基于EPR政策的耐用品设计寿命的决策研究——从计划报废的视角

本文探究如何安排延伸生产者责任(EPR)政策从而避免耐用品像快消品一样在短期产生大量废弃物的问题。文章在已有研究基础上,从计划报废的视角,构建了一个基于连续时间的动态耐用品模型,利用最优控制方法探究了集中式决策的最优结果和分散式决策的市场均衡,并基于二者的比较分析,揭示不同市场结构下EPR政策工具对生产者延长产品设计寿命的激励效果。最后基于理论模型的分析过程,通过数值模拟和案例分析对研究结论进行验证。研究表明,在市场完全竞争情形下,实施单一的庇古税或者仅通过押金-返还制度既可以将产出调节至最优水平,也能为生产者提供足够的激励延长其产品的设计寿命;在市场不完全竞争情形下,至少需要借助税收和补贴两种EPR政策工具的配合,才能实现产出和设计寿命的最优结果。     

Efficient frontier cutoff policies in credit portfolios

Historically, account acquisition in scored retail credit and loan portfolios has focused on risk management in the sense of minimizing default losses. We believe that acquisition policies should focus on a broader set of business measures that explicitly recognize tradeoffs between conflicting objectives of losses, volume and profit. Typical business challenges are: ‘How do I maximize portfolio profit while keeping acceptance rate (volume, size) at acceptable levels?’ ‘How do I maximize profit without incurring default losses above a given level?’ ‘How do I minimize the risk of large loss exposures for a given market share?’ In this paper we are not concerned with which combination of objectives are appropriate, but rather focus on the cutoff policies that allow us to capture a number of different portfolio objectives. When there are conflicting objectives we show that optimal policies yield meaningful tradeoffs and efficient frontiers and that optimal shadow prices allow us to develop risk-adjusted tradeoffs between profit and market share. Some of the graphical solutions that we obtain are simple to derive and easy to understand without explicit mathematical formulations but even simple constraints may require formal use of non-linear programming techniques. We concentrate on models and insights that yield decision strategies and cutoff policies rather than the techniques for developing good predictors.     

生产者对回收责任约束的参与意愿——强制性与自愿性的形成机理及驱动因素分析

绿色发展要求生产者承担回收、循环并再利用的延伸责任。政府通过合规计划约束生产者的行为,规制水平与获利驱动调控生产者的参与意愿而实现回收责任。本文以再制造作为废旧产品的价值恢复模式,导入了循环环节的环境成本,构建了基于经济效益和经济效益与环境效益相统一的生产者参与意愿决策模型,运用线性约束二次规划的K-T条件方法,确立了两种情境下的最优决策。研究结果给出了生产者强制性与自愿性的分型边界,分型边界受恢复价值和政府规制水平的联合驱动;评估了环境成本结构对强制性/自愿性的分型边界、效益的影响。     

Shortening cycle times in multi-product,capacitated production environments through quality level improvements and setup reduction

This paper addresses the issue of investing in reduced setup times and defect rates for a manufacturer of several products operating in a JIT environment. Production cycle times can be shortened by investing in setup time and defect rate reductions, respectively. The objective is to determine optimal levels of setup time and defect rate reductions along with the corresponding optimal levels of investments respectively, and the optimal production cycle time for each product. The problem is constrained by demand requirements, process improvement budget limitations, and manufacturing and warehousing capacity constraints. We consider the cases of product-specific quality improvements and joint-product quality improvements. A general nonlinear optimization models of these problems are formulated. A convex geometric programming approximation of these models is developed respectively, in order to solve them. The approximation can be made to any desired degree of accuracy. Our empirical findings provide insights into a number of managerial issues surrounding investment decisions in product-specific quality improvements and setup reductions due to a product redesign as well as in joint-product improvements due to a process redesign.     

