patterns of physiological responses and the thermal regulation of adult Nellore bulls. Six 30-mo-old Nellore bulls (669 ± 65 kg BW) were randomly assigned to four 6-h periods in a Latin Square design such that measurements of each animal cover a 24-h cycle. Meteorological variables (air temperature, relative humidity, local solar irradiance, ultraviolet radiation, wind speed and black globe temperature) were recorded at regular one-minute intervals with an automated weather station. Respiratory rate, ventilation rate, oxygen, carbon dioxide, methane, saturation pressure, air temperature of the exhaled air, saturation pressure in the air leaving the ventilated capsule placed over the animal surface, hair coat, skin surface and rectal temperature were assessed. The thermal equilibrium was determined according to the principles of the first law of thermodynamics using biophysical equations. Animals were evaluated in an area which was protected from solar radiation, rain, and had a range of ambient air temperature between 20.57 ± 0.07 and 30.86 ± 0.07 °C. Percentage of O 2 and CO 2 in the exhaled air changed moderately (P < 0.0001) throughout the 24 h, which resulted in an average metabolic heat production of 151.45 ± 13.60 W m -2 . At the largest thermal gradient (T S - T A ; from 24:00-07:00 h), heat transferred by long wave radiation and surface convection corresponded to near 60% of the metabolism. At 11:00 h the ambient temperature approached 29 °C and latent heat became the main way to cool the body. From this time until 17:00 h, cutaneous evaporation represented approximately 53% of total heat loss. In conclusion, results of the present study seem to be a good indicator of lower energy expenditure for body thermal regulation, high heat tolerance and adaptation of Nellore cattle to the tropical environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Roles of Urban Tree Canopy and Buildings in Urban Heat Island Effects: Parameterization and Preliminary Results

NASA Technical Reports Server (NTRS)

Loughner, Christopher P.; Allen, Dale J.; Zhang, Da-Lin; Pickering, Kenneth E.; Dickerson, Russell R.; Landry, Laura

2012-01-01

Urban heat island (UHI) effects can strengthen heat waves and air pollution episodes. In this study, the dampening impact of urban trees on the UHI during an extreme heat wave in the Washington, D.C., and Baltimore, Maryland, metropolitan area is examined by incorporating trees, soil, and grass into the coupled Weather Research and Forecasting model and an urban canopy model (WRF-UCM). By parameterizing the effects of these natural surfaces alongside roadways and buildings, the modified WRF-UCM is used to investigate how urban trees, soil, and grass dampen the UHI. The modified model was run with 50% tree cover over urban roads and a 10% decrease in the width of urban streets to make space for soil and grass alongside the roads and buildings. Results show that, averaged over all urban areas, the added vegetation decreases surface air temperature in urban street canyons by 4.1 K and road-surface and building-wall temperatures by 15.4 and 8.9 K, respectively, as a result of tree shading and evapotranspiration. These temperature changes propagate downwind and alter the temperature gradient associated with the Chesapeake Bay breeze and, therefore, alter the strength of the bay breeze. The impact of building height on the UHI shows that decreasing commercial building heights by 8 m and residential building heights by 2.5 m results in up to 0.4-K higher daytime surface and near-surface air temperatures because of less building shading and up to 1.2-K lower nighttime temperatures because of less longwave radiative trapping in urban street canyons.

An experimental study on the thermal characteristics and heating effect of arc-fault from Cu core in residential electrical wiring fires

PubMed Central

Du, Jian-Hua; Zeng, Yi; Pan, Leng; Zhang, Ren-Cheng

2017-01-01

The characteristics of a series direct current (DC) arc-fault including both electrical and thermal parameters were investigated based on an arc-fault simulator to provide references for multi-parameter electrical fire detection method. Tests on arc fault behavior with three different initial circuit voltages, resistances and arc gaps were conducted, respectively. The influences of circuit conditions on arc dynamic image, voltage, current or power were interpreted. Also, the temperature rises of electrode surface and ambient air were studied. The results showed that, first, significant variations of arc structure and light emitting were observed under different conditions. A thin outer burning layer of vapor generated from electrodes with orange light was found due to the extremely high arc temperature. Second, with the increasing electrode gap in discharging, the arc power was shown to have a non monotonic relationship with arc length for constant initial circuit voltage and resistance. Finally, the temperature rises of electrode surface caused by heat transfer from arc were found to be not sensitive with increasing arc length due to special heat transfer mechanism. In addition, temperature of ambient air showed a large gradient in radial direction of arc. PMID:28797055

An experimental study on the thermal characteristics and heating effect of arc-fault from Cu core in residential electrical wiring fires.

PubMed

Du, Jian-Hua; Tu, Ran; Zeng, Yi; Pan, Leng; Zhang, Ren-Cheng

2017-01-01

The characteristics of a series direct current (DC) arc-fault including both electrical and thermal parameters were investigated based on an arc-fault simulator to provide references for multi-parameter electrical fire detection method. Tests on arc fault behavior with three different initial circuit voltages, resistances and arc gaps were conducted, respectively. The influences of circuit conditions on arc dynamic image, voltage, current or power were interpreted. Also, the temperature rises of electrode surface and ambient air were studied. The results showed that, first, significant variations of arc structure and light emitting were observed under different conditions. A thin outer burning layer of vapor generated from electrodes with orange light was found due to the extremely high arc temperature. Second, with the increasing electrode gap in discharging, the arc power was shown to have a non monotonic relationship with arc length for constant initial circuit voltage and resistance. Finally, the temperature rises of electrode surface caused by heat transfer from arc were found to be not sensitive with increasing arc length due to special heat transfer mechanism. In addition, temperature of ambient air showed a large gradient in radial direction of arc.

Heat transfer in thermal barrier coated rods with circumferential and radial temperature gradients

NASA Astrophysics Data System (ADS)

Chung, B. T. F.; Kermani, M. M.; Braun, M. J.; Padovan, J.; Hendricks, R.

1984-06-01

To study the heat transfer in ceramic coatings applied to the heated side of internally cooled hot section components of the gas turbine engine, a mathematical model is developed for the thermal response of plasma-sprayed ZrO2-Y2O3 ceramic materials with a Ni-Cr-AL-Y bond coat on a Rene 41 rod substrate subject to thermal cycling. This multilayered cylinder with temperature dependent thermal properties is heated in a cross-flow by a high velocity flame and then cooled by ambient air. Due to high temperature and high velocity of the flame, both gas radiation and forced convection are taken into consideration. Furthermore, the local turbulent heat transfer coefficient is employed which varies with angular position as well as the surface temperature. The transient two-dimensional (heat transfer along axial direction is neglected) temperature distribution of the composite cylinder is determined numerically.

Heat transfer in thermal barrier coated rods with circumferential and radial temperature gradients

NASA Technical Reports Server (NTRS)

Chung, B. T. F.; Kermani, M. M.; Braun, M. J.; Padovan, J.; Hendricks, R.

1984-01-01

To study the heat transfer in ceramic coatings applied to the heated side of internally cooled hot section components of the gas turbine engine, a mathematical model is developed for the thermal response of plasma-sprayed ZrO2-Y2O3 ceramic materials with a Ni-Cr-AL-Y bond coat on a Rene 41 rod substrate subject to thermal cycling. This multilayered cylinder with temperature dependent thermal properties is heated in a cross-flow by a high velocity flame and then cooled by ambient air. Due to high temperature and high velocity of the flame, both gas radiation and forced convection are taken into consideration. Furthermore, the local turbulent heat transfer coefficient is employed which varies with angular position as well as the surface temperature. The transient two-dimensional (heat transfer along axial direction is neglected) temperature distribution of the composite cylinder is determined numerically.

Construction of a High Temperature Teg Measurement System for the Evaluation of Thermoelectric Oxide Modules

NASA Astrophysics Data System (ADS)

Populoh, S.; Trottmann, M.; Brunko, O. C.; Thiel, P.; Weidenkaff, A.

2013-08-01

A dedicated test stand was developed and built to characterize the efficiency, power output and open circuit voltage of various thermoelectric generators (TEGs) based on tellurides, heusler compounds and thermoelectric oxides. The test stand allows measurements of TEGs of sizes up to 4 cm × 4 cm at hot side temperatures up to 1150 K in different atmospheres. Special care was taken about the heat flux measurement by precise measurement of the temperature distribution within the reference block. In order to demonstrate the functionality of the test stand thermoelectric oxide modules (TOM) were built from n-type perovskite-type manganates and p-type cuprates. The modules were tested regarding their stability, maximum power output and efficiency at temperatures up to 1100 K. The TOMs withstand large temperature gradients and operated in ambient air yielding high power densities.

Thermospheric winds and exospheric temperatures from incoherent scatter radar measurements in four seasons

NASA Technical Reports Server (NTRS)

Antoniadis, D. A.

1976-01-01

The time-dependent equations of neutral air motion are solved subject to three constraints: two of them are the usual upper and lower boundary conditions and the third is the value of the wind-induced ion drift at any given height. Using incoherent radar data, this procedure leads to a fast, direct numerical integration of the two coupled differential equations describing the horizontal wind components and yields time dependent wind profiles and meridional exospheric neutral temperature gradients. The diurnal behavior of the neutral wind system and of the exospheric temperature is presented for two solstice and two equinox days. The data used were obtained by the St. Santin and the Millstone Hill incoherent scatter radars. The derived geographic distributions of the exospheric temperatures are compared with those predicted by the OGO-6 empirical thermospheric model.

Recent summer precipitation trends in the Greater Horn of Africa and the emerging role of Indian Ocean sea surface temperature

NASA Astrophysics Data System (ADS)

Williams, A. Park; Funk, Chris; Michaelsen, Joel; Rauscher, Sara A.; Robertson, Iain; Wils, Tommy H. G.; Koprowski, Marcin; Eshetu, Zewdu; Loader, Neil J.

2012-11-01

We utilize a variety of climate datasets to examine impacts of two mechanisms on precipitation in the Greater Horn of Africa (GHA) during northern-hemisphere summer. First, surface-pressure gradients draw moist air toward the GHA from the tropical Atlantic Ocean and Congo Basin. Variability of the strength of these gradients strongly influences GHA precipitation totals and accounts for important phenomena such as the 1960s-1980s rainfall decline and devastating 1984 drought. Following the 1980s, precipitation variability became increasingly influenced by the southern tropical Indian Ocean (STIO) region. Within this region, increases in sea-surface temperature, evaporation, and precipitation are linked with increased exports of dry mid-tropospheric air from the STIO region toward the GHA. Convergence of dry air above the GHA reduces local convection and precipitation. It also produces a clockwise circulation response near the ground that reduces moisture transports from the Congo Basin. Because precipitation originating in the Congo Basin has a unique isotopic signature, records of moisture transports from the Congo Basin may be preserved in the isotopic composition of annual tree rings in the Ethiopian Highlands. A negative trend in tree-ring oxygen-18 during the past half century suggests a decline in the proportion of precipitation originating from the Congo Basin. This trend may not be part of a natural cycle that will soon rebound because climate models characterize Indian Ocean warming as a principal signature of greenhouse-gas induced climate change. We therefore expect surface warming in the STIO region to continue to negatively impact GHA precipitation during northern-hemisphere summer.

Gradient structure-induced temperature responsiveness in styrene/methyl methacrylate gradient copolymers micelles.

PubMed

Zheng, Chao; Huang, Haiying; He, Tianbai

2014-02-01

In this work, micelles are formed by gradient copolymer of styrene and methyl methacrylate in acetone-water mixture and their temperature responsiveness is investigated in a narrow range near room temperature. Three different kinds of structural transitions could be induced by temperature: unimers to micelle transition, shrinkage/stretching of micelles, and morphological transition from spherical micelles to vesicles. In addition, a model analysis on the interface of gradient copolymer micelle is made to better understand these phenomena. It is found that both position and composition of the interface could alter in response to the change in temperature. According to the experiments and model analysis, it is proposed that temperature responsiveness might be an intrinsic and universal property of gradient copolymer micelles, which only originates from the gradient structure. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rapid solution casting under vacuum of very thick sheets of a segmented polyurethane elastomer

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.; Moacanin, J.

1981-01-01

A technique has been developed for rapidly casting from solution under vacuum smooth, bubble-free, clear-white and uniformly thick (about 0.20 cm) sheets of a segmented polyurethane elastomer. The casting is carried out from dimethylformamide solutions inside temperature-controlled air-circulated ovens in order to minimize the establishment of thermal gradients throughout the casting solution. The technique produces quality sheets in 9 days, compared with 40-45 days for an inferior film produced in open pans.

Performance Technology Program (PTP-S II), Volume IX. Evaluation of Reentry Vehicle Nosetip Transition and Heat Transfer in the AEDC Hyperballistics Track G

DTIC Science & Technology

1981-01-01

8217qround test programs, has shown that nosetip related effects markedly influence reentry vehicle performance. In clear air environments e’:he twc major...free flight configuration, extraneous shock layer radia- tion and surface chemiluminescence which may influence the sur- face temperature measurements...in the postf light model may result from range debris or thermal stress in the graphite from the large tem- perature gradients, their influence on

Ultrasonic Imaging System

NASA Technical Reports Server (NTRS)

Youngquist, Robert C. (Inventor); Moerk, Steven (Inventor)

1999-01-01

An imaging system is described which can be used to either passively search for sources of ultrasonics or as an active phase imaging system. which can image fires. gas leaks, or air temperature gradients. This system uses an array of ultrasonic receivers coupled to an ultrasound collector or lens to provide an electronic image of the ultrasound intensity in a selected angular region of space. A system is described which includes a video camera to provide a visual reference to a region being examined for ultrasonic signals.

Thermal gradients for the stabilization of a single domain wall in magnetic nanowires.

PubMed

Mejía-López, J; Velásquez, E A; Mazo-Zuluaga, J; Altbir, D

2018-08-24

By means of Monte Carlo simulations we studied field driven nucleation and propagation of transverse domain walls (DWs) in magnetic nanowires subjected to temperature gradients. Simulations identified the existence of critical thermal gradients that allow the existence of reversal processes driven by a single DW. Critical thermal gradients depend on external parameters such as temperature, magnetic field and wire length, and can be experimentally obtained through the measurement of the mean velocity of the magnetization reversal as a function of the temperature gradient. Our results show that temperature gradients provide a high degree of control over DW propagation, which is of great importance for technological applications.

Evidence for Ventilation through Collective Respiratory Movements in Giant Honeybee (Apis dorsata) Nests

PubMed Central

Kastberger, Gerald; Waddoup, Dominique; Weihmann, Frank; Hoetzl, Thomas

2016-01-01

The Asian giant honeybees (Apis dorsata) build single-comb nests in the open, which makes this species particularly susceptible to environmental strains. Long-term infrared (IR) records documented cool nest regions (CNR) at the bee curtain (nCNR = 207, nnests > 20) distinguished by marked negative gradients (ΔTCNR/d < -3°C / 5 cm) at their margins. CNRs develop and recede within minutes, predominantly at higher ambient temperatures in the early afternoon. The differential size (ΔACNR) and temperature (ΔTCNR) values per time unit correlated mostly positively (RAT > 0) displaying the Venturi effect, which evidences funnel properties of CNRs. The air flows inwards through CNRs, which is verified by the negative spatial gradient ΔTCNR/d, by the positive grading of TCNR with Tamb and lastly by fanners which have directed their abdomens towards CNRs. Rare cases of RAT < 0 (< 3%) document closing processes (for ΔACNR/Δt < -0.4 cm2/s) but also suggest ventilation of the bee curtain (for ΔACNR/Δt > +0.4 cm2/s) displaying “inhalation” and “exhalation” cycling. “Inhalation” could be boosted by bees at the inner curtain layers, which stretch their extremities against the comb enlarging the inner nest lumen and thus causing a pressure fall which drives ambient air inwards through CNR funnels. The relaxing of the formerly “activated” bees could then trigger the “exhalation” process, which brings the bee curtain, passively by gravity, close to the comb again. That way, warm, CO2-enriched nest-borne air is pressed outwards through the leaking mesh of the bee curtain. This ventilation hypothesis is supported by IR imaging and laser vibrometry depicting CNRs in at least four aspects as low-resistance convection funnels for maintaining thermoregulation and restoring fresh air in the nest. PMID:27487188

Evidence of counter-gradient growth in western pond turtles (Actinemys marmorata) across thermal gradients

Treesearch

Melissa L. Snover; Michael J. Adams; Donald T. Ashton; Jamie B. Bettaso; Hartwell H. Welsh

2015-01-01

Summary1. Counter-gradient growth, where growth per unit temperature increases as temperature decreases, can reduce the variation in ectothermic growth rates across environmental gradients. Understanding how ectothermic species respond to changing temperatures is essential to their conservation and management due to human-altered habitats and changing...

An assessment of precipitation and surface air temperature over China by regional climate models

NASA Astrophysics Data System (ADS)

Wang, Xueyuan; Tang, Jianping; Niu, Xiaorui; Wang, Shuyu

2016-12-01

An analysis of a 20-year summer time simulation of present-day climate (1989-2008) over China using four regional climate models coupled with different land surface models is carried out. The climatic means, interannual variability, linear trends, and extremes are examined, with focus on precipitation and near surface air temperature. The models are able to reproduce the basic features of the observed summer mean precipitation and temperature over China and the regional detail due to topographic forcing. Overall, the model performance is better for temperature than that of precipitation. The models reasonably grasp the major anomalies and standard deviations over China and the five subregions studied. The models generally reproduce the spatial pattern of high interannual variability over wet regions, and low variability over the dry regions. The models also capture well the variable temperature gradient increase to the north by latitude. Both the observed and simulated linear trend of precipitation shows a drying tendency over the Yangtze River Basin and wetting over South China. The models capture well the relatively small temperature trends in large areas of China. The models reasonably simulate the characteristics of extreme precipitation indices of heavy rain days and heavy precipitation fraction. Most of the models also performed well in capturing both the sign and magnitude of the daily maximum and minimum temperatures over China.

Stomatal Conductance, Plant Hydraulics, and Multilayer Canopies: A New Paradigm for Earth System Models or Unnecessary Uncertainty

NASA Astrophysics Data System (ADS)

Bonan, G. B.

2016-12-01

Soil moisture stress is a key regulator of canopy transpiration, the surface energy budget, and land-atmosphere coupling. Many land surface models used in Earth system models have an ad-hoc parameterization of soil moisture stress that decreases stomatal conductance with soil drying. Parameterization of soil moisture stress from more fundamental principles of plant hydrodynamics is a key research frontier for land surface models. While the biophysical and physiological foundations of such parameterizations are well-known, their best implementation in land surface models is less clear. Land surface models utilize a big-leaf canopy parameterization (or two big-leaves to represent the sunlit and shaded canopy) without vertical gradients in the canopy. However, there are strong biometeorological and physiological gradients in plant canopies. Are these gradients necessary to resolve? Here, I describe a vertically-resolved, multilayer canopy model that calculates leaf temperature and energy fluxes, photosynthesis, stomatal conductance, and leaf water potential at each level in the canopy. In this model, midday leaf water stress manifests in the upper canopy layers, which receive high amounts of solar radiation, have high leaf nitrogen and photosynthetic capacity, and have high stomatal conductance and transpiration rates (in the absence of leaf water stress). Lower levels in the canopy become water stressed in response to longer-term soil moisture drying. I examine the role of vertical gradients in the canopy microclimate (solar radiation, air temperature, vapor pressure, wind speed), structure (leaf area density), and physiology (leaf nitrogen, photosynthetic capacity, stomatal conductance) in determining above canopy fluxes and gradients of transpiration and leaf water potential within the canopy.

Influence of smooth temperature variation on hotspot ignition

DOE PAGES

Reinbacher, Fynn; Regele, Jonathan David

2017-10-06

Autoignition in thermally stratified reactive mixtures originates in localised hotspots. The ignition behaviour is often characterised using linear temperature gradients and more recently constant temperature plateaus combined with temperature gradients. Acoustic timescale characterisation of plateau regions has been successfully used to characterise the type of mechanical disturbance that will be created from a plateau core ignition. This work combines linear temperature gradients with superelliptic cores in order to more accurately account for a local temperature maximum of finite size and the smooth temperature variation contained inside realistic hotspot centres. A one-step Arrhenius reaction is used to model a H 2–airmore » reactive mixture. Using the superelliptic approach a range of behaviours for temperature distributions are investigated by varying the temperature profile between the gradient only and plateau and gradient bounding cases. Each superelliptic case is compared to a respective plateau and gradient case where simple acoustic timescale characterisation may be performed. It is shown that hot spots equivalent with excitation-to-acoustic timescale ratios sufficiently greater than unity exhibit behaviour very similar to a simple plateau-gradient model. Furthermore, for larger hot spots with timescale ratios sufficiently less than unity the reaction behaviour is highly dependent on the smooth temperature profile contained within the core region.« less

Influence of smooth temperature variation on hotspot ignition

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

Reinbacher, Fynn; Regele, Jonathan David

Autoignition in thermally stratified reactive mixtures originates in localised hotspots. The ignition behaviour is often characterised using linear temperature gradients and more recently constant temperature plateaus combined with temperature gradients. Acoustic timescale characterisation of plateau regions has been successfully used to characterise the type of mechanical disturbance that will be created from a plateau core ignition. This work combines linear temperature gradients with superelliptic cores in order to more accurately account for a local temperature maximum of finite size and the smooth temperature variation contained inside realistic hotspot centres. A one-step Arrhenius reaction is used to model a H 2–airmore » reactive mixture. Using the superelliptic approach a range of behaviours for temperature distributions are investigated by varying the temperature profile between the gradient only and plateau and gradient bounding cases. Each superelliptic case is compared to a respective plateau and gradient case where simple acoustic timescale characterisation may be performed. It is shown that hot spots equivalent with excitation-to-acoustic timescale ratios sufficiently greater than unity exhibit behaviour very similar to a simple plateau-gradient model. Furthermore, for larger hot spots with timescale ratios sufficiently less than unity the reaction behaviour is highly dependent on the smooth temperature profile contained within the core region.« less

Slow climate velocities of mountain streams portend their role as refugia for cold-water biodiversity

USGS Publications Warehouse

Isaak, Daniel J.; Young, Michael K; Luce, Charles H; Hostetler, Steven W.; Wengerd, Seth J.; Peterson, Erin E.; Ver Hoef, Jay; Groce, Matthew C.; Horan, Dona L.; Nagel, David E.

2016-01-01

The imminent demise of montane species is a recurrent theme in the climate change literature, particularly for aquatic species that are constrained to networks and elevational rather than latitudinal retreat as temperatures increase. Predictions of widespread species losses, however, have yet to be fulfilled despite decades of climate change, suggesting that trends are much weaker than anticipated and may be too subtle for detection given the widespread use of sparse water temperature datasets or imprecise surrogates like elevation and air temperature. Through application of large water-temperature databases evaluated for sensitivity to historical air-temperature variability and computationally interpolated to provide high-resolution thermal habitat information for a 222,000-km network, we estimate a less dire thermal plight for cold-water species within mountains of the northwestern United States. Stream warming rates and climate velocities were both relatively low for 1968–2011 (average warming rate = 0.101 °C/decade; median velocity = 1.07 km/decade) when air temperatures warmed at 0.21 °C/decade. Many cold-water vertebrate species occurred in a subset of the network characterized by low climate velocities, and three native species of conservation concern occurred in extremely cold, slow velocity environments (0.33–0.48 km/decade). Examination of aggressive warming scenarios indicated that although network climate velocities could increase, they remain low in headwaters because of strong local temperature gradients associated with topographic controls. Better information about changing hydrology and disturbance regimes is needed to complement these results, but rather than being climatic cul-de-sacs, many mountain streams appear poised to be redoubts for cold-water biodiversity this century.

Thermotransduction and heat stress in dental structures during orthodontic debonding : Effectiveness of various cooling strategies.

PubMed

Kley, Philipp; Frentzen, Matthias; Küpper, Katharina; Braun, Andreas; Kecsmar, Susann; Jäger, Andreas; Wolf, Michael

2016-05-01

Recent studies have indicated possible thermal damage to pulpal tissue during orthodontic debonding. This study aimed to analyze the thermal loads acting upon dental structures and their transfer to the pulp during orthodontic debonding. Specific goals were to analyze temperature changes in local dental tissues, thermotransduction to the pulp cavity, and the effectiveness of common cooling strategies and of simulated intrapulpal circulation. Metal brackets were bonded to five extracted human molars and subsequently removed. While a carbide bur was applied to debond the residual composite from the tooth surface, various cooling strategies (no/air/water cooling) were employed with or without simulated intrapulpal circulation, accompanied by temperature measurements with a thermographic infrared camera on the enamel surface and with measuring probes in the pulp cavity. Appropriate evaluation software was used to calculate the enamel-to-pulp temperature gradients and for statistical analysis. Significant differences in temperature rise and heat development over time, both on the enamel surfaces and in the pulp cavities were found. The mean temperature rises associated with no/air/water cooling were 90.7/46.6/9.2 °C on the enamel surface versus 9/8/4.6 °C inside the pulp. However, thermotransduction from enamel to pulp remained below 10 % of the surface measurements in all groups. Simulated intrapulpal microcirculation was found to significantly reduce intrapulpal temperature levels. During debonding of residual bracket adhesives, provided that a carbide bur is properly used, our data indicate a low risk of reaching critical intrapulpal temperatures even in the absence of dedicated cooling and no risk if the instrumentation is accompanied by air or water cooling.

Slow climate velocities of mountain streams portend their role as refugia for cold-water biodiversity

PubMed Central

Isaak, Daniel J.; Young, Michael K.; Luce, Charles H.; Hostetler, Steven W.; Wenger, Seth J.; Peterson, Erin E.; Ver Hoef, Jay M.; Groce, Matthew C.; Horan, Dona L.; Nagel, David E.

2016-01-01

The imminent demise of montane species is a recurrent theme in the climate change literature, particularly for aquatic species that are constrained to networks and elevational rather than latitudinal retreat as temperatures increase. Predictions of widespread species losses, however, have yet to be fulfilled despite decades of climate change, suggesting that trends are much weaker than anticipated and may be too subtle for detection given the widespread use of sparse water temperature datasets or imprecise surrogates like elevation and air temperature. Through application of large water-temperature databases evaluated for sensitivity to historical air-temperature variability and computationally interpolated to provide high-resolution thermal habitat information for a 222,000-km network, we estimate a less dire thermal plight for cold-water species within mountains of the northwestern United States. Stream warming rates and climate velocities were both relatively low for 1968–2011 (average warming rate = 0.101 °C/decade; median velocity = 1.07 km/decade) when air temperatures warmed at 0.21 °C/decade. Many cold-water vertebrate species occurred in a subset of the network characterized by low climate velocities, and three native species of conservation concern occurred in extremely cold, slow velocity environments (0.33–0.48 km/decade). Examination of aggressive warming scenarios indicated that although network climate velocities could increase, they remain low in headwaters because of strong local temperature gradients associated with topographic controls. Better information about changing hydrology and disturbance regimes is needed to complement these results, but rather than being climatic cul-de-sacs, many mountain streams appear poised to be redoubts for cold-water biodiversity this century. PMID:27044091

Snowmelt in a High Latitude Mountain Catchment: Effect of Vegetation Cover and Elevation

NASA Astrophysics Data System (ADS)

Pomeroy, J. W.; Essery, R. L.; Ellis, C. R.; Hedstrom, N. R.; Janowicz, R.; Granger, R. J.

2004-12-01

The energetics and mass balance of snowpacks in the premelt and melt period were compared from three elevation bands in a high latitude mountain catchment, Wolf Creek Research Basin, Yukon. Elevation is strongly correlated with vegetation cover and in this case the three elevation bands (low, middle, high) correspond to mature spruce forest, dense shrub tundra and sparse tundra (alpine). Measurements of radiation, ground heat flux, snow depth, snowfall, air temperature, wind speed were made on a half-hourly basis at the three elevations for a 10 year period. Sondes provided vertical gradients of air temperature, humidity, wind speed and air pressure. Snow depth and density surveys were conducted monthly. Comparisons of wind speed, air temperature and humidity at three elevations show that the expected elevational gradients in the free atmosphere were slightly enhanced just above the surface canopies, but that the climate at the snow surface was further influenced by complex canopy effects. Premelt snow accumulation was strongly affected by intercepted snow in the forest and blowing snow sublimation in the sparse tundra but not by the small elevational gradients in snowfall. As a result the maximum premelt SWE was found in the mid-elevation shrub tundra and was roughly double that of the sparse tundra or forest. Minimum variability of SWE was observed in the forest and shrub tundra (CV=0.25) while in the sparse tundra variability doubled (CV=0.5). Snowmelt was influenced by differences in premelt accumulation as well as differences in the net energy fluxes to snow. Elevation had a strong effect on the initiation of melt with the forest melt starting on average 16 days before the shrub tundra and 19 days before the sparse tundra. Mean melt rates showed a maximum in middle elevations and increased from 860 kJ/day in the forest to 1460 kJ/day in the sparse tundra and 2730 kJ/day in the shrub tundra. The forest canopy reduced melt while the shrub canopy enhanced it relative to the sparsely vegetated tundra. Duration of melt was similar in the forest and shrub tundra at 20 days while the sparse tundra was shorter at 13 days; the differences due to differing snow accumulation and melt rates. The greatest variability in the timing and rate of melt was found in the shrub tundra, where the effect of the shrub canopy over snow depends on snow depth and insolation and is reduced in years with high snow accumulation or extensive cloudy periods in spring. The results show that it is necessary to consider the combination of elevation and vegetation effects on snow microclimate and melt processes in high latitude mountain catchments, but that weather patterns induce substantial variability on the effect these factors.

Application of an online ion-chromatography-based instrument for gradient flux measurements of speciated nitrogen and sulfur

NASA Astrophysics Data System (ADS)

Rumsey, Ian C.; Walker, John T.

2016-06-01

The dry component of total nitrogen and sulfur atmospheric deposition remains uncertain. The lack of measurements of sufficient chemical speciation and temporal extent make it difficult to develop accurate mass budgets and sufficient process level detail is not available to improve current air-surface exchange models. Over the past decade, significant advances have been made in the development of continuous air sampling measurement techniques, resulting with instruments of sufficient sensitivity and temporal resolution to directly quantify air-surface exchange of nitrogen and sulfur compounds. However, their applicability is generally restricted to only one or a few of the compounds within the deposition budget. Here, the performance of the Monitor for AeRosols and GAses in ambient air (MARGA 2S), a commercially available online ion-chromatography-based analyzer is characterized for the first time as applied for air-surface exchange measurements of HNO3, NH3, NH4+, NO3-, SO2 and SO42-. Analytical accuracy and precision are assessed under field conditions. Chemical concentrations gradient precision are determined at the same sampling site. Flux uncertainty measured by the aerodynamic gradient method is determined for a representative 3-week period in fall 2012 over a grass field. Analytical precision and chemical concentration gradient precision were found to compare favorably in comparison to previous studies. During the 3-week period, percentages of hourly chemical concentration gradients greater than the corresponding chemical concentration gradient detection limit were 86, 42, 82, 73, 74 and 69 % for NH3, NH4+, HNO3, NO3-, SO2 and SO42-, respectively. As expected, percentages were lowest for aerosol species, owing to their relatively low deposition velocities and correspondingly smaller gradients relative to gas phase species. Relative hourly median flux uncertainties were 31, 121, 42, 43, 67 and 56 % for NH3, NH4+, HNO3, NO3-, SO2 and SO42-, respectively. Flux uncertainty is dominated by uncertainty in the chemical concentrations gradients during the day but uncertainty in the chemical concentration gradients and transfer velocity are of the same order at night. Results show the instrument is sufficiently precise for flux gradient applications.

Mapping Topoclimate and Microclimate in the Monarch Butterfly Biosphere Reserve, Mexico

NASA Astrophysics Data System (ADS)

Weiss, S. B.

2006-12-01

Overwintering monarch butterflies in Mexico select areas of the high elevation Oyamel fir -pine forest providing a canopy that protects them from extremes of cold, heat, sun, and wind. These exacting microclimatic conditions are found in relatively small areas of forest with appropriate topography and canopy cover. The major goal of this investigation is to map topoclimatic and microclimatic conditions within the Monarch Butterfly Biosphere Reserve by combining temperature monitoring (iButton Thermochrons), hemispherical canopy photography, multiple regression, and GIS modeling. Temperature measurements included base weather stations and arrays of Thermochrons (on the north-side of trees at 2m height) across local topographic and canopy cover gradients. Topoclimatic models of minimum temperatures included topographic position, slope, and elevation, and predicted that thermal belts on slopes and cold air drainage into canyons create local minimum temperature gradients of 2°C. Topoclimatic models of maximum temperatures models included elevation, topographic position, and relative solar exposure, with local gradients of 3°C. These models, which are independent of forest canopy structure, were then projected across the entire region. Forest canopy structure, including direct and diffuse solar radiation, was assessed with hemispherical photography at each Thermochron site. Canopy cover affected minimum temperatures primarily on the calmest, coldest nights. Maximum temperatures were predicted by direct radiation below the canopy. Fine- scale grids (25 m spacing) at three overwintering sites characterized effects of canopy gaps and edges on temperature and wind exposure. The effects of temperature variation were considered for lipid loss rates, ability to take flight, and freezing mortality. Lipid loss rates were estimated by measured hourly temperatures. Many of the closed canopy sites allowed for substantial lipid reserves at the end of the season (March 15), but increases in average temperature could effectively deplete lipids by that time. The large influence of canopy cover on daytime maximum temperatures demonstrates that forest thinning directly reduces habitat suitability. Monarchs' flight behavior under warmer conditions suggests that daytime temperatures drive the dynamics of monarch distribution within colonies. Thinning also decreases nighttime minimum temperatures, and increases wind exposure. These results create a basis for quantitative understanding of the combinations of topography and forest structure that provide high quality overwintering habitat.

Atmospheric composition and micro-climate in the Alhambra monument, Granada (Spain), in the context of preventive conservation

NASA Astrophysics Data System (ADS)

Horemans, B.; Schalm, O.; De Wael, K.; Cardell, C.; Van Grieken, R.

2012-07-01

The world famous Alhambra monument in Granada, Southern Spain, listed as UNESCO world cultural heritage since 1984, represents probably the most beautiful example of Islamic art and architecture from the Middle Ages in Europe. It is visited by ca. 2 million people annually. Granada is situated in a natural basin, surrounded by mountains with altitudes up to 3500 m. Due to this topography and the prevailing low wind speeds, pollution-derived and especially traffic-derived particulate matter often accumulates in the urban air. In order to evaluate the potential conservation risks from the surrounding air, the atmospheric composition in the Alhambra monument was evaluated. Indoor temperature and relative humidity fluctuations were evaluated for their potential degenerative effects. Furthermore, the atmospheric composition in the Alhambra was analyzed in terms of inorganic gases (NO2, SO2, O3, and NH3) and black carbon. It was found that the open architecture protected the indoor environments from developing a potentially harmful microclimate, such as the build-up of humidity resulting from the huge number of daily tourists. On the downside, the strong ventilation made the indoor air hardly different from outdoor air, as characterized by strong diurnal temperature and relative humidity gradients and high traffic-derived pollutant levels.

Response of Soft Continuous Structures and Topological Defects to a Temperature Gradient.

PubMed

Kurita, Rei; Mitsui, Shun; Tanaka, Hajime

2017-09-08

Thermophoresis, which is mass transport induced by a temperature gradient, has recently attracted considerable attention as a new way to transport materials. So far the study has been focused on the transport of discrete structures such as colloidal particles, proteins, and polymers in solutions. However, the response of soft continuous structures such as membranes and gels to a temperature gradient has been largely unexplored. Here we study the behavior of a lamellar phase made of stacked surfactant bilayer membranes under a temperature gradient. We find the migration of membranes towards a low-temperature region, causing the increase in the degree of membrane undulation fluctuations towards that direction. This is contrary to our intuition that the fluctuations are weaker at a lower temperature. We show that this can be explained by temperature-gradient-induced migration of membranes under the topological constraint coming from the connectivity of each membrane. We also reveal that the pattern of an edge dislocation array formed in a wedge-shaped cell can be controlled by a temperature gradient. These findings suggest that application of a temperature gradient provides a novel way to control the organization of soft continuous structures such as membranes, gels, and foams, in a manner essentially different from the other types of fields, and to manipulate topological defects.

Geologic and geophysical data for wells drilled at Raft River Valley, Cassia County, Idaho, in 1977-1978 and data for wells drilled previously

USGS Publications Warehouse

Nathenson, Manuel; Urban, Thomas C.; Covington, Harry R.

2014-01-01

For purposes of defining the thermal anomaly for the geothermal system, temperature gradients are calculated over long depth intervals on the basis of the appearance of reasonable linear segments on a temperature versus plot depth.  Temperature versus depth data for some drill holes can be represented by a single gradient, whereas others require multiple gradients to match the data.  Data for some drill holes clearly reflect vertical flows of water in the formation surrounding the drill holes, and water velocities are calculated for these drill holes.  Within The Narrows area, temperature versus depth data show reversals at different depth in different drill holes.  In the main thermal area, temperatures in intermediate-depth drill holes vary approximately linearly but with very high values of temperature gradient.  Temperature gradients on a map of the area can be reasonable divided into a large area of regional gradients and smaller areas defining the thermal anomalies.

The Effect of Temperature on Moisture Transport in Concrete.

PubMed

Wang, Yao; Xi, Yunping

2017-08-09

Most concrete structures and buildings are under temperature and moisture variations simultaneously. Thus, the moisture transport in concrete is driven by the moisture gradient as well as the temperature gradient. This paper presents an experimental approach for determining the effect of different temperature gradients on moisture distribution profiles in concrete. The effect of elevated temperatures under isothermal conditions on the moisture transport was also evaluated, and found not to be significant. The non-isothermal tests show that the temperature gradient accelerates the moisture transport in concrete. The part of increased moisture transfer due to the temperature gradient can be quantified by a coupling parameter D HT , which can be determined by the present test data. The test results indicated that D HT is not a constant but increases linearly with the temperature variation. A material model was developed for D HT based on the experimental results obtained in this study.

The Effect of Temperature on Moisture Transport in Concrete

PubMed Central

Wang, Yao; Xi, Yunping

2017-01-01

Most concrete structures and buildings are under temperature and moisture variations simultaneously. Thus, the moisture transport in concrete is driven by the moisture gradient as well as the temperature gradient. This paper presents an experimental approach for determining the effect of different temperature gradients on moisture distribution profiles in concrete. The effect of elevated temperatures under isothermal conditions on the moisture transport was also evaluated, and found not to be significant. The non-isothermal tests show that the temperature gradient accelerates the moisture transport in concrete. The part of increased moisture transfer due to the temperature gradient can be quantified by a coupling parameter DHT, which can be determined by the present test data. The test results indicated that DHT is not a constant but increases linearly with the temperature variation. A material model was developed for DHT based on the experimental results obtained in this study. PMID:28792460

Glass/ceramic coatings for implants

DOEpatents

Tomsia, Antoni P [Pinole, CA; Saiz, Eduardo [Berkeley, CA; Gomez-Vega, Jose M [Nagoya, JP; Marshall, Sally J [Larkspur, CA; Marshall, Grayson W [Larkspur, CA

2011-09-06

Glass coatings on metals including Ti, Ti6A14V and CrCo were prepared for use as implants. The composition of the glasses was tailored to match the thermal expansion of the substrate metal. By controlling the firing atmosphere, time, and temperature, it was possible to control the reactivity between the glass and the alloy and to fabricate coatings (25-150 .mu.m thick) with excellent adhesion to the substrate. The optimum firing temperatures ranged between 800 and 840.degree. C. at times up to 1 min in air or 15 min in N.sub.2. The same basic technique was used to create multilayered coatings with concentration gradients of hydroxyapatite (HA) particles and SiO.sub.2.

