等离子体压强对Line-tied扭曲不稳定性增长率和本征函数的影响

应用半解析方法,研究了直圆柱位形下等离子体压强P0分别为P0=0、P0=常数和P0=f(r)时Line-tied扭曲不稳定性的增长率和二维径向本征函数的演化规律。结果表明,P0=0和P0=常数时的轴向波数k的范围相同,但P0=常数时的增长率比P0=0时的小。P0=f(r)时的轴向波数k的范围和增长率则都比P0=0时的大,同时磁流体的速度变化也较大。因此,P0=f(r)更接近实际的物理模型(例如日冕的喷射问题)。     

微穿孔板吸声体的准确理论和设计

提出以等效电路的为基础的微穿孔板吸声体的准确理论。吸声体的特性参数是板的相对声阻r，穿孔直径d和共振频率f0，后二者合成穿孔板常数，它与r决定微穿孔板吸声体的结构和频率特性。吸声频带半宽△f／f0的最大值为（4／π）tan－1（1＋r），这是k值趋近于零时的极限，只要k小于1，相差也不大，这时空腔厚度接近四分之一波长。可见r值大时，带宽可达到极为可观的程度．k值大时，吸收带宽大为降低，同时空腔节厚度将成为比波长小得多的值。文中讨论微穿孔极吸声体的一般特性。     

含时库仑势和线性势的薛定谔方程的求解

利用Burgan等人的时空变换方法对一类特殊形式的具有含时库仑势加线性项的薛定谔方程进行了分析和计算,并进一步讨论了更普遍形式的含时势V(r,t)=–a0ξ12r+nk=1akrkξk2+1(其中ξ=at2+bt+c,a0,a1,a2,…,an,a,b,c是满足一定关系的常数)的波函数     

无碰撞电流片低频电磁模不稳定性：MHD模型

利用含无电阻广义Ohm定律的可压缩磁流体力学(MHD)理论，研究了在具有剪切磁场的无碰撞电流片中低频电磁模不稳定性，假定等离子体压力各向同性，推导出了三维扰动传播波模的色散关系.色散关系的数值求解集中在电流片中间平面(z=0)和半厚度边缘(z=1)上，并分别考虑了二维传播和三维传播，以及不同的离子惯性长度情况.主要结果如下：1)对 于二维扰动传播(k_z=0)的波，在z=0平面上，Alfven波增长率最大，不稳定的波 频率 和波数范围也更宽.离中间平面越远，增长率越小，波数区域越小.同时，随着离子惯性长度 的增大，Alfven波不稳定性的增长率变大.2)对于三维扰动传播(k_z≠0)的波， 哨声是 不稳定的.在电流片中间平面上，哨声有明显的增长率；而在离子惯性区外边，哨声的增长 率还变大.3)在电流片中间(z=0)平面上，低频波主要是电流不稳定性激发的.在离中间 平面较远处，电流、密度和压力的梯度不稳定性变得更重要. 关键词： 无碰撞电流片 磁流体力学 色散关系 不稳定性     

算符(f(“非汉字符号”))~k正交归一本征态的非经典特性

证明了算符 (a^ f(n^) ) k(k≥ 3)的k个正交归一本征态的完备性 ,引入了反聚束效应和一种新的高阶压缩 ,研究了算符 (a^ f(n^) ) k 的k个本征态的反聚束效应和高阶压缩特性 .结果表明 ,这些态可以构成一个完备的希尔伯特(Hilbert)空间 ,它们均可呈现反聚束效应 ,且当k为偶数时它们可呈现M阶 [M =(n +1 2 )k ;n =0 ,1,2 ,… ]压缩效应     

雨滴下落“ 紫外灾难”的消除

对于雨滴在下落过程中, 当采用空气阻力f=k 1 v时, 其a t图像变化率一直减小, 只适用于速度较小 情况; 而当采用阻力f=k 2 v 2 时, 其a t图像变化率先增大后减小, 只适用于速度较大情况. 只有当采用阻力f= k 1 v+k 2 v 2时, 其at图像变化率一直减小, 同时适用于速度较小和较大情况, 比前两种理想化模型更加符合实际情 况     

