Classification of Equilibrium Solutions of the Cometary Flow Equation and Explicit Solutions of the Euler Equations for Monatomic Ideal Gases

The set of smooth equilibrium solutions of a kinetic model for cometary flows is split into equivalence classes according to similarity transformations. For each equivalence class in the two- and three-dimensional cases a normal form is computed. Each such equilibrium solution gives rise to an explicit solution of the compressible Euler equations for monatomic gases. The set of these solutions is discussed with special emphasis on solutions containing vacuum regions.     

Large time behavior and asymptotic stability of the 2D Euler and linearized Euler equations

We study the asymptotic behavior and the asymptotic stability of the 2D Euler equations and of the 2D linearized Euler equations close to parallel flows. We focus on flows with spectrally stable profiles U(y) and with stationary streamlines y=y₀ (such that U^′(y₀)=0), a case that has not been studied previously. We describe a new dynamical phenomenon: the depletion of the vorticity at the stationary streamlines. An unexpected consequence is that the velocity decays for large times with power laws, similarly to what happens in the case of the Orr mechanism for base flows without stationary streamlines. The asymptotic behaviors of velocity and the asymptotic profiles of vorticity are theoretically predicted and compared with direct numerical simulations. We argue on the asymptotic stability of this ensemble of flow profiles even in the absence of any dissipative mechanisms.     

Interatomic potentials for the ground state X 0 and the two excited states 1, 0 of the intercombination cadmium line 326.1 nm broadened by Kr pressure

The temperature dependence of the Cd line absorption profile at 326.1 nm perturbed by Kr has been carefully studied over a spectral range extending from 800 cm⁻¹ in the blue wing to 1200 cm⁻¹ in the red wing using a high-resolution double-beam spectrometer. The atomic densities of krypton (N_Kr) and cadmium (N_Cd) were (2.015±0.07)×10¹⁹ and (3.62±0.05)×10¹⁸ cm⁻³, respectively. The temperature dependence of the studied line profile was analyzed in the framework of the quasi-static theory. The van der Waals coefficient differences between the ground ¹0⁺ state and the two excited states ³0⁺ and ³1 (ΔC₆⁰ and ΔC₆¹) were obtained from the near red wing profile using Kuhn's law. The values of ΔC₆⁰ and ΔC₆¹ are found to be equal to 37.8±2 and 58.5±3 eV Å⁶, respectively. The ground (X ¹0⁺), and the excited (³1, ³0⁺) state potentials at the internuclear separations from 3.2 to 6.3 Å were determined. The well depths with their positions for these states are respectively equal to 134±7 cm⁻¹, 3.95±0.2 Å; 72.3±4 cm⁻¹, 4.95±0.3 Å; and 471±12 cm⁻¹, 3.6 Å. The obtained well depths with their allowable errors are in good agreement with the values obtained before for the Cd-Kr system from some theoretical results and molecular beams experiments.     

On the unstable discrete spectrum of the linearized 2-D Euler equations in bounded domains

We investigate the behavior of the unstable discrete spectrum of the linearized 2-D Euler equation when the domain is smoothly perturbed. It is shown that when a self-adjoint Schrödinger-type operator undergoes a codimension-1 bifurcation it translates into a bifurcation in the linearized Euler equation associated with an instability either appearing or disappearing.We give sufficient conditions in order to observe smooth quadratic growth of the unstable eigencurves of the linearized Euler equation. The critical exponent is explicitly given as a function of the null-vector involved into the codimension-1 bifurcation using first and second-order moments of a Laplace transform.This analysis provides an explanation for the successive symmetry-breaking bifurcations observed in models of the mid-latitude oceans. An explicit example is also given.     

基于EtherCAT的ITER极向场电源现场层监控系统设计

根据ITER 大功率极向场电源高实时性与高可靠性控制的需求,选取了具有高实时通讯性能的工业以太网现场总线EtherCAT(以太网控制自动化技术)设计ITER 极向场电源现场层监控系统。依据ITER 极向场电源装置体积大、分布较为分散的特点,为保障高可靠性的数据传输,对比了可构成的两种EtherCAT 环网冗余拓扑的可靠性,选取从站单元中最末端从站是将E-BUS 转换为100BASE-TX/FX 的拓展模块的可靠性较高的环网冗余拓扑来设计极向场电源现场层监控系统的拓扑结构。使用了组态软件TwinCAT(基于Windows 的控制和自动化技术)对系统进行配置,同时绘制了具有可直观显示并控制现场信号等功能的HMI 界面。经测试,该系统可实现对现场层数百路模拟与数字量信号的实时监控,满足了ITER 极向场电源的高实时性与可靠性的控制需求。     

Model calculation and empirical investigation of enhanced field emission behavior of branched carbon nanostructures

