On using continuous flow lines to model discrete production lines

We extend previous research on the use of models ofcontinuous tandem (CT) lines for performance analysis ofdiscrete tandem (DT) production lines. We formalize the translation of input parameters from the DT line to the CT model, as well as the translation of performance measures (PMs) obtained from the CT model back to the DT line. We show that although the CT model conceptually represents a line with continuous fluid, it can be represented as a generalized semi-Markov process (GSMP). This representation leads to a simple and concise simulation algorithm for a CT model. We investigate the accuracy of the CT model for prediction of PMs in the DT line, and show that, with proper translation of parameters and PMs, the CT model provides reasonable estimates for the DT line PMs. We provide preliminary results on gradient estimation for CT models via infinitestimal perturbation analysis. The aim of the paper is to provide a firm foundation for the future exploration of CT models as a means to parameter optimization for DT lines.     

Buffer allocation and preventive maintenance optimization in unreliable production lines

In this paper, we consider a serial production line consisting of \(n\) unreliable machines with \(n-1\) buffers. The objective is to determine the optimal preventive maintenance policy and the optimal buffer allocation that will minimize the total system cost subject to a given system throughput level. We assume that the mean time between failure of all machines will be increased after performing periodic preventive maintenance. An analytical decomposition-type approximation is used to estimate the production line throughput. The optimal design problem is formulated as a combinatorial optimization one where the decision variables are buffer levels and times between preventive maintenance. To solve this problem, the extended great deluge algorithm is proposed. Illustrative numerical examples are presented to illustrate the model.     

Hidden Markov models combining discrete symbols and continuous attributes in handwriting recognition

Prior arts in handwritten word recognition model either discrete features or continuous features, but not both. This paper combines discrete symbols and continuous attributes into structural handwriting features and model, them by transition-emitting and state-emitting hidden Markov models. The models are rigorously defined and experiments have proven their effectiveness.     

Integrated production planning and preventive maintenance in deteriorating production systems

This paper discusses the issue of integrating production planning and preventive maintenance in manufacturing production systems. In particular, it tackles the problem of integrating production and preventive maintenance in a system composed of parallel failure-prone production lines. It is assumed that when a production line fails, a minimal repair is carried out to restore it to an ‘as-bad-as-old’ status. Preventive maintenance is carried out, periodically at the discretion of the decision maker, to restore the production line to an ‘as-good-as-new’ status. It is also assumed that any maintenance action, performed on a production line in a given period, reduces the available production capacity on the line during that period. The resulting integrated production and maintenance planning problem is modeled as a nonlinear mixed-integer program when each production line implements a cyclic preventive maintenance policy. When noncyclical preventive maintenance policies are allowed, the problem is modeled as a linear mixed-integer program. A Lagrangian-based heuristic procedure for the solution of the first planning model is proposed and discussed. Computational experiments are carried out to analyze the performance of the method for different failure rate distributions, and the obtained results are discussed in detail.     

农村电话用户线的障碍及维护

激烈的市场竞争,需要优质的通信质量作保障,农村的通信服务,不仅要有用户满意的事前、事后服务、更离不开通信线路的高质量作保证。 要提高农村电话通信质量,首先要求维护人员做到增加线路巡检频次,落实预检预修制度,及时掌握线路动态,将问题和故障消灭在萌芽状态。具体讲,维护人员在维修线路工作中要做到“三勤”。即勤宣传,减少人为原因造成的故障;勤巡检,及时发现故障;勤修理,及时排除故障。     

Robust production and maintenance planning in stochasticmanufacturing systems

In this paper the authors consider a preventive maintenance and production model of a flexible manufacturing system with machines that are subject to breakdown and repair. The preventive maintenance can be used to reduce the machine failure rates and improve the productivity of the system. The control variables are the rate of maintenance and the rate of production; the objective is to choose a control process that optimizes a robust cost of inventory/shortage, production, and maintenance. The value function is shown to be locally Lipschitz and to satisfy a Hamilton-Jacobi-Isaacs equation. A sufficient condition for optimal control is obtained. Finally, an algorithm is given for solving the optimal control problem numerically     

利用均匀离散曲波域LCHMM的图像降噪算法

提出了一种在均匀离散曲波域中利用局部上下文隐马尔可夫模型进行建模的图像降噪算法。介绍均匀离散曲波变换的特点,分析其系数的统计分布规律,表明适合用隐马尔可夫模型对其进行建模。通过期望最大化训练获取模型的参数,利用参数得到降噪图像的系数估计。分别对光学图像和高分辨率的SAR图像进行了降噪实验,与小波域、轮廓波域的局部上下文隐马尔可夫模型等降噪方法进行比较,结果表明,提出的算法能够有效地去除噪声,具有较强的边缘保持能力。     

A new method of analysis for discrete straight lines

The problem of finding the set of all continuous straight lines which lead to the same digitization is quite well known and has been studied in [1, 2, 3]. In this paper, we propose a new method of analysis which is simple and straightforward but is shown to be as powerful as the other techniques. Moreover, our scheme, being algebraic in nature, can be generalized to more complex shapes and figures and thus has a wider applicability.     

Information-measuring diagnostics complex for technical maintenance

Hardware-software complex for configuration, support and diagnostics of control systems in aircraft engines and allied devices is described. Application of certain algorithms based on a bank of Kalman filters to detect parametric faults in sensors and actuators is considered.     

