超精密机械结构多目标拓扑优化设计

为满足超精密工件台结构极高的静动性能要求,提出了一种基于目标分层的多目标结构拓扑优化方法,并将其应用于超精密工件台关键件的结构优化设计中。基于ANSYS的仿真实验结果表明,多目标结构拓扑优化方法能够有效地提高结构的静动性能和设计效率,满足超精密结构极高的性能要求,为现代工程结构的多目标优化设计和改进提供了理论依据和方法。     

立式加工中心VDL-1000数控机床增加四轴的研究

本文阐述了立式加工中心VDL-1000数控机床改造,设计了改造过程中的改造方案,研究件的安装、参数调试、机床精度检测等方面内容,实现了机床多轴联动,产生很好的经济效益,对今后数控机床的改造具有指导作用。     

Competitive Analysis of Network Load Balancing

This paper presents a theoretical analysis of the Load Balancing Problem (LBP) in a network of processing units. The performance objective is to minimize the makespan, i.e., the time spent to finish all jobs in a network of processing units. Because of the communication delay that results from the network topology, it is impossible to have a strategy which obtains the exact optimum under all load distributions. Instead, we measure the information efficiency of a load balancing policy by the worst case ratio of the solution (for each load distribution) of a load balancing policy to the optimal solution (for the same load distribution) assuming that processors have complete information about the load distribution over the network. This ratio is called the competitive ratio of this strategy [17, 24, 34]. In particular, a policy is calledcompetitiveif this ratio is bounded by a constant. As a first step, we discuss the centralized LBP, where all the processors have complete information of the load distribution over a network. Its solution serves as a benchmark to compare with realistic strategies, both in theoretical analysis, and experimental and simulational studies of distributed algorithms. We show that when jobs have different sizes, even with preemptive scheduling, LBP is NP–complete. When the jobs are of the same size, we give a polynomial algorithm, using network–flow techniques, which extends to approximate solutions for jobs of different sizes. We apply this benchmark solution in order to analyze the competitiveness for three network topologies: completely connected graphs, rings, and hierarchical completek-ary trees. The constant competitive ratio results for complete network and hierarchical completek-ary trees are applied to a study on the issues of network designs suitable for the LBP. We further discuss the problem for general networks with jobs of different sizes for slightly weaker results than those for the constant competitive ratio requirement. Finally, we comment on the related issues of job partitioning over parallel/distributed systems.     

一起溴化锂吸收式制冷机组故障分析

通过对浓溶液浓度的分析，得出溴化锂冷水机组制冷效果不佳是高温换热器传热管大面积破裂所致，给出了具体的处理方法。     

大型矿用挖掘机推压轴锻件热处理工艺的优化

通过延长淬火保温时间、采用水淬油冷的冷却方式，使材料为40CrNi2Mo钢的电铲推压轴锻件综合力学性能达到技术要求。     

On the complexity of market equilibria with maximum social welfare

We consider the computational complexity of the market equilibrium problem by exploring the structural properties of the Leontief exchange economy. We prove that, for economies guaranteed to have a market equilibrium, finding one with maximum social welfare or maximum individual welfare is NP-hard. In addition, we prove that counting the number of equilibrium prices is #P-hard.     

钢绞线拉索绞盘穿索施工技术

斜拉索安装是斜拉桥施工的关键环节,以合福铁路铜陵长江大桥斜拉索施工为例,介绍铜陵长江大桥单根钢绞线拉索安装的全新施工技术——钢绞线拉索塔端穿索施工技术。利用该技术有效的规避了常规施工方法中施工难度大、容易发生坠索、索体损伤严重的难题,同时确保了钢绞线拉索的安全、高效、高质的安装。     

线圈绕制装置的研制

介绍磁调制式电压传感器原边线圈的绕制技术,展示一种自行研制的绕线装置。     

Non-Clairvoyant Multiprocessor Scheduling of Jobs with Changing Execution Characteristics

This work theoretically proves that Equi-partition efficiently schedules multiprocessor batch jobs with different execution characteristics. Motwani, Phillips, and Torng (Proc. 4th Annu. ACM/SIAM Symp. on Discrete Algorithms, pp. 422–431, Austin, 1993) show that the mean response time of jobs is within two of optimal for fully parallelizable jobs. We extend this result by considering jobs with multiple phases of arbitrary nondecreasing and sublinear speedup functions. Having no knowledge of the jobs being scheduled (non-clairvoyant) one would not expect it to perform well. However, our main result shows that the mean response time obtained with Equi-partition is no more than times the optimal. The paper also considers schedulers with different numbers of preemptions and jobs with more general classes of speedup functions. Matching lower bounds are also proved.