Mathematical Problems in Engineering http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Dynamic Pricing for Airline Revenue Management under Passenger Mental Accounting Thu, 29 Jan 2015 14:20:15 +0000 http://www.hindawi.com/journals/mpe/2015/836434/ Mental accounting is a far-reaching concept, which is often used to explain various kinds of irrational behaviors in human decision making process. This paper investigates dynamic pricing problems for single-flight and multiple flights settings, respectively, where passengers may be affected by mental accounting. We analyze dynamic pricing problems by means of the dynamic programming method and obtain the optimal pricing strategies. Further, we analytically show that the passenger mental accounting depth has a positive effect on the flight’s expected revenue for the single flight and numerically illustrate that the passenger mental accounting depth has a positive effect on the optimal prices for the multiple flights. Yusheng Hu, Jinlin Li, and Lun Ran Copyright © 2015 Yusheng Hu et al. All rights reserved. Stability Criterion of Linear Stochastic Systems Subject to Mixed /Passivity Performance Thu, 29 Jan 2015 06:23:59 +0000 http://www.hindawi.com/journals/mpe/2015/831576/ The control scheme and passivity theory are applied to investigate the stability criterion of continuous-time linear stochastic system subject to mixed performance. Based on the stochastic differential equation, the stochastic behaviors can be described as multiplicative noise terms. For the considered system, the control scheme is applied to deal with the problem on minimizing output energy. And the asymptotical stability of the system can be guaranteed under desired initial conditions. Besides, the passivity theory is employed to constrain the effect of external disturbance on the system. Moreover, the Itô formula and Lyapunov function are used to derive the sufficient conditions which are converted into linear matrix inequality (LMI) form for applying convex optimization algorithm. Via solving the sufficient conditions, the state feedback controller can be established such that the asymptotical stability and mixed performance of the system are achieved in the mean square. Finally, the synchronous generator system is used to verify the effectiveness and applicability of the proposed design method. Cheung-Chieh Ku, Chih-Peng Lu, and Min-Ta Li Copyright © 2015 Cheung-Chieh Ku et al. All rights reserved. Wavelet Network Model Based on Multiple Criteria Decision Making for Forecasting Temperature Time Series Wed, 28 Jan 2015 12:36:23 +0000 http://www.hindawi.com/journals/mpe/2015/385876/ Due to nonlinear and multiscale characteristics of temperature time series, a new model called wavelet network model based on multiple criteria decision making (WNMCDM) has been proposed, which combines the advantage of wavelet analysis, multiple criteria decision making, and artificial neural network. One case for forecasting extreme monthly maximum temperature of Miyun Reservoir has been conducted to examine the performance of WNMCDM model. Compared with nearest neighbor bootstrapping regression (NNBR), the probability of relative error smaller than 10% increases from 65.79% to 84.21% (forecast period ) and from 51.35% to 91.89% by WNMCDM model. Similarly, the probability of relative error smaller than 20% increases from 84.21% to 97.37% and from 81.08% to 91.89% by WNMCDM model. Therefore, WNMCDM model is superior to NNBR model in forecasting temperature time series. Jian Zhang, Xiao-hua Yang, and Xiao-juan Chen Copyright © 2015 Jian Zhang et al. All rights reserved. Entropy Measures for Interval-Valued Intuitionistic Fuzzy Sets and Their Application in Group Decision-Making Wed, 28 Jan 2015 11:00:36 +0000 http://www.hindawi.com/journals/mpe/2015/563745/ Entropy measure is an important topic in the fuzzy set theory and has been investigated by many researchers from different points of view. In this paper, two new entropy measures based on the cosine function are proposed for intuitionistic fuzzy sets and interval-valued intuitionistic fuzzy sets. According to the features of the cosine function, the general forms of these two kinds of entropy measures are presented. Compared with the existing ones, the proposed entropy measures can overcome some shortcomings and be used to measure both fuzziness and intuitionism of these two fuzzy sets; as a result, the uncertain information of which can be described more sufficiently. These entropy measures have been applied to assess the experts’ weights and to solve multicriteria fuzzy group decision-making problems. Cuiping Wei and Yuzhong Zhang Copyright © 2015 Cuiping Wei and Yuzhong Zhang. All rights reserved. Retracted: Information Fields