Testing of Sapphire Optical Fiber and Sensors in Intense Radiation Fields When Subjected to Very High Temperatures

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

Blue, Thomas; Windl, Wolfgang

The primary objective of this project was to determine the optical attenuation and signal degradation of sapphire optical fibers & sensors (temperature & strain), in-situ, operating at temperatures up to 1500°C during reactor irradiation through experiments and modeling. The results will determine the feasibility of extending sapphire optical fiber-based instrumentation to extremely high temperature radiation environments. This research will pave the way for future testing of sapphire optical fibers and fiber-based sensors under conditions expected in advanced high temperature reactors.

Microstructure evolution and mechanical properties degradation of HPNb alloy after a five-year service

NASA Astrophysics Data System (ADS)

Guo, Jingfeng; Cao, Tieshan; Cheng, Congqian; Meng, Xianming; Zhao, Jie

2018-04-01

The microstructure and mechanical properties of ethylene cracking furnace tube (HPNb alloy) are investigated by scanning electronic microscopy (SEM), tensile tests and Charpy impact tests at room temperature, tensile tests and creep tests at high temperature in this paper. The primary carbides of HPNb alloy coarsened and formed a continuous network after a five-year service. Furthermore, a lot of fine secondary carbides precipitated in the dendrite interior. The primary carbides M7C3 and NbC transformed into M23C6 and G phase after service, respectively. The furnace tube after service exhibits higher yield strength, lower tensile strength, worse ductility and toughness than as-cast tube at room temperature. At high temperature, the tensile strength and yield strength of service tube are higher than as-cast tube, but its tensile elongation is lower. The creep strength of HPNb alloy at high temperature decreases after a five-year service. Both microstructure and mechanical properties of ethylene cracking furnace tube have deteriorated after a five-year service.

Structural changes in cartilage and collagen studied by high temperature Raman spectroscopy.

PubMed

Fields, Mark; Spencer, Nicholas; Dudhia, Jayesh; McMillan, Paul F

2017-06-01

Understanding the high temperature behavior of collagen and collagenous tissue is important for surgical procedures and biomaterials processing for the food, pharmaceutical, and cosmetics industries. One primary event for proteins is thermal denaturation that involves unfolding the polypeptide chains while maintaining the primary structure intact. Collagen in the extracellular matrix of cartilage and other connective tissue is a hierarchical material containing bundles of triple-helical fibers associated with water and proteoglycan components. Thermal analysis of dehydrated collagen indicates irreversible denaturation at high temperature between 135°C and 200°C, with another reversible event at ∼60-80°C for hydrated samples. We report high temperature Raman spectra for freeze-dried cartilage samples that show an increase in laser-excited fluorescence interpreted as conformational changes associated with denaturation above 140°C. Spectra for separated collagen and proteoglycan fractions extracted from cartilage indicate the changes are associated with collagen. The Raman data also show appearance of new features indicating peptide bond hydrolysis at high temperature implying that molecular H 2 O is retained within the freeze-dried tissue. This is confirmed by thermogravimetric analysis that show 5-7 wt% H 2 O remaining within freeze-dried cartilage that is released progressively upon heating up to 200°C. Spectra obtained after exposure to high temperature and re-hydration following recovery indicate that the capacity of the denatured collagen to re-absorb water is reduced. Our results are important for revealing the presence of bound H 2 O within the collagen component of connective tissue even after freeze-drying and its role in denaturation that is accompanied by or perhaps preceded by breakdown of the primary polypeptide structure. © 2017 Wiley Periodicals, Inc.

Microstructure Evolution in Cut Metal Chips of Ti-6Al-4V

NASA Technical Reports Server (NTRS)

Dong, L.; Schneider, J. A.

2008-01-01

The microstructural evolution following metal cutting was investigated within metal chips of Ti-6Al-4V. Metal cutting was used to impose a high strain rate on the order of approx.10(exp 5)/s within the primary shear zone as the metal was removed from the workpiece. The initial microstructure of the parent material (PM) was composed of a bi-modal microstructure with coarse prior beta grains and equiaxed primary alpha located at the boundaries. After metal cutting, the microstructure of the metal chips showed coarsening of the equiaxed primary alpha grains and beta lamellar. These metallographic findings suggest that the metal chips experienced high temperatures which remained below the beta transus temperature.

Dense simple plasmas as high-temperature liquid simple metals

NASA Technical Reports Server (NTRS)

Perrot, F.

1990-01-01

The thermodynamic properties of dense plasmas considered as high-temperature liquid metals are studied. An attempt is made to show that the neutral pseudoatom picture of liquid simple metals may be extended for describing plasmas in ranges of densities and temperatures where their electronic structure remains 'simple'. The primary features of the model when applied to plasmas include the temperature-dependent self-consistent calculation of the electron charge density and the determination of a density and temperature-dependent ionization state.

FHR Process Instruments

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

Holcomb, David Eugene

2015-01-01

Fluoride salt-cooled High temperature Reactors (FHRs) are entering into early phase engineering development. Initial candidate technologies have been identified to measure all of the required process variables. The purpose of this paper is to describe the proposed measurement techniques in sufficient detail to enable assessment of the proposed instrumentation suite and to support development of the component technologies. This paper builds upon the instrumentation chapter of the recently published FHR technology development roadmap. Locating instruments outside of the intense core radiation and high-temperature fluoride salt environment significantly decreases their environmental tolerance requirements. Under operating conditions, FHR primary coolant salt ismore » a transparent, low-vapor-pressure liquid. Consequently, FHRs can employ standoff optical measurements from above the salt pool to assess in-vessel conditions. For example, the core outlet temperature can be measured by observing the fuel s blackbody emission. Similarly, the intensity of the core s Cerenkov glow indicates the fission power level. Short-lived activation of the primary coolant provides another means for standoff measurements of process variables. The primary coolant flow and neutron flux can be measured using gamma spectroscopy along the primary coolant piping. FHR operation entails a number of process measurements. Reactor thermal power and core reactivity are the most significant variables for process control. Thermal power can be determined by measuring the primary coolant mass flow rate and temperature rise across the core. The leading candidate technologies for primary coolant temperature measurement are Au-Pt thermocouples and Johnson noise thermometry. Clamp-on ultrasonic flow measurement, that includes high-temperature tolerant standoffs, is a potential coolant flow measurement technique. Also, the salt redox condition will be monitored as an indicator of its corrosiveness. Both electrochemical techniques and optical spectroscopy are candidate fluoride salt redox measurement methods. Coolant level measurement can be performed using radar-level gauges located in standpipes above the reactor vessel. While substantial technical development remains for most of the instruments, industrially compatible instruments based upon proven technology can be reasonably extrapolated from the current state of the art.« less

Room-Temperature and High-Temperature Tensile Mechanical Properties of TA15 Titanium Alloy and TiB Whisker-Reinforced TA15 Matrix Composites Fabricated by Vacuum Hot-Pressing Sintering

PubMed Central

Feng, Yangju; Zhang, Wencong; Zeng, Li; Cui, Guorong; Chen, Wenzhen

2017-01-01

In this paper, the microstructure, the room-temperature and high-temperature tensile mechanical properties of monolithic TA15 alloy and TiB whisker-reinforced TA15 titanium matrix composites (TiBw/TA15) fabricated by vacuum hot-pressing sintering were investigated. The microstructure results showed that there were no obvious differences in the microstructure between monolithic TA15 alloy and TiBw/TA15 composites, except whether or not the grain boundaries contained TiBw. After sintering, the matrix microstructure presented a typical Widmanstätten structure and the size of primary β grain was consistent with the size of spherical TA15 titanium metallic powders. This result demonstrated that TiBw was not the only factor limiting grain coarsening of the primary β grain. Moreover, the grain coarsening of α colonies was obvious, and high-angle grain boundaries (HAGBs) were distributed within the primary β grain. In addition, TiBw played an important role in the microstructure evolution. In the composites, TiBw were randomly distributed in the matrix and surrounded by a large number of low-angle grain boundaries (LAGBs). Globularization of α phase occurred prior, near the TiBw region, because TiBw provided the nucleation site for the equiaxed α phase. The room-temperature and high-temperature tensile results showed that TiBw distributed at the primary β grain boundaries can strengthen the grain boundary, but reduce the connectivity of the matrix. Therefore, compared to the monolithic TA15 alloy fabricated by the same process, the tensile strength of the composites increased, and the tensile elongation decreased. Moreover, with the addition of TiBw, the fracture mechanism was changed to a mixture of brittle fracture and ductile failure (composites) from ductile failure (monolithic TA15 alloy). The fracture surfaces of TiBw/TA15 composites were the grain boundaries of the primary β grain where the majority of TiB whiskers distributed, i.e., the surfaces of the spherical TA15 titanium metallic powders. PMID:28772786

Room-Temperature and High-Temperature Tensile Mechanical Properties of TA15 Titanium Alloy and TiB Whisker-Reinforced TA15 Matrix Composites Fabricated by Vacuum Hot-Pressing Sintering.

PubMed

Feng, Yangju; Zhang, Wencong; Zeng, Li; Cui, Guorong; Chen, Wenzhen

2017-04-18

In this paper, the microstructure, the room-temperature and high-temperature tensile mechanical properties of monolithic TA15 alloy and TiB whisker-reinforced TA15 titanium matrix composites (TiBw/TA15) fabricated by vacuum hot-pressing sintering were investigated. The microstructure results showed that there were no obvious differences in the microstructure between monolithic TA15 alloy and TiBw/TA15 composites, except whether or not the grain boundaries contained TiBw. After sintering, the matrix microstructure presented a typical Widmanstätten structure and the size of primary β grain was consistent with the size of spherical TA15 titanium metallic powders. This result demonstrated that TiBw was not the only factor limiting grain coarsening of the primary β grain. Moreover, the grain coarsening of α colonies was obvious, and high-angle grain boundaries (HAGBs) were distributed within the primary β grain. In addition, TiBw played an important role in the microstructure evolution. In the composites, TiBw were randomly distributed in the matrix and surrounded by a large number of low-angle grain boundaries (LAGBs). Globularization of α phase occurred prior, near the TiBw region, because TiBw provided the nucleation site for the equiaxed α phase. The room-temperature and high-temperature tensile results showed that TiBw distributed at the primary β grain boundaries can strengthen the grain boundary, but reduce the connectivity of the matrix. Therefore, compared to the monolithic TA15 alloy fabricated by the same process, the tensile strength of the composites increased, and the tensile elongation decreased. Moreover, with the addition of TiBw, the fracture mechanism was changed to a mixture of brittle fracture and ductile failure (composites) from ductile failure (monolithic TA15 alloy). The fracture surfaces of TiBw/TA15 composites were the grain boundaries of the primary β grain where the majority of TiB whiskers distributed, i.e., the surfaces of the spherical TA15 titanium metallic powders.

The ice nucleation temperature determines the primary drying rate of lyophilization for samples frozen on a temperature-controlled shelf.

PubMed

Searles, J A; Carpenter, J F; Randolph, T W

2001-07-01

The objective of this study was to determine the influence of ice nucleation temperature on the primary drying rate during lyophilization for samples in vials that were frozen on a lyophilizer shelf. Aqueous solutions of 10% (w/v) hydroxyethyl starch were frozen in vials with externally mounted thermocouples and then partially lyophilized to determine the primary drying rate. Low- and high-particulate-containing samples, ice-nucleating additives silver iodide and Pseudomonas syringae, and other methods were used to obtain a wide range of nucleation temperatures. In cases where the supercooling exceeded 5 degrees C, freezing took place in the following three steps: (1) primary nucleation, (2) secondary nucleation encompassing the entire liquid volume, and (3) final solidification. The primary drying rate was dependent on the ice nucleation temperature, which is stochastic in nature but is affected by particulate content and the presence of ice nucleators. Sample cooling rates of 0.05 to 1 degrees C/min had no effect on nucleation temperatures and drying rate. We found that the ice nucleation temperature is the primary determinant of the primary drying rate. However, the nucleation temperature is not under direct control, and its stochastic nature and sensitivity to difficult-to-control parameters result in drying rate heterogeneity. Nucleation temperature heterogeneity may also result in variation in other morphology-related parameters such as surface area and secondary drying rate. Overall, these results document that factors such as particulate content and vial condition, which influence ice nucleation temperature, must be carefully controlled to avoid, for example, lot-to-lot variability during cGMP production. In addition, if these factors are not controlled and/or are inadvertently changed during process development and scaleup, a lyophilization cycle that was successful on the research scale may fail during large-scale production.

Primary radiation damage characterization of α-iron under irradiation temperature for various PKA energies

NASA Astrophysics Data System (ADS)

Sahi, Qurat-ul-ain; Kim, Yong-Soo

2018-04-01

The understanding of radiation-induced microstructural defects in body-centered cubic (BCC) iron is of major interest to those using advanced steel under extreme conditions in nuclear reactors. In this study, molecular dynamics (MD) simulations were implemented to examine the primary radiation damage in BCC iron with displacement cascades of energy 1, 5, 10, 20, and 30 keV at temperatures ranging from 100 to 1000 K. Statistical analysis of eight MD simulations of collision cascades were carried out along each [110], [112], [111] and a high index [135] direction and the temperature dependence of the surviving number of point defects and the in-cascade clustering of vacancies and interstitials were studied. The peak time and the corresponding number of defects increase with increasing irradiation temperature and primary knock-on atom (PKA) energy. However, the final number of surviving point defects decreases with increasing lattice temperature. This is associated with the increase of thermal spike at high PKA energy and its long timespan at higher temperatures. Defect production efficiency (i.e., surviving MD defects, per Norgett-Robinson-Torrens displacements) also showed a continuous decrease with the increasing irradiation temperature and PKA energy. The number of interstitial clusters increases with both irradiation temperature and PKA energy. However, the increase in the number of vacancy clusters with PKA energy is minimal-to-constant and decreases as the irradiation temperature increases. Similarly, the probability and cluster size distribution for larger interstitials increase with temperature, whereas only smaller size vacancy clusters were observed at higher temperatures.

Vaporization Would Cool Primary Battery

NASA Technical Reports Server (NTRS)

Bhandari, Pradeep; Miyake, Robert N.

1991-01-01

Temperature of discharging high-power-density primary battery maintained below specified level by evaporation of suitable liquid from jacket surrounding battery, according to proposal. Pressure-relief valve regulates pressure and boiling temperature of liquid. Less material needed in cooling by vaporization than in cooling by melting. Technique used to cool batteries in situations in which engineering constraints on volume, mass, and location prevent attachment of cooling fins, heat pipes, or like.

On the composition dependence of faceting behaviour of primary phases during solidification

NASA Astrophysics Data System (ADS)

Saroch, Mamta; Dubey, K. S.; Ramachandrarao, P.

1993-02-01

The entropy of solution of the primary aluminium-rich phase in the aluminium-tin melts has been evaluated as a function of temperature using available thermodynamic and phase equilibria data with a view to understand the faceting behaviour of this phase. It was noticed that the range of compositions in which alloys of aluminium and tin yield a faceted primary phase is correlated with the domain of compositions over which the entropy of solution shows a strong temperature dependence. It is demonstrated that both a high value of the entropy of solution and a strong temperature dependence of it are essential for providing faceting. A strong temperature dependence of the entropy of solution is in turn a consequence of negligible liquidus slope and existence of retrograde solubility. The AgBi and AgPb systems have similar features.

Room temperature acoustic transducers for high-temperature thermometry

NASA Astrophysics Data System (ADS)

Ripple, D. C.; Murdock, W. E.; Strouse, G. F.; Gillis, K. A.; Moldover, M. R.

2013-09-01

We have successfully conducted highly-accurate, primary acoustic thermometry at 600 K using a sound source and a sound detector located outside the thermostat, at room temperature. We describe the source, the detector, and the ducts that connected them to our cavity resonator. This transducer system preserved the purity of the argon gas, generated small, predictable perturbations to the acoustic resonance frequencies, and can be used well above 600 K.

Iridium/Rhenium Parts For Rocket Engines

NASA Technical Reports Server (NTRS)

Schneider, Steven J.; Harding, John T.; Wooten, John R.

1991-01-01

Oxidation/corrosion of metals at high temperatures primary life-limiting mechanism of parts in rocket engines. Combination of metals greatly increases operating temperature and longevity of these parts. Consists of two transition-element metals - iridium and rhenium - that melt at extremely high temperatures. Maximum operating temperature increased to 2,200 degrees C from 1,400 degrees C. Increases operating lifetimes of small rocket engines by more than factor of 10. Possible to make hotter-operating, longer-lasting components for turbines and other heat engines.

HIGH-RESOLUTION SPECTROSCOPY DURING ECLIPSE OF THE YOUNG SUBSTELLAR ECLIPSING BINARY 2MASS 0535-0546. II. SECONDARY SPECTRUM: NO EVIDENCE THAT SPOTS CAUSE THE TEMPERATURE REVERSAL

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

Mohanty, Subhanjoy; Stassun, Keivan G., E-mail: s.mohanty@imperial.ac.uk, E-mail: keivan.stassun@vanderbilt.edu

2012-10-10

We present high-resolution optical spectra of the young brown dwarf eclipsing binary 2M0535-05, obtained during eclipse of the higher-mass (primary) brown dwarf. Combined with our previous spectrum of the primary alone (Paper I), the new observations yield the spectrum of the secondary alone. We investigate, through a differential analysis of the two binary components, whether cool surface spots are responsible for suppressing the temperature of the primary. In Paper I, we found a significant discrepancy between the empirical surface gravity of the primary and that inferred via fine analysis of its spectrum. Here we find precisely the same discrepancy inmore » surface gravity, both qualitatively and quantitatively. While this may again be ascribed to either cool spots or model opacity errors, it implies that cool spots cannot be responsible for preferentially lowering the temperature of the primary: if they were, spot effects on the primary spectrum should be preferentially larger, and they are not. The T{sub eff}'s we infer for the primary and secondary, from the TiO-{epsilon} bands alone, show the same reversal, in the same ratio, as is empirically observed, bolstering the validity of our analysis. In turn, this implies that if suppression of convection by magnetic fields on the primary is the fundamental cause of the T{sub eff} reversal, then it cannot be a local suppression yielding spots mainly on the primary (though both components may be equally spotted), but a global suppression in the interior of the primary. We briefly discuss current theories of how this might work.« less

A new coating method for alleviating surface degradation of LiNi0.6Co0.2Mn0.2O2 cathode material: nanoscale surface treatment of primary particles.

PubMed

Kim, Hyejung; Kim, Min Gyu; Jeong, Hu Young; Nam, Haisol; Cho, Jaephil

2015-03-11

Structural degradation of Ni-rich cathode materials (LiNi(x)M(1-x)O2; M = Mn, Co, and Al; x > 0.5) during cycling at both high voltage (>4.3 V) and high temperature (>50 °C) led to the continuous generation of microcracks in a secondary particle that consisted of aggregated micrometer-sized primary particles. These microcracks caused deterioration of the electrochemical properties by disconnecting the electrical pathway between the primary particles and creating thermal instability owing to oxygen evolution during phase transformation. Here, we report a new concept to overcome those problems of the Ni-rich cathode material via nanoscale surface treatment of the primary particles. The resultant primary particles' surfaces had a higher cobalt content and a cation-mixing phase (Fm3̅m) with nanoscale thickness in the LiNi0.6Co0.2Mn0.2O2 cathode, leading to mitigation of the microcracks by suppressing the structural change from a layered to rock-salt phase. Furthermore, the higher oxidation state of Mn(4+) at the surface minimized the oxygen evolution at high temperatures. This approach resulted in improved structural and thermal stability in the severe cycling-test environment at 60 °C between 3.0 and 4.45 V and at elevated temperatures, showing a rate capability that was comparable to that of the pristine sample.

Fluorinated Carbon Composite Cathode for a High Energy Lithium Battery (Briefing Charts)

DTIC Science & Technology

2011-02-16

REPORT DOCUMENTATION PAGE Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 Form Approved OMB No. 0704-0188 The public reporting burden...monofluoride (Li/ CFx ) primary batteries have double energy density over state-of-the-art Li/MnO2 and Li/SO2 primary batteries (theoretically 2203 Wh/kg...temperature operating conditions. This invention relates to a high energy density Li/ CFx primary battery technology with substantial reduction in

Seasonal and Inter-Annual Variations in Carbon Dioxide Exchange over an Alpine Grassland in the Eastern Qinghai-Tibetan Plateau.

PubMed

Shang, Lunyu; Zhang, Yu; Lyu, Shihua; Wang, Shaoying

2016-01-01

This work analyzed carbon dioxide exchange and its controlling factors over an alpine grassland on the eastern Qinghai-Tibetan Plateau. The main results show that air temperature and photosynthetically active radiation are two dominant factors controlling daily gross primary production. Soil temperature and soil water content are the main factors controlling ecosystem respiration. Canopy photosynthetic activity is also responsible for the variation of daily ecosystem respiration other than environmental factors. No clear correlation between net ecosystem exchange and environmental factors was observed at daily scale. Temperature sensitive coefficient was observed to increase with larger soil water content. High values of temperature sensitive coefficient occurred during the periods when soil water content was high and grass was active. Annual integrated net ecosystem exchange, gross primary production and ecosystem respiration were -191, 1145 and 954 g C m-2 for 2010, and -250, 975 and 725 g C m-2 for 2011, respectively. Thus, this alpine grassland was a moderate carbon sink in both of the two years. Compared to alpine grasslands on the Qinghai-Tibetan Plateau, this alpine grassland demonstrated a much greater potential for carbon sequestration than others. Annual precipitation is a dominant factor controlling the variation of annual net ecosystem exchange over this grassland. The difference in gross primary production between the two years was not caused by the variation in annual precipitation. Instead, air temperature and the length of growing season had an important impact on annual gross primary production. Variation of annual ecosystem respiration was closely related to annual gross primary production and soil water content during the growing season.

Seasonal and Inter-Annual Variations in Carbon Dioxide Exchange over an Alpine Grassland in the Eastern Qinghai-Tibetan Plateau

PubMed Central

Shang, Lunyu; Zhang, Yu; Lyu, Shihua; Wang, Shaoying

2016-01-01

This work analyzed carbon dioxide exchange and its controlling factors over an alpine grassland on the eastern Qinghai-Tibetan Plateau. The main results show that air temperature and photosynthetically active radiation are two dominant factors controlling daily gross primary production. Soil temperature and soil water content are the main factors controlling ecosystem respiration. Canopy photosynthetic activity is also responsible for the variation of daily ecosystem respiration other than environmental factors. No clear correlation between net ecosystem exchange and environmental factors was observed at daily scale. Temperature sensitive coefficient was observed to increase with larger soil water content. High values of temperature sensitive coefficient occurred during the periods when soil water content was high and grass was active. Annual integrated net ecosystem exchange, gross primary production and ecosystem respiration were -191, 1145 and 954 g C m-2 for 2010, and -250, 975 and 725 g C m-2 for 2011, respectively. Thus, this alpine grassland was a moderate carbon sink in both of the two years. Compared to alpine grasslands on the Qinghai-Tibetan Plateau, this alpine grassland demonstrated a much greater potential for carbon sequestration than others. Annual precipitation is a dominant factor controlling the variation of annual net ecosystem exchange over this grassland. The difference in gross primary production between the two years was not caused by the variation in annual precipitation. Instead, air temperature and the length of growing season had an important impact on annual gross primary production. Variation of annual ecosystem respiration was closely related to annual gross primary production and soil water content during the growing season. PMID:27861616

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

Measurement of the Thermal Expansion Coefficient for Ultra-High Temperatures up to 3000 K

NASA Astrophysics Data System (ADS)

Kompan, T. A.; Kondratiev, S. V.; Korenev, A. S.; Puhov, N. F.; Inochkin, F. M.; Kruglov, S. K.; Bronshtein, I. G.

2018-03-01

The paper is devoted to a new high-temperature dilatometer, a part of the State Primary Standard of the thermal expansion coefficient (TEC) unit. The dilatometer is designed for investigation and certification of materials for TEC standards in the range of extremely high temperatures. The critical review of existing methods of TEC measurements is given. Also, the design, principles of operation and metrological parameters of the new device are described. The main attention is paid to the system of machine vision that allows accurate measurement of elongation at high temperatures. The results of TEC measurements for graphite GIP-4, single crystal Al2O3, and some other materials are also presented.

Reactions of butadiyne. 1: The reaction with hydrogen atoms

NASA Technical Reports Server (NTRS)

Schwanebeck, W.; Warnatz, J.

1984-01-01

The reaction of hydrogen (H) atoms with butadiene (C4H2) was studied at room temperature in a pressure range between w mbar and 10 mbar. The primary step was an addition of H to C4H2 which is in its high pressure range at p 1 mbar. Under these conditions the following addition of a second H atom lies in the transition region between low and high pressure range. Vibrationally excited C4H4 can be deactivated to form buten-(1)-yne-(3)(C4H4) or decomposes into two C2H2 molecules. The rate constant at room temperature for primary step is given. The second order rate constant for the consumption of buten-(1)-yne-(3) is an H atom excess at room temperature is given.

Primary and secondary room temperature molten salt electrochemical cells

NASA Astrophysics Data System (ADS)

Reynolds, G. F.; Dymek, C. J., Jr.

1985-07-01

Three novel primary cells which use room temperature molten salt electrolytes are examined and found to have high open circuit potentials in the 1.75-2.19 V range, by comparison with the Al/AlCl3-MEICl concentration cell; their cathodes were of FeCl3-MEICl, WCl6-MEICl, and Br2/reticulated vitreous carbon together with Pt. Also, secondary electrochemical cell candidates were examined which combined the reversible Al/AlCl3-MEICl electrode with reversible zinc and cadmium molten salt electrodes to yield open circuit potentials of about 0.7 and 1.0 V, respectively. Room temperature molten salts' half-cell reduction potentials are given.

Intestinal barrier function of Atlantic salmon (Salmo salar L.) post smolts is reduced by common sea cage environments and suggested as a possible physiological welfare indicator.

PubMed

Sundh, Henrik; Kvamme, Bjørn Olav; Fridell, Frode; Olsen, Rolf Erik; Ellis, Tim; Taranger, Geir Lasse; Sundell, Kristina

2010-11-09

Fish farmed under high intensity aquaculture conditions are subjected to unnatural environments that may cause stress. Therefore awareness of how to maintain good health and welfare of farmed fish is important. For Atlantic salmon held in sea cages, water flow, dissolved oxygen (DO) levels and temperature will fluctuate over time and the fish can at times be exposed to detrimentally low DO levels and high temperatures. This experimental study investigates primary and secondary stress responses of Atlantic salmon post smolts to long-term exposure to reduced and fluctuating DO levels and high water temperatures, mimicking situations in the sea cages. Plasma cortisol levels and cortisol release to the water were assessed as indicators of the primary stress response and intestinal barrier integrity and physiological functions as indicators of secondary responses to changes in environmental conditions. Plasma cortisol levels were elevated in fish exposed to low (50% and 60% saturation) DO levels and low temperature (9°C), at days 9, 29 and 48. The intestinal barrier function, measured as electrical resistance (TER) and permeability of mannitol at the end of the experiment, were reduced at 50% DO, in both proximal and distal intestine. When low DO levels were combined with high temperature (16°C), plasma cortisol levels were elevated in the cyclic 1:5 h at 85%:50% DO group and fixed 50% DO group compared to the control (85% DO) group at day 10 but not at later time points. The intestinal barrier function was clearly disturbed in the 50% DO group; TER was reduced in both intestinal regions concomitant with increased paracellular permeability in the distal region. This study reveals that adverse environmental conditions (low water flow, low DO levels at low and high temperature), that can occur in sea cages, elicits primary and secondary stress responses in Atlantic salmon post smolts. The intestinal barrier function was significantly affected by prolonged hypoxic stress even when no primary stress response was observed. This suggests that intestinal barrier function is a good experimental marker for evaluation of chronic stress and that it can be a valuable tool to study the impact of various husbandry conditions on health and welfare of farmed Atlantic salmon.

Intestinal barrier function of Atlantic salmon (Salmo salar L.) post smolts is reduced by common sea cage environments and suggested as a possible physiological welfare indicator

PubMed Central

2010-01-01

Background Fish farmed under high intensity aquaculture conditions are subjected to unnatural environments that may cause stress. Therefore awareness of how to maintain good health and welfare of farmed fish is important. For Atlantic salmon held in sea cages, water flow, dissolved oxygen (DO) levels and temperature will fluctuate over time and the fish can at times be exposed to detrimentally low DO levels and high temperatures. This experimental study investigates primary and secondary stress responses of Atlantic salmon post smolts to long-term exposure to reduced and fluctuating DO levels and high water temperatures, mimicking situations in the sea cages. Plasma cortisol levels and cortisol release to the water were assessed as indicators of the primary stress response and intestinal barrier integrity and physiological functions as indicators of secondary responses to changes in environmental conditions. Results Plasma cortisol levels were elevated in fish exposed to low (50% and 60% saturation) DO levels and low temperature (9°C), at days 9, 29 and 48. The intestinal barrier function, measured as electrical resistance (TER) and permeability of mannitol at the end of the experiment, were reduced at 50% DO, in both proximal and distal intestine. When low DO levels were combined with high temperature (16°C), plasma cortisol levels were elevated in the cyclic 1:5 h at 85%:50% DO group and fixed 50% DO group compared to the control (85% DO) group at day 10 but not at later time points. The intestinal barrier function was clearly disturbed in the 50% DO group; TER was reduced in both intestinal regions concomitant with increased paracellular permeability in the distal region. Conclusions This study reveals that adverse environmental conditions (low water flow, low DO levels at low and high temperature), that can occur in sea cages, elicits primary and secondary stress responses in Atlantic salmon post smolts. The intestinal barrier function was significantly affected by prolonged hypoxic stress even when no primary stress response was observed. This suggests that intestinal barrier function is a good experimental marker for evaluation of chronic stress and that it can be a valuable tool to study the impact of various husbandry conditions on health and welfare of farmed Atlantic salmon. PMID:21062437

High skin temperature and hypohydration impair aerobic performance.

PubMed

Sawka, Michael N; Cheuvront, Samuel N; Kenefick, Robert W

2012-03-01

This paper reviews the roles of hot skin (>35°C) and body water deficits (>2% body mass; hypohydration) in impairing submaximal aerobic performance. Hot skin is associated with high skin blood flow requirements and hypohydration is associated with reduced cardiac filling, both of which act to reduce aerobic reserve. In euhydrated subjects, hot skin alone (with a modest core temperature elevation) impairs submaximal aerobic performance. Conversely, aerobic performance is sustained with core temperatures >40°C if skin temperatures are cool-warm when euhydrated. No study has demonstrated that high core temperature (∼40°C) alone, without coexisting hot skin, will impair aerobic performance. In hypohydrated subjects, aerobic performance begins to be impaired when skin temperatures exceed 27°C, and even warmer skin exacerbates the aerobic performance impairment (-1.5% for each 1°C skin temperature). We conclude that hot skin (high skin blood flow requirements from narrow skin temperature to core temperature gradients), not high core temperature, is the 'primary' factor impairing aerobic exercise performance when euhydrated and that hypohydration exacerbates this effect.

Construction of Home-Made Tin Fixed-Point Cell at TUBITAK UME

NASA Astrophysics Data System (ADS)

Kalemci, M.; Arifovic, N.; Bağçe, A.; Aytekin, S. O.; Ince, A. T.

2015-08-01

TUBITAK UME Temperature Laboratory initiated a new study which focuses on the construction of a tin freezing-point cell as a primary temperature standard. The design is an open-cell type similar to the National Institute of Standards and Technology design. With this aim, a brand new vacuum and filling line employing an oil diffusion pump and two cold traps (liquid nitrogen and dry ice) was set-up. The graphite parts (crucible, thermometer well, etc.) have been baked at high temperature under vacuum. Each cell was filled with approximately 1 kg of high-purity tin (99.9999 %) in a three-zone furnace. Then several melting and freezing curves were obtained to assess the quality of the home-made cell, and also the new cell was compared with the existing reference cell of the laboratory. The results obtained are very close to the reference cell of UME, indicating that the method used for fabrication was promising and satisfactory and also seems to meet the requirements to have a primary level temperature standard.

X-ray tomography of feed-to-glass transition of simulated borosilicate waste glasses

DOE PAGES

Harris, William H.; Guillen, Donna P.; Klouzek, Jaroslav; ...

2017-05-10

The feed composition of a high level nuclear waste (HLW) glass melter affects the overall melting rate by influencing the chemical, thermophysical, and morphological properties of a relatively insulating cold cap layer over the molten phase where the primary feed vitrification reactions occur. Data from X ray computed tomography imaging of melting pellets comprised of a simulated high-aluminum HLW feed heated at a rate of 10°C/min reveal the distribution and morphology of bubbles, collectively known as primary foam, within this layer for various SiO 2/(Li 2CO 3+H 3BO 3+Na 2CO 3) mass fractions at temperatures between 600°C and 1040°C. Tomore » track melting dynamics, cross-sections obtained through the central profile of the pellet were digitally segmented into primary foam and a condensed phase. Pellet dimensions were extracted using Photoshop CS6 tools while the DREAM.3D software package was used to calculate pellet profile area, average and maximum bubble areas, and two-dimensional void fraction. The measured linear increase in the pellet area expansion rates – and therefore the increase in batch gas evolution rates – with SiO 2/(Li 2CO 3+H 3BO 3+Na 2CO 3) mass fraction despite an exponential increase in viscosity of the final waste glass at 1050°C and a lower total amount of gas-evolving species suggest that the retention of primary foam with large average bubble size at higher temperatures results from faster reaction kinetics rather than increased viscosity. However, viscosity does affect the initial foam collapse temperature by supporting the growth of larger bubbles. Because the maximum bubble size is limited by the pellet dimensions, larger scale studies are needed to understand primary foam morphology at high temperatures. This temperature-dependent morphological data can be used in future investigations to synthetically generate cold cap structures for use in models of heat transfer within a HLW glass melter.« less

X-ray tomography of feed-to-glass transition of simulated borosilicate waste glasses

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

Harris, William H.; Guillen, Donna P.; Klouzek, Jaroslav

The feed composition of a high level nuclear waste (HLW) glass melter affects the overall melting rate by influencing the chemical, thermophysical, and morphological properties of a relatively insulating cold cap layer over the molten phase where the primary feed vitrification reactions occur. Data from X ray computed tomography imaging of melting pellets comprised of a simulated high-aluminum HLW feed heated at a rate of 10°C/min reveal the distribution and morphology of bubbles, collectively known as primary foam, within this layer for various SiO 2/(Li 2CO 3+H 3BO 3+Na 2CO 3) mass fractions at temperatures between 600°C and 1040°C. Tomore » track melting dynamics, cross-sections obtained through the central profile of the pellet were digitally segmented into primary foam and a condensed phase. Pellet dimensions were extracted using Photoshop CS6 tools while the DREAM.3D software package was used to calculate pellet profile area, average and maximum bubble areas, and two-dimensional void fraction. The measured linear increase in the pellet area expansion rates – and therefore the increase in batch gas evolution rates – with SiO 2/(Li 2CO 3+H 3BO 3+Na 2CO 3) mass fraction despite an exponential increase in viscosity of the final waste glass at 1050°C and a lower total amount of gas-evolving species suggest that the retention of primary foam with large average bubble size at higher temperatures results from faster reaction kinetics rather than increased viscosity. However, viscosity does affect the initial foam collapse temperature by supporting the growth of larger bubbles. Because the maximum bubble size is limited by the pellet dimensions, larger scale studies are needed to understand primary foam morphology at high temperatures. This temperature-dependent morphological data can be used in future investigations to synthetically generate cold cap structures for use in models of heat transfer within a HLW glass melter.« less

Effects of defects on thermal decomposition of HMX via ReaxFF molecular dynamics simulations.

PubMed

Zhou, Ting-Ting; Huang, Feng-Lei

2011-01-20

Effects of molecular vacancies on the decomposition mechanisms and reaction dynamics of condensed-phase β-HMX at various temperatures were studied using ReaxFF molecular dynamics simulations. Results show that three primary initial decomposition mechanisms, namely, N-NO(2) bond dissociation, HONO elimination, and concerted ring fission, exist at both high and lower temperatures. The contribution of the three mechanisms to the initial decomposition of HMX is influenced by molecular vacancies, and the effects vary with temperature. At high temperature (2500 K), molecular vacancies remarkably promote N-N bond cleavage and concerted ring breaking but hinder HONO formation. N-N bond dissociation and HONO elimination are two primary competing reaction mechanisms, and the former is dominant in the initial decomposition. Concerted ring breaking of condensed-phase HMX is not favored at high temperature. At lower temperature (1500 K), the most preferential initial decomposition pathway is N-N bond dissociation followed by the formation of NO(3) (O migration), although all three mechanisms are promoted by molecular vacancies. The promotion effect on concerted ring breaking is considerable at lower temperature. Products resulting from concerted ring breaking appear in the defective system but not in the perfect crystal. The mechanism of HONO elimination is less important at lower temperature. We also estimated the reaction rate constant and activation barriers of initial decomposition with different vacancy concentrations. Molecular vacancies accelerate the decomposition of condensed-phase HMX by increasing the reaction rate constant and reducing activation barriers.

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

Stewart, Gary

The primary objective of this project was to demonstrate the feasibility and reliability of utilizing high-temperature superconducting (HTS) materials in a Transmission Level Superconducting Fault Current Limiter (SFCL) application. During the project, the type of high-temperature superconducting material used evolved from 1 st generation (1G) BSCCO-2212 melt cast bulk high-temperature superconductors to 2 nd generation (2G) YBCO-based high-temperature superconducting tape. The SFCL employed SuperPower's “Matrix” technology, that offers modular features to enable scale up to transmission voltage levels. The SFCL consists of individual modules that contain elements and parallel inductors that assist in carrying the current during the fault. Amore » number of these modules are arranged in an m x n array to form the current-limiting matrix.« less

Low-Cost Resin Transfer Molding Process Developed for High-Temperature Polyimide Matrix Composites

NASA Technical Reports Server (NTRS)

1996-01-01

The use of high-temperature polymer matrix composites (PMC's) in aircraft engine applications can significantly reduce engine weight and improve performance and fuel efficiency. High-temperature PMC's, such as those based on the PMR-15 polyimide matrix resin developed by the NASA Lewis Research Center, have been used extensively in military applications where performance improvements have justified their use regardless of the cost involved in producing the component. However, in commercial engines cost is a primary driver, and PMC components must be produced at costs comparable to those of the metal components that they will replace.

Titanium Dioxide Volatility in High Temperature Water Vapor

NASA Technical Reports Server (NTRS)

Nguyen, QynhGiao N.

2008-01-01

Titanium (Ti) containing materials are of high interest to the aerospace industry due to its high temperature capability, strength, and light weight. As with most metals an exterior oxide layer naturally exists in environments that contain oxygen (i.e. air). At high temperatures, water vapor plays a key role in the volatility of materials including oxide surfaces. This study will evaluate cold pressed titanium dioxide (TiO2) powder pellets at a temperature range of 1400 C - 1200 C in water containing environments to determine the volatile hydroxyl species using the transpiration method. The water content ranged from 0-76 mole% and the oxygen content range was 0-100 mole % during the 20-250 hour exposure times. Preliminary results indicate that oxygen is not a key contributor at these temperatures and the following reaction is the primary volatile equation for all three temperatures: TiO2 (s) + H2O (g) = TiO(OH)2 (g).

Creep Behavior of Posidonia Shale at Elevated Pressure and Temperature

NASA Astrophysics Data System (ADS)

Rybacki, E.; Herrmann, J.; Wirth, R.; Dresen, G.

2017-12-01

Unconventional reservoir rocks are usually stimulated by repeated hydraulic fracturing operations. However, the production rate often decays with time that may arise from creep-induced fracture closure by proppant embedment. To examine experimentally the creep behavior of shales, we deformed immature carbonate-rich Posidonia shale at constant stress conditions and elevated temperatures between 50° and 200°C and confining pressures of 50 to 200 MPa. Samples showed transient creep in the semibrittle regime with high deformation rates at high differential stress, high temperature, and low confinement. Strain was mainly accommodated by deformation of the weak organic matter and phyllosilicates and by pore space reduction. At relatively low stress the samples deformed in the primary creep regime with continuously decelerating strain rate. The relation between strain and time can be described by an empirical power law equation, where the fitted parameters vary with temperature, pressure and stress. Our results suggest that healing of hydraulic fractures at low stresses by creep-induced proppant embedment is unlikely within a creep period of several years. At high differential stress (85-90% of the triaxial strength), as may be expected in situ at contact areas due to stress concentrations, the shale showed secondary creep, followed by tertiary creep until failure. In this regime, stress corrosion may induce microcrack propagation and coalescence. Secondary creep rates were also described by a power law that predicts faster fracture closure rates than for primary creep and likely contributes to production rate decline. Comparison of our data with published primary creep data on other shales suggest that the long-term creep behavior of shales can be correlated to their brittleness estimated from composition. Low creep strain is supported by a high fraction of strong minerals that can build up a load-bearing framework.

Controlled metal-semiconductor sintering/alloying by one-directional reverse illumination

DOEpatents

Sopori, Bhushan L.

1993-01-01

Metal strips deposited on a top surface of a semiconductor substrate are sintered at one temperature simultaneously with alloying a metal layer on the bottom surface at a second, higher temperature. This simultaneous sintering of metal strips and alloying a metal layer on opposite surfaces of the substrate at different temperatures is accomplished by directing infrared radiation through the top surface to the interface of the bottom surface with the metal layer where the radiation is absorbed to create a primary hot zone with a temperature high enough to melt and alloy the metal layer with the bottom surface of the substrate. Secondary heat effects, including heat conducted through the substrate from the primary hot zone and heat created by infrared radiation reflected from the metal layer to the metal strips, as well as heat created from some primary absorption by the metal strips, combine to create secondary hot zones at the interfaces of the metal strips with the top surface of the substrate. These secondary hot zones are not as hot as the primary hot zone, but they are hot enough to sinter the metal strips to the substrate.

Probing M Dwarf Model-Data Discrepancies via Precise, Empirical Characterization of a Long-Period F+M Binary

NASA Astrophysics Data System (ADS)

Stevens, Daniel; Gaudi, Scott; Beatty, Thomas; Siverd, Robert

2018-05-01

Double-lined eclipsing binaries (EBs) have been the gold standard for direct, precise (less than a few percent), and accurate measurements of stellar masses and radii. However, with the availability of Gaia parallaxes and nearly complete spectral energy distributions (SEDs) of millions of stars, it will soon be possible to make such measurements for the much larger number of single-lined EBs such as high mass-ratio systems and transiting planets, both of which are routinely found by transit surveys. Combining high-precision eclipse photometry and radial velocity (RV) observations of the primary star enables measurements of the primary star's density, the ratio of stellar radii, and a combination of the stars' masses. Broad-band photometry from the ultraviolet to the infrared plus a Gaia parallax and an effective temperature of the primary from either the SED or high-resolution spectra, allow one to measure the radius (and mass via the density) of the primary. The radius and mass of the secondary can then be determined in the usual way with the radius ratio and RVs, and the companion's effective temperature can be determined from a secondary eclipse measurement and the primary star's effective temperature. For single-lined EBs, the precision of ingress/egress duration measurements dominates the error budget of the masses and companion radius. We propose to observe one primary and secondary eclipse of the F+M binary TYC 4223-1012-1, an M dwarf on a 16.5-day orbit around an F dwarf. Ground-based data poorly constrain TYC 4223-1012-1's masses due to the near-impossibility of observing the full 10-hr eclipse from the ground. By combining extant RV and SED data with the Spitzer data, we expect to measure the mass, radius, and effective temperature of the M dwarf to a few percent. This is comparable to the precision of the best-characterized literature M dwarfs, but at an orbital period far beyond the majority of such systems, where tidal effects should be negligible.

Comparative study of carbon free and carbon containing Li4Ti5O12 electrodes

NASA Astrophysics Data System (ADS)

Pohjalainen, Elina; Kallioinen, Jani; Kallio, Tanja

2015-04-01

Traditionally electrodes for lithium ion batteries are manufactured using carbon additives to increase the conductivity. However, in case of lithium titanate, Li4Ti5O12 (LTO), carbon free electrodes have gathered some interest lately. Therefore two LTO materials synthesized using the same synthesis but different end milling process resulting in materials with different particle size and surface area are compared here using electrodes manufactured with and without carbon additives. Both LTO samples (LTO-SP with small primary particle size and high surface area, and LTO-LP with larger primary particle size and small surface area) produce similar capacities and voltages with or without carbon additives at low C-rates at the room temperature. However, at high C-rates and/or sub-zero temperatures electrodes with carbon additives produce higher capacities and smaller ohmic losses and this behavior is more pronounced for the LTO electrodes with smaller primary particle size and larger surface area. These results show that the feasibility of carbon free LTO electrodes depends on the properties of LTO affecting the morphology of the electrode and consequently, the transport properties. This is most pronounced under conditions where electron and Li+ ion transfer become limiting (high C-rates and low temperature).

Warmer weather as a risk factor for hospitalisations due to urinary tract infections.

PubMed

Simmering, J E; Cavanaugh, J E; Polgreen, L A; Polgreen, P M

2018-02-01

The incidence of urinary tract infections (UTIs) is seasonal, and this seasonality may be explained by changes in weather, specifically, temperature. Using data from the Nationwide Inpatient Sample, we identified the geographic location for 581 813 hospital admissions with the primary diagnosis of a UTI and 56 630 773 non-UTI hospitalisations in the United States. Next, we used data from the National Climatic Data Center to estimate the monthly average temperature for each location. Using a case-control design, we modelled the odds of a hospital admission having a primary diagnosis of UTI as a function of demographics, payer, location, patient severity, admission month, year and the average temperature for the admission month. We found, after controlling for patient factors and month of admission, the odds of a UTI diagnosis increased with higher temperatures in a dose-dependent manner. For example, relative to months with average temperatures of 5-7.5 °C, an admission in a month with an average temperature of 27.5-30 °C has 20% higher odds of a primary diagnosis of UTI. However, in months with extremely high average temperatures (above 30 °C), the odds of a UTI admissions decrease, perhaps due to changes in behaviour. Thus, at a population level, UTI-related hospitalisations are associated with warmer weather.

High concentration agglomerate dynamics at high temperatures.

PubMed

Heine, M C; Pratsinis, S E

2006-11-21

The dynamics of agglomerate aerosols are investigated at high solids concentrations that are typical in industrial scale manufacture of fine particles (precursor mole fraction larger than 10 mol %). In particular, formation and growth of fumed silica at such concentrations by chemical reaction, coagulation, and sintering is simulated at nonisothermal conditions and compared to limited experimental data and commercial product specifications. Using recent chemical kinetics for silica formation by SiCl4 hydrolysis and neglecting aerosol polydispersity, the evolution of the diameter of primary particles (specific surface area, SSA), hard- and soft-agglomerates, along with agglomerate effective volume fraction (volume occupied by agglomerate) is investigated. Classic Smoluchowski theory is fundamentally limited for description of soft-agglomerate Brownian coagulation at high solids concentrations. In fact, these high concentrations affect little the primary particle diameter (or SSA) but dominate the soft-agglomerate diameter, structure, and volume fraction, leading to gelation consistent with experimental data. This indicates that restructuring and fragmentation should affect product particle characteristics during high-temperature synthesis of nanostructured particles at high concentrations in aerosol flow reactors.

Temperature rises during application of Er:YAG laser under different primary dentin thicknesses.

PubMed

Hubbezoglu, Ihsan; Unal, Murat; Zan, Recai; Hurmuzlu, Feridun

2013-05-01

The present study investigated the effects of the Er:YAG laser's different pulse repetition rates on temperature rise under various primary dentin thicknesses. The Er:YAG laser can be used for restorative approaches in clinics and is used to treat dental caries. There are some reports that explain the temperature rise effect of the Er:YAG laser. Recently, the Er:YAG laser has been found to play an important role in temperature rises during the application on dentin. Caries-free primary mandibular molars were prepared to obtain dentin discs with 0.5, 1, 1.5, and 2 mm thicknesses (n=10). These discs were placed between the Teflon mold cylinders of a temperature test apparatus. We preferred three pulse repetition rates of 10, 15, and 20 Hz with an energy density of 12.7 J/cm2 and a 230 μs pulse duration. All dentin discs were irradiated for 30 sec by the Er:YAG laser. Temperature rises were recorded using an L-type thermocouple and universal data loggers/scanners (E-680, Elimko Co., Turkey). Data were analyzed by two-way ANOVA and Tukey tests. Whereas the lowest temperature rise (0.44±0.09 °C) was measured from a 10 Hz pulse repetition rate at a dentin thickness of 2 mm, the highest temperature rise (3.86±0.43 °C) was measured from a 20 Hz pulse repetition rate at a 0.5 mm dentin thickness. Temperature rise did not reach critical value for pulpal injury in any primary dentin thicknesses irradiated by a high repetition rate of the Er:YAG laser.

Room temperature aerobic oxidation of amines by a nanocrystalline ruthenium oxide pyrochlore nafion composite catalyst.

PubMed

Venkatesan, Shanmuganathan; Kumar, Annamalai Senthil; Lee, Jyh-Fu; Chan, Ting-Shan; Zen, Jyh-Myng

2012-05-14

The aerobic oxidation of primary amines to their respective nitriles has been carried out at room temperature using a highly reusable nanocrystalline ruthenium oxide pyrochlore Nafion composite catalyst (see figure). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Topographic heterogeneity and temperature amplitude explain species richness patterns of birds in the Qinghai-Tibetan Plateau.

PubMed

Zhang, Chunlan; Quan, Qing; Wu, Yongjie; Chen, Youhua; He, Peng; Qu, Yanhua; Lei, Fumin

2017-04-01

Large-scale patterns of species richness have gained much attention in recent years; however, the factors that drive high species richness are still controversial in local regions, especially in highly diversified montane regions. The Qinghai-Tibetan Plateau (QTP) and the surrounding mountains are biodiversity hot spots due to a high number of endemic montane species. Here, we explored the factors underlying this high level of diversity by studying the relationship between species richness and environmental variables. The richness patterns of 758 resident bird species were summarized at the scale of 1°×1° grid cell at different taxonomic levels (order, family, genus, and species) and in different taxonomic groups (Passeriformes, Galliformes, Falconiformes, and Columbiformes). These richness patterns were subsequently analyzed against habitat heterogeneity (topographical heterogeneity and land cover), temperature amplitude (annual temperature, annual precipitation, precipitation seasonality, and temperature seasonality) and a vegetation index (net primary productivity). Our results showed that the highest richness was found in the southeastern part of the QTP, the eastern Himalayas. The lowest richness was observed in the central plateau of the QTP. Topographical heterogeneity and temperature amplitude are the primary factors that explain overall patterns of species richness in the QTP, although the specific effect of each environmental variable varies between the different taxonomic groups depending on their own evolutionary histories and ecological requirements. High species richness in the southeastern QTP is mostly due to highly diversified habitat types and temperature zones along elevation gradients, whereas the low species richness in the central plateau of the QTP may be due to environmental and energetic constraints, as the central plateau is harsh environment.

Sub-seafloor Processes and the Composition of Diffuse Hydrothermal Fluids

NASA Astrophysics Data System (ADS)

Butterfield, D. A.; Lilley, M. D.; Huber, J. A.; Baross, J. A.

2002-12-01

High-temperature water/rock reactions create the primary hydrothermal fluids that are diluted with cool, "crustal seawater" to produce low-temperature, diffuse hydrothermal vent fluids. By knowing the composition of each of the components that combine to produce diffuse fluids, one can compare the composition of calculated mixtures with the composition of sampled fluids, and thereby infer what chemical constituents have been affected by processes other than simple conservative mixing. Although there is always uncertainty in the composition of fluids from the sub-seafloor, some processes are significant enough to alter diffuse fluid compositions from the expected conservative mixtures of hot,primary fluid and "crustal seawater." When hydrothermal vents with a wide range of temperature are sampled, processes occurring in different thermal and chemical environments potentially can be discerned. At Axial Volcano (AV) on the Juan de Fuca ridge, methane clearly is produced in warm sub-seafloor environments at temperatures of ~ 100° or less. Based on culturing and phylogenetic analysis from the same water samples at AV, hyperthermophilic methanogens are present in water samples taken from vents ranging in temperature from 15 to 78° C. Ratios of hydrogen sulfide to pseudo-conservative tracers (dissolved silica or heat) at AV decrease when primary fluids are highly diluted with oxygenated seawater. Phylogenetic signatures of microbes closely related to sulfide-oxidizers are present in these same fluids. Hydrogen sulfide oxidation represents the dominant source of energy for chemosynthesis at AV, as in most hydrothermal systems, but a relatively small proportion of the total hydrogen sulfide available is actually oxidized, except at the very lowest temperatures.

Flow Characteristics of a Multiple Nozzle Exhaust Gas Eductor System.

DTIC Science & Technology

1981-03-01

these exhaust gases are a temperatures significantly above those of conventionally powered ships. A few of the problems caused by these high temperatures ...systems designed for marine gas turbine applications must substantially cool exhaust gases , present an exterior stack surface temperature which will not...stack in. H 02 R - Gas constant for air, 53.34 ft-lbf/Ibm-R s - Entropy, Btu/Ibm-R S - Primary dimension of mixing stack T - Absolute temperature , R

Effects of Heat Treatment on the Microstructures and High Temperature Mechanical Properties of Hypereutectic Al-14Si-Cu-Mg Alloy Manufactured by Liquid Phase Sintering Process

NASA Astrophysics Data System (ADS)

Heo, Joon-Young; Gwon, Jin-Han; Park, Jong-Kwan; Lee, Kee-Ahn

2018-05-01

Hypereutectic Al-Si alloy is an aluminum alloy containing at least 12.6 wt.% Si. It is necessary to evenly control the primary Si particle size and distribution in hypereutectic Al-Si alloy. In order to achieve this, there have been attempts to manufacture hypereutectic Al-Si alloy through a liquid phase sintering. This study investigated the microstructures and high temperature mechanical properties of hypereutectic Al-14Si-Cu-Mg alloy manufactured by liquid phase sintering process and changes in them after T6 heat treatment. Microstructural observation identified large amounts of small primary Si particles evenly distributed in the matrix, and small amounts of various precipitation phases were found in grain interiors and grain boundaries. After T6 heat treatment, the primary Si particle size and shape did not change significantly, but the size and distribution of CuAl2 ( θ) and AlCuMgSi ( Q) changed. Hardness tests measured 97.36 HV after sintering and 142.5 HV after heat treatment. Compression tests were performed from room temperature to 300 °C. The results represented that yield strength was greater after heat treatment (RT 300 °C: 351 93 MPa) than after sintering (RT 300 °C: 210 89 MPa). Fracture surface analysis identified cracks developing mostly along the interface between the primary Si particles and the matrix with some differences among temperature conditions. In addition, brittle fracture mode was found after T6 heat treatment.

A 'two-tank' seasonal storage concept for solar space heating of buildings

NASA Astrophysics Data System (ADS)

Cha, B. K.; Connor, D. W.; Mueller, R. O.

This paper presents an analysis of a novel 'two-tank' water storage system, consisting of a large primary water tank for seasonal storage of solar energy plus a much smaller secondary water tank for storage of solar energy collected during the heating season. The system offers the advantages of high collection efficiency during the early stages of the heating season, a period when the temperature of the primary tank is generally high. By preferentially drawing energy from the small secondary tank to meet load, its temperature can be kept well below that of the larger primary tank, thereby providing a lower-temperature source for collector inlet fluid. The resulting improvement in annual system efficiency through the addition of a small secondary tank is found to be substantial - for the site considered in the paper (Madison, Wisconsin), the relative percentage gain in annual performance is in the range of 10 to 20%. A simple computer model permits accurate hour-by-hour transient simulation of thermal performance over a yearly cycle. The paper presents results of detailed simulations of collectors and storage sizing and design trade-offs for solar energy systems supplying 90% to 100% of annual heating load requirements.

Rocket Motor Joint Construction Including Thermal Barrier

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Inventor); Dunlap, Patrick H., Jr. (Inventor)

2002-01-01

A thermal barrier for extremely high temperature applications consists of a carbon fiber core and one or more layers of braided carbon fibers surrounding the core. The thermal barrier is preferably a large diameter ring, having a relatively small cross-section. The thermal barrier is particularly suited for use as part of a joint structure in solid rocket motor casings to protect low temperature elements such as the primary and secondary elastomeric O-ring seals therein from high temperature gases of the rocket motor. The thermal barrier exhibits adequate porosity to allow pressure to reach the radially outward disposed O-ring seals allowing them to seat and perform the primary sealing function. The thermal barrier is disposed in a cavity or groove in the casing joint, between the hot propulsion gases interior of the rocket motor and primary and secondary O-ring seals. The characteristics of the thermal barrier may be enhanced in different applications by the inclusion of certain compounds in the casing joint, by the inclusion of RTV sealant or similar materials at the site of the thermal barrier, and/or by the incorporation of a metal core or plurality of metal braids within the carbon braid in the thermal barrier structure.

Microstructure and mechanical properties of zirconium doped NiAl/Cr(Mo) hypoeutectic alloy prepared by injection casting

NASA Astrophysics Data System (ADS)

Sheng, L. Y.; Du, B. N.; Guo, J. T.

2017-01-01

NiAl based materials has been considered as most potential candidate of turbine blade, due to its excellent high-temperature properties. However the bad room-temperature properties handicap its application. In the present paper, the zirconium doped NiAl/Cr(Mo) hypoeutectic alloy is fabricated by conventional casting and injection casting technology to improve its room-temperature properties. The microstructure and compressive properties at different temperatures of the conventionally-cast and injection-cast were investigated. The results exhibit that the conventionally-cast alloy comprises coarse primary NiAl phase and eutectic cell, which is dotted with irregular Ni2AlZr Heusler phase. Compared with the conventionally-cast alloy, the injection-cast alloy possesses refined the primary NiAl, eutectic cell and eutectic lamella. In addition, the Ni2AlZr Heusler phase become smaller and distribute uniformly. Moreover, the injection casting decrease the area fraction of primary NiAl phase at the cell interior or cell boundaries. The compressive ductility and yield strength of the injection-cast alloy at room temperature increase by about 100% and 35% over those of conventionally-cast alloy, which should be ascribed to the microstructure optimization.

Lightweight, Ultra-High-Temperature, CMC-Lined Carbon/Carbon Structures

NASA Technical Reports Server (NTRS)

Wright, Matthew J.; Ramachandran, Gautham; Williams, Brian E.

2011-01-01

Carbon/carbon (C/C) is an established engineering material used extensively in aerospace. The beneficial properties of C/C include high strength, low density, and toughness. Its shortcoming is its limited usability at temperatures higher than the oxidation temperature of carbon . approximately 400 C. Ceramic matrix composites (CMCs) are used instead, but carry a weight penalty. Combining a thin laminate of CMC to a bulk structure of C/C retains all of the benefits of C/C with the high temperature oxidizing environment usability of CMCs. Ultramet demonstrated the feasibility of combining the light weight of C/C composites with the oxidation resistance of zirconium carbide (ZrC) and zirconium- silicon carbide (Zr-Si-C) CMCs in a unique system composed of a C/C primary structure with an integral CMC liner with temperature capability up to 4,200 F (.2,315 C). The system effectively bridged the gap in weight and performance between coated C/C and bulk CMCs. Fabrication was demonstrated through an innovative variant of Ultramet fs rapid, pressureless melt infiltration processing technology. The fully developed material system has strength that is comparable with that of C/C, lower density than Cf/SiC, and ultra-high-temperature oxidation stability. Application of the reinforced ceramic casing to a predominantly C/C structure creates a highly innovative material with the potential to achieve the long-sought goal of long-term, cyclic high-temperature use of C/C in an oxidizing environment. The C/C substructure provided most of the mechanical integrity, and the CMC strengths achieved appeared to be sufficient to allow the CMC to perform its primary function of protecting the C/C. Nozzle extension components were fabricated and successfully hot-fire tested. Test results showed good thermochemical and thermomechanical stability of the CMC, as well as excellent interfacial bonding between the CMC liner and the underlying C/C structure. In particular, hafnium-containing CMCs on C/C were shown to perform well at temperatures exceeding 3,500 F (.1,925 C). The melt-infiltrated CMC-lined C/C composites offered a lower density than Cf/SiC. The melt-infiltrated composites offer greater use temperature than Cf/SiC because of the more refractory ceramic matrices and the C/C substructure provides greater high-temperature strength. The progress made in this work will allow multiple high-temperature components used in oxidizing environments to take advantage of the low density and high strength of C/C combined with the high-temperature oxidation resistance of melt-infiltrated CMCs.

Very high temperature fiber processing and testing through the use of ultrahigh solar energy concentration

NASA Astrophysics Data System (ADS)

Jacobson, Benjamin A.; Gleckman, Philip L.; Holman, Robert L.; Sagie, Daniel; Winston, Roland

1991-10-01

We have demonstrated the feasibility of a high temperature cool-wall optical furnace that harnesses the unique power of concentrated solar heating for advanced materials processing and testing. Out small-scale test furnace achieved temperatures as high as 2400 C within a 10 mm X 0.44 mm cylindrical hot-zone. Optimum performance and efficiency resulted from an innovative two-stage optical design using a long-focal length, point-focus, conventional primary concentrator and a non-imaging secondary concentrator specifically designed for the cylindrical geometry of the target fiber. A scale-up analysis suggests that even higher temperatures can be achieved over hot zones large enough for practical commercial fiber post- processing and testing.

Autoheated thermophilic aerobic digestion

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

Deeny, K.; Hahn, H.; Leonhard, D.

1991-10-01

Autothermal thermophilic aerobic digestion (ATAD) is first and foremost a digestion process, the primary purpose of which is to decompose a portion of the waste organic solids generated from wastewater treatment. As a result of the high operating temperature, digestion is expected to occur within a short time period (6 days) and accomplish a high degree of pathogen reduction. ATAD systems are two-stage aerobic digestion processes that operate under thermophilic temperature conditions (40 to 80C) without supplemental heat. Like composting, the systems rely on the conservation of heat released during digestion itself to attain and sustain the desired operating temperature.more » Typical ATAD systems operate at 55C and may reach temperatures of 60 to 65C in the second-stage reactor. Perhaps because of the high operating temperature, this process has been referred to as Liquid Composting.' Major advantages associated with thermophilic operation include high biological reaction rates and a substantial degree of pathogen reduction.« less

Creep of Posidonia Shale at Elevated Pressure and Temperature

NASA Astrophysics Data System (ADS)

Rybacki, E.; Herrmann, J.; Wirth, R.; Dresen, G.

2017-12-01

The economic production of gas and oil from shales requires repeated hydraulic fracturing operations to stimulate these tight reservoir rocks. Besides simple depletion, the often observed decay of production rate with time may arise from creep-induced fracture closure. We examined experimentally the creep behavior of an immature carbonate-rich Posidonia shale, subjected to constant stress conditions at temperatures between 50 and 200 °C and confining pressures of 50-200 MPa, simulating elevated in situ depth conditions. Samples showed transient creep in the semibrittle regime with high deformation rates at high differential stress, high temperature and low confinement. Strain was mainly accommodated by deformation of the weak organic matter and phyllosilicates and by pore space reduction. The primary decelerating creep phase observed at relatively low stress can be described by an empirical power law relation between strain and time, where the fitted parameters vary with temperature, pressure and stress. Our results suggest that healing of hydraulic fractures at low stresses by creep-induced proppant embedment is unlikely within a creep period of several years. At higher differential stress, as may be expected in situ at contact areas due to stress concentrations, the shale showed secondary creep, followed by tertiary creep until failure. In this regime, microcrack propagation and coalescence may be assisted by stress corrosion. Secondary creep rates were also described by a power law, predicting faster fracture closure rates than for primary creep, likely contributing to production rate decline. Comparison of our data with published primary creep data on other shales suggests that the long-term creep behavior of shales can be correlated with their brittleness estimated from composition. Low creep strain is supported by a high fraction of strong minerals that can build up a load-bearing framework.

Molecular modelling investigations on the possibility of phenanthrene dimers to be the primary nuclei of soot

NASA Astrophysics Data System (ADS)

Wei, Mingrui; Wu, Sheng; Li, Fan; Zhang, Dongju; Zhang, Tingting; Guo, Guanlun

2017-11-01

Pyrene dimerisation was successfully used to model the beginning of soot nucleation in some simulation models. However, the quantum mechanics (QM) calculations proved that the binding energy of a PAH dimer with three six-member rings was similar to that of a pyrene dimer. Meanwhile, the high concentration of phenanthrene at flame conditions indicated high probability of collisions among them. The small difference of the binding energy and high concentration indicated that PAHs structurally smaller than pyrene also could be involved in soot inception. Hence, binary collisions of phenanthrene were simulated to find out whether phenanthrene dimers can serve as soot primary nuclei or not by using non-equilibrium molecular dynamics (MD). Three temperatures, six collision orientations and 155 initial translational velocities (ITVs) were considered. The results indicated that the number of dimers with lifetime over 10 ps which can serve as soot nuclei decreased from 52 at 1000 K to 17 at 1600 K, and further to 6 at 2400 K, which means that low temperature was more favourable for phenanthrene to form soot nuclei. Meanwhile, no soot nuclei were formed at the high velocity region (HVR), compared to 43 and 9 at low and middle velocity regions (LVR and MVR), respectively, when temperature was 1000 K. Also, no soot nuclei were formed at HVR when the temperature was raised to 1600 K and 2400 K. This indicated that HVR was unfavourable for phenanthrene to form soot nuclei. The results computationally further illustrated that small PAHs such as phenanthrene could serve as soot primary nuclei, since they have similar mole fractions in some flames. This may be useful for future soot simulation models.

High temperature volatility and oxidation measurements of titanium and silicon containing ceramic materials

NASA Astrophysics Data System (ADS)

Nguyen, Quynhgiao N.

Titanium (Ti) containing materials are of high interest to the aerospace industry due to its high temperature capability, strength, and light weight. As with most metals an exterior oxide layer naturally exists in environments that contain oxygen (i.e. air). At high temperatures, water vapor plays a key role in the volatility of materials including oxide surfaces. This study first evaluates several hot-pressed Ti-containing compositions at high temperatures as a function of oxidation resistance. This study will also evaluate cold pressed titanium dioxide (TiO2) powder pellets at a temperature range of 1400°C--1200°C in water containing environments to determine the volatile hydoxyl species using the transpiration method. The water content ranged from 0-76 mole % and the oxygen content range was 0-100 mole % during the 20-250 hour exposure times. Preliminary results indicate that oxygen is not a key contributor at these temperatures and the following reaction is the primary volatile equation at all three temperatures: TiO 2 (s) + H2O (g) = TiO(OH)2 (g).

HYFIRE II: fusion/high-temperature electrolysis conceptual-design study. Annual report

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

Fillo, J.A.

1983-08-01

As in the previous HYFIRE design study, the current study focuses on coupling a Tokamak fusion reactor with a high-temperature blanket to a High-Temperature Electrolyzer (HTE) process to produce hydrogen and oxygen. Scaling of the STARFIRE reactor to allow a blanket power to 6000 MW(th) is also assumed. The primary difference between the two studies is the maximum inlet steam temperature to the electrolyzer. This temperature is decreased from approx. 1300/sup 0/ to approx. 1150/sup 0/C, which is closer to the maximum projected temperature of the Westinghouse fuel cell design. The process flow conditions change but the basic design philosophymore » and approaches to process design remain the same as before. Westinghouse assisted in the study in the areas of systems design integration, plasma engineering, balance-of-plant design, and electrolyzer technology.« less

Refractive Secondary Solar Concentrator Demonstrated High-Temperature Operation

NASA Technical Reports Server (NTRS)

Wong, Wayne A.

2002-01-01

Space applications that utilize solar thermal energy--such as electric power conversion systems, thermal propulsion systems, and furnaces--require highly efficient solar concentration systems. The NASA Glenn Research Center is developing the refractive secondary concentrator, which uses refraction and total internal reflection to efficiently concentrate and direct solar energy. When used in combination with advanced lightweight primary concentrators, such as inflatable thin films, the refractive secondary concentrator enables very high system concentration ratios and very high temperatures. Last year, Glenn successfully demonstrated a secondary concentrator throughput efficiency of 87 percent, with a projected efficiency of 93 percent using an antireflective coating. Building on this achievement, Glenn recently successfully demonstrated high-temperature operation of the secondary concentrator when it was used to heat a rhenium receiver to 2330 F. The high-temperature demonstration of the concentrator was conducted in Glenn's 68-ft long Tank 6 thermal vacuum facility equipped with a solar simulator. The facility has a rigid panel primary concentrator that was used to concentrate the light from the solar simulator onto the refractive secondary concentrator. NASA Marshall Space Flight Center provided a rhenium cavity, part of a solar thermal propulsion engine, to serve as the high-temperature receiver. The prototype refractive secondary concentrator, measuring 3.5 in. in diameter and 11.2 in. long, is made of single-crystal sapphire. A water-cooled splash shield absorbs spillage light outside of the 3.5-in. concentrator aperture. Multilayer foil insulation composed of tungsten, molybdenum, and niobium is used to minimize heat loss from the hightemperature receiver. A liquid-cooled canister calorimeter is used to measure the heat loss through the multilayer foil insulation.

High temperature braided rope seals for static sealing applications

NASA Technical Reports Server (NTRS)

Adams, Michael L.; Olsen, Andrew; Darolia, Ram; Steinetz, Bruce M.; Bartolotta, Paul A.

1996-01-01

Achieving efficiency and performance goals of advanced aircraft and industrial systems are leading designers to implement high temperature materials such as ceramics and intermetallics. Generally these advanced materials are applied selectively in the highest temperature sections of the engine system including the combustor and high pressure turbine, amongst others. Thermal strains that result in attaching the low expansion-rate components to high expansion rate superalloy structures can cause significant life reduction in the components. Seals are being designed to both seal and to serve as compliant mounts allowing for relative thermal growths between high temperature but brittle primary structures and the surrounding support structures. Designers require high temperature, low-leakage, compliant seals to mitigate thermal stresses and control parasitic and cooling airflow between structures. NASA is developing high temperature braided rope seals in a variety of configurations to help solve these problems. This paper will describe the types of seals being developed, describe unique test techniques used to assess seal performance, and present leakage flow data under representative pressure, temperature and scrubbing conditions. Feasibility of the braided rope seals for both an industrial tube seal and a turbine vane seal application is also demonstrated.

Effect of Mass Flow on Stack Eductor Performance.

DTIC Science & Technology

1984-06-01

absolute viscosity, lbf-sec/ft2 - density, Ibm/ft 3 "function of" ENGLISH LETTER SYMBOLS 2 A - area, in , ft B - atmospheric pressure, in Hg c - sonic... absolute temperature ratio T* - tertiary flow to primary flow absolute temperature t ratio - secondary -o primary mass flow rate ratio W* - tertiary to...secondary to primary absolute Tp temperature ratio TiL tertiary to primary absolute -TE temperature ratio secondary to primary flow density ratio

Ion thruster performance model

NASA Technical Reports Server (NTRS)

Brophy, J. R.

1984-01-01

A model of ion thruster performance is developed for high flux density, cusped magnetic field thruster designs. This model is formulated in terms of the average energy required to produce an ion in the discharge chamber plasma and the fraction of these ions that are extracted to form the beam. The direct loss of high energy (primary) electrons from the plasma to the anode is shown to have a major effect on thruster performance. The model provides simple algebraic equations enabling one to calculate the beam ion energy cost, the average discharge chamber plasma ion energy cost, the primary electron density, the primary-to-Maxwellian electron density ratio and the Maxwellian electron temperature. Experiments indicate that the model correctly predicts the variation in plasma ion energy cost for changes in propellant gas (Ar, Kr and Xe), grid transparency to neutral atoms, beam extraction area, discharge voltage, and discharge chamber wall temperature. The model and experiments indicate that thruster performance may be described in terms of only four thruster configuration dependent parameters and two operating parameters. The model also suggests that improved performance should be exhibited by thruster designs which extract a large fraction of the ions produced in the discharge chamber, which have good primary electron and neutral atom containment and which operate at high propellant flow rates.

Deoxygenation of Unhindered Alcohols via Reductive Dealkylation of Derived Phosphate Esters

DOE PAGES

Chowdhury, Sarwat; Standaert, Robert F.

2016-09-15

Primary alcohols can be deoxygenated cleanly and in high yield by reduction of derived diphenyl phosphate esters with lithium triethylborohydride in tetrahydrofuran at room temperature. Selective deoxygenation of a primary alcohol in the presence of a secondary alcohol was demonstrated. The two-step process can be performed in one pot, making it both simple and convenient.

Solid-solid phase change thermal storage application to space-suit battery pack

NASA Astrophysics Data System (ADS)

Son, Chang H.; Morehouse, Jeffrey H.

1989-01-01

High cell temperatures are seen as the primary safety problem in the Li-BCX space battery. The exothermic heat from the chemical reactions could raise the temperature of the lithium electrode above the melting temperature. Also, high temperature causes the cell efficiency to decrease. Solid-solid phase-change materials were used as a thermal storage medium to lower this battery cell temperature by utilizing their phase-change (latent heat storage) characteristics. Solid-solid phase-change materials focused on in this study are neopentyl glycol and pentaglycerine. Because of their favorable phase-change characteristics, these materials appear appropriate for space-suit battery pack use. The results of testing various materials are reported as thermophysical property values, and the space-suit battery operating temperature is discussed in terms of these property results.

Hydrogen and bioenergetics in the Yellowstone geothermal ecosystem

PubMed Central

Spear, John R.; Walker, Jeffrey J.; McCollom, Thomas M.; Pace, Norman R.

2005-01-01

The geochemical energy budgets for high-temperature microbial ecosystems such as occur at Yellowstone National Park have been unclear. To address the relative contributions of different geochemistries to the energy demands of these ecosystems, we draw together three lines of inference. We studied the phylogenetic compositions of high-temperature (>70°C) communities in Yellowstone hot springs with distinct chemistries, conducted parallel chemical analyses, and carried out thermodynamic modeling. Results of extensive molecular analyses, taken with previous results, show that most microbial biomass in these systems, as reflected by rRNA gene abundance, is comprised of organisms of the kinds that derive energy for primary productivity from the oxidation of molecular hydrogen, H2. The apparent dominance by H2-metabolizing organisms indicates that H2 is the main source of energy for primary production in the Yellowstone high-temperature ecosystem. Hydrogen concentrations in the hot springs were measured and found to range up to >300 nM, consistent with this hypothesis. Thermodynamic modeling with environmental concentrations of potential energy sources also is consistent with the proposed microaerophilic, hydrogen-based energy economy for this geothermal ecosystem, even in the presence of high concentrations of sulfide. PMID:15671178

Compensation of ocean acidification effects in Arctic phytoplankton assemblages

NASA Astrophysics Data System (ADS)

Hoppe, Clara Jule Marie; Wolf, Klara K. E.; Schuback, Nina; Tortell, Philippe D.; Rost, Björn

2018-06-01

The Arctic and subarctic shelf seas, which sustain large fisheries and contribute to global biogeochemical cycling, are particularly sensitive to ongoing ocean acidification (that is, decreasing seawater pH due to anthropogenic CO2 emissions). Yet, little information is available on the effects of ocean acidification on natural phytoplankton assemblages, which are the main primary producers in high-latitude waters. Here we show that coastal Arctic and subarctic primary production is largely insensitive to ocean acidification over a large range of light and temperature levels in different experimental designs. Out of ten CO2-manipulation treatments, significant ocean acidification effects on primary productivity were observed only once (at temperatures below 2 °C), and shifts in the species composition occurred only three times (without correlation to specific experimental conditions). These results imply a high capacity to compensate for environmental variability, which can be understood in light of the environmental history, tolerance ranges and intraspecific diversity of the dominant phytoplankton species.

High Temperature Tensile Properties of Unidirectional Hi-Nicalon/Celsian Composites In Air

NASA Technical Reports Server (NTRS)

Gyekenyesi, John Z.; Bansal, Narottam P.

