一类供应链系统在最大库存策略下的性能分析

为了增强企业的柔性、可靠性和响应性,根据环境变化实时做出决策,构建了一类链式供应链系统的动态模型。针对由一个制造商、一个分销商和一个零售商组成的供应链系统,建立了带有成员库存能力约束的离散时间状态空间模型,该模型可扩展为一般链式供应链系统。以客户满意度和平均周期费用为指标,通过仿真分析了最大库存策略下系统的性能特点,指出此时系统的动态性差,策略不够灵活。根据反馈控制理论提出了改进的最大库存策略,该策略可根据性能要求和需求模式改变控制参数。仿真分析表明,改进的最大库存策略的控制效果明显优于原策略。     

离心泵性能预测新方法

介绍了离心泵性能预测支持软件的新方法,不仅能更真实和准确地绘制和预测出泵的性能曲线,也为离心泵设计的性能预测提供了思路。     

应用CUSUM控制图监控过程变差方法的比较

累积和控制图监控过程均值偏移的应用较多,而用于监控过程变差较少。在机械零、部件的大批量、高精度生产过程中,需要同时监控过程均值和变差。在介绍三种主要的监控变差的CUSUM控制图方法基础上,结合案例给予比较,并指出各自的不足之处。     

Impact of ramp-up on the optimal capacity-related reconfiguration policy

This paper presents an optimal solution, based on Markov decision theory, for the problem of optimal capacity-related reconfiguration of manufacturing systems, under stochastic market demand. Both capacity expansion and reduction are considered. The solution quantitatively takes into account the effect of the ramp-up phenomenon, following each reconfiguration, on the optimal policy. A closed-form solution is presented for when product demand is independently and generally distributed over time. A real case concerning a flexible manufacturing line in the automotive sector is shown, to prove that ignoring the ramp-up effect in the decision process can lead to significant increases in overall costs.

基于ANN和SVM的质量预测方法研究

针对随机抽取的质量数据序列的特点,提出时序空间(Time Seauence Space,TSS)的概念,将人工神经网络(Artificial Neural Network,ANN)和支持向量机(Support VectorMachine,SVM)回归模型引入质量数据预测领域.并给出了相应的过程和算法.使用均方误差对拟合精度进行检验,用相对误差对预测精度进行检验.结果表明,相对于传统的多项式回归模型,人工神经网络和支持向量机回归模型的拟合精度较高,相对误差较小,泛化能力较强,可以作为质量数据的预测方法.     

谐波摩擦传动单级最小传动比研究

基于滚轮式波发生器的双波传动模型,分析谐波摩擦传动中柔轮的受力情况,由柔轮疲劳强度校核公式,推导出谐波摩擦传动单级最小传动比的公式,并分析影响单级最小传动比的诸多因素。     

Impact of aspect ratio and surface heating on pollutant transport in street canyons

This paper investigated the impacts of surface heating on pollutant transport and Air Exchange Rate (AER) in street canyons of different aspect ratios (building heightH to street widthW) using computational fluid dynamic (CFD) technique. Street canyons ofH/W varied from 0.1 to 2 were employed in the study. These street-canyon aspect ratios covered a range of basic flow regimes including skimming flow (H/W=1 and 2), wake interference flow (H/W=0.5), and isolated roughness flow (H/W=0.1). Different façade/surface heating imposed different influence on the flow field and pollutant transport in street canyons of differentH/W. The AER induced by vertical velocity fluctuationAER _w, and mean vertical velocityAER _w . AER of street canyon with differentH/W and different surface heating exhibited their unique characteristics.     