Navigation with Piece-Wise Polynomial Approximation for High-Performance OFDM in WSNs Tue, 27 Jan 2015 11:18:05 +0000 http://www.hindawi.com/journals/mpe/2015/146903/ Mathematical Problems in Engineering Copyright © 2015 Mathematical Problems in Engineering. All rights reserved. Measuring Loss-Based Process Capability Index and Its Generation with Fuzzy Numbers Tue, 27 Jan 2015 07:53:26 +0000 http://www.hindawi.com/journals/mpe/2015/217406/ Loss-based process capability indices are appropriate and realistic tools in order to measure the process capability. Among them, index and its generation are well-known loss-based process capability indices, whose concepts are based on the worth (the opposite concept of loss). Sometimes, in order to calculate and there are some uncertainties in observations, so fuzzy logic can be employed to manage the uncertainties. This paper investigates fuzzification of process capability index and its generation . In order to find the membership function of process capability indices and , the α-cuts of fuzzy observation were employed. Then with an example of fuzzy process capability index, and were calculated and compared. Results showed that fuzzy was more sensitive compared with and was increased while the target departs (asymmetric tolerance). This example also showed that, with departure from the target, variation of fuzzy and consequently its fuzziness were increased. Mohammad Abdolshah Copyright © 2015 Mohammad Abdolshah. All rights reserved. A Hybrid Approach to the Optimization of Multiechelon Systems Mon, 26 Jan 2015 13:01:41 +0000 http://www.hindawi.com/journals/mpe/2015/925675/ In freight transportation there are two main distribution strategies: direct shipping and multiechelon distribution. In the direct shipping, vehicles, starting from a depot, bring their freight directly to the destination, while in the multiechelon systems, freight is delivered from the depot to the customers through an intermediate points. Multiechelon systems are particularly useful for logistic issues in a competitive environment. The paper presents a concept and application of a hybrid approach to modeling and optimization of the Multi-Echelon Capacitated Vehicle Routing Problem. Two ways of mathematical programming (MP) and constraint logic programming (CLP) are integrated in one environment. The strengths of MP and CLP in which constraints are treated in a different way and different methods are implemented and combined to use the strengths of both. The proposed approach is particularly important for the discrete decision models with an objective function and many discrete decision variables added up in multiple constraints. An implementation of hybrid approach in the system using Eplex library is presented. The Two-Echelon Capacitated Vehicle Routing Problem (2E-CVRP) and its variants are shown as an illustrative example of the hybrid approach. The presented hybrid approach will be compared with classical mathematical programming on the same benchmark data sets. Paweł Sitek and Jarosław Wikarek Copyright © 2015 Paweł Sitek and Jarosław Wikarek. All rights reserved. PCNN-Based Image Fusion in Compressed Domain Mon, 26 Jan 2015 12:30:12 +0000 http://www.hindawi.com/journals/mpe/2015/536215/ This paper addresses a novel method of image fusion problem for different application scenarios, employing compressive sensing (CS) as the image sparse representation method and pulse-coupled neural network (PCNN) as the fusion rule. Firstly, source images are compressed through scrambled block Hadamard ensemble (SBHE) for its compression capability and computational simplicity on the sensor side. Local standard variance is input to motivate PCNN and coefficients with large firing times are selected as the fusion coefficients in compressed domain. Fusion coefficients are smoothed by sliding window in order to avoid blocking effect. Experimental results demonstrate that the proposed fusion method outperforms other fusion methods in compressed domain and is effective and adaptive in different image fusion applications. Yang Chen and Zheng Qin Copyright © 2015 Yang Chen and Zheng Qin. All rights reserved. Impact of Heterogeneous Consumers on Pricing Decisions under Dual-Channel Competition Mon, 26 Jan 2015 06:43:30 +0000 http://www.hindawi.com/journals/mpe/2015/584084/ This paper studies impact of heterogeneous consumer behavior on optimal pricing decisions under dual channel supply chain competition, which consists of one manufacturer and one retailer. The manufacturer is market leader with two sales channels: one is direct channel facing consumers directly and the other is indirect channel facing the retailer. Consumers decide whether to buy and from which channel to buy products. Purchasing