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排序方式: 共有437条查询结果,搜索用时 15 毫秒
1.
2.
Simultaneous solving of balancing and sequencing problems with station-dependent assembly times for mixed-model assembly lines 总被引:1,自引:0,他引:1
In spite of many studies, investigating balancing and sequencing problems in Mixed-Model Assembly Line (MMAL) individually, this paper solves them simultaneously aiming to minimize total utility work. A new Mixed-Integer Linear Programming (MILP) model is developed to provide the exact solution of the problem with station-dependent assembly times. Because of NP-hardness, a Simulated Annealing (SA) is applied and compared to the Co-evolutionary Genetic Algorithm (Co-GA) from the literature. To strengthen the search process, two main hypotheses, namely simultaneous search and feasible search, are developed contrasting Co-GA. Various parameters of SA are reviewed to calibrate the algorithm by means of Taguchi design of experiments. Numerical results statistically show the efficiency and effectiveness of the proposed SA in terms of both the quality of solution and the time of achieving the best solution. Finally, the contribution of each hypothesis in this superiority is analyzed. 相似文献
3.
Reserve estimation is a key to find the correct NPV in a mining project. The most important factor in reserve estimation is the metal price. Metal price fluctuations in recent years were exaggerated, and imposed a high degree of uncertainty to the re-serve estimation, and in consequence to the whole mine planning procedure. Real option approach is an efficient method of deci-sion making in the uncertain conditions. This approach has been used for evaluation of defined natural resources projects until now. This study considering the metal price uncertainty used real option approach to prepare a methodology for reserve estimation in open pit mines. This study was done on a copper cylindrical deposit, but the achieved methodology can be adjusted for all kinds of deposits. This methodology was comprehensively described through the examples in such a manner that can be used by the mine planners. 相似文献
4.
Mansoor Kazemimoghadam Afshin Pak Toraj Mohammadi 《Microporous and mesoporous materials》2004,70(1-3):127-134
In this research, dehydration of water/1-1-dimethylhydrazine (UDMH) mixtures by zeolite NaA and hydroxy sodalite membranes has been investigated. Support of these membranes has been tubular mullites that have been made by extruding a mixture of about 67–75% kaolin clay and 33–25% distilled water using an extruder. Zeolite NaA and hydroxy sodalite membranes have been coated on the external surface of the porous supports by the hydrothermal synthesis.
UDMH/water mixtures have been separated at ambient temperature and pressure by pervaporation (PV) using these zeolite membranes. These membranes showed very high selectivity of water for all UDMH mixtures. For the UDMH/water mixtures, separation factor as high as 10 000 has been obtained for UDMH feed concentration of 2%. Total mass fluxes of 1.05–0.2 kg/(m2 h) have been also obtained. 相似文献
5.
Fatemeh Ghods Hamed Yousefi Ali Mohammad Afshin Hemmatyar Ali Movaghar 《Computer Networks》2013,57(18):3812-3825
Data aggregation is a key, yet time-consuming functionality in wireless sensor networks (WSNs). Multi-channel design is a promising technique to alleviate interference as a primary reason for long latency of TDMA aggregation scheduling. Indeed, it provides more potential of parallel transmissions over different frequency channels, thus minimizing time latency. In this paper, we focus on designing a multi-channel minimum latency aggregation scheduling protocol, named MC-MLAS, using a new joint approach for tree construction, channel assignment, and transmission scheduling. To our best knowledge, this is the first work in the literature which combines orthogonal channels and partially overlapping channels to consider the total latency involved in data aggregation. Extensive simulations verify the superiority of MC-MLAS in WSNs. 相似文献
6.
Seong-Hwan Cho Afshin Karshenas Akhtarhusein A. Tayebali Murthy N. Guddati 《International Journal of Pavement Engineering》2017,18(12):1098-1110
The debonding distress in asphalt pavement structures is a critical problem that affects the performance of asphalt concrete pavements. It occurs at the layer interface due to the poor bond quality between adjacent asphalt concrete layers and/or when stresses at the layer interface exceed the strengths of the material at the interface. The debonding of the adjacent layers, especially the top surface layer of an asphalt pavement, is a contributing factor to the premature cracking of pavements. Hence, the debonding distress can lead to a reduction in the life of the pavement. This paper presents an analytical and experimental framework to evaluate the potential for debonding at the layer interface of asphalt concrete pavements. Computational analysis was performed to determine the critical stress and strain states in layered asphalt pavements under moving vehicle loads using the Layered ViscoElastic pavement analysis for Critical Distresses (LVECD) computer program developed at North Carolina State University. This computational analysis enables a greater understanding of the critical stress that is involved in debonding and the ways that such stress is affected by pavement design parameters and environmental conditions. In addition, a prediction model was developed that can determine the shear bond strength at the interface of asphalt concrete layers with different tack coat materials at various temperatures, loading rates and normal confining stresses. The systematic and mechanistic framework developed in this study employs the maximum shear ratio concept as a shear failure criterion and provides a tool to evaluate the effects of various loading, environmental and pavement factors on the debonding potential of asphalt pavements. The overall advantages of the mechanistic framework and approach using the LVECD analysis tool will help lead to better understanding of the debonding mechanism, proper selection of the tack coats, and economic benefit in highway pavement maintenance and rehabilitation costs. 相似文献
7.
