Developing a fuzzy linear programming model for locating recovery facility in a closed loop supply chain

In this research a closed loop supply chain is designed which incorporates reverse logistics and forward logistic system simultaneously. In the design of reverse logistic system, recovery options are embedded in traditional supply chain for treating returned products. The recovery system includes collection centres, remanufacturing plants and disposal centres. Since the product return is supply driven, there is an uncertainty about it. In the proposed configuration for closed loop supply chain, the optimised configuration for supply chain in terms of locating recovery plants is developed. Accordingly, a fuzzy mixed integer linear programming model develops to deal with the uncertainty of returning products by customers. A general-purpose solver (LINGO 8.0) and a Meta heuristic approach (genetics algorithm) are implemented to solve the proposed model. The answers are compared by defining indexes and then the optimal answer, configuration and variables are identified. This solution will suggest a new design of supply chain network in which waste of materials is minimised and the new raw materials are necessary only when the used products may not be recovered by recovery options.     

Management of two competitive closed-loop supply chains

The two competitive closed-loop supply chains under our study include three members: two manufacturers and one retailer. In this paper, we focus on the management of the wholesale prices, the retail prices and the collecting prices for the two competitive closed-loop supply chains. On the assumption that the return rate of the used-products is an increasing function of the collecting price, we obtain the optimal wholesale prices, the optimal retail prices and the optimal collecting prices based on the following models: Model MMC (two manufacturers for collecting), Model MRC (manufacturer one and retailer for collecting) and Model RRC (retailer for collecting). Furthermore, by comparing the optimal results, we find that the retailer for collecting is the best channel for the two competitive closed-loop supply chains if the two manufacturers would like to transfer all of their cost savings from remanufacturing to the retailer. At the end, we illustrate a numerical example to analyse the impacts of the market share ratio and the substitute ratio of the two products on the optimal results.     

System dynamics modeling for municipal water demand estimation in an urban region under uncertain economic impacts

Accurate prediction of municipal water demand is critically important to water utilities in fast-growing urban regions for drinking water system planning, design, and water utility asset management. Achieving the desired prediction accuracy is challenging, however, because the forecasting model must simultaneously consider a variety of factors associated with climate changes, economic development, population growth and migration, and even consumer behavioral patterns. Traditional forecasting models such as multivariate regression and time series analysis, as well as advanced modeling techniques (e.g., expert systems and artificial neural networks), are often applied for either short- or long-term water demand projections, yet few can adequately manage the dynamics of a water supply system because of the limitations in modeling structures. Potential challenges also arise from a lack of long and continuous historical records of water demand and its dependent variables. The objectives of this study were to (1) thoroughly review water demand forecasting models over the past five decades, and (2) propose a new system dynamics model to reflect the intrinsic relationship between water demand and macroeconomic environment using out-of-sample estimation for long-term municipal water demand forecasts in a fast-growing urban region. This system dynamics model is based on a coupled modeling structure that takes into account the interactions among economic and social dimensions, offering a realistic platform for practical use. Practical implementation of this water demand forecasting tool was assessed by using a case study under the most recent alternate fluctuations of economic boom and downturn environments.     

Determining advanced recycling fees and subsidies in "E-scrap" reverse supply chains

Primarily due to environmental concerns and legislative mandates, the disposition of end-of-life (EOL) electronics products has attracted much attention. Advanced recycling fees (ARFs) and government subsidies may play important roles in encouraging or curtailing the flows of recycled items. We present a Stackelberg-type model to determine ARFs and socially optimal subsidy fees in decentralized reverse supply chains where each entity independently acts according to its own interests. The model consists of one leader (the government) and two followers (a group of manufacturers, importers, and sellers (MISs) and a group of recyclers). To maximize social welfare, the government determines the ARFs paid by MIS and the subsidy fees for recyclers when MIS sells new products and recyclers process EOL products. We find that MIS and recyclers behave at the equilibrium status by choosing optimal selling quantity in the market and optimal reward money for customers bringing EOL products to recyclers. Under this approach the two fees achieve the maximum of social welfare at the equilibrium status, while both MIS and recyclers gain the maximum of profits. For comparative purposes, we also develop a conceptual model describing the current practice by which ARFs and the subsidy fees are determined on the basis of fund balance between revenues and costs along with recycling operations. We conclude that our results outperform current practice.     

