Lot sizing in case of defective items with investments to increase the speed of quality control

In many cases the quality of each item in a lot is checked. Speeding up the quality checking process increases the responsiveness of the system and saves cost. The percentage of defective items is a random variable and two models are proposed. In one of the models the system remains always at the same state, while in the other one after each order cycle, the state of the system may change, thus the percentage of defective items may be different in consecutive periods. In both cases the speed of the quality checking is a variable, and procedures are provided to find the optimal lot sizes and screening speed for general and specific investment cost functions. The characteristics of the two model settings will largely be different when the percentage of defective items is high. Among the important managerial insights gained is that a high unit backlogging cost, especially spurs the system to invest more intensively into improving the quality checking process.     

冷轧生产批量计划与调度问题模型及算法

对冷轧生产系统特点进行分析,将冷轧生产批量计划与调度问题抽象为多阶段、多品种带有中间库的批量计划与调度问题。针对该问题建立了数学模型,通过对库存成本和调整成本惩罚系数的控制可以协调库存水平和调整次数的关系。对所建立的模型,提出了基于二进制粒子群优化与局部搜索的混合求解算法。最后,通过对企业实际生产数据的计算和分析,验证了模型和算法的可行性和有效性。     

Leading Asian countries' HRD practices in the IT industry: a comparative study of South Korea and India

In order to examine the relationship between organizational change and organizational learning the authors conducted interviews with managers in 137 Estonian companies concerning changes implemented and learning outcomes. According to this survey, the relationship between organizational change and learning is seen differently in a country in transition.     

Evaluating the impact of lean practices on environmental performance: evidences from five manufacturing companies

Abstract

Previous evidence suggests that lean practices help organizations to enhance environmental performance. However, the impact of lean practices on the environment is still unclear. This study, therefore, aims to analyse the relationship between lean and environmental performance in two main stages: first, a review of the relevant literature was developed, followed by a multiple case study analysis conducted in five manufacturing companies. Onsite data were collected from the firms during a 5 years’ time span of research and developing semi-structured interviews. Findings indicate that the environmental performance of the companies analysed is generally enhanced in the long-term after the implementation of lean. Moreover, the results suggest that the environmental performance of the firms investigated is mainly improved by using JIT and TQM practices in a lean transformation context. The research findings provide further results remarking the possible negative impact of Kanban deliveries, 5S and TPM on various environmental performance indicators.     

Lean practices and their effect on performance: a literature review

This paper introduces a literature review of 83 studies dealing with the degree of adoption of lean manufacturing practices around the world, and the links between those practices and organisation performance. The results of this study revealed that lean practices application still occurs in a fragmented way, disregarding the systemic linkage that is essential to lean manufacturing. Forty-one articles have suggested a positive effect of lean practices in at least one operational, financial and/or environmental performance metric. Nevertheless, five studies indicated that some lean practices had a negative effect on operational or financial performance. High demand variability, a perceived result of long-term lean manufacturing implementation, a country/company’s organisational culture and the difficulty of traditional costing production systems to measure and compare investments and economic gains from adopting lean manufacturing over time are some of the reasons to explain that negative effect of lean practice on performance.     

Exploring the link between human resource practices and turnover in multi-brand companies: The role of brand units’ images

Using exploratory qualitative research undertaken in a multi-brand fashion company, this article investigates the role that brand units’ images play in the link between human resources management (HRM) practices and employee internal and external turnover. Our results suggest that the existence of imbalanced and differently attractive brand units’ images might weaken or remove the effectiveness of corporate HRM practices in keeping internal and external turnover rates low. This because employees may be interested in transferring to the most appealing brand(s) or, if not possible to do so, leaving the company. This article contributes to the debate regarding the use of HRM practices in multi-brand companies, especially in industries where both the brand and the product have a highly-symbolic content. Based on our conclusions, we recommend that brand units with less prestigious images compensate for their lower attractiveness with specific brand unit HRM practices to attract and retain their employees. Theoretical and policy implications of the findings are discussed.     

