Quality Control of Meteorological Data for the Chemical Stockpile Emergency Preparedness Program

DTIC Science & Technology

2009-03-01

Time constant 10 s — Solar radiation Eppley 8–48 pyranometer Resolution 10 W m22 10 W m22 Accuracy 65% 65% Time constant 5 s 5 s Spectral response 285...sensor above 90% RH. c 22 W m22 allows for the potential negative offset produced by radiative cooling of the dome of the pyranometer on clear nights...and the winds are light, which suggests that frost may be forming on the pyranometer dome during the night. (The pyranometers are not equipped with

Measurement of the spin temperature of optically cooled nuclei and GaAs hyperfine constants in GaAs/AlGaAs quantum dots

NASA Astrophysics Data System (ADS)

Chekhovich, E. A.; Ulhaq, A.; Zallo, E.; Ding, F.; Schmidt, O. G.; Skolnick, M. S.

2017-10-01

Deep cooling of electron and nuclear spins is equivalent to achieving polarization degrees close to 100% and is a key requirement in solid-state quantum information technologies. While polarization of individual nuclear spins in diamond and SiC (ref. ) reaches 99% and beyond, it has been limited to 50-65% for the nuclei in quantum dots. Theoretical models have attributed this limit to formation of coherent `dark' nuclear spin states but experimental verification is lacking, especially due to the poor accuracy of polarization degree measurements. Here we measure the nuclear polarization in GaAs/AlGaAs quantum dots with high accuracy using a new approach enabled by manipulation of the nuclear spin states with radiofrequency pulses. Polarizations up to 80% are observed--the highest reported so far for optical cooling in quantum dots. This value is still not limited by nuclear coherence effects. Instead we find that optically cooled nuclei are well described within a classical spin temperature framework. Our findings unlock a route for further progress towards quantum dot electron spin qubits where deep cooling of the mesoscopic nuclear spin ensemble is used to achieve long qubit coherence. Moreover, GaAs hyperfine material constants are measured here experimentally for the first time.

Aging dynamics in the polymer glass of poly(2-chlorostyrene): Dielectric susceptibility and volume

NASA Astrophysics Data System (ADS)

Fukao, Koji; Tahara, Daisuke

2009-11-01

Aging dynamics was investigated in the glassy states of poly(2-chlorostyrene) by measuring the complex electrical capacitance during aging below the glass transition temperature. The variations with time and temperature of the ac dielectric susceptibility and volume could be determined by simply measuring the variation in the complex electrical capacitance. Isothermal aging at a given temperature for several hours after an intermittent stop in constant-rate cooling is stored in the deviations of both the real and imaginary parts of the complex ac dielectric susceptibility and volume. During cooling after isothermal aging, the deviation of the ac dielectric susceptibility from the reference value decreases and almost vanishes at room temperature. By contrast, the deviation in volume induced during isothermal aging remains almost constant during cooling. The simultaneous measurement of ac dielectric susceptibility and volume clearly revealed that the ac dielectric susceptibility exhibits a full rejuvenation effect, whereas the volume does not show any rejuvenation effects. We discuss a plausible model that can reproduce the present experimental results.

Vibrational energy flow in photoactive yellow protein revealed by infrared pump-visible probe spectroscopy.

PubMed

Nakamura, Ryosuke; Hamada, Norio

2015-05-14

Vibrational energy flow in the electronic ground state of photoactive yellow protein (PYP) is studied by ultrafast infrared (IR) pump-visible probe spectroscopy. Vibrational modes of the chromophore and the surrounding protein are excited with a femtosecond IR pump pulse, and the subsequent vibrational dynamics in the chromophore are selectively probed with a visible probe pulse through changes in the absorption spectrum of the chromophore. We thus obtain the vibrational energy flow with four characteristic time constants. The vibrational excitation with an IR pulse at 1340, 1420, 1500, or 1670 cm(-1) results in ultrafast intramolecular vibrational redistribution (IVR) with a time constant of 0.2 ps. The vibrational modes excited through the IVR process relax to the initial ground state with a time constant of 6-8 ps in parallel with vibrational cooling with a time constant of 14 ps. In addition, upon excitation with an IR pulse at 1670 cm(-1), we observe the energy flow from the protein backbone to the chromophore that occurs with a time constant of 4.2 ps.

Storage peak gas-turbine power unit

NASA Technical Reports Server (NTRS)

Tsinkotski, B.

1980-01-01

A storage gas-turbine power plant using a two-cylinder compressor with intermediate cooling is studied. On the basis of measured characteristics of a .25 Mw compressor computer calculations of the parameters of the loading process of a constant capacity storage unit (05.3 million cu m) were carried out. The required compressor power as a function of time with and without final cooling was computed. Parameters of maximum loading and discharging of the storage unit were calculated, and it was found that for the complete loading of a fully unloaded storage unit, a capacity of 1 to 1.5 million cubic meters is required, depending on the final cooling.

Method of Estimating Continuous Cooling Transformation Curves of Glasses

NASA Technical Reports Server (NTRS)

Zhu, Dongmei; Zhou, Wancheng; Ray, Chandra S.; Day, Delbert E.

2006-01-01

A method is proposed for estimating the critical cooling rate and continuous cooling transformation (CCT) curve from isothermal TTT data of glasses. The critical cooling rates and CCT curves for a group of lithium disilicate glasses containing different amounts of Pt as nucleating agent estimated through this method are compared with the experimentally measured values. By analysis of the experimental and calculated data of the lithium disilicate glasses, a simple relationship between the crystallized amount in the glasses during continuous cooling, X, and the temperature of undercooling, (Delta)T, was found to be X = AR(sup-4)exp(B (Delta)T), where (Delta)T is the temperature difference between the theoretical melting point of the glass composition and the temperature in discussion, R is the cooling rate, and A and B are constants. The relation between the amount of crystallisation during continuous cooling and isothermal hold can be expressed as (X(sub cT)/X(sub iT) = (4/B)(sup 4) (Delta)T(sup -4), where X(sub cT) stands for the crystallised amount in a glass during continuous cooling for a time t when the temperature comes to T, and X(sub iT) is the crystallised amount during isothermal hold at temperature T for a time t.

Advanced ceramic coating development for industrial/utility gas turbine applications

NASA Technical Reports Server (NTRS)

Andersson, C. A.; Lau, S. K.; Bratton, R. J.; Lee, S. Y.; Rieke, K. L.; Allen, J.; Munson, K. E.

1982-01-01

The effects of ceramic coatings on the lifetimes of metal turbine components and on the performance of a utility turbine, as well as of the turbine operational cycle on the ceramic coatings were determined. When operating the turbine under conditions of constant cooling flow, the first row blades run 55K cooler, and as a result, have 10 times the creep rupture life, 10 times the low cycle fatigue life and twice the corrosion life with only slight decreases in both specific power and efficiency. When operating the turbine at constant metal temperature and reduced cooling flow, both specific power and efficiency increases, with no change in component lifetime. The most severe thermal transient of the turbine causes the coating bond stresses to approach 60% of the bond strengths. Ceramic coating failures was studied. Analytic models based on fracture mechanics theories, combined with measured properties quantitatively assessed both single and multiple thermal cycle failures which allowed the prediction of coating lifetime. Qualitative models for corrosion failures are also presented.

Kinetics of austenite-pearlite transformation in eutectoid carbon steel

NASA Astrophysics Data System (ADS)

Hawbolt, E. B.; Chau, B.; Brimacombe, J. K.

1983-09-01

The kinetics of the austenite-to-pearlite transformation have been measured under isothermal and continuous-cooling conditions on a eutectoid carbon (1080) steel using a diametral dilatometric technique. The isothermal transformation kinetics have been analyzed in terms of the Avrami Equation containing the two parameters n and b; the initiation of transformation was characterized by an empirically determined transformation-start time (tAv). The parameter n was found to be nearly constant; and neither n nor b was dependent on the cooling rate between T A1 and the test temperature. Continuous-cooling tests were performed with cooling rates ranging from 7.5 to 108 °C per second, and the initiation of transformation was determined. Comparison of this transformation-start time for different cooling rates with the measured slow cooling of a test coupon immersed in a salt bath indicates that, particularly at lower temperatures, the transformation in the traditional T-T-T test specimen may not be isothermal. The additivity rule was found to predict accurately the time taken, relative to tAv, to reach a given fraction of austenite transformed, even though there is some question that the isokinetic condition was met above 660 °C. However, the additivity rule does not hold for the pretransformation or incubation period, as originally proposed by Scheil, and seriously overestimates the incubation time. Application of the additivity rule to the prediction of transformation-finish time, based on transformation start at TA1, also leads to overestimates, but these are less serious. The isothermal parameters— n ( T), b ( T), and tAv ( T)—have been used to predict continuous-cooling transformation kinetics which are in close agreement with measurements at four cooling rates ranging from 7.5 to 64 °C per second.

Heat-transfer processes in air-cooled engine cylinders

NASA Technical Reports Server (NTRS)

Pinkel, Benjamin

1938-01-01

From a consideration of heat-transfer theory, semi-empirical expressions are set up for the transfer of heat from the combustion gases to the cylinder of an air-cooled engine and from the cylinder to the cooling air. Simple equations for the average head and barrel temperatures as functions of the important engine and cooling variables are obtained from these expressions. The expressions involve a few empirical constants, which may be readily determined from engine tests. Numerical values for these constants were obtained from single-cylinder engine tests for cylinders of the Pratt & Whitney 1535 and 1340-h engines. The equations provide a means of calculating the effect of the various engine and cooling variables on the cylinder temperatures and also of correlating the results of engine cooling tests. An example is given of the application of the equations to the correlation of cooling-test data obtained in flight.

The cooling of terrestrial basaltic lava flows and implications for lava flow emplacement on Venus from surface morphology and radar data

NASA Astrophysics Data System (ADS)

Hultgrien, Lynn Kerrell

Basalt is the most common surface rock on the terrestrial planets. Understanding the emplacement mechanisms for basaltic lava flows facilitates study of the geologic history of a planet and in volcanic hazards assessment. Lava flow cooling is examined through two different models, one applicable to aa and the second to pahoehoe. Occurrence of these basaltic flow types is evaluated in an extensive global survey of lava flows on Venus using Magellan data. First, a basic heat balance model is considered for as flow cooling with terms for conduction, radiation, viscous dissipation and entrainment of cooler material. Pahoehoe cooling is modeled through three different analytic solutions to the one-dimensional, time-dependent heat conduction equation, with constant surface temperature, linear heat transfer at the surface, and surface radiation. The models are compared with thermal data from the Hawaiian 1984 Mauna Loa and 1990 Puu Oo-Kupaianaha, Kilauea eruptions, for as and pahoehoe, respectively. Although commonly omitted in other models, heat conduction is found here to be important in the cooling of both aa and pahoehoe. Equally important is entrainment in as flows and both radiation and atmospheric convection for pahoehoe cooling. Morphology measurements and surface properties are determined for ninety individual lava flows from forty-four volcanic features on Venus. Radar backscatter and rms slope values, relative to terrestrial studies, indicate Venusian lavas are predominately pahoehoe. Emissivities and dielectric constants are consistent with basalt as the principal lithology. Effusion rates and flow velocities, determined using Earth-calibrated parametric relationships, and lava flow dimensions are greater than those found on Earth. Modeling lava flows on the terrestrial planets should involve careful consideration of the type of lava flow being studied. This investigation finds that heat conduction is an important limitation in the ability of a basalt flow to cool. Some models underestimate cooling time and flow dimensions because of their failure to include such effects. Pahoehoe and aa flows are emplaced by different mechanisms and require individualized models. The prevalence of pahoehoe lava flows on both Earth and Venus is a major element for deciphering the past evolution of each planet.

The Mass and Absorption Columns of Galactic Gaseous Halos

NASA Astrophysics Data System (ADS)

Qu, Zhijie; Bregman, Joel N.

2018-01-01

The gaseous halo surrounding the galaxy is a reservoir for the gas on the galaxy disk, supplying materials for the star formation. We developed a gaseous halo model connecting the galactic disk and the gaseous halo by assuming the star formation rate is equal to the radiative cooling rate. Besides the single-phase collisional gaseous halo, we also consider the photoionization effect and a time-independent cooling model that assumes the mass cooling rate is constant over all temperatures. The photoionization dominates the low mass galaxy and the outskirts of the massive galaxy due to the low-temperature or low-density nature. The multi-phase cooling model dominates the denser region within the cooling radius, where the efficient radiative cooling must be included. Applying these two improvements, our model can reproduce the most of observed high ionization state ions (i.e., O VI, O VII, Ne VIII and Mg X). Our models show that the O VI column density is almost a constant of around 10^14 cm^-2 over a wide stellar mass from M_\\star ~10^8 M_Sun to 10^11 M_Sun, which is constant with current observations. This model also implies the O VI is photoionized for the galaxy with a halo mass <~ 3 * 10^11 M_Sun, while for more massive galaxies, the O VI is from the cooling-down medium from higher temperature materials (collisional ionized). As higher ionization states, Mg X and Ne VIII are also consistent with observations with the column density of 10^13.5 - 10^14.0 cm^-2, however, the absorber-galaxy pair sample is few to constrain the connection with the galaxy. Based on our calculation, such a gaseous halo cannot close the census of baryonic materials in the galaxy, which shows the same tendency as the baryonic fraction function of the EAGLE simulation. Finally, our model predicts plateaus of the Ne VIII and the Mg X column densities above the sub-L^* galaxy, and the possibly detectable O VII and O VIII column densities for low-mass galaxies, which help to determine the required detection limit for the future observations and missions.

Effects of ventrolateral thalamic nucleus cooling on initiation of forelimb ballistic flexion movements by conditioned cats.

PubMed

Bénita, M; Condé, H; Dormont, J F; Schmied, A

1979-02-15

Five cats were trained to perform a forelimb ballistic flexion on a reaction time paradigm including an upper limit of about 400 ms for reinforcement (food pellets). They were implanted with a cyrogenic probe thermically insulated, except at the tip, by a vacuum jacket (outer diameter, 1.1 mm). Four cats had the probe inserted into the ventrolateral thalamic nucleus (VL), contralateral to the moving limb. During cooling they showed increased reaction times, which remained constant throughout daily sessions performed during many weeks, independent of the foreperiod but varying from 25 to 100 ms according to the subject. The temperatures used to upset the reaction times varied from +10 decrees C to -8 degrees C, depending on the localisation of the probe and on the insulation of the silver tip used to prevent nervous tissue reaction, but for each subject the reaction times always increased when the temperature was lowered. The fifth cat, with a probe inserted between VL and the Centre Median, showed a decrease of reaction times on cooling to 0 degrees C and an increase of the reaction times for a cooling at -10 degrees C. For one of the four cats with a probe properly inserted into the VL, strain-gauges were stuck on the lever to measure the latency of the decrease of the pressure exerted by the subject when the subject initiated the forelimb flexion in response to the CS. Reaction times and latencies of pressure changes were closely correlated with the movement onset, and they were equally delayed during cooling. This result demonstrates that it is not by slowing down movement velocity that reaction times are upset during VL cooling but by delaying the movement onset.

Forming chondrules in impact splashes. I. Radiative cooling model

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

Dullemond, Cornelis Petrus; Stammler, Sebastian Markus; Johansen, Anders

2014-10-10

The formation of chondrules is one of the oldest unsolved mysteries in meteoritics and planet formation. Recently an old idea has been revived: the idea that chondrules form as a result of collisions between planetesimals in which the ejected molten material forms small droplets that solidify to become chondrules. Pre-melting of the planetesimals by radioactive decay of {sup 26}Al would help produce sprays of melt even at relatively low impact velocity. In this paper we study the radiative cooling of a ballistically expanding spherical cloud of chondrule droplets ejected from the impact site. We present results from numerical radiative transfermore » models as well as analytic approximate solutions. We find that the temperature after the start of the expansion of the cloud remains constant for a time t {sub cool} and then drops with time t approximately as T ≅ T {sub 0}[(3/5)t/t {sub cool} + 2/5]{sup –5/3} for t > t {sub cool}. The time at which this temperature drop starts t {sub cool} depends via an analytical formula on the mass of the cloud, the expansion velocity, and the size of the chondrule. During the early isothermal expansion phase the density is still so high that we expect the vapor of volatile elements to saturate so that no large volatile losses are expected.« less

Anomalous heat transport and condensation in convection of cryogenic helium

PubMed Central

Urban, Pavel; Schmoranzer, David; Hanzelka, Pavel; Sreenivasan, Katepalli R.; Skrbek, Ladislav

2013-01-01

When a hot body A is thermally connected to a cold body B, the textbook knowledge is that heat flows from A to B. Here, we describe the opposite case in which heat flows from a colder but constantly heated body B to a hotter but constantly cooled body A through a two-phase liquid–vapor system. Specifically, we provide experimental evidence that heat flows through liquid and vapor phases of cryogenic helium from the constantly heated, but cooler, bottom plate of a Rayleigh–Bénard convection cell to its hotter, but constantly cooled, top plate. The bottom plate is heated uniformly, and the top plate is cooled by heat exchange with liquid helium maintained at 4.2 K. Additionally, for certain experimental conditions, a rain of helium droplets is detected by small sensors placed in the cell at about one-half of its height. PMID:23576759

Dynamic cooling during laser skin welding

NASA Astrophysics Data System (ADS)

Fried, Nathaniel M.; Walsh, Joseph T., Jr.

1999-06-01

Cryogen spray cooling of the tissue surface was investigated for laser welding applications. Benefits include reduced thermal damage to the papillary dermis and reduced operation time. Two-cm-long, full-thickness incisions were made on the backs of guinea pigs, in vivo. India ink was used as an absorber and clamps were used to appose the incision edges. Continuous-wave, 1.06-μm, Nd:YAG laser radiation was scanned over the incisions, producing ~100 ms pulses. A 4-mm-diameter laser spot was used with a constant power of 16 W. The total operation time was 60 or 120 s. Cryogen was delivered in spurt durations of 20, 60, or 100 ms, with 2 or 4 s between spurts. The working distance was approximately 12 cm, and the spray covered an area of about 5.0 x 5.0 cm. Control welds were irradiated for 20, 40, or 60 s. Total operation times were reduced from 10 min without dynamic cooling to 1 min with dynamic cooling. Optimal tensile strength was 1.7 +/- 0.7 kg/cm2, comparible to stengths of 2.1 +/- 0.7 kg/cm2 reported in previous studies without cryogen cooling (p>0.25). Thermal damage in the papillary dermis measured 320 +/- 80 μm.

History dependent crystallization of Zr41Ti14Cu12Ni10Be23 melts

NASA Astrophysics Data System (ADS)

Schroers, Jan; Johnson, William L.

2000-07-01

The crystallization of Zr41Ti14Cu12Ni10Be23 (Vit 1) melts during constant heating is investigated. (Vit 1) melts are cooled with different rates into the amorphous state and the crystallization temperature upon subsequent heating is studied. In addition, Vit 1 melts are cooled using a constant rate to different temperatures and subsequently heated from this temperature with a constant rate. We investigate the influence of the temperature to which the melt was cooled on the crystallization temperature measured upon heating. In both cases the onset temperature of crystallization shows strong history dependence. This can be explained by an accumulating process during cooling and heating. An attempt is made to consider this process in a simple model by steady state nucleation and subsequent growth of the nuclei which results in different crystallization kinetics during cooling or heating. Calculations show qualitative agreement with the experimental results. However, calculated and experimental results differ quantitatively. This difference can be explained by a decomposition process leading to a nonsteady nucleation rate which continuously increases with decreasing temperature.

Density controls the kinetic stability of ultrastable glasses

NASA Astrophysics Data System (ADS)

Fullerton, Christopher J.; Berthier, Ludovic

2017-08-01

We use a swap Monte Carlo algorithm to numerically prepare bulk glasses with kinetic stability comparable to that of glass films produced experimentally by physical vapor deposition. By melting these systems into the liquid state, we show that some of our glasses retain their amorphous structures longer than 105 times the equilibrium structural relaxation time. This “exceptional” kinetic stability cannot be achieved for bulk glasses produced by slow cooling. We perform simulations at both constant volume and constant pressure to demonstrate that the density mismatch between the ultrastable glass and the equilibrium liquid accounts for a major part of the observed kinetic stability.

Convergence Studies of Mass Transport in Disks with Gravitational Instabilities. I. The Constant Cooling Time Case

NASA Astrophysics Data System (ADS)

Michael, Scott; Steiman-Cameron, Thomas Y.; Durisen, Richard H.; Boley, Aaron C.

2012-02-01

We conduct a convergence study of a protostellar disk, subject to a constant global cooling time and susceptible to gravitational instabilities (GIs), at a time when heating and cooling are roughly balanced. Our goal is to determine the gravitational torques produced by GIs, the level to which transport can be represented by a simple α-disk formulation, and to examine fragmentation criteria. Four simulations are conducted, identical except for the number of azimuthal computational grid points used. A Fourier decomposition of non-axisymmetric density structures in cos (mphi), sin (mphi) is performed to evaluate the amplitudes Am of these structures. The Am , gravitational torques, and the effective Shakura & Sunyaev α arising from gravitational stresses are determined for each resolution. We find nonzero Am for all m-values and that Am summed over all m is essentially independent of resolution. Because the number of measurable m-values is limited to half the number of azimuthal grid points, higher-resolution simulations have a larger fraction of their total amplitude in higher-order structures. These structures act more locally than lower-order structures. Therefore, as the resolution increases the total gravitational stress decreases as well, leading higher-resolution simulations to experience weaker average gravitational torques than lower-resolution simulations. The effective α also depends upon the magnitude of the stresses, thus αeff also decreases with increasing resolution. Our converged αeff is consistent with predictions from an analytic local theory for thin disks by Gammie, but only over many dynamic times when averaged over a substantial volume of the disk.

Thermal and exhumation history of the central Rwenzori Mountains, Western Rift of the East African Rift System, Uganda

NASA Astrophysics Data System (ADS)

Bauer, F. U.; Glasmacher, U. A.; Ring, U.; Schumann, A.; Nagudi, B.

2010-10-01

The Rwenzori Mountains (Mtns) in west Uganda are the highest rift mountains on Earth and rise to more than 5,000 m. We apply low-temperature thermochronology (apatite fission-track (AFT) and apatite (U-Th-Sm)/He (AHe) analysis) for tracking the cooling history of the Rwenzori Mtns. Samples from the central and northern Rwenzoris reveal AFT ages between 195.0 (±8.4) Ma and 85.3 (±5.3) Ma, and AHe ages between 210.0 (±6.0) Ma to 24.9 (±0.5) Ma. Modelled time-temperature paths reflect a protracted cooling history with accelerated cooling in Permo-Triassic and Jurassic times, followed by a long period of constant and slow cooling, than succeeded by a renewed accelerated cooling in the Neogene. During the last 10 Ma, differentiated erosion and surface uplift affected the Rwenzori Mtns, with more pronounced uplift along the western flank. The final rock uplift of the Rwenzori Mtns that partly led to the formation of the recent topography must have been fast and in the near past (Pliocene to Pleistocene). Erosion could not compensate for the latest rock uplift, resulting in Oligocene to Miocene AHe ages.

Acid-base regulation during heating and cooling in the lizard, Varanus exanthematicus.

PubMed

Wood, S C; Johansen, K; Glass, M L; Hoyt, R W

1981-04-01

Current concepts of acid-base balance in ectothermic animals require that arterial pH vary inversely with body temperature in order to maintain a constant OH-/H+ and constant net charge on proteins. The present study evaluates acid-base regulation in Varanus exanthematicus under various regimes of heating and cooling between 15 and 38 degrees C. Arterial blood was sampled during heating and cooling at various rates, using restrained and unrestrained animals with and without face masks. Arterial pH was found to have a small temperature dependence, i.e., pH = 7.66--0.005 (T). The slope (dpH/dT = -0.005), while significantly greater than zero (P less than 0.05), is much less than that required for a constant OH-/H+ or a constant imidazole alphastat (dpH/dT congruent to 0.018). The physiological mechanism that distinguishes this species from most other ectotherms is the presence of a ventilatory response to temperature-induced changes in CO2 production and O2 uptake, i.e., VE/VO2 is constant. This results in a constant O2 extraction and arterial saturation (approx. 90%), which is adaptive to the high aerobic requirements of this species.

New Tests for Variations of the Fine Structure Constant

NASA Technical Reports Server (NTRS)

Prestage, John D.

1995-01-01

We describe a new test for possible variations of the fine structure constant, by comparisons of rates between clocks based on hyperfine transitions in alkali atomos with different atomic number Z. H- maser, Cs and Hg+ clocks have a different dependence on ia relativistic contributions of order (Z. Recent H-maser vs Hg+ clock comparison data improves laboratory limits on a time variation by 100-fold to giveFuture laser cooled clocks (Be+, Rb, Cs, Hg+, etc.), when compared, will yield the most senstive of all tests for.

Evidence for Widespread Cooling in an Active Region Observed with the SDO Atmospheric Imaging Assembly

NASA Technical Reports Server (NTRS)

Viall, Nicholeen M.; Klimchuk, James A.

2012-01-01

A well known behavior of EUV light curves of discrete coronal loops is that the peak intensities of cooler channels or spectral lines are reached at progressively later times. This time lag is understood to be the result of hot coronal loop plasma cooling through these lower respective temperatures. However, loops typically comprise only a minority of the total emission in active regions. Is this cooling pattern a common property of active region coronal plasma, or does it only occur in unique circumstances, locations, and times? The new SDO/AIA data provide a wonderful opportunity to answer this question systematically for an entire active region. We measure the time lag between pairs of SDO/AIA EUV channels using 24 hours of images of AR 11082 observed on 19 June 2010. We find that there is a time-lag signal consistent with cooling plasma, just as is usually found for loops, throughout the active region including the diffuse emission between loops for the entire 24 hour duration. The pattern persists consistently for all channel pairs and choice of window length within the 24 hour time period, giving us confidence that the plasma is cooling from temperatures of greater than 3 MK, and sometimes exceeding 7 MK, down to temperatures lower than approx. 0.8 MK. This suggests that the bulk of the emitting coronal plasma in this active region is not steady; rather, it is dynamic and constantly evolving. These measurements provide crucial constraints on any model which seeks to describe coronal heating.

History dependent crystallization of Zr{sub 41}Ti{sub 14}Cu{sub 12}Ni{sub 10}Be{sub 23} melts

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

Schroers, Jan; Johnson, William L.

The crystallization of Zr{sub 41}Ti{sub 14}Cu{sub 12}Ni{sub 10}Be{sub 23} (Vit 1) melts during constant heating is investigated. (Vit 1) melts are cooled with different rates into the amorphous state and the crystallization temperature upon subsequent heating is studied. In addition, Vit 1 melts are cooled using a constant rate to different temperatures and subsequently heated from this temperature with a constant rate. We investigate the influence of the temperature to which the melt was cooled on the crystallization temperature measured upon heating. In both cases the onset temperature of crystallization shows strong history dependence. This can be explained by anmore » accumulating process during cooling and heating. An attempt is made to consider this process in a simple model by steady state nucleation and subsequent growth of the nuclei which results in different crystallization kinetics during cooling or heating. Calculations show qualitative agreement with the experimental results. However, calculated and experimental results differ quantitatively. This difference can be explained by a decomposition process leading to a nonsteady nucleation rate which continuously increases with decreasing temperature. (c) 2000 American Institute of Physics.« less

Simulated Seasonal Photoperiods and Fluctuating Temperatures Have Limited Effects on Blood Feeding and Life History in Aedes triseriatus (Diptera: Culicidae)

PubMed Central

Westby, K. M.

2015-01-01

Biotic and abiotic factors change seasonally and impact life history in temperate-zone ectotherms. Temperature and photoperiod are factors that change in predictable ways. Most studies testing for effects of temperature on vectors use constant temperatures and ignore potential correlated effects of photoperiod. In two experiments, we tested for effects of larval rearing environments creating ecologically relevant temperatures and photoperiods simulating early and late season conditions (June and August), or constant temperatures (cool and warm) with the June or August photoperiods, respectively. We determined effects on survivorship, development, size, and a composite performance index in a temperate-zone population of Aedes triseriatus (Say). We followed cohorts of resulting females, all held under the same environmental conditions, to assess carry-over effects of rearing conditions for larvae on longevity, blood feeding, and egg production. Larval survivorship was affected by treatment in one experiment. Development time was greater in the June and cool treatments, but the constant and fluctuating temperatures did not differ. Significantly larger mosquitoes were produced in fluctuating versus constant temperature treatments. There were no significant treatment effects on the composite performance index. Adult female longevity was lower after rearing at constant versus fluctuating temperature, but there was no difference between June and August, nor did size affect longevity. There was no effect of treatments on blood feeding and a limited effect on egg production. We conclude that seasonal temperatures and photoperiods during development have limited effects on this population of A. triseriatus and find little evidence of strong effects of fluctuating versus constant temperatures. PMID:26336255

Time-dependent effects of heat advection and topography on cooling histories during erosion

NASA Astrophysics Data System (ADS)

Mancktelow, Neil S.; Grasemann, Bernhard

1997-03-01

Both erosion and surface topography cause a time-dependent variation in isotherm geometry that can result in significant errors in estimating natural exhumation rates from geochronologic data. Analytical solutions and two-dimensional numerical modelling are used to investigate the magnitude of these inaccuracies for conditions appropriate to many rapidly exhumed mountain chains of rugged relief. It is readily demonstrated that uplift of the topographic surface has a negligible effect on the cooling history of an exhumed rock sample and cannot be quantified by current geochronologic methods. The topography itself perturbs the isotherms to a depth that depends on both the vertical and horizontal scale of the surface relief. Estimations employing different isotopic systems in the same sample with higher closure temperatures (> 200°C) are not generally influenced by topography. However, direct conversion of cooling rates to exhumation rates assuming a simple constant linear geotherm markedly underestimates peak rates, due to variation of the geothermal gradient in time and space and to the time lag between exhumation and cooling. Estimations based on the altitude variation in apatite fission-track ages are less prone to such inaccuracies in geothermal gradient but are affected by near-surface time-dependent variation in isotherm depth due to advection and topography. In tectonically active mountain belts, high exhumation rates are coupled with rugged topography, and exhumation rates may be markedly overestimated, by factors of 2 or more. Even at lower exhumation rates on the order of 1 mm/a, the shape of the cooling curve is modified by advection and topography. A convex-concave shape to the cooling curve does not necessarily imply a change of exhumation rate; it may also be attained by a more complicated geothermal gradient induced by topographic relief. Very fast cooling below 100°C, often interpreted as reflecting faster exhumation, can be more simply explained by the lateral cooling effect of topographic relief, with samples exhumed in valleys displaying a different near-surface cooling history to those on ridge crests.

The temperature dependence of thermooptical properties of magnetooptical TAG ceramics doped with silicon and titanium

NASA Astrophysics Data System (ADS)

Starobor, Aleksey; Palashov, Oleg

2018-04-01

Thermal effects in terbium aluminum garnet (TAG) ceramics (thermal lens and thermally induced depolarization) doped with silicon and titanium were investigated in temperature range of 79-293K. Samples with low dopant concentrations shows decreasing of negative thermal effects with cooling to 79 K. However for most part of samples thermal depolarization starts increasing after initial decreasing with cooling. Apparently it is connected with defects in media. Best sample (0.4 at% of Si) as pure TAG shows monotonous decreasing of thermally induced depolarization and 3.5 times Verdet constant increasing with cooling to 79 K, that leads to 1.8-times advantage over common magnetooptical media - terbium gallium garnet. It allows to provide an isolation of 30 dB at a radiation power of more than 6 kW as estimated. However, the procedure for creating ceramics samples obviously needs improvement because of the large scatter in the quality of the samples.

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

Welch, B.L.; Briggs, S.F.; Johansen, J.H.

Big sagebrush (Artemisia tridentata Nutt.) seeds were stored in three different environments; cool, constant temperature (refrigerator 10 degs. C); room temperature (14 to 24 degs. C); and a nonheated warehouse (-28 to +44 degs. C). In all three cases, humidity was held constant and equal. Significant drop in seed viability occurred first in the seed stored in the nonheated warehouse, followed by seed stored at room temperatures, and then seed stored at cool temperatures. It appeared from this study and studies by others that humidity control is more important to maintaining seed viability than temperature control. The old adage simplymore » states `store seeds in a cool and dry place` - but first make sure the seeds have been properly dried. Drying sagebrush seed during the cool, wet weather of the harvesting period creates special challenges to the producer.« less

Static Mixer for Heat Transfer Enhancement for Mold Cooling Application

NASA Astrophysics Data System (ADS)

Becerra, Rodolfo; Barbosa, Raul; Lee, Kye-Hwan; Park, Younggil

Injection molding is the process by which a material is melted in a barrel and then it is injected through a nozzle in the mold cavity. When it cools down, the material solidifies into the shape of the cavity. Typical injection mold has cooling channels to maintain constant mold temperature during injection molding process. Even and constant temperature throughout the mold are very critical for a part quality and productivity. Conformal cooling improves the quality and productivity of injection molding process through the implementation of cooling channels that ``conform'' to the shape of the molded part. Recent years, the use of conformal cooling increases with advance of 3D printing technology such as Selective Laser Melting (SLM). Although it maximizes cooling, material and dimension limitations make SLM methods highly expensive. An alternative is the addition of static mixers in the molds with integrated cooling channels. A static mixer is a motionless mixing device that enhances heat transfer by producing improved flow mixing in the pipeline. In this study, the performance of the cooling channels will be evaluated with and without static mixers, by measuring temperature, pressure drop, and flow rate. The following question is addressed: Can a static mixer effectively enhance heat transfer for mold cooling application processes? This will provide insight on the development of design methods and guidelines that can be used to increase cooling efficiency at a lower cost.

Design of laser diode driver with constant current and temperature control system

NASA Astrophysics Data System (ADS)

Wang, Ming-cai; Yang, Kai-yong; Wang, Zhi-guo; Fan, Zhen-fang

2017-10-01

A laser Diode (LD) driver with constant current and temperature control system is designed according to the LD working characteristics. We deeply researched the protection circuit and temperature control circuit based on thermos-electric cooler(TEC) cooling circuit and PID algorithm. The driver could realize constant current output and achieve stable temperature control of LD. Real-time feedback control method was adopted in the temperature control system to make LD work on its best temperature point. The output power variety and output wavelength shift of LD caused by current and temperature instability were decreased. Furthermore, the driving current and working temperature is adjustable according to specific requirements. The experiment result showed that the developed LD driver meets the characteristics of LD.

A continuous dry 300 mK cooler for THz sensing applications.

PubMed

Klemencic, G M; Ade, P A R; Chase, S; Sudiwala, R; Woodcraft, A L

2016-04-01

We describe and demonstrate the automated operation of a novel cryostat design that is capable of maintaining an unloaded base temperature of less than 300 mK continuously, without the need to recycle the gases within the final cold head, as is the case for conventional single shot sorption pumped (3)He cooling systems. This closed dry system uses only 5 l of (3)He gas, making this an economical alternative to traditional systems where a long hold time is required. During testing, a temperature of 365 mK was maintained with a constant 20 μW load, simulating the cooling requirement of a far infrared camera.

Different thermal conductivity in drilling of cemented compared with cementless hip prostheses in the treatment of periprosthetic fractures of the proximal femur: an experimental biomechanical analysis.

PubMed

Brand, Stephan; Klotz, Johannes; Hassel, Thomas; Petri, Maximilian; Ettinger, Max; Krettek, Christian; Goesling, Thomas; Bach, Friedrich-Wilhelm

2013-10-01

The purpose of this study was to evaluate the different temperature levels whilst drilling cemented and cementless hip prostheses implanted in bovine femora, and to evaluate the insulating function of the cement layer. Standard hip prostheses were implanted in bovine donor diaphyses, with or without a cement layer. Drilling was then performed using high-performance-cutting drills with a reinforced core, a drilling diameter of 5.5 mm and cooling channels through the tip of the drill for constantly applied internal cooling solution. An open type cooling model was used in this setup. Temperature was continuously measured by seven thermocouples placed around the borehole. Thermographic scans were also performed during drilling. At the cemented implant surface, the temperature never surpassed 24.7 °C when constantly applied internal cooling was used. Without the insulating cement layer (i.e. during drilling of the cementless bone-prosthesis construct), the temperature increased to 47 °C. Constantly applied internal cooling can avoid structural bone and soft tissue damage during drilling procedures. With a cement layer, the temperatures only increased to non-damaging levels. The results could be useful in the treatment of periprosthetic fractures with intraprosthetic implant fixation.

Temperature stability limits for an isothermal demagnetization refrigerator

NASA Technical Reports Server (NTRS)

Kittel, P.

1984-01-01

It is pointed out that magnetic refrigeration can provide additional cooling for infrared detectors on space missions, taking into account the Shuttle Infrared Telescope Facility (SIRTF) and the Large Deployable Reflector (LDR). From a temperature of 2 K provided by the primary cryogens, magnetic refrigerators could cool bolometers or pumped photoconductors to 0.1 K or below. Such a reduction in operating temperature would increase the sensitivity for bolometers, while the response at longer wavelengths for pumped photoconductors would be improved. Two types of magnetic refrigeration cycles have been proposed. One type uses a complete demagnetization. The present investigation is concerned with the second type, which uses a feedback-controlled isothermal demagnetization, taking into account the temperature stability limits. Attention is given to control system resolution, thermometer noise, reaction time, and thermal time constants.

On the thermally-induced residual stresses in thick fiber-thermoplastic matrix (PEEK) cross-ply laminated plates

NASA Technical Reports Server (NTRS)

Hu, Shoufeng; Nairn, John A.

1992-01-01

An analytical method for calculating thermally-induced residual stresses in laminated plates is applied to cross-ply PEEK laminates. We considered three cooling procedures: slow cooling (uniform temperature distribution); convective and radiative cooling; and rapid cooling by quenching (constant surface temperature). Some of the calculated stresses are of sufficient magnitude to effect failure properties such as matrix microcracking.

Mechanism of bandwidth improvement in passively cooled SMA position actuators

NASA Astrophysics Data System (ADS)

Gorbet, R. B.; Morris, K. A.; Chau, R. C. C.

2009-09-01

The heating of shape memory alloy (SMA) materials leads to a thermally driven phase change which can be used to do work. An SMA wire can be thermally cycled by controlling electric current through the wire, creating an electro-mechanical actuator. Such actuators are typically heated electrically and cooled through convection. The thermal time constants and lack of active cooling limit the operating frequencies. In this work, the bandwidth of a still-air-cooled SMA wire controlled with a PID controller is improved through optimization of the controller gains. Results confirm that optimization can improve the ability of the actuator to operate at a given frequency. Overshoot is observed in the optimal controllers at low frequencies. This is a result of hysteresis in the wire's contraction-temperature characteristic, since different input temperatures can achieve the same output value. The optimal controllers generate overshoot during heating, in order to cause the system to operate at a point on the hysteresis curve where faster cooling can be achieved. The optimization results in a controller which effectively takes advantage of the multi-valued nature of the hysteresis to improve performance.

Experimental results for the rapid determination of the freezing point of fuels

NASA Technical Reports Server (NTRS)

Mathiprakasam, B.

1984-01-01

Two methods for the rapid determination of the freezing point of fuels were investigated: an optical method, which detected the change in light transmission from the disappearance of solid particles in the melted fuel; and a differential thermal analysis (DTA) method, which sensed the latent heat of fusion. A laboratory apparatus was fabricated to test the two methods. Cooling was done by thermoelectric modules using an ice-water bath as a heat sink. The DTA method was later modified to eliminate the reference fuel. The data from the sample were digitized and a point of inflection, which corresponds to the ASTM D-2386 freezing point (final melting point), was identified from the derivative. The apparatus was modifified to cool the fuel to -60 C and controls were added for maintaining constant cooling rate, rewarming rate, and hold time at minimum temperature. A parametric series of tests were run for twelve fuels with freezing points from -10 C to -50 C, varying cooling rate, rewarming rate, and hold time. Based on the results, an optimum test procedure was established. The results showed good agreement with ASTM D-2386 freezing point and differential scanning calorimetry results.

PROLONGED TRANSMURAL LOCAL MYOCARDIAL HYPOTHERMIA: A SIMPLIFIED METHOD

PubMed Central

Liotta, Domingo

1979-01-01

The plastic bag technique for epimyocardial and endomyocardial cooling described here offers a means of constantly cooling the heart while simultaneously isolating it from the higher temperature of the adjacent mediastinum. Images PMID:15216327

Decay of postexercise augmentation in the Lambert-Eaton myasthenic syndrome: effect of cooling.

PubMed

Maddison, P; Newsom-Davis, J; Mills, K R

1998-04-01

The effect of local cooling on surface recorded compound muscle action potential (CMAP) amplitude was studied in five patients with the Lambert-Eaton myasthenic syndrome (LEMS). The time course of decay of postexercise augmentation of CMAP amplitude characteristically seen in patients with LEMS was determined. We recorded the CMAP from abductor digiti minimi (ADM) in response to supramaximal stimulation of the ulnar nerve. Thirty consecutive stimuli were delivered at 1 Hz immediately after a 10-second period of maximal voluntary contraction. Skin surface temperature was recorded throughout. Initial testing at approximately 30 degrees C was repeated after cooling the hand and forearm by 6 to 12 degrees C. The effects of blood flow on temperature were counteracted by the application of a sphygmomanometer cuff, inflated above systolic blood pressure. The CMAP amplitude following contraction decayed in an exponential manner both during warm and cold conditions. The mean time constant for decay (1/b) in all patients was increased by approximately 25% after cooling. This prolongation of the period of postexercise augmentation of CMAP amplitude in LEMS after cooling concurs with patient reports of symptomatic improvement in cold weather. The mechanism for this benefit is thought to be due to reduction in the rate of removal of calcium ions from the nerve terminal following stimulation, similar to that seen in animal models of short-term synaptic enhancement.

The temporal behaviour of MHD waves in a partially ionized prominence-like plasma: Effect of heating and cooling

NASA Astrophysics Data System (ADS)

Ballester, J. L.; Carbonell, M.; Soler, R.; Terradas, J.

2018-01-01

Context. During heating or cooling processes in prominences, the plasma microscopic parameters are modified due to the change of temperature and ionization degree. Furthermore, if waves are excited on this non-stationary plasma, the changing physical conditions of the plasma also affect wave dynamics. Aims: Our aim is to study how temporal variation of temperature and microscopic plasma parameters modify the behaviour of magnetohydrodynamic (MHD) waves excited in a prominence-like hydrogen plasma. Methods: Assuming optically thin radiation, a constant external heating, the full expression of specific internal energy, and a suitable energy equation, we have derived the profiles for the temporal variation of the background temperature. We have computed the variation of the ionization degree using a Saha equation, and have linearized the single-fluid MHD equations to study the temporal behaviour of MHD waves. Results: For all the MHD waves considered, the period and damping time become time dependent. In the case of Alfvén waves, the cut-off wavenumbers also become time dependent and the attenuation rate is completely different in a cooling or heating process. In the case of slow waves, while it is difficult to distinguish the slow wave properties in a cooling partially ionized plasma from those in an almost fully ionized plasma, the period and damping time of these waves in both plasmas are completely different when the plasma is heated. The temporal behaviour of the Alfvén and fast wave is very similar in the cooling case, but in the heating case, an important difference appears that is related with the time damping. Conclusions: Our results point out important differences in the behaviour of MHD waves when the plasma is heated or cooled, and show that a correct interpretation of the observed prominence oscillations is very important in order to put accurate constraints on the physical situation of the prominence plasma under study, that is, to perform prominence seismology.

Atomic Clocks and Variations of the FIne Structure Constant

NASA Technical Reports Server (NTRS)

Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

1995-01-01

We describe a new test for possible variations of the fine structure constant alpha by comparisons of rates between clocks based on hyperfine transitions in alkali atoms with different atomic number Z. H-maser, Cs, and Hg(+) clocks have a different dependence on alpha via relativistic contributions of order (Z-alpha)(sup 2). Recent H-maser vs Hg(+) clock comparison data improve laboratory limits on a time variation by 100-fold to give dot-alpha less than or equal to 3.7 x 10(exp -14)/yr. Future laser cooled clocks (Be(+), Rb, Cs, Hg(+), etc.), when compared, will yield the most sensitive of all tests for dot-alpha/alpha.

A continuous dry 300 mK cooler for THz sensing applications

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

Klemencic, G. M., E-mail: Georgina.Klemencic@astro.cf.ac.uk; Ade, P. A. R.; Sudiwala, R.

We describe and demonstrate the automated operation of a novel cryostat design that is capable of maintaining an unloaded base temperature of less than 300 mK continuously, without the need to recycle the gases within the final cold head, as is the case for conventional single shot sorption pumped {sup 3}He cooling systems. This closed dry system uses only 5 l of {sup 3}He gas, making this an economical alternative to traditional systems where a long hold time is required. During testing, a temperature of 365 mK was maintained with a constant 20 μW load, simulating the cooling requirement ofmore » a far infrared camera.« less

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

NASA Technical Reports Server (NTRS)

Donoughe, Patrick L; Livingood, John N B

1955-01-01

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

Caries selective ablation: the handpiece

NASA Astrophysics Data System (ADS)

Hennig, Thomas; Rechmann, Peter; Holtermann, Andreas

1995-05-01

Caries selective ablation is fixed to a window of fluences predicted by the ablation thresholds of carious and healthy dentin, respectively. The aim of the study was to develop a dental handpiece which guarantees homogeneous fluence at the irradiated tooth surface. Furthermore the point of treatment should be cooled down without energy losses due to the cooling system. We suggest the direct coupling of the laser radiation into a laminar stream of liquid, which acts in turn as a lengthened beam guide. The impacts of the laser radiation and of the cooling medium fall exactly into the same point. Hot ablation debris is removed out of the crater by the flush of the water jet. Fluences are constant if the handpiece is used in contact mode or at a distance. Normally the surface of a bare fiber working in contact mode is destroyed after a few shots. Coupling the laser radiation into a stream of liquid prevents this destruction. Putting together the benefits of this special handpiece short overall treatment times seem to be possible. High average power can be applied to the tooth without the threat of thermal damage. Furthermore no time consuming cutting of the fiber prolongs the treatment time.

Temperature measurements during laser skin welding

NASA Astrophysics Data System (ADS)

Fried, Nathaniel M.; Choi, Bernard; Welch, Ashley J.; Walsh, Joseph T., Jr.

1999-06-01

A thermal camera was used to measure surface temperatures during laser skin welding to provide feedback for optimization of the laser parameters. Two-cm-long, full- thickness incisions were made in guinea pig skin. India ink was used as an absorber. Continuous-wave, 1.06-μm, Nd:YAG laser radiation was scanned over the incisions, producing a pulse duration of approximately 100 ms. Cooling durations between scans of 1.6, 4.0, and 8.0 s were studied with total operation times of 3, 5, and 10 min, respectively. A laser spot diameter of 5 mm was used with the power constant at 10 W. Thermal images were obtained at 30 frames per second with a thermal camera detecting 3.5 micrometers radiation. Surface temperatures were recorded at 0, 1, and 6 mm from the center line of the incision. Cooling durations between scans of 1.6 s and 4.0 s in vitro resulted in temperatures at the weld site remaining above ~65°C for prolonged periods of time. Cooling durations between scans as long as 8.0 s were sufficient both in vitro and in vivo to prevent a significant rise in baseline temperatures at the weld site over time.

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

NASA Technical Reports Server (NTRS)

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

1945-01-01

An analysis of rim cooling, which cools the blade by condition alone, was conducted. Gas temperatures ranged from 1300 degrees to 1900 degrees F and rim temperatures from 0 degrees to 1000 degrees F below gas temperatures. Results show that gas temperature increases up to 200 degrees F are permissible provided that the blades are cooled by 400 degrees to 500 degrees F below the gas temperature. Relatively small amounts of blade cooling, at constant gas temperature, give large increases in blade life. Dependence of rim cooling on heat-transfer coefficient, blade dimensions, and thermal conductivity is determined by a single parameter.

Inhibition of calcium carbonate crystal growth by organic additives using the constant composition method in conditions of recirculating cooling circuits

NASA Astrophysics Data System (ADS)

Chhim, Norinda; Kharbachi, Chams; Neveux, Thibaut; Bouteleux, Céline; Teychené, Sébastien; Biscans, Béatrice

2017-08-01

The cooling circuits used in power plants are subject to mineral crystallization which can cause scaling on the surfaces of equipment and construction materials reducing their heat exchange efficiency. Precipitated calcium carbonate is the predominant mineral scale commonly observed in cooling systems. Supersaturation is the key parameter controlling the nucleation and growth of calcite in these systems. The present work focuses on the precipitation of calcite using the constant composition method at constant supersaturation, through controlled addition of reactants to a semi-batch crystallizer, in order to maintain constant solution pH. The determination of the thermodynamic driving force (supersaturation) was based on the relevant chemical equilibria, total alkalinity and calculation of the activity coefficients. Calcite crystallization rates were derived from the experiments performed at supersaturation levels similar to those found in industrial station cooling circuits. Several types of seeds particles were added into the aqueous solution to mimic natural river water conditions in terms of suspended particulate matters content, typically: calcite, silica or illite particles. The effect of citric and copolycarboxylic additive inhibitors added to the aqueous solution was studied. The calcium carbonate growth rate was reduced by 38.6% in the presence of the citric additive and a reduction of 92.7% was observed when the copolycarboxylic additive was used under identical experimental conditions. These results are explained by the location of the adsorbed inhibitor at the crystal surface and by the degree of chemical bonding to the surface.

External Cooling Coupled to Reduced Extremity Pressure Device

NASA Technical Reports Server (NTRS)

Kuznetz, Lawrence H.

2011-01-01

Although suited astronauts are currently cooled with a Liquid Cooled Ventilation Garment (LCVG), which can remove up to 85 percent of body heat, their effectiveness is limited because cooling must penetrate layers of skin, muscle, fat, bone, and tissue to reach the bloodstream, where its effect is prominent. Vasoconstriction further reduces the effectiveness by limiting arterial flow when exposed to cold (the frostbite response), resulting in a time constant on the order of 20 minutes from application to maximum effect. This delay can be crucial in severe exposure to hypo- or hyper-thermic conditions, compromising homeostasis. The purpose of this innovation is to provide a lightweight, effective means of delivering heat or cold from an external source directly to the bloodstream. The effectiveness of this ECCREP (External Cooling Coupled to Reduced Extremity Pressure) device is based on not having to penetrate layers of skin, muscle, fat, and tissue, thereby avoiding the thermal lag associated with their mass and heat capacity. This is accomplished by means of an outer boot operating at a slightly reduced pressure than the rest of the body, combined with an inner boot cooled or heated by an external source via water or chemicals. Heat transfer from the external source to the foot takes place by means of circulating water or flexible heat pipes.

On-Orbit Performance of the TES Pulse Tube Cryocooler System and the Instrument - Six Years in Space

NASA Technical Reports Server (NTRS)

Rodriguez, J. I.; Na-Nakornpanom, A.

2011-01-01

The Tropospheric Emission Spectrometer (TES) instrument pulse tube cryocoolers began operation 36 days after launch of the NASA Earth Observing System (EOS) Aura spacecraft on July 15, 2004. TES is designed with four infrared Mercury Cadmium Telluride focal plane arrays in two separate housings cooled by a pair of Northrup Grumman Aerospace Systems (NGAS) single-stage pulse tube cryocoolers. The instrument also makes use of a two-stage passive cooler to cool the optical bench. The instrument is a high-resolution infrared imaging Fourier transform spectrometer with 3.3-15.4 micron spectral coverage. After four weeks of outgassing, the instrument optical bench and focal planes were cooled to their operating temperatures to begin science operations. During the early months of the mission, ice contamination of the cryogenic surfaces including the focal planes led to increased cryocooler loads and the need for periodic decontamination cycles. After a highly successful 5 years of continuous in-space operations, TES was granted a 2 year extension. This paper reports on the TES cryogenic system performance including the two-stage passive cooler. After a brief overview of the cryogenic design, the paper presents detailed data on the highly successful space operation of the pulse tube cryocoolers and instrument thermal design over the past six years since the original turn-on in 2004. The data shows the cryogenic contamination decreased substantially to where decontamination cycles are now performed every six months. The cooler stroke required for constant-temperature operation has not increased indicating near-constant cooler efficiency and the instrument's thermal design has also provided a nearly constant heat rejection sink. At this time TES continues to operate in space providing important Earth science data.

Temperature dependent relaxation of interface-states in graphene on SiO2

NASA Astrophysics Data System (ADS)

Singh, Anil Kumar; Gupta, Anjan Kumar

2018-04-01

We have studied the evolution of resistance relaxation with temperature in graphene field effect transistor on SiO2. At room temperature, piranha-cleaned-SiO2 devices show slow resistance relaxation while IPA-cleaned-SiO2 devices do not. With cooling the former devices show a decrease in magnitude and time constant of the slow relaxation and it becomes negligible at 250K. Relaxation study at elevated temperature of the IPA-cleaned devices show a gate voltage polarity dependent time constant with respect to the charge neutrality point but it remains almost independent of temperature. The magnitude of relaxation increases with temperature. Further, after annealing at elevated temperature, we found that the relaxation times become independent of gate voltage polarity and its magnitude becomes very small. These observations are discussed using increase in diffusion of interface-species with temperature.

Relationships between in situ protein degradability and grass developmental morphology.

PubMed

Mitchell, R B; Redfearn, D D; Moser, L E; Grant, R J; Moore, K J; Kirch, B H

1997-06-01

The objective of this research was to determine the relationships between the morphological development and in situ ruminally degradable protein (RDP), ruminally undegradable protein (RUP), and microbial protein of two cool season grasses (intermediate wheatgrass and smooth bromegrass) and two warm season grasses (switchgrass and big bluestem). The initial growth of grass tillers grown near Mead, Nebraska was clipped at ground level six times during the 1992 growing season and morphologically classified. Mean stage was calculated. Forage was ground to pass a 2-mm screen and was incubated in ruminally fistulated steers for 16 h. The RUP was adjusted for microbial protein and acid detergent insoluble N. The mean stage of cool season grasses was higher than that of warm season grasses throughout the growing season. The RDP decreased as plant maturity increased for all species. The RUP expressed as a percentage of crude protein for the cool season grasses was lower than that for warm season grasses. The RUP for intermediate wheatgrass, smooth bromegrass, and switchgrass remained constant across maturities, but RUP for big bluestem decreased as maturity increased. Microbial augmentation of RUP decreased as crude protein decreased in all species. The RUP corrected for acid detergent insoluble N and microbial protein was relatively constant across plant maturities. The quantification of RUP across a range of plant maturities provided information for incorporating RUP content of forage grasses into the diets of animals.

A cooling neutron star crust after recurrent outbursts: modelling the accretion outburst history of Aql X-1

NASA Astrophysics Data System (ADS)

Ootes, Laura S.; Wijnands, Rudy; Page, Dany; Degenaar, Nathalie

2018-07-01

With our neutron star crust cooling code NSCOOL, we track the thermal evolution of the neutron star in Aql X-1 over the full accretion outburst history from 1996 until 2015. For the first time, we model many outbursts (23 outbursts were detected) collectively and in great detail. This allows us to investigate the influence of previous outbursts on the internal temperature evolution and to test different neutron star crust cooling scenarios. Aql X-1 is an ideal test source for this purpose, because it shows frequent, short outbursts and thermally dominated quiescence spectra. The source goes into outburst roughly once a year for a few months. Assuming that the quiescent Swift/X-Ray Telescope observations of Aql X-1 can be explained within the crust cooling scenario, we find three main conclusions. First, the data are well reproduced by our model if the envelope composition and shallow heating parameters are allowed to change between outbursts. This is not the case if both shallow heating parameters (strength and depth) are tied throughout all accretion episodes, supporting earlier results that the properties of the shallow heating mechanism are not constant between outbursts. Secondly, from our models, shallow heating could not be connected to one specific spectral state during outburst. Thirdly, and most importantly, we find that the neutron star in Aql X-1 does not have enough time between outbursts to cool down to crust-core equilibrium and that heating during one outburst influences the cooling curves of the next.

Separation of variables solution for non-linear radiative cooling

NASA Technical Reports Server (NTRS)

Siegel, Robert

1987-01-01

A separation of variables solution has been obtained for transient radiative cooling of an absorbing-scattering plane layer. The solution applies after an initial transient period required for adjustment of the temperature and scattering source function distributions. The layer emittance, equal to the instantaneous heat loss divided by the fourth power of the instantaneous mean temperature, becomes constant. This emittance is a function of only the optical thickness of the layer and the scattering albedo; its behavior as a function of these quantities is considerably different than for a layer at constant temperature.

Seasonal radiative modeling of Titan's stratospheric temperatures at low latitudes

NASA Astrophysics Data System (ADS)

Bézard, Bruno; Vinatier, Sandrine; Achterberg, Richard K.

2018-03-01

We have developed a seasonal radiative-dynamical model of Titan's stratosphere to investigate the temporal variation of temperatures in the 0.2-4 mbar range observed by the Cassini/CIRS spectrometer. The model incorporates gas and aerosol vertical profiles derived from Cassini/CIRS and Huygens/DISR data to calculate the radiative heating and cooling rate profiles as a function of time and latitude. At 20°S in 2007, the heating rate is larger than the cooling rate at all altitudes, and more specifically by 20-35% in the 0.1-5 mbar range. A new calculation of the radiative relaxation time as a function of pressure level is presented, leading to time constants significantly lower than previous estimates. At 6°N around spring equinox, the radiative equilibrium profile is warmer than the observed one at all levels. Adding adiabatic cooling in the energy equation, with a vertical upward velocity profile approximately constant in pressure coordinates below the 0.02-mbar level (corresponding to 0.03-0.05 cm s-1 at 1 mbar), allows us to reproduce the observed profile quite well. The velocity profile above the ∼0.5-mbar level is however affected by uncertainties in the haze density profile. The model shows that the change in insolation due to Saturn's orbital eccentricity is large enough to explain the observed 4-K decrease in equatorial temperatures around 1 mbar between 2009 and 2016. At 30°N and S, the radiative model predicts seasonal variations of temperature much larger than observed. A seasonal modulation of adiabatic cooling/heating is needed to reproduce the temperature variations observed from 2005 to 2016 between 0.2 and 4 mbar. At 1 mbar, the derived vertical velocities vary in the range -0.05 (winter solstice) to 0.16 (summer solstice) cm s-1 at 30°S, -0.01 (winter solstice) to 0.14 (summer solstice) cm s-1 at 30°N, and 0.03-0.07 cm s-1 at the equator.

Evidence for Solar Cycle Influence on the Infrared Energy Budget and Radiative Cooling of the Thermosphere

NASA Technical Reports Server (NTRS)

Mlynczak, Martin G.; Martin-Torres, F. Javier; Marshall, B. Thomas; Thompson, R. Earl; Williams, Joshua; Turpin, TImothy; Kratz, D. P.; Russell, James M.; Woods, Tom; Gordley, Larry L.

2007-01-01

We present direct observational evidence for solar cycle influence on the infrared energy budget and radiative cooling of the thermosphere. By analyzing nearly five years of data from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, we show that the annual mean infrared power radiated by the nitric oxide (NO) molecule at 5.3 m has decreased by a factor of 2.9. This decrease is correlated (r = 0.96) with the decrease in the annual mean F10.7 solar index. Despite the sharp decrease in radiated power (which is equivalent to a decrease in the vertical integrated radiative cooling rate), the variability of the power as given in the standard deviation of the annual means remains approximately constant. A simple relationship is shown to exist between the infrared power radiated by NO and the F10.7 index, thus providing a fundamental relationship between solar activity and the thermospheric cooling rate for use in thermospheric models. The change in NO radiated power is also consistent with changes in absorbed ultraviolet radiation over the same time period.

Microtextured Surfaces for Turbine Blade Impingement Cooling

NASA Technical Reports Server (NTRS)

Fryer, Jack

2014-01-01

Gas turbine engine technology is constantly challenged to operate at higher combustor outlet temperatures. In a modern gas turbine engine, these temperatures can exceed the blade and disk material limits by 600 F or more, necessitating both internal and film cooling schemes in addition to the use of thermal barrier coatings. Internal convective cooling is inadequate in many blade locations, and both internal and film cooling approaches can lead to significant performance penalties in the engine. Micro Cooling Concepts, Inc., has developed a turbine blade cooling concept that provides enhanced internal impingement cooling effectiveness via the use of microstructured impingement surfaces. These surfaces significantly increase the cooling capability of the impinging flow, as compared to a conventional untextured surface. This approach can be combined with microchannel cooling and external film cooling to tailor the cooling capability per the external heating profile. The cooling system then can be optimized to minimize impact on engine performance.

Zonal flow evolution and overstability in accretion discs

NASA Astrophysics Data System (ADS)

Vanon, R.; Ogilvie, G. I.

2017-04-01

This work presents a linear analytical calculation on the stability and evolution of a compressible, viscous self-gravitating (SG) Keplerian disc with both horizontal thermal diffusion and a constant cooling time-scale when an axisymmetric structure is present and freely evolving. The calculation makes use of the shearing sheet model and is carried out for a range of cooling times. Although the solutions to the inviscid problem with no cooling or diffusion are well known, it is non-trivial to predict the effect caused by the introduction of cooling and of small diffusivities; this work focuses on perturbations of intermediate wavelengths, therefore representing an extension to the classical stability analysis on thermal and viscous instabilities. For density wave modes, the analysis can be simplified by means of a regular perturbation analysis; considering both shear and thermal diffusivities, the system is found to be overstable for intermediate and long wavelengths for values of the Toomre parameter Q ≲ 2; a non-SG instability is also detected for wavelengths ≳18H, where H is the disc scale-height, as long as γ ≲ 1.305. The regular perturbation analysis does not, however, hold for the entropy and potential vorticity slow modes as their ideal growth rates are degenerate. To understand their evolution, equations for the axisymmetric structure's amplitudes in these two quantities are analytically derived and their instability regions obtained. The instability appears boosted by increasing the value of the adiabatic index and of the Prandtl number, while it is quenched by efficient cooling.

Characterization of Plastic Flow Pertinent to the Evolution of Bulk Residual Stress in Powder-Metallurgy, Nickel-Base Superalloys

NASA Astrophysics Data System (ADS)

Semiatin, S. L.; Fagin, P. N.; Goetz, R. L.; Furrer, D. U.; Dutton, R. E.

2015-09-01

The plastic-flow behavior which controls the formation of bulk residual stresses during final heat treatment of powder-metallurgy (PM), nickel-base superalloys was quantified using conventional (isothermal) stress-relaxation (SR) tests and a novel approach which simulates concurrent temperature and strain transients during cooling following solution treatment. The concurrent cooling/straining test involves characterization of the thermal compliance of the test sample. In turn, this information is used to program the ram-displacement- vs-time profile to impose a constant plastic strain rate during cooling. To demonstrate the efficacy of the new approach, SR tests (in both tension and compression) and concurrent cooling/tension-straining experiments were performed on two PM superalloys, LSHR and IN-100. The isothermal SR experiments were conducted at a series of temperatures between 1144 K and 1436 K (871 °C and 1163 °C) on samples that had been supersolvus solution treated and cooled slowly or rapidly to produce starting microstructures comprising coarse gamma grains and coarse or fine secondary gamma-prime precipitates, respectively. The concurrent cooling/straining tests comprised supersolvus solution treatment and various combinations of subsequent cooling rate and plastic strain rate. Comparison of flow-stress data from the SR and concurrent cooling/straining tests showed some similarities and some differences which were explained in the context of the size of the gamma-prime precipitates and the evolution of dislocation substructure. The magnitude of the effect of concurrent deformation during cooling on gamma-prime precipitation was also quantified experimentally and theoretically.

Development of a force sensor using atom interferometry to constrain theories on dark matter and dark energy

NASA Astrophysics Data System (ADS)

Schlupf, Chandler; Niederriter, Robert; Bohr, Eliot; Khamis, Sami; Park, Youna; Szwed, Erik; Hamilton, Paul

2017-04-01

Atom interferometry has been used in many precision measurements such as Newton's gravitational constant, the fine structure constant, and tests of the equivalence principle. We will perform atom interferometry in an optical lattice to measure the force felt by an atom due to a test mass in search of new forces suggested by dark matter and dark energy theories. We will be developing a new apparatus using laser-cooled ytterbium to continuously measure this force by observing their Bloch oscillations. Interfering atoms in an optical lattice allows continuous measurements in a small volume over a long period of time, enabling our device to be sensitive to time-varying forces while minimizing vibrational noise. We present the details of this experiment and the progress on it thus far.

Heat pipe cooling of power processing magnetics

NASA Technical Reports Server (NTRS)

Hansen, I. G.; Chester, M.

1979-01-01

The constant demand for increased power and reduced mass has raised the internal temperature of conventionally cooled power magnetics toward the upper limit of acceptability. The conflicting demands of electrical isolation, mechanical integrity, and thermal conductivity preclude significant further advancements using conventional approaches. However, the size and mass of multikilowatt power processing systems may be further reduced by the incorporation of heat pipe cooling directly into the power magnetics. Additionally, by maintaining lower more constant temperatures, the life and reliability of the magnetic devices will be improved. A heat pipe cooled transformer and input filter have been developed for the 2.4 kW beam supply of a 30-cm ion thruster system. This development yielded a mass reduction of 40% (1.76 kg) and lower mean winding temperature (20 C lower). While these improvements are significant, preliminary designs predict even greater benefits to be realized at higher power. This paper presents the design details along with the results of thermal vacuum operation and the component performance in a 3 kW breadboard power processor.

Kinetics of Fe2+-Mg order-disorder in orthopyroxene: experimental studies and applications to cooling rates of rocks

NASA Astrophysics Data System (ADS)

Stimpfl, M.; Ganguly, J.; Molin, G.

2005-10-01

We determined the forward rate constant (K+) for the Fe2+-Mg order-disorder between the M2 and M1 sites of orthopyroxene (OPx), which is described by the homogeneous reaction Fe2+ (M2) + Mg(M1) ↔ Mg(M2) + Fe2+ (M1), by both ordering and disordering experiments at isothermal condition and also by continuous cooling experiments. The rate constant was determined as a function of temperature in the range of 550-750°C, oxygen fugacity between quartz-fayalite-iron and Ni-NiO buffers, and at compositions of 16 and 50 mol% ferrosilite component. The K+ value derived from disordering experiment was found to be larger than that derived from ordering experiment at 550°C, while at T>580°C, these two values are essentially the same. The fO2 dependence of the rate constant can be described by the relation K+ α (fO2) n with n=5.5-6.5, which is compatible with the theoretically expected relation. The Arrhenius relation at the WI buffer condition is given by ln (C_{text{o}} {text{K}}^+) = - {41511 - 12600{text{X}}_{{text{Fe}}} }/{{T({text{K}})}} + 28.26 + 5.27{text{X}}_{{text{Fe}}}, min^{-1} where C o represents the total number of M2 + M1 sites occupied by Fe2+ and Mg per unit volume of the crystal. The above relation can be used to calculate the cooling rates of natural OPx crystals around the closure temperature ( T c) of Fe-Mg ordering, which are usually below 300°C for slowly cooled rocks. We determined the Fe-Mg ordering states of several OPx crystals (˜ Fs50) from the Central Gneissic Complex (Khtada Lake), British Columbia, which yields T c ˜290°C. Numerical simulation of the change of Fe2+-Mg ordering in OPx as a function of temperature using the above expression of rate constant and a non-linear cooling model yields quenched values of ordering states that are in agreement with the observed values for cooling rates of 11-17°C/Myr below 300°C. The inferred cooling rate is in agreement with the available geochronological constraints.

A model for correlating flat plate film cooling effectiveness for rows of round holes

NASA Astrophysics Data System (ADS)

Lecuyer, M. R.; Soechting, F. O.

1985-09-01

An effective method of cooling, that has found widespread application in aircraft gas turbines, is the injection of a film of cooling air through holes into the hot mainstream gas to provide a buffer layer between the hot gas and the airfoil surface. Film cooling has been extensively investigated and the results have been reported in the literature. However, there is no generalized method reported in the literature to predict the film cooling performance as influenced by the major variables. A generalized film cooling correlation has been developed, utilizing data reported in the literature, for constant velocity and flat plate boundary layer development. This work provides a basic understanding of the complex interaction of the major variables effecting film cooling performance.

Hydrostatic Chandra X-ray analysis of SPT-selected galaxy clusters - I. Evolution of profiles and core properties

NASA Astrophysics Data System (ADS)

Sanders, J. S.; Fabian, A. C.; Russell, H. R.; Walker, S. A.

2018-02-01

We analyse Chandra X-ray Observatory observations of a set of galaxy clusters selected by the South Pole Telescope using a new publicly available forward-modelling projection code, MBPROJ2, assuming hydrostatic equilibrium. By fitting a power law plus constant entropy model we find no evidence for a central entropy floor in the lowest entropy systems. A model of the underlying central entropy distribution shows a narrow peak close to zero entropy which accounts for 60 per cent of the systems, and a second broader peak around 130 keV cm2. We look for evolution over the 0.28-1.2 redshift range of the sample in density, pressure, entropy and cooling time at 0.015R500 and at 10 kpc radius. By modelling the evolution of the central quantities with a simple model, we find no evidence for a non-zero slope with redshift. In addition, a non-parametric sliding median shows no significant change. The fraction of cool-core clusters with central cooling times below 2 Gyr is consistent above and below z = 0.6 (˜30-40 per cent). Both by comparing the median thermodynamic profiles, centrally biased towards cool cores, in two redshift bins, and by modelling the evolution of the unbiased average profile as a function of redshift, we find no significant evolution beyond self-similar scaling in any of our examined quantities. Our average modelled radial density, entropy and cooling-time profiles appear as power laws with breaks around 0.2R500. The dispersion in these quantities rises inwards of this radius to around 0.4 dex, although some of this scatter can be fitted by a bimodal model.

Performance of a kinetic model for intracellular ice formation based on the extent of supercooling.

PubMed

Pitt, R E; Chandrasekaran, M; Parks, J E

1992-06-01

Cryomicroscopy was used to study the incidence of intracellular ice formation (IIF) in protoplasts isolated from rye (Secale cereale) leaves during subfreezing isothermal periods and in in vitro mature bovine oocytes during cooling at constant rates. IIF in protoplasts occurred at random times during isothermal periods, and the kinetics of IIF were faster as isothermal temperature decreased. Mean IIF times decreased from approximately 1700 s at -4.0 degrees C to less than 1 s at -18.5 degrees C. Total incidence of IIF after 200 s increased from 4% at -4.0 degrees C to near 100% at -15.5 degrees C. IIF behavior in protoplasts was qualitatively similar to that for Drosophila melanogaster embryos over the same temperature ranges (Myers et al., Cryobiology 26, 472-484, 1989), but the kinetics of IIF were about five times faster in protoplasts. IIF observations in linear cooling of bovine oocytes indicated a median IIF temperature of -11 degrees C at 16 degrees C/min and total incidences of 97%, 50%, and 19% at 16, 8, and 4 degrees C/min, respectively. A stochastic model of IIF was developed which preserved certain features of an earlier model (Pitt et al. Cryobiology 28, 72-86, 1991), namely Weibull behavior in IIF temperatures during rapid linear cooling, but with a departure from the concept of a supercooling tolerance. Instead, the new model uses the osmotic state of the cell, represented by the extent of supercooling, as the independent variable governing the kinetics of IIF. Two kinetic parameters are needed for the model: a scale factor tau 0 dictating the sensitivity to supercooling, and an exponent rho dictating the strength of time dependency. The model was fit to the data presented in this study as well as those from Myers et al. and Pitt et al. for D. melanogaster embryos with and without cryoprotectant, and from Toner et al. (Cryobiology 28, 55-71, 1991) for mouse oocytes. In protoplasts, D. melanogaster embryos, and mouse oocytes, the parameters were estimated from IIF times in the early stages of isothermal periods, while the osmotic state of the cell was relatively constant. In bovine oocytes, the parameters were estimated from linear cooling data. Without further calibration, the model was used to predict total IIF incidence under different cooling regimes. For protoplasts, D. melanogaster embryos, and bovine oocytes, the model's predictions were quite accurate compared to the actual data. In mouse oocytes, adjustment of the hydraulic permeability coefficient (Lp) at 0 degree C was required to yield realistic behavior.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of effectiveness of convection-, transpiration-, and film-cooling methods with air as coolant

NASA Technical Reports Server (NTRS)

Eckert, E R G; Livingood, N B

1954-01-01

Various parts of aircraft propulsion engines that are in contact with hot gases often require cooling. Transpiration and film cooling, new methods that supposedly utilize cooling air more effectively than conventional convection cooling, have already been proposed. This report presents material necessary for a comparison of the cooling requirements of these three methods. Correlations that are regarded by the authors as the most reliable today are employed in evaluating each of the cooling processes. Calculations for the special case in which the gas velocity is constant along the cooled wall (flat plate) are presented. The calculations reveal that a comparison of the three cooling processes can be made on quite a general basis. The superiority of transpiration cooling is clearly shown for both laminar and turbulent flow. This superiority is reduced when the effects of radiation are included; for gas-turbine blades, however, there is evidence indicating that radiation may be neglected.