NO_2分子激光诱导荧光辐射寿命和碰撞猝灭速率的实验研究

实验测定了激发波长在 591～ 594nm范围 ,压力在 0 .1～ 15Pa时 ,NO2 分子激光诱导荧光衰减曲线 ,作几何修正后应用Stern Volmer模型 ,得到了零压辐射寿命τ0 ( =1/k0 )和碰撞猝灭速率常数kq,结果与文献报道基本一致。对NO2 分子激发态能级的反常长寿命和一定压力下出现的双指数衰减等进行了较详细的讨论。     

晶粒间界相及结构缺陷对HDDR 粘结磁体矫顽力的影响

本文根据氢化／歧化／脱氢／重组（HDDR）Nd-Fe-B 磁粉晶粒边界微结构的特点,建立了缺陷区内的磁晶各向异性常数K1´及交换积分常数A1´的双变量连续变化模型,研究了晶粒间界相厚度d及晶粒表面结构缺陷厚度r0对磁体矫顽力的影响。结果表明：晶粒表面各向异性常数K1(0)、交换积分常数A1(0)及r0取不同值时,磁体的矫顽力Hc均随d增加而增大。K1(0)和A1(0)取确定值时,相同的d值对应的Hc随r0的增大而上升。r0和d取确定值时,Hc随K1(0)或A1(0)的减小而增大。当d 为1nm,r0 在 (2~5) nm范围内,A1(0)和K1(0)的值分别在A1和K1值的(0.6~0.7)范围内变动时,计算的矫顽力与实验值符合得很好。     

晶粒间界相及结构缺陷对HDDR 粘结磁体矫顽力的影响

本文根据氢化／歧化／脱氢／重组（HDDR）Nd-Fe-B 磁粉晶粒边界微结构的特点,建立了缺陷区内的磁晶各向异性常数K1´及交换积分常数A1´的双变量连续变化模型,研究了晶粒间界相厚度d及晶粒表面结构缺陷厚度r0对磁体矫顽力的影响。结果表明：晶粒表面各向异性常数K1(0)、交换积分常数A1(0)及r0取不同值时,磁体的矫顽力Hc均随d增加而增大。K1(0)和A1(0)取确定值时,相同的d值对应的Hc随r0的增大而上升。r0和d取确定值时,Hc随K1(0)或A1(0)的减小而增大。当d 为1nm,r0 在 (2~5) nm范围内,A1(0)和K1(0)的值分别在A1和K1值的(0.6~0.7)范围内变动时,计算的矫顽力与实验值符合得很好。     

夫兰克-赫兹实验中的气体击穿现象与空间电荷影响

实验采用充汞夫兰克-赫兹管(F-H管)测定汞的第一激发态(6~3P_1态)电位。当_电子在加速场中所获得的能量小于原子第一激发态的能量时,电子与原子的碰撞只能是弹性碰撞,根据理论计算,碰撞后电子损失的动能与原有动能的比值为δ=4mM/(m+M)~2cos~2θ=4r/(1+k)~2cos~2θ(1)式中k=M/m为原子与电子的质量比,因k》1, δ_max=4k/(1+k)~2=4/k→0即弹性碰撞时,电子几乎不损失能量。而当电子在加速场中所获得的能量等于或大于原子某一激发态的能量时,原子将被激发,这时碰撞为非弹性碰撞,据计算     

微小等离子体反应器的导出机理研究

An extraction mechanism based on micronozzle in the bottom of the microhollow cathode and applied bias electrical field is proposed, and digitally simulated with a two dimensional fluid model. When the operating gas is SF₆ and its pressure is 2~9kPa, radius of the micronozzle is 0.25μm, maximum F atom flux density is between (1.53~5.62)×10¹⁴cm^-3·s^-1, maximum SF₅⁺ flux density is between (2.46~7.83)×10¹⁶cm^-3·s^-1. When gas pressur is  5kPa,average energy of F atom at sample surface is 3.82eV, dispersion angle is −14º~14º; average energy of SF is 25eV, dispersion angle is −13º~14º. When applied voltage across hollow cathode and sample is between 10~50V (sample as cathode), average energy of SF is between 52~58eV. The density of F and SF in the simulation result could satisfy the requirement for silicon etching, and the feasibility of scanning plasma etching validated.     

