一种新型双级Boost升压拓扑结构

传统的单级Boost升压电路拓扑结构升压幅度有限,不适用于升压幅度较大的场合。本文提出了一种新型双级Boost升压电路拓扑结构,它由两组单独的单级Boost升压电路组合而成,可以有效的解决该问题。仿真结果证明了这种新型拓扑结构的有效性。     

一种变频率约束限的结构拓扑优化方法

针对仅频率约束和重量最小的结构拓扑优化问题,基于ICM(独立、连续、映射)方法和渐进结构优化方法的思路,提出了一种变频率约束限的结构拓扑优化方法.在优化迭代循环的每一轮子循环迭代求解开始时,为了控制拓扑设计变量的变化量,依据结构频率和其约束限,形成和引进了新的频率约束限.另外,建立了单元删除阈值和几轮迭代循环的单元删除策略.为了确保优化迭代中结构非奇异和方法具有增添单元的功能,在结构孔洞和边界周围引入了一层人工材料单元.结合拉格朗日乘子法,形成了一种新的连续体结构的拓扑优化方法.给出的算例表明该方法没有目标函数的振荡现象,且验证了该方法的正确性和有效性.     

音频拓扑结构

1 音频拓扑结构 在多点音频传输的系统结构中,可以建立类似于网络传输结构的音频拓扑结构。对于不同的音频传输规模和实际情况,可以采用不同的结构。     

供应链拓扑结构模型研究

供应链是随着全球制造的兴起而出现的新型的管理模式。本文从企业与企业之间关系的角度提出了供应链的拓扑结构模型：链状模型、网状模型和石墨模型,相应地给出了供应链的子网、级、入点、出点等概念。本文针对不同的研究对象和研究阶段而提出的供应链概念和模型有助于对供应链的和认识和研究,对国有企业重组有启示意义。     

一种基于非概率可靠性的结构水平集拓扑优化

该文在研究水平集拓扑优化方法的基础上,对具有区间参数的不确定性结构的非概率可靠性约束进行了分析,经对有限元公式的推导、变换,提出了包涵非概率可靠度信息的拟安全系数形式,从而将非概率可靠性约束问题显式化处理,使得优化过程形式简单、便于计算,避免了复杂的迭代运算。通过对算例中数据及拓扑图形的对比研究,表明该文中模型的合理性和方法的有效性。     

空间桁架结构拓扑优化设计的线性规划方法

本文以杆件内力为设计变量,构造了多工况作用下空间桁架结构拓扑优化的线性规划模型,考虑了应力和位移约束,能够避免奇异最优拓扑和不稳定结构的产生。     

可变电抗器的新型拓扑结构设计

本文根据可变电抗器阻抗变换原理,设计了儿种新型电抗器拓扑结构,其新型拓扑结构有单绕组方式、单绕组分布式、多绕组分布式结构,该结构可应用于轻载和重载电机负荷的软起动。     

液压挖掘机斗杆结构的拓扑优化设计

为了提高斗杆的刚度并减小其质量,以BD85W型液压挖掘机的斗杆为例,应用变密度拓扑优化方法,以刚度最大为目标,以体积分数为约束,对斗杆结构进行优化设计,得到了液压挖掘机斗杆的新结构.斗杆的新旧结构对比表明:斗杆新结构体积减小18.22%,刚度增大6.58%,达到了预期的刚度要求.拓扑优化方法有利于提高产品的系列化程度和设计水平,能为挖掘机斗杆的结构分析和优化设计提供参考.     

硼磷酸盐络阴离子的拓扑结构及分类研究

从拓扑的角度出发,分析研究了硼磷酸盐络阴离子的结构特征,对目前所有的硼磷酸盐进行了统计分类,并简化键合模型给出了硼磷酸盐结构预测式,丰富了硼磷酸盐结构化学,为解析硼磷酸盐的晶体和拓扑结构提供帮助,同时也有助于设计和合成新的硼磷酸盐材料.     

A new low-cost RF built-in self-test measurement for system-on-chip transceivers

This paper presents a new RF built-in self-test (BIST) measurement and a new automatic-performance-compensation network for a system-on-chip (SoC) transceiver. We built a 5-GHz low noise amplifier (LNA) with an on-chip BIST circuit using 0.18-/spl mu/m SiGe technology. The BIST-measurement circuit contains a test amplifier and RF peak detectors. The complete measurement setup contains an LNA with a BIST circuit, an external RF source, RF relays, 50-/spl Omega/ load impedance, and a dc voltmeter. The proposed BIST circuit measures input impedance, gain, noise figure, input return loss, and output signal-to-noise ratio of the LNA. The test technique utilizes the output dc-voltage measurements, and these measured values are translated to the LNA specifications such as the gain through the developed equations. The performance of the LNA was improved by using the new automatic compensation network (ACN) that adjusts the performance of the LNA with the processor in the SoC transceiver.     

A hybrid topology optimization algorithm for structural design

A hybrid algorithm for solving structural topology optimization problems is presented. This hybrid algorithm combines the method of moving asymptotes (MMA) algorithm and the modified globally convergent version of the method of moving asymptotes (MGCMMA) algorithm in the optimization process. This hybrid algorithm preserves the advantages of both MMA and MGCMMA. The optimizer is switched from MMA to MGCMMA automatically, depending on the numerical oscillation value during the optimization. This hybrid algorithm has improved calculation efficiency and accelerated convergence when compared with the MMA or MGCMMA algorithm, which is demonstrated with three examples.     

