Research issues for multi-level lot sizing in MRP systems

What lot size model(s) to use in a Material Requirements Planning (MRP) system is an unresolved and often debated issue. The concept of dependent demand, the complex network defined by the product structure, the dynamics of an operating MRP-based system, and the subsequent use of the planned order release schedule by other company subsystems represent a totally new environment for making and managing lot size decisions.The purpose of this paper is to identify and briefly examine ten research issues related to lot sizing in a dependent demand product structure. These ten issues expand the solution space for lot sizing in an MRP-based system compared to a reorder point based system. Areas for further research are suggested.     

The element of surprise: the diverse impact of slightly alternative specifications of context on opinion formation in multi-level modeling

The rise of multi-level modeling in social sciences brings new challenges. Multi-level modeling, although used in a great variety of ways, aims at simultaneously assessing the impact of individual-level and context-level characteristics on a dependent variable that is measured at the individual level. However, comprehending how public opinion is affected by context and how people experience contextual changes is a challenge. Little scholarly attention has been paid to the way context is incorporated in these models. The current study compares the use of the same independent variable (GNI) measured in three different ways to predict attitudes regarding EU enlargement, trust in the EU, and European Unification in 25 EU countries, using data from the European Social Survey. We introduce an alternative way to measure change, taking a larger time span into consideration, and find that this is a good way to measure contextual surprise. Our findings show that the way a variable is measured greatly influences the size and even direction of the effect. Hence, it is crucial to assess both conceptually and methodologically the best way to measure context before one simply implements a variable and interprets empty results.     

基于逆向物流的MRP研究

文章探讨了逆向物流对传统的基于MRP的管理思想的影响，提出了适用于逆向物流环境下的MRP方法。     

Toward a better understanding of lead times in MRP systems

Lead times in MRP systems represent the planned amount of time allowed for orders to flow through the manufacturing system. Setting lead times is a major issue in the operation of MRP systems. There exists, however, very little documentation on just how lead times should be set.This study examines the effects lead times have on MRP-based manufacturing logistics systems. In particular, it examines the effects that lead times have on backlogs, order tardiness, and finished component inventories.A major finding is that changes to the level of planned lead times have both transient and steady state effects that may not necessarily operate in the same direction. A simple methodology is presented for setting the level of planned lead times when the criterion is finished component inventory.     

The cost of inflated planned lead times in MRP systems

Much of the current literature in the field of production and inventory control systems stresses the need to revise traditional forms of thinking regarding production processes, the role of inventories for work in process, and the need for reduced lead times or flow times. Group technology, manufacturing cells, and other means of incorporating repetitive manufacturing techniques into traditional job-shop settings constitute the leading edge in system development.Still, there is resistance to these dramatic changes, and traditional “business as usual” methods still predominate. This study attempts to illustrate graphically the cost justification associated with reduction in lead times which generally results from these new concepts. In most job shops today, lead times are much longer than they need to be due to inflation of lead time estimates. Actual lead times for the manufacture of fabricated and assembled products have been shown to be a direct consequence of the planning lead times used in the MRP planning process—a form of self-fulfilling prophesy.The research employs a simulation model of a factory using MRP as a planning tool in a multiproduct, multilevel production environment. Manufacturing costs constitute the dependent variable in the experiments, defined as the sum of material costs (including expedite premiums), direct labor costs (including overtime premiums), inventory carrying costs, and overhead costs. The independent variable being manipulated is the planned lead time offset used in the MRP planning process. Twenty values of planned lead time are evaluated ranging from a value that includes no slack time at all (pure assembly line) up to a value that allows 95% slack (queue) time which, unfortunately, is not uncommon in many job shops today. Stochastic variables in the model include customer demand and actual processing times—the sum of set-up and run times.The result of the study is a cost curve formed over the range of independent lead time variables that is constructed using nonlinear regression techniques. The conclusions from the resultant graph clearly indicate the cost consequences of long lead times, with exponential cost increases beyond the 80–90% queue time level. Total costs are 41% higher at the maximum lead time allowance compared to the minimum. Clearly, this study demonstrates the need for lead time reduction, either through downward adjustment of MRP planned lead times or by introducing new manufacturing concepts.     

