横摇运动下铅铋回路热工水力特性数值研究

为研究横摇运动下铅铋回路系统热工水力特性，利用商用CFD软件开发了铅铋回路系统的计算模型以及横摇运动的计算方法，并采用实验数据对数值计算结果进行了验证，其中，横摇运动流量的最大偏差在3%以内。计算结果表明，横摇运动会使回路系统的自然循环流量发生周期性波动，流量波动的周期与运动周期一致，波动的幅度会随着横摇运动最大幅度的增大、运动周期的减小而增大，在最大摇摆角20°摇摆周期7.5 s工况下流量的瞬时波动最大达到了140%,并在一些时刻产生倒流现象。横摇运动也会让系统的流动和传热特性参数发生周期性的瞬时波动，这种波动的规律与自然循环流量的波动规律相似，其中Nu的最大瞬时波动达到了515%,最大时均波动可达66%。本研究获得的结果对横摇运动下的铅铋回路系统设计优化具有重要的工程应用价值和科学意义。     

面对称磁场中粒子的六维传输特性

导出了（ｘ，ｘ＇，ｙ，ｙ＇，ｔ，ｔ＇）相空间中粒子的一般六维运动方程。对于面对称磁场，还导出了（ｘ，ｘ＇，ｙ，ｙ＇，τ，τ＇）相空间粒子运动的二阶运动方程及其严格的一阶和二阶形式解。最后，给出了偏转磁铁具体的一阶及二阶传输解。     

潜艇反应堆在摇摆运动中的自然循环和堆芯传热特性

在一个有摇摆运动的模型反应堆中进行了一系列的单相自然循环试验，以研究摇摆运动对其热工水力特性的影响。在每段管道中，流体由于摇摆运动的惯性力，流动速度随着摆动角度周期性地变化。当摇摆周期变短时环路流速振荡的幅度变大，摆动角度和环路流动速度振荡之间的相位差变大。另一方面，尽管堆芯的流速值随着摇摆周期变化，但是流速并不振荡。堆芯流速变化与摇摆运动的雷诺数和瑞利数密切相关，它是由热驱动头的变化和整个环路的压力损失的变化引起的。为了模拟堆芯流速随着摇摆速度的变化，建立了一个简单的一维分析模型，其正确性已被验证。由于摇摆运动产生局部流动，因此增强了堆芯中的传热。堆芯中的传热系数按摇摆运动的Richardson数的大小被分为三个区间。     

水压缸活塞环密封运动阻力研究

针对控制棒水压驱动机构单缸步进动态过程，根据水压缸活塞环密封机构的特点，分析水压缸单缸步进过程中运动阻力的来源，建立运动过程的动态理论模型。利用控制棒水压驱动机构单缸性能实验的结果，推导出水压缸单缸步进过程中运动阻力的变化过程。通过对运动阻力参数和步进过程中缸内压力以及步升速度动态参数的分析，得到了水压缸单缸步进过程中运动阻力的计算模型。由该模型计算所得步进动态位移曲线与控制棒水压驱动机构单缸步进实验位移曲线吻合得很好。本研究结果为控制棒水压驱动机构单缸步进过程的动态模拟以及控制棒水压驱动机构在步进过程中各部件的应力分析奠定了理论基础。     

用于探伤加速器的五维运动机构的研制

探伤加速器在工件质检工作中需移动到位，并以一定的角度方向对准工件的待检部位，五维的运动机构适应这样的工作需求。在射线屏蔽大厅内装配行车，实现水平的二维运动，内置升降机钢丝绳的伸缩柱实现垂直运动功能，伸缩柱下方的轭架可沿竖直轴线水平旋转，X射线机头装配在轭架上实现其俯仰动作。五维运动有5种电机驱动，分别使用2台小型PLC控制其运行逻辑。     

核动力船舶燃料组件瞬态动力学分析

针对核动力船舶燃料组件在船体运动状态下的结构安全问题，以海洋核动力平台为例，采用水动力学对平台进行频时域计算，得到船体重心的六自由度运动时历曲线。基于远程位移方法将船体运动传递到反应堆，实现对燃料组件随船体运动的数值模拟，并采用瞬态动力学对燃料组件的结构载荷进行计算。计算结果表明，与船体静止状态下相比，燃料组件的结构载荷在船体运动状态下明显增大。因此，在对燃料组件进行结构安全分析时，必须考虑船体的随机运动响应。      