EPR制度下的家电以旧换新回收策略优化模型

研究生产者责任延伸制度(EPR)约束下,家电生产销售企业集中决策下实施以旧换新进行废旧产品回收的问题。在对家电消费者市场结构进行分析基础上,建立以企业利润最大化为目标的实施以旧换新回收策略的优化模型,并根据我国家电行业EPR制度的特点,构建政府与企业间竞争的Stackelberg博弈模型,研究在政府环境效益最优时的补贴和基金征收标准下,企业以旧换新回收产品最优定价决策;同时,与企业不直接参与废旧产品回收时单一定价相应结果进行比较。结果表明:在EPR约束下,政府环境效益最优时的补贴和基金征收标准,对企业实施以旧换新回收策略的产品销量、总利润和废旧产品回收量的影响取决于企业成本结构、消费者结构、消费者效用和废旧产品回收处理能力。企业决策者需根据不同情形决定是否参与以旧换新回收实践。     

Take back costs and product durability

Extended Producer Responsibility (EPR) initiatives may require a manufacturer to be responsible in the future for taking back the products it produces today. A ramification of EPR is that take back costs may influence firms’ decisions regarding product durability. In the absence of EPR, prior literature has shown that a firm may intentionally lower durability, yielding planned obsolescence. We use a two period model to examine the impact of take back costs on a manufacturer’s product durability and pricing decisions, under both selling and leasing scenarios. We show that compared to selling, leasing provides a greater incentive to raise durability, thus extending a classic insight to a setting with product take backs. Interestingly, we also show that it is possible for the optimal product durability to decrease if the stipulated take back fraction increases. In such situations, were the take back fraction tied to durability rather than a fixed fraction, we demonstrate durability can increase. We explore the impact of take backs on profits and surplus by alternatively considering products for which take back costs are either increasing or decreasing functions of durability. When increasing durability implies higher take back costs, our results demonstrate that leasing can increase durability, profits, and surplus significantly compared to selling. In contrast, when increasing durability implies a lower take back cost, there is a built-in incentive for the firm to increase durability, which can make selling more efficient (i.e., surplus enhancing) than leasing.     

Assortment and inventory decisions with multiple quality levels

We consider the assortment and inventory decisions of a retailer under a locational consumer choice model where products can be differentiated both horizontally (e.g., color of a product) and vertically (e.g., quality of a product). The assortment and quantity decisions affect customer choice and, hence, the demand and sales for each product. In this paper, we investigate two different environments where product availability and assortment affect consumer choice and demand in different ways: make-to-order (MTO) and make-to-stock (MTS). In the MTO environment, customers order and purchase their most preferred product; that is, stockouts do not occur. In the MTS model, customers buy their most preferred product if it is in stock or do not buy if it is out of stock. In both environments we find conditions under which it is optimal to carry assortments of only a single quality level. In the MTS case, we show that an assortment of mixed quality levels can be optimal only within a narrow range of parameters.     

消费者偏好、市场准入与产品安全水平:基于双寡头两阶段博弈模型分析

考虑消费者产品安全偏好和产品安全水平等因素,针对采取不同产品安全战略的两个寡头制造商,建立了两阶段博弈模型:第一阶段为两制造商选择各自的产品安全度水平,第二阶段为两产品制造商确定各自的产品价格。通过数值仿真重点讨论了消费者产品安全偏好支付系数和产品安全市场准入值两参数变化带来的影响。结果表明:消费者安全偏好支付系数提高时,两制造商利润均增加;产品安全准入值提高时,低价战略采取者的利润下降;主动安全战略采取者利润增加。所得结论对于产品安全管理中政府及不同类型制造商的决策具有参考价值和指导意义。     

Nash equilibrium in a pay-as-bid electricity market Part 2 - best response of a producer

We consider a multi-leader-common-follower model of a pay-as-bid electricity market in which the producers provide the regulator with either linear or quadratic bids. We prove that for a given producer only linear bids can maximize his profit. Such linear bids are referred as the ‘best response’ of the given producer. They are obtained assuming the demand is known and some estimate of the bids of the other producers is available. Nevertheless we also show that whenever no best response exists, the optimal profit can be asymptotically attained by a sequence of quadratic bids converging to the so-called ‘limiting best response’. An explicit formula for such a sequence is provided.     

Non-causal models in long term planning via set contractive optimal control methods