Measuring the development impact of a proposed transportation system

This paper introduces a methodology of measuring economic development impact incident to a proposed transportation system and provides an empirical result of such estimation. As the methodology, a Multi-Regional Variable Input-Output (MRVIO) model is introduced, and as a case study, the proposed Coosa River Navigation project is discussed. The Coosa River project when completed is expected to reduce the cost of shipping commodities from origin to destination, and such reduction in shipping costs will stimulate the economy of the Coosa River Corridor, the Gulf-Coast Region, the Rest of Alabama, and the Remainder of the U.S. The empirical measurement was done in terms of industrial outputs, personal income, and employment of each of 31 industries in four regions in decennial years starting in 1990 and ending in 2039     

The paradox of paradoxical leadership: A multi-level conceptualization

Organizational systems are drenched in tensions and paradoxes. For a leader, addressing and engaging those tensions in constructive ways may unlock greater benefits for the followers, teams and the organization at large. A leader with a paradox mindset successfully deals with contradictory yet interdependent demands with their paradoxical thinking. While embracing these tensions leverages performance and innovation, experiencing these tensions may also lead to frustration and defensiveness, resulting in negative consequences. Considering the burgeoning importance of paradoxical leader behavior in paradox management and leadership literature, we conduct a systematic review of paradox theory of leadership. Based on the review we propose a multi-level conceptual model stating the dual effect of being a paradoxical leader. To do so, we unveil the individual and contextual factors influencing paradoxical leader behavior on the individual followers, teams and the organization. We present future research avenues and discuss theoretical and practical implications.     

A multi-level model for studying the context and impact of work–family policies and culture in organizations

The purpose of this paper was to provide an integrative multi-level framework that could help scholars study the impact of work–family policies on individual employees as well as assist practitioners in making informed decisions regarding the adoption, design, implementation, and allowance of these policies. This multi-level model illustrates the various macro- and mesolevel factors that may influence individual perceptions (i.e., equity perceptions, negotiation power, sense of entitlement) regarding work–family policies. By providing such a model, a common language may be developed for researchers from various disciplines studying this issue and better insight into the various linkages that are involved. Additionally, the framework can provide HR practitioners with a deeper understanding of the contextual factors that may influence the effectiveness of work–family policies in their organizations.     

The people side of MRP (materiel requirements planning)

A montage of ideas and concepts have been successfully used to train and motivate people to use MRP II systems more effectively. This is important today because many companies are striving to achieve World Class Manufacturing status. Closed loop Materiel Requirements Planning (MRP) systems are an integral part of the process of continuous improvement. Successfully using a formal management planning system, such as MRP II, is a fundamental stepping stone on the path toward World Class Excellence. Included in this article are techniques that companies use to reduce lead time, simplify bills of materiel, and improve schedule adherence. These and other steps all depend on the people who use the system. The focus will be on how companies use the MRP tool more effectively.     

MRP库存管理在冷藏箱调运中的应用

文中对MRP(Material Resources Planning)的原理进行了说明,结合某班轮公司的实际冷藏箱设备调运的流程,阐述MRP在调运冷藏箱中的运用,尽可能的降低库存,提高冷藏箱设备的周转率。     

蓄电池制造业的MRP实施关键点分析与研究

目的是探究一种适合蓄电池制造企业运行MRP的方法,并且推广成功的经验。只有把MRP作为反映业务数据及时性和准确性的重要考量标准,才能从根本上做好蓄电池制造业的信息化。其中使用了MRP相关的理论：安全库存、订货点法、产能计算等等。在成功实施了MRP之后,大幅提高了企业的运作能力,降低了成本。这些都说明,使用MRP来协调企业内部供应链,的确能给企业带来很大的效益,并从根本上提高企业的竞争力。     

The effects of marginal changes of ownership on multi-level objectives in corporate groups

Changes in the intra-group linkages affect the ownership of members of the group by their parents and can have different effects on the various objectives of the group. This paper shows how one can use the standard formula for calculating ownership in a group of companies to derive a linear approximation to the marginal changes in the group structure as the result of changes in intra-group linkages. These marginal effects can be used in linear multi-objective and/or decentralized planning systems in the group. An example is provided on some tax-planning effects of marginal changes of intra-group ownership.     

