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1
Davis, J. S., and M. E. Rodgers. "Force generation and temperature-jump and length-jump tension transients in muscle fibers." Biophysical Journal 68, no. 5 (May 1995): 2032–40. http://dx.doi.org/10.1016/s0006-3495(95)80380-2.
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Reiser, P. J., and B. D. Lindley. "Activation in frog atrial trabeculae: dependence on temperature and length." American Journal of Physiology-Heart and Circulatory Physiology 258, no. 4 (April 1, 1990): H1087—H1096. http://dx.doi.org/10.1152/ajpheart.1990.258.4.h1087.
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Isolated frog atrial trabeculae were activated using the method of Na+ withdrawal to induce contractures of relatively steady tension. External Na+ concentration [( Na+]o) during contractures was varied between 0.25 and 45 mM. Isometric contracture tension was measured at cold (4 degrees C) and warm (20 degrees C) temperatures. In addition, rapid temperature jumps (complete in approximately 400 ms) were imposed during cold contractures, resulting in tension transients that consisted of an initial increase in tension followed by a decrease, the latter phase being greater at small and moderate reductions in [Na+]o. Peak contracture tension varied with relative muscle length. The trabeculae became more sensitive with stretch to Na+ withdrawal at 20 degrees C and generated relatively greater tensions at a given [Na+]o. The initial tension increase after a temperature jump was directly proportional to the peak contracture tension immediately preceding the increase in temperature and was therefore interpreted as reflecting an effect of the higher temperature on the attached force-generating cross bridges. The effects of cold and warm steady temperatures and temperature jumps during isometric twitches were also studied. Peak twitch tension varied inversely with temperature (stimulus frequency = 0.2 Hz). In contrast, temperature jumps imposed during the rising phase of twitches at a steady cold temperature (approximately 4 degrees C) resulted in a large initial increase in tension followed by relaxation at a rate that was characteristic of the elevated temperature. The results suggest that, at the warmer temperature (approximately 20 degrees C), activation (i.e., number of attached cross bridges) of the myocardium is significantly less than maximal during the twitch response. The dependence of the tension vs. [Na+]o curves and the tension transients resulting from the temperature jumps on relative muscle length provide evidence for a length dependency of contractile activation in intact atrial trabeculae under conditions of steady-state tension development.
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Greetham, Gregory M., Ian P. Clark, Benjamin Young, Robby Fritsch, Lucy Minnes, Neil T. Hunt, and Mike Towrie. "Time-Resolved Temperature-Jump Infrared Spectroscopy at a High Repetition Rate." Applied Spectroscopy 74, no. 6 (March 30, 2020): 720–27. http://dx.doi.org/10.1177/0003702820913636.
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Time-resolved temperature-jump infrared absorption spectroscopy at a 0.5 to 1 kHz repetition rate is presented. A 1 kHz neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pumping an optical parametric oscillator provided >70 µJ, 3.75 µm pump pulses, which delivered a temperature jump via excitation of the O–D stretch of a D2O solution. A 10 kHz train of mid-infrared probe pulses was used to monitor spectral changes following the temperature jump. Calibration with trifluoroacetic acid solution showed that a temperature jump of 10 K lasting for tens of microseconds was achieved, sufficient to observe fast processes in functionally relevant biomolecular mechanisms. Modeling of heating profiles across ≤10 µm path length cells and subsequent cooling dynamics are used to describe the initial <100 ns cooling at the window surface and subsequent, >10 µs cooling dynamics of the bulk solution.
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Abdollahzadeh, Jamalabadia, Hyun Park, and Chang Lee. "Thermal radiation effects on the onset of unsteadiness of fluid flow in vertical microchannel filled with highly absorbing medium." Thermal Science 20, no. 5 (2016): 1585–96. http://dx.doi.org/10.2298/tsci140418124a.
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This study presents the effect of thermal radiation on the steady flow in a vertical micro channel filled with highly absorbing medium. The governing equations (mass, momentum and energy equation with Rosseland approximation and slip boundary condition) are solved analytically. The effects of thermal radiation parameter, the temperature parameter, Reynolds number, Grashof number, velocity slip length, and temperature jump on the velocity and temperature profiles, Nusselt number, and skin friction coefficient are investigated. Results show that the skin friction and the Nusselt number are increased with increase in Grashof number, velocity slip, and pressure gradient while temperature jump and Reynolds number have an adverse effect on them. Furthermore, a criterion for the flow unsteadiness based on the temperature parameter, thermal radiation parameter, and the temperature jump is presented.
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Menssen, Ryan J., and Andrei Tokmakoff. "Length-Dependent Melting Kinetics of Short DNA Oligonucleotides Using Temperature-Jump IR Spectroscopy." Journal of Physical Chemistry B 123, no. 4 (January 7, 2019): 756–67. http://dx.doi.org/10.1021/acs.jpcb.8b09487.
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TAWFIK, A., M. Z. SAID, and O. M. HEMEDA. "THE EFFECT OF AMOUNT TANTALUM DOPING ON THE PROPERTIES OF MgCuZn FERRITES." International Journal of Modern Physics B 25, no. 19 (July 30, 2011): 2583–91. http://dx.doi.org/10.1142/s0217979211100722.
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The systems MgCuZn Fe 2 O 4 doped (0–0.6 wt% Ta) are prepared by the general ceramic method using the sintering temperature at 1200°C. The variations of the sintered density, lattice parameter, jump length of electrons, and initial permeability were studied. A maximum density was obtained at 1200°C during the preparation process. The electrical resistivity decreases with increasing tantalum ( Ta ) content upto 0.1 wt% and then increases for higher concentrations. The initial permeability and the change carries mobility increase upto 0.1 Ta and then decreases. The jump length decreases with enhancing Ta ions because the substitution of Ta ion with small size instead of Fe 3+ at the A sites increase the concentration of iron ions at the B sites. The increase of the iron content causes the decrease of the jump length of electrons between Fe 3+ and Fe 2+. These improvements of the magnetic properties give some light about the importance of these compositions to be used in technology.
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Beikircher, T., N. Benz, and W. Spirkl. "A Modified Temperature-Jump Method for the Transition and Low-Pressure Regime." Journal of Heat Transfer 120, no. 4 (November 1, 1998): 965–70. http://dx.doi.org/10.1115/1.2825916.
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For modeling the gas heat conduction at arbitrary Knudsen numbers and for a broad range of geometries, we propose a modified temperature-jump method. Within the modified approach, we make a distinction between an inner convex surface and an outer concave surface enclosing the inner surface. For problems, where only a single geometric length is involved, i.e., for large parallel plates, long concentric cylinders and concentric spheres, the new method coincides at any Knudsen number with the interpolation formula according to Sherman, and therefore also with the known solutions of the Boltzmann equation obtained by the four momenta method. For the general case, where more than one geometric length is involved, the modified temperature method is trivially correct in the limit of high pressure and identical with Knudsen’s formula in the limit of low pressure. For intermediate pressure, where there is a lack of known solutions of the Boltzmann equation for general geometries, we present experimental data for the special two-dimensional plate-in-tube configuration and compare it with results of the modified temperature-jump method stating good agreement. The results match slightly better compared to the standard temperature method and significantly better compared to the interpolation formula according to Sherman. For arbitrary geometries and Knudsen numbers, the modified temperature method shows no principal restrictions and may be a simple approximative alternative to the solution of the Boltzmann equation, which is rather cumbersome.
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Menssen, Ryan J., and Andrei Tokmakoff. "Correction to “Length-Dependent Melting Kinetics of Short DNA Oligonucleotides Using Temperature-Jump IR Spectroscopy”." Journal of Physical Chemistry B 123, no. 10 (February 28, 2019): 2467. http://dx.doi.org/10.1021/acs.jpcb.9b01693.
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Cowley, Adam, Daniel Maynes, and Julie Crockett. "Effective temperature jump length and influence of axial conduction for thermal transport in superhydrophobic channels." International Journal of Heat and Mass Transfer 79 (December 2014): 573–83. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2014.08.033.
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Lutz, G. J., and L. C. Rome. "Muscle function during jumping in frogs. I. Sarcomere length change, EMG pattern, and jumping performance." American Journal of Physiology-Cell Physiology 271, no. 2 (August 1, 1996): C563—C570. http://dx.doi.org/10.1152/ajpcell.1996.271.2.c563.