Setups and effective capacity: the impact of lot sizing techniques in an MRP environment

This study investigates how lot sizing techniques influence the profit performance, inventory level, and order lardiness of an assembly job shop controlled by MRP. Four single-level lot sizing techniques are compared by simulation analysis under two levels of master schedule instability and two levels of end item demand. A second analysis investigates the influence of a multilevel lot sizing technique, the generalized constrained-K (GCK) cost modification, on the four single-level techniques at low demand and low nervousness. The analyses reveal a previously unreported phenomenon. Given the same inventory costs, the single-level lot sizing techniques generate substantially different average batch sizes. The lot sizing techniques maintain the following order of increasing average batch size (and decreasing total setup time):

economic order quantity (EOQ)

period order quantity (POQ)

least total cost (LTC)

Silver-Meal heuristic (SML)

The causes for different average batch sizes among the lot sizing techniques are analysed and explained. Demand lumpiness, inherent in multilevel manufacturing systems controlled by MRP, is found to be a major factor. The number of setups each lot sizing technique generates is the primary determinant of profit performance, inventory level, and order tardiness. EOQ, a fixed order quantity technique, is less sensitive to nervousness than the discrete lot sizing techniques. EOQ_, however, generates the smallest average batch size, and, therefore, the most setups. Since setups consume capacity, EOQ, is more sensitive to higher demand. SML generates the largest average batch sizes, and is, therefore, less sensitive to increased demand. At low demand, the other lot sizing techniques perform better on all criteria. They generate smaller batches and, therefore, shorter actual lead times. The GCK cost modification increases the average batch size generated by each lot sizing technique. GCK improves the profit and customer service level of EOQ the lot sizing technique with the smallest batches. GCK causes the other lot sizing techniques to generate excessively large batches and, therefore, excessively long actual lead times.     

配额——交易机制下动态批量生产和减排投资策略研究

随着我国碳排放交易市场的建立和发展,在碳排放约束下逐步降低单位产出的碳排放水平成为企业生产经营管理中的中长期约束性目标。本文在一个多周期决策模型中研究了配额-交易机制下企业的最优动态批量生产、碳排放权交易和减排投资联合决策问题。生产商在整个决策周期期初决定是否进行减排投资以及投资规模,根据每个周期的生产计划决定减排设备的运行计划。根据节能减排技术的特点,本文假设生产商运行减排设备时不仅降低了产品的单位生产碳排放量,而且降低了产品的单位生产成本。本文基于广义Benders分解法对模型进行了最优性分析,得到了最优生产决策和最优减排投资决策的一些基本性质,并通过数值实验分析了碳排放配额和碳排放权价格对生产商总成本、总排放以及减排投资决策的影响。本文的数值实验分析结果发现:(1)当碳交易市场上的碳排放权充足时,减少碳排放配额或改变碳排放配额的分配方式并不能影响生产商的碳排放水平;(2)碳排放权价格是影响生产商的碳排放水平和减排投资规模的关键因素;(3)随着碳排放权价格的上升,即使拥有足够的碳排放配额,生产商仍会不断提高减排投资规模以获得减排收益。研究结果对碳排放交易体系下生产企业进行减排技术投资具有较强的管理启示。     

一类新型批处理机调度问题的理论分析

钢卷在冷轧生产中,为了改进其性能,需要在罩式炉进行退火,退火过程由加热、保温和降温三段组成,而这三段处理时间由于工艺上的要求不能归结为一个时间,这与传统批处理机调度有明显的差别.对新型批处理机的总加权完成时间最小化问题建立了非线性整数规划模型,开发了基于动态规划的启发式算法.通过理论分析,获得该算法的误差性能比为3.对于三段中的某一段板卷的处理时间相同的情况,证明了启发式算法的误差性能比是2,而且证明是紧界.对于三段中的某二段板卷的处理时间相同的情况,证明了启发式算法是最优算法.对启发式算法扩展到带有任意段的加工时间的一般情况进行了性能分析.     

Analytic evaluation of the expectation and variance of different performance measures of a schedule on a single machine under processing time variability

In this paper, we present closed-form expressions, wherever possible, or devise algorithms otherwise, to determine the expectation and variance of a given schedule on a single machine. We consider a variety of completion time and due date-based objectives. The randomness in the scheduling process is due to variable processing times with known means and variances of jobs and, in some cases, a known underlying processing time distribution. The results that we present in this paper can enable evaluation of a schedule in terms of both the expectation and variance of a performance measure considered, and thereby, aid in obtaining a stable schedule. Additionally, the expressions and algorithms that are presented, can be incorporated in existing scheduling algorithms in order to determine expectation-variance efficient schedules.     