Analysis of the intraocular jet flows and pressure gradients induced by air and fluid infusion: mechanism of focal chorioretinal damage.

PubMed

Kim, Yong Joon; Jo, Sungkil; Moon, Daruchi; Joo, Youngcheol; Choi, Kyung Seek

2014-05-01

To comprehend the mechanism of focal chorioretinal damage by analysis of the pressure distribution and dynamic pressure induced by infused air during fluid-air exchange. A precise simulation featuring a model eye and a fluid circuit was designed to analyze fluid-air exchange. The pressure distribution, flow velocity, and dynamic pressure induced by infusion of air into an air-filled eye were analyzed using an approach based on fluid dynamics. The size of the port and the infusion pressure were varied during simulated iterations. We simulated infusion of an air-filled eye with balanced salt solution (BSS) to better understand the mechanism of chorioretinal damage induced by infused air. Infused air was projected straight toward a point on the retina contralateral to the infusion port (the "vulnerable point"). The highest pressure was evident at the vulnerable point, and the lowest pressure was recorded on most retinal areas. Simulations using greater infusion pressure and a port of larger size were associated with elevations in dynamic pressure and the pressure gradient. The pressure gradients were 2.8 and 5.1 mm Hg, respectively, when infusion pressures of 30 and 50 mm Hg were delivered through a 20-gauge port. The pressure gradient associated with BSS infusion was greater than that created by air, but lasted for only a moment. Our simulation explains the mechanism of focal chorioretinal damage in numerical terms. Infused air induces a prolonged increase in focal pressure on the vulnerable point, and this may be responsible for visual field defects arising after fluid-air exchange. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Temperature Gradients on the Cell Wall in the Critical Viscosity Experiment

NASA Technical Reports Server (NTRS)

Berg, Robert F.; Moldover, Michael R.

1993-01-01

Because of the diverging susceptibility delta rho/delta Tau near the liquid-vapor critical point, temperature gradients must be kept small to maintain adequate sample homogeneity. In our Science Requirements Document we paid particular attention to radial density gradients caused by equilibration of the xenon sample. Axial density gradients were addressed through the requirement that the cell's copper wall have a gradient less than 22 microK/m. This report re-examines the cell wall's temperature distribution in more detail by estimating all known significant contributions to temperature differences on the cell's wall.

The structure of the stably stratified internal boundary layer in offshore flow over the sea

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Ryan, B. F.

1989-04-01

Observations obtained mainly from a research aircraft are presented of the mean and turbulent structure of the stably stratified internal boundary layer (IBL) over the sea formed by warm air advection from land to sea. The potential temperature and humidity fields reveal the vertical extent of the IBL, for fetches out to several hundred of kilometres, geostrophic winds of 20 25 m s-1, and potential temperature differences between undisturbed continental air and the sea surface of 7 to 17 K. The dependence of IBL depth on these external parameters is discussed in the context of the numerical results of Garratt (1987), and some discrepancies are noted. Wind observations show the development of a low-level wind maximum (wind component normal to the coast) and rotation of the wind to smaller cross-isobar flow angles. Potential temperature (θ) profiles within the IBL reveal quite a different structure to that found in the nocturnal boundary layer (NBL) over land. Over the sea, θ profiles have large positive curvature with vertical gradients increasing monotonically with height; this reflects the dominance of turbulent cooling within the layer. The behaviour is consistent with known behaviour in the NBL over land where curvature becomes negative (vertical gradients of θ decreasing with height) as radiative cooling becomes dominant. Turbulent properties are discussed in terms of non-dimensional quantities, normalised by the surface friction velocity, as functions of normalised height using the IBL depth. Vertical profiles of these and the normalised wavelength of the spectral maximum agree well with known results for the stable boundary layer over land (Caughey et al., 1979).

Tripolar vortex formation in dense quantum plasma with ion-temperature-gradients

NASA Astrophysics Data System (ADS)

Qamar, Anisa; Ata-ur-Rahman, Mirza, Arshad M.

2012-05-01

We have derived system of nonlinear equations governing the dynamics of low-frequency electrostatic toroidal ion-temperature-gradient mode for dense quantum magnetoplasma. For some specific profiles of the equilibrium density, temperature, and ion velocity gradients, the nonlinear equations admit a stationary solution in the form of a tripolar vortex. These results are relevant to understand nonlinear structure formation in dense quantum plasmas in the presence of equilibrium ion-temperature and density gradients.

Impacts of interactive dust and its direct radiative forcing on interannual variations of temperature and precipitation in winter over East Asia: Impacts of Dust on IAVs of Temperature

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

Lou, Sijia; Russell, Lynn M.; Yang, Yang

We used 150-year pre-industrial simulations of the Community Earth System Model (CESM) to quantify the impacts of interactively-modeled dust emissions on the interannual variations of temperature and precipitation over East Asia during the East Asian Winter Monsoon (EAWM) season. The simulated December-January-February dust column burden and dust optical depth are lower over northern China in the strongest EAWM years than those of the weakest years, with regional mean values lower by 38.3% and 37.2%, respectively. The decrease in dust over the dust source regions (the Taklamakan and Gobi Deserts) and the downwind region (such as the North China Plain) leadsmore » to an increase in direct radiative forcing (RF) both at the surface and top of atmosphere by up to 1.5 and 0.75 W m-2, respectively. The effects of EAWM-related variations in surface winds, precipitation and their effects on dust emissions and wet removal contribute about 67% to the total dust-induced variations of direct RF at the surface and partly offset the cooling that occurs with the EAWM strengthening by heating the surface. The variations of surface air temperature induced by the changes in wind and dust emissions increase by 0.4-0.6 K over eastern coastal China, northeastern China, and Japan, which weakens the impact of EAWM on surface air temperature by 3–18% in these regions. The warming results from the combined effects of changes in direct RF and easterly wind anomalies that bring warm air from the ocean to these regions. Moreover, the feedback of the changes in wind on dust emissions weakens the variations of the sea level pressure gradient on the Siberian High while enhancing the Maritime Continent Low. Therefore, cold air is prevented from being transported from Siberia, Kazakhstan, western and central China to the western Pacific Ocean and decreases surface air temperature by 0.6 K and 2 K over central China and the Tibetan Plateau, respectively. Over eastern coastal China, the variations of large-scale precipitation induced by the feedback of EAWM-related changes in wind on dust emissions increase by 10-30% in winter because of the increase in surface air temperature and the anomalous circulation.« less

North Pacific Cloud Feedbacks Inferred from Synoptic-Scale Dynamic and Thermodynamic Relationships

NASA Technical Reports Server (NTRS)

Norris, Joel R.; Iacobellis, Sam F.

2005-01-01

This study analyzed daily satellite cloud observations and reanalysis dynamical parameters to determine how mid-tropospheric vertical velocity and advection over the sea surface temperature gradient control midlatitude North Pacific cloud properties. Optically thick clouds with high tops are generated by synoptic ascent, but two different cloud regimes occur under synoptic descent. When vertical motion is downward during summer, extensive stratocumulus cloudiness is associated with near surface northerly wind, while frequent cloudless pixels occur with southerly wind. Examinations of ship-reported cloud types indicates that midlatitude stratocumulus breaks up as the the boundary level decouples when it is advected equatorward over warmer water. Cumulus is prevalent under conditions of synoptic descent and cold advection during winter. Poleward advection of subtropical air over colder water causes stratification of the near-surface layer that inhibits upward mixing of moisture and suppresses cloudiness until a fog eventually forms. Averaging of cloud and radiation data into intervals of 500-hPa vertical velocity and advection over the SST gradient enables the cloud response to changes in temperature and the stratification of the lower troposphere to be investigated independent of the dynamics.

Femtosecond laser filament induced condensation and precipitation in a cloud chamber

PubMed Central

Ju, Jingjing; Liu, Jiansheng; Liang, Hong; Chen, Yu; Sun, Haiyi; Liu, Yonghong; Wang, Jingwei; Wang, Cheng; Wang, Tiejun; Li, Ruxin; Xu, Zhizhan; Chin, See Leang

2016-01-01

A unified picture of femtosecond laser induced precipitation in a cloud chamber is proposed. Among the three principal consequences of filamentation from the point of view of thermodynamics, namely, generation of chemicals, shock waves and thermal air flow motion (due to convection), the last one turns out to be the principal cause. Much of the filament induced chemicals would stick onto the existing background CCN’s (Cloud Condensation Nuclei) through collision making the latter more active. Strong mixing of air having a large temperature gradient would result in supersaturation in which the background CCN’s would grow efficiently into water/ice/snow. This conclusion was supported by two independent experiments using pure heating or a fan to imitate the laser-induced thermal effect or the strong air flow motion, respectively. Without the assistance of any shock wave and chemical CCN’s arising from laser filament, condensation and precipitation occurred. Meanwhile we believe that latent heat release during condensation /precipitation would enhance the air flow for mixing. PMID:27143227

Quasi-adiabatic vacuum-based column housing for very high-pressure liquid chromatography.

PubMed

Gritti, Fabrice; Gilar, Martin; Jarrell, Joseph A

2016-07-22

A prototype vacuum-based (10(-6)Torr) column housing was built to thermally isolate the chromatographic column from the external air environment. The heat transfer mechanism is solely controlled by surface radiation, which was minimized by wrapping the column with low-emissivity aluminum tape. The adiabaticity of the column housing was quantitatively assessed from the measurement of the operational pressure and fluid temperature at the outlet of a 2.1mm×100mm column (sub-2 μm particles). The pressure drop along the column was raised up to 1kbar. The enthalpy balance of the eluent (water, acetonitrile, and one water/acetonitrile mixture, 70/30, v/v) showed that less than 1% of the viscous heat generated by friction of the fluid against the packed bed was lost to the external air environment. Such a vacuum-based column oven minimizes the amplitude of the radial temperature gradients across the column diameter and maximizes its resolving power. Copyright © 2016 Elsevier B.V. All rights reserved.

Proteins at the air-water interface in a lattice model

NASA Astrophysics Data System (ADS)

Zhao, Yani; Cieplak, Marek

2018-03-01

We construct a lattice protein version of the hydrophobic-polar model to study the effects of the air-water interface on the protein and on an interfacial layer formed through aggregation of many proteins. The basic unit of the model is a 14-mer that is known to have a unique ground state in three dimensions. The equilibrium and kinetic properties of the systems with and without the interface are studied through a Monte Carlo process. We find that the proteins at high dilution can be pinned and depinned many times from the air-water interface. When pinned, the proteins undergo deformation. The staying time depends on the strength of the coupling to the interface. For dense protein systems, we observe glassy effects. Thus, the lattice model yields results which are similar to those obtained through molecular dynamics in off-lattice models. In addition, we study dynamical effects induced by local temperature gradients in protein films.

NASA satellite helps airliners avoid ozone concentrations

NASA Technical Reports Server (NTRS)

1981-01-01

Results from a test to determine the effectiveness of satellite data for helping airlines avoid heavy concentrations of ozone are reported. Information from the Total Ozone Mapping Spectrometer, aboard the Nimbus-7 was transmitted, for use in meteorological forecast activities. The results show: (1) Total Ozone Mapping Spectrometer profile of total ozone in the atmosphere accurately represents upper air patterns and can be used to locate meteorological activity; (2) route forecasting of highly concentrated ozone is feasible; (3) five research aircraft flights were flown in jet stream regions located by the Total Ozone Mapping Spectrometer to determine winds, temperatures, and air composition. It is shown that the jet stream is coincides with the area of highest total ozone gradient, and low total ozone amounts are found where tropospheric air has been carried along above the tropopause on the anticyclonic side of the subtropical jet stream.

[Life support of the Mars exploration crew. Control of a zeolite system for carbon dioxide removal from space cabin air within a closed air regeneration cycle].

PubMed

Chekov, Iu F

2009-01-01

The author describes a zeolite system for carbon dioxide removal integrated into a closed air regeneration cycle aboard spacecraft. The continuous operation of a double-adsorbent regeneration system with pCO2-dependable productivity is maintained through programmable setting of adsorption (desorption) semicycle time. The optimal system regulation curve is presented within the space of statistical performance family obtained in quasi-steady operating modes with controlled parameters of the recurrent adsorption-desorption cycle. The automatically changing system productivity ensures continuous intake of concentrated CO2. Control of the adsorption-desorption process is based on calculation of the differential adsorption (desorption) heat from gradient of adsorbent and test inert substance temperatures. The adaptive algorithm of digital control is implemented through the standard spacecraft interface with the board computer system and programmable microprocessor-based controllers.

Investigation of Zircaloy-2 oxidation model for SFP accident analysis

NASA Astrophysics Data System (ADS)

Nemoto, Yoshiyuki; Kaji, Yoshiyuki; Ogawa, Chihiro; Kondo, Keietsu; Nakashima, Kazuo; Kanazawa, Toru; Tojo, Masayuki

2017-05-01

The authors previously conducted thermogravimetric analyses on Zircaloy-2 in air. By using the thermogravimetric data, an oxidation model was constructed in this study so that it can be applied for the modeling of cladding degradation in spent fuel pool (SFP) severe accident condition. For its validation, oxidation tests of long cladding tube were conducted, and computational fluid dynamics analyses using the constructed oxidation model were proceeded to simulate the experiments. In the oxidation tests, high temperature thermal gradient along the cladding axis was applied and air flow rates in testing chamber were controlled to simulate hypothetical SFP accidents. The analytical outputs successfully reproduced the growth of oxide film and porous oxide layer on the claddings in oxidation tests, and validity of the oxidation model was proved. Influence of air flow rate for the oxidation behavior was thought negligible in the conditions investigated in this study.

Separating temperature from other factors in phenological measurements

NASA Astrophysics Data System (ADS)

Schwartz, Mark D.; Hanes, Jonathan M.; Liang, Liang

2014-09-01

Phenological observations offer a simple and effective way to measure climate change effects on the biosphere. While some species in northern mixed forests show a highly sensitive site preference to microenvironmental differences (i.e., the species is present in certain areas and absent in others), others with a more plastic environmental response (e.g., Acer saccharum, sugar maple) allow provisional separation of the universal "background" phenological variation caused by in situ (possibly biological/genetic) variation from the microclimatic gradients in air temperature. Moran's I tests for spatial autocorrelation among the phenological data showed significant ( α ≤ 0.05) clustering across the study area, but random patterns within the microclimates themselves, with isolated exceptions. In other words, the presence of microclimates throughout the study area generally results in spatial autocorrelation because they impact the overall phenological development of sugar maple trees. However, within each microclimate (where temperature conditions are relatively uniform) there is little or no spatial autocorrelation because phenological differences are due largely to randomly distributed in situ factors. The phenological responses from 2008 and 2009 for two sugar maple phenological stages showed the relationship between air temperature degree-hour departure and phenological change ranged from 0.5 to 1.2 days earlier for each additional 100 degree-hours. Further, the standard deviations of phenological event dates within individual microclimates (for specific events and years) ranged from 2.6 to 3.8 days. Thus, that range of days is inferred to be the "background" phenological variation caused by factors other than air temperature variations, such as genetic differences between individuals.

Design and proof of concept of an innovative very high temperature ceramic solar absorber

NASA Astrophysics Data System (ADS)

Leray, Cédric; Ferriere, Alain; Toutant, Adrien; Olalde, Gabriel; Peroy, Jean-Yves; Chéreau, Patrick; Ferrato, Marc

2017-06-01

Hybrid solar gas-turbine (HSGT) is an attractive technology to foster market penetration of CSP. HSGT offers some major advantages like for example high solar-to-electric conversion efficiency, reduced water requirement and low capital cost. A very high temperature solar receiver is needed when elevated solar share is claimed. A few research works, as reported by Karni et al. [8] and by Buck et al. [1], have been dedicated to solar receiver technologies able to deliver pressurized air at temperature above 750°C. The present work focuses on research aiming at developing an efficient and reliable solar absorber able to provide pressurized air at temperature up to 1000°C and more. A surface absorber technology is selected and a modular design of receiver is proposed in which each absorber module is made of BOOSTEC® SiC ceramic (silicon carbide) as bulk material with straight air channels inside. Early stage experimental works done at CNRS/PROMES on lab-scale absorbers showed that the thermo-mechanical behavior of this material is a critical issue, resulting in elevated probability of failure under severe conditions like large temperature gradient or steep variation of solar flux density in situations of cloud covering. This paper reports on recent progress made at CNRS/PROMES to address this critical issue. The design of the absorber has been revised and optimized according to thermo-mechanical numerical simulations, and an experimental proof of concept has been done on a pilot-scale absorber module at Themis solar tower facility.

A general strategy for performing temperature-programming in high performance liquid chromatography--further improvements in the accuracy of retention time predictions of segmented temperature gradients.

PubMed

Wiese, Steffen; Teutenberg, Thorsten; Schmidt, Torsten C

2012-01-27

In the present work it is shown that the linear elution strength (LES) model which was adapted from temperature-programming gas chromatography (GC) can also be employed for systematic method development in high-temperature liquid chromatography (HT-HPLC). The ability to predict isothermal retention times based on temperature-gradient as well as isothermal input data was investigated. For a small temperature interval of ΔT=40°C, both approaches result in very similar predictions. Average relative errors of predicted retention times of 2.7% and 1.9% were observed for simulations based on isothermal and temperature-gradient measurements, respectively. Concurrently, it was investigated whether the accuracy of retention time predictions of segmented temperature gradients can be further improved by temperature dependent calculation of the parameter S(T) of the LES relationship. It was found that the accuracy of retention time predictions of multi-step temperature gradients can be improved to around 1.5%, if S(T) was also calculated temperature dependent. The adjusted experimental design making use of four temperature-gradient measurements was applied for systematic method development of selected food additives by high-temperature liquid chromatography. Method development was performed within a temperature interval from 40°C to 180°C using water as mobile phase. Two separation methods were established where selected food additives were baseline separated. In addition, a good agreement between simulation and experiment was observed, because an average relative error of predicted retention times of complex segmented temperature gradients less than 5% was observed. Finally, a schedule of recommendations to assist the practitioner during systematic method development in high-temperature liquid chromatography was established. Copyright © 2011 Elsevier B.V. All rights reserved.

The temperature signature of an IMF-driven change to the global atmospheric electric circuit (GEC) in the Antarctic troposphere

NASA Astrophysics Data System (ADS)

Freeman, Mervyn; Lam, Mai Mai; Chisham, Gareth

2017-04-01

We use National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data to show that Antarctic surface air temperature anomalies result from differences in the daily-mean duskward component,By, of the interplanetary magnetic field (IMF). We find the anomalies have strong geographical and seasonal variations. Regional anomalies are evident poleward of 60˚ S and are of diminishing representative peak amplitude from autumn (3.2˚ C) to winter (2.4˚ C) to spring (1.6˚ C) to summer (0.9˚ C). We demonstrate that anomalies of statistically-significant amplitude are due to geostrophic wind anomalies, resulting from the same By changes, moving air across large meridional gradients in zonal mean air temperature between 60 and 80˚ S. Additionally, we find that the mean tropospheric temperature anomaly for geographical latitudes ≤ -70˚ peaks at about 0.7 K and is statistically significant at the 1 - 5% level between air pressures of 1000 and 500 hPa (i.e., ˜0.1 to 5.6 km altitude above sea level) and for time lags with respect to the IMF of up to 7 days. The signature propagates vertically between air pressure p ≥ 850 hPa (≤ 1.5 km) and p = 500 hPa (˜5.6 km). The characteristics of prompt response and vertical propagation within the troposphere have previously been seen in the correlation between the IMF and high-latitude air pressure anomalies, known as the Mansurov effect, at higher statistical significances (1%). We conclude that we have identified the temperature signature of the Mansurov effect in the Antarctic troposphere. Since these tropospheric anomalies have been associated with By-driven anomalies in the electric potential of the ionosphere, we further conclude that they are caused by IMF-induced changes to the global atmospheric electric circuit (GEC). Our results support the view that variations in the ionospheric potential act on the troposphere via the action of resulting variations in the downwards current of the GEC on tropospheric clouds.

Subsurface temperatures and geothermal gradients on the North Slope, Alaska

USGS Publications Warehouse

Collett, Timothy S.; Bird, Kenneth J.; Magoon, Leslie B.

1989-01-01

Geothermal gradients as interpreted from a series of high-resolution stabilized well-bore-temperature surveys from 46 North Slope, Alaska, wells vary laterally and vertically throughout the near-surface sediment (0-2,000 m). The data from these surveys have been used in conjunction with depths of ice-bearing permafrost, as interpreted from 102 well logs, to project geothermal gradients within and below the ice-bearing permafrost sequence. The geothermal gradients calculated from the projected temperature profiles are similar to the geothermal gradients measured in the temperature surveys. Measured and projected geothermal gradients in the ice-bearing permafrost sequence range from 1.5??C/100m in the Prudhoe Bay area to 5.1??C/100m in the National Petroleum Reserve in Alaska (NPRA).

Ultraflexible, large-area, physiological temperature sensors for multipoint measurements

PubMed Central

Yokota, Tomoyuki; Inoue, Yusuke; Terakawa, Yuki; Reeder, Jonathan; Kaltenbrunner, Martin; Ware, Taylor; Yang, Kejia; Mabuchi, Kunihiko; Murakawa, Tomohiro; Sekino, Masaki; Voit, Walter; Sekitani, Tsuyoshi; Someya, Takao

2015-01-01

We report a fabrication method for flexible and printable thermal sensors based on composites of semicrystalline acrylate polymers and graphite with a high sensitivity of 20 mK and a high-speed response time of less than 100 ms. These devices exhibit large resistance changes near body temperature under physiological conditions with high repeatability (1,800 times). Device performance is largely unaffected by bending to radii below 700 µm, which allows for conformal application to the surface of living tissue. The sensing temperature can be tuned between 25 °C and 50 °C, which covers all relevant physiological temperatures. Furthermore, we demonstrate flexible active-matrix thermal sensors which can resolve spatial temperature gradients over a large area. With this flexible ultrasensitive temperature sensor we succeeded in the in vivo measurement of cyclic temperatures changes of 0.1 °C in a rat lung during breathing, without interference from constant tissue motion. This result conclusively shows that the lung of a warm-blooded animal maintains surprising temperature stability despite the large difference between core temperature and inhaled air temperature. PMID:26554008

Ultraflexible, large-area, physiological temperature sensors for multipoint measurements.

PubMed

Yokota, Tomoyuki; Inoue, Yusuke; Terakawa, Yuki; Reeder, Jonathan; Kaltenbrunner, Martin; Ware, Taylor; Yang, Kejia; Mabuchi, Kunihiko; Murakawa, Tomohiro; Sekino, Masaki; Voit, Walter; Sekitani, Tsuyoshi; Someya, Takao

2015-11-24

We report a fabrication method for flexible and printable thermal sensors based on composites of semicrystalline acrylate polymers and graphite with a high sensitivity of 20 mK and a high-speed response time of less than 100 ms. These devices exhibit large resistance changes near body temperature under physiological conditions with high repeatability (1,800 times). Device performance is largely unaffected by bending to radii below 700 µm, which allows for conformal application to the surface of living tissue. The sensing temperature can be tuned between 25 °C and 50 °C, which covers all relevant physiological temperatures. Furthermore, we demonstrate flexible active-matrix thermal sensors which can resolve spatial temperature gradients over a large area. With this flexible ultrasensitive temperature sensor we succeeded in the in vivo measurement of cyclic temperatures changes of 0.1 °C in a rat lung during breathing, without interference from constant tissue motion. This result conclusively shows that the lung of a warm-blooded animal maintains surprising temperature stability despite the large difference between core temperature and inhaled air temperature.

Thermal Gradient Fining of Glass

NASA Technical Reports Server (NTRS)

Wilcox, W.

1983-01-01

Molten glass fined (cleared of bubbles) by heating with suitable temperature gradient, according to preliminary experiments. Temperature gradient produces force on gas bubbles trapped in molten glass pushing bubbles to higher temperature region where they are collected. Concept demonstrated in experiments on Earth and on rocket.

Biocompatible patterning of proteins on wettability gradient surface by thermo-transfer printing.

PubMed

Kim, Sungho; Ryu, Yong-Sang; Suh, Jeng-Hun; Keum, Chang-Min; Sohn, Youngjoo; Lee, Sin-Doo

2014-08-01

We develop a simple and biocompatible method of patterning proteins on a wettability gradient surface by thermo-transfer printing. The wettability gradient is produced on a poly(dimethylsiloxane) (PDMS)-modified glass substrate through the temperature gradient during thermo-transfer printing. The water contact angle on the PDMS-modified surface is found to gradually increase along the direction of the temperature gradient from a low to a high temperature region. Based on the wettability gradient, the gradual change in the adsorption and immobilization of proteins (cholera toxin B subunit) is achieved in a microfluidic cell with the PDMS-modified surface.

Hot and cold body reference noise generators from 0 to 40 GHz

NASA Technical Reports Server (NTRS)

Hornbostel, D. H.

1974-01-01

This article describes the design, development, and analysis of exceptionally accurate radiometric noise generators from 0-40 GHz to serve as standard references. Size, weight, power, and reliability are optimized to meet the requirements of NASA air- and space-borne radiometers. The radiometric noise temperature of these noise generators is, unavoidably, calculated from measured values rather than measured directly. The absolute accuracy and stability are equal to or better than those of reliable standards available for comparison. A noise generator has been developed whose measurable properties (VSWR, line loss, thermometric temperatures) have been optimized in order to minimize the effects of the uncertainty in the calculated radiometric noise temperatures. Each measurable property is evaluated and analyzed to determine the effects of the uncertainty of the measured value. Unmeasurable properties (primarily temperature gradients) are analyzed, and reasonable precautions are designed into the noise generator to guarantee that the uncertainty of the value remains within tolerable limits.

[Effect of temperature on performance of microbial fuel cell using beer wastewater].

PubMed

Wang, Xin; Feng, Yu-Jie; Qu, You-Peng; Li, Dong-Mei; Li, He; Ren, Nan-Qi

2008-11-01

The effects of temperature on performance and biological community structure were investigated in air-cathode microbial fuel cells (MFCs) using beer wastewater amended with 50 mmol/L phosphate buffer solution (PBS). The maximum power density decreased from 483 mW/m2 to 435 mW/m2 when the temperature varied from 30 degrees C to 20 degrees C, meanwhile just a little decreasing on coulombic efficiency and the COD removal rate were observed. Decreasing of temperature resulted in effects both on cathode potential and anode potential, but cathode potential behaved much more sensitive to temperature. The half-saturation constants (Ks) obtained from the fit of Monod-type equation were 228 mg/L (30 degrees C) and 293 mg/L (20 degrees C) respectively. Denaturing gradient gel electrophoresis (DGGE) analysis indicated that operating temperature not only affected the predominant population of the anodic bacterial community, but also had a great impact on the diversity of the cathodic microbial population.

The Meteorological Stations of the 1.5 and 0.84 m Telescopes of the OAN: Description and Results

NASA Astrophysics Data System (ADS)

Michel, R.; Bohigas, J.; Arroyo, E.; Zazueta, S.

2001-10-01

Meteorological stations for the 1.5 and 0.84 m telescopes at the Observatorio Astronómico Nacional at San Pedro Mártir (OAN) are described. The stations include devices for measuring temperature, atmospheric pressure, relative humidity and wind conditions. All the meteorological variables are monitored continuously and mean values are determined every 5 minutes and written on the hard disk of the control computer. This information is continuously refreshed in an HTML page that can be accessed from the OAN home page. In this paper we present the results of measurements taken over 2 years. We find that both primary mirrors are substantially warmer than the surrounding air during the night (up to ~ 5oC). This thermal gradient degrades image quality. For the primary mirror of the 1.5 m telescope this effect can be corrected with a temperature control system. For the 0.84 m telescope, where the primary mirror is located in a closed structure, ventilators moving air from the dome into the closed tube may suffice. During the night the air is colder within both domes than outside, and we conclude that no dome ventilation is necessary in these telescopes.

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

43 CFR 3252.12 - How deep may I drill a temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How deep may I drill a temperature... RESOURCE LEASING Conducting Exploration Operations § 3252.12 How deep may I drill a temperature gradient well? (a) You may drill a temperature gradient well to any depth that we approve in your exploration...

Modeling assisted evaluation of direct electricity generation from waste heat of wastewater via a thermoelectric generator.

PubMed

Zou, Shiqiang; Kanimba, Eurydice; Diller, Thomas E; Tian, Zhiting; He, Zhen

2018-04-22

The thermal energy represents a significant portion of energy potential in municipal wastewater and may be recovered as electricity by a thermoelectric generator (TEG). Converting heat to all-purpose electricity by TEG has been demonstrated with large heat gradients, but its application in waste heat recovery from wastewater has not been well evaluated. Herein, a bench-scale Bi 2 Te 3 -based waste heat recovery system was employed to generate electricity from a low temperature gradient through a combination of experiments and mathematical modeling. With an external resistance of 7.8 Ω and a water (hot side) flow rate of 75 mL min -1 , a maximum normalized energy recovery of 4.5 × 10 -4  kWh m -3 was achieved under a 2.8 °C temperature gradient (ΔT). Model simulation indicated a boost in both power output and energy conversion efficiency from 0.76 mW and 0.13% at ΔT = 2.8 °C to 61.83 mW and 1.15% at ΔT = 25 °C. Based on the data of two-year water/air temperature obtained from the Christiansburg Wastewater Treatment Plant, an estimated energy generation of 1094 to 70,986 kWh could be expected annually with a saving of $163 to $6076. Those results have revealed a potential for TEG-centered direct electricity generation from low-grade heat towards enhanced resource recovery from wastewater and encouraged further exploration of this approach. Copyright © 2018. Published by Elsevier B.V.

A Mosaic of Geothermal and Marine Features Shapes Microbial Community Structure on Deception Island Volcano, Antarctica.

PubMed

Bendia, Amanda G; Signori, Camila N; Franco, Diego C; Duarte, Rubens T D; Bohannan, Brendan J M; Pellizari, Vivian H

2018-01-01

Active volcanoes in Antarctica contrast with their predominantly cold surroundings, resulting in environmental conditions capable of selecting for versatile and extremely diverse microbial communities. This is especially true on Deception Island, where geothermal, marine, and polar environments combine to create an extraordinary range of environmental conditions. Our main goal in this study was to understand how microbial community structure is shaped by gradients of temperature, salinity, and geochemistry in polar marine volcanoes. Thereby, we collected surface sediment samples associated with fumaroles and glaciers at two sites on Deception, with temperatures ranging from 0 to 98°C. Sequencing of the 16S rRNA gene was performed to assess the composition and diversity of Bacteria and Archaea. Our results revealed that Deception harbors a combination of taxonomic groups commonly found both in cold and geothermal environments of continental Antarctica, and also groups normally identified at deep and shallow-sea hydrothermal vents, such as hyperthermophilic archaea. We observed a clear separation in microbial community structure across environmental gradients, suggesting that microbial community structure is strongly niche driven on Deception. Bacterial community structure was significantly associated with temperature, pH, salinity, and chemical composition; in contrast, archaeal community structure was strongly associated only with temperature. Our work suggests that Deception represents a peculiar "open-air" laboratory to elucidate central questions regarding molecular adaptability, microbial evolution, and biogeography of extremophiles in polar regions.

Fully kinetic Biermann battery and associated generation of pressure anisotropy

NASA Astrophysics Data System (ADS)

Schoeffler, K. M.; Loureiro, N. F.; Silva, L. O.

2018-03-01

The dynamical evolution of a fully kinetic, collisionless system with imposed background density and temperature gradients is investigated analytically. The temperature gradient leads to the generation of temperature anisotropy, with the temperature along the gradient becoming larger than that in the direction perpendicular to it. This causes the system to become unstable to pressure anisotropy driven instabilities, dominantly to the electron Weibel instability. When both density and temperature gradients are present and nonparallel to each other, we obtain a Biermann-like linear-in-time magnetic field growth. Accompanying particle-in-cell numerical simulations are shown to confirm our analytical results.

Continuous measurement of air-water gas exchange by underwater eddy covariance

NASA Astrophysics Data System (ADS)

Berg, Peter; Pace, Michael L.

2017-12-01

Exchange of gases, such as O2, CO2, and CH4, over the air-water interface is an important component in aquatic ecosystem studies, but exchange rates are typically measured or estimated with substantial uncertainties. This diminishes the precision of common ecosystem assessments associated with gas exchanges such as primary production, respiration, and greenhouse gas emission. Here, we used the aquatic eddy covariance technique - originally developed for benthic O2 flux measurements - right below the air-water interface (˜ 4 cm) to determine gas exchange rates and coefficients. Using an acoustic Doppler velocimeter and a fast-responding dual O2-temperature sensor mounted on a floating platform the 3-D water velocity, O2 concentration, and temperature were measured at high-speed (64 Hz). By combining these data, concurrent vertical fluxes of O2 and heat across the air-water interface were derived, and gas exchange coefficients were calculated from the former. Proof-of-concept deployments at different river sites gave standard gas exchange coefficients (k600) in the range of published values. A 40 h long deployment revealed a distinct diurnal pattern in air-water exchange of O2 that was controlled largely by physical processes (e.g., diurnal variations in air temperature and associated air-water heat fluxes) and not by biological activity (primary production and respiration). This physical control of gas exchange can be prevalent in lotic systems and adds uncertainty to assessments of biological activity that are based on measured water column O2 concentration changes. For example, in the 40 h deployment, there was near-constant river flow and insignificant winds - two main drivers of lotic gas exchange - but we found gas exchange coefficients that varied by several fold. This was presumably caused by the formation and erosion of vertical temperature-density gradients in the surface water driven by the heat flux into or out of the river that affected the turbulent mixing. This effect is unaccounted for in widely used empirical correlations for gas exchange coefficients and is another source of uncertainty in gas exchange estimates. The aquatic eddy covariance technique allows studies of air-water gas exchange processes and their controls at an unparalleled level of detail. A finding related to the new approach is that heat fluxes at the air-water interface can, contrary to those typically found in the benthic environment, be substantial and require correction of O2 sensor readings using high-speed parallel temperature measurements. Fast-responding O2 sensors are inherently sensitive to temperature changes, and if this correction is omitted, temperature fluctuations associated with the turbulent heat flux will mistakenly be recorded as O2 fluctuations and bias the O2 eddy flux calculation.

Thermal Gradient During Vacuum-Deposition Dramatically Enhances Charge Transport in Organic Semiconductors: Toward High-Performance N-Type Organic Field-Effect Transistors.

PubMed

Kim, Joo-Hyun; Han, Singu; Jeong, Heejeong; Jang, Hayeong; Baek, Seolhee; Hu, Junbeom; Lee, Myungkyun; Choi, Byungwoo; Lee, Hwa Sung

2017-03-22

A thermal gradient distribution was applied to a substrate during the growth of a vacuum-deposited n-type organic semiconductor (OSC) film prepared from N,N'-bis(2-ethylhexyl)-1,7-dicyanoperylene-3,4:9,10-bis(dicarboxyimide) (PDI-CN2), and the electrical performances of the films deployed in organic field-effect transistors (OFETs) were characterized. The temperature gradient at the surface was controlled by tilting the substrate, which varied the temperature one-dimensionally between the heated bottom substrate and the cooled upper substrate. The vacuum-deposited OSC molecules diffused and rearranged on the surface according to the substrate temperature gradient, producing directional crystalline and grain structures in the PDI-CN2 film. The morphological and crystalline structures of the PDI-CN2 thin films grown under a vertical temperature gradient were dramatically enhanced, comparing with the structures obtained from either uniformly heated films or films prepared under a horizontally applied temperature gradient. The field effect mobilities of the PDI-CN2-FETs prepared using the vertically applied temperature gradient were as high as 0.59 cm 2 V -1 s -1 , more than a factor of 2 higher than the mobility of 0.25 cm 2 V -1 s -1 submitted to conventional thermal annealing and the mobility of 0.29 cm 2 V -1 s -1 from the horizontally applied temperature gradient.

Indoor to outdoor air quality associations with self-pollution implications inside passenger car cabins

NASA Astrophysics Data System (ADS)

Abi-Esber, L.; El-Fadel, M.

2013-12-01

In this study, in-vehicle and out-vehicle concentrations of fine particulate matter (PM2.5) and carbon monoxide (CO) are measured to assess commuter's exposure in a commercial residential area and on a highway, under three popular ventilation modes namely, one window half opened, air conditioning on fresh air intake, and air conditioning on recirculation and examine its relationship to scarcely studied parameters including self pollution, out-vehicle sample intake location and meteorological gradients. Self pollution is the intrusion of a vehicle's own engine fumes into the passenger's compartment. For this purpose, six car makes with different ages were instrumented to concomitantly monitor in- and out-vehicle PM2.5 and CO concentrations as well as meteorological parameters. Air pollution levels were unexpectedly higher in new cars compared to old cars, with in-cabin air quality most correlated to that of out-vehicle air near the front windshield. Self-pollution was observed at variable rates in three of the six tested cars. Significant correlations were identified between indoor to outdoor pressure difference and PM2.5 and CO In/Out (IO) ratios under air recirculation and window half opened ventilation modes whereas temperature and humidity difference affected CO IO ratios only under the air recirculation ventilation mode.

Simulating stand climate, phenology, and photosynthesis of a forest stand with a process-based growth model.

PubMed

Rötzer, Thomas; Leuchner, Michael; Nunn, Angela J

2010-07-01

In the face of climate change and accompanying risks, forest management in Europe is becoming increasingly important. Model simulations can help to understand the reactions and feedbacks of a changing environment on tree growth. In order to simulate forest growth based on future climate change scenarios, we tested the basic processes underlying the growth model BALANCE, simulating stand climate (air temperature, photosynthetically active radiation (PAR) and precipitation), tree phenology, and photosynthesis. A mixed stand of 53- to 60-year-old Norway spruce (Picea abies) and European beech (Fagus sylvatica) in Southern Germany was used as a reference. The results show that BALANCE is able to realistically simulate air temperature gradients in a forest stand using air temperature measurements above the canopy and PAR regimes at different heights for single trees inside the canopy. Interception as a central variable for water balance of a forest stand was also estimated. Tree phenology, i.e. bud burst and leaf coloring, could be reproduced convincingly. Simulated photosynthesis rates were in accordance with measured values for beech both in the sun and the shade crown. For spruce, however, some discrepancies in the rates were obvious, probably due to changed environmental conditions after bud break. Overall, BALANCE has shown to respond to scenario simulations of a changing environment (e.g., climate change, change of forest stand structure).

