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91.
The behavior of an elastic–plastic contact between a deformable sphere and a rigid flat under combined normal and tangential
loading with full stick contact condition is investigated theoretically. Sliding inception is treated as a plastic yield failure
mechanism, which allows static friction modeling under highly adhesive conditions. Several contact parameters such as: junction
tangential stiffness, static friction force and static friction coefficient are extensively investigated. The phenomenon of
junction growth and the evolution of the plastic zone in the contact region are briefly described. It is found that at low
normal dimensionless loads the static friction coefficient decreases sharply with increasing normal load, in breach with the
classical laws of friction. As the normal load further increases the static friction coefficient approaches a constant value
that is about 0.3 for many material properties combinations. 相似文献
92.
In this paper, we propose a new spherical parallel robot for celestial orientation, and rehabilitation applications (TV satellite dish, tracking systems, solar panels, cameras, telescopes, table of the machine tools, ankle, shoulder, wrist and etc.). The proposed robot can completely rotate about an axis. After describing the robot and its inverse position analysis, using the genetic algorithm, the dimensional optimization to maximize the workspace of the robot is performed. The workspace analysis shows that the proposed robot has a relatively large workspace. Also, singularity analysis represents that the manipulator is a singularity-free workspace. It is a great advantage of the proposed robot. Next, an optimal approach is proposed for solving the direct position problem of the robot. According to the geometry of the robot, two coupled trigonometric equations are obtained through using a special form of Rodrigues' rotation formula. Next, the two coupled equations are transformed to a 8-degrees polynomial using the Sylvester's Dialytic elimination method. Finally, a numerical example for the robot with an asymmetric structure is given with eight real solutions. Therefore, the polynomial being minimal and the proposed approach is optimal. This greatly decreases computational time, which is necessary for dynamics, control and simulation. 相似文献
93.
《国际计算机数学杂志》2012,89(9):2123-2142
In this paper, we develop the mixed pseudospectral method for three-dimensional exterior problems. Some basic results on the mixed spherical harmonic-generalized Laguerre interpolation are established, which play important roles in the related pseudospectral methods. As examples, we provide the mixed pseudospectral schemes for two exterior problems with convergence analysis. Numerical results demonstrate the efficiency of this approach. 相似文献
94.
Most GPS positioning errors can be eliminated or removed by the differential technique or the modeling method, but the multipath effect is a special kind of system or gross error, so it is difficult to be simulated or eliminated. In order to improve the accuracy of GPS positioning, the single-epoch pseudorange multipath effects at GPS station were calculated, and firstly modeled based on the spherical cap harmonic (SCH), which is the function of satellite longitude and latitude with the robust method. The accuracy of the kinematic point positioning technique was improved by correcting pseudorange observations with the multipath effect calculated by the SCH model, especially in the elevation direction. The spherical cap harmonic can be used to model the pseudorange multipath effect. 相似文献
95.
Davood Iranshahi Ali Mohammad Bahmanpour Ehsan Pourazadi Mohammad Reza Rahimpour 《加拿大化工杂志》2012,90(5):1102-1111
In this study, the operating conditions of an axial flow spherical reactor have been optimised using a reliable optimisation technique and the results are compared with the results of non‐optimised conditions. The dynamic behaviour of the reactor has been considered in the optimisation process and orthogonal collocation method has been used in order to solve the obtained equations from mathematical modelling of the process. The goal of this study is to maximise the aromatics and hydrogen production rate. Therefore, the objective function is the combination of two terms which include the production rate of the mentioned components. The catalyst distribution for each reactor, the inlet pressure of the system, Length per radius for each reactor, the naphtha feed molar flow rate and the hydrogen mole fraction in the recycle stream as well as the inlet temperature of each reactor have been optimised in this study. © 2011 Canadian Society for Chemical Engineering 相似文献
96.
97.
The problem of how to develop a mathematical model of the heat processes that take place in the rotor of a spherical asynchronous motor under the influence of internal heat sources is considered. An analytic model of the process is suggested that makes it possible to solve the problems of determination of the extreme thermal modes of a motor and is well suitable for the searching procedures of the construction optimization problems. 相似文献
98.
通过液相法制得了球形Ni(OH)2,再与Mn(NO3)2、CH3COOLi通过固相法制备了富锂正极材料Li[Li0.2Ni0.2Mn0.6]O2。通过X射线衍射光谱法(XRD)、扫描电子显微镜法(SEM)、粒度分析仪、循环伏安、交流阻抗以及充放电测试对样品的结构、形貌和电化学性能进行了表征。结果表明,合成温度为900℃时,材料结晶度高,阳离子混排程度低,颗粒表面光滑均一;在20 m A/g时,首次放电比容量为174.02 m Ah/g,在60 m A/g的高倍率放电条件下比容量仍可达到80.56m Ah/g。 相似文献
99.
分别以湿法沉淀的球形四氧化三锰(Mn3O4)和商业电解二氧化锰(EMD)为锰源合成锰酸锂(Li Mn2O4)。通过杂质含量分析、XRD、SEM和充放电测试等,研究锰源对产物性能的影响。以粒度为10μm的球形Mn3O4为原料合成的Li Mn2O4保留了锰源的物化特征,以1.0 C在3.00~4.35 V充放电,首次放电比容量为117.2 m Ah/g,常温、55℃高温循环100次的容量保持率分别为94.6%和91.0%,高于以EMD为原料合成的Li Mn2O4(分别为87.9%和72.9%)。循环性能的提高,与球形Li Mn2O4的粒度分布集中、比表面积小及杂质含量低有关。 相似文献
100.