明渠湍流床面附近跃移层面颗粒浓度垂线分布

本文以动理学理论的Boltzmann方程为基础，考虑明渠湍流床面附近猝发喷射和清扫运动对跃移层内运动颗粒的不同作用，分析了明渠中泥沙颗粒浓度垂线分布问题，得到了适用于包括跃移层、悬移层在内的统一浓度垂线分布公式。文中着重研究了跃移层内运动颗粒的浓度垂线分布，并将本文结果与实测跃移层内浓度垂线分布及实测跃移层顶部浓度进行了对比，结果表明理论与实验两者符合较好。     

隔振技术入门(一)

一、振动的起因 机械振动是工程中常见的现象,其存在形式也是多种多样的。最简单的,如时钟挂摆的摆动,悬挂在弹簧上质块的颤动,比较复杂的,如机器运转时机体表面的跳动,车辆运行时车身的(扌晃)动,等等。种类繁多的机械振动,它们的运动规律千差万别,很难做出完整、确切的定义。然而可以这样认为,所谓机械振动(或振动)是运动物体的运动量(用位移、速度及加速度来描述)大小相对其平均值或者基准值,从小到大与从大到小在时间上做重复交替的变化。     

PVC／NBR／HDPE共混体系相容性研究（Ⅰ）增容剂对力学性能的影响

采用丁腈橡胶（ＮＢＲ）及其氢化还原后产物（ＨＮＢＲ）为ＰＶＣ／ＨＤＰＥ共混体系的增容剂，研究了增容剂结构、用量及丙烯腈含量对共混体系相容性的影响。发现丁腈橡胶（ＮＢＲ２９及ＨＮＢＲ２９）对ＰＶＣ／ＨＤＰＥ体系有较好的增容作用，而ＮＢＲ４０及ＨＮＢＲ４０较差。当增容剂用量为２％，ＰＥ含量为８％～１２％时，共混物具有较好的相容性，力学性能得到改善。     

Thixoforming of SiC ceramic matrix composites in pseudo-semi-solid state

1INTRODUCTIONIt has great economic profit to exploit the uti-lization of SiC ceramic material for its strength,hardness,wear resistance,corrosion resistanceand high temperature resistance,abundant re-source and low price.But the brittle charactergreatly restricts its application in the field of engi-neering structure materials.Recently a series ofceramic matrix composites with exi mious perform-ance have been developed by reinforcing the matrixmaterial with other materials.Al/SiC is a la…     

政府门户网站安全体系中的技术要点分析

政府门户网站是我国各级政府机关履行职能、面向社会提供服务的官方网站,是政府机关实现政务信息公开、服务企业和社会公众、互动交流的重要渠道。但是由于门户网站具有开放性、公开性以及广泛性的特点,其网站安全体系又有待完善,因此门户网站的安全管理工作得不到有效落实,这导致其网站的运作面临着许多潜在风险,进而造成损失。本文,从门户网站的相关内容入手,分析了政府门户网站面临的安全风险,总结政府门户网站安全体系中的技术要点。     

一种新型零电压零电流开关移相全桥变换器

为了解决传统零电压零电流开关（ZVZCS）PWMDC/DC变换器滞后桥臂零压范围较小、环流损耗大的问题,采用串联双变压器、滞后桥臂带辅助网络和倍压整流电路,提出了一种新型零电压零电流移相全桥变换器.首先分析了变换器在稳态下的各种工作状态,给出了相关计算公式,并制作了一台实验样机进行原理验证.实验结果表明：该变换器能够在较宽的负载范围内实现滞后桥臂的零电压开通,重载下实现零电流开通,从而极大地降低高频电路初级开关损耗和次级电磁干扰.     

Effect of Zr content on quench sensitivity of AlZnMgCu alloys

The effect of Zr content on quench sensitivity of AlZnMgCu alloys was investigated by mechanical properties testing and microstructure observations. The results show that with the increase of Zr the quench sensitivity relative to hardness and strength increases, while that relative to elongation decreases. From hardness and strength viewpoints, the low quench sensitivity is observed for the Zr-free and 0.05% Zr-containing alloys, which is quite quench sensitive from the ductility viewpoint. The largest quench sensitivity relative to hardness and strength is observed for 0.1% Zr-containing alloy, this is mainly due to large amount of high angle grain boundaries and incoherent Al3Zr dispersoids caused by recrystallization, which may efficiently promote heterogeneous precipitation during air quenching. More than 0.05% Zr can significantly decrease the quench sensitivity relative to ductility, which can be primarily attributed to recrystallization inhibiting and grain refining effects of Zr.     

Mechanism of strengthening of cube texture for high purity aluminum foils by additional-annealing

1　INTRODUCTIONHighpurityaluminumfoilsareusedastheanodematerialofhighvoltageelectrolyticcapacitorswhichneedstrongcubetexture { 0 0 1}〈10 0〉forlargeeffec tivesurfacefromchanneletching[1] .Becauseofitstechnicalimportance ,alotofeffortshavebeenmadetodevelopstrongcubetextureinhigh purityalu minumfoils[2 8] .Itwasfoundthatthecubetextureinthefoilscanbestrengthenedviaanannealingpro cessfollowedbyalowcoldrolling[7,8] ,andsuchanannealingiscalledadditional annealinginthispaper .Buttherewerefewinv…     

Water hammer in coarse grained solid liquid flows in hydraulic hoisting for ocean mining

1　ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｄｅｅｐ ｓｅａｍｉｎｉｎｇ ,ｔｈｅ ｐｏｌｙｍｅｔａｌｌｉｃｎｏｄｕｌｅｓ ,ｇａｔｈｅｒｅｄｂｙｃｏｌｌｅｃｔｉｎｇｕｔｉｌｉｔｉｅｓｓｕｃｈａｓｕｎｄｅｒｗａｔｅｒｒｏｂｏｔｓ ,ｍｕｓｔｂｅｔｒａｎｓｐｏｒｔｅｄｔｏｍｉｎ