Continuous gradient temperature Raman spectroscopy of oleic and linoleic acids from -100 to 50°C

USDA-ARS?s Scientific Manuscript database

Gradient Temperature Raman spectroscopy (GTRS) applies the temperature gradients utilized in differential scanning calorimetry (DSC) to Raman spectroscopy, providing a straightforward technique to identify molecular rearrangements that occur near and at phase transitions. Herein we apply GTRS and DS...

Lateral Temperature-Gradient Method for High-Throughput Characterization of Material Processing by Millisecond Laser Annealing.

PubMed

Bell, Robert T; Jacobs, Alan G; Sorg, Victoria C; Jung, Byungki; Hill, Megan O; Treml, Benjamin E; Thompson, Michael O

2016-09-12

A high-throughput method for characterizing the temperature dependence of material properties following microsecond to millisecond thermal annealing, exploiting the temperature gradients created by a lateral gradient laser spike anneal (lgLSA), is presented. Laser scans generate spatial thermal gradients of up to 5 °C/μm with peak temperatures ranging from ambient to in excess of 1400 °C, limited only by laser power and materials thermal limits. Discrete spatial property measurements across the temperature gradient are then equivalent to independent measurements after varying temperature anneals. Accurate temperature calibrations, essential to quantitative analysis, are critical and methods for both peak temperature and spatial/temporal temperature profile characterization are presented. These include absolute temperature calibrations based on melting and thermal decomposition, and time-resolved profiles measured using platinum thermistors. A variety of spatially resolved measurement probes, ranging from point-like continuous profiling to large area sampling, are discussed. Examples from annealing of III-V semiconductors, CdSe quantum dots, low-κ dielectrics, and block copolymers are included to demonstrate the flexibility, high throughput, and precision of this technique.

Spatial models reveal the microclimatic buffering capacity of old-growth forests

PubMed Central

Frey, Sarah J. K.; Hadley, Adam S.; Johnson, Sherri L.; Schulze, Mark; Jones, Julia A.; Betts, Matthew G.

2016-01-01

Climate change is predicted to cause widespread declines in biodiversity, but these predictions are derived from coarse-resolution climate models applied at global scales. Such models lack the capacity to incorporate microclimate variability, which is critical to biodiversity microrefugia. In forested montane regions, microclimate is thought to be influenced by combined effects of elevation, microtopography, and vegetation, but their relative effects at fine spatial scales are poorly known. We used boosted regression trees to model the spatial distribution of fine-scale, under-canopy air temperatures in mountainous terrain. Spatial models predicted observed independent test data well (r = 0.87). As expected, elevation strongly predicted temperatures, but vegetation and microtopography also exerted critical effects. Old-growth vegetation characteristics, measured using LiDAR (light detection and ranging), appeared to have an insulating effect; maximum spring monthly temperatures decreased by 2.5°C across the observed gradient in old-growth structure. These cooling effects across a gradient in forest structure are of similar magnitude to 50-year forecasts of the Intergovernmental Panel on Climate Change and therefore have the potential to mitigate climate warming at local scales. Management strategies to conserve old-growth characteristics and to curb current rates of primary forest loss could maintain microrefugia, enhancing biodiversity persistence in mountainous systems under climate warming. PMID:27152339

Damage Characterization of EBC-SiCSiC Ceramic Matrix Composites Under Imposed Thermal Gradient Testing

NASA Technical Reports Server (NTRS)

Appleby, Matthew P.; Morscher, Gregory N.; Zhu, Dongming

2014-01-01

Due to their high temperature capabilities, Ceramic Matrix Composite (CMC) components are being developed for use in hot-section aerospace engine applications. Harsh engine environments have led to the development of Environmental Barrier Coatings (EBCs) for silicon-based CMCs to further increase thermal and environmental capabilities. This study aims at understanding the damage mechanisms associated with these materials under simulated operating conditions. A high heat-flux laser testing rig capable of imposing large through-thickness thermal gradients by means of controlled laser beam heating and back-side air cooling is used. Tests are performed on uncoated composites, as well as CMC substrates that have been coated with state-of-the-art ceramic EBC systems. Results show that the use of the EBCs may help increase temperature capability and creep resistance by reducing the effects of stressed oxidation and environmental degradation. Also, the ability of electrical resistance (ER) and acoustic emission (AE) measurements to monitor material condition and damage state during high temperature testing is shown; suggesting their usefulness as a valuable health monitoring technique. Micromechanics models are used to describe the localized stress state of the composite system, which is utilized along with ER modeling concepts to develop an electromechanical model capable of characterizing material behavior.

Spatial models reveal the microclimatic buffering capacity of old-growth forests.

PubMed

Frey, Sarah J K; Hadley, Adam S; Johnson, Sherri L; Schulze, Mark; Jones, Julia A; Betts, Matthew G

2016-04-01

Climate change is predicted to cause widespread declines in biodiversity, but these predictions are derived from coarse-resolution climate models applied at global scales. Such models lack the capacity to incorporate microclimate variability, which is critical to biodiversity microrefugia. In forested montane regions, microclimate is thought to be influenced by combined effects of elevation, microtopography, and vegetation, but their relative effects at fine spatial scales are poorly known. We used boosted regression trees to model the spatial distribution of fine-scale, under-canopy air temperatures in mountainous terrain. Spatial models predicted observed independent test data well (r = 0.87). As expected, elevation strongly predicted temperatures, but vegetation and microtopography also exerted critical effects. Old-growth vegetation characteristics, measured using LiDAR (light detection and ranging), appeared to have an insulating effect; maximum spring monthly temperatures decreased by 2.5°C across the observed gradient in old-growth structure. These cooling effects across a gradient in forest structure are of similar magnitude to 50-year forecasts of the Intergovernmental Panel on Climate Change and therefore have the potential to mitigate climate warming at local scales. Management strategies to conserve old-growth characteristics and to curb current rates of primary forest loss could maintain microrefugia, enhancing biodiversity persistence in mountainous systems under climate warming.

Cold hands, warm feet: sleep deprivation disrupts thermoregulation and its association with vigilance.

PubMed

Romeijn, Nico; Verweij, Ilse M; Koeleman, Anne; Mooij, Anne; Steimke, Rosa; Virkkala, Jussi; van der Werf, Ysbrand; Van Someren, Eus J W

2012-12-01

Vigilance is affected by induced and spontaneous skin temperature fluctuations. Whereas sleep deprivation strongly affects vigilance, no previous study examined in detail its effect on human skin temperature fluctuations and their association with vigilance. In a repeated-measures constant routine design, skin temperatures were assessed continuously from 14 locations while performance was assessed using a reaction time task, including eyes-open video monitoring, performed five times a day for 2 days, after a normal sleep or sleep deprivation night. Participants were seated in a dimly lit, temperature-controlled laboratory. Eight healthy young adults (five males, age 22.0 ± 1.8 yr (mean ± standard deviation)). One night of sleep deprivation. Mixed-effect regression models were used to evaluate the effect of sleep deprivation on skin temperature gradients of the upper (ear-mastoid), middle (hand-arm), and lower (foot-leg) body, and on the association between fluctuations in performance and in temperature gradients. Sleep deprivation induced a marked dissociation of thermoregulatory skin temperature gradients, indicative of attenuated heat loss from the hands co-occurring with enhanced heat loss from the feet. Sleep deprivation moreover attenuated the association between fluctuations in performance and temperature gradients; the association was best preserved for the upper body gradient. Sleep deprivation disrupts coordination of fluctuations in thermoregulatory skin temperature gradients. The dissociation of middle and lower body temperature gradients may therefore be evaluated as a marker for sleep debt, and the upper body gradient as a possible aid in vigilance assessment when sleep debt is unknown. Importantly, our findings suggest that sleep deprivation affects the coordination between skin blood flow fluctuations and the baroreceptor-mediated cardiovascular regulation that prevents venous pooling of blood in the lower limbs when there is the orthostatic challenge of an upright posture.

Ocean currents modify the coupling between climate change and biogeographical shifts.

PubMed

García Molinos, J; Burrows, M T; Poloczanska, E S

2017-05-02

Biogeographical shifts are a ubiquitous global response to climate change. However, observed shifts across taxa and geographical locations are highly variable and only partially attributable to climatic conditions. Such variable outcomes result from the interaction between local climatic changes and other abiotic and biotic factors operating across species ranges. Among them, external directional forces such as ocean and air currents influence the dispersal of nearly all marine and many terrestrial organisms. Here, using a global meta-dataset of observed range shifts of marine species, we show that incorporating directional agreement between flow and climate significantly increases the proportion of explained variance. We propose a simple metric that measures the degrees of directional agreement of ocean (or air) currents with thermal gradients and considers the effects of directional forces in predictions of climate-driven range shifts. Ocean flows are found to both facilitate and hinder shifts depending on their directional agreement with spatial gradients of temperature. Further, effects are shaped by the locations of shifts in the range (trailing, leading or centroid) and taxonomic identity of species. These results support the global effects of climatic changes on distribution shifts and stress the importance of framing climate expectations in reference to other non-climatic interacting factors.

Thin film instabilities: Rayleigh-Taylor with thermocapillarity and Kolmogorov flow in a soap film

NASA Astrophysics Data System (ADS)

Burgess, John Matthew

The Rayleigh-Taylor instability occurs when a more dense fluid layer is suspended above a less dense fluid layer in a gravitational field. The horizontal interface between the two fluids is unstable to infinitesimal deformations and the dense fluid falls. To counteract the destabilizing effects of gravity on the interface between two thin fluid layers, we apply a vertical temperature gradient, heating from below. The dependence of surface tension on temperature (``thermocapillarity'') can cause spatially-varying interfacial forces between two immiscible fluid layers if a variation in temperature along the interface is introduced. With an applied vertical temperature gradient, the deforming interface spontaneously develops temperature variations which locally adjust the surface tension to restore a flat interface. We find that these surface tension gradients can stabilize a more dense thin fluid layer (silicone oil, 0.015 cm thick) above a less dense thin fluid layer (air, 0.025 cm thick) in a gravitational field, in qualitative agreement with linear stability analysis. This is the first experimental observation of the stabilization of Rayleigh-Taylor instability by thermocapillary forces. We also examine the instability of a soap film flow driven by a time-independent force that is spatially periodic in the direction perpendicular to the forcing (Kolmogorov flow). The film is in the x- y plane, where the forcing approximates a shape sin (y)x̂. Linear stability analysis of an idealized model of this flow predicts a critical Reynolds number Rc~2 . In our soap film experiment, we find a critical value Rc~70 . This discrepancy can be ascribed to frictional effects from viscous coupling of gas to the film, which is neglected in the idealized model. The kinematic viscosity of the surrounding gas and the thickness of gas layers on each side of the soap film are varied in the experiments to better understand these frictional effects. We conclude that flows in soap films cannot be decoupled from flows in the surrounding gas.

Weather Types, temperature and relief relationship in the Iberian Peninsula: A regional adiabatic processes under directional weather types

NASA Astrophysics Data System (ADS)

Peña Angulo, Dhais; Trigo, Ricardo; Cortesi, Nicola; Gonzalez-Hidalgo, Jose Carlos

2016-04-01

We have analyzed at monthly scale the spatial distribution of Pearson correlation between monthly mean of maximum (Tmax) and minimum (Tmin) temperatures with weather types (WTs) in the Iberian Peninsula (IP), represent them in a high spatial resolution grid (10km x 10km) from MOTEDAS dataset (Gonzalez-Hidalgo et al., 2015a). The WT classification was that developed by Jenkinson and Collison, adapted to the Iberian Peninsula by Trigo and DaCamara, using Sea Level Pressure data from NCAR/NCEP Reanalysis dataset (period 1951-2010). The spatial distribution of Pearson correlations shows a clear zonal gradient in Tmax under the zonal advection produced in westerly (W) and easterly (E) flows, with negative correlation in the coastland where the air mass come from but positive correlation to the inland areas. The same is true under North-West (NW), North-East (NE), South-West (SW) and South-East (SE) WTs. These spatial gradients are coherent with the spatial distribution of the main mountain chain and offer an example of regional adiabatic phenomena that affect the entire IP (Peña-Angulo et al., 2015b). These spatial gradients have not been observed in Tmin. We suggest that Tmin values are less sensitive to changes in Sea Level Pressure and more related to local factors. These directional WT present a monthly frequency over 10 days and could be a valuable tool for downscaling processes. González-Hidalgo J.C., Peña-Angulo D., Brunetti M., Cortesi, C. (2015a): MOTEDAS: a new monthly temperature database for mainland Spain and the trend in temperature (1951-2010). International Journal of Climatology 31, 715-731. DOI: 10.1002/joc.4298 Peña-Angulo, D., Trigo, R., Cortesi, C., González-Hidalgo, J.C. (2015b): The influence of weather types on the monthly average maximum and minimum temperatures in the Iberian Peninsula. Submitted to Hydrology and Earth System Sciences.

Remote Sensing of Niches for Thermotropic Life.

NASA Astrophysics Data System (ADS)

Muller, A. W.

2002-12-01

The recognized biological energy sources are light and food. Mechanical systems can gain free energy from heat using a temperature difference or thermal cycling. Imagine that biological systems could also live on heat. Call the process `thermosynthesis' and let it occur in a thermal gradient or convection cell. Many candidate niches for thermosynthesizers then exist. Temperature differences are present across many interfaces: soil/air, rock/air, natural water (ocean, lake, river)/air, ice (also snow)/air, soil/snow, water (ocean,lake)/surface-ice. Within natural waters large temperature gradients are found; thermoclines separate the warm surface from the cold deep. Convection occurs in hot springs, in many other natural waters, and in the Earth's atmosphere. On Earth, organism presence is conspicuous in all these candidate niches. The Solar System contains many candidate niches as well. They should be detectable by IR methods. They can be categorized in five types: (1) Convection. Convecting oceans (Mars and Venus in the past) or atmospheres (Venus, Big Outer Planets). (2) Convecting Aquifer (Mars). (3) Surface-Ice Cover. Some of the Moons of the Outer Planets. (4) Shaded Crater Iterior. The poles of Mercury and The Moon. (5) Spinners. Small objects rotating in the sunlight: ice-covered meteorites, asteroids, comets. They could transport thermosynthesizers within the Solar System. How plausible is thermosynthesis? It can be shown that thermosynthesis (1) could be effected using parts of the contemporary photosynthetic machinery, and (2) may have supported early evolution. The standard biological energy carrier, ATP, would be synthesized during thermal cycling of a progenitor of the F1 moiety of the contemporary ATPsynthase enzyme; this progenitor is thermally folded/unfolded during the cycle. Contemporary ATPsynthase works according to the `binding change mechanism': substrates are bound in a local, dehydrated enzymatic cleft, where they condense to form a bound product with a high-energy phosphate bond, released upon an external work input. The first ATPsynthases are proposed to have similarly synthesized a bound peptide bond product during thermal cycling, released upon the thermal unfolding. In a simple model for the origin of life the first ATPsynthases, the first replicators, synthesize randomly constituted daughter polypeptides of which a small fraction has the same synthetic capabilities as their mothers. Hence thermosynthesis is not implausible, the Solar System may be teeming with thermosynthesizers, and IR remote sensing methods should permit to locate their niches.

Forest productivity varies with soil moisture more than temperature in a small montane watershed

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

Wei, Liang; Zhou, Hang; Link, Timothy E

Mountainous terrain creates variability in microclimate, including nocturnal cold air drainage and resultant temperature inversions. Driven by the elevational temperature gradient, vapor pressure deficit (VPD) also varies with elevation. Soil depth and moisture availability often increase from ridgetop to valley bottom. These variations complicate predictions of forest productivity and other biological responses. We analyzed spatiotemporal air temperature (T) and VPD variations in a forested, 27-km 2 catchment that varied from 1000 to 1650 m in elevation. Temperature inversions occurred on 76% of mornings in the growing season. The inversion had a clear upper boundary at midslope (~1370 m a.s.l.). Vapormore » pressure was relatively constant across elevations, therefore VPD was mainly controlled by T in the watershed. Here, we assessed the impact of microclimate and soil moisture on tree height, forest productivity, and carbon stable isotopes (δ 13C) using a physiological forest growth model (3-PG). Simulated productivity and tree height were tested against observations derived from lidar data. The effects on photosynthetic gas-exchange of dramatic elevational variations in T and VPD largely cancelled as higher temperature (increasing productivity) accompanies higher VPD (reducing productivity). Although it was not measured, the simulations suggested that realistic elevational variations in soil moisture predicted the observed decline in productivity with elevation. Therefore, in this watershed, the model parameterization should have emphasized soil moisture rather than precise descriptions of temperature inversions.« less

Forest productivity varies with soil moisture more than temperature in a small montane watershed

DOE PAGES

Wei, Liang; Zhou, Hang; Link, Timothy E; ...

2018-05-16

Mountainous terrain creates variability in microclimate, including nocturnal cold air drainage and resultant temperature inversions. Driven by the elevational temperature gradient, vapor pressure deficit (VPD) also varies with elevation. Soil depth and moisture availability often increase from ridgetop to valley bottom. These variations complicate predictions of forest productivity and other biological responses. We analyzed spatiotemporal air temperature (T) and VPD variations in a forested, 27-km 2 catchment that varied from 1000 to 1650 m in elevation. Temperature inversions occurred on 76% of mornings in the growing season. The inversion had a clear upper boundary at midslope (~1370 m a.s.l.). Vapormore » pressure was relatively constant across elevations, therefore VPD was mainly controlled by T in the watershed. Here, we assessed the impact of microclimate and soil moisture on tree height, forest productivity, and carbon stable isotopes (δ 13C) using a physiological forest growth model (3-PG). Simulated productivity and tree height were tested against observations derived from lidar data. The effects on photosynthetic gas-exchange of dramatic elevational variations in T and VPD largely cancelled as higher temperature (increasing productivity) accompanies higher VPD (reducing productivity). Although it was not measured, the simulations suggested that realistic elevational variations in soil moisture predicted the observed decline in productivity with elevation. Therefore, in this watershed, the model parameterization should have emphasized soil moisture rather than precise descriptions of temperature inversions.« less

RESPONSE OF HATCHLING AND YEARLING TURTLES TO THERMAL GRADIENTS: COMPARISON OF CHELYDRA SERPENTINA AND TRACHEMYS SCRIPTA

EPA Science Inventory

In laboratory test, young Chelydra serpentina and Trachemys scripta altered their distribution in the presence of a temperature gradient. Selection of temperatures in the gradient for hatchlings and yearlings showed that body temperature (Tbs) of C. serpentina were lower tha...

Thermotropism by primary roots of maize

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

Fortin, M.-C.; Poff, K.L.

1990-05-01

Sensing in the roots of higher plants has long been recognized to be restricted mainly to gravitropism and thigmotropism. However, root responses to temperature gradients have not been extensively studied. We have designed experiments under controlled conditions to test if and how root direction of maize can be altered by thermal gradients perpendicular to the gravity vector. Primary roots of maize grown on agar plates exhibit positive thermotropism (curvature toward the warmer temperature) when exposed to gradients of 0.5 to 4.2{degree}C cm{sup {minus}1}. The extent of thermotropism depends on the temperature gradient and the temperature at which the root ismore » placed within the gradient. The curvature cannot be accounted for by differential growth as a direct effect of temperature on each side of the root.« less

Skin temperature and core-peripheral temperature gradient as markers of hemodynamic status in critically ill patients: a review.

PubMed

Schey, Bernadette M; Williams, David Y; Bucknall, Tracey

2010-01-01

To examine the evidential basis underpinning the monitoring of skin temperature and core-peripheral temperature gradient as elements of hemodynamic assessment in critically ill and adult cardiac surgical patients. Twenty-six studies examining the efficacy of skin temperature or temperature gradient as markers of hemodynamic status were selected as part of an integrative review. Evidence pertaining to the efficacy of these parameters as markers of cardiac function is equivocal and has not been well appraised in the adult cardiac surgical population. Skin temperature and systemic vascular resistance are also affected by factors other than cardiac output. Skin temperature and core-peripheral temperature gradient should not be considered in isolation from other hemodynamic parameters when assessing cardiac status until they are validated by further large-scale prospective studies. 2010. Published by Mosby, Inc.

Subsurface temperatures and geothermal gradients on the north slope of Alaska

USGS Publications Warehouse

Collett, T.S.; Bird, K.J.; Magoon, L.B.

1993-01-01

On the North Slope of Alaska, geothermal gradient data are available from high-resolution, equilibrated well-bore surveys and from estimates based on well-log identification of the base of ice-bearing permafrost. A total of 46 North Slope wells, considered to be in or near thermal equilibrium, have been surveyed with high-resolution temperatures devices and geothermal gradients can be interpreted directly from these recorded temperature profiles. To augment the limited North Slope temperature data base, a new method of evaluating local geothermal gradients has been developed. In this method, a series of well-log picks for the base of the ice-bearing permafrost from 102 wells have been used, along with regional temperature constants derived from the high-resolution stabilized well-bore temperature surveys, to project geothermal gradients. Geothermal gradients calculated from the high-resolution temperature surveys generally agree with those projected from known ice-bearing permafrost depths over most of the North Slope. Values in the ice-bearing permafrost range from ??? 1.5??C 100 m in the Prudhoe Bay area to ??? 4.5??C 100 m in the east-central portion of the National Petroleum Reserve in Alaska. Geothermal gradients below the ice-bearing permafrost sequence range from ??? 1.6??C 100 m to ??? 5.2??C 100 m. ?? 1993.

Mathematical modeling as a tool to investigate the design and operation of the zymotis packed-bed bioreactor for solid-state fermentation.

PubMed

Mitchell, D A; von Meien, O F

2000-04-20

Zymotis bioreactors for solid-state fermentation (SSF) are packed-bed bioreactors with internal cooling plates. This design has potential to overcome the problem of heat removal, which is one of the main challenges in SSF. In ordinary packed-bed bioreactors, which lack internal plates, large axial temperature gradients arise, leading to poor microbial growth in the end of the bed near the air outlet. The Zymotis design is suitable for SSF processes in which the substrate bed must be maintained static, but little is known about how to design and operate Zymotis bioreactors. We use a two-dimensional heat transfer model, describing the growth of Aspergillus niger on a starchy substrate, to provide guidelines for the optimum design and operation of Zymotis bioreactors. As for ordinary packed-beds, the superficial velocity of the process air is a key variable. However, the Zymotis design introduces other important variables, namely, the spacing between the internal cooling plates and the temperature of the cooling water. High productivities can be achieved at large scale, but only if small spacings between the cooling plates are used, and if the cooling water temperature is varied during the fermentation in response to bed temperatures. Copyright 2000 John Wiley & Sons, Inc.

Measurement of impinging butane flame using combined optical system with digital speckle tomography

NASA Astrophysics Data System (ADS)

Ko, Han Seo; Ahn, Seong Soo; Kim, Hyun Jung

2011-11-01

Three-dimensional density distributions of an impinging and eccentric flame were measured experimentally using a combined optical system with digital speckle tomography. In addition, a three-dimensional temperature distribution of the flame was reconstructed from an ideal gas equation based on the reconstructed density data. The flame was formed by the ignition of premixed butane/air from air holes and impinged upward against a plate located 24 mm distance from the burner nozzle. In order to verify the reconstruction process for the experimental measurements, numerically synthesized phantoms of impinging and eccentric flames were derived and reconstructed using a developed three-dimensional multiplicative algebraic reconstruction technique (MART). A new scanning technique was developed for the accurate analysis of speckle displacements necessary for investigating the wall jet regions of the impinging flame at which a sharp variation of the flow direction and pressure gradient occur. The reconstructed temperatures by the digital speckle tomography were applied to the boundary condition for numerical analysis of a flame impinged plate. Then, the numerically calculated temperature distribution of the upper side of the flame impinged plate was compared to temperature data taken by an infrared camera. The absolute average uncertainty between the numerical and infrared camera data was 3.7%.

Urban Forest Ecosystem Service Optimization, Tradeoffs, and Disparities

NASA Astrophysics Data System (ADS)

Bodnaruk, E.; Kroll, C. N.; Endreny, T. A.; Hirabayashi, S.; Yang, Y.

2014-12-01

Urban land area and the proportion of humanity living in cities is growing, leading to increased urban air pollution, temperature, and stormwater runoff. These changes can exacerbate respiratory and heat-related illnesses and affect ecosystem functioning. Urban trees can help mitigate these threats by removing air pollutants, mitigating urban heat island effects, and infiltrating and filtering stormwater. The urban environment is highly heterogeneous, and there is no tool to determine optimal locations to plant or protect trees. Using spatially explicit land cover, weather, and demographic data within biophysical ecosystem service models, this research expands upon the iTree urban forest tools to produce a new decision support tool (iTree-DST) that will explore the development and impacts of optimal tree planting. It will also heighten awareness of environmental justice by incorporating the Atkinson Index to quantify disparities in health risks and ecosystem services across vulnerable and susceptible populations. The study area is Baltimore City, a location whose urban forest and environmental justice concerns have been studied extensively. The iTree-DST is run at the US Census block group level and utilizes a local gradient approach to calculate the change in ecosystem services with changing tree cover across the study area. Empirical fits provide ecosystem service gradients for possible tree cover scenarios, greatly increasing the speed and efficiency of the optimization procedure. Initial results include an evaluation of the performance of the gradient method, optimal planting schemes for individual ecosystem services, and an analysis of tradeoffs and synergies between competing objectives.

Effects of equivalence ratio variation on lean, stratified methane-air laminar counterflow flames

NASA Astrophysics Data System (ADS)

Richardson, E. S.; Granet, V. E.; Eyssartier, A.; Chen, J. H.

2010-11-01

The effects of equivalence ratio variations on flame structure and propagation have been studied computationally. Equivalence ratio stratification is a key technology for advanced low emission combustors. Laminar counterflow simulations of lean methane-air combustion have been presented which show the effect of strain variations on flames stabilized in an equivalence ratio gradient, and the response of flames propagating into a mixture with a time-varying equivalence ratio. 'Back supported' lean flames, whose products are closer to stoichiometry than their reactants, display increased propagation velocities and reduced thickness compared with flames where the reactants are richer than the products. The radical concentrations in the vicinity of the flame are modified by the effect of an equivalence ratio gradient on the temperature profile and thermal dissociation. Analysis of steady flames stabilized in an equivalence ratio gradient demonstrates that the radical flux through the flame, and the modified radical concentrations in the reaction zone, contribute to the modified propagation speed and thickness of stratified flames. The modified concentrations of radical species in stratified flames mean that, in general, the reaction rate is not accurately parametrized by progress variable and equivalence ratio alone. A definition of stratified flame propagation based upon the displacement speed of a mixture fraction dependent progress variable was seen to be suitable for stratified combustion. The response times of the reaction, diffusion, and cross-dissipation components which contribute to this displacement speed have been used to explain flame response to stratification and unsteady fluid dynamic strain.

Influence of temperature gradients on charge transport in asymmetric nanochannels.

PubMed

Benneker, Anne M; Wendt, Hans David; Lammertink, Rob G H; Wood, Jeffery A

2017-10-25

Charge selective asymmetric nanochannels are used for a variety of applications, such as nanofluidic sensing devices and energy conversion applications. In this paper, we numerically investigate the influence of an applied temperature difference over tapered nanochannels on the resulting charge transport and flow behavior. Using a temperature-dependent formulation of the coupled Poisson-Nernst-Planck and Navier-Stokes equations, various nanochannel geometries are investigated. Temperature has a large influence on the total ion transport, as the diffusivity of ions and viscosity of the solution are strongly affected by temperature. We find that the selectivity of the nanochannels is enhanced with increasing asymmetry ratios, while the total current is reduced at higher asymmetry cases. Most interestingly, we find that applying a temperature gradient along the electric field and along the asymmetry direction of the nanochannel enhances the selectivity of the tapered channels even further, while a temperature gradient countering the electric field reduces the selectivity of the nanochannel. Current rectification is enhanced in asymmetric nanochannels if a temperature gradient is applied, independent of the direction of the temperature difference. However, the degree of rectification is dependent on the direction of the temperature gradient with respect to the channel geometry and the electric field direction. The enhanced selectivity of nanochannels due to applied temperature gradients could result in more efficient operation in energy harvesting or desalination applications, motivating experimental investigations.

A Study on the Role of Grain-Boundary Engineering in Promoting High-Cycle Fatigue Resistance and Improving Reliability in Metallic Alloys for Propulsion Systems

DTIC Science & Technology

2005-04-30

in addition, air cooling instead of water or oil quenching was adopted to avoid quench cracking. Based on a series of preliminary multi -parametric...microstructures were then grain- boundary engineered using four cycles of strain and high-temperature annealing of the single- phase alloy, specifically...automated load- shedding at a normalized K-gradient of -0.08 mm-, as specified in the standard. Multi -sample tests were conducted to verify the effect of

Correlations between quasi-coherent fluctuations and the pedestal evolution during the inter-edge localized modes phase on DIII-D

DOE PAGES

Diallo, A.; Groebner, R. J.; Rhodes, T. L.; ...

2015-05-15

Direct measurements of the pedestal recovery during an edge-localized mode cycle provide evidence that quasi-coherent fluctuations (QCFs) play a role in the inter-ELM pedestal dynamics. When using fast Thomson scattering measurements, we found that the pedestal density and temperature evolutions are probed on sub-millisecond time scales to show a fast recovery of the density gradient compared to the temperature gradient. The temperature gradient appears to provide a drive for the onset of quasi-coherent fluctuations (as measured with the magnetic probe and the density diagnostics) localized in the pedestal. The amplitude evolution of these QCFs tracks the temperature gradient evolution includingmore » its saturation. Such correlation suggests that these QCFs play a key role in limiting the pedestal temperature gradient. Moreover, the saturation of the QCFs coincides with the pressure gradient reaching the kinetic-ballooning mode (KBM) critical gradient as predicted by EPED1. Furthermore, linear microinstability analysis using GS2 indicates that the steep gradient is near the KBM threshold. Finally, the modeling and the observations together suggest that QCFs are consistent with dominant KBMs, although microtearing cannot be excluded as subdominant.« less

Crystal growth and annealing method and apparatus

DOEpatents

Gianoulakis, Steven E.; Sparrow, Robert

2001-01-01

A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing. An embodiment of the present invention comprises a secondary heater incorporated into a conventional crystal growth and annealing apparatus. The secondary heater supplies heat to minimize the temperature gradients in the crystal during the annealing process. The secondary heater can mount near the bottom of the crucible to effectively maintain appropriate temperature gradients.

Relating Paleoclimate Data and Past Temperature Gradients: Some Suggestive Rules

NASA Technical Reports Server (NTRS)

Rind, David

1999-01-01

Understanding tropical sensitivity is perhaps the major concern confronting researchers, for both past and future climate change issues. Tropical data has been beset by contradictions, and many techniques applicable to the extratropics are either unavailable or fraught with uncertainty when applied at low latitudes. Paleoclimate data, if interpreted within the context of the latitudinal temperature gradient data they imply, can be used to estimate what happened to tropical temperatures in the past, and provide a first guess for what might happen in the future. The approach is made possible by the modeling result that atmospheric dynamical changes, and the climate impacts they produce, respond primarily to temperature gradient changes. Here we review some "rules" obtained from GCM (General Circulation Model) experiments with different sea surface temperature gradients and different forcing, that can be used to relate paleoclimate reconstructions to the likely temperature gradient changes they suggest.

Interfacial free energy and stiffness of aluminum during rapid solidification

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

Brown, Nicholas T.; Martinez, Enrique; Qu, Jianmin

Using molecular dynamics simulations and the capillary fluctuation method, we have calculated the anisotropic crystal-melt interfacial free energy and stiffness of aluminum in a rapid solidification system where a temperature gradient is applied to enforce thermal non-equilibrium. To calculate these material properties, the standard capillary fluctuation method typically used for systems in equilibrium has been modified to incorporate a second-order Taylor expansion of the interfacial free energy term. The result is a robust method for calculating interfacial energy, stiffness and anisotropy as a function of temperature gradient using the fluctuations in the defined interface height. This work includes the calculationmore » of interface characteristics for temperature gradients ranging from 11 to 34 K/nm. The captured results are compared to a thermal equilibrium case using the same model and simulation technique with a zero gradient definition. We define the temperature gradient as the change in temperature over height perpendicular to the crystal-melt interface. The gradients are applied in MD simulations using defined thermostat regions on a stable solid-liquid interface initially in thermal equilibrium. The results of this work show that the interfacial stiffness and free energy for aluminum are dependent on the magnitude of the temperature gradient, however the anisotropic parameters remain independent of the non-equilibrium conditions applied in this analysis. As a result, the relationships of the interfacial free energy/stiffness are determined to be linearly related to the thermal gradient, and can be interpolated to find material characteristics at additional temperature gradients.« less

Interfacial free energy and stiffness of aluminum during rapid solidification

DOE PAGES

Brown, Nicholas T.; Martinez, Enrique; Qu, Jianmin

2017-05-01

Using molecular dynamics simulations and the capillary fluctuation method, we have calculated the anisotropic crystal-melt interfacial free energy and stiffness of aluminum in a rapid solidification system where a temperature gradient is applied to enforce thermal non-equilibrium. To calculate these material properties, the standard capillary fluctuation method typically used for systems in equilibrium has been modified to incorporate a second-order Taylor expansion of the interfacial free energy term. The result is a robust method for calculating interfacial energy, stiffness and anisotropy as a function of temperature gradient using the fluctuations in the defined interface height. This work includes the calculationmore » of interface characteristics for temperature gradients ranging from 11 to 34 K/nm. The captured results are compared to a thermal equilibrium case using the same model and simulation technique with a zero gradient definition. We define the temperature gradient as the change in temperature over height perpendicular to the crystal-melt interface. The gradients are applied in MD simulations using defined thermostat regions on a stable solid-liquid interface initially in thermal equilibrium. The results of this work show that the interfacial stiffness and free energy for aluminum are dependent on the magnitude of the temperature gradient, however the anisotropic parameters remain independent of the non-equilibrium conditions applied in this analysis. As a result, the relationships of the interfacial free energy/stiffness are determined to be linearly related to the thermal gradient, and can be interpolated to find material characteristics at additional temperature gradients.« less

Heat-shock response and antioxidant defense during air exposure in Patagonian shallow-water limpets from different climatic habitats.

PubMed

Pöhlmann, Kevin; Koenigstein, Stefan; Alter, Katharina; Abele, Doris; Held, Christoph

2011-11-01

Climate warming involves not only a rise of air temperature means, but also more frequent heat waves in many regions on earth, and is predicted to intensify physiological stress especially in extremely changeable habitats like the intertidal. We investigated the heat-shock response (HSR) and enzymatic antioxidant defense levels of Patagonian shallow-water limpets, adapted to distinct tidal exposure conditions in the sub- and intertidal. Limpets were sampled in the temperate Northern Patagonia and the subpolar Magellan region. Expression levels of two Hsp70 genes and activities of the antioxidants superoxide dismutase (SOD) and catalase (CAT) were measured in submerged and 2- and 12-h air-exposed specimens. Air-exposed Patagonian limpets showed a tiered HSR increasing from South to North on the latitudinal gradient and from high to low shore levels on a tidal gradient. SOD activities in the Magellan region correlated with the tidal rhythm and were higher after 2 and 12 h when the tide was low at the experimental site compared to the 6 h value taken at high tide. This pattern was observed in intertidal and subtidal specimens, although subtidal individuals are little affected by tides. Our study shows that long-term thermal adaptation shapes the HSR in limpets, while the oxidative stress response is linked to the tidal rhythm. Close to the warm border of their distribution range, energy expenses to cope with stress might become overwhelming and represent one cause why the limpets are unable to colonize the shallow intertidal zone.

Hot Air Balloon Experiments to Measure the Break-up of the Nocturnal Drainage Flow in Complex Terrain.

NASA Astrophysics Data System (ADS)

Berman, N. S.; Fernando, H. J. S.; Colomer, J.; Levy, M.; Zieren, L.

1997-11-01

In order to extend our understanding of the thermally driven atmospheric winds and their influence on pollutant transport, a hot air balloon experiment was conducted over a four day period in June, 1997 near Nogales, Arizona. The focus was on the early morning break-up of the stable down-slope and down-valley flow and the establishment of a convective boundary layer near the surface in the absence of synoptic winds. Temperature, elevation, position and particulate matter concentration were measured aloft and temperature gradient and wind velocity were measured at ground level. The wind velocity within the stable layer was generally less than 1.5 m/s. Just above the stable layer (about 300 meters above the valley) the wind shifted leading to an erosion of the stable layer from above. Surface heating after sunrise created a convective layer which rose from the ground until the stable layer was destroyed. Examples of temperature fluctuation measurements at various elevations during the establishment of the convective flow will be presented. Implications of results for turbulence parameterizations needed for numerical models of wind fields in complex terrain will be discussed.

Evaluation of surface energy and radiation balance systems for FIFE

NASA Technical Reports Server (NTRS)

Fritschen, Leo J.; Qian, Ping

1988-01-01

The energy balance and radiation balance components were determined at six sites during the First International Satellite Land Surface Climatology Project Field Experiment (FIFE) conducted south of Manhattan, Kansas during the summer of 1987. The objectives were: to determine the effect of slope and aspect, throughout a growing season, on the magnitude of the surface energy balance fluxes as determined by the Energy Balance Method (EBM); to investigate the calculation of the soil heat flux density at the surface as calculated from the heat capacity and the thermal conductivity equations; and to evaluate the performance of the Surface Energy and Radiation Balance System (SERBS). A total of 17 variables were monitored at each site. They included net, solar (up and down), total hemispherical (up and down), and diffuse radiation, soil temperature and heat flux density, air and wet bulb temperature gradients, wind speed and direction, and precipitation. A preliminary analysis of the data, for the season, indicate that variables including net radiation, air temperature, vapor pressure, and wind speed were quite similar at the sites even though the sites were as much as 16 km apart and represented four cardinal slopes and the top of a ridge.

Temperature and deflection data from the asymmetric heating of cross-ply composite tubes

NASA Technical Reports Server (NTRS)

Hyer, Michael W.; Cooper, David E.; Tompkins, S. S.; Cohen, David

1987-01-01

Data generated while heating several cross-ply graphite-epoxy tubes on one side, along their lengths, and cooling them on the other side are presented. This heating arrangement produces a circumferential temperature gradient, and the data show that the gradient can be represented by a cosinusoidal temperature distribution. The thermally induced bending deflections caused by the temperature gradient are also presented.

Nutrient status: a missing factor in phenological and pollen research?

