关于第一推动力及多级推动力的问题

第一推动力是伴随着宇宙大爆炸的发生一并出现的,它在本质上是一种惯性力。第二推动力是在宇宙大爆炸后出现阴阳开合之时发生的,它既是为了抵御第一推动力的递减应运而生,又为宇宙间产生生命而提供了前提条件。阴阳两种物质在宇宙的某个特定的时空发生碰撞,一个物种便诞生了。伴随着生命的产生就出现了第三推动力。第三推动力的出现,既是阴阳两种物质赋予生命的运动形式,也是第二推动力向第三推动力部分转化的结果。

论图书馆读者满意度量化指标的开发与应用

本文对高等学校图书馆读者满意度测评工作的意义、作用以及如何提高测评的应用效果进行了探讨,建议高校图书馆主管部门积极组织推动高校图书馆统一进行这项工作,以获取满意效果。

用传统文化打造书香校园

中华优秀传统文化是民族的灵魂和脊梁,也是自身发展不可或缺的平台,是建设中华民族共有精神家园的深厚文化根基。在小学阶段做好中华优秀传统文化传承工作,对于全面提高学生素质,继承和弘扬中华民族优秀的传统文化,培养爱国主义情操,增强民族凝聚力,都具有十分重要的意义。近几年来,学校将弘扬中华优秀传统文化工作纳入到常规活动中,渗透到语言文字应用能力的活动中,用传统文化打造书香校园。

谈高职院校数学专业学生自主学习能力培养模式

通过三种方法即推动式的方法、激励式的方法、监督式的方法形成培养高职院校数学专业学生自主学习能力的模式.

借力传统文化,更新校园气象

优秀的中华传统文化是国家的灵魂和骨干,也是自身发展不可或缺的平台。这是建设中华民族共同的精神家园的深厚文化底蕴。在全面提高学生素质,继承和发扬中华优秀传统文化,培养爱国主义情感,培养中华民族优秀传统文化的基础上,做好继承小学优秀传统文化工作具有重要意义。增强民族凝聚力。近年来,学校将优秀的中国传统文化工作纳入其经常性活动,渗透语文和写作能力活动,并利用传统文化打造书香校园。

高校构建教学督导机制探讨

教学督导作为高校质量保障体系的重要组成部分,对学校教学质量的提高及教师教学水平的提升有着非常重要的意义,教学督导有监督、指导、激励、桥梁、参考咨询等功能,高校需要以一种新的思路去构建教学督导机制,建立一支学历、职称、年龄等结构合理、专兼职相结合的教学督导队伍,创新督导理念,采取多样化的督导模式,促使教学督导达到应有的效果。

A recursive formulation based on corotational frame for flexible planar beams with large displacement

A forward recursive formulation based on corotational frame is proposed for flexible planar beams with large displacement.The traditional recursive formulation has been successfully used for flexible mutibody dynamics to improve the computational efficiency based on floating frame,in which the assumption of small strain and deflection is adopted.The proposed recursive formulation could be used for large displacement problems based on the corotational frame.It means that the recursive scheme is used not only for adjacent bodies but also for adjacent beam elements.The nodal relative rotation coordinates of the planar beam are used to obtain equations with minimal generalized coordinates in present formulation.The proposed formulation is different from absolute nodal coordinate formulation and the geometrically exact beam formulation in which the absolute coordinates are used.The recursive scheme and minimal set of dynamic equations lead to a high computational efficiency in numerical integration.Numerical examples are carried out to demonstrate the accuracy and validity of this formulation.For all of the examples,the results of the present formulation are in good agreement with results obtained using commercial software and the published results.Moreover,it is shown that the present formulation is more efficient than the formulation in ANSYS based on GEBF.

An Unstructured Finite Volume Method for Impact Dynamics of a Thin Plate

The examination of an unstructured finite volume method for structural dynamics is assessed for simulations of systematic impact dynamics. A robust display dual-time stepping method is utilized to obtain time accurate solutions. The study of impact dynamics is a complex problem that should consider strength models and state equations to describe the mechanical behavior of materials. The current method has several features, l） Discrete equations of unstructured finite volume method naturally follow the conservation law. 2） Display dual-time stepping method is suitable for the analysis of impact dynamic problems of time accurate solutions. 3） The method did not produce grid distortion when large deformation appeared. The method is validated by the problem of impact dynamics of an elastic plate with initial conditions and material properties. The results validate the finite element numerical data

Structure buckling and non-probabilistic reliability analysis of supercavitating vehicles