2000-01-01

High temperature tensile properties of unidirectional BN/SiC-coated Hi-Nicalon SiC fiber reinforced celsian matrix composites have been measured from room temperature to 1200 C (2190 F) in air. Young's modulus, the first matrix cracking stress, and the ultimate strength decreased from room temperature to 1200 C (2190 F). The applicability of various micromechanical models, in predicting room temperature values of various mechanical properties for this CMC, has also been investigated. The simple rule of mixtures produced an accurate estimate of the primary composite modulus. The first matrix cracking stress estimated from ACK theory was in good agreement with the experimental value. The modified fiber bundle failure theory of Evans gave a good estimate of the ultimate strength.

Potential Temperatures of Sources of MORB, OIB and LIPs Based on AL Partitioning Between Olivine and Spinel

NASA Astrophysics Data System (ADS)

Sobolev, A. V.; Batanova, V. G.; Krasheninnikov, S.; Borisov, A.; Arndt, N.; Kuzmin, D.; Krivolutskaya, N.; Sushevskaya, N.

2013-12-01

Knowledge of potential temperatures of convecting mantle is required for the understanding the global processes on the Earth [1]. The common way to estimate these is the reconstruction of primary melt compositions and liquidus temperatures based on the Fe-Mg partitioning between olivine and melt. This approach requires knowledge of the compositions of primitive melts in equilibrium with olivine alone as well as composition of olivine equilibrium with primary melts. This information is in most cases unavailable or of questionable quality. Here we report a new approach to obtain crystallization temperatures of primary melts based on the olivine-spinel Al-Cr geothermometer [2]. The advantages of this approach are: (1) low rate of diffusion of Al in the olivine, which promises to preserve high magmatic temperatures and (2) common presence of spinel in assemblage with high-Mg olivine. In order to decipher influence of elevated Ti concentrations in spinel we have run several experiments at high temperatures (1400-1200 degree C), atmospheric pressure and controled oxygen fugacity. We also analysed over two thousand spinel inclusions and high-Mg host olivines from different MORB, OIB, LIP and Archean komatiites on the JXA-8230 EPMA at ISTerre, Grenoble, France. Concentrations of Al, Ti, Na, P, Zn, Cr, Mn, Ca, Co, Ni were determined with a precision of 10 ppm (2 standard errors) using a newly developed protocol [3]. When available, we also analysed matrix glass and glass inclusions in olivine and found that temperature estimations from olivine-spinel (Al-Cr) and olivine-melt (Fe-Mg) [4] equilibrium match within (+/-30 degree C). The results show contrasting crystallization temperatures of Mg-rich olivine of the same Fo content from different types of mantle-derived magmas, from the lowest (down to 1220 degree C) for MORB to the highest (up to 1550 degree C) for komatiites and Siberian meimechites. These results match predictions from Fe-Mg olivine-melt equilibrium and confirm the relatively low temperature of the convecting mantle source of MORB and higher temperatures in the mantle plumes that produce the OIB of Iceland, Hawaii, Gorgona, Archean komatiites and several LIPs (e.g. Siberian, Decan). [1] McKenzie & Bickle, 1988, J. Petr. 29, p 625-679. [2] Wan et al, 2008, Am. Min. 93, p1142-1147. [3] Batanova & Sobolev, 2013, Min. Mag.,p 667, DOI :10.1180/minmag2013.077.5.2 [4] Ford et al, 1983, J. Petr. 24, p 256-265.

Computational Modeling of Arc-Slag Interaction in DC Furnaces

NASA Astrophysics Data System (ADS)

Reynolds, Quinn G.

2017-02-01

The plasma arc is central to the operation of the direct-current arc furnace, a unit operation commonly used in high-temperature processing of both primary ores and recycled metals. The arc is a high-velocity, high-temperature jet of ionized gas created and sustained by interactions among the thermal, momentum, and electromagnetic fields resulting from the passage of electric current. In addition to being the primary source of thermal energy, the arc jet also couples mechanically with the bath of molten process material within the furnace, causing substantial splashing and stirring in the region in which it impinges. The arc's interaction with the molten bath inside the furnace is studied through use of a multiphase, multiphysics computational magnetohydrodynamic model developed in the OpenFOAM® framework. Results from the computational solver are compared with empirical correlations that account for arc-slag interaction effects.

Gasification of high ash, high ash fusion temperature bituminous coals

DOEpatents

Liu, Guohai; Vimalchand, Pannalal; Peng, WanWang

2015-11-13

This invention relates to gasification of high ash bituminous coals that have high ash fusion temperatures. The ash content can be in 15 to 45 weight percent range and ash fusion temperatures can be in 1150.degree. C. to 1500.degree. C. range as well as in excess of 1500.degree. C. In a preferred embodiment, such coals are dealt with a two stage gasification process--a relatively low temperature primary gasification step in a circulating fluidized bed transport gasifier followed by a high temperature partial oxidation step of residual char carbon and small quantities of tar. The system to process such coals further includes an internally circulating fluidized bed to effectively cool the high temperature syngas with the aid of an inert media and without the syngas contacting the heat transfer surfaces. A cyclone downstream of the syngas cooler, operating at relatively low temperatures, effectively reduces loading to a dust filtration unit. Nearly dust- and tar-free syngas for chemicals production or power generation and with over 90%, and preferably over about 98%, overall carbon conversion can be achieved with the preferred process, apparatus and methods outlined in this invention.

Ultra-high temperature isothermal furnace liners (IFLS) for copper freeze point cells

NASA Astrophysics Data System (ADS)

Dussinger, P. M.; Tavener, J. P.

2013-09-01

Primary Laboratories use large fixed-point cells in deep calibration furnaces utilizing heat pipes to achieve temperature uniformity. This combination of furnace, heat pipe, and cell gives the smallest of uncertainties. The heat pipe, also known as an isothermal furnace liner (IFL), has typically been manufactured with Alloy 600/601 as the envelope material since the introduction of high temperature IFLs over 40 years ago. Alloy 600/601 is a widely available high temperature material, which is compatible with Cesium, Potassium, and Sodium and has adequate oxidation resistance and reasonable high temperature strength. Advanced Cooling Technologies, Inc. (ACT) Alloy 600/Sodium IFLs are rated to 1100°C for approximately 1000 hours of operation (based on creep strength). Laboratories interested in performing calibrations and studies around the copper freezing point (1084.62°C) were frustrated by the 1000 hours at 1100°C limitation and the fact that expensive freeze-point cells were getting stuck and/or crushed inside the IFL. Because of this growing frustration/need, ACT developed an Ultra High Temperature IFL to take advantage of the exceptional high temperature strength properties of Haynes 230.

Productivity and sea surface temperature are correlated with the pelagic larval duration of damselfishes in the Red Sea.

PubMed

Robitzch, Vanessa S N; Lozano-Cortés, Diego; Kandler, Nora M; Salas, Eva; Berumen, Michael L

2016-04-30

We examined the variation of pelagic larval durations (PLDs) among three damselfishes, Dascyllus aruanus, D. marginatus, and D. trimaculatus, which live under the influence of an environmental gradient in the Red Sea. PLDs were significantly correlated with latitude, sea surface temperature (SST), and primary production (CHLA; chlorophyll a concentrations). We find a consistent decrease in PLDs with increasing SST and primary production (CHLA) towards the southern Red Sea among all species. This trend is likely related to higher food availability and increased metabolic rates in that region. We suggest that food availability is a potentially stronger driver of variation in PLD than temperature, especially in highly oligotrophic regions. Additionally, variations in PLDs were particularly high among specimens of D. marginatus, suggesting a stronger response to local environmental differences for endemic species. We also report the first average PLD for this species over a broad geographic range (19.82 ± 2.92 days). Copyright © 2015 Elsevier Ltd. All rights reserved.

Improved photosynthetic efficacy of maize (Zea mays) plants with arbuscular mycorrhizal fungi (AMF) under high temperature stress.

PubMed

Mathur, Sonal; Sharma, Mahaveer P; Jajoo, Anjana

2018-03-01

In this study, pot experiments were performed to investigate the effects of high temperature stress (44 °C) in maize plants colonized with and without arbuscular mycorrhizal fungi (AMF). Various parameters characterizing photosynthetic activity were measured in order to estimate the photosynthetic efficiency in maize plants. It was observed that density of active reaction centers of PSII, quantum efficiency of photosystem II (PSII), linear electron transport, excitation energy trapping, performance index, net photosynthesis rate increased in AMF (+) plants at 44 °C ± 0.2 °C. Efficiency of primary photochemical reaction (represented as F v /F o ) increased in AMF (+) plants as compared to AMF (-) plants. AMF seems to have protected water splitting complex followed by enhanced primary photochemistry of PSII under high temperature. Basic morphological parameters like leaf width, plant height and cob number increased in AMF (+) plants as compared to AMF (-) plants. AMF (+) plants grew faster than AMF (-) plants due to larger root systems. Chl content increased in AMF (+) plants as compared to AMF (-) maize plants. AMF hyphae likely increased Mg uptake which in turn increased the total chlorophyll content in AMF (+) maize plants. This subsequently led to a higher production in photosynthate and biomass. Thus AMF (+) plants have shown better photosynthesis performance as compared to AMF (-) maize plants under high temperature stress. Copyright © 2018 Elsevier B.V. All rights reserved.

Application of tire chips to reduce the temperature of secondary geomembranes in municipal solid waste landfills.

PubMed

Hoor, Azadeh; Rowe, R Kerry

2012-05-01

Heat generated by the biodegradation of waste and other chemical processes in a landfill can potentially affect the long-term performance of landfill liner system, in particular that of a high-density polyethylene geomembrane. In a double liner system, the difference in leachate exposure and temperature might improve the long-term performance of the secondary geomembrane compared to that of the primary geomembrane. However, in some cases, the temperature is likely to be high enough to substantially reduce the service-life of the secondary geomembrane. This study explores the possible effectiveness of using tire chips as thermal insulation between primary and secondary liners to reduce the temperature of secondary geomembranes as compared to traditional soil materials. Heat and contaminant migration analyses are performed for cases with no insulation and for cases in which a layer of soil or tire chips has been used as thermal insulation between the primary and secondary liners. The effect of insulation on prolonging the service-life of a secondary geomembrane and, consequently, on contaminant transport through a liner system is examined for the case of a volatile organic compound (dichloromethane) found in landfill leachate. The study suggests that the use of tire chips warrants consideration, however there are other practical issues that require consideration in the detailed design and construction of landfill liners. Issues such as finite service-life, low working temperature, excessive settlement, ability to generate internal heat, leaching of tire chips and limitations in performing electrical resistivity leak detection tests are identified. Copyright © 2012 Elsevier Ltd. All rights reserved.

High temperature thermocouple and heat flux gauge using a unique thin film-hardware hot juncture

NASA Technical Reports Server (NTRS)

Liebert, C. H.; Holanda, R.; Hippensteele, S. A.; Andracchio, C. A.

1984-01-01

A special thin film-hardware material thermocouple (TC) and heat flux gauge concept for a reasonably high temperature and high flux flat plate heat transfer experiment was fabricated and tested to gauge temperatures of 911 K. This concept was developed for minimal disturbance of boundary layer temperature and flow over the plates and minimal disturbance of heat flux through the plates. Comparison of special heat flux gauge Stanton number output at steady-state conditions with benchmark literature data was good and agreement was within a calculated uncertainty of the measurement system. Also, good agreement of special TC and standard TC outputs was obtained and the results are encouraging. Oxidation of thin film thermoelements was a primary failure mode after about 5 of operation.

High-temperature thermocouple and heat flux gauge using a unique thin film-hardware hot junction

NASA Technical Reports Server (NTRS)

Liebert, C. H.; Holanda, R.; Hippensteele, S. A.; Andracchio, C. A.

1985-01-01

A special thin film-hardware material thermocouple (TC) and heat flux gauge concept for a reasonably high temperature and high flux flat plate heat transfer experiment was fabricated and tested to gauge temperatures of 911 K. This concept was developed for minimal disturbance of boundary layer temperature and flow over the plates and minimal disturbance of heat flux through the plates. Comparison of special heat flux gauge Stanton number output at steady-state conditions with benchmark literature data was good and agreement was within a calculated uncertainty of the measurement system. Also, good agreement of special TC and standard TC outputs was obtained and the results are encouraging. Oxidation of thin film thermoelements was a primary failure mode after about 5 of operation.

Elevated Temperature Crack Growth Behavior in HSCT Structural Materials

NASA Technical Reports Server (NTRS)

Saxena, Ashok

1998-01-01

Structures in super-sonic aircraft are subjected to conditions of high temperature and cyclic and sustained loading for extended periods of time. The durability of structures fabricated from aluminum and certain titanium alloys in such demanding conditions is of primary concern to the designers and manufacturers of futuristic transport aircraft. Accordingly, the major goal of this project was to evaluate the performance and durability of high temperature aluminum and titanium alloys for use in high speed civil transport (HSCT) structures. Additional goals were to develop time-dependent fracture mechanics methodology and test methods for characterizing and predicting elevated temperature crack growth behavior in creep-brittle materials such as ones being considered for use in HSCT structures and to explore accelerated methods of simulating microstructural degradation during service and measuring degraded properties in these materials.

Effect of shroud geometry on the effectiveness of a short mixing stack gas eductor model

NASA Astrophysics Data System (ADS)

Kavalis, A. E.

1983-06-01

An existing apparatus for testing models of gas eductor systems using high temperature primary flow was modified to provide improved control and performance over a wide range of gas temperature and flow rates. Secondary flow pumping, temperature and pressure data were recorded for two gas eductor system models. The first, previously tested under hot flow conditions, consists of a primary plate with four tilted-angled nozzles and a slotted, shrouded mixing stack with two diffuser rings (overall L/D = 1.5). A portable pyrometer with a surface probe was used for the second model in order to identify any hot spots at the external surface of the mixing stack, shroud and diffuser rings. The second model is shown to have almost the same mixing and pumping performance with the first one but to exhibit much lower shroud and diffuser surface temperatures.

Identifying Changes in the Probability of High Temperature, High Humidity Heat Wave Events

NASA Astrophysics Data System (ADS)

Ballard, T.; Diffenbaugh, N. S.

2016-12-01

Understanding how heat waves will respond to climate change is critical for adequate planning and adaptation. While temperature is the primary determinant of heat wave severity, humidity has been shown to play a key role in heat wave intensity with direct links to human health and safety. Here we investigate the individual contributions of temperature and specific humidity to extreme heat wave conditions in recent decades. Using global NCEP-DOE Reanalysis II daily data, we identify regional variability in the joint probability distribution of humidity and temperature. We also identify a statistically significant positive trend in humidity over the eastern U.S. during heat wave events, leading to an increased probability of high humidity, high temperature events. The extent to which we can expect this trend to continue under climate change is complicated due to variability between CMIP5 models, in particular among projections of humidity. However, our results support the notion that heat wave dynamics are characterized by more than high temperatures alone, and understanding and quantifying the various components of the heat wave system is crucial for forecasting future impacts.

Effect of temperature- and frequency-dependent dynamic properties of rail pads on high-speed vehicle-track coupled vibrations

NASA Astrophysics Data System (ADS)

Wei, Kai; Wang, Feng; Wang, Ping; Liu, Zi-xuan; Zhang, Pan

2017-03-01

The soft under baseplate pad of WJ-8 rail fastener frequently used in China's high-speed railways was taken as the study subject, and a laboratory test was performed to measure its temperature and frequency-dependent dynamic performance at 0.3 Hz and at -60°C to 20°C with intervals of 2.5°C. Its higher frequency-dependent results at different temperatures were then further predicted based on the time-temperature superposition (TTS) and Williams-Landel-Ferry (WLF) formula. The fractional derivative Kelvin-Voigt (FDKV) model was used to represent the temperature- and frequency-dependent dynamic properties of the tested rail pad. By means of the FDKV model for rail pads and vehicle-track coupled dynamic theory, high-speed vehicle-track coupled vibrations due to temperature- and frequency-dependent dynamic properties of rail pads was investigated. Finally, further combining with the measured frequency-dependent dynamic performance of vehicle's rubber primary suspension, the high-speed vehicle-track coupled vibration responses were discussed. It is found that the storage stiffness and loss factor of the tested rail pad are sensitive to low temperatures or high frequencies. The proposed FDKV model for the frequency-dependent storage stiffness and loss factors of the tested rail pad can basically meet the fitting precision, especially at ordinary temperatures. The numerical simulation results indicate that the vertical vibration levels of high-speed vehicle-track coupled systems calculated with the FDKV model for rail pads in time domain are higher than those calculated with the ordinary Kelvin-Voigt (KV) model for rail pads. Additionally, the temperature- and frequency-dependent dynamic properties of the tested rail pads would alter the vertical vibration acceleration levels (VALs) of the car body and bogie in 1/3 octave frequencies above 31.5 Hz, especially enlarge the vertical VALs of the wheel set and rail in 1/3 octave frequencies of 31.5-100 Hz and above 315 Hz, which are the dominant frequencies of ground vibration acceleration and rolling noise (or bridge noise) caused by high-speed railways respectively. Since the fractional derivative value of the adopted rubber primary suspension, unlike the tested rail pad, is very close to 1, its frequency-dependent dynamic performance has little effect on high-speed vehicle-track coupled vibration responses.

Separating heat stress from moisture stress: analyzing yield response to high temperature in irrigated maize

NASA Astrophysics Data System (ADS)

Carter, Elizabeth K.; Melkonian, Jeff; Riha, Susan J.; Shaw, Stephen B.

2016-09-01

Several recent studies have indicated that high air temperatures are limiting maize (Zea mays L.) yields in the US Corn Belt and project significant yield losses with expected increases in growing season temperatures. Further work has suggested that high air temperatures are indicative of high evaporative demand, and that decreases in maize yields which correlate to high temperatures and vapor pressure deficits (VPD) likely reflect underlying soil moisture limitations. It remains unclear whether direct high temperature impacts on yields, independent of moisture stress, can be observed under current temperature regimes. Given that projected high temperature and moisture may not co-vary the same way as they have historically, quantitative analyzes of direct temperature impacts are critical for accurate yield projections and targeted mitigation strategies under shifting temperature regimes. To evaluate yield response to above optimum temperatures independent of soil moisture stress, we analyzed climate impacts on irrigated maize yields obtained from the National Corn Growers Association (NCGA) corn yield contests for Nebraska, Kansas and Missouri. In irrigated maize, we found no evidence of a direct negative impact on yield by daytime air temperature, calculated canopy temperature, or VPD when analyzed seasonally. Solar radiation was the primary yield-limiting climate variable. Our analyses suggested that elevated night temperature impacted yield by increasing rates of phenological development. High temperatures during grain-fill significantly interacted with yields, but this effect was often beneficial and included evidence of acquired thermo-tolerance. Furthermore, genetics and management—information uniquely available in the NCGA contest data—explained more yield variability than climate, and significantly modified crop response to climate. Thermo-acclimation, improved genetics and changes to management practices have the potential to partially or completely offset temperature-related yield losses in irrigated maize.

Climatic controls of aboveground net primary production in semi-arid grasslands along a latitudinal gradient portend low sensitivity to warming

USGS Publications Warehouse

Mowll, Whitney; Blumenthal, Dana M.; Cherwin, Karie; Smith, Anine; Symstad, Amy J.; Vermeire, Lance; Collins, Scott L.; Smith, Melinda D.; Knapp, Alan K.

2015-01-01

Although climate models forecast warmer temperatures with a high degree of certainty, precipitation is the primary driver of aboveground net primary production (ANPP) in most grasslands. Conversely, variations in temperature seldom are related to patterns of ANPP. Thus forecasting responses to warming is a challenge, and raises the question: how sensitive will grassland ANPP be to warming? We evaluated climate and multi-year ANPP data (67 years) from eight western US grasslands arrayed along mean annual temperature (MAT; ~7-14 °C) and mean annual precipitation (MAP; ~250-500 mm) gradients. Weused regression and analysis of covariance to assess relationships between ANPP and temperature, as well as precipitation (annual and growing season) to evaluate temperature sensitivity of ANPP. We also related ANPP to the standardized precipitation evaporation index (SPEI), which combines precipitation and evapotranspiration to better represent moisture available for plant growth. Regression models indicated that variation in growing season temperature was negatively related to total and graminoid ANPP, but precipitation was a stronger predictor than temperature. Growing season temperature was also a significant parameter in more complex models, but again precipitation was consistently a stronger predictor of ANPP. Surprisingly, neither annual nor growing season SPEI were as strongly related to ANPP as precipitation. We conclude that forecasted warming likely will affect ANPP in these grasslands, but that predicting temperature effects from natural climatic gradients is difficult. This is because, unlike precipitation, warming effects can be positive or negative and moderated by shifts in the C3/C4 ratios of plant communities.

[Medical and ecological assessment of climate effects on urolithiasis morbidity in population of Primorsky territory].

PubMed

Koval'chuk, V K

2004-01-01

The article presents medicoecological estimation of quantitative relations between monsoon climate and urolithiasis primary morbidity in the Primorsky Territory. Quantitative estimation of the climate was performed by V. I. Rusanov (1973) who calculated daily meteorological data for 1 p.m. throughout 1991-1999. Primary urolithiasis morbidity for this period of time was provided by regional health department. The data were processed by methods of medical mapping and paired correlation analysis. In the Territory, mapping revealed the same location of the zones with high frequency of discomfortable weather of class V and VI causing chilblain in positive air temperatures and zones with elevated primary urolithiasis morbidity in children and adults. Correlation analysis confirmed mapping results and determined significant negative correlations between frequency of relatively comfortable moment weather classes II-IV and morbidity of children and adults, positive correlation between frequency of discomfortable class VI and adult morbidity. Thus, high frequency of days per year with discomfortable classes of moment weather in low positive air temperatures may be one of the factors of urolithiasis risk in population of the Primorsky Territory. Climatic factors should be taken into consideration in planning primary prophylaxis of this disease in the Primorsky Territory.

Computational design of high efficiency release targets for use at ISOL facilities

NASA Astrophysics Data System (ADS)

Liu, Y.; Alton, G. D.; Middleton, J. W.

1999-06-01

This report describes efforts made at the Oak Ridge National Laboratory to design high-efficiency-release targets that simultaneously incorporate the short diffusion lengths, high permeabilities, controllable temperatures, and heat removal properties required for the generation of useful radioactive ion beam (RIB) intensities for nuclear physics and astrophysics research using the isotope separation on-line (ISOL) technique. Short diffusion lengths are achieved either by using thin fibrous target materials or by coating thin layers of selected target material onto low-density carbon fibers such as reticulated vitreous carbon fiber (RVCF) or carbon-bonded-carbon-fiber (CBCF) to form highly permeable composite target matrices. Computational studies which simulate the generation and removal of primary beam deposited heat from target materials have been conducted to optimize the design of target/heat-sink systems for generating RIBs. The results derived from diffusion release-rate simulation studies for selected targets and thermal analyses of temperature distributions within a prototype target/heat-sink system subjected to primary ion beam irradiation will be presented in this report.

High-efficiency-release targets for use at ISOL facilities: computational design

NASA Astrophysics Data System (ADS)

Liu, Y.; Alton, G. D.

1999-12-01

This report describes efforts made at the Oak Ridge National Laboratory to design high-efficiency-release targets that simultaneously incorporate the short diffusion lengths, high permeabilities, controllable temperatures, and heat-removal properties required for the generation of useful radioactive ion beam (RIB) intensities for nuclear physics and astrophysics research using the isotope separation on-line (ISOL) technique. Short diffusion lengths are achieved either by using thin fibrous target materials or by coating thin layers of selected target material onto low-density carbon fibers such as reticulated-vitreous-carbon fiber (RVCF) or carbon-bonded-carbon fiber (CBCF) to form highly permeable composite target matrices. Computational studies that simulate the generation and removal of primary beam deposited heat from target materials have been conducted to optimize the design of target/heat-sink systems for generating RIBs. The results derived from diffusion release-rate simulation studies for selected targets and thermal analyses of temperature distributions within a prototype target/heat-sink system subjected to primary ion beam irradiation are presented in this report.

Continental-scale decrease in net primary productivity in streams due to climate warming

NASA Astrophysics Data System (ADS)

Song, Chao; Dodds, Walter K.; Rüegg, Janine; Argerich, Alba; Baker, Christina L.; Bowden, William B.; Douglas, Michael M.; Farrell, Kaitlin J.; Flinn, Michael B.; Garcia, Erica A.; Helton, Ashley M.; Harms, Tamara K.; Jia, Shufang; Jones, Jeremy B.; Koenig, Lauren E.; Kominoski, John S.; McDowell, William H.; McMaster, Damien; Parker, Samuel P.; Rosemond, Amy D.; Ruffing, Claire M.; Sheehan, Ken R.; Trentman, Matt T.; Whiles, Matt R.; Wollheim, Wilfred M.; Ballantyne, Ford

2018-06-01

Streams play a key role in the global carbon cycle. The balance between carbon intake through photosynthesis and carbon release via respiration influences carbon emissions from streams and depends on temperature. However, the lack of a comprehensive analysis of the temperature sensitivity of the metabolic balance in inland waters across latitudes and local climate conditions hinders an accurate projection of carbon emissions in a warmer future. Here, we use a model of diel dissolved oxygen dynamics, combined with high-frequency measurements of dissolved oxygen, light and temperature, to estimate the temperature sensitivities of gross primary production and ecosystem respiration in streams across six biomes, from the tropics to the arctic tundra. We find that the change in metabolic balance, that is, the ratio of gross primary production to ecosystem respiration, is a function of stream temperature and current metabolic balance. Applying this relationship to the global compilation of stream metabolism data, we find that a 1 °C increase in stream temperature leads to a convergence of metabolic balance and to a 23.6% overall decline in net ecosystem productivity across the streams studied. We suggest that if the relationship holds for similarly sized streams around the globe, the warming-induced shifts in metabolic balance will result in an increase of 0.0194 Pg carbon emitted from such streams every year.

Comparison of primary and secondary particle formation from natural gas engine exhaust and of their volatility characteristics

NASA Astrophysics Data System (ADS)

Alanen, Jenni; Simonen, Pauli; Saarikoski, Sanna; Timonen, Hilkka; Kangasniemi, Oskari; Saukko, Erkka; Hillamo, Risto; Lehtoranta, Kati; Murtonen, Timo; Vesala, Hannu; Keskinen, Jorma; Rönkkö, Topi

2017-07-01

Natural gas usage in the traffic and energy production sectors is a growing trend worldwide; thus, an assessment of its effects on air quality, human health and climate is required. Engine exhaust is a source of primary particulate emissions and secondary aerosol precursors, which both contribute to air quality and can cause adverse health effects. Technologies, such as cleaner engines or fuels, that produce less primary and secondary aerosols could potentially significantly decrease atmospheric particle concentrations and their adverse effects. In this study, we used a potential aerosol mass (PAM) chamber to investigate the secondary aerosol formation potential of natural gas engine exhaust. The PAM chamber was used with a constant UV-light voltage, which resulted in relatively long equivalent atmospheric ages of 11 days at most. The studied retro-fitted natural gas engine exhaust was observed to form secondary aerosol. The mass of the total aged particles, i.e., particle mass measured downstream of the PAM chamber, was 6-268 times as high as the mass of the emitted primary exhaust particles. The secondary organic aerosol (SOA) formation potential was measured to be 9-20 mg kgfuel-1. The total aged particles mainly consisted of organic matter, nitrate, sulfate and ammonium, with the fractions depending on exhaust after-treatment and the engine parameters used. Also, the volatility, composition and concentration of the total aged particles were found to depend on the engine operating mode, catalyst temperature and catalyst type. For example, a high catalyst temperature promoted the formation of sulfate particles, whereas a low catalyst temperature promoted nitrate formation. However, in particular, the concentration of nitrate needed a long time to stabilize - more than half an hour - which complicated the conclusions but also indicates the sensitivity of nitrate measurements on experimental parameters such as emission source and system temperatures. Sulfate was measured to have the highest evaporation temperature, and nitrate had the lowest. The evaporation temperature of ammonium depended on the fractions of nitrate and sulfate in the particles. The average volatility of the total aged particles was measured to be lower than that of primary particles, indicating better stability of the aged natural gas engine-emitted aerosol in the atmosphere. According to the results of this study, the exhaust of a natural gas engine equipped with a catalyst forms secondary aerosol when the atmospheric ages in a PAM chamber are several days long. The secondary aerosol matter has different physical characteristics from those of primary particulate emissions.

Enhanced late gas generation potential of petroleum source rocks via recombination reactions: Evidence from the Norwegian North Sea

NASA Astrophysics Data System (ADS)

Erdmann, Michael; Horsfield, Brian

2006-08-01

Gas generation in the deep reaches of sedimentary basins is usually considered to take place via the primary cracking of short alkyl groups from overmature kerogen or the secondary cracking of petroleum. Here, we show that recombination reactions ultimately play the dominant role in controlling the timing of late gas generation in source rocks which contain mixtures of terrigeneous and marine organic matter. These reactions, taking place at low levels of maturation, result in the formation of a thermally stable bitumen, which is the major source of methane at very high maturities. The inferences come from pyrolysis experiments performed on samples of the Draupne Formation (liptinitic Type II kerogen) and Heather Formation (mixed marine-terrigeneous Type III kerogen), both Upper Jurassic source rocks stemming from the Norwegian northern North Sea Viking Graben system. Non-isothermal closed system micro scale sealed vessel (MSSV) pyrolysis, non-isothermal open system pyrolysis and Rock Eval type pyrolysis were performed on the solvent extracted, concentrated kerogens of the two immature samples. The decrease of C 6+ products in the closed system MSSV pyrolysis provided the basis for the calculation of secondary gas (C 1-5) formation. Subtraction of the calculated secondary gas from the total observed gas yields a "remaining" gas. In the case of the Draupne Formation this is equivalent to primary gas cracked directly from the kerogen, as detected by a comparison with multistep open pyrolysis data. For the Heather Formation the calculated remaining gas formation profile is initially attributable to primary gas but there is a second major gas pulse at very high temperature (>550 °C at 5.0 K min -1) that is not primary. This has been explained by a recondensation process where first formed high molecular weight compounds in the closed system yield a macromolecular material that undergoes secondary cracking at elevated temperatures. The experiments provided the input for determination of kinetic parameters of the different gas generation types, which were used for extrapolations to a linear geological heating rate of 10 -11 K min -1. Peak generation temperatures for the primary gas generation were found to be higher for Heather Formation ( Tmax = 190 °C, equivalent to Ro appr. 1.7%) compared to Draupne Formation ( Tmax = 175 °C, equivalent to appr. Ro 1.3%). Secondary gas peak generation temperatures were calculated to be 220 °C for the Heather Formation and 205 to 215 °C for the Draupne Formation, respectively, with equivalent vitrinite reflectance values ( Ro) between 2.4% and 2.0%. The high temperature secondary gas formation from cracking of the recombination residue as detected for the Heather Formation is quantitatively important and is suggested to occur at very high temperatures ( Tmax approx. 250 °C) for geological heating rates. The prediction of a significant charge of dry gas from the Heather Formation at very high maturity levels has important implications for petroleum exploration in the region, especially to the north of the Viking Graben where Upper Jurassic sediments are sufficiently deep buried to have experienced such a process.

The Paralinear Oxidation of SiC in Combustion Environments

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.; Greenbauer-Seng, Leslie (Technical Monitor)

2000-01-01

SiC is proposed for structural applications in high pressure, high temperature. high gas velocity environments of turbine and rocket engines. These environments are typically composed of complex gas mixtures containing carbon dioxide, oxygen, water vapor, and nitrogen. It is known that the primary oxidant for SiC in these environments is water vapor.

Late Holocene SST and primary productivity variations in the northeastern Arabian Sea as a recorder for winter monsoon variability

NASA Astrophysics Data System (ADS)

Böll, Anna; Gaye, Birgit; Lückge, Andreas

2014-05-01

Variability in the oceanic environment of the Arabian Sea region is strongly influenced by the seasonal monsoon cycle of alternating wind directions. Strong south-westerly winds during the summer monsoon induce upwelling of nutrient rich waters along the coast off Somalia, Oman and southwest India, which result in high rates of primary production. In the northeastern Arabian Sea off Pakistan on the other hand, primary production and sea surface temperatures are linked to northeast monsoonal winds that cool the sea surface and drive convective mixing and high surface ocean productivity during the winter season. In this study, we analyzed alkenone-derived sea surface temperature (SST) variations and proxies of primary productivity (organic carbon and δ15N) in a well-laminated sediment core from the Pakistan continental margin to establish the first high-resolution record of winter monsoon variability for the late Holocene. Over the last 2400 years reconstructed SST in the northeastern Arabian Sea decreased whereas productivity increased, imaging a long-term trend of northeast monsoon strengthening in response to insolation-induced southward migration of the Intertropical Convergence Zone. The comparison of our winter monsoon record with records of summer monsoon intensity suggests that summer and winter monsoon strength was essentially anti-correlated over the late Holocene throughout the Asian monsoon system. In addition, SST variations recorded off Pakistan match very well with Northern Hemisphere temperature records supporting the growing body of evidence that Asian climate is linked to Northern Hemisphere climate change. It reveals a consistent pattern of increased summer monsoon activity in the northeastern Arabian Sea during northern hemispheric warm periods (Medieval Warm Period, Roman Warm Period) and strengthened winter monsoon activity during hemispheric colder periods (Little Ice Age).

Johnson Noise Thermometry in the range 505 K to 933 K

NASA Astrophysics Data System (ADS)

Tew, Weston; Labenski, John; Nam, Sae Woo; Benz, Samuel; Dresselhaus, Paul; Martinis, John

2006-03-01

The International Temperature Scale of 1990 (ITS-90) is an artifact-based temperature scale, T90, designed to approximate thermodynamic temperature T. The thermodynamic errors of the ITS-90, characterized as the value of T-T90, only recently have been quantified by primary thermodynamic methods. Johnson Noise Thermometry (JNT) is a primary method which can be applied over wide temperature ranges, and NIST is currently using JNT to determine T-T90 in the range 505 K to 933 K, overlapping both acoustic gas-based and radiation-based thermometry. Advances in digital electronics have now made the computationally intensive processing required for JNT viable using noise voltage correlation in the frequency domain. We have also optimized the design of the 5-wire JNT temperature probes to minimize electromagnetic interference and transmission line effects. Statistical uncertainties under 50 μK/K are achievable using relatively modest bandwidths of ˜100 kHz. The NIST JNT system will provide critical data for T-T90 linking together the highly accurate acoustic gas-based data at lower temperatures with the higher-temperature radiation-based data, forming the basis for a new International Temperature Scale with greatly improved thermodynamic accuracy.

Studies of the Crystallization Process of Aluminum-Silicon Alloys Using a High Temperature Microscope. Thesis

NASA Technical Reports Server (NTRS)

Justi, S.

1985-01-01

It is shown that primary silicon crystals grow polyhedral in super-eutectic AlSi melts and that phosphorus additives to the melt confirm the strong seeding capacity. Primary silicon exhibits strong dendritic seeding effects in eutectic silicon phases of various silicon alloys, whereas primary aluminum does not possess this capacity. Sodium addition also produces a dendritic silicon network growth in the interior of the sample that is attributed to the slower silicon diffusion velocity during cooling.

Nuclear fuel elements made from nanophase materials

DOEpatents

Heubeck, Norman B.

1998-01-01

A nuclear reactor core fuel element is composed of nanophase high temperature materials. An array of the fuel elements in rod form are joined in an open geometry fuel cell that preferably also uses such nanophase materials for the cell structures. The particular high temperature nanophase fuel element material must have the appropriate mechanical characteristics to avoid strain related failure even at high temperatures, in the order of about 3000.degree. F. Preferably, the reactor type is a pressurized or boiling water reactor and the nanophase material is a high temperature ceramic or ceramic composite. Nanophase metals, or nanophase metals with nanophase ceramics in a composite mixture, also have desirable characteristics, although their temperature capability is not as great as with all-ceramic nanophase material. Combinations of conventional or nanophase metals and conventional or nanophase ceramics can be employed as long as there is at least one nanophase material in the composite. The nuclear reactor so constructed has a number of high strength fuel particles, a nanophase structural material for supporting a fuel rod at high temperature, a configuration to allow passive cooling in the event of a primary cooling system failure, an ability to retain a coolable geometry even at high temperatures, an ability to resist generation of hydrogen gas, and a configuration having good nuclear, corrosion, and mechanical characteristics.

Nuclear fuel elements made from nanophase materials

DOEpatents

Heubeck, N.B.

1998-09-08

A nuclear reactor core fuel element is composed of nanophase high temperature materials. An array of the fuel elements in rod form are joined in an open geometry fuel cell that preferably also uses such nanophase materials for the cell structures. The particular high temperature nanophase fuel element material must have the appropriate mechanical characteristics to avoid strain related failure even at high temperatures, in the order of about 3000 F. Preferably, the reactor type is a pressurized or boiling water reactor and the nanophase material is a high temperature ceramic or ceramic composite. Nanophase metals, or nanophase metals with nanophase ceramics in a composite mixture, also have desirable characteristics, although their temperature capability is not as great as with all-ceramic nanophase material. Combinations of conventional or nanophase metals and conventional or nanophase ceramics can be employed as long as there is at least one nanophase material in the composite. The nuclear reactor so constructed has a number of high strength fuel particles, a nanophase structural material for supporting a fuel rod at high temperature, a configuration to allow passive cooling in the event of a primary cooling system failure, an ability to retain a coolable geometry even at high temperatures, an ability to resist generation of hydrogen gas, and a configuration having good nuclear, corrosion, and mechanical characteristics. 5 figs.

Design and experimental investigation of a neon cryogenic loop heat pipe

NASA Astrophysics Data System (ADS)

He, Jiang; Guo, Yuandong; Zhang, Hongxing; Miao, Jianyin; Wang, Lu; Lin, Guiping

2017-11-01

Next generation space infrared sensor and detector have pressing requirement for cryogenic heat transport technology in the temperature range of 30-40 K. Cryogenic loop heat pipe (CLHP) has excellent thermal performance and particular characteristics such as high flexibility transport lines and no moving parts, thus it is regarded as an ideal thermal control solution. A neon CLHP referring to infrared point-to-point heat transfer element in future space application has been designed and experimented. And it could realize supercritical startup successfully. Experimental results show that the supercritical startup were realized successfully at cases of 1.5 W secondary evaporator power, but the startup was failed when 0.5 and 1 W heat load applied to secondary evaporator. The maximum heat transport capability of primary evaporator is between 4.5 and 5 W with proper auxiliary heat load. Before startup, even the heat sink temperature decreased to 35 K, the primary evaporator can still maintain at almost 290 K; and the primary evaporator temperature increased at once when the powers were cut off, which indicated the CLHP has a perfect function of thermal switch. The CLHP could adapt to sudden changes of the primary evaporator power, and reach a new steady-state quickly. Besides, some failure phenomena were observed during the test, which indicated that proper secondary evaporator power and heat sink temperature play important roles on the normal operation.

Injection molding of high precision optics for LED applications made of liquid silicone rubber

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

Hopmann, Christian; Röbig, Malte

Light Emitting Diodes (LED) conquer the growing global market of lighting technologies. Due to their advantages, they are increasingly used in consumer products, in lighting applications in the home and in the mobility sector as well as in industrial applications. Particularly, with regard to the increasing use of high-power LED (HP-LED) the materials in the surrounding area of the light emitting semiconductor chip are of utmost importance. While the materials behind the semiconductor chip are optimized for maximum heat dissipation, the materials currently used for the encapsulation of the semiconductor chip (primary optics) and the secondary optics encounter their limitsmore » due to the high temperatures. In addition certain amounts of blue UV radiation degrade the currently used materials such as epoxy resins or polyurethanes for primary optics. In the context of an ongoing joint research project with various partners from the industry, an innovative manufacturing method for high precision optics for LED applications made of liquid silicone rubber (LSR) is analyzed at the Institut of Plastics Processing (IKV), Aachen. The aim of this project is to utilize the material-specific advantages of high transparent LSR, especially the excellent high temperature resistance and the great freedom in design. Therefore, a high integrated injection molding process is developed. For the production of combined LED primary and secondary optics a LED board is placed in an injection mold and overmolded with LSR. Due to the integrated process and the reduction of subcomponents like the secondary optics the economics of the production process can be improved significantly. Furthermore combined LED optics offer an improved effectiveness, because there are no losses of the light power at the transition of the primary and secondary optics.« less

Effect of Thermomechanical Processing on the Microstructure, Properties, and Work Behavior of a Ti50.5 Ni29.5 Pt20 High-Temperature Shape Memory Alloy

NASA Technical Reports Server (NTRS)

Noebe, Ronald; Draper, Susan; Gaydosh, Darrell; Garga, Anita; Lerch, Brad; Penney, Nicholas; Begelow, Glen; Padula, Santo, II; Brown, Jeff

2006-01-01

TiNiPt shape memory alloys are particularly promising for use as solid state actuators in environments up to 300 C, due to a reasonable balance of properties, including acceptable work output. However, one of the challenges to commercializing a viable high-temperature shape memory alloy (HTSMA) is to establish the appropriate primary and secondary processing techniques for fabrication of the material in a required product form such as rod and wire. Consequently, a Ti(50.5)Ni(29.5)Pt20 alloy was processed using several techniques including single-pass high-temperature extrusion, multiple-pass high-temperature extrusion, and cold drawing to produce bar stock, thin rod, and fine wire, respectively. The effects of heat treatment on the hardness, grain size, room temperature tensile properties, and transformation temperatures of hot- and cold-worked material were examined. Basic tensile properties as a function of temperature and the strain-temperature response of the alloy under constant load, for the determination of work output, were also investigated for various forms of the Ti(50.5)Ni(29.5)Pt20 alloy, including fine wire.

Overview of NASA battery technology program

NASA Technical Reports Server (NTRS)

Riebling, R. W.

1980-01-01

Highlights of NASA's technology program in batteries for space applications are presented. Program elements include: (1) advanced ambient temperature alkaline secondaries, which are primarily nickel-cadmium cells in batteries; (2) a toroidal nickel cadmium secondaries with multi-kilowatt-hour storage capacity primarily for lower orbital applications; (3) ambient temperature lithium batteries, both primary and secondaries, primarily silver hydrogen and high-capacity nickel hydrogen.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Cellular mechanisms contributing to multiple stress tolerance in Saccharomyces cerevisiae strains with potential use in high-temperature ethanol fermentation.

PubMed

Kitichantaropas, Yasin; Boonchird, Chuenchit; Sugiyama, Minetaka; Kaneko, Yoshinobu; Harashima, Satoshi; Auesukaree, Choowong

2016-12-01

High-temperature ethanol fermentation has several benefits including a reduction in cooling cost, minimizing risk of bacterial contamination, and enabling simultaneous saccharification and fermentation. To achieve the efficient ethanol fermentation at high temperature, yeast strain that tolerates to not only high temperature but also the other stresses present during fermentation, e.g., ethanol, osmotic, and oxidative stresses, is indispensable. The C3253, C3751, and C4377 Saccharomyces cerevisiae strains, which have been previously isolated as thermotolerant yeasts, were found to be multiple stress-tolerant. In these strains, continuous expression of heat shock protein genes and intracellular trehalose accumulation were induced in response to stresses causing protein denaturation. Compared to the control strains, these multiple stress-tolerant strains displayed low intracellular reactive oxygen species levels and effective cell wall remodeling upon exposures to almost all stresses tested. In response to simultaneous multi-stress mimicking fermentation stress, cell wall remodeling and redox homeostasis seem to be the primary mechanisms required for protection against cell damage. Moreover, these strains showed better performances of ethanol production than the control strains at both optimal and high temperatures, suggesting their potential use in high-temperature ethanol fermentation.

Spermidine affects the transcriptome responses to high temperature stress in ripening tomato fruit.

PubMed

Cheng, Lin; Sun, Rong-rong; Wang, Fei-yan; Peng, Zhen; Kong, Fu-ling; Wu, Jian; Cao, Jia-shu; Lu, Gang

2012-04-01

High temperature adversely affects quality and yield of tomato fruit. Polyamine can alleviate heat injury in plants. This study is aimed to investigate the effects of polyamine and high temperature on transcriptional profiles in ripening tomato fruit. An Affymetrix tomato microarray was used to evaluate changes in gene expression in response to exogenous spermidine (Spd, 1 mmol/L) and high temperature (33/27 °C) treatments in tomato fruits at mature green stage. Of the 10101 tomato probe sets represented on the array, 127 loci were differentially expressed in high temperature-treated fruits, compared with those under normal conditions, functionally characterized by their involvement in signal transduction, defense responses, oxidation reduction, and hormone responses. However, only 34 genes were up-regulated in Spd-treated fruits as compared with non-treated fruits, which were involved in primary metabolism, signal transduction, hormone responses, transcription factors, and stress responses. Meanwhile, 55 genes involved in energy metabolism, cell wall metabolism, and photosynthesis were down-regulated in Spd-treated fruits. Our results demonstrated that Spd might play an important role in regulation of tomato fruit response to high temperature during ripening stage.

Carbonic fluid inclusions in amphibolite-facies pelitic schists from Bodonch area, western Mongolian Altai

NASA Astrophysics Data System (ADS)

Zorigtkhuu, Oyun-Erdene; Tsunogae, Toshiaki; Dash, Batulzii

We report first fluid inclusion data on amphibolite-facies pelitic schists from Bodonch area of western Mongolian Altai in the Central Asian Orogenic Belt. Three categories of fluid inclusions have been observed in quartz: dominant primary and secondary inclusions, and least dominant pseudosecondary inclusions. The melting temperatures of all the categories of inclusions lie in the narrow range of -57.5 °C to -56.6 °C, close to the triple point of pure CO2. Homogenization of fluids occurs into liquid phase at temperature between -33.3 °C to +19.4 °C, which convert into densities in the range of 0.78 g/cm3 to 1.09 g/cm3. The estimated CO2 isochores for primary and pseudosecondary high-density inclusions is broadly consistent with the peak metamorphic condition of the studied area (6.3-7.3 kbar at 655 °C). The results of this study, together with the primary and pseudosecondary nature of the inclusions, indicate CO2 was the dominant fluid component during the peak amphibolite-facies metamorphism of the study area. The examined quartz grains are texturally associated with biotite, kyanite and staurolite, which are regarded as high-grade minerals formed during prograde to peak metamorphism. Therefore quartz probably formed by high-grade metamorphism and the primary fluid inclusions trapped in the minerals probably preserve fluids at around peak metamorphism.

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

Bouchard, P.J.

A forthcoming revision to the R6 Leak-before-Break Assessment Procedure is briefly described. Practical application of the LbB concepts to safety-critical nuclear plant is illustrated by examples covering both low temperature and high temperature (>450{degrees}C) operating regimes. The examples highlight a number of issues which can make the development of a satisfactory LbB case problematic: for example, coping with highly loaded components, methodology assumptions and the definition of margins, the effect of crack closure owing to weld residual stresses, complex thermal stress fields or primary bending fields, the treatment of locally high stresses at crack intersections with free surfaces, the choicemore » of local limit load solution when predicting ligament breakthrough, and the scope of calculations required to support even a simplified LbB case for high temperature steam pipe-work systems.« less

Influence of temperature and electrolyte on the performance of activated-carbon supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Ping; Verbrugge, Mark; Soukiazian, Souren

For hybrid electric vehicle traction applications, energy storage devices with high power density and energy efficiency are required. A primary attribute of supercapacitors is that they retain their high power density and energy efficiency even at -30 °C, the lowest temperature at which unassisted starting must be provided to customers. More abuse-tolerant electrolytes are preferred to the high-conductivity acetonitrile-based systems commonly employed. Propylene carbonate based electrolytes are a promising alternative. In this work, we compare the electrochemical performance of two high-power density electrical double layer supercapacitors employing acetonitrile and propylene carbonate as solvents. From this study, we are able to elucidate phenomena that control the resistance of supercapacitor at lower temperatures, and quantify the difference in performance associated with the two electrolytes.

Electrolyte bi-layering strategy to improve the performance of an intermediate temperature solid oxide fuel cell: A review

NASA Astrophysics Data System (ADS)

Shri Prakash, B.; Pavitra, R.; Senthil Kumar, S.; Aruna, S. T.

2018-03-01

Lowering of operation temperature has become one of the primary goals of solid oxide fuel (SOFC) research as reduced temperature improves the prospects for widespread commercialization of this energy system. Reduced operational temperature also mitigates the issues associated with high temperature SOFCs and paves way not only for the large scale stationary power generation but also makes SOFCs viable for portable and transport applications. However, there are issues with electrolyte and cathode materials at low temperatures, individually as well as in association with other components, which makes the performance of the SOFCs less satisfactory than expected at lowered temperatures. Bi-layering of electrolytes and impregnation of cathodes have emerged as two important strategies to overcome these issues and achieve higher performance at low temperatures. This review article provides the perspective on the strategy of bi-layering of electrolyte to achieve the desired high performance from SOFC at low to intermediate temperatures.

Metasomatic hydration of the Oeyama forearc peridotites: Tectonic implications

NASA Astrophysics Data System (ADS)

Nozaka, Toshio

2014-01-01

In contrast to the widely recognized aspects of serpentinization, initial stages of hydration and tectonic processes of unserpentinized peridotites are still unclear, but have important implications for understanding the lithospheric architecture of supra-subduction zones. This study provides petrological evidence from the Oeyama ophiolite, SW Japan, of the effects of high-temperature metasomatic hydration immediately before the cooling and ductile deformation of forearc peridotites. Key findings in this study are: 1) complex association of high-temperature metasomatic minerals: tremolitic amphibole, cummingtonite, phlogopite, chlorite, olivine and orthopyroxene in veins and in mylonites; 2) the systematic variation in Si and Na + K contents of the tremolitic amphibole, corresponding to its mode of occurrence and mineral association; and 3) the presence of thin (< 0.7 mm) veins of fine-grained olivine accompanied by a narrow diffusion zone of the host primary olivine. On the basis of petrography and mineral chemistry, the temporal sequence of hydration and deformation of the Oeyama ophiolite is considered as follows: 1) infiltration of slab-derived fluids, causing decomposition of primary pyroxene and chemical modification of primary olivine, 2) metasomatic formation of variable modal amounts of amphibole, phlogopite, chlorite, vein-forming olivine and secondary orthopyroxene at 650-750 °C; 3) early-stage mylonitization of the hydrous peridotites in localized shear zones; and 4) syntectonic serpentinization at 400-600 °C to form serpentinite mylonites. Paragenesis and amphibole compositions suggest comparable temperature conditions for metasomatism and early-stage mylonitization. Mylonitization occurred exclusively in hydrous peridotites, and the peridotite mylonites were preferentially overprinted by syntectonic serpentinization. Diffusion profiles of olivine cut by a vein suggest rapid cooling immediately after the metasomatic fluid infiltration. From these observations and calculations, it is concluded that the exhumation of the forearc peridotites was closely related to the infiltration of high-temperature metasomatic fluids and hydration occurred under a wide range of temperature conditions.

Selective hydrogenation of amides to alcohols in water solvent over a heterogeneous CeO2-supported Ru catalyst.

PubMed

Tamura, Masazumi; Ishikawa, Susumu; Betchaku, Mii; Nakagawa, Yoshinao; Tomishige, Keiichi

2018-06-20

CeO2-supported Ru (Ru/CeO2) worked as an effective and reusable heterogeneous catalyst for the selective dissociation of the C-N bond in amides, particularly primary amides, with H2 in water solvent at low reaction temperature of 333 K, and high yields of the corresponding alcohols were obtained from primary amides.

Low cost solar energy collection system

NASA Technical Reports Server (NTRS)

Miller, C. G.; Stephans, J. B. (Inventor)

1977-01-01

A fixed, linear, ground-based primary reflector having an extended, curved sawtooth contoured surface covered with a metallized polymeric reflecting material, reflected solar energy to a movably supported collector that was kept at the concentrated line focus of the reflector primary. Efficient utilization leading to high temperatures from the reflected solar energy was obtained by cylindrical shaped secondary reflectors that directed off-angle energy to the absorber pipe.

Materials Compositions for Lithium Ion Batteries with Extended Thermal Stability

NASA Astrophysics Data System (ADS)

Kalaga, Kaushik

Advancements in portable electronics have generated a pronounced demand for rechargeable energy storage devices with superior capacity and reliability. Lithium ion batteries (LIBs) have evolved as the primary choice of portable power for several such applications. While multiple variations have been developed, safety concerns of commercial technologies limit them to atmospheric temperature operability. With several niche markets such as aerospace, defense and oil & gas demanding energy storage at elevated temperatures, there is a renewed interest in developing rechargeable batteries that could survive temperatures beyond 100°C. Instability of critical battery components towards extreme thermal and electrochemical conditions limit their usability at high temperatures. This study deals with developing material configurations for LIB components to stabilize them at such temperatures. Flammable organic solvent based electrolytes and low melting polymer based separators have been identified as the primary bottleneck for LIBs to survive increasing temperature. Furthermore, thermally activated degradation processes in oxide based electrodes have been identified as the reason for their limited lifetime. A quasi-solid composite comprising of room temperature ionic liquids (RTILs) and Clay was developed as an electrolyte/separator hybrid and tested to be stable up to 120°C. These composites facilitate complete reversible Li intercalation in lithium titanate (LTO) with a stable capacity of 120 mAh g-1 for several cycles of charge and discharge while simultaneously resisting severe thermal conditions. Modified phosphate based electrodes were introduced as a reliable alternative for operability at high temperatures in this study. These systems were shown to deliver stable reversible capacity for numerous charge/discharge cycles at elevated temperatures. Higher lithium intercalation potential of the developed cathode materials makes them interesting candidates for high voltage lithium batteries, which may be dubbed as the next generation devices. Architectural engineering of battery components to amplify the device performance is also discussed. 3D electrode structures developed using CVD and electrodeposition techniques demonstrated significant enhancement in performance when compared to their 2D analogues. The study has established the prospects of LIBs at high temperatures through material tuning and engineering approaches and envisage a scope for viable devices.

Stability of the surface layer and its relation to the dispersion of primary pollutants in St. Louis

NASA Technical Reports Server (NTRS)

Remsberg, E. E.; Woodbury, G. E.

1983-01-01

The effects of atmospheric stability on the dispersion of primary pollutants such as CO, total hydrocarbons (THC), and NO were examined in St. Louis. The pollutant levels were measured at 25 stations, temperature at 12 stations at 5 and 30 m height, and wind speed and direction at the 30 m level at 12 stations. Correlation coefficients were generated for pairs of the vertical temperature differences, the log of the mean wind speed reciprocal, the bulk Richardson number, and specific pollutant concentrations. A high correlation was obtained between the thermal stability and the urban concentration of the primary pollutants in the lowest part of the boundary layer. A restricted nighttime dispersion of the pollutants was observed, indicating near-ground increased concentrations at times when the source emissions actually decrease.

High-rate lithium thionyl chloride cells

NASA Technical Reports Server (NTRS)

Goebel, F.

1982-01-01

A high-rate C cell with disc electrodes was developed to demonstrate current rates which are comparable to other primary systems. The tests performed established the limits of abuse beyond which the cell becomes hazardous. Tests include: impact, shock, and vibration tests; temperature cycling; and salt water immersion of fresh cells.

Presence and persistence of a highly ordered lipid phase state in the avian stratum corneum.

PubMed

Champagne, Alex M; Pigg, Victoria A; Allen, Heather C; Williams, Joseph B

2018-06-07

To survive high temperatures in a terrestrial environment, animals must effectively balance evaporative heat loss and water conservation. In passerine birds, cutaneous water loss (CWL) is the primary avenue of water loss at thermoneutral temperatures and increases slightly as ambient temperature increases, indicating a change in the permeability of the skin. In the stratum corneum (SC), the outermost layer of the skin, lipids arranged in layers called lamellae serve as the primary barrier to CWL in birds. The permeability of these lamellae depends in large part on the ability of lipid molecules to pack closely together in an ordered orthorhombic phase state. However, as temperature increases, lipids of the SC become more disordered, and may pack in more permeable hexagonal or liquid crystalline phase states. In this study, we used Fourier transform infrared spectroscopy to monitor the phase state of lipids in the SC of house sparrows ( Passer domesticus ) at skin temperatures ranging from 25 to 50°C. As temperature increased, lipids became slightly more disordered, but remained predominantly in the orthorhombic phase, consistent with the small increase in CWL observed in house sparrows as ambient temperature increases. These results differ considerably from studies on mammalian SC, which find a predominantly hexagonal arrangement of lipids at temperatures above 37°C, and the increased order in avian SC may be explained by longer lipid chain length, scarcity of cholesterol and the presence of cerebrosides. Our results lend further insight into the arrangement and packing of individual lipid molecules in avian SC. © 2018. Published by The Company of Biologists Ltd.

Intramolecular Hydroamination of Unbiased and Functionalized Primary Aminoalkenes Catalyzed by a Rhodium Aminophosphine Complex

PubMed Central

Julian, Lisa D.; Hartwig, John F.

2010-01-01

We report a rhodium catalyst that exhibits high reactivity for the hydroamination of primary aminoalkenes that are unbiased toward cyclization and that possess functional groups that would not be tolerated in hydroaminations catalyzed by more electrophilic systems. This catalyst contains an unusual diaminophosphine ligand that binds to rhodium in a κ3-P,O,P mode. The reactions catalyzed by this complex typically proceed at mild temperatures (room temperature to 70 °C), occur with primary aminoalkenes lacking substituents on the alkyl chain that bias the system toward cyclization, occur with primary aminoalkenes containing chloride, ester, ether, enolizable ketone, nitrile, and unprotected alcohol functionality, and occur with primary aminoalkenes containing internal olefins. Mechanistic data imply that these reactions occur with a turnover-limiting step that is different from that of reactions catalyzed by late transition metal complexes of Pd, Pt, and Ir. This change in the turnover-limiting step and resulting high activity of the catalyst stem from favorable relative rates for protonolysis of the M-C bond to release the hydroamination product vs reversion of the aminoalkyl intermediate to regenerate the acyclic precursor. Probes for the origin of the reactivity of the rhodium complex of L1 imply that the aminophosphine groups lead to these favorable rates by effects beyond steric demands and simple electron donation to the metal center. PMID:20839807

Thermal niche evolution of functional traits in a tropical marine phototroph.

PubMed

Baker, Kirralee G; Radford, Dale T; Evenhuis, Christian; Kuzhiumparam, Unnikrishnan; Ralph, Peter J; Doblin, Martina A

2018-06-14

Land-based plants and ocean-dwelling microbial phototrophs known as phytoplankton, are together responsible for almost all global primary production. Habitat warming associated with anthropogenic climate change has detrimentally impacted marine primary production, with the effects observed on regional and global scales. In contrast to slower-growing higher plants, there is considerable potential for phytoplankton to evolve rapidly with changing environmental conditions. The energetic constraints associated with adaptation in phytoplankton are not yet understood, but are central to forecasting how global biogeochemical cycles respond to contemporary ocean change. Here, we demonstrate a number of potential trade-offs associated with high-temperature adaptation in a tropical microbial eukaryote, Amphidinium massartii (dinoflagellate). Most notably, the population became high-temperature specialized (higher fitness within a narrower thermal envelope and higher thermal optimum), and had a greater nutrient requirement for carbon, nitrogen and phosphorus. Evidently, the energetic constraints associated with living at elevated temperature alter competiveness along other environmental gradients. While high-temperature adaptation led to an irreversible change in biochemical composition (i.e., an increase in fatty acid saturation), the mechanisms underpinning thermal evolution in phytoplankton remain unclear, and will be crucial to understanding whether the trade-offs observed here are species-specific or are representative of the evolutionary constraints in all phytoplankton. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

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.

Non-isothermal electrochemical model for lithium-ion cells with composite cathodes

NASA Astrophysics Data System (ADS)

Basu, Suman; Patil, Rajkumar S.; Ramachandran, Sanoop; Hariharan, Krishnan S.; Kolake, Subramanya Mayya; Song, Taewon; Oh, Dukjin; Yeo, Taejung; Doo, Seokgwang

2015-06-01

Transition metal oxide cathodes for Li-ion batteries offer high energy density and high voltage. Composites of these materials have shown excellent life expectancy and improved thermal performance. In the present work, a comprehensive non-isothermal electrochemical model for a Lithium ion cell with a composite cathode is developed. The present work builds on lithium concentration-dependent diffusivity and thermal gradient of cathode potential, obtained from experiments. The model validation is performed for a wide range of temperature and discharge rates. Excellent agreement is found for high and room temperature with moderate success at low temperatures, which can be attributed to the low fidelity of material properties at low temperature. Although the cell operation is limited by electronic conductivity of NCA at room temperature, at low temperatures a shift in controlling process is seen, and operation is limited by electrolyte transport. At room temperature, the lithium transport in Cathode appears to be the main source of heat generation with entropic heat as the primary contributor at low discharge rates and ohmic heat at high discharge rates respectively. Improvement in electronic conductivity of the cathode is expected to improve the performance of these composite cathodes and pave way for its wider commercialization.

High Temperature Mechanical Behavior of UHTC Coatings for Thermal Protection of Re-Entry Vehicles

NASA Astrophysics Data System (ADS)

Pulci, G.; Tului, M.; Tirillò, J.; Marra, F.; Lionetti, S.; Valente, T.

2011-01-01

In this work, the high temperature mechanical properties of ultra high temperature ceramics (UHTC) coatings deposited by plasma spraying have been investigated; particularly the stress-strain relationship of ZrB2-based thick films has been evaluated by means of 4-point bending tests up to 1500 °C in air. Results show that at each investigated temperature (500, 1000, and 1500 °C) modulus of rupture (MOR) values are higher than the ones obtained at room temperature (RT); moreover at 1500 °C the UHTC coatings exhibit a marked plastic behavior, maintaining a flexural strength 25% higher compared to RT tested samples. The coefficient of linear thermal expansion (CTE) has been evaluated up to 1500 °C: obtained data are of primary importance for substrate selection, interface design and to analyze the thermo-mechanical behavior of coating-substrate coupled system. Finally, SEM-EDS analyses have been carried out on as-sprayed and tested materials in order to understand the mechanisms of reinforcement activated by high temperature exposure and to identify the microstructural modifications induced by the combination of mechanical loads and temperature in an oxidizing environment.

Durability of structural lumber products at high temperatures. Part I, 66C at 75% RH and 82C at 30% RH

Treesearch

David W. Green; James W. Evans; Bruce A. Craig

2003-01-01

The effect of temperature on properties can be separated into reversible and permanent effects. The National Design Specification (NDS) provides factors (Ct) for reducing properties for reversible effects but provides little guidance on permanent effects. The primary objective of this paper is to evaluate the effect of prolonged heating (permanent effect) on the...

X-ray tomography as a non-destructive tool for evaluating the preservation of primary isotope signatures and mineralogy of Mesozoic fossils

NASA Astrophysics Data System (ADS)

Santillan, J. D.; Boyce, J. W.; Eagle, R.; Martin, T.; Tuetken, T.; Eiler, J.

2010-12-01

The stable isotope compositions of carbonate and phosphate components in fossil teeth and bone are widely used to infer information on paleoclimate and the physiology of extinct organisms. Recently the potential for measuring the body temperatures of extinct vertebrates from analyses of 13C-18O bond ordering in fossil teeth has been demonstrated (Eagle et al. 2010). The interpretation of these isotopic signatures relies on an assessment of the resistance of fossil bioapatite to alteration, as diffusion within, and partial recrystallization, or replacement of the original bioapatite will lead to measured compositions that represent mixtures between primary and secondary phases and/or otherwise inaccurate apparent temperatures. X-ray computed tomography (CT) allows 3-D density maps of teeth to be made at micron-scale resolution. Such density maps have the potential to record textural evidence for alteration, recrystallization, or replacement of enamel. Because it is non-destructive, CT can be used prior to stable isotope analysis to identify potentially problematic samples without consuming or damaging scientifically significant specimens. As a test, we have applied CT to tooth fragments containing both dentin and enamel from Late Jurassic sauropods and a Late Cretaceous theropod that yielded a range of clumped isotope temperatures from anomalously high ˜60oC to physiologically plausible ≤40oC. This range of temperatures suggests partial, high-temperature modification of some specimens, but possible preservation of primary signals in others. Three-dimensional CT volumes generated using General Electric Phoenix|x-ray CT instruments were compared with visible light and back-scattered electron images of the same samples. The tube-detector combination used for the CT study consisted of a 180 kV nanofocus transmission tube coupled with a 127 micron pixel pitch detector ( ˜3-12μ m voxel edges), allowing us to clearly map out alteration zones in high contrast, while reducing edge effects and beam hardening artifacts. CT images of these teeth show a range of replacement textures. One tooth -- thought to be the least altered -- shows only localized positive density anomalies near fractures, while a second -- thought to be highly altered -- contains high-density replacement mineralization. A third tooth -- one suspected of possible partial alteration -- shows a network of rectilinear density anomalies in the enamel similar to 2-D transmitted light and back-scattered electron images. This may represent recrystallization or replacement of the primary bioapatite. Unlike 2-D imaging techniques, 3-D volumes can be used to quickly and easily make quantitative measurements of the volumes of altered and unaltered materials: For example, in the enamel of sample 3, we observe a ratio of high density to low density material of ˜ 3:2.

Development of a TDLAS sensor for temperature and concentration of H2 O in high speed and high temperature flows

NASA Astrophysics Data System (ADS)

Sheehe, Suzanne; O'Byrne, Sean

2017-06-01

The development of a sensor for simultaneous temperature concentration of H2 O and temperature in high speed flows is presented. H2 O is a desirable target sensing species because it is a primary product in combustion systems; both temperature and concentration profiles can be used to assess both the extent of the combustion and the flow field characteristics. Accurate measurements are therefore highly desirable. The sensor uses a vertical-cavity surface emitting laser (VCSEL) scanned at 50 kHz from 7172 to 7186 cm-1. Temperatures and concentrations are extracted from the spectra by fitting theoretical spectra to the experimental data. The theoretical spectra are generated using GENSPECT in conjunction with line parameters from the HITRAN 2012 database. To validate the theoretical spectra, experimental spectra of H2 O were obtained at known temperatures (290-550 K) and pressures (30 torr) in a heated static gas cell. The results show that some theoretical lines deviate from the experimental lines. New line-strengths are calculated assuming that the line assignments and broadening parameters in HITRAN are correct. This data is essential for accurate H2 O concentration and temperature measurements at low pressure and high temperature conditions. US Air Force Asian Office of Aerospace Research and Development Grant FA2386-16-1-4092.

New Primary Dew-Point Generators at HMI/FSB-LPM in the Range from -70 °C to +60 °C

NASA Astrophysics Data System (ADS)

Zvizdic, Davor; Heinonen, Martti; Sestan, Danijel

2012-09-01

To extend the dew-point range and to improve the uncertainties of the humidity scale realization at HMI/FSB-LPM, new primary low- and high-range dew-point generators were developed and implemented in cooperation with MIKES, in 2009 through EUROMET Project No. 912. The low-range saturator is designed for primary realization of the dew-point temperature scale from -70 °C to + 5 °C, while the high-range saturator covers the range from 1 °C to 60 °C. The system is designed as a single-pressure, single-pass dew-point generator. MIKES designed and constructed both the saturators to be implemented in dew-point calibration systems at LPM. The LPM took care of purchasing and adapting liquid baths, of implementing the temperature and pressure measurement equipment appropriate for use in the systems, and development of gas preparation and flow control systems as well as of the computer-based automated data acquisition. The principle and the design of the generator are described in detail and schematically depicted. The tests were performed at MIKES to investigate how close both the saturators are to an ideal saturator. Results of the tests show that both the saturators are efficient enough for a primary realization of the dew-point temperature scale from -70 °C to + 60 °C, in the specified flow-rate ranges. The estimated standard uncertainties due to the non-ideal saturation efficiency are between 0.02 °C and 0.05 °C.

Review of deformation behavior of tungsten at temperature less than 0.2 absolute melting temperature

NASA Technical Reports Server (NTRS)

Stephens, J. R.

1972-01-01

The deformation behavior of tungsten at temperatures 0.2 T sub m is reviewed, with primary emphasis on the temperature dependence of the yield stress and the ductile-brittle transition temperature. It appears that a model based on the high Peierls stress of tungsten best accounts for the observed mechanical behavior at low temperatures. Recent research is discussed which suggests an important role of electron concentration and bonding on the mechanical behavior of tungsten. It is concluded that future research on tungsten should include studies to define more clearly the correlation between electron concentration and mechanical behavior of tungsten alloys and other transition metal alloys.

Similitude of membrane helical coil with membrane serpentine tube for characteristics of high-pressure syngas: A review

NASA Astrophysics Data System (ADS)

Gaddamwar, Sagar. S.; Pawar, Anand N.; Naik, Pramod A.

2018-05-01

Heat exchangers remain one primary engineering methods besides this broad category of purposes including various waste heat recovery systems, power sectors, nuclear reactors. Natural convection is a method concerning heat transfer, during which flow of fluid occurs by density variations in the fluid occurring due to different temperature conditions. A fluid which encompasses a heat reservoir holds heat becomes light dense and rises. Operating fluid that is enclosing the high-temperature liquid remains frozen and later flows in to supplant it. Following this chilling liquid gets heated, and this method persists, resulting from convection flow. Forced convection into a heat exchanger is this movement of heat from one moving water to different stream through the surface from a pipe. The low-temperature liquid extracts heat of this comparatively high-temperature water because that flows along or over it.

Soybean

USDA-ARS?s Scientific Manuscript database

The primary vulnerability of soybean production to climate change is likely to be from the effects of drought, which may be exacerbated by high temperature events. Technological adaptation can likely take advantage of warming in some production areas and rising concentrations of atmospheric carbon ...

Eutrophication effects on greenhouse gas fluxes from shallow-lake mesocosms override those of climate warming.

PubMed

Davidson, Thomas A; Audet, Joachim; Svenning, Jens-Christian; Lauridsen, Torben L; Søndergaard, Martin; Landkildehus, Frank; Larsen, Søren E; Jeppesen, Erik

2015-12-01

Fresh waters make a disproportionately large contribution to greenhouse gas (GHG) emissions, with shallow lakes being particular hot spots. Given their global prevalence, how GHG fluxes from shallow lakes are altered by climate change may have profound implications for the global carbon cycle. Empirical evidence for the temperature dependence of the processes controlling GHG production in natural systems is largely based on the correlation between seasonal temperature variation and seasonal change in GHG fluxes. However, ecosystem-level GHG fluxes could be influenced by factors, which while varying seasonally with temperature are actually either indirectly related (e.g. primary producer biomass) or largely unrelated to temperature, for instance nutrient loading. Here, we present results from the longest running shallow-lake mesocosm experiment which demonstrate that nutrient concentrations override temperature as a control of both the total and individual GHG flux. Furthermore, testing for temperature treatment effects at low and high nutrient levels separately showed only one, rather weak, positive effect of temperature (CH4 flux at high nutrients). In contrast, at low nutrients, the CO2 efflux was lower in the elevated temperature treatments, with no significant effect on CH4 or N2 O fluxes. Further analysis identified possible indirect effects of temperature treatment. For example, at low nutrient levels, increased macrophyte abundance was associated with significantly reduced fluxes of both CH4 and CO2 for both total annual flux and monthly observation data. As macrophyte abundance was positively related to temperature treatment, this suggests the possibility of indirect temperature effects, via macrophyte abundance, on CH4 and CO2 flux. These findings indicate that fluxes of GHGs from shallow lakes may be controlled more by factors indirectly related to temperature, in this case nutrient concentration and the abundance of primary producers. Thus, at ecosystem scale, response to climate change may not follow predictions based on the temperature dependence of metabolic processes. © 2015 John Wiley & Sons Ltd.

Thermal analysis of heat and power plant with high temperature reactor and intermediate steam cycle

NASA Astrophysics Data System (ADS)

Fic, Adam; Składzień, Jan; Gabriel, Michał

2015-03-01

Thermal analysis of a heat and power plant with a high temperature gas cooled nuclear reactor is presented. The main aim of the considered system is to supply a technological process with the heat at suitably high temperature level. The considered unit is also used to produce electricity. The high temperature helium cooled nuclear reactor is the primary heat source in the system, which consists of: the reactor cooling cycle, the steam cycle and the gas heat pump cycle. Helium used as a carrier in the first cycle (classic Brayton cycle), which includes the reactor, delivers heat in a steam generator to produce superheated steam with required parameters of the intermediate cycle. The intermediate cycle is provided to transport energy from the reactor installation to the process installation requiring a high temperature heat. The distance between reactor and the process installation is assumed short and negligable, or alternatively equal to 1 km in the analysis. The system is also equipped with a high temperature argon heat pump to obtain the temperature level of a heat carrier required by a high temperature process. Thus, the steam of the intermediate cycle supplies a lower heat exchanger of the heat pump, a process heat exchanger at the medium temperature level and a classical steam turbine system (Rankine cycle). The main purpose of the research was to evaluate the effectiveness of the system considered and to assess whether such a three cycle cogeneration system is reasonable. Multivariant calculations have been carried out employing the developed mathematical model. The results have been presented in a form of the energy efficiency and exergy efficiency of the system as a function of the temperature drop in the high temperature process heat exchanger and the reactor pressure.

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

Lewis, Antony, E-mail: antony@cosmologist.info

Rayleigh scattering from neutral hydrogen during and shortly after recombination causes the CMB anisotropies to be significantly frequency dependent at high frequencies. This may be detectable with Planck, and would be a strong signal in any future space-based CMB missions. The later peak of the Rayleigh visibility compared to Thomson scattering gives an increased large-scale CMB polarization signal that is a greater than 4% effect for observed frequencies ν ∼> 500GHz. There is a similar magnitude suppression on small scales from additional damping. Due to strong correlation between the Rayleigh and primary signal, measurement of the Rayleigh component is limitedmore » by noise and foregrounds, not cosmic variance of the primary CMB, and should observable over a wide range of angular scales at frequencies 200GHz ∼< ν ∼< 800GHz. I give new numerical calculations of the temperature and polarization power spectra, and show that future CMB missions could measure the temperature Rayleigh cross-spectrum at high precision, detect the polarization from Rayleigh scattering, and also accurately determine the cross-spectra between the Rayleigh temperature signal and primary polarization. The Rayleigh scattering signal may provide a powerful consistency check on recombination physics. In principle it can be used to measure additional horizon-scale primordial perturbation modes at recombination, and distinguish a significant tensor mode B-polarization signal from gravitational lensing at the power spectrum level.« less

Study of the electromagnetic characteristics of multiple HTSPPT modules based on the configuration of toroidal structure for inductive pulsed power supply

NASA Astrophysics Data System (ADS)

Zhang, Cunshan; Zheng, Xinxin; Li, Haitao; Li, Zhenmei; Zhang, Tao; Jiao, Can

2018-04-01

High temperature superconducting pulsed power transformer (HTSPPT) is an important device for pulsed power supplies. It consists of a superconducting primary and a normal conducting secondary, which is used for energy storage and current amplification. The critical current density, the energy storage, and the coupling coefficient are three main performance indexes. They are affected by the geometry parameters of HTSPPT modules, such as the height and the width of the superconducting coils. In addition, the hoop stress of the HTSPPT coils is limited by the maximum tensile strength of high temperature superconducting (HTS) tapes. In this paper, Bi-2223/Ag HTS tapes are selected as the wire of primary inductor and the toroidal structure model is selected for multiple HTSPPT modules. The relationships between the geometry parameters of HTSPPT modules and the electrical performance are studied.

Solar Total Energy Project (STEP) Performance Analysis of High Temperature Energy Storage Subsystem

NASA Technical Reports Server (NTRS)

Moore, D. M.

1984-01-01

The 1982 milestones and lessons learned; performance in 1983; a typical day's operation; collector field performance and thermal losses; and formal testing are highlighted. An initial test that involves characterizing the high temperature storage (hts) subsystem is emphasized. The primary element is on 11,000 gallon storage tank that provides energy to the steam generator during transient solar conditions or extends operating time. Overnight, thermal losses were analyzed. The length of time the system is operated at various levels of cogeneration using stored energy is reviewed.