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We determined the influence of temperature on muscle function during jumping to better understand how the frog muscular system is designed to generate a high level of mechanical power. Maximal jumping performance and the in vivo operating conditions of the semimembranosus muscle (SM), a hip extensor, were measured and related to the mechanical properties of the isolated SM in the accompanying paper [Muscle function during jumping in frogs. II. Mechanical properties of muscle: implication for system design. Am. J. Physiol. 271 (Cell Physiol. 40): C571-C578, 1996]. Reducing temperature from 25 to 15 degrees C caused a 1.75-fold decline in peak mechanical power generation and a proportional decline in aerial jump distance. The hip and knee joint excursions were nearly the same at both temperatures. Accordingly, sarcomeres shortened over the same range (2.4 to 1.9 microns) at both temperatures, corresponding to myofilament overlap at least 90% of maximal. At the low temperature, however, movements were made more slowly. Angular velocities were 1.2- to 1.4-fold lower, and ground contact time was increased by 1.33-fold at 15 degrees C. Average shortening velocity of the SM was only 1.2-fold lower at 15 degrees C than at 25 degrees C. The low Q10 of velocity is in agreement with that predicted for muscles shortening against an inertial load.
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Ren, F. Y., and J. M. Harris. "Temperature-Jump Investigation of Alkyl Chain Length Effects on Sorption/Desorption Kinetics at Reversed-Phase Chromatographic Interfaces." Analytical Chemistry 68, no. 9 (January 1996): 1651–57. http://dx.doi.org/10.1021/ac950935b.
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Machrafi, Hatim. "Temperature Distribution through a Nanofilm by Means of a Ballistic-Diffusive Approach." Inventions 4, no. 1 (January 3, 2019): 2. http://dx.doi.org/10.3390/inventions4010002.
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As microelectronic devices are important in many applications, their heat management needs to be improved, in order to prolong their lifetime, and to reduce the risk of damage. In nanomaterials, heat transport shows different behaviors than what can be observed at macroscopic sizes. Studying heat transport through nanofilms is a necessary tool for nanodevice thermal management. This work proposes a thermodynamic model incorporating both ballistic, introduced by non-local effects, and diffusive phonon transport. Extended thermodynamics principles are used in order to develop a constitutive equation for the ballistic behavior of heat conduction at small-length scales. Being an irreversible process, the present two-temperature model contains a one-way transition of ballistic to diffusive phonons as time proceeds. The model is compared to the classical Fourier and Cattaneo laws. These laws were not able to present the non-locality that our model shows, which is present in cases when the length scale of the material is of the same order of magnitude or smaller than the phonon mean free path, i.e., when the Knudsen number K n ≤ O ( 1 ) . Moreover, for small K n numbers, our model predicted behaviors close to that of the classical laws, with a weak temperature jump at both sides of the nanofilm. However, as K n increases, the behavior changes completely, the ballistic component becomes more important, and the temperature jump at both sides of the nanofilms becomes more pronounced. For comparison, a model using Fourier’s and Cattaneo’s laws with an effective thermal conductivity has shown, with reasonable qualitative comparison for small Knudsen numbers and large times.
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Zhang, Guang Liang, Zhang Wei Wang, and Shi Hong Zhang. "A Fast Optimization Approach for Multi-Pass Wire Drawing Processes with a Penalty Fitness Function." Materials Science Forum 762 (July 2013): 307–12. http://dx.doi.org/10.4028/www.scientific.net/msf.762.307.
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A fast optimization approach is demonstrated for design optimization of the multi-pass wire drawing process with the multi-objective genetic algorithm, and with the aims at minimizing both power consumption and temperature, via optimizing the process parameters involving pass number, pass schedule, die angle, bearing length and loops on capstan etc. A jump fitness function and a penalty fitness function are proposed for the survival of good designs and killing the bad designs which temperature, die wear factor, delta factor, or ratio of drawing stress to yield stress exceed the limits during optimization. The numerical examples show that the optimizer with the penalty fitness function, when its parameternranges from 1 to 2, presents the best performance in finding the minimum power consumption with a limit in temperature. Compared with a reference design, a significant reduction in the total power consumption about 300W, with the well control in temperature, delta factor and die life, has been achieved by the optimization. The penalty fitness function presents the better performance in the reduction of the iteration generations and computational cost to the jump fitness function.
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Nagaoka, Naomi, Takahiro Ueda, and Nobuo Nakamura. "Dynamics of some n-Alkanes Adsorbed in the Micropore of (±)-[Co(en)3]Cl3 as Studied by 2H NMR." Zeitschrift für Naturforschung A 57, no. 6-7 (July 1, 2002): 435–40. http://dx.doi.org/10.1515/zna-2002-6-726.
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The dynamic behavior of n-hexane-d14 and n-decane-d22, adsorbed in the micropore of [Co(en)3]Cl3 crystal was studied by 2H NMR at 144 - 345 K. The quadrupole coupling constants (QCC) are 160 kHz for the methylene group and 60 kHz for methyl group below 144 K for hexane and below 178 K for decane, suggesting that the molecular reorientation about the molecular long axis is frozen below these temperatures. The QCC of CD2 group in hexane decreases from 160 kHz to 80 kHz on heating up to 170 K. Similar reduction of QCC of CD2 observed above 280 K for decane. Assuming the three-site jump model of the guest molecule about its molecular long axis, we reproduced the experimental spectrum, and obtained the rate of the molecular motion in each guest. The temperature dependence of jump rates leads to the activation energies for the molecular reorientation of 20 kJ mol-1 and 30 kJ mol-1 for n-hexane and n-decane, respectively, suggesting that the length of the guest molecule influences greatly its dynamics in the micropore
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Redhammer, Günther J., Haruo Ohashi, and Georg Roth. "Single-crystal structure refinement of NaTiSi2O6 clinopyroxene at low temperatures (298 < T < 100 K)." Acta Crystallographica Section B Structural Science 59, no. 6 (November 25, 2003): 730–46. http://dx.doi.org/10.1107/s0108768103022018.
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The alkali-metal clinopyroxene NaTi3+Si2O6, one of the rare compounds with trivalent titanium, was synthesized at high temperature/high pressure and subsequently investigated by single-crystal X-ray diffraction methods between 298 and 100 K. One main difference between the high- and the low-temperature form is the sudden appearance of two different Ti3+—Ti3+ interatomic distances within the infinite chain of the TiO6 octahedra just below 197 K. This change can be seen as direct evidence for the formation of Ti—Ti singlet pairs in the low-temperature phase. Mean Ti—O bond lengths smoothly decrease with decreasing temperature and the phase transition is associated with a slight jump in the Ti—O bond length. The break in symmetry, however, causes distinct variations, especially with respect to the two Ti—Oapex bond lengths, but also with respect to the four Ti—O bonds in the equatorial plane of the octahedron. The TiO6 octahedron appears to be stretched in the chain direction with a slightly larger elongation in the P\bar 1 low-temperature phase compared with the C2/c high-temperature phase. Polyhedral distortion parameters such as bond-length distortion and octahedral angle variance suggest the TiO6 octahedron in P\bar 1 to be closer to the geometry of an ideal octahedron than in C2/c. Mean Na—O bond lengths decrease with decreasing temperature and the variations in individual Na—O bond lengths are the result of variations in the geometry of the octahedral site. The tetrahedral site acts as a rigid unit, which does not show pronounced changes upon cooling and through the phase transitions. There are neither large changes in bond lengths and angles nor in polyhedral distortion parameters, for the tetrahedral site, when they are plotted. In contrast with the C2/c → P21/c phase transition, found especially in LiMSi2O6 clinopyroxenes, no very large variations are found for the tetrahedral bridging angle. Thus, it is concluded that the main factor inducing the phase transition and controlling the structural variations is the M1 octahedral site.
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Dong, Hui, Yan Han, Yong Zhou, Xiao Li, Jian-Tao Yao, and Yan Li. "The Temperature Distribution in Plasma-Sprayed Thermal-Barrier Coatings During Crack Propagation and Coalescence." Coatings 8, no. 9 (September 4, 2018): 311. http://dx.doi.org/10.3390/coatings8090311.
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A Finite-Element Model (FEM) for thermal-barrier coatings was employed to elaborate the temperature distribution on yttria-stabilized zirconia (YSZ) free surface during cracks coalescing, then the influence of sintering of YSZ induced by heat-transfer overlapping on energy release rate was quantificationally evaluated. A three-dimensional model including three layers was fabricated. Two types of cracks, with and without depth variations in YSZ coating, were introduced into the model, respectively. The temperature rise of YSZ coating over the crack is independent of each other at the beginning of crack propagation. As crack distance shortens, the independent temperature-rise regions begin to overlap, while maximum temperature is still located at the crack center before crack coalescence. The critical distance that the regions of temperature rise, just overlapping, is the sum of half lengths of two coalescing cracks (i.e., a1 + a2), which is independent of cracking path. The maximum temperature in YSZ sharply increases once cracks coalesce. Compared with one delamination crack, the effective energy-release rate induced by heat-transfer overlapping increases in the range of 0.2%–15%, depending on crack length and crack distance, which is on some level comparable to that of deterioration of thermal expansion misfit induced by temperature jump between crack faces.
