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131.
132.
A. Kaveh V. Kalatjari 《International journal for numerical methods in engineering》2003,58(5):771-791
In this article size/topology optimization of trusses is performed using a genetic algorithm (GA), the force method and some concepts of graph theory. One of the main difficulties with optimization with a GA is that the parameters involved are not completely known and the number of operations needed is often quite high. Application of some concepts of the force method, together with theory of graphs, make the generation of a suitable initial population well‐matched with critical paths for the transformation of internal forces feasible. In the process of optimization generated topologically unstable trusses are identified without any matrix manipulation and highly penalized. Identifying a suitable range for the cross‐section of each member for the ground structure in the list of profiles, the length of the substrings representing the cross‐sectional design variables are reduced. Using a contraction algorithm, the length of the strings is further reduced and a GA is performed in a smaller domain of design space. The above process is accompanied by efficient methods for selection, and by using a suitable penalty function in order to reduce the number of numerical operations and to increase the speed of the optimization toward a global optimum. The efficiency of the present method is illustrated using some examples, and compared to those of previous studies. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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134.
A note on the Gauss-Jacobi quadrature formulae for singular integral equations of the second kind 总被引:1,自引:0,他引:1
A fast and efficient numerical method based on the Gauss-Jacobi quadrature is described that is suitable for solving Fredholm
singular integral equations of the second kind that are frequently encountered in fracture and contact mechanics. Here we
concentrate on the case when the unknown function is singular at both ends of the interval. Quadrature formulae involve fixed
nodal points and provide exact results for polynomials of degree 2n − 1, where n is the number of nodes. Finally, an application of the method to a plane problem involving complete contact is presented. 相似文献
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137.
Electro-organic synthesis without supporting electrolyte: Possibilities of solid polymer electrolyte technology 总被引:1,自引:0,他引:1
J. Jörissen 《Journal of Applied Electrochemistry》2003,33(10):969-977
The application of ion exchange membranes as solid polymer electrolytes (SPE) in fuel cells is state-of-the-art. This technology needs no supporting electrolyte; consequently it can be applied for electro-organic syntheses in order to save process steps. In this case the process is not predetermined to a maximized energy efficiency so that the selection of the cell design, of the electrode materials and of the operating conditions can be focused on a high selectivity of the electrode reactions. The electro-osmotic stream, which is caused by the solvation shells of the ions during their migration through the membrane, and hence is a typical property of SPE technology, has a significant effect on the electrode reactions. It generates enhanced mass transfer at the electrodes, which is beneficial for reaction selectivity. It can be influenced by the choice of, and possibly by the preparation of, the membrane. An additional remarkable advantage of SPE technology is the exceptional long durability of oxide coated electrodes. By combination of several process engineering methods stable operation of SPE cells has been realized, even for examples of non-aqueous reaction systems. Experiments up to 6000 h duration and in cells of up to 250 cm2 membrane area show the potential for industrial application. 相似文献
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139.
Measurement Method of the Thickness Uniformity for Polymer Films 总被引:1,自引:0,他引:1
YANGHong-liang RENQuan FANYun-zheng 《半导体光子学与技术》2003,9(2):128-132
Several methods for investigating the thickness uniformity of polymer thin films are presented as well their measurement principles.A comparison of these experimental methods is given.The cylindrical lightwave feflection method is found to can obtain the thickness distribution along a certain direction.It is simple and suitable method to evaluate the film thickness uniformity. 相似文献
140.
低温低渗透砂岩油藏窜流大孔道深部封堵技术研究 总被引:4,自引:0,他引:4
所用堵剂为高强度的淀粉接枝聚丙烯酰胺交联凝胶SAMG-1,由<6%淀粉、4.5%-5.5%丙烯酰胺、0.003%-0.006%交联剂组成,35℃成胶时间受淀粉和交联剂用量控制,为18-20小时以上,成胶前黏度-100 mPa.s。该堵剂具有长期稳定性,在储层岩心中注入深度15 cm的堵剂,在35℃候凝48小时后及老化90天后,封堵强度分别为0.61和0.59 MPa/cm,封堵率分别为98.6%和98.1%。该堵剂优先进入高渗层,注入0.5 PV并成胶后,2组双填砂管组成的模型低、高渗管渗透率保留率分别为68.4%、0.7%和69.4%、0.0%。吉林扶余油田西一区+15-8.2区块有水井6口,油井13口,含水率达91.5%,注入水最快在5天内到达油井。报道了该区块整体深部调剖封堵窜流通道的情况,详细叙述了+15-9.2井施工中通过注入压力和井底回压控制注入流量,使堵剂陆续进入原生和次生孔道的工艺作业,该井设计注入堵剂92 m3。6口水井整体调剖后,油井产液量差别减小,产油量增加,有效期已超过了9个月,共增油843 t,含水平均下降3.87%。图7表1参8。 相似文献