Dynamic characteristics for wide magneto-hydrodynamic slider bearings with a power-law film profile

The magneto-hydrodynamic (MHD) dynamic characteristics of a wide power-law film-profile slider bearing lubricated with an electrically conducting fluid under the application of transverse magnetic fields has been proposed. A closed-form solution is obtained for the MHD power-law film-shape slider bearings, in which special bearing characteristics of the inclined-plane shape and the parabolic-film profile can also be included. Comparing with the non-conducting-fluid power-law film-shape bearing, the MHD bearing provides an increase in the load capacity, and the stiffness and damping coefficients. Comparing with the MHD inclined-plane slider bearing, the MHD parabolic-film bearing signifies an improvement in the steady performances and the dynamic characteristics.     

Robust quantum secure direct communication with a quantum one-time pad over a collective-noise channel

We present two robust quantum secure direct communication (QSDC) schemes with a quantum one-time pad over a collective-noise channel. Each logical qubit is made up of two physical qubits and it is invariant over a collective-noise channel. The two photons in each logical qubit can be produced with a practically entangled source, i.e., a parametric down-conversion source with a beta barium borate crystal and a pump pulse of ultraviolet light. The information is encoded on each logical qubit with two logical ...     

考虑滚道波纹度的推力球轴承油膜的测量与计算

使用能够模拟推力球轴承工作的光干涉油膜测量系统,在静态时基于Hertz接触理论测量得到了该轴承座圈滚道的波纹度变化,并测量了轴承工作一周的油膜变化情况.依据试验参数进行了钢球与玻璃盘接触以及钢球与座圈滚道接触的弹性流体动压润滑（EHL）数值分析.试验和理论分析均较好地验证了表面波纹度对润滑状态的影响,发现推力球轴承运动时油膜的变化和滚道的表面波纹度密切相关.     

微纳间隙受限液体的界面黏着机理研究

利用球-盘接触黏着试验仪对微量受限液体的界面黏着行为的研究发现：临界体积范围内（皮升到纳升）的受限液滴达到临界厚度后将出现自动铺展和瞬时收缩行为（分别对应球-盘趋进和分离过程）,并同时提供一定幅值的法向黏着力及伴随出现力的突变;该界面黏着力与液滴体积、球的直径等相关,并很好地揭示了昆虫或树蛙爪垫与光滑表面间的湿黏着行为.在进一步试验的基础上,利用球—面接触模型的毛细黏着力公式对所观察到的试验现象进行了机理揭示,认为临界体积受限液滴出现的自动铺展和瞬时收缩行为与接触副的刚度相关,最大法向黏着力随液体体积的减小而减小,与接触副之间受限液体的中心区厚度有关.结合生物黏着爪垫进行了受限液体界面黏着控制机理的分析,可以指导仿生黏着爪垫的设计与控制. 关键词： 生物黏着爪垫 毛细黏着力 受限液体     

高密度光盘径向倾斜对DPD循轨误差信号影响分析

根据高密度光盘参数 ,计算了聚焦光斑在光盘表面扫描过程中每个位置的光瞳光强分布 ,得到DPD(Differ entialPhaseDetection)循轨误差信号。考虑盘片的径向倾斜 ,在光瞳光强分布方程中引入盘片的径向倾斜角度参数 ,计算了高密度盘片产生径向倾斜时DPD循轨误差信号的变化 ,进而分析了盘片的径向倾斜引入的循轨伺服误差及其对循轨伺服的负面影响。结果表明 ,高密度盘片产生 0 .5°的径向倾斜相当于引入了 0 .0 12 μm的循轨误差     

Synclinic and anticlinic properties of (R,S) 4′-(1-methylheptyloxycarbonyl)biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy)heptyl-1-oxy]benzoates

Four racemic mixtures were synthesized and characterized. Their mesomorphic properties, such as phase transitions temperatures and enthalpies, were measured by a polarizing optical microscope and differential scanning calorimetry. The influence of one racemic mixture on the properties of the OAFLC mixture W-1000 was studied. The results show a wide temperature range of the SmC_A* phase in this new mixture. The helical pitch was measured by spectrophotometry method. The electro-optical properties of the mixture were also presented and discussed.     

