二、锥蜗杆蜗轮传动的数学基础

一、齿轮轮齿的一阶作用的普遍规律如果将有关齿轮轮齿的作用的某些基本概念弄清楚了,那么锥蜗杆蜗轮是比较容易了解的。实际上,锥蜗杆蜗轮就是这些概念的系统化的阐述,用这些概念来发展新的齿轮。大多数的齿轮是绕固定轴转动的,它们之间的角速度比是恒定的。这些固定轴可以是平行的、相交的或交叉的,而各类齿轮就是按这些相对位置的运动加工出来的。所有这些齿轮的共轭作用可由与之完全通用的齿轮轮齿的一阶作用的普遍规律表示,关于这个规     

湍流边界层分离区的瞬间测量和统计描述

一、前言 正如大家所熟悉的,在层流边界层的情况下,只要主流是定常的,那么分离的位置就是确定的。但是湍流边界层则不同,即使主流是定常的,分离的位置也是变动的,并且不会是二维的。湍流边界层的这个性质的发现,引起了人们的兴趣和对于分离概念的     

飞控系统的模糊模型及其研究

在Takagi-Sugeno模型的基础上,建立了飞控系统的模糊模型。讨论了该模型的整体渐近稳定性,给出了判定该模型的整体渐近稳定的充分条件和满足一定条件的控制器的设计方法。最后对国产某飞机的纵向短周期运动系统的分析说明本文的模型是合适的,方法是有效的。     

温度、密度对目标等离子体隐身效果影响的FDTD分析

采用等温近似,给出覆盖目标的不均匀的、各项同性的、热的、碰撞的、等离子体的电磁反射的三维FDTD算法的公式。在一维条件下,计算了不同密度分布、不同温度的等离子体对电磁波的反射系数。给出了温度、密度对电磁波在等离子体中的碰撞吸收的影响。结果显示,增大等离子体的温度和密度将有利于等离子体对电磁波的吸收,增大吸收的带宽,减小等离子体覆盖目标对电磁波的反射。     

对地攻击飞机的作战方式和性能要求

对地攻击飞机是现代战争的主力，在最近几次局部战争中发挥着重要的作用，目前世界各国将攻击飞机作为发展空中力量的重点。军事技术的发展和武器装备的改进使现代战争的作战环境发生了巨大的变化，为对地攻击飞机提供了更多的发挥优势的机会。对地攻击既是进攻的主要方式，也是防御的积极手段。利用我方的攻击力量，对可能会袭击我方的敌方作战力量予以摧毁，是阻止敌人进攻的最有效的手段。为了适应作战环境的变化，发挥攻击飞机的作战优势，要求采用高新技术，提高攻击飞机的作战性能，为攻击飞机的作战方式的变化提供物质基础。现代战争对攻击飞机提出了新的要求，航空技术的发展为飞机性能的提高奠定了技术基础，两者协调统一构成了攻击飞机的发展方向。     

论新型城镇化背景下的人的现代化

城镇化是现代化的必由之路,尽管在发展的硬指标上新型城镇化的任务还比较艰巨,但也不能因此而忽视城镇化的软指标,即人的现代化.人的现代化的核心在于文化观念的转换,传统文化的观念系统存在着诸多影响现代化发展的因素.开展持久的关于现代文化意识的启蒙教育,在政治、经济制度领域实现彻底的现代转型,是实现人的现代化的关键.     

独立指数分布期望参数的Γ极小极大估计

在参数的部分先验信息已知的条件下所获得的Γ极小极大估计是一种介于有确定的先验分布函数的Bayes估计和无先验信息的极小极大估计之间的估计方法,因而更切合实际.以往的研究对二项分布参数的线性组合及负二项分布的参数在某些限制条件下的Γ极小极大估计做了讨论.本文给出了独立指数分布的期望参数在一般的先验矩限制下的Γ极小极大估计,同时讨论了两种特殊情况,即给出了在仅有先验二阶矩限制下的以及有确定的先验一阶矩和二阶矩限制下的指数分布的期望参数的Γ极小极大估计.     

感受奢华Versace Unique

Versace Unique给人在视觉上的感觉都是无与伦比的,是Versace制造的一种延续。把美杜莎标志刻在金属的机体上,并且压入背部的皮套中,当您需要使用手机内部的技术时(如时钟),映入眼帘的首先就是该图案。手机的墙纸采用的是可自行定制的丰富多彩的巴洛克式设计,外加完美的     

关于安全管理体系培训问题的探讨

<正>随着世界经济的快速发展,中西方的接触与交融达到了前所未有的程度,中西方管理的差异也越来越引起人们的重视。这种差异性有着深层次的文化因素,中国传统的管理主要基于对过去长期积累的经验和认知,属于"悟性化"的管理智慧;而源于西方的管理思想强调"体系化"的思想,更加重视管理方法的程序化、定量化,管理手段的自动化以及管理活动的有效性,更体现了现代管理的科学性。     

学习型组织理论与民航人力资源开发

建立学习型组织是知识经济时代发展的要求。民航人力资源的开发对民航行业的发展起着巨大的推动作用。本文试图从学习型组织的提出、学习型组织的内涵、创建学习型组织的意义等方面,结合我国民航的具体情况,阐明如何将学习型组织的理念引入民航人力资源开发以及学习型组织的理念引入对民航人力资源开发具有深远而重大的意义。一什么是学习型组织?所谓学习型组织,是指通过培养组织的学习气氛、充分发挥员工的创造性而建立起来的一种有机的、柔性的、扁平的、人性的、持续发展的组织。它具有如下几个要素:拥有终身学习的理论和机制;建有多元回…     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.     

An SOR Implicit Time-accurate Scheme in Calculating Unsteady Flows

A new time-accurate marching scheme for unsteady flow calculations is proposed in the present work. This method is the combination of classical Successive Over-Relaxation (SOR) iteration method and Jacobian matrix diagonally dominant splitting method of LUSGS. One advantage of this algorithm is the second-order accuracy because of no factorization error. Another advantage is the low computational cost because the Jacobian matrices and fluxes are only calculated once in each physical time step. And, the SOR algorithm has better convergence property than Gauss-Seidel. To investigate its accuracy and convergency, several unsteady flow computa- tional tests are carried out by using the proposed SOR algorithm. Roe’s FDS scheme is used to discritize the inviscid flux terms. Un- steady computational results of SOR are compared with the experiment results and those of Gauss-Seidel. Results reveal that the numerical results agree well with the experimental data and the second-order accuracy can be obtained as the Gauss-Seidel for unsteady flow computations. The impact of SOR factor is investigated for unsteady computations by using different SOR factors in this algorithm to simulate each computational test. Different numbers of inner iterations are needed to converge to the same criterion for different SOR factors and optimal choice of SOR factor can improve the computational efficiency greatly.