Optimal stock picking decisions in automatic storage and retrieval systems

Recent technological developments have brought on a revolution in the design and operation of warehousing systems. Automatic storage/retrieval systems (AS/RS) driven by embedded computers are becoming increasingly more prevalent. The increased use of AS/RS is creating the need for computerized control algorithms to support the scheduling and logistical decisions in such automated warehouses. In this research we explore the problem of deciding which storage locations to retrieve when confronted with a set of discrete orders for a given inventory item. In addition to the normal costs associated with the retrieval decision, this support introduces the cost of a location “breakdown” as a complicating factor in the retrieval decision. The problem is formulated as a type of mixed zero-one integer program. Computational results from a sample set of problems are reported.     

Evaluation of a class-based storage scheduling technique applied to dual-shuttle automated storage and retrieval systems

Research to improve the performance of automated storage and retrieval systems has concentrated on developing more effective system designs or scheduling control programs to reduce the time a shuttle spends travelling in a rack. Sarker et al. (1991) showed that a dual-shuttle AS/RS operating under a nearest-neighbour scheduling model would significantly improve system throughput performance over a single-load shuttle system. The study was limited in that it only considered dual-shuttle improvements under the nearest-neighbour model. This research exploits the benefits of a dual-shuttle system by integrating the technology with a more effective scheduling technique, the class-based storage model, for reducing the shuttle travel time. The dual-shuttle, class-based storage model produced a significant reduction in shuttle travel time and thus higher throughput results over the dual-shuttle, nearest-neighbour model. This study further supports the premise that a dual-capacity shuttle is an effective way of improving the productivity of an automated storage and retrieval system.     

自动化立体仓库中的储位分配及存取路径优化

储位分配和存取作业路径优化是仓储管理中的两个重要决策问题。本文研究如何在自动化立体仓库中对这两个问题进行同时决策。提出了一个混合整数规划模型对该问题进行优化建模,设计开发了一个基于有向连接图的两阶段优化算法对问题求初始解,并利用禁忌搜索算法对所求得的解进行改进。算法第一阶段解决储位分配问题,在此基础上第二阶段利用Hungarian算法对堆垛机的存取作业路径优化问题进行求解。最后利用实例对算法效率和精度进行分析评价,计算结果验证了算法的有效性。     

自动化立体仓库中出入库任务顺序与出库位置选择集成优化研究

具有多个出口的自动化立体仓库系统是一种将存储和分拣相结合的新型仓储技术,其最典型的特征是在货架底层有很多个出库位置以供取货人员分拣。研究此系统中出入库任务排序与出口选择的集成优化问题,以最小化堆垛机完成所有任务的移动距离为目标,将此问题转化为一个混合整数规划模型。根据问题的特点设计了两阶段启发式算法求解此问题,数值结果表明设计的算法能在较短时间内给出近似最优解,同时与企业常用的先到先服务方法相比,该算法可以缩短超过20%的移动距离。     

Job-shop scheduling-joint consideration of production,transport, and storage/retrieval systems

This paper proposes a new problem by integrating the job shop scheduling, the part feeding, and the automated storage and retrieval problems. These three problems are intertwined and the performance of each of these problems influences and is influenced by the performance of the other problems. We consider a manufacturing environment composed of a set of machines (production system) connected by a transport system and a storage/retrieval system. Jobs are retrieved from storage and delivered to a load/unload area (LU) by the automated storage retrieval system. Then they are transported to and between the machines where their operations are processed on by the transport system. Once all operations of a job are processed, the job is taken back to the LU and then returned to the storage cell. We propose a mixed-integer linear programming (MILP) model that can be solved to optimality for small-sized instances. We also propose a hybrid simulated annealing (HSA) algorithm to find good quality solutions for larger instances. The HSA incorporates a late acceptance hill-climbing algorithm and a multistart strategy to promote both intensification and exploration while decreasing computational requirements. To compute the optimality gap of the HSA solutions, we derive a very fast lower bounding procedure. Computational experiments are conducted on two sets of instances that we also propose. The computational results show the effectiveness of the MILP on small-sized instances as well as the effectiveness, efficiency, and robustness of the HSA on medium and large-sized instances. Furthermore, the computational experiments clearly shown that importance of optimizing the three problems simultaneous. Finally, the importance and relevance of including the storage/retrieval activities are empirically demonstrated as ignoring them leads to wrong and misleading results.

