A visual interactive approach for scenario-based stochastic multi-objective problems and an application

In many practical applications of stochastic programming, discretization of continuous random variables in the form of a scenario tree is required. In this paper, we deal with the randomness in scenario generation and present a visual interactive method for scenario-based stochastic multi-objective problems. The method relies on multi-variate statistical analysis of solutions obtained from a multi-objective stochastic problem to construct joint confidence regions for the objective function values. The decision maker (DM) explores desirable parts of the efficient frontier using a visual representation that depicts the trajectories of the objective function values within confidence bands. In this way, we communicate the effects of randomness inherent in the problem to the DM to help her understand the trade-offs and the levels of risk associated with each objective.     

Comparing frontier methods for economic–environmental trade-off analysis

This paper uses a mechanistic frontier approach as a reference to evaluate the ability of conventional parametric (SFA) and non-parametric (DEA) frontier approaches for analyzing economic–environmental trade-offs. Conventional frontier approaches are environmentally adjusted through incorporating the materials balance principle. The analysis is worked out for the Flemish pig finishing case, which is both representative and didactic. Results show that, on average, SFA and DEA yield adequate economic–environmental trade-offs. Both methods are good estimators for technical efficiency. Cost allocative and environmental allocative efficiency scores are less robust, due to the well-known methodological advantages and disadvantages of SFA and DEA. For particular firms, SFA, DEA and the mechanistic approach may yield different economic–environmental trade-offs. One has therefore to be careful when using conventional frontier approaches for firm-specific decision support. The mechanistic approach allows for optimizing performances per average present finisher, which is the production unit in pig finishing. Conventional frontier methods do not allow for this optimization since the number of average present finishers varies along the production functions. Since the mechanistic production function is based on underlying growth, feed uptake and mortality functions, additional firm-specific indicators can also be calculated at each point of the production function.     

Recovery decisions of a producer in a legislative disposal fee environment

The main objectives of the environmental legislation originating from extended producer responsibility (EPR) principle are to lead producers to undertake recovery initiatives for their end-of-use products and to promote environmentally desirable product design. It is still controversial whether current implementations of EPR principle are effective in attaining these objectives. This study seeks to answer the following questions: (1) What is the impact of EPR legislation on the product recovery decisions of producers? (2) How do the redesign opportunities (i.e., design for disassembly) affect the willingness of producers for product recovery? (3) How do the investment needs to start recovery practices and the reluctance of producers to allocate sufficient funds for this purpose affect the optimal recovery decisions? We use stylized economic models to represent the implementation in practice and solving our models we obtain closed form and numerical solutions that help us to see the impact of various parameters on the optimal decisions of a producer. Our findings indicate that redesign opportunities encourage producers for more recovery, however the reluctance of producers to cover the initial investments may substantially reduce the effectiveness of the legislation and the recovery amounts.     

Groups and facilitators within problem structuring processes

In problem structuring methods, facilitators often ask of themselves questions such as: what makes a ‘good’ problem structuring group (PSG) and indeed what does ‘good’ mean? How can group dynamics be improved and does it matter in terms of the quality of the problem structuring that that group engages in? On the surface these questions seem to be straightforward. Indeed, those who have helped facilitate many participatory workshops will think they intuitively know the answers to these questions; they can, from their professional practice, ‘feel’ which PSGs are doing well and producing novel insights and those which are functioning less well and perhaps generating something that is less imaginative and more routine as a consequence. The intuitive, practice-learned insight will depend upon a rich array of visual signals that become more obvious with experience. This paper asks whether there is value in being much more open and analytical about these questions and answers. If so, then how can we make the unwritten processes and outcomes of PSGs written? Indeed, open to whom? Finally, how much of any insights learned by facilitators should be shared with those engaged in workshops?     

Lag synchronization of complex networks via pinning control

This paper mainly investigates the lag synchronization of complex networks via pinning control. Without assuming the symmetry and irreducibility of the coupling matrix, sufficient conditions of lag synchronization are obtained by adding controllers to a part of nodes. Particularly, the following two questions are solved: (1) How many controllers are needed to pin a coupled complex network to a homogeneous solution? (2) How should we distribute these controllers? Finally, a simple example is provided to demonstrate the effectiveness of the theory.     

