Characterization of raw and burnt oil shale from Dotternhausen: Petrographical and mineralogical evolution with temperature

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

Thiéry, Vincent, E-mail: vincent.thiery@mines-douai.fr; Université de Lille; Bourdot, Alexandra, E-mail: alexandra.bourdot@gmail.com

The Toarcian Posidonia shale from Dotternhausen, Germany, is quarried and burnt in a fluidized bed reactor to produce electricity. The combustion residue, namely burnt oil shale (BOS), is used in the adjacent cement work as an additive in blended cements. The starting material is a typical laminated oil shale with an organic matter content ranging from 6 to 18%. Mineral matter consists principally of quartz, feldspar, pyrite and clays. After calcination in the range, the resulting product, burnt oil shale, keeps the macroscopic layered texture however with different mineralogy (anhydrite, lime, iron oxides) and the formation of an amorphous phase.more » This one, studied under STEM, reveals a typical texture of incipient partial melting due to a long retention time (ca. 30 min) and quenching. An in-situ high temperature X-ray diffraction (HTXRD) allowed studying precisely the mineralogical changes associated with the temperature increase. - Highlights: • We present oil shale/burnt oil shale characterization. • The Posidonia Shale is burnt in a fluidized bed. • Mineralogical evolution with temperature is complex. • The burnt oil shale is used in composite cements.« less

Application of time-division-multiplexed lasers for measurements of gas temperature and CH4 and H2O concentrations at 30 kHz in a high-pressure combustor.

PubMed

Caswell, Andrew W; Kraetschmer, Thilo; Rein, Keith; Sanders, Scott T; Roy, Sukesh; Shouse, Dale T; Gord, James R

2010-09-10

Two time-division-multiplexed (TDM) sources based on fiber Bragg gratings were applied to monitor gas temperature, H(2)O mole fraction, and CH(4) mole fraction using line-of-sight absorption spectroscopy in a practical high-pressure gas turbine combustor test article. Collectively, the two sources cycle through 14 wavelengths in the 1329-1667 nm range every 33 μs. Although it is based on absorption spectroscopy, this sensing technology is fundamentally different from typical diode-laser-based absorption sensors and has many advantages. Specifically, the TDM lasers allow efficient, flexible acquisition of discrete-wavelength information over a wide spectral range at very high speeds (typically 30 kHz) and thereby provide a multiplicity of precise data at high speeds. For the present gas turbine application, the TDM source wavelengths were chosen using simulated temperature-difference spectra. This approach is used to select TDM wavelengths that are near the optimum values for precise temperature and species-concentration measurements. The application of TDM lasers for other measurements in high-pressure, turbulent reacting flows and for two-dimensional tomographic reconstruction of the temperature and species-concentration fields is also forecast.

A broadening temperature sensitivity range with a core-shell YbEr@YbNd double ratiometric optical nanothermometer

NASA Astrophysics Data System (ADS)

Marciniak, L.; Prorok, K.; Francés-Soriano, L.; Pérez-Prieto, J.; Bednarkiewicz, A.

2016-02-01

The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ~980 to the more relevant ~808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd --> Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ~808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale.The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ~980 to the more relevant ~808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd --> Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ~808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale. Electronic supplementary information (ESI) available: Characterization, structural and morphological characterization of nanocrystals, the measurement setup. See DOI: 10.1039/c5nr08223d

Phase states and thermomorphologic, thermotropic, and magnetomorphologic properties of lyotropic mesophases: Sodium lauryl sulphate-water-1-decanol liquid-crystalline system

NASA Astrophysics Data System (ADS)

Özden, Pınar; Nesrullajev, Arif; Oktik, Şener

2010-12-01

Phase states in sodium lauryl sulphate-water-1-decanol lyotropic liquid-crystalline system have been investigated for different temperature ranges. The dependence of triangle phase diagram types, phase boundaries, and sequence of lyotropic mesophases vs temperature has been found. The thermomorphologic, thermotropic, and magnetomorphologic properties of hexagonal E, lamellar D, nematic-calamitic NC , nematic-discotic ND , and biaxial nematic Nbx mesophases have been studied in detail. Dynamics of transformations of magnetically induced textures has been investigated. Peculiarities of typical and magnetically induced textures have been investigated in detail. Triangle phase diagrams of sodium lauryl sulphate-water-1-decanol lyotropic liquid-crystalline system for different temperatures and typical and magnetically induced textures of E, D, NC , ND , and Nbx mesophases are presented.

Temperature dependence of piezoelectric properties for textured SBN ceramics.

PubMed

Kimura, Masahiko; Ogawa, Hirozumi; Kuroda, Daisuke; Sawada, Takuya; Higuchi, Yukio; Takagi, Hiroshi; Sakabe, Yukio

2007-12-01

Temperature dependences of piezoelectric properties were studied for h001i textured ceramics of bismuth layer-structured ferroelectrics, SrBi(2)Nb(2)O(9) (SBN). The textured ceramics with varied orientation degrees were fabricated by templated, grain-growth method, and the temperature dependences of resonance frequency were estimated. Excellent temperature stability of resonance frequency was obtained for the 76% textured ceramics. The resonance frequency of the 76% textured specimens varied almost linearly over a wide temperature range. Therefore, the variation was slight, even in a high temperature region above 150 degrees C. Temperature stability of a quartz crystal oscillator is generally higher than that of a ceramic resonator around room temperature. The variation of resonance frequency for the 76% textured SrBi(2)Nb(2)O(9) was larger than that of oscillation frequency for a typical quartz oscillator below 150 degrees C also in this study. However, the variation of the textured SrBi(2)Nb(2)O(9) was smaller than that of the quartz oscillator over a wide temperature range from -50 to 250 degrees C. Therefore, textured SrBi(2)Nb(2)O(9) ceramics is a major candidate material for the resonators used within a wide temperature range.

[IR spectral-analysis-based range estimation for an object with small temperature difference from background].

PubMed

Fu, Xiao-Ning; Wang, Jie; Yang, Lin

2013-01-01

It is a typical passive ranging technology that estimation of distance of an object is based on transmission characteristic of infrared radiation, it is also a hotspot in electro-optic countermeasures. Because of avoiding transmitting energy in the detection, this ranging technology will significantly enhance the penetration capability and infrared conceal capability of the missiles or unmanned aerial vehicles. With the current situation in existing passive ranging system, for overcoming the shortage in ranging an oncoming target object with small temperature difference from background, an improved distance estimation scheme was proposed. This article begins with introducing the concept of signal transfer function, makes clear the working curve of current algorithm, and points out that the estimated distance is not unique due to inherent nonlinearity of the working curve. A new distance calculation algorithm was obtained through nonlinear correction technique. It is a ranging formula by using sensing information at 3-5 and 8-12 microm combined with background temperature and field meteorological conditions. The authors' study has shown that the ranging error could be mainly kept around the level of 10% under the condition of the target and background apparent temperature difference equal to +/- 5 K, and the error in estimating background temperature is no more than +/- 15 K.

Determination of design allowable strength properties of elevated-temperature alloys. Part 1: Coated columbium alloys

NASA Technical Reports Server (NTRS)

Favor, R. J.; Maykuth, D. J.; Bartlett, E. S.; Mindlin, H.

1972-01-01

A program to determine the characteristics of two coated columbium alloy systems for spacecraft structures is discussed. The alloy was evaluated as coated base material, coated butt-welded material, and material thermal/pressure cycled prior to testing up to 30 cycles. Evaluation was by means of tensile tests covering the temperature range to 2400 F. Design allowables were computed and are presented as tables of data. The summary includes a room temperature property table, effect of temperature curves, and typical stress-strain curves.

Measuring Seebeck Coefficient

NASA Technical Reports Server (NTRS)

Snyder, G. Jeffrey (Inventor)

2015-01-01

A high temperature Seebeck coefficient measurement apparatus and method with various features to minimize typical sources of errors is described. Common sources of temperature and voltage measurement errors which may impact accurate measurement are identified and reduced. Applying the identified principles, a high temperature Seebeck measurement apparatus and method employing a uniaxial, four-point geometry is described to operate from room temperature up to 1300K. These techniques for non-destructive Seebeck coefficient measurements are simple to operate, and are suitable for bulk samples with a broad range of physical types and shapes.

Development of a HEC-RAS temperature model for the North Santiam River, northwestern Oregon

USGS Publications Warehouse

Stonewall, Adam J.; Buccola, Norman L.

2015-01-01

Much of the error in temperature predictions resulted from the model’s inability to accurately simulate the full range of diurnal fluctuations during the warmest months. Future iterations of the model could be improved by the collection and inclusion of additional streamflow and temperature data, especially near the mouth of the South Santiam River. Presently, the model is able to predict hourly and daily water temperatures under a wide variety of conditions with a typical error of 0.8 and 0.7 °C, respectively.

Thermal expansion behavior of LDEF metal matrix composites

NASA Technical Reports Server (NTRS)

Le, T. D.; Steckel, G. L.

1992-01-01

The effects of the space environment on the thermal expansion stability of metal matrix composites (graphite/Al and graphite/Mg) will be presented. A sample from each category of metal matrix composites mounted on the leading and trailing edge was chosen for analysis of the temperature-time-thermal strain histories. Typical thermal expansion curves over the same range of temperature were selected at the beginning, mid, and end of the recording duration. The thermal expansion of selected post-flight LDEF samples were measured over the same range of temperature in the laboratory using a Michelson laser interferometer. The thermal strains were monitored concurrently with a laser interferometer and a mounted strain gage.

Bypass diode integration

NASA Technical Reports Server (NTRS)

Shepard, N. F., Jr.

1981-01-01

Protective bypass diodes and mounting configurations which are applicable for use with photovoltaic modules having power dissipation requirements in the 5 to 50 watt range were investigated. Using PN silicon and Schottky diode characterization data on packaged diodes and diode chips, typical diodes were selected as representative for each range of current carrying capacity, an appropriate heat dissipating mounting concept along with its environmental enclosure was defined, and a thermal analysis relating junction temperature as a function of power dissipation was performed. In addition, the heat dissipating mounting device dimensions were varied to determine the effect on junction temperature. The results of the analysis are presented as a set of curves indicating junction temperature as a function of power dissipation for each diode package.

Piezoelectricity above the Curie temperature? Combining flexoelectricity and functional grading to enable high-temperature electromechanical coupling

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

Mbarki, R.; Baccam, N.; Dayal, Kaushik

Most technologically relevant ferroelectrics typically lose piezoelectricity above the Curie temperature. This limits their use to relatively low temperatures. In this Letter, exploiting a combination of flexoelectricity and simple functional grading, we propose a strategy for high-temperature electromechanical coupling in a standard thin film configuration. We use continuum modeling to quantitatively demonstrate the possibility of achieving apparent piezoelectric materials with large and temperature-stable electromechanical coupling across a wide temperature range that extends significantly above the Curie temperature. With Barium and Strontium Titanate, as example materials, a significant electromechanical coupling that is potentially temperature-stable up to 900 °C is possible.

The mechanisms of delayed fluorescence in charge-transfer crystal of tetracyanobenzene-hexamethylbenzene

NASA Astrophysics Data System (ADS)

Kozankiewicz, B.; Prochorow, J.

1989-08-01

Fluorescence, phosphorescence and delayed fluorescence emission characteristics of tetracyanobenzene-hexamethylbenzene (TCNB-HMB) charge-transfer crystal have been studied in the 1.7-340 K temperature range. Delayed fluorescence, originating from heterogeneous triplet-triplet annihilation indicates the presence of mobile charge-transfer triplet excitons at a temperature as low as 1.7 K. However, the behaviour of triplet excitons in TCNB-HMB crystal is strongly controlled by a very efficient trapping process in the whole temperature range investigated. It was found that thermally activated delayed fluorescence, which is a dominating emission of the crystal at elevated temperatures (>60 K), has a different origin (a different initial state) at different temperatures. These observations were analysed and interpreted in terms of a photokinetic model, which is considered to be typical for charge-transfer crystals with high charge-transfer character of triplet excitons.

Molecular Insight into the Slipperiness of Ice.

PubMed

Weber, Bart; Nagata, Yuki; Ketzetzi, Stefania; Tang, Fujie; Smit, Wilbert J; Bakker, Huib J; Backus, Ellen H G; Bonn, Mischa; Bonn, Daniel

2018-05-16

Measurements of the friction coefficient of steel-on-ice over a large temperature range reveal very high friction at low temperatures (-100 °C) and a steep decrease in the friction coefficient with increasing temperature. Very low friction is only found over the limited temperature range typical for ice skating. The strong decrease in the friction coefficient with increasing temperature exhibits Arrhenius behavior with an activation energy of E a ≈ 11.5 kJ mol -1 . Remarkably, molecular dynamics simulations of the ice-air interface reveal a very similar activation energy for the mobility of surface molecules. Weakly hydrogen-bonded surface molecules diffuse over the surface in a rolling motion, their number and mobility increasing with increasing temperature. This correlation between macroscopic friction and microscopic molecular mobility indicates that slippery ice arises from the high mobility of its surface molecules, making the ice surface smooth and the shearing of the weakly bonded surface molecules easy.

Novel sensor for color control in solid state lighting applications

NASA Astrophysics Data System (ADS)

Gourevitch, Alex; Thurston, Thomas; Singh, Rajiv; Banachowicz, Bartosz; Korobov, Vladimir; Drowley, Cliff

2010-02-01

LED wavelength and luminosity shifts due to temperature, dimming, aging, and binning uncertainty can cause large color errors in open-loop light-mixing illuminators. Multispectral color light sensors combined with feedback circuits can compensate for these LED shifts. Typical color light sensor design variables include the choice of light-sensing material, filter configuration, and read-out circuitry. Cypress Semiconductor has designed and prototyped a color sensor chip that consists of photodiode arrays connected to a I/F (Current to Frequency) converter. This architecture has been chosen to achieve high dynamic range (~100dB) and provide flexibility for tailoring sensor response. Several different optical filter configurations were evaluated in this prototype. The color-sensor chip was incorporated into an RGB light color mixing system with closed-loop optical feedback. Color mixing accuracy was determined by calculating the difference between (u',v') set point values and CIE coordinates measured with a reference colorimeter. A typical color precision ▵u'v' less than 0.0055 has been demonstrated over a wide range of colors, a temperature range of 50C, and light dimming up to 80%.

Torque Sensor Based on Tunnel-Diode Oscillator

NASA Technical Reports Server (NTRS)

Chui, Talso; Young, Joseph

2008-01-01

A proposed torque sensor would be capable of operating over the temperature range from 1 to 400 K, whereas a typical commercially available torque sensor is limited to the narrower temperature range of 244 to 338 K. The design of this sensor would exploit the wide temperature range and other desirable attributes of differential transducers based on tunnel-diode oscillators as described in "Multiplexing Transducers Based on Tunnel-Diode Oscillators". The proposed torque sensor would include three flexural springs that would couple torque between a hollow outer drive shaft and a solid inner drive shaft. The torque would be deduced from the torsional relative deflection of the two shafts, which would be sensed via changes in capacitances of two capacitors defined by two electrodes attached to the inner shaft and a common middle electrode attached to the outer shaft.

Extreme climatic events constrain space use and survival of a ground-nesting bird.

PubMed

Tanner, Evan P; Elmore, R Dwayne; Fuhlendorf, Samuel D; Davis, Craig A; Dahlgren, David K; Orange, Jeremy P

2017-05-01

Two fundamental issues in ecology are understanding what influences the distribution and abundance of organisms through space and time. While it is well established that broad-scale patterns of abiotic and biotic conditions affect organisms' distributions and population fluctuations, discrete events may be important drivers of space use, survival, and persistence. These discrete extreme climatic events can constrain populations and space use at fine scales beyond that which is typically measured in ecological studies. Recently, a growing body of literature has identified thermal stress as a potential mechanism in determining space use and survival. We sought to determine how ambient temperature at fine temporal scales affected survival and space use for a ground-nesting quail species (Colinus virginianus; northern bobwhite). We modeled space use across an ambient temperature gradient (ranging from -20 to 38 °C) through a maxent algorithm. We also used Andersen-Gill proportional hazard models to assess the influence of ambient temperature-related variables on survival through time. Estimated available useable space ranged from 18.6% to 57.1% of the landscape depending on ambient temperature. The lowest and highest ambient temperature categories (<-15 °C and >35 °C, respectively) were associated with the least amount of estimated useable space (18.6% and 24.6%, respectively). Range overlap analysis indicated dissimilarity in areas where Colinus virginianus were restricted during times of thermal extremes (range overlap = 0.38). This suggests that habitat under a given condition is not necessarily a habitat under alternative conditions. Further, we found survival was most influenced by weekly minimum ambient temperatures. Our results demonstrate that ecological constraints can occur along a thermal gradient and that understanding the effects of these discrete events and how they change over time may be more important to conservation of organisms than are average and broad-scale conditions as typically measured in ecological studies. © 2016 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

Stability of a Crystal Oscillator, Type Si530, Inside and Beyond its Specified Operating Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2011-01-01

Data acquisition and control systems depend on timing signals for proper operation and required accuracy. These clocked signals are typically provided by some form of an oscillator set to produce a repetitive, defined signal at a given frequency. Crystal oscillators are commonly used because they are less expensive, smaller, and more reliable than other types of oscillators. Because of the inherent characteristics of the crystal, the oscillators exhibit excellent frequency stability within the specified range of operational temperature. In some cases, however, some compensation techniques are adopted to further improve the thermal stability of a crystal oscillator. Very limited data exist on the performance and reliability of commercial-off-the-shelf (COTS) crystal oscillators at temperatures beyond the manufacturer's specified operating temperature range. This information is very crucial if any of these parts were to be used in circuits designed for use in space exploration missions where extreme temperature swings and thermal cycling are encountered. This report presents the results of the work obtained on the operation of Silicon Laboratories crystal oscillator, type Si530, under specified and extreme ambient temperatures.

Interfaces in Si/Ge atomic layer superlattices on (001)Si: Effect of growth temperature and wafer misorientation

NASA Astrophysics Data System (ADS)

Baribeau, J.-M.; Lockwood, D. J.; Syme, R. W. G.

1996-08-01

We have used x-ray diffraction, specular reflectivity, and diffuse scattering, complemented by Raman spectroscopy, to study the interfaces in a series of (0.5 nm Ge/2 nm Si)50 atomic layer superlattices on (001)Si grown by molecular beam epitaxy in the temperature range 150-650 °C. X-ray specular reflectivity revealed that the structures have a well-defined periodicity with interface widths of about 0.2-0.3 nm in the 300-590 °C temperature range. Offset reflectivity scans showed that the diffuse scattering peaks at values of perpendicular wave vector transfer corresponding to the superlattice satellite peaks, indicating that the interfaces are vertically correlated. Transverse rocking scans of satellite peaks showed a diffuse component corresponding to an interface corrugation of typical length scale of ˜0.5 μm. The wavelength of the undulations is a minimum along the miscut direction and is typically 30-40 times larger than the surface average terrace width assuming monolayer steps, independently of the magnitude of the wafer misorientation. The amplitude of the undulation evolves with growth temperature and is minimum for growth at ˜460 °C and peaks at ˜520 °C. Raman scattering showed the chemical abruptness of the interfaces at low growth temperatures and indicated a change in the growth mode near 450 °C.

Temperature dependence of ice-on-rock friction at realistic glacier conditions

PubMed Central

Savage, H.; Nettles, M.

2017-01-01

Using a new biaxial friction apparatus, we conducted experiments of ice-on-rock friction in order to better understand basal sliding of glaciers and ice streams. A series of velocity-stepping and slide–hold–slide tests were conducted to measure friction and healing at temperatures between −20°C and melting. Experimental conditions in this study are comparable to subglacial temperatures, sliding rates and effective pressures of Antarctic ice streams and other glaciers, with load-point velocities ranging from 0.5 to 100 µm s−1 and normal stress σn = 100 kPa. In this range of conditions, temperature dependences of both steady-state friction and frictional healing are considerable. The friction increases linearly with decreasing temperature (temperature weakening) from μ = 0.52 at −20°C to μ = 0.02 at melting. Frictional healing increases and velocity dependence shifts from velocity-strengthening to velocity-weakening behaviour with decreasing temperature. Our results indicate that the strength and stability of glaciers and ice streams may change considerably over the range of temperatures typically found at the ice–bed interface. This article is part of the themed issue ‘Microdynamics of ice’. PMID:28025297

Microbial degradation of livestock-generated ammonia using biofilters at typical ambient temperatures.

PubMed

Kalingan, A E; Liao, Chung-Min; Chen, Jein-Wen; Chen, Szu-Chieh

2004-01-01

The purpose of this research was to neutralize livestock-generated ammonia by using biofilters packed with inexpensive inorganic and organic packing material combined with multicultural microbial load at typical ambient temperatures. Peat and inorganic supporting materials were used as biofiltration matrix packed in a perfusion column through which gas was transfused. Results show the ammonia removal significantly fell in between 99 and 100% when ammonia concentration of 200 ppmv was used at different gas flow rates ranged from 0.030 to 0.060 m3 h(-1) at a fluctuating room temperature of 27.5 +/- 4.5 C (Mean +/- SD). Under these conditions, the emission concentration of ammonia that is liberated after biofiltration is less than 1 ppmv (0.707 mg m(-3)) over the period of our study, suggesting the usage of low-cost biofiltration systems for long-term function is effective at wider ranges of temperature fluctuations. The maximum (100%) ammonia removal efficiency was obtained in this biofilter was having an elimination capacity of 2.217 g m(-3) h(-1). This biofilter had high nitrification efficiencies and hence controlled ammonia levels with the reduced backpressure. The response of this biofilter to shut down and start up operation showed that the biofilm has a superior stability.

Very low threshold-current temperature sensitivity in constricted double-heterojunction AlGaAs lasers

NASA Technical Reports Server (NTRS)

Botez, D.; Connolly, J. C.; Gilbert, D. B.; Ettenberg, M.

1981-01-01

The temperature dependence of threshold currents in constricted double-heterojunction diode lasers with strong lateral mode confinement is found to be significantly milder than for other types of lasers. The threshold-current relative variations with ambient temperature are typically two to three times less than for other devices of CW-operation capability. Over the interval 10-70 C the threshold currents fit the empirical exponential law exp/(T2-T1)/T0/ with T0 values in the 240-375 C range in pulsed operation, and in the 200-310 C range in CW operation. The external differential quantum efficiency and the mode far-field pattern near threshold are virtually invariant with temperature. The possible causes of high-T0 behavior are analyzed, and a new phenomenon - temperature-dependent current focusing - is presented to explain the results.

Experiment to determine properties of packed particle beds and regenerators at cryogenic temperatures

NASA Technical Reports Server (NTRS)

Barclay, J. A.; Overton, W. C., Jr.; Stewart, W. F.; Sarangi, S.

1984-01-01

Studies related to the development of magnetic refrigeration and heat pump systems in temperature ranges from 4 K to ambient temperature and above have been conducted, taking into account the testing of the properties of packed-particle beds and regenerators at cryogenic temperatures as low as 4 K as an essential part of these studies. The present paper provides a description of the developed experimental apparatus and presents the results of recent measurements on packed-particle beds in the liquid helium and liquid nitrogen temperature ranges. Attention is given to a schematic of the apparatus and the data acquisition system, the various modes of gas flow, a schematic of a typical test bed with thermocouple positions, the calculation of transient heat transfer rates at different positions in the bed, the governing equations, and the procedures used for solving these equations.

Thermoelectric power of PrMg3

NASA Astrophysics Data System (ADS)

Isikawa, Yosikazu; Somiya, Kazuya; Koyanagi, Huruto; Mizushima, Toshio; Kuwai, Tomohiko; Tayama, Takashi

2010-01-01

PrMg3 is supposed to be one of the strongly correlated electron systems originated from the hybridization between the Pr 4f and conduction electrons, because the gigantic electronic specific heat coefficient C/T was observed at low temperatures. However, a typical behaviour of - ln T dependence was not observed in the temperature dependence of the electrical resistivity. The thermoelectric power S is a powerful tool to investigate the density of states at the Fermi energy. We measured carefully the thermoelectric power of PrMg3 in the temperature range between 2 and 300 K. S is extremely small, ranged within ±1 μV/K over the whole temperature. The value of S/T at low temperature limit was also significantly smaller than expected from the specific heat results. We therefore conclude that the density of state at the Fermi level is not enhanced in PrMg3.

Digital control of diode laser for atmospheric spectroscopy

NASA Technical Reports Server (NTRS)

Menzies, R. T.; Rutledge, C. W. (Inventor)

1985-01-01

A system is described for remote absorption spectroscopy of trace species using a diode laser tunable over a useful spectral region of 50 to 200 cm(-1) by control of diode laser temperature over range from 15 K to 100 K, and tunable over a smaller region of typically 0.1 to 10 cm(-1) by control of the diode laser current over a range from 0 to 2 amps. Diode laser temperature and current set points are transmitted to the instrument in digital form and stored in memory for retrieval under control of a microprocessor during measurements. The laser diode current is determined by a digital to analog converter through a field effect transistor for a high degree of ambient temperature stability, while the laser diode temperature is determined by set points entered into a digital to analog converter under control of the microprocessor. Temperature of the laser diode is sensed by a sensor diode to provide negative feedback to the temperature control circuit that responds to the temperature control digital to analog converter.

Behavioral thermal tolerances of free-ranging rattlesnakes (Crotalus oreganus) during the summer foraging season.

PubMed

Putman, Breanna J; Clark, Rulon W

2017-04-01

Increasing temperature due to climate change is one of the greatest challenges for wildlife worldwide. Behavioral data on free-ranging individuals is necessary to determine at what temperatures animals modify activity as this would determine their capacity to continue to move, forage, and mate under altered thermal regimes. In particular, high temperatures could limit available surface activity time and time spent on fitness-related activities. Conversely, performance, such as feeding rate, can increase with temperature potentially having positive fitness effects. Here, we examine how the hunting behaviors of free-ranging Northern Pacific Rattlesnakes (Crotalus oreganus) associate with air temperature and body temperature. We continuously recorded snakes in the field using videography, capturing behaviors rarely considered in past studies such as movements in and out of refuge and strikes on prey. We found that as mean daily air temperature increased, hunting activity and the likelihood of hunting at night decreased, while the number of movements and distance moved per day increased. Snakes typically retreated to refuge before body temperatures reached 31°C. Body temperatures of snakes hunting on the surface were lower compared to temperatures of non-hunting snakes in refuge in the morning, while this relationship was inverted in the afternoon. Snake body size influenced the disparity of these temperatures. Finally, strike initiation and success occurred across a wide range of body temperatures, indicating hunting performance may not be strongly constrained by temperature. These results on the temperatures at which free-ranging rattlesnakes exhibit fitness-related behaviors could be valuable for understanding their vulnerabilities to future climates. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterization by thermoelectric power of a commercial aluminum-iron-silicon alloy (8011) during isothermal precipitation

NASA Astrophysics Data System (ADS)

Luiggi, Ney José A.

1998-11-01

We have characterized a commercial 8011 (Al-Fe-Si) alloy by studying samples under different initial states of strain hardening and iron and silicon supersaturation using thermoelectric power as a measurement technique. Isothermal kinetics of precipitation are obtained in the temperature range between 225 °C and 600 °C. We determine the atom fraction precipitated for each microstructural condition, identifying the dominant alloying additions and evaluating the typical parameters of the precipitated phases, such as, for example, the apparent activation energy. Finally, we determine the time-temperature-transformation (TTT) diagrams. Our results prove that iron is the alloying addition that controls the precipitation kinetics of the 8011 alloy in the temperature range studied.

10 000-hr Cyclic Oxidation Behavior of 68 High-Temperature Co-, Fe-, and Ni- Base Alloys Evaluated at 982 deg. C (1800 deg. F)

NASA Technical Reports Server (NTRS)

Barrett, Charles A.

1999-01-01

Power systems with operating temperatures in the range of 815 to 982 C (1500 to 1800 F) frequently require alloys that can operate for long times at these temperatures. A critical requirement is that these alloys have adequate oxidation resistance. The alloys used in these power systems require thousands of hours of operating life with intermittent shutdown to room temperature. Intermittent power plant shutdowns, however, offer the possibility that the protective scale will tend to spall (i.e., crack and flake off) upon cooling, increasing the rate of oxidative attack in subsequent heating cycles. Thus, it is critical that candidate alloys be evaluated for cyclic oxidation behavior. It was determined that exposing test alloys to ten 1000-hr cycles in static air at 982 10 000-hr Cyclic Oxidation Behavior of 68 High-Temperature Co-, Fe-, and Ni-Base Alloys Evaluated at 982 C (1800 F) could give a reasonable simulation of long-time power plant operation. Iron- (Fe-), nickel- (Ni-), and cobalt- (Co-) based high-temperature alloys with sufficient chromium (Cr) and/or aluminum (Al) content can exhibit excellent oxidation resistance. The protective oxides formed by these classes of alloys are typically Cr2O3 and/or Al2O3, and are usually influenced by their Cr, or Cr and Al, content. Sixty-eight Co-, Fe-, and Ni-base high-temperature alloys, typical of those used at this temperature or higher, were used in this study. At the NASA Lewis Research Center, the alloys were tested and compared on the basis of their weight change as a function of time, x-ray diffraction of the protective scale composition, and the physical appearance of the exposed samples. Although final appearance and x-ray diffraction of the final scale products were two factors used to evaluate the oxidation resistance of each alloy, the main criterion was the oxidation kinetics inferred from the specific weight change versus time data. These data indicated a range of oxidation behavior including parabolic (typical of isothermal oxidation), paralinear, linear, and mixed-linear kinetics.

A comparison of the temperature and density structure in high and low speed thermal proton flows

NASA Technical Reports Server (NTRS)

Raitt, W. J.; Schunk, R. W.; Banks, P. M.

1975-01-01

Steady-state altitude profiles of H(+) density, drift velocity, and temperature and O(+) density and temperature were deduced for a wide range of H(+) outflow velocities from subsonic to supersonic flow for plasma densities typical of both undisturbed and trough regions of the ionsophere. Allowance was made for the effects of inertia, parallel stress, and the velocity dependence of the H(+) collision frequencies. It was found that at supersonic outflow velocities there is a decrease in H(+) temperature with increasing outflow velocity. The H(+) temperatures are substantially increased above the O(+) temperatures when H(+) is flowing, with T(H+)/T(O+) reaching a maximum ratio of about 3:1.

A numerical analysis of phase-change problems including natural convection

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

Cao, Y.; Faghri, A.

1990-08-01

Fixed grid solutions for phase-change problems remove the need to satisfy conditions at the phase-change front and can be easily extended to multidimensional problems. The two most important and widely used methods are enthalpy methods and temperature-based equivalent heat capacity methods. Both methods in this group have advantages and disadvantages. Enthalpy methods (Shamsundar and Sparrow, 1975; Voller and Prakash, 1987; Cao et al., 1989) are flexible and can handle phase-change problems occurring both at a single temperature and over a temperature range. The drawback of this method is that although the predicted temperature distributions and melting fronts are reasonable, themore » predicted time history of the temperature at a typical grid point may have some oscillations. The temperature-based fixed grid methods (Morgan, 1981; Hsiao and Chung, 1984) have no such time history problems and are more convenient with conjugate problems involving an adjacent wall, but have to deal with the severe nonlinearity of the governing equations when the phase-change temperature range is small. In this paper, a new temperature-based fixed-grid formulation is proposed, and the reason that the original equivalent heat capacity model is subject to such restrictions on the time step, mesh size, and the phase-change temperature range will also be discussed.« less

Acid precipitation effects on soil pH and base saturation of exchange sites

Treesearch

W. W. McFee; J. M. Kelly; R. H. Beck

1976-01-01

The typical values and probable ranges of acid-precipitation are evaluated in terms of their theoretical effects on pH and cation exchange equilibrium of soils characteristic of the humid temperature region. The extent of probable change in soil pH and the time required to cause such a change are calculated for a range of common soils. Hydrogen ion input by acid...

Medium Deep High Temperature Heat Storage

NASA Astrophysics Data System (ADS)

Bär, Kristian; Rühaak, Wolfram; Schulte, Daniel; Welsch, Bastian; Chauhan, Swarup; Homuth, Sebastian; Sass, Ingo

2015-04-01

Heating of buildings requires more than 25 % of the total end energy consumption in Germany. Shallow geothermal systems for indirect use as well as shallow geothermal heat storage systems like aquifer thermal energy storage (ATES) or borehole thermal energy storage (BTES) typically provide low exergy heat. The temperature levels and ranges typically require a coupling with heat pumps. By storing hot water from solar panels or thermal power stations with temperatures of up to 110 °C a medium deep high temperature heat storage (MDHTS) can be operated on relatively high temperature levels of more than 45 °C. Storage depths of 500 m to 1,500 m below surface avoid conflicts with groundwater use for drinking water or other purposes. Permeability is typically also decreasing with greater depth; especially in the crystalline basement therefore conduction becomes the dominant heat transport process. Solar-thermal charging of a MDHTS is a very beneficial option for supplying heat in urban and rural systems. Feasibility and design criteria of different system configurations (depth, distance and number of BHE) are discussed. One system is designed to store and supply heat (300 kW) for an office building. The required boreholes are located in granodioritic bedrock. Resulting from this setup several challenges have to be addressed. The drilling and completion has to be planned carefully under consideration of the geological and tectonical situation at the specific site.

Improved Wide Operating Temperature Range of Li-Ion Cells

NASA Technical Reports Server (NTRS)

Smart, Marshall C.; Bugga, Ratnakumar V.

2013-01-01

Future NASA missions aimed at exploring the Moon, Mars, and the outer planets require rechargeable batteries that can operate over a wide temperature range (-60 to +60 C) to satisfy the requirements of various applications including landers, rovers, penetrators, CEV, CLV, etc. This work addresses the need for robust rechargeable batteries that can operate well over a wide temperature range. The Department of Energy (DoE) has identified a number of technical barriers associated with the development of Liion rechargeable batteries for PHEVs. For this reason, DoE has interest in the development of advanced electrolytes that will improve performance over a wide range of temperatures, and lead to long life characteristics (5,000 cycles over a 10-year life span). There is also interest in improving the high-voltage stability of these candidate electrolyte systems to enable the operation of up to 5 V with high specific energy cathode materials. Currently, the state-of-the-art lithium-ion system has been demonstrated to operate over a wide range of temperatures (-40 to +40 C); however, the rate capability at the lower temperatures is very poor. In addition, the low-temperature performance typically deteriorates rapidly upon being exposed to high temperatures. A number of electrolyte formulations were developed that incorporate the use of electrolyte additives to improve the high-temperature resilience, low-temperature power capability, and life characteristics of methyl propionate (MP)-based electrolyte solutions. These electrolyte additives include mono-fluoroethylene carbonate (FEC), lithium oxalate, vinylene carbonate (VC), and lithium bis(oxalate borate) (LiBOB), which have previously been shown to result in improved high-temperature resilience of all carbonate-based electrolytes. These MP-based electrolytes with additives have been shown to have improved performance in experiments with MCMB-LiNiCoAlO2 cells.

Magnetism and structural chemistry of ternary borides RE2MB 6 ( RE = rare earth, M = Ru, Os)

NASA Astrophysics Data System (ADS)

Hiebl, K.; Rogl, P.; Nowotny, H.

1984-10-01

The magnetic behavior of the ternary borides RE2RuB 6 and RE2OsB 6 ( RE = Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) was studied in the temperature range 1.5 K < T < 1100 K. All compounds crystallize with the Y 2ReB 6-type structure and are characterized by direct RE- RE contacts and the formation of planar infinite two-dimensional rigid boron nets. The magnetic properties reveal a typical Van Vleck paramagnetism of free RE3+-ions at temperatures higher than 200 K with ferromagnetic interaction in the low-temperature range T < 55 K. The ferromagnetic ordering temperatures vary with the De Gennes factor. There is no indication for a magnetic contribution from the Ru(Os)-sublattice. Above 1.8 K none of the samples were found to be superconducting.

Analysis and Sizing for Transient Thermal Heating of Insulated Aerospace Vehicle Structures

NASA Technical Reports Server (NTRS)

Blosser, Max L.

2012-01-01

An analytical solution was derived for the transient response of an insulated structure subjected to a simplified heat pulse. The solution is solely a function of two nondimensional parameters. Simpler functions of these two parameters were developed to approximate the maximum structural temperature over a wide range of parameter values. Techniques were developed to choose constant, effective thermal properties to represent the relevant temperature and pressure-dependent properties for the insulator and structure. A technique was also developed to map a time-varying surface temperature history to an equivalent square heat pulse. Equations were also developed for the minimum mass required to maintain the inner, unheated surface below a specified temperature. In the course of the derivation, two figures of merit were identified. Required insulation masses calculated using the approximate equation were shown to typically agree with finite element results within 10%-20% over the relevant range of parameters studied.

An Analytical Solution for Transient Thermal Response of an Insulated Structure

NASA Technical Reports Server (NTRS)

Blosser, Max L.

2012-01-01

An analytical solution was derived for the transient response of an insulated aerospace vehicle structure subjected to a simplified heat pulse. This simplified problem approximates the thermal response of a thermal protection system of an atmospheric entry vehicle. The exact analytical solution is solely a function of two non-dimensional parameters. A simpler function of these two parameters was developed to approximate the maximum structural temperature over a wide range of parameter values. Techniques were developed to choose constant, effective properties to represent the relevant temperature and pressure-dependent properties for the insulator and structure. A technique was also developed to map a time-varying surface temperature history to an equivalent square heat pulse. Using these techniques, the maximum structural temperature rise was calculated using the analytical solutions and shown to typically agree with finite element simulations within 10 to 20 percent over the relevant range of parameters studied.

Iridium material for hydrothermal oxidation environments

DOEpatents

Hong, Glenn T.; Zilberstein, Vladimir A.

1996-01-01

A process for hydrothermal oxidation of combustible materials in which, during at least a part of the oxidation, corrosive material is present and makes contact with at least a portion of the apparatus over a contact area on the apparatus. At least a portion of the contact surface area comprises iridium, iridium oxide, an iridium alloy, or a base metal overlaid with an iridium coating. Iridium has been found to be highly resistant to environments encountered in the process of hydrothermal oxidation. Such environments typically contain greater than 50 mole percent water, together with oxygen, carbon dioxide, and a wide range of acids, bases and salts. Pressures are typically about 27.5 to about 1000 bar while temperatures range as high as 800.degree. C.

Influence of temperature, needle gauge and injection rate on the size distribution, concentration and acoustic responses of ultrasound contrast agents at high frequency.

PubMed

Sun, Chao; Panagakou, Ioanna; Sboros, Vassilis; Butler, Mairead B; Kenwright, David; Thomson, Adrian J W; Moran, Carmel M

2016-08-01

This paper investigated the influence of needle gauge (19G and 27G), injection rate (0.85ml·min(-1), 3ml·min(-1)) and temperature (room temperature (RT) and body temperature (BT)) on the mean diameter, concentration, acoustic attenuation, contrast to tissue ratio (CTR) and normalised subharmonic intensity (NSI) of three ultrasound contrast agents (UCAs): Definity, SonoVue and MicroMarker (untargeted). A broadband substitution technique was used to acquire the acoustic properties over the frequency range 17-31MHz with a preclinical ultrasound scanner Vevo770 (Visualsonics, Canada). Significant differences (P<0.001-P<0.05) between typical in vitro setting (19G needle, 3ml·min(-1) at RT) and typical in vivo setting (27G needle, 0.85ml·min(-1) at BT) were found for SonoVue and MicroMarker. Moreover we found that the mean volume-based diameter and concentration of both SonoVue and Definity reduced significantly when changing from typical in vitro to in vivo experimental set-ups, while those for MicroMarker did not significantly change. From our limited measurements of Definity, we found no significant change in attenuation, CTR and NSI with needle gauge. For SonoVue, all the measured acoustic properties (attenuation, CTR and NSI) reduced significantly when changing from typical in vitro to in vivo experimental conditions, while for MicroMarker, only the NSI reduced, with attenuation and CTR increasing significantly. These differences suggest that changes in physical compression and temperature are likely to alter the shell structure of the UCAs resulting in measureable and significant changes in the physical and high frequency acoustical properties of the contrast agents under typical in vitro and preclinical in vivo experimental conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

Early Life-Stage Responses of a Eurythemal Estuarine Fish, Mummichog (Fundulus hetereoclitus) to Fixed and Fluctuating Thermal Regimes

NASA Astrophysics Data System (ADS)

Shaifer, J.

2016-02-01

The mummichog (Fundulus hetereoclitus) is an intertidal spawning fish that ranges from the Gulf of St. Lawrence to northeastern Florida. A notoriously hardy species, adults can tolerate a wide range of temperature typical of inshore, estuarine waters. This experiment assessed how a wide range of constant and fluctuating temperatures affect the survival, development, and condition of embryos and young larvae. Captive adults were provided nightly with spawning substrates that were inspected each morning for fertilized eggs. Young ( 8 hr post-fertilization) embryos (N = 25 per population) were assigned to either one of a wide range of constant temperatures (8 to 34 °C) generated by a thermal gradient block (TGB), or to one of 10 daily oscillating temperature regimes that spanned the TGB's mid temperature (21 °C). Water was changed and populations inspected for mortalities and hatching at 12-hr intervals. Hatch dates and mortalities were recorded, and larvae were either anesthetized and measured for size by analyzing digital images, or evaluated for persistence in a food-free environment. Mummichog embryos withstood all but the coldest constant regimes and the entire range of fluctuating ones although age at hatching varied substantially within and among experimental populations. Embryos incubated at warmer temperatures hatched out earlier and at somewhat smaller sizes than those experiencing cooler temperatures. Temperatures experienced by embryos had an inverse effect on persistence of larvae relying on yolk nutrition alone. Mummichog exhibited an especially plastic response to thermal challenges which reflects the highly variable nursery habitat used by this species.

Temperature effects on snapping performance in the common snapper Chelydra serpentina (Reptilia, Testudines).

PubMed

Vervust, Bart; Brecko, Jonathan; Herrel, Anthony

2011-01-01

Studies on the effect of temperature on whole-animal performance traits other than locomotion are rare. Here we investigate the effects of temperature on the performance of the turtle feeding apparatus in a defensive context. We measured bite force and the kinematics of snapping in the Common Snapping Turtle (Chelydra serpentina) over a wide range of body temperatures. Bite force performance was thermally insensitive over the broad range of temperatures typically experienced by these turtles in nature. In contrast, neck extension (velocity, acceleration, and deceleration) and jaw movements (velocity, acceleration, and deceleration) showed clear temperature dependence with peak acceleration and deceleration capacity increasing with increasing temperatures. Our results regarding the temperature dependence of defensive behavior are reflected by the ecology and overall behavior of this species. These data illustrate the necessity for carefully controlling T(b) when carrying out behavioral and functional studies on turtles as temperature affects the velocity, acceleration, and deceleration of jaw and neck extension movements. More generally, these data add to the limited but increasing number of studies showing that temperature may have important effects on feeding and defensive performance in ectotherms. © 2010 Wiley-Liss, Inc.

Thermal sterilization of heat-sensitive products using high-temperature short-time sterilization.

PubMed

Mann, A; Kiefer, M; Leuenberger, H

2001-03-01

High-temperature short-time (HTST) sterilization with a continuous-flow sterilizer, developed for this study, was evaluated. The evaluation was performed with respect to (a) the chemical degradation of two heat-sensitive drugs in HTST range (140-160 degrees C) and (b) the microbiological effect of HTST sterilization. Degradation kinetics of two heat-sensitive drugs showed that a high peak temperature sterilization process resulted in less chemical degradation for the same microbiological effect than a low peak temperature process. Both drugs investigated could be sterilized with acceptable degradation at HTST conditions. For the evaluation of the microbiological effect, Bacillus stearothermophilus ATCC 7953 spores were used as indicator bacteria. Indicator spore kinetics (D(T), z value, k, and E(a)), were determined in the HTST range. A comparison between the Bigelow model (z value concept) and the Arrhenius model, used to describe the temperature coefficient of the microbial inactivation, demonstrated that the Bigelow model is more accurate in prediction of D(T) values in the HTST range. The temperature coefficient decreased with increasing temperature. The influence of Ca(2+) ions and pH value on the heat resistance of the indicator spores, which is known under typical sterilization conditions, did not change under HTST conditions.

Temperature dependent micro-rheology of a glass-forming polymer melt studied by molecular dynamics simulation.

PubMed

Kuhnhold, A; Paul, W

2014-09-28

We present a Molecular Dynamics simulation study of a micro-rheological probing of the glass transition in a polymer melt. Our model system consists of short bead-spring chains and the temperature ranges from well above the glass transition temperature to about 10% above it. The nano-particle clearly couples to the slowing down of the polymer segments and the calculated storage and loss moduli reveal the approach to the glass transition. At temperatures close to the mode coupling Tc of the polymer melt, the micro-rheological moduli measure the local viscoelastic response of the cage of monomers surrounding the nano-particle and no longer reveal the true melt moduli. The incoherent scattering function of the nano-particle exhibits a stretched exponential decay, typical for the α-process in glass forming systems. We find no indication of a strong superdiffusive regime as has been deduced from a recent experiment in the same temperature range but for smaller momentum transfers.

Influence of Chromium Doping on Electrical and Magnetic Behavior of Nd0.5Sr0.5MnO3 System

NASA Astrophysics Data System (ADS)

Lalitha, G.; Pavan Kumar, N.; Venugopal Reddy, P.

2018-04-01

With a view to understand the influence of chromium doping at the Mn site on the electrical and magnetic behavior of the Nd0.5Sr0.5MnO3 manganite system, a series of samples were prepared by the citrate sol-gel route method. The samples were characterized structurally by XRD. A systematic investigation of electrical resistivity over a temperature range 5-300 K was carried out mainly to understand the magneto-transport behavior in these materials. Studies on the variation of magnetization with temperature over a temperature range 80-330 K were undertaken. Investigation of magnetization at different magnetic fields at two different temperatures, viz. 80 and 300 K, was also carried out. The results show that chromium doping gave typical electrical and magnetic properties. It has been concluded that the coexistence of charge ordered and ferromagnetic phases induced by chromium doping plays an important role in the low-temperature behavior of the system.

An activated energy approach for accelerated testing of the deformation of UHMWPE in artificial joints.

PubMed

Galetz, Mathias Christian; Glatzel, Uwe

2010-05-01

The deformation behavior of ultrahigh molecular polyethylene (UHMWPE) is studied in the temperature range of 23-80 degrees C. Samples are examined in quasi-static compression, tensile and creep tests to determine the accelerated deformation of UHMWPE at elevated temperatures. The deformation mechanisms under compression load can be described by one strain rate and temperature dependent Eyring process. The activation energy and volume of that process do not change between 23 degrees C and 50 degrees C. This suggests that the deformation mechanism under compression remains stable within this temperature range. Tribological tests are conducted to transfer this activated energy approach to the deformation behavior under loading typical for artificial knee joints. While this approach does not cover the wear mechanisms close to the surface, testing at higher temperatures is shown to have a significant potential to reduce the testing time for lifetime predictions in terms of the macroscopic creep and deformation behavior of artificial joints. Copyright 2010. Published by Elsevier Ltd.

Pair-breaking mechanisms in superconductor—normal-metal—superconductor junctions

NASA Astrophysics Data System (ADS)

Yang, H. C.; Finnemore, D. K.

1984-08-01

The critical current density Jc has been measured for superconductor—normal-metal—superconductor (S-N-S) junctions over a wide range of temperature and composition in order to determine the depairing effects of magnetic impurities. Junctions, which are in a sandwich geometry with the N layer typically 600 nm thick, show well-defined diffraction patterns indicating that the junctions are of high quality. Below 4.2 K, the temperature dependence of Jc is found to follow a modified bridge theory based on the work of Makeev et al.

Polymer Deposition from a Quasi-Vapor Phase as a New Route to Access a Wide Temperature Range for Crystallization

NASA Astrophysics Data System (ADS)

Jeong, Hyuncheol; Arnold, Craig; Priestley, Rodney

Polymer crystallization is strongly governed by kinetics where crystallization temperature (Tc) plays an important role in determining materials properties. Due to the high entropic barrier required for reorganization, the long-chain molecules typically form folded-chain crystals, whose thickness and thermal stability decrease as Tc is lowered. Interesting questions remain regarding crystallization in the deeply supercooled regime. This is partially due to the difficulty in accessing the low Tc range without nucleation. For a strong crystal-former like polyethylene (PE), cooling from a melt or solution always confronts the onset of nucleation at a high Tc followed by rapid crystal growth. Here, we introduce an alternative approach to grow polymer crystals via Matrix Assisted Pulsed Laser Evaporation (MAPLE). This methodology achieves the crystallization of polymers from a quasi-vapor phase at a controlled temperature, allowing for the study of the empirical relationship between Tc and crystal structure over a wide range of Tc. With PE as a model polymer, we investigated the morphological and thermal properties of crystals grown over a wide temperature range down to 120 °C below bulk crystallization point.

Determination of spin polarization using an unconventional iron superconductor

DOE PAGES

Gifford, J. A.; Chen, B. B.; Zhang, J.; ...

2016-11-21

Here, an unconventional iron superconductor, SmO 0.7F 0.3FeAs, has been utilized to determine the spin polarization and temperature dependence of a highly spin-polarized material, La 0.67Sr 0.33MnO 3, with Andreev reflection spectroscopy. The polarization value obtained is the same as that determined using a conventional superconductor Pb but the temperature dependence of the spin polarization can be measured up to 52 K, a temperature range, which is several times wider than that using a typical conventional superconductor. The result excludes spin-parallel triplet pairing in the iron superconductor.

Engineering support for magnetohydrodynamic power plant analysis and design studies

NASA Technical Reports Server (NTRS)

Carlson, A. W.; Chait, I. L.; Marchmont, G.; Rogali, R.; Shikar, D.

1980-01-01

The major factors which influence the economic engineering selection of stack inlet temperatures in combined cycle MHD powerplants are identified and the range of suitable stack inlet temperatures under typical operating conditions is indicated. Engineering data and cost estimates are provided for four separately fired high temperature air heater (HTAH) system designs for HTAH system thermal capacity levels of 100, 250, 500 and 1000 MWt. An engineering survey of coal drying and pulverizing equipment for MHD powerplant application is presented as well as capital and operating cost estimates for varying degrees of coal pulverization.

Characterization of 720 and 940 MHz Oscillators with Chip Antenna for Wireless Sensors from Room Temperature to 200 and 250 deg C

NASA Technical Reports Server (NTRS)

Scardelletti, Maximilian C.; Ponchak, George E.

2011-01-01

Oscillators that operate at 720 and 940 MHz and characterized over a temperature range of 25 C to 200 C and 250 C, respectively, are presented. The oscillators are designed on alumina substrates with typical integrated circuit fabrication techniques. Cree SiC MESFETs, thin film metal-insulator-metal capacitors and spiral inductors, and Johanson miniature chip antennas make-up the circuits. The output power and phase noise are presented as a function of temperature and frequency. Index Terms MESFETS, chip antennas, oscillators SiC alumina.

Temperature environment for 9975 packages stored in KAC

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

Daugherty, W. L.

Plutonium materials are stored in the K Area Complex (KAC) in shipping packages, typically the 9975 shipping package. In order to estimate realistic degradation rates for components within the shipping package (i.e. the fiberboard overpack and O-ring seals), it is necessary to understand actual facility temperatures, which can vary daily and seasonally. Relevant facility temperature data available from several periods throughout its operating history have been reviewed. The annual average temperature within the Crane Maintenance Area has ranged from approximately 70 to 74 °F, although there is significant seasonal variation and lesser variation among different locations within the facility. Themore » long-term average degradation rate for 9975 package components is very close to that expected if the component were to remain continually at the annual average temperature. This result remains valid for a wide range of activation energies (which describes the variation in degradation rate as the temperature changes), if the activation energy remains constant over the seasonal range of component temperatures. It is recommended that component degradation analyses and service life estimates incorporate these results. Specifically, it is proposed that future analyses assume an average facility ambient air temperature of 94 °F. This value is bounding for all packages, and includes margin for several factors such as increased temperatures within the storage arrays, the addition of more packages in the future, and future operational changes.« less

Effect and control on temperature measurement accuracy of the fiber- optic colorimeter by emissivity of different temperatures

NASA Astrophysics Data System (ADS)

Liu, Yu-fang; Han, Xin; Shi, De-heng

2008-03-01

Based on the Kirchhoff's Law, a practical dual-wavelength fiber-optic colorimeter, with the optimal work wavelength centered at 2.1 μm and 2.3 μm is presented. The effect of the emissivity on the precision of the measured temperature has been explored under various circumstances (i.e. temperature, wavelength) and for different materials. In addition, by fitting several typical material emissivity-temperature dependencies curves, the influence of the irradiation (radiant flux originating from the surroundings) and the surface reflected radiation on the temperature accuracy is studied. The results show that the calibration of the measured temperature for reflected radiant energy is necessary especially in low target temperature or low target emissivity, and the temperature accuracy is suitable for requirements in the range of 400-1200K.

Recombination of H atoms on the dust in fusion plasmas

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

Bakhtiyari-Ramezani, M., E-mail: mahdiyeh.bakhtiyari@gmail.com; Alinejad, N., E-mail: nalinezhad@aeoi.org.ir; Mahmoodi, J., E-mail: mahmoodi@qom.ac.ir

2015-07-15

We survey a model for theoretical study of the interaction of hydrogen and dust surface and apply our results for dusty plasmas to fusion devices. In this model, considering the mobility of ad-atoms from one physisorbed, or chemisorbed site, to other one by thermal diffusion, we describe the formation of H{sub 2} on grain surfaces. Finally, we calculate the formation rate on the high temperature dust surfaces for a range of temperature and density in typical conditions of divertor of tokamak.

Low-temperature mechanical dissipation of thermally evaporated indium film for use in interferometric gravitational wave detectors

NASA Astrophysics Data System (ADS)

Murray, Peter G.; Martin, Iain W.; Cunningham, Liam; Craig, Kieran; Hammond, Giles D.; Hofmann, Gerd; Hough, James; Nawrodt, Ronny; Reifert, David; Rowan, Sheila

2015-06-01

Indium bonding is under consideration for use in the construction of cryogenic mirror suspensions in future gravitational wave detectors. This paper presents measurements of the mechanical loss of a thermally evaporated indium film over a broad range of frequencies and temperatures. It provides an estimate of the resulting thermal noise at 20 K for a typical test mass geometry for a cryogenic interferometric gravitational wave detector from an indium layer between suspension elements.

On the Dielectric Constant for Acetanilide: Experimental Measurements and Effect on Energy Transport

NASA Astrophysics Data System (ADS)

Careri, G.; Compatangelo, E.; Christiansen, P. L.; Halding, J.; Skovgaard, O.

1987-01-01

Experimental measurements of the dielectric constant for crystalline acetanilide powder for temperatures ranging from - 140°C to 20°C and for different hydration levels are presented. A Davydov-soliton computer model predicts dramatic changes in the energy transport and storage for typically increased values of the dielectric constant.

A modified impulse-response representation of the global near-surface air temperature and atmospheric concentration response to carbon dioxide emissions

NASA Astrophysics Data System (ADS)

Millar, Richard J.; Nicholls, Zebedee R.; Friedlingstein, Pierre; Allen, Myles R.

2017-06-01

Projections of the response to anthropogenic emission scenarios, evaluation of some greenhouse gas metrics, and estimates of the social cost of carbon often require a simple model that links emissions of carbon dioxide (CO2) to atmospheric concentrations and global temperature changes. An essential requirement of such a model is to reproduce typical global surface temperature and atmospheric CO2 responses displayed by more complex Earth system models (ESMs) under a range of emission scenarios, as well as an ability to sample the range of ESM response in a transparent, accessible and reproducible form. Here we adapt the simple model of the Intergovernmental Panel on Climate Change 5th Assessment Report (IPCC AR5) to explicitly represent the state dependence of the CO2 airborne fraction. Our adapted model (FAIR) reproduces the range of behaviour shown in full and intermediate complexity ESMs under several idealised carbon pulse and exponential concentration increase experiments. We find that the inclusion of a linear increase in 100-year integrated airborne fraction with cumulative carbon uptake and global temperature change substantially improves the representation of the response of the climate system to CO2 on a range of timescales and under a range of experimental designs.

Spectroscopic survey of Kepler stars - II. FIES/NOT observations of A- and F-type stars

NASA Astrophysics Data System (ADS)

Niemczura, E.; Polińska, M.; Murphy, S. J.; Smalley, B.; Kołaczkowski, Z.; Jessen-Hansen, J.; Uytterhoeven, K.; Lykke, J. M.; Triviño Hage, A.; Michalska, G.

2017-09-01

We have analysed high-resolution spectra of 28 A and 22 F stars in the Kepler field, observed using the Fibre-Fed Échelle Spectrograph at the Nordic Optical Telescope. We provide spectral types, atmospheric parameters and chemical abundances for 50 stars. Balmer, Fe I and Fe II lines were used to derive effective temperatures, surface gravities and microturbulent velocities. We determined chemical abundances and projected rotational velocities using a spectrum synthesis technique. Effective temperatures calculated by spectral energy distribution fitting are in good agreement with those determined from the spectral line analysis. The stars analysed include chemically peculiar stars of the Am and λ Boo types, as well as stars with approximately solar chemical abundances. The wide distribution of projected rotational velocity, vsin I, is typical for A and F stars. The microturbulence velocities obtained are typical for stars in the observed temperature and surface gravity ranges. Moreover, we affirm the results of Niemczura et al. that Am stars do not have systematically higher microturbulent velocities than normal stars of the same temperature.

Aerial thermography studies of power plant heated lakes

NASA Astrophysics Data System (ADS)

Villa-Aleman, Eliel; Garrett, Alfred J.; Kurzeja, Robert J.; Pendergast, Malcolm M.

2000-03-01

Remote sensing temperature measurements of water bodies is complicated by the temperature differences between the true surface or `skin' water and the bulk water below. Weather conditions control the reduction of the skin temperature relative to the bulk water temperature. Typical skin temperature depressions range from a few tenths of a degree Celsius to more than one degree. In this research project, the Savannah River Technology Center used aerial thermography and surface-based meteorological and water temperature measurements to study a power plant cooling lake in South Carolina. Skin and bulk water temperatures were measured simultaneously for imagery calibration and to product a database for modeling of skin temperature depressions as a function of weather and bulk water temperatures. This paper will present imagery that illustrates how the skin temperature depression was affected by different conditions in several locations on the lake and will present skin temperature modeling results.

Relaxorlike dielectric behavior in Ba0.7Sr0.3TiO3 thin films

NASA Astrophysics Data System (ADS)

Zednik, Ricardo J.; McIntyre, Paul C.; Baniecki, John D.; Ishii, Masatoshi; Shioga, Takeshi; Kurihara, Kazuaki

2007-03-01

We present the results of a systematic dielectric study for sputter deposited barium strontium titanate thin film planar capacitors measured over a wide temperature range of 20-575K for frequencies between 1kHz and 1MHz. Our observations of dielectric loss peaks in the temperature and frequency domains cannot be understood in the typical framework of intrinsic phonon losses. We find that the accepted phenomenological Curie-von Schweidler dielectric behavior (universal relaxation law) in our barium strontium titanate films is only applicable over a narrow temperature range. An excellent fit to the Vogel-Fulcher expression suggests relaxorlike behavior in these films. The activation energy of the observed phenomenon suggests that oxygen ion motion play a role in the apparent relaxor behavior, although further experimental work is required to test this hypothesis.

[Temperature sensitivity of soil organic carbon mineralization and β-glucosidase enzymekinetics in the northern temperate forests at different altitudes, China].

PubMed

Fan, Jin-juan; Li, Dan-dan; Zhang, Xin-yu; He, Nian-peng; Bu, Jin-feng; Wang, Qing; Sun, Xiao-min; Wen, Xue-fa

2016-01-01

Soil samples, which were collected from three typical forests, i.e., Betula ermanii forest, coniferous mixed broad-leaved forest, and Pinus koraiensis forest, at different altitudes along the southern slope of Laotuding Mountain of Changbai Mountain range in Liaoning Province of China, were incubated over a temperature gradient in laboratory. Soil organic carbon mineralization rates (Cmin), soil β-1,4-glucosidase (βG) kinetics and their temperature sensitivity (Q₁₀) were measured. The results showed that both altitude and temperature had significant effects on Cmin · Cmin increased with temperature and was highest in the B. ermanii forest. The temperature sensitivity of Cmin [Q₁₀(Cmin)] ranked in order of B. ermanii forest > P. koraiensis forest > coniferous mixed broad-leaved forest, but did not differ significantly among the three forests. Both the maximum activity (Vmax) and the Michaelis constant (Km) of the βG responded positively to temperature for all the forests. The temperature sensitivity of Vmax [Q₁₀(Vmax)] ranged from 1.78 to 1.90, and the temperature sensitivity of Km [Q₁₀(Km)] ranged from 1.79 to 2.00. The Q₁₀(Vmax)/Q10(Km) ratios were significantly greater in the B. ermanii soil than in the other two forest soils, suggesting that the βG kinetics-dependent impacts of the global warming or temperature increase on the decomposition of soil organic carbon were temperature sensitive for the forests at the higher altitudes.

Performance characterization and transient investigation of multipropellant resistojets

NASA Technical Reports Server (NTRS)

Braunscheidel, Edward P.

1989-01-01

The multipropellant resistojet thruster design initially was characterized for performance in a vacuum tank using argon, carbon dioxide, nitrogen, and hydrogen, with gas inlet pressures ranging from 13.7 to 310 kPa (2 to 45 psia) over a heat exchanger temperature range of ambient to 1200 C (2200 F). Specific impulse, the measure of performance, had values ranging from 120 to 600 seconds for argon and hydrogen respectively, with a constant heat exchanger temperature of 1200 C (2200 F). When operated under ambient conditions typical specific impulse values obtained for argon and hydrogen ranged from 55 to 290 seconds, respectively. Performance measured with several mixtures of argon and nitrogen showed no significant deviation from predictions obtained by directly weighting the argon and nitrogen individual performance results. Another aspect of the program investigating transient behavior, showed responses depended heavily on the start-up scenario used. Steady state heater temperatures were achieved in 20 to 75 minutes for argon, and in 10 to 90 minutes for hydrogen. Steady state specific impulses were achieved in 25 to 60, and 20 to 60 minutes respectively.

"Soft"or "hard" ionisation? Investigation of metastable gas temperature effect on direct analysis in real-time analysis of Voriconazole.

PubMed

Lapthorn, Cris; Pullen, Frank

2009-01-01

The performance of the direct analysis in real-time (DART) technique was evaluated across a range of metastable gas temperatures for a pharmaceutical compound, Voriconazole, in order to investigate the effect of metastable gas temperature on molecular ion intensity and fragmentation. The DART source has been used to analyse a range of analytes and from a range of matrices including drugs in solid tablet form and preparations, active ingredients in ointment, naturally occurring plant alkaloids, flavours and fragrances, from thin layer chromatography (TLC) plates, melting point tubes and biological matrices including hair, urine and blood. The advantages of this technique include rapid analysis time (as little as 5 s), a reduction in sample preparation requirements, elimination of mobile phase requirement and analysis of samples not typically amenable to atmospheric pressure ionisation (API) techniques. This technology has therefore been proposed as an everyday tool for identification of components in crude organic reaction mixtures.

Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature

DOE PAGES

Davis, Eric S.; Sturtevant, Blake T.; Sinha, Dipen N.; ...

2016-09-04

Resonant Ultrasound Spectroscopy was used in this paper to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α-quartz at room temperature and pressure. Finally, it was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385more » K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.« less

Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature

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

Davis, Eric S.; Sturtevant, Blake T.; Sinha, Dipen N.

Resonant Ultrasound Spectroscopy was used in this paper to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α-quartz at room temperature and pressure. Finally, it was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385more » K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.« less

Temperature behavior of the antiferromagnetic susceptibility of nanoferrihydrite from the measurements of the magnetization curves in fields of up to 250 kOe

NASA Astrophysics Data System (ADS)

Balaev, D. A.; Popkov, S. I.; Krasikov, A. A.; Balaev, A. D.; Dubrovskiy, A. A.; Stolyar, S. V.; Yaroslavtsev, R. N.; Ladygina, V. P.; Iskhakov, R. S.

2017-10-01

The cross-breeding problem of the temperature dependence of the antiferromagnetic susceptibility of ferrihydrite nanoparticles is considered. Iron ions Fe3+ in ferrihydrite are ordered antiferromagnetically; however, the existence of defects on the surface and in the bulk of nanoparticles induces a noncompensated magnetic moment that leads to a typical superparamagnetic behavior of ensemble of the nanoparticles with a characteristic blocking temperature. In an unblocked state, magnetization curves of such objects are described as a superposition of the Langevin function and the linear-in-field contribution of the antiferromagnetic "core" of the nanoparticles. According to many studies of the magnetization curves performed on ferrihydrite (and related ferritin) nanoparticles in fields to 60 kOe, dependence χAF( T) decreases as temperature increases, which was related before to the superantiferromagnetism effect. As the magnetic field range increases to 250 kOe, the values of χAF obtained from an analysis of the magnetization curves become lower in magnitude; however, the character of the temperature evolution of χAF is changed: now, dependence χAF( T) is an increasing function. The latter is typical for a system of AF particles with random orientation of the crystallographic axes. To correctly determine the antiferromagnetic susceptibility of AF nanoparticles (at least, ferrihydrite) and to search for effects related to the superantiferromagnetism effect, it is necessary to use in experiments the range of magnetic field significantly higher than that the standard value 60 kOe used in most experiments. The study of the temperature evolution of the magnetization curves shows that the observed crossover is due to the existence of small magnetic moments in the samples.

Concentration and variability of ice nuclei in the subtropical maritime boundary layer

NASA Astrophysics Data System (ADS)

Welti, André; Müller, Konrad; Fleming, Zoë L.; Stratmann, Frank

2018-04-01

Measurements of the concentration and variability of ice nucleating particles in the subtropical maritime boundary layer are reported. Filter samples collected in Cabo Verde over the period 2009-2013 are analyzed with a drop freezing experiment with sensitivity to detect the few rare ice nuclei active at low supercooling. The data set is augmented with continuous flow diffusion chamber measurements at temperatures below -24 °C from a 2-month field campaign in Cabo Verde in 2016. The data set is used to address the following questions: what are typical concentrations of ice nucleating particles active at a certain temperature? What affects their concentration and where are their sources? Concentration of ice nucleating particles is found to increase exponentially by 7 orders of magnitude from -5 to -38 °C. Sample-to-sample variation in the steepness of the increase indicates that particles of different origin, with different ice nucleation properties (size, composition), contribute to the ice nuclei concentration at different temperatures. The concentration of ice nuclei active at a specific temperature varies over a range of up to 4 orders of magnitude. The frequency with which a certain ice nuclei concentration is measured within this range is found to follow a lognormal distribution, which can be explained by random dilution during transport. To investigate the geographic origin of ice nuclei, source attribution of air masses from dispersion modeling is used to classify the data into seven typical conditions. While no source could be attributed to the ice nuclei active at temperatures higher than -12 °C, concentrations at lower temperatures tend to be elevated in air masses originating from the Sahara.

Copper nanocluster growth at experimental conditions using temperature accelerated dynamics

NASA Astrophysics Data System (ADS)

Dias, C. S.; Cadilhe, A. C.; Voter, A. F.

2009-03-01

We study the dynamics of vapor phase cluster growth near experimental conditions of pressure at temperatures below 200K. To this end, we carried out temperature accelerated dynamics (TAD) simulations at different vapor pressures to characterize the morphology of the resulting nanoparticles, which leads to a range of values of the flux of impinging atoms at fixed vapor temperature. At typical experimental pressures of 10-3-10-4 bar TAD provides substantial boost over regular Molecular Dynamics (MD). TAD is also advantageous over MD, regarding the sampling of the network of visited states, which provides a deeper understanding of the evolution of the system. We characterize the growth of such clusters at different vapor pressures.

Ceramic coating system or water oxidation environments

DOEpatents

Hong, Glenn T.

1996-01-01

A process for water oxidation of combustible materials in which during at least a part of the oxidation corrosive material is present and makes contact with at least a portion of the apparatus over a contact area on the apparatus. At least a portion of the contact surface area comprises titanium dioxide coated onto a titanium metal substrate. Such ceramic composites have been found to be highly resistant to environments encountered in the process of supercritical water oxidation. Such environments typically contain greater than 50 mole percent water, together with oxygen, carbon dioxide, and a wide range of acids, bases, and salts. Pressures are typically about 27.5 to about 1000 bar while temperatures range as high as 700.degree. C. The ceramic composites are also resistant to degradation mechanisms caused by thermal stresses.

Monitoring soft tissue coagulation by optical spectroscopy

NASA Astrophysics Data System (ADS)

Lihachev, A.; Lihacova, I.; Heinrichs, H.; Spigulis, J.; Trebst, T.; Wehner, M.

2017-12-01

Laser tissue welding (LTW) or laser tissue soldering (LTS) is investigated since many years for treatment of incisions, wound closure and anastomosis of vessels [1, 2]. Depending on the process, a certain temperature in the range between 65 °C to 85 °C must be reached and held for a few seconds. Care has to be taken not to overheat the tissue, otherwise necrosis or tissue carbonization may occur and will impair wound healing. Usually the temperature is monitored during the process to control the laser power [3]. This requires either bulky equipment or expensive and fragile infrared fibers to feed the temperature signal to an infrared detector. Alternatively, changes in tissue morphology can be directly observed by analysis of spectral reflectance. We investigate spectral changes in the range between 400 nm to 900 nm wavelength. Characteristic spectral changes occur when the temperature of tissue samples increase above 70 °C which is a typical setpoint value for temperature control of coagulation. We conclude that simple spectroscopy in the visible range can provide valuable information during LTS and LTW and probably replace the delicate measurement of temperature. A major advantage is that optical measurements can be performed using standard optical fibers and can be easily integrated into a surgical tool.

Extreme temperature packaging: challenges and opportunities

NASA Astrophysics Data System (ADS)

Johnson, R. Wayne

2016-05-01

Consumer electronics account for the majority of electronics manufactured today. Given the temperature limits of humans, consumer electronics are typically rated for operation from -40°C to +85°C. Military applications extend the range to -65°C to +125°C while underhood automotive electronics may see +150°C. With the proliferation of the Internet of Things (IoT), the goal of instrumenting (sensing, computation, transmission) to improve safety and performance in high temperature environments such as geothermal wells, nuclear reactors, combustion chambers, industrial processes, etc. requires sensors, electronics and packaging compatible with these environments. Advances in wide bandgap semiconductors (SiC and GaN) allow the fabrication of high temperature compatible sensors and electronics. Integration and packaging of these devices is required for implementation into actual applications. The basic elements of packaging are die attach, electrical interconnection and the package or housing. Consumer electronics typically use conductive adhesives or low melting point solders for die attach, wire bonds or low melting solder for electrical interconnection and epoxy for the package. These materials melt or decompose in high temperature environments. This paper examines materials and processes for high temperature packaging including liquid transient phase and sintered nanoparticle die attach, high melting point wires for wire bonding and metal and ceramic packages. The limitations of currently available solutions will also be discussed.

Estimate of the influence of muzzle smoke on function range of infrared system

NASA Astrophysics Data System (ADS)

Luo, Yan-ling; Wang, Jun; Wu, Jiang-hui; Wu, Jun; Gao, Meng; Gao, Fei; Zhao, Yu-jie; Zhang, Lei

2013-09-01

Muzzle smoke produced by weapons shooting has important influence on infrared (IR) system while detecting targets. Based on the theoretical model of detecting spot targets and surface targets of IR system while there is muzzle smoke, the function range for detecting spot targets and surface targets are deduced separately according to the definition of noise equivalent temperature difference(NETD) and minimum resolution temperature difference(MRTD). Also parameters of muzzle smoke affecting function range of IR system are analyzed. Base on measured data of muzzle smoke for single shot, the function range of an IR system for detecting typical targets are calculated separately while there is muzzle smoke and there is no muzzle smoke at 8-12 micron waveband. For our IR system function range has reduced by over 10% for detecting tank if muzzle smoke exists. The results will provide evidence for evaluating the influence of muzzle smoke on IR system and will help researchers to improve ammo craftwork.

Cooling of Gas Turbines. 2; Effectiveness of Rim Cooling of Blades

NASA Technical Reports Server (NTRS)

Wolfenstein, Lincoln; Meyer, Gene L.; McCarthy, John S.

1947-01-01

An analysis is presented of rim cooling of gas-turbine blades; that is, reducing the temperature at the base of the blade (wheel rim), which cools the blade by conduction alone. Formulas for temperature and stress distributions along the blade are derived and, by the use of experimental stress-rupture data for a typical blade alloy, a relation is established between blade life (time for rupture), operating speed, and amount of rim cooling for several gas temperatures. The effect of blade parameter combining the effects of blade dimensions, blade thermal conductivity, and heat-transfer coefficient is determined. The effect of radiation on the results is approximated. The gas temperatures ranged from 1300F to 1900F and the rim temperature, from 0F to 1000F below the gas temperature. This report is concerned only with blades of uniform cross section, but the conclusions drawn are generally applicable to most modern turbine blades. For a typical rim-cooled blade, gas temperature increases are limited to about 200F for 500F of cooling of the blade base below gas temperature, and additional cooling brings progressively smaller increases. In order to obtain large increases in thermal conductivity or very large decreases in heat-transfer coefficient or blade length or necessary. The increases in gas temperature allowable with rim cooling are particularly small for turbines of large dimensions and high specific mass flows. For a given effective gas temperature, substantial increases in blade life, however, are possible with relatively small amounts of rim cooling.

Physical characteristics and chemical quality of selected springs in parts of Juab, Millard, Tooele, and Utah counties, Utah

USGS Publications Warehouse

Wilberg, D.E.; Stolp, B.J.

1985-01-01

Hydrologic, geologic, and partial water quality data were collected at 90 selected springs in west-central Utah, and chemical analyses performed on water samples from 62 of the springs. Descriptions of the physiographic and geologic conditions, climate, and vegetation patterns for the study area are included. Allowable limits of certain chemical constituents in water for human and livestock consumption are included with the water quality data. Three classifications of springs were established based on physical characteristics of the springs, and chemical composition of the springflow: (1) mountain springs; (2) non-thermal valley springs, and (3) thermal valley springs. Mountain springs are in and near recharge areas, have seasonal variations of discharge and temperature, typically discharge from extrusive and metamorphic geohydrologic units, and generally discharge freshwater. Non-thermal valley springs are peripheral to recharge areas, have seasonal variations of discharge and temperature, typically discharge from a variety of geohydrologic units, and have variable water composition. Thermal valley springs are near topographic low areas of valleys , and have little seasonal variation of discharge or temperature. They typically discharge from unconsolidated deposits (but the discharge probably has flowed through buried carbonate geohydrologic units). They also have a considerable range of water composition that reflects the relative complexity of the groundwater system. (Author 's abstract)

Temporal variation of ecosystem scale methane emission from a boreal fen in relation to common model drivers

NASA Astrophysics Data System (ADS)

Rinne, J.; Tuittila, E. S.; Peltola, O.; Li, X.; Raivonen, M.; Alekseychik, P.; Haapanala, S.; Pihlatie, M.; Aurela, M.; Mammarella, I.; Vesala, T.