The notion of consistency for optimal plans introduced in [F.E. Kydland, E.C. Prescott, Rules rather than decisions: The inconsistency of optimal plans, J. Polit. Econ. 85 (3) (1977) 473–491] is studied in relation to dynamic programming and to multi-objective optimal control. It is demonstrated that the consistency condition for an optimal sequence of n policies for periods from 1 to n corresponding to a sequence of n economic agents’ decisions that together constitute an optimal plan for an agreed-upon social objective function is equivalent to a multi-objective problem with n+1 criteria. An optimal plan is consistent if and only if the corresponding (n+1)-criteria problem is balanced, and consistent optimal plans do exist in such economic situations. Otherwise, the consistency requirement generates the balance set and a set of Pareto solutions, and both can be computed as illustrated in the inflation–unemployment example extended for two periods with three objectives to optimize. The procedure of “consistent planning for the infinite horizon” considered in [F.E. Kydland, E.C. Prescott, Rules rather than decisions: The inconsistency of optimal plans, J. Polit. Econ. 85 (3) (1977) 473–491] is shown to concur with Bellman’s principle of optimality that may be invalid in many practical cases including the case considered in [F.E. Kydland, E.C. Prescott, Rules rather than decisions: The inconsistency of optimal plans, J. Polit. Econ. 85 (3) (1977) 473–491]. Finitely causal and non-causal models are introduced for long term planning in a multi-objective (Pareto) framework, and it is demonstrated how to deal with non-causal models using new set-contractive methods for multi-objective global optimization. The results are illustrated by examples.     

Aggregate production planning for process industries under oligopolistic competition

We consider a competitive version of the traditional aggregate production planning model with capacity constraints. In the general case, multiple products are produced by a few competing producers (oligopoly) with limited capacities. Production quantities, prices and consequently profits depend on production and allocation decisions of each producer. In addition, there is competition for the raw material whose supplies are limited, and where prices reflect these limitations. Such situations have recently occurred in several process industry settings including petro-refining, petrochemicals, basic chemicals, cement, fertilizers, pharmaceuticals, rubber, paper, food processing and metals. We use a successive “Bertrand–Cournot” framework to address this problem and to determine optimal production quantities, prices and profits at the producers and at the raw material supplier. Our analysis allows a new way to understand and evaluate the marginal value of additional capacity when there is competition for the market and raw materials.     

Moral mid-level principles in modeling

Modelers, especially in operational research, are becoming increasingly aware that their role in decision-making raises moral problems. This paper discusses two questions: How do moral issues in modeling arise? How can these moral issues be addressed? I propose a framework that (1) provides tools for discovering moral issues raised by models, and (2) provides practical guidance for solving moral problems in modeling. As regards (1), I discuss three moral perspectives on modeling: a perspective that focuses on the beneficial or harmful consequences of using a model; a perspective that focuses on the intentions of using a model; and a perspective that focuses on whether a model promotes virtuous behavior. In order to achieve practical action guidance, (2), four moral mid-level principles are introduced: (i) The principle of transparency expresses the obligations to explain the structure, assumptions and further properties of the model; (ii) the principle of integrity demands for the application of professional standards; (iii) the principle of comprehensiveness stresses that all moral concerns should be acknowledged thoroughly; and finally, (iv) the principle of efficacy states that models should evaluate moral issues explicitly.     

Models of wayfinding in emergency evacuations

How do people select their movement paths in a complex building? How do evacuees find their way to the exits? How do customers orient themselves within a shopping center? The paper presents the wayfinding problem in a mathermatical setting, providing numerous models of wayfinding behaviour, ranging from the simplest random walk models to more complex shortest path rules. The models are analyzed numerically to illustrate their implications on the performance of the wayfinding process. Such models are of great importance when one studies how persons evacuate from a building. The maze at Hampton Court has served as an example, clearly demonstrating the wayfinding problems for an evacuating person.     

Optimal production planning and cap setting under cap-and-trade regulation

This paper investigates the optimal production decisions of a self-pricing manufacturer and the optimal cap-setting decisions of a regulator under the cap-and-trade regulation. The objectives of the manufacturer and the regulator are to maximize profit and to maximize social welfare, respectively. We first derive the optimal production decisions and the corresponding total emissions of the manufacturer, with given parameters of the cap-and-trade regulation. Based on these results, we then solve the optimal cap-setting problem of the regulator. Furthermore, through sensitive analyses, we show that as the emissions intensity (i.e., the emissions generated from one unit of product) increases, both the optimal total emissions and the optimal cap first increase and then decrease.     

Sequencing interval situations and related games

Uncertainty accompanies almost every situation in real world and it influences our decisions. In sequencing situations it may affect parameters used to determine an optimal order in the queue, and consequently the decision of whether (or not) to rearrange the queue by sharing the realized cost savings. This paper extends the analysis of one-machine sequencing situations and their related cooperative games to a setting with interval data, i.e. when the agents’ costs per unit of time and/or processing time in the system lie in intervals of real numbers obtained by forecasting their values. The question addressed here is: How to determine an optimal order (if the initial order in the queue is not so) and which approach should be used to motivate the agents to adopt the optimal order? This question is an important one that deserves attention both in theory and practice.     

