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根据反向积分原理编写了流场反演程序,并开展了程序验证计算。在反演区域内,由临界面速度反演出与辐射流体力学程序MULTI计算结果几乎一致的结果;由Saturn加速器上实验测试的单个样品后自由面速度反演出了加载压强历史、多种厚度样品后自由面粒子速度历史等信息,与文献对比发现,反演结果与由加速器工作电流推出结果、WONDY程序计算结果、实验测试结果相吻合。本工作为即将开展的激光驱动准等熵压缩实验奠定了技术基础。     

三维笛卡儿坐标系中Lagrange流体力学的显式相容有限元方法(英文)

将Caramana等人提出的相容算法思想和有限元方法相结合,提出三维笛卡儿坐标系中Lagrange流体力学的显式相容有限元方法.采用三线性六面体单元和交错网格进行空间离散,利用质量集中进行显式求解,无需求解线性代数方程组.时间离散可采用两步显式Runge-Kutta格式.用边人工粘性消除激波振荡,用子网格扰动压力抑制网格的非物理变形.给出若干标准算例.数值算例表明,该方法具有较高的计算精度和计算效率,同时具有很好的对称性和总能量守恒性,总能量计算误差为计算机浮点计算截断误差.     

二维多介质可压缩流的RKDG有限元方法

应用RKDG(Runge-Kutta Discontinuous Galerkin)有限元方法、Level Set方法和Ghost Fluid方法数值模拟二维多介质可压缩流,其中Euler方程组、Level Set方程和重新初始化方程的空间离散采用DG(Discontinuous Galerkin)有限元方法,时间离散采用Runge-Kutta方法.对二维的气-气和气-液两相流进行了数值计算,得到了分辨率较高的计算结果.     

包含夸克碎块效应的相对论性流体力学方程组的数值解法

采用守恒型差分方法求解带源项的相对论性流体力学方程组，给出了差分离散化的详细步骤，同时在计算过程中计入了ＱＧＰ相变的影响，得到反映物理现象的若干图象，并与相关文献结果进行了比较 。     

微结构表面热辐射光谱特性的分析方法

微结构表面热辐射光谱特性研究分析的一个主要问题在于表面微结构复杂的空间自由度以及计算方法.针对以上问题本文建立了任意微结构表面的物理模型,基于电磁波理论给出了微结构表面热辐射满足的麦克斯韦方程组.将时域有限差分方法(FDTD)用于麦克斯韦方程组的离散求解,引入场分离处理方法,直接计算提取反射场量,进而采用坡印廷定理计算得到能流以及光谱特性.最后,分别计算了随机微结构表面和微腔表面的热辐射光谱特性,并与相关文献的实验以及计算结果进行了比较.     

半导体器件数值模拟中电子连续性方程的求解算法

针对电子连续性方程的离散代数方程组,对离散线性系统的矩阵进行分析,得到矩阵的三类特点;针对大规模电子连续性方程的离散方程组,采用预处理Krylov子空间方法进行求解,并比较和分析几类预处理方法的效果。结果表明：代数多重网格(AMG)预处理Krylov子空间方法在求解离散电子连续性方程方面非常有效。开展AMG预处理Krylov子空间方法求解离散电子连续性方程的大规模并行可扩展性测试,比较和分析了AMG方法中三类关键算法参数的选取。     

流体力学方程的间断有限元方法

在二维区域三角形网格上应用一阶、二阶和三阶精度间断有限元方法,对流体力学方程和方程组进行了数值模拟.计算结果与差分方法计算结果比较,认为间断有限元方法在求解复杂边界条件和区域问题上有一定的优势.     

电子束辐照效应的数值模拟

论述了电子束辐照材料时的能量沉积Monte-Carlo计算,在此基础上,与弹塑性流体力学方程组相结合,给出电子束激发的热一力学效应的数值模拟方法.对一系列电子束打铝靶实验进行了实际计算,得到与实验比较一致的结果.     

强爆炸火球数值模拟中的算子分裂方法

采用算子分裂方法将辐射流体力学方程组分裂为对流项和刚性源项,设计一种高效求解刚性源项方程组的数值方法.数值实验表明:该方法对时间步长不敏感,计算精度能够满足工程计算要求.在不对方程组做任何近似的情况下,数值给出了较长时间内火球冲击波阵面压力峰值及阵面位置的变化,结果与实际强爆炸中的经验公式吻合较好.     

