Improved NSGA-II Multi-objective Genetic Algorithm Based on Hybridization-encouraged Mechanism

To improve performances of multi-objective optimization algorithms, such as convergence and diversity, a hybridization- encouraged mechanism is proposed and realized in elitist nondominated sorting genetic algorithm （NSGA-Ⅱ）. This mechanism uses the normalized distance to evaluate the difference among genes in a population. Three possible modes of crossover operators--＂Max Distance＂, ＂Min-Max Distance＂, and ＂Neighboring-Max＂--are suggested and analyzed. The mode of ＂Neighboring-Max＂, which not only takes advantage of hybridization but also improves the distribution of the population near Pareto optimal front, is chosen and used in NSGA-Ⅱ on the basis of hybridization-encouraged mechanism （short for HEM-based NSGA-Ⅱ）. To prove the HEM-based algorithm, several problems are studied by using standard NSGA-Ⅱ and the presented method. Different evaluation criteria are also used to judge these algorithms in terms of distribution of solutions, convergence, diversity, and quality of solutions. The numerical results indicate that the application of hybridization-encouraged mechanism could effectively improve the performances of genetic algorithm. Finally, as an example in engineering practices, the presented method is used to design a longitudinal flight control system, which demonstrates the obtainability of a reasonable and correct Pareto front.     

新型航空发动机空气冷却器流动传热性能试验

空气冷却器是航空发动机中空气热量交换的重要场所,针对传统扰动结构强化换热不足问题,重点研究了空气冷却器 中扰动结构的结构形貌特征与流动换热的关系。以三周期极小曲面结构为基础,设计制造了D型极小曲面扰动结构、P型极小曲 面扰动结构和基于Sigmoid函数杂化方法的D-P型（P-D型）结构。并利用纳米CT重构出样品的3维数字特征,试验研究了不同结 构来流速度与压降、换热性能和综合换热性能的关系。结果表明：D型极小曲面结构具有最优的压降、换热性能和综合换热性能： D-P型杂化极小曲面结构的阻力系数f最大,比D型结构的高56.81%;D型的平均努塞尔数Nu比P型的高18.49%,P-D和D-P杂 化结构的换热性能比P型结构的有效提高;P-D型D-P型杂化结构的Nu分别比P型结构的高2%和8.27%。在4种结构中,D型结 构的综合换热性能最优,分别比P型、P-D型、D-P型结构的高40.35%、57.2%、71.02%。     

纳米粒子原位杂化酚醛/炭纤维烧蚀防热研究

采用原位杂化方法分别制备了SiC、SiO2和Al2 O3 3种纳米粒子杂化酚醛树脂,扫描电镜观察发现,纳米粒子均匀分散在酚醛树脂中,与酚醛树脂形成“海-岛”结构;热重分析结果显示,纳米粒子杂化酚醛树脂的降解过程分为3个阶段,通过Kissinger法对杂化酚醛树脂热分解活化能进行计算,发现纳米粒子能够降低树脂第1阶段的热...     

应用于空间微生物防护的多尺度杂化抗菌剂研究

由于航天员的参与,载人航天活动中难以避免微生物防护的问题,而航天器环境密闭、空间狭小,难以采用地面常用的喷洒一次性有机消毒剂、紫外线杀菌等方式进行微生物防护。通过采用无机抗菌剂,结合纳米技术和杂化结构耦合所产生的协同作用来获得综合性能优异的无机抗菌剂,并采用适当的技术将其应用到航天器上是一种可行的办法。通过热分解前驱体和还原金属离子的方法分别在T-ZnO和CNTs上杂化纳米银和纳米铜,获得了多尺度纳米杂化抗菌剂。采用表面涂覆、浸渍和挤压法及活化接枝的方法分别探究了纳米抗菌剂在铝合金、芳纶布和树脂等材料中的应用。3种基体材料经抗菌改性后对大肠杆菌、金黄色葡萄球菌、白色念珠菌的抗菌率都可达到99.9%,对黑曲霉及其孢子的防霉等级都达到了0级,而且改性后的材料具有很好的耐老化、耐水性及良好的耐擦洗性能。该方法在深空探测活动中的微生物防护方面有很大发展前景。     

Improved NSGA-Ⅱ Multi-objective Genetic Algorithm Based on Hybridization-encouraged Mechanism

To improve performances of multi-objective optimization algorithms,such as convergence and diversity,a hybridization-encour-aged mechanism is proposed and realized in elitist nondominated sorting genetic algorithm (NSGA-Ⅱ).This mechanism uses the nor-malized distance to evaluate the difference among genes in a population.Three possible modes of crossover operators-"Max Distance","Min-Max Distance",and "Neighboring-Max"-are suggested and analyzed.The mode of "Neighboring-Max",which not only takes advantage of hybridization but also improves the distribution of the population near Pareto optimal front,is chosen and used in NSGA-II on the basis of hybridization-encouraged mechanism (short for HEM-based NSGA-Ⅱ).To prove the HEM-based algorithm,several problems are studied by using standard NSGA-II and the presented method.Different evaluation criteria are also used to judge these algorithms in terms of distribution of solutions,convergence,diversity,and quality of solutions.The numerical results indicate that the application of hybridization-encouraged mechanism could effectively improve the performances of genetic algorithm.Finally,as an example in engineering practices,the presented method is used to design a longitudinal flight control system,which demonstrates the obtainability of a reasonable and correct Pareto front.     

一种全长cDNA抑制缩减杂交方法及其水稻诱导表达基因分离的应用

以缩减杂交的原理和SMART cDNA合成方法为基础,开发了一种全长cDNA缩减杂交方法.该方法从微量的2个RNA样品合成全长cDNA,经PCR扩增和在两端连接不同的接头,通过2次缩减杂交获得含有高度浓缩的差异表达的全长或较大的基因片段,克隆后筛选出差异表达的基因.以噻菌灵(Probenazole,PBZ)为诱导剂处理水稻,获得了2个上调表达和1个下调表达基因的较长的cDNA片段.     

碳纤维在石墨化处理过程中的sp2 结构转变

利用激光拉曼光谱的方法,研究了国产PAN 基碳纤维CCF300 在石墨化过程中碳化学结构的变

化规律。通过对散射谱图进行分峰分析,根据不同振动峰的归属,提出了sp2结构转化度琢,即

IG

IG +IC

这一表征纤

维由碳纤维向石墨材料转变进程的结构参数。结果表明:随着处理温度的不断升高,纤维中的无序碳结构逐渐

减少,在1 700益之前sp3杂化向sp2杂化结构转变的速率较快;在1 700益之后,转变速率明显变慢,逐步形成了

最终石墨纤维的规整六元环结构基础。