decisions are based on considerations of prices posted on different channels, preference or loyalty to specific channels, and degree of rationality in decision-making process. Due to the complexity of heterogeneous consumer decision behavior, traditional mathematical analysis to the pricing problem becomes quite challenging. An agent-based modeling and simulation approach is then proposed and implemented. Simulation results reveal that consumer behavior influences both prices and profits. When consumers are increasingly loyal to the retailing channel, the retailer can make a higher selling price and more benefits. On the other hand, when consumers are increasingly loyal to the direct channel, the number of purchases from the direct channel increases and the manufacturer is better off. It is also interesting to note that as rationality level increases, selling prices for both channels slightly decrease. Ying Wei and Feng Li Copyright © 2015 Ying Wei and Feng Li. All rights reserved. The Newsvendor Problem with Different Delivery Time, Resalable Returns, and an Additional Order Mon, 26 Jan 2015 06:17:55 +0000 http://www.hindawi.com/journals/mpe/2015/505268/ In a B2C scenario, the retailer is confronted with two kinds of demand. One requires an immediate delivery after placing an order, while the other prefers a delayed shipment due to some personal reasons. Considering demands for different delivery time, we explore a newsvendor model with resalable returns and an additional order to optimize the procurement decision under a stochastic demand distribution. The impact of the proportion of the instant delivery needs and the return rate on the order quantity and the expected profit is illustrated through numerical tests. It is shown that the expected profit decreases as the ratios of immediate delivery needs and returned products increase. Besides, if the sum of the percentage of the instant delivery needs and the return rate is less than 1, the expected profit is always greater than the result if the sum of them is equal to or greater than 1. Management implications are also discussed. Fue Zeng, Yunjia Chi, and Jinhui Zheng Copyright © 2015 Fue Zeng et al. All rights reserved. Finite-Time Spacecraft’s Soft Landing on Asteroids Using PD and Nonsingular Terminal Sliding Mode Control Thu, 22 Jan 2015 14:24:20 +0000 http://www.hindawi.com/journals/mpe/2015/510618/ This paper presents a continuous control law of probe, which consists of PD (proportional-derivative) controller and nonsingular terminal sliding mode controller for probe descending and landing phases, respectively, in the case of the asteroid irregular shape and low gravity. The probe dynamic model is deduced in the landing site coordinate system firstly. Then the reference trajectory based on optimal polynomial in open-loop state is designed, with the suboptimal fuel consumption. Taking into account different characteristics of phases, PD controller and nonsingular terminal sliding mode controller can be employed in the descending phase and the landing phase, respectively, to track the designed reference trajectory. The controller which used the corresponding control methods can meet the motion characteristics and requirements of each stage. Finally simulation experiments are carried out to demonstrate the effectiveness of the proposed method, which can ensure the safe landing of probe and achieve continuous control. Keping Liu, Fengxia Liu, Shenquan Wang, and Yuanchun Li Copyright © 2015 Keping Liu et al. All rights reserved. Customized Transportation, Equity Participation, and Cooperation Performance within Logistics Supply Chains Thu, 22 Jan 2015 14:23:31 +0000 http://www.hindawi.com/journals/mpe/2015/792792/ Customized transportation has received growing concerns by researchers and practitioners in recent years. Despite the fact that one consignor often holds partial ownership of its carrier within a supply chain, the existing interpretations behind them remain relatively unexplored. Based on the game models, we find that a simple take-or-pay contract is not likely to solve the low-efficient customized production problem, and equity participation mechanism plus simple contract may improve the cooperation performance of customized transportation. In the case of the owner-managed carrier, only when purchasing at par can it be ensured to obtain the socially optimal customization investment, but when purchasing at premium or discount, the optimal partial ownership selected by consignor cannot motivate the carrier to make the most efficient customization investment. With the optimal solutions, we also provide a theoretic foundation for calculating the optimal partial ownership and for interpreting why the interfirm share-holding ratios