A Kinetic Study of the Effect of Basicity on the Mold Fluxes Crystallization

NASA Astrophysics Data System (ADS)

Zhou, Lejun; Wang, Wanlin; Ma, Fanjun; Li, Jin; Wei, Juan; Matsuura, Hiroyuki; Tsukihashi, Fumitaka

2012-04-01

The effect of basicity on the mold fluxes crystallization was investigated in this article. The time-temperature-transformation (TTT) diagrams and continuous-cooling-transformation (CCT) diagrams of mold fluxes with different basicity were constructed by using single, hot thermocouple technology (SHTT). The results showed that with the increase of basicity, the incubation time of isothermal crystallization became shorter, the crystallization temperature was getting higher, and the critical cooling rate of continuous cooling crystallization became faster. The X-ray diffraction analysis suggested that calcium silicate (CaO·SiO2) was precipitated at the upper part of the TTT diagram and cuspidine (Ca4Si2O7F2) was formed at the lower part, when the basicity of mold fluxes was within 1.0 to 1.2. However, when basicity was 0.8, only the cuspidine phase was formed. A kinetic study of isothermal crystallization process indicated that the increase of the basicity tended to enhance the mold flux crystallization, and the crystallization activation energy became smaller. The crystallization mechanism of cupsidine was changing from one-dimensional growth to three-dimensional growth with a constant number of nuclei, when the basicity of mold fluxes varied from 0.8 to 1.2.

Global temperature responses to current emissions from the transport sectors

PubMed Central

Berntsen, Terje; Fuglestvedt, Jan

2008-01-01

Transport affects climate directly and indirectly through mechanisms that cause both warming and cooling of climate, and the effects operate on very different timescales. We calculate climate responses in terms of global mean temperature and find large differences between the transport sectors with respect to the size and mix of short- and long-lived effects, and even the sign of the temperature response. For year 2000 emissions, road transport has the largest effect on global mean temperature. After 20 and 100 years the response in net temperature is 7 and 6 times higher, respectively, than for aviation. Aviation and shipping have strong but quite uncertain short-lived warming and cooling effects, respectively, that dominate during the first decades after the emissions. For shipping the net cooling during the first 4 decades is due to emissions of SO2 and NOx. On a longer timescale, the current emissions from shipping cause net warming due to the persistence of the CO2 perturbation. If emissions stay constant at 2000 levels, the warming effect from road transport will continue to increase and will be almost 4 times larger than that of aviation by the end of the century. PMID:19047640

Effects of internal electrode cooling on irreversible electroporation using a perfused organ model.

PubMed

O'Brien, Timothy J; Bonakdar, Mohammad; Bhonsle, Suyashree; Neal, Robert E; Aardema, Charles H; Robertson, John L; Goldberg, S Nahum; Davalos, Rafael V

2018-05-28

This study evaluates the effects of active electrode cooling, via internal fluid circulation, on the irreversible electroporation (IRE) lesion, deployed electric current and temperature changes using a perfused porcine liver model. A bipolar electrode delivered IRE electric pulses with or without activation of internal cooling to nine porcine mechanically perfused livers. Pulse schemes included a constant voltage, and a preconditioned delivery combined with an arc-mitigation algorithm. After treatment, organs were dissected, and treatment zones were stained using triphenyl-tetrazolium chloride (TTC) to demonstrate viability. Thirty-nine treatments were performed with an internally cooled applicator and 21 with a non-cooled applicator. For the constant voltage scenario, the average final electrical current measured was 26.37 and 29.20 A for the cooled and uncooled electrodes respectively ([Formula: see text]). The average final temperature measured was 33.01 and 42.43 °C for the cooled and uncooled electrodes respectively ([Formula: see text]). The average measured ablations (fixed lesion) were 3.88-by-2.08 cm and 3.86-by-2.12 cm for the cooled and uncooled electrode respectively ([Formula: see text], [Formula: see text]). Similarly, the preconditioned/arc-mitigation scenario yielded an average final electrical current measurement of a 41.07 and 47.20 A for the cooled and uncooled electrodes respectively ([Formula: see text]). The average final temperature measured was 34.93 and 44.90 °C for the cooled and uncooled electrodes respectively ([Formula: see text]). The average measured ablations (fixed lesion) were 3.67-by-2.27 cm and 3.58-by-2.09 cm for the cooled and uncooled applicators ([Formula: see text]). The internally-cooled bipolar applicator offers advantages that could improve clinical outcomes. Thermally mitigating internal perfusion technology reduced tissue temperatures and electric current while maintaining similar lesion sizes.

Analytical investigation of chord size and cooling methods on turbine blade cooling requirements. Book 1: Sections 1 through 8 and appendixes A through I

NASA Technical Reports Server (NTRS)

Faulkner, F. E.

1971-01-01

A study was conducted to determine the effect of chord size on air cooled turbine blades. In the preliminary design phase, eight turbine blade cooling configurations in 0.75-in., 1.0-in., and 1.5-in. chord sizes were analyzed to determine the maximum turbine inlet temperature capabilities. A pin fin convection cooled configuration and a film-impingement cooled configuration were selected for a final design analysis in which the maximum turbine inlet temperature was determined as a function of the cooling air inlet temperature and the turbine inlet total pressure for each of the three chord sizes. The cooling air flow requirements were also determined for a varying cooling air inlet temperature with a constant turbine inlet temperature. It was determined that allowable turbine inlet temperature increases with increasing chord for the convection cooled and transpiration cooled designs, however, the film-convection cooled designs did not have a significant change in turbine inlet temperature with chord.

Temperature Stabilization of the NIFFTE Time Projection Chamber

NASA Astrophysics Data System (ADS)

Hicks, Caleb

2017-09-01

The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) is a collaboration measuring nuclear fission cross sections for use in advanced nuclear reactors. A neutron beam incident on targets of Uranium-235, Uranium-238, and Plutonium-239 is used to measure the neutron induced fission cross sections for these isotopes. A Time Projection Chamber (TPC) is used to record these reactions. Significant heat is generated by the readout cards mounted on the TPC, which are cooled by fans. One proposed measurement of the experiment is to compare the cross sections of the target to a proton target of gaseous hydrogen. A constant temperature inside the TPC's pressure vessel is desirable to maintain a constant number of hydrogen target atoms. In addition, a constant temperature minimizes the strain and wrinkles on an amplifying mesh inside the TPC. This poster describes the successful work to develop, build, and install a fan controller using a Raspberry Pi, an Arduino, and a custom circuit board to implement an algorithm called Proportional-Integral-Derivative control. This research was supported by US DOE MENP Grant DE-FG02-03ER41243.

An annual model of SSM/I radiobrightness for dry soil

NASA Technical Reports Server (NTRS)

Liou, Yuei-An; England, A. W.

1992-01-01

An annual model is presented of the temperature structure within a homogeneous, dry soil halfspace that is subject to both diurnal and annual insolation, radiant heating from the atmosphere, sensible heat exchange with the atmosphere, and radiant cooling. The thermal constitutive properties of the soil are assumed to be constant so that the heat flow equation can be solved analytically. For computational economy, a variable time interval Laplace transform method is developed to predict the temperature.

Effects of substrate temperature on properties of pulsed dc reactively sputtered tantalum oxide films

NASA Astrophysics Data System (ADS)

Jain, Pushkar; Juneja, Jasbir S.; Bhagwat, Vinay; Rymaszewski, Eugene J.; Lu, Toh-Ming; Cale, Timothy S.

2005-05-01

The effects of substrate heating on the stoichiometry and the electrical properties of pulsed dc reactively sputtered tantalum oxide films over a range of film thickness (0.14 to 5.4 μm) are discussed. The film stoichiometry, and hence the electrical properties, of tantalum oxide films; e.g., breakdown field, leakage current density, dielectric constant, and dielectric loss are compared for two different cases: (a) when no intentional substrate/film cooling is provided, and (b) when the substrate is water cooled during deposition. All other operating conditions are the same, and the film thickness is directly related to deposition time. The tantalum oxide films deposited on the water-cooled substrates are stoichiometric, and exhibit excellent electrical properties over the entire range of film thickness. ``Noncooled'' tantalum oxide films are stoichiometric up to ~1 μm film thickness, beyond that the deposited oxide is increasingly nonstoichiometric. The presence of partially oxidized Ta in thicker (>~1 μm) noncooled tantalum oxide films causes a lower breakdown field, higher leakage current density, higher apparent dielectric constant, and dielectric loss. The growth of nonstoichiometric tantalum oxide in thicker noncooled films is attributed to decreased surface oxygen concentration due to oxygen recombination and desorption at higher film temperatures (>~100 °C). The quantitative results presented reflect experience with a specific piece of equipment; however, the procedures presented can be used to characterize deposition processes in which film stoichiometry can change.

Fabrication of catalyzed ion transport membrane systems

DOEpatents

Carolan, Michael Francis; Kibby, Charles Leonard

2013-06-04

Process for fabricating a catalyzed ion transport membrane (ITM). In one embodiment, an uncatalyzed ITM is (a) contacted with a non-reducing gaseous stream while heating to a temperature and for a time period sufficient to provide an ITM possessing anion mobility; (b) contacted with a reducing gaseous stream for a time period sufficient to provide an ITM having anion mobility and essentially constant oxygen stoichiometry; (c) cooled while contacting the ITM with the reducing gaseous stream to provide an ITM having essentially constant oxygen stoichiometry and no anion mobility; and (d) treated by applying catalyst to at least one of (1) a porous mixed conducting multicomponent metallic oxide (MCMO) layer contiguous with a first side of a dense layer of MCMO and (2) a second side of the dense MCMO layer. In another embodiment, these steps are carried out in the alternative order of (a), (d), (b), and (c).

Time-dependent heat transfer in the spherical Earth: Implications on the power and thermal evolution of the core

NASA Astrophysics Data System (ADS)

Hofmeister, A. M.; Criss, R. E.

2015-12-01

We quantitatively investigate the time-dependence of heat conduction for a post-core, spherical Earth that is not convecting, due to compositional layering, based on hundreds of measurements of thermal diffusivity (D) for insulators and metals. Consistency of our solutions for widely ranging input parameters indicates how additional heat transfer mechanisms (mantle magmatism and convection) affect thermal evolution of the core. We consider 1) interior starting temperatures (T) of 273-5000 K, which represent variations in primordial heat, 2) different distributions and decay of long-lived radioactive isotopes, 3) additional heat sources in the core (primordial or latent heat), and 4) variable depth-T dependence of D. Our new analytical solution for cooling of a constant D sphere validates our numerical results. The bottom line is that the thermally insulating nature of minerals, combined with constraints of spherical geometry, limits steep thermal gradients to the upper mantle, consistent with the short length scale (x ~700 km) of cooling over t = 4.5 Ga indicated by dimensional analysis [x2 ~ 4Dt], and with plate tectonics. Consequently, interior temperatures vary little so the core has remained hot and is possibly warming. Findings include: 1) Constant vs. variable D affects thermal profiles only in detail, with D for the metallic core being inconsequential. 2) The hottest zone in Earth may lie in the uppermost lower mantle; 3) Most radiogenic heat is released in Earth's outermost 1000 km thereby driving an active outer shell; 4) Earth's core is essentially isothermal and is thus best described by the liquid-solid phase boundary; 5) Deeply sequestered radioactivity or other heat will melt the core rather than by run the dynamo (note that the heat needed to have melted the outer core is 10% of radiogenic heat generated over Earth's history); 6) Inefficient cooling of an Earth-sized mass means that heat essentially remains where it is generated, until it is removed by magmatism; 7) Importantly, the observed plate velocities are consistent with a Nusselt number of 1, i.e. the present day cooling is essentially conductive. Conductive cooling plus magmatism largely governs Earth's thermal structure and dynamics, below a unicellular upper mantle. Core dynamics and magnetism are likely driven by rotational effects.

Femtosecond Heterodyne Transient Grating Detection of Conformational Dynamics in the S0 (11Ag-) State of Carotenoids After Nonradiative Decay of the S2 (11Bu+) State

NASA Astrophysics Data System (ADS)

Roscioli, Jerome D.; Ghosh, Soumen; Bishop, Michael M.; Lafountain, Amy M.; Frank, Harry A.; Beck, Warren F.

Transient grating spectroscopy was used to study the dynamics of nonradiative decay of the S1 (21Ag-) state in ß-carotene and peridinin after optical preparation of the S2) state. The kinetics of the recovery of the absorption and dispersion components of the third-order signal exhibit significantly different time constants. For β-carotene in benzonitrile, the absorption and dispersion recovery time constants are 11.6 and 10.2 ps. For peridinin in methanol, the time constants are 9.9 and 7.4 ps. These results indicate that the initial product of the decay of the S1 state is a conformationally displaced structure. The decay rate for the S1 state and the conformational relaxation rate are both slowed in peridinin as the polarity of the solvent decreases; in ethyl acetate, the conformational relaxation time constant is 45 ps, which rules out a dominant contribution from vibrational cooling. These results indicate that the S1 state develops intramolecular charge transfer character owing to distortions along torsional and out-of-plane coordinates, with a pyramidal structure favored as the most stable conformation. Recovery of the photoselected ground state conformation involves a reverse charge-transfer event followed by relaxation to a planar structure. Work supported by Photosynthetic Systems Program of the U.S. Department of Energy under Grant DE-SC0010847.

The cooling time of fertile chicken eggs at different stages of incubation.

PubMed

Mortola, Jacopo P; Gaonac'h-Lovejoy, Vanda

2016-01-01

We asked whether or not the thermal characteristics of fertile avian eggs changed throughout incubation. The cooling and warming times, expressed by the time constant τ of the egg temperature response to a rapid change in ambient temperature, were measured in fertile chicken eggs at early (E7), intermediate (E11) and late (E20) stages of embryonic development. Same measurements were conducted on eggs emptied of their content and refilled with water by various amounts. The results indicated that (1) the τ of a freshly laid egg was ~50 min; (2) τ decreased linearly with the drop in egg water volume; (3) the dry eggshell had almost no thermal resistance but its wet inner membrane contributed about one-third to the stability of egg temperature; (4) the egg constituents (yolk, albumen and embryonic tissues) and the chorioallantoic circulation had no measurable effect on τ; (5) the presence of an air pocket equivalent in volume to the air cell of fertile eggs reduced τ by about 3 min (E7), 5 min (E11) and 11 min (E20). Hence, in response to warming the egg τ at E20 was slightly shorter than at E7. In response to cooling, the egg τ at E20 was similar to, or longer than, E7 because embryonic thermogenesis (evaluated by measurements of oxygen consumption during cold) offset the reduction in τ introduced by the air cell. In conclusion, until the onset of thermogenesis the thermal behavior of a fertile egg is closely approximated by that of a water-filled egg with an air volume equivalent to the air cell. It is possible to estimate the cooling τ of avian eggs of different species from their weight and incubation time. Copyright © 2015 Elsevier Ltd. All rights reserved.

Enhanced heat transport during phase separation of liquid binary mixtures

NASA Astrophysics Data System (ADS)

Molin, Dafne; Mauri, Roberto

2007-07-01

We show that heat transfer in regular binary fluids is enhanced by induced convection during phase separation. The motion of binary mixtures is simulated using the diffuse interface model, where convection and diffusion are coupled via a nonequilibrium, reversible Korteweg body force. Assuming that the mixture is regular, i.e., its components are van der Waals fluids, we show that the two parameters that describe the mixture, namely the Margules constant and the interfacial thickness, depend on temperature as T-1 and T-1/2, respectively. Two quantities are used to measure heat transfer, namely the heat flux at the walls and the characteristic cooling time. Comparing these quantities with those of very viscous mixtures, where diffusion prevails over convection, we saw that the ratio between heat fluxes, which defines the Nusselt number, NNu, equals that between cooling times and remains almost constant in time. The Nusselt number depends on the following: the Peclet number, NPe, expressing the ratio between convective and diffusive mass fluxes; the Lewis number, NLe, expressing the ratio between thermal and mass diffusivities; the specific heat of the mixture, as it determines how the heat generated by mixing can be stored within the system; and the quenching depth, defined as the distance of the temperature at the wall from its critical value. In particular, the following results were obtained: (a) The Nusselt number grows monotonically with the Peclet number until it reaches an asymptotic value at NNu≈2 when NPe≈106; (b) the Nusselt number increases with NLe when NLe<1, remains constant at 11; (c) the Nusselt number is hardly influenced by the specific heat; (d) the Nusselt number decreases as the quenching rate increases. All these results can be explained by physical considerations. Predictably, considering that convection is within the creeping flow regime, the Nusselt number is always of o(10).

Low temperature ion source for calutrons

DOEpatents

Veach, Allen M.; Bell, Jr., William A.; Howell, Jr., George D.

1981-01-01

A new ion source assembly for calutrons has been provided for the efficient separation of elements having high vapor pressures. The strategic location of cooling pads and improved insulation permits operation of the source at lower temperatures. A vapor valve constructed of graphite and located in a constantly increasing temperature gradient provides reliable control of the vapor flow from the charge bottle to the arc chamber. A pronounced saving in calutron operating time and equipment maintenance has been achieved with the use of the present ion source.

Low temperature ion source for calutrons

DOEpatents

Veach, A.M.; Bell, W.A. Jr.; Howell, G.D. Jr.

1979-10-10

A new ion source assembly for calutrons has been provided for the efficient separation of elements having high vapor pressures. The strategic location of cooling pads and improved insulation permits operation of the source at lower temperatures. A vapor valve constructed of graphite and located in a constantly increasing temperature gradient provides reliable control of the vapor flow from the charge bottle to the arc chamber. A pronounced saving in calutron operating time and equipment maintenance has been achieved with the use of the present ion source.

Transformations of Supercooled Austenite in a Promising High-Strength Steel Grade Under Continuous Cooling Conditions

NASA Astrophysics Data System (ADS)

Maisuradze, M. V.; Ryzhkov, M. A.; Yudin, Yu. V.; Kuklina, A. A.

2017-11-01

Special features of the transformations of supercooled austenite occurring under continuous cooling of a promising high-strength steel grade not standardized in the Russian Federation are determined. A method for evaluating the volume fractions of structure constituents formed in the steel as a result of cooling from 925°C at various constant rates within 0.025 - 75 K/sec is proposed and tested. The results are generalized in the form of a thermokinetic diagram of transformations of supercooled austenite.

Performance and Thrust-to-Weight Optimization of the Dual-Expander Aerospike Nozzle Upper Stage Rocket Engine

DTIC Science & Technology

2012-06-01

calculates a constant convection heat transfer coefficient on the hot and cold side of the cooling jacket wall. The calculated maximum wall temperature for...regeneratively cools the combustion chamber and nozzle. The heat transferred to the fuel from cooling provides enough power to the turbine to power both... heat transfer at the throat compared to a bell nozzle. This increase in heat transfer surface area means more power to the turbine, increased chamber

Time-resolved x-ray diffraction and calorimetric studies at low scan rates

PubMed Central

Yao, Haruhiko; Hatta, Ichiro; Koynova, Rumiana; Tenchov, Boris

1992-01-01

The phase transitions of dipalmitoylphosphatidylethanolamine (DPPE) in excess water have been examined by low-angle time-resolved x-ray diffraction and calorimetry at low scan rates. The lamellar subgel/lamellar liquid-crystalline (Lc → Lα), lamellar gel/lamellar liquid-crystalline (Lβ → Lα), and lamellar liquid-crystalline/lamellar gel (Lα → Lβ) phase transitions proceed via coexistence of the initial and final phases with no detectable intermediates at scan rates 0.1 and 0.5°C/min. At constant temperature within the region of the Lβ → Lα transition the ratio of the two coexisting phases was found to be stable for over 30 min. The state of stable phase coexistence was preceded by a 150-s relaxation taking place at constant temperature after termination of the heating scan in the transition region. While no intermediate structures were present in the coexistence region, a well reproducible multipeak pattern, with at least four prominent heat capacity peaks separated in temperature by 0.4-0.5°C, has been observed in the cooling transition (Lα → Lβ) by calorimetry. The multipeak pattern became distinct with an increase of incubation time in the liquid-crystalline phase. It was also clearly resolved in the x-ray diffraction intensity versus temperature plots recorded at slow cooling rates. These data suggest that the equilibrium state of the Lα phase of hydrated DPPE is represented by a mixture of domains that differ in thermal behavior, but cannot be distinguished structurally by x-ray scattering. Imagesp689-aFIGURE 9 PMID:19431820

Diffusion of neon in white dwarf stars.

PubMed

Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K

2010-12-01

Sedimentation of the neutron rich isotope 22Ne may be an important source of gravitational energy during the cooling of white dwarf stars. This depends on the diffusion constant for 22Ne in strongly coupled plasma mixtures. We calculate self-diffusion constants D(i) from molecular dynamics simulations of carbon, oxygen, and neon mixtures. We find that D(i) in a mixture does not differ greatly from earlier one component plasma results. For strong coupling (coulomb parameter Γ> few), D(i) has a modest dependence on the charge Z(i) of the ion species, D(i)∝Z(i)(-2/3). However, D(i) depends more strongly on Z(i) for weak coupling (smaller Γ). We conclude that the self-diffusion constant D(Ne) for 22Ne in carbon, oxygen, and neon plasma mixtures is accurately known so that uncertainties in D(Ne) should be unimportant for simulations of white dwarf cooling.

[Determination of benzo(alpha)pyrene in food with microwave-assisted extraction].

PubMed

Zhou, Na; Luo, He-Dong; Li, Na; Li, Yao-Qun

2014-03-01

Coupling derivative technique and constant-energy synchronous fluorescence scanning technique, a method of determining benzo[alpha] pyrene in foods by second derivative constant-energy synchronous spectrofluorimetry after microwave-assisted treatment of samples was established using domestic microwave oven. The main factors of influencing the efficiency of microwave extraction were discussed, including the extraction solvent types and amounts, the microwave extraction time, microwave radiation power and cooling time. And the comparison with ultrasonic extraction was made. Low-fat food samples, which were just microwave-extracted with mixed-solvents, could be analyzed immediately by the spectrofluorimetric technique. For high-fat food samples, microwave-assisted saponification and extraction were made at the same time, thus simplifying operation steps and reducing sample analysis time. So the whole sample analysis process could be completed within one hour. This method was simple, rapid and inexpensive. In consequence, it was applied to determine benzo(a)pyrene in food with good reproducibility and the recoveries of benzo(alpha) pyrene ranged from 90.0% to 105.0% for the low fat samples and 83.3% to 94.6% for high-fat samples.

Jet-cooled laser-induced fluorescence spectroscopy of cyclohexoxy: rotational and fine structure of molecules in nearly degenerate electronic States.

PubMed

Liu, Jinjun; Miller, Terry A

2014-12-26

The rotational structure of the previously observed B̃(2)A' ← X̃(2)A″ and B̃(2)A' ← Ã(2)A' laser-induced fluorescence spectra of jet-cooled cyclohexoxy radical (c-C6H11O) [ Zu, L.; Liu, J.; Tarczay, G.; Dupré, P; Miller, T. A. Jet-cooled laser spectroscopy of the cyclohexoxy radical. J. Chem. Phys. 2004 , 120 , 10579 ] has been analyzed and simulated using a spectroscopic model that includes the coupling between the nearly degenerate X̃ and à states separated by ΔE. The rotational and fine structure of these two states is reproduced by a 2-fold model using one set of molecular constants including rotational constants, spin-rotation constants (ε's), the Coriolis constant (Aζt), the quenched spin-orbit constant (aζed), and the vibronic energy separation between the two states (ΔE0). The energy level structure of both states can also be reproduced using an isolated-state asymmetric top model with rotational constants and effective spin-rotation constants (ε's) and without involving Coriolis and spin-orbit constants. However, the spin-orbit interaction introduces transitions that have no intensity using the isolated-state model but appear in the observed spectra. The line intensities are well simulated using the 2-fold model with an out-of-plane (b-) transition dipole moment for the B̃ ← X̃ transitions and in-plane (a and c) transition dipole moment for the B̃ ← à transitions, requiring the symmetry for the X̃ (Ã) state to be A″ (A'), which is consistent with a previous determination and opposite to that of isopropoxy, the smallest secondary alkoxy radical. The experimentally determined Ã-X̃ separation and the energy level ordering of these two states with different (A' and A″) symmetries are consistent with quantum chemical calculations. The 2-fold model also enables the independent determination of the two contributions to the Ã-X̃ separation: the relativistic spin-orbit interaction (magnetic effect) and the nonrelativistic vibronic separation between the lowest vibrational energy levels of these two states due to both electrostatic interaction (Coulombic effect) and difference in zero-point energies (kinetic effect).

Influence of the cooling method on the structure of 55AlZn coatings

NASA Astrophysics Data System (ADS)

Mendala, J.

2011-05-01

In metallization processes, metals or metal alloys are used which have a low melting point and good anticorrosion properties. Moreover, they must form durable intermetallic compounds with iron or its alloys. The most common hot-dip metallization technology involves galvanizing, however, molten multi-component metal alloys are used as well. An addition of aluminium to the zinc bath causes an increase in corrosion resistance of the obtained coatings. The article presents results of tests of obtaining coatings by the batch hot-dip method in an 55AlZn bath. Kinetics of the coating growth in the tested alloys were determined in the changeable conditions of bath temperature, dip time and type of cooling. The structure of coatings and their phase composition were revealed. As a result of the tests performed, it has been found that an increase in total thickness of the coatings as a function of the dipping time at a constant temperature is almost of a parabolic nature, whereas an increase in the transient layer is of a linear nature. The structure was identified by the XRD analysis and the morphology of the coatings was tested by means of SEM. It has been found that the cooling process with the use of higher rates of cooling causes a size reduction of the structure in the outer layer and a reduction of thickness of both the intermediate diffusion layer and the whole coating by ca. 25 %.

Wet cooling towers: rule-of-thumb design and simulation

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

Leeper, Stephen A.

1981-07-01

A survey of wet cooling tower literature was performed to develop a simplified method of cooling tower design and simulation for use in power plant cycle optimization. The theory of heat exchange in wet cooling towers is briefly summarized. The Merkel equation (the fundamental equation of heat transfer in wet cooling towers) is presented and discussed. The cooling tower fill constant (Ka) is defined and values derived. A rule-of-thumb method for the optimized design of cooling towers is presented. The rule-of-thumb design method provides information useful in power plant cycle optimization, including tower dimensions, water consumption rate, exit air temperature,more » power requirements and construction cost. In addition, a method for simulation of cooling tower performance at various operating conditions is presented. This information is also useful in power plant cycle evaluation. Using the information presented, it will be possible to incorporate wet cooling tower design and simulation into a procedure to evaluate and optimize power plant cycles.« less

Ultrasensitive detection of nitric oxide at 5.33 μm by using external cavity quantum cascade laser-based Faraday rotation spectroscopy

PubMed Central

Lewicki, Rafał; Doty, James H.; Curl, Robert F.; Tittel, Frank K.; Wysocki, Gerard

2009-01-01

A transportable prototype Faraday rotation spectroscopic system based on a tunable external cavity quantum cascade laser has been developed for ultrasensitive detection of nitric oxide (NO). A broadly tunable laser source allows targeting the optimum Q3/2(3/2) molecular transition at 1875.81 cm−1 of the NO fundamental band. For an active optical path of 44 cm and 1-s lock-in time constant minimum NO detection limits (1σ) of 4.3 parts per billion by volume (ppbv) and 0.38 ppbv are obtained by using a thermoelectrically cooled mercury–cadmium–telluride photodetector and liquid nitrogen-cooled indium–antimonide photodetector, respectively. Laboratory performance evaluation and results of continuous, unattended monitoring of atmospheric NO concentration levels are reported. PMID:19625625

Heat-transfer tests of aqueous ethylene glycol solutions in an electrically heated tube

NASA Technical Reports Server (NTRS)

Bernardo, Everett; Eian, Carroll S

1945-01-01

As part of an investigation of the cooling characteristics of liquid-cooled engines, tests were conducted with an electrically heated single-tube heat exchanger to determine the heat-transfer characteristics of an-e-2 ethylene glycol and other ethylene glycol-water mixtures. Similar tests were conducted with water and commercial butanol (n-butyl alcohol) for check purposes. The results of tests conducted at an approximately constant liquid-flow rate of 0.67 pound per second (Reynolds number, 14,500 to 112,500) indicate that at an average liquid temperature 200 degrees f, the heat-transfer coefficients obtained using water, nominal (by volume) 30 percent-70 percent and 70 percent-30 percent glycol-water mixtures are approximately 3.8, 2.8, and 1.4 times higher, respectively, than the heat-transfer coefficients obtained using an-e-2 ethylene glycol.

Optical-spectrum-synthesizer design within an all-optical semiconductor gate to reduce waveform distortion induced by carrier-cooling relaxation at sub-Teraherz frequencies

NASA Astrophysics Data System (ADS)

Ueno, Yoshiyasu; Nakamoto, Ryouichi; Sakaguchi, Jun; Suzuki, Rei

2006-12-01

In frequency ranges above 200-300 GHz, the second slowest relaxation in the optical response (such as carrier-cooling relaxation having a time constant of 1-2 ps) of a semiconductor optical amplifier inside the conventional delayed-interference signal-wavelength converter (DISC) scheme is thought to start the distortion of all-optically gated waveforms. In this work, we design a digital optical-spectrum-synthesizer block that is part of the expanded DISC scheme. Our numerically calculated spectra, waveforms, and eye diagrams with assumed pseudorandom digital data pulses indicate that this synthesizer significantly removes strong distortion from the gated waveforms. A signal-to-noise ratio of 20 dB was obtained from our random-data eye diagram, providing proof of effectiveness in principle.

Analytical and numerical study on cooling flow field designs performance of PEM fuel cell with variable heat flux

NASA Astrophysics Data System (ADS)

Afshari, Ebrahim; Ziaei-Rad, Masoud; Jahantigh, Nabi

2016-06-01

In PEM fuel cells, during electrochemical generation of electricity more than half of the chemical energy of hydrogen is converted to heat. This heat of reactions, if not exhausted properly, would impair the performance and durability of the cell. In general, large scale PEM fuel cells are cooled by liquid water that circulates through coolant flow channels formed in bipolar plates or in dedicated cooling plates. In this paper, a numerical method has been presented to study cooling and temperature distribution of a polymer membrane fuel cell stack. The heat flux on the cooling plate is variable. A three-dimensional model of fluid flow and heat transfer in cooling plates with 15 cm × 15 cm square area is considered and the performances of four different coolant flow field designs, parallel field and serpentine fields are compared in terms of maximum surface temperature, temperature uniformity and pressure drop characteristics. By comparing the results in two cases, the constant and variable heat flux, it is observed that applying constant heat flux instead of variable heat flux which is actually occurring in the fuel cells is not an accurate assumption. The numerical results indicated that the straight flow field model has temperature uniformity index and almost the same temperature difference with the serpentine models, while its pressure drop is less than all of the serpentine models. Another important advantage of this model is the much easier design and building than the spiral models.

Optimization of cooling strategy and seeding by FBRM analysis of batch crystallization

NASA Astrophysics Data System (ADS)

Zhang, Dejiang; Liu, Lande; Xu, Shijie; Du, Shichao; Dong, Weibing; Gong, Junbo

2018-03-01

A method is presented for optimizing the cooling strategy and seed loading simultaneously. Focused beam reflectance measurement (FBRM) was used to determine the approximating optimal cooling profile. Using these results in conjunction with constant growth rate assumption, modified Mullin-Nyvlt trajectory could be calculated. This trajectory could suppress secondary nucleation and has the potential to control product's polymorph distribution. Comparing with linear and two step cooling, modified Mullin-Nyvlt trajectory have a larger size distribution and a better morphology. Based on the calculating results, the optimized seed loading policy was also developed. This policy could be useful for guiding the batch crystallization process.

Towards Laser Cooling Trapped Ions with Telecom Light

NASA Astrophysics Data System (ADS)

Dungan, Kristina; Becker, Patrick; Donoghue, Liz; Liu, Jackie; Olmschenk, Steven

2015-05-01

Quantum information has many potential applications in communication, atomic clocks, and the precision measurement of fundamental constants. Trapped ions are excellent candidates for applications in quantum information because of their isolation from external perturbations, and the precise control afforded by laser cooling and manipulation of the quantum state. For many applications in quantum communication, it would be advantageous to interface ions with telecom light. We present progress towards laser cooling and trapping of doubly-ionized lanthanum, which should require only infrared, telecom-compatible light. Additionally, we present progress on optimization of a second-harmonic generation cavity for laser cooling and trapping barium ions, for future sympathetic cooling experiments. This research is supported by the Army Research Office, Research Corporation for Science Advancement, and Denison University.

Effects of wind application on thermal perception and self-paced performance.

PubMed

Teunissen, L P J; de Haan, A; de Koning, J J; Daanen, H A M

2013-07-01

Physiological and perceptual effects of wind cooling are often intertwined and have scarcely been studied in self-paced exercise. Therefore, we aimed to investigate (1) the independent perceptual effect of wind cooling and its impact on performance and (2) the responses to temporary wind cooling during self-paced exercise. Ten male subjects completed four trials involving 15 min standardized incremental intensity cycling, followed by a 15-km self-paced cycling time trial. Three trials were performed in different climates inducing equivalent thermal strain: hot humid with wind (WIND) and warm humid (HUMID) and hot dry (DRY) without wind. The fourth trial (W3-12) was equal to HUMID, except that wind cooling was unexpectedly provided during kilometers 3-12. Physiological, perceptual and performance parameters were measured. Subjects felt generally cooler during the WIND than the HUMID and DRY trials, despite similar heart rate, rectal and skin temperatures and a WBGT of ~4 °C higher. The cooler thermal sensation was not reflected in differences in thermal comfort or performance. Comparing W3-12 to HUMID, skin temperature was 1.47 ± 0.43 °C lower during the wind interval, leading to more favorable ratings of perceived exertion, thermal sensation and thermal comfort. Overall, power output was higher in the W3-12 than the HUMID-trial (256 ± 29 vs. 246 ± 22 W), leading to a 67 ± 48 s faster finish time. In conclusion, during self-paced exercise in the heat, wind provides immediate and constant benefits in physiological strain, thermal perception and performance. Independent of physiological changes, wind still provides a greater sensation of coolness, but does not impact thermal comfort or performance.

Possible Economies in Air-Conditioning by Accepting Temperature Swings.

ERIC Educational Resources Information Center

Loudon, A. G.; Petherbridge, P.

Public building air conditioning systems, which use constant and varying heat and cooling loads, are compared and investigated. Experiments indicated that constant temperature controls based on outside air temperature alone were inefficient. Ventilating a building with outside air and the methods of doing so are cited as being the most economical…

Verification and rectification of the physical analogy of simulated annealing for the solution of the traveling salesman problem.

PubMed

Hasegawa, M

2011-03-01

The aim of the present study is to elucidate how simulated annealing (SA) works in its finite-time implementation by starting from the verification of its conventional optimization scenario based on equilibrium statistical mechanics. Two and one supplementary experiments, the design of which is inspired by concepts and methods developed for studies on liquid and glass, are performed on two types of random traveling salesman problems. In the first experiment, a newly parameterized temperature schedule is introduced to simulate a quasistatic process along the scenario and a parametric study is conducted to investigate the optimization characteristics of this adaptive cooling. In the second experiment, the search trajectory of the Metropolis algorithm (constant-temperature SA) is analyzed in the landscape paradigm in the hope of drawing a precise physical analogy by comparison with the corresponding dynamics of glass-forming molecular systems. These two experiments indicate that the effectiveness of finite-time SA comes not from equilibrium sampling at low temperature but from downward interbasin dynamics occurring before equilibrium. These dynamics work most effectively at an intermediate temperature varying with the total search time and thus this effective temperature is identified using the Deborah number. To test directly the role of these relaxation dynamics in the process of cooling, a supplementary experiment is performed using another parameterized temperature schedule with a piecewise variable cooling rate and the effect of this biased cooling is examined systematically. The results show that the optimization performance is not only dependent on but also sensitive to cooling in the vicinity of the above effec-tive temperature and that this feature is interpreted as a consequence of the presence or absence of the workable interbasin dynamics. It is confirmed for the present instances that the effectiveness of finite-time SA derives from the glassy relaxation dynamics occurring in the "landscape-influenced" temperature regime and that its naive optimization scenario should be rectified by considering the analogy with vitrification phenomena. A comprehensive guideline for the design of finite-time SA and SA-related algorithms is discussed on the basis of this rectified analogy.

Low field magnetocaloric effect in bulk and ribbon alloy La(Fe0.88Si0.12)13

NASA Astrophysics Data System (ADS)

Vuong, Van-Hiep; Do-Thi, Kim-Anh; Nguyen, Duy-Thien; Nguyen, Quang-Hoa; Hoang, Nam-Nhat

2018-03-01

Low-field magnetocaloric effect occurred in itinerant metamagnetic materials is at core for magnetic cooling application. This works reports the magnetocaloric responses obtained at 1.35 T for the silicon-doped iron-based binary alloy La(Fe0.88Si0.12)13 in the bulk and ribbon form. Both samples possess a same symmetry but with different crystallite sizes and lattice parameters. The ribbon sample shows a larger maximum entropy change (nearly 8.5 times larger) and a higher Curie temperature (5 K higher) in comparison with that of the bulk sample. The obtained relative cooling power for the ribbon is also larger and very promising for application (RCP = 153 J/kg versus 25.2 J/kg for the bulk). The origin of the effect observed is assigned to the occurrence of negative magnetovolume effect in the ribbon structure with limit crystallization, caused by rapid cooling process at the preparation, which induced smaller crystallite size and large lattice constant at the overall weaker local crystal field.

Lessons learned from twenty-year operation of the Large Helical Device poloidal coils made from cable-in-conduit conductors

NASA Astrophysics Data System (ADS)

Takahata, Kazuya; Moriuchi, Sadatomo; Ooba, Kouki; Takami, Shigeyuki; Iwamoto, Akifumi; Mito, Toshiyuki; Imagawa, Shinsaku

2018-04-01

The Large Helical Device (LHD) superconducting magnet system consists of two pairs of helical coils and three pairs of poloidal coils. The poloidal coils use cable-in-conduit (CIC) conductors, which have now been adopted in many fusion devices, with forced cooling by supercritical helium. The poloidal coils were first energized with the helical coils on March 27, 1998. Since that time, the coils have experienced 54,600 h of steady cooling, 10,600 h of excitation operation, and nineteen thermal cycles for twenty years. During this period, no superconducting-to-normal transition of the conductors has been observed. The stable operation of the poloidal coils demonstrates that a CIC conductor is suited to large-scale superconducting magnets. The AC loss has remained constant, even though a slight decrease was observed in the early phase of operation. The hydraulic characteristics have been maintained without obstruction over the entire period of steady cooling. The experience gained from twenty years of operation has also provided lessons regarding malfunctions of peripheral equipment.

Shock Corrugation by Rayleigh-Taylor Instability in Gamma-Ray Burst Afterglow Jets

NASA Astrophysics Data System (ADS)

Duffell, Paul C.; MacFadyen, Andrew I.

2014-08-01

Afterglow jets are Rayleigh-Taylor unstable and therefore turbulent during the early part of their deceleration. There are also several processes which actively cool the jet. In this Letter, we demonstrate that if cooling significantly increases the compressibility of the flow, the turbulence collides with the forward shock, destabilizing and corrugating it. In this case, the forward shock is turbulent enough to produce the magnetic fields responsible for synchrotron emission via small-scale turbulent dynamo. We calculate light curves assuming the magnetic field is in energy equipartition with the turbulent kinetic energy and discover that dynamic magnetic fields are well approximated by a constant magnetic-to-thermal energy ratio of 1%, though there is a sizeable delay in the time of peak flux as the magnetic field turns on only after the turbulence has activated. The reverse shock is found to be significantly more magnetized than the forward shock, with a magnetic-to-thermal energy ratio of the order of 10%. This work motivates future Rayleigh-Taylor calculations using more physical cooling models.

The Henry's constant of monochloramine.

PubMed

Garcia, Miguel A; Anderson, Michael A

2018-02-01

Monochloramine is a secondary disinfectant used in drinking water and is also formed in chlorinated wastewater. While known to hydrolyze over time and react with dissolved organic matter, its partitioning between the aqueous and gas phase has not been extensively studied. Preliminary experiments demonstrated that monochloramine concentrations in solutions open to the atmosphere or actively aerated decreased more rapidly than in sealed solutions, indicating significant losses to the atmosphere. For example, a monochloramine solution open to the atmosphere yielded a loss rate constant of 0.08 d -1 , a value twice that for sealed samples without headspace (0.04 d -1 ) where loss occurs exclusively as a result of hydrolysis. A solution aerated at 10 mL s -1 had a loss rate constant nearly 10× greater than that for hydrolysis alone (0.35 d -1 ). To better understand partitioning of monochloramine to the gas phase and potential for volatilization, the dimensionless Henry's law constants of monochloramine (K H ) were determined using an equilibrium headspace technique at five different temperatures (11, 16, 21, 27, and 32 °C). The resulting values ranged from 8 × 10 -3 to 4 × 10 -2 , indicating a semi-volatile compound, and were found to be consistent with quantitative structure activity relationship predictions. At 20 °C, monochloramine exhibits a dimensionless Henry's constant of about 1.7 × 10 -2 which is 35 times greater than ammonia but comparable to the Henry's constant of inorganic semi-volatile compounds such sulfur dioxide. The Henry's constant values for monochloramine suggests that volatilization could be a relevant loss process in open systems such as rivers receiving chlorinated wastewater effluent, swimming pools and cooling towers. Copyright © 2017 Elsevier Ltd. All rights reserved.

Multiverse understanding of cosmological coincidences

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

Bousso, Raphael; Hall, Lawrence J.; Nomura, Yasunori

2009-09-15

There is a deep cosmological mystery: although dependent on very different underlying physics, the time scales of structure formation, of galaxy cooling (both radiatively and against the CMB), and of vacuum domination do not differ by many orders of magnitude, but are all comparable to the present age of the universe. By scanning four landscape parameters simultaneously, we show that this quadruple coincidence is resolved. We assume only that the statistical distribution of parameter values in the multiverse grows towards certain catastrophic boundaries we identify, across which there are drastic regime changes. We find order-of-magnitude predictions for the cosmological constant,more » the primordial density contrast, the temperature at matter-radiation equality, the typical galaxy mass, and the age of the universe, in terms of the fine structure constant and the electron, proton and Planck masses. Our approach permits a systematic evaluation of measure proposals; with the causal patch measure, we find no runaway of the primordial density contrast and the cosmological constant to large values.« less

Detonation in TATB Hemispheres

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

Druce, B; Souers, P C; Chow, C

2004-03-17

Streak camera breakout and Fabry-Perot interferometer data have been taken on the outer surface of 1.80 g/cm{sup 3} TATB hemispherical boosters initiated by slapper detonators at three temperatures. The slapper causes breakout to occur at 54{sup o} at ambient temperatures and 42{sup o} at -54 C, where the axis of rotation is 0{sup o}. The Fabry velocities may be associated with pressures, and these decrease for large timing delays in breakout seen at the colder temperatures. At room temperature, the Fabry pressures appear constant at all angles. Both fresh and decade-old explosive are tested and no difference is seen. Themore » problem has been modeled with reactive flow. Adjustment of the JWL for temperature makes little difference, but cooling to -54 C decreases the rate constant by 1/6th. The problem was run both at constant density and with density differences using two different codes. The ambient code results show that a density difference is probably there but it cannot be quantified.« less

DESIGN OF A SIMPLE SLOW COOLING DEVICE FOR CRYOPRESERVATION OF SMALL BIOLOGICAL SAMPLES.

PubMed

de Paz, Leonardo Juan; Robert, Maria Celeste; Graf, Daniel Adolfo; Guibert, Edgardo Elvio; Rodriguez, Joaquin Valentin

2015-01-01

Slow cooling is a cryopreservation methodology where samples are cooled to its storage temperature at controlled cooling rates. Design, construction and evaluation of a simple and low cost device for slow cooling of small biological samples. The device was constructed based on Pye's freezer idea. A Dewar flask filled with liquid nitrogen was used as heat sink and a methanol bath containing the sample was cooled at constant rates using copper bars as heat conductor. Sample temperature may be lowered at controlled cooling rate (ranging from 0.4°C/min to 6.0°C/min) down to ~-60°C, where it could be conserved at lower temperatures. An example involving the cryopreservation of Neuro-2A cell line showed a marked influence of cooling rate over post preservation cell viability with optimal values between 2.6 and 4.6°C/min. The cooling device proved to be a valuable alternative to more expensive systems allowing the assessment of different cooling rates to evaluate the optimal condition for cryopreservation of such samples.

Dynamic PID loop control

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

Pei, L.; Klebaner, A.; Theilacker, J.

2011-06-01

The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight 9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic control system, how to hold liquid level constant in the cryostat by regulation of its Joule-Thompson JT-valve is very important after cryostat cool down to 2.0 K. The 72-cell cryostat liquid level response generally takes a long time delay after regulating its JT-valve; therefore, typical PID control loop should result in some cryostat parameter oscillations. This paper presents a type of PID parameter self-optimal and Time-Delay control method used to reduce cryogenic system parameters oscillation.

Ultrafast carrier dynamics in a GaN/Al 0.18Ga0.82N superlattice

NASA Astrophysics Data System (ADS)

Mahler, Felix; Tomm, Jens W.; Reimann, Klaus; Woerner, Michael; Elsaesser, Thomas; Flytzanis, Christos; Hoffmann, Veit; Weyers, Markus

2018-04-01

Relaxation processes of photoexcited carriers in a GaN /Al0.18Ga0.82N superlattice are studied in femtosecond spectrally resolved reflectivity measurements at ambient temperature. The transient reflectivity reveals electron trapping into defect states close to the conduction-band minimum with a 150-200 fs time constant, followed by few-picosecond carrier cooling. A second slower trapping process into a different manifold of defect states is observed on a time scale of approximately 10 ps. Our results establish the prominent role of structural defects and disorder for ultrafast carrier dynamics in nitride semiconductor structures.

Warpage minimization on wheel caster by optimizing process parameters using response surface methodology (RSM)

NASA Astrophysics Data System (ADS)

Safuan, N. S.; Fathullah, M.; Shayfull, Z.; Nasir, S. M.; Hazwan, M. H. M.

2017-09-01

In injection moulding process, it is important to keep the productivity increase constantly with least of waste produced such as warpage defect. Thus, this study is concerning on minimizing warpage defect on wheel caster part. Apart from eliminating product wastes, this project also giving out best optimization techniques using response surface methodology. This research studied on five parameters A-packing pressure, B-packing time, C-mold temperature, D-melting temperature and E-cooling time. The optimization showed that packing pressure is the most significant parameter. Warpage have been improved 42.64% from 0.6524 mm to 0.3742mm.

Efficient radiative transfer techniques in hydrodynamic simulations

NASA Astrophysics Data System (ADS)

Mercer, A.; Stamatellos, D.; Dunhill, A.

2018-05-01

Radiative transfer is an important component of hydrodynamic simulations as it determines the thermal properties of a physical system. It is especially important in cases where heating and cooling regulate significant processes, such as in the collapse of molecular clouds, the development of gravitational instabilities in protostellar discs, disc-planet interactions, and planet migration. We compare two approximate radiative transfer methods which indirectly estimate optical depths within hydrodynamic simulations using two different metrics: (i) the gravitational potential and density of the gas (Stamatellos et al.), and (ii) the pressure scale-height (Lombardi et al.). We find that both methods are accurate for spherical configurations e.g. in collapsing molecular clouds and within clumps that form in protostellar discs. However, the pressure scale-height approach is more accurate in protostellar discs (low and high-mass discs, discs with spiral features, discs with embedded planets). We also investigate the β-cooling approximation which is commonly used when simulating protostellar discs, and in which the cooling time is proportional to the orbital period of the gas. We demonstrate that the use of a constant β cannot capture the wide range of spatial and temporal variations of cooling in protostellar discs, which may affect the development of gravitational instabilities, planet migration, planet mass growth, and the orbital properties of planets.

On numerical heat transfer characteristic study of flat surface subjected to variation in geometric thickness

NASA Astrophysics Data System (ADS)

Umair, Siddique Mohammed; Kolawale, Abhijeet Rangnath; Bhise, Ganesh Anurath; Gulhane, Nitin Parashram

Thermal management in the looming world of electronic packaging system is the most prior and conspicuous issue as far as the working efficiency of the system is concerned. The cooling in such systems can be achieved by impinging air jet over the heat sink as jet impingement cooling is one of the cooling technologies which are widely studied now. Here the modulation in impinging and geometric parameters results in the establishment of the characteristic cooling rate over the target surface. The characteristic cooling curve actually resembles non-uniformity in cooling rate. This non-uniformity favors the area average heat dissipation rate. In order to study the non-uniformity in cooling characteristic, the present study takes an initiative in plotting the local Nusselt number magnitude against the non-dimensional radial distance of the different thickness of target surfaces. For this, the steady temperature distribution over the target surface under the impingement of air jet is being determined numerically. The work is completely inclined towards the determination of critical value of geometric thickness below which the non-uniformity in the Nusselt profile starts. This is done by numerically examining different target surfaces under constant Reynolds number and nozzle-target spacing. The occurrences of non-uniformity in Nusselt profile contributes to over a 42% enhancement in area average Nusselt magnitude. The critical value of characteristic thickness (t/d) reported in the present investigation approximate to 0.05. Below this value, the impingement of air jet generates a discrete pressure zones over the target surface in the form of pressure spots. As a result of this, the air flowing in contact with the target surface experiences a damping potential, in due of which it gets more time and contact with the surface to dissipate heat.

Method of freezing living cells and tissues with improved subsequent survival

DOEpatents

Senkan, Selim M.; Hirsch, Gerald P.

1980-01-01

This invention relates to an improved method for freezing red blood cells, ther living cells, or tissues with improved subsequent survival, wherein constant-volume freezing is utilized that results in significantly improved survival compared with constant-pressure freezing; optimization is attainable through the use of different vessel geometries, cooling baths and warming baths, and sample concentrations.

Co nanoparticles inserted into a porous carbon amorphous matrix: the role of cooling field and temperature on the exchange bias effect.

PubMed

Fernández-García, María Paz; Gorria, Pedro; Sevilla, Marta; Fuertes, Antonio B; Boada, Roberto; Chaboy, Jesús; Aquilanti, Giuliana; Blanco, Jesús A

2011-01-21

We report unusual cooling field dependence of the exchange bias in oxide-coated cobalt nanoparticles embedded within the nanopores of a carbon matrix. The size-distribution of the nanoparticles and the exchange bias coupling observed up to about 200 K between the Co-oxide shell (∼3-4 nm) and the ferromagnetic Co-cores (∼4-6 nm) are the key to understand the magnetic properties of this system. The estimated values of the effective anisotropy constant and saturation magnetization obtained from the fit of the zero-field cooling and field cooling magnetization vs. temperature curves agree quite well with those of the bulk fcc-Co.

Application of Rapid Solidification Techniques to Aluminum Alloys

DTIC Science & Technology

1980-10-01

relatkonship h e 4r eoTs/(T5 TG) (3.7) 32 where e is the surface emissivity, a is the Stefan Boltzmann constant, Ts and TG are the droplet and cooling...their fully implicit form and solved by a Gauss Seidel iteration routine. The results are I I 40I compared with the equivalent Newtonian case and...temperature respectively, Fo is the Fourier number or dimensionless time, Fo = aLt/r2 (5.2) and Ste is the Stefan number, Ste = CL (TM - TG)/AHM (5.3) which

Ageing dynamics of a superspin glass

NASA Astrophysics Data System (ADS)

Svante Andersson, Mikael; De Toro, Jose Angel; Lee, Su Seong; Mathieu, Roland; Nordblad, Per

2014-10-01

Magnetization dynamics of a model superspin glass system consisting of nearly monodispersed close-packed maghemite particles of diameter 8 nm is investigated. The observed non-equilibrium features of the dynamics are qualitatively similar to those of atomic spin glass systems. The intrinsic relaxation function, as observed in zero-field-cooled magnetization relaxation experiments, depends on the time the sample has been kept at constant temperature (ageing). Accompanying low-field experiments show that the archetypal spin glass characteristics —ageing, memory and rejuvenation— are reproduced in this dense system of dipolar-dipolar interacting superspins.

Fluid extravasation during cardiopulmonary bypass in piglets--effects of hypothermia and different cooling protocols.

PubMed

Farstad, M; Heltne, J K; Rynning, S E; Lund, T; Mongstad, A; Eliassen, F; Husby, P

2003-04-01

Hypothermic cardiopulmonary bypass (CPB) is associated with capillary fluid leak and edema generation which may be secondary to hemodilution, inflammation and hypothermia. We evaluated how hypothermia and different cooling strategies influenced the fluid extravasation rate during CPB. Fourteen piglets were given 60 min normothermic CPB, followed by randomization to two groups: 1: rapid cooling (RC-group) ( approximately 15 min to 28 degrees C); 2: slow cooling (SC-group) ( approximately 60 min to 28 degrees C). Ringer's solution was used as CPB prime and for fluid supplementation. Fluid input/losses, plasma volume, colloid osmotic pressures (plasma, interstitial fluid), hematocrit, serum-proteins and total tissue water (TTW) were measured and fluid extravasation rates calculated. Start of normothermic CPB resulted in a 25% hemodilution. During the first 5-10 min the fluid level of the reservoir fell markedly due to an intravascular volume loss necessitating fluid supplementation. Thereafter a steady state was reached with a constant fluid need of 0.14 +/- 0.04 ml kg-1 min-1. After start of cooling the fluid needs increased in the following 30 min to 0.91 +/- 0.11 ml kg-1 min-1 in the RC group (P < 0.001) and 0.63 +/- 0.10 ml kg-1 min-1 in the SC-group (P < 0.001) with no statistical between-group differences. Fluid extravasation rates after start of hypothermic CPB increased from 0.20 +/- 0.08 ml kg-1 min-1 to 0.71 +/- 0.13 (P < 0.01) and 0.62 +/- 0.13 ml kg-1 min-1 (P < 0.05) in the RC- and SC-groups, respectively, without any changes in degree of hemodilution. TTW increased in most tissues, whereas the intravascular albumin and protein masses remained constant with no between group differences. Hypothermia increased fluid extravasation during CPB independent of cooling strategy. Intravascular albumin and protein masses remained constant. Since inflammatory fluid leakage usually results in protein rich exudates, our data with no net protein leakage may indicate that mechanisms other than inflammation could contribute to fluid extravasation during hypothermic CPB.

Theoretical study of some experimentally relevant states of dysprosium

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

Dzuba, V. A.; Flambaum, V. V.

2010-05-15

Configuration interaction method is used to calculate transition amplitudes and other properties of the low states of dysprosium which are used in cooling and in the study of the time variation of the fine structure constant and violation of fundamental symmetries. The branching ratio for the cooling state to decay to states other than ground states is found to be smaller than 10{sup -4}. The matrix element of the weak interaction between degenerate states at E=19797.96 cm{sup -1} is about 4 Hz which is consistent with the experimental limit |H{sub W}|=|2.3{+-}2.9(stat.){+-}0.7(syst.)| Hz [A. T. Nguyen, D. Budker, D. DeMille, andmore » M. Zolotorev, Phys. Rev. A 56, 3453 (1997)] and points to feasibility of its experimental measurement. Applications include the search for physics beyond the standard model using the parity nonconservation (PNC) isotopic chain approach.« less

Possible implications of global climate change on global lightning distributions and frequencies

NASA Technical Reports Server (NTRS)

Price, Colin; Rind, David

1994-01-01

The Goddard Institute for Space Studies (GISS) general circulation model (GCM) is used to study the possible implications of past and future climate change on global lightning frequencies. Two climate change experiments were conducted: one for a 2 x CO2 climate (representing a 4.2 degs C global warming) and one for a 2% decrease in the solar constant (representing a 5.9 degs C global cooling). The results suggest at 30% increase in global lightning activity for the warmer climate and a 24% decrease in global lightning activity for the colder climate. This implies an approximate 5-6% change in global lightning frequencies for every 1 degs C global warming/cooling. Both intracloud and cloud-to-ground frequencies are modeled, with cloud-to-ground lightning frequencies showing larger sensitivity to climate change than intracloud frequencies. The magnitude of the modeled lightning changes depends on season, location, and even time of day.

Gaseous film cooling investigation in a multi-element splash platelet injector

NASA Astrophysics Data System (ADS)

Yin, Liang; Liu, Weiqiang

2018-03-01

Film cooling is an effective technique that protects chamber walls in rocket combustion against chemical attacks and heat fluxes. This study discusses cooling effect in a multi-element GO2/CH4 splash platelet injector. Influence parameters, such as slot height, slot number, percentage of coolant, and injection position on cooling effect, were investigated. GCH4 with 298.15 K was applied as film coolant. In the first step, slot heights of 0.2 and 0.4 mm were compared by applying a constant film mass flow rate. Temperature, CH4 mole fraction distribution, and flow field structure were obtained. The effects of slot number, percentage of coolant, and injection position on wall temperature distribution were then determined. Finally, the reasons for the low cooling efficiency were analyzed. Improvement in the method is proposed to achieve improved cooling effect for splash platelet injectors.

Inhomogeneous quasistationary state of dense fluids of inelastic hard spheres

NASA Astrophysics Data System (ADS)

Fouxon, Itzhak

2014-05-01

We study closed dense collections of freely cooling hard spheres that collide inelastically with constant coefficient of normal restitution. We find inhomogeneous states (ISs) where the density profile is spatially nonuniform but constant in time. The states are exact solutions of nonlinear partial differential equations that describe the coupled distributions of density and temperature valid when inelastic losses of energy per collision are small. The derivation is performed without modeling the equations' coefficients that are unknown in the dense limit (such as the equation of state) using only their scaling form specific for hard spheres. Thus the IS is the exact state of this dense many-body system. It captures a fundamental property of inelastic collections of particles: the possibility of preserving nonuniform temperature via the interplay of inelastic cooling and heat conduction that generalizes previous results. We perform numerical simulations to demonstrate that arbitrary initial state evolves to the IS in the limit of long times where the container has the geometry of the channel. The evolution is like a gas-liquid transition. The liquid condenses in a vanishing part of the total volume but takes most of the mass of the system. However, the gaseous phase, which mass grows only logarithmically with the system size, is relevant because its fast particles carry most of the energy of the system. Remarkably, the system self-organizes to dissipate no energy: The inelastic decay of energy is a power law [1+t/tc]-2, where tc diverges in the thermodynamic limit. This is reinforced by observing that for supercritical systems the IS coincide in most of the space with the steady states of granular systems heated at one of the walls. We discuss the relation of our results to the recently proposed finite-time singularity in other container's geometries.

Rocket engine hot-spot detector

NASA Astrophysics Data System (ADS)

Collamore, F. N.

1985-04-01

On high performance devices such as rocket engines it is desirable to know if local hot spots or areas of reduced cooling margin exist. The objective of this program is to design, fabricate and test an electronic hot spot detector capable of sensing local hot spot on the exterior circumference of a regeneratively cooled combustion chamber in order to avoid hardware damage. The electronic hot spot sensor consists of an array of 120 thermocouple elements which are bonded in a flexible belt of polyimide film. The design temperature range is from +30 F to +400 F continuously with an intermittent temperature of 500 F maximum. The thermocouple belt consists of 120 equally spaced copper-Constantan thermocouple junctions which is wrapped around the OMS liquid rocket engine combustion chamber, to monitor temperatures of individual cooling channels. Each thermocouple is located over a cooling channel near the injector end of the combustion chamber. The thermocouple array sensor is held in place by a spring loaded clamp band. Analyses show that in the event of a blocked cooling channel the surface temperature of the chamber over the blocked channel will rise from a normal operating temperature of approx. 300 F to approx. 600 F. The hot spot detector will respond quickly to this change with a response time constant less than 0.05 seconds. The hot spot sensor assembly is fabricated with a laminated construction of layers of Kapton film and an outer protective layer of fiberglass reinforced silicone rubber.

The Thermal Regulation of Gravitational Instabilities in Protoplanetary Disks. II. Extended Simulations with Varied Cooling Rates

NASA Astrophysics Data System (ADS)

Mejía, Annie C.; Durisen, Richard H.; Pickett, Megan K.; Cai, Kai

2005-02-01

In order to investigate mass transport and planet formation through gravitational instabilities (GIs), we have extended our three-dimensional hydrodynamic simulations of protoplanetary disks from a previous paper. Our goal is to determine the asymptotic behavior of GIs and how it is affected by different constant cooling times. Initially, Rdisk=40 AU, Mdisk=0.07 Msolar, M*=0.5 Msolar, and Qmin=1.5. Sustained cooling, with tcool=2 ORPs (outer rotation periods; 1ORP~250 yr), drives the disk to instability in about 4 ORPs. This calculation is followed for 23.5 ORPs. After 12 ORPs, the disk settles into a quasi-steady state with sustained nonlinear instabilities, an average Q=1.44 over the outer disk, a well-defined power law Σ(r), and a roughly steady M~5×10-7 Msolar yr-1. The transport is driven by global low-order spiral modes. We restart the calculation at 11.2 ORPs with tcool=1 and 1/4 ORPs. The latter case is also run at high azimuthal resolution. We find that shorter cooling times lead to increased M-values, denser and thinner spiral structures, and more violent dynamic behavior. The asymptotic total internal energy and the azimuthally averaged Q(r) are insensitive to tcool. Fragmentation occurs only in the high-resolution tcool=1/4 ORP case; however, none of the fragments survive for even a quarter of an orbit. Ringlike density enhancements appear and grow near the boundary between GI-active and GI-inactive regions. We discuss the possible implications of these rings for gas giant planet formation.

Precise Measurements of the Masses of Cs, Rb and Na A New Route to the Fine Structure Constant

NASA Astrophysics Data System (ADS)

Rainville, Simon; Bradley, Michael P.; Porto, James V.; Thompson, James K.; Pritchard, David E.

2001-01-01

We report new values for the atomic masses of the alkali 133Cs, 87Rb, 85Rb, and 23Na with uncertainties ≤ 0.2 ppb. These results, obtained using Penning trap single ion mass spectrometry, are typically two orders of magnitude more accurate than previously measured values. Combined with values of h/m atom from atom interferometry measurements and accurate wavelength measurements for different atoms, these values will lead to new ppb-level determinations of the molar Planck constant N A h and the fine structure constant α. This route to α is based on simple physics. It can potentially achieve the several ppb level of accuracy needed to test the QED determination of α extracted from measurements of the electron g factor. We also demonstrate an electronic cooling technique that cools our detector and ion below the 4 K ambient temperature. This technique improves by about a factor of three our ability to measure the ion's axial motion.

Effects of superheated steam on Geobacillus stearothermophilus spore viability.

PubMed

Head, D S; Cenkowski, S; Holley, R; Blank, G

2008-04-01

To examine the effect of processing with superheated steam (SS) on Geobacillus stearothermophilus ATCC 10149 spores. Two inoculum levels of spores of G. stearothermophilus were mixed with sterile sand and exposed to SS at 105-175 degrees C. The decimal reduction time (D-value) and the thermal resistance constant (z-value) were calculated. The effect of cooling of spores between periods of exposure to SS was also examined. A mean z-value of 25.4 degrees C was calculated for both inoculum levels for SS processing temperatures between 130 degrees C and 175 degrees C. Spore response to SS treatment depends on inoculum size. SS treatment may be effective for reduction in viability of thermally resistant bacterial spores provided treatments are separated by intermittent cooling periods. There is a need for technologies that require short thermal processing times to eliminate bacterial spores in foods. The SS processing technique has the potential to reduce microbial load and to modify food texture with less energy in comparison to commonly used hot air treatment. This work provides information on the effect of SS processing parameters on the viability of G. stearothermophilus spores.

Effective Alphas and Mixing for Disks with Gravitational Instabilities: Convergence Testing in Global 3D Simulations

NASA Astrophysics Data System (ADS)

Michael, Scott A.; Steiman-Cameron, T.; Durisen, R.; Boley, A.

2008-05-01

Using 3D simulations of a cooling disk undergoing gravitational instabilities (GIs), we compute the effective Shakura and Sunyaev (1973) alphas due to gravitational torques and compare them to predictions from an analytic local theory for thin disks by Gammie (2001). Our goal is to determine how accurately a locally defined alpha can characterize mass and angular momentum transport by GIs in disks. Cases are considered both with cooling by an imposed constant global cooling time (Mejia et al. 2005) and with realistic radiative transfer (Boley et al. 2007). Grid spacing in the azimuthal direction is varied to investigate how the computed alpha is affected by numerical resolution. The azimuthal direction is particularly important, because higher resolution in azimuth allows GI power to spread to higher-order (multi-armed) modes that behave more locally. We find that, in many important respects, the transport of mass and angular momentum by GIs is an intrinsically global phenomenon. Effective alphas are variable on a dynamic time scale over global spatial scales. Nevertheless, preliminary results at the highest resolutions for an imposed cooling time show that our computed alphas, though systematically higher, tend on average to follow Gammie's prediction to within perhaps a factor of two. Our computed alphas include only gravitational stresses, while in Gammie's treatment the effective alpha is due equally to hydrodynamic (Reynolds) and gravitational stresses. So Gammie's prediction may significantly underestimate the true average stresses in a GI-active disk. Our effective alphas appear to be reasonably well converged for 256 and 512 azimuthal zones. We also have a high-resolution simulation under way to test the extent of radial mixing by GIs of gas and its entrained dust for comparison with Stardust observations. Results will be presented if available at the time of the meeting.

Uncovering dental implants using a new thermo-optically powered (TOP) technology with tissue air-cooling.

PubMed

Romanos, Georgios E; Belikov, Andrey V; Skrypnik, Alexei V; Feldchtein, Felix I; Smirnov, Michael Z; Altshuler, Gregory B

2015-07-01

Uncovering implants with lasers, while bloodless, has been associated with a risk of implant and bone overheating. The present study evaluated the effect of using a new generation of high-power diode lasers on the temperature of a dental implant and the surrounding tissues using an in vitro model. The implant temperature was measured at three locations using micro thermocouples. Collateral thermal damage of uncovered soft tissues was evaluated using NTBC stain. Implant temperature rise during and collateral thermal soft-tissue damage following implant uncovering with and without tissue air-cooling was studied using both the classic operational mode and the new thermo-optically powered (TOP) technology. For the classic surgical mode using a cork-initiated tip and constant laser power set at 3.4 W, the maximum temperature rise in the coronal and apical parts of the implant was 23.2 ± 4.1°С and 9.5 ± 1.8°С, respectively, while 1.5 ± 0.5 mm of collateral thermal damage of the soft tissue surrounding the implant model occurred. Using the TOP surgical tip with constant laser power reduced implant overheating by 30%; collateral thermal soft-tissue damage was 0.8 ± 0.2 mm. Using the TOP surgical mode with a tip temperature setting of 800°C and air-cooling reduced the implant temperature rise by more than 300%, and only 0.2 ± 0.1 mm of collateral thermal soft-tissue damage occurred, typical for optimized CO2 laser surgery. Furthermore, use of the new generation diode technology (TOP surgical mode) appeared to reduce the time required for implant uncovering by a factor of two, compared to the standard surgical mode. Use of the new generation diode technology (TOP surgical mode) may significantly reduce overheating of dental implants during uncovering and seems to be safer for the adjacent soft and hard tissues. Use of such diode lasers with air-cooling can radically reduce the rise in implant temperatures (by more than three times), potentially making this technology safe and effective for implant uncovering. © 2015 Wiley Periodicals, Inc.

Magnetic trapping of buffer-gas-cooled chromium atoms and prospects for the extension to paramagnetic molecules

NASA Astrophysics Data System (ADS)

Bakker, Joost M.; Stoll, Michael; Weise, Dennis R.; Vogelsang, Oliver; Meijer, Gerard; Peters, Achim

2006-10-01

We report the successful buffer-gas cooling and magnetic trapping of chromium atoms with densities exceeding 1012 atoms per cm3 at a temperature of 350 mK for the trapped sample. The possibilities of extending the method to buffer-gas cool and magnetically trap molecules are discussed. To minimize the most important loss mechanism in magnetic trapping, molecules with a small spin spin interaction and a large rotational constant are preferred. Both the CrH (6Σ+ ground state) and MnH (7Σ+) radicals appear to be suitable systems for future experiments.

Cooling Panel Optimization for the Active Cooling System of a Hypersonic Aircraft

NASA Technical Reports Server (NTRS)

Youn, B.; Mills, A. F.

1995-01-01

Optimization of cooling panels for an active cooling system of a hypersonic aircraft is explored. The flow passages are of rectangular cross section with one wall heated. An analytical fin-type model for incompressible flow in smooth-wall rectangular ducts with coupled wall conduction is proposed. Based on this model, the a flow rate of coolant to each design minimum mass flow rate or coolant for a single cooling panel is obtained by satisfying hydrodynamic, thermal, and Mach number constraints. Also, the sensitivity of the optimal mass flow rate of coolant to each design variable is investigated. In addition, numerical solutions for constant property flow in rectangular ducts, with one side rib-roughened and coupled wall conduction, are obtained using a k-epsilon and wall function turbulence model, these results are compared with predictions of the analytical model.

Cooled radiofrequency ablation for bilateral greater occipital neuralgia.

PubMed

Vu, Tiffany; Chhatre, Akhil

2014-01-01

This report describes a case of bilateral greater occipital neuralgia treated with cooled radiofrequency ablation. The case is considered in relation to a review of greater occipital neuralgia, continuous thermal and pulsed radiofrequency ablation, and current medical literature on cooled radiofrequency ablation. In this case, a 35-year-old female with a 2.5-year history of chronic suboccipital bilateral headaches, described as constant, burning, and pulsating pain that started at the suboccipital region and radiated into her vertex. She was diagnosed with bilateral greater occipital neuralgia. She underwent cooled radiofrequency ablation of bilateral greater occipital nerves with minimal side effects and 75% pain reduction. Cooled radiofrequency ablation of the greater occipital nerve in challenging cases is an alternative to pulsed and continuous RFA to alleviate pain with less side effects and potential for long-term efficacy.

Cooled Radiofrequency Ablation for Bilateral Greater Occipital Neuralgia

PubMed Central

Chhatre, Akhil

2014-01-01

This report describes a case of bilateral greater occipital neuralgia treated with cooled radiofrequency ablation. The case is considered in relation to a review of greater occipital neuralgia, continuous thermal and pulsed radiofrequency ablation, and current medical literature on cooled radiofrequency ablation. In this case, a 35-year-old female with a 2.5-year history of chronic suboccipital bilateral headaches, described as constant, burning, and pulsating pain that started at the suboccipital region and radiated into her vertex. She was diagnosed with bilateral greater occipital neuralgia. She underwent cooled radiofrequency ablation of bilateral greater occipital nerves with minimal side effects and 75% pain reduction. Cooled radiofrequency ablation of the greater occipital nerve in challenging cases is an alternative to pulsed and continuous RFA to alleviate pain with less side effects and potential for long-term efficacy. PMID:24716017

Offshore Floating Wind Turbine-driven Deep Sea Water Pumping for Combined Electrical Power and District Cooling

NASA Astrophysics Data System (ADS)

Sant, T.; Buhagiar, D.; Farrugia, R. N.

2014-06-01

A new concept utilising floating wind turbines to exploit the low temperatures of deep sea water for space cooling in buildings is presented. The approach is based on offshore hydraulic wind turbines pumping pressurised deep sea water to a centralised plant consisting of a hydro-electric power system coupled to a large-scale sea water-cooled air conditioning (AC) unit of an urban district cooling network. In order to investigate the potential advantages of this new concept over conventional technologies, a simplified model for performance simulation of a vapour compression AC unit was applied independently to three different systems, with the AC unit operating with (1) a constant flow of sea surface water, (2) a constant flow of sea water consisting of a mixture of surface sea water and deep sea water delivered by a single offshore hydraulic wind turbine and (3) an intermittent flow of deep sea water pumped by a single offshore hydraulic wind turbine. The analysis was based on one year of wind and ambient temperature data for the Central Mediterranean that is known for its deep waters, warm climate and relatively low wind speeds. The study confirmed that while the present concept is less efficient than conventional turbines utilising grid-connected electrical generators, a significant portion of the losses associated with the hydraulic transmission through the pipeline are offset by the extraction of cool deep sea water which reduces the electricity consumption of urban air-conditioning units.

Calculations of Laminar Heat Transfer Around Cylinders of Arbitrary Cross Section and Transpiration-Cooled Walls with Application to Turbine Blade Cooling

NASA Technical Reports Server (NTRS)

Eckert, E.R.G.; Livingood, John N.B.

1951-01-01

An approximate method for development of flow and thermal boundary layers in laminar regime on cylinders with arbitrary cross section and transpiration-cooled walls is obtained by use of Karman's integrated momentum equation and an analogous heat-flow equation. Incompressible flow with constant property values throughout boundary layer is assumed. Shape parameters for approximated velocity and temperature profiles and functions necessary for solution of boundary-layer equations are presented as charts, reducing calculations to a minimum. The method is applied to determine local heat-transfer coefficients and surface temperature-cooled turbine blades for a given flow rate. Coolant flow distributions necessary for maintaining uniform blade temperatures are also determined.