A Stackelberg-Nash model for new product design

Existing conjoint approaches to optimal new product design have focused on the Nash equilibrium concept to model competitive reactions. Whereas these approaches have treated all competing firms equally as Nash players, one firm may have an advantage over its rivals, e.g., more pre-experience on competitors’ behavior and/or a first-mover advantage. This paper proposes a Stackelberg-Nash (leader-followers) model which can accomodate such information for decision making. The optimal product design problem is formulated from the perspective of a profit-maximizing new entrant (the leader) who wants to launch a brand onto an existing product market and acts with foresight by anticipating price-design reactions of the incumbent firms (the Nash followers). In the absence of closed-form solutions, we use a sequential iterative procedure to compute a Stackelberg-Nash equilibrium and to establish its uniqueness. The new conjoint model is illustrated under several competitive scenarios and price, design and profit implications are compared to a simple Nash equilibrium model. We find that a Stackelberg leader strategy may not only yield a much higher profit for the new entrant than a Nash strategy, but may also lead to strong profit asymmetries between competitors with still higher profits for the incumbent firms. In other words, the incumbent firms may also benefit strongly from a new entrant choosing a Stackelberg leader strategy.     

Multiobjective optimal topology design of structures

The multiobjective topology optimization designs have been tried in this paper. The minimum compliance and the maximum fundamental eigenvalue are the two objectives pursued. The constraint is the amount of material which is allowed to use in a specified design space. The design variables are the normalized densities of the finite elements in the design space. To minimize the number of elements whose design variables have values between 0 and 1, penalties are added to those design variables to force them to be either 0 (nonexistence) or 1 (existence). The timing of adding the penalty is also studied. Topologies obtained in two dimensional design space with or without penalty and using different timing approaches are compared and discussed.     

Evolutionary topology and shape design for general physical field problems

 As a practical tool for design engineers, evolutionary techniques for structural topology, shape and size optimisation have successfully resolved the whole range of structural problems from frames to 2D and 3D continuums with design criteria of stress, stiffness, frequency and buckling. In view of the generality of the finite element formulation using either a variational calculus or weighted residual approach, it is logical to extend its applications to other steady state field problems in mathematical physics governed by partial differential equations. The range of physical problems falling to this category includes heat conduction, incompressible fluid flow, elastic torsion, electrostatics and magnetostatics, etc. This paper discusses the general principles involved in setting up the adaptive evolutionary algorithms that have finite element techniques as the analysis engines. To avoid the complexity of classical solutions, the proposed method develops a simple outer loop procedure consisting of finite element analysis and design modifications. Illustrative examples are presented to demonstrate the capability in solving the above-mentioned physical field situations.     

Graph partitioning strategy for the topology design of industrial network

Network topology design problem in industrial network is formulated, which is shown to be equivalent to a multi-constraint optimisation problem: the network design should minimise the amount of inter-network communication, and simultaneously balance the communication load and network size evenly over the resultant sub-networks. To solve this optimisation problem, a graph partitioning strategy is proposed, which can give a good network design by partitioning a graph- based representation of the network optimisation problem. Then, the network optimisation procedures using the graph partitioning strategy are detailed and two experimental, examples are studied. In the experiments, the network designs obtained by the graph partitioning strategy are compared with those obtained by a random partitioning method. The experimental results demonstrate the network designs obtained by the graph partitioning strategy are significantly better than those obtained by the random partitioning method.     

新型高精度超声波流量计的设计

文章报导了一种新型高精度超声波流量计的系统设计。利用传统流量计的原理，结合目前先进的可偏程逻辑器件(CPLD)设计和高频电路设计技术，针对高精度、宽量程的要求，设计出具有数字自动增益控制(AGC)系统、自动纠错系统、高频计数系统的新型超声波流量计，它具有主从处理器并行工作结构和多种输出方式，可为多种工业输出标准提供接口。文章给出了该系统在实验室和工业环境中测试的结果。     

A new systematic approach for water network design

This paper presents a systematic procedure involving two key steps for water minimization. In the first step, water targeting, the load problem table (LPT) has been used to establish the minimum water requirement for maximum water recovery and minimum wastewater generated. This table has been adapted from the load interval diagram (LID) recently proposed by El-Halwagi and Almutlaq (2004). In the next step, the design approach, designers can select the most practical network from a range of options, all of which can satisfy the raw water and wastewater targets. It is based on a special strategy of mixing the water sources in order to satisfy the given water demands, and on some guidelines about water distribution within a network. Several test problems are solved to illustrate the ease and applicability of the proposed methodology.     

Valid inequalities for the topology optimization problem in gas network design

One quarter of Europe’s energy demand is provided by natural gas distributed through a vast pipeline network covering the whole of Europe. At a cost of 1 million Euro per km extending the European pipeline network is already a multi-billion Euro business. Therefore, automatic planning tools that support the decision process are desired. Unfortunately, current mathematical methods are not capable of solving the arising network design problems due to their size and complexity. In this article, we will show how to apply optimization methods that can converge to a proven global optimal solution. By introducing a new class of valid inequalities that improve the relaxation of our mixed-integer nonlinear programming model, we are able to speed up the necessary computations substantially.     

A new approach for the design of ultrasono-therapy transducers

In this paper we describe a new approach for the design of ultrasono-therapy transducers. Usually, in this kind of transducer, a lambda/2 front plate is inserted only in order to ensure a good mechanical protection of the active crystal from the surrounding medium. However, with an accurate design, the plate can also be used to match the piezoelectric element to the load both in terms of gain and bandwidth. To this end we apply the technique normally used in acoustical imaging and nondestructive testing, and, by means of a distributed matrix model, we optimize the thickness and impedance of the plate in order to obtain a strong response and a large bandwidth at the working frequency. Using a front plate of thickness about lambda/3, the model predicts better performances than the ones obtained with the classical design, also in terms of efficiency. An experimental comparison between a transducer realized according to the proposed design and a commercial half wave transducer shows better performances the former and therefore validates the new design criterion.