并行数据库系统PAROⅡ连接算法

提出了并行数据库系统的哈希轮转（Hash-Round-Robin）数据划分方法以及其于该划分方法的并行记录分布B^n树，给出了基于该树的并行连接算法，分析了该算法的效率，这种连接算法充分利用了数据的已有分布及B^n树的特性，还利用了哈希轮转划分的特性，提高了并行连接的效率，该算法已经在自主研制的并行数据库管理系统PAROⅡ中得到实现。     

中国球体积公式溯源

本文详尽地记述了中国传统数学中关于球体体积公式的产生和发展,并部分做出了简要的证明和说明,以及与世界其他国家有关球体积工作之比较.     

机床热检方法的探讨

本文通过对精密万能外圆磨床各敏感零部件,在不同工况下的温升及热位移的实际测定,在分析的基础上,提出了以部件平均温升限定值作为机床热检指标的新方法及制定途径。     

两种合金化Ti-Al合金的高温氧化行为

　The isothermal oxidation behavior of two kinds of alloying Ti-Al alloyTi-48Al-2Cr-2Nb and Ti-47Al-1Cr-1V-2.5Nb at 800℃ and 900℃ is investigated.Their high temperature oxidation character and the influence of the alloying element upon the oxida－tion behavior are discussed.The study shows that the oxidation resistance of two alloying Ti-Al alloy at 800℃ is poorer than that of 48Al.However,their oxidation properties at 900℃ are considerably improved,and the oxidation speed is much lower than that of 48 Alalloy.At the two oxidation temperatures,Ti-48Al-2Cr-2Nb alloy shows better oxidation resistance than that of Ti-47Al-1Cr-1V-     

量子化学方法研究HZSM-5沸石结构酸性(Ⅳ)

HZSM-5沸石分子筛硅铝骨架结构基本单元为五元环,它通过氧桥联接而得到单元为四元环、六元环。本文采用CNDO/2半经验量子化学的方法,对HZSM-5沸石基本结构单元—四、五、六元环的电荷分布进行计算。依据Mortier等人处理y型沸石分子筛酸性的基本思想,从而得到了HZSM-5沸石分子筛酸性结构参数α_0。Barthomeuf等认为沸石分子筛可作为一个多元酸的电解质溶液,因此其质子酸度应用活度来表示。a_(H~+)=[H~+]f_(H~+),而活度系数f_(H~+)为结构参数乘以一个常数,f_(H~+)=Kα_0,我们取K=32,[H~+]=nH~+αN_(A_1)/Z_(cat),从理论上求出HZSM-5沸石分子筛在不同硅铝比时的活度,其结果和实验值相一致。这为从理论上计算HZSM-5沸石分子筛的酸性提供了一个参考方法。     

GCC box in<Emphasis Type="Italic">Arabidopsis PDF1.2</Emphasis> promoter is an essential and sufficient cis-acting element in response to MeJA treatment

The expression of Arabidopsis PDF1.2 gene isregulated by jasmonic acid (JA) and ethylene (ET). It also has been well documented that GCC box is an element responsive to ET, however, the responsive mechanism of JA in such plant defense gene expression is unclear. In this paper, the authors define the essential cis-acting element in PDF1.2 promoter responsive to methyl jasmonate (MeJA) through fragment deletions and site-directed mutageneses combiningAgrobacterium-mediated transient reporter gene expression in tobacco leaves. Firstly, the MeJA inducible expression o fPDF1.2 was confirmed by using the upstream -1.86 kb fragment of PDFI.2 gene. Secondly, the upstream -300— -243 bp fragment of the promoter was evidenced to respond to MeJA. To further characterize this promoter region, three point mutations were introduced into the -300— -243 bp fragment of the promoter. This result showed that the mutation of GCC box abolished MeJA induction, whereas the mutations of the G box-like and the imperfect palindrome sequence did not significantly decrease MeJA inducible effect, indicating that GCC box in PDFI.2 is essential for MeJA induction. The sufficient responsiveness to MeJA of this GCC box was further investigated by 4xGCC fused upstream to the CaMV 35S minimal promoter. This result suggested that the fused promoter was able to activate reporter gene expression in response to MeJA. Thus these results indicate that the GCC box in PDFI.2 is an essential and sufficient element to confer MeJA induction.     

VEGF links hippocampal activity with neurogenesis, learning and memory

An enriched environment is associated with hippocampal plasticity, including improved cognitive performance and increased neurogenesis. Here, we show that hippocampal expression of vascular endothelial growth factor (VEGF) is increased by both an enriched environment and performance in a spatial maze. Hippocampal gene transfer of VEGF in adult rats resulted in approximately 2 times more neurogenesis associated with improved cognition. In contrast, overexpression of placental growth factor, which signals through Flt1 but not kinase insert domain protein receptors (KDRs), had negative effects on neurogenesis and inhibited learning, although it similarly increased endothelial cell proliferation. Expression of a dominant-negative mutant KDR inhibited basal neurogenesis and impaired learning. Coexpression of mutant KDR antagonized VEGF-enhanced neurogenesis and learning without inhibiting endothelial cell proliferation. Furthermore, inhibition of VEGF expression by RNA interference completely blocked the environmental induction of neurogenesis. These data support a model in which VEGF, acting through KDR, mediates the effect of the environment on neurogenesis and cognition.     

溴酸钾和维生素C对面包焙烤品质的影响

研究选用氧化剂溴酸钾、维生素C ,以改善面粉面筋强度 ,从而改善面包的纹理结构 ,通过对实验结果的评判 ,来判断它们对面包焙烤的影响 ,确立它们在面包制作过程中的添加量。对溴酸钾存在的安全性问题也进行了分析讨论     

Application of improved equivalent edge currents in synthetic aperture radar imaging

Target modeling and scattering function calculating are important prerequisites and groundwork for the synthetic aperture radar (SAR) imaging simulation. According to the difficult problems that normal methods cannot calculate the scattering function of electrically large object under the condition to wideband, an effective method of improved equivalent edge currents is presented and applied to SAR imaging simulation for the first time. This method improves calculating velocity and has relatively high precision. The concrete steps of applying the method are given. By way of the simulation experiment, the effectiveness of the method is verified.     

Design and implementation of DBC based on dynamic AOP

Traditional approach of design by contract, due to mixing the contract code with application code, is difficult for the extensibility and reusability of software system. This paper presents a framework named JADBC for design by contract based on Aspect-Oriented Programming (AOP) to resolve these problems. By providing a new modularized element, aspect, the framework successfully separates the contracts in design by contract, from functional codes. The implementation of this framework is based on dynamic AOP which can have the contract changed at runtime, consequently, enhancing program flexibility. JADBC framework modularizes the contracts in a clear-cut fashion that is easier to design, implement, and maintain. Biography: WEN Jing (1982–), female, Ph.D. candidate, research directions: software engineer, aspect-oriented software development.