Fatigue behaviour and modelling of talc‐filled and short glass fibre reinforced thermoplastics,including temperature and mean stress effects 下载免费PDF全文
Effects of temperature and mean stress on fatigue behaviour of talc‐filled polypropylene (PP‐T) and short glass fibre reinforced polypropylene (PP‐G), polyamide‐66 (PA66), and a blend of polyphenylene ether and polystyrene (PPE/PS) were investigated. Load‐controlled fatigue tests were conducted under positive stress ratios (R = 0.1 and 0.3) and at several temperatures (T = 23, 85 and 120 °C). Larson–Miller parameter was used and a shift factor of Arrhenius type was developed to correlate fatigue data at various temperatures. Effect of mean stress on fatigue life was significant for some of the studied materials; however, for the PPE/PS blend no effect of mean stress was observed. Modified Goodman and Walker mean stress equations were evaluated for their ability to correlate mean stress data. A general fatigue life prediction model was also used to account for the effects of mean stress, temperature, anisotropy and frequency. 相似文献
8.
Spillways are hydraulic structures which transfer water to the downstream. Stepped spillways areseriously attended to, since they are highly efficient regarding energy dissipation. In this study, the flow pattern over stepped spillways was simulated with five different pool configurations. The VOF method was used to simulate the flow free surface, and K??(RNG) was employed to model turbulence. The results obtained fromthe numerical model were fairly consistent with the experimental results. The results demonstrated that theflow velocity and the residual head showed significant differences in the spillway width with regard to different pool configurations. The pool configuration in which the pools were installed as staggered configuration of flat and pooled steps showed the least residual head at the downstream and as a result the greatest energy dissipation. 相似文献
9.
J. Behnamian M. Zandieh S. M. T. Fatemi Ghomi 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2011,15(7):1313-1331
In the literature of multi-objective problem, there are different algorithms to solve different optimization problems. This
paper presents a min–max multi-objective procedure for a dual-objective, namely make span, and sum of the earliness and tardiness
of jobs in due window machine scheduling problems, simultaneously. In formulation of min–max method when this method is combined
with the weighting method, the decision maker can have the flexibility of mixed use of weights and distance parameter to yield
a set of Pareto-efficient solutions. This research extends the new hybrid metaheuristic (HMH) to solve parallel machines scheduling
problems with sequence-dependent setup time that comprises three components: an initial population generation method based
on an ant colony optimization (ACO), a simulated annealing (SA) as an evolutionary algorithm employs certain probability to
avoid becoming trapped in a local optimum, and a variable neighborhood search (VNS) which involves three local search procedures
to improve the population. In addition, two VNS-based HMHs, which are a combination of two methods, SA/VNS and ACO/VNS, are
also proposed to solve the addressed scheduling problems. A design of experiments approach is employed to calibrate the parameters.
The non-dominated sets obtained from HMH and two best existing bi-criteria scheduling algorithms are compared in terms of
various indices and the computational results show that the proposed algorithm is capable of producing a number of high-quality
Pareto optimal scheduling plans. Aside, an extensive computational experience is carried out to analyze the different parameters
of the algorithm. 相似文献
10.
This paper investigates scheduling job shop problems with sequence-dependent setup times under minimization of makespan. We develop an effective metaheuristic, simulated annealing with novel operators, to potentially solve the problem. Simulated annealing is a well-recognized algorithm and historically classified as a local-search-based metaheuristic. The performance of simulated annealing critically depends on its operators and parameters, in particular, its neighborhood search structure. In this paper, we propose an effective neighborhood search structure based on insertion neighborhoods as well as analyzing the behavior of simulated annealing with different types of operators and parameters by the means of Taguchi method. An experiment based on Taillard benchmark is conducted to evaluate the proposed algorithm against some effective algorithms existing in the literature. The results show that the proposed algorithm outperforms the other algorithms. 相似文献