2017-12-01

Models for calculating methane emission from wetland ecosystems typically relate the methane emission to carbon dioxide assimilation. Other parameters that control emission in these models are e.g. peat temperature and water table position. Many of these relations are derived from spatial variation between chamber measurements by space-for-time approach. Continuous longer term ecosystem scale methane emission measurements by eddy covariance method provide us independent data to assess the validity of the relations derived by space-for-time approach.We have analyzed eleven-year methane flux data-set, measured at a boreal fen, together with data on environmental parameters and carbon dioxide exchange to assess the relations to typical model drivers. The data was obtained by the eddy covariance method at Siikaneva mire complex, Southern Finland, during 2005-2015. The methane flux showed seasonal cycles in methane emission, with strongest correlation with peat temperature at 35 cm depth. The temperature relation was exponential throughout the whole peat temperature range of 0-16°C. The methane emission normalized to remove temperature dependence showed a non-monotonous relation on water table and positive correlation with gross primary production (GPP). However, inclusion of these as explaining variables improved algorithm-measurement correlation only slightly, with r2=0.74 for exponential temperature dependent algorithm, r2=0.76 for temperature - water table algorithm, and r2=0.79 for temperature - GPP algorithm. The methane emission lagged behind net ecosystem exchange (NEE) and GPP by two to three weeks. Annual methane emission ranged from 8.3 to 14 gC m-2, and was 20 % of NEE and 2.8 % of GPP. The inter-annual variation of methane emission was of similar magnitude as that of GPP and ecosystem respiration (Reco), but much smaller than that of NEE. The interannual variability of June-September average methane emission correlated significantly with that of GPP indicating a close link between these two processes in boreal fen ecosystems.

Characterization of photocathode dark current vs. temperature in image intensifier tube modules and intensified televisions

NASA Astrophysics Data System (ADS)

Bender, Edward J.; Wood, Michael V.; Hart, Steve; Heim, Gerald B.; Torgerson, John A.

2004-10-01

Image intensifiers (I2) have gained wide acceptance throughout the Army as the premier nighttime mobility sensor for the individual soldier, with over 200,000 fielded systems. There is increasing need, however, for such a sensor with a video output, so that it can be utilized in remote vehicle platforms, and/or can be electronically fused with other sensors. The image-intensified television (I2TV), typically consisting of an image intensifier tube coupled via fiber optic to a solid-state imaging array, has been the primary solution to this need. I2TV platforms in vehicles, however, can generate high internal heat loads and must operate in high-temperature environments. Intensifier tube dark current, called "Equivalent Background Input" or "EBI", is not a significant factor at room temperature, but can seriously degrade image contrast and intra-scene dynamic range at such high temperatures. Cooling of the intensifier's photocathode is the only practical solution to this problem. The US Army RDECOM CERDEC Night Vision & Electronic Sensors Directorate (NVESD) and Ball Aerospace have collaborated in the reported effort to more rigorously characterize intensifier EBI versus temperature. NVESD performed non-imaging EBI measurements of Generation 2 and 3 tube modules over a large range of ambient temperature, while Ball performed an imaging evaluation of Generation 3 I2TVs over a similar temperature range. The findings and conclusions of this effort are presented.

Warming reduces metabolic rate in marine snails: adaptation to fluctuating high temperatures challenges the metabolic theory of ecology.

PubMed

Marshall, David J; McQuaid, Christopher D

2011-01-22

The universal temperature-dependence model (UTD) of the metabolic theory of ecology (MTE) proposes that temperature controls mass-scaled, whole-animal resting metabolic rate according to the first principles of physics (Boltzmann kinetics). Controversy surrounds the model's implication of a mechanistic basis for metabolism that excludes the effects of adaptive regulation, and it is unclear how this would apply to organisms that live in fringe environments and typically show considerable metabolic adaptation. We explored thermal scaling of metabolism in a rocky-shore eulittoral-fringe snail (Echinolittorina malaccana) that experiences constrained energy gain and fluctuating high temperatures (between 25°C and approximately 50°C) during prolonged emersion (weeks). In contrast to the prediction of the UTD model, metabolic rate was often negatively related to temperature over a benign range (30-40°C), the relationship depending on (i) the temperature range, (ii) the degree of metabolic depression (related to the quiescent period), and (iii) whether snails were isolated within their shells. Apparent activation energies (E) varied between 0.05 and -0.43 eV, deviating excessively from the UTD's predicted range of between 0.6 and 0.7 eV. The lowering of metabolism when heated should improve energy conservation in a high-temperature environment and challenges both the theory's generality and its mechanistic basis.

High temperature tensile and creep behaviour of low pressure plasma-sprayed Ni-Co-Cr-Al-Y coating alloy

NASA Technical Reports Server (NTRS)

Hebsur, M. G.; Miner, R. V.

1986-01-01

The high temperature tensile and creep behavior of low pressure plasma-sprayed plates of a typical Ni-Co-Cr-Al-Y alloy has been studied. From room temperature to 800 K, the Ni-Co-Cr-Al-Y alloy studied has nearly a constant low ductility and a high strength. At higher temperatures, it becomes weak and highly ductile. At and above 1123 K, the behavior is highly dependent on strain rate and exhibits classic superplastic characteristics with a high ductility at intermediate strain rates and a strain rate sensitivity of about 0.5. At either higher or lower strain rates, the ductility decreases and the strain rate sensitivities are about 0.2. In the superplastic deformation range, the activation energy for creep is 120 + or - 20 kJ/mol, suggesting a diffusion-aided grain boundary sliding mechanism. Outside the superplastic range, the activation energy for creep is calculated to be 290 + or - 20 kJ/mol.

Effect of molecular structure on the hydration of structurally related antidepressant drugs

NASA Astrophysics Data System (ADS)

Cheema, M. A.; Taboada, P.; Barbosa, S.; Siddiq, M.; Mosquera, V.

Apparent molal volumes and adiabatic compressibilities of aqueous solutions of the amphiphilic cationic antidepressant drugs butriptyline and doxepin hydrochlorides have been determined from density and ultrasound velocity measurements in the temperature range 20-50°C. Critical concentrations for aggregation of these drugs were obtained from ultrasound velocity measurements. Negative deviations from the Debye-Hückel limiting law of the apparent molal volume were obtained from both drugs in all temperature ranges, except for doxepin at 50°C, which provides evidence of no pre-association at concentrations below the critical concentration. Apparent molal adiabatic compressibilities of the aggregates formed by these drugs were typical of those corresponding for an aggregate formed by a stacking process.

B11 NMR in the layered diborides OsB2 and RuB2

NASA Astrophysics Data System (ADS)

Suh, B. J.; Zong, X.; Singh, Y.; Niazi, A.; Johnston, D. C.

2007-10-01

B11 nuclear magnetic resonance (NMR) measurements have been performed on B11 enriched OsB2 and RuB2 polycrystalline powder samples in an external field of 4.7T and in the temperature range, 4.2K

Communication: Equilibrium rate coefficients from atomistic simulations: The O((3)P) + NO((2)Π) → O2(X(3)Σg(-)) + N((4)S) reaction at temperatures relevant to the hypersonic flight regime.

PubMed

Castro-Palacio, Juan Carlos; Bemish, Raymond J; Meuwly, Markus

2015-03-07

The O((3)P) + NO((2)Π) → O2(X(3)Σg(-)) + N((4)S) reaction is among the N- and O- involving reactions that dominate the energetics of the reactive air flow around spacecraft during hypersonic atmospheric re-entry. In this regime, the temperature in the bow shock typically ranges from 1000 to 20,000 K. The forward and reverse rate coefficients for this reaction derived directly from trajectory calculations over this range of temperature are reported in this letter. Results compare well with the established equilibrium constants for the same reaction from thermodynamic quantities derived from spectroscopy in the gas phase which paves the way for large-scale in silico investigations of equilibrium rates under extreme conditions.

Effect of ambient temperature and internal relative humidity on spectral sensitivity of broadband UV detectors

NASA Astrophysics Data System (ADS)

Huber, Martin; Blumthaler, Mario; Schreder, Josef

2002-01-01

Within the frame of the Austrian UV Monitoring Network, repeated recalibrations of Solar Light Sunburn Meters between December 1997 and March 2000 have shown significant temporal changes in the instruments' relative spectral response function as well as in their absolute calibration. Therefore, laboratory investigations of the effects of ambient temperature and internal relative humidity on the behavior of two Sunburn Meters have been performed. Despite internal temperature stabilization, both instruments show significant dependence of their spectral response function on ambient temperature. When the outside temperature of the detector's housing varies between 13 degree(s)C and 44 degree(s)C, spectral sensitivity changes by up to 10% in the UVB range and by up to a factor of 2 in the UVA range, depending on internal relative humidity. As a consequence, output voltage variations of 10% are observed when the detector is mounted in front of a 1000 W halogen lamp and its internal relative humidity is changed while its ambient temperature is kept constant. Whereas temperature effects take place within several hours, instabilities due to variations in internal relative humidity show typical time constants in the order of several days.

Design and experimental investigation of a cryogenic system for environmental test applications

NASA Astrophysics Data System (ADS)

Yan, Lutao; Li, Hong; Liu, Yue; Han, Che; Lu, Tian; Su, Yulei

2015-04-01

This paper is concerned with the design, development and performance testing of a cryogenic system for use in high cooling power instruments for ground-based environmental testing. The system provides a powerful tool for a combined environmental test that consists of high pressure and cryogenic temperatures. Typical cryogenic conditions are liquid hydrogen (LH2) and liquid oxygen (LO2), which are used in many fields. The cooling energy of liquid nitrogen (LN2) and liquid helium (LHe) is transferred to the specimen by a closed loop of helium cycle. In order to minimize the consumption of the LHe, the optimal design of heat recovery exchangers has been used in the system. The behavior of the system is discussed based on experimental data of temperature and pressure. The results show that the temperature range from room temperature to LN2 temperature can be achieved by using LN2, the pressurization process is stable and the high test pressure is maintained. Lower temperatures, below 77 K, can also be obtained with LHe cooling, the typical cooling time is 40 min from 90 K to 22 K. Stable temperatures of 22 K at the inlet of the specimen have been observed, and the system in this work can deliver to the load a cooling power of several hundred watts at a pressure of 0.58 MPa.

A Passive Radio-Frequency Identification (RFID) Gas Sensor With Self-Correction Against Fluctuations of Ambient Temperature

PubMed Central

Potyrailo, Radislav A.; Surman, Cheryl

2013-01-01

Uncontrolled fluctuations of ambient temperature in the field typically greatly reduce accuracy of gas sensors. In this study, we developed an approach for the self-correction against fluctuations of ambient temperature of individual gas and vapor sensors. The main innovation of our work is in the temperature correction which is accomplished without the need for a separate uncoated reference sensor or a separate temperature sensor. Our sensors are resonant inductor-capacitor-resistor (LCR) transducers coated with sensing materials and operated as multivariable passive (battery-free) radio-frequency identification (RFID) sensors. Using our developed approach, we performed quantitation of an exemplary vapor over the temperature range from 25 to 40 °C. This technical solution will be attractive in numerous applications where temperature stabilization of a gas sensor or addition of auxiliary temperature or uncoated reference sensors is prohibitive. PMID:23956496

Distribution, abundance, and resting microhabitat of burbot on Julian's Reef, southwestern Lake Michigan

USGS Publications Warehouse

Edsall, Thomas A.; Kennedy, Gregory W.; Horns, William H.

1993-01-01

We used a remotely operated submersible vehicle equipped with a color video camera to videotape the lake bed and document the distribution and abundance of burbot Lota lota on a 156-hectare portion of Julian's Reef in southwestern Lake Michigan. The substrates and bathymetry of the study area had been mapped recently by side-scan sonar. Burbot density determined from videotapes covering 6,900 m2 of lake bed at depths of 23-41 m averaged 139 individuals/ hectare (range, 0-571/hectare). This density was substantially higher than the highest burbot density (59-95/hectare) reported in the literature. Burbot were present on the lake bed at depths of 23-36 m, but were most abundant near the crest of the reef at 23-28 m, where the water temperature was 8-13°C, their preferred summer temperature range. Substrates in that temperature range on the reef were bedrock, bedrock ridges, and bedrock and rubble. Burbot were most abundant on the bedrock and rubble. Small fish and macroinvertebrates typically eaten by burbot elsewhere in western Lake Michigan were distributed on the reef according to their summer preferred temperatures and were not seen in abundance where burbot density was highest. We saw no lake trout Salvelinus namaycush on Julian's Reef, although large numbers of juvenile lake trout have been stocked there annually and temperatures on the reef were in the preferred summer temperature range for lake trout.

Distribution, abundance, and resting microhabitat of burbot on Julian's Reef, southwestern Lake Michigan

USGS Publications Warehouse

Edsall, Thomas A.; Kennedy, Gregory W.; Horns, William H.

1993-01-01

We used a remotely operated submersible vehicle equipped with a color video camera to videotape the lake bed and document the distribution and abundance of burbot Lota lotaon a 156-hectare portion of Julian's Reef in southwestern Lake Michigan. The substrates and bathymetry of the study area had been mapped recently by side-scan sonar. Burbot density determined from videotapes covering 6,900 m2 of lake bed at depths of 23–41 m averaged 139 individuals/ hectare (range, 0–571/hectare). This density was substantially higher than the highest burbot density (59–95/hectare) reported in the literature. Burbot were present on the lake bed at depths of 23–36 m, but were most abundant near the crest of the reef at 23–28 m, where the water temperature was 8–13°C, their preferred summer temperature range. Substrates in that temperature range on the reef were bedrock, bedrock ridges, and bedrock and rubble. Burbot were most abundant on the bedrock and rubble. Small fish and macroinvertebrates typically eaten by burbot elsewhere in western Lake Michigan were distributed on the reef according to their summer preferred temperatures and were not seen in abundance where burbot density was highest. We saw no lake trout Salvelinus namaycush on Julian's Reef, although large numbers of juvenile lake trout have been stocked there annually and temperatures on the reef were in the preferred summer temperature range for lake trout.

Hysteresis of thin film IPRTs in the range 100 °C to 600 °C

NASA Astrophysics Data System (ADS)

Zvizdić, D.; Šestan, D.

2013-09-01

As opposed to SPRTs, the IPRTs succumb to hysteresis when submitted to change of temperature. This uncertainty component, although acknowledged as omnipresent at many other types of sensors (pressure, electrical, magnetic, humidity, etc.) has often been disregarded in their calibration certificates' uncertainty budgets in the past, its determination being costly, time-consuming and not appreciated by customers and manufacturers. In general, hysteresis is a phenomenon that results in a difference in an item's behavior when approached from a different path. Thermal hysteresis results in a difference in resistance at a given temperature based on the thermal history to which the PRTs were exposed. The most prominent factor that contributes to the hysteresis error in an IPRT is a strain within the sensing element caused by the thermal expansion and contraction. The strains that cause hysteresis error are closely related to the strains that cause repeatability error. Therefore, it is typical that PRTs that exhibit small hysteresis also exhibit small repeatability error, and PRTs that exhibit large hysteresis have poor repeatability. Aim of this paper is to provide hysteresis characterization of a batch of IPRTs using the same type of thin-film sensor, encapsulated by same procedure and same company and to estimate to what extent the thermal hysteresis obtained by testing one single thermometer (or few thermometers) can serve as representative of other thermometers of the same type and manufacturer. This investigation should also indicate the range of hysteresis departure between IPRTs of the same type. Hysteresis was determined by cycling IPRTs temperature from 100 °C through intermediate points up to 600 °C and subsequently back to 100 °C. Within that range several typical sub-ranges are investigated: 100 °C to 400 °C, 100 °C to 500 °C, 100 °C to 600 °C, 300 °C to 500 °C and 300 °C to 600 °C . The hysteresis was determined at various temperatures by comparison calibration with SPRT. The results of investigation are presented in a graphical form for all IPRTs, ranges and calibration points.

Assessment of the Interconnection between Tampa Bay and the Floridan Aquifer, Florida.

DTIC Science & Technology

1983-06-01

8217 CANAL T. P PESBR SAI 30 MANATEE MEXIC SARSOT COUNTYY MAAE CIT ADECUT 271do Figure .-- ypiANANspEii odcac itiuini ap a (from Got RadGodi, 90)?2 BRADENTO... turbidity of the well water there could change. Typically, the temperature of water in the Floridan aquifer is a constant 230C, and temperature of...water in Hillsborough Bay may range from 14°C to 30°C (Goetz and Goodwin, 1980); while turbidity of water in the Floridan aqui- fer is less than 1 JTU

Discontinuous precipitation in a Cd-6 at.% Ag alloy

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

Manna, I.; Bala, P.K.; Pabi, S.K.

1996-11-01

Discontinuous precipitation (DP) in a Cd-6 at.% Ag alloy has been investigated for the first time. The precipitate phase maintains a lamellar morphology and statistically constant interlamellar spacing under a given isothermal condition in the temperature range studied (333--523 K). The interlamellar spacing increases with an increase in isothermal temperature. The reaction front velocity registers a typical C-curve variation with the inverse of temperature. The reaction rate is maximum at 470 K. The predicted upper limit of DP occurrence in this alloy is 23 K lower than the concerned equilibrium solvus temperature. Continuous precipitation accompanies DP at all temperatures, especiallymore » beyond a certain time, and adversely affects the growth kinetics of DP colonies by reducing the local chemical driving force and/or posing physical hindrance to the reaction front migration. An extensive kinetic analysis of DP using the models by Turnbull, Aaronson and Liu, and Petermann and Hornbogen has yielded the grain boundary chemical diffusivity data in Cd-6 At.% Ag for the first time, the activation energy of which lies in the range 55--77 kJ/mol.« less

4He sample probe for combined microwave and dc transport measurements

NASA Astrophysics Data System (ADS)

Dobrovolskiy, Oleksandr V.; Franke, Jörg; Huth, Michael

2015-03-01

Combined microwave and dc electrical transport measurements at low temperatures represent a valuable experimental method in many research areas. In particular, when samples are conventional superconductors, a typical experiment requires a combination of helium temperatures, a wide range of magnetic fields, and the utilization of coaxial lines along with the usual dc wiring. We report on the general design features and the microwave performance of a custom-made low-temperature sample probe, with a measurement bandwidth tested from dc to 20 GHz. Equipped with six coaxial cables, a heater, Hall and temperature sensors, the probe fits into a ⊘32 mm shaft. We present our setup, analyze its microwave performance, and describe two representative experiments enabled by this system. The proposed setup will be essential for a systematic study of the dc and ac response of the vortex dynamics in nanopatterned superconductors subject to combined dc and microwave stimuli. Besides, it will be valuable for the investigation of a broad class of nonlinear stochastic systems where a combination of dc and high-frequency ac driving in a wide temperature range is necessary.

Raman microspectroscopy of noncancerous and cancerous human breast tissues. Identification and phase transitions of linoleic and oleic acids by Raman low-temperature studies.

PubMed

Brozek-Pluska, Beata; Kopec, Monika; Surmacki, Jakub; Abramczyk, Halina

2015-04-07

We present the results of Raman studies in the temperature range of 293-77 K on vibrational properties of linoleic and oleic acids and Raman microspectroscopy of human breast tissues at room temperature. Our results confirmed the significant role of unsaturated fatty acids in differentiation of noncancerous and cancerous breast tissues and the role of vibrational spectroscopy in phase transition identification. We have found that vibrational properties are very sensitive indicators to specify phases and phase transitions typical of unsaturated fatty acids at the molecular level. Using Raman spectroscopy we have identified high-temperature, middle-temperature and low-temperature phases of linoleic acid. Results obtained for linoleic acid were compared with parameters characteristic of α and γ phases of oleic acid - the parent compound of polyunsaturated fatty acids.

DMAC and NMP as Electrolyte Additives for Li-Ion Cells

NASA Technical Reports Server (NTRS)

Smart, Marshall; Bugga, Ratnakumar; Lucht, Brett

2008-01-01

Dimethyl acetamide (DMAC) and N-methyl pyrrolidinone (NMP) have been found to be useful as high-temperature-resilience-enhancing additives to a baseline electrolyte used in rechargeable lithium-ion electrochemical cells. The baseline electrolyte, which was previously formulated to improve low-temperature performance, comprises LiPF6 dissolved at a concentration of 1.0 M in a mixture comprising equal volume proportions of ethylene carbonate, diethyl carbonate, and dimethyl carbonate. This and other electrolytes comprising lithium salts dissolved in mixtures of esters (including alkyl carbonates) have been studied in continuing research directed toward extending the lower limits of operating temperatures and, more recently, enhancing the high-temperature resilience of such cells. This research at earlier stages, and the underlying physical and chemical principles, were reported in numerous previous NASA Tech Briefs articles. Although these electrolytes provide excellent performance at low temperatures (typically as low as -40 C), when the affected Li-ion cells are subjected to high temperatures during storage and cycling, there occur irreversible losses of capacity accompanied by power fade and deterioration of low-temperature performance. The term "high-temperature resilience" signifies, loosely, the ability of a cell to resist such deterioration, retaining as much as possible of its initial charge/discharge capacity during operation or during storage in the fully charged condition at high temperature. For the purposes of the present development, a temperature is considered to be high if it equals or exceeds the upper limit (typically, 30 C) of the operating-temperature range for which the cells in question are generally designed.

Seeing the light: the effects of particles, dissolved materials, and temperature on in situ measurements of DOM fluorescence in rivers and streams

USGS Publications Warehouse

Downing, Bryan D.; Pellerin, Brian A.; Bergamaschi, Brian A.; Saraceno, John Franco; Kraus, Tamara E.C.

2012-01-01

Field-deployable sensors designed to continuously measure the fluorescence of colored dissolved organic matter (FDOM) in situ are of growing interest. However, the ability to make FDOM measurements that are comparable across sites and over time requires a clear understanding of how instrument characteristics and environmental conditions affect the measurements. In particular, the effects of water temperature and light attenuation by both colored dissolved material and suspended particles may be significant in settings such as rivers and streams. Using natural standard reference materials, we characterized the performance of four commercially-available FDOM sensors under controlled laboratory conditions over ranges of temperature, dissolved organic matter (DOM) concentrations, and turbidity that spanned typical environmental ranges. We also examined field data from several major rivers to assess how often attenuation artifacts or temperature effects might be important. We found that raw (uncorrected) FDOM values were strongly affected by the light attenuation that results from dissolved substances and suspended particles as well as by water temperature. Observed effects of light attenuation and temperature agreed well with theory. Our results show that correction of measured FDOM values to account for these effects is necessary and feasible over much of the range of temperature, DOM concentration, and turbidity commonly encountered in surface waters. In most cases, collecting high-quality FDOM measurements that are comparable through time and between sites will require concurrent measurements of temperature and turbidity, and periodic discrete sample collection for laboratory measurement of DOM.

Atypical transitions in material response during constant strain rate, hot deformation of austenitic steel

NASA Astrophysics Data System (ADS)

Borah, Utpal; Aashranth, B.; Samantaray, Dipti; Kumar, Santosh; Davinci, M. Arvinth; Albert, Shaju K.; Bhaduri, A. K.

2017-10-01

Work hardening, dynamic recovery and dynamic recrystallization (DRX) occurring during hot working of austenitic steel have been extensively studied. Various empirical models describe the nature and effects of these phenomena in a typical framework. However, the typical model is sometimes violated following atypical transitions in deformation mechanisms of the material. To ascertain the nature of these atypical transitions, researchers have intentionally introduced discontinuities in the deformation process, such as interrupting the deformation as in multi-step rolling and abruptly changing the rate of deformation. In this work, we demonstrate that atypical transitions are possible even in conventional single-step, constant strain rate deformation of austenitic steel. Towards this aim, isothermal, constant true strain rate deformation of austenitic steel has been carried out in a temperature range of 1173-1473 K and strain rate range of 0.01-100 s-1. The microstructural response corresponding to each deformation condition is thoroughly investigated. The conventional power-law variation of deformation grain size (D) with peak stress (σp) during DRX is taken as a typical model and experimental data is tested against it. It is shown that σp-D relations exhibit an atypical two-slope linear behaviour rather than a continuous power law relation. Similarly, the reduction in σp with temperature (T) is found to consist of two discrete linear segments. In practical terms, the two linear segments denote two distinct microstructural responses to deformation. As a consequence of this distinction, the typical model breaks down and is unable to completely relate microstructural evolution to flow behaviour. The present work highlights the microstructural mechanisms responsible for this atypical behavior and suggests strategies to incorporate the two-slope behaviour in the DRX model.

Sweeprate and temperature effects on crackling noise

NASA Astrophysics Data System (ADS)

White, Robert Allen

Crackling noise, defined as separate bursts characterized by power law behavior of the frequency histograms over many decades, is observed in many driven systems far from equilibrium. Examples of such systems pepper a remarkable range of length and energy scales from jerky domain wall motion of disordered magnets, to the sometimes devastating crackling of the earth to the bursty release of energy in the photosphere of the sun dwarfing that of our most horrible WMD. Typically, crackling noise is modeled in the infinitely slow driving rate limit at zero temperature. In this dissertation I investigate the effects of relaxing these limits. First I consider the crackling system at zero temperature and finite sweeprate. I discuss how the temporal overlap of power law bursts can account for a wide range of scaling behavior and provide a criterion for sweeprate controlled exponents based on exponents obtained in the infinitely slowly driven limit. I also discuss scaling arguments for hitherto unexplained results in the power spectrum of crackling response in disordered magnets, commonly referred to as Barkhausen noise. Scaling arguments and numerical results are compared to Barkhausen noise measurements in two materials representing distinct adiabatically driven universality classes. Relaxation of the zero temperature constraint cannot be done without considering finite sweeprates due to global relaxation timescales that arise at finite temperatures. We investigate the connection between sweeprate and thermal fluctuations in the far from equilibrium limit typical of crackling systems. Again, using scaling arguments and numerical simulations of the random field Ising model near a disorder-induced critical point we analyze interesting crossover phenomena in the power spectra which are also observed in Barkhausen noise but have yet to be explained.

A Fully Transparent Flexible Sensor for Cryogenic Temperatures Based on High Strength Metallurgical Graphene

PubMed Central

Pawlak, Ryszard; Lebioda, Marcin; Rymaszewski, Jacek; Szymanski, Witold; Kolodziejczyk, Lukasz; Kula, Piotr

2016-01-01

Low-temperature electronics operating in below zero temperatures or even below the lower limit of the common −65 to 125 °C temperature range are essential in medical diagnostics, in space exploration and aviation, in processing and storage of food and mainly in scientific research, like superconducting materials engineering and their applications—superconducting magnets, superconducting energy storage, and magnetic levitation systems. Such electronic devices demand special approach to the materials used in passive elements and sensors. The main goal of this work was the implementation of a fully transparent, flexible cryogenic temperature sensor with graphene structures as sensing element. Electrodes were made of transparent ITO (Indium Tin Oxide) or ITO/Ag/ITO conductive layers by laser ablation and finally encapsulated in a polymer coating. A helium closed-cycle cryostat has been used in measurements of the electrical properties of these graphene-based temperature sensors under cryogenic conditions. The sensors were repeatedly cooled from room temperature to cryogenic temperature. Graphene structures were characterized using Raman spectroscopy. The observation of the resistance changes as a function of temperature indicates the potential use of graphene layers in the construction of temperature sensors. The temperature characteristics of the analyzed graphene sensors exhibit no clear anomalies or strong non-linearity in the entire studied temperature range (as compared to the typical carbon sensor). PMID:28036036

A Fully Transparent Flexible Sensor for Cryogenic Temperatures Based on High Strength Metallurgical Graphene.

PubMed

Pawlak, Ryszard; Lebioda, Marcin; Rymaszewski, Jacek; Szymanski, Witold; Kolodziejczyk, Lukasz; Kula, Piotr

2016-12-28

Low-temperature electronics operating in below zero temperatures or even below the lower limit of the common -65 to 125 °C temperature range are essential in medical diagnostics, in space exploration and aviation, in processing and storage of food and mainly in scientific research, like superconducting materials engineering and their applications-superconducting magnets, superconducting energy storage, and magnetic levitation systems. Such electronic devices demand special approach to the materials used in passive elements and sensors. The main goal of this work was the implementation of a fully transparent, flexible cryogenic temperature sensor with graphene structures as sensing element. Electrodes were made of transparent ITO (Indium Tin Oxide) or ITO/Ag/ITO conductive layers by laser ablation and finally encapsulated in a polymer coating. A helium closed-cycle cryostat has been used in measurements of the electrical properties of these graphene-based temperature sensors under cryogenic conditions. The sensors were repeatedly cooled from room temperature to cryogenic temperature. Graphene structures were characterized using Raman spectroscopy. The observation of the resistance changes as a function of temperature indicates the potential use of graphene layers in the construction of temperature sensors. The temperature characteristics of the analyzed graphene sensors exhibit no clear anomalies or strong non-linearity in the entire studied temperature range (as compared to the typical carbon sensor).

Achieving thermography with a thermal security camera using uncooled amorphous silicon microbolometer image sensors

NASA Astrophysics Data System (ADS)

Wang, Yu-Wei; Tesdahl, Curtis; Owens, Jim; Dorn, David

2012-06-01

Advancements in uncooled microbolometer technology over the last several years have opened up many commercial applications which had been previously cost prohibitive. Thermal technology is no longer limited to the military and government market segments. One type of thermal sensor with low NETD which is available in the commercial market segment is the uncooled amorphous silicon (α-Si) microbolometer image sensor. Typical thermal security cameras focus on providing the best image quality by auto tonemaping (contrast enhancing) the image, which provides the best contrast depending on the temperature range of the scene. While this may provide enough information to detect objects and activities, there are further benefits of being able to estimate the actual object temperatures in a scene. This thermographic ability can provide functionality beyond typical security cameras by being able to monitor processes. Example applications of thermography[2] with thermal camera include: monitoring electrical circuits, industrial machinery, building thermal leaks, oil/gas pipelines, power substations, etc...[3][5] This paper discusses the methodology of estimating object temperatures by characterizing/calibrating different components inside a thermal camera utilizing an uncooled amorphous silicon microbolometer image sensor. Plots of system performance across camera operating temperatures will be shown.

Electrical and switching properties of the Se 90Te 10-xAg x (0⩽ x⩽6) films

NASA Astrophysics Data System (ADS)

Afifi, M. A.; Hegab, N. A.; Bekheet, A. E.; Sharaf, E. R.

2009-08-01

Amorphous Se 90Te 10-xAg x (0⩽ x⩽6) films are obtained by thermal evaporation technique under vacuum from the synthesized bulk materials on pyrographite and glass substrates. X-ray analysis shows the amorphous nature of the obtained films. The dc electrical conductivity was studied for different thicknesses (165-711 nm) as a function of temperature in the range (298-323 K) below the corresponding T g for the studied films. The obtained results show that the conduction activation energy has a single value through the investigated range of temperature which can be explained in accordance with Mott and Davis model. The I- V characteristic curves for the film compositions are found to be typical for a memory switch. The mean value of the threshold voltage Vbar increases linearly with increasing film thickness (165-711 nm), while it decreases exponentially with increasing temperature in the investigated range for the studied compositions. The results are explained in accordance with the electrothermal model for the switching process. The effect of Ag on the studied parameters is also investigated.

Industrial uses and applications of ionic liquids

NASA Astrophysics Data System (ADS)

Gutowski, Keith E.

2018-02-01

Ionic liquids are salts that melt at low temperatures (usually defined as less than 100 °C) and have a number of interesting properties that make them useful for industrial applications. Typical ionic liquid properties include high thermal stabilities, negligible vapor pressures, wide liquidus ranges, broad electrochemical windows, and unique solvation properties. Furthermore, the potential combinations of cations and anions provide nearly unlimited chemical tunability. This article will describe the diverse industrial uses of ionic liquids and how their unique properties are leveraged, with examples ranging from chemical processing to consumer packaged goods.

Meteoric precipitation at Yucca Mountain, Nevada: Chemical and stable isotope analyses, 2006-09

USGS Publications Warehouse

Moscati, Richard J.; Scofield, Kevin M.

2011-01-01

Cumulatively, &delta18O values range from 3.0 to -20.4 per mil (%o) and &deltaD values range from 10 to -14%o. Winter-season precipitation commonly has isotopically lighter compositions. The cumulative &delta18O plotted against &deltaD shows that precipitation samples define a line with slope of 6.4, less than the 8 of the Global Meteoric Water Line. This difference in slope, typical of arid environments, is chiefly the result of evaporation of falling raindrops due to warmer air temperatures. ;

Effective temperature of an ultracold electron source based on near-threshold photoionization.

PubMed

Engelen, W J; Smakman, E P; Bakker, D J; Luiten, O J; Vredenbregt, E J D

2014-01-01

We present a detailed description of measurements of the effective temperature of a pulsed electron source, based on near-threshold photoionization of laser-cooled atoms. The temperature is determined by electron beam waist scans, source size measurements with ion beams, and analysis with an accurate beam line model. Experimental data is presented for the source temperature as a function of the wavelength of the photoionization laser, for both nanosecond and femtosecond ionization pulses. For the nanosecond laser, temperatures as low as 14 ± 3 K were found; for femtosecond photoionization, 30 ± 5 K is possible. With a typical source size of 25 μm, this results in electron bunches with a relative transverse coherence length in the 10⁻⁴ range and an emittance of a few nm rad. © 2013 Elsevier B.V. All rights reserved.

Applications of high pressure differential scanning calorimetry to aviation fuel thermal stability research

NASA Technical Reports Server (NTRS)

Neveu, M. C.; Stocker, D. P.

1985-01-01

High pressure differential scanning calorimetry (DSC) was studied as an alternate method for performing high temperature fuel thermal stability research. The DSC was used to measure the heat of reaction versus temperature of a fuel sample heated at a programmed rate in an oxygen pressurized cell. Pure hydrocarbons and model fuels were studied using typical DSC operating conditions of 600 psig of oxygen and a temperature range from ambient to 500 C. The DSC oxidation onset temperature was determined and was used to rate the fuels on thermal stability. Kinetic rate constants were determined for the global initial oxidation reaction. Fuel deposit formation is measured, and the high temperature volatility of some tetralin deposits is studied by thermogravimetric analysis. Gas chromatography and mass spectrometry are used to study the chemical composition of some DSC stressed fuels.

High Temperature Annealing of MBE-grown Mg-doped GaN

NASA Astrophysics Data System (ADS)

Contreras, S.; Konczewicz, L.; Peyre, H.; Juillaguet, S.; Khalfioui, M. Al; Matta, S.; Leroux, M.; Damilano, B.; Brault, J.

2017-06-01

In this report, are shown the results of high temperature resistivity and Hall Effect studies of Mg-doped GaN epilayers. The samples studied were grown on (0001) (c-plane) sapphire by molecular beam epitaxy and 0.5 μm GaN:Mg layers have been achieved on low temperature buffers of GaN (30 nm) and AlN ( 150 nm). The experiments were carried out in the temperature range from 300 K up to 900 K. Up to about 870 K a typical thermally activated conduction process has been observed with the activation energy value EA = 215 meV. However, for higher temperatures, an annealing effect is observed in all the investigated samples. The increase of the free carrier concentration as a function of time leads to an irreversible decrease of sample resistivity of more than 60%.

Temperature and rate of dehydration of major constituents of carbonaceous chondrites under vacuum conditions

NASA Astrophysics Data System (ADS)

Pohl, Leos; Britt, Daniel

2017-10-01

Some sub-types of carbonaceous chondrites contain a significant amount of hydrated minerals which produce specific absorption lines, typically due to the presence of hydroxyls. However, if these asteroids have come close enough to the Sun during their history, the high temperatures might have resulted in mineral decomposition and consequent loss of hydroxyl (or water) molecules in the surface layer and even to certain depths. Determination of the hydration state of phyllosilicates typically found on asteroids as well as the relative quantities of hydrated to desiccated phyllosilicates relies on experimental data - the temperature and rate of dehydration. Both dehydration temperature and rate depend on pressure. The rate also depends on the temperature. Experimentally determined phase curves for serpentine, that show for example decomposition of antigorite to forsterite and enstatite or talc and water, exist for GPa pressure levels. For antigorite, these temperatures span the range 500-750°C for pressures between 0.1 GPa and 8 GPa. However, these data are not suitable for vacuum environment found on asteroids; further, at lower pressures, the available data suggest a monotonically decreasing dehydration temperature with decreasing pressure. Also, the available data suggest dependence of both dehydration temperature and rate on the grain size distribution of the mineral. We have determined the temperature and rate of dehydration of the serpentine polymorphs antigorite, lizardite, cronstedtite, under high vacuum conditions and for various grain size distributions. The grain size distributions have been determined by particle analyzer and each sample source was also analyzed using X-Ray Diffraction.

Heat Transfer in a Superelliptic Transition Duct

NASA Technical Reports Server (NTRS)

Poinsatte, Philip; Thurman, Douglas; Hippensteele, Steven

2008-01-01

Local heat transfer measurements were experimentally mapped using a transient liquid-crystal heat transfer technique on the surface of a circular-to-rectangular transition duct. The transition duct had a length-to-diameter ratio of 1.5 and an exit-plane aspect ratio of 3. The crosssectional geometry was defined by the equation of a superellipse. The cross-sectional area was the same at the inlet and exit but varied up to 15 percent higher through the transition. The duct was preheated to a uniform temperature (nominally 64 C) before allowing room temperature air to be suddenly drawn through it. As the surface cooled, the resulting isothermal contours on the duct surface were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the surface temperature and time data for all points on the duct surfaces during each test. Using this surface temperature-time data together with the temperature of the air flowing through the model and the initial temperature of the model wall, the heat transfer coefficient was calculated by employing the classic one-dimensional, semi-infinite wall heat transfer conduction model. Test results are reported for inlet diameter-based Reynolds numbers ranging from 0.4x106 to 2.4x106 and two grid-generated freestream turbulence intensities of about 1 percent, which is typical of wind tunnels, and up to 16 percent, which may be more typical of real engine conditions.

Analysis and Design of Cryogenic Pressure Vessels for Automotive Hydrogen Storage

NASA Astrophysics Data System (ADS)

Espinosa-Loza, Francisco Javier

Cryogenic pressure vessels maximize hydrogen storage density by combining the high pressure (350-700 bar) typical of today's composite pressure vessels with the cryogenic temperature (as low as 25 K) typical of low pressure liquid hydrogen vessels. Cryogenic pressure vessels comprise a high-pressure inner vessel made of carbon fiber-coated metal (similar to those used for storage of compressed gas), a vacuum space filled with numerous sheets of highly reflective metalized plastic (for high performance thermal insulation), and a metallic outer jacket. High density of hydrogen storage is key to practical hydrogen-fueled transportation by enabling (1) long-range (500+ km) transportation with high capacity vessels that fit within available spaces in the vehicle, and (2) reduced cost per kilogram of hydrogen stored through reduced need for expensive structural material (carbon fiber composite) necessary to make the vessel. Low temperature of storage also leads to reduced expansion energy (by an order of magnitude or more vs. ambient temperature compressed gas storage), potentially providing important safety advantages. All this is accomplished while simultaneously avoiding fuel venting typical of cryogenic vessels for all practical use scenarios. This dissertation describes the work necessary for developing and demonstrating successive generations of cryogenic pressure vessels demonstrated at Lawrence Livermore National Laboratory. The work included (1) conceptual design, (2) detailed system design (3) structural analysis of cryogenic pressure vessels, (4) thermal analysis of heat transfer through cryogenic supports and vacuum multilayer insulation, and (5) experimental demonstration. Aside from succeeding in demonstrating a hydrogen storage approach that has established all the world records for hydrogen storage on vehicles (longest driving range, maximum hydrogen storage density, and maximum containment of cryogenic hydrogen without venting), the work also demonstrated a methodology for computationally efficient detailed modeling of cryogenic pressure vessels. The work continues with support of the US Department of Energy to demonstrate a new generation of cryogenic vessels anticipated to improve on the hydrogen storage performance figures previously imposed in this project. The author looks forward to further contributing to a future of long-range, inexpensive, and safe zero emissions transportation.

Friction and wear behavior of aluminum and composite I-beam stiffened airplane skins

NASA Technical Reports Server (NTRS)

Jackson, K. E.

1985-01-01

Friction and wear behavior was determined for I-beam stiffened skins constructed of aluminum, graphite-epoxy composite, and glass hybrid composite under abrasive loading conditions typical of those occurring on the underside of a transport airplane during an emergency belly landing. A test apparatus was developed to abrade the test specimens on actual runway surface under a range of pressures (2-5 psi) and velocities (16-50 mph). These parameters were chosen to fall within the range of conditions typical of an airframe sliding on a runway surface. The effects of the test variables on the wear rate and the coefficient of friction are discussed and comparisons are made between the composite materials and aluminum. In addition, the test apparatus was equipped to monitor the temperature variations on the backside of the skins during abrasion and these results are presented.

Fiber-optic epoxy composite cure sensor. I. Dependence of refractive index of an autocatalytic reaction epoxy system at 850 nm on temperature and extent of cure

NASA Astrophysics Data System (ADS)

Lam, Kai-Yuen; Afromowitz, Martin A.

1995-09-01

We discuss the behavior of the refractive index of a typical epoxy-aromatic diamine system. Near 850 nm the index of refraction is found to be largely controlled by the density of the epoxy. Models are derived to describe its dependence on temperature and extent of cure. Within the range of temperatures studied, the refractive index decreases linearly with increasing temperature. In addition, as the epoxy is cured, the refractive index increases linearly with conversion to the gel point. >From then on, shrinkage in the volume of the epoxy is restricted by local viscosity. Therefore the linear relationship between the refractive index and the extent of cure does not hold beyond the gel point.

Long-range energy transport in single supramolecular nanofibres at room temperature

NASA Astrophysics Data System (ADS)

Haedler, Andreas T.; Kreger, Klaus; Issac, Abey; Wittmann, Bernd; Kivala, Milan; Hammer, Natalie; Köhler, Jürgen; Schmidt, Hans-Werner; Hildner, Richard

2015-07-01

Efficient transport of excitation energy over long distances is a key process in light-harvesting systems, as well as in molecular electronics. However, in synthetic disordered organic materials, the exciton diffusion length is typically only around 10 nanometres (refs 4, 5), or about 50 nanometres in exceptional cases, a distance that is largely determined by the probability laws of incoherent exciton hopping. Only for highly ordered organic systems has the transport of excitation energy over macroscopic distances been reported--for example, for triplet excitons in anthracene single crystals at room temperature, as well as along single polydiacetylene chains embedded in their monomer crystalline matrix at cryogenic temperatures (at 10 kelvin, or -263 degrees Celsius). For supramolecular nanostructures, uniaxial long-range transport has not been demonstrated at room temperature. Here we show that individual self-assembled nanofibres with molecular-scale diameter efficiently transport singlet excitons at ambient conditions over more than four micrometres, a distance that is limited only by the fibre length. Our data suggest that this remarkable long-range transport is predominantly coherent. Such coherent long-range transport is achieved by one-dimensional self-assembly of supramolecular building blocks, based on carbonyl-bridged triarylamines, into well defined H-type aggregates (in which individual monomers are aligned cofacially) with substantial electronic interactions. These findings may facilitate the development of organic nanophotonic devices and quantum information technology.

Comparison between 1-minute and 15-minute averages of turbulence parameters

NASA Technical Reports Server (NTRS)

Noble, John M.

1993-01-01

Sonic anemometers are good instruments for measuring temperature and wind speed and are fast enough to calculate the temperature and wind structure parameters used to calculate the variance in the acoustic index of refraction. However, the turbulence parameters are typically 15-minute averaged point measurements. There are several problems associated with making point measurements and using them to represent a turbulence field. Some of the sonic anemometer data analyzed from the Joint Acoustic Propagation Experiment (JAPE) conducted during July 1991 at DIRT Site located at White Sands Missile Range, New Mexico, are examined.

The influence of chilling requirement on the southern distribution limit of exotic Russian olive (Elaeagnus angustifolia) in western North America

USGS Publications Warehouse

Guilbault, Kimberly R.; Brown, C.S.; Friedman, J.M.; Shafroth, P.B.

2012-01-01

Russian olive (Elaeagnus angustifolia L.), a Eurasian tree now abundant along rivers in western North America, has an apparent southern distribution limit running through southern California, Arizona, New Mexico and Texas. We used field observations to precisely define this limit in relation to temperature variables. We then investigated whether lack of cold temperatures south of the limit may prevent the accumulation of sufficient chilling, inhibiting dormancy loss of seeds and buds. We found that Russian olive occurrence was more strongly associated with low winter temperatures than with high summer temperatures, and results of controlled seed germination and vegetative bud-break experiments suggest that the chilling requirements for germination and bud-break are partly responsible for the southern range limit. Both seed germination proportion and germination time decreased under conditions simulating those south of the range limit. Similarly, percentage bud break decreased when chilling dropped below values typical of the range limit. In 17–65% of the years from 1980 to 2000, the chilling accumulated at a site near the range limit (El Paso, TX) would lead to a 10% or more decrease in bud-break. The potential decline in growth could have large fitness consequences for Russian olive. If climate change exhibits a warming trend, our results suggest the chilling requirement for bud-break of Russian olive trees will not be met in some years and its southern range limit may retreat northward.

Uncooled radiometric camera performance

NASA Astrophysics Data System (ADS)

Meyer, Bill; Hoelter, T.

1998-07-01

Thermal imaging equipment utilizing microbolometer detectors operating at room temperature has found widespread acceptance in both military and commercial applications. Uncooled camera products are becoming effective solutions to applications currently using traditional, photonic infrared sensors. The reduced power consumption and decreased mechanical complexity offered by uncooled cameras have realized highly reliable, low-cost, hand-held instruments. Initially these instruments displayed only relative temperature differences which limited their usefulness in applications such as Thermography. Radiometrically calibrated microbolometer instruments are now available. The ExplorIR Thermography camera leverages the technology developed for Raytheon Systems Company's first production microbolometer imaging camera, the Sentinel. The ExplorIR camera has a demonstrated temperature measurement accuracy of 4 degrees Celsius or 4% of the measured value (whichever is greater) over scene temperatures ranges of minus 20 degrees Celsius to 300 degrees Celsius (minus 20 degrees Celsius to 900 degrees Celsius for extended range models) and camera environmental temperatures of minus 10 degrees Celsius to 40 degrees Celsius. Direct temperature measurement with high resolution video imaging creates some unique challenges when using uncooled detectors. A temperature controlled, field-of-view limiting aperture (cold shield) is not typically included in the small volume dewars used for uncooled detector packages. The lack of a field-of-view shield allows a significant amount of extraneous radiation from the dewar walls and lens body to affect the sensor operation. In addition, the transmission of the Germanium lens elements is a function of ambient temperature. The ExplorIR camera design compensates for these environmental effects while maintaining the accuracy and dynamic range required by today's predictive maintenance and condition monitoring markets.

Influence of Environmental Variables on Gambierdiscus spp. (Dinophyceae) Growth and Distribution

PubMed Central

Xu, Yixiao; Richlen, Mindy L.; Liefer, Justin D.; Robertson, Alison; Kulis, David; Smith, Tyler B.; Parsons, Michael L.; Anderson, Donald M.

2016-01-01

Benthic dinoflagellates in the genus Gambierdiscus produce the ciguatoxin precursors responsible for the occurrence of ciguatera toxicity. The prevalence of ciguatera toxins in fish has been linked to the presence and distribution of toxin-producing species in coral reef ecosystems, which is largely determined by the presence of suitable benthic habitat and environmental conditions favorable for growth. Here using single factor experiments, we examined the effects of salinity, irradiance, and temperature on growth of 17 strains of Gambierdiscus representing eight species/phylotypes (G. belizeanus, G. caribaeus, G. carolinianus, G. carpenteri, G. pacificus, G. silvae, Gambierdiscus sp. type 4–5), most of which were established from either Marakei Island, Republic of Kiribati, or St. Thomas, United States Virgin Island (USVI). Comparable to prior studies, growth rates fell within the range of 0–0.48 divisions day-1. In the salinity and temperature studies, Gambierdiscus responded in a near Gaussian, non-linear manner typical for such studies, with optimal and suboptimal growth occurring in the range of salinities of 25 and 45 and 21.0 and 32.5°C. In the irradiance experiment, no mortality was observed; however, growth rates at 55μmol photons · m-2 · s-1 were lower than those at 110–400μmol photons · m-2 · s-1. At the extremes of the environmental conditions tested, growth rates were highly variable, evidenced by large coefficients of variability. However, significant differences in intraspecific growth rates were typically found only at optimal or near-optimal growth conditions. Polynomial regression analyses showed that maximum growth occurred at salinity and temperature levels of 30.1–38.5 and 23.8–29.2°C, respectively. Gambierdiscus growth patterns varied among species, and within individual species: G. belizeanus, G. caribaeus, G. carpenteri, and G. pacificus generally exhibited a wider range of tolerance to environmental conditions, which may explain their broad geographic distribution. In contrast, G. silvae and Gambierdiscus sp. types 4–5 all displayed a comparatively narrow range of tolerance to temperature, salinity, and irradiance. PMID:27074134

The role of temperature in the variability and extremes of electricity and gas demand in Great Britain

NASA Astrophysics Data System (ADS)

Thornton, H. E.; Hoskins, B. J.; Scaife, A. A.

2016-11-01

The daily relationship of electricity and gas demand with temperature in Great Britain is analysed from 1975 to 2013 and 1996 to 2013 respectively. The annual mean and annual cycle amplitude of electricity demand exhibit low frequency variability. This low frequency variability is thought to be predominantly driven by socio-economic changes rather than temperature variation. Once this variability is removed, both daily electricity and gas demand have a strong anti-correlation with temperature (r elec = -0.90 , r gas = -0.94). However these correlations are inflated by the changing demand-temperature relationship during spring and autumn. Once the annual cycles of temperature and demand are removed, the correlations are {r}{{elec}}=-0.60 and {r}{{gas}}=-0.83. Winter then has the strongest demand-temperature relationship, during which a 1 °C reduction in daily temperature typically gives a ˜1% increase in daily electricity demand and a 3%-4% increase in gas demand. Extreme demand periods are assessed using detrended daily temperature observations from 1772. The 1 in 20 year peak day electricity and gas demand estimates are, respectively, 15% (range 14%-16%) and 46% (range 44%-49%) above their average winter day demand during the last decade. The risk of demand exceeding recent extreme events, such as during the winter of 2009/2010, is also quantified.

Heat Transfer In High-Temperature Multilayer Insulation

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Miller, Stephen D.; Cunnington, George R.

2006-01-01

The combined radiation/conduction heat transfer in high-temperature multilayer insulations for typical reentry of reusable launch vehicles from low Earth orbit was investigated experimentally and numerically. The high-temperature multilayer insulation investigated consisted of gold-coated reflective foils separated by alumina fibrous insulation spacers. The steady-state heat transfer through four multilayer insulation configurations was investigated experimentally over the temperature range of 300-1300 K and environmental pressure range of 1.33 10(exp -5)-101.32 kPa. It was shown that including the reflective foils reduced the effective thermal conductivity compared to fibrous insulation sample at 1.5 times the density of the multilayer sample. A finite volume numerical model was developed to solve the governing combined radiation/conduction heat transfer equations. The radiation heat transfer in the fibrous insulation spacers was modeled using the modified two-flux approximation assuming anisotropic scattering and gray medium. The numerical model was validated by comparison with steady-state experimental data. The root mean square deviation between the predicted and measured effective thermal conductivity of the samples was 9.5%.

Operation of a New COTS Crystal Oscillator - CXOMHT over a Wide Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2011-01-01

Crystal oscillators are extensively used in electronic circuits to provide timing or clocking signals in data acquisition, communications links, and control systems, to name a few. They are affordable, small in size, and reliable. Because of the inherent characteristics of the crystal, the oscillator usually exhibits extreme accuracy in its output frequency within the intrinsic crystal stability. Stability of the frequency could be affected under varying load levels or other operational conditions. Temperature is one of those important factors that influence the frequency stability of an oscillator; as it does to the functionality of other electronic components. Electronics designed for use in NASA deep space and planetary exploration missions are expected to be exposed to extreme temperatures and thermal cycling over a wide range. Thus, it is important to design and develop circuits that are able to operate efficiently and reliably under in these harsh temperature environments. Most of the commercial-off-the-shelf (COTS) devices are very limited in terms of their specified operational temperature while very few custom-made commercial and military-grade parts have the ability to operate in a slightly wider range of temperature than those of the COTS parts. These parts are usually designed for operation under one temperature extreme, i.e. hot or cold, and do not address the wide swing in the operational temperature, which is typical of the space environment. For safe and successful space missions, electronic systems must therefore be designed not only to withstand the extreme temperature exposure but also to operate efficiently and reliably. This report presents the results obtained on the evaluation of a new COTS crystal oscillator under extreme temperatures.

Physical Processes Controlling the Spatial Distributions of Relative Humidity in the Tropical Tropopause Layer Over the Pacific

NASA Technical Reports Server (NTRS)

Jensen, Eric J.; Thornberry, Troy D.; Rollins, Andrew W.; Ueyama, Rei; Pfister, Leonhard; Bui, Thaopaul; Diskin, Glenn S.; Digangi, Joshua P.; Hintsa, Eric; Gao, Ru-Shan;

A programmable, multichannel power supply for SIPMs with temperature compensation loop and Ethernet interface

NASA Astrophysics Data System (ADS)

Querol, M.; Rodríguez, J.; Toledo, J.; Esteve, R.; Álvarez, V.; Herrero, V.

2016-12-01

Among the different techniques available, the SiPM power supply described in this paper uses output voltage and sensor temperature feedback. A high-resolution ADC digitizes both the output voltage and an analog signal proportional to the SiPM temperature for each of its 16 independent outputs. The appropriate change in the bias voltage is computed in a micro-controller and this correction is applied via a high resolution DAC to the control input of a DC/DC module that produces the output voltage. This method allows a reduction in gain variations from typically 30% to only 0.5% in a 10 °C range. The power supply is housed in a 3U-height aluminum box. A 2.8'' touch screen on the front panel provides local access to the configuration and monitoring functions using a graphical interface. The unit has an Ethernet interface on its rear side to provide remote operation and integration in slow control systems using the encrypted and secure SSH protocol. A LabVIEW application with SSH interface has been designed to operate the power supply from a remote computer. The power supply has good characteristics, such as 85 V output range with 1 mV resolution and stability better than 2 mVP, excellent output load regulation and programmable rise and fall voltage ramps. Commercial power supplies from well-known manufacturers can show far better specifications though can also result in an over featured and over costly solution for typical applications.

Low Temperature Double-layer Capacitors with Improved Energy Density: An Overview of Recent Development Efforts

NASA Technical Reports Server (NTRS)

Brandon, Erik J.; West, William C.; Smart, Marshall C.; Korenblit, Yair; Kajdos, Adam; Kvit, Alexander; Jagiello, Jacek; Yushin, Gleb

2012-01-01

Electrochemical double-layer capacitors are finding increased use in a wide range of energy storage applications, particularly where high pulse power capabilities are required. Double-layer capacitors store charge at a liquid/solid interface, making them ideal for low temperature power applications, due to the facile kinetic processes associated with the rearrangement of the electrochemical double-layer at these temperatures. Potential low temperature applications include hybrid and electric vehicles, operations in polar regions, high altitude aircraft and aerospace avionics, and distributed environmental and structural health monitoring. State-of-the-art capacitors can typically operate to -40 C, with a subsequent degradation in power performance below room temperature. However, recent efforts focused on advanced electrolyte and electrode systems can enable operation to temperatures as low as -70 C, with capacities similar to room temperature values accompanied by reasonably low equivalent series resistances. This presentation will provide an overview of recent development efforts to extend and improve the wide temperature performance of these devices.

Study on the properties of infrared wavefront coding athermal system under several typical temperature gradient distributions

NASA Astrophysics Data System (ADS)

Cai, Huai-yu; Dong, Xiao-tong; Zhu, Meng; Huang, Zhan-hua

2018-01-01

Wavefront coding for athermal technique can effectively ensure the stability of the optical system imaging in large temperature range, as well as the advantages of compact structure and low cost. Using simulation method to analyze the properties such as PSF and MTF of wavefront coding athermal system under several typical temperature gradient distributions has directive function to characterize the working state of non-ideal temperature environment, and can effectively realize the system design indicators as well. In this paper, we utilize the interoperability of data between Solidworks and ZEMAX to simplify the traditional process of structure/thermal/optical integrated analysis. Besides, we design and build the optical model and corresponding mechanical model of the infrared imaging wavefront coding athermal system. The axial and radial temperature gradients of different degrees are applied to the whole system by using SolidWorks software, thus the changes of curvature, refractive index and the distance between the lenses are obtained. Then, we import the deformation model to ZEMAX for ray tracing, and obtain the changes of PSF and MTF in optical system. Finally, we discuss and evaluate the consistency of the PSF (MTF) of the wavefront coding athermal system and the image restorability, which provides the basis and reference for the optimal design of the wavefront coding athermal system. The results show that the adaptability of single material infrared wavefront coding athermal system to axial temperature gradient can reach the upper limit of temperature fluctuation of 60°C, which is much higher than that of radial temperature gradient.

Communication: Equilibrium rate coefficients from atomistic simulations: The O({sup 3}P) + NO({sup 2}Π) → O{sub 2}(X{sup 3}Σ{sub g}{sup −}) + N({sup 4}S) reaction at temperatures relevant to the hypersonic flight regime

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

Castro-Palacio, Juan Carlos; Bemish, Raymond J.; Meuwly, Markus, E-mail: m.meuwly@unibas.ch

2015-03-07

The O({sup 3}P) + NO({sup 2}Π) → O{sub 2}(X{sup 3}Σ{sub g}{sup −}) + N({sup 4}S) reaction is among the N- and O- involving reactions that dominate the energetics of the reactive air flow around spacecraft during hypersonic atmospheric re-entry. In this regime, the temperature in the bow shock typically ranges from 1000 to 20 000 K. The forward and reverse rate coefficients for this reaction derived directly from trajectory calculations over this range of temperature are reported in this letter. Results compare well with the established equilibrium constants for the same reaction from thermodynamic quantities derived from spectroscopy in the gasmore » phase which paves the way for large-scale in silico investigations of equilibrium rates under extreme conditions.« less

Properties of AGN coronae in the NuSTAR era - II. Hybrid plasma

NASA Astrophysics Data System (ADS)

Fabian, A. C.; Lohfink, A.; Belmont, R.; Malzac, J.; Coppi, P.

2017-05-01

The corona, a hot cloud of electrons close to the centre of the accretion disc, produces the hard X-ray power-law continuum commonly seen in luminous active galactic nuclei. The continuum has a high-energy turnover, typically in the range of one to several 100 keV and is suggestive of Comptonization by thermal electrons. We are studying hard X-ray spectra of AGN obtained with NuSTAR after correction for X-ray reflection and under the assumption that coronae are compact, being only a few gravitational radii in size as indicated by reflection and reverberation modelling. Compact coronae raise the possibility that the temperature is limited and indeed controlled by electron-positron pair production, as explored earlier (Paper I). Here, we examine hybrid plasmas in which a mixture of thermal and non-thermal particles is present. Pair production from the non-thermal component reduces the temperature leading to a wider temperature range more consistent with observations.

Evaporation of Water Droplets Moving Through High-Temperature Gases

NASA Astrophysics Data System (ADS)

Kuznetsov, G. V.; Strizhak, P. A.

2018-01-01

With the use of high-speed recording and diagnostic facilities, an experimental study has been made of the evaporation of droplets (of characteristic size Rm ≈ 0.05-0.035 mm) of atomized flow of water-based suspensions with typical soil impurities (silt and clay) moving in a high-temperature (about 1100 K) gaseous medium (with the example of acetone combustion products). The relative mass concentration of soil components in the suspension was varied over the range of γ = 0-1%. A strong influence of the above impurities on the main characteristic of evaporation — the relative change in the droplet radius ΔR — has been established. The influence of the initial temperature (varied over the range of Tw = 278-320 K) of the atomized suspension on the evaporation rate of the latter has been determined. It has been shown that the values of integral characteristics of the process of evaporation of suspensions with soil impurities can be much (2-3 times) higher than for water without these components.

Switching phenomenon in a Se{70}Te{30-x}Cd{x} films

NASA Astrophysics Data System (ADS)

Afifi, M. A.; Bekheet, A. E.; Hegab, N. A.; Wahab, L. A.; Shehata, H. A.

2007-11-01

Amorphous Se{70}Te{30-x}Cd{x} (x = 0, 10) are obtained by thermal evaporation under vacuum of bulk materials on pyrographite and glass substrates. The I-V characteristic curves for the two film compositions are typical for a memory switch. They exhibited a transition from an ohmic region in the lower field followed by non-ohmic region in the high field region in the preswitching region, which has been explained by the Poole-Frenkel effect. The temperature dependence of current in the ohmic region is found to be of thermally activated process. The mean value of the threshold voltage bar{V}th increases linearly with increasing film thickness in the thickness range (100 491 nm), while it decreases exponentially with increasing temperature in the temperature range (293 343 K) for both compositions. The results are explained in accordance with the electrothermal model for the switching process. The effect of Cd on these parameters is also investigated.

The effect of simulated cold weather transport on core body temperature and behavior of broilers.

PubMed

Strawford, M L; Watts, J M; Crowe, T G; Classen, H L; Shand, P J

2011-11-01

During the winter in Western Canada, broilers are routinely transported in ambient temperatures ranging from 0°C to -40°C, yet there is little research in this area. This study examined the physiology and behavior of broilers undergoing simulated transport at typical Western Canadian winter temperatures. Groups of 15 broilers aged 32 to 33 d were exposed to an air stream regulated to -5, -10, or -15°C. Birds were placed into a typical transport drawer. Following baseline observations, the drawer was placed into a test chamber where cold air was drawn past the birds for 3 h. Three replications were conducted at each temperature. The birds adjusted their position within the drawer based upon the temperature distribution within the drawer. In comparison to the baseline period, exposing the birds to a cold air stream caused them to avoid the front plane (P = 0.003) which was the coldest area within the drawer. The birds did not adjust their usage of the middle (P = 0.308) and rear (P = 0.640) planes, because these were the warmer areas within the drawer. The total amount of space the birds occupied within the drawer did not decrease when exposed to the test chamber (P = 0.669). The core body temperature (CBT) did not vary and was within the known normal range during the normal (P = 0.528), pre-chamber (P = 0.060), and post-chamber (P = 0.285) periods. The CBT of the birds significantly decreased during the in-chamber period (P < 0.001) and then increased during the lairage period (P < 0.001). The shrink loss (P = 0.981) and amount of time to resume feed consumption (P = 0.357) were not affected by exposing the birds to temperatures of -5°C and colder. Exposing birds to temperatures of -5°C and colder had a negative effect on the CBT of the birds. However, the birds demonstrated behaviors which mitigated the negative effect that cold exposure could have on their CBT.

High Temperature Catalytic Combustion Suppports Final Report CRADA No. TSB-0841-94

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

Hair, Lucy; Magno, Scott

This Small Business CRADA between LLNL and Catalytica was executed on January 25, 1995. The total estimated cost of this project was 113K. LLNL's contribution was estimated at $50K funded under the DOE/Defense Program Small Business Initiative. Catalytica's in-kind contribution was estimated at 63K. Catalytic combusion catalyst systems operate at temperatures from 600°C to above 1300°C. Catalytica has developed technology that limits the catalyst temperature to below 1000°C. At temperatures in the range of 850 to 1000°C, the thermal stability of the catalyst is an important issue. Typical supports such as stabilized aluminas, hexaluminates, zirconia and stabilized zirconia supports aremore » typically used but lack either thermal stability or other desirable properties. Catalytica had developed a new concept for thermally stable mixed oxide supports but this concept required the preparation of molecularly uniform precursors; that is, prior to high temperature treatment of these materials, the elements that make up the mixed oxide must be as nearly uniform as possible on a molecular level. The technique of sol gel processing appeared to be the preferred technique to make these molecularly uniform precursors, and a cooperative program with LLNL was established to prepare and test the proposed compounds. Catalytica proposed the composition and concentration levels for the materials to be prepared.« less

Parametric Study of Solder Flux Hygroscopicity: Impact of Weak Organic Acids on Water Layer Formation and Corrosion of Electronics

NASA Astrophysics Data System (ADS)

Piotrowska, Kamila; Ud Din, Rameez; Grumsen, Flemming Bjerg; Jellesen, Morten Stendahl; Ambat, Rajan

2018-07-01

The presence of solder flux residues on the printed circuit board assembly surface is an important factor contributing to humidity-related reliability issues that affect device lifetime. This investigation focuses on understanding the hygroscopic nature of typical wave solder flux activators—weak organic acids—under varied temperature conditions. In situ x-ray diffraction measurements assessed the effect of high temperature on the crystal structure of organic activators. The hygroscopicity studies were carried out under relative humidity (RH) levels varying from 30% to ˜ 99% and at temperatures 25°C, 40°C, and 60°C. Water absorption levels were determined using the gravimetric method, and the influence on reliability was assessed using electrochemical impedance and leak current measurements performed on the surface insulation resistance comb patterns. The corrosion studies were correlated with the hygroscopicity results and solubility data. Corrosion morphology was analysed using the optical microscopy and scanning electron microscopy. The results show that the hygroscopic nature of typical solder flux residue depends on its chemical structure and temperature. An increase of temperature shifts the critical RH level for water vapour absorption towards lower RH range, accelerating the formation of a conductive electrolyte and the occurrence of ion transport-induced electrochemical migration. The overall ranking of flux activators with the increasing order of aggressivity is: palmitic < suberic < adipic < succinic < glutaric < dl-malic acid.

Parametric Study of Solder Flux Hygroscopicity: Impact of Weak Organic Acids on Water Layer Formation and Corrosion of Electronics

NASA Astrophysics Data System (ADS)

Piotrowska, Kamila; Ud Din, Rameez; Grumsen, Flemming Bjerg; Jellesen, Morten Stendahl; Ambat, Rajan

2018-04-01

The presence of solder flux residues on the printed circuit board assembly surface is an important factor contributing to humidity-related reliability issues that affect device lifetime. This investigation focuses on understanding the hygroscopic nature of typical wave solder flux activators—weak organic acids—under varied temperature conditions. In situ x-ray diffraction measurements assessed the effect of high temperature on the crystal structure of organic activators. The hygroscopicity studies were carried out under relative humidity (RH) levels varying from 30% to ˜ 99% and at temperatures 25°C, 40°C, and 60°C. Water absorption levels were determined using the gravimetric method, and the influence on reliability was assessed using electrochemical impedance and leak current measurements performed on the surface insulation resistance comb patterns. The corrosion studies were correlated with the hygroscopicity results and solubility data. Corrosion morphology was analysed using the optical microscopy and scanning electron microscopy. The results show that the hygroscopic nature of typical solder flux residue depends on its chemical structure and temperature. An increase of temperature shifts the critical RH level for water vapour absorption towards lower RH range, accelerating the formation of a conductive electrolyte and the occurrence of ion transport-induced electrochemical migration. The overall ranking of flux activators with the increasing order of aggressivity is: palmitic < suberic < adipic < succinic < glutaric < uc(dl)-malic acid.

Effect of test temperature and strain rate on the tensile properties of high-strength, high-conductivity copper alloys

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

Zinkle, S.J.; Eatherly, W.S.

1997-04-01

The unirradiated tensile properties of wrought GlidCop AL25 (ITER grade zero, IGO) solutionized and aged CuCrZr, and cold-worked and aged and solutionized and aged Hycon 3HP{trademark} CuNiBe have been measured over the temperature range of 20-500{degrees}C at strain rates between 4 x 10{sup {minus}4} s{sup {minus}1} and 0.06 s{sup {minus}1}. The measured room temperature electrical conductivity ranged from 64 to 90% IACS for the different alloys. All of the alloys were relatively insensitive to strain rate at room temperature, but the strain rate sensitivity of GlidCop Al25 increased significantly with increasing temperature. The CuNiBe alloys exhibited the best combination ofmore » high strength and high conductivity at room temperature. The strength of CuNiBe decreased slowly with increasing temperature. However, the ductility of CuNiBe decreased rapidly with increasing temperature due to localized deformation near grain boundaries, making these alloy heats unsuitable for typical structural applications above 300{degrees}C. The strength and uniform elongation of GlidCop Al25 decreased significantly with increasing temperature at a strain rate of 1 x 10{sup {minus}3} s{sup {minus}1}, whereas the total elongation was independent of test temperature. The strength and ductility of CuCrZr decreased slowly with increasing temperature.« less

Fulgurites: a rock magnetic study of mineralogical changes caused by lightning

NASA Astrophysics Data System (ADS)

Begnini, G. S.; Tohver, E.; Schmieder, M.

2013-05-01

Fulgurites are natural glass samples produced by lightning strikes on rock or soil substrates. Instantaneous electrical discharges of 10-200 kA are typical, and the temperatures produced by lightning strikes exceed 1700C, the melting temperature of quartz. Paleomagnetic observations of lightning strikes typically include high intensity remanent magnetizations with highly-variable to random magnetic directions. Alternating field demagnetization is commonly used to remove the overprinting effects of Lightning Induced Remanent Magnetization (LIRM), indicating low coercivities of the magnetic carriers. We conducted a rock magnetic analysis of 15 specimens of natural fulgurite from South Africa including hysteresis and thermoremanent heating and cooling experiments using a Variable Field Translational Balance. The analysed specimens demonstrate two distinct ranges of Curie temperature: 440-600C and 770-778C, suggesting the presence of both iron oxides (likely Fe-rich magnetite) and a reduced iron alloy, likely kamacite. High temperature, highly reduced assemblages have been reported from petrological observations of fulgurites. Our rock magnetic observations of a metallic iron phase in the fulgurite samples from a terrestrial, surficial environment demonstrates a mineralogical resemblance to differentiated, iron-rich meteorites. We suggest that LIRMs in lightning-struck localities may include a chemical remagnetization associated with lightning-induced electrolysis or reduction of iron oxides.

Design study of shaft face seal with self-acting lift augmentation. 4: Force balance

NASA Technical Reports Server (NTRS)

Ludwig, L. P.; Zuk, J.; Johnson, R. L.

1972-01-01

A method for predicting the operating film thickness of self-acting seals is described. The analysis considers a 16.76-cm mean diameter seal that is typical of large gas turbines for aircraft. Four design points were selected to cover a wide range of operation for advanced engines. This operating range covered sliding speeds of 61 to 153 m/sec, sealed pressures of 45 to 217 N/sq cm abs, and gas temperatures of 311 to 977 K. The force balance analysis revealed that the seal operated without contact over the operating range with gas film thicknesses ranging between 0.00046 to 0.00119 cm, and with gas leakage rates between 0.01 to 0.39 scmm.

Observations of the effect of wind on the cooling of active lava flows

USGS Publications Warehouse

Keszthelyi, L.; Harris, A.J.L.; Dehn, J.

2003-01-01

We present the first direct observations of the cooling of active lava flows by the wind. We confirm that atmospheric convective cooling processes (i.e., the wind) dominate heat loss over the lifetime of a typical pahochoe lava flow. In fact, the heat extracted by convection is greater than predicted, especially at wind speeds less than 5 m/s and surface temperatures less than 400??C. We currently estimate that the atmospheric heat transfer coefficient is about 45-50 W m-2 K-1 for a 10 m/s wind and a surface temperature ???500??C. Further field experiments and theoretical studies should expand these results to a broader range of surface temperatures and wind speeds.

Assessment of Turbulent CFD Against STS-128 Hypersonic Flight Data

NASA Technical Reports Server (NTRS)

Wood, William A.; Kleb, William L.; Hyatt, Andrew J.

2010-01-01

Turbulent CFD simulations are compared against surface temperature measurements of the space shuttle orbiter windward tiles at reentry flight conditions. Algebraic turbulence models are used within both the LAURA and DPLR CFD codes. The flight data are from temperature measurements obtained by seven thermocouples during the STS-128 mission (September 2009). The flight data indicate boundary layer transition onset over the Mach number range 13.5{15.5, depending upon the location on the vehicle. But the boundary layer flow appeared to be transitional down through Mach 12, based upon the flight data and CFD trends. At Mach 9 the simulations match the flight data on average within 20 F/11 C, where typical surface temperatures were approximately 1600 F/870 C.

Cryogenic High-Sensitivity Magnetometer

NASA Technical Reports Server (NTRS)

Day, Peter; Chui, Talso; Goodstein, David

2005-01-01

A proposed magnetometer for use in a cryogenic environment would be sensitive enough to measure a magnetic-flux density as small as a picogauss (10(exp -16) Tesla). In contrast, a typical conventional flux-gate magnetometer cannot measure a magnetic-flux density smaller that about 1 microgauss (10(exp -10) Tesla). One version of this device, for operation near the low end of the cryogenic temperature range, would include a piece of a paramagnetic material on a platform, the temperature of which would be controlled with a periodic variation. The variation in temperature would be measured by use of a conventional germanium resistance thermometer. A superconducting coil would be wound around the paramagnetic material and coupled to a superconducting quantum interference device (SQUID) magnetometer.

Estimating vapor pressures of pure liquids

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

Haraburda, S.S.

1996-03-01

Calculating the vapor pressures for pure liquid chemicals is a key step in designing equipment for separation of liquid mixtures. Here is a useful way to develop an equation for predicting vapor pressures over a range of temperatures. The technique uses known vapor pressure points for different temperatures. Although a vapor-pressure equation is being showcased in this article, the basic method has much broader applicability -- in fact, users can apply it to develop equations for any temperature-dependent model. The method can be easily adapted for use in software programs for mathematics evaluation, minimizing the need for any programming. Themore » model used is the Antoine equation, which typically provides a good correlation with experimental or measured data.« less

Homogeneous freezing of single sulfuric and nitric acid solution drops levitated in an acoustic trap

NASA Astrophysics Data System (ADS)

Diehl, Karoline; Ettner-Mahl, Matthias; Hannemann, Anke; Mitra, Subir K.

2009-10-01

The freezing temperatures of single supercooled drops of binary and ternary sulfuric and nitric acid solutions were measured while varying the acid concentration. An acoustic levitator was used which allows to freely suspend single solution drops in air without electrical charges thereby avoiding any electrical influences which may affect the freezing process. The drops of typically 500 µm in radius were monitored by a video camera during cooling cycles down to - 85 °C to simulate the upper tropospheric and stratospheric temperature range. The present data confirm that liquid solution droplets can be supercooled far below the equilibrium melting point by approximately 35 °C. They follow the general trend of the expected freezing temperatures for homogeneous ice nucleation.