提高连铸机装机水平的技术措施

提高连铸机装机水平的技术措施包括确保连铸机稳定生产的技术措施,浇铸中低合金和其它钢种的技术措施以及确保铸坯质量必须采取的措施,这些都做到了,就可以保证连铸机高效高质量的生产。     

基于柔度比优化设计杠杆式柔性铰链放大机构

分析与研究了柔性铰链的柔度特性,用于柔性放大机构的优化设计。提出了一个通用的柔度比参数λ,探讨了具有不同柔度比λ的柔性铰链主要输出位移形式的灵敏度,分析了它对常用柔性铰链的柔度特性的影响规律。然后,以柔性铰链的柔度比λ为基本参数,在考虑柔性铰链转动中心偏移量的基础上,推导了二级杠杆式柔性铰链放大机构放大率的理论计算方法,并依据柔性铰链的柔度比特性提出了柔性放大机构的优化设计方法。开展了有限元仿真和实验研究。结果显示,优化后的柔性放大机构的放大率比优化前的放大率分别提高了0.234和0.23。实验表明,依据柔性铰链的柔度比λ对柔性放大机构进行优化设计能够有效地提高柔性放大机构的位移放大率与工作行程,进而提高放大机构的末端运动及定位精度。     

Genetic cell formation using ratio level data in cellular manufacturing systems

Manufacturing cell formation is a useful strategy in batch type production industries for enhancing productivity and flexibility. The basic idea rests on grouping the parts into part families and the machines into machine cells. Most of the literature used zero-one incidence matrix representing the part visiting a particular machine as one and zero otherwise. The output is generated in the form of block diagonal structure where each block represents a machine cell and a part family. In such models real life production factors such as operation time and sequence of operations are not accounted for. In this paper, the operational time of the parts required for processing in the machines is considered. It is attempted to develop an algorithm using genetic algorithm (GA) with a combined objective of minimizing the total cell load variation and the exceptional elements. The results are compared with the solutions obtained from K-means clustering and C-linkage clustering algorithms.     

锻比各种计算方法的看法与新公式的提出

这里归纳了计算锻比的各种方法,讨论了拔长锻比与镦粗锻比的关系及折算当量的计算问题,给出了新的锻造比计算公式。     

Prediction of the variance of stereological volume estimates from systematic sections using computer-intensive methods

The Cavalieri method is an unbiased estimator of the total volume of a body from its transectional areas on systematic sections. The coefficient of error (CE) of the Cavalieri estimator was predicted by a computer‐intensive method. The method is based on polynomial regression of area values on section number and simulation of systematic sectioning. The measurement function is modelled as a quadratic polynomial, with an error term superimposed. The relative influence of the trend and the error component is estimated by techniques of analysis of variance. This predictor was compared with two established short‐cut estimators of the CE based on transitive theory. First, all predictors were applied to data sets from six deterministic models with analytically known CE. For these models, the CE was best predicted by the older short‐cut estimator and by the computer‐intensive approach, if the measurement function had finite jumps. The best prediction was provided by the newer short‐cut estimator when the measurement function was continuous. The predictors were also applied to published empirical datasets. The first data set consisted of 10 series of areas of systematically sectioned rat hearts with 10–13 items, the second data set consisted of 13 series of systematically sampled transectional areas of various biological structures with 38–90 items. On the whole, similar mean values for the predicted CE were obtained with the older short‐cut estimator and the computer‐intensive method. These ranged in the same order of magnitude as resampling estimates of the CE from the empirical data sets, which were used as a cross‐check. The mean values according to the newer short‐cut CE estimator ranged distinctly lower than the resampling estimates. However, for individual data sets, it happened that the closest prediction as compared to the cross‐check value could be provided by any of the three methods. This finding is discussed in terms of the statistical variability of the resampling estimate itself.     

两种计算行星齿轮机构传动比方法的联合应用

探讨计算行星齿轮机构传动比的两种方法--转化机构法和速度图解法联合应用的可行性.转化机构法是研究行星齿轮传动运动学最常用的方法;速度田解法在用于对行星齿轮机构进行运动学分析时,虽可计算单排行星齿轮传动的传动比,但无法对两排及两排以上行星齿轮机构的传动比进行求解.本文结合具体实例,尝试先用速度田解法后用转化机构法,求解两排行星齿轮机构的传动比,两种方法的联合应用为行星齿轮传动机构的设计和计算提供了参考.     