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LU, JING, and LIYUAN ZHANG. "TWO-COMPONENT SUPERCONDUCTIVITY FOR DOPED FULLERENES." Modern Physics Letters B 10, no. 17 (July 20, 1996): 823–29. http://dx.doi.org/10.1142/s0217984996000936.
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The combining mechanism of the itinerant carrier pair and the local carrier pair (two-component model) is considered for doped fullerenes. The superconducting transition temperature T c , penetration depth λ, coherent length ξ, thermodynamic critical field H c and specific heat jump ΔC/T c are calculated and there is overall consistency between the calculations and the experiments for both alkali-metal-doped fullerenes ( Na 3 C 60, K 3 C 60, Rb 3 C 60 and RbCs 2 C 60) and alkaline-earth doped fullerenes ( Ba 6 C 60).
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Gholamalizadeh, Ehsan, Farzad Pahlevanzadeh, Kamal Ghani, Arash Karimipour, Truong Khang Nguyen, and Mohammad Reza Safaei. "Simulation of water/FMWCNT nanofluid forced convection in a microchannel filled with porous material under slip velocity and temperature jump boundary conditions." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 5 (June 17, 2019): 2329–49. http://dx.doi.org/10.1108/hff-01-2019-0030.
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Purpose This study aims to numerically study the forced convection effects on a two-dimensional microchannel filled with a porous material containing the water/FMWCNT nanofluid. The upper and lower microchannel walls were fully insulated thermally along 15 per cent of their lengths at each end of the microchannel, with the in-between length being exposed to a constant temperature. The slip velocity boundary condition was applied along the microchannel walls. Design/methodology/approach The Navier–Stokes equations were discretized before being solved numerically via a FORTRAN computer code. The following ranges were considered for the studied parameters: slip factor (B) equal to 0.001, 0.01 and 0.1; Reynolds number (Re) between 10 and 100; solid nanoparticle mass fraction (ϕ) between 0.0012 and 0.0025; Darcy number (Da) between 0.001 and 0.1; and porosity factor (ε) between 0.4 and 0.9. Findings Increasing the Da caused a greater increase in the velocity profile than increasing Re, whereas increasing porosity did not affect the velocity profile growth at all. Originality/value This paper is the continuation of the authors’ previous studies. Using the water/FMWCNT nanofluid as the working fluid in microchannels is among the achievements of this study.
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Milicev, Snezana, and Nevena Stevanovic. "A microbearing gas flow with different walls´ temperatures." Thermal Science 16, no. 1 (2012): 119–32. http://dx.doi.org/10.2298/tsci110804086m.
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An analytical solution for the non-isothermal two-dimensional compressible gas flow in a slider microbearing with different temperatures of walls is presented in this paper. The slip flow is defined by the continuity, Navier-Stokes and energy continuum equations, along with the velocity slip and the temperature jump first order boundary conditions. Knudsen number is in the range of 10-3-10-1, which corresponds to the slip flow. The ratio between the exit microbearing height and the microbearing length is taken to be a small parameter. Moreover, it is assumed that the microbearing cross section varies slowly, which implies that all physical quantities vary slowly in x-direction. The model solution is treated by developing a perturbation scheme. The first approximation corresponds to the continuum flow conditions, while the second one involves the influence of rarefaction effect. The analytical solutions of the pressure, velocity and temperature for moderately high Reynolds numbers are presented here. For these flow conditions the inertia, convection, dissipation and rate at which work is done in compressing the element of fluid are also presented in the second approximation.
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Bovin, J. O., T. Huber, O. Balmes, J. O. Malm, and G. Karlsson. "Jump Ratio Elemental Mapping in Amorphous Ice Cryo-EFTEM Opens the Window to Solution Chemistry." Microscopy and Microanalysis 5, S2 (August 1999): 644–45. http://dx.doi.org/10.1017/s1431927600016548.
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The preparation of frozen amorphous thin films of solutions containing crystals, and imaging with cryo energy filtered TEM, opens for the first time the possibility to image the chemistry of solids interacting with liquids. The future possible areas of research include: dynamic of crystal growth processes, adsorption mechanisms, ion exchange, structure determination of solids in equilibrium with solutions, etc.The sample preparation uses a controlled-environment vitrification system1. Vitrification of the liquid phase was achieved by plunging the grid into liquid ethane. The vitrified specimen was transferred into the microscope by an Oxford CT3500 cryo-holder. The specimen temperature in the microscope column can be kept at -−183 °C. The thickness of the vitrified films, including the crystals, should be about 250 nm or preferably less. The Philips CM120 BioTWIN Cryo, here used for cryo-TEM, has a focal length of 6 mm and a structural resolution of 0.4 nm.
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Smalley, John F. "Indirect Laser-Induced Temperature Jump Study of the Chain-Length Dependence of the pKa's of ω-Mercaptoalkanoic Acid Monolayers Self-Assembled on Gold." Langmuir 19, no. 22 (October 2003): 9284–89. http://dx.doi.org/10.1021/la0348968.
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Vajravelu, K., S. Sreenadh, and R. Saravana. "Influence of velocity slip and temperature jump conditions on the peristaltic flow of a Jeffrey fluid in contact with a Newtonian fluid." Applied Mathematics and Nonlinear Sciences 2, no. 2 (October 18, 2017): 429–42. http://dx.doi.org/10.21042/amns.2017.2.00034.
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AbstractIn this paper, we investigate the peristaltic transport of a two layered fluid model consisting of a Jeffrey fluid in the core region and a Newtonian fluid in the peripheral region. The channel is bounded by permeable heat conducting walls. The analysis is carried out in the wave reference frame under the assumptions of long wave length and low Reynolds number. The analytical expressions for stream function, temperature field, pressure-rise and the frictional force per wavelength in both the regions are obtained. The effects of the physical parameters associated with the flow and heat transfer are presented graphically and analyzed. It is noticed that the pressure rise decrease with increasing slip parameter β in the pumping region (ΔP > 0). The temperature field decreases with increasing Jeffrey number and the velocity slip parameter; whereas the temperature field increases with increasing thermal slip parameter. Furthermore, the size of the trapped bolus increases with increasing Jeffrey number and decreases with increasing slip parameter. We believe that this model can help in understanding the behavior of two immiscible physiological fluids in living objects.
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Begg, E., D. Khrustalev, and A. Faghri. "Complete Condensation of Forced Convection Two-Phase Flow in a Miniature Tube." Journal of Heat Transfer 121, no. 4 (November 1, 1999): 904–15. http://dx.doi.org/10.1115/1.2826081.
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A physical and mathematical model of annular film condensation in a miniature tube has been developed. In the model the liquid flow has been coupled with the vapor flow along the liquid-vapor interface through the interfacial temperature, heat flux, shear stress, and pressure jump conditions due to surface tension effects. The model predicts the shape of the liquid-vapor interface along the condenser and the length of the two-phase flow region. The numerical results show that complete condensation of the incoming vapor is possible at comparatively low heat loads. Observations from a flow visualization experiment of water vapor condensing in a horizontal glass tube confirm the existence and qualitative features of annular film condensation leading to the complete condensation phenomenon in small diameter (d < 3.5 mm) circular tubes.
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Lu, Chang, Die Meng, and Ming Gao Yu. "Study on Material Parameters Effects on Smoldering and Transition from Smoldering to Flaming Combustion." Advanced Materials Research 261-263 (May 2011): 571–75. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.571.
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The polyurethane foam is a most common fuel in smoldering fire. A small scale experimental compartment was built. The width, thickness and density of polyurethane foam material were changed several times in the experiments. Temperature histories measurement and analysis gaseous were used to explore the transition’s mechanism. The results show that with the width increased, the surface area and the air flow rate which access to the inside of material have also increased, and the quantity of oxygen is sufficient, heat release quantity by carbon oxidation is increased. When the width reaches a certain value, polyurethane foam material transformed easier from smoldering to flaming combustion. The polyurethane foam transforms to the flaming combustion not only depends on the length, width size but also relates to the thickness closely. When thickness reached a certain size, the temperature also reaches a whole jump. And the material transforms to the flaming combustion finally. The oxidation of larger density polyurethane foam material produces more heat, and then accumulates heat in the polyurethane foam center to reach the required temperature of gas phase reaction and ultimately transforms to flaming combustion from smoldering.
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Pathak, Harshad, Alexander Späh, Niloofar Esmaeildoost, Jonas A. Sellberg, Kyung Hwan Kim, Fivos Perakis, Katrin Amann-Winkel, et al. "Enhancement and maximum in the isobaric specific-heat capacity measurements of deeply supercooled water using ultrafast calorimetry." Proceedings of the National Academy of Sciences 118, no. 6 (February 1, 2021): e2018379118. http://dx.doi.org/10.1073/pnas.2018379118.
