共查询到20条相似文献,搜索用时 168 毫秒
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汽化器是LNG汽车燃料系统的重要设备。本文提出将汽化器换热过程分为过冷段、沸腾段与过热段的简化方法,并进行了LNG汽车起步阶段与正常行驶阶段汽化器性能模拟实验研究。 相似文献
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基于密度泛函理论构建了钙钛矿结构ZrBeO3晶体模型,计算了该晶体模型结合能,表明了该构型热力学稳定性;计算出该结构在不同压力下的弹性常数,并据此计算了ZrBeO3的体积模量、剪切模量、杨氏模量、泊松比、BH/GH(体模量/剪切模量)等参数,结果表明该材料具有机械稳定性,随着等静压力增加,材料由脆性向韧性转变;计算了零压下ZrBeO3的硬度,为34.5 GPa,表明该结构晶体应为超硬材料;计算了ZrBeO3的声子能谱,结果表明ZrBeO3在低温零压下热动力学不稳定,为此分析比较了不同压力下的声子能谱、不同原子轨道及化学键布居值,研究表明随着压力增加,Be原子sp杂化后形成的Be-O共价键成分增强、Zr-O键离子键成分增强,晶格动力学趋于稳定。 相似文献
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T. V. Bazhenova S. V. Golovastov V. V. Golub I. N. Laskin N. V. Semin 《Russian Journal of Physical Chemistry B, Focus on Physics》2009,3(6):917-922
The results of a numerical study of the pulsed outflow of hydrogen into an air-filled channel are presented. The adjustable parameters were the initial pressure of hydrogen in the reservoir and the distance from the diaphragm to the ignition point. The pressure, temperature, and water vapor mass fraction profiles along the channel wall at various moments of time were calculated. The autoignition parameters were calculated with account of turbulence, boundary layer formation, heat transfer, and diaphragm opening time. It was demonstrated that the boundary layer effect promotes hydrogen autoignition. The dependence of the distance from the diaphragm to the autoignition point was calculated as a function of the pressure in the reservoir with hydrogen. The simulation results were found to be in close agreement with the available experimental data. 相似文献
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Density-functional theory study of the effect of pressure on the elastic properties of CaB6 下载免费PDF全文
Under high pressure, the long believed single-phase material CaB6 was latterly discovered to have a new phase tI56. Based on the density-functional theory, the pressure effects on the structural and elastic properties of CaB6 are obtained. The calculated bulk, shear, and Young's moduli of the recently synthesized high pressure phase tI56-CaB6 are larger than those of the low pressure phase. Moreover, the high pressure phase of CaB6 has ductile behaviors, and its ductility increases with the increase of pressure. On the contrary, the calculated results indicate that the low pressure phase of CaB6 is brittle. The calculated Debye temperature indicates that the thermal conductivity of CaB6 is not very good. Furthermore, based on the Christoffel equation, the slowness surface of the acoustic waves is obtained. 相似文献
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Abstract In this paper, we report the high pressure band structure and superconductivity calculated for Bi at 9 GPa. The band structure calculation was performed using the LMTO method. The theoretically calculated value of superconducting transition temperature is found to be in good agreement with the experimentally observed value. It is concluded that the same mechanism of s → electron transfer under pressure, which has been used by us for explaining the pressure induced superconductivity in many solids, is found to be responsible for promoting T, in Bi also. 相似文献
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The sound velocities and their pressure and temperature variations of Se and As2Se3 glasses have been determined by means of a pulse superpositions method, and other elastic constants and their pressure and temperature derivatives were calculated from these data. The bulk modulus was found to be 94·6 kbar for Se glass and 143·7 kbar As2Se3 glass, both of which are higher than the values calculated from the previous compression data. No anomaly was observed in any of the pressure and temperature dependence of elastic behavior of these glassses. Furthermore, the comparison of the pressure and temperature derivatives of the bulk modulus indicates that the thermodynamic self-consistency is satisfied on these materials. The bulk moduli of these glasses and crystalline As and Se were used to obtain an empirical bulk modulus-volume relationship for compounds in the As?Se system. The acoustic Grüneisen parameter was calculated and compared with the thermal Grüneisen parameter. 相似文献
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Bin Wen Seiichi TakamiYoshiyuki Kawazoe Tadafumi Adschiri 《Physica B: Condensed Matter》2011,406(13):2654-2657
The pressure-dependent energetic and mechanical stabilities of simple cubic carbon were studied using first-principles calculations. The enthalpies of graphite, diamond, BC8, and simple cubic carbon were calculated, and it was found that simple cubic carbon was the most energetically stable polytype above 2700 GPa. Elastic constants were calculated as a function of pressure. Simple cubic carbon was mechanically unstable below 400 GPa, but became mechanically stable above 400 GPa. Our calculated results also indicated that the bulk module of simple cubic carbon increased linearly with increasing pressure. 相似文献
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The pressure dependence of point-defect concentrations is calculated on the basis of two recently published models. It is demonstrated that the effective formation volume of vacancies shows asymmetrical character about stoichiometry. For Ni-rich and stoichiometric compositions, the concentration of Ni vacancies versus pressure can be described by a simple exponential function. The concentration of Ni antisite defects is independent of pressure. For Al-rich compositions, the concentration of Ni vacancies shows a more complex behaviour. At low pressures the vacancy concentration is independent of pressure, the effective formation volume is zero, while above a critical pressure the vacancy concentration becomes pressure dependent. This can be explained by the annihilation reaction of Ni vacancies. The pressure of complete replacement depends on the stoichiometry and has proved to be very sensitive to the input parameters used in the different models. The changes expected in diffusion activation energy and activation volume with composition are discussed on the basis of calculated temperature and pressure dependence of Ni vacancy concentration, assuming vacancy-mediated diffusion. The pressure effect on the boundary that separates regions in which triple defects or interbranch defects dominate was also investigated. It was observed that pressure expands the region in which Al interbranch defects dominate. 相似文献
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Abstract Raman phonon spectra of 9, 10-dinitroanthracene have been recorded in the pressure range 0-6GPa. No phase transition is detected up to the maximum pressure studied. Quasi Harmonic Lattice Dynamics calculations, based on an atom-atom potential previously modeled on homologous 9,10-disubstituted anthracenes, have been performed. The optimized potential was used to calculate the equilibrium geometry and the lattice phonon frequencies as a function of pressure. The calculated structure at ambient conditions closely resembles the experimental one. The calculated phonon frequencies show a good agreement with the experimental values at all pressures measured. 相似文献
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Vocal fold impact pressures were studied using a self-oscillating finite-element model capable of simulating vocal fold vibration and airflow. The calculated airflow pressure is applied on the vocal fold as the driving force. The airflow region is then adjusted according to the calculated vocal fold displacement. The interaction between airflow and the vocal folds produces a self-oscillating solution. Lung pressures between 0.2 and 2.5 kPa were used to drive this self-oscillating model. The spatial distribution of the impact pressure was studied. Studies revealed that the tissue collision during phonation produces a very large impact pressure which correlates with the lung pressure and glottal width. Larger lung pressure and a narrower glottal width increase the impact pressure. The impact pressure was found to be roughly the square root of lung pressure. In the inferior-superior direction, the maximum impact pressure is related to the narrowest glottis. In the anterior-posteriorfirection, the greatest impact pressure appears at the midpoint of the vocal fold. The match between our numerical simulations and clinical observations suggests that this self-oscillating finite-element model might be valuable for predicting mechanical trauma of the vocal folds. 相似文献