The specific character of work on reducing the stress level in pipelines using magnetic-testing methods

This paper is devoted to the problems of increasing the reliability of industrial pipelines of compressor stations (CSs) that are subjected to bending loads. The results of the bending load simulation at a tube test bench are presented and variations in the stressed state under load are analyzed. Practical methods for reducing and testing bending stresses in pipelines are considered in the second part for different designs of gas transporting apparatuses.     

微型土压平衡盾构机刀盘开口率对排土率的影响

刀盘开口率是刀盘设计的关键参数,是决定盾构机是否稳定掘进的关键参数之一.在充分理解刀盘与开挖面相互作用的基础上,分析了开口率对排土率的影响,并推导出最大排土率与最小排土率的计算方法.根据该计算方法,研究了不同直径的刀盘在砂砾石地层掘进时,排土率随开口率变化的情况.分析结果表明:在砂砾石地层中直径为3m的刀盘开口率取值为70%~85%时有利于开挖面的稳定.     

复杂武器系统技术成熟度评估方法研究

复杂武器系统研制风险高,在预研阶段需充分论证.分析现有复杂武器装备技术成熟度评估方法,针对现有方法的不足,在成熟度矩阵算法的基础上,设计了一种新的计算技术成熟度方法.引入信息熵理论,采用主观赋值与客观赋值相结合的方式.调整单项技术在系统中的权重,并能融合专家权重,提高评估结果的合理性.对专家评定的关键技术权重和集成成熟度进行主观赋值偏差一致性检验,确保结果的有效性和可靠性.实例表明,该方法更能反映出系统的实际技术成熟度等级,避免单纯采用矩阵方法带来的偏差,更接近系统实际值.     

混沌预测模型改进及在电力日负荷预测中的应用

针对电力日负荷预测中基于最大Lyapunov指数的传统混沌预测模型的缺陷,提出以下改进思想:采用微分熵法同时确定嵌入维数和延迟时间,改善相空间重构质量的同时,有效减少计算量;引入夹角参数,在与中心点距离最短的点中,筛选夹角最小的点作为最终邻近点;基于相似性原理,引入取舍规则,使得计算结果唯一确定。本文方法解决了传统预测模型计算量大、运算速度慢、预测精度不高以及正负号选取等问题。通过对典型混沌系统数值验证和某地区实际电力负荷系统的预测分析证明了本文方法的可靠性和高效性,为电力日负荷预测提供了一种新的有效途径。     

放射性液位计的常见故障及检测方法

论述放射性液位计的测量原理及对它的一般检测方法。     

Generation of offset surface for tool path in NC machining through level set methods

Surface offset is always necessary for ball-end milling during computer-aided manufacturing period. Self-intersection may occur in offsetting complex surfaces. Many solutions for surface self-intersection are always complicated with algorithms for approximation, and they are always based on surfaces which are represented by special mathematical expressions. This paper proposes level set methods in the surface offsetting progress. The surface offset problem is regarded as the generation of a new interface from a dynamic initial surface with constant normal speed. Numerical computing results demonstrate that accurate solutions can be obtained through the level set methods with an appropriate numerical flux. The self-intersections are naturally eliminated while topology stability is kept.     

Obtaining fine emulsions of a controlled level of dispersion by wave methods

New results of experimental studies performed at the Scientific Center of Nonlinear Wave Mechanics and Technology of the Russian Academy of Sciences (NTs NVMT RAN) on the investigation of wave processes in dispersed media, aimed at the application of wave effects for processing and obtaining microheterogeneous emulsions, are presented. The possibility of controlling the drop sizes of the dispersed phase due to variations in the wave processing mode is shown using the example of cosmetic creams. The energy efficiency of the wave method for processing and obtaining the microheterogeneous emulsions is presented.