循环荷载作用下饱和黏性土的弹塑性双面模型

基于作者新近提出的一种混合塑性硬化准则和临界状态土力学理论建立了一个三维形式表述的适于饱和黏性土的弹塑性双面模型,此硬化准则是著名的M asing方法在三维应力空间中的推广。该模型的二维形式已采用饱和黏性土样室内动态三轴不排水剪切试验的结果进行了验证并已在另文发表。本文所建的三维弹塑性动本构模型与一个半经验的孔隙水压力增长模式相结合,通过有限元程序ABAQUS*对一个循环荷载作用下的条形基础下部地基土层内的位移、应力分布和超孔隙水压力随时间的变化进行了分析,计算结果表明模型预测的地基土的力学响应是符合实际的。     

基于"替换法"的汉字加、解密实现技术

文章讨论的基于“替换法”的汉字信息加、解密实现技术,改变了传统的汉字加密结果,使加密后的密文仍是可以识别和再利用的汉字,发送者可以在任何可编辑汉字的通讯设备上发送和接收密文,确保中文信息传输过程中的安全性。加、解密算法实现的代码语言为VFP6.0。     

无功功率的补偿方法

介绍采用同步电动机和并联电容器进行无功补偿等常用的无功功率补偿方法，以提高用电设备的功率因数。     

应用地应力模拟技术研究断块区剩余油分布

应力场数值模拟不仅能够重塑出不同阶段地应力场，而且还可以定量一半定量地预测破裂的发生、裂缝的方向和密度，进一步探讨时间和空间上油气运移的规律，为油田勘探、开发提供必要的依据。本文以大庆萨北开发区北二西断层区为研究对象，通过应力场数值模拟研究了流体运移势场与剩余油分布的关系、流体运移与构造应力的关系、裂缝形成与剩余油分布的关系，确定了剩余油分布的有利区域，为油田注采系统的设计、部署和油田开发及措施调整提供了依据。     

海底天然气渗漏地震探测方法的研究进展

海底天然气渗漏可以指示沉积层中的烃类聚集带，渗漏出的大量气体（主要是甲烷）还可能影响全球的气候变化。此外，与海底渗漏相关的浅层气改变了海底沉积物的土工性质，可能对海底工程构成威胁。因此对海底天然气渗漏进行研究意义重大。在海底渗漏探测方面，地震是一种有效的方法，它不仅能反映深部构造，为海底渗漏提供气体来源和运移通道信息；而且还可以直接用来寻找渗漏相关特征，为海底观测和取样提供依据。在地震剖面上，与海底天然气渗漏相关的浅层气表现为声混浊、声空白、亮点、多次波、速度下拉、气烟囱等特征，泥火山、泥底辟表现为隆起的地震透明带，而麻坑则表现为“V”字形截面和半透明状地震混浊。     

管内材料高温放气性能的测试及应用研究

管内材料放气性能的优劣直接影响着整管的性能和寿命.本文简介了测试管内材料高温放气性能的原理、装置和方法.文中列举的几项应用实例表明,本项测试结果对产品质量控制、工艺技术改进和材料进厂检验及国产化攻关都具有指导意义.     

New accurate two-noded shear-flexible curved beam elements

 There are two purposes of this work. One is to present two accurate two-noded finite elements which are derived from the potential energy principle and the Hellinger–Reissner functional principle respectively. The second is to show the successful application of the internal displacement parameters in developing a high-order related displacement-rotation interpolation field. Because the derived interpolation field is capable of accurately modeling deformation modes in extreme thin curved beams and nearly straight beams, both shear locking and membrane shocking are avoided. Several standard numerical tests display superior behaviors of the present elements. Received: 5 February 2002 / Accepted: 16 September 2002     

非AWGN环境下调制类型自动识别

在非AWGN环境下，针对CW，AM，FM，OOK，PSK，QPSK，16QAM，FSK，MSK，SSB十种混合调制信号，对调制类型特征提取方法和自动识别算法进行了分析、综合、设计和计算机仿真。提出了梯层电平分析方法、频率瞬时信号分析、剔除载波的归一化能量分析、平方后信号的频谱分析、四次方后的信号频谱分析等方法。当SNR=10dB时，计算机仿真结果是正确识别率不低于95％，自动识别的平均处理时间为不超过10s。     

ECAP细化晶粒法的仿真与分析

ECAP(Equal Channel Angular Extrusion)方法，是实现材料纯剪切变形的有效方法。本文采用有限元（FEA）分析软件ANSYS对Al的挤压过程进行仿真与分析。分析结果表明：外切角Φ、圆角半径、试样与凹模之间的摩擦系数、凹模本身的特性（如弹性模量、泊松比等）等等，对材料的变形量都有不同程度的影响。     

Non‐reflecting artificial boundaries for transient scalar wave propagation in a two‐dimensional infinite homogeneous layer

This paper presents an exact non‐reflecting boundary condition for dealing with transient scalar wave propagation problems in a two‐dimensional infinite homogeneous layer. In order to model the complicated geometry and material properties in the near field, two vertical artificial boundaries are considered in the infinite layer so as to truncate the infinite domain into a finite domain. This treatment requires the appropriate boundary conditions, which are often referred to as the artificial boundary conditions, to be applied on the truncated boundaries. Since the infinite extension direction is different for these two truncated vertical boundaries, namely one extends toward x →∞ and another extends toward x→‐ ∞, the non‐reflecting boundary condition needs to be derived on these two boundaries. Applying the variable separation method to the wave equation results in a reduction in spatial variables by one. The reduced wave equation, which is a time‐dependent partial differential equation with only one spatial variable, can be further changed into a linear first‐order ordinary differential equation by using both the operator splitting method and the modal radiation function concept simultaneously. As a result, the non‐reflecting artificial boundary condition can be obtained by solving the ordinary differential equation whose stability is ensured. Some numerical examples have demonstrated that the non‐reflecting boundary condition is of high accuracy in dealing with scalar wave propagation problems in infinite and semi‐infinite media. Copyright © 2003 John Wiley & Sons, Ltd.