     

中国包容性绿色增长绩效评价体系的构建及应用

在总结经典文献和权威机构观点的基础上，从包容性绿色增长的理论内涵出发，尝试运用指标海选、定量分析和定性分析相结合的方法构建包含经济发展、社会机会公平、绿色生产消费、生态环境保护四大维度的包容性绿色增长绩效评价体系，并利用熵权法评价2000-2015年中国包容性绿色增长绩效及各维度。研究表明：中国包容性绿色增长绩效呈现显著升高的态势，符合国家的发展大势，具体可以分为初始阶段、企稳回升阶段和显著上升阶段，这归因于四大维度的协同作用；经济发展和社会机会公平维度的协调发展对中国包容性绿色增长绩效的升高具有显著贡献；而绿色生产消费和生态环境保护维度的波动上升总体上促进了中国包容性绿色增长绩效的提高。     

Complementarity between CSR dimensions and innovation: behaviour,objective or both?

This research assesses the impact of combining the economic, social and environmental dimensions of the corporate social responsibility (CSR) on firm innovation. In particular, we test whether the three dimensions of CSR (economic, social and environmental) are interrelated (behavioural complementarity), and whether their joined adoption will generate super-additive innovation performance effects (objective complementarity). To that end, we draw on the Community Innovation Survey (CIS) for Spain during the period 2009–2014. The analyses confirm behavioural complementarity among the three dimensions of CSR, as well as differences on objective complementarities depending on the innovation performance measure considered. In particular, the combination of the social dimension with any of the two others (economic and environmental) is the one that gives the best results in terms of radical innovation, whereas both the economic and environmental dimensions of CSR seem to be fundamental to foster incremental innovation. These results have implications for academics and practitioners, since they provide useful guidelines for the design of CSR in order to enhance firm innovation.     

Sustainable storage assignment and dwell-point policies for automated storage and retrieval systems

Picking time reduction has been the traditional perspective for warehouse optimisation. When sustainability is considered, optimisation of warehouse operations should be read in terms of energy efficiency other than response time. Each location in the rack of an automated storage and retrieval system is associated with the value of energy consumed by the crane to reach it. Since picking performance strictly depends on storage location assignments, the time-based full turnover strategy is compared to the energy-based one. Three models of energy consumption are considered for traditional and new-generation cranes. Assignments are then compared in terms of dedicated zone shapes, time and energy performances within a given time horizon. Different shapes of the rack and product ABC curves are analysed. Dwell-point policies are also analysed from the new sustainable perspective, adding energy-saving performance to the traditional picking time reduction.     

Online Corporate Environmental Reporting: Improvements and Innovation to Enhance Stakeholder Value

Corporate environmental/sustainability reporting is a growing trend among top global companies. In many cases, these reports have been made available online. Although the internet has provided reporting companies with a new channel to convey environmental information to the public, effective use of this media requires careful thought.Usability is a primary consideration that is not being addressed in many online corporate environmental/sustainability reports (CER). Often, these reports are difficult for users to locate from the corporate homepage, the search option does not render the correct page, some are only available in PDF format, and navigation within the report can be difficult. Current online reporting can also be ineffective if the technology is not oriented towards a framework of maximizing stakeholder value.If approached properly, internet technology allows for interactivity between a company and its stakeholders, provision of real-time updates of information and specialized information retrieval depending on the needs of users. This paper focuses on the current state of online CER reporting and suggests methods and practices for enhancing stakeholder value.     