Growth and photosynthesis of Chlorella strains from polar, temperate and tropical freshwater environments under temperature stress

NASA Astrophysics Data System (ADS)

Lee, Kok-Keong; Lim, Phaik-Eem; Poong, Sze-Wan; Wong, Chiew-Yen; Phang, Siew-Moi; Beardall, John

2017-09-01

Elevated temperatures as a consequence of global warming have significant impacts on the adaptation and survival of microalgae which are important primary producers in many ecosystems. The impact of temperature on the photosynthesis of microalgae is of great interest as the primary production of algal biomass is strongly dependent on the photosynthetic rates in a dynamic environment. Here, we examine the effects of elevated temperature on Chlorella strains originating from different latitudes, namely Antarctic, Arctic, temperate and tropical regions. Chlorophyll fluorescence was used to assess the photosynthetic responses of the microalgae. Rapid light curves (RLCs) and maximum quantum yield (F v/F m) were recorded. The results showed that Chlorella originating from different latitudes portrayed different growth trends and photosynthetic performance. The Chlorella genus is eurythermal, with a broad temperature tolerance range, but with strain-specific characteristics. However, there was a large overlap between the tolerance range of the four strains due to their "eurythermal adaptivity". Changes in the photosynthetic parameters indicated temperature stress. The ability of the four strains to reactivate photosynthesis after inhibition of photosynthesis under high temperatures was also studied. The Chlorella strains were shown to recover in terms of photosynthesis and growth (measured as Chl a) when they were returned to their ambient temperatures. Polar strains showed faster recovery in their optimal temperature compared to that under the ambient temperature from which they were isolated.

Atomization, drop size, and penetration for cross-stream water injection at high-altitude reentry conditions with application to the RAM C-1 and C-3 flights

NASA Technical Reports Server (NTRS)

Gooderum, P. B.; Bushnell, D. M.

1972-01-01

Atomization, drop size, and penetration data are presented for cross stream water injection at conditions simulating high altitude reentry (low Weber number, high static temperature, high Knudsen number, and low static pressure). These results are applied to the RAM C-1 and C-3 flights. Two primary breakup modes are considered, vapor pressure or flashing and aerodynamic atomization. Results are given for breakup boundaries and mean drop size for each of these atomization mechanisms. Both standard and flight orifice geometries are investigated. The data were obtained in both a static environment and in conventional aerodynamic facilities at Mach numbers of 4.5 and 8. The high temperature aspects of reentry were simulated in a Mach 5.5 cyanogen-oxygen tunnel with total temperature of 4500 K.

Nanotwin Formation in High-Manganese Austenitic Steels Under Explosive Shock Loading

NASA Astrophysics Data System (ADS)

Canadinc, D.; Uzer, B.; Elmadagli, M.; Guner, F.

2018-04-01

The micro-deformation mechanisms active in a high-manganese austenitic steel were investigated upon explosive shock loading. Single system of nanotwins forming within primary twins were shown to govern the deformation despite the elevated temperatures attained during testing. The benefits of nanotwin formation for potential armor materials were demonstrated.

9 Cr-- 1 Mo steel material for high temperature application

DOEpatents

Jablonski, Paul D; Alman, David; Dogan, Omer; Holcomb, Gordon; Cowen, Christopher

2012-11-27

One or more embodiments relates to a high-temperature, titanium alloyed, 9 Cr-1 Mo steel exhibiting improved creep strength and oxidation resistance at service temperatures up to 650.degree. C. The 9 Cr-1 Mo steel has a tempered martensite microstructure and is comprised of both large (0.5-3 .mu.m) primary titanium carbides and small (5-50 nm) secondary titanium carbides in a ratio of. from about 1:1.5 to about 1.5:1. The 9 Cr-1 Mo steel may be fabricated using exemplary austenizing, rapid cooling, and tempering steps without subsequent hot working requirements. The 9 Cr-1 Mo steel exhibits improvements in total mass gain, yield strength, and time-to-rupture over ASTM P91 and ASTM P92 at the temperature and time conditions examined.

Structure and microhardness of Al-Si-Cu-Ni alloy after severe plastic deformation and high-temperature annealing

NASA Astrophysics Data System (ADS)

Shvets, Karina; Khalikova, Gulnara; Korznikova, Elena; Trifonov, Vadim

2015-10-01

The effect of severe plastic deformation by high-pressure torsion (HPT) and subsequent annealing on the microstructure and microhardness of squeeze casting Al-22%Si-3%Cu-1.7%Ni alloy was investigated. HPT was performed at room temperature with 5 rotations under the pressure of 4 GPa. Annealing temperature range varied from 300 to 500°C for 5 min. HPT resulted in refinement and partial dissolution of the primary silicon and intermetallic particles in aluminum matrix and structure fragmentation that caused the microhardness increase. Subsequent annealing lead to the decomposition of the supersaturated solid solution that took place simultaneously with recovery and recrystallization of the fragmented structure. Increase of annealing temperature resulted in decrease of microhardness values.

Sol-Gel assembly of CdSe nanoparticles to form porous aerogel networks.

PubMed

Arachchige, Indika U; Brock, Stephanie L

2006-06-21

A detailed study of CdSe aerogels prepared by oxidative aggregation of primary nanoparticles (prepared at room temperature and high temperature conditions, >250 degrees C), followed by CO2 supercritical drying, is described. The resultant materials are mesoporous, with an interconnected network of colloidal nanoparticles, and exhibit BET surface areas up to 224 m2/g and BJH average pore diameters in the range of 16-32 nm. Powder X-ray diffraction studies indicate that these materials retain the crystal structure of the primary nanoparticles, with a slight increase in primary particle size upon gelation and aerogel formation. Optical band gap measurements and photoluminescence studies show that the as-prepared aerogels retain the quantum-confined optical properties of the nanoparticle building blocks despite being connected into a 3-D network. The specific optical characteristics of the aerogel can be further modified by surface ligand exchange at the wet-gel stage, without destroying the gel network.

Detection and analysis of high-temperature events in the BIRD mission

NASA Astrophysics Data System (ADS)

Zhukov, Boris; Briess, Klaus; Lorenz, Eckehard; Oertel, Dieter; Skrbek, Wolfgang

2005-01-01

The primary mission objective of a new small Bi-spectral InfraRed Detection (BIRD) satellite is detection and quantitative analysis of high-temperature events like fires and volcanoes. An absence of saturation in the BIRD infrared channels makes it possible to improve false alarm rejection as well as to retrieve quantitative characteristics of hot targets, including their effective fire temperature, area and the radiative energy release. Examples are given of detection and analysis of wild and coal seam fires, of volcanic activity as well as of oil fires in Iraq. The smallest fires detected by BIRD, which were verified on ground, had an area of 12m2 at daytime and 4m2 at night.

Effect of MgO on Liquidus Temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2-MgO System in Equilibrium with Metallic Iron

NASA Astrophysics Data System (ADS)

Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

2011-06-01

The phase equilibria in the ZnO-"FeO"-Al2O3-CaO-SiO2-MgO system have been determined experimentally in equilibrium with metallic iron. Synthetic slags were equilibrated at a high temperature, quenched, and then the compositions of the phases in equilibrium were measured using electron probe X-ray microanalysis. Pseudoternary sections of the form ZnO-"FeO"-(Al2O3 + CaO + SiO2) for CaO/SiO2 = 0.71, (CaO + SiO2)/Al2O3 = 5 and fixed MgO concentrations of 2, 4, and 6 wt pct have been constructed. Wustite (Fe2+,Mg,Zn)O and spinel (Fe2+,Mg,Zn)O·(Al,Fe3+)2O3 are the major primary phases in the temperature and composition ranges investigated. The liquidus temperatures are increased by 140 K in the wustite primary phase field and by 70 K in the spinel primary phase field with the addition of 6 wt pct MgO in the slag. The partitioning of MgO and ZnO between the solid and liquid phases has been discussed.

Isotopic composition of sulphates from meteoric precipitation as an indicator of pollutant origin in Wrocław (SW Poland).

PubMed

Gorka, Maciej; Jedrysek, Mariusz-Orion; Strapoc, Dariusz

2008-06-01

This paper describes the results of isotopic analyses of (i) hydrogen and oxygen in water (delta DH2O and delta18OH2O ) and (ii) sulphur and oxygen in sulphates (delta34Ssulphate and delta18Osulphate) from atmospheric precipitation collected within a one-year period between 25 May 2004 and 25 May 2005 in Wrocław (SW Poland). The resulting equation of Local Meteoric Water Line for Wrocław is delta D=6.373xdelta18O-0.047, (r2=0.97, n=32). The delta34Ssulphate varies from 1.1 to 4.2 per thousand (with an average of 2.5 per thousand), delta18Osulphate varies from 9.0 to 16.7 per thousand (with an average of 13.8 per thousand) and delta18OH2O varies from-0.8 to-16.3 per thousand (with an average of-8.2 per thousand). The above results indicate two main sources of sulphates in Wrocław precipitation: (i) low-temperature secondary sulphates forming in situ in Wrocław from the atmospheric SO2 as well as precipitation water (heterogeneous and homogeneous pathways oxidation) and (ii) high-temperature primary sulphates forming in rapid high-temperature hydratation of SO3- in an immediate proximity of industrial chimneys. We hypothesise that the secondary low-temperature type of sulphates is probably formed from the local sulphur and oxygen reservoirs, whereas the primary high-temperature type is allochthonous and it is probably transported from industrial areas located outside of Wrocław.

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

DOE PAGES

Stoica, G. M.; Stoica, A. D.; Miller, M. K.; ...

2014-10-10

Nanostructured ferritic alloys (NFA) are a new class of ultrafine-grained oxide dispersion-strengthened steels, promising for service in extreme environments of high temperature and high irradiation in the next-generation of nuclear reactors. This is owing to the remarkable stability of their complex microstructures containing a high density of Y-Ti-O nanoclusters within grains and along the grain boundaries. While nanoclusters have been recognized to be the primary contributor to the exceptional resistance to irradiation and high-temperature creep, very little is known about the mechanical roles of the polycrystalline grains that constitute the bulk ferritic matrix. Here we report the mesoscale characterization ofmore » anisotropic responses of the ultrafine NFA grains to tensile stresses at various temperatures using the state-of-the-art in situ neutron diffraction. We show the first experimental determination of temperature-dependent single-crystal elastic constants for the NFA, and reveal a strong temperature-dependent elastic anisotropy due to a sharp decrease in the shear stiffness constant [c'=(c_11-c_12)/2] when a critical temperature ( T_c ) is approached, indicative of elastic softening and instability of the ferritic matrix. We also show, from anisotropy-induced intergranular strain/stress accumulations, that a common dislocation slip mechanism operates at the onset of yielding for low temperatures, while there is a deformation crossover from low-temperature lattice hardening to high temperature lattice softening in response to extensive plastic deformation.« less

Experimental study of the maximum resolution and packing density achievable in sintered and non-sintered binder-jet 3D printed steel microchannels

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

Elliott, Amy M; Mehdizadeh Momen, Ayyoub; Benedict, Michael

2015-01-01

Developing high resolution 3D printed metallic microchannels is a challenge especially when there is an essential need for high packing density of the primary material. While high packing density could be achieved by heating the structure to the sintering temperature, some heat sensitive applications require other strategies to improve the packing density of primary materials. In this study the goal is to develop high green or pack densities microchannels on the scale of 2-300 microns which have a robust mechanical structure. Binder-jet 3D printing is an additive manufacturing process in which droplets of binder are deposited via inkjet into amore » bed of powder. By repeatedly spreading thin layers of powder and depositing binder into the appropriate 2D profiles, complex 3D objects can be created one layer at time. Microchannels with features on the order of 500 microns were fabricated via binder jetting of steel powder and then sintered and/or infiltrated with a secondary material. The average particle size of the steel powder was varied along with the droplet volume of the inkjet-deposited binder. The resolution of the process, packing density of the primary material, the subsequent features sizes of the microchannels, and the overall microchannel quality were characterized as a function of particle size distribution, droplet sizes and heat treatment temperatures.« less

Influence of initial heating during final high temperature annealing on the offset of primary and secondary recrystallization in Cu-bearing grain oriented electrical steels

NASA Astrophysics Data System (ADS)

Rodriguez-Calvillo, P.; Leunis, E.; Van De Putte, T.; Jacobs, S.; Zacek, O.; Saikaly, W.

2018-04-01

The industrial production route of Grain Oriented Electrical Steels (GOES) is complex and fine-tuned for each grade. Its metallurgical process requires in all cases the abnormal grain growth (AGG) of the Goss orientation during the final high temperature annealing (HTA). The exact mechanism of AGG is not yet fully understood, but is controlled by the different inhibition systems, namely MnS, AlN and CuxS, their size and distribution, and the initial primary recrystallized grain size. Therefore, among other parameters, the initial heating stage during the HTA is crucial for the proper development of primary and secondary recrystallized microstructures. Cold rolled 0.3 mm Cu-bearing Grain Oriented Electrical Steel has been submitted to interrupted annealing experiments in a lab tubular furnace. Two different annealing cycles were applied:• Constant heating at 30°C/h up to 1000°C. Two step cycle with initial heating at 100°C/h up to 600°C, followed by 18 h soaking at 600°C and then heating at 30°C/h up to 1050°C. The materials are analyzed in terms of their magnetic properties, grain size, texture and precipitates. The characteristic magnetic properties are analyzed for the different extraction temperatures and Cycles. As the annealing was progressing, the coercivity values (Hc 1.7T [A/m]) decreased, showing two abrupt drops, which can be associated to the on-set of primary and secondary recrystallization. The primary recrystallized grain sizes and recrystallized fractions are fitted to a model using a non-isothermal approach. This analysis shows that, although the resulting grain sizes were similar, the kinetics for the two step annealing were faster due to the lower recovery. The on-set of secondary recrystallization was also shifted to higher temperatures in the case of the continuous heating cycle, which might end in different final grain sizes and final magnetic properties. In both samples, nearly all the observed precipitates are Al-Si-Mn nitrides, ranging from pure AlN to Si4Mn-nitride.

Modeling the Effect of Storage Temperatures on the Growth of Listeria monocytogenes on Ready-to-Eat Ham and Sausage.

PubMed

Luo, Ke; Hong, Sung-Sam; Oh, Deog-Hwan

2015-09-01

The aim of this study was to model the growth kinetics of Listeria monocytogenes on ready-to-eat ham and sausage at different temperatures (4 to 35°C). The observed data fitted well with four primary models (Baranyi, modified Gompertz, logistic, and Huang) with high coefficients of determination (R(2) > 0.98) at all measured temperatures. After the mean square error (0.009 to 0.051), bias factors (0.99 to1.06), and accuracy factors (1.01 to 1.09) were obtained in all models, the square root and the natural logarithm model were employed to describe the relation between temperature and specific growth rate (SGR) and lag time (LT) derived from the primary models. These models were validated against the independent data observed from additional experiments using the acceptable prediction zone method and the proportion of the standard error of prediction. All secondary models based on each of the four primary models were acceptable to describe the growth of the pathogen in the two samples. The validation results indicate that the optimal primary model for estimating the SGR was the Baranyi model, and the optimal primary model for estimating LT was the logistic model in ready-to-eat (RTE) ham. The Baranyi model was also the optimal model to estimate the SGR and LT in RTE sausage. These results could be used to standardize predictive models, which are commonly used to identify critical control points in hazard analysis and critical control point systems or for the quantitative microbial risk assessment to improve the food safety of RTE meat products.

Effects of Nutrient Dynamics, Light and Temperature on the Patchiness of Phytoplankton and Primary Production in the Estuarine and Coastal Zones of Liaodong Bay, China: A Typical Case Study

NASA Astrophysics Data System (ADS)

Pei, S.; Laws, E. A.; Ye, S.

2017-12-01

Fluvial inputs of nutrients and efficient nutrient recycling mechanisms make estuarine and coastal zones highly productive bodies of water. For the same reasons, they are susceptible to eutrophication problems. In China, eutrophication problems along coasts are becoming serious because of discharges of domestic sewage and industrial wastewater and runoff of agricultural fertilizer. Addressing these problems requires an informed assessment of the factors that controlling algal production. Our study aims at determining the factors that controlling patchiness of phytoplankton and primary production in Liaodong Bay, China that receives large inputs of nutrients from human activities in its watershed, and examining the variation patterns of phytoplankton photosynthesis under both stressors of climate change and human activities. Results of our field study suggest that nutrient concentrations were above growth-rate-saturating concentrations throughout Liaodong bay, with the possible exception of phosphate at some stations. This assessment was consistent with the results of nutrient enrichment experiments and the values of light-saturated photosynthetic rates and areal photosynthetic rates. Two large patches of high biomass and production with dimensions on the order of 10 km reflect the effects of water temperature and variation of light penetration restricted by water turbidity. To examine the effects of irradiance and temperature on light-saturated photosynthetic rates normalized to chlorophyll a concentrations (Popt), light-conditioned Popt values were modeled as a function of the temperature with a satisfactory fit to our field data (R2 = 0.60, p = 0.003). In this model, light-conditioned Popt values increased with temperatures from 22°C to roughly 25°C but declined precipitously at higher temperatures. The relatively high Popt values and low ratios of light absorbed to photosynthesis at coastal stations suggest the highly efficient usage of absorbed light by phytoplankton under replete nutrient levels and favorable temperatures. Comparatively, the low Popt values and high ratios of light absorbed to photosynthesis at estuarine stations suggest rather extreme light limitation and lowly efficient usage of absorbed light in photosynthesis in the Liaohe River estuary.

Preliminary results of lab-scale investigations of products of incomplete combustion during incineration of primary and mixed digested sludge.

PubMed

Braguglia, C M; Bagnuolo, G; Gianico, A; Mininni, G; Pastore, C; Mascolo, G

2016-03-01

Separation between primary and secondary sludge treatment could be a valuable solution for sludge management. According to this approach, secondary sludge can be conveniently used in agriculture while primary sludge could be easily dried and incinerated. It follows that some concern may arise from incinerating primary sludge with respect to the current practice to incinerate mixed digested sludge. Incineration of primary and mixed digested municipal sludge was investigated with a lab-scale equipment in terms of emissions of products of incomplete combustion (PICs) during incineration failure modes. PICs can be grouped in three sub-categories, namely aliphatic hydrocarbons (alkanes and alkenes), compounds with a single aromatic ring, and polycyclic aromatic hydrocarbons (PAHs). After-burning temperature was the most important parameter to be controlled in order to minimize emissions of alkanes and alkenes. As for mono-aromatic compounds, benzene and toluene are the most thermally resistant compounds, and in some cases, an after-burning temperature of 1100 °C was not enough to get the complete destruction of benzene leading to a residual emission of 18 mg/kgsludge. PAHs showed an opposite trend with respect to aliphatic and mono-aromatic hydrocarbons being the thermal failure mode the main responsible of PIC emissions. A proper oxygen concentration is more important than elevated temperature thus reflecting the high thermal stability of PAHs. Overall, obtained results, even though obtained under flameless conditions that are different from those of the industrial plants, demonstrated that separation of primary and secondary sludge does not pose any drawbacks or concern regarding primary sludge being disposed of by incineration even though it is more contaminated than mixed digested sludge in terms of organic pollutants.

Peri-equatorial paleolatitudes for Jurassic radiolarian cherts of Greece

USGS Publications Warehouse

Aiello, I.W.; Hagstrum, J.T.; Principi, G.

2008-01-01

Radiolarian-rich sediments dominated pelagic deposition over large portions of the Tethys Ocean during middle to late Jurassic time as shown by extensive bedded chert sequences found in both continental margin and ophiolite units of the Mediterranean region. Which paleoceanographic mechanisms and paleotectonic setting favored radiolarian deposition during the Jurassic, and the nature of a Tethys-wide change from biosiliceous to biocalcareous (mainly nannofossil) deposition at the beginning of Cretaceous time, have remained open questions. Previous paleomagnetic analyses of Jurassic red radiolarian cherts in the Italian Apennines indicate that radiolarian deposition occurred at low peri-equatorial latitudes, similar to modern day deposition of radiolarian-rich sediments within equatorial zones of high biologic productivity. To test this result for other sectors of the Mediterranean region, we undertook paleomagnetic study of Mesozoic (mostly middle to upper Jurassic) red radiolarian cherts within the Aegean region on the Peloponnesus and in continental Greece. Sampled units are from the Sub-Pelagonian Zone on the Argolis Peninsula, the Pindos-Olonos Zone on the Koroni Peninsula, near Karpenissi in central Greece, and the Ionian Zone in the Varathi area of northwestern Greece. Thermal demagnetization of samples from all sections removed low-temperature viscous and moderate-temperature overprint magnetizations that fail the available fold tests. At Argolis and Koroni, however, the cherts carry a third high-temperature magnetization that generally exhibits a polarity stratigraphy and passes the available fold tests. We interpret the high-temperature component to be the primary magnetization acquired during chert deposition and early diagenesis. At Kandhia and Koliaky (Argolis), the primary declinations and previous results indicate clockwise vertical-axis rotations of ??? 40?? relative to "stable" Europe. Due to ambiguities in hemispheric origin (N or S) and thus paleomagnetic polarity, the observed declinations could indicate either clockwise (CW) or counterclockwise (CCW) vertical-axis rotations. Thus at Adriani (Koroni), the primary declinations indicate either CW or CCW rotations of ??? 95?? or ??? 84??, depending on paleomagnetic polarity and age. The primary inclinations for all Peloponnesus sites indicate peri-equatorial paleolatitudes similar to those found for coeval radiolarian cherts exposed in other Mediterranean orogenic belts. Our new paleomagnetic data support the interpretation that Mesozoic radiolarites within the Tethys Ocean were originally deposited along peri-equatorial belts of divergence and high biologic productivity. ?? 2007 Elsevier B.V. All rights reserved.

Heritable Variation for Sex Ratio under Environmental Sex Determination in the Common Snapping Turtle (Chelydra Serpentina)

PubMed Central

Janzen, F. J.

1992-01-01

The magnitude of quantitative genetic variation for primary sex ratio was measured in families extracted from a natural population of the common snapping turtle (Chelydra serpentina), which possesses temperature-dependent sex determination (TSD). Eggs were incubated at three temperatures that produced mixed sex ratios. This experimental design provided estimates of the heritability of sex ratio in multiple environments and a test of the hypothesis that genotype X environment (G X E) interactions may be maintaining genetic variation for sex ratio in this population of C. serpentina. Substantial quantitative genetic variation for primary sex ratio was detected in all experimental treatments. These results in conjunction with the occurrence of TSD in this species provide support for three critical assumptions of Fisher's theory for the microevolution of sex ratio. There were statistically significant effects of family and incubation temperature on sex ratio, but no significant interaction was observed. Estimates of the genetic correlations of sex ratio across environments were highly positive and essentially indistinguishable from +1. These latter two findings suggest that G X E interaction is not the mechanism maintaining genetic variation for sex ratio in this system. Finally, although substantial heritable variation exists for primary sex ratio of C. serpentina under constant temperatures, estimates of the effective heritability of primary sex ratio in nature are approximately an order of magnitude smaller. Small effective heritability and a long generation time in C. serpentina imply that evolution of sex ratios would be slow even in response to strong selection by, among other potential agents, any rapid and/or substantial shifts in local temperatures, including those produced by changes in the global climate. PMID:1592234

Primary Radiometry for the mise-en-pratique: The Laser-Based Radiance Method Applied to a Pyrometer

NASA Astrophysics Data System (ADS)

Briaudeau, S.; Sadli, M.; Bourson, F.; Rougi, B.; Rihan, A.; Zondy, J.-J.

2011-12-01

A new setup has been implemented at LCM-LNE-CNAM for the determination "of the spectral responsivity of radiation thermometers for the determination" of the thermodynamic temperature of high-temperature blackbodies at the temperature of a metal-carbon eutectic phase transition. In this new setup, an innovative acoustic-optic modulator feedback loop is used to stabilize the radiance of a wavelength tunable laser. The effect of residual optical interferences on the calibration of a test pyrometer is analyzed. The full uncertainty budget is presented.

Integrating Omics and Alternative Splicing Reveals Insights into Grape Response to High Temperature1[OPEN

PubMed Central

Jiang, Jianfu; Liu, Xinna; Liu, Guotian; Li, Shaohua

2017-01-01

Heat stress is one of the primary abiotic stresses that limit crop production. Grape (Vitis vinifera) is a cultivated fruit with high economic value throughout the world, with its growth and development often influenced by high temperature. Alternative splicing (AS) is a widespread phenomenon increasing transcriptome and proteome diversity. We conducted high-temperature treatments (35°C, 40°C, and 45°C) on grapevines and assessed transcriptomic (especially AS) and proteomic changes in leaves. We found that nearly 70% of the genes were alternatively spliced under high temperature. Intron retention (IR), exon skipping, and alternative donor/acceptor sites were markedly induced under different high temperatures. Among all differential AS events, IR was the most abundant up- and down-regulated event. Moreover, the occurrence frequency of IR events at 40°C and 45°C was far higher than at 35°C. These results indicated that AS, especially IR, is an important posttranscriptional regulatory event during grape leaf responses to high temperature. Proteomic analysis showed that protein levels of the RNA-binding proteins SR45, SR30, and SR34 and the nuclear ribonucleic protein U1A gradually rose as ambient temperature increased, which revealed a reason why AS events occurred more frequently under high temperature. After integrating transcriptomic and proteomic data, we found that heat shock proteins and some important transcription factors such as MULTIPROTEIN BRIDGING FACTOR1c and HEAT SHOCK TRANSCRIPTION FACTOR A2 were involved mainly in heat tolerance in grape through up-regulating transcriptional (especially modulated by AS) and translational levels. To our knowledge, these results provide the first evidence for grape leaf responses to high temperature at simultaneous transcriptional, posttranscriptional, and translational levels. PMID:28049741

Integrating Omics and Alternative Splicing Reveals Insights into Grape Response to High Temperature.

PubMed

Jiang, Jianfu; Liu, Xinna; Liu, Chonghuai; Liu, Guotian; Li, Shaohua; Wang, Lijun

2017-02-01

Heat stress is one of the primary abiotic stresses that limit crop production. Grape (Vitis vinifera) is a cultivated fruit with high economic value throughout the world, with its growth and development often influenced by high temperature. Alternative splicing (AS) is a widespread phenomenon increasing transcriptome and proteome diversity. We conducted high-temperature treatments (35°C, 40°C, and 45°C) on grapevines and assessed transcriptomic (especially AS) and proteomic changes in leaves. We found that nearly 70% of the genes were alternatively spliced under high temperature. Intron retention (IR), exon skipping, and alternative donor/acceptor sites were markedly induced under different high temperatures. Among all differential AS events, IR was the most abundant up- and down-regulated event. Moreover, the occurrence frequency of IR events at 40°C and 45°C was far higher than at 35°C. These results indicated that AS, especially IR, is an important posttranscriptional regulatory event during grape leaf responses to high temperature. Proteomic analysis showed that protein levels of the RNA-binding proteins SR45, SR30, and SR34 and the nuclear ribonucleic protein U1A gradually rose as ambient temperature increased, which revealed a reason why AS events occurred more frequently under high temperature. After integrating transcriptomic and proteomic data, we found that heat shock proteins and some important transcription factors such as MULTIPROTEIN BRIDGING FACTOR1c and HEAT SHOCK TRANSCRIPTION FACTOR A2 were involved mainly in heat tolerance in grape through up-regulating transcriptional (especially modulated by AS) and translational levels. To our knowledge, these results provide the first evidence for grape leaf responses to high temperature at simultaneous transcriptional, posttranscriptional, and translational levels. © 2017 American Society of Plant Biologists. All Rights Reserved.

Estimated effects of temperature on secondary organic aerosol concentrations.

PubMed

Sheehan, P E; Bowman, F M

2001-06-01

The temperature-dependence of secondary organic aerosol (SOA) concentrations is explored using an absorptive-partitioning model under a variety of simplified atmospheric conditions. Experimentally determined partitioning parameters for high yield aromatics are used. Variation of vapor pressures with temperature is assumed to be the main source of temperature effects. Known semivolatile products are used to define a modeling range of vaporization enthalpy of 10-25 kcal/mol-1. The effect of diurnal temperature variations on model predictions for various assumed vaporization enthalpies, precursor emission rates, and primary organic concentrations is explored. Results show that temperature is likely to have a significant influence on SOA partitioning and resulting SOA concentrations. A 10 degrees C decrease in temperature is estimated to increase SOA yields by 20-150%, depending on the assumed vaporization enthalpy. In model simulations, high daytime temperatures tend to reduce SOA concentrations by 16-24%, while cooler nighttime temperatures lead to a 22-34% increase, compared to constant temperature conditions. Results suggest that currently available constant temperature partitioning coefficients do not adequately represent atmospheric SOA partitioning behavior. Air quality models neglecting the temperature dependence of partitioning are expected to underpredict peak SOA concentrations as well as mistime their occurrence.

A review of the deformation behavior of tungsten at temperatures less than 0.2 of the melting point /K/

NASA Technical Reports Server (NTRS)

Stephens, J. R.

1974-01-01

The deformation behavior of tungsten at temperatures below 0.2 times the absolute melting temperature is reviewed with primary emphasis on the temperature dependence of the yield stress and the ductile-brittle transition. It is concluded that a model based on the high Peierls stress of tungsten best accounts for the observed mechanical behavior at low temperatures. Recent research suggests an important role of electron concentration and bonding on the mechanical behavior of tungsten. Future research on tungsten should include studies to define more clearly the correlation between electron concentration and mechanical behavior of alloys of tungsten and other transition metal alloys.

Progress in the Fabrication and Testing of Telescope Mirrors for The James Webb Space Telescope

NASA Astrophysics Data System (ADS)

Bowers, Charles W.; Clampin, M.; Feinberg, L.; Keski-Kuha, R.; McKay, A.; Chaney, D.; Gallagher, B.; Ha, K.

2012-01-01

The telescope of the James Webb Space Telescope (JWST) is an f/20, three mirror anastigmat design, passively cooled (40K) in an L2 orbit. The design provides diffraction limited performance (Strehl ≥ 0.8) at λ=2μm. To fit within the launch vehicle envelope (Arianne V), the 6.6 meter primary mirror and the secondary mirror support structure are folded for launch, then deployed and aligned in space. The primary mirror is composed of 18 individual, 1.3 meter (flat:flat) hexagonal segments, each adjustable in seven degrees of freedom (six rigid body + radius of curvature) provided by a set of high precision actuators. The actuated secondary mirror ( 0.74m) is similarly positioned in six degrees of rigid body motion. The .70x.51m, fixed tertiary and 0.17m, flat fine steering mirror complete the telescope mirror complement. The telescope is supported by a composite structure optimized for performance at cryogenic temperatures. All telescope mirrors are made of Be with substantial lightweighting (21kg for each 1.3M primary segment). Additional Be mounting and supporting structure for the high precision ( 10nm steps) actuators are attached to the primary segments and secondary mirror. All mirrors undergo a process of thermal stabilization to reduce stress. An extensive series of interferometric measurements guide each step of the polishing process. Final polishing must account for any deformation between the ambient temperature of polishing and the cryogenic, operational temperature. This is accomplished by producing highly precise, cryo deformation target maps of each surface which are incorporated into the final polishing cycle. All flight mirrors have now completed polishing, coating with protected Au and final cryo testing, and the telescope is on track to meet all system requirements. We here review the measured performance of the component mirrors and the predicted performance of the flight telescope.

Phase Equilibria in the System "FeO"-CaO-SiO2-Al2O3-MgO at Different CaO/SiO2 Ratios

NASA Astrophysics Data System (ADS)

Jang, Kyoung-oh; Ma, Xiaodong; Zhu, Jinming; Xu, Haifa; Wang, Geoff; Zhao, Baojun

2017-06-01

The "FeO"-containing slags play an important role in the operation of an ironmaking blast furnace (BF), in particular the primary slags such as the system "FeO"-CaO-SiO2-Al2O3-2 mass pct MgO with CaO/SiO2 weight ratios of 1.3, 1.5, and 1.8 saturated with metallic iron. To investigate the characteristics of such a slag system and its behavior in BF, the phase equilibria and liquidus temperatures in the slag system have been experimentally determined using the high-temperature equilibration and quenching technique followed by an electron probe X-ray microanalysis (EPMA). Isotherms between 1553 K and 1603 K (1280 °C and 1330 °C) were determined in the primary phase fields of dicalcium silicate, melilite, spinel, and monoxide [(Mg,Fe2+)O]. Pseudo-ternary phase diagrams of (CaO + SiO2)-Al2O3-"FeO" with a fixed MgO concentration at 2 mass pct and at CaO/SiO2 ratios of 1.3, 1.5, and 1.8 have been discussed, respectively, simplifying the complexity of the slag system for easy understanding and applying in BF operation. It was found that the liquidus temperatures increase in melilite and spinel primary phase fields, but decrease in dicalcium silicate and monoxide primary phase fields with increasing Al2O3/(CaO + SiO2) ratio. In addition, the liquidus temperatures decrease with increasing "FeO" concentration in dicalcium silicate and melilite primary phase fields, while showing an increasing trend in the spinel and monoxide primary phase fields. The data resulted from this study can be used to improve and optimize currently available database of thermodynamic models used in FactSage.

Growth rate variation and potential paleoceanographic proxies in Primnoa pacifica: Insights from high-resolution trace element microanalysis

NASA Astrophysics Data System (ADS)

Aranha, Renita; Edinger, Evan; Layne, Graham; Piercey, Glenn

2014-01-01

Red tree coral, Primnoa pacifica, is one of the more common habitat-forming deep-sea gorgonian corals in the northeast Pacific Ocean, growing in colonies up to 2 m high and living for decades to hundreds of years. Growth characteristics of P. pacifica were studied in Dixon Entrance, northern British Columbia, and the Olympic Coast National Marine Sanctuary, Washington State, USA, based on samples collected in July 2008. To minimize the impact of scientific sampling on coral populations, only dead coral skeletons and dislodged live corals were collected. Ages and growth rates were measured using band counts, and checked against AMS-14C ages of gorgonin rings. Ba/Ca, Mg/Ca, Na/Ca and Sr/Ca ratios in the calcite cortex were measured using radial Secondary Ion Mass Spectrometer (SIMS) transects with a spot size of <20 μm and separation distance of 25 μm. Growth banding was consistent in width between the central mixed zone consisting of calcite and gorgonin and the dominantly calcite cortex. Average annual radial growth rate of the nine corals analysed ranged from 0.23 to 0.58 mm/yr, with an average growth rate of 0.32 mm/yr in Dixon Entrance and 0.36 m/yr in OCNMS. These growth rates are slightly higher than P. pacifica growth rates from the Gulf of Alaska, and more than four times the growth rates of sister species Primnoa resedaeformis in the northwest Atlantic. Primary productivity is likely a more important driver of geographic variation in Primnoa growth rates than temperature or current strength. Both Dixon Entrance and OCNMS are areas with high primary productivity and strong tidal currents. Lack of post-Atomic Bomb radiocarbon in all but one of the gorgonin samples, and long radiocarbon reservoir ages in the Northeast Pacific, made radiocarbon-based verification of coral ages and growth rates difficult due to wide errors in calibrated age estimates. Mg/Ca and Sr/Ca ratios were inversely correlated in two of the three corals analyzed, and showed evidence of interannual variation. Mg/Ca ratios ranged from 70 to 136 mmol mol-1, and Sr/Ca ratios from 2.041 to 3.14 mmol mol-1. Previously published relationships between gorgonian calcite Mg/Ca and seawater temperature yielded average temperatures matching ambient measurements, but the intra- and inter-annual variation in apparent temperature based on the Mg/Ca ratios was more than double the observed variation in modern seawater temperature ranges in the region. Annual variation in Mg/Ca and Sr/Ca could be related to seasonal changes in precipitation efficiency, which is likely a function of short-term fluctuations in coral growth rate, in turn related to variation in primary productivity. Seasonal and interannual variations in food availability, driven by primary productivity, may affect skeletal growth rate, hence Mg/Ca and Sr/Ca ratios. Primnoid coral skeletal microgeochemistry probably records temporal changes in both temperature and primary productivity.

Prediction of soot and thermal radiation in a model gas turbine combustor burning kerosene fuel spray at different swirl levels

NASA Astrophysics Data System (ADS)

Ghose, Prakash; Patra, Jitendra; Datta, Amitava; Mukhopadhyay, Achintya

2016-05-01

Combustion of kerosene fuel spray has been numerically simulated in a laboratory scale combustor geometry to predict soot and the effects of thermal radiation at different swirl levels of primary air flow. The two-phase motion in the combustor is simulated using an Eulerian-Lagragian formulation considering the stochastic separated flow model. The Favre-averaged governing equations are solved for the gas phase with the turbulent quantities simulated by realisable k-ɛ model. The injection of the fuel is considered through a pressure swirl atomiser and the combustion is simulated by a laminar flamelet model with detailed kinetics of kerosene combustion. Soot formation in the flame is predicted using an empirical model with the model parameters adjusted for kerosene fuel. Contributions of gas phase and soot towards thermal radiation have been considered to predict the incident heat flux on the combustor wall and fuel injector. Swirl in the primary flow significantly influences the flow and flame structures in the combustor. The stronger recirculation at high swirl draws more air into the flame region, reduces the flame length and peak flame temperature and also brings the soot laden zone closer to the inlet plane. As a result, the radiative heat flux on the peripheral wall decreases at high swirl and also shifts closer to the inlet plane. However, increased swirl increases the combustor wall temperature due to radial spreading of the flame. The high incident radiative heat flux and the high surface temperature make the fuel injector a critical item in the combustor. The injector peak temperature increases with the increase in swirl flow mainly because the flame is located closer to the inlet plane. On the other hand, a more uniform temperature distribution in the exhaust gas can be attained at the combustor exit at high swirl condition.

The role of Gulf Coast oysters harvested in warmer months in Vibrio vulnificus infections in the United States, 1988-1996. Vibrio Working Group.

PubMed

Shapiro, R L; Altekruse, S; Hutwagner, L; Bishop, R; Hammond, R; Wilson, S; Ray, B; Thompson, S; Tauxe, R V; Griffin, P M

1998-09-01

Vibrio vulnificus infections are highly lethal and associated with consumption of raw shellfish and exposure of wounds to seawater. V. vulnificus infections were reported to the Centers for Disease Control and Prevention from 23 states. For primary septicemia infections, oyster trace-backs were performed and water temperature data obtained at harvesting sites. Between 1988 and 1996, 422 infections were reported; 45% were wound infections, 43% primary septicemia, 5% gastroenteritis, and 7% from undetermined exposure. Eighty-six percent of patients were male, and 96% with primary septicemia consumed raw oysters. Sixty-one percent with primary septicemia died; underlying liver disease was associated with fatal outcome. All trace-backs with complete information implicated oysters harvested in the Gulf of Mexico; 89% were harvested in water >22 degrees C, the mean annual temperature at the harvesting sites (P < .0001). Control measures should focus on the increased risk from oysters harvested from the Gulf of Mexico during warm months as well as education about host susceptibility factors.

Thermal analysis and cooling structure design of the primary collimator in CSNS/RCS

NASA Astrophysics Data System (ADS)

Zou, Yi-Qing; Wang, Na; Kang, Ling; Qu, Hua-Min; He, Zhe-Xi; Yu, Jie-Bing

2013-05-01

The rapid cycling synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton ring with beam power of 100 kW. In order to control the residual activation to meet the requirements of hands-on maintenance, a two-stage collimation system has been designed for the RCS. The collimation system consists of one primary collimator made of thin metal to scatter the beam and four secondary collimators as absorbers. Thermal analysis is an important aspect in evaluating the reliability of the collimation system. The calculation of the temperature distribution and thermal stress of the primary collimator with different materials is carried out by using ANSYS code. In order to control the temperature rise and thermal stress of the primary collimator to a reasonable level, an air cooling structure is intended to be used. The mechanical design of the cooling structure is presented, and the cooling efficiency with different chin numbers and wind velocity is also analyzed. Finally, the fatigue lifetime of the collimator under thermal shocks is estimated.

Component testing of a ground based gas turbine steam cooled rich-burn primary zone combustor for emissions control of nitrogeneous fuels

NASA Technical Reports Server (NTRS)

Schultz, D. F.

1986-01-01

This effort summarizes the work performed on a steam cooled, rich-burn primary zone, variable geometry combustor designed for combustion of nitrogeneous fuels such as heavy oils or synthetic crude oils. The steam cooling was employed to determine its feasibility and assess its usefulness as part of a ground based gas turbine bottoming cycle. Variable combustor geometry was employed to demonstrate its ability to control primary and secondary zone equivalence ratios and overall pressure drop. Both concepts proved to be highly successful in achieving their desired objectives. The steam cooling reduced peak liner temperatures to less than 800 K. This low temperature offers the potential of both long life and reduced use of strategic materials for liner fabrication. These degrees of variable geometry were successfully employed to control air flow distribution within the combustor. A variable blade angle axial flow air swirler was used to control primary zone air flow, while the secondary and tertiary zone air flows were controlled by rotating bands which regulated air flow to the secondary zone quench holes and the dilutions holes respectively.

Thermal design of composite material high temperature attachments

NASA Technical Reports Server (NTRS)

1972-01-01

An evaluation has been made of the thermal aspects of utilizing advanced filamentary composite materials as primary structures on the shuttle vehicle. The technical objectives of this study are to: (1) establish and design concepts for maintaining material temperatures within allowable limits at TPS attachments and or penetrations applicable to the space shuttle; and (2) verify the thermal design analysis by testing selected concepts. Specific composite materials being evaluated are boron epoxy, graphite/epoxy, boron polyimide, and boron aluminum; graphite/polyimide has been added to this list for property data identification and preliminary evaluation of thermal design problems. The TPS standoff to composite structure attachment over-temperature problem is directly related to TPS maximum surface temperature. To provide a thermally comprehensive evaluation of attachment temperature characteristics, maximum surface temperatures of 900 F, 1200 F, 1800 F, 2500 F and 3000 F are considered in this study. This range of surface temperatures and the high and low maximum temperature capability of the selected composite materials will result in a wide range of thermal requirements for composite/TPS standoff attachments.

Membrane-based systems for carbon capture and hydrogen purification

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

Berchtold, Kathryn A

2010-11-24

This presentation describes the activities being conducted at Los Alamos National Laboratory to develop carbon capture technologies for power systems. This work is aimed at continued development and demonstration of a membrane based pre- and post-combustion carbon capture technology and separation schemes. Our primary work entails the development and demonstration of an innovative membrane technology for pre-combustion capture of carbon dioxide that operates over a broad range of conditions relevant to the power industry while meeting the US DOE's Carbon Sequestration Program goals of 90% CO{sub 2} capture at less than a 10% increase in the cost of energy services.more » Separating and capturing carbon dioxide from mixed gas streams is a first and critical step in carbon sequestration. To be technically and economically viable, a successful separation method must be applicable to industrially relevant gas streams at realistic temperatures and pressures as well as be compatible with large gas volumes. Our project team is developing polymer membranes based on polybenzimidazole (PBI) chemistries that can purify hydrogen and capture CO{sub 2} at industrially relevant temperatures. Our primary objectives are to develop and demonstrate polymer-based membrane chemistries, structures, deployment platforms, and sealing technologies that achieve the critical combination of high selectivity, high permeability, chemical stability, and mechanical stability all at elevated temperatures (> 150 C) and packaged in a scalable, economically viable, high area density system amenable to incorporation into an advanced Integrated Gasification Combined-Cycle (IGCC) plant for pre-combustion CO{sub 2} capture. Stability requirements are focused on tolerance to the primary synthesis gas components and impurities at various locations in the IGCC process. Since the process stream compositions and conditions (temperature and pressure) vary throughout the IGCC process, the project is focused on the optimization of a technology that could be positioned upstream or downstream of one or more of the water-gas-shift reactors (WGSRs) or integrated with a WGSR.« less

Mechanical and Microstructure Study of Nickel-Based ODS Alloys Processed by Mechano-Chemical Bonding and Ball Milling

NASA Astrophysics Data System (ADS)

Amare, Belachew N.

Due to the need to increase the efficiency of modern power plants, land-based gas turbines are designed to operate at high temperature creating harsh environments for structural materials. The elevated turbine inlet temperature directly affects the materials at the hottest sections, which includes combustion chamber, blades, and vanes. Therefore, the hottest sections should satisfy a number of material requirements such as high creep strength, ductility at low temperature, high temperature oxidation and corrosion resistance. Such requirements are nowadays satisfied by implementing superalloys coated by high temperature thermal barrier coating (TBC) systems to protect from high operating temperature required to obtain an increased efficiency. Oxide dispersive strengthened (ODS) alloys are being considered due to their high temperature creep strength, good oxidation and corrosion resistance for high temperature applications in advanced power plants. These alloys operating at high temperature are subjected to different loading systems such as thermal, mechanical, and thermo-mechanical combined loads at operation. Thus, it is critical to study the high temperature mechanical and microstructure properties of such alloys for their structural integrity. The primary objective of this research work is to investigate the mechanical and microstructure properties of nickel-based ODS alloys produced by combined mechano-chemical bonding (MCB) and ball milling subjected to high temperature oxidation, which are expected to be applied for high temperature turbine coating with micro-channel cooling system. Stiffness response and microstructure evaluation of such alloy systems was studied along with their oxidation mechanism and structural integrity through thermal cyclic exposure. Another objective is to analyze the heat transfer of ODS alloy coatings with micro-channel cooling system using finite element analysis (FEA) to determine their feasibility as a stand-alone structural coating. During this project it was found that stiffness response to increase and remain stable to a certain level and reduce at latter stages of thermal cyclic exposure. The predominant growth and adherent Ni-rich outer oxide scale was found on top of the alumina scale throughout the oxidation cycles. The FEA analysis revealed that ODS alloys could be potential high temperature turbine coating materials if micro-channel cooling system is implemented.

Characterization of photosynthetic ferredoxin from the Antarctic alga Chlamydomonas sp. UWO241 reveals novel features of cold adaptation.

PubMed

Cvetkovska, Marina; Szyszka-Mroz, Beth; Possmayer, Marc; Pittock, Paula; Lajoie, Gilles; Smith, David R; Hüner, Norman P A

2018-05-08

The objective of this work was to characterize photosynthetic ferredoxin from the Antarctic green alga Chlamydomonas sp. UWO241, a key enzyme involved in distributing photosynthetic reducing power. We hypothesize that ferredoxin possesses characteristics typical of cold-adapted enzymes, namely increased structural flexibility and high activity at low temperatures, accompanied by low stability at moderate temperatures. To address this objective, we purified ferredoxin from UWO241 and characterized the temperature dependence of its enzymatic activity and protein conformation. The UWO241 ferredoxin protein, RNA, and DNA sequences were compared with homologous sequences from related organisms. We provide evidence for the duplication of the main ferredoxin gene in the UWO241 nuclear genome and the presence of two highly similar proteins. Ferredoxin from UWO241 has both high activity at low temperatures and high stability at moderate temperatures, representing a novel class of cold-adapted enzymes. Our study reveals novel insights into how photosynthesis functions in the cold. The presence of two distinct ferredoxin proteins in UWO241 could provide an adaptive advantage for survival at cold temperatures. The primary amino acid sequence of ferredoxin is highly conserved among photosynthetic species, and we suggest that subtle differences in sequence can lead to significant changes in activity at low temperatures. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Application of process analytical technology for monitoring freeze-drying of an amorphous protein formulation: use of complementary tools for real-time product temperature measurements and endpoint detection.

PubMed

Schneid, Stefan C; Johnson, Robert E; Lewis, Lavinia M; Stärtzel, Peter; Gieseler, Henning

2015-05-01

Process analytical technology (PAT) and quality by design have gained importance in all areas of pharmaceutical development and manufacturing. One important method for monitoring of critical product attributes and process optimization in laboratory scale freeze-drying is manometric temperature measurement (MTM). A drawback of this innovative technology is that problems are encountered when processing high-concentrated amorphous materials, particularly protein formulations. In this study, a model solution of bovine serum albumin and sucrose was lyophilized at both conservative and aggressive primary drying conditions. Different temperature sensors were employed to monitor product temperatures. The residual moisture content at primary drying endpoints as indicated by temperature sensors and batch PAT methods was quantified from extracted sample vials. The data from temperature probes were then used to recalculate critical product parameters, and the results were compared with MTM data. The drying endpoints indicated by the temperature sensors were not suitable for endpoint indication, in contrast to the batch methods endpoints. The accuracy of MTM Pice data was found to be influenced by water reabsorption. Recalculation of Rp and Pice values based on data from temperature sensors and weighed vials was possible. Overall, extensive information about critical product parameters could be obtained using data from complementary PAT tools. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

The primary creep behavior of single crystal, nickel base superalloys PWA 1480 and PWA 1484

NASA Astrophysics Data System (ADS)

Wilson, Brandon Charles

Primary creep occurring at intermediate temperatures (650°C to 850°C) and loads greater than 500 MPa has been shown to result in severe creep strain, often exceeding 5-10%, during the first few hours of creep testing. This investigation examines how the addition of rhenium and changes in aging heat treatment affect the primary creep behavior of PWA 1480 and PWA 1484. To aid in the understanding of rhenium's role in primary creep, 3wt% Re was added to PWA 1480 to create a second generation version of PWA 1480. The age heat treatments used for creep testing were either 704°C/24 hr. or 871°C/32hr. All three alloys exhibited the presence of secondary gamma' confirmed by scanning electron microscopy and local electrode atom probe techniques. These aging heat treatments resulted in the reduction of the primary creep strain produced in PWA 1484 from 24% to 16% at 704°C/862 MPa and produced a slight dependence of the tensile properties of PWA 1480 on aging heat treatment temperature. For all test temperatures, the high temperature age resulted in a significant decrease in primary creep behavior of PWA 1484 and a longer lifetime for all but the lowest test temperature. The primary creep behavior of PWA 1480 and PWA 1480+Re did not display any significant dependence on age heat treatment. The creep rupture life of PWA 1480 is greater than PWA 1484 at 704°C, but significantly shorter at 760°C and 815°C. PWA 1480+Re, however, displayed the longest lifetime of all three alloys at both 704°C and 815°C (PWA 1480+Re was not tested at 760°C). Qualitative TEM analysis revealed that PWA 1484 deformed by large dislocation "ribbons" spanning large regions of material. PWA 1480, however, deformed primarily due to matrix dislocations and the creation of interfacial dislocation networks between the gamma and gamma' phases. PWA 1480+ contained stacking faults as well, though they acted on multiple slip systems generating work hardening and forcing the onset of secondary creep. X-ray diffraction and JMatPro calculations were also used to gain insight into the cause of the differences in behaviors.

Uncertainty analysis as essential step in the establishment of the dynamic Design Space of primary drying during freeze-drying.

PubMed

Mortier, Séverine Thérèse F C; Van Bockstal, Pieter-Jan; Corver, Jos; Nopens, Ingmar; Gernaey, Krist V; De Beer, Thomas

2016-06-01

Large molecules, such as biopharmaceuticals, are considered the key driver of growth for the pharmaceutical industry. Freeze-drying is the preferred way to stabilise these products when needed. However, it is an expensive, inefficient, time- and energy-consuming process. During freeze-drying, there are only two main process variables to be set, i.e. the shelf temperature and the chamber pressure, however preferably in a dynamic way. This manuscript focuses on the essential use of uncertainty analysis for the determination and experimental verification of the dynamic primary drying Design Space for pharmaceutical freeze-drying. Traditionally, the chamber pressure and shelf temperature are kept constant during primary drying, leading to less optimal process conditions. In this paper it is demonstrated how a mechanistic model of the primary drying step gives the opportunity to determine the optimal dynamic values for both process variables during processing, resulting in a dynamic Design Space with a well-known risk of failure. This allows running the primary drying process step as time efficient as possible, hereby guaranteeing that the temperature at the sublimation front does not exceed the collapse temperature. The Design Space is the multidimensional combination and interaction of input variables and process parameters leading to the expected product specifications with a controlled (i.e., high) probability. Therefore, inclusion of parameter uncertainty is an essential part in the definition of the Design Space, although it is often neglected. To quantitatively assess the inherent uncertainty on the parameters of the mechanistic model, an uncertainty analysis was performed to establish the borders of the dynamic Design Space, i.e. a time-varying shelf temperature and chamber pressure, associated with a specific risk of failure. A risk of failure acceptance level of 0.01%, i.e. a 'zero-failure' situation, results in an increased primary drying process time compared to the deterministic dynamic Design Space; however, the risk of failure is under control. Experimental verification revealed that only a risk of failure acceptance level of 0.01% yielded a guaranteed zero-defect quality end-product. The computed process settings with a risk of failure acceptance level of 0.01% resulted in a decrease of more than half of the primary drying time in comparison with a regular, conservative cycle with fixed settings. Copyright © 2016. Published by Elsevier B.V.

Development of an experimental setup for testing the properties of γ/γ' superalloys

NASA Astrophysics Data System (ADS)

Christophe, Siret; Bernard, Viguier; Claude, Salabura Jean; Eric, Andrieu; Sandrine, Lesterlin

2010-07-01

Certification tests on turboshaft engines for helicopters can expose components as high pressure turbine blades to very high temperature during short time periods. To simulate these complex temperature and mechanical stress loadings and to study dimensional and microstructural stability under severe testing conditions, an experimental set-up has been recently developed. In this paper, we first present this new device and describe its performances. Then, the device is used to study the effect of heating procedure on creep results at 1200°C and rafting during primary creep on the single crystal nickel-based superalloy MC2.

Fluorinated Graphene Prepared by Direct Fluorination of N, O-Doped Graphene Aerogel at Different Temperatures for Lithium Primary Batteries.

PubMed

Bi, Xu; Li, Yanyan; Qiu, Zhipeng; Liu, Chao; Zhou, Tong; Zhuo, Shuping; Zhou, Jin

2018-06-25

Fluorinated graphene (FG) has been a star material as a new derivative of graphene. In this paper, a series of fluorinated graphene materials are prepared by using N, O-doped graphene aerogel as precursor via a direct fluorination method, and the effect of fluorination temperature on the FG structure is investigated. The prepared FG samples are systematically characterized by scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. It is found that the structure of FG, including features such as layer size, chemical composition, chemical bond state of the component elements, etc., is significantly related to the fluorination temperature. With the change of the fluorination temperature, fluorine atoms enter the graphene framework by a substitution process of the N, O-containing groups, including residual phenol, ether, carbonyl groups, or C⁻N groups, and the addition to CC bonds, subsequently forming a fluoride with different fluorine contents. The fluorine content increases as the fluorination temperature increases from 200 °C to 300 °C, but decreases at a fluorination temperature of 350 °C due to the decomposition of the fluorinated graphene. The prepared FG samples are used as cathode material for lithium primary batteries. The FG sample prepared at 300 °C gives a high specific capacity of 632 mAh g −1 and a discharge plateau of 2.35 V at a current density of 10 mA g −1 , corresponding to a high energy density of 1485 Wh kg −1 .

Experiments on high speed ejectors

NASA Technical Reports Server (NTRS)

Wu, J. J.

1986-01-01

Experimental studies were conducted to investigate the flow and the performance of thrust augmenting ejectors for flight Mach numbers in the range of 0.5 to 0.8, primary air stagnation pressures up to 107 psig (738 kPa), and primary air stagnation temperatures up to 1250 F (677 C). The experiment verified the existence of the second solution ejector flow, where the flow after complete mixing is supersonic. Thrust augmentation in excess of 1.2 was demonstrated for both hot and cold primary jets. The experimental ejector performed better than the corresponding theoretical optimal first solution ejector, where the mixed flow is subsonic. Further studies are required to realize the full potential of the second solution ejector. The research program was started by the Flight Dynamics Research Corporation (FDRC) to investigate the characteristic of a high speed ejector which augments thrust of a jet at high flight speeds.

Adaptive tuned vibration absorber based on magnetorheological elastomer-shape memory alloy composite

NASA Astrophysics Data System (ADS)

Kumbhar, Samir B.; Chavan, S. P.; Gawade, S. S.

2018-02-01

Shape memory alloy (SMA) is an attractive smart material which could be used as stiffness tuning element in adaptive tuned vibration absorber (ATVA). The sharp modulus change in SMA material during phase transformation creates difficulties for smooth tuning to track forcing frequency to minimize vibrations of primary system. However, high hysteresis damping at low temperature martensitic phase degrades performance of vibration absorber. This paper deals with the study of dynamic response of system in which SMA and magnetorheological elastomer (MRE) are combined together to act as a smart spring- mass-damper system in a tuned vibration absorber. This composite is used as two way stiffness tuning element in ATVA for smooth and continuous tuning and to minimize the adverse effect at low temperature by increasing equivalent stiffness. The stiffnesses of SMA element and MRE are varied respectively by changing temperature and strength of external magnetic field. The two way stiffness tuning ability and adaptivity have been demonstrated analytically and experimentally. The experimental results show good agreement with analytical results. The proposed composite is able to shift the stiffness consequently the natural frequency of primary system as well as reduce the vibration level of primary system by substantial mount.

Combined elevated temperature and soil waterlogging stresses inhibit cell elongation by altering osmolyte composition of the developing cotton (Gossypium hirsutum L.) fiber.

PubMed

Chen, Yinglong; Wang, Haimiao; Hu, Wei; Wang, Shanshan; Wang, Youhua; Snider, John L; Zhou, Zhiguo

2017-03-01

Soil waterlogging events and high temperature conditions occur frequently in the Yangtze River Valley, yet the effects of these co-occurring stresses on fiber elongation have received little attention. In the current study, the combined effect of elevated temperature (ET) and soil waterlogging (SW) more negatively affected final fiber length (reduced by 5.4%-11.3%) than either stress alone by altering the composition of osmotically active solutes (sucrose, malate, and K + ), where SW had the most pronounced effect. High temperature accelerated early fiber development, but limited the duration of elongation, thereby limiting final fiber length. Treatment of ET alone altered fiber sucrose content mainly through decreased source strength and the expression of the sucrose transporter gene GhSUT-1, making sucrose availability the primary determinant of final fiber length under ET. Waterlogging stress alone decreased source strength, down-regulated GhSUT-1 expression and enhanced SuSy catalytic activity for sucrose reduction. Waterlogging treatment alone also limited fiber malate production by down-regulating GhPEPC-1 & -2. However, combined elevated temperature and waterlogging limited primary cell wall synthesis by affecting GhCESAs genes and showed a negative impact on all three major osmotic solutes through the regulation of GhSUT-1, GhPEPC-1 & -2 and GhKT-1 expression and altered SuSy activity, which functioned together to produce a shorter fiber length. Copyright © 2017 Elsevier B.V. All rights reserved.

Biaxial Thermal Creep of Alloy 617 and Alloy 230 for VHTR Applications

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

Mo, Kun; Lv, Wei; Tung, Hsiao-Ming

2016-05-18

In this study, we employed pressurized creep tubes to investigate the biaxial thermal creep behavior of Inconel 617 (alloy 617) and Haynes 230 (alloy 230). Both alloys are considered to he the primary candidate structural materials for very high-temperature reactors (VITITRs) due to their exceptional high-temperature mechanical properties. The current creep experiments were conducted at 900 degrees C for the effective stress range of 15-35 MPa. For both alloys, complete creep strain development with primary, secondary, and tertiary regimes was observed in all the studied conditions. Tertiary creep was found to he dominant over the entire creep lives of bothmore » alloys. With increasing applied creep stress, the fraction of the secondary creep regime decreases. The nucleation, diffusion, and coarsening of creep voids and carbides on grain boundaries were found to be the main reasons for the limited secondary regime and were also found to be the major causes of creep fracture. The creep curves computed using the adjusted creep equation of the form epsilon= cosh 1(1 rt) + P-sigma ntm agree well with the experimental results for both alloys at die temperatures of 850-950 degrees C.« less

Dilution effects on ultrafine particle emissions from Euro 5 and Euro 6 diesel and gasoline vehicles

NASA Astrophysics Data System (ADS)

Louis, Cédric; Liu, Yao; Martinet, Simon; D'Anna, Barbara; Valiente, Alvaro Martinez; Boreave, Antoinette; R'Mili, Badr; Tassel, Patrick; Perret, Pascal; André, Michel

2017-11-01

Dilution and temperature used during sampling of vehicle exhaust can modify particle number concentration and size distribution. Two experiments were performed on a chassis dynamometer to assess exhaust dilution and temperature on particle number and particle size distribution for Euro 5 and Euro 6 vehicles. In the first experiment, the effects of dilution (ratio from 8 to 4 000) and temperature (ranging from 50 °C to 150 °C) on particle quantification were investigated directly from tailpipe for a diesel and a gasoline Euro 5 vehicles. In the second experiment, particle emissions from Euro 6 diesel and gasoline vehicles directly sampled from the tailpipe were compared to the constant volume sampling (CVS) measurements under similar sampling conditions. Low primary dilutions (3-5) induced an increase in particle number concentration by a factor of 2 compared to high primary dilutions (12-20). Low dilution temperatures (50 °C) induced 1.4-3 times higher particle number concentration than high dilution temperatures (150 °C). For the Euro 6 gasoline vehicle with direct injection, constant volume sampling (CVS) particle number concentrations were higher than after the tailpipe by a factor of 6, 80 and 22 for Artemis urban, road and motorway, respectively. For the same vehicle, particle size distribution measured after the tailpipe was centred on 10 nm, and particles were smaller than the ones measured after CVS that was centred between 50 nm and 70 nm. The high particle concentration (≈106 #/cm3) and the growth of diameter, measured in the CVS, highlighted aerosol transformations, such as nucleation, condensation and coagulation occurring in the sampling system and this might have biased the particle measurements.

Phase Transformation and Creep Behavior in Ti50Pd30Ni20 High Temperature Shape Memory Alloy in Compression

NASA Technical Reports Server (NTRS)

Kumar, Parikshith K.; Desai, Uri; Monroe, James; Lagoudas, Dimitris C.; Karaman, Ibrahim; Noebe, Ron; Bigelow, Glenn

2010-01-01

The creep behavior and the phase transformation of Ti50Pd30Ni20 High Temperature Shape Memory Alloy (HTSMA) is investigated by standard creep tests and thermomechanical tests. Ingots of the alloy are induction melted, extruded at high temperature, from which cylindrical specimens are cut and surface polished. A custom high temperature test setup is assembled to conduct the thermomechanical tests. Following preliminary monotonic tests, standard creep tests and thermally induced phase transformation tests are conducted on the specimen. The creep test results suggest that over the operating temperatures and stresses of this alloy, the microstructural mechanisms responsible for creep change. At lower stresses and temperatures, the primary creep mechanism is a mixture of dislocation glide and dislocation creep. As the stress and temperature increase, the mechanism shifts to predominantly dislocation creep. If the operational stress or temperature is raised even further, the mechanism shifts to diffusion creep. The thermally induced phase transformation tests show that actuator performance can be affected by rate independent irrecoverable strain (transformation induced plasticity + retained martensite) as well as creep. The rate of heating and cooling can adversely impact the actuators performance. While the rate independent irrecoverable strain is readily apparent early in the actuators life, viscoplastic strain continues to accumulate over the lifespan of the HTSMA. Thus, in order to get full actuation out of the HTSMA, the heating and cooling rates must be sufficiently high enough to avoid creep.

Lithium Iron Phosphate Cell Performance Evaluations for Lunar Extravehicular Activities

NASA Technical Reports Server (NTRS)

Reid, Concha

2007-01-01

Lithium-ion battery cells are being evaluated for their ability to provide primary power and energy storage for NASA s future Exploration missions. These missions include the Orion Crew Exploration Vehicle, the Ares Crew Launch Vehicle Upper Stage, Extravehicular Activities (EVA, the advanced space suit), the Lunar Surface Ascent Module (LSAM), and the Lunar Precursor and Robotic Program (LPRP), among others. Each of these missions will have different battery requirements. Some missions may require high specific energy and high energy density, while others may require high specific power, wide operating temperature ranges, or a combination of several of these attributes. EVA is one type of mission that presents particular challenges for today s existing power sources. The Portable Life Support System (PLSS) for the advanced Lunar surface suit will be carried on an astronaut s back during eight hour long sorties, requiring a lightweight power source. Lunar sorties are also expected to occur during varying environmental conditions, requiring a power source that can operate over a wide range of temperatures. Concepts for Lunar EVAs include a primary power source for the PLSS that can recharge rapidly. A power source that can charge quickly could enable a lighter weight system that can be recharged while an astronaut is taking a short break. Preliminary results of Al23 Ml 26650 lithium iron phosphate cell performance evaluations for an advanced Lunar surface space suit application are discussed in this paper. These cells exhibit excellent recharge rate capability, however, their specific energy and energy density is lower than typical lithium-ion cell chemistries. The cells were evaluated for their ability to provide primary power in a lightweight battery system while operating at multiple temperatures.

In vitro pulp chamber temperature rise from irradiation and exotherm of flowable composites.

PubMed

Baroudi, Kusai; Silikas, Nick; Watts, David C

2009-01-01

The aim of this study was to investigate the pulpal temperature rise induced during the polymerization of flowable and non-flowable composites using light-emitting diode (LED) and halogen (quartz-tungsten-halogen) light-curing units (LCUs). Five flowable and three non-flowable composites were examined. Pulpal temperature changes were recorded over 10 min in a sample primary tooth by a thermocouple. A conventional quartz-tungsten-halogen source and two LEDs, one of which was programmable, were used for light curing the resin composites. Three repetitions per material were made for each LCU. There was a wide range of temperature rises among the materials (P < 0.05). Temperature rises ranged between 1.3 degrees C for Filtek Supreme irradiated by low-power LED and 4.5 degrees C for Grandio Flow irradiated by high-power LED. The highest temperature rises were observed with both the LED high-power and soft-start LCUs. The time to reach the exothermic peak varied significantly between the materials (P < 0.05). Pulpal temperature rise is related to both the radiant energy output from LCUs and the polymerization exotherm of resin composites. A greater potential risk for heat-induced pulp damage might be associated with high-power LED sources. Flowable composites exhibited higher temperature rises than non-flowable materials, because of higher resin contents.

Organic tracers of primary biological aerosol particles at subtropical Okinawa Island in the western North Pacific Rim

NASA Astrophysics Data System (ADS)

Zhu, Chunmao; Kawamura, Kimitaka; Kunwar, Bhagawati

2015-06-01

Primary biological aerosol particles (PBAPs) play an important role in affecting atmospheric physical and chemical properties. Aerosol samples were collected at Cape Hedo, Okinawa Island, Japan, from October 2009 to February 2012 and analyzed for five primary saccharides and four sugar alcohols as PBAP tracers. We detected high levels of sucrose in spring when blossoming of plants happens and prolifically emits pollen to the air. Concentrations of glucose, fructose, and trehalose showed levels higher than the other saccharides in spring in 2010. In comparison, primary saccharide levels were mutually comparable in spring, summer, and autumn in 2011, indicating the interannual variability of their local production in subtropical forests, which is driven by local temperature and radiation. High trehalose events were found to be associated with Asian dust outflows, indicating that Asian dust also contributes to PBAPs at Okinawa. Sugar alcohols peaked in summer and correlated with local precipitation and temperature, indicating high microbial activities. Positive matrix factorization analysis confirmed that the PBAPs are mainly derived from local vegetation, pollen, and fungal spores. A higher contribution of PBAP tracers to water-soluble organic carbon (WSOC) was found in summer (14.9%). The annual mean ambient loadings of fungal spores and PBAPs were estimated as 0.49 µg m-3 and 4.12 µg m-3, respectively, using the tracer method. We report, for the first time, year-round biomarkers of PBAP and soil dust and their contributions to WSOC in the subtropical outflow region of the Asian continent.

Room-temperature in situ nuclear spin hyperpolarization from optically pumped nitrogen vacancy centres in diamond

DOE PAGES

King, Jonathan P.; Jeong, Keunhong; Vassiliou, Christophoros C.; ...

2015-12-07

Low detection sensitivity stemming from the weak polarization of nuclear spins is a primary limitation of magnetic resonance spectroscopy and imaging. Methods have been developed to enhance nuclear spin polarization but they typically require high magnetic fields, cryogenic temperatures or sample transfer between magnets. Here we report bulk, room-temperature hyperpolarization of 13C nuclear spins observed via high-field magnetic resonance. The technique harnesses the high optically induced spin polarization of diamond nitrogen vacancy centres at room temperature in combination with dynamic nuclear polarization. We observe bulk nuclear spin polarization of 6%, an enhancement of ~170,000 over thermal equilibrium. The signal ofmore » the hyperpolarized spins was detected in situ with a standard nuclear magnetic resonance probe without the need for sample shuttling or precise crystal orientation. In conclusion, hyperpolarization via optical pumping/dynamic nuclear polarization should function at arbitrary magnetic fields enabling orders of magnitude sensitivity enhancement for nuclear magnetic resonance of solids and liquids under ambient conditions.« less

Fractography of the high temperature hydrogen attack of a medium carbon steel

NASA Technical Reports Server (NTRS)

Melson, H. G.; Moorhead, R. D.

1975-01-01

Microscopic fracture processes were studied which are associated with hydrogen attack of a medium carbon steel in a well-controlled, high-temperature, high-purity hydrogen environment. Exposure to a hydrogen pressure and temperature of 3.5 MN/m2 and 575 C was found to degrade room temperature tensile properties with increasing exposure time. After 408 hr, yield and ultimate strengths were reduced by more than 40 percent and elongation was reduced to less than 2 percent. Initial fissure formation was found to be associated with manganese rich particles, most probably manganese oxide, aligned in the microstructure during the rolling operation. Fissure growth was found to be associated with a reduction in carbide content of the microstructure and was inhibited by the depletion of carbon. The interior surfaces of sectioned fissures or bubbles exhibit both primary and secondary cracking by intergranular separation. The grain surfaces were rough and rounded, suggesting a diffusion-associated separation process. Specimens that failed at room temperature after exposure to hydrogen were found to exhibit mixed mode fracture having varying amounts of intergranular separation, dimple formation, and cleavage, depending on exposure time.

The primary solar-type atmosphere surrounding the accreting Earth: H2O-induced high surface temperature.

NASA Astrophysics Data System (ADS)

Sasaki, S.

In the solar nebula, a growing planet attracts ambient gas to form a solar-type atmosphere. The structure of this H2-He atmosphere is calculated assuming the Earth was formed in the nebula. The blanketing effect of the atmosphere renders the planetary surface molten when the planetary mass exceeds 0.2 ME (ME being the present Earth's mass). Reduction of the surface melt by atmospheric H2 should add a large amount of H2O to the atmosphere: under the quartz-iron-fayalite oxygen buffer, partial pressure ratio P(H2O)/P(H2) becomes higher than 0.1. Enhancing opacity and gas mean molecular weight, the excess H2O raises the temperature and renders the atmosphere in convective equilibrium, while the dissociation of H2 suppresses the adiabatic temperature gradient. The surface temperature of the proto-Earth can be as high as 4700K when its mass is 1 ME. Such a high temperature may accelerate the evaporation of surface materials. A deep totally-molten magma ocean should exist in the accretion Earth.

Preconceptual design of a fluoride high temperature salt-cooled engineering demonstration reactor: Motivation and overview

DOE PAGES

Qualls, A. Louis; Betzler, Benjamin R.; Brown, Nicholas R.; ...

2016-12-21

Engineering demonstration reactors are nuclear reactors built to establish proof of concept for technology options that have never been built. Examples of engineering demonstration reactors include Peach Bottom 1 for high temperature gas-cooled reactors (HTGRs) and Experimental Breeder Reactor-II (EBR-II) for sodium-cooled fast reactors. Historically, engineering demonstrations have played a vital role in advancing the technology readiness level of reactor technologies. Our paper details a preconceptual design for a fluoride salt-cooled engineering demonstration reactor. The fluoride salt-cooled high-temperature reactor (FHR) demonstration reactor (DR) is a concept for a salt-cooled reactor with 100 megawatts of thermal output (MWt). It would usemore » tristructural-isotropic (TRISO) particle fuel within prismatic graphite blocks. FLiBe (2 7LiF-BeF2) is the reference primary coolant. The FHR DR is designed to be small, simple, and affordable. Development of the FHR DR is a necessary intermediate step to enable near-term commercial FHRs. The design philosophy of the FHR DR was focused on safety, near-term deployment, and flexibility. Lower risk technologies are purposely included in the initial FHR DR design to ensure that the reactor can be built, licensed, and operated as an engineering demonstration with minimal risk and cost. These technologies include TRISO particle fuel, replaceable core structures, and consistent structural material selection for core structures and the primary and intermediate loops, and tube-and-shell primary-to-intermediate heat exchangers. Important capabilities to be demonstrated by building and operating the FHR DR include fabrication and operation of high temperature reactors; heat exchanger performance (including passive decay heat removal); pump performance; and reactivity control; salt chemistry control to maximize vessel life; tritium management; core design methodologies; salt procurement, handling, maintenance and ultimate disposal. It is recognized that non-nuclear separate and integral test efforts (e.g., heated salt loops or loops using simulant fluids) are necessary to develop the technologies that will be demonstrated in the FHR DR.« less

Preconceptual design of a fluoride high temperature salt-cooled engineering demonstration reactor: Motivation and overview

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

Qualls, A. Louis; Betzler, Benjamin R.; Brown, Nicholas R.

Engineering demonstration reactors are nuclear reactors built to establish proof of concept for technology options that have never been built. Examples of engineering demonstration reactors include Peach Bottom 1 for high temperature gas-cooled reactors (HTGRs) and Experimental Breeder Reactor-II (EBR-II) for sodium-cooled fast reactors. Historically, engineering demonstrations have played a vital role in advancing the technology readiness level of reactor technologies. Our paper details a preconceptual design for a fluoride salt-cooled engineering demonstration reactor. The fluoride salt-cooled high-temperature reactor (FHR) demonstration reactor (DR) is a concept for a salt-cooled reactor with 100 megawatts of thermal output (MWt). It would usemore » tristructural-isotropic (TRISO) particle fuel within prismatic graphite blocks. FLiBe (2 7LiF-BeF2) is the reference primary coolant. The FHR DR is designed to be small, simple, and affordable. Development of the FHR DR is a necessary intermediate step to enable near-term commercial FHRs. The design philosophy of the FHR DR was focused on safety, near-term deployment, and flexibility. Lower risk technologies are purposely included in the initial FHR DR design to ensure that the reactor can be built, licensed, and operated as an engineering demonstration with minimal risk and cost. These technologies include TRISO particle fuel, replaceable core structures, and consistent structural material selection for core structures and the primary and intermediate loops, and tube-and-shell primary-to-intermediate heat exchangers. Important capabilities to be demonstrated by building and operating the FHR DR include fabrication and operation of high temperature reactors; heat exchanger performance (including passive decay heat removal); pump performance; and reactivity control; salt chemistry control to maximize vessel life; tritium management; core design methodologies; salt procurement, handling, maintenance and ultimate disposal. It is recognized that non-nuclear separate and integral test efforts (e.g., heated salt loops or loops using simulant fluids) are necessary to develop the technologies that will be demonstrated in the FHR DR.« less

Comparison of Near-Surface Air Temperatures and MODIS Ice-Surface Temperatures at Summit, Greenland (2008-2013)

NASA Technical Reports Server (NTRS)

Shuman, Christopher A.; Hall, Dorothy K.; DiGirolamo, Nicolo E.; Mefford, Thomas K.; Schnaubelt, Michael J.

2014-01-01

We have investigated the stability of the MODerate resolution Imaging Spectroradiometer (MODIS) infrared-derived ice surface temperature (IST) data from Terra for use as a climate quality data record. The availability of climate quality air temperature data (TA) from a NOAA Global Monitoring Division observatory at Greenlands Summit station has enabled this high temporal resolution study of MODIS ISTs. During a 5 year period (July 2008 to August 2013), more than 2500 IST values were compared with 3-minute average TA values derived from the 1-minute data from NOAAs primary 2 m air temperature sensor. These data enabled an expected small offset between air and surface temperatures at this the ice sheet location to be investigated over multiple annual cycles.

High temperature UF6 RF plasma experiments applicable to uranium plasma core reactors

NASA Technical Reports Server (NTRS)

Roman, W. C.

1979-01-01

An investigation was conducted using a 1.2 MW RF induction heater facility to aid in developing the technology necessary for designing a self critical fissioning uranium plasma core reactor. Pure, high temperature uranium hexafluoride (UF6) was injected into an argon fluid mechanically confined, steady state, RF heated plasma while employing different exhaust systems and diagnostic techniques to simulate and investigate some potential characteristics of uranium plasma core nuclear reactors. The development of techniques and equipment for fluid mechanical confinement of RF heated uranium plasmas with a high density of uranium vapor within the plasma, while simultaneously minimizing deposition of uranium and uranium compounds on the test chamber peripheral wall, endwall surfaces, and primary exhaust ducts, is discussed. The material tests and handling techniques suitable for use with high temperature, high pressure, gaseous UF6 are described and the development of complementary diagnostic instrumentation and measurement techniques to characterize the uranium plasma, effluent exhaust gases, and residue deposited on the test chamber and exhaust system components is reported.