Elastic precursor wave decay in shock-compressed aluminum over a wide range of temperature

NASA Astrophysics Data System (ADS)

Austin, Ryan A.

2018-01-01

The effect of temperature on the dynamic flow behavior of aluminum is considered in the context of precursor wave decay measurements and simulations. In this regard, a dislocation-based model of high-rate metal plasticity is brought into agreement with previous measurements of evolving wave profiles at 300 to 933 K, wherein the amplification of the precursor structure with temperature arises naturally from the dislocation mechanics treatment. The model suggests that the kinetics of inelastic flow and stress relaxation are governed primarily by phonon scattering and radiative damping (sound wave emission from dislocation cores), both of which intensify with temperature. The manifestation of these drag effects is linked to low dislocation density ahead of the precursor wave and the high mobility of dislocations in the face-centered cubic lattice. Simulations performed using other typical models of shock wave plasticity do not reproduce the observed temperature-dependence of elastic/plastic wave structure.

The effects of host size and temperature on the emergence of Echinoparyphium recurvatum cercariae from Lymnaea peregra under natural light conditions.

PubMed

Morley, N J; Adam, M E; Lewis, J W

2010-09-01

The production of cercariae from their snail host is a fundamental component of transmission success in trematodes. The emergence of Echinoparyphium recurvatum (Trematoda: Echinostomatidae) cercariae from Lymnaea peregra was studied under natural sunlight conditions, using naturally infected snails of different sizes (10-17 mm) within a temperature range of 10-29 degrees C. There was a single photoperiodic circadian cycle of emergence with one peak, which correlated with the maximum diffuse sunlight irradiation. At 21 degrees C the daily number of emerging cercariae increased with increasing host snail size, but variations in cercarial emergence did occur between both individual snails and different days. There was only limited evidence of cyclic emergence patterns over a 3-week period, probably due to extensive snail mortality, particularly those in the larger size classes. Very few cercariae emerged in all snail size classes at the lowest temperature studied (10 degrees C), but at increasingly higher temperatures elevated numbers of cercariae emerged, reaching an optimum between 17 and 25 degrees C. Above this range emergence was reduced. At all temperatures more cercariae emerged from larger snails. Analysis of emergence using the Q10 value, a measure of physiological processes over temperature ranges, showed that between 10 and 21 degrees C (approximately 15 degrees C) Q10 values exceeded 100 for all snail size classes, indicating a substantially greater emergence than would be expected for normal physiological rates. From 14 to 25 degrees C (approximately 20 degrees C) cercarial emergence in most snail size classes showed little change in Q10, although in the smallest size class emergence was still substantially greater than the typical Q10 increase expected over this temperature range. At the highest range of 21-29 degrees C (approximately 25 degrees C), Q10 was much reduced. The importance of these results for cercarial emergence under global climate change is discussed.

Global Assessment of Land Surface Temperature From Geostationary Satellites and Model Estimates

NASA Technical Reports Server (NTRS)

Reichle, Rolf H.; Liu, Q.; Minnis, P.; daSilva, A. M., Jr.; Palikonda, R.; Yost, C. R.

2012-01-01

Land surface (or 'skin') temperature (LST) lies at the heart of the surface energy balance and is a key variable in weather and climate models. In this research we compare two global and independent data sets: (i) LST retrievals from five geostationary satellites generated at the NASA Langley Research Center (LaRC) and (ii) LST estimates from the quasi-operational NASA GEOS-5 global modeling and assimilation system. The objective is to thoroughly understand both data sets and their systematic differences in preparation for the assimilation of the LaRC LST retrievals into GEOS-5. As expected, mean differences (MD) and root-mean-square differences (RMSD) between modeled and retrieved LST vary tremendously by region and time of day. Typical (absolute) MD values range from 1-3 K in Northern Hemisphere mid-latitude regions to near 10 K in regions where modeled clouds are unrealistic, for example in north-eastern Argentina, Uruguay, Paraguay, and southern Brazil. Typically, model estimates of LST are higher than satellite retrievals during the night and lower during the day. RMSD values range from 1-3 K during the night to 2-5 K during the day, but are larger over the 50-120 W longitude band where the LST retrievals are derived from the FY2E platform

Key optical components for spaceborne lasers

NASA Astrophysics Data System (ADS)

Löhring, J.; Winzen, M.; Faidel, H.; Miesner, J.; Plum, D.; Klein, J.; Fitzau, O.; Giesberts, M.; Brandenburg, W.; Seidel, A.; Schwanen, N.; Riesters, D.; Hengesbach, S.; Hoffmann, H.-D.

2016-03-01

Spaceborne lidar (light detection and ranging) systems have a large potential to become powerful instruments in the field of atmospheric research. Obviously, they have to be in operation for about three years without any maintenance like readjusting. Furthermore, they have to withstand strong temperature cycles typically in the range of -30 to +50 °C as well as mechanical shocks and vibrations, especially during launch. Additionally, the avoidance of any organic material inside the laser box is required, particularly in UV lasers. For atmospheric research pulses of about several 10 mJ at repetition rates of several 10 Hz are required in many cases. Those parameters are typically addressed by DPSSL that comprise components like: laser crystals, nonlinear crystals in pockels cells, faraday isolators and frequency converters, passive fibers, diode lasers and of course a lot of mirrors and lenses. In particular, some components have strong requirements regarding their tilt stability that is often in the 10 μrad range. In most of the cases components and packages that are used for industrial lasers do not fulfil all those requirements. Thus, the packaging of all these key components has been developed to meet those specifications only making use of metal and ceramics beside the optical component itself. All joints between the optical component and the laser baseplate are soldered or screwed. No clamps or adhesives are used. Most of the critical properties like tilting after temperature cycling have been proven in several tests. Currently, these components are used to build up first prototypes for spaceborne systems.

Simulations of magnetic hysteresis loops at high temperatures

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

Plumer, M. L.; Whitehead, J. P.; Fal, T. J.

2014-09-28

The kinetic Monte-Carlo algorithm as well as standard micromagnetics are used to simulate MH loops of high anisotropy magnetic recording media at both short and long time scales over a wide range of temperatures relevant to heat-assisted magnetic recording. Microscopic parameters, common to both methods, were determined by fitting to experimental data on single-layer FePt-based media that uses the Magneto-Optic Kerr effect with a slow sweep rate of 700 Oe/s. Saturation moment, uniaxial anisotropy, and exchange constants are given an intrinsic temperature dependence based on published atomistic simulations of FePt grains with an effective Curie temperature of 680 K. Ourmore » results show good agreement between micromagnetics and kinetic Monte Carlo results over a wide range of sweep rates. Loops at the slow experimental sweep rates are found to become more square-shaped, with an increasing slope, as temperature increases from 300 K. These effects also occur at higher sweep rates, typical of recording speeds, but are much less pronounced. These results demonstrate the need for accurate determination of intrinsic thermal properties of future recording media as input to micromagnetic models as well as the sensitivity of the switching behavior of thin magnetic films to applied field sweep rates at higher temperatures.« less

Chemical compatibility of some ceramic matrix composite structures with fusion reactor helium coolant at high temperatures

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

Perez, F.J.; Ghoniem, N.M.

The thermodynamic stability of SiC/SiC composite structures proposed for fusion applications is presented in this paper. Minimization of the free energy for reacting species in the temperature range 773-1273 K is achieved by utilizing the NASA-Lewis Chemical Equilibrium Thermodynamics Code (CET). The chemical stability of the matrix (SiC), as well as several potential fiber coatings are studied. Helium coolant is assumed to contain O{sub 2} and water moisture impurities in the range 100-1000 ppm. The work is applied to recent Magnetic and Inertial Confinement Conceptual designs. The present study indicated that the upper useful temperature limit for SiC/SiC composites, frommore » the standpoint of high-temperature corrosion, will be in the neighborhood of 1273 K. Up to this temperature, corrosion of SiC is shown to be negligible. The main mechanism of weight loss will be by evaporation to the plasma side. The presence of a protective SiO{sub 2} condensed phase is discussed, and is shown to result in further reduction of high-temperature corrosion. The thermodynamic stability of C and BN is shown to be very poor under typical fusion reactor conditions. Further development of chemically stable interface materials is required.« less

Packaging of fiber lasers and components for use in harsh environments

NASA Astrophysics Data System (ADS)

Creeden, Daniel; Johnson, Benjamin R.; Jones, Casey; Ibach, Charles; Lemons, Michael; Budni, Peter A.; Zona, James P.; Marcinuk, Adam; Willis, Chris; Sweeney, James; Setzler, Scott D.

2016-03-01

High power continuous and pulsed fiber lasers and amplifiers have become more prevalent in laser systems over the last ten years. In fielding such systems, strong environmental and operational factors drive the packaging of the components. These include large operational temperature ranges, non-standard wavelengths of operation, strong vibration, and lack of water cooling. Typical commercial fiber components are not designed to survive these types of environments. Based on these constraints, we have had to develop and test a wide range of customized fiber-based components and systems to survive in these conditions. In this paper, we discuss some of those designs and detail the testing performed on those systems and components. This includes the use of commercial off-the-shelf (COTS) components, modified to survive extended temperature ranges, as well as customized components designed specifically for performance in harsh environments. Some of these custom components include: ruggedized/monolithic fiber spools; detachable and repeatable fiber collimators; low loss fiber-to-fiber coupling schemes; and high power fiber-coupled isolators.

Infrared and infrared emission spectroscopic study of typical Chinese kaolinite and halloysite.

PubMed

Cheng, Hongfei; Frost, Ray L; Yang, Jing; Liu, Qinfu; He, Junkai

2010-12-01

The structure and thermal stability between typical Chinese kaolinite and halloysite were analysed by X-ray diffraction (XRD), infrared spectroscopy, infrared emission spectroscopy (IES) and Raman spectroscopy. Infrared emission spectroscopy over the temperature range of 300-700°C has been used to characterise the thermal decomposition of both kaolinite and halloysite. Halloysite is characterised by two bands in the water bending region at 1629 and 1648 cm(-1), attributed to structural water and coordinated water in the interlayer. Well defined hydroxyl stretching bands at around 3695, 3679, 3652 and 3625 cm(-1) are observed for both kaolinite and halloysite. The 550°C infrared emission spectrum of halloysite is similar to that of kaolinite in 650-1350 cm(-1) spectral region. The infrared emission spectra of halloysite were found to be considerably different to that of kaolinite at lower temperatures. These differences are attributed to the fundamental difference in the structure of the two minerals. Copyright © 2010 Elsevier B.V. All rights reserved.

Atmospheric controls on elephant communication.

PubMed

Garstang, M; Larom, D; Raspet, R; Lindeque, M

1995-04-01

Atmospheric conditions conducive to long-range transmission of low-frequency sound as used by elephants are found to exist in the Etosha National Park in Namibia during the late dry season. Meteorological measurements show that strong temperature inversions form at the surface before sunset and decay with sunrise, often accompanied by calm wind conditions during the early evening. These observations are used in an acoustic model to determine the sensitivity of infrasound to the effects of (a) the strength, thickness and elevation of temperature inversions, and (b) the growth and decay of an inversion typical of dry, elevated African savannas. The results suggest that the range over which elephants communicate more than doubles at night. Optimum conditions occur 1-2 h after sunset on clear, relatively cold, calm nights. At these times, ranges of over 10 km are likely, with the greatest amplification occurring at the lowest frequency tested. This strong diurnal cycle in communication range may be reflected in longer-lasting changes in weather and may exert a significant influence on elephant behaviour on time scales from days to many years.

Measurement of the Water Relaxation Time of ɛ-Polylysine Aqueous Solutions

NASA Astrophysics Data System (ADS)

Shirakashi, Ryo; Amano, Yuki; Yamada, Jun

2017-05-01

ɛ-Polylysine is an effective food preservative. In this paper, the β-relaxation time of ɛ-polylysine aqueous solutions, which represents the rotational speed of a single water molecule, was measured by broadband dielectric spectroscopy at various temperatures and concentrations. The broadband dielectric spectrum of each sample containing water ranging from 35 wt% to 75 wt% at temperatures ranging from 0°C to 25°C was measured using a co-axial semirigid cable probe. The measured dielectric spectra of the samples were composed of several Debye relaxation peaks, including a shortest single molecular rotational relaxation time of water, the β-relaxation time, longer than that of pure water. This result represents that ɛ-polylysine suppresses the molecular kinetics of water. It is also found that the β-relaxation time of an ɛ-polylysine solution that contained more than 35 wt% water showed a typical Arrhenius plot in the temperature range from 0°C to 25°C. The activation energy of each sample depends on the water content ratio of the sample. As indicated by its long β-relaxation time, ɛ-polylysine is expected to possess high abilities of suppressing freezing and ice coarsening.

Temperature regulation and metabolism of an Australian bat, Chalinolobus gouldii (Chiroptera:Vespertilionidae) when euthermic and torpid.

PubMed

Hosken, D J; Withers, P C

1997-01-01

The thermal and metabolic physiology of Chalinolobus gouldii, an Australian vespertilionid bat, was studied in the laboratory using flow-through respirometry. Chalinolobus gouldii exhibits a clear pattern of euthermic thermoregulation, typical of endotherms with respect to body temperature and rate of oxygen consumption. The basal metabolic rate of euthermic Chalinolobus gouldii is approximately 86% of that predicted for a 17.5-g mammal and falls into the range of mass-specific basal metabolic rates ascribed to vespertilionid bats. However, like most vespertilionid bats, Chalinolobus gouldii displays extreme thermolability. It is able to enter into torpor and spontaneously arouse at ambient temperatures as low as 5 degrees C. Torpid bats thermoconform at moderate ambient temperature, with body temperature approximately ambient temperature, and have a low rate of oxygen consumption determined primarily by Q10 effects. At low ambient temperature (< 10 degrees C), torpid C. gouldii begin to regulate their body temperature by increased metabolic heat production; they tend to maintain a higher body temperature at low ambient temperature than do many northern hemisphere hibernating bats. Use of torpor leads to significant energy savings. The evaporative water loss of euthermic bats is relatively high, which seems unusual for a bat whose range includes extremely arid areas of Australia, and is reduced during torpor. The thermal conductance of euthermic C. gouldii is less than that predicted for a mammal of its size. The thermal conductance is considerably lower for torpid bats at intermediate body temperature and ambient temperature, but increases to euthermic values for torpid bats when thermoregulating at low ambient temperature.

Sensitivity of fields generated within magnetically shielded volumes to changes in magnetic permeability

NASA Astrophysics Data System (ADS)

Andalib, T.; Martin, J. W.; Bidinosti, C. P.; Mammei, R. R.; Jamieson, B.; Lang, M.; Kikawa, T.

2017-09-01

Future experiments seeking to measure the neutron electric dipole moment (nEDM) require stable and homogeneous magnetic fields. Normally these experiments use a coil internal to a passively magnetically shielded volume to generate the magnetic field. The stability of the magnetic field generated by the coil within the magnetically shielded volume may be influenced by a number of factors. The factor studied here is the dependence of the internally generated field on the magnetic permeability μ of the shield material. We provide measurements of the temperature-dependence of the permeability of the material used in a set of prototype magnetic shields, using experimental parameters nearer to those of nEDM experiments than previously reported in the literature. Our measurements imply a range of 1/μ dμ/dT from 0-2.7%/K. Assuming typical nEDM experiment coil and shield parameters gives μ/B0 dB0/dμ = 0.01, resulting in a temperature dependence of the magnetic field in a typical nEDM experiment of dB0/dT = 0 - 270 pT/K for B0 = 1 μT. The results are useful for estimating the necessary level of temperature control in nEDM experiments.

Crystal zoning in a large-volume ignimbrite: constraints on the thermal history of a supervolcano magma system

NASA Astrophysics Data System (ADS)

Matthews, N. E.; Pyle, D. M.; Wilson, C. J.

2009-12-01

Chemical zoning of crystals provides an important archive of information that allows for the reconstruction of complex thermal histories and changes in melt composition of the magma reservoir during crystallization. Here we investigate cathodoluminescence (CL) and Ti zonation in quartz crystals extracted from pumices from the Whakamaru and Rangitaiki ignimbrite units (part of the large-volume Whakamaru Group Ignimbrites), New Zealand, to reconstruct the thermal history of the parent magma chamber(s). CL intensity images are taken as a proxy for Ti content and temperature variation during crystal growth, and direct estimates of temperature are made using the TitaniQ geothermometer (Wark & Watson 2006 Cont. Min. Pet.) based on Ti concentration in quartz. These results are reviewed in comparison with temperatures from Fe-Ti oxide geothermometry. Quartz zoning is also compared to zonation in feldspars (using BSE imaging) from the same pumice clasts in order to establish the degree to which different crystal species record similar or contrasting magmatic histories. Quartz crystals in Whakamaru pumice display a variety of CL zoning patterns and resorption boundaries. Overgrowths typically appear to truncate CL growth zoning within the crystal core, indicating periods of resorption and subsequent re-growth - consistent with magma recharge causing a marked change in conditions (temperature and/or volatile saturation) and multi-stage crystallisation. Crystals typically display a dark (lower Ti) resorbed core, with an abrupt change to a CL-bright rim, although irregular textures and complex variations between crystals are observed. Core-to-rim profiles of Ti concentration in analysed quartz crystals show Ti variations within the range 50-225 ppm, corresponding to crystallisation temperatures of 733-935°C (assuming TiO2 activity in the melt of 0.6), with the lowest values recorded in the crystal core, increasing in a step-wise pattern towards the rim. These values are consistent with Fe-Ti oxide temperature data for the same pumice clasts which provide a temperature range of 660-933°C. It is inferred that the major steps in Ti content (and thus CL brightness) represent short-term temperature fluctuations due to magma chamber recharge and rejuvenation of a crystal mush, while rim temperatures are likely to record the magma temperature at the time of eruption.

The thermal regime around buried submarine high-voltage cables

NASA Astrophysics Data System (ADS)

Emeana, C. J.; Hughes, T. J.; Dix, J. K.; Gernon, T. M.; Henstock, T. J.; Thompson, C. E. L.; Pilgrim, J. A.

2016-08-01

The expansion of offshore renewable energy infrastructure and the need for trans-continental shelf power transmission require the use of submarine high-voltage (HV) cables. These cables have maximum operating surface temperatures of up to 70 °C and are typically buried 1-2 m beneath the seabed, within the wide range of substrates found on the continental shelf. However, the heat flow pattern and potential effects on the sedimentary environments around such anomalously high heat sources in the near-surface sediments are poorly understood. We present temperature measurements from a 2-D laboratory experiment representing a buried submarine HV cable, and identify the thermal regimes generated within typical unconsolidated shelf sediments—coarse silt, fine sand and very coarse sand. We used a large (2 × 2.5 m2) tank filled with water-saturated spherical glass beads (ballotini) and instrumented with a buried heat source and 120 thermocouples to measure the time-dependent 2-D temperature distributions. The observed and corresponding Finite Element Method simulations of the steady state heat flow regimes and normalized radial temperature distributions were assessed. Our results show that the heat transfer and thus temperature fields generated from submarine HV cables buried within a range of sediments are highly variable. Coarse silts are shown to be purely conductive, producing temperature increases of >10 °C up to 40 cm from the source of 60 °C above ambient; fine sands demonstrate a transition from conductive to convective heat transfer between cf. 20 and 36 °C above ambient, with >10 °C heat increases occurring over a metre from the source of 55 °C above ambient; and very coarse sands exhibit dominantly convective heat transfer even at very low (cf. 7 °C) operating temperatures and reaching temperatures of up to 18 °C above ambient at a metre from the source at surface temperatures of only 18 °C. These findings are important for the surrounding near-surface environments experiencing such high temperatures and may have significant implications for chemical and physical processes operating at the grain and subgrain scale; biological activity at both microfaunal and macrofaunal levels; and indeed the operational performance of the cables themselves, as convective heat transport would increase cable current ratings, something neglected in existing standards.

Modeling Control Strategies and Range Impacts for Electric Vehicle Integrated Thermal Management Systems with MATLAB/Simulink

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

Titov, Gene; Lustbader, Jason Aaron

The National Renewable Energy Laboratory's (NREL's) CoolSim MATLAB/Simulink modeling framework was used to explore control strategies for an electric vehicle combined loop system. Three system variants of increased complexity and efficiency were explored: a glycol-based positive temperature coefficient heater (PTC), PTC with power electronics and electric motor (PEEM) waste heat recovery, and PTC with PEEM waste heat recovery plus heat pump versions. Additionally, the benefit of electric motor preheating was considered. A two-level control strategy was developed where the mode selection and component control were treated separately. Only the parameters typically available by vehicle sensors were used to control themore » system. The control approach included a mode selection algorithm and controllers for the compressor speed, cabin blower flow rate, coolant flow rate, and the front-end heat exchanger coolant bypass rate. The electric motor was bypassed by the cooling circuit until its temperature exceeded the coolant inlet temperature. The impact of these thermal systems on electric vehicle range during warmup was simulated for the Urban Dynamometer Driving Schedule (UDDS) and Highway Fuel Economy Test (HWFET2X) drive cycles weighted 45%/55% respectively. A range of ambient temperatures from -20 degrees C to +20 degrees C was considered. NREL's Future Automotive Systems Technology Simulator (FASTSim) vehicle modeling tool showed up to a 10.9% improvement in range for the full system over the baseline during warmup from cold soak. The full system with preheat showed up to 17% improvement in range.« less

Determination and Use of the Local Recovery Factor for Calculating the Effectiveness Gas Temperature for Turbine Blades / Jack B. Esgar and Alfred L. Lea

NASA Technical Reports Server (NTRS)

Esgar, Jack B; Lea, Alfred L

1951-01-01

In an in experimental investigation of local recovery factors for a blade having a pressure distribution similar to that of a typical reaction-type turbine blade, it a was found that the recovery factors were essentially independent of Mach number, Reynolds number, pressure gradient, and position on the blade surface except for regions where the boundary layer was probably in the transition range from laminar to turbulent. The recommended value of local subsonic recovery factor for use in calculating the effective gas temperature for gas turbine blades was 0.89.

Myelin basic protein reduces molecular motions in DMPA, an elastic neutron scattering study

NASA Astrophysics Data System (ADS)

Natali, F.; Gliozzi, A.; Rolandi, R.; Cavatorta, P.; Deriu, A.; Fasano, A.; Riccio, P.

2001-07-01

We have studied the effect of physiological amounts of myelin basic protein (MBP) on pure dimyristoyl L- α-phosphatidic acid (DMPA) vesicles using the elastic neutron scattering technique. Elastic scans have been performed in a wide temperature range (20-300 K). In the lower temperature region the behaviour of the integrated elastic intensity was the typical one of harmonic systems. The analysis of the Q and T dependence performed in terms of an asymmetric double well potential clearly showed that the effect of the protein consisted in a significant reduction of the conformational mobility of the DMPA bilayers and in the stabilisation of the membrane.

Leakage conduction behavior in electron-beam-cured nanoporous silicate films

NASA Astrophysics Data System (ADS)

Liu, Po-Tsun; Tsai, T. M.; Chang, T. C.

2005-05-01

This letter explores the application of electron-beam curing on nanoporous silicate films. The electrical conduction mechanism for the nanoporous silicate film cured by electron-beam radiation has been studied with metal-insulator-semiconductor capacitors. Electrical analyses over a varying temperature range from room temperature to 150°C provide evidence for space-charge-limited conduction in the electron-beam-cured thin film, while Schottky-emission-type leaky behavior is seen in the counterpart typically cured by a thermal furnace. A physical model consistent with electrical analyses is also proposed to deduce the origin of conduction behavior in the nanoporous silicate thin film.

Dimension dependent immunity of X-ray irradiation on low-temperature polycrystalline-silicon TFTs

NASA Astrophysics Data System (ADS)

Wei, Yin-Chang; Li, Yi-Chieh; Lee, I.-Che; Cheng, Huang-Chung

2017-06-01

Typically, each element in a large-area flat-panel X-ray image sensor consists of a photodetector and amorphous silicon (a-Si) thin-film transistor (TFT) switches. In order to reduce noise, increase sensor dynamic range, and increase carrying capacity, the low-temperature polycrystalline-silicon (LTPS) TFTs have been proposed as a candidate to replace the a-Si TFTs. However, there are concerns regarding the impact of X-ray radiation in LTPS-TFTs, and several studies have been conducted to inquire into the same. In this paper, we show that LTPS TFTs with small channel length (<2 µm) are almost immune to X-ray radiation.

Geophysical logging of bedrock wells for geothermal gradient characterization in New Hampshire, 2013

USGS Publications Warehouse

Degnan, James R.; Barker, Gregory; Olson, Neil; Wilder, Leland

2014-01-01

Maximum groundwater temperatures at the bottom of the logs ranged from 11.2 to 15.4 degrees Celsius. Geothermal gradients were generally higher than those 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 4 of the 10 wells studied but only obscured the part of the geothermal gradient signal where groundwater actually flowed into, out of, or through the well. Temperature gradients varied by mapped bedrock type but can also vary by localized differences in mineralogy or rock type within the wells.

Hotter nests produce hatchling lizards with lower thermal tolerance.

PubMed

Dayananda, Buddhi; Murray, Brad R; Webb, Jonathan K

2017-06-15

In many regions, the frequency and duration of summer heatwaves is predicted to increase in future. Hotter summers could result in higher temperatures inside lizard nests, potentially exposing embryos to thermally stressful conditions during development. Potentially, developmentally plastic shifts in thermal tolerance could allow lizards to adapt to climate warming. To determine how higher nest temperatures affect the thermal tolerance of hatchling geckos, we incubated eggs of the rock-dwelling velvet gecko, Amalosia lesueurii , at two fluctuating temperature regimes to mimic current nest temperatures (mean 23.2°C, range 10-33°C, 'cold') and future nest temperatures (mean 27.0°C, range 14-37°C, 'hot'). Hatchlings from the hot incubation group hatched 27 days earlier and had a lower critical thermal maximum (CT max 38.7°C) and a higher critical thermal minimum (CT min 6.2°C) than hatchlings from cold incubation group (40.2 and 5.7°C, respectively). In the field, hatchlings typically settle under rocks near communal nests. During the hatching period, rock temperatures ranged from 13 to 59°C, and regularly exceeded the CT max of both hot- and cold-incubated hatchlings. Because rock temperatures were so high, the heat tolerance of lizards had little effect on their ability to exploit rocks as retreat sites. Instead, the timing of hatching dictated whether lizards could exploit rocks as retreat sites; that is, cold-incubated lizards that hatched later encountered less thermally stressful environments than earlier hatching hot-incubated lizards. In conclusion, we found no evidence that CT max can shift upwards in response to higher incubation temperatures, suggesting that hotter summers may increase the vulnerability of lizards to climate warming. © 2017. Published by The Company of Biologists Ltd.

Temperature dependence of the Raman spectrum of 1-(4-chlorophenyl)-3-(2-thienyl)prop-2-en-1-one

NASA Astrophysics Data System (ADS)

de Toledo, T. A.; da Costa, R. C.; Al-Maqtari, H. M.; Jamalis, J.; Pizani, P. S.

2017-06-01

The heterocyclic chalcone containing thiophene ring 1-(4-chlorophenyl)-3-(2-thienyl)prop-2-en-1-one, C13H9ClOS was synthesized and investigated using experimental techniques such as nuclear magnetic resonance (1H and 13C NMR), Fourier transform infrared spectroscopy (FTIR) at room temperature, differential scanning calorimeter (DSC) from room temperature to 500 K and Raman scattering at the temperature range 10-413 K in order to study its structure and vibrational properties as well as stability and possible phase transition. Density functional theory (DFT) calculations were performed to determine the vibrational spectrum viewing to improve the knowledge of the material properties. A reasonable agreement was observed between theoretical and experimental Raman spectrum taken at 10 K since anharmonic effects of the molecular motion is reduced at low temperatures, leading to a more comprehensive assignment of the vibrational modes. Increasing the temperature up to 393 K, was observed the typical phonon anharmonicity behavior associated to changes in the Raman line intensities, line-widths and red-shift, in special in the external mode region, whereas the internal modes region remains almost unchanged due its strong chemical bonds. Furthermore, C13H9ClOS goes to melting phase transition in the temperature range 393-403 K and then sublimates in the temperature range 403-413 K. This is denounced by the disappearance of the external modes and the absence of internal modes in the Raman spectra, in accordance with DSC curve. The enthalpy (ΔH) obtained from the integration of the endothermic peak in DSC curve centered at 397 K is founded to be 121.5 J/g.

Noncatalytic thermocouple coatings produced with chemical vapor deposition for flame temperature measurements.

PubMed

Bahlawane, N; Struckmeier, U; Kasper, T S; Osswald, P

2007-01-01

Chemical vapor deposition (CVD) and metal-organic chemical vapor deposition (MOCVD) have been employed to develop alumina thin films in order to protect thermocouples from catalytic overheating in flames and to minimize the intrusion presented to the combustion process. Alumina films obtained with a CVD process using AlCl(3) as the precursor are dense, not contaminated, and crystallize in the corundum structure, while MOCVD using Al(acetyl acetone)(3) allows the growth of corundum alumina with improved growth rates. These films, however, present a porous columnar structure and show some carbon contamination. Therefore, coated thermocouples using AlCl(3)-CVD were judged more suitable for flame temperature measurements and were tested in different fuels over a typical range of stoichiometries. Coated thermocouples exhibit satisfactory measurement reproducibility, no temporal drifts, and do not suffer from catalytic effects. Furthermore, their increased radiative heat loss (observed by infrared spectroscopy) allows temperature measurements over a wider range when compared to uncoated thermocouples. A flame with a well-known temperature profile established with laser-based techniques was used to determine the radiative heat loss correction to account for the difference between the apparent temperature measured by the coated thermocouple and the true flame temperature. The validity of the correction term was confirmed with temperature profile measurements for several flames previously studied in different laboratories with laser-based techniques.

Blackbody Cavity for Calibrations at 200 to 273 K

NASA Technical Reports Server (NTRS)

Howell, Dane; Ryan, Robert; Ryan, Jim; Henderson, Doug; Clayton, Larry

2004-01-01

A laboratory blackbody cavity has been designed and built for calibrating infrared radiometers used to measure radiant temperatures in the range from about 200 to about 273 K. In this below-room-temperature range, scattering of background infrared radiation from room-temperature surfaces could, potentially, contribute significantly to the spectral radiance of the blackbody cavity, thereby contributing a significant error to the radiant temperature used as the calibration value. The present blackbody cavity is of an established type in which multiple reflections from a combination of conical and cylindrical black-coated walls are exploited to obtain an effective emissivity greater than the emissivity value of the coating material on a flat exposed surface. The coating material in this case is a flat black paint that has an emissivity of approximately of 0.91 in the thermal spectral range and was selected over other, higher-emissivity materials because of its ability to withstand thermal cycling. We found many black coatings cracked and flaked after thermal cycling due to differences in the coefficient of expansion differences. On the basis of theoretical calculations, the effective emissivity is expected to approach 0.999. The cylindrical/conical shell enclosing the cavity is machined from copper, which is chosen for its high thermal conductivity. In use, the shell is oriented vertically, open end facing up, and inserted in a Dewar flask filled with isopropyl alcohol/dry-ice slush. A flange at the open end of the shell is supported by a thermally insulating ring on the lip of the Dewar flask. The slush cools the shell (and thus the black-body cavity) to the desired temperature. Typically, the slush starts at a temperature of about 194 K. The slush is stirred and warmed by bubbling dry air or nitrogen through it, thereby gradually increasing the temperature through the aforementioned calibration range during an interval of several hours. The temperature of the slush is monitored by use of a precise thermocouple probe.

Crystallization of Chicken Egg White Lysozyme from Sulfate Salts

NASA Technical Reports Server (NTRS)

Forsythe, Elizabeth; Pusey, Marc

1998-01-01

It has been "known" that chicken egg white lysozyme does not crystallize from sulfate, particularly ammonium sulfate, salts, but instead gives amorphous precipitates. This has been the basis of several studies using lysozyme comparing macromolecule crystal nucleation and amorphous precipitation. Recently Ries-Kautt et al (Acta Cryst D50, (1994) 366) have shown that purified isoionic CEWL could be crystallized from low concentrations of sulfate at basic pH, and we subsequently showed that in fact CEWL could be purified in both the tetragonal and orthorhombic forms using ammonium sulfate over the pH range 4.0 to 7.8 (Acta Cryst D53, (1997) 795). We have now extended these observations to include a range of common sulfate salts, specifically sodium, potassium, rubidium, magnesium, and manganese sulfates. In all cases but the manganese sulfates both the familiar tetragonal and orthorhombic forms were obtained, with unit cell dimensions close to those known for the "classic" sodium chloride crystallized forms. Manganese sulfate has only yielded orthorhombic crystals to date. All crystallizations were carried out using low (typically less than or equal to 6 M) salt and high (greater than approximately 90 mg/ml) protein concentrations. As with ammonium sulfate, the tetragonal - orthorhombic phase shift appears to be a function of both the temperature and the protein concentration, with higher temperatures and concentrations favoring the orthorhombic and lower the tetragonal form. The phase change range is somewhat reduced for the sulfate salts, depending upon conditions being typically between approximately 15 - 20 C. Both the magnesium and manganese sulfates gave crystals at salt concentrations over 0.6 M as well, with magnesium sulfate giving a very slowly nucleating and growing hexagonal form. A triclinic crystal form, characterized by aggressively small crystals (typically 0.1 mm in size) has been occasionally obtained from ammonium sulfate. Finally, preliminary spot solubility determinations have suggested that in some cases the solubility increases with increasing salt concentrations.

The effects of body temperature and mass on the postprandial metabolic responses of the African egg-eating snakes Dasypeltis scabra and Dasypeltis inornata.

PubMed

Greene, Sara; McConnachie, Suzanne; Secor, Stephen; Perrin, Mike

2013-06-01

African egg-eating snakes (Dasypeltis) feed only on freshly laid bird eggs which they perforate within their esophagus before swallowing the liquid contents and regurgitating the empty shell. Compared to a snake's typical intact meal, the liquid diet of Dasypeltis would expectedly generate a more moderate postprandial metabolic response and specific dynamic action (SDA). Free-ranging Dasypeltis feed over a range of ambient temperatures and thereby experience predicted temperature-dependent shifts in the duration and magnitude of their postprandial metabolic response. Such shifts would undoubtedly be shared among different species and age classes of Dasypeltis. To examine these expectations, we measured pre- and postprandial metabolic rates of adult Dasypeltis inornata and adult and neonate Dasypeltis scabra in response to liquid egg meals weighing 20% of snake body mass at 20, 25, 27, 30, and 32 °C. With an increase in body temperature, postprandial metabolic profiles of neonate and adult snakes became narrower and shorter in duration. Specific dynamic action varied among temperature treatments, increasing from 20 to 32 °C. Standard metabolic rate, postprandial peak metabolic rate, and SDA scaled with mass exponents that typically did not differ from 1.0. As expected, Dasypeltis digesting a liquid egg diet experienced a more modest postprandial response and SDA, expending on average only 10.6% of the meal's energy on the breakdown, absorption, and assimilation of the egg meal, whereas other colubrids consuming intact rodent or fish meals expend on average 16.3% of the meal's energy on digestion and assimilation. Actively foraging and feeding throughout the avian egg laying season enable Dasypeltis to survive when eggs are not available. The adaptive suite of traits that enable Dasypeltis to consume eggs of large relative size and ingest only the liquid contents may also be joined by physiological adaptations specific to their liquid diet and extended bouts of fasting. Copyright © 2013 Elsevier Inc. All rights reserved.

A Low Temperature Limit for Life on Earth

PubMed Central

Clarke, Andrew; Morris, G. John; Fonseca, Fernanda; Murray, Benjamin J.; Price, Hannah C.

2013-01-01

There is no generally accepted value for the lower temperature limit for life on Earth. We present empirical evidence that free-living microbial cells cooling in the presence of external ice will undergo freeze-induced desiccation and a glass transition (vitrification) at a temperature between −10°C and −26°C. In contrast to intracellular freezing, vitrification does not result in death and cells may survive very low temperatures once vitrified. The high internal viscosity following vitrification means that diffusion of oxygen and metabolites is slowed to such an extent that cellular metabolism ceases. The temperature range for intracellular vitrification makes this a process of fundamental ecological significance for free-living microbes. It is only where extracellular ice is not present that cells can continue to metabolise below these temperatures, and water droplets in clouds provide an important example of such a habitat. In multicellular organisms the cells are isolated from ice in the environment, and the major factor dictating how they respond to low temperature is the physical state of the extracellular fluid. Where this fluid freezes, then the cells will dehydrate and vitrify in a manner analogous to free-living microbes. Where the extracellular fluid undercools then cells can continue to metabolise, albeit slowly, to temperatures below the vitrification temperature of free-living microbes. Evidence suggests that these cells do also eventually vitrify, but at lower temperatures that may be below −50°C. Since cells must return to a fluid state to resume metabolism and complete their life cycle, and ice is almost universally present in environments at sub-zero temperatures, we propose that the vitrification temperature represents a general lower thermal limit to life on Earth, though its precise value differs between unicellular (typically above −20°C) and multicellular organisms (typically below −20°C). Few multicellular organisms can, however, complete their life cycle at temperatures below ∼−2°C. PMID:23840425

A Low Temperature Limit for Life on Earth.

PubMed

Clarke, Andrew; Morris, G John; Fonseca, Fernanda; Murray, Benjamin J; Acton, Elizabeth; Price, Hannah C

2013-01-01

There is no generally accepted value for the lower temperature limit for life on Earth. We present empirical evidence that free-living microbial cells cooling in the presence of external ice will undergo freeze-induced desiccation and a glass transition (vitrification) at a temperature between -10°C and -26°C. In contrast to intracellular freezing, vitrification does not result in death and cells may survive very low temperatures once vitrified. The high internal viscosity following vitrification means that diffusion of oxygen and metabolites is slowed to such an extent that cellular metabolism ceases. The temperature range for intracellular vitrification makes this a process of fundamental ecological significance for free-living microbes. It is only where extracellular ice is not present that cells can continue to metabolise below these temperatures, and water droplets in clouds provide an important example of such a habitat. In multicellular organisms the cells are isolated from ice in the environment, and the major factor dictating how they respond to low temperature is the physical state of the extracellular fluid. Where this fluid freezes, then the cells will dehydrate and vitrify in a manner analogous to free-living microbes. Where the extracellular fluid undercools then cells can continue to metabolise, albeit slowly, to temperatures below the vitrification temperature of free-living microbes. Evidence suggests that these cells do also eventually vitrify, but at lower temperatures that may be below -50°C. Since cells must return to a fluid state to resume metabolism and complete their life cycle, and ice is almost universally present in environments at sub-zero temperatures, we propose that the vitrification temperature represents a general lower thermal limit to life on Earth, though its precise value differs between unicellular (typically above -20°C) and multicellular organisms (typically below -20°C). Few multicellular organisms can, however, complete their life cycle at temperatures below ∼-2°C.

Laboratory Studies of Hydrogen Gas Generation Using the Cobalt Chloride Catalyzed Sodium Borohydride-Water Reaction

DTIC Science & Technology

2015-07-01

already use hydrogen for weather balloons . Besides cost, hydrogen has other advantages over helium. Hydrogen has more lift than helium, so larger...of water vapor entering the gas stream, and avoid damaging the balloon /aerostat (aerostats typically have an operational temperature range of -50 to...Aerostats: “Gepard” Tethered Aerostats with Mobile Mooring Systems. Available at http://rosaerosystems.com/aero/obj7. Accessed June 4, 2015. 11

Spectral Processing Analysis System (SPANS).

DTIC Science & Technology

1980-11-01

Approximately 750 pounds Temperature Range: 60 - 80 degrees Farenheit Humidity: 40 - 70 percent (relative) Duty Cycle: Continuous Power Requirements: 5 wire, 3...displayed per display frame, local or absolute scaling, number of display points per line and waveform av- A eraging. A typical display is shown in Figure 3...the waveform. In the case of white noise, a high degree of correlation is found at zero lag only with the remaining lags showing little correlation

How should forensic anthropologists correct national weather service temperature data for use in estimating the postmortem interval?

PubMed

Dabbs, Gretchen R

2015-05-01

This study examines the correlation between site-specific and retrospectively collected temperature data from the National Weather Service (NWS) over an extended time period. Using iButtonLink thermochrons (model DS1921G), hourly temperature readings were collected at 15 sites (1 validation; 14 experimental) from December 2010 to January 2012. Comparison between the site-specific temperature data and data retrieved from an official reporter of NWS temperature data shows statistically significant differences between the two in 71.4% (10/14) of cases. The difference ranged between 0.04 and 2.81°C. Examination of both regression and simple adjustment of the mean difference over extended periods (1, 2, 3, 4, 5, 6, & 9 months) suggests that on the timescale typical in forensic anthropology cases neither method of correction is consistent or reliable and that forensic anthropologists would be better suited using uncorrected NWS temperature data when the postmortem interval is extended. © 2015 American Academy of Forensic Sciences.

Observation of chemical erosion of carbon based wall materials in the TEXTOR tokamak

NASA Astrophysics Data System (ADS)

Philipps, V.; Pospieszczyk, A.; Erdweg, M.; Schweer, B.; Vietzke, E.; Winter, J.

1996-01-01

Mass spectroscopy and optical spectroscopy have been used to measure the formation of methane, higher hydrocarbons and of CO during the interaction of limiters with the boundary plasma and of special carbon targets with the scrape-off-layer plasma (SOL) of TEXTOR. Mass spectroscopic data are obtained by the Sniffer probe in the SOL under carbon, boronized and siliconized wall conditions. At target temperatures <=100 °C, methane yields range typically between 0.7 and 1.2%. They vary only little with changing plasma conditions. C2-hydrocarbon formation dominates the overall carbon erosion under many conditions. Their yields increase with decreasing plasma temperature. Siliconization of the walls reduces the methane formation only little but suppresses the formation of higher hydrocarbons significantly. CO formation is dominated by the actual oxygen impurity fluxes and ranges between 0.2% up to 1.5% depending on the wall conditioning. Supporting data on hydrocarbon and CO formation are obtained from the outgassing after the discharge. Optical spectroscopy has been used to determine methane formation yields from CH band emission in front of graphite test limiters positioned at the last closed flux surface. The yields are typically in the range between 1.5 and 5% and are generally a factor 2-3 higher compared to those from mass spectroscopy. The CH4 formation is nearly constant between 200 °C up to 700 °C and decreases beyond 800-1000 °C. It decreases with increasing flux density. C2 hydrocarbon emission from the limiters has not been observed by molecular band emission within the range of normal plasma conditions. They show up only for detached plasma conditions.

Effect of Temperature and Process on Quantity and Composition of Laboratory-generated Bitumen Emissions.

PubMed

Bolliet, Christophe; Kriech, Anthony J; Juery, Catherine; Vaissiere, Mathieu; Brinton, Michael A; Osborn, Linda V

2015-01-01

In this study we investigated the impact of temperature on emissions as related to various bitumen applications and processes used in commercial products. Bitumen emissions are very complex and can be influenced in quantity and composition by differences in crude source, refining processes, application temperature, and work practices. This study provided a controlled laboratory environment to study five bitumen test materials from three European refineries; three paving grade, one used for primarily roofing and some paving applications, and one oxidized industrial specialty bitumen. Emissions were generated at temperatures between 140°C and 230°C based on typical application temperatures of each product. Emissions were characterized by aerodynamic particle size, total organic matter (TOM), simulated distillation, 40 individual PACs, and fluorescence (FL-PACs) spectroscopy. Results showed that composition of bitumen emissions is influenced by temperature under studied experimental conditions. A distinction between the oxidized bitumen with flux oil (industrial specialty bitumen) and the remaining bitumens was observed. Under typical temperatures used for paving (150°C-170°C), the TOM and PAC concentrations in the emissions were low. However, bitumen with flux oil produced significantly higher emissions at 230°C, laden with high levels of PACs. Flux oil in this bitumen mixture enhanced release of higher boiling-ranged compounds during application conditions. At 200°C and below, concentrations of 4-6 ring PACs were ≤6.51 μg/m(3) for all test materials, even when flux oil was used. Trends learned about emission temperature-process relationships from this study can be used to guide industry decisions to reduce worker exposure during processing and application of hot bitumen.

Testing Planetary Volcanism Models with Multi-Wavelength Near Infrared Observations of Kilauea Flows and Fountains

NASA Astrophysics Data System (ADS)

Howell, Robert R.; Radebaugh, Jani; M. C Lopes, Rosaly; Kerber, Laura; Solomonidou, Anezina; Watkins, Bryn

2017-10-01

Using remote sensing of planetary volcanism on objects such as Io to determine eruption conditions is challenging because the emitting region is typically not resolved and because exposed lava cools so quickly. A model of the cooling rate and eruption mechanism is typically used to predict the amount of surface area at different temperatures, then that areal distribution is convolved with a Planck blackbody emission curve, and the predicted spectra is compared with observation. Often the broad nature of the Planck curve makes interpretation non-unique. However different eruption mechanisms (for example cooling fire fountain droplets vs. cooling flows) have very different area vs. temperature distributions which can often be characterized by simple power laws. Furthermore different composition magmas have significantly different upper limit cutoff temperatures. In order to test these models in August 2016 and May 2017 we obtained spatially resolved observations of spreading Kilauea pahoehoe flows and fire fountains using a three-wavelength near-infrared prototype camera system. We have measured the area vs. temperature distribution for the flows and find that over a relatively broad temperature range the distribution does follow a power law matching the theoretical predictions. As one approaches the solidus temperature the observed area drops below the simple model predictions by an amount that seems to vary inversely with the vigor of the spreading rate. At these highest temperatures the simple models are probably inadequate. It appears necessary to model the visco-elastic stretching of the very thin crust which covers even the most recently formed surfaces. That deviation between observations and the simple models may be particularly important when using such remote sensing observations to determine magma eruption temperatures.

A study of electron and thermal transport in layered titanium disulphide single crystals

NASA Astrophysics Data System (ADS)

Suri, Dhavala; Siva, Vantari; Joshi, Shalikram; Senapati, Kartik; Sahoo, P. K.; Varma, Shikha; Patel, R. S.

2017-12-01

We present a detailed study of thermal and electrical transport behavior of single crystal titanium disulphide flakes, which belong to the two dimensional, transition metal dichalcogenide class of materials. In-plane Seebeck effect measurements revealed a typical metal-like linear temperature dependence in the range of 85-285 K. Electrical transport measurements with in-plane current geometry exhibited a nearly T 2 dependence of resistivity in the range of 42-300 K. However, transport measurements along the out-of-plane current geometry showed a transition in temperature dependence of resistivity from T 2 to T 5 beyond 200 K. Interestingly, Au ion-irradiated TiS2 samples showed a similar T 5 dependence of resistivity beyond 200 K, even in the current-in-plane geometry. Micro-Raman measurements were performed to study the phonon modes in both pristine and ion-irradiated TiS2 crystals.

Utilization of plasmas for graphene synthesis

NASA Astrophysics Data System (ADS)

Shashurin, Alexey; Keidar, Michael

2013-10-01

Graphene is a one-atom-thick planar sheet of carbon atoms that are densely packed in a honeycomb crystal lattice. Grapheen has tremendous range of potential applications ranging from high-speed transistors to electrochemical energy storage devices and biochemical sensors. Methods of graphene synthesis include mechanical exfoliation, epitaxial growth on SiC, CVD and colloidal suspensions. In this work the utilization of plasmas in synthesis process is considered. Types of carbonaceous structures produced by the anodic arc and regions of their synthesis were studied. Ultimate role of substrate temperature and transformations occurring with various carbonaceous structures generated in plasma discharge were considered. Formation of graphene film on copper substrate was detected at temperatures around the copper melting point. The film was consisted of several layers graphene flakes having typical sizes of about 200 nm. Time required for crystallization of graphene on externally heated substrates was determined. This work was supported by National Science Foundation (NSF Grant No. CBET-1249213).

CHARMS: The Cryogenic, High-Accuracy Refraction Measuring System

NASA Technical Reports Server (NTRS)

Frey, Bradley; Leviton, Douglas

2004-01-01

The success of numerous upcoming NASA infrared (IR) missions will rely critically on accurate knowledge of the IR refractive indices of their constituent optical components at design operating temperatures. To satisfy the demand for such data, we have built a Cryogenic, High-Accuracy Refraction Measuring System (CHARMS), which, for typical 1R materials. can measure the index of refraction accurate to (+ or -) 5 x 10sup -3 . This versatile, one-of-a-kind facility can also measure refractive index over a wide range of wavelengths, from 0.105 um in the far-ultraviolet to 6 um in the IR, and over a wide range of temperatures, from 10 K to 100 degrees C, all with comparable accuracies. We first summarize the technical challenges we faced and engineering solutions we developed during the construction of CHARMS. Next we present our "first light," index of refraction data for fused silica and compare our data to previously published results.

Potential effects of global warming on the distribution of a temperate univoltine insect

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

Rooney, T.P.; Hurd, L.E.

1993-06-01

Poleward migration to remain within temperature tolerance ranges as the earth warms poses a problem for species with limited dispersal abilities. The life cycle of a typical temperate univoltine insect, Tenodera sinensis (Mantodea: Mantidae), is constrained by degree-days per season: too few prevent maturation before killing frost in the fall; too many allow egg hatch prior to killing frost. We combined field observations of dispersal ability with laboratory measurements of the relationship between temperature and maturation rate, and applied these to a global warming model to predict the effect of climate change on regional distribution of this insect by 2100more » A.D. Based on the simplified biological assumptions of our model, T, sinensis would be reduced to local populations in the northern portions and higher elevations of its present broadly contiguous range, and species with similar life histories may face regional or total extinction.« less

Modeling Long-term Creep Performance for Welded Nickel-base Superalloy Structures for Power Generation Systems

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

Shen, Chen

2015-01-01

We report here a constitutive model for predicting long-term creep strain evolution in’ strengthened Ni-base superalloys. Dislocation climb-bypassing’, typical in intermediate’ volume fraction (~20%) alloys, is considered as the primary deformation mechanism. Dislocation shearing’ to anti-phase boundary (APB) faults and diffusional creep are also considered for high-stress and high-temperature low-stress conditions, respectively. Additional damage mechanism is taken into account for rapid increase in tertiary creep strain. The model has been applied to Alloy 282, and calibrated in a temperature range of 1375-1450°F, and stress range of 15-45ksi. The model parameters and a MATLAB code are provided. This report is preparedmore » by Monica Soare and Chen Shen at GE Global Research. Technical discussions with Dr. Vito Cedro are greatly appreciated. This work was supported by DOE program DE-FE0005859« less

Handheld chemiresistive gas sensor readout system

NASA Astrophysics Data System (ADS)

Joubert, Trudi-Heleen; du Toit, Jurie; Mkwakikunga, Bonex; Bosscha, Peter

2016-02-01

Low-cost and non-invasive diabetes diagnosis is increasingly important [1], and this paper presents a handheld readout system for chemiresistive gas sensors in a breath acetone diagnostic application. The sensor contains reference and detection devices, used for the detection of gas concentration. Fabrication is by dropcasting a metaloxide nanowire solution onto gold interdigitated electrodes, which had been manufactured on silicon. The resulting layer is a wide bandgap n-type semiconductor material sensitive to acetone, producing a change in resistance between the electrode terminals [2]. Chemiresistive sensors typically require temperatures of 300-500 °C, while variation of sensing temperature is also employed for selective gas detection. The nano-structured functional material requires low temperatures due to large surface area, but heating is still required for acceptable recovery kinetics. Furthermore, UV illumination improves the sensor recovery [3], and is implemented in this system. Sensor resistances range from 100 Ω to 50 MΩ, while the sensor response time require a sampling frequency of 10Hz. Sensor resistance depends on temperature, humidity, and barometric pressure. The GE CC2A23 temperature sensor is used over a range of -10°C to 60°C, the Honeywell HIH5031 humidity sensor operates up to 85% over this temperature range, and the LPS331AP barometric pressure sensor measures up to 1.25 bar. Honeywell AWM43300V air flow sensors monitor the flow rate up to 1000 sccm. An LCD screen displays all the sensor data, as well as real time date and time, while all measurements are also logged in CSV-format. The system operates from a rechargeable battery.

Thermal resistance of pressed contacts of aluminum and niobium at liquid helium temperatures

DOE PAGES

Dhuley, R. C.; Geelhoed, M. I.; Thangaraj, J. C. T.

2018-06-15

Here, we examine the resistance to heat flow across contacts of mechanically pressed aluminum and niobium near liquid helium temperatures for designing a thermally conducting joint of aluminum and superconducting niobium. Measurements in the temperature range of 3.5 K to 5.5 K show the thermal contact resistance to grow as a near-cubic function of decreasing temperature, indicating phonons to be the primary heat carriers across the interface. In the 4 kN to 14 kN range of pressing force the contact resistance shows linear drop with the increasing force, in agreement with the model of micro-asperity plastic deformation at pressed contacts.more » Several thermal contact resistance models as well as the phonon diffuse mismatch model of interface thermal resistance are compared with the experimental data. The diffuse mismatch model shows closest agreement. The joints are further augmented with thin foil of indium, which lowers the joint resistance by an order of magnitude. The developed joint has nearly 1 K*cm2/W of thermal resistance at 4.2 K, is demountable, and free of the thermally resistive interfacial alloy layer that typically exists at welded, casted, or soldered joints of dissimilar metals.« less

Performance of MEMS Silicon Oscillator, ASFLM1, under Wide Operating Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2008-01-01

Over the last few years, MEMS (Micro-Electro-Mechanical Systems) resonator-based oscillators began to be offered as commercial-off-the-shelf (COTS) parts by a few companies [1-2]. These quartz-free, miniature silicon devices could compete with the traditional crystal oscillators in providing the timing (clock function) for many digital and analog electronic circuits. They provide stable output frequency, offer great tolerance to shock and vibration, and are immune to electro-static discharge [1-2]. In addition, they are encapsulated in compact lead-free packages, cover a wide frequency range (1 MHz to 125 MHz), and are specified, depending on the grade, for extended temperature operation from -40 C to +85 C. The small size of the MEMS oscillators along with their reliability and thermal stability make them candidates for use in space exploration missions. Limited data, however, exist on the performance and reliability of these devices under operation in applications where extreme temperatures or thermal cycling swings, which are typical of space missions, are encountered. This report presents the results of the work obtained on the evaluation of an ABRACON Corporation MEMS silicon oscillator chip, type ASFLM1, under extreme temperatures.

Thermal resistance of pressed contacts of aluminum and niobium at liquid helium temperatures

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

Dhuley, R. C.; Geelhoed, M. I.; Thangaraj, J. C. T.

Here, we examine the resistance to heat flow across contacts of mechanically pressed aluminum and niobium near liquid helium temperatures for designing a thermally conducting joint of aluminum and superconducting niobium. Measurements in the temperature range of 3.5 K to 5.5 K show the thermal contact resistance to grow as a near-cubic function of decreasing temperature, indicating phonons to be the primary heat carriers across the interface. In the 4 kN to 14 kN range of pressing force the contact resistance shows linear drop with the increasing force, in agreement with the model of micro-asperity plastic deformation at pressed contacts.more » Several thermal contact resistance models as well as the phonon diffuse mismatch model of interface thermal resistance are compared with the experimental data. The diffuse mismatch model shows closest agreement. The joints are further augmented with thin foil of indium, which lowers the joint resistance by an order of magnitude. The developed joint has nearly 1 K*cm2/W of thermal resistance at 4.2 K, is demountable, and free of the thermally resistive interfacial alloy layer that typically exists at welded, casted, or soldered joints of dissimilar metals.« less

High-Energy-Density, Low-Temperature Li/CFx Primary Cells

NASA Technical Reports Server (NTRS)

Whitacre, Jay; Bugga, Ratnakumar; Smart, Marshall; Prakash, G.; Yazami, Rachid

2007-01-01

High-energy-density primary (nonrechargeable) electrochemical cells capable of relatively high discharge currents at temperatures as low as -40 C have been developed through modification of the chemistry of commercial Li/CFx cells and batteries. The commercial Li/CFx units are not suitable for high-current and low-temperature applications because they are current limited and their maximum discharge rates decrease with decreasing temperature. The term "Li/CFx" refers to an anode made of lithium and a cathode made of a fluorinated carbonaceous material (typically graphite). In commercial cells, x typically ranges from 1.05 to 1.1. This cell composition makes it possible to attain specific energies up to 800 Wh/kg, but in order to prevent cell polarization and the consequent large loss of cell capacity, it is typically necessary to keep discharge currents below C/50 (where C is numerically equal to the current that, flowing during a charge or discharge time of one hour, would integrate to the nominal charge or discharge capacity of a cell). This limitation has been attributed to the low electronic conductivity of CFx for x approx. 1. To some extent, the limitation might be overcome by making cathodes thinner, and some battery manufacturers have obtained promising results using thin cathode structures in spiral configurations. The present approach includes not only making cathodes relatively thin [.2 mils (.0.051 mm)] but also using sub-fluorinated CFx cathode materials (x < 1) in conjunction with electrolytes formulated for use at low temperatures. The reason for choosing sub-fluorinated CFx cathode materials is that their electronic conductivities are high, relative to those for which x > 1. It was known from recent prior research that cells containing sub-fluorinated CFx cathodes (x between 0.33 and 0.66) are capable of retaining substantial portions of their nominal low-current specific energies when discharged at rates as high as 5C at room temperature. However, until experimental cells were fabricated following the present approach and tested, it was not known whether or to what extent low-temperature performance would be improved.

Continuous salinity and temperature data from san francisco estuary, 19822002: Trends and the salinity-freshwater inflow relationship

USGS Publications Warehouse

Shellenbarger, G.G.; Schoellhamer, D.H.

2011-01-01

The U.S. Geological Survey and other federal and state agencies have been collecting continuous temperature and salinity data, two critical estuarine habitat variables, throughout San Francisco estuary for over two decades. Although this dynamic, highly variable system has been well studied, many questions remain relating to the effects of freshwater inflow and other physical and biological linkages. This study examines up to 20 years of publically available, continuous temperature and salinity data from 10 different San Francisco Bay stations to identify trends in temperature and salinity and quantify the salinityfreshwater inflow relationship. Several trends in the salinity and temperature records were identified, although the high degree of daily and interannual variability confounds the analysis. In addition, freshwater inflow to the estuary has a range of effects on salinity from -0.0020 to -0.0096 (m3 s-1) -1 discharge, depending on location in the estuary and the timescale of analyzed data. Finally, we documented that changes in freshwater inflow to the estuary that are within the range of typical management actions can affect bay-wide salinities by 0.61.4. This study reinforces the idea that multidecadal records are needed to identify trends from decadal changes in water management and climate and, therefore, are extremely valuable. ?? 2011 Coastal Education & Research Foundation.

Direct evidence for the participation of band-tails and excited-state tunnelling in the luminescence of irradiated feldspars

NASA Astrophysics Data System (ADS)

Poolton, N. R. J.; Kars, R. H.; Wallinga, J.; Bos, A. J. J.

2009-12-01

The significance and extent of band-tail states in the luminescence and dosimetry properties of natural aluminosilicates (feldspars) is investigated by means of studies using low temperature (10 K) irradiation and optically stimulated luminescence (OSL) stimulation spectroscopy, and thermoluminescence (TL) in the range 10-200 K, made in comparison with high temperature (300 K) irradiation and photo-transferred OSL and TL investigations undertaken at low temperature. These measurements allow mappings of the band-tails to be made; they are found to be ~0.4 eV in extent in the typical materials studied. Furthermore, by populating charge trapping centres at high temperature (300 K) and monitoring the OSL stimulation spectra at temperatures in the range 10-300 K, clear evidence is presented for the presence of both thermally activated and non-thermally activated OSL processes; it is argued that the former result from thermally activated hopping through the band-tail states, whilst the latter are due to tunnelling processes, either from the excited state of the OSL centres or through the tail states. The spectral measurements are supported by analysis of the temporal dependence of the OSL signals, which correspond to either tunnelling or general order kinetic decay processes.

Magnetic properties of Mn3-xFexSn compounds with tuneable Curie temperature by Fe content for thermomagnetic motors

NASA Astrophysics Data System (ADS)

Felez, Marissol R.; Coelho, Adelino A.; Gama, Sergio

2017-12-01

Mn3-xFexSn system (0.00 ≤ x ≤ 3.00 with Δx = 0.25) alloys present the Curie temperature (TC) or transition temperature (TT) tuneable by the Fe content. A piece-wise linear profile for TC,T as a function of x is observed in a two wide temperature ranges, between 155 K up to 759 K and 259 K up to 155 K. Their equations are TC,T = (59 ± 15) + (240 ± 7)·x and TC,T = (257 ± 1) - (206 ± 4)·x, respectively. The alloys are low cost and easy manufacturing, rare earth free, with second order magnetic transition (SOMT), and have good magnetic properties. These features suggest an immediate application of the material in cascade thermomagnetic motors that operate with a large temperature range between hot and cold sources. Furthermore, SOMT Mn-Fe-Sn system materials are also reported with advantages that could make alloys of the Mn3-xFexSn system, (0.88 ≤ x ≤ 1.20), promising candidate for magnetic refrigeration. The typical ferromagnetic behaviour is achieved only by samples with x ≥ 1. The samples with x between 0.00 and 0.75 do not show the saturation magnetization even using fields up to 13 T.

Analysis of a space emergency ammonia dump using the FLOW-NET two-phase flow program

NASA Technical Reports Server (NTRS)

Navickas, J.; Rivard, W. C.

1992-01-01

Venting of cryogenic and non-cryogenic fluids to a vacuum or a very low pressure will take place in many space-based systems that are currently being designed. This may cause liquid freezing either internally within the flow circuit or on external spacecraft surfaces. Typical ammonia flow circuits were investigated to determine the effect of the geometric configuration and initial temperature, pressure, and void fraction on the freezing characteristics of the system. The analysis was conducted also to investigate the ranges of applicability of the FLOW-NET program. It was shown that a typical system can be vented to very low liquid fractions before freezing occurs. However, very small restrictions in the flow circuit can hasten the inception of freezing. The FLOW-NET program provided solutions over broad ranges of system conditions, such as venting of an ammonia tank, initially completely filled with liquid, through a series of contracting and expanding line cross sections to near-vacuum conditions.

The Impact of Cycling Temperature on the Transmission of West Nile Virus.

PubMed

Danforth, Mary E; Reisen, William K; Barker, Christopher M

2016-05-01

West Nile virus (WNV) is an important cause of disease in humans and animals. Risk of WNV infection varies seasonally, with the greatest risk during the warmest parts of the year due in part to the accelerated extrinsic incubation rate of the virus in mosquitoes. Rates of extrinsic incubation have been shown in constant-temperature studies to increase as an approximately linear function of temperature, but for other vector-borne pathogens, such as malaria or dengue virus, nonlinear relationships have been demonstrated under cycling temperatures near the thermal limits of pathogen replication. Using typical daily air temperature profiles from three key periods of WNV amplification in a hyperendemic area of WNV activity in California's Central Valley, as well as a fourth temperature profile based on exposures that would result from daily mosquito host-seeking and resting behavior, we explored the impacts of cycling temperatures on WNV transmission by Culex tarsalis Coquillett, one of the principal vectors in the western United States. The daily cycling temperature ranges studied were representative of those that occur across much of California, but they did not significantly alter the extrinsic incubation period of WNV compared with estimates from mean temperatures alone. This suggests that within the relatively broad range we studied, WNV incubation rates are a simple function of mean temperature. Realistic daily temperature patterns that reflected mosquitoes' avoidance of daytime high temperatures during summer reduced transmission over time compared with air temperatures, indicating that adjustment for mosquito exposure temperatures would be prudent for calculating risk. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Improved AIOMFAC model parameterisation of the temperature dependence of activity coefficients for aqueous organic mixtures

NASA Astrophysics Data System (ADS)

Ganbavale, G.; Zuend, A.; Marcolli, C.; Peter, T.

2015-01-01

This study presents a new, improved parameterisation of the temperature dependence of activity coefficients in the AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) model applicable for aqueous as well as water-free organic solutions. For electrolyte-free organic and organic-water mixtures the AIOMFAC model uses a group-contribution approach based on UNIFAC (UNIversal quasi-chemical Functional-group Activity Coefficients). This group-contribution approach explicitly accounts for interactions among organic functional groups and between organic functional groups and water. The previous AIOMFAC version uses a simple parameterisation of the temperature dependence of activity coefficients, aimed to be applicable in the temperature range from ~ 275 to ~ 400 K. With the goal to improve the description of a wide variety of organic compounds found in atmospheric aerosols, we extend the AIOMFAC parameterisation for the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon to atmospherically relevant low temperatures. To this end we introduce a new parameterisation for the temperature dependence. The improved temperature dependence parameterisation is derived from classical thermodynamic theory by describing effects from changes in molar enthalpy and heat capacity of a multi-component system. Thermodynamic equilibrium data of aqueous organic and water-free organic mixtures from the literature are carefully assessed and complemented with new measurements to establish a comprehensive database, covering a wide temperature range (~ 190 to ~ 440 K) for many of the functional group combinations considered. Different experimental data types and their processing for the estimation of AIOMFAC model parameters are discussed. The new AIOMFAC parameterisation for the temperature dependence of activity coefficients from low to high temperatures shows an overall improvement of 28% in comparison to the previous model version, when both versions are compared to our database of experimentally determined activity coefficients and related thermodynamic data. When comparing the previous and new AIOMFAC model parameterisations to the subsets of experimental data with all temperatures below 274 K or all temperatures above 322 K (i.e. outside a 25 K margin of the reference temperature of 298 K), applying the new parameterisation leads to 37% improvement in each of the two temperature ranges considered. The new parameterisation of AIOMFAC agrees well with a large number of experimental data sets. Larger model-measurement discrepancies were found particularly for some of the systems containing multi-functional organic compounds. The affected systems were typically also poorly represented at room temperature and further improvements will be necessary to achieve better performance of AIOMFAC in these cases (assuming the experimental data are reliable). The performance of the AIOMFAC parameterisation is typically better for systems containing relatively small organic compounds and larger deviations may occur in mixtures where molecules of high structural complexity such as highly oxygenated compounds or molecules of high molecular mass (e.g. oligomers) prevail. Nevertheless, the new parameterisation enables the calculation of activity coefficients for a wide variety of different aqueous/water-free organic solutions down to the low temperatures present in the upper troposphere.

Nanoelectronic primary thermometry below 4 mK

PubMed Central

Bradley, D. I.; George, R. E.; Gunnarsson, D.; Haley, R. P.; Heikkinen, H.; Pashkin, Yu. A.; Penttilä, J.; Prance, J. R.; Prunnila, M.; Roschier, L.; Sarsby, M.

2016-01-01

Cooling nanoelectronic structures to millikelvin temperatures presents extreme challenges in maintaining thermal contact between the electrons in the device and an external cold bath. It is typically found that when nanoscale devices are cooled to ∼10 mK the electrons are significantly overheated. Here we report the cooling of electrons in nanoelectronic Coulomb blockade thermometers below 4 mK. The low operating temperature is attributed to an optimized design that incorporates cooling fins with a high electron–phonon coupling and on-chip electronic filters, combined with low-noise electronic measurements. By immersing a Coulomb blockade thermometer in the 3He/4He refrigerant of a dilution refrigerator, we measure a lowest electron temperature of 3.7 mK and a trend to a saturated electron temperature approaching 3 mK. This work demonstrates how nanoelectronic samples can be cooled further into the low-millikelvin range. PMID:26816217

Molecular Modeling for Calculation of Mechanical Properties of Epoxies with Moisture Ingress

NASA Technical Reports Server (NTRS)

Clancy, Thomas C.; Frankland, Sarah J.; Hinkley, J. A.; Gates, T. S.

2009-01-01

Atomistic models of epoxy structures were built in order to assess the effect of crosslink degree, moisture content and temperature on the calculated properties of a typical representative generic epoxy. Each atomistic model had approximately 7000 atoms and was contained within a periodic boundary condition cell with edge lengths of about 4 nm. Four atomistic models were built with a range of crosslink degree and moisture content. Each of these structures was simulated at three temperatures: 300 K, 350 K, and 400 K. Elastic constants were calculated for these structures by monitoring the stress tensor as a function of applied strain deformations to the periodic boundary conditions. The mechanical properties showed reasonably consistent behavior with respect to these parameters. The moduli decreased with decreasing crosslink degree with increasing temperature. The moduli generally decreased with increasing moisture content, although this effect was not as consistent as that seen for temperature and crosslink degree.

Large scale synthesis of nanostructured zirconia-based compounds from freeze-dried precursors

NASA Astrophysics Data System (ADS)

Gómez, A.; Villanueva, R.; Vie, D.; Murcia-Mascaros, S.; Martínez, E.; Beltrán, A.; Sapiña, F.; Vicent, M.; Sánchez, E.

2013-01-01

Nanocrystalline zirconia powders have been obtained at the multigram scale by thermal decomposition of precursors resulting from the freeze-drying of aqueous acetic solutions. This technique has equally made possible to synthesize a variety of nanostructured yttria or scandia doped zirconia compositions. SEM images, as well as the analysis of the XRD patterns, show the nanoparticulated character of those solids obtained at low temperature, with typical particle size in the 10-15 nm range when prepared at 673 K. The presence of the monoclinic, the tetragonal or both phases depends on the temperature of the thermal treatment, the doping concentration and the nature of the dopant. In addition, Rietveld refinement of the XRD profiles of selected samples allows detecting the coexistence of the tetragonal and the cubic phases for high doping concentration and high thermal treatment temperatures. Raman experiments suggest the presence of both phases also at relatively low treatment temperatures.

A compact cryogen-free platform operating at 1 K or 50 mK

NASA Astrophysics Data System (ADS)

Matthews, A. J.; Patton, M.; Marsh, T.; van der Vliet, H.

2018-03-01

We report the design and performance characteristics of a compact cryogen-free platform. The system is based around a continuous 1 K pot which operates using a small (10 m3 h‑1) room temperature circulation pump. The pot cools an experimental plate to ≈ 1.2 K, and has a cooling capacity of 100 mW at a temperature ≈ 1.9 K. Cooling the pot from room temperature to < 2 K takes around 12 hours. The temperature range of the platform can be lowered to < 50 mK with the addition of a small dilution refrigerator, using the 1 K pot as a pre-cooling stage for the circulating 3He. The dilution stage has a typical (continuous) cooling capacity of 30 µW at 100 mK (300 µW at 250 mK) and is designed to operate with just 3 litres of (NTP) 3He.

Transition from poor ductility to room-temperature superplasticity in a nanostructured aluminum alloy.

PubMed

Edalati, Kaveh; Horita, Zenji; Valiev, Ruslan Z

2018-04-30

Recent developments of nanostructured materials with grain sizes in the nanometer to submicrometer range have provided ground for numerous functional properties and new applications. However, in terms of mechanical properties, bulk nanostructured materials typically show poor ductility despite their high strength, which limits their use for structural applications. The present article shows that the poor ductility of nanostructured alloys can be changed to room-temperature superplastisity by a transition in the deformation mechanism from dislocation activity to grain-boundary sliding. We report the first observation of room-temperature superplasticity (over 400% tensile elongations) in a nanostructured Al alloy by enhanced grain-boundary sliding. The room-temperature grain-boundary sliding and superplasticity was realized by engineering the Zn segregation along the Al/Al boundaries through severe plastic deformation. This work introduces a new boundary-based strategy to improve the mechanical properties of nanostructured materials for structural applications, where high deformability is a requirement.

High efficiency digital cooler electronics for aerospace applications

NASA Astrophysics Data System (ADS)

Kirkconnell, C. S.; Luong, T. T.; Shaw, L. S.; Murphy, J. B.; Moody, E. A.; Lisiecki, A. L.; Ellis, M. J.

2014-06-01

Closed-cycle cryogenic refrigerators, or cryocoolers, are an enabling technology for a wide range of aerospace applications, mostly related to infrared (IR) sensors. While the industry focus has tended to be on the mechanical cryocooler thermo mechanical unit (TMU) alone, implementation on a platform necessarily consists of the combination of the TMU and a mating set of command and control electronics. For some applications the cryocooler electronics (CCE) are technologically simple and low cost relative to the TMU, but this is not always the case. The relative cost and complexity of the CCE for a space-borne application can easily exceed that of the TMU, primarily due to the technical constraints and cost impacts introduced by the typical space radiation hardness and reliability requirements. High end tactical IR sensor applications also challenge the state of the art in cryocooler electronics, such as those for which temperature setpoint and frequency must be adjustable, or those where an informative telemetry set must be supported, etc. Generally speaking for both space and tactical applications, it is often the CCE that limits the rated lifetime and reliability of the cryocooler system. A family of high end digital cryocooler electronics has been developed to address these needs. These electronics are readily scalable from 10W to 500W output capacity; experimental performance data for nominally 25W and 100W variants are presented. The combination of a FPGA-based controller and dual H-bridge motor drive architectures yields high efficiency (>92% typical) and precision temperature control (+/- 30 mK typical) for a wide range of Stirling-class mechanical cryocooler types and vendors. This paper focuses on recent testing with the AIM INFRAROT-MODULE GmbH (AIM) SX030 and AIM SF100 cryocoolers.

Evaluation of Low-Gravity Smoke Particulate for Spacecraft Fire Detection

NASA Technical Reports Server (NTRS)

Urban, David; Ruff, Gary A.; Mulholland George; Meyer, Marit; Yuan, Zeng guang; Cleary, Thomas; Yang, Jiann; Greenberg, Paul; Bryg, Victoria

2013-01-01

Tests were conducted on the International Space Station to evaluate the smoke particulate size from materials and conditions that are typical of those expected in spacecraft fires. Five different materials representative of those found in spacecraft (Teflon, Kapton, cotton, silicone rubber and Pyrell) were heated to temperatures below the ignition point with conditions controlled to provide repeatable sample surface temperatures and air flow. The air flow past the sample during the heating period ranged from quiescent to 8 cm/s. The effective transport time to the measurement instruments was varied from 11 to 800 seconds to simulate different smoke transport conditions in spacecraft. The resultant aerosol was evaluated by three instruments which measured different moments of the particle size distribution. These moment diagnostics were used to determine the particle number concentration (zeroth moment), the diameter concentration (first moment), and the mass concentration (third moment). These statistics were combined to determine the diameter of average mass and the count mean diameter and by assuming a log-normal distribution, the geometric mean diameter and the geometric standard deviations were also calculated. Smoke particle samples were collected on TEM grids using a thermal precipitator for post flight analysis. The TEM grids were analyzed to determine the particle morphology and shape parameters. The different materials produced particles with significantly different morphologies. Overall the majority of the average smoke particle sizes were found to be in the 200 to 400 nanometer range with the quiescent cases and the cases with increased transport time typically producing with substantially larger particles. The results varied between materials but the smoke particles produced in low gravity were typically twice the size of particles produced in normal gravity. These results can be used to establish design requirements for future spacecraft smoke detectors.

