平面多边形Newell公式的运用与推广

Newell公式在计算机图形学中常被用于计算多边形面积和平面法向量。论文主要讨论了Newell公式的运用与推广。首先将其推广三维空间中用于计算多面体体积的公式。其次讨论了在异面多边形的情况下,Newell公式的几何意义。最后,从数值计算的角度分析了Newell公式的计算方法。     

A model calculation of the tip field distribution for a carbon nanotube array and the optimum intertube distance

In a previous paper, the model of a floating top segment was proposed and used successfully to calculate the field enhancement factor as well as the field distribution on the top surface for a single carbon nanotube (CNT). In this paper, the model is extended to a CNT array. A set of modified linear charge equations has been derived for the CNT array using an approximation of multipole potential expansion. Fictitious charges inside a specific segment can be solved from these equations to calculate the field around the tips. Some numerical calculations of the field enhancement factor have been carried out, quantitatively accounting for the reduction of the factor with decreasing intertube distance. The relative field strength distribution on the top hemisphere of a CNT array is calculated too; it is observed to be close to that of a single CNT. Using the Fowler-Nordheim formula, the field emission intensity of a CNT array is maximized with varying intertube distance. The resulting optimum intertube distance to height ratio decreases gradually with increasing height to radius ratio, and is close to 2 only for height to radius ratio around 3 × 10(2).     

冲击波反射超压沿刚性墙面的分布规律

为得到冲击波反射超压峰值沿刚性墙体高度分布的规律,利用AUTODYN软件建立数值计算模型并进行求解,并与美军常规武器防护设计手册(TM5-855-1)计算结果进行对比分析。通过拟合得到了刚性地面上不同比例距离处冲击波超压峰值沿刚性墙体高度分布的计算公式,可为防爆墙及结构抗爆设计提供参考。     

Analysis of operator-machine configuration for single and multi-processor machines

The research addresses the issue of determining optimal machine-operator configuration so that the ideal machine-operator ratio can be found and the operator efficiency can be calculated as a part of the overall input efficiency. Formula for optimal machine-operator ratio for single and multiple processor machines are derived. The formula allows us how to determine the best machine-operator ratio and calculate the operator usage efficiency. Simulations are used to verify the formula with matching product releasing times and machine utilisation rate. Data from a wafer reclaim factory is used to illustrate the calculation of equipment usage efficiency. Opportunity for doubling operator usage efficiency is identified using the derived formula. Contributions of this work include: (1) deriving a set of formula to calculate optimal operator-machine configuration and the operator usage efficiency for multi-processor machine sets; (2) identifying the inherent unusable time of operator due to the process time distribution of the machine tools; and (3) doubling the operator usage efficiency of the subject factory.     

Angular Dependence of Transport AC Losses in Superconducting Wire with Position-Dependent Critical Current Density in a DC Magnetic Field

Transport AC losses play a very important role in high temperature superconductors (HTSs), which usually carry AC transport current under applied magnetic field in typical application-like conditions. In this paper, we propose the analytical formula for transport AC losses in HTS wire by considering critical current density of both inhomogeneous and anisotropic field dependent. The angular dependence of critical current density is described by effective mass theory, and the HTS wire has inhomogeneous distribution cross-section of critical current density. We calculate the angular dependence of normalized AC losses under different DC applied magnetic fields. The numerical results of this formula agree well with the experiment data and are better than the results of Norris formula. This analytical formula can explain the deviation of experimental transport current losses from the Norris formula and apply to calculate transport AC losses in realistic practical condition.     

