p-Median and p-dispersion problems: A bi-criteria analysis

Given a collection of n locations and a symmetric measure of distance (difference) between each pair of locations, we seek to identify (select) a subset of p locations so as to achieve two distinct objectives. The first objective is to use the selected locations as centers (medians) of p groups that would partition the entire collection and minimize the total distance between the locations and their respective group medians. The second objective is to maximize the minimum distance (diversity) among the selected locations themselves. We study this problem as a multi-objective optimization problem and propose an iterative algorithm to obtain its non-dominated frontier. At each iteration we construct and solve a 0–1 integer programming problem. Through a computational experiment we show that this algorithm is computationally effective for small to medium size instances of the problem. We also propose a Lagrangian heuristic algorithm for solving larger instances of this problem.     

Competitive closed-loop supply chain network design under uncertainty

This paper studies the competition between two closed-loop supply chains including manufacturers, retailers and recyclers in an uncertain environment. The competition factors are the retail prices of new products and incentives paid to consumers for taking back the used products. Market demands are price sensitive and also the amount of returned products is sensitive to incentives. The primary goal of this paper is to investigate the impact of simultaneous and Stackelberg competitions between two closed-loop supply chains on their profits, demands and returns. A game theoretic approach which is empowered by possibility theory is applied to obtain the optimal solutions under uncertain condition. Finally the theoretical results are analyzed using sample data inspired by a real industrial case.     

A Constitutive Equation of Thermoelasticity for Solid Materials

A new constitutive equation of thermoelasticity for crystals is presented based on the interatomic potential and solid mechanics at finite temperature. Using the new constitutive equation, the calculations for crystal copper and graphene are carried out under different loading paths at different temperatures. The calculated results are in good agreement with those of the previous thermoelasticity constitutive equation based on quantum mechanics, which clearly indicates that our new constitutive equation of thermoelasticity is correct. A lot of comparisons also show that the present theory is more concise and efficient than the previous thermal stress theory in the practical application.     

Theoretical investigation of the interaction between aromatic sulfur compounds and [BMIM]+[FeCl4]− ionic liquid in desulfurization: A novel charge transfer mechanism

In this work, interaction nature between a group of aromatic sulfur compounds and [BMIM]⁺[FeCl₄]⁻ have been investigated by density functional theory (DFT). A coordination structure is found to be critical to the mechanism of extractive desulfurization. Interaction energy and extractive selectivity follow the order: thiophene (TH) < dibenzothiophene (DBT) ≈ benzothiophene (BT). Alkylation of TH or BT (e.g. 3-methylthiophene, and 3-methylbenzothiophene) leads to a stronger interaction with ionic liquid, but steric hindrance effects of some alkylic derivatives (e.g. 2,7-dimethylbenzothiophene) lead to a weaker interaction with ionic liquid. The mechanism of extractive desulfurization is attributed to the charge transfer effect. During extractive desulfurization, electrons on aromatic sulfur compounds transfer into the Lewis part of ionic liquid, namely, [FeCl₄]⁻. Furthermore, it is better to consider the Lewis acidity of Fe-containing ionic liquid by the whole unit (such as [FeCl₄]⁻ and aromatic sulfur compounds (X)) rather than only Fe or S atom.     

Robust skin detection in real-world images

Human skin detection in images is desirable in many practical applications, e.g., human–computer interaction and adult-content filtering. However, existing methods are mainly suffer from confusing backgrounds in real-world images. In this paper, we try to address this issue by exploring and combining several human skin properties, i.e. color property, texture property and region property. First, images are divided into superpixels, and robust skin seeds and background seeds are acquired through color property and texture property of skin. Then we combining color, region and texture properties of skin by proposing a novel skin color and texture based graph cuts (SCTGC) to acquire the final skin detection results. Comprehensive and comparative experiments show that the proposed method achieves promising performance and outperforms many state-of-the-art methods over publicly available challenging datasets with a great part of hard images.     

First-principles density functional calculations of physical properties of orthorhombic Au2Al crystal

The study attempts to perform a systematical investigation of the thermodynamic, mechanical and electronic properties of orthorhombic Au₂Al crystal by using first-principles calculations incorporated with a quasi-harmonic Debye model. In addition, their temperature, hydrostatic pressure and direction dependences are also addressed. The investigation begins with evaluation of the equilibrated lattice constants and elastic constants of Au₂Al single crystal. Next, the mechanical features of the single crystal, such as ductile-brittle characteristic and elastic anisotropy, are assessed based on the Cauchy pressures, shear anisotropy factors and directional Young's modulus. Alternatively, the pressure-dependence of polycrystalline mechanical properties of Au₂Al, including bulk, shear and Young's moduli, and ductility, brittleness and microhardness characteristics are also estimated. Furthermore, the study also characterizes the temperature-dependence of thermodynamic properties of Au₂Al single crystal, namely, Debye temperature and heat capacity. At last, electronic characteristic analysis is carried out to predict the electronic band structures and density of states profiles of the crystal.The calculation results indicate that Au₂Al crystal is an elastically anisotropic material at zero pressure and a highly ductile material with low stiffness. In addition, the Young's moduli of the crystal would be markedly enhanced with the increase of the hydrostatic pressure. It is also found that the heat capacity of Au₂Al at low temperature strictly sticks to the Debye T³ law.     

基于期权合约的战备物资储备激励机制研究

针对通用战备物资依托企业合同储备问题,从合作博弈的角度出发,引入期权合约理论,构建期权合约下合同储备激励机制模型。分析影响各方博弈主体策略选择的因素,对不同策略下参与主体双方的利润期望进行比较分析,确立期权合约理论下合理的期权价格范围,寻求军地双赢策略。实例分析表明,提出的方法具有可行性和有效性。     

An approach for evaluating collaboration attributes in cluster-based companies

This paper presents an approach for evaluating collaboration attributes in companies operating in industrial clusters. From the literature review, we identified governance, geographic proximity, and trust as the main collaboration attributes in industrial clusters. For each of them, there is a set of related sub-attributes that composed the evaluation model. For developing the model, we used the graph theoretic approach (GTA), a methodology for multi-attribute assessment that considers interdependencies among elements of a system to provide an overall evaluation. We applied the model to five companies of a furniture cluster. The results showed the model allows for systematizing relationship management because it highlights the collaboration attributes that need to be improved. Furthermore, the application of the model may contribute to encouraging companies to develop collaborative practices.