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Knowledge of the temperature dependence of the isobaric specific heat (Cp) upon deep supercooling can give insights regarding the anomalous properties of water. If a maximum in Cp exists at a specific temperature, as in the isothermal compressibility, it would further validate the liquid–liquid critical point model that can explain the anomalous increase in thermodynamic response functions. The challenge is that the relevant temperature range falls in the region where ice crystallization becomes rapid, which has previously excluded experiments. Here, we have utilized a methodology of ultrafast calorimetry by determining the temperature jump from femtosecond X-ray pulses after heating with an infrared laser pulse and with a sufficiently long time delay between the pulses to allow measurements at constant pressure. Evaporative cooling of ∼15-µm diameter droplets in vacuum enabled us to reach a temperature down to ∼228 K with a small fraction of the droplets remaining unfrozen. We observed a sharp increase in Cp, from 88 J/mol/K at 244 K to about 218 J/mol/K at 229 K where a maximum is seen. The Cp maximum is at a similar temperature as the maxima of the isothermal compressibility and correlation length. From the Cp measurement, we estimated the excess entropy and self-diffusion coefficient of water and these properties decrease rapidly below 235 K.
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Dhiman, R. L., S. P. Taneja, and V. R. Reddy. "Structural and Mössbauer Spectral Studies of Nanosized Aluminum Doped Manganese Zinc Ferrites." Advances in Condensed Matter Physics 2008 (2008): 1–7. http://dx.doi.org/10.1155/2008/839536.
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Nanoparticles of aluminum-substituted manganese zinc ferrites,Mn1.05Zn0.05AlxFe1.9−xO4with0.4≤x≤1.0were synthesized by solid-state reaction route and characterized by XRD, TEM, and Mössbauer spectroscopy measurements. The particle size is found to very from 46 to 28 nm with increase of aluminum ions concentration. The unit cell parameter “aO” is found to decrease linearly with aluminum ions concentration due to smaller ionic radius of aluminum. The cation distributions were estimated from X-ray diffraction intensities of various planes. The theoretical lattice parameter, bulk density, porosity, X-ray density, oxygen positional parameter, ionic radii, jump length, as well as bonds and edges lengths of the tetrahedral (A-) and octahedral (B-) sites were determined.Fe57Mössbauer spectra recorded at room temperature were fitted with two sextets corresponding toFe3+ions at tetrahedral (A-) and octahedral (B-) sites. The magnetic hyperfine fields at A- and B-sites show a gradual decrease with increase ofAl3+ion concentration, which has been explained on the basis of supertransferred hyperfine field. The cation distribution obtained from X-ray intensities and Mössbauer data indicates a decrease inFe3+(B)/Fe3+(A)ratio with increasing aluminum concentration thereby suggesting a decrease in ferrimagnetic behavior.
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Thompson, Andrew F., and William R. Young. "Two-Layer Baroclinic Eddy Heat Fluxes: Zonal Flows and Energy Balance." Journal of the Atmospheric Sciences 64, no. 9 (September 1, 2007): 3214–31. http://dx.doi.org/10.1175/jas4000.1.
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Abstract The eddy heat flux generated by statistically equilibrated baroclinic turbulence supported on a uniform, horizontal temperature gradient is examined using a two-layer β-plane quasigeostrophic model. The dependence of the eddy diffusivity of temperature, Dτ, on external parameters such as β, bottom friction κ, the deformation radius λ, and the velocity jump 2U, is provided by numerical simulations at 110 different points in the parameter space β* = βλ2/U and κ* = κλ/U. There is a special “pivot” value of β*, βpiv* ≈ 11/16, at which Dτ depends weakly on κ*. But otherwise Dτ has a complicated dependence on both β* and κ*, highlighted by the fact that reducing κ* leads to increases (decreases) in Dτ if β is less than (greater than) βpiv*. Existing heat-flux parameterizations, based on Kolmogorov cascade theories, predict that Dτ is nonzero and independent of κ* in the limit κ* → 0. Simulations show indications of this regime provided that κ* ≤ 0.04 and 0.25 ≤ β* ≤ 0.5. All important length scales in this problem, namely the mixing length, the scale of the energy containing eddies, the Rhines scale, and the spacing of the zonal jets, converge to a common value as bottom friction is reduced. The mixing length and jet spacing do not decouple in the parameter regime considered here, as predicted by cascade theories. The convergence of these length scales is due to the formation of jet-scale eddies that align along the eastward jets. The baroclinic component of these eddies helps force the zonal mean flow, which occurs through nonzero Reynolds stress correlations in the upper layer, as opposed to the barotropic mode. This behavior suggests that the dynamics of the inverse barotropic cascade are insufficient to fully describe baroclinic turbulence.
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Gerber, H., G. Frick, S. P. Malinowski, J.-L. Brenguier, and F. Burnet. "Holes and Entrainment in Stratocumulus." Journal of the Atmospheric Sciences 62, no. 2 (February 1, 2005): 443–59. http://dx.doi.org/10.1175/jas-3399.1.
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Abstract Aircraft flights through stratocumulus clouds (Sc) during the Dynamics and Chemistry of Marine Stratocumulus II (DYCOMS-II) study off the California coast found narrow in-cloud regions with less liquid water content (LWC) and cooler temperatures than average background values. The regions are named cloud holes and are assumed to be a result of water evaporated by the entrainment of dryer air from above the Sc. While such features have been noted previously, this study provided a unique opportunity to investigate in much greater detail the nature of the holes, as well as their relationship to the entrainment rate, because high-speed temperature and LWC probes with maximum spatial resolution of 10 cm were flown together for the first time. Nine long-duration flights were made through mostly unbroken Sc for which conditional sampling was used to identify the location and size of the holes. The holes are concentrated near cloud top, their average width near cloud top is about 5 m, their relative length distribution is nearly constant for all flights, and they can penetrate hundreds of meters deep into the Sc before being lost by mixing. Entrainment velocities at cloud top are estimated from measurements of fluxes of reduced LWC and vapor mixing ratios in holes, the fraction of cloud area covered by holes, and the total water jump between cloud top and the free atmosphere. Rates as large as 10 mm s−1 are found for nocturnal flights, and these rates are about 3 times larger than for daytime flight segments. The rates correlate best with the size of the buoyancy jump above the Sc; the present conditional-sampling approach for measuring the rates gives larger rates than the “flux jump” rates determined by others for the same flights by a factor of about 2. The stability criterion for all Sc predicts thinning and breakup of the Sc, which does not occur. The minimal amount of cloud-top evaporative cooling caused by entrainment contributes little to the top-down convection dominated by radiative cooling during nocturnal flights; however, evaporative cooling caused by the mixing of holes as they subduct with the large-scale eddy circulation in the Sc may contribute, but with an as-of-yet unknown amount.
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MA, Y. L., and X. X. DAI. "PHENOMENOLOGICAL IMPLICATIONS OF HIGH-Tc SUPERCONDUCTIVITY." International Journal of Modern Physics B 06, no. 14 (July 20, 1992): 2499–519. http://dx.doi.org/10.1142/s0217979292001250.
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We develop a phenomenological model for high-T c superconductors. Some main features are emerging in copper oxides: characteristic quasi two-dimensional Cu-O planes, strong correlation of antiferromagnetism, existence of a vortex lattice structure, and observation of a small coherence length and a large penetration depth. These features indicate that the superconductive pair is reasonably constrained to a small volume in real space and may be conceived of as a string-carrying vortex, and therefore can be well simulated by the dual phenomenological local boson fields [Formula: see text] and Φ. The various mean-field ground states of the system are discussed. The field equations of motion are originally solved to get approximate analytical soliton solutions. The effective Hamiltonian is formulated by a variational method for finite temperatures. The model parameter behaviour described by the relationship of the variational parameters is investigated. We discuss the critical temperature T c , the specific heat cV and its jump Δc at T c , and the critical magnetic fields H c1 and H c2 . These results are in agreement with experimental observations, especially the critical behaviours and the zero temperature values. The model also allows interpretation of the variation of T c with oxygen vacancy x and that with doping fraction δ in Cu-O planes, as well as the dependence of γ (defined as the specific heat coefficient of the T-linear term) on δ.
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Clarke, Garry K. C. "Hydraulics of subglacial outburst floods: new insights from the Spring–Hutter formulation." Journal of Glaciology 49, no. 165 (2003): 299–313. http://dx.doi.org/10.3189/172756503781830728.
