Fabrication of bulk superconductors YBa2Cu3?xTexO7?δ with highly oriented layer structure using the melt-texture growth process

We report on the successful fabrication of bulk samples satisfying the nominal composition YBa₂Cu_3–x Te _x O_7– and containing highly single-crystal-like texture. While this type of crystal growing process is not new, our process requires only the existence of spatial temperature gradient in some parts of the common tube furnace. The samples with tellurium were found to be much more stable and better superconductors than the Y-123 specimen. Large layer textures with cross-section 50×500m² were observed to grow inside the usual bulk sample. The critical currents were measured by the d.c. magnetization method and found to be easily greater than 6000 A cm^–2 for the samples with Te.     

高温空气介质下U71Mn钢氧化动力学实验研究

为了研究重轨钢(U71Mn)在空气介质下高温氧化动力学规律,对其在900～1 300℃之间进行了5组恒温50min的氧化实验,分别绘制了在这些温度下的氧化增重曲线,并计算出了不同实验温度下该钢种的氧化动力学速率.结果表明,重轨钢在900～1300℃时氧化动力学曲线遵守直线规律.     

基于单芯片架构的三相电子式电能表设计

针对市场对高可靠性低成本的三相电子式电能表的需求,设计了一种基于71M6513H的单芯片结构三相电子式电能表,介绍了电表的结构和工作原理,详细阐述了利用电阻分压网络、CT与电阻网络获得测量信号并通过内部集成ADC采样的电能表数据采集电路,以及以71M6513H内部集成MCU为核心的测量数据后续处理方法,探讨了电能计量的比差、角差校正以及温度补偿方法;检验表明,文中设计的三相电子式电能表在全波条件下有功测量误差≤0.2%,无功测量误差≤1%,满足IEC62053和ANSIC12.20对三相电子式电能表的性能与功能要求。     

An Explicit Formula for the L 2-Discrepancy of (n α)-Sequences

Assume that α is an irrational number with continued fraction expansion [a₀;a₁, . . .] and convergents ,n= 0, 1 . . . . Every positive integer N has a unique expansion N=b₀q₀+b₁q₁+ . . . +b_mq_m, where the digits b_i are nonnegative integers with b₀<a₁,b_i≤a_i+1 and such that b_i=a_i+1 implies b_i−1=0, the so-called Ostrowski expansion of N to base α. On the other hand let c_[0,x) be the characteristic function of the half-open interval [0,x) and let be the L₂-discrepancy of the sequence (nα) mod 1, where {y} denotes the fractional part of the real number y. In this paper, we give an explicit formula for D*⁽²⁾_N(α) entirely in terms of the digits b₀, . . . ,b_m. This formula enables one to compute the L₂-discrepancy in at most O(log⁴N) steps, where the O-constant does not depend on α, while in the classical formulae for the L₂-discrepancy N²/2 calculation steps are necessary. The fastest algorithm so far was found by S. Heinrich [3] and works (for all sequences) in O(N log N) steps. Dedicated to Prof. W. G. Nowak on the occasion of his 50th birthday.     

基于BANK SWITCH技术实现MCS51存储空间的扩展

对BANK SWITCH技术进行了详细的分析,提出了两种基于MCS51内核的单片机实现大程序编写的方法,以及对实现BANK SWITCH技术所需要的硬件支持和软件配置进行了详细介绍。介绍了如何将程序代码放到确定的位置并对存储空间分BANK,解决了基于MCS51内核的单片机程序最大存储空间受限于64KB的问题。     

硫酸镁对人脐静脉血管内皮细胞的辐射防护作用

对数生长期的人脐静脉血管内皮细胞(Human umbilical vein endothelial cells,HUVECs)分3组进行不同处理后采用流式细胞仪检测细胞周期分布;Annexin V/PI双染法测定细胞凋亡率;Western blot检测Bcl-2蛋白的表达情况;RT-PCR法检测Bcl-2 mRNA的表达情况。结果显示,硫酸镁可以在X-射线照射24 h后改善HUVECs细胞G2/M期阻滞;在辐照后24、48、72 h可以提高细胞对X-射线的辐射敏感性,并增加细胞凋亡率(t=4.24、7.19、3.20,p0.05);在辐照后48、72 h能明显抑制抗凋亡蛋白Bcl-2蛋白的表达;照后24、48、72 h的Bcl-2 mRNA表达量减少(t=3.034、6.182、3.957,p0.05)。结果提示,硫酸镁可以缓解X-射线照射后细胞G2/M期阻滞,增加照射后HUVECs的细胞凋亡率,降低X-射线诱导的抗凋亡蛋白Bcl-2的表达。     

Crossed Andreev reflection in superconducting junctions

In this work crossed Andreev reflection (CAR) and elastic cotunneling (EC) are studied for junctions (N₁ISIN₂), where N₁ and N₂ are normal metals, S is a high T_c superconductor and I is an insulator. This study is carried out based on the analytical solutions of Bogoliubov de Gennes equations for anisotropic superconductors. The influence of different pair potential symmetries on the CAR and crossed conductance is analyzed. We show that CAR and EC are higher in d_x²-y² symmetry than in s symmetry. In the case of normal electrodes without magnetization, EC is the predominantly process for d_x²-y² symmetry, while in s symmetry, both processes decay with the same amplitude.     

基于71M6521的数字单相多功能电能表的设计

介绍了单相多功能电能计量芯片71M6521的基本功能和特点.在此基础上,设计了计最精度高、工作稳定、成本相对较低的数字单相多功能电能表,以实现对三相电流、电压,有功、无功功率,电能脉冲的输出等的计量.该数字单相多功能表可用于电力系统、工矿企业、智能大厦的电力临控.     

用Winsock控件实现对Melsec Net／10网络的访问

介绍了选用ＴＣＰ／ＩＰ协议集成Ｍｅｌｓｅｃ Ｎｅｔ／１０与以太网的方法,并结合实践经验重点描述了用Ｗｉｎｓｏｃｋ控件访问Ｍｅｌｓｅｃ Ｎｅｔ／１０网络的Ｃｌｉｅｎｔ／Ｓｅｒｖｅｒ程序设计步骤。     

Simulation of methane conversion to syngas in a membrane reactor: Part I A model including product oxidation

A one-dimensional dense membrane reactor (DMR) model has been developed to simulate the partial oxidation of methane to syngas. A combustion–reforming mechanism was adopted and the oxidation of reforming products, i.e. H₂ and CO, was considered. The performance of the DMR and a conventional fixed-bed reactor was compared and discussed. The results show that the incorporation of the product oxidation steps has a significant effect on the simulation results of a DMR and provides a reasonable explanation of the experimental data. The model is therefore more reasonable than those ignoring the product oxidation reactions.