二维可压缩流体力学Lagrange有限点方法

提出二维可压缩流体力学问题的拉格朗日有限点方法,将求解区域离散为适当的点集.在每个时间步,每个离散点与其周围适当的五个邻点组成一个基本计算单元.在每个计算单元上,利用有限点方法中的典型微分算子的五点近似公式直接离散流体力学方程中的微分算子,并在每个方程中加上一个人为拉普拉斯粘性项,达到稳定格式的目的.给出时间步长的自动选取算法.数值算例结果验证了算法的有效性,初步展示了其计算大变形流体问题的良好发展潜力.     

Load characteristics of high power sandwich piezoelectric ultrasonic transducers

Based on the equivalent circuit theory, the load characteristics of high power piezoelectric ultrasonic sandwich transducers are studied. Two types of loads are studied. One is liquid load as in ultrasonic cleaning, and the other is solid load as in ultrasonic drilling and machining. The effect of load and structure of the transducer on the resonance frequency of the transducer is analyzed. It is shown that the effect of load on the resonance frequency of sandwich transducers with different structures is different. For liquid load as in ultrasonic cleaning, the effect of the load on the resonance frequency of the sandwich transducer with symmetrical structure is the largest. It is the smallest for the transducer with its displacement node in the back metal cylinder. For solid load as in ultrasonic drilling and machining, the effect of the load on the resonance frequency of the sandwich transducer with its displacement node in the front metal cylinder is the largest. It is also the smallest for the transducer with its displacement node in the back metal cylinder. On the other hand, for some applications, such as ultrasonic drilling, when the lateral dimension of the tool is much less than that of the transducer, its effect on the resonance frequency of the transducer is small. The conclusions are useful in designing vibrating systems for different ultrasonic applications.     

Modeling and Performance Optimization of an Irreversible Two-Stage Combined Thermal Brownian Heat Engine

Based on finite time thermodynamics, an irreversible combined thermal Brownian heat engine model is established in this paper. The model consists of two thermal Brownian heat engines which are operating in tandem with thermal contact with three heat reservoirs. The rates of heat transfer are finite between the heat engine and the reservoir. Considering the heat leakage and the losses caused by kinetic energy change of particles, the formulas of steady current, power output and efficiency are derived. The power output and efficiency of combined heat engine are smaller than that of single heat engine operating between reservoirs with same temperatures. When the potential filed is free from external load, the effects of asymmetry of the potential, barrier height and heat leakage on the performance of the combined heat engine are analyzed. When the potential field is free from external load, the effects of basic design parameters on the performance of the combined heat engine are analyzed. The optimal power and efficiency are obtained by optimizing the barrier heights of two heat engines. The optimal working regions are obtained. There is optimal temperature ratio which maximize the overall power output or efficiency. When the potential filed is subjected to external load, effect of external load is analyzed. The steady current decreases versus external load; the power output and efficiency are monotonically increasing versus external load.     

On the occurrence of flutter in the lateral-torsional instabilities of circular arches under follower loads

The lateral-torsional stability of circular arches subjected to radial and follower distributed loading is treated herein. Three loading cases are studied, including the radial load with constant direction, the radial load directed towards the arch centre, and the follower radial load (hydrostatic load), as treated by Nikolai in 1918. For the three cases, the buckling loads are first obtained from a static analysis. As the case of the follower radial load (hydrostatic load) is a non-conservative problem, the dynamic approach is also used to calculate the instability load. The governing equations for out-of-plane vibrations of circular arches under radial loading are then derived, both with and without Wagner's effect. Flutter instabilities may appear for sufficiently large values of opening angle, but flutter cannot occur before divergence for the parameters of interest (civil engineering applications). Therefore, it is concluded that the static approach necessarily leads to the same result as the dynamic approach, even in the non-conservative case.     

给水加热型联合循环的变工况性能

在联合循环改造的各种方案中,给水加热型具有投资少、改动少、耗用优质燃料较少、尤其是简单易行及技术难度小等特点,因此在我国现有的技术经济水平、特别是以煤为主的国情下,有一定应用市场。本文分析比较了多种变工况运行方式的性能及可能出现的问题,并在此基础上提出综合性能较好的运行模式。     

直线加速器Kanthal合金高功率同轴负载设计及功率分布

 为满足辐照直线加速器的小型化需求,提出利用同轴负载代替波导式负载结构的方案,其关键技术是利用涂敷在加速腔内壁的微波吸收材料直接吸收剩余微波功率。针对面吸收型负载材料Kanthal(Fe-Cr-Al)合金,采用2π/3模式6腔2周期谐振腔结构,运用CST仿真进行S波段同轴负载设计。对涂层涂敷位置及面积对负载腔工作频率和品质因子的影响进行了详细的仿真分析,并得到了满足2 856 MHz工作频率的腔体尺寸补偿值;设计了一种6腔2周期同轴负载,单路衰减可达-18.63 dB。吸波涂层及腔体铜壁表面功率损耗密度的计算结果表明,腔体周向功率损耗呈均匀分布,阑片表面呈抛物线型分布。     

