Study on Multi-stream Heat Exchanger Network Synthesis with Parallel Genetic/Simulated Annealing Algorithm

The multi-stream heat exchanger network synthesis (HENS) problem can be formulated as a mixed integer nonlinear programming model according to Yee et al. Its nonconvexity nature leads to existence of more than one optimum and computational difficulty for traditional algorithms to find the global optimum. Compared with deterministic algorithms, evolutionary computation provides a promising approach to tackle this problem. In this paper, a mathematical model of multi-stream heat exchangers network synthesis problem is setup. Different from the assumption of isothermal mixing of stream splits and thus linearity constraints of Yee et al., non-isothermal mixing is supported. As a consequence, nonlinear constraints are resulted and nonconvexity of the objective function is added. To solve the mathematical model, an algorithm named GA/SA (parallel genetic/simulated annealing algorithm) is detailed for application to the multi-stream heat exchanger network synthesis problem. The performance of the proposed approach is demonstrated with three examples and the obtained solutions indicate the presented approach is effective for multi-stream HENS.

辨证分型联合氯沙坦治疗老年高血压合并左心室肥厚随机平行对照研究

[目的]观察辨证分型联合氯沙坦治疗老年高血压合并左心室肥厚疗效。[方法]使用随机平行对照方法,将144例门诊患者按就诊顺序号随机分为两组。对照组72例氯沙坦,50mg/次,1次/d,根据血压调整剂量。治疗组72例辨证分型治疗,肝火亢盛-杞菊地黄汤(枸杞、桑寄生、菊花、熟地黄、山茱萸、山药各9g,女贞子、赤芍、石斛各6g,鳖甲10g,牛膝、杜仲、牡蛎、珍珠母,钩藤、麦冬各5g);阴阳两虚-肾气丸(熟地黄24g,山萸肉、山药各12g、杜仲、肉桂3g,丹皮、茯苓各9g,牛膝、牡蛎、黄芪、酸枣仁各6g,附子3g);痰湿壅盛-半夏白术天麻汤(半夏9g,白术18g,天麻、钩藤、橘红、茯苓各6g,甘草、生姜、大枣、远志各5g),水煎400mL,早晚温服;氯沙坦治疗同对照组。连续治疗6个月为1疗程。观测临床表现、舒张压、收缩压、左心室舒张末期内径、室间隔舒张末期厚度、左室后壁舒张末期厚度、不良反应。治疗1疗程(6个月),判定疗效。[结果]治疗组显效42例,有效27例,无效3例,总有效率95. 83%;对照组显效35例,有效26例,无效11例,总有效率84. 72%;治疗组疗效优于对照组(P <0. 05)。DBP、SBP、LVEDD、IVST、LVPWT两组均有改善(P <0. 05,P <0. 01),治疗组改善优于对照组(P <0. 01)。[结论]辨证分型联合氯沙坦治疗老年高血压合并左心室肥,疗效满意,无严重不良反应,值得推广。