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AbstractUsing a slightly modified form of the Spring–Hutter equations, glacial outburst floods are simulated from three classic sites, “Hazard Lake”, Yukon, Canada, Summit Lake, British Columbia, Canada, and Grímsvötn, Iceland, in order to calibrate the hydraulic roughness associated with subglacial conduits. Previous work has suggested that the Manning roughness of the conduits is remarkably high, but the new calibration yields substantially lower values that are representative of those for natural streams and rivers. The discrepancy can be traced to a poor assumption about the effectiveness of heat transfer at the conduit walls. The simulations reveal behaviour that cannot be inferred from simplified theories: (1) During flood onset, water pressure over much of the conduit can exceed the confining pressure of surrounding ice. (2) Local values of fluid potential gradient can differ substantially from the value averaged over the length of the conduit, contradicting an assumption of simple theories. (3) As the flood progresses, the location of flow constrictions that effectively control the flood magnitude can jump rapidly over large distances. (4) Predicted water temperature at the conduit outlet exceeds that suggested by measurements of exit water temperature.
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FUJITA, S., Y. TAKATO, and A. SUZUKI. "THEORY OF THE ELECTRICAL TRANSPORT IN METALLIC SINGLE-WALL NANOTUBES." Modern Physics Letters B 25, no. 04 (February 10, 2011): 223–42. http://dx.doi.org/10.1142/s0217984911025675.
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A metallic (semiconducting) single-wall nanotube contains an irrational (integral) number of carbon hexagons in the pitch. The room-temperature conductivity is higher by two to three orders of magnitude in metallic nanotubes than in semiconducting nanotubes. Tans et al. [Nature386 (1997) 474] measured the electrical currents in metallic single-wall carbon nanotubes under bias and gate voltages, and observed non-Ohmic behaviors. The original authors interpreted their data in terms of a ballistic transport due to the Coulomb blockage on the electron-carrier model. The mystery of why a ballistic electron is not scattered by impurities and phonons is unexplained, however. An alternate interpretation is presented based on the Cooper pair (pairon)–carrier model. Superconducting states are generated by the Bose–Einstein condensation of the ± pairons at momenta 2πℏn/L, where L is the tube length and n a small integer. As the gate voltage changes the charging state of the tube, the superconducting states jump between different n. The normal current peak shapes appearing in the transition are found to be temperature-dependent, which is caused by the electron–optical phonon scattering.
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Dhiman, R. L., S. P. Taneja, and V. R. Reddy. "Preparation and Characterization of Manganese Ferrite Aluminates." Advances in Condensed Matter Physics 2008 (2008): 1–7. http://dx.doi.org/10.1155/2008/703479.
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Aluminum doped manganese ferritesMnAlxFe2−xO4with0.0≤x≤1.0have been prepared by the double ceramic route. The formation of mixed spinel phase has been confirmed by X-ray diffraction analysis. The unit cell parameter `aO' is found to decrease linearly with aluminum concentration due to smaller ionic radius of aluminum. The cation distributions were estimated from X-ray diffraction intensities of various planes. The theoretical lattice parameter, X-ray density, oxygen positional parameter, ionic radii, jump length, and bonds and edges lengths of the tetrahedral (A) and octahedral (B) sites were determined.57Fe Mössbauer spectra recorded at room temperature were fitted with two sextets corresponding to Fe3+ions at A- and B-sites. In the present ferrite system, the area ratio of Fe3+ions at the A- and B-sites determined from the spectral analysis of Mössbauer spectra gives evidence that Al3+ions replace iron ions at B-sites. This change in the site preference reflects an abrupt change in magnetic hyperfine fields at A- and B-sites as aluminum concentration increases, which has been explained on the basis of supertransferred hyperfine field. On the basis of estimated cation distribution, it is concluded that aluminum doped manganese ferrites exhibit a 55% normal spinel structure.
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Myronchuk, G. L., O. V. Zamurueva, K. Oźga, M. Szota, A. M. El-Naggar, N. S. Alzayed, L. V. Piskach, et al. "Photoinduced Optical Properties Of Tl1−xIn1−xSixSe2 Single Crystals." Archives of Metallurgy and Materials 60, no. 2 (June 1, 2015): 1051–55. http://dx.doi.org/10.1515/amm-2015-0258.
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Abstract The influence of temperature on electroconductivity and photoinduced changes of the absorption at 0.15 eV under influence of the second harmonic generation of CO2 laser for the two type of single crystals were investigated. The single crystals Tl1−xIn1−xSixSe2 (x=0.1 and 0.2) have been grown by the two-zone Bridgaman-Stockbarger method. The temperature studies of electroconductivity were done in cryostat with thermoregulation in the temperature 77 - 300 K, with stabilization ±0.1 K. Photoinduced treatment of the investigated single crystals were performed using the 180 ns pulses second harmonic generation of the CO2 laser operating at 5.3 μm. Experimental studies have shown that for the Tl1−xIn1−xSixSe2 single crystals with decreasing temperature from 300 up to 240 K and from 315 up to 270 K the conductivity is realized by thermally excited impurities with activation energies equal to about 0.24 eV and 0.22 eV for x= 0.1 and 0.2, respectively. Photoinduced absorption achieves its maximum at a power density below 100 mJ/cm2. Has been shown that the samples with x=0.2 demonstrated higher changes of the photoinduced absorption with respect to the x=0.1. With further decreasing temperature is observed monotonic decrease in the activation energy of conductivity. The origin of these effects is caused by the excitations of both the electronic as well as phonon subsystem. At some power densities the anharmonic excitations become dominant and as a consequence the photoinduced absorption dependence is saturated what were observed. Additionally, we were evaluated at given temperature the average jump length of R for localized states near Fermi level.
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Roznik, Elizabeth A., Natalia Cano, Kerri L. Surbaugh, Chloe T. Ramsay, and Jason R. Rohr. "Invasive Cuban Treefrogs (Osteopilus septentrionalis) Have More Robust Locomotor Performance Than Two Native Treefrogs (Hyla spp.) in Florida, USA, in Response to Temperature and Parasitic Infections." Diversity 13, no. 3 (March 5, 2021): 109. http://dx.doi.org/10.3390/d13030109.
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Introduced species pose a threat to biodiversity, and ecological and physiological factors are important in determining whether an introduced species becomes successfully established in a new region. Locomotor performance is one such factor that can influence the abundance and distribution of an introduced species. We investigated the effects of temperature and parasitism by the intestinal nematode Aplectana hamatospicula on the maximum jump distance and endurance in one invasive and two native treefrogs in Florida, USA. We collected frogs from the wild, estimated their parasite loads, and tested their locomotor performance at three temperatures. Contrary to expectations, invasive Cuban treefrogs (Osteopilus septentrionalis), which are adapted to a warmer climate in the Caribbean, outperformed pinewoods treefrogs (Hyla femoralis) and squirrel treefrogs (H. squirella) at each temperature, even when controlling for body size differences. In all three species, maximum jump distance was positively related to temperature, and this relationship was stronger for larger frogs. Parasites influenced both the maximum jump distance and endurance of frogs. In all three species, larger frogs jumped farther maximum distances than smaller frogs, but this relationship was stronger when frogs had lower, rather than higher, parasite loads. Parasitism had little effect on endurance in invasive frogs, but it tended to decrease the endurance of native frogs at high temperatures. Furthermore, at low temperatures, the lengths of consecutive jumps of infected native frogs tended to increase, suggesting that parasites limited the distances of initial jumps. Effects of temperature and parasites on the locomotor performance of frogs could influence their abilities to forage, escape predators, and disperse. The tremendous locomotor performance of O. septentrionalis, which is maintained across temperatures and parasite loads, likely contributes to the invasion success of this species.
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Jakkula, Puneeth, Georg Ganzenmüller, Samuel Beisel, and Stefan Hiermaier. "Investigating slow shock in low-impedance materials using a direct impact Hopkinson bar setup." EPJ Web of Conferences 250 (2021): 06009. http://dx.doi.org/10.1051/epjconf/202125006009.
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This work implements a direct impact Hopkinson bar, suitable for investigating the evolution of dynamic force equilibrium in low-impedance materials. Polycarbonate as the bar material favours for a long pulse duration of 2.6 ms for an overall length of only 5 m, allowing to compress large specimens to high strains. This setup is applied to polyurethane foams with different densities ranging from 80 - 240 kg/m3. Dynamic compression tests are performed at strain rates of 0.0017, 0.5 and 500 /s on the foams at room temperature. Depending on density, they show a saturation in increase of yield strength at strain rates of 500 /s, or even show a negative strain rate sensitivity for the lowest density. This behaviour is explained by comparing the dynamic force equilibrium to a phenomenon similar to shock in solid materials: For low densities and high rates of strain, homogeneous compression is replaced by a localized collapse front with a jump in stress across the front. Digital image correlation is performed to analyse elastic and plastic compaction waves by means of Lagrange diagrams.
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Rzayev, A. H., G. A. Guluyev, F. H. Pashayev, As H. Rzayev, and R. Sh Asadova. "Mathematical Models for Determining the Distribution of Fluid Flow Temperature along the Wellbore and Horizontal Pipeline." Mekhatronika, Avtomatizatsiya, Upravlenie 21, no. 6 (June 4, 2020): 337–47. http://dx.doi.org/10.17587/mau.21.337-347.