of the member-firms within the familial-type logistic supply chains are much larger than the ratios within the public-type logistic supply chains. Finally, our results show that the familial-type logistic supply chains may choose more efficient customized production level than public-type logistic supply chains. Xudong Lin, Lijun Ma, and Zunxin Zheng Copyright © 2015 Xudong Lin et al. All rights reserved. Fusion Estimation Algorithm with Uncertain Noises and Its Application in Navigation System Thu, 22 Jan 2015 14:21:15 +0000 http://www.hindawi.com/journals/mpe/2015/218561/ In order to solve the problem of uncertain noise during the measurement of actual system, an extended Kalman filter fusion estimation method based on multisensor fusion algorithm with uncertain effects is proposed. Then the equivalent measurement and the corresponding error matrix are estimated by the proposed uncertain fusing algorithm. Submit the results into the system model for filter processing and the optimal estimation can be obtained by the filtering method. Finally, the algorithm is verified in the GPS/INS navigation system which shows that the fusion result with uncertainty effect is much better than then fusion result with independent noise due to the consideration of correlated noise and uncertain effects for the actual system. This is also validates the effectiveness and practicality of the proposed algorithm. Zhiping Ren and Huili Wang Copyright © 2015 Zhiping Ren and Huili Wang. All rights reserved. Dynamical Analysis of a Viral Infection Model with Delays in Computer Networks Thu, 22 Jan 2015 14:15:50 +0000 http://www.hindawi.com/journals/mpe/2015/280856/ This paper is devoted to the study of an SIRS computer virus propagation model with two delays and multistate antivirus measures. We demonstrate that the system loses its stability and a Hopf bifurcation occurs when the delay passes through the corresponding critical value by choosing the possible combination of the two delays as the bifurcation parameter. Moreover, the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions are determined by means of the center manifold theorem and the normal form theory. Finally, some numerical simulations are performed to illustrate the obtained results. Zizhen Zhang and Huizhong Yang Copyright © 2015 Zizhen Zhang and Huizhong Yang. All rights reserved. Adaptive Synchronization Control of Multiple Vessels with Switching Communication Topologies and Time Delay Thu, 22 Jan 2015 14:02:14 +0000 http://www.hindawi.com/journals/mpe/2015/143597/ Recently, synchronization movement control of multiple vessels has been studied broadly. In most of the studies, the communication network among vessels is considered to be fixed and the time delay is often ignored. However, the communication network among vessels maybe vary because of switching of different tasks, and the time delay is necessary to be considered when the communication network is unreliable. In this paper, the synchronization movement of multiple vessels with switching connected communication topologies is studied, and an adaptive synchronization control algorithm that is based on backstepping sliding mode control is proposed. The control algorithm is achieved by defining cross coupling error which is combination of the trajectory tracking error and velocity tracking error. And an adaptive control term is used to estimate the external disturbances, so that the unknown external disturbances can be compensated. Furthermore, the robustness of the control law to time-varying time delay is also discussed. At last, some simulations are carried out to validate the effectiveness of the proposed synchronization control algorithm. Fuguang Ding, Yanqin Ma, Yuanwei Zhou, and Jiangjun Li Copyright © 2015 Fuguang Ding et al. All rights reserved. A Problem-Reduction Evolutionary Algorithm for Solving the Capacitated Vehicle Routing Problem Thu, 22 Jan 2015 13:29:49 +0000 http://www.hindawi.com/journals/mpe/2015/165476/ Assessment of the components of a solution helps provide useful information for an optimization problem. This paper presents a new population-based problem-reduction evolutionary algorithm (PREA) based on the solution components assessment. An individual solution is regarded as being constructed by basic elements, and the concept of acceptability is introduced to evaluate them. The PREA consists of a searching phase and an evaluation phase. The acceptability of basic elements is calculated in the evaluation phase and passed to the searching phase. In the searching phase, for each individual solution, the original optimization problem is reduced to a new smaller-size problem. With the evolution of the algorithm, the number of common basic elements in the population