中国聚变工程试验堆360°全堆建模与初步核分析北大核心CSCD

基于自动化建模软件平台cosVMPT的发展,建立了包含厂房结构的中国聚变工程试验堆(CFETR)360°全堆模型,主要结构包括中心螺线管线圈、真空室、纵场线圈、极向场线圈、内外冷屏、杜瓦,以及精细结构的水冷包层和偏滤器。空间布置上包括16个上/下窗口和6个中窗口,2个斜窗口作为NBI束通道,其余窗口内设为屏蔽块。引入“on-the-fly”(OTF)全局减方差方法以获得可靠的中子、光子通量,结果显示其在厂房内的分布不对称。验证了cosVMPT平台和OTF方法的可靠性,并与扇段模型所获得的结果进行对比,进一步确认能够通过扇段模型来简化建模计算过程的使用范围。     

高镍正极材料(LiNi0.83Co0.12Mn0.05O2)45°C循环失效机理研究

本文研究了高镍NCM811材料LiNi_0.83Co_0.12Mn_0.05O₂高温45 °C循环失效机理. 通过电化学交流阻抗谱（EIS）技术分析发现45 °C循环失效前后SEI膜阻抗（R_SEI）和电荷转移阻抗（R_ct）增长率最快,分别达到83.43%和211.34%. 采用XPS、TEM及FFT转换、XRD、XANES等手段分别分析了R_SEI和R_ct增长的主要影响因素. 其中,R_SEI增长因素主要包括部分有机SEI膜组分转化成碳酸锂等无机成分,同时反应生成的LiF富集在活性物质周围,SEI膜厚度增长,阻抗升高. R_ct增长因素主要包括晶体结构被破坏,层状晶相结构向尖晶石和岩盐相的转化,材料开裂,使电荷转移阻抗增加. 此外,对固相传质阻抗（R_w）影响因素也进行了分析,主要包括锂镍混排加剧,过渡金属元素溶出导致锂离子固相传质阻抗上升.     

Lateral photovoltage measurements in hydrogenated amorphous silicon and silicon-oxygen thin films

Hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous silicon-oxide alloy films (a-SiO_x:H) were investigated by temperature dependence of lateral photovoltage (LPV) measurements. The suboxide sample with [O] = 27 at.%, was found to exhibit larger LPV compared to the unalloyed sample. It is difficult to simply correlate LPV measurements to related diffusion length measurements, only. On the other hand, the observed magnitude of LPV in a-Si:H and its decrease with temperature, could be explained based on an internal electric field induced by diffusion electron and hole currents, and multiple trapping of the photocarriers.     

Amorphous silicon formation by shearing at ultrahigh pressure

Transmission X-ray diffraction pattern taken from silicon sheared at 10 GPa revealed 8 halo rings. Their densest radii correspond to spacings of 308.4, 264.7, 187.2, 160.5, 152.8, 124.8, 104.9, and 91.5 pm, respectively. The ratios of these values correspond to those of interplanar spacings (1 1 1), (2 0 0), (2 2 0), (3 1 1), (2 2 2), (4 0 0), (3 3 1) and (4 2 0) of face-centered cubic (fcc) lattice. These facts suggest the formation of amorphous state based on fcc structure. This state remains at atmospheric pressure.     

Cauchy问题解的不唯一性定理

设P是R~n上常系数m阶齐次线性偏微分算子,m>1,则对于任何给定的正数c、b、ε,下述Cauchy问题 存在非平凡解u,满足     

Glass-forming Mg-Cu-RE (RE = Gd, Pr, Nd, Tb, Y, and Dy) alloys with strong oxygen resistance in manufacturability

One of the unsolved problems for the manufacturability and the applications of bulk metallic glasses is that their glass-forming ability is very sensitive to the preparation vacuum and impurity of components because oxygen in the environments would markedly deteriorate the glass-forming ability. Here we report that the addition of rare earth elements can significantly improve the glass-forming ability and manufacturability of Mg-based alloys. The Mg-based glass-forming alloys can withstand very low vacuum in preparation process. The beneficial effects of the Gd addition on the glass-forming ability and oxygen resistance during the Mg-based glass formation are explored.     

用傅里叶谱位相方法对运动目标定位

介绍一种利用运动目标图象傅里叶谱位相信息实现对目标定位的新方法，该方法具有较高定位精度，且不受运动目标姿态发迹的影响。文中介绍原理，给出计算机仿真和实验测量结果，并讨论实际应用的可行性。     

Two-Valued Solutions in the Problem of Salt Precipitation during Groundwater Evaporation

The problem of the evaporation of groundwater containing a dissolved admixture is studied. It is shown that in the salt precipitation regime the solution is nonunique. At critical parameter values the solutions merge and in a certain region the solution of the problem disappears. The nonexistence of a solution corresponds to clogging of the pore space with precipitated salt.     

Existence and Nonuniqueness of Weak Solutions of the Initial-Boundary Value Problem for u_t = u~σdiv(|u|~(p-2)u)

In this paper, we study the existence and nonuniqueness of weak solutions of the initial and boundary value problem for ut= uσdiv(|△u|p-2△u) with σ≥1. Localization property of weak solutions is also discussed.