Modeling and measurement of active parameters and workpiece home position of a multi-axis machine tool

The complex structures of a multi-axis machine tool may produce inaccuracies at the tool tip caused by dimensional errors in the machine's link parameters. This paper addresses two important issues for precision machining: (1) which link parameters (denoted as active parameters) of a machine tool can affect the machining accuracy of a workpiece and (2) how to measure the active parameters by using a grinding wheel as a measuring probe. To achieve this, a modified Denavit–Hartenberg (D–H) notation is introduced to model a multi-axis machine tool. The NC data equations are then derived in terms of the machine's link parameters. It is found that the link parameters of a machine tool can be divided into two types: active and nonactive parameters. The prerequisite for obtaining an accurately machined workpiece is to have correct values of the active parameters and the workpiece home position. Based on the developed NC data equations of a multi-axis machine tool, this paper also addresses the technique of using a grinding wheel as a measuring probe to determine the active parameters and the workpiece home position. Experimental results are also given with illustrative examples.     

A model for biomass screw feeding

Successful feeding is critical to biomass utilization processes, but trouble-free delivery is difficult due to particle heterogeneity, physical characteristics and moisture content. A model, extended from previous models in the literature, is proposed to delineate what limits screw feeding in terms of the mechanisms of blockage and to predict torque requirements for biomass materials. Predictions on feeding of wood pellets, sawdust, hog fuel and wood shavings in a screw feeder/lock hopper system are in good agreement with our earlier experimental findings. The choke section and seal plug are shown to play important roles in determining the torque requirements for biomass screw feeding, although they are rarely mentioned in previous research on screw feeding of other materials.     

UV Disinfection of E. coli Between Concentric Cylinders: Effects of the Boundary Layer and a Wavy Wall

UV inactivation of E. coli in a plug flow reactor between concentric cylinders was investigated. The concentration boundary layer thickness was computed for laminar, turbulent and Taylor-Couette flow in terms of the respective mass transfer Sherwood number. It is demonstrated that the concentration boundary layer is thin and that the mass transfer coefficient is large and comparable in size for both turbulent and laminar Taylor-Couette flow in contrast to laminar flow. Computation of the fluence distribution for each flow pattern indicate that turbulent and especially Taylor-Couette flow subject E. coli to an equal flux of photons corresponding to ideal plug flow. However, experiments with turbulent flow that require large axial velocities indicate that very long reactor lengths are necessary to inactivate E. coli. Finally, rotor wavy wall modifications are explored to increase the inactivation of microorganisms in Taylor-Couette flow.     

Model reduction and control of multi-scale reaction-convection processes

This paper focuses on non-isothermal plug flow reactors with fast and slow reactions. These processes are modeled by first order hyperbolic partial differential equations with large and small parameters, which results in stiffness and multi-scale behavior. Through a combination of the method of characteristics and singular perturbation techniques, a model reduction method is developed for obtaining a non-stiff representation of the dominant dynamics of these systems. The application of the method and the advantages of using the reduced models for model-based control are illustrated through a case study.     

基于Pro/E插座面板注射3D模设计

本文介绍了以Pro/E软件作为开发平台设计插座面板的全过程,叙述了对模具进行结构自动化设计、仿真充型和运动仿真的过程,着重阐述了模具中斜销机构的分型与抽芯设计。实现了智能软件与实际设计的结合,提高了模具设计的效率及塑料制品的生产率。     

一种高回弹性井壁承压封堵剂

井壁稳定是保证钻井施工安全顺利的前提,也是钻井作业关注的重点和难点。弹性石墨因为其独有的回弹特性,在井壁增强和封堵承压方面具有其它封堵材料无可取代的优势。井壁承压封堵剂PF-RG是国内自主生产的弹性石墨材料,具有完全惰性、无磁性、高抗温性等优良性能,在水基钻井液和油基钻井液有良好的适应性,不影响流变性,降低润滑系数的同时大幅度降低滤失量。经过压弹性实验评价,该材料具有非常高的回弹特性,回弹率超过20%,最高达到100%以上,与国外同类产品相媲美。目前井壁承压封堵剂PF-RG已经在现场作业中成功应用,证明了该材料具有优良的承压封堵能力。     

一种新的油层污染解堵剂—ClO2体系

由于细菌粘液、钻井液体系中的有机物、有机凝冻胶的影响,目前油水井的酸化效果不太理想,因此引进了一种新的油层污染解堵剂－ＣｌＯ２体系。通过室内试验评价了ＣｌＯ２解堵体系对有机聚合物、调剖化堵所用凝冻胶体系的降解、降粘作用对ＴＧＢ、ＳＲＢ等的杀菌效果。在合理选井的基础上,将该体系投入矿场使用,效果良好,为解除油层污染提供了一条新途径。     

后现代风格设计在家居陈设中的应用

通过后现代风格陈设设计元素的分析及设计实例的解读（即一套家居的陈设设计,包括家具、灯具、装饰的配置等）,对后现代风格家居陈设设计进行了研究。     

催化裂化装置沉降器藏量失灵原因分析及改进

针对青岛石油化工有限公司1．4Mt／a催化裂化装置沉降器藏量失灵以及汽提段上部密度大幅度波动的现象,对待生催化剂塞阀以及沉降器藏量的测量进行了考察分析。通过采用改变沉降器藏量正压室引压点位置的措施解决了待生催化剂塞阀误动作以及汽提段上部密度大幅度波动的问题,达到了平稳操作的目的。     

Effects of home preparation on pesticide residues in cabbage

Experiment was carried out to evaluate the pesticides (chlorpyrifos, p,p-DDT, cypermethrin, chlorothalonil) residue levels in cabbage in the process of home preparation by washing with different concentrations of acetic acid and sodium chlorine, and tap water, preserving in refrigerator, and stir-frying for different time. Results showed that washing by tap water and/or detergent solution for cooking are necessary to decrease the concentration of pesticide residues in cabbage. Washing with acetic acid solutions (at 10% concentration for 20 min) caused 79.8%, 65.8%, 74.0% and 75.0% loss of the above pesticides, respectively. Washing with NaCl solutions (at 10% concentration for 20 min) produced 67.2%, 65.0%, 73.3% and 74.1% loss, respectively, and washing by tap water (for 20 min) were 17.6%, 17.1%, 19.1% and 15.2% loss, respectively. The reductions due to the refrigeration (for 48 h) were 3.4%, 2.6%, 3.1% and 3.6%, respectively, and those due to the stir-frying (for 5 min) were 86.6%, 67.5%, 84.7% and 84.8%, respectively. The data indicated that washing by detergent solutions and stir-frying of cabbage are the most effective home preparations for the elimination of pesticide residues.