increases until all individual solutions are exactly the same which is supposed to be the near-optimal solution of the optimization problem. The new algorithm is applied to a large variety of capacitated vehicle routing problems (CVRP) with customers up to nearly 500. Experimental results show that the proposed algorithm has the advantages of fast convergence and robustness in solution quality over the comparative algorithms. Wanfeng Liu and Xia Li Copyright © 2015 Wanfeng Liu and Xia Li. All rights reserved. Dynamic Energy Storage Control for Reducing Electricity Cost in Data Centers Thu, 22 Jan 2015 13:12:08 +0000 http://www.hindawi.com/journals/mpe/2015/380926/ As the scale of the data centers increases, electricity cost is becoming the fastest-growing element in their operation costs. In this paper, we investigate the electricity cost reduction opportunities utilizing energy storage facilities in data centers used as uninterrupted power supply units (UPS). Its basic idea is to combine the temporal diversity of electricity price and the energy storage to conceive a strategy for reducing the electricity cost. The electricity cost minimization is formulated in the framework of finite state-action discounted cost Markov decision process (MDP). We apply -Learning algorithm to solve the MDP optimization problem and derive a dynamic energy storage control strategy, which does not require any priori information on the Markov process. In order to address the slow-convergence problem of the -Learning based algorithm, we introduce a Speedy -Learning algorithm. We further discuss the offline optimization problem and obtain the optimal offline solution as the lower bound on the performance of the online and learning theoretic problem. Finally, we evaluate the performance of the proposed scheme by using real workload traces and electricity price data sets. The experimental results show the effectiveness of the proposed scheme. Shuben Zhang, Jian Yang, Youkang Shi, Xiaomin Wu, and Yongyi Ran Copyright © 2015 Shuben Zhang et al. All rights reserved. Optimal Ordering and Disposing Policies in the Presence of an Overconfident Retailer: A Stackelberg Game Thu, 22 Jan 2015 13:04:54 +0000 http://www.hindawi.com/journals/mpe/2015/385289/ This paper investigates the impact of the retailer’s overconfident behavior on supply chain performance. We start with a basic model on the rational newsvendor model and investigate the retailer’s optimal ordering decision and expected profit. Next, we extend the basic model and introduce an overconfident retailer. We find that the retailer’s overconfident behavior does not necessarily damage the supply chain compared with the basic model when the overconfident level does not exceed a threshold. We also design the cooperation and buyback mechanism and conduct numerical analysis to compare the manufacturer’s and retailer’s expected profits and real profits with those in the basic newsvendor model. It can achieve Pareto improvement in the supply chain when the overconfident level is low. When the retailer’s overconfident level exceeds a threshold, the retailer’s ordering decision cannot make the whole supply chain sustainable development. Zhigang Wang, Zhenchao Zhang, Chunfa Li, Lei Xu, and Chang You Copyright © 2015 Zhigang Wang et al. All rights reserved. Research on Fuzzy Immune Self-Adaptive PID Algorithm Based on New Smith Predictor for Networked Control System Thu, 22 Jan 2015 12:48:21 +0000 http://www.hindawi.com/journals/mpe/2015/343416/ We first analyze the effect of network-induced delay on the stability of networked control systems (NCSs). Then, aiming at stochastic characteristics of the time delay, we introduce a new Smith predictor to remove the exponential function with the time delay in the closed-loop characteristic equation of the NCS. Furthermore, we combine the fuzzy PID algorithm with the fuzzy immune control algorithm and present a fuzzy immune self-adaptive PID algorithm to compensate the influence of the model deviation of the controlled object. At last, a kind of fuzzy immune self-adaptive PID algorithm based on new Smith predictor is presented to apply to the NCS. The simulation research on a DC motor is given to show the effectiveness of the proposed algorithm. Haitao Zhang, Jinbo Hu, and Wenshao Bu Copyright © 2015 Haitao Zhang et al. All rights reserved. A Hybrid MCDM Model for New Product Development: Applied on the Taiwanese LiFePO4 Industry Thu, 22 Jan 2015 12:47:51 +0000 http://www.hindawi.com/journals/mpe/2015/462929/ Recent years, since problems with respect to atmosphere pollution hasten countries to accentuate green-related policy regarding the sustainable energy, the lithium-iron phosphate (LiFePO4) battery has been appealed to the