溪洛渡拱坝坝基接缝安全监控指标拟定

为研究影响溪洛渡拱坝坝基接缝的各主要因素的作用规律,对坝基接缝监测数据进行分析,构建效应量中水压、温度和时效等分量的具体数学表达式,据此提出监测效应量的单测点安全监控统计模型.统计模型结果与实测值拟合较好,能合理反映拱坝坝基接缝开合度的变化趋势.同时,采用置信区间法拟定坝基接缝的安全监控指标,用于蓄水初期的安全预警.随着监测资料系列的延长和边界条件的变化,安全监控模型和监控指标体系均会发生变化,应定期根据实测资料进行修正,确保大坝长期安全正常运行.     

避暑山庄的选址

造园首在选址。选址得当,可以事半功倍。计成在《园冶》中指出,只有“相地合宜”,才能“构园得体”。地址要好,清洁卫生,有丘有壑,草地和树林相间”。避暑山庄之所以能够在造园史上独树一帜,选址得当是其中一个重要原因。避暑山庄当时所以选择这块地方建造宫苑,除政治上的原因之外,主要是因为它具有优越的自然条件。避暑山庄的园林艺术成就,已得到世人的公认,造园家相地择址的匠心,也会给我们许多有益的启示。     

载重汽车焊接车轮断裂失效原因分析

通过对断裂的汽车车轮进行失效分析发现,焊缝处存在严重咬边和气孔等焊接缺陷,这是造成车轮断裂的主要原因,其它工序中残留的内应力也是不可忽视的一个因素.所以,制造中各工序严格执行工艺规范和标准要求,是提高焊接件质量和安全可靠性的保证.     

砂土介质中废旧轮胎加筋条带拉拔特性

为减少废旧轮胎大量堆放对环境造成的严重污染及潜在安全隐患,基于废旧轮胎良好的抗拉伸、耐老化及界面粗糙等特性,本研究提出将废旧轮胎切割成条,制成加筋条带,用作土工加筋材料的新型利用方法。通过调整砂土不同密实度条件,对比开展废旧轮胎条带及土工格栅拉拔特性试验研究。结果表明,砂土介质中废旧轮胎条带达到极限拉拔力之前,拉拔位移随拉拔力的增长而线性增长;极限拉拔力统计表明,加筋条带界面抗剪强度符合摩尔-库仑强度准则,并由此建立界面抗剪强度与界面摩擦角及似黏聚力的线性关系。通过对比土工格栅加筋性能,发现废旧轮胎条带的剪应力峰值约为土工格栅的2.5~3.2倍;达到剪应力峰值所需要的位移约为土工格栅的5倍。研究成果验证了废旧轮胎条带作为加筋材料的可行性,为进一步开展理论研究及工程应用奠定了基础。     

Preparation and hydrogen sorption properties of Mg-Cu-Y-H systems

Mg-xwt.%CuY (x=15, 20, 25) composites were successfully prepared by reactive mechanical alloying (RMA).X-ray diffraction (XRD) measurement shows that main phases of the as milled composites are MgH2 and Mg2Cu, and they converted into Mg and MgCu2 after dehydrogenation, respectively.Pressure-Composition-Isotherm (PCI) test shows that the composites exhibit double pressure plateau at each isothermal desorption process.The hydrogen absorption and desorption kinetics of the composites become worse with increasing x content, indicating that Mg-Cu phase has a negative effect on the hydrogen sorption properties of the composites.It is supposed that the good hydrogen sorption properties of the composites attribute to the catalyst effect of yttrium hydride distributed in Mg substrate and the particles size reduction and crystal defects formed by RMA.     

不同空泡动力学模型在空泡振荡预测中的应用探讨

空泡动力学问题一直是水力机械领域关注的热点问题之一.空泡动力学的研究起源于水力机械的空蚀现象,弄清空泡运动(主要指单空泡生长、发展和溃灭过程)对空蚀机理研究有重要意义.本文探究了Rayleigh-Plesset(R-P)模型、Gilmore模型和Keller-Miksis(K-M)模型在预测空泡振荡过程中的应用,重点关注空泡生长和收缩回弹两个阶段,根据R-P模型、Gilmore模型和K-M模型分别计算得到空泡运动相应阶段的半径值,并与空泡实验值对比分析.结果表明:Gilmore模型和K-M模型在空泡生长和收缩回弹阶段空泡运动预测方面更具有优势,同时Gilmore模型对微米尺度回弹空泡溃灭点的预测更为准确.     

建筑门窗五金绿色电镀锌-铁合金工艺

以Q235钢为基体,依次进行电镀Zn-Fe合金、无铬蓝白钝化和封闭.研究了钝化工艺参数和封闭剂对样品耐蚀性的影响,得到较佳的钝化工艺条件为:Na2MoO4·2H2O 45 g/L,丙二酸10 g/L,NiSO4·6H2O 1.2 g/L,植酸10 mL/L,氧化剂1.8 g/L,十二烷基苯磺酸钠2 g/L,pH 1.5,温度15°C,时间10 s.在较优条件下所得钝化膜呈均匀光亮的蓝白色,耐蚀性良好.采用36 g/L苯并三氮唑封闭后,耐蚀性进一步提高.     

Effects of surfactant and particle size on the microstructure and strength of Si3N4 foams with high porosity

The highly porous Si₃N₄ ceramic foams were prepared by direct foaming with mixed surfactants. The surface tension and viscosity of slurries were tailored by different carbon chain length of surfactants and different mean Si₃N₄ particle size to achieve the pore size controlling. The nearly linear relationship between the pore size and the ratio of surface tension to viscosity was observed, which indicates that the pore size could be precisely tailored by the slurry properties. Si₃N₄ ceramic foams with porosity of nearly 94%, mean pore size of 110–230 µm, and compressive strength of 1.24–3.51 MPa were obtained.     

Research and Applications of Semi-solid Processing

Since it was pioneered by Flemings and otherresearchers [11, the semi-solid metal processingtechnique has been widely stUdied in the world.Especially in the past decade, SSM as a newproduct forming technique has been rapidly developed and put into commercial applications[2, 31. In recent years, with the development ofthe ado-industry of China, a lot of researchwork on SSM has been done, including the preparation of slumes, reheating and thixoforming[Al6]; moreover, great achievements have …     

SOLID SOLUBILITIES OF Ce AND Nd IN α-Fe

<正> 一、前言 稀土在Fe中的固溶度是长期争论的问题。曾报道Ce在Fe中固溶度为0.4wt-％(81.5—1015℃),0.35—0.4wt-％(<600℃);La≯0.1at.-％(共晶温度下),0.085—0.09,0.2wt-％(室温)和0.4—0.5wt-％(高温),0.11wt-％(室温);