Resonance condition for asymmetrical triple-barrier structures

The resonance condition for triple-barrier structures with arbitrary potential is studied systematically. The quasisymmetrical triple-barrier (QST) resonance mode and the quasi-asymmetrical double-barrier (QAD) resonance mode may both exist in asymmetric triple-barrier structures. The QST consists of two submodes: a normal mode (doublet) and a degenerate mode (singlet). The critical condition for distinguishing the two modes is examined. It is confirmed that there are both unity resonant transmission and below-unit resonant transmission in the asymmetrical triple-barrier structure. Furthermore, the wavefunctions of an electron at resonance level are calculated and the confining phenomenon is studied.     

Neutron total cross-sections and resonance parameters of Mo and Ta

Experimental results of transmissions for the samples of natural molybdenum with thickness 0.0192 atoms/barn and for the four samples of natural tantalum with thickness 0.0222, 0.0111, 0.0055 and 0.0025 atoms/barn are presented in this work. Measurements were carried out at the Pohang Neutron Facility which consists of a 100 MeV Linac, water-cooled tantalum target, and 12 m flight path length. Effective total cross-sections were extracted from the transmission data, and resonance parameters were obtained by using the code SAMMY. The present measurements were compared with other measurements and with the evaluated nuclear data file ENDF/B-VI.8.      

Measurement of neutron cross sections and resonance parameters of ^169Tm below 100 eV

The neutron total cross-sections of thulium （^169Tm） were measured in the neutron energy region from 0.01 eV to 100 eV by using the time-of-flight method at the Pohang Neutron Facility, which consists of an electron linac, a water-cooled tantalum target with a water moderator, and a 12 m time of flight path, Two thulium plates with different thicknesses were used for the neutron transmission measurement. The background level was determined by using a notch-filter of Co, In, and Cd sheets. The present measurement was compared with the previous ones, and a new set of resonance parameters of ^169Tm isotope was obtained from the transmission rate by using the SAMMY code, with a comparison with the recommended parameters by Mughabghab.     

Measurement of neutron cross sections and resonance parameters of ~(169)Tm below 100 eV

The neutron total cross-sections of thulium (~(169)Tm) were measured in the neutron energy region from 0.01 eV to 100 eV by using the time-of-flight method at the Pohang Neutron Facility, which consists of an electron linac, a water-cooled tantalum target with a water moderator, and a 12 m time of flight path. Two thulium plates with different thicknesses were used for the neutron transmission measurement. The background level was determined by using a notch-filter of Co, In, and Cd sheets. The present measurement was compared with the previous ones, and a new set of resonance parameters of ~(169)Tm isotope was obtained from the transmission rate by using the SAMMY code, with a comparison with the recommended parameters by Mughabghab.     

弯曲振动薄圆盘的共振频率和等效电路参数研究

机电等效电路是分析复合换能器常用的一种解析方法, 但对薄圆盘而言, 由于弯曲振动的复杂性, 其等效集中参数很难获得, 该方法很少被应用. 本文从分布参数系统与集中参数系统等效角度, 根据动能相等原则和势能相等原则, 给出了弯曲振动薄圆盘的集中参数: 等效质量和等效弹性系数, 得到了共振频率方程, 并用ATILA软件模拟了其振动分布情况, 可以看出解析结果与数值结果趋于一致. 最后给出了分析复合振动系统时薄圆盘集中参数模型的等效电路. 本文的结果对弯曲振动复合换能器的设计提供了理论参考.     

Measurement of neutron cross sections and resonance parameters of ~(169)Tm below 100 eV

The neutron total cross-sections of thulium(169Tm) were measured in the neutron energy region from 0.01 eV to 100 eV by using the time-of-flight method at the Pohang Neutron Facility,which consists of an electron linac,a water-cooled tantalum target with a water moderator,and a 12 m time of flight path.Two thulium plates with different thicknesses were used for the neutron transmission measurement.The background level was determined by using a notch-filter of Co,In,and Cd sheets.The present measurement was ...     

Splitting of the resonance levels of double-barrier structures in a high microwave electric field

The dependence of the width and shape of the resonance levels of asymmetric double-barrier resonance-tunneling structures with high narrow barriers on the amplitude of the resonance microwave field and specific features of the electron transport in the case of ballistic passage of electrons near the resonance levels has been investigated. It has been found that a resonance level can be first broadened significantly and be further split into two absolutely transparent levels with an increase in the microwave field amplitude. The conditions have been formulated under which nonresonance scattering channels near the resonance levels also become absolutely transparent.     

