Impact of singularity of Navier-Stokes equation upon atmospheric motion equations

Some conclusions about the smooth function classes stability for the basic system of equations of atmospheric motion and instability for Navier-Stokes equation are summarized. On the basis of this, by taking the basic system of equations of atmospheric motion via Boussinesq approximation as example to explain in detail that the instability about some simplified models of the basic system of equations for atmospheric motion is caused by the instability of Navier-Stokes equation, thereby, a principle to guarantee the stability of simplified equation is drawn in simplifying the basic system of equations.     

Probing the nature of the contact between fine particles by using ultrasound propagation

The propagation velocity (vs) of an ultrasonic signal through a granular material depends on the type of interparticle contact. For noncohesive glass beads, a power law behavior for consolidation stresses applied (σc) above 1 MPa has been measured in previous work. This equation is compatible with Hertz's interaction law between elastic solids. In the present work, we have tested the propagation velocity of ultrasound signals through a sample of fine powder. The tensile strength and compactivity of the powder were previously measured by means of the Seville powder tester (SPT), indicating plastic deformation of the surface asperities in contact for small to moderate consolidation stresses. However, the measurements of ultrasound propagation at high consolidations presented here are compatible with Hertz's law. This finding suggests that for high consolidation stresses, surface asperities are flattened, and it is therefore the elastic deformation of the bulk of the particles that determines the transmission of ultrasonic pulses.     

超声波无触点支承陀螺仪技术的理论分析及实现

提出了一种超声无触点支承方案，详细介绍了超声无触点支承原理。通过对声辐射理论的研究，获得超声无触点支承的理论依据。实验证明实现这种超声波无触点支承是可行的。根据这一理论，对三轴无触点支承结构进行了选择设计。     

爆轰波拐角传播三维数值模拟

为了研究爆轰波在拐角中的传播特性以及拐角爆轰低压流场现象,用LSDYNA 3D程序对三种常见的拐角装药的爆轰波传播特性进行了数值模拟,清晰显示了爆轰波因拐角处爆轰波传播面积的变化而产生的衰减 增长过程,讨论了侧向三通中爆速的变化情况,并得到了拐角处低压爆轰区的尺寸。     

梁波传播的固有特性

以分布参数的理论为基础，分析了梁波传播的一些固有特性，说明了它们与周期性结构的关系，讨论了支持条件对波传播特性的影响，指出了如果把近似方法应用于波传播分析中，可能引起的一些问题．本文的结果可直接应用于周期性结构的分析中     

砼受压全过程发射b值与分形维数的研究

声发射ｂ值反映了材料内部微裂缝发展，本文在ＭＴＳ试验系统进行了砼受压全过程实验同时，检测了砼声发射的幅值和事件数变化，并根据实验结果对ｂ值进行了研究。研究表明：在应力－应变全曲线峰值处ｂ值最小。此外，还根据分形理论对砼受压全过程分形维数进行了研究。     

弱正交异性材料残余应力测量的声弹性方法

为了适应工程材料的残余应力无损测量的要求,本文将横波和纵波声弹性相结合,建立适用於弱正交异性材料的平面声弹性残余应力测量方法,并应用该方法及自行研制的横波换能器对焊接试件的二维残余应力进行了测试。     

三相介质饱和土自由场中爆炸波的传播规律

饱和土是由固体上颗粒、水和少量封闭的空气组成的三相介质。介绍了爆炸波作用下三相介质饱和土有限元基本方程的建立过程，推导了引进人工粘性项的动力有限元方程，得到在饱和土自由场中爆炸波的传播规律；不同空气含量饱和土中爆炸波随深度的衰减规律。文中还给出了有限元与有限差分间断分解结果的比较，以说明本文理论方法的有效性。     

联邦滤波在飞机组合导航中的应用

研究了中等精度捷联惯导系统(SINS),大气数据系统(ADS)和塔康系统(TACAN)构成的机载组合导航系统.在分析SINS、ADS、TACAN各自特点的基础上,提出了SISN/ADS/TACAN组合导航系统的联邦滤波方案,并建立了相应的组合导航系统的数学模型.以一条典型的飞行轨迹进行了全航线的仿真研究,仿真结果为:基于联邦滤波的SINS/ADS/TACAN组合导航系统的位置精度约为70 m(CEP),速度精度约为0.75 m/s(1),航向精度为约为 (1)和姿态精度约为 (1),由此可见基于联邦滤波的SINS/ADS/TACAN组合导航系统可以充分利用各机载导航子系统信息,满足飞机导航定位的精度要求.     

SYMPLECTIC STRUCTURE OF POISSON SYSTEM

When the Poisson matrix of Poisson system is non-constant, classical symplectic methods, such as symplectic Runge-Kutta method, generating function method, cannot preserve the Poisson structure. The non-constant Poisson structure was transformed into the symplectic structure by the nonlinear transform.Arbitrary order symplectic method was applied to the transformed Poisson system. The Euler equation of the free rigid body problem was transformed into the symplectic structure and computed by the midpoint scheme. Numerical results show the effectiveness of the nonlinear transform.