The electric properties and the current-controlled differential negative resistance of cBN crystal

The electric properties of nonintentionally doped n-cubic boron nitride (cBN) crystal are investigated. The cBN crystal was transformed from hexagonal-boron nitride (h-BN) under high pressure (HP) and high temperature (HT) using magnesium powder as catalyst. At room temperature, the current-voltage (I-V) characteristics of cBN crystal are measured and found to be nonlinear. When the electric field is in the range of (1−1.5) × 10⁵ V/cm, the avalanche breakdown occurs inside the whole cBN crystal. At this same time, the bright blue-violet with the wavelength of 380–400 nm from the cBN crystal is observed. When measuring the I–V curve after breakdown of cBN crystal, the current-controlled differential negative resistance phenomenon is observed. The breakdown is repeatable. Supported by the Research Foundation of Zhuhai College of Jinan University for recruited excellent talents (Grant No. 510062)     

Water Diffusion from a Bacterial Cell in Low‐Moisture Foods

We used a Fick's unsteady state diffusion equation to estimate the time required for a single spherical shaped bacterium (assuming Enterococcus faecium as the target microorganism) in low‐moisture foods to equilibrate with the environment. We generated water sorption isotherms of freeze‐dried E. faecium. The water activity of bacterial cells at given water content increased considerably as temperature increased from 20 to 80 °C, as observed in the sorption isotherms of bacterial cells. When the water vapor diffusion coefficient was assumed as between 10^?12 and 10^?10 m²/s for bacterial cells, the predicted equilibration times (t_eq) ranged from 8.24×10^?4 to 8.24×10^?2 s. Considering a cell membrane barrier with a lower water diffusion coefficient (10^?15 m²/s) around the bacterial cell with a water diffusion coefficient of 10^?12 m²/s, the t_eq predicted using COMSOL Multiphysics program was 3.8×10^?1 s. This result suggests that a single bacterium equilibrates rapidly (within seconds) with change in environmental humidity and temperature.     

过热器管爆管金相分析

文章采用化学元素分析、机械性能试验、宏观检查及金相分析等手段，对青海盐湖钾肥电厂１＾＃锅炉高温段过热器管的爆管原因进行了分析，认为爆管原因为过热。与此同时提出了相应的改进措施。     

现场可编程逻辑门阵列（FPGA）技术及其应用

本文阐述了现场可编程逻辑门阵列（ＦＰＧＡ）技术的基本概念、原理及其进展，并介绍了作者在应用ＦＰＧＡ技术中所获得的点滴经验与体会。     

量子化学参数研究聚苯乙烯类玻璃化温度的定量构效关系

用密度泛函理论在6—31G（D）基组上优化了67种聚苯乙烯类结构单元,得到了其单元的结构参数,探讨了这些参数与聚苯乙烯类玻璃化转变温度（Tg）的关系,计算表明,影响聚苯乙烯类Tg的因素有苯环上取代基长度,取代基的分支数,取代基位置,原子的最大负电荷数,氢原子的最大正电荷数,主链碳原子之间的电子布居数,分子偶极矩以及分子的内能等参数。用逐步回归,岭回归和人工神经网络方法分别建立了这些参数与,。的定量关系,并对这3种方法建立的定量模型进行了比较,3种方法的计算结果与实验值的相关系数分别为0．9583,0．9491,0．9853,标准偏差分别为18．44,19．18,10．41,人工神经网络的拟合值和预测值均优于前2种线性回归方法。     

Formal proof of integer adders using all-prefix-sums operation

Addition of two binary numbers is a fundamental operation in electronic circuits.Several integer adder architectures have been proposed.Their formal properties are well known,but the proofs are either incomplete or difficult to find.In this paper,we present a formal proof for the correctness of prefix adders.Both sequential and parallel algorithms are formalized and proved.In contrast to previous proofs using higher order functions and rewriting systems,our work is based on first order recursive equations,which are familiar to the computer arithmetic community and are therefore understandable by people working on VLSI circuit design.This study sets up a basis for further work on formal proofs of computer arithmetic algorithms.     

Effects of grain size on phase transition behavior of nanocrystalline shape memory alloys

We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that when GS<60 nm,the superelastic stress-strain hysteresis loop area(H)of the polycrystal decreases rapidly with GS and tends to vanish as GS approaches 10 nanometers.At the same time,the temperature dependence of the transition stress also decreases with GS and eventually approaches zero,leading to a wide superelastic temperature window and breakdown of the Clausius-Claperyon relationship.Rate dependence of the stress-strain responses is significantly reduced and the cyclic stability of the material is improved by the nanocrystallization.It is proposed that the emergence of such significant changes in the behavior of the material with GS reduction originate from the large increase in the area-to-volume ratios of the nanometer-thick interfaces(grain boundary and Austenite-Martensite(A-M)interface)in the polycrystal.In particular,with GS reduction,interfacial energy terms will gradually become dominant over the bulk energy of the crystallite,eventually bring fundamental changes in the phase transition responses of the material.Modelling strategy leading to the establishment of quantitative relationships among GS,grain boundary,A-M interfaces and the macroscopic responses of the material are outlined.     

GB18580—2001与EN120：1992穿孔法测定人造板甲醛释放量的比较与分析

对GB18580—2001《室内装饰装修材料人造板及其制品中甲醛释放限量》中采用的穿孔萃取法和欧洲标准EN120：1992《Wood—based panel products Determination of formaldehyde content Extraction method（known as perforator method）（以下简称EN120）中的穿孔萃取法进行方法对比和试验结果比较，提出修改GB18580—2001中采用的穿孔萃取法，建议等同采用EN120：1992中的穿孔萃取法。     

山乌龟中九种微量元素的分析测定

本文用火焰原子吸收光谱法测定了山乌龟中常见的8种微量元素Zn、Fe、Ca、Cu、K、Na、Mn、Mg的含量,系统地试验了测定条件,用SrCL_2消除了共存元素间的干扰,实现了在同一溶液中测定多种元素,方法简便、快速、准确;同时采用钼锑抗比色法测定了磷的含量,结果令人满意。