711 resultados para closed-loop supply chain,


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Researchers and managers broadly agree that original equipment manufacturers (OEMs), which have opportunities to produce both new and remanufactured products, are better off by centrally controlling their manufacturing and remanufacturing activities. Thus, OEMs should not remanufacture used products until the remanufacturing cost is sufficiently low to overcome the negative impact of new product cannibalisation. In this paper, we present a contrasting view of the manufacturing–remanufacturing conflict: OEMs sometimes benefit from the decentralised control mode under which they ignore the internal cannibalisation rather than the remanufacturing option. We consider a decentralised closed-loop supply chain in which one OEM can purchase new components from one supplier to produce new products and collect used products from consumers to produce remanufactured products. The key feature of our model is that the OEM can select a centralised or decentralised control mode to manage its manufacturing and remanufacturing activities before the supplier prices the new component. In a steady state period setting, we analyse the players’ optimal decisions and compare the OEM's profits under centralised and decentralised control modes. Our analytic results reveal that the decentralised control within the OEM can outperform the centralised control when the cost structure of producing new and remanufactured products satisfies certain conditions. Finally, the key findings are distilled in a conceptual framework and its managerial implications are discussed.

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This paper reports on the development of elements of an e-supply chain management system for managing maintenance, repair and overhaul (MRO) relationships in the aerospace industry. A standard systems development methodology has been followed to produce a process model (i.e. the AMSCR model); an information model (i.e. business rules) and a computerised information management capability (i.e. automated optimisation). The proof of concept for this web-based MRO supply chain system has been established through the collaboration with a sample of the different types of supply chain members. The proven benefit is a reduction in the stock-holding costs for the whole supply chain whilst also minimising non-flying time of the aircraft that the supply chain supports. This type of system is now vital in an industry that has continuously decreasing profit margins, which in turn means pressure to reduce servicing times and increase the interval between maintenance actions.

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This PhD dissertation is framed in the emergent fields of Reverse Logistics and ClosedLoop Supply Chain (CLSC) management. This subarea of supply chain management has gained researchers and practitioners' attention over the last 15 years to become a fully recognized subdiscipline of the Operations Management field. More specifically, among all the activities that are included within the CLSC area, the focus of this dissertation is centered in direct reuse aspects. The main contribution of this dissertation to current knowledge is twofold. First, a framework for the so-called reuse CLSC is developed. This conceptual model is grounded in a set of six case studies conducted by the author in real industrial settings. The model has also been contrasted with existing literature and with academic and professional experts on the topic as well. The framework encompasses four building blocks. In the first block, a typology for reusable articles is put forward, distinguishing between Returnable Transport Items (RTI), Reusable Packaging Materials (RPM), and Reusable Products (RP). In the second block, the common characteristics that render reuse CLSC difficult to manage from a logistical standpoint are identified, namely: fleet shrinkage, significant investment and limited visibility. In the third block, the main problems arising in the management of reuse CLSC are analyzed, such as: (1) define fleet size dimension, (2) control cycle time and promote articles rotation, (3) control return rate and prevent shrinkage, (4) define purchase policies for new articles, (5) plan and control reconditioning activities, and (6) balance inventory between depots. Finally, in the fourth block some solutions to those issues are developed. Firstly, problems (2) and (3) are addressed through the comparative analysis of alternative strategies for controlling cycle time and return rate. Secondly, a methodology for calculating the required fleet size is elaborated (problem (1)). This methodology is valid for different configurations of the physical flows in the reuse CLSC. Likewise, some directions are pointed out for further development of a similar method for defining purchase policies for new articles (problem (4)). The second main contribution of this dissertation is embedded in the solutions part (block 4) of the conceptual framework and comprises a two-level decision problem integrating two mixed integer linear programming (MILP) models that have been formulated and solved to optimality using AIMMS as modeling language, CPLEX as solver and Excel spreadsheet for data introduction and output presentation. The results obtained are analyzed in order to measure in a client-supplier system the economic impact of two alternative control strategies (recovery policies) in the context of reuse. In addition, the models support decision-making regarding the selection of the appropriate recovery policy against the characteristics of demand pattern and the structure of the relevant costs in the system. The triangulation of methods used in this thesis has enabled to address the same research topic with different approaches and thus, the robustness of the results obtained is strengthened.

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We present a new model formulation for a multi-product lot-sizing problem with product returns and remanufacturing subject to a capacity constraint. The given external demand of the products has to be satisfied by remanufactured or newly produced goods. The objective is to determine a feasible production plan, which minimizes production, holding, and setup costs. As the LP relaxation of a model formulation based on the well-known CLSP leads to very poor lower bounds, we propose a column-generation approach to determine tighter bounds. The lower bound obtained by column generation can be easily transferred into a feasible solution by a truncated branch-and-bound approach using CPLEX. The results of an extensive numerical study show the high solution quality of the proposed solution approach.

