两同心旋转球间流动的弱解的存在唯一性

研究了两个同心旋转球间的轴对称不可压缩的粘性流动。该流动广泛应用于大气物理和地球物理等学科中,为了得到流动的流函数－速度形式的Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程的弱解的存在性和唯一性,首先发现了该方程中非线性项之间关系,并引入一个有限维的辅助问题,通过紧性而得到了结论。     

非定常流函数涡量方程的一种数值解法的研究

对非定常流函数涡量方程的数值求解方法进行了改进,其中流函数一阶导数即速度项采用四阶精度的Hermitian公式,对流项由一般二阶精度的中心差分提高到四阶精度离散差分,包含温度方程在内的离散方程组采用ADI迭代方法求得定常解．以无内热体及有一内热体的封闭方腔内自然对流为例,进行了不同瑞利数（Ra）条件下的数值研究．结果表明,该方法推导简单,求解精度高且计算稳定,适用于封闭腔内高瑞利数复杂混合对流的数值模拟．     

半潜式海上浮式风机气动阻尼特性研究

由于海上漂浮式风机具有较大的支撑平台运动,气动阻尼效应对海上漂浮式风机的运动响应带来了重要的影响, 日渐受到相关国内外学者的关注. 为了研究海上浮式风机的气动阻尼特性,本文推导了海上浮式风机气动阻尼力的数学模型,并借助模型实验和数值计算的方法,研究了半潜式海上浮式风机的气动阻尼特性及其作用规律. 结果表明,浮式风机的风轮旋转时的气动阻尼比风轮非旋转状态时更加明显;在作业工况下,气动阻尼对半潜式浮式风机平台的纵荡、纵摇、机舱的运动有明显的抑制作用,且主要体现为对半潜式浮式风机的平台运动固有频率响应的抑制作用,对波频范围的平台运动作用甚微. 其变化规律与风速大小、波浪载荷等有关,在风机的额定工况之前,气动阻尼通常与风速呈正相关关系,但是增长率有逐渐减小的趋势;在控制系统作用下,当入流风速接近或超过风机额定风速时,容易出现气动负阻尼现象,反而进一步强化浮式风机的运动响应,此时通过降低变桨距控制器的比例系数,即降低变桨距控制器的灵敏度,有助于增加海上浮式风机的气动阻尼效果,并且在一定程度上减缓负的气动阻尼的发生,改善海上浮式风机的运动响应.      

Dy和Y掺杂改性对CuO/CeZrO_2催化剂在富氢气氛中CO优先氧化催化性能的影响

采用水热-浸渍法制备了系列Dy和Y掺杂改性的CuO/CeZrO_2催化剂,使用X射线粉末衍射(XRD)、N_2吸附脱附和程序升温还原(H_2-TPR)等手段对催化剂进行了表征,研究了Dy和Y掺杂改性对CuO/CeZrO_2在富氢气氛中CO优先氧化催化性能的影响。结果表明,所制备的CuO-CeZrO_2催化剂均为萤石结构;添加适当比例的Dy_2O_3和Y_2O_3能增强活性组分与载体间的相互作用,有利于CuO活性组分的分散和低温还原能力的提高,从而改善了CuO/CeZrO_2用于CO优先氧化的催化活性。同时,掺杂Dy和Y能够提高CuO/CeZrO_2催化剂的抗CO_2抑制作用的能力,改善其催化稳定性。     

自动消解仪—ICP法测定水系沉积物中6种重金属元素

建立了自动消解仪-电感耦合等离子体发射光谱法(ICP-OES)同时测定水系沉积物中Cu、Zn、Ni、Cr、Pb、Co六种元素含量的方法。该方法的相关系数好、检出限低。方法经国家标准物质(GBW07361)验证,准确度和精密度均能达到环境监测分析的要求,为水系沉积物中重金属元素含量的测定提供了简单可靠的分析方法。     

Projection methods for the solution of one class of singular integrodifferential equations

In this paper we propose a computational scheme of the general projection method for the solution of singular integrodifferential equations in the theory of stream lines and thermal conductivity. We theoretically substantiate this scheme from the standpoint of the theory of approximate methods of functional analysis. We consider particular cases of the general projection method, namely, the method of moments and the collocation method.     

基于可视化荷载路径的结构混凝土拉-压杆模型

通过荷载路径可以直观地了解结构实现其功能的方式。本文首先根据荷载路径的定义，介绍一种基于平衡原理，将有限元方法和流线追踪算法结合，确定二维线弹性结构中荷载路径的方法。采用这种方法结合商用有限元软件Algor13和商用数据处理软件Tecplot9．0，把前者得到的结构应力计算结果及对应的有限元网格信息通过数据文件输入后者，以得到结构内连续的可视化荷载路径。最后，本文将这种方法用于确定牛腿结构中的可视化荷载路径，并在此基础上建立该结构的拉杆-压杆模型。     

Development of the direct stress solution technique for three-dimensional hydrodynamic models using finite elements

Velocity varies rapidly near sheared boundaries. Therefore in many practical fluid problems it can be inefficient to solve discrete equations with velocity as the dependent variable. Conversely, shear stress varies slowly near sheared boundaries, suggesting that it may be well suited for use as the dependent variable in discrete equations. This paper describes a formulation of the internal mode equations for a three-dimensional hydrodynamic model using shear stress as the dependent variable. The resulting direct stress solution (DSS), coupled with a spatial discretization using linear finite elements, yields a system matrix that can be set up and solved with the efficiency of a banded matrix with bandwidth 8. If the eddy viscosity distribution is assumed to be piecewise linear over the depth (with an arbitrary number of time-varying segments), the recovery of velocity from stress can be easily accomplished in closed form, thereby avoiding any difficulty resulting from the logarithmic singularity in the velocity profile that occurs at a boundary. Results from tidal and wind-driven test cases with realistic boundary layers are used to demonstrate the accuracy and computational advantages of a DSS formulation versus a standard velocity-based formulation.     

电子束与等离子体相互作用中的反常效应

本文对强流相对论性电子束与靶等离子体相互作用的反常吸收效应进行了理论研究。从符拉索夫方程出发,导出了强流相对论性电子束双流不稳定性效应解,并进行了弱碰撞修正,得到了相应的等离子体波增长率,对不同情况下出现反常效应的条件及机制进行了研究和讨论。     

Effect of ZrO<Subscript>2</Subscript> morphology in copper–cerium–zirconium oxide systems on their catalytic properties in the reaction of co oxidation in hydrogen-rich mixtures

We studied the catalytic properties of copper–cerium oxide systems, deposited on supports obtained by calcination of yttrium-stabilized zirconium dioxide at 300-1000 °C, in the reaction of selective oxidation of CO in a stream of hydrogen. We have shown that the catalytic activity of the samples obtained correlates with the activity of the original supports in the reaction of CO oxidation: the highest CO conversion is observed on catalysts with the highest and the lowest specific surface area. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 2, pp. 115-120, March-April, 2009.