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排序方式: 共有297条查询结果,搜索用时 15 毫秒
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Pressurized fabric tubes, pressure-stabilized beams (known as air beams) and air-inflated structures are considered to be valuable technologies for lightweight, rapidly deployable structures. Design optimization of an inflated structure depends on a thorough understanding of woven fabric mechanics. In this paper the bending response of woven pressure-stabilized beams have been experimentally tested and analytically investigated. Additionally, the micromechanical effects of interacting tows have been studied through finite element models containing contact surfaces and nonlinear slip/stick conditions. Local unit cell models consisting of pairs of woven tows were created to characterize the effective constitutive relations. The material properties from the unit cell models were then used for the global continuum model subjected to 4-point flexure. An experimental set-up was designed and manufactured for testing of Vectran and PEN air beams. The air beam mid-span deflections were measured as functions of inflation pressure and bending load. Plots of the elastic and shear moduli with respect to the pressure and coefficient of friction have been generated. It was determined that the effective elastic and shear moduli were functions of inflation pressure, the material used and the geometry of the weave. It was shown that pneumatic or pressurized tube structures differ fundamentally from conventional metal structures. 相似文献
3.
Mohammadi Hossein Mohammadi Mohammad Amiri Iraj Sadegh Hosseinghadiry Mahdiar 《SILICON》2021,13(3):747-755
Silicon - In this paper, a new structure: triple work function metal gate SOI MESFET, intended for integration into the deep-submicron CMOS technology, is proposed. The gate of the device consists... 相似文献
4.
Jalil Layegh Fariborz Jolai Mohsen Sadegh Amalnik 《Advances in Engineering Software》2009,40(10):1074-1077
In this paper, we consider minimizing total weighted completion time criteria on a single machine. Jobs processing times are step function of its starting time and all jobs have a common due date. First, we present some new lemmas and dominance properties for this NP-hard problem, and then a memetic algorithm using these properties is developed. We compare the solutions of the memetic algorithm with optimal solutions obtained from complete enumeration. The results show that the average percentage error of the proposed algorithm from optimal solutions is about 2% and as the variance of processing time increase, the percentage errors decrease. 相似文献
5.
Interaction between refractory crucible materials and the melted NiTi shape-memory alloy 总被引:2,自引:0,他引:2
S. K. Sadrnezhad Sadegh Badakhshan Raz 《Metallurgical and Materials Transactions B》2005,36(3):395-403
Attempts have been made to quantify the amount of contaminants absorbed by liquid metal from commercial ZrO2-, Al2O3-, and SiC-base crucibles used for vacuum melting of Ni-45 wt pct Ti alloy. The molten alloy was held under vacuum for 90
minutes at 1450 °C to become homogenized. Reactions between the liquid metal and the crucible were investigated by visual
observation, chemical analysis, scanning electron microscopy (SEM) image processing, and X-ray mapping. The relative degree
of contamination declined in the following sequence: commercially pure SiC>SiC-5 wt pct Al2O3-5 wt pct SiO2>slurry cast alumina>recrystallized alumina>zircon type A>oxygen deficient high-purity zirconia. Thermodynamic calculations
showed a difference between the equilibrium and the experimental data, indicating that except for commercially pure SiC crucible,
the amount of the crucible elements entering the melt is greater than the calculated equilibrium values. This discrepancy
seems to be due to the immersion into the melt of the undissolved chemical compounds formed due to the reactions between the
crucible and the liquid phase. 相似文献
6.
The simultaneous perturbation stochastic approximation (SPSA) algorithm has attracted considerable attention for challenging optimization problems where it is difficult or impossible to obtain a direct gradient of the objective (say, loss) function. The approach is based on a highly efficient simultaneous perturbation approximation to the gradient based on loss function measurements. SPSA is based on picking a simultaneous perturbation (random) vector in a Monte Carlo fashion as part of generating the approximation to the gradient. This paper derives the optimal distribution for the Monte Carlo process. The objective is to minimize the mean square error of the estimate. The authors also consider maximization of the likelihood that the estimate be confined within a bounded symmetric region of the true parameter. The optimal distribution for the components of the simultaneous perturbation vector is found to be a symmetric Bernoulli in both cases. The authors end the paper with a numerical study related to the area of experiment design 相似文献
7.
In a Stirling cycle a huge amount of energy is wasted due to the losses. This wasted energy may be utilised as a heat source for the boiler of an organic Rankine cycle (ORC). Combination of these two cycles leads to an increased cycle efficiency compared to a single Stirling cycle and the analysis and optimisation of the integrated system is carried out. Optimisation is performed using the genetic algorithm and considering three decision variables: the temperature of the cold tank of the Stirling cycle, the pressure ratio and the temperature of the ORC condenser. In optimisation, the efficiency is considered as the objective function and the highest value is achieved by adjusting the decision variables. Using this method, the efficiency of the overall combined cycle was improved in which the highest efficiency was obtained to be 41.5%. 相似文献
8.
Sotoodeh Mahmood Tajeripour Farshad Teimori Sadegh Jorgensen Kirk 《Multimedia Tools and Applications》2018,77(13):16833-16866
Multimedia Tools and Applications - Optical Music Recognition (OMR) can be divided into three main phases: (i) staff line detection and removal. The goal of this phase is to detect and to remove... 相似文献
9.
10.
广域保护中基于能量守恒原理的母线及输电线差动保护 总被引:3,自引:3,他引:0
提出一种基于能量守恒原理的纵联差动保护,对线路两端或母线各端的有功功率进行比较,若各端功率的和超出整定值,则判定为区内故障。在典型400 kV输电系统模型上,运用MATLAB仿真软件对所提出的原理进行了仿真验证。仿真结果表明,该方法比传统电流比率差动保护更加可靠且计算量小,因而可缩短动作时间。该方法能检测所有故障类型,适应于超高压远距离输电线路。 相似文献