Cation reordering in natural titanomagnetites and implications for paleointensity studies

NASA Astrophysics Data System (ADS)

Bowles, J. A.; Jackson, M. J.; Gee, J. S.

2013-05-01

Successful paleointensity experiments hinge on the underlying assumption of reciprocity; the remanence acquired over a particular temperature range should be fully removed over the same temperature range, and vice versa. This means that the blocking (TB) and unblocking (TUB) temperature spectra are identical and do not change during the course of the experiment. We will present the results of recent work demonstrating that some natural titanomagnetites undergo cation reordering on laboratory timescales and at temperatures at or below the Curie temperature (TC). The bulk composition of the titanomagnetites (Fe3-xTixO4) varies between approximately 0.2 < x < 0.4, with moderate degrees of Mg and Al substitution. Although there is no attendant structural or chemical alteration, the re-distribution of ferric and ferrous iron cations results in reversible changes in Curie temperature of up to 150°C. This necessarily changes the blocking temperature spectrum as a function of prior thermal history. These changes in TC, TUB and TB clearly pose problems for all paleointensity experiments, but the effects may be most apparent during Thellier-type experiments where the sample is step-wise heated to increasingly higher temperatures. The blocking temperature distribution will be expected to change over the course of the experiment even in the absence of chemical alteration, and one can expect the experiment to fail. We will explore the effects of cation redistribution on paleointensity experiments through numerical models and by comparison with paleointensity data from pumice samples taken from the 1980 pyroclastic flows at Mt. St. Helens (MSH). In the MSH samples, two phases are typically present: a predominantly multi-domain, homogeneous titanomagnetite (associated with the cation reordering) and an oxyexsolved, single-domain to pseudo-single-domain phase with ilmenite lamellae in a magnetite-rich host. Samples that result in technically successful paleointensity experiments that give the correct field value are most likely to be dominated by the oxyexsolved phase. By contrast, samples with a considerable proportion of the homogeneous phase typically fail the paleointensity experiments and have unstable magnetization behavior at temperatures associated with cation reordering on laboratory time scales. In many samples with both phases, pTRM checks pass at both low (<300°C) and high (>500°C) temperatures, but fail in the intermediate temperature window. The composition of the titanomagnetites that exhibit this cation reordering effect are extremely common in rocks of andesitic, dacitic, and rhyolitic composition, as well as in some basalts. Cation reordering may therefore be a previously unrecognized cause for failure in paleointensity experiments.

Insights to primitive replication derived from structures of small oligonucleotides

NASA Technical Reports Server (NTRS)

Smith, G. K.; Fox, G. E.

1995-01-01

Available information on the structure of small oligonucleotides is surveyed. It is observed that even small oligomers typically exhibit defined structures over a wide range of pH and temperature. These structures rely on a plethora of non-standard base-base interactions in addition to the traditional Watson-Crick pairings. Stable duplexes, though typically antiparallel, can be parallel or staggered and perfect complementarity is not essential. These results imply that primitive template directed reactions do not require high fidelity. Hence, the extensive use of Watson-Crick complementarity in genes rather than being a direct consequence of the primitive condensation process, may instead reflect subsequent selection based on the advantage of accuracy in maintaining the primitive genetic machinery once it arose.

Spectral constraints on models of gas in clusters of galaxies

NASA Technical Reports Server (NTRS)

Henriksen, M. J.; Mushotzky, R.

1985-01-01

The HEAO 1A2 spectra of clusters of galaxies are used to determine the temperature profile which characterizes the X-ray emitting gas. Strong evidence of nonisothermality is found for the Coma, A85, and A1795 clusters. Properties of the cluster potential which binds the gas are calculated for a range of model parameters. The typical binding mass, if the gas is adiabatic, is 2-4E14 solar masses and is quite centrally concentrated. In addition, the Fe abundance in Coma is .26 + or - .06 solar, less than the typical value (.5) found for rich clusters. The results for the gas in Coma may imply a physical description of the cluster which is quite different from what was previously believed.

Structural transformations in (1 -x ) Na0.5Bi0.5TiO3-x BaTiO3 single crystals studied by Raman spectroscopy

NASA Astrophysics Data System (ADS)

de la Flor, G.; Malcherek, T.; Gorfman, S.; Mihailova, B.

2017-12-01

Hard-mode Raman spectroscopy was applied to analyze the temperature-induced transformation processes in perovskite-type (ABO3) single crystals of (1 -x ) Na0.5Bi0.5TiO3-x BaTiO3 (NBT-x BT ) in a wide temperature range between 100 and 1010 K and a composition range of x =0 -0.074 across the morphotropic phase boundary (MPB). The results show abundant uncoupled ferroic structural distortions even at 1010 K and coexistence of two types of mesoscopic-scale ferroic order at lower temperatures. Octahedral BO6 tilting is typical of pure NBT, while the incorporation of A-site Ba2 + suppresses the tilting and promotes the off centering of BO6 octahedra. The temperature evolution of the phonon modes clearly reveals the two macroscopically observed critical temperatures Tm and Td as well as, in the case of x ≠0 , two characteristic temperatures T' and T'' preceding the Tm and Td, respectively, which are attributed to mesoscopic-scale antiferroelectric and ferroelectric coupling processes within the A-site-cation subsystem. At x

The Cooling History and Structure of the Ordinary Chondrite Parent Bodies

NASA Technical Reports Server (NTRS)

Benoit, P. H.; Sears, D. W. G.

1996-01-01

Most major meteorite classes exhibit significant ranges of metamorphism. The effects of metamorphism have been extensively characterized, but the heat source(s) and the metamorphic environment are unknown. Proposed beat sources include Al-26, Fe-60, electromagnetic induction, and impact. It is typically assumed that metamorphism occurred in parent bodies of some sort, but it uncertain whether these bodies were highly structured ("onion skins") or were chaotic mixes of material ("rubble piles"). The lack of simple trends of metallographic cooling rates with petrologic type has been considered supportive of both concepts. In this study, we use induced thermoluminescence (TL) as an indicator of thermal history. The TL of ordinary chondrites is produced by sodic feldspar, and the induced TL peak temperature is related to its crystallographic order/disorder. Ordered feldspar has TL peak temperatures of approx. 120 C, and disordered feldspar has TL peak temperatures of approx. 220 C. While ordered feldspar can be easily disordered in the laboratory by heating above 650 C and is easily quenched in the disordered form, producing ordered feldspar requires cooling at geologic cooling rates. We have measured the induced TL properties of 101 equilibrated ordinary chondrites, including 49 H, 29 L, and 23 LL chondrites. For the H chondrites there is an apparent trend of decreasing induced TL peak temperature with increasing petrologic type. H4 chondrites exhibit a tight range of TL peak temperatures, 190 C - 200 C, while H6 chondrites exhibit TL peak temperatures between 180 C and 190 C. H5 chondrites cover the range between H4 and H6, and also extend up to 210 C. Similar results are obtained for LL chondfiles and most L6 chondrites have lower induced TL peak temperatures than L5 chondrites.

Cloacal evaporative cooling: a previously undescribed means of increasing evaporative water loss at higher temperatures in a desert ectotherm, the Gila monster Heloderma suspectum.

PubMed

DeNardo, Dale F; Zubal, Tricia E; Hoffman, Ty C M

2004-02-01

The Gila monster Heloderma suspectum is an active forager in an environment that, at times, can be extremely hot and arid. Thus, Gila monsters face extreme thermostatic and hydrostatic demands. For a desert ectotherm routinely risking dehydration, evaporative water loss (EWL) is typically viewed as detrimental. Yet evaporation simultaneously dehydrates and cools an animal. We explored EWL in Gila monsters by measuring cutaneous, ventilatory and cloacal EWL at five ambient temperatures between 20.5 degrees C and 40 degrees C. Our results show that Gila monsters have high EWL rates relative to body mass. Cutaneous EWL underwent a consistent, temperature-dependent increase over the entire range of test temperatures (Q(10)=1.61, with EWL ranging from 0.378 to 0.954 mg g(-1) h(-1)). Ventilatory EWL did not show a significant temperature-dependent response, but ranged from 0.304 to 0.663 mg g(-1) h(-1). Cloacal EWL was extremely low and relatively constant between 20.5 degrees C and 35 degrees C, but rose dramatically above 35 degrees C (Q(10) >8.3 x 10(7), from 0.0008 at 35 degrees C to 7.30 mg g(-1) h(-1) at 40 degrees C). This steep rise in cloacal EWL coincided with an increasing suppression of body temperature relative to ambient temperature. Dehydration to 80% of initial body mass led to a delay in the onset and an attenuation of the dramatic increase in cloacal EWL. These results emphasize the potential value of EWL for thermoregulation in ectotherms and demonstrate for the first time the role of the cloaca in this process.

Thermocouple Errors when Mounted on Cylindrical Surfaces in Abnormal Thermal Environments.

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

Nakos, James T.; Suo-Anttila, Jill M.; Zepper, Ethan T.

Mineral-insulated, metal-sheathed, Type-K thermocouples are used to measure the temperature of various items in high-temperature environments, often exceeding 1000degC (1273 K). The thermocouple wires (chromel and alumel) are protected from the harsh environments by an Inconel sheath and magnesium oxide (MgO) insulation. The sheath and insulation are required for reliable measurements. Due to the sheath and MgO insulation, the temperature registered by the thermocouple is not the temperature of the surface of interest. In some cases, the error incurred is large enough to be of concern because these data are used for model validation, and thus the uncertainties of themore » data need to be well documented. This report documents the error using 0.062" and 0.040" diameter Inconel sheathed, Type-K thermocouples mounted on cylindrical surfaces (inside of a shroud, outside and inside of a mock test unit). After an initial transient, the thermocouple bias errors typically range only about +-1-2% of the reading in K. After all of the uncertainty sources have been included, the total uncertainty to 95% confidence, for shroud or test unit TCs in abnormal thermal environments, is about +-2% of the reading in K, lower than the +-3% typically used for flat shrouds. Recommendations are provided in Section 6 to facilitate interpretation and use of the results. .« less

Mechanism of Phase Formation in the Batch Mixtures for Slag-Bearing Glass Ceramics - 12207

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

Stefanovsky, Sergey V.; Stefanovsky, Olga I.; Malinina, Galina A.

2012-07-01

Slag surrogate was produced from chemicals by heating to 900 deg. C and keeping at this temperature for 1 hr. The product obtained was intermixed with either sodium di-silicate (75 wt.% waste loading) or borax (85 wt.% slag loading). The mixtures were heat-treated within a temperature range of 25 to 1300 deg. C. The products were examined by X-ray diffraction and infrared spectroscopy. The products prepared at temperatures of up to 1000 deg. C contained both phase typical of the source slag and intermediate phases as well as phases typical of the materials melted at 1350 deg. C such asmore » nepheline, britholite, magnetite and matrix vitreous phase. Vitrification process in batch mixtures consisting of slag surrogate and either sodium di-silicate or sodium tetraborate runs through formation of intermediate phases mainly silico-phosphates capable to incorporate Sm as trivalent actinides surrogate. Reactions in the batch mixtures are in the whole completed by ∼1000 deg. C but higher temperatures are required to homogenize the products. If in the borate-based system the mechanism is close to simple dissolution of slag constituents in the low viscous borate melt, then in the silicate-based system the mechanism was found to be much complicated and includes re-crystallization during melting with segregation of newly-formed nepheline type phase. (authors)« less

Astronomical near-infrared echelle gratings

NASA Astrophysics Data System (ADS)

Hinkle, Kenneth H.; Joyce, Richard R.; Liang, Ming

2014-07-01

High-resolution near-infrared echelle spectrographs require coarse rulings in order to match the free spectral range to the detector size. Standard near-IR detector arrays typically are 2 K x 2 K or 4 K x 4 K. Detectors of this size combined with resolutions in the range 30000 to 100000 require grating groove spacings in the range 5 to 20 lines/mm. Moderately high blaze angles are desirable to reduce instrument size. Echelle gratings with these characteristics have potential wide application in both ambient temperature and cryogenic astronomical echelle spectrographs. We discuss optical designs for spectrographs employing immersed and reflective echelle gratings. The optical designs set constraints on grating characteristics. We report on market choices for obtaining these gratings and review our experiments with custom diamond turned rulings.

Waste heat generation: A comprehensive review.

PubMed

Yeşiller, Nazli; Hanson, James L; Yee, Emma H

2015-08-01

A comprehensive review of heat generation in various types of wastes and of the thermal regime of waste containment facilities is provided in this paper. Municipal solid waste (MSW), MSW incineration ash, and mining wastes were included in the analysis. Spatial and temporal variations of waste temperatures, thermal gradients, thermal properties of wastes, average temperature differentials, and heat generation values are provided. Heat generation was influenced by climatic conditions, mean annual earth temperatures, waste temperatures at the time of placement, cover conditions, and inherent heat generation potential of the specific wastes. Time to onset of heat generation varied between months and years, whereas timelines for overall duration of heat generation varied between years and decades. For MSW, measured waste temperatures were as high as 60-90°C and as low as -6°C. MSW incinerator ash temperatures varied between 5 and 87°C. Mining waste temperatures were in the range of -25 to 65°C. In the wastes analyzed, upward heat flow toward the surface was more prominent than downward heat flow toward the subsurface. Thermal gradients generally were higher for MSW and incinerator ash and lower for mining waste. Based on thermal properties, MSW had insulative qualities (low thermal conductivity), while mining wastes typically were relatively conductive (high thermal conductivity) with ash having intermediate qualities. Heat generation values ranged from -8.6 to 83.1MJ/m(3) and from 0.6 to 72.6MJ/m(3) for MSW and mining waste, respectively and was 72.6MJ/m(3) for ash waste. Conductive thermal losses were determined to range from 13 to 1111MJ/m(3)yr. The data and analysis provided in this review paper can be used in the investigation of heat generation and thermal regime of a wide range of wastes and waste containment facilities located in different climatic regions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Liquid crystal 'blue phases' with a wide temperature range.

PubMed

Coles, Harry J; Pivnenko, Mikhail N

2005-08-18

Liquid crystal 'blue phases' are highly fluid self-assembled three-dimensional cubic defect structures that exist over narrow temperature ranges in highly chiral liquid crystals. The characteristic period of these defects is of the order of the wavelength of visible light, and they give rise to vivid specular reflections that are controllable with external fields. Blue phases may be considered as examples of tuneable photonic crystals with many potential applications. The disadvantage of these materials, as predicted theoretically and proved experimentally, is that they have limited thermal stability: they exist over a small temperature range (0.5-2 degrees C) between isotropic and chiral nematic (N*) thermotropic phases, which limits their practical applicability. Here we report a generic family of liquid crystals that demonstrate an unusually broad body-centred cubic phase (BP I*) from 60 degrees C down to 16 degrees C. We prove this with optical texture analysis, selective reflection spectroscopy, Kössel diagrams and differential scanning calorimetry, and show, using a simple polarizer-free electro-optic cell, that the reflected colour is switched reversibly in applied electric fields over a wide colour range in typically 10 ms. We propose that the unusual behaviour of these blue phase materials is due to their dimeric molecular structure and their very high flexoelectric coefficients. This in turn sets out new theoretical challenges and potentially opens up new photonic applications.

Aster leafhopper survival and reproduction, and Aster yellows transmission under static and fluctuating temperatures, using ddPCR for phytoplasma quantification.

PubMed

Bahar, Md H; Wist, Tyler J; Bekkaoui, Diana R; Hegedus, Dwayne D; Olivier, Chrystel Y

2018-01-10

Aster yellows (AY) is an important disease of Brassica crops and is caused by Candidatus Phytoplasma asteris and transmitted by the insect vector, Aster leafhopper (Macrosteles quadrilineatus). Phytoplasma-infected Aster leafhoppers were incubated at various constant and fluctuating temperatures ranging from 0 to 35 °C with the reproductive host plant barley (Hordium vulgare). At 0 °C, leafhopper adults survived for 18 days, but failed to reproduce, whereas at 35 °C insects died within 18 days, but successfully reproduced before dying. Temperature fluctuation increased thermal tolerance in leafhoppers at 25 °C and increased fecundity of leafhoppers at 5 and 20 °C. Leafhopper adults successfully infected and produced AY-symptoms in canola plants after incubating for 18 days at 0-20 °C on barley, indicating that AY-phytoplasma maintains its virulence in this temperature range. The presence and number of AY-phytoplasma in insects and plants were confirmed by droplet digital PCR (ddPCR) quantification. The number of phytoplasma in leafhoppers increased over time, but did not differ among temperatures. The temperatures associated with a typical crop growing season on the Canadian Prairies will not limit the spread of AY disease by their predominant insect vector. Also, ddPCR quantification is a useful tool for early detection and accurate quantification of phytoplasma in plants and insects.

Prediction of temperature and thermal inertia effect in the maturation stage and stockpiling of a large composting mass

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

Barrena, R.; Canovas, C.; Sanchez, A.

2006-07-01

A macroscopic non-steady state energy balance was developed and solved for a composting pile of source-selected organic fraction of municipal solid waste during the maturation stage (13,500 kg of compost). Simulated temperature profiles correlated well with temperature experimental data (ranging from 50 to 70 deg. C) obtained during the maturation process for more than 50 days at full scale. Thermal inertia effect usually found in composting plants and associated to the stockpiling of large composting masses could be predicted by means of this simplified energy balance, which takes into account terms of convective, conductive and radiation heat dissipation. Heat lossesmore » in a large composting mass are not significant due to the similar temperatures found at the surroundings and at the surface of the pile (ranging from 15 to 40 deg. C). In contrast, thermophilic temperature in the core of the pile was maintained during the whole maturation process. Heat generation was estimated with the static respiration index, a parameter that is typically used to monitor the biological activity and stability of composting processes. In this study, the static respiration index is presented as a parameter to estimate the metabolic heat that can be generated according to the biodegradable organic matter content of a compost sample, which can be useful in predicting the temperature of the composting process.« less

Mechanical and functional behavior of high-temperature Ni-Ti-Pt shape memory alloys

DOE PAGES

Buchheit, Thomas E.; Susan, Donald F.; Massad, Jordan E.; ...

2016-01-22

A series of Ti-rich Ni-Ti-Pt ternary alloys with 13 to 18 at. pct Pt were processed by vacuum arc melting and characterized for their transformation behavior to identify shape memory alloys (SMA) that undergo transformation between 448 K and 498 K (175 °C and 225 °C) and achieve recoverable strain exceeding 2 pct. From this broader set of compositions, three alloys containing 15.5 to 16.5 at. pct Pt exhibited transformation temperatures in the vicinity of 473 K (200 °C), thus were targeted for more detailed characterization. Preliminary microstructural evaluation of these three compositions revealed a martensitic microstructure with small amountsmore » of Ti 2(Ni,Pt) particles. Room temperature mechanical testing gave a response characteristic of martensitic de-twinning followed by a typical work-hardening behavior to failure. Elevated mechanical testing, performed while the materials were in the austenitic state, revealed yield stresses of approximately 500 MPa and 3.5 pct elongation to failure. Thermal strain recovery characteristics were more carefully investigated with unbiased incremental strain-temperature tests across the 1 to 5 pct strain range, as well as cyclic strain-temperature tests at 3 pct strain. As a result, the unbiased shape recovery results indicated a complicated strain recovery path, dependent on prestrain level, but overall acceptable SMA behavior within the targeted temperature and recoverable strain range.« less

Zodiacal emission. III - Dust near the asteroid belt

NASA Technical Reports Server (NTRS)

Reach, William T.

1992-01-01

Properties of the zodiacal dust bands are derived from fits to Infrared Astronomical Satellite profiles of the ecliptic. Three observations lead to the conclusion that the dust-band material is spread over a range of heliocentric distances between the asteroid belt and the sun: parallax, color temperature, and wavelength dependence of the band latitudes. The orientations of the midplanes of the bands are found to be typical of asteroids. A model of 'migrating bands', wherein dust is produced near the asteroid belt and spirals into the sun under the influence of Poynting-Robertson drag, is used to explain the range of heliocentric distances of dust-band material.

Handbook of infrared radiation from combustion gases

NASA Technical Reports Server (NTRS)

Ludwig, C. B.; Malkmus, W.; Reardon, J. E.; Thomson, J. A. L.; Goulard, R. (Editor)

1973-01-01

The treatment of radiant emission and absorption by combustion gases are discussed. Typical applications include: (1) rocket combustion chambers and exhausts, (2) turbojet engines and exhausts, and (3) industrial furnaces. Some mention is made of radiant heat transfer problems in planetary atmospheres, in stellar atmospheres, and in reentry plasmas. Particular consideration is given to the temperature range from 500K to 3000K and the pressure range from 0.001 atmosphere to 30 atmospheres. Strong emphasis is given to the combustion products of hydrocarbon fuels with oxygen, specifically to carbon dioxide, water vapor, and carbon monoxide. In addition, species such as HF, HC1, CN, OH, and NO are treated.

Space shuttle maneuvering engine reusable thrust chamber program. Task 11: Low epsilon stability test report data dump

NASA Technical Reports Server (NTRS)

Pauckert, R. P.

1974-01-01

The stability characteristics of the like-doublet injector were defined over the range of OME chamber pressures and mixture ratios. This was accomplished by bomb testing the injector and cavity configurations in solid wall thrust chamber hardware typical of a flight contour with fuel heated to regenerative chamber outlet temperatures. It was found that stability in the 2600-2800 Hz region depends upon injector hydraulics and on chamber acoustics.

ATM observations - X-ray results. [solar coronal structure from Skylab experiments

NASA Technical Reports Server (NTRS)

Vaiana, G. S.; Zombeck, M.; Krieger, A. S.; Timothy, A. F.

1976-01-01

Preliminary results of the solar X-ray observations from Skylab are reviewed which indicate a highly structured nature for the corona, with closed magnetic-loop structures over a wide range of size scales. A description of the S-054 experiments is provided, and values are given for the parameters - including size, density, and temperature - describing a variety of typical coronal features. The structure and evolution of active regions, coronal holes, and bright points are discussed.

New Fluorinated and Sulfonated Block Copolymers Final Report

DTIC Science & Technology

2009-04-23

use polymers namely, Polymer Electrolyte Membrane Fuel Cells ( PEMFC ) and Direct Methanol Fuel Cells (DMFC) The DMFC can be seen as a variant of...the PEMFC . The membranes are typically the same; however, the feed for DMFC is methanol in an aqueous 1-2 M solution or in its vapor form. This fuel...the existing liquid fuels infrastructure can be used for methanol. Catalysts, as well as operating temperature ranges, are very similar to the PEMFC

Toxicity of pesticide and fertilizer mixtures simulating corn production to eggs of snapping turtles (Chelydra serpentina).

PubMed

de Solla, Shane Raymond; Martin, Pamela Anne; Mikoda, Paul

2011-09-15

Many reptiles oviposit in soils associated with agricultural landscapes. We evaluated the toxicity of a pesticide and fertilizer regime similar to those used in corn production in Ontario on the survivorship of exposed snapping turtle (Chelydra serpentina) eggs. The herbicides atrazine, dimethenamid, and glyphosate, the pyrethroid insecticide tefluthrin, and the fertilizer ammonia, were applied to clean soil, both as partial mixtures within chemical classes, as well as complete mixtures. Eggs were incubated in the soil in a garden plot in which these mixtures were applied at a typical field application rate, and higher rates. Otherwise, the eggs were unmanipulated and were subject to ambient temperature and weather conditions. Eggs were also exposed at male producing temperatures in the laboratory in covered bins in the same soil, where there was less opportunity for loss through volatilization or leaching. Egg mortality was 100% at 10× the typical field application rate of the complete mixture, both with and without tefluthrin. At typical field application rates, hatching success ranged between 91.7 and 95.8%. Eggs exposed only to herbicides were not negatively affected at any application rates. Although fertilizer treatments at typical field application rates did not affect eggs, mortality was remarkably higher at three times this rate, and 100% at higher rates. The frequency of deformities of hatchlings was elevated at the highest application rate of the insecticide tefluthrin. The majority of the toxicity of the mixture was not due to the herbicides or insecticide, but was due to the ammonia fertilizer. At typical field application rates, the chemical regime associated with corn production does not appear to have any detrimental impacts upon turtle egg development; however toxicity dramatically increases if this threshold is passed. Copyright © 2011. Published by Elsevier B.V.

Estimates of Stellar Weak Interaction Rates for Nuclei in the Mass Range A=65-80

NASA Astrophysics Data System (ADS)

Pruet, Jason; Fuller, George M.

2003-11-01

We estimate lepton capture and emission rates, as well as neutrino energy loss rates, for nuclei in the mass range A=65-80. These rates are calculated on a temperature/density grid appropriate for a wide range of astrophysical applications including simulations of late time stellar evolution and X-ray bursts. The basic inputs in our single-particle and empirically inspired model are (i) experimentally measured level information, weak transition matrix elements, and lifetimes, (ii) estimates of matrix elements for allowed experimentally unmeasured transitions based on the systematics of experimentally observed allowed transitions, and (iii) estimates of the centroids of the GT resonances motivated by shell model calculations in the fp shell as well as by (n, p) and (p, n) experiments. Fermi resonances (isobaric analog states) are also included, and it is shown that Fermi transitions dominate the rates for most interesting proton-rich nuclei for which an experimentally determined ground state lifetime is unavailable. For the purposes of comparing our results with more detailed shell model based calculations we also calculate weak rates for nuclei in the mass range A=60-65 for which Langanke & Martinez-Pinedo have provided rates. The typical deviation in the electron capture and β-decay rates for these ~30 nuclei is less than a factor of 2 or 3 for a wide range of temperature and density appropriate for presupernova stellar evolution. We also discuss some subtleties associated with the partition functions used in calculations of stellar weak rates and show that the proper treatment of the partition functions is essential for estimating high-temperature β-decay rates. In particular, we show that partition functions based on unconverged Lanczos calculations can result in errors in estimates of high-temperature β-decay rates.

Generalized Procedure for Improved Accuracy of Thermal Contact Resistance Measurements for Materials With Arbitrary Temperature-Dependent Thermal Conductivity

DOE PAGES

Sayer, Robert A.

2014-06-26

Thermal contact resistance (TCR) is most commonly measured using one-dimensional steady-state calorimetric techniques. In the experimental methods we utilized, a temperature gradient is applied across two contacting beams and the temperature drop at the interface is inferred from the temperature profiles of the rods that are measured at discrete points. During data analysis, thermal conductivity of the beams is typically taken to be an average value over the temperature range imposed during the experiment. Our generalized theory is presented and accounts for temperature-dependent changes in thermal conductivity. The procedure presented enables accurate measurement of TCR for contacting materials whose thermalmore » conductivity is any arbitrary function of temperature. For example, it is shown that the standard technique yields TCR values that are about 15% below the actual value for two specific examples of copper and silicon contacts. Conversely, the generalized technique predicts TCR values that are within 1% of the actual value. The method is exact when thermal conductivity is known exactly and no other errors are introduced to the system.« less

Sorption of hydrogen by silica aerogel at low-temperatures

NASA Astrophysics Data System (ADS)

Dolbin, A. V.; Khlistyuck, M. V.; Esel'son, V. B.; Gavrilko, V. G.; Vinnikov, N. A.; Basnukaeva, R. M.; Martsenuk, V. E.; Veselova, N. V.; Kaliuzhnyi, I. A.; Storozhko, A. V.

2018-02-01

The programmed thermal desorption method is used at temperatures of 7-95 K to study the sorption and subsequent desorption of hydrogen by a sample of silica aerogel. Physical sorption of hydrogen owing to the weak van-der-Waals interaction of hydrogen molecules with the silicon dioxide walls of the pores of the sample was observed over the entire temperature range. The total capacity of the aerogel sample for hydrogen was ˜1.5 mass %. It was found that when the sample temperature was lowered from 95 to 60 K, the characteristic sorption times for hydrogen by the silica aerogel increase; this is typical of thermally activated diffusion (Ea ≈ 408 K). For temperatures of 15-45 K the characteristic H2 sorption times depended weakly on temperature, presumably because of the predominance of a tunnel mechanism for diffusion over thermally activated diffusion. Below 15 K the characteristic sorption times increase somewhat as the temperature is lowered; this may be explained by the formation of a monolayer of H2 molecules on the surface of the aerogel grains.

Plasma protein denaturation with graded heat exposure.

PubMed

Vazquez, R; Larson, D F

2013-11-01

During cardiopulmonary bypass (CPB), perfusion at tepid temperatures (33-35 °C) is recommended to avoid high temperature cerebral hyperthermia during and after the operation. However, the ideal temperature for uncomplicated adult cardiac surgery is an unsettled question. Typically, the heat exchanger maximum temperature is monitored between 40-42 °C to prevent denaturation of plasma proteins, but studies have not been performed to make these conclusions. Therefore, our hypothesis was to determine the temperature in which blood plasma protein degradation occurs after 2 hours of heat exposure. As a result, blood plasma proteins were exposed to heat in the 37-50 °C range for 2 hours. Plasma protein samples were loaded onto an 8-12% gradient gel for SDS-PAGE and low molecular weight plasma protein degradation was detected with graded heat exposure. Protein degradation was first detected between 43-45 °C of heat exposure. This study supports the practice of monitoring the heat exchanger between 40-42 °C to prevent denaturation of plasma proteins.

Pollutant emissions from flat-flame burners at high pressures

NASA Technical Reports Server (NTRS)

Maahs, H. G.; Miller, I. M.

1980-01-01

Maximum flame temperatures and pollutant emission measurements for NOx, CO, and UHC (unburned hydrocarbons) are reported for premixed methane air flat flames at constant total mass flow rate over the pressure range from 1.9 to 30 atm and for equivalence ratios from 0.84 to 1.12. For any given pressure, maxima typically occur in both the temperature and NOx emissions curves slightly to the lean side of stoichiometric conditions. The UHC emissions show minima at roughly the same equivalence ratios. The CO emissions, however, increase continually with increasing equivalence ratio. Flame temperature and NOx emissions decrease with increasing pressure, while the opposite is true for the CO and UHC emissions. The NOx data correlate reasonably well as a function of flame temperature only. Four flameholders, differing only slightly, were used. In general, the temperature and emissions data from these four flameholders are similar, but some differences also exist. These differences appear to be related to minor variations in the condition of the flameholder surfaces.

Oxidation effects on the mechanical properties of SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.

1989-01-01

The room temperature mechanical properties of SiC fiber reinforced reaction bonded silicon nitride composites were measured after 100 hrs exposure at temperatures to 1400 C in nitrogen and oxygen environments. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers in a reaction bonded Si3N4 matrix. The results indicate that composites heat treated in a nitrogen environment at temperatures to 1400 C showed deformation and fracture behavior equivalent to that of the as-fabricated composites. Also, the composites heat treated in an oxidizing environment beyond 400 C yielded significantly lower tensile strength values. Specifically in the temperature range from 600 to 1000 C, composites retained approx. 40 percent of their as-fabricated strength, and those heat treated in the temperatures from 1200 to 1400 C retained 70 percent. Nonetheless, for all oxygen heat treatment conditions, composite specimens displayed strain capability beyond the matrix fracture stress; a typical behavior of a tough composite.

A potential remote sensor of CO in vehicle exhausts using 2.3 µm diode lasers

NASA Astrophysics Data System (ADS)

Wang, Jian; Maiorov, Mikhail; Jeffries, Jay B.; Garbuzov, Dmitri Z.; Connolly, John C.; Hanson, Ronald K.

2000-11-01

The potential for on-road remote sensing of vehicle exhausts using 2.3 µm diode-laser-absorption-based CO sensors is examined. Using a wavelength-modulation- spectroscopy (WMS) technique, 20 ppm sensitivity with a detection bandwidth of ≃1.5 kHz is demonstrated in laboratory experiments, which implies the ability to monitor CO emissions from even the cleanest combustion-powered vehicles. The influence of the temperature and composition of the exhaust gas on the inferred CO concentration through both linestrength and linewidth is also investigated and we propose a novel approach to reduce these effects to ±3% in the typical exhaust temperature range of 300-700 K. Thus, sensitive and remote measurements of vehicular CO effluent are possible without knowing the exact temperature or composition of the exhaust. This influence of temperature is further exploited to suggest a two-line CO2-absorption thermometry method with a large temperature sensitivity to identify cold-start vehicles.

M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C

NASA Technical Reports Server (NTRS)

Niedra, J. M.

1992-01-01

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as long-term consequence of thermal agitation of domains and of metallurgical change, and also as an immediate consequence of too large an applied field. Investigated here is the short-term demagnetization resistance to applied fields derived from basic M-H data. These quasistatic demagnetization data were obtained for commercial, high-intrinsic-coercivity, Sm2Co17-type magnets from 5 sources, in the temperature range 23 to 300 C. An electromagnet driven, electronic hysteresigraph was used to test the 1-cm cubic samples. The observed variation of the 2nd quadrant M-H characteristics was a typical rapid loss of M-coercivity and a relatively lesser loss of remanence with increasing temperature.

Heat Sponge: A Concept for Mass-Efficient Heat Storage

NASA Technical Reports Server (NTRS)

Splinter, Scott C.; Blosser, Max L.; Gifford, Andrew R.

2008-01-01

The heat sponge is a device for mass-efficient storage of heat. It was developed to be incorporated in the substructure of a re-entry vehicle to reduce thermal- protection-system requirements. The heat sponge consists of a liquid/vapor mixture contained within a number of miniature pressure vessels that can be embedded within a variety of different types of structures. As temperature is increased, pressure in the miniature pressure vessels also increases so that heat absorbed through vaporization of the liquid is spread over a relatively large temperature range. Using water as a working fluid, the heat-storage capacity of the liquid/vapor mixture is many times higher than that of typical structural materials and is well above that of common phase change materials over a temperature range of 200 F to 700 F. The use of pure ammonia as the working fluid provides a range of application between 432 deg R and 730 deg R, or the use of the more practical water-ammonia solution provides a range of application between 432 deg R and 1160 deg R or in between that of water and pure ammonia. Prototype heat sponges were fabricated and characterized. These heat sponges consisted of 1.0-inch-diameter, hollow, stainless-steel spheres with a wall thickness of 0.020 inches which had varying percentages of their interior volumes filled with water and a water-ammonia solution. An apparatus to measure the heat stored in these prototype heat sponges was designed, fabricated, and verified. The heat-storage capacity calculated from measured temperature histories is compared to numerical predictions.

Contributions of different degrees of freedom to thermal transport in the C60 molecular crystal

NASA Astrophysics Data System (ADS)

Kumar, Sushant; Shao, Cheng; Lu, Simon; McGaughey, Alan J. H.

2018-03-01

Three models of the C60 molecular crystal are studied using molecular dynamics simulations to resolve the roles played by intermolecular and intramolecular degrees of freedom (DOF) in its structural, mechanical, and thermal properties at temperatures between 35 and 400 K. In the full DOF model, all DOF are active. In the rigid body model, the intramolecular DOF are frozen, such that only center of mass (COM) translations and molecular rotations/librations are active. In the point mass model, the molecule is replaced by a point mass, such that only COM translations are active. The zero-pressure lattice constants and bulk moduli predicted from the three models fall within ranges of 0.15 and 20%. The thermal conductivity of the point mass model is the largest across the temperature range, showing a crystal-like temperature dependence (i.e., it decreases with increasing temperature) due to the presence of phonon modes associated with the COM translations. The rigid body model thermal conductivity is the smallest and follows two distinct regimes. It is crystal-like at low temperatures and becomes temperature invariant at high temperatures. The latter is typical of the behavior of an amorphous material. By calculating the rotational diffusion coefficient, the transition between the two regimes is found to occur at the temperature where the molecules begin to rotate freely. Above this temperature, phonons related to COM translations are scattered by the rotational DOF. The full DOF model thermal conductivity is larger than that of the rigid body model, indicating that intramolecular DOF contribute to thermal transport.

Determination of Scattering and Absorption Coefficients for Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings at Elevated Temperatures

NASA Technical Reports Server (NTRS)

Eldridge, Jeffrey I.; Spuckler, Charles M.; Markham, James R.

2009-01-01

The temperature dependence of the scattering and absorption coefficients for a set of freestanding plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) was determined at temperatures up to 1360 C in a wavelength range from 1.2 micrometers up to the 8YSZ absorption edge. The scattering and absorption coefficients were determined by fitting the directional-hemispherical reflectance and transmittance values calculated by a four-flux Kubelka Munk method to the experimentally measured hemispherical-directional reflectance and transmittance values obtained for five 8YSZ thicknesses. The scattering coefficient exhibited a continuous decrease with increasing wavelength and showed no significant temperature dependence. The scattering is primarily attributed to the relatively temperature-insensitive refractive index mismatch between the 8YSZ and its internal voids. The absorption coefficient was very low (less than 1 per centimeter) at wavelengths between 2 micrometers and the absorption edge and showed a definite temperature dependence that consisted of a shift of the absorption edge to shorter wavelengths and an increase in the weak absorption below the absorption edge with increasing temperature. The shift in the absorption edge with temperature is attributed to strongly temperature-dependent multiphonon absorption. While TBC hemispherical transmittance beyond the absorption edge can be predicted by a simple exponential decrease with thickness, below the absorption edge, typical TBC thicknesses are well below the thickness range where a simple exponential decrease in hemispherical transmittance with TBC thickness is expected. [Correction added after online publication August 11, 2009: "edge to a shorter wavelengths" has been updated as edge to shorter wavelengths."

Requirements for a reliable millennium temperature reconstruction

NASA Astrophysics Data System (ADS)

Christiansen, Bo; Ljungqvist, Fredrik

2014-05-01

Quantitative temperature reconstructions are hampered by several problems. Proxy records are sparse which is witnessed by the fact that roughly half of all available high-resolution millennia-long proxy data have been published in the last five years. Moreover, proxies are inhomogeneously distributed around the globe and they often have coarse temporal resolution. The period of overlap between proxies and instrumental observations - the calibration period - is brief and dominated by a strong warming trend. Furthermore, proxies are often only weakly correlated to temperature and it is common that some form of screening procedure is applied to select only informative proxies. We study the influence of these limitations on the reliability of temperature reconstructions for the previous millennium. This influence depends on the spatial and temporal correlation structure of the surface temperature field. It also depends on the reconstruction methodology. We use gridded surface temperature data from GISTEMP and HadCRUT4 to investigate the geographical distribution of the spatial decorrelation length and of the temporal decorrelation time. The spatial decorrelation length varies with more than a factor of 5 with the largest values in the region dominated by the El Nino-Southern Oscillation. The temporal decorrelation time varies less with typical values of 1-2 years over land and 2-5 years over ocean. We also investigate the correlations between proxies and local temperatures (using the 91 proxies from Christiansen and Ljungqvist 2012) and between local temperatures and the NH mean temperature. These correlations have typical values around 0.3 but cover a wide range from weakly negative to larger than 0.8. The results outlined above allow us to identify regions where the effect of the lack of proxies is most important. They also inform us on the consequences of the short calibration period and on the influence of the recent trend. Finally, we demonstrate the effect of a weak proxy/temperature relationship on three different simple reconstruction methodologies. We show that the size and strength of this effect depends strongly on the chosen methodology.

Understanding and quantifying foliar temperature acclimation for Earth System Models

NASA Astrophysics Data System (ADS)

Smith, N. G.; Dukes, J.

2015-12-01

Photosynthesis and respiration on land are the two largest carbon fluxes between the atmosphere and Earth's surface. The parameterization of these processes represent major uncertainties in the terrestrial component of the Earth System Models used to project future climate change. Research has shown that much of this uncertainty is due to the parameterization of the temperature responses of leaf photosynthesis and autotrophic respiration, which are typically based on short-term empirical responses. Here, we show that including longer-term responses to temperature, such as temperature acclimation, can help to reduce this uncertainty and improve model performance, leading to drastic changes in future land-atmosphere carbon feedbacks across multiple models. However, these acclimation formulations have many flaws, including an underrepresentation of many important global flora. In addition, these parameterizations were done using multiple studies that employed differing methodology. As such, we used a consistent methodology to quantify the short- and long-term temperature responses of maximum Rubisco carboxylation (Vcmax), maximum rate of Ribulos-1,5-bisphosphate regeneration (Jmax), and dark respiration (Rd) in multiple species representing each of the plant functional types used in global-scale land surface models. Short-term temperature responses of each process were measured in individuals acclimated for 7 days at one of 5 temperatures (15-35°C). The comparison of short-term curves in plants acclimated to different temperatures were used to evaluate long-term responses. Our analyses indicated that the instantaneous response of each parameter was highly sensitive to the temperature at which they were acclimated. However, we found that this sensitivity was larger in species whose leaves typically experience a greater range of temperatures over the course of their lifespan. These data indicate that models using previous acclimation formulations are likely incorrectly simulating leaf carbon exchange responses to future warming. Therefore, our data, if used to parameterize large-scale models, are likely to provide an even greater improvement in model performance, resulting in more reliable projections of future carbon-clime feedbacks.

Extraordinary range expansion in a common bat: the potential roles of climate change and urbanisation.

PubMed

Ancillotto, L; Santini, L; Ranc, N; Maiorano, L; Russo, D

2016-04-01

Urbanisation and climate change are two global change processes that affect animal distributions, posing critical threats to biodiversity. Due to its versatile ecology and synurbic habits, Kuhl's pipistrelle (Pipistrellus kuhlii) offers a unique opportunity to explore the relative effects of climate change and urbanisation on species distributions. In a climate change scenario, this typically Mediterranean species is expected to expand its range in response to increasing temperatures. We collected 25,132 high-resolution occurrence records from P. kuhlii European range between 1980 and 2013 and modelled the species' distribution with a multi-temporal approach, using three bioclimatic variables and one proxy of urbanisation. Temperature in the coldest quarter of the year was the most important factor predicting the presence of P. kuhlii and showed an increasing trend in the study period; mean annual precipitation and precipitation seasonality were also relevant, but to a lower extent. Although urbanisation increased in recently colonised areas, it had little effect on the species' presence predictability. P. kuhlii expanded its geographical range by about 394 % in the last four decades, a process that can be interpreted as a response to climate change.

Extraordinary range expansion in a common bat: the potential roles of climate change and urbanisation

NASA Astrophysics Data System (ADS)

Ancillotto, L.; Santini, L.; Ranc, N.; Maiorano, L.; Russo, D.

2016-04-01

Urbanisation and climate change are two global change processes that affect animal distributions, posing critical threats to biodiversity. Due to its versatile ecology and synurbic habits, Kuhl's pipistrelle ( Pipistrellus kuhlii) offers a unique opportunity to explore the relative effects of climate change and urbanisation on species distributions. In a climate change scenario, this typically Mediterranean species is expected to expand its range in response to increasing temperatures. We collected 25,132 high-resolution occurrence records from P. kuhlii European range between 1980 and 2013 and modelled the species' distribution with a multi-temporal approach, using three bioclimatic variables and one proxy of urbanisation. Temperature in the coldest quarter of the year was the most important factor predicting the presence of P. kuhlii and showed an increasing trend in the study period; mean annual precipitation and precipitation seasonality were also relevant, but to a lower extent. Although urbanisation increased in recently colonised areas, it had little effect on the species' presence predictability. P. kuhlii expanded its geographical range by about 394 % in the last four decades, a process that can be interpreted as a response to climate change.

Formation of lobate debris aprons on Mars: Assessment of regional ice sheet collapse and debris-cover armoring

NASA Astrophysics Data System (ADS)

Fastook, James L.; Head, James W.; Marchant, David R.

2014-01-01

Lobate debris aprons (LDA) are lobate-shaped aprons surrounding scarps and isolated massifs that are concentrated in the vicinity of the northern Dichotomy Boundary on Mars. LDAs have been interpreted as (1) ice-cemented talus aprons undergoing viscous flow, (2) local debris-covered alpine-like glaciers, or (3) remnants of the collapse of a regional retreating ice sheet. We investigate the plausibility that LDAs are remnants of a more extensive regional ice sheet by modeling this process. We find that as a regional ice sheet collapses, the surface drops below cliff and massif bedrock margins, exposing bedrock and regolith, and initiating debris deposition on the surface of a cold-based glacier. Reduced sublimation due to debris-cover armoring of the proto-LDA surface produces a surface slope and consequent ice flow that carries the armoring debris away from the rock outcrops. As collapse and ice retreat continue the debris train eventually reaches the substrate surface at the front of the glacier, leaving the entire LDA armored by debris cover. Using a simplified ice flow model we are able to characterize the temperature and sublimation rate that would be necessary to produce LDAs with a wide range of specified lateral extents and thicknesses. We then apply this method to a database of documented LDA parameters (height, lateral extent) from the Dichotomy Boundary region, and assess the implications for predicted climate conditions during their formation and the range of formation times implied by the model. We find that for the population examined here, typical temperatures are in the range of -85 to -40 °C and typical sublimation rates lie in the range of 6-14 mm/a. Lobate debris apron formation times (from the point of bedrock exposure to complete debris cover) cluster near 400-500 ka. These results show that LDA length and thickness characteristics are consistent with climate conditions and a formation scenario typical of the collapse of a regional retreating ice sheet and exposure of bedrock cliffs. This scenario helps resolve many of the unusual characteristics of lobate debris aprons (LDA) and lineated valley fill (LVF). For example, the distribution of LVF is very consistent with extensive flow of glacial ice from plateau icefields, and the acquisition of a debris cover in the waning stages of retreat of the regional cover as the bedrock scarps are exposed. The typical concentric development of LDA around massifs is much more consistent with ice sheet retreat than insolation-related local accumulation and flow. We thus conclude that the retreating ice-sheet model is robust and should be investigated and tested in more detail. In addition, these results clearly show that the lobate debris aprons in the vicinity of the Dichotomy Boundary could not have attained temperatures near or above the ice melting point and retained their current shape, a finding that supports subzero temperatures for the last several hundred million years, the age of the LDA surfaces. A further implication is that the LDA ice has been preserved for at least several hundred million years, and could potentially contain the record of the climate of Mars, preserved since that time below a sublimation lag deposit.

Entropy production and optimization of geothermal power plants

NASA Astrophysics Data System (ADS)

Michaelides, Efstathios E.

2012-09-01

Geothermal power plants are currently producing reliable and low-cost, base load electricity. Three basic types of geothermal power plants are currently in operation: single-flashing, dual-flashing, and binary power plants. Typically, the single-flashing and dual-flashing geothermal power plants utilize geothermal water (brine) at temperatures in the range of 550-430 K. Binary units utilize geothermal resources at lower temperatures, typically 450-380 K. The entropy production in the various components of the three types of geothermal power plants determines the efficiency of the plants. It is axiomatic that a lower entropy production would improve significantly the energy utilization factor of the corresponding power plant. For this reason, the entropy production in the major components of the three types of geothermal power plants has been calculated. It was observed that binary power plants generate the lowest amount of entropy and, thus, convert the highest rate of geothermal energy into mechanical energy. The single-flashing units generate the highest amount of entropy, primarily because they re-inject fluid at relatively high temperature. The calculations for entropy production provide information on the equipment where the highest irreversibilities occur, and may be used to optimize the design of geothermal processes in future geothermal power plants and thermal cycles used for the harnessing of geothermal energy.

Measurement and calculation of ternary oxide mixtures for thin films for ultra short pulse laser optics

NASA Astrophysics Data System (ADS)

Jupé, M.; Mende, M.; Kolleck, C.; Ristau, D.; Gallais, L.; Mangote, B.

2011-12-01

The femto-second technology gains of increasing importance in industrial applications. In this context, a new generation of compact and low cost laser sources has to be provided on a commercial basis. Typical pulse durations of these sources are specified in the range from a few hundred femtoup to some pico-seconds, and typical wavelengths are centered around 1030-1080nm. As a consequence, also the demands imposed on high power optical components for these laser sources are rapidly increasing, especially in respect to their power handling capability in the ultra-short pulse range. The present contribution is dedicated to some aspects for improving this quality parameter of optical coatings. The study is based on a set of hafnia and silica mixtures with different compositions and optical band gaps. This material combination displays under ultra-short pulse laser irradiation effects, which are typically for thermal processes. For instance, melting had been observed in the morphology of damaged sides. In this context, models for a prediction of the laser damage thresholds and scaling laws are scrutinized, and have been modified calculating the energy of the electron ensemble. Furthermore, a simple first order approach for the calculation of the temperature was included.

Paramagnetic ionic liquids for measurements of density using magnetic levitation.

PubMed

Bwambok, David K; Thuo, Martin M; Atkinson, Manza B J; Mirica, Katherine A; Shapiro, Nathan D; Whitesides, George M

2013-09-03

Paramagnetic ionic liquids (PILs) provide new capabilities to measurements of density using magnetic levitation (MagLev). In a typical measurement, a diamagnetic object of unknown density is placed in a container containing a PIL. The container is placed between two magnets (typically NdFeB, oriented with like poles facing). The density of the diamagnetic object can be determined by measuring its position in the magnetic field along the vertical axis (levitation height, h), either as an absolute value or relative to internal standards of known density. For density measurements by MagLev, PILs have three advantages over solutions of paramagnetic salts in aqueous or organic solutions: (i) negligible vapor pressures; (ii) low melting points; (iii) high thermal stabilities. In addition, the densities, magnetic susceptibilities, glass transition temperatures, thermal decomposition temperatures, viscosities, and hydrophobicities of PILs can be tuned over broad ranges by choosing the cation-anion pair. The low melting points and high thermal stabilities of PILs provide large liquidus windows for density measurements. This paper demonstrates applications and advantages of PILs in density-based analyses using MagLev.

Bose-Einstein Condensation of Long-Lifetime Polaritons in Thermal Equilibrium.

PubMed

Sun, Yongbao; Wen, Patrick; Yoon, Yoseob; Liu, Gangqiang; Steger, Mark; Pfeiffer, Loren N; West, Ken; Snoke, David W; Nelson, Keith A

2017-01-06

The experimental realization of Bose-Einstein condensation (BEC) with atoms and quasiparticles has triggered wide exploration of macroscopic quantum effects. Microcavity polaritons are of particular interest because quantum phenomena such as BEC and superfluidity can be observed at elevated temperatures. However, polariton lifetimes are typically too short to permit thermal equilibration. This has led to debate about whether polariton condensation is intrinsically a nonequilibrium effect. Here we report the first unambiguous observation of BEC of optically trapped polaritons in thermal equilibrium in a high-Q microcavity, evidenced by equilibrium Bose-Einstein distributions over broad ranges of polariton densities and bath temperatures. With thermal equilibrium established, we verify that polariton condensation is a phase transition with a well-defined density-temperature phase diagram. The measured phase boundary agrees well with the predictions of basic quantum gas theory.

Dynamic spectral shifts of molecular anions in organic glasses. [Pulse radiolysis

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

Huddleston, R.K.; Miller, J.R.

1982-06-24

Time-dependent spectra of the radical anions of pyromellitic dianhydride and p-dinitrobenzene have been observed after formation by pulse radiolysis in frozen 2-methyltetrahydrofuran and triacetin glasses. At temperatures near the glass transition, the spectra shift toward the blue over the entire observed time range 100 ns to 100 s), while at temperatures well below the glass transition, the spectral shifts can be stopped or greatly slowed. The magnitudes of the shifts are not large (typically approx. = to 10 nm), but because they are larger than the vibrational line widths, dramatic kinetics may be observed: the absorbance grows or decays bymore » more than a factor of five at some wavelengths. The observations are consistent with a solvent molecule reorientation mechanism for spectral shifts of molecular ions in low-temperature organic glasses. 6 figures.« less

Analytical pair correlations in ideal quantum gases: temperature-dependent bunching and antibunching.

PubMed

Bosse, J; Pathak, K N; Singh, G S

2011-10-01

The fluctuation-dissipation theorem together with the exact density response spectrum for ideal quantum gases has been utilized to yield a new expression for the static structure factor, which we use to derive exact analytical expressions for the temperature-dependent pair distribution function g(r) of the ideal gases. The plots of bosonic and fermionic g(r) display "Bose pile" and "Fermi hole" typically akin to bunching and antibunching as observed experimentally for ultracold atomic gases. The behavior of spin-scaled pair correlation for fermions is almost featureless, but bosons show a rich structure including long-range correlations near T(c). The coherent state at T=0 shows no correlation at all, just like single-mode lasers. The depicted decreasing trend in correlation with decrease in temperature for T

Magneto-optical spectroscopy of ferromagnetic shape-memory Ni-Mn-Ga alloy

NASA Astrophysics Data System (ADS)

Veis, M.; Beran, L.; Zahradnik, M.; Antos, R.; Straka, L.; Kopecek, J.; Fekete, L.; Heczko, O.

2014-05-01

Magneto-optical properties of single crystal of Ni50.1Mn28.4Ga21.5 magnetic shape memory alloy in martensite and austenite phase were systematically studied. Crystal orientation was approximately along {100} planes of parent cubic austenite. At room temperature, the sample was in modulated 10M martensite phase and transformed to cubic austenite at 323 K. Spectral dependence of polar magneto-optical Kerr effect was obtained by generalized magneto-optical ellipsometry with rotating analyzer in the photon energy range from 1.2 to 4 eV, and from room temperature to temperature above the Curie point. The Kerr rotation spectra exhibit prominent features typical for complexes containing Mn atoms. Significant spectral changes during transformation to austenite can be explained by different optical properties caused by changes in density of states near the Fermi energy.

In-depth analysis and modelling of self-heating effects in nanometric DGMOSFETs

NASA Astrophysics Data System (ADS)

Roldán, J. B.; González, B.; Iñiguez, B.; Roldán, A. M.; Lázaro, A.; Cerdeira, A.

2013-01-01

Self-heating effects (SHEs) in nanometric symmetrical double-gate MOSFETs (DGMOSFETs) have been analysed. An equivalent thermal circuit for the transistors has been developed to characterise thermal effects, where the temperature and thickness dependency of the thermal conductivity of the silicon and oxide layers within the devices has been included. The equivalent thermal circuit is consistent with simulations using a commercial technology computer-aided design (TCAD) tool (Sentaurus by Synopsys). In addition, a model for DGMOSFETs has been developed where SHEs have been considered in detail, taking into account the temperature dependence of the low-field mobility, saturation velocity, and inversion charge. The model correctly reproduces Sentaurus simulation data for the typical bias range used in integrated circuits. Lattice temperatures predicted by simulation are coherently reproduced by the model for varying silicon layer geometry.

Critical shear stress for erosion of cohesive soils subjected to temperatures typical of wildfires

USGS Publications Warehouse

Moody, J.A.; Dungan, Smith J.; Ragan, B.W.

2005-01-01

[1] Increased erosion is a well-known response after wildfire. To predict and to model erosion on a landscape scale requires knowledge of the critical shear stress for the initiation of motion of soil particles. As this soil property is temperature-dependent, a quantitative relation between critical shear stress and the temperatures to which the soils have been subjected during a wildfire is required. In this study the critical shear stress was measured in a recirculating flume using samples of forest soil exposed to different temperatures (40??-550??C) for 1 hour. Results were obtained for four replicates of soils derived from three different types of parent material (granitic bedrock, sandstone, and volcanic tuffs). In general, the relation between critical shear stress and temperature can be separated into three different temperature ranges (275??C), which are similar to those for water repellency and temperature. The critical shear stress was most variable (1.0-2.0 N m-2) for temperatures 2.0 N m-2) between 175?? and 275??C, and was essentially constant (0.5-0.8 N m-2) for temperatures >275??C. The changes in critical shear stress with temperature were found to be essentially independent of soil type and suggest that erosion processes in burned watersheds can be modeled more simply than erosion processes in unburned watersheds. Wildfire reduces the spatial variability of soil erodibility associated with unburned watersheds by eliminating the complex effects of vegetation in protecting soils and by reducing the range of cohesion associated with different types of unburned soils. Our results indicate that modeling the erosional response after a wildfire depends primarily on determining the spatial distribution of the maximum soil temperatures that were reached during the wildfire. Copyright 2005 by the American Geophysical Union.

NASA GRC's High Pressure Burner Rig Facility and Materials Test Capabilities

NASA Technical Reports Server (NTRS)

Robinson, R. Craig

1999-01-01

The High Pressure Burner Rig (HPBR) at NASA Glenn Research Center is a high-velocity. pressurized combustion test rig used for high-temperature environmental durability studies of advanced materials and components. The facility burns jet fuel and air in controlled ratios, simulating combustion gas chemistries and temperatures that are realistic to those in gas turbine engines. In addition, the test section is capable of simulating the pressures and gas velocities representative of today's aircraft. The HPBR provides a relatively inexpensive. yet sophisticated means for researchers to study the high-temperature oxidation of advanced materials. The facility has the unique capability of operating under both fuel-lean and fuel-rich gas mixtures. using a fume incinerator to eliminate any harmful byproduct emissions (CO, H2S) of rich-burn operation. Test samples are easily accessible for ongoing inspection and documentation of weight change, thickness, cracking, and other metrics. Temperature measurement is available in the form of both thermocouples and optical pyrometery. and the facility is equipped with quartz windows for observation and video taping. Operating conditions include: (1) 1.0 kg/sec (2.0 lbm/sec) combustion and secondary cooling airflow capability: (2) Equivalence ratios of 0.5- 1.0 (lean) to 1.5-2.0 (rich), with typically 10% H2O vapor pressure: (3) Gas temperatures ranging 700-1650 C (1300-3000 F): (4) Test pressures ranging 4-12 atmospheres: (5) Gas flow velocities ranging 10-30 m/s (50-100) ft/sec.: and (6) Cyclic and steady-state exposure capabilities. The facility has historically been used to test coupon-size materials. including metals and ceramics. However complex-shaped components have also been tested including cylinders, airfoils, and film-cooled end walls. The facility has also been used to develop thin-film temperature measurement sensors.

What Limits the Distribution of Liriomyza huidobrensis and Its Congener Liriomyza sativae in Their Native Niche: When Temperature and Competition Affect Species' Distribution Range in Guatemala.

PubMed

Rodríguez-Castañeda, G; MacVean, C; Cardona, C; Hof, A R

2017-07-01

Factors limiting distribution range for most species are generally unknown regardless of whether they are native or invasive. We studied factors that could enable or restrict the distribution of two cosmopolitan invasive leafminer fly species, Liriomyza huidobrensis (Blanchard) and Liriomyza sativae (Blanchard) in their native niche. In order to test which ecological and environmental factors affect leafminer distribution we conducted thermal tolerance assays, sampled along elevation gradients and modeled species distribution. Findings from the field and rearing chambers showed a physiological restriction due to high temperatures for L. huidobrensis at 28-29 °C, above which adult emergence is compromised. We also found that maximum temperatures below 22 °C, typical of tropical highlands, favored L. huidobrensis. L. sativae was found across a wider temperature range (i.e., from 21 to 36 °C) in Guatemala. Our finding of a physiological threshold in temperature for L. huidobrensis may enable us to predict its invasive risk when combined with the environmental conditions at horticultural ports of entry and the global agricultural landscape. Further, it strengthens our predictions on shifts in distribution of the leafminer fly under future climate. We also found a temperature mediated competitive exclusion interaction between the two herbivore species, where L. sativae occurred at temperatures < 22 °C only in the absence of L. huidobrensis. We show that parasitoids had a negative effect on the leafminer flies, which varied with host plant. Finally, we show the importance of taking a multiaspect approach when investigating what limits distribution and invasiveness of a species. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America.

Paleomagnetic and Anisotropy of Magnetic Susceptibility (AMS) Documentation of the Formation of Large-Scale Rheomorphic Structures in the 2.06 Ma Huckleberry Ridge Tuff, Eastern Idaho

NASA Astrophysics Data System (ADS)

Geissman, J. W.; Holm, D.; Harlan, S. S.

2006-12-01

In the Teton River Valley, east of Rexburg, Idaho, the ca. 2.06 Ma Huckleberry Ridge Tuff is about 130 m thick, exceedingly well-exposed, and displays large-scale (100-150 m+ amplitude) rheomorphic folds, with eutaxitic fabrics that are parallel to inferred primary internal zonation (e.g. boundary between basal vitrophyre and overlying devitrified part of the pyroclastic deposit) as well as the basal contact with older deposits defining the fold geometries. One 150 m amplitude fold , is well-exposed on the north side of the valley about 2.5 km east of Teton Dam, has a NW trending fold axis and has a southwest limb that is overturned by about 45o. Samples were collected from 16 sites in this fold, on both limbs and the hinge area, to test the hypothesis that folding took place above maximum TRM blocking temperatures (about 580C). Progressive AF and thermal demagnetization both yield characteristic magnetizations of southwest to south-southwest declination and shallow inclination removed over a range of peak fields (typically between 20 and 80 mT) and laboratory unblocking temperatures (typically between 350 and 580C). The preliminary determination of an in situ mean based on the 16 sites is about D = 215°, I = -5°, a95= 5°, N = 16 site means). The direction of this ChRM is statistically indistinguishable from that reported by previous studies of the tuff (e.g. Reynolds, 1977, JGR; Byrd et al., 1994, JGR). The trend of the fold axis is orthogonal to this declination; the paleomagnetic fold test applied to these data is negative, with k values continuously decreasing upon unfolding, thus indicating that the entire structure in the tuff formed after the well-developed compaction fabric was acquired, at a temperature above maximum blocking temperatures of the ChRM. Post-compaction, high temperature deformation is consistent with field evidence indicating plastic secondary deformation of much of the tuff prior to devitrification. Rapid strain rates probably contributed to the formation of brittle features in the uppermost parts of the tuff (joints and fissures). AMS fabrics, at the site level, are typically very well-defined, with AMS foliations roughly parallel to compaction fabric, with K1 (maximum principal susceptibility) axes typically directed in a southwest-northeast orientation.

Materials erosion and redeposition studies at the PISCES-facility: net erosion under redeposition

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

Hirooka, Y.; Goebel, D.M.; Conn, R.W.

1986-05-01

Simultaneous erosion and redeposition of copper and 304 stainless steel under controlled and continuous plasma (D,He,Ar) bombardment has been investigated in the PISCES-facility, which generates typical edge-plasma conditions of magnetic fusion devices. The plasma bombardment conditions are: incident ion flux in the range from 10/sup 17/ to 10/sup 18/ ions/sec/cm/sup 2/, ion bombarding energy of 100 eV, electron temperature in the range from 5 to 15 eV, plasma density in the range from 10/sup 11/ to 10/sup 13/ cm/sup -3/, target temperature in the range from 300 to 900K, and the total ion fluence in the range from 10/sup 20/more » to 10/sup 22/ ions/cm/sup 2/. The net erosion yield under redeposition is found to be significantly smaller than the classical sputtering yield data. A first-order modeling is attempted to interpret the erosion and redeposition behavior of materials under plasma bombardment. It is pointed out both theoretically and experimentally that the mean free path for electron impact ionization of the sputtered material is the key parameter to control the overall mechanism of erosion and redeposition. Strongly modified surface morphologies of bombarded targets are observed and indicate a retrapping effect.« less

Quantum dynamics of the Eley-Rideal hydrogen formation reaction on graphite at typical interstellar cloud conditions.

PubMed

Casolo, Simone; Martinazzo, Rocco; Bonfanti, Matteo; Tantardini, Gian Franco

2009-12-31

Eley-Rideal formation of hydrogen molecules on graphite, as well as competing collision induced processes, are investigated quantum dynamically at typical interstellar cloud conditions, focusing in particular on gas-phase temperatures below 100 K, where much of the chemistry of the so-called diffuse clouds takes place on the surface of bare carbonaceous dust grains. Collisions of gas-phase hydrogen atoms with both chemisorbed and physisorbed species are considered using available potential energy surfaces (Sha et al., J. Chem. Phys.2002 116, 7158), and state-to-state, energy-resolved cross sections are computed for a number of initial vibrational states of the hydrogen atoms bound to the surface. Results show that (i) product molecules are internally hot in both cases, with vibrational distributions sharply peaked around few (one or two) vibrational levels, and (ii) cross sections for chemisorbed species are 2-3x smaller than those for physisorbed ones. In particular, we find that H(2) formation cross sections out of chemically bound species decrease steadily when the temperature drops below approximately 1000 K, and this is likely due to a quantum reflection phenomenon. This suggests that such Eley-Rideal reaction is all but efficient in the relevant gas-phase temperature range, even when gas-phase H atoms happen to chemisorb barrierless to the surface as observed, e.g., for forming so-called para dimers. Comparison with results from classical trajectory calculations highlights the need of a quantum description of the dynamics in the astrophysically relevant energy range, whereas preliminary results of an extensive first-principles investigation of the reaction energetics reveal the importance of the adopted substrate model.

Design Guidance for Command, Control, Communications, and Intelligence (C3I) Facility Cooling Systems

DTIC Science & Technology

1989-05-01

Typical ranges are from 50 to 70 OF. If a chiller is dedicated to serving water-cooled electronic equipment, the chilled water temperature setpoint can...can be satisfied with 50 OF chilled water. The COP of the dedicated chiller is improved by raising the chilled water setpoint , and the total life-cycle...USACERL TECHNICAL REPORT E-89/10 May 1989 Studies in Optimizing HVAC Hardware for C31 Facilities US Army Corps of Engineers Construction Engineering

Nonideal isentropic gas flow through converging-diverging nozzles

NASA Technical Reports Server (NTRS)

Bober, W.; Chow, W. L.

1990-01-01

A method for treating nonideal gas flows through converging-diverging nozzles is described. The method incorporates the Redlich-Kwong equation of state. The Runge-Kutta method is used to obtain a solution. Numerical results were obtained for methane gas. Typical plots of pressure, temperature, and area ratios as functions of Mach number are given. From the plots, it can be seen that there exists a range of reservoir conditions that require the gas to be treated as nonideal if an accurate solution is to be obtained.

Effect of steam addition on cycle performance of simple and recuperated gas turbines

NASA Technical Reports Server (NTRS)

Boyle, R. J.

1979-01-01

Results are presented for the cycle efficiency and specific power of simple and recuperated gas turbine cycles in which steam is generated and used to increase turbine flow. Calculations showed significant improvements in cycle efficiency and specific power by adding steam. The calculations were made using component efficiencies and loss assumptions typical of stationary powerplants. These results are presented for a range of operating temperatures and pressures. Relative heat exchanger size and the water use rate are also examined.

Improved Thermal-Insulation Systems for Low Temperatures

NASA Technical Reports Server (NTRS)

Fesmire, James E.; Augustynowicz, Stanislaw D.

2003-01-01

Improved thermal-insulation materials and structures and the techniques for manufacturing them are undergoing development for use in low-temperature applications. Examples of low-temperature equipment for which these thermal insulation systems could provide improved energy efficiency include storage tanks for cryogens, superconducting electric-power-transmission equipment, containers for transport of food and other perishable commodities, and cold boxes for low-temperature industrial processes. These systems could also be used to insulate piping used to transfer cryogens and other fluids, such as liquefied natural gas, refrigerants, chilled water, crude oil, or low-pressure steam. The present thermal-insulation systems are layer composites based partly on the older class of thermal-insulation systems denoted generally as multilayer insulation (MLI). A typical MLI structure includes an evacuated jacket, within which many layers of radiation shields are stacked or wrapped close together. Low-thermal-conductivity spacers are typically placed between the reflection layers to keep them from touching. MLI can work very well when a high vacuum level (less than 10(exp-4) torr) is maintained and utmost care is taken during installation, but its thermal performance deteriorates sharply as the pressure in the evacuated space rises into the soft vacuum range [pressures greater than 0.1 torr (greater than 13 Pa)]. In addition, the thermal performance of MLI is extremely sensitive to mechanical compression and edge effects and can easily decrease from one to two orders of magnitude from its ideal value even when the MLI is kept under high vacuum condition. The present thermal-insulation systems are designed to perform well under soft vacuum level, in particular the range of 1 to 10 torr. They are also designed with larger interlayer spacings to reduce vulnerability to compression (and consequent heat leak) caused by installation and use. The superiority of these systems is the synergistic effect of improvements in materials, design, and manufacture.

Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transformation temperature

NASA Technical Reports Server (NTRS)

Antolovich, Stephen D.; Saxena, Ashok; Cullers, Cheryl

1992-01-01

One of the ongoing challenges of the aerospace industry is to develop more efficient turbine engines. Greater efficiency entails reduced specific strength and larger temperature gradients, the latter of which means higher operating temperatures and increased thermal conductivity. Continued development of nickel-based superalloys has provided steady increases in engine efficiency and the limits of superalloys have probably not been realized. However, other material systems are under intense investigation for possible use in high temperature engines. Ceramic, intermetallic, and various composite systems are being explored in an effort to exploit the much higher melting temperatures of these systems. NiAl is considered a potential alternative to conventional superalloys due to its excellent oxidation resistance, low density, and high melting temperature. The fact that NiAl is the most common coating for current superalloy turbine blades is a tribute to its oxidation resistance. Its density is one-third that of typical superalloys and in most temperature ranges its thermal conductivity is twice that of common superalloys. Despite these many advantages, NiAl requires more investigation before it is ready to be used in engines. Binary NiAl in general has poor high-temperature strength and low-temperature ductility. On-going research in alloy design continues to make improvements in the high-temperature strength of NiAl. The factors controlling low temperature ductility have been identified in the last few years. Small, but reproducible ductility can now be achieved at room temperature through careful control of chemical purity and processing. But the mechanisms controlling the transition from brittle to ductile behavior are not fully understood. Research in the area of fatigue deformation can aid the development of the NiAl system in two ways. Fatigue properties must be documented and optimized before NiAl can be applied to engineering systems. More importantly though, probing the deformation mechanisms operating in fatigue will lead to a better understanding of NiAl's unique characteristics. Low cycle fatigue properties have been reported on binary NiAl in the past year, yet those studies were limited to two temperature ranges: room temperature and near 1000 K. Eventually, fatigue property data will be needed for a wide range of temperatures and compositions. The intermediate temperature range near the brittle-to-ductile transition was chosen for this study to ascertain whether the sharp change occurring in monotonic behavior also occurs under cyclic conditions. An effort was made to characterize the dislocation structures which evolved during fatigue testing and comment on their role in the deformation process.

Low-temperature atomic layer deposition of TiO{sub 2} thin layers for the processing of memristive devices

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

Porro, Samuele, E-mail: samuele.porro@polito.it; Conti, Daniele; Guastella, Salvatore

2016-01-15

Atomic layer deposition (ALD) represents one of the most fundamental techniques capable of satisfying the strict technological requirements imposed by the rapidly evolving electronic components industry. The actual scaling trend is rapidly leading to the fabrication of nanoscaled devices able to overcome limits of the present microelectronic technology, of which the memristor is one of the principal candidates. Since their development in 2008, TiO{sub 2} thin film memristors have been identified as the future technology for resistive random access memories because of their numerous advantages in producing dense, low power-consuming, three-dimensional memory stacks. The typical features of ALD, such asmore » self-limiting and conformal deposition without line-of-sight requirements, are strong assets for fabricating these nanosized devices. This work focuses on the realization of memristors based on low-temperature ALD TiO{sub 2} thin films. In this process, the oxide layer was directly grown on a polymeric photoresist, thus simplifying the fabrication procedure with a direct liftoff patterning instead of a complex dry etching process. The TiO{sub 2} thin films deposited in a temperature range of 120–230 °C were characterized via Raman spectroscopy and x-ray photoelectron spectroscopy, and electrical current–voltage measurements taken in voltage sweep mode were employed to confirm the existence of resistive switching behaviors typical of memristors. These measurements showed that these low-temperature devices exhibit an ON/OFF ratio comparable to that of a high-temperature memristor, thus exhibiting similar performances with respect to memory applications.« less

Mars Atmospheric Temperature and Dust Storm Tracking

NASA Image and Video Library

2016-06-09

This graphic overlays Martian atmospheric temperature data as curtains over an image of Mars taken during a regional dust storm. The temperature profiles extend from the surface to about 50 miles (80 kilometers) up. Temperatures are color coded, ranging from minus 243 degrees Fahrenheit (minus 153 degrees Celsius) where coded purple to minus 9 F (minus 23 C) where coded red. The temperature data and global image were both recorded on Oct. 18, 2014, by instruments on NASA's Mars Reconnaissance Orbiter: Mars Climate Sounder and Mars Color Imager. On that day a regional dust storm was active in the Acidalia Planitia region of northern Mars, at the upper center of this image. A storm from this area in typically travels south and grows into a large regional storm in the southern hemisphere during southern spring. That type of southern-spring storm and two other large regional dust storms repeat as a three-storm series most Martian years. The pattern has been identified from their effects on atmospheric temperature in a layer about 16 miles (25 kilometers) above the surface. http://photojournal.jpl.nasa.gov/catalog/PIA20747

Heating rates in furnace atomic absorption using the L'vov platform

USGS Publications Warehouse

Koirtyohann, S.R.; Giddings, R.C.; Taylor, Howard E.

1984-01-01

Heating rate profiles for the furnace tube wall, the furnace atmosphere, and a L'vov platform were established for a range of conditions in a cyclically heated graphite atomizer. The tube wall profile was made by direct observation with a recording optical pyrometer. The sodium line reversal method was used to establish the heating rate of the furnace atmosphere, and appearance temperatures for a series metals of differing volatility was used to establish platform profiles. The tube wall heating rate was nearly linear at 2240??C s- until the desired temperature was reached after which the temperature remained constant. The furnace atmosphere reached a given temperature 0.2-0.4 s later than the tube wall through most of the atomize cycle. The platform lagged the tube wall 0.5-0.8 s. Under typical operating conditions the furnace atmosphere was 100-200??C cooler than the tube wall and at nearly constant temperature when the analyte vaporized from the platform. The L'vov platform causes the cyclically heated commercial furnace to approximate the behavior of a constant temperature furnace during atomization. ?? 1984.

GRCop-84 Rolling Parameter Study

NASA Technical Reports Server (NTRS)

Loewenthal, William S.; Ellis, David L.

2008-01-01

This report is a section of the final report on the GRCop-84 task of the Constellation Program and incorporates the results obtained between October 2000 and September 2005, when the program ended. NASA Glenn Research Center (GRC) has developed a new copper alloy, GRCop-84 (Cu-8 at.% Cr-4 at.% Nb), for rocket engine main combustion chamber components that will improve rocket engine life and performance. This work examines the sensitivity of GRCop-84 mechanical properties to rolling parameters as a means to better define rolling parameters for commercial warm rolling. Experiment variables studied were total reduction, rolling temperature, rolling speed, and post rolling annealing heat treatment. The responses were tensile properties measured at 23 and 500 C, hardness, and creep at three stress-temperature combinations. Understanding these relationships will better define boundaries for a robust commercial warm rolling process. The four processing parameters were varied within limits consistent with typical commercial production processes. Testing revealed that the rolling-related variables selected have a minimal influence on tensile, hardness, and creep properties over the range of values tested. Annealing had the expected result of lowering room temperature hardness and strength while increasing room temperature elongations with 600 C (1112 F) having the most effect. These results indicate that the process conditions to warm roll plate and sheet for these variables can range over wide levels without negatively impacting mechanical properties. Incorporating broader process ranges in future rolling campaigns should lower commercial rolling costs through increased productivity.