Identifying new dimensions of business incubation: A multi-level analysis of Karolinska Institute's incubation system

Relying on an in-depth case study of the incubator related to the Swedish medical university Karolinska Institute's (KI), this paper identifies new analytical and strategic dimensions of incubation. Departing from the current literature's prevalent focus on incubators as organizations performing a predefined set of activities for incubatees (facility renting, coaching, training and connecting), we perform a multilevel analysis embracing, next to the organizational and the project-specific levels, also the broader institutional and inter-organizational level. Our analysis relies on seven key components of incubation, namely its time, place, sources, resources, control/governance, activities/services and outcomes. Further, we view incubators as strategic actors engaged in value creation on a broader arena than the strict incubation context, even an international arena, where incubators' choices and interactions can be analyzed with the help of concepts from various streams in the business strategy literature. The specific strategic drivers of business incubation that we identify in the KI incubator's case are six: positioning in the value chain, risk taking/time perspective, revenue model, governance/control, internationalization, and cooperation/competition. The paper concludes with managerial implications urging incubators to take more of a strategic perspective rather than focussing only on the established components of their operations.     

华兴磷矿压风自救系统建设方案

文章针对华兴磷矿压风自救系统,设计一套独立的枝状管网,自地表+652 m主巷口压风机房内安装螺杆式空压机,铺设钢管至避灾硐室、采掘工作面。对压风自救系统最大用风量、空压机的选型、管路内径等进行了设计计算,对压风自救管网进行了校核。该设计方案已进行实施,对类似矿山的压风自救系统设计及建设具有借鉴意义。     

Employee involvement and group incentives in manufacturing companies: a multi-level analysis

The effects of employee involvement and group incentives on organisational commitment and turnover intention were examined using data from a survey of over 4,000 employees in 29 manufacturing companies. Using the mediated moderation model, we investigated the moderating role of capital intensity on the relationships between employee involvement and group incentives and these outcomes, and the mediating role of organisational commitment on the effects of employee involvement and group incentives on turnover intention. The findings revealed that employee involvement is more effective in capital-intensive companies than in labour-intensive companies, but group incentives are more effective in labour-intensive companies. The moderated effects on turnover intention were mediated through organisational commitment. Implications for company policies and future research are discussed.     

Estimation of a dynamic multi-level factor model with possible long-range dependence

A dynamic multi-level factor model with possible stochastic time trends is proposed. In the model, long-range dependence and short memory dynamics are allowed in global and local common factors as well as model innovations. Estimation of global and local common factors is performed on the prewhitened series, for which the prewhitening parameter is estimated semiparametrically from the cross-sectional and local average of the observable series. Employing canonical correlation analysis and a sequential least-squares algorithm on the prewhitened series, the resulting multi-level factor estimates have centered asymptotic normal distributions under certain rate conditions depending on the bandwidth and cross-section size. Asymptotic results for common components are also established. The selection of the number of global and local factors is discussed. The methodology is shown to lead to good small-sample performance via Monte Carlo simulations. The method is then applied to the Nord Pool electricity market for the analysis of price comovements among different regions within the power grid. The global factor is identified to be the system price, and fractional cointegration relationships are found between local prices and the system price, motivating a long-run equilibrium relationship. Two forecasting exercises are then discussed.     

单位工程施工进度计划中施工过程的合理安排

建筑工程中单位工程的施工进度计划是施工项目管理中较为重要的一个施工组织过程,它包括工艺参数、空间参数、时间参数等,但其中位居首要的是工艺参数中施工过程(在网络计划中称为工作)的合理安排。     

Entrepreneur subsidiary of business groups from emerging markets: a multi-level perspective

International Entrepreneurship and Management Journal - This study examines the effects of firm resources on entrepreneur subsidiaries of business groups. Resource-based theory is the foundation...     

HR flexibility and firm performance: analysis of a multi-level causal model

Human resource flexibility as a construct, how it develops, and its effect on firm performance have not received adequate attention in strategic HRM literature in spite of their obvious importance in today's dynamic competitive environment. Based on a study of 98 manufacturing and 103 service firms in India, this paper addresses these issues by developing and testing a multi-level model that attempts to explore the ‘black box’ of the interlinkages between the various components of HR flexibility and firm-level human, operational, and financial outcomes. The results suggest that a certain set of ambidextrous HR practices constitute a distinct dimension of HR flexibility, beyond the dimensions of flexibilities of skill, behaviour and HR practices as already identified in the existing literature. Evidences from both manufacturing and service sectors support the notion of HR value chain that suggests that HR system has a direct impact on firm-level HR outcomes which are most proximal, and its effects on increasingly more distal operational and financial outcomes are mediated by HR outcomes that it produces. Another important finding is that HR practices as a system have both direct and indirect (mediated by behavioural flexibility) effects on firm-level HR outcomes. Existence of significant direct effects highlights the important role that HR practices play as a structural mechanism in achieving superior firm performance.