Eco-efficient supply chain networks: development of a design framework and application to a real case study

This paper presents a supply chain network design framework that is based on multi-objective mathematical programming and that can identify ‘eco-efficient’ configuration alternatives that are both efficient and ecologically sound. This work is original in that it encompasses the environmental impact of both transportation and warehousing activities. We apply the proposed framework to a real-life case study (i.e. Lindt & Sprüngli) for the distribution of chocolate products. The results show that cost-driven network optimisation may lead to beneficial effects for the environment and that a minor increase in distribution costs can be offset by a major improvement in environmental performance. This paper contributes to the body of knowledge on eco-efficient supply chain design and closes the missing link between model-based methods and empirical applied research. It also generates insights into the growing debate on the trade-off between the economic and environmental performance of supply chains, supporting organisations in the eco-efficient configuration of their supply chains.     

Storing Fresh Produce for Fast Retrieval in an Automated Compact Cross‐Dock System

We study temporary storage of fresh produce in a cross‐dock center. In order to minimize cooling cost, compact storage systems are used. A major disadvantage of these systems is that additional retrieval time is needed, caused by necessary reshuffles due to the improper storage sequence of unit loads. In practice therefore, a dedicated storage policy is used in which every storage lane in the system accommodates only one product. However, this policy does not use the planned arrival time information of the outbound trucks. To exploit this information, this study proposes a mathematical model for a shared storage policy that minimizes total retrieval time. The policy allows different products to share the same lane. In order to solve real‐sized problems, an effective and efficient heuristic is proposed, based on a greedy construction and an improvement part, which provides near optimal solutions. The gaps between the results of the heuristic and the lower bound are mostly less than 1%. The resulting shared storage policy is generally robust against disturbances in arrival or departure times. We compare our shared storage heuristic with dedicated storage to determine which policy performs best under which circumstances. For most practical cases, shared storage appears to outperform dedicated storage, with a shorter response time and better storage lane utilization.     

一种基于网状版本模型的复杂产品设计数据管理方法研究

产品设计过程中产生的大量数据是历史设计知识的重要来源.在对象划分、关系定义及数据存储模式设计的基础上,建立了"对象过程版本库+项目版本库"的数据管理架构,提出网状关系模型实现对对象版本和项目版本的综合管理,为不同历史时期的设计知识检索提供支持.并讨论了版本控制的几种关键技术.最后以航空发动机涡轮设计数据管理为例验证了该方法的有效性.实际应用证明,这种包含了设计数据演进过程的网状版本管理方式能解决当前数据管理的难题,为工程设计提供强有力的帮助,提高设计效率和质量.     

顾客有限“碳行为”偏好对选址-路径-库存联合优化的影响

针对考虑顾客有限“碳行为”偏好的选址-路径-库存联合优化问题,引入环保度系数作为碳排放量的特征向量,在低碳产品加价率存在的情况下,刻画了顾客有限“碳行为”偏好和市场逆需求系数对低碳产品需求量的影响,构建了选址-路径-库存系统中考虑有“碳行为”偏好的联合优化模型,并分析了顾客行为偏好对企业收益的影响。使用基于NNC的多目标求解方法,对考虑成本和碳排放的双目标问题进行处理并得到一组Pareto解集,数值实验证明了产品环保度、顾客有限“碳行为”偏好对企业运作方案和收益水平的影响。     

Nuclear Waste Management under Approaching Disaster: A Comparison of Decommissioning Strategies for the German Repository Asse II