Banach lattice algebras: some questions,but very few answers

We pose a number of questions and problems about Banach lattice algebras. These concern: What should the definition be? How to add an identity. Order theoretic properties of the multiplication. Order theoretic properties of the left regular representation.

     

An analytic network process approach to the selection of logistics service providers for air cargo

Nowadays, enterprises typically outsource their logistics needs to logisticsagents, who have become vital partners in managing supply chains. The logisticsneeds in a supply chain consist of many different interrelated services, eachwith its own set of requirements and constraints. A logistics agent mightspecialize in the provision of a single logistics service or might provide arange of services. The selection of logistics agent(s) cannot be separated intoa series of stand-alone selections as the decisions are interrelated. Decisionmakers must assess the merits of individual activity-agent combinations, as wellas their interrelationships along the entire supply chain. Such an evaluation isnon-trivial, because both tangible and intangible elements are involved. In thisresearch, we model the selection problem using analytic network process, amultiattribute decision-making methodology suitable for assessing interdependentelements, both tangible and intangible. We examine the significance ofintegration and consolidation of shipments, the trade-offs between costs,benefits and risks within activities of the logistics process, and the differingroles of traditional freight forwarders and integrators.     

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.     

Middle school students’ reasoning about data and context through storytelling with repurposed local data

Publicly-available datasets, though useful for education, are often constructed for purposes that are quite different from students’ own. To investigate and model phenomena, then, students must learn how to repurpose the data. This paper reports on an emerging line of research that builds on work in data modeling, exploratory data analysis, and storytelling to examine and support students’ data repurposing. We ask: What opportunities emerge for students to reason about the relationship between data, context, and uncertainty when they repurpose public data to explore questions about their local communities? And, How can these opportunities be supported in classroom instruction and activity design? In two exploratory studies, students were asked to pose questions about their communities, use publicly-available data to investigate those questions, and create visual displays and written stories about their findings. Across both enactments, opportunities for reasoning emerged especially when students worked to reconcile (1) their own knowledge and experiences of the context from which data were collected with details of the data provided; and (2) their different emerging stories about the data with one another. We review how these opportunities unfolded within each enactment at the level of group and classroom, with attention to facilitator support.     

Multistage reverse logistics of assembly systems in extended MRP Theory consisting of all material flows

In this paper we will address the issue of environmental problems in connection with extended MRP Theory. It is based on Grubbstr?m??s well developed MRP Theory (Grubbstr?m in Z für BetrWirthsch 77(3):297?C324, 2007). A major advantage of this theory is that timing and its impact on net present value can be easily calculated even for extended multilevel, multistage production-inventory systems and also for perturbed production systems consisting of many production cells. Theory has recently been extended by including reverse logistics of final and used products (Grubbstr?m et?al. in A compact representation of distribution and reverse logistics in the value chain. Faculty of Economics, Ljubljana, 2007). At each activity cell a certain percentage of scrapes is produced and sent for recycling after quality control. Here we present an input?Coutput model which includes all possible flows into a recycling sub-process with several stages of recycling. This model is presented in a generalized form of input and output matrices which has not been developed before. The model will be presented in two different ways which differ in the level of detailed information they contain. Contribution of recycling to the net present value of all activities in a supply chain is expressed and can be compared to environmental damage that could occur if reverse processes are not introduced. Using this approach, the losses and gains in both the economy and the environment could be evaluated more accurately considering all individual flows in the system. No other approaches besides input?Coutput analysis and Laplace transforms have been found so successful in compound supply systems.     

Bootstrap estimation of the efficient frontier

In this paper, we propose a bootstrap resampling methodology to obtain the confidence intervals for efficient portfolios weights and the sample characteristics of the mean-variance efficient frontier. We provide an estimate of efficient portfolios, compute the confidence region of the efficient frontier and get the prediction densities of the future efficient portfolio returns without distributional assumptions on returns. An extensive simulation study evaluates the finite-sample performance of these bootstrap intervals and stresses the advantages of such approach. Interestingly, the methodology can be easily modified to make inferences that incorporate our modelling of returns in the predictive efficient frontier estimation with or without additional managerial restrictions.     

