Grain-size effects in the quasi-static fracture resistance of a thermally embrittled RPV steel (quenched and tempered microstructures)

The elastic-plastic fracture toughness and crack extension behavior under the quasi-static loading regimen of several thermally embrittled conditions of a nuclear reactor pressure vessel (RPV) steel were assessed on the basis of microstructural parameters. It was discovered that the bainite packet size is the fracture properties controlling parameter of single-phase quenched and tempered microstructures. Results were found in close agreement to those obtained in a parallel study with dual-phase annealed microstructures derived from the same low alloy steel. Similarly, it was concluded that a Hall-Petch type relationship correlates J-fracture mechanics criteria to the grain size.     

离心铸造梯度功能材料凝固过程中第二相的迁移行为

金属液在离心铸造下将发生第二相质点的径向移动。本文分析了第二相质点的移动规律。     

高碳钢钢丝在铅浴和CMC水溶液中的冷却行为

利用钢丝探头分别测量了含碳0.70%的钢丝在铅浴和CMC水溶液中的冷却过程。用冷却曲线分析法阐释了钢丝的冷却过程和相变规律。钢丝的“体积效应”和在其冷却介质中的热扩散能力共同决定了铅浴淬火过程及钢丝的相变过程。高碳钢钢丝在0.25%CMC水溶液中可完全转变为珠光体组织,但其转变温度由于其连续冷却转变特性而高于在铅浴中的转变温度。根据铅浴淬火的冷却本质和CMC水溶液的冷却特性,用于替代铅浴的淬火介质应设法加快初始阶段冷却速率。     

离心泵性能参数的自动测定和自动控制

通过将计算机技术应用于离心泵性能参数的研究，实现了离心泵性能参数的自动测定和自动控制。     

Pervaporation performance analysis and prediction—using a hybrid solution-diffusion and pore-flow model

A hybrid mathematic model for pervaporation is proposed which incorporates the concepts of solution-diffusion model and pore model. The model allows performance prediction as well as the establishment of the internal concentration and pressure profiles within the membrane. The model parameters specific to the particular membrane and mixture system are determined using liquid sorption and pervaporation experimental data. The model is experimentally examined using ethanol–water mixtures and poly(dimethyl siloxane)–poly(vinyldiene fluoride) (PDMS–PVDF) composite membranes. The characteristics of flux and separation factor predicted using the model are in fair agreement with the experimental data under various feed concentrations and downstream pressures for different membrane arrangements, including single-layer, reverse single-layer and double-layer PDMS–PVDF composite membranes. Internal profiles of pressure, concentration and component mole fraction can be established using the model. Concentration polarization phenomena for ethanol and water are located at membrane interfaces and vapor–liquid interfaces, respectively. Performances of several different membrane designs are compared using the model.     

应力交变下微型土压力计的标定及应用

为了研究土压力计在不同应力状态下的敏感系数,利用镶嵌有微型土压力计的模型桩,按照两种方式设计应力交变加载模式进行标定:(a)从初始零应力状态分级加载—卸载至零;(b)从初始零应力状态加载到应力最大值,分级卸载—加载,逐渐到零应力状态。研究结果表明:初始应力为零的加载曲线线性较好,敏感系数可用线性函数进行拟合;初始应力不为零的加载曲线线性也较好,敏感系数也可用线性函数进行拟合;而卸载曲线包含显著的非线性和滞后效应,此时敏感系数就不是一个固定值,可采用指数曲线来进行拟合。将获取的标定系数应用于水平受荷模型桩的桩身应力分析中,在加载过程中3.5D~5.5D深处桩身应力一直变大,且变化幅度最大。研究成果可为水利工程中板桩、抗滑桩等水平受荷桩桩身截面尺寸及配筋设计提供参考。     

Packed-microtubes model for flowthrough chromatography of protein

A mathematical model for flowthrough (perfusion) chromatography, namely packed-microtubes (PMT) model, has been proposed for a column packed with biporous (BiP) anion exchanger in which the mesopores and flowthrough pores are created with liquid and solid porogens, respectively. The model is established based on the assumption that the BiP particle is made up of packed microtubes. Bovine serum albumin (BSA) is used as a model protein and three kinds of anion exchangers (i.e., mesoporous, macroporous and BiP resins) are used as adsorbents to determine the model parameters and to evaluate the model. Adsorption equilibrium and finite bath experiments are performed to determine the adsorption isotherms and kinetics parameters. Both the bound amounts of the protein on the surface of the mesopores and macropores are experimentally determined and taken into account in the mathematical model. With all the model parameters determined by independent experiments or calculated from available correlations, model simulations are performed and compared with the experimentally determined breakthrough profiles of the BiP column. It is found that the model predictions agree reasonably well with the experimental data obtained under various conditions and the PMT model fit experimental data better than the modified double linear driving force (LLDF) model proposed by Leitão and Rodriogues (1999. Biochemical Engineering Journal 3, 131) in which the adsorbent particle is considered to be made up of packed microparticles. The results indicate that the PMT model is more reasonable for this kind of BiP adsorbent.     

Admittance—Frequency Response in Zinc Oxide Varistor Ceramics

The lumped parameter/complex plane analysis technique revealed several contributions to the terminal admittance of the ZnO—Bi₂O₃ based varistor grain-boundary ac response. The terminal capacitance has been elucidated via the multiple trapping phenomena, a barrier layer polarization, and a resonance effect in the frequency range 10⁻²≤ f ≤ 10⁹ Hz. The characterization of the trapping relaxation behavior near ∼ 10⁵ Hz (∼ 10⁻⁶ s) provided a better understanding of a previously reported loss-peak. The possible nonuniformity in this trapping activity associated with its conductance term observed via the depression angle of a semicircular relaxation in the complex capacitance ( C *) plane has been postulated.     

热压2％（mol）Y_2O_3－ZrO_2陶瓷中t－m相等温转变

用热膨胀分析、Ｘ射线衍射研究了热压２％（ｍｏｌ）Ｙ＿２Ｏ＿３－ＺｒＯ＿２陶瓷中ｔ－ｍ等温转变动力学。结果表明：经过快速冷却而得到的四方相（ｔ）在随后２００～４００℃区间保温时发生了四方相（ｔ）到单斜相（ｍ）的转变。该转变的时间－温度－转变量（ＴＴＴ）曲线呈Ｃ形，鼻子温度为３００℃。高于或低于上述温度范围，未出现ｍ相，可用Ａｖｒａｍｉ方程的一般形式来描述动力学曲线。该相变的形核与长大均是时间的函数，相变激活能为２８．６７ｋＪ／ｍｏｌ。ｔ相的亚稳性不仅与稳定剂分布及晶粒尺寸有关，而且还受冷却速度所控制。