In this paper, we propose the novel branched carbon nanotubes (B-CNTs) as efficient candidate for field emission applications. We believe that the double-stage structure of B-CNTs, beside formation of multiple thin branches at the apex of each vertical CNT, is responsible for the observed enhanced field emission behavior in B-CNTs. In this regard, we have derived an analytical model to evaluate the field enhancement factor (β) of the B-CNTs in comparison with CNTs, as the most popular cathode for field emission applications in the scientific society. The presented model also allows investigating the effect of different structural parameters on the field emission characteristic. We have also, compared the field emission characteristics of the B-CNTs with vertical CNTs experimentally. We observed a β value for B-CNTs which was around three times higher than CNTs. The observed enhancement in the experimental data was in good agreement with the presented analytical model.     

Far field detection of terahertz near field enhancement of sub-wavelength slits using Kirchhoff integral formalism

We demonstrate that the near field enhancement of sub-wavelength slits can be experimentally determined in the far field by using a reference aperture. Our simple model derived from the Kirchhoff integral formalism shows that enhancement of the near field at a slit exit with respect to the incident wave can be read in the transmitted amplitude through the slit attached on a reference aperture, normalized by the transmitted amplitude through the reference aperture. Furthermore, the near field enhancement obtained in such a way is essentially independent of the reference aperture size. By performing terahertz time domain spectroscopy we experimentally confirm the inverse frequency dependence of the near field enhancement of extremely narrow slits and measure the maximum field enhancement reaching 200 at 0.1 THz for a 500-nm-width slit.     

用explicit Euler 方法研究含时受迫谐振子的演化及对系统循环初态的讨论

利用Ioan Sturzu 提出的explicit Euler方法 (EEM) 计算了含时受迫谐振子的系统初态随时间的演化及概率分布规律，分析了EEM的可行性及适用性，并由相干态讨论了受迫谐振子系统循环初态的存在条件以及非绝热几何相. 关键词： explicit Euler 方法 含时受迫谐振子 循环初态 非绝热几何相     

Calculation and error analysis for magnetic field parameters of a standard saddle coil

The calculation and measurement of field parameters and their derivatives play a very important role in designing and constructing saddle-shaped bipolar-magnetic coils [1]. In this article, new distribution function F_n and its derivatives along z-axis are defined, formularized and presented. Calculation and error analysis for the magnetic field parameters of a standard saddle coil are conducted and presented using the formulas. It is shown that the method and formulas can be used in calculating the field parameters, derivatives and the magnetic vector H for the bipolar-magnetic coils.     

光学速调管改造后辐射段磁场垫补和测量

 合肥国家同步辐射实验室正在开展储存环相干谐波自由电子激光研究，并对原来的光学速调管进行了改造。磁场的垫补和测量方法由原来的整体测量改为分段进行，垫补的使用使各段积分场及位相误差都尽可能小。详述了合肥储存环的光学速调管辐射段磁场垫补的三种方式，测量了垫补前后不同间隙下积分场分布、位相误差及横向均匀度，各项指标都达到了要求。同样的方法将用于色散段和调制段磁场垫补与测量中，为相干谐波自由电子激光研究提供实验保障。     

Relativistic quantum mechanic calculation of photoionization cross-section of hydrogenic and non-hydrogenic states using analytical potentials

Photoionization process is a subject of special importance in many areas of physics. Numerical methods must be used in order to obtain photoionization cross-sections for non-hydrogenic levels. The atomic data required to calculate them is huge so self-consistent calculations increase computing time considerably. Analytical potentials are a useful alternative because they avoid the iterative procedures typical in self-consistent models. In this work, we present a relativistic quantum calculation of photoionization cross-sections for isolated ions based on an analytical potential to obtain the required atomic data, which is valid both for hydrogenic and non-hydrogenic ions. Comparisons between our results and others obtained using either widely used analytical expressions for the cross-sections or more sophisticated calculations are done.     

有限长线声源斜面声场分析

为了进一步研究有限长线声源的声场特性,完善有限长线声源声场理论,建立了有限长线声源斜面声场的模型,提出了其理论计算方法。基于仿真结果和数据分析,探讨并得到了有限长线声源斜面声场特性的三个参数与斜面声场特性之间的关系。通过调整斜面倾角α、交点的位置r0以及有限长线声源的长度L,可以有效改善斜面声场的分布。     

平行双线BCI等效替代强场连续波电磁辐射实验研究

由于互联系统信号传输的基础是双线,以低频线缆耦合通道中比较典型的平行双线为研究对象,针对互联系统单端为非线性受试设备的电磁辐射敏感度进行实验研究。讨论了典型互联系统辐射与注入的等效以及在高场强下的外推条件,对所选非线性器件是否满足实验要求进行了实验验证。分析了大电流注入法等效替代强场连续波电磁辐射的实验结果,并对辐照时天线极化方式不同以及有无大电流注入探头对辐射与注入等效研究的影响进行了分析。     

一维电荷分布系统的电场线

推导一维电荷分布系统的电场线满足的方程,并使用数学软件MatLab将其电场线精确地作出来,其图像既具科学性而又优于传统的手绘图像.     