混凝土面板堆石坝自振周期的简化公式

针对用原有的计算堆石坝自振周期经验公式与实测值有一定差别的问题，以混凝土面板堆石坝（ＣｏｎｃｒｅｔｅＦａｃｅｄＲｏｃｋｆｉｌｌＤａｍｓ，以下简称为ＣＦＲＤ）为研究对象，考虑坝高、堆石材料性质、面板和边坡坡比等对ＣＦＲＤ自振周期的影响，结合已建的ＣＦＲＤ堆石材料动力特性，提出了ＣＦＲＤ自振周期简化公式。这一公式对ＣＦＲＤ，尤其是ＣＦＲＤ高坝的抗震设计和地震反应分析具有实用价值。     

用FDTD方法研究颗粒型复合材料微波等效介电常数

本文提出了复合材料等效电磁参数的FDTD计算方法,介绍了FDTD方法计算吸波材料等效电磁参数的步骤.通过对立方体模型、球形模型、连续模型和十字叉模型的仿真计算,讨论了颗粒形状和接触情况对等效介电常数的影响.通过计算不同体积分数的材料模型的等效电磁参数,得到了颗粒型复合材料等效介电常数的计算公式.通过实测复合材料的介电常数,证明了本文提出的公式是有效的.     

相似旋风除尘器的特性及其应用

某一旋风除尘器的分级效率曲线是在特定工况下试验求得的，不能任意推广应用。作者通过对相似旋风除尘器特性的理论分析和试验研究，提出了相似旋风除尘器的基本关系式，并把该关系式应用于推算其它工况下性能，对不同型号旋风除尘器进行性能比较和旋风除尘器设计计算。     

无加劲方钢管柱-H形钢梁节点弹性刚度的级数解答

按照欧洲规范EU3(EN1993-1-8)的计算方法,平面无加劲方钢管柱与H 形钢梁直接焊接节点一般情况下是半刚性的,其半刚性主要是由于柱壁平面外变形引起的.为准确计算包含这种节点的结构的位移、构件内力,需要确定节点弹性刚度.日本规范《钢构造接合部设计指针》根据试验和数值分析结果拟合出了该刚度的计算公式,但在力学概念上存在缺陷,且当梁与柱材料屈服强度取不同值时的计算结果与实际情况差异较大.该文从经典弹性板壳理论出发,依据数值分析建立的梁翼缘截面应力分布模型,推导出与柱壁变形相关的刚度的级数解答,其结果与试验数据、有限元数值结果能较好吻合.     

基于双粘本构模型的汽车磁流变液减振器阻尼特性分析

将磁流变液在环形阻尼通道的流动简化为无限宽平板间的准稳态流动,建立了磁流变液平板准静态流动方程,利用磁流变液的双粘本构模型、边界条件和相容条件,得出了磁流变液速度分布,并分析了不同粘度比对磁流变液的流动速度分布的影响,在给定活塞速度和环形通道的几何尺寸条件下,对汽车磁流变减振器的阻尼特性进行理论预测,并研究了磁流变液减振器的双粘阻尼特性.按照长安之星微型汽车前悬架的技术要求,设计和制作了微型汽车磁流变减振器,在山川减振器公司对此进行了台架试验研究,试验结果表明应用所提出的理论分析模型和设计原理是可行的.     

高速铁路简支梁桥有载动力特性分析

本文根据车-桥系统相互作用模型，推导了铁路简支梁桥竖向有载自振频率的计算公式，并给出了简便的计算方法，同时，还对不同跨度的简支梁桥的竖向有载自振频率进行了深入的研究。     

预应力混凝土压力管道设计方法

根据环形预应力作用机理,结合弹性地基梁理论,提出了预应力混凝土压力管道在结构施工阶段的验算方法,给出了预应力筋束的最大间距,确定了预应力筋束分步张拉施工与荷载控制的方法。结合多层圆筒轴对称平面形变计算理论,提出了预应力混凝土压力管道运行阶段抗裂性能的验算方法,同时给出了预应力混凝土压力管道极限承载能力计算公式。所作的工作对预应力混凝土压力管道的设计与施工具有重要的应用价值。     

Results of investigation of the solubility of ice and water in compressed gases

Analysis is made of the experimental data available from the literature on the solubility of ice and water in various compressed gases in a wide range of temperature and pressure. A new formula is derived that relates the equilibrium concentration x_eq of steam in moist gas at preassigned temperature and pressure to the constants of the equations of state for condensed water and to the virial coefficients. This formula enables one to directly calculate the solubility of steam in compressed gas without using the previously suggested solution of the set of equations. The derived formula makes it possible to describe the entire array of experimental data in the range of parameters from 200 to 400 K and from 0.1 to 10 MPa with an error equal to or less than the experimental error     

