Impact of investing in quality improvement on (Q,r, L) model involving the imperfect production process

This paper investigates the impact of quality improvement on the modified lot size reorder point models involving variable lead time and partial backorders. The formulated models include the imperfect production process and an investing option of improving the process quality. The objective is simultaneously optimizing the lot size, reorder point, process quality level and lead time. We first assume that the lead time demand follows a normal distribution, then relax this assumption to consider the distribution-free case where only the mean and standard deviation of lead time demand are known. An algorithm procedure of finding the optimal solution is developed, and two numerical examples are given to illustrate the results.     

A new EPQ model: integrating lower pricing,rework and reject situations

The economic production quantity (EPQ) is a well-known and commonly used inventory control technique. It has been used for well over 50 years to optimize lot sizes in transportation/production. The standard results are easy to apply but are based on a number of assumptions. A common assumption in the EPQ model is that all units produced are of perfect quality, this will underestimate the actual required quantity. Many researchers have studied the effects after relaxing this assumption on the EPQ model. The previous studies had considered that imperfect quality and defective items are either to be reworked instantaneously and kept in stock or rejected at a cost. The objective of this paper is to provide a framework to integrate lower pricing, rework and reject situations into a single EPQ model. A 100% inspection is performed in order to identify the amount of good quality items, imperfect quality items and defective items in each lot. This model assumes that items of imperfect quality, not necessarily defective, could be used in another production situation or sold to a particular purchaser at a lower price. The electronic and clothing industries give good examples for such situations. A mathematical model is developed and a numerical example is presented to illustrate the solution procedures. It is found that the time factor of when to sell the imperfect items is critical, as this decision will affect the inventory cost and the batch quantities.     

A BRANCH AND BOUND PROCEDURE FOR SETUP PROBLEMS IN FLEXIBLE MANUFACTURING SYSTEMS

We address a medium- to short-term production planning problem in a flexible manufacturing environment. First we present a single-machine, mixed integer programming model for part type selection and lot-sizing problems over a T-period planning horizon. Demand for part types changes dynamically through the periods. The objective is to meet the demand for part types during the periods they are demanded. Available machine time and tool magazine capacities are the system constraints in our models. We next extend on the single- machine model to include multiple machines. In addition to part type selection and lotsizing decisions, the extended model also addresses the machine-loading decision. We present exact branch and bound procedures based on linear programming relaxations for the two models. We also report the results of our computational experiments.     

Discrete time-varying demand lot-sizing models with learning and forgetting effects

This paper deals with the problem of incorporating both learning and forgetting effects into discrete timevarying demand lot-sizing models to determine lot sizes. Forgetting is retrogression in learning which causes a loss of labour productivity due to breaks between intermittent production runs. Formulae are derived for calculating the production cost required to produce the first unit of each successive lot over a finite planning horizon. An optimal lotsizing model and three heuristic models are developed by extending the existing models without learning and forgetting considerations. Numerical examples and computational experience indicate that larger lot sizes are needed when the phenomenon of learning and forgetting exists. Several important conclusions are drawn from a comparison of the three heuristic solutions with the optimal solution, and suggestions for future research and for lot-size users to choose an appropriate lot-sizing technique are made.     

Quality management and performance: a comparison between the UK and Turkey

Purpose: The aim of this article is to detail the correlation between quality management, specifically its tools and critical success factors, and performance in terms of primary operational and secondary organisational performances.

Design/methodology/approach: Survey data from the UK and Turkey were analysed using exploratory factor analyses, structural equation modelling and regression analysis.

Findings: The results show that quality management has a significant and positive impact on both primary and secondary performances; that Turkish and UK attitudes to quality management are similar; and that quality management is widely practised in manufacturing and service industries but has more statistical emphasis in the manufacturing sector. The main challenge for making quality management practice more effective lies in an appropriate balanced use of the different sorts of the tools and critical success factors.

Originality/value: This study takes a novel approach by: (i) exploring the relationship between primary operational and secondary organisational performances, (ii) using service and manufacturing data and (iii) making a cross-country comparison between the UK (a developed economy) and Turkey (a developing economy).

Limitations: Detailed contrast provided between only two countries.     

An optimal lotsizing determination in a two-echelon purchasing/production system

Multi-stage optimal lotsizing problems are extremely intractable and hard to solve. This paper discusses an economical lotsizing problem in a two-echelon purchasing/production system, where material losses caused by deterioration and failure in stock and production stages are taken into consideration. With the aid of the techniques of first and second derivatives, economic order quantity (EOQ) can be expressed by means of economic production quantity (EPQ). It is possible to derive cost reductions in the purchasing/production system. This system was applied using data from a DPE (Developing, Printing and Enlarging) factory and numerical experiments demonstrated that the total cost was reduced by 22-4%.     

