推进中国农村流通现代化研究

推进农村流通现代化不仅是解决农村流通不畅的关键之举,也是发展现代农业和加快形成城乡一体化格局的重要任务.基于城乡视角对农村商流、物流和信息流进行了分析,指出了农村流通中存在的很多问题,并以此提出了一些建议.     

Innovation output and state ownership: empirical evidence from China’s listed firms

Abstract

China has experienced a surge in innovation output in which state-owned enterprises (SOE) play an essential role. Using panel data of Chinese listed firms, this paper examines the influence of state ownership on innovation output at the firm level. Controlling for size, we analyse the effects of central and local government control on the number of firms’ patent applications in different time periods. Doing so, standard assumptions on state ownership’s inhibiting character are confirmed. However, we then qualify these findings by running separate models for different regions and sectors finding that the impact of state-control on innovation performance depends on a number of conditions. More precisely, state control of firms has a negative impact on innovation output in particular in China’s Northeast region and in mid-tech sectors whereas under other circumstances it does either not matter or can even exert a positive influence.     

Research on corrosion performance of 6061 aluminum alloy in salt spray environment

Salt spray corrosion test was carried out on 6061 aluminum alloy, and quasi-static tensile test at room temperature was carried out on the sample with universal testing machine. The effect of salt spray corrosion on the mechanical properties of 6061 aluminum alloy was studied by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and electrochemistry. The corrosion rate of 6061 aluminum alloy was quantitatively characterized by different corrosion parameters. It was found that local corrosion of 6061 aluminum alloy occurred in salt spray environment, mainly pitting corrosion and intergranular corrosion. With the increase of corrosion time, the polarization resistance of 6061 aluminum alloy decreases, and the corrosion rate significantly increases. The average corrosion rate and the maximum corrosion rate of 6061 aluminum alloy were characterized by corrosion weight loss and corrosion pit depth. And they can be transformed into each other. The mechanical properties of 6061 aluminum alloy were mainly affected by the depth of corrosion pit. With the increase of corrosion time, the tensile strength and fracture strain decreased, resulting in poor plasticity of the sample. At the same time, the change of elongation of 6061 aluminum alloy can be accurately predicted by the depth of corrosion pit.     

Solidification microstructure characteristics of Ti–44Al–4Nb–2Cr–0.1B alloy under various cooling rates during mushy zone

Beta-solidifying TiAl alloy has great potential in the field of aero-industry as a cast alloy.In the present work,the influence of cooling rate during mushy zone on solidification behavior of Ti-44Al-4Nb-2Cr-0.1B alloy was investigated.A vacuum induction heating device combining with temperature control system was used.The Ti-44Al-4Nb-2Cr-0.1B alloy solidified from superheated was melted to β phase with the cooling rates of 10,50,100,200,400 and 700 K·min~(-1),respectively.Results show that with the increase in cooling rate from 10 to 700 K·min~(-1),the colony size of α_2/γ lamella decreases from 1513 to48 urn and the solidification segregation significantly decreases.Also the content of residual B2 phase within α_2/γlamellar colony decreases with the increase in cooling rate.In addition,the alloy in local interdendritic regions would solidify in a hypo-peritectic way,which can be attributed to the solute redistribution and enrichment of Al element in solidification.     

不同锰铬含量对贝氏体钢组织转变的影响

文章利用全自动相变仪对不同锰铬含量的贝氏体钢组织转变进行了试验研究,对比分析了不同锰铬元素含量对贝氏体钢过冷奥氏体相变点的影响,并研究了不同转变温度对贝氏体钢组织转变的影响,试验结果表明贝氏体钢组织转变的最佳温度为330℃,为贝氏体钢生产工艺开发提供了理论依据。     

Mechanical properties and miscibility of polyethersulfone/phenoxy blends

The blends of polyethersulfone and phenoxy were prepared by melt mixing in a Brabenderlike apparatus. The specimens for measurements were made by compression molding and then were water-quenched at room temperature under pressure. The tensile strength, tensile modulus, elongation at break and yield, density, thermal analysis, and dynamic mechanical properties were each measured. The dependence of tensile strength, tensile modulus, elongation at break and yield, and density on composition was obtained. The relationship between tensile modulus and elongation at break and yield and speed of the crosshead at different weight ratios of the blends is shown. The effects of composition and miscibility on the mechanical properties are discussed. © 1996 John Wiley & Sons, Inc.     

数字视频压缩的大容量记录系统设计

介绍用ARM7微控制器LPC2214和MPEG-1压缩芯片SZ1510实现数字视频压缩记录的嵌入式系统。SZ1510在LPC2214的控制下,完成音频和视频数据的实时压缩和码流合成,LPC2214同时完成码流的传输和存储控制。利用LPC2214的I／O端口实现IDE接口的扩展,可直接驱动大容量硬盘和CF存储卡。     

基于人工神经网络的IT项目风险评价模型

[摘要]：首先本文在构建IT项目风险评价体系的基础上,提出一种基于人工神经网络的多指标综合风险评价模型。其次,利用神经网络的自学习和自适应能力,经过训练的神经网络系统能够将专家评价思想以连接权的方式赋予风险评价模型。最后,通过实际IT项目评价数据的验证,该风险评价模型能够准确地按照专家评价法进行工作。     

多聚半乳糖醛酸酶(PG)反义基因对加工番茄果实成熟的影响

采用农杆茵(agrobacterium tumefaciens)介导法将多聚半乳糖醛酸酶(PG)反义基因导入新疆加工番茄(lycopersicon esculentum,品种代号98-75)。通过卡那霉素抗性筛选获得10株转化植株,PCR和Southern blot分析表明,其中4株为阳性植株,反义PG基因已整合到这4株加工番茄基因组中。转基因加工番茄的硬度和可溶性固形物含量高于同期对照果实;果实饱满有光泽;此4株转基因番茄果实的PG活性分别为对照番茄果实的83％、88％、63％和46％;脂氧合酶(LOX)活性下降;可溶性果胶含量在同期低于对照。Northem blot分析表明,转基因番茄果实的PG、LOX和LeEXPl基因表达水平下降。研究结果表明,转反义PG基因加工番茄果实成熟软化进程被延缓,果实品质有一定改善。     

分期实施地铁车站破墙接驳技术的工程实践

随着我国城市轨道交通建设的快速发展,车站分期实施的情况越来越多,既有车站与后期车站的合理对接,对确保既有车站的结构安全、运营安全至关重要。以北京地铁宋家庄枢纽站既有5号线与后期亦庄线车站接口实施方案为工程背景,研究了设计预留接口条件与设计未预留接口条件两种典型情况的工程处理原则和措施,总结了工程实施过程中的经验教训,其分析思路和采取的工程措施,对类似工程的设计和施工有一定的借鉴参考价值。