In situ electron backscatter diffraction investigation of recrystallization in a copper wire.

PubMed

Brisset, François; Helbert, Anne-Laure; Baudin, Thierry

2013-08-01

The microstructural evolution of a cold drawn copper wire (reduction area of 38%) during primary recrystallization and grain growth was observed in situ by electron backscatter diffraction. Two thermal treatments were performed, and successive scans were acquired on samples undergoing heating from ambient temperature to a steady state of 200°C or 215°C. During a third in situ annealing, the temperature was continuously increased up to 600°C. Nuclei were observed to grow at the expense of the deformed microstructure. This growth was enhanced by the high stored energy difference between the nuclei and their neighbors (driving energy in recrystallization) and by the presence of high-angle grain boundaries of high mobility. In the early stages of growth, the nuclei twin and the newly created orientations continue to grow to the detriment of the strained copper. At high temperatures, the disappearance of some twins was evidenced by the migration of the incoherent twin boundaries. Thermal grooving of grain boundaries is observed at these high temperatures and affects the high mobile boundaries but tends to preserve the twin boundaries of lower energy. Thus, grooving may contribute to the twin vanishing.

Testing of a Shrouded, Short Mixing Stack Gas Eductor Model Using High Temperature Primary Flow.

DTIC Science & Technology

1982-10-01

problem but of less significance than the heated surfaces of shipboard structure. Various types of electronic equipments and sensors carried by a combatant...here was to validate current procedures by comparison with previous data it was not considered essential to rein- stall these sensors or duplicate...sec) 205 tABLE XIX Mixing Stack Temperatura Data, Model B Thermocouple Axial Mixing Stack Temperature _ mbjr Posii--- .. (I IF) . Uptake 180 850 950

Microstructure Evolution during Friction Stir Welding of Mill-Annealed Ti-6Al-4V (Preprint)

DTIC Science & Technology

2011-05-01

welding . One of the primary concerns regarding FSW of higher temperature materials like titanium is the welding tool. High temperature materials... welds as compared to aluminum alloys. This is related to the low thermal conductivity of titanium alloys which is typically lower than that of the...of the tools and workpieces in aluminum and titanium friction stir welds . Aluminum has a greater conductivity and thermal diffusivity than the tool

Creep Deformation of Allvac 718Plus

DOE PAGES

Hayes, Robert W.; Unocic, Raymond R.; Nasrollahzadeh, Maryam

2014-11-11

The creep deformation behavior of Allvac 718Plus was studied over the temperature range 650° to 732°C at initial applied stress levels ranging from 517 to 655 MPa. Over the entire experimental temperature stress regime this alloy exhibits Class M type creep behavior with all creep curves exhibiting a decelerating strain rate with strain or time throughout primary creep. However, unlike pure metals or simple solid solution alloys this gamma prime strengthened superalloy does not exhibit steady state creep. Rather, primary creep is instantly followed by a long duration of accelerating strain rate with strain or time. These creep characteristics aremore » common amongst the gamma prime strengthened superalloys. Allvac 718Plus also exhibits a very high temperature dependence of creep rate. Detailed TEM examination of the deformation structures of selected creep samples reveals dislocation mechanisms similar to those found in high volume fraction gamma prime strengthened superalloys. Strong evidence of microtwinning is found in several of the deformation structures. The presence of microtwinning may account for the strong temperature dependence of creep rate observed in this alloy. In addition, due to the presence of Nb and thus, grain boundary delta phase, matrix dislocation activity which is not present in non Nb bearing superalloys occurs in this alloy. The creep characteristics and dislocation mechanisms are presented and discussed in detail.« less

Cyclic development of igneous features and their relationship to high-temperature hydrothermal features in the Henderson porphyry molybdenum deposit, Colorado

USGS Publications Warehouse

Carten, R.B.; Geraghty, E.P.; Walker, B.M.

1988-01-01

The Henderson porphyry molybdenum deposit was formed by the superposition of coupled alteration and mineralization events, of varying intensity and size, that were associated with each of at least 11 intrusions. Deposition of molybdenite was accompanied by time-equivalent silicic and potassic alteration. High-temperature alteration and mineralization are spatially and temporally linked to the crystallization of compositionally zoned magma in the apex of stocks. Differences in hydrothermal features associated with each intrusion (e.g., mass of ore, orientation and type of veins, density of veins, and intensity of alteration) correlate with differences in primary igneous features (e.g., composition, texture, morphology, and size). The systematic relations between hydrothermal and magmatic features suggest that primary magma compositions, including volatile contents, largely control the geometry, volume, level of emplacement, and mechanisms of crystallization of stocks. These elements in turn govern the orientations and densities of fractures, which ultimately determine the distribution patterns of hydrothermal alteration and mineralization. -from Authors

Relationships Between Solidification Parameters in A319 Aluminum Alloy

NASA Astrophysics Data System (ADS)

Vandersluis, E.; Ravindran, C.

2018-03-01

The design of high-performance materials depends on a comprehensive understanding of the alloy-specific relationships between solidification and properties. However, the inconsistent use of a particular solidification parameter for presenting materials characterization in the literature impedes inter-study comparability and the interpretation of findings. Therefore, there is a need for accurate expressions relating the solidification parameters for each alloy. In this study, A319 aluminum alloy castings were produced in a permanent mold with various preheating temperatures in order to control metal cooling. Analysis of the cooling curve for each casting enabled the identification of its liquidus, Al-Si eutectic, and solidus temperatures and times. These values led to the calculation of the primary solidification rate, total solidification rate, primary solidification time, and local solidification time for each casting, which were related to each other as well as to the average casting SDAS and material hardness. Expressions for each of their correlations have been presented with high coefficients of determination, which will aid in microstructural prediction and casting design.

Low Cost Nuclear Thermal Rocket Cermet Fuel Element Environment Testing

NASA Technical Reports Server (NTRS)

Bradley, David E.; Mireles, Omar R.; Hickman, Robert R.

2011-01-01

Deep space missions with large payloads require high specific impulse (Isp) and relatively high thrust in order to achieve mission goals in reasonable time frames. Conventional, storable propellants produce average Isp. Nuclear thermal rockets (NTR) capable of high Isp thrust have been proposed. NTR employs heat produced by fission reaction to heat and therefore accelerate hydrogen which is then forced through a rocket nozzle providing thrust. Fuel element temperatures are very high (up to 3000K) and hydrogen is highly reactive with most materials at high temperatures. Data covering the effects of high temperature hydrogen exposure on fuel elements is limited. The primary concern is the mechanical failure of fuel elements which employ high-melting-point metals, ceramics or a combination (cermet) as a structural matrix into which the nuclear fuel is distributed. It is not necessary to include fissile material in test samples intended to explore high temperature hydrogen exposure of the structural support matrices. A small-scale test bed designed to heat fuel element samples via non-contact RF heating and expose samples to hydrogen is being developed to assist in optimal material and manufacturing process selection without employing fissile material. This paper details the test bed design and results of testing conducted to date.

Compact Fuel Element Environment Test

NASA Technical Reports Server (NTRS)

Bradley, D. E.; Mireles, O. R.; Hickman, R. R.; Broadway, J. W.

2012-01-01

Deep space missions with large payloads require high specific impulse (I(sub sp)) and relatively high thrust to achieve mission goals in reasonable time frames. Conventional, storable propellants produce average I(sub sp). Nuclear thermal rockets (NTRs) capable of high I(sub sp) thrust have been proposed. NTR employs heat produced by fission reaction to heat and therefore accelerate hydrogen, which is then forced through a rocket nozzle providing thrust. Fuel element temperatures are very high (up to 3,000 K) and hydrogen is highly reactive with most materials at high temperatures. Data covering the effects of high-temperature hydrogen exposure on fuel elements are limited. The primary concern is the mechanical failure of fuel elements that employ high melting point metals, ceramics, or a combination (cermet) as a structural matrix into which the nuclear fuel is distributed. It is not necessary to include fissile material in test samples intended to explore high-temperature hydrogen exposure of the structural support matrices. A small-scale test bed designed to heat fuel element samples via noncontact radio frequency heating and expose samples to hydrogen for typical mission durations has been developed to assist in optimal material and manufacturing process selection without employing fissile material. This Technical Memorandum details the test bed design and results of testing conducted to date.

Catastrophic shifts in the aquatic primary production revealed by a small low-flow section of tropical downstream after dredging.

PubMed

Marotta, H; Enrich-Prast, A

2015-11-01

Dredging is a catastrophic disturbance that directly affects key biological processes in aquatic ecosystems, especially in those small and shallow. In the tropics, metabolic responses could still be enhanced by the high temperatures and solar incidence. Here, we assessed changes in the aquatic primary production along a small section of low-flow tropical downstream (Imboassica Stream, Brazil) after dredging. Our results suggested that these ecosystems may show catastrophic shifts between net heterotrophy and autotrophy in waters based on three short-term stages following the dredging: (I) a strongly heterotrophic net primary production -NPP- coupled to an intense respiration -R- likely supported by high resuspended organic sediments and nutrients from the bottom; (II) a strongly autotrophic NPP coupled to an intense gross primary production -GPP- favored by the high nutrient levels and low solar light attenuation from suspended solids or aquatic macrophytes; and (III) a NPP near to the equilibrium coupled to low GPP and R rates following, respectively, the shading by aquatic macrophytes and high particulate sedimentation. In conclusion, changes in aquatic primary production could be an important threshold for controlling drastic shifts in the organic matter cycling and the subsequent silting up of small tropical streams after dredging events.

Thermodynamic temperature assignment to the point of inflection of the melting curve of high-temperature fixed points.

PubMed

Woolliams, E R; Anhalt, K; Ballico, M; Bloembergen, P; Bourson, F; Briaudeau, S; Campos, J; Cox, M G; del Campo, D; Dong, W; Dury, M R; Gavrilov, V; Grigoryeva, I; Hernanz, M L; Jahan, F; Khlevnoy, B; Khromchenko, V; Lowe, D H; Lu, X; Machin, G; Mantilla, J M; Martin, M J; McEvoy, H C; Rougié, B; Sadli, M; Salim, S G R; Sasajima, N; Taubert, D R; Todd, A D W; Van den Bossche, R; van der Ham, E; Wang, T; Whittam, A; Wilthan, B; Woods, D J; Woodward, J T; Yamada, Y; Yamaguchi, Y; Yoon, H W; Yuan, Z

2016-03-28

The thermodynamic temperature of the point of inflection of the melting transition of Re-C, Pt-C and Co-C eutectics has been determined to be 2747.84 ± 0.35 K, 2011.43 ± 0.18 K and 1597.39 ± 0.13 K, respectively, and the thermodynamic temperature of the freezing transition of Cu has been determined to be 1357.80 ± 0.08 K, where the ± symbol represents 95% coverage. These results are the best consensus estimates obtained from measurements made using various spectroradiometric primary thermometry techniques by nine different national metrology institutes. The good agreement between the institutes suggests that spectroradiometric thermometry techniques are sufficiently mature (at least in those institutes) to allow the direct realization of thermodynamic temperature above 1234 K (rather than the use of a temperature scale) and that metal-carbon eutectics can be used as high-temperature fixed points for thermodynamic temperature dissemination. The results directly support the developing mise en pratique for the definition of the kelvin to include direct measurement of thermodynamic temperature. © 2016 The Author(s).

BE Ursae Majoris: A detached binary with a unique reprocessing spectrum

NASA Technical Reports Server (NTRS)

Steiner, Joao E.; Ferguson, Donald H.; Liebert, James; Tokarz, Susan; Cutri, Roc; Green, Richard F.; Willner, S. P.

1987-01-01

New infrared photometry, optical and UV spectrophotometry, and a photographic ephemeris are presented for the detached binary BE UMa. Results show the primary to be a DO white dwarf with an effective temperature of 80,000 + or - 15,000 K and a mass of 0.6 + or - 0.1 solar masses. No evidence is found for variability of the primary. The main sequence secondary star is shown to be of early M spectral type, with a formal range of M1 to M5 being possible. A reflection effect in reprocessed line and continuum radiation is produced by EUV radiation from the primary incident on the secondary atmosphere. It is suggested that the temperature of the reprocessed component of the secondary's atmosphere is in the 5000 to 8500 K range, and that emission lines of decreasing ionization form deeper in the irradiated envelope. Relatively narrow He II and high excitation metal lines are formed from recombination and continuum fluorescence processes.

Fluid channeling system

NASA Technical Reports Server (NTRS)

Davis, Donald Y. (Inventor); Hitch, Bradley D. (Inventor)

1994-01-01

A fluid channeling system includes a fluid ejector, a heat exchanger, and a fluid pump disposed in series flow communication The ejector includes a primary inlet for receiving a primary fluid, and a secondary inlet for receiving a secondary fluid which is mixed with the primary fluid and discharged therefrom as ejector discharge. Heat is removed from the ejector discharge in the heat exchanger, and the heat exchanger discharge is compressed in the fluid pump and channeled to the ejector secondary inlet as the secondary fluid In an exemplary embodiment, the temperature of the primary fluid is greater than the maximum operating temperature of a fluid motor powering the fluid pump using a portion of the ejector discharge, with the secondary fluid being mixed with the primary fluid so that the ejector discharge temperature is equal to about the maximum operating temperature of the fluid motor.

Modeling Initial Stage of Ablation Material Pyrolysis: Graphitic Precursor Formation and Interfacial Effects

NASA Technical Reports Server (NTRS)

Desai, Tapan G.; Lawson, John W.; Keblinski, Pawel

2010-01-01

Reactive molecular dynamics simulations are used to study initial stage of pyrolysis of ablation materials and their composites with carbon nanotubes and carbon fibers. The products formed during pyrolysis are characterized and water is found as the primary product in all cases. The water formation mechanisms are analyzed and the value of the activation energy for water formation is estimated. A detailed study on graphitic precursor formation reveals the presence of two temperature zones. In the lower temperature zone (less than 2000 K) polymerization occurs resulting in formation of large, stable graphitic precursors, and in the high temperature zone (greater than 2000 K) polymer scission results in formation of short polymer chains/molecules. Simulations performed in the high temperature zone on the phenolic resin composites (with carbon nanotubes and carbon fibers) shows that the presence of interfaces had no substantial effect on the chain scission rate or the activation energy value for water formation.

Temperature effects on stocks and stability of a phytoplankton-zooplankton model and the dependence on light and nutrients

USGS Publications Warehouse

Norberg, J.; DeAngelis, D.L.

1997-01-01

A model of a closed phytoplankton—zooplankton ecosystem was analyzed for effects of temperature on stocks and stability and the dependence of these effects on light and total nutrient concentration of the system. An analysis of the steady state equations showed that the effect of temperature on zooplankton and POM biomass was levelled when primary production is nutrient limited. Temperature increase had a generally negative effect on all biomasses at high nutrient levels due to increased maintenance costs. Nutrient limitation of net primary production is the main factor governing the effect of stocks and flows as well as the stability of the system. All components of the system, except for phytoplankton biomass, are proportional to net production and thus to the net effect of light on photosynthesis. However, temperature determines the slope of that relationship. The resilience of the system was measured by calculating the eigenvalues of the steady state. Under oligotrophic conditions, the system can be stable, but an increase in temperature can cause instability or a decrease in resilience. This conclusion is discussed in the face of recent models that take spatial heterogeneity into account and display far more stable behavior, in better agreement to empirical data. Using simulations, we found that the amplitude of fluctuations of the herbivore stock increases with temperature while the mean biomass and minimum values decrease in comparison with steady state predictions

A High Pressure Flowing Oil Switch For Gigawatt, Repetitive Applications

DTIC Science & Technology

2005-06-01

for testing the high pressure switch concept under repetitive pulse conditions is a 4.8 Ω, 70 ns water pulse forming line (PFL). The water PFL is...Cox Instruments. A pair of Hedland variable area flow sensors monitored relative flow rates in the two oil lines that fed the high pressure switch . High... pressure switch was tested under both single shot and repetitive conditions over a range of pressures, flow rates and temperatures. The primary

High-Temperature Graphitization Failure of Primary Superheater Tube

NASA Astrophysics Data System (ADS)

Ghosh, D.; Ray, S.; Roy, H.; Mandal, N.; Shukla, A. K.

2015-12-01

Failure of boiler tubes is the main cause of unit outages of the plant, which further affects the reliability, availability and safety of the unit. So failure analysis of boiler tubes is absolutely essential to predict the root cause of the failure and the steps are taken for future remedial action to prevent the failure in near future. This paper investigates the probable cause/causes of failure of the primary superheater tube in a thermal power plant boiler. Visual inspection, dimensional measurement, chemical analysis, metallographic examination and hardness measurement are conducted as the part of the investigative studies. Apart from these tests, mechanical testing and fractographic analysis are also conducted as supplements. Finally, it is concluded that the superheater tube is failed due to graphitization for prolonged exposure of the tube at higher temperature.

Possible role of oceanic heat transport in early Eocene climate

NASA Technical Reports Server (NTRS)

Sloan, L. C.; Walker, J. C.; Moore, T. C. Jr

1995-01-01

Increased oceanic heat transport has often been cited as a means of maintaining warm high-latitude surface temperatures in many intervals of the geologic past, including the early Eocene. Although the excess amount of oceanic heat transport required by warm high latitude sea surface temperatures can be calculated empirically, determining how additional oceanic heat transport would take place has yet to be accomplished. That the mechanisms of enhanced poleward oceanic heat transport remain undefined in paleoclimate reconstructions is an important point that is often overlooked. Using early Eocene climate as an example, we consider various ways to produce enhanced poleward heat transport and latitudinal energy redistribution of the sign and magnitude required by interpreted early Eocene conditions. Our interpolation of early Eocene paleotemperature data indicate that an approximately 30% increase in poleward heat transport would be required to maintain Eocene high-latitude temperatures. This increased heat transport appears difficult to accomplish by any means of ocean circulation if we use present ocean circulation characteristics to evaluate early Eocene rates. Either oceanic processes were very different from those of the present to produce the early Eocene climate conditions or oceanic heat transport was not the primary cause of that climate. We believe that atmospheric processes, with contributions from other factors, such as clouds, were the most likely primary cause of early Eocene climate.

High Temperature Transparent Furnace Development

NASA Technical Reports Server (NTRS)

Bates, Stephen C.

1997-01-01

This report describes the use of novel techniques for heat containment that could be used to build a high temperature transparent furnace. The primary objective of the work was to experimentally demonstrate transparent furnace operation at 1200 C. Secondary objectives were to understand furnace operation and furnace component specification to enable the design and construction of a low power prototype furnace for delivery to NASA in a follow-up project. The basic approach of the research was to couple high temperature component design with simple concept demonstration experiments that modify a commercially available transparent furnace rated at lower temperature. A detailed energy balance of the operating transparent furnace was performed, calculating heat losses through the furnace components as a result of conduction, radiation, and convection. The transparent furnace shells and furnace components were redesigned to permit furnace operation at at least 1200 C. Techniques were developed that are expected to lead to significantly improved heat containment compared with current transparent furnaces. The design of a thermal profile in a multizone high temperature transparent furnace design was also addressed. Experiments were performed to verify the energy balance analysis, to demonstrate some of the major furnace improvement techniques developed, and to demonstrate the overall feasibility of a high temperature transparent furnace. The important objective of the research was achieved: to demonstrate the feasibility of operating a transparent furnace at 1200 C.

Elevated temperature biaxial fatigue

NASA Technical Reports Server (NTRS)

Jordan, E. H.

1984-01-01

A three year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for non-proportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved undertanding were through several critical non-proportional loading experiments. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C.

Multi-Purpose Thermal Hydraulic Loop: Advanced Reactor Technology Integral System Test (ARTIST) Facility for Support of Advanced Reactor Technologies

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

James E. O'Brien; Piyush Sabharwall; SuJong Yoon

2001-11-01

Effective and robust high temperature heat transfer systems are fundamental to the successful deployment of advanced reactors for both power generation and non-electric applications. Plant designs often include an intermediate heat transfer loop (IHTL) with heat exchangers at either end to deliver thermal energy to the application while providing isolation of the primary reactor system. In order to address technical feasibility concerns and challenges a new high-temperature multi-fluid, multi-loop test facility “Advanced Reactor Technology Integral System Test facility” (ARTIST) is under development at the Idaho National Laboratory. The facility will include three flow loops: high-temperature helium, molten salt, and steam/water.more » Details of some of the design aspects and challenges of this facility, which is currently in the conceptual design phase, are discussed« less

Initialization of a mesoscale model for April 10, 1979, using alternative data sources

NASA Technical Reports Server (NTRS)

Kalb, M. W.

1984-01-01

A 35 km grid limited area mesoscale model was initialized with high density SESAME radiosonde data and high density TIROS-N satellite temperature profiles for April 10, 1979. These data sources were used individually and with low level wind fields constructed from surface wind observations. The primary objective was to examine the use of satellite temperature data for initializing a mesoscale model by comparing the forecast results with similar experiments employing radiosonde data. The impact of observed low level winds on the model forecasts was also investigated with experiments varying the method of insertion. All forecasts were compared with each other and with mesoscale observations for precipitation, mass and wind structure. Several forecasts produced convective precipitation systems with characteristics satisfying criteria for a mesoscale convective complex. High density satellite temperature data and balanced winds can be used in a mesoscale model to produce forecasts which verify favorably with observations.

Power plant I - Fused salt

NASA Astrophysics Data System (ADS)

Roche, M.

A solar thermal power plant using fused salt as the heat transfer fluid for steam power generation is analyzed for the feasibility of economic operation. The salt is also stored in a tank reservoir for maintaining the primary heat loop at temperatures high enough for the salts to remain liquid, and also to provide reserve power for the steam generator. Initial studies were with eutectic (hitec) salt comprising Na, KOH, and nitrites melting at 146 C, and further studies were performed employing draw salt, which has no nitrite, is more stable at high temperature, and melts at 225 C. The use of draw salt was found to allow a 5 percent reduction in storage capacity. Further examinations of the effects of the hitec salts on corrosion and composition degradation at high temperatures are indicated. The molten salt system is projected to offer an efficiency of 26 percent.

Advanced setup for high-pressure and low-temperature neutron diffraction at hydrostatic conditions

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

Lokshin, Konstantin A.; Zhao Yusheng

2005-06-15

We describe a design of the experimental setup for neutron diffraction studies at low temperatures and hydrostatic pressure. The significant benefit of the setup, compared to the previous methods, is that it makes possible the simultaneous collection of neutrons diffracted at the 30 deg. -150 deg. range with no contamination by the primary scattering from the sample surroundings and without cutting out the incident and diffracted beams. The suggested design is most useful for third-generation time-of-flight diffractometers and constant wavelength instruments. Application of the setup expands the capabilities of high-pressure neutron diffraction, allowing time-resolved kinetics and structural studies, multihistogram Rietveld,more » and pair distribution function and texture analyses. The high efficiency of the setup was proven for the HIPPO diffractometer at Los Alamos Neutron Science Center under pressures up to 10 kbar and temperatures from 4 to 300 K.« less

Preparation, characterization and dissolution of passive oxide film on the 400 series stainless steel surfaces

NASA Astrophysics Data System (ADS)

Sathyaseelan, V. S.; Rufus, A. L.; Chandramohan, P.; Subramanian, H.; Velmurugan, S.

2015-12-01

Full system decontamination of Primary Heat Transport (PHT) system of Pressurised Heavy Water Reactors (PHWRs) resulted in low decontamination factors (DF) on stainless steel (SS) surfaces. Hence, studies were carried out with 403 SS and 410 SS that are the material of construction of "End-Fitting body" and "End-Fitting Liner tubes". Three formulations were evaluated for the dissolution of passive films formed over these alloys viz., i) Two-step process consisting of oxidation and reduction reactions, ii) Dilute Chemical Decontamination (DCD) and iii) High Temperature Process. The two-step and high temperature processes could dissolve the oxide completely while the DCD process could remove only 60%. Various techniques like XRD, Raman spectroscopy and SEM-EDX were used for assessing the dissolution process. The two-step process is time consuming, laborious while the high temperature process is less time consuming and is recommended for SS decontamination.

Model of climate evolution based on continental drift and polar wandering

NASA Technical Reports Server (NTRS)

Donn, W. L.; Shaw, D. M.

1977-01-01

The thermodynamic meteorologic model of Adem is used to trace the evolution of climate from Triassic to present time by applying it to changing geography as described by continental drift and polar wandering. Results show that the gross changes of climate in the Northern Hemisphere can be fully explained by the strong cooling in high latitudes as continents moved poleward. High-latitude mean temperatures in the Northern Hemisphere dropped below the freezing point 10 to 15 m.y. ago, thereby accounting for the late Cenozoic glacial age. Computed meridional temperature gradients for the Northern Hemisphere steepened from 20 to 40 C over the 200-m.y. period, an effect caused primarily by the high-latitude temperature decrease. The primary result of the work is that the cooling that has occurred since the warm Mesozoic period and has culminated in glaciation is explainable wholly by terrestrial processes.

Ice formation and development in aged, wintertime cumulus over the UK : observations and modelling

NASA Astrophysics Data System (ADS)

Crawford, I.; Bower, K. N.; Choularton, T. W.; Dearden, C.; Crosier, J.; Westbrook, C.; Capes, G.; Coe, H.; Connolly, P.; Dorsey, J. R.; Gallagher, M. W.; Williams, P.; Trembath, J.; Cui, Z.; Blyth, A.

2011-11-01

In-situ high resolution aircraft measurements of cloud microphysical properties were made in coordination with ground based remote sensing observations of Radar and Lidar as part of the Aerosol Properties, PRocesses And InfluenceS on the Earth's climate (APPRAISE) project. A narrow but extensive line (~100 km long) of shallow convective clouds over the southern UK was studied. Cloud top temperatures were observed to be higher than ~-8 °C, but the clouds were seen to consist of supercooled droplets and varying concentrations of ice particles. No ice particles were observed to be falling into the cloud tops from above. Current parameterisations of ice nuclei (IN) numbers predict too few particles will be active as ice nuclei to account for ice particle concentrations at the observed near cloud top temperatures (~-7 °C). The role of biological particles, consistent with concentrations observed near the surface, acting as potential efficient high temperature IN is considered important in this case. It was found that very high concentrations of ice particles (up to 100 L-1) could be produced by powerful secondary ice particle production emphasising the importance of understanding primary ice formation in slightly supercooled clouds. Aircraft penetrations at -3.5 °C, showed peak ice crystal concentrations of up to 100 L-1 which together with the characteristic ice crystal habits observed (generally rimed ice particles and columns) suggested secondary ice production had occurred. To investigate whether the Hallett-Mossop (HM) secondary ice production process could account for these observations, ice splinter production rates were calculated. These calculated rates and observations could only be reconciled provided the constraint that only droplets >24 μm in diameter could lead to splinter production, was relaxed slightly by 2 μm. Model simulations of the case study were also performed with the WRF (Weather, Research and Forecasting) model and ACPIM (Aerosol Cloud and Precipitation Interactions Model) to investigate the likely origins of the ice phase in these slightly supercooled clouds and to assess the role played by the HM process in this and in controlling precipitation formation under these conditions. WRF results showed that while HM does act to increase the mass and number concentration of ice particles produced in the model simulations, in the absence of HM, the ice number concentration arising from primary ice nucleation alone (several L-1) was apparently sufficient to sustain precipitation although the distribution of the precipitation was changed. Thus in the WRF model the HM process was shown to be non-critical for the formation of precipitation in this particular case. However, this result is seen to be subject to an important caveat concerning the simulation of the cloud macrostructure. The model was unable to capture a sharp temperature inversion seen in the radiosonde profiles at 2 km, and consequently the cloud top temperature in the model was able to reach lower values than observed in-situ or obtained from satellite data. ACPIM simulations confirmed the HM process to be a very powerful mechanism for producing the observed high ice concentrations, provided that primary nucleation occured to initiate the ice formation, and large droplets were present which then fell collecting the primary ice particles to form instant rimer particles. However, the time to generate the observed peak ice concentrations was found to be dependant on the number of primary IN present (decreasing with increasing IN number). This became realistic (around 20 min) only when the temperature input to the existing IN parameterisation was 6 °C lower than observed at cloud top, highlighting the requirement to improve basic knowledge of the number and type of IN active at these high temperatures. In simulations where cloud droplet numbers were realistic the precipitation rate was found to be unaffected by HM, with warm rain processes dominating precipitation development in this instance.

Phytoplankton Productivity numerical model: calibration via laboratory cultures

NASA Astrophysics Data System (ADS)

Zavatarelli, Marco; fiori, Emanuela; Carolina, Amadio

2017-04-01

The primary production module of the "Biogeochemical Flux Model" (BFM) has been used to replicate results from laboratory phytoplankton cultures of diatoms, dinoflagellates and picophytoplankton. The model explicitly solve for the phytoplankton, chlorophyll, carbon, phosphorus, nitrogen and (diatoms only) silicon content. Simulations of the temporal evolution of the cultured phytoplankton biomass, have been carried out in order to provide a correct parameterization of the temperature role in modulating the growth dynamics, and to gain insight in the process of chlorophyll turnover, with particular reference to the phytoplankton biomass decay in condition of nutrient stress. Results highligthed some limitation of the Q10 approach in defining the temperature constraints on the primary production (particularly at relatively high temperature) This required a modification of such approach. Moreover, the decay of the chlorophyll concentration under nutrient stress, appeared (as expected) significantly decoupled from the evolution of the carbon content. The implementation of a specific procedure (based on the laboratory culture results) adressing such decoupling, allowed for the achievement of better agreement between model and observations.

Composite Thermal Switch

NASA Technical Reports Server (NTRS)

McDonald, Robert; Brawn, Shelly; Harrison, Katherine; O'Toole, Shannon; Moeller, Michael

2011-01-01

Lithium primary and lithium ion secondary batteries provide high specific energy and energy density. The use of these batteries also helps to reduce launch weight. Both primary and secondary cells can be packaged as high-rate cells, which can present a threat to crew and equipment in the event of external or internal short circuits. Overheating of the cell interior from high current flows induced by short circuits can result in exothermic reactions in lithium primary cells and fully charged lithium ion secondary cells. Venting of the cell case, ejection of cell components, and fire have been reported in both types of cells, resulting from abuse, cell imperfections, or faulty electronic control design. A switch has been developed that consists of a thin layer of composite material made from nanoscale particles of nickel and Teflon that conducts electrons at room temperature and switches to an insulator at an elevated temperature, thus interrupting current flow to prevent thermal runaway caused by internal short circuits. The material is placed within the cell, as a thin layer incorporated within the anode and/or the cathode, to control excess currents from metal-to-metal or metal-to-carbon shorts that might result from cell crush or a manufacturing defect. The safety of high-rate cells is thus improved, preventing serious injury to personnel and sensitive equipment located near the battery. The use of recently available nanoscale particles of nickel and Teflon permits an improved, homogeneous material with the potential to be fine-tuned to a unique switch temperature, sufficiently below the onset of a catastrophic chemical reaction. The smaller particles also permit the formation of a thinner control film layer (<50 m), which can be incorporated into commercial high-rate lithium primary and secondary cells. The innovation permits incorporation in current lithium and lithium-ion cell designs with a minimal impact on cell weight and volume. The composite thermal switch (CTS(TradeMark)) coating can be incorporated in either the anode or cathode or both. The coating can be applied in a variety of different processes that permits incorporation in the cell and electrode manufacturing processes. The CTS responds quickly and halts current flow in the hottest parts of the cell first. The coating can be applied to metal foil and supplied as a cell component onto which the active electrode materials are coated.

Gearbox Instrumentation for the Investigation of Bearing Axial Cracking

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

Keller, Jonathan A; Lambert, Scott R

Failures in gearbox bearings have been the primary source of reliability issues for wind turbine drivetrains, leading to costly downtime and unplanned maintenance. The most common failure mode is attributed to so-called axial cracks or white-etching cracks, which primarily affect the intermediate and high-speed-stage bearings. The high-speed-shaft and bearing loads and sliding will be measured with a specially instrumented gearbox installed in a 1.5-megawatt turbine at the National Wind Technology Center in an upcoming test campaign. Additional instrumentation will also measure the tribological environment of these bearings, including bearing temperatures, lubricant temperature and water content, air temperature and humidity, andmore » stray electrical current across the bearings. This paper fully describes the instrumentation package and summarizes initial results.« less

Use of manometric temperature measurement (MTM) and SMART freeze dryer technology for development of an optimized freeze-drying cycle.

PubMed

Gieseler, Henning; Kramer, Tony; Pikal, Michael J

2007-12-01

This report provides, for the first time, a summary of experiments using SMART Freeze Dryer technology during a 9 month testing period. A minimum ice sublimation area of about 300 cm(2) for the laboratory freeze dryer, with a chamber volume 107.5 L, was found consistent with data obtained during previous experiments with a smaller freeze dryer (52 L). Good reproducibility was found for cycle design with different type of excipients, formulations, and vials used. SMART primary drying end point estimates were accurate in the majority of the experiments, but showed an over prediction of primary cycle time when the product did not fully achieve steady state conditions before the first MTM measurement was performed. Product resistance data for 5% sucrose mixtures at varying fill depths were very reproducible. Product temperature determined by SMART was typically in good agreement with thermocouple data through about 50% of primary drying time, with significant deviations occurring near the end of primary drying, as expected, but showing a bias much earlier in primary drying for high solid content formulations (16.6% Pfizer product) and polyvinylpyrrolidone (40 kDa) likely due to water "re-adsorption" by the amorphous product during the MTM test. (c) 2007 Wiley-Liss, Inc.

Effect of calcination temperature on the electrochemical properties of nickel-rich LiNi 0.76Mn 0.14Co 0.10O 2 cathodes for lithium-ion batteries

DOE PAGES

Zheng, Jianming; Yan, Pengfei; Estevez, Luis; ...

2018-05-01

High energy density, nickel (Ni)-rich, layered LiNi xMn yCo zO 2 (NMC, x ≥ 0.6) materials are promising cathodes for lithium-ion batteries. However, several technical challenges, such as fast capacity fading and high voltage instability, hinder their large-scale application. Herein, we identified an optimum calcining temperature range for the Ni-rich cathode LiNi 0.76Mn 0.14Co 0.10O 2 (NMC76). NMC76 calcined at 750–775 °C exhibits a high discharge capacity (~215 mAh g –1 when charged to 4.5 V) and retains ca. 79% of its initial capacity after 200 cycles. It also exhibits an excellent high-rate capability, delivering a capacity of more thanmore » 160 mAh g –1 even at a 10 C rate. The high performance of NMC76 is directly related to the optimized size of its primary particles (100–300 nm) (which onstitute the spherical secondary particles of >10 µm) and cation mixing. Higher calcination temperature (≥800 °C) leads to rapid increase of primary particle size, poor cycling stability, and inferior rate capability of NMC76 due to severe micro-strain and -crack formation upon repeated lithium-ion de/intercalations. Furthermore, NMC76 calcined at 750–775 °C is a very good candidate for the next generation of Li ion batteries.« less

Effect of calcination temperature on the electrochemical properties of nickel-rich LiNi 0.76Mn 0.14Co 0.10O 2 cathodes for lithium-ion batteries

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

Zheng, Jianming; Yan, Pengfei; Estevez, Luis

High energy density, nickel (Ni)-rich, layered LiNi xMn yCo zO 2 (NMC, x ≥ 0.6) materials are promising cathodes for lithium-ion batteries. However, several technical challenges, such as fast capacity fading and high voltage instability, hinder their large-scale application. Herein, we identified an optimum calcining temperature range for the Ni-rich cathode LiNi 0.76Mn 0.14Co 0.10O 2 (NMC76). NMC76 calcined at 750–775 °C exhibits a high discharge capacity (~215 mAh g –1 when charged to 4.5 V) and retains ca. 79% of its initial capacity after 200 cycles. It also exhibits an excellent high-rate capability, delivering a capacity of more thanmore » 160 mAh g –1 even at a 10 C rate. The high performance of NMC76 is directly related to the optimized size of its primary particles (100–300 nm) (which onstitute the spherical secondary particles of >10 µm) and cation mixing. Higher calcination temperature (≥800 °C) leads to rapid increase of primary particle size, poor cycling stability, and inferior rate capability of NMC76 due to severe micro-strain and -crack formation upon repeated lithium-ion de/intercalations. Furthermore, NMC76 calcined at 750–775 °C is a very good candidate for the next generation of Li ion batteries.« less

Study on chemical hydrography, chlorophyll-a and primary productivity in Liaodong Bay, China

NASA Astrophysics Data System (ADS)

Pei, Shaofeng; Laws, Edward A.; Zhang, Haibo; Ye, Siyuan; Kemper, Marc T.; Yuan, Hongming; Xu, Gang; Yang, Shixiong; Liu, Haiyue; Zhu, Yaxuan

2018-03-01

A field study was carried out during the summer of 2013 in Liaodong Bay, China to determine the dynamics of the phytoplankton in the bay and the extent to which primary production in the bay was constrained by environmental factors. There was little or no evidence of limitation of phytoplankton production by nutrient concentrations at any of the sampling stations, with the possible exception of a few offshore stations where phosphate concentrations were less than 30 nM. This assessment was consistent with the results of nutrient enrichment experiments and the values of light-saturated photosynthetic rates and areal photosynthetic rates. To examine the effects of irradiance and temperature on light-saturated photosynthetic rates normalized to chlorophyll a concentrations (Poptb) at twelve stations where photosynthetic rates were measured by 14C method, light-conditioned values were modeled as a function of the temperature with a satisfactory fit to our field data (R2 = 0.60, p = 0.003). According to this model, the light-conditioned Poptb values increased with temperatures from 22 °C to roughly 25 °C but declined precipitously at higher temperatures, and Poptb values and corresponding areal photosynthetic rates at all 66 stations were estimated to be 7.6 ± 2.4 g C g-1 Chl a h-1 and 532 ± 429 gC m-2 d-1 in average, respectively. The quanta absorbed per carbon atom fixed averaged 14 ± 2 and 37 ± 10 at six coastal stations and six estuarine stations, respectively. The relatively high Poptb values and low quantum requirements at the coastal stations implied the highly efficient usage of absorbed light by phytoplankton under nutrient-replete conditions and favorable temperatures. Comparatively, the low Poptb values and high quantum requirements at the estuarine stations suggested rather extreme light limitation and lowly efficient usage of absorbed light in photosynthesis in the Liaohe River estuary. Areal production in Liaodong Bay appears to be controlled by a combination of temperature and light limitation.

Paraheliotropic leaf movement in Siratro as a protective mechanism against drought-induced damage to primary photosynthetic reactions: damage by excessive light and heat.

PubMed

Ludlow, M M; Björkman, O

1984-11-01

Damage to primary photosynthetic reactions by drought, excess light and heat in leaves of Macroptilium atropurpureum Dc. cv. Siratro was assessed by measurements of chlorophyll fluorescence emission kinetics at 77 K (-196°C). Paraheliotropic leaf movement protected waterstressed Siratro leaves from damage by excess light (photoinhibition), by heat, and by the interactive effects of excess light and high leaf temperatures. When the leaves were restrained to a horizontal position, photoinhibition occurred and the degree of photoinhibitory damage increased with the time of exposure to high levels of solar radiation. Severe inhibition was followed by leaf death, but leaves gradually recovered from moderate damage. This drought-induced photoinhibitory damage seemed more closely related to low leaf water potential than to low leaf conductance. Exposure to leaf temperatures above 42°C caused damage to the photosynthetic system even in the dark and leaves died at 48°C. Between 42 and 48°C the degree of heat damage increased with the time of exposure, but recovery from moderate heat damage occurred over several days. The threshold temperature for direct heat damage increased with the growth temperature regime, but was unaffected by water-stress history or by current leaf water status. No direct heat damage occurred below 42°C, but in water-stressed plants photoinhibition increased with increasing leaf temperature in the range 31-42°C and with increasing photon flux density up to full sunglight values. Thus, water stress evidently predisposes the photosynthetic system to photoinhibition and high leaf temperature exacerbates this photoinhibitory damage. It seems probable that, under the climatic conditions where Siratro occurs in nature, but in the absence of paraheliotropic leaf movement, photoinhibitory damage would occur more frequently during drought than would direct heat damage.

High-temperature annealing of proton irradiated beryllium – A dilatometry-based study

DOE PAGES

Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; ...

2016-04-07

S—200 F grade beryllium has been irradiated with 160 MeV protons up to 1.2 10 20 cm –2 peak fluence and irradiation temperatures in the range of 100–200 °C. To address the effect of proton irradiation on dimensional stability, an important parameter in its consideration in fusion reactor applications, and to simulate high temperature irradiation conditions, multi-stage annealing using high precision dilatometry to temperatures up to 740 °C were conducted in air. X-ray diffraction studies were also performed to compliment the macroscopic thermal study and offer a microscopic view of the irradiation effects on the crystal lattice. The primary objectivemore » was to qualify the competing dimensional change processes occurring at elevated temperatures namely manufacturing defect annealing, lattice parameter recovery, transmutation 4He and 3H diffusion and swelling and oxidation kinetics. Further, quantification of the effect of irradiation dose and annealing temperature and duration on dimensional changes is sought. Here, the study revealed the presence of manufacturing porosity in the beryllium grade, the oxidation acceleration effect of irradiation including the discontinuous character of oxidation advancement, the effect of annealing duration on the recovery of lattice parameters recovery and the triggering temperature for transmutation gas diffusion leading to swelling.« less

Temperature sensing by primary roots of maize

NASA Technical Reports Server (NTRS)

Poff, K. L.

1990-01-01

Zea mays L. seedlings, grown on agar plates at 26 degrees C, reoriented the original vertical direction of their primary root when exposed to a thermal gradient applied perpendicular to the gravity vector. The magnitude and direction of curvature can not be explained simply by either a temperature or a humidity effect on root elongation. It is concluded that primary roots of maize sense temperature gradients in addition to sensing the gravitational force.

Microstructural investigation of D2 tool steel during rapid solidification

NASA Astrophysics Data System (ADS)

Delshad Khatibi, Pooya

Solidification is considered as a key processing step in developing the microstructure of most metallic materials. It is, therefore, important that the solidification process can be designed and controlled in such a way so as to obtain the desirable properties in the final product. Rapid solidification refers to the system's high undercooling and high cooling rate, which can yield a microstructure with unique chemical composition and mechanical properties. An area of interest in rapid solidification application is high-chromium, high-carbon tool steels which experience considerable segregation of alloying elements during their solidification in a casting process. In this dissertation, the effect of rapid solidification (undercooling and cooling rate) of D2 tool steel on the microstructure and carbide precipitation during annealing was explored. A methodology is described to estimate the eutectic and primary phase undercooling of solidifying droplets. The estimate of primary phase undercooling was confirmed using an online measurement device that measured the radiation energy of the droplets. The results showed that with increasing primary phase and eutectic undercooling and higher cooling rate, the amount of supersaturation of alloying element in metastable retained austenite phase also increases. In the case of powders, the optimum hardness after heat treatment is achieved at different temperatures for constant periods of time. Higher supersaturation of austenite results in obtaining secondary hardness at higher annealing temperature. D2 steel ingots generated using spray deposition have high eutectic undercooling and, as a result, high supersaturation of alloying elements. This can yield near net shape D2 tool steel components with good mechanical properties (specifically hardness). The data developed in this work would assist in better understanding and development of near net shape D2 steel spray deposit products with good mechanical properties.

Shell tile thermal protection system

NASA Technical Reports Server (NTRS)

Macconochie, I. O.; Lawson, A. G.; Kelly, H. N. (Inventor)

1984-01-01

A reusable, externally applied thermal protection system for use on aerospace vehicles subject to high thermal and mechanical stresses utilizes a shell tile structure which effectively separates its primary functions as an insulator and load absorber. The tile consists of structurally strong upper and lower metallic shells manufactured from materials meeting the thermal and structural requirements incident to tile placement on the spacecraft. A lightweight, high temperature package of insulation is utilized in the upper shell while a lightweight, low temperature insulation is utilized in the lower shell. Assembly of the tile which is facilitated by a self-locking mechanism, may occur subsequent to installation of the lower shell on the spacecraft structural skin.

High temperature insulation barrier composite

NASA Technical Reports Server (NTRS)

Onstott, Joseph W. (Inventor)

1989-01-01

A composite material suitable for providing insulation for the nozzle structure of the Space Shuttle and other similar surfaces is disclosed. The composite layer is comprised of an outer skin layer of nickel chromium and an interleaved inner region comprising a top layer of nickel chromium foil which acts as a primary convective shield. There are at least two layers of alumina batting adjacent to the layers of silicon carbide fabric. An additional layer of nickel chromium foil is used as a secondary convective shield. The composite is particularly advantageous for use as nozzle insulation because of its ability to withstand high reentry temperatures, its flexibility, oxidation resistance, low conductivity, and light weight.

Ecosystem responses to recent oceanographic variability in high-latitude Northern Hemisphere ecosystems

NASA Astrophysics Data System (ADS)

Mueter, Franz J.; Broms, Cecilie; Drinkwater, Kenneth F.; Friedland, Kevin D.; Hare, Jonathan A.; Hunt, George L., Jr.; Melle, Webjørn; Taylor, Maureen

2009-04-01

As part of the international MENU collaboration, we compared and contrasted ecosystem responses to climate-forced oceanographic variability across several high latitude regions of the North Pacific (Eastern Bering Sea (EBS) and Gulf of Alaska (GOA)) and North Atlantic Oceans (Gulf of Maine/Georges Bank (GOM/GB) and the Norwegian/Barents Seas (NOR/BAR)). Differences in the nitrate content of deep source waters and incoming solar radiation largely explain differences in average primary productivity among these ecosystems. We compared trends in productivity and abundance at various trophic levels and their relationships with sea-surface temperature. Annual net primary production generally increases with annual mean sea-surface temperature between systems and within the EBS, BAR, and GOM/GB. Zooplankton biomass appears to be controlled by both top-down (predation by fish) and bottom-up forcing (advection, SST) in the BAR and NOR regions. In contrast, zooplankton in the GOM/GB region showed no evidence of top-down forcing but appeared to control production of major fish populations through bottom-up processes that are independent of temperature variability. Recruitment of several fish stocks is significantly and positively correlated with temperature in the EBS and BAR, but cod and pollock recruitment in the EBS has been negatively correlated with temperature since the 1977 shift to generally warmer conditions. In each of the ecosystems, fish species showed a general poleward movement in response to warming. In addition, the distribution of groundfish in the EBS has shown a more complex, non-linear response to warming resulting from internal community dynamics. Responses to recent warming differ across systems and appear to be more direct and more pronounced in the higher latitude systems where food webs and trophic interactions are simpler and where both zooplankton and fish species are often limited by cold temperatures.

Characterisation of diode-connected SiGe BiCMOS HBTs for space applications

NASA Astrophysics Data System (ADS)

Venter, Johan; Sinha, Saurabh; Lambrechts, Wynand

2016-02-01

Silicon-germanium (SiGe) bipolar complementary metal-oxide semiconductor (BiCMOS) transistors have vertical doping profiles reaching deeper into the substrate when compared to lateral CMOS transistors. Apart from benefiting from high-speed, high current gain and low-output resistance due to its vertical profile, BiCMOS technology is increasingly becoming a preferred technology for researchers to realise next-generation space-based optoelectronic applications. BiCMOS transistors have inherent radiation hardening, to an extent predictable cryogenic performance and monolithic integration potential. SiGe BiCMOS transistors and p-n junction diodes have been researched and used as a primary active component for over the last two decades. However, further research can be conducted with diode-connected heterojunction bipolar transistors (HBTs) operating at cryogenic temperatures. This work investigates these characteristics and models devices by adapting standard fabrication technology components. This work focuses on measurements of the current-voltage relationship (I-V curves) and capacitance-voltage relationships (C-V curves) of diode-connected HBTs. One configuration is proposed and measured, which is emitterbase shorted. The I-V curves are measured for various temperature points ranging from room temperature (300 K) to the temperature of liquid nitrogen (77 K). The measured datasets are used to extract a model of the formed diode operating at cryogenic temperatures and used as a standard library component in computer aided software designs. The advantage of having broad-range temperature models of SiGe transistors becomes apparent when considering implementation of application-specific integrated circuits and silicon-based infrared radiation photodetectors on a single wafer, thus shortening interconnects and lowering parasitic interference, decreasing the overall die size and improving on overall cost-effectiveness. Primary applications include space-based geothermal radiation sensing and cryogenic terahertz radiation sensing.

High Temperature Oxidation-Resistant Thruster Research

DTIC Science & Technology

1990-02-01

substrates: Refractory metals, ! Ceramics, Composites and I Carbon - carbon . Rhenium and hafnium carbide were selected based on their properties I and... carbon . Rhenium was selected as the primary refractory metal candidate because of its high melting point, no ductile-to- brittle transition in the...of rhenium (Re) with those of other refractory metals. Rhenium has the second highest melting point of the elements, 3013 C, second only to tungsten

Conduction-coupled Tesla transformer.

PubMed

Reed, J L

2015-03-01

A proof-of-principle Tesla transformer circuit is introduced. The new transformer exhibits the high voltage-high power output signal of shock-excited transformers. The circuit, with specification of proper circuit element values, is capable of obtaining extreme oscillatory voltages. The primary and secondary portions of the circuit communicate solely by conduction. The destructive arcing between the primary and secondary inductors in electromagnetically coupled transformers is ubiquitous. Flashover is eliminated in the new transformer as the high-voltage inductors do not interpenetrate and so do not possess an annular volume of electric field. The inductors are remote from one another. The high voltage secondary inductor is isolated in space, except for a base feed conductor, and obtains earth by its self-capacitance to the surroundings. Governing equations, for the ideal case of no damping, are developed from first principles. Experimental, theoretical, and circuit simulator data are presented for the new transformer. Commercial high-temperature superconductors are discussed as a means to eliminate the counter-intuitive damping due to small primary inductances in both the electromagnetic-coupled and new conduction-coupled transformers.

A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

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

Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han

The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This paper aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide amore » comparative assessment of their high-temperature structural performance. The K JQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Finally, irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.« less

A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

DOE PAGES

Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; ...

2016-12-07

The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This paper aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide amore » comparative assessment of their high-temperature structural performance. The K JQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Finally, irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.« less

A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

NASA Astrophysics Data System (ADS)

Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; Maloy, Stuart A.

2017-02-01

The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This study aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide a comparative assessment of their high-temperature structural performance. The KJQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.

Spatial contrast in phytoplankton, bacteria and microzooplankton grazing between the eutrophic Yellow Sea and the oligotrophic South China Sea

NASA Astrophysics Data System (ADS)

Zhang, Yafeng; Wang, Xutao; Yin, Kedong

2018-01-01

Three cruises were conducted to investigate the distributions of nutrients, chlorophyll a (Chl- a), new and regenerated primary production, bacterial abundance and production, and microzooplankton grazing rates in the Yellow Sea (YS) and the South China Sea (SCS) during March and May. As the water column moved from low to high temperature, weak to strong stratification and high to low nutrients from the YS to the SCS, Chl- a, primary production and bacterial biomass decreased. In contrast, bacterial production, microzooplankton grazing and size preference increased from the YS to the SCS. The increasing grazing activity and decreasing f-ratio from the YS to the SCS suggest roles of regenerated nutrients in the supporting the community increased and more bacteria played important roles in the carbon flow in the oligotrophic SCS than in the eutrophic YS. These variabilities force the classical food chain dominated community in the eutrophic waters into the microbial loop, which is dominant in oligotrophic waters. As nutrients decrease, temperature and grazing activity increase from the YS to the SCS. The increasing ratio of integrated bacterial production to integrated primary production indicates that communities change from autotrophy to heterotrophy and waters change from a carbon sink to a carbon source.

Development of Oxidation Protection Coatings for Gamma Titanium Aluminide Alloys

NASA Technical Reports Server (NTRS)

Wallace, T. A.; Bird, R. K.; Sankaran, S. N.

2003-01-01

Metallic material systems play a key role in meeting the stringent weight and durability requirements for reusable launch vehicle (RLV) airframe hot structures. Gamma titanium aluminides (gamma-TiAl) have been identified as high-payoff materials for high-temperature applications. The low density and good elevated temperature mechanical properties of gamma-TiAl alloys make them attractive candidates for durable lightweight hot structure and thermal protection systems at temperatures as high as 871 C. However, oxidation significantly degrades gamma-TiAl alloys under the high-temperature service conditions associated with the RLV operating environment. This paper discusses ongoing efforts at NASA Langley Research Center to develop durable ultrathin coatings for protecting gamma-TiAl alloys from high-temperature oxidation environments. In addition to offering oxidation protection, these multifunctional coatings are being engineered to provide thermal control features to help minimize heat input into the hot structures. This paper describes the coating development effort and discusses the effects of long-term high-temperature exposures on the microstructure of coated and uncoated gamma-TiAl alloys. The alloy of primary consideration was the Plansee alloy gamma-Met, but limited studies of the newer alloy gamma-Met-PX were also included. The oxidation behavior of the uncoated materials was evaluated over the temperature range of 704 C to 871 C. Sol-gel-based coatings were applied to the gamma-TiAl samples by dipping and spraying, and the performance evaluated at 871 C. Results showed that the coatings improve the oxidation resistance, but that further development is necessary.

Generation of Primary Kilauea Magmas: Constraints on Pressure, Temperature and Composition of Melts

NASA Astrophysics Data System (ADS)

Gudfinnsson, G. H.; Presnall, D. C.

2004-12-01

Picrite glasses from the submarine extension of Kilauea, Puna Ridge, which contain up to 15.0 wt% MgO, are the most magnesian glass samples reported from Hawaii. Their compositions form a distinct olivine fractionation trend. A comparison of this trend with phase relations of garnet lherzolite in the CaO-MgO-Al2O3-SiO2 (CMAS) and CaO-MgO-Al2O3-SiO2-Na2O-FeO (CMASNF) system indicates that melts parental to the Hawaiian picrites are produced by melting of a garnet lherzolite source at a pressure of 5 ± 1 GPa. The primary melt composition for Kilauea proposed by Clague et al. (1995), which has 18.4 wt% MgO, is close to the expected 5 GPa melt composition. By using the pressure-independent CMASNF geothermometer (Gudfinnsson and Presnall, 2001), we obtain a temperature of formation of 1450° C for the most magnesian Puna Ridge glass after correction for the presence of 0.4 wt% H2O and 0.7 wt% CO2. This assumes that the glass is not much modified after separation from the lherzolite source. However, comparison with phase relations in the CMAS system strongly suggests that the most magnesian Puna Ridge glasses are the product of some olivine fractionation, and therefore give temperature considerably lower than that of the source. When applied to the proposed Kilauea primary melt composition of Clague et al. (1995), the CMASNF geothermometer gives a melting temperature of 1596° C or about 1565° C after correction for the presence of volatiles. This compares well with the anhydrous solidus temperature of 1600 ± 15° C at 5 GPa for the fertile KR4003 lherzolite (Lesher et al., 2003), which has the complete garnet lherzolite phase assemblage present at the solidus at this pressure. This consistency supports use of phase relations from the CMAS system and the CMASNF geothermometer to the Puna Ridge picrite compositions. With the pressure and temperature of melting known, one can calculate the potential temperature of the Hawaiian mantle, provided certain conditions are met. The calculation assumes that the temperature at the point of melt segregation is close to the temperature of the solid adiabat. If extensive melting has occurred prior to the segregation, this will be incorrect. Secondly, it is assumed that the melting is occurring at the non-conducting part of the geotherm. Provided this is the case and the Kilauea primary melt composition truly represents a near-primary melt composition, we derive a potential temperature for the mantle beneath Kilauea of about 1500° C. The very high temperature and pressure conditions for magma generation at Hawaii appear to be unmatched by any other currently active volcanism on the Earth. Thus, of all the candidates for plume status, Hawaii appears to be the most robust.

Subcooled Pool Boiling Heat Transfer Mechanisms in Microgravity: Terrier-improved Orion Sounding Rocket Experiment

NASA Technical Reports Server (NTRS)

Kim, Jungho; Benton, John; Kucner, Robert

2000-01-01

A microscale heater array was used to study boiling in earth gravity and microgravity. The heater array consisted of 96 serpentine heaters on a quartz substrate. Each heater was 0.27 square millimeters. Electronic feedback loops kept each heater's temperature at a specified value. The University of Maryland constructed an experiment for the Terrier-Improved Orion sounding rocket that was delivered to NASA Wallops and flown. About 200 s of high quality microgravity and heat transfer data were obtained. The VCR malfunctioned, and no video was acquired. Subsequently, the test package was redesigned to fly on the KC-135 to obtain both data and video. The pressure was held at atmospheric pressure and the bulk temperature was about 20 C. The wall temperature was varied from 85 to 65 C. Results show that gravity has little effect on boiling heat transfer at wall superheats below 25 C, despite vast differences in bubble behavior between gravity levels. In microgravity, a large primary bubble was surrounded by smaller bubbles, which eventually merged with the primary bubble. This bubble was formed by smaller bubbles coalescing, but had a constant size for a given superheat, indicating a balance between evaporation at the base and condensation on the cap. Most of the heaters under the bubble indicated low heat transfer, suggesting dryout at those heaters. High heat transfer occurred at the contact line surrounding the primary bubble. Marangoni convection formed a "jet" of fluid into the bulk fluid that forced the bubble onto the heater.

The effect of ambient temperature on type-2-diabetes: case-crossover analysis of 4+ million GP consultations across England.

PubMed

Hajat, S; Haines, A; Sarran, C; Sharma, A; Bates, C; Fleming, L E

2017-07-12

Given the double jeopardy of global increases in rates of obesity and climate change, it is increasingly important to recognise the dangers posed to diabetic patients during periods of extreme weather. We aimed to characterise the associations between ambient temperature and general medical practitioner consultations made by a cohort of type-2 diabetic patients. Evidence on the effects of temperature variation in the primary care setting is currently limited. Case-crossover analysis of 4,474,943 consultations in England during 2012-2014, linked to localised temperature at place of residence for each patient. Conditional logistic regression was used to assess associations between each temperature-related consultation and control days matched on day-of-week. There was an increased odds of seeking medical consultation associated with high temperatures: Odds ratio (OR) = 1.097 (95% confidence interval = 1.041, 1.156) per 1 °C increase above 22 °C. Odds during low temperatures below 0 °C were also significantly raised: OR = 1.024 (1.019, 1.030). Heat-related consultations were particularly high among diabetics with cardiovascular comorbidities: OR = 1.171 (1.031, 1.331), but there was no heightened risk with renal failure or neuropathy comorbidities. Surprisingly, lower odds of heat-related consultation were associated with the use of diuretics, anticholinergics, antipsychotics or antidepressants compared to non-use, especially among those with cardiovascular comorbidities, although differences were not statistically significant. Type-2 diabetic patients are at increased odds of medical consultation during days of temperature extremes, especially during hot weather. The common assumption that certain medication use heightens the risk of heat illness was not borne-out by our study on diabetics in a primary care setting and such advice may need to be reconsidered in heat protection plans.

Sputtering and ion plating for aerospace applications

NASA Technical Reports Server (NTRS)

Spalvins, T.

1981-01-01

Sputtering and ion plating technologies are reviewed in terms of their potential and present uses in the aerospace industry. Sputtering offers great universality and flexibility in depositing any material or in the synthesis of new ones. The sputter deposition process has two areas of interest: thin film and fabrication technology. Thin film sputtering technology is primarily used for aerospace mechanical components to reduce friction, wear, erosion, corrosion, high temperature oxidation, diffusion and fatigue, and also to sputter-construct temperature and strain sensors for aircraft engines. Sputter fabrication is used in intricate aircraft component manufacturing. Ion plating applications are discussed in terms of the high energy evaporant flux and the high throwing power. Excellent adherence and 3 dimensional coverage are the primary attributes of this technology.

Sputtering and ion plating for aerospace applications

NASA Technical Reports Server (NTRS)

Spalvins, T.

1981-01-01

Sputtering and ion plating technologies are reviewed in terms of their potential and present uses in the aerospace industry. Sputtering offers great universality and flexibility in depositing any material or in the synthesis of new ones. The sputter deposition process has two areas of interest: thin film and fabrication technology. Thin film sputtering technology is primarily used for aerospace mechanical components to reduce friction, wear, erosion, corrosion, high temperature oxidation, diffusion and fatigue, and also to sputter-construct temperature and strain sensors for aircraft engines. Sputter fabrication is used in intricate aircraft component manufacturing. Ion plating applications are discussed in terms of the high energy evaporant flux and the high throwing power. Excellent adherence and 3-dimensional coverage are the primary attributes of this technology.

Impacts of climate extremes on gross primary production under global warming

DOE PAGES

Williams, I. N.; Torn, M. S.; Riley, W. J.; ...

2014-09-24

The impacts of historical droughts and heat-waves on ecosystems are often considered indicative of future global warming impacts, under the assumption that water stress sets in above a fixed high temperature threshold. Historical and future (RCP8.5) Earth system model (ESM) climate projections were analyzed in this study to illustrate changes in the temperatures for onset of water stress under global warming. The ESMs examined here predict sharp declines in gross primary production (GPP) at warm temperature extremes in historical climates, similar to the observed correlations between GPP and temperature during historical heat-waves and droughts. However, soil moisture increases at themore » warm end of the temperature range, and the temperature at which soil moisture declines with temperature shifts to a higher temperature. The temperature for onset of water stress thus increases under global warming and is associated with a shift in the temperature for maximum GPP to warmer temperatures. Despite the shift in this local temperature optimum, the impacts of warm extremes on GPP are approximately invariant when extremes are defined relative to the optimal temperature within each climate period. The GPP sensitivity to these relative temperature extremes therefore remains similar between future and present climates, suggesting that the heat- and drought-induced GPP reductions seen recently can be expected to be similar in the future, and may be underestimates of future impacts given model projections of increased frequency and persistence of heat-waves and droughts. The local temperature optimum can be understood as the temperature at which the combination of water stress and light limitations is minimized, and this concept gives insights into how GPP responds to climate extremes in both historical and future climate periods. Both cold (temperature and light-limited) and warm (water-limited) relative temperature extremes become more persistent in future climate projections, and the time taken to return to locally optimal climates for GPP following climate extremes increases by more than 25% over many land regions.« less

Impacts of climate extremes on gross primary production under global warming

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

Williams, I. N.; Torn, M. S.; Riley, W. J.

The impacts of historical droughts and heat-waves on ecosystems are often considered indicative of future global warming impacts, under the assumption that water stress sets in above a fixed high temperature threshold. Historical and future (RCP8.5) Earth system model (ESM) climate projections were analyzed in this study to illustrate changes in the temperatures for onset of water stress under global warming. The ESMs examined here predict sharp declines in gross primary production (GPP) at warm temperature extremes in historical climates, similar to the observed correlations between GPP and temperature during historical heat-waves and droughts. However, soil moisture increases at themore » warm end of the temperature range, and the temperature at which soil moisture declines with temperature shifts to a higher temperature. The temperature for onset of water stress thus increases under global warming and is associated with a shift in the temperature for maximum GPP to warmer temperatures. Despite the shift in this local temperature optimum, the impacts of warm extremes on GPP are approximately invariant when extremes are defined relative to the optimal temperature within each climate period. The GPP sensitivity to these relative temperature extremes therefore remains similar between future and present climates, suggesting that the heat- and drought-induced GPP reductions seen recently can be expected to be similar in the future, and may be underestimates of future impacts given model projections of increased frequency and persistence of heat-waves and droughts. The local temperature optimum can be understood as the temperature at which the combination of water stress and light limitations is minimized, and this concept gives insights into how GPP responds to climate extremes in both historical and future climate periods. Both cold (temperature and light-limited) and warm (water-limited) relative temperature extremes become more persistent in future climate projections, and the time taken to return to locally optimal climates for GPP following climate extremes increases by more than 25% over many land regions.« less

Advance High Temperature Inspection Capabilities for Small Modular Reactors: Part 1 - Ultrasonics

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

Bond, Leonard J.; Bowler, John R.

The project objective was to investigate the development non-destructive evaluation techniques for advanced small modular reactors (aSMR), where the research sought to provide key enabling inspection technologies needed to support the design and maintenance of reactor component performance. The project tasks for the development of inspection techniques to be applied to small modular reactor are being addressed through two related activities. The first is focused on high temperature ultrasonic transducers development (this report Part 1) and the second is focused on an advanced eddy current inspection capability (Part 2). For both inspection techniques the primary aim is to develop in-servicemore » inspection techniques that can be carried out under standby condition in a fast reactor at a temperature of approximately 250°C in the presence of liquid sodium. The piezoelectric material and the bonding between layers have been recognized as key factors fundamental for development of robust ultrasonic transducers. Dielectric constant characterization of bismuth scantanate-lead titanate ((1-x)BiScO 3-xPbTiO 3) (BS-PT) has shown a high Curie temperature in excess of 450°C , suitable for hot stand-by inspection in liquid metal reactors. High temperature pulse-echo contact measurements have been performed with BS-PT bonded to 12.5 mm thick 1018-low carbon steel plate from 20C up to 260 C. High temperature air-backed immersion transducers have been developed with BS-PT, high temperature epoxy and quarter wavlength nickel plate, needed for wetting ability in liquid sodium. Ultrasonic immersion measurements have been performed in water up to 92C and in silicone oil up to 140C. Physics based models have been validated with room temperature experimental data with benchmark artifical defects.« less

ASME code considerations for the compact heat exchanger

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

Nestell, James; Sham, Sam

2015-08-31

The mission of the U.S. Department of Energy (DOE), Office of Nuclear Energy is to advance nuclear power in order to meet the nation's energy, environmental, and energy security needs. Advanced high temperature reactor systems such as sodium fast reactors and high and very high temperature gas-cooled reactors are being considered for the next generation of nuclear reactor plant designs. The coolants for these high temperature reactor systems include liquid sodium and helium gas. Supercritical carbon dioxide (sCO₂), a fluid at a temperature and pressure above the supercritical point of CO₂, is currently being investigated by DOE as a workingmore » fluid for a nuclear or fossil-heated recompression closed Brayton cycle energy conversion system that operates at 550°C (1022°F) at 200 bar (2900 psi). Higher operating temperatures are envisioned in future developments. All of these design concepts require a highly effective heat exchanger that transfers heat from the nuclear or chemical reactor to the chemical process fluid or the to the power cycle. In the nuclear designs described above, heat is transferred from the primary to the secondary loop via an intermediate heat exchanger (IHX) and then from the intermediate loop to either a working process or a power cycle via a secondary heat exchanger (SHX). The IHX is a component in the primary coolant loop which will be classified as "safety related." The intermediate loop will likely be classified as "not safety related but important to safety." These safety classifications have a direct bearing on heat exchanger design approaches for the IHX and SHX. The very high temperatures being considered for the VHTR will require the use of very high temperature alloys for the IHX and SHX. Material cost considerations alone will dictate that the IHX and SHX be highly effective; that is, provide high heat transfer area in a small volume. This feature must be accompanied by low pressure drop and mechanical reliability and robustness. Classic shell and tube designs will be large and costly, and may only be appropriate in steam generator service in the SHX where boiling inside the tubes occurs. For other energy conversion systems, all of these features can be met in a compact heat exchanger design. This report will examine some of the ASME Code issues that will need to be addressed to allow use of a Code-qualified compact heat exchanger in IHX or SHX nuclear service. Most effort will focus on the IHX, since the safety-related (Class A) design rules are more extensive than those for important-to-safety (Class B) or commercial rules that are relevant to the SHX.« less

Influence of primary α-phase volume fraction on the mechanical properties of Ti-6Al-4V alloy at different strain rates and temperatures

NASA Astrophysics Data System (ADS)

Ren, Yu; Zhou, Shimeng; Luo, Wenbo; Xue, Zhiyong; Zhang, Yajing

2018-03-01

Bimodal microstructures with primary α-phase volume fractions ranging from 14.3% to 57.1% were gained in Ti-6Al-4V (Ti-64) alloy through annealed in two-phase region at various temperatures below the β-transus point. Then the influence of the primary α-phase volume fraction on the mechanical properties of Ti-64 were studied. The results show that, at room temperature and a strain rate of 10‑3 s‑1, the yield stress decreases but the fracture strain augments with added primary α-phase volume fraction. The equiaxed primary α-phase possesses stronger ability to coordinate plastic deformation, leading to the improvement of the ductile as well as degradation of the strength of Ti-64 with higher primary α-phase volume fraction. As the temperature goes up to 473 K, the quasi-static yield stress and ultimate strength decrease first and then increase with the incremental primary α-phase volume fraction, due to the interaction between the work hardening and the softening caused by the DRX and the growth of the primary α-phase. At room temperature and a strain rate of 3×103 s‑1, the varying pattern of strength with the primary α-phase volume fraction resembles that at a quasi-static strain rate. However, the flow stress significantly increases but the strain-hardening rate decreases compared to those at quasi-static strain rate due to the competition between the strain rate hardening and the thermal softening during dynamic compression process.

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

Aronhime, Natan; Zoghlin, Eli; Keylin, Vladimir

Fe-Ni based metal amorphous nanocomposites (MANCs) are investigated in the pseudo-binary alloys (Fe 100–xNi x) 80Nb 4Si 2B 14. To optimize the soft magnetic properties of the nanocomposites, primary and secondary crystallization kinetics must be understood. As such, primary and secondary crystallization temperatures are determined by differential scanning calorimetry, and activation energies are calculated, along with the resulting crystalline phases. Time-temperature-transformation diagrams for primary and secondary crystallization in (Fe 70Ni 30) 80Nb 4Si 2B 14 are presented. Saturation magnetization and Curie temperature are determined. In conclusion, the shape of magnetization vs. time curves for (Fe 30Ni 70) 80Nb 4Si 2Bmore » 14 at various temperatures suggest that the secondary crystal product often consumes some of the primary crystalline product.« less

Simulation of atmospheric temperature effects on cosmic ray muon flux

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

Tognini, Stefano Castro; Gomes, Ricardo Avelino

2015-05-15

The collision between a cosmic ray and an atmosphere nucleus produces a set of secondary particles, which will decay or interact with other atmosphere elements. This set of events produced a primary particle is known as an extensive air shower (EAS) and is composed by a muonic, a hadronic and an electromagnetic component. The muonic flux, produced mainly by pions and kaons decays, has a dependency with the atmosphere’s effective temperature: an increase in the effective temperature results in a lower density profile, which decreases the probability of pions and kaons to interact with the atmosphere and, consequently, resulting inmore » a major number of meson decays. Such correlation between the muon flux and the atmosphere’s effective temperature was measured by a set of experiments, such as AMANDA, Borexino, MACRO and MINOS. This phenomena can be investigated by simulating the final muon flux produced by two different parameterizations of the isothermal atmospheric model in CORSIKA, where each parameterization is described by a depth function which can be related to the muon flux in the same way that the muon flux is related to the temperature. This research checks the agreement among different high energy hadronic interactions models and the physical expected behavior of the atmosphere temperature effect by analyzing a set of variables, such as the height of the primary interaction and the difference in the muon flux.« less

Catalytic chemical amide synthesis at room temperature: one more step toward peptide synthesis.

PubMed

Mohy El Dine, Tharwat; Erb, William; Berhault, Yohann; Rouden, Jacques; Blanchet, Jérôme

2015-05-01

An efficient method has been developed for direct amide bond synthesis between carboxylic acids and amines via (2-(thiophen-2-ylmethyl)phenyl)boronic acid as a highly active bench-stable catalyst. This catalyst was found to be very effective at room temperature for a large range of substrates with slightly higher temperatures required for challenging ones. This methodology can be applied to aliphatic, α-hydroxyl, aromatic, and heteroaromatic acids as well as primary, secondary, heterocyclic, and even functionalized amines. Notably, N-Boc-protected amino acids were successfully coupled in good yields with very little racemization. An example of catalytic dipeptide synthesis is reported.

Creep Strain and Strain Rate Response of 2219 Al Alloy at High Stress Levels

NASA Technical Reports Server (NTRS)

Taminger, Karen M. B.; Wagner, John A.; Lisagor, W. Barry

1998-01-01

As a result of high localized plastic deformation experienced during proof testing in an International Space Station connecting module, a study was undertaken to determine the deformation response of a 2219-T851 roll forging. After prestraining 2219-T851 Al specimens to simulate strains observed during the proof testing, creep tests were conducted in the temperature range from ambient temperature to 107 C (225 F) at stress levels approaching the ultimate tensile strength of 2219-T851 Al. Strain-time histories and strain rate responses were examined. The strain rate response was extremely high initially, but decayed rapidly, spanning as much as five orders of magnitude during primary creep. Select specimens were subjected to incremental step loading and exhibited initial creep rates of similar magnitude for each load step. Although the creep rates decreased quickly at all loads, the creep rates dropped faster and reached lower strain rate levels for lower applied loads. The initial creep rate and creep rate decay associated with primary creep were similar for specimens with and without prestrain; however, prestraining (strain hardening) the specimens, as in the aforementioned proof test, resulted in significantly longer creep life.

Low-temperature synthesis of LiNi0.5Mn1.5O4 grains using a water vapor-assisted solid-state reaction

NASA Astrophysics Data System (ADS)

Kozawa, Takahiro; Hirobe, Daiki; Uehara, Kunika; Naito, Makio

2018-07-01

LiNi0.5Mn1.5O4 (LNMO) spinel is one of the candidates for the cathodes of high-energy lithium-ion batteries because of its high operating voltage of 4.7 V. However, its use at high voltages leads to the decomposition of common organic electrolytes, resulting in a cycle degradation of the batteries. Although morphological control of LNMO particles involving their size and shape is an effective approach to suppressing electrolyte decomposition, the particle growth relying on diffusion in the solids has limitations of temperature and time. Here, we report the particle growth of LNMO at a low temperature using water vapor. By heating porous Mn2O3 spheres with Li and Ni sources as a precursor, we obtain spherical LNMO particles at 500 °C in both air and water vapor. The growth of primary particles is promoted by water vapor, and consequently, the obtained LNMO cathode exhibits better properties than those observed in air. Water vapor also affects the change of shape of LNMO at higher temperatures, leading to the formation of truncated particles from the spheres. Compared to conventional heating processes, this water vapor-assisted particle growth offers a low-temperature control of particle morphologies, particularly for materials that decompose easily at high temperatures.

Investigation of applications for high-power, self-critical fissioning uranium plasma reactors

NASA Technical Reports Server (NTRS)

Rodgers, R. J.; Latham, T. S.; Krascella, N. L.

1976-01-01

Analytical studies were conducted to investigate potentially attractive applications for gaseous nuclear cavity reactors fueled by uranium hexafluoride and its decomposition products at temperatures of 2000 to 6000 K and total pressures of a few hundred atmospheres. Approximate operating conditions and performance levels for a class of nuclear reactors in which fission energy removal is accomplished principally by radiant heat transfer from the high temperature gaseous nuclear fuel to surrounding absorbing media were determined. The results show the radiant energy deposited in the absorbing media may be efficiently utilized in energy conversion system applications which include (1) a primary energy source for high thrust, high specific impulse space propulsion, (2) an energy source for highly efficient generation of electricity, and (3) a source of high intensity photon flux for heating working fluid gases for hydrogen production or MHD power extraction.

Producing the high temperature reusable surface insulation for the thermal protection system of the Space Shuttle

NASA Technical Reports Server (NTRS)

Forgsberg, K.

1979-01-01

The primary insulation system used to protect the space shuttle orbiter on reentry is an externally attached, rigidized, fibrous silica which has been machined into tiles. The tiles constitute the temperature reusable surface insulation system and are used on over 70 percent of the vehicle exterior surface where peak temperatures range from 400 to 1260 C. Cargon-carbon leading edges are used in areas where peak temperatures exceed 1650 C and a felt flexible insulation is used in regions below 400 C. Approximately 32,000 tiles are used in the HRST system and because of vehicle configuration, aerodynamic requirements, and weight considerations no two tiles are alike. Fabrication and quality control procedures are described.

Iridium-Coated Rhenium Radiation-Cooled Rockets

NASA Technical Reports Server (NTRS)

Reed, Brian D.; Biaglow, James A.; Schneider, Steven J.

