基于德拜模型讨论晶格比热

晶格比热是反映晶体热学性质的一个重要物理量。对晶格比热的具体求解是一个相当复杂的问题,在一般讨论中,常采用爱因斯坦模型及德拜模型。本文基于德拜模型系统地研究了一维简单晶格,二维简单晶格以及三维晶格的晶格比热,并讨论了高低温极限,对进一步理解德拜模型的物理思想,及其讨论具体问题的方法有重要意义。     

Numerical simulation of water mitigation effects on shock wave with SPH method

The water mitigation effect on the propagation of shock wave was investigated numerically. The traditional smoothed particle hydrodynamics (SPH) method was modified based on Riemann solution. The comparison of numerical results with the analytical solution indicated that the modified SPH method has more advantages than the traditional SPH method. Using the modified SPH algorithm, a series of one-dimensional planar wave propagation problems were investigated, focusing on the influence of the air-gap between the high-pressure air and water and the thickness of water. The numerical results showed that water mitigation effect is significant. Up to 60% shock wave pressure reduction could be achieved with the existence of water, and the shape of shock wave was also changed greatly. It is seemly that the small air-gap between the high-pressure air and water has more influence on water mitigation effect.     

Effect of Shock Wave on Fabricated Anti-Blast Wall and Distribution Law Around the Wall Under Near Surface Explosion

The loads of shock wave effect on fabricated anti-blast wall and distribution law around the wall were investigated by using near surface explosion test method and FEM.The pressure-time histories and variety law on the foreside and backside of the anti-blast wall were adopted in the tests of variety of different explosion distances and dynamites,as well as in the comparison between the test and numerical calculation.The test results show that the loads of shock wave effect on the anti-blast wall were essen-tially consistent with calculation results using criterion under surface explosion when explosion distances exceed 2 m,the distribution of overpressure behind wall was gained according to variety law based on small-large-small.It is also demonstrated that the peak overpressure behind wall had commonly appeared in wall height by 1.5--2.5 multiples,and the peak overpressures of protective building behind wall could be reduced effectively by using the fabricated anti-blast wall.     

Mesh size effect in numerical simulation of blast wave propagation and interaction with structures

Numerical method is popular in analysing the blast wave propagation and interaction with structures.However,because of the extremely short duration of blast wave and energy trans-mission between different grids,the numerical results are sensitive to the finite element mesh size.Previous numerical simulations show that a mesh size acceptable to one blast scenario might not be proper for another case,even though the difference between the two scenarios is very small,indicating a simple numerical mesh size convergence test might not be enough to guarantee accu-rate numerical results.Therefore,both coarse mesh and fine mesh were used in different blast scenarios to investigate the mesh size effect on numerical results of blast wave propagation and interaction with structures.Based on the numerical results and their comparison with field test re-sults and the design charts in TM5-1300,a numerical modification method was proposed to correct the influence of the mesh size on the simulated results.It can be easily used to improve the accu-racy of the numerical results of blast wave propagation and blast loads on structures.     

对称正则长波方程的奇异孤立波解

利用扩展双曲函数法和齐次平衡原理,将方程的孤波解表示为双曲函数的多项式,从而将非线性对称正则长波方程的求解问题转化为非线性代数方程组的求解问题,得出了对称正则长波方程的奇异孤立波解。     

有机化合物极谱催化氢波研究进展

通过50多篇文献简要地综述了有机化合物极谱催化氢波的历史进程，其过去与现在的发展状况。并由此展望了催化氢波的发展前景。     

黑洞物理研究进展

在现代物理学中,黑洞是最错综复杂的物体之一。它们为类星体和其他活动星系核提供能量,也有助于透彻地理解量子引力。我们回顾一下黑洞的观测上的证据并简单地讨论它们的一些特性,也阐述了一些近年来涉及宇宙监督和黑洞熵统计起源的进展情况。     

High-Temperature Corrosion of Protective Coatings for Boiler Tubes in Thermal Power Plants

High-temperature corrosion is a serious problem for the water-wall tubes of boilers used in thermal power plants. Oxidation, sulfidation and molten salt corrosion are main corrosion ways.Thereinto, the most severe corrosion occurs in molten salt corrosion environment. Materials rich in oxides formers, such as chromium and aluminum, are needed to resist corrosion in high-temperature and corrosive environment, but processability of such bulk alloys is very limited. High velocity electric arc spraying (HVAS) technology is adopted to produce coatings with high corrosion resistance. By comparison, NiCr (Ni-45Cr-4Ti) is recommended as a promising alloy coating for the water-wall tubes, which can even resist molten salt corrosion attack. In the study of corrosion mechanism, the modern material analysis methods, such as scanning electron microscopy ( SEM ), X-ray diffractometry (XRD) and energy dispersive spectrometry (EDS), are used. It is found that the corrosion resistances of NiCr and FeCrAl coatings are much better than that of 20g steel, that the NiCr coatings have the best anti-corrosion properties, and that the NiCr coatings have slightly lower pores than FeCrAI coatings. It is testified that corrosion resistance of coatings is mainly determined by chromium content, and the microstructure of a coating is as important as the chemical composition of the material. In addition, the fracture mechanisms of coatings in the cycle of heating and cooling are put forward. The difference of the thermal physical properties between coatings and base metals results in the thermal stress inside the coatings. Consequently, the coatings spall from the base metal.     

LM317可调式集成稳压电源的设计

LM317系列芯片是目前应用较为灵活的集成稳压器,本文对由LM317构成可调式稳压电源的各部份电路组成、基本工作原理、器件的要求、电源保护功能等作了较为详细的介绍,给出了设计过程的基本理论及实测数据。     

空洞探测问题的概率排序算法

研究了空洞探测问题 ,提出了用概率方法这一新颖思想来确定空洞在平板中的位置 .在一定概率范围内 ,求出了平板内空洞的位置 ,得到在此范围内能够确定平板内空洞位置的前提下 ,减少波源接收器的方法 .特别指出的是 ,随着给定问题所要求概率范围不同 ,所得到的结果亦不同 ,同时空洞的形状也可能不同