Microstructural, textural and thermal evolution of an exhumed strike-slip fault and insights into localization and rheological transition

NASA Astrophysics Data System (ADS)

Cao, Shuyun; Neubauer, Franz; Liu, Junlai; Bernroider, Manfred; Genser, Johann

2016-04-01

The presence of deep exhumed crustal rocks with a dominant but contrasting mineralogy results in shear concentration in the rheological weakest layer, which exhibits contrasting patterns of fabrics and thermal conditions during their formation. We tested a combination of methodologies including microstructural and textural investigations, geochronology and geothermometry on deformed rocks from exhumed strike-slip fault, Ailao Shan-Red River, SE, Asian. Results indicate that the exhumed deep crustal rocks since late Oligocene (ca. 28 Ma) to Pliocene (ca. 4 Ma) typically involve dynamic microstructural, textural and thermal evolution processes, which typically record a progressive deformation and syn-kinematic reactions from ductile to semi-ductile and brittle behavior during exhumation. This transformation also resulted in dramatic strength reduction that promoted strain localization along the strike-slip and transtensional faults. Detailed analysis has revealed the co-existence of microfabrics ranging from high-temperatures (granulite facies conditions) to overprinting low-temperatures (lower greenschist facies conditions). The high-temperature microstructures and textures are in part or entirely altered by subsequent, overprinting low-temperature shearing. In quartz-rich rocks, quartz was deformed in the dislocation creep regime and records transition of microfabrics and slip systems during decreasing temperature, which lasted until retrogression related to final exhumation. As a result, grain-size reduction associated by fluids circulating within the strike-slip fault zone at brittle-ductile transition leads to rock softening, which resulted in strain localization, weak rock rheology and the overall hot thermal structure of the crust. Decompression occurred during shearing and as a result of tectonic exhumation. All these results demonstrate that the ductile to ductile-brittle transition involves a combination of different deformation mechanisms, rheological transition features and feedbacks between deformation, decreasing temperature and fluids.

The influence of loading frequency on the high-temperature fatigue behavior of a Nicalon-fabric-reinforced polymer-derived ceramic-matrix composite

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

Vanswijgenhoven, E.; Holmes, J.; Wevers, M.

Fiber-reinforced ceramic-matrix composites are under development for high-temperature structural applications. These applications involve fatigue loading under a wide range of frequencies. To date, high-temperature fatigue experiments have typically been performed at loading frequencies of 10 Hz or lower. At higher frequencies, a strong effect of loading frequency on fatigue life has been demonstrated for certain CMC`s tested at room temperature. The fatigue life of CMC`s with weak fiber-matrix interfaces typically decreases as the loading frequency increases. This decrease is attributed to frictional heating and frequency dependent interface and fiber damage. More recently, it has been shown that the room temperaturemore » fatigue life of a Nicalon-fabric-reinforced composite with a strong interface (SYLRAMIC{trademark}) appears to be independent of loading frequency. The high-temperature low-frequency fatigue behavior of the SYLRAMIC composite has also been investigated. For a fatigue peak stress {sigma}{sub peak} above a proportional limit stress of 70 MPa, the number of cycles to failure N{sub f} decreased with an increase in {sigma}{sub peak}. The material endured more than 10{sup 6} cycles for {sigma}{sub peak} below 70 MPa. In this paper, the influence of loading frequency on the high-temperature fatigue behavior of the SYLRAMIC composite is reported. It will be shown that the fatigue limit is unaffected by the loading frequency, that the number of fatigue cycles to failure N{sub f} increases with an increase in frequency, and that the time to failure t{sub f} decreases with an increase in frequency.« less

Evaluation of methods for characterizing the melting curves of a high temperature cobalt-carbon fixed point to define and determine its melting temperature

NASA Astrophysics Data System (ADS)

Lowe, David; Machin, Graham

2012-06-01

The future mise en pratique for the realization of the kelvin will be founded on the melting temperatures of particular metal-carbon eutectic alloys as thermodynamic temperature references. However, at the moment there is no consensus on what should be taken as the melting temperature. An ideal melting or freezing curve should be a completely flat plateau at a specific temperature. Any departure from the ideal is due to shortcomings in the realization and should be accommodated within the uncertainty budget. However, for the proposed alloy-based fixed points, melting takes place over typically some hundreds of millikelvins. Including the entire melting range within the uncertainties would lead to an unnecessarily pessimistic view of the utility of these as reference standards. Therefore, detailed analysis of the shape of the melting curve is needed to give a value associated with some identifiable aspect of the phase transition. A range of approaches are or could be used; some purely practical, determining the point of inflection (POI) of the melting curve, some attempting to extrapolate to the liquidus temperature just at the end of melting, and a method that claims to give the liquidus temperature and an impurity correction based on the analytical Scheil model of solidification that has not previously been applied to eutectic melting. The different methods have been applied to cobalt-carbon melting curves that were obtained under conditions for which the Scheil model might be valid. In the light of the findings of this study it is recommended that the POI continue to be used as a pragmatic measure of temperature but where required a specified limits approach should be used to define and determine the melting temperature.

Thermopower of CexR1-xB6 (R=La, Pr and Nd)

NASA Astrophysics Data System (ADS)

Kim, Moo‑Sung; Nakai, Yuki; Tou, Hideki; Sera, Masafumi; Iga, Fumitoshi; Takabatake, Toshiro; Kunii, Satoru

2006-06-01

The thermopower, S, of CexR1-xB6 (R=La, Pr, Nd) was investigated. S with a positive sign shows a typical behavior observed in the Ce Kondo system, an increase with decreasing temperature at high temperatures and a maximum at low temperatures. The S values of all the systems at high temperatures are roughly linearly dependent on the Ce concentration, indicating the conservation of the single-impurity character of the Kondo effect in a wide x range. However, the maximum value of S, Smax, and the temperature, Tmax, at which Smax is observed exhibit different x dependences between CexLa1-xB6 and CexR1-xB6 (R=Pr, Nd). In CexLa1-xB6, Tmax, which is ˜8 K in CeB6, decreases with decreasing x and converges to ˜1 K in a very dilute alloy and Smax shows an increase below x ˜ 0.1 after decreasing with decreasing x. In CexR1-xB6 (R=Pr, Nd), Tmax shows a weak x dependence but Smax shows a roughly linear decrease in x. These results are discussed from the standpoint of the chemical pressure effect and the Ce-Ce interaction. S in the long-range ordered phase shows very different behaviors between CexPr1-xB6 and CexNd1-xB6.

Some tests of flat plate photovoltaic module cell temperatures in simulated field conditions

NASA Technical Reports Server (NTRS)

Griffith, J. S.; Rathod, M. S.; Paslaski, J.

1981-01-01

The nominal operating cell temperature (NOCT) of solar photovoltaic (PV) modules is an important characteristic. Typically, the power output of a PV module decreases 0.5% per deg C rise in cell temperature. Several tests were run with artificial sun and wind to study the parametric dependencies of cell temperature on wind speed and direction and ambient temperature. It was found that the cell temperature is extremely sensitive to wind speed, moderately so to wind direction and rather insensitive to ambient temperature. Several suggestions are made to obtain data more typical of field conditions.

Thermal Analysis of a Disposable, Instrument-Free DNA Amplification Lab-on-a-Chip Platform.

PubMed

Pardy, Tamás; Rang, Toomas; Tulp, Indrek

2018-06-04

Novel second-generation rapid diagnostics based on nucleic acid amplification tests (NAAT) offer performance metrics on par with clinical laboratories in detecting infectious diseases at the point of care. The diagnostic assay is typically performed within a Lab-on-a-Chip (LoC) component with integrated temperature regulation. However, constraints on device dimensions, cost and power supply inherent with the device format apply to temperature regulation as well. Thermal analysis on simplified thermal models for the device can help overcome these barriers by speeding up thermal optimization. In this work, we perform experimental thermal analysis on the simplified thermal model for our instrument-free, single-use LoC NAAT platform. The system is evaluated further by finite element modelling. Steady-state as well as transient thermal analysis are performed to evaluate the performance of a self-regulating polymer resin heating element in the proposed device geometry. Reaction volumes in the target temperature range of the amplification reaction are estimated in the simulated model to assess compliance with assay requirements. Using the proposed methodology, we demonstrated our NAAT device concept capable of performing loop-mediated isothermal amplification in the 20⁻25 °C ambient temperature range with 32 min total assay time.

Characterization and Evaluation of a Mass Efficient Heat Storage Device.

NASA Technical Reports Server (NTRS)

Splinter, Scott C.; Blosser, Max L.; Gifford, Andrew R.

2007-01-01

The heat sponge is a device for mass-efficient storage of heat. It was developed to be incorporated in the substructure of a reentry or hypersonic vehicle to reduce thermal protection system requirements. The heat sponge consists of a liquid-vapor mixture contained within a number of miniature pressure vessels that can be embedded within a variety of different types of structures. As temperature is increased, pressure in the miniature pressure vessels also increases so that heat absorbed through vaporization of the liquid is spread over a relatively large temperature range. Using water as a working fluid, the heat storage capacity of the liquid-vapor mixture is many times higher than that of typical structural materials and is well above that of common phase change materials over the temperature range of 660oR to 1160oR. Prototype heat sponges were fabricated and characterized. These heat sponges consisted of 1.0 inch diameter hollow stainless steel spheres with a wall thickness of 0.020 inches which had varying percentages of their interior volumes filled with water. An apparatus to measure the heat stored in these prototype heat sponges was designed, fabricated, and verified. The heat storage capacity calculated from measured temperature histories is compared to numerical predictions.

Corneal collagen denaturation in laser thermokeratoplasty

NASA Astrophysics Data System (ADS)

Brinkmann, Ralf; Kampmeier, Juergen; Grotehusmann, Ulf; Vogel, Alfred; Koop, Norbert; Asiyo-Vogel, Mary; Birngruber, Reginald

1996-05-01

In laserthermokeratoplasty (LTK) thermal denaturation and shrinkage of corneal collagen is used to correct hyperopia and astigmatism. In order to optimize dosimetry, the temperature at which maximal shrinkage of collagen fibrils occurs is of major interest. Since the exposure time in clinical LTK-treatment is limited to a few seconds, the kinetics of collagen denaturation as a rate process has to be considered, thus the time of exposure is of critical importance for threshold and shrinkage temperatures. We investigated the time-temperature correlation for corneal collagen denaturation within different time domains by turbidimetry of scattered HeNe laser probe light using a temperature controlled water bath and pulsed IR laser irradiation. In the temperature range of 60 degree(s)C to 95 degree(s)C we found an exponential relation between the denaturation time and temperature. For the typical LTK-treatment time of 2 s, a temperature of 95 degree(s)C is needed to induce thermal damage. Use of pulsed Holmium laser radiation gave significant scattering of HeNe laser probe light at calculated temperatures of around 100 degree(s)DC. Rate parameters according to the formalism of Arrhenius were fitted to these results. Force measurements showed the simultaneous onset of light scattering and collagen shrinkage.

Combined tunable diode laser absorption spectroscopy and monochromatic radiation thermometry in ammonium dinitramide-based thruster

NASA Astrophysics Data System (ADS)

Zeng, Hui; Ou, Dongbin; Chen, Lianzhong; Li, Fei; Yu, Xilong

2018-02-01

Nonintrusive temperature measurements for a real ammonium dinitramide (ADN)-based thruster by using tunable diode laser absorption spectroscopy and monochromatic radiation thermometry are proposed. The ADN-based thruster represents a promising future space propulsion employing green, nontoxic propellant. Temperature measurements in the chamber enable quantitative thermal analysis for the thruster, providing access to evaluate thermal properties of the thruster and optimize thruster design. A laser-based sensor measures temperature of combustion gas in the chamber, while a monochromatic thermometry system based on thermal radiation is utilized to monitor inner wall temperature in the chamber. Additional temperature measurements of the outer wall temperature are conducted on the injector, catalyst bed, and combustion chamber of the thruster by using thermocouple, respectively. An experimental ADN thruster is redesigned with optimizing catalyst bed length of 14 mm and steady-state firing tests are conducted under various feed pressures over the range from 5 to 12 bar at a typical ignition temperature of 200°C. A threshold of feed pressure higher than 8 bar is required for the thruster's normal operation and upstream movement of the heat release zone is revealed in the combustion chamber out of temperature evolution in the chamber.

Cyclic fatigue analysis of rocket thrust chambers. Volume 1: OFHC copper chamber low cycle fatigue

NASA Technical Reports Server (NTRS)

Miller, R. W.

1974-01-01

A three-dimensional finite element elasto-plastic strain analysis was performed for the throat section of a regeneratively cooled rocket combustion chamber. The analysis employed the RETSCP finite element computer program. The analysis included thermal and pressure loads, and the effects of temperature dependent material properties, to determine the strain range corresponding to the chamber operating cycle. The analysis was performed for chamber configuration and operating conditions corresponding to a hydrogen-oxygen combustion chamber which was fatigue tested to failure. The computed strain range at typical chamber operating conditions was used in conjunction with oxygen-free, high-conductivity (OHFC) copper isothermal fatigue test data to predict chamber low-cycle fatigue life.

A novel amperometric biosensor based on banana peel (Musa cavendish) tissue homogenate for determination of phenolic compounds.

PubMed

Ozcan, Hakki Mevlut; Sagiroglu, Ayten

2010-08-01

In this study the biosensor was constructed by immobilizing tissue homogenate of banana peel onto a glassy carbon electrode surface. Effects of immobilization materials amounts, effects of pH, buffer concentration and temperature on biosensor response were studied. In addition, the detection ranges of 13 phenolic compounds were obtained with the help of the calibration graphs. Storage stability, repeatability of the biosensor, inhibitory effect and sample applications were also investigated. A typical calibration curve for the sensor revealed a linear range of 10-80 microM catechol. In reproducibility studies, variation coefficient and standard deviation were calculated as 2.69%, 1.44 x 10(-3) microM, respectively.

Electron trapping and transport by supersonic solitons in one-dimensional systems

NASA Technical Reports Server (NTRS)

Zmuidzinas, J. S.

1978-01-01

A one-dimensional chain of ions or molecules and electrons described by a Froehlich-type Hamiltonian with quartic phonon anharmonicities is investigated. It is shown that the anharmonic lattice supports supersonic solitons which under favorable circumstances may trap electrons and transport them along the lattice. For a lattice constant/soliton spatial extent quotient of the order of 0.1, rough estimates give electron trapping energies in the meV range. They imply a useful temperature range, up to tens of degrees K, for observing the new effect. The activation energy of a lattice soliton is proportional to the molecular mass and is therefore quite high (about 1 eV) for typical quasi-one-dimensional organic systems.

Hydrothermal frictional strengths of rock and mineral samples relevant to the creeping section of the San Andreas Fault

USGS Publications Warehouse

Moore, Diane E.; Lockner, David A.; Hickman, Stephen H.

2016-01-01

We compare frictional strengths in the temperature range 25–250 °C of fault gouge from SAFOD (CDZ and SDZ) with quartzofeldspathic wall rocks typical of the central creeping section of the San Andreas Fault (Great Valley sequence and Franciscan Complex). The Great Valley and Franciscan samples have coefficients of friction, μ > 0.35 at all experimental conditions. Strength is unchanged between 25° and 150 °C, but μ increases at higher temperatures, exceeding 0.50 at 250 °C. Both samples are velocity strengthening at room temperature but show velocity-weakening behavior beginning at 150 °C and stick-slip motion at 250 °C. These rocks, therefore, have the potential for unstable seismic slip at depth. The CDZ gouge, with a high saponite content, is weak (μ = 0.09–0.17) and velocity strengthening in all experiments, and μ decreases at temperatures above 150 °C. Behavior of the SDZ is intermediate between the CDZ and wall rocks: μ < 0.2 and does not vary with temperature. Although saponite is probably not stable at depths greater than ∼3 km, substitution of the frictionally similar minerals talc and Mg-rich chlorite for saponite at higher temperatures could potentially extend the range of low strength and stable slip down to the base of the seismogenic zone.

Substituted Quaternary Ammonium Salts Improve Low-Temperature Performance of Double-Layer Capacitors

NASA Technical Reports Server (NTRS)

Brandon, Erik J.; Smart, Marshall C.; West, William C.

2011-01-01

Double-layer capacitors are unique energy storage devices, capable of supporting large current pulses as well as a very high number of charging and discharging cycles. The performance of doublelayer capacitors is highly dependent on the nature of the electrolyte system used. Many applications, including for electric and fuel cell vehicles, back-up diesel generators, wind generator pitch control back-up power systems, environmental and structural distributed sensors, and spacecraft avionics, can potentially benefit from the use of double-layer capacitors with lower equivalent series resistances (ESRs) over wider temperature limits. Higher ESRs result in decreased power output, which is a particular problem at lower temperatures. Commercially available cells are typically rated for operation down to only 40 C. Previous briefs [for example, Low Temperature Supercapacitors (NPO-44386), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), p. 32, and Supercapacitor Electrolyte Solvents With Liquid Range Below 80 C (NPO-44855), NASA Tech Briefs, Vol. 34, No. 1 (January 2010), p. 44] discussed the use of electrolytes that employed low-melting-point co-solvents to depress the freezing point of traditional acetonitrile-based electrolytes. Using these modified electrolyte formulations can extend the low-temperature operational limit of double-layer capacitors beyond that of commercially available cells. This previous work has shown that although the measured capacitance is relatively insensitive to temperature, the ESR can rise rapidly at low temperatures, due to decreased electrolyte conductance within the pores of the high surface- area carbon electrodes. Most of these advanced electrolyte systems featured tetraethylammonium tetrafluoroborate (TEATFB) as the salt. More recent work at JPL indicates the use of the asymmetric quaternary ammonium salt triethylmethylammonium tetrafluoroborate (TEMATFB) or spiro-(l,l')-bipyrrolidium tetrafluoroborate (SBPBF4) in a 1:1 by volume solvent mixture of acetonitrile (AN) and methyl formate (MF) enables double-layer capacitor cells to operate well below -40 C with a relatively low ESR. Typically, a less than twofold increase in ESR is observed at -65 C relative to room-temperature values, when these modified electrolyte blends are used in prototype cells. Double-layer capacitor coin cells filled with these electrolytes have displayed the lowest measured ESR for an organic electrolyte to date at low temperature (based on a wide range of electrolyte screening studies at JPL). The cells featured high-surface-area (approximately equal to 2,500 m/g) carbon electrodes that were 0.50 mm thick and 1.6 cm in diameter, and coated with a thin layer of platinum to reduce cell resistance. A polyethylene separator was used to electrically isolate the electrodes.

Ginzburg criterion for ionic fluids: the effect of Coulomb interactions.

PubMed

Patsahan, O

2013-08-01

The effect of the Coulomb interactions on the crossover between mean-field and Ising critical behavior in ionic fluids is studied using the Ginzburg criterion. We consider the charge-asymmetric primitive model supplemented by short-range attractive interactions in the vicinity of the gas-liquid critical point. The model without Coulomb interactions exhibiting typical Ising critical behavior is used to calibrate the Ginzburg temperature of the systems comprising electrostatic interactions. Using the collective variables method, we derive a microscopic-based effective Hamiltonian for the full model. We obtain explicit expressions for all the relevant Hamiltonian coefficients within the framework of the same approximation, i.e., the one-loop approximation. Then we consistently calculate the reduced Ginzburg temperature t(G) for both the purely Coulombic model (a restricted primitive model) and the purely nonionic model (a hard-sphere square-well model) as well as for the model parameters ranging between these two limiting cases. Contrary to the previous theoretical estimates, we obtain the reduced Ginzburg temperature for the purely Coulombic model to be about 20 times smaller than for the nonionic model. For the full model including both short-range and long-range interactions, we show that t(G) approaches the value found for the purely Coulombic model when the strength of the Coulomb interactions becomes sufficiently large. Our results suggest a key role of Coulomb interactions in the crossover behavior observed experimentally in ionic fluids as well as confirm the Ising-like criticality in the Coulomb-dominated ionic systems.

Thermal Evolution and Radiative Output of Solar Flares Observed by the EUV Variability Experiment (EVE)

NASA Technical Reports Server (NTRS)

Chamberlin, P. C.; Milligan, R. O.; Woods, T. N.

2012-01-01

This paper describes the methods used to obtain the thermal evolution and radiative output during solar flares as observed by the Extreme u ltraviolet Variability Experiment (EVE) onboard the Solar Dynamics Ob servatory (SDO). Presented and discussed in detail are how EVE measur ements, due to its temporal cadence, spectral resolution and spectral range, can be used to determine how the thermal plasma radiates at v arious temperatures throughout the impulsive and gradual phase of fla res. EVE can very accurately determine the radiative output of flares due to pre- and in-flight calibrations. Events are presented that sh ow the total radiated output of flares depends more on the flare duration than the typical GOES X-ray peak magnitude classification. With S DO observing every flare throughout its entire duration and over a la rge temperature range, new insights into flare heating and cooling as well as the radiative energy release in EUV wavelengths support exis ting research into understanding the evolution of solar flares.

Magnon spectrum of the helimagnetic insulator Cu 2OSeO 3

DOE PAGES

Portnichenko, P. Y.; Romhányi, J.; Onykiienko, Y. A.; ...

2016-02-25

We report that complex low-temperature-ordered states in chiral magnets are typically governed by a competition between multiple magnetic interactions. The chiral-lattice multiferroic Cu 2OSeO 3 became the first insulating helimagnetic material in which a long-range order of topologically stable spin vortices known as skyrmions was established. Here we employ state-of-the-art inelastic neutron scattering to comprehend the full three-dimensional spin-excitation spectrum of Cu 2OSeO 3 over a broad range of energies. Distinct types of high- and low-energy dispersive magnon modes separated by an extensive energy gap are observed in excellent agreement with the previously suggested microscopic theory based on a modelmore » of entangled Cu 4 tetrahedra. The comparison of our neutron spectroscopy data with model spin-dynamical calculations based on these theoretical proposals enables an accurate quantitative verification of the fundamental magnetic interactions in Cu 2OSeO 3 that are essential for understanding its abundant low-temperature magnetically ordered phases.« less

Magnon spectrum of the helimagnetic insulator Cu2OSeO3

PubMed Central

Portnichenko, P. Y.; Romhányi, J.; Onykiienko, Y. A.; Henschel, A.; Schmidt, M.; Cameron, A. S.; Surmach, M. A.; Lim, J. A.; Park, J. T.; Schneidewind, A.; Abernathy, D. L.; Rosner, H.; van den Brink, Jeroen; Inosov, D. S.

2016-01-01

Complex low-temperature-ordered states in chiral magnets are typically governed by a competition between multiple magnetic interactions. The chiral-lattice multiferroic Cu2OSeO3 became the first insulating helimagnetic material in which a long-range order of topologically stable spin vortices known as skyrmions was established. Here we employ state-of-the-art inelastic neutron scattering to comprehend the full three-dimensional spin-excitation spectrum of Cu2OSeO3 over a broad range of energies. Distinct types of high- and low-energy dispersive magnon modes separated by an extensive energy gap are observed in excellent agreement with the previously suggested microscopic theory based on a model of entangled Cu4 tetrahedra. The comparison of our neutron spectroscopy data with model spin-dynamical calculations based on these theoretical proposals enables an accurate quantitative verification of the fundamental magnetic interactions in Cu2OSeO3 that are essential for understanding its abundant low-temperature magnetically ordered phases. PMID:26911567

The UTCI-clothing model.

PubMed

Havenith, George; Fiala, Dusan; Błazejczyk, Krzysztof; Richards, Mark; Bröde, Peter; Holmér, Ingvar; Rintamaki, Hannu; Benshabat, Yael; Jendritzky, Gerd

2012-05-01

The Universal Thermal Climate Index (UTCI) was conceived as a thermal index covering the whole climate range from heat to cold. This would be impossible without considering clothing as the interface between the person (here, the physiological model of thermoregulation) and the environment. It was decided to develop a clothing model for this application in which the following three factors were considered: (1) typical dressing behaviour in different temperatures, as observed in the field, resulting in a model of the distribution of clothing over the different body segments in relation to the ambient temperature, (2) the changes in clothing insulation and vapour resistance caused by wind and body movement, and (3) the change in wind speed in relation to the height above ground. The outcome was a clothing model that defines in detail the effective clothing insulation and vapour resistance for each of the thermo-physiological model's body segments over a wide range of climatic conditions. This paper details this model's conception and documents its definitions.

SNAP 19 Viking Program. Bimonthly technical progress report, April-May 1980

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

Not Available

1980-01-01

Monitoring and evaluation of Viking Lander 1 power system data continued. The RTG series power range as measured at the PCDA was 65 to 67 watts at finroot temperatures between 280/sup 0/F and 310/sup 0/F. The Mars Lander performance history of Viking 1 include both the minimum and maximum data for each of the SOL days. Final available power system data for Viking Lander 2 are shown. Typical SOL day cycles for mission day 1193 are presented. The RTG series power ranged from 69 to 70 watts at finroot temperatures between 270/sup 0/F and 300/sup 0/F. The Mars Lander performancemore » history for Viking 2 is shown. Power system performance data for Pioneer 10 and Pioneer Saturn (initially designated Pioneer 11) were monitored through the reporting period. After adjusting for the telemetry characteristics, the estimated RTG system net power was 114 watts for both Pioneer 10 and Pioneer Saturn.« less

Magnon spectrum of the helimagnetic insulator Cu2OSeO3.

PubMed

Portnichenko, P Y; Romhányi, J; Onykiienko, Y A; Henschel, A; Schmidt, M; Cameron, A S; Surmach, M A; Lim, J A; Park, J T; Schneidewind, A; Abernathy, D L; Rosner, H; van den Brink, Jeroen; Inosov, D S

2016-02-25

Complex low-temperature-ordered states in chiral magnets are typically governed by a competition between multiple magnetic interactions. The chiral-lattice multiferroic Cu2OSeO3 became the first insulating helimagnetic material in which a long-range order of topologically stable spin vortices known as skyrmions was established. Here we employ state-of-the-art inelastic neutron scattering to comprehend the full three-dimensional spin-excitation spectrum of Cu2OSeO3 over a broad range of energies. Distinct types of high- and low-energy dispersive magnon modes separated by an extensive energy gap are observed in excellent agreement with the previously suggested microscopic theory based on a model of entangled Cu4 tetrahedra. The comparison of our neutron spectroscopy data with model spin-dynamical calculations based on these theoretical proposals enables an accurate quantitative verification of the fundamental magnetic interactions in Cu2OSeO3 that are essential for understanding its abundant low-temperature magnetically ordered phases.

Influence of external factors on the self-assembly of two structurally related antidepressant drugs: a thermodynamic study

NASA Astrophysics Data System (ADS)

Gutiérrez-Pichel, Manuel; Attwood, David; Taboada, Pablo; Mosquera, Víctor

Apparent molal volumes and adiabatic compressibilities of aqueous solutions of the amphiphilic antidepressant drugs imipramine and desipramine hydrochlorides have been determined from density and ultrasound velocity measurements in the temperature range 288.15-313.15 K in buffered solution of pH 3.0 and 5.5. Critical concentrations for aggregation of these drugs were obtained from inflections on the plots of the sound velocity against drug concentration. Positive deviation from the Debye-Hückel limiting law of the apparent molal volume of imipramine provides evidence of limited association at concentrations below the critical concentration over the temperature range studied. Apparent molal adiabatic compressibilities of the aggregates formed by the drugs, calculated by combining the ultrasound velocity and density data, were typical of those for a stacked aggregate. The critical concentration and energy involved in the aggregation process of these drugs have been evaluated using isothermal titration calorimetry. The solvent-aggregate interactions have been discussed from compressibility and calorimetry data.

Time Dependent Solution for the He I Line Ratio Electron Temperature and Density Diagnostic in TEXTOR and DIII-D

NASA Astrophysics Data System (ADS)

Munoz Burgos, J. M.; Schmitz, O.; Unterberg, E. A.; Loch, S. D.; Balance, C. P.

2010-11-01

We developed a time dependent solution for the He I line ratio diagnostic. Stationary solution is applied for L-mode at TEXTOR. The radial range is typically limited to a region near the separatrix due to metastable effects, and the atomic data used. We overcome this problem by applying a time dependent solution and thus avoid unphysical results. We use a new R-Matrix with Pseudostates and Convergence Cross-Coupling electron impact excitation and ionization atomic data set into the Collisional Radiative Model (CRM). We include contributions from higher Rydberg states into the CRM by means of the projection matrix. By applying this solution (to the region near the wall) and the stationary solution (near the separatrix), we triple the radial range of the current diagnostic. We explore the possibility of extending this approach to H-mode plasmas in DIII-D by estimating line emission profiles from electron temperature and density Thomson scattering data.

High performance humidity sensor and photodetector based on SnSe nanorods

NASA Astrophysics Data System (ADS)

Pawbake, Amit S.; Jadkar, Sandesh R.; Late, Dattatray J.

2016-10-01

Tin selenide (SnSe) nanorods were synthesized using a one-step solvothermal route and their humidity sensing and photodetection performance at room temperature were investigated. The results depict that SnSe nanorod-based humidity and photosensors have good long-term stability, are highly sensitive and have fast response and recovery times. In the case of the humidity sensor it was observed that the resistance of the films decreased with increasing relative humidity (RH). The humidity sensing behaviors were investigated in the range 11-97% RH at room temperature. A response time of ˜68 s and recovery time of ˜149 s were observed for the humidity sensor. The photosensing behavior showed typical response /recovery times of ˜3 s with highly reproducible behavior.

Note: A new design for a low-temperature high-intensity helium beam source

NASA Astrophysics Data System (ADS)

Lechner, B. A. J.; Hedgeland, H.; Allison, W.; Ellis, J.; Jardine, A. P.

2013-02-01

A high-intensity supersonic beam source is a key component of any atom scattering instrument, affecting the sensitivity and energy resolution of the experiment. We present a new design for a source which can operate at temperatures as low as 11.8 K, corresponding to a beam energy of 2.5 meV. The new source improves the resolution of the Cambridge helium spin-echo spectrometer by a factor of 5.5, thus extending the accessible timescales into the nanosecond range. We describe the design of the new source and discuss experiments characterizing its performance. Spin-echo measurements of benzene/Cu(100) illustrate its merit in the study of a typical slow-moving molecular adsorbate species.

Setup for irradiation and characterization of materials and Si particle detectors at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Väyrynen, S.; Pusa, P.; Sane, P.; Tikkanen, P.; Räisänen, J.; Kuitunen, K.; Tuomisto, F.; Härkönen, J.; Kassamakov, I.; Tuominen, E.; Tuovinen, E.

2007-03-01

A novel facility for proton irradiation with sample cryocooling has been developed at the Accelerator Laboratory of Helsinki University (equipped with a 5 MV tandem accelerator). The setup enables unique experiments to be carried out within the temperature range of 10-300 K. The setup has been constructed for "on-line" studies of vacancies with positron annihilation spectroscopy (PAS) including the option for optical ionization of the vacancies, and for current-voltage ( IV) measurements of irradiated silicon particle detectors. The setup is described in detail and typical performance characteristics are provided. The facility functionality was tested by performing PAS experiments with high-resistivity silicon and by IV measurements for two types of irradiated silicon particle detectors.

Non-Instrumented Incubation of a Recombinase Polymerase Amplification Assay for the Rapid and Sensitive Detection of Proviral HIV-1 DNA

PubMed Central

Lillis, Lorraine; Lehman, Dara; Singhal, Mitra C.; Cantera, Jason; Singleton, Jered; Labarre, Paul; Toyama, Anthony; Piepenburg, Olaf; Parker, Mathew; Wood, Robert; Overbaugh, Julie; Boyle, David S.

2014-01-01

Sensitive diagnostic tests for infectious diseases often employ nucleic acid amplification technologies (NAATs). However, most NAAT assays, including many isothermal amplification methods, require power-dependent instrumentation for incubation. For use in low resource settings (LRS), diagnostics that do not require consistent electricity supply would be ideal. Recombinase polymerase amplification (RPA) is an isothermal amplification technology that has been shown to typically work at temperatures ranging from 25–43°C, and does not require a stringent incubation temperature for optimal performance. Here we evaluate the ability to incubate an HIV-1 RPA assay, intended for use as an infant HIV diagnostic in LRS, at ambient temperatures or with a simple non-instrumented heat source. To determine the range of expected ambient temperatures in settings where an HIV-1 infant diagnostic would be of most use, a dataset of the seasonal range of daily temperatures in sub Saharan Africa was analyzed and revealed ambient temperatures as low as 10°C and rarely above 43°C. All 24 of 24 (100%) HIV-1 RPA reactions amplified when incubated for 20 minutes between 31°C and 43°C. The amplification from the HIV-1 RPA assay under investigation at temperatures was less consistent below 30°C. Thus, we developed a chemical heater to incubate HIV-1 RPA assays when ambient temperatures are between 10°C and 30°C. All 12/12 (100%) reactions amplified with chemical heat incubation from ambient temperatures of 15°C, 20°C, 25°C and 30°C. We also observed that incubation at 30 minutes improved assay performance at lower temperatures where detection was sporadic using 20 minutes incubation. We have demonstrated that incubation of the RPA HIV-1 assay via ambient temperatures or using chemical heaters yields similar results to using electrically powered devices. We propose that this RPA HIV-1 assay may not need dedicated equipment to be a highly sensitive tool to diagnose infant HIV-1 in LRS. PMID:25264766

Non-instrumented incubation of a recombinase polymerase amplification assay for the rapid and sensitive detection of proviral HIV-1 DNA.

PubMed

Lillis, Lorraine; Lehman, Dara; Singhal, Mitra C; Cantera, Jason; Singleton, Jered; Labarre, Paul; Toyama, Anthony; Piepenburg, Olaf; Parker, Mathew; Wood, Robert; Overbaugh, Julie; Boyle, David S

2014-01-01

Sensitive diagnostic tests for infectious diseases often employ nucleic acid amplification technologies (NAATs). However, most NAAT assays, including many isothermal amplification methods, require power-dependent instrumentation for incubation. For use in low resource settings (LRS), diagnostics that do not require consistent electricity supply would be ideal. Recombinase polymerase amplification (RPA) is an isothermal amplification technology that has been shown to typically work at temperatures ranging from 25-43°C, and does not require a stringent incubation temperature for optimal performance. Here we evaluate the ability to incubate an HIV-1 RPA assay, intended for use as an infant HIV diagnostic in LRS, at ambient temperatures or with a simple non-instrumented heat source. To determine the range of expected ambient temperatures in settings where an HIV-1 infant diagnostic would be of most use, a dataset of the seasonal range of daily temperatures in sub Saharan Africa was analyzed and revealed ambient temperatures as low as 10°C and rarely above 43°C. All 24 of 24 (100%) HIV-1 RPA reactions amplified when incubated for 20 minutes between 31°C and 43°C. The amplification from the HIV-1 RPA assay under investigation at temperatures was less consistent below 30°C. Thus, we developed a chemical heater to incubate HIV-1 RPA assays when ambient temperatures are between 10°C and 30°C. All 12/12 (100%) reactions amplified with chemical heat incubation from ambient temperatures of 15°C, 20°C, 25°C and 30°C. We also observed that incubation at 30 minutes improved assay performance at lower temperatures where detection was sporadic using 20 minutes incubation. We have demonstrated that incubation of the RPA HIV-1 assay via ambient temperatures or using chemical heaters yields similar results to using electrically powered devices. We propose that this RPA HIV-1 assay may not need dedicated equipment to be a highly sensitive tool to diagnose infant HIV-1 in LRS.

Thermodynamic framework for compact q-Gaussian distributions

NASA Astrophysics Data System (ADS)

Souza, Andre M. C.; Andrade, Roberto F. S.; Nobre, Fernando D.; Curado, Evaldo M. F.

2018-02-01

Recent works have associated systems of particles, characterized by short-range repulsive interactions and evolving under overdamped motion, to a nonlinear Fokker-Planck equation within the class of nonextensive statistical mechanics, with a nonlinear diffusion contribution whose exponent is given by ν = 2 - q. The particular case ν = 2 applies to interacting vortices in type-II superconductors, whereas ν > 2 covers systems of particles characterized by short-range power-law interactions, where correlations among particles are taken into account. In the former case, several studies presented a consistent thermodynamic framework based on the definition of an effective temperature θ (presenting experimental values much higher than typical room temperatures T, so that thermal noise could be neglected), conjugated to a generalized entropy sν (with ν = 2). Herein, the whole thermodynamic scheme is revisited and extended to systems of particles interacting repulsively, through short-ranged potentials, described by an entropy sν, with ν > 1, covering the ν = 2 (vortices in type-II superconductors) and ν > 2 (short-range power-law interactions) physical examples. One basic requirement concerns a cutoff in the equilibrium distribution Peq(x) , approached due to a confining external harmonic potential, ϕ(x) = αx2 / 2 (α > 0). The main results achieved are: (a) The definition of an effective temperature θ conjugated to the entropy sν; (b) The construction of a Carnot cycle, whose efficiency is shown to be η = 1 -(θ2 /θ1) , where θ1 and θ2 are the effective temperatures associated with two isothermal transformations, with θ1 >θ2; (c) Thermodynamic potentials, Maxwell relations, and response functions. The present thermodynamic framework, for a system of interacting particles under the above-mentioned conditions, and associated to an entropy sν, with ν > 1, certainly enlarges the possibility of experimental verifications.

Development of cast alumina-forming austenitic stainless steels

DOE PAGES

Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; ...

2016-09-06

Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt. % are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt. % Ni with good creep strength and the ability to form a protective alumina scale for use atmore » temperatures up to 800 C - 850 C in H 2O-, S-, and C- containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloy along with improved oxidation resistance typical of alumina-forming alloys. Lastly, challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.« less

Complex hydrides as room-temperature solid electrolytes for rechargeable batteries

NASA Astrophysics Data System (ADS)

de Jongh, P. E.; Blanchard, D.; Matsuo, M.; Udovic, T. J.; Orimo, S.

2016-03-01

A central goal in current battery research is to increase the safety and energy density of Li-ion batteries. Electrolytes nowadays typically consist of lithium salts dissolved in organic solvents. Solid electrolytes could facilitate safer batteries with higher capacities, as they are compatible with Li-metal anodes, prevent Li dendrite formation, and eliminate risks associated with flammable organic solvents. Less than 10 years ago, LiBH4 was proposed as a solid-state electrolyte. It showed a high ionic conductivity, but only at elevated temperatures. Since then a range of other complex metal hydrides has been reported to show similar characteristics. Strategies have been developed to extend the high ionic conductivity of LiBH4 down to room temperature by partial anion substitution or nanoconfinement. The present paper reviews the recent developments in complex metal hydrides as solid electrolytes, discussing in detail LiBH4, strategies towards for fast room-temperature ionic conductors, alternative compounds, and first explorations of implementation of these electrolytes in all-solid-state batteries.

Development of Cast Alumina-Forming Austenitic Stainless Steels

NASA Astrophysics Data System (ADS)

Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; Walker, L. R.; Meyer, H. M., III; Leonard, D. N.

2016-11-01

Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt.% are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt.% Ni with good creep strength and the ability to form a protective alumina scale for use at temperatures up to 800-850°C in H2O-, S-, and C-containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloys along with improved oxidation resistance typical of alumina-forming alloys. Challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.

Characterization of Combustion and Emission of Several Kinds of Herbaceous Biomass Pellets in a Circulating Fluidized Bed Combustor

NASA Astrophysics Data System (ADS)

Li, S. Y.; Teng, H. P.; Jiao, W. H.; Shang, L. L.; Lu, Q. G.

Characterizations of combustion and emission of four kinds of herbaceous biomass pellets were investigated in a 0.15 MWt circulating fluidized bed. Corn stalk, wheat stalk, cotton stalk and king grass, which are typical herbaceous biomass in China, were chosen for this study. Temperature profile, emission in flue gas and agglomeration were studied by changing the combustion temperature between 750°C and 880°C. The combustion efficiencies are in the range from 97.4% to 99.4%, which are relatively high due to the homogeneous temperature profiles and good circulating fluidization of bed material. Suitable combustion temperatures for the different herbaceous biomass are mainly depended on the emission and bed agglomeration. SO2 and HCl concentrations in flue gas are in direct proportion to the sulfur and chlorine contents of the herbaceous biomass. Agglomeration at the cyclone leg and the loop seal is the main reason for defluidization in the CFB combustor.

Microstructural evolution and grain growth kinetics of GZ31 magnesium alloy

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

Roostaei, M., E-mail: miladroustaei68@ut.ac.ir

2016-08-15

Grain growth behavior of Mg–3Gd–1Zn (GZ31) magnesium alloy was studied in a wide range of annealing time and temperature to clarify the kinetics of grain growth, microstructural evolution and related metallurgical phenomena. This material exhibited typical normal grain growth mode under annealing conditions with annealing temperature of lower than 300 °C and soaking time of lower than 240 min. However, the abnormality in grain growth was also evident at annealing temperature of 400 °C and 500 °C. The dependence of abnormal grain growth (AGG) at mentioned annealing temperatures upon microstructural features such as dispersed precipitates, which were rich in Znmore » and Gd, was investigated by optical micrographs, X-ray diffraction patterns, scanning electron microscopy images, and energy dispersive X-ray analysis spectra. The bimodality in grain-size distribution histograms also signified the occurrence of AGG. Based on the experimental data on grain growth obtained by annealing treatments, the grain growth exponent and the activation energy were also figured out.« less

Tuning magnetic spirals beyond room temperature with chemical disorder

NASA Astrophysics Data System (ADS)

Morin, Mickaël; Canévet, Emmanuel; Raynaud, Adrien; Bartkowiak, Marek; Sheptyakov, Denis; Ban, Voraksmy; Kenzelmann, Michel; Pomjakushina, Ekaterina; Conder, Kazimierz; Medarde, Marisa

2016-12-01

In the past years, magnetism-driven ferroelectricity and gigantic magnetoelectric effects have been reported for a number of frustrated magnets featuring ordered spiral magnetic phases. Such materials are of high-current interest due to their potential for spintronics and low-power magnetoelectric devices. However, their low-magnetic ordering temperatures (typically <100 K) greatly restrict their fields of application. Here we demonstrate that the onset temperature of the spiral phase in the perovskite YBaCuFeO5 can be increased by more than 150 K through a controlled manipulation of the Fe/Cu chemical disorder. Moreover, we show that this novel mechanism can stabilize the magnetic spiral state of YBaCuFeO5 above the symbolic value of 25 °C at zero magnetic field. Our findings demonstrate that the properties of magnetic spirals, including its wavelength and stability range, can be engineered through the control of chemical disorder, offering a great potential for the design of materials with magnetoelectric properties beyond room temperature.

Tuning magnetic spirals beyond room temperature with chemical disorder

PubMed Central

Morin, Mickaël; Canévet, Emmanuel; Raynaud, Adrien; Bartkowiak, Marek; Sheptyakov, Denis; Ban, Voraksmy; Kenzelmann, Michel; Pomjakushina, Ekaterina; Conder, Kazimierz; Medarde, Marisa

2016-01-01

In the past years, magnetism-driven ferroelectricity and gigantic magnetoelectric effects have been reported for a number of frustrated magnets featuring ordered spiral magnetic phases. Such materials are of high-current interest due to their potential for spintronics and low-power magnetoelectric devices. However, their low-magnetic ordering temperatures (typically <100 K) greatly restrict their fields of application. Here we demonstrate that the onset temperature of the spiral phase in the perovskite YBaCuFeO5 can be increased by more than 150 K through a controlled manipulation of the Fe/Cu chemical disorder. Moreover, we show that this novel mechanism can stabilize the magnetic spiral state of YBaCuFeO5 above the symbolic value of 25 °C at zero magnetic field. Our findings demonstrate that the properties of magnetic spirals, including its wavelength and stability range, can be engineered through the control of chemical disorder, offering a great potential for the design of materials with magnetoelectric properties beyond room temperature. PMID:27982127

Thermosensitive Triterpenoid-Appended Polymers with Broad Temperature Tunability Regulated by Host-Guest Chemistry.

PubMed

Hao, Jie; Gao, Yuxia; Li, Ying; Yan, Qiang; Hu, Jun; Ju, Yong

2017-09-05

Thermoresponsive water-soluble polymers are of great importance since they typically show a lower critical solution temperature (LCST) in aqueous media. In this research, the LCST change in broad temperature ranges of copolymers composed of natural glycyrrhetinic acid (GA)-based methacrylate and N,N'-dimethylacrylamides (DMAs) was investigated as a function of the concentration and the content of GA pendants. By complexation of GA pendants with β-cyclodextrin (β-CD), a side-chain polypseudorotaxane was obtained, which exhibited a significant increase in the LCST of copolymers. Moreover, the precisely reversible control of the LCST behavior was realized through adding a competing guest molecule, sodium 1-admantylcarboxylate. This work illustrates a simple and effective approach to endow water-soluble polymers with broad temperature tunability and helps us further understand the effect of a biocompatible host-guest complementary β-CD/GA pair on the thermoresponsive process. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fast Risetime Reverse Bias Pulse Failures in SiC PN Junction Diodes

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Fazi, Christian; Parsons, James D.

1996-01-01

SiC-based high temperature power devices are being developed for aerospace systems which will require high reliability. One behavior crucial to power device reliability. To date, it has necessarily been assumed to date is that the breakdown behavior of SiC pn junctions will be similar to highly reliable silicon-based pn junctions. Challenging this assumption, we report the observation of anomalous unreliable reverse breakdown behavior in moderately doped (2-3 x 10(exp 17) cm(exp -3)) small-area 4H- and 6H-SiC pn junction diodes at temperatures ranging from 298 K (25 C) to 873 K (600 C). We propose a mechanism in which carrier emission from un-ionized dopants and deep level defects leads to this unstable behavior. The fundamental instability mechanism is applicable to all wide bandgap semiconductors whose dopants are significantly un-ionized at typical device operating temperatures.

Quantum phase slip phenomenon in ultra-narrow superconducting nanorings

NASA Astrophysics Data System (ADS)

Arutyunov, Konstantin Yu.; Hongisto, Terhi T.; Lehtinen, Janne S.; Leino, Leena I.; Vasiliev, Alexander L.

2012-02-01

The smaller the system, typically - the higher is the impact of fluctuations. In narrow superconducting wires sufficiently close to the critical temperature Tc thermal fluctuations are responsible for the experimentally observable finite resistance. Quite recently it became possible to fabricate sub-10 nm superconducting structures, where the finite resistivity was reported within the whole range of experimentally obtainable temperatures. The observation has been associated with quantum fluctuations capable to quench zero resistivity in superconducting nanowires even at temperatures T-->0. Here we demonstrate that in tiny superconducting nanorings the same phenomenon is responsible for suppression of another basic attribute of superconductivity - persistent currents - dramatically affecting their magnitude, the period and the shape of the current-phase relation. The effect is of fundamental importance demonstrating the impact of quantum fluctuations on the ground state of a macroscopically coherent system, and should be taken into consideration in various nanoelectronic applications.

Volcanic ash melting under conditions relevant to ash turbine interactions.

PubMed

Song, Wenjia; Lavallée, Yan; Hess, Kai-Uwe; Kueppers, Ulrich; Cimarelli, Corrado; Dingwell, Donald B

2016-03-02

The ingestion of volcanic ash by jet engines is widely recognized as a potentially fatal hazard for aircraft operation. The high temperatures (1,200-2,000 °C) typical of jet engines exacerbate the impact of ash by provoking its melting and sticking to turbine parts. Estimation of this potential hazard is complicated by the fact that chemical composition, which affects the temperature at which volcanic ash becomes liquid, can vary widely amongst volcanoes. Here, based on experiments, we parameterize ash behaviour and develop a model to predict melting and sticking conditions for its global compositional range. The results of our experiments confirm that the common use of sand or dust proxy is wholly inadequate for the prediction of the behaviour of volcanic ash, leading to overestimates of sticking temperature and thus severe underestimates of the thermal hazard. Our model can be used to assess the deposition probability of volcanic ash in jet engines.

Magneto-optical spectroscopy of ferromagnetic shape-memory Ni-Mn-Ga alloy

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

Veis, M., E-mail: veis@karlov.mff.cuni.cz; Beran, L.; Zahradnik, M.

2014-05-07

Magneto-optical properties of single crystal of Ni{sub 50.1}Mn{sub 28.4}Ga{sub 21.5} magnetic shape memory alloy in martensite and austenite phase were systematically studied. Crystal orientation was approximately along (100) planes of parent cubic austenite. At room temperature, the sample was in modulated 10M martensite phase and transformed to cubic austenite at 323 K. Spectral dependence of polar magneto-optical Kerr effect was obtained by generalized magneto-optical ellipsometry with rotating analyzer in the photon energy range from 1.2 to 4 eV, and from room temperature to temperature above the Curie point. The Kerr rotation spectra exhibit prominent features typical for complexes containing Mn atoms. Significantmore » spectral changes during transformation to austenite can be explained by different optical properties caused by changes in density of states near the Fermi energy.« less

Low temperature electrical properties of some Pb-free solders

NASA Astrophysics Data System (ADS)

Kisiel, Ryszard; Pekala, Marek

2006-03-01

The electronic industry is engaged in developing Pb-free technologies for more than ten years. However till now not all properties of new solders are described. The aim of the paper is to present some electrical properties of new series of Pb-free solders (eutectic SnAg, near eutectic SnAgCu with and without Bi) in low temperature ranges 10 K to 273K. The following parameters were analyzed: electrical resistivity, temperature coefficient of resistance and thermoelectric power. The electrical resistivity at temperatures above 50 K is a monotonically rising function of temperature for Pb-free solders studied. The electrical resistivity of the Bi containing alloys is higher as compared to the remaining ones. The thermoelectric power values at room temperature are about -8 μV/K to -6 μV/K for Pb-free solders studied, being higher as compared to typical values -3 μVK of SnPb solder. The relatively low absolute values as well as the smooth and weak temperature variation of electrical resistivity in lead free solders enable the possible low temperature application. The moderate values of thermoelectric power around and above the room temperature show that when applying the solders studied the temperature should be kept as uniform as possible, in order to avoid spurious or noise voltages.

High-resolution TEM Studies of Carbon Nanotubes and Catalyst Nanoparticles Produced During CVD from Metal Multilayer Films

NASA Astrophysics Data System (ADS)

Howe, Jane Y.; Puretzky, Alex A.; Geohegan, David B.; Cui, Hongtao; Eres, Varela; Maria, Alex A.; Lowndes, Douglas H.

2003-03-01

The structure of single-wall and multiwall carbon nanotubes and associated metal catalyst nanoparticles produced during chemical vapor deposition from multilayered metal films deposited on Si and Mo substrates were studied by high-resolution TEM and EDS. Electron beam-evaporated metal multilayer films (e.g. Al-Fe-Mo, typically 11-50 nm total thickness) roughen upon heat treatment to form a variety of catalyst particle sizes suitable for carbon nanotube growth by chemical vapor deposition using acetylene, hydrogen, and argon flow gases. This study investigates these nanoparticles, the type of nanotubes grown, their wall, tip, and basal structures, as well as the associated amounts of amorphous carbon deposited on their walls in different temperature and pressure ranges. Mixtures of SWNT and MWNT are found even for low growth temperatures (650-700 C), while rapid growth of vertically-aligned multiwall nanotubes (VA-MWNTs) predominate in a narrow temperature range at a given pressure. Arrested growth experiments were performed to determine the time periods for SWNT vs. MWNT growth. The nature of the catalyst nanoparticles, their support structure, and insights on the mechanisms of growth will be discussed.

Magnetic and thermodynamic properties of Nd3NiGe2

NASA Astrophysics Data System (ADS)

Matsumoto, Keisuke T.; Hiraoka, Koichi

2018-05-01

We here report the magnetization, M, and specific heat, C, of Nd3NiGe2 , which crystallizes in the orthorhombic Gd3NiSi2 -type structure. Nd ions occupy three nonequivalent sites in a unit cell. Upon cooling, magnetization divided by magnetic field, M / B , increased sharply at the Curie temperature, TC, of 87 K and below 40 K. The former result indicates that the increase in M / B observed at TC is due to the long-range ferromagnetic order. The increase below 40 K is derived from a short-range correlation because of the absence of clear anomaly in C (T) . At 10 K and 2 K, the values of M undergo metamagnetic transitions. The value of magnetic specific heat divided by temperature shows a shoulder-like anomaly at around 20 K, which is attributed to antiferromagnetic behavior. Furthermore, two peaks in C (T) were observed at 4.5 K and 3.8 K, and these peaks occurred at lower temperatures in the presence of a magnetic field. This behavior is typical of materials with antiferromagnetic order. These observations are attributed to the competition between ferromagnetic and antiferromagnetic interactions, which is a result of the three nonequivalent Nd sites.

Cable tunnel fire experiment study based on linear optical fiber fire detectors

NASA Astrophysics Data System (ADS)

Fan, Dian; Ding, Hongjun

2013-09-01

Aiming at exiting linear temperature fire detection technology including temperature sensing cable, fiber Raman scattering, fiber Bragg grating, this paper establish an experimental platform in cable tunnel, set two different experimental scenes of the fire and record temperature variation and fire detector response time in the processing of fire simulation. Since a small amount of thermal radiation and no flame for the beginning of the small-scale fire, only directly contacting heat detectors can make alarm response and the rest of other non- contact detectors are unable to respond. In large-scale fire, the alarm response time of the fiber Raman temperature sensing fire detector and fiber Bragg grating temperature sensing fire detector is about 30 seconds, and depending on the thermocouples' record the temperature over the fire is less than 35° in first 60 seconds of large-scale fire, while the temperature rising is more than 5°/min within the range of +/- 3m. According to the technical characteristics of the three detectors, the engineering suitability of the typical linear heat detectors in cable tunnels early fire detection is analyzed, which provide technical support for the preparation of norms.

Temperature-Dependent Conformations of Model Viscosity Index Improvers

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

Ramasamy, Uma Shantini; Cosimbescu, Lelia; Martini, Ashlie

2015-05-01

Lubricants are comprised of base oils and additives where additives are chemicals that are deliberately added to the oil to enhance properties and inhibit degradation of the base oils. Viscosity index (VI) improvers are an important class of additives that reduce the decline of fluid viscosity with temperature [1], enabling optimum lubricant performance over a wider range of operating temperatures. These additives are typically high molecular weight polymers, such as, but not limited to, polyisobutylenes, olefin copolymer, and polyalkylmethacrylates, that are added in concentrations of 2-5% (w/w). Appropriate polymers, when dissolved in base oil, expand from a coiled to anmore » uncoiled state with increasing temperature [2]. The ability of VI additives to increase their molar volume and improve the temperature-viscosity dependence of lubricants suggests there is a strong relationship between molecular structure and additive functionality [3]. In this work, we aim to quantify the changes in polymer size with temperature for four polyisobutylene (PIB) based molecular structures at the nano-scale using molecular simulation tools. As expected, the results show that the polymers adopt more conformations at higher temperatures, and there is a clear indication that the expandability of a polymer is strongly influenced by molecular structure.« less

Autoignition characteristics of aircraft-type fuels

NASA Technical Reports Server (NTRS)

Spadaccini, L. J.; Tevelde, J. A.

1980-01-01

The ignition delay characteristics of Jet A, JP 4, no. 2 diesel, cetane and an experimental referee broad specification (ERBS) fuel in air at inlet temperatures up to 1000 K, pressures of 10, 15, 20, 25 and 30 atm, and fuel air equivalence ratios of 0.3, 0.5, 0.7 and 1.0 were mapped. Ignition delay times in the range of 1 to 50 msec at freestream flow velocities ranging from 20 to 100 m/sec were obtained using a continuous flow test apparatus which permitted independent variation and evaluation of the effect of temperature, pressure, flow rate, and fuel/air ratio. The ignition delay times for all fuels tested appeared to correlate with the inverse of pressure and the inverse exponent of temperature. With the exception of pure cetane, which had the shortest ignition delay times, the differences between the fuels tested did not appear to be significant. The apparent global activation energies for the typical gas turbine fuels ranged from 38 to 40 kcal/mole, while the activation energy determined for cetane was 50 kcal/mole. In addition, the data indicate that for lean mixtures, ignition delay times decrease with increasing equivalence ratio. It was also noted that physical (apparatus dependent) phenomena, such as mixing (i.e., length and number of injection sites) and airstream cooling (due to fuel heating, vaporization and convective heat loss) can have an important effect on the ignition delay.

Colossal dielectric behavior of semiconducting Sr2TiMnO6 ceramics

NASA Astrophysics Data System (ADS)

Meher, K. R. S. Preethi; Varma, K. B. R.

2009-02-01

Manganitelike double perovskite Sr2TiMnO6 (STMO) ceramics fabricated from the powders synthesized via the solid-state reaction route, exhibited dielectric constants as high as ˜105 in the low frequency range (100 Hz-10 kHz) at room temperature. The Maxwell-Wagner type of relaxation mechanism was found to be more appropriate to rationalize such high dielectric constant values akin to that observed in materials such as KxTiyNi(1-x-y)O and CaCu3Ti4O12. The dielectric measurements carried out on the samples with different thicknesses and electrode materials reflected the influence of extrinsic effects. The impedance studies (100 Hz-10 MHz) in the 180-300 K temperature range revealed the presence of two dielectric relaxations corresponding to the grain boundary and the electrode. The dielectric response of the grain boundary was found to be weakly dependent on the dc bias field (up to 11 V/cm). However, owing to the electrode polarization, the applied ac/dc field had significant effect on the low frequency dielectric response. At low temperatures (100-180 K), the dc conductivity of STMO followed a variable range hopping behavior. Above 180 K, it followed the Arrhenius behavior because of the thermally activated conduction process. The bulk conductivity relaxation owing to the localized hopping of charge carriers obeyed the typical universal dielectric response.

Multi-Group Reductions of LTE Air Plasma Radiative Transfer in Cylindrical Geometries

NASA Technical Reports Server (NTRS)

Scoggins, James; Magin, Thierry Edouard Bertran; Wray, Alan; Mansour, Nagi N.

2013-01-01

Air plasma radiation in Local Thermodynamic Equilibrium (LTE) within cylindrical geometries is studied with an application towards modeling the radiative transfer inside arc-constrictors, a central component of constricted-arc arc jets. A detailed database of spectral absorption coefficients for LTE air is formulated using the NEQAIR code developed at NASA Ames Research Center. The database stores calculated absorption coefficients for 1,051,755 wavelengths between 0.04 µm and 200 µm over a wide temperature (500K to 15 000K) and pressure (0.1 atm to 10.0 atm) range. The multi-group method for spectral reduction is studied by generating a range of reductions including pure binning and banding reductions from the detailed absorption coefficient database. The accuracy of each reduction is compared to line-by-line calculations for cylindrical temperature profiles resembling typical profiles found in arc-constrictors. It is found that a reduction of only 1000 groups is sufficient to accurately model the LTE air radiation over a large temperature and pressure range. In addition to the reduction comparison, the cylindrical-slab formulation is compared with the finite-volume method for the numerical integration of the radiative flux inside cylinders with varying length. It is determined that cylindrical-slabs can be used to accurately model most arc-constrictors due to their high length to radius ratios.

The Martian Neutral Atmosphere from the Radio Science Experiment MaRS on Mars Express

NASA Astrophysics Data System (ADS)

Tellmann, Silvia; Paetzold, Martin; Haeusler, Bernd; Tyler, G. L.; Hinson, David P.

The Mars Express Radio Science Experiment (MaRS) has been sounding the Martian atmo-sphere and ionosphere by means of radio occultation since 2004. To date more than 570 sound-ings covering all latitudes during almost all seasons have been obtained in seven occultation seasons, mostly in the northern hemisphere. The highly elliptical orbit of Mars Express provides access to a large range of local times and locations which we use to investigate latitudinal, diurnal, and seasonal behavior of the atmosphere. Observed radial profiles of neutral number density, n[r], are used to obtain accurate measurements of temperature, T[r], and pressure, p[r], from the surface boundary layer to altitudes of 50 km with a vertical resolution of only a few hundred metres. Typical measurement accuracies of the temperature are in the range of ten percent at the upper boundary and fractions of a Kelvin near the surface. Several soundings are located in the polar regions of both hemispheres. These measurements will be used to examine the seasonal variations at high latitudes. The high vertical resolution and accuracy of the temperature profiles allows us to investigate the CO2 supersaturation and condensation near the poles. Atmospheric waves can be identified and will be investigated with regard to their spatial oc-currence over all latitude ranges. The MaRS experiment is funded by DLR under grant 50QM0701.

Bioprospecting the thermal waters of the Roman baths: isolation of oleaginous species and analysis of the FAME profile for biodiesel production

PubMed Central

2013-01-01

The extensive diversity of microalgae provides an opportunity to undertake bioprospecting for species possessing features suited to commercial scale cultivation. The outdoor cultivation of microalgae is subject to extreme temperature fluctuations; temperature tolerant microalgae would help mitigate this problem. The waters of the Roman Baths, which have a temperature range between 39°C and 46°C, were sampled for microalgae. A total of 3 green algae, 1 diatom and 4 cyanobacterial species were successfully isolated into ‘unialgal’ culture. Four isolates were filamentous, which could prove advantageous for low energy dewatering of cultures using filtration. Lipid content, profiles and growth rates of the isolates were examined at temperatures of 20, 30, 40°C, with and without nitrogen starvation and compared against the oil producing green algal species, Chlorella emersonii. Some isolates synthesized high levels of lipids, however, all were most productive at temperatures lower than those of the Roman Baths. The eukaryotic algae accumulated a range of saturated and polyunsaturated FAMEs and all isolates generally showed higher lipid accumulation under nitrogen deficient conditions (Klebsormidium sp. increasing from 1.9% to 16.0% and Hantzschia sp. from 31.9 to 40.5%). The cyanobacteria typically accumulated a narrower range of FAMEs that were mostly saturated, but were capable of accumulating a larger quantity of lipid as a proportion of dry weight (M. laminosus, 37.8% fully saturated FAMEs). The maximum productivity of all the isolates was not determined in the current work and will require further effort to optimise key variables such as light intensity and media composition. PMID:23369619

Atmospheric components of the surface energy budget over young sea ice: Results from the N-ICE2015 campaign

NASA Astrophysics Data System (ADS)

Walden, Von P.; Hudson, Stephen R.; Cohen, Lana; Murphy, Sarah Y.; Granskog, Mats A.

2017-08-01

The Norwegian young sea ice campaign obtained the first measurements of the surface energy budget over young, thin Arctic sea ice through the seasonal transition from winter to summer. This campaign was the first of its kind in the North Atlantic sector of the Arctic. This study describes the atmospheric and surface conditions and the radiative and turbulent heat fluxes over young, thin sea ice. The shortwave albedo of the snow surface ranged from about 0.85 in winter to 0.72-0.80 in early summer. The near-surface atmosphere was typically stable in winter, unstable in spring, and near neutral in summer once the surface skin temperature reached 0°C. The daily average radiative and turbulent heat fluxes typically sum to negative values (-40 to 0 W m-2) in winter but then transition toward positive values of up to nearly +60 W m-2 as solar radiation contributes significantly to the surface energy budget. The sensible heat flux typically ranges from +20-30 W m-2 in winter (into the surface) to negative values between 0 and -20 W m-2 in spring and summer. A winter case study highlights the significant effect of synoptic storms and demonstrates the complex interplay of wind, clouds, and heat and moisture advection on the surface energy components over sea ice in winter. A spring case study contrasts a rare period of 24 h of clear-sky conditions with typical overcast conditions and highlights the impact of clouds on the surface radiation and energy budgets over young, thin sea ice.

Lattice parameters and structural phase transition of lanthanum titanate perovskite, La0.68(Ti0.95,Al0.05)O3.

PubMed

Ali, Roushown; Yashima, Masatomo

2003-05-01

Lattice parameters and the structural phase transition of La(0.68)(Ti(0.95),Al(0.05))O(3) have been investigated in situ in the temperature range 301-689 K by the synchrotron radiation powder diffraction (SR-PD) technique. High-angular-resolution SR-PD is confirmed to be a powerful technique for determining precise lattice parameters around a phase-transition temperature. The title compound exhibits a reversible phase transition between orthorhombic and tetragonal phases at 622.3 +/- 0.6 K. The following results were obtained: (i) the lattice parameters increased continuously with temperature, while the b/a ratio decreased continuously with temperature and became unity at the orthorhombic-tetragonal transition point; (ii) no hysteresis was observed between the lattice-parameter values measured on heating and on cooling. Results (i) and (ii) indicate that the orthorhombic-tetragonal phase transition is continuous and reversible. The b/a ratio is found to exhibit a more continuous temperature evolution than does the order parameter for a typical second-order phase transition based on Landau theory.

Treated mine drainage effluent benefits Maryland and West Virginia fisherman

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

Ashby, J.C.

1995-12-31

In January of 1994, the Maryland Department of Natural Resources-Freshwater Fisheries Division and Mettiki Coal Corporation of Oakland, Maryland entered into a cooperative agreement to construct a trout rearing facility within Mettiki`s 10 million gallons per day acid mine drainage treatment system to supplement the DNR stockings in the newly revitalized North Branch of the Potomac River. Due to pyrite oxidation and a lack of alkaline buffering capacity in the Freeport coal strata, seven thousand gallons per minute of acidic water containing oxidized sulfide minerals must be pumped through Mettiki`s AMD treatment systems and elevated to Federal standards prior tomore » discharge into the Upper North Branch of the Potomac River. Utilizing hydrated lime, aeration, flocculation, sedimentation, and sludge recirculation, Mettiki`s treatment imparts superior trout propagation qualities to the discharge (pH of 8.1, dissolved oxygen of 8.0 ppm, temperature ranges of from 52 to 60 degrees Fahrenheit) and has allowed for weight gain throughout the typically dormant winter months. Presently, 30,000 brown, rainbow, and cutthroat trout are suspended in floating net pens within the systems` discharge collection pond where pH, flow, temperature, feed assimilation, and growth rates were compared with typical stream diversion hatcheries. Growth rates, lack of significant disease, and quality parameters coupled with ideal temperatures suggests treated acidic mine effluent can offer successful fish propagation opportunities.« less

Typical and darkened Portland cement concrete pavement: temperature, moisture, and roughness analyses : final report.

DOT National Transportation Integrated Search

2017-01-01

The objectives of this research were to 1) investigate the effects of lower concrete albedo on the thermal behavior of concrete pavement by directly comparing temperatures and moisture contents of typical and darkened concrete pavements and 2) invest...

Derivation and test of elevated temperature thermal-stress-free fastener concept

NASA Technical Reports Server (NTRS)

Sawyer, J. W.; Blosser, M. L.; Mcwithey, R. R.

1985-01-01

Future aerospace vehicles must withstand high temperatures and be able to function over a wide temperature range. New composite materials are being developed for use in designing high-temperature lightweight structures. Due to the difference between coefficients of thermal expansion for the new composite materials and conventional high-temperature metallic fasteners, innovative joining techniques are needed to produce tight joints at all temperatures without excessive thermal stresses. A thermal-stress-free fastening technique is presented that can be used to provide structurally tight joints at all temperatures even when the fastener and joined materials have different coefficients of thermal expansion. The derivation of thermal-stress-free fasteners and joint shapes is presented for a wide variety of fastener materials and materials being joined together. Approximations to the thermal-stress-free shapes that result in joints with low-thermal-stresses and that simplify the fastener/joint shape are discussed. The low-thermal-stress fastener concept is verified by thermal and shear tests in joints using oxide-dispersion-strengthened alloy fasteners in carbon-carbon material. The test results show no evidence of thermal stress damage for temperatures up to 2000 F and the resulting joints carried shear loads at room temperature typical of those for conventional joints.

Development of high performance refractory fibers with enhanced insulating properties and longer service lifetimes

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

Martin, P.C.; DePoorter, G.L.; Munoz, D.R.

1991-02-01

We have initiated a three phase investigation of the development of high performance refractory fibers with enhanced insulating properties and longer usable lifetimes. This report presents the results of the first phase of the study, performed from Aug. 1989 through Feb. 1991, which shows that significant energy saving are possible through the use of high temperature insulating fibers that better retain their efficient insulating properties during the service lifetime of the fibers. The remaining phases of this program include the pilot scale development and then full scale production feasibility development and evaluation of enhanced high temperature refractory insulting fibers. Thismore » first proof of principle phase of the program presents a summary of the current use patterns of refractory fibers, a laboratory evaluation of the high temperature performance characteristics of selected typical refractory fibers and an analysis of the potential energy savings through the use of enhanced refractory fibers. The current use patterns of refractory fibers span a wide range of industries and high temperature furnaces within those industries. The majority of high temperature fiber applications are in furnaces operating between 2000 and 26000{degrees}F. The fibers used in furnaces operating within this range provide attractive thermal resistance and low thermal storage at reasonable cost. A series of heat treatment studies performed for this phase of the program has shown that the refractory fibers, as initially manufactured, have attractive thermal conductivities for high temperature applications but the fibers go through rapid devitrification and subsequent crystal growth upon high temperature exposure. Development of improved fibers, maintaining the favorable characteristics of the existing as-manufactured fibers, could save between 1 and 4% of the energy consumed in high temperature furnaces using refractory fibers.« less

Empirical High-Temperature Calibration for the Carbonate Clumped Isotopes Paleothermometer

NASA Astrophysics Data System (ADS)

Kluge, T.; John, C. M.; Jourdan, A.; Davis, S.; Crawshaw, J.

2013-12-01

The clumped isotope paleothermometer is being used in a wide range of applications related to carbonate mineral formation, focusing on temperature and fluid δ18O reconstruction. Whereas the range of typical Earth surface temperatures has been the focus of several studies based on laboratory experiments and biogenic carbonates of known growth temperatures, the clumped isotope-temperature relationship above 70 °C has not been assessed by direct precipitation of carbonates. We investigated the clumped isotope-temperature relationship by precipitating carbonates between 20 and 200°C in the laboratory. The setup consists of a pressurized vessel in which carbonate minerals are precipitated from the mixture of two solutions (CaCl2, NaHCO3). Both solutions are thermally and isotopically equilibrated before injection in the pressure vessel. Minerals precipitated in this setup generally consist of calcite. Samples were reacted with 105% orthophosphoric acid for 10 min at 90°C. The evolved CO2 was continuously collected and subsequently purified with a Porapak trap held at -35°C. Measurements were performed on a MAT 253 using the protocol of Huntington et al. (2009) and Dennis et al. (2011). Clumped isotope values from 20-90°C are consistent with carbonates that were precipitated from a CaCO3 super-saturated solution using the method of McCrea (1950). This demonstrates that the experimental setup does not induce any kinetic fractionation, and can be used for high-temperature carbonate precipitation. The new clumped isotope calibration at high temperature follows the theoretical calculations of Schauble et al. (2006) adjusted for phosphoric acid digestion at 90°C. We gratefully acknowledge funding from Qatar Petroleum, Shell and the Qatar Science and Technology Park.

Polishability of thin electrolytic and electroless NiP layers

NASA Astrophysics Data System (ADS)

Kinast, Jan; Beier, Matthias; Gebhardt, Andreas; Risse, Stefan; Tünnermann, Andreas

2015-10-01

Ultra-precise metal optics are key components of sophisticated scientific instrumentation in astronomy and space applications, covering a wide spectral range. Especially for applications in the visible or ultra-violet spectral ranges, a low roughness of the optics is required. Therefore, a polishable surface is necessary. State of the art is an amorphous nickel-phosphorus (NiP) layer, which enables several polishing techniques achieving a roughness of <1 nm RMS. Typically, these layers are approximately 30 μm to 60 μm thick. Deposited on Al6061, the bimetallic effect leads to a restricted operational temperature, caused by different coefficients of thermal expansion of Al6061 and NiP. Thinner NiP layers reduce the bimetallic effect. Hence, the possible operating temperature range. A deterministic shape correction via Magnetorheological Finishing of the substrate Al6061 leads to low shape deviations prior to the NiP deposition. This allows for depositing thin NiP-layers, which are polishable via a chemical mechanical polishing technique aiming at ultra-precise metal optics. The present article shows deposition processes and polishability of electroless and electrolytic NiP layers with thicknesses between 1 μm and 10 μm.

Coolant effectiveness in dental cutting with air-turbine handpieces.

PubMed

Leung, Brian T W; Dyson, John E; Darvell, Brian W

2012-03-01

To establish a strategy for evaluating coolant effectiveness and to compare typical cooling conditions used in dental cutting. A test system comprising a resistive heat source and an array of four type K thermocouples was used to compare the cooling effectiveness of air alone, water stream alone, and an air-water spray, as delivered by representative air-turbine handpieces. Mean temperature change at the four sites was recorded for a range of water flow rates in the range 10 to 90 mL min(-1), with and without air, and with and without the turbine running. The thermal resistance of the system, R, was calculated as the temperature change per watt (KW(-1)). For wet cooling (water stream and air-water spray), R was 5.1 to 11.5 KW(-1), whereas for air coolant alone the range was 18.5 to 30.7 KW(-1). R for air-water spray was lower than for water stream cooling at the same flow rate. The thermal resistivity approach is a viable means of comparative testing of cooling efficacy in simulated dental cutting. It may provide a reliable means of testing handpiece nozzle design, thus enabling the development of more efficient cooling.

The viscoelastic characterization of polymer materials exposed to the low-Earth orbit environment

NASA Technical Reports Server (NTRS)

Strganac, Thomas; Letton, Alan

1992-01-01

Recent accomplishments in our research efforts have included the successful measurement of the thermal mechanical properties of polymer materials exposed to the low-earth orbit environment. In particular, viscoelastic properties were recorded using the Rheometrics Solids Analyzer (RSA 2). Dynamic moduli (E', the storage component of the elastic modulus, and E'', the loss component of the elastic modulus) were recorded over three decades of frequency (0.1 to 100 rad/sec) for temperatures ranging from -150 to 150 C. Although this temperature range extends beyond the typical use range of the materials, measurements in this region are necessary in the development of complete viscoelastic constitutive models. The experimental results were used to provide the stress relaxation and creep compliance performance characteristics through viscoelastic correspondence principles. Our results quantify the differences between exposed and control polymer specimens. The characterization is specifically designed to elucidate a constitutive model that accurately predicts the change in behavior of these materials due to exposure. The constitutive model for viscoelastic behavior reflects the level of strain, the rate of strain, and the history of strain as well as the thermal history of the material.