1997-01-01

Radiation-cooled rockets are used for a range of low-thrust propulsion functions, including apogee insertion, attitude control, and repositioning of satellites, reaction control of launch vehicles, and primary propulsion for planetary space- craft. The key to high performance and long lifetimes for radiation-cooled rockets is the chamber temperature capability. The material system that is currently used for radiation-cooled rockets, a niobium alloy (C103) with a fused silica coating, has a maximum operating temperature of 1370 C. Temperature limitations of C103 rockets force the use of fuel film cooling, which degrades rocket performance and, in some cases, imposes a plume contamination issue from unburned fuel. A material system composed of a rhenium (Re) substrate and an iridium (Ir) coating has demonstrated operation at high temperatures (2200 C) and for long lifetimes (hours). The added thermal margin afforded by iridium-coated rhenium (Ir/Re) allows reduction or elimination of fuel film cooling. This, in turn, leads to higher performance and cleaner spacecraft environments. There are ongoing government- and industry-sponsored efforts to develop flight Ir/ Re engines, with the primary focus on 440-N, apogee insertion engines. Complementing these Ir/Re engine development efforts is a program to address specific concerns and fundamental characterization of the Ir/Re material system, including (1) development of Ir/Re rocket fabrication methods, (2) establishment of critical Re mechanical properly data, (3) development of reliable joining methods, and (4) characterization of Ir/Re life-limiting mechanisms.

The acclimation process of phytoplankton biomass, carbon fixation and respiration to the combined effects of elevated temperature and pCO2 in the northern South China Sea.

PubMed

Gao, Guang; Jin, Peng; Liu, Nana; Li, Futian; Tong, Shanying; Hutchins, David A; Gao, Kunshan

2017-05-15

We conducted shipboard microcosm experiments at both off-shore (SEATS) and near-shore (D001) stations in the northern South China Sea (NSCS) under three treatments, low temperature and low pCO 2 (LTLC), high temperature and low pCO 2 (HTLC), and high temperature and high pCO 2 (HTHC). Biomass of phytoplankton at both stations were enhanced by HT. HTHC did not affect phytoplankton biomass at station D001 but decreased it at station SEATS. HT alone increased net primary productivity by 234% at station SEATS and by 67% at station D001 but the stimulating effect disappeared when HC was combined. HT also increased respiration rate by 236% at station SEATS and by 87% at station D001 whereas HTHC reduced it by 61% at station SEATS and did not affect it at station D001. Overall, our findings indicate that the positive effect of ocean warming on phytoplankton assemblages in NSCS could be damped or offset by ocean acidification. Copyright © 2017 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

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

Wright, Caradee Y; Street, Renée A; Cele, Nokulunga; Kunene, Zamantimande; Balakrishna, Yusentha; Albers, Patricia N; Mathee, Angela

2017-01-06

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'.

Phase I Final Scientific Report

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

Lu, Xijia; Fetvedt, Jeremy; Dimmig, Walker

This Final Scientific Report addresses the accomplishments achieved during Phase I of DE- FE0023985, Coal Syngas Combustor Development for Supercritical CO 2 Power Cycles. The primary objective of the project was to develop a coal syngas-fueled combustor design for use with high-pressure, high-temperature, oxy-fuel, supercritical CO 2 power cycles, with particular focus given to the conditions required by the Allam Cycle. The primary goals, from the Statement of Project Objectives, were to develop: (1) a conceptual design of a syngas-fueled combustor-turbine block for a 300MWe high-pressure, oxy-fuel, sCO2 power plant; (2) the preliminary design of a 5MWt test combustor; andmore » (3) the definition of a combustor test program. Accomplishments for each of these goals are discussed in this report.« less

Burst annealing of high temperature GaAs solar cells

NASA Technical Reports Server (NTRS)

Brothers, P. R.; Horne, W. E.

1991-01-01

One of the major limitations of solar cells in space power systems is their vulnerability to radiation damage. One solution to this problem is to periodically heat the cells to anneal the radiation damage. Annealing was demonstrated with silicon cells. The obstacle to annealing of GaAs cells was their susceptibility to thermal damage at the temperatures required to completely anneal the radiation damage. GaAs cells with high temperature contacts and encapsulation were developed. The cells tested are designed for concentrator use at 30 suns AMO. The circular active area is 2.5 mm in diameter for an area of 0.05 sq cm. Typical one sun AMO efficiency of these cells is over 18 percent. The cells were demonstrated to be resistant to damage after thermal excursions in excess of 600 C. This high temperature tolerance should allow these cells to survive the annealing of radiation damage. A limited set of experiments were devised to investigate the feasibility of annealing these high temperature cells. The effect of repeated cycles of electron and proton irradiation was tested. The damage mechanisms were analyzed. Limitations in annealing recovery suggested improvements in cell design for more complete recovery. These preliminary experiments also indicate the need for further study to isolate damage mechanisms. The primary objective of the experiments was to demonstrate and quantify the annealing behavior of high temperature GaAs cells. Secondary objectives were to measure the radiation degradation and to determine the effect of repeated irradiation and anneal cycles.

Overview of CMC Development Activities in NASA's Ultra-Efficient Engine Technology (UEET) Program

NASA Technical Reports Server (NTRS)

Brewer, Dave

2001-01-01

The primary objective of the UEET (Ultra-Efficient Engine Technology) Program is to address two of the most critical propulsion issues: performance/efficiency and reduced emissions. High performance, low emissions engine systems will lead to significant improvement in local air quality, minimum impact on ozone depletion and level to an overall reduction in aviation contribution to global warming. The Materials and Structures for High Performance project will develop and demonstrate advanced high temperature materials to enable high-performance, high efficiency, and environmentally compatible propulsion systems.

Mathematical modelling of temperature effect on growth kinetics of Pseudomonas spp. on sliced mushroom (Agaricus bisporus).

PubMed

Tarlak, Fatih; Ozdemir, Murat; Melikoglu, Mehmet

2018-02-02

The growth data of Pseudomonas spp. on sliced mushrooms (Agaricus bisporus) stored between 4 and 28°C were obtained and fitted to three different primary models, known as the modified Gompertz, logistic and Baranyi models. The goodness of fit of these models was compared by considering the mean squared error (MSE) and the coefficient of determination for nonlinear regression (pseudo-R 2 ). The Baranyi model yielded the lowest MSE and highest pseudo-R 2 values. Therefore, the Baranyi model was selected as the best primary model. Maximum specific growth rate (r max ) and lag phase duration (λ) obtained from the Baranyi model were fitted to secondary models namely, the Ratkowsky and Arrhenius models. High pseudo-R 2 and low MSE values indicated that the Arrhenius model has a high goodness of fit to determine the effect of temperature on r max . Observed number of Pseudomonas spp. on sliced mushrooms from independent experiments was compared with the predicted number of Pseudomonas spp. with the models used by considering the B f and A f values. The B f and A f values were found to be 0.974 and 1.036, respectively. The correlation between the observed and predicted number of Pseudomonas spp. was high. Mushroom spoilage was simulated as a function of temperature with the models used. The models used for Pseudomonas spp. growth can provide a fast and cost-effective alternative to traditional microbiological techniques to determine the effect of storage temperature on product shelf-life. The models can be used to evaluate the growth behaviour of Pseudomonas spp. on sliced mushroom, set limits for the quantitative detection of the microbial spoilage and assess product shelf-life. Copyright © 2017 Elsevier B.V. All rights reserved.

Texture studies of hot compressed near alpha titanium alloy (IMI 834) at 1000°C with different strain rates

NASA Astrophysics Data System (ADS)

Kodli, B. K.; Saxena, K. K.; Dey, S. R.; Pancholi, V.; Bhattacharjee, A.

2015-04-01

IMI 834 Titanium alloy is a near alpha (hcp) titanium alloy used for high temperature applications with the service temperature up to 600°C. Generally, this alloy is widely used in gas turbine engine applications such as low pressure compressor discs. For these applications, good fatigue and creep properties are required, which have been noticed better in a bimodal microstructure, containing 15-20% volume fraction of primary alpha grains (αp) and remaining bcc beta (β) grains transformed secondary alpha laths (αs). The bimodal microstructure is achieved during processing of IMI 834 in the high temperature α+β region. The major issue of bimodal IMI 834 during utilization is its poor dwell fatigue life time caused by textured macrozones. Textured macrozone is the spatial accumulation of similar oriented grains in the microstructure generated during hot processing in the high temperature α+β region. Textured macrozone can be mitigated by controlling the hot deformation with certain strain rate under stable plastic conditions having β grains undergoing dynamic recrystallization. Hence, a comprehensive study is required to understand the deformation behavior of α and β grains at different strain rates in that region. Hot compression tests up to 5°% strain of the samples are performed with five different strain rates i.e. 10-3 s-1, 10-2 s-1, 10-1 s-1, 1 s-1 and 10 s-1 at 1000°C using Gleeble 3800. The resultant bimodal microstructure and the texture studies of primary alpha grains (αp) and secondary alpha laths (αs) are carried out using scanning electron microscopy (SEM)-electron back scattered diffraction (EBSD) method.

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

NASA Technical Reports Server (NTRS)

Poff, K. L.

1991-01-01

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

Population Structure, Genetic Diversity and Molecular Marker-Trait Association Analysis for High Temperature Stress Tolerance in Rice

PubMed Central

Barik, Saumya Ranjan; Sahoo, Ambika; Mohapatra, Sudipti; Nayak, Deepak Kumar; Mahender, Anumalla; Meher, Jitandriya; Anandan, Annamalai

2016-01-01

Rice exhibits enormous genetic diversity, population structure and molecular marker-traits associated with abiotic stress tolerance to high temperature stress. A set of breeding lines and landraces representing 240 germplasm lines were studied. Based on spikelet fertility percent under high temperature, tolerant genotypes were broadly classified into four classes. Genetic diversity indicated a moderate level of genetic base of the population for the trait studied. Wright’s F statistic estimates showed a deviation of Hardy-Weinberg expectation in the population. The analysis of molecular variance revealed 25 percent variation between population, 61 percent among individuals and 14 percent within individuals in the set. The STRUCTURE analysis categorized the entire population into three sub-populations and suggested that most of the landraces in each sub-population had a common primary ancestor with few admix individuals. The composition of materials in the panel showed the presence of many QTLs representing the entire genome for the expression of tolerance. The strongly associated marker RM547 tagged with spikelet fertility under stress and the markers like RM228, RM205, RM247, RM242, INDEL3 and RM314 indirectly controlling the high temperature stress tolerance were detected through both mixed linear model and general linear model TASSEL analysis. These markers can be deployed as a resource for marker-assisted breeding program of high temperature stress tolerance. PMID:27494320

Population Structure, Genetic Diversity and Molecular Marker-Trait Association Analysis for High Temperature Stress Tolerance in Rice.

PubMed

Pradhan, Sharat Kumar; Barik, Saumya Ranjan; Sahoo, Ambika; Mohapatra, Sudipti; Nayak, Deepak Kumar; Mahender, Anumalla; Meher, Jitandriya; Anandan, Annamalai; Pandit, Elssa

2016-01-01

Rice exhibits enormous genetic diversity, population structure and molecular marker-traits associated with abiotic stress tolerance to high temperature stress. A set of breeding lines and landraces representing 240 germplasm lines were studied. Based on spikelet fertility percent under high temperature, tolerant genotypes were broadly classified into four classes. Genetic diversity indicated a moderate level of genetic base of the population for the trait studied. Wright's F statistic estimates showed a deviation of Hardy-Weinberg expectation in the population. The analysis of molecular variance revealed 25 percent variation between population, 61 percent among individuals and 14 percent within individuals in the set. The STRUCTURE analysis categorized the entire population into three sub-populations and suggested that most of the landraces in each sub-population had a common primary ancestor with few admix individuals. The composition of materials in the panel showed the presence of many QTLs representing the entire genome for the expression of tolerance. The strongly associated marker RM547 tagged with spikelet fertility under stress and the markers like RM228, RM205, RM247, RM242, INDEL3 and RM314 indirectly controlling the high temperature stress tolerance were detected through both mixed linear model and general linear model TASSEL analysis. These markers can be deployed as a resource for marker-assisted breeding program of high temperature stress tolerance.

Evolution mechanisms of the primary α and β phases during α/β deformation of an α/β titanium alloy TC8

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

Wang, Ke, E-mail: study_ke@cqu.edu.cn

A TC8 titanium alloy was isothermally compressed at the strain rates of 10–50 s{sup −1} in the two-phase region of 820–940 °C, and the evolution mechanisms of the primary α and β phases, including grain morphology, dynamic recovery (DRV) and dynamic recrystallization (DRX), were investigated by optical microscopy (OM) and transmission electron microscopy (TEM). OM reveals that the phase content and grain morphology are more significantly influenced by the deformation temperature than the strain rate. The β grains achieve refinement only at 940 °C due to DRX in the β phase. TEM reveals the remarkable variations of the DRX grains,more » subgrains, sub-boundaries and dislocations morphology with temperature and strain rate related to DRV and DRX in the primary α phase. The DRX in the primary α phase appears most strongly at a middle temperature of 860 °C, and DRV dominates in the primary α phase at 940 °C. While the dominant mechanism varies from DRV to DRX in the β phase as the temperature increases. Finally, the influence mechanism of deformation parameters on the primary α grain morphology is revealed based on the combined effect of DRV and DRX in the primary α phase and diffusion of the β phase. - Highlights: •The β grains achieve refinement only at 940 °C due to DRX in the β phase. •The DRX in the primary α phase is most remarkable at 860 °C. •The dominant mechanism in β phase varies from DRV to DRX with increasing temperature. •The interaction between the primary α and β phases depends on the phase content.« less

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.

High power densities from high-temperature materials interactions. [thermionic energy conversion and metallic fluid heat pipes

NASA Technical Reports Server (NTRS)

Morris, J. F.

1981-01-01

Thermionic energy converters and metallic-fluid heat pipes are well suited to serve together synergistically. The two operating cycles appear as simple and isolated as their material problems seem forebodingly deceptive and complicated. Simplified equations verify material properties and interactions as primary influences on the operational effectiveness of both. Each experiences flow limitations in thermal emission and vaporization because of temperature restrictions redounding from thermophysicochemical stability considerations. Topics discussed include: (1) successful limitation of alkali-metal corrosion; (2) protection against external hot corrosive gases; (3) coping with external and internal vaporization; (4) controlling interfacial reactions and diffusion; and (5) meeting other thermophysical challenges; expansion matches and creep.

Experimentally increased temperature and hypoxia affect stability of social hierarchy and metabolism of the Amazonian cichlid Apistogramma agassizii.

PubMed

Kochhann, Daiani; Campos, Derek Felipe; Val, Adalberto Luis

2015-12-01

The primary goal of this study was to understand how changes in temperature and oxygen could influence social behaviour and aerobic metabolism of the Amazonian dwarf cichlid Apistogramma agassizii. Social hierarchies were established over a period of 96h by observing the social interactions, feeding behaviour and shelter use in groups of four males. In the experimental environment, temperature was increased to 29°C in the high-temperature treatment, and oxygen lowered to 1.0mg·L(-1)O2 in the hypoxia treatment. Fish were maintained at this condition for 96h. The control was maintained at 26°C and 6.6mg·L(-1)O2. After the experimental exposure, metabolism was measured as routine metabolic rate (RMR) and electron transport system (ETS) activity. There was a reduction in hierarchy stability at high-temperature. Aggression changed after environmental changes. Dominant and subdominant fish at high temperatures increased their biting, compared with control-dominant. In contrast, hypoxia-dominant fish decreased their aggressive acts compared with all other fish. Shelter use decreased in control and hypoxic dominant fish. Dominant fish from undisturbed environments eat more than their subordinates. There was a decrease of RMR in fish exposed to the hypoxic environment when compared with control or high-temperature fish, independent of social position. Control-dominant fish had higher RMR than their subordinates. ETS activity increased in fish exposed to high temperatures; however, there was no effect on social rank. Our study reinforces the importance of environmental changes for the maintenance of hierarchies and their characteristics and highlights that most of the changes occur in the dominant position. Copyright © 2015 Elsevier Inc. All rights reserved.

Solubility of crude oil in methane as a function of pressure and temperature

USGS Publications Warehouse

Price, L.C.; Wenger, L.M.; Ging, T.; Blount, C.W.

1983-01-01

The solubility of a 44?? API (0.806 sp. gr.) whole crude oil has been measured in methane with water present at temperatures of 50 to 250??C and pressures of 740 to 14,852 psi, as have the solubilities of two high molecular weight petroleum distillation fractions at temperatures of 50 to 250??C and pressures of 4482 to 25,266 psi. Both increases in pressure and temperature increase the solubility of crude oil and petroleum distillation fractions in methane, the effect of pressure being greater than that of temperature. Unexpectedly high solubility levels (0.5-1.5 grams of oil per liter of methane-at laboratory temperature and pressure) were measured at moderate conditions (50-200??C and 5076-14504 psi). Similar results were found for the petroleum distillation fractions, one of which was the highest molecular weight material of petroleum (material boiling above 266??C at 6 microns pressure). Unexpectedly mild conditions (100??C and 15,200 psi; 200??C and 7513 psi) resulted in cosolubility of crude oil and methane. Under these conditions, samples of the gas-rich phase gave solubility values of 4 to 5 g/l, or greater. Qualitative analyses of the crude-oil solute samples showed that at low pressure and temperature equilibration conditions, the solute condensate would be enriched in C5-C15 range hydrocarbons and in saturated hydrocarbons in the C15+ fraction. With increases in temperature and especially pressure, these tendencies were reversed, and the solute condensate became identical to the starting crude oil. The data of this study, compared to that of previous studies, shows that methane, with water present, has a much greater carrying capacity for crude oil than in dry systems. The presence of water also drastically lowers the temperature and pressure conditions required for cosolubility. The data of this and/or previous studies demonstrate that the addition of carbon dioxide, ethane, propane, or butane to methane also has a strong positive effect on crude oil solubility, as does the presence of fine grained rocks. The n-paraffin distributions (as well as the overall composition) of the solute condensates are controlled by the temperature and pressure of solution and exsolution, as well as by the composition of the original starting material. It appears quite possible that primary migration by gaseous solution could 'strip' a source rock of crude-oil like components leaving behind a bitumen totally unlike the migrated crude oil. The data of this study demonstrate previous criticisms of primary petroleum migration by gas solution are invalid; that primary migration by gaseous solution cannot occur because methane cannot dissolve sufficient volumes of crude oil or cannot dissolve the highest molecular weight components of petroleum (tars and asphaltenes). ?? 1983.

Biophysical drivers of seasonal variability in Sphagnum gross primary production in a northern temperate bog

Treesearch

Anthony P. Walker; Kelsey R. Carter; Lianhong Gu; Paul J. Hanson; Avni Malhotra; Richard J. Norby; Stephen D. Sebestyen; Stan D. Wullschleger; David J. Weston

2017-01-01

Sphagnum mosses are the keystone species of peatland ecosystems. With rapid rates of climate change occurring in high latitudes, vast reservoirs of carbon accumulated over millennia in peatland ecosystems are potentially vulnerable to rising temperature and changing precipitation. We investigate the seasonal drivers of Sphagnum...

Picritic glasses from Hawaii

USGS Publications Warehouse

Clague, D.A.; Weber, W.S.; Dixon, J.E.

1991-01-01

ESTIMATES of the MgO content of primary Hawaiian tholeiitic melts range from 8wt% to as high as 25wt% (refs 1, 2). In general, these estimates are derived from analysis of the whole-rock composition of lavas, coupled with the compositions of the most magnesian olivine phenocrysts observed. But the best estimate of magma composition comes from volcanic glass, as it represents the liquid composition at the time of quenching; minimal changes occur during the quenching process. Here we report the discovery of tholeiitic basalt glasses, recovered offshore of Kilauea volcano, that contain up to 15.0 wt% MgO. To our knowledge, these are the most magnesian glasses, and have the highest eruption temperatures (??? 1,316 ??C), yet found. The existence of these picritic (high-MgO) liquids provides constraints on the temperature structure of the upper mantle, magma transport and the material and thermal budgets of the Hawaiian volcanoes. Furthermore, picritic melts are affected little by magma-reservoir processes, and it is therefore relatively straightforward to extrapolate back to the composition of the primary melt and its volatile contents.

Mechanical Properties of T650-35/AFR-PE-4 at Elevated Temperatures for Lightweight Aeroshell Designs

NASA Technical Reports Server (NTRS)

Whitley, Karen S.; Collins, TImothy J.

2006-01-01

Considerable efforts have been underway to develop multidisciplinary technologies for aeroshell structures that will significantly increase the allowable working temperature for the aeroshell components, and enable the system to operate at higher temperatures while sustaining performance and durability. As part of these efforts, high temperature polymer matrix composites and fabrication technologies are being developed for the primary load bearing structure (heat shield) of the spacecraft. New high-temperature resins and composite material manufacturing techniques are available that have the potential to significantly improve current aeroshell design. In order to qualify a polymer matrix composite (PMC) material as a candidate aeroshell structural material, its performance must be evaluated under realistic environments. Thus, verification testing of lightweight PMC's at aeroshell entry temperatures is needed to ensure that they will perform successfully in high-temperature environments. Towards this end, a test program was developed to characterize the mechanical properties of two candidate material systems, T650-35/AFR-PE-4 and T650-35/RP46. The two candidate high-temperature polyimide resins, AFR-PE-4 and RP46, were developed at the Air Force Research Laboratory and NASA Langley Research Center, respectively. This paper presents experimental methods, strength, and stiffness data of the T650-35/AFR-PE-4 material as a function of elevated temperatures. The properties determined during the research test program herein, included tensile strength, tensile stiffness, Poisson s ratio, compressive strength, compressive stiffness, shear modulus, and shear strength. Unidirectional laminates, a cross-ply laminate and two eight-harness satin (8HS)-weave laminates (4-ply and 10-ply) were tested according to ASTM standard methods at room and elevated temperatures (23, 316, and 343 C). All of the relevant test methods and data reduction schemes are outlined along with mechanical data. These data contribute to a database of material properties for high-temperature polyimide composites that will be used to identify the material characteristics of potential candidate materials for aeroshell structure applications.

Reforming and decomposition of glucose in an aqueous phase

NASA Technical Reports Server (NTRS)

Amin, S.; Reid, R. C.; Modell, M.

1975-01-01

Exploratory experiments have been carried out to study the decomposition of glucose, a typical carbohydrate, in a high temperature-high pressure water reactor. The objective of the study was to examine the feasibility of such a process to decompose cellulosic waste materials in long-term space missions. At temperatures below the critical point of water, glucose decomposed to form liquid products and char. Little gas was noted with or without reforming catalysts present. The rate of the primary glucose reaction increased significantly with temperature. Partial identification of the liquid phase was made and the C:H:O ratios determined for both the liquid and solid products. One of the more interesting results from this study was the finding that when glucose was injected into a reactor held at the critical temperature (and pressure) of water, no solid products formed. Gas production increased, but the majority of the carbon was found in soluble furans (and furan derivatives). This significant result is now being investigated further.

On the determination of growth stress during oxidation of pure zirconium at elevated temperature

NASA Astrophysics Data System (ADS)

Kurpaska, L.; Favergeon, J.; Lahoche, L.; Moulin, G.

2018-07-01

An experimental approach have been proposed to evaluate growth of stress during high temperature oxidation of pure zirconium. The development of stress in the oxide scale has been investigated experimentally in in-situ conditions by combining the Deflection Test in Monofacial Oxidation (DTMO) with Acoustic Emission analysis (AE). Microstructure of the sample were studied by using Scanning Electron Microscopy technique. Oxidation experiments were performed continuously during 24 h at 400 °C and 500 °C in air under normal atmospheric pressure. Taking into account purely elastic behaviour of the material, primary evolution of growth stress developed in the oxide scale during oxidation process have been estimated. Presented study of the Zr/ZrO2 system revealed two opposite phenomena of stress relief when cooling from 400 °C and 500 °C to room temperature. This study is presented as a tool to understand the phenomena of stress evolution in the zirconia layer during isothermal treatment at high temperature and after cooling.

Prevention of hypothermia in patients undergoing orthotopic liver transplantation using the humigard® open surgery humidification system: a prospective randomized pilot and feasibility clinical trial.

PubMed

Weinberg, Laurence; Huang, Andrew; Alban, Daniel; Jones, Robert; Story, David; McNicol, Larry; Pearce, Brett

2017-01-23

Perioperative thermal disturbances during orthotopic liver transplantation (OLT) are common. We hypothesized that in patients undergoing OLT the use of a humidified high flow CO 2 warming system maintains higher intraoperative temperatures when compared to standardized multimodal strategies to maintain thermoregulatory homeostasis. We performed a randomized pilot study in adult patients undergoing primary OLT. Participants were randomized to receive either open wound humidification with a high flow CO 2 warming system in addition to standard care (Humidification group) or to standard care alone (Control group). The primary end point was nasopharyngeal core temperature measured 5 min immediately prior to reperfusion of the donor liver (Stage 3 - 5 min). Secondary endpoints included intraoperative PaCO 2 , minute ventilation and the use of vasoconstrictors. Eleven patients were randomized to each group. Both groups were similar for age, body mass index, MELD, SOFA and APACHE II scores, baseline temperature, and duration of surgery. Immediately prior to reperfusion (Stage 3 - 5 min) the mean (SD) core temperature was higher in the Humidification Group compared to the Control Group: 36.0 °C (0.13) vs. 35.4 °C (0.22), p = 0.028. Repeated measured ANOVA showed that core temperatures over time during the stages of the transplant were higher in the Humidification Group compared to the Control Group (p < 0.0001). There were no significant differences in the ETCO 2 , PaCO 2 , minute ventilation, or inotropic support. The humidified high flow CO 2 warming system was superior to standardized multimodal strategies in maintaining normothermia in patients undergoing OLT. Use of the device was feasible and did not interfere with any aspects of surgery. A larger study is needed to investigate if the improved thermoregulation observed is associated with improved patient outcomes. ACTRN12616001631493 . Retrospectively registered 25 November 2016.

Amorphous metallizations for high-temperature semiconductor device applications

NASA Technical Reports Server (NTRS)

Wiley, J. D.; Perepezko, J. H.; Nordman, J. E.; Kang-Jin, G.

1981-01-01

The initial results of work on a class of semiconductor metallizations which appear to hold promise as primary metallizations and diffusion barriers for high temperature device applications are presented. These metallizations consist of sputter-deposited films of high T sub g amorphous-metal alloys which (primarily because of the absence of grain boundaries) exhibit exceptionally good corrosion-resistance and low diffusion coefficients. Amorphous films of the alloys Ni-Nb, Ni-Mo, W-Si, and Mo-Si were deposited on Si, GaAs, GaP, and various insulating substrates. The films adhere extremely well to the substrates and remain amorphous during thermal cycling to at least 500 C. Rutherford backscattering and Auger electron spectroscopy measurements indicate atomic diffussivities in the 10 to the -19th power sq cm/S range at 450 C.

Bis(4-(3,4-dimethylenepyrrolidyl)-phenyl) methane

NASA Technical Reports Server (NTRS)

Ottenbrite, Raphael M. (Inventor)

1989-01-01

It is the primary object of the present invention to prepare high temperature polymeric materials, especially linear aromatic polyimides, which maintain their integrity and toughness during long exposure times at elevated temperatures. According to the present invention, this object is achieved, and the attending benefits are obtained, by first providing the bis(exocyclodiene) bis(4-(3,4-dinethylene pyrrolidyl) phenyl) methane, which is formed from the monomer N-phenyl 3,4-dimethylene pyrrolidine. This bis-(exocyclodiene) undergoes Diels-Alder reaction with a bismaleimide without the evolution of gaseous by-products, to form the aromatic polyimide.

Thermal conductivity of zirconia thermal barrier coatings

NASA Technical Reports Server (NTRS)

Dinwiddie, R. B.; Beecher, S. C.; Nagaraj, B. A.; Moore, C. S.

1995-01-01

Thermal barrier coatings (TBC's) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBC's is of primary importance. Physical vapor description (PVD) and plasma spraying (PS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The PS coatings were applied with either standard power or hollow sphere particles. The hollow sphere particles yielded a lower density and lower thermal conductivity coating. The thermal conductivity of both fully and partially stabilized zirconia, before and after thermal aging, will be compared. The thermal conductivity of the coatings permanently increase upon being exposed to high temperatures. These increases are attributed to microstructural changes within the coatings. Sintering of the as fabricated plasma sprayed lamellar structure is observed by scanning electron microscopy of coatings isothermally heat treated at temperatures greater than 1100 C. During this sintering process the planar porosity between lamella is converted to a series of small spherical pores. The change in pore morphology is the primary reason for the observed increase in thermal conductivity. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the PVD coatings are less susceptible to thermal aging effects, preliminary results suggest that they have a higher thermal conductivity than PS coatings, both before and after thermal aging. The increases in thermal conductivity due to thermal aging for partially stabilized plasma sprayed zirconia have been found to be less than for fully stabilized plasma sprayed zirconia coatings. The high temperature thermal diffusivity data indicates that if these coatings reach a temperature above 1100 C during operation, they will begin to lose their effectiveness as a thermal barrier.

Thermal conductivity of zirconia thermal barrier coatings

NASA Technical Reports Server (NTRS)

Dinwiddie, R. B.; Beecher, S. C.; Nagaraj, B. A.; Moore, C. S.

1995-01-01

Thermal barrier coatings (TBC's) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBC's is of primary importance. Physical vapor deposition (PVD) and plasma spraying (PS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The PS coatings were applied with either standard powder or hollow sphere particles. The hollow sphere particles yielded a lower density and lower thermal conductivity coating. The thermal conductivity of both fully and partially stabilized zirconia, before and after thermal aging, will be compared. The thermal conductivity of the coatings permanently increases upon exposed to high temperatures. These increases are attributed to microstructural changes within the coatings. Sintering of the as-fabricated plasma sprayed lamellar structure is observed by scanning electron microscopy of coatings isothermally heat treated at temperatures greater than 1100 C. During this sintering process the planar porosity between lamella is converted to a series of small spherical pores. The change in pore morphology is the primary reason for the observed increase in thermal conductivity. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the PVD coatings are less susceptible to thermal aging effects, preliminary results suggest that they have a higher thermal conductivity than PS coatings, both before and after thermal aging. The increases in thermal conductivity due to thermal aging for partially stabilized plasma sprayed zirconia have been found to be less than for fully stabilized plasma sprayed zirconia coatings. The high temperature thermal diffusivity data indicate that if these coatings reach a temperature above 1100 C during operation, they will begin to lose their effectiveness as a thermal barrier.

Fuel development for gas-cooled fast reactors

NASA Astrophysics Data System (ADS)

Meyer, M. K.; Fielding, R.; Gan, J.

2007-09-01

The Generation IV Gas-cooled Fast Reactor (GFR) concept is proposed to combine the advantages of high-temperature gas-cooled reactors (such as efficient direct conversion with a gas turbine and the potential for application of high-temperature process heat), with the sustainability advantages that are possible with a fast-spectrum reactor. The latter include the ability to fission all transuranics and the potential for breeding. The GFR is part of a consistent set of gas-cooled reactors that includes a medium-term Pebble Bed Modular Reactor (PBMR)-like concept, or concepts based on the Gas Turbine Modular Helium Reactor (GT-MHR), and specialized concepts such as the Very High-Temperature Reactor (VHTR), as well as actinide burning concepts [A Technology Roadmap for Generation IV Nuclear Energy Systems, US DOE Nuclear Energy Research Advisory Committee and the Generation IV International Forum, December 2002]. To achieve the necessary high power density and the ability to retain fission gas at high temperature, the primary fuel concept proposed for testing in the United States is dispersion coated fuel particles in a ceramic matrix. Alternative fuel concepts considered in the US and internationally include coated particle beds, ceramic clad fuel pins, and novel ceramic 'honeycomb' structures. Both mixed carbide and mixed nitride-based solid solutions are considered as fuel phases.

The effect of temperature on pulsed positive streamer discharges in air over the range 292 K–1438 K

NASA Astrophysics Data System (ADS)

Ono, Ryo; Ishikawa, Yuta

2018-05-01

The effect of temperature on pulsed positive streamer discharges in air is measured by comparing atmospheric-pressure, high-temperature discharges with low-pressure, room-temperature discharges at the same air densities n and discharge voltages. Both discharges have the same reduced electric field E/n, so the differences between the two discharges only depend on the temperature, which is varied from 292 K to 1438 K. Temperature affects the discharge pulse energy most significantly; at 1438 K, the energy of an atmospheric-pressure discharge pulse is approximately 30 times larger than that of the corresponding 20.5 kPa, room-temperature discharge. Temperature also affects the shapes of the streamers when K, but no significant effect is observed for K. There is also no significant temperature effect on the spatially integrated intensity of N2(C–B) emission. However, temperature strongly affects the ratio of the integrated emission intensity to the discharge energy. No effect of the temperature is observed on the propagation velocity of the primary streamer or on the length of the secondary streamer.

The temperature of primary melts and mantle sources of komatiites, OIBs, MORBs and LIPs

NASA Astrophysics Data System (ADS)

Sobolev, Alexander

2015-04-01

There is general agreement that the convecting mantle, although mostly peridotitic in composition, is compositionally and thermally heterogeneous on different spatial scales. The amount, sizes, temperatures and compositions of these heterogeneities significantly affect mantle dynamics because they may diverge greatly from dominant peridotites in their density and fusibility. Differences in potential temperature and composition of mantle domains affect magma production and cannot be easily distinguished from each other. This has led to radically different interpretations of the melting anomalies that produce ocean-island basalts, large igneous provinces and komatiites: most scientists believe that they originate as hot, deep-sourced mantle plumes; but a small though influential group (e.g. Anderson 2005, Foulger, 2010) propose that they derive from high proportions of easily fusible recycled or delaminated crust, or in the case of komatiites contain large amount of H2O (e.g. Grove & Parman, 2004). The way to resolve this ambiguity is an independent estimation of temperature and composition of mantle sources of various types of magma. In this paper I report application of newly developed olivine-spinel-melt geothermometers based on partition of Al, Cr, Sc and Y for different primitive lavas from mid-ocean ridges, ocean-island basalts, large igneous provinces and komatiites. The results suggest significant variations of crystallization temperature for the same Fo of high magnesium olivines of different types of mantle-derived magmas: from the lowest (down to 1220 degree C) for MORB to the highest (up to over 1500 degree C) for komatiites and Siberian meimechites. These results match predictions from Fe-Mg olivine-melt equilibrium and confirm the relatively low temperature of the mantle source of MORB and higher temperatures in the mantle plumes that produce the OIB of Iceland, Hawaii, Gorgona, Archean komatiites and several LIPs (e.g Siberian and NAMP). The established liquidus temperatures and compositions of primary melts allow estimating potential temperatures and compositions of their mantle sources. The results strongly confirm mantle plume theory and presence of variable amounts of recycled crustal material in the mantle sources. This study has been founded by Russian Science Foundation grant 14-17-00491.

Stacking Defects in Synthetic and Meteoritic Hibonites: Implications for High-Temperature Processes in the Solar Nebula

NASA Technical Reports Server (NTRS)

Han, J.; Keller, L. P.; Brearley, A. J.; Danielson, L. R.

2016-01-01

Hibonite (CaAl12O19) is a primary, highly refractory phase occurring in many Ca-Al-rich inclusions (CAIs) from different chondrite groups, except CI chondrites. Hibonite is predicted to be one of the earliest minerals to condense during cooling of the solar nebula at higher temperatures than any other major CAI mineral. Therefore, hibonite has great potential to reveal the processes and conditions of the very early, high-temperature stages of the solar nebular evolution. Previous microstructural studies of hibonite in CAIs and their Wark-Lovering (WL) rims showed the presence of numerous stacking defects in hibonite. These defects are interpreted as the modification of the stacking sequences of spinel and Ca-containing blocks within the ideal hexagonal hibonite structure, as shown by experimental studies of reaction-sintered ceramic CaO-Al2O3 compounds. We performed preliminary experiments in the CaO-Al2O3-MgO system to understand the formation processes and conditions of defect-structured hibonite found in meteorites.

Fracture Mechanisms For SiC Fibers And SiC/SiC Composites Under Stress-Rupture Conditions at High Temperatures

NASA Technical Reports Server (NTRS)

DiCarlo, James A.; Yun, Hee Mann; Hurst, Janet B.; Viterna, L. (Technical Monitor)

2002-01-01

The successful application of SiC/SiC ceramic matrix composites as high-temperature structural materials depends strongly on maximizing the fracture or rupture life of the load-bearing fiber and matrix constituents. Using high-temperature data measured under stress-rupture test conditions, this study examines in a mechanistic manner the effects of various intrinsic and extrinsic factors on the creep and fracture behavior of a variety of SiC fiber types. It is shown that although some fiber types fracture during a large primary creep stage, the fiber creep rate just prior to fracture plays a key role in determining fiber rupture time (Monkman-Grant theory). If it is assumed that SiC matrices rupture in a similar manner as fibers with the same microstructures, one can develop simple mechanistic models to analyze and optimize the stress-rupture behavior of SiC/SiC composites for applied stresses that are initially below matrix cracking.

A high temperature hybrid photovoltaic-thermal receiver employing spectral beam splitting for linear solar concentrators

NASA Astrophysics Data System (ADS)

Mojiri, Ahmad; Stanley, Cameron; Rosengarten, Gary

2015-09-01

Hybrid photovoltaic/thermal (PV-T) solar collectors are capable of delivering heat and electricity concurrently. Implementing such receivers in linear concentrators for high temperature applications need special considerations such as thermal decoupling of the photovoltaic (pv) cells from the thermal receiver. Spectral beam splitting of concentrated light provides an option for achieving this purpose. In this paper we introduce a relatively simple hybrid receiver configuration that spectrally splits the light between a high temperature thermal fluid and silicon pv cells using volumetric light filtering by semi-conductor doped glass and propylene glycol. We analysed the optical performance of this device theoretically using ray tracing and experimentally through the construction and testing of a full scale prototype. The receiver was mounted on a commercial parabolic trough concentrator in an outdoor experiment. The prototype receiver delivered heat and electricity at total thermal efficiency of 44% and electrical efficiency of 3.9% measured relative to the total beam energy incident on the primary mirror.

A combined temperature-dependent electron and single-crystal X-ray diffraction study of the fresnoite compound Rb 2V 4+V 25+O 8

NASA Astrophysics Data System (ADS)

Withers, Ray L.; Höche, Thomas; Liu, Yun; Esmaeilzadeh, Saeid; Keding, Ralf; Sales, Brian

2004-10-01

High-purity Rb2V3O8 has been grown and temperature-dependent electron and single-crystal X-ray diffraction used to carefully investigate its fresnoite-type reciprocal lattice. In contrast to other recently investigated representatives of the fresnoite family of compounds, Rb2V3O8 is not incommensurately modulated with an incommensurate basal plane primary modulation wave vector given by q∼0.3 <110>*. A careful low-temperature electron diffraction study has, however, revealed the existence of weak incommensurate satellite reflections characterized by the primitive primary modulation wave vector q1∼0.16c*. The reciprocal space positioning of these incommensurate satellite reflections, the overall (3+1)-d superspace group symmetry, as well as the shapes of the refined displacement ellipsoids determined from single-crystal XRD refinement, are all consistent with their arising from a distinct type of condensed rigid unit modes (RUMs) of distortion of the Rb2V3O8 parent structure.

Factors controlling the geochemical evolution of fumarolic encrustations, Valley of Ten Thousand Smokes, Alaska

USGS Publications Warehouse

Kodosky, L.G.; Keith, T.E.C.

1993-01-01

Factor and canonical correlation analysis of geochemical data from eight fossil fumaroles suggest that six major factors controlled the formation and evolution of fumarolic encrustations on the 1912 ash-flow sheet in the Valley of Ten Thousand Smokes (VTTS). The six-factor solution model explains a large proportion (low of 74% for Ni to high of 99% for Si) of the individual element data variance. Although the primary fumarolic deposits have been degraded by secondary alteration reactions and up to 75 years of weathering, the relict encrustations still preserve a signature of vapor-phase element transport. This vapor-phase transport probably occurred as halide or oxyhalide species and was significant for As, Sb and Br. At least three, and possibly four, varied temperature leaching events affected the fumarolic deposits. High-temperature gases/liquids heavily altered the ejecta glass and mineral phases adjacent to the fumarolic conduit. As the fumaroles cooled. Fe-rich acidic condensate leached the ejecta and primary fumarolic deposits and resulted in the subsequent precipitation of Fe-hydroxides and/or Fe-oxides. Low- to ambient-temperature leaching and hydration reactions generated abundant hydrated amorphous phases. Up to 87% of the individual element data variance is apparently controlled by the chemistry of the ejecta on which the relict encrustations are found. This matrix chemistry factor illustrates that the primary fumarolic minerals surrounding the active VTTS vents observed by earlier workers have been effectively removed by the dissolution reactions. Element enrichment factors calculated for the VTTS relict encrustations support the statistical factor interpretations. On the average, the relict encrustations are enriched, relative to visibly unaltered matrix protolith, in As, Br, Cr, Sb, Cu, Ni, Pb, Fe, and LOI (an indirect measure of sample H2O content). ?? 1993.

Approximate similarity principle for a full-scale STOVL ejector

NASA Astrophysics Data System (ADS)

Barankiewicz, Wendy S.; Perusek, Gail P.; Ibrahim, Mounir B.

1994-03-01

Full-scale ejector experiments are expensive and difficult to implement at engine exhaust temperatures. For this reason the utility of using similarity principles, in particular the Munk and prim principle for isentropic flow, was explored. Static performance test data for a full-scale thrust augmenting ejector were analyzed for primary flow temperature up to 1560 R. At different primary temperatures, exit pressure contours were compared for similarity. A nondimensional flow parameter is then used to eliminate primary nozzle temperature dependence and verify similarity between the hot and cold flow experiments. Under the assumption that an appropriate similarity principle can be established, properly chosen performance parameters were found to be similar for both flow and cold flow model tests.

Magnetic properties and crystallization kinetics of (Fe 100–xNi x) 80Nb 4Si 2B 14 metal amorphous nanocomposites

DOE PAGES

Aronhime, Natan; Zoghlin, Eli; Keylin, Vladimir; ...

2017-09-26

Fe-Ni based metal amorphous nanocomposites (MANCs) are investigated in the pseudo-binary alloys (Fe 100–xNi x) 80Nb 4Si 2B 14. To optimize the soft magnetic properties of the nanocomposites, primary and secondary crystallization kinetics must be understood. As such, primary and secondary crystallization temperatures are determined by differential scanning calorimetry, and activation energies are calculated, along with the resulting crystalline phases. Time-temperature-transformation diagrams for primary and secondary crystallization in (Fe 70Ni 30) 80Nb 4Si 2B 14 are presented. Saturation magnetization and Curie temperature are determined. In conclusion, the shape of magnetization vs. time curves for (Fe 30Ni 70) 80Nb 4Si 2Bmore » 14 at various temperatures suggest that the secondary crystal product often consumes some of the primary crystalline product.« less

A 28-ka history of sea surface temperature, primary productivity and planktonic community variability in the western Arabian Sea

NASA Astrophysics Data System (ADS)

Pourmand, Ali; Marcantonio, Franco; Bianchi, Thomas S.; Canuel, Elizabeth A.; Waterson, Elizabeth J.

2007-12-01

Uranium series radionuclides and organic biomarkers, which represent major groups of planktonic organisms, were measured in western Arabian Sea sediments that span the past 28 ka. Variability in the past strength of the southwest and northeast monsoons and its influence on primary productivity, sea surface temperature (SST), and planktonic community structure were investigated. The average alkenone-derived SST for the last glacial period was ˜3°C lower than that measured for the Holocene. Prior to the deglacial, the lowest SSTs coincide with the highest measured fluxes of organic biomarkers, which represent primarily a planktonic suite of diatoms, coccolithophorids, dinoflagellates, and zooplankton. We propose that intensification of winter northeast monsoon winds during the last glacial period resulted in deep convective mixing, cold SSTs and enhanced primary productivity. In contrast, postdeglacial (<17 ka) SSTs are warmer during times in which biomarker fluxes are high. Associated with this transition is a planktonic community structure change, in which the ratio of the average cumulative flux of diatom biomarkers to the cumulative flux of coccolithophorid biomarkers is twice as high during the deglacial and Holocene than the average ratio during the last glacial period. We suggest that this temporal transition represents a shift from a winter northeast monsoon-dominated (pre-17 ka) to a summer southwest monsoon-dominated (post-17 ka) wind system.

Habitat of calling blue and fin whales in the Southern California Bight

NASA Astrophysics Data System (ADS)

Sirovic, A.; Chou, E.; Roch, M. A.

2016-02-01

Northeast Pacific blue whale B calls and fin whale 20 Hz calls were detected from passive acoustic data collected over seven years at 16 sites in the Southern California Bight (SCB). Calling blue whales were most common in the coastal areas, during the summer and fall months. Fin whales began calling in fall and continued through winter, in the southcentral SCB. These data were used to develop habitat models of calling blue and fin whales in areas of high and low abundance in the SCB, using remotely sensed variables such as sea surface temperature, sea surface height, chlorophyll a, and primary productivity as model covariates. A random forest framework was used for variable selection and generalized additive models were developed to explain functional relationships, evaluate relative contribution of each significant variable, and investigate predictive abilities of models of calling whales. Seasonal component was an important feature of all models. Additionally, areas of high calling blue and fin whale abundance both had a positive relationship with the sea surface temperature. In areas of lower abundance, chlorophyll a concentration and primary productivity were important variables for blue whale models and sea surface height and primary productivity were significant covariates in fin whale models. Predictive models were generally better for predicting general trends than absolute values, but there was a large degree of variation in year-to-year predictability across different sites.

Methods and systems for the production of hydrogen

DOEpatents

Oh, Chang H [Idaho Falls, ID; Kim, Eung S [Ammon, ID; Sherman, Steven R [Augusta, GA

2012-03-13

Methods and systems are disclosed for the production of hydrogen and the use of high-temperature heat sources in energy conversion. In one embodiment, a primary loop may include a nuclear reactor utilizing a molten salt or helium as a coolant. The nuclear reactor may provide heat energy to a power generation loop for production of electrical energy. For example, a supercritical carbon dioxide fluid may be heated by the nuclear reactor via the molten salt and then expanded in a turbine to drive a generator. An intermediate heat exchange loop may also be thermally coupled with the primary loop and provide heat energy to one or more hydrogen production facilities. A portion of the hydrogen produced by the hydrogen production facility may be diverted to a combustor to elevate the temperature of water being split into hydrogen and oxygen by the hydrogen production facility.

New Method for Characterizing the State of Optical and Opto-Mechanical Systems

NASA Technical Reports Server (NTRS)

Keski-Kuha, Ritva; Saif, Babak; Feinberg, Lee; Chaney, David; Bluth, Marcel; Greenfield, Perry; Hack, Warren; Smith, Scott; Sanders, James

2014-01-01

James Webb Space Telescope Optical Telescope Element (OTE) is a three mirror anastigmat consisting of a 6.5 m primary mirror (PM), secondary mirror (SM) and a tertiary mirror. The primary mirror is made out of 18 segments. The telescope and instruments will be assembled at Goddard Space Flight Center (GSFC) to make it the Optical Telescope Element-Integrated Science Instrument Module (OTIS). The OTIS will go through environmental testing at GSFC before being transported to Johnson Space Center for testing at cryogenic temperature. The objective of the primary mirror Center of Curvature test (CoC) is to characterize the PM before and after the environmental testing for workmanship. This paper discusses the CoC test including both a surface figure test and a new method for characterizing the state of the primary mirror using high speed dynamics interferometry.

Synthesis of diamond films at low temperature and study of nonlinear dynamic synthesis process

NASA Astrophysics Data System (ADS)

Zhao, Qingxun; Shang, Yong; Dong, Lifang; Fu, Guangsheng; Yan, Zheng; Yang, Jingfa

2002-09-01

In this paper, the experimental synthesis of diamond films and optical emission spectroscopy (OES) of the gaseous phase species are studied in the range of substrate temperature from Ts = 300°C to 850°C. The high quality sub-microcrystalline diamond films are successfully deposited at substrate temperature (330 ≍ 340)°C by adopting glow plasma assisted hot filament chemical vapor deposition (GPCVD). For the first time, in situ OES is applied to diagnose weak signal of GPCVD system when CH4 and H2 are used as the input gas, and the reactive species are identified in diamond growth processes. A primary model of diamond films growing at low temperature is presented by studying dynamic behavior for nonequilibrium plasma reactions.

Superalloy for high-temperature hydrogen environmental applications

NASA Technical Reports Server (NTRS)

McKannan, Eugene C. (Inventor); McPherson, William B. (Inventor); Ahmed, Shaffiq (Inventor); Chandler, Shirley S. (Inventor)

1991-01-01

A nickel-based superalloy is provided which is resistant to deterioration in hydrogen at high operating temperatures and pressures, and which thus can be used in hydrogen-fueled spacecraft such as the Space Shuttle. The superalloy is characterized by a two-phase microstructure and consists of a gamma-prime precipitated phase in a gamma matrix. The gamma matrix phase is a primary solid solution and the gamma precipitated phase will be an intermetallic compound of the type A.sub.3 B, such as nickel aluminide or titanide. Both phases are coherent, ordered, and compatible, and thus will retain most of their strength at elevated temperatures. The alloy consists essentially of (by weight): Ni 50-60%, Cr 10-20%, Al 2-6%, Co 2-5%, Ti 3-8%, W 5-12%, Mo 5-10%, Nb 1-3%, wherein the ratio W/MO is approximately equal to 1, and Ti/Al ranges from about 1 to about 2.

A fiber-optic current sensor for aerospace applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Rose, A. H.; Tang, D.; Day, G. W.

1990-01-01

A robust, accurate, broad-band, alternating current sensor using fiber optics is being developed for space applications at power frequencies as high as 20 kHz. It can also be used in low and high voltage 60 Hz terrestrial power systems and in 400 Hz aircraft systems. It is intrinsically electromagnetic interference (EMI) immune and has the added benefit of excellent isolation. The sensor uses the Faraday effect in optical fiber and standard polarimetric measurements to sense electrical current. The primary component of the sensor is a specially treated coil of single-mode optical fiber, through which the current carrying conductor passes. Improved precision is accomplished by temperature compensation by means of signals from a novel fiber-optic temperature sensor embedded in the sensing head. The technology contained in the sensor is examined and the results of precision tests conducted at various temperatures within the wide operating range are given. The results of early EMI tests are also given.

A fiber-optic current sensor for aerospace applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Rose, A. H.; Tang, D.; Day, G. W.

1990-01-01

A robust, accurate, broadband, alternating current sensor using fiber optics is being developed for space applications at power frequencies as high as 20 kHz. It can also be used in low and high voltage 60-Hz terrestrial power systems and in 400-Hz aircraft systems. It is intrinsically electromagnetic interference (EMI) immune and has the added benefit of excellent isolation. The sensor uses the Faraday effect in optical fiber and standard polarimetric measurements to sense electrical current. The primary component of the sensor is a specially treated coil of single-mode optical fiber, through which the current carrying conductor passes. Improved precision is accomplished by temperature compensation by means of signals from a novel fiber-optic temperature sensor embedded in the sensing head. The technology used in the sensor is examined and the results of precision tests conducted at various temperatures within the wide operating range are given. The results of early EMI tests are also given.

A fiber-optic current sensor for aerospace applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Rose, A. H.; Tang, D.; Day, G. W.

1990-01-01

A robust, accurate, broadband, alternating current sensor using fiber optics is being developed for space applications at power frequencies as high as 20 kHz. It can also be used in low- and high-voltage 60-Hz terrestrial power systems and in 400-Hz aircraft systems. It is intrinsically EMI (electromagnetic interference) immune and has the added benefit of excellent isolation. The sensor uses the Faraday effect in optical fiber and standard polarimetric measurements to sense electrical current. The primary component of the sensor is a specially treated coil of single-mode optical fiber, through which the current carrying conductor passes. Improved precision is accomplished by temperature compensation by means of signals from a fiber-optic temperature sensor embedded in the sensing head. The authors report on the technology contained in the sensor and also relate the results of precision tests conducted at various temperatures within the wide operating range. The results of early EMI tests are shown.

Importance of Electronic Correlations and Unusual Excitonic Effects in Formamidinium Lead Halide Perovskites

NASA Astrophysics Data System (ADS)

Whitcher, T. J.; Zhu, J.-X.; Chi, X.; Hu, H.; Zhao, Daming; Asmara, T. C.; Yu, X.; Breese, M. B. H.; Castro Neto, A. H.; Lam, Y. M.; Wee, A. T. S.; Chia, Elbert E. M.; Rusydi, A.

2018-04-01

Hybrid inorganic-organic perovskites have recently attracted much interest because of both rich fundamental sciences and potential applications such as the primary energy-harvesting material in solar cells. However, an understanding of electronic and optical properties, particularly the complex dielectric function, of these materials is still lacking. Here, we report on the electronic and optical properties of selective perovskites using temperature-dependent spectroscopic ellipsometry, x-ray absorption spectroscopy supported by first-principles calculations. Surprisingly, the perovskite FA0.85Cs0.15PbI2.9Br0.1 has a very high density of low-energy excitons that increases with increasing temperature even at room temperature, which is not seen in any other material. This is found to be due to the strong, unscreened electron-electron and partially screened electron-hole interactions, which then tightly connect low- and high-energy bands caused by doping.

Bromide-free TEMPO-mediated oxidation of primary alcohol groups in starch and methyl alpha-D-glucopyranoside.

PubMed

Bragd, P L; Besemer, A C; van Bekkum, H

2000-09-22

TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)-mediated oxidation of potato starch and methyl alpha-D-glucopyranoside (MGP) was performed in the absence of sodium bromide (NaBr) as co-catalyst, solely using sodium hypochlorite (NaOCl) as the primary oxidant. The low reaction rate associated with a bromide-free process was increased by performing the oxidation at increased temperatures. The reaction proceeded stoichiometrically and with high selectivity and with only minor depolymerisation, provided that temperature and pH were kept < or = 20 degrees C and < 9.0, respectively. At 20 degrees C and pH 8.5, the reaction rate was comparable to that of a corresponding oxidation catalysed by NaBr at 2 degrees C. Consequently, this is a simple approach to raise the TEMPO/NaOCl reaction rate under bromide-free conditions while still maintaining good product properties. At higher oxidation temperatures (> or = 25 degrees C) and under more alkaline conditions (pH > or = 9.0) degradation of the starch skeleton occurred. Simultaneously, side-reactions of the nitrosonium ion lowered the yield of the oxidation. Despite the absence of the NaBr catalyst, the reaction rate-controlling step was found to be the oxidation of the primary hydroxyl groups with the nitrosonium ion. The reaction was first-order in MGP and in TEMPO.

Feasibility Assessment of Thermal Barrier Seals for Extreme Transient Temperatures

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Dunlap, Patrick H., Jr.

1998-01-01

The assembly joints of modem solid rocket motor cases are generally sealed using conventional O-ring type seals. The 5500+ F combustion gases produced by rocket motors are kept a safe distance away from the seals by thick layers of phenolic insulation. Special compounds are used to fill insulation gaps leading up to the seals to prevent a direct flowpath to them. Design criteria require that the seals should not experience torching or charring during operation, or their sealing ability would be compromised. On limited occasions, NASA has observed charring of the primary O-rings of the Space Shuttle solid rocket nozzle assembly joints due to parasitic leakage paths opening up in the gap-fill compounds during rocket operation. NASA is investigating different approaches for preventing torching or charring of the primary O-rings. One approach is to implement a braided rope seal upstream of the primary O-ring to serve as a thermal barrier that prevents the hot gases from impinging on the O-ring seals. This paper presents flow, resiliency, and thermal resistance for several types of NASA rope seals braided out of carbon fibers. Burn tests were performed to determine the time to burn through each of the seals when exposed to the flame of an oxyacetylene torch (5500 F), representative of the 5500 F solid rocket motor combustion temperatures. Rope seals braided out of carbon fibers endured the flame for over six minutes, three times longer than solid rocket motor burn time. Room and high temperature flow tests are presented for the carbon seals for different amounts of linear compression. Room temperature compression tests were performed to assess seal resiliency and unit preloads as a function of compression. The thermal barrier seal was tested in a subscale "char" motor test in which the seal sealed an intentional defect in the gap insulation. Temperature measurements indicated that the seal blocked 2500 F combustion gases on the upstream side with very little temperature rise on the downstream side.

Experimental constraints on metasomatism of mantle wedge peridotites by hybridized adakitic melts

NASA Astrophysics Data System (ADS)

Corgne, Alexandre; Schilling, Manuel E.; Grégoire, Michel; Langlade, Jessica

2018-05-01

In this study, a series of high-pressure (1.5 GPa) and high-temperature (1000-1300 °C) experiments were performed to investigate the petrological imprints of adakitic metasomatism on mantle wedge peridotites. Reaction couples were prepared using a powdered adakite from Cerro Pampa, Argentina (Mg# 0.7) placed in contact with a cored sample of medium-grained protogranular depleted spinel lherzolite from Pali Aike (Chile). Textural and chemical analyses of the run products allow us to identify key features of modal metasomatism by hybridized adakitic melts. The main changes in phase relations are associated with the following metasomatic reactions: incongruent dissolution of olivine and associated precipitation of secondary orthopyroxene, dissolution of primary spinel and subsequent replacement by secondary high-Cr spinel. In experiments with high water contents (9-12 wt%), precipitation of pargasitic amphibole also occurred, possibly at the expense of primary clinopyroxene. Neither phlogopite nor Ti-oxides were precipitated in any of these experiments. As expected, primary pyroxenes do not show evidence of being significantly altered following the interaction with the produced siliceous melts. Within the adakitic portion of the experimental charge, it was also observed the crystallization of secondary Ti-rich, Cr- and Na-poor diopsidic clinopyroxene, andesine plagioclase and, at low temperature, Fe-enriched secondary orthopyroxene. Considering textural criteria, we interpreted the formation of these minerals as crystallization products of the adakite component and not as true products of metasomatic reactions. The experimental results are used to discuss some of the petrological evidences presented to support modal metasomatism by slab-derived melts of mantle xenoliths extracted from several suprasubduction settings located around the Pacific Ring of Fire.

A full-scale STOVL ejector experiment

NASA Technical Reports Server (NTRS)

Barankiewicz, Wendy S.

1993-01-01

The design and development of thrust augmenting short take-off and vertical landing (STOVL) ejectors has typically been an iterative process. In this investigation, static performance tests of a full-scale vertical lift ejector were performed at primary flow temperatures up to 1560 R (1100 F). Flow visualization (smoke generators, yarn tufts and paint dots) was used to assess inlet flowfield characteristics, especially around the primary nozzle and end plates. Performance calculations are presented for ambient temperatures close to 480 R (20 F) and 535 R (75 F) which simulate 'seasonal' aircraft operating conditions. Resulting thrust augmentation ratios are presented as functions of nozzle pressure ratio and temperature. Full-scale experimental tests such as this are expensive, and difficult to implement at engine exhaust temperatures. For this reason the utility of using similarity principles -- in particular, the Munk and Prim similarity principle for isentropic flow -- was explored. At different primary temperatures, exit pressure contours are compared for similarity. A nondimensional flow parameter is then shown to eliminate primary nozzle temperature dependence and verify similarity between the hot and cold flow experiments. Under the assumption that an appropriate similarity principle can be established, then properly chosen performance parameters should be similar for both hot flow and cold flow model tests.

The main factors controlling petrophysical alteration in hydrothermal systems of the Kuril-Kamchatka island arch

NASA Astrophysics Data System (ADS)

Frolova, J.; Ladygin, V.; Rychagov, S.; Shanina, V.; Blyumkina, M.

2009-04-01

This report is based on the results of petrophysical studies obtained on a number of hydrothermal systems in the Kuril-Kamchatka island arc (Pauzhetsky, Mutnovsky, Koshelevsky, Essovsky, a volcano of Ebeko, Oceansky). Mineral composition and pore-space structure of primary rocks change intensively during hydrothermal process, results in alteration of petrophysical properties - porosity, density, permeability, hygroscopy, sonic velocity, elastic modulus, mechanical properties, thermal and magnetic characteristics. Petrophysical alterations gradually lead to the change of the structure of hydrothermal system, and its hydrodynamic and temperature regime. The tendency of petrophysical alteration can be different. In some cases rocks "improvement" is observed i.e. consolidation, hardening, decrease of porosity and permeability, removal of hygroscopy. In other cases rocks "deterioration" occurs, i.e. formation of secondary porosity and permeability, a decrease of density, strength, and elastic modulus, and occurrence of hygroscopic moisture. The classical example of cardinal petrophysical alteration is the transformation of hard basalts to plastic clays. The opposite example is the transformation of only slightly consolidates porous tuffs to hard and dense secondary quartzite. The character of petrophysical alteration depends on a number of factors including peculiarities of primary rocks, temperature, pressure and composition of thermal fluids, duration of fluid-rock interaction, and condition of fluid (steam, water, boiling water). The contribution of each factor to change of volcanic rocks properties is considered and analyzed in details. In particular, primary rocks controls speed, intensity and character of petrophysical alterations. Factors favorable for alteration are high porosity and permeability, micro crakes, weak cementation, glassy structure, basaltic composition. Kuril-Kamchatka region represents the volcanic island arch so host rocks in hydrothermal systems are mainly volcanic or volcaniclastic types of Neogene-Quaternary age. Volcanic rocks (lava rocks) are dense with high strength and elastic modulus and low porosity and permeability. The speed of their alteration is low. Basically volcanic rocks form impermeable horizons in the structure of hydrothermal system. But sometimes they form fracture-type reservoir. The origin of fracturing can be various. Volcanoclastic rocks are characterized by lower physical and mechanical properties, higher porosity and permeability. Due to high porosity and permeability they are greatly exposed to thermal fluids so they are altered intensively. Volcaniclastic rocks are the most common host rocks of geothermal reservoirs. Typically they form porous or fracture-porous aquifers. But in some cases they form water confining layers. The well-studied example is Pauzhetskaya hydrothermal system. The main reservoir is composed of highly porous (30-40%) and permeable medium-grained tuffs. The caprock is composed of fine-grained argillized tuffs. They are highly porous but due to small pore size porosity is un-effective for fluid and permeability is low. The temperature and pressure in a hydrothermal system cardinally influence on rocks properties. High-temperature deep fluids (Т>200C) cause the perfect tendency of petrophysical alteration - consolidation, hardening, a decrease of porosity and permeability, and removal of a hygroscopic moisture. This petrophysical tendency is observed independently of composition of fluids. This is the result of the development of high-temperature secondary minerals, which fill pores and cracks, and substitute matrix and phenocrystals. The contacts between grains become strong and dense, intergranular porosity is disappeared that reinforces cementation of rock. The petrophysical alteration caused by low-temperature subsurface fluids (Т<150C) are more difficult and diverse. Depending on what process prevails - rocks leaching, sedimentation of secondary minerals in pores and cracks or replacement of primary minerals by secondary minerals, it can lead to both: an increase or a decrease in petrophysical properties. Financial support from RFBR (project 05-07-00118-a)

Thermal testing results of an electroformed nickel secondary (M2) mirror

NASA Astrophysics Data System (ADS)

Smith, David R.; Gale, David M.; Cabrera Cuevas, Lizeth; Lucero Álvarez, Maribel; Castro Santos, David; Olmos Tapia, Arak

2016-07-01

To support higher-frequency operation, the Large Millimeter Telescope/Gran Telescopio Milimetrico (or LMT/GTM) is replacing its existing monolithic aluminum secondary mirror (M2). The new mirror is a segmented design based on the same electroformed nickel reflector panel technology that is already in use for the primary reflector segments. While the new M2 is lighter and has better surface accuracy than the original mirror, the electroformed panels are more sensitive to high temperatures. During the design phase, concerns were raised over the level of temperature increase that could occur at M2 during daytime observations. Although the panel surface is designed to scatter visible light, the LMT primary mirror is large enough to cause substantial solar heating, even at significant angular separation from the Sun. To address these concerns, the project conducted a series of field tests, within the constraint of having minimum impact on night time observations. The supplier sent two coupon samples of a reflector panel prepared identically to their proposed M2 surface. Temperature sensors were mounted on the samples and they were temporarily secured to the existing M2 mirror at different distances from the center. The goal was to obtain direct monitoring of the surface temperature under site thermal conditions and the concentration effects from the primary reflector. With the sensors installed, the telescope was then commanded to track the Sun with an elevation offset. Initially, elevation offsets from as far as 40 degrees to as close as 6 degrees were tested. The 6 degree separation test quickly passed the target maximum temperature and the telescope was returned to a safer separation. Based on these initial results, a second set of tests was performed using elevation separations from 30 degrees to 8 degrees. To account for the variability of site conditions, the temperature data were analyzed using multiple metrics. These metrics included maximum temperature, final time average temperature, and an curve fit for heating/ cooling. The results indicate that a solar separation angle of 20 degrees should be suitable for full performance operation of the LMT/GTM. This separation not only is sufficient to avoid high temperatures at the mirror, but also provides time to respond to any emergency conditions that could occur (e.g., switching to a generator after a power failure) for observations that are ahead of the motion of the Sun. Additionally, even approaches of 10 to 15 degrees of angular separation on the sky may be achievable for longer wavelength observations, though these would likely be limited to positions that are behind the position of the Sun along its motion.

Refractive Secondary Solar Concentrator Being Designed and Developed

NASA Technical Reports Server (NTRS)

Macosko, Robert P.; Donovan, Richard M.

1998-01-01

As the need for achieving super high temperatures (2000 K and above) in solar heat receivers has developed so has the need for secondary concentrators. These concentrators refocus the already highly concentrated solar energy provided by a primary solar collector, thereby significantly reducing the light entrance aperture of the heat receiver and the resulting infrared radiation heat loss from the receiver cavity. Although a significant amount of research and development has been done on nonimaging hollow reflective concentrators, there has been no other research or development to date on solid, single crystal, refractive concentrators that can operate at temperatures above 2000 K. The NASA Lewis Research Center recently initiated the development of single-crystal, optically clear, refractive secondary concentrators that, combined with a flux extractor, offer a number of significant advantages over the more conventional, hollow, reflective concentrators at elevated temperatures. Such concentrators could potentially provide higher throughput (efficiency), require no special cooling device, block heat receiver material boiloff from the receiver cavity, provide for flux tailoring in the cavity via the extractor, and potentially reduce infrared heat loss via an infrared block coating.The many technical challenges of designing and fabricating high-temperature refractive secondary concentrators and flux extractors include identifying optical materials that can survive the environment (high-temperature, vacuum and/or hydrogen atmosphere), developing coatings for enhanced optical and thermal performance, and developing crystal joining techniques and hardware that can survive launch loads.

An electron microscopy examination of primary recrystallization in TD-nickel.

NASA Technical Reports Server (NTRS)

Petrovic, J. J.; Ebert, L. J.

1972-01-01

Primary recrystallization in TD-nickel 1 in. bar has previously been regarded as the process by which the initial fine grain structure is converted to a coarse grain size (increases in grain size by 500 times) under suitable deformation and annealing conditions. This process is dependent on deformation mode. While it occurs readily after rolling transverse to the bar axis and annealing (800 C), it is completely inhibited by longitudinal rolling and swaging deformations, even for very high (1320 C) annealing temperatures. A transmission electron microscopy examination of deformation and annealing substructures indicates that primary recrystallization in TD-nickel 1 in. bar actually occurs on the sub-light optical level, to produce a grain structure similar in size to the initial fine grained state.

Effect of temperature-humidity index on live performance in broiler chickens grown from 49 to 63 days of age

USDA-ARS?s Scientific Manuscript database

The thermal environment in poultry housing is a primary influence on production efficiency and live performance. Heavy broilers (body weight > 3.2 kg) typically require high ventilation rates to maintain thermal comfort and production efficiency. However, large birds are observed to pant in mild to ...

High temperature effects on rice growth, yield, and grain quality

USDA-ARS?s Scientific Manuscript database

Rice (Oryza sativa L.) is a globally important cereal plant, and as a primary source of food it accounts for 35-75% of the calorie intake of more than 3 billion humans. With the likely growth of world’s population towards 10 billion by 2050, the demand for rice will grow faster than for other crops....

Study on the Microstructure and Liquid Phase Formation in a Semisolid Gray Cast Iron

NASA Astrophysics Data System (ADS)

Benati, Davi Munhoz; Ito, Kazuhiro; Kohama, Kazuyuki; Yamamoto, Hajime; Zoqui, Eugenio José

2017-10-01

The development of high-quality semisolid raw materials requires an understanding of the phase transformations that occur as the material is heated up to the semisolid state, i.e., its melting behavior. The microstructure of the material plays a very important role during semisolid processing as it determines the flow behavior of the material when it is formed, making a thorough understanding of the microstructural evolution essential. In this study, the phase transformations and microstructural evolution in Fe2.5C1.5Si gray cast iron specially designed for thixoforming processes as it was heated to the semisolid state were observed using in situ high-temperature confocal laser scanning microscopy. At room temperature, the alloy has a matrix of pearlite and ferrite with fine interdendritic type D flake graphite. During heating, the main transformations observed were graphite precipitation inside the grains and at the austenite grain boundaries; graphite flakes and graphite precipitates growing and becoming coarser with the increasing temperature; and the beginning of melting at around 1413 K to 1423 K (1140 °C to 1150 °C). Melting begins with the eutectic phase ( i.e., the carbon-rich phase) and continues with the primary phase (primary austenite), which is consumed as the temperature increases. Melting of the eutectic phase composed by coarsened interdendritic graphite flakes produced a semi-continuous liquid network homogeneously surrounding and wetting the dendrites of the solid phase, causing grains to detach from each other and producing the intended solid globules immersed in liquid.

Bioclimatic conditions of the winter months in Western Kazakhstan and their dynamics in relation to climate change

NASA Astrophysics Data System (ADS)

Nyssanbayeva, Aiman S.; Cherednichenko, Alexandr V.; Cherednichenko, Vladimir S.; Abayev, Nurlan N.; Madibekov, Azamat S.

2018-03-01

The territory of West Kazakhstan is an intensively developing region. The main oil and gas fields are concentrated there. In addition, this region is well-known as a region of nomad cattle breeding. Both of industry and agriculture demand a lot of employees, working in the open air in wintertime. Severe winter conditions, primary very low temperatures, and strong winds characterize the region. In this work, we calculated and analyzed the spatial and temporal distributions of effective temperatures in the region and their dynamics due to the global warming in the last decades. To calculate the equivalent temperature (WCET) was used the method of OFCM 2003. Nowadays, it is known as a common method for similar studies. It was shown that in the observed region, WCET is significantly lower than the ambient temperature. Repeatability of WCET, corresponding to «increasing risk», «high risk» is high in the main part of the region. Global warming in the region results in returning extremely high temperatures of the air, decreasing repeatability of the average gradation of WCET approximately on 4%, but there is no any visible changing repeatability of extreme WCET. Obtained results can be used for planning any construction work in the open air and agriculture branches.

Bioclimatic conditions of the winter months in Western Kazakhstan and their dynamics in relation to climate change.

PubMed

Nyssanbayeva, Aiman S; Cherednichenko, Alexandr V; Cherednichenko, Vladimir S; Abayev, Nurlan N; Madibekov, Azamat S

2018-03-05

The territory of West Kazakhstan is an intensively developing region. The main oil and gas fields are concentrated there. In addition, this region is well-known as a region of nomad cattle breeding. Both of industry and agriculture demand a lot of employees, working in the open air in wintertime. Severe winter conditions, primary very low temperatures, and strong winds characterize the region. In this work, we calculated and analyzed the spatial and temporal distributions of effective temperatures in the region and their dynamics due to the global warming in the last decades. To calculate the equivalent temperature (WCET) was used the method of OFCM 2003. Nowadays, it is known as a common method for similar studies. It was shown that in the observed region, WCET is significantly lower than the ambient temperature. Repeatability of WCET, corresponding to «increasing risk», «high risk» is high in the main part of the region. Global warming in the region results in returning extremely high temperatures of the air, decreasing repeatability of the average gradation of WCET approximately on 4%, but there is no any visible changing repeatability of extreme WCET. Obtained results can be used for planning any construction work in the open air and agriculture branches.

Evaluation of High Temperature Knitted Spring Tubes for Structural Seal Applications

NASA Technical Reports Server (NTRS)

Taylor, Shawn C.; DeMange, Jeffrey J.; Dunlap, Patrick H., Jr.; Steinetz, Bruce M.

2004-01-01

Control surface seals are crucial to current and future space vehicles, as they are used to seal the gaps surrounding body flaps, elevons, and other actuated exterior surfaces. During reentry, leakage of high temperature gases through these gaps could damage underlying lower temperature structures such as rudder drive motors and mechanical actuators, resulting in impaired vehicle control. To be effective, control surface seals must shield lower temperature structures from heat transfer by maintaining sufficient resiliency to remain in contact with opposing sealing surfaces through multiple compression cycles. The current seal exhibits significant loss of resiliency after a few compression cycles at elevated temperatures (i.e., 1900 F) and therefore would be inadequate for advanced space vehicles. This seal utilizes a knitted Inconel X-750 spring tube as its primary resilient element. As part of a larger effort to enhance seal resiliency, researchers at the NASA Glenn Research Center performed high temperature compression testing (up to 2000 F) on candidate spring tube designs employing material substitutions and modified geometries. These tests demonstrated significant improvements in spring tube resiliency (5.5x better at 1750 F) through direct substitution of heat treated Rene 41 alloy in the baseline knit design. The impact of geometry modification was minor within the range of parameters tested, however trends did suggest that moderate resiliency improvements could be obtained by optimizing the current spring tube geometry.

Chromosome numbers in three species groups of freshwater flatworms increase with increasing latitude.

PubMed

Lorch, Sven; Zeuss, Dirk; Brandl, Roland; Brändle, Martin

2016-03-01

Polyploidy in combination with parthenogenesis offers advantages for plasticity and the evolution of a broad ecological tolerance of species. Therefore, a positive correlation between the level of ploidy and increasing latitude as a surrogate for environmental harshness has been suggested. Such a positive correlation is well documented for plants, but examples for animals are still rare. Species of flatworms (Platyhelminthes) are widely distributed, show a remarkably wide range of chromosome numbers, and offer therefore good model systems to study the geographical distribution of chromosome numbers. We analyzed published data on counts of chromosome numbers and geographical information of three flatworm "species" (Phagocata vitta, Polycelis felina and Crenobia alpina) sampled across Europe (220 populations). We used the mean chromosome number across individuals of a population as a proxy for the level of ploidy within populations, and we tested for relationships of this variable with latitude, mode of reproduction (sexual, asexual or both) and environmental variables (annual mean temperature, mean diurnal temperature range, mean precipitation and net primary production). The mean chromosome numbers of all three species increased with latitude and decreased with mean annual temperature. For two species, chromosome number also decreased with mean precipitation and net primary production. Furthermore, high chromosome numbers within species were accompanied with a loss of sexual reproduction. The variation of chromosome numbers within individuals of two of the three species increased with latitude. Our results support the hypothesis that polyploid lineages are able to cope with harsh climatic conditions at high latitudes. Furthermore, we propose that asexual reproduction in populations with high levels of polyploidization stabilizes hybridization events. Chromosomal irregularities within individuals tend to become more frequent at the extreme environments of high latitudes, presumably because of mitotic errors and downsizing of the genome.

Noise shielding by a hot subsonic jet

NASA Technical Reports Server (NTRS)

Vijayaraghavan, A.; Parthasarathy, S. P.

1981-01-01

An analysis is conducted of the shielding of the noise emitted by a high speed round jet by a hot, subsonic, semicircular jet. A plane wave front in the primary jet is resolved into elementary plane waves which undergo multiple reflections at the jet boundaries of the primary and the shielding jets. The jet boundaries are idealized to be vortex sheets. The far field sound is evaluated asymptotically by a superposition of the waves that penetrate the shielding jet. The angular directivities are plotted for several values of jet temperature and velocity to examine the effectiveness of shielding by the semicircular jet layer.

Global Ocean Phytoplankton

NASA Technical Reports Server (NTRS)

Franz, B. A.; Behrenfeld, M. J.; Siegel, D. A.; Werdell, P. J.