Mapping the dark matter in the NGC 5044 group with ROSAT: Evidence for a nearly homogeneous cooling flow with a cooling wake

NASA Technical Reports Server (NTRS)

David, Laurence P.; Jones, Christine; Forman, William; Daines, Stuart

1994-01-01

The NGC 5044 group of galaxies was observed by the ROSAT Position Sensitive Proportional Counter (PSPC) for 30 ks during its reduced pointed phase (1991 July). Due to the relatively cool gas temperature in the group (kT = 0.98 +/- 0.02 keV) and the excellent photon statistics (65,000 net counts), we are able to determine precisely a number of fundamental properties of the group within 250 kpc of the central galaxy. In particular, we present model-independent measurements of the total gravitating mass, the temperature and abundance profiles of the gas, and the mass accretion rate. Between 60 and 250 kpc, the gas is nearly isothermal with T varies as r(exp (-0.13 +/- 0.03)). The total gravitating mass of the group can be unambiguously determined from the observed density and temperature profiles of the gas using the equation of hydrostatic equilibrium. Within 250 kpc, the gravitating mass is 1.6 x 10(exp 13) solar mass, yielding a mass-to-light ratio of 130 solar mass/solar luminosity. The baryons (gas and stars) comprise 12% of the total mass within this radius. At small radii, the temperature clearly increases outward and attains a maximum value at 60 kpc. The positive temperature gradient in the center of the group confirms the existence of a cooling flow. The cooling flow region extends well beyond the temperature maximum with a cooling radius between 100 and 150 kpc. There are two distinct regions in the cooling flow separated by the temperature maximum. In the outer region, the gas is nearly isothermal with a unifor m Fe abundance of approximately 80% solar, the flow is nearly homogeneous with dot-M= 20 to 25 solar mass/year, the X-ray contours are spherically symmetric, and rho(sub gas) varies as r(exp -1.6). In the inner region, the temperature profile has a positive gradient, the mass accretion rate decreases rapidly inward, the gas density profile is steeper, and the X-ray image shows some substrucutre. NGC 5044 is offset from the centroid of the outer X-ray contours indicating that the central galaxy may have a residual velocity with respect to the center of the group potential. There is also a linear X-ray feature with an extent of approximately 30 kpc with one end coincident with NGC 5044. The X-ray emission from this feature is softer than the ambient gas. We interpret this feature as a 'cooling wake' formed by the accreting gas as it is gravitationally focused into the wake of NGC 5044. One of the most surprising results of our PSPC observation is the discovery of a nearly homogeneous cooling flow. Prior results concerning the mass accretion profile in cooling flows indicate that dot-M varies as r. This relation implies that significant mass deposition occurs at large radii which generates an inhomogeneous flow. The mass accretion rate in the NGC 5044 group is essentially a constant beyond 40 kpc (well within the cooling radius). Significant mass deposition (a declining dot-M) does not commence until the gas accretes to within 40 kpc of the group center where the radiative cooling time is approximately equals 10(exp 9) year. Th is radius also corresponds to the temperature maximum, the break in gas density profile, and the onset of structure in the X-ray image. A Hubble constant of H(sub 0) = 50 km/sec/Mpc is used throughout the paper.

SPICA sub-Kelvin cryogenic chains

NASA Astrophysics Data System (ADS)

Duband, L.; Duval, J. M.; Luchier, N.; Prouve, T.

2012-04-01

SPICA, a Japanese led mission, is part of the JAXA future science program and is planned for launch in 2018. SPICA will perform imaging and spectroscopic observations in the mid- and far-IR waveband, and is developing instrumentation spanning the 5-400 μm range. The SPICA payload features several candidate instruments, some of them requiring temperature down to 50 mK. This is currently the case for SAFARI, a core instrument developed by a European-based consortium, and BLISS proposed by CALTECH/JPL in the US. SPICA's distinctive feature is to actively cool its telescope to below 6 K. In addition, SPICA is a liquid cryogen free satellite and all the cooling will be provided by radiative cooling (L2 orbit) down to 30 K and by mechanical coolers for lower temperatures. The satellite will launch warm and slowly equilibrate to its operating temperatures once in orbit. This warm launch approach makes it possible to eliminate a large liquid cryogen tank and to use the mass saved to launch a large diameter telescope (3.2 m). This 4 K cooled telescope significantly reduces its own thermal radiation, offering superior sensitivity in the infrared region. The cryogenic system that enables this warm launch/cooled telescope concept is a key issue of the mission. This cryogenic chain features a number of cooling stages comprising passive radiators, Stirling coolers and several Joule Thomson loops, offering cooling powers at typically 20, 4.5, 2.5 and 1.7 K. The SAFARI and BLISS detectors require cooling to temperatures as low as 50 mK. The instrument coolers will be operated from these heat sinks. They are composed of a small demagnetization refrigerator (ADR) pre cooled by either a single or a double sorption cooler, respectively for SAFARI and BLISS. The BLISS cooler maintains continuous cooling at 300 mK and thus suppresses the thermal equilibrium time constant of the large focal plane. These hybrid architectures allow designing low weight coolers able to reach 50 mK. Because the sorption cooler has extremely low mass for a sub-Kelvin cooler, it allows the stringent mass budget to be met. These concepts are discussed in this paper.

Cooled variable-area radial turbine technology program

NASA Technical Reports Server (NTRS)

Large, G. D.; Meyer, L. J.

1982-01-01

The objective of this study was a conceptual evaluation and design analyses of a cooled variable-area radial turbine capable of maintaining nearly constant high efficiency when operated at a constant speed and pressure ratio over a range of flows corresponding to 50- to 100-percent maximum engine power. The results showed that a 1589K (2400 F) turbine was feasible that would satisfy a 4000-hour duty cycle life goal. The final design feasibility is based on 1988 material technology goals. A peak aerodynamic stage total efficiency of 0.88 was predicted at 100 percent power. Two candidate stators were identified: an articulated trailing-edge and a locally movable sidewall. Both concepts must be experimentally evaluated to determine the optimum configuration. A follow-on test program is proposed for this evaluation.

Extracerebral deep-body cold sensitivity in the Pekin duck.

PubMed

Inomoto, T; Simon, E

1981-09-01

Pekin ducks, in which cerebral cold sensitivity is negligible, were submitted to general body cooling at warm, thermoneutral, and cold ambient temperature (Ta) with an intestinal thermode. In some animals, hypothermia was enhanced by additional hypothalamic cooling that suppressed cold defense. In other animals, the spinal cord was cooled, either selectively or during intestinal cooling. From core temperature (Tc) and metabolic heat production (M) an overall cold sensitivity of about -5 to -6 W . kg-1 . degrees C-1 was determined at thermoneutrality. Maximum M amounted to four to five times the resting M of 3.8 W . kg-1 and was attained when Tc fell by 2.5 degrees C or more. In the cold, threshold Tc for the activation of M was elevated; overall cold sensitivity remained constant. In the warmth, threshold Tc was lowered; overall cold sensitivity was reduced, if mean skin temperature (Tsk) remained at aout 39 degrees C or higher. Spinal cold sensitivity amounted to about -0.25 W . kg-1 . degrees C-1 at normal Tc and thermoneutral and warm Ta; it increased to aout -0.50 W . kg-1 . degrees C-1 in the cold and during hypothermia. Peripheral cold sensitivity was estimated from Tsk and M as -0.4 to -0.8 W . kg-1 . degrees C-1. It is concluded that overall cold sensitivity in ducks mainly depends on deep-body temperature sensors outside of the central nervous system.

Microwave, irrigated, pulsed, or conventional radiofrequency energy source: which energy source for which catheter ablation?

PubMed

Erdogan, Ali; Grumbrecht, Stephan; Neumann, Thomas; Neuzner, Joerg; Pitschner, Heinz F

2003-01-01

The aim of the study was to compare the diameter of endomyocardial lesions induced with the delivery of microwave, cooled, or pulsed energy versus conventional RF energy. In vitro tests were performed in fresh endomyocardial preparations of pig hearts in a 10-L bath of NaCl 0.9% solution at 37 degrees C and constant 1.5 L/min flow. Ablation 7 Fr catheters with 4-mm tip electrodes were used, except for the delivery of microwave energy. Energy delivery time was set to 60 s/50 W in all experiments. Cooled energy delivery was performed with a closed irrigation catheter. Pulsed energy delivery was performed using a special controller with a duty-cycle of 5 ms. Microwave energy was delivered with a 2.5-GHz generator and 10-mm antenna. Electrode temperature and impedance were measured simultaneously. After ablation, lesion length, width, and depth were measured with microcalipers, and volume calculated by a formula for ellipsoid bodies. Each energy delivery mode was tested in ten experiments. The deepest lesions were created with cooled energy delivery, and the largest volume by microwave energy delivery. Pulsed RF produced significantly deeper lesions than conventional RF energy delivery. Cooled or pulsed RF energy delivery created deeper transmural lesions than conventional RF. To create linear lesions at anatomically complex sites (isthmus), microwave energy seemed superior by rapidly creating deep and long lesions.

Improving crystal size distribution by internal seeding combined cooling/antisolvent crystallization with a cooling/heating cycle

NASA Astrophysics Data System (ADS)

Lenka, Maheswata; Sarkar, Debasis

2018-03-01

This work investigates the effect of internal seeding and an initial cooling/heating cycle on the final crystal size distribution (CSD) during a combined cooling/antisolvent crystallization of L-asparagine monohydrate from it's aqueous solution using isopropyl-alcohol as antisolvent. Internal seeds were generated by one-pot addition of various amounts of antisolvent to the crystallizer. It was then followed by a cooling/heating cycle to dissolve the fines produced and thus obtain a suitable initial seed. A combined cooling/antisolvent crystallization was then followed by employing a linear cooling profile with simultaneous addition of antisolvent with a constant mass flow rate to promote the growth of the internally generated seeds. The amount of initial antisolvent influences the characteristics of the internal seeds generated and the effect of initial amount of antisolvent on the final CSD is investigated. It was found that the introduction of a single cooling/heating cycle significantly improves the reproducibility of final CSD as well as the mean size. Overall, the study indicates that the application of internal seeding with a single cooling/heating cycle for fines dissolution is an effective technique to tailor crystal size distribution.

Ground-state IVR of jet-cooled p-alkylphenols and p-alkylanilines studied by stimulated emission ion dip and stimulated Raman-UV optical double-resonance spectroscopies

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

Ebata, T.; Ito, M.

1992-04-16

This paper reports the intramolecular vibrational redistribution (IVR) of the jet-cooled p-alkylphenols and p-alkylanilines in S{sub 0} state by using stimulated emission ion dip and stimulated raman-UV optical double-resonance spectroscopy. The IVR rate constants of several vibrational levels localized in the benzene ring are estimated. 31 refs., 12 figs., 4 tabs.

IRAS observations of R Coronae Borealis - Detection and study of a fossil shell

NASA Technical Reports Server (NTRS)

Gillett, F. C.; Backman, D. E.; Beichman, C.; Neugebauer, G.

1986-01-01

IRAS observations of the extreme hydrogen-deficient supergiant R CrB are presented and discussed. The star is surrounded by an enormous cool dust cloud which is tentatively identified as a fossil remnant of the hydrogen-rich envelope of the star. The angular extent of the emission corresponds to a linear extent of 8 pc, 20 times larger than the largest previously known shell around a late-type star. The radiating material is distributed very symmetrically over a wide range of radial distances from the star. The dust temperature is nearly constant throughout the extended shell. The total mass in the shell is about 0.3 solar mass. The ejection process appears to have occurred in a spherically symmetric fashion with a nearly constant mass loss rate and expansion velocity over a period of about 150,000 yr, terminating about 26,000 yr ago.

Translational Diffusion Coefficient and Partition Coefficient of a Spin-Labeled Solute in Lecithin Bilayer Membranes

PubMed Central

Dix, James A.; Diamond, Jared M.; Kivelson, Daniel

1974-01-01

The translational diffusion coefficient and the partition coefficient of a spin-labeled solute, di-t-butyl nitroxide, in an aqueous suspension of dipalmitoyl lecithin vesicles have been studied by electron spin resonance spectroscopy. When the lecithin is cooled through its phase transition temperature near 41°C, some solute is “frozen out” of the bilayer, and the standard partial molar enthalpy and entropy of partition go more positive by a factor of 8 and 6, respectively. However, the apparent diffusion constant in the lecithin phase is only slightly smaller than that in water, both above and below the transition temperature. The fraction of bilayer volume within which solute is distributed may increase with temperature, contributing to the positive enthalpy of partition. Comparison of time constants suggests that there is a permeability barrier to this solute in the periphery of the bilayer. PMID:4360944

Thermal Modelling Analysis of Spiral Wound Supercapacitor under Constant-Current Cycling

PubMed Central

Wang, Kai; Li, Liwei; Yin, Huaixian; Zhang, Tiezhu; Wan, Wubo

2015-01-01

A three-dimensional modelling approach is used to study the effects of operating and ambient conditions on the thermal behaviour of the spiral wound supercapacitor. The transient temperature distribution during cycling is obtained by using the finite element method with an implicit predictor-multicorrector algorithm. At the constant current of 2A, the results show that the maximum temperature appears in core area. After 5 cycles, the maximum temperature is 34.5°C, while in steady state, it’s up to 42.5°C. This paper further studies the relationship between the maximum temperature and charge-discharge current. The maximum temperature will be more than 60°C after 5 cycles at the current of 4A, and cooling measurements should be taken at that time. It can provide thoughts on inner temperature field distribution and structure design of the spiral wound supercapacitor in working process. PMID:26444687

Southern hemisphere observations of a long-term decrease in F region altitude and thermospheric wind providing possible evidence for global thermospheric cooling

NASA Astrophysics Data System (ADS)

Jarvis, M. J.; Jenkins, B.; Rodgers, G. A.

1998-09-01

F region peak heights, derived from ionospheric scaled parameters through 38-year data series from both Argentine Islands (65°S, 64°W) and Port Stanley (52°S, 58°W) have been analyzed for signatures of secular change. Long-term changes in altitude, which vary with month and time of day, were found at both sites. The results can be interpreted either as a constant decrease in altitude combined with a decreasing thermospheric wind effect or as a constant decrease in altitude which is altitude-dependent. Both interpretations leave inconsistencies when the results from the two sites are compared. The estimated long-term decrease in altitude is of a similar order of magnitude to that which has been predicted to result in the thermosphere from anthropogenic change related to greenhouse gases. Other possibilities should not, however, be ruled out.

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

Dentz, Jordan; Ansanelli, Eric; Henderson, Hugh

Domestic hot water (DHW) heating is the second largest energy end use in U.S. buildings, exceeded only by space conditioning. Recirculation systems consisting of a pump and piping loop(s) are commonly used in multifamily buildings to reduce wait time for hot water at faucets; however, constant pumping increases energy consumption by exposing supply and return line piping to continuous heat loss, even during periods when there is no demand for hot water. In this study, ARIES installed and tested two types of recirculation controls in a pair of buildings in order to evaluate their energy savings potential. Demand control, temperaturemore » modulation controls, and the simultaneous operation of both were compared to the baseline case of constant recirculation. Additionally, interactive effects between DHW control fuel reductions and space conditioning (heating and cooling) were estimated in order to make more realistic predictions of the payback and financial viability of retrofitting DHW systems with these controls. Results showed that DHW fuel consumption reduced by 7% after implementing the demand control technique, 2% after implementing temperature modulation, and 15% after implementing demand control and temperature modulation techniques simultaneously; recirculation pump runtime was reduced to 14 minutes or less per day. With space heating and cooling interactions included, the estimated annual cost savings were 8%, 1%, and 14% for the respective control techniques. Possible complications in the installation, commissioning and operation of the controls were identified and solutions offered.« less

Simultaneous droplet impingement dynamics and heat transfer on nano-structured surfaces

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

Shen, Jian; Graber, Christof; Liburdy, James

This study examines the hydrodynamics and temperature characteristics of distilled deionized water droplets impinging on smooth and nano-structured surfaces using high speed (HS) and infrared (IR) imaging at We = 23.6 and Re = 1593, both based on initial drop impingement parameters. Results for a smooth and nano-structured surface for a range of surface temperatures are compared. Droplet impact velocity, transient spreading diameter and dynamic contact angle are measured. The near surface average droplet fluid temperatures are evaluated for conditions of evaporative cooling and boiling. Also included are surface temperature results using a gold layered IR opaque surface on silicon.more » Four stages of the impingement process are identified: impact, boiling, near constant surface diameter evaporation, and final dry-out. For the boiling conditions there is initial nucleation followed by severe boiling, then near constant diameter evaporation resulting in shrinking of the droplet height. When a critical contact angle is reached during evaporation the droplet rapidly retracts to a smaller diameter reducing the contact area with the surface. This continues as a sequence of retractions until final dry out. The basic trends are the same for all surfaces, but the nano-structured surface has a lower dissipated energy during impact and enhances the heat transfer for evaporative cooling with a 20% shorter time to achieve final dry out. (author)« less

Preliminary engineering design of sodium-cooled CANDLE core

NASA Astrophysics Data System (ADS)

Takaki, Naoyuki; Namekawa, Azuma; Yoda, Tomoyuki; Mizutani, Akihiko; Sekimoto, Hiroshi

2012-06-01

The CANDLE burning process is characterized by the autonomous shifting of burning region with constant reactivity and constant spacial power distribution. Evaluations of such critical burning process by using widely used neutron diffusion and burning codes under some realistic engineering constraints are valuable to confirm the technical feasibility of the CANDLE concept and to put the idea into concrete core design. In the first part of this paper, it is discussed that whether the sustainable and stable CANDLE burning process can be reproduced even by using conventional core analysis tools such as SLAROM and CITATION-FBR. As a result, it is certainly possible to demonstrate it if the proper core configuration and initial fuel composition required as CANDLE core are applied to the analysis. In the latter part, an example of a concrete image of sodium cooled, metal fuel, 2000MWt rating CANDLE core has been presented by assuming an emerging inevitable technology of recladding. The core satisfies engineering design criteria including cladding temperature, pressure drop, linear heat rate, and cumulative damage fraction (CDF) of cladding, fast neutron fluence and sodium void reactivity which are defined in the Japanese FBR design project. It can be concluded that it is feasible to design CADLE core by using conventional codes while satisfying some realistic engineering design constraints assuming that recladding at certain time interval is technically feasible.

An evaluation of benthic macroinvertebrate biomass methodology : Part 1. Laboratory analytical methods.

PubMed

Mason, W T; Lewis, P A; Weber, C I

1983-03-01

Evaluation of analytical methods employed for wet weight (live or preserved samples) of benthic macroinvertebrates reveals that centrifugation at 140 x gravity for one minute yields constant biomass estimates. Less relative centrifugal force increases chance of incomplete removal of body moisture and results in weighing error, while greater force may rupture fragile macroinvertebrates, such as mayflies. Duration of specimen exposure in ethanol, formalin, and formol (formaling-ethanol combinations) causes significant body weight loss with within 48 hr formalin and formol cause less body weight loss than ethanol. However, as all preservatives tested cause body weight loss, preservation time of samples collected for comparative purposes should be treated uniformly. Dry weight estimates of macroinvertebrates are not significantly affected by kind of preservative or duration of exposure. Constant dry weights are attained by oven drying at 103 °C at a minimum of four hours or vacuum oven drying (15 inches of mercury pressure) at 103 °C for a minimum of one hour. Although requiring more time in preparation than oven drying and inalterably changing specimen body shape, freeze drying (10 microns pressure, -55 °C, 24 hr) provides constant dry weights and is advantageous for long term sample storage by minimizing curatorial attention. Constant ash-free dry weights of macroinvertebrate samples are attained by igniting samples at 500-550 °C for a minimum of one hour with slow cooling to room temperature in desiccators before weighing.

Continental emergence and growth on a cooling earth

NASA Astrophysics Data System (ADS)

Vlaar, N. J.

2000-07-01

Isostasy considerations are connected to a 1-D model of mantle differentiation due to pressure release partial melting to obtain a model for the evolution of the relative sea level with respect to the continent during the earth secular cooling. In this context, a new mechanism is derived for the selective exhumation of exposed ancient cratons. The model results in a quantitative scenario for sea-level fall due to the changing thicknesses of the oceanic basaltic crust and its harzburgite residual layer as a function of falling mantle temperature. It is also shown that the buoyancy of the harzburgite root of a stabilized continental craton has an important effect on sea-level and on the isostatic readjustment and exhumation of exposed continental surface during the earth's secular cooling. The model does not depend on the usual assumption of constant continental freeboard and crustal thickness and its application is not restricted to the post-Archaean. It predicts large-scale continental emergence near the end of the Archaean and the early Proterozoic. This provides an explanation for reported late Archaean emergence and the subsequent formation of late Archaean cratonic platforms and early Proterozoic sedimentary basins. For a period of secular cooling of 3.8 Ga, corresponding to the length of the geological record, the model predicts a fall of the ocean floor of some 4 km or more. For a constant ocean depth, this implies a sea-level fall of the same magnitude. A formula is derived that allows for an increasing ocean depth due to either the changing ratio of continental with respect to oceanic area, or to a possible increase of the oceanic volume during the geological history. Increasing ocean depth results in a later emergence of submarine ancient geological formations compared to the case when ocean depth is constant. Selective exhumation is studied for the case of constant ocean depth. It is shown that for this case, early exposed continental crust can be exhumed to a lower crustal depth, which explains the relative vertical displacement of low-grade- with respect to high-grade terrain. Increasing ocean depth is not expected to result in diminished exhumation.

Mechanical properties of shape memory polymers for morphing aircraft applications

NASA Astrophysics Data System (ADS)

Keihl, Michelle M.; Bortolin, Robert S.; Sanders, Brian; Joshi, Shiv; Tidwell, Zeb

2005-05-01

This investigation addresses basic characterization of a shape memory polymer (SMP) as a suitable structural material for morphing aircraft applications. Tests were performed for monotonic loading in high shear at constant temperature, well below, or just above the glass transition temperature. The SMP properties were time-and temperature-dependent. Recovery by the SMP to its original shape needed to be unfettered. Based on the testing SMPs appear to be an attractive and promising component in the solution for a skin material of a morphing aircraft. Their multiple state abilities allow them to easily change shape and, once cooled, resist large loads.

Design and testing of a liquid cooled garment for hot environments.

PubMed

Guo, Tinghui; Shang, Bofeng; Duan, Bin; Luo, Xiaobing

2015-01-01

Liquid cooled garments (LCGs) are considered a viable method to protect individuals from hyperthermia and heat-related illness when working in thermally stressful environments. While the concept of LCGs was proposed over 50 years ago, the design and testing of these systems is undeveloped and stands in need of further study. In this study, a detailed heat transfer model of LCG in a hot environment was built to analyze the effects of different factors on the LCG performance, and to identify the main limitations to achieve maximum performance. An LCG prototype was designed and fabricated. Series of tests were done by a modified thermal manikin method to validate the heat transfer model and to evaluate the thermal properties. Both experimental and predicted results show that the heat flux components match the heat balance equation with an error of less than 10% at different flowrate. Thermal resistance analysis also manifests that the thermal resistance between the cooling water and the ambient (R2) is more sensitive to the flowrate than to the one between the skin surface and the cooling water (R1). When the flowrate increased from 225 to 544 mL/min, R2 decreased from 0.5 to 0.3 °C m(2)/W while R1 almost remained constant. A specific duration time was proposed to assess the durability and an optimized value of 1.68 h/kg was found according to the heat transfer model. The present heat transfer model and specific duration time concept could be used to optimize and evaluate this kind of LCG respectively. Copyright © 2015 Elsevier Ltd. All rights reserved.

The induction of water to the inlet air as a means of internal cooling in aircraft-engine cylinders

NASA Technical Reports Server (NTRS)

Rothrock, Addison M; Krsek, Alois, Jr; Jones, Anthony W

1943-01-01

Report presents the results of investigations conducted on a full-scale air-cooled aircraft-engine cylinder of 202-cubic inch displacement to determine the effects of internal cooling by water induction on the maximum permissible power and output of an internal-combustion engine. For a range of fuel-air and water-fuel ratios, the engine inlet pressure was increased until knock was detected aurally, the power was then decreased 7 percent holding the ratios constant. The data indicated that water was a very effective internal coolant, permitting large increases in engine power as limited by either knock or by cylinder temperatures.

[Estimation of the time of death based on the measurements of the eye temperature in comparison with other body sites].

PubMed

Kaliszan, Michał; Hauser, Roman

2007-01-01

A systematic two-stage study was conducted in pigs to verify the models of postmortem body temperature decrease currently employed in forensic medicine. During the investigations, temperature recordings were performed in four body sites (eyeballs, orbit soft tissues, muscles and rectums). The results of the study support the possible use of the eyeball and also the orbit soft tissues as temperature measuring sites at the early phase after death; they have narrowed the significance of rectum temperature measurements to the late stage of postmortem body temperature decrease, shown insignificant correlations between the body weight and the temperature decrease rate constant and illustrated the functional increase of the time of death estimation error as the body cools, expressed in the distinct tendency to overestimate the calculated time of death as compared to the actual one. In the second stage of the experiment, a lack of a plateau phase was demonstrated, at least from 30 min post mortem. It was also found that in the very early post mortem period, the kinetics of cooling of all the body sites studied was better described by the two-exponential model than the single exponential one. The study also showed that the weak airflow present in the experimental conditions did not practically affect the course of cooling of the investigated body sites. Eyeball temperature measurements with an infra-red laser thermometer performed during the experiment proved to be of no use for determination of the time of death. The experiments allowed for defining the so far unreported value of physiological temperature of pig eyeball as 38 degrees C.

21 CFR 352.70 - Standard sunscreen.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 82 °C, with constant stirring, until the contents of each part are solubilized. Add preparation A slowly to preparation B while stirring. Continue stirring until the emulsion formed is cooled to room...

21 CFR 352.70 - Standard sunscreen.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 82 °C, with constant stirring, until the contents of each part are solubilized. Add preparation A slowly to preparation B while stirring. Continue stirring until the emulsion formed is cooled to room...

Energy Efficient School Designed for the Future

ERIC Educational Resources Information Center

Modern Schools, 1977

1977-01-01

When completed, the planned Greeley Elementary School will be able to accommodate any future changes in enrollment and technological developments, while maintaining a constant energy efficient heating and cooling operation. (Author/MLF)

Guide to Altitude Decompression Sickness Research

DTIC Science & Technology

2010-05-01

Night Vision Goggles (NVGs) and effects of hypoxia on PRK surgery recovery, F-16 APECS, F-22 Cooling Garment, U-2 Full Pressure Suit, Aircrew...1. Severity 0 No pain 1-2 Mild 3-4 Moderate 5-7 Strong 8-9 Severe 10 Strongest imaginable 2. Intermittent vs . Constant a...symptoms. 2. Intermittent vs . Constant Paresthesia a. Intermittent (Transient) is defined as lasting fewer than 60 seconds each occurrence, in a

Performance degradation of space Stirling cryocoolers due to gas contamination

NASA Astrophysics Data System (ADS)

Liu, Xin-guang; Wu, Yi-nong; Yang, Shao-hua; Zhang, Xiao-ming; Lu, Guo-hua; Zhang, Li

2011-08-01

With extensive application of infrared detective techniques, Stirling cryocoolers, used as an active cooling source, have been developed vigorously in China. After the cooler's cooling performance can satisfy the mission's request, its reliability level is crucial for its application. Among all the possible failure mechanisms, gas contamination has been found to be the most notorious cause of cooler's performance degradation by failure analyses. To analyze the characteristic of gas contamination, some experiments were designed and carried out to quantitatively analyze the relationship between failure and performance. Combined with the test results and the outgassing characteristic of non-metal materials in the cryocooler, a degradation model of cooling performance was given by T(t)=T0+A[1-exp(-t/B)] under some assumptions, where t is the running time, T is the Kelvin cooling temperature, and T0, A, B are model parameters, which can be given by the least square method. Here T0 is the fitting initial cooling temperature, A is the maximum range of performance degradation, and B is the time dependent constant of degradation. But the model parameters vary when a cryocooler is running at different cooling temperature ranges, or it is treated by different cleaning process. In order to verify the applicability of the degradation model, data fit analysis on eight groups of cooler's lifetime test was carried out. The final work indicated this model fit well with the performance degradation of space Stirling cryocoolers due to gas contamination and this model could be used to predict or evaluation the cooler's lifetime. Gaseous contamination will not arouse severe performance degradation until the contaminants accumulate to a certain amount, but it could be fatal when it works. So it is more serious to the coolers whose lifetime is more than 10,000 h. The measures taken to control or minimize its damage were discussed as well. To the long-life cryocooler, internal materials must be baked and organic/epoxy materials should be used as few as possible. Further more, pipeline for filling working fluid must have purifying facilities.

Indirect Measurement of Local Condensing Heat-Transfer Coefficient Around Horizontal Finned Tubes

DTIC Science & Technology

1987-09-01

vapor-sidp coefficients exceeded Nusselt values by factors of approximately 7 to 9 (for a constant temperature drop across the condensate film). Honda...3/8 in.) diameter water-cooled copper tubes helically coiled to a height of 457 mm (le In.). The auxiliary condenser was cooled by a continuous...NAVAL POSTGRADUATE SCHOOL Monterey, California , " I - . 0) I DECI 41987S:,• c ý ! i, THESIS INDIRECT MEASUREMENT OF LOCAL CONDENSING HEAT-TRANSFER

Passively cooled direct drive wind turbine

DOEpatents

Costin, Daniel P [Chelsea, VT

2008-03-18

A wind turbine is provided that passively cools an electrical generator. The wind turbine includes a plurality of fins arranged peripherally around a generator house. Each of the fins being oriented at an angle greater than zero degrees to allow parallel flow of air over the fin. The fin is further tapered to allow a constant portion of the fin to extend beyond the air stream boundary layer. Turbulence initiators on the nose cone further enhance heat transfer at the fins.

Symposium on Numerical and Physical Aspects of Aerodynamic Flows

DTIC Science & Technology

1992-01-15

ReT/R. -1 wide range of Mach numbers including pressure gradient, a = - (a*) (10) surface roughness. surface heating and cooling . and surface 9 I + ReT...and specific heat at constant pressure, respectively. Favre equation is then obtained by contracting the Reynolds-stress decomposition is applied to...their near- wall behavior. In other words, if highly cooled -wall flows are to be predicted correctly, heat fluxes should be modeled e = 2ak + 4bky

Cooling Duct Analysis for Transpiration/Film Cooled Liquid Propellant Rocket Engines

NASA Technical Reports Server (NTRS)

Micklow, Gerald J.

1996-01-01

The development of a low cost space transportation system requires that the propulsion system be reusable, have long life, with good performance and use low cost propellants. Improved performance can be achieved by operating the engine at higher pressure and temperature levels than previous designs. Increasing the chamber pressure and temperature, however, will increase wall heating rates. This necessitates the need for active cooling methods such as film cooling or transpiration cooling. But active cooling can reduce the net thrust of the engine and add considerably to the design complexity. Recently, a metal drawing process has been patented where it is possible to fabricate plates with very small holes with high uniformity with a closely specified porosity. Such a metal plate could be used for an inexpensive transpiration/film cooled liner to meet the demands of advanced reusable rocket engines, if coolant mass flow rates could be controlled to satisfy wall cooling requirements and performance. The present study investigates the possibility of controlling the coolant mass flow rate through the porous material by simple non-active fluid dynamic means. The coolant will be supplied to the porous material by series of constant geometry slots machined on the exterior of the engine.

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

Jacobsen, A. J.

In a method of the type where petrol is recovered from a mixture of petrol vapor and air by absorption of the petrol in a cooled petroleum distillate, a petroleum distillate having a boiling point range higher than that of the petrol is used, and this petroleum distillate is in sequence cooled by heat exchange with a cold reservoir, brought into direct contact with the petrol/air mixture to absorb petrol, transferred to a buffer tank and transferred from the buffer tank to a stripping means which may be a distillation column. By combining cooling condensation and absorption of the petrolmore » vapor and controlling the amount of cooled petroleum distillate brought into contact with the petrol/air mixture so that the petrol concentration in the petroleum distillate transferred to the buffer tank is substantially constant, an unprecedented optimum control of the petrol absorbing process can be obtained both in peak load and in average load operations. A system for carrying out the method is advantageous in that only the absorption means need be dimensioned for peak load operation, while the other components, such as the distillation column or a heat exchanger with associated conduits can be dimensioned for average loads, a buffer tank being provided to temporarily receive the petroleum distillate which owing to the above-mentioned control has a substantially constant, maximum petrol concentration so that the system can cope with peak loads with a surprisingly small buffer tank.« less

The effect of starting or stopping skin cooling on the thermoregulatory responses during leg exercise in humans.

PubMed

Demachi, K; Yoshida, T; Kume, M; Tsuneoka, H

2012-07-01

To assess the effects of starting or stopping leg cooling on the thermoregulatory responses during exercise, 60 min of cycling exercise at 30% of maximal oxygen uptake was performed under 4 conditions using tube trouser perfused with water at 10 °C; no leg cooling (NC), starting of leg cooling after 30 min of exercise (delayed cooling, DC), continuous leg cooling (CC), and stopping of continuous leg cooling after 30 min of exercise (SC) at an environmental temperature of 28.5 °C. During exercise under the DC conditions, an instantaneous increase in the esophageal temperature (Tes), a suppression of the cutaneous vascular conductance at the forearm (%CVC), and a decrease in the mean skin temperature (Tsk) were observed after leg cooling. The total sweat loss (Δm sw,tot) was lower under the DC than the NC condition. In the SC study, however, the Tes remained constant, while the %CVC increased gradually after leg cooling was stopped, and the Δm sw,tot was greater than that under the CC condition. These results suggest that during exercise, rapid skin cooling of the leg may cause an increase in core temperature, while also enhancing thermal stress. However, stopping skin cooling did not significantly affect the core temperature long-term, because the skin blood flow and sweat rate subsequently increased. © Georg Thieme Verlag KG Stuttgart · New York.

Transient high-field behavior of niobium superconducting cavities

NASA Astrophysics Data System (ADS)

Campisi, I. E.; Farkas, Z. D.; Deruyter, H.; Hogg, H. A.

1983-03-01

The breakdown behavior of a TM010 mode, S-band niobium cavity at low temperatures was examined. Unloaded Q's of 9 x 10(7) at 4.2 K and of 7 x 10(9) at 1.35 K were measured. The response of the cavity at 4.2 K to 1 MW, 2.5 (SIGMA)s pulses was tested in several cool downs. In these tests the cavity was heavily overcoupled to lower its time constant to a value of 0.80 times the RF pulse length of 2.5 (SIGMA)s. This condition maximizes the energy transfer from the klystron source to the cavity. It is indicated that fields of about 50 MV/m are reached in the cavity without breakdown.

Smart catheter flow sensor for real-time continuous regional cerebral blood flow monitoring

NASA Astrophysics Data System (ADS)

Li, Chunyan; Wu, Pei-Ming; Hartings, Jed A.; Wu, Zhizhen; Ahn, Chong H.; LeDoux, David; Shutter, Lori A.; Narayan, Raj K.

2011-12-01

We present a smart catheter flow sensor for real-time, continuous, and quantitative measurement of regional cerebral blood flow using in situ temperature and thermal conductivity compensation. The flow sensor operates in a constant-temperature mode and employs a periodic heating and cooling technique. This approach ensures zero drift and provides highly reliable data with microelectromechanical system-based thin film sensors. The developed flow sensor has a sensitivity of 0.973 mV/ml/100 g/min in the range from 0 to 160 ml/100 g/min with a linear correlation coefficient of R2 = 0.9953. It achieves a resolution of 0.25 ml/100 g/min and an accuracy better than 5 ml/100 g/min.

Effects of heating durations on normal concrete residual properties: compressive strength and mass loss

NASA Astrophysics Data System (ADS)

Nazri, Fadzli Mohamed; Shahidan, Shahiron; Khaida Baharuddin, Nur; Beddu, Salmia; Hisyam Abu Bakar, Badorul

2017-11-01

This study investigates the effects of high temperature with five different heating durations on residual properties of 30 MPa normal concrete. Concrete cubes were being heated up to 600°C for 30, 60, 90, 120 and 150 minutes. The temperature will keep constant for 30, 60, 90, 120 and 150 minutes. The standard temperature-time curve ISO 834 is referred to. After heating the specimen were left to cool in the furnace and removed. After cooling down to ambient temperature, the residual mass and residual compressive strength were observed. The obtained result shows that, the compressive strength of concrete decrease as the heating duration increases. This heating duration influence, might affects the loss of free water present and decomposition of hydration products in concrete. As the heating duration increases, the amount of water evaporated also increases led to loss in concrete mass. Conclusively, the percentage of mass and compressive strength loss increased as the heating duration increased.

Heat Transfer Through Dipolar Coupling: Sympathetic cooling without contact

NASA Astrophysics Data System (ADS)

Oktel, Mehmet; Renklioglu, Basak; Tanatar, Bilal

We consider two parallel layers of dipolar ultracold gases at different temperatures and calculate the heat transfer through dipolar coupling. As the simplest model we consider a system in which both of the layers contain two-dimensional spin-polarized Fermi gases. The effective interactions describing the correlation effects and screening between the dipoles are obtained by the Euler-Lagrange Fermi-hypernetted-chain approximation in a single layer. We use the random-phase approximation (RPA) for the interactions across the layers. We find that heat transfer through dipolar coupling becomes efficient when the layer separation is comparable to dipolar interaction length scale. We characterize the heat transfer by calculating the time constant for temperature equilibration between the layers and find that for the typical experimental parameter regime of dipolar molecules this is on the order of milliseconds. We generalize the initial model to Boson-Boson and Fermion-Boson layers and suggest that contactless sympathetic cooling may be used for ultracold dipolar molecules. Supported by TUBITAK 1002-116F030.

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

Skillman, Evan D.; Hidalgo, Sebastian L.; Monelli, Matteo

We present an analysis of the star formation history (SFH) of a field near the half-light radius in the Local Group dwarf irregular galaxy IC 1613 based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. Our observations reach the oldest main sequence turn-off, allowing a time resolution at the oldest ages of ∼1 Gyr. Our analysis shows that the SFH of the observed field in IC 1613 is consistent with being constant over the entire lifetime of the galaxy. These observations rule out an early dominant episode of star formation in IC 1613. We compare the SFH ofmore » IC 1613 with expectations from cosmological models. Since most of the mass is in place at early times for low-mass halos, a naive expectation is that most of the star formation should have taken place at early times. Models in which star formation follows mass accretion result in too many stars formed early and gas mass fractions that are too low today (the 'over-cooling problem'). The depth of the present photometry of IC 1613 shows that, at a resolution of ∼1 Gyr, the star formation rate is consistent with being constant, at even the earliest times, which is difficult to achieve in models where star formation follows mass assembly.« less

ADVANCEMENTS IN TIME-SPECTRA ANALYSIS METHODS FOR LEAD SLOWING-DOWN SPECTROSCOPY

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

Smith, Leon E.; Anderson, Kevin K.; Gesh, Christopher J.

2010-08-11

Direct measurement of Pu in spent nuclear fuel remains a key challenge for safeguarding nuclear fuel cycles of today and tomorrow. Lead slowing-down spectroscopy (LSDS) is an active nondestructive assay method that has the potential to provide independent, direct measurement of Pu and U isotopic mass with an uncertainty lower than the approximately 10 percent typical of today’s confirmatory assay methods. Pacific Northwest National Laboratory’s (PNNL) previous work to assess the viability of LSDS for the assay of pressurized water reactor (PWR) assemblies indicated that the method could provide direct assay of Pu-239 and U-235 (and possibly Pu-240 and Pu-241)more » with uncertainties less than a few percent, assuming suitably efficient instrumentation, an intense pulsed neutron source, and improvements in the time-spectra analysis methods used to extract isotopic information from a complex LSDS signal. This previous simulation-based evaluation used relatively simple PWR fuel assembly definitions (e.g. constant burnup across the assembly) and a constant initial enrichment and cooling time. The time-spectra analysis method was founded on a preliminary analytical model of self-shielding intended to correct for assay-signal nonlinearities introduced by attenuation of the interrogating neutron flux within the assembly.« less

The high-resolution infrared spectrum of the ν3 +ν5 combination band of jet-cooled propyne

NASA Astrophysics Data System (ADS)

Doney, K. D.; Zhao, D.; Bouwman, J.; Linnartz, H.

2017-09-01

We present the first detection of the high-resolution ro-vibrational spectrum of the ν3 +ν5 combination band of propyne around 3070 cm-1. The fully resolved spectrum is recorded for supersonically jet-cooled propyne using continuous wave cavity ring-down spectroscopy (cw-CRDS). The assignments are supported with the help of accurate ab initio vibration-rotation interaction constants (αi) and anharmonic frequencies. A detailed analysis of the rotationally cold spectrum is given.

Vacuum Ultraviolet Photoelectron Emission Spectroscopy of Water and Aqueous Solutions.

DTIC Science & Technology

1980-02-01

Siegbahn, Nouv. J. Chim. 1, 191 (1977). 26T. Shibaguchi, H . Onuki and R. Onaka, J. Phys. Soc. Japan 42, 152 (1977). 27I. Abbati, L. Braicovich and B. De...application of the Brodsky- Tsarevsky theory of photoelectronemtssion by solutions: 8.7, 7.9. 7.2, 8.4 eV, respectively, for CIT. Brr. V. H ions. The...externally cooled nitrogen gas flowed. The temperature of the liquid was monitored with thermistor H and kept constant at 1.50C by controlling the cooled gas

Gravitational Instabilities in Disks with Radiative Cooling

NASA Astrophysics Data System (ADS)

Mejía, A. C.; Durisen, R. H.; Pickett, B. K.

Previous simulations of self-gravitating protoplanetary disks by our group have shown that, once developed, gravitational instabilities are enhanced by cooling the disk constantly during its evolution (Pickett et al. 2002). These earlier calculations included a very simple form of volumetric cooling which acted against the stabilizing effects of shock heating. The present work incorporates more realistic treatments of energy transport. The initial disk model extends from 2.3 to 40 AU, has a mass of 0.07 M⊙, and orbits a 0.5 M⊙ star. The models evolve for a period of over 2500 years, during which the structure of the disks is profoundly altered, transient clumps form in one case, but no permanent bound companion objects develop.

Cooling of Gas Turbines. 6; Computed Temperature Distribution Through Cross Section of Water-Cooled Turbine Blade

NASA Technical Reports Server (NTRS)

Livingood, John N. B.; Sams, Eldon W.

1947-01-01

A theoretical analysis of the cross-sectional temperature distribution of a water-cooled turbine blade was made using the relaxation method to solve the differential equation derived from the analysis. The analysis was applied to specific turbine blade and the studies icluded investigations of the accuracy of simple methods to determine the temperature distribution along the mean line of the rear part of the blade, of the possible effect of varying the perimetric distribution of the hot gas-to -metal heat transfer coefficient, and of the effect of changing the thermal conductivity of the blade metal for a constant cross sectional area blade with two quarter inch diameter coolant passages.

Effects of processing parameters on immersion vacuum cooling time and physico-chemical properties of pork hams.

PubMed

Feng, Chao-Hui; Drummond, Liana; Zhang, Zhi-Hang; Sun, Da-Wen

2013-10-01

The effects of agitation (1002 rpm), different pressure reduction rates (60 and 100 mbar/min), as well as employing cold water with different initial temperatures (IWT: 7 and 20°C) on immersion vacuum cooling (IVC) of cooked pork hams were experimentally investigated. Final pork ham core temperature, cooling time, cooling loss, texture properties, colour and chemical composition were evaluated. The application for the first time of agitation during IVC substantially reduced the cooling time (47.39%) to 4.6°C, compared to IVC without agitation. For the different pressure drop rates, there was a trend that shorter IVC cooling times were achieved with lower cooling rate, although results were not statistically significant (P>0.05). For both IWTs tested, the same trend was observed: shorter cooling time and lower cooling loss were obtained under lower linear pressure drop rate of 60 mbar/min (not statistically significant, P>0.05). Compared to the reference cooling method (air blast cooling), IVC achieved higher cooling rates and better meat quality. Copyright © 2013 Elsevier Ltd. All rights reserved.

Cooling rate and thermal structure determined from progressive magnetization of the dacite dome at Mount St. Helens, Washington

USGS Publications Warehouse

Dzurisin, D.; Denlinger, R.P.; Rosenbaum, J.G.

1990-01-01

Our study of a magnetic anomaly associated with the recently active dacite dome at Mount St. Helens suggests that the dome consists of a hot, nonmagnetized core surrounded by a cool, magnetized carapace and flanking talus. Temporal changes in the magnetic anomaly indicate that the magnetized carapace thickened at an average rate of 0.03 ?? 0.01 m/d from 1984 to 1986. Petrographic and rock magnetic properties of dome samples indicate that the dominant process responsible for these changes is magnetization of extensively oxidized rock at progressively deeper levels within the dome as the rock cools through its blocking temperature, rather than subsequent changes in magnetization caused by further oxidation. Newly extruded material cools rapidly for a short period as heat is conducted outward in response to convective heat loss from its surface. The cooling rate gradually declines for several weeks, and thereafter the material cools at a relatively constant rate by convective heat loss from its interior along fractures that propagate inward. -from Authors

Candidates for direct laser cooling of diatomic molecules with the simplest 1Σ -1Σ electronic system

NASA Astrophysics Data System (ADS)

Li, Chuanliang; Li, Yachao; Ji, Zhonghua; Qiu, Xuanbing; Lai, Yunzhong; Wei, Jilin; Zhao, Yanting; Deng, Lunhua; Chen, Yangqin; Liu, Jinjun

2018-06-01

We propose to utilize the 1Σ-1Σ electronic transition system for direct laser cooling of heteronuclear diatomic molecules. AgH, as well as its deuterium isotopolog AgD, is used as an example to illustrate the cooling schemes. Potential-energy curves and relevant molecular parameters of both AgH and AgD, including the spin-orbit constants and the electronic transition dipole moments, are determined in internally contracted multiconfiguration-reference configuration interaction calculations. The highly diagonal Franck-Condon matrices of the A 1Σ+-X 1Σ+ transitions predicted by the calculations suggest the existence of quasi-closed-cycle transitions, which renders these molecules suitable for direct laser cooling. By solving rate equations numerically, we demonstrated that both AgH and AgD molecules can be cooled from 25 K to 2 mK temperature in approximately 20 ms. Our investigation elucidates and supports the hypothesis that molecules in the simplest 1Σ-1Σ system can serve as favorable candidates for direct laser cooling.

CFD simulation of simultaneous monotonic cooling and surface heat transfer coefficient

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

Mihálka, Peter, E-mail: usarmipe@savba.sk; Matiašovský, Peter, E-mail: usarmat@savba.sk

The monotonic heating regime method for determination of thermal diffusivity is based on the analysis of an unsteady-state (stabilised) thermal process characterised by an independence of the space-time temperature distribution on initial conditions. At the first kind of the monotonic regime a sample of simple geometry is heated / cooled at constant ambient temperature. The determination of thermal diffusivity requires the determination rate of a temperature change and simultaneous determination of the first eigenvalue. According to a characteristic equation the first eigenvalue is a function of the Biot number defined by a surface heat transfer coefficient and thermal conductivity ofmore » an analysed material. Knowing the surface heat transfer coefficient and the first eigenvalue the thermal conductivity can be determined. The surface heat transport coefficient during the monotonic regime can be determined by the continuous measurement of long-wave radiation heat flow and the photoelectric measurement of the air refractive index gradient in a boundary layer. CFD simulation of the cooling process was carried out to analyse local convective and radiative heat transfer coefficients more in detail. Influence of ambient air flow was analysed. The obtained eigenvalues and corresponding surface heat transfer coefficient values enable to determine thermal conductivity of the analysed specimen together with its thermal diffusivity during a monotonic heating regime.« less

Transient thermoelectric supercooling: Isosceles current pulses from a response surface perspective and the performance effects of pulse cooling a heat generating mass

NASA Astrophysics Data System (ADS)

Piggott, Alfred J., III

With increased public interest in protecting the environment, scientists and engineers aim to improve energy conversion efficiency. Thermoelectrics offer many advantages as thermal management technology. When compared to vapor compression refrigeration, above approximately 200 to 600 watts, cost in dollars per watt as well as COP are not advantageous for thermoelectrics. The goal of this work was to determine if optimized pulse supercooling operation could improve cooling capacity or efficiency of a thermoelectric device. The basis of this research is a thermal-electrical analogy based modeling study using SPICE. Two models were developed. The first model, a standalone thermocouple with no attached mass to be cooled. The second, a system that includes a module attached to a heat generating mass. With the thermocouple study, a new approach of generating response surfaces with characteristic parameters was applied. The current pulse height and pulse on-time was identified for maximizing Net Transient Advantage, a newly defined metric. The corresponding pulse height and pulse on-time was utilized for the system model. Along with the traditional steady state starting current of Imax, Iopt was employed. The pulse shape was an isosceles triangle. For the system model, metrics new to pulse cooling were Qc, power consumption and COP. The effects of optimized current pulses were studied by changing system variables. Further studies explored time spacing between pulses and temperature distribution in the thermoelement. It was found net Q c over an entire pulse event can be improved over Imax steady operation but not over steady I opt operation. Qc can be improved over Iopt operation but only during the early part of the pulse event. COP is reduced in transient pulse operation due to the different time constants of Qc and Pin. In some cases lower performance interface materials allow more Qc and better COP during transient operation than higher performance interface materials. Important future work might look at developing innovative ways of biasing Joule heat to Th..

Computation of Turbulent Recirculating Flow in Channels, and for Impingement Cooling

NASA Technical Reports Server (NTRS)

Chang, Byong Hoon

1992-01-01

Fully elliptic forms of the transport equations have been solved numerically for two flow configurations. The first is turbulent flow in a channel with transverse rectangular ribs, and the second is impingement cooling of a plane surface. Both flows are relevant to proposed designs for active cooling of hypersonic vehicles using supercritical hydrogen as the coolant. Flow downstream of an abrupt pipe expansion and of a backward-facing step were also solved with various near-wall turbulence models as benchmark problems. A simple form of periodicity boundary condition was used for the channel flow with transverse rectangular ribs. The effects of various parameters on heat transfer in channel flow with transverse ribs and in impingement cooling were investigated using the Yap modified Jones and Launder low Reynolds number k-epsilon turbulence model. For the channel flow, predictions were in adequate agreement with experiment for constant property flow, with the results for friction superior to those for heat transfer. For impingement cooling, the agreement with experiment was generally good, but the results suggest that improved modelling of the dissipation rate of turbulence kinetic energy is required in order to obtain improved heat transfer prediction, especially near the stagnation point. The k-epsilon turbulence model was used to predict the mean flow and heat transfer for constant and variable property flows. The effect of variable properties for channel flow was investigated using the same turbulence model, but comparison with experiment yielded no clear conclusions. Also, the wall function method was modified for use in the variable properties flow with a non-adiabatic surface, and an empirical model is suggested to correctly account for the behavior of the viscous sublayer with heating.

Regional cooling facilitates termination of spiral-wave reentry through unpinning of rotors in rabbit hearts.

PubMed

Yamazaki, Masatoshi; Honjo, Haruo; Ashihara, Takashi; Harada, Masahide; Sakuma, Ichiro; Nakazawa, Kazuo; Trayanova, Natalia; Horie, Minoru; Kalifa, Jérôme; Jalife, José; Kamiya, Kaichiro; Kodama, Itsuo

2012-01-01

Moderate global cooling of myocardial tissue was shown to destabilize 2-dimensional (2-D) reentry and facilitate its termination. This study sought to test the hypothesis that regional cooling destabilizes rotors and facilitates termination of spontaneous and DC shock-induced subepicardial reentry in isolated, endocardially ablated rabbit hearts. Fluorescent action potential signals were recorded from 2-D subepicardial ventricular myocardium of Langendorff-perfused rabbit hearts. Regional cooling (by 5.9°C ± 1.3°C) was applied to the left ventricular anterior wall using a transparent cooling device (10 mm in diameter). Regional cooling during constant stimulation (2.5 Hz) prolonged the action potential duration (by 36% ± 9%) and slightly reduced conduction velocity (by 4% ± 4%) in the cooled region. Ventricular tachycardias (VTs) induced during regional cooling terminated earlier than those without cooling (control): VTs lasting >30 seconds were reduced from 17 of 39 to 1 of 61. When regional cooling was applied during sustained VTs (>120 seconds), 16 of 33 (48%) sustained VTs self-terminated in 12.5 ± 5.1 seconds. VT termination was the result of rotor destabilization, which was characterized by unpinning, drift toward the periphery of the cooled region, and subsequent collision with boundaries. The DC shock intensity required for cardioversion of the sustained VTs decreased significantly by regional cooling (22.8 ± 4.1 V, n = 16, vs 40.5 ± 17.6 V, n = 21). The major mode of reentry termination by DC shocks was phase resetting in the absence of cooling, whereas it was unpinning in the presence of cooling. Regional cooling facilitates termination of 2-D reentry through unpinning of rotors. Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Building America Case Study: Control Retrofits for Multifamily Domestic Hot Water Recirculation Systems, Brooklyn, New York

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

Domestic hot water (DHW) heating is the second largest energy end use in U.S. buildings, exceeded only by space conditioning. Recirculation systems consisting of a pump and piping loop(s) are commonly used in multifamily buildings to reduce wait time for hot water at faucets; however, constant pumping increases energy consumption by exposing supply and return line piping to continuous heat loss, even during periods when there is no demand for hot water. In this study, ARIES installed and tested two types of recirculation controls in a pair of buildings in order to evaluate their energy savings potential. Demand control, temperaturemore » modulation controls, and the simultaneous operation of both were compared to the baseline case of constant recirculation. Additionally, interactive effects between DHW control fuel reductions and space conditioning (heating and cooling) were estimated in order to make more realistic predictions of the payback and financial viability of retrofitting DHW systems with these controls. Results showed that DHW fuel consumption reduced by 7 percent after implementing the demand control technique, 2 percent after implementing temperature modulation, and 15 percent after implementing demand control and temperature modulation techniques simultaneously; recirculation pump runtime was reduced to 14 minutes or less per day. With space heating and cooling interactions included, the estimated annual cost savings were 8 percent, 1 percent, and 14 percent for the respective control techniques. Possible complications in the installation, commissioning and operation of the controls were identified and solutions offered.« less

Building America Case Study: Control Retrofits for Multifamily Domestic Hot Water Recirculation Systems, Brooklyn, New York

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

J. Dentz; E. Ansanelli, H. Henderson, Jr.; K. Varshney

Domestic hot water (DHW) heating is the second largest energy end use in U.S. buildings, exceeded only by space conditioning. Recirculation systems consisting of a pump and piping loop(s) are commonly used in multifamily buildings to reduce wait time for hot water at faucets; however, constant pumping increases energy consumption by exposing supply and return line piping to continuous heat loss, even during periods when there is no demand for hot water. In this study, ARIES installed and tested two types of recirculation controls in a pair of buildings in order to evaluate their energy savings potential. Demand control, temperaturemore » modulation controls, and the simultaneous operation of both were compared to the baseline case of constant recirculation. Additionally, interactive effects between DHW control fuel reductions and space conditioning (heating and cooling) were estimated in order to make more realistic predictions of the payback and financial viability of retrofitting DHW systems with these controls. Results showed that DHW fuel consumption reduced by 7% after implementing the demand control technique, 2% after implementing temperature modulation, and 15% after implementing demand control and temperature modulation techniques simultaneously; recirculation pump runtime was reduced to 14 minutes or less per day. With space heating and cooling interactions included, the estimated annual cost savings were 8%, 1%, and 14% for the respective control techniques. Possible complications in the installation, commissioning and operation of the controls were identified and solutions offered.« less

Control Strategies to Reduce the Energy Consumption of Central Domestic Hot Water Systems

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

Dentz, Jordan; Ansanelli, Eric; Henderson, Hugh

Domestic hot water (DHW) heating is the second largest energy end use in U.S. buildings, exceeded only by space conditioning. Recirculation systems consisting of a pump and piping loop(s) are commonly used in multifamily buildings to reduce wait time for hot water at faucets; however, constant pumping increases energy consumption by exposing supply and return line piping to continuous heat loss, even during periods when there is no demand for hot water. In this study, ARIES installed and tested two types of recirculation controls in a pair of buildings in order to evaluate their energy savings potential. Demand control, temperaturemore » modulation controls, and the simultaneous operation of both were compared to the baseline case of constant recirculation. Additionally, interactive effects between DHW control fuel reductions and space conditioning (heating and cooling) were estimated in order to make more realistic predictions of the payback and financial viability of retrofitting DHW systems with these controls. Results showed that DHW fuel consumption reduced by 7% after implementing the demand control technique, 2% after implementing temperature modulation, and 15% after implementing demand control and temperature modulation techniques simultaneously; recirculation pump runtime was reduced to 14 minutes or less per day. With space heating and cooling interactions included, the estimated annual cost savings were 8%, 1%, and 14% for the respective control techniques. Possible complications in the installation, commissioning and operation of the controls were identified and solutions offered.« less

How to keep cool in tough times.

PubMed

Muller-Smith, P

1999-02-01

Reengineering is no longer an event that has a beginning and an end. It is an ongoing process of change that continues to occur in all types of businesses. Because there is no longer the sense of security that doing a job well will guarantee continued employment, workers have to approach career planning from a different perspective. Moving up the career ladder in a single organization can no longer serve as the benchmark of success. The contemporary approach to success will be more geared toward the ability to constantly reinvent your unique set of job skills that are transferable from one job setting to another, thus ensuring employability.

Simulation of a 20-ton LiBr/H{sub 2}O absorption cooling system

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

Wardono, B.; Nelson, R.M.

The possibility of using solar energy as the main heat input for cooling systems has led to several studies of available cooling technologies that use solar energy. The results show that double-effect absorption cooling systems give relatively high performance. To further study absorption cooling systems, a computer code was developed for a double-effect lithium bromide/water (LiBr/H{sub 2}O) absorption system. To evaluate the performance, two objective functions were developed including the coefficient of performance (COP) and the system cost. Based on the system cost, an optimization to find the minimum cost was performed to determine the nominal heat transfer areas ofmore » each heat exchanger. The nominal values of other system variables, such as the mass flow rates and inlet temperatures of the hot water, cooling water, and chilled water, are specified as commonly used values for commercial machines. The results of the optimization show that there are optimum heat transfer areas. In this study, hot water is used as the main energy input. Using a constant load of 20 tons cooling capacity, the effects of various variables including the heat transfer ares, mass flow rates, and inlet temperatures of hot water, cooling water, and chilled water are presented.« less

Protostellar Disk Evolution over Million-year Timescales with a Prescription for Magnetized Turbulence

NASA Astrophysics Data System (ADS)

Landry, Russell; Dodson-Robinson, Sarah E.; Turner, Neal J.; Abram, Greg

2013-07-01

Magnetorotational instability (MRI) is the most promising mechanism behind accretion in low-mass protostellar disks. Here we present the first analysis of the global structure and evolution of non-ideal MRI-driven T-Tauri disks on million-year timescales. We accomplish this in a 1+1D simulation by calculating magnetic diffusivities and utilizing turbulence activity criteria to determine thermal structure and accretion rate without resorting to a three-dimensional magnetohydrodynamical (MHD) simulation. Our major findings are as follows. First, even for modest surface densities of just a few times the minimum-mass solar nebula, the dead zone encompasses the giant planet-forming region, preserving any compositional gradients. Second, the surface density of the active layer is nearly constant in time at roughly 10 g cm-2, which we use to derive a simple prescription for viscous heating in MRI-active disks for those who wish to avoid detailed MHD computations. Furthermore, unlike a standard disk with constant-α viscosity, the disk midplane does not cool off over time, though the surface cools as the star evolves along the Hayashi track. Instead, the MRI may pile material in the dead zone, causing it to heat up over time. The ice line is firmly in the terrestrial planet-forming region throughout disk evolution and can move either inward or outward with time, depending on whether pileups form near the star. Finally, steady-state mass transport is an extremely poor description of flow through an MRI-active disk, as we see both the turnaround in the accretion flow required by conservation of angular momentum and peaks in \\dot{M}(R) bracketing each side of the dead zone. We caution that MRI activity is sensitive to many parameters, including stellar X-ray flux, grain size, gas/small grain mass ratio and magnetic field strength, and we have not performed an exhaustive parameter study here. Our 1+1D model also does not include azimuthal information, which prevents us from modeling the effects of Rossby waves.

PROTOSTELLAR DISK EVOLUTION OVER MILLION-YEAR TIMESCALES WITH A PRESCRIPTION FOR MAGNETIZED TURBULENCE

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

Landry, Russell; Dodson-Robinson, Sarah E.; Turner, Neal J.

2013-07-10

Magnetorotational instability (MRI) is the most promising mechanism behind accretion in low-mass protostellar disks. Here we present the first analysis of the global structure and evolution of non-ideal MRI-driven T-Tauri disks on million-year timescales. We accomplish this in a 1+1D simulation by calculating magnetic diffusivities and utilizing turbulence activity criteria to determine thermal structure and accretion rate without resorting to a three-dimensional magnetohydrodynamical (MHD) simulation. Our major findings are as follows. First, even for modest surface densities of just a few times the minimum-mass solar nebula, the dead zone encompasses the giant planet-forming region, preserving any compositional gradients. Second, themore » surface density of the active layer is nearly constant in time at roughly 10 g cm{sup -2}, which we use to derive a simple prescription for viscous heating in MRI-active disks for those who wish to avoid detailed MHD computations. Furthermore, unlike a standard disk with constant-{alpha} viscosity, the disk midplane does not cool off over time, though the surface cools as the star evolves along the Hayashi track. Instead, the MRI may pile material in the dead zone, causing it to heat up over time. The ice line is firmly in the terrestrial planet-forming region throughout disk evolution and can move either inward or outward with time, depending on whether pileups form near the star. Finally, steady-state mass transport is an extremely poor description of flow through an MRI-active disk, as we see both the turnaround in the accretion flow required by conservation of angular momentum and peaks in M-dot (R) bracketing each side of the dead zone. We caution that MRI activity is sensitive to many parameters, including stellar X-ray flux, grain size, gas/small grain mass ratio and magnetic field strength, and we have not performed an exhaustive parameter study here. Our 1+1D model also does not include azimuthal information, which prevents us from modeling the effects of Rossby waves.« less

The effects of Venus' thermal structure on buoyant magma ascent

NASA Technical Reports Server (NTRS)

Sakimoto, S. E. H.; Zuber, M. T.

1992-01-01

The recent Magellan images have revealed a broad spatial distribution of surface volcanism on Venus. Previous work in modeling the ascent of magma on both Venus and Earth has indicated that the planetary thermal structure significantly influences the magmatic cooling rates and thus the amount of magma that can be transported to the surface before solidification. In order to understand which aspects of the thermal structure have the greatest influence on the cooling of ascending magma, we have constructed magma cooling curves for both plutonic and crack buoyant ascent mechanisms, and evaluated the curves for variations in the planetary mantle temperature, thermal gradient curvature with depth, surface temperature gradient, and surface temperature. The planetary thermal structure is modeled as T/T(sub 0) = 1-tau(1-Z/Z(sub 0)(exp n), where T is the temperature, T(sub 0) is the source depth temperature, tau = 1-(T(sub s)/T(sub 0)) where T(sub s) is the planetary surface temperature, Z is the depth, Z(sub 0) is the source depth, and n is a constant that controls thermal gradient curvature with depth. The equation is used both for mathematical convenience and flexibility, as well as its fit to the thermal gradients predicted by the cooling half-space models. We assume a constant velocity buoyant ascent, body-averaged magma temperatures and properties, an initially crystal-free magma, and the same liquidus and solidus for both Venus and Earth.

Advanced turbine study. [airfoil coling in rocket turbines

NASA Technical Reports Server (NTRS)

1982-01-01

Experiments to determine the available increase in turbine horsepower achieved by increasing turbine inlet temperature over a range of 1800 to 2600 R, while applying current gas turbine airfoil cling technology are discussed. Four cases of rocket turbine operating conditions were investigated. Two of the cases used O2/H2 propellant, one with a fuel flowrate of 160 pps, the other 80 pps. Two cases used O2/CH4 propellant, each having different fuel flowrates, pressure ratios, and inlet pressures. Film cooling was found to be the required scheme for these rocket turbine applications because of the high heat flux environments. Conventional convective or impingement cooling, used in jet engines, is inadequate in a rocket turbine environment because of the resulting high temperature gradients in the airfoil wall, causing high strains and low cyclic life. The hydrogen-rich turbine environment experienced a loss, or no gain, in delivered horsepower as turbine inlet temperature was increased at constant airfoil life. The effects of film cooling with regard to reduced flow available for turbine work, dilution of mainstream gas temperature and cooling reentry losses, offset the relatively low specific work capability of hydrogen when increasing turbine inlet temperature over the 1800 to 2600 R range. However, the methane-rich environment experienced an increase in delivered horsepower as turbine inlet temperature was increased at constant airfoil life. The results of a materials survey and heat transfer and durability analysis are discussed.

Laser Measurements of the H Atom + Ozone Rate Constant at Atmospheric Temperatures

NASA Astrophysics Data System (ADS)

Liu, Y.; Smith, G. P.; Peng, J.; Reppert, K. J.; Callahan, S. L.

2015-12-01

The exothermic H + O3 reaction produces OH(v) Meinel band emissions, used to derive mesospheric H concentrations and chemical heating rates. We have remeasured its rate constant to reduce resulting uncertainties and the measurement extend to lower mesospheric temperatures using modern laser techniques. H atoms are produced by pulsed ultraviolet laser trace photolysis of O3, followed by reaction of O(D) with added H2. A second, delayed, frequency-mixed dye laser measures the reaction decay rate with the remaining ozone by laser induced fluorescence. We monitor either the H atom decay by 2 photon excitation at 205 nm and detection of red fluorescence, or the OH(v=9) product time evolution with excitation of the B-X (0,9) band at 237 nm and emission in blue B-A bands. By cooling the enclosed low pressure flow cell we obtained measurements from 146-305 K. Small kinetic modeling corrections are made for secondary regeneration of H atoms. The results fully confirm the current NASA JPL recommendation for this rate constant, and establish its extrapolation down to the lower temperatures of the mesosphere. This work was supported by the NSF Aeronomy Program and an NSF Physics summer REU student grant.

Effect of controlled ice nucleation on primary drying stage and protein recovery in vials cooled in a modified freeze-dryer.

PubMed

Passot, Stéphanie; Tréléa, Ioan Cristian; Marin, Michèle; Galan, Miquel; Morris, G John; Fonseca, Fernanda

2009-07-01

The freezing step influences lyophilization efficiency and protein stability. The main objective of this work was to investigate the impact on the primary drying stage of an ultrasound controlled ice nucleation technology, compared with usual freezing protocols. Lyophilization cycles involving different freezing protocols (applying a constant shelf cooling rate of 1 degrees C/min or 0.2 degrees C/min, putting vials on a precooled shelf, and controlling nucleation by ultrasounds or by addition of a nucleating agent) were performed in a prototype freeze-dryer. Three protective media including sucrose or maltodextrin and differing by their thermal properties and their ability to preserve a model protein (catalase) were used. The visual aspect of the lyophilized cake, residual water content, and enzymatic activity recovery of catalase were assessed after each lyophilization cycle and after 1 month of storage of the lyophilized product at 4 degrees C and 25 degrees C. The freezing protocols allowing increasing nucleation temperature (precooled shelf and controlled nucleation by using ultrasounds or a nucleating agent) induced a faster sublimation step and higher sublimation rate homogeneity. Whatever the composition of the protective medium, applying the ultrasound technology made it possible to decrease the sublimation time by 14%, compared with the freezing method involving a constant shelf cooling rate of 1 degrees C/min. Concerning the enzyme activity recovery, the impact of the freezing protocol was observed only for the protective medium involving maltodextrin, a less effective protective agent than sucrose. Higher activity recovery results were obtained after storage when the ultrasound technology or the precooled shelf method was applied. Controlling ice nucleation during the freezing step of the lyophilization process improved the homogeneity of the sublimation rates, which will, in turn, reduce the intervial heterogeneity. The freeze-dryer prototype including the system of controlled nucleation by ultrasounds appears to be a promising tool in accelerating sublimation and improving intrabatch homogeneity.

Analysis of Time-Dependent Tritium Breeding Capability of Water Cooled Ceramic Breeder Blanket for CFETR

NASA Astrophysics Data System (ADS)

Gao, Fangfang; Zhang, Xiaokang; Pu, Yong; Zhu, Qingjun; Liu, Songlin

2016-08-01

Attaining tritium self-sufficiency is an important mission for the Chinese Fusion Engineering Testing Reactor (CFETR) operating on a Deuterium-Tritium (D-T) fuel cycle. It is necessary to study the tritium breeding ratio (TBR) and breeding tritium inventory variation with operation time so as to provide an accurate data for dynamic modeling and analysis of the tritium fuel cycle. A water cooled ceramic breeder (WCCB) blanket is one candidate of blanket concepts for the CFETR. Based on the detailed 3D neutronics model of CFETR with the WCCB blanket, the time-dependent TBR and tritium surplus were evaluated by a coupling calculation of the Monte Carlo N-Particle Transport Code (MCNP) and the fusion activation code FISPACT-2007. The results indicated that the TBR and tritium surplus of the WCCB blanket were a function of operation time and fusion power due to the Li consumption in breeder and material activation. In addition, by comparison with the results calculated by using the 3D neutronics model and employing the transfer factor constant from 1D to 3D, it is noted that 1D analysis leads to an over-estimation for the time-dependent tritium breeding capability when fusion power is larger than 1000 MW. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB108004, 2015GB108002, and 2014GB119000), and by National Natural Science Foundation of China (No. 11175207)

Development of a single-phase thermosiphon for cold collection and storage of radiative cooling

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

Zhao, Dongliang; Martini, Christine Elizabeth; Jiang, Siyu

A single-phase thermosiphon is developed for cold collection and storage of radiative cooling. Compared to the conventional nocturnal radiative cooling systems that use an electric pump to drive the heat transfer fluid, the proposed single-phase thermosiphon uses the buoyancy force to drive heat transfer fluid. This solution does not require electricity, therefore improving the net gain of the radiative cooling system. A single-phase thermosiphon was built, which consists of a flat panel, a cold collection tank, a water return tube, and a water distribution tank. Considering that outdoor radiative cooling flux is constantly changing (i.e. uncontrollable), an indoor testing facilitymore » was developed to provide a controllable cooling flux (comparable to a radiative cooling flux of 100 W/m2) for the evaluation of thermosiphon performance. The testing apparatus is a chilled aluminum flat plate that has a controlled air gap separation relative to the flat panel surface of the thermosiphon to emulate radiative cooling. With an average of 105 W/m2 cooling flux, the 18 liters of water in the thermosiphon was cooled to an average temperature of 12.5 degrees C from an initial temperature of 22.2 degrees C in 2 h, with a cold collection efficiency of 96.8%. The results obtained have demonstrated the feasibility of using a single-phase thermosiphon for cold collection and storage of radiative cooling. Additionally, the effects of the thermosiphon operation conditions, such as tilt angle of the flat panel, initial water temperature, and cooling energy flux, on the performance have been experimentally investigated. Modular design of the single-phase thermosiphon gives flexibility for its scalability. A radiative cooling system with multiple thermosiphon modules is expected to play an important role in cooling buildings and power plant condensers.« less

Thermal protection performance of opposing jet generating with solid fuel

NASA Astrophysics Data System (ADS)

Shen, Binxian; Liu, Weiqiang

2018-03-01

A light and small gas supply device, which uses fuel gas generating with solid fuel as coolant gas, is introduced for opposing jet thermal protection in hypersonic vehicles. A numerical study on heat flux reduction in hypersonic flow with opposing jet is conducted to investigate the cooling efficiency of fuel gas. Flow field and cooling efficiency at different jet temperatures, as well as the effect of fuel gas, are determined. Detailed results show that shock stand-off distance changes with an increase in jet pressure ratio and remains constant with an increase in jet temperature. Cooling efficiency weakens with an increase in jet temperature and can be strengthened by enhancing jet pressure. Lastly, a remarkable heat flux reduction is observed with fuel gas injection with respect to no fuel gas injection when jet temperature reaches 900 K, thereby proving the positive cooling efficiency of fuel gas.

LD side-pumped Nd:YAG Q-switched laser without water cooling

NASA Astrophysics Data System (ADS)

Ling, Ming; Jin, Guang-yong; Tan, Xue-chun; Wu, Zhi-chao; Liang, Zhu

2009-07-01

A novel LD side-pumped Nd:YAG Q-switched solid-state laser, which made use of the special pumping strcture with conductive cooling instead of water cooling, was investigated.After selecting an appropriate length and diameter of Nd:YAG laser crystal rod and using three groups of laser diode centimeter bar which was composed by 12 laser diodes and uniformly arranged according to the angle of 120°,side-pumping structure of laser was accomplished.Adopting plano-concave resonator ,mending double end face of laser crystal and designing heat-stability resonator made the resonator steadily oscillate.Laser crystal rod which was tight fastened by copper net was conductively cooled and radiation block was furnished on the external of copper net for increasing the radiation capacity.High reflection gold film was plated on the cooling wall in the opposite way of pumping light, so that the laser crystal was uniformly pumped and the laser with low order mode output.Making the use of pillar lens focus and ray trace computing, reasonable parameters were caculated to couple pumping light to laser with high-efficiency.It was the electrooptic Q-switched which was made to be micro-integration eliminating voltage by KD*P crystal that improved the ratio between acting and unacting.Inner heat radiated from laser in good time with TE cooler and the laser ran at constant temperature with water cooling when the big external heat sink emanated a steady heat to periphery. Experiments revealed that the syetem pumping efficiency riseed by 18% and the laser threshold energy was 192 mJ under the condition of this novel pumping structure. The low mode output of 10-12ns pulse width and the maximum output energy of 98 mJ was achieved with an incident pump energy of 720 mJ in 1064nm.The optical-to-optical conversion efficiency was up to 13. 6 %,and the power instability in 24 h was better than +/-1. 7 %.

Axial to transverse energy mixing dynamics in octupole-based magnetostatic antihydrogen traps

NASA Astrophysics Data System (ADS)

Zhong, M.; Fajans, J.; Zukor, A. F.

2018-05-01

The nature of the trajectories of antihydrogen atoms confined in an octupole minimum-B trap is of great importance for upcoming spectroscopy, cooling, and gravity experiments. Of particular interest is the mixing time between the axial and transverse energies for the antiatoms. Here, using computer simulations, we establish that almost all trajectories are chaotic, and then quantify the characteristic mixing time between the axial and transverse energies. We find that there are two classes of trajectories: for trajectories whose axial energy is higher than about 20% of the total energy, the axial energy substantially mixes within about 10 s, whereas for trajectories whose axial energy is lower than about 10% of the total energy, the axial energy remains nearly constant for 1000 s or longer.