This article compares different strategies for handling low‐ and medium‐level nuclear waste buried in a retired potassium mine in Germany (Asse II) that faces significant risk of uncontrollable brine intrusion and, hence, long‐term groundwater contamination. We survey the policy process that has resulted in the identification of three possible so‐called decommissioning options: complete backfilling, relocation of the waste to deeper levels in the mine, and retrieval. The selection of a decommissioning strategy must compare expected investment costs with expected social damage costs (economic, environmental, and health damage costs) caused by flooding and subsequent groundwater contamination. We apply a cost minimization approach that accounts for the uncertainty regarding the stability of the rock formation and the risk of an uncontrollable brine intrusion. Since economic and health impacts stretch out into the far future, we examine the impact of different discounting methods and rates. Due to parameter uncertainty, we conduct a sensitivity analysis concerning key assumptions. We find that retrieval, the currently preferred option by policymakers, has the lowest expected social damage costs for low discount rates. However, this advantage is overcompensated by higher expected investment costs. Considering all costs, backfilling is the best option for all discounting scenarios considered.     

基于时间的自动化立体仓库货位优化模型研究

内外环境变化时进行自动化立体仓库货位优化十分必要与重要。本文构建了以医药为例,考虑自动化立体仓库货物移动前后的相关数据能有效记录,以及货物出入库效率高,相似货物摆放一起,货物移动距离最短三个因素的基于时间的货位优化多目标模型,通过对算例采取遗传算法的结果显示：本文方法能有效实现自动化立体仓库货位优化,优化前后数据记录能有效进入仓储自动管理环节,是降低仓储管理成本、提高仓储管理效率与效益的有效方法与途径。     

电力消耗、经济增长与CO2排放量的实证分析——基于中国面板数据

本文运用计量经济学方法,如协整检验和格兰杰因果关系检验、脉冲响应函数等,深入研究了中国在1990-2013期间电力消耗、经济增长与二氧化碳排放量之间的关系。研究结果表明,电力消耗、经济增长与二氧化碳排放量之间存在协整关系,即长期均衡关系;经济增长与电力消耗之间存在双向的格兰杰因果关系,但不存在电力消耗与二氧化碳排放量,经济增长与二氧化碳排放量之间的格兰杰因果关系。与此同时,VAR模型估计结果显示,滞后一期的电力消耗对当期经济增长和二氧化碳排放量产生正向的作用,滞后一期的电力消耗促进当期的电力消耗,同时也促进当期经济增长和CO₂排放量增加;经济增长的滞后期对当期电力消耗和二氧化碳排放量产生负向的作用,而二氧化碳排放量的滞后期对当期经济增长没有显著影响。基于此,实证分析结果表明经济增长在短期内会造成二氧化碳排放量的增加,但正如环境库兹涅茨曲线描述的结论一样,从长期来看,经济增长促进了技术的进步和能源效率的提高,进而导致二氧化碳排放量的减少。该发现对于中国发展低碳经济和电力部门能源政策的制定都将有着重要现实意义。     

产能过剩偏向性与环境污染——基于中介效应的检验

如何从矫正制度性缺失来破解我国环境污染较难根治且易于反复之谜是我国当前亟待解决的问题之一。本文尝试从行业和企业两个维度,基于中介效应模型,以产能过剩偏向性为视角来廓清中国环境污染治理之殇,并以顶层设计为抓手来明晰环境污染治理之道。研究发现:(1)产能过剩与环境污染的关系依赖于产能过剩在行业和企业维度上的偏向性,产能过剩是影响我国环境污染的重要原因,不同维度产能过剩的偏向性能够对环境污染产生较为显著的影响;(2)产能过剩偏向于污染密集型行业主要通过能源结构锁定效应和产业结构固化效应而加剧环境污染,产能过剩偏向于国有企业主要通过技术结构低端化效应而影响环境污染;(3)产能过剩偏向性作用于环境污染的路径不仅存在显著的市场化程度的调节效应,还存在着严重的区域异质性、水平异质性和阶段异质性。文章为推进制度变革、优化存量产能和有效治理环境污染提供了理论支持。     

