高阶微商场论中奇异拉氏量系统的量子正则对称性

给出了高阶徽商场论中奇异拉氏量系统规范生成元的构成.从相空间中Green函数的生成泛函出发,导出了约束Hamilton系统正则形式的Ward恒等式.指出该系统的量子正则方程与由Dirac猜想得到的经典正则方程不同.给出了与Chern-Simons理论等价的一个广义动力学系统的量子化.将正则Ward恒等式初步应用于该系统,不作出对正则动量的路径积分,也可导出场的传播子与正规顶角之间的某些关系.     

自对偶引力的局部对称性与约束

在Ashtekar形式下，广义相对论的相空间被嵌入到复SU（2）Yang-Mils理论的相空间里．将一般场论中分析局部对称性与约束的方法推广到复的场论，从自对偶Palatini形式的位形空间构造出Ashtekar形式的相空间，进而讨论了位形空间上的局部对称性与相空间上的约束的关系． 关键词：     

有限温度QED中的轫致辐射修正

用有限温度场论方法,通过计算费曼图分析了在QED中由于温度效应导致的新红外发散.结果表明零温场论中的红外发散和由温度效应引起的红外发散可以用描写虚过程的费曼图同时消除.计算了轫致辐射中光子的辐射几率,在Eikonal近似下所得到的结果和半经典近似给出的结果一致.     

超对称电动力学系统的Faddeev-Senjanovic量子化

用Faddeev-Senjanovic量子化方法对超对称电动力学系统在一般情况下进行了量子化, 得到了格林函数的生成泛函. 通过对一些约束作线性组合获得了另一个第一类约束, 构造出了该体系的规范生成元, 导出了该系统的规范不变的对称变. 由一个规范条件的自恰性导出了另一个规范条件, 发现超对称电动力学系统的次级第一类约束对应物理电荷守恒律, 从而使过去要算很多次级约束才能截断的约束自然截断, 因而使超对称电动力学系统在一般情况下的Faddeev-Senjanovic量子化被简化.     

生成泛函与真空结构

本文讨论由量子力学的生成泛函过渡到场论的生成泛函时如何考虑起始态与终了态的基态,即真空态的问题。特别是近来在规范理论中真空的结构的讨论使这一问题的讨论更属必要。     

非平衡统计场论中闭路格林函数的重整化

本文讨论了非平衡统计场论中引进的闭路格林函数的重整化问题.在对初始关联函数作一些合理限制的条件下,用通常场论中紫外发散的对消项就可以消除闭路格林函数的紫外发散.采用在场论中由维数调整法所决定的重整化因子,求得了闭路顶点函数所满足的重整化群方程.     

含Chern-Simons项的旋量电动力学的量子正则对称性

构造了含Chern-Simons(CS)项的旋量电动力学的规范变换生成元.按约束Hamilton系统的Faddeev-Senjanovic(FS)路径积分量子化方案,给出了该系统Green函数的相空间生成泛函;导出了正则Ward恒等式;分析了系统的量子守恒角动量,指出它具有分数自旋性质.     

规范场论的发展和超对称性

对称性是宇宙间普遍存在的一种性质,在物理学中它表现为物理定律在某种对称变换下的不变性.现代物理学的两大支柱——量子力学和相对论的发展使这种对称性占有了特殊重要的地位. 最近二十多年里发展起来的规范场论便是以规范变换群下的不变性为特征来说明各种基本物理现象的理论.由于这一理论为描述各种基本自然力提供了一个适当的框架,自六十年代末期起,它在统一描述基本自然力的方面取得了重大进展,使爱因斯坦在晚期从事多年而未获得成功的统一场论研究在新的条件下重新获得了生命,因此很多人也把规范场论直接叫做统一场论.不过,规范场论…     