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考虑一类同时具有再分销、再制造和再利用的闭环供应链在逆向物流流量不确定环境下的运作问题.采用具有已知概率的离散情景描述逆向物流流量的不确定性,利用基于情景分析的鲁棒线性优化方法建立该闭环供应链的多目标运作模型.设计了一个数值算例,其结果验证了运作策略的鲁棒性.在该算例基础上,分析了逆向物流流量的大小对闭环供应链系统运作性能的影响.

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Objective To assess the impact of a closed-loop electronic prescribing and automated dispensing system on the time spent providing a ward pharmacy service and the activities carried out. Setting Surgical ward, London teaching hospital. Method All data were collected two months pre- and one year post-intervention. First, the ward pharmacist recorded the time taken each day for four weeks. Second, an observational study was conducted over 10 weekdays, using two-dimensional work sampling, to identify the ward pharmacist's activities. Finally, medication orders were examined to identify pharmacists' endorsements that should have been, and were actually, made. Key findings Mean time to provide a weekday ward pharmacy service increased from 1 h 8 min to 1 h 38 min per day (P = 0.001; unpaired t-test). There were significant increases in time spent prescription monitoring, recommending changes in therapy/monitoring, giving advice or information, and non-productive time. There were decreases for supply, looking for charts and checking patients' own drugs. There was an increase in the amount of time spent with medical and pharmacy staff, and with 'self'. Seventy-eight per cent of patients' medication records could be assessed for endorsements pre- and 100% post-intervention. Endorsements were required for 390 (50%) of 787 medication orders pre-intervention and 190 (21%) of 897 afterwards (P < 0.0001; chi-square test). Endorsements were made for 214 (55%) of endorsement opportunities pre-intervention and 57 (30%) afterwards (P < 0.0001; chi-square test). Conclusion The intervention increased the overall time required to provide a ward pharmacy service and changed the types of activity undertaken. Contact time with medical and pharmacy staff increased. There was no significant change in time spent with patients. Fewer pharmacy endorsements were required post-intervention, but a lower percentage were actually made. The findings have important implications for the design, introduction and use of similar systems.

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Collaboration is acknowledged as a key to continued growth in the Australian construction industry. Government, as a major industry client, has an important role to play with respect to fostering collaboration and ensuring the global competitiveness of the industry. The paper draws upon data collected for the Construction 2020 study and aims to demonstrate that government can a) help to break down the adversarial situation that currently exists between clients, project managers and subcontractors; and b) allow the supply chain to collaborate more effectively in terms of satisfying the relational and financial needs of all parties. Government can also provide a clear set of guidelines (backed up by a functional dispute resolution system) that will promote confidence with respect to forging relationships. Thus, the paper will discuss the way in which public policy can be more closely aligned with actual industry needs in order to promote greater collaboration.

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The purpose of this paper is to gain a better understanding of the types of relational capabilities supply chain participants develop to enable ongoing supply chain innovation capacity building that produces improved business outcomes. This is exploratory research using qualitative data gathered by using five interviews, with the Australian road freight industry as the context. Two key relational capabilities and the improvement of four key business outcomes were identified as being present in the interaction of freight transport service providers with members of their supply chain. The data also demonstrates that by entering into competence building relationships with customers and suppliers firms can build capabilities that will increase their capacity for supply chain innovation. Even in short term arm’s length relationships firms can acquire improved skills behaviours and practices that enhance their operation effectiveness and the efficiency of the supply chain relationships.

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The supply chain in the construction industry is less well developed than in manufacturing. This project proposes to bring world class international business profile benchmarking to assist in the development of small and medium sized (SME) subcontractors. This approach has been widely used in Europe and has enabled significant sectoral supply chain development. The construction SME supply chain is a critical component in the delivery of all construction projects. Furthermore, it undermines the sustainability of the individual enterprise and puts construction projects and jobs at risk. Government procurement agencies view this as construction industry capacity building. In the developed and developing worlds, SME sector firms routinely make up over 95% of companies. The construction industry supply chain is dominated by such firms. Supply chain development and capacity building have been largely neglected in the construction sector, despite rhetoric about the importance of the SME sector to the economy This project seeks to investigate the potential to apply the International Business Profile Benchmarking instrument with the construction industry. The project recognises that there are many facets to the quest for continuous improvement in the construction industry and in wider workplace in general. This first interim report reviews the international literature relating to construction industry performance measurement and performance improvement. A summary of the findings follow. ‘Best value’ is dealt with in a separate interim report.