Directional Cluster Analysis on a Sphere: Retrieval of Archean Magnetic Directions from Data with High Dispersion

NASA Astrophysics Data System (ADS)

Bono, R. K.; Dare, M. S.; Tarduno, J. A.; Cottrell, R. D.

2016-12-01

Magnetic directions from coarse clastic rocks are typically highly scattered, to the point that the null hypothesis that they are drawn from a random distribution, using the iconic test of Watson (1956), cannot be rejected at a high confidence level (e.g. 95%). Here, we use an alternative approach of searching for directional clusters on a sphere. When applied to a new data set of directions from quartzites from the Jack Hills of Western Australia, we find evidence for distinct and meaningful magnetic directions at low (200 to 300 degrees C) and intermediate ( 350 to 450 degrees C) unblocking temperatures, whereas the test of Watson (1956) fails to draw a distinction from random distributions for the ensemble of directions at these unblocking temperature ranges. The robustness of the directional groups identified by the cluster analysis is confirmed by non-parametric resampling tests. The lowest unblocking temperature directional mode appears related to the present day field, perhaps contaminated by viscous magnetizations. The intermediate temperature magnetization matches an overprint recorded by the secondary mineral fuchsite (Cottrell et al., 2016) acquired at ca. 2.65 Ga. These data thus indicate that the Jack Hills carry an overprint at intermediate unblocking temperatures of Archean age. We find no evidence for a 1 Ga remagnetization. In general, the application of cluster analysis on a sphere, with directions confirmed by nonparametric tests, represents a new approach that should be applied when evaluating data with high dispersion, such as those that typically come from weak coarse-grained clastic sedimentary rocks, and/or rocks that have seen several tectonic events that could have imparted multiple magnetic overprints.

A high-sensitivity torsional pendulum for polymeric films and fibres

NASA Technical Reports Server (NTRS)

Aghili-Kermani, H.; Obrien, T.; Armeniades, C. D.; Roberts, J. M.

1976-01-01

A free oscillation torsion pendulum is described, which has been designed to measure accurately the dynamic shear modulus and logarithmic decrement of polymeric thin films and fibers, at frequencies of 0.1 to 10 Hz and a temperature range of 4.2 to 450 K. The instrument can also provide in situ tensile deformations of up to 5%. The specimen geometry necessary to obtain reliable modulus measurements with thin films is discussed, and typical data are presented which exhibit hitherto unreported relaxation processes, discernible by this instrument.

Thermal management of instruments on space platforms using a high capacity two-phase heat transport system

NASA Technical Reports Server (NTRS)

Ollendorf, S.; Fowle, A.; Almgren, D.

1981-01-01

A system utilizing a pumped, two-phase single component working fluid for heat exchange and transport services necessary to meet the temperature control requirements of typical orbiting instrument payloads on space platforms is described. The design characteristics of the system is presented, together with a presentation of a laboratory apparatus for demonstration of proof of concept. Results indicate that the pumped two-phase design concept can meet a wide range of thermal performance requirements with the only penalty being the requirement for a small liquid pump.

Evaluation of Turbulence-Model Performance as Applied to Jet-Noise Prediction

NASA Technical Reports Server (NTRS)

Woodruff, S. L.; Seiner, J. M.; Hussaini, M. Y.; Erlebacher, G.

1998-01-01

The accurate prediction of jet noise is possible only if the jet flow field can be predicted accurately. Predictions for the mean velocity and turbulence quantities in the jet flowfield are typically the product of a Reynolds-averaged Navier-Stokes solver coupled with a turbulence model. To evaluate the effectiveness of solvers and turbulence models in predicting those quantities most important to jet noise prediction, two CFD codes and several turbulence models were applied to a jet configuration over a range of jet temperatures for which experimental data is available.

Pregnant women maintain body temperatures within safe limits during moderate-intensity aqua-aerobic classes conducted in pools heated up to 33 degrees Celsius: an observational study.

PubMed

Brearley, Amanda L; Sherburn, Margaret; Galea, Mary P; Clarke, Sandy J

2015-10-01

What is the body temperature response of healthy pregnant women exercising at moderate intensity in an aqua-aerobics class where the water temperature is in the range of 28 to 33 degrees Celsius, as typically found in community swimming pools? An observational study. One hundred and nine women in the second and third trimester of pregnancy who were enrolled in a standardised aqua-aerobics class. Tympanic temperature was measured at rest pre-immersion (T1), after 35minutes of moderate-intensity aqua-aerobic exercise (T2), after a further 10minutes of light exercise while still in the water (T3) and finally on departure from the facility (T4). The range of water temperatures in seven indoor community pools was 28.8 to 33.4 degrees Celsius. Body temperature increased by a mean of 0.16 degrees Celsius (SD 0.35, p<0.001) at T2, was maintained at this level at T3 and had returned to pre-immersion resting values at T4. Regression analysis demonstrated that the temperature response was not related to the water temperature (T2 r = -0.01, p = 0.9; T3 r = -0.02, p=0.9; T4 r=0.03, p=0.8). Analysis of variance demonstrated no difference in body temperature response between participants when grouped in the cooler, medium and warmer water temperatures (T2 F=0.94, p=0.40; T3 F=0.93, p=0.40; T4 F=0.70, p=0.50). Healthy pregnant women maintain body temperatures within safe limits during moderate-intensity aqua-aerobic exercise conducted in pools heated up to 33 degrees Celsius. The study provides evidence to inform guidelines for safe water temperatures for aqua-aerobic exercise during pregnancy. Copyright © 2015 Australian Physiotherapy Association. Published by Elsevier B.V. All rights reserved.

Salinity and Temperature Tolerance Experiments on Selected Florida Bay Mollusks

USGS Publications Warehouse

Murray, James B.; Wingard, G. Lynn

2006-01-01

The ultimate goal of the Comprehensive Everglades Restoration Plan (CERP) is to restore and preserve the unique ecosystems of South Florida, including the estuaries. Understanding the effect of salinity and temperature changes, beyond typical oscillations, on the biota of South Florida's estuaries is a necessary component of achieving the goal of restoring the estuaries. The U.S. Geological Survey has been actively involved in researching the history of the South Florida Ecosystem, to provide targets, performance measures, and baseline data for restoration managers. These experiments addressed two aspects of ecosystem history research: 1) determining the utility of using molluscan shells as recorders of change in water chemistry parameters, primarily salinity, and 2) enhancing our in situ observations on modern assemblages by exceeding typically observed aquatic conditions. This set of experiments expanded our understanding of the effects of salinity, temperature and other water chemistry parameters on the reproduction, growth and overall survivability of key species of mollusks used in interpreting sediment core data. Observations on mollusks, plants and microbes made as part of these experiments have further refined our knowledge and understanding of the effects of ecosystem feedback and the role salinity and temperature play in ecosystem stability. The results have demonstrated the viability of several molluscan species as indicators of atypical salinity, and possibly temperature, modulations. For example Cerithium muscarum and Bulla striata demonstrated an ability to withstand a broad salinity and temperature range, with reproduction occurring in atypically high salinities and temperatures. These experiments also provided calibration data for the shell biogeochemistry of Chione cancellata and the possible use of this species as a water chemistry recorder. Observations made in the mesocosms, on a scale not normally observable in the field, have led to new questions about the influence of salinity on the localized ecosystem. The next phase of these experiments; to calibrate growth rate and reproductive viability in atypical salinities is currently underway.

Accurate Temperature Feedback Control for MRI-Guided, Phased Array HICU Endocavitary Therapy

NASA Astrophysics Data System (ADS)

Salomir, Rares; Rata, Mihaela; Cadis, Daniela; Lafon, Cyril; Chapelon, Jean Yves; Cotton, François; Bonmartin, Alain; Cathignol, Dominique

2007-05-01

Effective treatment of malignant tumours demands well controlled energy deposition in the region of interest. Generally, two major steps must be fulfilled: 1. pre-operative optimal planning of the thermal dosimetry and 2. per-operative active spatial-and-temporal control of the delivered thermal dose. The second issue is made possible by using fast MR thermometry data and adjusting on line the sonication parameters. This approach is addressed here in the particular case of the ultrasound therapy for endocavitary tumours (oesophagus, colon or rectum) with phased array cylindrical applicators of High Intensity Contact Ultrasound (HICU). Two specific methodological objectives have been defined for this study: 1. to implement a robust and effective temperature controller for the specific geometry of endocavitary HICU and 2. to determine the stability (ie convergence) domain of the controller with respect to possible errors affecting the empirical parameters of the underlying physical model. Experimental setup included a Philips 1.5T clinical MR scanner and a cylindrical phased array transducer (64 elements) driven by a computer-controlled multi-channel generator. Performance of the temperature controller was tested ex vivo on fresh meat samples with planar and slightly focused beams, for a temperature elevation range from 10°C to 30°C. During the steady state regime, typical error of the temperature mean value was inferior to 1%, while the typical standard deviation of the temperature was inferior to 2% (relative to the targeted temperature elevation). Further, the empirical parameters of the physical model have been deliberately set to erroneous values and the impact on the controller stability was evaluated. Excellent tolerance of the controller was demonstrated, as this one failed to performed stable feedback only in the extreme case of a strong underestimation for the ultrasound absorption parameter by a factor of 4 or more.

The Thermal Regime Around Buried Submarine High-Voltage Cables

NASA Astrophysics Data System (ADS)

Emeana, C. J.; Dix, J.; Henstock, T.; Gernon, T.; Thompson, C.; Pilgrim, J.

2015-12-01

The expansion of offshore renewable energy infrastructure and the desire for "trans-continental shelf" power transmission, all require the use of submarine High Voltage (HV) cables. These cables have maximum operating surface temperatures of up to 70oC and are typically buried at depths of 1-2 m beneath the seabed, within the wide range of substrates found on the continental shelf. However, the thermal properties of near surface shelf sediments are poorly understood and this increases the uncertainty in determining the required cable current ratings, cable reliability and the potential effects on the sedimentary environments. We present temperature measurements from a 2D laboratory experiment, designed to represent a buried, submarine HV cable. We used a large (2.5 m-high) tank, filled with water-saturated ballotini and instrumented with 120 thermocouples, which measured the time-dependent 2D temperature distributions around the heat source. The experiments use a buried heat source to represent a series of realistic cable surface temperatures with the aim for identifying the thermal regimes generated within typical non-cohesive shelf sediments: coarse silt, fine sand and very coarse sand. The steady state heat flow regimes, and normalised and radial temperature distributions were assessed. Our results show that at temperatures up to 60°C above ambient, the thermal regimes are conductive for the coarse silt sediments and convective for the very coarse sand sediments even at 7°C above ambient. However, the heat flow pattern through the fine sand sediment shows a transition from conductive to convective heat flow at a temperature of approximately 20°C above ambient. These findings offer an important new understanding of the thermal regimes associated with submarine HV cables buried in different substrates and has huge impacts on cable ratings as the IEC 60287 standard only considers conductive heat flow as well as other potential near surface impacts.

Damping in aerospace composite materials

NASA Astrophysics Data System (ADS)

Agneni, A.; Balis Crema, L.; Castellani, A.

Experimental results are presented on specimens of carbon and Kevlar fibers in epoxy resin, materials used in many aerospace structures (control surfaces and wings in aircraft, large antennas in spacecraft, etc.). Some experimental methods of estimating damping ratios are first reviewed, either in the time domain or in the frequency domain. Some damping factor estimates from experimental tests are then shown; in order to evaluate the effects of the aerospace environment, damping factors have been obtained in a typical range of temperature, namely between +120 C and -120 C, and in the pressure range from room pressure to 10 exp -6 torr. Finally, a theoretical approach for predicting the bounds of the damping coefficients is shown, and prediction data are compared with experimental results.

Performance, optimization, and latest development of the SRI family of rotary cryocoolers

NASA Astrophysics Data System (ADS)

Dovrtel, Klemen; Megušar, Franc

2017-05-01

In this paper the SRI family of Le-tehnika rotary cryocoolers is presented (SRI401, SRI423/SRI421 and SRI474). The Stirling coolers cooling power range starts from 0.25W to 0.75W at 77K with available temperature range from 60K to 150K and are fitted to typical dewar detector sizes and powers supply voltages. The DDCA performance optimizing procedure is presented. The procedure includes cooler steady state performance mapping and optimization and cooldown optimization. The current cryogenic performance status and reliability evaluation method and figures are presented on the existing and new units. The latest improved SRI401 demonstrated MTTF close to 25'000 hours and the test is still on going.

Recent progress in the development of MCT hot detectors

NASA Astrophysics Data System (ADS)

Wollrab, R.; Schirmacher, W.; Schallenberg, T.; Lutz, H.; Wendler, J.; Haiml, M.; Ziegler, J.

2017-11-01

To push HOT-performance, AIMs existing n-on-p technology has been improved by introducing Gold as an acceptor and reducing its concentration to the lower 1015/cm3 range as well as by optimizing the passivation process. This results in a substantial reduction in dark current density, a prerequisite for HOT operation. Recent dark current data are compared to ones previously obtained as well as to Tennant`s Rule07 [1], a generally accepted bench mark in this context. Furthermore, we present electro-optical parameters obtained in the temperature range from 120 K to 170 K on resulting FPAs with 640x512 pixels, a pitch of 15 μm and a typical (80 K) cutoff wavelength of 5.1 μm.

The Charging of Dust Grains in the Inner Heliosheath

NASA Astrophysics Data System (ADS)

Avinash, K.; Slavin, J.; Zank, G. P.; Frisch, P.

2008-12-01

Equilibrium electric charge and surface potential on a dust grain in the heliosheath are calculated. The grain is charged due to heliosheath plasma flux, photo electrons flux, secondary electron emission flux and transmission flux. Realistically, the heliosheath plasma consists of solar electrons, solar wind ions [SWI] and pick up ions [PUI]. These species interact differently with TS and thus have different characteristics down stream in the heliosheath. The PUI suffer multiple reflections at TS and are accelerated to high energies in the range of ~ 106 K. The solar electrons, on the other hand, are heated adiabatically through the TS and have temperature in the range ~ 5x105 K. The SWI may have a smaller temperature typically in the range 1-5x104 K The density of electrons could be in the range ~5 x 10-4 cm-3, while the ratio of PUI to SWI density could range from 0.1 to 0.5. Taking into account these parameters, grain charging due to different plasma species and other fluxes mentioned earlier, is calculated. Our results show that (a) surface potential is very sensitive to electron temp. It goes through a maxima and for realistic values close to or less than 5x105 K it can be as big as 26V which is twice the value calculated by Kimura and Mann1. This may have implications for electrostatic disruption and the size distribution of dust particles in the heliosheath. With PUI density the surface potential increases about 10 to 20 %. Though temperature of PUI is significantly larger than that of electrons, it is not large enough to make up for the mass ratio of electrons to protons. On account small temperature and electron/proton mass ratio, the effect of SWI on dust charge is very weak. (1) H. Kimura and I. Mann, Ap.J. 499, 454 (1998).

Europa Lander Material Selection Considerations

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

Tappan, Alexander S.; Heller, Mellisa

2017-01-10

Energetic materials (EMs, explosives, pyrotechnics, propellants) provide high-power output of high temperature reaction products. These products can be solid, liquid, or gaseous during reaction or after the products have equilibrated with the surroundings. For example, high explosives typically consist of carbon, hydrogen, nitrogen, and oxygen bonded within a single molecule, and produce almost exclusively gaseous products. Conversely, intermetallics consist of physical mixtures of metals and metalloids, and produce almost exclusively condensed products. Other materials such as pyrotechnics and propellants have intermediate behavior. All energetic materials react in a self-propagating manner that after ignition, does not necessarily require energy input frommore » the surroundings. The range of reaction velocities can range from mm/s for intermetallics, to km/s for high explosives. Energetic material selection depends on numerous requirements specific to the needs of a system. High explosives are used for applications where high pressure gases are necessary for pushing or fracturing materials (e.g., rock, metal) or creating shock waves or air blast. Propellants are used to produce moderate-pressure, high-temperature products without a shock wave. Pyrotechnics are used to produce numerous effects including: high-temperature products, gases, light, smoke, sound, and others. Thermites are used to produce heat, high-temperature products, materials, and other effects that require condensed products. Intermetallics are used to produce high-temperature condensed products and materials, with very little gas production. Numerous categories of energetic materials exist with overlapping definitions, effects, and properties.« less

Unusually sharp paramagnetic phase transition in thin film Fe3Pt invar

NASA Astrophysics Data System (ADS)

Drisko, Jasper; Cumings, John

2013-03-01

Invar alloys, typically 3d transition metal rich systems, are most commonly known for their extremely low coefficients of thermal expansion (CTE) over a wide range of temperatures close to room temperature. This anomalous behavior in the CTE lends Invar to a variety of important applications in precision mechanical devices, scientific instruments, and sensors, among others. Many theoretical models of Invar have been proposed over the years, the most promising of which is a system described by two coexisting phases, one high-spin high-volume and the other low-spin low-volume, that compete to stabilize the volume of the material as the temperature is changed. However, no theory has yet been able to explain all experimental observations across the range of Invar alloys, especially at finite temperature. We have fabricated thin films of a Fe3Pt Invar alloy and investigate them using Lorentz Transmission Electron Microscopy (TEM). 23nm films are deposited onto SiN membrane substrates via radio-frequency magnetron sputtering from a pure Fe target decorated with Pt pieces. We observe novel magnetic domain structures and an unusually sharp phase transition between ferromagnetic (FM) and paramagnetic (PM) regions of the film under a temperature gradient. This sharp transition suggests that the FM-to-PM transition may be first order, perhaps containing a structural-elastic component to the order parameter. However, electron diffraction reveals that both the FM and PM regions have the same FCC crystal structure.

High-performance IR detectors at SCD present and future

NASA Astrophysics Data System (ADS)

Nesher, O.; Klipstein, P. C.

2005-09-01

For over 27 years, SCD has been manufacturing and developing a wide range of high performance infra-red detectors, designed to operate in either the mid-wave (MWIR) or the long-wave (LWIR) atmospheric windows. These detectors have been integrated successfully into many different types of system including missile seekers, Time Delay Integration scanning systems, Hand-Held cameras, Missile Warning Systems and many others. SCD's technology for the MWIR wavelength range is based on its well established 2-D arrays of InSb photodiodes. The arrays are flip-chip bonded to SCD's analogue or digital signal processors, all of which have been designed in-house. The 2-D Focal Plane Array (FPA) detectors have a format of 320×256 elements for a 30 μm pitch and 480×384 or 640×512 elements for a 20 μm pitch. Typical operating temperatures are around 77-85K. Five years ago SCD began to develop a new generation of MWIR detectors based on the epitaxial growth of Antimonide Based Compound Semiconductors (ABCS). This ABCS technology allows band-gap engineering of the detection material which enables higher operating temperatures and multi-spectral detection. This year SCD presented its first prototype FPA from this program, an InAlSb based detector operating at a temperature of 100 K. By the end of this year SCD will introduce the first prototype MWIR detector with a 640×512 element format and a pitch of 15 μm. For the LWIR wave-length range SCD manufactures both linear Hg1-xCdxTe (MCT) detectors with a line of 250 elements and Time Delay and Integration (TDI) detectors with formats of 288×4 and 480×6. Recently, SCD has demonstrated its first prototype un-cooled detector which is based on VOx technology and which has a format of 384×288 elements, a pitch of 25 μm and a typical NETD of 50mK at F/1. In this paper we describe the present technologies and products of SCD and the future evolution of our detectors for the MWIR and LWIR detection.

Freeze-In dark matter with displaced signatures at colliders

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

Co, Raymond T.; D'Eramo, Francesco; Hall, Lawrence J.

2015-12-01

Dark matter, X, may be generated by new physics at the TeV scale during an early matter-dominated (MD) era that ends at temperature T{sub R} || TeV. Compared to the conventional radiation-dominated (RD) results, yields from both Freeze-Out and Freeze-In processes are greatly suppressed by dilution from entropy production, making Freeze-Out less plausible while allowing successful Freeze-In with a much larger coupling strength. Freeze-In is typically dominated by the decay of a particle B of the thermal bath, B → X. For a large fraction of the relevant cosmological parameter space, the decay rate required to produce the observed dark matter abundance leadsmore » to displaced signals at LHC and future colliders, for any m{sub X} in the range keV  < m{sub X} < m{sub B} and for values of m{sub B} accessible to these colliders. This result applies whether the early MD era arises after conventional inflation, when T{sub R} is the usual reheat temperature, or is a generic MD era with an alternative origin. In the former case, if m{sub X} is sufficiently large to be measured from kinematics, the reheat temperature T{sub R} can be extracted. Our result is independent of the particular particle physics implementation of B → X, and can occur via any operator of dimension less than 8 (4) for a post-inflation (general MD) cosmology. An interesting example is provided by DFS axion theories with TeV-scale supersymmetry and axino dark matter of mass GeV to TeV, which is typically overproduced in a conventional RD cosmology. If B is the higgsino, h-tilde , Higgs, W and Z particles appear at the displaced decays, h-tilde  →  h-tilde  a, Z ã and h-tilde {sup ±} → W{sup ±} ã. The scale of axion physics, f, is predicted to be in the range (3×10{sup 8}—10{sup 12}) GeV and, over much of this range, can be extracted from the decay length.« less

Activation of Peptide ions by blackbody radiation: factors that lead to dissociation kinetics in the rapid energy exchange limit.

PubMed

Price, W D; Williams, E R

1997-11-20

Unimolecular rate constants for blackbody infrared radiative dissociation (BIRD) were calculated for the model protonated peptide (AlaGly)(n) (n = 2-32) using a variety of dissociation parameters. Combinations of dissociation threshold energies ranging from 0.8 to 1.7 eV and transition entropies corresponding to Arrhenius preexponential factors ranging from very "tight" (A(infinity) = 10(9.9) s(-1)) to "loose" (A(infinity) = 10(16.8) s(-1)) were selected to represent dissociation parameters within the experimental temperature range (300-520 K) and kinetic window (k(uni) = 0.001-0.20 s(-1)) typically used in the BIRD experiment. Arrhenius parameters were determined from the temperature dependence of these values and compared to those in the rapid energy exchange (REX) limit. In this limit, the internal energy of a population of ions is given by a Boltzmann distribution, and kinetics are the same as those in the traditional high-pressure limit. For a dissociation process to be in this limit, the rate of photon exchange between an ion and the vacuum chamber walls must be significantly greater than the dissociation rate. Kinetics rapidly approach the REX limit either as the molecular size or threshold dissociation energy increases or as the transition-state entropy or experimental temperature decreases. Under typical experimental conditions, peptide ions larger than 1.6 kDa should be in the REX limit. Smaller ions may also be in the REX limit depending on the value of the threshold dissociation energy and transition-state entropy. Either modeling or information about the dissociation mechanism must be known in order to confirm REX limit kinetics for these smaller ions. Three principal factors that lead to the size dependence of REX limit kinetics are identified. With increasing molecular size, rates of radiative absorption and emission increase, internal energy distributions become relatively narrower, and the microcanonical dissociation rate constants increase more slowly over the energy distribution of ions. Guidelines established here should make BIRD an even more reliable method to obtain information about dissociation energetics and mechanisms for intermediate size molecules.

Activation of Peptide Ions by Blackbody Radiation: Factors That Lead to Dissociation Kinetics in the Rapid Energy Exchange Limit

PubMed Central

Price, William D.

2005-01-01

Unimolecular rate constants for blackbody infrared radiative dissociation (BIRD) were calculated for the model protonated peptide (AlaGly)n (n = 2–32) using a variety of dissociation parameters. Combinations of dissociation threshold energies ranging from 0.8 to 1.7 eV and transition entropies corresponding to Arrhenius preexponential factors ranging from very “tight” (A∞ = 109.9 s−1) to “loose” (A∞ = 1016.8 s−1) were selected to represent dissociation parameters within the experimental temperature range (300–520 K) and kinetic window (kuni = 0.001–0.20 s−1) typically used in the BIRD experiment. Arrhenius parameters were determined from the temperature dependence of these values and compared to those in the rapid energy exchange (REX) limit. In this limit, the internal energy of a population of ions is given by a Boltzmann distribution, and kinetics are the same as those in the traditional high-pressure limit. For a dissociation process to be in this limit, the rate of photon exchange between an ion and the vacuum chamber walls must be significantly greater than the dissociation rate. Kinetics rapidly approach the REX limit either as the molecular size or threshold dissociation energy increases or as the transition-state entropy or experimental temperature decreases. Under typical experimental conditions, peptide ions larger than 1.6 kDa should be in the REX limit. Smaller ions may also be in the REX limit depending on the value of the threshold dissociation energy and transition-state entropy. Either modeling or information about the dissociation mechanism must be known in order to confirm REX limit kinetics for these smaller ions. Three principal factors that lead to the size dependence of REX limit kinetics are identified. With increasing molecular size, rates of radiative absorption and emission increase, internal energy distributions become relatively narrower, and the microcanonical dissociation rate constants increase more slowly over the energy distribution of ions. Guidelines established here should make BIRD an even more reliable method to obtain information about dissociation energetics and mechanisms for intermediate size molecules. PMID:16604162

High-performance IR detectors at SCD present and future

NASA Astrophysics Data System (ADS)

Nesher, O.; Klipstein, P. C.

2006-03-01

For over 27 years, SCD has been manufacturing and developing a wide range of high performance infrared detectors, designed to operate in either the mid-wave (MWIR) or the long-wave (LWIR) atmospheric windows. These detectors have been integrated successfully into many different types of system including missile seekers, time delay integration scanning systems, hand-held cameras, missile warning systems and many others. SCD's technology for the MWIR wavelength range is based on its well established 2D arrays of InSb photodiodes. The arrays are flip-chip bonded to SCD's analogue or digital signal processors, all of which have been designed in-house. The 2D focal plane array (FPA) detectors have a format of 320×256 elements for a 30-μm pitch and 480×384 or 640×512 elements for a 20-μm pitch. Typical operating temperatures are around 77-85 K. Five years ago SCD began to develop a new generation of MWIR detectors based on the epitaxial growth of antimonide based compound semiconductors (ABCS). This ABCS technology allows band-gap engineering of the detection material which enables higher operating temperatures and multi-spectral detection. This year SCD presented its first prototype FPA from this program, an InAlSb based detector operating at a temperature of 100 K. By the end of this year SCD will introduce the first prototype MWIR detector with a 640×512 element format and a pitch of 15 μm. For the LWIR wavelength range SCD manufactures both linear Hg1-xCdxTe (MCT) detectors with a line of 250 elements and time delay and integration (TDI) detectors with formats of 288×4 and 480×6. Recently, SCD has demonstrated its first prototype uncooled detector which is based on VOx technology and which has a format of 384×288 elements, a pitch of 25 μm, and a typical NETD of 50 mK at F/1. In this paper, we describe the present technologies and products of SCD and the future evolution of our detectors for the MWIR and LWIR detection.

NMR study of heavy fermion compound EuNi2P2

NASA Astrophysics Data System (ADS)

Magishi, K.; Watanabe, R.; Hisada, A.; Saito, T.; Koyama, K.; Fujiwara, T.

2015-03-01

We report the results of 31P-nuclear magnetic resonance (NMR) measurements on heavy fermion compound EuNi2P2 in order to investigate the magnetic properties at low temperatures from a microscopic view point. The Knight shift has a negative value in an entire temperature range, and the absolute value increases with decreasing temperature but exhibits a broad maximum around 40 K, which is similar to the behavior of the magnetic susceptibility. Also, the nuclear spin-lattice relaxation rate 1/T1 is almost constant at high temperatures above 200 K, which is reminiscent of the relaxation mechanism dominated by the interaction of the 31P nucleus with fluctuating Eu-4f moments. Below 200 K, 1/T1 gradually decreases on cooling due to the change of the valence in the Eu ion. At low temperatures, 1/T1 does not obey the Korringa relation, in contrast to typical heavy fermion compounds. The nuclear spin-spin relaxation rate 1/T2 shows the similar behavior as 1/T1 at high temperatures. But, below 50 K, 1/T2 increases upon cooling due to the development of the magnetic excitation.

A multi-physics model for ultrasonically activated soft tissue.

PubMed

Suvranu De, Rahul

2017-02-01

A multi-physics model has been developed to investigate the effects of cellular level mechanisms on the thermomechanical response of ultrasonically activated soft tissue. Cellular level cavitation effects have been incorporated in the tissue level continuum model to accurately determine the thermodynamic states such as temperature and pressure. A viscoelastic material model is assumed for the macromechanical response of the tissue. The cavitation model based equation-of-state provides the additional pressure arising from evaporation of intracellular and cellular water by absorbing heat due to structural and viscoelastic heating in the tissue, and temperature to the continuum level thermomechanical model. The thermomechanical response of soft tissue is studied for the operational range of frequencies of oscillations and applied loads for typical ultrasonically activated surgical instruments. The model is shown to capture characteristics of ultrasonically activated soft tissue deformation and temperature evolution. At the cellular level, evaporation of water below the boiling temperature under ambient conditions is indicative of protein denaturation around the temperature threshold for coagulation of tissues. Further, with increasing operating frequency (or loading), the temperature rises faster leading to rapid evaporation of tissue cavity water, which may lead to accelerated protein denaturation and coagulation.

8.0-Tesla human MR system: temperature changes associated with radiofrequency-induced heating of a head phantom.

PubMed

Kangarlu, Allahyar; Shellock, Frank G; Chakeres, Donald W

2003-02-01

To investigate if the heat induced in biological tissues by typical radio frequency (RF) energy associated with an 8.0-Tesla magnetic resonance (MR) system causes excessive temperature changes. Fluoroptic thermometry was used to measure temperatures in multiple positions in a head phantom made of ground turkey breast. A series of experiments were conducted with measurements obtained at RF power levels ranging from a specific absorption rate (SAR) of up to 4.0 W/kg for 10 minutes. The highest temperature increases were up to 0.7 degrees C. An inhomogeneous heating pattern was observed. In general, the deep regions within the phantom registered higher temperature increases compared to the peripheral sites. The expectation of an inhomogeneous RF distribution in ultra high field systems (> 4 T) was confirmed. At a frequency of 340 MHz and in-tissue RF wave length of about 10 cm, the RF inhomogeneity was measured to create higher temperatures in deeper regions of a human head phantom compared to peripheral tissues. Our results agree with the computational electromagnetic calculations for such frequencies. Importantly, these experiments indicated that there were no regions of heating that exceeded the current FDA guidelines. Copyright 2003 Wiley-Liss, Inc.

Effects of temperature distribution on boundary layer stability for a circular cone at Mach 10

NASA Astrophysics Data System (ADS)

Rigney, Jeffrey M.

A CFD analysis was conducted on a circular cone at 3 degrees angle of attack at Mach 10 using US3D and STABL 3D to determine the effect of wall temperature on the stability characteristics that lead to laminar-to-turbulent transition. Wall temperature distributions were manipulated while all other flow inputs and geometric qualities were held constant. Laminar-to-turbulent transition was analyzed for isothermal and adiabatic wall conditions, a simulated short-duration wind tunnel case, and several hot-nose temperature distributions. For this study, stability characteristics include maximum N-factor growth and the corresponding frequency range, disturbance spatial amplification rate and the corresponding modal frequency, and stability neutral point location. STABL 3D analysis indicates that temperature distributions typical of those in short-duration hypersonic wind tunnels do not result in any significant difference on the stability characteristics, as compared to an isothermal wall boundary condition. Hypothetical distributions of much greater temperatures at and past the nose tip do show a trend of dampening of second-mode disturbances, most notably on the leeward ray. The most pronounced differences existed between the isothermal and adiabatic cases.

Deciphering the Environmental Impacts on Rice Quality for Different Rice Cultivated Areas.

PubMed

Li, Xiukun; Wu, Lian; Geng, Xin; Xia, Xiuhong; Wang, Xuhong; Xu, Zhengjin; Xu, Quan

2018-01-19

Rice (Oryza sativa L.) is cultivated in a wide range of climatic conditions, and is one of mankind's major staple foods. The interaction of environmental factors with genotype effects major agronomic traits such as yield, quality, and resistance in rice. However, studies on the environmental factors affecting agronomic traits are often difficult to conduct because most environmental factors are dynamic and constantly changing. A series of recombinant inbred lines (RILs) derived from an indica/japonica cross were planted into four typical rice cultivated areas arranging from latitude N22° to N42°. The environmental data from the heading to mature (45 days) stages were recorded for each RIL in the four areas. We determined that light, temperature, and humidity significantly affected the milling quality and cooking quality overall the four areas. Within each area, these environmental factors mainly affected the head rice ratio, grain length, alkali consumption, and amylose and protein content. Moreover, the effect of these environmental factors dynamically changed from heading to mature stage. Compared to light and humidity, temperature was more stable and predictable, and night temperature showed a stronger correlation efficiency to cooking quality than day temperature, and the daily temperature range had contrary effects compared to day and night temperature on grain quality. The present study evaluated the critical phase during the grain filling stage by calculating the dynamic changes of correlation efficiency between the quality traits and climate parameters. Our findings suggest that the sowing date could be adjusted to improve rice quality so as to adjust for environmental changes.

Optimal bus temperature for thermal comfort during a cool day.

PubMed

Velt, K B; Daanen, H A M

2017-07-01

A challenge for electric buses is to minimize heating and cooling power to maximally extend the driving range, but still provide sufficient thermal comfort for the driver and passengers. Therefore, we investigated the thermal sensation (TS) and thermal comfort (TC) of passengers in buses during a cool day (temperature 13.4 ± 0.5 °C, relative humidity (RH) 60 ± 5.8%) typical for the Dutch temperate maritime climate. 28 Males and 72 females rated TS and TC and gave information on age, stature, body weight and worn garments. The temperature in the bus of 22.5 ± 1.1 °C and RH of 59.9 ± 5.8% corresponded to a slightly warm feeling (TS = 0.85 ± 1.06) and TC of 0.39 ± 0.65. TS related significantly to bus temperature, clothing insulation and age. Linear regression based on these parameters showed that the temperature in the bus corresponding to TC = 0 and TS = 0 would have been 20.9 ± 0.6 °C. In conclusion, a 1.6 °C lower bus temperature during the investigated cool day probably would have led to less thermal discomfort and energy savings of electrical busses. The methodology to relate climatic measurements to subjective assessments is currently employed in a wider climatic range and may prove to be useful to find a better balance between thermal comfort and energy savings of the bus. Copyright © 2017 Elsevier Ltd. All rights reserved.

Porous silicon-VO{sub 2} based hybrids as possible optical temperature sensor: Wavelength-dependent optical switching from visible to near-infrared range

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

Antunez, E. E.; Salazar-Kuri, U.; Estevez, J. O.

Morphological properties of thermochromic VO{sub 2}—porous silicon based hybrids reveal the growth of well-crystalized nanometer-scale features of VO{sub 2} as compared with typical submicron granular structure obtained in thin films deposited on flat substrates. Structural characterization performed as a function of temperature via grazing incidence X-ray diffraction and micro-Raman demonstrate reversible semiconductor-metal transition of the hybrid, changing from a low-temperature monoclinic VO{sub 2}(M) to a high-temperature tetragonal rutile VO{sub 2}(R) crystalline structure, coupled with a decrease in phase transition temperature. Effective optical response studied in terms of red/blue shift of the reflectance spectra results in a wavelength-dependent optical switching withmore » temperature. As compared to VO{sub 2} film over crystalline silicon substrate, the hybrid structure is found to demonstrate up to 3-fold increase in the change of reflectivity with temperature, an enlarged hysteresis loop and a wider operational window for its potential application as an optical temperature sensor. Such silicon based hybrids represent an exciting class of functional materials to display thermally triggered optical switching culminated by the characteristics of each of the constituent blocks as well as device compatibility with standard integrated circuit technology.« less

Canaveral National Seashore Water Quality and Aquatic Resource Inventory

NASA Technical Reports Server (NTRS)

Hall, C. R.; Provancha, J. A.; Oddy, D. M.; Lowers, R. L.; Drese, J. D.

2001-01-01

Mosquito Lagoon is a shallow, bar-built estuary located on the east central Florida Coast, primarily within the KSC boundary. The lagoon and watershed cover approximately 327 sq km (79422 acres) .The Lagoon occupies 159 sq km (37853 acres). Water depths average approximately 1m. The lagoon volume is approximately 1.6 x 10(exp 8)cu m. Water quality in Mosquito Lagoon is good. Salinity data typically range between 20 ppt and 35 ppt. The lowest value recorded was 4.5 ppt and the highest value was 37 ppt. Water temperatures fluctuate 2 - 3 C over a 24 h period. Cold front passage can rapidly alter water temperatures by 5 - 10 C or more in a short period of time. The highest temperature was 33.4 C and the lowest temperature was 8.8 C after a winter storm. Dissolved oxygen concentrations ranged from a low of 0.4 mg/l to a high of 15.3 mg/l. Extended periods of measurements below the Florida Department of Environmental Protection criteria of 4.0 mg/l were observed in fall and spring months suggesting high system respiration and oxygen demand. Metals such as antimony, arsenic, molybdenum and mercury were report as below detection limits for all samples. Cadmium, copper, chromium, silver, and zinc were found to be periodically above the Florida Department of Environmental Protection criteria for Class II and Class III surface waters.

Improving Resonance Characteristics of Gas Sensors by Chemical Etching of Quartz Plates

NASA Astrophysics Data System (ADS)

Raicheva, Z.; Georgieva, V.; Grechnikov, A.; Gadjanova, V.; Angelov, Ts; Vergov, L.; Lazarov, Y.

2012-12-01

The paper presents the results of the influence of the etching process of AT-cut quartz plates on the resonance parameters and the QCM sensors. Quartz wafers (100 μm thick, with a diameter of 8 mm), divided into five groups, have been etched in [NH4]2 F2: H2O = 1:1 solution at temperatures in the range from 70°C to 90°C. The influence of etching temperature on the surface morphology of quartz wafers has been estimated by Atomic Force Microscopy (AFM). A correlation between the etching temperature and the dynamic characteristics is obtained. The optimal etching conditions for removing the surface damages caused by the mechanical treatment of the quartz wafers and for obtaining a clean surface were determined. The typical parameters of fabricated resonators on the quartz plates etched in the temperature range from 70°C to 90°C are as follows: Frequency, Fs 16 MHz ± 100 kHz Motional resistance, Rs less 10 Ω Motional inductance, Lq higher than 3 mH Motional capacitance, Cq less 30 fF Static capacitance, Co around 5 pF Quality factor, Q from 46 000 to 70 000 Sorption properties of QCM - MoO3 are evaluated at NH3 concentrations in the interval from 100 ppm to 500 ppm.

ZnO core spike particles and nano-networks and their wide range of applications

NASA Astrophysics Data System (ADS)

Wille, S.; Mishra, Y. K.; Gedamu, D.; Kaps, S.; Jin, X.; Koschine, T.; Bathnagar, A.; Adelung, R.

2011-05-01

In our approach we are producing a polymer composite material with ZnO core spike particles as concave fillers. The core spike particles are synthesized by a high throughput method. Using PDMS (Polydimethylsiloxane) as a matrix material the core spike particles achieve not only a high mechanical reinforcement but also influence other material properties in a very interesting way, making such a composite very interesting for a wide range of applications. In a very similar synthesis route a nanoscopic ZnO-network is produced. As a ceramic this network can withstand high temperatures like 1300 K. In addition this material is quite elastic. To find a material with these two properties is a really difficult task, as polymers tend to decompose already at lower temperatures and metals melt. Especially under ambient conditions, often oxygen creates a problem for metals at these temperatures. If this material is at the same time a semiconductor, it has a high potential as a multifunctional material. Ceramic or classical semiconductors like III-V or IIVI type are high temperature stable, but typically brittle. This is different on the nanoscale. Even semiconductor wires like silicon with a very small diameter do not easily built up enough stress that leads to a failure while being bent, because in a first order approximation the maximum stress of a fiber scales with its diameter.

Ceramic Bearings For Gas-Turbine Engines

NASA Technical Reports Server (NTRS)

Zaretsky, Erwin V.

1989-01-01

Report reviews data from three decades of research on bearings containing rolling elements and possibly other components made of ceramics. Ceramic bearings attractive for use in gas-turbine engines because ceramics generally retain strengths and resistances to corrosion over range of temperatures greater than typical steels used in rolling-element bearings. Text begins with brief description of historical developments in field. Followed by discussion of effects of contact stress on fatigue life of rolling element. Supplemented by figures and tables giving data on fatigue lives of rolling elements made of various materials. Analyzes data on effects of temperature and speed on fatigue lives for several materials and operating conditions. Followed by discussion of related topic of generation of heat in bearings, with consideration of effects of bearing materials, lubrication, speeds, and loads.

Py4CAtS - Python tools for line-by-line modelling of infrared atmospheric radiative transfer

NASA Astrophysics Data System (ADS)

Schreier, Franz; García, Sebastián Gimeno

2013-05-01

Py4CAtS — Python scripts for Computational ATmospheric Spectroscopy is a Python re-implementation of the Fortran infrared radiative transfer code GARLIC, where compute-intensive code sections utilize the Numeric/Scientific Python modules for highly optimized array-processing. The individual steps of an infrared or microwave radiative transfer computation are implemented in separate scripts to extract lines of relevant molecules in the spectral range of interest, to compute line-by-line cross sections for given pressure(s) and temperature(s), to combine cross sections to absorption coefficients and optical depths, and to integrate along the line-of-sight to transmission and radiance/intensity. The basic design of the package, numerical and computational aspects relevant for optimization, and a sketch of the typical workflow are presented.

The importance of Soret transport in the production of high purity silicon for solar cells

NASA Technical Reports Server (NTRS)

Srivastava, R.

1985-01-01

Temperature-gradient-driven diffusion, or Soret transport, of silicon vapor and liquid droplets is analyzed under conditions typical of current production reactors for obtaining high purity silicon for solar cells. Contrary to the common belief that Soret transport is negligible, it is concluded that some 15-20 percent of the silicon vapor mass flux to the reactor walls is caused by the high temperature gradients that prevail inside such reactors. Moreover, since collection of silicon is also achieved via deposition of silicon droplets onto the walls, the Soret transport mechanism becomes even more crucial due to size differences between diffusing species. It is shown that for droplets in the 0.01 to 1 micron diameter range, collection by Soret transport dominates both Brownian and turbulent mechanisms.

SSME main combustion chamber life prediction

NASA Technical Reports Server (NTRS)

Cook, R. T.; Fryk, E. E.; Newell, J. F.

1983-01-01

Typically, low cycle fatigue life is a function of the cyclic strain range, the material properties, and the operating temperature. The reusable life is normally defined by the number of strain cycles that can be accrued before severe material degradation occurs. Reusable life is normally signified by the initiation or propagation of surface cracks. Hot-fire testing of channel wall combustors has shown significant mid-channel wall thinning or deformation during accrued cyclic testing. This phenomenon is termed cyclic-creep and appears to be significantly accelerated at elevated surface temperatures. This failure mode was analytically modelled. The cyclic life of the baseline SSME-MCC based on measured calorimeter heat transfer data, and the life sensitivity of local hot spots caused by injector effects were determined. Four life enhanced designs were assessed.

The recent warming of permafrost in Alaska

NASA Astrophysics Data System (ADS)

Osterkamp, T. E.

2005-12-01

This paper reports results of an experiment initiated in 1977 to determine the effects of climate on permafrost in Alaska. Permafrost observatories with boreholes were established along a north-south transect of Alaska in undisturbed permafrost terrain. The analysis and interpretation of annual temperature measurements in the boreholes and daily temperature measurements of the air, ground and permafrost surfaces made with automated temperature loggers are reported. Permafrost temperatures warmed along this transect coincident with a statewide warming of air temperatures that began in 1977. At two sites on the Arctic Coastal Plain, the warming was seasonal, greatest during "winter" months (October through May) and least during "summer" months (June through September). Permafrost temperatures peaked in the early 1980s and then decreased in response to slightly cooler air temperatures and thinner snow covers. Arctic sites began warming again typically about 1986 and Interior Alaska sites about 1988. Gulkana, the southernmost site, has been warming slowly since it was drilled in 1983. Air temperatures were relatively warm and snow covers were thicker-than-normal from the late 1980s into the late 1990s allowing permafrost temperatures to continue to warm. Temperatures at some sites leveled off or cooled slightly at the turn of the century. Two sites (Yukon River Bridge and Livengood) cooled during the period of observations. The magnitude of the total warming at the surface of the permafrost (through 2003) was 3 to 4 °C for the Arctic Coastal Plain, 1 to 2 °C for the Brooks Range including its northern and southern foothills, and 0.3 to 1 °C south of the Yukon River. While the data are sparse, permafrost is warming throughout the region north of the Brooks Range, southward along the transect from the Brooks Range to the Chugach Mountains (except for Yukon River and Livengood), in Interior Alaska throughout the Tanana River region, and in the region south of the Alaska Range from Tok westward to Gulkana (in the Copper River Valley) and beyond to the Talkeetna Mountains. Thermal offset allows permafrost to survive in the presence of positive annual mean ground surface temperatures and was observed repeatedly since 1987 at two sites. The observed warming has not produced an increasing trend in maximum active layer thicknesses due to its seasonality. Near Healy, permafrost has been thawing at the top since the late 1980s at about 10 cm/yr. At Gulkana, permafrost was thawing from the bottom at a rate of 4 cm/yr that accelerated to 9 cm/yr after 2000.

Thermal reaction norms and the scale of temperature variation: latitudinal vulnerability of intertidal nacellid limpets to climate change.

PubMed

Morley, Simon A; Martin, Stephanie M; Day, Robert W; Ericson, Jess; Lai, Chien-Houng; Lamare, Miles; Tan, Koh-Siang; Thorne, Michael A S; Peck, Lloyd S

2012-01-01

The thermal reaction norms of 4 closely related intertidal Nacellid limpets, Antarctic (Nacella concinna), New Zealand (Cellana ornata), Australia (C. tramoserica) and Singapore (C. radiata), were compared across environments with different temperature magnitude, variability and predictability, to test their relative vulnerability to different scales of climate warming. Lethal limits were measured alongside a newly developed metric of "duration tenacity", which was tested at different temperatures to calculate the thermal reaction norm of limpet adductor muscle fatigue. Except in C. tramoserica which had a wide optimum range with two break points, duration tenacity did not follow a typical aerobic capacity curve but was best described by a single break point at an optimum temperature. Thermal reaction norms were shifted to warmer temperatures in warmer environments; the optimum temperature for tenacity (T(opt)) increased from 1.0°C (N. concinna) to 14.3°C (C. ornata) to 18.0°C (an average for the optimum range of C. tramoserica) to 27.6°C (C. radiata). The temperature limits for duration tenacity of the 4 species were most consistently correlated with both maximum sea surface temperature and summer maximum in situ habitat logger temperature. Tropical C. radiata, which lives in the least variable and most predictable environment, generally had the lowest warming tolerance and thermal safety margin (WT and TSM; respectively the thermal buffer of CT(max) and T(opt) over habitat temperature). However, the two temperate species, C. ornata and C. tramoserica, which live in a variable and seasonally unpredictable microhabitat, had the lowest TSM relative to in situ logger temperature. N. concinna which lives in the most variable, but seasonally predictable microhabitat, generally had the highest TSMs. Intertidal animals live at the highly variable interface between terrestrial and marine biomes and even small changes in the magnitude and predictability of their environment could markedly influence their future distributions.

Thermal Reaction Norms and the Scale of Temperature Variation: Latitudinal Vulnerability of Intertidal Nacellid Limpets to Climate Change

PubMed Central

Morley, Simon A.; Martin, Stephanie M.; Day, Robert W.; Ericson, Jess; Lai, Chien-Houng; Lamare, Miles; Tan, Koh-Siang; Thorne, Michael A. S.; Peck, Lloyd S.

2012-01-01

The thermal reaction norms of 4 closely related intertidal Nacellid limpets, Antarctic (Nacella concinna), New Zealand (Cellana ornata), Australia (C. tramoserica) and Singapore (C. radiata), were compared across environments with different temperature magnitude, variability and predictability, to test their relative vulnerability to different scales of climate warming. Lethal limits were measured alongside a newly developed metric of “duration tenacity”, which was tested at different temperatures to calculate the thermal reaction norm of limpet adductor muscle fatigue. Except in C. tramoserica which had a wide optimum range with two break points, duration tenacity did not follow a typical aerobic capacity curve but was best described by a single break point at an optimum temperature. Thermal reaction norms were shifted to warmer temperatures in warmer environments; the optimum temperature for tenacity (Topt) increased from 1.0°C (N. concinna) to 14.3°C (C. ornata) to 18.0°C (an average for the optimum range of C. tramoserica) to 27.6°C (C. radiata). The temperature limits for duration tenacity of the 4 species were most consistently correlated with both maximum sea surface temperature and summer maximum in situ habitat logger temperature. Tropical C. radiata, which lives in the least variable and most predictable environment, generally had the lowest warming tolerance and thermal safety margin (WT and TSM; respectively the thermal buffer of CTmax and Topt over habitat temperature). However, the two temperate species, C. ornata and C. tramoserica, which live in a variable and seasonally unpredictable microhabitat, had the lowest TSM relative to in situ logger temperature. N. concinna which lives in the most variable, but seasonally predictable microhabitat, generally had the highest TSMs. Intertidal animals live at the highly variable interface between terrestrial and marine biomes and even small changes in the magnitude and predictability of their environment could markedly influence their future distributions. PMID:23285194

The ultraviolet variability of early-type supergiants

NASA Technical Reports Server (NTRS)

Underhill, A. B.

1984-01-01

Four early-type supergiants - HD 79186 (B5 Ia), HD 96919 (B9 Ia), HD 105056 (ON9.7 Iae), and HD 148379 (B2 Iae) - have been observed with the low-resolution spectrographs of IUE in the large aperture on 14 days. The behavior of the ultraviolet fluxes with time is studied. The light from all four stars seems to vary. Typically the dispersion about the mean magnitude at any wavelength corresponds to + or - 0.085, + or - 0.080, + or - 0.101, and + or - 0.106 mag, respectively. These amplitudes exceed the typical uncertainty in an IUE measurement of flux by about a factor of 3; they are somewhat larger than the variations known in the visible wavelength range. There are insufficient data to investigate periodicity in the observed light changes. The effective temperatures and angular diameters of the stars have been estimated using the present ultraviolet photometry, published UBV and uvby photometry, and the model-atmosphere fluxes reported by Kurucz in 1979. The program stars have dimensions typical for their spectral types. A brief discussion is given of possible causes of the variability of hot supergiants.

Quantifying the Δ63-Δ47 offset: Determining mineral- and temperature-dependent acid fractionation factors through mass spectrometric analyses of stochastically-reordered carbonates

NASA Astrophysics Data System (ADS)

Mitsunaga, B.; Mosenfelder, J. L.; Tripati, A.

2017-12-01

"Clumped" isotope thermometry—the relationship between the formation temperature of a carbonate mineral and the relative abundance of 13C—18O bonds in its crystal lattice—is a novel geochemical proxy with a wide range of applications in paleoclimatology, geobiology, and paleoceanography. It is based on the thermodynamic propensity for rare, heavy isotopes to bond at greater rates at lower temperatures, while at high temperatures, a stochastic distribution of heavy isotopologues is achieved. Unfortunately, precision mass spectrometric determination of the abundance of isotopologues in solid materials has proven difficult; instead, the isotopic composition of carbonates has traditionally been measured through acid digestion and subsequent analysis of the product CO2 gas. For example, clumped isotope thermometry typically relates formation temperature to Δ47, the abundance of 47-amu isotopologues relative to the predicted stochastic distribution. As a consequence, the degree of fractionation that occurs between solid (Δ63) and gaseous (Δ47) phases has largely gone unstudied. By melting calcite and witherite powder at high pressures and temperatures ( 1650ºC), we have produced a suite of carbonates predicted to have stochastic distributions of CO32- isotopologues (i.e., Δ63 values of 0‰). Thus, the measured Δ47 values of CO2 produced from these samples through acid digestion should equal the degree of fractionation that occurs. We perform these measurements at a range of acid temperatures on several digestion apparatuses in order to deduce and quantify controls on acid digestion fractionation factors. We also calculate acid digestion fractionation factors using different sets of constants and compare our results to previously published estimates.

Positive Selection at the Polyhomeotic Locus Led to Decreased Thermosensitivity of Gene Expression in Temperate Drosophila melanogaster

PubMed Central

Voigt, Susanne; Laurent, Stefan; Litovchenko, Maria; Stephan, Wolfgang

2015-01-01

Drosophila melanogaster as a cosmopolitan species has successfully adapted to a wide range of different environments. Variation in temperature is one important environmental factor that influences the distribution of species in nature. In particular for insects, which are mostly ectotherms, ambient temperature plays a major role in their ability to colonize new habitats. Chromatin-based gene regulation is known to be sensitive to temperature. Ambient temperature leads to changes in the activation of genes regulated in this manner. One such regulatory system is the Polycomb group (PcG) whose target genes are more expressed at lower temperatures than at higher ones. Therefore, a greater range in ambient temperature in temperate environments may lead to greater variability (plasticity) in the expression of these genes. This might have detrimental effects, such that positive selection acts to lower the degree of the expression plasticity. We provide evidence for this process in a genomic region that harbors two PcG-regulated genes, polyhomeotic proximal (ph-p) and CG3835. We found a signature of positive selection in this gene region in European populations of D. melanogaster and investigated the region by means of reporter gene assays. The target of selection is located in the intergenic fragment between the two genes. It overlaps with the promoters of both genes and an experimentally validated Polycomb response element (PRE). This fragment harbors five sequence variants that are highly differentiated between European and African populations. The African alleles confer a temperature-induced plasticity in gene expression, which is typical for PcG-mediated gene regulation, whereas thermosensitivity is reduced for the European alleles. PMID:25855066

Locomotion response of airborne, ambulatory and aquatic insects to thermal stimulation using piezoceramic microheaters

NASA Astrophysics Data System (ADS)

Visvanathan, Karthik; Gianchandani, Yogesh B.

2011-12-01

This paper reports the locomotion response of airborne, ambulatory and aquatic insects to thermal stimulation. A finite element model has been developed to predict the variation of insect-stimulator interface temperature with input power. Piezothermal stimulators have been fabricated from lead zirconate titanate (PZT) using a batch mode micro ultrasonic machining process. Typical sizes range from 200 µm to 3.2 mm. For PZT stimulators, the temperature and thermal efficiency reach the maximum value around the resonance frequency which is typically in the range of 650 kHz to 47 MHz. Experiments have been conducted on green June beetles (GJBs), Madagascar hissing roaches and green diving beetles (GDBs) in order to show the versatility of the proposed technique. The stimulators have been implanted near the antennae of the GJBs and on either side of the thorax of the Madagascar hissing roaches and GDBs, respectively. In all cases, the insects move away from the direction of the actuated stimulator. The left and right turns are statistically similar. Thermal stimulation achieves an overall success rate of 78.7%, 92.8% and 61.6% in GJBs, roaches and GDBs, respectively. On average, thermal stimulation results in an angle turn of about 13.7°-16.2° on GJBs, 30°-45° on the roaches and 30°-50° on GDBs. The corresponding average input power is 360, 330 and 100 mW for GJBs, roach and GDBs, respectively. Scaling limits of the PZT stimulators for operating these stimulators are also discussed.

Calibration of the OHREX high-resolution imaging crystal spectrometer at the Livermore electron beam ion traps

NASA Astrophysics Data System (ADS)

Hell, N.; Beiersdorfer, P.; Magee, E. W.; Brown, G. V.

2016-11-01

We report the calibration of the Orion High-Resolution X-ray (OHREX) imaging crystal spectrometer at the EBIT-I electron beam ion trap at Livermore. Two such instruments, dubbed OHREX-1 and OHREX-2, are fielded for plasma diagnostics at the Orion laser facility in the United Kingdom. The OHREX spectrometer can simultaneously house two spherically bent crystals with a radius of curvature of r = 67.2 cm. The focusing properties of the spectrometer allow both for larger distance to the source due to the increase in collected light and for observation of extended sources. OHREX is designed to cover a 2.5°-3° spectral range at Bragg angles around 51.3°. The typically high resolving powers at these large Bragg angles are ideally suited for line shape diagnostics. For instance, the nominal resolving power of the instrument (>10 000) is much higher than the effective resolving power associated with the Doppler broadening due to the temperature of the trapped ions in EBIT-I. The effective resolving power is only around 3000 at typical EBIT-I conditions, which nevertheless is sufficient to set up and test the instrument's spectral characteristics. We have calibrated the spectral range for a number of crystals using well known reference lines in the first and second order and derived the ion temperatures from these lines. We have also made use of the 50 μm size of the EBIT-I source width to characterize the spatial focusing of the spectrometer.

Calibration of the OHREX high-resolution imaging crystal spectrometer at the Livermore electron beam ion traps

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

Hell, N.; Dr. Remeis-Sternwarte and ECAP, Universität Erlangen-Nürnberg, Bamberg 96049; Beiersdorfer, P.

2016-11-15

We report the calibration of the Orion High-Resolution X-ray (OHREX) imaging crystal spectrometer at the EBIT-I electron beam ion trap at Livermore. Two such instruments, dubbed OHREX-1 and OHREX-2, are fielded for plasma diagnostics at the Orion laser facility in the United Kingdom. The OHREX spectrometer can simultaneously house two spherically bent crystals with a radius of curvature of r = 67.2 cm. The focusing properties of the spectrometer allow both for larger distance to the source due to the increase in collected light and for observation of extended sources. OHREX is designed to cover a 2.5°–3° spectral range atmore » Bragg angles around 51.3°. The typically high resolving powers at these large Bragg angles are ideally suited for line shape diagnostics. For instance, the nominal resolving power of the instrument (>10 000) is much higher than the effective resolving power associated with the Doppler broadening due to the temperature of the trapped ions in EBIT-I. The effective resolving power is only around 3000 at typical EBIT-I conditions, which nevertheless is sufficient to set up and test the instrument’s spectral characteristics. We have calibrated the spectral range for a number of crystals using well known reference lines in the first and second order and derived the ion temperatures from these lines. We have also made use of the 50 μm size of the EBIT-I source width to characterize the spatial focusing of the spectrometer.« less

IR radiation characteristics and operating range research for a quad-rotor unmanned aircraft vehicle.

PubMed

Gong, Mali; Guo, Rui; He, Sifeng; Wang, Wei

2016-11-01

The security threats caused by multi-rotor unmanned aircraft vehicles (UAVs) are serious, especially in public places. To detect and control multi-rotor UAVs, knowledge of IR characteristics is necessary. The IR characteristics of a typical commercial quad-rotor UAV are investigated in this paper through thermal imaging with an IR camera. Combining the 3D geometry and IR images of the UAV, a 3D IR characteristics model is established so that the radiant power from different views can be obtained. An estimation of operating range to detect the UAV is calculated theoretically using signal-to-noise ratio as the criterion. Field experiments are implemented with an uncooled IR camera in an environment temperature of 12°C and a uniform background. For the front view, the operating range is about 150 m, which is close to the simulation result of 170 m.

First year growth in the lithodids Lithodes santolla and Paralomis granulosa reared at different temperatures

NASA Astrophysics Data System (ADS)

Calcagno, J. A.; Lovrich, G. A.; Thatje, S.; Nettelmann, U.; Anger, K.

2005-10-01

The southern king crab, Lithodes santolla Molina, and stone crab, Paralomis granulosa Jacquinot, inhabit the cold-temperate waters of southernmost South America (southern Chile and Argentina), where stocks of both species are endangered by overfishing. Recent investigations have shown that these crabs show life-cycle adaptations to scarcity of food and low temperatures prevailing in subantarctic regions, including complete lecithotrophy of all larval stages and prolonged periods of brooding and longevity. However, growth and development to maturity are slow under conditions of low temperatures, which may explain the particular vulnerability of subpolar lithodids to fisheries. In the present study, juvenile L. santolla and P. granulosa were individually reared in the laboratory at constant temperatures ranging from 3-15 °C, and rates of survival and development through successive instars were monitored throughout a period of about nine months from hatching. When the experiments were terminated, L. santolla had maximally reached juvenile instar IV (at 6 °C), V (9 °C), or VII (15 °C). In P. granulosa the maximum crab instar reached was II (at 3 °C), V (6 °C), V (9 °C), or VII (15 °C). The intermoult period decreased with increasing temperature, while it increased in successively later instars. In consequence, growth rate showed highly significant differences among temperatures (P<0.001). Growth-at-moult was highest at 9 °C. Rates of survival decreased significantly in juvenile P. granulosa with increasing temperature. Only at 15 °C in L. santolla, was a significantly enhanced mortality found compared with lower temperatures. Our results indicate that juvenile stages of L. santolla and P. granulosa are well adapted to 5-10°C, the range of temperatures typically prevailing in subantarctic marine environments. In spite of causing higher mortality rates, higher rearing temperatures (12-15 °C) should accelerate the rates of growth and maturation, which may be favourable for projects aiming at aquaculture or repopulation of overexploited king crab stocks.

Time-Separating Heating and Sensor Functions of Thermistors in Precision Thermal Control Applications

NASA Technical Reports Server (NTRS)

Cho, Hyung J.; Sukhatme, Kalyani G.; Mahoney, John C.; Penanen, Konstantin Penanen; Vargas, Rudolph, Jr.

2010-01-01

A method allows combining the functions of a heater and a thermometer in a single device, a thermistor, with minimal temperature read errors. Because thermistors typically have a much smaller thermal mass than the objects they monitor, the thermal time to equilibrate the thermometer to the temperature of the object is typically much shorter than the thermal time of the object to change its temperature in response to an external perturbation.

Dynamics and complexity of body temperature in preterm infants nursed in incubators

PubMed Central

Jost, Kerstin; Pramana, Isabelle; Delgado-Eckert, Edgar; Kumar, Nitin; Datta, Alexandre N.; Frey, Urs; Schulzke, Sven M.

2017-01-01

Background Poor control of body temperature is associated with mortality and major morbidity in preterm infants. We aimed to quantify its dynamics and complexity to evaluate whether indices from fluctuation analyses of temperature time series obtained within the first five days of life are associated with gestational age (GA) and body size at birth, and presence and severity of typical comorbidities of preterm birth. Methods We recorded 3h-time series of body temperature using a skin electrode in incubator-nursed preterm infants. We calculated mean and coefficient of variation of body temperature, scaling exponent alpha (Talpha) derived from detrended fluctuation analysis, and sample entropy (TSampEn) of temperature fluctuations. Data were analysed by multilevel multivariable linear regression. Results Data of satisfactory technical quality were obtained from 285/357 measurements (80%) in 73/90 infants (81%) with a mean (range) GA of 30.1 (24.0–34.0) weeks. We found a positive association of Talpha with increasing levels of respiratory support after adjusting for GA and birth weight z-score (p<0.001; R2 = 0.38). Conclusion Dynamics and complexity of body temperature in incubator-nursed preterm infants show considerable associations with GA and respiratory morbidity. Talpha may be a useful marker of autonomic maturity and severity of disease in preterm infants. PMID:28448569

Thermal relationships and exercise physiology in anuran amphibians: integration and evolutionary implications.

PubMed

Navas, Carlos A; Gomes, Fernando R; Carvalho, José Eduardo

2008-11-01

Thermal and water balance are coupled in anurans, and species with particularly permeable skin avoid overheating more effectively than minimizing variance of body temperature. In turn, temperature affects muscle performance in several ways, so documenting the mean and variance of body temperature of active frogs can help explain variation in behavioral performance. The two types of activities studied in most detail, jumping and calling, differ markedly in duration and intensity, and there are distinct differences in the metabolic profile and fiber type of the supporting muscles. Characteristics of jumping and calling also vary significantly among species, and these differences have a number of implications that we discuss in some detail throughout this paper. One question that emerges from this topic is whether anuran species exhibit activity temperatures that match the temperature range over which they perform best. Although this seems the case, thermal preferences are variable and may not necessarily reflect typical activity temperatures. The performance versus temperature curves and the thermal limits for anuran activity reflect the thermal ecology of species more than their systematic position. Anuran thermal physiology, therefore, seems to be phenotypically plastic and susceptible to adaptive evolution. Although generalizations regarding the mechanistic basis of such adjustments are not yet possible, recent attempts have been made to reveal the mechanistic basis of acclimation and acclimatization.

Dynamics and complexity of body temperature in preterm infants nursed in incubators.

PubMed

Jost, Kerstin; Pramana, Isabelle; Delgado-Eckert, Edgar; Kumar, Nitin; Datta, Alexandre N; Frey, Urs; Schulzke, Sven M

2017-01-01

Poor control of body temperature is associated with mortality and major morbidity in preterm infants. We aimed to quantify its dynamics and complexity to evaluate whether indices from fluctuation analyses of temperature time series obtained within the first five days of life are associated with gestational age (GA) and body size at birth, and presence and severity of typical comorbidities of preterm birth. We recorded 3h-time series of body temperature using a skin electrode in incubator-nursed preterm infants. We calculated mean and coefficient of variation of body temperature, scaling exponent alpha (Talpha) derived from detrended fluctuation analysis, and sample entropy (TSampEn) of temperature fluctuations. Data were analysed by multilevel multivariable linear regression. Data of satisfactory technical quality were obtained from 285/357 measurements (80%) in 73/90 infants (81%) with a mean (range) GA of 30.1 (24.0-34.0) weeks. We found a positive association of Talpha with increasing levels of respiratory support after adjusting for GA and birth weight z-score (p<0.001; R2 = 0.38). Dynamics and complexity of body temperature in incubator-nursed preterm infants show considerable associations with GA and respiratory morbidity. Talpha may be a useful marker of autonomic maturity and severity of disease in preterm infants.

Investigating crater lake warming using ASTER thermal imagery: Case studies at Ruapehu, Poás, Kawah Ijen, and Copahué Volcanoes

NASA Astrophysics Data System (ADS)

Trunk, Laura; Bernard, Alain

2008-12-01

A two-channel or split-window algorithm designed to correct for atmospheric conditions was applied to thermal images taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) of Lake Yugama on Kusatsu-Shirane volcano in Japan in order to measure the temperature of its crater lake. These temperature calculations were validated using lake water temperatures that were collected on the ground. Overall, the agreement between the temperatures calculated using the split-window method and ground truth is quite good, typically ± 1.5 °C for cloud-free images. Data from fieldwork undertaken in the summer of 2004 at Kusatsu-Shirane allow a comparison of ground-truth data with the radiant temperatures measured using ASTER imagery. Further images were analyzed of Ruapehu, Poás, Kawah Ijen, and Copahué volcanoes to acquire time-series of lake temperatures. A total of 64 images of these 4 volcanoes covering a wide range of geographical locations and climates were analyzed. Results of the split-window algorithm applied to ASTER images are reliable for monitoring thermal changes in active volcanic lakes. These temperature data, when considered in conjunction with traditional volcano monitoring techniques, lead to a better understanding of whether and how thermal changes in crater lakes aid in eruption forecasting.

A Second Glass Transition in Pressure Collapsed Type II Clathrate Hydrates.

PubMed

Andersson, Ove; Häussermann, Ulrich

2018-04-19

Type II clathrate hydrates (CHs) M·17 H 2 O, with M = tetrahydrofuran (THF) or 1,3-dioxolane, are known to collapse, or amorphize, on pressurization to ∼1.3 GPa in the temperature range 77-140 K. On heating at 1 GPa, these pressure-amorphized CH states show a weak, stretched sigmoid-shaped, heat-capacity increase because of a glass transition. Here we use thermal conductivity and heat capacity measurements to show that also type II CH with M = cyclobutanone (CB) collapses on isothermal pressurization and undergoes a similar, weak, glass transition upon heating at 1 GPa. Furthermore, we reveal for both THF CH and CB CH a second, much more pronounced, glass transition at temperatures above the thermally weak glass transition on heating in the 0.2-0.7 GPa range. This result suggests the general occurrence of two glass transitions in water-rich (94 mol %) pressure-collapsed CHs. Because of a large increase in dielectric permittivity concurrently as the weak heat capacity increase, the first glass transition must be due to kinetic unfreezing of water molecules. The thermal features of the second glass transition, measured on isobaric temperature cycling, are typical of a glass-liquid-glass transition, which suggests that pressure-amorphized CHs transform reversibly to liquids.

Design and market considerations for axial flux superconducting electric machine design

NASA Astrophysics Data System (ADS)

Ainslie, M. D.; George, A.; Shaw, R.; Dawson, L.; Winfield, A.; Steketee, M.; Stockley, S.

2014-05-01

In this paper, the authors investigate a number of design and market considerations for an axial flux superconducting electric machine design that uses high temperature superconductors. The axial flux machine design is assumed to utilise high temperature superconductors in both wire (stator winding) and bulk (rotor field) forms, to operate over a temperature range of 65-77 K, and to have a power output in the range from 10s of kW up to 1 MW (typical for axial flux machines), with approximately 2-3 T as the peak trapped field in the bulk superconductors. The authors firstly investigate the applicability of this type of machine as a generator in small- and medium-sized wind turbines, including the current and forecasted market and pricing for conventional turbines. Next, a study is also carried out on the machine's applicability as an in-wheel hub motor for electric vehicles. Some recommendations for future applications are made based on the outcome of these two studies. Finally, the cost of YBCO-based superconducting (2G HTS) wire is analysed with respect to competing wire technologies and compared with current conventional material costs and current wire costs for both 1G and 2G HTS are still too great to be economically feasible for such superconducting devices.

Optimization of cellulose nanocrystal length and surface charge density through phosphoric acid hydrolysis

NASA Astrophysics Data System (ADS)

Vanderfleet, Oriana M.; Osorio, Daniel A.; Cranston, Emily D.

2017-12-01

Cellulose nanocrystals (CNCs) are emerging nanomaterials with a large range of potential applications. CNCs are typically produced through acid hydrolysis with sulfuric acid; however, phosphoric acid has the advantage of generating CNCs with higher thermal stability. This paper presents a design of experiments approach to optimize the hydrolysis of CNCs from cotton with phosphoric acid. Hydrolysis time, temperature and acid concentration were varied across nine experiments and a linear least-squares regression analysis was applied to understand the effects of these parameters on CNC properties. In all but one case, rod-shaped nanoparticles with a high degree of crystallinity and thermal stability were produced. A statistical model was generated to predict CNC length, and trends in phosphate content and zeta potential were elucidated. The CNC length could be tuned over a relatively large range (238-475 nm) and the polydispersity could be narrowed most effectively by increasing the hydrolysis temperature and acid concentration. The CNC phosphate content was most affected by hydrolysis temperature and time; however, the charge density and colloidal stability were considered low compared with sulfuric acid hydrolysed CNCs. This study provides insight into weak acid hydrolysis and proposes `design rules' for CNCs with improved size uniformity and charge density. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

Numerical characterization of the edge transport conditions and limiter fluxes of the HIDRA stellarator

NASA Astrophysics Data System (ADS)

Marcinko, Steven; Curreli, Davide

2018-02-01

The Hybrid Illinois Device for Research and Applications (HIDRA) is a new device for education and Plasma-Material Interaction research at the University of Illinois at Urbana-Champaign. In advance of its first operational campaign, EMC3-EIRENE simulations have been run on the device. EMC3-EIRENE has been modified to calculate a per-plasma-cell relaxed Bohm-like diffusivity simultaneously with the electron temperature at each iteration. In our characterization, the electron temperature, diffusivity, heat fluxes, and particle fluxes have been obtained for varying power levels on a HIDRA magnetic grid, and scaling laws have been extracted, using constraints from previous experimental data taken when the device was operated in Germany (WEGA facility). Peak electron temperatures and heat fluxes were seen to follow a power-law dependence on the deposited radiofrequency (RF) power of type f (PR F)∝a PRF b , with typical exponents in the range of b ˜0.55 to 0.60. Higher magnetic fields have the tendency to linearize the heat flux dependence on the RF power, with exponents in the range of b ˜ 0.75. Particle fluxes are seen to saturate first, and then slightly decline for RF powers above 120 kW in the low-field case and 180 kW in the high-field case.

Investigation of two-phase thermosyphon performance filled with modern HFC refrigerants

NASA Astrophysics Data System (ADS)

Gorecki, Grzegorz

2018-02-01

Two-phase closed thermosyphons (TPCTs) are widely utilized as heat exchanger elements in waste heat recovery systems and as passive heating/cooling devices. They are popular because of their high thermal conductivity, simple construction and reliability. Previous researches indicate that refrigerants are performing better than typical TPCT working fluids like deionized water or alcohols in the low temperature range. In the present study three HFC (Hydrofluorocarbons) refrigerants were tested: R134a, R404A and R407C. The total length of the investigated TPCT is 550 mm with equal length (245 mm) condenser and evaporator sections. Its outer diameter is 22 mm with 1 mm wall thickness. The evaporator section was heated by hot water with varying inlet temperature by 5 K step in the range of 288 K - 323 K. The condenser was cooled by cold water with inlet temperature kept at a constant value of 283 K. It was found that using R134a and R404A as working fluids heat transfer rates are the highest. For both refrigerants 10% is optimal filling ratio. They can be utilized interchangeably because the differences between their throughputs are within uncertainty bands. R407C performance was 50% lower. Other disadvantages of using this refrigerant are relatively high working pressures and higher optimal filling ratio (30%).

Investigation of two-phase thermosyphon performance filled with modern HFC refrigerants

NASA Astrophysics Data System (ADS)

Gorecki, Grzegorz

2018-07-01

Two-phase closed thermosyphons (TPCTs) are widely utilized as heat exchanger elements in waste heat recovery systems and as passive heating/cooling devices. They are popular because of their high thermal conductivity, simple construction and reliability. Previous researches indicate that refrigerants are performing better than typical TPCT working fluids like deionized water or alcohols in the low temperature range. In the present study three HFC (Hydrofluorocarbons) refrigerants were tested: R134a, R404A and R407C. The total length of the investigated TPCT is 550 mm with equal length (245 mm) condenser and evaporator sections. Its outer diameter is 22 mm with 1 mm wall thickness. The evaporator section was heated by hot water with varying inlet temperature by 5 K step in the range of 288 K - 323 K. The condenser was cooled by cold water with inlet temperature kept at a constant value of 283 K. It was found that using R134a and R404A as working fluids heat transfer rates are the highest. For both refrigerants 10% is optimal filling ratio. They can be utilized interchangeably because the differences between their throughputs are within uncertainty bands. R407C performance was 50% lower. Other disadvantages of using this refrigerant are relatively high working pressures and higher optimal filling ratio (30%).