world. However, more and more firms invest the LiFePO4 batteries production that has launched a fierce competition. Successful new product development (NPD) processes have been considered the key for LiFePO4 battery firms to increase their competitive advantage. Firms must make correct decision faster due to the rapid development of technology and the decreasing product life cycle. This study proposes a hybrid multiple criteria decision making (MCDM) model based on the literature review and consultation with the experts, interpretive structural modeling (ISM), and fuzzy analytic network process (FANP) for evaluating various strategies for NPD. First of all, reviewing of literature and meeting with the experts are used to screen factors and select the criteria. Then, an ISM is managed to determine the feedback and interdependency of those factors in a network. Finally, a fuzzy theory is applied to resolve the linguistic hedges and an ANP is adopted to obtain the weights of all the factors. A case study is undertaken to validate the model in a Taiwanese company that provides professional packing and design for lithium-iron phosphate battery. Wen-Chin Chen, Li-Yi Wang, and Meng-Chen Lin Copyright © 2015 Wen-Chin Chen et al. All rights reserved. Dynamic Analysis and Control of an Automatic Transmission for Start-Stop Function and Efficiency Improvement Thu, 22 Jan 2015 12:44:52 +0000 http://www.hindawi.com/journals/mpe/2015/209276/ An electric oil pump (EOP) was integrated into the hydraulic system and an automatic transmission (AT) mechanical oil pump (MOP) was downsized. These processes were performed to combine a start-stop function with the AT and further improve the transmission efficiency. Furthermore, this study established a dynamics model of power loss and leakage of an 8-speed AT; a flow-based control algorithm of the EOP was then developed to realize the start-stop function and support the MOP to meet the flow requirement of the system. Based on a driving simulation method, sizes of the MOP and EOP that ensured optimal fuel economy were selected. A control strategy for the starting clutch was also developed to minimize the starting delay of the test vehicle. A test environment on a rig and prototype vehicle was established to verify the feasibility of the proposed control strategies. The test results indicated that the transmission functioned favorably with the novel two-pump system presented, and a quick and smooth starting performance was achieved when the engine was restarted. The findings in this study are extremely valuable for forward designs of an AT for realizing start-stop function and improving efficiency. Yang Liu, Shuhan Wang, Peng Dong, and Xiangyang Xu Copyright © 2015 Yang Liu et al. All rights reserved. A New Globally Exponential Stability Criterion for Neural Networks with Discrete and Distributed Delays Thu, 22 Jan 2015 12:32:55 +0000 http://www.hindawi.com/journals/mpe/2015/807150/ This paper concerns the problem of the globally exponential stability of neural networks with discrete and distributed delays. A novel criterion for the globally exponential stability of neural networks is derived by employing the Lyapunov stability theory, homomorphic mapping theory, and matrix theory. The proposed result improves the previously reported global stability results. Finally, two illustrative numerical examples are given to show the effectiveness of our results. Hao Chen, Shouming Zhong, and Jinxiang Yang Copyright © 2015 Hao Chen et al. All rights reserved. Modeling and Coordinated Control Strategy of Large Scale Grid-Connected Wind/Photovoltaic/Energy Storage Hybrid Energy Conversion System Thu, 22 Jan 2015 12:28:17 +0000 http://www.hindawi.com/journals/mpe/2015/682321/ An AC-linked large scale wind/photovoltaic (PV)/energy storage (ES) hybrid energy conversion system for grid-connected application was proposed in this paper. Wind energy conversion system (WECS) and PV generation system are the primary power sources of the hybrid system. The ES system, including battery and fuel cell (FC), is used as a backup and a power regulation unit to ensure continuous power supply and to take care of the intermittent nature of wind and photovoltaic resources. Static synchronous compensator (STATCOM) is employed to support the AC-linked bus voltage and improve low voltage ride through (LVRT) capability of the proposed system. An overall power coordinated control strategy is designed to manage real-power and reactive-power flows among the different energy sources, the storage unit, and the STATCOM system in the hybrid system. A simulation case study carried out on Western System Coordinating Council (WSCC) 3-machine 9-bus test system for the large scale hybrid energy conversion system has