Impact of strategic and operational risk management practices on firm performance: An empirical investigation

Increasingly, creating and delivering value through complex supply chain networks involves substantial risks. However, strategy development under business risk conditions is not well-understood. This cross-country research examines how, under conditions of supply chain network risk, firms develop effective risk management practices. Using a literature review and survey research of managers from global firms; we present a research model, and empirically test the hypothesized relationships. The results show that under conditions of uncertainty, management decision-making is more likely to be cautious until visible forms of risks emerge, and prudent response mechanisms are put in place. This study identifies the crucial role of supply chain exploration and exploitation practices, and their influence in development of network risk management practices, leading to competitive financial outcomes.     

An evaluation of flow-shop scheduling algorithms for makespan reduction in a stochastic environment

This paper addresses the problem of makespan reduction and improvement in related performance measures in the stochastic flow shop. The experimental design addresses the issues of the problem size in terms of the number of jobs and machines, the bottleneck location within the production facility, and the processing time distribution and sensitivity to variance. In other words, many of the assumptions that are typically made in the published literature are violated in favour of a more realistic production basis. Experiments are performed via simulation to examine the performance of several well known flow-shop scheduling algorithms and one new algorithm in this challenging environment. The authors conclude that distributional effects and bottleneck considerations can play a role in the performance of the various algorithms considered. This paper further indicates that the problem size also tends to drive the effectiveness of the scheduling strategies examined, and presents information regarding interesting interaction effects between the problem size and the other elements of experimental concern.     

Environmental practices and firm performance in emerging markets: the mediating role of product quality

Environmental practices have not received as much research attention in emerging market contexts as traditional topics like quality. However, the importance of environmental practices for a firm’s production strategy has been increasing at an unprecedented level across the globe. Our research objective is, therefore, to investigate the interplay between environmental practices and quality in the pursuit of firm performance. Relying on 492 responses from Turkish manufacturers to test our hypotheses, we show that environmental practices directly improve the quality of products over and above the effect of quality management practices in emerging markets. Product quality, in turn, is important for increasing firm performance, acting as a mediator for the positive effects of environmental practices on performance. Thus, we reveal that product quality functions as an instrumental conduit between environmental practices and firm performance in emerging markets like Turkey where stakeholder pressures are weak, and regulations are often not properly enforced.     

Internal audit function quality and financial reporting: results of a survey on German listed companies

Most prior studies on internal audit function (IAF) quality and financial reporting have focused on the US setting and have found a positive association between IAF quality proxies and both financial reporting quality and audit efficiency. In this study, we apply the German setting that is characterized by a two-tier board system of corporate governance and different prerequisites for the serving-two-masters problem. This might weaken the IAF’s ability to monitor financial reporting-related processes. To analyze this, we use survey data to measure IAF quality in the German setting and run multiple regressions to examine the association of several IAF quality characteristics and a self-developed IAF quality score with financial reporting quality and audit efficiency. The results show that also in a two-tier system, a high-quality IAF is able to contribute to both financial reporting quality and audit efficiency. Our findings support the notion that the IAF serves as an essential element of effective corporate governance and plays an important role in financial reporting. Moreover, as a practical implication of interest to regulators and managers, we identify that the external certification of the IAF and internal audit-related certifications of IAF employees may contribute to higher financial reporting quality and lower audit fees.     

大规模定制模式下供应链计划调度优化分析

大规模定制模式下供应链生产计划调度问题是一个典型的随机需求与随机资源约束的 多目标动态优化问题. 在对该问题特征翔实描述,分析所总结的理论研究成果基础上,提出了 完整的随机多目标动态优化数学模型. 通过实例简要分析了优化目标的成熟性及模型的可行 性. 最后,指出了较为重要的动态优化调度过程的实现,并进行了实践应用过程的验证与说明     

Offshoring practices of Danish and Swedish SMEs: effects on operations configuration

This paper examines how small and medium enterprises (SMEs) configure their operations on the global scale and how this affects their home bases in terms of operations requirements and priorities. In order to relate SMEs’ offshoring initiatives with their operations configuration attributes, we draw on the operations networks literature and survey responses from 675 Danish and 410 Swedish companies. On the basis of the survey results, we find that although the SMEs are less experienced and less advanced in their offshoring ventures than large companies, they are building dispersed operations networks. Although still in their infancy, these networks are, as expected, creating new demands for their home bases in terms of demands for formalisation of work processes, systems development and managerial capability related to orchestrating operations across national borders, but more fundamentally, it also challenges the strategic foundations of the home base. Based on these observations, we discuss future global operations management challenges, practices and priorities of SMEs.