PubMed Central

Jochner, Susanne; Höfler, Josef; Beck, Isabelle; Göttlein, Axel; Ankerst, Donna Pauler; Traidl-Hoffmann, Claudia; Menzel, Annette

2013-01-01

Phenology ranks among the best ecosystem processes for fingerprinting climate change since temperature explains a high percentage of the interannual or spatial variation in phenological onset dates. However, roles of other environmental variables, such as foliar nutrient concentrations, are far from adequately understood. This observational study examined the effects of air temperature and 11 nutrients on spring phenology of Betula pendula Roth (birch) along an urban–rural gradient in Munich, Germany, during the years 2010/2011. Moreover, the influence of temperature, nutrients, and air pollutants (NO2 and O3) on the amounts of pollen and catkin biomass in 2010 was evaluated. In addition to the influence of higher temperatures advancing phenological onset dates, higher foliar concentrations of potassium, boron, zinc, and calcium were statistically significantly linked to earlier onset dates. Since flushing of leaves is a turgor-driven process and all the influential nutrients are involved in cell extension, membrane function, and stability, there might be a reasonable physiological interpretation of the observed association. The amounts of pollen were negatively correlated with temperature, atmospheric NO2, and foliar iron concentration, suggesting that these variables restrict pollen production. The results of this study suggested an influence of nutritional status on both phenology and pollen production. The interaction of urbanization and climate change should be considered in the assessment of the impact of global warming on ecosystems and human health. PMID:23630329

Thermal Transmission through Existing Building Enclosures: Destructive Monitoring in Intermediate Layers versus Non-Destructive Monitoring with Sensors on Surfaces.

PubMed

Echarri, Víctor; Espinosa, Almudena; Rizo, Carlos

2017-12-08

Opaque enclosures of buildings play an essential role in the level of comfort experienced indoors and annual energy demand. The impact of solar radiation and thermal inertia of the materials that make up the multi-layer enclosures substantially modify thermal transmittance behaviour of the enclosures. This dynamic form of heat transfer, additionally affected by indoor HVAC systems, has a substantial effect on the parameters that define comfort. It also has an impact on energy demand within a daily cycle as well as throughout a one-year use cycle. This study describes the destructive monitoring of an existing block of flats located in Alicante. Once the enclosure was opened, sensors of temperature (PT100), air velocity, and relative humidity were located in the different layers of the enclosure, as well as in the interior and exterior surfaces. A pyranometer was also installed to measure solar radiation levels. A temperature data correction algorithm was drawn up to address irregularities produced in the enclosure. The algorithm was applied using a Raspberry Pi processor in the data collection system. The comparative results of temperature gradients versus non-destructive monitoring systems are presented, providing measures of the transmittance value, surface temperatures and indoor and outdoor air temperatures. This remote sensing system can be used in future studies to quantify and compare the energy savings of different enclosure construction solutions.

Thermal Transmission through Existing Building Enclosures: Destructive Monitoring in Intermediate Layers versus Non-Destructive Monitoring with Sensors on Surfaces

PubMed Central

Echarri, Víctor; Espinosa, Almudena; Rizo, Carlos

2017-01-01

Opaque enclosures of buildings play an essential role in the level of comfort experienced indoors and annual energy demand. The impact of solar radiation and thermal inertia of the materials that make up the multi-layer enclosures substantially modify thermal transmittance behaviour of the enclosures. This dynamic form of heat transfer, additionally affected by indoor HVAC systems, has a substantial effect on the parameters that define comfort. It also has an impact on energy demand within a daily cycle as well as throughout a one-year use cycle. This study describes the destructive monitoring of an existing block of flats located in Alicante. Once the enclosure was opened, sensors of temperature (PT100), air velocity, and relative humidity were located in the different layers of the enclosure, as well as in the interior and exterior surfaces. A pyranometer was also installed to measure solar radiation levels. A temperature data correction algorithm was drawn up to address irregularities produced in the enclosure. The algorithm was applied using a Raspberry Pi processor in the data collection system. The comparative results of temperature gradients versus non-destructive monitoring systems are presented, providing measures of the transmittance value, surface temperatures and indoor and outdoor air temperatures. This remote sensing system can be used in future studies to quantify and compare the energy savings of different enclosure construction solutions. PMID:29292781

Air filtration in the free molecular flow regime: a review of high-efficiency particulate air filters based on carbon nanotubes.

PubMed

Li, Peng; Wang, Chunya; Zhang, Yingying; Wei, Fei

2014-11-01

Air filtration in the free molecular flow (FMF) regime is important and challenging because a higher filtration efficiency and lower pressure drop are obtained when the fiber diameter is smaller than the gas mean free path in the FMF regime. In previous studies, FMF conditions have been obtained by increasing the gas mean free path through reducing the pressure and increasing the temperature. In the case of carbon nanotubes (CNTs) with nanoscale diameters, it is possible to filtrate in the FMF regime under normal conditions. This paper reviews recent progress in theoretical and experimental studies of air filtration in the FMF regime. Typical structure models of high-efficiency particulate (HEPA) air filters based on CNTs are introduced. The pressure drop in air filters operated in the FMF regime is less than that predicted by the conventional air filtration theory. The thinnest HEPA filters fabricated from single-walled CNT films have an extremely low pressure drop. CNT air filters with a gradient nanostructure are shown to give a much better filtration performance in dynamic filtration. CNT air filters with a hierarchical structure and an agglomerated CNT fluidized bed air filter are also introduced. Finally, the challenges and opportunities for the application of CNTs in air filtration are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Buoyancy-Driven Heat Transfer During Application of a Thermal Gradient for the Study of Vapor Deposition at Low Pressure Using and Ideal Gas

NASA Technical Reports Server (NTRS)

Frazier, D. O.; Hung, R. J.; Paley, M. S.; Penn, B. G.; Long, Y. T.

1996-01-01

A mathematical model has been developed to determine heat transfer during vapor deposition of source materials under a variety of orientations relative to gravitational accelerations. The model demonstrates that convection can occur at total pressures as low as 10-2 mm Hg. Through numerical computation, using physical material parameters of air, a series of time steps demonstrates the development of flow and temperature profiles during the course of vapor deposition. These computations show that in unit gravity vapor deposition occurs by transport through a fairly complicated circulating flow pattern when applying heat to the bottom of the vessel with parallel orientation with respect to the gravity vector. The model material parameters for air predict the effect of kinematic viscosity to be of the same order as thermal diffusivity, which is the case for Prandtl number approx. 1 fluids. Qualitative agreement between experiment and the model indicates that 6-(2-methyl-4-nitroanilino)-2,4-hexadiyn-l-ol (DAMNA) at these pressures indeed approximates an ideal gas at the experiment temperatures, and may validate the use of air physical constants. It is apparent that complicated nonuniform temperature distribution in the vapor could dramatically affect the homogeneity, orientation, and quality of deposited films. The experimental test i's a qualitative comparison of film thickness using ultraviolet-visible spectroscopy on films generated in appropriately oriented vapor deposition cells. In the case where heating of the reaction vessel occurs from the top, deposition of vapor does not normally occur by convection due to a stable stratified medium. When vapor deposition occurs in vessels heated at the bottom, but oriented relative to the gravity vector between these two extremes, horizontal thermal gradients induce a complex flow pattern. In the plane parallel to the tilt axis, the flow pattern is symmetrical and opposite in direction from that where the vessel is positioned vertically. The ground-based experiments are sufficient preliminary tests of theory and should be of significant interest regarding vapor deposited films in microgravity.

Partially turbulated trailing edge cooling passages for gas turbine nozzles

DOEpatents

Thatcher, Jonathan Carl; Burdgick, Steven Sebastian

2001-01-01

A plurality of passages are spaced one from the other along the length of a trailing edge of a nozzle vane in a gas turbine. The passages lie in communication with a cavity in the vane for flowing cooling air from the cavity through the passages through the tip of the trailing edge into the hot gas path. Each passage is partially turbulated and includes ribs in an aft portion thereof to provide enhanced cooling effects adjacent the tip of the trailing edge. The major portions of the passages are smooth bore. By this arrangement, reduced temperature gradients across the trailing edge metal are provided. Additionally, the inlets to each of the passages have a restriction whereby a reduced magnitude of compressor bleed discharge air is utilized for trailing edge cooling purposes.

Sound control by temperature gradients

NASA Astrophysics Data System (ADS)

Sánchez-Dehesa, José; Angelov, Mitko I.; Cervera, Francisco; Cai, Liang-Wu

2009-11-01

This work reports experiments showing that airborne sound propagation can be controlled by temperature gradients. A system of two heated tubes is here used to demonstrate the collimation and focusing of an ultrasonic beam by the refractive index profile created by the temperature gradients existing around the tubes. Numerical simulations supporting the experimental findings are also reported.

43 CFR 3252.16 - How must I abandon a temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well? (a...

43 CFR 3252.15 - When must I abandon a temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well? When...

43 CFR 3252.16 - How must I abandon a temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well? (a...

43 CFR 3252.16 - How must I abandon a temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well? (a...

43 CFR 3252.15 - When must I abandon a temperature gradient well?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well? When...

43 CFR 3252.16 - How must I abandon a temperature gradient well?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false How must I abandon a temperature gradient well? 3252.16 Section 3252.16 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.16 How must I abandon a temperature gradient well? (a...

43 CFR 3252.15 - When must I abandon a temperature gradient well?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well? When...

43 CFR 3252.15 - When must I abandon a temperature gradient well?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false When must I abandon a temperature gradient well? 3252.15 Section 3252.15 Public Lands: Interior Regulations Relating to Public Lands (Continued... LEASING Conducting Exploration Operations § 3252.15 When must I abandon a temperature gradient well? When...

Temperature change rate actuated bubble mixing for homogeneous rehydration of dry pre-stored reagents in centrifugal microfluidics.

PubMed

Hin, S; Paust, N; Keller, M; Rombach, M; Strohmeier, O; Zengerle, R; Mitsakakis, K

2018-01-16

In centrifugal microfluidics, dead volumes in valves downstream of mixing chambers can hardly be avoided. These dead volumes are excluded from mixing processes and hence cause a concentration gradient. Here we present a new bubble mixing concept which avoids such dead volumes. The mixing concept employs heating to create a temperature change rate (TCR) induced overpressure in the air volume downstream of mixing chambers. The main feature is an air vent with a high fluidic resistance, representing a low pass filter with respect to pressure changes. Fast temperature increase causes rapid pressure increase in downstream structures pushing the liquid from downstream channels into the mixing chamber. As air further penetrates into the mixing chamber, bubbles form, ascend due to buoyancy and mix the liquid. Slow temperature/pressure changes equilibrate through the high fluidic resistance air vent enabling sequential heating/cooling cycles to repeat the mixing process. After mixing, a complete transfer of the reaction volume into the downstream fluidic structure is possible by a rapid cooling step triggering TCR actuated valving. The new mixing concept is applied to rehydrate reagents for loop-mediated isothermal amplification (LAMP). After mixing, the reaction mix is aliquoted into several reaction chambers for geometric multiplexing. As a measure for mixing efficiency, the mean coefficient of variation (C[combining macron]V[combining macron], n = 4 LabDisks) of the time to positivity (t p ) of the LAMP reactions (n = 11 replicates per LabDisk) is taken. The C[combining macron]V[combining macron] of the t p is reduced from 18.5% (when using standard shake mode mixing) to 3.3% (when applying TCR actuated bubble mixing). The bubble mixer has been implemented in a monolithic fashion without the need for any additional actuation besides rotation and temperature control, which are needed anyhow for the assay workflow.

Temperature logging of groundwater in bedrock wells for geothermal gradient characterization in New Hampshire, 2012

USGS Publications Warehouse

Degnan, James; Barker, Gregory; Olson, Neil; Wilder, Leland

2012-01-01

Maximum groundwater temperatures at the bottom of the logs were between 11.7 and 17.3 degrees Celsius. Geothermal gradients were generally higher than typically reported for other water wells in the United States. Some of the high gradients were associated with high natural gamma emissions. Groundwater flow was discernible in 5 of the 10 wells studied but only obscured the portion of the geothermal gradient signal where groundwater actually flowed through the well. Temperature gradients varied by mapped bedrock type but can also vary by differences in mineralogy or rock type within the wells.

TEMPERATURE-GRADIENT PLATES FOR GROWTH OF MICROORGANISMS

PubMed Central

Landman, Otto E.; Bausum, Howard T.; Matney, Thomas S.

1962-01-01

Landman, Otto E. (Fort Detrick, Frederick, Md.), Howard T. Bausum, and Thomas S. Matney. Temperature-gradient plates for growth of microorganisms. J. Bacteriol. 83:463–469. 1962.—Different temperature-gradient plates have been devised for the study of microbial growth on solid media through continuous temperature ranges or in liquid media at finely graded temperatures. All plates are made of heavy-gauge aluminum; heat supplied at one end is dissipated along the length of the metal so that a gradient is produced. The shape and range of the gradient depends on the amount of heat supplied, the insulation, the ambient temperature, and other factors. Differences of 0.2 C in temperature sensitivity between bacterial strains can be detected. The plates are simple to construct and operate. The dimensions of the aluminum, the mode of temperature measurement, and the method of heating may all be modified without diminishing the basic utility of the device. A sharp growth front develops at the maximal temperature of growth of bacteria. In most strains, all bacteria below the front form colonies and all bacteria above the front are killed, except for a few temperature-resistant mutants. Images PMID:14461975

Identifying Time Periods of Minimal Thermal Gradient for Temperature-Driven Structural Health Monitoring.

PubMed

Reilly, John; Glisic, Branko

2018-03-01

Temperature changes play a large role in the day to day structural behavior of structures, but a smaller direct role in most contemporary Structural Health Monitoring (SHM) analyses. Temperature-Driven SHM will consider temperature as the principal driving force in SHM, relating a measurable input temperature to measurable output generalized strain (strain, curvature, etc.) and generalized displacement (deflection, rotation, etc.) to create three-dimensional signatures descriptive of the structural behavior. Identifying time periods of minimal thermal gradient provides the foundation for the formulation of the temperature-deformation-displacement model. Thermal gradients in a structure can cause curvature in multiple directions, as well as non-linear strain and stress distributions within the cross-sections, which significantly complicates data analysis and interpretation, distorts the signatures, and may lead to unreliable conclusions regarding structural behavior and condition. These adverse effects can be minimized if the signatures are evaluated at times when thermal gradients in the structure are minimal. This paper proposes two classes of methods based on the following two metrics: (i) the range of raw temperatures on the structure, and (ii) the distribution of the local thermal gradients, for identifying time periods of minimal thermal gradient on a structure with the ability to vary the tolerance of acceptable thermal gradients. The methods are tested and validated with data collected from the Streicker Bridge on campus at Princeton University.

Temperature gradient effects on vapor diffusion in partially-saturated porous media

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

Webb, S.W.

1999-07-01

Vapor diffusion in porous media in the presence of its own liquid may be enhanced due to pore-scale processes, such as condensation and evaporation across isolated liquid islands. Webb and Ho (1997) developed one-and two-dimensional mechanistic pore-scale models of these processes in an ideal porous medium. For isothermal and isobaric boundary conditions with a concentration gradient, the vapor diffusion rate was significantly enhanced by these liquid island processes compared to a dry porous media. The influence of a temperature gradient on the enhanced vapor diffusion rate is considered in this paper. The two-dimensional pore network model which is used inmore » the present study is shown. For partially-saturated conditions, a liquid island is introduced into the top center pore. Boundary conditions on the left and right sides of the model are specified to give the desired concentration and temperature gradients. Vapor condenses on one side of the liquid island and evaporates off the other side due to local vapor pressure lowering caused by the interface curvature, even without a temperature gradient. Rather than acting as an impediment to vapor diffusion, the liquid island actually enhances the vapor diffusion rate. The enhancement of the vapor diffusion rate can be significant depending on the liquid saturation. Vapor diffusion is enhanced by up to 40% for this single liquid island compared to a dry porous medium; enhancement factors of up to an order of magnitude have been calculated for other conditions by Webb and Ho (1997). The dominant effect on the enhancement factor is the concentration gradient; the influence of the temperature gradient is smaller. The significance of these results, which need to be confirmed by experiments, is that the dominant model of enhanced vapor diffusion (EVD) by Philip and deVries (1957) predicts that temperature gradients must exist for EVD to occur. If there is no temperature gradient, there is no enhancement. The present results indicate that EVD is predominantly driven by concentration gradients; temperature gradients are less important. Therefore, the EVD model of Philip and deVries may need to be modified to reflect these results.« less

Sound beam manipulation based on temperature gradients

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

Qian, Feng; School of Physics & Electronic Engineering, Changshu Institute of Technology, Changshu 215500; Quan, Li

Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest tomore » fields such as noise control or acoustic cloaking.« less

Numerical heat transfer analysis of transcritical hydrocarbon fuel flow in a tube partially filled with porous media

NASA Astrophysics Data System (ADS)

Jiang, Yuguang; Feng, Yu; Zhang, Silong; Qin, Jiang; Bao, Wen

2016-01-01

Hydrocarbon fuel has been widely used in air-breathing scramjets and liquid rocket engines as coolant and propellant. However, possible heat transfer deterioration and threats from local high heat flux area in scramjet make heat transfer enhancement essential. In this work, 2-D steady numerical simulation was carried out to study different schemes of heat transfer enhancement based on a partially filled porous media in a tube. Both boundary and central layouts were analyzed and effects of gradient porous media were also compared. The results show that heat transfer in the transcritical area is enhanced at least 3 times with the current configuration compared to the clear tube. Besides, the proper use of gradient porous media also enhances the heat transfer compared to homogenous porous media, which could help to avoid possible over-temperature in the thermal protection.

Regional volume changes in canine lungs suspended in air

NASA Technical Reports Server (NTRS)

Abbrecht, Peter H.; Kyle, Richard R.; Bryant, Howard J.; Feuerstein, Irwin

1995-01-01

The purpose of this study was to determine the effect of the absence of a pleural pressure gradient (simulating the presumed condition found in microgravity) upon regional expansion of the lung. We attempted to produce a uniform pressure over the surface of the lung by suspending excised lungs in air. Such studies should help determine whether or not the absence of a pleural pressure gradient leads to uniform ventilation. A preparation in which there is no pleural pressure gradient should also be useful in studying non-gravitational effects on ventilation distribution.

Hardware/Software Data Acquisition System for Real Time Cell Temperature Monitoring in Air-Cooled Polymer Electrolyte Fuel Cells

PubMed Central

Bartolucci, Veronica

2017-01-01

This work presents a hardware/software data acquisition system developed for monitoring the temperature in real time of the cells in Air-Cooled Polymer Electrolyte Fuel Cells (AC-PEFC). These fuel cells are of great interest because they can carry out, in a single operation, the processes of oxidation and refrigeration. This allows reduction of weight, volume, cost and complexity of the control system in the AC-PEFC. In this type of PEFC (and in general in any PEFC), the reliable monitoring of temperature along the entire surface of the stack is fundamental, since a suitable temperature and a regular distribution thereof, are key for a better performance of the stack and a longer lifetime under the best operating conditions. The developed data acquisition (DAQ) system can perform non-intrusive temperature measurements of each individual cell of an AC-PEFC stack of any power (from watts to kilowatts). The stack power is related to the temperature gradient; i.e., a higher power corresponds to a higher stack surface, and consequently higher temperature difference between the coldest and the hottest point. The developed DAQ system has been implemented with the low-cost open-source platform Arduino, and it is completed with a modular virtual instrument that has been developed using NI LabVIEW. Temperature vs time evolution of all the cells of an AC-PEFC both together and individually can be registered and supervised. The paper explains comprehensively the developed DAQ system together with experimental results that demonstrate the suitability of the system. PMID:28698497

Hardware/Software Data Acquisition System for Real Time Cell Temperature Monitoring in Air-Cooled Polymer Electrolyte Fuel Cells.

PubMed

Segura, Francisca; Bartolucci, Veronica; Andújar, José Manuel

2017-07-09

This work presents a hardware/software data acquisition system developed for monitoring the temperature in real time of the cells in Air-Cooled Polymer Electrolyte Fuel Cells (AC-PEFC). These fuel cells are of great interest because they can carry out, in a single operation, the processes of oxidation and refrigeration. This allows reduction of weight, volume, cost and complexity of the control system in the AC-PEFC. In this type of PEFC (and in general in any PEFC), the reliable monitoring of temperature along the entire surface of the stack is fundamental, since a suitable temperature and a regular distribution thereof, are key for a better performance of the stack and a longer lifetime under the best operating conditions. The developed data acquisition (DAQ) system can perform non-intrusive temperature measurements of each individual cell of an AC-PEFC stack of any power (from watts to kilowatts). The stack power is related to the temperature gradient; i.e., a higher power corresponds to a higher stack surface, and consequently higher temperature difference between the coldest and the hottest point. The developed DAQ system has been implemented with the low-cost open-source platform Arduino, and it is completed with a modular virtual instrument that has been developed using NI LabVIEW. Temperature vs time evolution of all the cells of an AC-PEFC both together and individually can be registered and supervised. The paper explains comprehensively the developed DAQ system together with experimental results that demonstrate the suitability of the system.

Outdoor surface temperature measurement: ground truth or lie?

NASA Astrophysics Data System (ADS)

Skauli, Torbjorn

2004-08-01

Contact surface temperature measurement in the field is essential in trials of thermal imaging systems and camouflage, as well as for scene modeling studies. The accuracy of such measurements is challenged by environmental factors such as sun and wind, which induce temperature gradients around a surface sensor and lead to incorrect temperature readings. In this work, a simple method is used to test temperature sensors under conditions representative of a surface whose temperature is determined by heat exchange with the environment. The tested sensors are different types of thermocouples and platinum thermistors typically used in field trials, as well as digital temperature sensors. The results illustrate that the actual measurement errors can be much larger than the specified accuracy of the sensors. The measurement error typically scales with the difference between surface temperature and ambient air temperature. Unless proper care is taken, systematic errors can easily reach 10% of this temperature difference, which is often unacceptable. Reasonably accurate readings are obtained using a miniature platinum thermistor. Thermocouples can perform well on bare metal surfaces if the connection to the surface is highly conductive. It is pointed out that digital temperature sensors have many advantages for field trials use.

Temperature Inversions and Permafrost Distribution in a Mountain Valley: Preliminary Results From Wolf Creek, Yukon Territory, Canada

NASA Astrophysics Data System (ADS)

Lewkowicz, A. G.; Smith, K. M.

2004-12-01

The BTS (Basal Temperature of Snow) method to predict permafrost probability in mountain basins uses elevation as an easily available and spatially distributed independent variable. The elevation coefficient in the BTS regression model is, in effect, a substitute for ground temperature lapse rates. Previous work in Wolf Creek (60° 8'N 135° W), a mountain basin near Whitehorse, has shown that the model breaks down in a mid-elevation valley (1250 m asl) where actual permafrost probability is roughly twice that predicted by the model (60% vs. 20-30%). The existence of a double tree-line at the site suggested that air temperature inversions might be the cause of this inaccuracy (Lewkowicz and Ednie, 2004). This paper reports on a first year (08/2003-08/2004) of hourly air and ground temperature data collected along an altitudinal transect within the valley in upper Wolf Creek. Measurements were made at sites located 4, 8, 22, 82 and 162 m above the valley floor. Air temperature inversions between the lowest and highest measurement points occurred 42% of the time and in all months, but were most frequent and intense in winter (>60% of December and January) and least frequent in September (<25% of time). They generally developed after sunset and reached a maximum amplitude before sunrise. Only 11 inversions that lasted through more than one day occurred during the year, and only from October to February. The longest continuous duration was 145 h while the greatest inversion magnitude measured over the 160 m transect was 19° C. Ground surface temperatures are more difficult to interpret because of differences in soils and vegetation cover along the transect and the effects of seasonal snow cover. In many cases, however, air temperature inversions are not duplicated in the ground temperature record. Nevertheless, the annual altitudinal ground temperature gradient is much lower than would be expected from a standard atmospheric lapse rate, suggesting that the inversions do have an important impact on permafrost distribution at this site. More generally, therefore, it appears probable that any reduction in inversion frequency resulting from a more vigorous atmospheric circulation in the context of future climate change, would have a significant effect on permafrost distribution in mountain basins.

Influences of meteorological parameters on indoor radon concentrations (222Rn) excluding the effects of forced ventilation and radon exhalation from soil and building materials.

PubMed

Schubert, Michael; Musolff, Andreas; Weiss, Holger

2018-06-13

Elevated indoor radon concentrations ( 222 Rn) in dwellings pose generally a potential health risk to the inhabitants. During the last decades a considerable number of studies discussed both the different sources of indoor radon and the drivers for diurnal and multi day variations of its concentration. While the potential sources are undisputed, controversial opinions exist regarding their individual relevance and regarding the driving influences that control varying radon indoor concentrations. These drivers include (i) cyclic forced ventilation of dwellings, (ii) the temporal variance of the radon exhalation from soil and building materials due to e.g. a varying moisture content and (iii) diurnal and multi day temperature and pressure patterns. The presented study discusses the influences of last-mentioned temporal meteorological parameters by effectively excluding the influences of forced ventilation and undefined radon exhalation. The results reveal the continuous variation of the indoor/outdoor pressure gradient as key driver for a constant "breathing" of any interior space, which affects the indoor radon concentration with both diurnal and multi day patterns. The diurnally recurring variation of the pressure gradient is predominantly triggered by the day/night cycle of the indoor temperature that is associated with an expansion/contraction of the indoor air volume. Multi day patterns, on the other hand, are mainly due to periods of negative air pressure indoors that is triggered by periods of elevated wind speeds as a result of Bernoulli's principle. Copyright © 2018 Elsevier Ltd. All rights reserved.

Ion-temperature-gradient sensitivity of the hydrodynamic instability caused by shear in the magnetic-field-aligned plasma flow

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

Mikhailenko, V. V., E-mail: vladimir@pusan.ac.kr; Mikhailenko, V. S.; Faculty of Transportation Systems, Kharkiv National Automobile and Highway University, 61002 Kharkiv

2014-07-15

The cross-magnetic-field (i.e., perpendicular) profile of ion temperature and the perpendicular profile of the magnetic-field-aligned (parallel) plasma flow are sometimes inhomogeneous for space and laboratory plasma. Instability caused either by a gradient in the ion-temperature profile or by shear in the parallel flow has been discussed extensively in the literature. In this paper, (1) hydrodynamic plasma stability is investigated, (2) real and imaginary frequency are quantified over a range of the shear parameter, the normalized wavenumber, and the ratio of density-gradient and ion-temperature-gradient scale lengths, and (3) the role of inverse Landau damping is illustrated for the case of combinedmore » ion-temperature gradient and parallel-flow shear. We find that increasing the ion-temperature gradient reduces the instability threshold for the hydrodynamic parallel-flow shear instability, also known as the parallel Kelvin-Helmholtz instability or the D'Angelo instability. We also find that a kinetic instability arises from the coupled, reinforcing action of both free-energy sources. For the case of comparable electron and ion temperature, we illustrate analytically the transition of the D'Angelo instability to the kinetic instability as (a) the shear parameter, (b) the normalized wavenumber, and (c) the ratio of density-gradient and ion-temperature-gradient scale lengths are varied and we attribute the changes in stability to changes in the amount of inverse ion Landau damping. We show that near a normalized wavenumber k{sub ⊥}ρ{sub i} of order unity (i) the real and imaginary values of frequency become comparable and (ii) the imaginary frequency, i.e., the growth rate, peaks.« less

Reduction of particle deposition on substrates using temperature gradient control

DOEpatents

Rader, Daniel J.; Dykhuizen, Ronald C.; Geller, Anthony S.

2000-01-01

A method of reducing particle deposition during the fabrication of microelectronic circuitry is presented. Reduction of particle deposition is accomplished by controlling the relative temperatures of various parts of the deposition system so that a large temperature gradient near the surface on which fabrication is taking place exists. This temperature gradient acts to repel particles from that surface, thereby producing cleaner surfaces, and thus obtaining higher yields from a given microelectronic fabrication process.

The influence of vegetation, mesoclimate and meteorology on urban atmospheric microclimates across a coastal to desert climate gradient.

PubMed

Crum, Steven M; Shiflett, Sheri A; Jenerette, G Darrel

2017-09-15

Many cities are increasing vegetation in part due to the potential for microclimate cooling. However, the magnitude of vegetation cooling and sensitivity to mesoclimate and meteorology are uncertain. To improve understanding of the variation in vegetation's influence on urban microclimates we asked: how do meso- and regional-scale drivers influence the magnitude and timing of vegetation-based moderation on summertime air temperature (T a ), relative humidity (RH) and heat index (HI) across dryland cities? To answer this question we deployed a network of 180 temperature sensors in summer 2015 over 30 high- and 30 low-vegetated plots in three cities across a coastal to inland to desert climate gradient in southern California, USA. In a followup study, we deployed a network of temperature and humidity sensors in the inland city. We found negative T a and HI and positive RH correlations with vegetation intensity. Furthermore, vegetation effects were highest in evening hours, increasing across the climate gradient, with reductions in T a and increases in RH in low-vegetated plots. Vegetation increased temporal variability of T a , which corresponds with increased nighttime cooling. Increasing mean T a was associated with higher spatial variation in T a in coastal cities and lower variation in inland and desert cities, suggesting a climate dependent switch in vegetation sensitivity. These results show that urban vegetation increases spatiotemporal patterns of microclimate with greater cooling in warmer environments and during nighttime hours. Understanding urban microclimate variation will help city planners identify potential risk reductions associated with vegetation and develop effective strategies ameliorating urban microclimate. Published by Elsevier Ltd.

Experimental feasibility of investigating acoustic waves in Couette flow with entropy and pressure gradients

NASA Technical Reports Server (NTRS)

Parrott, Tony L.; Zorumski, William E.; Rawls, John W., Jr.

1990-01-01

The feasibility is discussed for an experimental program for studying the behavior of acoustic wave propagation in the presence of strong gradients of pressure, temperature, and flow. Theory suggests that gradients effects can be experimentally observed as resonant frequency shifts and mode shape changes in a waveguide. A convenient experimental geometry for such experiments is the annular region between two co-rotating cylinders. Radial temperature gradients in a spinning annulus can be generated by differentially heating the two cylinders via electromagnetic induction. Radial pressure gradients can be controlled by varying the cylinder spin rates. Present technology appears adequate to construct an apparatus to allow independent control of temperature and pressure gradients. A complicating feature of a more advanced experiment, involving flow gradients, is the requirement for independently controlled cylinder spin rates. Also, the boundary condition at annulus terminations must be such that flow gradients are minimally disturbed. The design and construction of an advanced apparatus to include flow gradients will require additional technology development.

The Influence of Wavelength-Dependent Absorption and Temperature Gradients on Temperature Determination in Laser-Heated Diamond-Anvil Cells

NASA Astrophysics Data System (ADS)

Deng, J.; Lee, K. K. M.; Du, Z.; Benedetti, L. R.

2016-12-01

In situ temperature measurements in the laser-heated diamond-anvil cell (LHDAC) are among the most fundamental experiments undertaken in high-pressure science. Despite its importance, few efforts have been made to examine the alteration of thermal radiation spectra of hot samples by wavelength-dependent absorption of the sample itself together with temperature gradients within samples while laser heating and their influence on temperature measurement. For example, iron-bearing minerals show strong wavelength dependent absorption in the wavelength range used to determine temperature, which, together with temperature gradients can account for largely aliased apparent temperatures (e.g., 1200 K deviation for a 4000 K melting temperature) in some experiments obtained by fitting of detected thermal radiation intensities. As such, conclusions of melting temperatures, phase diagrams and partitioning behavior, may be grossly incorrect for these materials. In general, wavelength-dependent absorption and temperature gradients of samples are two key factors to consider in order to rigorously constrain temperatures, which have been largely ignored in previous LHDAC studies. A reevaluation of temperatures measured in recent high-profile papers will be reviewed.

Environmental gradients and grassland trait variation: Insight into the effects of climate change

NASA Astrophysics Data System (ADS)

Tardella, Federico M.; Piermarteri, Karina; Malatesta, Luca; Catorci, Andrea

2016-10-01

The research aim was to understand how variation of temperature and water availability drives trait assemblage of seminatural grasslands in sub-Mediterranean climate, where climate change is expected to intensify summer aridity. In the central Italy, we recorded species abundance and elevation, slope aspect and angle in 129 plots. The traits we analysed were life span, growth form, clonality, belowground organs, leaf traits, plant height, seed mass, and palatability. We used Ellenberg's indicators as a proxy to assess air temperature and soil moisture gradients. From productive to harsh conditions, we observed a shift from tolerance to avoidance strategies, and a change in resource allocation strategies to face competition and stress or that maximize exploitation of patchily distributed soil resource niches. In addition, we found that the increase of temperature and water scarcity leads to the establishment of regeneration strategies that enable plants to cope with the unpredictability of changes in stress intensity and duration. Since the dry habitats of higher elevations are also constrained by winter cold stress, we argue that, within the sub-Mediterranean bioclimate, climate change will likely lead to a variation in dominance inside plant communities rather than a shift upwards of species ranges. At higher elevations, drought-adaptive traits might become more abundant on south-facing slopes that are less stressed by winter low temperatures; traits related to productive conditions and cold stress would be replaced on north-facing slopes by those adapted to overcome both the drought and the cold stresses.

The Potential of Tropospheric Gradients for Regional Precipitation Prediction

NASA Astrophysics Data System (ADS)

Boisits, Janina; Möller, Gregor; Wittmann, Christoph; Weber, Robert

2017-04-01

Changes of temperature and humidity in the neutral atmosphere cause variations in tropospheric path delays and tropospheric gradients. By estimating zenith wet delays (ZWD) and gradients using a GNSS reference station network the obtained time series provide information about spatial and temporal variations of water vapour in the atmosphere. Thus, GNSS-based tropospheric parameters can contribute to the forecast of regional precipitation events. In a recently finalized master thesis at TU Wien the potential of tropospheric gradients for weather prediction was investigated. Therefore, ZWD and gradient time series at selected GNSS reference stations were compared to precipitation data over a period of six months (April to September 2014). The selected GNSS stations form two test areas within Austria. All required meteorological data was provided by the Central Institution for Meteorology and Geodynamics (ZAMG). Two characteristics in ZWD and gradient time series can be anticipated in case of an approaching weather front. First, an induced asymmetry in tropospheric delays results in both, an increased magnitude of the gradient and in gradients pointing towards the weather front. Second, an increase in ZWD reflects the increased water vapour concentration right before a precipitation event. To investigate these characteristics exemplary test events were processed. On the one hand, the sequence of the anticipated increase in ZWD at each GNSS station obtained by cross correlation of the time series indicates the direction of the approaching weather front. On the other hand, the corresponding peak in gradient time series allows the deduction of the direction of movement as well. To verify the results precipitation data from ZAMG was used. It can be deduced, that tropospheric gradients show high potential for predicting precipitation events. While ZWD time series rather indicate the orientation of the air mass boundary, gradients rather indicate the direction of movement of an approaching weather front. Additionally our investigations have shown that gradients are able to capture the characteristics of an approaching weather front twenty to thirty hours before the precipitation event, which allows a first indication well in advance. Thus in conclusion, the utilization of GNSS tropospheric parameters, in particular tropospheric gradients, has the potential to contribute substantially to weather forecasting models.

Temperature gradient interaction chromatography of polymers: A molecular statistical model.

PubMed

Radke, Wolfgang; Lee, Sekyung; Chang, Taihyun

2010-11-01

A new model describing the retention in temperature gradient interaction chromatography of polymers is developed. The model predicts that polymers might elute in temperature gradient interaction chromatography in either an increasing or decreasing order or even nearly independent of molar mass, depending on the rate of the temperature increase relative to the flow rate. This is in contrast to solvent gradient elution, where polymers elute either in order of increasing molar mass or molar mass independent. The predictions of the newly developed model were verified with the literature data as well as new experimental data. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental Study on the Flow Regimes and Pressure Gradients of Air-Oil-Water Three-Phase Flow in Horizontal Pipes

PubMed Central

Al-Hadhrami, Luai M.; Shaahid, S. M.; Tunde, Lukman O.; Al-Sarkhi, A.

2014-01-01

An experimental investigation has been carried out to study the flow regimes and pressure gradients of air-oil-water three-phase flows in 2.25 ID horizontal pipe at different flow conditions. The effects of water cuts, liquid and gas velocities on flow patterns and pressure gradients have been studied. The experiments have been conducted at 20°C using low viscosity Safrasol D80 oil, tap water and air. Superficial water and oil velocities were varied from 0.3 m/s to 3 m/s and air velocity varied from 0.29 m/s to 52.5 m/s to cover wide range of flow patterns. The experiments were performed for 10% to 90% water cuts. The flow patterns were observed and recorded using high speed video camera while the pressure drops were measured using pressure transducers and U-tube manometers. The flow patterns show strong dependence on water fraction, gas velocities, and liquid velocities. The observed flow patterns are stratified (smooth and wavy), elongated bubble, slug, dispersed bubble, and annular flow patterns. The pressure gradients have been found to increase with the increase in gas flow rates. Also, for a given superficial gas velocity, the pressure gradients increased with the increase in the superficial liquid velocity. The pressure gradient first increases and then decreases with increasing water cut. In general, phase inversion was observed with increase in the water cut. The experimental results have been compared with the existing unified Model and a good agreement has been noticed. PMID:24523645

Experimental study on the flow regimes and pressure gradients of air-oil-water three-phase flow in horizontal pipes.

PubMed

Al-Hadhrami, Luai M; Shaahid, S M; Tunde, Lukman O; Al-Sarkhi, A

2014-01-01

An experimental investigation has been carried out to study the flow regimes and pressure gradients of air-oil-water three-phase flows in 2.25 ID horizontal pipe at different flow conditions. The effects of water cuts, liquid and gas velocities on flow patterns and pressure gradients have been studied. The experiments have been conducted at 20 °C using low viscosity Safrasol D80 oil, tap water and air. Superficial water and oil velocities were varied from 0.3 m/s to 3 m/s and air velocity varied from 0.29 m/s to 52.5 m/s to cover wide range of flow patterns. The experiments were performed for 10% to 90% water cuts. The flow patterns were observed and recorded using high speed video camera while the pressure drops were measured using pressure transducers and U-tube manometers. The flow patterns show strong dependence on water fraction, gas velocities, and liquid velocities. The observed flow patterns are stratified (smooth and wavy), elongated bubble, slug, dispersed bubble, and annular flow patterns. The pressure gradients have been found to increase with the increase in gas flow rates. Also, for a given superficial gas velocity, the pressure gradients increased with the increase in the superficial liquid velocity. The pressure gradient first increases and then decreases with increasing water cut. In general, phase inversion was observed with increase in the water cut. The experimental results have been compared with the existing unified Model and a good agreement has been noticed.

Passive microwave mapping of ice thickness. Final Report. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Apinis, J. J.; Peake, W. H.

1976-01-01

Basic calculations are presented for evaluating the feasibility of a scanning microwave radiometer system for mapping the thickness of lake ice. An analytical model for the apparent brightness temperature as a function of ice thickness has been developed, and elaborated to include such variables as galactic and atmospheric noise, aspect angle, polarization, temperature gradient in the ice, the presence of transition layers such as snow, slush, and water, increased loss due to air inclusions in the ice layer, and the presence of multiple ice thicknesses within the antenna footprint. It was found that brightness temperature measurements at six or seven frequencies in the range of 0.4 to 0.7 GHz were required to obtain unambiquous thickness estimates. A number of data processing methods were examined. The effects of antenna beamwidth, scanning rate, receiver bandwidth, noise figure, and integration time were studied.

