TECHNICAL NOTE: LYAPUNOV THEORY IN STRUCTURAL DESIGN

The design of structures to a given performance or response index while ensuring certain dynamic stability properties may be based on Lyapunov's second or direct method. For structures subject to initial disturbances and modelled in state equation form, the stiffness/damping/mass requirements may be optimally chosen according to an integral square error (or deviation) criterion.     

Balancing Multi-Manned Assembly Lines With Walking Workers: Problem Definition,Mathematical Formulation,and an Electromagnetic Field Optimisation Algorithm

Assembly lines are widely used in industrial environments that produce standardised products in high volumes. Multi-manned assembly line is a special version of them that allows simultaneous operation of more than one worker at the same workstation. These lines are widely used in large-sized product manufacturing since they have many advantages over the simple one. This article has dealt with multi-manned assembly line balancing problem with walking workers for minimising the number of workers and workstations as the first and second objectives, respectively. A linear mixed-integer programming formulation of the problem has been firstly addressed after the problem definition is given. Besides that, a metaheuristic based on electromagnetic field optimisation algorithm has been improved. In addition to the classical electromagnetic field optimisation algorithm, a regeneration strategy has been applied to enhance diversification. A particle swarm optimisation algorithm from assembly line balancing literature has been modified to compare with the proposed algorithm. A group of test instances from many precedence diagrams were generated for evaluating the performances of all solution methods. Deviations from lower bound values of the number of workers/workstations and the number of optimal solutions obtained by these methods are concerned as performance criteria. The results obtained by the proposed programming formulations have been also compared with the solutions obtained by the traditional mathematical model of the multi-manned assembly line. Through the experimental results, the performance of the metaheuristic has been found very satisfactory according to the number of obtained optimal solutions and deviations from lower bound values.     

面向产品族的混流装配线平衡研究

基于产品族的模块化与通用性,研究了面向产品族装配的混流线平衡问题.基于对一族产品装配过程的聚类分析,提出了面向产品族的混流装配线的平衡设计方法和模型,可以为大规模定制企业实现面向产品族的混流装配提供参考,并用案例说明本文方法的应用.     

TECHNICAL NOTE: Nonparametric estimation and variate generation for a nonhomogeneous Poisson process from event count data

Given a finite time horizon that has been partitioned into subintervals over which event counts have been accumulated for multiple realizations of a population NonHomogeneous Poisson Process (NHPP), this paper develops point and confidence-interval estimators for the cumulative intensity (or mean value) function of the population process evaluated at each subinterval endpoint. As the number of realizations tends to infinity, each point estimator is strongly consistent and the corresponding confidence-interval estimator is asymptotically exact. If the NHPP has a piecewise constant intensity (rate) function, then the proposed point and confidence-interval estimators for the cumulative intensity function are valid over the entire time horizon and not just at the subinterval endpoints; and in this case algorithms are presented for generating event times from the estimated NHPP. Event count data from a call center illustrate the point and interval estimators.     

Long Division: An Example of Dynamic Programming

The familiar method of long division provides an excellent example of dynamic programming. A five-step division problem is solved by both methods. The five steps make up a five-stage dynamic program. The first step involves selecting a trial divisor, a decision, which minimizes the remainder after even division. This remainder is the state carried over to the next stage. Division proceeds recursively until the final stage is reached. Thus as is typical of the dynamic programming technique, one problem in five unknowns (the five-digit quotient) replaces the original problem by five simpler problems each of one unknown.     

基于eM-Plant对注塑企业的生产线建模仿真

分析了注塑企业生产流程,并建立其生产工序的数学模型和仿真程序。根据企业的订单数量、车间生产线的规模等因素,通过对生产过程中批量的控制,研究批量和在制品库存水平的关系,提出了通过控制批量实现控制在制品的数学关系。     

遗传禁忌搜索算法在混流装配线排序中的应用

针对混流装配线排序问题，提出了一种混合遗传禁忌搜索算法，在每一代遗传演化之后，按一定比例随机选择部分解进行禁总搜索，以提高算法的全局搜索能力和收敛性。通过一个混流装配线排序实验，分别利用遗传算法和遗传禁忌搜索算法进行求解，结果表明遗传禁忌搜索算法具有更好的全局搜索能力和收敛性能。     

Comparative Analyses of Fixed and Removable Item Mixed Model Assembly Lines

Three designs of mixed model assembly lines: a moving belt with fixed items, a moving conveyor with removable items, and an accumulation conveyor with removable items are compared with respect to total station idle time, unfinished jobs, and production rate. The conditions required to avoid idle time and unfinished items are analyzed. Simulation is used to confirm the advantage of using an accumulation conveyor with removable items over a moving belt assembly line with fixed items.     

The Effect Of Robots With Overlapping Envelopes On The Performance Of Flexible Transfer Lines

The overlapping envelopes of flexible transfer line robots allow continued processing of the products in case of robot failures. Markovian and simulation models are developed to estimate the effects of the different types of failure and repair processes on the performance of such lines.     