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Construction sector policy makers have the opportunity to create improvements and develop economic, social and environmental sustainability through supply chain economics. The idea of the supply chain concept to improve firm behaviour and industry performance is not new. However there has been limited application and little or no measurement to monitor successful implementation. Often purchasing policies have been developed with sound strategic procurement principles but even these have had limited penetration in to the processes and practices of infrastructure agencies. The research reported in this paper documents an action research study currently being undertaken in the Australian construction sector which aims to explore supply chain economic policy implementation for sectoral change by two government agencies. The theory which informs this study is the emerging area of construction supply chain economics. There are five stages to the project including; demand analysis, chain analysis, government agency organizational audit, supplier strategy and strategic alignment. The overall objective is towards the development of a Supplier Group Strategy Map for two public sector agencies. Two construction subsectors are examined in detail; construction and demolition waste and precast concrete. Both of these subsectors are critical to the economic and environmental sustainability performance of the construction sector and the community as a whole in the particular jurisdictions. The local and state government agencies who are at the core of the case studies rely individually on the performance of these sectors. The study is set within the context of a sound state purchasing policy that has however, had limited application by the two agencies. Partial results of the study are presented and early findings indicate that the standard risk versus expenditure procurement model does not capture the complexities of project, owner and government risk considerations. A new model is proposed in this paper, which incorporates the added dimension of time. The research results have numerous stakeholders; they will hold particular value for those interested in regional construction sector economics, government agencies who develop and implement policy and who have a large construction purchasing imprint and the players involved in the two subsectors. Even though this is a study in Australia it has widespread applicability as previous research indicates that procurement reform is of international significance and policy implementation is problematic.

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Purpose: In this research we examined, by means of case studies, the mechanisms by which relationships can be managed and by which communication and cooperation can be enhanced in sustainable supply chains. The research was predicated on the contention that the development of a sustainable supply chain depends, in part, on the transfer of knowledge and capabilities from the larger players in the supply chain. Design/Methodology/Approach: The research adopted a triangulated approach in which quantitative data were collected by questionnaire, interviews were conducted to explore and enrich the quantitative data and case studies were undertaken in order to illustrate and validate the findings. Handy‟s (1985) view of organisational culture, Allen & Meyer‟s (1990) concepts of organisational commitment and Van de Ven & Ferry‟s (1980) measures of organisational structuring have been combined into a model to test and explain how collaborative mechanisms can affect supply chain sustainability. Findings: It has been shown that the degree of match and mismatch between organisational culture and structure has an impact on staff‟s commitment level. A sustainable supply chain depends on convergence – that is the match between organisational structuring, organisation culture and organisation commitment. Research Limitations/implications: The study is a proof of concept and three case studies have been used to illustrate the nature of the model developed. Further testing and refinement of the model in practice should be the next step in this research. Practical implications: The concept of relationship management needs to filter down to all levels in the supply chain if participants are to retain commitment and buy-in to the relationship. A sustainable supply chain requires proactive relationship management and the development of an appropriate organisational culture, and trust. By legitimising individuals‟ expectations of the type of culture which is appropriate to their company and empowering employees to address mismatches that may occur a situation can be created whereby the collaborating organisations develop their competences symbiotically and so facilitate a sustainable supply chain. Originality/value: The culture/commitment/structure model developed from three separate strands of management thought has proved to be a powerful tool for analysing collaboration in supply chains and explaining how and why some supply chains are sustainable, and others are not.

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In this paper, a fixed-switching-frequency closed-loop modulation of a voltage-source inverter (VSI), upon the digital implementation of the modulation process, is analyzed and characterized. The sampling frequency of the digital processor is considered as an integer multiple of the modulation switching frequency. An expression for the determination of the modulation design parameter is developed for smooth modulation at a fixed switching frequency. The variation of the sampling frequency, switching frequency, and modulation index has been analyzed for the determination of the switching condition under closed loop. It is shown that the switching condition determined based on the continuous-time analysis of the closed-loop modulation will ensure smooth modulation upon the digital implementation of the modulation process. However, the stability properties need to be tested prior to digital implementation as they get deteriorated at smaller sampling frequencies. The closed-loop modulation index needs to be considered maximum while determining the design parameters for smooth modulation. In particular, a detailed analysis has been carried out by varying the control gain in the sliding-mode control of a two-level VSI. The proposed analysis of the closed-loop modulation of the VSI has been verified for the operation of a distribution static compensator. The theoretical results are validated experimentally on both single- and three-phase systems.