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应用准光学原理设计了HL-2A装置电子回旋共振加热(ECRH)系统新的集束天线,该天线能使4束68GHz/500kW/1s电子回旋波通过椭球镜聚焦和平面镜的反射,从一个直径350mm装置窗口同时注入托卡马克,对等离子体实现加热。根据基模高斯束的传播原理得出,在装置环向横截面中心处单条波束的功率密度为158MW•m-2,功率密度降为中心密度的1/e2的半径为31.7mm,微波束经过镜面聚焦和反射产生的欧姆损失和衍射损失分别为0.27%和0.64%。利用有限元分析软件Ansys对镜面进行热分析得到,在1s脉冲载荷下最大镜面温升仅为0.47℃,镜面可以自然冷却。     

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研究了在托卡马克装置中中性束注入时快离子自举电流的产生。利用快离子分布函数在两小增量δ=ρp/a (ρp是极向拉莫尔半径,a是小半径)和δ*=τB/τs(τB是俘获粒子反弹周期,τs是慢化时间)下进行展开的方法求解漂移动力学方程;给出了快离子自举电流的一般表达式。计算了圆截面大纵横比托卡马克中快离子自举电流密度分布和总的快离子自举电流的大小,研究表明：在中性束垂直注入时快离子自举电流约占总电流10%;自举电流的大小既敏感地依赖于中性束注入的角度——平行注入时较小、接近垂直时迅速增大,同时也较强的依赖于快离子的产生速度与临界速度的比值,即vb/vc,而vb2∝E(束能量);自举电流的大小随注入束能量的增加而迅速增大。     

A remark on tensor representations

The identity $$\sum\limits_{v = 0} {\left( {\begin{array}{*{20}c} {n + 1} \\ v \\ \end{array} } \right)\left[ {\left( {\begin{array}{*{20}c} {n - v} \\ v \\ \end{array} } \right) - \left( {\begin{array}{*{20}c} {n - v} \\ {v - 1} \\ \end{array} } \right)} \right] = ( - 1)^n } $$ is proved and, by means of it, the coefficients of the decomposition ofD ₁ ⁿ into irreducible representations are found. It holds: ifD ₁ ⁿ \(\mathop {\sum ^n }\limits_{m = 0} A_{nm} D_m \) , then $$A_{nm} = \mathop \sum \limits_{\lambda = 0} \left( {\begin{array}{*{20}c} n \\ \lambda \\ \end{array} } \right)\left[ {\left( {\begin{array}{*{20}c} \lambda \\ {n - m - \lambda } \\ \end{array} } \right) - \left( {\begin{array}{*{20}c} \lambda \\ {n - m - \lambda - 1} \\ \end{array} } \right)} \right].$$      

On the Meissner effect in a superconductor with 4-fermion attraction

A presence of a Meissner-Ochsenfeld effect in a gas of spin 1/2 fermions with an interaction , where is a volume of a region in real space which is taken by thesystem and with , satisfying Fermi anticommutation relations, is investigated. The effect proves to be weaker than in BCS by a factor 3/4 at T = 0, implying a greater penetration depth of external magnetic field. V ₄ is nonzero only within a thin layer of 1-fermion energies around the chemical potential .Received: 14 June 2004, Published online: 12 October 2004PACS: 74.20.-z Theories and models of superconducting state - 74.20.Fg BCS theory and its development     

Internal Lifschitz singularities for one dimensional Schrödinger operators

The integrated density of states of the periodic plus random one-dimensional Schrödinger operator ;f0,q _i ()0, has Lifschitz singularities at the edges of the gaps inSp(H ). We use Dirichlet-Neumann bracketing based on a specifically one-dimensional construction of bracketing operators without eigenvalues in a given gap of the periodic ones.     

