摘要：Traditional simulation methods are unable to meet the requirements of lunar takeo simulations, such as high force output precision, low cost, and repeated use. Considering that cable-driven parallel mechanisms have the advantages of high payload to weight ratio, potentially large workspace, and high-speed motion, these mechanisms have the potential to be used for lunar takeo simulations. Thus, this paper presents a parallel mechanism driven by nine cables. The purpose of this study is to optimize the dimensions of the cable-driven parallel mechanism to meet dynamic workspace requirements under cable tension constraints. The dynamic workspace requirements are derived from the kinematical function requests of the lunar takeo simulation equipment. Experimental design and response surface methods are adopted for building the surrogate mathematical model linking the optimal variables and the optimization indices. A set of dimensional parameters are determined by analyzing the surrogate mathematical model. The volume of the dynamic workspace increased by 46% after optimization. Besides, a force control method is proposed for calculating output vector and sinusoidal forces. A force control loop is introduced into the traditional position control loop to adjust the cable force precisely, while controlling the cable length. The e ectiveness of the proposed control method is verified through experiments. A 5% vector output accuracy and 12 Hz undulation force output can be realized. This paper proposes a cable-driven parallel mechanism which can be used for lunar takeo simulation.

摘要：The present work reviews different decision making tools(material comparing and choosing tools)used for selecting the best material considering different *** this review work,the authors have tried to address the following important enquiries:1)the engineering applications addressed by the different material choosing and ranking methods;2)the predominantly used decision making tools addressing the optimal material selection for the engineering applications;3)merits and demerits of decision making tools used;4)the dominantly used criteria or objectives considered while selecting a suitable alternative material;5)overview of DEA on material selection *** authors have surveyed literatures from different regions of the globe and considered literatures since *** present review not only stresses the importance of material selection in the early design stage of the product development but also aids the design and material engineers to apply different decision making tools systematically.

摘要：Performance-based design is more holistic and flexible than prescriptive design for providing safety in large complex buildings. Here, a multi-agent method to model the egress patterns of evacuees is combined with a microscopic pedestrian simulation model used to analyze the forces between individuals in a densely populated enclosed space in a crowd crushing and trampling analysis （CroC＆Ts）. The system is used to model egress patterns in a typical crowd evacuation simulation. The simulations indicate that some individuals will die from crushing in 2 m and 4 m wide exits in emergencies. The simulations also show that the fatality probability increases when barriers obstacled the path and when the egress distances were lar- ger. The simulations validate the conclusions of the stranded crowd model （SCM） and provide quantitative predictions of the crowd crushing and trampling risk. Therefore, the CroC＆Ts can provide performancebased egress designs for large pubic buildings and improve crowd safety management and emergency planning.

摘要：This study was carried out to investigate the possibility of titanium alloy metal powder production using low-power plasma *** argon DC non-transferred arc plasma torch was designed,and numerical analysis was conducted to determine the plasma jet properties and wire *** highest velocities inside the nozzle attachment were between 838 and 1178 m/*** velocities of the jets at the apex were between 494 and 645 m/s for different gas flow *** studied plasma gas flow rates had no significant effect on the effective plasma jet *** was shown that the plasma jet length can be estimated by numerical analysis using the temperature and velocity changes of the plasma jet over *** was observed that the powders produced were spherical without any *** a result of this study,a plasma torch was developed and powder production was performed successfully by using relatively low torch power.

摘要：本文对选择性激光熔化的17-4 PH不锈钢进行了参数化研究和表征。通过改变工艺参数包括激光功率和扫描速度以及扫描方式(设计参数)来研究试样的相对密度和显微硬度的变化。当使用中等能量密度和内外六角扫描方式时,试样的相对密和显微硬度最大;当使用低能量密度和交替带状扫描方式时,试样的相对密和显微硬度最小。在光学和扫描电子显微组织中,试样侧面有奥氏体、铁素体和小熔池。能量色散光谱分析表明,试样的化学成分变化导致相对密度和显微硬度发生变化。X射线衍射结果表明,中等能量密度试样的奥氏体相和铁素体峰强度最高。背散射电子衍射结果表明,随着能量密度的增加,奥氏体相增加,导致试样的显微硬度变化。相比于中等能密度试样,低能量密度试样易诱发更多的残余应力。采用不同能量密度得到的样品都具有较强的耐蚀性(0.05 mm/a),未出现明显的腐蚀裂纹。

