Long-time behavior of solutions for full compressible quantum model in R3

In this paper, long-time behavior of solutions for full compressible quantum flows in three-dimensional whole space is studied. We establish the optimal time decay rates for higher-order spatial derivatives of density, velocity and temperature, which will improve the work of Pu and Guo (2016).     

Global well-posedness and time-decay for the full compressible non-resistive MHD equations in a 3D infinite slab

This paper is concerned with the global well-posedness and time-decay of the system of full compressible viscous non-resistive MHD fluids in a three-dimensional horizontally infinite slab with finite height. We reformulate our analysis to Lagrangian coordinates, and then develop a new mathematical approach to establish global well-posedness of the MHD system, which requires no compatibility conditions on the initial data.     

Wheels' performance of Mars exploration rovers: Experimental study from the perspective of terramechanics and structural mechanics

The soft ground and stones on the surface of Mars may cause sinkage of and damage to the wheels of a Mars rover. Therefore, we analyzed the performance of a wheel-step Mars rover from the perspective of terramechanics and structural mechanics. Using China’s Mars rover wheel prototype and wheel-soil interaction testbed, we obtained the driving performance of the wheels of a Mars rover under various conditions, including full skidding conditions. The vertical load set in the tests was determined using the gravity of Mars and the mass of the wheel-step Mars rover. The results indicate that the driving torque, sinkage, and resistance coefficient have a linear relationship with the wheel vertical load. An analysis of the structural mechanical characteristics of the wheel of the Mars rover was conducted by testing the radial, axial, torsional, and deflection stiffness. We found that the wheel ribs can improve the stiffness of the wheel but may reduce its driving performance. The analysis methods and evaluation indices can be used to analyze the performance of the wheels of other Mars rovers. Furthermore, the findings of this study can be used to optimize wheel design and motion control of wheel-step Mars exploration rovers.     

反射相移对MEMS滤波器半峰全宽影响分析

以典型的基于MEMS的FP腔结构为例,用传输矩阵方法推导了考虑反射相移的半峰全宽的解析表达式.利用此解析表达式分别模拟了考虑反射相移的半峰全宽与干涉级次和FP腔两反射镜间距的关系,并将其与不考虑反射相移的半峰全宽进行了对比;同时将反射相移和反射率对半峰全宽的影响进行了比较分析.     

A new construction of factors of type III1

We give in this paper a new construction of factors of type III₁. Under certain assumptions, we can, thanks to a result by Popa, give a complete classification for this family of factors. Although these factors are never full, we can nevertheless, in many cases, compute Connes' τ invariant. We obtain a new example of an uncountable family of pairwise non-isomorphic factors of type III₁ with the same τ invariant.     

A new family of high-order compact upwind difference schemes with good spectral resolution

This paper presents a new family of high-order compact upwind difference schemes. Unknowns included in the proposed schemes are not only the values of the function but also those of its first and higher derivatives. Derivative terms in the schemes appear only on the upwind side of the stencil. One can calculate all the first derivatives exactly as one solves explicit schemes when the boundary conditions of the problem are non-periodic. When the proposed schemes are applied to periodic problems, only periodic bi-diagonal matrix inversions or periodic block-bi-diagonal matrix inversions are required. Resolution optimization is used to enhance the spectral representation of the first derivative, and this produces a scheme with the highest spectral accuracy among all known compact schemes. For non-periodic boundary conditions, boundary schemes constructed in virtue of the assistant scheme make the schemes not only possess stability for any selective length scale on every point in the computational domain but also satisfy the principle of optimal resolution. Also, an improved shock-capturing method is developed. Finally, both the effectiveness of the new hybrid method and the accuracy of the proposed schemes are verified by executing four benchmark test cases.     

拉曼-光荧光光谱热壁外延生长GaAs/Si薄膜晶体质量研究

本文研究了用热壁外延（HWE）技术在Si衬底上,不同工艺条件生长的GaAs薄膜的拉曼（Raman)和光荧光（PL）光谱。研究表明,在室温下,GaAs晶膜的拉曼光谱的265cm^-1模声子（TO）峰和290cm^-1纵声子（LO）峰的峰值和面积之比随晶膜质量的变化而逐渐变大,FWHM变窄且峰值频移变小,而PL光谱出现在900nm光谱的FWHM较窄,这表明所测得的薄膜为单晶晶膜,在另外一些工艺条件下生长的GaAs薄膜拉曼光谱峰形好,但测不出PL光谱,所生的膜不是单晶,同时对同一晶膜也可判断出其均匀程度,因此我们可以通过拉曼光谱和荧光光谱相结合评定外延膜晶体质量。     

基于波段带宽的谱段测温的优化测量分析

基于窄波段内普适性的线性发射率模型,采用具有Gauss分布的传感器设计,将三波长(单色)辐射温度测量拓展到三波段(谱段)辐射温度测量,提出了使测量具有最佳温度分辨精度的优化准则。讨论优化测量的主要方式是通过改变Gauss分布的半宽度,实现从单色测量到谱段测量的逐渐递进,因而优化分析从传统的分析波长选择上,过渡到分析波段带宽的选择上。对于特定的辐射情形,依据优化准则,数值模拟结果给出了最佳温度分辨精度的波段带宽(即Gauss分布半宽度)分布。最优半宽度的分析表明,单色辐射测量往往并非是最优测量,文章的分析将给辐射优化测量提供重要的理论指导。     

大分子溶致凝聚过程中的几个分界浓度

按照现代高分子凝聚态物理学观点,高分子溶液按浓度分为:极稀溶液、稀溶液、亚浓溶液、浓溶液、极浓溶液5个层次,各层次间的分界浓度分别称为动态接触浓度、接触浓度、缠结浓度和全高斯链浓度,其中全高斯链浓度由本文作者命名。文中给出各分界浓度的定义,介绍各分界浓度的物理意义,特别说明命名全高斯链浓度的依据。同时详细讨论了不同浓度溶液中大分子链的构象及其变化、链间相互作用的本质和微观图像、以及溶液浓度变化对溶液性质的影响。     

A multi-spectral reordering technique for the full spectrum SLMB modeling of radiative heat transfer in nonuniform gaseous mixtures

A Multi-Spectral Reordering (MSR) scheme is introduced to improve the performances of the Spectral-Line Moment-Based (SLMB) modeling for the handling of full spectrum radiative heat transfer calculations in nonuniform media. Using this simultaneous reordering of the spectrum for several thermophysical conditions together with employing approximate formulations to evaluate path-averaged transmission functions for nonisothermal and nonhomogenous gaseous paths, a novel full spectrum gas radiation modeling method in nonuniform gaseous mixtures is constituted. The method is presented in details as well as the building of associated databases for CO₂ and H₂O at atmospheric pressure and for the temperature range of 300-2700 K. The new model is validated against line-by-line reference computations for a series of existing benchmarks and for a flame configuration. The MSR-SLMB modeling is shown to perform accurately and better than the standard SLMB one, while involving reasonable additional computational costs.