Dehydration in the lower Antarctic stratosphere in late winter and spring

NASA Technical Reports Server (NTRS)

Kelly, K. K.; Tuck, A. F.; Fahey, D. W.; Proffitt, M. H.; Murphy, D. M.; Jones, R. L.; Mckenna, D. S.; Heidt, L. E.; Ferry, G. V.; Loewenstein, M.

1988-01-01

The history of minimum temperatures at 50 and 70 mb is examined from NMC, UK Met 0 and ECMWF analyses. MSU channel 24 data are similarly inspected. South Pole sonde data are used to calculate saturation humidity mixing ratio as a function of altitude and time throughout 1987. Saturation with respect to ice could be maintained for water mixing ratios of 3.5 ppmv for a period of about 80 days from mid-June to mid-September. Dehydration to mixing ratios of 1 ppmv or less was possible sporadically. Data from the ER-2 flights between 53 S and 72 S are used in conjunction with particle size measurements and air parcel trajectories to demonstrate the dehydration occurring over Antarctica. Water mixing ratios at the latitude of Punta Arenas (53 S), in conjunction with tracer measurements and trajectory analysis, show that at potential temperatures from about 325 to 400 K, the dryness (less than 3 ppmv) had its origin over Antarctica rather than in the tropics. Water mixing ratios within the Antarctic vortex varied from 1.5 to 3.8 ppmv, with a strong isentropic gradient being evident in the region of high potential vorticity gradients.

Dehydration in the lower Antarctic stratosphere during late winter and early spring, 1987

NASA Technical Reports Server (NTRS)

Kelly, K. K.; Tuck, A. F.; Murphy, D. M.; Fahey, D. W.; Proffitt, M. H.; Jones, R. L.; Mckenna, D. S.; Loewenstein, M.; Podolske, J. P.; Strahan, S. E.

1989-01-01

The history of minimum temperatures at 50 and 70 mb is examined from NMC, UK Met O and ECMWF analyses. MSU channel 24 data are similarly inspected. South Pole sonde data are used to calculate saturation humidity mixing ratio as a function of altitude and time throughout 1987. Saturation with respect to ice could be maintained for water mixing ratios of 3.5 ppmv for a period of about 80 days from mid-June to mid-September. Dehydration to mixing ratios of 1 ppmv or less was possible sporadically. Data from the ER-2 flights between 53 S and 72 S are used in conjunction with particle size measurements and air parcel trajectories to demonstrate the dehydration occurring over Antarctica. Water mixing ratios at the latitude of Punta Arens (53 S), in conjunction with tracer measurements and trajectory analysis, show that at potential temperatures from about 325 to 400 K, the dryness (less than 3 ppmv) had its origin over Antarctica rather than in the tropics. Water mixing ratios within the Antarctic vortex varied from 1.5 to 3.8 ppmv, with a strong isentropic gradient being evident in the region of high potential vorticity gradients.

Comparison of forced-air warming systems with lower body blankets using a copper manikin of the human body.

PubMed

Bräuer, A; English, M J M; Lorenz, N; Steinmetz, N; Perl, T; Braun, U; Weyland, W

2003-01-01

Forced-air warming has gained high acceptance as a measure for the prevention of intraoperative hypothermia. However, data on heat transfer with lower body blankets are not yet available. This study was conducted to determine the heat transfer efficacy of six complete lower body warming systems. Heat transfer of forced-air warmers can be described as follows:[1]Qdot;=h.DeltaT.A where Qdot; = heat transfer [W], h = heat exchange coefficient [W m-2 degrees C-1], DeltaT = temperature gradient between blanket and surface [ degrees C], A = covered area [m2]. We tested the following forced-air warmers in a previously validated copper manikin of the human body: (1) Bair Hugger and lower body blanket (Augustine Medical Inc., Eden Prairie, MN); (2) Thermacare and lower body blanket (Gaymar Industries, Orchard Park, NY); (3) WarmAir and lower body blanket (Cincinnati Sub-Zero Products, Cincinnati, OH); (4) Warm-Gard(R) and lower body blanket (Luis Gibeck AB, Upplands Väsby, Sweden); (5) Warm-Gard and reusable lower body blanket (Luis Gibeck AB); and (6) WarmTouch and lower body blanket (Mallinckrodt Medical Inc., St. Luis, MO). Heat flux and surface temperature were measured with 16 calibrated heat flux transducers. Blanket temperature was measured using 16 thermocouples. DeltaT was varied between -10 and +10 degrees C and h was determined by a linear regression analysis as the slope of DeltaT vs. heat flux. Mean DeltaT was determined for surface temperatures between 36 and 38 degrees C, because similar mean skin temperatures have been found in volunteers. The area covered by the blankets was estimated to be 0.54 m2. Heat transfer from the blanket to the manikin was different for surface temperatures between 36 degrees C and 38 degrees C. At a surface temperature of 36 degrees C the heat transfer was higher (between 13.4 W to 18.3 W) than at surface temperatures of 38 degrees C (8-11.5 W). The highest heat transfer was delivered by the Thermacare system (8.3-18.3 W), the lowest heat transfer was delivered by the Warm-Gard system with the single use blanket (8-13.4 W). The heat exchange coefficient varied between 12.5 W m-2 degrees C-1 and 30.8 W m-2 degrees C-1, mean DeltaT varied between 1.04 degrees C and 2.48 degrees C for surface temperatures of 36 degrees C and between 0.50 degrees C and 1.63 degrees C for surface temperatures of 38 degrees C. No relevant differences in heat transfer of lower body blankets were found between the different forced-air warming systems tested. Heat transfer was lower than heat transfer by upper body blankets tested in a previous study. However, forced-air warming systems with lower body blankets are still more effective than forced-air warming systems with upper body blankets in the prevention of perioperative hypothermia, because they cover a larger area of the body surface.

Extending the potential of evaporative cooling for heat-stress relief.

PubMed

Berman, A

2006-10-01

Factors were analyzed that limit the range of environmental conditions in which stress from heat may be relieved by evaporative cooling in shaded animals. Evaporative cooling reduces air temperature (Ta), but increases humidity. Equations were developed to predict Ta reduction as a function of ambient temperature and humidity and of humidity in cooled air. Predictions indicated that a reduction of Ta becomes marginal at humidities beyond 45%. A reduction of Ta lessens with rising ambient Ta. The impact of increasing humidity on respiratory heat loss (Hre) was estimated from existing data published on Holstein cattle. Respiratory heat loss is reduced by increased humidity up to 45%, but is not affected by higher humidity. Skin evaporative and sensible heat losses are determined not only by the humidity and temperature gradient, but also by air velocity close to the body surface. At higher Ta, the reduction in sensible heat loss is compensated for by an increased demand for Hre. High Hre may become a stressor when panting interferes with resting and rumination. Effects of temperature, humidity, air velocity, and body surface exposure to free air on Hre were estimated by a thermal balance model for lactating Holstein cows yielding 35 kg/d. The predictions of the simulations were supported by respiratory rate observations. The Hre was assumed to act as a stressor when exceeding 50% of the maximal capacity. When the full body surface was exposed to a 1.5 m/s air velocity, humidity (15 to 75%) had no significant predicted effect on Hre. For an air velocity of 0.3 m/s, Hre at 50% of the maximum rate was predicted at 34, 32.5, and 31.5 degrees C for relative humidities of 55, 65, and 75%, respectively. Similar results were predicted for an animal with two-thirds of its body surface exposed to 1.5 m/s air velocity. If air velocity was reduced for such animals to 0.3 m/s, the rise in Hre was expected to occur at approximately 25 degrees C and 50% relative humidity. Maximal rates of Hre were estimated at 27 to 30 degrees C when ambient humidity was 55% relative humidity and higher. High humidity may stress animals in evaporative cooling systems. Humidity stress may be prevented by a higher air velocity on the body surface of the animal, particularly in sheltered areas in which the exposed body surface is reduced, such as mangers and stalls. This may extend the use of evaporative cooling to less dry environments.

A sandwich-designed temperature-gradient incubator for studies of microbial temperature responses.

PubMed

Elsgaard, Lars; Jørgensen, Leif Wagner

2002-03-01

A temperature-gradient incubator (TGI) is described, which produces a thermal gradient over 34 aluminium modules (15x30x5 cm) intersected by 2-mm layers of partly insulating graphite foil (SigraFlex Universal). The new, sandwich-designed TGI has 30 rows of six replicate sample wells for incubation of 28-ml test tubes. An electric plate heats one end of the TGI, and the other end is cooled by thermoelectric Peltier elements in combination with a liquid cooling system. The TGI is equipped with 24 calibrated Pt-100 temperature sensors and insulated by polyurethane plates. A PC-operated SCADA (Supervisory Control And Data Acquisition) software (Genesis 4.20) is applied for temperature control using three advanced control loops. The precision of the TGI temperature measurements was better than +/-0.12 degrees C, and for a 0-40 degrees C gradient, the temperature at the six replicate sample wells varied less than +/-0.04 degrees C. Temperatures measured in incubated water samples closely matched the TGI temperatures, which showed a linear relationship to the sample row number. During operation for 8 days with a gradient of 0-40 degrees C, the temperature at the cold end was stable within +/-0.02 degrees C, while the temperatures at the middle and the warm end were stable within +/-0.08 degrees C (n=2370). Using the new TGI, it was shown that the fine-scale (1 degrees C) temperature dependence of S(o) oxidation rates in agricultural soil (0-29 degrees C) could be described by the Arrhenius relationship. The apparent activation energy (E(a)) for S(o) oxidation was 79 kJ mol(-1), which corresponded to a temperature coefficient (Q(10)) of 3.1. These data demonstrated that oxidation of S(o) in soil is strongly temperature-dependent. In conclusion, the new TGI allowed a detailed study of microbial temperature responses as it produced a precise, stable, and certifiable temperature gradient by the new and combined use of sandwich-design, thermoelectric cooling, and advanced control loops. The sandwich-design alone reduced the disadvantageous thermal gradient over individual sample wells by 56%.

Low Velocity Difference Thermal Shear Layer Mixing Rate Measurements

NASA Technical Reports Server (NTRS)

Bush, Robert H.; Culver, Harry C. M.; Weissbein, Dave; Georgiadis, Nicholas J.

2013-01-01

Current CFD modeling techniques are known to do a poor job of predicting the mixing rate and persistence of slot film flow in co-annular flowing ducts with relatively small velocity differences but large thermal gradients. A co-annular test was devised to empirically determine the mixing rate of slot film flow in a constant area circular duct (D approx. 1ft, L approx. 10ft). The axial rate of wall heat-up is a sensitive measure of the mixing rate of the two flows. The inflow conditions were varied to simulate a variety of conditions characteristic of moderate by-pass ratio engines. A series of air temperature measurements near the duct wall provided a straightforward means to measure the axial temperature distribution and thus infer the mixing rate. This data provides a characterization of the slot film mixing rates encountered in typical jet engine environments. The experimental geometry and entrance conditions, along with the sensitivity of the results as the entrance conditions vary, make this a good test for turbulence models in a regime important to modern air-breathing propulsion research and development.

Heat transfer rate within non-spherical thick grains

NASA Astrophysics Data System (ADS)

Huchet, Florian; Richard, Patrick; Joniot, Jules; Le Guen, Laurédan

2017-06-01

The prediction of the internal heat conduction into non-spherical thick grains constitutes a significant issue for physical modeling of a large variety of application involving convective exchanges between fluid and grains. In that context, the present paper deals with heat rate measurements of various sizes of particles, the thermal sensors being located at the interface fluid/grain and into the granular materials. Their shape is designed as cuboid in order to control the surface exchanges. In enclosed coneshaped apparatus, a sharp temperature gradient is ensured from a hot source releasing the air stream temperature equal to about 400°C. Two orientations of grain related to the air stream are considered: diagonally and straight arrangements. The thermal diffusivity of the grains and the Biot numbers are estimated from an analytical solution established for slab. The thermal kinetics evolution is correlated to the sample granular mass and its orientation dependency is demonstrated. Consequently, a generalized scaling law is proposed which is funded from the effective area of the heat transfer at the grain-scale, the dimensionless time being defined from the calculated diffusional coefficients.

Agricultural scene understanding

NASA Technical Reports Server (NTRS)

Landgrebe, D. A. (Principal Investigator); Bauer, M. E.; Silva, L.; Hoffer, R. M.; Baumgardner, M. F.

1977-01-01

The author has identified the following significant results. The LACIE field measurement data were radiometrically calibrated. Calibration enabled valid comparisons of measurements from different dates, sensors, and/or locations. Thermal band canopy results included: (1) Wind velocity had a significant influence on the overhead radiance temperature and the effect was quantized. Biomass and soil temperatures, temperature gradient, and canopy geometry were altered. (2) Temperature gradient was a function of wind velocity. (3) Temperature gradient of the wheat canopy was relatively constant during the day. (4) The laser technique provided good quality geometric characterization.

Observed Decrease of North American Winter Temperature Variability

NASA Astrophysics Data System (ADS)

Rhines, A. N.; Tingley, M.; McKinnon, K. A.; Huybers, P. J.

2015-12-01

There is considerable interest in determining whether temperature variability has changed in recent decades. Model ensembles project that extratropical land temperature variance will detectably decrease by 2070. We use quantile regression of station observations to show that decreasing variability is already robustly detectable for North American winter during 1979--2014. Pointwise trends from GHCND stations are mapped into a continuous spatial field using thin-plate spline regression, resolving small-scales while providing uncertainties accounting for spatial covariance and varying station density. We find that variability of daily temperatures, as measured by the difference between the 95th and 5th percentiles, has decreased markedly in winter for both daily minima and maxima. Composites indicate that the reduced spread of winter temperatures primarily results from Arctic amplification decreasing the meridional temperature gradient. Greater observed warming in the 5th relative to the 95th percentile stems from asymmetric effects of advection during cold versus warm days; cold air advection is generally from northerly regions that have experienced greater warming than western or southwestern regions that are generally sourced during warm days.

Identifying Time Periods of Minimal Thermal Gradient for Temperature-Driven Structural Health Monitoring

PubMed Central

Reilly, John; Glisic, Branko

2018-01-01

Temperature changes play a large role in the day to day structural behavior of structures, but a smaller direct role in most contemporary Structural Health Monitoring (SHM) analyses. Temperature-Driven SHM will consider temperature as the principal driving force in SHM, relating a measurable input temperature to measurable output generalized strain (strain, curvature, etc.) and generalized displacement (deflection, rotation, etc.) to create three-dimensional signatures descriptive of the structural behavior. Identifying time periods of minimal thermal gradient provides the foundation for the formulation of the temperature–deformation–displacement model. Thermal gradients in a structure can cause curvature in multiple directions, as well as non-linear strain and stress distributions within the cross-sections, which significantly complicates data analysis and interpretation, distorts the signatures, and may lead to unreliable conclusions regarding structural behavior and condition. These adverse effects can be minimized if the signatures are evaluated at times when thermal gradients in the structure are minimal. This paper proposes two classes of methods based on the following two metrics: (i) the range of raw temperatures on the structure, and (ii) the distribution of the local thermal gradients, for identifying time periods of minimal thermal gradient on a structure with the ability to vary the tolerance of acceptable thermal gradients. The methods are tested and validated with data collected from the Streicker Bridge on campus at Princeton University. PMID:29494496

Radial growth of two dominant montane conifer tree species in response to climate change in North-Central China.

PubMed

Jiang, Yuan; Zhang, Wentao; Wang, Mingchang; Kang, Muyi; Dong, Manyu

2014-01-01

North-Central China is a region in which the air temperature has clearly increased for several decades. Picea meyeri and Larix principis-rupprechtii are the most dominant co-occurring tree species within the cold coniferous forest belt ranging vertically from 1800 m to 2800 m a.s.l. in this region. Based on a tree-ring analysis of 292 increment cores sampled from 146 trees at different elevations, this study aimed to examine if the radial growth of the two species in response to climate is similar, whether the responses are consistent along altitudinal gradients and which species might be favored in the future driven by the changing climate. The results indicated the following: (1) The two species grew in different rhythms at low and high elevation respectively; (2) Both species displayed inconsistent relationships between radial growth and climate data along altitudinal gradients. The correlation between radial growth and the monthly mean temperature in the spring or summer changed from negative at low elevation into positive at high elevation, whereas those between the radial growth and the total monthly precipitation displayed a change from positive into negative along the elevation gradient. These indicate the different influences of the horizontal climate and vertical mountainous climate on the radial growth of the two species; (3) The species-dependent different response to climate in radial growth appeared mainly in autumn of the previous year. The radial growth of L. principis-rupprechtii displayed negative responses both to temperature and to precipitation in the previous September, October or November, which was not observed in the radial growth of P. meyeri. (4) The radial growth of both species will tend to be increased at high elevation and limited at low elevation, and L. principis-rupprechtii might be more favored in the future, if the temperature keeps rising.

Microfludic Device for Creating Ionic Strength Gradients over DNA Microarrays for Efficient DNA Melting Studies and Assay Development

PubMed Central

Petersen, Jesper; Poulsen, Lena; Birgens, Henrik; Dufva, Martin

2009-01-01

The development of DNA microarray assays is hampered by two important aspects: processing of the microarrays is done under a single stringency condition, and characteristics such as melting temperature are difficult to predict for immobilized probes. A technical solution to these limitations is to use a thermal gradient and information from melting curves, for instance to score genotypes. However, application of temperature gradients normally requires complicated equipment, and the size of the arrays that can be investigated is restricted due to heat dissipation. Here we present a simple microfluidic device that creates a gradient comprising zones of defined ionic strength over a glass slide, in which each zone corresponds to a subarray. Using this device, we demonstrated that ionic strength gradients function in a similar fashion as corresponding thermal gradients in assay development. More specifically, we noted that (i) the two stringency modulators generated melting curves that could be compared, (ii) both led to increased assay robustness, and (iii) both were associated with difficulties in genotyping the same mutation. These findings demonstrate that ionic strength stringency buffers can be used instead of thermal gradients. Given the flexibility of design of ionic gradients, these can be created over all types of arrays, and encompass an attractive alternative to temperature gradients, avoiding curtailment of the size or spacing of subarrays on slides associated with temperature gradients. PMID:19277213

Microfludic device for creating ionic strength gradients over DNA microarrays for efficient DNA melting studies and assay development.

PubMed

Petersen, Jesper; Poulsen, Lena; Birgens, Henrik; Dufva, Martin

2009-01-01

The development of DNA microarray assays is hampered by two important aspects: processing of the microarrays is done under a single stringency condition, and characteristics such as melting temperature are difficult to predict for immobilized probes. A technical solution to these limitations is to use a thermal gradient and information from melting curves, for instance to score genotypes. However, application of temperature gradients normally requires complicated equipment, and the size of the arrays that can be investigated is restricted due to heat dissipation. Here we present a simple microfluidic device that creates a gradient comprising zones of defined ionic strength over a glass slide, in which each zone corresponds to a subarray. Using this device, we demonstrated that ionic strength gradients function in a similar fashion as corresponding thermal gradients in assay development. More specifically, we noted that (i) the two stringency modulators generated melting curves that could be compared, (ii) both led to increased assay robustness, and (iii) both were associated with difficulties in genotyping the same mutation. These findings demonstrate that ionic strength stringency buffers can be used instead of thermal gradients. Given the flexibility of design of ionic gradients, these can be created over all types of arrays, and encompass an attractive alternative to temperature gradients, avoiding curtailment of the size or spacing of subarrays on slides associated with temperature gradients.

IMPROVED TEMPERATURE GRADIENT FOR MONITORING BEHAVIORAL THERMOREGULATION IN THE RAT

EPA Science Inventory

Past studies have found that the laboratory rat placed In a temperature gradient prefers temperatures that are markedly below its lower critical ambient temperature (LCT), whereas other rodents (e.g., mouse, hamster, and guinea pig) generally select thermal environments associate...

Measurement of physiological traits of paddy rice in temperature gradient chamber using Normalized Difference Vegetation Index and Photochemical Reflectance Index

NASA Astrophysics Data System (ADS)

Ryu, J. H.; Oh, D.; Cho, J.

2017-12-01

Global warming has been affecting the phenological and physiological conditions of crop plants due to heat stress. Thus, the scientific understanding of not only crop-yield change, but also growth progress during high temperature condition is necessary. In this study, growth response and yield of paddy rice depending on air temperature (Ta) has been studied in a Temperature Gradient Chamber (TGC) that is composed of higher Ta than actual Ta (ambient temperature). The results on imitating experiment of global warming provided the reduced production of crop by heat stress. Therefore, it is important to quickly detect the condition of a plant in order to minimize damage to heat stress on global warming. Phenological and physiological changes depending on Ta was detected using optical spectroscopy sensors because remote sensing is useful and efficient technology to monitor quickly and continually. Two vegetation indices, Normalized Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI), were applied to monitor paddy rice growth using hyperspectral and multispectral radiometer. Ta in TGC was gradually set from actual Ta + 0 ° to actual Ta + 3 °. The variations of NDVI and PRI were different during rice growth period, and also these patterns were changed depending on Ta condition. NDVI and PRI under +3 ° condition increase faster than ambient temperature. After heading stage, the values of NDVI and PRI were dropped. However, the NDVI and PRI of rice under heat stress were relatively slowly decreased. In addition, we found that the yield of rice decreased in the case of delayed drop patterns of NDVI and PRI after heading stage. Our results will be useful to understand crop plant conditions using vegetation index under global warming situations.

Changes in Hardware in Order to Accommodate Compliant Foil Air Bearings of a Larger Size

NASA Technical Reports Server (NTRS)

Zeszotek, Michelle

2004-01-01

Compliant foil air bearings are at the forefront of the Oil-Free turbomachinery revolution of supporting gas turbine engines with air lubricated hydrodynamic bearings. Foil air bearings have existed for almost fifty years, yet their commercialization has been confined to relatively small, high-speed systems characterized by low temperatures and loads, such as in air cycle machines, turbocompressors and micro-turbines. Recent breakthroughs in foil air bearing design and solid lubricant coating technology, have caused a resurgence of research towards applying Oil-Free technology to more demanding applications on the scale of small and mid range aircraft gas turbine engines. In order to foster the transition of Oil-Free technology into gas turbine engines, in-house experiments need to be performed on foil air bearings to further the understanding of their complex operating principles. During my internship at NASA Glenn in the summer of 2003, a series of tests were performed to determine the internal temperature profile in a compliant bump- type foil journal air bearing operating at room temperature under various speeds and load conditions. From these tests, a temperature profile was compiled, indicating that the circumferential thermal gradients were negligible. The tests further indicated that both journal rotational speed and radial load are responsible for heat generation with speed playing a more significant role in the magnitude of the temperatures. As a result of the findings from the tests done during the summer of 2003, it was decided that further testing would need to be done, but with a bearing of a larger diameter. The bearing diameter would now be increased from two inches to three inches. All of the currently used testing apparatus was designed specifically for a bearing that was two inches in diameter. Thus, my project for the summer of 2004 was to focus specifically on the scatter shield put around the testing rig while running the bearings. Essentially I was to design a scatter shield that would be able to accommodate the three inch bearing and that would also meet all safety requirements. Furthermore, the new scatter shield also had to house a heater, used for high-speed and temperature testing. Using Solidworks, a computer aided modeling program, I was able to accomplish the task set out for me and designed the new scatter shield. Furthermore, I also guided the fabrication process. As a result of this containment shield being designed, the Oil-Free turbomachinery team now has the ability to test bearings of larger diameters. Finally, it is expected that these tests will provide information useful for the validation of future analytical modeling codes.

Influence of natural temperature gradients on measurements of xylem sap flow with thermal dissipation probes. 1. Field observations and possible remedies.

PubMed

Do, F; Rocheteau, A

2002-06-01

The thermal dissipation method is simple and widely used for measuring sap flow in large stems. As with several other thermal methods, natural temperature gradients are assumed to be negligible in the sapwood being measured. We studied the magnitude and variability of natural temperature gradients in sapwood of Acacia trees growing in the Sahelian zone of Senegal, analyzed their effects on sap flow measurements, and investigated possible solutions. A new measurement approach employing cyclic heating (45 minutes of heating and 15 minutes of cooling; 45/15) was also tested. Three-day measurement sequences that included 1 day without heating, a second day with continuous heating and a third day with cyclic heating were recorded during a 6.5-month period using probes installed at three azimuths in a tree trunk. Natural temperature gradients between the two probes of the sensor unit, spaced 8 to 10 cm vertically, were rarely negligible (i.e., < 0.2 degrees C): they were positive during the night and negative during the day, with an amplitude ranging from 0.3 to 3.5 degrees C depending on trunk azimuth, day and season. These temperature gradients had a direct influence on the signal from the continuously heated sensors, inducing fluctuations in the nighttime reference signal. The resulting errors in sap flow estimates can be greater than 100%. Correction protocols have been proposed in previous studies, but they were unsuitable because of the high spatial and temporal variability of the natural temperature gradients. We found that a measurement signal derived from a noncontinuous heating system could be an attractive solution because it appears to be independent of natural temperature gradients. The magnitude and variability of temperature gradients that we observed were likely exacerbated by the combination of open stand, high solar radiation and low sap flow rate. However, for all applications of the thermal dissipation method, it is wise to check regularly for natural temperature gradients by switching off the heater.

Computational fluid dynamics modeling and analysis for the Giant Magellan Telescope (GMT)

NASA Astrophysics Data System (ADS)

Ladd, John; Slotnick, Jeffrey; Norby, William; Bigelow, Bruce; Burgett, William

2016-08-01

The Giant Magellan Telescope (GMT) is planned for construction at a summit of Cerro Las Campanas at the Los Campanas Observatory (LCO) in Chile. GMT will be the most powerful ground-based telescope in operation in the world. Aero-thermal interactions between the site topography, enclosure, internal systems, and optics are complex. A key parameter for optical quality is the thermal gradient between the terrain and the air entering the enclosure, and how quickly that gradient can be dissipated to equilibrium. To ensure the highest quality optical performance, careful design of the telescope enclosure building, location of the enclosure on the summit, and proper venting of the airflow within the enclosure is essential to minimize the impact of velocity and temperature gradients in the air entering the enclosure. High-fidelity Reynolds-Averaged Navier Stokes (RANS) Computational Fluid Dynamics (CFD) analysis of the GMT, enclosure, and LCO terrain is performed to study (a) the impact of either an open or closed enclosure base soffit external shape design, (b) the effect of telescope/enclosure location on the mountain summit, and (c) the effect of enclosure venting patterns. Details on the geometry modeling, grid discretization, and flow solution are first described. Then selected computational results are shown to quantify the quality of the airflow entering the GMT enclosure based on soffit, site location, and venting considerations. Based on the results, conclusions are provided on GMT soffit design, site location, and enclosure venting. The current work is not used to estimate image quality but will be addressed in future analyses as described in the conclusions.

Characterization of a novel micro-pressure swirl reactor for removal of chemical oxygen demand and total nitrogen from domestic wastewater at low temperature.

PubMed

Ren, Qingkai; Yu, Yang; Zhu, Suiyi; Bian, Dejun; Huo, Mingxin; Zhou, Dandan; Huo, Hongliang

2017-06-01

A novel micro-pressure swirl reactor (MPSR) was designed and applied to treat domestic wastewater at low temperature by acclimating microbial biomass with steadily decreasing temperature from 15 to 3 °C. Chemical oxygen demand (COD) was constantly removed by 85% and maintained below 50 mg L -1 in the effluent during the process. When the air flow was controlled at 0.2 m 3  h -1 , a swirl circulation was formed in the reactor, which created a dissolved oxygen (DO) gradient with a low DO zone in the center and a high DO zone in the periphery for denitrification and nitrification. 81% of total nitrogen was removed by this reactor, in which ammonium was reduced by over 90%. However, denitrification was less effective because of the presence of low levels of oxygen. The progressively decreasing temperature favored acclimation of psychrophilic bacteria in the reactor, which replaced mesophilic bacteria in the process of treatment.

Effect of Sequence Blockiness on the Morphologies of Surface-grafted Elastin-like Polypeptides

NASA Astrophysics Data System (ADS)

Albert, Julie; Sintavanon, Kornkanok; Mays, Robin; MacEwan, Sarah; Chilkoti, Ashutosh; Genzer, Jan

2014-03-01

The inter- and intra- molecular interactions among monomeric units of copolymers and polypeptides depend strongly on monomer sequence distribution and dictate the phase behavior of these species both in solution and on surfaces. To study the relationship between sequence and phase behavior, we have designed a series of elastin-like polypeptides (ELPs) with controlled monomer sequences that mimic copolymers with various co-monomer sequence distributions and attached them covalently to silicon substrates from buffer solutions at temperatures below and above the bulk ELPs' lower critical solution temperatures (LCSTs). The dependence of ELP grafting density on solution temperature was examined by ellipsometry and the resultant surface morphologies were examined in air and under water with atomic force microscopy. Depositions performed above the LCST resulted in higher grafting densities and greater surface roughness of ELPs relative to depositions carried out below the LCST. In addition, we are using gradient substrates to examine the effect of ELP grafting density on temperature responsiveness.

Assessment of VAS soundings in the analysis of a preconvective environment

NASA Technical Reports Server (NTRS)

Mostek, A.; Uccellini, L. W.; Petersen, R. A.; Chesters, D.

1985-01-01

Retrievals from the VISSR Atmospheric Sounder (VAS) are combined with conventional data to assess the impact of geosynchronous satellite soundings upon the analysis of a preconvective environment. VAS retrievals of temperature, dewpoint, equivalent potential temperature, precipitable water, and lifted index are derived with 60 km resolution at 3 hour intervals. When VAS fields are combined with analyses from conventional data sources, mesoscale regions with convective instability are more clearly delineated prior to the rapid development of the thunderstorms. The retrievals differentiate isolated areas in which air extends throughout the lower troposphere from those regions where moisture is confined to a thin layer near the Earth's surface. The analyses of the VAS retrievals identify significant spatial gradients and temporal changes in the thermal and moisture fields, especially in the regions between radiosonde observations.

Propagation of sound through the Earth's atmosphere. 1: Measurement of sound absorption in the air: 2: Measurement of ground impedance

NASA Technical Reports Server (NTRS)

Meredith, R. W.; Becher, J.

1981-01-01

Parts were fabricated for the acoustic ground impedance meter and the instrument was tested. A rubber hose was used to connect the resonator neck to the chamber in order to suppress vibration from the volume velocity source which caused chatter. An analog to digital converter was successfully hardwired to the computer detection system. The cooling system for the resonant tube was modified to use liquid nitrogen cooling. This produced the required temperature for the tube, but the temperature gradients within each of the four tube sections reached unacceptable levels. Final measurements of the deexcitation of nitrogen by water vapor indicate that the responsible physical process is not the direct vibration-translation energy transfer, but is a vibration-vibration energy transfer.

Remote atmospheric probing by ground to ground line of sight optical methods

NASA Technical Reports Server (NTRS)

Lawrence, R. S.

1969-01-01

The optical effects arising from refractive-index variations in the clear air are qualitatively described, and the possibilities are discussed of using those effects for remotely sensing the physical properties of the atmosphere. The effects include scintillations, path length fluctuations, spreading of a laser beam, deflection of the beam, and depolarization. The physical properties that may be measured include the average temperature along the path, the vertical temperature gradient, and the distribution along the path of the strength of turbulence and the transverse wind velocity. Line-of-sight laser beam methods are clearly effective in measuring the average properties, but less effective in measuring distributions along the path. Fundamental limitations to the resolution are pointed out and experiments are recommended to investigate the practicality of the methods.

Humidity data for 9975 shipping packages with cane fiberboard

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

Daugherty, W. L.

The 9975 surveillance program is developing a technical basis to support extending the storage period of 9975 packages in K-Area Complex beyond the currently approved 15 years. A key element of this effort is developing a better understanding of degradation of the fiberboard assembly under storage conditions. This degradation is influenced greatly by the moisture content of the fiberboard, which is not well characterized on an individual package basis. Direct measurements of humidity and fiberboard moisture content have been made on two test packages with cane fiberboard and varying internal heat levels from 0 up to 19W. With an internalmore » heat load, a temperature gradient in the fiberboard assembly leads to varying relative humidity in the air around the fiberboard. However, the absolute humidity tends to remain approximately constant throughout the package. The moisture content of fiberboard varies under the influence of several phenomena. Changes in local fiberboard temperature (from an internal heat load) can cause fiberboard moisture changes through absorption or evaporation. Fiberboard degradation at elevated temperature will produce water as a byproduct. And the moisture level within the package is constantly seeking equilibrium with that of the surrounding room air, which varies on a daily and seasonal basis. One indicator of the moisture condition within a 9975 package might be obtained by measuring the relative humidity in the upper air space, by inserting a humidity probe through a caplug hole. However, the data indicate that for the higher internal heat loads (15 and 19 watts), a large variation in internal moisture conditions produces little or no variation in the air space relative humidity. Therefore, this approach does not appear to be sensitive to fiberboard moisture variations at the higher heat loads which are of most interest to maintaining fiberboard integrity.« less

Experimental evaluation of the sensitivity to fuel utilization and air management on a 100 kW SOFC system

NASA Astrophysics Data System (ADS)

Santarelli, M.; Leone, P.; Calì, M.; Orsello, G.

The tubular SOFC generator CHP-100, built by Siemens Power Generation (SPG) Stationary Fuel Cells (SFC), is running at the Gas Turbine Technologies (GTT) in Torino (Italy), in the framework of the EOS Project. The nominal load of the generator ensures a produced electric power of around 105 kW e ac and around 60 kW t of thermal power at 250 °C to be used for the custom tailored HVAC system. Several experimental sessions have been scheduled on the generator; the aim is to characterize the operation through the analysis of some global performance index and the detailed control of the operation of the different bundles of the whole stack. All the scheduled tests have been performed by applying the methodology of design of experiment; the main obtained results show the effect of the change of the analysed operating factors in terms of distribution of voltage and temperature over the stack. Fuel consumption tests give information about the sensitivity of the voltage and temperature distribution along the single bundles. On the other hand, since the generator is an air cooled system, the results of the tests on the air stoichs have been used to analyze the generator thermal management (temperature distribution and profiles) and its effect on the polarization. The sensitivity analysis of the local voltage to the overall fuel consumption modifications can be used as a powerful procedure to deduce the local distribution of fuel utilization (FU) along the single bundles: in fact, through a model obtained by deriving the polarization curve respect to FU, it is possible to link the distribution of voltage sensitivities to FC to the distribution of the local FU. The FU distribution will be shown as non-uniform, and this affects the local voltage and temperatures, causing a high warming effect in some rows of the generator. Therefore, a discussion around the effectiveness of the thermal regulation made by the air stoichs, in order to reduce the non-uniform distribution of temperature and the overheating (increasing therefore the voltage behavior along the generator) has been performed. It is demonstrated that the utilization of one air plenum is not effective in the thermal regulation of the whole generator, in particular in the reduction of the temperature gradients linked to the non-uniform fuel distribution.

Intensified Indian Ocean climate variability during the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Thirumalai, K.; DiNezro, P.; Tierney, J. E.; Puy, M.; Mohtadi, M.

2017-12-01

Climate models project increased year-to-year climate variability in the equatorial Indian Ocean in response to greenhouse gas warming. This response has been attributed to changes in the mean climate of the Indian Ocean associated with the zonal sea-surface temperature (SST) gradient. According to these studies, air-sea coupling is enhanced due to a stronger SST gradient driving anomalous easterlies that shoal the thermocline in the eastern Indian Ocean. We propose that this relationship between the variability and the zonal SST gradient is consistent across different mean climate states. We test this hypothesis using simulations of past and future climate performed with the Community Earth System Model Version 1 (CESM1). We constrain the realism of the model for the Last Glacial Maximum (LGM) where CESM1 simulates a mean climate consistent with a stronger SST gradient, agreeing with proxy reconstructions. CESM1 also simulates a pronounced increase in seasonal and interannual variability. We develop new estimates of climate variability on these timescales during the LGM using δ18O analysis of individual foraminifera (IFA). IFA data generated from four different cores located in the eastern Indian Ocean indicate a marked increase in δ18O-variance during the LGM as compared to the late Holocene. Such a significant increase in the IFA-δ18O variance strongly supports the modeling simulations. This agreement further supports the dynamics linking year-to-year variability and an altered SST gradient, increasing our confidence in model projections.

Effects of low central fuelling on density and ion temperature profiles in reversed shear plasmas on JT-60U

NASA Astrophysics Data System (ADS)

Takenaga, H.; Ide, S.; Sakamoto, Y.; Fujita, T.; JT-60 Team

2008-07-01

Effects of low central fuelling on density and ion temperature profiles have been investigated using negative ion based neutral beam injection and electron cyclotron heating (ECH) in reversed shear plasmas on JT-60U. Strong internal transport barrier (ITB) was maintained in density and ion temperature profiles, when central fuelling was decreased by switching positive ion based neutral beam injection to ECH after the strong ITB formation. Similar density and ion temperature ITBs were formed for the low and high central fuelling cases during the plasma current ramp-up phase. Strong correlation between the density gradient and the ion temperature gradient was observed, indicating that particle transport and ion thermal transport are strongly coupled or the density gradient assists the ion temperature ITB formation through suppression of drift wave instabilities such as ion temperature gradient mode. These results support that the density and ion temperature ITBs can be formed under reactor relevant conditions.

Results of temperature gradient and heat flow in Santiam Pass Area, Oregon, Volume 1

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

Cox, B.L.; Gardner, M.C.; Koenig, J.B.

The conclusions of this report are: (1) There is a weakly defined thermal anomaly within the area examined by temperature-gradient holes in the Santiam Pass area. This is a relict anomaly showing differences in permeability between the High Cascades and Western Cascades areas, more than a fundamental difference in shallow crustal temperatures. (2) The anomaly as defined by the 60 F isotherms at 400 feet follows a north-south trend immediately westward of the Cascade axis in the boundary region. It is clear that all holes spudded into High Cascades rocks result in isothermal and reversal gradients. Holes spudded in Westernmore » Cascades rocks result in positive gradients. (3) Cold groundwater flow influences and masks temperature gradients in the High Cascades to a depth of at least 700 feet, especially eastward from the major north-south trending faults. Pleistocene and Holocene rocks are very permeable aquifers. (4) Shallow gradient drilling in the lowlands westward of the faults provides more interpretable information than shallow drilling in the cold-water recharge zones. Topographic and climatological effects can be filtered out of the temperature gradient results. (5) The thermal anomaly seems to have 2 centers: one in the Belknap-Foley area, and one northward in the Sand Mountain area. The anomalies may or may not be connected along a north-south trend. (6) A geothermal effect is seen in holes downslope of the Western-High Cascade boundary. Mixing with cold waters is a powerful influence on temperature gradient data. (7) The temperature-gradient program has not yet examined and defined the geothermal resources potential of the area eastward of the Western Cascades-High Cascades boundary. Holes to 1500-2000 feet in depth are required to penetrate the high permeability-cold groundwater regime. (8) Drilling conditions are unfavorable. There are very few accessible level drill sites. Seasonal access problems and environmental restrictions together with frequent lost circulation results in very high costs per foot drilled.« less

Ion temperature gradient mode driven solitons and shocks

NASA Astrophysics Data System (ADS)

Zakir, U.; Adnan, Muhammad; Haque, Q.; Qamar, Anisa; Mirza, Arshad M.

