Proposing channel coordination and horizontal cooperation in two competitive three‐echelon reverse supply chains

Considering and analyzing various kinds of cooperation among supply chain members is an option for better managing each channel. It is noteworthy that in many real‐world cases, each of vertical and horizontal cooperation has an important role in the success of supply chains. Nevertheless, only vertical cooperation in most previous research is considered. This paper addresses both vertical and horizontal cooperation in two competitive reverse supply chains, each of which includes one collector, one remanufacturer, and one retailer. Our primary concern is to analyze quality improvement competition between the remanufacturers. Moreover, retail price competition between the retailers and the quality competition are simultaneously considered in the extended model. In this research, the investigated system has been analyzed under different structures including decentralized, centralized, horizontal cooperation, and coordinated decision‐making models. The results show that when the remanufacturers cooperate horizontally, the profit of each collector and that of the retailer will decrease compared with those in the decentralized structure. To overcome this problem, a new coordination contract named multiple‐link two‐part tariff is proposed to simultaneously coordinate the members of each chain. The proposed contract effectively convinces the remanufacturers to participate in the coordination model instead of the horizontal cooperation. Moreover, it provides a win–win–win condition for all chain members and improves the quality level of the remanufactured products. The results indicate the proper performance of the proposed contract in improving the benefits of the competing chains, especially when there exists no intense competition between the remanufacturers (i.e., when the market sensitivity to the quality of the remanufactured products is low and consequently less effort is needed to increase the quality of the remanufactured products). Moreover, the proposed contract not only is able to simultaneously increase both remanufactured products demand and of end‐of‐life products supply but also involves both economic and environmental benefits.     

Propagation mechanism of neighboring cracks in rock-like cylindrical specimens under uniaxial compression

The mechanism of cracks propagation and coalescence of neighboring cracks existing in precracked rock like cylindrical specimens has been studied experimentally and numerically by considering multiple cracks in the middle part of each specimen. The pre-cracked cylindrical specimens of rock like materials are experimentally tested under uniaxial compression in a rock mechanics laboratory. Then these experiments are numerically simulated by a modified higher order displacement discontinuity method (HODDM) using cubic displacement discontinuity elements and three special crack tip elements for crack tip behavior to increase the accuracy of the Mode I and Mode II stress intensity factors (SIFs) obtained based on linear elastic fracture mechanics (LEFM) theory. The crack propagation and coalescence paths of the internal inclined crack are estimated by implementing a suitable iteration algorithm of incremental crack length extension in a direction predicted by using the maximum tangential stress criterion. The numerical and experimental results are compared showing the validity, applicability and accuracy of the present work. Finally, a numerical simulation has been accomplished to study the effect of interaction among neighboring cracks on the SIFs.     

Investigating the Failure Behavior of Gypsum Specimens with Non-Persistent Vertical Notch Under Uniaxial Compression

Strength of Materials - The failure behavior and mechanism of fracturing in the gypsum specimens containing vertical notches under uniaxial compression was investigated in this study. The...     

Integrated guidance and control of elastic flight vehicle based on robust MPC

Integrated guidance and control of an elastic flight vehicle based on constrained robust model predictive control is proposed. The design is based on a partial state feedback control law that minimizes a cost function within the framework of linear matrix inequalities. It is shown that the solution of the defined optimization problem stabilizes the nonlinear plant. Nonlinear kinematics and dynamics are taken into account, and internal stability of the closed‐loop nonlinear system is guaranteed. The performance and effectiveness of the proposed integrated guidance and control against non‐maneuvering and weaving targets are evaluated using computer simulations. Copyright © 2014 John Wiley & Sons, Ltd.     

Evolutionary coincidence-based ontology mapping extraction

Abstract: Ontology matching is a process for selection of a good alignment across entities of two (or more) ontologies. This can be viewed as a two-phase process of (1) applying a similarity measure to find the correspondence of each pair of entities from two ontologies, and (2) extraction of an optimal or near optimal mapping. This paper is focused on the second phase and introduces our evolutionary approach for that. To be able to do so, we need a mechanism to score different possible mappings. Our solution is a weighting mechanism named coincidence-based weighting . A genetic algorithm is then introduced to create better mappings in successive iterations. We will explain how we code a mapping as well as our crossover and mutation functions. Evaluation of the algorithm is shown and discussed.     

CDM-based design and performance evaluation of a robust AQM method for dynamic TCP/AQM networks

A new robust AQM strategy for dynamically varying TCP/AQM networks is proposed and its performance is investigated through computer simulations in MATLAB and ns-2 environments. The developed AQM is designed based on coefficient diagram method (CDM), which is a new indirect pole placement method that considers the speed, stability and robustness of the closed loop system in terms of time domain specifications. Simulation results indicate that the new method (CDM-AQM) performs very well for network variations both in topology and traffic. Besides, a new adaptive controller based on CDM as an AQM method is introduced. In the developed adaptive AQM (ACDM), the output feedback pole placement is implemented in an indirect model reference adaptive control (MRAC) scheme, in which the closed loop characteristic polynomial is determined by CDM and the system parameters are estimated using a modified recursive gradient method. This method preserves the existing features of CDM controller in the control of networks with unknown or time-varying parameters. Simulation results illustrate high capability of the controller in coping with the network variations.     

Design of an RMPC with a time‐varying terminal constraint set for tracking problem

This paper presents a robust model predictive control algorithm with a time‐varying terminal constraint set for systems with model uncertainty and input constraints. In this algorithm, the nonlinear system is approximated by a linear model where the approximation error is considered as an unstructured uncertainty that can be represented by a Lipschitz nonlinear function. A continuum of terminal constraint sets is constructed off‐line, and robust stability is achieved on‐line by using a variable control horizon. This approach significantly reduces the computational complexity. The proposed robust model predictive controller with a terminal constraint set is used in tracking set‐points for nonlinear systems. The effectiveness of the proposed method is illustrated with a numerical example. Copyright © 2015 John Wiley & Sons, Ltd.     

Model predictive control versus traditional proportional delay differentiation algorithms

An approximated quadratic programming optimization is proposed to determine a model predictive controller to guarantee end-to-end delay in the DiffServ architecture. The proposed algorithm, called the suboptimal model predictive control scheduler (SMPCS), regulates the service rates of aggregated traffic classes dynamically, such that some constraints on proportional or absolute delay can be guaranteed. This paper investigates SMPCS complexity and its implementation problems in high-speed routers. The main problem of model predictive control (and one which has limited its use to slow processes) is its complexity. Optimization is the most computationally complex part in a model predictive controller. To enable efficient implementation of such a computationally expensive algorithm, this paper proposes to reduce the precision of the optimizer while maintaining near-optimal values for the manipulated variables (service rates). Both control-theoretic analysis and simulations demonstrate that SMPCS performs stable and acceptable quality-of-service differentiations at core routers while maintaining end-to-end delay constraints.     

Periodic characteristic ratio (PCR) method: An alternative method to determine the characteristic polynomial

This paper proposes an alternative method to determine the characteristic polynomial based on closed loop desired transient response. To develop the method, we have found optimal characteristic rations in simple arrangement of these parameters via performance map method. Despite its simplicity, the resulted system exhibits better transient response in comparison with the systems obtained from existing methods of determining the characteristics polynomials. Numerical simulations are used to illustrate the specifications of the proposed method.     

GaP electroluminescent memory switch

M.I.S. structures in which the semiconductor is GaP and the insulator a native oxide of GaP exhibit switchtng and non volatile memory properties as well as electroluminescence that is green under forward bias and orange under reverse bias. The switching and memory properties are thought to be due to a forming process in the oxide layer.