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This paper presents a proposed new indirect method determining instantly oil well debit using developed mathematical models. As a result integrated analysis using the models it has been revealed correlation between oil well debit and well throw out flow temperature. Therefore putting purpose was obtained. Mathematical models are developed for the distribution of fluid flow temperature along the length of the tubing from the well bottom to the wellhead and along the length of the oil pipeline from the collector of oil wells to the oil treatment unit. On the basis of experimental data, the authors propose formulas in the form of the relationship between oil emulsion (OE) viscosity, the flow temperature and concentration of water globule in OE and the coefficient of heat transfer from the fluid flow in the wellbore (WB) to the rock, and heat capacity and thermal conductivity of gas, water, rock and steel of the WB walls. This effect is demonstrated in the constructed diagrams. It is shown bottom temperature jump as a result of the Joule Thomson drosseling effect then connective transmitted up at flow rate v. In such case well-head or well outlet oil mixture (OM) flow temperature depend more of volume of stream flow than of bottom hole temperature. Thought in the paper, do not taking into consideration great casing annulus areas influence to the well outlet flow temperature. As shown from supporting paper the relative values og the thermal conductivity of the liquid column and gas column present in the casing annulus order less than well bore (WB) wall thermal conductivity. Consequently well outlet OM flow temperature will depends not only of the volume of stream flow, also of the bottom hole temperature and of the gas column and liquid column.A new method for determining the oil well flow rate by measuring the downstream temperature is developed. A mathematical model is proposed that allows calculating the thermal profile of the fluid along the wellbore for determining the oil well flow rate with account of the geothermal gradient in the rock surrounding the wellbore. It is shown, that unlike the existing methods the new proposed method allows determining the instantaneous discharge of a well very easily. One of the actual challenges in fluid (oil, water and gas) transportation from wells to oil treatment installation is determination of a law of temperature distribution along the length of a pipeline at low ambient temperature. That temperature leads to increase in viscosity and deposition of wax on inner surface of a pipe. To overcome that challenge it is needed to consider several defining characteristics of formation fluid (FF) flow. Complexity of a solution is caused by two factors. From the one hand, in most cases (especially on a late stage of field development) FF is an oil emulsion (OE) that contains gas bubbles. From the other hand, temperature gradient between fluid flow and the environment has significant value (especially in the winter period of the year). At the same time, the higher content of emulsified water droplets (EWD) in OE and lower flow temperature, the higher FF viscosity, and consequently productivity (efficiency) of oil pumping system is reduced. Performed research and analysis of field experimental data showed that a function of oil viscosity versus temperature has a hyperbolic law; a function of OE viscosity versus concentration of EWD has a parabolic one. A heat balance for a certain section of a pipeline in steady state of fluid motion using a method of separation of variables was established taking into account above mentioned factors, Fourier’s empirical laws on heat conductivity and Newton’s law on heat transfer. As a result, unlike existing works, an exponential law of distribution of temperature along the length of a pipeline is obtained. A law takes into account nonlinear nature of change in viscosity of OE from change in temperature of flow and concentration of water in an emulsion. As a result, in contrast to the existing works, the proposed exponential law of temperature distribution along the length of the pipeline is obtained, taking into account the nonlinear nature of variation of OE viscosity with the change in the flow temperature and the concentration of water in the emulsion. The results of the calculation are presented in the form of a table and graphs.
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Peplowski, M. M., and R. L. Marsh. "Work and power output in the hindlimb muscles of Cuban tree frogs Osteopilus septentrionalis during jumping." Journal of Experimental Biology 200, no. 22 (November 1, 1997): 2861–70. http://dx.doi.org/10.1242/jeb.200.22.2861.
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It has been suggested that small frogs use a catapult mechanism to amplify muscle power production during the takeoff phase of jumping. This conclusion was based on an apparent discrepancy between the power available from the hindlimb muscles and that required during takeoff. The present study provides integrated data on muscle contractile properties, morphology and jumping performance that support this conclusion. We show here that the predicted power output during takeoff in Cuban tree frogs Osteopilus septentrionalis exceeds that available from the muscles by at least sevenfold. We consider the sartorius muscle as representative of the bulk of the hindlimb muscles of these animals, because this muscle has properties typical of other hindlimb muscles of small frogs. At 25 degrees C, this muscle has a maximum shortening velocity (Vmax) of 8.77 +/- 0.62 L0 s-1 (where L0 is the muscle length yielding maximum isometric force), a maximum isometric force (P0) of 24.1 +/- 2.3 N cm-2 and a maximum isotonic power output of 230 +/- 9.2 W kg-1 of muscle (mean +/- S.E.M.). In contrast, the power required to accelerate the animal in the longest jumps measured (approximately 1.4 m) is more than 800 W kg-1 of total hindlimb muscle. The peak instantaneous power is expected to be twice this value. These estimates are probably conservative because the muscles that probably power jumping make up only 85% of the total hindlimb muscle mass. The total mechanical work required of the muscles is high (up to 60 J kg-1), but is within the work capacities predicted for vertebrate skeletal muscle. Clearly, a substantial portion of this work must be performed and stored prior to takeoff to account for the high power output during jumping. Interestingly, muscle work output during jumping is temperature-dependent, with greater work being produced at higher temperatures. The thermal dependence of work does not follow from simple muscle properties and instead must reflect the interaction between these properties and the other components of the skeletomuscular system during the propulsive phase of the jump.
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Широкий, Ю. В., and Г. І. Костюк. "МОДЕЛЮВАННЯ ДУГОВОГО РОЗРЯДУ НА МІДНОМУ КАТОДІ ДЛЯ ГЕНЕРАЦІЇ НАНОСТРУКТУР." Open Information and Computer Integrated Technologies, no. 91 (June 18, 2021): 62–76. http://dx.doi.org/10.32620/oikit.2021.91.05.
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The paper considers the model of processes acting in the ionization layer of the cathode assembly during plasma generation of nanostructures. In the given model the processes in electrodynamic and gas - dynamic layers of plasma and their coordination are rather densely considered. Therefore, the solution of the model allows to adequately determine the magnitude of the cathode potential jump in the electrodynamic layer, which allows to compensate for all energy losses during the generation of nanostructures, and the magnitude of ion and electron fluxes at the cathode. The calculations were performed at a constant value of the elongation of the ionization layer, because it has little effect on the change in the ion current density along the length of the cathode layers. Also, the calculations confirmed a non-significant dependence of the initial pressure from the ionization layer on the temperature of the electrons. The obtained dependences, the fraction of ionic current at the cathode and the cathode potential drop from the current density at different cathode temperatures, showed that the change in the proportion of ionic current makes it possible to compensate for energy costs to maintain the cathode temperature. And consideration of the equation of energy balance allowed to establish the range of losses of the working fluid at which it is possible not to take into account the energy of evaporation of the working fluid and steam heating. To determine the current density at the cathode, the dependence of the thermoemission current on the cathode temperature and the dependence of the current density on the cathode on the plasma concentration at different cathode drops and different representations of electric field strengths were obtained. This allowed to determine the cathode temperature due to the ionic current density and to estimate the plasma concentration. Depending on the plasma concentration, the electric transfer coefficient for different emission mechanisms and cathode drops is obtained. All this allowed us to determine the dependence of the specific gravity leaving the cathode per unit time per unit area, on the cathode temperature and heat flux density for the copper cathode. Determining the specific gravity and the transfer coefficient makes it possible to determine the life of the cathode during plasma generation of nanostructures.
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Roy, Ansu K., Amrita Singh, Karishma Kumari, K. Amar Nath, Ashutosh Prasad, and K. Prasad. "Electrical Properties and AC Conductivity of (Bi0.5Na0.5)0.94Ba0.06TiO3 Ceramic." ISRN Ceramics 2012 (October 15, 2012): 1–10. http://dx.doi.org/10.5402/2012/854831.
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Lead-free perovskite (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBT06) was prepared by conventional ceramic fabrication technique at 1160°C/3h in air atmosphere. The crystal structure, microstructure, dielectric, polarization, piezoelectric properties, and ac conductivity of the sample were studied. X-ray diffraction data confirmed the formation of a single phase tetragonal unit cell. Williamson-Hall plot was used to calculate the lattice strain and the apparent particle size. The experimental relative density of BNBT06 was found to be ~96-97% of the theoretical one with an average grain size ~4 μm. Room temperature dielectric constant and loss factor at 1 kHz were found to be equal to 781 and 0.085, respectively. Longitudinal piezoelectric charge coefficient of the poled sample under 2.5 kV/mm at 80°C in silicone bath was found to be equal to 124 pC/N. Complex impedance and electric modulus spectroscopic analyses showed the dielectric relaxation in the material to be of non-Debye type. The Nyquist plots and conductivity studies showed the NTCR character of BNBT06. The correlated barrier hopping model (CBHM) as well as jump relaxation model (JRM) was found to successfully explain the mechanism of charge transport in BNBT06. The ac conductivity data were used to evaluate the minimum hopping length, apparent activation energy, and density of states at Fermi level.