Performance improvement potential of sensor embedded products in environmental supply chains

Environmental supply chain is a desirable alternative to traditional supply chain due to new and stricter environmental regulations by local governments and increasing consumer awareness towards environmental issues. The two most common types of environmental supply chains are reverse supply chains and closed-loop supply chains. In reverse or closed-loop supply chains, collected used products are subjected to one of four recovery options, viz., reuse, recycling, remanufacturing or disposal. Regardless of the chosen recovery option, all products are disassembled up to some level. However, there is a high level of uncertainty associated with the disassembly yield due to non-functional and/or missing components. Sensor embedded products (SEPs) is a viable approach to cope with this uncertainty since they involve sensors which can detect non-functional and/or missing components prior to disassembly. This study presents a quantitative assessment of the impact of SEPs on the various performance measures of a kanban-controlled disassembly line. First, separate design of experiments studies based on Orthogonal Arrays are carried out for conventional products and SEPs. Then, the results of paired t-tests comparing the two cases based on different performance measures are presented.     

Optimal production and pricing policy for a closed loop system

A closed loop system is investigated, in which the manufacturer has two channels to satisfy the demand: manufacturing brand-new products and remanufacturing returns into as-new products. Remanufactured products have no difference from brand-new products and can be sold in the same market at the same price. The demand is uncertain and sensitive to the selling price, while the return is also stochastic and sensitive to the acquisition price of used products. A mathematical model is developed to maximize the overall profit of the system by simultaneously determining the selling price, the production quantities for brand-new products and remanufactured products, and the acquisition price of used products. Some properties of the problem are analyzed, based on which a solution procedure is presented. Through a numerical example, the impacts of the uncertainties of both demand and return on the production plan, selling price, and the acquisition price of used products are analyzed.     

氧气瓶内附油脂充氧过程爆炸分析与计算

分析总结了氧气钢瓶物理爆炸和化学爆炸的原因。针对2009年某市发生的一起氧气瓶内含油脂爆炸事故,系统分析了国内曾经发生的几次因油脂导致气瓶爆炸事故。油脂进入到氧气瓶内大都是由于误操作。油脂与高压纯氧接触会发生剧烈的自燃氧化放热,使瓶内的氧气迅速升温升压,超出气瓶承压极限导致爆炸破裂。分析比较发现由油脂导致的气瓶爆炸,其破坏程度不如混入可燃气体导致的气瓶爆炸剧烈,一般不是粉碎性爆炸。在正常的充氧过程中,氧气瓶温度会升高,采用变质量热力学中的方法,计算说明气瓶在充装过程中氧气温度的具体变化。充氧温度计算为充氧工作人员提供参考,如发现异常情况,可以及时地控制和预防。由现场压力表可知氧气瓶在充装至12MPa时发生爆炸,而氧气瓶最小爆炸压力为37.6MPa,油脂燃烧放热,计算可知致使钢瓶爆炸破裂所需要的最小油脂量,为66.4-79.6g。不同的充装压力下发生爆炸,所需要的最小油脂量不同,充装压力越高,爆炸所需要的最小油脂量越少。     

环境因素对供应链中生产者食品安全行为的影响机制仿真分析

通过食品安全环境因素的改善和规范,来提高食品安全效果是具有现实意义的。本文归纳了影响食品安全的环境因素,特别是影响生产者食品安全行为的环境因素;环境因素对供应链食品安全的影响主要体现在生产者食品安全行为的选择上,为此,设计了环境因素对供应链生产者食品安全行为影响机制;为了分析环境因素对供应链中生产者食品安全的影响,从生产者食品安全行为的影响机制中选取了消费者食品安全意愿、生产者市场占有率、罚款金额等环境因素,以生鲜蔬果供应链中覆盖流通领域的那个部分提出了生产者食品安全行为选择策略的仿真模型,使用Netlogo软件进行了多主体仿真。通过仿真发现,食品监管的手法还宜细化,提升技术因素可以有效改善中国的食品安全水平。     

Designing a mixed performance measurement system for environmental supply chain management using evolutionary game theory and balanced scorecard: A case study of an auto industry supply chain

This paper proposes a mixed performance measurement system using a combination of evolutionary game theory and the balanced scorecard (BSC) in environmental supply chain management (ESCM) that measures and evaluates business operations using the four different perspectives of finance, customer, internal business process, and learning and growth. ESCM plays an important role in the supply chain which leads to the reduction, reuse and recycling of resources involved in both upstream and downstream activities. This paper presents guidance for practical managers in evaluating and measuring ESCM by developing a knowledge-based BSC and evolutionary game theory. The primary purpose of this paper is to apply the proposed method in a case study to one of Iran's biggest auto industry supply chain SAIPA Company. The results of this study indicate that the adoption of ESCM, in the absence of regulatory pressures and cost-saving measures is triggered by public pressures and its implementation is limited by organizational factors and strategic myopia.     

关于农村污水治理项目供给主体的探讨

从农村污水治理项目的社区性公共物品属性出发,说明农村污水治理项目不应完全由政府供给。通过梳理以日本为代表的发达国家的具体做法,提出了多元化供给的观点,并初步探讨了各供给主体的责任和义务。