Assessment of Operation of EMK21 MEMS Silicon Oscillator Over Wide Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2009-01-01

Electronic control systems, data-acquisition instrumentation, and microprocessors require accurate timing signals for proper operation. Traditionally, ceramic resonators and crystal oscillators provided this clock function for the majority of these systems. Over the last few years, MEMS (Micro-Electro-Mechanical Systems) resonator-based oscillators began to surface as commercial-off-the-shelf (COTS) parts by a few companies. These quartz-free, miniature silicon devices could easily replace the traditional crystal oscillators in providing the timing/clock function for many digital and analog circuits. They are reported to provide stable output frequency, offer great tolerance to shock and vibration, and are immune to electro-static discharge [ 1-2]. In addition, they are encapsulated in compact lead-free packages and cover a wide frequency range (1 MHz to 125 MHz). The small size of the MEMS oscillators along with their thermal stability make them ideal candidates for use in space exploration missions. Limited data, however, exist on the performance and reliability of these devices under operation in applications where extreme temperatures or thermal cycling swings, which are typical of space missions, are encountered. This report presents the results of the work obtained on the evaluation of an Ecliptek Corporation MEMS silicon oscillator chip under extreme temperatures.

Thermoelectric Power Measurements of xSb-(60- x)V2O5-40TeO2 Glasses

NASA Astrophysics Data System (ADS)

Souri, Dariush; Siahkali, Zahra; Moradi, Mohammad

2016-01-01

Bulk xSb-(60- x)V2O5-40TeO2 glass systems (with 0 ≤ x ≤ 15 in mol.%) were prepared by using the standard melt quenching procedure, and their Seebeck coefficients, S, were measured within the temperature range of 250-470 K. For the understudied samples, the thermoelectric powers at typical temperatures of 296 K, 370 K and 407 K were measured, and were in the ranges (-405) to (-698) μVK-1, (-394) to (-685) μVK-1 and (-392) to (-691) μVK-1, respectively. The selection of typical temperatures aims at the evaluation of the trend of figure of merit in these glasses. Based on the negative sign of S, the present glasses were found to be n-type semiconductors; also, the experimental relationship between S and C V ( C V = [V4+]/ V tot is the ratio of the content of reduced vanadium ions) satisfied the theoretical Heikes formula, relating S to ln( C V/1 - C V), and also the Mackenzie formula, relating S to ln([V5+]/[V4+]). The parameter α^' in Heikes formula was determined to be ≪1 and so the small polaron hopping conduction mechanism was certified to occur in these glasses; this result confirms the previously reported results of direct current (DC) electrical conduction experiments on the same samples. Results of thermoelectric measurements show the compositional dependence of S on Sb content and C V, indicating that S increases with the increase in Sb content; these results show that the dominant factor determining S is C V. Also, figure of merit was determined for these glasses, which show the highest value for 60V2O5-40TeO2 glass system, as a good candidate in thermoelectric applications.

Rehabilitation reliability of the road pavement structure with recycled base course with foamed bitumen

NASA Astrophysics Data System (ADS)

Buczyński, P.

2018-05-01

This article presents a new approach to reliability assessment of the road structure in which the base layer will be constructed in the process of cold deep recycling with foamed bitumen. In order to properly assess the reliability of the structure with the recycled base, it is necessary to determine the distribution of stress and strain in typical pavement layer systems. The true stress and strain values were established for particular structural layers using the complex modulus (E*) determined based on the master curves. The complex modulus was determined by the direct tension-compression test on cylindrical specimens (DTC-CY) at five temperatures (-7°C, 5°C, 13°C, 25°C, 40°C) and six loading times (0.1 Hz, 0.3 Hz, 1 Hz, 3 Hz, 10 Hz, 20 Hz) in accordance with EN 12697-26 in the linear viscoelasticity (LVE) range for small strains ranging from 25 to 50 με. The master curves of the complex modulus were constructed using the Richards model for the mixtures typically incorporated in structural layers, i.e., SMA11, AC16W, AC22P and MCAS. The values of the modulus characterizing particular layers were determined with temperature distribution in the structure taken into account, when the surface temperature was 40°C. The stress distribution was established for those calculation models. The stress values were used to evaluate the fatigue life under controlled stress conditions (IT-FT). This evaluation, with the controlled stress corresponding to that in the structure, facilitated the quality assessment of the rehabilitated recycled base course. Results showed that the recycled base mixtures having the indirect tensile strength (ITSDRY) similar to the stress in the structure under analysis needed an additional fatigue life evaluation in the indirect tensile test ITT. This approach to the recycled base quality assessment will allow eliminating the damage induced by overloading.

Hydrologic monitoring of a landslide-prone hillslope in the Elliott State Forest, Southern Coast Range, Oregon, 2009-2012

USGS Publications Warehouse

Smith, Joel B.; Godt, Jonathan W.; Baum, Rex L.; Coe, Jeffrey A.; Burns, William J.; Morse, Michael M.; Sener-Kaya, Basak; Kaya, Murat

2014-01-01

The Oregon Coast Range is dissected by numerous unchanneled headwater basins, which can generate shallow landslides and debris flows during heavy or prolonged rainfall. An automated monitoring system was installed in an unchanneled headwater basin to measure rainfall, volumetric water content, groundwater temperature, and pore pressures at 15-minute intervals. The purpose of this report is to describe and present the methods used for the monitoring as well as the preliminary data collected during the period from 2009 to 2012. Observations show a pronounced seasonal variation in volumetric water content and pore pressures. Increases in pore pressures and volumetric water content from dry-season values begin with the onset of the rainy season in the fall (typically early to mid October). High water contents and pore pressures tend to persist throughout the rainy season, which typically ends in May. Heavy or prolonged rainfall during the wet season that falls on already moist soils often generates positive pore pressures that are observed in the deeper instruments. These data provide a record of the basin’s hydrologic response to rainfall and provide a foundation for understanding the conditions that lead to landslide and debris-flow occurrence.

Experimental and analytical investigation of a freezing point depressant fluid ice protection system. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Albright, A. E.

1984-01-01

A glycol-exuding porous leading edge ice protection system was tested in the NASA Icing Research Tunnel. Stainless steel mesh, laser drilled titanium, and composite panels were tested on two general aviation wing sections. Two different glycol-water solutions were evaluated. Minimum glycol flow rates required for anti-icing were obtained as a function of angle of attack, liquid water content, volume median drop diameter, temperature, and velocity. Ice accretions formed after five minutes of icing were shed in three minutes or less using a glycol fluid flow equal to the anti-ice flow rate. Two methods of predicting anti-ice flow rates are presented and compared with a large experimental data base of anti-ice flow rates over a wide range of icing conditions. The first method presented in the ADS-4 document typically predicts flow rates lower than the experimental flow rates. The second method, originally published in 1983, typically predicts flow rates up to 25 percent higher than the experimental flow rates. This method proved to be more consistent between wing-panel configurations. Significant correlation coefficients between the predicted flow rates and the experimental flow rates ranged from .867 to .947.

Properties of Cathodoluminescence for Cryogenic Applications of SiO2-based Space Observatory Optics and Coatings

NASA Technical Reports Server (NTRS)

Evans, Amberly; Dennison, J.R.; Wilson, Gregory; Dekany, Justin; Bowers Charles W.; Meloy, Robert; Heaney, James B.

2013-01-01

Disordered thin film SiO2SiOx coatings undergoing electron-beam bombardment exhibit cathodoluminescence, which can produce deleterious stray background light in cryogenic space-based astronomical observatories exposed to high-energy electron fluxes from space plasmas. As future observatory missions push the envelope into more extreme environments and more complex and sensitive detection, a fundamental understanding of the dependencies of this cathodoluminescence becomes critical to meet performance objectives of these advanced space-based observatories. Measurements of absolute radiance and emission spectra as functions of incident electron energy, flux, and power typical of space environments are presented for thin (60-200 nm) SiO2SiOx optical coatings on reflective metal substrates over a range of sample temperatures (40-400 K) and emission wavelengths (260-5000 nm). Luminescent intensity and peak wavelengths of four distinct bands were observed in UVVISNIR emission spectra, ranging from 300 nm to 1000 nm. A simple model is proposed that describes the dependence of cathodoluminescence on irradiation time, incident flux and energy, sample thickness, and temperature.

Large deviation probabilities for correlated Gaussian stochastic processes and daily temperature anomalies

NASA Astrophysics Data System (ADS)

Massah, Mozhdeh; Kantz, Holger

2016-04-01

As we have one and only one earth and no replicas, climate characteristics are usually computed as time averages from a single time series. For understanding climate variability, it is essential to understand how close a single time average will typically be to an ensemble average. To answer this question, we study large deviation probabilities (LDP) of stochastic processes and characterize them by their dependence on the time window. In contrast to iid variables for which there exists an analytical expression for the rate function, the correlated variables such as auto-regressive (short memory) and auto-regressive fractionally integrated moving average (long memory) processes, have not an analytical LDP. We study LDP for these processes, in order to see how correlation affects this probability in comparison to iid data. Although short range correlations lead to a simple correction of sample size, long range correlations lead to a sub-exponential decay of LDP and hence to a very slow convergence of time averages. This effect is demonstrated for a 120 year long time series of daily temperature anomalies measured in Potsdam (Germany).

Colossal magnetic phase transition asymmetry in mesoscale FeRh stripes

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

Uhlir, V.; Arregi, J. A.; Fullerton, E. E.

Coupled order parameters in phase-transition materials can be controlled using various driving forces such as temperature, magnetic and electric field, strain, spin-polarized currents and optical pulses. Tuning the material properties to achieve efficient transitions would enable fast and low-power electronic devices. Here we show that the first-order metamagnetic phase transition in FeRh films becomes strongly asymmetric in mesoscale structures. In patterned FeRh stripes we observed pronounced supercooling and an avalanche-like abrupt transition from the ferromagnetic to the antiferromagnetic phase, while the reverse transition remains nearly continuous over a broad temperature range. Although modest asymmetry signatures have been found in FeRhmore » films, the effect is dramatically enhanced at the mesoscale. The activation volume of the antiferromagnetic phase is more than two orders of magnitude larger than typical magnetic heterogeneities observed in films. Finally, the collective behaviour upon cooling results from the role of long-range ferromagnetic exchange correlations that become important at the mesoscale and should be a general property of first-order metamagnetic phase transitions.« less

Carbon nanotube-sensor-integrated microfluidic platform for real-time chemical concentration detection.

PubMed

Yang, Li; Li, Minglin; Qu, Yanli; Dong, Zaili; Li, Wen J

2009-09-01

This paper presents the development of a chemical sensor employing electronic-grade carbon nanotubes (EG-CNTs) as the active sensing element for sodium hypochlorite detection. The sensor, integrated in a PDMS-glass microfluidic chamber, was fabricated by bulk aligning of EG-CNTs between gold microelectrode pairs using dielectrophoretic technique. Upon exposure to sodium hypochlorite solution, the characteristics of the carbon nanotube chemical sensor were investigated at room temperature under constant current mode. The sensor exhibited responsivity, which fits a linear logarithmic dependence on concentration in the range of 1/32 to 8 ppm, a detection limit lower than 5 ppb, while saturating at 16 ppm. The typical response time of the sensor at room temperature is on the order of minutes and the recovery time is a few hours. In particular, the sensor showed an obvious sensitivity to the volume of detected solution. It was found that the activation power of the sensor was extremely low, i.e. in the range of nanowatts. These results indicate great potential of EG-CNT for advanced nanosensors with superior sensitivity, ultra-low power consumption, and less fabrication complexity.

Colossal magnetic phase transition asymmetry in mesoscale FeRh stripes

DOE PAGES

Uhlir, V.; Arregi, J. A.; Fullerton, E. E.

2016-10-11

Coupled order parameters in phase-transition materials can be controlled using various driving forces such as temperature, magnetic and electric field, strain, spin-polarized currents and optical pulses. Tuning the material properties to achieve efficient transitions would enable fast and low-power electronic devices. Here we show that the first-order metamagnetic phase transition in FeRh films becomes strongly asymmetric in mesoscale structures. In patterned FeRh stripes we observed pronounced supercooling and an avalanche-like abrupt transition from the ferromagnetic to the antiferromagnetic phase, while the reverse transition remains nearly continuous over a broad temperature range. Although modest asymmetry signatures have been found in FeRhmore » films, the effect is dramatically enhanced at the mesoscale. The activation volume of the antiferromagnetic phase is more than two orders of magnitude larger than typical magnetic heterogeneities observed in films. Finally, the collective behaviour upon cooling results from the role of long-range ferromagnetic exchange correlations that become important at the mesoscale and should be a general property of first-order metamagnetic phase transitions.« less

Negative to positive crossover of the magnetoresistance in layered WS{sub 2}

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

Zhang, Yangwei; Ning, Honglie; Li, Yanan

2016-04-11

The discovery of graphene ignited intensive investigation of two-dimensional materials. A typical two-dimensional material, transition metal dichalcogenide (TMDC), attracts much attention because of its excellent performance in field effect transistor measurements and applications. Particularly, when TMDC reaches the dimension of a few layers, a wide range of electronic and optical properties can be detected that are in striking contrast to bulk samples. In this letter, we synthesized WS{sub 2} single-crystal nanoflakes using physical vapor deposition and carried out a series of measurements of the contact resistance and magnetoresistance. Focused ion beam (FIB) technology was applied to deposit Pt electrodes onmore » the WS{sub 2} flakes, and the FIB-deposited contacts exhibited linear electrical characteristics. Resistance versus temperature measurements showed similar Mott variable range hopping behavior in different magnetic fields. Additionally, a temperature-modulated negative-to-positive magnetoresistance transition was observed. Our work reveals the magnetotransport characteristics of WS{sub 2} flakes, which may stimulate further studies of the properties of TMDC and its corresponding electronic and optoelectronic applications.« less

Acceleration of high-pressure-ratio single-spool turbojet engine as determined from component performance characteristics I : effect of air bleed at compressor outlet

NASA Technical Reports Server (NTRS)

Rebeske, John J , Jr; Rohlik, Harold E

1953-01-01

An analytical investigation was made to determine from component performance characteristics the effect of air bleed at the compressor outlet on the acceleration characteristics of a typical high-pressure-ratio single-spool turbojet engine. Consideration of several operating lines on the compressor performance map with two turbine-inlet temperatures showed that for a minimum acceleration time the turbine-inlet temperature should be the maximum allowable, and the operating line on the compressor map should be as close to the surge region as possible throughout the speed range. Operation along such a line would require a continuously varying bleed area. A relatively simple two-step area bleed gives only a small increase in acceleration time over a corresponding variable-area bleed. For the modes of operation considered, over 84 percent of the total acceleration time was required to accelerate through the low-speed range ; therefore, better low-speed compressor performance (higher pressure ratios and efficiencies) would give a significant reduction in acceleration time.

Macroscopic behavior and microscopic magnetic properties of nanocarbon

NASA Astrophysics Data System (ADS)

Lähderanta, E.; Ryzhov, V. A.; Lashkul, A. V.; Galimov, D. M.; Titkov, A. N.; Matveev, V. V.; Mokeev, M. V.; Kurbakov, A. I.; Lisunov, K. G.

2015-06-01

Here are presented investigations of powder and glass-like samples containing carbon nanoparticles, not intentionally doped and doped with Ag, Au and Co. The neutron diffraction study reveals an amorphous structure of the samples doped with Au and Co, as well as the magnetic scattering due to a long-range FM order in the Co-doped sample. The composition and molecular structure of the sample doped with Au is clarified with the NMR investigations. The temperature dependence of the magnetization, M (T), exhibits large irreversibility in low fields of B=1-7 mT. M (B) saturates already above 2 T at high temperatures, but deviates from the saturation behavior below 50 (150 K). Magnetic hysteresis is observed already at 300 K and exhibits a power-law temperature decay of the coercive field, Bc (T). The macroscopic behavior above is typical of an assembly of partially blocked magnetic nanoparticles. The values of the saturation magnetization, Ms, and the blocking temperature, Tb, are obtained as well. However, the hysteresis loop in the Co-doped sample differs from that in other samples, and the values of Bc and Ms are noticeably increased.

Facile and rapid auto-combustion synthesis of nano-porous γ-Al2O3 by application of hexamethylenetetramine in fuel composition

NASA Astrophysics Data System (ADS)

Salem, Shiva; Salem, Amin; Parni, Mohammad Hosein; Jafarizad, Abbas

2018-06-01

In this article, urea, glycine and hexamethylenetetramine were blended in accordance with the mixture design algorithm to prepare γ-Al2O3 by auto-combustion technique. Aluminum nitrate was then mixed with the stoichiometric contents of prepared fuel solutions to obtain gel systems. The gels exhibited a typical self-propagating combustion behavior at low temperature, directly resulting amorphous materials. The precursors were calcined at various temperatures ranging from 700 to 900 °C. The treated powders were evaluated by determining the methylene blue (MB) adsorption efficiency. The production condition to obtain γ-Al2O3 with maximum surface area depends on fuel composition and calcination temperature. The alumina powder fabricated by this procedure was uniformly distributed and contains nano-sized secondary particles with diameter about 10-30 nm in which the average pore size is 3.2 nm induced large surface area, 240 m2g-1. The employment of hexamethylenetetramine provides a potential for synthesis of γ-Al2O3 at lower temperature, 700 °C, with maximum MB removal efficiency.

Scanning Electron Microscopy-Energy-Dispersive X-Ray (SEM/EDX): A Rapid Diagnostic Tool to Aid the Identification of Burnt Bone and Contested Cremains.

PubMed

Ellingham, Sarah T D; Thompson, Tim J U; Islam, Meez

2018-03-01

This study investigates the use of Scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) as a diagnostic tool for the determination of the osseous origin of samples subjected to different temperatures. Sheep (Ovis aries) ribs of two experimental groups (fleshed and defleshed) were burned at temperatures of between 100°C and 1100°C in 100°C increments and subsequently analyzed with the SEM-EDX to determine the atomic percentage of present elements. Three-factor ANOVA analysis showed that neither the exposure temperature, nor whether the burning occurred with or without soft tissue present had any significant influence on the bone's overall elemental makeup (p > 0.05). The Ca/P ratio remained in the osseous typical range of between 1.6 and 2.58 in all analyzed samples. This demonstrates that even faced with high temperatures, the overall gross elemental content and atomic percentage of elements in bone remain stable, creating a unique "fingerprint" for osseous material, even after exposure to extreme conditions. © 2017 American Academy of Forensic Sciences.

Approach of the Molten Salt Chemistry for Aluminium Production: High Temperature NMR Measurements, Molecular Dynamics and DFT Calculations

NASA Astrophysics Data System (ADS)

Machado, Kelly; Zanghi, Didier; Sarou-Kanian, Vincent; Cadars, Sylvian; Burbano, Mario; Salanne, Mathieu; Bessada, Catherine

In aluminum production, the electrolyte is a molten fluorides mixture typically around 1000°C. In order to have a better understanding of the industrial process, it is necessary to have a model which will describe the molten salts on a wide range of compositions and temperatures, to accurately cover all the combinations that may be encountered in an operating electrolysis vessel. The aim of this study is to describe the speciation in the electrolyte in terms of anionic species in the bulk materials far from electrodes. To determine the speciation in situ at high temperature in the absence of an electrical field, we develop an original approach combining experimental methods such as Nuclear Magnetic Resonance spectroscopy (NMR) at high temperature with Molecular Dynamics (MD) simulation coupled with first principle calculations based on Density Functional Theory (DFT). This approach allows the calculation of NMR parameters and the comparison with the experimental ones. It will be provide an additional validation and constraint of the model used for MD. We test this approach on the model NaF-AlF3 system.

Thermoresponsive Cellulose Acetate-Poly(N-isopropylacrylamide) Core-Shell Fibers for Controlled Capture and Release of Moisture.

PubMed

Thakur, Neha; Sargur Ranganath, Anupama; Sopiha, Kostiantyn; Baji, Avinash

2017-08-30

In this study, we used core-shell electrospinning to fabricate cellulose acetate-poly(N-isopropylacrylamide) (CA-PNIPAM) fibrous membranes and demonstrated the ability of these fibers to capture water from a high humid atmosphere and release it when thermally stimulated. The wettability of the fibers was controlled by using thermoresponsive PNIPAM as the shell layer. Scanning electron and fluorescence microscopes are used to investigate the microstructure of the fibers and confirm the presence of the core and shell phases within the fibers. The moisture capturing and releasing ability of these core-shell CA-PNIPAM fibers was compared with those of the neat CA and neat PNIPAM fibers at room temperature as well as at an elevated temperature. At room temperature, the CA-PNIPAM core-shell fibers are shown to have the maximum moisture uptake capacity among the three samples. The external temperature variations which trigger the moisture response behavior of these CA-PNIPAM fibers fall within the range of typical day and night cycles of deserts, demonstrating the potential use of these fibers for water harvesting applications.

Multistage crack seal vein and hydrothermal Ni enrichment in serpentinized ultramafic rocks (Koniambo massif, New Caledonia)

NASA Astrophysics Data System (ADS)

Cathelineau, Michel; Myagkiy, Andrey; Quesnel, Benoit; Boiron, Marie-Christine; Gautier, Pierre; Boulvais, Philippe; Ulrich, Marc; Truche, Laurent; Golfier, Fabrice; Drouillet, Maxime

2017-10-01

Sets of fractures and breccia sealed by Ni-rich silicates and quartz occur within saprock of the New Caledonian regolith developed over ultramafic rocks. The crystallization sequence in fractures is as follows: (1) serpentine stage: lizardite > polygonal serpentine > white lizardite; (2) Ni stage: Ni-Mg kerolite followed by red-brown microcrystalline quartz; and (3) supergene stages. The red-brown microcrystalline quartz corresponds to the very last stage of the Ni sequence and is inferred to have precipitated within the 50-95 °C temperature range. It constitutes also the main cement of breccia that has all the typical features of hydraulic fracturing. The whole sequence is therefore interpreted as the result of hydrothermal fluid circulation under medium to low temperature and fluctuating fluid pressure. Although frequently described as the result of a single downward redistribution of Ni and Mg leached in the upper part of the regolith under ambient temperature, the Ni silicate veins thus appear as the result of recurrent crack and seal process, corresponding to upward medium temperature fluid convection, hydraulic fracturing and subsequent fluid mixing, and mineral deposition.

Combustion efficiency determined from wall pressure and temperature measurement in a Mach 2 combustor

NASA Technical Reports Server (NTRS)

Segal, Corin; Mcdaniel, James C.; Whitehurst, Robert B.; Krauss, Roland H.

1991-01-01

A study of transverse hydrogen injection behind a rearward facing step in a Mach 2 airflow was conducted to determine the combustion efficiency and the combustor/inlet interactions at the low temperature lean-mixture operational end of a scramjet combustor model. The fuel was injected at sonic conditions into the electrically heated airstream, which was maintained at 850 K or below. The static pressure delivered at the entrance of the combustor ranged between 0.25 to 0.5 atm. Injector configurations included single and staged injectors placed at 3 or 3-and-7 step-heights downstream of the step, respectively, with injector diameters of 1, 1.5, and 2 mm. Ignition was achieved by initially unstarting the test section. The constant area combustor and the low initial temperatures caused thermal choking and upstream interaction to occur at very low equivalence ratios. Typically, most of the fuel was burned in the recirculation region behind the step and around the jets. The effects of initial conditions (temperature and pressure), fuel-to-air dynamic pressure ratio, and boundaries (thermal vs adiabatic) are presented.

Solute–solute correlations responsible for the prepeak in structure factors of undercooled Al-rich liquids: A molecular dynamics study

DOE PAGES

Zhang, Feng; Sun, Yang; Ye, Zhuo; ...

2015-05-06

In this study, we have performed molecular dynamics simulations on a typical Al-based alloy Al 90Sm 10. The short-range and medium-range correlations of the system are reliably produced by ab initio calculations, whereas the long-range correlations are obtained with the assistance of a semi-empirical potential well-fitted to ab initio data. Our calculations show that a prepeak in the structure factor of this system emerges well above the melting temperature, and the intensity of the prepeak increases with increasing undercooling of the liquid. These results are in agreement with x-ray diffraction experiments. The interplay between the short-range order of the systemmore » originating from the large affinity between Al and Sm atoms, and the intrinsic repulsion between Sm atoms gives rise to a stronger correlation in the second peak than the first peak in the Sm–Sm partial pair correlation function (PPCF), which in turn produces the prepeak in the structure factor.« less

Wave-Particle Interactions Involving Correlated Electron Bursts and Whistler Chorus in Earth's Radiation Belts

NASA Astrophysics Data System (ADS)

Echterling, N.; Schriver, D.; Roeder, J. L.; Fennell, J. F.

2017-12-01

During the recovery phase of substorm plasma injections, the Van Allen Probes commonly observe events of quasi-periodic energetic electron bursts correlating with simultaneously detected upper-band, whistler-mode chorus emissions. These electron bursts exhibit narrow ranges of pitch angles (75-80° and 100-105°) and energies (20-40 keV). Electron cyclotron harmonic (ECH) emissions are also commonly detected, but typically do not display correlation with the electron bursts. To examine sources of free energy and the generation of these wave emissions, an observed electron velocity distribution on January 13, 2013 is used as the starting condition for a particle in cell (PIC) simulation. Effects of temperature anisotropy (perpendicular temperature greater than parallel temperature), the presence of a loss cone and a cold electron population on the generation of whistler and ECH waves are examined to understand wave generation and nonlinear interactions with the particle population. These nonlinear interactions produce energy diffusion along with strong pitch angle scattering into the loss cone on the order of milliseconds, which is faster than a typical bounce period of seconds. To examine the quasi-periodic nature of the electron bursts, a loss-cone recycling technique is implemented to model the effects of the periodic emptying of the loss cone and electron injection on the growth of whistler and ECH waves. The results of the simulations are compared to the Van Allen Probe observations to determine electron acceleration, heating and transport in Earth's radiation belts due to wave-particle interactions.

Passive in-situ chemical sensor

DOEpatents

Morrell, Jonathan S [Farragut, TN; Ripley, Edward B [Knoxville, TN

2012-02-14

A chemical sensor for assessing a chemical of interest. In typical embodiments the chemical sensor includes a first thermocouple and second thermocouple. A reactive component is typically disposed proximal to the second thermal couple, and is selected to react with the chemical of interest and generate a temperature variation that may be detected by a comparison of a temperature sensed by the second thermocouple compared with a concurrent temperature detected by the first thermocouple. Further disclosed is a method for assessing a chemical of interest and a method for identifying a reaction temperature for a chemical of interest in a system.

The effect of prolonged exposure to 750 C air on the tribological performance of PM212

NASA Technical Reports Server (NTRS)

Bemis, Kirk; Bogdanski, Michael S.; Dellacorte, Christopher; Sliney, Harold E.

1994-01-01

The effect of prolonged exposure to 750 C air on the tribological performance and dimensional stability of PM212, a high temperature, self-lubricating composite, is studied. PM212, by weight, contains 70 percent metal-bonded Cr3C2, 15 percent BaF2/CaF2 eutectic, and 15 percent silver. Rub blocks were fabricated from PM212 by cold isostatic pressing followed by sintering. Prior to tribo-testing, the rub blocks were exposed to 750 C air for periods ranging from 100 to 1000 hours. Then, the rub blocks were slid against nickel-based superalloy disks in a double-rub-block tribometer in air under a 66 N load at temperatures from 25 to 750 C with a sliding velocity of 0.36 m/s. Unexposed rub blocks were tested for baseline comparison. Friction coefficients ranged from 0.24 to 0.37 for the unexposed rub blocks and from 0.32 to 0.56 for the exposed ones. Wear for both the composite blocks and superalloy disks was typically in the moderate to low range of 10(exp -5) to 10(exp -6) mm(exp 3)/N-m. Friction and wear data were similar for the rub blocks exposed for 100, 500, and 1000 hours. Prolonged exposure to 750 C air increased friction and wear of the PM212 rub blocks at room temperature, but their triboperformance remained unaffected at higher temperatures, probably due to the formation of lubricious metal oxides. Dimensional stability of the composite was studied by exposing specimens of varying thicknesses for 500 hours in air at 750 C. Block thicknesses were found to increase with increased exposure time until steady state was reached after 100 hours of exposure, probably due to oxidation.

Diagnostic Imaging in Flames with Instantaneous Planar Coherent Raman Spectroscopy.

PubMed

Bohlin, A; Kliewer, C J

2014-04-03

Spatial mapping of temperature and molecular species concentrations is vitally important in studies of gaseous chemically reacting flows. Temperature marks the evolution of heat release and energy transfer, while species concentration gradients provide critical information on mixing and chemical reaction. Coherent anti-Stokes Raman spectroscopy (CARS) was pioneered in measurements of such processes almost 40 years ago and is authoritative in terms of the accuracy and precision it may provide. While a reacting flow is fully characterized in three-dimensional space, a limitation of CARS has been its applicability as a point-wise measurement technique, motivating advancement toward CARS imaging, and attempts have been made considering one-dimensional probing. Here, we report development of two-dimensional CARS, with the first diagnostics of a planar field in a combusting flow within a single laser pulse, resulting in measured isotherms ranging from 450 K up to typical hydrocarbon flame temperatures of about 2000 K with chemical mapping of O2 and N2.

The activation energy for nanocrystalline diamond films deposited from an Ar/H2/CH4 hot-filament reactor.

PubMed

Barbosa, D C; Melo, L L; Trava-Airoldi, V J; Corat, E J

2009-06-01

In this work we have investigated the effect of substrate temperature on the growth rate and properties of nanocrystalline diamond thin films deposited by hot filament chemical vapor deposition (HFCVD). Mixtures of 0.5 vol% CH4 and 25 vol% H2 balanced with Ar at a pressure of 50 Torr and typical deposition time of 12 h. We present the measurement of the activation energy by accurately controlling the substrate temperature independently of other CVD parameters. Growth rates have been measured in the temperature range from 550 to 800 degrees C. Characterization techniques have involved Raman spectroscopy, high resolution X-ray difractometry and scanning electron microscopy. We also present a comparison with most activation energy for micro and nanocrystalline diamond determinations in the literature and propose that there is a common trend in most observations. The result obtained can be an evidence that the growth mechanism of NCD in HFCVD reactors is very similar to MCD growth.

Frequency-dependent impedance spectroscopy on the 0.925(Bi0.5Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 ceramic

NASA Astrophysics Data System (ADS)

Ullah, Amir; Rahman, Muneeb-ur; Iqbal, Muhammad Javid; Ahn, Chang Won; Kim, Ill Won; Ullah, Aman

2016-06-01

The electrical properties of the 0.925(Bi0.5(Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 (0.925BNKT-0.075BST) ceramic were investigated by using AC impedance spectroscopy over a wide range of frequencies (10 -2 ~ 105 Hz). The X-ray diffraction patterns confirmed the formation of a single-phase compound. A single semicircular arc in the impedance spectrum indicates that the main contribution of the bulk resistance ( R b ) were due to grain effects, with Rb decreasing with increasing temperature. The conductivity of the ceramics increased with increasing temperature, and the activation energy resulting from the DC conductivity was 0.86 eV. The ceramic displayed a typical negative temperature coefficient of resistance (NTCR) behavior, like that of a semiconductor.

A model for studying the composition and chemical effects of stratospheric aerosols

NASA Technical Reports Server (NTRS)

Tabazadeh, Azadeh; Turco, Richard P.; Jacobson, Mark Z.

1994-01-01

We developed polynomial expressions for the temperature dependence of the mean binary and water activity coefficients for H2SO4 and HNO3 solutions. These activities were used in an equilibrium model to predict the composition of stratospheric aerosols under a wide range of environmental conditions. For typical concentrations of H2O, H2SO4, HNO3, HCl, HBr, HF, and HOCl in the lower stratosphere, the aerosol composition is estimated as a function of the local temperature and the ambient relative humidity. For temperatures below 200 K, our results indicate that (1) HNO3 contributes a significant mass fraction to stratospheric aerosols, and (2) HCl solubility is considerably affected by HNO3 dissolution into sulfate aerosols. We also show that, in volcanically disturbed periods, changes in stratospheric aerosol composition can significantly alter the microphysics that leads to the formation of polar stratospheric clouds. The effects caused by HNO3 dissolution on the physical and chemical properties of stratospheric aerosols are discussed.

Elastic anomaly and order-disorder nature of multiferroic barium sodium niobate studied by broadband brillouin scattering

NASA Astrophysics Data System (ADS)

Ota, Shiori; Matsumoto, Kazuya; Suzuki, Kohei; Kojima, Seiji

2014-03-01

The successive phase transitions of multiferroic barium sodium niobate, Ba2NaNb5O15 (BNN), were studied by Brillouin scattering. The LA, TA modes, and central peak were measured in a large temperature range from room temperature up to 750 °C. In the vicinity of a ferroelectric phase transition at about TC = 585 °C from the prototypic tetragonal 4/mmm to ferroelectric 4mm phases, elastic anomaly was observed for LA and TA modes. In addition, the order-disorder nature was observed by the temperature dependence of a central peak. For further cooling another elastic anomaly was also observed in the vicinity of a ferroelastic incommensurate phase transition at about TIC = 285 °C into orthorhombic 2mm phase with the appearance of incommensurate modulation. The large thermal hysteresis of elastic anomaly near TIC can be attributed the typical feature of the type III incommensurate phase transition predicted recently by Ishibashi and Iwata (2013 J. Phys. Soc. Jpn. 82 044703).

Instrument for Study of Microbial Thermal Inactivation

PubMed Central

Dickerson, R. W.; Read, R. B.

1968-01-01

An instrument was designed for the study of thermal inactivation of microorganisms using heating times of less than 1 sec. The instrument operates on the principle of rapid automatic displacement of the microorganism to and from a saturated steam atmosphere, and the operating temperature range is 50 to 90 C. At a temperature of 70 C, thermometric lag (time required to respond to 63.2% of a step change) of the fluid sample containing microorganisms was 0.12 sec. Heating time required to heat the sample to within 0.1 C of the exposure temperature was less than 1 sec, permitting exposure periods as brief as 1 sec, provided the proper corrections are made for the lethal effect of heating. The instrument is most useful for heat exposure periods of less than 5 min, and, typically, more than 500 samples can be processed for microbial inactivation determinations within an 8-hr period. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 7 Fig. 8 PMID:4874466

Inelastic properties of ice Ih at low temperatures and high pressures

USGS Publications Warehouse

Kirby, S.H.; Durham, W.B.; Beeman, M.L.; Heard, H.C.; Daley, M.A.

1987-01-01

The aim of our research programme is to explore the rheological behavior of H2O ices under conditions appropriate to the interiors of the icy satellites of the outer planets in order to give insight into their deformation. To this end, we have performed over 100 constant-strain-rate compression tests at pressures to 500 MPa and temperatures as low as 77 K. At P > 30 MPa, ice Ih fails by a shear instability producing faults in the maximum shear stress orientation and failure strength typically is independent of pressure. This unusual faulting behavior is thought to be connected with phase transformations localized in the shear zones. The steady-state strength follows rheological laws of the thermally-activated power-law type, with different flow law parameters depending on the range of test temperatures. The flow laws will be discussed with reference to the operating deformation mechanisms as deduced from optical-scale microstructures and comparison with other work.

Volcanic ash melting under conditions relevant to ash turbine interactions

PubMed Central

Song, Wenjia; Lavallée, Yan; Hess, Kai-Uwe; Kueppers, Ulrich; Cimarelli, Corrado; Dingwell, Donald B.

2016-01-01

The ingestion of volcanic ash by jet engines is widely recognized as a potentially fatal hazard for aircraft operation. The high temperatures (1,200–2,000 °C) typical of jet engines exacerbate the impact of ash by provoking its melting and sticking to turbine parts. Estimation of this potential hazard is complicated by the fact that chemical composition, which affects the temperature at which volcanic ash becomes liquid, can vary widely amongst volcanoes. Here, based on experiments, we parameterize ash behaviour and develop a model to predict melting and sticking conditions for its global compositional range. The results of our experiments confirm that the common use of sand or dust proxy is wholly inadequate for the prediction of the behaviour of volcanic ash, leading to overestimates of sticking temperature and thus severe underestimates of the thermal hazard. Our model can be used to assess the deposition probability of volcanic ash in jet engines. PMID:26931824

Ground-based observations of Saturn's auroral H3+: short- and long-term trends in thermospheric temperature

NASA Astrophysics Data System (ADS)

O'Donoghue, J.; Melin, H.; Stallard, T.; Moore, L.

2014-04-01

The observations presented here used the 10-m Keck telescope situated on Mauna Kea, Hawaii. They were designed to be an integral part of the Saturn Auroral Observing Campaign of April-May 2013 (to be published in the Icarus special issue of 2014). These overlap with observations performed by the Cassini spacecraft, Hubble space telescope and the NASA infrared telescope facility (IRTF). During the observations, Saturn's sub-solar latitude was 18 degrees, i.e. Saturn was well into northern springtime/ southern autumn. In three nights of data we have found 1) the northern hemisphere is on average ~50 K cooler than the southern. This is consistent with previous work, which suggests that magnetic field strength is inversely proportional to the total heating rate. 2) the combined northern and southern temperatures range typically between 380 and 500 K on time-scales of hours/days. 3) there may be a correlation between planetary period oscillation (PPO) phase and temperature in the northern main auroral oval.

Methane seep carbonates yield clumped isotope signatures out of equilibrium with formation temperatures

DOE PAGES

Loyd, S. J.; Sample, J.; Tripati, R. E.; ...

2016-07-22

Here, methane cold seep systems typically exhibit extensive buildups of authigenic carbonate minerals, resulting from local increases in alkalinity driven by methane oxidation. Here, we demonstrate that modern seep authigenic carbonates exhibit anomalously low clumped isotope values (Δ47), as much as ~0.2‰ lower than expected values. In modern seeps, this range of disequilibrium translates into apparent temperatures that are always warmer than ambient temperatures, by up to 50 °C. We examine various mechanisms that may induce disequilibrium behaviour in modern seep carbonates, and suggest that the observed values result from several factors including kinetic isotopic effects during methane oxidation, mixingmore » of inorganic carbon pools, pH effects and rapid precipitation. Ancient seep carbonates studied here also exhibit potential disequilibrium signals. Ultimately, these findings indicate the predominance of disequilibrium clumped isotope behaviour in modern cold seep carbonates that must be considered when characterizing environmental conditions in both modern and ancient cold seep settings.« less

Microgravity fluid management requirements of advanced solar dynamic power systems

NASA Technical Reports Server (NTRS)

Migra, Robert P.

1987-01-01

The advanced solar dynamic system (ASDS) program is aimed at developing the technology for highly efficient, lightweight space power systems. The approach is to evaluate Stirling, Brayton and liquid metal Rankine power conversion systems (PCS) over the temperature range of 1025 to 1400K, identify the critical technologies and develop these technologies. Microgravity fluid management technology is required in several areas of this program, namely, thermal energy storage (TES), heat pipe applications and liquid metal, two phase flow Rankine systems. Utilization of the heat of fusion of phase change materials offers potential for smaller, lighter TES systems. The candidate TES materials exhibit large volume change with the phase change. The heat pipe is an energy dense heat transfer device. A high temperature application may transfer heat from the solar receiver to the PCS working fluid and/or TES. A low temperature application may transfer waste heat from the PCS to the radiator. The liquid metal Rankine PCS requires management of the boiling/condensing process typical of two phase flow systems.

IC Ku-band Impatt Amplifier. [solid state spacecraft transmitter

NASA Technical Reports Server (NTRS)

Sokolov, V.; Namordi, M. R.; Doerbeck, F. H.; Wisseman, W. R.

1979-01-01

High efficiency GaAs low-high-low IMPATTs were investigated. Theoretical analyses were employed to establish a design window for the material parameters to maximize microwave performance. Single mesa devices yielded typically 2 to 3 W with 16 to 23% efficiency in waveguide oscillator test circuits. IMPATTs with high reliability Pt/TiW/Pt/Au metallizations were subjected to temperature stress, non-rf bias-temperature stress, and rf bias-temperature stress. Assuming that temperature is the driving force behind the dominant failure mechanism, a mean-time-to-failure considerably greater than 500,000 hours is indicated by the stress tests. A 15 GHz, 4W, 56 dB gain microstrip amplifier was realized using GaAs FETs and IMPATTs. Power combining using a 3 db Lange coupler is employed in the power output stage having an intrinsic power-added efficiency of 15.7%. Overall dc-to-rf efficiency of the amplifier is 10.8%. The amplifier has greater than a 250 MHz, 1 db bandwidth; operates over the 0 deg to 50 C (base plate) temperature range with less than 0.5 db change in the power output; weighs 444 grams; and has a volume of 220 cu cm.

Unusual kinetics of thermal decay of dim-light photoreceptors in vertebrate vision

PubMed Central

Guo, Ying; Sekharan, Sivakumar; Liu, Jian; Batista, Victor S.; Tully, John C.; Yan, Elsa C. Y.

2014-01-01

We present measurements of rate constants for thermal-induced reactions of the 11-cis retinyl chromophore in vertebrate visual pigment rhodopsin, a process that produces noise and limits the sensitivity of vision in dim light. At temperatures of 52.0–64.6 °C, the rate constants fit well to an Arrhenius straight line with, however, an unexpectedly large activation energy of 114 ± 8 kcal/mol, which is much larger than the 60-kcal/mol photoactivation energy at 500 nm. Moreover, we obtain an unprecedentedly large prefactor of 1072±5 s−1, which is roughly 60 orders of magnitude larger than typical frequencies of molecular motions! At lower temperatures, the measured Arrhenius parameters become more normal: Ea = 22 ± 2 kcal/mol and Apref = 109±1 s−1 in the range of 37.0–44.5 °C. We present a theoretical framework and supporting calculations that attribute this unusual temperature-dependent kinetics of rhodopsin to a lowering of the reaction barrier at higher temperatures due to entropy-driven partial breakup of the rigid hydrogen-bonding network that hinders the reaction at lower temperatures. PMID:25002518

Temperature Variation of the Resistivity and Magnetoresistance in Cobalt-Enhanced Spin-Valve Structures

NASA Astrophysics Data System (ADS)

Lottis, D. K.; Szucs, J.; O'Brien, T.; Gangopadhyay, S.; Mao, S.

1996-03-01

Several FeMn exchange-biased spin-valve structures have been prepared in an ion-beam sputtering system. The magnitude of the MR in these permalloy-based structures has been enhanced by the inclusion of Co at the interfaces with the Cu spacer layer (S.S.P. Parkin, PRL 71), 1641 (1993). Typical values for the MR in our spin-valves are 3% at room temperature and 7% at 8K. Both R and MR have been measured over the entire range from 8K to 325K, and exhibit an anomaly at a temperature near 250K. The resistance exhibits a local minimum, similar to what has been observed in Cr-based alloys (E. Fawcett et al, Rev. Mod. Phys. 66), 25 (1994) and multilayers (E. Fullerton et al, PRL 75), 330 (1995) at the Néel temperature. This anomaly is also visible in both the MR vs. T and the Δ R vs. T curves. These results, which suggest the presence of another Mn-based antiferromagnetic alloy in our samples, are particularly relevant for the development of applications where the nature of the temperature variation of the MR is crucial.

Unusual kinetics of thermal decay of dim-light photoreceptors in vertebrate vision.

PubMed

Guo, Ying; Sekharan, Sivakumar; Liu, Jian; Batista, Victor S; Tully, John C; Yan, Elsa C Y

2014-07-22

We present measurements of rate constants for thermal-induced reactions of the 11-cis retinyl chromophore in vertebrate visual pigment rhodopsin, a process that produces noise and limits the sensitivity of vision in dim light. At temperatures of 52.0-64.6 °C, the rate constants fit well to an Arrhenius straight line with, however, an unexpectedly large activation energy of 114 ± 8 kcal/mol, which is much larger than the 60-kcal/mol photoactivation energy at 500 nm. Moreover, we obtain an unprecedentedly large prefactor of 10(72±5) s(-1), which is roughly 60 orders of magnitude larger than typical frequencies of molecular motions! At lower temperatures, the measured Arrhenius parameters become more normal: Ea = 22 ± 2 kcal/mol and Apref = 10(9±1) s(-1) in the range of 37.0-44.5 °C. We present a theoretical framework and supporting calculations that attribute this unusual temperature-dependent kinetics of rhodopsin to a lowering of the reaction barrier at higher temperatures due to entropy-driven partial breakup of the rigid hydrogen-bonding network that hinders the reaction at lower temperatures.

Effect of inlet temperature on the performance of a catalytic reactor. [air pollution control

NASA Technical Reports Server (NTRS)

Anderson, D. N.

1978-01-01

A 12 cm diameter by 15 cm long catalytic reactor was tested with No. 2 diesel fuel in a combustion test rig at inlet temperatures of 700, 800, 900, and 1000 K. Other test conditions included pressures of 3 and 6 x 10 to the 5th power Pa, reference velocities of 10, 15, and 20 m/s, and adiabatic combustion temperatures in the range 1100 to 1400 K. The combustion efficiency was calculated from measurements of carbon monoxide and unburned hydrocarbon emissions. Nitrogen oxide emissions and reactor pressure drop were also measured. At a reference velocity of 10 m/s, the CO and unburned hydrocarbons emissions, and, therefore, the combustion efficiency, were independent of inlet temperature. At an inlet temperature of 1000 K, they were independent of reference velocity. Nitrogen oxides emissions resulted from conversion of the small amount (135 ppm) of fuel-bound nitrogen in the fuel. Up to 90 percent conversion was observed with no apparent effect of any of the test variables. For typical gas turbine operating conditions, all three pollutants were below levels which would permit the most stringent proposed automotive emissions standards to be met.

Cumulative effects of heat exposure and storage conditions of Oxytocin-in-Uniject in rural Ghana: implications for scale up

PubMed Central

Mullany, Luke C; Newton, Sam; Afari-Asiedu, Samuel; Adiibokah, Edward; Agyemang, Charlotte T; Cofie, Patience; Brooke, Steve; Owusu-Agyei, Seth; Stanton, Cynthia K

2014-01-01

ABSTRACT Objective: Postpartum hemorrhage can be reduced substantially in home deliveries attended by community-based workers by using Oxytocin-in-Uniject (OIU) devices affixed with temperature-time indicators. We characterized the distribution of time to discard of these devices when stored under normal field conditions in Ghana. Methods: Two drug storage simulation studies were conducted in rural Ghana in 2011 and 2012. Devices were transported under refrigeration from manufacture (Argentina) to storage at the study site. Twenty-three field workers each stored at home (unrefrigerated) 25 OIU devices and monitored them daily to record: (1) time to transition from usable to unusable, and (2) continuous digital ambient temperature to determine heat exposure over the simulation period. Time to discard was estimated and compared with mean kinetic temperature exposure of the devices during the shipment and storage phases and with characteristics of the storage locations using Weibull regression models. We used the time to discard distributions in a Monte Carlo simulation to estimate wastage rates in a hypothetical program setting. Results: Time for shipment and transfer to long-term refrigerated storage and mean kinetic temperature during the shipment phase was 8.6 days/10.3°C and 13.4 days/12.1°C, for the first and second simulation studies, respectively. Median (range) time to discard when stored under field conditions (unrefrigerated) was 43 (6 to 59) days and 33 (14 to 50) days, respectively. Mean time to discard was 10.0 days shorter in the second simulation, during which mean kinetic temperature exposure was 3.9°C higher. Simulating a monthly distribution system and assuming typical usage, predicted wastage of product was less than 10%. Conclusion: The time to discard of devices was highly sensitive to small changes in temperature exposure. Under field conditions typical in rural Ghana, OIU packages will have a half-life of approximately 30 to 40 days based on the temperature monitor used during the study. Program managers will need to carefully consider variations in both ambient temperature and rate of use to allocate the appropriate supply level that will maximize coverage and minimize stock loss. PMID:25276588

Cumulative effects of heat exposure and storage conditions of Oxytocin-in-Uniject in rural Ghana: implications for scale up.

PubMed

Mullany, Luke C; Newton, Sam; Afari-Asiedu, Samuel; Adiibokah, Edward; Agyemang, Charlotte T; Cofie, Patience; Brooke, Steve; Owusu-Agyei, Seth; Stanton, Cynthia K

2014-08-01

Postpartum hemorrhage can be reduced substantially in home deliveries attended by community-based workers by using Oxytocin-in-Uniject (OIU) devices affixed with temperature-time indicators. We characterized the distribution of time to discard of these devices when stored under normal field conditions in Ghana. Two drug storage simulation studies were conducted in rural Ghana in 2011 and 2012. Devices were transported under refrigeration from manufacture (Argentina) to storage at the study site. Twenty-three field workers each stored at home (unrefrigerated) 25 OIU devices and monitored them daily to record: (1) time to transition from usable to unusable, and (2) continuous digital ambient temperature to determine heat exposure over the simulation period. Time to discard was estimated and compared with mean kinetic temperature exposure of the devices during the shipment and storage phases and with characteristics of the storage locations using Weibull regression models. We used the time to discard distributions in a Monte Carlo simulation to estimate wastage rates in a hypothetical program setting. Time for shipment and transfer to long-term refrigerated storage and mean kinetic temperature during the shipment phase was 8.6 days/10.3°C and 13.4 days/12.1°C, for the first and second simulation studies, respectively. Median (range) time to discard when stored under field conditions (unrefrigerated) was 43 (6 to 59) days and 33 (14 to 50) days, respectively. Mean time to discard was 10.0 days shorter in the second simulation, during which mean kinetic temperature exposure was 3.9°C higher. Simulating a monthly distribution system and assuming typical usage, predicted wastage of product was less than 10%. The time to discard of devices was highly sensitive to small changes in temperature exposure. Under field conditions typical in rural Ghana, OIU packages will have a half-life of approximately 30 to 40 days based on the temperature monitor used during the study. Program managers will need to carefully consider variations in both ambient temperature and rate of use to allocate the appropriate supply level that will maximize coverage and minimize stock loss.

Coupled CaAl-NaSi diffusion in plagioclase feldspar: Experiments and applications to cooling rate speedometry

NASA Astrophysics Data System (ADS)

Grove, Timothy L.; Baker, Michael B.; Kinzler, Rosamond J.

1984-10-01

The rate of CaAl-NaSi interdiffusion in plagioclase feldspar was determined under 1 atm anhydrous conditions over the temperature range 1400° to 1000°C in calcic plagioclase (An 80-81) by homogenizing coherent exsolution lamellae. The dependence of the average interdiffusion coefficient on temperature is given by the expression: D˜ = 10.99 ( cm 2/sec) exp (-123.4( kcal/mol)/RT), (T in °K). This value is for diffusion perpendicular to the (03 1¯) interface of the lamellae. CaAl-NaSi interdiffusion is 4 to 5 orders of magnitude slower than oxygen diffusion in the temperature range 1400° to 1200°C and possibly 10 orders of magnitude slower at subsolidus temperatures. The large differences in diffusion rates explain the apparent contradiction posed by the plagioclases of large layered intrusions ( e.g., the Skaergaard), which retain delicate Ca, Na compositional zoning profiles on the micron scale, but have undergone complete oxygen isotopic exchange with heated meteoric groundwater from the surrounding wall rocks. CaAl-NaSi diffusion is slow, the closure temperature is high (within the solidus-liquidus interval), and Ca-Na zoning is preserved. Oxygen diffusion is faster, the closure temperature is lower (350°-400°C) and the feldspars exchange oxygen with the low-temperature hydrothermal fluids. The complex micron-scale oscillatory zones in plagioclase can also be used as cooling rate speedometers for volcanic and plutonic plagioclase. Cooling histories typical of large mafic intrusions ( e.g. the Stillwater) are slow, begin at high initial temperatures (1200°C) and result in homogenization of oscillatory zones on the scale of 10 microns. The oscillatory zones found in the plagioclase of granodioritic plutons are preserved because cooling is initiated at a lower temperature (1000°C) limiting diffusion to submicron length scales despite the slow cooling rate of the intrusion.

APPLICATIONS OF CATHODOLUMINESCENCE OF QUARTZ AND FELDSPAR TO SEDIMENTARY PETROLOGY.

USGS Publications Warehouse

Ruppert, Leslie F.

1987-01-01

Cathodoluminescence (CL), the emission of visible light during electron bombardment, was first used in sandstone petrology in the mid-1960's. CL techniques are especially useful for determining the origin and source of quartz and feldspar, two of the most common constituents in clastic rocks. CL properties of both minerals are dependent on their temperature of crystallization, duration of cooling, and/or history of deformation. Detrital quartz and feldspar are typically derived from igneous and metamorphic sources and luminesce in the visible range whereas authigenic quartz and feldspar form at low temperatures and do not luminesce. Quantification of luminescent and non-luminescent quartz and feldspar with the scanning electron microscope, electron microprobe, or a commercial CL device can allow for the determination of origin, diagenesis, and source of clastic rocks when used in conjunction with field and other petrographic analyses.

Kondo effect in single cobalt phthalocyanine molecules adsorbed on Au(111) monoatomic steps

NASA Astrophysics Data System (ADS)

Zhao, Aidi; Hu, Zhenpeng; Wang, Bing; Xiao, Xudong; Yang, Jinlong; Hou, J. G.

2008-06-01

The Kondo effect in single dehydrogenated cobalt phthalocyanine (CoPc) molecules adsorbed on Au(111) monoatomic steps was studied with a low temperature scanning tunneling microscope. The CoPc molecules adsorbed on Au(111) monoatomic steps show two typical configurations, which can be dehydrogenated to reveal Kondo effect. Moreover, the Kondo temperatures (TK) measured for different molecules vary in a large range from ~150 to ~550 K, increasing monotonically with decreasing Co-Au distance. A simple model consisting of a single Co 3dz2 orbital and a Au 6s orbital is considered and gives a qualitative explanation to the dependence. The large variation of TK is attributed to the variation of the interaction between the magnetic-active cobalt ion and the Au substrate resulted from different Co-Au distances.

Compressed exponential relaxation in liquid silicon: Universal feature of the crossover from ballistic to diffusive behavior in single-particle dynamics

NASA Astrophysics Data System (ADS)

Morishita, Tetsuya

2012-07-01

We report a first-principles molecular-dynamics study of the relaxation dynamics in liquid silicon (l-Si) over a wide temperature range (1000-2200 K). We find that the intermediate scattering function for l-Si exhibits a compressed exponential decay above 1200 K including the supercooled regime, which is in stark contrast to that for normal "dense" liquids which typically show stretched exponential decay in the supercooled regime. The coexistence of particles having ballistic-like motion and those having diffusive-like motion is demonstrated, which accounts for the compressed exponential decay in l-Si. An attempt to elucidate the crossover from the ballistic to the diffusive regime in the "time-dependent" diffusion coefficient is made and the temperature-independent universal feature of the crossover is disclosed.

Clathrate type 2 hydrate formation in vacuo under astrophysical conditions

NASA Technical Reports Server (NTRS)

Blake, D. F.; Allamandola, L. J.; Sandford, S. A.; Freund, F.

1991-01-01

The properties of clathrate hydrates were used to explain the complex and poorly understood physical processes taking place within cometary nuclei and other icy solar system bodies. Most of all the experiments previously conducted used starting compositions which would yield clathrate types I hydrates. The main criterion for type I vs. type II clathrate hydrate formation is the size of the guest molecule. The stoichiometry of the two structure types is also quite different. In addition, the larger molecules which would form type II clathrate hydrates typically have lower vapor pressures. The result of these considerations is that at temperatures where we identified clathrate formation (120-130 K), it is more likely that type II clathrate hydrates will form. We also formed clathrate II hydrates of methanol by direct vapor deposition in the temperature range 125-135 K.

Model atmospheres and radiation of magnetic neutron stars. I - The fully ionized case

NASA Technical Reports Server (NTRS)

Shibanov, Iu. A.; Zavlin, V. E.; Pavlov, G. G.; Ventura, J.

1992-01-01

Model neutron star atmospheres are calculated for typical cooling stars with a strong magnetic field and effective temperatures of 10 exp 5 to 10 exp 6 K. The effect of anisotropic photon diffusion in two normal modes are examined under the assumption that the opacity is due solely to the bremsstrahlung and Thomson scattering processes under conditions of LTE that are expected to prevail at the temperatures and densities obtained. The main aspects of anisotropic photon diffusion, and an original procedure for calculating model atmospheres and emitted spectra are discussed. Representative calculated spectra are given, and it is found that the hard spectral excess characterizing the nonmagnetic case, while still present, becomes less prominent in the presence of magnetic fields in the range of 10 exp 11 to 10 exp 13 G.

Cooling without contact in bilayer dipolar Fermi gases

NASA Astrophysics Data System (ADS)

Tanatar, Bilal; Renklioglu, Basak; Oktel, M. Ozgur

2016-05-01

We consider two parallel layers of dipolar ultracold Fermi gases at different temperatures and calculate the heat transfer between them. The effective interactions describing screening and correlation effects between the dipoles in a single layer are modelled within the Euler-Lagrange Fermi-hypernetted chain approximation. The random-phase approximation is employed for the interactions across the layers. We investigate the amount of transferred power between the layers as a function of the temperature difference. Energy transfer proceeds via the long-range dipole-dipole interactions. A simple thermal model is developed to investigate the feasibility of using the contactless sympathetic cooling of the ultracold polar atoms/molecules. Our calculations indicate that dipolar heat transfer is effective for typical polar molecule experiments and may be utilized as a cooling process. Supported by TUBA and TUBITAK (112T974).

Phase Evaluation in Al2O3 Fiber-Reinforced Ti2AlC During Sintering in the 1300 degrees C-1500 degrees C Temperature Range

DTIC Science & Technology

2011-01-01

composition: 97% Al2O3 and 3% SiO2] fibers. In both cases, the fibers were chopped with a razor blade into 5 cm lengths. Mixing of the powder and...the presence of XRD amorphous Ti- aluminides (see below) or other phases cannot be ruled out at this juncture. When the XRD spectrum of the as-received...not shown). No peaks belonging to any Ti- aluminide were found suggesting them to be amorphous or at most nano-crystalline. A typical TEM micrograph of

Collisional Dynamics, Lasing and Stimulated Raman Scattering in Optically Pumped Cesium and Potassium Vapors

DTIC Science & Technology

2012-03-22

10 4. Three level energy diagram of an OPAL . N0 is a ground S1/2 state, and N1 and N2 are the 2P1/2 and 2P3/2 states, respectively...refer to these lasers by the more general term, OPAL for Optically-Pumped Alkali Laser. An OPAL is a three level laser where the ground state , N0, is...contains the buffer gas and alkali metal vapor. The temperature of OPAL lasers is typically in the range of 90 to 130 ◦C which amounts to a density of about

A 20 GHz low noise, low cost receiver for digital satellite communication system, ground terminal applications

NASA Technical Reports Server (NTRS)

Allen, Glen

1988-01-01

A 45 month effort for the development of a 20 GHz, low-noise, low-cost receiver for digital, satellite communication system, ground terminal applications is discussed. Six proof-of-concept receivers were built in two lots of three each. Performance was generally consistent between the two lots. Except for overall noise figure, parameters were within or very close to specification. While noise figure was specified as 3.5 dB, typical performance was measured at 3.0 to 5.5 dB, over the full temperature range of minus 30 C to plus 75 C.

Proceedings of Damping 󈨟, 13-15 February 1991, San Diego, California; Volume 1 (Pages AAC-1 through DCC-19)

DTIC Science & Technology

1991-08-01

typical flight conditions for which high load factor maneuver data was gathered. The range of dynamic pressure, 350 psf to 500 psf, for the 12...because PED systems do not outgas and are stable with respect to environmental temperature variations. In addition PED system performance is easily...0 (15) Equation (15) is rearranged to give: X2H2i + X3H21 + XAHAl + XsH5l + + + Xl+X2 + X3+X< + Xs X2 Y + X3(H2 + ^)+ XA(H2 + H3 + ^-) + XS (H2

Energy harvesting using a thermoelectric material

DOEpatents

Nersessian, Nersesse [Van Nuys, CA; Carman, Gregory P [Los Angeles, CA; Radousky, Harry B [San Leandro, CA

2008-07-08

A novel energy harvesting system and method utilizing a thermoelectric having a material exhibiting a large thermally induced strain (TIS) due to a phase transformation and a material exhibiting a stress induced electric field is introduced. A material that exhibits such a phase transformation exhibits a large increase in the coefficient of thermal expansion over an incremental temperature range (typically several degrees Kelvin). When such a material is arranged in a geometric configuration, such as, for a example, a laminate with a material that exhibits a stress induced electric field (e.g. a piezoelectric material) the thermally induced strain is converted to an electric field.

MEGA16 - Computer program for analysis and extrapolation of stress-rupture data

NASA Technical Reports Server (NTRS)

Ensign, C. R.

1981-01-01

The computerized form of the minimum commitment method of interpolating and extrapolating stress versus time to failure data, MEGA16, is described. Examples are given of its many plots and tabular outputs for a typical set of data. The program assumes a specific model equation and then provides a family of predicted isothermals for any set of data with at least 12 stress-rupture results from three different temperatures spread over reasonable stress and time ranges. It is written in FORTRAN 4 using IBM plotting subroutines and its runs on an IBM 370 time sharing system.

Bias sputtered NbN and superconducting nanowire devices

NASA Astrophysics Data System (ADS)

Dane, Andrew E.; McCaughan, Adam N.; Zhu, Di; Zhao, Qingyuan; Kim, Chung-Soo; Calandri, Niccolo; Agarwal, Akshay; Bellei, Francesco; Berggren, Karl K.

2017-09-01

Superconducting nanowire single photon detectors (SNSPDs) promise to combine near-unity quantum efficiency with >100 megacounts per second rates, picosecond timing jitter, and sensitivity ranging from x-ray to mid-infrared wavelengths. However, this promise is not yet fulfilled, as superior performance in all metrics is yet to be combined into one device. The highest single-pixel detection efficiency and the widest bias windows for saturated quantum efficiency have been achieved in SNSPDs based on amorphous materials, while the lowest timing jitter and highest counting rates were demonstrated in devices made from polycrystalline materials. Broadly speaking, the amorphous superconductors that have been used to make SNSPDs have higher resistivities and lower critical temperature (Tc) values than typical polycrystalline materials. Here, we demonstrate a method of preparing niobium nitride (NbN) that has lower-than-typical superconducting transition temperature and higher-than-typical resistivity. As we will show, NbN deposited onto unheated SiO2 has a low Tc and high resistivity but is too rough for fabricating unconstricted nanowires, and Tc is too low to yield SNSPDs that can operate well at liquid helium temperatures. By adding a 50 W RF bias to the substrate holder during sputtering, the Tc of the unheated NbN films was increased by up to 73%, and the roughness was substantially reduced. After optimizing the deposition for nitrogen flow rates, we obtained 5 nm thick NbN films with a Tc of 7.8 K and a resistivity of 253 μΩ cm. We used this bias sputtered room temperature NbN to fabricate SNSPDs. Measurements were performed at 2.5 K using 1550 nm light. Photon count rates appeared to saturate at bias currents approaching the critical current, indicating that the device's quantum efficiency was approaching unity. We measured a single-ended timing jitter of 38 ps. The optical coupling to these devices was not optimized; however, integration with front-side optical structures to improve absorption should be straightforward. This material preparation was further used to fabricate nanocryotrons and a large-area imager device, reported elsewhere. The simplicity of the preparation and promising device performance should enable future high-performance devices.

Influence of sensor ingestion timing on consistency of temperature measures.

PubMed

Goodman, Daniel A; Kenefick, Robert W; Cadarette, Bruce S; Cheuvront, Samuel N

2009-03-01

The validity and the reliability of using intestinal temperature (T int) via ingestible temperature sensors (ITS) to measure core body temperature have been demonstrated. However, the effect of elapsed time between ITS ingestion and T int measurement has not been thoroughly studied. Eight volunteers (six men and two women) swallowed ITS 5 h (ITS-5) and 29 h (ITS-29) before 4 h of varying intensity activity. T int was measured simultaneously from both ITS, and T int differences between the ITS-5 and the ITS-29 over the 4 h of activity were plotted and compared relative to a meaningful threshold of acceptance (+/-0.25 degrees C). The percentage of time in which the differences between paired ITS (ITS-5 vs ITS-29) were greater than or less than the threshold of acceptance was calculated. T int values showed no systematic bias, were normally distributed, and ranged from 36.94 degrees C to 39.24 degrees C. The maximum T int difference between paired ITS was 0.83 degrees C with a minimum difference of 0.00 degrees C. The typical magnitude of the differences (SE of the estimate) was 0.24 degrees C, and these differences were uniform across the entire range of observed temperatures. Paired T int measures fell outside of the threshold of acceptance 43.8% of the time during the 4 h of activity. The differences between ITS-5 and ITS-29 were larger than the threshold of acceptance during a substantial portion of the observed 4-h activity period. Ingesting an ITS more than 5 h before activity will not completely eliminate confounding factors but may improve accuracy and consistency of core body temperature.

A temperature rise reduces trial-to-trial variability of locust auditory neuron responses.

PubMed

Eberhard, Monika J B; Schleimer, Jan-Hendrik; Schreiber, Susanne; Ronacher, Bernhard

2015-09-01

The neurophysiology of ectothermic animals, such as insects, is affected by environmental temperature, as their body temperature fluctuates with ambient conditions. Changes in temperature alter properties of neurons and, consequently, have an impact on the processing of information. Nevertheless, nervous system function is often maintained over a broad temperature range, exhibiting a surprising robustness to variations in temperature. A special problem arises for acoustically communicating insects, as in these animals mate recognition and mate localization typically rely on the decoding of fast amplitude modulations in calling and courtship songs. In the auditory periphery, however, temporal resolution is constrained by intrinsic neuronal noise. Such noise predominantly arises from the stochasticity of ion channel gating and potentially impairs the processing of sensory signals. On the basis of intracellular recordings of locust auditory neurons, we show that intrinsic neuronal variability on the level of spikes is reduced with increasing temperature. We use a detailed mathematical model including stochastic ion channel gating to shed light on the underlying biophysical mechanisms in auditory receptor neurons: because of a redistribution of channel-induced current noise toward higher frequencies and specifics of the temperature dependence of the membrane impedance, membrane potential noise is indeed reduced at higher temperatures. This finding holds under generic conditions and physiologically plausible assumptions on the temperature dependence of the channels' kinetics and peak conductances. We demonstrate that the identified mechanism also can explain the experimentally observed reduction of spike timing variability at higher temperatures. Copyright © 2015 the American Physiological Society.

A temperature rise reduces trial-to-trial variability of locust auditory neuron responses

PubMed Central

Schleimer, Jan-Hendrik; Schreiber, Susanne; Ronacher, Bernhard

2015-01-01

The neurophysiology of ectothermic animals, such as insects, is affected by environmental temperature, as their body temperature fluctuates with ambient conditions. Changes in temperature alter properties of neurons and, consequently, have an impact on the processing of information. Nevertheless, nervous system function is often maintained over a broad temperature range, exhibiting a surprising robustness to variations in temperature. A special problem arises for acoustically communicating insects, as in these animals mate recognition and mate localization typically rely on the decoding of fast amplitude modulations in calling and courtship songs. In the auditory periphery, however, temporal resolution is constrained by intrinsic neuronal noise. Such noise predominantly arises from the stochasticity of ion channel gating and potentially impairs the processing of sensory signals. On the basis of intracellular recordings of locust auditory neurons, we show that intrinsic neuronal variability on the level of spikes is reduced with increasing temperature. We use a detailed mathematical model including stochastic ion channel gating to shed light on the underlying biophysical mechanisms in auditory receptor neurons: because of a redistribution of channel-induced current noise toward higher frequencies and specifics of the temperature dependence of the membrane impedance, membrane potential noise is indeed reduced at higher temperatures. This finding holds under generic conditions and physiologically plausible assumptions on the temperature dependence of the channels' kinetics and peak conductances. We demonstrate that the identified mechanism also can explain the experimentally observed reduction of spike timing variability at higher temperatures. PMID:26041833

Time-dependent compressibility of poly (methyl methacrylate) (PMMA) : an experimental and molecular dynamics investigation

NASA Astrophysics Data System (ADS)

Sane, Sandeep Bhalchandra

This thesis contains three chapters, which describe different aspects of an investigation of the bulk response of Poly(Methyl Methacrylate) (PMMA). The first chapter describes the physical measurements by means of a Belcher/McKinney-type apparatus. Used earlier for the measurement of the bulk response of Poly(Vinyl Acetate), it was now adapted for making measurements at higher temperatures commensurate with the glass transition temperature of PMMA. The dynamic bulk compliance of PMMA was measured at atmospheric pressure over a wide range of temperatures and frequencies, from which the master curves for the bulk compliance were generated by means of the time-temperature superposition principle. It was found that the extent of the transition ranges for the bulk and shear response were comparable. Comparison of the shift factors for bulk and shear responses supports the idea that different molecular mechanisms contribute to shear and bulk deformations. The second chapter delineates molecular dynamics computations for the bulk response for a range of pressures and temperatures. The model(s) consisted of 2256 atoms formed into three polymer chains with fifty monomer units per chain per unit cell. The time scales accessed were limited to tens of pico seconds. It was found that, in addition to the typical energy minimization and temperature annealing cycles for establishing equilibrium models, it is advantageous to subject the model samples to a cycle of relatively large pressures (GPa-range) for improving the equilibrium state. On comparing the computations with the experimentally determined "glassy" behavior, one finds that, although the computations were limited to small samples in a physical sense, the primary limitation rests in the very short times (pico seconds). The molecular dynamics computations do not model the physically observed temperature sensitivity of PMMA, even if one employs a hypothetical time-temperature shift to account for the large difference in time scales between experiment and computation. The values computed by the molecular dynamics method do agree with the values measured at the coldest temperature and at the highest frequency of one kiloHertz. The third chapter draws on measurements of uniaxial, shear and Poisson response conducted previously in our laboratory. With the availability of four time or frequency-dependent material functions for the same material, the process of interconversion between different material functions was investigated. Computed material functions were evaluated against the direct experimental measurements and the limitations imposed on successful interconversion due to the experimental errors in the underlying physical data were explored. Differences were observed that are larger than the experimental errors would suggest.

Fluid inclusion and stable isotopes studies of epithermal gold-bearing veins in the SE Afar Rift (Djibouti)

NASA Astrophysics Data System (ADS)

Moussa, N.; Boiron, M. C.; Grassineau, N.; Fouquet, Y.; Le Gall, B.; Mohamed, J.

2015-12-01

The Afar rift results from the interaction of a number of actively-propagating tectono-magmatic axes. Recent field investigations in the SE Afar rift have emphasized the importance of hydrothermal system in rift-related volcanic complexes. Mineralization occur as gold-silver bearing veins and are associated with felsic volcanism. Late carbonate veins barren of sulfides and gold are common. The morphologies and textures of quartz show crustiform colloform banding, massive and breccias. Microthermometric measurements were made on quartz-hosted two phases (liquid + vapor) inclusions; mean homogenization temperature range from 150°C to 340°C and ice-melting temperatures range from -0.2° to 1.6°C indicating that inclusion solutions are dilute and contain 0.35 to 2.7 equivalent wt. % NaCl. Furthermore, δ18O and δ13C values from calcite range from 3.7 to 26.6 ‰ and -7.5 to 0.3‰, respectively. The presence of platy calcite and adularia indicate that boiling condition existed. This study shows that precious-metal deposition mainly occurred from hydrothermal fluids at 200°C at around 300 and 450 m below the present-day surface in a typical low-sulphidation epithermal environment.

Spatially heterogeneous impact of climate change on small mammals of montane California

PubMed Central

Rowe, Kevin C.; Rowe, Karen M. C.; Tingley, Morgan W.; Koo, Michelle S.; Patton, James L.; Conroy, Chris J.; Perrine, John D.; Beissinger, Steven R.; Moritz, Craig

2015-01-01

Resurveys of historical collecting localities have revealed range shifts, primarily leading edge expansions, which have been attributed to global warming. However, there have been few spatially replicated community-scale resurveys testing whether species' responses are spatially consistent. Here we repeated early twentieth century surveys of small mammals along elevational gradients in northern, central and southern regions of montane California. Of the 34 species we analysed, 25 shifted their ranges upslope or downslope in at least one region. However, two-thirds of ranges in the three regions remained stable at one or both elevational limits and none of the 22 species found in all three regions shifted both their upper and lower limits in the same direction in all regions. When shifts occurred, high-elevation species typically contracted their lower limits upslope, whereas low-elevation species had heterogeneous responses. For high-elevation species, site-specific change in temperature better predicted the direction of shifts than change in precipitation, whereas the direction of shifts by low-elevation species was unpredictable by temperature or precipitation. While our results support previous findings of primarily upslope shifts in montane species, they also highlight the degree to which the responses of individual species vary across geographically replicated landscapes. PMID:25621330

Monitoring the Near-infrared Volcanic Flux from Io's Jupiter-facing Hemisphere from Fan Mountain Observatory

NASA Astrophysics Data System (ADS)

Skrutskie, Michael F.; Nelson, Matthew J.; Schmidt, Carl

2016-10-01

Fan Mountain Observatory, near Charlottesville, Virginia, is a dark-sky site that supports a number of telescopes including a 31-inch reflecting telescope equipped with a 1024x1024 HgCdTe 1-2.5 um (YJHK) imager. Reflected sunlight ordinarily overwhelms Io's comparatively weak K-band (2.0-2.4 um) volcanic emission in unresolved observations, however when Io is eclipsed in Jupiter's shadow even a small infrared-equipped telescope can detect Io's volcanic emission. The Fan Mountain Infrared Camera observed Io in eclipse at regular intervals, typically weekly, during the few months before and after Jupiter's March 2016 opposition. When in eclipse Io's Jupiter-facing hemisphere is oriented toward Earth with sub-Earth longitudes at the time of observation ranging from 345 - 360 degrees (pre-opposition) to 0 - 15 degrees (post-opposition). A K-band filter (2.04-2.42 um) provided a bulk measurement of Io's volcanic flux weighted largely toward the 2.4 um end of this filter given the typical 500K color temperature of the volcanic emission. Most epochs also included observation in a narrowband filter centered at 2.12 um that, when combined with the broadband "long" wavelength measurement, provided a proxy for color temperature. The K-band flux of Io varied by more than 2 magnitudes during the 7 month observation interval. The [2.12 um - K-band] color of the emission strongly correlated with the K-band flux in the expected sense that the color temperature of the emission increased when Io's broadband volcanic flux was the greatest. One epoch of TripleSpec near-IR Io eclipse spectroscopy (0.90 - 2.45 um; R~3000) from the Apache Point Observatory 3.5-meter telescope provided ground truth for transforming the filter photometry into quantitative temperatures.

Quantification of CO2 generation in sedimentary basins through carbonate/clays reactions with uncertain thermodynamic parameters

NASA Astrophysics Data System (ADS)

Ceriotti, G.; Porta, G. M.; Geloni, C.; Dalla Rosa, M.; Guadagnini, A.