2013-01-01

Phytoplankton are free-floating algae that grow in the euphotic zone of the upper ocean, converting carbon dioxide, sunlight, and available nutrients into organic carbon through photosynthesis. Despite their microscopic size, these photoautotrophs are responsible for roughly half the net primary production on Earth (NPP; gross primary production minus respiration), fixing atmospheric CO2 into food that fuels our global ocean ecosystems. Phytoplankton thus play a critical role in the global carbon cycle, and their growth patterns are highly sensitive to environmental changes such as increased ocean temperatures that stratify the water column and prohibit the transfer of cold, nutrient richwaters to the upper ocean euphotic zone.

Primary gas thermometry by means of laser-absorption spectroscopy: determination of the Boltzmann constant.

PubMed

Casa, G; Castrillo, A; Galzerano, G; Wehr, R; Merlone, A; Di Serafino, D; Laporta, P; Gianfrani, L

2008-05-23

We report on a new optical implementation of primary gas thermometry based on laser-absorption spectrometry in the near infrared. The method consists in retrieving the Doppler broadening from highly accurate observations of the line shape of the R(12) nu1+2nu2(0)+nu3 transition in CO2 gas at thermodynamic equilibrium. Doppler width measurements as a function of gas temperature, ranging between the triple point of water and the gallium melting point, allowed for a spectroscopic determination of the Boltzmann constant with a relative accuracy of approximately 1.6 x 10(-4).

Primary Gas Thermometry by Means of Laser-Absorption Spectroscopy: Determination of the Boltzmann Constant

NASA Astrophysics Data System (ADS)

Casa, G.; Castrillo, A.; Galzerano, G.; Wehr, R.; Merlone, A.; di Serafino, D.; Laporta, P.; Gianfrani, L.

2008-05-01

We report on a new optical implementation of primary gas thermometry based on laser-absorption spectrometry in the near infrared. The method consists in retrieving the Doppler broadening from highly accurate observations of the line shape of the R(12) ν1+2ν20+ν3 transition in CO2 gas at thermodynamic equilibrium. Doppler width measurements as a function of gas temperature, ranging between the triple point of water and the gallium melting point, allowed for a spectroscopic determination of the Boltzmann constant with a relative accuracy of ˜1.6×10-4.

Advanced Electrical Materials and Components Being Developed

NASA Technical Reports Server (NTRS)

Schwarze, Gene E.

2004-01-01

All aerospace systems require power management and distribution (PMAD) between the energy and power source and the loads. The PMAD subsystem can be broadly described as the conditioning and control of unregulated power from the energy source and its transmission to a power bus for distribution to the intended loads. All power and control circuits for PMAD require electrical components for switching, energy storage, voltage-to-current transformation, filtering, regulation, protection, and isolation. Advanced electrical materials and component development technology is a key technology to increasing the power density, efficiency, reliability, and operating temperature of the PMAD. The primary means to develop advanced electrical components is to develop new and/or significantly improved electronic materials for capacitors, magnetic components, and semiconductor switches and diodes. The next important step is to develop the processing techniques to fabricate electrical and electronic components that exceed the specifications of presently available state-of-the-art components. The NASA Glenn Research Center's advanced electrical materials and component development technology task is focused on the following three areas: 1) New and/or improved dielectric materials for the development of power capacitors with increased capacitance volumetric efficiency, energy density, and operating temperature; 2) New and/or improved high-frequency, high-temperature soft magnetic materials for the development of transformers and inductors with increased power density, energy density, electrical efficiency, and operating temperature; 3) Packaged high-temperature, high-power density, high-voltage, and low-loss SiC diodes and switches.

Application of Sol-Gel Method as a Protective Layer on a Specular Reflective Surface for Secondary Reflector in a Solar Receiver

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

Afrin, Samia; Dagdelen, John; Ma, Zhiwen

Highly-specular reflective surfaces that can withstand elevated-temperatures are desirable for many applications including reflective heat shielding in solar receivers and secondary reflectors, which can be used between primary concentrators and heat collectors. A high-efficiency, high-temperature solar receiver design based on arrays of cavities needs a highly-specular reflective surface on its front section to help sunlight penetrate into the absorber tubes for effective flux spreading. Since this application is for high-temperature solar receivers, this surface needs to be durable and to maintain its optical properties through the usable life. Degradation mechanisms associated with elevated temperatures and thermal cycling, which include cracking,more » delamination, corrosion/oxidation, and environmental effects, could cause the optical properties of surfaces to degrade rapidly in these conditions. Protected mirror surfaces for these applications have been tested by depositing a thin layer of SiO2 on top of electrodeposited silver by means of the sol-gel method. To obtain an effective thin film structure, this sol-gel procedure has been investigated extensively by varying process parameters that affect film porosity and thickness. Endurance tests have been performed in a furnace at 150 degrees C for thousands of hours. This paper presents the sol-gel process for intermediate-temperature specular reflective coatings and provides the long-term reliability test results of sol-gel protected silver-coated surfaces.« less

Developmental temperature affects the expression of ejaculatory traits and the outcome of sperm competition in Callosobruchus maculatus.

PubMed

Vasudeva, R; Deeming, D C; Eady, P E

2014-09-01

The outcome of post-copulatory sexual selection is determined by a complex set of interactions between the primary reproductive traits of two or more males and their interactions with the reproductive traits of the female. Recently, a number of studies have shown the primary reproductive traits of both males and females express phenotypic plasticity in response to the thermal environment experienced during ontogeny. However, how plasticity in these traits affects the dynamics of sperm competition remains largely unknown. Here, we demonstrate plasticity in testes size, sperm size and sperm number in response to developmental temperature in the bruchid beetle Callosobruchus maculatus. Males reared at the highest temperature eclosed at the smallest body size and had the smallest absolute and relative testes size. Males reared at both the high- and low-temperature extremes produced both fewer and smaller sperm than males reared at intermediate temperatures. In the absence of sperm competition, developmental temperature had no effect on male fertility. However, under conditions of sperm competition, males reared at either temperature extreme were less competitive in terms of sperm offence (P(2)), whereas those reared at the lowest temperature were less competitive in terms of sperm defence (P(1)). This suggests the developmental pathways that regulate the phenotypic expression of these ejaculatory traits are subject to both natural and sexual selection: natural selection in the pre-ejaculatory environment and sexual selection in the post-ejaculatory environment. In nature, thermal heterogeneity during development is commonplace. Therefore, we suggest the interplay between ecology and development represents an important, yet hitherto underestimated component of male fitness via post-copulatory sexual selection. © 2014 The Authors. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Electronic structure basis for the extraordinary magnetoresistance in WTe 2

DOE PAGES

Pletikosić, I.; Ali, Mazhar N.; Fedorov, A. V.; ...

2014-11-19

The electronic structure basis of the extremely large magnetoresistance in layered non-magnetic tungsten ditelluride has been investigated by angle-resolved photoelectron spectroscopy. Hole and electron pockets of approximately the same size were found at the Fermi level, suggesting that carrier compensation should be considered the primary source of the effect. The material exhibits a highly anisotropic, quasi one-dimensional Fermi surface from which the pronounced anisotropy of the magnetoresistance follows. As a result, a change in the Fermi surface with temperature was found and a high-density-of-states band that may take over conduction at higher temperatures and cause the observed turn-on behavior ofmore » the magnetoresistance in WTe₂ was identified.« less

Unique reliability characteristics of fully depleted silicon-on-insulator tunneling FET

NASA Astrophysics Data System (ADS)

Kang, Soo Cheol; Lim, Donghwan; Lim, Sung Kwan; Noh, Jinwoo; Kim, Seung-Mo; Lee, Sang Kyung; Choi, Changhwan; Lee, Byoung Hun

2018-04-01

This study investigated the unique reliability characteristics of tunneling field effect transistors (TFETs) by comparing the effects of positive bias temperature instability (PBTI) and hot carrier injection (HCI) stresses. In case of hot carrier injection (HCI) stress, the interface trap generation near a p/n+ region was the primary degradation mechanism. However, strong recovery after a high-pressure hydrogen annealing and weak degradation at low temperature indicates that the degradation mechanism of TFET under the HCI stress is different from the high-energy carrier stress induced permanent defect generation mechanism observed in MOSFETs. Further study is necessary to identify the exact location and defect species causing TFET degradation; however, a significant difference is evident between the dominant reliability mechanism of TFET and MOSFET.

Laser-Induced Fluorescence and Synthetic Jet Fuel Analysis in the Ultra Compact Combustor

DTIC Science & Technology

2009-12-01

In the primary zone, high- temperature, high-pressure air enters from the compressor and flows around fuel injectors spraying atomized liquid -droplet...chemical reaction in which synthesis gas , a mixture of carbon monoxide and hydrogen, is converted into liquid hydrocarbons of various forms. The most...the fuel lines needed to be rebuilt due to a recent COAL lab renovation. The liquid fuel system had not been used for nearly two years so some

Thermal Analysis of the Divertor Primary Heat Transfer System Piping During the Gas Baking Process

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

Yoder Jr, Graydon L; Harvey, Karen; Ferrada, Juan J

A preliminary analysis has been performed examining the temperature distribution in the Divertor Primary Heat Transfer System (PHTS) piping and the divertor itself during the gas baking process. During gas baking, it is required that the divertor reach a temperature of 350 C. Thermal losses in the piping and from the divertor itself require that the gas supply temperature be maintained above that temperature in order to ensure that all of the divertor components reach the required temperature. The analysis described in this report was conducted in order to estimate the required supply temperature from the gas heater.

High temperature superconductors applications in telecommunications

NASA Technical Reports Server (NTRS)

Kumar, A. Anil; Li, Jiang; Zhang, Ming Fang

1995-01-01

The purpose of this paper is twofold: (1) to discuss high temperature superconductors with specific reference to their employment in telecommunications applications; and (2) to discuss a few of the limitations of the normally employed two-fluid model. While the debate on the actual usage of high temperature superconductors in the design of electronic and telecommunications devices - obvious advantages versus practical difficulties - needs to be settled in the near future, it is of great interest to investigate the parameters and the assumptions that will be employed in such designs. This paper deals with the issue of providing the microwave design engineer with performance data for such superconducting waveguides. The values of conductivity and surface resistance, which are the primary determining factors of a waveguide performance, are computed based on the two-fluid model. A comparison between two models - a theoretical one in terms of microscopic parameters (termed Model A) and an experimental fit in terms of macroscopic parameters (termed Model B) - shows the limitations and the resulting ambiguities of the two-fluid model at high frequencies and at temperatures close to the transition temperature. The validity of the two-fluid model is then discussed. Our preliminary results show that the electrical transport description in the normal and superconducting phases as they are formulated in the two-fluid model needs to be modified to incorporate the new and special features of high temperature superconductors. Parameters describing the waveguide performance - conductivity, surface resistance and attenuation constant - will be computed. Potential applications in communications networks and large scale integrated circuits will be discussed. Some of the ongoing work will be reported. In particular, a brief proposal is made to investigate of the effects of electromagnetic interference and the concomitant notion of electromagnetic compatibility (EMI/EMC) of high T(sub c) superconductors.

High temperature superconductors applications in telecommunications

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

Kumar, A.A.; Li, J.; Zhang, M.F.

1994-12-31

The purpose of this paper is twofold: to discuss high temperature superconductors with specific reference to their employment in telecommunications applications; and to discuss a few of the limitations of the normally employed two-fluid model. While the debate on the actual usage of high temperature superconductors in the design of electronic and telecommunications devices-obvious advantages versus practical difficulties-needs to be settled in the near future, it is of great interest to investigate the parameters and the assumptions that will be employed in such designs. This paper deals with the issue of providing the microwave design engineer with performance data formore » such superconducting waveguides. The values of conductivity and surface resistance, which are the primary determining factors of a waveguide performance, are computed based on the two-fluid model. A comparison between two models-a theoretical one in terms of microscopic parameters (termed Model A) and an experimental fit in terms of macroscopic parameters (termed Model B)-shows the limitations and the resulting ambiguities of the two-fluid model at high frequencies and at temperatures close to the transition temperature. The validity of the two-fluid model is then discussed. Our preliminary results show that the electrical transport description in the normal and superconducting phases as they are formulated in the two-fluid model needs to be modified to incorporate the new and special features of high temperature superconductors. Parameters describing the waveguide performance-conductivity, surface resistance and attenuation constant-will be computed. Potential applications in communications networks and large scale integrated circuits will be discussed. Some of the ongoing work will be reported. In particular, a brief proposal is made to investigate of the effects of electromagnetic interference and the concomitant notion of electromagnetic compatibility (EMI/EMC) of high T{sub c} superconductors.« less

Cooling Performance Analysis of ThePrimary Cooling System ReactorTRIGA-2000Bandung

NASA Astrophysics Data System (ADS)

Irianto, I. D.; Dibyo, S.; Bakhri, S.; Sunaryo, G. R.

2018-02-01

The conversion of reactor fuel type will affect the heat transfer process resulting from the reactor core to the cooling system. This conversion resulted in changes to the cooling system performance and parameters of operation and design of key components of the reactor coolant system, especially the primary cooling system. The calculation of the operating parameters of the primary cooling system of the reactor TRIGA 2000 Bandung is done using ChemCad Package 6.1.4. The calculation of the operating parameters of the cooling system is based on mass and energy balance in each coolant flow path and unit components. Output calculation is the temperature, pressure and flow rate of the coolant used in the cooling process. The results of a simulation of the performance of the primary cooling system indicate that if the primary cooling system operates with a single pump or coolant mass flow rate of 60 kg/s, it will obtain the reactor inlet and outlet temperature respectively 32.2 °C and 40.2 °C. But if it operates with two pumps with a capacity of 75% or coolant mass flow rate of 90 kg/s, the obtained reactor inlet, and outlet temperature respectively 32.9 °C and 38.2 °C. Both models are qualified as a primary coolant for the primary coolant temperature is still below the permitted limit is 49.0 °C.

Microstructural Evolution and Phase Formation in 2nd-Generation Refractory-Based High Entropy Alloys

PubMed Central

Eshed, Eyal; Larianovsky, Natalya; Kovalevsky, Alexey; Popov, Vladimir; Gorbachev, Igor; Popov, Vladimir; Katz-Demyanetz, Alexander

2018-01-01

Refractory-based high entropy alloys (HEAs) of the 2nd-generation type are new intensively-studied materials with a high potential for structural high-temperature applications. This paper presents investigation results on microstructural evolution and phase formation in as-cast and subsequently heat-treated HEAs at various temperature-time regimes. Microstructural examination was performed by means of scanning electron microscopy (SEM) combined with the energy dispersive spectroscopy (EDS) mode of electron probe microanalysis (EPMA) and qualitative X-ray diffraction (XRD). The primary evolutionary trend observed was the tendency of Zr to gradually segregate as the temperature rises, while all the other elements eventually dissolve in the BCC solid solution phase once the onset of Laves phase complex decomposition is reached. The performed thermodynamic modelling was based on the Calculation of Phase Diagrams method (CALPHAD). The BCC A2 solid solution phase is predicted by the model to contain increasing amounts of Cr as the temperature rises, which is in perfect agreement with the actual results obtained by SEM. However, the model was not able to predict the existence of the Zr-rich phase or the tendency of Zr to segregate and form its own solid solution—most likely as a result of the Zr segregation trend not being an equilibrium phenomenon. PMID:29360763

Influence of Annealing on Microstructure and Mechanical Properties of Refractory CoCrMoNbTi0.4 High-Entropy Alloy

NASA Astrophysics Data System (ADS)

Zhang, Mina; Zhou, Xianglin; Zhu, Wuzhi; Li, Jinghao

2018-04-01

A novel refractory CoCrMoNbTi0.4 high-entropy alloy (HEA) was prepared via vacuum arc melting. After annealing treatment at different temperatures, the microstructure evolution, phase stability, and mechanical properties of the alloy were investigated. The alloy was composed of two primary body-centered cubic structures (BCC1 and BCC2) and a small amount of (Co, Cr)2Nb-type Laves phase under different annealing conditions. The microhardness and compressive strength of the heat-treated alloy was significantly enhanced by the solid-solution strengthening of the BCC phase matrix and newborn Laves phase. Especially, the alloy annealed at 1473 K (1200 °C) achieved the maximum hardness and compressive strength values of 959 ± 2 HV0.5 and 1790 MPa, respectively, owing to the enhanced volume fraction of the dispersed Laves phase. In particular, the HEAs exhibited promising high-temperature mechanical performance, when heated to an elevated temperature of 1473 K (1200 °C), with a compressive fracture strength higher than 580 MPa without fracture at a strain of more than 20 pct. This study suggests that the present refractory HEAs have immense potential for engineering applications as a new class of high-temperature structural materials.

Characterization of heavy oil by capillary supercritical fluid chromatography

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

Fuhr, B.J.; Holloway, L.R.; Reichert, C.

1989-01-01

Using supercritical CO/sub 2/ as the mobile phase with a 30m x 100{mu} ID SPB-5 capillary column and temperature of 90{sup 0}C, high boiling fractions of heavy oils could be characterized. A linear restrictor placed as close as possible to the flame ionization detector jet prevented the characteristic spiking often observed in these systems, and also allowed the study of high molecular weight material without plugging of the restrictor. The boiling points of model saturate and aromatic compounds correlate with retention time providing the capability to study heavy oils without exposing them to the high temperature necessary in gas chromatography.more » Individual peaks can be resolved for the n-paraffins in waxes up to C/sub 90/. Primary production, fireflood and steamflood heavy oils and bitumens were compared by this technique.« less

Testing the effect of increased temperature and river water input on benthic and pelagic metabolism using a large scale experimental pond ecosystem

NASA Astrophysics Data System (ADS)

Rodriguez, Patricia; Geibrink, Erik; Vasconcelos, Francisco; Hedström, Per; Byström, Pär; Karlsson, Jan

2013-04-01

We performed a large scale experimental study to test the effect of increased temperatures and concentration of allochthonous dissolved organic carbon (DOC) on benthic and pelagic primary production and respiration. The experiment was carried out during one ice-free season (May-October 2012) in a clear-water pond ecosystem divided into 16 enclosures (each 120 m3 and 1.6 m deep) including natural benthic and pelagic habitats and fish as top consumers (40 adult three-spine sticklebacks were introduced at the beginning of the experiment). Treatments included input of brown river water (23 mg/L in DOC) and heating (3° C above ambient temperature) in a factorial design: 4 enclosures were kept as controls (clear-cold), 4 enclosures were heated (clear-hot), 4 received river water (dark-cold) and 4 were both heated and received river water (dark-hot). Physical and chemical variables were monitored weekly meanwhile benthic, pelagic and ecosystems metabolism were estimated from free-water oxygen data and incubation studies. The 3° C difference in temperature between hot and cold enclosures was consistent during the study and DOC concentrations averaged 4 and 8 mg/L in clear water and dark enclosures, respectively; without any interaction effect between temperature and DOC concentration. Vertical light attenuation coefficient (Kd) showed significant differences between treatments with (0.62±0.40 m-1) and without river water (0.24±0.13 m-1). Total nitrogen concentrations ranged between 187 and 300 μg/L, with higher values in the dark-cold enclosures. The same pattern of higher values in dark-cold enclosures was found in phytoplankton chlorophyll a and primary production. Preliminary results show that gross benthic primary production (higher in clear-cold enclosures) largely exceeded phytoplankton production at the beginning of the experiment. Due to high respiration compared to gross primary production the net ecosystem production was in general negative in the pelagic habitat and did not show any effect of temperature or river water treatment. Our results suggest that input of river water may affect relatively shallow lake ecosystems differently compared to what is generally assumed based on studies of deeper systems.

Microstructure and high-temperature oxidation resistance of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding

NASA Astrophysics Data System (ADS)

Zhang, Xiaowei; Liu, Hongxi; Wang, Chuanqi; Zeng, Weihua; Jiang, Yehua

2010-11-01

A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600°C and 800°C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface modification technique for Ti6Al4V alloy.

An experimental test plan for the characterization of molten salt thermochemical properties in heat transport systems

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

Pattrick Calderoni

2010-09-01

Molten salts are considered within the Very High Temperature Reactor program as heat transfer media because of their intrinsically favorable thermo-physical properties at temperatures starting from 300 C and extending up to 1200 C. In this context two main applications of molten salt are considered, both involving fluoride-based materials: as primary coolants for a heterogeneous fuel reactor core and as secondary heat transport medium to a helium power cycle for electricity generation or other processing plants, such as hydrogen production. The reference design concept here considered is the Advanced High Temperature Reactor (AHTR), which is a large passively safe reactormore » that uses solid graphite-matrix coated-particle fuel (similar to that used in gas-cooled reactors) and a molten salt primary and secondary coolant with peak temperatures between 700 and 1000 C, depending upon the application. However, the considerations included in this report apply to any high temperature system employing fluoride salts as heat transfer fluid, including intermediate heat exchangers for gas-cooled reactor concepts and homogenous molten salt concepts, and extending also to fast reactors, accelerator-driven systems and fusion energy systems. The purpose of this report is to identify the technical issues related to the thermo-physical and thermo-chemical properties of the molten salts that would require experimental characterization in order to proceed with a credible design of heat transfer systems and their subsequent safety evaluation and licensing. In particular, the report outlines an experimental R&D test plan that would have to be incorporated as part of the design and operation of an engineering scaled facility aimed at validating molten salt heat transfer components, such as Intermediate Heat Exchangers. This report builds on a previous review of thermo-physical properties and thermo-chemical characteristics of candidate molten salt coolants that was generated as part of the same project [1]. However, this work focuses on two materials: the LiF-BeF2 eutectic (67 and 33 mol%, respectively, also known as flibe) as primary coolant and the LiF-NaF-KF eutectic (46.5, 11.5, and 52 mol%, respectively, also known as flinak) as secondary heat transport fluid. At first common issues are identified, involving the preparation and purification of the materials as well as the development of suitable diagnostics. Than issues specific to each material and its application are considered, with focus on the compatibility with structural materials and the extension of the existing properties database.« less

Numerical calculation of primary slot leakage inductance of a Single-sided HTS linear induction motor used for linear metro

NASA Astrophysics Data System (ADS)

Li, Dong; Wen, Yinghong; Li, Weili; Fang, Jin; Cao, Junci; Zhang, Xiaochen; Lv, Gang

2017-03-01

In the paper, the numerical method calculating asymmetric primary slot leakage inductances of Single-sided High-Temperature Superconducting (HTS) Linear Induction Motor (HTS LIM) is presented. The mathematical and geometric models of three-dimensional nonlinear transient electromagnetic field are established and the boundary conditions are also given. The established model is solved by time-stepping Finite Element Method (FEM). Then, the three-phase asymmetric primary slot leakage inductances under different operation conditions are calculated by using the obtained electromagnetic field distribution. The influences of the special effects such as longitudinal end effects, transversal edge effects, etc. on the primary slot leakage inductance are investigated. The presented numerical method is validated by experiments carried out on a 3.5 kW prototype with copper wires which has the same structures with the HTS LIM.

Monolith catalysts for closed-cycle carbon dioxide lasers

NASA Technical Reports Server (NTRS)

Herz, Richard K.

1994-01-01

The general subject area of the project involved the development of solid catalysts that have high activity at low temperature for the oxidation of gases such as CO. The original application considered was CO oxidation in closed-cycle CO2 lasers. The scope of the project was subsequently extended to include oxidation of gases in addition to CO and applications such as air purification and exhaust gas emission control. The primary objective of the final phase grant was to develop design criteria for the formulation of new low-temperature oxidation catalysts utilizing Monte Carlo simulations of reaction over NASA-developed catalysts.

Effect of high temperature creep and oxidation on residual room temperature properties for several thin sheet superalloys

NASA Technical Reports Server (NTRS)

Royster, D. M.; Lisagor, W. B.

1972-01-01

Superalloys are being considered for the primary heat shields and supports in the thermal protection system of both hypersonic transport and space shuttle vehicles. Since conservative design philosophy dictates designs based on residual material properties at the end of the service life, material characterization after exposure to the environmental conditions imposed by the flight requirements of these two classes of vehicles is needed on the candidate alloys. An investigation was conducted to provide some of the necessary data, with emphasis placed on oxidation, creep, and residual properties of thin-gage sheet material.

Ligand-Free Pd-Catalyzed Double Carbonylation of Aryl Iodides with Amines to α-Ketoamides under Atmospheric Pressure of Carbon Monoxide and at Room Temperature.

PubMed

Du, Hongyan; Ruan, Qing; Qi, Minghao; Han, Wei

2015-08-07

A general Pd-catalyzed double carbonylation of aryl iodides with secondary or primary amines to produce α-ketoamides at atmospheric CO pressure has been developed. This transformation proceeds successfully even at room temperature and in the absence of any ligand and additive. A wide range of aryl iodides and amines can be coupled to the desired α-ketoamides in high yields with excellent chemoselectivities. Importantly, the current methodology has been demonstrated to be applied in the synthesis of bioactive molecules and chiral α-ketoamides.

Magnetic property zonation in a thick lava flow

NASA Astrophysics Data System (ADS)

Audunsson, Haraldur; Levi, Shaul; Hodges, Floyd

1992-04-01

Intraflow structures and magmatic evolution in an extensive and thick (30-60 m) basaltic lava flow are examined on the basis of grain size and composition-dependent magnetic properties of titanomagnetite materials. Microprobe data indicate that the intraflow oxidation state Fe(3+)/Fe(2+) of the initially precipitated primary titanomagnetites increases with falling equilibrium temperature from the flow margins to a maximum near the center, the position of lowest equilibrium temperature. In contrast, Curie temperature measurements indicate that titanomagnetite oxidation increases with height in the flow. Modification of the initially symmetric equilibrium titanomagnetite compositions was caused by subsolidus high-temperature oxidation possibly due to hydrogen loss produced by dissociation of magmatic water, as well as unknown contributions of circulating air and percolating water from above. The titanomagnetites of the basal layer of the flow remain essentially unaltered.

Morphology and nano-structure analysis of soot particles sampled from high pressure diesel jet flames under diesel-like conditions

NASA Astrophysics Data System (ADS)

Jiang, Hao; Li, Tie; Wang, Yifeng; He, Pengfei

2018-04-01

Soot particles emitted from diesel engines have a significant impact on the atmospheric environment. Detailed understanding of soot formation and oxidation processes is helpful for reducing the pollution of soot particles, which requires information such as the size and nano-structure parameters of the soot primary particles sampled in a high-temperature and high-pressure diesel jet flame. Based on the thermophoretic principle, a novel sampling probe minimally disturbing the diesel jet flame in a constant volume combustion vessel is developed for analysing soot particles. The injected quantity of diesel fuel is less than 10 mg, and the soot particles sampled by carriers with a transmission electron microscope (TEM) grid and lacey TEM grid can be used to analyse the morphologies of soot aggregates and the nano-structure of the soot primary particles, respectively. When the quantity of diesel fuel is more than 10 mg, in order to avoid burning-off of the carriers in higher temperature and pressure conditions, single-crystal silicon chips are employed. Ultrasonic oscillations and alcohol extraction are then implemented to obtain high quality soot samples for observation using a high-resolution transmission electron microscope. An in-house Matlab-based code is developed to extract the nano-structure parameters of the soot particles. A complete sampling and analysis procedure of the soot particles is provided to study the formation and oxidation mechanism of soot.

μ Eridani from MOST and from the ground: an orbit, the SPB component's fundamental parameters and the SPB frequencies

NASA Astrophysics Data System (ADS)

Jerzykiewicz, M.; Lehmann, H.; Niemczura, E.; Molenda-Żakowicz, J.; Dymitrov, W.; Fagas, M.; Guenther, D. B.; Hartmann, M.; Hrudková, M.; Kamiński, K.; Moffat, A. F. J.; Kuschnig, R.; Leto, G.; Matthews, J. M.; Rowe, J. F.; Ruciński, S. M.; Sasselov, D.; Weiss, W. W.

2013-06-01

MOST time series photometry of μ Eri, an SB1 eclipsing binary with a rapidly rotating SPB primary, is reported and analysed. The analysis yields a number of sinusoidal terms, mainly due to the intrinsic variation of the primary, and the eclipse light curve. New radial-velocity observations are presented and used to compute parameters of a spectroscopic orbit. Frequency analysis of the radial-velocity residuals from the spectroscopic orbital solution fails to uncover periodic variations with amplitudes greater than 2 km s-1. A Rossiter-McLaughlin anomaly is detected from observations covering ingress. From archival photometric indices and the revised Hipparcos parallax, we derive the primary's effective temperature, surface gravity, bolometric correction and the luminosity. An analysis of a high signal-to-noise spectrogram yields the effective temperature and surface gravity in good agreement with the photometric values. From the same spectrogram, we determine the abundance of He, C, N, O, Ne, Mg, Al, Si, P, S, Cl and Fe. The eclipse light curve is solved by means of EBOP. For a range of mass of the primary, a value of mean density, very nearly independent of assumed mass, is computed from the parameters of the system. Contrary to a recent report, this value is approximately equal to the mean density obtained from the star's effective temperature and luminosity. Despite limited frequency resolution of the MOST data, we were able to recover the closely spaced SPB frequency quadruplet discovered from the ground in 2002-2004. The other two SPB terms seen from the ground were also recovered. Moreover, our analysis of the MOST data adds 15 low-amplitude SPB terms with frequencies ranging from 0.109 to 2.786 d-1.

High follicle density does not decrease sweat gland density in Huacaya alpacas.

PubMed

Moore, K E; Maloney, S K; Blache, D

2015-01-01

When exposed to high ambient temperatures, mammals lose heat evaporatively by either sweating from glands in the skin or by respiratory panting. Like other camelids, alpacas are thought to evaporate more water by sweating than panting, despite a thick fleece, unlike sheep which mostly pant in response to heat stress. Alpacas were brought to Australia to develop an alternative fibre industry to sheep wool. In Australia, alpacas can be exposed to ambient temperatures higher than in their native South America. As a young industry there is a great deal of variation in the quality and quantity of the fleece produced in the national flock. There is selection pressure towards animals with finer and denser fleeces. Because the fibre from secondary follicles is finer than that from primary follicles, selecting for finer fibres might alter the ratio of primary and secondary follicles. In turn the selection might alter sweat gland density because the sweat glands are associated with the primary follicle. Skin biopsy and fibre samples were obtained from the mid-section of 33 Huacaya alpacas and the skin sections were processed into horizontal sections at the sebaceous gland level. Total, primary, and secondary follicles and the number of sweat gland ducts were quantified. Fibre samples from each alpaca were further analysed for mean fibre diameter. The finer-fibred animals had a higher total follicle density (P<0.001) and more sweat glands (P<0.001) than the thicker-fibred animals. The fibre diameter and total follicle density were negatively correlated (R(2)=0.56, P<0.001). Given that the finer-fibred animals had higher follicle density and more sweat glands than animals with thicker fibres, we conclude that alpacas with high follicle density should not be limited for potential sweating ability. Copyright © 2014 Elsevier Ltd. All rights reserved.

Stress Corrosion Cracking of Ni-Fe-Cr Alloys Relevant to Nuclear Power Plants

NASA Astrophysics Data System (ADS)

Persaud, Suraj

Stress corrosion cracking (SCC) of Ni-Fe-Cr alloys and weld metals was investigated in simulated environments representative of high temperature water used in the primary and secondary circuits of nuclear power plants. The mechanism of primary water SCC (PWSCC) was studied in Alloys 600, 690, 800 and Alloy 82 dissimilar metal welds using the internal oxidation model as a guide. Initial experiments were carried out in a 480°C hydrogenated steam environment considered to simulate high temperature reducing primary water. Ni alloys underwent classical internal oxidation intragranularly resulting in the expulsion of the solvent metal, Ni, to the surface. Selective intergranular oxidation of Cr in Alloy 600 resulted in embrittlement, while other alloys were resistant owing to their increased Cr contents. Atom probe tomography was used to determine the short-circuit diffusion path used for Ni expulsion at a sub-nanometer scale, which was concluded to be oxide-metal interfaces. Further exposures of Alloys 600 and 800 were done in 315°C simulated primary water and intergranular oxidation tendency was comparable to 480°C hydrogenated steam. Secondary side work involved SCC experiments and electrochemical measurements, which were done at 315°C in acid sulfate solutions. Alloy 800 C-rings were found to undergo acid sulfate SCC (AcSCC) to a depth of up to 300 microm in 0.55 M sulfate solution at pH 4.3. A focused-ion beam was used to extract a crack tip from a C-ring and high resolution analytical electron microscopy revealed a duplex oxide structure and the presence of sulfur. Electrochemical measurements were taken on Ni alloys to complement crack tip analysis; sulfate was concluded to be the aggressive anion in mixed sulfate and chloride systems. Results from electrochemical measurements and crack tip analysis suggested a slip dissolution-type mechanism to explain AcSCC in Ni alloys.

Complex and interactive effects of ocean acidification and temperature on epilithic and endolithic coral-reef turf algal assemblages

NASA Astrophysics Data System (ADS)

Johnson, Maggie D.; Comeau, Steeve; Lantz, Coulson A.; Smith, Jennifer E.

2017-12-01

Turf algal assemblages are ubiquitous primary producers on coral reefs, but little is known about the response of this diverse group to ocean acidification (OA) across different temperatures. We tested the hypothesis that CO2 influences the functional response of epilithic and endolithic turf assemblages to increasing temperature. Replicate carbonate plugs covered by turf were collected from the reef and exposed to ambient and high pCO2 (1000 µatm) conditions for 3 weeks. Each pCO2 treatment was replicated across six temperatures (24.0-31.5 °C) that spanned the full seasonal temperature range on a fringing reef in Moorea, French Polynesia, and included one warming treatment (3 °C above daily average temperatures). Temperature and CO2 enrichment had complex, and sometimes interactive, effects on turf metabolism and growth. Photosynthetic and respiration rates were enhanced by increasing temperature, with an interactive effect of CO2 enrichment. Photosynthetic rates were amplified by high CO2 in the warmest temperatures, while the increase in respiration rates with temperature were enhanced under ambient CO2. Epilithic turf growth rates were not affected by temperature, but increased in response to CO2 enrichment. We found that CO2 and temperature interactively affected the endolithic assemblage, with the highest growth rates under CO2 enrichment, but only at the warmest temperatures. These results demonstrate how OA may influence algal physiology and growth across a range of ecologically relevant temperatures, and indicate that the effects of CO2 enrichment on coral-reef turf assemblages can be temperature dependent. The complex effects of CO2 enrichment and temperature across a suite of algal responses illustrates the importance of incorporating multiple stressors into global change experiments.

Warm Anomaly Effects on California Current Phytoplankton

NASA Astrophysics Data System (ADS)

Gomez Ocampo, E.; Gaxiola-Castro, G.; Beier, E.; Durazo, R.

2016-02-01

Positive temperature anomalies were reported in the NE Pacific Ocean since the boreal winter of 2013-2014. Previous studies showed that these anomalies were caused by lower than normal rates of heat loss from the ocean to the atmosphere and by relatively weak cold water advection to the upper ocean. Anomalous Sea Surface Temperature (SST), Absolute Dynamic Topography (ADT), and Chlorophyll (CHL) obtained from monthly remote sensing data were registered in the California Current region during August 2014. Anomalies appeared around the coastal and oceanic zones, particularly in the onshore zone between Monterey Bay, California and Magdalena Bay, Baja California. High positive SST anomalous values up to 4ºC above the long-term mean, 20 cm in ADT, and less of 4.5 mg m-3 of CHL were registered. Changes of 20 cm in ADT above the average are equivalent to 50 m thermocline deepening considering typical values of stratification for the area, which in turn influenced the availability of nutrients and light for phytoplankton growth in the euphotic zone. To examine the influence of the warm anomaly on phytoplankton production, we fitted with Generalized Additive Models the relationship between monthly primary production satellite data and ADT. Primary production inferred from the model, showed during August 2014 high negative anomalies (up to 0.5 gC m-2 d1) in the coastal zone. The first empirical orthogonal function of ADT and PP revealed that the highest ADT anomalies and the lowest primary production occurred off the Baja California Peninsula, between Punta Eugenia and Cabo San Lucas. Preliminary conclusions showed that warm anomaly affected negatively to phytoplankton organisms during August 2014, being this evident by low biomass and negative primary production anomalies as result of pycnocline deepens.

Thermal design of composite materials high temperature attachments

NASA Technical Reports Server (NTRS)

1972-01-01

The thermal aspects of using filamentary composite materials as primary airframe structures on advanced atmospheric entry spacecraft such as the space shuttle vehicle were investigated to identify and evaluate potential design approaches for maintaining composite structures within allowable temperature limits at thermal protection system (TPS) attachments and/or penetrations. The investigation included: (1) definition of thermophysical data for composite material structures; (2) parametric characterization and identification of the influence of the aerodynamic heating and attachment design parameters on composite material temperatures; (3) conceptual design, evaluation, and detailed thermal analyses of temperature limiting design concepts; and (4) the development of experimental data for assessment of the thermal design methodologies and data used for evaluation of the temperature-limiting design concepts. Temperature suppression attachment concepts were examined for relative merit. The simple isolator was identified as the most weight-effective concept and was selected for detail design, thermal analysis, and testing. Tests were performed on TPS standoff attachments to boron/aluminum, boron/polyimide and graphite/epoxy composite structures.

A Highly Practical Copper(I)/TEMPO Catalyst System for Chemoselective Aerobic Oxidation of Primary Alcohols

PubMed Central

Hoover, Jessica M.; Stahl, Shannon S.

2011-01-01

Aerobic oxidation reactions have been the focus of considerable attention, but their use in mainstream organic chemistry has been constrained by limitations in their synthetic scope and by practical factors, such as the use of pure O2 as the oxidant or complex catalyst synthesis. Here, we report a new (bpy)CuI/TEMPO catalyst system that enables efficient and selective aerobic oxidation of a broad range of primary alcohols, including allylic, benzylic and aliphatic derivatives, to the corresponding aldehydes using readily available reagents, at room temperature with ambient air as the oxidant. The catalyst system is compatible with a wide range of functional groups and the high selectivity for 1° alcohols enables selective oxidation of diols that lack protecting groups. PMID:21861488

Lithium nickel cobalt manganese oxide synthesized using alkali chloride flux: morphology and performance as a cathode material for lithium ion batteries.

PubMed

Kim, Yongseon

2012-05-01

Li(Ni(0.8)Co(0.1)Mn(0.1))O(2) (NCM811) was synthesized using alkali chlorides as a flux and the performance as a cathode material for lithium ion batteries was examined. Primary particles of the powder were segregated and grown separately in the presence of liquid state fluxes, which induced each particle to be composed of one primary particle with well-developed facet planes, not the shape of agglomerates as appears with commercial NCMs. The new NCM showed far less gas emission during high temperature storage at charged states, and higher volumetric capacity thanks to its high bulk density. The material is expected to provide optimal performances for pouch type lithium ion batteries, which require high volumetric capacity and are vulnerable to deformation caused by gas generation from the electrode materials.

Ground-based thermography of fluvial systems at low and high discharge reveals potential complex thermal heterogeneity driven by flow variation and bioroughness

USGS Publications Warehouse

Cardenas, M.B.; Harvey, J.W.; Packman, A.I.; Scott, D.T.

2008-01-01

Temperature is a primary physical and biogeochemical variable in aquatic systems. Field-based measurement of temperature at discrete sampling points has revealed temperature variability in fluvial systems, but traditional techniques do not readily allow for synoptic sampling schemes that can address temperature-related questions with broad, yet detailed, coverage. We present results of thermal infrared imaging at different stream discharge (base flow and peak flood) conditions using a handheld IR camera. Remotely sensed temperatures compare well with those measured with a digital thermometer. The thermal images show that periphyton, wood, and sandbars induce significant thermal heterogeneity during low stages. Moreover, the images indicate temperature variability within the periphyton community and within the partially submerged bars. The thermal heterogeneity was diminished during flood inundation, when the areas of more slowly moving water to the side of the stream differed in their temperature. The results have consequences for thermally sensitive hydroelogical processes and implications for models of those processes, especially those that assume an effective stream temperature. Copyright ?? 2008 John Wiley & Sons, Ltd.

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

Ponomarenko, N. S.; Poluektov, O. G.; Bylina, E. J.

High-field electron paramagnetic resonance (HF EPR) has been employed to investigate the primary electron donor electronic structure of Blastochloris viridis heterodimer mutant reaction centers (RCs). In these mutants the amino acid substitution His(M200)Leu or His(L173)Leu eliminates a ligand to the primary electron donor, resulting in the loss of a magnesium in one of the constituent bacteriochlorophylls (BChl). Thus, the native BChl/BChl homodimer primary donor is converted into a BChl/bacteriopheophytin (BPhe) heterodimer. The heterodimer primary donor radical in chemically oxidized RCs exhibits a broadened EPR line indicating a highly asymmetric distribution of the unpaired electron over both dimer constituents. Observed tripletmore » state EPR signals confirm localization of the excitation on the BChl half of the heterodimer primary donor. Theoretical simulation of the triplet EPR lineshapes clearly shows that, in the case of mutants, triplet states are formed by an intersystem crossing mechanism in contrast to the radical pair mechanism in wild type RCs. Photooxidation of the mutant RCs results in formation of a BPhe anion radical within the heterodimer pair. The accumulation of an intradimer BPhe anion is caused by the substantial loss of interaction between constituents of the heterodimer primary donor along with an increase in the reduction potential of the heterodimer primary donor D/D{sup +} couple. This allows oxidation of the cytochrome even at cryogenic temperatures and reduction of each constituent of the heterodimer primary donor individually. Despite a low yield of primary donor radicals, the enhancement of the semiquinone-iron pair EPR signals in these mutants indicates the presence of kinetically viable electron donors.« less

Thermal storage technologies for solar industrial process heat applications

NASA Technical Reports Server (NTRS)

Gordon, L. H.

1979-01-01

The state-of-the-art of thermal storage subsystems for the intermediate and high temperature (100 C to 600 C) solar industrial process heat generation is presented. Primary emphasis is focused on buffering and diurnal storage as well as total energy transport. In addition, advanced thermal storage concepts which appear promising for future solar industrial process heat applications are discussed.

The role of leaf epicuticular wax in the adaptation of wheat (Triticum aestivum L.) to high temperatures and moisture deficit conditions

USDA-ARS?s Scientific Manuscript database

Water deficit is one of the primary causes of decreasing wheat (Triticum aestivum L.) yields globally, resulting in 50–90% yield reduction for at least 60 Mha of cropland in developing countries (Reynolds et al. 2000). Previous studies have identified associations in genomic regions with cooler cano...

Correlated phonons and the Tc-dependent dynamical phonon anomalies

NASA Astrophysics Data System (ADS)

Hakioğlu, T.; Türeci, H.

1997-11-01

Anomalously large low-temperature phonon anharmonicities can lead to static as well as dynamical changes in the low-temperature properties of the electron-phonon system. In this work, we focus our attention on the dynamically generated low-temperature correlations in an interacting electron-phonon system using a self-consistent dynamical approach in the intermediate coupling range. In the context of the model, the polaron correlations are produced by the charge-density fluctuations which are generated dynamically by the electron-phonon coupling. Conversely, the latter is influenced in the presence of the former. The purpose of this work is to examine the dynamics of this dual mechanism between the two using the illustrative Fröhlich model. In particular, the influence of the low-temperature phonon dynamics on the superconducting properties in the intermediate coupling range is investigated. The influence on the Holstein reduction factor as well as the enhancement in the zero-point fluctuations and in the electron-phonon coupling are calculated numerically. We also examine these effects in the presence of superconductivity. Within this model, the contribution of the electron-phonon interaction as one of the important elements in the mechanisms of superconductivity can reach values as high as 15-20% of the characteristic scale of the lattice vibrational energy. The second motivation of this work is to understand the nature of the Tc-dependent temperature anomalies observed in the Debye-Waller factor, dynamical pair correlations, and average atomic vibrational energies for a number of high-temperature superconductors. In our approach we do not claim nor believe that the electron-phonon interaction is the primary mechanism leading to high-temperature superconductivity. Nevertheless, our calculations suggest that the dynamically induced low-temperature phonon correlation model can account for these anomalies and illustrates their possible common origin. Finally, the relevance of incorporating these low-temperature effects into more realistic models of high-temperature superconductivity including both the charge and spin degrees and other similar ideas existing in the literature are discussed.

Jet Noise Scaling in Dual Stream Nozzles

NASA Technical Reports Server (NTRS)

Khavaran, Abbas; Bridges, James

2010-01-01

Power spectral laws in dual stream jets are studied by considering such flows a superposition of appropriate single-stream coaxial jets. Noise generation in each mixing region is modeled using spectral power laws developed earlier for single stream jets as a function of jet temperature and observer angle. Similarity arguments indicate that jet noise in dual stream nozzles may be considered as a composite of four single stream jets representing primary/secondary, secondary/ambient, transition, and fully mixed zones. Frequency filter are designed to highlight spectral contribution from each jet. Predictions are provided at an area ratio of 2.0--bypass ratio from 0.80 to 3.40, and are compared with measurements within a wide range of velocity and temperature ratios. These models suggest that the low frequency noise in unheated jets is dominated by the fully mixed region at all velocity ratios, while the high frequency noise is dominated by the secondary when the velocity ratio is larger than 0.80. Transition and fully mixed jets equally dominate the low frequency noise in heated jets. At velocity ratios less than 0.50, the high frequency noise from primary/bypass becomes a significant contributing factor similar to that in the secondary/ambient jet.

Signatures of asymmetry in neutron spectra and images predicted by three-dimensional radiation hydrodynamics simulations of indirect drive implosions

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

Chittenden, J. P., E-mail: j.chittenden@imperial.ac.uk; Appelbe, B. D.; Manke, F.

2016-05-15

We present the results of 3D simulations of indirect drive inertial confinement fusion capsules driven by the “high-foot” radiation pulse on the National Ignition Facility. The results are post-processed using a semi-deterministic ray tracing model to generate synthetic deuterium-tritium (DT) and deuterium-deuterium (DD) neutron spectra as well as primary and down scattered neutron images. Results with low-mode asymmetries are used to estimate the magnitude of anisotropy in the neutron spectra shift, width, and shape. Comparisons of primary and down scattered images highlight the lack of alignment between the neutron sources, scatter sites, and detector plane, which limits the ability tomore » infer the ρr of the fuel from a down scattered ratio. Further calculations use high bandwidth multi-mode perturbations to induce multiple short scale length flows in the hotspot. The results indicate that the effect of fluid velocity is to produce a DT neutron spectrum with an apparently higher temperature than that inferred from the DD spectrum and which is also higher than the temperature implied by the DT to DD yield ratio.« less

Pre-Service Primary Science Teachers' Understandings of the Effect of Temperature and Pressure on Solid-Liquid Phase Transition of Water

ERIC Educational Resources Information Center

Yalcin, Fatma Aggul

2012-01-01

The aim of this study was to explore pre-service primary teachers' understandings of the effect of temperature and pressure on the solid-liquid phase transition of water. In the study a survey approach was used, and the sample consisted of one-hundred and three, third year pre-service primary science teachers. As a tool for data collection, a test…

Feasibility Study of Vapor-Mist Phase Reaction Lubrication Using a Thioether Liquid

NASA Technical Reports Server (NTRS)

Morales, Wilfredo; Handschuh, Robert F.; Krantz, Timothy L.

2007-01-01

A primary technology barrier preventing the operation of gas turbine engines and aircraft gearboxes at higher temperatures is the inability of currently used liquid lubricants to survive at the desired operating conditions over an extended time period. Current state-of-the-art organic liquid lubricants rapidly degrade at temperatures above 300 C; hence, another form of lubrication is necessary. Vapor or mist phase reaction lubrication is a unique, alternative technology for high temperature lubrication. The majority of past studies have employed a liquid phosphate ester that was vaporized or misted, and delivered to bearings or gears where the phosphate ester reacted with the metal surfaces generating a solid lubricious film. This method resulted in acceptable operating temperatures suggesting some good lubrication properties, but the continuous reaction between the phosphate ester and the iron surfaces led to wear rates unacceptable for gas turbine engine or aircraft gearbox applications. In this study, an alternative non-phosphate liquid was used to mist phase lubricate a spur gearbox rig operating at 10,000 rpm under highly loaded conditions. After 21 million shaft revolutions of operation the gears exhibited only minor wear.

Performance and emission characteristics of swirl-can combustors to near-stoichiometric fuel-air ratio

NASA Technical Reports Server (NTRS)

Diehl, L. A.; Trout, A. M.

1976-01-01

Emissions and performance characteristics were determined for two full annular swirl-can combustors operated to near stoichiometric fuel-air ratio. Test condition variations were as follows: combustor inlet-air temperatures, 589, 756, 839, and 894 K; reference velocities, 24 to 37 meters per second; inlet pressure, 62 newtons per square centimeter; and fuel-air ratios, 0.015 to 0.065. The combustor average exit temperature and combustor efficiency were calculated from the combustor exhaust gas composition. For fuel-air ratios greater than 0.04, the combustion efficiency decreased with increasing fuel-air ratios in a near-linear manner. Increasing the combustor inlet air temperature tended to offset this decrease. Maximum oxides of nitrogen emission indices occurred at intermediate fuel-air ratios and were dependent on combustor design. Carbon monoxide levels were extremely high and were the primary cause of poor combustion efficiency at the higher fuel-air ratios. Unburned hydrocarbons were low for all test conditions. For high fuel-air ratios SAE smoke numbers greater than 25 were produced, except at the highest inlet-air temperatures.

Choosing An Alloy For Automotive Stirling Engines

NASA Technical Reports Server (NTRS)

Stephens, Joseph R.

1988-01-01

Report describes study of chemical compositions and microstructures of alloys for automotive Stirling engines. Engines offer advantages of high efficiency, low pollution, low noise, and ability to use variety of fuels. Twenty alloys evaluated for resistance to corrosion permeation by hydrogen, and high temperature. Iron-based alloys considered primary candidates because of low cost. Nickel-based alloys second choice in case suitable iron-based alloy could not be found. Cobalt-based alloy included for comparison but not candidate, because it is expensive strategic material.

Polynuclear aromatic hydrocarbon and particulate emissions from two-stage combustion of polystyrene: the effects of the secondary furnace (afterburner) temperature and soot filtration.

PubMed

Wang, Jun; Richter, Henning; Howard, Jack B; Levendis, Yiannis A; Carlson, Joel

2002-02-15

Laboratory experiments were conducted in a two-stage horizontal muffle furnace in order to monitor emissions from batch combustion of polystyrene (PS) and identify conditions that minimize them. PS is a dominant component of municipal and hospital waste streams. Bench-scale combustion of small samples (0.5 g) of shredded styrofoam cups was conducted in air, using an electrically heated horizontal muffle furnace, kept at Tgas = 1000 degrees C. Upon devolatilization, combustion of the polymer took place in a diffusion flame over the sample. The gaseous combustion products were mixed with additional air in a venturi and were channeled to a secondary muffle furnace (afterburner) kept at Tgas = 900-1100 degrees C; residence time therein varied between 0.6 and 0.8 s. At the exits of the primary and the secondary furnace the emissions of CO, CO2, O2, NOx, particulates as well as volatile and semivolatile hydrocarbons, such as polycyclic aromatic hydrocarbons (PAH), were monitored. Online analyzers, gravimetric techniques, and gas chromatography coupled to mass spectrometry (GC-MS) were used. Experiments were also conducted with a high-temperature barrier filter, placed just before the exit of the primary furnace to prevent the particulates from entering into the secondary furnace. Results demonstrated the beneficial effect of the afterburner in reducing PAH concentrations, including those of mutagenic species such as benzo[a]pyrene. Concentrations of individual PAH exhibited a pronounced after burner temperature dependence, typically ranging from a small decrease at 900 degrees C to a larger degree of consumption at 1100 degrees C. Consumption of PAH was observed to be the dominant feature at 900 degrees C, while significant quantities of benzene and some of its derivatives, captured by means of carbosieve/Carbotrap adsorbents, were formed in the afterburner at a temperature of 1000 degrees C. In the primary furnace, about 30% of the mass of the initial polystyrene was converted into soot, while the total mass of PAH represented about 3% of the initial mass of combustible. The afterburner reduced the particulate (soot) emissions by only 20-30%, which indicates that once soot is formed its destruction is rather difficult because its oxidation kinetics are slow undertypical furnace conditions. Moreover, increasing the afterburnertemperature resulted in an increasing trend of soot emissions therefrom, which might indicate competition between soot oxidation and formation, with some additional formation occurring at the higher temperatures. Contrary to the limited effect of the afterburner, high-temperature filtration of the combustion effluent prior to the exit of the primary furnace allowed for effective soot oxidation inside of the ceramic filter. Filtration drastically reduced soot emissions, by more than 90%. Limited soot formation in the afterburner was again observed with increasing temperatures. The yields of both CO and CO2 were largely unaffected by the temperature of the afterburner but increased at the presence of the filter indicating oxidation therein. A previously developed kinetic model was used to identify major chemical reaction pathways involving PAH in the afterburner. The experimental data at the exit of the primary furnace was used as input to these model computations. A first evaluation of the predictive capability of the model was conducted for the case with ceramic filter and a temperature of 900 degrees C. The afterburner was approximated as a plug-flow reactor, and model predictions at a residence time of 0.8 s were compared to experimental data collected at its exit. In agreement with the experimental PAH concentration, only a minor impact of the afterburner treatment was observed for most species at 900 degrees C. OH was deduced to be the major reactant with a mole fraction about 4 orders of magnitudes higher than that of hydrogen radicals. Evidence for the need of further work on the quantitative assessment of oxidation of PAH and their radicals is given.

Effect of increased temperature, CO2, and iron on nitrate uptake and primary productivity in the coastal Ross Sea

NASA Astrophysics Data System (ADS)

Bronk, D. A.; Spackeen, J.; Sipler, R. E.; Bertrand, E. M.; Roberts, Q. N.; Xu, K.; Baer, S. E.; McQuaid, J.; Zhu, Z.; Walworth, N. G.; Hutchins, D. A.; Allen, A. E.

2016-02-01

Western Antarctic Seas are rapidly changing as a result of elevated concentrations of CO2 and rising sea surface temperatures. It is critical to determine how the structure and function of microbial communities will be impacted by these changes in the future because the Southern Ocean has seasonally high rates of primary production, is an important sink for anthropogenic CO2, and supports a diverse assemblage of higher trophic level organisms. During the Austral summer of 2013 and 2015, a collaborative research group conducted a series of experiments to understand how the individual and combined effects of temperature, CO2, and iron impact Ross Sea microorganisms. Our project used a variety of approaches, including batch experiments, semi-continuous experiments, and continuous-culturing over extended time intervals, to determine how future changes may shift Ross Sea microbial communities and how nutrient cycling and carbon biogeochemistry may subsequently be altered. Chemical and biological parameters were measured throughout the experiments to assess changes in community composition and nutrient cycling, including uptake rate measurements of nitrate and bicarbonate by different size fractions of microorganisms. Relative to the control, nitrate uptake rates significantly increased when temperature and iron were elevated indicating that temperature and iron are important physical drivers that influence nutrient cycling. Elevations in temperature and iron independently and synergistically produced higher rates than elevated CO2. Our nutrient uptake results also suggest that the physiology of large microorganisms will be more impacted by climate change variables than small microorganisms.

Prediction of pathogen growth on iceberg lettuce under real temperature history during distribution from farm to table.

PubMed

Koseki, Shigenobu; Isobe, Seiichiro

2005-10-25

The growth of pathogenic bacteria Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes on iceberg lettuce under constant and fluctuating temperatures was modelled in order to estimate the microbial safety of this vegetable during distribution from the farm to the table. Firstly, we examined pathogen growth on lettuce at constant temperatures, ranging from 5 to 25 degrees C, and then we obtained the growth kinetic parameters (lag time, maximum growth rate (micro(max)), and maximum population density (MPD)) using the Baranyi primary growth model. The parameters were similar to those predicted by the pathogen modelling program (PMP), with the exception of MPD. The MPD of each pathogen on lettuce was 2-4 log(10) CFU/g lower than that predicted by PMP. Furthermore, the MPD of pathogens decreased with decreasing temperature. The relationship between mu(max) and temperature was linear in accordance with Ratkowsky secondary model as was the relationship between the MPD and temperature. Predictions of pathogen growth under fluctuating temperature used the Baranyi primary microbial growth model along with the Ratkowsky secondary model and MPD equation. The fluctuating temperature profile used in this study was the real temperature history measured during distribution from the field at harvesting to the retail store. Overall predictions for each pathogen agreed well with observed viable counts in most cases. The bias and root mean square error (RMSE) of the prediction were small. The prediction in which mu(max) was based on PMP showed a trend of overestimation relative to prediction based on lettuce. However, the prediction concerning E. coli O157:H7 and Salmonella spp. on lettuce greatly overestimated growth in the case of a temperature history starting relatively high, such as 25 degrees C for 5 h. In contrast, the overall prediction of L. monocytogenes under the same circumstances agreed with the observed data.

Low Cost Nuclear Thermal Rocket Cermet Fuel Element Environment Testing

NASA Technical Reports Server (NTRS)

Bradley, D. E.; Mireles, O. R.; Hickman, R. R.

2011-01-01

Deep space missions with large payloads require high specific impulse and relatively high thrust to achieve mission goals in reasonable time frames.1,2 Conventional storable propellants produce average specific impulse. Nuclear thermal rockets capable of producing high specific impulse are proposed. Nuclear thermal rockets employ heat produced by fission reaction to heat and therefore accelerate hydrogen, which is then forced through a rocket nozzle providing thrust. Fuel element temperatures are very high (up to 3000 K), and hydrogen is highly reactive with most materials at high temperatures. Data covering the effects of high-temperature hydrogen exposure on fuel elements are limited.3 The primary concern is the mechanical failure of fuel elements that employ high-melting-point metals, ceramics, or a combination (cermet) as a structural matrix into which the nuclear fuel is distributed. The purpose of the testing is to obtain data to assess the properties of the non-nuclear support materials, as-fabricated, and determine their ability to survive and maintain thermal performance in a prototypical NTR reactor environment of exposure to hydrogen at very high temperatures. The fission process of the planned fissile material and the resulting heating performance is well known and does not therefore require that active fissile material be integrated in this testing. A small-scale test bed designed to heat fuel element samples via non-contact radio frequency heating and expose samples to hydrogen is being developed to assist in optimal material and manufacturing process selection without employing fissile material. This paper details the test bed design and results of testing conducted to date.

Corrosion of oxide dispersion strengthened iron-chromium steels and tantalum in fluoride salt coolant: An in situ compatibility study for fusion and fusion-fission hybrid reactor concepts

NASA Astrophysics Data System (ADS)

El-Dasher, Bassem; Farmer, Joseph; Ferreira, James; de Caro, Magdalena Serrano; Rubenchik, Alexander; Kimura, Akihiko

2011-12-01

Primary candidate classes of materials for future nuclear power plants, whether they be fission, fusion or hybrids, include oxide dispersion strengthened (ODS) ferritic steels which rely on a dispersion of nano-oxide particles in the matrix for both mechanical strength and swelling resistance, or tantalum alloys which have an inherent neutron-induced swelling resistance and high temperature strength. For high temperature operation, eutectic molten lithium containing fluoride salts are attractive because of their breeding capability as well as their relatively high thermal capacity, which allow for a higher average operating temperature that increases power production. In this paper we test the compatibility of Flinak (LiF-NaF-KF) salts on ODS steels, comparing the performance of current generation ODS steels developed at Kyoto University with the commercial alloy MA956. Pure tantalum was also tested for comparative purposes. In situ data was obtained for temperatures ranging from 600 to 900 °C using a custom-built high temperature electrochemical impedance spectroscopy cell. Results for ODS steels show that steel/coolant interfacial resistance increases from 600 to 800 °C due to an aluminum enriched layer forming at the surface, however an increase in temperature to 900 °C causes this layer to break up and aggressive attack to occur. Performance of current generation ODS steels surpassed that of the MA956 ODS steel, with an in situ impedance behavior similar or better than that of pure tantalum.

28-ka History of Sea Surface Temperature, Primary Productivity and Planktonic Community Variability in the Western Arabian Sea

NASA Astrophysics Data System (ADS)

Pourmand, A.; Marcantonio, F.; Bianchi, T.

2006-12-01

Uranium-series radionuclides and organic compounds, which represent major groups of planktonic organisms, have been measured in western Arabian Sea sediments that span the past 28 ka. Variability of the Indian Ocean monsoons and their influence on primary productivity, sea surface temperature (SST), and planktonic community structure has been investigated. The average alkenone-derived SST for the glacial was ~3°C lower than that measured for the Holocene. We also identify, for the first time, an interval of exceptionally low SSTs between 19-18.1 ka BP (15.3°C at 18.5 ka). During this time, the low SSTs coincide with high cumulative biomarker fluxes (CBF). We propose that intensification of winter northeast monsoon winds during the glacial period resulted in cold SSTs, deep convective mixing, and enhanced primary productivity. Following the last termination, and within the Holocene, SSTs vary by ~2°C with high CBFs occurring at times of relatively warmer SSTs. The fluxes of dinoflagellates and zooplankton relative to the total flux of organisms remain constant throughout the record. However, transitioning from the glacial to the Holocene, diatom fluxes comparatively increase relative to the total flux of organisms, while those of coccolithophorids decrease. Considering that the Indian Ocean monsoons are an important component of the global climate system, a shift in the planktonic ecosystem structure in the Arabian Sea may have important implications for the global biogeochemical cycle of carbon.

Microwave conductance properties of aligned multiwall carbon nanotube textile sheets

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

Brown, Brian L.; Martinez, Patricia; Zakhidov, Anvar A.

2015-07-06

Understanding the conductance properties of multi-walled carbon nanotube (MWNT) textile sheets in the microwave regime is essential for their potential use in high-speed and high-frequency applications. To expand current knowledge, complex high-frequency conductance measurements from 0.01 to 50 GHz and across temperatures from 4.2 K to 300 K and magnetic fields up to 2 T were made on textile sheets of highly aligned MWNTs with strand alignment oriented both parallel and perpendicular to the microwave electric field polarization. Sheets were drawn from 329 and 520 μm high MWNT forests that resulted in different DC resistance anisotropy. For all samples, themore » microwave conductance can be modeled approximately by a shunt capacitance in parallel with a frequency-independent conductance, but with no inductive contribution. Finally, this is consistent with diffusive Drude conduction as the primary transport mechanism up to 50 GHz. Further, it is found that the microwave conductance is essentially independent of both temperature and magnetic field.« less

Mediation pathways and effects of green structures on respiratory mortality via reducing air pollution

NASA Astrophysics Data System (ADS)

Shen, Yu-Sheng; Lung, Shih-Chun Candice

2017-02-01

Previous studies have shown both health and environmental benefits of green spaces, especially in moderating temperature and reducing air pollution. However, the characteristics of green structures have been overlooked in previous investigations. In addition, the mediation effects of green structures on respiratory mortality have not been assessed. This study explores the potential mediation pathways and effects of green structure characteristics on respiratory mortality through temperature, primary and secondary air pollutants separately using partial least squares model with data from Taiwan. The measurable characteristics of green structure include the largest patch percentage, landscape proportion, aggregation, patch distance, and fragmentation. The results showed that mortality of pneumonia and chronic lower respiratory diseases could be reduced by minimizing fragmentation and increasing the largest patch percentage of green structure, and the mediation effects are mostly through reducing air pollutants rather than temperature. Moreover, a high proportion of but fragmented green spaces would increase secondary air pollutants and enhance health risks; demonstrating the deficiency of traditional greening policy with primary focus on coverage ratio. This is the first research focusing on mediation effects of green structure characteristics on respiratory mortality, revealing that appropriate green structure planning can be a useful complementary strategy in environmental health management.

Mediation pathways and effects of green structures on respiratory mortality via reducing air pollution.

PubMed

Shen, Yu-Sheng; Lung, Shih-Chun Candice

2017-02-23

Previous studies have shown both health and environmental benefits of green spaces, especially in moderating temperature and reducing air pollution. However, the characteristics of green structures have been overlooked in previous investigations. In addition, the mediation effects of green structures on respiratory mortality have not been assessed. This study explores the potential mediation pathways and effects of green structure characteristics on respiratory mortality through temperature, primary and secondary air pollutants separately using partial least squares model with data from Taiwan. The measurable characteristics of green structure include the largest patch percentage, landscape proportion, aggregation, patch distance, and fragmentation. The results showed that mortality of pneumonia and chronic lower respiratory diseases could be reduced by minimizing fragmentation and increasing the largest patch percentage of green structure, and the mediation effects are mostly through reducing air pollutants rather than temperature. Moreover, a high proportion of but fragmented green spaces would increase secondary air pollutants and enhance health risks; demonstrating the deficiency of traditional greening policy with primary focus on coverage ratio. This is the first research focusing on mediation effects of green structure characteristics on respiratory mortality, revealing that appropriate green structure planning can be a useful complementary strategy in environmental health management.

Simulations and Experiments of the Nonisothermal Forging Process of a Ti-6Al-4V Impeller

NASA Astrophysics Data System (ADS)

Prabhu, T. Ram

2016-09-01

In the present study, a nonisothermal precision forging process of a Ti-6Al-4V first-stage impeller for the gas turbine engine was simulated using the finite element software. The simulation results such as load requirements, damage, velocity field, stress, strain, and temperature distributions are discussed in detail. Simulations predicted the maximum load requirement of about 80 MN. The maximum temperature loss was observed at the contour surface regions. The center and contour regions are the high-strained regions in the part. To validate the model, forging experiments mimicking simulations were performed in the α + β phases region (930 °C). The selected locations of the part were characterized for tensile properties at 27 and 200 °C, hardness, microstructure, grain size, and the amount of primary α phase based on the strain distribution results. The soundness of the forged part was verified using fluorescent penetrant test (Mil Std 2175 Grade A) and ultrasonic test (AMS 2630 class A1). From the experimental results, it was found that the variations in the hardness, tensile properties at room, and elevated temperature are not significant. The microstructure, grain size, and primary α phase content are nearly same.

Chemical Composition of RR Lyn - an Eclipsing Binary System with Am and λ Boo Type Components

NASA Astrophysics Data System (ADS)

Jeong, Yeuncheol; Yushchenko, Alexander V.; Doikov, Dmytry N.; Gopka, Vira F.; Yushchenko, Volodymyr O.

2017-06-01

High-resolution spectroscopic observations of the eclipsing binary system RR Lyn were made using the 1.8 m telescope at the Bohuynsan Optical Astronomical Observatory in Korea. The spectral resolving power was R = 82,000, with a signal to noise ratio of S/N > 150. We found the effective temperatures and surface gravities of the primary and secondary components to be equal to Teff = 7,920 & 7,210 K and log(g) = 3.80 & 4.16, respectively. The abundances of 34 and 17 different chemical elements were found in the atmospheric components. Correlations between the derived abundances with condensation temperatures and the second ionization potentials of these elements are discussed. The primary component is a typical metallic line star with the abundances of light and iron group elements close to solar values, while elements with atomic numbers Z > 30 are overabundant by 0.5-1.5 dex with respect to solar values. The secondary component is a λ Boo type star. In this type of stars, CNO abundances are close to solar values, while the abundance pattern shows a negative correlation with condensation temperatures.

Impact of ocean acidification and warming on the productivity of a rock pool community.

PubMed

Legrand, Erwann; Riera, Pascal; Bohner, Olivier; Coudret, Jérôme; Schlicklin, Ferdinand; Derrien, Marie; Martin, Sophie

2018-05-01

This study examined experimentally the combined effect of ocean acidification and warming on the productivity of rock pool multi-specific assemblages, composed of coralline algae, fleshy algae, and grazers. Natural rock pool communities experience high environmental fluctuations. This may confer physiological advantage to rock pool communities when facing predicted acidification and warming. The effect of ocean acidification and warming have been assessed at both individual and assemblage level to examine the importance of species interactions in the response of assemblages. We hypothesized that rock pool assemblages have physiological advantage when facing predicted ocean acidification and warming. Species exhibited species-specific responses to increased temperature and pCO 2 . Increased temperature and pCO 2 have no effect on assemblage photosynthesis, which was mostly influenced by fleshy algal primary production. The response of coralline algae to ocean acidification and warming depended on the season, which evidenced the importance of physiological adaptations to their environment in their response to climate change. We suggest that rock pool assemblages are relatively robust to changes in temperature and pCO 2 , in terms of primary production. Copyright © 2018 Elsevier Ltd. All rights reserved.

Noise thermometry at ultra-low temperatures.

PubMed

Rothfuss, D; Reiser, A; Fleischmann, A; Enss, C

2016-03-28

The options for primary thermometry at ultra-low temperatures are rather limited. In practice, most laboratories are using (195)Pt NMR thermometers in the microkelvin range. In recent years, current sensing direct current superconducting quantum interference devices (DC-SQUIDs) have enabled the use of noise thermometry in this temperature range. Such devices have also demonstrated the potential for primary thermometry. One major advantage of noise thermometry is the fact that no driving current is needed to operate the device and thus the heat dissipation within the thermometer can be reduced to a minimum. Ultimately, the intrinsic power dissipation is given by the negligible back action of the readout SQUID. For thermometry in low-temperature experiments, current noise thermometers and magnetic flux fluctuation thermometers have proved to be most suitable. To make use of such thermometers at ultra-low temperatures, we have developed a cross-correlation technique that reduces the amplifier noise contribution to a negligible value. For this, the magnetic flux fluctuations caused by the Brownian motion of the electrons in our noise source are measured inductively by two DC-SQUID magnetometers simultaneously and the signals from these two channels are cross-correlated. Experimentally, we have characterized a thermometer made of a cold-worked high-purity copper cylinder with a diameter of 5 mm and a length of 20 mm for temperatures between 42 μK and 0.8 K. For a given temperature, a measuring time below 1 min is sufficient to reach a precision of better than 1%. The extremely low power dissipation in the thermometer allows continuous operation without heating effects. © 2016 The Author(s).

Polycyclic aromatic hydrocarbon and particulate emissions from two-stage combustion of polystyrene: the effect of the primary furnace temperature.

PubMed

Wang, J; Levendis, Y A; Richter, H; Howard, J B; Carlson, J

2001-09-01

A study is presented on laboratory-scale combustion of polystyrene (PS) to identify staged-combustion conditions that minimize emissions. Batch combustion of shredded PS was conducted in fixed beds placed in a bench-scale electrically heated horizontal muffle furnace. In most cases, combustion of the samples occurred by forming gaseous diffusion flames in atmospheric pressure air. The combustion effluent was mixed with additional air, and it was channeled to a second muffle furnace (afterburner) placed in series. Further reactions took place in the secondary furnace at a residence time of 0.7 s. The gas temperature of the primary furnace was varied in the range of 500-1,000 degrees C, while that of the secondary furnace was kept fixed at 1,000 degrees C. Sampling for CO, CO2, O2, soot, and unburned hydrocarbon emissions (volatile and semivolatile, by GC-MS) was performed at the exits of the two furnaces. Results showed that the temperature of the primary furnace, where PS gasifies, is of paramount importance to the formation and subsequent emissions of organic species and soot. Atthe lowesttemperatures explored, mostly styrene oligomers were identified at the outlet of the primary furnace, but they did not survive the treatment in the secondary furnace. The formation and emission of polycyclic aromatic hydrocarbons (PAH) and soot were suppressed. As the temperature in the first furnace was raised, increasing amounts of a wide range of both unsubstituted and substituted PAH containing up to at least seven condensed aromatic rings were detected. A similar trend was observed for total particulate yields. The secondary furnace treatment reduced the yields of total PAH, but it had an ambiguous effect on individual species. While most low molecular mass PAH were reduced in the secondary furnace, concentrations of some larger PAH increased under certain conditions. Thus, care in the selection of operating conditions of both the primary furnace (gasifier/ burner) and the secondary furnace (afterburner) must be exercised to minimize the emission of hazardous pollutants. The emissions of soot were also reduced in the afterburner but not drastically. This indicates that soot is indeed resistant to oxidation; thus, it would be best to avoid its formation in the first place. An oxidative pyrolysis temperature of PS in the vicinity of 600 degrees C appears to accomplish exactly that. An additional afterburner treatment at a sufficiently high temperature (1,000 degrees C) may be a suitable setting for minimization of most pollutants. To obtain deeper understanding of chemical processes, the experimental results were qualitatively compared with preliminary predictions of a detailed kinetic model that describes formation and destruction pathways of chemical species including most PAH observed in the present work. The modeling was performed forthe secondary furnace assuming plug-flow conditions therein. The experimentally determined chemical composition at the outlet of the primary furnace was part of the input parameters of the model calculation.

Assessment of High Temperature Superconducting (HTS) electric motors for rotorcraft propulsion

NASA Technical Reports Server (NTRS)

Doernbach, Jay

1990-01-01

The successful development of high temperature superconductors (HTS) could have a major impact on future aeronautical propulsion and aeronautical flight vehicle systems. Applications of high temperature superconductors have been envisioned for several classes of aeronautical systems, including subsonic and supersonic transports, hypersonic aircraft, V/STOL aircraft, rotorcraft and solar powered aircraft. The potential of HTS electric motors and generators for providing primary shaft power for rotorcraft propulsion is examined. Three different sized production helicopters were investigated; namely, the Bell Jet Ranger, the Sikorsky Black Hawk and the Sikorsky Super Stallion. These rotorcraft have nominal horsepower ratings of 500, 3600, and 13400 respectively. Preliminary results indicated that an all-electric HTS drive system produces an improvement in rotorcraft Takeoff Gross Weight (TOGW) for those rotorcraft with power ratings above 2000 horsepower. The predicted TOGW improvements are up to 9 percent for the medium-sized Sikorsky Black Hawk and up to 20 percent for the large-sized Sikorsky Super Stallion. The small-sized Bell Jet Ranger, however, experienced a penalty in TOGW with the all-electric HTS drive system.

Cryogenic adhesives and sealants: Abstracted publications

NASA Technical Reports Server (NTRS)

Williamson, F. R.; Olien, N. A.

1977-01-01

Abstracts of primary documents containing original experimental data on the properties of adhesives and sealants at cryogenic temperatures are presented. The most important references mentioned in each document are cited. In addition, a brief annotation is given for documents considered secondary in nature, such as republications or variations of original reports, progress reports leading to final reports included as primary documents, and experimental data on adhesive properties at temperatures between about 130 K and room temperature.

Extending the validation of multi-mode model for anomalous transport to high beta poloidal tokamak scenario in DIII-D

NASA Astrophysics Data System (ADS)

Pankin, A. Y.; Kritz, A. H.; Rafiq, T.; Garofalo, A. M.; Holod, I.; Weiland, J.

2018-05-01

The Multi-Mode Model (MMM7.1) for anomalous transport is tested in predictive modeling of temperature profiles of a high beta poloidal DIII-D discharge. This new H-mode plasma regime, with high beta poloidal and high bootstrap currents, has been studied in DIII-D tokamak discharges [A. Garofalo et al., Nucl. Fusion 55, 123025 (2015)]. The role of instabilities that can drive the anomalous transport described by MMM7.1 is investigated. The temperature profiles for a high beta poloidal DIII-D discharge are computed using the NCLASS model for the neoclassical transport and the Weiland and Electron Temperature Gradient (ETG) components of the MMM7.1 model for the anomalous transport. The neoclassical transport is found to be the main contributor to the ion thermal transport in the plasma core. The contributions from the ion temperature gradient driven modes are found to be important only outside of the internal transport barrier. The magnitudes of the predicted temperature profiles are found to be in a reasonable agreement with experimental profiles. The simulation results approximately reproduce the internal transport barrier in the ion temperature profile but not in the electron temperature profile due to a weak dependence of the ETG driven transport on the Shafranov shift in the ETG component of MMM7.1. Possible effects that can contribute to stabilization of these modes, for example, effects associated with the large beta poloidal such as the Shafranov shift stabilization in the MMM7.1 model, are discussed. It is demonstrated that the E × B flow shear has a relatively small effect in the formation of the internal transport barrier in the high beta poloidal DIII-D discharge 154406. The Shafranov shift (alpha stabilization) and small or reversed magnetic shear profiles are found to be the primary reasons for quenched anomalous transport in this discharge.