三维空间液滴运动模型数值解法研究

提出了数值求解三维空间液滴运动模型的算子分裂算法（OS算法），并与常用的显式单步长Runge-Kutta（RK）算法进行了比较。简述了三维空间液滴运动模型的具体形式，提出了求解该模型的OS算法，以求解不同直径液滴在波形板汽水分离器内的运动轨迹作为算例，从OS算法的相容性、稳定性、计算精度和计算效率（CPU耗时）等方面，与4级4阶显式单步长RK算法进行了比较。结果表明，OS算法所构造的离散格式与液滴运动模型相容，采用此算法计算得到的液滴运动轨迹与RK算法得到的结果相似，而OS算法的稳定性和计算效率均优于RK算法。因此，OS算法的提出为数值计算波形板的分离效率提供了较为稳定、高效的算法。     

融合反应中质量参数的理论研究

在研究原子核大振幅的集体运动过程中，质量参数是描述反应体系属性的重要参量。目前，采用的理论模型主要包括基于流体力学理论的宏观模型与基于推转思想的微观模型，两者对核物质运动采取了不同的近似处理。在理论处理和实际应用方面均存在不少问题，因此，对质量参数的研究始终是核物理研究中的重要课题。     

冷液中运动高温球传热阻力耦合特性实验研究

高温颗粒与冷液接触会引发剧烈的沸腾蒸发瞬变现象，涉及到工程安全，是一高速瞬变多相传热问题。本实验室设计建立了高温颗粒下落冷液沸腾可视化实验装置，初次实验将1个或有限几个高温球形颗粒坠入水中，利用高速摄像机记录其在冷液中的运动速度，证实了确实存在由周围冷液快速蒸发引起的作用在运动中高温颗粒上的特殊阻力，验证了高温颗粒的蒸发曳力模型。     

声场驱动下泡壁运动方程的理论分析

声场驱动条件下的泡壁运动方程一直是泡动力学领域的重要研究内容。当泡壁运动方程用于预测高马赫数下的气泡振荡特性时，为满足计算精度的需求，应该充分考虑液体的可压缩性。在声场驱动条件下，本文数值研究了含二阶马赫数修正的泡壁运动方程（简称“二阶方程”）在不同马赫数条件下对气泡振荡特性重要物理量的预测。围绕声场振幅和声场频率两个物理参数，将二阶方程与一阶马赫数修正的泡壁运动方程（简称“一阶方程”）的预测结果进行深入地对比分析。研究发现，在高马赫数条件下，一阶方程和二阶方程预测的气泡半径、泡壁速度和泡壁加速度均存在较大的差异，导致二者所预测的声耗散功率和热耗散功率也存在较为明显的差异。本研究为声场驱动下的泡动力学领域提供了理论模型的选择依据。     

带电粒子轨迹的随机跟踪与图形分析

为了真实地描述带电粒子束的光学特性,文章对粒子轨迹跟踪中粒子初始条件的随机抽样进行了探讨。粒子的发射面包括平面、圆柱面和球面;分布函数既可由解析形式表示,又可由数值形式给出。其次,为了有效地利用轨迹跟踪结果对带电粒子束特性进行系统的分析,文章还探讨了粒子轨迹的图形处理和分析,内容包括轨迹的样条拟合、轨迹和束包络图形的绘制、象的尺寸及其位置的确定,以及任意横截面上粒子分布图形的绘制。     

均匀二极磁场的李代数分析

用要代数方法分析了带电粒子在二级磁场中的传输及其像差问题。     

二极磁铁的三级Lie映射

用Ｌｉｅ代数方法分析了带电粒子在二极磁铁中的运动，得到在六维相空间中相对论凿子的三级近似轨迹。     

Study of talcum charging status in parallel plate electrostatic separator based on particle trajectory analysis

Electrostatic separation has been extensively used in mineral processing, and has the potential to separate gangue minerals from raw talcum ore. As for electrostatic separation, the particle charging status is one of important influence factors. To describe the talcum particle charging status in a parallel plate electrostatic separator accurately, this paper proposes a modern images processing method. Based on the actual trajectories obtained from sequence images of particle movement and the analysis of physical forces applied on a charged particle, a numerical model is built, which could calculate the charge-to-mass ratios represented as the charging status of particle and simulate the particle trajectories. The simulated trajectories agree well with the experimental results obtained by images processing. In addition, chemical composition analysis is employed to reveal the relationship between ferrum gangue mineral content and charge-tomass ratios. Research results show that the proposed method is effective for describing the particle charging status in electrostatic separation.     

