备件库存分类控制与策略匹配研究及应用

针对备件库存控制策略决策的复杂性,以提高备件分类的有效性,降低库存成本为目标,提出了一种基于DEA备件分类的库存控制策略模型。首先,根据备件使用和管理所关注的不同属性,建立备件分类指标体系,从部门决策的角度利用SE-DEA模型和AHP求得赋权效率值进而对备件重要性进行评价,结合备件的周转率构建备件库存策略二维决策网格对备件进行二维分类,并匹配具体的库存控制策略,之后使用Plant Simulation仿真软件通过实验设计获取不同类别备件的最优库存参数。最后,将该模型应用于L公司的备件库存控制策略改善项目中,验证了模型的准确性和有效性。     

考虑备件随机折损的备件订货与设备维修策略

为研究随机的备件库存管理与设备维修问题,提出了按照设备重要性对故障设备进行分类,并将备件库存在各级故障设备之间进行分配的设备维修策略.通过构建动态规划模型,得出最优备件补货策略和设备维修策略,给出为各级设备提供即时维修的动态备件库存临界点.通过算例将该策略同先出现故障先维修策略进行比较,结果表明该策略能显著降低设备维护费用,减少备件折损损失.     

考虑休眠的两部件系统可用度马氏建模方法

针对Metric模型中假设备件需求不依赖于可用系统数而导致可用度被低估的问题,考虑部件的休眠状态(即故障系统中无故障部件不产生备件需求的情况),提出一种两部件系统可用度马氏建模方法。利用可用系统数、备件库存以及备件短缺数描述备件状态,根据连续时间马尔可夫链方法,分析不同部件的故障修复过程对状态转移的影响,构建了两组马尔可夫随机过程;随后,分析两种随机过程间的联系,将其合并后建立了备件的马尔可夫状态转移模型;进而利用该模型求解各备件期望短缺数EBO(expected backorders)以及系统可用度的稳态值与瞬时值;最后将模型应用于数值案例,得到了比Metric模型更接近仿真值的备件期望短缺数与系统可用度。     

可修组件的视情更换维修与备件订购联合优化

针对可修复杂关键组件提出周期性视情更换式维修与连续检查的(S,s)备件订购联合优化策略。在考虑确定的维修时间和非完美维修效果的基础上,分析了维修能力与维修策略、库存策略之间的权衡关系,建立了以检测周期、预防维修阈值、库存参数及维修能力为决策变量,以单位设备无限时间范围内的平均费用率最小为目标的仿真优化模型。采用离散事件仿真和遗传算法相结合的方法对模型进行求解。仿真结果表明,更换式维修和连续检查的备件订购策略相结合可以减少系统停机、提高系统可用度、降低维修成本。灵敏度分析结果表明,维修策略、备件策略和维修能力之间存在一定的权衡。     

性能保障模式下关键设备市场扩张期的二级备件库存优化及案例

针对由中央仓库和多个区域仓库构成的二级备件服务系统,提出一种自适应分段近似方法,将时变备件需求处理为多阶段稳定需求,采用多阶段(Q,R)库存策略和以备件可用度为参数的分级服务收益函数,建立性能保障模式下的备件服务收益最大化模型。新型CT机售后服务案例分析证实:分段近似方法能够根据区域市场增长累积及时调整阶段库存策略;性能保障模式能够激励供应商改善备件服务性能、增加服务收益。上述研究为关键设备在市场扩张期的二级备件库存控制提供了有效决策工具。     

航材可修备件最优订购时间研究

准确预测航空公司备件需求是装备保障的一项基本工作,但是备件采购时间过早或者采购数量过多都会使库存成本增加。因此基于指数分布对马尔科夫系统可修备件最优订购时间进行研究,建立了在一定航材保障率下的最优订购数量、最优订购时间的求解模型,并通过算例仿真验证了模型的可行性及实用性。该研究结果对航空公司缩减库存成本有一定的指导意义。     

基于年龄更换策略的多-单维修备件库存控制优化

针对多-单维修备件库存控制系统,建立了结合年龄更换策略的维修备件库存控制数学模型,提出了迭代求解算法。系统仿真验证了模型及算法的有效性,结果表明预防性更换周期影响着供应仓库选择和总成本,扩建库存控制参数受额定存储能力限制的仓库和降低单件储存费用可以有效降低系统成本。     

设备备件库存管理、消耗及订购模式分析

本文在总结北京奔驰汽车有限公司设备维护中心维修用备件库存管理、消耗及订购情况的基础上,基于库存管理的ABC分类分析法,分析冲压车间各类备件库存的种类和分布。同时,以装焊车间为例,依据备件的消耗历史,制定了利用SAP系统规范车间备件领用的策略。最后,基于备件的定量订货模型,提出了ABC三类备件的补货策略,为进一步优化维修备件的库存管理,消耗控制及自动补货工作提供了相关参考。     

基于年龄更换策略的多-单维修备件库存控制优化

针对多-单维修备件库存控制系统,建立了结合年龄更换策略的维修备件库存控制数学模型,提出了迭代求解算法.系统仿真验证了模型及算法的有效性,结果表明预防性更换周期影响着供应仓库选择和总成本,扩建库存控制参数受额定存储能力限制的仓库和降低单件储存费用可以有效降低系统成本.     

基于Witness的随机库存系统仿真研究

选用合适的库存策略可在给定服务水平下有效降低库存总成本.利用witness仿真软件建立了库存系统的仿真模型,充分考虑了库存需求时间间隔、需求量以及提前期的随机性.模型的运行阶段,采用系统优化模块OPTIMIZER,得到库存策略的最优组合.通过对最佳库存策略的进一步分析,得到该库存策略下的服务水平,使得本文对随机库存系统所做的分析研究更加接近企业实际.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.