On the Uniqueness of Weak Weyl Representations of the Canonical Commutation Relation

Let (T, H) be a weak Weyl representation of the canonical commutation relation (CCR) with one degree of freedom. Namely T is a symmetric operator and H is a self-adjoint operator on a complex Hilbert space satisfying the weak Weyl relation: for all (the set of real numbers), e^−itH D(T) ⊂ D(T) (i is the imaginary unit and D(T) denotes the domain of T) and . In the context of quantum theory where H is a Hamiltonian, T is called a strong time operator of H. In this paper we prove the following theorem on uniqueness of weak Weyl representations: Let be separable. Assume that H is bounded below with and , where is the set of complex numbers and, for a linear operator A on a Hilbert space, σ(A) denotes the spectrum of A. Then ( is the closure of T) is unitarily equivalent to a direct sum of the weak Weyl representation on the Hilbert space , where is the multiplication operator by the variable and with . Using this theorem, we construct a Weyl representation of the CCR from the weak Weyl representation . This work is supported by the Grant-in-Aid No.17340032 for Scientific Research from Japan Society for the Promotion of Science (JSPS).     

Study of hypercharge exchange reactions of the type 0−1/2+→2+1/2+ at 4GeV/c

Results are presented for the quasi two-body hypercharge exchange reactions of the type 0^?1/2⁺→2⁺1/2⁺: $$\begin{gathered} \pi ^ - p \to K^0 (1420)(\Lambda ,\sum ^0 ), \hfill \\ K^ - p \to f^0 (1270)(\Lambda ,\sum ^0 ), \hfill \\ K^ - p \to f\prime (1515)(\Lambda ,\sum ^0 ), \hfill \\ \end{gathered} $$ using data from two high statistics bubble chamber experiments. The total and differential cross sections are presented and compared with those obtained for the corresponding vector meson reactions and with simple phenomenological ideas.     

Separable coordinates for four-dimensional Riemannian spaces

We present a complete list of all separable coordinate systems for the equations and with special emphasis on nonorthogonal coordinates. Applications to general relativity theory are indicated.     

Measurements of hyperon semileptonic decays at the CERN Super Proton Synchrotron

The charged hyperon beam at the CERN Super Proton Synchrotron (SPS) has been used to collect data on semileptonic decays of Σ^?, Ξ^?, andΛ. A magnetic channel selected 100 GeV/c negatively charged particles produced in the forward direction by interaction of a 210 GeV/c proton beam on a BeO target. The Σ^? and Ξ^? hyperons were concurrently identified in a DISC ?erenkov counter, and their decay products were analysed by a magnetic spectrometer. Electron-hadron discrimination was achieved by the combined use of lead glass and lead/scintillator counters, transition radiation detectors, and a ?erenkov counter. In this article we report results on the \(\Xi \to \Lambda \pi (\Lambda \to pe\bar v), \Xi \to \Lambda e\bar v(\Lambda \to p\pi ),\) and \(\Xi \to \sum ^0 e\bar v(\sum ^0 \to \Lambda \gamma ) (\Lambda \to p\pi )\) decay modes. Samples of 7,111 \(\Lambda \to pe\bar v, 2,608 \Xi \to \Lambda e\bar v\) , and \(154 \Xi \to \Sigma ^0 e\bar v\) were used in our analysis. The branching ratio measurements gave values of (8.57±0.36)×10^?4, (5.64±0.31)×10^?4, and (0.87±0.17)×10^?4 for \(\Lambda \to pe\bar v, \Xi \to \Lambda e\bar v\) , and \( \Xi \to \sum ^0 e\bar v\) , respectively. Measurements of the Λ polarization and of the centre-of-mass distributions yield the axial vector to vector form factor ratio,g ₁/f ₁=+0.70±0.03 for \(\Lambda \to pe\bar v\) , andg ₁/f ₁=+0.25±0.05 for \(\Xi \to \Lambda e\bar v\) . The effects ofq ²-dependence off ₁ andg ₁ and of radiative corrections, the measurement of the weak magnetism termf ₂, and the effect of possible second-class current terms are discussed. Results on the \(\sum \to \Lambda e\bar v\) and \(\sum \to ne\bar v\) decay modes are reported in separate articles.