Cooling of Gas Turbines. 3; Analysis of Rotor and Blade Temperatures in Liquid-Cooled Gas Turbines

NASA Technical Reports Server (NTRS)

Brown, W. Byron; Livingood, John N. B.

1947-01-01

A theoretical analysis of the radial temperature distribution through the rotor and constant cross sectional area blades near the coolant passages of liquid cooled gas turbines was made. The analysis was applied to obtain the rotor and blade temperatures of a specific turbine using a gas flow of 55 pounds per second, a coolant flow of 6.42 pounds per second, and an average coolant temperature of 200 degrees F. The effect of using kerosene, water, and ethylene glycol was determined. The effect of varying blade length and coolant passage lengths with water as the coolant was also determined. The effective gas temperature was varied from 2000 degrees to 5000 degrees F in each investigation.

Water droplet evaporation from sticky superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Lee, Moonchan; Kim, Wuseok; Lee, Sanghee; Baek, Seunghyeon; Yong, Kijung; Jeon, Sangmin

2017-07-01

The evaporation dynamics of water from sticky superhydrophobic surfaces was investigated using a quartz crystal microresonator and an optical microscope. Anodic aluminum oxide (AAO) layers with different pore sizes were directly fabricated onto quartz crystal substrates and hydrophobized via chemical modification. The resulting AAO layers exhibited hydrophobic or superhydrophobic characteristics with strong adhesion to water due to the presence of sealed air pockets inside the nanopores. After placing a water droplet on the AAO membranes, variations in the resonance frequency and Q-factor were measured throughout the evaporation process, which were related to changes in mass and viscous damping, respectively. It was found that droplet evaporation from a sticky superhydrophobic surface followed a constant contact radius (CCR) mode in the early stage of evaporation and a combination of CCR and constant contact angle modes without a Cassie-Wenzel transition in the final stage. Furthermore, AAO membranes with larger pore sizes exhibited longer evaporation times, which were attributed to evaporative cooling at the droplet interface.

Julius Edgar Lilienfeld Prize Talk: Measuring the Electron Magnetic Moment and the Fine Structure Constant

NASA Astrophysics Data System (ADS)

Gabrielse, Gerald

2011-05-01

The electron magnetic moment in Bohr magnetons has been measured to a precision of 3 parts in 1013. This measurement, with quantum electrodynamics (AED) theory, provides the most precise value of the fine structure constant. This measurement, with a value of the fine structure from other measurements, also tests QED and sets a limit on the internal structure of the electron. A one-electron quantum cyclotron is at the heart of the measurement -- an electron suspended in a magnetic field and cooled enough that its lowest cyclotron and spin quantum states can be deduced with quantum nondemolition (QND) measurements. A cylindrical Penning trap cavity inhibits spontaneous emission and feedback methods make the electron excite and sustain its own motion for detection. A new apparatus is being commissioned in pursuit of more precise measurements. Adapted methods are promising for observing a proton spin flip, which should make it possible to compare the antiproton and proton magnetic moments a million times more accurately than is currently possible.

Crosslinked polyarylene ether nitrile film as flexible dielectric materials with ultrahigh thermal stability.

PubMed

Yang, Ruiqi; Wei, Renbo; Li, Kui; Tong, Lifen; Jia, Kun; Liu, Xiaobo

2016-11-09

Dielectric film with ultrahigh thermal stability based on crosslinked polyarylene ether nitrile is prepared and characterized. The film is obtained by solution-casting of polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) combined with post self-crosslinking at high temperature. The film shows a 5% decomposition temperature over 520 °C and a glass transition temperature (T g ) around 386 °C. Stable dielectric constant and low dielectric loss are observed for this film in the frequency range of 100-200 kHz and in the temperature range of 25-300 °C. The temperature coefficient of dielectric constant is less than 0.001 °C -1 even at 400 °C. By cycling heating and cooling up to ten times or heating at 300 °C for 12 h, the film shows good reversibility and robustness of the dielectric properties. This crosslinked PEN film will be a potential candidate as high performance film capacitor electronic devices materials used at high temperature.

Crosslinked polyarylene ether nitrile film as flexible dielectric materials with ultrahigh thermal stability

NASA Astrophysics Data System (ADS)

Yang, Ruiqi; Wei, Renbo; Li, Kui; Tong, Lifen; Jia, Kun; Liu, Xiaobo

2016-11-01

Dielectric film with ultrahigh thermal stability based on crosslinked polyarylene ether nitrile is prepared and characterized. The film is obtained by solution-casting of polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) combined with post self-crosslinking at high temperature. The film shows a 5% decomposition temperature over 520 °C and a glass transition temperature (Tg) around 386 °C. Stable dielectric constant and low dielectric loss are observed for this film in the frequency range of 100-200 kHz and in the temperature range of 25-300 °C. The temperature coefficient of dielectric constant is less than 0.001 °C-1 even at 400 °C. By cycling heating and cooling up to ten times or heating at 300 °C for 12 h, the film shows good reversibility and robustness of the dielectric properties. This crosslinked PEN film will be a potential candidate as high performance film capacitor electronic devices materials used at high temperature.

Effects of Nitrite and Erythorbate on Clostridium perfringens Growth during Extended Cooling of Cured Ham.

PubMed

Osterbauer, Katie J; King, Amanda M; Seman, Dennis L; Milkowksi, Andrew L; Glass, Kathleen A; Sindelar, Jeffrey J

2017-10-01

To control the growth of Clostridium perfringens in cured meat products, the meat and poultry industries commonly follow stabilization parameters outlined in Appendix B, "Compliance Guidelines for Cooling Heat-Treated Meat and Poultry Products (Stabilization)" ( U.S. Department of Agriculture, Food Safety and Inspection Service [USDA-FSIS], 1999 ) to achieve cooling (54.4 to 4.4°C) within 15 h after cooking. In this study, extended cooling times and their impact on C. perfringens growth were examined. Phase 1 experiments consisted of cured ham with 200 mg/kg ingoing sodium nitrite and 547 mg/kg sodium erythorbate following five bilinear cooling profiles: a control (following Appendix B guidelines: stage A cooling [54.4 to 26.7°C] for 5 h, stage B cooling [26.7 to 4.4°C] for 10 h), extended stage A cooling for 7.5 or 10 h, and extended stage B cooling for 12.5 or 15 h. A positive growth control with 0 mg/kg nitrite added (uncured) was also included. No growth was observed in any treatment samples except the uncured control (4.31-log increase within 5 h; stage A). Phase 2 and 3 experiments were designed to investigate the effects of various nitrite and erythorbate concentrations and followed a 10-h stage A and 15-h stage B bilinear cooling profile. Phase 2 examined the effects of nitrite concentrations of 0, 50, 75, 100, 150, and 200 mg/kg at a constant concentration of erythorbate (547 mg/kg). Results revealed changes in C. perfringens populations for each treatment of 6.75, 3.59, 2.43, -0.38, -0.48, and -0.50 log CFU/g, respectively. Phase 3 examined the effects of various nitrite and erythorbate concentrations at 100 mg/kg nitrite with 0 mg/kg erythorbate, 100 with 250, 100 with 375, 100 with 547, 150 with 250, and 200 with 250, respectively. The changes in C. perfringens populations for each treatment were 4.99, 2.87, 2.50, 1.47, 0.89, and -0.60 log CFU/g, respectively. Variability in C. perfringens growth for the 100 mg/kg nitrite with 547 mg/kg erythorbate treatment was observed between phases 2 and 3 and may have been due to variations in treatment pH and NaCl concentrations. This study revealed the importance of nitrite and erythorbate for preventing growth of C. perfringens during a much longer (25 h) cooling period than currently specified in the USDA-FSIS Appendix B.

Non-Friedmann cosmology for the Local Universe, significance of the universal Hubble constant, and short-distance indicators of dark energy

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Teerikorpi, P.; Baryshev, Yu. V.

2006-09-01

Based on the increasing evidence of the cosmological relevance of the local Hubble flow, we consider a simple analytical cosmological model for the Local Universe. This is a non-Friedmann model with a non-uniform static space-time. The major dynamical factor controlling the local expansion is the antigravity produced by the omnipresent and permanent dark energy of the cosmic vacuum (or the cosmological constant). The antigravity dominates at larger distances than 1-2 Mpc from the center of the Local group. The model gives a natural explanation of the two key quantitative characteristics of the local expansion flow, which are the local Hubble constant and the velocity dispersion of the flow. The observed kinematical similarity of the local and global flows of expansion is clarified by the model. We analytically demonstrate the efficiency of the vacuum cooling mechanism that allows one to see the Hubble law this close to the Local group. The "universal Hubble constant" HV (≈60 km s-1 Mpc-1), depending only on the vacuum density, has special significance locally and globally. The model makes a number of verifiable predictions. It also unexpectedly shows that the dwarf galaxies of the local flow with the shortest distances and lowest redshifts may be the most sensitive indicators of dark energy in our neighborhood.

Observations of Space Weather and Space Climate Over the Past 15 Years From SABER (And Longer!)

NASA Technical Reports Server (NTRS)

Mlynczak, Marty; Hunt, Linda; Russell, James M., III

2016-01-01

The global infrared (IR) energy budget of the thermosphere has been reconstructed back 70 years (to 1947). IR cooling, integrated over a solar cycle, is relatively constant over the 5 complete cycles (19 -23) studied. Result implies that solar energy (particles and photons) has similar, small (< 7%) variation from one cycle to next. From Earth's upper atmosphere perspective, solar cycles are really more similar than different, over their length. No consistent relationship between peak of IR cooling and sunspot number peak. Results submitted to GRL 8/2016.

(DARPA) Optical Radiation Cooling and Heating In Integrated Devices: Circuit cavity optomechanics for cooling and amplification on a silicon chip

DTIC Science & Technology

2015-07-16

0.02(λ/ n )3 modal volumes while preserving optical cavity Q up to5×106 [Fig. 4(f)-(i)]. The mechanical mode is modeled to have fundamental resonance Qm...addition, a 30.64-MHz resonance is observed and identified as one of the wineglass modes (circumferential number n = 4, “square” mode [40]) with a measured...main challenge is that mechanical resonators operating at high frequencies are extremely stiff, having spring constant on the order of 107 N /m. This

Synthesis and magnetic properties of nickel nanoparticles

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

Singh, Jaiveer, E-mail: jaiveer24singh@gmail.com, E-mail: netramkaurav@yahoo.co.uk; Patel, Tarachand; Okram, Gunadhor S.

2016-05-23

Monodisperse nickel nanoparticles (Ni-NPs) were synthesized via a thermal decomposition process. The NPs were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). They were spherical with mean diameter of 4 nm. Zero field cooled (ZFC) and field cooled (FC) magnetization versus temperature data displayed interesting magnetic interactions. ZFC showed a peak at 4.49 K, indicating the super paramagnetic behavior. Magnetic anisotropic constant was estimated to be 4.62×10{sup 5} erg/cm{sup 3} and coercive field was 168 Oe at 3 K.

Effect of fast mold surface temperature evolution on iPP part morphology gradients

NASA Astrophysics Data System (ADS)

Liparoti, Sara; Sorrentino, Andrea; Guzman, Gustavo; Cakmak, Mukerrem; Titomanlio, Giuseppe

2016-03-01

The control of mold surface temperature is an important factor that affects the sample surface morphology as well as the structural gradients (orientation crystal size, and type) as well as cooling stresses. The frozen layer thickness formed during the filling stage also has a very significant effect on the flow resistance and thus on the resulting pressure drop and flow length in thin wall parts. The possibility to have a hot mold during filling and a quick cooling soon afterward is a significant process enhancement particularly for specialized applications such as micro injection molding and for the reproduction of micro structured surfaces. Up to now, several methods (electromagnetic, infrared, hot vapor fleshing etc,) were tried to achieve fast temperature evolution of the mold. Unfortunately, all these methods require a complex balance between thermal and mechanical problems, equipment cost, energy consumption, safety, molding cycle time and part quality achievable. In this work, a thin electrical resistance was designed and used to generate a fast and confined temperature variation on mold surface (by joule effect). Since the whole temperature evolution can take place in a few seconds, one can couple the advantages of a high surface temperature during filling with the advantages of a low mold temperature, fast cooling and low heating dissipation. Some experiments were performed with a commercial iPP resin. The effects of the surface temperature and of the heating time (under constant electric power) on surface finishing and on the final morphology (thickness and structure of the different layers) are explored and discussed.

Effect of fast mold surface temperature evolution on iPP part morphology gradients

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

Liparoti, Sara; Sorrentino, Andrea; Guzman, Gustavo

The control of mold surface temperature is an important factor that affects the sample surface morphology as well as the structural gradients (orientation crystal size, and type) as well as cooling stresses. The frozen layer thickness formed during the filling stage also has a very significant effect on the flow resistance and thus on the resulting pressure drop and flow length in thin wall parts. The possibility to have a hot mold during filling and a quick cooling soon afterward is a significant process enhancement particularly for specialized applications such as micro injection molding and for the reproduction of micromore » structured surfaces. Up to now, several methods (electromagnetic, infrared, hot vapor fleshing etc,) were tried to achieve fast temperature evolution of the mold. Unfortunately, all these methods require a complex balance between thermal and mechanical problems, equipment cost, energy consumption, safety, molding cycle time and part quality achievable. In this work, a thin electrical resistance was designed and used to generate a fast and confined temperature variation on mold surface (by joule effect). Since the whole temperature evolution can take place in a few seconds, one can couple the advantages of a high surface temperature during filling with the advantages of a low mold temperature, fast cooling and low heating dissipation. Some experiments were performed with a commercial iPP resin. The effects of the surface temperature and of the heating time (under constant electric power) on surface finishing and on the final morphology (thickness and structure of the different layers) are explored and discussed.« less

Isolating the roles of different forcing agents in global stratospheric temperature changes using model integrations with incrementally added single forcings

NASA Astrophysics Data System (ADS)

Aquila, V.; Swartz, W. H.; Waugh, D. W.; Colarco, P. R.; Pawson, S.; Polvani, L. M.; Stolarski, R. S.

2016-07-01

Satellite instruments show a cooling of global stratospheric temperatures over the whole data record (1979-2014). This cooling is not linear and includes two descending steps in the early 1980s and mid-1990s. The 1979-1995 period is characterized by increasing concentrations of ozone-depleting substances (ODSs) and by the two major volcanic eruptions of El Chichón (1982) and Mount Pinatubo (1991). The 1995-present period is characterized by decreasing ODS concentrations and by the absence of major volcanic eruptions. Greenhouse gas (GHG) concentrations increase over the whole time period. In order to isolate the roles of different forcing agents in the global stratospheric temperature changes, we performed a set of simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model with prescribed sea surface temperatures. We find that in our model simulations the cooling of the stratosphere from 1979 to present is mostly driven by changes in GHG concentrations in the middle and upper stratosphere and by GHG and ODS changes in the lower stratosphere. While the cooling trend caused by increasing GHGs is roughly constant over the satellite era, changing ODS concentrations cause a significant stratospheric cooling only up to the mid-1990s, when they start to decrease because of the implementation of the Montreal Protocol. Sporadic volcanic events and the solar cycle have a distinct signature in the time series of stratospheric temperature anomalies but do not play a statistically significant role in the long-term trends from 1979 to 2014. Several factors combine to produce the step-like behavior in the stratospheric temperatures: in the lower stratosphere, the flattening starting in the mid-1990s is due to the decrease in ozone-depleting substances; Mount Pinatubo and the solar cycle cause the abrupt steps through the aerosol-associated warming and the volcanically induced ozone depletion. In the middle and upper stratosphere, changes in solar irradiance are largely responsible for the step-like behavior of global temperature anomalies, together with volcanically induced ozone depletion and water vapor increases in the post-Pinatubo years.

Isolating the Roles of Different Forcing Agents in Global Stratospheric Temperature Changes Using Model Integrations with Incrementally Added Single Forcings

NASA Technical Reports Server (NTRS)

Aquila, V.; Swartz, W. H.; Waugh, D. W.; Colarco, P. R.; Pawson, S.; Polvani, L. M.; Stolarski, R. S.

2016-01-01

Satellite instruments show a cooling of global stratospheric temperatures over the whole data record (1979-2014). This cooling is not linear and includes two descending steps in the early 1980s and mid-1990s. The 1979-1995 period is characterized by increasing concentrations of ozone depleting substances (ODS) and by the two major volcanic eruptions of El Chichon (1982) and Mount Pinatubo (1991). The 1995-present period is characterized by decreasing ODS concentrations and by the absence of major volcanic eruptions. Greenhouse gas (GHG) concentrations increase over the whole time period. In order to isolate the roles of different forcing agents in the global stratospheric temperature changes, we performed a set of AMIP-style simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM). We find that in our model simulations the cooling of the stratosphere from 1979 to present is mostly driven by changes in GHG concentrations in the middle and upper stratosphere and by GHG and ODS changes in the lower stratosphere. While the cooling trend caused by increasing GHGs is roughly constant over the satellite era, changing ODS concentrations cause a significant stratospheric cooling only up to the mid-1990s, when they start to decrease because of the implementation of the Montreal Protocol. Sporadic volcanic events and the solar cycle have a distinct signature in the time series of stratospheric temperature anomalies but do not play a statistically significant role in the long-term trends from 1979 to 2014. Several factors combine to produce the step-like behavior in the stratospheric temperatures: in the lower stratosphere, the flattening starting in the mid-1990s is due to the decrease in ozone-depleting substances; Mount Pinatubo and the solar cycle cause the abrupt steps through the aerosol-associated warming and the volcanically induced ozone depletion. In the middle and upper stratosphere, changes in solar irradiance are largely responsible for the step-like behavior of global temperature anomalies, together with volcanically induced ozone depletion and water vapor increases in the post-Pinatubo years.

Isolating the roles of different forcing agents in global stratospheric temperature changes using model integrations with incrementally added single forcings.

PubMed

Aquila, V; Swartz, W H; Waugh, D W; Colarco, P R; Pawson, S; Polvani, L M; Stolarski, R S

2016-07-16

Satellite instruments show a cooling of global stratospheric temperatures over the whole data record (1979-2014). This cooling is not linear, and includes two descending steps in the early 1980s and mid-1990s. The 1979-1995 period is characterized by increasing concentrations of ozone depleting substances (ODS) and by the two major volcanic eruptions of El Chichón (1982) and Mount Pinatubo (1991). The 1995-present period is characterized by decreasing ODS concentrations and by the absence of major volcanic eruptions. Greenhouse gas (GHG) concentrations increase over the whole time period. In order to isolate the roles of different forcing agents in the global stratospheric temperature changes, we performed a set of AMIP-style simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM). We find that in our model simulations the cooling of the stratosphere from 1979 to present is mostly driven by changes in GHG concentrations in the middle and upper stratosphere and by GHG and ODS changes in the lower stratosphere. While the cooling trend caused by increasing GHGs is roughly constant over the satellite era, changing ODS concentrations cause a significant stratospheric cooling only up to the mid-1990s, when they start to decrease because of the implementation of the Montreal Protocol. Sporadic volcanic events and the solar cycle have a distinct signature in the time series of stratospheric temperature anomalies but do not play a statistically significant role in the long-term trends from 1979 to 2014. Several factors combine to produce the step-like behavior in the stratospheric temperatures: in the lower stratosphere, the flattening starting in the mid 1990's is due to the decrease in ozone depleting substances; Mount Pinatubo and the solar cycle cause the abrupt steps through the aerosol-associated warming and the volcanically induced ozone depletion. In the middle and upper stratosphere, changes in solar irradiance are largely responsible for the step-like behavior of global temperatures anomalies, together with volcanically induced ozone depletion and water vapor increases in the post-Pinatubo years.

Isolating the roles of different forcing agents in global stratospheric temperature changes using model integrations with incrementally added single forcings

PubMed Central

Aquila, V.; Swartz, W. H.; Waugh, D. W.; Colarco, P. R.; Pawson, S.; Polvani, L. M.; Stolarski, R. S.

2018-01-01

Satellite instruments show a cooling of global stratospheric temperatures over the whole data record (1979–2014). This cooling is not linear, and includes two descending steps in the early 1980s and mid-1990s. The 1979–1995 period is characterized by increasing concentrations of ozone depleting substances (ODS) and by the two major volcanic eruptions of El Chichón (1982) and Mount Pinatubo (1991). The 1995-present period is characterized by decreasing ODS concentrations and by the absence of major volcanic eruptions. Greenhouse gas (GHG) concentrations increase over the whole time period. In order to isolate the roles of different forcing agents in the global stratospheric temperature changes, we performed a set of AMIP-style simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM). We find that in our model simulations the cooling of the stratosphere from 1979 to present is mostly driven by changes in GHG concentrations in the middle and upper stratosphere and by GHG and ODS changes in the lower stratosphere. While the cooling trend caused by increasing GHGs is roughly constant over the satellite era, changing ODS concentrations cause a significant stratospheric cooling only up to the mid-1990s, when they start to decrease because of the implementation of the Montreal Protocol. Sporadic volcanic events and the solar cycle have a distinct signature in the time series of stratospheric temperature anomalies but do not play a statistically significant role in the long-term trends from 1979 to 2014. Several factors combine to produce the step-like behavior in the stratospheric temperatures: in the lower stratosphere, the flattening starting in the mid 1990’s is due to the decrease in ozone depleting substances; Mount Pinatubo and the solar cycle cause the abrupt steps through the aerosol-associated warming and the volcanically induced ozone depletion. In the middle and upper stratosphere, changes in solar irradiance are largely responsible for the step-like behavior of global temperatures anomalies, together with volcanically induced ozone depletion and water vapor increases in the post-Pinatubo years. PMID:29593948

An Analog Earth Climate Model

NASA Astrophysics Data System (ADS)

Varekamp, J. C.

2010-12-01

The earth climate is broadly governed by the radiative power of the sun as well as the heat retention and convective cooling of the atmosphere. I have constructed an analog earth model for an undergraduate climate class that simulates mean climate using these three parameters. The ‘earth’ is a hollow, black, bronze sphere (4 cm diameter) mounted on a thin insulated rod, and illuminated by two opposite optic fibers, with light focused on the sphere by a set of lenses. The sphere is encased in a large double-walled aluminum cylinder (34 cm diameter by 26 cm high) with separate water cooling jackets at the top, bottom, and sides. The cylinder can be filled with a gas of choice at a variety of pressures or can be run in vacuum. The exterior is cladded with insulation, and the temperature of the sphere, atmosphere and walls is monitored with thermocouples. The temperature and waterflow of the three cooling jackets can be monitored to establish the energy output of the whole system; the energy input is the energy yield of the two optic fibers. A small IR transmissive lens at the top provides the opportunity to hook up the fiber of a hyper spectrometer to monitor the emission spectrum of the black ‘earth’ sphere. A pressure gauge and gas inlet-outlet system for flushing of the cell completes it. The heat yield of the cooling water at the top is the sum of the radiative and convective components, whereas the bottom jacket only carries off the radiative heat of the sphere. Undergraduate E&ES students at Wesleyan University have run experiments with dry air, pure CO2, N2 and Ar at 1 atmosphere, and a low vacuum run was accomplished to calibrate the energy input. For each experiment, the lights are flipped on, the temperature acquisition routine is activated, and the sphere starts to warm up until an equilibrium temperature has been reached. The lights are then flipped off and the cooling sequence towards ambient is registered. The energy input is constant for a given experiment. For each time increment the radiative heat loss of the sphere is calculated from the Stefan Boltzman expression using the observed temperature at that time. The heating of the ‘earth sphere’ is accounted for in the energy balance equation by applying the temperature increase per time increment with the specific heat of bronze. The remaining energy term is the sum of the convective cooling and greenhouse effect. The heat budgets of the cooling trajectories were calculated analogous, with radiative and convective cooling causing the temperature drop per time increment. The greenhouse component again is lumped with the convective term. Equilibrium temperatures of 50-70 C were reached, with ambient temperature at 22 C. Somewhat surprising, experiments with radiatively neutral pure Argon gas yielded the highest equilibrium temperatures. Argon had the lowest specific heat of the gases used, and the observed equilibrium temperatures for different cell gases broadly scaled inversely with the heat capacity of those gases. Apparently, the efficiency of the free convective cooling strongly impacts the equilibrium temperatures. The greenhouse effects possibly have only a minor impact on final temperature as a result of the short cell pathlength. Experiments at higher cell filling pressures may provide more insight in this.

On the Importance of High Frequency Gravity Waves for Ice Nucleation in the Tropical Tropopause Layer

NASA Technical Reports Server (NTRS)

Jensen, Eric J.

2016-01-01

Recent investigations of the influence of atmospheric waves on ice nucleation in cirrus have identified a number of key processes and sensitivities: (1) ice concentrations produced by homogeneous freezing are strongly dependent on cooling rates, with gravity waves dominating upper tropospheric cooling rates; (2) rapid cooling driven by high-frequency waves are likely responsible for the rare occurrences of very high ice concentrations in cirrus; (3) sedimentation and entrainment tend to decrease ice concentrations as cirrus age; and (4) in some situations, changes in temperature tendency driven by high-frequency waves can quench ice nucleation events and limit ice concentrations. Here we use parcel-model simulations of ice nucleation driven by long-duration, constant-pressure balloon temperature time series, along with an extensive dataset of cold cirrus microphysical properties from the recent ATTREX high-altitude aircraft campaign, to statistically examine the importance of high-frequency waves as well as the consistency between our theoretical understanding of ice nucleation and observed ice concentrations. The parcel-model simulations indicate common occurrence of peak ice concentrations exceeding several hundred per liter. Sedimentation and entrainment would reduce ice concentrations as clouds age, but 1-D simulations using a wave parameterization (which underestimates rapid cooling events) still produce ice concentrations higher than indicated by observations. We find that quenching of nucleation events by high-frequency waves occurs infrequently and does not prevent occurrences of large ice concentrations in parcel simulations of homogeneous freezing. In fact, the high-frequency variability in the balloon temperature data is entirely responsible for production of these high ice concentrations in the simulations.

3-Dimensional numerical study of cooling performance of a heat sink with air-water flow through mini-channel

NASA Astrophysics Data System (ADS)

Majumder, Sambit; Majumder, Abhik; Bhaumik, Swapan

2016-07-01

The present microelectronics market demands devices with high power dissipation capabilities having enhanced cooling per unit area. The drive for miniaturizing the devices to even micro level dimensions is shooting up the applied heat flux on such devices, resulting in complexity in heat transfer and cooling management. In this paper, a method of CPU processor cooling is introduced where active and passive cooling techniques are incorporated simultaneously. A heat sink consisting of fins is designed, where water flows internally through the mini-channel fins and air flows externally. Three dimensional numerical simulations are performed for large set of Reynolds number in laminar region using finite volume method for both developing flows. The dimensions of mini-channel fins are varied for several aspect ratios such as 1, 1.33, 2 and 4. Constant temperature (T) boundary condition is applied at heat sink base. Channel fluid temperature, pressure drop are analyzed to obtain best cooling option in the present study. It has been observed that as the aspect ratio of the channel decreases Nusselt number decreases while pressure drop increases. However, Nusselt number increases with increase in Reynolds number.

Development and Experimental Evaluation of Passive Fuel Cell Thermal Control

NASA Technical Reports Server (NTRS)

Colozza, Anthony J.; Jakupca, Ian J.; Castle, Charles H.; Burke, Kenneth A.

2014-01-01

To provide uniform cooling for a fuel cell stack, a cooling plate concept was evaluated. This concept utilized thin cooling plates to extract heat from the interior of a fuel cell stack and move this heat to a cooling manifold where it can be transferred to an external cooling fluid. The advantages of this cooling approach include a reduced number of ancillary components and the ability to directly utilize an external cooling fluid loop for cooling the fuel cell stack. A number of different types of cooling plates and manifolds were developed. The cooling plates consisted of two main types; a plate based on thermopyrolytic graphite (TPG) and a planar (or flat plate) heat pipe. The plates, along with solid metal control samples, were tested for both thermal and electrical conductivity. To transfer heat from the cooling plates to the cooling fluid, a number of manifold designs utilizing various materials were devised, constructed, and tested. A key aspect of the manifold was that it had to be electrically nonconductive so it would not short out the fuel cell stack during operation. Different manifold and cooling plate configurations were tested in a vacuum chamber to minimize convective heat losses. Cooling plates were placed in the grooves within the manifolds and heated with surface-mounted electric pad heaters. The plate temperature and its thermal distribution were recorded for all tested combinations of manifold cooling flow rates and heater power loads. This testing simulated the performance of the cooling plates and manifold within an operational fuel cell stack. Different types of control valves and control schemes were tested and evaluated based on their ability to maintain a constant temperature of the cooling plates. The control valves regulated the cooling fluid flow through the manifold, thereby controlling the heat flow to the cooling fluid. Through this work, a cooling plate and manifold system was developed that could maintain the cooling plates within a minimal temperature band with negligible thermal gradients over power profiles that would be experienced within an operating fuel cell stack.

Post-hypothermic cardiac left ventricular systolic dysfunction after rewarming in an intact pig model

PubMed Central

2010-01-01

Introduction We developed a minimally invasive, closed chest pig model with the main aim to describe hemodynamic function during surface cooling, steady state severe hypothermia (one hour at 25°C) and surface rewarming. Methods Twelve anesthetized juvenile pigs were acutely catheterized for measurement of left ventricular (LV) pressure-volume loops (conductance catheter), cardiac output (Swan-Ganz), and for vena cava inferior occlusion. Eight animals were surface cooled to 25°C, while four animals were kept as normothermic time-matched controls. Results During progressive cooling and steady state severe hypothermia (25°C) cardiac output (CO), stroke volume (SV), mean arterial pressure (MAP), maximal deceleration of pressure in the cardiac cycle (dP/dtmin), indexes of LV contractility (preload recruitable stroke work, PRSW, and maximal acceleration of pressure in the cardiac cycle, dP/dtmax) and LV end diastolic and systolic volumes (EDV and ESV) were significantly reduced. Systemic vascular resistance (SVR), isovolumetric relaxation time (Tau), and oxygen content in arterial and mixed venous blood increased significantly. LV end diastolic pressure (EDP) remained constant. After rewarming all the above mentioned hemodynamic variables that were depressed during 25°C remained reduced, except for CO that returned to pre-hypothermic values due to an increase in heart rate. Likewise, SVR and EDP were significantly reduced after rewarming, while Tau, EDV, ESV and blood oxygen content normalized. Serum levels of cardiac troponin T (TnT) and tumor necrosis factor-alpha (TNF-α) were significantly increased. Conclusions Progressive cooling to 25°C followed by rewarming resulted in a reduced systolic, but not diastolic left ventricular function. The post-hypothermic increase in heart rate and the reduced systemic vascular resistance are interpreted as adaptive measures by the organism to compensate for a hypothermia-induced mild left ventricular cardiac failure. A post-hypothermic increase in TnT indicates that hypothermia/rewarming may cause degradation of cardiac tissue. There were no signs of inadequate global oxygenation throughout the experiments. PMID:21092272

Investigation of Spray Cooling Schemes for Dynamic Thermal Management

NASA Astrophysics Data System (ADS)

Yata, Vishnu Vardhan Reddy

This study aims to investigate variable flow and intermittent flow spray cooling characteristics for efficiency improvement in active two-phase thermal management systems. Variable flow spray cooling scheme requires control of pump input voltage (or speed), while intermittent flow spray cooling scheme requires control of solenoid valve duty cycle and frequency. Several testing scenarios representing dynamic heat load conditions are implemented to characterize the overall performance of variable flow and intermittent flow spray cooling cases in comparison with the reference, steady flow spray cooling case with constant flowrate, continuous spray cooling. Tests are conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. HFE-7100 dielectric liquid is selected as the working fluid. Two types of test samples are prepared on 10 mm x 10 mm x 2 mm copper substrates with matching size thick film resistors attached onto the opposite side, to generate heat and simulate high heat flux electronic devices. The test samples include: (i) plain, smooth surface, and (ii) microporous surface featuring 100 ?m thick copper-based coating prepared by dual stage electroplating technique. Experimental conditions involve HFE-7100 at atmospheric pressure and 30°C and 10°C subcooling. Steady flow spray cooling tests are conducted at flow rates of 2-5 ml/cm2.s, by controlling the heat flux in increasing steps, and recording the corresponding steady-state temperatures to obtain cooling curves in the form of surface superheat vs. heat flux. Variable flow and intermittent flow spray cooling tests are done at selected flowrate and subcooling conditions to investigate the effects of dynamic flow conditions on maintaining the target surface temperatures defined based on reference steady flow spray cooling performance.

Watering the Tree of Science: Science Education, Local Knowledge, and Agency in Zambia's PSA Program

NASA Astrophysics Data System (ADS)

Lample, Emily

With increased public interest in protecting the environment, scientists and engineers aim to improve energy conversion efficiency. Thermoelectrics offer many advantages as thermal management technology. When compared to vapor compression refrigeration, above approximately 200 to 600 watts, cost in dollars per watt as well as COP are not advantageous for thermoelectrics. The goal of this work was to determine if optimized pulse supercooling operation could improve cooling capacity or efficiency of a thermoelectric device. The basis of this research is a thermal-electrical analogy based modeling study using SPICE. Two models were developed. The first model, a standalone thermocouple with no attached mass to be cooled. The second, a system that includes a module attached to a heat generating mass. With the thermocouple study, a new approach of generating response surfaces with characteristic parameters was applied. The current pulse height and pulse on-time was identified for maximizing Net Transient Advantage, a newly defined metric. The corresponding pulse height and pulse on-time was utilized for the system model. Along with the traditional steady state starting current of Imax, Iopt was employed. The pulse shape was an isosceles triangle. For the system model, metrics new to pulse cooling were Qc, power consumption and COP. The effects of optimized current pulses were studied by changing system variables. Further studies explored time spacing between pulses and temperature distribution in the thermoelement. It was found net Q c over an entire pulse event can be improved over Imax steady operation but not over steady I opt operation. Qc can be improved over Iopt operation but only during the early part of the pulse event. COP is reduced in transient pulse operation due to the different time constants of Qc and Pin. In some cases lower performance interface materials allow more Qc and better COP during transient operation than higher performance interface materials. Important future work might look at developing innovative ways of biasing Joule heat to Th..

Recent advances in chemical synthesis methodology of inorganic materials and theoretical computations of metal nanoparticles/carbon interfaces

NASA Astrophysics Data System (ADS)

Harris, Andrew G.

With increased public interest in protecting the environment, scientists and engineers aim to improve energy conversion efficiency. Thermoelectrics offer many advantages as thermal management technology. When compared to vapor compression refrigeration, above approximately 200 to 600 watts, cost in dollars per watt as well as COP are not advantageous for thermoelectrics. The goal of this work was to determine if optimized pulse supercooling operation could improve cooling capacity or efficiency of a thermoelectric device. The basis of this research is a thermal-electrical analogy based modeling study using SPICE. Two models were developed. The first model, a standalone thermocouple with no attached mass to be cooled. The second, a system that includes a module attached to a heat generating mass. With the thermocouple study, a new approach of generating response surfaces with characteristic parameters was applied. The current pulse height and pulse on-time was identified for maximizing Net Transient Advantage, a newly defined metric. The corresponding pulse height and pulse on-time was utilized for the system model. Along with the traditional steady state starting current of Imax, Iopt was employed. The pulse shape was an isosceles triangle. For the system model, metrics new to pulse cooling were Qc, power consumption and COP. The effects of optimized current pulses were studied by changing system variables. Further studies explored time spacing between pulses and temperature distribution in the thermoelement. It was found net Q c over an entire pulse event can be improved over Imax steady operation but not over steady I opt operation. Qc can be improved over Iopt operation but only during the early part of the pulse event. COP is reduced in transient pulse operation due to the different time constants of Qc and Pin. In some cases lower performance interface materials allow more Qc and better COP during transient operation than higher performance interface materials. Important future work might look at developing innovative ways of biasing Joule heat to Th..

Network performance analysis and management for cyber-physical systems and their applications

NASA Astrophysics Data System (ADS)

Emfinger, William A.

With increased public interest in protecting the environment, scientists and engineers aim to improve energy conversion efficiency. Thermoelectrics offer many advantages as thermal management technology. When compared to vapor compression refrigeration, above approximately 200 to 600 watts, cost in dollars per watt as well as COP are not advantageous for thermoelectrics. The goal of this work was to determine if optimized pulse supercooling operation could improve cooling capacity or efficiency of a thermoelectric device. The basis of this research is a thermal-electrical analogy based modeling study using SPICE. Two models were developed. The first model, a standalone thermocouple with no attached mass to be cooled. The second, a system that includes a module attached to a heat generating mass. With the thermocouple study, a new approach of generating response surfaces with characteristic parameters was applied. The current pulse height and pulse on-time was identified for maximizing Net Transient Advantage, a newly defined metric. The corresponding pulse height and pulse on-time was utilized for the system model. Along with the traditional steady state starting current of Imax, Iopt was employed. The pulse shape was an isosceles triangle. For the system model, metrics new to pulse cooling were Qc, power consumption and COP. The effects of optimized current pulses were studied by changing system variables. Further studies explored time spacing between pulses and temperature distribution in the thermoelement. It was found net Q c over an entire pulse event can be improved over Imax steady operation but not over steady I opt operation. Qc can be improved over Iopt operation but only during the early part of the pulse event. COP is reduced in transient pulse operation due to the different time constants of Qc and Pin. In some cases lower performance interface materials allow more Qc and better COP during transient operation than higher performance interface materials. Important future work might look at developing innovative ways of biasing Joule heat to Th..

Soft error aware physical synthesis

NASA Astrophysics Data System (ADS)

Assis, Thiago Rocha de

With increased public interest in protecting the environment, scientists and engineers aim to improve energy conversion efficiency. Thermoelectrics offer many advantages as thermal management technology. When compared to vapor compression refrigeration, above approximately 200 to 600 watts, cost in dollars per watt as well as COP are not advantageous for thermoelectrics. The goal of this work was to determine if optimized pulse supercooling operation could improve cooling capacity or efficiency of a thermoelectric device. The basis of this research is a thermal-electrical analogy based modeling study using SPICE. Two models were developed. The first model, a standalone thermocouple with no attached mass to be cooled. The second, a system that includes a module attached to a heat generating mass. With the thermocouple study, a new approach of generating response surfaces with characteristic parameters was applied. The current pulse height and pulse on-time was identified for maximizing Net Transient Advantage, a newly defined metric. The corresponding pulse height and pulse on-time was utilized for the system model. Along with the traditional steady state starting current of Imax, Iopt was employed. The pulse shape was an isosceles triangle. For the system model, metrics new to pulse cooling were Qc, power consumption and COP. The effects of optimized current pulses were studied by changing system variables. Further studies explored time spacing between pulses and temperature distribution in the thermoelement. It was found net Q c over an entire pulse event can be improved over Imax steady operation but not over steady I opt operation. Qc can be improved over Iopt operation but only during the early part of the pulse event. COP is reduced in transient pulse operation due to the different time constants of Qc and Pin. In some cases lower performance interface materials allow more Qc and better COP during transient operation than higher performance interface materials. Important future work might look at developing innovative ways of biasing Joule heat to Th..

The NICMOS Cooling SYSTEM-5 Years of Successful On-Orbit Operation

NASA Astrophysics Data System (ADS)

Swift, W. L.; Dolan, F. X.; Zagarola, M. V.

2008-03-01

The NICMOS Cooling System consists of a closed-loop turbo-Brayton cryocooler coupled with a cryogenic circulator that provides refrigeration to the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope (HST). The cryocooler heat is rejected to space through a capillary pumped loop connected to radiators mounted on the side of the telescope. The system was deployed and integrated with NICMOS by astronauts during STS-109 (Space Shuttle Columbia) in March 2002. It has operated nearly continuously without performance degradation since that time, maintaining NICMOS detectors at a constant temperature of 77 K. Miniature, high-speed turbomachines are used in the cryocooler and the circulator loop to provide vibration-free, long-life operation. A small centrifugal compressor and miniature turboalternator are key elements of the closed loop cryocooler. A miniature cryogenic centrifugal circulator in a separate pressurized neon loop transports heat from the NICMOS instrument to the cryocooler interface heat exchanger. This paper describes the development of the system, key operational features, ground and orbital tests prior to its deployment, and operational results during its five-year operational history on orbit.

Improvement in Stability of SPring-8 Standard X-Ray Monochromators with Water-Cooled Crystals

NASA Astrophysics Data System (ADS)

Yamazaki, Hiroshi; Shimizu, Yasuhiro; Miura, Takanori; Tanaka, Masayuki; Kishimoto, Hikaru; Matsuzaki, Yasuhisa; Shimizu, Nobtaka; Kawano, Yoshiaki; Kumasaka, Takashi; Yamamoto, Masaki; Koganezawa, Tomoyuki; Sato, Masugu; Hirosawa, Ichiro; Senba, Yasunori; Ohashi, Haruhiko; Goto, Shunji; Ishikawa, Tetsuya

2010-06-01

SPring-8 standard double-crystal monochromators containing water-cooled crystals were stabilized to a sufficient level to function as a part of optics components to supply stable microfocused x-ray beams, by determining causes of the instability and then removing them. The instability was caused by two factors—thermal deformation of fine stepper stages in the monochromator, which resulted in reduction in beam intensity with time, and vibrations of coolant supply units and vacuum pumps, which resulted in fluctuation in beam intensity. We remodeled the crystal holders to maintain the stage temperatures constant with water, attached x-ray and electron shields to the stages in order to prevent their warming up, introduced accumulators in the water circuits to absorb pressure pulsation, used polyurethane tubes to stabilize water flow, and placed rubber cushions un der scroll vacuum pumps. As a result, the intensity reduction rate of the beam decreased from 26% to 1% per hour and the intensity fluctuation from 13% to 1%. The monochromators were also modified to prevent radiation damage to the crystals, materials used as a water seal, and motor cables.

Growth, structural, thermal, dielectric and optical studies on HBST crystal: A potential THz emitter

NASA Astrophysics Data System (ADS)

Ma, Yuzhe; Teng, Bing; Cao, Lifeng; Zhong, Degao; Ji, Shaohua; Teng, Fei; Liu, Jiaojiao; Yao, Yuan; Tang, Jie; Tong, Jiaming

2018-02-01

The efficient organic nonlinear optical material 4-hydroxy benzaldehyde-N-methyl 4-stilbazolium tosylate (HBST) was grown from methanol by slope nucleation method combined with slow cooling (SNM-SC) for the first time. The optimum growth conditions based on the cooling rate was further investigated. The single crystal X-ray diffraction (XRD) revealed that the chromophores of HBST crystal make an angle of about 33° with respect to the a-axis, which is close to the optimum of Terahertz (THz)-wave generation and electro-optics applications. NMR and FT-IR spectral studies have been performed to ascertain various functional groups present in the sample. Futhermore, the thermal stability and decomposition stages were analyzed through TG-DTA and DSC techniques. The dielectric constant and dielectric loss of HBST crystal have been studied. Critical optical properties like the absorption coefficient, refractive index, cut-off wavelength and band gap energy were calculated. Photoluminescence (PL) exication studies indicated green emission occured at 507 nm. All the results of HBST crystal make it a promising candidate in the fields of optoelectronic and the generation of THz.

Understanding homogeneous nucleation in solidification of aluminum by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Mahata, Avik; Asle Zaeem, Mohsen; Baskes, Michael I.

2018-02-01

Homogeneous nucleation from aluminum (Al) melt was investigated by million-atom molecular dynamics simulations utilizing the second nearest neighbor modified embedded atom method potentials. The natural spontaneous homogenous nucleation from the Al melt was produced without any influence of pressure, free surface effects and impurities. Initially isothermal crystal nucleation from undercooled melt was studied at different constant temperatures, and later superheated Al melt was quenched with different cooling rates. The crystal structure of nuclei, critical nucleus size, critical temperature for homogenous nucleation, induction time, and nucleation rate were determined. The quenching simulations clearly revealed three temperature regimes: sub-critical nucleation, super-critical nucleation, and solid-state grain growth regimes. The main crystalline phase was identified as face-centered cubic, but a hexagonal close-packed (hcp) and an amorphous solid phase were also detected. The hcp phase was created due to the formation of stacking faults during solidification of Al melt. By slowing down the cooling rate, the volume fraction of hcp and amorphous phases decreased. After the box was completely solid, grain growth was simulated and the grain growth exponent was determined for different annealing temperatures.

Magnetic properties of electron-doped La0.23Ca0.77MnO3 nanoparticles

NASA Astrophysics Data System (ADS)

Markovich, V.; Jung, G.; Wisniewski, A.; Mogilyansky, D.; Puzniak, R.; Kohn, A.; Wu, X. D.; Suzuki, K.; Gorodetsky, G.

2012-09-01

Magnetic properties of electron-doped La0.23Ca0.77MnO3 manganite nanoparticles, with average size of 12 and 60 nm, prepared by the glycine-nitrate method, have been investigated in the temperature range 5-300 K and magnetic fields up to 90 kOe. It is suggested that weak ferromagnetic moment results from ferromagnetic shells of the basically antiferromagnetic nanoparticles and from domains of frustrated disordered phase in the core. Assumption of two distinct sources of ferromagnetism is supported by the appearance of two independent ferromagnetic contributions in the fit of the T 3/2 Bloch law to spontaneous magnetization. The ferromagnetic components, which are more pronounced in smaller particles, occupy only a small fraction of the nanoparticle volume and the antiferromagnetic ground state remains stable. It is found that the magnetic hysteresis loops following field cooled processes, display size-dependent horizontal and vertical shifts, namely, exhibiting exchange bias effect. Time-dependent magnetization dynamics demonstrating two relaxation rates were observed at constant magnetic fields upon cooling to T < 100 K.

Magnetic and dielectric study of Fe-doped CdSe nanoparticles

NASA Astrophysics Data System (ADS)

Das, Sayantani; Banerjee, Sourish; Bandyopadhyay, Sudipta; Sinha, Tripurari Prasad

2018-01-01

Nanoparticles of cadmium selenide (CdSe) and Fe (5% and 10%) doped CdSe have been synthesized by soft chemical route and found to have cubic structure. The magnetic field dependent magnetization measurement of the doped samples indicates the presence of anti-ferromagnetic order. The temperature dependent magnetization (M-T) measurement under zero field cooled and field cooled conditions has also ruled out the presence of ferromagnetic component in the samples at room temperature as well as low temperature. In order to estimate the anti-ferromagnetic coupling among the doped Fe atoms, an M-T measurement at 500 Oe has been carried out, and the Curie-Weiss temperature θ of the samples has been estimated from the inverse of susceptibility versus temperature plots. The dielectric relaxation peaks are observed in the spectra of imaginary part of dielectric constant. The temperature dependent relaxation time is found to obey the Arrhenius law having activation energy 0.4 eV for Fe doped samples. The frequency dependent conductivity spectra are found to obey the power law. [Figure not available: see fulltext.

Experimental study on the cool storage performance of super absorbent polymers for cool storage clothes

NASA Astrophysics Data System (ADS)

Li, Shidong; Mo, Caisong; Wang, Junze; Zheng, Jingfu; Tian, Ruhong

2017-11-01

In this paper, a kind of cool storage clothes which can cool the human body in high temperature condition is put forward. super absorbent polymers was selected as a cold storage material, through at the normal and extreme environment simulation, the cold storage materials were prepared with different composition, and their performance was tested. Test results show that:under normal temperature conditions, the 1:50 concentration of super absorbent polymers continued to release the longest cooling time, compared with pure water, cooling time extended 43 minutes by about 30%; under the condition of 37°C, the 1:100 concentration of super absorbent polymers continued to release the longest cooling time, compared with pure water, cooling time extended 105 minutes by about 50%.

Isopods Failed to Acclimate Their Thermal Sensitivity of Locomotor Performance during Predictable or Stochastic Cooling

PubMed Central

Schuler, Matthew S.; Cooper, Brandon S.; Storm, Jonathan J.; Sears, Michael W.; Angilletta, Michael J.

2011-01-01

Most organisms experience environments that vary continuously over time, yet researchers generally study phenotypic responses to abrupt and sustained changes in environmental conditions. Gradual environmental changes, whether predictable or stochastic, might affect organisms differently than do abrupt changes. To explore this possibility, we exposed terrestrial isopods (Porcellio scaber) collected from a highly seasonal environment to four thermal treatments: (1) a constant 20°C; (2) a constant 10°C; (3) a steady decline from 20° to 10°C; and (4) a stochastic decline from 20° to 10°C that mimicked natural conditions during autumn. After 45 days, we measured thermal sensitivities of running speed and thermal tolerances (critical thermal maximum and chill-coma recovery time). Contrary to our expectation, thermal treatments did not affect the thermal sensitivity of locomotion; isopods from all treatments ran fastest at 33° to 34°C and achieved more than 80% of their maximal speed over a range of 10° to 11°C. Isopods exposed to a stochastic decline in temperature tolerated cold the best, and isopods exposed to a constant temperature of 20°C tolerated cold the worst. No significant variation in heat tolerance was observed among groups. Therefore, thermal sensitivity and heat tolerance failed to acclimate to any type of thermal change, whereas cold tolerance acclimated more during stochastic change than it did during abrupt change. PMID:21698113

Quantum Cascade Laser-Based Photoacoustic Sensor for Trace Detection of Formaldehyde Gas

PubMed Central

Elia, Angela; Di Franco, Cinzia; Spagnolo, Vincenzo; Lugarà, Pietro Mario; Scamarcio, Gaetano

2009-01-01

We report on the development of a photoacoustic sensor for the detection of formaldehyde (CH2O) using a thermoelectrically cooled distributed-feedback quantum cascade laser operating in pulsed mode at 5.6 μm. A resonant photoacoustic cell, equipped with four electret microphones, is excited in its first longitudinal mode at 1,380 Hz. The absorption line at 1,778.9 cm−1 is selected for CH2O detection. A detection limit of 150 parts per billion in volume in nitrogen is achieved using a 10 seconds time constant and 4 mW laser power. Measurements in ambient air will require water vapour filters. PMID:22574040

Experimental and numerical study of windage losses in the small gap region of a high speed electric motor

NASA Astrophysics Data System (ADS)

Anderson, Kevin; Lin, Jun T.; Wong, Alexander J.

2017-11-01

Research findings of an experimental and numerical investigation of windage losses in the small annular air gap region between the stator and rotor of a high speed electric motor are presented herein. The experimental set-up is used to empirically measure the windage losses in the motor by measuring torque and rotational speed. The motor rotor spins at roughly 30,000 rpm and the rotor sets up windage losses on the order of 100 W. Axial air flow of 200 L/min is used to cool the motor, thus setting up a pseudo Taylor-Couette Poiseuille type of flow. Details of the experimental test apparatus, instrumentation and data acquisition are given. Experimental data for spin-down (both actively and passively cooled) and calibration of bearing windage losses are discussed. A Computational Fluid Dynamics (CFD) model is developed and used to predict the torque speed curve and windage losses in the motor. The CFD model is correlated with the experimental data. The CFD model is also used to predict the formation of the Taylor-Couette cells in the small gap region of the high speed motor. Results for windage losses, spin-down time constant, bearing losses, and torque of the motor versus cooling air mass flow rate and rotational speed are presented in this study. Mechanical Engineering.

A quiet tunnel investigation of hypersonic boundary-layer stability over a cooled, flared cone

NASA Technical Reports Server (NTRS)

Blanchard, Alan E.; Selby, Gregory V.; Wilkinson, Stephen P.

1996-01-01

A flared-cone model under adiabatic and cooled-wall conditions was placed in a calibrated, low-disturbance Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same 'N = 10' criterion used to predict boundary-layer transition in subsonic, transonic, and supersonic flows under low freestream noise conditions was found to be applicable for the hypersonic flow regime as well. Under cooled-wall conditions, a unique set of spectral data was acquired that documents the linear, nonlinear, and breakdown regions associated with the transition of hypersonic flow under low-noise conditions.

WATER BOILER REACTOR

DOEpatents

King, L.D.P.

1960-11-22

As its name implies, this reactor utilizes an aqueous solution of a fissionable element salt, and is also conventional in that it contains a heat exchanger cooling coil immersed in the fuel. Its novelty lies in the utilization of a cylindrical reactor vessel to provide a critical region having a large and constant interface with a supernatant vapor region, and the use of a hollow sleeve coolant member suspended from the cover assembly in coaxial relation with the reactor vessel. Cool water is circulated inside this hollow coolant member, and a gap between its outer wall and the reactor vessel is used to carry off radiolytic gases for recombination in an external catalyst chamber. The central passage of the coolant member defines a reflux condenser passage into which the externally recombined gases are returned and condensed. The large and constant interface between fuel solution and vapor region prevents the formation of large bubbles and minimizes the amount of fuel salt carried off by water vapor, thus making possible higher flux densities, specific powers and power densities.

Thermal Components Boost Performance of HVAC Systems

NASA Technical Reports Server (NTRS)

2012-01-01

As the International Space Station (ISS) travels 17,500 miles per hour, normal is having a constant sensation of free-falling. Normal is no rain, but an extreme amount of shine.with temperatures reaching 250 F when facing the Sun. Thanks to a number of advanced control systems onboard the ISS, however, the interior of the station remains a cool, comfortable, normal environment where astronauts can live and work for extended periods of time. There are two main control systems on the ISS that make it possible for humans to survive in space: the Thermal Control System (TCS) and the Environmental Control and Life Support system. These intricate assemblies work together to supply water and oxygen, regulate temperature and pressure, maintain air quality, and manage waste. Through artificial means, these systems create a habitable environment for the space station s crew. The TCS constantly works to regulate the temperature not only for astronauts, but for the critical instruments and machines inside the spacecraft as well. To do its job, the TCS encompasses several components and systems both inside and outside of the ISS. Inside the spacecraft, a liquid heat-exchange process mechanically pumps fluids in closed-loop circuits to collect, transport, and reject heat. Outside the ISS, an external system circulates anhydrous ammonia to transport heat and cool equipment, and radiators release the heat into space. Over the years, NASA has worked with a variety of partners.public and private, national and international. to develop and refine the most complex thermal control systems ever built for spacecraft, including the one on the ISS.

Cool down time optimization of the Stirling cooler

NASA Astrophysics Data System (ADS)

Xia, M.; Chen, X. P.; Y Li, H.; Gan, Z. H.

2017-12-01

The cooling power is one of the most important performances of a Stirling cooler. However, in some special fields, the cool down time is more important. It is a great challenge to improve the cool down time of the Stirling cooler. A new split Stirling linear cryogenic cooler SCI09H was designed in this study. A new structure of linear motor is used in the compressor, and the machine spring is used in the expander. In order to reduce the cool down time, the stainless-steel mesh of regenerator is optimized. The weight of the cooler is 1.1 kg, the cool down time to 80K is 2 minutes at 296K with a 250J thermal mass, the cooling power is 1.1W at 80K, and the input power is 50W.

Application of autoclaving-cooling cycling treatment to improve resistant starch content of corn-based rice analogues

NASA Astrophysics Data System (ADS)

Hidayat, B.; Muslihudin, M.; Akmal, S.

2018-01-01

Resistant starch is one important component determining the characteristics of a functional food. The aim of the research was to determine the cooling time optimum in the autoclaving-cooling treatment to increase the resistance starch content corn-based rice analogues, with 6 level of cooling time (0 hours/control, 12 hours, 24 hours, 36 hours, 48 hours and 60 hours). The results showed that cooling at 4°C for 60 hours would increase the resistant starch content (6.27% to 15.38%), dietary fiber content (14.53% to 20.17%); and decrease the digestible starch content (61.81% to 52.70%). Cooling time level at 4°C for 24 hours, would increase the sensory score of corn-based rice analogues then back down until cooling time level of 60 hours. Microscopic analysis of granular structure using SEM indicated that cooling time had a linear correlation with cracks intensity on the granule surface of the corn-based rice analogues. The high content of resistant starch showed that the application of cooling time level at 4°C for 24 hours would improve the functional properties of corn-based rice analogues with sensory characteristics remain favorable to panelists.

Cycle time improvement for plastic injection moulding process by sub groove modification in conformal cooling channel

NASA Astrophysics Data System (ADS)

Kamarudin, K.; Wahab, M. S.; Batcha, M. F. M.; Shayfull, Z.; Raus, A. A.; Ahmed, Aqeel

2017-09-01

Mould designers have been struggling for the improvement of the cooling system performance, despite the fact that the cooling system complexity is physically limited by the fabrication capability of the conventional tooling methods. However, the growth of Solid Free Form Technology (SFF) allow the mould designer to develop more than just a regular conformal cooling channel. Numerous researchers demonstrate that conformal cooling channel was tremendously given significant result in the improvement of productivity and quality in the plastic injection moulding process. This paper presents the research work that applies the passive enhancement method in square shape cooling channel to enhance the efficiency of cooling performance by adding the sub groove to the cooling channel itself. Previous design that uses square shape cooling channel was improved by adding various numbers of sub groove to meet the best sub groove design that able reduced the cooling time. The effect of sub groove design on cooling time was investigated by Autodesk Modlflow Insight software. The simulation results showed that the various sub groove designs give different values to ejection time. The Design 7 showed the lowest value of ejection time with 24.3% increment. The addition of sub groove significantly increased a coolant velocity and a rate of heat transfer from molten plastic to coolant.

Remote actuated cryocooler for superconducting generator and method of assembling the same

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

Stautner, Ernst Wolfgang; Haran, Kiruba Sivasubramaniam; Fair, Ruben Jeevanasan

2017-02-14

In one embodiment, a cryocooler assembly for cooling a heat load is provided. The cryocooler assembly includes a vacuum vessel surrounding the heat load and a cryocooler at least partially inserted into the vacuum vessel, the cryocooler including a coldhead. The assembly further includes an actuator coupled to the cryocooler. The actuator is configured to translate the cryocooler coldhead into thermal engagement with the heat load and to maintain constant pressure of the coldhead against the heat load to facilitate maintaining thermal engagement with the heat load as the heat load shrinks during a cool down process.

High voltage solar cell power generating system

NASA Technical Reports Server (NTRS)

Levy, E., Jr.; Opjorden, R. W.; Hoffman, A. C.

1974-01-01

A laboratory solar power system regulated by on-panel switches has been delivered for operating high power (3 kW), high voltage (15,000 volt) loads (communication tubes, ion thrusters). The modular system consists of 26 solar arrays, each with an integral light source and cooling system. A typical array contains 2,560 series-connected cells. Each light source consists of twenty 500-watt tungsten iodide lamps providing plus or minus 5 percent uniformity at one solar constant. An array temperature of less than 40 C is achieved using an infrared filter, a water-cooled plate, a vacuum hold-down system, and air flushing.

Electrolyte changes in the blood plasma of broilers as influenced by cooling during summer

NASA Astrophysics Data System (ADS)

Sharma, M. L.; Gangwar, P. C.

1987-09-01

High temperature significantly (P < 0.01) decreased the Na+ and K+ concentrations in the blood plasma of both the sexes of broilers during 4 to 8 weeks of age. Relatively constant levels of these electrolytes were observed during this phase of growth and the sex of the bird had no significant effect on their levels. Greater broiler weights and higher levels of plasma electrolyte were achieved by the use of cooling systems (which were more effective in the hot dry part of the summer than in the hot humid part).

Aging and domain growth in K1-xLixTaO3 (x<=0.05)

NASA Astrophysics Data System (ADS)

Alberici-Kious, F.; Bouchaud, J.-P.; Cugliandolo, L. F.; Doussineau, P.; Levelut, A.

2000-12-01

We present experimental results on the dielectric constant in orientational glasses K1-xLixTaO3 (KLT) with x<=0.05, together with the detailed (analytic and numerical) study of a model which attributes the observed aging to the motion of the walls of polarization domains. We show that the dielectric constant after a positive temperature jump goes through a maximum as a function of the subsequent time. This observation and those previously reported (aging, cooling rate dependence, etc.) are compared with the predictions of the model, in which the variations of the dielectric constant are attributed to the change of polarization domain wall area. The total area decreases by domain growth and increases by nucleation of new small domains inside the larger ones. These two opposite variations are both hindered by static random fields (equivalent to energy barriers) due to the frozen dipoles borne by the off-center Li+ ions. Many results are well explained by the model with a single energy barrier. However, some effects can only be understood if a broad distribution of energy barriers is assumed. We use the experimental data to determine this distribution and find it to be unimodal with a width comparable to its most probable value.

Highly c-axis-oriented monocrystalline Pb(Zr, Ti)O₃ thin films on si wafer prepared by fast cooling immediately after sputter deposition.

PubMed

Yoshida, Shinya; Hanzawa, Hiroaki; Wasa, Kiyotaka; Esashi, Masayoshi; Tanaka, Shuji

2014-09-01

We successfully developed sputter deposition technology to obtain a highly c-axis-oriented monocrystalline Pb(Zr, Ti)O3 (PZT) thin film on a Si wafer by fast cooling (~-180°C/min) of the substrate after deposition. The c-axis orientation ratio of a fast-cooled film was about 90%, whereas that of a slow-cooled (~-40°C/min) film was only 10%. The c-axis-oriented monocrystalline Pb(Zr0.5, Ti0.5)O3 films showed reasonably large piezoelectric coefficients, e(31,f) = ~-11 C/m(2), with remarkably small dielectric constants, ϵ(r) = ~220. As a result, an excellent figure of merit (FOM) was obtained for piezoelectric microelectromechanical systems (MEMS) such as a piezoelectric gyroscope. This c-axis orientation technology on Si will extend industrial applications of PZT-based thin films and contribute further to the development of piezoelectric MEMS.

Hands-On Science: Cool Ways to Teach about Warm-Blooded Animals.

ERIC Educational Resources Information Center

VanCleave, Janice

1998-01-01

Presents three activities for teaching elementary students about the built-in mechanisms that help warm-blooded animals maintain constant internal body temperatures. The activities help students understand why humans sweat, why dogs pant, and why blubber keeps whales warm in frigid water. (SM)

SEARCHING FOR COOLING SIGNATURES IN STRONG LENSING GALAXY CLUSTERS: EVIDENCE AGAINST BARYONS SHAPING THE MATTER DISTRIBUTION IN CLUSTER CORES

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

Blanchard, Peter K.; Bayliss, Matthew B.; McDonald, Michael

2013-07-20

The process by which the mass density profile of certain galaxy clusters becomes centrally concentrated enough to produce high strong lensing (SL) cross-sections is not well understood. It has been suggested that the baryonic condensation of the intracluster medium (ICM) due to cooling may drag dark matter to the cores and thus steepen the profile. In this work, we search for evidence of ongoing ICM cooling in the first large, well-defined sample of SL selected galaxy clusters in the range 0.1 < z < 0.6. Based on known correlations between the ICM cooling rate and both optical emission line luminositymore » and star formation, we measure, for a sample of 89 SL clusters, the fraction of clusters that have [O II]{lambda}{lambda}3727 emission in their brightest cluster galaxy (BCG). We find that the fraction of line-emitting BCGs is constant as a function of redshift for z > 0.2 and shows no statistically significant deviation from the total cluster population. Specific star formation rates, as traced by the strength of the 4000 A break, D{sub 4000}, are also consistent with the general cluster population. Finally, we use optical imaging of the SL clusters to measure the angular separation, R{sub arc}, between the arc and the center of mass of each lensing cluster in our sample and test for evidence of changing [O II] emission and D{sub 4000} as a function of R{sub arc}, a proxy observable for SL cross-sections. D{sub 4000} is constant with all values of R{sub arc}, and the [O II] emission fractions show no dependence on R{sub arc} for R{sub arc} > 10'' and only very marginal evidence of increased weak [O II] emission for systems with R{sub arc} < 10''. These results argue against the ability of baryonic cooling associated with cool core activity in the cores of galaxy clusters to strongly modify the underlying dark matter potential, leading to an increase in SL cross-sections.« less

Determination of Diffusion Parameters of Mean Moderation by Means of a Pulsed Neutron Source. I. Dowtherm A at 20 C; DETERMINAZIONE DEI PARAMETRI DI DIFFUSIONE DEI MEZZI MODERANTI CONIL METODO DELLA SORGENTE DI NEUTRONI PULSATA. I.DOWTHERM A (TEMPERATURE 20 C)

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

Demanins, F.; Rado, V.; Vinci, F.

1963-04-01

The macroscopic absorption cross section, diffusion constant, diffusion cooling constant, transport mean free patu, extrapolated distance, diffusion length, and mean life for thermal neutrons were determined for Dowtherm A at 20 deg C, using a pulsed neutron source. The experimental assembly and data analysis method are described, and the results are compared with other determinations. (auth)

Effect of Forced Convection Heat Transfer on Weld Pools.

DTIC Science & Technology

1986-01-01

Cooling Curves for GTAW Welds Superimposed on CCT Diagram ............. 26 11 - Photomacrographs Showing Weld Macrostructure (TS Plane...decomposition kinetics. Superposition of the weld metal cooling rates measured in this study on the CCT diagram shows that the time for nucleation and growth...m - TABLE 2 - TRANSFORMATION AND COOLING TIMES FROM CCT DIAGRAM *II I I. I I I Cooling Rate I Transformation I Time to Cool tL-I- I Heat Input I

Joint inversion of shear wave travel time residuals and geoid and depth anomalies for long-wavelength variations in upper mantle temperature and composition along the Mid-Atlantic Ridge

NASA Technical Reports Server (NTRS)

Sheehan, Anne F.; Solomon, Sean C.

1991-01-01

Measurements were carried out for SS-S differential travel time residuals for nearly 500 paths crossing the northern Mid-Atlantic Ridge, assuming that the residuals are dominated by contributions from the upper mantle near the surface bounce point of the reflected phase SS. Results indicate that the SS-S travel time residuals decrease linearly with square root of age, to an age of 80-100 Ma, in general agreement with the plate cooling model. A joint inversion was formulated of travel time residuals and geoid and bathymetric anomalies for lateral variation in the upper mantle temperature and composition. The preferred inversion solutions were found to have variations in upper mantle temperature along the Mid-Atlantic Ridge of about 100 K. It was calculated that, for a constant bulk composition, such a temperature variation would produce about a 7-km variation in crustal thickness, larger than is generally observed.

The suitability of barium monofluoride for laser cooling from ab initio study

NASA Astrophysics Data System (ADS)

Kang, Shuying; Kuang, Fangguang; Jiang, Gang; Du, Jiguang

2016-03-01

The feasibility of laser cooling the 138Ba19F molecule is performed using ab initio quantum chemistry. Three low-lying doublet electronic states X 2Σ+, A' 2Δ and A 2Π are determined by the multireference configuration-interaction (MRCI) method, where the spin-orbit coupling (SOC) effect is also taken into account in the electronic structure calculations. The computed spectroscopic constants and permanent dipole moments agree well with the available experimental data. The Franck-Condon factors of the A 2П → X 2Σ+ transition show highly diagonal dominance (f00 = 0.981, f11 = 0.940, f22 = 0.896) and the A 2П state has a radiative lifetime of τ = 37.8 ns, allowing for rapid laser cooling. Our calculation indicates that the laser-cooling scheme require only three lasers at 822 nm, 855 nm and 856 nm proceeded on the A 2П (ν‧) ← X 2Σ+ (ν‧‧) transitions. The appeared intervening state A' 2Δ between the X 2Σ+ and A 2П states is the main challenge for laser cooling this molecule. In fact, the calculated vibrational branching loss ratio to the intermediate A' 2Δ state is almost negligible at a level of η < 4.5 × 10-9. Thus, BaF is a promising laser-cooling candidate with a relatively simple laser-cooling scheme.

Cold cardioplegia versus hypothermia for myocardial protection. Randomized clinical study.

PubMed

Conti, V R; Bertranou, E G; Blackstone, E H; Kirklin, J W; Digerness, S B

1978-11-01

Seventeen of 34 consecutive patients undergoing coronary artery bypass grafting were randomly assigned to one of two methods of myocardial preservation. With the cold cardioplegic method (Group A), a 4 degrees C. asanguineous solution with 30 mEq. of potassium per liter was infused into the aortic root for about 2 minutes immediately after aortic cross-clamping and again after about 45 minutes or when myocardial temperature rose above 19 degrees C. External cardiac cooling was provided by constant infusion of 4 degrees C. Ringer's solution into the pericardium. Seventeen patients were assigned to simple cardiac cooling by hypothermic systemic perfusion before aortic cross-clamping plus external cardiac cooling (Group B). Electromechanical activity ceased within 1 to 2 minutes in Group A but continued throughout the ischemic period in 14 patients in Group B. Myocardial temperature (mean for all observations) during aortic cross-clamping was 17.2 +/- 0.44 degrees C. In Group A and 24.0 +/- 0.70 degrees C. in Group B. Operating conditions were better in Group A. Card-ac function early postoperatively was good in both groups clinically and according to measurements, but only in the cold cardioplegic group (A) was cardiac index not adversely affected by longer cross-clamp time. Myocardial necrosis occurred in both groups but was probably less in the cold cardioplegic group. Thirteen patients (76 percent) in Group A had no electrocardiographic evidence of myocardial injury, compared with eight (47 percent) in Group B (p = 0.08). Eleven (65 percent of Group A had no or short-lived appearance of ceatine phosphokinase isoenzyme (CK-MB), compared with six (35 percent) of Group B (p = 0.08). Time-related CK-MB and SGOT mean levels were consistently lower in Group A.

Absorption cooling sources atmospheric emissions decrease by implementation of simple algorithm for limiting temperature of cooling water

NASA Astrophysics Data System (ADS)

Wojdyga, Krzysztof; Malicki, Marcin

2017-11-01

Constant strive to improve the energy efficiency forces carrying out activities aimed at reduction of energy consumption hence decreasing amount of contamination emissions to atmosphere. Cooling demand, both for air-conditioning and process cooling, plays an increasingly important role in the balance of Polish electricity generation and distribution system in summer. During recent years' demand for electricity during summer months has been steadily and significantly increasing leading to deficits of energy availability during particularly hot periods. This causes growing importance and interest in trigeneration power generation sources and heat recovery systems producing chilled water. Key component of such system is thermally driven chiller, mostly absorption, based on lithium-bromide and water mixture. Absorption cooling systems also exist in Poland as stand-alone systems, supplied with heating from various sources, generated solely for them or recovered as waste or useless energy. The publication presents a simple algorithm, designed to reduce the amount of heat for the supply of absorption chillers producing chilled water for the purposes of air conditioning by reducing the temperature of the cooling water, and its impact on decreasing emissions of harmful substances into the atmosphere. Scale of environmental advantages has been rated for specific sources what enabled evaluation and estimation of simple algorithm implementation to sources existing nationally.

Effect of Air Cooling of Turbine Disk on Power and Efficiency of Turbine from Turbo Engineering Corporation TT13-18 Turbosupercharger.

NASA Technical Reports Server (NTRS)

Berkey, William E.

1949-01-01

An investigation was conducted to determine the effect of turbine-disk cooling with air on the efficiency and the power output of the radial-flow turbine from the Turbo Engineering Corporation TT13-18 turbosupercharger. The turbine was operated at a constant range of ratios of turbine-inlet total pressure to turbine-outlet static pressure of 1,5 and 2.0, turbine-inlet total pressure of 30 inches mercury absolute, turbine-inlet total temperature of 12000 to 20000 R, and rotor speeds of 6000 to 22,000 rpm, Over the normal operating range of the turbine, varying the corrected cooling-air weight flow from approximately 0,30 to 0.75 pound per second produced no measurable effect on the corrected turbine shaft horsepower or the turbine shaft adiabatic efficiency. Varying the turbine-inlet total temperature from 12000 to 20000 R caused no measurable change in the corrected cooling-air weight flow. Calculations indicated that the cooling-air pumping power in the disk passages was small and was within the limits of the accuracy of the power measurements. For high turbine power output, the power loss to the compressor for compressing the cooling air was approximately 3 percent of the total turbine shaft horsepower.

A Novel Method to Calculate the Carbides Fraction from Dilatometric Measurements During Cooling in Hot-Work Tool Steel

NASA Astrophysics Data System (ADS)

Zhao, Xiaoli; Li, Chuanwei; Han, Lizhan; Gu, Jianfeng

2018-06-01

Dilatometry is a useful technique to obtain experimental data concerning transformation. In this paper, a dilation conversional model was established to calculate carbides fraction in AISI H13 hot-work tool steel based on the measured length changes. After carbides precipitation, the alloy contents in the matrix changed. In the usual models, the content of carbon atoms after precipitation is considered as the only element that affects the lattice constant and the content of the alloy elements such as Cr, Mo, Mn, V are often ignored. In the model introduced in this paper, the alloying elements (Cr, Mo, Mn, V) changes caused by carbides precipitation are incorporated. The carbides were identified using scanning electron microscope and transmission electron microscope. The relationship between lattice constant of carbides and temperature are measured by high-temperature X-ray diffraction. The results indicate that the carbides observed in all specimens cooled at different rates are V-rich MC and Cr-rich M23C6, and most of them are V-rich MC, only very few are Cr-rich M23C6. The model including the effects of substitutional alloying elements shows a good improvement on carbides fraction predictions. In addition, lower cooling rate advances the carbides precipitation for AISI H13 specimens. The results between experiments and mathematical model agree well.

Direct flow crystal growth system

DOEpatents

Montgomery, Kenneth E.; Milanovich, Fred P.

1992-01-01

A crystal is grown in a constantly filtered solution which is flowed directly into the growing face of a crystal. In a continuous flow system, solution at its saturation temperature is removed from a crystal growth tank, heated above its saturation temperature, filtered, cooled back to its saturation temperature, and returned to the tank.

Programmable random interval generator

NASA Technical Reports Server (NTRS)

Lindsey, R. S., Jr.