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Weatherhead, Elizabeth C., Jerald Harder, Eduardo A. Araujo-Pradere, Greg Bodeker, Jason M. English, Lawrence E. Flynn, Stacey M. Frith, et al. "How long do satellites need to overlap? Evaluation of climate data stability from overlapping satellite records." Atmospheric Chemistry and Physics 17, no. 24 (December 20, 2017): 15069–93. http://dx.doi.org/10.5194/acp-17-15069-2017.
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Abstract. Sensors on satellites provide unprecedented understanding of the Earth's climate system by measuring incoming solar radiation, as well as both passive and active observations of the entire Earth with outstanding spatial and temporal coverage. A common challenge with satellite observations is to quantify their ability to provide well-calibrated, long-term, stable records of the parameters they measure. Ground-based intercomparisons offer some insight, while reference observations and internal calibrations give further assistance for understanding long-term stability. A valuable tool for evaluating and developing long-term records from satellites is the examination of data from overlapping satellite missions. This paper addresses how the length of overlap affects the ability to identify an offset or a drift in the overlap of data between two sensors. Ozone and temperature data sets are used as examples showing that overlap data can differ by latitude and can change over time. New results are presented for the general case of sensor overlap by using Solar Radiation and Climate Experiment (SORCE) Spectral Irradiance Monitor (SIM) and Solar Stellar Irradiance Comparison Experiment (SOLSTICE) solar irradiance data as an example. To achieve a 1 % uncertainty in estimating the offset for these two instruments' measurement of the Mg II core (280 nm) requires approximately 5 months of overlap. For relative drift to be identified within 0.1 % yr−1 uncertainty (0.00008 W m−2 nm−1 yr−1), the overlap for these two satellites would need to be 2.5 years. Additional overlap of satellite measurements is needed if, as is the case for solar monitoring, unexpected jumps occur adding uncertainty to both offsets and drifts; the additional length of time needed to account for a single jump in the overlap data may be as large as 50 % of the original overlap period in order to achieve the same desired confidence in the stability of the merged data set. Results presented here are directly applicable to satellite Earth observations. Approaches for Earth observations offer additional challenges due to the complexity of the observations, but Earth observations may also benefit from ancillary observations taken from ground-based and in situ sources. Difficult choices need to be made when monitoring approaches are considered; we outline some attempts at optimizing networks based on economic principles. The careful evaluation of monitoring overlap is important to the appropriate application of observational resources and to the usefulness of current and future observations.
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JIN, Y. K., M. W. LEE, Y. KIM, S. H. NAM, and K. J. KIM. "Gas hydrate volume estimations on the South Shetland continental margin, Antarctic Peninsula." Antarctic Science 15, no. 2 (May 20, 2003): 271–82. http://dx.doi.org/10.1017/s0954102003001275.
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Multi-channel seismic data acquired on the South Shetland margin, northern Antarctic Peninsula, show that Bottom Simulating Reflectors (BSRs) are widespread in the area, implying large volumes of gas hydrates. In order to estimate the volume of gas hydrate in the area, interval velocities were determined using a 1-D velocity inversion method and porosities were deduced from their relationship with sub-bottom depth for terrigenous sediments. Because data such as well logs are not available, we made two baseline models for the velocities and porosities of non-gas hydrate-bearing sediments in the area, considering the velocity jump observed at the shallow sub-bottom depth due to joint contributions of gas hydrate and a shallow unconformity. The difference between the results of the two models is not significant. The parameters used to estimate the total volume of gas hydrate in the study area were 145 km of total length of BSRs identified on seismic profiles, 350 m thickness and 15 km width of gas hydrate-bearing sediments, and 6.3% of the average volume gas hydrate concentration (based on the second baseline model). Assuming that gas hydrates exist only where BSRs are observed, the total volume of gas hydrates along the seismic profiles in the area is about 4.8 × 1010 m3 (7.7 × 1012 m3 volume of methane at standard temperature and pressure).
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Ebrahimi, Amin, Vahid Shahabi, and Ehsan Roohi. "Pressure-Driven Nitrogen Flow in Divergent Microchannels with Isothermal Walls." Applied Sciences 11, no. 8 (April 16, 2021): 3602. http://dx.doi.org/10.3390/app11083602.
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Gas flow and heat transfer in confined geometries at micro-and nanoscales differ considerably from those at macro-scales, mainly due to nonequilibrium effects such as velocity slip and temperature jump. Nonequilibrium effects increase with a decrease in the characteristic length-scale of the fluid flow or the gas density, leading to the failure of the standard Navier–Stokes–Fourier (NSF) equations in predicting thermal and fluid flow fields. The direct simulation Monte Carlo (DSMC) method is employed in the present work to investigate pressure-driven nitrogen flow in divergent microchannels with various divergence angles and isothermal walls. The thermal fields obtained from numerical simulations are analysed for different inlet-to-outlet pressure ratios (1.5≤Π≤2.5), tangential momentum accommodation coefficients, and Knudsen numbers (0.05≤Kn≤12.5), covering slip to free-molecular rarefaction regimes. The thermal field in the microchannel is predicted, heat-lines are visualised, and the physics of heat transfer in the microchannel is discussed. Due to the rarefaction effects, the direction of heat flow is largely opposite to that of the mass flow. However, the interplay between thermal and pressure gradients, which are affected by geometrical configurations of the microchannel and the applied boundary conditions, determines the net heat flow direction. Additionally, the occurrence of thermal separation and cold-to-hot heat transfer (also known as anti-Fourier heat transfer) in divergent microchannels is explained.
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Catalano, Franco, and Antonio Cenedese. "High-Resolution Numerical Modeling of Thermally Driven Slope Winds in a Valley with Strong Capping." Journal of Applied Meteorology and Climatology 49, no. 9 (September 1, 2010): 1859–80. http://dx.doi.org/10.1175/2010jamc2385.1.
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Abstract The complete day–night cycle of the circulation over a slope under simplified idealized boundary conditions is investigated by means of large-eddy simulations (LES). The thermal forcing is given with a time-varying law for the surface temperature. A surface layer parameterization based on the Monin–Obukhov similarity theory is used as a wall layer model. The domain geometry is symmetric, having an infinitely long straight valley in the y direction. Since the depth of the katabatic flow in midlatitude climates is limited to 5–30 m, the authors introduced a vertically stretched grid to obtain a finer mesh near the ground. The length scale for the calculation of eddy viscosities is modified to take into account the grid anisotropy. A preintegration of 24 h is made to obtain a capping inversion over the valley. Results show that the model is able to reproduce microscale circulation dynamics driven by thermal forcing over sloping terrain. The diurnal growth of the convective boundary layer leading to the development of the anabatic wind as well as the evolution of the cold pool in the valley during the night and its interaction with the katabatic flow are shown. Waves develop at the interface between the anabatic current and the return flow. During the day, as a combined effect of the geometry and the forcing, a horizontal breeze develops directed from the middle of the valley toward the ridges. The impact of the gravity current on the quiescent atmosphere in the valley generates a weak hydraulic jump during the night.
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Princevac, M., J. C. R. Hunt, and H. J. S. Fernando. "Quasi-Steady Katabatic Winds on Slopes in Wide Valleys: Hydraulic Theory and Observations." Journal of the Atmospheric Sciences 65, no. 2 (February 1, 2008): 627–43. http://dx.doi.org/10.1175/2007jas2110.1.
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Abstract Theoretical and field observational studies on mean velocity and temperature fields of quasi-steady nocturnal downslope (katabatic) flows on sloping surfaces are reported for the case of very wide valleys in the presence of weak synoptic winds. Because of the lateral constraints on the flow, Coriolis effects are considered negligible. The layer-averaged equations of Manins and Sawford were used for the analysis. It is shown that (i) in the absence of significant turbulent entrainment into the current (i.e., at large Richardson numbers Ri = Δh cosα/U2) the downslope flow velocity U is related to the slope length (LH), slope angle (α), and the buoyancy jump between the current and the background atmosphere (Δ) as U = λu(ΔLH sinα)1/2, where λu is a constant and h is the flow depth; (ii) on very long slopes h is proportional to Lh(tanα)1/2; and (iii) under highly stable conditions (i.e., Ri > 1) the katabatic flow exhibits pulsations with period T0 = 2π/N sinα, where N is the buoyancy frequency of the background atmosphere. These predictions are verified principally using observations made during the Vertical Transport and Mixing Experiment (VTMX) conducted in Salt Lake City, Utah, in October 2000. By assuming the flow follows a straight line trajectory to the nearest ridgeline a good agreement was found between the predictions and observations over appropriate Richardson number ranges. For Ri > 1.5, λu ≈ 0.2, although λu was a decreasing function of Ri at lesser stabilities. Oscillations with period T0 are simply alongslope (critical) internal-wave oscillations with a slope-normal wavenumber, which are liable for degeneration into turbulence during their reflection. These critical internal waves may be responsible, at least partly, for weak sustained turbulence often observed in complex-terrain nocturnal boundary layer flows.