1+1维非线性σ模型的BRST变换的等价性和Ward恒等式

在依据Dirac约束规范理论和作推广后的条件下,导出了规范生成元,推导出了1+1维O(3)非线性σ模型的一般条件(β≠0)下的BRST变换,给出了其BRST变换与Dirac规范变换的等价关系,得到了鬼场的新的一般对易关系,且其一般参数β为零时就回到通常的鬼场的对易关系.并由规范生成元导出了BRST荷,进而完成了此模型的一种BRST量子化.还在此基础上进一步导出了此系统的Green函数生成泛函、连通Green函数生成泛函和正规顶角生成泛函,获得了3种不同的Ward恒等式     

有效拉氏量理论

按照现代场论观点,所有现在所用的描述现实相互作用的理论都是某种更基本的理论的有效理论,有效理论的一个主要特点是其相互作用项一般是无穷多项.它与通常的可重整场论有很大差别.这里主要讨论一类特殊的有效理论——强作用手征有效拉氏量的理论特点及研究现状.没有涉及强作用中重夸克有效场论理论,NRQCD理论及它们与手征有效拉氏量结合而形成的理论.     

A signal generator for testing of hearing protectors

The measurement of the acoustical attenuation of hearing protectors requires a signal generator whose characteristics are specified in the ANSI S3.19-1974 Standard. This paper describes such a generator which was constructed by modifying a regular screening audiometer, including a pink noise generator followed by nine one-third octave band filters and an additional 2·5 dB attenuator. Detailed information on the construction and performance of the generator is provided in the paper. The generator, which is relatively easy to build, has proved to be reliable for uses in the laboratory, as well as in the field.     

基于电磁感应的脉冲功率发生器试验研究

为了验证基于电磁感应原理的脉冲发生器的可行性,设计了一种小型脉冲发生器试验模型。对发生器的初始磁场与磁芯转变过程进行了分析与计算,建立了发生器的等效电路模型,并结合试验测量的负载电阻电压得出发生器的感应电压。设计的发生器整体直径约70mm,长度约85mm,其中磁芯直径为25mm,长度为25mm,提供初始磁场的永磁体厚度为10mm,试验得出发生器感应电压峰值为784.5V,与理论计算结果基本吻合,验证了发生器的可行性。     

模块化Marx发生器机芯的力学环境适应性分析及优化设计

为研究Marx发生器机芯在公路运输条件下的力学环境适应性,基于随机振动理论和有限元分析方法对Marx机芯进行了仿真分析和随机振动试验。首先,建立了八级模块化Marx机芯的有限元动力学仿真模型,模拟确定了机芯的应力集中点;然后,通过振动台运输振动摸底试验修正了有限元模型,对机芯结构进行了优化设计,使Marx机芯整体一阶频率由15.4 Hz提高到19.7 Hz,降低了整机垂向的动力学响应,提高了机芯的力学环境适应性。试验结果表明,Marx发生器结构设计需要重点考虑其在垂直方向的可靠性;振动过程中,机芯整体连接稳定,振动应力集中于机芯与U型支撑杆连接处、支撑杆与支撑板连接的角片处,以及开关连接件处,是结构设计的薄弱环节。     

百kV级纳秒脉冲源的设计与实验研究

GW级Tesla型脉冲源在触发开关技术研究中作为触发脉冲源使用,抖动较大,触发开关工作不稳定,需要为其研制一台触发器以解决这一问题。结合其他使用需求,设计了一台百kV级纳秒脉冲源,该脉冲源采用Tesla变压器结合单筒脉冲形成线结构,进行了Tesla变压器结构、Tesla变压器初次级参数、Tesla开路磁芯与初级电路设计,调试结果为:最高输出电压100 kV,峰值功率250 MW,重复频率1~100 Hz,输出脉冲宽度约4 ns,前沿约1 ns。该脉冲源作为触发器使用,可以将GW级Tesla型纳秒脉冲源抖动由500 ns降低至150 ns,满足触发开关研究需求,还可用于产生超宽谱短脉冲进行辐射。     

A generator coordinate approach for the description of pairing vibrations in the seniority-zero space

The application of the generator coordinate method is extended to non-harmonic systems. The many-dimensional Hill-Wheeler integral equation is reduced to a one-dimensional integral equation by expressing all independent parameters in the generator function by a single parameter. It is shown that the subspace spanned by a proper single-parameter family is the same as that spanned by the many-parametric family of generator functions.     