1973-01-01

Random pulse generator can supply constant-amplitude randomly distributed pulses with average rate ranging from a few counts per second to more than one million counts per second. Generator requires no high-voltage power supply or any special thermal cooling apparatus. Device is uniquely versatile and provides wide dynamic range of operation.

40 CFR 86.237-08 - Dynamometer test run, gaseous emissions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... temperature recorder, the vehicle cooling fan, and the heated THC analysis recorder (diesel-cycle only). (The heat exchanger of the constant volume sampler, if used, petroleum-fueled diesel-cycle THC analyzer continuous sample line and filter, methanol-fueled vehicle THC, methanol and formaldehyde sample lines, if...

40 CFR 86.237-08 - Dynamometer test run, gaseous emissions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... temperature recorder, the vehicle cooling fan, and the heated THC analysis recorder (diesel-cycle only). (The heat exchanger of the constant volume sampler, if used, petroleum-fueled diesel-cycle THC analyzer continuous sample line and filter, methanol-fueled vehicle THC, methanol and formaldehyde sample lines, if...

Analysis of Energy Conservation Alternatives for Standard Army Building

DTIC Science & Technology

1983-03-01

existing system because of the constant cooling and heating required. The fixed set-point with a temperature ecnomizer me, ECIP criteria in the colder... essential to completing other portions of the project. Care must, be taken to ensure that energy savings are not duplicated between projects or portions of

Cooling of solar flares plasmas. 1: Theoretical considerations

NASA Technical Reports Server (NTRS)

Cargill, Peter J.; Mariska, John T.; Antiochos, Spiro K.

1995-01-01

Theoretical models of the cooling of flare plasma are reexamined. By assuming that the cooling occurs in two separate phase where conduction and radiation, respectively, dominate, a simple analytic formula for the cooling time of a flare plasma is derived. Unlike earlier order-of-magnitude scalings, this result accounts for the effect of the evolution of the loop plasma parameters on the cooling time. When the conductive cooling leads to an 'evaporation' of chromospheric material, the cooling time scales L(exp 5/6)/p(exp 1/6), where the coronal phase (defined as the time maximum temperature). When the conductive cooling is static, the cooling time scales as L(exp 3/4)n(exp 1/4). In deriving these results, use was made of an important scaling law (T proportional to n(exp 2)) during the radiative cooling phase that was forst noted in one-dimensional hydrodynamic numerical simulations (Serio et al. 1991; Jakimiec et al. 1992). Our own simulations show that this result is restricted to approximately the radiative loss function of Rosner, Tucker, & Vaiana (1978). for different radiative loss functions, other scaling result, with T and n scaling almost linearly when the radiative loss falls off as T(exp -2). It is shown that these scaling laws are part of a class of analytic solutions developed by Antiocos (1980).

Operating characteristics of a three-piece-inner-ring large-bore roller bearing to speeds of 3 million DN

NASA Technical Reports Server (NTRS)

Schuller, F. T.

1984-01-01

A 118 mm bore roller bearing with a three piece inner ring ran successfully at 300,000 DN for 20 hr. Provisions were made for lubrication and cooling through the inner ring. In some tests the outer ring was also cooled. Power loss within the bearing increased with both speed and total oil flow rate to the inner ring. Outer ring temperature decreased by as much as 22 K (40 F) when outer ring cooling was employed whereas inner ring temperature remained essentially constant. Cage slip was greatly reduced or even eliminated by using a bearing with a very tight clearance at operating speed. A three piece inner ring bearing had higher inner ring temperatures and less temperature difference between the inner and outer rings than a conventional one piece inner ring bearing.

Kinetics of Water Loss from Cells at Subzero Temperatures and the Likelihood of Intracellular Freezing

PubMed Central

Mazur, Peter

1963-01-01

The survival of various cells subjected to low temperature exposure is higher when they are cooled slowly. This increase is consistent with the view that slow cooling decreases the probability of intracellular freezing by permitting water to leave the cell rapidly enough to keep the protoplasm at its freezing point. The present study derives a quantitative relation between the amount of water in a cell and temperature. The relation is a differential equation involving cooling rate, surface-volume ratio, membrane permeability to water, and the temperature coefficient of the permeability constant. Numerical solutions to this equation give calculated water contents which permit predictions as to the likelihood of intracellular ice formation. Both the calculated water contents and the predictions on internal freezing are consistent with the experimental observations of several investigators. PMID:14085017

Loading Mode and Environment Effects on Surface Profile Characteristics of Martensite Plates in Cu-Based SMAs

NASA Astrophysics Data System (ADS)

Suru, Marius-Gabriel; Paraschiv, Adrian-Liviu; Lohan, Nicoleta Monica; Pricop, Bogdan; Ozkal, Burak; Bujoreanu, Leandru-Gheorghe

2014-07-01

The present work reports the influence of the loading mode provided during training under constant stress, in bending, applied to lamellar specimens of Cu-Zn-Al shape memory alloys (SMAs). During training, the specimens were bent by a load fastened at their free end, while being martensitic at room temperature and they lifted the load by one-way effect (1WE), during heating up to austenitic field. On cooling to martensite field, the lower concave surface of bent specimens was compressed, and during heating it was elongated, being subjected to a series of tension-compression cycles, during heating-cooling, respectively. Conversely, the upper convex surface of bent specimens was elongated during cooling and compressed during heating, being subjected to compression-tension cycles. Furthermore, 2WE-trained actuators were tested by means of a hydraulic installation where, this time heating-cooling cycles were performed in oil conditions. Considering that the lower concave surface of the specimens was kept in compressed state, while the upper convex surface was kept in elongated state, the study reveals the influence of the two loading modes and environments on the width of martensite plates of the specimens trained under various numbers of cycles. In this purpose, Cu-Zn-Al specimens, trained under 100-300-500 cycles, were prepared and analyzed by atomic force microscopy (AFM) as well as optical and scanning electron microscopy (OM and SEM, respectively). The analysis also included AFM micrographs corroborated with statistical evaluations in order to reveal the effects of loading mode (tension or compression) in different environmental conditions of the specimens, on the surface profile characteristics of martensite plates, revealed by electropolishing.

Redistribution of blood within the body is important for thermoregulation in an ectothermic vertebrate (Crocodylus porosus).

PubMed

Seebacher, Frank; Franklin, Craig E

2007-11-01

Changes in blood flow are a principal mechanism of thermoregulation in vertebrates. Changes in heart rate will alter blood flow, although multiple demands for limited cardiac output may compromise effective thermoregulation. We tested the hypothesis that regional differences in blood flow during heating and cooling can occur independently from changes in heart rate. We measured heart rate and blood pressure concurrently with blood flow in the crocodile, Crocodylus porosus. We measured changes in blood flow by laser Doppler flowmetry, and by injecting coloured microspheres. All measurements were made under different heat loads, with and without blocking cholinergic and beta-adrenergic receptors (autonomic blockade). Heart rates were significantly faster during heating than cooling in the control animals, but not when autonomic receptors were blocked. There were no significant differences in blood flow distribution between the control and autonomic blockade treatments. In both treatments, blood flow was directed to the dorsal skin and muscle and away from the tail and duodenum during heating. When the heat source was switched off, there was a redistribution of blood from the dorsal surface to the duodenum. Blood flow to the leg skin and muscle, and to the liver did not change significantly with thermal state. Blood pressure was significantly higher during the autonomic blockade than during the control. Thermal time constants of heating and cooling were unaffected by the blockade of autonomic receptors. We concluded that animals partially compensated for a lack of differential heart rates during heating and cooling by redistributing blood within the body, and by increasing blood pressure to increase flow. Hence, measures of heart rate alone are insufficient to assess physiological thermoregulation in reptiles.

Minimizing temperature instability of heat recovery hot water system utilizing optimized thermal energy storage

NASA Astrophysics Data System (ADS)

Suamir, I. N.; Sukadana, I. B. P.; Arsana, M. E.

2018-01-01

One energy-saving technology that starts gaining attractive for hotel industry application in Indonesia is the utilization of waste heat of a central air conditioning system to heat water for domestic hot water supply system. Implementing the technology for such application at a hotel was found that hot water capacity generated from the heat recovery system could satisfy domestic hot water demand of the hotel. The gas boilers installed in order to back up the system have never been used. The hot water supply, however, was found to be instable with hot water supply temperature fluctuated ranging from 45 °C to 62 °C. The temperature fluctuations reaches 17 °C, which is considered instable and can reduce hot water usage comfort level. This research is aimed to optimize the thermal energy storage in order to minimize the temperature instability of heat recovery hot water supply system. The research is a case study approach based on cooling and hot water demands of a hotel in Jakarta-Indonesia that has applied water cooled chillers with heat recovery systems. The hotel operation with 329 guest rooms and 8 function rooms showed that hot water production in the heat recovery system completed with 5 m3 thermal energy storage (TES) could not hold the hot water supply temperature constantly. The variations of the cooling demand and hot water demands day by day were identified. It was found that there was significant mismatched of available time (hours) between cooling demand which is directly correlated to the hot water production from the heat recovery system and hot water usage. The available TES system could not store heat rejected from the condenser of the chiller during cooling demand peak time between 14.00 and 18.00 hours. The extra heat from the heat recovery system consequently increases the temperature of hot water up to 62 °C. It is about 12 K above 50 °C the requirement hot water temperature of the hotel. In contrast, the TES could not deliver proper temperature of hot water during peak hot water demand and on that time between 06.00 and 10.00 hours, the hotel also experiences a low cooling demand. Subsequently, the temperature of hot water supplied drops down as low as 45 °C. The study was found that optimization on the TES can significantly minimize temperature variation of the hot water supplied to the hotel appliances. A TES of 30 m3 storage capacity is considered the optimum capacity which can reduce the temperature fluctuation from 17 K down to 3 K. The study also found that maintaining the storage temperature relatively lower than the condenser temperature could increase hot water production of the heat recovery system.

Magnetic heat pumping

NASA Technical Reports Server (NTRS)

Brown, G. V. (Inventor)

1978-01-01

A ferromagnetic or ferrimagnetic element is used to control the temperature and applied magnetic field of the element to cause the state of the element as represented on a temperature-magnetic entropy diagram to repeatedly traverse a loop. The loop may have a first portion of concurrent substantially isothermal or constant temperature and increasing applied magnetic field, a second portion of lowering temperature and constant applied magnetic field, a third portion of isothermal and decreasing applied magnetic field, and a fourth portion of increasing temperature and constant applied magnetic field. Other loops may be four-sided, with two isotherms and two adiabats. Preferably, a regenerator is used to enhance desired cooling or heating effects, with varied magnetic fields, or varying temperatures including three-sided figures traversed by the representative point.

Influence of argon pressure and current density on substrate temperature during magnetron sputtering of hot titanium target

NASA Astrophysics Data System (ADS)

Komlev, Anton A.; Minzhulina, Ekaterina A.; Smirnov, Vladislav V.; Shapovalov, Viktor I.

2018-01-01

The paper describes physical characteristics of the hot target sputtering process, which have not been known before. To switch a magnetron over to the hot target regime, a titanium disk of 1 mm thick with a 1-mm-gap was attached on a 4-mm-thick copper plate cooled by running water. A thermocouple sensor was used to investigate the thermal processes occurring in substrates. The study was performed at the discharge current density of 20-40 mA/cm2 and argon pressure of 3-7 mTorr. The accuracy of temperature measurement appeared to be within ± 5%, due the application of a chromel-copel thermocouple. The study reveals that under these conditions the heating curves have the inflection points positioned proportionally to the discharge current density and argon pressure on a time axis. The inflection point appears in the kinetic curves due to the finite value of the target heating time constant. The study shows that the substrate fixed temperature and substrate heating time constant depend on the argon pressure and relate to the current density by the polynomials of the first and second degrees, respectively. The influence of a target on the substrate heating kinetics is considered in an analytical description by the introduction of a multiplier in the form of an exponential function of time. The results of the research make a novel contribution to the field of the sputtering process.

Results of 20- versus 45-min post-infusion scalp cooling time in the prevention of docetaxel-induced alopecia.

PubMed

Komen, Manon M C; Breed, Wim P M; Smorenburg, Carolien H; van der Ploeg, Tjeerd; Goey, S H; van der Hoeven, Jacobus J M; Nortier, Johan W R; van den Hurk, Corina J G

2016-06-01

For patients, chemotherapy-induced alopecia (CIA) is one of the most distressing side effects of treatment. Scalp cooling can prevent or minimise CIA; the results may depend on the duration of cooling. Since a previous study on post-infusion cooling time in patients treated with docetaxel chemotherapy found no difference between 90 and 45 min, we investigated whether hair-preserving results could be maintained with a shorter post-infusion cooling time. In this prospective, multi-centre randomised study, 134 patients who started treatment with docetaxel 75-100 mg/m(2) in a 3-weekly schedule were randomly assigned in a 1:1 ratio to a post-infusion cooling time of 45 or 20 min. The primary end point was the need for a wig or other head covering as assessed by the patient. A visual analogue scale (VAS) with a range from 0 (not tolerable) to 10 (very tolerable) was used to measure tolerance. Scalp cooling results were similar for 45- and 20-min post-infusion cooling times. Thirty-three out of 45 patients (73 %) treated with 20 min of post-infusion cooling did not need a form of head covering, compared with 41 out of 52 patients (79 %) treated with 45 min of post-infusion cooling (p = 0.5). The procedure was well tolerated (mean visual analogue score 8.3). Six patients stopped due to intolerance during the first treatment cycle. A 20-min post-infusion cooling time is effective and tolerable for patients treated with scalp cooling to prevent docetaxel-induced alopecia. Trialregister.nl Identifier, NTR 1856.

Kicking atoms with finite duration pulses

NASA Astrophysics Data System (ADS)

Fekete, Julia; Chai, Shijie; Daszuta, Boris; Andersen, Mikkel F.

2016-05-01

The atom optics delta-kicked particle is a paradigmatic system for experimental studies of quantum chaos and classical-quantum correspondence. It consists of a cloud of laser cooled atoms exposed to a periodically pulsed standing wave of far off-resonant laser light. A purely quantum phenomena in such systems are quantum resonances which transfers the atoms into a coherent superposition of largely separated momentum states. Using such large momentum transfer ``beamsplitters'' in atom interferometers may have applications in high precision metrology. The growth in momentum separation cannot be maintained indefinitely due to finite laser power. The largest momentum transfer is achieved by violating the usual delta-kick assumption. Therefore we explore the behavior of the atom optics kicked particle with finite pulse duration. We have developed a semi-classical model which shows good agreement with the full quantum description as well as our experiments. Furthermore we have found a simple scaling law that helps to identify optimal parameters for an atom interferometer. We verify this by measurements of the ``Talbot time'' (a measurement of h/m) which together with other well-known constants constitute a measurement of the fine structure constant.

Crosslinked polyarylene ether nitrile film as flexible dielectric materials with ultrahigh thermal stability

PubMed Central

Yang, Ruiqi; Wei, Renbo; Li, Kui; Tong, Lifen; Jia, Kun; Liu, Xiaobo

2016-01-01

Dielectric film with ultrahigh thermal stability based on crosslinked polyarylene ether nitrile is prepared and characterized. The film is obtained by solution-casting of polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) combined with post self-crosslinking at high temperature. The film shows a 5% decomposition temperature over 520 °C and a glass transition temperature (Tg) around 386 °C. Stable dielectric constant and low dielectric loss are observed for this film in the frequency range of 100–200 kHz and in the temperature range of 25–300 °C. The temperature coefficient of dielectric constant is less than 0.001 °C−1 even at 400 °C. By cycling heating and cooling up to ten times or heating at 300 °C for 12 h, the film shows good reversibility and robustness of the dielectric properties. This crosslinked PEN film will be a potential candidate as high performance film capacitor electronic devices materials used at high temperature. PMID:27827436

Stacking with stochastic cooling

NASA Astrophysics Data System (ADS)

Caspers, Fritz; Möhl, Dieter

2004-10-01

Accumulation of large stacks of antiprotons or ions with the aid of stochastic cooling is more delicate than cooling a constant intensity beam. Basically the difficulty stems from the fact that the optimized gain and the cooling rate are inversely proportional to the number of particles 'seen' by the cooling system. Therefore, to maintain fast stacking, the newly injected batch has to be strongly 'protected' from the Schottky noise of the stack. Vice versa the stack has to be efficiently 'shielded' against the high gain cooling system for the injected beam. In the antiproton accumulators with stacking ratios up to 105 the problem is solved by radial separation of the injection and the stack orbits in a region of large dispersion. An array of several tapered cooling systems with a matched gain profile provides a continuous particle flux towards the high-density stack core. Shielding of the different systems from each other is obtained both through the spatial separation and via the revolution frequencies (filters). In the 'old AA', where the antiproton collection and stacking was done in one single ring, the injected beam was further shielded during cooling by means of a movable shutter. The complexity of these systems is very high. For more modest stacking ratios, one might use azimuthal rather than radial separation of stack and injected beam. Schematically half of the circumference would be used to accept and cool new beam and the remainder to house the stack. Fast gating is then required between the high gain cooling of the injected beam and the low gain stack cooling. RF-gymnastics are used to merge the pre-cooled batch with the stack, to re-create free space for the next injection, and to capture the new batch. This scheme is less demanding for the storage ring lattice, but at the expense of some reduction in stacking rate. The talk reviews the 'radial' separation schemes and also gives some considerations to the 'azimuthal' schemes.

On the nature of the liquid-to-glass transition equation

NASA Astrophysics Data System (ADS)

Sanditov, D. S.

2016-09-01

Within the model of delocalized atoms, it is shown that the parameter δ T g , which enters the glasstransition equation qτ g = δ T g and characterizes the temperature interval in which the structure of a liquid is frozen, is determined by the fluctuation volume fraction {f_g} = {( {{{Δ {V_e}} / V _{T = {T_g}}} frozen at the glass-transition temperature T g and the temperature T g itself. The parameter δ T g is estimated by data on f g and T g . The results obtained are in agreement with the values of δ T g calculated by the Williams-Landel-Ferry (WLF) equation, as well as with the product qτ g —the left-hand side of the glass-transition equation ( q is the cooling rate of the melt, and τ g is the structural relaxation time at the glass-transition temperature). Glasses of the same class with f g ≈ const exhibit a linear correlation between δ T g and T g . It is established that the currently used methods of Bartenev and Nemilov for calculating δ T g yield overestimated values, which is associated with the assumption, made during deriving the calculation formulas, that the activation energy of the glass-transition process is constant. A generalized Bartenev equation is derived for the dependence of the glass-transition temperature on the cooling rate of the melt with regard to the temperature dependence of the activation energy of the glasstransition process. A modified version of the kinetic glass-transition criterion is proposed. A conception is developed that the fluctuation volume fraction f = Δ V e / V can be interpreted as an internal structural parameter analogous to the parameter ξ in the Mandelstam-Leontovich theory, and a conjecture is put forward that the delocalization of an active atom—its critical displacement from the equilibrium position—can be considered as one of possible variants of excitation of a particle in the Vol'kenshtein-Ptitsyn theory. The experimental data used in the study refer to a constant cooling rate of q = 0.05 K/s (3 K/min).

A cryofuge for cold-collision experiments with slow polar molecules

NASA Astrophysics Data System (ADS)

Wu, Xing; Gantner, Thomas; Koller, Manuel; Zeppenfeld, Martin; Chervenkov, Sotir; Rempe, Gerhard

2017-11-01

Ultracold molecules represent a fascinating research frontier in physics and chemistry, but it has proven challenging to prepare dense samples at low velocities. Here, we present a solution to this goal by means of a nonconventional approach dubbed cryofuge. It uses centrifugal force to bring cryogenically cooled molecules to kinetic energies below 1 K × kB in the laboratory frame, where kB is the Boltzmann constant, with corresponding fluxes exceeding 1010 per second at velocities below 20 meters per second. By attaining densities higher than 109 per cubic centimeter and interaction times longer than 25 milliseconds in samples of fluoromethane as well as deuterated ammonia, we observed cold dipolar collisions between molecules and determined their collision cross sections.

Energy conservation for pasteurizer apparatus

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

Huling, J.K.

In the pasteurizing of beverages in closed containers, the containers arrive generally in a chilled state and are progressively raised in temperature approaching the pasteurizing temperature and, after being pasteurized for an appropriate time, are progressively cooled down. Apparatus of this type is provided with a source of chilled water which is available for use when skips occur in the supply of the containers, the chilled water being accumulated from the incoming containers and from common outside sources. The accumulated water in its chilled state saves substantial amounts of energy by eliminating mechanical or other means to produce the chillmore » effect, and such source of water is constantly available under control which senses the presence of a skip in the supply of containers.« less

Real-Time Thermal Mapping for Heat & Cool Archipelagos of Bengaluru, India

NASA Astrophysics Data System (ADS)

Gopinath, Rajesh; Banerjee, Aditya; Sachin, S.; Tiwari, Prakhar; Wilson, Sunny

2017-12-01

Blessed with a salubrious climate, the city of Bengaluru over the past few decades has constantly witnessed thermal discomfort owing to several Urban Heat islands that have mushroomed within the city. The subsequent increase in builtup area, consequent loss of productive agricultural lands/green zones, encroachment of surface water bodies coupled with the ill-preparedness of decision makers to handle the demand for land have invariably crumbled the natural micro-climate of the city. In this present research, an attempt has been made to detect the distribution of Urban Heat Islands in Bengaluru City by conducting real-time survey at 100 observatories marked across the entire urban & rural locations; with thermohygrometers as per the W.M.O. guidelines. The study confirmed the violation of the Human Thermal Comfort Range in 9, 83, 98, 99, 98 and 80 observatories for the monitoring at 6 AM, 9 AM, 12 PM, 3 PM, 6 PM and 9 PM respectively.

Auger recombination in Dirac materials: A tangle of many-body effects

NASA Astrophysics Data System (ADS)

Alymov, Georgy; Vyurkov, Vladimir; Ryzhii, Victor; Satou, Akira; Svintsov, Dmitry

2018-05-01

The peculiar electron dispersion in Dirac materials makes lowest-order Auger processes prohibited or marginally prohibited by energy and momentum conservation laws. Thus, Auger recombination (AR) in these materials is very sensitive to many-body effects. We incorporate them at the level of the G W approximation into the nonequilibrium Green's functions approach to AR and study the role of dynamic screening, spectrum broadening, and renormalization in the case of weakly pumped undoped graphene. We find that incorrect treatment of many-body effects can lead to an order-of-magnitude error in the recombination rate. We show that the AR time depends weakly (sublinearly) on the background dielectric constant, which limits the possibility to control recombination by the choice of substrate. However, the AR time can be considerably prolonged by placing graphene under a metal gate or by introducing a band gap. With carrier cooling taken into account, our results comply with experiments on photoexcited graphene.

Temperature dependence of the hydrated electron's excited-state relaxation. I. Simulation predictions of resonance Raman and pump-probe transient absorption spectra of cavity and non-cavity models

NASA Astrophysics Data System (ADS)

Zho, Chen-Chen; Farr, Erik P.; Glover, William J.; Schwartz, Benjamin J.

2017-08-01

We use one-electron non-adiabatic mixed quantum/classical simulations to explore the temperature dependence of both the ground-state structure and the excited-state relaxation dynamics of the hydrated electron. We compare the results for both the traditional cavity picture and a more recent non-cavity model of the hydrated electron and make definite predictions for distinguishing between the different possible structural models in future experiments. We find that the traditional cavity model shows no temperature-dependent change in structure at constant density, leading to a predicted resonance Raman spectrum that is essentially temperature-independent. In contrast, the non-cavity model predicts a blue-shift in the hydrated electron's resonance Raman O-H stretch with increasing temperature. The lack of a temperature-dependent ground-state structural change of the cavity model also leads to a prediction of little change with temperature of both the excited-state lifetime and hot ground-state cooling time of the hydrated electron following photoexcitation. This is in sharp contrast to the predictions of the non-cavity model, where both the excited-state lifetime and hot ground-state cooling time are expected to decrease significantly with increasing temperature. These simulation-based predictions should be directly testable by the results of future time-resolved photoelectron spectroscopy experiments. Finally, the temperature-dependent differences in predicted excited-state lifetime and hot ground-state cooling time of the two models also lead to different predicted pump-probe transient absorption spectroscopy of the hydrated electron as a function of temperature. We perform such experiments and describe them in Paper II [E. P. Farr et al., J. Chem. Phys. 147, 074504 (2017)], and find changes in the excited-state lifetime and hot ground-state cooling time with temperature that match well with the predictions of the non-cavity model. In particular, the experiments reveal stimulated emission from the excited state with an amplitude and lifetime that decreases with increasing temperature, a result in contrast to the lack of stimulated emission predicted by the cavity model but in good agreement with the non-cavity model. Overall, until ab initio calculations describing the non-adiabatic excited-state dynamics of an excess electron with hundreds of water molecules at a variety of temperatures become computationally feasible, the simulations presented here provide a definitive route for connecting the predictions of cavity and non-cavity models of the hydrated electron with future experiments.

High voltage solar cell power generating system for regulated solar array development

NASA Technical Reports Server (NTRS)

Levy, E., Jr.; Hoffman, A. C.

1973-01-01

A laboratory solar power system regulated by on-panel switches has been delivered for operating high power (3 kw), high voltage (15,000 volt) loads (communication tubes, ion thrusters). The modular system consists of 26 solar arrays, each with an integral light source and cooling system. A typical array contains 2560 series-connected cells. Each light source consists of twenty 500 watt tungsten iodide lamps providing plus or minus 5 per cent uniformity at one solar constant. An array temperature of less than 40 C is achieved using an infrared filter, a water cooled plate, a vacuum hold-down system, and air flushing.

A study of cooling time reduction of interferometric cryogenic gravitational wave detectors using a high-emissivity coating

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

Sakakibara, Y.; Yamamoto, K.; Chen, D.

In interferometric cryogenic gravitational wave detectors, there are plans to cool mirrors and their suspension systems (payloads) in order to reduce thermal noise, that is, one of the fundamental noise sources. Because of the large payload masses (several hundred kg in total) and their thermal isolation, a cooling time of several months is required. Our calculation shows that a high-emissivity coating (e.g. a diamond-like carbon (DLC) coating) can reduce the cooling time effectively by enhancing radiation heat transfer. Here, we have experimentally verified the effect of the DLC coating on the reduction of the cooling time.

Immersion freezing of internally and externally mixed mineral dust species analyzed by stochastic and deterministic models

NASA Astrophysics Data System (ADS)

Wong, B.; Kilthau, W.; Knopf, D. A.

2017-12-01

Immersion freezing is recognized as the most important ice crystal formation process in mixed-phase cloud environments. It is well established that mineral dust species can act as efficient ice nucleating particles. Previous research has focused on determination of the ice nucleation propensity of individual mineral dust species. In this study, the focus is placed on how different mineral dust species such as illite, kaolinite and feldspar, initiate freezing of water droplets when present in internal and external mixtures. The frozen fraction data for single and multicomponent mineral dust droplet mixtures are recorded under identical cooling rates. Additionally, the time dependence of freezing is explored. Externally and internally mixed mineral dust droplet samples are exposed to constant temperatures (isothermal freezing experiments) and frozen fraction data is recorded based on time intervals. Analyses of single and multicomponent mineral dust droplet samples include different stochastic and deterministic models such as the derivation of the heterogeneous ice nucleation rate coefficient (J­­het), the single contact angle (α) description, the α-PDF model, active sites representation, and the deterministic model. Parameter sets derived from freezing data of single component mineral dust samples are evaluated for prediction of cooling rate dependent and isothermal freezing of multicomponent externally or internally mixed mineral dust samples. The atmospheric implications of our findings are discussed.

Catastrophic cooling and cessation of heating in the solar corona

NASA Astrophysics Data System (ADS)

Peter, H.; Bingert, S.; Kamio, S.

2012-01-01

Context. Condensations in the more than 106 K hot corona of the Sun are commonly observed in the extreme ultraviolet (EUV). While their contribution to the total solar EUV radiation is still a matter of debate, these condensations certainly provide a valuable tool for studying the dynamic response of the corona to the heating processes. Aims: We investigate different distributions of energy input in time and space to investigate which process is most relevant for understanding these coronal condensations. Methods: For a comparison to observations we synthesize EUV emission from a time-dependent, one-dimensional model for coronal loops, where we employ two heating scenarios: simply shutting down the heating and a model where the heating is very concentrated at the loop footpoints, while keeping the total heat input constant. Results: The heating off/on model does not lead to significant EUV count rates that one observes with SDO/AIA. In contrast, the concentration of the heating near the footpoints leads to thermal non-equilibrium near the loop top resulting in the well-known catastrophic cooling. This process gives a good match to observations of coronal condensations. Conclusions: This shows that the corona needs a steady supply of energy to support the coronal plasma, even during coronal condensations. Otherwise the corona would drain very fast, too fast to even form a condensation. Movies are available in electronic form at http://www.aanda.org

The Onset of Thermally Unstable Cooling from the Hot Atmospheres of Giant Galaxies in Clusters: Constraints on Feedback Models

NASA Astrophysics Data System (ADS)

Hogan, M. T.; McNamara, B. R.; Pulido, F. A.; Nulsen, P. E. J.; Vantyghem, A. N.; Russell, H. R.; Edge, A. C.; Babyk, Iu.; Main, R. A.; McDonald, M.

2017-12-01

We present accurate mass and thermodynamic profiles for 57 galaxy clusters observed with the Chandra X-ray Observatory. We investigate the effects of local gravitational acceleration in central cluster galaxies, and explore the role of the local free-fall time ({t}{ff}) in thermally unstable cooling. We find that the radially averaged cooling time ({t}{cool}) is as effective an indicator of cold gas, traced through its nebular emission, as the ratio {t}{cool}/{t}{ff}. Therefore, {t}{cool} primarily governs the onset of thermally unstable cooling in hot atmospheres. The location of the minimum {t}{cool}/{t}{ff}, a thermodynamic parameter that many simulations suggest is key in driving thermal instability, is unresolved in most systems. Consequently, selection effects bias the value and reduce the observed range in measured {t}{cool}/{t}{ff} minima. The entropy profiles of cool-core clusters are characterized by broken power laws down to our resolution limit, with no indication of isentropic cores. We show, for the first time, that mass isothermality and the K\\propto {r}2/3 entropy profile slope imply a floor in {t}{cool}/{t}{ff} profiles within central galaxies. No significant departures of {t}{cool}/{t}{ff} below 10 are found. This is inconsistent with models that assume thermally unstable cooling ensues from linear perturbations at or near this threshold. We find that the inner cooling times of cluster atmospheres are resilient to active galactic nucleus (AGN)-driven change, suggesting gentle coupling between radio jets and atmospheric gas. Our analysis is consistent with models in which nonlinear perturbations, perhaps seeded by AGN-driven uplift of partially cooled material, lead to cold gas condensation.

Recent advances in cooled-semen technology.

PubMed

Aurich, Christine

2008-09-01

The majority of horse registries approve the use of artificial insemination, and horse breeding has widely taken benefit from the use of cooled-stored semen. New insights into cooled-semen technology open possibilities to reduce problems such as impaired semen quality after cooled-storage in individual stallions. The stallion itself has major impacts on quality and fertility of cooled-stored semen. Dietary supplementation of antioxidants and polyunsaturated fatty acids improves semen quality in a variety of species, but only few studies on this topic exist in the horse. Proper semen collection and handling is the main key to the maintenance of semen quality during cooled-storage. Semen collection should be achieved by minimal sexual stimulation with a single mount; this results in high sperm concentration, low content of seminal plasma and minimal contamination with bacteria. Milk-based semen extenders are most popular for semen processing and storage. The development of more defined extenders containing only the beneficial milk ingredients has made extender quality more constant and reliable. Semen is often centrifuged to decrease the seminal plasma content. Centrifugation results in a recovery rate of only 75% of spermatozoa in the semen pellet. Recovery rates after centrifugation may be improved with use of a "cushion technique" allowing higher centrifugation force and duration. However, this is not routinely used in cooled-semen technology. After slow-cooling, semen-storage and shipping is best performed at 5 degrees C, maintaining semen motility, membrane integrity and DNA integrity for up to 40 h after collection. Shipping containers created from Styrofoam boxes provide maintenance of semen quality at low cost.

THz spectroscopy of D2H+

NASA Astrophysics Data System (ADS)

Yu, S.; Pearson, J. C.; Amano, T.; Matsushima, F.

2017-01-01

We extended the measurements of the rotational transitions of D2H+ up to 3 THz by using the JPL frequency multiplier chains and a TuFIR system at Toyama. D2H+ was generated in an extended negative glow discharge cell cooled to liquid nitrogen temperature. We observed five new THz lines. All the available rotational transition frequencies together with the combination differences derived from the three fundamental bands were subject to least square analysis to determine the molecular constants. New THz measurements are definitely useful for better characterization of spectroscopic properties. The improved molecular constants provide better predictions of other unobserved rotational transitions.

Steady-State Vacuum Ultraviolet Exposure Facility With Automated Lamp Calibration and Sample Positioning Fabricated

NASA Technical Reports Server (NTRS)

Sechkar, Edward A.; Steuber, Thomas J.; Banks, Bruce A.; Dever, Joyce A.

2000-01-01

The Next Generation Space Telescope (NGST) will be placed in an orbit that will subject it to constant solar radiation during its planned 10-year mission. A sunshield will be necessary to passively cool the telescope, protecting it from the Sun s energy and assuring proper operating temperatures for the telescope s instruments. This sunshield will be composed of metalized polymer multilayer insulation with an outer polymer membrane (12 to 25 mm in thickness) that will be metalized on the back to assure maximum reflectance of sunlight. The sunshield must maintain mechanical integrity and optical properties for the full 10 years. This durability requirement is most challenging for the outermost, constantly solar-facing polymer membrane of the sunshield. One of the potential threats to the membrane material s durability is from vacuum ultraviolet (VUV) radiation in wavelengths below 200 nm. Such radiation can be absorbed in the bulk of these thin polymer membrane materials and degrade the polymer s optical and mechanical properties. So that a suitable membrane material can be selected that demonstrates durability to solar VUV radiation, ground-based testing of candidate materials must be conducted to simulate the total 10- year VUV exposure expected during the Next Generation Space Telescope mission. The Steady State Vacuum Ultraviolet exposure facility was designed and fabricated at the NASA Glenn Research Center at Lewis Field to provide unattended 24-hr exposure of candidate materials to VUV radiation of 3 to 5 times the Sun s intensity in the wavelength range of 115 to 200 nm. The facility s chamber, which maintains a pressure of approximately 5 10(exp -6) torr, is divided into three individual exposure cells, each with a separate VUV source and sample-positioning mechanism. The three test cells are separated by a water-cooled copper shield plate assembly to minimize thermal effects from adjacent test cells. Part of the interior sample positioning mechanism of one test cell is shown in the illustration. Of primary concern in VUV exposure is the maintenance of constant measured radiation intensity so that the sample s total exposure can be determined in equivalent Sun hours. This is complicated by the fact that a VUV lamp s intensity degrades over time, necessitating a decrease in the distance between the test samples and the lamp. The facility overcomes this challenge by periodically measuring the lamp s intensity with a cesium-iodide phototube and adjusting the sample distance as required to maintain constant exposure intensity. Sample positioning and periodic phototube location under the lamp are both achieved by a single lead-screw assembly. The lamps can be isolated from the main vacuum chamber for cleaning or replacement so that samples are not exposed to the atmosphere during a test.

Comparison of the magnetic properties of glass from Luna 20 with similar properties of glass from the Apollo missions

USGS Publications Warehouse

Senftle, F.E.; Thorpe, A.N.; Alexander, C.C.; Briggs, C.L.

1973-01-01

Magnetic susceptibility measurements have been made on four glass spherules and fragments from the Luna 20 fines; two at 300??K and two from 300??K to 4??K. From these data the magnetic susceptibility extrapolated to infinite field, the magnetization at low fields and also the saturation magnetization at high fields, the Curie constant, the Weiss temperature, and the temperature-independent susceptibility were determined. Using a model previously proposed for the Apollo specimens, the Curie constant of the antiferromagnetic inclusions and a zero field splitting parameter were calculated for the same specimens. The data show the relatively low concentration of iron in all forms in these specimens. In addition, the Weiss temperature is lower than that measured for the Apollo specimens, and can be attributed almost entirely to the ligand field distortion about the Fe2+ ions in the glassy phase. The data further suggest that the Luna 20 specimens cooled more slowly than those of the Apollo missions, and that some of the antiferromagnetic inclusions in the glass may have crystallized from the glass during cooling. ?? 1973.

Influence of emissivity on behavior of metallic dust particles in plasmas

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

Tanaka, Y.; Smirnov, R. D.; Pigarov, A. Yu.

Influence of thermal radiation emissivity on the lifetime of a dust particle in plasmas is investigated for different fusion relevant metals (Li, Be, Mo, and W). The thermal radiation is one of main cooling mechanisms of the dust in plasmas especially for dust with evaporation temperature higher than 2500 K. In this paper, the temperature- and radius-dependent emissivity of dust particles is calculated using Mie theory and temperature-dependent optical constants for the above metallic materials. The lifetime of a dust particle in uniform plasmas is estimated with the calculated emissivity using the dust transport code DUSTT[A. Pigarov et al., Physicsmore » of Plasmas 12, 122508 (2005)], considering other dust cooling and destruction processes such as physical and chemical sputtering, melting and evaporation, electron emission etc. The use of temperature-dependent emissivity calculated with Mie theory provides a longer lifetime of the refractory metal dust particle compared with that obtained using conventional emissivity constants in the literature. The dynamics of heavy metal dust particles are also presented using the calculated emissivity in a tokamak plasma.« less

How coagulation zone size is underestimated in computer modeling of RF ablation by ignoring the cooling phase just after RF power is switched off.

PubMed

Irastorza, Ramiro M; Trujillo, Macarena; Berjano, Enrique

2017-11-01

All the numerical models developed for radiofrequency ablation so far have ignored the possible effect of the cooling phase (just after radiofrequency power is switched off) on the dimensions of the coagulation zone. Our objective was thus to quantify the differences in the minor radius of the coagulation zone computed by including and ignoring the cooling phase. We built models of RF tumor ablation with 2 needle-like electrodes: a dry electrode (5 mm long and 17G in diameter) with a constant temperature protocol (70°C) and a cooled electrode (30 mm long and 17G in diameter) with a protocol of impedance control. We observed that the computed coagulation zone dimensions were always underestimated when the cooling phase was ignored. The mean values of the differences computed along the electrode axis were always lower than 0.15 mm for the dry electrode and 1.5 mm for the cooled electrode, which implied a value lower than 5% of the minor radius of the coagulation zone (which was 3 mm for the dry electrode and 30 mm for the cooled electrode). The underestimation was found to be dependent on the tissue characteristics: being more marked for higher values of specific heat and blood perfusion and less marked for higher values of thermal conductivity. Copyright © 2017 John Wiley & Sons, Ltd.

Treelike networks accelerating capillary flow.

PubMed

Shou, Dahua; Ye, Lin; Fan, Jintu

2014-05-01

Transport in treelike networks has received wide attention in natural systems, oil recovery, microelectronic cooling systems, and textiles. Existing studies are focused on transport behaviors under a constant potential difference (including pressure, temperature, and voltage) in a steady state [B. Yu and B. Li, Phys. Rev. E 73, 066302 (2006); J. Chen, B. Yu, P. Xu, and Y. Li, Phys. Rev. E 75, 056301 (2007)]. However, dynamic (time-dependent) transport in such systems has rarely been concerned. In this work, we theoretically investigate the dynamics of capillary flow in treelike networks and design the distribution of radius and length of local branches for the fastest capillary flow. It is demonstrated that capillary flow in the optimized tree networks is faster than in traditional parallel tube nets under fixed constraints. As well, the flow time of the liquid is found to increase approximately linearly with penetration distance, which differs from Washburn's classic description that flow time increases as the square of penetration distance in a uniform tube.

Atomic-scale reversibility in sheared glasses

NASA Astrophysics Data System (ADS)

Fan, Meng; Wang, Minglei; Liu, Yanhui; Schroers, Jan; Shattuck, Mark; O'Hern, Corey

Systems become irreversible on a macroscopic scale when they are sheared beyond the yield strain and begin flowing. Using computer simulations of oscillatory shear, we investigate atomic scale reversibility. We employ molecular dynamics simulations to cool binary Lennard-Jones liquids to zero temperature over a wide range of cooling rates. We then apply oscillatory quasistatic shear at constant pressure to the zero-temperature glasses and identify neighbor-switching atomic rearrangement events. We determine the critical strain γ*, beyond which atoms in the system do not return to their original positions upon reversing the strain. We show that for more slowly cooled glasses, the average potential energy is lower and the typical size of atomic rearrangements is smaller, which correlates with larger γ*. Finally, we connect atomic- and macro-scale reversibility by determining the number of and correlations between the atomic rearrangements that occur as the system reaches the yield strain.

State of Fukushima nuclear fuel debris tracked by Cs137 in cooling water.

PubMed

Grambow, B; Mostafavi, M

2014-11-01

It is still difficult to assess the risk originating from the radioactivity inventory remaining in the damaged Fukushima nuclear reactors. Here we show that cooling water analyses provide a means to assess source terms for potential future releases. Until now already about 34% of the inventories of (137)Cs of three reactors has been released into water. We found that the release rate of (137)Cs has been constant for 2 years at about 1.8% of the inventory per year indicating ongoing dissolution of the fuel debris. Compared to laboratory studies on spent nuclear fuel behavior in water, (137)Cs release rates are on the higher end, caused by the strong radiation field and oxidant production by water radiolysis and by impacts of accessible grain boundaries. It is concluded that radionuclide analyses in cooling water allow tracking of the conditions of the damaged fuel and the associated risks.

Thermal performance of a Concrete Cool Roof under different climatic conditions of Mexico

DOE PAGES

Hernández-Pérez, I.; Álvarez, G.; Gilbert, H.; ...

2014-11-27

A cool roof is an ordinary roof with a reflective coating on the exterior surface which has a high solar reflectance and high thermal emittance. These properties let the roof keep a lower temperature than a standard roof under the same conditions. In this work, the thermal performance of a concrete roof with and without insulation and with two colors has been analyzed using the finite volume method. The boundary conditions of the external roof surface were taken from hourly averaged climatic data of four cities. For the internal surface, it is considered that the building is air-conditioned and themore » inside air has a constant temperature. The interior surface temperature and the heat flux rates into the roofs were obtained for two consecutive days in order to assess the benefits of a cool roofs in different climates.« less

The Effect of Piston-Head Temperature on Knock-Limited Power

NASA Technical Reports Server (NTRS)

Imming, Harry S.

1944-01-01

To determine the effect of piston-head temperature on knock-limited power. Tests were made in a supercharged CFR engine over a range of fuel-air ratios from 0.055 to 0.120, using S-3 reference fuel, AN-F-28, Amendment-2, aviation gasoline, and AN-F-28 plus 2 percent xylidines by weight. Tests were run at a compression ratio of 7.0 with inlet-air temperatures of 150 F and 250 F and at a compression ratio of 8.0 with an inlet-air temperature of 250 F. All other engine conditions were held constant. The piston-head temperature was varied by circulation of oil through passages in the crown of a liquid-cooled piston. This method of piston cooling decreased the piston-head temperature about 80 F. The data are not intended to constitute a recommendation as to the advisability of piston cooling in practice.

Liquid cooled plate heat exchanger for battery cooling of an electric vehicle (EV)

NASA Astrophysics Data System (ADS)

Rahman, M. M.; Rahman, H. Y.; Mahlia, T. M. I.; Sheng, J. L. Y.

2016-03-01

A liquid cooled plate heat exchanger was designed to improve the battery life of an electric vehicle which suffers from premature aging or degradation due to the heat generation during discharging and charging period. Computational fluid dynamics (CFD) was used as a tool to analyse the temperature distribution when a constant surface heat flux was set at the bottom surface of the battery. Several initial and boundary conditions were set based on the past studies on the plate heat exchanger in the simulation software. The design of the plate heat exchanger was based on the Nissan Leaf battery pack to analyse the temperature patterns. Water at different mass flow rates was used as heat transfer fluid. The analysis revealed the designed plate heat exchanger could maintain the surface temperature within the range of 20 to 40°C which is within the safe operating temperature of the battery.

Evaporative cooling of speleothem drip water

PubMed Central

Cuthbert, M. O.; Rau, G. C.; Andersen, M. S.; Roshan, H.; Rutlidge, H.; Marjo, C. E.; Markowska, M.; Jex, C. N.; Graham, P. W.; Mariethoz, G.; Acworth, R. I.; Baker, A.

2014-01-01

This study describes the first use of concurrent high-precision temperature and drip rate monitoring to explore what controls the temperature of speleothem forming drip water. Two contrasting sites, one with fast transient and one with slow constant dripping, in a temperate semi-arid location (Wellington, NSW, Australia), exhibit drip water temperatures which deviate significantly from the cave air temperature. We confirm the hypothesis that evaporative cooling is the dominant, but so far unattributed, control causing significant disequilibrium between drip water and host rock/air temperatures. The amount of cooling is dependent on the drip rate, relative humidity and ventilation. Our results have implications for the interpretation of temperature-sensitive, speleothem climate proxies such as δ18O, cave microecology and the use of heat as a tracer in karst. Understanding the processes controlling the temperature of speleothem-forming cave drip waters is vital for assessing the reliability of such deposits as archives of climate change. PMID:24895139

Metastable phase equilibria in co-deposited Ni(1-x)Zr(x) thin films

NASA Astrophysics Data System (ADS)

Rubin, J. B.; Schwarz, R. B.

We determine the glass forming range (GFR) of co-deposited Ni(1-x)Zr(x) (0 less than x less than 1) thin films by measuring their electrical resistance during in situ constant-heating-rate anneals. The measured GFR is continuous for 0.10 less than x less than 0.87. We calculate the GFR of Ni-Zr melts as a function of composition and cooling rate using homogeneous nucleation theory and a published CALPHAD-type thermodynamic modeling of the equilibrium phase diagram. Assuming that the main competition to the retention of the amorphous structure during the cooling of the liquid comes from the partitionless crystallization of the terminal solid solutions, we calculate that for dT/dt = 10(exp 12) K/s, the GFR extends to x = 0.05 and x = 0.96. Better agreement with the measured values is obtained assuming a lower effective cooling rate during the condensation of the films.

Improvement in Stability of SPring-8 Standard X-Ray Monochromators with Water-Cooled Crystals

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

Yamazaki, Hiroshi; Shimizu, Nobtaka; Kumasaka, Takashi

2010-06-23

SPring-8 standard double-crystal monochromators containing water-cooled crystals were stabilized to a sufficient level to function as a part of optics components to supply stable microfocused x-ray beams, by determining causes of the instability and then removing them. The instability was caused by two factors--thermal deformation of fine stepper stages in the monochromator, which resulted in reduction in beam intensity with time, and vibrations of coolant supply units and vacuum pumps, which resulted in fluctuation in beam intensity. We remodeled the crystal holders to maintain the stage temperatures constant with water, attached x-ray and electron shields to the stages in ordermore » to prevent their warming up, introduced accumulators in the water circuits to absorb pressure pulsation, used polyurethane tubes to stabilize water flow, and placed rubber cushions under scroll vacuum pumps. As a result, the intensity reduction rate of the beam decreased from 26% to 1% per hour and the intensity fluctuation from 13% to 1%. The monochromators were also modified to prevent radiation damage to the crystals, materials used as a water seal, and motor cables.« less

Growth, structural, thermal, dielectric and optical studies on HBST crystal: A potential THz emitter.

PubMed

Ma, Yuzhe; Teng, Bing; Cao, Lifeng; Zhong, Degao; Ji, Shaohua; Teng, Fei; Liu, Jiaojiao; Yao, Yuan; Tang, Jie; Tong, Jiaming

2018-02-05

The efficient organic nonlinear optical material 4-hydroxy benzaldehyde-N-methyl 4-stilbazolium tosylate (HBST) was grown from methanol by slope nucleation method combined with slow cooling (SNM-SC) for the first time. The optimum growth conditions based on the cooling rate was further investigated. The single crystal X-ray diffraction (XRD) revealed that the chromophores of HBST crystal make an angle of about 33° with respect to the a-axis, which is close to the optimum of Terahertz (THz)-wave generation and electro-optics applications. NMR and FT-IR spectral studies have been performed to ascertain various functional groups present in the sample. Futhermore, the thermal stability and decomposition stages were analyzed through TG-DTA and DSC techniques. The dielectric constant and dielectric loss of HBST crystal have been studied. Critical optical properties like the absorption coefficient, refractive index, cut-off wavelength and band gap energy were calculated. Photoluminescence (PL) exication studies indicated green emission occured at 507nm. All the results of HBST crystal make it a promising candidate in the fields of optoelectronic and the generation of THz. Copyright © 2017 Elsevier B.V. All rights reserved.

Environmental fluctuations and host skin bacteria shift survival advantage between frogs and their fungal pathogen.

PubMed

Longo, Ana V; Zamudio, Kelly R

2017-02-01

Fluctuating environments can modulate host-pathogen interactions by providing a temporary advantage to one of the interacting organisms. However, we know very little about how environmental conditions facilitate beneficial interactions between hosts and their microbial communities, resulting in individual persistence with a particular pathogen. Here, we experimentally infected Eleutherodactylus coqui frogs with the fungal pathogen Batrachochytrium dendrobatidis (Bd) under environmental conditions known to confer the survival advantage to the host during the warm-wet season, or alternatively to the pathogen during the cool-dry season. We used 16S rRNA amplicon sequencing to quantify changes in bacterial richness and phylogenetic diversity, and identified operational taxonomic units (OTUs) that became overrepresented or suppressed as a consequence of Bd infection. During the warm-wet season, frogs limited Bd infections, recruited putatively beneficial bacteria and returned to pre-infection levels of richness and phylogenetic diversity. In contrast, during the cool-dry season, Bd infections kept increasing through time, and bacterial diversity remained constant. Our findings confirm that infection outcome not only depends on abiotic factors, but also on biotic interactions between hosts and their associated bacterial communities.

An experimental study of PCM based finned and un-finned heat sinks for passive cooling of electronics

NASA Astrophysics Data System (ADS)

Usman, Hazrat; Ali, Hafiz Muhammad; Arshad, Adeel; Ashraf, Muhammad Junaid; Khushnood, Shahab; Janjua, Muhammad Mansoor; Kazi, S. N.

2018-05-01

This experimental study determines and compares the thermal performance of unfinned and finned PCM based heat sinks. For the analysis considering pin-fins as thermal conductivity enhancer (TCE), triangular configuration is considered. It is further classified into inline and staggered pin-fin arrangements. Three popular variants of paraffin namely paraffin wax, RT-44 and RT-35HC are incorporated as phase change materials (PCMs) inside the heat sink. The volume fraction of pin-fins and PCMs are kept constant at 9% and 90% respectively. The heat input at the base of heat sinks ranges from 5 W to 8 W. The results are presented in two different cases, charging and discharging, and the analysis of temperature variation and comparison of fin arrangements in three different heat sinks with and without PCM. Further the enhancement ratios are determined to quantify the thermal performance in operation time of heat sink for passive cooling with the influence of PCMs and TCEs. The results suggest triangular inline pin-fin as the dominant heat sink geometry and RT-44 as the most efficient PCM for passive thermal management of electronic devices.

Dissipative advective accretion disc solutions with variable adiabatic index around black holes

NASA Astrophysics Data System (ADS)

Kumar, Rajiv; Chattopadhyay, Indranil

2014-10-01

We investigated accretion on to black holes in presence of viscosity and cooling, by employing an equation of state with variable adiabatic index and multispecies fluid. We obtained the expression of generalized Bernoulli parameter which is a constant of motion for an accretion flow in presence of viscosity and cooling. We obtained all possible transonic solutions for a variety of boundary conditions, viscosity parameters and accretion rates. We identified the solutions with their positions in the parameter space of generalized Bernoulli parameter and the angular momentum on the horizon. We showed that a shocked solution is more luminous than a shock-free one. For particular energies and viscosity parameters, we obtained accretion disc luminosities in the range of 10- 4 - 1.2 times Eddington luminosity, and the radiative efficiency seemed to increase with the mass accretion rate too. We found steady state shock solutions even for high-viscosity parameters, high accretion rates and for wide range of composition of the flow, starting from purely electron-proton to lepton-dominated accretion flow. However, similar to earlier studies of inviscid flow, accretion shock was not obtained for electron-positron pair plasma.

Experimental Investigation on Heat Transfer Characteristics of Different Metallic Fin Arrays

NASA Astrophysics Data System (ADS)

Sangewar, Ravi Kumar

2018-04-01

The reliability of electronic equipment depends on the reliability of the system. For small applications natural convection cooling is sufficient, but for the electronic equipment having number of heat generating components, forced convection cooling is essential. In number of cases, pin fin arrangement is preferred for augmentation of heat transfer. Here, the performance of pin fin array of copper and aluminum material with in-line, as well as staggered arrangement over a flat plate is studied. Constant heat input was given to the inline, staggered arrangement of copper as well as aluminium pin fin arrays. In the present experimental study, heat input and airflow rates are the variables. It was found that the heat transfer coefficient for staggered array is 15% more than that of the in-line array, at the same time pressure drop across the staggered array is more by 10% than the in-line array. The pressure drop was observed to be increasing with increase in flow rate as expected. Endeavor of the present work is to find the optimum spacing between the fins in an array for maximum heat transfer rate, by investigating the heat transfer characteristics.

Intensive probing of a clear air convective field by radar and instrumental drone aircraft.

NASA Technical Reports Server (NTRS)

Rowland, J. R.

1973-01-01

An instrumented drone aircraft was used in conjunction with ultrasensitive radar to study the development of a convective field in the clear air. Radar data are presented which show an initial constant growth rate in the height of the convective field of 3.8 m/min, followed by a short period marked by condensation and rapid growth at a rate in excess of 6.1 m/min. Drone aircraft soundings show general features of a convective field including progressive lifting of the inversion at the top of the convection and a cooling of the air at the top of the field. Calculations of vertical heat flux as a function of time and altitude during the early stages of convection show a linear decrease in heat flux with altitude to near the top of the convective field and a negative heat flux at the top. Evidence is presented which supports previous observations that convective cells overshoot their neutral buoyancy level into a region where they are cool and moist compared to their surroundings. Furthermore, only that portion of the convective cell that has overshot its neutral buoyancy level is generally visible to the radar.

Personal cooling with phase change materials to improve thermal comfort from a heat wave perspective.

PubMed

Gao, C; Kuklane, K; Wang, F; Holmér, I

2012-12-01

The impact of heat waves arising from climate change on human health is predicted to be profound. It is important to be prepared with various preventive measures for such impacts on society. The objective of this study was to investigate whether personal cooling with phase change materials (PCM) could improve thermal comfort in simulated office work at 34°C. Cooling vests with PCM were measured on a thermal manikin before studies on human subjects. Eight male subjects participated in the study in a climatic chamber (T(a) = 34°C, RH = 60%, and ν(a) = 0.4 m/s). Results showed that the cooling effect on the manikin torso was 29.1 W/m(2) in the isothermal condition. The results on the manikin using a constant heating power mode reflect directly the local cooling effect on subjects. The results on the subjects showed that the torso skin temperature decreased by about 2-3°C and remained at 33.3°C. Both whole body and torso thermal sensations were improved. The findings indicate that the personal cooling with PCM can be used as an option to improve thermal comfort for office workers without air conditioning and may be used for vulnerable groups, such as elderly people, when confronted with heat waves. Wearable personal cooling integrated with phase change materials has the advantage of cooling human body's micro-environment in contrast to stationary personalized cooling and entire room or building cooling, thus providing greater mobility and helping to save energy. In places where air conditioning is not usually used, this personal cooling method can be used as a preventive measure when confronted with heat waves for office workers, vulnerable populations such as the elderly and disabled people, people with chronic diseases, and for use at home. © 2012 John Wiley & Sons A/S.

Thermal Load Considerations for Detonative Combustion-Based Gas Turbine Engines

NASA Technical Reports Server (NTRS)

Paxson, Daniel E.; Perkins, H. Douglas

2004-01-01

An analysis was conducted to assess methods for, and performance implications of, cooling the passages (tubes) of a pulse detonation-based combustor conceptually installed in the core of a gas turbine engine typical of regional aircraft. Temperature-limited material stress criteria were developed from common-sense engineering practice, and available material properties. Validated, one-dimensional, numerical simulations were then used to explore a variety of cooling methods and establish whether or not they met the established criteria. Simulation output data from successful schemes were averaged and used in a cycle-deck engine simulation in order to assess the impact of the cooling method on overall performance. Results were compared to both a baseline engine equipped with a constant-pressure combustor and to one equipped with an idealized detonative combustor. Major findings indicate that thermal loads in these devices are large, but potentially manageable. However, the impact on performance can be substantial. Nearly one half of the ideally possible specific fuel consumption (SFC) reduction is lost due to cooling of the tubes. Details of the analysis are described, limitations are presented, and implications are discussed.

Museum lighting: Why are some illuminants preferred?

NASA Astrophysics Data System (ADS)

Scuello, Michael; Abramov, Israel; Gordon, James; Weintraub, Steven

2004-02-01

We had shown earlier that viewers prefer to look at artworks under illuminants of ~3600 K. In the latest paper we tested the hypothesis that the preferred illuminant is one that appears neither warm nor cool and repeated the settings at each of four illuminances to test the stability of the findings. Observers looked at a neutral white reflectance standard hung on a matte-gray wall lit by overhead banks of lamps whose combined value could be adjusted continuously between 3000 and 4400 K while illuminance was kept constant. Illuminance ranged from 50 to 2000 lux. Observers adjusted color temperature until they were satisfied that the standard looked neither warm nor cool. The mean for a group of eight observers was approximately 3700, independent of intensity; this corresponds to a dominant wavelength of ~580 nm. In a separate study four observers scaled the apparent warmth or coolness of flashes of equiluminant monochromatic lights; the warm-cool transition was between 560 and 580 nm; warmness was completely predicted by the perceived redness of each light as derived from hue and saturation scaling functions from the same group.

ANSYS-Based Simulation and Optimization on Temperature Field of Amorphous Ingot Made by Water Quenching

NASA Astrophysics Data System (ADS)

Zhao, W.; Sun, Z.; Tang, Z.; Liaw, P. K.; Li, J.; Liu, R. P.; Li, Gong

2014-05-01

2D finite element analysis was conducted on the temperature field to create an amorphous ingot by vacuum water quenching. An optimized analysis document was then written by ANSYS parametric design language, and the optimal design modules of ANSYS were used to study the inside diameter and wall thickness of the quartz tube, as well as the water temperature. The microstructure and the phase structure of the amorphous ingot were evaluated by scanning electron microscopy and X-ray diffraction, respectively. Results show that during the cooling process, the thinner wall thickness, smaller diameter of the ingot, or lower temperature of the water environment can result in higher cooling rate at a given temperature. Besides, the gap between the different cooling rates induced by wall thickness or diameter of the ingot narrows down as the temperature decreases, and the gap between the different cooling rates induced by temperature of the water environment remains constant. The process parameters in creating an amorphous ingot, which is optimized by the finite element analysis on the temperature field, are reliable.

Experimental Heat Transfer and Bulk Air Temperature Measurements for a Multipass Internal Cooling Model with Ribs and Bleed

NASA Technical Reports Server (NTRS)

Thurman, Douglas; Poinsatte, Philip

2001-01-01

An experimental study was made to obtain heat transfer and air temperature data for a simple three-leg serpentine test section that simulates a turbine blade internal cooling passage with trip strips and bleed holes. The objectives were to investigate the interaction of ribs and various bleed conditions on internal cooling and to gain a better understanding of bulk air temperature in an internal passage. Steady-state heat transfer measurements were obtained using a transient technique with thermochromic liquid crystals. Trip strips were attached to one wall of the test section and were located either between or near the bleed holes. The bleed holes, used for film cooling, were metered to simulate the effect of external pressure on the turbine blade. Heat transfer enhancement was found to be greater for ribs near bleed holes compared to ribs between holes, and both configurations were affected slightly by bleed rates upstream. Air temperature measurements were taken at discrete locations along one leg of the model. Average bulk air temperatures were found to remain fairly constant along one leg of the model.

Experimental Heat Transfer and Bulk Air Temperature Measurements for a Multipass Internal Cooling Model with Ribs and Bleed

NASA Technical Reports Server (NTRS)

Thurman, Douglas; Poinsatte, Philip

2000-01-01

An experimental study was made to obtain heat transfer and air temperature data for a simple 3-leg serpentine test section that simulates a turbine blade internal cooling passage with trip strips and bleed holes. The objectives were to investigate the interaction of ribs and various bleed conditions on internal cooling and to gain a better understanding of bulk air temperature in an internal passage. Steady state heat transfer measurements were obtained using a transient technique with thermochromic liquid crystals. Trip strips were attached to one wall of the test section and were located either between or near the bleed holes. The bleed holes, used for film cooling, were metered to simulate the effect of external pressure on the turbine blade. Heat transfer enhancement was found to be greater for ribs near bleed holes compared to ribs between holes, and both configurations were affected slightly by bleed rates upstream. Air temperature measurements were taken at discreet locations along one leg of the model. Average bulk air temperatures were found to remain fairly constant along one leg of the model.

Study on core radius minimization for long life Pb-Bi cooled CANDLE burnup scheme based fast reactor

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

Afifah, Maryam, E-mail: maryam.afifah210692@gmail.com; Su’ud, Zaki; Miura, Ryosuke

2015-09-30

Fast Breeder Reactor had been interested to be developed over the world because it inexhaustible source energy, one of those is CANDLE reactor which is have strategy in burn-up scheme, need not control roads for control burn-up, have a constant core characteristics during energy production and don’t need fuel shuffling. The calculation was made by basic reactor analysis which use Sodium coolant geometry core parameter as a reference core to study on minimum core reactor radius of CANDLE for long life Pb-Bi cooled, also want to perform pure coolant effect comparison between LBE and sodium in a same geometry design.more » The result show that the minimum core radius of Lead Bismuth cooled CANDLE is 100 cm and 500 MWth thermal output. Lead-Bismuth coolant for CANDLE reactor enable to reduce much reactor size and have a better void coefficient than Sodium cooled as the most coolant for FBR, then we will have a good point in safety analysis.« less

Geometry effects on cooling in a standing wave cylindrical thermoacousic resonator

NASA Astrophysics Data System (ADS)

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

2012-06-01

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

Idealized Cloud-System Resolving Modeling for Tropical Convection Studies

NASA Astrophysics Data System (ADS)

Anber, Usama M.

A three-dimensional limited-domain Cloud-Resolving Model (CRM) is used in idealized settings to study the interaction between tropical convection and the large scale dynamics. The model domain is doubly periodic and the large-scale circulation is parameterized using the Weak Temperature Gradient (WTG) Approximation and Damped Gravity Wave (DGW) methods. The model simulations fall into two main categories: simulations with a prescribed radiative cooling profile, and others in which radiative cooling profile interacts with clouds and water vapor. For experiments with a prescribed radiative cooling profile, radiative heating is taken constant in the vertical in the troposphere. First, the effect of turbulent surface fluxes and radiative cooling on tropical deep convection is studied. In the precipitating equilibria, an increment in surface fluxes produces a greater increase in precipitation than an equal increment in column-integrated radiative heating. The gross moist stability remains close to constant over a wide range of forcings. With dry initial conditions, the system exhibits hysteresis, and maintains a dry state with for a wide range of net energy inputs to the atmospheric column under WTG. However, for the same forcings the system admits a rainy state when initialized with moist conditions, and thus multiple equilibria exist under WTG. When the net forcing is increased enough that simulations, which begin dry, eventually develop precipitation. DGW, on the other hand, does not have the tendency to develop multiple equilibria under the same conditions. The effect of vertical wind shear on tropical deep convection is also studied. The strength and depth of the shear layer are varied as control parameters. Surface fluxes are prescribed. For weak wind shear, time-averaged rainfall decreases with shear and convection remains disorganized. For larger wind shear, rainfall increases with shear, as convection becomes organized into linear mesoscale systems. This non-monotonic dependence of rainfall on shear is observed when the imposed surface fluxes are moderate. For larger surface fluxes, convection in the unsheared basic state is already strongly organized, but increasing wind shear still leads to increasing rainfall. In addition to surface rainfall, the impacts of shear on the parameterized large-scale vertical velocity, convective mass fluxes, cloud fraction, and momentum transport are also discussed. For experiments with interactive radiative cooling profile, the effect of cloud-radiation interaction on cumulus ensemble is examined in sheared and unsheared environments with both fixed and interactive sea surface temperature (SST). For fixed SST, interactive radiation, when compared to simulations in which radiative profile has the same magnitude and vertical shape but does not interact with clouds or water vapor, is found to suppress mean precipitation by inducing strong descent in the lower troposphere, increasing the gross moist stability. For interactive SST, using a slab ocean mixed layer, there exists a shear strength above which the system becomes unstable and develops oscillatory behavior. Oscillations have periods of wet precipitating states followed by periods of dry non-precipitating states. The frequencies of oscillations are intraseasonal to subseasonal, depending on the mixed layer depth. Finally, the model is coupled to a land surface model with fully interactive radiation and surface fluxes to study the diurnal and seasonal radiation and water cycles in the Amazon basin. The model successfully captures the afternoon precipitation and cloud cover peak and the greater latent heat flux in the dry season for the first time; two major biases in GCMs with implications for correct estimates of evaporation and gross primary production in the Amazon. One of the key findings is that the fog layer near the surface in the west season is crucial for determining the surface energy budget and precipitation. This suggests that features on the diurnal time scale can significantly impact climate on the seasonal time scale.

Fourier transform spectroscopy of the Swan (d(sup 3)pi(sub g) - a(sup 3)pi(sub u)) system of the jet-cooled C2 molecule

NASA Technical Reports Server (NTRS)

Prasad, C. V. V.; Bernath, P. F.

1994-01-01

The Swan (d(sup 3)pi(sub g) - a(sup 3)pi(sub u)) system of the C2 molecule was produced in a jet-cooled corona excited supersonic expansion of helium using diazoacetonitrile as a percursor molecule. This spectrum was recorded using the McMath Fourier transform spectrometer of the National Solar Observatory at Kitt Peak. A total of nine bands with v prime = 0 to 3 and v prime prime = 0 to 4 in the range 16,570-22,760/cm were observed and rotationally analyzed. The C2 molecules in this source had a rotational temperature of only 90 K so that only the low-J lines were present in the spectrum. In some sense the low temperatures in the jet source simulate conditions in the interstellar medium. The Swan system of C2 was also produced in a composite wall hollow cathode made Al4C3/Cu, and the rotational structure of the 1-0, 2-1, 3-2, 0-0, and 1-1 bands were analyzed. The data obtained from both these spectra were fitted together along with some recently published line positions. The rotational constants, lambda doubling parameters and the vibrational constants were estimated from this global fit. Our work on jet-cooled C2 follows similar work on the violet and red systems of CN. A summary of this CN work is also presented. also presented.

Assessing the effusion rate of lava flows from their thermal radiated energy: theoretical study and lab-scale experiments

NASA Astrophysics Data System (ADS)

Garel, F.; Kaminski, E.; Tait, S.; Limare, A.

2010-12-01

A quantitative monitoring of lava flow is required to manage a volcanic crisis, in order to assess where the flow will go, and when will it stop. As the spreading of lava flows is mainly controlled by its rheology and the eruptive mass flux, the key question is how to evaluate them during the eruption (rather than afterwards.) A relationship between the lava flow temperature and the eruption rate is likely to exist, based on the first-order argument that higher eruption rates should correspond to larger energy radiated by a lava flow. The semi-empirical formula developed by Harris and co-workers (e.g. Harris et al., 2007) is used to estimate lava flow rate from satellite observations. However, the complete theoretical bases of this technique, especially its domain of validity, remain to be firmly established. Here we propose a theoretical study of the cooling of a viscous axisymmetric gravity current fed at constant flux rate to investigate whether or not this approach can and/or should be refined and/or modify to better assess flow rates. Our study focuses on the influence of boundary conditions at the surface of the flow, where cooling can occur both by radiation and convection, and at the base of the flow. Dimensionless numbers are introduced to quantify the relative interplay between the model parameters, such as the lava flow rate and the efficiency of the various cooling processes (conduction, convection, radiation.) We obtain that the thermal evolution of the flow can be described as a two-stage evolution. After a transient phase of dynamic cooling, the flow reaches a steady state, characterized by a balance between surface and base cooling and heat advection in the flow, in which the surface temperature structure is constant. The duration of the transient phase and the radiated energy in the steady regime are shown to be a function of the dimensionless numbers. In the case of lava flows, we obtain that the steady state regime is reached after a few days. In this regime, a thermal image provides a consistent estimate of the flow rate if the external cooling conditions are reasonably well constrained.

Teaching Social Communication Skills Using a Cool versus Not Cool Procedure plus Role-Playing and a Social Skills Taxonomy

ERIC Educational Resources Information Center

Leaf, Justin B.; Taubman, Mitchell; Milne, Christine; Dale, Stephanie; Leaf, Jeremy; Townley-Cochran, Donna; Tsuji, Kathleen; Kassardjian, Alyne; Alcalay, Aditt; Leaf, Ronald; McEachin, John

2016-01-01

We utilized a cool versus not cool procedure plus role-playing to teach social communication skills to three individuals diagnosed with autism spectrum disorder. The cool versus not cool procedure plus role-playing consisted of the researcher randomly demonstrating the behavior correctly (cool) two times and the behavior incorrectly (not cool) two…

Evaluation of conditioning time and temperature on gelatinized starch and vitamin retention in a pelleted swine diet.

PubMed

Lewis, L L; Stark, C R; Fahrenholz, A C; Bergstrom, J R; Jones, C K

2015-02-01

Two key feed processing parameters, conditioning temperature and time, were altered to determine their effects on concentration of gelatinized starch and vitamin retention in a pelleted finishing swine diet. Diet formulation (corn–soybean meal based with 30% distillers dried grains with solubles) was held constant. Treatments were arranged in a 2 × 3 factorial design plus a control with 2 conditioning temperatures (77 vs. 88°C) and 3 conditioner retention times (15, 30, and 60 s). In addition, a mash diet not subjected to conditioning served as a control for a total of 7 treatments. Samples were collected after conditioning but before pelleting (hot mash), after pelleting but before cooling (hot pellet), and after pelleting and cooling (cold pellet) and analyzed for percentage total starch, percentage gelatinized starch, and riboflavin, niacin, and vitamin D3 concentrations. Total percentage starch was increased by greater conditioning temperature (P = 0.041) but not time (P > 0.10), whereas higher temperature and longer time both increased (P < 0.05) percentage gelatinized starch, with increasing time resulting in a linear increase in percentage starch gelatinization (P = 0.013). The interaction between conditioning temperature and time increased percentage gelatinized starch (P = 0.003) but not percentage total starch (P > 0.10). Sample location also affected both percentage total starch and gelatinized starch (P < 0.05), with the greatest increase in percentage gelatinized starch occurring between hot mash and hot pellet samples. As expected, the pelleting process increased percentage gelatinized starch (P = 0.035; 7.3 vs. 11.7% gelatinized starch for hot mash vs. hot pellet samples, respectively), but there was no difference in total starch concentrations (P > 0.10). Finally, neither conditioning temperature nor time affected riboflavin, niacin, or vitamin D3 concentrations (P > 0.10). In summary, both increasing conditioningtemperature and time effect percentage gelatinized starch, but not to the extent of forcing the diet through a pelleting die.

Cool-Water Carbonates, SEPM Special Publication No. 56

NASA Astrophysics Data System (ADS)

Hallock, Pamela

Doesn't field work on modern carbonates mean scuba diving on spectacular coral reefs in gin-clear water teeming with brightly colored fish? Not if you are one of the researchers that Jonathan Clarke of the Western Mining Corporation Ltd., in Preston, Victoria, Australia, assembled at a workshop in Geelong, Victoria, in January 1995. Their field work involves research cruises in high-latitude oceans, where mal de mer and chilling winds are constant companions. Many braved 10-m seas in modest-sized research vessels to sample shelves stripped of fine sediments by storm waves whose effects can reach to depths exceeding 200 m. Noel James of Queen's University in Kingston, Ontario, carefully lays the groundwork for the book in a paper titled, “The Cool-Water Carbonate Depositional Realm,” which will assuredly become a standard reading assignment in advanced undergraduate-and graduate-level courses in carbonate sedimentology. James skillfully shows how cool-water carbonates are part of the greater carbonate depositional spectrum. By expanding recognition of the possible range of carbonate environments, sedimentologists expand their ability to understand and interpret ancient carbonates, particularly Paleozoic limestones that often show striking similarities to modern cool-water sediments. James' paper is followed by nine papers on modern cool-water carbonates, seven on Tertiary environments, and seven examples from Mesozoic and Paleozoic limestones

Comparison of performance of high-power mid-IR QCL modules in actively and passively cooled mode

NASA Astrophysics Data System (ADS)

Münzhuber, F.; Denzel, H.; Tholl, H. D.

2017-10-01

We report on the effects of active and passive cooling on the performance of high power mid-IR QCL modules (λ ≈ 3.9 μm) in quasi-cw mode. In active cooling mode, a thermo-electrical cooler attached with its hot side to a heat sink of constant temperature, a local thermometer in close proximity to the QCL chip (epi-down mounted) as well as a control unit has been used for temperature control of the QCL submount. In contrast, the passive cooling was performed by attaching the QCL module solely to the heat sink. Electro-optical light-current- (L-I-) curves are measured in a quasi-cw mode, from which efficiencies can be deduced. Waiving of the active cooling elements results in a drop of the maximum intensity of less than 5 %, compared to the case wherein the temperature of the submount is stabilized to the temperature of the heat sink. The application of a model of electro-optical performance to the data shows good agreement and captures the relevant observations. We further determine the heat resistance of the module and demonstrate that the system performance is not limited by the packaging of the module, but rather by the heat dissipation on the QCL chip itself.