2017-09-01

We develop a methodological framework and mathematical formulation which yields estimates of the uncertainty associated with the amounts of CO2 generated by Carbonate-Clays Reactions (CCR) in large-scale subsurface systems to assist characterization of the main features of this geochemical process. Our approach couples a one-dimensional compaction model, providing the dynamics of the evolution of porosity, temperature and pressure along the vertical direction, with a chemical model able to quantify the partial pressure of CO2 resulting from minerals and pore water interaction. The modeling framework we propose allows (i) estimating the depth at which the source of gases is located and (ii) quantifying the amount of CO2 generated, based on the mineralogy of the sediments involved in the basin formation process. A distinctive objective of the study is the quantification of the way the uncertainty affecting chemical equilibrium constants propagates to model outputs, i.e., the flux of CO2. These parameters are considered as key sources of uncertainty in our modeling approach because temperature and pressure distributions associated with deep burial depths typically fall outside the range of validity of commonly employed geochemical databases and typically used geochemical software. We also analyze the impact of the relative abundancy of primary phases in the sediments on the activation of CCR processes. As a test bed, we consider a computational study where pressure and temperature conditions are representative of those observed in real sedimentary formation. Our results are conducive to the probabilistic assessment of (i) the characteristic pressure and temperature at which CCR leads to generation of CO2 in sedimentary systems, (ii) the order of magnitude of the CO2 generation rate that can be associated with CCR processes.

Mountain Climates on the Move: Implications for Past and Future Vegetation Shifts in the Northeastern United States

NASA Astrophysics Data System (ADS)

Wason, J. W., III; Dovciak, M.; Bevilacqua, E.

2015-12-01

Climate change in the northeastern United States is expected to shift climatic (temperature) envelopes for spruce-fir forests upslope and northward decreasing their area in the region by 2100. Coarse scale landscape models however, may not incorporate heterogeneity in climatic conditions in mountains that can create climatic refugia for species in high-elevation spruce-fir forests. To determine spatial and temporal trends in climate of mountain spruce-fir forests we measured microclimate at 98 forest plots in 2012 and 2013 on 12 mountains in New York, Vermont, New Hampshire, and Maine. By linking regional climate trends with our spatial climate data we calculated elevational shifts in temperature envelopes during the last 50 years. Additionally we linked our spatial dataset to a range of future climate conditions for 2100 based on Representative Concentration Pathways (1 to 5°C warming). We hypothesized that climates have already changed to an extent that spruce-fir forests should begin to respond and that future climate conditions may shift suitable habitat for spruce-fir forests beyond their current range. We found that regional climate change over the last 50 years has resulted in warming of 0.66 and 1.62°C for average annual daily maximum (Tmax) and minimum (Tmin) temperatures in the region. When linked to our spatial microclimate model, this warming results in a 100 (Tmax) and 312m (Tmin) upslope shift in temperature envelopes. Future climate projections suggest that by 2100 Tmax may shift upslope between 152 and 758m for the 1 and 5°C scenarios respectively, while Tmin may shift upslope between 192 and 962m. Spruce-fir forests typically occupy an elevation range of ~500m suggesting that the climate experienced in these forests 50 years ago may not be found within their elevation range by 2100. These results are discussed in the context of responses of tree populations and growth rates observed along the elevation gradients of northeastern United States.

Desorption of a methamphetamine surrogate from wallboard under remediation conditions

NASA Astrophysics Data System (ADS)

Poppendieck, Dustin; Morrison, Glenn; Corsi, Richard

2015-04-01

Thousands of homes in the United States are found to be contaminated with methamphetamine each year. Buildings used to produce illicit methamphetamine are typically remediated by removing soft furnishings and stained materials, cleaning and sometimes encapsulating surfaces using paint. Methamphetamine that has penetrated into paint films, wood and other permanent materials can be slowly released back into the building air over time, exposing future occupants and re-contaminating furnishings. The objective of this study was to determine the efficacy of two wallboard remediation techniques for homes contaminated with methamphetamine: 1) enhancing desorption by elevating temperature and relative humidity while ventilating the interior space, and 2) painting over affected wallboard to seal the methamphetamine in place. The emission of a methamphetamine surrogate, N-isopropylbenzylamine (NIBA), from pre-dosed wallboard chambers over 20 days at 32 °C and two values of relative humidity were studied. Emission rates from wallboard after 15 days at 32 °C ranged from 35 to 1400 μg h-1 m-2. Less than 22% of the NIBA was removed from the chambers over three weeks. Results indicate that elevating temperatures during remediation and latex painting of impacted wallboard will not significantly reduce freebase methamphetamine emissions from wallboard. Raising the relative humidity from 27% to 49% increased the emission rates by a factor of 1.4. A steady-state model of a typical home using the emission rates from this study and typical residential building parameters and conditions shows that adult inhalation reference doses for methamphetamine will be reached when approximately 1 g of methamphetamine is present in the wallboard of a house.

Aerodynamic drag characterization and deposition studies of irregular particles. Part 3: Analysis of flow and temperature field inside the Combustion Deposition Entrained Reactor (CDER)

NASA Astrophysics Data System (ADS)

Celik, I.; Katragadda, S.; Nagarajan, R.

1990-01-01

An experimental and numerical analysis was performed of the temperature and flow field involved in co-axial, confined, non-reacting heated jets in a drop tube reactor. An electrically heated 2-inch (50.8 mm) diameter drop tube reactor was utilized to study the jet characteristics. Profiles of gas temperature, typically in the range of 800 to 1600 K were measured in the mixing zone of the jet with a K-Type thermocouple. Measured temperatures were corrected for conduction, convection, and radiation heat losses. Because of limited access to the mixing zone, characterization of the flow field at high temperatures with laser Doppler or hot wire anemometry were impractical. A computer program which solves the full equations of motion and energy was employed to simulate the temperature and flow fields. The location of the recirculation region, the flow regimes, and the mixing phenomena were studied. The wall heating, laminar and turbulent flow regimes were considered in the simulations. The predictions are in fairly good agreement with the corrected temperature measurements provided that the flow is turbulent. The results of this study demonstrate how a numerical method and measurement can be used together to analyze the flow conditions inside a reactor which has limited access because of very high temperatures.

Glasslike dynamical behavior of the plastocyanin hydration water

NASA Astrophysics Data System (ADS)

Bizzarri, Anna Rita; Paciaroni, Alessandro; Cannistraro, Salvatore

2000-09-01

The dynamical behavior of water around plastocyanin has been investigated in a wide temperature range by molecular dynamics simulation. The mean square displacements of water oxygen atoms show, at long times, a tα trend for all temperatures. Below 150 K, α is constant and equal to 1; at higher temperatures it drops to a value significantly smaller than 1, and thereafter decreases with increasing temperature. The occurrence of such an anomalous diffusion matches the onset of the dynamical transition observed in the protein. The intermediate scattering function of water is characterized, at high temperature, by a stretched exponential decay evolving, at low temperature, toward a two step relaxation behavior, which becomes more evident on increasing the exchanged wave vector q. Both the mean square displacements and the intermediate scattering functions show, beyond the ballistic regime, a plateau, which progressively extends for longer times as long as the temperature is lowered, such behavior reflecting trapping of water molecules within a cage formed by the nearest neighbors. At low temperature, a low frequency broad inelastic peak is observed in the dynamical structure factor of hydration water; such an excess of vibrational modes being reminiscent of the boson peak, characteristic of disordered, amorphous systems. All these features, which are typical of complex systems, can be traced back to the glassy character of the hydration water and suggest a dynamical coupling occurring at the macromolecule-solvent interface.

CMOS compatible thin-film ALD tungsten nanoelectromechanical devices

NASA Astrophysics Data System (ADS)

Davidson, Bradley Darren

This research focuses on the development of a novel, low-temperature, CMOS compatible, atomic-layer-deposition (ALD) enabled NEMS fabrication process for the development of ALD Tungsten (WALD) NEMS devices. The devices are intended for use in CMOS/NEMS hybrid systems, and NEMS based micro-processors/controllers capable of reliable operation in harsh environments not accessible to standard CMOS technologies. The majority of NEMS switches/devices to date have been based on carbon-nano-tube (CNT) designs. The devices consume little power during actuation, and as expected, have demonstrated actuation voltages much smaller than MEMS switches. Unfortunately, NEMS CNT switches are not typically CMOS integrable due to the high temperatures required for their growth, and their fabrication typically results in extremely low and unpredictable yields. Thin-film NEMS devices offer great advantages over reported CNT devices for several reasons, including: higher fabrication yields, low-temperature (CMOS compatible) deposition techniques like ALD, and increased control over design parameters/device performance metrics, i.e., device geometry. Furthermore, top-down, thin-film, nano-fabrication techniques are better capable of producing complicated device geometries than CNT based processes, enabling the design and development of multi-terminal switches well-suited for low-power hybrid NEMS/CMOS systems as well as electromechanical transistors and logic devices for use in temperature/radiation hard computing architectures. In this work several novel, low-temperature, CMOS compatible fabrication technologies, employing WALD as a structural layer for MEMS or NEMS devices, were developed. The technologies developed are top-down nano-scale fabrication processes based on traditional micro-machining techniques commonly used in the fabrication of MEMS devices. Using these processes a variety of novel WALD NEMS devices have been successfully fabricated and characterized. Using two different WALD fabrication technologies two generations of 2-terminal WALD NEMS switches have been developed. These devices have functional gap heights of 30-50 nm, and actuation voltages typically ranging from 3--5 Volts. Via the extension of a two terminal WALD technology novel 3-terminal WALD NEMS devices were developed. These devices have actuation voltages ranging from 1.5--3 Volts, reliabilities in excess of 2 million cycles, and have been designed to be the fundamental building blocks for WALD NEMS complementary inverters. Through the development of these devices several advancements in the modeling and design of thin-film NEMS devices were achieved. A new model was developed to better characterize pre-actuation currents commonly measured for NEMS switches with nano-scale gate-to-source gap heights. The developed model is an extension of the standard field-emission model and considers the electromechanical response, and electric field effects specific to thin-film NEMS switches. Finally, a multi-physics FEM/FD based model was developed to simulate the dynamic behavior of 2 or 3-terminal electrostatically actuated devices whose electrostatic domains have an aspect ratio on the order of 10-3. The model uses a faux-Lagrangian finite difference method to solve Laplaces equation in a quasi-statatically deforming domain. This model allows for the numerical characterization and design of thin-film NEMS devices not feasible using typical non-specialized BEM/FEM based software. Using this model several novel and feasible designs for fixed-fixed 3-terminal WALD NEMS switches capable for the construction of complementary inverters were discovered.

Micro solid oxide fuel cells: a new generation of micro-power sources for portable applications

NASA Astrophysics Data System (ADS)

Chiabrera, Francesco; Garbayo, Iñigo; Alayo, Nerea; Tarancón, Albert

2017-06-01

Portable electronic devices are already an indispensable part of our daily life; and their increasing number and demand for higher performance is becoming a challenge for the research community. In particular, a major concern is the way to efficiently power these energy-demanding devices, assuring long grid independency with high efficiency, sustainability and cheap production. In this context, technologies beyond Li-ion are receiving increasing attention, among which the development of micro solid oxide fuel cells (μSOFC) stands out. In particular, μSOFC provides a high energy density, high efficiency and opens the possibility to the use of different fuels, such as hydrocarbons. Yet, its high operating temperature has typically hindered its application as miniaturized portable device. Recent advances have however set a completely new range of lower operating temperatures, i.e. 350-450°C, as compared to the typical <900°C needed for classical bulk SOFC systems. In this work, a comprehensive review of the status of the technology is presented. The main achievements, as well as the most important challenges still pending are discussed, regarding (i.) the cell design and microfabrication, and (ii.) the integration of functional electrolyte and electrode materials. To conclude, the different strategies foreseen for a wide deployment of the technology as new portable power source are underlined.

Use of a liquid-crystal, heater-element composite for quantitative, high-resolution heat transfer coefficients on a turbine airfoil, including turbulence and surface roughness effects

NASA Astrophysics Data System (ADS)

Hippensteele, Steven A.; Russell, Louis M.; Torres, Felix J.

1987-05-01

Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at roon temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

Use of a liquid-crystal and heater-element composite for quantitative, high-resolution heat-transfer coefficients on a turbine airfoil including turbulence and surface-roughness effects

NASA Astrophysics Data System (ADS)

Hippensteele, S. A.; Russell, L. M.; Torres, F. J.

Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

Use of a liquid-crystal, heater-element composite for quantitative, high-resolution heat transfer coefficients on a turbine airfoil, including turbulence and surface roughness effects

NASA Technical Reports Server (NTRS)

Hippensteele, Steven A.; Russell, Louis M.; Torres, Felix J.

1987-01-01

Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at roon temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

On the design of capacitive sensors using flexible electrodes for multipurpose measurements

NASA Astrophysics Data System (ADS)

Thibault, Pierre; Diribarne, Pantxo; Fournier, Thierry; Perraud, Sylvain; Puech, Laurent; Wolf, P.-Etienne; Rousset, Bernard; Vallcorba, Roser

2007-04-01

This article evaluates the potential of capacitive measurements using flexible electrodes to access various physical quantities. These electrodes are made of a thin metallic film, typical thickness 0.2 μm, evaporated on a plastic substrate. Their large flexibility enables them to be mounted in complex geometries such as curved surfaces. In the configuration of planar condensers, using a very sensitive commercial capacitive bridge and a three-terminal measurement method, several measurements are presented. A relative resolution of 10-8 for the thermal expansion of samples is obtained at low temperature in a differential configuration. The same technique adopted for pressure gauge measurements at low temperature led to a typical 0.1 Pa resolution over a dynamic range of 104 Pa. In the configuration of interleaved electrodes, condensers have been used to measure wetting by either bulk liquid helium or by thin continuous helium films in a cylindrical pipe. Both experimental and numerical evidence is provided, showing that the close proximity of a reference ground potential significantly increases the relative sensitivity to fluid wetting. Further, interleaved electrodes can be used to access both the area that is covered by a liquid film but also to determine the thickness of this film, provided it is comparable to the periodicity of the electrode pattern.

Growth Stresses in Thermally Grown Oxides on Nickel-Based Single-Crystal Alloys

NASA Astrophysics Data System (ADS)

Rettberg, Luke H.; Laux, Britta; He, Ming Y.; Hovis, David; Heuer, Arthur H.; Pollock, Tresa M.

2016-03-01

Growth stresses that develop in α-Al2O3 scale that form during isothermal oxidation of three Ni-based single crystal alloys have been studied to elucidate their role in coating and substrate degradation at elevated temperatures. Piezospectroscopy measurements at room temperature indicate large room temperature compressive stresses in the oxides formed at 1255 K or 1366 K (982 °C or 1093 °C) on the alloys, ranging from a high of 4.8 GPa for René N4 at 1366 K (1093 °C) to a low of 3.8 GPa for René N5 at 1255 K (982 °C). Finite element modeling of each of these systems to account for differences in coefficients of thermal expansion of the oxide and substrate indicates growth strains in the range from 0.21 to 0.44 pct at the oxidation temperature, which is an order of magnitude higher than the growth strains measured in the oxides on intermetallic coatings that are typically applied to these superalloys. The magnitudes of the growth strains do not scale with the parabolic oxidation rate constants measured for the alloys. Significant spatial inhomogeneities in the growth stresses were observed, due to (i) the presence of dendritic segregation and (ii) large carbides in the material that locally disrupts the structure of the oxide scale. The implications of these observations for failure during cyclic oxidation, fatigue cycling, and alloy design are considered.

A review of high magnetic moment thin films for microscale and nanotechnology applications

DOE PAGES

Scheunert, Gunther; Heinonen, O.; Hardeman, R.; ...

2016-02-17

Here, the creation of large magnetic fields is a necessary component in many technologies, ranging from magnetic resonance imaging, electric motors and generators, and magnetic hard disk drives in information storage. This is typically done by inserting a ferromagnetic pole piece with a large magnetisation density M S in a solenoid. In addition to large M S, it is usually required or desired that the ferromagnet is magnetically soft and has a Curie temperature well above the operating temperature of the device. A variety of ferromagnetic materials are currently in use, ranging from FeCo alloys in, for example, hard diskmore » drives, to rare earth metals operating at cryogenic temperatures in superconducting solenoids. These latter can exceed the limit on M S for transition metal alloys given by the Slater-Pauling curve. This article reviews different materials and concepts in use or proposed for technological applications that require a large M S, with an emphasis on nanoscale material systems, such as thin and ultra-thin films. Attention is also paid to other requirements or properties, such as the Curie temperature and magnetic softness. In a final summary, we evaluate the actual applicability of the discussed materials for use as pole tips in electromagnets, in particular, in nanoscale magnetic hard disk drive read-write heads; the technological advancement of the latter has been a very strong driving force in the development of the field of nanomagnetism.« less

Nonlinear dynamics of the CAM circadian rhythm in response to environmental forcing.

PubMed

Hartzell, Samantha; Bartlett, Mark S; Virgin, Lawrence; Porporato, Amilcare

2015-03-07

Crassulacean acid metabolism (CAM) photosynthesis functions as an endogenous circadian rhythm coupled to external environmental forcings of energy and water availability. This paper explores the nonlinear dynamics of a new CAM photosynthesis model (Bartlett et al., 2014) and investigates the responses of CAM plant carbon assimilation to different combinations of environmental conditions. The CAM model (Bartlett et al., 2014) consists of a Calvin cycle typical of C3 plants coupled to an oscillator of the type employed in the Van der Pol and FitzHugh-Nagumo systems. This coupled system is a function of environmental variables including leaf temperature, leaf moisture potential, and irradiance. Here, we explore the qualitative response of the system and the expected carbon assimilation under constant and periodically forced environmental conditions. The model results show how the diurnal evolution of these variables entrains the CAM cycle with prevailing environmental conditions. While constant environmental conditions generate either steady-state or periodically oscillating responses in malic acid uptake and release, forcing the CAM system with periodic daily fluctuations in light exposure and leaf temperature results in quasi-periodicity and possible chaos for certain ranges of these variables. This analysis is a first step in quantifying changes in CAM plant productivity with variables such as the mean temperature, daily temperature range, irradiance, and leaf moisture potential. Results may also be used to inform model parametrization based on the observed fluctuating regime. Copyright © 2014 Elsevier Ltd. All rights reserved.

Development of a sensor for temperature and water concentration in combustion gases using a single tunable diode laser

NASA Astrophysics Data System (ADS)

Zhou, Xin; Liu, Xiang; Jeffries, Jay B.; Hanson, R. K.

2003-08-01

The water vapour spectrum in the 1-2 µm near-infrared region is systematically analysed to find the best absorption transitions for sensitive measurement of H2O concentration and temperature in combustion environments using a single tunable diode laser with typical distributed feedback single-mode scanning range (1 cm-1). The use of a single laser, even with relatively narrow tuning range, can offer distinct advantages over wavelength-multiplexing techniques. The strategy and spectroscopic criteria for selecting optimum wavelength regions and absorption line combinations are discussed. It should be stressed that no single figure of merit can be derived to simplify the selection process, and the optimum line pair should be chosen case by case. Our investigation reveals that the 1.8 µm spectral region is especially promising, and we have identified 10 of the best water line pairs in this spectral region for temperature measurements in flames. Based on these findings, a pair of H2O transitions near 1.8 µm was targeted for the design and development of an initial single-laser sensor for simultaneously measuring H2O concentration and temperature in atmospheric-pressure flames. As part of the sensor development effort, fundamental spectroscopic parameters including the line strength, line-centre frequency and lower state energies of the probed transitions were measured experimentally to improve the current databases. We conclude with demonstration results in a steady and a forced atmospheric-pressure laboratory combustor.

ACBC to Balcite: Bioinspired Synthesis of a Highly Substituted High-Temperature Phase from an Amorphous Precursor

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

Whittaker, Michael L.; Joester, Derk

2017-04-28

Energy-efficient synthesis of materials locked in compositional and structural states far from equilibrium remains a challenging goal, yet biomineralizing organisms routinely assemble such materials with sophisticated designs and advanced functional properties, often using amorphous precursors. However, incorporation of organics limits the useful temperature range of these materials. Herein, the bioinspired synthesis of a highly supersaturated calcite (Ca0.5Ba0.5CO3) called balcite is reported, at mild conditions and using an amorphous calcium–barium carbonate (ACBC) (Ca1- x Ba x CO3·1.2H2O) precursor. Balcite not only contains 50 times more barium than the solubility limit in calcite but also displays the rotational disorder on carbonate sitesmore » that is typical for high-temperature calcite. It is significantly harder (30%) and less stiff than calcite, and retains these properties after heating to elevated temperatures. Analysis of balcite local order suggests that it may require the formation of the ACBC precursor and could therefore be an example of nonclassical nucleation. These findings demonstrate that amorphous precursor pathways are powerfully enabling and provide unprecedented access to materials far from equilibrium, including high-temperature modifications by room-temperature synthesis.« less

High Temperature Deformation of Twin-Roll Cast Al-Mn-Based Alloys after Equal Channel Angular Pressing.

PubMed

Málek, Přemysl; Šlapáková Poková, Michaela; Cieslar, Miroslav

2015-11-12

Twin roll cast Al-Mn- and Al-Mn-Zr-based alloys were subjected to four passes of equal channel angular pressing. The resulting grain size of 400 nm contributes to a significant strengthening at room temperature. This microstructure is not fully stable at elevated temperatures and recrystallization and vast grain growth occur at temperatures between 350 and 450 °C. The onset of these microstructure changes depends on chemical and phase composition. Better stability is observed in the Al-Mn-Zr-based alloy. High temperature tensile tests reveal that equal channel angular pressing results in a softening of all studied materials at high temperatures. This can be explained by an active role of grain boundaries in the deformation process. The maximum values of ductility and strain rate sensitivity parameter m found in the Al-Mn-Zr-based alloy are below the bottom limit of superplasticity (155%, m = 0.25). However, some features typical for superplastic behavior were observed-the strain rate dependence of the parameter m , the strengthening with increasing grain size, and the fracture by diffuse necking. Grain boundary sliding is believed to contribute partially to the overall strain in specimens where the grain size remained in the microcrystalline range.

Isothermal Time-Temperature-Precipitation Diagram for an Aluminum Alloy 6005A by In Situ DSC Experiments

PubMed Central

Milkereit, Benjamin; Giersberg, Lydia; Kessler, Olaf; Schick, Christoph

2014-01-01

Time-temperature-precipitation (TTP) diagrams deliver important material data, such as temperature and time ranges critical for precipitation during the quenching step of the age hardening procedure. Although the quenching step is continuous, isothermal TTP diagrams are often applied. Together with a so-called Quench Factor Analysis, they can be used to describe very different cooling paths. Typically, these diagrams are constructed based on mechanical properties or microstructures after an interrupted quenching, i.e., ex situ analyses. In recent years, an in situ calorimetric method to record continuous cooling precipitation diagrams of aluminum alloys has been developed to the application level by our group. This method has now been transferred to isothermal experiments, in which the whole heat treatment cycle was performed in a differential scanning calorimeter. The Al-Mg-Si-wrought alloy 6005A was investigated. Solution annealing at 540 °C and overcritical quenching to several temperatures between 450 °C and 250 °C were followed by isothermal soaking. Based on the heat flow curves during isothermal soaking, TTP diagrams were determined. An appropriate evaluation method has been developed. It was found that three different precipitation reactions in characteristic temperature intervals exist. Some of the low temperature reactions are not accessible in continuous cooling experiments and require isothermal studies. PMID:28788587

Thermal overload characteristics of extruded dielectric cables: Final report

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

Dima, A.; Katz, C.; Eager, G.S. Jr.

1988-06-01

This report addresses characteristics of thermoset extruded dielectric power cables in the 15--35 kV class, operated under thermal overload conditions. It presents a methodical study to determine the suitability of extruded type cable for operation at elevated temperatures. The results provide utilities with knowledge on the behavior of thermoset insulated cables at temperatures in the 130 to 175/degree/C conductor temperature range. Present industry specifications recommend a maximum emergency conductor temperature of 130/degree/C. The suitability of this temperature and the time it is to be maintained had been questioned. The present report indicates that crosslinked polyethylene and ethylene propylene insulated cable,more » both new and service aged, are suitable for emergency operation during extended periods at 130/degree/C. When these cables are provided with polyvinyl chloride jackets, long term exposure to temperatures greater than 130/degree/C can adversely affect the integrity of the jacket. Investigations on new cables were performed on short samples in ovens and on long samples in simulated ducts in the laboratory and in a typical utility duct bank. Investigations on cables recovered from service were performed in the laboratory with the cables installed in simulated ducts. 10 refs., 49 figs., 73 tabs.« less

Phase behavior and dynamics of a micelle-forming triblock copolymer system

NASA Astrophysics Data System (ADS)

Mohan, P. Harsha; Bandyopadhyay, Ranjini

2008-04-01

Synperonic F-108 (generic name, “pluronic”) is a micelle forming triblock copolymer of type ABA , where A is polyethylene oxide (PEO) and B is polypropylene oxide (PPO). At high temperatures, the hydrophobicity of the PPO chains increase, and the pluronic molecules, when dissolved in an aqueous medium, self-associate into spherical micelles with dense PPO cores and hydrated PEO coronas. At appropriately high concentrations, these micelles arrange in a face centered cubic lattice to show inverse crystallization, with the samples exhibiting high-temperature crystalline and low-temperature fluidlike phases. By studying the evolution of the elastic and viscous moduli as temperature is increased at a fixed rate, we construct the concentration-temperature phase diagram of Synperonic F-108. For a certain range of temperatures and at appropriate sample concentrations, we observe a predominantly elastic response. Oscillatory strain amplitude sweep measurements on these samples show pronounced peaks in the loss moduli, a typical feature of soft solids. The soft solidlike nature of these materials is further demonstrated by measuring their frequency-dependent mechanical moduli. The storage moduli are significantly larger than the loss moduli and are almost independent of the applied angular frequency. Finally, we perform strain rate frequency superposition experiments to measure the slow relaxation dynamics of this soft solid.

Isothermal Time-Temperature-Precipitation Diagram for an Aluminum Alloy 6005A by In Situ DSC Experiments.

PubMed

Milkereit, Benjamin; Giersberg, Lydia; Kessler, Olaf; Schick, Christoph

2014-03-28

Time-temperature-precipitation (TTP) diagrams deliver important material data, such as temperature and time ranges critical for precipitation during the quenching step of the age hardening procedure. Although the quenching step is continuous, isothermal TTP diagrams are often applied. Together with a so-called Quench Factor Analysis, they can be used to describe very different cooling paths. Typically, these diagrams are constructed based on mechanical properties or microstructures after an interrupted quenching, i.e ., ex situ analyses. In recent years, an in situ calorimetric method to record continuous cooling precipitation diagrams of aluminum alloys has been developed to the application level by our group. This method has now been transferred to isothermal experiments, in which the whole heat treatment cycle was performed in a differential scanning calorimeter. The Al-Mg-Si-wrought alloy 6005A was investigated. Solution annealing at 540 °C and overcritical quenching to several temperatures between 450 °C and 250 °C were followed by isothermal soaking. Based on the heat flow curves during isothermal soaking, TTP diagrams were determined. An appropriate evaluation method has been developed. It was found that three different precipitation reactions in characteristic temperature intervals exist. Some of the low temperature reactions are not accessible in continuous cooling experiments and require isothermal studies.

Below room temperature: How the photocatalytic activity of dense and mesoporous TiO2 coatings is affected

NASA Astrophysics Data System (ADS)

Cedillo-González, Erika Iveth; Riccò, Raffaele; Costacurta, Stefano; Siligardi, Cristina; Falcaro, Paolo

2018-03-01

Different parameters such as morphology, porosity, crystalline phase or doping agents affect the self-cleaning performance of photocatalytic TiO2-based coatings. However, also environmental conditions have been found to play a major role on the photocatalytic self-cleaning property. Substrate temperature is a significant environmental variable that can drastically affect this process. This variable becomes of great importance especially for outdoor applications: many self-cleaning photocatalytic materials have been designed to be exposed to outdoor environments and consequently, can be exposed to variable temperatures depending on the season of the year and the typical weather of the geographical zone. Thus, understanding the influence of the most common outdoor temperatures on the self-cleaning performance of TiO2-based coatings is essential for the fabrication of any kind of photocatalytic self-cleaning materials (fabricated by coating technology) that is expected to be subjected to outdoor environments. In this work, the photocatalytic activity was studied by Fourier Transformed Infrared (FTIR) Spectroscopy varying the temperature in the 0 to 30 °C range for dense and mesoporous TiO2 coatings. The temperature conditions at which these coatings present better performances were identified, providing a deeper insight for the practical application of TiO2-based self-cleaning coatings.

Evaluation of novel thermo-resistant Micractinium and Scenedesmus sp. for efficient biomass and lipid production under different temperature and nutrient regimes.

PubMed

Sonmez, Cagla; Elcin, Evrim; Akın, Dilan; Oktem, Huseyin Avni; Yucel, Meral

2016-07-01

Despite the vast interest in microalgae as feedstock for biodiesel production, relatively few studies examined their response to diurnal temperature fluctuation. Here, we describe biomass and lipid productivities and fatty acid profiles of thermo-resistant Micractinium sp. and Scenedesmus sp. grown in batch cultures in a laboratory set-up that mimics a typically warm summer day in Central Anatolia with a 16-h light temperature of 30°C and 8-h dark temperature of 16°C (30°C (day)/16°C (night)). Both strains can survive a temperature range of 10-50°C. We found the lipid productivities of Micractinium sp. and Scenedesmus sp. as 30/21mgL(-1)d(-1) and 6/7mgL(-1)d(-1), respectively during the 30°C (day)/16°C (night) cycle. Saturated fatty acid content increased with increasing temperature. Additionally, we cultured Micractinium sp. under Nitrogen (N) and Phosphorus (P) limiting conditions. Highest lipid productivity of 85.4±2mgL(-1)d(-1) was obtained under P-depletion during exponential growth phase. Oleic acid amount also increased eight fold during P-deplete. Copyright © 2016 Elsevier Ltd. All rights reserved.

High Temperature Deformation of Twin-Roll Cast Al-Mn-Based Alloys after Equal Channel Angular Pressing

PubMed Central

Málek, Přemysl; Šlapáková Poková, Michaela; Cieslar, Miroslav

2015-01-01

Twin roll cast Al-Mn- and Al-Mn-Zr-based alloys were subjected to four passes of equal channel angular pressing. The resulting grain size of 400 nm contributes to a significant strengthening at room temperature. This microstructure is not fully stable at elevated temperatures and recrystallization and vast grain growth occur at temperatures between 350 and 450 °C. The onset of these microstructure changes depends on chemical and phase composition. Better stability is observed in the Al-Mn-Zr-based alloy. High temperature tensile tests reveal that equal channel angular pressing results in a softening of all studied materials at high temperatures. This can be explained by an active role of grain boundaries in the deformation process. The maximum values of ductility and strain rate sensitivity parameter m found in the Al-Mn-Zr-based alloy are below the bottom limit of superplasticity (155%, m = 0.25). However, some features typical for superplastic behavior were observed—the strain rate dependence of the parameter m, the strengthening with increasing grain size, and the fracture by diffuse necking. Grain boundary sliding is believed to contribute partially to the overall strain in specimens where the grain size remained in the microcrystalline range. PMID:28793667

Properties of Martian Hematite at Meridiani Planum by Simultaneous Fitting of Mars Mossbauer Spectra

NASA Technical Reports Server (NTRS)

Agresti, D. G.; Fleischer, I.; Klingelhoefer, G.; Morris, R. V.

2010-01-01

Mossbauer spectrometers [1] on the two Mars Exploration Rovers (MERs) have been making measurements of surface rocks and soils since January 2004, recording spectra in 10-K-wide temperature bins ranging from 180 K to 290 K. Initial analyses focused on modeling individual spectra directly as acquired or, to increase statistical quality, as sums of single-rock or soil spectra over temperature or as sums over similar rock or soil type [2, 3]. Recently, we have begun to apply simultaneous fitting procedures [4] to Mars Mossbauer data [5-7]. During simultaneous fitting (simfitting), many spectra are modeled similarly and fit together to a single convergence criterion. A satisfactory simfit with parameter values consistent among all spectra is more likely than many single-spectrum fits of the same data because fitting parameters are shared among multiple spectra in the simfit. Consequently, the number of variable parameters, as well as the correlations among them, is greatly reduced. Here we focus on applications of simfitting to interpret the hematite signature in Moessbauer spectra acquired at Meridiani Planum, results of which were reported in [7]. The Spectra. We simfit two sets of spectra with large hematite content [7]: 1) 60 rock outcrop spectra from Eagle Crater; and 2) 46 spectra of spherule-rich lag deposits (Table 1). Spectra of 10 different targets acquired at several distinct temperatures are included in each simfit set. In the table, each Sol (martian day) represents a different target, NS is the number of spectra for a given sol, and NT is the number of spectra for a given temperature. The spectra are indexed to facilitate definition of parameter relations and constraints. An example spectrum is shown in Figure 1, together with a typical fitting model. Results. We have shown that simultaneous fitting is effective in analyzing a large set of related MER Mossbauer spectra. By using appropriate constraints, we derive target-specific quantities and the temperature dependence of certain parameters. By examining different fitting models, we demonstrate an improved fit for martian hematite modeled with two sextets rather than as a single sextet, and show that outcrop and spherule hematite are distinct. For outcrop, the weaker sextet indicates a Morin transition typical of well-crystallized and chemically pure hematite, while most of the outcrop hematite remains in a weakly ferromagnetic state at all temperatures. For spherule spectra, both sextets are consistent with weakly ferromagnetic hematite with no Morin transition. For both hematites, there is evidence for a range of particle sizes.

Performance of a plastic-wrapped composting system for biosecure emergency disposal of disease-related swine mortalities.

PubMed

Glanville, Thomas D; Ahn, Heekwon; Akdeniz, Neslihan; Crawford, Benjamin P; Koziel, Jacek A

2016-02-01

A passively-ventilated plastic-wrapped composting system initially developed for biosecure disposal of poultry mortalities caused by avian influenza was adapted and tested to assess its potential as an emergency disposal option for disease-related swine mortalities. Fresh air was supplied through perforated plastic tubing routed through the base of the compost pile. The combined air inlet and top vent area is ⩽∼1% of the gas exchange surface of a conventional uncovered windrow. Parameters evaluated included: (1) spatial and temporal variations in matrix moisture content (m.c.), leachate production, and matrix O2 concentrations; (2) extent of soft tissue decomposition; and (3) internal temperature and the success rate in achieving USEPA time/temperature (T) criteria for pathogen reduction. Six envelope materials (wood shavings, corn silage, ground cornstalks, ground oat straw, ground soybean straw, or ground alfalfa hay) and two initial m.c.'s (15-30% w.b. for materials stored indoors, and 45-65% w.b. to simulate materials exposed to precipitation) were tested to determine their effect on performance parameters (1-3). Results of triple-replicated field trials showed that the composting system did not accumulate moisture despite the 150kg carcass water load (65% of 225kg total carcass mass) released during decomposition. Mean compost m.c. in the carcass layer declined by ∼7 percentage points during 8-week trials, and a leachate accumulation was rare. Matrix O2 concentrations for all materials other than silage were ⩾10% using the equivalent of 2m inlet/vent spacing. In silage O2 dropped below 5% in some cases even when 0.5m inlet/vent spacing was used. Eight week soft tissue decomposition ranged from 87% in cornstalks to 72% in silage. Success rates for achievement of USEPA Class B time/temperature criteria ranged from 91% for silage to 33-57% for other materials. Companion laboratory biodegradation studies suggest that Class B success rates can be improved by slightly increasing envelope material m.c. Moistening initially dry (15% m.c.) envelope materials to 35% m.c. nearly doubled their heat production potential, boosting it to levels ⩾silage. The 'contradictory' silage test results showing high temperatures paired with slow soft tissue degradation are likely due to this material's high density, low gas permeability and low water vapor loss. While slow decomposition typically suggests low microbial activity and heat production, it does not rule out high internal temperatures if the heat produced is conserved. Occasional short-term odor releases during the first 2weeks of composting were associated with top-to-bottom gas flow which is contrary to the typical bottom-to-top flow typically observed in conventional compost piles. In cases where biosecurity concerns are paramount, results of this study show the plastic-wrapped passively-ventilated composting method to have good potential for above-ground swine mortality disposal. Copyright © 2015 Elsevier Ltd. All rights reserved.

Initial fuel temperature effects on burning rate of pool fire.

PubMed

Chen, Bing; Lu, Shou-Xiang; Li, Chang-Hai; Kang, Quan-Sheng; Lecoustre, Vivien

2011-04-15

The influence of the initial fuel temperature on the burning behavior of n-heptane pool fire was experimentally studied at the State Key Laboratory of Fire Science (SKLFS) large test hall. Circular pool fires with diameters of 100mm, 141 mm, and 200 mm were considered with initial fuel temperatures ranging from 290 K to 363 K. Burning rate and temperature distributions in fuel and vessel wall were recorded during the combustion. The burning rate exhibited five typical stages: initial development, steady burning, transition, bulk boiling burning, and decay. The burning rate during the steady burning stage was observed to be relatively independent of the initial fuel temperature. In contrast, the burning rate of the bulk boiling burning stage increases with increased initial fuel temperature. It was also observed that increased initial fuel temperature decreases the duration of steady burning stage. When the initial temperature approaches the boiling point, the steady burning stage nearly disappears and the burning rate moves directly from the initial development stage to the transition stage. The fuel surface temperature increases to its boiling point at the steady burning stage, shortly after ignition, and the bulk liquid reaches boiling temperature at the bulk boiling burning stage. No distinguished cold zone is formed in the fuel bed. However, boiling zone is observed and the thickness increases to its maximum value when the bulk boiling phenomena occurs. Copyright © 2011 Elsevier B.V. All rights reserved.

The influence of hypoxia on the thermal sensitivity of skin colouration in the bearded dragon, Pogona vitticeps.

PubMed

de Velasco, Jesus Barraza; Tattersall, Glenn J

2008-09-01

One physiological mechanism used by reptiles to remain within thermal optima is their ability to reversibly alter skin colour, imparting changes in overall reflectance, and influencing the rate of heat gain from incident radiation. The ability to lighten or darken their skin is caused by the movement of pigment within the dermal chromatophore cells. Additionally, lizards, as ectotherms, significantly lower their preferred body temperatures when experiencing stressors such as hypoxia. This decrease in preferred temperature has been proposed to be the result of a downward adjustment of the thermal set-point, the temperature around which the body temperature is typically defended. We tested the hypothesis that lightening of the skin in lizards would be modified by hypoxia in a manner consistent with the known reduction in preferred temperatures. Skin colouration values of the dorsal skin of bearded dragons were analysed at three different levels of oxygen (20.8, 9.9 and 4.9 kPa) and at temperatures spanning the preferred temperature range (30, 32, 34, 36, 38 and 40 C). Hypoxic lizards lightened their skin at lower ambient temperatures more than normoxic ones, and in an oxygen-dependent fashion. The orchestrated adjustment of skin reflectance suggests that this physiological trait is being regulated at a new and lower set-point. Evidence from this study demonstrates that skin colouration plays a role in body temperature regulation and that the reduction in temperature set-point so prevalent in hypoxia is also manifested in this physiological trait.

Effects of hot, humid weather on milk temperature, dry matter intake, and milk yield of lactating dairy cows.

PubMed

West, J W; Mullinix, B G; Bernard, J K

2003-01-01

Lactating cows were exposed to moderate and hot, humid weather to determine the effect of increasing ambient temperature, relative humidity, or temperature-humidity index (THI) on intake, milk yield, and milk temperature. Minimum and maximum temperatures averaged 17.9 and 29.5 degrees C (cool period) and 22.5 and 34.4 degrees C (hot period), and minimum and maximum THI averaged 63.8 and 76.6 (cool period) and 72.1 and 83.6 (hot period). Environmental conditions had minor effects on intake and milk yield during the cool period. During the hot period, the THI 2 d earlier and mean air temperature 2 d earlier had the greatest impact on milk yield and DMI, respectively. Both breeds maintained milk temperature within normal ranges during the cool period, but Holstein and Jersey p.m. milk temperatures averaged 39.6 and 39.2 degrees C during the hot period. Current day mean air temperature during the hot period had the greatest impact on cow p.m. milk temperature, and minimum air temperature had the greatest influence on a.m. milk temperature. Dry matter intake and milk yield declined linearly with respective increases in air temperature or THI during the hot period and milk temperature increased linearly with increasing air temperature. Dry matter intake and milk yield both exhibited a curvilinear relationship with milk temperature. Environmental modifications should target the effects of high temperatures on cow body temperature and should modify the environment at critical times during the day when cows are stressed, including morning hours when ambient temperatures are typically cooler and cows are not assumed to be stressed.

Exsolution as an Example of Complex-System Behavior

NASA Astrophysics Data System (ADS)

Mogk, D. W.; Dutrow, B. L.

2010-12-01

Exsolution in minerals is an important process that occurs in a wide range of mineral groups (e.g. alkali feldspars, pyroxenes, amphiboles, carbonates, oxides, sulfides) in response to changing physical conditions. Exsolution describes a physical process in which a mineral with an initially homogeneous solid solution separates into at least two distinct derivative minerals of disparate composition and is typically interpreted as the product of unmixing in response to lattice strain during slow cooling. Such a process is typically taught in introductory mineralogy and petrology courses, in part because exsolution textures can be readily observed in hand sample or thin section. Exsolution is typically represented on equilibrium binary phase diagrams (T-X), and compositions of the unmixed products can be used in geothermobarometry to calculate temperatures and pressures of initial equilibration or compositions of the unmixed products. Although central to course content, traditional approaches to teaching exsolution are largely descriptive, and do not address the underlying principles that drive this phenomenon: that is, dissipation of energy results in segregating and self-organizing behavior of the system. This process exemplifies complex-system behavior. We use perthite formation (i.e. exsolution in the alkali feldspar system) in a series of scaffolded exercises to teach and more completely demonstrate complex-system behavior. These exercises include the use of: 1) hand samples and a series of optical and TEM photomicrographs to display the scale invariance of perthite textures; 2) a puzzle activity in which a chessboard is used as an analog model of atomic positions and nickels and pennies are used to represent individual atoms (Na and K respectively); sequential moves to optimize contacts with similar coins approximates minimization of lattice energies and reveals a power-law relationship as the system becomes increasingly segregated as a function of time to create exsolution textures; 3) the NetLogo computer modeling program to demonstrate segregating behavior; 4) visualizations based on the binary alkali feldspar phase diagram to demonstrate changes to the state of the system over a range of temperatures, and 5) a series of follow-on thought questions. An interesting apparent paradox that our students should consider concerns the flow of mass and energy in natural systems. Commonly, we simply note that mass and energy typically flow down natural gradients (thermal, chemical potential) to attain a homogeneous equilibrium state; however, exsolution produces a segregated state of the system in the lowest energy configuration. Why? Complex-system behavior can be discovered in a wide range of geological phenomena such as exsolution, and could be explicitly identified throughout the geoscience curriculum as a mechanism to teach about interacting systems.

New estimates of temperature response of leaf photosynthesis in Amazon forest trees, its acclimation to mean temperature change and consequences for modelling climate response to rain forests.

NASA Astrophysics Data System (ADS)

Kruijt, B.; Jans, W.; Vasconcelos, S.; Tribuzy, E. S.; Felsemburgh, C.; Eliane, M.; Rowland, L.; da Costa, A. C. L.; Meir, P.

2014-12-01

In many dynamic vegetation models, degradation of the tropical forests is induced because they assume that productivity falls rapidly when temperatures rise in the region of 30-40°C. Apart plant respiration, this is due to the assumptions on the temperature optima of photosynthetic capacity, which are low and can differ widely between models, where in fact hardly any empirical information is available for tropical forests. Even less is known about the possibility that photosynthesis will acclimate to changing temperatures. The objective of this study to is to provide better estimates for optima, as well as to determine whether any acclimation to temperature change is to be expected. We present both new and hitherto unpublished data on the temperature response of photosynthesis of Amazon rainforest trees, encompassing three sites, several species and five field campaigns. Leaf photosynthesis and its parameters were determined at a range of temperatures. To study the long-term (seasonal) acclimation of this response, this was combined with an artificial, in situ, multi-season leaf heating experiment. The data show that, on average for all non-heated cases, the photosynthetic parameter Vcmax weakly peaks between 35 and 40 ˚C, while heating does not have a clearly significant effect. Results for Jmax are slightly different, with sharper peaks. Scatter was relatively high, which could indicate weak overall temperature dependence. The combined results were used to fit new parameters to the various temperature response curve functions in a range of DGVMs. The figure shows a typical example: while the default Jules model assumes a temperature optimum for Vcmax at around 33 ˚C, the data suggest that Vcmax keeps rising up to at least 40 ˚C. Of course, calculated photosynthesis, obtained by applying this Vcmax in the Farquhar model, peaks at lower temperature. Finally, the implication of these new model parameters for modelled climate change impact on modelled Amazon forests will be assessed, where it is expected that predicted die-back will be less.

Microstructural Evolution and Mechanical Properties of Ti-22Al-25Nb (At.%) Orthorhombic Alloy with Three Typical Microstructures

NASA Astrophysics Data System (ADS)

Wang, Wei; Zeng, Weidong; Liu, Yantao; Xie, Guoxin; Liang, Xiaobo

2018-01-01

Microstructural evolution, tensile and creep behavior of Ti-22Al-25Nb (at.%) orthorhombic alloy with three typical microstructures were investigated. The three typical microstructures were obtained by different solution and age treatment temperatures and analyzed by the BSE technique. The tensile strengths of the alloy at room temperature and 650 °C were investigated. The creep behaviors of the three typical microstructures were also studied at 650 °C/150 MPa for 100 h in air. The phase transformation mechanisms in creep deformation were also found. The experimental results showed that the formations of the three typical microstructures were decided by the isothermal forging and heat treatment. It was supposed that the high-temperature solution treatment might be dominant for the volume fraction and diameter of the equiaxed particles. While the double age treatment would lead to lamellar O phases. Due to grain refinement strengthening, the equiaxed microstructure presented the best tensile strength and ductility. The fully lamellar microstructure had the best creep resistance than that of other microstructures. In this paper, the phenomenon of creep-induced α 2 phase decomposition was occurred during creep deformation of the equiaxed microstructure.

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

Gitti, Myriam; Nulsen, Paul E. J.; David, Laurence P.

We present the results of a Chandra study of the Hydra A galaxy cluster, where a powerful active galactic nucleus (AGN) outburst created a large-scale cocoon shock. We investigated possible azimuthal variations in shock strength and shape, finding indications for a weak shock with a Mach number in the range {approx}1.2-1.3. We measured the temperature change across the shock front. However, the detection of a temperature rise in the regions immediately inside of the front is complicated by the underlying temperature profile of the cluster atmosphere. We measured the global temperature profile of the cluster up to 700 kpc, whichmore » represents the farthest measurement obtained with Chandra for this cluster. A 'plateau' in the temperature profile in the range {approx}70-150 kpc indicates the presence of cool gas, which is likely the result of uplift of material by the AGN outburst. After masking the cool filaments visible in the hardness ratio map, the plateau disappears and the temperature profile recovers a typical shape with a peak around 190 kpc, just inside the shock front. However, it is unlikely that such a temperature feature is produced by the shock as it is consistent with the general shape of the temperature profiles observed for relaxed galaxy clusters. We studied the spectral properties of the cool filaments finding evidence that {approx}10{sup 11} M{sub sun} of low-entropy material has been dredged up by the rising lobes from the central 30 kpc to the observed current position of 75-150 kpc. The energy required to lift the cool gas is {approx}> 2.2 x 10{sup 60} erg, which is comparable to the work required to inflate the cavities and is {approx}25% of the total energy of the large-scale shock. Our results show that the AGN feedback in Hydra A is acting not only by directly heating the gas, but also by removing a substantial amount of potential fuel for the supermassive black hole.« less

Limits to global and Australian temperature change this century based on expert judgment of climate sensitivity

NASA Astrophysics Data System (ADS)

Grose, Michael R.; Colman, Robert; Bhend, Jonas; Moise, Aurel F.

2017-05-01

The projected warming of surface air temperature at the global and regional scale by the end of the century is directly related to emissions and Earth's climate sensitivity. Projections are typically produced using an ensemble of climate models such as CMIP5, however the range of climate sensitivity in models doesn't cover the entire range considered plausible by expert judgment. Of particular interest from a risk-management perspective is the lower impact outcome associated with low climate sensitivity and the low-probability, high-impact outcomes associated with the top of the range. Here we scale climate model output to the limits of expert judgment of climate sensitivity to explore these limits. This scaling indicates an expanded range of projected change for each emissions pathway, including a much higher upper bound for both the globe and Australia. We find the possibility of exceeding a warming of 2 °C since pre-industrial is projected under high emissions for every model even scaled to the lowest estimate of sensitivity, and is possible under low emissions under most estimates of sensitivity. Although these are not quantitative projections, the results may be useful to inform thinking about the limits to change until the sensitivity can be more reliably constrained, or this expanded range of possibilities can be explored in a more formal way. When viewing climate projections, accounting for these low-probability but high-impact outcomes in a risk management approach can complement the focus on the likely range of projections. They can also highlight the scale of the potential reduction in range of projections, should tight constraints on climate sensitivity be established by future research.

Calibration of the OHREX high-resolution imaging crystal spectrometer at the Livermore electron beam ion traps [Calibration of the OHREX high-resolution imaging crystal spectrometer at the Livermore EBIT

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

Hell, N.; Beiersdorfer, P.; Magee, E. W.

2016-08-04

Here, we report the calibration of the Orion High-Resolution X-ray (OHREX) imaging crystal spectrometer at the EBIT-I electron beam ion trap at Livermore. Two such instruments, dubbed OHREX-1 and OHREX-2, are fielded for plasma diagnostics at the Orion laser facility in the United Kingdom. The OHREX spectrometer can simultaneously house two spherically bent crystals with a radius of curvature of r=67.2 cm. The focusing properties of the spectrometer allow both for larger distance to the source due to the increase in collected light and for observation of extended sources. OHREX is designed to cover a 2.5–3 degree spectral range atmore » Bragg angles around 51.3 degree. The typically high resolving powers at these large Bragg angles are ideally suited for line shape diagnostics. For instance, the nominal resolving power of the instrument (> 10000) is much higher than the effective resolving power associated with the Doppler broadening due to the temperature of the trapped ions in EBIT-I. The effective resolving power is only around 3000 at typical EBIT-I conditions, which nevertheless is sufficient to set up and test the instrument’s spectral characteristics. We have calibrated the spectral range for a number of crystals using well known reference lines in first and second order, and derived the ion temperatures from these lines. We have also made use of the 50µm size of the EBIT-I source width to characterize the spatial focusing of the spectrometer.« less

AC electrothermal technique in microchannels

NASA Astrophysics Data System (ADS)

Salari, Alinaghi; Navi, Maryam; Dalton, Colin

2017-02-01

Electrokinetic techniques have a wide range of applications in droplet, particle, and fluid manipulation systems. In general, they can be categorized into different subgroups including electroosmosis, electrothermal, electrophoresis, dielectrophoresis, etc. The AC electrothermal (ACET) technique has been shown to be very effective in applications which involve high conductivity fluids, such as blood, which are typically used in biomedical applications. In the past few years, the ACET effect has received considerable attention. Unlike AC electroosmosis (ACEO), the ACET effect shows plateaus in force in a wide frequency range. In other words, with electrothermal force, velocity is more steady and predictable at different frequencies, compared to ACEO and dielectrophoresis (DEP). Although electrothermal microflows form as a result of Joule heating in the fluid, due to high conduction of heat to the ambience, the temperature rise in the fluid is not so high as to threaten the nature of the biofluids. The average temperature rise resulting from the ACET effect is below 5 °K. In order to generate high strength AC electric fields, microfabricated electrode arrays are commonly used in microchannels. For pumping applications, it is essential to create asymmetry in the electric field, typically by having asymmetrical electrode pairs. There is no defined border between many electrokinetic techniques, and as such the point where electrothermal processes interferes with other electrokinetic techniques is not clear in the literature. In addition, there have been comprehensive reviews on micropumps, electrokinetics, and their subcategories, but the literature lacks a detailed up-to-date review on electrothermal microdevices. In this paper, a brief review is made specifically on electric fields in ACET devices, in order to provide an insight for the reader about the importance of this aspect of ACET devices and the improvements made to date.

Three-dimensional modeling of the neutron spectrum to infer plasma conditions in cryogenic inertial confinement fusion implosions

NASA Astrophysics Data System (ADS)

Weilacher, F.; Radha, P. B.; Forrest, C.

2018-04-01

Neutron-based diagnostics are typically used to infer compressed core conditions such as areal density and ion temperature in deuterium-tritium (D-T) inertial confinement fusion (ICF) implosions. Asymmetries in the observed neutron-related quantities are important to understanding failure modes in these implosions. Neutrons from fusion reactions and their subsequent interactions including elastic scattering and neutron-induced deuteron breakup reactions are tracked to create spectra. It is shown that background subtraction is important for inferring areal density from backscattered neutrons and is less important for the forward-scattered neutrons. A three-dimensional hydrodynamic simulation of a cryogenic implosion on the OMEGA Laser System [Boehly et al., Opt. Commun. 133, 495 (1997)] using the hydrodynamic code HYDRA [Marinak et al., Phys. Plasmas 8, 2275 (2001)] is post-processed using the tracking code IRIS3D. It is shown that different parts of the neutron spectrum from the view can be mapped into different regions of the implosion, enabling an inference of an areal-density map. It is also shown that the average areal-density and an areal-density map of the compressed target can be reconstructed with a finite number of detectors placed around the target chamber. Ion temperatures are inferred from the width of the D-D and D-T fusion neutron spectra. Backgrounds can significantly alter the inferred ion temperatures from the D-D reaction, whereas they insignificantly influence the inferred D-T ion temperatures for the areal densities typical of OMEGA implosions. Asymmetries resulting in fluid flow in the core are shown to influence the absolute inferred ion temperatures from both reactions, although relative inferred values continue to reflect the underlying asymmetry pattern. The work presented here is part of the wide range of the first set of studies performed with IRIS3D. This code will continue to be used for post-processing detailed hydrodynamic simulations and interpreting observed neutron spectra in ICF implosions.

The effective temperature of Peptide ions dissociated by sustained off-resonance irradiation collisional activation in fourier transform mass spectrometry.

PubMed

Schnier, P D; Jurchen, J C; Williams, E R

1999-01-28

A method for determining the internal energy of biomolecule ions activated by collisions is demonstrated. The dissociation kinetics of protonated leucine enkephalin and doubly protonated bradykinin were measured using sustained off-resonance irradiation (SORI) collisionally activated dissociation (CAD) in a Fourier transform mass spectrometer. Dissociation rate constants are obtained from these kinetic data. In combination with Arrhenius parameters measured with blackbody infrared radiative dissociation, the "effective" temperatures of these ions are obtained. Effects of excitation voltage and frequency and the ion cell pressure were investigated. With typical SORI-CAD experimental conditions, the effective temperatures of these peptide ions range between 200 and 400 degrees C. Higher temperatures can be easily obtained for ions that require more internal energy to dissociate. The effective temperatures of both protonated leucine enkephalin and doubly protonated bradykinin measured with the same experimental conditions are similar. Effective temperatures for protonated leucine enkephalin can also be obtained from the branching ratio of the b(4) and (M + H - H(2)O)(+) pathways. Values obtained from this method are in good agreement with those obtained from the overall dissociation rate constants. Protonated leucine enkephalin is an excellent "thermometer" ion and should be well suited to establishing effective temperatures of ions activated by other dissociation techniques, such as infrared photodissociation, as well as ionization methods, such as matrix assisted laser desorption/ionization.

The Effective Temperature of Peptide Ions Dissociated by Sustained Off-Resonance Irradiation Collisional Activation in Fourier Transform Mass Spectrometry

PubMed Central

Schnier, Paul D.; Jurchen, John C.; Williams, Evan R.

2005-01-01

A method for determining the internal energy of biomolecule ions activated by collisions is demonstrated. The dissociation kinetics of protonated leucine enkephalin and doubly protonated bradykinin were measured using sustained off-resonance irradiation (SORI) collisionally activated dissociation (CAD) in a Fourier transform mass spectrometer. Dissociation rate constants are obtained from these kinetic data. In combination with Arrhenius parameters measured with blackbody infrared radiative dissociation, the “effective” temperatures of these ions are obtained. Effects of excitation voltage and frequency and the ion cell pressure were investigated. With typical SORI–CAD experimental conditions, the effective temperatures of these peptide ions range between 200 and 400 °C. Higher temperatures can be easily obtained for ions that require more internal energy to dissociate. The effective temperatures of both protonated leucine enkephalin and doubly protonated bradykinin measured with the same experimental conditions are similar. Effective temperatures for protonated leucine enkephalin can also be obtained from the branching ratio of the b4 and (M + H − H2O)+ pathways. Values obtained from this method are in good agreement with those obtained from the overall dissociation rate constants. Protonated leucine enkephalin is an excellent “thermometer” ion and should be well suited to establishing effective temperatures of ions activated by other dissociation techniques, such as infrared photodissociation, as well as ionization methods, such as matrix assisted laser desorption/ionization. PMID:16614752

Evaluation of a 2.5 kWel automotive low temperature PEM fuel cell stack with extended operating temperature range up to 120 °C

NASA Astrophysics Data System (ADS)

Ruiu, Tiziana; Dreizler, Andreas M.; Mitzel, Jens; Gülzow, Erich

2016-01-01

Nowadays, the operating temperature of polymer electrolyte membrane fuel cell stacks is typically limited to 80 °C due to water management issues of membrane materials. In the present work, short-term operation at elevated temperatures up to 120 °C and long-term steady-state operation under automotive relevant conditions at 80 °C are examined using a 30-cell stack developed at DLR. The high temperature behavior is investigated by using temperature cycles between 90 and 120 °C without adjustment of the gases dew points, to simulate a short-period temperature increase, possibly caused by an extended power demand and/or limited heat removal. This galvanostatic test demonstrates a fully reversible performance decrease of 21 ± 1% during each thermal cycle. The irreversible degradation rate is about a factor of 6 higher compared to the one determined by the long-term test. The 1200-h test at 80 °C demonstrates linear stack voltage decay with acceptable degradation rate, apart from a malfunction of the air compressor, which results in increased catalyst degradation effects on individual cells. This interpretation is based on an end-of-life characterization, aimed to investigate catalyst, electrode and membrane degradation, by determining hydrogen crossover rates, high frequency resistances, electrochemically active surface areas and catalyst particle sizes.

Cold tolerance of the Australian spur-throated locust, Austracris guttulosa.

PubMed

Woodman, James D

2012-03-01

The cold tolerance of overwintering adult Spur-throated locusts, Austracris guttulosa, was examined using measures of supercooling point relative to gender, environmental acclimation and feeding state as well as mortality for a range of sub-zero temperature exposure treatments. Freezing was lethal and supercooling points ranged from -6 to -12.8°C, but were statistically independent of fresh mass, body water content, acclimation, and/or gut content in fed and starved individuals. A significant interaction effect of gender and feeding status showed that the larger bodied females had decreased supercooling capacity with increased food material in the digestive tract. Post-freezing dissections revealed differences in the amount of freshly consumed and retained food material in the digestive tract between fed and starved individuals of each gender, which could explain this effect based on inoculation of ice crystallisation by food particles. Above supercooling temperatures, neither gender nor the rate of cooling had a significant effect on mortality. When cooled from 25°C at 0.1 or 0.5°Cmin(-1) to a range of experimental minimum temperatures held for 3h, survival was ~74% to -7°C, but declined sharply to ~37% when cooled to -8°C or lower. Although the laboratory experiments reported here suggest that A. guttulosa is not freeze tolerant and unable to rapidly cold harden, exposure to typical cold and frosty nights that very rarely reach below -8°C as a night minimum in the field would be unlikely to cause mortality in the vast majority of overwintering aggregations. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

Investigating factors affecting the body temperature of dogs competing in cross country (canicross) races in the UK.

PubMed

Carter, Anne J; Hall, Emily J

2018-02-01

Increasing numbers of people are running with their dogs, particularly in harness through the sport canicross. Whilst canicross races are typically held in the winter months, some human centred events are encouraging running with dogs in summer months, potentially putting dogs at risk of heat related injuries, including heatstroke. The aim of this project was to investigate the effects of ambient conditions and running speed on post-race temperature of canicross dogs in the UK, and investigate the potential risk of heatstroke to canicross racing dogs. The effects of canine characteristics (e.g. gender, coat colour) were explored in order to identify factors that could increase the risk of exercise-induced hyperthermia (defined as body temperature exceeding the upper normal limit of 38.8°C).108 dogs were recruited from 10 race days, where ambient conditions ranged from - 5 to 11°C measured as universal thermal comfort index (UTCI). 281 post race tympanic membrane temperatures were recorded, ranging from 37.0-42.5°C. There was a weak correlation between speed and post-race temperature (r = 0.269, P < 0.001). Whilst no correlation between any single environmental factor or UTCI and post-race temperature was found, the proportion of dogs developing exercise-induced hyperthermia during the race increased with UTCI (r = 0.688, P = 0.028). Male dogs (χ(1) = 18.286, P < 0.001), and dark coated dogs (χ(2) = 8.234, P = 0.014), were significantly more likely to finish the race with a temperature exceeding 40.6°C. Prolonged elevati°n of body temperature above this temperature is likely to cause heatstroke. At every race dogs exceeded this critical temperature, with 10.7% (n = 30) of the overall study population exceeding this temperature throughout the study period. The results suggest male dogs, dark coloured dogs, and increased speed of running all increase the risk of heatstroke in racing canicross dogs. Further research is required to investigate the impact of environmental conditions on post-race cooling, to better understand safe running conditions for dogs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Investigating Low Temperature Properties of Rubber Seals - 13020

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

Jaunich, M.; Wolff, D.; Stark, W.

To achieve the required tightness levels of containers for low and intermediate level radioactive wastes rubbers are widely applied as main sealing materials. The save encapsulation of the radioactive container contents has to be guaranteed according to legislation and appropriate guidelines for long storage periods as well as down to temperatures of -40 deg. C during transportation. Therefore the understanding of failure mechanisms that lead to leakage at low temperatures is of high importance. It is known that the material properties of rubbers are strongly influenced by temperature. At low temperatures this is caused by the rubber-glass transition (abbr. glassmore » transition). During continuous cooling the material changes from rubber-like entropy-elastic to stiff energy-elastic behaviour, that allows nearly no strain or retraction. Therefore, rubbers are normally used above their glass transition but the minimum working temperature limit is not defined precisely, what can cause problems during application. The temperature range where full functionality is possible is strongly dependent on the application conditions and the material. For this investigation mainly ethylene propylene diene (EPDM) and fluorocarbon rubbers (FKM) were selected as they are often used for radioactive waste containers. Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) are typically used for the determination of the temperature range of the glass transition process. The standardized compression set measurement according to ISO 815 is common for investigation of rubber sealing materials as the test simulates the seal behaviour after release. To reduce the test time of the standard tests a faster technique giving the same information was developed. Additionally, the breakdown temperature of the sealing function of complete O-ring seals is measured in a component test setup to compare it with the results of the other tests. The experimental setup is capable of measuring the leakage rate at low temperatures by the pressure rise method. A model was developed that allows calculating the minimum working temperature limit of a seal by combining the results of the applied methods. (authors)« less

Biophysical control of leaf temperature

NASA Astrophysics Data System (ADS)

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

2014-12-01

In principle sunlit leaves can maintain their temperatures within a narrower range than ambient temperatures. This is an important and long-known (but now overlooked) prediction of energy balance theory. Net radiation at leaf surface in steady state (which is reached rapidly) must be equal to the combination of sensible and latent heat exchanges with surrounding air, the former being proportional to leaf-to-air temperature difference (ΔT), the latter to the transpiration rate. We present field measurements of ΔT which confirm the existence of a 'crossover temperature' in the 25-30˚C range for species in a tropical savanna and a tropical rainforest environment. This finding is consistent with a simple representation of transpiration as a function of net radiation and temperature (Priestley-Taylor relationship) assuming an entrainment factor (ω) somewhat greater than the canonical value of 0.26. The fact that leaves in tropical forests are typically cooler than surrounding air, often already by solar noon, is consistent with a recently published comparison of MODIS day-time land-surface temperatures with air temperatures. Theory further predicts a strong dependence of leaf size (which is inversely related to leaf boundary-layer conductance, and therefore to absolute magnitude of ΔT) on moisture availability. Theoretically, leaf size should be determined by either night-time constraints (risk of frost damage to active leaves) or day-time constraints (risk of heat stress damage),with the former likely to predominate - thereby restricting the occurrence of large leaves - at high latitudes. In low latitudes, daytime maximum leaf size is predicted to increase with temperature, provided that water is plentiful. If water is restricted, however, transpiration cannot proceed at the Priestley-Taylor rate, and it quickly becomes advantageous for plants to have small leaves, which do not heat up much above the temperature of their surroundings. The difference between leaf and air temperature is generally neglected in terrestrial ecosystem and carbon cycle models. This is a significant omission that could lead to an over-estimation of the heat-stress vulnerability of carbon uptake in the wet tropics. Leaf energy balance theory is well established, and should be included in the next generation of models.

In situ temperature relationships of biochemical and stomatal controls of photosynthesis in four lowland tropical tree species.

PubMed

Slot, Martijn; Winter, Klaus

2017-12-01

Net photosynthetic carbon uptake of Panamanian lowland tropical forest species is typically optimal at 30-32 °C. The processes responsible for the decrease in photosynthesis at higher temperatures are not fully understood for tropical trees. We determined temperature responses of maximum rates of RuBP-carboxylation (V CMax ) and RuBP-regeneration (J Max ), stomatal conductance (G s ), and respiration in the light (R Light ) in situ for 4 lowland tropical tree species in Panama. G s had the lowest temperature optimum (T Opt ), similar to that of net photosynthesis, and photosynthesis became increasingly limited by stomatal conductance as temperature increased. J Max peaked at 34-37 °C and V CMax ~2 °C above that, except in the late-successional species Calophyllum longifolium, in which both peaked at ~33 °C. R Light significantly increased with increasing temperature, but simulations with a photosynthesis model indicated that this had only a small effect on net photosynthesis. We found no evidence for Rubisco-activase limitation of photosynthesis. T Opt of V CMax and J Max fell within the observed in situ leaf temperature range, but our study nonetheless suggests that net photosynthesis of tropical trees is more strongly influenced by the indirect effects of high temperature-for example, through elevated vapour pressure deficit and resulting decreases in stomatal conductance-than by direct temperature effects on photosynthetic biochemistry and respiration. © 2017 John Wiley & Sons Ltd.

A Lattice Boltzmann Framework for the simulation of boiling hydrodynamics in BWRs.

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

Jain, P. K.; Tentner, A.; Uddin, R.

2008-01-01

Multi phase and multi component flows are ubiquitous in nature as well as in many man-made processes. A specific example is the Boiling Water Reactor (BWR) core, in which the coolant enters the core as liquid, undergoes a phase change as it traverses the core and exits as a high quality two-phase mixture. Two-phase flows in BWRs typically manifest a wide variety of geometrical patterns of the co-existing phases depending on the local system conditions. Modeling of such flows currently relies on empirical correlations (for example, in the simulation of bubble nucleation, bubble growth and coalescence, and inter-phase surface topologymore » transitions) that hinder the accurate simulation of two-phase phenomena using Computational Fluid Dynamics (CFD) approaches. The Lattice Boltzmann Method (LBM) is in rapid development as a modeling tool to understand these macro-phenomena by coupling them with their underlying micro-dynamics. This paper presents a consistent LBM formulation for the simulation of a two-phase water-steam system. Results of initial model validation in a range of thermodynamic conditions typical for BWRs are also shown. The interface between the two coexisting phases is captured from the dynamics of the model itself, i.e., no interface tracking is needed. The model is based on the Peng-Robinson (P-R) non-ideal equation of state and can quantitatively approximate the phase-coexistence curve for water at different temperatures ranging from 125 to 325 oC. Consequently, coexisting phases with large density ratios (up to {approx}1000) may be simulated. Two-phase models in the 200-300 C temperature range are of significant importance to nuclear engineers since most BWRs operate under similar thermodynamic conditions. Simulation of bubbles and droplets in a gravity-free environment of the corresponding coexisting phase until steady state is reached satisfies Laplace law at different temperatures and thus, yield the surface tension of the fluid. Comparing the LBM surface tension thus calculated using the LBM to the corresponding experimental values for water, the LBM lattice unit (lu) can be scaled to the physical units. Using this approach, spatial scaling of the LBM emerges from the model itself and is not imposed externally.« less

Tunable filters for multispectral imaging of aeronomical features

NASA Astrophysics Data System (ADS)

Goenka, C.; Semeter, J. L.; Noto, J.; Dahlgren, H.; Marshall, R.; Baumgardner, J.; Riccobono, J.; Migliozzi, M.

2013-10-01

Multispectral imaging of optical emissions in the Earth's upper atmosphere unravels vital information about dynamic phenomena in the Earth-space environment. Wavelength tunable filters allow us to accomplish this without using filter wheels or multiple imaging setups, but with identifiable caveats and trade-offs. We evaluate one such filter, a liquid crystal Fabry-Perot etalon, as a potential candidate for the next generation of imagers for aeronomy. The tunability of such a filter can be exploited in imaging features such as the 6300-6364 Å oxygen emission doublet, or studying the rotational temperature of N2+ in the 4200-4300 Å range, observations which typically require multiple instruments. We further discuss the use of this filter in an optical instrument, called the Liquid Crystal Hyperspectral Imager (LiCHI), which will be developed to make simultaneous measurements in various wavelength ranges.

Quantum-Well Thermophotovoltaic Cells

NASA Technical Reports Server (NTRS)

Freudlich, Alex; Ignatiev, Alex

2009-01-01

Thermophotovoltaic cells containing multiple quantum wells have been invented as improved means of conversion of thermal to electrical energy. The semiconductor bandgaps of the quantum wells can be tailored to be narrower than those of prior thermophotovoltaic cells, thereby enabling the cells to convert energy from longer-wavelength photons that dominate the infrared-rich spectra of typical thermal sources with which these cells would be used. Moreover, in comparison with a conventional single-junction thermophotovoltaic cell, a cell containing multiple narrow-bandgap quantum wells according to the invention can convert energy from a wider range of wavelengths. Hence, the invention increases the achievable thermal-to-electrical energy-conversion efficiency. These thermophotovoltaic cells are expected to be especially useful for extracting electrical energy from combustion, waste-heat, and nuclear sources having temperatures in the approximate range from 1,000 to 1,500 C.

Evaluation of electrical conductivity of Cu and Al through sub microsecond underwater electrical wire explosion

NASA Astrophysics Data System (ADS)

Sheftman, D.; Shafer, D.; Efimov, S.; Krasik, Ya. E.

2012-03-01

Sub-microsecond timescale underwater electrical wire explosions using Cu and Al materials have been conducted. Current and voltage waveforms and time-resolved streak images of the discharge channel, coupled to 1D magneto-hydrodynamic simulations, have been used to determine the electrical conductivity of the metals for the range of conditions between hot liquid metal and strongly coupled non-ideal plasma, in the temperature range of 10-60 KK. The results of these studies showed that the conductivity values obtained are typically lower than those corresponding to modern theoretical electrical conductivity models and provide a transition between the conductivity values obtained in microsecond time scale explosions and those obtained in nanosecond time scale wire explosions. In addition, the measured wire expansion shows good agreement with equation of state tables.

Effect of temperature on removal of trace organic chemicals in managed aquifer recharge systems.

PubMed

Alidina, Mazahirali; Shewchuk, Justin; Drewes, Jörg E

2015-03-01

This study was undertaken to investigate whether changes in temperature experienced in MAR systems affect attenuation of trace organic chemicals (TOrCs). A set of laboratory-scale soil columns were placed in a temperature-controlled environmental chamber and operated at five different temperature set-points (30, 20, 10, 8 and 4°C) covering the range of typical groundwater temperatures in cold, moderate and arid climate regions. Removal of bulk organic carbon both in the infiltration zone as well as during deeper infiltration was independent of temperature. Of the 22 TOrCs investigated, only six chemicals exhibited changes in attenuation as a function of temperature. Attenuation of four of the compounds (diclofenac, gemfibrozil, ketoprofen and naproxen) decreased as the temperature was reduced from 30°C to 4°C, likely due to decreased microbial activity at lower temperatures. As the temperature was decreased, however, attenuation of oxybenzone and trimethoprim were noted to increase. This increased attenuation was likely due to more efficient sorption at lower temperatures, though possible changes in the microbial composition as the temperature decreased may also have contributed to this change. Changes in rate constants of attenuation (ka) for the biotransformed TOrCs with temperature suggested the existence of a critical temperature at 10°C for three of the four TOrCs, where significant changes to rates of attenuation occurred. Results from this study indicated that for most TOrCs, changes in temperature do not impact their attenuation. Thus, seasonal changes in temperature are not considered to be a major concern for attenuation of most TOrCs in MAR systems. Copyright © 2014 Elsevier Ltd. All rights reserved.

Indoor Temperatures in Patient Waiting Rooms in Eight Rural Primary Health Care Centers in Northern South Africa and the Related Potential Risks to Human Health and Wellbeing

PubMed Central

Wright, Caradee Y.; Street, Renée A.; Cele, Nokulunga; Kunene, Zamantimande; Balakrishna, Yusentha; Albers, Patricia N.; Mathee, Angela

2017-01-01

Increased temperatures affect human health and vulnerable groups including infants, children, the elderly and people with pre-existing diseases. In the southern African region climate models predict increases in ambient temperature twice that of the global average temperature increase. Poor ventilation and lack of air conditioning in primary health care clinics, where duration of waiting time may be as long as several hours, pose a possible threat to patients seeking primary health care. Drawing on information measured by temperature loggers installed in eight clinics in Giyani, Limpopo Province of South Africa, we were able to determine indoor temperatures of waiting rooms in eight rural primary health care facilities. Mean monthly temperature measurements inside the clinics were warmer during the summer months of December, January and February, and cooler during the autumn months of March, April and May. The highest mean monthly temperature of 31.4 ± 2.7 °C was recorded in one clinic during February 2016. Maximum daily indoor clinic temperatures exceeded 38 °C in some clinics. Indoor temperatures were compared to ambient (outdoor) temperatures and the mean difference between the two showed clinic waiting room temperatures were higher by 2–4 °C on average. Apparent temperature (AT) incorporating relative humidity readings made in the clinics showed ‘realfeel’ temperatures were >4 °C higher than measured indoor temperature, suggesting a feeling of ‘stuffiness’ and discomfort may have been experienced in the waiting room areas. During typical clinic operational hours of 8h00 to 16h00, mean ATs fell into temperature ranges associated with heat–health impact warning categories of ‘caution’ and ‘extreme caution’. PMID:28067816