2016-04-01

Ion temperature gradient (ITG) driven solitons and shocks are studied in a plasma having gradients in the equilibrium number density and equilibrium ion temperature. In the linear regime, it is found that the ion temperature and the ratio of the gradient scale lengths, ηi=Ln/LT , affect both the real frequency and the growth rate of the ITG driven wave instability. In the nonlinear regime, for the first time we derive a Korteweg de Vries-type equation for the ITG mode, which admits solitary wave solution. It is found that the ITG mode supports only compressive solitons. Further, it is noticed that the soliton amplitude and width are sensitive to the parameter ηi=Ln/LT . Second, in the presence of dissipation in the system, we obtain a Burger type equation, which admits the shock wave solution. This work may be useful to understand the low frequency electrostatic modes in inhomogeneous electron-ion plasma having density and ion temperature gradients. For illustration, the model has been applied to tokamak plasma.

To cool, but not too cool: that is the question--immersion cooling for hyperthermia.

PubMed

Taylor, Nigel A S; Caldwell, Joanne N; Van den Heuvel, Anne M J; Patterson, Mark J

2008-11-01

Patient cooling time can impact upon the prognosis of heat illness. Although ice-cold-water immersion will rapidly extract heat, access to ice or cold water may be limited in hot climates. Indeed, some have concerns regarding the sudden cold-water immersion of hyperthermic individuals, whereas others believe that cutaneous vasoconstriction may reduce convective heat transfer from the core. It was hypothesized that warmer immersion temperatures, which induce less powerful vasoconstriction, may still facilitate rapid cooling in hyperthermic individuals. Eight males participated in three trials and were heated to an esophageal temperature of 39.5 degrees C by exercising in the heat (36 degrees C, 50% relative humidity) while wearing a water-perfusion garment (40 degrees C). Subjects were cooled using each of the following methods: air (20-22 degrees C), cold-water immersion (14 degrees C), and temperate-water immersion (26 degrees C). The time to reach an esophageal temperature of 37.5 degrees C averaged 22.81 min (air), 2.16 min (cold), and 2.91 min (temperate). Whereas each of the between-trial comparisons was statistically significant (P < 0.05), cooling in temperate water took only marginally longer than that in cold water, and one cannot imagine that the 45-s cooling time difference would have any meaningful physiological or clinical implications. It is assumed that this rapid heat loss was due to a less powerful peripheral vasoconstrictor response, with central heat being more rapidly transported to the skin surface for dissipation. Although the core-to-water thermal gradient was much smaller with temperate-water cooling, greater skin and deeper tissue blood flows would support a superior convective heat delivery. Thus, a sustained physiological mechanism (blood flow) appears to have countered a less powerful thermal gradient, resulting in clinically insignificant differences in heat extraction between the cold and temperate cooling trials.

Sensitivity of idealised baroclinic waves to mean atmospheric temperature and meridional temperature gradient changes

NASA Astrophysics Data System (ADS)

Rantanen, Mika; Räisänen, Jouni; Sinclair, Victoria A.; Järvinen, Heikki

2018-06-01

The sensitivity of idealised baroclinic waves to different atmospheric temperature changes is studied. The temperature changes are based on those which are expected to occur in the Northern Hemisphere with climate change: (1) uniform temperature increase, (2) decrease of the lower level meridional temperature gradient, and (3) increase of the upper level temperature gradient. Three sets of experiments are performed, first without atmospheric moisture, thus seeking to identify the underlying adiabatic mechanisms which drive the response of extra-tropical storms to changes in the environmental temperature. Then, similar experiments are performed in a more realistic, moist environment, using fixed initial relative humidity distribution. Warming the atmosphere uniformly tends to decrease the kinetic energy of the cyclone, which is linked both to a weaker capability of the storm to exploit the available potential energy of the zonal mean flow, and less efficient production of eddy kinetic energy in the wave. Unsurprisingly, the decrease of the lower level temperature gradient weakens the resulting cyclone regardless of the presence of moisture. The increase of the temperature gradient in the upper troposphere has a more complicated influence on the storm dynamics: in the dry atmosphere the maximum eddy kinetic energy decreases, whereas in the moist case it increases. Our analysis suggests that the slightly unexpected decrease of eddy kinetic energy in the dry case with an increased upper tropospheric temperature gradient originates from the weakening of the meridional heat flux by the eddy. However, in the more realistic moist case, the diabatic heating enhances the interaction between upper- and low-level potential vorticity anomalies and hence helps the surface cyclone to exploit the increased upper level baroclinicity.

A novel approach to determine the effect of irrigation on temperature and failure of Ni-Ti endodontic rotary files

PubMed Central

Mousavi, Sayed Ali; Kargar-Dehnavi, Vida; Mousavi, Sayed Amir

2012-01-01

Background: Nickel-titanium (Ni-Ti) rotary instrument files are important devices in Endodontics in root canal preparation. Ni-Ti file breakage is a critical and problematic issue and irrigation techniques were applied to decrease risk of file failure root. The aim of the present study was to compare the temperature gradient change of different irrigation solutions with Ni-Ti rotary instrument system during root canal preparation and also to define their effects on the file failure. Materials and Methods: A novel computerized instrumentation was utilized and thirty standard (ProFile #25/.04) files were divided into three groups and subjected to a filing in the root canal test. Changes in temperature on teeth under constant instrumental conditions with custom-designed computerized experimental apparatus were measured by using a temperature sensor bonded to the apical hole. A rotary instrument for canal preparation in three series of solution was used and the changes in temperature after each solution were compared. Finally, the file failure results were mentored according to each step of test. Comparisons were performed between group status clinically by using ANOVA (t) test, once the sample showed up normal and differences of P<0.01 were considered significant. All data collected were computerized and analyzed for frequency, distribution, and statistical description. Results: There was a decrease in the temperature of the instruments, which were immersed in 5% NaOCl, when compared with the water group (P<0.01). There was also a decrease in the temperature of the instruments immersed in water, when compared with the no solution group (P<0.01). Test results showed that sodium hypochlorite, water, or air of root canals does alter the properties of gradual temperature change and contributes to the failure of the instruments. Conclusion: By immersing the file in 5% NaOCl, the temperature gradient decreased and instrument failure was reduced. PMID:23087732

Effect of temperature gradient on the optical quality of mercurous chloride crystals

NASA Technical Reports Server (NTRS)

Singh, N. B.; Davies, D. K.; Gottlieb, M.; Henningsen, T.; Mazelsky, R.

1989-01-01

Single crystals of mercurous chloride were grown at temperature gradients of 8, 11 and 17 K/cm by the physical vapor transport method. The optical quality of these crystals was evaluated by measuring bulk scattering and inhomogeneity of refractive index by birefringence interferometry. It was observed that a high temperature gradient at the solid-vapor interface induced thermal stresses and crystals showed higher scattering and irregular fringes.

Influence of the Latitudinal Temperature Gradient on Soil Dust Concentration and Deposition in Greenland

NASA Technical Reports Server (NTRS)

Tegen, Ina; Rind, David

2000-01-01

To investigate the effects of changes in the latitudinal temperature gradient and the global mean temperature on dust concentration in the Northern Hemisphere, experiments with the Goddard Institute for Space Studies General Circulation Model (GISS GCM) are performed. The dust concentration over Greenland is calculated from sources in central and eastern Asia, which are integrated on-line in the model. The results show that an increase in the latitudinal temperature gradient increases both the Asian dust source strength and the concentration over Greenland. The source increase is the result of increased surface winds, and to a minor extent, the increase in Greenland dust is also associated with increased northward transport. Cooling the climate in addition to this increased gradient leads to a decrease in precipitation scavenging, which helps produce a further (slight) increase in Greenland dust in this experiment. Reducing the latitudinal gradient reduces the surface wind and hence the dust source, with a subsequent reduction in Greenland dust concentrations. Warming the climate in addition to this reduced gradient leads to a further reduction in Greenland dust due to enhanced precipitation scavenging. These results can be used to evaluate the relationship of Greenland ice core temperature changes to changes in the latitudinal and global temperatures.

CFD simulation of simultaneous monotonic cooling and surface heat transfer coefficient

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

Mihálka, Peter, E-mail: usarmipe@savba.sk; Matiašovský, Peter, E-mail: usarmat@savba.sk

The monotonic heating regime method for determination of thermal diffusivity is based on the analysis of an unsteady-state (stabilised) thermal process characterised by an independence of the space-time temperature distribution on initial conditions. At the first kind of the monotonic regime a sample of simple geometry is heated / cooled at constant ambient temperature. The determination of thermal diffusivity requires the determination rate of a temperature change and simultaneous determination of the first eigenvalue. According to a characteristic equation the first eigenvalue is a function of the Biot number defined by a surface heat transfer coefficient and thermal conductivity ofmore » an analysed material. Knowing the surface heat transfer coefficient and the first eigenvalue the thermal conductivity can be determined. The surface heat transport coefficient during the monotonic regime can be determined by the continuous measurement of long-wave radiation heat flow and the photoelectric measurement of the air refractive index gradient in a boundary layer. CFD simulation of the cooling process was carried out to analyse local convective and radiative heat transfer coefficients more in detail. Influence of ambient air flow was analysed. The obtained eigenvalues and corresponding surface heat transfer coefficient values enable to determine thermal conductivity of the analysed specimen together with its thermal diffusivity during a monotonic heating regime.« less

The influence of surface roughness and turbulence on heat fluxes from an oil palm plantation in Jambi, Indonesia

NASA Astrophysics Data System (ADS)

June, Tania; Meijide, Ana; Stiegler, Christian; Purba Kusuma, Alan; Knohl, Alexander

2018-05-01

Oil palm plantations are expanding vastly in Jambi, resulted in altered surface roughness and turbulence characteristics, which may influence exchange of heat and mass. Micrometeorological measurements above oil palm canopy were conducted for the period 2013–2015. The oil palms were 12.5 years old, canopy height 13 meters and 1.5 years old canopy height 2.5 m. We analyzed the influence of surface roughness and turbulence strenght on heat (sensible and latent) fluxes by investigating the profiles and gradient of wind speed, and temperature, surface roughness (roughness length, zo, and zero plane displacement, d), and friction velocity u*. Fluxes of heat were calculated using profile similarity methods taking into account atmospheric stability calculated using Richardson number Ri and the generalized stability factor ζ. We found that roughness parameters (zo, d, and u*) directly affect turbulence in oil palm canopy and hence heat fluxes; they are affected by canopy height, wind speed and atmospheric stability. There is a negative trend of d towards air temperature above the oil palm canopy, indicating the effect of plant volume and height in lowering air temperature. We propose studying the relation between zero plane displacement d with a remote sensing vegetation index for scaling up this point based analysis.

Modelling Hot Air Balloons.

ERIC Educational Resources Information Center

Brimicombe, M. W.

1991-01-01

A macroscopic way of modeling hot air balloons using a Newtonian approach is presented. Misleading examples using a car tire and the concept of hot air rising are discussed. Pressure gradient changes in the atmosphere are used to explain how hot air balloons work. (KR)

Radon daughters' concentration in air and exposure of joggers at the university campus of Bangalore, India.

PubMed

Ashok, G V; Nagaiah, N; Shiva Prasad, N G

2008-09-01

The concentration of radon daughters in outdoor air was measured continuously from January 2006 to December 2006 near the Department of Physics, Bangalore University campus, Bangalore. The concentration was measured by collecting air samples at a height of 1 m above the ground level on a glass micro fibre filter paper with a known air flow rate. The results show that the radon progeny concentration exhibits distinct seasonal and diurnal variations that are predominantly caused by changes in the temperature gradient at the soil-atmosphere interface. The concentration was found to be high from 20.00 to 8.00 hrs, when the turbulence mixing was minimum and low during the rest of the time. In terms of the monthly concentration, January was found to be the highest with September/August being the lowest. The diurnal variations in the concentrations of radon progeny were found to exhibit positive correlation with the relative humidity and anti-correlation with the atmospheric temperature. From the measured concentration, an attempt was made to establish the annual effective dose to the general public of the region and was found to be 0.085 mSv/a. In addition, an attempt was also made for the first time to study the variation of inhalation dose with respect to the physical activity levels. Results show that in the light of both the effect of chemical pollutants and radiation dose due to inhalation of radon daughters, evening jogging is advisable.

A tentative record of the last 1,000 years of Greenland temperature from occluded air in the GISP2 ice core

NASA Astrophysics Data System (ADS)

Kobashi, T.; Severinghaus, J. P.; Barnola, J.; Kawamura, K.; Beaudette, R.

2005-12-01

Ice borehole temperature inversion has been used to reconstruct Greenland surface temperature during the last millennium (Dahl-Jensen et al, Science, 1998). However, this technique does not preserve high frequencies because of diffusion of heat in the ice. Here, we present a tentative reconstruction of the past 1,000 years of central Greenland temperature using nitrogen and argon isotopes from occluded air in the GISP2 ice core. This technique preserves decadal-to-centennial-scale temperature variations and complements the borehole technique. Nitrogen and argon isotopes in the porous snow layer (~80m) experience two isotopic fractionations by gravitation and temperature gradients (ΔT) between the top and bottom of the snow layer. The simultaneous analysis of argon and nitrogen isotopes allows us to separate these two effects, and obtain a history of ΔT in the layer. To a first approximation, ΔT change on decadal to centennial time scales is a surface temperature history because the heat conductivity of snow is much smaller than that of ice, and the heat capacity of the ice sheet is quite large. The preliminary ΔT history (20-year interval) shows a Medieval Warm Period in the 11th to 12th centuries and the Little Ice Age in the 15th to 19th centuries. Furthermore, the record shows a clear similarity with the Be-10 record (a proxy for solar activity) with Wolf, Sporer, Maunder, and Dalton minima clearly seen in the cold periods. This finding is consistent with the hypothesis that solar activity influenced Greenland temperature during the past 1000 years.

Gradient porous electrode architectures for rechargeable metal-air batteries

DOEpatents

Dudney, Nancy J.; Klett, James W.; Nanda, Jagjit; Narula, Chaitanya Kumar; Pannala, Sreekanth

2016-03-22

A cathode for a metal air battery includes a cathode structure having pores. The cathode structure has a metal side and an air side. The porosity decreases from the air side to the metal side. A metal air battery and a method of making a cathode for a metal air battery are also disclosed.

An index of anomalous convective instability to detect tornadic and hail storms

NASA Astrophysics Data System (ADS)

Qian, Weihong; Leung, Jeremy Cheuk-Hin; Luo, Weimeng; Du, Jun; Gao, Jidong

2017-12-01

In this article, the synoptic-scale spatial structures for raising tornadic and hail storms are compared by analyzing the total and anomalous variable fields from the troposphere to the stratosphere. 15 cases of tornado outbreaks and 20 cases of hail storms that occurred in the central United States during 1980-2011 were studied. The anomalous temperature-height field shows that a tornadic or hail storm usually occurs at the boundary of anomalous warm and cold air masses horizontally in the troposphere. In one side, an anomalous warm air mass in the mid-low troposphere and an anomalous cold air mass in the stratosphere are vertically separated by a positive center of height anomalies at the upper troposphere. In another side, an opposite vertical pattern shows that an anomalous cold air mass in the mid-low troposphere and an anomalous warm air mass in the stratosphere are separated by a negative center of height anomalies at the upper troposphere. Therefore, two pairs of adjacent anomalous warm/cold centers and one pair of anomalous high/low centers combining together form a major tornadic or hail storm paradigm, which can be physically considered as the storage of anomalous potential energy (APE) to generate severe weather. To quantitatively measure the APE, we define an index of anomalous convective instability (ACI) which is a difference of integrating temperature anomalies based on two vertically opposite anomalous air masses. The APE transformation to anomalous kinetic energy, which reduces horizontal and vertical gradients of temperature anomalies, produces anomalous rising and sinking flows in the lower-layer anomalous warm and cold air mass sides, respectively. The intensity of ACI index for tornadic storm cases is 1.5 times larger than that of hail storm cases in average. Thus, this expression of anomalous variables is better than total variables used in the traditional synoptic chart and the ACI index is better than other indices to detect potential tornadic and hail storms in order to understand the environmental conditions affecting severe weather in analytical and model output datasets.

Infrared Images of Boundary Layer Transition on the D8 Transport Configuration in the LaRC 14- by 22-Foot Subsonic Tunnel

NASA Technical Reports Server (NTRS)

Mason, Michelle L.; Gatlin, Gregory M.

2015-01-01

Grit, trip tape, or trip dots are routinely applied on the leading-edge regions of the fuselage, wings, tails or nacelles of wind tunnel models to trip the flow from laminar to turbulent. The thickness of the model's boundary layer is calculated for nominal conditions in the wind tunnel test to determine the effective size of the trip dots, but the flow over the model may not transition as intended for runs with different flow conditions. Temperature gradients measured with an infrared camera can be used to detect laminar to turbulent boundary layer transition on a wind tunnel model. This non-intrusive technique was used in the NASA Langley 14- by 22-Foot Subsonic Tunnel to visualize the behavior of the flow over a D8 transport configuration model. As the flow through the wind tunnel either increased to or decreased from the run conditions, a sufficient temperature difference existed between the air and the model to visualize the transition location (due to different heat transfer rates through the laminar and the turbulent boundary layers) for several runs in this test. Transition phenomena were visible without active temperature control in the atmospheric wind tunnel, whether the air was cooler than the model or vice-versa. However, when the temperature of the model relative to the air was purposely changed, the ability to detect transition in the infrared images was enhanced. Flow characteristics such as a wing root horseshoe vortex or the presence of fore-body vortical flows also were observed in the infrared images. The images of flow features obtained for this study demonstrate the usefulness of current infrared technology in subsonic wind tunnel tests.

Seasonal Variability of Saturn's Tropospheric Temperatures, Winds and Para-H2 from Cassini Far-IR Spectroscopy

NASA Technical Reports Server (NTRS)

Fletcher, Leigh N.; Irwin, P. G. J; Achterberg, R. K.; Orton, G. S.; Flasar, F. M.

2015-01-01

Far-IR 16-1000 micrometer spectra of Saturn's hydrogen-helium continuum measured by Cassini's Composite Infrared Spectrometer (CIRS) are inverted to construct a near-continuous record of upper tropospheric (70-700 mbar) temperatures and para-H2 fraction as a function of latitude, pressure and time for a third of a saturnian year (2004-2014, from northern winter to northern spring). The thermal field reveals evidence of reversing summertime asymmetries superimposed onto the belt/zone structure. The temperature structure is almost symmetric about the equator by 2014, with seasonal lag times that increase with depth and are qualitatively consistent with radiative climate models. Localised heating of the tropospheric hazes (100-250 mbar) create a distinct perturbation to the temperature profile that shifts in magnitude and location, declining in the autumn hemisphere and growing in the spring. Changes in the para-H2 (f(sub p)) distribution are subtle, with a 0.02-0.03 rise over the spring hemisphere (200-500 mbar) perturbed by (i) low-f(sub p) air advected by both the springtime storm of 2010 and equatorial upwelling; and (ii) subsidence of high-f(sub p) air at northern high latitudes, responsible for a developing north-south asymmetry in f(sub p). Conversely, the shifting asymmetry in the para-H2 disequilibrium primarily reflects the changing temperature structure (and hence the equilibrium distribution of f(sub p)), rather than actual changes in f(sub p) induced by chemical conversion or transport. CIRS results interpolated to the same point in the seasonal cycle as re-analysed Voyager-1 observations (early northern spring) show qualitative consistency from year to year (i.e., the same tropospheric asymmetries in temperature and f(sub p)), with the exception of the tropical tropopause near the equatorial zones and belts, where downward propagation of a cool temperature anomaly associated with Saturn's stratospheric oscillation could potentially perturb tropopause temperatures, para-H2 and winds. Quantitative differences between the Cassini and Voyager epochs suggest that the oscillation is not in phase with the seasonal cycle at these tropospheric depths (i.e., it should be described as quasi-periodic rather than 'semi annual'). Variability in the zonal wind field derived from latitudinal thermal gradients is small (less than 10 m/s per scale height near the tropopause) and mostly affects the broad retrograde jets, with the notable exception of large variability on the northern flank of the equatorial jet. The meridional potential vorticity (PV) gradient, and hence the 'staircase of PV' associated with spatial variations in the vigour of vertical mixing, has varied over the course of the mission but maintained its overall shape. PV gradients in latitude and altitude are used to estimate the atmospheric refractive index for the propagation of stationary planetary (Rossby) waves, predicting that such wave activity would be confined to regions of real refractivity (tropical regions plus bands at 35-45 in both hemispheres). The penetration depth of these regions into the upper troposphere is temporally variable (potentially associated with stratification changes), whereas the latitudinal structure is largely unchanged over time (associated with the zonal jet system).

Response of hatchling and yearling turtles to thermal gradients: Comparison of Chelydra serpentina and Trachemys scripta

USGS Publications Warehouse

Bury, R. Bruce; Nebeker, A.B.; Adams, Michael J.

2000-01-01

In laboratory tests, young Chelydra serpentina and Trachemys scripta altered their distribution in the presence of a temperature gradient. Selection of temperatures in the gradient for hatchlings and yearlings showed that body temperatures (Tbs) of C. serpentina were lower than T. scripta, but the difference was insignificant. Relatively low Tbs could allow greater activity range and reduced metabolic maintenance cost for C. serpentina, which seldom leaves water.

Crystal growth and annealing for minimized residual stress

DOEpatents

Gianoulakis, Steven E.

2002-01-01

A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing.

Method for single crystal growth of photovoltaic perovskite material and devices

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

Huang, Jinsong; Dong, Qingfeng

Systems and methods for perovskite single crystal growth include using a low temperature solution process that employs a temperature gradient in a perovskite solution in a container, also including at least one small perovskite single crystal, and a substrate in the solution upon which substrate a perovskite crystal nucleates and grows, in part due to the temperature gradient in the solution and in part due to a temperature gradient in the substrate. For example, a top portion of the substrate external to the solution may be cooled.

Temperature gradient measurements by using thermoelectric effect in CNTs-silicone adhesive composite.

PubMed

Chani, Muhammad Tariq Saeed; Karimov, Kh S; Asiri, Abdullah M; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved

2014-01-01

This work presents the fabrication and investigation of thermoelectric cells based on composite of carbon nanotubes (CNT) and silicone adhesive. The composite contains CNT and silicon adhesive 1∶1 by weight. The current-voltage characteristics and dependences of voltage, current and Seebeck coefficient on the temperature gradient of cell were studied. It was observed that with increase in temperature gradient the open circuit voltage, short circuit current and the Seebeck coefficient of the cells increase. Approximately 7 times increase in temperature gradient increases the open circuit voltage and short circuit current up to 40 and 5 times, respectively. The simulation of experimental results is also carried out; the simulated results are well matched with experimental results.

Temperature Gradient Measurements by Using Thermoelectric Effect in CNTs-Silicone Adhesive Composite

PubMed Central

Chani, Muhammad Tariq Saeed; Karimov, Kh. S.; Asiri, Abdullah M.; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved

2014-01-01

This work presents the fabrication and investigation of thermoelectric cells based on composite of carbon nanotubes (CNT) and silicone adhesive. The composite contains CNT and silicon adhesive 1∶1 by weight. The current-voltage characteristics and dependences of voltage, current and Seebeck coefficient on the temperature gradient of cell were studied. It was observed that with increase in temperature gradient the open circuit voltage, short circuit current and the Seebeck coefficient of the cells increase. Approximately 7 times increase in temperature gradient increases the open circuit voltage and short circuit current up to 40 and 5 times, respectively. The simulation of experimental results is also carried out; the simulated results are well matched with experimental results. PMID:24748375

Dimensional and Structural Control of Silica Aerogel Membranes for Miniaturized Motionless Gas Pumps.

PubMed

Zhao, Shanyu; Jiang, Bo; Maeder, Thomas; Muralt, Paul; Kim, Nayoung; Matam, Santhosh Kumar; Jeong, Eunho; Han, Yen-Lin; Koebel, Matthias M

2015-08-26

With growing public interest in portable electronics such as micro fuel cells, micro gas total analysis systems, and portable medical devices, the need for miniaturized air pumps with minimal electrical power consumption is on the rise. Thus, the development and downsizing of next-generation thermal transpiration gas pumps has been investigated intensively during the last decades. Such a system relies on a mesoporous membrane that generates a thermomolecular pressure gradient under the action of an applied temperature bias. However, the development of highly miniaturized active membrane materials with tailored porosity and optimized pumping performance remains a major challenge. Here we report a systematic study on the manufacturing of aerogel membranes using an optimized, minimal-shrinkage sol-gel process, leading to low thermal conductivity and high air conductance. This combination of properties results in superior performance for miniaturized thermomolecular air pump applications. The engineering of such aerogel membranes, which implies pore structure control and chemical surface modification, requires both chemical processing know-how and a detailed understanding of the influence of the material properties on the spatial flow rate density. Optimal pumping performance was found for devices with integrated membranes with a density of 0.062 g cm(-3) and an average pore size of 142.0 nm. Benchmarking of such low-density hydrophobic active aerogel membranes gave an air flow rate density of 3.85 sccm·cm(-2) at an operating temperature of 400 °C. Such a silica aerogel membrane based system has shown more than 50% higher pumping performance when compared to conventional transpiration pump membrane materials as well as the ability to withstand higher operating temperatures (up to 440 °C). This study highlights new perspectives for the development of miniaturized thermal transpiration air pumps while offering insights into the fundamentals of molecular pumping in three-dimensional open-mesoporous materials.

Geology and hydrogeology of Naval Air Station Chase Field and Naval Auxiliary Landing Field Goliad, Bee and Goliad counties, Texas

USGS Publications Warehouse

Snyder, G.L.

1995-01-01

Large vertical hydraulic-head gradients are present between the unconfined Evangeline aquifer and confined Fleming aquifers at Naval Air Station Chase Field and Naval Auxiliary Landing Field Goliad. These gradients, together with the results of the aquifer test at Naval Air Station Chase Field and assumed characteristics of the confining units, indicate that downward flow of ground water probably occurs from the water-table aquifer to the underlying aquifers. The rate of downward flow between the two confined Fleming aquifers (from A-sand to B-sand) can be approximated using an estimate of vertical hydraulic conductivity of the intervening confining unit obtained from assumed storage characteristics and data from the aquifer test. Under the relatively high vertical hydraulic-head gradient induced by the aquifer test, ground-water movement from the A-sand aquifer to the B-sand aquifer could require about 490 years; and about 730 years under the natural gradient. Future increases in ground-water withdrawals from the B-sand aquifer might increase downward flow in the aquifer system of the study area.

The influence of process parameters in production of lipopeptide iturin A using aerated packed bed bioreactors in solid-state fermentation.

PubMed

Piedrahíta-Aguirre, C A; Bastos, R G; Carvalho, A L; Monte Alegre, R

2014-08-01

The strain Bacillus iso 1 co-produces the lipopeptide iturin A and biopolymer poly-γ-glutamic acid (γ-PGA) in solid-state fermentation of substrate consisting of soybean meal, wheat bran with rice husks as an inert support. The effects of pressure drop, oxygen consumption, medium permeability and temperature profile were studied in an aerated packed bed bioreactor to produce iturin A, diameter of which was 50 mm and bed height 300 mm. The highest concentrations of iturin A and γ-PGA were 5.58 and 3.58 g/kg-dry substrate, respectively, at 0.4 L/min after 96 h of fermentation. The low oxygen uptake rates, being 23.34 and 22.56 mg O2/kg-dry solid substrate for each air flow rate tested generated 5.75 W/kg-dry substrate that increased the fermentation temperature at 3.7 °C. The highest pressure drop was 561 Pa/m at 0.8 L/min in 24 h. This is the highest concentration of iturin A produced to date in an aerated packed bed bioreactor in solid-state fermentation. The results can be useful to design strategies to scale-up process of iturin A in aerated packed bed bioreactors. Low concentration of γ-PGA affected seriously pressure drop, decreasing the viability of the process due to generation of huge pressure gradients with volumetric air flow rates. Also, the low oxygenation favored the iturin A production due to the reduction of free void by γ-PGA production, and finally, the low oxygen consumption generated low metabolic heat. The results show that it must control the pressure gradients to scale-up the process of iturin A production.

Optical ray tracing method for simulating beam-steering effects during laser diagnostics in turbulent media.

PubMed

Wang, Yejun; Kulatilaka, Waruna D

2017-04-10

In most coherent spectroscopic methods used in gas-phase laser diagnostics, multiple laser beams are focused and crossed at a specific location in space to form the probe region. The desired signal is then generated as a result of nonlinear interactions between the beams in this overlapped region. When such diagnostic schemes are implemented in practical devices having turbulent reacting flow fields with refractive index gradients, the resulting beam steering can give rise to large measurement uncertainties. The objective of this work is to simulate beam-steering effects arising from pressure and temperature gradients in gas-phase media using an optical ray tracing approach. The ZEMAX OpticStudio software package is used to simulate the beam crossing and uncrossing effects in the presence of pressure and temperature gradients, specifically the conditions present in high-pressure, high-temperature combustion devices such as gas turbine engines. Specific cases involving two-beam and three-beam crossing configurations are simulated. The model formulation, the effects of pressure and temperature gradients, and the resulting beam-steering effects are analyzed. The results show that thermal gradients in the range of 300-3000 K have minimal effects, while pressure gradients in the range of 1-50 atm result in pronounced beam steering and the resulting signal fluctuations in the geometries investigated. However, with increasing pressures, the temperature gradients can also have a pronounced effect on the resultant signal levels.

Bacterial chemotaxis along vapor-phase gradients of naphthalene.

PubMed

Hanzel, Joanna; Harms, Hauke; Wick, Lukas Y

2010-12-15

The role of bacterial growth and translocation for the bioremediation of organic contaminants in the vadose zone is poorly understood. Whereas air-filled pores restrict the mobility of bacteria, diffusion of volatile organic compounds in air is more efficient than in water. Past research, however, has focused on chemotactic swimming of bacteria along gradients of water-dissolved chemicals. In this study we tested if and to what extent Pseudomonas putida PpG7 (NAH7) chemotactically reacts to vapor-phase gradients forming above their swimming medium by the volatilization from a spot source of solid naphthalene. The development of an aqueous naphthalene gradient by air-water partitioning was largely suppressed by means of activated carbon in the agar. Surprisingly, strain PpG7 was repelled by vapor-phase naphthalene although the steady state gaseous concentrations were 50-100 times lower than the aqueous concentrations that result in positive chemotaxis of the same strain. It is thus assumed that the efficient gas-phase diffusion resulting in a steady, and possibly toxic, naphthalene flux to the cells controlled the chemotactic reaction rather than the concentration to which the cells were exposed. To our knowledge this is the first demonstration of apparent chemotactic behavior of bacteria in response to vapor-phase effector gradients.

Impact of the Rhône and Durance valleys on sea-breeze circulation in the Marseille area

NASA Astrophysics Data System (ADS)

Bastin, Sophie; Drobinski, Philippe; Dabas, Alain; Delville, Patricia; Reitebuch, Oliver; Werner, Christian

2005-03-01

Sea-breeze dynamics in the Marseille area, in the south of France, is investigated in the framework of the ESCOMPTE experiment conducted during summer 2001 in order to evaluate the role of thermal circulations on pollutant transport and ventilation. Under particular attention in this paper is the sea-breeze channelling by the broad Rhône valley and the narrow Durance valley, both oriented nearly-north-south, i.e., perpendicular to the coastline, and its possible impact on the sea-breeze penetration, intensity and depth, which are key information for air pollution issues. One situation of slight synoptic pressure gradient leading to a northerly flow in the Rhône valley (25 June 2001) and one situation of a weak onshore prevailing synoptic wind (26 June 2001) are compared. The impact of the Rhône and Durance valleys on the sea-breeze dynamics on these two typical days is generalized to the whole ESCOMPTE observing period. The present study shows by combining simple scaling analysis with wind data from meteorological surface stations and Doppler lidars that (i) the Durance valley always affects the sea breeze by accelerating the flow. A consequence is that the Durance valley contributes to weaken the temperature gradient along the valley and thus the sea-breeze circulation. In some cases, the acceleration of the channelled flow in the Durance valley suppresses the sea-breeze flow by temperature gradient inhibition; (ii) the Rhône valley does not generally affect the sea breeze significantly. However, if the sea breeze is combined with an onshore flow, it leads to further penetration inland and intensification of the low-level southerly flow. In this situation, lateral constriction may accelerate the sea breeze. Simple scaling analysis suggests that Saint Paul (44.35°N, about 100 km from the coastline) is the lower limit where sea breeze can be affected by the Rhône valley. These conclusions have implications in air quality topics as channelled sea breeze may advect far inland pollutants which may be incorporated into long-range transport, particularly in the Durance valley.

Investigating the biophysical controls on mass and energy cycling in Southwestern US ecosystems using the New Mexico Elevation Gradient of flux towers.

NASA Astrophysics Data System (ADS)

Krofcheck, D. J.; Morillas, L.; Litvak, M. E.

2014-12-01

Drylands and semi-arid ecosystems cover over 45% of the global landmass. These biomes have been shown to be extremely sensitive to changes in climate, specifically decreases in precipitation and increases in air temperature. Therefore, inter-annual variability in climate has the potential to dramatically impact the carbon budget at regional and global scales. In the Southwestern US, we are in a unique position to investigate these relationships by leveraging eight years of data from the New Mexico Elevation Gradient (NMEG), eight flux towers that span six representative biomes across the semi-arid Southwest. From C4 desert grasslands to subalpine mixed conifer forests, the NMEG flux towers use identical instrumentsand processing, and afford a unique opportunity to explore patterns in biome-specific ecosystem processes and climate sensitivity. Over the last eight years the gradient has experienced climatic variability that span from wet years to an episodic megadrought. Here we report the effects of this extreme inter-annual variability in climate on the ability of semi-arid ecosystems to cycle and store energy and carbon. We also investigated biome-specific patterns of ecosystem light and water use efficiency during a series of wet and dry years, and how these vary in response to air temperature, vapor pressure deficit, evaporative fraction, and precipitation. Our initial results suggest that significant drought reduced the maximum ecosystem assimilation of carbon most at the C4 grasslands, creosote shrublands, juniper savannas, and ponderosa pine forests, with 60%, 50%, 35%, and 50% reduction respectively, relative to a wet year. Ecosystem light use efficiency tends to show the highest maximum values at the low elevation sites as a function of water availability, with the highest annual values consistently at the middle elevation and ponderosa pine sites. Water use efficiency was strongly biome dependent with the middle elevation sites showing the highest efficiencies, and the greatest within year variability at the lower elevation sites, with strong sensitivities to vapor pressure deficit. By quantifying the biome-specific ecosystem processes and functional responses, this network provides valuable insight about how vulnerable this range of semi-arid ecosystems is to future climate scenarios.

High resolution temperature mapping of gas turbine combustor simulator exhaust with femtosecond laser induced fiber Bragg gratings

NASA Astrophysics Data System (ADS)

Walker, Robert B.; Yun, Sangsig; Ding, Huimin; Charbonneau, Michel; Coulas, David; Lu, Ping; Mihailov, Stephen J.; Ramachandran, Nanthan

2017-04-01

Femtosecond infrared (fs-IR) laser written fiber Bragg gratings (FBGs), have demonstrated great potential for extreme sensing. Such conditions are inherent in advanced gas turbine engines under development to reduce greenhouse gas emissions; and the ability to measure temperature gradients in these harsh environments is currently limited by the lack of sensors and controls capable of withstanding the high temperature, pressure and corrosive conditions present. This paper discusses fabrication and deployment of several fs-IR written FBG arrays, for monitoring exhaust temperature gradients of a gas turbine combustor simulator. Results include: contour plots of measured temperature gradients, contrast with thermocouple data.

Sapwood temperature gradients between lower stems and the crown do not influence estimates of stand-level stem CO(2) efflux.

PubMed

Bowman, William P; Turnbull, Matthew H; Tissue, David T; Whitehead, David; Griffin, Kevin L

2008-10-01

Temperature plays a critical role in the regulation of respiration rates and is often used to scale measurements of respiration to the stand-level and calculate annual respiratory fluxes. Previous studies have indicated that failure to consider temperature gradients between sun-exposed stems and branches in the crown and shaded lower stems may result in errors when deriving stand-level estimates of stem CO(2) efflux. We measured vertical gradients in sapwood temperature in a mature lowland podocarp rain forest in New Zealand to: (1) estimate the effects of within-stem temperature variation on the vertical distribution of stem CO(2) efflux; and (2) use these findings to estimate stand-level stem CO(2) efflux for this forest. Large within-stem gradients in sapwood temperature (1.6 +/- 0.1 to 6.0 +/- 0.5 degrees C) were observed. However, these gradients did not significantly influence the stand-level estimate of stem CO(2) efflux in this forest (536 +/- 42 mol CO(2) ha(-1) day(-1)) or the vertical distribution of stem CO(2) efflux, because of the opposing effects of daytime warming and nighttime cooling on CO(2) efflux in the canopy, and the small fraction of the woody biomass in the crowns of forest trees. Our findings suggest that detailed measurements of within-stand temperature gradients are unlikely to greatly improve the accuracy of tree- or stand-level estimates of stem CO(2) efflux.

A Study on Temperature and Precipitation Variability in Pre-monsoon Period of 2016 in the Dudh Khola River Valley, Manang, Nepal

NASA Astrophysics Data System (ADS)

Kayastha, R.; Kayastha, R. B.; Chand, M. B.; Armstrong, R. L.

2016-12-01

Meteorological data are the key parameter for deeper and better understanding the local to regional climate variability. Temperature and precipitation are highly dependent on elevation and it is foremost important in water resource management. The runoff from glacierized catchments is greatly influenced by the variation in temperature and precipitation. However, inaccessibility limits the hydro-meteorological data observation in high altitudes. In this study, temperature and precipitation data are observed and analyzed from six stations including two weather stations in different elevation ranging from 1926 to 3908 m a.s.l. in the Dudh Khola River basin, a sub basin of Marsyangdi River basin from March to June 2016 (pre-monsoon period). Clear spatial and temporal variability of temperature lapse rate (TLR) is observed which is related to the extent of humid air. The hourly mean TLR shows highly heterogeneous between the different elevations from - 0.72 o C, -0.51 o C, -0.77 o C, -0.68 to +0.42 o C per 100 m and the hourly linear regression of TLR is - 0.54 o C per 100 m. Similarly, vertical precipitation gradients (PG) between Dharapani & Goa, Goa & Yak Kharka, and Yak Kharka & glacier station are 0.040, 0.037 and 0.032 per meter respectively. Horizontal precipitation gradient from lower station to the higher station in a distance of 16 km is 0.0015 mm per meter. The TLR from the recorded period are less than the environmental lapse rate in the Dudh Khola Valley in pre-monsoon season. From this study it can be concluded that hourly and daily lapse rates and PGs can be used to improve the output of the glacio-hydrological and energy balance modelling in glacierized river basin.