摘要：Ti Ni shape memory alloys（SMAs） have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditional machining of SMAs is quite complex due to these properties. Hence, the wire electric discharge machining（WEDM） characteristics of Ti Ni SMA was studied. The experiments were planned as per L27 orthogonal array to minimize the experiments, each experiment was performed under different conditions of pulse duration, pulse off time, servo voltage, flushing pressure and wire speed. A multi-response optimization method using Taguchi design with utility concept has been proposed for simultaneous optimization. The analysis of means（ANOM） and analysis of variance（ANOVA） on signal to noise（S/N） ratio were performed for determining the optimal parameter levels. Taguchi analysis reveals that a combination of 1 μs pulse duration, 3.8 μs pulse off time, 40 V servo voltage, 1.8×105 Pa flushing pressure and 8 m/min wire speed is beneficial for simultaneously maximizing the material removal rate（MRR） and minimizing the surface roughness. The optimization results of WEDM of Ti Ni SMA also indicate that pulse duration significantly affects the material removal rate and surface roughness. The discharged craters, micro cracks and recast layer were observed on the machined surface at large pulse duration.

摘要：Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerically and experimentally studied. After finding a good correlation between the numerical and experimental results, more comprehensive FE analyses were carried out. Different die geometrical parameters were considered and their effects on the induced plastic strain, stress distribution, velocity field and forming load of the process were investigated. It was found that by this process with a suitable set of die geometrical parameters, higher induced effective strain and more homogeneous strain distribution could be achieved in comparison with ECLE operation.

摘要：Piezoelectric actuators fundamentally possess hysteresis behavior. Estimation of the hysteresis is usually demanded for enhancing the performance of piezo-actuated systems. This paper presents an observer-based scheme to estimate the hysteresis in piezo—actuated flexible beams. The observer is based on a nonlinearity observer method. The discrete-time Kalman-filter algorithm is adopted for determination of the observer gains. The major advantages of the presented scheme include ease of implementation and robustness to uncertainty of hysteresis parameters. Simulation results demonstrate that the observer is able to estimate the hysteresis efficiently and has better robustness compared to the previous scheme existing in the literature. The present scheme was also successfully applied to a real-life system. Moreover, a control application example is included to demonstrate the effectiveness of the scheme.

摘要：Cancer growth in the bone due to its random shape disables bone strength and thus changes its capacity to support body weight or muscles,which can crucially affect the quality of human life in terms of normal walking or daily *** successful patient recovery,it is necessary to remove the cancer-affected minimal bone area and quickly replace it with a biocompatible metal implant within less than 2 *** electron beam-melted Ti-6Al-4V implant was designed and applied in a patient to preserve the natural knee joint close to the bone *** developed implant fits the bone defect well,and the independent ambulatory function of the natural knee joint was restored in the patient within six weeks after surgery.A delayed fracture occurred six months after the successful replacement of cancer-affected bone with Ti-6Al-4V implant at the proximal meshed junction of the implant because of a minor downward ***,mechanical,and computational analyses were conducted for the fractured area to find the main reason for the delayed *** findings pertaining to the mechanical and material investigation can help realize the safe implantation of the three-dimensionally printed titanium implant to preserve the natural joints of patients with massive bone defects of the extremities.

摘要：Turbine cascade optimum design, the typical non-convex optimal problem, has long been a design challenge in the engineering fields. The new type hybrid Genetic Algorithms-whole annealing GeneticAlgorithms have been developed in this paper. Simulated annealing selection and non-uniform mutation are adopted in the whole annealing Genetic Algorithms. Whole annealing Genetic Algorithmsoptimal performance have been tested through mathematical test functions. On this basis, turbinecascade inverse design using whole annealing Genetic Algorithms have been presented. The B-Splinefunction is applied to represent the cascade shape. C-type grid and Godunov scheme are adopted toanalysis the cascade aerodynamic performance. The optimal problem aims to obtain an cascade shapefrom different initial cascade through the given target pressure distribution. The optimum cascadeshape is in well agreement with the target cascade shape. The numerical results show that the wholeannealing Genetic Algorithms are the powerful optimum tools for turbine optimum design or othercomplex engineering design problems.