To perform structure buckling and reliability analysis on supercavitating vehicles with high velocity in the submarine,supercavitating vehicles were simplified as variable cross section beam firstly.Then structural buckling analysis of supercavitating vehicles with or without engine thrust was conducted,and the structural buckling safety margin equation of supercavitating vehicles was established.The indefinite information was described by interval set and the structure reliability analysis was performed by using non-probabilistic reliability method.Considering interval variables as random variables which satisfy uniform distribution,the Monte-Carlo method was used to calculate the non-probabilistic failure degree.Numerical examples of supercavitating vehicles were presented.Under different ratios of base diameter to cavitator diameter,the change tendency of non-probabilistic failure degree of structural buckling of supercavitating vehicles with or without engine thrust was studied along with the variety of speed.

Development of HEP-XXMF Series Hall Thrusters in BICE

Hall thruster is a type of electric propulsion thruster which is often regarded as a moderate specific im- pulse space propulsion technology and is used primarily for station keeping and orbit maintenance tasks. Magnetic field is the most important aspect in Hall thruster＇s design. Each time the performance improvement of Hall thrusters is accompanied with the regeneration of magnetic field design. Now, all the maior space nations treat the magnetic field design as the key technology for Hall thrusters, and many Hall thrusters have emerged in recent years, for example, BPT-4000 and NASA- 173M. In China, based on magnetic focus technology, the Beijing Institute of Control Engineer- ing （BICE） has been developing Hall thrusters ranged from hundreds of watts to 5 kilowatts, including the IS00 W HEP- 100MF and the 5 kW HEP- 140blF Hall thrusters. This paper briefly reviews the development of the HEP-XXMF series Hall thruster. The principle of the Hall thruster, the design methods and the current status of HEP-100MF and HEP- 140MF are discussed in the paper.

Finger Flexion Motion Inference from sEMG Signals

This paper provides a method to infer finger flexing motions using a 4-channel surface Electronyogram （sEMG）. Surface EMGs are hannless to the humnan body and easily done. However, they do not reflect the activity of specific nerves or muscles, unlike invasive EMCs. On the other hand, the non-invasive type is difficult to use for discriminating various motions while using only a small number of electrodes. Surface EMG data in this study were obtained from four electodes placed around the forearm. The motions were the flexion of each 5 single fingers （thumb, index finger, middle finger, ring finger, and little fingers）. One subject was trained with these motions and another left was untrained. The maximum likelihood estimation method was used to infer the finger motion. Experimental results have showed that this method could be useful for recognizing finger motions.The average accuracy was as high as 95%.

Fault diagnosis of rocket engine ground testing bed with self-organizing maps(SOMs)

To solve the fault diagnosis problem of liquid propellant rocket engine ground testing bed,a fault diagnosis approach based on self-organizing map(SOM)is proposed.The SOM projects the multidimensional ground testing bed data into a two-dimensional map.Visualization of the SOM is used to cluster the ground testing bed data.The out map of the SOM is divided to several regions.Each region is represented for one fault mode.The fault mode of testing data is determined according to the region of their labels belonged to.The method is evaluated using the testing data of a liquid-propellant rocket engine ground testing bed with sixteen fault states.The results show that it is a reliable and effective method for fault diagnosis with good visualization property.

Simulation of two-phase plume field of liquid thruster

When the liquid propellant thruster works,its plume field would contain many propellant liquid droplets,especially at pulse state.Liquid droplets may move along with the gas flow and deposit on the components of spacecraft as contamination.The simulation of the plume field involving the gas molecules and liquid droplets is an important part in contamination studies of thruster plume.Based on the PWS software developed by Beihang University(BUAA),axial-symmetric two-phase direct simulation Monte Carlo(DSMC) method is used with the liquid droplet taken as a kind of solid particle.The computation of gas-to-particle effect and gas reflection on the particle surface are decoupled.The inter-particle collision is also considered.The gas parameters at nozzle exit of 120N engine after 20 ms pulse work are taken as the entrance condition of the numerical simulation.Four test cases are conducted for comparison of different collision modules.Simulation results show that the effects of liquid propellant droplets mainly concentrate near the axis line of engine.The particle-to-gas collision would cause evident differences in the gas field and subtle differences in the particle phase.The liquid droplets in the plume field are generally accelerated and convected by the gas molecules.The DSMC method is proved to be a feasible solver to numerically simulate the two-phase flow involving solid phase and rarefied gas flow.