Optimal Stopping Problems in Lévy Models with Random Observations

In the standard optimal stopping problems, actions are artificially restricted to the moments of observations of costs or benefits. In the standard experimentation and learning models based on two-armed Poisson bandits, it is possible to take an action between two sequential observations. The latter models do not recognize the fact that timing decisions depend not only on the rate of arrival of observations, but also on the stochastic dynamics of costs or benefits. We combine these two strands of literature and consider optimal stopping problems with random observations and updating. We formulate the dichotomy principle, an extension of the smooth pasting principle.

     

Problems and methods with multiple objective functions

LetA be a set of feasible alternatives or decisions, and supposen different indices, measures, or objectives are associated with each possible decision ofA. How can a “best” feasible decision be made? What methods can be used or experimented with to reach some decision? The purpose of this paper is to attempt a synthesis of the main approaches to this problem which have been studied to date. Four different classes of approaches are distinguished: (1) aggregation of multiple objective functions into a unique function defining a complete preference order; (2) progressive definition of preference together with exploration of the feasible set; (3) definition of a partial order stronger than the product of then complete orders associated with then objective functions; and (4) maximum reduction of uncertainty and incomparability.     

Day-ahead market bidding for a Nordic hydropower producer: taking the Elbas market into account

In many power markets around the world the energy generation decisions result from two-sided auctions in which producing and consuming agents submit their price-quantity bids. The determination of optimal bids in power markets is a complicated task that has to be undertaken every day. In the present work, we propose an optimization model for a price-taker hydropower producer in Nord Pool that takes into account the uncertainty in market prices and both production and physical trading aspects. The day-ahead bidding takes place a day before the actual operation and energy delivery. After this round of bidding, but before actual operation, some adjustments in the dispatched power (accepted bids) have to be done, due to uncertainty in prices, inflow and load. Such adjustments can be done in the Elbas market, which allows for trading physical electricity up to one hour before the operation hour. This paper uses stochastic programming to determine the optimal bidding strategy and the impact of the possibility to participate in the Elbas. ARMAX and GARCH techniques are used to generate realistic market price scenarios taking into account both day-ahead price and Elbas price uncertainty. The results show that considering Elbas when bidding in the day-ahead market does not significantly impact neither the profit nor the recommended bids of a typical hydro producer.     

供应链纵向结构对EPR政策激励效果的影响研究

为了揭示供应链纵向结构对EPR政策激励效果的影响,本文通过构建EPR政策约束下由上游制造商和下游客户所组成的供应链决策模型,分别在纵向一体化和纵向分离两种典型的供应链纵向市场结构下,考察了EPR政策对制造商环保性能和可循环性设计决策的激励影响。结果表明:在不同的供应链纵向结构下,由于制造商与客户之间的利益协调机制存在着差异,使得EPR政策对制造商环境设计选择的激励效果将发生变化。在纵向一体化结构下EPR政策对制造商可循环性的激励效果更强;而EPR政策对环保性能的激励在哪种供应链纵向结构下更强是不确定的,最终还取决于行业本身在生产成本和环境成本等方面的特征。最后,基于本文的研究结论给出了EPR政策与产业政策相配套的政策建议。     

Multiple objective data envelopment analysis as applied to the Indian Pharmaceutical Industry

The change of Intellectual Property Protection (IPP) from a softer process patenting to a stronger product patenting in Indian Pharmaceutical Industry (IPI) is attracting many global drug majors to source their production from India, which is the fourth largest producer of pharmaceuticals in the world. In this paper, the interests of different stake holders like the buyers (multinational enterprises), who are searching for efficient partners and the vendors (Indian drug producers) that are competing for the contracts, are analysed for a suitable efficiency evaluation criterion. The primary objective of this paper is to study how various firms in the IPI with different business strategies, competing for the same opportunities can find suitable benchmarking peer groups to meet the challenges of a dynamic business environment using data envelopment analysis (DEA). A multiple objective DEA model that determines suitable peer groups for inefficient companies is discussed along with more traditional DEA models. The proposed model has the flexibility to include inputs like R&D expenditure and outputs like Exports that are not homogeneously distributed across the firms and address the interests of various stake holders like buyers and vendors simultaneously.