HAMILTONIAN SYSTEM AND SIMPLETIC GEOMETRY IN MECHANICS OF COMPOSITE MATERIALS (Ⅰ)——FUNDAMENTAL THEORY

For the first time, Hamiltonian system used in dynamics is introduced to formulate statics and Hamdtonian equation is derived corresponding to the original governing equation, which enables separation of variables to work and eigen function to be obtained for the boundary problem. Consequently, analytical and semi-analytical solutions can be got. The method is especially suitable to solve rectangular plane problem and spatial prism in elastic mechanics. The paper presents a new idea to solve partially differential equation in solid mechanics. The flexural problem and phane stress problem of laminated plate are studied in detail.     

硼中子俘获治疗实验装置射频功率源系统

中国科学院高能物理研究所建造了一台基于加速器的硼中子俘获治疗（BNCT）实验装置。射频功率源系统为352.2 MHz射频四极加速器（RFQ）提供高频功率,使束流离开RFQ时,其能量达到3.5 MeV。BNCT射频功率源系统主要包括速调管功率源、数字低电平控制系统、射频传输系统。本文介绍了BNCT射频功率源系统,主要包括物理需求、系统组成、关键设备、安装和调试。目前该装置已进行动物实验,加速器打靶束流功率4.3 kW,加速器射频功率源系统运行稳定。     

CSNS H^- ion source test stand

The Penning surface plasma source is adopted as the China Spallation Neutron Source (CSNS) H^- ion source. The designed energy and beam current of the source are 50 keV and 20 mA, respectively, with a normalized root mean square (norm. rms.) emittance of 0.2 πmm·mrad. The construction of a H^- ion source test stand has been completed, and the commissioning of the source is in progress. Stable H^- ion beams with energy of 50 keV and current up to 50 mA are attained. Emittance measurement for the H^- beam is being prepared.     

RFQ加速器中二极模稳定杆作用机理的研究

RFQ加速器中的二极模场给束流施加一个偏转力,导致束流损失在机器上.因此,必须采取降低二极模场的措施.人们提出采用二极模稳定杆使二极模频率远离四极工作模.在一台RFQ冷模上开展的实验研究中,发现了一些与二极模稳定杆作用机理相关的新现象,本文报告这些实验结果,并对其进行分析解释.根据这些结果,提出,利用非对称性地插入二极模稳定杆,可以降低非对称RFQ腔体中的二极模场分量.     

CRITERIA OF FINITE ELEMFNT ALGORITHM FOR A CLASS OF PARABOLIC EQUATION

In finite element analysis of transient temperature field,it is quite notorious that thenumerical solution may quite likely oscillate and/or exceed the redsonable scope,whichviolates the natural law of heat conduction For this reason,we put forward the concept oftime monotony and spatial monotony and then derive several sufficient conditions formonolonic solutions in time dimension for3-D passive heat conduction equations with agroup of finite difference schemes.For some special boundary conditions and regularelement meshes,the lower and upper bounds for△t/△x~2 can be obtained from thoseconditions so that reasonable numerical solutions are guaranteed.Spatial monotony is alsodiscussed.Finally,the lumped mass method is analyzed.We creatively give several new criteria for the finite element solutions of a class ofparabolic equation represented by heat conduction equation.     

HAMILTONIAN SYSTEM AND SIMPLETIC GEOMETRY IN MECHANICS OF COMPOSITE MATERIALS (Ⅱ)——PLANE STRESS PROBLEM

Fundamental theory presented in Part (Ⅰ) is used to analyze anisotropic plane stress problems. First we construct the generalized variational principle to enter Hamiltonian system and get Hamiltonian differential operator matrix, then we solve eigen problem; finally, we present the process of obtaining analytical solutions and semi-analytical solutions for anisotropic plane stress porblems on rectangular area.     

南海南部表层碳酸盐沉积

本文应用研究区内127个站表层样品,研究了碳酸盐沉积物特征,并综合分析了沉积物类型和碳酸盐沉积物的生物、矿物、地球化学组成等。根据碳酸盐沉积和岩性参数变化和相应的沉积环境及沉积作用,将本区分成6个沉积相,并阐明各沉积相的分布和特征。     

Electromagnetic modeling of the CSNS Hion source extraction system

A Penning surface H^- ion source test stand has been developed for the China Spallation Neutron Source (CSNS) at the Institute of High Energy Physics (IHEP). H^- beams with a current up to 50 mA and a pulse length up to 520μs at a repetition rate of 25 Hz are obtained at present. In order to improve the extraction system based on both the results of the emittance measurements in experiment and the simulation results of the effect of the extraction system on the beam emittance, three dimensional electromagnetic finite element analysis and particle tracking are undertaken. First, the magnetic field of the deflecting magnet is studied in detail, and then the effect of the extraction geometry on the beam transport is also investigated.