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Singh, Harpreet, and Rho Shin Myong. "Critical Review of Fluid Flow Physics at Micro- to Nano‐scale Porous Media Applications in the Energy Sector." Advances in Materials Science and Engineering 2018 (December 4, 2018): 1–31. http://dx.doi.org/10.1155/2018/9565240.
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While there is a consensus in the literature that embracing nanodevices and nanomaterials helps in improving the efficiency and performance, the reason for the better performance is mostly subscribed to the nanosized material/structure of the system without sufficiently acknowledging the role of fluid flow mechanisms in these systems. This is evident from the literature review of fluid flow modeling in various energy-related applications, which reveals that the fundamental understanding of fluid transport at micro- and nanoscale is not adequately adapted in models. Incomplete or insufficient physics for the fluid flow can lead to untapped potential of these applications that can be used to increase their performance. This paper reviews the current state of research for the physics of gas and liquid flow at micro- and nanoscale and identified critical gaps to improve fluid flow modeling in four different applications related to the energy sector. The review for gas flow focuses on fundamentals of gas flow at rarefied conditions, the velocity slip, and temperature jump conditions. The review for liquid flow provides fundamental flow regimes of liquid flow, and liquid slip models as a function of key modeling parameters. The four porous media applications from energy sector considered in this review are (i) electrokinetic energy conversion devices, (ii) membrane-based water desalination through reverse osmosis, (iii) shale reservoirs, and (iv) hydrogen storage, respectively. Review of fluid flow modeling literature from these applications reveals that further improvements can be made by (i) modeling slip length as a function of key parameters, (ii) coupling the dependency of wettability and slip, (iii) using a reservoir-on-chip approach that can enable capturing the subcontinuum effects contributing to fluid flow in shale reservoirs, and (iv) including Knudsen diffusion and slip in the governing equations of hydrogen gas storage.
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Ludwig, H. G., B. Freytag, and M. Steffen. "An Improved Calibration of the Mixing-Length Based on Simulations of Solar-Type Convection." Symposium - International Astronomical Union 185 (1998): 115–16. http://dx.doi.org/10.1017/s0074180900238394.
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Based on detailed 2D numerical radiation hydrodynamics (RHD) calculations of time-dependent compressible convection, we have studied the dynamics and thermal structure of the convective surface layers of stars in the range of effective temperatures and gravities between 4500 K ≤ Teff ≤ 7100 K and 2.54 ≤ log g ≤ 4.74. Although our hydrodynamical models describe only the shallow, strongly superadiabatic layers at the top of the convective stellar envelope, they provide information about the value of the entropy s∗ of the deeper, adiabatically stratified regions. E.g. in the solar case the helioseismically measured entropy jump is predicted within 9% of its actual value.
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Bendeif, El-Eulmi, Claude Lecomte, and Slimane Dahaoui. "Following an isosymmetric phase transition by changes in bond lengths and anisotropic displacement parameters: the case of meta-carboxyphenylammonium phosphite." Acta Crystallographica Section B Structural Science 65, no. 1 (January 15, 2009): 59–67. http://dx.doi.org/10.1107/s0108768108042298.
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Crystal structure studies in the 100–345 K temperature range were performed to relate the molecular structure changes of meta-carboxyphenylammonium phosphite (m-CPAMP) to its first-order phase transition at T c = 246 (2) K. Thermal displacement parameters and most bond distances show an abrupt jump at the transition. Such a structural change is related to collective effects leading to competition between intra- and intermolecular interactions.
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SHORT, MARK, and JAMES J. QUIRK. "On the nonlinear stability and detonability limit of a detonation wave for a model three-step chain-branching reaction." Journal of Fluid Mechanics 339 (May 25, 1997): 89–119. http://dx.doi.org/10.1017/s002211209700503x.
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The nonlinear stability of a pulsating detonation wave driven by a three-step chain-branching reaction is studied. The reaction model consists sequentially of a chain-initiation step and a chain-branching step, both governed by Arrhenius kinetics, followed by a temperature-independent chain-termination step. The model mimics the essential dynamics of a real chain-branching chemical system, but is sufficiently idealized that a theoretical analysis of the instability is possible. We introduce as a bifurcation parameter the chain-branching cross-over temperature (TB), which is the temperature at which the chain-branching and chain-termination rates are equal. In the steady detonation structure, this parameter controls the ratio of the chain-branching induction length to the length of the recombination zone. When TB is at the lower end of the range studied, the steady detonation structure, which is dominated by the temperature-independent recombination zone, is found to be stable. Increasing TB increases the length of the chain-branching induction region relative to the length of the recombination zone, and a critical value of TB is reached where the detonation becomes unstable, with the detonation shock pressure evolving as a single-mode low-frequency pulsating oscillation. This single-mode nonlinear oscillation becomes progressively less stable as TB is increased further, persisting as the long-term dynamical behaviour for a significant range of TB before eventually undergoing a period-doubling bifurcation to a two-mode oscillation. Further increases in TB lead to a chaotic behaviour, where the detonation shock pressure history consists of a sequence of substantive discontinuous jumps, followed by lower-amplitude continuous oscillations. Finally, for further increases in TB a detonability limit is reached, where during the early onset of the detonation instability, the detonation shock temperature drops below the chain-branching cross-over temperature causing the wave to quench.
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Ekanayake, Ruwini S. K., Christopher T. Chantler, Daniel Sier, Martin J. Schalken, Alexis J. Illig, Martin D. de Jonge, Bernt Johannessen, Peter Kappen, and Chanh Q. Tran. "High-accuracy measurement of mass attenuation coefficients and the imaginary component of the atomic form factor of zinc from 8.51 keV to 11.59 keV, and X-ray absorption fine structure with investigation of zinc theory and nanostructure." Journal of Synchrotron Radiation 28, no. 5 (July 19, 2021): 1492–503. http://dx.doi.org/10.1107/s1600577521005981.
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High-accuracy X-ray mass attenuation coefficients were measured from the first X-ray Extended Range Technique (XERT)-like experiment at the Australian Synchrotron. Experimentally measured mass attenuation coefficients deviate by ∼50% from the theoretical values near the zinc absorption edge, suggesting that improvements in theoretical tabulations of mass attenuation coefficients are required to bring them into better agreement with experiment. Using these values the imaginary component of the atomic form factor of zinc was determined for all the measured photon energies. The zinc K-edge jump ratio and jump factor are determined and results raise significant questions regarding the definitions of quantities used and best practice for background subtraction prior to X-ray absorption fine-structure (XAFS) analysis. The XAFS analysis shows excellent agreement between the measured and tabulated values and yields bond lengths and nanostructure of zinc with uncertainties of from 0.1% to 0.3% or 0.003 Å to 0.008 Å. Significant variation from the reported crystal structure was observed, suggesting local dynamic motion of the standard crystal lattice. XAFS is sensitive to dynamic correlated motion and in principle is capable of observing local dynamic motion beyond the reach of conventional crystallography. These results for the zinc absorption coefficient, XAFS and structure are the most accurate structural refinements of zinc at room temperature.
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Vovk, Ruslan V., Georgij Ya Khadzhai, and Oleksandr V. Dobrovolskiy. "Conductivity anisotropy in Y1-yPryBa2Cu3O7-δ single crystals in a wide range of praseodymium concentrations." Modern Physics Letters B 28, no. 31 (December 20, 2014): 1450245. http://dx.doi.org/10.1142/s0217984914502455.
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Anisotropies of different conductivity mechanisms in Y 1-y Pr y Ba 2 Cu 3 O 7-δ single crystals in a wide range of praseodymium concentrations are reported, assuming a transition from the metallic conductivity to the semiconductor-like regime, in conjunction with the fluctuation conductivity within the 3D Aslamazov–Larkin model. The Tc anisotropy grows with increasing y, with a most drastic rise when approaching the non-superconducting composition. As the praseodymium concentration increases, the ideal resistance anisotropy passes through a maximum at y ≈ 0.19. The temperature dependence of the semiconductor-like resistance anisotropy exhibits a maximum associated with variable-range jumps along the c-axis. The temperature dependence of the fluctuation conductivity anisotropy passes through a maximum due to a significant anisotropy of the coherence length.