Process optimization of helium cryo plant operation for SST-1 superconducting magnet system

NASA Astrophysics Data System (ADS)

Panchal, P.; Panchal, R.; Patel, R.; Mahesuriya, G.; Sonara, D.; Srikanth G, L. N.; Garg, A.; Christian, D.; Bairagi, N.; Sharma, R.; Patel, K.; Shah, P.; Nimavat, H.; Purwar, G.; Patel, J.; Tanna, V.; Pradhan, S.

2017-02-01

Several plasma discharge campaigns have been carried out in steady state superconducting tokamak (SST-1). SST-1 has toroidal field (TF) and poloidal field (PF) superconducting magnet system (SCMS). The TF coils system is cooled to 4.5 - 4.8 K at 1.5 - 1.7 bar(a) under two phase flow condition using 1.3 kW helium cryo plant. Experience revealed that the PF coils demand higher pressure heads even at lower temperatures in comparison to TF coils because of its longer hydraulic path lengths. Thermal run away are observed within PF coils because of single common control valve for all PF coils in distribution system having non-uniform lengths. Thus it is routine practice to stop the cooling of PF path and continue only TF cooling at SCMS inlet temperature of ˜ 14 K. In order to achieve uniform cool down, different control logic is adopted to make cryo stable system. In adopted control logic, the SCMS are cooled down to 80 K at constant inlet pressure of 9 bar(a). After authorization of turbine A/B, the SCMS inlet pressure is gradually controlled by refrigeration J-T valve to achieve stable operation window for cryo system. This paper presents process optimization for cryo plant operation for SST-1 SCMS.

Heat Convection at the Density Maximum Point of Water

ERIC Educational Resources Information Center

Balta, Nuri; Korganci, Nuri

2018-01-01

Water exhibits a maximum in density at normal pressure at around 4° degree temperature. This paper demonstrates that during cooling, at around 4 °C, the temperature remains constant for a while because of heat exchange associated with convective currents inside the water. Superficial approach implies it as a new anomaly of water, but actually it…

Time-dependent Cooling in Photoionized Plasma

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

Gnat, Orly, E-mail: orlyg@phys.huji.ac.il

I explore the thermal evolution and ionization states in gas cooling from an initially hot state in the presence of external photoionizing radiation. I compute the equilibrium and nonequilibrium cooling efficiencies, heating rates, and ion fractions for low-density gas cooling while exposed to the ionizing metagalactic background radiation at various redshifts ( z = 0 − 3), for a range of temperatures (10{sup 8}–10{sup 4} K), densities (10{sup −7}–10{sup 3} cm{sup −3}), and metallicities (10{sup −3}–2 times solar). The results indicate the existence of a threshold ionization parameter, above which the cooling efficiencies are very close to those in photoionization equilibriummore » (so that departures from equilibrium may be neglected), and below which the cooling efficiencies resemble those in collisional time-dependent gas cooling with no external radiation (and are thus independent of density).« less

Experimental study on the heat transfer characteristics of a nuclear reactor containment wall cooled by gravitationally falling water

NASA Astrophysics Data System (ADS)

Pasek, Ari D.; Umar, Efrison; Suwono, Aryadi; Manalu, Reinhard E. E.

2012-06-01

Gravitationally falling water cooling is one of mechanism utilized by a modern nuclear Pressurized Water Reactor (PWR) for its Passive Containment Cooling System (PCCS). Since the cooling is closely related to the safety, water film cooling characteristics of the PCCS should be studied. This paper deals with the experimental study of laminar water film cooling on the containment model wall. The influences of water mass flow rate and wall heat rate on the heat transfer characteristic were studied. This research was started with design and assembly of a containment model equipped with the water cooling system, and calibration of all measurement devices. The containment model is a scaled down model of AP 1000 reactor. Below the containment steam is generated using electrical heaters. The steam heated the containment wall, and then the temperatures of the wall in several positions were measure transiently using thermocouples and data acquisition. The containment was then cooled by falling water sprayed from the top of the containment. The experiments were done for various wall heat rate and cooling water flow rate. The objective of the research is to find the temperature profile along the wall before and after the water cooling applied, prediction of the water film characteristic such as means velocity, thickness and their influence to the heat transfer coefficient. The result of the experiments shows that the wall temperatures significantly drop after being sprayed with water. The thickness of water film increases with increasing water flow rate and remained constant with increasing wall heat rate. The heat transfer coefficient decreases as film mass flow rate increase due to the increases of the film thickness which causes the increasing of the thermal resistance. The heat transfer coefficient increases slightly as the wall heat rate increases. The experimental results were then compared with previous theoretical studied.

Infrared photoemitting diode having reduced work function

DOEpatents

Hirschfeld, T.B.

1982-05-06

In electro-optical detectors which include as elements a photoemitting photocathode and anode, a photoemitting diode is fabricated which lowers the diode's work function, thus reducing the cooling requirement typically needed for this type of device. The work function is reduced by sandwiching between the photocathode and anode a liquid meidum of the formula NR/sub 3/ and having an electron affinity for the electrons of the photocathode, which liquid medium permits free electrons leaving the photocathode to remain as stable solvated species in the liquid medium. Thus, highly light-absorbent, and therefore thin, metallic layers can be used for detection, thereby reducing dark current at a given temperature, with a consequent reduction in cooling requirements at constant detector performance.

Infrared photoemitting diode having reduced work function

DOEpatents

Hirschfeld, Tomas B.

1984-01-01

In electro-optical detectors which include as elements a photoemitting photocathode and anode, a photoemitting diode is fabricated which lowers the diode's work function, thus reducing the cooling requirement typically needed for this type of device. The work function is reduced by sandwiching between the photocathode and anode a liquid medium of the formula NR.sub.3 and having an electron affinity for the electrons of the photocathode, which liquid medium permits free electrons leaving the photocathode to remain as stable solvated species in the liquid medium. Thus, highly light-absorbent, and therefore thin, metallic layers can be used for detection, thereby reducing dark current at a given temperature, with a consequent reduction in cooling requirements at constant detector performance.

Simulation of forced convection in a channel with nanofluid by the lattice Boltzmann method

PubMed Central

2013-01-01

This paper presents a numerical study of the thermal performance of fins mounted on the bottom wall of a horizontal channel and cooled with either pure water or an Al2O3-water nanofluid. The bottom wall of the channel is heated at a constant temperature and cooled by mixed convection of laminar flow at a relatively low temperature. The results of the numerical simulation indicate that the heat transfer rate of fins is significantly affected by the Reynolds number (Re) and the thermal conductivity of the fins. The influence of the solid volume fraction on the increase of heat transfer is more noticeable at higher values of the Re. PMID:23594696

A Novel Compact Pyroelectric X-Ray and Neutron Source

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

Yaron Danon

2007-08-31

This research was focused on the utilization of pyroelectric crystals for generation of radiation. When in constant temperature pyroelectric crystals are spontaneously polarized. The polarization causes internal charges to accumulate near the crystal faces and masking charges from the environment are attracted to the crystal faces and neutralize the charge. When a pyroelectric crystal is heated or cooled it becomes depolarized and the surface charges become available. If the heating or cooling is done on a crystal in vacuum where no masking charges are available, the crystal becomes a charged capacitor and because of its small capacitance large potential developsmore » across the faces of the crystal.« less

Analysis of isothermal and cooling rate dependent immersion freezing by a unifying stochastic ice nucleation model

NASA Astrophysics Data System (ADS)

Alpert, P. A.; Knopf, D. A.

2015-05-01

Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature (T) and relative humidity (RH) at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling rate dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nuclei (IN) all have the same IN surface area (ISA), however the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses physically observable parameters including the total number of droplets (Ntot) and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets, droplets in a continuous flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time dependent isothermal frozen fractions exhibiting non-exponential behavior with time can be readily explained by this model considering varying ISA. An apparent cooling rate dependence ofJhet is explained by assuming identical ISA in each droplet. When accounting for ISA variability, the cooling rate dependence of ice nucleation kinetics vanishes as expected from classical nucleation theory. The model simulations allow for a quantitative experimental uncertainty analysis for parameters Ntot, T, RH, and the ISA variability. In an idealized cloud parcel model applying variability in ISAs for each droplet, the model predicts enhanced immersion freezing temperatures and greater ice crystal production compared to a case when ISAs are uniform in each droplet. The implications of our results for experimental analysis and interpretation of the immersion freezing process are discussed.

Experimental study of the surface thermal signature of gravity currents: application to the assessment of lava flow effusion rate

NASA Astrophysics Data System (ADS)

Garel, F.; Kaminski, E.; Tait, S.; Limare, A.

2011-12-01

During an effusive volcanic eruption, the crisis management is mainly based on the prediction of lava flows advance and its velocity. As the spreading of lava flows is mainly controlled by its rheology and the eruptive mass flux, the key question is how to evaluate them during the eruption (rather than afterwards.) A relationship between the heat flux lost by the lava at its surface and the eruption rate is likely to exist, based on the first-order argument that higher eruption rates should correspond to larger power radiated by a lava flow. The semi-empirical formula developed by Harris and co-workers (e.g. Harris et al., Bull. Volc. 2007) is currently used to estimate lava flow rate from satellite surveys yielding the surface temperatures and area of the lava flow field. However, this approach is derived from a static thermal budget of the lava flow and does not explicitly model the time-evolution of the surface thermal signal. Here we propose laboratory experiments and theoretical studies of the cooling of a viscous axisymmetric gravity current fed at constant flux rate. We first consider the isoviscous case, for which the spreading is well-know. The experiments using silicon oil and the theoretical model both reveal the establishment of a steady surface thermal structure after a transient time. The steady state is a balance between surface cooling and heat advection in the flow. The radiated heat flux in the steady regime, a few days for a basaltic lava flow, depends mainly on the effusion rate rather than on the viscosity. In this regime, one thermal survey of the radiated power could provide a consistent estimate of the flow rate if the external cooling conditions (wind) are reasonably well constrained. We continue to investigate the relationship between the thermal radiated heat flux and the effusion rate by using in the experiments fluids with temperature-dependent viscosity (glucose syrup) or undergoing solidification while cooling (PEG wax). We observe a transient evolution of the radiated heat flux closely related to the variations of the flow area. The study of experiments with time-variable effusion rates finally gives first leads on the inertia of the thermal surface structure. This is to be related to the time-period over which the thermal proxy averages the actual effusion rate, hence to the acquisition frequency appropriate for a thermal monitoring of effusive volcanic eruptions.

Kinematics, Exhumation, and Sedimentation of the North Central Andes (Bolivia): An Integrated Thermochronometer and Thermokinematic Modeling Approach

NASA Astrophysics Data System (ADS)

Rak, Adam J.; McQuarrie, Nadine; Ehlers, Todd A.

2017-11-01

Quantifying mountain building processes in convergent orogens requires determination of the timing and rate of deformation in the overriding plate. In the central Andes, large discrepancies in both timing and rate of deformation prevent evaluating the shortening history in light of internal or external forcing factors. Geologic map patterns, age and location of reset thermochronometer systems, and synorogenic sediment distribution are all a function of the geometry, kinematics, and rate of deformation in a fold-thrust-belt-foreland basin (FTB-FB) system. To determine the timing and rate of deformation in the northern Bolivian Andes, we link thermokinematic modeling to a sequentially forward modeled, balanced cross section isostatically accounting for thrust loads and erosion. Displacement vectors, in 10 km increments, are assigned variable ages to create velocity fields in a thermokinematic model for predicting thermochronometer ages. We match both the pattern of predicted cooling ages with the across strike pattern of measured zircon fission track, apatite fission track, and apatite (U-Th)/He cooling ages as well as the modeled age of FB formations to published sedimentary sections. Results indicate that northern Bolivian FTB deformation started at 50 Ma and may have begun as early as 55 Ma. Acceptable rates of shortening permit either a constant rate of shortening ( 4-5 mm/yr) or varying shortening rates with faster rates (7-10 mm/yr) at 45-50 Ma and 12-8 Ma, significantly slower rates (2-4 mm/yr) from 35 to 15 Ma and indicate the northern Bolivian Subandes started deforming between 19 and 14 Ma.

Bolometric detector systems for IR and mm-wave space astronomy

NASA Technical Reports Server (NTRS)

Church, S. E.; Lange, A. E.; Mauskopf, P. D.; Hristov, V.; Bock, J. J.; DelCastillo, H. M.; Beeman, J.; Ade, P. A. R.; Griffin, M. J.

1996-01-01

Recent developments in bolometric detector systems for millimeter and submillimeter wave space astronomy are described. Current technologies meet all the requirements for the high frequency instrument onboard the cosmic background radiation anisotropy satellite/satellite for the measurement of background anisotropies (COBRAS/SAMBA) platform. It is considered that the technologies that are currently being developed will significantly reduce the effective time constant and/or the cooling requirements of bolometric detectors. These technologies lend themselves to the fabrication of the large format arrays required for the Far Infrared and Submillimeter Space Telescope (FIRST). The scientific goals and detector requirements of the COBRAS/SAMBA platform that will use infrared bolometers are reviewed and the baseline detector system is described, including the feed optics, the infrared filters, the cold amplifiers and the warm readout electronics.

The small chill: mild hypothermia for cardioprotection?

PubMed

Tissier, Renaud; Chenoune, Mourad; Ghaleh, Bijan; Cohen, Michael V; Downey, James M; Berdeaux, Alain

2010-12-01

Reducing the heart's temperature by 2-5°C is a potent cardioprotective treatment in animal models of coronary artery occlusion. The anti-infarct benefit depends upon the target temperature and the time at which cooling is instituted. Protection primarily results from cooling during the ischaemic period, whereas cooling during reperfusion or beyond offers little protection. In animal studies, protection is proportional to both the depth and duration of cooling. An optimal cooling protocol must appreciably shorten the normothermic ischaemic time to effectively salvage myocardium. Patients presenting with acute myocardial infarction could be candidates for mild hypothermia since the current door-to-balloon time is typically 90 min. But they would have to be cooled quickly shortly after their arrival. Several strategies have been proposed for ultra-fast cooling, but most like liquid ventilation and pericardial perfusion are too invasive. More feasible strategies might include cutaneous cooling, peritoneal lavage with cold solutions, and endovascular cooling with intravenous thermodes. This last option has been investigated clinically, but the results have been disappointing possibly because the devices lacked capacity to cool the patient quickly or cooling was not implemented soon enough. The mechanism of hypothermia's protection has been assumed to be energy conservation. However, whereas deep hypothermia clearly preserves ATP, mild hypothermia has only a modest effect on ATP depletion during ischaemia. Some evidence suggests that intracellular signalling pathways might be responsible for the protection. It is unknown how cooling could trigger these pathways, but, if true, then it might be possible to duplicate cooling's protection pharmacologically.

Effect of Temperature Reversion on Hot Ductility and Flow Stress-Strain Curves of C-Mn Continuously Cast Steels

NASA Astrophysics Data System (ADS)

Dong, Zhihua; Li, Wei; Long, Mujun; Gui, Lintao; Chen, Dengfu; Huang, Yunwei; Vitos, Levente

2015-08-01

The influence of temperature reversion in secondary cooling and its reversion rate on hot ductility and flow stress-strain curve of C-Mn steel has been investigated. Tensile specimens were cooled at various regimes. One cooling regime involved cooling at a constant rate of 100 °C min-1 to the test temperature, while the others involved temperature reversion processes at three different reversion rates before deformation. After hot tensile test, the evolution of mechanical properties of steel was analyzed at various scales by means of microstructure observation, ab initio prediction, and thermodynamic calculation. Results indicated that the temperature reversion in secondary cooling led to hot ductility trough occurring at higher temperature with greater depth. With increasing temperature reversion rate, the low temperature end of ductility trough extended toward lower temperature, leading to wider hot ductility trough with slightly reducing depth. Microstructure examinations indicated that the intergranular fracture related to the thin film-like ferrite and (Fe,Mn)S particles did not changed with varying cooling regimes; however, the Widmanstatten ferrite surrounding austenite grains resulted from the temperature reversion process seriously deteriorated the ductility. In addition, after the temperature reversion in secondary cooling, the peak stress on the flow curve slightly declined and the peak of strain to peak stress occurred at higher temperature. With increasing temperature reversion rate, the strain to peak stress slightly increased, while the peak stress showed little variation. The evolution of plastic modulus and strain to peak stress of austenite with varying temperature was in line with the theoretical prediction on Fe.

Method of fabricating a uranium-bearing foil

DOEpatents

Gooch, Jackie G [Seymour, TN; DeMint, Amy L [Kingston, TN

2012-04-24

Methods of fabricating a uranium-bearing foil are described. The foil may be substantially pure uranium, or may be a uranium alloy such as a uranium-molybdenum alloy. The method typically includes a series of hot rolling operations on a cast plate material to form a thin sheet. These hot rolling operations are typically performed using a process where each pass reduces the thickness of the plate by a substantially constant percentage. The sheet is typically then annealed and then cooled. The process typically concludes with a series of cold rolling passes where each pass reduces the thickness of the plate by a substantially constant thickness amount to form the foil.

Adimensional theory of shielding in ultracold collisions of dipolar rotors

NASA Astrophysics Data System (ADS)

González-Martínez, Maykel L.; Bohn, John L.; Quéméner, Goulven

2017-09-01

We investigate the electric field shielding of ultracold collisions of dipolar rotors, initially in their first rotational excited state, using an adimensional approach. We establish a map of good and bad candidates for efficient evaporative cooling based on this shielding mechanism, by presenting the ratio of elastic over quenching processes as a function of a rescaled rotational constant B ˜=B /sE3 and a rescaled electric field F ˜=d F /B . B ,d ,F ,andsE 3 are respectively the rotational constant, the full electric dipole moment of the molecules, the applied electric field, and a characteristic dipole-dipole energy. We identify two groups of bi-alkali-metal dipolar molecules. The first group, including RbCs, NaK, KCs, LiK, NaRb, LiRb, NaCs, and LiCs, is favorable with a ratio over 1000 at collision energies equal to (or even higher than) their characteristic dipolar energy. The second group, including LiNa and KRb, is not favorable. More generally, for molecules well described by Hund's case b, our adimensional study provides the conditions of efficient evaporative cooling. The range of appropriate rescaled rotational constant and rescaled field is approximately B ˜≥108 and 3.25 ≤F ˜≤3.8 , with a maximum ratio reached for F ˜≃3.4 for a given B ˜. We also discuss the importance of the electronic van der Waals interaction on the adimensional character of our study.

Controlled cooling of an electronic system based on projected conditions

DOEpatents

David, Milnes P.; Iyengar, Madhusudan K.; Schmidt, Roger R.

2016-05-17

Energy efficient control of a cooling system cooling an electronic system is provided based, in part, on projected conditions. The control includes automatically determining an adjusted control setting(s) for an adjustable cooling component(s) of the cooling system. The automatically determining is based, at least in part, on projected power consumed by the electronic system at a future time and projected temperature at the future time of a heat sink to which heat extracted is rejected. The automatically determining operates to reduce power consumption of the cooling system and/or the electronic system while ensuring that at least one targeted temperature associated with the cooling system or the electronic system is within a desired range. The automatically determining may be based, at least in part, on an experimentally obtained model(s) relating the targeted temperature and power consumption of the adjustable cooling component(s) of the cooling system.

Controlled cooling of an electronic system based on projected conditions

DOEpatents

David, Milnes P.; Iyengar, Madhusudan K.; Schmidt, Roger R.

2015-08-18

Energy efficient control of a cooling system cooling an electronic system is provided based, in part, on projected conditions. The control includes automatically determining an adjusted control setting(s) for an adjustable cooling component(s) of the cooling system. The automatically determining is based, at least in part, on projected power consumed by the electronic system at a future time and projected temperature at the future time of a heat sink to which heat extracted is rejected. The automatically determining operates to reduce power consumption of the cooling system and/or the electronic system while ensuring that at least one targeted temperature associated with the cooling system or the electronic system is within a desired range. The automatically determining may be based, at least in part, on an experimentally obtained model(s) relating the targeted temperature and power consumption of the adjustable cooling component(s) of the cooling system.

Kinetics of Death of Bacterial Spores at Elevated Temperatures

PubMed Central

Wang, Daniel I-C.; Scharer, Jeno; Humphrey, Arthur E.

1964-01-01

The kinetics of death of Bacillus stearothermophilus spores (FS 7954) suspended in phosphate buffer (pH 7) were studied over a temperature range of 127.2 to 143.8 C and exposure times of 0.203 to 4.150 sec. These short exposure were achieved by use of a tubular flow reactor in which a suspension of spores was injected into a hot flowing stream at the entrance of the reactor. Thermal equilibria of the suspension with the hot stream was achieved within 0.0006 sec. After flow through a fixed length of reactor, the stream containing the spores was cooled by flash vaporization and then assayed for viable count. The death rate data were fitted by a logarithmic expression. However, logarithmic death rate was only approximated in the tail or high-kill regions of exposure. Death rate constants obtained from this portion of the data were found to correlate by Arrhenius as well as Absolute Reaction Rate Theory relationships. Thermal-death time curves were found to correlate the data rather poorly. The activation energy and frequency constant for an Arrhenius relationship fit of the data were found to be 83.6 kcal/gmole and 1047.2 min-1, respectively. The standard enthalpy and entropy changes for an Absolute Reaction Rate Theory relationship fit of the data were found to be 84.4 kcal/gmole and 157 cal/gmole-K, respectively. PMID:14215978

The effects of magnetic fields on the growth of thermal instabilities in cooling flows

NASA Technical Reports Server (NTRS)

David, Laurence P.; Bregman, Joel N.

1989-01-01

The effects of heat conduction and magnetic fields on the growth of thermal instabilities in cooling flows are examined using a time-dependent hydrodynamics code. It is found that, for magnetic field strengths of roughly 1 micro-Gauss, magnetic pressure forces can completely suppress shocks from forming in thermally unstable entropy perturbations with initial length scales as large as 20 kpc, even for initial amplitudes as great as 60 percent. Perturbations with initial amplitudes of 50 percent and initial magnetic field strengths of 1 micro-Gauss cool to 10,000 K on a time scale which is only 22 percent of the initial instantaneous cooling time. Nonlinear perturbations can thus condense out of cooling flows on a time scale substantially less than the time required for linear perturbations and produce significant mass deposition of cold gas while the accreting intracluster gas is still at large radii.

Experimental Investigation of Thermal Performance of Miniature Heat Pipe Using SiO2-Water Nanofluids.

PubMed

Niu, Yan-Fang; Zhao, Wei-Lin; Gong, Yu-Ying

2015-04-01

The four miniature heat pipes filled with DI water and SiO2-water nanofluids containing different volume concentrations (0.2%, 0.6% and 1.0%) are experimentally measured on the condition of air and water cooling. The wall temperature and the thermal resistance are investigated for three inclination angles. At the same of inlet heat water temperature in the heat system, it is observed that the total wall temperatures on the evaporator section are almost retaining constant by air cooling and the wall temperatures at the front end of the evaporator section are slightly reduced by water cooling. However, the wall temperatures at the condenser section using SiO2-water nanofluids are all higher than that for DI water on the two cooling conditions. As compared with the heat pipe using DI water, the decreasing of the thermal resistance in heat pipe using nanofluids is about 43.10%-74.46% by air cooling and 51.43%-72.22% by water cooling. These indicate that the utilization of SiO2-water nanofluids as working fluids enhances the performance of the miniature heat pipe. When the four miniature heat pipes are cut to examine at the end of the experiment, a thin coating on the surface of the screen mesh of the heat pipe using SiO2-water nanofluids is found. This may be one reason for reinforcing the heat transfer performance of the miniature heat pipe.

Short post-infusion scalp cooling time in the prevention of docetaxel-induced alopecia.

PubMed

van den Hurk, C J G; Breed, W P M; Nortier, J W R

2012-12-01

The patient impact of chemotherapy-induced alopecia (CIA) is high. Scalp cooling is applied to reduce CIA. The potential optimum post-infusion cooling times (PICTs) are currently unknown. Scalp cooling was applied in 53 patients receiving docetaxel chemotherapy with 90-min PICT (observational part). Also 15 non-scalp-cooled patients were included. If hair preservation was observed in >80 % of the patients, randomisation between 45 and 90-min PICT was planned. Patients reported tolerance of scalp cooling and use of head covering. Observational study: 81 % of scalp-cooled patients did not require head covering versus 27 % of non-scalp-cooled patients. Randomised study: 79 % of 38 patients with 90-min PICT did not need head covering versus 95 % of 38 patients with 45-min PICT (p = 0.04). Scalp cooling was very well tolerated (visual analogue scale = 79). A 45-min PICT can be recommended in 3-weekly docetaxel regimens with a dose of 75 or 100 mg/m(2), administered in 60 min. The shorter PICT is a major advantage in time investment for patients. Patients (women and men) who receive docetaxel, except combined with doxorubicin and cyclophosphamide (taxotere, adriamycin and cyclophosphamide (TAC)) should be informed about the protective effect and high tolerability of scalp cooling in avoiding CIA.

Ice Thermal Storage Systems for LWR Supplemental Cooling and Peak Power Shifting

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

Haihua Zhao; Hongbin Zhang; Phil Sharpe

2010-06-01

Availability of enough cooling water has been one of the major issues for the nuclear power plant site selection. Cooling water issues have frequently disrupted the normal operation at some nuclear power plants during heat waves and long draught. The issues become more severe due to the new round of nuclear power expansion and global warming. During hot summer days, cooling water leaving a power plant may become too hot to threaten aquatic life so that environmental regulations may force the plant to reduce power output or even temporarily to be shutdown. For new nuclear power plants to be builtmore » at areas without enough cooling water, dry cooling can be used to remove waste heat directly into the atmosphere. However, dry cooling will result in much lower thermal efficiency when the weather is hot. One potential solution for the above mentioned issues is to use ice thermal storage systems (ITS) that reduce cooling water requirements and boost the plant’s thermal efficiency in hot hours. ITS uses cheap off-peak electricity to make ice and uses those ice for supplemental cooling during peak demand time. ITS is suitable for supplemental cooling storage due to its very high energy storage density. ITS also provides a way to shift large amount of electricity from off peak time to peak time. Some gas turbine plants already use ITS to increase thermal efficiency during peak hours in summer. ITSs have also been widely used for building cooling to save energy cost. Among three cooling methods for LWR applications: once-through, wet cooling tower, and dry cooling tower, once-through cooling plants near a large water body like an ocean or a large lake and wet cooling plants can maintain the designed turbine backpressure (or condensation temperature) during 99% of the time; therefore, adding ITS to those plants will not generate large benefits. For once-through cooling plants near a limited water body like a river or a small lake, adding ITS can bring significant economic benefits and avoid forced derating and shutdown during extremely hot weather. For the new plants using dry cooling towers, adding the ice thermal storage systems can effectively reduce the efficiency loss and water consumption during hot weather so that new LWRs could be considered in regions without enough cooling water. \\ This paper presents the feasibility study of using ice thermal storage systems for LWR supplemental cooling and peak power shifting. LWR cooling issues and ITS application status will be reviewed. Two ITS application case studies will be presented and compared with alternative options: one for once-through cooling without enough cooling for short time, and the other with dry cooling. Because capital cost, especially the ice storage structure/building cost, is the major cost for ITS, two different cost estimation models are developed: one based on scaling method, and the other based on a preliminary design using Building Information Modeling (BIM), an emerging technology in Architecture/Engineering/Construction, which enables design options, performance analysis and cost estimating in the early design stage.« less

Scalp cooling with adjuvant/neoadjuvant chemotherapy for breast cancer and the risk of scalp metastases: systematic review and meta-analysis.

PubMed

Rugo, Hope S; Melin, Susan A; Voigt, Jeff

2017-06-01

The risk of scalp metastases in patients using scalp cooling for preservation of hair during chemotherapy has been a concern but is poorly described. A systematic review and meta-analysis of longitudinal studies was undertaken to evaluate the effect of scalp cooling versus no scalp cooling on the risk of scalp metastasis in patients treated for breast cancer with chemotherapy. Electronic databases, journal specific, and hand searches of articles identified were searched. Patients were matched based on disease, treatment, lack of metastatic disease, and sex. A total of 24 full-text articles were identified for review. Of these articles, ten quantified the incidence of scalp metastasis with scalp cooling over time. For scalp cooling, 1959 patients were evaluated over an estimated mean time frame of 43.1 months. For no scalp cooling, 1238 patients were evaluated over an estimated mean time frame of 87.4 months. The incidence rate of scalp metastasis in the scalp cooling group versus the no scalp cooling group was 0.61% (95% CI 0.32-1.1%) versus 0.41% (95% CI 0.13-0.94%); P = 0.43. The incidence of scalp metastases was low regardless of scalp cooling. This analysis suggests that scalp cooling does not increase the incidence of scalp metastases.

Geomagnetic fluctuations during a polarity transition

NASA Astrophysics Data System (ADS)

Audunsson, Haraldur; Levi, Shaul

1997-01-01

The extensive Roza Member of the Columbia River Basalt Group (Washington State) has intermediate paleomagnetic directions, bracketed by underlying normal and overlying reverse polarity flows. A consistent paleomagnetic direction was measured at 11 widely distributed outcrops; the average direction has a declination of 189° and an inclination of -5°, with greater variation in the inclination [Rietman, 1966]. In this study the Roza Member was sampled in two Pasco Basin drillcores, where it is a single cooling unit and its thickness exceeds 50 m. Excellent core recovery allowed uniform and dense sampling of the drillcores. During its protracted cooling, the Roza flow in the drillcores recorded part of a 15.5 Ma geomagnetic polarity transition. The inclination has symmetric, quasicyclic intraflow variation, while the declination is nearly constant, consistent with the results from the outcrops. Thermal models of the cooling flow provide the timing for remanence acquisition. The inclination is inferred to have progressed from 0° to -15° and back to -3°over a period of 15 to 60 years, at rates of 1.6° to 0.5°/yr. Because the geomagnetic intensity was probably weak during the transition, these apparently high rates of change are not significantly different from present-day secular variation. These results agree with the hypothesis that normal secular variation persists through geomagnetic transitions. The Iow-amplitude quasicyclical fluctuations of the field over tens of years, recorded by Roza, suggest that the geomagnetic field reverses in discrete steps, and that more than 15-60 years were required to complete this reversal.

Heat Transfer Experiments in the Internal Cooling Passages of a Cooled Radial Turbine Rotor

NASA Technical Reports Server (NTRS)

Johnson, B. V.; Wagner, J. H.

1996-01-01

An experimental study was conducted (1) to experimentally measure, assess and analyze the heat transfer within the internal cooling configuration of a radial turbine rotor blade and (2) to obtain heat transfer data to evaluate and improve computational fluid dynamics (CFD) procedures and turbulent transport models of internal coolant flows. A 1.15 times scale model of the coolant passages within the NASA LERC High Temperature Radial Turbine was designed, fabricated of Lucite and instrumented for transient beat transfer tests using thin film surface thermocouples and liquid crystals to indicate temperatures. Transient heat transfer tests were conducted for Reynolds numbers of one-fourth, one-half, and equal to the operating Reynolds number for the NASA Turbine. Tests were conducted for stationary and rotating conditions with rotation numbers in the range occurring in the NASA Turbine. Results from the experiments showed the heat transfer characteristics within the coolant passage were affected by rotation. In general, the heat transfer increased and decreased on the sides of the straight radial passages with rotation as previously reported from NASA-HOST-sponsored experiments. The heat transfer in the tri-passage axial flow region adjacent to the blade exit was relatively unaffected by rotation. However, the heat transfer on one surface, in the transitional region between the radial inflow passage and axial, constant radius passages, decreased to approximately 20 percent of the values without rotation. Comparisons with previous 3-D numerical studies indicated regions where the heat transfer characteristics agreed and disagreed with the present experiment.

Development of measurement simulation of the laser dew-point hygrometer using an optical fiber cable

NASA Astrophysics Data System (ADS)

Matsumoto, Shigeaki

2005-02-01

In order to improve the initial and the response times of the Laser Dew-Point Hygrometer (LDH), the measurement simulation was developed on the basis of the loop computation of the surface temperature of a gold plate for dew depostition, the quantity of deposited dew and the intensity of scattered light from the surface of the plate at time interval of 5 sec during measurement. A more detailed relationship between the surface temperature of the plate and the cooling current, and the time constant of the integrator in the control circuit of the LDH were introduced in the simulation program as a function of atmospheric temperature. The simulation was more close to the actual measurement by the LDH. The simulation results indicated the possibility of improving both the times of teh LDH by the increase of the sensitivity of dew and that of the mass transfer coefficient of dew deposited on the plate surface. It was concluded that the initial and the response times could be improved to below 100sec and 120 sec, respectively in the dew-point range at room temperature, that are almost half of the those times of the original LDH.

Arrhenius activation energy of damage to catalase during spray-drying.

PubMed

Schaefer, Joachim; Lee, Geoffrey

2015-07-15

The inactivation of catalase during spray-drying over a range of outlet gas temperatures could be closely represented by the Arrhenius equation. From this an activation energy for damage to the catalase could be calculated. The close fit to Arrhenius suggests that the thermally-induced part of inactivation of the catalase during the complex drying and particle-formation processes takes place at constant temperature. These processes are rapid compared with the residence time of the powder in the collecting vessel of the cyclone where dried catalase is exposed to a constant temperature equal to approximately the drying gas outlet temperature. A lower activation energy after spray drying with the ultrasonic nozzle was found than with the 2-fluid nozzle under otherwise identical spray drying conditions. It is feasible that the ultrasonic nozzle when mounted in the lid of the spray dryer heats up toward the drying gas inlet temperature much more that the air-cooled 2-fluid nozzle. Calculation of the Arrhenius activation energy also showed how the stabilizing efficacy of trehalose and mannitol on the catalase varies in strength across the range of drying gas inlet and outlet temperatures examined. Copyright © 2015 Elsevier B.V. All rights reserved.

The laser-induced fluorescence spectroscopy of TiF in the ultraviolet region

NASA Astrophysics Data System (ADS)

Zhang, Zhaoxia; Guo, Jingru; Yu, Xufeng; Zhen, Junfeng; Chen, Yang

2009-02-01

The laser-induced fluorescence (LIF) spectrum of jet-cooled 48TiF has been obtained in the wavelength region of 245-270 nm for the first time. Six pairs of vibronic bands were observed and assigned to two new transitions [37.8] 4Φ-X 4Φ and 4Δ-X 4Φ. Rotational analysis was carried out for the ( ν' = 0-3 to ν″ = 0) vibrational bands of the [37.8] 4Φ 3/2-X 4Φ 3/2 and [37.8] 4Φ 5/2-X 4Φ 5/2 subbands, and also, the ( ν', 0) and ( ν'+1, 0) vibrational bands of the 4Δ 1/2-X 4Φ 3/2 and 4Δ 3/2-X 4Φ 5/2 subbands. The effective equilibrium molecular constants for the [37.8] 4Φ 3/2 and [37.8] 4Φ 3/2 upper states were determined. In addition, lifetime measurements were carried out for all of the observed bands under collision-free conditions. On the basis of the spectroscopic constants and lifetime measurements, the electronic transitions involved in the observed high-lying electronic states are discussed.

The effects of passive heating and head-cooling on perception of exercise in the heat.

PubMed

Simmons, Shona E; Mündel, Toby; Jones, David A

2008-09-01

The capacity to perform exercise is reduced in a hot environment when compared to cooler conditions. A limiting factor appears to be a higher core body temperature (T (core)) and it has been suggested that an elevated T (core) reduces the drive to exercise, this being reflected in higher ratings of perceived exertion (RPE). The purpose of the present study was to determine whether passive heating to increase T (core) would have a detrimental effect on RPE and thermal comfort during subsequent exercise in the heat and whether head-cooling during passive heating would attenuate these unpleasant sensations of an elevated T (core) during subsequent exercise in the heat. Nine physically-active, non-heat-acclimated volunteers [6 males, 3 females; age: 21 +/- 1 year, VO(2max) 50 +/- 9 ml kg(-1).min(-1), peak power output: 286 +/- 43 W (mean +/- SD)] performed two 12-minute constant-load cycling tests at 70% VO(2max) in a warm-dry environment (34 +/- 1 degrees C, relative humidity <30%) separated by a period of passive heating in a sauna (68 +/- 3 degrees C) to increase T (core). In one trial, subjects had their head and face cooled continually in the sauna (HC), the other trial was a control (CON). Passive heating increased T (core) by 1.22 +/- 0.03 degrees C in the CON and by 0.75 +/- 0.07 degrees C in the HC trial (P < 0.01). Passive heating increased weighted mean skin temperature (T (msk)) in both the CON and HC trials (P < 0.01), however, head-cooling lowered T (msk) during passive heating (P < 0.05). Exercise time following passive heating was reduced in both the CON and HC trials (P < 0.05). Passive heating increased RPE (P < 0.01), however, RPE was lower following passive heating with head-cooling (P < 0.05). There was a significant correlation between T (core) and RPE (r = 0.82, P < 0.001). In conclusion, our results suggest increased RPE during exercise in the heat is primarily due to the increase in T (core). Furthermore, head-cooling attenuates the rise in T (core) and the effect on RPE is proportional to the rise on T (core).

Cooled-Spool Piston Compressor

NASA Technical Reports Server (NTRS)

Morris, Brian G.

1994-01-01

Proposed cooled-spool piston compressor driven by hydraulic power and features internal cooling of piston by flowing hydraulic fluid to limit temperature of compressed gas. Provides sufficient cooling for higher compression ratios or reactive gases. Unlike conventional piston compressors, all parts of compressed gas lie at all times within relatively short distance of cooled surface so that gas cooled more effectively.

Hydrodynamic Models of Line-Driven Accretion Disk Winds III: Local Ionization Equilibrium

NASA Technical Reports Server (NTRS)

Pereyra, Nicolas Antonio; Kallman, Timothy R.; White, Nicholas E. (Technical Monitor)

2002-01-01

We present time-dependent numerical hydrodynamic models of line-driven accretion disk winds in cataclysmic variable systems and calculate wind mass-loss rates and terminal velocities. The models are 2.5-dimensional, include an energy balance condition with radiative heating and cooling processes, and includes local ionization equilibrium introducing time dependence and spatial dependence on the line radiation force parameters. The radiation field is assumed to originate in an optically thick accretion disk. Wind ion populations are calculated under the assumption that local ionization equilibrium is determined by photoionization and radiative recombination, similar to a photoionized nebula. We find a steady wind flowing from the accretion disk. Radiative heating tends to maintain the temperature in the higher density wind regions near the disk surface, rather than cooling adiabatically. For a disk luminosity L (sub disk) = solar luminosity, white dwarf mass M(sub wd) = 0.6 solar mass, and white dwarf radii R(sub wd) = 0.01 solar radius, we obtain a wind mass-loss rate of M(sub wind) = 4 x 10(exp -12) solar mass yr(exp -1) and a terminal velocity of approximately 3000 km per second. These results confirm the general velocity and density structures found in our earlier constant ionization equilibrium adiabatic CV wind models. Further we establish here 2.5D numerical models that can be extended to QSO/AGN winds where the local ionization equilibrium will play a crucial role in the overall dynamics.

Heat convection at the density maximum point of water

NASA Astrophysics Data System (ADS)

Balta, Nuri; Korganci, Nuri

2018-01-01

Water exhibits a maximum in density at normal pressure at around 4° degree temperature. This paper demonstrates that during cooling, at around 4 °C, the temperature remains constant for a while because of heat exchange associated with convective currents inside the water. Superficial approach implies it as a new anomaly of water, but actually it is not.

Identification of parameters through which surface chemistry determines the lifetimes of hot electrons in small Au nanoparticles

PubMed Central

Aruda, Kenneth O.; Tagliazucchi, Mario; Sweeney, Christina M.; Hannah, Daniel C.; Schatz, George C.; Weiss, Emily A.

2013-01-01

This paper describes measurements of the dynamics of hot electron cooling in photoexcited gold nanoparticles (Au NPs) with diameters of ∼3.5 nm, and passivated with either a hexadecylamine or hexadecanethiolate adlayer, using ultrafast transient absorption spectroscopy. Fits of these dynamics with temperature-dependent Mie theory reveal that both the electronic heat capacity and the electron–phonon coupling constant are larger for the thiolated NPs than for the aminated NPs, by 40% and 30%, respectively. Density functional theory calculations on ligand-functionalized Au slabs show that the increase in these quantities is due to an increased electronic density of states near the Fermi level upon ligand exchange from amines to thiolates. The lifetime of hot electrons, which have thermalized from the initial plasmon excitation, increases with increasing electronic heat capacity, but decreases with increasing electron–phonon coupling, so the effects of changing surface chemistry on these two quantities partially cancel to yield a hot electron lifetime of thiolated NPs that is only 20% longer than that of aminated NPs. This analysis also reveals that incorporation of a temperature-dependent electron–phonon coupling constant is necessary to adequately fit the dynamics of electron cooling. PMID:23440215

Evaporative cooling of air in an adiabatic channel with partially wetted zones

NASA Astrophysics Data System (ADS)

Terekhov, V. I.; Gorbachev, M. V.; Khafaji, H. Q.

2016-03-01

The paper deals with the numerical study of heat and mass transfer in the process of direct evaporation air cooling in the laminar flow of forced convection in a channel between two parallel insulated plates with alternating wet and dry zones along the length. The system of Navier-Stokes equations and equations of energy and steam diffusion are being solved in two-dimensional approximation. At the channel inlet, all thermal gas-dynamic parameters are constant over the cross section, and the channel walls are adiabatic. The studies were carried out with varying number of dry zones ( n = 0-16), their relative length ( s/l = 0-1) and Reynolds number Re = 50-1000 in the flow of dry air (φ0 = 0) with a constant temperature at the inlet (T 0 = 30 °C). The main attention is paid to optimization analysis of evaporation cell characteristics. It is shown that an increase in the number of alternating steps leads to an increase in the parameters of thermal and humid efficiency. With an increase in Re number and a decrease in the extent of wet areas, the efficiency parameter reduces.

Conformational and orientational order and disorder in solid polytetrafluoroethylene

NASA Astrophysics Data System (ADS)

Sprik, Michiel; Rothlisberger, Ursula; Klein, Michael L.

The low pressure phase diagram of solid polytetrafluoroethylene (PTFE/Teflon) has been investigated using constant temperature-constant pressure molecular dynamics techniques and a new all-atom potential model for fluorocarbons. The simulation was started in an ordered low temperature phase in which the molecules are parallel and have a helical conformation with a pitch of uniform magnitude and sign (chirality). In accordance with experiment, a transition to an orientationally disordered state is observed upon heating. The coherent helical winding of CF2 groups also disappears abruptly at the transition but short helical segments remain and become equally distributed between left and right chirality with increasing temperature. The orientational and conformational disorder is accompanied by translational diffusion along the chain direction. At a still higher temperature melting sets in. On cooling, the disordered solid phase is recovered and its structure is shown to be identical to that generated on heating. On further cooling, a spontaneous ordering transition is observed but the system fails to recover a uniform helical ground state. Instead, the high pressure ordered monoclinic all- trans (alkane-like) structure is obtained: an observation that indicates a deficiency in the potential model.

Time to Cooling Is Associated with Resuscitation Outcomes

PubMed Central

Janata, Andreas; Peacock, W. Frank; Deal, Nathan S.; Kalra, Sarathi; Sterz, Fritz

2016-01-01

Our purpose was to analyze evidence related to timing of cooling from studies of targeted temperature management (TTM) after return of spontaneous circulation (ROSC) after cardiac arrest and to recommend directions for future therapy optimization. We conducted a preliminary review of studies of both animals and patients treated with post-ROSC TTM and hypothesized that a more rapid cooling strategy in the absence of volume-adding cold infusions would provide improved outcomes in comparison with slower cooling. We defined rapid cooling as the achievement of 34°C within 3.5 hours of ROSC without the use of volume-adding cold infusions, with a ≥3.0°C/hour rate of cooling. Using the PubMed database and a previously published systematic review, we identified clinical studies published from 2002 through 2014 related to TTM. Analysis included studies with time from collapse to ROSC of 20–30 minutes, reporting of time from ROSC to target temperature and rate of patients in ventricular tachycardia or ventricular fibrillation, and hypothermia maintained for 20–24 hours. The use of cardiopulmonary bypass as a cooling method was an exclusion criterion for this analysis. We compared all rapid cooling studies with all slower cooling studies of ≥100 patients. Eleven studies were initially identified for analysis, comprising 4091 patients. Two additional studies totaling 609 patients were added based on availability of unpublished data, bringing the total to 13 studies of 4700 patients. Outcomes for patients, dichotomized into faster and slower cooling approaches, were determined using weighted linear regression using IBM SPSS Statistics software. Rapid cooling without volume-adding cold infusions yielded a higher rate of good neurological recovery than slower cooling methods. Attainment of a temperature below 34°C within 3.5 hours of ROSC and using a cooling rate of more than 3°C/hour appear to be beneficial. PMID:27906641

Concept Doped-Silicon Thermopile Detectors for Future Planetary Thermal Imaging Instruments

NASA Astrophysics Data System (ADS)

Lakew, Brook; Barrentine, Emily M.; Aslam, Shahid; Brown, Ari D.

2016-10-01

Presently, uncooled thermopiles are the detectors of choice for thermal mapping in the 4.6-100 μm spectral range. Although cooled detectors like Ge or Si thermistor bolometers, and MgB2 or YBCO superconducting bolometers, have much higher sensitivity, the required active or passive cooling mechanisms add prohibitive cost and mass for long duration missions. Other uncooled detectors, likepyroelectrics, require a motor mechanism to chop against a known reference temperature, which adds unnecessary mission risk. Uncooled vanadium oxide or amorphous Si microbolometer arrays with integrated CMOS readout circuits, not only have lower sensitivity, but also have not been proven to be radiation hard >100 krad (Si) total ionizing dose, and barring additional materials and readout development, their performance has reached a plateau.Uncooled and radiation hard thermopiles with D* ~1x109 cm√Hz/W and time constant τ ~100 ms have been integrated into thermal imaging instruments on several past missions and have extensive flight heritage (Mariner, Voyager, Cassini, LRO, MRO). Thermopile arrays are also on the MERTIS instrument payload on-board the soon to be launched BepiColombo Mission.To date, thermopiles used for spaceflight instrumentation have consisted of either hand assembled "one-off" single thermopile pixels or COTS thermopile pixel arrays both using Bi-Sb or Bi-Te thermoelectric materials. For future high performance imagers, thermal detector arrays with higher D*, lower τ, and high efficiency delineated absorbers are desirable. Existing COTS and other flight thermopile designs require highly specialized and nonstandard processing techniques to fabricate both the Bi-Sb or Bi-Te thermocouples and the gold or silver black absorbers, which put limitations on further development.Our detector arrays will have a D* ≥ 3x109 cm√Hz/W and a thermal time constant ≤ 30 ms at 170 K. They will be produced using proven, standard semiconductor and MEMS fabrication techniques, which will enable the future integration of other ancillary structures like high efficiency broadband absorbers, which will result in D* ≥ 5x109 cm√Hz/W.

A Unified Theory for the Great Plains Nocturnal Low-Level Jet

NASA Astrophysics Data System (ADS)

Shapiro, A.; Fedorovich, E.; Rahimi, S.

2014-12-01

The nocturnal low-level jet (LLJ) is a warm-season atmospheric boundary layer phenomenon common to the Great Plains of the United States and other places worldwide, typically in regions east of mountain ranges. Low-level jets develop around sunset in fair weather conditions conducive to strong radiational cooling, reach peak intensity in the pre-dawn hours, and then dissipate with the onset of daytime convective mixing. In this study we consider the LLJ as a diurnal oscillation of a stably stratified atmosphere overlying a planar slope on the rotating Earth. The oscillations arise from diurnal cycles in both the heating of the slope (mechanism proposed by Holton in 1967) and the turbulent mixing (mechanism proposed by Blackadar in 1957). The governing equations are the equations of motion, incompressibility condition, and thermal energy in the Boussinesq approximation, with turbulent heat and momentum exchange parameterized through spatially constant but diurnally varying turbulent diffusion coefficients (diffusivities). Analytical solutions are obtained for diffusivities with piecewise constant waveforms (step-changes at sunrise and sunset) and slope temperatures/buoyancies with piecewise linear waveforms (saw-tooth function with minimum at sunrise and maximum before sunset). The jet characteristics are governed by eleven parameters: slope angle, Coriolis parameter, environmental buoyancy frequency, geostrophic wind strength, daytime and nighttime diffusivities, maximum (daytime) and minimum (nighttime) slope buoyancies, duration of daylight, lag time between peak slope buoyancy and sunset, and a Newtonian cooling time scale. An exploration of the parameter space yields results that are broadly consistent with findings particular to the Holton and Blackadar theories, and agree with climatological observations, for example, that stronger jets tend to occur over slopes of 0.15-0.25 degrees characteristic of the Great Plains. The solutions also yield intriguing predictions that peak jet strength increases with attenuation of the minimum surface buoyancy, and that the single most important parameter determining jet height is the nighttime diffusivity, with weaker nightime diffusion associated with smaller jet heights. These and other highlights will be discussed in the presentation.

Current Pulses Momentarily Enhance Thermoelectric Cooling

NASA Technical Reports Server (NTRS)

Snyder, G. Jeffrey; Fleurial, Jean-Pierre; Caillat, Thierry; Chen, Gang; Yang, Rong Gui

2004-01-01

The rates of cooling afforded by thermoelectric (Peltier) devices can be increased for short times by applying pulses of electric current greater than the currents that yield maximum steady-state cooling. It has been proposed to utilize such momentary enhancements of cooling in applications in which diode lasers and other semiconductor devices are required to operate for times of the order of milliseconds at temperatures too low to be easily obtainable in the steady state. In a typical contemplated application, a semiconductor device would be in contact with the final (coldest) somewhat taller stage of a multistage thermoelectric cooler. Steady current would be applied to the stages to produce steady cooling. Pulsed current would then be applied, enhancing the cooling of the top stage momentarily. The principles of operation are straightforward: In a thermoelectric device, the cooling occurs only at a junction at one end of the thermoelectric legs, at a rate proportional to the applied current. However, Joule heating occurs throughout the device at a rate proportional to the current squared. Hence, in the steady state, the steady temperature difference that the device can sustain increases with current only to the point beyond which the Joule heating dominates. If a pulse of current greater than the optimum current (the current for maximum steady cooling) is applied, then the junction becomes momentarily cooled below its lowest steady temperature until thermal conduction brings the resulting pulse of Joule heat to the junction and thereby heats the junction above its lowest steady temperature. A theoretical and experimental study of such transient thermoelectric cooling followed by transient Joule heating in response to current pulses has been performed. The figure presents results from one of the experiments. The study established the essential parameters that characterize the pulse cooling effect, including the minimum temperature achieved, the maximum temperature overshoot, the time to reach minimum temperature, the time while cooled, and the time between pulses. It was found that at large pulse amplitude, the amount of pulse supercooling is about a fourth of the maximum steady-state temperature difference. For the particular thermoelectric device used in one set of the experiments, the practical optimum pulse amplitude was found to be about 3 times the optimum steady-state current. In a further experiment, a pulse cooler was integrated into a small commercial thermoelectric threestage cooler and found to provide several degrees of additional cooling for a time long enough to operate a semiconductor laser in a gas sensor.

Optical cryocooling of diamond

NASA Astrophysics Data System (ADS)

Kern, M.; Jeske, J.; Lau, D. W. M.; Greentree, A. D.; Jelezko, F.; Twamley, J.

2017-06-01

The cooling of solids by optical means only using anti-Stokes emission has a long history of research and achievements. Such cooling methods have many advantages ranging from no moving parts or fluids through to operation in vacuum and may have applications to cryosurgery. However, achieving large optical cryocooling powers has been difficult to manage except in certain rare-earth crystals but these are mostly toxic and not biocompatible. Through study of the emission and absorption cross sections we find that diamond, containing either nitrogen vacancy (NV) or silicon vacancy defects, shows potential for optical cryocooling and, in particular, NV doping shows promise for optical refrigeration. We study the optical cooling of doped diamond microcrystals ranging 10-250 μ m in diameter trapped either in vacuum or in water. For the vacuum case we find NV-doped microdiamond optical cooling below room temperature could exceed |Δ T |>10 K for irradiation powers of Pin<100 mW. We predict that such temperature changes should be easily observed via large alterations in the diffusion constant for optically cryocooled microdiamonds trapped in water in an optical tweezer or via spectroscopic signatures such as the zero-phonon line width or Raman line.

Potential for luminosity improvement for low-energy RHIC operation with long bunches

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

Fedotov, A.; Blaskiewicz, M.

Electron cooling was proposed to increase luminosity of the RHIC collider for heavy ion beams at low energies. Luminosity decreases as the square of bunch intensity due to the beam loss from the RF bucket as a result of the longitudinal intra beam scattering (IBS), as well as due to the transverse emittance growth because of the transverse IBS. Both transverse and longitudinal IBS can be counteracted with electron cooling. This would allow one to keep the initial peak luminosity close to constant throughout the store essentially without the beam loss. In addition, the phase-space density of the hadron beamsmore » can be further increased by providing stronger electron cooling. Unfortunately, the defining limitation for low energies in RHIC is expected to be the space charge. Here we explore an idea of additional improvement in luminosity, on top of the one coming from just IBS compensation and longer stores, which may be expected if one can operate with longer bunches at the space-charge limit in a collider. This approach together with electron cooling may result in about 10-fold improvement in total luminosity for low-energy RHIC program.« less

Effectiveness of a night radiative cooling system in different geographical latitudes

NASA Astrophysics Data System (ADS)

Tsoy, A. P.; Granovskiy, A. S.; Baranenko, A. V.; Tsoy, D. A.

2017-08-01

Growth of world energy consumption and depletion of energy resources make humanity to constantly work on the creation of the energy efficient technologies and increase usage of the alternative and renewable sources of energy. One of such alternative sources of energy is the night radiative cooling (NRC). NRC is an alternative and renewable source of energy, derived from the effective radiation of the Earth into the Space. If the given surface is located so that it looks to the night sky, then under the particular condition more energy can be generated under the effect of radiative cooling, than received from the atmosphere. As a result the temperature of the surface can be kept lower than the temperature of the ambient air. This effect can be used for creation of the refrigeration systems with the low energy consumption and as a result lower negative influence on the environment. During the research it has been identified that the possibility of the NRC usage is mostly predetermined by the specifics of the climate of the each region. In particular climate conditions the refrigeration systems working on night radiative cooling will be more effective that in others.

Effect of field cooling heights on the levitation force of pure and starch/polystyrene/MWCNT added bulk MgB2 superconductors

NASA Astrophysics Data System (ADS)

Tripathi, D.; Dey, T. K.

2014-12-01

A series of MgB2 pellets with and without addition of carbon from different sources (viz. starch, polystyrene and carbon nanotubes) have been synthesized by solid state reaction under argon atmosphere. XRD analysis indicates a decrease in lattice parameters of MgB2 with addition of starch, polystyrene (PS) and MWCNT and confirms substitution of carbon in boron sites. The presence of nanosized carbon inclusions between the grain boundaries in the present set of samples is evident in TEM photographs. Resistivity data confirms a decrease in superconducting transition temperature (Tc0) for MgB2 doped with starch/PS/MWCNT. The effect of different field cooling heights (HIFC) at 20 K on maximum levitation force (FMLF) and maximum attractive force (FMAF) of pure MgB2 and MgB2 doped with starch/PS/MWCNT have been investigated. Except for MWCNT, doping of starch and PS in MgB2 is found to improve FMLF and FMAF and the best result is obtained for MgB2 doped with 1 wt.% PS. Levitation force measured as a function of decreasing initial field cooling height indicates exponential dependence of both maximum levitation force (FMLF) and maximum attractive force (FMAF). However, the gap distance between PM and the sample (H0AF and HMAF) corresponding to maximum attractive force (FMAF) and zero attractive force (F0AF) varies linearly and their difference remains constant. This constancy in (HMAF - H0AF) is understood in terms of constant reduction rate of magnetic flux density between H0AF and HMAF.

Studies of the water adsorption on Lampung’s natural zeolite of Indonesia for cooling application

NASA Astrophysics Data System (ADS)

Wulandari, D. A.; Nasruddin; Lemington

2018-03-01

Part of minerals that originally formed from volcanic rock and ash layers reacting further with alkaline groundwater is called natural zeolite, where its sources are not always available in all countries. Indonesia is located in the ring of fire which have a huge sources of zeolite, one of the area is Lampung, South Sumatra. Natural zeolite has been considered as one of potential heat adsorbent medium which can contribute to the energy consumption and reduce air pollution in the using of cooling application. The characteristic of this Lampung natural zeolite such as adsorption kinetics, adsorption water uptake, and adsorption capacity were test with ASAP 2020 system. Sorption kinetics by this experiment of zeolite samples were carried out in a constant temperature and humidity chamber. The chamber can supply constant air condition with deviations of ±0.5 °C for temperature and ±3% for relative humidity. The data based on rate of adsorption and the defined working condition was set as 20°C and 70% RH. Pore volume is a significant parameter for determining the limitation of water uptake, which can describe the saturated condition of zeolite. Sorption isotherm models used to describe sorption phenomena are commonly deduced from the Polanyi potential theory were investigated. The water adsorption quantity increased with the increase of relative pressure. To sum up, this pure zeolite has a less heat and mass transfer performance so its need to be activated before using in cooling application to get their great potential and by being coated in a desiccant heat exchanger systems.

Can Structural Optimization Explain Slow Dynamics of Rocks?

NASA Astrophysics Data System (ADS)

Kim, H.; Vistisen, O.; Tencate, J. A.

2009-12-01

Slow dynamics is a recovery process that describes the return to an equilibrium state after some external energy input is applied and then removed. Experimental studies on many rocks have shown that a modest acoustic energy input results in slow dynamics. The recovery process of the stiffness has consistently been found to be linear to log(time) for a wide range of geomaterials and the time constants appear to be unique to the material [TenCate JA, Shankland TJ (1996), Geophys Res Lett 23, 3019-3022]. Measurements of this nonequilibrium effect in rocks (e.g. sandstones and limestones) have been linked directly to the cement holding the individual grains together [Darling TW, TenCate JA, Brown DW, Clausen B, Vogel SC (2004), Geophys Res Lett 31, L16604], also suggesting a potential link to porosity and permeability. Noting that slow dynamics consistently returns the overall stiffness of rocks to its maximum (original) state, it is hypothesized that the original state represents the global minimum strain energy state. Consequently the slow dynamics process represents the global minimization or optimization process. Structural optimization, which has been developed for engineering design, minimises the total strain energy by rearranging the material distribution [Kim H, Querin OM, Steven GP, Xie YM (2002), Struct Multidiscip Optim 24, 441-448]. The optimization process effectively rearranges the way the material is cemented. One of the established global optimization methods is simulated annealing (SA). Derived from cooling of metal to a thermal equilibrium, SA finds an optimum solution by iteratively moving the system towards the minimum energy state with a probability of 'uphill' moves. It has been established that the global optimum can be guaranteed by applying a log(time) linear cooling schedule [Hajek B (1988, Math Ops Res, 15, 311-329]. This work presents the original study of applying SA to the maximum stiffness optimization problem. Preliminary results indicate that the maximum stiffness solutions are achieved when using log(time) linear cooling schedule. The optimization history reveals that the overall stiffness of the structure is increased linearly to log(time). The results closely resemble the slow dynamics stiffness recovery of geomaterials and support the hypothesis that the slow dynamics is an optimization process for strain energy. [Work supported by the Department of Energy through the LANL/LDRD Program].

High resolution in-line analyses of precipitation at two UK ground locations, and possible relevance to convective cooling at cloud level.

NASA Astrophysics Data System (ADS)

Durham, Brian

2015-04-01

Wet deposition of many molecular pollutants can be simulated `sufficiently well' by a simple meteorological model, including the poorly soluble ozone (Tost et al, 2007, 2754). Carbon dioxide (CO2) has a Henry constant similar to that of ozone, but perhaps because its boundary layer presence is three orders of magnitude greater than ozone it has been widely assumed to be immune to significant cleansing by scavenging and deposition. In 2009 this `elephant' was approached (cautiously!) at the first of two UK locations using high time-resolution analyses of delivered rainwater, and some initial observations seem relevant to the `organised convection' theme of the present session. Six variables are measured every second, averaged every 60 seconds, including: conductivity; acidity ([H3O+] = 10 ^-pH ) and; stripped CO2 (by NDIRS). Convective precipitation typically delivers significantly more CO2 than predicted from Henry's Law, is supersaturated on arrival and shows a characteristic `spiky' profile against time. In assessing the above, this paper revisits eighty years of measurements of the Henry's Law equilibrium for the CO2/water system at partial pressures less than 1 atmosphere, and (more recently) low-pressure solubility at temperatures down to 4°C (Carroll, Slupski and Mather, 1991, 1203; Faraday Discuss. 2013, 167, 462-3). The observed solute load and supersaturation would become plausible if the reported upturn in solubility between 20°C and 4°C continued into the super-cooled zone. In a cloud, super-cooling will arise under convection when condensing droplets are chilled by adiabatic expansion of the carrier air. Droplets will increase in molar volume by up to 2.5% at -34°C (the temperature of spontaneous ice nucleation, Hare and Sorensen, 1987), offering a physical framework for the observed characteristics, and the possibility that `spikiness' reflects the degree of organisation of convection.

Development of a Split Bitter-type Magnet System for Dusty Plasma Experiments

NASA Astrophysics Data System (ADS)

Bates, Evan; Romero-Talamas, Carlos A.; Birmingham, William J.; Rivera, William F.

2014-10-01

A 10 Tesla Bitter-type magnetic system is under development at the Dusty Plasma Laboratory of the University of Maryland, Baltimore County (UMBC). We present here an optimization technique that uses differential evolution to minimize the omhic heating produced by the coils, while constraining the magnetic field in the experimental volume. The code gives us the optimal dimensions for the coil system including: coil length, turn thickness, disks radii, resistance, and total current required for a constant magnetic field. Finite element parametric optimization is then used to establish the optimal design for water cooling holes. Placement of the cooling holes will also take into consideration the magnetic forces acting on the copper alloy disks to ensure the material strength is not compromised during operation. The proposed power and cooling water delivery subsystems for the coils are also presented. Upon completion and testing of the magnet system, planned experiments include the propagation of magnetized waves in dusty plasma crystals under various boundary conditions, and viscosity in rotational shear flow, among others.

An Experimental Investigation of Wall-Cooling Effects on Hypersonic Boundary-Layer Stability in a Quiet Wind Tunnel

NASA Technical Reports Server (NTRS)

Blanchard, Alan E.; Selby, Gregory V.

1996-01-01

One of the primary reasons for developing quiet tunnels is for the investigation of high-speed boundary-layer stability and transition phenomena without the transition-promoting effects of acoustic radiation from tunnel walls. In this experiment, a flared-cone model under adiabatic- and cooled-wall conditions was placed in a calibrated, 'quiet' Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same 'N=10' criterion used to predict boundary-layer transition in subsonic, transonic, and supersonic flows was found to be applicable for the hypersonic flow regime as well. Under cooled-wall conditions, a unique set of continuous spectra data was acquired that documents the linear, nonlinear, and breakdown regions associated with the transition of hypersonic flow under low-noise conditions.

Performance analysis on a large scale borehole ground source heat pump in Tianjin cultural centre

NASA Astrophysics Data System (ADS)

Yin, Baoquan; Wu, Xiaoting

2018-02-01

In this paper, the temperature distribution of the geothermal field for the vertical borehole ground-coupled heat pump was tested and analysed. Besides the borehole ground-coupled heat pump, the system composed of the ice storage, heat supply network and cooling tower. According to the operation data for nearly three years, the temperature constant zone is in the ground depth of 40m -120m with a temperature gradient of about 3.0°C/100m. The temperature of the soil dropped significantly in the heating season, increased significantly in the cooling season, and reinstated in the transitional season. With the energy balance design of the heating and cooling and the existence of the soil thermal inertia, the soil temperature stayed in a relative stable range and the ground source heat pump system was operated with a relative high efficiency. The geothermal source heat pump was shown to be applicable for large scale utilization.

Ecological and Toxicological Characteristics of Metalworking Fluids Used in Finishing Processing in Russian Federation

NASA Astrophysics Data System (ADS)

Grigoriev, S. N.; Bobrovskij, N. M.; Melnikov, P. A.; Bobrovskij, I. N.; Levitskih, O. O.

2017-05-01

Nowadays, metalworking fluids (MWF) in the design of technological processes in most cases are considered as mandatory persistant components despite the constant improvement of the technology of machining, tools and equipment. Three main functions of MWF: cooling, lubrication, waste chips removal - seems to be the essential condition for stable process. In most cases, cooling reduces wear of tool and improves the quality of the processed surface. The cooling characteristics of the MWF affect not only the heat capacity and thermal conductivity, but metal surfaces wettability and vaporization. If processing speed and temperature of the fluid are high then it may not be in direct contact with the surface of the tool due to low wettability or vapor blankets. Improvement of machining process with applying the MWF is accompanied with negative factors. Due to the high temperatures in the treatment area it is exposed to MWF vaporization. This article presents estimation of the applicable in Russian Federation MWF: fire risk, toxicological and environmental hazards.

Deterministic optical polarisation in nitride quantum dots at thermoelectrically cooled temperatures.

PubMed

Wang, Tong; Puchtler, Tim J; Patra, Saroj K; Zhu, Tongtong; Jarman, John C; Oliver, Rachel A; Schulz, Stefan; Taylor, Robert A

2017-09-21

We report the successful realisation of intrinsic optical polarisation control by growth, in solid-state quantum dots in the thermoelectrically cooled temperature regime (≥200 K), using a non-polar InGaN system. With statistically significant experimental data from cryogenic to high temperatures, we show that the average polarisation degree of such a system remains constant at around 0.90, below 100 K, and decreases very slowly at higher temperatures until reaching 0.77 at 200 K, with an unchanged polarisation axis determined by the material crystallography. A combination of Fermi-Dirac statistics and k·p theory with consideration of quantum dot anisotropy allows us to elucidate the origin of the robust, almost temperature-insensitive polarisation properties of this system from a fundamental perspective, producing results in very good agreement with the experimental findings. This work demonstrates that optical polarisation control can be achieved in solid-state quantum dots at thermoelectrically cooled temperatures, thereby opening the possibility of polarisation-based quantum dot applications in on-chip conditions.

An Experimental Study of the Effect of Wake Passing on Turbine Blade Film Cooling

NASA Technical Reports Server (NTRS)

Heidmann, James D.; Lucci, Barbara L.; Reshotko, Eli

1997-01-01

The effect of wake passing on the showerhead film cooling performance of a turbine blade has been investigated experimentally. The experiments were performed in an annular turbine cascade with an upstream rotating row of cylindrical rods. Nickel thin-film gauges were used to determine local film effectiveness and Nusselt number values for various injectants, blowing ratios, and Strouhal numbers. Results indicated a reduction in film effectiveness with increasing Strouhal number, as well as the expected increase in film effectiveness with blowing ratio. An equation was developed to correlate the span-average film effectiveness data. The primary effect of wake unsteadiness was found to be correlated by a streamwise-constant decrement of 0.094.St. Steady computations were found to be in excellent agreement with experimental Nusselt numbers, but to overpredict experimental film effectiveness values. This is likely due to the inability to match actual hole exit velocity profiles and the absence of a credible turbulence model for film cooling.

The Effect of Wake Passing on Turbine Blade Film Cooling

NASA Technical Reports Server (NTRS)

Heidmann, James David

1996-01-01

The effect of upstream blade row wake passing on the showerhead film cooling performance of a downstream turbine blade has been investigated through a combination of experimental and computational studies. The experiments were performed in a steady-flow annular turbine cascade facility equipped with an upstream rotating row of cylindrical rods to produce a periodic wake field similar to that found in an actual turbine. Spanwise, chordwise, and temporal resolution of the blade surface temperature were achieved through the use of an array of nickel thin-film surface gauges covering one unit cell of showerhead film hole pattern. Film effectiveness and Nusselt number values were determined for a test matrix of various injectants, injectant blowing ratios, and wake Strouhal numbers. Results indicated a demonstratable reduction in film effectiveness with increasing Strouhal number, as well as the expected increase in film effectiveness with blowing ratio. An equation was developed to correlate the span-average film effectiveness data. The primary effect of wake unsteadiness was found to be correlated well by a chordwise-constant decrement of 0.094-St. Measurable spanwise film effectiveness variations were found near the showerhead region, but meaningful unsteady variations and downstream spanwise variations were not found. Nusselt numbers were less sensitive to wake and injection changes. Computations were performed using a three-dimensional turbulent Navier-Stokes code which was modified to model wake passing and film cooling. Unsteady computations were found to agree well with steady computations provided the proper time-average blowing ratio and pressure/suction surface flow split are matched. The remaining differences were isolated to be due to the enhanced mixing in the unsteady solution caused by the wake sweeping normally on the pressure surface. Steady computations were found to be in excellent agreement with experimental Nusselt numbers, but to overpredict experimental film effectiveness values. This is likely due to the inability to match actual hole exit velocity profiles and the absence of a credible turbulence model for film cooling.

The effects of face cooling during hyperthermic exercise in man: evidence for an integrated thermal, neuroendocrine and behavioural response.

PubMed

Mündel, Toby; Bunn, Sabrina J; Hooper, Paula L; Jones, David A

2007-01-01

The present study investigated whether face cooling reduced both the perceived exertion (RPE) and prolactin (PRL) release during hyperthermic exercise. Ten, non-heat-acclimated males (23 +/- 2 years; maximal oxygen consumption, 56 +/- 7 ml kg(-1) min(-1) [mean +/- s.d.]) exercised for 40 min on a cycle ergometer at 65% of their peak aerobic power, at an ambient temperature of 33 degrees C (27% relative humidity) with (FC) and without face cooling as a control (CON). With FC, forehead temperature was maintained approximately 6 degrees C lower than CON, while other skin sites were similar or slightly warmer in the FC condition. Rectal temperature increased by approximately 1.5 degrees C with the same time course in both conditions. A relative bradycardia was observed during FC, with heart rate approximately 5 beats min(-1) lower than CON (P < 0.05). Mean plasma lactate was lower during FC (FC, 5.0 +/- 0.3 mmol l(-1); CON, 5.9 +/- 0.3 mmol l(-1); P < 0.05) but no differences were observed for plasma glucose, which remained constant during exercise. Levels of PRL were maintained at 175 +/- 17 mIU l(-1) during exercise for FC, while values for CON increased to a peak of 373 +/- 22 mIU l(-1) so that towards the end of the exercise, for the same rectal temperature, PRL was significantly lower in the FC condition (P < 0.05). Global and breathing RPE were reduced but only towards the end of the 40 min of exercise during FC, whilst subjective thermal comfort was significantly lower during FC (P < 0.05). We confirm the substantial effect that FC has on the secretion of PRL during hyperthermic exercise but show that it makes a relatively small contribution to the perception of effort when compared to the effect of a cool total skin area as occurs with exercise in a thermoneutral environment.

Thermal Scanning Conductometry (TSC) as a General Method for Studying and Controlling the Phase Behavior of Conductive Physical Gels.

PubMed

Bielejewski, Michal

2018-01-23

The thermal scanning conductometry protocol is a new approach in studying ionic gels based on low molecular weight gelators. The method is designed to follow the dynamically changing state of the ionogels, and to deliver more information and details about the subtle change of conductive properties with an increase or decrease in the temperature. Moreover, the method allows the performance of long term (i.e. days, weeks) measurements at a constant temperature to investigate the stability and durability of the system and the aging effects. The main advantage of the TSC method over classical conductometry is the ability to perform measurements during the gelation process, which was impossible with the classical method due to temperature stabilization, which usually takes a long time before the individual measurement. It is a well-known fact that to obtain the physical gel phase, the cooling stage must be fast; moreover, depending on the cooling rate, different microstructures can be achieved. The TSC method can be performed with any cooling/heating rate that can be assured by the external temperature system. In our case, we can achieve linear temperature change rates between 0.1 and approximately 10 °C/min. The thermal scanning conductometry is designed to work in cycles, continuously changing between heating and cooling stages. Such an approach allows study of the reproducibility of the thermally reversible gel-sol phase transition. Moreover, it allows the performance of different experimental protocols on the same sample, which can be refreshed to initial state (if necessary) without removal from the measuring cell. Therefore, the measurements can be performed faster, in a more efficient way, and with much higher reproducibility and accuracy. Additionally, the TSC method can be also used as a tool to manufacture the ionogels with targeted properties, like microstructure, with an instant characterization of conductive properties.

Heating and Cooling of Coronal Loops with Turbulent Suppression of Parallel Heat Conduction.

PubMed

Bian, Nicolas; Emslie, A Gordon; Horne, Duncan; Kontar, Eduard P

2018-01-10

Using the "enthalpy-based thermal evolution of loops" (EBTEL) model, we investigate the hydrodynamics of the plasma in a flaring coronal loop in which heat conduction is limited by turbulent scattering of the electrons that transport the thermal heat flux. The EBTEL equations are solved analytically in each of the two (conduction-dominated and radiation-dominated) cooling phases. Comparison of the results with typical observed cooling times in solar flares shows that the turbulent mean free path λ T lies in a range corresponding to a regime in which classical (collision-dominated) conduction plays at most a limited role. We also consider the magnitude and duration of the heat input that is necessary to account for the enhanced values of temperature and density at the beginning of the cooling phase and for the observed cooling times. We find through numerical modeling that in order to produce a peak temperature ≃1.5 × 10 7 K and a 200 s cooling time consistent with observations, the flare-heating profile must extend over a significant period of time; in particular, its lingering role must be taken into consideration in any description of the cooling phase. Comparison with observationally inferred values of post-flare loop temperatures, densities, and cooling times thus leads to useful constraints on both the magnitude and duration of the magnetic energy release in the loop, as well as on the value of the turbulent mean free path λ T .

