勃劳特换热器的性能

勃劳特换热器的性能周绪美，陈建铭，张鹏远，冯元鼎，丁华（北京化工大学化学工程系）关键词勃劳特换热器；压降１引言在生产过程中，气体与气体之间进行热量交换的换热器，在性能评比时，应该用两项指标来衡量。其一是单位产品所需传热面积要小，其二是单位压降的传热膜...     

气—液鼓泡塔中流动域和气含率的分布

利用压力传感器测定了气、液两相鼓泡塔内不同轴、径向位置上压强的脉动信号,分析了压强的脉动特征,计算了各种操作条件下塔内不同轴向位置截面上的平均气含率,发现在不同操作条件下,塔内可能出现不同的流动域分布,即全塔均匀鼓泡域、全塔过渡域、全塔湍动鼓泡域以及均匀鼓泡域,过渡域和湍动鼓泡域中的相邻2种或3种流域同时出现在塔内不同高度上。提出了不同轴向位置流域转变的判据。并发现,同一截面的不同径向位置基本处于同一流域内。同时研究了鼓泡塔内气含率在轴向上的分布规律,给出了不同流动域内气含率的关系式。     

肝脏血管的医学图象三维重建

提出了一种体素三维重建快速算法，它根据三维空间中体素相邻的定义，把体素表面元素的相邻与环绕体素表面的环路相关，重新进行了目标表面的描述，并对人体肝脏ＣＴ图象进行了三维重建和显示，得到了直观的肝脏门静脉的分支和走向图象，达到了无损伤的解剖的目的。为肝脏病变的ＣＴ、ＭＲＩ等定位诊断，定向介入治疗以及规则性肝叶、肝段切除提供了实验依据和理论基础。     

功率晶体管芯片的电泳法玻璃钝化研究

本文介绍了电泳法淀积7801—5锌系玻璃粉钝化功率晶体管芯,并对电泳法原理、影响因素、玻璃粉烧结工艺进行了探讨;对钝化前后的器件做了测试;管芯反向漏电流得到改善,钝化后管芯分别在250℃和175℃温度下进行高温贮存试验取得满意结果.说明电泳法淀积7801—5锌系玻璃粉钝化工艺可提高半导体器件的稳定性和可靠性.     

地下巷道支护钢拱架动力响应测量与分析

为了解某地下钢拱架支护巷道在爆炸冲击作用下的稳定性,分析支护钢拱架的动力响应参数,对距离爆源100 m的巷道测量断面进行测量并分析了支护钢拱架动态应变和加速度参数。结果表明:测量断面的巷道和支护结构主要受低频振动影响,其主要振动频率在20 Hz以下;测量断面巷道表面加速度在20 m/s2左右;支护钢拱架动态与静态应变叠加测量值最大为414×10-6,认为钢拱架在爆破冲击作用下仍在弹性变形范围内。     

加氢炉321和347型不锈钢炉管问题讨论

国内加氢炉炉管大量使甩321或347型不锈钢已有三十多年了,但有一些问题常常还争论不休。文章以问答形式对加氢炉321和347型不锈钢炉管经常遇到的问题进行讨论。     

Characterization of calcium-modified zinc phosphate conversion coatings and their influences on corrosion resistance of AZ31 alloy

Two kinds of phosphate conversion coatings, including zinc phosphate coating and zinc-calcium phosphate coating, were prepared on the surface of AZ31 alloy in phosphate baths. The morphologies of these coatings were observed using scanning electron microscopy. Their chemical compositions and structures were characterized using energy-dispersive X-ray spectrum, X-ray photoelectron spectroscopy and X-ray diffraction. The corrosion resistance of the coatings was evaluated by potentiodynamic polarization technique. The results show that the flowerlike Zn-Ca phosphate conversion coatings are mainly composed of hopeite (Zn₃(PO₄)₂·4H₂O). They have a quite different morphology from the dry-riverbed-like Zn phosphate coatings that consist of MgO, MgF₂, Zn or ZnO and hopeite. Both of the zinc and zinc-calcium phosphate coatings can remarkably reduce the corrosion current density of the substrates. The Zn-Ca coating exhibits better corrosion resistance than the Zn coating. Introduction of calcium into the phosphate baths leads to the full crystallinity of the Zn-Ca coating.     

Cr原子在Fe_3Al金属间化合物亚点阵中占位测定SCIEI

利用中子衍射方法确定了Ｃｒ原子在Ｄ０_３有序结构的Ｆｅ－２８Ａｌ一５Ｃｒ合金亚点阵中的占位．结果表明：Ｃｒ原子仅替代Ｆｅ原子的位置，并占位于与Ａｌ原子次近邻的亚点阵，由于次近邻反相畴界能的降低，该合金四分位错组态中次近邻反相畴界的宽度变大，从而使交滑移变得容易，材料的变形能力得到改善，这一分析已分别为本工作对合金拉伸试样的表面滑移线金相观察和位错组态的ＴＥＭ研究所证实．     

Strain-induced Microstructural Changes and Effects of Alloying Elements for Fe_3Al-based Alloys

The strain-induced microstructural changes of Fe3Al-based alloys during room temperature deformation and high temperature creep were investigated. The results illustrated the strain-induced disor dering occured during room temperature deformation. Creep strain could induced two opposite processes, which are strain-induced disordering and creep recovery-induced reordering. These two opposite creep induced processes during creep result in reducing the influence of primary microstructure on the rupture life.