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For optimizing the operation plan when strike packages attack multiple targets, this article suggests a new mathematical model and a parallel hybrid genetic algorithm (PHGA) as a solution methodology. In the model, a package can assault multiple targets on a sortie and permitted the use of mixed munitions for a target. Furthermore, because the survival probability of a package depends on a flight route, it is formulated as a mixed integer programming which is synthesized the models for vehicle routing and weapon-target assignment. The hybrid strategy of the solution method (PHGA) is also implemented by the separation of functions of a GA and an exact solution method using ILOG CPLEX. The GA searches the flight routes of packages, and CPLEX assigns the munitions of a package to the targets on its way. The parallelism enhances the likelihood seeking the optimal solution via the collaboration among the HGAs.
The fundamental reason of noise in gear system is transmission error due to deflection of gear teeth. The vibration from transmission error moves to shaft and bearing. This vibration generates bearing force which exite gear box and finally radiate as noise outside. Therefore, studying transmission error is the most important to predict which is the fundamental reason of gear noise. In this paper, transmission error due to teeth deflection was predicted and shaft torsion was not considered in order to find only teeth deflection. For this reason, shaft was modeled as rigid, and only gear pair was modeled as flexible body. transmission error was predicted by Abaqus, FEA program, and this was compared for Spur and Helical type.
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The topic of this study is the field of humanitarian logistics for disaster response. Many existing studies have revealed that compliance with the golden time in response to a disaster determines the success or failure of relief activities, and logistics costs account for 80% of the disaster response cost. Besides, the agility, responsiveness, and effectiveness of the humanitarian logistics system are emphasized in consideration of the disaster situation’s characteristics, such as the urgency of life-saving and rapid environmental changes. In other words, they emphasize the importance of logistics activities in disaster response, which includes the effective and efficient distribution of relief supplies. This study proposes a mathematical model for establishing a transport plan to distribute relief supplies in a disaster situation. To determine vehicles’ route and the amount of relief for cities suffering a disaster, it mainly considers the urgency, effectiveness (restoration rate), and uncertainty in the logistics system. The model is initially developed as a mixed-integer nonlinear programming (MINLP) model containing some nonlinear functions and transform into a Mixed-integer linear programming (MILP) model using a logarithmic transformation and piecewise linear approximation method. Furthermore, a minimax problem is suggested to search for breakpoints and slopes to define a piecewise linear function that minimizes the linear approximation error. A numerical experiment is performed to verify the MILP model, and linear approximation error is also analyzed in the experiment.
In this article, a stochastic model is suggested to analyze the performance of a system in which territorially distributed subsystems share their capabilities. Each subsystem is considered as an M/M/K/K queueing model, and the stochastic model is formulated by structuring the transition rate matrices (TRMs) of the subsystems according to a cooperative structure. In other words, the structuring rules for the TRMs are presented to describe various collaborative networks. Furthermore, through numerical experiments on some examples, the instances of the effectiveness analysis for capacity pooling systems with full/partial pooling strategies are presented, and the optimal resource allocation problem is reviewed by considering system performance and the cooperative cost of subsystems. The problems show the possibility that partial pooling strategy can substitute full pooling system through the optimal design of cooperative network including resource allocation.
Purpose: In this study, the lifetime distribution of a k-out-of- n system with heterogeneous components is suggested as Markov model, and the time-to-failure (TTF) distribution of each component is considered as phase-type distribution (PHD). Furthermore, based on the model, a redundancy allocation problem with a mix of components (RAPMC) is proposed. Methods: The lifetime distribution model for the system is formulated by the structured Markov chain. From the model, the various information on the system lifetime can be ascertained by the matrix-analytic (or-geometric) method. Conclusion: By the generalization of TTF distribution (PHD) and the consideration of heterogeneous components, the lifetime distribution model can delineate many real systems and be exploited for developing system operation policies such as preventive maintenance, warranty. Moreover, the effectiveness of the proposed RAPMC is verified by numerical experiments. That is, under the equivalent design conditions, it presented a system with higher reliability than RAP without component mixing (RAPCM).
The conventional transmission path analysis method has the advantage that it is possible to predict the excitation force and analyze the contribution according to the transmission path, so that the problem can be clearly identified. However, in order to avoid interference between transmission paths, it is required to separate the powertrain from the vehicle, which adds to the cost. In order to improve this, this study performed the prediction of the electric vehicle compressor excitation force using the blocked force TPA technique. This predicted blocking force can be used to predict the sound pressure inside the vehicle or design the compressor mount.
In this paper, the analysis of the contact stress in helical gear tooth flanks presents due to impact loading such as the sudden engagement and disengagement of gear. The stress analysis was implemented for different roll positions to find out the most critical roll angle and dynamic analysis is performed for this critical roll position to evaluate variation of stresses and tooth contact force with respect to time. Dynamic analysis was implemented by Implicit time integration method in Abaqus/Implicit. In order to make the accurate results, Analysis was conducted in very short interval based on time.
The transmission error in gear causes vibration in the gear system, which is transferred to the gear shaft and transferred to the bearing connected to the shaft. Throughout this process of transmission, vibration is amplified and eventually transferred to the housing of the gear system, which is released into the air by noise from the mechanical system. In this paper, we present predictions on analytical verification for bearing vibration reduction based on contact stiffness for the most widely used pair of spurs.
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신뢰도란 임의의 시스템이 주어진 환경 하에서 의도하는 기간 동안 의도한 목적의 기능을 정상적으로 발휘할 확률로 정의되며, 실제 산업현장에서 제품설계 시 중요한 척도로 고려되고 있다. 혼합 중복전략을 고려하는 신뢰도-중복 최적화 문제는 비용, 무게 등의 제약 내에서 시스템의 신뢰도를 최대화하는 대안부품, 중복설계 부품수, 그리고, 중복전략을 동시에 선택하는 문제이다. 기존 연구들은 Cold-standby 중복 k-out-of-n 서브시스템의 정확한 신뢰도 평가가 난해함에 따라 근사 신뢰도 모형을 적용하고 있다. 따라서 본 연구에서는 Cold-standby 중복이 적용되고, 고장감지기를 Imperfect S/W로 고려한 k-out-of-n 서브시스템의 정확한 신뢰도를 평가할 수 있는 연속시간 마코프체인(CTMC) 모형을 제안하였다. 또한, 수치실험을 통해 기존 연구의 근사 신뢰도 모형 사용에 유의하여야 함을 보였으며, CTMC 신뢰도 모형을 기반으로 RROP의 Benchmark 문제의 최적해를 제시하였다. The reliability is defined as a probability that a system will operate properly for a specified period of time under the design operating conditions without failure and it has been considered as one of the major design parameters in the field of industries. Reliability-Redundancy Optimization Problem(RROP) with choice of redundancy strategies involves selection of components with multiple choices, redundancy levels and strategies(active and cold standby) for maximizing system reliability with constraints such as cost. weight, etc. In existing studies. the approximated reliability stochastic model was used because it is hard to obtain the exact reliability for k-out-of-n subsystem designed by cold standby. Therefore, this paper suggests the Continuous Time Markov Chain(CTMC) model in order to calculate the exact reliability of k-out-of-n subsystem applied cold standby with imperfect switching. The error of approximate reliability stochastic model of existing studies is analyzed by numerical experiment and the result show that it should be carefully used. Also, the optimal solutions of benchmark problem for RROP is provided based on CTMC model is suggested in this study.