Bar Graphs and Histograms

<正>When am I ever going to use this?ANIMALS The cheetah is the fastest known and animal.The table shows its fastest speed and the top speeds of four other land animals.1.What are the fastest and slowest speeds recorded in the table?2.How can you create a visual representation to summarize the data?3.Do any of these representations show both the animal name and its speed?Abar graphis one method of comparing data by using solid bars to represent quantities.     

连续对策的公平性和刺激性

本文用刺激性(感)来描述游戏一个零和对策的两个局中人的风险性和侥幸取胜性,游戏不同的零和对策可能有不同的刺激感,刺激性越大,对策结果的公平性越小;反之亦然,本文解决了如下问题;(1)刺激性和公平性的数学描述是什么?(2)局中人如何保证他们的一局对策的对策结果是最公平的或最有刺激感的?(3)如果两个局中人希望对策结果尽量公平或尽量有刺激感,他们最好从给定的连续对策中选择哪个?     

Time-consistent investment-proportional reinsurance strategy with random coefficients for mean–variance insurers

In this study, we consider an insurer who manages her underlying risk by purchasing proportional reinsurance and investing in a financial market consisting of a risk-free bond and a risky asset. The objective of the insurer is to identify an investment–reinsurance strategy that minimizes the mean–variance cost function. We obtain a time-consistent open-loop equilibrium strategy and the corresponding efficient frontier in explicit form using two systems of backward stochastic differential equations. Furthermore, we apply our results to Vasiček’s stochastic interest rate model and Heston’s stochastic volatility model. In both cases, we obtain a closed-form solution.     

Optimal investment–reinsurance with delay for mean–variance insurers: A maximum principle approach

This paper is concerned with an optimal investment and reinsurance problem with delay for an insurer under the mean–variance criterion. A three-stage procedure is employed to solve the insurer’s mean–variance problem. We first use the maximum principle approach to solve a benchmark problem. Then applying the Lagrangian duality method, we derive the optimal solutions for a variance-minimization problem. Based on these solutions, we finally obtain the efficient strategy and the efficient frontier of the insurer’s mean–variance problem. Some numerical examples are also provided to illustrate our results.     

Frontier estimation via kernel regression on high power-transformed data

We present a new method for estimating the frontier of a multidimensional sample. The estimator is based on a kernel regression on the power-transformed data. We assume that the exponent of the transformation goes to infinity while the bandwidth of the kernel goes to zero. We give conditions on these two parameters to obtain complete convergence and asymptotic normality. The good performance of the estimator is illustrated on some finite sample situations.     

考虑即时采购价格的物流服务供应链优化

物流服务市场的不确定性会影响物流服务供应链的服务水平和收益。在考虑随机即时采购价格以及基础物流提供商在正常情况和应急情况下具有不同物流能力投资成本的情形下,引入期权机制研究不确定市场环境下物流服务供应链的优化决策,以提高物流服务供应链柔性和降低市场不确定性带来的风险。构建物流服务供应链的期权契约模型,采用Stackelberg博弈理论和优化算法分析和求得物流服务集成商的最优期权采购和即时采购策略,以及基础物流提供商的最优物流能力投资策略。结果表明即时采购价格将影响基础物流提供商和物流服务集成商的决策。最后通过数值分析研究即时采购价格的不确定程度对物流服务集成商和提供商的优化策略和利润的影响。     

Equivalences between Data Envelopment Analysis and the theory of redundancy in linear systems

This paper establishes how the non-parametric frontier estimation methodology of Data Envelopment Analysis (DEA) and the classical problem of detecting redundancy in a system of linear inequalities are connected. We present an analysis of the sets generated in two of DEA's models from where the empirical efficient production frontier is established from the point of view of polyhedral set theory. This yields convenient alternative characterizations of these sets which provide new insights about their properties. We use these insights to show how these polyhedral sets connect DEA to redundancy in linear systems. This means that DEA can benefit from a rich and well-established collection of computational and theoretical results which apply directly from redundancy in linear systems.     

The effects of adding objectives to an optimisation problem on the solution set

Suppose that an additional objective function is introduced into a (multicriteria or singlecriterion) optimisation problem. The following questions are considered: How does the set of (properly, weakly, or strictly) efficient points changes when instead of the old problem the new problem is considered? What happens in the value space?