导线X射线瞬态响应的数值计算

 针对裸线和带保护层导线两种不同的物理结构,分别应用Holland细线模型和时域传输线模型,结合实验结论,计算了负载大小、导线半径、X射线能量以及保护层厚度等对导线X射线瞬态响应的影响。计算结果表明,负载较小时,负载变化对负载电压电流、负载功率和负载能量的影响不大,负载较大时,对响应的影响比较大;负载增大时,负载电流响应脉宽增加、幅度减小,负载功率存在最大值,但是,负载吸收能量却一直增大;负载响应与导线半径成正比、与X射线能量成反比;变化保护层厚度时,负载响应存在峰值;由于保护层内负电荷的影响,相同X射线和导线半径条件下,带保护层导线比裸线的响应至少小一个量级。     

Steady state response of an infinite beam on a viscoelastic foundation with moving distributed mass and load

Compared with the moving concentrated load model, it is more realistic and proper to use the moving distributed mass and load model to simulate the dynamics of a train moving along a railway track. In the problem of a moving concentrated load, there is only one critical velocity, which divides the load moving velocity into two categories: subcritical and supercritical. The locus of a concentrated load demarcates the space into two parts: the waves in these two domains are called the front and rear waves,respectively. In comparison, in the problem of moving distributed mass and load, there are two critical velocities, which results in three categories of the distributed mass moving velocity. Due to the presence of the distributed mass and load, the space is divided into three domains, in which three different waves exist. Much richer and different variation patterns of wave shapes arise in the problem of the moving distributed mass and load. The mechanisms responsible for these variation patterns are systematically studied. A semi-analytical solution to the steady-state is also obtained, which recovers that of the classical problem of a moving concentrated load when the length of the distributed mass and load approaches zero.     

“强光一号”装置上部分Z箍缩实验结果的物理分析

从原子的电离能和维持等离子体所需能量出发，给出了估算任一元素材料，要产生任一壳层的X射线辐射，每个离子(原子)所需要的基本能量和要达到的内爆箍缩速度的方法.对“强光一号”加速器上典型的氪喷气和部分钨丝阵Z箍缩实验的电流和电压波形所蕴涵的丰富物理信息进行了分析，得到了电感和洛伦兹(Lorentz)力做功等物理量的变化规律以及负载参数变化对它们的影响.该电感与基于壳层模型计算出的电感有较大的差异.前者随箍缩开始而缓慢增大，甚至在箍缩到心和飞散后还在增大，最后大致稳定在100 nH附近.差异可能是由于壳层模型过于简化和电流电压的测点同负载有一定的距离而造成的.当丝阵直径为8 mm时，洛伦兹力做功最大；当丝阵直径相同时，丝数较大时，洛伦兹力做功也较大.同时还对该加速器的喷气和丝阵负载的线质量进行了优化，表明也是直径为8 mm的钨丝阵为最佳负载，这同实验的优化结果也一致.     

The non-stationary freefield response for a moving load with a random amplitude

This paper presents a stochastic solution procedure for the calculation of the non-stationary freefield response due to a moving load with a random amplitude. In this case, a non-stationary autocorrelation function and a time-dependent spectral density are required to characterize the response at a fixed point in the freefield. The non-stationary solution is derived from the solution in the case of a moving load with a deterministic amplitude. It is shown how the deterministic solution can be calculated in an efficient way by means of integral transformation methods if the problem geometry exhibits a translational invariance in the direction of the moving load. A key ingredient is the transfer function between the source and the receiver that represents the fundamental response in the freefield due to an impulse load at a fixed location. The solution in the case of a moving load with a random amplitude is formulated in terms of the double forward Fourier transform of the non-stationary autocorrelation function. The solution procedure is illustrated with an example where the non-stationary autocorrelation function and the time-dependent standard deviation of the freefield response are computed for a moving harmonic load with a random phase shift. The results are compared with the response in the deterministic case.     

Load optimal design for a primary test stand facility based on a zero-dimensional load model

In order to couple the numerical simulation of a primary test stand driver with an optimal load design, a zero-dimensional wire array load model is designed based on the Saturn load model using PSPICE, which is an upgraded version of the Simulation Program with Integrated Circuit Emphasis (SPICE) designed by the ORCAD Corporation to perform circuit simulations. This paper calculates different load parameters and discusses factors influencing the driving current curve. With appropriate driving current curves chosen, further magneto-hydrodynamic calculations are carried out and discussed to provide the best results for experiments. The suggested optimal load parameters play an important role in experimental load design.