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排序方式: 共有2681条查询结果,搜索用时 234 毫秒
991.
Majid Vaseghi Ali Karimi Taheri Hyoung Seop Kim 《Metals and Materials International》2010,16(3):363-369
In the present study, the plastic deformation and dynamic strain ageing behavior of Al-6082 (Al-Mg-Si) alloy treated with
elevated temperature equal channel angular pressing (ECAP) were investigated using upper bound analyses. Tensile tests were
carried out over wide ranges of temperature and strain rate in order to evaluate the dynamic ageing conditions. ECAP processing
was then experimentally performed at temperatures from room temperature up to 200 °C under various strain rates ranging between
10−4s−1 and 10−1s−1. The upper bound analysis solutions and the experimental results are comparable. A theoretical dynamic ageing region was
found to be in the temperature range of 90 °C to 260 °C, which is in agreement with the experimental observations in the temperature
range of 75 °C to 175 °C. 相似文献
992.
We present a heuristic approach to solve a general framework of serial–parallel redundancy problem where the reliability of the system is maximized subject to some general linear constraints. The complexity of the redundancy problem is generally considered to be NP-Hard and the optimal solution is not normally available. Therefore, to evaluate the performance of the proposed method, a hybrid genetic algorithm is also implemented whose parameters are calibrated via Taguchi's robust design method. Then, various test problems are solved and the computational results indicate that the proposed heuristic approach could provide us some promising reliabilities, which are fairly close to optimal solutions in a reasonable amount of time. 相似文献
993.
In drilling operation,a large saving in time and money would be achieved by reducing the drilling time,since some of the costs are time-dependent.Drilling time could be minimized by raising the penetration rate.In the comparative optimization method,by using the records of the first drilled wells and comparing the criteria like penetration rate,cost per foot and specific energy,the drilling parameters of the next wells being drilled can be optimized in each depth interval.In the mathematical optimization technique,some numerical equations to model the penetration rate,bit wear rate and hydraulics would be used to minimize the drilling cost and time as much as possible and improve the results of the primary comparative optimization.In this research,as a case study the Iranian Khangiran gas field has been evaluated to optimize the drilling costs.A combination of the mentioned optimization techniques resulted in an optimal well which reduced the drilling time and cost considerably in comparison with the wells already drilled. 相似文献
994.
Seyed Jalil Poormohammadian Parviz Darvishi Abdol Mohammad Ghalambor Dezfuli 《中国化学工程学报》2019,27(1):100-109
Electrospun polymers have many applications in the industry.However, the structure of these polymers has been less widely considered by researchers.In this work, the structural effect of electrospun and casted films of polyacrylonitrile(PAN) and polyvinylidene fluoride(PVDF) polymers on water vapor transmission were investigated.Sorption of water vapor was measured at 35, 60 and 80 ℃ and different relative humidities.The diffusion coefficients were calculated based on mass changes of the polymer sample.The water vapor transmission rate(WVTR) was also measured at 35 ℃ and 90% relative humidity.The results indicated that electrospun nano-fibrous polymers(ESNPs) absorb much higher water vapor compared to non-porous casted polymers.The interaction of water molecules with mentioned polymers was investigated based on Flory-Huggins theory.The Flory-Huggins interaction parameter of electrospun films was less than casted films, suggesting much better interaction of water molecules with electrospun films.It was also found that electrospun films have anomalous kinetic behavior and do not obey the Fickian diffusion model.Finally, it was revealed that ESNPs show less resistance to water vapor transmission and they are good candidates for the applications of water vapor separation using membranes. 相似文献
995.
996.
997.
Energy consumption in greenhouses and selection of an optimized heating system with minimum energy consumption 总被引:1,自引:0,他引:1
In this paper, heat loss is precisely computed by a proposed code considering different climates. Estimating the costs of different central heating system, unit heaters were selected as the most feasible system. Finally, considering the heating capacity and unit heater's dimensions a computational fluid dynamics model was developed to find the optimized configuration of unit heaters in a typical greenhouse. Using this model, the required thermal load for a greenhouse based on the daily temperature of Arak city in 2017 was computed with a smart control system. It was found that savings in energy consumption were approximately 5447 m3 of natural gas each year. 相似文献
998.
Hossein Shokouhmand Amirmohammad Sattari Seyed Erfan Hosseini‐Doost Ali Maghooli 《亚洲传热研究》2018,47(2):404-419
Analysis of porous fins for their higher heat transfer in comparison with solid fins with identical volumes has attracted significant attention. In this paper, a two‐dimensional thermal analysis of a porous fin having variable thermal conductivity coefficient is performed using finite difference method. Heat transfer through porous media is simulated using passage velocity from Darcy's model. The thermal conductivity of the solid phase is considered as a linear function of temperature. It is found that the temperature profile of the fin is completely two‐dimensional even for high Rayleigh and Darcy numbers (Ra = 103~104, Da = 0.01), because the temperature changes significantly along the transverse axis especially for lower Rayleigh and Darcy numbers. Also, the effects of important nondimensional parameters such as Rayleigh and Darcy numbers, porosity, Nusselt, thermal conductivity, and aspect ratio on the temperature profile are investigated. The results demonstrate that the temperature distribution is strongly dependent on the Rayleigh and Darcy numbers. 相似文献
999.
Seyed Hossein Hosseini Nazhad Ghazani 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(5):579-585
Hydrate formation and water accumulation during transmission process can be prevented by effective dehydration of gas streams. This study investigates the application of support vector machine to estimate natural gas dew point temperature using contactor temperature and TEG purity as independent variables. A data set comprised of 173 data points is extracted from the literature. The proposed model is considered a great help for engineers to have precise dew point temperature predictive tool in wide ranges of concerning variables. Results obtained from the proposed model show R-squared and mean square error of 0.992 and 5.556, respectively. Accordingly, the remarkable agreement between predicted and experimental values is observed. 相似文献
1000.
Steady and dynamic shear rheological behavior of semi dilute Alyssum homolocarpum seed gum solutions: influence of concentration,temperature and heating–cooling rate
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