Allocation of Buffer Capacities for a Class of Fixed Cycle Production Lines

The sequential relay model of a fixed cycle production: line is considered in which integer buffer capacities can be allocated between each pair of adjacent production facilities. The feasible sizes of any set of allocations is constrained by a general system of linear constraints. Upper and lower bounds are established for the steady-state system output and certain concave, separable programs are formulated to determine buffer capacities. The result of the optimization process is integrated into a simulation model for comparison and evaluation.     

An Analysis of Automated Storage and Retrieval Systems in Manufacturing Assembly Lines

An automated storage/retrieval system is a material handling system that can be used to pick and to deliver materials in a direct access fashion. An M/G/1 queueing model is used to study the system performance under a first-come-first-served dispatching rule. More detailed studies for different dispatching rules have been done by simulation. A number of cases with different hardware characteristics and workloads have been investigated. Conclusion is drawn based upon the results obtained from analysis as well as numerical experiments.     

利用多米诺效应控制爆破拆除长渡槽

某渡槽为34跨,每跨23.5 m,最大架高17 m,全长799 m.出于对人身安全和设施不受损失考虑,围绕人工机械与爆破拆除两种方案进行论证后,决定用控制爆破拆除渡槽.文章论述了此工程爆破方案设计、技术参数及安全措施,最后取得圆满的爆破效果.     

过冷度对地热发电非共沸工质有机朗肯循环热力性能的影响

有机朗肯循环（organic Rankine cycle,ORC）是利用中低温地热能（< 150℃）发电的主要途径,在实际运行中,非共沸工质往往会冷凝至过冷状态。分析了冷凝过冷度对非共沸工质ORC热力性能的影响,建立了ORC、内回热（internal heat exchanger,IHE）ORC的热力学模型,以净输出功最大为目标函数优化了工质的蒸发压力,并开展了系统的㶲分析。结果表明：过冷度影响了工质与冷源换热流体间的温度匹配特性,受夹点温差的限制,随着过冷度的增加,工质的冷凝压力上升;过冷度亦改变了预热器和蒸发器的热量分摊,随着过冷度的增加,最佳蒸发压力亦上升。混合工质异丁烷/异戊烷的质量配比为0.4：0.6时,净输出功受过冷度的影响最大,当过冷度为2℃时,净输出功下降了4.36%。IHE回收膨胀机排汽的余热,提高了预热器入口温度,可提高过冷ORC系统净输出功0.55%。过冷度增大了冷凝器的㶲损失;采用内回热冷凝器的㶲损失降低了24.7%。     

Self‐Assembly: I‐Motif Nanospheres: Unusual Self‐Assembly of Long Cytosine Strands (Small 8/2011)

The synthesis and characterization of novel DNA structures based on tetraplex cytosine (C) arrangements, known as i‐motifs or i‐tetraplexes, is reported. Atomic force microscopy (AFM) investigation shows that long C‐strands in mild acidic conditions form compact spherically shaped nanostructures. The DNA nanospheres are characterized by a typical uniform shape and narrow height distribution. Electrostatic force microscopy (EFM) measurements performed on the i‐motif spheres clearly show their electrical polarizability. Further investigations by scanning tunneling microscopy (STM) at ultrahigh vacuum reveals that the structures exhibit an average voltage gap of 1.9 eV, which is narrower than the voltage gap previously measured for poly(dG)–poly(dC) molecules in similar conditions.     

混合粒子群算法在混流装配线优化调度中的应用

应用粒子群算法求解混流装配线的优化调度问题,给出粒子的构造方法,并针对算法中存在过早收敛的问题,提出了一种与局部优化和粒子微变异方法相结合的混合粒子群算法.给出了一个实例,实例应用粒子群算法和混合粒子群算法分别进行求解,与其他一些方法比较表明,混合粒子群算法可以有效、快速地求得混流装配线优化调度问题的解.     

连续档架空输电线路非均匀脱冰动力响应分析

为分析输电线路非均匀脱冰动态特性,以实际220 kV两档输电线路为研究对象,利用ABAQUS有限元软件对线路非均匀脱冰典型工况进行了数值模拟,研究了脱冰方式、脱冰率和非脱冰档覆冰厚度等因素对脱冰跳跃和档间不平衡张力的影响,并通过单档脱冰试验验证了模拟结果的有效性.结果表明:单档完全脱冰时,相邻档覆冰厚度增加,脱冰档跳跃高度减小,但最大不平衡张力显著增大,两档覆冰厚度相近时,非脱冰档反向位移较大;单档局部脱冰时,脱冰率越大,两档跳跃幅值越大,且较大的脱冰率会使最大不平衡张力显著增加,脱冰率相同时,4种脱冰方式中两侧端部脱冰引起的动力响应最弱,是较为安全的除冰方式.