The effects of new dimensions of psychological job demands and job control on active learning and occupational health

Abstract

Recent changes in job content may have led to changes in job demands and control, and earlier operationalizations of the demand concept may be too general (MT). The aim of this paper is to show how new dimensions of psychological job demands are related to two sets of outcome variables, employee health and active learning, and how these relationships are modified or interact with social support and types of job control. The study was carried out as a survey among employees of 13 electric companies in Norway, N=2435. Lisrel was used to assess the fit of the proposed models. Compared to the traditional demands control model, an extended version used in this study increased the explained variance on an average by 4% on various occupational health variables. It was found that various dimensions of demands were differentially related to the outcome variables. Skill discretion uniformly reduced the effect of the demands: for groups low in skill discretion there was a stronger relationship between demands and outcomes than for groups high in skill discretion. The interaction pattern for the remaining control and support variables was however more complicated and warrants further study. The practical implications are that employers should carefully consider the quality of work. Special attention should be given to the quantitative demands of the jobs, since there seems to be few moderators for the relationship between those demands and job stress and subjective health complaints.     

基于Lagrange松弛分解法的供应链生产-定位-路径集成问题优化

本文研究了集成生产批量、配送中心定位和车辆运输路径问题的一个复杂大系统,并建立了相应的数学模型。为了便于理解和求解这一大系统,将这一系统运用Lagrange松弛法分解成了生产、配送中心和定位-路径等三个相对独立的子系统。基于次梯度优化算法提出了一种优化协调机制,实现了系统的整体优化,并进行了数值实验分析。     

An examination of the ISO 9001:2000 standard and its influence on the integration of management systems

Abstract

Analysis of the literature and examination of the various models of integration and testing in the field, have revealed five key issues relating to management system integration. This paper examines the recently published ISO 9001 : 2000 quality management system standard to see how it addresses these issues, under the headings of compatibility, scope and organizational culture. The examination reveals that while compatibility with the ISO 14001 and OHSAS 18001 standards has been improved in some areas, a different approach and model of a management system has been used. The paper suggests that differences in the scope of the standards are also likely to give rise to different sub-cultures which will hinder integration, and scope and culture are more important than compatibility. This leads the authors to conclude that new models of integration should be based on an approach and definitions which can be used in any management system, as well as an integrated one. Models of an integrated management system should also emphasize the need for no significant differences in the scope of the integrated systems, and a strong culture which supports the main requirements of TQM.     

The Danish psychosocial work environment and symptoms of stress: The main,mediating and moderating role of sense of coherence

The aim of this cross-sectional study was to explore the main, mediating and moderating role of sense of coherence (SOC) on stress symptoms and on the association between perceived psychosocial work environment and stress symptoms. The sample includes 2053 Danish employees from 52 workplaces. Hierarchical regression models were applied for each measure of stress. The results strongly supported the presence of a main effect for SOC. People with high levels of SOC experienced fewer stress symptoms. A mediating effect of SOC was also supported. Thus, SOC in part explained the association between work environment and stress symptoms. In addition, some support for a moderating effect of SOC was found, suggesting that people with higher SOC coped more efficiently with work environmental strain that people with lower SOC. Taken together the regression models explained 11–32% of the variance in stress symptoms. The results suggest that measures of individual factors such as SOC should be included in analyses of the effects of work environmental factors on stress and well-being.     

Modelling end-of-life product recovery chains - a case study

European Union legislation, and existing national legislation of many European countries, mandates that manufacturers take back and recover their electronic and electrical equipment. If manufacturers are to comply with legislation, models need to be developed for these activities. Whilst infrastructural and technological deficits exist and must be addressed, so too must the organization of recovery, from a business perspective. In this paper, models of resource recovery are presented and a case study described.     

Integrating risk and performance management in quality management systems for the development of complex bespoke systems (CBSs)

Abstract

Risk and performance management are at the core of complex bespoke systems (CBSs). CBSs are developed to customer–specified requirements in terms of structure, functionality and conformance. This article examines how risk and performance management are integrated as essential systems in the successful development of projects across multi-organizational functions in complex bespoke system (CBS) organizations. The article argues for the development of a quality management system that consists of two sub-processes: quality control and quality development. Using three case studies from engineering companies, we provide evidence and insights of the way change control, quality development and quality performance are developed in innovating business solutions.     

Subjective health and its relationship with working time variables and job stressors: Sequence or general factor model?

