功能梯度材料结构热力耦合概率分析方法

基于自洽平均微观力学W-T(Wakashima-Tsukamoto)模型和拉丁超立方抽样,建立一种功能梯度平板热力耦合概率分析方法.以材料物理属性和空间分布的不确定性随机参数作为概率分析的输入,以热应力作为输出,基于本征正交分解POD(Proper Orthogonal Decomposition)对热应力的随机时间历...     

Theoretical study of the central depression of nuclear charge density distribution by electron scattering

The charge form factors of elastic electron scattering for isotones with N=20 and N=28 are calculated using the phase-shift analysis method, with corresponding charge density distributions from relativistic mean-field theory. The results show that there are sharp variations at the inner parts of charge distributions with the proton number decreasing. The corresponding charge form factors are divided into two groups because of the unique properties of the s-states wave functions, though the proton numbers change uniformly in two isotonic chains. Meanwhile, the shift regularities of the minima are also discussed, and we give a clear relation between the minima of the charge form factors and the corresponding charge radii. This relation is caused by the diffraction effect of the electron. Under this conclusion, we calculate the charge density distributions and the charge form factors of the A=44 nuclei chain. The results are also useful for studying the central depression in light exotic nuclei.     

LOCAL EXISTENCE OF SOLUTION TO FREE BOUNDARY VALUE PROBLEM FOR COMPRESSIBLE NAVIER-STOKES EQUATIONS

This paper is concerned with the free boundary value problem for multidimensional Navier-Stokes equations with density-dependent viscosity where the flow density vanishes continuously across the free boundary. Local (in time) existence of a weak solution is established; in particular, the density is positive and the solution is regular away from the free boundary.     

球形微米镍颗粒的液相体系制备及应用

本研究采用液相还原法,选用六水合硫酸镍为镍源,水合肼为还原剂,在封端剂聚乙烯吡咯烷酮的辅助下,制备得到球形微米镍颗粒。所制备的球形微米镍颗粒粒径约为3 μm,粒径分布均匀,表面粗糙度较低。为了获得球形微米镍颗粒的最优工艺方案,分别探究了PVP浓度、氢氧化钠和水合肼用量及反应温度等工艺参数对产物形貌的影响。研究发现,PVP能够有效控制镍原子的排布和沉积,NaOH可调节反应的pH值,确保水合肼持续还原Ni₂₊^,温度会影响体系的还原反应速率。结果表明：当反应体系使用的PVP浓度为0.5 M、NaOH用量为2.5 mL、水合肼用量为5 mL时,在 60 ℃下水浴反应可获得表面粗糙度低的球形微米镍颗粒,其电导率为5×10₅ S.m_-1^,饱和磁化强度为49.34 emu.g_-1^{。通过添加去离子水、异丙醇和羧甲基纤维素的混合溶液},将球形微米镍颗粒配制成25 wt%的导电油墨,并在纸基表面绘制导电线路,经测试该线路的电导率为1.28×10₃ ^S.m_-1^,此电路在弯折条件下,呈现出良好的工作稳定性。     

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利用电流丝模型对SUNIST球形托卡马克等离子体边界重构进行了模拟计算。结果表明,用电流丝模型能够比较好地对等离子体自由边界进行快速识别,与EFIT平衡计算的边界径向平均误差小于6mm。     

Influence of Positive Bias on Electrical Properties of Undoped Nanocrystalline Diamond Films

By means of electron assisted hot filament chemical vapour deposition technology, nanocrystalline diamond films are deposited on polished n-（100）Si wafer surface at I kPa gas pressure. The deposited films are characterized with a Raman spectrometer, atomic force microscope, semiconductor characterization system and Hall effect measurement system. The results show that, when bias current is larger than 2 A, sheet hole concentration can increase to a value greater than 1013 cm-2 and undoped nanocrystalline diamond films with a p-type semiconducting characteristic form. Heterojunction between n-Si substrate and the nanocrystalline diamond films deposited with 2 A and 6 A bias current has an evident junction effect. Hole formation mechanisms in the films are discussed.     

HL-2M 极向场线圈支撑结构分析评估

基于二维轴对称模型分析了极向场(TF)线圈在单零(SN)、双零(DN)、雪花(SF)和鼎位形下的电磁响 应,并评估了 4 种位形极限工况下支撑的力学性能。分析表明,PF6 线圈在放电初始时刻所受垂直电磁力最大, 可达到 1.9MN。在放电平顶结束时 PF5 线圈所受电磁力最大。在鼎位形下,PF5L 电磁力可达 2.6MN;雪花和双 零位形下,可达到 2.06MN。在这样极端的运行工况下,结构力学计算结果表明 PF 线圈支撑结构出现了局部塑性 变形。采用 ASMEVIII.2 作为评判准则,对局部高应力区进行评估,评估表明结构不存在塑性塌陷和局部失效。 而在上端主辐梁内侧支撑墩位置,螺栓所受轴力最大,需施加大于 50kN 的预紧力。     

结晶紫酰肼的合成及其在测定亚硝酸盐中的应用

合成了结晶紫酰肼，利用结晶紫酰肼与亚硝酸盐的呈色反应，建立了光度法测定亚硝酸盐的方法。亚硝酸盐与吸光度在3.0×10^-7～1.8×10^-6 mol/L范围内呈现良好的线性关系，对5.0×10^-7 mol/L亚硝酸盐重复测定9次，相对标准偏差为2.4%，重现性良好。用建立的方法测定人体唾液和食品小米辣中的亚硝酸盐含量，与使用标准方法测定的结果一致。方法快速、灵敏度较高、试剂空白吸收值低。     

烷基苯上5-H溴代反应新方法的研究(Ⅰ)

研究了一种新的烷基苯上 α-H的溴化方法 ,发现使用 KBr O3/Na HSO3作为溴化剂 ,对系列烷基苯 ,尤其是有第二类取代基存在的烷基苯 ,在较低温度 ( 50℃～ 55℃ )及白炽光照射等溴化工艺条件下 ,能获得纯度较好 ,收率较高的α-溴代烷基苯衍生物。该新方法反应条件温和、操作简便、溴的利用率高、无腐蚀性气体 HBr产生     

谈变式教学中习题引申应注意的几个问题

“引申”是探索引申 ,内化回味 ,构建新知 .主要是指对例题习题进行变通推广 ,重新认识 .恰当合理的引申能营造一种生动活泼、宽松自由的氛围 ,它能开阔学生的视野 ,激活学生的情趣 ,有助于培养学生的探索精神和创新意识 ,并能使学生举一反三 ,事半功倍 .笔者在教学视导中发现 ,有些教师对引申“度”的把握不准确 ,不能因材施教 ,单纯地为了引申而引申 ,给学生造成了过重的学习和心理负担 ,使学生产生了逆反心理 ,“高投入、低产出” ,事倍而功半 .下面就引申要注意的几个问题谈一下本人的看法 .1　引申要在原例题习题的基础上进行 ,要自然…