12 HRM and Distributed Work

Abstract

The phenomenon of managing work that is distributed over geographical distance is not new but is increasing in both frequency and intentionality as a function of globalization and knowledge-centric strategies. I review the literature on geographically distributed work, both that which highlights liabilities of loss of proximity and more recent research that emphasizes “virtual teams” as an intentional organizing device. I explore the adaptations, remedies, and countervailing strategies deployed to support such teams, contrasting those that minimize distance with those that increase individual and group capacity for coping with distance. I also emphasize that other dimensions of distance—cultural, administrative, and economic—affect the organization of work, the experiences of those doing the work, and individual and organizational outcomes. Here I highlight the “blended workforce” in which standard (traditional employees) and nonstandard (temporary and contract) workers are organized to accomplish interdependent tasks—and again contrast problems of distance with emergent adaptations. Finally, I explore the implications for human resource management (HRM), first considering which HR systems are best suited to work distributed over different types of distance, and then reviewing literature on specific HR practices—selection, training, task/job design, compensation, and performance appraisal. I close by arguing that HRM research must reach beyond its past focus on managing employees within a single firm over a prolonged career under collocated conditions. As the world generates countless new distance-related phenomena, our research must tackle the challenges of managing both standard and non-standard workers engaged in interdependent tasks of limited duration across multiple employers/clients and involving multiple dimensions of distance.     

A Tiered Framework for Risk‐Relevant Characterization and Ranking of Chemical Exposures: Applications to the National Children's Study (NCS)

A challenge for large‐scale environmental health investigations such as the National Children's Study (NCS), is characterizing exposures to multiple, co‐occurring chemical agents with varying spatiotemporal concentrations and consequences modulated by biochemical, physiological, behavioral, socioeconomic, and environmental factors. Such investigations can benefit from systematic retrieval, analysis, and integration of diverse extant information on both contaminant patterns and exposure‐relevant factors. This requires development, evaluation, and deployment of informatics methods that support flexible access and analysis of multiattribute data across multiple spatiotemporal scales. A new “Tiered Exposure Ranking” (TiER) framework, developed to support various aspects of risk‐relevant exposure characterization, is described here, with examples demonstrating its application to the NCS. TiER utilizes advances in informatics computational methods, extant database content and availability, and integrative environmental/exposure/biological modeling to support both “discovery‐driven” and “hypothesis‐driven” analyses. “Tier 1” applications focus on “exposomic” pattern recognition for extracting information from multidimensional data sets, whereas second and higher tier applications utilize mechanistic models to develop risk‐relevant exposure metrics for populations and individuals. In this article, “tier 1” applications of TiER explore identification of potentially causative associations among risk factors, for prioritizing further studies, by considering publicly available demographic/socioeconomic, behavioral, and environmental data in relation to two health endpoints (preterm birth and low birth weight). A “tier 2” application develops estimates of pollutant mixture inhalation exposure indices for NCS counties, formulated to support risk characterization for these endpoints. Applications of TiER demonstrate the feasibility of developing risk‐relevant exposure characterizations for pollutants using extant environmental and demographic/socioeconomic data.     

On the impact of collaborative strategies for goods delivery in city logistics

Abstract

City logistics refers to the process of total optimisation of the logistics and transport activities in urban areas while considering economic, environmental, social and safety aspects. This paper considers a collaborative scenario for the urban goods transport planning and management as a way to reduce transport costs, congestion and environmental impact of this activity. An approach from the Operations Management field, using mathematical modelling, for tactical and operational decision-making is proposed to discuss and compare both collaborative and non-collaborative scenarios. This approach is validated using real data taken from the city of Bogotá, Colombia. Results put in evidence the quantitative benefits that can be achieved when collaborative logistics operations are implemented, represented in both transportation costs and environmental impacts. Although these results might not be surprising (like in the field of supply chain management), the contribution of this paper is centred in the fact that the impacts of collaboration in city logistics have not yet been quantified until now. This allows an ‘ex ante’ evaluation of the benefits of collaborative goods transport in cities.