Joint production and maintenance strategy for economic production quantity model with imperfect production processes

In this study, an economic production quantity (EPQ) model is generalized by considering maintenance and production programs for an imperfect process involving a deteriorating production system with increasing hazard rate. There are two types of preventive maintenance (PM), namely imperfect PM and perfect PM. The probability that perfect PM is performed depends on the number of imperfect maintenance operations performed since the last renewal cycle. Following a failure, the delayed repair performs some restorations and reduces production rate to restore the system into an operating state (in-control state), but leaves its lower production rate until perfect PM is performed. That is, the production run period not always starts in normal production rate. This study considers backorders, as well as loss of inventory due to the lower production rate. For the EPQ model, the optimum run time, which minimizes the total cost, is discussed. Various special cases are considered, including the maintenance learning effect. Finally, a numerical example is presented to illustrate the effects of PM ability, repair cost and production decreasing rate on total costs and production period.     

Broadcast digital subscriber lines using discrete multitone for broadband access

Broadcast digital subscriber lines (BDSL) can provide a cost-effective architecture to deploy digital broadcast services in the near future by utilizing the in-place unshielded twisted-pairs. In the BDSL system, all broadcasting channels can share the same transmitter to reduce the cost. Because all twisted-pairs transmit the same BDSL signal in the downstream direction, both near- and far-end crosstalk can be eliminated. While HDSL and Asymmetrical Digital Subscriber Lines (ADSL) signals are carried at low frequency band, BDSL signals can be transmitted at higher frequency band. A discrete multitone based modulation method is used to increase the efficiency of BDSL. Compared to scheme employing identical modulation for all subchannels, the channel though-put of low frequency subchannels can be increased because of their smaller channel losses and the high frequency subchannels can be utilized even if their signal-to-noise ratios are small. The combination of HDSL, ADSL, and BDSL can provide subscribers many digital one-to-one and broadcasting broadband services.     

基于维护计划的卷烟生产线设备运维管理系统

介绍了一个基于维护计划的卷烟生产线设备运维管理系统,分别从系统功能模型、计划业务流程等角度描述了系统的设计思想。并阐述了系统涉及的设备润滑计划制定、派工、运行维护数据分析、系统开发与应用等关键技术。开发的系统具有一定的可集成性、可扩展性和可重构性,与移动通讯技术、数据采集技术相结合,集成在制造执行系统中,可以实现卷烟生产企业制丝、卷包生产线的实时设备运行与维护保养管理。     

A discrete de Rham complex with enhanced smoothness

Abstract Discrete de Rham complexes are fundamental tools in the construction of stable elements for some finite element methods. The purpose of this paper is to discuss a new discrete de Rham complex in three space dimensions, where the finite element spaces have extra smoothness compared to the standard requirements. The motivation for this construction is to produce discretizations which have uniform stability properties for certain families of singular perturbation problem. In particular, we show how the spaces constructed here lead to discretizations of Stokes type systems which have uniform convergence properties as the Stokes flow approaches a Darcy flow. Keywords: Discrete exact sequences, nonconforming finite elements, Darcy–Stokes flow, uniform error estimates. Mathematics Subject Classification (1991): Primary 65N12, 65N15, 65N30     

Short term adjustments to production lines

This paper presents a heuristic procedure and the computer software for solving the short term or dynamic production line balancing problem. The procedure is intended for use on periodic basis to determine how many operators should be assigned to each work station on a production line. The objective is to control work in process inventories and minimize idle labor while producing the required amount of final product. The production line is assumed to be balanced in its static state and work elements will not be re-allocated. The computer software is in BASIC, requires very little main core storage and can be readily adapted to run on micro and mini computers.     

流程工业生产和维修计划数学模型

在流程工业生产中维修计划是极其重要的.在同时考虑生产和定期维修计划的情况下,开发了流程工业混合整数线性规划模型.该模型可安排生产和定期维修计划,实现生产、延期交货、故障维修和定期维修的综合成本最小化.模型考虑到前期维修期间的设备故障的可能性.模型表达式具有通用性,因此适合多种生产环境.     

Optimal lot-sizing problem with imperfect maintenance and imperfect production

In this paper, we develop an integrated model for the joint determination of both economic production quantity and level of preventive maintenance (PM) for an imperfect production process. This process has a general deterioration distribution with increasing hazard rate. The effect of PM activities on the deterioration pattern of the process is modelled using the imperfect maintenance concept. In this concept, it is assumed that after performing PM, the ageing of the system is reduced in proportion to the PM level. After a period of time in production, the process may shift to out-of-control states, either type I or type II. A minimal repair will remove the type I out-of-control state. If a type II out-of-control state occurs, the production process has to stop, and then restoration work is carried out. Examples of Weibull shock models are given to show that the use of PM reduces costs.     

A vectorial algorithm for tracing discrete straight lines inN-dimensional generalized grids

This paper presents an algorithm to trace discrete straight lines in regular grids of any dimension. Most known line tracing algorithms have been developed in Z² and Z³ orthogonal grids. The contribution of this paper is the definition of a method to trace lines in nonorthogonal grids in any dimension. This method is not restricted to being used with a specific grid connectivity as other widespread methods are. Good performance can be achieved because only additions are used during line tracing