螺旋线型微秒级高压长脉冲发生器

为研究长脉冲强流电子束产生技术,设计了一台螺旋线型高压长脉冲发生器。该发生器主要由Marx发生器、充电电感、脉冲形成线、高压开关、脉冲传输线及平板二极管构成,形成线内导体为螺旋线,工作介质为去离子水,其指标为输出电压500 kV,电流40 kA,脉冲宽度1μs,单脉冲能量20 kJ。简要介绍了该长脉冲发生器的结构、给出了结构和电气参数,讨论了各部分设计应注意的问题。     

Electrical behavior of a simple helical flux compression generatorfor code benchmarking

A variety of basic magnetic flux compression (MFC) generator geometries have been tested during the last three decades. Though size and operating regimes differ widely, it is apparent that the helical flux compression generator is the most promising concept with respect to current amplification and compactness. Though the geometry of the helical generator (dynamically expanding armature in the center of a current carrying helix) seems to be basic, it turns out that the understanding of all involved processes is rather difficult. This fact is apparent from the present lack of a computer model that is solely based on physical principles and manages without heuristic factors. A simple generator was designed to address flux and current losses of the helical generator. The generator's maximum current amplitude is given as a function of the seed current and the resulting “seed-current” spread is compared to the output of state-of-the-art computer models. Temporally resolved current and current time derivative signals are compared as well. The detailed generator geometry is introduced in order to facilitate future computer code bench marking or development. The impact of this research on the present understanding of magnetic flux losses in helical MFC generators is briefly discussed     

Numerical study on performance of disk MHD generator using frozen inert gas plasma

In an magnetohydrodynamic (MHD) generator using a frozen inert gas plasma (FIP), the availability of a frozen argon plasma, the influence of plasma uniformity at the generator inlet on the performance, and the feasibility of a large-scale generator are numerically examined by /spl gamma/-/spl theta/ two-dimensional simulation. The FIP is produced by pre-ionizing inert gas without an alkali metal seed at the generator inlet, then the ionization degree of the plasma is kept almost constant in the whole of the channel because of considerable slow recombination of the inert gas just like frozen reaction plasma. It is found that not only helium, but also argon frozen plasma MHD generation is realized, although highly accurate control of inlet ionization degree is necessary for argon. It is important to reduce the nonuniformity of plasma properties at the generator inlet in order to raise the maximum enthalpy extraction ratio. Even for the large-scale generator with 1000-MW thermal input, the ionization degree is kept almost constant in the whole of the channel and the high performance is obtainable. This result is extremely attractive for the FIP MHD generator.     

Calculations of the parameters of the air plasma produced by an electron beam in the channel of an MHD generator with a nonequilibrium conductivity

Approximate analytic expressions for calculating the electron density in both steady and unsteady plasmas produced by pulsed electron beams are derived and proved to agree well with numerical calculations. It is shown that the algorithm for calculating the parameters of a nonequilibrium plasma in the channel of an MHD plasma generator depends on the type of generator. The effect of the magnetic field strength on the electron density and electric conductivity of the air plasma produced by an electron beam in the channel of a Faraday MHD generator is investigated. The influence of the parameters of the flow and ionizer on the efficiency of an MHD generator with a nonequilibrium conductivity is analyzed.     

300 kV高压脉冲发生器

介绍了脉冲X光机驱动源300 kV高压脉冲发生器的研制,高压脉冲发生器选择双边充电回路的Marx发生器结构,采用紫铜火花隙开关和隔离电感为发生器的结构元件,低感陶瓷电容为储能元件,这种结构不仅减小了回路电感,同时实现了脉冲发生器的小型化与模块化。所设计的高压脉冲发生器在75 负载上获得脉冲半高宽小于等于100 ns、幅值200～300 kV可调的输出电压。高压脉冲发生器内可直接安装X光管也可通过高压电缆与X光管连接,很好地满足了X光机的需要,研制的高压脉冲发生器具有性能稳定、结构紧凑、使用方便等特点。