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The response of a single TE102 and double TE104 rectangular cavity to the insertion of samples contained in tubes with variable wall thickness and a quartz Dewar into the cavity has been analyzed. A direct, indirect, and concurrent (positive or negative) “lens effect” inside the double TE104 rectangular cavity is discussed. The experimental dependence of the EPR signal intensity on the wall thickness of the sample tube, δ, for the line-like samples with identical length of the sample material column, L=30 mm, recorded in the microwave cavity showed a directly proportional increase of the relative “lens effect” with the increase of the wall thickness of the tube in the interval, δ∈<0.1 mm, >0.5 mm. The insertion of the variable-temperature double-wall quartz Dewar (home-built, resonant frequency shift, ca. −300 MHz) into the single TE102 rectangular cavity showed the same relative “lens effect”, with ca. 1.5-time increase of the EPR signal intensity, for a point-like sample and the line-like samples with material columns of diameter of 1 and 1.3 mm, and wall thickness of the sample tubes, δ∈<0.1 mm, >0.5 mm. The increased effect of the Dewar arises because the active volume of the quartz Dewar tube walls is always much more larger than the active volume of the sample tube wall. In the case of the double TE104 rectangular cavity, the insertion of the quartz Dewar: (i) into the same cavity, in which the sample is present, caused a direct “lens effect”, with ca. 1.8-fold increase of the EPR signal intensity; however, (ii) into the complementary cavity, in which the sample is absent, caused an indirect “lens effect”, with ca. 0.6-fold decrease of the EPR signal intensity. With the Dewar and sample in one cavity and a large empty sample tube in the complementary cavity, a concurrent (positive or negative) “lens effect” can be observed. Thus, the possible increase/decrease of the EPR signal intensity depends on the volume ratio of the quartz Dewar tube walls and large sample tube wall inserted into the double TE104 rectangular cavity. Each of the above phenomena may be a significant source error in quantitative EPR spectrometry unless the samples to be compared in the quantitative EPR analysis are contained in sample tubes having the same wall thickness and each EPR spectra should be recorded inside an identical quartz Dewar. 相似文献
64.
失效波的研究始于Rasorenov和Kanel发现K1 9玻璃样品后自由表面速度时程曲线上有反常再压缩信号。失效波是二十世纪九十年代冲击动力学研究领域的一个重要发现 ,它是指在一维平面应变冲击压缩下 ,在玻璃等脆性材料中由冲击波引起的一种独特的失效或破坏现象。较为系统地回顾近年来对失效波的研究工作 ,评述了研究现状、最新结果、发展趋势、研究方法和实验手段 ,对尚存的问题进行了分析讨论 ,并介绍了玻璃材料的基本特性。最后简单汇报了作者在这方面的研究工作和取得的阶段性结果。 相似文献
65.
Zhiwei Cao Zhifeng Liu Xiaohong Wang Anfeng Shi Haishan Luo Benoît Noetinger 《国际流体数值方法杂志》2017,85(4):247-263
In this paper, a numerical method to capture the shock wave propagation in 1‐dimensional fluid flow problems with 0 numerical dissipation is presented. Instead of using a traditional discrete grid, the new numerical method is built on a range‐discrete grid, which is obtained by a direct subdivision of values around the shock area. The range discrete grid consists of 2 types: continuous points and shock points. Numerical solution is achieved by tracking characteristics and shocks for the movements of continuous and shock points, respectively. Shocks can be generated or eliminated when triggering entropy conditions in a marking step. The method is conservative and total variation diminishing. We apply this new method to several examples, including solving Burgers equation for aerodynamics, Buckley‐Leverett equation for fractional flow in porous media, and the classical traffic flow. The solutions were verified against analytical solutions under simple conditions. Comparisons with several other traditional methods showed that the new method achieves a higher accuracy in capturing the shock while using much less grid number. The new method can serve as a fast tool to assess the shock wave propagation in various flow problems with good accuracy. 相似文献
66.
In this paper, we are concerned with the behavior of shock waves in a 2 × 2 balance law with discontinuous source terms. We obtain the existence of a local shock wave solution of this problem and deduce that the discontinuous source terms create a weak discontinuity in this solution. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
67.
LIU QingMing BAI ChunHua JIANG Li DAI WenXi & NIU Fang State Key Lab of Explosion Science Technology Beijing Institute of Technology Beijing China 《中国科学:物理学 力学 天文学(英文版)》2011,(3)
The deflagration-to-detonation transitions (DDTs) for clouds of spherical aluminum dust (SAD) mixed with air or epoxypropane mist (EPM) and air were investigated in a 29.6-m-long experimental tube of 199 mm in diameter. The clouds formed through the injection of SAD and SAD/liquid epoxypropane samples into the experimental tube. Explosions of the SAD/air mixture were initiated using a 7-m-long EPM/air cloud explosion ignited by a 40-J electric spark. Explosions in SAD/EPM/air clouds were initiated using a 1... 相似文献
68.
Qiuhua Liang 《国际流体数值方法杂志》2012,69(2):442-458
This paper presents a new simplified grid system that provides local refinement and dynamic adaptation for solving the 2D shallow water equations (SWEs). Local refinement is realized by simply specifying different subdivision levels to the cells on a background uniform coarse grid that covers the computational domain. On such a non‐uniform grid, the structured property of a regular Cartesian mesh is maintained and neighbor information is determined by simple algebraic relationships, i.e. data structure becomes unnecessary. Dynamic grid adaptation is achieved by changing the subdivision level of a background cell. Therefore, grid generation and adaptation is greatly simplified and straightforward to implement. The new adaptive grid‐based SWE solver is tested by applying it to simulate three idealized test cases and promising results are obtained. The new grid system offers a simplified alternative to the existing approaches for providing adaptive mesh refinement in computational fluid dynamics. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
69.
We study the propagation of anisotropic sound and shock waves in dipolar Bose-Einstein condensate in three dimensions (3D) as well as in quasi-two (2D, disk shape) and quasi-one (1D, cigar shape) dimensions using the mean-field approach. In 3D, the propagation of sound and shock waves are distinct in directions parallel and perpendicular to dipole axis with the appearance of instability above a critical value corresponding to attraction. Similar instability appears in 1D and not in 2D. The numerical anisotropic Mach angle agrees with theoretical prediction. The numerical sound velocity in all cases agrees with that calculated from Bogoliubov theory. A movie of the anisotropic wave propagation in a dipolar condensate is made available as supplementary material. 相似文献
70.
Jiankun Shao Rishav Choudhary David F. Davidson Ronald K. Hanson Samuel Barak Subith Vasu 《Proceedings of the Combustion Institute》2019,37(4):4555-4562
The need for more efficient power cycles has attracted interest in super-critical CO2 (sCO2) cycles. However, the effects of high CO2 dilution on auto-ignition at extremely high pressures has not been studied in depth. As part of the effort to understand oxy-fuel combustion with massive CO2 dilution, we have measured shock tube ignition delay times (IDT) for methane/O2/CO2 mixtures and hydrogen/O2/CO2 mixtures using sidewall pressure and OH* emission near 306?nm. Ignition delay time was measured in two different facilities behind reflected shock waves over a range of temperatures, 1045–1578?K, in different pressures and mixture regimes, i.e., CH4/O2/CO2 mixtures at 27–286 atm and H2/O2/CO2 mixtures at 37–311 atm. The measured data were compared with the predictions of two recent kinetics models. Fair agreement was found between model and experiment over most of the operating conditions studied. For those conditions where kinetic models fail, the current ignition delay time measurements provide useful target data for development and validation of the mechanisms. 相似文献