Hotspots and key periods of Greenland climate change during the past six decades

NASA Astrophysics Data System (ADS)

Abermann, J.; Hansen, B. U.; Lund, M.; Wacker, S.; Karami, M.; Cappelen, J.

2016-12-01

We investigate spatial gradients of air temperature and pressure and their trends in Greenland and compare these considering varying time window lengths since 1958. Both latitudinal temperature and pressure gradients are strongest during winter. An overall temperature increase of up to 0.15°C yr-1 has been observed for 1996-2014. The strongest warming happened during February at the West Coast (up to 0.6°C/yr), weaker but significant warming occurred during summer months (up to 0.3°C/yr) both in West and in East Greenland. Pressure trends are mainly negative if at all, but largely not significant. We discuss the relevance of these findings in an upscaling context of an extensive ecosystem monitoring program that was established in 1996 in Northeast Greenland (Zackenberg, www.g-e-m.dk). Improving the understanding of the interaction between the individual components of the ecosystem is its core idea, climate being the main driver. A series of studies highlights trends and variability for biotic and abiotic parameters for this period on a point scale. In order to expand trend assessments to a Greenland-wide scale, local climate trends in Zackenberg have to be put into a larger spatio-temporal context. We find that temperature trends in Northeast Greenland and the area around Zackenberg follow the general pattern but are smaller than the average in Greenland. Compared with other time windows in the past 6 decades, the study period 1996 - 2014 marks an above average warming trend; peak warming however occurred half a decade earlier. We therefore conclude that temperature-driven ecosystem changes observed in Zackenberg mark a lower boundary for environmental changes in Greenland.

Measurement of DDT fluxes from a historically treated agricultural soil in Canada.

PubMed

Kurt-Karakus, Perihan Binnur; Bidleman, Terry F; Staebler, Ralf M; Jones, Kevin C

2006-08-01

Organocohlorine pesticide (OCP) residues in agricultural soils are of concern due to the uptake of these compounds by crops, accumulation in the foodchain, and reemission from soils to the atmosphere. Although it has been about three decades since DDT was banned for agricultural uses in Canada, residues persist in soils of some agricultural areas. Emission of DDT compounds to the atmosphere from a historically treated field in southern Ontario was determined in fall 2004 and spring 2005. The sigmaDDTs concentration in the high organic matter (71%) soil was 19 +/- 4 microg g(-1) dry weight. Concentration gradients in the air were measured at 5, 20, 72, and 200 cm above soil using glass fiber filter-polyurethane foam cartridges. Air concentrations of sigmaDDTs averaged 5.7 +/- 5.1 ng m(-3) at 5 cm and decreased to 1.3 +/- 0.8 ng m(-3) at 200 cm and were 60-300 times higher than levels measured at a background site 30 km away. Soil-air fugacity fractions, fs/(fs + fa), of p,p'-DDE, p,p'-DDD, and p,p'-DDT ranged from 0.42 to 0.91 using air concentrations measured above the soil and > or = 0.99 using background air concentrations, indicating that the soil was a net source to the background air. Fractionation of DDT compounds during volatilization was predicted using either liquid-phase vapor pressures (PL) or octanol-air partition coefficients (KOA). Relative emissions of p,p'-DDE and p,p'-DDT were better described by PL than KOA, whereas either PL or KOA successfully accounted for the fractionation of p,p'-DDT and o,p'-DDT. Soil-to-air fluxes were calculated from air concentration gradients and turbulent exchange coefficients determined from micrometeorological measurements. Average fluxes of sigmaDDTs were 90 +/- 24 ng m(-2) h(-1) in fall and 660 +/- 370 ng m(-2) h(-1) in spring. Higher soil temperatures in spring accounted for the higher fluxes. A volatilization half-life of approximately 200 y was estimated for sigmaDDT in the upper 5 cm of the soil column, assuming the average flux rate for 12 h d-(1) over 8 months of the year. Thus, in the absence of other dissipation processes, the soil will continue to be a source of atmospheric contamination for a very long time.

Air-ice CO2 fluxes and pCO2 dynamics in the Arctic coastal area (Amundsen Gulf, Canada)

NASA Astrophysics Data System (ADS)

Geilfus, Nicolas-Xavier; Tison, Jean Louis; Carnat, Gauthier; Else, Brent; Borges, Alberto V.; Thomas, Helmuth; Shadwick, Elizabeth; Delille, Bruno

2010-05-01

Sea ice covers about 7% of the Earth surface at its maximum seasonal extent. For decades sea ice was assumed to be an impermeable and inert barrier for air - sea exchange of CO2 so that global climate models do not include CO2 exchange between the oceans and the atmosphere in the polar regions. However, uptake of atmospheric CO2 by sea ice cover was recently reported raising the need to further investigate pCO2 dynamics in the marine cryosphere realm and related air-ice CO2 fluxes. In addition, budget of CO2 fluxes are poorly constrained in high latitudes continental shelves [Borges et al., 2006]. We report measurements of air-ice CO2 fluxes above the Canadian continental shelf and compare them to previous measurements carried out in Antarctica. We carried out measurements of pCO2 within brines and bulk ice, and related air-ice CO2 fluxes (chamber method) in Antarctic first year pack ice ("Sea Ice Mass Balance in Antarctica -SIMBA" drifting station experiment September - October 2007) and in Arctic first year land fast ice ("Circumpolar Flaw Lead" - CFL, April - June 2008). These 2 experiments were carried out in contrasted sites. SIMBA was carried out on sea ice in early spring while CFL was carried out in from the middle of the winter to the late spring while sea ice was melting. Both in Arctic and Antarctic, no air-ice CO2 fluxes were detected when sea ice interface was below -10°C. Slightly above -10°C, fluxes toward the atmosphere were observed. In contrast, at -7°C fluxes from the atmosphere to the ice were significant. The pCO2 of the brine exhibits a same trend in both hemispheres with a strong decrease of the pCO2 anti-correlated with the increase of sea ice temperature. The pCO2 shifted from a large over-saturation at low temperature to a marked under-saturation at high temperature. These air-ice CO2 fluxes are partly controlled by the permeability of the air-ice interface, which depends of the temperature of this one. Moreover, air-ice CO2 fluxes are driven by the air-ice pCO2 gradient. Hence, while the temperature is a leading factor in controlling magnitude of air-ice CO2 fluxes, pCO2 of the ice controls both magnitude and direction of fluxes. However, pCO2 in Arctic is significantly higher than in Antarctica. This difference could be due to a higher level of organic matter in Arctic. The degradation of this organic matter fuel CO2 efflux from the ice to the atmosphere in early spring. We observed evidence of CaCO3 precipitation, but only at the top of the ice. Implications in term of air-ice CO2 transfer of such CaCO3 precipitation will be discussed. In addition, salt-rich snow appears to strongly affect air-ice CO2 fluxes in the arctic. Borges, A. V., et al. (2006), Carbon dioxide in European coastal waters, Estuar. Coast. Shelf Sci., 70(3), 375-387.

Connections between density, wall-normal velocity, and coherent structure in a heated turbulent boundary layer

NASA Astrophysics Data System (ADS)

Saxton-Fox, Theresa; Gordeyev, Stanislav; Smith, Adam; McKeon, Beverley

2015-11-01

Strong density gradients associated with turbulent structure were measured in a mildly heated turbulent boundary layer using an optical sensor (Malley probe). The Malley probe measured index of refraction gradients integrated along the wall-normal direction, which, due to the proportionality of index of refraction and density in air, was equivalently an integral measure of density gradients. The integral output was observed to be dominated by strong, localized density gradients. Conditional averaging and Pearson correlations identified connections between the streamwise gradient of density and the streamwise gradient of wall-normal velocity. The trends were suggestive of a process of pick-up and transport of heat away from the wall. Additionally, by considering the density field as a passive marker of structure, the role of the wall-normal velocity in shaping turbulent structure in a sheared flow was examined. Connections were developed between sharp gradients in the density and flow fields and strong vertical velocity fluctuations. This research is made possible by the Department of Defense through the National Defense & Engineering Graduate Fellowship (NDSEG) Program and by the Air Force Office of Scientific Research Grant # FA9550-12-1-0060.

Continuous gradient temperature Raman spectroscopy of unsaturated fatty acids

USDA-ARS?s Scientific Manuscript database

A new innovative technique gradient temperature, Raman spectroscopy (GTRS), identifies Raman frequency shifts in solid or liquid samples, and correlates them with specific temperature ranges within which flexible structures absorb heat. GTRS can easily detect changes that occur within one celcius te...

Parallelism between gradient temperature raman spectroscopy and differential scanning calorimetry results

USDA-ARS?s Scientific Manuscript database

Temperature dependent Raman spectroscopy (TDR) applies the temperature gradients utilized in differential scanning calorimetry (DSC) to Raman spectroscopy, providing a straightforward technique to identify molecular rearrangements that occur just prior to phase transitions. Herein we apply TDR and D...

CENTRIFUGAL SEPARATORS

DOEpatents

Skarstrom, C.

1959-03-10

A centrifugal separator is described for separating gaseous mixtures where the temperature gradients both longitudinally and radially of the centrifuge may be controlled effectively to produce a maximum separation of the process gases flowing through. Tbe invention provides for the balancing of increases and decreases in temperature in various zones of the centrifuge chamber as the result of compression and expansions respectively, of process gases and may be employed effectively both to neutralize harmful temperature gradients and to utilize beneficial temperaturc gradients within the centrifuge.

Correlation of Aerogravity and BHT Data to Develop a Geothermal Gradient Map of the Northern Western Desert of Egypt using an Artificial Neural Network

NASA Astrophysics Data System (ADS)

Mohamed, Haby S.; Abdel Zaher, Mohamed; Senosy, Mahmoud M.; Saibi, Hakim; El Nouby, Mohamed; Fairhead, J. Derek

2015-06-01

The northern part of the Western Desert of Egypt represents the second most promising area of hydrocarbon potential after the Gulf of Suez province. An artificial neural network (ANN) approach was used to develop a new predictive model for calculation of the geothermal gradients in this region based on gravity and corrected bottom-hole temperature (BHT) data. The best training data set was obtained with an ANN architecture composed of seven neurons in the hidden layer, which made it possible to predict the geothermal gradient with satisfactory efficiency. The BHT records of 116 deep oil wells (2,000-4,500 m) were used to evaluate the geothermal resources in the northern Western Desert. Corrections were applied to the BHT data to obtain the true formation equilibrium temperatures, which can provide useful constraints on the subsurface thermal regime. On the basis of these corrected data, the thermal gradient was computed for the linear sections of the temperature-versus-depth data at each well. The calculated geothermal gradient using temperature log data was generally 30 °C/km, with a few local high geothermal gradients in the northwestern parts of the study area explained by potential local geothermal fields. The Bouguer gravity values from the study area ranged from -60 mGal in the southern parts to 120 mGal in the northern areas, and exhibited NE-SW and E-W trends associated with geological structures. Although the northern Western Desert of Egypt has low regional temperature gradients (30 °C/km), several potential local geothermal fields were found (>40 °C/km). The heat flow at each well was also computed by combining sets of temperature gradients and thermal conductivity data. Aerogravity data were used to delineate the subsurface structures and tectonic framework of the region. The result of this study is a new geothermal gradient map of the northern Western Desert developed from gravity and BHT log data.

Modeling Air Temperature/Water Temperature Relations Along a Small Mountain Stream Under Increasing Urban Influence

NASA Astrophysics Data System (ADS)

Fedders, E. R.; Anderson, W. P., Jr.; Hengst, A. M.; Gu, C.

2017-12-01

Boone Creek is a headwater stream of low to moderate gradient located in Boone, North Carolina, USA. Total impervious surface coverage in the 5.2 km2 catchment drained by the 1.9 km study reach increases from 13.4% in the upstream half of the reach to 24.3% in the downstream half. Other markers of urbanization, including culverting, lack of riparian shade vegetation, and bank armoring also increase downstream. Previous studies have shown the stream to be prone to temperature surges on short timescales (minutes to hours) caused by summer runoff from the urban hardscaping. This study investigates the effects of urbanization on the stream's thermal regime at daily to yearly timescales. To do this, we developed an analytical model of daily average stream temperatures based on daily average air temperatures. We utilized a two-part model comprising annual and biannual components and a daily component consisting of a 3rd-order Markov process in order to fit the thermal dynamics of our small, gaining stream. Optimizing this model at each of our study sites in each studied year (78 total site-years of data) yielded annual thermal exchange coefficients (K) for each site. These K values quantify the strength of the relationship between stream and air temperature, or inverse thermal stability. In a uniform, pristine catchment environment, K values are expected to decrease downstream as the stream gains discharge volume and, therefore, thermal inertia. Interannual average K values for our study reach, however, show an overall increase from 0.112 furthest upstream to 0.149 furthest downstream, despite a near doubling of stream discharge between these monitoring points. K values increase only slightly in the upstream, less urban, half of the reach. A line of best fit through these points on a plot of reach distance versus K value has a slope of 2E-6. But the K values of downstream, more urbanized sites increase at a rate of 2E-5 per meter of reach distance, an order of magnitude greater. This indicates a possible tipping point in the stream temperature-water temperature relationship at which increased urbanization overpowers increasing stream thermal inertia.

Characterization of freezing precipitation events through other meteorological variables and their recent changes over Northern Extratropics

NASA Astrophysics Data System (ADS)

Groisman, P. Y.; Yin, X.; Bulygina, O.

2017-12-01

Freezing precipitation events intertwine with agriculture, recreation, energy consumption, and seasonal transportation cycles of human activities. Using supplementary synoptic reports at 1,500 long-term stations of North America and Northern Eurasia, we created climatology of freezing precipitation near the surface and found significant changes (increases) in these occurrences in the past decade at high latitudes/elevations (Groisman et al. 2016; updated). Firstly, we document narrow boundaries of near surface temperature and humidity fields when freezing precipitation events occur; these are necessary but insufficient conditions of their occurrence. Secondly, using the upper air data at the sites collocated with in situ observations of freezing events, we quantify the typical pattern of lower troposphere temperature anomalies during freezing events: At the same locations and Julian days, the presence of freezing event at the surface is associated with significantly warmer temperatures in the lower troposphere; comparison of temperatures at nearest days before and after the freezing events with days during these events also shows statistically significant positive temperature anomalies in the lower troposphere to 500 hPa (on average, +3 to 4 °C) In the days with freezing events, vertical air temperature gradients between surface and 850 hPa become less than usual with frequent inversions, when the tropospheric air is warmer than at the surface. The above features of the lower tropospheric temperature, near-surface temperature and humidity represent a combination of weather conditions conducive for precipitation, if it happens, falling in the freezing rain form. The in situ reports of freezing events at synoptic stations allow us to estimate temporary and spatial distributions of such "special weather conditions". Thus, a posteriori high probability of freezing events under these weather conditions invokes similar probabilities of freezing rain over the ungauged terrain, where we do not have special synoptic reports but can reproduce these "special weather conditions" from less sophisticated observational networks and/or reanalyses. Reference: Groisman et al. 2016: Recent changes in the frequency of freezing precipitation in North America and Northern Eurasia. Environ Res Lett 11 045007.

Customised spatiotemporal temperature gradients created by a liquid metal enabled vortex generator.

PubMed

Zhu, Jiu Yang; Thurgood, Peter; Nguyen, Ngan; Ghorbani, Kamran; Khoshmanesh, Khashayar

2017-11-07

Generating customised temperature gradients in miniaturised flow-free liquid chambers is challenging due to the dominance of diffusion. Inducing internal flows in the form of vortices is an effective strategy for overcoming the limitations of diffusion in such environments. Vortices can be produced by applying pressure, temperature and electric potential gradients via miniaturised actuators. However, the difficulties associated with the fabrication, integration, maintenance and operation of such actuators hinder their utility. Here, we utilise liquid metal enabled pumps to induce vortices inside a miniaturised liquid chamber. The configuration and rotational velocity of these vortices can be controlled by tuning the polarity and frequency of the energising electrical signal. This allows creation of customised spatial temperature gradients inside the chamber. The absence of conventional moving elements in the pumps facilitates the rapid reconfiguration of vortices. This enables quick transition from one temperature profile to another, and creates customised spatiotemporal temperature gradients. This allows temperature oscillation from 35 to 62 °C at the hot spot, and from 25 to 27 °C at the centre of the vortex within 15 seconds. Our liquid metal enabled vortex generator can be fabricated, integrated and operated easily, and offers opportunities for studying thermo-responsive materials and biological samples.

Temperature sensitivity and enzymatic mechanisms of soil organic matter decomposition along an altitudinal gradient on Mount Kilimanjaro

NASA Astrophysics Data System (ADS)

Blagodatskaya, Evgenia; Blagodatsky, Sergey; Khomyakov, Nikita; Myachina, Olga; Kuzyakov, Yakov

2016-02-01

Short-term acceleration of soil organic matter decomposition by increasing temperature conflicts with the thermal adaptation observed in long-term studies. Here we used the altitudinal gradient on Mt. Kilimanjaro to demonstrate the mechanisms of thermal adaptation of extra- and intracellular enzymes that hydrolyze cellulose, chitin and phytate and oxidize monomers (14C-glucose) in warm- and cold-climate soils. We revealed that no response of decomposition rate to temperature occurs because of a cancelling effect consisting in an increase in half-saturation constants (Km), which counteracts the increase in maximal reaction rates (Vmax with temperature). We used the parameters of enzyme kinetics to predict thresholds of substrate concentration (Scrit) below which decomposition rates will be insensitive to global warming. Increasing values of Scrit, and hence stronger canceling effects with increasing altitude on Mt. Kilimanjaro, explained the thermal adaptation of polymer decomposition. The reduction of the temperature sensitivity of Vmax along the altitudinal gradient contributed to thermal adaptation of both polymer and monomer degradation. Extrapolating the altitudinal gradient to the large-scale latitudinal gradient, these results show that the soils of cold climates with stronger and more frequent temperature variation are less sensitive to global warming than soils adapted to high temperatures.

Tecuamburro Volcano, Guatemala: exploration geothermal gradient drilling and results

USGS Publications Warehouse

Goff, S.J.; Goff, F.; Janik, C.J.

1992-01-01

Results of geological, volcanological, hydrogeochemical, and geophysical field studies conducted in 1988 and 1989 at the Tecuamburro geothermal site, Guatemala, indicate that there is a substantial shallow heat source beneath the area of youngest volcanism. Gases from acid-sulfate springs near Laguna Ixpaco consistently yield maximum estimated subsurface temperatures of 300??C. To obtain information on subsurface temperatures and temperature gradients, stratigraphy, fracturing, hydrothermal alteration, and hydrothermal fluids, a geothermal gradient core hole (TCB-1) was drilled to 808 m low on the northern flank of the Tecuamburro Volcano complex. The hole is located 300 m south of a 300m-diameter phreatic crater. Laguna Ixpaco, dated at 2910 years. TCB-1 temperature logs do not indicate isothermal conditions at depth and the calculated thermal gradient from 500-800 m is 230??C/km. Bottom hole temperature is close to 240??C. Calculated heat flow values are around 350-400 mW/m2. Fluid-inclusion and secondary-alteration studies indicate that veins and secondary minerals were formed at temperatures equal to or slightly less than present temperatures; thus, the Tecuamburro geothermal system may still be heating up. The integration of results from the TCB-1 gradient core hole with results from field studies provides strong evidence that the Tecuamburro area holds great promise for geothermal resource development. ?? 1992.

Survey and bibliography on attainment of laminar flow control in air using pressure gradient and suction, volume 1

NASA Technical Reports Server (NTRS)

Bushnell, D. M.; Tuttle, M. H.

1979-01-01

A survey was conducted and a bibliography compiled on attainment of laminar flow in air through the use of favorable pressure gradient and suction. This report contains the survey, summaries of data for both ground and flight experiments, and abstracts of referenced reports. Much early information is also included which may be of some immediate use as background material for LFC applications.

Effects of solid-propellant temperature gradients on the internal ballistics of the Space Shuttle

NASA Technical Reports Server (NTRS)

Sforzini, R. H.; Foster, W. A., Jr.; Shackelford, B. W., Jr.

1978-01-01

The internal ballistic effects of combined radial and circumferential grain temperature gradients are evaluated theoretically for the Space Shuttle solid rocket motors (SRMs). A simplified approach is devised for representing with closed-form mathematical expressions the temperature distribution resulting from the anticipated thermal history prior to launch. The internal ballistic effects of the gradients are established by use of a mathematical model which permits the propellant burning rate to vary circumferentially. Comparative results are presented for uniform and axisymmetric temperature distributions and the anticipated gradients based on an earlier two-dimensional analysis of the center SRM segment. The thrust imbalance potential of the booster stage is also assessed based on the difference in the thermal loading of the individual SRMs of the motor pair which may be encountered in both summer and winter environments at the launch site. Results indicate that grain temperature gradients could cause the thrust imbalance to be approximately 10% higher in the Space Shuttle than the imbalance caused by SRM manufacturing and propellant physical property variability alone.

High-Thermal- and Air-Stability Cathode Material with Concentration-Gradient Buffer for Li-Ion Batteries.

PubMed

Shi, Ji-Lei; Qi, Ran; Zhang, Xu-Dong; Wang, Peng-Fei; Fu, Wei-Gui; Yin, Ya-Xia; Xu, Jian; Wan, Li-Jun; Guo, Yu-Guo

2017-12-13

Delivery of high capacity with high thermal and air stability is a great challenge in the development of Ni-rich layered cathodes for commercialized Li-ion batteries (LIBs). Herein we present a surface concentration-gradient spherical particle with varying elemental composition from the outer end LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM) to the inner end LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA). This cathode material with the merit of NCM concentration-gradient protective buffer and the inner NCA core shows high capacity retention of 99.8% after 200 cycles at 0.5 C. Furthermore, this cathode material exhibits much improved thermal and air stability compared with bare NCA. These results provide new insights into the structural design of high-performance cathodes with high energy density, long life span, and storage stability materials for LIBs in the future.

In Search for Diffuse Hydrothermal Venting at North Pond, Western Flank of the Mid-Atlantic-Ridge

NASA Astrophysics Data System (ADS)

Villinger, H. W.; Becker, K.; Hulme, S.; Kaul, N. E.; Müller, P.; Wheat, C. G.

2015-12-01

We present results from temperature measurements made with a ROV temperature lance in sediments deposited on the slopes of abyssal hills and small basins surrounding North Pond. North Pond is a ~8x15 km large sediment basin located on ~7 Ma year old crust west of the Mid-Atlantic Ridge at 23°N. Data were collected with the ROV Jason II during cruise MSM37 on the German RV Maria S. Merian in April 2014. The temperature lance consists of a 60 cm long stainless steel tube (o.d. 12 mm) housing 8 thermistors with a spacing of 80 mm, resulting in an active length of 56 cm. Data are logged with an 8-channel data logger (XR-420-T8, RBR, Ottawa) and transmitted online to the control van of the ROV. Data reduction and temperature gradient calculation is done according to the HFRED algorithm (Villinger & Davis, 1987). 90 sites in total were visited, 88 gave good data for temperature gradient calculation. Calculated gradients are usually of good to very good quality. The gradients vary between less than 20 to more than 1000 mK/m reflecting the very heterogeneous distribution of geothermal heat flow. The expected conductive lithospheric heat flow for North Pond is ~190 mW/m2 (geothermal gradient of ~190 mK/m with a thermal conductivity of 1 W/Km). The highest temperature gradients are measured in places where temperature ~50 cm below the sediment-water boundary exceeds bottom water temperature by ~0.5 K . These high temperature gradients may reflect local hydrothermal circulation within the pillow lavas, however no focused discharge was detected. The analysis of temperature measurements made with the ROV-mounted CTD shows clearly detectable bottom water temperature anomalies. We infer that they are either caused by hydrothermal discharge through the thin sediment cover or through unsedimented pillow basalts nearby. Hydrothermal circulation in a North-Pond-like environment appears to be diffuse in nature, hence very difficult if not impossible to detect and to quantify.

Mangrove species' responses to winter air temperature extremes in China

USGS Publications Warehouse

Chen, Luzhen; Wang, Wenqing; Li, Qingshun Q.; Zhang, Yihui; Yang, Shengchang; Osland, Michael J.; Huang, Jinliang; Peng, Congjiao

2017-01-01

The global distribution and diversity of mangrove forests is greatly influenced by the frequency and intensity of winter air temperature extremes. However, our understanding of how different mangrove species respond to winter temperature extremes has been lacking because extreme freezing and chilling events are, by definition, relatively uncommon and also difficult to replicate experimentally. In this study, we investigated species-specific variation in mangrove responses to winter temperature extremes in China. In 10 sites that span a latitudinal gradient, we quantified species-specific damage and recovery following a chilling event, for mangrove species within and outside of their natural range (i.e., native and non-native species, respectively). To characterize plant stress, we measured tree defoliation and chlorophyll fluorescence approximately one month following the chilling event. To quantify recovery, we measured chlorophyll fluorescence approximately nine months after the chilling event. Our results show high variation in the geographic- and species-specific responses of mangroves to winter temperature extremes. While many species were sensitive to the chilling temperatures (e.g., Bruguiera sexangula and species in the Sonneratia and Rhizophora genera), the temperatures during this event were not cold enough to affect certain species (e.g., Kandelia obovata, Aegiceras corniculatum, Avicennia marina, and Bruguiera gymnorrhiza). As expected, non-native species were less tolerant of winter temperature extremes than native species. Interestingly, tidal inundation modulated the effects of chilling. In comparison with other temperature-controlled mangrove range limits across the world, the mangrove range limit in China is unique due to the combination of the following three factors: (1) Mangrove species diversity is comparatively high; (2) winter air temperature extremes, rather than means, are particularly intense and play an important ecological role; and (3) due to afforestation and restoration efforts, several species of non-native mangroves have been introduced beyond their natural range limits. Hence, from a global perspective, mangroves in China provide valuable opportunities to advance understanding of the effects of freezing and chilling temperatures on mangroves. Within the context of climate change, our findings provide a foundation for better understanding and preparing for mangrove species-specific responses to future changes in the duration and intensity of winter temperature extremes.

Estimating ammonia volatilization and deposition from fertilized vegetation

NASA Astrophysics Data System (ADS)

Heuer, M. W.; Myles, L.

2010-12-01

Deposition of reactive nitrogen in the form of atmospheric ammonia (NH3) affects ecosystem dynamics. Large amounts of atmospheric ammonia can volatilize from fertilized vegetation and deposit to adjacent areas, contributing to changes in soil and plant chemistry. To study the air-surface exchange of ammonia, instrumentation was installed from February 15 through April 12, 2010 at an agricultural research area of managed crops and grassland near Knoxville, TN. A Picarro ammonia analyzer was deployed to measure ammonia at two heights (z = 0.5 m and 2 m) near a plot of winter wheat fertilized with urea. Integrated samples of ammonia were also collected with annular denuder systems at both heights. Concentrations from the Picarro averaged 3-4 ppb of ammonia, but increased by a factor of 20 during fertilization. Fluxes were derived from concurrent measurements of ammonia concentration and air temperature using the flux-gradient method.

Characteristics of ozone vertical profile observed in the boundary layer around Beijing in autumn.

PubMed

Ma, Zhiqiang; Zhang, Xiaoling; Xu, Jing; Zhao, Xiujuan; Meng, Wei

2011-01-01

In the autumn of 2008, the vertical profiles of ozone and meteorological parameters in the low troposphere (0-1000 m) were observed at two sites around Beijing, specifically urban Nanjiao and rural Shangdianzi. At night and early morning, the lower troposphere divided into two stratified layers due to temperature inversion. Ozone in the lower layer showed a large gradient due to the titration of NO. Air flow from the southwest brought ozone-rich air to Beijing, and the ozone profiles were marked by a continuous increase in the residual layer at night. The accumulated ozone in the upper layer played an important role in the next day's surface peak ozone concentration, and caused a rapid increase in surface ozone in the morning. Wind direction shear and wind speed shear exhibited different influences on ozone profiles and resulted in different surface ozone concentrations in Beijing.

Dynamic contraction of the positive column of a self-sustained glow discharge in air flow

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

Shneider, M. N.; Mokrov, M. S.; Milikh, G. M.

We study the dynamic contraction of a self-sustained glow discharge in air in a rectangular duct with convective cooling. A two dimensional numerical model of the plasma contraction was developed in a cylindrical frame. The process is described by a set of time-dependent continuity equations for the electrons, positive and negative ions; gas and vibrational temperature; and equations which account for the convective heat and plasma losses by the transverse flux. Transition from the uniform to contracted state was analyzed. It was shown that such transition experiences a hysteresis, and that the critical current of the transition increases when themore » gas density drops. Possible coexistence of the contracted and uniform state of the plasma in the discharge, where the current flows along the density gradient of the background gas, is discussed.« less

Thermophoresis of dissolved molecules and polymers: Consideration of the temperature-induced macroscopic pressure gradient

NASA Astrophysics Data System (ADS)

Semenov, Semen; Schimpf, Martin

2004-01-01

The movement of molecules and homopolymer chains dissolved in a nonelectrolyte solvent in response to a temperature gradient is considered a consequence of temperature-induced pressure gradients in the solvent layer surrounding the solute molecules. Local pressure gradients are produced by nonuniform London van der Waals interactions, established by gradients in the concentration (density) of solvent molecules. The density gradient is produced by variations in solvent thermal expansion within the nonuniform temperature field. The resulting expression for the velocity of the solute contains the Hamaker constants for solute-solvent and solute-solute interactions, the radius of the solute molecule, and the viscosity and cubic coefficient of thermal expansion of the solvent. In this paper we consider an additional force that arises from directional asymmetry in the interaction between solvent molecules. In a closed cell, the resulting macroscopic pressure gradient gives rise to a volume force that affects the motion of dissolved solutes. An expression for this macroscopic pressure gradient is derived and the resulting force is incorporated into the expression for the solute velocity. The expression is used to calculate thermodiffusion coefficients for polystyrene in several organic solvents. When these values are compared to those measured in the laboratory, the consistency is better than that found in previous reports, which did not consider the macroscopic pressure gradient that arises in a closed thermodiffusion cell. The model also allows for the movement of solute in either direction, depending on the relative values of the solvent and solute Hamaker constants.

High temperature skin friction measurement

NASA Technical Reports Server (NTRS)

Tcheng, Ping; Holmes, Harlan K.; Supplee, Frank H., Jr.

1989-01-01

Skin friction measurement in the NASA Langley hypersonic propulsion facility is described. The sensor configuration utilized an existing balance, modified to provide thermal isolation and an increased standoff distance. For test run times of about 20 sec and ambient-air cooling of the test section and balance, the modified balance performed satisfactorily, even when it was subjected to acoustic and structural vibration. The balance is an inertially balanced closed-loop servo system where the current to a moving-coil motor needed to restore or null the output from the position sensor is a measure of the force or skin friction tending to displace the moving element. The accuracy of the sensor is directly affected by the position sensor in the feedback loop, in this case a linear-variable differential transformer which has proven to be influenced by temperature gradients.

Towards quantum superposition of a levitated nanodiamond with a NV center

NASA Astrophysics Data System (ADS)

Li, Tongcang

2015-05-01

Creating large Schrödinger's cat states with massive objects is one of the most challenging goals in quantum mechanics. We have previously achieved an important step of this goal by cooling the center-of-mass motion of a levitated microsphere from room temperature to millikelvin temperatures with feedback cooling. To generate spatial quantum superposition states with an optical cavity, however, requires a very strong quadratic coupling that is difficult to achieve. We proposed to optically trap a nanodiamond with a nitrogen-vacancy (NV) center in vacuum, and generate large spatial superposition states using the NV spin-optomechanical coupling in a strong magnetic gradient field. The large spatial superposition states can be used to study objective collapse theories of quantum mechanics. We have optically trapped nanodiamonds in air and are working towards this goal.

A Simple Temperature Gradient Apparatus To Determine Thermal Preference in "Daphnia."

ERIC Educational Resources Information Center

Fenske, Christiane; McCauley, Robert

2002-01-01

Explores the dominant factor controlling the distribution of Daphnia. Describes components of a temperature gradient apparatus that can be assembled from materials readily obtainable in the laboratory and hardware stores. Investigates whether the mean depth of Daphnia is determined by temperature. (KHR)

Comment on "the one dimensional acoustic field with arbitrary mean axial temperature gradient and mean flow" (J.Li and A.S.Morgans, Journal of Sound and Vibration 400 (2017) 248-269)

NASA Astrophysics Data System (ADS)

Dokumaci, Erkan

2017-12-01

In a recent study, Li and Morgans [1] present an ingenious WKB approximation for the acoustic plane wave field in a straight uniform duct with mean temperature gradient and mean flow. The authors state that the previous solutions are limited to small linear mean temperature gradients and low mean flow Mach numbers and claim that their solution applies for arbitrary mean temperature profiles and moderate-to-large mean flow velocity Mach numbers at both low and high frequencies.

Air-Lubricated Thermal Processor For Dry Silver Film

NASA Astrophysics Data System (ADS)

Siryj, B. W.

1980-09-01

Since dry silver film is processed by heat, it may be viewed on a light table only seconds after exposure. On the other hand, wet films require both bulky chemicals and substantial time before an image can be analyzed. Processing of dry silver film, although simple in concept, is not so simple when reduced to practice. The main concern is the effect of film temperature gradients on uniformity of optical film density. RCA has developed two thermal processors, different in implementation but based on the same philosophy. Pressurized air is directed to both sides of the film to support the film and to conduct the heat to the film. Porous graphite is used as the medium through which heat and air are introduced. The initial thermal processor was designed to process 9.5-inch-wide film moving at speeds ranging from 0.0034 to 0.008 inch per second. The processor configuration was curved to match the plane generated by the laser recording beam. The second thermal processor was configured to process 5-inch-wide film moving at a continuously variable rate ranging from 0.15 to 3.5 inches per second. Due to field flattening optics used in this laser recorder, the required film processing area was plane. In addition, this processor was sectioned in the direction of film motion, giving the processor the capability of varying both temperature and effective processing area.

Air flow analysis in the upper Río Negro Valley (Argentina)

NASA Astrophysics Data System (ADS)

Cogliati, M. G.; Mazzeo, N. A.

2006-06-01

The so called Upper Río Negro Valley in Argentina is one of the most important fruit and vegetable production regions of the country. It comprises the lower valleys of the Limay and Neuquén rivers and the upper Negro river valley. Out of the 41,671 cultivated hectares, 84.6% are cultivated with fruit trees, especially apple, pear and stone fruit trees. Late frosts occurring when trees are sensitive to low temperatures have a significant impact on the regional production. This study presents an analysis of air flow characteristics in the Upper Río Negro Valley and its relationship with ambient air flow. To such effect, observations made when synoptic-scale weather patterns were favorable for radiative frosts (light wind and clear sky) or nocturnal temperature inversion in the lower layer were used. In the Negro river valley, both wind channeling and downward horizontal momentum transport from ambient wind were observed; in nighttime, very light wind events occurred, possibly associated with drainage winds from the nearby higher levels of the barda. In the Neuquén river valley, the prevailing effect appeared to be forced channeling, consistent with the results obtained in valleys where the synoptic scale wind crossed the axis of the valley. In the Limay river valley, the flow was observed to blow parallel to the longitudinal valley axis, possibly influenced by pressure gradient and forced channeling.

Ocean-Atmosphere Interaction Over Agulhas Extension Meanders

NASA Technical Reports Server (NTRS)

Liu, W. Timothy; Xie, Xiaosu; Niiler, Pearn P.

2007-01-01

Many years of high-resolution measurements by a number of space-based sensors and from Lagrangian drifters became available recently and are used to examine the persistent atmospheric imprints of the semi-permanent meanders of the Agulhas Extension Current (AEC), where strong surface current and temperature gradients are found. The sea surface temperature (SST) measured by the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) and the chlorophyll concentration measured by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) support the identification of the meanders and related ocean circulation by the drifters. The collocation of high and low magnitudes of equivalent neutral wind (ENW) measured by Quick Scatterometer (QuikSCAT), which is uniquely related to surface stress by definition, illustrates not only the stability dependence of turbulent mixing but also the unique stress measuring capability of the scatterometer. The observed rotation of ENW in opposition to the rotation of the surface current clearly demonstrates that the scatterometer measures stress rather than winds. The clear differences between the distributions of wind and stress and the possible inadequacy of turbulent parameterization affirm the need of surface stress vector measurements, which were not available before the scatterometers. The opposite sign of the stress vorticity to current vorticity implies that the atmosphere spins down the current rotation through momentum transport. Coincident high SST and ENW over the southern extension of the meander enhance evaporation and latent heat flux, which cools the ocean. The atmosphere is found to provide negative feedback to ocean current and temperature gradients. Distribution of ENW convergence implies ascending motion on the downwind side of local SST maxima and descending air on the upwind side and acceleration of surface wind stress over warm water (deceleration over cool water); the convection may escalate the contrast of ENW over warm and cool water set up by the dependence of turbulent mixing on stability; this relation exerts a positive feedback to the ENW-SST relation. The temperature sounding measured by the Atmospheric Infrared Sounder(AIRS) is consistent with the spatial coherence between the cloud-top temperature provided by the International Satellite Cloud Climatology Project (ISCCP) and SST. Thus ocean mesoscale SST anomalies associated with the persistent meanders may have a long-term effect well above the midlatitude atmospheric boundary layer, an observation not addressed in the past.

Comparison of Alcator C data with the Rebut-Lallia-Watkins critical gradient scaling

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

Hutchinson, I.H.

The critical temperature gradient model of Rebut, Lallia and Watkins is compared with data from Alcator C. The predicted central electron temperature is derived from the model, and a simple analytic formula is given. It is found to be in quite good agreement with the observed temperatures on Alcator C under ohmic heating conditions. However, the thermal diffusivity postulated in the model for gradients that exceed the critical is not consistent with the observed electron heating by Lower Hybrid waves.

Coarsening Dynamics and Marangoni Effects in Thin Liquid Crystal Bubbles in Microgravity

NASA Technical Reports Server (NTRS)

Clark, Noel; Glaser, Matthew; Maclennan, Joseph; Park, Cheol; Tin, Padetha; Hall, Nancy R.; Sheehan, Christopher; Storck, Jennifer

2015-01-01

The Observation and Analysis of Smectic Islands in Space (OASIS) flight hardware was successfully launched on SpaceX-6 on April 15, 2015 and was operated in the Microgravity Science Glovebox (MSG) on board the International Space Station (ISS). The OASIS project comprises a series of experiments that probe the interfacial and hydrodynamic behavior of spherical-bubble freely suspended liquid crystal (FSLC) membranes in space. These are the thinnest known stable condensed phase structures, making them ideal for studies of two-dimensional (2D) coarsening dynamics and thermocapillary phenomena in microgravity. The OASIS experimental investigation was carried out using four different smectic A and C liquid crystal materials in four separate sample chambers housed inside the MSG. In this report, we present the behavior of collective dynamics on 2D bubble surface, including the equilibrium spatial organization and interaction of islands in electric fields and temperature gradients, and the diffusion and coalescence-driven coarsening dynamics of island emulsions in microgravity. We have observed spontaneous bubble thickening behavior caused by gradients between the bubble-blowing needle and ambient air temperatures. A uniform, thicker band forms during coarsening as a result of non-uniform heating by the LED illumination panels. These are proposed to be a result of Marangoni convection on the bubble surface.

