潜艇垂直面运动标准化仿真模型研究

本文根据刚体动力学理论所建立的动力学运动方程,结合面向对象编程设计法则,开发出具有良好延展性和可移植性的潜艇垂直面运动标准化仿真模型,并将模型成功运用在潜艇水下六自由度运动仿真系统中,该模型将在潜艇操纵系统的作战使用、故障应急处理及维修的研究工作中起到积极的辅助作用。     

三维RANS方程求解斜航船体粘性绕流

本文在三维船体贴体坐标系下,运用有限解析解法控制方程进行离散,采用压力与速度耦合的改进的SIMPLER计算方法结合标准的k-ε方程湍流模式,数值求解三维RANS方程,对作斜航运动的Wigley船体的粘性绕流场进行了计算,并与他人结果进行了比较,验证了理论计算方法和数值离散技术的可行性和有效性。     

Hoop stress approximation in offshore design codes

For a circular cylindrical vessel with an elastic material, Lame equations can accurately predict hoop stress variation within the vessel wall. However, because of the complexity involved in Lame formulations they are seldom used in design. In this paper, Lame equations are reproduced in terms of vessel outer and material cross-sectional areas and presented in a very simple format that enables hoop stress calculation without use of any approximation. Lame equations are also presented in terms of diameter-to-wall-thickness ratios in order to perform parametric studies. For a practical range of diameter-to-wall-thickness ratios the Lame hoop stress predictions are compared with approximate solutions of a selected design codes. For a range of loading conditions, comparison of results shows that a number of design codes overestimate the hoop stress. In contrast, a selection of offshore codes is shown to underestimate the hoop stress and, for a certain loading condition some codes ignore the hoop stress effect completely. The present paper also shows how the hoop stress approximation may lead to onerous results when the true wall axial stress is derived based on design code hoop stress formulations. It is concluded that what makes the present hoop stress formulations so important in design is their ability to interpret the mechanics of behavior that Lame equations strived to reveal.     

Real-time capable vehicle–trailer coupling by algorithms for differential-algebraic equations

The real-time simulation of vehicle trains requires an accurate and numerically feasible representation of the vehicle–trailer coupling. Although the equations of motion for the chassis instances can be reduced to systems of ordinary differential equations, additional constraints on the relative motion of vehicle and trailer are introduced when considering the hitch. In this article, we present a strategy for the simulation of vehicle–trailer combinations, where the algebraic constraints of the coupling are treated explicitly. Although this approach allows exact modeling of the respective joint geometry and realistic calculation of the coupling forces, a suitable numerical algorithm is required in order to solve the resulting differential-algebraic system of index 3 in real-time. The implementation in a commercial vehicle dynamics program is discussed and real-time simulation results are shown, which prove its feasibility for different coupling joints and demanding driving maneuvers.     

关于换行逆修正法

给出了求解非线性方程组Ｆ（ｘ）＝０的一种不含求逆运算的换行法。该方法保护了Ｆ‘（ｘ）的稀疏性的传递性，避免了矩阵求道，具有适用范围广，计算量少等优点。     

灵敏电流计动力学特性的研究

通过对灵敏电流计线圈动力学方程的深入分析，提示了三种运动情形的物理内涵及进行《灵敏电流计》实验的理论根据，并澄清了一些模糊认识。     

一维波动方程反问题的一种迭代解法及其敛速估计

对地震勘探中的一维波动方程反问题，给出了一种迭代解法，并证明了该算法的收敛性。     

摆线齿轮加工节圆为任意值时滚刀齿形曲线的计算

本文以点齿代换法为媒介,从运动学和几何学出发,导出了摆线针轮减速器中摆线齿轮在任意加工节圆时,计算滚刀齿形曲线的通用方程式,此方法避免了现行啮合计算法中繁杂的微积分等数学运算,是一种较为简便的计算方法.     

A new generalized heterogeneous data model (GHDM) to jointly model mixed types of dependent variables

This paper formulates a generalized heterogeneous data model (GHDM) that jointly handles mixed types of dependent variables—including multiple nominal outcomes, multiple ordinal variables, and multiple count variables, as well as multiple continuous variables—by representing the covariance relationships among them through a reduced number of latent factors. Sufficiency conditions for identification of the GHDM parameters are presented. The maximum approximate composite marginal likelihood (MACML) method is proposed to estimate this jointly mixed model system. This estimation method provides computational time advantages since the dimensionality of integration in the likelihood function is independent of the number of latent factors. The study undertakes a simulation experiment within the virtual context of integrating residential location choice and travel behavior to evaluate the ability of the MACML approach to recover parameters. The simulation results show that the MACML approach effectively recovers underlying parameters, and also that ignoring the multi-dimensional nature of the relationship among mixed types of dependent variables can lead not only to inconsistent parameter estimation, but also have important implications for policy analysis.     

准饱和土地基中瑞利波的传播特性

基于Biot两相饱和多孔介质理论,推导了准饱和土中瑞利波弥散特征方程,并研究了饱和度对准饱和土中瑞利波的弥散特性和位移分布的影响。结果表明,气相的存在对准饱和土中瑞利波速及弥散特性影响不大,但含气量变化对土骨架和流相的位移会产生很大的影响。