非均匀多导体传输线高频场线耦合分析中的边界条件

场线耦合问题是电磁兼容分析与电磁效应评估中的重要课题。经典场线耦合模型受限于准TEM波近似,在较高频率时将导致不可接受的模型误差。传输线超理论（TLST）建立了高频场线耦合模型,解决了经典场线耦合模型的困难。基于TLST介绍了非均匀多导体传输线的高频场线耦合模型,提出了三种不同终端负载情况下对应边界条件的设置方法。最后通过具体算例对比了高频模型和经典模型以及全波分析计算结果,证实了高频场线耦合模型的普遍适用性、边界条件设置的有效性和数值实现过程的准确性。     

用模拟退火法进行纯永磁波荡器磁块组合优化

 纯永磁波荡器由多个磁块组成,磁块的剩磁离散性会引起波荡器磁场误差,从而影响储存环工作状态和自发辐射谱质量。在波荡器磁块安装之前,使用模拟退火法对磁块进行组合排序优化,可以使峰值场强误差降低到10 ^-4量级以下,磁场一次积分降低到10^-6 T·m量级,二次积分降低到10 ^-6 T·m ²量级,优化结果不依赖于初始状态的选择。给出优化的详细过程,提出了根据磁块剩磁快速计算波荡器峰值场强误差和积分场的方法。     

Time-domain analytic solutions of two-wire transmission line excited by a plane-wave field

This paper reports that an analytic method is used to calculate the load responses of the two-wire transmission line excited by a plane-wave directly in the time domain. By the frequency-domain Baum Liu-Tesehe （BLT） equation, the time-domain analytic solutions are obtained and expressed in an infinite geometric series. Moreover, it is shown that there exist only finite nonzero terms in the infinite geometric series if the time variate is at a finite interval. In other word, the time-domain analytic solutions are expanded in a finite geometric series indeed if the time variate is at a finite interval. The computed results are subsequently compared with transient responses obtained by using the frequency-domain BLT equation via a fast Fourier transform, and the agreement is excellent.     

Growth and field emission property of coiled carbon nanostructure using copper as catalyst

Coiled carbon nanostructure (CNS) is prepared by a catalytic chemical vapor deposition (CVD) process on copper/chromium films deposited by radio frequency (RF) sputtering. Uniform CNS with coiled structure is fabricated by changing the size of the catalyst particles. The effects of Cu catalyst size and RF sputtering power, on the growth of the coiled CNS are discussed, and the results importantly conclude that Cu-catalyzed CVD offers a preferable control of coiled CNS to optimize the field emission property for application.     

金属腔内场线耦合干扰敏感性

研究了金属腔内电磁场与单导线耦合对线两端部件产生干扰的敏感性问题。利用并矢格林函数计算腔内场分布, 利用Agrawal模型计算获得导线两端负载的干扰响应, 从腔体尺寸、内部干扰源位置及导线位置三个方面分析了建模的微小变化对导线负载干扰的影响。结果表明, 腔体尺寸的微小变化会带来负载干扰响应的很大变化, 在谐振点处该影响尤其明显;腔内干扰源位置的微小变化可能会带来负载干扰响应的巨大变化;干扰响应对导线距离金属腔壁高度的微小变化不敏感, 但单导线位置的微小变化可能带来负载干扰的较大变化。     

Influence of a weak constant magnetic field on the Hβ line of a t-tube plasma

Measurements of the additional shift of the Hβ spectral line emitted by a plasma in a magnetic field are performed. The magnitudes of the shift are distinguished by good reproducibility. The magnetic field strength was 0.5 and 2.1 T. Comparison is made of the Hβ line profiles recorded in the presence of the magnetic field and without it, all other things being equal. Consideration is given to a number of possible causes of the additional shift (they include the dependence of the shift on the density of electrons, their temperature, and on the velocity of the plasma flux). The additional shift of the Hβ line in the presence of the magnetic field is qualitatively substantiated. Presented at the 1th Belorussian-Yugoslavian Symposium on the Physics and Diagnostics of Laboratory and Astrophysical Plasmas, 1–3 July, 1996, Misnk. Institute of Physics, 4, Obradović St., Novi Sad, 21000, Yugoslavia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 566–574, September–October, 1997.