Estimators for particulate sampling derived from a multinomial distribution

Counting the number of units is not always practical during the sampling of particulate materials: it is often much easier to sample a fixed volume or fixed mass of particles. Hence, a class of sampling designs is proposed which leads to samples that have approximately a constant mass or a constant volume. For these sampling designs, estimators were derived which are a ratio of arbitrary sample totals. A Taylor expansion was used to obtain a first-order approximation for the expected value and variance in the limit of a large batch-to-sample size ratio. Furthermore, a π -estimator for a ratio of batch totals was found by deriving expressions for the first- and second-order inclusion probabilities. Practical application of the π -estimator is limited because it requires inaccessible batch information. However, when the denominator of the estimated batch ratio is the batch size, the π -estimator becomes equal to a sample total divided by the sample size in the limit of a large sample-to-particle size ratio. As a consequence, the obtained sample ratio becomes an unbiased estimator for the corresponding batch ratio. Retaining unbiasedness, the Horvitz–Thompson estimator for the variance, which also contains inaccessible batch information, is replaced by an estimator containing sample information only. Practical application of this estimator is illustrated for the sampling of slag, produced during the production of steel.     

钢轧一体化生产计划的体系结构

制造执行系统是钢铁企业信息化的核心,钢轧一体化生产计划系统则是钢铁企业制造执行系统的关键功能之一,能实现订单、工艺、质量、设备和生产等各种信息的高度集成和处理。本文分析了铜轧一体化生产计划问题的特点,提出了铜轧一体化生产计划的体系结构模型．并分别从层次的观点、过程的观点、功能的观点和集成的观点深入地探讨了钢轧一体化生产计划体系结构模型的核心内容。其中。层次观点对定位和界定钢轧一体化生产计划起着重要的作用：功能结构观点为构筑基于组件技术的钢轧一体化生产计划系统提供了功能结构和技术框架：过程观点明确了钢轧一体化生产计划内部过程的循环结构．体现出钢轧一体化生产计划是联系各个外部系统的主线;集成观点强调协调炉次批量计划、浇次批量计划和轧制批量计划在钢轧一体化生产计划编制中的作用。本文有利于拓展钢轧一体化生产计划问题的建模思路和求解方法,对钢轧一体化管理系统的开发具有一定的指导意义。     

Performance assessment and improvement of control charts for statistical batch process monitoring

This paper describes the concepts of statistical batch process monitoring and the associated problems. It starts with an introduction to process monitoring in general which is then extended to batch process monitoring. The performance of control charts for batch process monitoring is discussed by means of two performance indices: the overall type I error and the action signal time. Problems associated with the existing approach are discussed and highlighted. Improvements are suggested and checked with the performance indices. To evaluate the effect of the proposed improvements as well as to assess the performance of the existing approach, an industrial batch production process is used.     

基于Java的通用批处理作业系统的设计与实现

为了解决当前业务数据处理中客户群庞大、业务数据大、人工操作繁杂、重复性高等问题，针对现有核心系统构架并非针对完全连线化的设计，提出了同一Job内批次作业平行处理的通用批处理作业系统框架模型，采用断点续接、参数化和模块化设计等实现了该系统。研究结果表明：通过调节参数，Batch循环流程控制，以满足气象、电信等不同业务的需要，系统能为其提供业务数据的快捷处理手段，提高了操作效率，减少了人工误操作率，达到了通用批处理作业的效果。     

Overlapping operations in material requirements planning

Material requirements planning (MRP) is a planning and information system that has widespread application in discrete-parts manufacturing. The purpose of this article is to introduce ideas that can improve the flow of material through complex manufacturing systems operating under MRP, and that can increase the applicability of MRP within diverse manufacturing environments.MRP models the flow of material by assuming that items flow from work station to work station in the same batches that are used in production. That is, once work starts on a batch of a certain item at a certain work station, the entire batch will be produced before any part of the batch will be transported to the next work station on its routing plan. Clearly, efficiency can be increased if some parallelism can be introduced. The form of parallelism investigated here is overlapping operations.Overlapping operations occurs when the transportation of partial batches to a downstream work station is allowed while work proceeds to complete the batch at the upstream work station. The potential efficiencies to be gained are the following:

• Reduced work-in-process inventory

• Reduced floor space requirements

• Reduced size of transfer vehicles

Additional costs may accrue through additional cost of transportation of partial batches and through additional costs of control.Some MRP software vendors provide the data processing capability for overlapping operations. However, the user is given little or no guidance on overlapping percentages or amounts. It is our intent to provide a simple, robust technique to MRP users who would like to overlap operations and gain some or all of the above efficiencies.An optimal lot-sizing technique is derived by considering a generic two work station segment of a manufacturing system. Under the assumptions of constant demand and identical production rates, a cost function that considers setup costs, inventory holding costs and transportation costs is derived. This cost function is minimized subject to the constraint that the production batch is an integer multiple of the transfer batch. We solve for the optimal production batch, the optimal transfer batch, and the integer number relating them. Solutions are obtained as closed form, easy to-evaluate formulas.By introducing more parallelism, overlapping operations can reduce lead time. However, this will not happen without modification of MRP logic to accommodate such reduced lead time. We derive a formula that shows how a significant lead time compression can easily be obtained and implemented in MRP.We consider an example to illustrate the application of the technique on typical data from the electronics industry. The outcome showed a cost savings of approximately 22.5% over the standard MRP approach.Overlapping operations allows the applicability of MRP to an increasing number of situations that are not modeled faithfully by conventional MRP logic. Three such situations that occur often are the following:

• Limited size of transfer vehicles dictate that several transfers should be planned.

• Lead time requirements prohibit nonoverlapped operations.

Our analysis suggests how to accommodate these difficult practical situations into MRP.Overlapping operations in material requirements planning provides an enhancement that allows wider applicability, shortened lead times, and lower total costs. It may be applied selectively to any two work stations where it is deemed appropriate. Due to the structure of the cost function, it is possible to make the transfer lot-sizing decisions independent of the production lot-sizing decisions. Therefore, significant improvements can be made through overlapping with minimum disruption to the existing MRP system machinery. It is our conviction that overlapping operations is an important concept that can and will impact MRP. We suggest the approach presented here as a systematic way to implement overlapping.     

MRP with high uncertain yield losses

Certain manufacturing systems, notably those in high technology precision casting and integrated circuit production suffer from process yield losses which are both significant in quantity terms and are also highly unpredictable. This poses special problems for the provisioning of materials to support a manufacturing program and for the detailed scheduling necessary to update the priorities of work in process batches as losses occur. This paper establishes a framework of analysis to handle this problem in MRP logic. It describes the mechanisms available and discusses their relevance to the market environments in which the company is operating.The key conclusion of this paper is that different solutions are required for different market circumstances. The four key strategies developed are:

1. A: For continuous schedules, make-for-stock: Use mean yield rate and fixed buffer stocks.

2. B: For continuous schedules, make-to-order: Use mean yield rate, fixed buffers and a yield to finish monitoring system.

3. C1: For single batch production make-to-order: As for B but using a desired service level yield rate.

4. C2: For multiple batch production, make-to-order: As B but using a variable yield rate by batch.

The implementation of each of these is described in relation to the business objectives of cost effectiveness and customer satisfaction.     

高职院校基于文件读写的试题库批量添加功能的实现

文章介绍了文件的分类和相关的文件读写函数,着重说明了C＋＋语言的文件读写函数,并利用这些文件读写函数编程,实现了桂林旅游高等专科学校网络在线考试系统数据库的批量添加功能,极大地减少了该校计算机在线考试系统的试题添加工作量。     

狄克·狄维士:安利遭遇中国难题 公关底牌失效

姑且不论安利是否能顺利拿到中国首批直销牌照,但6个月内中国颁发第一批直销牌照的可能性还只能打上问号。如果狄克·狄维士在卸任“主席”之前看不到安利将直销牌照揽入囊中,是否会成为他的又一声叹息呢?     

海洋工程项目中物资追踪管理研究

本文通过研究海洋工程项目的建造特点,阐述了如何使用批次管理方法对海洋工程物资进行管理。在海洋工程项目的建造过程中,通过对物资的批次进行追踪达到对物资的管理,能够简化物资追踪过程、提高物资追踪精度,达到提高质量、节约成本、缩短周期的目的。     

白车身质量关键控制点的设立和控制方法

随着汽车行业的迅猛发展,批量生产的制造模式,生产节拍越来越快,用户对汽车的制造质量以及安全性能也更为关注,如何在生产过程中保证关键环节的质量要求,避免出现批量质量问题变得越来越重要。文章通过介绍白车身焊点结构特点,对白车身关键点的设立原则及控制方法进行研究,从根本上保证白车身的关键过程制造质量。     

基于谱分析的连续加工过程检验批量的确定

在连续加工过程中 ,合理地确定检验批量 ,不仅可以反映加工过程的稳定性 ,而且也是确定抽样检验方案及检验频次的基础。本文主要利用时间序列的谱分析方法对连续加工过程的质量检测数据进行周期划分 ,从而确定抽样检验的批量 ,并根据周期分析结果 ,指出了导致加工质量产生波动的一些原因。     