Minimum maximum temperature gradient coil design.

PubMed

While, Peter T; Poole, Michael S; Forbes, Larry K; Crozier, Stuart

2013-08-01

Ohmic heating is a serious problem in gradient coil operation. A method is presented for redesigning cylindrical gradient coils to operate at minimum peak temperature, while maintaining field homogeneity and coil performance. To generate these minimaxT coil windings, an existing analytic method for simulating the spatial temperature distribution of single layer gradient coils is combined with a minimax optimization routine based on sequential quadratic programming. Simulations are provided for symmetric and asymmetric gradient coils that show considerable improvements in reducing maximum temperature over existing methods. The winding patterns of the minimaxT coils were found to be heavily dependent on the assumed thermal material properties and generally display an interesting "fish-eye" spreading of windings in the dense regions of the coil. Small prototype coils were constructed and tested for experimental validation and these demonstrate that with a reasonable estimate of material properties, thermal performance can be improved considerably with negligible change to the field error or standard figures of merit. © 2012 Wiley Periodicals, Inc.

Large polarization gradients and temperature-stable responses in compositionally-graded ferroelectrics

DOE PAGES

Damodaran, Anoop R.; Pandya, Shishir; Qi, Yubo; ...

2017-05-10

A range of modern applications require large and tunable dielectric, piezoelectric or pyroelectric response of ferroelectrics. Such effects are intimately connected to the nature of polarization and how it responds to externally applied stimuli. Ferroelectric susceptibilities are, in general, strongly temperature dependent, diminishing rapidly as one transitions away from the ferroelectric phase transition (T C). In turn, researchers seek new routes to manipulate polarization to simultaneously enhance susceptibilities and broaden operational temperature ranges. Here, we demonstrate such a capability by creating composition and strain gradients in Ba 1-xSr xTiO 3 films which result in spatial polarization gradients as large asmore » 35 μC cm -2 across a 150 nm thick film. These polarization gradients allow for large dielectric permittivity with low loss (ε r≈775, tan δ<0.05), negligible temperature-dependence (13% deviation over 500 °C) and high-dielectric tunability (greater than 70% across a 300 °C range). The role of space charges in stabilizing polarization gradients is also discussed.« less

Large polarization gradients and temperature-stable responses in compositionally-graded ferroelectrics

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

Damodaran, Anoop R.; Pandya, Shishir; Qi, Yubo

A range of modern applications require large and tunable dielectric, piezoelectric or pyroelectric response of ferroelectrics. Such effects are intimately connected to the nature of polarization and how it responds to externally applied stimuli. Ferroelectric susceptibilities are, in general, strongly temperature dependent, diminishing rapidly as one transitions away from the ferroelectric phase transition (T C). In turn, researchers seek new routes to manipulate polarization to simultaneously enhance susceptibilities and broaden operational temperature ranges. Here, we demonstrate such a capability by creating composition and strain gradients in Ba 1-xSr xTiO 3 films which result in spatial polarization gradients as large asmore » 35 μC cm -2 across a 150 nm thick film. These polarization gradients allow for large dielectric permittivity with low loss (ε r≈775, tan δ<0.05), negligible temperature-dependence (13% deviation over 500 °C) and high-dielectric tunability (greater than 70% across a 300 °C range). The role of space charges in stabilizing polarization gradients is also discussed.« less

Temperature and diet effects on omnivorous fish performance: Implications for the latitudinal diversity gradient in herbivorous fishes

USGS Publications Warehouse

Behrens, M.D.; Lafferty, K.D.

2007-01-01

Herbivorous fishes show a clear latitudinal diversity gradient, making up a larger proportion of the fish species in a community in tropical waters than in temperate waters. One proposed mechanism that could drive this gradient is a physiological constraint due to temperature. One prediction based on this mechanism is that if herbivorous fishes could shift their diet to animal material, they would be better able to grow, survive, and reproduce in cold waters. We tested this prediction on the omnivore Girella nigricans under different temperature and diet regimes using RNA-DNA ratios as an indicator of performance. Fish had increased performance (100%) at low temperatures (12??C) when their diet was supplemented with animal material. In contrast, at higher temperatures (17, 22, and 27??C) fish showed no differences between diets. This indicates that omnivorous fishes could increase their performance at low temperatures by consuming more animal matter. This study supports the hypothesis that a relative increase in the nutritional value of plant material at warmer temperatures could drive the latitudinal diversity gradient in herbivorous fishes. ?? 2007 NRC.

Active thermal fine laser tuning in a broad spectral range and optical properties of cholesteric liquid crystal.

PubMed

Jeong, Mi-Yun; Kwak, Keumcheol

2016-11-20

In this study, we achieved active fine laser tuning in a broad spectral range with dye-doped cholesteric liquid crystal wedge-type cells through temperature control. The spatial pitch gradient of each position of the wedge cell at room temperature was almost maintained after developing a temperature gradient. To achieve the maximum tuning range, the chiral dopant concentration, thickness, thickness gradient, and temperature gradient on the wedge cell should be matched properly. In order to understand the laser tuning mechanism for temperature change, we studied the temperature dependence of optical properties of the photonic bandgap of cholesteric liquid crystals. In our cholesteric liquid crystal samples, when temperature was increased, photonic bandgaps were shifted toward blue, while the width of the photonic bandgap was decreased, regardless of whether the helicity was left-handed or right-handed. This is mainly due to the combination of decreased refractive indices, higher molecular anisotropy of chiral molecules, and increased chiral molecular solubility. We envisage that this kind of study will prove useful in the development of practical active tunable CLC laser devices.

Tracing Thermal Creep Through Granular Media

NASA Astrophysics Data System (ADS)

Steinpilz, Tobias; Teiser, Jens; Koester, Marc; Schywek, Mathias; Wurm, Gerhard

2017-08-01

A temperature gradient within a granular medium at low ambient pressure drives a gas flow through the medium by thermal creep. We measured the resulting air flow for a sample of glass beads with particle diameters between 290 μ m and 420 μ m for random close packing. Ambient pressure was varied between 1 Pa and 1000 Pa. The gas flow was quantified by means of tracer particles during parabolic flights. The flow varies systematically with pressure between 0.2 cm/s and 6 cm/s. The measured flow velocities are in quantitative agreement to model calculations that treat the granular medium as a collection of linear capillaries.

Atmospheric tides on Venus. III - The planetary boundary layer

NASA Technical Reports Server (NTRS)

Dobrovolskis, A. R.

1983-01-01

Diurnal solar heating of Venus' surface produces variable temperatures, winds, and pressure gradients within a shallow layer at the bottom of the atmosphere. The corresponding asymmetric mass distribution experiences a tidal torque tending to maintain Venus' slow retrograde rotation. It is shown that including viscosity in the boundary layer does not materially affect the balance of torques. On the other hand, friction between the air and ground can reduce the predicted wind speeds from about 5 to about 1 m/sec in the lower atmosphere, more consistent with the observations from Venus landers and descent probes. Implications for aeolian activity on Venus' surface and for future missions are discussed.

Data Report. Volume I. Velocity and Temperature Profile Data for Zero Pressure Gradient, Fully Turbulent Boundary Layers.

DTIC Science & Technology

1981-01-01

Werle I DAft’Janu’_Lt 8 5 NO. OF PAGES 326 COPY NO. ____ 3AIR T𔃺r12 Or tC OF CIDWIMZ RUR (47SC) NO nifE OF TPRANSMTTL TO DDC T17J2 ! nch:ical report...integral properties are determined B W) displacement thickness y dy o Pe Ue (ii) momentum thickness f( dy 0 PC Ue (iii) energy-dissipation thickness a~ 0...NO. I BOUNDARY LAYER PROPERTIES STANDARD LINEAR SUBLAYER INTERPOLATION FUNCTION FROM TO WALL WALL TO Y*=35 FREE STREAM VELOCITY = 98,579 98.579 FREE

A new approach to modeling the effective thermal conductivity of ceramics porous media using a generalized self-consistent method

NASA Astrophysics Data System (ADS)

Edrisi, Siroos; Bidhendi, Norollah Kasiri; Haghighi, Maryam

2017-01-01

Effective thermal conductivity of the porous media was modeled based on a self-consistent method. This model estimates the heat transfer between insulator surface and air cavities accurately. In this method, the pore size and shape, the temperature gradient and other thermodynamic properties of the fluid was taken into consideration. The results are validated by experimental data for fire bricks used in cracking furnaces at the olefin plant of Maroon petrochemical complexes well as data published for polyurethane foam (synthetic polymers) IPTM and IPM. The model predictions present a good agreement against experimental data with thermal conductivity deviating <1 %.

Stability of Gas Hydrates on Continental Margins: Implications of Subsurface Fluid Flow

NASA Astrophysics Data System (ADS)

Nunn, J. A.

2008-12-01

Gas hydrates are found at or just below the sediment-ocean interface in continental margins settings throughout the world. They are also found on land in high latitude regions such as the north slope of Alaska. While gas hydrate occurrence is common, gas hydrates are stable under a fairly restricted range of temperatures and pressures. In a purely conductive thermal regime, near surface temperatures depend on basal heat flow, thermal conductivity of sediments, and temperature at the sediment-water or sediment-air interface. Thermal conductivity depends on porosity and sediment composition. Gas hydrates are most stable in areas of low heat flow and high thermal conductivity which produce low temperature gradients. Older margins with thin continental crust and coarse grained sediments would tend to be colder. Another potentially important control on subsurface temperatures is advective heat transport by recharge/discharge of groundwater. Upward fluid flow depresses temperature gradients over a purely conductive regime with the same heat flow which would make gas hydrates more stable. Downward fluid flow would have the opposite effect. However, regional scale fluid flow may substantially increase heat flow in discharge areas which would destabilize gas hydrates. For example, discharge of topographically driven groundwater along the coast in the Central North Slope of Alaska has increased surface heat flow in some areas by more than 50% over a purely conductive thermal regime. Fluid flow also alters the pressure regime which can affect gas hydrate stability. Modeling results suggest a positive feedback between gas hydrate formation/disassociation and fluid flow. Disassociation of gas hydrates or permafrost due to global warming could increase permeability. This could enhance fluid flow and associated heat transport causing a more rapid and/or more spatially extensive gas hydrate disassociation than predicted solely from conductive propagation of temporal changes in surface or water bottom temperature. Model results from both the North Slope of Alaska and the Gulf of Mexico are compared.

Motorcycle waste heat energy harvesting

NASA Astrophysics Data System (ADS)

Schlichting, Alexander D.; Anton, Steven R.; Inman, Daniel J.

2008-03-01

Environmental concerns coupled with the depletion of fuel sources has led to research on ethanol, fuel cells, and even generating electricity from vibrations. Much of the research in these areas is stalling due to expensive or environmentally contaminating processes, however recent breakthroughs in materials and production has created a surge in research on waste heat energy harvesting devices. The thermoelectric generators (TEGs) used in waste heat energy harvesting are governed by the Thermoelectric, or Seebeck, effect, generating electricity from a temperature gradient. Some research to date has featured platforms such as heavy duty diesel trucks, model airplanes, and automobiles, attempting to either eliminate heavy batteries or the alternator. A motorcycle is another platform that possesses some very promising characteristics for waste heat energy harvesting, mainly because the exhaust pipes are exposed to significant amounts of air flow. A 1995 Kawasaki Ninja 250R was used for these trials. The module used in these experiments, the Melcor HT3-12-30, produced an average of 0.4694 W from an average temperature gradient of 48.73 °C. The mathematical model created from the Thermoelectric effect equation and the mean Seebeck coefficient displayed by the module produced an average error from the experimental data of 1.75%. Although the module proved insufficient to practically eliminate the alternator on a standard motorcycle, the temperature data gathered as well as the examination of a simple, yet accurate, model represent significant steps in the process of creating a TEG capable of doing so.

Thermal Remote Sensing and the Thermodynamics of Ecosystem Development

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Rickman, Doug; Fraser, Roydon F.

2013-01-01

Thermal remote sensing can provide environmental measuring tools with capabilities for measuring ecosystem development and integrity. Recent advances in applying principles of nonequilibrium thermodynamics to ecology provide fundamental insights into energy partitioning in ecosystems. Ecosystems are nonequilibrium systems, open to material and energy flows, which grow and develop structures and processes to increase energy degradation. More developed terrestrial ecosystems will be more effective at dissipating the solar gradient (degrading its exergy content) and can be measured by the effective surface temperature of the ecosystem on a landscape scale. Ecosystems are viewed as open thermodynamic systems with a large gradient impressed on them by the exergy flux from the sun. Ecosystems, according to the restated second law, develop in ways that systematically increases their ability to degrade the incoming solar exergy, hence negating it's ability to set up even larger gradients. Thus it should be expected that more mature ecosystems degrade the exergy they capture more completely than a less developed ecosystem. The degree to which incoming solar exergy is degraded is a function of the surface temperature of the ecosystem. If a group of ecosystems receives the same amount of incoming radiation, we would expect that the most mature ecosystem would reradiate its energy at the lowest quality level and thus would have the lowest surface temperature (coldest black body temperature). Initial development work was done using NASA's airborne Thermal Infrared Multispectral Scanner (TIMS) followed by the use of a multispectral visible and thermal scanner-Airborne Thermal and Land Applications Sensor (ATLAS). Luvall and his coworkers have documented ecosystem energy budgets, including tropical forests, midlatitude varied ecosystems, and semiarid ecosystems. These data show that under similar environmental conditions (air temperature, relative humidity, winds, and solar irradiance) and within a given biome type, the more developed the ecosystem, the cooler it's surface temperature and the more degraded the quality of it's reradiated energy. HyspIRI is a hyperspectral visible/Near IR and multispectral thermal future global satellite mission that will collect data to study the world's ecosystems and will provide a benchmark on the state of the worlds ecosystems against which future changes can be assessed. HyspIRI will provide global data sets that will provide a means for measuring ecosystem development and integrity.

Thermal Remote Sensing and the Thermodynamics of Ecosystem Development

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Rickman, Doug.; Fraser, Roydon F.

2013-01-01

Thermal remote sensing can provide environmental measuring tools with capabilities for measuring ecosystem development and integrity. Recent advances in applying principles of nonequilibrium thermodynamics to ecology provide fundamental insights into energy partitioning in ecosystems. Ecosystems are nonequilibrium systems, open to material and energy flows, which grow and develop structures and processes to increase energy degradation. More developed terrestrial ecosystems will be more effective at dissipating the solar gradient (degrading its exergy content) and can be measured by the effective surface temperature of the ecosystem on a landscape scale. Ecosystems are viewed as open thermodynamic systems with a large gradient impressed on them by the exergy flux from the sun. Ecosystems, according to the restated second law, develop in ways that systematically increases their ability to degrade the incoming solar exergy, hence negating it's ability to set up even larger gradients. Thus it should be expected that more mature ecosystems degrade the exergy they capture more completely than a less developed ecosystem. The degree to which incoming solar exergy is degraded is a function of the surface temperature of the ecosystem. If a group of ecosystems receives the same amount of incoming radiation, we would expect that the most mature ecosystem would reradiate its energy at the lowest quality level and thus would have the lowest surface temperature (coldest black body temperature). Initial development work was done using NASA's airborne Thermal Infrared Multispectral Scanner (TIMS) followed by the use of a multispectral visible and thermal scanner- Airborne Thermal and Land Applications Sensor (ATLAS). Luvall and his coworkers have documented ecosystem energy budgets, including tropical forests, midlatitude varied ecosystems, and semiarid ecosystems. These data show that under similar environmental conditions (air temperature, relative humidity, winds, and solar irradiance) and within a given biome type, the more developed the ecosystem, the cooler it's surface temperature and the more degraded the quality of it's reradiated energy. HyspIRI is a hyperspectral visible/Near IR and multispectral thermal future global satellite mission that will collect data to study the world's ecosystems and will provide a benchmark on the state of the worlds ecosystems against which future changes can be assessed. HyspIRI will provide global data sets that will provide a means for measuring ecosystem development and integrity.

Convective mixing of air in firn at four polar sites

NASA Astrophysics Data System (ADS)

Kawamura, Kenji; Severinghaus, Jeffrey P.; Ishidoya, Shigeyuki; Sugawara, Satoshi; Hashida, Gen; Motoyama, Hideaki; Fujii, Yoshiyuki; Aoki, Shuji; Nakazawa, Takakiyo

2006-04-01

Air withdrawn from the firn at four polar sites (Dome Fuji, H72 and YM85, Antarctica and North GRIP, Greenland) was measured for δ15N of N 2 and δ18O of O 2 to test for the presence of convective air mixing in the top part of the firn, known as the "convective zone". Understanding the convective zone and its possible relationship to surface conditions is important for constructing accurate ice-core greenhouse gas chronologies and their phasing with respect to climate change. The thickness of the convective zone was inferred from a regression line with barometric slope of the data in the deep firn. It is less than a few meters at H72 and NGRIP, whereas a substantial convective zone is found at Dome Fuji (8.6 ± 2.6 m) and YM85 (14.0 ± 1.8 m). By matching the outputs of a diffusion model to the data, effective eddy diffusivities required to mix the firn air are found. At the surface of Dome Fuji and YM85, these are found to be several times greater than the molecular diffusivity in free air. The crossover from dominance of convection to molecular diffusion takes place at 7 ± 2, 11 ± 2 and 0.5 ± 0.5 m at Dome Fuji, YM85 and NGRIP, respectively. These depths can be used as an alternative definition of the convective zone thickness. The firn permeability at Dome Fuji is expected to be high because of intense firn metamorphism due to the low accumulation rate and large seasonal air temperature variation at the site. The firn layers in the top several meters are exposed to strong temperature gradients for several decades, leading to large firn grains and depth hoar that enhance permeability. The thick convective zone at YM85 is unexpected because the temperature, accumulation rate and near-surface density are comparable to NGRIP. The strong katabatic wind at YM85 is probably responsible for creating the deep convection. The largest convective zone found in this study is still only half of the current inconsistency implied from the deep ice core gas isotopes and firn densification models.

A flux-gradient system for simultaneous measurement of the CH4, CO2, and H2O fluxes at a lake-air interface.

PubMed

Xiao, Wei; Liu, Shoudong; Li, Hanchao; Xiao, Qitao; Wang, Wei; Hu, Zhenghua; Hu, Cheng; Gao, Yunqiu; Shen, Jing; Zhao, Xiaoyan; Zhang, Mi; Lee, Xuhui

2014-12-16

Inland lakes play important roles in water and greenhouse gas cycling in the environment. This study aims to test the performance of a flux-gradient system for simultaneous measurement of the fluxes of water vapor, CO2, and CH4 at a lake-air interface. The concentration gradients over the water surface were measured with an analyzer based on the wavelength-scanned cavity ring-down spectroscopy technology, and the eddy diffusivity was measured with a sonic anemometer. Results of a zero-gradient test indicate a flux measurement precision of 4.8 W m(-2) for water vapor, 0.010 mg m(-2) s(-1) for CO2, and 0.029 μg m(-2) s(-1) for CH4. During the 620 day measurement period, 97%, 69%, and 67% of H2O, CO2, and CH4 hourly fluxes were higher in magnitude than the measurement precision, which confirms that the flux-gradient system had adequate precision for the measurement of the lake-air exchanges. This study illustrates four strengths of the flux-gradient method: (1) the ability to simultaneously measure the flux of H2O, CO2, and CH4; (2) negligibly small density corrections; (3) the ability to resolve small CH4 gradient and flux; and (4) continuous and noninvasive operation. The annual mean CH4 flux (1.8 g CH4 m(-2) year(-1)) at this hypereutrophic lake was close to the median value for inland lakes in the world (1.6 g CH4 m(-2) year(-1)). The system has adequate precision for CH4 flux for broad applications but requires further improvement to resolve small CO2 flux in many lakes.

Tunable electroresistance and electro-optic effects of transparent molecular ferroelectrics

DOE PAGES

Zhang, Zhuolei; Li, Peng-Fei; Tang, Yuan-Yuan; ...

2017-08-30

Recent progress in molecular ferroelectrics (MOFEs) has been overshadowed by the lack of high-quality thin films for device integration. We report a water-based air-processable technique to prepare large-area MOFE thin films, controlled by supersaturation growth at the liquid-air interface under a temperature gradient and external water partial pressure. We used this technique to fabricate ImClO4 thin films and found a large, tunable room temperature electroresistance: a 20-fold resistance variation upon polarization switching. The as-grown films are transparent and consist of a bamboo-like structure of (more » $$2,\\overline{1},0$$) and ($$1,0,\\overline{2}$$) structural variants of R3m symmetry with a reversible polarization of 6.7 μC/cm 2. The resulting ferroelectric domain structure leads to a reversible electromechanical response of d 33 = 38.8 pm/V. Polarization switching results in a change of the refractive index, n, of single domains, $$\\frac{Δn}{n}$$ = 0.3. The remarkable combination of these characteristics renders MOFEs a prime candidate material for new nanoelectronic devices. The information that we present in this work will open a new area of MOFE thin-film technologies.« less

Tunable electroresistance and electro-optic effects of transparent molecular ferroelectrics

PubMed Central

Zhang, Zhuolei; Li, Peng-Fei; Tang, Yuan-Yuan; Wilson, Andrew J.; Willets, Katherine; Wuttig, Manfred; Xiong, Ren-Gen; Ren, Shenqiang

2017-01-01

Recent progress in molecular ferroelectrics (MOFEs) has been overshadowed by the lack of high-quality thin films for device integration. We report a water-based air-processable technique to prepare large-area MOFE thin films, controlled by supersaturation growth at the liquid-air interface under a temperature gradient and external water partial pressure. We used this technique to fabricate ImClO4 thin films and found a large, tunable room temperature electroresistance: a 20-fold resistance variation upon polarization switching. The as-grown films are transparent and consist of a bamboo-like structure of (2,1¯,0) and (1,0,2¯) structural variants of R3m symmetry with a reversible polarization of 6.7 μC/cm2. The resulting ferroelectric domain structure leads to a reversible electromechanical response of d33 = 38.8 pm/V. Polarization switching results in a change of the refractive index, n, of single domains, Δnn=0.3. The remarkable combination of these characteristics renders MOFEs a prime candidate material for new nanoelectronic devices. The information that we present in this work will open a new area of MOFE thin-film technologies. PMID:28875167

Geological support for the Umbrella Effect as a link between geomagnetic field and climate

PubMed Central

Kitaba, Ikuko; Hyodo, Masayuki; Nakagawa, Takeshi; Katoh, Shigehiro; Dettman, David L.; Sato, Hiroshi

2017-01-01

The weakening of the geomagnetic field causes an increase in galactic cosmic ray (GCR) flux. Some researchers argue that enhanced GCR flux might lead to a climatic cooling by increasing low cloud formation, which enhances albedo (umbrella effect). Recent studies have reported geological evidence for a link between weakened geomagnetic field and climatic cooling. However, more work is needed on the mechanism of this link, including whether the umbrella effect is playing a central role. In this research, we present new geological evidence that GCR flux change had a greater impact on continental climate than on oceanic climate. According to pollen data from Osaka Bay, Japan, the decrease in temperature of the Siberian air mass was greater than that of the Pacific air mass during geomagnetic reversals in marine isotope stages (MIS) 19 and 31. Consequently, the summer land-ocean temperature gradient was smaller, and the summer monsoon was weaker. Greater terrestrial cooling indicates that a reduction of insolation is playing a key role in the link between the weakening of the geomagnetic field and climatic cooling. The most likely candidate for the mechanism seems to be the increased albedo of the umbrella effect. PMID:28091595

Geological support for the Umbrella Effect as a link between geomagnetic field and climate.

PubMed

Kitaba, Ikuko; Hyodo, Masayuki; Nakagawa, Takeshi; Katoh, Shigehiro; Dettman, David L; Sato, Hiroshi

2017-01-16

The weakening of the geomagnetic field causes an increase in galactic cosmic ray (GCR) flux. Some researchers argue that enhanced GCR flux might lead to a climatic cooling by increasing low cloud formation, which enhances albedo (umbrella effect). Recent studies have reported geological evidence for a link between weakened geomagnetic field and climatic cooling. However, more work is needed on the mechanism of this link, including whether the umbrella effect is playing a central role. In this research, we present new geological evidence that GCR flux change had a greater impact on continental climate than on oceanic climate. According to pollen data from Osaka Bay, Japan, the decrease in temperature of the Siberian air mass was greater than that of the Pacific air mass during geomagnetic reversals in marine isotope stages (MIS) 19 and 31. Consequently, the summer land-ocean temperature gradient was smaller, and the summer monsoon was weaker. Greater terrestrial cooling indicates that a reduction of insolation is playing a key role in the link between the weakening of the geomagnetic field and climatic cooling. The most likely candidate for the mechanism seems to be the increased albedo of the umbrella effect.

The effects of temperature gradient and growth rate on the morphology and fatigue properties of MAR-M246(Hf)

NASA Technical Reports Server (NTRS)

Schmidt, D. D.; Alter, W. S.; Hamilton, W. D.; Parr, R. A.

1989-01-01

MAR-M246(Hf) is a nickel based superalloy used in the turbopump blades of the Space Shuttle main engines. The effects are considered of temperature gradient (G) and growth rate (R) on the microstructure and fatigue properties of this superalloy. The primary dendrite arm spacings were found to be inversely proportional to both temperature gradient and growth rate. Carbide and gamma - gamma prime morphology trends were related to G/R ratios. Weibull analysis of fatigue results shows the characteristic life to be larger by a factor of 10 for the low gradient/fast rate pairing of G and R, while the reliability (beta) was lower.

Gradient Driven Fluctuations

NASA Technical Reports Server (NTRS)

Cannell, David

2005-01-01

We have worked with our collaborators at the University of Milan (Professor Marzio Giglio and his group-supported by ASI) to define the science required to measure gradient driven fluctuations in the microgravity environment. Such a study would provide an accurate test of the extent to which the theory of fluctuating hydrodynamics can be used to predict the properties of fluids maintained in a stressed, non-equilibrium state. As mentioned above, the results should also provide direct visual insight into the behavior of a variety of fluid systems containing gradients or interfaces, when placed in the microgravity environment. With support from the current grant, we have identified three key systems for detailed investigation. These three systems are: 1) A single-component fluid to be studied in the presence of a temperature gradient; 2) A mixture of two organic liquids to be studied both in the presence of a temperature gradient, which induces a steady-state concentration gradient, and with the temperature gradient removed, but while the concentration gradient is dying by means of diffusion; 3) Various pairs of liquids undergoing free diffusion, including a proteidbuffer solution and pairs of mixtures having different concentrations, to allow us to vary the differences in fluid properties in a controlled manner.

TEMPERATURE SELECTION BY HATCHLING AND YEARLING FLORIDA RED-BELLIED TURTLES (PSEUDEMYS NELSONI) IN THERMAL GRADIENTS

EPA Science Inventory

We tested hatchling and yearling Florida red-bellied turtles (Pseudemys nelsoni) in laboratory thermal gradient chambers to determine if they would prefer particular temperatures. Most 1995 hatchlings selected the highest temperature zone of 27degrees C (Test 1) and 30 degrees ...

Remote steering of laser beams by radar- and laser-induced refractive-index gradients in the atmosphere Remote steering of laser beams

NASA Astrophysics Data System (ADS)

Zheltikov, A. M.; Shneider, M. N.; Voronin, A. A.; Sokolov, A. V.; Scully, M. O.

2012-01-01

Refractive-index gradients induced in the atmospheric air by properly tailored laser and microwave fields are shown to enable a remote steering of laser beams. Heating-assisted modulation of the refractive index of the air by microwave radiation is shown to support small-angle laser-beam bending with bending angles on the order of 10-2. Ionization of the atmospheric air by dyads of femto- and nanosecond laser pulses, on the other hand, can provide beam deflection angles in excess of π/5, offering an attractive strategy for radiation transfer, free-space communications, and laser-based standoff detection.

Analysis of Thermal Structure of Arctic Lakes at Local and Regional Scales Using in Situ and Multidate Landsat-8 Data

NASA Astrophysics Data System (ADS)

Huang, Yan; Liu, Hongxing; Hinkel, Kenneth; Yu, Bailang; Beck, Richard; Wu, Jianping

2017-11-01

The Arctic coastal plain is covered with numerous thermokarst lakes. These lakes are closely linked to climate and environmental change through their heat and water budgets. We examined the intralake thermal structure at the local scale and investigated the water temperature pattern of lakes at the regional scale by utilizing extensive in situ measurements and multidate Landsat-8 remote sensing data. Our analysis indicates that the lake skin temperatures derived from satellite thermal sensors during most of the ice-free summer period effectively represent the lake bulk temperature because the lakes are typically well-mixed and without significant vertical stratification. With the relatively high-resolution Landsat-8 thermal data, we were able to quantitatively examine intralake lateral temperature differences and gradients in relation to geographical location, topography, meteorological factors, and lake morphometry for the first time. Our results suggest that wind speed and direction not only control the vertical stratification but also influences lateral differences and gradients of lake surface temperature. Wind can considerably reduce the intralake temperature gradient. Interestingly, we found that geographical location (latitude, longitude, distance to the ocean) and lake morphometry (surface size, depth, volume) not only control lake temperature regionally but also affect the lateral temperature gradient and homogeneity level within each individual lake. For the Arctic coastal plain, at regional scales, inland and southern lakes tend to have larger horizontal temperature differences and gradients compared to coastal and northern lakes. At local scales, large and shallow lakes tend to have large lateral temperature differences relative to small and deep lakes.

Numerical Modelling of Airflow and Temperature Distribution in a Living Room with Different Heat Exchange Conditions

NASA Astrophysics Data System (ADS)

Gendelis, S.; Jakovičs, A.

2010-01-01

Numerical mathematical modelling of the indoor thermal conditions and of the energy losses for separate rooms is an important part of the analysis of the heat-exchange balance and energy efficiency in buildings. The measurements of heat transfer coefficients for bounding structures, the air-tightness tests and thermographic diagnostics done for a building allow the influence of those factors to be predicted more correctly in developed numerical models. The temperature distribution and airflows in a typical room (along with the heat losses) were calculated for different heater locations and solar radiation (modelled as a heat source) through the window, as well as various pressure differences between the openings in opposite walls. The airflow velocities and indoor temperature, including its gradient, were also analysed as parameters of thermal comfort conditions. The results obtained show that all of the listed factors have an important influence on the formation of thermal comfort conditions and on the heat balance in a room.

Microfluid oscillator based on thermocapillarity

NASA Astrophysics Data System (ADS)

Huang, Teng-chao; Shen, Yi-bing; Liu, Xu; Bai, Jian; Hou, Xiyun; Ye, Hui; Lou, Di

2004-12-01

A novel micro fluid oscillator with a boron diffused resistor is proposed in this paper. The actuation principle is based on the combination of Marangoni effect. The contemporary microfabrication technique enables us to fabricate microheater tiny enough to control temperature so quickly and precisely in micro length scale. The devices exhibiting the Marangoni effect in square channels were designed and fabricated from one silicon substrate and two quartz substrates. And the three substrates were aligned, bonded and packaged for testing. In this actuator there is a pair of micro-heaters to produce a thermal gradient along the slit. The driving wattage is about 0.1W and the resistors can make a temperature difference about 100 degrees during 0.1s with a pulsewidth of 20us for 0.1A current pulses. Then the movement is driven towards the lower temperature direction by the interfacial tension of the air-liquid interface. This micro fluid actuator can play important role in many liquid micro-systems such as in micromotor and micro valve.

Modern quantitative schlieren techniques

NASA Astrophysics Data System (ADS)

Hargather, Michael; Settles, Gary

2010-11-01

Schlieren optical techniques have traditionally been used to qualitatively visualize refractive flowfields in transparent media. Modern schlieren optics, however, are increasingly focused on obtaining quantitative information such as temperature and density fields in a flow -- once the sole purview of interferometry -- without the need for coherent illumination. Quantitative data are obtained from schlieren images by integrating the measured refractive index gradient to obtain the refractive index field in an image. Ultimately this is converted to a density or temperature field using the Gladstone-Dale relationship, an equation of state, and geometry assumptions for the flowfield of interest. Several quantitative schlieren methods are reviewed here, including background-oriented schlieren (BOS), schlieren using a weak lens as a "standard," and "rainbow schlieren." Results are presented for the application of these techniques to measure density and temperature fields across a supersonic turbulent boundary layer and a low-speed free-convection boundary layer in air. Modern equipment, including digital cameras, LED light sources, and computer software that make this possible are also discussed.

Measurement and Analysis of the Temperature Gradient of Blackbody Cavities, for Use in Radiation Thermometry

NASA Astrophysics Data System (ADS)

De Lucas, Javier; Segovia, José Juan

2018-05-01

Blackbody cavities are the standard radiation sources widely used in the fields of radiometry and radiation thermometry. Its effective emissivity and uncertainty depend to a large extent on the temperature gradient. An experimental procedure based on the radiometric method for measuring the gradient is followed. Results are applied to particular blackbody configurations where gradients can be thermometrically estimated by contact thermometers and where the relationship between both basic methods can be established. The proposed procedure may be applied to commercial blackbodies if they are modified allowing secondary contact temperature measurement. In addition, the established systematic may be incorporated as part of the actions for quality assurance in routine calibrations of radiation thermometers, by using the secondary contact temperature measurement for detecting departures from the real radiometrically obtained gradient and the effect on the uncertainty. On the other hand, a theoretical model is proposed to evaluate the effect of temperature variations on effective emissivity and associated uncertainty. This model is based on a gradient sample chosen following plausible criteria. The model is consistent with the Monte Carlo method for calculating the uncertainty of effective emissivity and complements others published in the literature where uncertainty is calculated taking into account only geometrical variables and intrinsic emissivity. The mathematical model and experimental procedure are applied and validated using a commercial type three-zone furnace, with a blackbody cavity modified to enable a secondary contact temperature measurement, in the range between 400 °C and 1000 °C.

Study of the possibility of growing germanium single crystals under low temperature gradients

NASA Astrophysics Data System (ADS)

Moskovskih, V. A.; Kasimkin, P. V.; Shlegel, V. N.; Vasiliev, Y. V.; Gridchin, V. A.; Podkopaev, O. I.; Zhdankov, V. N.

2014-03-01

The possibility of growing germanium single crystals under low temperature gradients in order to produce a dislocation-free material has been studied. Germanium crystals with a dislocation density of about 100-200 cm-2 have been grown in a system with a weight control of crystal growth at maximum axial gradients of about 1.5 K/cm.

Solution for Minimizing Surface Heating Effect for Fast Open-Path CO2 Flux Measurements in Cold Environments

NASA Astrophysics Data System (ADS)

Hupp, J. R.; Burba, G. G.; McDermitt, D. K.; Anderson, D. J.; Eckles, R. D.

2010-12-01

Open-path design of the high speed gas analyzers is a well-established configuration widely used for measurements of CO2 fluxes and concentrations. This configuration has advantages and deficiencies. Advantages include excellent frequency response, long-term stability, low sensitivity to window contamination, low-power pump-free operation, and infrequent calibration requirements. Deficiencies include susceptibility to precipitation and icing, and a potential need for instrument surface heating correction in extremely cold environments. In spite of the deficiencies, open-path measurements often provide data coverage that would not have been possible using traditional closed-path approach. Data loss from precipitation and icing may not always be prevented for the open-path instruments, while heating effect does not pose a problem for CO2 flux in warm environments. Even in cold environments, the impact of heating on CO2 flux is much smaller than other well-known effects, such as Webb-Pearman-Leuning terms, or frequency response corrections for closed-path analyzers. Nonetheless, instrument surface heating effect in cold environments could be addressed scientifically, via developing the theoretical corrections, and instrumentally, via measuring fast integrated air temperature in the optical path, or via enclosing the open-path instrument into a low-power short-intake design. Here we provide an alternative way to minimize or eliminate open-path heating effect, achieved by minimizing or eliminating the temperature gradient between the instrument surface and ambient air. Open-path low temperature controlled design is discussed in comparison with two other approaches (e.g., traditional open-path design and closed-path design) in terms of their field performance for Eddy Covariance flux measurements in the cold. This study presents field data from a new open-path CO2/H2O gas analyzer, LI-7500A, based on the LI-7500 model modified to produce substantially less heat during extremely cold conditions. Two regiments of the temperature control for internal electronics were examined across a wide range of temperatures: (i) the traditional control temperature of about 30oC, and (ii) new regiment controlling parts of internal electronics at 5oC. When new 5oC regiment was activated, the following changes were observed: heat dissipation from the surface reduced several folds, surface-to-air temperature gradients reduced 2-50 times; and the number of false uptake hours were reduced by 3.5 times, to the same level as a closed-path standard. Significant advantage of the new regiment was also observed in the magnitude of CO2 fluxes, especially in cold weather below -10oC. At such cold temperatures, CO2 fluxes from a 30oC controlled LI-7500 were 19% below those of the closed-path standard, while fluxes from a 5oC controlled LI-7500A were, on average, within 1% of the standard. These are strong experimental evidence that open-path instrument heating can be substantially reduced or eliminated via such simple hardware based solution. This allows continued and expanded use of this ultimately lowest-power remote solution for fast gas measurements.

Extent of partial melting beneath the Cascade Range, Oregon: Constraints from gravity anomalies and ideal-body theory

NASA Astrophysics Data System (ADS)

Blakely, Richard J.

1994-02-01

The spatial correlation between a horizontal gradient in heat flow and a horizontal gradient in residual gravity in the Western Cascades of central Oregon has been interpreted by others as evidence of the western edge of a pervasive zone of high temperatures and partial melting at midcrustal depths (5-15 km). Both gradients are steep and relatively linear over north-south distances in excess of 150 km. The Western Cascades gravity gradient is the western margin of a broad gravity depression over most of the Oregon Cascade Range, implying that the midcrustal zone of anomalous temperatures lies throughout this region. Ideal-body theory applied to the gravity gradient, however, shows that the source of the Western Cascades gravity gradient cannot be deeper than about 2.5 km and is considerably shallower in some locations. These calculations are unique determinations, assuming that density contrasts associated with partial melting and elevated temperatures in the crust do not exceed 500 kg/cu m. Consequently, the gravity gradient and the heat flow gradient in the Western Cascades cannot be caused directly by the same source if the heat flow gradient originates at midcrustal depths. This conclusion in itself does not disprove the existence of a widespread midcrustal zone of anomalously high temperatures and partial melting in this area, but it does eliminate a major argument in support of its existence. The gravity gradient is most likely caused by lithologic varitions in the shallow crust, perhaps reflecting a relict boundary between the Cascade extensional trough to the west and Tertiary oceanic crust to the west. The boundary must have formed prior to Oligocene time, the age of the oldest rocks that now conceal it.