been developed using the DIgSILENT/Power Factory software platform. The hybrid system performance under different scenarios has been verified by simulation studies using practical load demand profiles and real weather data. Lingguo Kong, Guowei Cai, Sidney Xue, and Shaohua Li Copyright © 2015 Lingguo Kong et al. All rights reserved. Screw Theory Based Singularity Analysis of Lower-Mobility Parallel Robots considering the Motion/Force Transmissibility and Constrainability Thu, 22 Jan 2015 12:28:00 +0000 http://www.hindawi.com/journals/mpe/2015/487956/ Singularity is an inherent characteristic of parallel robots and is also a typical mathematical problem in engineering application. In general, to identify singularity configuration, the singular solution in mathematics should be derived. This work introduces an alternative approach to the singularity identification of lower-mobility parallel robots considering the motion/force transmissibility and constrainability. The theory of screws is used as the mathematic tool to define the transmission and constraint indices of parallel robots. The singularity is hereby classified into four types concerning both input and output members of a parallel robot, that is, input transmission singularity, output transmission singularity, input constraint singularity, and output constraint singularity. Furthermore, we take several typical parallel robots as examples to illustrate the process of singularity analysis. Particularly, the input and output constraint singularities which are firstly proposed in this work are depicted in detail. The results demonstrate that the method can not only identify all possible singular configurations, but also explain their physical meanings. Therefore, the proposed approach is proved to be comprehensible and effective in solving singularity problems in parallel mechanisms. Xiang Chen, Xin-Jun Liu, and Fugui Xie Copyright © 2015 Xiang Chen et al. All rights reserved. Stochastic Linear Quadratic Optimal Control with Indefinite Control Weights and Constraint for Discrete-Time Systems Thu, 22 Jan 2015 12:01:06 +0000 http://www.hindawi.com/journals/mpe/2015/476545/ The Karush-Kuhn-Tucker (KKT) theorem is used to study stochastic linear quadratic optimal control with terminal constraint for discrete-time systems, allowing the control weighting matrices in the cost to be indefinite. A generalized difference Riccati equation is derived, which is different from those without constraint case. It is proved that the well-posedness and the attainability of stochastic linear quadratic optimal control problem are equivalent. Moreover, an optimal control can be denoted by the solution of the generalized difference Riccati equation. Xikui Liu, Guiling Li, and Yan Li Copyright © 2015 Xikui Liu et al. All rights reserved. Two-Echelon Inventory Optimization for Imperfect Production System under Quality Competition Environment Thu, 22 Jan 2015 11:54:39 +0000 http://www.hindawi.com/journals/mpe/2015/326919/ This paper develops two integrated optimization models of two-echelon inventory for imperfect production system under quality competition environment, in which the vendor’s production process is assumed to be imperfect, and JIT delivery policy is implemented to ship product from the vendor to the buyer. In the first model, product defect rate is fixed, and, in the second model, quality improvement investment is function of defect rate. The optimal policies of ordering quantity of buyer and shipment from vendor to buyer are obtained to minimize the expected annual total cost of vendor and buyer. Numerical examples are used to demonstrate the effectiveness and feasibility of the models. Sensitivity analysis is taken to analyze the impact of demand, production rate, and defect rate on the solution. Implications are highlighted in that both the vendor and the buyer can benefit from the vendor’s investing in quality improvement. Xinfeng Lai, Zhixiang Chen, Bibhas C. Giri, and Chun-Hung Chiu Copyright © 2015 Xinfeng Lai et al. All rights reserved. Multiple Objective Fuzzy Sourcing Problem with Multiple Items in Discount Environments Thu, 22 Jan 2015 11:38:12 +0000 http://www.hindawi.com/journals/mpe/2015/497826/ The selection of proper supply sources plays a vital role to maintain companies’ competitiveness. In this study a multiple criteria fuzzy sourcing problem with multiple items in discount environment is considered as a multiple objective mixed integer linear programming problem. Fuzzy parameters are demand level and/or aspiration levels of objectives. Three objective functions are minimization of the total production and ordering costs, the total number of rejected units, and the total number of late delivered units, respectively. The model