Abstract

This study compares two theoretical models that make different assumptions about the structure of subjective health constructs and about the effects of job stressors and working time variables on health. The first model, the sequence model, is based on sequential models of the development of ill-health and posits that chronic fatigue and sleep problems mediate the effects of job stressors and working time variables on depression and somatic complaints. The second model, the general strain factor model, posits that specific health constructs (e.g. fatigue, depression, and somatic complaints) are reflections of a common general strain factor (i.e. detrimental job conditions increase the individual's sensitization to strain). In this way the study expands traditional models of stress-related effects on health. The analyses were carried out in a sample of 365 individuals in Germany. Although both models fitted the data, the general strain factor model was found to be superior. Furthermore, the effects of job stressors and working time on the health constructs fatigue and sleep quality were mediated by the general strain factor. Also, a negative relationship emerged between working time duration and general strain. It is suggested that the general strain model could be useful in future health psychology research.     

Pull system performance measures: a review of approaches for system design and control

Abstract

Research into the effect of three factors on four major system performance measures for pull system design and control are reviewed. The three factors are: (1) qualitative or quantitative nature of the approach, (2) traditional production control or pull system approach, and (3) systems/integrative characteristics of the approach for the performance measures. The four performance measures are: (I) throughput, (2) quality, (3) material Dow, and (4) flexibility. Articles were evaluated in terms of the performance measures and factors with several articles discussed in depth, Journals and other sources were chosen to be searched based on the source having published refereed articles related to pull system performance evaluation. Articles on quantitative pull systems are not well represented in the literature. Traditional approach methods     

The effects of component commonality in an infinite horizon inventory model

This paper studies the effects of component commonality in the context of an infinite horizon inventory model. Three models are proposed that are characterized by different degrees of component commonality. Assuming the three models all follow the same inventory policy, exact service level measures are derived and incorporated into cost optimization problems. With the infinite horizon assumption, potential setup cost reductions can be evaluated due to the inclusion of common components. The results indicate that, as expected, commonality incurs significant cost savings; what is new and unique is that setup cost may increase or decrease when commonality is present. In addition, when the behaviour of the optimal solutions is examined, it is found that some of the well-known properties suggested by the existing one-period models do not hold for this infinite horizon model.     

Business drivers not sector membership determine the most effective production planning and control; a novel approach to a perennial problem

This paper outlines research aimed at developing novel planning and scheduling reference models for industrial sectors where the MRPII paradigm is not appropriate. It outlines the process mapping approach adopted, the data capture method developed for the case study companies, the use of ARIS (Scheer's) enterprise modelling tool, and the first stages in the production of sector reference models.     

The disassembly line: balancing and modeling,by S.M. McGovern and S.M. Gupta

This note addresses a problem faced by an actual firm. The problem is to decide on the optimal level of product quality. In performing the economic analysis to determine product quality level, the firm considers revenue, production costs, and research and development costs. However, this note shows that ignoring inventory costs in the analysis will lead to suboptimal product quality levels. Also, including inventory costs in the analysis will lead to reduced production lot sizes. Numerical examples are used to illustrate the results of the model.     

The shortest path improvement problems under Hamming distance

In this paper, we consider the shortest path improvement problems under Hamming distance (SPIH), where the weights of edges can be modified only within given intervals. Two models are considered: the general SPIH problem and the SPIH problem with a single pair of required vertices. For the first problem, we show that it is strongly NP-hard. For the second problem, we show that even if the network is a chain network, it is still NP-hard.This paper is dedicated to Dr. Yong He.     

How smart cities transform operations models: a new research agenda for operations management in the digital economy

Abstract

The notion of smart cities is growing in prominence in the digital economy. The integration of urban infrastructures with information and communication technologies enables the development of new operations models. Digitised infrastructures offer opportunities for public and private organisations to design and deliver more customer-centric products or services, particularly for those that require geographical proximity with consumers in the online to offline (O2O) context. A framework is developed and used to analyse three case examples. These cases illustrate the emergence of new operations models and, demonstrate how smart cities are redefining the characteristics of operations models around their scalability, analytical output and connectivity. We also explore the feasibility, vulnerability and acceptability of each new operation. This paper contributes to our understanding of how smart cities can potentially transform operational models, and sets out a research agenda for operations management in smart cities in the digital economy.     

Simulation investigation of the stochastic behaviour of selected group technology similarity coefficients

Abstract

Abstract. The problem of restructuring manufacturing facilities into a cellular format has been addressed using a variety of approaches, including block-diagonalization of the machine-component matrix, mathematical programming formulations and cluster analyses. This paper addresses the problem of assessing whether or not the machine-component mix of a particular facility is amenable to cellular restructuring. The focus is cluster analytic; specifically a number of recently developed similarity coefficients are applied to problems generated via Monte Carlo simulation. The results show that, in a number of cases, the quality of the original block diagonal structure had a significant effect on the shape (in particular, skewncss and kurtosis) of the distribution of similarity coefficient values.