Temperature control system for a J-module heat exchanger

DOEpatents

Basdekas, Demetrios L.; Macrae, George; Walsh, Joseph M.

1978-01-01

The level of primary fluid is controlled to change the effective heat transfer area of a heat exchanger utilized in a liquid metal nuclear power plant to eliminate the need for liquid metal control valves to regulate the flow of primary fluid and the temperature of the effluent secondary fluid.

Summer primary productivity and phytoplankton community composition driven by different hydrographic structures in the East/Japan Sea and the Western Subarctic Pacific

NASA Astrophysics Data System (ADS)

Kwak, Jung Hyun; Lee, Sang Heon; Hwang, Jeomshik; Suh, Young-Sang; Je Park, Hyun; Chang, Kyung-Il; Kim, Kyung-Ryul; Kang, Chang-Keun

2014-07-01

The East/Japan Sea (EJS) is a highly productive marginal sea in the northwest Pacific, consisting of three basins (Ulleung Basin: UB, Yamato Basin: YB, and Japan Basin: JB). To find causes of the reportedly high primary productivity in summer in the EJS, especially in the UB, we measured primary productivity, phytoplankton composition, and other environmental variables. The water column was strongly stratified in the EJS compared with the Western Subarctic Pacific (WSP). Integrated primary productivity was two times higher in the EJS (612 mg C m-2 d-1) than in the WSP (291 mg C m-2 d-1). The vertical distributions of physicochemical and biological factors confirmed that production in the subsurface chlorophyll maximum layer in the study regions was an important factor regulating primary productivity within the water column. While picoplankton (<2.7 µm) dominated in the WSP, JB, and YB, micro/nanoplankton (≥2.7 µm) dominated in the UB. Contribution by picoplankton to total biomass and primary productivity in the UB was significantly lower than in the other regions. CHEMTAX analysis using marker pigments showed that diverse phytoplankton groups inhabited the study regions. Cluster and canonical correspondence analyses showed high correlation between the spatial variation in phytoplankton assemblages with the water mass properties mainly represented by water temperature and nitrate concentration. Overall, our results suggest that the hydrographic structure of water column in the study region is an important controlling factor of the biomass and productivity of phytoplankton as well as their diversity in size and taxonomic groups.

Microbial Community Structure of Deep-sea Hydrothermal Vents on the Ultraslow Spreading Southwest Indian Ridge

PubMed Central

Ding, Jian; Zhang, Yu; Wang, Han; Jian, Huahua; Leng, Hao; Xiao, Xiang

2017-01-01

Southwest Indian Ridge (SWIR) is a typical oceanic ultraslow spreading ridge with intensive hydrothermal activities. The microbial communities in hydrothermal fields including primary producers to support the entire ecosystem by utilizing geochemical energy generated from rock-seawater interactions. Here we have examined the microbial community structures on four hydrothermal vents from SWIR, representing distinct characteristics in terms of temperature, pH and metal compositions, by using Illumina sequencing of the 16S small subunit ribosomal RNA (rRNA) genes, to correlate bacterial and archaeal populations with the nature of the vents influenced by ultraslow spreading features. Epsilon-, Gamma-, Alpha-, and Deltaproteobacteria and members of the phylum Bacteroidetes and Planctomycetes, as well as Thaumarchaeota, Woesearchaeota, and Euryarchaeota were dominant in all the samples. Both bacterial and archaeal community structures showed distinguished patterns compared to those in the fast-spreading East Pacific Ridge or the slow-spreading Mid-Atlantic Ridge as previously reported. Furthermore, within SWIR, the microbial communities are highly correlated with the local temperatures. For example, the sulfur-oxidizing bacteria were dominant within bacteria from low-temperature vents, but were not represented as the dominating group recovered from high temperature (over 300°C) venting chimneys in SWIR. Meanwhile, Thaumarchaeota, the ammonium oxidizing archaea, only showed high relative abundance of amplicons in the vents with high-temperature in SWIR. These findings provide insights on the microbial community in ultraslow spreading hydrothermal fields, and therefore assist us in the understanding of geochemical cycling therein. PMID:28659873

Factors Influencing the Stability of Au-Incorporated Metal-Oxide Supported Thin Films for Optical Gas Sensing

DOE PAGES

Baltrus, John P.; Holcomb, Gordon R.; Tylczak, Joseph H.; ...

2017-02-24

There is interest in using Au-nanoparticle incorporated oxide films as functional sensor layers for high-temperature applications in optical-based sensors for measurements in both highly-oxidizing and highly-reducing atmospheres at temperatures approaching 900°C-1000°C because of a relatively high melting temperature combined with the inert nature of Au nanoparticles. This study includes a systematic series of experiments and theoretical calculations targeted at further understanding stability of Au-nanoparticle incorporated TiO 2 films as archetype sensing materials. A combination of thermodynamic modeling and long-term exposure tests were utilized to unambiguously determine that gas stream composition-dependent reactive evaporation of Au (to form predominately Au(g) or AuH(g),more » depending upon the environment) at the surface of the nanoparticles is the dominant mechanism for mass loss of Au. Primary factors dictating the rate of reactive evaporation, and hence the associated film stability, were determined to be the gas stream temperature and the concentration of H 2, with the former playing a more significant role over the ranges of temperatures (700°C - 800°C) and H 2 concentrations (1% to 29% H 2 by volume) explored. The mitigation of Au-mass loss through reactive evaporation was also successfully demonstrated by depositing a SiO 2 overlayer on the Au-nanoparticle embedded films to prevent direct Au-nanoparticle/vapor-phase contact.« less

Factors Influencing the Stability of Au-Incorporated Metal-Oxide Supported Thin Films for Optical Gas Sensing

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

Baltrus, John P.; Holcomb, Gordon R.; Tylczak, Joseph H.

There is interest in using Au-nanoparticle incorporated oxide films as functional sensor layers for high-temperature applications in optical-based sensors for measurements in both highly-oxidizing and highly-reducing atmospheres at temperatures approaching 900°C-1000°C because of a relatively high melting temperature combined with the inert nature of Au nanoparticles. This study includes a systematic series of experiments and theoretical calculations targeted at further understanding stability of Au-nanoparticle incorporated TiO 2 films as archetype sensing materials. A combination of thermodynamic modeling and long-term exposure tests were utilized to unambiguously determine that gas stream composition-dependent reactive evaporation of Au (to form predominately Au(g) or AuH(g),more » depending upon the environment) at the surface of the nanoparticles is the dominant mechanism for mass loss of Au. Primary factors dictating the rate of reactive evaporation, and hence the associated film stability, were determined to be the gas stream temperature and the concentration of H 2, with the former playing a more significant role over the ranges of temperatures (700°C - 800°C) and H 2 concentrations (1% to 29% H 2 by volume) explored. The mitigation of Au-mass loss through reactive evaporation was also successfully demonstrated by depositing a SiO 2 overlayer on the Au-nanoparticle embedded films to prevent direct Au-nanoparticle/vapor-phase contact.« less

The inverse microconglomerate test: Definition and application to the preservation of Paleoarchean to Hadean magnetizations in metasediments of the Jack Hills, Western Australia

NASA Astrophysics Data System (ADS)

Cottrell, Rory; Tarduno, John; Bono, Richard; Dare, Matthew

2016-04-01

We introduce a new paleomagnetic field test, the inverse microconglomerate test. In contrast with traditional conglomerate tests, which target specimens that might preserve primary magnetizations, the inverse microconglomerate test focuses on magnetic carriers having unblocking temperatures less than peak metamorphic temperatures. These mineral carriers are expected to carry a consistent direction of remagnetization. Hence, the inverse microconglomerate test evaluates whether coherent magnetizations are retained on a grain/mineral scale in a given sedimentary rock sample. By defining the remagnetization direction, it also serves as a benchmark for comparison of magnetizations from other grains/minerals having unblocking temperatures higher than peak metamorphic conditions (i.e., potential primary magnetizations). We apply this new test to sediments of the Jack Hills (JH), Yilgarn craton, Western Australia. For the JH sediments we focus on fuchsite, a secondary Cr-mica that contains relict Cr-Fe spinels capable of recording remanent magnetizations. We find that JH fuchsite grains retain consistent magnetic directions at unblocking temperatures between ˜270 and 340 oC, which defines a positive test. This direction does not reproduce a nominal 1078-1070 Ma remagnetization reported by Weiss et al. (EPSL, 2015) that we interpret as an artifact of inappropriate use of averaging and statistics. The thermochemical remanent magnetization recorded by the fuchsite was most likely imparted during peak JH metamorphic conditions at ˜2650 Ma. Our inverse microconglomerate test complements a positive microconglomerate test and large scale positive conglomerate test conducted on JH cobbles (Tarduno and Cottrell, EPSL, 2013), further supporting evidence that JH zircons record Paleoarchean to Hadean primary magnetizations at high (greater than 550 oC) unblocking temperatures (Tarduno et al., Science, 2015). More generally, the new inverse microconglomerate test may aid in understanding the timing of peak metamorphism and deformation in complex terrains that have undergone multiple episodes of folding.

Dynamic Predictive Model for Growth of Bacillus cereus from Spores in Cooked Beans.

PubMed

Juneja, Vijay K; Mishra, Abhinav; Pradhan, Abani K

2018-02-01

Kinetic growth data for Bacillus cereus grown from spores were collected in cooked beans under several isothermal conditions (10 to 49°C). Samples were inoculated with approximately 2 log CFU/g heat-shocked (80°C for 10 min) spores and stored at isothermal temperatures. B. cereus populations were determined at appropriate intervals by plating on mannitol-egg yolk-polymyxin agar and incubating at 30°C for 24 h. Data were fitted into Baranyi, Huang, modified Gompertz, and three-phase linear primary growth models. All four models were fitted to the experimental growth data collected at 13 to 46°C. Performances of these models were evaluated based on accuracy and bias factors, the coefficient of determination ( R 2 ), and the root mean square error. Based on these criteria, the Baranyi model best described the growth data, followed by the Huang, modified Gompertz, and three-phase linear models. The maximum growth rates of each primary model were fitted as a function of temperature using the modified Ratkowsky model. The high R 2 values (0.95 to 0.98) indicate that the modified Ratkowsky model can be used to describe the effect of temperature on the growth rates for all four primary models. The acceptable prediction zone (APZ) approach also was used for validation of the model with observed data collected during single and two-step dynamic cooling temperature protocols. When the predictions using the Baranyi model were compared with the observed data using the APZ analysis, all 24 observations for the exponential single rate cooling were within the APZ, which was set between -0.5 and 1 log CFU/g; 26 of 28 predictions for the two-step cooling profiles also were within the APZ limits. The developed dynamic model can be used to predict potential B. cereus growth from spores in beans under various temperature conditions or during extended chilling of cooked beans.

Linking Microbial Dynamics and Physicochemical Processes in High-temperature Acidic Fe(III)- Mineralizing Systems

NASA Astrophysics Data System (ADS)

Inskeep, W.

2014-12-01

Microbial activity is responsible for the mineralization of Fe(III)-oxides in high-temperature chemotrophic communities that flourish within oxygenated zones of low pH (2.5 - 4) geothermal outflow channels (Yellowstone National Park, WY). High-temperature Fe(II)-oxidizing communities contain several lineages of Archaea, and are excellent model systems for studying microbial interactions and spatiotemporal dynamics across geochemical gradients. We hypothesize that acidic Fe(III)-oxide mats form as a result of constant interaction among primary colonizers including Hydrogenobaculum spp. (Aquificales) and Metallosphaera spp. (Sulfolobales), and subsequent colonization by archaeal heterotrophs, which vary in abundance as a function of oxygen, pH and temperature. We are integrating a complementary suite of geochemical, stable isotope, genomic, proteomic and modeling analyses to study the role of microorganisms in Fe(III)-oxide mat development, and to elucidate the primary microbial interactions that are coupled with key abiotic events. Curated de novo assemblies of major phylotypes are being used to analyze additional -omics datasets from these microbial mats. Hydrogenobaculum spp. (Aquificales) are the dominant bacterial population(s) present, and predominate during early mat development (< 30 d). Other Sulfolobales populations known to oxidize Fe(II) and fix carbon dioxide (e.g., Metallosphaera spp.) represent a secondary stage of mat development (e.g., 14 - 30 d). Hydrogenobaculum filaments appear to promote the nucleation and subsequent mineralization of Fe(III)-oxides, which likely affect the growth and turnover rates of these organisms. Other heterotrophs colonize Fe(III)-oxide mats during succession (> 30 d), including novel lineages of Archaea and representatives within the Crenarchaeota, Euryarchaeota, Thaumarchaeota and Nanoarchaeota. In situ oxygen consumption rates show that steep gradients occur within the top 1 mm of mat surface, and which correlate with changes in the abundance of different organisms that occupy these microenvironments. The relative consumption of oxygen by different members of Fe(II)-oxidizing mat communities has implications for autotroph-heterotroph associations and the dynamic micromorphology of active Fe(III)-oxide terraces.

Application analysis of solar total energy systems to the residential sector. Volume III, conceptual design. Final report

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

Not Available

1979-07-01

The objective of the work described in this volume was to conceptualize suitable designs for solar total energy systems for the following residential market segments: single-family detached homes, single-family attached units (townhouses), low-rise apartments, and high-rise apartments. Conceptual designs for the total energy systems are based on parabolic trough collectors in conjunction with a 100 kWe organic Rankine cycle heat engine or a flat-plate, water-cooled photovoltaic array. The ORC-based systems are designed to operate as either independent (stand alone) systems that burn fossil fuel for backup electricity or as systems that purchase electricity from a utility grid for electrical backup.more » The ORC designs are classified as (1) a high temperature system designed to operate at 600/sup 0/F and (2) a low temperature system designed to operate at 300/sup 0/F. The 600/sup 0/F ORC system that purchases grid electricity as backup utilizes the thermal tracking principle and the 300/sup 0/F ORC system tracks the combined thermal and electrical loads. Reject heat from the condenser supplies thermal energy for heating and cooling. All of the ORC systems utilize fossil fuel boilers to supply backup thermal energy to both the primary (electrical generating) cycle and the secondary (thermal) cycle. Space heating is supplied by a central hot water (hydronic) system and a central absorption chiller supplies the space cooling loads. A central hot water system supplies domestic hot water. The photovoltaic system uses a central electrical vapor compression air conditioning system for space cooling, with space heating and domestic hot water provided by reject heat from the water-cooled array. All of the systems incorporate low temperature thermal storage (based on water as the storage medium) and lead--acid battery storage for electricity; in addition, the 600/sup 0/F ORC system uses a therminol-rock high temperature storage for the primary cycle. (WHK)« less

Creep Laboratory manual

NASA Astrophysics Data System (ADS)

Osgerby, S.; Loveday, M. S.

1992-06-01

A manual for the NPL Creep Laboratory, a collective name given to two testing laboratories, the Uniaxial Creep Laboratory and the Advanced High Temperature Mechanical Testing Laboratory, is presented. The first laboratory is devoted to uniaxial creep testing and houses approximately 50 high sensitivity creep machines including 10 constant stress cam lever machines. The second laboratory houses a low cycle fatigue testing machine of 100 kN capacity driven by a servo-electric actuator, five machines for uniaxial tensile creep testing of engineering ceramics at temperatures up to 1600C, and an electronic creep machine. Details of the operational procedures for carrying out uniaxial creep testing are given. Calibration procedures to be followed in order to comply with the specifications laid down by British standards, and to provide traceability back to the primary standards are described.

Fecal Immunochemical Test (FIT) for Colon Cancer Screening: Variable Performance with Ambient Temperature

PubMed Central

Doubeni, Chyke A.; Jensen, Christopher D.; Fedewa, Stacey A.; Quinn, Virginia P.; Zauber, Ann G.; Schottinger, Joanne E.; Corley, Douglas A.; Levin, Theodore R.

2017-01-01

Introduction Fecal immunochemical tests (FITs) are widely used in colorectal cancer (CRC) screening, but hemoglobin degradation, due to exposure of the collected sample to high temperatures, could reduce test sensitivity. We examined the relation of ambient temperature exposure with FIT positivity rate and sensitivity. Methods This was a retrospective cohort study of patients 50 to 75 years in Kaiser Permanente Northern California’s CRC screening program, which began mailing FIT kits annually to screen-eligible members in 2007. Primary outcomes were FIT positivity rate and sensitivity to detect CRC. Predictors were month, season, and daily ambient temperatures of test result dates based on US National Oceanic and Atmospheric Administration data. Results Patients (n =472,542) completed 1,141,162 FITs. Weekly test positivity rate ranged from 2.6% to 8.0% (median, 4.4%) and varied significantly by month (June/July vs December/January rate ratio [RR] =0.79, 95% confidence interval [CI], 0.76 to 0.83) and season. FIT sensitivity was lower in June/July (74.5%; 95% CI, 72.5 to 76.6) than January/December (78.9%; 95% CI, 77.0 to 80.7). Conclusions FITs completed during high ambient temperatures had lower positivity rates and lower sensitivity. Changing kit design, specimen transportation practices, or avoiding periods of high ambient temperatures may help optimize FIT performance, but may also increase testing complexity and reduce patient adherence, requiring careful study. PMID:28076249

Dynamic T2-mapping during magnetic resonance guided high intensity focused ultrasound ablation of bone marrow

NASA Astrophysics Data System (ADS)

Waspe, Adam C.; Looi, Thomas; Mougenot, Charles; Amaral, Joao; Temple, Michael; Sivaloganathan, Siv; Drake, James M.

2012-11-01

Focal bone tumor treatments include amputation, limb-sparing surgical excision with bone reconstruction, and high-dose external-beam radiation therapy. Magnetic resonance guided high intensity focused ultrasound (MR-HIFU) is an effective non-invasive thermotherapy for palliative management of bone metastases pain. MR thermometry (MRT) measures the proton resonance frequency shift (PRFS) of water molecules and produces accurate (<1°C) and dynamic (<5s) thermal maps in soft tissues. PRFS-MRT is ineffective in fatty tissues such as yellow bone marrow and, since accurate temperature measurements are required in the bone to ensure adequate thermal dose, MR-HIFU is not indicated for primary bone tumor treatments. Magnetic relaxation times are sensitive to lipid temperature and we hypothesize that bone marrow temperature can be determined accurately by measuring changes in T2, since T2 increases linearly in fat during heating. T2-mapping using dual echo times during a dynamic turbo spin-echo pulse sequence enabled rapid measurement of T2. Calibration of T2-based thermal maps involved heating the marrow in a bovine femur and simultaneously measuring T2 and temperature with a thermocouple. A positive T2 temperature dependence in bone marrow of 20 ms/°C was observed. Dynamic T2-mapping should enable accurate temperature monitoring during MR-HIFU treatment of bone marrow and shows promise for improving the safety and reducing the invasiveness of pediatric bone tumor treatments.

Factors affecting in-hospital heat-related mortality: a multi-city case-crossover analysis.

PubMed

Stafoggia, M; Forastiere, F; Agostini, D; Caranci, N; de'Donato, F; Demaria, M; Michelozzi, P; Miglio, R; Rognoni, M; Russo, A; Perucci, C A

2008-03-01

Several studies have identified strong effects of high temperatures on mortality at population level; however, individual vulnerability factors associated with heat-related in-hospital mortality are largely unknown. The objective of the study was to evaluate heat-related in-hospital mortality using a multi-city case-crossover analysis. We studied residents of four Italian cities, aged 65+ years, who died during 1997-2004. For 94,944 individuals who died in hospital and were hospitalised two or more days before death, demographics, chronic conditions, primary diagnoses of last event and hospital wards were considered. A city-specific case-crossover analysis was performed to evaluate the association between apparent temperature and mortality. Pooled odds ratios (OR) of dying on a day with a temperature of 30 degrees C compared to a day with a temperature of 20 degrees C were estimated with a random-effects meta-analysis. We estimated an overall OR of 1.32 (95% confidence interval: 1.25, 1.39). Age, marital status and hospital ward were important risk indicators. Patients in general medicine were at higher risk than those in high and intensive care units. A history of psychiatric disorders and cerebrovascular diseases gave a higher vulnerability. Mortality was greater among patients hospitalised for heart failure, stroke and chronic pulmonary diseases. In-hospital mortality is strongly associated with high temperatures. A comfortable temperature in hospitals and increased attention to vulnerable patients during heatwaves, especially in general medicine, are necessary preventive measures.

Acoustic and microwave tests in a cylindrical cavity for acoustic gas thermometry at high temperature

PubMed Central

Zhang, K.; Feng, X.J.; Gillis, K.; Moldover, M.; Zhang, J.T.; Lin, H.; Qu, J.F.; Duan, Y.N.

2016-01-01

Relative primary acoustic gas thermometry determines the ratios of thermodynamic temperatures from measured ratios of acoustic and microwave resonance frequencies in a gas-filled metal cavity on isotherms of interest. When measured in a cavity with known dimensions, the frequencies of acoustic resonances in a gas determine the speed of sound, which is a known function of the thermodynamic temperature T. Changes in the dimensions of the cavity are measured using the frequencies of the cavity's microwave resonances. We explored techniques and materials for acoustic gas thermometry at high temperatures using a cylindrical cavity with remote acoustic transducers. We used gas-filled ducts as acoustic waveguides to transmit sound between the cavity at high temperatures and the acoustic transducers at room temperature. We measured non-degenerate acoustic modes in a cylindrical cavity in the range 295 K < T < 797 K. The fractional uncertainty of the measured acoustic frequencies increased from 2×10−6 at 295 K to 5×10−6 at 797 K. In addition, we measured the frequencies of several transverse magnetic (TM) microwave resonances up to 1000 K in order to track changes in the cavity's length L and radius R. The fractional standard deviation of the values of L deduced from three TM modes increased from 3×10−6 for T < 600 K to 57×10−6 at 1000 K. We observed similar inconsistencies in a previous study. PMID:26903106

Creep Response and Deformation Processes in Nanocluster Strengthened Ferritic Steels

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

Hayashi, Taisuke; Sarosi, P. M.; Schneibel, Joachim H

2008-01-01

There is increasing demand for oxide-dispersion-strengthened ferritic alloys that possess both high-temperature strength and irradiation resistance. Improvement of the high-temperature properties requires an understanding of the operative deformation mechanisms. In this study, the microstructures and creep properties of the oxide-dispersion-strengthened alloy 14YWT have been evaluated as a function of annealing at 1000 C for 1 hour up to 32 days. The ultra-fine initial grain size (approx. 100nm) is stable after the shortest annealing time, and even after subsequent creep at 800 C. Longer annealing periods lead to anomalous grain growth that is further enhanced following creep. Remarkably, the minimum creepmore » rate is relatively insensitive to this dramatic grain-coarsening. The creep strength is attributed to highly stable, Ti-rich nanoclusters that appear to pin the initial primary grains, and present strong obstacles to dislocation motion in the large, anomalously grown grains.« less

Use of an approximate similarity principle for the thermal scaling of a full-scale thrust augmenting ejector

NASA Technical Reports Server (NTRS)

Barankiewicz, Wendy S.; Perusek, Gail P.; Ibrahim, Mounir B.

1992-01-01

Full temperature ejector model simulations are expensive, and difficult to implement experimentally. If an approximate similarity principle could be established, properly chosen performance parameters should be similar for both hot and cold flow tests if the initial Mach number and total pressures of the flow field are held constant. Existing ejector data is used to explore the utility of one particular similarity principle; the Munk and Prim similarity principle for isentropic flows. Static performance test data for a full-scale thrust augmenting ejector are analyzed for primary flow temperatures up to 1560 R. At different primary temperatures, exit pressure contours are compared for similarity. A nondimensional flow parameter is then used to eliminate primary nozzle temperature dependence and verify similarity between the hot and cold flow experiments.

Use of an approximate similarity principle for the thermal scaling of a full-scale thrust augmenting ejector

NASA Technical Reports Server (NTRS)

Barankiewicz, Wendy; Perusek, Gail P.; Ibrahim, Mounir

1992-01-01

Full temperature ejector model simulations are expensive, and difficult to implement experimentally. If an approximate similarity principle could be established, properly chosen performance parameters should be similar for both hot and cold flow tests if the initial Mach number and total pressures of the flow field are held constant. Existing ejector data is used to explore the utility of one particular similarity principle; the Munk and Prim similarity principle for isentropic flows. Static performance test data for a full-scale thrust augmenting ejector are analyzed for primary flow temperatures up to 1560 R. At different primary temperatures, exit pressure contours are compared for similarity. A nondimensional flow paramenter is then used to eliminate primary nozzle temperature dependence and verify similarity between the hot and cold flow experiments.

Modeling Allometric Relationships in Leaves of Young Rapeseed (Brassica napus L.) Grown at Different Temperature Treatments

PubMed Central

Tian, Tian; Wu, Lingtong; Henke, Michael; Ali, Basharat; Zhou, Weijun; Buck-Sorlin, Gerhard

2017-01-01

Functional–structural plant modeling (FSPM) is a fast and dynamic method to predict plant growth under varying environmental conditions. Temperature is a primary factor affecting the rate of plant development. In the present study, we used three different temperature treatments (10/14°C, 18/22°C, and 26/30°C) to test the effect of temperature on growth and development of rapeseed (Brassica napus L.) seedlings. Plants were sampled at regular intervals (every 3 days) to obtain growth data during the length of the experiment (1 month in total). Total leaf dry mass, leaf area, leaf mass per area (LMA), width-length ratio, and the ratio of petiole length to leaf blade length (PBR), were determined and statistically analyzed, and contributed to a morphometric database. LMA under high temperature was significantly smaller than LMA under medium and low temperature, while leaves at high temperature were significantly broader. An FSPM of rapeseed seedlings featuring a growth function used for leaf extension and biomass accumulation was implemented by combining measurement with literature data. The model delivered new insights into growth and development dynamics of winter oilseed rape seedlings. The present version of the model mainly focuses on the growth of plant leaves. However, future extensions of the model could be used in practice to better predict plant growth in spring and potential cold damage of the crop. PMID:28377775

Factors affecting the estimate of primary production from space

NASA Technical Reports Server (NTRS)

Balch, W. M.; Byrne, C. F.

1994-01-01

Remote sensing of primary production in the euphotic zone has been based mostly on visible-band and water-leaving radiance measured with the coastal zone color scanner. There are some robust, simple relationships for calculating integral production based on surface measurements, but they also require knowledge for photoadaptive parameters such as maximum photosynthesis which currently cannot be obtained from spave. A 17,000-station data set is used to show that space-based estimates of maximum photosynthesis could improve predictions of psi, the water column light utiliztion index, which is an important term in many primary productivity models. Temperature is also examined as a factor for predicting hydrographic structure and primary production. A simple model is used to relate temperature and maximum photosynthesis; the model incorporates (1) the positive relationship between maximum photosynthesis and temperature and (2) the strongly negative relationship between temperature and nitrate in the ocean (which directly affects maximum growth rates via nitrogen limitation). Since these two factors relate to carbon and nitrogen, 'balanced carbon/nitrogen assimilation' was calculated using the Redfield ratio, It is expected that the relationship between maximum balanced carbon assimilation versus temperature is concave-down, with the peak dependent on nitrate uptake kinetics, temperature-nitrate relationships,a nd the carbon chlorophyll ration. These predictions were compared with the sea truth data. The minimum turnover time for nitrate was also calculated using this approach. Lastly, sea surface temperature gradients were used to predict the slope of isotherms (a proxy for the slope of isopycnals in many waters). Sea truth data show that at size scales of several hundred kilometers, surface temperature gradients can provide information on the slope of isotherms in the top 200 m of the water column. This is directly relevant to the supply of nutrients into the surface mixed layer, which is useful for predicting integral biomass and primary production.

Holocene dinoflagellate cyst record of climate and marine primary productivity change in the Santa Barbara Basin, southern California.

NASA Astrophysics Data System (ADS)

Pospelova, Vera; Mertens, Kenneth N.; Hendy, Ingrid, L.; Pedersen, Thomas F.

2015-04-01

High-resolution sedimentary records of dinoflagellate cysts and other marine palynomorphs from the Santa Barbara Basin (Ocean Drilling Program Hole 893A) demonstrate large variability of primary productivity during the Holocene, as the California Current System responded to climate change. Throughout the sequence, dinoflagellate cyst assemblages are characterized by the dominance of cysts produced by heterotrophic dinoflagellates, and particularly by Brigantedinium, accompanied by other upwelling-related taxa such as Echinidinium and cysts of Protoperidinium americanum. During the early Holocene (~12-7 ka), the species richness is relatively low (16 taxa) and genius Brigantedinium reaches the highest relative abundance, thus indicating nutrient-rich and highly productive waters. The middle Holocene (~7-3.5 ka) is characterized by relatively constant cyst concentrations, and dinoflagellate cyst assemblages are indicative of a slight decrease in sea-surface temperature. A noticeable increase and greater range of fluctuations in the cyst concentrations during the late Holocene (~3.5-1 ka) indicate enhanced marine primary productivity and increased climatic variability, most likely related to the intensification of El Niño-like conditions. Keywords: dinoflagellate cysts, Holocene, North Pacific, climate, primary productivity.

Ecosystem response to climatic variables - air temperature and precipitation: How can these variables alter plant productions in C4-grass dominant ecosystem?

NASA Astrophysics Data System (ADS)

Jung, C. G.; Jiang, L.; Luo, Y.

2017-12-01

Understanding net primary production (NPP) response to the key climatic variables, temperature and precipitation, is essential since the response could be represented by one of future consequences from ecosystem responses. Under future climatic warming, fluctuating precipitation is expected. In addition, NPP solely could not explain whole ecosystem response; therefore, not only NPP, but also above- and below-ground NPP (ANPP and BNPP, respectively) need to be examined. This examination needs to include how the plant productions response along temperature and precipitation gradients. Several studies have examined the response of NPP against each of single climatic variable, but understanding the response of ANPP and BNPP to the multiple variables is notably poor. In this study, we used the plant productions data (NPP, ANPP, and BNPP) with climatic variables, i.e., air temperature and precipitation, from 1999 to 2015 under warming and clipping treatments (mimicking hay-harvesting) in C4-grass dominant ecosystem located in central Oklahoma, United States. Firstly, we examined the nonlinear relationships with the climatic variables for NPP, ANPP and BNPP; and then predicted possible responses in the temperature - precipitation space by using a linear mixed effect model. Nonlinearities of NPP, ANPP and BNPP to the climatic variables have been found to show unimodal curves, and nonlinear models have better goodness of fit as shown lower Akaike information criterion (AIC) than linear models. Optimum condition for NPP is represented at high temperature and precipitation level whereas BNPP is maximized at moderate precipitation levels while ANPP has same range of NPP's optimum condition. Clipping significantly reduced ANPP while there was no clipping effect on NPP and BNPP. Furthermore, inclining NPP and ANPP have shown in a range from moderate to high precipitation level with increasing temperature while inclining pattern for BNPP was observed in moderate precipitation level. Overall, the C4-grass dominant ecosystem has a potential for considerable increases in NPP in hotter and wetter conditions as shown a range from moderate to high temperature and precipitation levels; ANPP has peaked at the high temperature and precipitation level, but maximum BNPP needs moderate precipitation level and high temperature.

Chemoenzymatic dynamic kinetic resolution of primary amines using a recyclable palladium nanoparticle catalyst together with lipases.

PubMed

Gustafson, Karl P J; Lihammar, Richard; Verho, Oscar; Engström, Karin; Bäckvall, Jan-E

2014-05-02

A catalyst consisting of palladium nanoparticles supported on amino-functionalized siliceous mesocellular foam (Pd-AmP-MCF) was used in chemoenzymatic dynamic kinetic resolution (DKR) to convert primary amines to amides in high yields and excellent ee's. The efficiency of the nanocatalyst at temperatures below 70 °C enables reaction conditions that are more suitable for enzymes. In the present study, this is exemplified by subjecting 1-phenylethylamine (1a) and analogous benzylic amines to DKR reactions using two commercially available lipases, Novozyme-435 (Candida antartica Lipase B) and Amano Lipase PS-C1 (lipase from Burkholderia cepacia) as biocatalysts. The latter enzyme has not previously been used in the DKR of amines because of its low stability at temperatures over 60 °C. The viability of the heterogeneous Pd-AmP-MCF was further demonstrated in a recycling study, which shows that the catalyst can be reused up to five times.

Mars observer radio science (MORS) observations in polar regions

NASA Technical Reports Server (NTRS)

Simpson, Richard A.

1992-01-01

MORS observations will focus on two major areas of study: (1) the gravity field of Mars and its interpretation in terms of internal structure and history and (2) the structure of the atmosphere, with emphasis on both temperature-pressure profiles of the background atmosphere and small scale inhomogeneities resulting from turbulence. Scattering of cm wavelength radio signals from Mars' surface at highly oblique angles will also be studied during the primary mission; nongrazing scattering experiments may be possible during an extended mission. During the MORS primary mission, measurements of the spacecraft distance and velocity with respect to Earth based tracking stations will be used to develop models of the global gravity field. The improvement in knowledge of the gravity field will be especially evident in polar regions. The spatial and temporal coverage of atmospheric radio occultation measurements are determined by the geometry of the spacecraft orbit and the direction to the Earth. Profiles of atmospheric temperature and pressure will extend from the surface to altitudes of 50 to 70 km.

Method for removing cesium from a nuclear reactor coolant

DOEpatents

Colburn, R.P.

1983-08-10

A method of and system for removing cesium from a liquid metal reactor coolant including a carbon packing trap in the primary coolant system for absorbing a major portion of the radioactive cesium from the coolant flowing therethrough at a reduced temperature. A regeneration subloop system having a secondary carbon packing trap is selectively connected to the primary system for isolating the main trap therefrom and connecting it to the regeneration system. Increasing the temperature of the sodium flowing through the primary trap diffuses a portion of the cesium inventory thereof further into the carbon matrix while simultaneously redispersing a portion into the regeneration system for absorption at a reduced temperature by the secondary trap.

Practical acoustic thermometry with twin-tube and single-tube sensors

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

De Podesta, M.; Sutton, G.; Edwards, G.

2015-07-01

Accurate measurement of high temperatures in a nuclear environment presents unique challenges. All secondary techniques inevitably drift because the thermometric materials in thermocouples and resistance sensors are sensitive not just to temperature, but also their own chemical and physical composition. The solution is to use primary methods that rely on fundamental links between measurable physical properties and temperature. In the nuclear field the best known technique is the measurement of Johnson Noise in a resistor (See Paper 80 at this conference). In this paper we describe the measurement of temperature in terms of the speed of sound in a gasmore » confined in a tube - an acoustic waveguide. Acoustic thermometry is the most accurate technique of primary thermometry ever devised with the best uncertainty of measurement below 0.001 C. In contrast, the acoustic technique described in this work has a much larger uncertainty, approximately 1 deg. C. But the cost and ease of use are improved by several orders of magnitude, making implementation eminently practical. We first describe the basic construction and method of operation of thermometers using twin-tubes and single tubes. We then present results using a twin-tube design showing that showing long term stability (i.e. no detectable drift) at 700 deg. C over periods of several weeks. We then outline how the technique may be developed for different nuclear applications. (authors)« less

Genetic susceptibility, colony size, and water temperature drive white-pox disease on the coral Acropora palmata.

PubMed

Muller, Erinn M; van Woesik, Robert

2014-01-01

Outbreaks of coral diseases are one of the greatest threats to reef corals in the Caribbean, yet the mechanisms that lead to coral diseases are still largely unknown. Here we examined the spatial-temporal dynamics of white-pox disease on Acropora palmata coral colonies of known genotypes. We took a Bayesian approach, using Integrated Nested Laplace Approximation algorithms, to examine which covariates influenced the presence of white-pox disease over seven years. We showed that colony size, genetic susceptibility of the coral host, and high-water temperatures were the primary tested variables that were positively associated with the presence of white-pox disease on A. palmata colonies. Our study also showed that neither distance from previously diseased individuals, nor colony location, influenced the dynamics of white-pox disease. These results suggest that white-pox disease was most likely a consequence of anomalously high water temperatures that selectively compromised the oldest colonies and the most susceptible coral genotypes.

Genetic Susceptibility, Colony Size, and Water Temperature Drive White-Pox Disease on the Coral Acropora palmata

PubMed Central

Muller, Erinn M.; van Woesik, Robert

2014-01-01

Outbreaks of coral diseases are one of the greatest threats to reef corals in the Caribbean, yet the mechanisms that lead to coral diseases are still largely unknown. Here we examined the spatial-temporal dynamics of white-pox disease on Acropora palmata coral colonies of known genotypes. We took a Bayesian approach, using Integrated Nested Laplace Approximation algorithms, to examine which covariates influenced the presence of white-pox disease over seven years. We showed that colony size, genetic susceptibility of the coral host, and high-water temperatures were the primary tested variables that were positively associated with the presence of white-pox disease on A. palmata colonies. Our study also showed that neither distance from previously diseased individuals, nor colony location, influenced the dynamics of white-pox disease. These results suggest that white-pox disease was most likely a consequence of anomalously high water temperatures that selectively compromised the oldest colonies and the most susceptible coral genotypes. PMID:25372835

Processing and Characterization of Peti Composites Fabricated by High Temperature Vartm (Section)

NASA Technical Reports Server (NTRS)

Ghose, Sayata; Cano, Roberto J.; Watson, Kent A.; Britton, Sean M.; Jensen, Brian J.; Connell, John W.; Smith, Joseph G., Jr.; Loos, Alfred C.; Heider, Dirk

2011-01-01

The use of composites as primary structures on aerospace vehicles has increased dramatically over the past decade, but so have the production costs associated with their fabrication. For certain composites, high temperature vacuum assisted resin transfer molding (HT-VARTM) can offer reduced fabrication costs compared to conventional autoclave techniques. The process has been successfully used with phenylethynyl terminated imide (PETI) resins developed by NASA Langley Research Center (LaRC). In the current study, three PETI resins have been used to make test specimens using HT-VARTM. Based on previous work at NASA LaRC, larger panels with a quasi-isotropic lay-up were fabricated. The resultant composite specimens exhibited void contents of 3% by volume depending on the type of carbon fabric preform used. Mechanical properties of the panels were determined at both room and elevated temperatures. Fabric permeability characterizations and limited process modeling efforts were carried out to determine infusion times and composite panel size limitations. In addition, new PETI based resins were synthesized specifically for HT-VARTM.

Estimation of Monthly Near Surface Air Temperature Using Geographically Weighted Regression in China

NASA Astrophysics Data System (ADS)

Wang, M. M.; He, G. J.; Zhang, Z. M.; Zhang, Z. J.; Liu, X. G.

2018-04-01

Near surface air temperature (NSAT) is a primary descriptor of terrestrial environment conditions. The availability of NSAT with high spatial resolution is deemed necessary for several applications such as hydrology, meteorology and ecology. In this study, a regression-based NSAT mapping method is proposed. This method is combined remote sensing variables with geographical variables, and uses geographically weighted regression to estimate NSAT. The altitude was selected as geographical variable; and the remote sensing variables include land surface temperature (LST) and Normalized Difference vegetation index (NDVI). The performance of the proposed method was assessed by predict monthly minimum, mean, and maximum NSAT from point station measurements in China, a domain with a large area, complex topography, and highly variable station density, and the NSAT maps were validated against the meteorology observations. Validation results with meteorological data show the proposed method achieved an accuracy of 1.58 °C. It is concluded that the proposed method for mapping NSAT is very operational and has good precision.

Respiratory alkalosis and primary hypocapnia in Labrador Retrievers participating in field trials in high-ambient-temperature conditions.

PubMed

Steiss, Janet E; Wright, James C

2008-10-01

To determine whether Labrador Retrievers participating in field trials develop respiratory alkalosis and hypocapnia primarily in conditions of high ambient temperatures. 16 Labrador Retrievers. At each of 5 field trials, 5 to 10 dogs were monitored during a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]; 36 assessments); ambient temperatures ranged from 2.2 degrees to 29.4 degrees C. For each dog, rectal temperature was measured and a venous blood sample was collected in a heparinized syringe within 5 minutes of test completion. Blood samples were analyzed on site for Hct; pH; sodium, potassium, ionized calcium, glucose, lactate, bicarbonate, and total CO2 concentrations; and values of PvO2 and PvCO2. Scatterplots of each variable versus ambient temperature were reviewed. Regression analysis was used to evaluate the effect of ambient temperature (< or = 21 degrees C and > 21 degrees C) on each variable. Compared with findings at ambient temperatures < or = 21 degrees C, venous blood pH was increased (mean, 7.521 vs 7.349) and PvCO2 was decreased (mean, 17.8 vs 29.3 mm Hg) at temperatures > 21 degrees C; rectal temperature did not differ. Two dogs developed signs of heat stress in 1 test at an ambient temperature of 29 degrees C; their rectal temperatures were higher and PvCO2 values were lower than findings in other dogs. When running distances frequently encountered at field trials, healthy Labrador Retrievers developed hyperthermia regardless of ambient temperature. Dogs developed respiratory alkalosis and hypocapnia at ambient temperatures > 21 degrees C.

Power-processing unit

NASA Technical Reports Server (NTRS)

Wessel, Frank J. (Inventor); Hancock, Donald J. (Inventor)

1987-01-01

Power-processing unit uses AC buses (30, 32) to supply all current dependent needs such as connections (54, 56) to an ion thruster through an inductor (88) and the primary of a transformer (90), to assure limited currents to such loads. Where temperature control is also required, such as to the main discharge vaporizer heater connection (36, 38), switches (100, 102) are serially connected with inductor (96) and the primary of transformer (98). Temperature sensor (104) controls the switches (100, 102) for temperature regulation.

Quantification of a thermal damage threshold for astrocytes using infrared laser generated heat gradients.

PubMed

Liljemalm, Rickard; Nyberg, Tobias

2014-04-01

The response of cells and tissues to elevated temperatures is highly important in several research areas, especially in the area of infrared neural stimulation. So far, only the heat response of neurons has been considered. In this study, primary rat astrocytes were exposed to infrared laser pulses of various pulse lengths and the resulting cell morphology changes and cell migration was studied using light microscopy. By using a finite element model of the experimental setup the temperature distribution was simulated and the temperatures and times to induce morphological changes and migration were extracted. These threshold temperatures were used in the commonly used first-order reaction model according to Arrhenius to extract the kinetic parameters, i.e., the activation energy, E a, and the frequency factor, A c, for the system. A damage signal ratio threshold was defined and calculated to be 6% for the astrocytes to change morphology and start migrating.

Low-temperature nitridation of manganese and iron oxides using NaNH2 molten salt.

PubMed

Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro

2013-10-21

Manganese and iron nitrides are important functional materials, but their synthesis processes from oxides often require high temperatures. Herein, we show a novel meta-synthesis method for manganese and iron nitrides by low-temperature nitridation of their oxides using NaNH2 molten salt as the nitrogen source in an autoclave at 240 °C. With this method, nitridation of micrometer-sized oxide particles kept their initial morphologies, but the size of the primary particles decreased. The thermodynamic driving force is considered to be the conversion of oxides to sodium hydroxide, and the kinetic of nitridation is improved by the decrease of particle size and the low melting point of NaNH2. This technique as developed here has the advantages of low reaction temperature, reduced consumption of ammonia, employing nonspecialized equipment, and providing facile control of the reactions for producing nitrides from oxides.

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

Frequency-Temperature Compensation Techniques for High-Q Microwave Resonators

NASA Astrophysics Data System (ADS)

Hartnett, John G.; Tobar, Michael E.

Low-noise high-stability resonator oscillators based on high-Q monolithic sapphire ``Whispering Gallery'' (WG)-mode resonators have become important devices for telecommunication, radar and metrological applications. The extremely high quality factor of sapphire, of 2 x10^5 at room temperature, 5 x10^7 at liquid nitrogen temperature and 5 x10^9 at liquid helium temperature has enabled the lowest phase noise and highly frequency-stable oscillators in the microwave regime to be constructed. To create an oscillator with exceptional frequency stability, the resonator must have its frequency-temperature dependence annulled at some temperature, as well as a high quality factor. The Temperature Coefficient of Permittivity (TCP) for sapphire is quite large, at 10-100parts per million/K above 77K. This mechanism allows temperature fluctuations to transform to resonator frequency fluctuations.A number of research groups worldwide have investigated various methods of compensating the TCP of a sapphire dielectric resonator at different temperatures. The usual electromagnetic technique of annulment involves the use of paramagnetic impurities contributing an opposite temperature coefficient of the magnetic susceptibility to the TCP. This technique has only been realized successfully in liquid helium environments. Near 4K the thermal expansion and permittivity effects are small and only small quantities of the paramagnetic ions are necessary to compensate the mode frequency. Compensation is due to impurity ions that were incidentally left over from the manufacturing process.Recently, there has been an effort to dispense with the need for liquid helium and make a compact flywheel oscillator for the new generation of primary frequency standards such as the cesium fountain at the Laboratoire Primaire du Temps et des Fréquences (LPTF), France. To achieve the stability limit imposed by quantum projection noise requires that the local oscillator stability is of the order of 10^-14. Currently work is under way to achieve this goal in space-borne and mobile liquid-nitrogen-cooled systems. The work appears promising and, as at early 2000, the realization of this goal should not be far off.In this contribution we review techniques that cancel the TCP of sapphire and other dielectric resonators. Details of the temperature control system required to achieve current and target frequency stabilities are discussed.

Mechanics of Failure of High Temperature Metal Matrix Composites

DTIC Science & Technology

1993-12-22

by two inhomogeneities that sustain an eigenstrain loading, proportional to the difference of fiber/matrx thermal expansion coefficients. Utilizing the...appropriate eigenstrain field. sustained by the fiber cross sections. Our primary interest is to determine how the fiber interaction relates to the local...inhomogeneities (fiber cross sections). with a central distance c. undergo an eigenstrain loading. Utilizing the di. -Sacement potentials approach. an

Temperature Regimes Impact Coral Assemblages along Environmental Gradients on Lagoonal Reefs in Belize

PubMed Central

Townsend, Joseph E.; Courtney, Travis A.; Aichelman, Hannah E.; Davies, Sarah W.; Lima, Fernando P.; Castillo, Karl D.

2016-01-01

Coral reefs are increasingly threatened by global and local anthropogenic stressors such as rising seawater temperature, nutrient enrichment, sedimentation, and overfishing. Although many studies have investigated the impacts of local and global stressors on coral reefs, we still do not fully understand how these stressors influence coral community structure, particularly across environmental gradients on a reef system. Here, we investigate coral community composition across three different temperature and productivity regimes along a nearshore-offshore gradient on lagoonal reefs of the Belize Mesoamerican Barrier Reef System (MBRS). A novel metric was developed using ultra-high-resolution satellite-derived estimates of sea surface temperatures (SST) to classify reefs as exposed to low (lowTP), moderate (modTP), or high (highTP) temperature parameters over 10 years (2003 to 2012). Coral species richness, abundance, diversity, density, and percent cover were lower at highTP sites relative to lowTP and modTP sites, but these coral community traits did not differ significantly between lowTP and modTP sites. Analysis of coral life history strategies revealed that highTP sites were dominated by hardy stress-tolerant and fast-growing weedy coral species, while lowTP and modTP sites consisted of competitive, generalist, weedy, and stress-tolerant coral species. Satellite-derived estimates of Chlorophyll-a (chl-a) were obtained for 13-years (2003–2015) as a proxy for primary production. Chl-a concentrations were highest at highTP sites, medial at modTP sites, and lowest at lowTP sites. Notably, thermal parameters correlated better with coral community traits between site types than productivity, suggesting that temperature (specifically number of days above the thermal bleaching threshold) played a greater role in defining coral community structure than productivity on the MBRS. Dominance of weedy and stress-tolerant genera at highTP sites suggests that corals utilizing these two life history strategies may be better suited to cope with warmer oceans and thus may warrant protective status under climate change. PMID:27606598

Temperature Regimes Impact Coral Assemblages along Environmental Gradients on Lagoonal Reefs in Belize.

PubMed

Baumann, Justin H; Townsend, Joseph E; Courtney, Travis A; Aichelman, Hannah E; Davies, Sarah W; Lima, Fernando P; Castillo, Karl D

2016-01-01

Coral reefs are increasingly threatened by global and local anthropogenic stressors such as rising seawater temperature, nutrient enrichment, sedimentation, and overfishing. Although many studies have investigated the impacts of local and global stressors on coral reefs, we still do not fully understand how these stressors influence coral community structure, particularly across environmental gradients on a reef system. Here, we investigate coral community composition across three different temperature and productivity regimes along a nearshore-offshore gradient on lagoonal reefs of the Belize Mesoamerican Barrier Reef System (MBRS). A novel metric was developed using ultra-high-resolution satellite-derived estimates of sea surface temperatures (SST) to classify reefs as exposed to low (lowTP), moderate (modTP), or high (highTP) temperature parameters over 10 years (2003 to 2012). Coral species richness, abundance, diversity, density, and percent cover were lower at highTP sites relative to lowTP and modTP sites, but these coral community traits did not differ significantly between lowTP and modTP sites. Analysis of coral life history strategies revealed that highTP sites were dominated by hardy stress-tolerant and fast-growing weedy coral species, while lowTP and modTP sites consisted of competitive, generalist, weedy, and stress-tolerant coral species. Satellite-derived estimates of Chlorophyll-a (chl-a) were obtained for 13-years (2003-2015) as a proxy for primary production. Chl-a concentrations were highest at highTP sites, medial at modTP sites, and lowest at lowTP sites. Notably, thermal parameters correlated better with coral community traits between site types than productivity, suggesting that temperature (specifically number of days above the thermal bleaching threshold) played a greater role in defining coral community structure than productivity on the MBRS. Dominance of weedy and stress-tolerant genera at highTP sites suggests that corals utilizing these two life history strategies may be better suited to cope with warmer oceans and thus may warrant protective status under climate change.

High-efficiency VCSEL arrays for illumination and sensing in consumer applications

NASA Astrophysics Data System (ADS)

Seurin, Jean-Francois; Zhou, Delai; Xu, Guoyang; Miglo, Alexander; Li, Daizong; Chen, Tong; Guo, Baiming; Ghosh, Chuni

2016-03-01

There has been increased interest in vertical-cavity surface-emitting lasers (VCSELs) for illumination and sensing in the consumer market, especially for 3D sensing ("gesture recognition") and 3D image capture. For these applications, the typical wavelength range of interest is 830~950nm and power levels vary from a few milli-Watts to several Watts. The devices are operated in short pulse mode (a few nano-seconds) with fast rise and fall times for time-of-flight applications (ToF), or in CW/quasi-CW for structured light applications. In VCSELs, the narrow spectrum and its low temperature dependence allows the use of narrower filters and therefore better signal-to-noise performance, especially for outdoor applications. In portable devices (mobile devices, wearable devices, laptops etc.) the size of the illumination module (VCSEL and optics) is a primary consideration. VCSELs offer a unique benefit compared to other laser sources in that they are "surface-mountable" and can be easily integrated along with other electronics components on a printed circuit board (PCB). A critical concern is the power-conversion efficiency (PCE) of the illumination source operating at high temperatures (>50 deg C). We report on various VCSEL based devices and diffuser-integrated modules with high efficiency at high temperatures. Over 40% PCE was achieved in broad temperature range of 0-70 °C for either low power single devices or high power VCSEL arrays, with sub- nano-second rise and fall time. These high power VCSEL arrays show excellent reliability, with extracted mean-time-to-failure (MTTF) of over 500 years at 60 °C ambient temperature and 8W peak output.

Temperature impacts on deep-sea biodiversity.

PubMed

Yasuhara, Moriaki; Danovaro, Roberto

2016-05-01

Temperature is considered to be a fundamental factor controlling biodiversity in marine ecosystems, but precisely what role temperature plays in modulating diversity is still not clear. The deep ocean, lacking light and in situ photosynthetic primary production, is an ideal model system to test the effects of temperature changes on biodiversity. Here we synthesize current knowledge on temperature-diversity relationships in the deep sea. Our results from both present and past deep-sea assemblages suggest that, when a wide range of deep-sea bottom-water temperatures is considered, a unimodal relationship exists between temperature and diversity (that may be right skewed). It is possible that temperature is important only when at relatively high and low levels but does not play a major role in the intermediate temperature range. Possible mechanisms explaining the temperature-biodiversity relationship include the physiological-tolerance hypothesis, the metabolic hypothesis, island biogeography theory, or some combination of these. The possible unimodal relationship discussed here may allow us to identify tipping points at which on-going global change and deep-water warming may increase or decrease deep-sea biodiversity. Predicted changes in deep-sea temperatures due to human-induced climate change may have more adverse consequences than expected considering the sensitivity of deep-sea ecosystems to temperature changes. © 2014 Cambridge Philosophical Society.

Temperature properties in the tropical tropopause layer and their correlations with Outgoing Longwave Radiation: FORMOSAT-3/COSMIC observations

NASA Astrophysics Data System (ADS)

Wang, Kaiti; Wu, Yi-chao; Lin, Jia-Ting; Tan, Pei-Hua

2018-06-01

The properties of temperature at the level of lapse rate minimum (LRM) in the tropical tropopause layer between 20°S and 20°N are investigated using 3-year radio occultation observations based on the FORMOSAT-3/COSMIC mission from November of 2006 to October of 2009. The correlations between this LRM temperature and Outgoing Longwave Radiation (OLR) are analyzed by 5° × 5° grids in longitude and latitude. Two primary regions, one from 60°E to 180°E and the other from 90°W to 30°E, are found to have higher correlations and can be associated with regions of lower OLR values. The patterns of this spatial distributions of regions with higher correlations begin to change more obviously when the altitude ascends to the level of Cold Point Tropopause (CPT). This correlation at the LRM altitude in annual and seasonal scales also shows spatial distributions associated with OLR intensities. The altitudinal dependence of the correlations between temperature and OLR is further analyzed based on grids of high correlations with significance at LRM altitude, for the two primary regions. The results show that for the different time scales in this analysis (3-year, annual, and seasonal), the correlations all gradually decrease above the LRM levels but maintain a significant level to as high as 2.5-3.5 km. Below the LRM level, the correlation decreases with a slower rate as the altitude descends and still keeps significant at the deep 5 km level. These suggest that the vertical temperature profiles could be affected by the convection mechanism for a wide range of altitudes in the troposphere even above LRM altitude. Applying the same analysis on one complete La Niña event during the survey period also reveals similar features.

Rapid fluid disruption: A source for self-potential anomalies on volcanoes

USGS Publications Warehouse

Johnston, M.J.S.; Byerlee, J.D.; Lockner, D.

2001-01-01

Self-potential (SP) anomalies observed above suspected magma reservoirs, dikes, etc., on various volcanoes (Kilauea, Hawaii; Mount Unzen, Japan; Piton de la Fournaise, Reunion Island, Miyake Jima, Japan) result from transient surface electric fields of tens of millivolts per kilometer and generally have a positive polarity. These SP anomalies are usually attributed to electrokinetic effects where properties controlling this process are poorly constrained. We propose an alternate explanation that contributions to electric fields of correct polarity should be expected from charge generation by fluid vaporization/disruption. As liquids are vaporized or removed as droplets by gas transport away from hot dike intrusions, both charge generation and local increase in electrical resistivity by removal of fluids should occur. We report laboratory observations of electric fields in hot rock samples generated by pulses of fluid (water) through the rock at atmospheric pressure. These indicate the relative amplitudes of rapid fluid disruption (RFD) potentials and electrokinetic potentials to be dramatically different and the signals are opposite in sign. Above vaporization temperatures, RFD effects of positive sign in the direction of gas flow dominate, whereas below these temperatures, effects of negative sign dominate. This suggests that the primary contribution to observed self-potential anomalies arises from gas-related charge transport processes at temperatures high enough to produce vigorous boiling and vapor transport. At lower temperatures, the primary contribution is from electrokinetic effects modulated perhaps by changing electrical resistivity and RFD effects from high-pressure but low-temperature CO2 and SO2 gas flow ripping water molecules from saturated crustal rocks. If charge generation is continuous, as could well occur above a newly emplaced dike, positive static potentials will be set up that could be sustained for many years, and the simplest method for identifying these hot, active regions would be to identify the SP anomalies they generate.

Crystal Lattice Controlled SiGe Thermoelectric Materials with High Figure of Merit

NASA Technical Reports Server (NTRS)

Kim, Hyun-Jung; Park, Yeonjoon; King, Glen C.; Lee, Kunik; Choi, Sang H.

2010-01-01

Direct energy conversion between thermal and electrical energy, based on thermoelectric (TE) effect, has the potential to recover waste heat and convert it to provide clean electric power. The energy conversion efficiency is related to the thermoelectric figure of merit ZT expressed as ZT=S(exp 2)(sigma)T/Kappa, T is temperature, S is the Seebeck coefficient, sigma is conductance and Kappa is thermal conductivity. For a lower thermal conductivity Kappa and high power factor (S(exp 2)(sigma)), our current strategy is the development of rhombohedrally strained single crystalline SiGe materials that are highly [111]-oriented twinned. The development of a SiGe "twin lattice structure (TLS)" plays a key role in phonon scattering. The TLS increases the electrical conductivity and decreases thermal conductivity due to phonon scattering at stacking faults generated from the 60 X rotated primary twin structure. To develop high performance materials, the substrate temperature, chamber working pressure, and DC sputtering power are controlled for the aligned growth production of SiGe layer and TLS on a c-plane sapphire. Additionally, a new elevated temperature thermoelectric characterization system, that measures the thermal diffusivity and Seebeck effect nondestructively, was developed. The material properties were characterized at various temperatures and optimized process conditions were experimentally determined. The present paper encompasses the technical discussions toward the development of thermoelectric materials and the measurement techniques.

Experimental and numerical studies of burning velocities and kinetic modeling for practical and surrogate fuels

NASA Astrophysics Data System (ADS)

Zhao, Zhenwei

To help understand the fuel oxidation process in practical combustion environments, laminar flame speeds and high temperature chemical kinetic models were studied for several practical fuels and "surrogate" fuels, such as propane, dimethyl ether (DME), and primary reference fuel (PRF) mixtures, gasoline and n-decane. The PIV system developed for the present work is described. The general principles for PIV measurements are outlined and the specific considerations are also reported. Laminar flame speeds were determined for propane/air over a range of equivalence ratios at initial temperature of 298 K, 500 K and 650 K and atmospheric pressure. Several data sets for propane/air laminar flame speeds with N 2 dilution are also reported. These results are compared to the literature data collected at the same conditions. The propane flame speed is also numerically calculated with a detailed kinetic model and multi component diffusion, including Soret effects. This thesis also presents experimentally determined laminar flame speeds for primary reference fuel (PRF) mixtures of n-heptane/iso-octane and real gasoline fuel at different initial temperature and at atmospheric pressure. Nitrogen dilution effects on the laminar flame speed are also studied for selected equivalence ratios at the same conditions. A minimization of detailed kinetic model for PRF mixtures on laminar flame speed conditions was performed and the measured flame speeds were compared with numerical predictions using this model. The measured laminar flame speeds of n-decane/air mixtures at 500 K and at atmospheric pressure with and without dilution were determined. The measured flame speeds are significantly different that those predicted using existing published kinetic models, including a model validated previously against high temperature data from flow reactor, jet-stirred reactor, shock tube ignition delay, and burner stabilized flame experiments. A significant update of this model is described which continues to predict the earlier validation experiments as well as the newly acquired laminar flame speed data and other recently published shock tube ignition delay measurements. A high temperature decomposition and oxidation model based on a hierarchical nature of reacting systems to reflect the new development in the small molecule and radical kinetics and thermochemistry and to evaluate recent measurements of DME laminar flame speeds is developed. The, thermal decomposition of DME was studied theoretically by using the RRKM/master equation approach and the high temperature model was then compared with the literature experimental data. The new model predicts well high temperature flow reactor data, high temperature shock tube ignition delays, and the species profiles from the burner-stabilized flames. Predictions of laminar flame speed and jet-stirred reactor data also reasonably agree with the available experimental data. The remaining uncertainties that need to be addressed for further model improvement will also be discussed. This thesis also presents a novel temperature-dependent feature sensitivity analysis methodology for combustion modeling. The obtained information is demonstrated to be of critical relevance in optimizing complex reaction schemes against multiple experimental targets. Applications of the presented approach are not limited to sensitivities with respect to reaction rate coefficients; the method can also be used to investigate any temperature-dependent property of interest (such as binary diffusion coefficients). This application is also demonstrated in this thesis.

Thermal model development and validation for rapid filling of high pressure hydrogen tanks

DOE PAGES

Johnson, Terry A.; Bozinoski, Radoslav; Ye, Jianjun; ...

2015-06-30

This paper describes the development of thermal models for the filling of high pressure hydrogen tanks with experimental validation. Two models are presented; the first uses a one-dimensional, transient, network flow analysis code developed at Sandia National Labs, and the second uses the commercially available CFD analysis tool Fluent. These models were developed to help assess the safety of Type IV high pressure hydrogen tanks during the filling process. The primary concern for these tanks is due to the increased susceptibility to fatigue failure of the liner caused by the fill process. Thus, a thorough understanding of temperature changes ofmore » the hydrogen gas and the heat transfer to the tank walls is essential. The effects of initial pressure, filling time, and fill procedure were investigated to quantify the temperature change and verify the accuracy of the models. In this paper we show that the predictions of mass averaged gas temperature for the one and three-dimensional models compare well with the experiment and both can be used to make predictions for final mass delivery. Furthermore, due to buoyancy and other three-dimensional effects, however, the maximum wall temperature cannot be predicted using one-dimensional tools alone which means that a three-dimensional analysis is required for a safety assessment of the system.« less

Effect of soil moisture on the temperature sensitivity of Northern soils

NASA Astrophysics Data System (ADS)

Minions, C.; Natali, S.; Ludwig, S.; Risk, D.; Macintyre, C. M.

2017-12-01

Arctic and boreal ecosystems are vast reservoirs of carbon and are particularly sensitive to climate warming. Changes in the temperature and precipitation regimes of these regions could significantly alter soil respiration rates, impacting atmospheric concentrations and affecting climate change feedbacks. Many incubation studies have shown that both temperature and soil moisture are important environmental drivers of soil respiration; this relationship, however, has rarely been demonstrated with in situ data. Here we present the results of a study at six field sites in Alaska from 2016 to 2017. Low-power automated soil gas systems were used to measure soil surface CO2 flux from three forced diffusion chambers and soil profile concentrations from three soil depth chambers at hourly intervals at each site. HOBO Onset dataloggers were used to monitor soil moisture and temperature profiles. Temperature sensitivity (Q10) was determined at each site using inversion analysis applied over different time periods. With highly resolved data sets, we were able to observe the changes in soil respiration in response to changes in temperature and soil moisture. Through regression analysis we confirmed that temperature is the primary driver in soil respiration, but soil moisture becomes dominant beyond a certain threshold, suppressing CO2 flux in soils with high moisture content. This field study supports the conclusions made from previous soil incubation studies and provides valuable insights into the impact of both temperature and soil moisture changes on soil respiration.

Extending the upper temperature range of gas chromatography with all-silicon microchip columns using a heater/clamp assembly.

PubMed

Ghosh, Abhijit; Johnson, Jacob E; Nuss, Johnathan G; Stark, Brittany A; Hawkins, Aaron R; Tolley, Luke T; Iverson, Brian D; Tolley, H Dennis; Lee, Milton L

2017-09-29

Miniaturization of gas chromatography (GC) instrumentation is of interest because it addresses current and future issues relating to compactness, portability and field application. While incremental advancements continue to be reported in GC with columns fabricated in microchips (referred to in this paper as "microchip columns"), the current performance is far from acceptable. This lower performance compared to conventional GC is due to factors such as pooling of the stationary phase in corners of non-cylindrical channels, adsorption of sensitive compounds on incompletely deactivated surfaces, shorter column lengths and less than optimum interfacing to injector and detector. In this work, a GC system utilizing microchip columns was developed that solves the latter challenge, i.e., microchip interfacing to injector and detector. A microchip compression clamp was constructed to heat the microchip (i.e., primary heater), and seal the injector and detector fused silica interface tubing to the inlet and outlet ports of the microchip channels with minimum extra-column dead volume. This clamp allowed occasional operation up to 375°C and routine operation up to 300°C. The compression clamp was constructed of a low expansion alloy, Kovar™, to minimize leaking due to thermal expansion mismatch at the interface during repeated thermal cycling, and it was tested over several months for more than one hundred injections without forming leaks. A 5.9m long microcolumn with rectangular cross section of 158μm×80μm, which approximately matches a 100μm i.d. cylindrical fused silica column, was fabricated in a silicon wafer using deep reactive ion etching (DRIE) and high temperature fusion bonding; finally, the channel was coated statically with a 1% vinyl, 5% phenyl, 94% methylpolysiloxane stationary phase. High temperature separations of C10-C40 n-alkanes and a commercial diesel sample were demonstrated using the system under both temperature programmed GC (TPGC) and thermal gradient GC (TGGC) conditions. TGGC analysis of a complex essential oil sample was also demonstrated. Addition of a secondary heater and polyimide insulation proved to be helpful in achieving the desired elution temperature without having to raise the primary heater temperature above 300°C for high boiling point compounds. Copyright © 2017 Elsevier B.V. All rights reserved.

Role of nuclear grade graphite in controlling oxidation in modular HTGRs

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

Windes, Willaim; Strydom, G.; Kane, J.

2014-11-01

The passively safe High Temperature Gas-cooled Reactor (HTGR) design is one of the primary concepts considered for Generation IV and Small Modular Reactor (SMR) programs. The helium cooled, nuclear grade graphite moderated core achieves extremely high operating temperatures allowing either industrial process heat or electricity generation at high efficiencies. In addition to their neutron moderating properties, nuclear grade graphite core components provide excellent high temperature stability, thermal conductivity, and chemical compatibility with the high temperature nuclear fuel form. Graphite has been continuously used in nuclear reactors since the 1940’s and has performed remarkably well over a wide range of coremore » environments and operating conditions. Graphite moderated, gas-cooled reactor designs have been safely used for research and power production purposes in multiple countries since the inception of nuclear energy development. However, graphite is a carbonaceous material, and this has generated a persistent concern that the graphite components could actually burn during either normal or accident conditions [ , ]. The common assumption is that graphite, since it is ostensibly similar to charcoal and coal, will burn in a similar manner. While charcoal and coal may have the appearance of graphite, the internal microstructure and impurities within these carbonaceous materials are very different. Volatile species and trapped moisture provide a source of oxygen within coal and charcoal allowing them to burn. The fabrication process used to produce nuclear grade graphite eliminates these oxidation enhancing impurities, creating a dense, highly ordered form of carbon possessing high thermal diffusivity and strongly (covalently) bonded atoms.« less

DESIGN CHARACTERISTICS OF THE IDAHO NATIONAL LABORATORY HIGH-[TEMPERATURE GAS-COOLED TEST REACTOR

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

Sterbentz, James; Bayless, Paul; Strydom, Gerhard

A point design for a graphite-moderated, high-temperature, gas-cooled test reactor (HTG TR) has been developed by Idaho National Laboratory (INL) as part of a United States (U.S.) Department of Energy (DOE) initiative to explore and potentially expand the existing U.S. test reactor capabilities. This paper provides a summary of the design and its main attributes. The 200 MW HTG TR is a thermal-neutron spectrum reactor composed of hexagonal prismatic fuel and graphite reflector blocks. Twelve fuel columns (96 fuel blocks total and 6.34 m active core height) are arranged in two hexagonal rings to form a relatively compact, high-power density,more » annular core sandwiched between inner, outer, top, and bottom graphite reflectors. The HTG-TR is designed to operate at 7 MPa with a coolant inlet/outlet temperature of 325°C/650°C, and utilizes TRISO particle fuel from the DOE AGR Program with 425 ?m uranium oxycarbide (UCO) kernels and an enrichment of 15.5 wt% 235U. The primary mission of the HTG TR is material irradiation and therefore the core has been specifically designed and optimized to provide the highest possible thermal and fast neutron fluxes. The highest thermal neutron flux (3.90E+14 n/cm2s) occurs in the outer reflector, and the maximum fast flux levels (1.17E+14 n/cm2s) are produced in the central reflector column where most of the graphite has been removed. Due to high core temperatures under accident conditions, all the irradiation test facilities have been located in the inner and outer reflectors where fast flux levels decline. The core features a large number of irradiation positions with large test volumes and long test lengths, ideal for thermal neutron irradiation of large test articles. The total available test volume is more than 1100 liters. Up to four test loop facilities can be accommodated with pressure tube boundaries to isolate test articles and test fluids (e.g., liquid metal, liquid salt, light water) from the helium primary coolant system.« less

Microphytobenthic primary production as 14C uptake in sublittoral sediments of the Gulf of Trieste (northern Adriatic Sea): Methodological aspects and data analyses

NASA Astrophysics Data System (ADS)

Cibic, Tamara; Blasutto, Oriana; Burba, Nicoletta; Fonda Umani, Serena

2008-03-01

From January 2003 to December 2004 microphytobenthic primary production was estimated both from in situ (MPPs) and in the laboratory (MPPp) 14C-incubation of slurries collected in a coastal site of the Gulf of Trieste (northern Adriatic Sea). MPPs values varied from -7.54 ± 3.12 to 34.59 ± 7.66 mg C m -2 h -1 over the whole period. The lowest MPPs were observed in November 2003 and August 2004, while the highest MPPs in July 2003 and May 2004, in correspondence with high PAR at the bottom. Significant correlations between MPPs and the microphytobenthic biomass (BIOM) ( r = 0.75, p < 0.001), between MPPs and PAR at the bottom ( r = 0.54, p < 0.01) and between MPPs and OXY ( r = 0.50, p < 0.05) were revealed. MPPp values were higher than MPPs ones in 15 out of 23 observations, with the highest MPPp recorded in July 2003. At 17 m depth a seasonal pattern of sampling months was revealed by the cluster analysis. The role of abiotic parameters in determining this seasonal pattern was highlighted by the PCA, with the first axis correlated with MPPs and PAR, and the second one with temperature. Applying the fuzzy sets it resulted that spring months showed a higher degree of membership with MPPs, summer months with temperature and autumn-winter months with OXY. The microphytobenthic community did not seem to be photosynthetically active throughout the study period. From August-September to December low or negative MPPs values were recorded. We infer that during these months a shift from the autotrophic to heterotrophic metabolism of the benthic microalgae occurred in correspondence with low PAR and/or high temperature at the bottom. Despite the progressive lowering of the trophy of the study area occurred during the last 20 years, we found higher primary production values than those estimated two decades earlier.

A primary exploration to quasi-two-dimensional rare-earth ferromagnetic particles: holmium-doped MoS2 sheet as room-temperature magnetic semiconductor

NASA Astrophysics Data System (ADS)

Chen, Xi; Lin, Zheng-Zhe

2018-05-01

Recently, two-dimensional materials and nanoparticles with robust ferromagnetism are even of great interest to explore basic physics in nanoscale spintronics. More importantly, room-temperature magnetic semiconducting materials with high Curie temperature is essential for developing next-generation spintronic and quantum computing devices. Here, we develop a theoretical model on the basis of density functional theory calculations and the Ruderman-Kittel-Kasuya-Yoshida theory to predict the thermal stability of two-dimensional magnetic materials. Compared with other rare-earth (dysprosium (Dy) and erbium (Er)) and 3 d (copper (Cu)) impurities, holmium-doped (Ho-doped) single-layer 1H-MoS2 is proposed as promising semiconductor with robust magnetism. The calculations at the level of hybrid HSE06 functional predict a Curie temperature much higher than room temperature. Ho-doped MoS2 sheet possesses fully spin-polarized valence and conduction bands, which is a prerequisite for flexible spintronic applications.

Optical-fiber-coupled inferometric measurement of tympanic membrane temperature: a new diagnostic tool for acute otitis media

NASA Astrophysics Data System (ADS)

DeRowe, Ari; Ophir, Eyal; Sade, Sharon; Fishman, Gadi; Ophir, Dov; Grankin, Mila; Katzir, Abraham

1998-07-01

A novel infrared (IR) transparent optical fiber coupled to a hand held otoscope and a radiometer was constructed and used to measure the temperatures of the tympanic membrane (TM) and to distinguish between diseased and healthy middle ears. A greater temperature difference between TM readings was found when Acute Otitis Media (AOM) existed in one of the ears examined. This supports the hypothesis that acute inflammation of the middle ear will result in elevated local temperature when measured in such a way that the reading is taken only from the TM without interference of the external canal. The use of an optical fiber enabled temperature measurements of the TM with high spatial resolution eliminating the external ear canal interference. A small patient population was examined and the initial results were statistically significant. In the hands of the primary care physician, this tool would prevent misdiagnosis of AOM preventing indiscriminate use of antibiotics and avoiding complications by early diagnosis.

Lubricated Bearing Lifetimes of a Multiply Alkylated Cyclopentane and a Linear Perfluoropolyether Fluid in Oscillatory Motion at Elevated Temperatures in Ultrahigh Vacuum

NASA Technical Reports Server (NTRS)

Braza, Joseph; Jansen, Mark J.; Jones, William R.

2009-01-01

Bearing life tests in vacuum with three space liquid lubricants, two multiply alkylated cyclopentanes (MACs) and a linear perfluoropolyether (PFPE) were performed. Test conditions included: an 89 N axial load (mean Hertzian stress 0.66 GPa), vacuum level below 7x10(exp -4) Pa, and a +/-30deg dither angle. Dither rate was 75 cycles per minute. Higher (110 to 122 C) and lower temperature tests (75 C) were performed. For the higher temperature tests, the PFPE, Fomblin (Ausimont SpA) Z25 outperformed Pennzane (Shell Global Solutions) X-2000 by more than an order of magnitude. Lubricant evaporation played a key role in these high temperature results. At 75 C, the order was reversed with both Pennzane X-1000 and X-2000 outperforming Fomblin Z25 by more than an order of magnitude. Most Pennzane tests were suspended without failure. The primary failure mechanism in these lower temperature tests was lubricant consumption in the tribocontacts.

Textile composite fuselage structures development

NASA Technical Reports Server (NTRS)

Jackson, Anthony C.; Barrie, Ronald E.; Chu, Robert L.

1993-01-01

Phase 2 of the NASA ACT Contract (NAS1-18888), Advanced Composite Structural Concepts and Materials Technology for Transport Aircraft Structures, focuses on textile technology, with resin transfer molding or powder coated tows. The use of textiles has the potential for improving damage tolerance, reducing cost and saving weight. This program investigates resin transfer molding (RTM), as a maturing technology for high fiber volume primary structures and powder coated tows as an emerging technology with a high potential for significant cost savings and superior structural properties. Powder coated tow technology has promise for significantly improving the processibility of high temperature resins such as polyimides.

Corrosion behavior of alloy 800H (Fe-21Cr-32Ni) in supercritical water

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

Tan, Lizhen; Allen, Todd R.; Yang, Ying

2011-01-01

The effect of testing conditions (temperature, time, and oxygen content) and material's microstructure (the as-received and the grain boundary engineered conditions) on the corrosion behavior of alloy 800H in high-temperature pressurized water was studied using a variety of characterization techniques. Oxidation was observed as the primary corrosion behavior on the samples. Oxide exfoliation was significantly mitigated on the grain boundary engineered samples compared to the as-received ones. The oxide formation, including some 'mushroom-shaped oxidation', is predicted via a combination of thermodynamics and kinetics influenced by the preferential diffusion of specific species using short-cut diffusion paths.

The Regional Differences of Gpp Estimation by Solar Induced Fluorescence

NASA Astrophysics Data System (ADS)

Wang, X.; Lu, S.

2018-04-01

Estimating gross primary productivity (GPP) at large spatial scales is important for studying the global carbon cycle and global climate change. In this study, the relationship between solar-induced chlorophyll fluorescence (SIF) and GPP is analysed in different levels of annual average temperature and annual total precipitation respectively using simple linear regression analysis. The results showed high correlation between SIF and GPP, when the area satisfied annual average temperature in the range of -5 °C to 15 °C and the annual total precipitation is higher than 200 mm. These results can provide a basis for future estimation of GPP research.

Abiotic gas formation drives nitrogen loss from a desert ecosystem.