is developed for the all-units discount scheme. For the incremental discount and volume discount environment, modification requirements of the model are mentioned. The previously proposed interactive fuzzy approach combined with three fuzzy mathematical models is employed to obtain most satisfactory solution which is also a nondominated one. This study provides a realistic mathematical model and promising solution strategy to multiple item-single period sourcing problem in discount environment. Consideration of fuzziness makes the obtained nondominated solution implementable for the real cases. Feyzan Arikan Copyright © 2015 Feyzan Arikan. All rights reserved. Optimal Control Algorithm of Constrained Fuzzy System Integrating Sliding Mode Control and Model Predictive Control Thu, 22 Jan 2015 09:12:07 +0000 http://www.hindawi.com/journals/mpe/2015/897853/ The sliding mode control and the model predictive control are connected by the value function of the optimal control problem for constrained fuzzy system. New conditions for the existence and stability of a sliding mode are proposed. Those conditions are more general conditions for the existence and stability of a sliding mode. When it is applied to the controller design, the design procedures are different from other sliding mode control (SMC) methods in that only the decay rate of the sliding mode motion is specified. The obtained controllers are state-feedback model predictive control (MPC) and also SMC. From the viewpoint of SMC, sliding mode surface does not need to be specified previously and the sliding mode reaching conditions are not necessary in the controller design. From the viewpoint of MPC, the finite time horizon is extended to the infinite time horizon. The difference with other MPC schemes is that the dependence on the feasibility of the initial point is canceled and the control schemes can be implemented in real time. Pseudosliding mode model predictive controllers are also provided. Closed loop systems are proven to be asymptotically stable. Simulation examples are provided to demonstrate proposed methods. Chonghui Song Copyright © 2015 Chonghui Song. All rights reserved. Energy-Efficient Relay Selection Scheme for Physical Layer Security in Cognitive Radio Networks Thu, 22 Jan 2015 06:45:10 +0000 http://www.hindawi.com/journals/mpe/2015/587104/ Security is a critical issue in cognitive radio (CR) relay networks. Most previous work concentrates on maximizing secrecy capacity (SC) as a criterion to guarantee the security requirements in CR relay networks. However, under the requirement of “green” radio communication, the energy consumption is largely ignored. This paper proposes a relay selection scheme which jointly considers the best relay selection and dynamic power allocation in order to maximize SC and to minimize energy consumption. Moreover, we consider finite-state Markov channels and residual relay energy in the relay selection and power allocation process. Specifically, the formulation of the proposed relay selection and power allocation scheme is based on the restless bandit problem, which is solved by the primal-dual index heuristic algorithm. Additionally, the obtained optimal relay selection policy has an indexability property that dramatically reduces the computational complexity. Numerical results are presented to show that our proposed scheme has the maximum SC and minimum energy consumption compared to the existing ones. Li Jiang and Hui Tian Copyright © 2015 Li Jiang and Hui Tian. All rights reserved. Fat Tail Model for Simulating Test Systems in Multiperiod Unit Commitment Wed, 21 Jan 2015 14:30:33 +0000 http://www.hindawi.com/journals/mpe/2015/738215/ This paper describes the use of Chambers-Mallows-Stuck method for simulating stable random variables in the generation of test systems for economic analysis in power systems. A study that focused on generating test electrical systems through fat tail model for unit commitment problem in electrical power systems is presented. Usually, the instances of test systems in Unit Commitment are generated using normal distribution, but in this work, simulations data are based on a new method. For simulating, we used three original systems to obtain the demand behavior and thermal production costs. The estimation of stable parameters for the simulation of stable random variables was based on three generally accepted methods: (a) regression, (b) quantiles, and (c) maximum likelihood, choosing one that has the best fit of the tails of the distribution. Numerical results illustrate the applicability of the proposed method by solving several unit commitment problems. J. A. Marmolejo and R. Rodriguez Copyright © 2015 J. A. Marmolejo and R. Rodriguez. All rights reserved.