Design criteria for an angle resolved electron spectrometer of novel toroidal geometry

A charged particle analyser based on the use of polar trajectories in a toroidal sector is described in which a large number of particle emission angles are detected simultaneously. An analysis of the trajectories of particles in this class of analyser is presented and we develop transfer matrices which enable the imaging properties of such devices to be determined analytically. Expressions for the axial and radial magnification and for the energy resolving power are also derived. The analysis and the derived properties are compared with a numerical simulation and with all available published data.     

Computer simulation of polarization characteristics of channeling radiation for relativistic electrons

A computation method for the polarization characteristics of relativistic particle radiation in a crystal has been developed. This method is based on the computer simulation of particle trajectories. Formation of the total radiation spectrum and the Stokes parameters by averaging over the possible electron trajectories under planar channeling has been analyzed. A comparison with experimental data has been made.     

Analog Computer for Quadrupole Magnet Design

In the design of particle accelerators, magnets are sometimes used to bend the paths of charged particles in linear accelerators for focusing and defocusing purposes. These magnets, in the present case, are known as quadrupoles. Their design hinges on the solution of certain mathematical expressions of particle trajectories. A computer of the analog type was constructed to solve the equations and so facilitate magnet design. The analog computer for this application has dials labeled "L", "?", and "?". The settings of these dials represent the design parameters under study. The operator can set the dials of each stage to any of thousands of different combinations of L, ?, and ?. The results of his settings may be observed on a CRO screen. He can then proceed to search for the best combination of control settings with regard to their effect on particle trajectories. Once having found a satisfactory combination, the corresponding magnet design parameters are obtained from the settings of the controls. Three features of construction required special consideration. These were: the high gain, minimum phase shift, and minimum crosstalk. These items and others are discussed in the article from the practical as well as the theoretical point of view.     

An ab initio Monte Carlo study of low energy positron and electron implantation in elemental metals and multilayers

A Monte Carlo code developed at Brookhaven to study positron and electron implantation in solids will be discussed. This code models the trajectories of a large number of positrons or electrons as they move through the material and uses this information to calculate stopping profiles, backscattered fractions and transmitted fractions. The particle-atom interactions are incorporated via elastic and inelastic scattering cross-sections. The incident particle energies vary from 1 to 10 keV and the simulation stops when the particle energy goes down to 25 eV or if the particle is backscattered. Main results of our Monte Carlo simulations of the mean implantation depth and implantation profiles for both semi-infinite metallic elements and multilayers will be discussed.     

Optimizing the geometry of a negative ion sputter source

In order to avoid isotope fractionating effects due to slight fluctuations in the position, direction or divergence of the emerging beam, the emittance of an AMS ion source has to be lower than the acceptance of the following beam handling system. The emittance of a negative ion sputter source is determined by the energy spread of the sputtered ions and by its extraction geometry. For various configurations of the latter, we have calculated particle trajectories. Greatly reduced aberrations are attained if the electric field close to the emitting surface is nearly uniform and only weakly focussing and if the acceleration takes place in at least two lens sections. The single acceleration gap of our Hortig-type ion source [1] has therefore been replaced by a two-stage accelerating lens. Further, the curvature of the field at the surface of the sputter target is controlled by an additional electrode.     

Tagged Particles in Monte Carlo Calculations of Radiation Transfer Using the Prizma Computer Program

The additional possibilities due to the introduction into the PRIZMA program, intended for performing Monte Carlo calculations of linear radiation transfer problems, of a particle tagging technique are studied. In calculations, it is often necessary to estimate the contribution of particles which were in some particular situation. The tagged-particle method was developed to obtain such results. A particle is tagged with a marker and the results are recorded as a function of whether or not the particle is tagged. To solve multivariant problems, arising in the calculation of the effects due to small perturbations, a special method was developed for simulating trajectories using tagged particles. This method makes it possible to obtain in a single calculation correlated results for all variants of the problem. The possibilities of the tagged-particle method and the special method of simulation are illustrated for numerical examples.__________Translated from Atomnaya Energiya, Vol. 98, No. 5, pp. 386–393, May 2005.