白车身质量关键控制点的设立和控制方法

随着汽车行业的迅猛发展，批量生产的制造模式，生产节拍越来越快，用户对汽车的制造质量以及安全性能也更为关注，如何在生产过程中保证关键环节的质量要求，避免出现批量质量问题变得越来越重要。文章通过介绍白车身焊点结构特点，对白车身关键点的设立原则及控制方法进行研究，从根本上保证白车身的关键过程制造质量。     

创新是高等职业教育可持续发展的动力

高职院校同时面临机遇和挑战,不创新发展就要被社会淘汰。黑龙江建筑职业技术学院成为国家首批28所示范性高等职业院校重点建设单位之一,教育部、建设部紧缺人才示范性培养培训基地,就是在创新中发展起来的。     

数控车床加工稳定性影响因素分析

为了提高批量加工零件的稳定性,对于经济数车和普及型数车的加工精度需要进行控制。通过对生产批量稳定性指标的了解以及相关计算,对于批量生产的工序能力进行评价,并指出为达到Cp值要求,加工部位应具备精车刀具,刀具应锐利,刀尖角小,必要时后角也大些,以避免挤压造成的精度不稳定。     

基于供需不平衡下海南旅游人数与酒店数量分析

本文从海南省国际旅游岛的建设背景出发,揭示了海南省酒店供求管理中存在的不平衡问题,深刻剖析了供求不平衡的原因和弊端,并进行了实证分析。在人数预测上,选用累积和逐期增长量两个指标,从增长的绝对量和增长程度两个角度有效把握目前的人数变化趋势,运用Eviews,进行一元回归模型分析。在酒店数量方面,根据预测人数和酒店行业入住率标准,确定最佳酒店数量。最后结合海南省实际情况,提出酒店供求管理在今后发展过程中的对策和建议。     

Multi-server Batch-service Systems

In this paper we analyse a multi-server batch-service queueing model. Customers arrive one by one according to a Poisson process. They are served in batches under the following threshold policy: when a server becomes available a new batch of waiting customers is taken into service as soon as their number reaches a threshold a . The maximum allowable batch size is equal to b . Two classes of batch service time distributions are considered: Coxian-2 and Erlang- r distributions. In both cases the queueing model can be described by a Markov process. For this process it is shown that the equilibrium probabilities for states with all servers busy can be expressed as a finite sum of geometric terms. This form is used to derive a closed form expression for the waiting time distribution.     

Time dependent solution of a queueing problem with correlated batch arrivals and general service time distribution

This paper considers the transient behaviour of queueing problem in which (i) the arrivals occur in batches of variable size (ii) the arrival and no arrival of a batch at two consecutive transition marks are correlated (iii) the service time distribution for each, unit is general with probability density functionD(x). TheLaplace transform of various probability generating functions of queue length are obtained and some particular cases are derived therefrom.     

基于VC#的Excel表格与SQL Server数据库的批量数据导入导出技术研究

在信息管理系统实际应用中,批量数据导入导出技术是提高数据录入速度和方便用户将数据库信息以多种报表方式予以输出的有效途径。文章详细介绍基于VC#开发平台实现Excel表格与SQLServer数据库之间批量数据导入导出技术的流程、步骤和实现方法。     

M-estimation in the presence of unequal scale

Abstract  The class of weighted M-estimators is defined. The ratio of the asymptotic variance of the weighted estimator to the asymptotic variance of the optimally weighted estimator is defined as the inefficiency. A K antorovich inequality is proved, its implications are investigated for the misweighted mean and misweighted median, and the results are applied to a batch of demographic data.     

De omvang van de steekproef bij een enkelvoudig steekproefsysteem

Summary  (Sample size for a single sampling scheme).
The operating characteristic of a sampling scheme may be specified by the producers 1 in 20 risk point ( p ₁), at which the probability of rejecting a batch is 0.05, and the consumers 1 in 20 risk point ( p ₂) at which the probability of accepting a batch of that quality is also 0.05.
A nomogram is given (fig. 2) to determine for single sampling schemes and for given values of p₁ and p ₂ the necessary sample size ( n ) and the allowable number of defectives in the sample ( c ).
The nomogram may reversedly be used to determine the producers and consumers 1 in 20 risk points for a given single sampling scheme.
The curves in this nomogram were computed from a table of percentage points of the χ² distribution. For v > 30 Wilson and Hilferty's approximation to the χ² distribution was used.