基于库存销售比的VMI补货策略

在信任与合作的前提下,销售商提供库存与销售信息,供应商通过库存销售比(存销比)确定补货时间和补货量进行补货.这种补货策略通过信息共享与无订单补货,达到消除供应链中牛鞭效应的目的.     

基于O-S反馈控制的牛鞭效应问题研究

采用传统统计学库存策略和线性控制理论方法相结合,着重研究了具有O-S反馈控制的一级动力学库存模型,提出可以采用延迟订单反馈和实际库存反馈来定义目标库存的大小.借助动力学仿真模型得到的转移方程来研究当采用跃迁输入时,实际库存水平和订单水平的变化,通过调节反馈控制参数Ks、Ko可以改善系统输出值,找到合理的库存位置.通过对动力学系统频率响应曲线的分析,得到量化牛鞭效应大小的方法,从而找到实际工作环境下,合理缓解牛鞭效应的新方法.     

多供应链间库存互补系统动力学仿真模型

以两条或多条由生产商、批发商和零售商组成的三级供应链为研究对象,首先分别建立了两条供应链环境下零售商、批发商和生产商各级节点企业库存互补系统动力学仿真模型,然后把两链间库存互补问题扩展到多链间库存互补情况.研究表明,两条供应链各级节点企业问库存互补均能减少供应链系统的库存总量和总物流成本、减弱牛鞭效应、提高顾客服务水平...     

两种库存管理方法下的牛鞭效应比较分析

建立了ARIMA供应链需求模型,利用订货量方差和需求方差的比值,分别对Order-up库存管理方法和基于MRP的库存管理方法下的牛鞭效应进行了量化.比值大于1则牛鞭效应存在且与比值成正比,反之则牛鞭效应不存在.模拟试验对两种库存管理方法作了对比,结果表明基于MRP的库存管理方法在多数情况下产生了较小的牛鞭效应.     

集群式闭环供应链系统动态模型及牛鞭效应分析

以集群式闭环供应链为研究对象,建立了不确定需求下两个闭环供应链跨链合作的交叉库存补充动态模型,分析了集群式闭环供应链的鲁棒运作问题.针对系统运作过程中需求不确定干扰问题,给出了解决集群式闭环供应链牛鞭效应的鲁棒H∞控制策略及线性矩阵不等式(LMI)算法.最后,通过算例仿真,对比分析了有无跨链合作时两供应链库存、订货(生...     

信息共享对瞬时补货多级供应链牛鞭效应影响的建模分析

对不稳定市场需求下的瞬时补货多级供应链系统进行建模,定量地分析了需求信息共享前后供应链各节点企业的牛鞭效应,并进行了数值实验.研究表明:无需求信息共享时,牛鞭效应始终存在;需求信息共享后,牛鞭效应明显地减小,在一定条件下会出现反牛鞭效应.     

基于横向补货的库存协调近似模型

以给定零售商独自拟定订货策略为前提,提出了一种在横向补货允许的情况下,能够有效地刻画系统库存的近似模型.该模型在"最近邻居"优先补货原则下,详细地阐述了系统中的产品需求走势和相应的需求满足率.并通过和仿真试验的数值结果进行比较,验证了该模型的有效性,还对横向补货允许和补货不允许两种不同情况下的系统库存成本进行了比较,形象地给出了横向补货策略在优化库存成本方面的绩效.关于单个零售商订货策略一般性的拓展以及系统联合订货策略的可能性研究也给予了相关说明.     

基于联合库存的供应链系统动力学研究

采用联合库存管理为库存管理模式,运用系统动力学(Vensim5．0)软件建立了供应链动态仿真模型。通过仿真结果输出,从瓶颈、长鞭效应、成本等三方面对模型进行分析和优化;通过计算机仿真对系统未来行为进行的描述,形成了供应链管理策略的实验室。从而既保证了该系统在实际运行时的效果,又避免了系统策略实施可能带来的风险。     

带有横向调度的易变质商品两级库存系统分析与优化

在对库存控制策略研究的基础上,针对一对多的易变质商品两级库存系统,在需求率、变质率随时间变化和二级库存之间存在横向调度的情况下,建立了一对多的易变质商品两级库存优化数学模型,提出了基于牛顿法的求解算法,得出了在一定时间水平上的两级库存系统的最优控制策略。通过算例仿真验证了模型的正确性和求解算法的有效性。分析了两级库存控制参数与补货周期、系统总成本的关系,结果表明:在二级库存之间的横向调度不仅可以缩短补货周期,还可以有效降低库存系统的总成本;变质率的增加使得极大库存水平的波动加剧。     

VMI技术的运作协调性及在制造业的应用研究

传统供应链因结构性内生的问题--牛鞭效应往往使企业响应迟缓,库存大量积压.本文通过定量的理论分析,认为VMI模式不仅有助于解决牛鞭效应的问题,同时有助于整个供应链的获利能力的提高.并以一个家电企业与零件供应商之间的VMI系统为例介绍VMI在制造供应链上游的应用.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...