Ruddlesden-Popper结构杂化非本征铁电体及其多铁性

正杂化非本征铁电性是指在具有钙钛矿结构单元的金属氧化物中由氧八面体面内旋转和面外倾侧耦合诱导出的二阶铁电序,其有望在室温强磁电耦合多铁性材料中获得重要应用,并将极大地拓展铁电体物理学的内涵和外延.本文在阐述杂化非本征铁电性物理起源及其内禀电控磁性的基础上,总结了有关Ruddlesden-Popper结构杂化非本征铁电体及多铁性的主要研究进展与面临的挑战,并展望了发展方向.     

An improved constant volume cycle model for performance analysis and shape design of PDRE nozzle

An improved constant volume cycle(CVC) model is developed to analyze the nozzle effects on the thrust and specific impulse of pulse detonation rocket engine(PDRE).Theoretically, this model shows that the thrust coefficient/specific impulse of PDRE is a function of the nozzle contraction/expansion ratio and the operating frequency. The relationship between the nozzle contraction ratio and the operation frequency is obtained by introducing the duty ratio, by which the key problem in the theoretical design can be solved. Therefore, the performance of PDRE can be accessed to guide the preliminary shape design of nozzle conveniently and quickly. The higher the operating frequency of PDRE is, the smaller the nozzle contraction ratio should be. Besides, the lower the ambient pressure is, the larger the expansion ratio of the nozzle should be. When the ambient pressure is 1.013 × 105 Pa, the optimal expansion ratio will be less than 2.26.When the ambient pressure is reduced to vacuum, the extremum of the optimal thrust coefficient is 2.236 9, and the extremum of the specific impulse is 321.01 s. The results of the improved model are verified by numerical simulation.     

Atomistic simulations of effect of hydrogen atoms on mechanical behaviour of an α-Fe with symmetric tilt grain boundaries

The effects of the hydrogen concentration, crystal orientation and grain size on the mechanical properties of an α-Fe bicrystal with symmetric tilt grain boundaries under tensile loading are investigated by molecular dynamics simulation. The results indicate that regardless of crystal orientation, the yield strength of bicrystal α-Fe decreases with the increase of hydrogen concentration. Hydrogen atoms have no influence on the primary dislocation (or twin) nucleation mechanism, but rather influence their multiplication process. The results also show that the degree of hydrogen embrittlement is obviously dependent on the misorientation angle, but it is almost independent of the grain size.     

State Estimation of an Underwater Markov Chain Maneuvering Target Using Intelligent Computing

In this study, an application of deep learning-based neural computing is proposed for efficient real-time state estimation of the Markov chain underwater maneuvering object. The designed intelligent strategy is exploiting the strength of nonlinear autoregressive with an exogenous input (NARX) network model, which has the capability for estimating the dynamics of the systems that follow the discrete-time Markov chain. Nonlinear Bayesian filtering techniques are often applied for underwater maneuvering state estimation applications by following state-space methodology. The robustness and precision of NARX neural network are efficiently investigated for accurate state prediction of the passive Markov chain highly maneuvering underwater target. A continuous coordinated turning trajectory of an underwater maneuvering object is modeled for analyzing the performance of the neural computing paradigm. State estimation modeling is developed in the context of bearings only tracking technology in which the efficiency of the NARX neural network is investigated for ideal and complex ocean environments. Real-time position and velocity of maneuvering object are computed for five different cases by varying standard deviations of white Gaussian measured noise. Sufficient Monte Carlo simulation results validate the competence of NARX neural computing over conventional generalized pseudo-Bayesian filtering algorithms like an interacting multiple model extended Kalman filter and an interacting multiple model unscented Kalman filter.