PubMed

McCalley, Carmody K; Sparks, Jed P

2009-11-06

In arid environments such as deserts, nitrogen is often the most limiting nutrient for biological activity. The majority of the ecosystem nitrogen flux is typically thought to be driven by production and loss of reactive nitrogen species by microorganisms in the soil. We found that high soil-surface temperatures (greater than 50 degrees C), driven by solar radiation, are the primary cause of nitrogen loss in Mojave Desert soils. This abiotic pathway not only enables the balancing of arid ecosystem nitrogen budgets, but also changes our view of global nitrogen cycling and the predicted impact of climate change and increased temperatures on nitrogen bioavailability.

Seasonal oceanography from physics to micronekton in the south-west Pacific

NASA Astrophysics Data System (ADS)

Menkes, C. E.; Allain, V.; Rodier, M.; Gallois, F.; Lebourges-Dhaussy, A.; Hunt, B. P. V.; Smeti, H.; Pagano, M.; Josse, E.; Daroux, A.; Lehodey, P.; Senina, I.; Kestenare, E.; Lorrain, A.; Nicol, S.

2015-03-01

Tuna catches represent a major economic and food source in the Pacific Ocean, yet are highly variable. This variability in tuna catches remains poorly explained. The relationships between the distributions of tuna and their forage (micronekton) have been mostly derived from model estimates. Observations of micronekton and other mid-trophic level organisms, and their link to regional oceanography, however are scarce and constitute an important gap in our knowledge and understanding of the dynamics of pelagic ecosystems. To fill this gap, we conducted two multidisciplinary cruises (Nectalis1 and Nectalis2) in the New Caledonian Exclusive Economic Zone (EEZ) at the southeastern edge the Coral Sea, in 2011 to characterize the oceanography of the region during the cool (August) and the hot (December) seasons. The physical and biological environments were described by hydrology, nutrients and phytoplankton size structure and biomass. Zooplankton biomass was estimated from net sampling and acoustics and micronecton was estimated from net sampling, the SEAPODYM ecosystem model, a dedicated echosounder and non-dedicated acoustics. Results demonstrated that New Caledonia is located in an oligotrophic area characterized by low nutrient and low primary production which is dominated by a high percentage of picoplankton cyanobacteria Prochlorococcus (>90%). The area exhibits a large-scale north-south temperature and salinity gradient. The northern area is influenced by the equatorial Warm Pool and the South Pacific Convergence Zone and is characterized by higher temperature, lower salinity, lower primary production and micronekton biomass. The southern area is influenced by the Tasman Sea and is characterized by cooler temperature, higher salinity, higher primary production and micronekton biomass. The dynamic oceanography and the complex topography create a myriad of mesoscale features including eddies, inducing patchy structures in the ecosystem. During the cool season, a tight coupling existed between the ocean dynamics and primary production, while there was a stronger decoupling during the hot season. There was little difference in the composition of mid-trophic level organisms (zooplankton and micronekton) between the two seasons. This may be due to different turn-over times and delays in the transmission of primary production to upper trophic levels. Examination of various sampling gears for zooplankton and micronekton showed that net biomass estimates and acoustic-derived estimates compared reasonably well. Estimates of micronekton from net observations and the SEAPODYM model were in the same range. The non-dedicated acoustics adequately reproduced trends observed in zooplankton from nets, but the acoustics could not differentiate between zooplankton and micronekton and absolute biomasses could not be calculated. Understanding the impact of mesoscale features on higher trophic levels will require further investigation and patchiness induced by eddies raises the question of how to best sample highly dynamic areas via sea experiments.

Multiple jet study data correlations. [data correlation for jet mixing flow of air jets

NASA Technical Reports Server (NTRS)

Walker, R. E.; Eberhardt, R. G.

1975-01-01

Correlations are presented which allow determination of penetration and mixing of multiple cold air jets injected normal to a ducted subsonic heated primary air stream. Correlations were obtained over jet-to-primary stream momentum flux ratios of 6 to 60 for locations from 1 to 30 jet diameters downstream of the injection plane. The range of geometric and operating variables makes the correlations relevant to gas turbine combustors. Correlations were obtained for the mixing efficiency between jets and primary stream using an energy exchange parameter. Also jet centerplane velocity and temperature trajectories were correlated and centerplane dimensionless temperature distributions defined. An assumption of a Gaussian vertical temperature distribution at all stations is shown to result in a reasonable temperature field model. Data are presented which allow comparison of predicted and measured values over the range of conditions specified above.

Wear compensating seal means for rotary piston coal feeder

DOEpatents

Gencsoy, Hasan T.; Gardner, John F.

1979-01-01

The present invention is directed to a wear compensating seal arrangement for use in a rotary piston feeder utilized for feeding pulverized coal into a gasifier operating at relatively high pressures and elevated temperatures. The rotary piston feeder has a circular casing with a coal loading opening therein diametrically opposed from a coal discharge and contains a rotatable disoidal rotor having a cylinder in which a reciprocatable piston is disposed. The reciprocation of the piston within the cylinder is provided by a stationary conjugate cam whereby pulverized coal from a coal hopper at atmospheric pressure can be introduced into the cylinder and then discharged therefrom into the high pressure gasifier while maintaining minimal losses of producer gas and the expenditure of minimal energy which would detract from the efficiency of the gasification. The seal arrangement of the present invention is disposed between the rotor and the casing about the coal discharge and prevents the high pressure gases from within the gasifier from escaping between these relatively movable parts during operation of the coal feeder. The seal utilizes a primary seal in contact with the rotor and a secondary seal supporting the primary seal. The primary seal is continuously urged towards the rotor by springs and the high pressure producer gas.

High efficiency vapor-fed AMTEC system for direct conversion. Final report

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

Anderson, W.G.; Bland, J.J.

1997-05-23

The Alkali Metal Thermal to Electric Converter (AMTEC) is a high temperature, high efficiency system for converting thermal to electrical energy, with no moving parts. It is based on the unique properties of {beta}{double_prime}-alumina solid electrolyte (BASE), which is an excellent conductor of sodium ions, but an extremely poor conductor of electrons. When the inside of the BASE is maintained at a higher temperature and pressure, a concentration gradient is created across the BASE. Electrons and sodium atoms cannot pass through the BASE. However, the sodium atoms are ionized, and the sodium ions move through the BASE to the lowermore » potential (temperature) region. The electrons travel externally to the AMTEC cell, providing power. There are a number of potential advantages to a wick-pumped, vapor-fed AMTEC system when compared with other designs. A wick-pumped system uses capillary forces to passively return liquid to the evaporator, and to distribute the liquid in the evaporator. Since the fluid return is self-regulating, multiple BASE tubes can use a single remote condenser, potentially improving efficiency in advanced AMTEC designs. Since the system is vapor-fed, sodium vapor is supplied at a uniform temperature and flux to the BASE tube, even with non-uniform heat fluxes and temperatures at the evaporator. The primary objective of the Phase 2 program was to develop wick-pumped AMTEC cells. During the program, procedures to fabricate wicks with smaller pore sizes were developed, to allow operation of an AMTEC cell at 800 C. A revised design was made for a High-Temperature, Wick-Fed AMTEC cell. In addition to the smaller wick pore size, several other changes were made to increase the cell efficiency: (1) internal artery return of condensate; (2) high temperature electrical feedthrough; and (3) separate heat pipe for providing heat to the BASE.« less

Thermally regenerative hydrogen/oxygen fuel cell power cycles

NASA Technical Reports Server (NTRS)

Morehouse, J. H.

1986-01-01

Two innovative thermodynamic power cycles are analytically examined for future engineering feasibility. The power cycles use a hydrogen-oxygen fuel cell for electrical energy production and use the thermal dissociation of water for regeneration of the hydrogen and oxygen. The TDS (thermal dissociation system) uses a thermal energy input at over 2000 K to thermally dissociate the water. The other cycle, the HTE (high temperature electrolyzer) system, dissociates the water using an electrolyzer operating at high temperature (1300 K) which receives its electrical energy from the fuel cell. The primary advantages of these cycles is that they are basically a no moving parts system, thus having the potential for long life and high reliability, and they have the potential for high thermal efficiency. Both cycles are shown to be classical heat engines with ideal efficiency close to Carnot cycle efficiency. The feasibility of constructing actual cycles is investigated by examining process irreversibilities and device efficiencies for the two types of cycles. The results show that while the processes and devices of the 2000 K TDS exceed current technology limits, the high temperature electrolyzer system appears to be a state-of-the-art technology development. The requirements for very high electrolyzer and fuel cell efficiencies are seen as determining the feasbility of the HTE system, and these high efficiency devices are currently being developed. It is concluded that a proof-of-concept HTE system experiment can and should be conducted.

Freeze-drying process design by manometric temperature measurement: design of a smart freeze-dryer.

PubMed

Tang, Xiaolin Charlie; Nail, Steven L; Pikal, Michael J

2005-04-01

To develop a procedure based on manometric temperature measurement (MTM) and an expert system for good practices in freeze drying that will allow development of an optimized freeze-drying process during a single laboratory freeze-drying experiment. Freeze drying was performed with a FTS Dura-Stop/Dura-Top freeze dryer with the manometric temperature measurement software installed. Five percent solutions of glycine, sucrose, or mannitol with 2 ml to 4 ml fill in 5 ml vials were used, with all vials loaded on one shelf. Details of freezing, optimization of chamber pressure, target product temperature, and some aspects of secondary drying are determined by the expert system algorithms. MTM measurements were used to select the optimum shelf temperature, to determine drying end points, and to evaluate residual moisture content in real-time. MTM measurements were made at 1 hour or half-hour intervals during primary drying and secondary drying, with a data collection frequency of 4 points per second. The improved MTM equations were fit to pressure-time data generated by the MTM procedure using Microcal Origin software to obtain product temperature and dry layer resistance. Using heat and mass transfer theory, the MTM results were used to evaluate mass and heat transfer rates and to estimate the shelf temperature required to maintain the target product temperature. MTM product dry layer resistance is accurate until about two-thirds of total primary drying time is over, and the MTM product temperature is normally accurate almost to the end of primary drying provided that effective thermal shielding is used in the freeze-drying process. The primary drying times can be accurately estimated from mass transfer rates calculated very early in the run, and we find the target product temperature can be achieved and maintained with only a few adjustments of shelf temperature. The freeze-dryer overload conditions can be estimated by calculation of heat/mass flow at the target product temperature. It was found that the MTM results serve as an excellent indicator of the end point of primary drying. Further, we find that the rate of water desorption during secondary drying may be accurately measured by a variation of the basic MTM procedure. Thus, both the end point of secondary drying and real-time residual moisture may be obtained during secondary drying. Manometric temperature measurement and the expert system for good practices in freeze drying does allow development of an optimized freeze-drying process during a single laboratory freeze-drying experiment.

BVRI Photometric Study of the High Mass Ratio, Detached, Pre-contact W UMa Binary GQ Cancri

NASA Astrophysics Data System (ADS)

Samec, R. G.; Olson, A.; Caton, D.; Faulkner, D. R.

2017-12-01

CCD BVRcIc light curves of GQ Cancri were observed in April 2013 using the SARA North 0.9-meter Telescope at Kitt Peak National Observatory in Arizona in remote mode. It is a high-amplitude (V 0.9 magnitude) K0±V type eclipsing binary (T1 5250 K) with a photometrically-determined mass ratio of M2 / M1 = 0.80. Its spectral color type classifies it as a pre-contact W UMa Binary (PCWB). The Wilson-Devinney Mode 2 solutions show that the system has a detached binary configuration with fill-outs of 94% and 98% for the primary and secondary component, respectively. As expected, the light curve is asymmetric due to spot activity. Three times of minimum light were calculated, for two primary eclipses and one secondary eclipse, from our present observations. In total, some 26 times of minimum light covering nearly 20 years of observation were used to determine linear and quadratic ephemerides. It is noted that the light curve solution remained in a detached state for every iteration of the computer runs. The components are very similar with a computed temperature difference of only 4 K, and the flux of the primary component accounts for 53±55% of the system's light in B, V, Rc, and Ic. A 12-degree radius high latitude white spot (faculae) was iterated on the primary component.

Induction Heating Model of Cermet Fuel Element Environmental Test (CFEET)

NASA Technical Reports Server (NTRS)

Gomez, Carlos F.; Bradley, D. E.; Cavender, D. P.; Mireles, O. R.; Hickman, R. R.; Trent, D.; Stewart, E.

2013-01-01

Deep space missions with large payloads require high specific impulse and relatively high thrust to achieve mission goals in reasonable time frames. Nuclear Thermal Rockets (NTR) are capable of producing a high specific impulse by employing heat produced by a fission reactor to heat and therefore accelerate hydrogen through a rocket nozzle providing thrust. Fuel element temperatures are very high (up to 3000 K) and hydrogen is highly reactive with most materials at high temperatures. Data covering the effects of high-temperature hydrogen exposure on fuel elements are limited. The primary concern is the mechanical failure of fuel elements due to large thermal gradients; therefore, high-melting-point ceramics-metallic matrix composites (cermets) are one of the fuels under consideration as part of the Nuclear Cryogenic Propulsion Stage (NCPS) Advance Exploration System (AES) technology project at the Marshall Space Flight Center. The purpose of testing and analytical modeling is to determine their ability to survive and maintain thermal performance in a prototypical NTR reactor environment of exposure to hydrogen at very high temperatures and obtain data to assess the properties of the non-nuclear support materials. The fission process and the resulting heating performance are well known and do not require that active fissile material to be integrated in this testing. A small-scale test bed; Compact Fuel Element Environmental Tester (CFEET), designed to heat fuel element samples via induction heating and expose samples to hydrogen is being developed at MSFC to assist in optimal material and manufacturing process selection without utilizing fissile material. This paper details the analytical approach to help design and optimize the test bed using COMSOL Multiphysics for predicting thermal gradients induced by electromagnetic heating (Induction heating) and Thermal Desktop for radiation calculations.

Documentation of meteorological data from the coniferous forest biome primary station in Oregon.

Treesearch

R.H. Waring; H.R. Holbo; R.P. Bueb; R.L. Fredriksen

1978-01-01

As part of the International Biological Program, a primary meteorological station was installed in the west-central Cascade Range of Oregon. Short-wave solar radiation, air temperature, dewpoint temperature, windspeed, and precipitation are recorded continuously. Climatic data are summarized in a daily record available from May 11, 1972, to date. This report details...

Discovery of hydrothermally active and extinct talc mounds on the Mid-Cayman Rise

NASA Astrophysics Data System (ADS)

Hodgkinson, M.; Murton, B. J.; Roberts, S.

2013-12-01

Since 1977, hydrothermal vents have been the subject of intense scientific interest due to their role in cooling the oceanic crust and global geochemical cycles. Until now, two types of hydrothermal system have been identified: one, driven by magmatic heat extruding ';black smoker' fluids; and another, involving serpentinisation of ultramafic rocks and the precipitation of carbonate/brucite chimneys. Here, we present details of a new, off-axis type of hydrothermal system consisting of mounds of predominately botryoidal talc (a magnesium-silicate) with accessory silica and copper sulphides, and chimneys exhaling fluids of moderate temperature and pH. Discovered on the Mid-Cayman Rise (MCR) in 2010, the Von Damm Vent Field (VDVF) features a NNW-ESE-trending line of four overlapping cones, the largest of which is 75 m high by 150 m in diameter. The VDVF is hosted in the gabbroic footwall of the Mount Dent Oceanic Core Complex (MDOCC), which includes serpentinised peridotite at depth. The largest cone vents clear fluids from two main orifices at its summit, with primary temperatures of 215°C. Elsewhere, both focussed and diffuse flow areas emit fluids with temperatures of up to 150°C. The surrounding ~1 m thick pelagic sediment contains abundant pockmarks that emit methane-rich fluids at temperatures of less than 10°C. During the return to the MCR in early 2013, several other talc mounds were discovered within a kilometre of the active VDVF. These inactive mounds also comprise an assemblage of botryoidal talc, silica, disseminated sulphides (including chalcopyrite) and sulphates. One of these mounds (Mystic Mount) is double the volume of the active VDVF. The unique dominance of talc as the major mineral forming the hydrothermal structures indicates unusual vent fluid compositions that are able to carry both copper (at high-temperatures) and precipitate magnesium silicate. Thermodynamic modelling indicates that talc precipitates on mixing a moderately acidic, silica rich fluid (e.g. the primary VDVF fluids) with only 2% of seawater. At lower pH (e.g. typical ';black smoker' fluids), the ratio jumps to over 90% while at high pH (e.g. ';Lost City' fluids) brucite and carbonate dominate. Estimates using recently measured vent temperatures and fluid fluxes indicate a heat flux of ~800 MW for the active VDVF. Assuming the primary vent fluid has remained largely unchanged, the VDVF could have grown in under 1000 years and Mystic Mount in ~2000 years. Both the hydrothermal mounds and faults in the surrounding gabbro share a NNW-ESE orientation that is consistent with a brittle structural control imposed by the flexural curvature of the MDOCC in response to the uplift of the lower oceanic crust along a low-angle detachment fault. We propose that these flexural faults provide pathways for fluids to ingress deep into the MDOCC where they react with both mafic rocks (producing high-temperature, low pH, sulphide and copper-bearing fluids), peridotites and carbonates (increasing the pH) resulting in a moderate pH, silica-rich fluid that precipitates talc on mixing with seawater. The presence of further, inactive, talc mounds within 1 km of the VDVF indicates hydrothermal activity on OCCs has been widespread and represents a significant but hitherto overlooked mechanism of crustal heat loss and chemical interaction with the ocean at slow-spreading ridges.

High-Efficiency Solar Thermal Vacuum Demonstration Completed for Refractive Secondary Concentrator

NASA Technical Reports Server (NTRS)

Wong, Wayne A.

2001-01-01

Common to many of the space applications that utilize solar thermal energy--such as electric power conversion, thermal propulsion, and furnaces--is a need for highly efficient, solar concentration systems. An effort is underway at the NASA Glenn Research Center to develop the refractive secondary concentrator, which uses refraction and total internal reflection to efficiently concentrate and direct solar energy. When used in combination with advanced lightweight primary concentrators, the refractive secondary concentrator enables very high system concentration ratios (10,000 to 1) and very high temperatures (>2000 K). The innovative refractive secondary concentrator offers significant advantages over all other types of secondary concentrators. The refractive secondary offers the highest throughput efficiency, provides for flux tailoring, requires no active cooling, relaxes the pointing and tracking requirements of the primary concentrator, and enables very high system concentration ratios. This technology has broad applicability to any system that requires the conversion of solar energy to heat. Glenn initiated the development of the refractive secondary concentrator in support of Shooting Star, a solar thermal propulsion flight experiment, and continued the development in support of Space Solar Power.

Prototyping a new, high-temperature SQUID magnetometer system

NASA Astrophysics Data System (ADS)

Grappone, J. Michael; Shaw, John; Biggin, Andrew J.

2017-04-01

High-sensitivity Superconducting Quantum Inference Devices (SQUIDs) and μ-metal shielding have largely solved paleomagnetic noise problems. Combing the two allows successful measurements of previously unusable samples, generally sediments with very weak (<10 pAm2) magnetizations. The improved sensitivity increases the fidelity of magnetic field variation surveys, but surveys continue to be somewhat slow. SQUIDs have historically been expensive to buy and operate, but technological advances now allow them to operate at liquid nitrogen temperatures (77 K), drastically reducing their costs. Step-wise thermal paleomagnetics studies cause large lag times during later steps as a result of heating from and cooling to room temperature for measurements. If the cooling step is removed entirely, however, the lag time drops by at least half. Available magnetometers currently provide either SQUID-level (0.1 - 1 pAm2) sensitivity or continuous heating. Combining a SQUID magnetometer with a high temperature oven is the logical next step to uncover the mysteries of the paleofield. However, the few that currently offer high temperature capabilities with noise levels approaching 10 pAm2 require either spinning or vibrating the sample, necessitating additional handling and potentially causing damage to the sample. Two primary factors have plagued previous developments: noise levels and temperature gradients. Our entire system is shielded from the environment using 4 layers of μ-metal. Our sample oven (designed for 7 mm diameter samples) sits inside a copper pipe and operates at high-frequency AC voltages. High frequency (10 kHz) AC current reduces the skin depth of radio frequency (RF) electromagnetic noise, which allows the 2 mm-thick copper shielding to reduce RF noise by ˜94%, leaving a residual field of ˜1.5 nT at the SQUID's location, 14.9 mm from the oven. A computer-controlled Eurotherm 3216 thermal controller regulates the temperature within ± 0.5 ˚ C. To reach 700 ˚ C, just above the Curie temperature of Hematite, a temperature difference of nearly 900 ˚ C between the sample and the SQUID is required. Since dipole fields decay rapidly with distance (∝ r -3 ), the equipment is designed to handle temperature gradients above 500 ˚ C cm-1 for maximum sensitivity using a passive double-vacuum separation system. All the parts used are commercially available to help reduce the operating costs and increase versatility.

Parametric optimisation of heat treated recycling aluminium (AA6061) by response surface methodology

NASA Astrophysics Data System (ADS)

Ahmad, A.; Lajis, M. A.; Yusuf, N. K.; Shamsudin, S.; Zhong, Z. W.

2017-09-01

Alternating typical primary aluminium production with recycling route should benefit various parties, including the environment since the need of high cost and massive energy consumption will be ruled out. At present, hot extrusion is preferred as the effective solid-state recycling process compared to the typical method of melting the swarf at high temperature. However, the ideal properties of extruded product can only be achieved through a controlled process used to alter the microstructure to impart properties which benefit the working life of a component, which also known as heat treatment process. To that extent, this work ought to investigate the effect of extrusion temperature and ageing time on the hardness of the recycled aluminium chips. By employing Analysis of Variance (ANOVA) for full factorial design with centre point, a total of 11 runs were carried out randomly. Three dissimilar extrusion temperatures were used to obtain gear-shape billet. Extruded billets were cut and ground before entering the treatment phase at three different ageing times. Ageing time was found as the influential factor to affect the material hardness, rather than the extrusion temperature. Sufficient ageing time allows the impurity atoms to interfere the dislocation phenomena and yield great hardness. Yet, the extrusion temperatures still act to assist the bonding activities via interparticle diffusion transport matter.

Influence of fluid temperature gradient on the flow within the shaft gap of a PLR pump

NASA Astrophysics Data System (ADS)

Qian, W.; Rosic, B.; Zhang, Q.; Khanal, B.

2016-03-01

In nuclear power plants the primary-loop recirculation (PLR) pump circulates the high temperature/high-pressure coolant in order to remove the thermal energy generated within the reactor. The pump is sealed using the cold purge flow in the shaft seal gap between the rotating shaft and stationary casing, where different forms of Taylor-Couette flow instabilities develop. Due to the temperature difference between the hot recirculating water and the cold purge water (of order of 200 °C), the flow instabilities in the gap cause temperature fluctuations, which can lead to shaft or casing thermal fatigue cracks. The present work numerically investigated the influence of temperature difference and rotating speed on the structure and dynamics of the Taylor-Couette flow instabilities. The CFD solver used in this study was extensively validated against the experimental data published in the open literature. Influence of temperature difference on the fluid dynamics of Taylor vortices was investigated in this study. With large temperature difference, the structure of the Taylor vortices is greatly stretched at the interface region between the annulus gap and the lower recirculating cavity. Higher temperature difference and rotating speed induce lower fluctuating frequency and smaller circumferential wave number of Taylor vortices. However, the azimuthal wave speed remains unchanged with all the cases tested. The predicted axial location of the maximum temperature fluctuation on the shaft is in a good agreement with the experimental data, identifying the region potentially affected by the thermal fatigue. The physical understandings of such flow instabilities presented in this paper would be useful for future PLR pump design optimization.

Dynamic System Simulation of the KRUSTY Experiment

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

Klein, Steven Karl; Kimpland, Robert Herbert

2016-05-09

The proposed KRUSTY experiment is a demonstration of a reactor operating at power. The planned experimental configuration includes a highly enriched uranium (HEU) reflected core, cooled by multiple heat pipes leading to Stirling engines for primary heat rejection. Operating power is expected to be approximately four (4) to five (5) kilowatts with a core temperature above 1,000 K. No data is available on any historical reactor employing HEU metal that operated over the temperature range required for the KRUSTY experiment. Further, no reactor has operated with heat pipes as the primary cooling mechanism. Historic power reactors have employed either naturalmore » or forced convection so data on their operation is not directly applicable to the KRUSTY experiment. The primary purpose of the system model once developed and refined by data from these component experiments, will be used to plan the KRUSTY experiment. This planning will include expected behavior of the reactor from start-up, through various transient conditions where cooling begins to become present and effective, and finally establishment of steady-state. In addition, the model can provide indicators of anticipated off-normal events and appropriate operator response to those conditions. This information can be used to develop specific experiment operating procedures and aids to guide the operators in conduct of the experiment.« less

Body temperature - a marker of infarct size in the era of early reperfusion.

PubMed

Ben-Dor, Itsik; Haim, Moti; Rechavia, Eldad; Murininkas, Daniel; Nahon, Merav; Harell, Daniella; Porter, Avital; Iakobishvili, Zaza; Scapa, Erez; Battler, Alexander; Hasdai, David

2005-01-01

We measured body temperature in 40 consecutive patients treated for a first ST elevation acute myocardial infarction (AMI) with primary percutaneous coronary interventions. Left ventricular function was assessed by echocardiography, and blood samples were drawn for highly sensitive C-reactive protein (hs-CRP), white blood cell (WBC) count, fibrinogen, creatine kinase (CK), and cardiac troponin I levels (cTnI). The median (25th, 75th quartiles) peak 24-hour temperature was 37.4 degrees C (36.9 degrees C, 37.6 degrees C). Variables significantly associated with peak 24-hour temperature were CK (p = 0.01, r = 0.42), wall motion index (p = 0.01, r = 0.41), hs-CRP (p = 0.01, r = 0.41), and cTnI (p = 0.03, r = 0.35). There was no significant correlation between peak 24-hour temperature and WBC count (p = 0.39, r = 0.14) and fibrinogen (p = 0.12, r = 0.21). Thus, peak 24-hour body temperature after ST elevation AMI probably reflects infarct size rather than a nonspecific inflammatory response. Copyright 2005 S. Karger AG, Basel.

Temperature changes in the pulpal chamber and the sealing performance of various methods of direct pulp capping of primary teeth.

PubMed

Yilmaz, Y; Keles, S; Mete, A

2013-06-01

To compare changes in pulpal chamber temperature during the visible-light curing of direct pulp capping compounds and various modes of diode laser irradiation without prior placement of a pulp capping compound and the resultant seals. Pulp exposure holes were made in 100 extracted human primary first molars, which were randomly assigned to ten equal groups. The holes were sealed by (a= Group 1, 2, 3, 4, 5, 6 and 7) different pulp capping compounds which were cured using various types of visible-light curing units or (b=Group 8, 9 and 10) diode laser irradiation without prior application of a pulp capping compound. Pulpal chamber temperatures were recorded during the procedure, and the resultant seals were examined under a scanning electron microscope. Visible-light curing of the pulp capping compounds and diode laser irradiation at a 0.7 W output power can cause non-injurious temperature rises in the pulpal chamber. At higher output powers of the diode laser, the temperature rises are sufficient to cause thermal injury. The seals were complete when pulp capping compounds were used for direct pulp capping, but were incomplete when laser irradiation without prior placement of a pulp capping compound was used for the identical purpose. The visible-light curing of pulp capping compounds is not harmful to vital pulp, and provides an effective seal of the pulp exposure hole. Laser irradiation is not an effective sealant, and can cause thermal injury to vital pulp at high output powers.

Characteristic and magnetic field analysis of a high temperature superconductor axial-flux coreless induction maglev motor.

PubMed

Wei, Qin; Yu, Fan; Jin, Fang; Shuo, Li; Guoguo, Li; Gang, Lv

2012-04-01

A new high temperature superconductor axial-flux coreless maglev motor (HTS AFIM) is proposed, of which the primary windings are made of HTS tapes and the secondary is a non-magnetic conductor. The main works of this paper are the magnetic-field computation and characteristics analysis of HTS AFIM. For the first one, the reduction of magnetic fields near outer and inner radius of the HTS AFIM is solved by introducing the sub-loop electro-magnetic model along the radial position. For the second one, the AC losses of HTS coils are calculated. The relationships between the device's characteristics and device parameters are presented, and the results indicate that under certain frequency and current levitation device can output enough lift force. The conclusions are verified by finite element calculations.

Characteristic and magnetic field analysis of a high temperature superconductor axial-flux coreless induction maglev motor

PubMed Central

Wei, Qin; Yu, Fan; Jin, Fang; Shuo, Li; Guoguo, Li; Gang, Lv

2012-01-01

A new high temperature superconductor axial-flux coreless maglev motor (HTS AFIM) is proposed, of which the primary windings are made of HTS tapes and the secondary is a non-magnetic conductor. The main works of this paper are the magnetic-field computation and characteristics analysis of HTS AFIM. For the first one, the reduction of magnetic fields near outer and inner radius of the HTS AFIM is solved by introducing the sub-loop electro-magnetic model along the radial position. For the second one, the AC losses of HTS coils are calculated. The relationships between the device’s characteristics and device parameters are presented, and the results indicate that under certain frequency and current levitation device can output enough lift force. The conclusions are verified by finite element calculations. PMID:22393268

The interactive effects of temperature and light on biological nitrogen fixation in boreal forests.

PubMed

Gundale, Michael J; Nilsson, Madeleine; Bansal, Sheel; Jäderlund, Anders

2012-04-01

Plant productivity is predicted to increase in northern latitudes as a result of climate warming; however, this may depend on whether biological nitrogen (N)-fixation also increases. We evaluated how the variation in temperature and light affects N-fixation by two boreal feather mosses, Pleurozium schreberi and Hylocomium splendens, which are the primary source of N-fixation in most boreal environments. We measured N-fixation rates 2 and 4 wk after exposure to a factorial combination of environments of normal, intermediate and high temperature (16.3, 22.0 and 30.3°C) and light (148.0, 295.7 and 517.3 μmol m(-2) s(-1)). Our results showed that P. schreberi achieved higher N-fixation rates relative to H. splendens in response to warming treatments, but that the highest warming treatment eventually caused N-fixation to decline for both species. Light strongly interacted with warming treatments, having positive effects at low or intermediate temperatures and damaging effects at high temperatures. These results suggest that climate warming may increase N-fixation in boreal forests, but that increased shading by the forest canopy or the occurrence of extreme temperature events could limit increases. They also suggest that P. schreberi may become a larger source of N in boreal forests relative to H. splendens as climate warming progresses. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Thermal Decomposition Mechanism of CL-20 at Different Temperatures by ReaxFF Reactive Molecular Dynamics Simulations.

PubMed

Wang, Fuping; Chen, Lang; Geng, Deshen; Wu, Junying; Lu, Jianying; Wang, Chen

2018-04-26

Hexanitrohexaazaisowurtzitane (CL-20) has a high detonation velocity and pressure, but its sensitivity is also high, which somewhat limits its applications. Therefore, it is important to understand the mechanism and characteristics of thermal decomposition of CL-20. In this study, a ε-CL-20 supercell was constructed and ReaxFF-lg reactive molecular dynamics simulations were performed to investigate thermal decomposition of ε-CL-20 at various temperatures (2000, 2500, 2750, 3000, 3250, and 3500 K). The mechanism of thermal decomposition of CL-20 was analyzed from the aspects of potential energy evolution, the primary reactions, and the intermediate and final product species. The effect of temperature on thermal decomposition of CL-20 is also discussed. The initial reaction path of thermal decomposition of CL-20 is N-NO 2 cleavage to form NO 2 , followed by C-N cleavage, leading to the destruction of the cage structure. A small number of clusters appear in the early reactions and disappear at the end of the reactions. The initial reaction path of CL-20 decomposition is the same at different temperatures. However, as the temperature increases, the decomposition rate of CL-20 increases and the cage structure is destroyed earlier. The temperature greatly affects the rate constants of H 2 O and N 2 , but it has little effect on the rate constants of CO 2 and H 2 .

Climate change decouples oceanic primary and export productivity and organic carbon burial

PubMed Central

Lopes, Cristina; Kucera, Michal; Mix, Alan C.

2015-01-01

Understanding responses of oceanic primary productivity, carbon export, and burial to climate change is essential for model-based projection of biological feedbacks in a high-CO2 world. Here we compare estimates of productivity based on the composition of fossil diatom floras with organic carbon burial off Oregon in the Northeast Pacific across a large climatic transition at the last glacial termination. Although estimated primary productivity was highest during the Last Glacial Maximum, carbon burial was lowest, reflecting reduced preservation linked to low sedimentation rates. A diatom size index further points to a glacial decrease (and deglacial increase) in the fraction of fixed carbon that was exported, inferred to reflect expansion, and contraction, of subpolar ecosystems that today favor smaller plankton. Thus, in contrast to models that link remineralization of carbon to temperature, in the Northeast Pacific, we find dominant ecosystem and sea floor control such that intervals of warming climate had more efficient carbon export and higher carbon burial despite falling primary productivity. PMID:25453073

Effect of high-dose irradiation on quality characteristics of ready-to-eat broiler breast fillets stored at room temperature.

PubMed

Baptista, R F; Teixeira, C E; Lemos, M; Monteiro, M L G; Vital, H C; Mársico, E T; Júnior, C A Conte; Mano, S B

2014-10-01

The effect of high-dose irradiation on the physical, chemical, and bacteriological parameters of ready-to-eat vacuum-packed broiler breast meat after 430 d of storage at room temperature was investigated. Ready-to-eat broiler breast fillets were immersed in brine with garlic powder and then drained, grilled, and vacuum-packed (primary packaging). The high-dose irradiation used was approximately 48 kGy. The treatments were designated as A (irradiated samples stored at room temperature), B (irradiated samples stored at -25°C), and C (nonirradiated samples stored at -25°C). All samples were packaged in polyethylene bags containing aluminum to exclude light (secondary packaging). Proximate composition, pH, 2-thiobarbituric acid reactive substance (TBARS), and heterotrophic aerobic mesophilic bacteria were analyzed during 430 d of storage. Results were analyzed using 1-way ANOVA and the Tukey test. Linear regression was used to analyze the correlation between the results for each parameter and storage time of the different treatments. The gamma radiation caused slight changes (P < 0.05) in the moisture and fat content, regardless of storage temperature. After storage d 110, TBARS values remained stable (P > 0.05) in all the treatments. The preservation methods used were effective in maintaining the mesophilic counts below the detection level during the entire storage period. We concluded that, among the treatments studied, high-dose irradiation with storage at room temperature showed potential for the preservation of ready-to-eat products made from poultry meat, to provide foods safe for consumption. ©2014 Poultry Science Association Inc.

Shifting plant species composition in response to climate change stabilizes grassland primary production.

PubMed

Liu, Huiying; Mi, Zhaorong; Lin, Li; Wang, Yonghui; Zhang, Zhenhua; Zhang, Fawei; Wang, Hao; Liu, Lingli; Zhu, Biao; Cao, Guangmin; Zhao, Xinquan; Sanders, Nathan J; Classen, Aimée T; Reich, Peter B; He, Jin-Sheng

2018-04-17

The structure and function of alpine grassland ecosystems, including their extensive soil carbon stocks, are largely shaped by temperature. The Tibetan Plateau in particular has experienced significant warming over the past 50 y, and this warming trend is projected to intensify in the future. Such climate change will likely alter plant species composition and net primary production (NPP). Here we combined 32 y of observations and monitoring with a manipulative experiment of temperature and precipitation to explore the effects of changing climate on plant community structure and ecosystem function. First, long-term climate warming from 1983 to 2014, which occurred without systematic changes in precipitation, led to higher grass abundance and lower sedge abundance, but did not affect aboveground NPP. Second, an experimental warming experiment conducted over 4 y had no effects on any aspect of NPP, whereas drought manipulation (reducing precipitation by 50%), shifted NPP allocation belowground without affecting total NPP. Third, both experimental warming and drought treatments, supported by a meta-analysis at nine sites across the plateau, increased grass abundance at the expense of biomass of sedges and forbs. This shift in functional group composition led to deeper root systems, which may have enabled plant communities to acquire more water and thus stabilize ecosystem primary production even with a changing climate. Overall, our study demonstrates that shifting plant species composition in response to climate change may have stabilized primary production in this high-elevation ecosystem, but it also caused a shift from aboveground to belowground productivity.

Visible light induced green transformation of primary amines to imines using a silicate supported anatase photocatalyst.

PubMed

Zavahir, Sifani; Zhu, Huaiyong

2015-01-26

Catalytic oxidation of amine to imine is of intense present interest since imines are important intermediates for the synthesis of fine chemicals, pharmaceuticals, and agricultural chemicals. However, considerable efforts have been made to develop efficient methods for the oxidation of secondary amines to imines, while little attention has until recently been given to the oxidation of primary amines, presumably owing to the high reactivity of generated imines of primary amines that are easily dehydrogenated to nitriles. Herein, we report the oxidative coupling of a series of primary benzylic amines into corresponding imines with dioxygen as the benign oxidant over composite catalysts of TiO2 (anatase)-silicate under visible light irradiation of λ > 460 nm. Visible light response of this system is believed to be as a result of high population of defects and contacts between silicate and anatase crystals in the composite and the strong interaction between benzylic amine and the catalyst. It is found that tuning the intensity and wavelength of the light irradiation and the reaction temperature can remarkably enhance the reaction activity. Water can also act as a green medium for the reaction with an excellent selectivity. This report contributes to the use of readily synthesized, environmentally benign, TiO2 based composite photocatalyst and solar energy to realize the transformation of primary amines to imine compounds.

Oxidation Resistance of Alloys from Nb-Si-Cr System for High Temperature Applications

DTIC Science & Technology

2013-01-02

higher education for undergraduate students while prepare the graduate students for professional careers in research (at one of the ONR facilities...generate interest in students to pursue higher education for undergraduate students while prepare the graduate students for professional careers in...reduces the amount of primary a significantly but still contains a rather coarser eutectic like microconstituent. A NbßSi (3-1 silicide ) silicide phase

Influence of environmental factors on activity patterns of Incisitermes minor (Isoptera: Kalotermitidae) in naturally infested logs.

PubMed

Lewis, Vernard R; Leighton, Shawn; Tabuchi, Robin; Baldwin, James A; Haverty, Michael I

2013-02-01

Acoustic emission (AE) activity patterns were measured from seven loquat [Eriobotrya japonica (Thunb.) Lindl.] logs, five containing live western drywood termite [Incisitermes minor (Hagen)] infestations, and two without an active drywood termite infestation. AE activity, as well as temperature, were monitored every 3 min under unrestricted ambient conditions in a small wooden building, under unrestricted ambient conditions but in constant darkness, or in a temperature-controlled cabined under constant darkness. Logs with active drywood termite infestations displayed similar diurnal cycles of AE activity that closely followed temperature with a peak of AE activity late in the afternoon (1700-1800 hours). When light was excluded from the building, a circadian pattern continued and apparently was driven by temperature. When the seven logs were kept at a relatively constant temperature (approximately 23 +/- 0.9 degrees C) and constant darkness, the pattern of activity was closely correlated with temperature, even with minimal changes in temperature. Temperature is the primary driver of activity of these drywood termites, but the effects are different when temperature is increasing or decreasing. At constant temperature, AE activity was highly correlated with the number of termites in the logs. The possible implications of these findings on our understanding of drywood termite biology and how this information may affect inspections and posttreatment evaluations are discussed.

Carbon isotope variations in a solar pond microbial mat: Role of environmental gradients as steering variables

NASA Astrophysics Data System (ADS)

Schidlowski, Manfred; Gorzawski, Hendrik; Dor, Inka

1994-05-01

A biogeochemical traverse is presented for a juvenile benthic mat covering the depth profile of an artificially stratified and eutrophicated hypersaline heliothermal pond with known gradients of temperature, salinity, pH, and light transmission. It can be shown that visual mat development depends primarily on temperature and salinity as main environmental steering variables whose increase with depth goes along with the attenuation and final disappearance of a visible microbial film in the pond's hypolimnic compartment. Recorded biogeochemical parameters (C org content, cell numbers, chlorophyll-a content) evidently reflect, as either biomass- or productivity-related index functions, the visually perceptible growth gradient of the microbial ecosystem along the pond slope. The observed coincidence of maxima in these index functions with maxima in δ13Corg clearly identifies high rates of primary productivity as the agent ultimately responsible for the generation of isotopically heavy ( 13C-enriched) biomass in these and related environments. Extreme demands placed on the local feeder pool of dissolved inorganic carbon by high rates of primary productivity entertained by the mat-forming microbenthos obviously give rise to severe CO 2 limitation, enforcing the operation of a diffusion-(supply-)limited assimilatory pathway with an isotopically indiscriminate metabolization of the available CO 2 resources.

Effects of backlash and dead band on temperature control of the primary loop of a conceptual nuclear Brayton space powerplant

NASA Technical Reports Server (NTRS)

Petrick, E. J.

1973-01-01

An analytical study was made of the stability of a closed-loop liquid-lithium temperature control of the primary loop of a conceptual nuclear Brayton space powerplant. The operating point was varied from 20 to 120 percent of design. A describing-function technique was used to evaluate the effects of temperature dead band and control coupling backlash. From the system investigation, it was predicted that a limit cycle will not exist with a temperature dead band, but a limit cycle will not exist when backlash is present. The results compare favorably with a digital computer simulation.

Fiber optic quench detection via optimized Rayleigh Scattering in high-field YBCO accelerator magnets

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

Flanagan, Gene

Yttrium barium copper oxide (YBCO) coated conductors are known for their ability to operate in the superconducting state at relatively high temperatures, even above the boiling point of liquid nitrogen (77 K). When these same conductors are operated at lower temperatures, they are able to operate in much higher magnetic fields than traditional superconductors like NiTi or Nb 3Sn. Thus, YBCO superconducting magnets are one of the primary options for generating the high magnetic fields needed for future high energy physics devices. Due to slow quench propagation, quench detection remains one of the primary limitations to YBCO magnets. Fiber opticmore » sensing, based upon Rayleigh scattering, has the potential for spatial resolution approaching the wavelength of light, or very fast temporal resolution at low spatial resolution, and a continuum of combinations in between. This project has studied, theoretically and experimentally, YBCO magnets and Rayleigh scattering quench detection systems to demonstrate feasibility of the systems for YBCO quench protection systems. Under this grant an experimentally validated 3D quench propagation model was used to accurately define the acceptable range of spatial and temporal resolutions for effective quench detection in YBCO magnets and to evaluate present-day and potentially improved YBCO conductors. The data volume and speed requirements for quench detection via Rayleigh scattering required the development of a high performance fiber optic based quench detection/data acquisition system and its integration with an existing voltage tap/thermo-couple based system. In this project, optical fibers are tightly co-wound into YBCO magnet coils, with the fiber on top of the conductor as turn-to-turn insulation. Local changes in the temperature or strain of the conductor are sensed by the optical fiber, which is in close thermal and mechanical contact with the conductor. Intrinsic imperfections in the fiber reflect Rayleigh backscattered laser signals that are shifted by the changes in the fiber that are induced by a local change in the YBCO temperature or strain. One goal of this project was to show that modern technology can be used to interrogate the signals from a (very expensive) YBCO magnet to detect an impending quench in time to protect it from self-destruction. The results show that Rayleigh-backscattering interrogated optical fibers (RIOF) have significant advantages over traditional techniques, including very high spatial resolution and the ability to detect a hot-spot well before the peak local temperature becomes so high that the conductor can be damaged. RIOF quench detection is intrinsically faster than voltage taps, and this intrinsic advantage is greater as the coil size and/or current margin increases. We describe the development and testing program performed under the grant.« less

Experiment and Modeling of Simultaneous Creep, Plasticity and Transformation of High Temperature Shape Memory Alloys During Cyclic Actuation

NASA Technical Reports Server (NTRS)

Kumar, Parikshith K.; Desai, Uri; Chatzigeorgiou, George; Lagoudas, Dimitris C.; Monroe, James; Karaman, Ibrahim; Noebe, Ron; Bigelow, Glen

2010-01-01

The present work is focused on studying the cycling actuation behavior of HTSMAs undergoing simultaneous creep and transformation. For the thermomechanical testing, a high temperature test setup was assembled on a MTS frame with the capability to test up to temperatures of 600 C. Constant stress thermal cycling tests were conducted to establish the actuation characteristics and the phase diagram for the chosen HTSMA. Additionally, creep tests were conducted at constant stress levels at different test temperatures to characterize the creep behavior of the alloy over the operational range. A thermodynamic constitutive model is developed and extended to take into account a) the effect of multiple thermal cycling on the generation of plastic strains due to transformation (TRIP strains) and b) both primary and secondary creep effects. The model calibration is based on the test results. The creep tests and the uniaxial tests are used to identify the viscoplastic behavior of the material. The parameters for the SMA properties, regarding the transformation and transformation induced plastic strain evolutions, are obtained from the material phase diagram and the thermomechanical tests. The model is validated by predicting the material behavior at different thermomechanical test conditions.

Corrosion of aluminum clad spent nuclear fuel in the 70 ton cask during transfer from L area to H-canyon

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

Mickalonis, J. I.

2015-08-31

Aluminum-clad spent nuclear fuel will be transported for processing in the 70-ton nuclear fuel element cask from L Basin to H-canyon. During transport these fuels would be expected to experience high temperature aqueous corrosion from the residual L Basin water that will be present in the cask. Cladding corrosion losses during transport were calculated for material test reactor (MTR) and high flux isotope reactors (HFIR) fuels using literature and site information on aqueous corrosion at a range of time/temperature conditions. Calculations of the cladding corrosion loss were based on Arrhenius relationships developed for aluminum alloys typical of cladding material withmore » the primary assumption that an adherent passive film does not form to retard the initial corrosion rate. For MTR fuels a cladding thickness loss of 33 % was found after 1 year in the cask with a maximum temperature of 263 °C. HFIR fuels showed a thickness loss of only 6% after 1 year at a maximum temperature of 180 °C. These losses are not expected to impact the overall confinement function of the aluminum cladding.« less

Corrosion of aluminum clad spent nuclear fuel in the 70 ton cask during transfer from L area to H-canyon

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

Mickalonis, J. I.

2015-08-01

Aluminum-clad spent nuclear fuel will be transported for processing in the 70-ton nuclear fuel element cask from L Basin to H-canyon. During transport these fuels would be expected to experience high temperature aqueous corrosion from the residual L Basin water that will be present in the cask. Cladding corrosion losses during transport were calculated for material test reactor (MTR) and high flux isotope reactors (HFIR) fuels using literature and site information on aqueous corrosion at a range of time/temperature conditions. Calculations of the cladding corrosion loss were based on Arrhenius relationships developed for aluminum alloys typical of cladding material withmore » the primary assumption that an adherent passive film does not form to retard the initial corrosion rate. For MTR fuels a cladding thickness loss of 33% was found after 1 year in the cask with a maximum temperature of 263 °C. HFIR fuels showed a thickness loss of only 6% after 1 year at a maximum temperature of 180 °C. These losses are not expected to impact the overall confinement function of the aluminum cladding.« less

Hydrochemistry dynamics in remote mountain lakes and its relation to catchment and atmospheric features: the case study of Sabocos Tarn, Pyrenees.

PubMed

Santolaria, Zoe; Arruebo, Tomas; Urieta, José Santiago; Lanaja, Francisco Javier; Pardo, Alfonso; Matesanz, José; Rodriguez-Casals, Carlos

2015-01-01

Increasing the understanding of high mountain lake dynamics is essential to use these remote aquatic ecosystems as proxies of global environmental changes. With this aim, at Sabocos, a Pyrenean cirque glacial lake or tarn, this study shows the main results of a morphological and catchment characterization, along with statistical analyses of its hydrochemical trends and their concomitant driving factors from 2010 to 2013. Dissolved oxygen, water temperature stratification, and its snow and ice cover composition and dynamics have been also investigated. According to morphological analyses, Sabocos can be classified as a medium-large and deep lake, having a circular contour and a long water retention time as compared to Pyrenean glacial lake average values. Sabocos hydrochemistry is mainly determined by very high alkalinity, pH and conductivity levels, and high Ca(2+), Mg(2+), and SO4(2-) content, coming from the easily weatherable limestone-dolomite bedrock. Thus, lake water is well buffered, and therefore, Sabocos tarn is non-sensitive to acidification processes. On the other hand, the main source of K(+), Na(+), and Cl(-) (sea salts) and nutrients (NH4(+), NO3(-), and phosphorous) to lake water appears to be atmospheric deposition. Primary production is phosphorous limited, and due to the N-saturation stage of the poorly developed soils of Sabocos catchment, NO3(-) is the chief component in the total nitrogen pool. External temperature seems to be the major driver regulating lake productivity, since warm temperatures boot primary production. Although precipitation might also play an important role in lake dynamics, especially regarding to those parameters influenced by the weathering of the bedrock, its influence cannot be easily assessed due to the seasonal isolation produced by the ice cover. Also, as occurs in the whole Pyrenean lake district, chemical composition of bulk deposition is highly variable due to the contribution of air masses with different origin.

Development of a HTSMA-Actuated Surge Control Rod for High-Temperature Turbomachinery Applications

NASA Technical Reports Server (NTRS)

Padula, Santo, II; Noebe, Ronald; Bigelow, Glen; Culley, Dennis; Stevens, Mark; Penney, Nicholas; Gaydosh, Darrell; Quackenbush, Todd; Carpenter, Bernie

2007-01-01

In recent years, a demand for compact, lightweight, solid-state actuation systems has emerged, driven in part by the needs of the aeronautics industry. However, most actuation systems used in turbomachinery require not only elevated temperature but high-force capability. As a result, shape memory alloy (SMA) based systems have worked their way to the forefront of a short list of viable options to meet such a technological challenge. Most of the effort centered on shape memory systems to date has involved binary NiTi alloys but the working temperatures required in many aeronautics applications dictate significantly higher transformation temperatures than the binary systems can provide. Hence, a high temperature shape memory alloy (HTSMA) based on NiTiPdPt, having a transformation temperature near 300 C, was developed. Various thermo-mechanical processing schemes were utilized to further improve the dimensional stability of the alloy and it was later extruded/drawn into wire form to be more compatible with envisioned applications. Mechanical testing on the finished wire form showed reasonable work output capability with excellent dimensional stability. Subsequently, the wire form of the alloy was incorporated into a benchtop system, which was shown to provide the necessary stroke requirements of approx.0.125 inches for the targeted surge-control application. Cycle times for the actuator were limited to 4 seconds due to control and cooling constraints but this cycle time was determined to be adequate for the surge control application targeted as the primary requirement was initial actuation of a surge control rod, which could be completed in approximately one second.

Thermal adaptation of net ecosystem exchange

DOE PAGES

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

2011-06-06

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

Thermal adaptation of net ecosystem exchange

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

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

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

Evaluation of coated columbium alloy heat shields for space shuttle thermal protection system application. Volume 3, phase 3: Full size TPS evaluation

NASA Technical Reports Server (NTRS)

Baer, J. W.; Black, W. E.

1974-01-01

The thermal protection system (TPS), designed for incorporation with space shuttle orbiter systems, consists of one primary heat shield thermally and structurally isolated from the test fixture by eight peripheral guard panels, all encompassing an area of approximately 12 sq ft. TPS components include tee-stiffened Cb 752/R-512E heat shields, bi-metallic support posts, panel retainers, and high temperature insulation blankets. The vehicle primary structure was simulated by a titanium skin, frames, and stiffeners. Test procedures, manufacturing processes, and methods of analysis are fully documented. For Vol. 1, see N72-30948; for Vol. 2, see N74-15660.

Axillary, Oral and Rectal Routes of Temperature Measurement During Treatment of Acute Kawasaki Disease.

PubMed

Kanegaye, John T; Jones, Jefferson M; Burns, Jane C; Jain, Sonia; Sun, Xiaoying; Jimenez-Fernandez, Susan; Berry, Erika; Pancheri, Joan M; Jaggi, Preeti; Ramilo, Octavio; Tremoulet, Adriana H

2016-01-01

Important therapeutic decisions are made based on the presence or absence of fever in patients with Kawasaki disease (KD), yet no standard method or threshold exists for temperature measurement during the diagnosis and treatment of these patients. We sought to compare surface and internal (rectal or oral) routes of temperature measurement for the detection of fever as a marker of treatment resistance. From a randomized, placebo-controlled trial of infliximab as an adjunct to primary intravenous immunoglobulin treatment for acute KD, we collected concurrent (within 5 minutes) axillary and internal temperature measurements and performed receiver-operating characteristic and Bland-Altman analyses. We also determined the ability of surface temperatures to detect treatment resistance defined by internal temperature measurements. Among 452 oral-axillary and 439 rectal-axillary pairs from 159 patients, mean axillary temperatures were 0.25 and 0.43 °C lower than oral and rectal temperatures and had high receiver-operating characteristic areas under curves. However, axillary temperatures ≥ 38.0 °C had limited sensitivity to detect fever defined by internal temperatures. Axillary thresholds of 37.5 and 37.2 °C provided maximal sensitivity and specificity to detect oral and rectal temperatures ≥ 38.0 °C, respectively. Axillary temperatures are an insensitive metric for fevers defining treatment resistance. Clinical trials should adopt temperature measurement by the oral or rectal routes for adjudication of treatment resistance in KD.

Diatom Cell Size, Coloniality and Motility: Trade-Offs between Temperature, Salinity and Nutrient Supply with Climate Change

PubMed Central

Svensson, Filip; Norberg, Jon; Snoeijs, Pauline

2014-01-01

Reduction in body size has been proposed as a universal response of organisms, both to warming and to decreased salinity. However, it is still controversial if size reduction is caused by temperature or salinity on their own, or if other factors interfere as well. We used natural benthic diatom communities to explore how “body size” (cells and colonies) and motility change along temperature (2–26°C) and salinity (0.5–7.8) gradients in the brackish Baltic Sea. Fourth-corner analysis confirmed that small cell and colony sizes were associated with high temperature in summer. Average community cell volume decreased linearly with 2.2% per °C. However, cells were larger with artificial warming when nutrient concentrations were high in the cold season. Average community cell volume increased by 5.2% per °C of artificial warming from 0 to 8.5°C and simultaneously there was a selection for motility, which probably helped to optimize growth rates by trade-offs between nutrient supply and irradiation. Along the Baltic Sea salinity gradient cell size decreased with decreasing salinity, apparently mediated by nutrient stoichiometry. Altogether, our results suggest that climate change in this century may polarize seasonality by creating two new niches, with elevated temperature at high nutrient concentrations in the cold season (increasing cell size) and elevated temperature at low nutrient concentrations in the warm season (decreasing cell size). Higher temperature in summer and lower salinity by increased land-runoff are expected to decrease the average cell size of primary producers, which is likely to affect the transfer of energy to higher trophic levels. PMID:25279720

Diatom cell size, coloniality and motility: trade-offs between temperature, salinity and nutrient supply with climate change.

PubMed

Svensson, Filip; Norberg, Jon; Snoeijs, Pauline

2014-01-01

Reduction in body size has been proposed as a universal response of organisms, both to warming and to decreased salinity. However, it is still controversial if size reduction is caused by temperature or salinity on their own, or if other factors interfere as well. We used natural benthic diatom communities to explore how "body size" (cells and colonies) and motility change along temperature (2-26°C) and salinity (0.5-7.8) gradients in the brackish Baltic Sea. Fourth-corner analysis confirmed that small cell and colony sizes were associated with high temperature in summer. Average community cell volume decreased linearly with 2.2% per °C. However, cells were larger with artificial warming when nutrient concentrations were high in the cold season. Average community cell volume increased by 5.2% per °C of artificial warming from 0 to 8.5°C and simultaneously there was a selection for motility, which probably helped to optimize growth rates by trade-offs between nutrient supply and irradiation. Along the Baltic Sea salinity gradient cell size decreased with decreasing salinity, apparently mediated by nutrient stoichiometry. Altogether, our results suggest that climate change in this century may polarize seasonality by creating two new niches, with elevated temperature at high nutrient concentrations in the cold season (increasing cell size) and elevated temperature at low nutrient concentrations in the warm season (decreasing cell size). Higher temperature in summer and lower salinity by increased land-runoff are expected to decrease the average cell size of primary producers, which is likely to affect the transfer of energy to higher trophic levels.

Method for removing cesium from a nuclear reactor coolant

DOEpatents

Colburn, Richard P.

1986-01-01

A method of and system for removing cesium from a liquid metal reactor coolant including a carbon packing trap in the primary coolant system for absorbing a major portion of the radioactive cesium from the coolant flowing therethrough at a reduced temperature. A regeneration subloop system having a secondary carbon packing trap is selectively connected to the primary system for isolating the main trap therefrom and connecting it to the regeneration system. Increasing the temperature of the sodium flowing through the primary trap diffuses a portion of the cesium

Low-Temperature Synchrotron Photoionization Study of 2-Methyl-3-buten-2-ol (MBO) Oxidation Initiated by O(3P) Atoms in the 298-650 K Range.

PubMed

Fathi, Yasmin; Price, Chelsea; Meloni, Giovanni

2017-04-20

This work studies the oxidation of 2-methyl-3-buten-2-ol initiated by O( 3 P) atoms. The oxidation was investigated at room temperature, 550, and 650 K. Using the synchrotron radiation from the Advanced Light Source (ALS) of the Lawrence Berkley National Laboratory, reaction intermediates and products were studied by multiplexed photoionization mass spectrometry. Mass-to-charge ratios, kinetic time traces, photoionization spectra, and adiabatic ionization energies for each primary reaction species were obtained and used to characterize their identity. Using electronic structure calculations, potential energy surface scans of the different species produced throughout the oxidation were examined and presented in this paper to further validate the primary chemistry occurring. Branching fractions of primary products at all three temperatures were also provided. At room temperature only three primary products formed: ethenol (26.6%), acetaldehyde (4.2%), and acetone (53.4%). At 550 and 650 K the same primary products were observed in addition to propene (5.1%, 11.2%), ethenol (18.1%, 2.8%), acetaldehyde (8.9%, 5.7%), cyclobutene (1.6%, 10.8%), 1-butene (2.0%, 10.9%), trans-2-butene (3.2%, 23.1%), acetone (50.4%, 16.8%), 3-penten-2-one (1.0%, 11.5%), and 3-methyl-2-butenal (0.9%, 2.5%), where the first branching fraction value in parentheses corresponds to the 550 K data. At the highest temperature, a small amount of propyne (1.0%) was also observed.

Mechanical behavior and modelisation of Ti-6Al-4V titanium sheet under hot stamping conditions

NASA Astrophysics Data System (ADS)

Sirvin, Q.; Velay, V.; Bonnaire, R.; Penazzi, L.

2017-10-01

The Ti-6Al-4V titanium alloy is widely used for the manufacture of aeronautical and automotive parts (solid parts). In aeronautics, this alloy is employed for its excellent mechanical behavior associated with low density, outstanding corrosion resistance and good mechanical properties up to 600°C. It is especially used for the manufacture of fuselage frames, on the pylon for carrying out the primary structure (machining forged blocks) and the secondary structure in sheet form. In this last case, the sheet metal forming can be done through various methods: at room temperature by drawing operation, at very high temperature (≃900°C) by superplastic forming (SPF) and at intermediate temperature (≥750°C) by hot forming (HF). In order to reduce production costs and environmental troubles, the cycle times reduction associated with a decrease of temperature levels are relevant. This study focuses on the behavior modelling of Ti-6Al-4V alloy at temperatures above room temperature to obtained greater formability and below SPF condition to reduce tools workshop and energy costs. The displacement field measurement obtained by Digital Image Correlation (DIC) is based on innovative surface preparation pattern adapted to high temperature exposures. Different material parameters are identified to define a model able to predict the mechanical behavior of Ti-6Al-4V alloy under hot stamping conditions. The hardening plastic model identified is introduced in FEM to simulate an omega shape forming operation.

Photosynthesis and Photosynthetic Electron Flow in the Alpine Evergreen Species Quercus guyavifolia in Winter

PubMed Central

Huang, Wei; Hu, Hong; Zhang, Shi-Bao

2016-01-01

Alpine evergreen broadleaf tree species must regularly cope with low night temperatures in winter. However, the effects of low night temperatures on photosynthesis in alpine evergreen broadleaf tree species are unclear. We measured the diurnal photosynthetic parameters before and after cold snap for leaves of Quercus guyavifolia growing in its native habitat at 3290 m. On 11 and 12 December 2013 (before cold snap), stomatal and mesophyll conductances (gs and gm), CO2 assimilation rate (An), and total electron flow through PSII (JPSII) at daytime were maintained at high levels. The major action of alternative electron flow was to provide extra ATP for primary metabolisms. On 20 December 2013 (after cold snap), the diurnal values of gs, gm, An, and JPSII at daytime largely decreased, mainly due to the large decrease in night air temperature. Meanwhile, the ratio of photorespiration and alternative electron flow to JPSII largely increased on 20 December. Furthermore, the high levels of alternative electron flow were accompanied with low rates of extra ATP production. A quantitative limitation analysis reveals that the gm limitation increased on 20 December with decreased night air temperature. Therefore, the night air temperature was an important determinant of stomatal/mesophyll conductance and photosynthesis. When photosynthesis is inhibited following freezing night temperatures, photorespiration and alternative electron flow are important electron sinks, which support the role of photorespiration and alternative electron flow in photoportection for alpine plants under low temperatures. PMID:27812359

Is the distribution of nitrogen-fixing cyanobacteria in the oceans related to temperature?

PubMed

Stal, Lucas J

2009-07-01

Approximately 50% of the global natural fixation of nitrogen occurs in the oceans supporting a considerable part of the new primary production. Virtually all nitrogen fixation in the ocean occurs in the tropics and subtropics where the surface water temperature is 25°C or higher. It is attributed almost exclusively to cyanobacteria. This is remarkable firstly because diazotrophic cyanobacteria are found in other environments irrespective of temperature and secondly because primary production in temperate and cold oceans is generally limited by nitrogen. Cyanobacteria are oxygenic phototrophic organisms that evolved a variety of strategies protecting nitrogenase from oxygen inactivation. Free-living diazotrophic cyanobacteria in the ocean are of the non-heterocystous type, namely the filamentous Trichodesmium and the unicellular groups A-C. I will argue that warm water is a prerequisite for these diazotrophic organisms because of the low-oxygen solubility and high rates of respiration allowing the organism to maintain anoxic conditions in the nitrogen-fixing cell. Heterocystous cyanobacteria are abundant in freshwater and brackish environments in all climatic zones. The heterocyst cell envelope is a tuneable gas diffusion barrier that optimizes the influx of both oxygen and nitrogen, while maintaining anoxic conditions inside the cell. It is not known why heterocystous cyanobacteria are absent from the temperate and cold oceans and seas.

Effects of rolling conditions on recrystallization microstructure and texture in magnetostrictive Fe-Ga-Al rolled sheets

NASA Astrophysics Data System (ADS)

Li, Jiheng; Liu, Yangyang; Li, Xiaojuan; Mu, Xing; Bao, Xiaoqian; Gao, Xuexu

2018-07-01

The effects of different rolling conditions on the microstructure and texture of primary and secondary recrystallization in magnetostrictive Fe82Ga9Al9+0.1at%NbC alloy sheets were investigated. After the primary recrystallization annealing at 850 °C for 5 min, the as-rolled sheets prepared by warm-cold rolling with an intermediate annealing, can be fully recrystallized, and obtain the homogeneous matrix in which the fine dispersed NbC precipitate particles are distributed. The primary recrystallization textures of sheets with different rolling conditions consist mostly of strong {1 0 0} textures, γ-fiber textures, {4 1 1}〈1 4 8〉 texture and weak Goss texture. In the primary recrystallized sheets prepared by warm-cold rolling with an intermediate annealing, the high energy grain boundaries and ∑9 boundaries have the highest proportion. After high temperature annealing, the secondary recrystallizations of Goss grains in these sheets are more complete, and the size of abnormal grown Goss grain is up to several centimeters, which results in the strongest Goss texture. Correspondingly, the largest magnetostriction of 183 ppm is observed. The sample prepared by warm-cold rolling with an intermediate annealing, has homogeneous primary matrix, special texture components and grain boundary distribution, all of which provide a better surrounding for the abnormal growth of Goss grains. This work indicates that the control of rolling conditions of Fe-Ga-Al alloy sheets is necessary to achieve the strong Goss texture and obtain a possible high magnetostriction if other appropriate conditions (stress, domain structure) are achieved.

Product Chemistry and Process Efficiency of Biomass Torrefaction, Pyrolysis and Gasification Studied by High-Throughput Techniques and Multivariate Analysis

NASA Astrophysics Data System (ADS)

Xiao, Li

Despite the great passion and endless efforts on development of renewable energy from biomass, the commercialization and scale up of biofuel production is still under pressure and facing challenges. New ideas and facilities are being tested around the world targeting at reducing cost and improving product value. Cutting edge technologies involving analytical chemistry, statistics analysis, industrial engineering, computer simulation, and mathematics modeling, etc. keep integrating modern elements into this classic research. One of those challenges of commercializing biofuel production is the complexity from chemical composition of biomass feedstock and the products. Because of this, feedstock selection and process optimization cannot be conducted efficiently. This dissertation attempts to further evaluate biomass thermal decomposition process using both traditional methods and advanced technique (Pyrolysis Molecular Beam Mass Spectrometry). Focus has been made on data base generation of thermal decomposition products from biomass at different temperatures, finding out the relationship between traditional methods and advanced techniques, evaluating process efficiency and optimizing reaction conditions, comparison of typically utilized biomass feedstock and new search on innovative species for economical viable feedstock preparation concepts, etc. Lab scale quartz tube reactors and 80il stainless steel sample cups coupled with auto-sampling system were utilized to simulate the complicated reactions happened in real fluidized or entrained flow reactors. Two main high throughput analytical techniques used are Near Infrared Spectroscopy (NIR) and Pyrolysis Molecular Beam Mass Spectrometry (Py-MBMS). Mass balance, carbon balance, and product distribution are presented in detail. Variations of thermal decomposition temperature range from 200°C to 950°C. Feedstocks used in the study involve typical hardwood and softwood (red oak, white oak, yellow poplar, loblolly pine), fast growing energy crops (switchgrass), and popular forage crop (alfalfa), as well as biochar derived from those materials and their mixtures. It demonstrated that Py-MBMS coupled with MVA could be used as fast analytical tools for the study of not only biomass composition but also its thermal decomposition behaviors. It found that the impact of biomass composition heavily depends on the thermal decomposition temperature because at different temperature, the composition of biomass decomposed and the impact of minerals on the decomposition reaction varies. At low temperature (200-500°C), organic compounds attribute to the majority of variation in thermal decomposition products. At higher temperature, inorganics dramatically changed the pyrolysis pathway of carbohydrates and possibly lignin. In gasification, gasification tar formation is also observed to be impacted by ash content in vapor and char. In real reactor, biochar structure also has interactions with other fractions to make the final pyrolysis and gasification product. Based on the evaluation of process efficiencies during torrefaction, temperature ranging from 275°C to 300°C with short residence time (<10min) are proposed to be optimal torrefaction conditions. 500°C is preferred to 700°C as primary pyrolysis temperature in two stage gasification because higher primary pyrolysis temperature resulted in more tar and less gasification char. Also, in terms of carbon yield, more carbon is lost in tar while less carbon is retained in gas product using 700°C as primary pyrolysis temperature. In addition, pyrolysis char is found to produce less tar and more gas during steam gasification compared with gasification of pyrolysis vapor. Thus it is suggested that torrefaction might be an efficient pretreatment for biomass gasification because it can largely improve the yield of pyrolysis char during the primary pyrolysis step of gasification thus reduce the total tar of the overall gasification products. Future work is suggested in the end.

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

Cojocaru, Claudiu; Mui, Bryan; McEwen, Malcolm

Purpose: To investigate the stability of a water calorimetry system as a primary standard for absorbed dose to water using measurements performed in cobalt-60 and high-energy linac photon beams over a span of more than a decade. Methods: Calorimetry measures adsorbed dose directly by recording the amount of heat created when ionizing radiation passes through matter. The radiation-induced temperature rise was measured using two thermistors calibrated against the NRC temperature primary standard, using an AC bridge with lock-in amplifier for precise measurement. The calorimeter system was operated under thermal equilibrium at 4 °C (to eliminate convection) with drifts in watermore » temperature less than 0.1 mK/min. Seven water vessels of various designs were used to make repeated measurements over the course of 17 years. Results: The standard uncertainty achieved for a set of ten calorimeter measurements (4 Gy delivered) was generally well below 0.15 % while the variation between multiple sets for a given vessel was consistent with this value. The long-term stability of the system combined with inter-vessel variations indicated that there was good control of the radiochemistry (chemical heat defect). Conclusions: The measurements performed over a period of several years showed that the combined water calorimeters showed stability at +/− 0.25 % level. Thus, rather than relying on a particular vessel as an artifact one can realize the Gray through the more generalized method of combining a glass vessel, high-purity water and thermistor probes. This provides increased robustness in the dissemination of absorbed dose to Canadian users.« less

Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde

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

Sivaramakrishnan, Raghu; Michael, Joe V.; Harding, Lawrence B.

2015-07-16

The mechanism for the thermal decomposition of acetaldehyde has been revisited with an analysis of literature kinetics experiments using theoretical kinetics. The present modeling study was motivated by recent observations, with very sensitive diagnostics, of some unexpected products in high temperature micro-tubular reactor experiments on the thermal decomposition of CH3CHO and its deuterated analogs, CH3CDO, CD3CHO, and CD3CDO. The observations of these products prompted the authors of these studies to suggest that the enol tautomer, CH2CHOH (vinyl alcohol), is a primary intermediate in the thermal decomposition of acetaldehyde. The present modeling efforts on acetaldehyde decomposition incorporate a master equation re-analysismore » of the CH3CHO potential energy surface (PES). The lowest energy process on this PES is an isomerization of CH3CHO to CH2CHOH. However, the subsequent product channels for CH2CHOH are substantially higher in energy, and the only unimolecular process that can be thermally accessed is a re-isomerization to CH3CHO. The incorporation of these new theoretical kinetics predictions into models for selected literature experiments on CH3CHO thermal decomposition confirms our earlier experiment and theory based conclusions that the dominant decomposition process in CH3CHO at high temperatures is C-C bond fission with a minor contribution (~10-20%) from the roaming mechanism to form CH4 and CO. The present modeling efforts also incorporate a master-equation analysis of the H + CH2CHOH potential energy surface. This bimolecular reaction is the primary mechanism for removal of CH2CHOH, which can accumulate to minor amounts at high temperatures, T > 1000 K, in most lab-scale experiments that use large initial concentrations of CH3CHO. Our modeling efforts indicate that the observation of ketene, water and acetylene in the recent micro-tubular experiments are primarily due to bimolecular reactions of CH3CHO and CH2CHOH with H-atoms, and have no bearing on the unimolecular decomposition mechanism of CH3CHO. The present simulations also indicate that experiments using these micro-tubular reactors when interpreted with the aid of high-level theoretical calculations and kinetics modeling can offer insights into the chemistry of elusive intermediates in high temperature pyrolysis of organic molecules.« less

Biophysical regulation of carbon fluxes over an alpine meadow ecosystem in the eastern Tibetan Plateau.

PubMed

Wang, Shaoying; Zhang, Yu; Lü, Shihua; Su, Peixi; Shang, Lunyu; Li, Zhaoguo

2016-06-01

The eddy covariance method was used to measure net ecosystem CO2 exchange (NEE) between atmosphere and an alpine meadow ecosystem in the eastern Tibetan Plateau of China in 2010. Our results show that photosynthesis was reduced under low air temperature (T a), high vapor pressure deficit (VPD), and medium soil water content (SWC) conditions, when compared to that under other T a (i.e., medium and high), VPD (i.e., low and medium), and SWC (i.e., low and high) conditions. The apparent temperature sensitivity of ecosystem respiration (Q 10) declined with progressing phenology during the growing season and decreased with an increase of soil temperature (T s) during the non-growing season. Increased ecosystem respiration (R eco) was measured during spring soil thawing. By the path analysis, T a, T s, and VPD were the main control factors of CO2 exchange at 30-min scale in this alpine meadow. Integrated NEE, gross primary production (GPP), and R eco over the measured year were -156.4, 1164.3, and 1007.9 g C m(-2), respectively. Zoige alpine meadow was a medium carbon sink based on published data for grassland ecosystems.

Additive Manufacturing of Reactive In Situ Zr Based Ultra-High Temperature Ceramic Composites

NASA Astrophysics Data System (ADS)

Sahasrabudhe, Himanshu; Bandyopadhyay, Amit

2016-03-01

Reactive in situ multi-material additive manufacturing of ZrB2-based ultra-high-temperature ceramics in a Zr metal matrix was demonstrated using LENS™. Sound metallurgical bonding was achieved between the Zr metal and Zr-BN composites with Ti6Al4V substrate. Though the feedstock Zr power had α phase, LENS™ processing of the Zr powder and Zr-BN premix powder mixture led to the formation of some β phase of Zr. Microstructure of the Zr-BN composite showed primary grains of zirconium diboride phase in zirconium metal matrix. The presence of ZrB2 ceramic phase was confirmed by X-ray diffraction (XRD) analysis. Hardness of pure Zr was measured as 280 ± 12 HV and, by increasing the BN content in the feedstock, the hardness was found to increase. In Zr-5%BN composite, the hardness was 421 ± 10 HV and the same for Zr-10%BN composite was 562 ± 10 HV. It is envisioned that such multi-materials additive manufacturing will enable products in the future that cannot be manufactured using traditional approaches particularly in the areas of high-temperature metal-ceramic composites with compositional and functional gradation.

Making the case for high temperature low sag (htls) overhead transmission line conductors

NASA Astrophysics Data System (ADS)

Banerjee, Koustubh

The future grid will face challenges to meet an increased power demand by the consumers. Various solutions were studied to address this issue. One alternative to realize increased power flow in the grid is to use High Temperature Low Sag (HTLS) since it fulfills essential criteria of less sag and good material performance with temperature. HTLS conductors like Aluminum Conductor Composite Reinforced (ACCR) and Aluminum Conductor Carbon Composite (ACCC) are expected to face high operating temperatures of 150-200 degree Celsius in order to achieve the desired increased power flow. Therefore, it is imperative to characterize the material performance of these conductors with temperature. The work presented in this thesis addresses the characterization of carbon composite core based and metal matrix core based HTLS conductors. The thesis focuses on the study of variation of tensile strength of the carbon composite core with temperature and the level of temperature rise of the HTLS conductors due to fault currents cleared by backup protection. In this thesis, Dynamic Mechanical Analysis (DMA) was used to quantify the loss in storage modulus of carbon composite cores with temperature. It has been previously shown in literature that storage modulus is correlated to the tensile strength of the composite. Current temperature relationships of HTLS conductors were determined using the IEEE 738-2006 standard. Temperature rise of these conductors due to fault currents were also simulated. All simulations were performed using Microsoft Visual C++ suite. Tensile testing of metal matrix core was also performed. Results of DMA on carbon composite cores show that the storage modulus, hence tensile strength, decreases rapidly in the temperature range of intended use. DMA on composite cores subjected to heat treatment were conducted to investigate any changes in the variation of storage modulus curves. The experiments also indicates that carbon composites cores subjected to temperatures at or above 250 degree Celsius can cause permanent loss of mechanical properties including tensile strength. The fault current temperature analysis of carbon composite based conductors reveal that fault currents eventually cleared by backup protection in the event of primary protection failure can cause damage to fiber matrix interface.

Vacuum Studies of a Prototype Composite Coil Dewar for HTSC Transformers

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

Schwenterly, S W; Zhang, Y.; Pleva, Ed

2010-01-01

Oak Ridge National Laboratory (ORNL) is collaborating with Waukesha Electric Systems (WES) to develop a high-temperature superconducting (HTSC) utility power transformer with primary and secondary coils cooled by liquid nitrogen. Since the vacuuminsulated cryogenic coil dewar surrounds the magnetic core limb and cannot form a shorted turn, non-conductive materials are required. Two test vessels and a small prototype dewar have been fabricated by Scorpius Space Launch Company with epoxy/fiberglass composites, using their proprietary PRESSURMAXX vessel technology. The effects of pumping time, bakeout temperature, and cryogenic vessel temperature on vacuum outgassing rates have been investigated. Outgassing rates of the individual materialsmore » used in vessel construction have also been measured. The results will be scaled up to determine the required pumping capacity for a full-size 25-MVA commercial transformer dewar.« less