Passive cooling during transport of asphyxiated term newborns

PubMed Central

O’Reilly, Deirdre; Labrecque, Michelle; O’Melia, Michael; Bacic, Janine; Hansen, Anne; Soul, Janet S

2014-01-01

Objective To evaluate the efficacy and safety of passive cooling during transport of asphyxiated newborns. Study Design Retrospective medical record review of newborns with perinatal asphyxia transported for hypothermia between July 2007 and June 2010. Results Forty-three newborns were transported, 27 of whom were passively cooled. Twenty (74%) passively cooled newborns arrived with axillary temperature between 32.5 and 34.5 °C. One newborn (4%) arrived with a subtherapeutic temperature, and 6 (22%) had temperatures >34.5 °C. Time from birth to hypothermia was significantly shorter among passively cooled newborns compared with newborns not cooled (215 vs. 327 minutes, p<0.01), even though time from birth to arrival was similar (252 vs. 259 minutes, p=0.77). There were no significant adverse events related to passive cooling. Conclusions Exclusive passive cooling for hypoxic-ischemic encephalopathy results in significantly earlier achievement of effective therapeutic hypothermia without significant adverse events. PMID:23154670

Relationships between molecular structure and kinetic and thermodynamic controls in lipid systems. Part III. Crystallization and phase behavior of 1-palmitoyl-2,3-stearoyl-sn-glycerol (PSS) and tristearoylglycerol (SSS) binary system.

PubMed

Bouzidi, Laziz; Narine, Suresh S

2012-01-01

The phase behavior of 1-palmitoyl-2,3-distearoyl-sn-glycerol (PSS)/tristearoylglycerol (SSS) binary system was investigated in terms of polymorphism, crystallization and melting behavior, microstructure and solid fat content (SFC) using widely different constant cooling rates. Kinetic phase diagrams were experimentally determined from the DSC heating thermograms and analyzed using a thermodynamic model to account for non-ideality of mixing. The kinetic phase diagram presented a typical eutectic behavior with a eutectic point at the 0.5(PSS) mixture with a probable precipitation line from 0.5(PSS) to 1.0(PSS), regardless of the rate at which the sample was cooled. The eutectic temperature decreased only slightly with increasing cooling rate. PSS has a strong effect on the physical properties of the PSS-SSS mixtures. In fact, the overall phase behavior of the PSS-SSS binary system was determined, for a very large part, by the asymmetrical TAG. Moreover, PSS is a key driver of the high stability observed in crystal growth, polymorphism and phase development. Levels as low as 10% PSS, when cooled slowly, and 30% when cooled rapidly, were found to be sufficient to suppress the effect of thermal processing. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Effect of Water-Alcohol Injection and Maximum Economy Spark Advance on Knock-Limited Performance and Fuel Economy of a Large Air-Cooled Cylinder

NASA Technical Reports Server (NTRS)

Heinicke, Orville H.; Vandeman, Jack E.

1945-01-01

An investigation was conducted to determine the effect of a coolant solution of 25 percent ethyl alcohol, 25 percent methyl alcohol, and 50 percent water by volume and maximum-economy spark advance on knock-limited performance and fuel economy of a large air-cooled cylinder. The knock-limited performance of the cylinder at engine speeds of 2100 and 2500 rpm was determined for coolant-fuel ratios of 0.0, 0.2, and 0.4. The effect of water-alcohol injection on fuel economy was determined in constant charge-air flow tests. The tests were conducted at a spark advance of 20 deg B.T.C. and maximum-economy spark advance.

Jet-cooled infrared absorption spectrum of the v4 fundamental band of HCOOH and HCOOD

NASA Astrophysics Data System (ADS)

Luo, Wei; Zhang, Yulan; Li, Wenguang; Duan, Chuanxi

2017-04-01

The jet-cooled absorption spectrum of the v4 fundamental band of normal formic acid (HCOOH) and deuterated formic acid (HCOOD) was recorded in the frequency range of 1370-1392 cm-1 with distributed-feedback quantum cascade lasers (DFB-QCLs) as the tunable infrared radiations. A segmented rapid-scan data acquisition scheme was developed for pulsed supersonic jet infrared laser absorption spectroscopy based on DFB-QCLs with a moderate vacuum pumping capacity. The unperturbed band-origin and rotational constants in the excited vibrational state were determined for both HCOOH and HCOOD. The unperturbed band-origin locates at 1379.05447(11) cm-1 for HCOOH, and 1366.48430(39) cm-1 for HCOOD, respectively.

Method of Minimizing Size of Heat Rejection Systems for Thermoelectric Coolers to Cool Detectors in Space

NASA Technical Reports Server (NTRS)

Choi, Michael K.

2014-01-01

A thermal design concept of attaching the thermoelectric cooler (TEC) hot side directly to the radiator and maximizing the number of TECs to cool multiple detectors in space is presented. It minimizes the temperature drop between the TECs and radiator. An ethane constant conductance heat pipe transfers heat from the detectors to a TEC cold plate which the cold side of the TECs is attached to. This thermal design concept minimizes the size of TEC heat rejection systems. Hence it reduces the problem of accommodating the radiator within a required envelope. It also reduces the mass of the TEC heat rejection system. Thermal testing of a demonstration unit in vacuum verified the thermal performance of the thermal design concept.

Renesting by American woodcocks (Scolopax minor) in Maine

USGS Publications Warehouse

McAuley, D.G.; Longcore, J.R.; Sepik, G.F.

1990-01-01

The American Woodcock (Scolopax minor) is one of the earliest ground-nesting birds in the northeastern United States. In Maine, nesting begins in early April when temperatures can drop below freezing and significant snowfall can accumulate. Nests are usually in open woods, where eggs are laid on the ground in a shallow depression (Pettingill 1936, Mendall and Aldous 1943, Sheldon 1967). Peak hatching occurs in early May (Dwyer et al. 1982), when temperatures are cool and precipitation is common. Woodcock chicks are dependent on the female for most of their food for at least seven days after hatching (Gregg 1984). During cool, wet weather, chicks require constant brooding by females; prolonged periods of inclement weather may lead to substantial mortality of chicks (Dwyer et al. 1988).

Beyond Newton's law of cooling - estimation of time since death

NASA Astrophysics Data System (ADS)

Leinbach, Carl

2011-09-01

The estimate of the time since death and, thus, the time of death is strictly that, an estimate. However, the time of death can be an important piece of information in some coroner's cases, especially those that involve criminal or insurance investigations. It has been known almost from the beginning of time that bodies cool after the internal mechanisms such as circulation of the blood stop. A first attempt to link this phenomenon to the determination of the time of death used a crude linear relationship. Towards the end of the nineteenth century, Newton's law of cooling using body temperature data obtained by the coroner was used to make a more accurate estimate. While based on scientific principles and resulting in a better estimate, Newton's law does not really describe the cooling of a non-homogeneous human body. This article will discuss a more accurate model of the cooling process based on the theoretical work of Marshall and Hoare and the laboratory-based statistical work of Claus Henssge. Using DERIVE®6.10 and the statistical work of Henssge, the double exponential cooling formula developed by Marshall and Hoare will be explored. The end result is a tool that can be used in the field by coroner's scene investigators to determine a 95% confidence interval for the time since death and, thus, the time of death.

Sideband cooling of micromechanical motion to the quantum ground state.

PubMed

Teufel, J D; Donner, T; Li, Dale; Harlow, J W; Allman, M S; Cicak, K; Sirois, A J; Whittaker, J D; Lehnert, K W; Simmonds, R W

2011-07-06

The advent of laser cooling techniques revolutionized the study of many atomic-scale systems, fuelling progress towards quantum computing with trapped ions and generating new states of matter with Bose-Einstein condensates. Analogous cooling techniques can provide a general and flexible method of preparing macroscopic objects in their motional ground state. Cavity optomechanical or electromechanical systems achieve sideband cooling through the strong interaction between light and motion. However, entering the quantum regime--in which a system has less than a single quantum of motion--has been difficult because sideband cooling has not sufficiently overwhelmed the coupling of low-frequency mechanical systems to their hot environments. Here we demonstrate sideband cooling of an approximately 10-MHz micromechanical oscillator to the quantum ground state. This achievement required a large electromechanical interaction, which was obtained by embedding a micromechanical membrane into a superconducting microwave resonant circuit. To verify the cooling of the membrane motion to a phonon occupation of 0.34 ± 0.05 phonons, we perform a near-Heisenberg-limited position measurement within (5.1 ± 0.4)h/2π, where h is Planck's constant. Furthermore, our device exhibits strong coupling, allowing coherent exchange of microwave photons and mechanical phonons. Simultaneously achieving strong coupling, ground state preparation and efficient measurement sets the stage for rapid advances in the control and detection of non-classical states of motion, possibly even testing quantum theory itself in the unexplored region of larger size and mass. Because mechanical oscillators can couple to light of any frequency, they could also serve as a unique intermediary for transferring quantum information between microwave and optical domains.

The Interplanetary Transport Effects on the Fe/O Ratio of Large Solar Energetic Particle Events

NASA Astrophysics Data System (ADS)

Qin, G.; Wang, Y.

2016-12-01

Mason and coauthors in 2006 invested the intensities of O and Fe in large western solar energetic particle (SEP) events observed by ACE spacecraft. It was found that the Fe/O ratio decreases with time at the same kinetic energy per nucleon during the rising phase of time-intensity profile, and the Fe/O ratio gradually becomes a constant during the decay phase of intensity. However, if the O intensity is compared at a higher kinetic energy with the Fe intensity, the behaviors of intensity profiles of O and Fe are similar. So they concluded that for such kind of events the injection profiles of Fe and O are similar near the Sun, and that scattering effects dominates. With numerical simulations, we find that in order to get such kind of SEPs behavior, Fe and O have to have similar injection profiles near the Sun, and similar diffusion and adiabatic cooling processes in the interplanetary space.

Fast, high sensitivity dewpoint hygrometer

NASA Technical Reports Server (NTRS)

Hoenk, Michael E. (Inventor)

1998-01-01

A dewpoint/frostpoint hygrometer that uses a surface moisture-sensitive sensor as part of an RF oscillator circuit with feedback control of the sensor temperature to maintain equilibrium at the sensor surface between ambient water vapor and condensed water/ice. The invention is preferably implemented using a surface acoustic wave (SAW) device in an RF oscillator circuit configured to generate a condensation-dependent output signal, a temperature sensor to measure the temperature of the SAW device and to distinguish between condensation-dependent and temperature-dependent signals, a temperature regulating device to control the temperature of the SAW device, and a feedback control system configured to keep the condensation-dependent signal nearly constant over time in the presence of time-varying humidity, corrected for temperature. The effect of this response is to heat or cool the surface moisture-sensitive device, which shifts the equilibrium with respect to evaporation and condensation at the surface of the device. The equilibrium temperature under feedback control is a measure of dewpoint or frostpoint.

The role of zonal flows in disc gravito-turbulence

NASA Astrophysics Data System (ADS)

Vanon, R.

2018-07-01

The work presented here focuses on the role of zonal flows in the self-sustenance of gravito-turbulence in accretion discs. The numerical analysis is conducted using a bespoke pseudo-spectral code in fully compressible, non-linear conditions. The disc in question, which is modelled using the shearing sheet approximation, is assumed to be self-gravitating, viscous, and thermally diffusive; a constant cooling time-scale is also considered. Zonal flows are found to emerge at the onset of gravito-turbulence and they remain closely linked to the turbulent state. A cycle of zonal flow formation and destruction is established, mediated by a slow mode instability (which allows zonal flows to grow) and a non-axisymmetric instability (which disrupts the zonal flow), which is found to repeat numerous times. It is in fact the disruptive action of the non-axisymmetric instability to form new leading and trailing shearing waves, allowing energy to be extracted from the background flow and ensuring the self-sustenance of the gravito-turbulent regime.

The cooling time scales of growing sunspots

NASA Technical Reports Server (NTRS)

Chou, Dean-Yi

1987-01-01

The evolution of brightness and magnetic fields of growing sunspots is studied. Growing sunspots are found to be brighter (or less dark) than stable sunspots with the same magnetic field strength. From comparison of brightness and magnetic fields of a growing sunspot with those of stable sunspots, a dynamical parameter, the cooling time, of the growing sunspot is obtained. Ten growing sunspots are studied, and cooling times of 0.5 to 9 hr are found. Two models, the inhibition model and the Alfven wave model, give cooling times of about 0.05 hr, based on linear theory. The discrepancy between theory and observation may be due to the fact that the observed sunspots are in the nonlinear regime.

Optimization and Simulation of Plastic Injection Process using Genetic Algorithm and Moldflow

NASA Astrophysics Data System (ADS)

Martowibowo, Sigit Yoewono; Kaswadi, Agung

2017-03-01

The use of plastic-based products is continuously increasing. The increasing demands for thinner products, lower production costs, yet higher product quality has triggered an increase in the number of research projects on plastic molding processes. An important branch of such research is focused on mold cooling system. Conventional cooling systems are most widely used because they are easy to make by using conventional machining processes. However, the non-uniform cooling processes are considered as one of their weaknesses. Apart from the conventional systems, there are also conformal cooling systems that are designed for faster and more uniform plastic mold cooling. In this study, the conformal cooling system is applied for the production of bowl-shaped product made of PP AZ564. Optimization is conducted to initiate machine setup parameters, namely, the melting temperature, injection pressure, holding pressure and holding time. The genetic algorithm method and Moldflow were used to optimize the injection process parameters at a minimum cycle time. It is found that, an optimum injection molding processes could be obtained by setting the parameters to the following values: T M = 180 °C; P inj = 20 MPa; P hold = 16 MPa and t hold = 8 s, with a cycle time of 14.11 s. Experiments using the conformal cooling system yielded an average cycle time of 14.19 s. The studied conformal cooling system yielded a volumetric shrinkage of 5.61% and the wall shear stress was found at 0.17 MPa. The difference between the cycle time obtained through simulations and experiments using the conformal cooling system was insignificant (below 1%). Thus, combining process parameters optimization and simulations by using genetic algorithm method with Moldflow can be considered as valid.

LASER BIOLOGY AND MEDICINE: Optoacoustic laser monitoring of cooling and freezing of tissues

NASA Astrophysics Data System (ADS)

Larin, Kirill V.; Larina, I. V.; Motamedi, M.; Esenaliev, R. O.

2002-11-01

Real-time monitoring of cooling and freezing of tissues, cells, and other biological objects with a high spatial and time resolution, which is necessary for selective destruction of cancer and benign tumours during cryotherapy, as well as for preventing any damage to the structure and functioning of biological objects in cryobiology, is considered. The optoacoustic method, based on the measurement and analysis of acoustic waves induced by short laser pulses, is proposed for monitoring the cooling and freezing of the tissue. The effect of cooling and freezing on the amplitude and time profile of acoustic signals generated in real tissues and in a model object is studied. The experimental results indicate that the optoacoustic laser technique can be used for real-time monitoring of cooling and freezing of biological objects with a submillimeter spatial resolution and a high contrast.

Routine sampling and the control of Legionella spp. in cooling tower water systems.

PubMed

Bentham, R H

2000-10-01

Cooling water samples from 31 cooling tower systems were cultured for Legionella over a 16-week summer period. The selected systems were known to be colonized by Legionella. Mean Legionella counts and standard deviations were calculated and time series correlograms prepared for each system. The standard deviations of Legionella counts in all the systems were very large, indicating great variability in the systems over the time period. Time series analyses demonstrated that in the majority of cases there was no significant relationship between the Legionella counts in the cooling tower at time of collection and the culture result once it was available. In the majority of systems (25/28), culture results from Legionella samples taken from the same systems 2 weeks apart were not statistically related. The data suggest that determinations of health risks from cooling towers cannot be reliably based upon single or infrequent Legionella tests.

Electro-optical SLS devices for operating at new wavelength ranges

DOEpatents

Osbourn, Gordon C.

1986-01-01

An intrinsic semiconductor electro-optical device includes a p-n junction intrinsically responsive, when cooled, to electromagnetic radiation in the wavelength range of 8-12 um. The junction consists of a strained-layer superlattice of alternating layers of two different III-V semiconductors having mismatched lattice constants when in bulk form. A first set of layers is either InAs.sub.1-x Sb.sub.x (where x is aobut 0.5 to 0.7) or In.sub.1-x Ga.sub.x As.sub.1-y Sb.sub.y (where x and y are chosen such that the bulk bandgap of the resulting layer is about the same as the minimum bandgap in the In.sub.1-x Ga.sub.x As.sub.1-y Sb.sub.y family). The second set of layers has a lattice constant larger than the lattice constant of the layers in the first set.

SST Patterns, Atmospheric Variability, and Inferred Sensitivities in the CMIP5 Model Archive

NASA Astrophysics Data System (ADS)

Marvel, K.; Pincus, R.; Schmidt, G. A.

2017-12-01

An emerging consensus suggests that global mean feedbacks to increasing temperature are not constant in time. If feedbacks become more positive in the future, the equilibrium climate sensitivity (ECS) inferred from recent observed global energy budget constraints is likely to be biased low. Time-varying feedbacks are largely tied to evolving sea-surface temperature patterns. In particular, recent anomalously cool conditions in the tropical Pacific may have triggered feedbacks that are not reproduced in equilibrium simulations where the tropical Pacific and Southern Ocean have had time to warm. Here, we use AMIP and CMIP5 historical simulations to explore the ECS that may be inferred over the recent historical period. We find that in all but one CMIP5 model, the feedbacks triggered by observed SST patterns are significantly less positive than those arising from historical simulations in which SST patterns are allowed to evolve unconstrained. However, there are substantial variations in feedbacks even when the SST pattern is held fixed, suggesting that atmospheric and land variability contribute to uncertainty in the estimates of ECS obtained from recent observations of the global energy budget.

Kinetics of Hydrogen Oxidation Downstream of Lean Propane and Hydrogen Flames

NASA Technical Reports Server (NTRS)

Fine, Burton

1961-01-01

The decay of hydrogen was measured downstream of lean, flat, premixed hydrogen and propane-air flames seated on cooled porous burners. Experimental variables included temperature, pressure, initial equivalence ratio and diluent. Sampling of burned gas was done through uncooled quartz orifice probes, and the analysis was based on gas chromatography. An approximate treatment of the data in which diffusion was neglected led to the following rate expression for the zone downstream of hydrogen flames d[H (sub 2)] divided by (d times t) equals 1.7 times 10 (sup 10) [H (sub 2)] (sup 3) divided by (sub 2) [O (sub 2)]e (sup (-8100 divided by RT)) moles per liters per second. On the basis of a rate expression of this form, the specific rate constant for the reaction downstream of hydrogen flames was about three times as great as that determined downstream of propane flames. This result was explained on the basis of the existence of a steady state between hydrogen and carbon monoxide in the burned gas downstream of propane flames.

A predictive model to evaluate the impact of the cooling profile on growth of psychrotrophic bacteria in raw milk from conventional and robotic milking.

PubMed

Christiansson, Anders

2017-08-01

This Research Communication explores the usefulness of predictive modelling to explain bacterial behaviour during cooling. A simple dynamic lag phase model was developed and validated. The model takes into account the effect of the cooling profile on the lag phase and growth in bulk tank milk. The time before the start of cooling was the most critical and should not exceed 1 h. The cooling rate between 30 and approximately 10 °C was the second most critical period. Cooling from 30 to 10 °C within 2 h ensured minimal growth of psychrotrophic bacteria in the milk. The cooling rate between 10 and 4 °C (the slowest phase of cooling) was of surprisingly little importance. Given a normal cooling profile to 10 °C, several hours of prolonged cooling time made practically no difference in psychrotrophic counts. This behaviour can be explained by the time/temperature dependence of the work needed by the bacteria to complete the lag phase at low temperature. For milk quality advisors, it is important to know that slow cooling below 10 °C does not result in high total counts of bacteria. In practice, slow cooling is occasionally found at farms with robotic milking. However, when comparing psychrotrophic growth in bulk milk tanks designed for robotic milking or conventional milking, the model predicted less growth for robotic milking for identical cooling profiles. It is proposed that due to the different rates of milk entering the tank, fewer bacteria will exit the lag phase during robotic milking and they will be more diluted than in conventional milking systems. At present, there is no international standard that specifies the cooling profile in robotic systems. The information on the insignificant effect of the cooling rate below 10 °C may be useful in the development of a standard.

Chemical formation and spectroscopy of S2 in a free jet expansion

NASA Astrophysics Data System (ADS)

Heaven, M.; Miller, Terry A.; Bondybey, V. E.

1984-01-01

H2S seeded in a free jet expansion of Ar is photolyzed by an ArF laser. The liberated free radical fragments react to form S2 molecules, cooled rotationally by the jet to ≲20 K. A detailed rotational analysis of the laser induced fluorescence spectrum of the 2-3, B-X band of S2 reveals localized perturbations due to the B″ 3Πu state of S2. A deperturbation analysis for both 32S2 and 32S34S spectra yields, in conjunction with recent work by Patino and Barrow, values for the rotational constant, spin-orbit coupling constant, and Te for B″ 3ΠuS2.

H T P21/ c- C2/ c phase transition and kinetics of Fe2+-Mg order-disorder of an Fe-poor pigeonite: implications for the cooling history of ureilites

NASA Astrophysics Data System (ADS)

Alvaro, Matteo; Cámara, Fernando; Domeneghetti, M. Chiara; Nestola, Fabrizio; Tazzoli, Vittorio

2011-09-01

A natural Ca-poor pigeonite (Wo6En76Fs18) from the ureilite meteorite sample PCA82506-3, free of exsolved augite, was studied by in situ high-temperature single-crystal X-ray diffraction. The sample, monoclinic P21/ c, was annealed up to 1,093°C to induce a phase transition from P21/ c to C2/ c symmetry. The variation with increasing temperature of the lattice parameters and of the intensity of the b-type reflections ( h + k = 2 n + 1, present only in the P21/ c phase) showed a displacive phase transition P21/ c to C2/ c at a transition temperature T Tr = 944°C, first order in character. The Fe-Mg exchange kinetics was studied by ex situ single-crystal X-ray diffraction in a range of temperatures between the closure temperature of the Fe-Mg exchange reaction and the transition temperature. Isothermal disordering annealing experiments, using the IW buffer, were performed on three crystals at 790, 840 and 865°C. Linear regression of ln k D versus 1/ T yielded the following equation: ln k_{{D}} = - 3717( ± 416)/T(K) + 1.290( ± 0.378);quad (R2 = 0.988) . The closure temperature ( T c) calculated using this equation was ˜740(±30)°C. Analysis of the kinetic data carried out taking into account the e.s.d.'s of the atomic fractions used to define the Fe-Mg degree of order, performed according to Mueller's model, allowed us to retrieve the disordering rate constants C 0 K {dis/+} for all three temperatures yielding the following Arrhenius relation: ln ( {C0 K_{{dis}}^{ + } } ) = ln K0 - Q/(RT) = 20.99( ± 3.74) - 26406( ± 4165)/T(K);quad (R2 = 0.988) . An activation energy of 52.5(±4) kcal/mol for the Fe-Mg exchange process was obtained. The above relation was used to calculate the following Arrhenius relation modified as a function of X Fe (in the range of X Fe = 0.20-0.50): ln ( {C0 K_{{dis}}^{ + } } ) = (21.185 - 1.47X_{{Fe}} ) - {{(27267 - 4170X_{{Fe}} )}/T(K)} . The cooling time constant, η = 6 × 10-1 K-1 year-1 calculated on the PCA82506-3 sample, provided a cooling rate of the order of 1°C/min consistent with the extremely fast late cooling history of the ureilite parent body after impact excavation.

Personal cooling in nuclear power stations. Final report

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

Kamon, E.

1983-03-01

Two approaches to personal, non-restrictive cooling of workers exposed to high-temperature work environments in nuclear power plants were evaluated. Both approaches involved a cooling garment designed to be worn under the protective clothing donned in penetration into radiation areas. One garmet was developed to cool by direct body contact with small packets of frozen water enclosed in the pockets of a shirt. The other garmets cooled by circulating a cooled liquid through capillaries in a vest and head cap (System A) or a vest (System B). Testing was conducted in a laboratory simulation of high ambient temperature (55/sup 0/C) andmore » moderate metabolic heat production (200 to 300 kcal/h). Exposure time without cooling (control) was 52 minutes (Group 1) for the workloads demanding 200 kcal/h (48 minutes for Group 2). A long garmet with 7.2 kg of frozen water (LFWG) increased mean exposure time over the control by 242% (163% for the same garmet with 6.2 kg of frozen water). A short-version garmet with 3.8 kg of frozen water (SFWG) increased the stay time by 115%. The circulating-liquid garmets increased mean exposure time 35% (System A) and 27% (System B) over the control. In field observation, the LFWG with 6.2 kg of frozen water improved stay time by 125%.« less

Convergence Studies of Mass Transport in Disks with Gravitational Instabilities. II. The Radiative Cooling Case

NASA Astrophysics Data System (ADS)

Steiman-Cameron, Thomas Y.; Durisen, Richard H.; Boley, Aaron C.; Michael, Scott; McConnell, Caitlin R.

2013-05-01

We conduct a convergence study of a protoplanetary disk subject to gravitational instabilities (GIs) at a time of approximate balance between heating produced by the GIs and radiative cooling governed by realistic dust opacities. We examine cooling times, characterize GI-driven spiral waves and their resultant gravitational torques, and evaluate how accurately mass transport can be represented by an α-disk formulation. Four simulations, identical except for azimuthal resolution, are conducted with a grid-based three-dimensional hydrodynamics code. There are two regions in which behaviors differ as resolution increases. The inner region, which contains 75% of the disk mass and is optically thick, has long cooling times and is well converged in terms of various measures of structure and mass transport for the three highest resolutions. The longest cooling times coincide with radii where the Toomre Q has its minimum value. Torques are dominated in this region by two- and three-armed spirals. The effective α arising from gravitational stresses is typically a few × 10-3 and is only roughly consistent with local balance of heating and cooling when time-averaged over many dynamic times and a wide range of radii. On the other hand, the outer disk region, which is mostly optically thin, has relatively short cooling times and does not show convergence as resolution increases. Treatment of unstable disks with optical depths near unity with realistic radiative transport is a difficult numerical problem requiring further study. We discuss possible implications of our results for numerical convergence of fragmentation criteria in disk simulations.

Determination of time of death in forensic science via a 3-D whole body heat transfer model.

PubMed

Bartgis, Catherine; LeBrun, Alexander M; Ma, Ronghui; Zhu, Liang

2016-12-01

This study is focused on developing a whole body heat transfer model to accurately simulate temperature decay in a body postmortem. The initial steady state temperature field is simulated first and the calculated weighted average body temperature is used to determine the overall heat transfer coefficient at the skin surface, based on thermal equilibrium before death. The transient temperature field postmortem is then simulated using the same boundary condition and the temperature decay curves at several body locations are generated for a time frame of 24h. For practical purposes, curve fitting techniques are used to replace the simulations with a proposed exponential formula with an initial time delay. It is shown that the obtained temperature field in the human body agrees very well with that in the literature. The proposed exponential formula provides an excellent fit with an R 2 value larger than 0.998. For the brain and internal organ sites, the initial time delay varies from 1.6 to 2.9h, when the temperature at the measuring site does not change significantly from its original value. The curve-fitted time constant provides the measurement window after death to be between 8h and 31h if the brain site is used, while it increases 60-95% at the internal organ site. The time constant is larger when the body is exposed to colder air, since a person usually wears more clothing when it is cold outside to keep the body warm and comfortable. We conclude that a one-size-fits-all approach would lead to incorrect estimation of time of death and it is crucial to generate a database of cooling curves taking into consideration all the important factors such as body size and shape, environmental conditions, etc., therefore, leading to accurate determination of time of death. Copyright © 2016 Elsevier Ltd. All rights reserved.

Isotopic composition of ice core air reveals abrupt Antarctic warming during and after Heinrich Event 1a

NASA Astrophysics Data System (ADS)

Morgan, J. D.; Bereiter, B.; Baggenstos, D.; Kawamura, K.; Shackleton, S. A.; Severinghaus, J. P.

2017-12-01

Antarctic temperature variations during Heinrich events, as recorded by δ18O­ice­, generally show more gradual changes than the abrupt warmings seen in Greenland ice. However, quantitative temperature interpretation of the water isotope temperature proxy is difficult as the relationship between δ18Oice and temperature is not constant through time. Fortunately, ice cores offer a second temperature proxy based on trapped gases. During times of surface warming, thermal fractionation of gases in the column of unconsolidated snow (firn) on top of the ice sheet results in isotopically heavier nitrogen (N2) and argon (Ar) being trapped in the ice core bubbles. During times of surface cooling, isotopically lighter gases are trapped. Measurements of δ15N and δ40Ar can therefore be used, in combination with a model for the height of the column of firn, to quantitatively reconstruct surface temperatures. In the WAIS Divide Ice Core, the two temperature proxies show a brief disagreement during Heinrich Stadial 1. Despite δ18Oice recording relatively constant temperature, the nitrogen and argon isotopes imply an abrupt warming between 16 and 15.8 kyr BP, manifest as an abrupt 1.25oC increase in the firn temperature gradient. To our knowledge, this would be the first evidence that such abrupt climate change has been recorded in an Antarctic climate proxy. If confirmed by more detailed studies, this event may represent warming due to an extreme southward shift of the Earth's thermal equator (and the southern hemisphere westerly wind belt), caused by the 16.1 ka Heinrich Event.

Virtual Special Issue Preface: Forest Response to Environmental Stress: Impacts and Adaptation

Treesearch

Steven McNulty; Enzai Du; Elena Paoletti

2017-01-01

The current distribution of forest typeswas largely established at the beginning of the Holocene epoch (approximately 12,000 BCE), but forests are constantly in flux. Many regional scale stresses (e.g., drought, heat, fire, and insect) and even a few multi-regional or global stresses (e.g., 8200 BCE cooling, or the medievalwarming period) have occurred over the past 12...

Determining the Enthalpy of Vaporization of Salt Solutions Using the Cooling Effect of a Bubble Column Evaporator

ERIC Educational Resources Information Center

Fan, Chao; Pashley, Richard M.

2016-01-01

The enthalpy of vaporization (?H[subscript vap]) of salt solutions is not easily measured, as a certain quantity of pure water has to be evaporated from a solution, at constant composition, and at a fixed temperature and pressure; then the corresponding heat input has to be measured. However, a simple bubble column evaporator (BCE) was used as a…

Surface Tension Confines Cryogenic Liquid

NASA Technical Reports Server (NTRS)

Castles, Stephen H.; Schein, Michael E.

1989-01-01

New type of Dewar provides passive, constant-temperature cryogenic cooling for scientific instruments under normal-to low-gravity conditions. Known as Surface-Tension-Contained Liquid Cryogen Cooler (STCLCC), keeps liquid cryogen in known location inside the Dewar by trapping liquid inside spongelike material. Unique sponge material fills most of volume of inner tank. Sponge is all-silica, open-cell material similar to that used for Space Shuttle thermal-protection tiles.

Modeling Chilled-Water Storage System Components for Coupling to a Small Modular Reactor in a Nuclear Hybrid Energy System

NASA Astrophysics Data System (ADS)

Misenheimer, Corey Thomas

The intermittency of wind and solar power puts strain on electric grids, often forcing carbonbased and nuclear sources of energy to operate in a load-follow mode. Operating nuclear reactors in a load-follow fashion is undesirable due to the associated thermal and mechanical stresses placed on the fuel and other reactor components. Various Thermal Energy Storage (TES) elements and ancillary energy applications can be coupled to nuclear (or renewable) power sources to help absorb grid instabilities caused by daily electric demand changes and renewable intermittency, thereby forming the basis of a candidate Nuclear Hybrid Energy System (NHES). During the warmer months of the year in many parts of the country, facility air-conditioning loads are significant contributors to the increase in the daily peak electric demand. Previous research demonstrated that a stratified chilled-water storage tank can displace peak cooling loads to off-peak hours. Based on these findings, the objective of this work is to evaluate the prospect of using a stratified chilled-water storage tank as a potential TES reservoir for a nuclear reactor in a NHES. This is accomplished by developing time-dependent models of chilled-water system components, including absorption chillers, cooling towers, a storage tank, and facility cooling loads appropriate for a large office space or college campus, as a callable FORTRAN subroutine. The resulting TES model is coupled to a high-fidelity mPower-sized Small Modular Reactor (SMR) Simulator, with the goal of utilizing excess reactor capacity to operate several sizable chillers in order to keep reactor power constant. Chilled-water production via single effect, lithium bromide (LiBr) absorption chillers is primarily examined in this study, although the use of electric chillers is briefly explored. Absorption chillers use hot water or low-pressure steam to drive an absorption-refrigeration cycle. The mathematical framework for a high-fidelity dynamic absorption chiller model is presented. The transient FORTRAN model is grounded on time-dependent mass, species, and energy conservation equations. Due to the vast computational costs of the high-fidelity model, a low-fidelity absorption chiller model is formulated and calibrated to mimic the behavior of the high-fidelity model. Stratified chilled-water storage tank performance is characterized using Computational Fluid Dynamics (CFD). The geometry employed in the CFD model represents a 5-million-gallon storage tank currently in use at a North Carolina college campus. Simulation results reveal the laminar numerical model most closely aligns with actual tank charging and discharging data. A subsequent parametric study corroborates storage tank behavior documented throughout literature and industry. Two absorption chiller configurations are considered. The first involves bypassing lowpressure steam from the low-pressure turbine to absorption chillers during periods of excess reactor capacity in order to keep reactor power constant. Simulation results show steam conditions downstream of the turbine control valves are a strong function of turbine load, and absorption chiller performance is hindered by reduced turbine impulse pressures at reduced turbine demands. A more suitable configuration entails integrating the absorption chillers into a flash vessel system that is thermally coupled to a sensible heat storage system. The sensible heat storage system is able to maintain reactor thermal output constant at 100% and match turbine output with several different electric demand profiles. High-pressure condensate in the sensible heat storage system is dropped across a let-down orifice and flashed in an ideal separator. Generated steam is sent to a bank of absorption chillers. Simulation results show enough steam is available during periods of reduced turbine demand to power four large absorption chillers to charge a 5-million-gallon stratified chilled-water storage tank, which is used to offset cooling loads in an adjacent facility. The coupled TES systems operating in conjunction with an SMR comprise the foundation of a tightly coupled NHES.

Equilibrium, quasi-equilibrium, and nonequilibrium freezing of mammalian embryos.

PubMed

Mazur, P

1990-08-01

The first successful freezing of early embryos to -196 degrees C in 1972 required that they be cooled slowly at approximately 1 degree C/min to about -70 degrees C. Subsequent observations and physical/chemical analyses indicate that embryos cooled at that rate dehydrate sufficiently to maintain the chemical potential of their intracellular water close to that of the water in the partly frozen extracellular solution. Consequently, such slow freezing is referred to as equilibrium freezing. In 1972 and since, a number of investigators have studied the responses of embryos to departures from equilibrium freezing. When disequilibrium is achieved by the use of higher constant cooling rates to -70 degrees C, the results is usually intracellular ice formation and embryo death. That result is quantitatively in accord with the predictions of the physical/chemical analysis of the kinetics of water loss as a function of cooling rate. However, other procedures involving rapid nonequilibrium cooling do not result in high mortality. One common element in these other nonequilibrium procedures is that, before the temperature has dropped to a level that permits intracellular ice formation, the embryo water content is reduced to the point at which the subsequent rapid nonequilibrium cooling results in either the formation of small innocuous intracellular ice crystals or the conversion of the intracellular solution into a glass. In both cases, high survival requires that subsequent warming be rapid, to prevent recrystallization or devitrification. The physical/chemical analysis developed for initially nondehydrated cells appears generally applicable to these other nonequilibrium procedures as well.

Late-time Cooling of Neutron Star Transients and the Physics of the Inner Crust

NASA Astrophysics Data System (ADS)

Deibel, Alex; Cumming, Andrew; Brown, Edward F.; Reddy, Sanjay

2017-04-01

An accretion outburst onto a neutron star transient heats the neutron star’s crust out of thermal equilibrium with the core. After the outburst, the crust thermally relaxes toward equilibrium with the neutron star core, and the surface thermal emission powers the quiescent X-ray light curve. Crust cooling models predict that thermal equilibrium of the crust will be established ≈ 1000 {days} into quiescence. Recent observations of the cooling neutron star transient MXB 1659-29, however, suggest that the crust did not reach thermal equilibrium with the core on the predicted timescale and continued to cool after ≈ 2500 {days} into quiescence. Because the quiescent light curve reveals successively deeper layers of the crust, the observed late-time cooling of MXB 1659-29 depends on the thermal transport in the inner crust. In particular, the observed late-time cooling is consistent with a low thermal conductivity layer near the depth predicted for nuclear pasta that maintains a temperature gradient between the neutron star’s inner crust and core for thousands of days into quiescence. As a result, the temperature near the crust-core boundary remains above the critical temperature for neutron superfluidity, and a layer of normal neutrons forms in the inner crust. We find that the late-time cooling of MXB 1659-29 is consistent with heat release from a normal neutron layer near the crust-core boundary with a long thermal time. We also investigate the effect of inner crust physics on the predicted cooling curves of the accreting transient KS 1731-260 and the magnetar SGR 1627-41.

Work stress associated cool down reactions among nurses and hospital physicians and their relation to burnout symptoms.

PubMed

Büssing, Arndt; Falkenberg, Zarah; Schoppe, Carina; Recchia, Daniela Rodrigues; Poier, Désirée

2017-08-10

Hospital staff experience high level of work stress and they have to find strategies to adapt and react to it. When they perceive emotional exhaustion and job dissatisfaction in response to constant work stress, one reaction might be emotional withdrawal. This emotional distancing can be seen as an adaptive strategy to keep 'functionality' in the job. Both, perception of emotional exhaustion and emotional distancing as a strategy, can be operationalized as 'Cool Down'. We assume that work stress associated variables are positively associated with Cool Down reactions, while internal and external resources are negatively associated and might function as a buffer against emotional distancing. Moreover, we assume that the perception of stress and work burden might be different between nurses and physicians and women and men, but not their cool down reactions as a strategy. Anonymous cross-sectional survey with standardized instruments among 1384 health care professionals (66% nurses, 34% hospital physicians). Analyses of variance, correlation and also stepwise regression analyses were performed to analyze the influence of demands and resources on Cool Down reactions. As measured with the Cool Down Index (CDI), frequency and strength of Cool Down reactions did not significantly differ between women and men, while women and men differ significantly for their burnout symptoms, stress perception and perceived work burden. With respect to profession, Cool Down and stress perception were not significantly different, but burnout and work burden. For nurses, "Emotional Exhaustion" was the best CDI predictor (51% explained variance), while in physicians it was "Depersonalization" (44% explained variance). Among putative resources which might buffer against Cool Down reactions, only team satisfaction and situational awareness had some influence, but not self-efficacy expectation. The perceptions of emotional exhaustion and distancing of nurses and physicians (and women and men) seems to be different, but not their adaptive Cool Down reactions. Data would support the notion that a structural approach of support would require first to control and eliminate work stressors, and second a multifaceted approach to strengthen and support hospital staff's resources and resilience.

Rapid Induction of Therapeutic Hypothermia Using Transnasal High Flow Dry Air

PubMed Central

Chava, Raghuram; Raghavan, Madhavan Srinivas; Halperin, Henry; Maqbool, Farhan; Geocadin, Romergryko; Quinones-Hinojosa, Alfredo; Kolandaivelu, Aravindan; Rosen, Benjamin A.

2017-01-01

Early induction of therapeutic hypothermia (TH) is recommended in out-of-hospital cardiac arrest (CA); however, currently no reliable methods exist to initiate cooling. We investigated the effect of high flow transnasal dry air on brain and body temperatures in adult porcine animals. Adult porcine animals (n = 23) under general anesthesia were subject to high flow of transnasal dry air. Mouth was kept open to create a unidirectional airflow, in through the nostrils and out through the mouth. Brain, internal jugular, and aortic temperatures were recorded. The effect of varying airflow rate and the air humidity (0% or 100%) on the temperature profiles were recorded. The degree of brain cooling was measured as the differential temperature from baseline. A 10-minute exposure of high flow dry air caused rapid cooling of brain and gradual cooling of the jugular and the aortic temperatures in all animals. The degree of brain cooling was flow dependent and significantly higher at higher airflow rates (0.8°C ± 0.3°C, 1.03°C ± 0.6°C, and 1.3°C ± 0.7°C for 20, 40, and 80 L, respectively, p < 0.05 for all comparisons). Air temperature had minimal effect on the brain cooling over 10 minutes with similar decrease in temperature at 4°C and 30°C. At a constant flow rate (40 LPM) and temperature, the degree of cooling over 10 minutes during dry air exposure was significantly higher compared to humid air (100% saturation) (1.22°C ± 0.35°C vs. 0.21°C ± 0.12°C, p < 0.001). High flow transnasal dry air causes flow dependent cooling of the brain and the core temperatures in intubated porcine animals. The mechanism of cooling appears to be evaporation of nasal mucus as cooling is mitigated by humidifying the air. This mechanism may be exploited to initiate TH in CA. PMID:27635468

Rapid Induction of Therapeutic Hypothermia Using Transnasal High Flow Dry Air.

PubMed

Chava, Raghuram; Zviman, Menekhem; Raghavan, Madhavan Srinivas; Halperin, Henry; Maqbool, Farhan; Geocadin, Romergryko; Quinones-Hinojosa, Alfredo; Kolandaivelu, Aravindan; Rosen, Benjamin A; Tandri, Harikrishna

2017-03-01

Early induction of therapeutic hypothermia (TH) is recommended in out-of-hospital cardiac arrest (CA); however, currently no reliable methods exist to initiate cooling. We investigated the effect of high flow transnasal dry air on brain and body temperatures in adult porcine animals. Adult porcine animals (n = 23) under general anesthesia were subject to high flow of transnasal dry air. Mouth was kept open to create a unidirectional airflow, in through the nostrils and out through the mouth. Brain, internal jugular, and aortic temperatures were recorded. The effect of varying airflow rate and the air humidity (0% or 100%) on the temperature profiles were recorded. The degree of brain cooling was measured as the differential temperature from baseline. A 10-minute exposure of high flow dry air caused rapid cooling of brain and gradual cooling of the jugular and the aortic temperatures in all animals. The degree of brain cooling was flow dependent and significantly higher at higher airflow rates (0.8°C ± 0.3°C, 1.03°C ± 0.6°C, and 1.3°C ± 0.7°C for 20, 40, and 80 L, respectively, p < 0.05 for all comparisons). Air temperature had minimal effect on the brain cooling over 10 minutes with similar decrease in temperature at 4°C and 30°C. At a constant flow rate (40 LPM) and temperature, the degree of cooling over 10 minutes during dry air exposure was significantly higher compared to humid air (100% saturation) (1.22°C ± 0.35°C vs. 0.21°C ± 0.12°C, p < 0.001). High flow transnasal dry air causes flow dependent cooling of the brain and the core temperatures in intubated porcine animals. The mechanism of cooling appears to be evaporation of nasal mucus as cooling is mitigated by humidifying the air. This mechanism may be exploited to initiate TH in CA.

The Effect of Cooling Conditions on the Evolution of Non-metallic Inclusions in High Manganese TWIP Steels

NASA Astrophysics Data System (ADS)

Wang, Yu-Nan; Yang, Jian; Xin, Xiu-Ling; Wang, Rui-Zhi; Xu, Long-Yun

2016-04-01

In the present study, the effect of cooling conditions on the evolution of non-metallic inclusions in high manganese TWIP steels was investigated based on experiments and thermodynamic calculations. In addition, the formation and growth behavior of AlN inclusions during solidification under different cooling conditions were analyzed with the help of thermodynamics and dynamics. The inclusions formed in the high manganese TWIP steels are classified into nine types: (1) AlN; (2) MgO; (3) CaS; (4) MgAl2O4; (5) AlN + MgO; (6) MgO + MgS; (7) MgO + MgS + CaS; (8) MgO + CaS; (9) MgAl2O4 + MgS. With the increase in the cooling rate, the volume fraction and area ratio of inclusions are almost constant; the size of inclusions decreases and the number density of inclusions increases in the steels. The thermodynamic results of inclusion types calculated with FactSage are consistent with the observed results. With increasing cooling rate, the diameter of AlN decreases. When the cooling rate increases from 0.75 to 4.83 K s-1, the measured average diameter of AlN decreases from 4.49 to 2.42 μm. Under the high cooling rate of 4.83 K s-1, the calculated diameter of AlN reaches 3.59 μm at the end of solidification. However, the calculated diameter of AlN increases to approximately 5.93 μm at the end of solidification under the low cooling rate of 0.75 K s-1. The calculated diameter of AlN decreases with increasing cooling rate. The theoretical calculation results of the change in diameter of AlN under the different cooling rates have the same trend with the observed results. The existences of inclusions in the steels, especially AlN which average sizes are 2.42 and 4.49 μm, respectively, are not considered to have obvious influences on the hot ductility.

Tissue oxidative metabolism can increase the difference between local temperature and arterial blood temperature by up to 1.3oC: Implications for brain, brown adipose tissue, and muscle physiology.

PubMed

Zaretsky, Dmitry V; Romanovsky, Andrej A; Zaretskaia, Maria V; Molkov, Yaroslav I

2018-01-01

Tissue temperature increases, when oxidative metabolism is boosted. The source of nutrients and oxygen for this metabolism is the blood. The blood also cools down the tissue, and this is the only cooling mechanism, when direct dissipation of heat from the tissue to the environment is insignificant, e.g. , in the brain. While this concept is relatively simple, it has not been described quantitatively. The purpose of the present work was to answer two questions: 1) to what extent can oxidative metabolism make the organ tissue warmer than the body core, and, 2) how quickly are changes in the local metabolism reflected in the temperature of the tissue? Our theoretical analysis demonstrates that, at equilibrium, given that heat exchange with the organ is provided by the blood, the temperature difference between the organ tissue and the arterial blood is proportional to the arteriovenous difference in oxygen content, does not depend on the blood flow, and cannot exceed 1.3 o C. Unlike the equilibrium temperature difference, the rate of change of the local temperature, with respect to time, does depend on the blood flow. In organs with high perfusion rates, such as the brain and muscles, temperature changes occur on a time scale of a few minutes. In organs with low perfusion rates, such changes may have characteristic time constants of tens or hundreds of minutes. Our analysis explains, why arterial blood temperature is the main determinant of the temperature of tissues with limited heat exchange, such as the brain.

Analysis of isothermal and cooling-rate-dependent immersion freezing by a unifying stochastic ice nucleation model

NASA Astrophysics Data System (ADS)

Alpert, Peter A.; Knopf, Daniel A.

2016-02-01

Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature, T, and relative humidity, RH, at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling-rate-dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nucleating particles (INPs) all have the same INP surface area (ISA); however, the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. Descriptions of ice active sites and variability of contact angles have been successfully formulated to describe ice nucleation experimental data in previous research; however, we consider the ability of a stochastic freezing model founded on classical nucleation theory to reproduce previous results and to explain experimental uncertainties and data scatter. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses parameters including the total number of droplets, Ntot, and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA-dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets, droplets in a continuous-flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time-dependent isothermal frozen fractions exhibiting non-exponential behavior can be readily explained by this model considering varying ISA. An apparent cooling-rate dependence of Jhet is explained by assuming identical ISA in each droplet. When accounting for ISA variability, the cooling-rate dependence of ice nucleation kinetics vanishes as expected from classical nucleation theory. The model simulations allow for a quantitative experimental uncertainty analysis for parameters Ntot, T, RH, and the ISA variability. The implications of our results for experimental analysis and interpretation of the immersion freezing process are discussed.

Safety of LigaSure in recurrent laryngeal nerve dissection-porcine model using continuous monitoring.

PubMed

Dionigi, Gianlorenzo; Chiang, Feng-Yu; Kim, Hoon Yub; Randolph, Gregory W; Mangano, Alberto; Chang, Pi-Ying; Lu, I-Cheng; Lin, Yi-Chu; Chen, Hui-Chun; Wu, Che-Wei

2017-07-01

This study investigated recurrent laryngeal nerve (RLN) real-time electromyography (EMG) data to define optimal safety parameters of the LigaSure Small Jaw (LSJ) instrument during thyroidectomy. Prospective animal model. Dynamic EMG tracings were recorded from 32 RLNs (16 piglets) during various applications of LSJ around using continuous electrophysiologic monitoring. At varying distances from the RLN, the LSJ was activated (activation study). The LSJ was also applied to the RLN at timed intervals after activation and after a cooling maneuver through placement on the sternocleidomastoid muscle (cooling study). In the activation study, there was no adverse EMG event at 2 to 5 mm distance (16 RLNs, 96 tests). In the cooling study, there was no adverse EMG event after 2-second cooling time (16 RLNs, 96 tests) or after the LSJ cooling maneuver on the surrounding muscle before reaching the RLNs (8 RLNs, 24 tests). Based on EMG functional assessment, the safe distance for LSJ activation was 2 mm. Further LSJ-RLN contact was safe if the LSJ was cooled for more than 2 seconds or cooled by touch muscle maneuver. The LSJ should be used with these distance and time parameters in mind to avoid RLN injury. N/A. Laryngoscope, 127:1724-1729, 2017. © 2016 The American Laryngological, Rhinological and Otological Society, Inc.

Hypothermic Cooling Measured by Thermal Magnetic Resonance Imaging; Feasibility and Implications for Virtual Imaging in the Urogenital Pelvis.

PubMed

Skarecky, Douglas; Yu, Hon; Linehan, Jennifer; Morales, Blanca; Su, Min-Ying; Fwu, Peter; Ahlering, Thomas

2017-10-01

To study the combination of thermal magnetic resonance imaging (MRI) and novel hypothermic cooling, via an endorectal cooling balloon (ECB), to assess the effective dispersion and temperature drop in pelvic tissue to potentially reduce inflammatory cascade in surgical applications. Three male subjects, before undergoing robot-assisted radical prostatectomy, were cooled via an ECB, rendered MRI compatible for patient safety before ECB hypothermia. MRI studies were performed using a 3T scanner and included T2-weighted anatomic scan for the pelvic structures, followed by a temperature mapping scan. The sequence was performed repeatedly during the cooling experiment, whereas the phase data were collected using an integrated MR-high-intensity focused ultrasound workstation in real time. Pelvic cooling was instituted with a cooling console located outside the MRI magnet room. The feasibility of pelvic cooling measured a temperature drop of the ECB of 20-25 degrees in real time was achieved after an initial time delay of 10-15 seconds for the ECB to cool. The thermal MRI anatomic images of the prostate and neurovascular bundle demonstrate cooling at this interface to be 10-15 degrees, and also that cooling extends into the prostate itself ~5 degrees, and disperses into the pelvic region as well. An MRI-compatible ECB coupled with thermal MRI is a feasible method to assess effective hypothermic diffusion and saturation to pelvic structures. By inference, hypothermia-induced rectal cooling could potentially reduce inflammation, scarring, and fistula in radical prostatectomy, as well as other urologic tissue procedures of high-intensity focused ultrasound, external beam radiation therapy, radioactive seed implants, transurethral microwave therapy, and transurethral resection of the prostate. Copyright © 2017 Elsevier Inc. All rights reserved.

On the role of mantle depletion and small-scale convection in post rift basin evolution (Invited)

NASA Astrophysics Data System (ADS)

Petersen, K.; Nielsen, S. B.

2013-12-01

Subsidence and heat flow evolution of the oceanic lithosphere appears to be consistent with the conductive cooling of a ~100 km plate overlying asthenospheric mantle of constant entropy. The physical mechanism behind plate-like subsidence has been suggested to be the result of small-scale convective instabilities which transport heat energy to the base of the lithosphere and cause an eventual departure from half space-like cooling by inhibiting subsidence of old ocean floor and causing an asymptotic surface heat flow of ~50 mW/m^2. Here, we conduct a number of numerical thermo-mechanical experiments of oceanic lithosphere cooling for different models of temperature- and pressure-dependent viscosity. We show that uniform (P, T-dependent) mantle viscosity cannot both explain half space-like subsidence for young (<70 Mr) lithosphere as well as a relatively high (>50 mW/m^2) surface heat flow which is observed above old (>100 Myr) lithosphere. The latter requires vigorous sub lithospheric convection which would lead to early (~1Myr) onset of convective instability at shallow depth (<60 km) and therefore insufficient initial subsidence. To resolve this paradox, we employ models which account for the density decrease and viscosity increase due to depletion during mid-ocean ridge melting. We demonstrate that the presence of a mantle restite layer within the lithosphere hinders convection at shallow depth and therefore promotes plate-like cooling. A systematic parameter search among 280 different numerical experiments indicates that models with 60-80 km depletion thickness minimize misfit with subsidence and heat flow data. This is consistent with existing petrological models of mid-ocean ridge melting. Our models further indicate that the post-rift subsidence pattern where little or no melting occurred during extension (e.g. non-volcanic margins and continental rifts) may differ from typical oceanic plate-like subsidence by occurring at a nearly constant rate rather than at an exponentially decaying rate. Model comparison with subsidence histories inferred from backstripping analysis implies that this is indeed often the case. Accordingly, existing thermal models of continental rifting which assume plate-like cooling (and is often calibrated from oceanic data) are likely to yield inaccurate predictions in terms of subsidence and heat flow evolution.

Microbial analysis of meatballs cooled with vacuum and conventional cooling.

PubMed

Ozturk, Hande Mutlu; Ozturk, Harun Kemal; Koçar, Gunnur

2017-08-01

Vacuum cooling is a rapid evaporative cooling technique and can be used for pre-cooling of leafy vegetables, mushroom, bakery, fishery, sauces, cooked food, meat and particulate foods. The aim of this study was to apply the vacuum cooling and the conventional cooling techniques for the cooling of the meatball and to show the vacuum pressure effect on the cooling time, the temperature decrease and microbial growth rate. The results of the vacuum cooling and the conventional cooling (cooling in the refrigerator) were compared with each other for different temperatures. The study shows that the conventional cooling was much slower than the vacuum cooling. Moreover, the microbial growth rate of the vacuum cooling was extremely low compared with the conventional cooling. Thus, the lowest microbial growth occurred at 0.7 kPa and the highest microbial growth was observed at 1.5 kPa for the vacuum cooling. The mass loss ratio for the conventional cooling and vacuum cooling was about 5 and 9% respectively.

Like night and day: Reversals of thermal gradients across ghost crab burrows and their implications for thermal ecology

NASA Astrophysics Data System (ADS)

Watson, Gregory S.; Gregory, Emily A.; Johnstone, Charmaine; Berlino, Manuel; Green, David W.; Peterson, Nicola R.; Schoeman, David S.; Watson, Jolanta A.

2018-04-01

Ghost crabs, Ocypode cordimanus, inhabit relatively hostile environments subject to thermal fluctuations, including both diurnal and seasonal cycles. For many ectotherms, including ghost crabs, a major challenge is to remain cool during hot daytime temperatures. This can be achieved by adopting a fossorial lifestyle, taking advantage of thermal refuge afforded by burrows of sufficient depth. Another consideration, often overlooked, is the potential advantage associated with ready access to a thermal energy source (a "charging station") when surface temperatures are cooler. Being able to rapidly elevate body temperature during cool periods would enhance the crab's ability to maintain rate processes and carry out essential activities. We have measured ghost crab burrow temperature profiles at two times of the day with contrasting sun exposure (06:00 and 14:00), demonstrating how effective burrow depth (up to a maximum of 40 cm) provides thermal regulation below the surface of the sand (e.g., at dawn (06:00) and early afternoon (14:00) at a depth of 5 cm, temperatures (±SD) of 16.32 ± 0.96 °C and 25.04 ± 1.47 °C were recorded, respectively. Corresponding temperatures at a depth of 30 cm were 19.17 ± 0.59 °C and 19.78 ± 1.60 °C, respectively). This demonstrates that while temperature conditions at the surface vary dramatically from night to day, ghost crab burrows can maintain relatively constant temperatures at the burrow base throughout the diurnal cycle, at least during winter. As a consequence, the burrow heat signatures undergo a corresponding thermal gradient reversal between night and day, as revealed by infra-red photography. Complementing these field observations, we also determined heating and cooling times/constants for O. cordimanus in the laboratory (τ = 17.54 and 16.59 JK-1, respectively), and analysed chemical composition of their carapace (external (with β Chitin evident) and internal (predominance of α Chitin)), which is the primary thermal interface with the environment. We find that ghost crabs both gain and lose heat relatively rapidly, which likely affects the range and duration of surface activities under different thermal conditions, and renders the thermal characteristics of their burrows vital for their persistence on beaches. Finally, we speculate that the distinctly contrasting thermal signatures of ghost crab burrows in comparison to the surrounding sand could in principle be used by crabs as spatial markers for navigation and to identify holes on return from nightly excursions, being identified either by direct thermal sensing or odours rising from the burrow base as a consequence of the thermal flux.

Radiometer for accurate (+ or - 1%) measurement of solar irradiance equal to 10,000 solar constants

NASA Technical Reports Server (NTRS)

Kendall, J. M., Sr.

1981-01-01

The 10,000 solar constant radiometer was developed for the accurate (+ or - 1%) measurement of the irradiance produced in the image formed by a parabolic reflector or by a multiple mirror solar installation. This radiometer is water cooled, weighs about 1 kg, and is 5 cm (2 in.) in diameter by 10 cm (4 in.) long. A sting is provided for mounting the radiometer in the solar installation capable of measuring irradiances as high as 20,000 solar constants, the instrument is self calibrating. Its accuracy depends on the accurate determination of the cavity aperture, and absorptivity of the cavity, and accurate electrical measurements. The spectral response is flat over the entire spectrum from far UV to far IR. The radiometer responds to a measurement within 99.7% of the final value within 8 s. During a measurement of the 10,000 solar constant irradiance, the temperature rise of the water is about 20 C. The radiometer has perfect cosine response up to 60 deg off the radiometer axis.

Laboratory Experiments to Investigate Breakout and Bifurcation of Lava Flows on Mars

NASA Astrophysics Data System (ADS)

Miyamoto, H.; Zimbelman, J. R.; Tokunaga, T.; Tosaka, H.

2001-05-01

Mars Orbiter Camera (MOC) images show that many lava flows on Mars have morphologies quite similar to aa lava flows. Such flows often have many lobes and branches that overlap each other, making a compound flow unit. These features cannot be explained by any simple flow model because longer effusion duration will simply make the flow longer, although actual lavas often will bifurcate to make additonal flow units. Similarly, formation of a lava tube is difficult to predict by a model that does not contain preset conditions for their formation. Treatment of the surface crust is very important to the flow morphology, especially for effusion over a long duration. To understand the effect of a crust on flow morphology, paraffin wax is especially useful in laboratory experiments. In our experiments, a flow on a constant slope typically progresses with a constant width at first. Then, the flow front cools to form a crust, which inhibits the progress of the flow. At that time, the flow sometimes becomes sinuous or ceases its movement. With a sufficient flux after that, uplift of thickness (inflation) can occur. Uplift sometimes attains a sufficient thickening to produce a breakout at the side of the flow, bifurcating to form a new cooling unit. Bifurcated flows do not always follow the main flow (some branches moved several cm away from the initial flow). The bifurcations continue to develop into a complicated flow field, given a sufficiently long duration of effusion. Although the movement of the flow with a surface crust is difficult to predict, our simple analysis suggests that the maximum thickness attained by the inflation (by fluid continuing to enter a stopped flow) before a breakout can occur is roughly estimated by a balance between the overpressure and the crust tensile strength. The maximum extent of a bifurcated flow after a breakout can probably be constrained, which will be a significant goal for future modeling of compound flows.

Muscle-Cooling Intervention to Reduce Fatigue and Fatigue-Induced Tremor in Novice and Experienced Surgeons: A Preliminary Investigation.

PubMed

Jensen, Lauren; Dancisak, Michael; Korndorffer, James

2016-10-01

A localized, intermittent muscle-cooling protocol was implemented to determine cooling garment efficacy in reducing upper extremity muscular fatigue and tremor in novice ( n  = 10) and experienced surgeons ( n  = 9). Subjects wore a muscle-cooling garment while performing multiple trials of a forearm exercise and paired suturing task to induce muscular fatigue and exercise-induced tremor. A reduction in tremor amplitude and an extension in time to fatigue were expected with muscle cooling as compared with control trials. Each subject completed an intervention session (5°C cooling condition) and a control session (32°C or thermal neutral condition). A paired samples t test indicated that tremor amplitude was significantly reduced ( t [8] = 1.89458; p  < 0.05) in experienced surgeons in two dimensions (up and down, and back and forth). Tremor amplitude was reduced in novice surgeons but the effect was not significant. Time to fatigue and suture time improved in both cohorts with muscle cooling, but the effect did not reach significance. Results from the pilot work suggest muscle cooling as an intervention for reduction of fatigue and tremor is very promising, warranting further investigation. Surgical specialties that require prolonged procedures might benefit more from this intervention.

Impact of upper body precooling during warm-up on subsequent time trial paced cycling in the heat.

PubMed

Katica, Charles P; Wingo, Jonathan E; Herron, Robert L; Ryan, Greg A; Bishop, Stacy H; Richardson, Mark

2018-06-01

The purpose of this study was to test the hypothesis that cooling the upper body during a warm-up enhances performance during a subsequent 16.1-km simulated cycling time trial in a hot environment. Counterbalanced, repeated measures design. Eight trained, male cyclists (peak oxygen uptake=57.8±5.0mLkg -1 min -1 ) completed two simulated 16.1-km time trials in a hot environment (35.0±0.5°C, 43.8±2.0% relative humidity) each separated by 72h. Treatments were counterbalanced; participants warmed up for 20min while either wearing head and neck ice wraps and an ice vest (COOLING) or no cooling apparatus (CONTROL). Following the warm-up mean skin temperature (T¯ sk ), mean body temperature (T¯ b ) and rating of thermal comfort were significantly lower than baseline following the COOLING trial (all P<0.05); however, rectal temperature was unaffected (P=0.35). Because the effects of precooling on T¯ sk and T¯ b were not sustained during exercise, values for COOLING and CONTROL were not different throughout the time trial (P=0.38). Nonetheless, time to completion was significantly faster following the COOLING intervention when compared to the CONTROL (29.3±3.6min, vs. 30.3±3.1min; P=0.04). These data suggest that in short distance time trials in hot conditions cyclists may benefit from utilizing a cooling modality during the warm-up. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

[Net power and energy of cooled antenna microwave ablation:ex vivo versus in vivo results in porcine liver].

PubMed

Jiang, Hua; Fan, Wei-jun; Zhang, Liang; Li, Xin; Zhang, Jian-lei

2012-09-18

To explore the net power and net energy of a cooled antenna radiator in ex vivo and in vivo porcine livers. All animal experiments complied with the guidelines of our animal use committee. Microwave ablation (MWA) was performed in ex vivo and in vivo porcine livers with a cooled-shaft antenna in different microwave ablation parameter groups (50, 80 and 110 W for 10 min). The energy losses from the microwave antenna or cables were calculated. And the net power, net energy and the relationship between net power and power readout were determined. When the power displayed by the machine indicated 50 W, 80 W and 110 W, the net power during MWA was 31.3 ± 0.6, 47.3 ± 0.8 and 62.1 ± 0.9 W ex vivo and 31.8 ± 0.8, 47.4 ± 0.3 and 61.7 ± 1.5 W in vivo. For the same power readout, the ex vivo or in vivo effective power was the same (P = 0.841, P = 0.133, P = 0.551). For both ex vivo and in vivo experiments, the ratio of microwave antenna energy loss to microwave antenna input energy was relatively constant (P = 0.613, 0.326). For the same treatment time and net power, the difference was significant between ex vivo and in vivo ablation volumes (P = 0.001, 0.006, 0.001). Using net power as a reference during MWA is more accurate compared to the traditional power readout. And net energy offers a more realistic reflection of MWA energy in tissues.

High-temperature experimental analogs of primitive meteoritic metal-sulfide-oxide assemblages

NASA Astrophysics Data System (ADS)

Schrader, Devin L.; Lauretta, Dante S.

2010-03-01

We studied the oxidation-sulfidation behavior of an Fe-based alloy containing 4.75 wt.% Ni, 0.99 wt.% Co, 0.89 wt.% Cr, and 0.66 wt.% P in H 2-H 2O-CO-CO 2-H 2S gas mixtures at 1000 °C. The samples were cooled at rates of ˜3000 °C/h, comparable to estimates of the conditions after a chondrule-formation event in the early Solar System. Gas compositions were monitored in real time by a quadrupole mass spectrometer residual gas analyzer. Linear rate constants associated with gas-phase adsorption were determined. Reaction products were analyzed by optical microscopy, wavelength-dispersive-spectroscopy X-ray elemental mapping, and electron probe microanalysis. Based on analysis of the Fe-Ni-S ternary phase diagram and the reaction products, the primary corrosion product is a liquid of composition 66.6 wt.% Fe, 3.5 wt.% Ni, 29.9 wt.% S, and minor amounts of P, Cr, and Co. Chromite (FeCr 2O 4) inclusions formed by oxidation and are present in the metal foil and at the outer boundary between the sulfide and experimental atmosphere. During cooling the liquid initially crystallizes into taenite (average composition ˜15 wt.% Ni), monosulfide solid solution [mss, (Fe,Ni,Co,Cr) 1-xS], and Fe-phosphates. Upon further cooling, kamacite exsolves from this metal, enriching the taenite in Ni. The remnant metal core is enriched in P and Co and depleted in Cr at the reaction interface, relative to the starting composition. The unreacted metal core composition remains unchanged, suggesting the reactions did not reach equilibrium. We present a detailed model of reaction mechanisms based on the observed kinetics and sample morphologies, and discuss meteoritic analogs in the CR chondrite MacAlpine Hills 87320.

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.

Stochastic simulation for the propagation of high-frequency acoustic waves through a random velocity field

NASA Astrophysics Data System (ADS)

Lu, B.; Darmon, M.; Leymarie, N.; Chatillon, S.; Potel, C.

2012-05-01

In-service inspection of Sodium-Cooled Fast Reactors (SFR) requires the development of non-destructive techniques adapted to the harsh environment conditions and the examination complexity. From past experiences, ultrasonic techniques are considered as suitable candidates. The ultrasonic telemetry is a technique used to constantly insure the safe functioning of reactor inner components by determining their exact position: it consists in measuring the time of flight of the ultrasonic response obtained after propagation of a pulse emitted by a transducer and its interaction with the targets. While in-service the sodium flow creates turbulences that lead to temperature inhomogeneities, which translates into ultrasonic velocity inhomogeneities. These velocity variations could directly impact the accuracy of the target locating by introducing time of flight variations. A stochastic simulation model has been developed to calculate the propagation of ultrasonic waves in such an inhomogeneous medium. Using this approach, the travel time is randomly generated by a stochastic process whose inputs are the statistical moments of travel times known analytically. The stochastic model predicts beam deviations due to velocity inhomogeneities, which are similar to those provided by a determinist method, such as the ray method.

Palaeozoic gas charging in the Ahnet-Timimoun basin, Algeria

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

Cawley, S.J.; Wilson, N.P.; Primmer, T.

1995-08-01

The Ahnet-Timimoun Basin, Southern Algeria, contains significant gas reserves expelled from originally oil prone Silurian and Frasnian shales. The gas is reservoired in Devonian and Carboniferous clastics in inversion anticlines formed, primarily, during the Hercynian orogeny. Integration of organic and inorganic geochemical techniques, such as AFTA, ZFTA, fluid inclusion analysis, vitrinite and chitinizoan reflectance, is entirely consistent with gas generation 300 +/- 30MY, immediately prior to or synchronous with the Hercynian orogeny. Data from gas fields has shown the remobilisation of gas during post Hercynian tectonics. A {open_quotes}two-event{close_quotes} heating/cooling history is proposed: (1) Maximum burial and palaeotemperature at ca. 300more » +/- 30MY prior to or synchronous with Hercynian uplift and cooling. (2) Cooling from a secondary peak (lower than maximum) palaeotemperature at ca. 30-60My following Creataceous burial. Calibrated thermal modelling indicates that Palaeozoic source rocks were heated above 200{degrees}C in the Late Carboniferous. Such high temperatures are consistent with the widespread occurrence of pyrophyllite in Silurian shales. Two end-member thermal models can account for the observed maturities. The first is a constant high Pre-Hercynian heat flow which rapidly decreases during Hercynian uplift to remain at Present day values of 50-75mW/m{sup 2}. Gas expulsion in this case commences much earlier than trap formation. The second is {open_quotes}normal{close_quotes} heat flow of ca. 50mW/m{sup 2} until ca. 310My with a rapid increase at ca. 290My followed by an equally rapid drop to constant present day values - in this model, petroleum generation and expulsion is late in relation to structuring.« less

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

Lagier, B.; Rousset, B.; Hoa, C.

Superconducting magnets used in tokamaks undergo periodic heat load caused by cycling plasma operations inducing AC losses, neutrons fluxes and eddy currents in magnet structures. In the cryogenic system of JT60-SA tokamak, the Auxiliary Cold Box (ACB) distributes helium from the refrigerator to the cryogenic users and in particular to the superconducting magnets. ACB comprises a saturated helium bath with immersed heat exchangers, extracting heat from independent cooling loops. The supercritical helium flow in each cooling loop is driven by a cold circulator. In order to safely operate the refrigerator during plasma pulses, the interface between the ACB and themore » refrigerator shall be as stable as possible, with well-balanced bath inlet and outlet mass flows during cycling operation. The solution presented in this paper relies on a combination of regulations to smooth pulsed heat loads and to keep a constant refrigeration power during all the cycle. Two smoothing strategies are presented, both regulating the outlet mass flow of the bath: the first one using the bath as a thermal buffer and the second one storing energy in the loop by varying the cold circulator speed. The bath outlet mass flow is also controlled by an immersed resistive heater which enables a constant evaporation rate in the bath when power coming from the loops is decreasing. The refrigeration power is controlled so that the compensating power remains within an acceptable margin. Experimental validation is achieved using the HELIOS facility. This facility running at CEA Grenoble since 2010 is a scaled down model of the ACB bath and Central Solenoid magnet cooling loop of the JT60-SA tokamak. Test results show performances and robustness of the regulations.« less

Temperature-based death time estimation with only partially known environmental conditions.

PubMed

Mall, Gita; Eckl, Mona; Sinicina, Inga; Peschel, Oliver; Hubig, Michael

2005-07-01

The temperature-oriented death time determination is based on mathematical model curves of postmortem rectal cooling. All mathematical models require knowledge of the environmental conditions. In medico-legal practice homicide is sometimes not immediately suspected at the death scene but afterwards during external examination of the body. The environmental temperature at the death scene remains unknown or can only be roughly reconstructed. In such cases the question arises whether it is possible to estimate the time since death from rectal temperature data alone recorded over a longer time span. The present study theoretically deduces formulae which are independent of the initial and environmental temperatures and thus proves that the information needed for death time estimation is contained in the rectal temperature data. Since the environmental temperature at the death scene may differ from that during the temperature recording, an additional factor has to be used. This is that the body core is thermally well isolated from the environment and that the rectal temperature decrease after a sudden change of environmental temperature will continue for some time at a rate similar to that before the sudden change. The present study further provides a curve-fitting procedure for such scenarios. The procedure was tested in rectal cooling data of from 35 corpses using the most commonly applied model of Henssge. In all cases the time of death was exactly known. After admission to the medico-legal institute the bodies were kept at a constant environmental temperature for 12-36 h and the rectal temperatures were recorded continuously. The curve-fitting procedure led to valid estimates of the time since death in all experiments despite the unknown environmental conditions before admission to the institute. The estimation bias was investigated statistically. The 95% confidence intervals amounted to +/-4 h, which seems reasonable compared to the 95% confidence intervals of the Henssge model with known environmental temperature. The presented method may be of use for determining the time since death even in cases in which the environmental temperature and rectal temperature at the death scene have unintentionally not been recorded.

Application of the zone-melting technique to metal chelate systems-VI A new apparatus for zone-melting chromatography.

PubMed

Maeda, S; Kobayashi, H; Ueno, K

1973-07-01

An improved apparatus has been constructed for zone-melting chromatography. An essential feature of the apparatus is that the length of the molten zone can be kept constant during a zone-melting operation, by employing heating and cooling compartments which are separated from each other by double partition plates. Each compartment is heated or cooled with jets of hot or cold air. The apparatus is suitable for organic materials melting in the range between 40 degrees and 180 degrees . The distribution of metal ion along the column after zone melting of copper acetylacetonate in 2-methoxynaphthalene was a smooth curve. The plot of the position of maximum concentration, x(max), against the number of zone passes, n, gave a relationship in accordance with theoretical prediction.

Lead magnesium niobate actuator for micropositioning

DOEpatents

Swift, Charles D.; Bergum, John W.

1994-01-01

An improved lead magnesium niobate actuator is disclosed comprising a cylindrical lead magnesium niobate crystal stack mounted in a cylindrical casing wherein a bias means, such as one or more belleville washers, is located between one end of the crystal stack and a partially closed end of the casing; and adjustment means are provided which bear against the opposite end of the crystal stack, whereby an adjustable compressive force is constantly applied against the crystal stack, whether the crystal stack is actuated in an extended position, or is in an unactuated contracted position. In a preferred embodiment, cooling ports are provided for the circulation of coolant in the actuator to cool the crystal stack, and provision is made for removal and replacement of the crystal stack without disconnecting the actuator from the external device being actuated.