利用外方内圆模型预测单向连续纤维增强树脂基复合材料的横向弹性模量

为了对连续纤维增强树脂基复合材料的横向弹性模量进行较高精度的解析计算,利用代表性体积单元横截面为正方形基体包裹圆形纤维的外方内圆模型,采用先并联后串联和先串联后并联的两种计算方式进行公式推导,借助于Mathematica软件进行符号积分运算,获得了横向弹性模量的2组解析解,将其中间值作为预测值,给出了预测值的近似公式,并与一组实验数据进行了比较。研究表明,外方内圆模型能较好地反映客观实际,利用Mathematica软件可以解决计算困难的问题;将解析解的中间值作为横向弹性模量的预测值,与一组实验数据比较,显示解析计算的相对误差基本在10%以内;给出的近似公式形式简单,且其曲线能较好地吻合中间值曲线,在纤维体积分数小于75%的范围内,近似公式与中间值公式计算结果之间的最大误差不超过7%。     

地震作用下桥墩动水压力及Morison方程适用性试验研究EI北大核心CSCD

深水桥梁的抗震分析需要考虑地震作用下动水压力的影响。目前,广泛采用的Morison方程由波浪力的计算公式演化而来,用于计算地震动水压力尚缺乏验证;同时,对于地震作用下桥墩动水压力的变化规律缺乏试验研究。该文设计一套水下振动台试验系统,以不同尺寸的桥墩试件为研究对象,采用正弦波为输入激励,通过不同工况的振动台试验,研究桥墩加速度和地震动水压力的分布规律及其随激励幅值、激励频率、截面直径和水深的变化规律;将动水压力的试验结果与Morison方程的计算结果进行对比,以验证地震作用下Morison方程的适用性。结果表明:地震作用下桥墩加速度和动水压力应考虑激励幅值、激励频率、截面直径和水深的影响,Morison方程不适用于计算地震作用下桥墩动水压力,应通过大量的水下振动台试验加以修正。     

融合概率语言的VIKOR方法在中药饮片包装材料 评价中的应用

通过将概率语言术语集（PLTS）融入VIKOR方法的决策过程,解决中药饮片包装材料的评价问题。首先使用PLTS对评价信息进行转化,根据PLTS及相关理论采用概率语言术语集的距离公式计算得到两个PLTS之间的距离;然后结合VIKOR方法构建PLTS-VIKOR多指标决策模型,用以解决多指标决策问题;最后以中药饮片包装材料评价问题为例进行算例分析。研究结果表明：运用概率语言术语集的距离公式计算两个PLTS之间的距离,能够更充分地运用原始评价信息,反映决策者偏好,提高决策效率,得到更稳定的决策结果。     

工程计算中关于翅片效率的一个问题

形成扩展表面的翅片管是强化换热中普遍采用的重要方法。但工程上关于翅片效率的计算却出现了混乱,特别是在现行的教科书和工程设计手册中。本文对此情况进行分析,指出正确的工程计算式,以免这一混乱现象继续存在。     

Linear systems with polynomials of filtered Poisson processes

Moment equations are calculated exactly for the response of linear systems subjected polynomials of filtered Poisson processes. The Itô formula for stochastic differential equations driven by Poisson white noise is applied to derive moment equations. It is shown that the set of moment equations is closed. The proposed method is used to calculate moments up to the fourth order for the response of two linear systems subjected to quadratic forms of filtered Poisson processes. Results by Monte Carlo simulations are also presented for comparison.     

双参数元的误差估计

双参数方法是构造高阶问题有限元(例如薄板弯曲问题单元)的有效方法。双参数元是一种非标准元,以往文献中只证明了它的收敛性。本文针对具体双参数板元给出它的误差估计式,并分析了节点参数的扰动量。     

基于遗传算法的干涉图像样的最佳熵研究

将遗传算法用于计算云纹干涉图像的二值化阈值，提出基于改进遗传算法的图像分割方法，采用Otsu公式，找出分割图像最优阈值。通过算法实现表明，利用遗传算法所得到的最佳阚值进行二值化处理，效果非常好。