摘要：A modified multi-objective particle swarm optimization method is proposed for obtaining Pareto-optimal solutions effectively. Different from traditional multiobjective particle swarm optimization methods, Kriging meta-models and the trapezoid index are introduced and integrated with the traditional one. Kriging meta-models are built to match expensive or black-box functions. By applying Kriging meta-models, function evaluation numbers are decreased and the boundary Pareto-optimal solutions are identified rapidly. For bi-objective optimization problems, the trapezoid index is calculated as the sum of the trapezoid’s area formed by the Pareto-optimal solutions and one objective axis. It can serve as a measure whether the Pareto-optimal solutions converge to the Pareto front. Illustrative examples indicate that to obtain Paretooptimal solutions, the method proposed needs fewer function evaluations than the traditional multi-objective particle swarm optimization method and the non-dominated sorting genetic algorithm II method, and both the accuracy and the computational efficiency are improved. The proposed method is also applied to the design of a deepwater composite riser example in which the structural performances are calculated by numerical analysis. The design aim was to enhance the tension strength and minimize the cost. Under the buckling constraint, the optimal trade-off of tensile strength and material volume is obtained. The results demonstrated that the proposed method can effec tively deal with multi-objective optimizations with black-box functions.

摘要：本文介绍了对Si/Si_(1-x)Ge_x异质结双极晶体管(HBT)和硅双极结晶体管(BjT)高频性能进行模拟比较的结果,其结构参数是为获得最高f_T≈f_(max)设计的。模拟研究表明,(1)Si/Si_(1-x)Ge_xHBT具有64GHz的峰值f_T(=f_(max)),它比Si BjT提高了16.4％;(2)发射极充电时间对高频性能有相当大的影响,即使电流密度高达80kAcm^(-2)时也是如此;(3)SiGe基区组分梯度和基区掺杂分布强烈影响着f_T和f_(max)。研究发现高斯梯度分布具有最高的峰值f_T=f_(max),据估计其峰值截止频率比均匀掺杂分布高30％;(4)高频性能对集电极设计的依赖关系表明,要在f_T、f_(max)和BV_(CBO)间进行折衷处理;并且(5)通过降低发射区或基区掺杂浓度,可设计出f_T超过100GHz的Si_(1-x)Ge_xHBT。同样,通过提高基区掺杂浓度和降低非本征电容和电阻,可实现100GHz的f_(max)。

摘要：为了优化传统AlGaN/GaN high electron mobility transistors结构表面电场分布,提高器件击穿电压和可靠性,本文利用不影响AlGaN/GaN异质结极化效应的Si3N4钝化层电荷分布,提出了一种Si3N4钝化层部分固定正电荷AlGaN/GaN high electron mobility transistors新结构.Si3N4钝化层中部分固定正电荷通过电场调制效应使表面电场分布中产生新的电场峰而趋于均匀.新电场峰使得新结构栅边缘和漏端高电场有效降低,器件击穿电压从传统结构的296V提高到新结构的650V,而且可靠性改善.通过Si3N4与AlGaN界面横、纵向电场分布,说明了产生表面电场峰的电场调制效应,为设计Si3N4层部分固定正电荷新结构提供了科学依据.Si3N4钝化层部分固定正电荷的补偿作用,使沟道二维电子气浓度增加,导通电阻减小,输出电流提高.

摘要：针对浙江北部某污水处理项目,开展了淹没式前置反硝化滤池/淹没式好氧滤池/后置深床反硝化滤池处理城市污水的脱氮除磷中试研究。经过5个月的运行结果表明,在进水污染物浓度高、水质波动大的情况下,系统的出水水质仍达到了GB18918—2002标准的一级A排放标准,使BOD5、NH4+-N、TN分别从200、82.5、82.5mg/L左右降到1.9、2.3、11.1mg/L,在出水中未检测到SS,TP可通过在深床反硝化滤池的进水中投加絮凝剂而去除。中试数据已用于浙江北部某污水处理项目的工程设计,并于2008年8月通水运行。