Nucleation kinetics from metastable zone widths for sonocrystallization of l-phenylalanine.

PubMed

Hazi Mastan, T; Lenka, Maheswata; Sarkar, Debasis

2017-05-01

This study investigates the effect of ultrasound on metastable zone width (MSZW) during crystallization of l-phenylalanine from aqueous solution. The solubility of l-phenylalanine in water was measured gravimetrically in the temperature range of 293.15-333.15K. The MSZW was measured by conventional polythermal method for four different cooling rates at five different saturation temperatures in absence and presence of ultrasound. The MSZW increased with increase in cooling rates and decreased with increase in saturation temperature. The application of ultrasound considerably reduced the MSZW for all the experiments. The obtained MSZW data are analysed using four different approaches to calculate various nucleation parameters. In presence of ultrasound, the apparent nucleation order decreased and nucleation rate constant increased significantly. Copyright © 2016 Elsevier B.V. All rights reserved.

Orbital glass state of the nearly metallic spinel cobalt vanadate

DOE PAGES

Koborinai, R.; Dissanayake, Sachith E.; Reehuis, M.; ...

2016-01-19

Strain, magnetization, dielectric relaxation, and unpolarized and polarized neutron diffraction measurements were performed to study the magnetic and structural properties of spinel Co 1–xV 2+xO 4. The strain measurement indicates that, upon cooling, ΔL/L in the order of ~10 –4 starts increasing below T C, becomes maximum at T max, and then decreases and changes its sign at T*. Neutron measurements indicate that a collinear ferrimagnetic order develops below T C and upon further cooling noncollinear ferrimagnetic ordering occurs below T max. At low temperatures, the dielectric constant exhibits a frequency dependence, indicating slow dynamics. Lastly, these results indicate themore » existence of an orbital glassy state at low temperatures in this nearly metallic frustrated magnet.« less

The impact of the weather conditions on the cooling performance of the heat pump driven by an internal natural gas combustion engine

NASA Astrophysics Data System (ADS)

Janovcová, Martina; Jandačka, Jozef; Malcho, Milan

2015-05-01

Market with sources of heat and cold offers unlimited choice of different power these devices, design technology, efficiency and price categories. New progressive technologies are constantly discovering, about which is still little information, which include heat pumps powered by a combustion engine running on natural gas. A few pieces of these installations are in Slovakia, but no studies about their work and effectiveness under real conditions. This article deals with experimental measurements of gas heat pump efficiency in cooling mode. Since the gas heat pump works only in system air - water, air is the primary low - energy source, it is necessary to monitor the impact of the climate conditions for the gas heat pump performance.

Contingency power for small turboshaft engines using water injection into turbine cooling air

NASA Technical Reports Server (NTRS)

Biesiadny, Thomas J.; Klann, Gary A.; Clark, David A.; Berger, Brett

1987-01-01

Because of one engine inoperative requirements, together with hot-gas reingestion and hot day, high altitude takeoff situations, power augmentation for multiengine rotorcraft has always been of critical interest. However, power augmentation using overtemperature at the turbine inlet will shorten turbine life unless a method of limiting thermal and mechanical stresses is found. A possible solution involves allowing the turbine inlet temperature to rise to augment power while injecting water into the turbine cooling air to limit hot-section metal temperatures. An experimental water injection device was installed in an engine and successfully tested. Although concern for unprotected subcomponents in the engine hot section prevented demonstration of the technique's maximum potential, it was still possible to demonstrate increases in power while maintaining nearly constant turbine rotor blade temperature.

A dual-mode textile for human body radiative heating and cooling

DOE PAGES

Hsu, Po -Chun; Liu, Chong; Song, Alex Y.; ...

2017-11-10

Maintaining human body temperature is one of the most basic needs for living, which often consumes a huge amount of energy to keep the ambient temperature constant. To expand the ambient temperature range while maintaining human thermal comfort, the concept of personal thermal management has been recently demonstrated in heating and cooling textiles separately through human body infrared radiation control. Realizing these two opposite functions within the same textile would represent an exciting scientific challenge and a significant technological advancement. We demonstrate a dual-mode textile that can perform both passive radiative heating and cooling using the same piece of textilemore » without any energy input. The dual-mode textile is composed of a bilayer emitter embedded inside an infrared-transparent nanoporous polyethylene (nanoPE) layer. We demonstrate that the asymmetrical characteristics of both emissivity and nanoPE thickness can result in two different heat transfer coefficients and achieve heating when the low-emissivity layer is facing outside and cooling by wearing the textile inside out when the high-emissivity layer is facing outside. This can expand the thermal comfort zone by 6.5°C. As a result, numerical fitting of the data further predicts 14.7°C of comfort zone expansion for dual-mode textiles with large emissivity contrast.« less

A dual-mode textile for human body radiative heating and cooling

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

Hsu, Po -Chun; Liu, Chong; Song, Alex Y.

Maintaining human body temperature is one of the most basic needs for living, which often consumes a huge amount of energy to keep the ambient temperature constant. To expand the ambient temperature range while maintaining human thermal comfort, the concept of personal thermal management has been recently demonstrated in heating and cooling textiles separately through human body infrared radiation control. Realizing these two opposite functions within the same textile would represent an exciting scientific challenge and a significant technological advancement. We demonstrate a dual-mode textile that can perform both passive radiative heating and cooling using the same piece of textilemore » without any energy input. The dual-mode textile is composed of a bilayer emitter embedded inside an infrared-transparent nanoporous polyethylene (nanoPE) layer. We demonstrate that the asymmetrical characteristics of both emissivity and nanoPE thickness can result in two different heat transfer coefficients and achieve heating when the low-emissivity layer is facing outside and cooling by wearing the textile inside out when the high-emissivity layer is facing outside. This can expand the thermal comfort zone by 6.5°C. As a result, numerical fitting of the data further predicts 14.7°C of comfort zone expansion for dual-mode textiles with large emissivity contrast.« less

A dual-mode textile for human body radiative heating and cooling

PubMed Central

Hsu, Po-Chun; Liu, Chong; Song, Alex Y.; Zhang, Ze; Peng, Yucan; Xie, Jin; Liu, Kai; Wu, Chun-Lan; Catrysse, Peter B.; Cai, Lili; Zhai, Shang; Majumdar, Arun; Fan, Shanhui; Cui, Yi

2017-01-01

Maintaining human body temperature is one of the most basic needs for living, which often consumes a huge amount of energy to keep the ambient temperature constant. To expand the ambient temperature range while maintaining human thermal comfort, the concept of personal thermal management has been recently demonstrated in heating and cooling textiles separately through human body infrared radiation control. Realizing these two opposite functions within the same textile would represent an exciting scientific challenge and a significant technological advancement. We demonstrate a dual-mode textile that can perform both passive radiative heating and cooling using the same piece of textile without any energy input. The dual-mode textile is composed of a bilayer emitter embedded inside an infrared-transparent nanoporous polyethylene (nanoPE) layer. We demonstrate that the asymmetrical characteristics of both emissivity and nanoPE thickness can result in two different heat transfer coefficients and achieve heating when the low-emissivity layer is facing outside and cooling by wearing the textile inside out when the high-emissivity layer is facing outside. This can expand the thermal comfort zone by 6.5°C. Numerical fitting of the data further predicts 14.7°C of comfort zone expansion for dual-mode textiles with large emissivity contrast. PMID:29296678

Magnon-induced superconductivity in field-cooled spin-1/2 antiferromagnets

NASA Astrophysics Data System (ADS)

Karchev, Naoum

2017-12-01

If, during the preparation, an external magnetic field is applied upon cooling we say it has been field cooled. A novel mechanism for insulator-metal transition and superconductivity in field-cooled spin-1 /2 antiferromagnets on bcc lattice is discussed. Applying a magnetic field along the sublattice B magnetization, we change the magnetic and transport properties of the material. There is a critical value Hcr1. When the magnetic field is below the critical one H Hcr1 the sublattice A electrons are delocalized and the material is metal. There is a second critical value Hcr2>Hcr1 . When H =Hcr2 , it is shown that the Zeeman splitting of the sublattice A electrons is zero and they do not contribute to the magnetization of the system. At this quantum partial order point (QPOP) the sublattice B transversal spin fluctuations (magnons) interact with sublattice A electrons inducing spin antiparallel p -wave superconductivity which coexists with magnetism. At zero temperature the magnetic moment of sublattice B electrons is maximal. Below the Néel temperature (TN) the gap is approximately constant with a small increase when the system approaches TN. It abruptly falls down to zero at temperatures above TN.

Comparison of Calculated and Experimental Temperatures and Coolant Pressure Losses for a Cascade of Small Air-Cooled Turbine Rotor Blades

NASA Technical Reports Server (NTRS)

Stepka, Francis S

1958-01-01

Average spanwise blade temperatures and cooling-air pressure losses through a small (1.4-in, span, 0.7-in, chord) air-cooled turbine blade were calculated and are compared with experimental nonrotating cascade data. Two methods of calculating the blade spanwise metal temperature distributions are presented. The method which considered the effect of the length-to-diameter ratio of the coolant passage on the blade-to-coolant heat-transfer coefficient and assumed constant coolant properties based on the coolant bulk temperature gave the best agreement with experimental data. The agreement obtained was within 3 percent at the midspan and tip regions of the blade. At the root region of the blade, the agreement was within 3 percent for coolant flows within the turbulent flow regime and within 10 percent for coolant flows in the laminar regime. The calculated and measured cooling-air pressure losses through the blade agreed within 5 percent. Calculated spanwise blade temperatures for assumed turboprop engine operating conditions of 2000 F turbine-inlet gas temperature and flight conditions of 300 knots at a 30,000-foot altitude agreed well with those obtained by the extrapolation of correlated experimental data of a static cascade investigation of these blades.

Intra-Abdominal Cooling System Limits Ischemia-Reperfusion Injury During Robot-Assisted Renal Transplantation.

PubMed

Meier, R P H; Piller, V; Hagen, M E; Joliat, C; Buchs, J-B; Nastasi, A; Ruttimann, R; Buchs, N C; Moll, S; Vallée, J-P; Lazeyras, F; Morel, P; Bühler, L

2018-01-01

Robot-assisted kidney transplantation is feasible; however, concerns have been raised about possible increases in warm ischemia times. We describe a novel intra-abdominal cooling system to continuously cool the kidney during the procedure. Porcine kidneys were procured by standard open technique. Groups were as follows: Robotic renal transplantation with (n = 11) and without (n = 6) continuous intra-abdominal cooling and conventional open technique with intermittent 4°C saline cooling (n = 6). Renal cortex temperature, magnetic resonance imaging, and histology were analyzed. Robotic renal transplantation required a longer anastomosis time, either with or without the cooling system, compared to the open approach (70.4 ± 17.7 min and 74.0 ± 21.5 min vs. 48.7 ± 11.2 min, p-values < 0.05). The temperature was lower in the robotic group with cooling system compared to the open approach group (6.5 ± 3.1°C vs. 22.5 ± 6.5°C; p = 0.001) or compared to the robotic group without the cooling system (28.7 ± 3.3°C; p < 0.001). Magnetic resonance imaging parenchymal heterogeneities and histologic ischemia-reperfusion lesions were more severe in the robotic group without cooling than in the cooled (open and robotic) groups. Robot-assisted kidney transplantation prolongs the warm ischemia time of the donor kidney. We developed a novel intra-abdominal cooling system that suppresses the noncontrolled rewarming of donor kidneys during the transplant procedure and prevents ischemia-reperfusion injuries. © 2017 The Authors. American Journal of Transplantation published by Wiley Periodicals, Inc. on behalf of American Society of Transplant Surgeons.

Probing aerosol indirect effect on deep convection using idealized cloud-resolving simulations with parameterized large-scale dynamics.

NASA Astrophysics Data System (ADS)

Anber, U.; Wang, S.; Gentine, P.; Jensen, M. P.

2017-12-01

A framework is introduced to investigate the indirect impact of aerosol loading on tropical deep convection using 3-dimentional idealized cloud-system resolving simulations with coupled large-scale circulation. The large scale dynamics is parameterized using a spectral weak temperature gradient approximation that utilizes the dominant balance in the tropics between adiabatic cooling and diabatic heating. Aerosol loading effect is examined by varying the number concentration of nuclei (CCN) to form cloud droplets in the bulk microphysics scheme over a wide range from 30 to 5000 without including any radiative effect as the radiative cooling is prescribed at a constant rate, to isolate the microphysical effect. Increasing aerosol number concentration causes mean precipitation to decrease monotonically, despite the increase in cloud condensates. Such reduction in precipitation efficiency is attributed to reduction in the surface enthalpy fluxes, and not to the divergent circulation, as the gross moist stability remains unchanged. We drive a simple scaling argument based on the moist static energy budget, that enables a direct estimation of changes in precipitation given known changes in surfaces enthalpy fluxes and the constant gross moist stability. The impact on cloud hydrometers and microphysical properties is also examined and is consistent with the macro-physical picture.

Superconducting-electromagnetic hybrid bearing using YBCO bulk blocks for passive axial levitation

NASA Astrophysics Data System (ADS)

Nicolsky, R.; de Andrade, R., Jr.; Ripper, A.; David, D. F. B.; Santisteban, J. A.; Stephan, R. M.; Gawalek, W.; Habisreuther, T.; Strasser, T.

2000-06-01

A superconducting/electromagnetic hybrid bearing has been designed using active radial electromagnetic positioning and a superconducting passive axial levitator. This bearing has been tested for an induction machine with a vertical shaft. The prototype was conceived as a four-pole, two-phase induction machine using specially designed stator windings for delivering torque and radial positioning simultaneously. The radial bearing uses four eddy-current sensors, displaced 90° from each other, for measuring the shaft position and a PID control system for feeding back the currents. The stator windings have been adapted from the ones of a standard induction motor. The superconducting axial bearing has been assembled with commercial NdFeB permanent magnets and a set of seven top-seeded-melt-textured YBCO large-grain cylindrical blocks. The bearing set-up was previously simulated by a finite element method for different permanent magnet-superconductor block configurations. The stiffness of the superconducting axial bearing has been investigated by measuring by a dynamic method the vertical and transversal elastic constants for different field cooling processes. The resulting elastic constants show a linear dependence on the air gap, i.e. the clearance between the permanent magnet assembly and the set of superconducting large-grain blocks, which is dependent on cooling distance.

The metallicity of the intracluster medium over cosmic time: further evidence for early enrichment

NASA Astrophysics Data System (ADS)

Mantz, Adam B.; Allen, Steven W.; Morris, R. Glenn; Simionescu, Aurora; Urban, Ondrej; Werner, Norbert; Zhuravleva, Irina

2017-12-01

We use Chandra X-ray data to measure the metallicity of the intracluster medium (ICM) in 245 massive galaxy clusters selected from X-ray and Sunyaev-Zel'dovich (SZ) effect surveys, spanning redshifts 0 < z < 1.2. Metallicities were measured in three different radial ranges, spanning cluster cores through their outskirts. We explore trends in these measurements as a function of cluster redshift, temperature and surface brightness 'peakiness' (a proxy for gas cooling efficiency in cluster centres). The data at large radii (0.5-1 r500) are consistent with a constant metallicity, while at intermediate radii (0.1-0.5 r500) we see a late-time increase in enrichment, consistent with the expected production and mixing of metals in cluster cores. In cluster centres, there are strong trends of metallicity with temperature and peakiness, reflecting enhanced metal production in the lowest entropy gas. Within the cool-core/sharply peaked cluster population, there is a large intrinsic scatter in central metallicity and no overall evolution, indicating significant astrophysical variations in the efficiency of enrichment. The central metallicity in clusters with flat surface brightness profiles is lower, with a smaller intrinsic scatter, but increases towards lower redshifts. Our results are consistent with other recent measurements of ICM metallicity as a function of redshift. They reinforce the picture implied by observations of uniform metal distributions in the outskirts of nearby clusters, in which most of the enrichment of the ICM takes place before cluster formation, with significant later enrichment taking place only in cluster centres, as the stellar populations of the central galaxies evolve.

How the Plant Temperature Links to the Air Temperature in the Desert Plant Artemisia ordosica.

PubMed

Yu, Ming-Han; Ding, Guo-Dong; Gao, Guang-Lei; Sun, Bao-Ping; Zhao, Yuan-Yuan; Wan, Li; Wang, De-Ying; Gui, Zi-Yang

2015-01-01

Plant temperature (Tp) is an important indicator of plant health. To determine the dynamics of plant temperature and self-cooling ability of the plant, we measured Tp in Artemisia ordosica in July, in the Mu Us Desert of Northwest China. Related factors were also monitored to investigate their effects on Tp, including environmental factors, such as air temperature (Ta), relative humidity, wind speed; and physiological factors, such as leaf water potential, sap flow, and water content. The results indicate that: 1) Tp generally changes in conjunction with Ta mainly, and varies with height and among the plant organs. Tp in the young branches is most constant, while it is the most sensitive in the leaves. 2) Correlations between Tp and environmental factors show that Tp is affected mainly by Ta. 3) The self-cooling ability of the plant was effective by midday, with Tp being lower than Ta. 4) Increasing sap flow and leaf water potential showed that transpiration formed part of the mechanism that supported self-cooling. Increased in water conductance and specific heat at midday may be additional factors that contribute to plant cooling ability. Therefore, our results confirmed plant self-cooling ability. The response to high temperatures is regulated by both transpiration speed and an increase in stem water conductance. This study provides quantitative data for plant management in terms of temperature control. Moreover, our findings will assist species selection with taking plant temperature as an index.

Low-Flow Liquid Desiccant Air-Conditioning: Demonstrated Performance and Cost Implications

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

Kozubal, E.; Herrmann, L.; Deru, M.

2014-09-01

Cooling loads must be dramatically reduced when designing net-zero energy buildings or other highly efficient facilities. Advances in this area have focused primarily on reducing a building's sensible cooling loads by improving the envelope, integrating properly sized daylighting systems, adding exterior solar shading devices, and reducing internal heat gains. As sensible loads decrease, however, latent loads remain relatively constant, and thus become a greater fraction of the overall cooling requirement in highly efficient building designs, particularly in humid climates. This shift toward latent cooling is a challenge for heating, ventilation, and air-conditioning (HVAC) systems. Traditional systems typically dehumidify by firstmore » overcooling air below the dew-point temperature and then reheating it to an appropriate supply temperature, which requires an excessive amount of energy. Another dehumidification strategy incorporates solid desiccant rotors that remove water from air more efficiently; however, these systems are large and increase fan energy consumption due to the increased airside pressure drop of solid desiccant rotors. A third dehumidification strategy involves high flow liquid desiccant systems. These systems require a high maintenance separator to protect the air distribution system from corrosive desiccant droplet carryover and so are more commonly used in industrial applications and rarely in commercial buildings. Both solid desiccant systems and most high-flow liquid desiccant systems (if not internally cooled) add sensible energy which must later be removed to the air stream during dehumidification, through the release of sensible heat during the sorption process.« less

Experimental investigations on cryogenic cooling by liquid nitrogen in the end milling of hardened steel

NASA Astrophysics Data System (ADS)

Ravi, S.; Pradeep Kumar, M.

2011-09-01

Milling of hardened steel generates excessive heat during the chip formation process, which increases the temperature of cutting tool and accelerates tool wear. Application of conventional cutting fluid in milling process may not effectively control the heat generation also it has inherent health and environmental problems. To minimize health hazard and environmental problems caused by using conventional cutting fluid, a cryogenic cooling set up is developed to cool tool-chip interface using liquid nitrogen (LN 2). This paper presents results on the effect of LN 2 as a coolant on machinability of hardened AISI H13 tool steel for varying cutting speed in the range of 75-125 m/min during end milling with PVD TiAlN coated carbide inserts at a constant feed rate. The results show that machining with LN 2 lowers cutting temperature, tool flank wear, surface roughness and cutting forces as compared with dry and wet machining. With LN 2 cooling, it has been found that the cutting temperature was reduced by 57-60% and 37-42%; the tool flank wear was reduced by 29-34% and 10-12%; the surface roughness was decreased by 33-40% and 25-29% compared to dry and wet machining. The cutting forces also decreased moderately compared to dry and wet machining. This can be attributed to the fact that LN 2 machining provides better cooling and lubrication through substantial reduction in the cutting zone temperature.

MoXy fiber with active cooling cap for bovine prostate vaporization with high power 200W 532 nm laser

NASA Astrophysics Data System (ADS)

Peng, Steven Y.; Kang, Hyun Wook; Pirzadeh, Homa; Stinson, Douglas

2011-03-01

A novel MoXyTM fiber delivery device with Active Cooling Cap (ACCTM) is designed to transmit up to 180W of 532 nm laser light to treat benign prostatic hyperplasia (BPH). Under such high power tissue ablation, effective cooling is key to maintaining fiber power transmission and ensuring the reliability of the fiber delivery device To handle high power and reduce fiber degradation, the MoXy fiber features a larger core size (750 micrometer) and an internal fluid channel to ensure better cooling of the fiber tip to prevent the cap from burning, detaching, or shattering during the BPH treatment. The internal cooling channel was created with a metal cap and tubing that surrounds the optical fiber. In this study MoXy fibers were used to investigate the effect of power levels of 120 and 200 W on in-vitro bovine prostate ablation using a 532 nm XPSTM laser system. For procedures requiring more than 100 kJ, the MoXy fiber at 200W removed tissue at twice the rate of the current HPS fiber at 120W. The fiber maintained a constant tissue vaporization rate during the entire tissue ablation process. The coagulation at 200W was about 20% thicker than at 120W. In conclusion, the new fibers at 200W doubled the tissue removal rate, maintained vaporization efficiency throughout delivery of 400kJ energy, and induced similar coagulation to the existing HPS fiber at 120W.

Cenozoic topographic build-up of the Iranien plateau: first constraints from low-temperature thermochronology

NASA Astrophysics Data System (ADS)

François, Thomas; Agard, Philippe; Meyer, Bertrand; Zarrinkoub, Mohammad; Chung, Sun-Lin; Bernet, Matthias; Burov, Evgueni

2013-04-01

The Iranian plateau is a smooth topographic high at the rear of the Zagros mountains, with average elevation of c. 1.5 km. Its formation is thought to result from the collision between the Arabian and Eurasian plates since ~35 Myrs, following a long-standing subduction, and represents an interesting analogue to the so far better documented Tibetan plateau. Yet, while the Zagros orogeny was reappraised by numerous authors over the past few years, the topographic build-up of both the Zagros and the Iranian plateau remains ill-constrained. We herein present (U-Th)/He and fission track (FT) thermochronology results to reconstruct the Cenozoic tectonic evolution of the Iranien plateau and quantify the age and amount of vertical movements. Apatite and zircon single grain cooling age data were collected on plutonic rocks (for which crystallization ages were already available: Chiu et al., 2010) from the internal domains of Sanandaj-Sirjan Zone (SSZ), Urumieh-Doktar magmatic arc (UDMA), Central Iran and, for comparison, Kopet Dagh. We stress that an important milestone for topographic build-up is the presence of the marine Qom formation (coeval with the external Asmari formation) in the UDMA and part of the SSZ, indicating that the plateau was at or near sea level at 20 Ma. Temperature time paths inferred from low temperature thermochronology suggest a spatial and temporal separation of exhumation processes. The results show that the SSZ was exhumed very early in the collision process (essentially before 20 Ma), with a likely acceleration around the Oligocene (i.e., at the onset of continental collision) from 0.05 to 0.3 mm/yr. Post-collision cooling along the UDMA is marked by an average, constant exhumation rate of 0.3-0.4 mm/yr, which suggests that no significant increase or decrease of erosion occurred since continental collision. In Central Iran, the overlap (within error) of ZrFT, AFT and AHe ages from gneissic samples points to their rapid cooling during the upper Eocene (~42°C/Ma). These results are consistent with the reported formation of several small metamorphic core-complexes in Central Iran towards the end of oceanic subduction, possibly associated with slab rollback. Our thermochronological data allow to locate major topographic and erosional changes during the Cenozoic. Topographic build-up occurred in the SSZ during oceanic subduction and onset of collision (35 Ma) and shifted to the UDMA during continental collision (20 Ma), while progressing towards the external parts of the belt during the Mio-Pliocene (5-10 Ma). Most importantly, we conclude that the uplift of the Iranian plateau was a constant, steady process over the last 20 Ma, at least as a first approximation, as inferred from the combination of constant exhumation in the UDMA and sedimentary records of the central Iranian basin.

Compton cooling and the signature of Quasi Periodic Oscillations for the transient black hole candidate H 1743-322

NASA Astrophysics Data System (ADS)

Mondal, S.; Chakrabarti, S. K.; Debnath, D.; Jana, A.; Molla, A. A.

In black hole accretion cooling of the Compton cloud has an enormous effect on the dynamics of post-shock flow. We demonstrate that the Compton cooling is highly responsible for the origin of Quasi Periodic Oscillations (QPOs) during the outburst time of the galactic black hole candidates (BHCs). Our study shows that the disk oscillation will take place when infall time from the shock roughly agrees with cooling time in the post-shock region i.e., the resonance condition. We believe that this oscillation is responsible for the origin of QPOs and will occur only when a particular disk condition (disk rate, halo rate and shock strength) satisfies. We also confirm that shock moves with an average velocity of a few meters/sec for the transient BHC H1743-322 due to the presence of Compton cooling.

Modeling and Comparison of Options for the Disposal of Excess Weapons Plutonium in Russia

DTIC Science & Technology

2002-04-01

fuel LWR cooling time LWR Pu load rate LWR net destruction frac ~ LWR reactors op life mox core frac Excess Separated Pu HTGR Cycle Pu in Waste LWR MOX...reflecting the cycle used in this type of reactor. For the HTGR , the entire core consists of plutonium fuel , therefore a core fraction is not specified...cooling time Time spent fuel unloaded from HTGR reactor must cool before permanently stored 3 years Mox core fraction Fraction of

Early formation and long-term stability of continents resulting from decompression melting in a convecting mantle

NASA Astrophysics Data System (ADS)

De Smet, J.; Van den Berg, A. P.; Vlaar, N. J.

2000-07-01

The origin of stable old continental cratonic roots is still debated. We present numerical modelling results which show rapid initial formation during the Archaean of continental roots of ca. 200 km thick. These results have been obtained from an upper mantle thermal convection model including differentiation by pressure release partial melting of mantle peridotite. The upper mantle model includes time-dependent radiogenic heat production and thermal coupling with a heat reservoir representing the Earth's lower mantle and core. This allows for model experiments including secular cooling on a time-scale comparable to the age of the Earth. The model results show an initial phase of rapid continental root growth of ca. 0.1 billion year, followed by a more gradual increase of continental volume by addition of depleted material produced through hot diapiric, convective upwellings which penetrate the continental root from below. Within ca. 0.6 Ga after the start of the experiment, secular cooling of the mantle brings the average geotherm below the peridotite solidus thereby switching off further continental growth. At this time the thickness of the continental root has grown to ca. 200 km. After 1 Ga of secular cooling small scale thermal instabilities develop at the bottom of the continental root causing continental delamination without breaking up the large scale layering. This delaminated material remixes with the deeper layers. Two more periods, each with a duration of ca. 0.5 Ga and separated by quiescent periods were observed when melting and continental growth was reactivated. Melting ends at 3 Ga. Thereafter secular cooling proceeds and the compositionally buoyant continental root is stabilized further through the increase in mechanical strength induced by the increase of the temperature dependent mantle viscosity. Fluctuating convective velocity amplitudes decrease to below 10 mma -1 and the volume average temperature of the sub-continental convecting mantle has decreased ca. 340 K after 4 Ga. Surface heatflow values decrease from 120 to 40 mW m -2 during the 4 Ga model evolution. The surface heatflow contribution from an almost constant secular cooling rate was estimated to be 6 mW m -2, in line with recent observational evidence. The modelling results show that the combined effects of compositional buoyancy and strong temperature dependent rheology result in continents which overall remain stable for a duration longer than the age of the Earth. Tracer particles have been used for studying the patterns of mantle differentiation in greater detail. The observed ( p, T, F, t)-paths are consistent with proposed stratification and thermo-mechanical history of the depleted continental root, which have been inferred from mantle xenoliths and other upper mantle samples. In addition, the particle tracers have been used to derive the thermal age of the modelled continental root, defined by a hypothetical closing temperature.

System Would Regulate Low Gas Pressure

NASA Technical Reports Server (NTRS)

Frazer, Robert E.

1994-01-01

System intended to maintain gases in containers at pressures near atmospheric. Includes ballast volume in form of underinflated balloon that communicates with working volume. Balloon housed in rigid chamber not subjected to extremes of temperature of working volume. Pressure in chamber surrounding balloon regulated at ambient atmospheric pressure or at constant small differential pressure above or below ambient. Expansion and contraction of balloon accommodates expansion or contraction of gas during operational heating or cooling in working volume, maintaining pressure in working volume at ambient or constant differential above or below ambient. Gas lost from system due to leakage or diffusion, low-pressure sensor responds, signaling valve actuators to supply more gas to working volume. If pressure rises too high, overpressure relief valve opens before excessive pressure damages system.

Magnetic and dielectric behavior of chromium substituted Co-Mg ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Jadoun, Priya; Jyoti, Prashant, B. L.; Dolia, S. N.; Bhatnagar, D.; Saxena, V. K.

2016-05-01

The chromium doped Co-Mg ferrite with composition Co0.5Mg0.5Cr0.2Fe1.8O4 has been synthesized using sol-gel auto combustion method. The crystal structure has been analyzed by X-ray diffraction (XRD) technique. XRD pattern reveals the formation of single phase cubic spinel structure. The magnetic measurements show ferromagnetic behavior at room temperature and large coercivity is observed on cooling down the temperature to 20 K. Dielectric constant (ɛ') and dielectric loss tangent (tan δ) have been determined at room temperature as a function of frequency in the frequency range 75 kHz to 80 MHz. The decrease in dielectric constant with increasing frequency attributes to Maxwell Wagner model and conduction mechanism in ferrites.

Dielectric evidence for possible type-II multiferroicity in α-RuCl3

NASA Astrophysics Data System (ADS)

Zheng, JiaCheng; Cui, Yi; Li, TianRun; Ran, KeJing; Wen, JinSheng; Yu, WeiQiang

2018-05-01

$\\alpha$-RuCl$_3$ is a Mott insulator with a honeycomb lattice with strong spin-orbit coupling. We report dielectric measurements on $\\alpha$-RuCl$_3$ single crystals under field. At zero field, the dielectric constant, $\\epsilon$, drops rapidly when cooled through the magnetic transition temperature T$_N$. With increasing field, the onset of the drop in $\\epsilon$ tracks the T$_N$. Such behavior is absent with field above a critical value H$_c$ ~ 7.5 T, indicating the onset of a quantum phase transition. Our data suggest that the dielectric constant can be used as a probe of magnetic ordering in $\\alpha$-RuCl$_3$, and $\\alpha$-RuCl$_3$ is a possible type-II multiferroics.

Optimisation of multi-layer rotationally moulded foamed structures

NASA Astrophysics Data System (ADS)

Pritchard, A. J.; McCourt, M. P.; Kearns, M. P.; Martin, P. J.; Cunningham, E.

2018-05-01

Multi-layer skin-foam and skin-foam-skin sandwich constructions are of increasing interest in the rotational moulding process for two reasons. Firstly, multi-layer constructions can improve the thermal insulation properties of a part. Secondly, foamed polyethylene sandwiched between solid polyethylene skins can increase the mechanical properties of rotationally moulded structural components, in particular increasing flexural properties and impact strength (IS). The processing of multiple layers of polyethylene and polyethylene foam presents unique challenges such as the control of chemical blowing agent decomposition temperature, and the optimisation of cooling rates to prevent destruction of the foam core; therefore, precise temperature control is paramount to success. Long cooling cycle times are associated with the creation of multi-layer foam parts due to their insulative nature; consequently, often making the costs of production prohibitive. Devices such as Rotocooler®, a rapid internal mould water spray cooling system, have been shown to have the potential to significantly decrease cooling times in rotational moulding. It is essential to monitor and control such devices to minimise the warpage associated with the rapid cooling of a moulding from only one side. The work presented here demonstrates the use of threaded thermocouples to monitor the polymer melt in multi-layer sandwich constructions, in order to analyse the cooling cycle of multi-layer foamed structures. A series of polyethylene skin-foam test mouldings were produced, and the effect of cooling medium on foam characteristics, mechanical properties, and process cycle time were investigated. Cooling cycle time reductions of 45%, 26%, and 29% were found for increasing (1%, 2%, and 3%) chemical blowing agent (CBA) amount when using internal water cooling technology from ˜123°C compared with forced air cooling (FAC). Subsequently, a reduction of IS for the same skin-foam parts was found to be 1%, 4%, and 16% compared with FAC.

Heat transfer characteristics of hypersonic waveriders with an emphasis on the leading edge effects. M.S. Thesis, 1991

NASA Technical Reports Server (NTRS)

Vanmol, Denis O.; Anderson, John D., Jr.

1992-01-01

The heat transfer characteristics in surface radiative equilibrium and the aerodynamic performance of blunted hypersonic waveriders are studied along two constant dynamic pressure trajectories for four different Mach numbers. The inviscid leading edge drag was found to be a small (4 to 8 percent) but not negligible fraction of the inviscid drag of the vehicle. Although the viscous drag at the leading edge can be neglected, the presence of the leading edge will influence the transition pattern of the upper and the lower surfaces and therefore affect the viscous drag of the entire vehicle. For an application similar to the National Aerospace Plane (NASP), the present study demonstrates that the waverider remains a valuable concept at high Mach numbers if a state-of-the-art active cooling device is used along the leading edge. At low Mach number (less than 5), the study shows the surface radiative cooling might be sufficient. In all cases, radiative cooling is sufficient for the upper and lower surfaces of the vehicle if ceramic composites are used as thermal protection.

Heat transfer and performance characteristics of axial cooling fans with downstream guide vanes

NASA Astrophysics Data System (ADS)

Terzis, Alexandros; Stylianou, Ioannis; Kalfas, Anestis I.; Ott, Peter

2012-04-01

This study examines experimentally the effect of stators on the performance and heat transfer characteristics of small axial cooling fans. A single fan impeller, followed by nine stator blades in the case of a complete stage, was used for all the experimental configurations. Performance measurements were carried out in a constant speed stage performance test rig while the transient liquid crystal technique was used for the heat transfer measurements. Full surface heat transfer coefficient distributions were obtained by recording the temperature history of liquid crystals on a target plate. The experimental data indicated that the results are highly affected by the flow conditions at the fan outlet. Stators can be beneficial in terms of pressure drop and efficiency, and thus more economical operation, as well as, in the local heat transfer distribution at the wake of the stator blades if the fan is installed very close to the cooling object. However, as the separation distance increases, enhanced heat transfer rate in the order of 25% is observed in the case of the fan impeller.

Laser Cooling for Heavy-Ion Fusion (HIF)

NASA Astrophysics Data System (ADS)

Ho, D. D.-M.; Brandon, S.; Lee, Y.

1997-05-01

A critical requirement for HIF is the ability to focus space-charge dominated beams onto a millimeter-size spot. However, chromatic aberration can result in a substantial fraction of the beam ions falling outside the spot radius. Because of the space-charge force, correcting the chromatic aberration using sextupoles is impractical. Success in laser cooling of low-current ion beams in storage rings leads us to explore the application of laser cooling to HIF. Basic scheme: After the beams have been accelerated to the desired energy by the recirculating induction linac, we let the beams coast around at constant energy. For efficient interaction between the laser and the beam ions, we use Ba+ beams. We use two lasers to pump the transitions in the Ba+ for generating the laser force FL. There is also an auxiliary force Fa, which is in the opposition direction of FL, provided by the induction cores. The momentum spread along the beam can be compressed by FL and Fa. We will present preliminary PIC simulations using the PIC code CONDOR. Potential difficulties caused by velocity space instabilities will be discussed.

The numerical analysis of the rotational theory for the formation of lunar globules

NASA Technical Reports Server (NTRS)

Ross, J.; Bastin, J.; Stewart, K.

1982-01-01

The morphology of lunar globules is studied through the application of a numerical analysis of their rotation in space during cooling. It is assumed that molten rock is shot from the surface of the moon, solidifies in space above the moon and then falls back to the surface. The rotational theory studied makes the following assumptions: the volume of the molten rock does not change during cooling; the angular momentum is conserved; there are no internal motions because of the high viscosity of the molten rock, i.e., in equilibrium the globule is rotating as a rigid body; finally, the kinetic reaction of the globule to the forces is fast relative to the rate of cooling, i.e., the globule reaches equilibrium at constant energy. These assumptions are subjected to numerical analysis yielding good agreement between the actual globule shapes and the numerical results, but leaving some doubt as to the validity of the rotational theory due to the failure to establish the existence of true local minima and an incomplete understanding of the thermokentics.

X-Ray spectroscopy of cooling flows

NASA Technical Reports Server (NTRS)

Prestwich, Andrea

1996-01-01

Cooling flows in clusters of galaxies occur when the cooling time of the gas is shorter than the age of the cluster; material cools and falls to the center of the cluster potential. Evidence for short X-ray cooling times comes from imaging studies of clusters and X-ray spectroscopy of a few bright clusters. Because the mass accretion rate can be high (a few 100 solar mass units/year) the mass of material accumulated over the lifetime of a cluster can be as high as 10(exp 12) solar mass units. However, there is little evidence for this material at other wavelengths, and the final fate of the accretion material is unknown. X-ray spectra obtained with the Einstein SSS show evidence for absorption; if confirmed this result would imply that the accretion material is in the form of cool dense clouds. However ice on the SSS make these data difficult to interpret. We obtained ASCA spectra of the cooling flow cluster Abell 85. Our primary goals were to search for multi-temperature components that may be indicative of cool gas; search for temperature gradients across the cluster; and look for excess absorption in the cooling region.

The Relationship Between Brightest Cluster Galaxy Star Formation and the Intracluster Medium in CLASH

NASA Astrophysics Data System (ADS)

Fogarty, Kevin; Postman, Marc; Larson, Rebecca; Donahue, Megan; Moustakas, John

2017-09-01

We study the nature of feedback mechanisms in the 11 CLASH brightest cluster galaxies (BCGs) that exhibit extended ultraviolet and nebular line emission features. We estimate star formation rates (SFRs), dust masses, and starburst durations using a Bayesian photometry-fitting technique that accounts for both stellar and dust emission from the UV through far-IR. By comparing these quantities to intracluster medium (ICM) cooling times and freefall times derived from X-ray observations and lensing estimates of the cluster mass distribution, we discover a tight relationship between the BCG SFR and the ICM cooling time to freefall time ratio, {t}{cool}/{t}{ff}, with an upper limit on the intrinsic scatter of 0.15 dex. Furthermore, starburst durations may correlate with ICM cooling times at a radius of 0.025 {R}500, and the two quantities converge upon reaching the gigayear regime. Our results provide a direct observational link between the thermodynamical state of the ICM and the intensity and duration of BCG star formation activity, and appear consistent with a scenario where active galactic nuclei induce condensation of thermally unstable ICM overdensities that fuel long-duration (>1 Gyr) BCG starbursts. This scenario can explain (a) how gas with a low cooling time is depleted without causing a cooling flow and (b) the scaling relationship between SFR and {t}{cool}/{t}{ff}. We also find that the scaling relation between SFR and dust mass in BCGs with SFRs < 100 {M}⊙ yr-1 is similar to that in star-forming field galaxies; BCGs with large (> 100 {M}⊙ yr-1) SFRs have dust masses comparable to extreme starbursts.

Influence of solar variability on the infrared radiative cooling of the thermosphere from 2002 to 2014.

PubMed

Mlynczak, Martin G; Hunt, Linda A; Mertens, Christopher J; Thomas Marshall, B; Russell, James M; Woods, Thomas; Earl Thompson, R; Gordley, Larry L

2014-04-16

Infrared radiative cooling of the thermosphere by carbon dioxide (CO 2 , 15 µm) and by nitric oxide (NO, 5.3 µm) has been observed for 12 years by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite. For the first time we present a record of the two most important thermospheric infrared cooling agents over a complete solar cycle. SABER has documented dramatic variability in the radiative cooling on time scales ranging from days to the 11 year solar cycle. Deep minima in global mean vertical profiles of radiative cooling are observed in 2008-2009. Current solar maximum conditions, evidenced in the rates of radiative cooling, are substantially weaker than prior maximum conditions in 2002-2003. The observed changes in thermospheric cooling correlate well with changes in solar ultraviolet irradiance and geomagnetic activity during the prior maximum conditions. NO and CO 2 combine to emit 7 × 10 18 more Joules annually at solar maximum than at solar minimum. First record of thermospheric IR cooling rates over a complete solar cycleIR cooling in current solar maximum conditions much weaker than prior maximumVariability in thermospheric IR cooling observed on scale of days to 11 years.

Laser cooling of BH and GaF: insights from an ab initio study.

PubMed

Gao, Yu-feng; Gao, Tao

2015-04-28

The feasibility of laser cooling BH and GaF is investigated using ab initio quantum chemistry. The ground state X (1)Σ(+) and first two excited states (3)Π and (1)Π of BH and GaF are calculated using the multireference configuration interaction (MRCI) level of theory. For GaF, the spin-orbit coupling effect is also taken into account in the electronic structure calculations at the MRCI level. Calculated spectroscopic constants for BH and GaF show good agreement with available theoretical and experimental results. The highly diagonal Franck-Condon factors (BH: f00 = 0.9992, f11 = 0.9908, f22 = 0.9235; GaF: f00 = 0.997, f11 = 0.989, f22 = 0.958) for the (1)Π (v' = 0-2) → X (1)Σ(+) (v = 0-2) transitions in BH and GaF are determined, which are found to be in good agreement with the theoretical and experimental data. Radiative lifetime calculations of the (1)Π (v' = 0-2) state (BH: 131, 151, and 187 ns; GaF: 2.26, 2.36, and 2.48 ns) are found to be short enough for rapid laser cooling. The proposed laser cooling schemes that drive the (1)Π (v' = 0) → X (1)Σ(+) (v = 0) transition use just one laser wavelength λ00 (BH: 436 nm, GaF: 209 nm). Though the cooling wavelength of GaF is deep in the UVC, a frequency quadrupled Ti:sapphire laser (189-235 nm) could be capable of generating useful quantities of light at this wavelength. The present results indicate that BH and GaF are two good choices of molecules for laser cooling.

Solar cycle variability of nonmigrating tides in the infrared cooling of the thermosphere

NASA Astrophysics Data System (ADS)

Nischal, N.; Oberheide, J.; Mlynczak, M. G.; Marsh, D. R.

2017-12-01

Nitric Oxide (NO) at 5.3 μm and Carbon dioxide (CO2) at 15 μm are the major infrared emissions responsible for the radiative cooling of the thermosphere. We study the impact of two important diurnal nonmigrating tides, the DE2 and DE3, on NO and CO2 infrared emissions over a complete solar cycle (2002-2013) by (i) analyzing NO and CO2 cooling rate data from SABER and (ii) photochemical modeling using dynamical tides from a thermospheric empirical tidal model, CTMT. Both observed and modeled results show that the NO cooling rate amplitudes for DE2 and DE3 exhibit strong solar cycle dependence. NO 5.3 μm cooling rate tides are relatively unimportant for the infrared energy budget during solar minimum but important during solar maximum. On the other hand DE2 and DE3 in CO2 show comparatively small variability over a solar cycle. CO2 15 μm cooling rate tides remain, to a large extent, constant between solar minimum and maximum. This different responses by NO and CO2 emissions to the DE2 and DE3 during a solar cycle comes form the fact that the collisional reaction rate for NO is highly sensitive to the temperature comparative to that for CO2. Moreover, the solar cycle variability of these nonmigrating tides in thermospheric infrared emissions shows a clear QBO signals substantiating the impact of tropospheric weather system on the energy budget of the thermosphere. The relative contribution from the individual tidal drivers; temperature, density and advection to the observed DE2 and DE3 tides does not vary much over the course of the solar cycle, and this is true for both NO and CO2 emissions.

Temperature range of the liquid-glass transition

NASA Astrophysics Data System (ADS)

Sanditov, D. S.; Darmaev, M. V.; Sanditov, B. D.

2016-02-01

It has been shown that the currently used method for calculating the temperature range of δ T g in the glass transition equation qτ g = δ T g as the difference δ T g = ( T 12- T 13) results in overestimated values, which is explained by the assumption of a constant activation energy of glass transition in deriving the calculation equation ( T 12 and T 13 are the temperatures corresponding to the logarithmic viscosity values of logη = 12 and logη = 13). The methods for the evaluation of δ T g using the Williams-Landel-Ferry equation and the model of delocalized atoms are considered, the results of which are in satisfactory agreement with the product qτ g ( q is the cooling rate of the melt and τ g is the structural relaxation time at the glass transition temperature). The calculation of τ g for inorganic glasses and amorphous organic polymers is proposed.

Modelling of photodegradation in solar cell modules of substrate and superstrate design made with ethylene-vinyl acetate as pottant material

NASA Technical Reports Server (NTRS)

Somersall, A. C.; Guillet, J. E.

1983-01-01

A computer model was developed which can generate realistic concentration versus time profiles of the chemical species formed during photooxidation of hydrocarbon polymers using as input data a set of elementary reactions with corresponding rate constants and initial conditions. The results of computer simulation have been shown to be consistent with the general experimental observations of the photooxidation of polyethylene exposed to sunlight at ambient temperatures. The useful lifetime (5% oxidation) of the unstabilized polyethylene is predicted to vary from a few months in hot weather (100 F) to almost two years in cool weather (45 F) with an apparent net activation energy of 10 kcal/mol. Modelling studies of alternate mechanisms for stabilization of clear, amorphous, linear polyethylene suggest that the optimum stabilizer would be a molecularly dispensed additive in very low concentration which can trap peroxy radicals and also decompose hydroperoxides.

Self-organization of S adatoms on Au(111): √3R30° rows at low coverage

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

Walen, Holly, E-mail: hwalen@iastate.edu; Liu, Da-Jiang; Oh, Junepyo

Using scanning tunneling microscopy, we observe an adlayer structure that is dominated by short rows of S atoms, on unreconstructed regions of a Au(111) surface. This structure forms upon adsorption of low S coverage (less than 0.1 monolayer) on a fully reconstructed clean surface at 300 K, then cooling to 5 K for observation. The rows adopt one of three orientations that are rotated by 30° from the close-packed directions of the Au(111) substrate, and adjacent S atoms in the rows are separated by √3 times the surface lattice constant, a. Monte Carlo simulations are performed on lattice-gas models, derivedmore » using a limited cluster expansion based on density functional theory energetics. Models which include long-range pairwise interactions (extending to 5a), plus selected trio interactions, successfully reproduce the linear rows of S atoms at reasonable temperatures.« less

Self-organization of S adatoms on Au(111): √3R30° rows at low coverage

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

Walen, Holly; Liu, Da -Jiang; Oh, Junepyo

Using scanning tunneling microscopy, we observe an adlayer structure that is dominated by short rows of S atoms, on unreconstructed regions of a Au(111) surface. This structure forms upon adsorption of low S coverage (less than 0.1 monolayer) on a fully reconstructed cleansurface at 300 K, then cooling to 5 K for observation. The rows adopt one of three orientations that are rotated by 30° from the close-packed directions of the Au(111) substrate, and adjacent S atoms in the rows are separated by √3 times the surface lattice constant, a. Monte Carlo simulations are performed on lattice-gas models, we derivedmore » using a limited cluster expansion based on density functional theory energetics. Furthermore, models which include long-range pairwise interactions (extending to 5a), plus selected trio interactions, successfully reproduce the linear rows of S atoms at reasonable temperatures.« less

Self-organization of S adatoms on Au(111): √3R30° rows at low coverage

DOE PAGES

Walen, Holly; Liu, Da -Jiang; Oh, Junepyo; ...

2015-07-06

Using scanning tunneling microscopy, we observe an adlayer structure that is dominated by short rows of S atoms, on unreconstructed regions of a Au(111) surface. This structure forms upon adsorption of low S coverage (less than 0.1 monolayer) on a fully reconstructed cleansurface at 300 K, then cooling to 5 K for observation. The rows adopt one of three orientations that are rotated by 30° from the close-packed directions of the Au(111) substrate, and adjacent S atoms in the rows are separated by √3 times the surface lattice constant, a. Monte Carlo simulations are performed on lattice-gas models, we derivedmore » using a limited cluster expansion based on density functional theory energetics. Furthermore, models which include long-range pairwise interactions (extending to 5a), plus selected trio interactions, successfully reproduce the linear rows of S atoms at reasonable temperatures.« less

Self-organization of S adatoms on Au(111): √3R30° rows at low coverage.

PubMed

Walen, Holly; Liu, Da-Jiang; Oh, Junepyo; Lim, Hyunseob; Evans, J W; Kim, Yousoo; Thiel, P A

2015-07-07

Using scanning tunneling microscopy, we observe an adlayer structure that is dominated by short rows of S atoms, on unreconstructed regions of a Au(111) surface. This structure forms upon adsorption of low S coverage (less than 0.1 monolayer) on a fully reconstructed clean surface at 300 K, then cooling to 5 K for observation. The rows adopt one of three orientations that are rotated by 30° from the close-packed directions of the Au(111) substrate, and adjacent S atoms in the rows are separated by √3 times the surface lattice constant, a. Monte Carlo simulations are performed on lattice-gas models, derived using a limited cluster expansion based on density functional theory energetics. Models which include long-range pairwise interactions (extending to 5a), plus selected trio interactions, successfully reproduce the linear rows of S atoms at reasonable temperatures.

Thermal analyses of the IF-300 shipping cask

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

Meier, J.K.

1978-07-01

In order to supply temperature data for structural testing and analysis of shipping casks, a series of thermal analyses using the TRUMP thermal analyzer program were performed on the GE IF-300 spent fuel shipping cask. Major conclusions of the analyses are: (1) Under normal cooling conditions and a cask heat load of 262,000 BTU/h, the seal area of the cask will be roughly 100/sup 0/C (180/sup 0/F) above the ambient surroundings. (2) Under these same conditions the uranium shield at the midpoint of the cask will be between 69/sup 0/C (125/sup 0/F) and 92/sup 0/C (166/sup 0/F) above the ambientmore » surroundings. (3) Significant thermal gradients are not likely to develop between the head studs and the surrounding metal. (4) A representative time constant for the cask as a whole is on the order of one day.« less

Stratospheric aerosol geoengineering

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

Robock, Alan

2015-03-30

The Geoengineering Model Intercomparison Project, conducting climate model experiments with standard stratospheric aerosol injection scenarios, has found that insolation reduction could keep the global average temperature constant, but global average precipitation would reduce, particularly in summer monsoon regions around the world. Temperature changes would also not be uniform; the tropics would cool, but high latitudes would warm, with continuing, but reduced sea ice and ice sheet melting. Temperature extremes would still increase, but not as much as without geoengineering. If geoengineering were halted all at once, there would be rapid temperature and precipitation increases at 5–10 times the rates frommore » gradual global warming. The prospect of geoengineering working may reduce the current drive toward reducing greenhouse gas emissions, and there are concerns about commercial or military control. Because geoengineering cannot safely address climate change, global efforts to reduce greenhouse gas emissions and to adapt are crucial to address anthropogenic global warming.« less

Development of a compact freeze vacuum drying for jelly fish (Schypomedusae)

NASA Astrophysics Data System (ADS)

Alhamid, M. Idrus; Yulianto, M.; Nasruddin

2012-06-01

A new design of a freeze vacuum drying with internal cooling and heater from condenser's heat loss was built and tested. The dryer was used to dry jelly fish (schypomedusae), to study the effect of drying parameters such as the temperature within the drying chamber on mass losses (evaporation) during the freezing stage and the moisture ratio at the end of the drying process. The midili thin layer mathematical drying model was used to estimate and predict the moisture ratio curve based on different drying chamber temperatures. This experiment shows that decreasing the drying chamber temperature with constant pressure results in less mass loss during the freezing stage Drying time was reduced with an increase in drying temperature. Decreasing the drying chamber temperature results in lower pressure saturation of the material has no effect of drying chamber pressure on mass transfer.

Genotypic variability and persistence of Legionella pneumophila PFGE patterns in 34 cooling towers from two different areas.

PubMed

Sanchez, Inma; Garcia-Nuñez, Marian; Ragull, Sonia; Sopena, Nieves; Pedro-Botet, Maria Luisa; Estere, Maria; Rey-Joly, Celestino; Sabria, Miquel; Esteve, Maria

2008-02-01

Genotypic variability and clonal persistence are important concepts in molecular epidemiology as they facilitate the search for the source of sporadic cases or outbreaks of legionellosis. We studied the genotypic variability and persistence of Legionella pulsed-field gel electrophoresis (PFGE) patterns over time (period > 6 months) in 34 positive cooling towers from two different areas. In area A, radius of 70 km, 52 indistinguishable PFGE patterns were differentiated among the 27 cooling towers. In 13 cooling towers we observed >or= 2 PFGE patterns. Each cooling tower had its own indistinguishable Legionella PFGE pattern which was not shared with any other cooling tower. In area B, radius of 1 km, 10 indistinguishable PFGE patterns were obtained from the seven cooling towers. In four, we observed >or= 2 PFGE patterns. Three of these 10 indistinguishable PFGE patterns were shared by more than one cooling tower. In 27 of 34 cooling towers the same PFGE pattern was recovered after 6 months to up to 5 years of follow-up. The large genotypic diversity of Legionella observed in the cooling towers aids in the investigation of community outbreaks of Legionnaires' disease. However, shared patterns in small areas may confound the epidemiological investigation. The persistence of some PFGE patterns in cooling towers makes the recovery of the Legionella isolate causing the outbreak possible over time.

Provision of servo-controlled cooling during neonatal transport.

PubMed

Johnston, Ewen D; Becher, Julie-Clare; Mitchell, Anne P; Stenson, Benjamin J

2012-09-01

Therapeutic hypothermia is a time critical intervention for infants who have experienced a hypoxic-ischaemic event. Previously reported methods of cooling during transport do not demonstrate the same stability achieved in the neonatal unit. The authors developed a system which allowed provision of servo-controlled cooling throughout transport, and present their first year's experience. Retrospective review of routinely collected patient data. 14 out-born infants were referred for cooling during a 12-month period. Nine infants were managed with the servo-controlled system during transport. Cooling was commenced in all infants before 6 h of life. Median time from team arrival to the infant having a temperature in the target range (33-34°C) was 45 min. Median temperature during transfer was 33.5°C (range 33-34°C). Temperature on arrival at the cooling centre ranged from 33.4°C to 33.8°C. Servo-controlled cooling during transport is feasible and provides an optimal level of thermal control.

Cooling rate effects in sodium silicate glasses: Bridging the gap between molecular dynamics simulations and experiments

NASA Astrophysics Data System (ADS)

Li, Xin; Song, Weiying; Yang, Kai; Krishnan, N. M. Anoop; Wang, Bu; Smedskjaer, Morten M.; Mauro, John C.; Sant, Gaurav; Balonis, Magdalena; Bauchy, Mathieu

2017-08-01

Although molecular dynamics (MD) simulations are commonly used to predict the structure and properties of glasses, they are intrinsically limited to short time scales, necessitating the use of fast cooling rates. It is therefore challenging to compare results from MD simulations to experimental results for glasses cooled on typical laboratory time scales. Based on MD simulations of a sodium silicate glass with varying cooling rate (from 0.01 to 100 K/ps), here we show that thermal history primarily affects the medium-range order structure, while the short-range order is largely unaffected over the range of cooling rates simulated. This results in a decoupling between the enthalpy and volume relaxation functions, where the enthalpy quickly plateaus as the cooling rate decreases, whereas density exhibits a slower relaxation. Finally, we show that, using the proper extrapolation method, the outcomes of MD simulations can be meaningfully compared to experimental values when extrapolated to slower cooling rates.

Cryogen spray cooling during laser tissue welding.

PubMed

Fried, N M; Walsh, J T

2000-03-01

Cryogen cooling during laser tissue welding was explored as a means of reducing lateral thermal damage near the tissue surface and shortening operative time. Two centimetre long full-thickness incisions were made on the epilated backs of guinea pigs, in vivo. India ink was applied to the incision edges then clamps were used to appose the edges. A 4 mm diameter beam of 16 W, continuous-wave, 1.06 microm, Nd:YAG laser radiation was scanned over the incisions, producing approximately 100 ms pulses. There was a delay of 2 s between scans. The total irradiation time was varied from 1-2 min. Cryogen was delivered to the weld site through a solenoid valve in spurt durations of 20, 60 and 100 ms. The time between spurts was either 2 or 4 s, corresponding to one spurt every one or two laser scans. Histology and tensile strength measurements were used to evaluate laser welds. Total irradiation times were reduced from 10 min without surface cooling to under 1 min with surface cooling. The thermal denaturation profile showed less denaturation in the papillary dermis than in the mid-dermis. Welds created using optimized irradiation and cooling parameters had significantly higher tensile strengths (1.7 +/- 0.4 kg cm(-2)) than measured in the control studies without cryogen cooling (1.0 +/- 0.2 kg cm(-2)) (p < 0.05). Cryogen cooling of the tissue surface during laser welding results in increased weld strengths while reducing thermal damage and operative times. Long-term studies will be necessary to determine weld strengths and the amount of scarring during wound healing.

Is magma cooling responsible for the periodic activity of Soufrière Hills volcano, Montserrat, West Indies?

NASA Astrophysics Data System (ADS)

Caricchi, Luca; Simpson, Guy; Chelle-Michou, Cyril; Neuberg, Jürgen

2016-04-01

After 400 years of quiescence, Soufrière Hills volcano on Montserrat (SHV) started erupting in 1995. Ongoing deformation and sulphur dioxide emission demonstrate that this volcanic systems is still restless, however, after 5 years of inactivity it remains unclear whether magma extrusion will restart. Also, if such periodically observed activity at SHV will restart, can we use past monitoring data to attempt to forecast the reawakening of this volcano? Cooling of volatile saturated magma leads to crystallisation, the formation of gas bubbles and expansion. Such volumetric variations are not only potentially responsible for deformation signals observed at the surface (Caricchi et al., 2014), but also lead to pressurisation of the magmatic reservoir and eventually renewed magma extrusion (Tait et al., 1989). We postulate that volcanic activity observed at SHM over the last 20 years could be essentially the result of the unavoidable progressive cooling of a magmatic body, which was probably assembled over thousands of years and experienced internal segregation of eruptible lenses of magma (Christopher et al., 2015). To test this hypothesis, we performed thermal modelling to test if the cooling of a shallow magma body emplaced since 1990 could account for the monitoring signals observed at SHV. The results show that progressive cooling of a 4km3 volume of melt could explain the deformation rate currently observed. Using the deformation rate obtained from the modelling for the first 15 years of cooling, a reservoir volume of about 13 km3 (Paulatto et al., 2012) and a critical value of overpressure of 10 MPa, it would have taken approximately only 3 years to pressurise the reservoir to the critical pressure and restart magma extrusion. This is in agreement with the time interval between previous pauses at SHV before 2010. Considering the current deformation rates, we speculate that magma extrusion could restart in 6-8 years after the end of the last event in 2010, hence in the period 2016-2018. Because cooling affects mainly the outer portions of the magmatic reservoir, pressurisation by cooling and crystallisation lead to the release of magma from the inner part of the reservoir with essentially constant composition, as observed at SHV over the last 20 years. REFERENCES Caricchi, L., Biggs, J., Annen, C., & Ebmeier, S. (2014). Earth and Planetary Science Letters, 388, 166-174. doi.org/10.1016/j.epsl.2013.12.002. Christopher, T. E., Blundy, J., Cashman, K., Cole, P., Edmonds, M., Smith, P. J., et al. (2015). Geochemistry Geophysics Geosystems, 16(9), 2797-2811. doi.org/10.1002/2015GC005791. Paulatto, M., Annen, C., Henstock, T. J., Kiddle, E., Minshull, T. A., Sparks, R. S. J., & Voight, B. (2012). Geochemistry Geophysics Geosystems, 13(1), doi.org/10.1029/2011GC003892. Tait, S., Jaupart, C., & Vergniolle, S. (1989). Earth and Planetary Science Letters, 92(1), 107-123. doi.org/10.1016/0012-821X(89)90025-3

ATHENA X-IFU 300 K-50 mK cryochain demonstrator cryostat

NASA Astrophysics Data System (ADS)

Prouvé, T.; Duval, J. M.; Charles, I.; Yamasaki, N. Y.; Mitsuda, K.; Nakagawa, T.; Shinozaki, K.; Tokoku, C.; Yamamoto, R.; Minami, Y.; Le Du, M.; Andre, J.; Daniel, C.; Linder, M.

2018-01-01

In the framework of the ESA X-ray mission ATHENA, scheduled for launch in 2028, an ESA Core Technology Program (CTP) was started in 2016 to build a flight like cryostat demonstrator in parallel with the phase A studies of the ATHENA/X-IFU instrument [1,2]. As part of this CTP, called the Detector Cooling System (DCS), design, manufacturing and test of a cryostat including existing space coolers will be done. In addition to the validation of thermal performance, a Focal Plan Assembly (FPA) demonstrator using Transition Edge Sensors (TES) detector technology will be also integrated and its performance characterized versus the environment provided by the cryostat. This is a unique opportunity to validate many crucial issues of the cryogenic part of such a sensitive instrument. A dedicated activity within this CTP-DCS is the demonstration of the 300 K-50 mK cooling chain in a Ground System Equipment (GSE) cryostat. The studies are focused on the operation of the space coolers, which is made possible by the use of a ground cooler for cooling cryogenic shields and mechanical supports. Thanks to the modularity of the cryostat, several cooling chains could be tested. In the base line configuration described here, the low temperature stage is the CEA hybrid sorption/ADR 50 mK cooler with thermal interfaces at 4 K and 2 K. 4 K cooling is accomplished by a 4 K Joule-Thomson (JT) cryocooler and its Stirling precooler provided by JAXA. Regarding the 2 K stage, at first a 2 K JT from JAXA will be used. Alternatively, a 2 K JT cooler from RAL could replace the JAXA 2 K JT. In both cases new prototype(s) of a 2 K JT will be implemented, precooled by the EM 15 K pule tube cooler from Air Liquide. This test program is also the opportunity to validate the operation of the cryochain with respect to various requirements, such as time constant and temperature stabilities. This would bring us valuable inputs to integrate the cryochain in DCS cryostat or for the X-IFU phase A studies. This cryochain demonstration is also a critical milestone for the SPICA mission [3]. The design of the cryostat and first thermal validations both before and after integration of the JAXA JT coolers are presented in this paper.

The Tethered Moon

NASA Technical Reports Server (NTRS)

Zahnle, Kevin; Lupu, Roxana Elena; Dubrovolskis, A. R.

2014-01-01

A reasonable initial condition on Earth after the Moonforming impact is that it begins as a hot global magma ocean1,2. We therefore begin our study with the mantle as a liquid ocean with a surface temperature on the order of 3000- 4000 K at a time some 100-1000 years after the impact, by which point we can hope that early transients have settled down. A 2nd initial condition is a substantial atmosphere, 100-1000 bars of H2O and CO2, supplemented by smaller amounts of CO, H2, N2, various sulfur-containing gases, and a suite of geochemical volatiles evaporated from the magma. Third, we start the Moon with its current mass at the relevant Roche limit. The 4th initial condition is the angular momentum of the Earth-Moon system. Canonical models hold this constant, whilst some recent models begin with considerably more angular momentum than is present today. Here we present a ruthlessly simplified model of Earth's cooling magmasphere based on a full-featured atmosphere and including tidal heating by the newborn Moon. Thermal blanketing by H2O-CO2 atmospheres slows cooling of a magma ocean. Geochemical volatiles - chiefly S, Na, and Cl - raise the opacity of the magma ocean's atmosphere and slow cooling still more. We assume a uniform mantle with a single internal (potential) temperature and a global viscosity. The important "freezing point" is the sharp rheological transition between a fluid carrying suspended crystals and a solid matrix through which fluids percolate. Most tidal heating takes place at this "freezing point" in a gel that is both pliable and viscous. Parameterized convection links the cooling rate to the temperature and heat generation inside the Earth. Tidal heating is a major effect. Tidal dissipation in the magma ocean is described by viscosity. The Moon is entwined with Earth by the negative feedback between thermal blanketing and tidal heating that comes from the temperature-dependent viscosity of the magma ocean. Because of this feedback, the rate that the Moon's orbit evolves is limited by the modest radiative cooling rate of Earth's atmosphere, which in effect tethers the Moon to the Earth. Consequently the Moon's orbit evolves orders of magnitude more slowly than in conventional models. Slow orbital evolution promotes capture by orbital resonances that may have been important in the Earth-Moon system

Global Survey of the Relationship Between Cloud Droplet Size and Albedo Using ISCCP

NASA Technical Reports Server (NTRS)

Han, Qingyuan; Rossow, William B.; Chou, Joyce; Welch, Ronald M.

1997-01-01

Aerosols affect climate through direct and indirect effects. The direct effect of aerosols (e.g., sulfates) includes reflection of sunlight back toward space and for some aerosols (e.g., smoke particles), absorption in the atmosphere; both effects cool the Earth's surface. The indirect effect of aerosols refers to the modification of cloud microphysical properties, thereby affecting the radiation balance. Higher concentrations of Cloud Condensation Nuclei (CCN) generally produce higher concentrations of cloud droplets, which are also usually assumed to lead to decreased cloud droplet sizes. The result is an increase in cloud albedo, producing a net radiative cooling, opposite to the warming caused by greenhouse gases (Charlson et al. 1992). The change in clouds that is directly induced by an increase of aerosol concentration is an increase of cloud droplet number density, N; but is is usually assumed that cloud droplet size decreases as if the water mass density Liquid Water Content (LWC) were constant. There is actually no reason why this should be the case. Shifting the cloud droplet size distribution to more numerous smaller droplets can change the relative rates of condensational and coalescence growth, leading to different LWC (e.g., Rossow 1978). Moreover, the resulting change in cloud albedo is usually ascribed to more efficient scattering by smaller droplets, when in fact it is the increase in droplet number density (assuming constant LWC) that produces the most important change in cloud albedo: e.g., holding N constant and decreasing the droplet size would actually decrease the scattering cross-section and, thus, the albedo much more than it is increased by the increased scattering efficiency.

Warpage optimisation on the moulded part with straight-drilled and conformal cooling channels using response surface methodology (RSM) and glowworm swarm optimisation (GSO)

NASA Astrophysics Data System (ADS)

Hazwan, M. H. M.; Shayfull, Z.; Sharif, S.; Nasir, S. M.; Zainal, N.

2017-09-01

In injection moulding process, quality and productivity are notably important and must be controlled for each product type produced. Quality is measured as the extent of warpage of moulded parts while productivity is measured as a duration of moulding cycle time. To control the quality, many researchers have introduced various of optimisation approaches which have been proven enhanced the quality of the moulded part produced. In order to improve the productivity of injection moulding process, some of researches have proposed the application of conformal cooling channels which have been proven reduced the duration of moulding cycle time. Therefore, this paper presents an application of alternative optimisation approach which is Response Surface Methodology (RSM) with Glowworm Swarm Optimisation (GSO) on the moulded part with straight-drilled and conformal cooling channels mould. This study examined the warpage condition of the moulded parts before and after optimisation work applied for both cooling channels. A front panel housing have been selected as a specimen and the performance of proposed optimisation approach have been analysed on the conventional straight-drilled cooling channels compared to the Milled Groove Square Shape (MGSS) conformal cooling channels by simulation analysis using Autodesk Moldflow Insight (AMI) 2013. Based on the results, melt temperature is the most significant factor contribute to the warpage condition and warpage have optimised by 39.1% after optimisation for straight-drilled cooling channels and cooling time is the most significant factor contribute to the warpage condition and warpage have optimised by 38.7% after optimisation for MGSS conformal cooling channels. In addition, the finding shows that the application of optimisation work on the conformal cooling channels offers the better quality and productivity of the moulded part produced.

The Origin of Molecular Clouds in Central Galaxies

NASA Astrophysics Data System (ADS)

Pulido, F. A.; McNamara, B. R.; Edge, A. C.; Hogan, M. T.; Vantyghem, A. N.; Russell, H. R.; Nulsen, P. E. J.; Babyk, I.; Salomé, P.

2018-02-01

We present an analysis of 55 central galaxies in clusters and groups with molecular gas masses and star formation rates lying between {10}8 {and} {10}11 {M}ȯ and 0.5 and 270 {M}ȯ {{yr}}-1, respectively. Molecular gas mass is correlated with star formation rate, Hα line luminosity, and central atmospheric gas density. Molecular gas is detected only when the central cooling time or entropy index of the hot atmosphere falls below ∼1 Gyr or ∼35 keV cm2, respectively, at a (resolved) radius of 10 kpc. These correlations indicate that the molecular gas condensed from hot atmospheres surrounding the central galaxies. We explore the origins of thermally unstable cooling by evaluating whether molecular gas becomes prevalent when the minimum of the cooling to free-fall time ratio ({t}{cool}/{t}{ff}) falls below ∼10. We find that (1) molecular gas-rich systems instead lie between 10< \\min ({t}{cool}/{t}{ff})< 25, where {t}{cool}/{t}{ff}=25 corresponds approximately to cooling time and entropy thresholds of 1 Gyr and 35 {keV} {{cm}}2, respectively; (2) \\min ({t}{cool}/{t}{ff}) is uncorrelated with molecular gas mass and jet power; and (3) the narrow range 10< \\min ({t}{cool}/{t}{ff})< 25 can be explained by an observational selection effect, although a real physical effect cannot be excluded. These results and the absence of isentropic cores in cluster atmospheres are in tension with models that assume thermal instability ensues from linear density perturbations in hot atmospheres when {t}{cool}/{t}{ff}≲ 10. Some of the molecular gas may instead have condensed from atmospheric gas lifted outward by buoyantly rising X-ray bubbles or by dynamically induced uplift (e.g., mergers, sloshing).

Waiting time effect of a GM type orifice pulse tube refrigerator

NASA Astrophysics Data System (ADS)

Zhu, Shaowei; Kakimi, Yasuhiro; Matsubara, Yoichi

In a general GM type orifice pulse tube refrigerator, there are two short periods during which both the high pressure valve and the low pressure valve are closed in one cycle. We call the short period `waiting time'. The pressure differences across the high pressure valve and the low pressure valve are decreased by using long waiting time. The pressure difference loss is decreased. Thus, the cooling capacity and the efficiency are increased, and the no-load temperature is decreased. The mechanism of the waiting time is discussed with numerical analysis and verified by experiments. Experiments show that there is an optimum waiting time for the no-load temperature, the cooling capacity and the efficiency, respectively. The no-load temperature of 40.3 K was achieved with a 90° waiting time. The cooling capacity of 58 W at 80 K was achieved with a 60° waiting time. The no-load temperature of 45.1 K and the cooling capacity of 45 W at 80 K were achieved with a 1° waiting time.

Quiescent deformation of the Aniakchak Caldera, Alaska mapped by InSAR

USGS Publications Warehouse

Kwoun, Oh-Ig; Lu, Zhong; Neal, Christina; Wicks, Charles W.

2006-01-01

The 10-km-wide caldera of the historically active Aniakchak volcano, Alaska, subsides ∼13 mm/yr, based on data from 19 European Remote Sensing Satellite (ERS-1 and ERS-2) interferometric synthetic aperture radar (InSAR) images from 1992 through 2002. The pattern of subsidence does not reflect the distribution of pyroclastic deposits from the last eruption in 1931 and therefore is not related to compaction of fragmental debris. Weighted least-squares inversion of the deformation maps indicates a relatively constant subsidence rate. Modeling the deformation with a Mogi point source locates the source of subsidence at ∼4 km below the central caldera floor, which is consistent with the inferred depth of magma storage before the 1931 eruption. Magmatic CO2 and He have been measured at a warm soda spring within the caldera, and several sub-boiling fumaroles persist elsewhere in the caldera. These observations suggest that recent subsidence can be explained by the cooling or degassing of a shallow magma body (∼4 km deep), and/or the reduction of the pore-fluid pressure of a cooling hydrothermal system. Ongoing deformation of the volcano detected by InSAR, in combination with magmatic gas output from at least one warm spring, and infrequent low-level bursts of seismicity below the caldera, indicate that the volcanic system is still active and requires close attention for the timely detection of possible hazards.

Semiempirical limits on the thermal conductivity of intracluster gas

NASA Technical Reports Server (NTRS)

David, Laurence P.; Hughes, John P.; Tucker, Wallace H.

1992-01-01

A semiempirical method for establishing lower limits on the thermal conductivity of hot gas in clusters of galaxies is described. The method is based on the observation that the X-ray imaging data (e.g., Einstein IPC) for clusters are well described by the hydrostatic-isothermal beta model, even for cooling flow clusters beyond about one core radius. In addition, there are strong indications that noncooling flow clusters (like the Coma Cluster) have a large central region (up to several core radii) of nearly constant gas temperature. This suggests that thermal conduction is an effective means of transporting and redistributing the thermal energy of the gas. This in turn has implications for the extent to which magnetic fields in the cluster are effective in reducing the thermal conductivity of the gas. Time-dependent hydrodynamic simulations for the gas in the Coma Cluster under two separate evolutionary scenarios are presented. One scenario assumes that the cluster potential is static and that the gas has an initial adiabatic distribution. The second scenario uses an evolving cluster potential. These models along with analytic results show that the thermal conductivity of the gas in the Coma Cluster cannot be less than 0.1 of full Spitzer conductivity. These models also show that high gas conductivity assists rather than hinders the development of radiative cooling in the central regions of clusters.