基于材料反射率谐振特性测试电磁参数的自由空间法

自由空间法具有非接触、非破坏性测试特点,适于材料的电磁参数测试．根据材料反射率扫频测试的特性,提出了一种基于谐振特性测试材料电磁参数的新的自由空间法．通过理论分析,研究了发生相消和相长干涉的条件,给出了应用干涉位置和材料厚度测试材料介电常数实部的理论计算公式．利用谐振峰,谷的位置及其相互关系可以计算材料介电常数虚部,而利用波谷比值法比驻波比值法容易达到更高的计算精度．     

Conduction-electron spin resonance in two-dimensional structures

The influence of the conduction-electron spin magnetization density, induced in a two-dimensional electron layer by a microwave electromagnetic field, on the reflection and transmission of the field is considered. Because of the induced magnetization and electric current, both the electric and magnetic components of the field should have jumps on the layer. A way to match the waves on two sides of the layer, valid when the quasi-two-dimensional electron gas is in the one-mode state, is proposed. By following this way, the amplitudes of transmitted and reflected waves as well as the absorption coefficient are evaluated.     

由同时具有磁谐振和电谐振结构组成的左手材料

为了在同一结构中同时实现负介电常数和负磁导率(双负),采用一种“巨”字形结构,利用丝网印刷技术在氧化铝基板上进行加工制作,并通过仿真和实验测试证实了这种结构的“双负”特性. 与利用磁谐振器和电谐振器组阵实现左手材料的方法相比,这种单一结构可以同时实现负介电常数和负磁导率,制作方便,等效电路简单,双负频段较宽. 利用丝网印刷技术进行样品的制作,工艺简单,成本低廉. 关键词： 左手材料 磁谐振 电谐振     

Study of K*(892) mass and width splitting caused by model difference

According to the new K*(892)0 and K*(892)- masses reported by the BELLE experiment and the K*(892)0 mass reported by the FOCUS experiment, mass splitting between neutral and charged K*(892) becomes very small. This is significantly different from the current world average values given by the Particle Data Group 2008. We find that there are differences between models used to fit the K*(892) decay invariant mass spectra in different measurements and study the model dependence in the measurement of K*(892) parameters. We refit the K*(892)0 mass spectra of the BELLE and FOCUS experiments with the formula used by BELLE in fitting K*(892)- to get new mass and width. After refitting, the K*(892)0 mass of the BELLE experiment becomes 1.4 MeV/c2 larger than the initial value and that of the FOCUS experiment is 1 MeV/c2 smaller than the initial value. We also fit the spectra of some other experiments to extract the K*(892) parameters using the BELLE K* (892)- parametrization.     

大参数周期信号随机共振解析

通过调节双稳系统参数实现大参数频率范围内周期信号的随机共振, 在工程上具有重要意义. 推导了双稳系统参数的归一化变换, 利用归一化变换原理对大参数周期信号的随机共振进行了数值仿真, 阐明该原理适用于任意频率周期信号. 对大参数随机共振用电路模拟进行了实验验证, 揭示了通过调节双稳系统参数可以实现大参数频率范围内的随机共振. 分析了二次采样实现大参数周期信号随机共振的机理, 通过数值仿真与参数归一化变换方法进行了比较. 仿真结果表明, 在输入信号幅度变化的情况下, 二次采样方法易出现发散现象, 而归一化变换具有更好的稳定性与适应性.     

Extraction of resonance parameters from meson production reaction

We have developed an analytic continuation method for extracting parameters of nucleon resonances within a Hamiltonian formulation of meson-nucleon reactions. The method was tested for simple solvable models and then applied for our recent coupled channels model （πN, ηN, π△, ρN, and σN ） of the π＊N and γ＊N reactions. The resonance pole positions and their properties are studied for P11and P11 channels.     

Spectral-line width measurements in Ar II from a laser-heated gas-puff plasma

Stark profiles for certain non-blended spectral lines radiating in the visible spectral region from Ar II multiplets were measured at the University of Maryland in a plasma created by the laser heating of a puff of gas at high pressure. The resulting line widths are found to agree within a ±30% experimental precision with previous ±25% measurements obtained at lower densities and temperatures in long-burning arcs, as well as with semi-classical calculations.     

Voltage and temperature dependence of current noise in double-barrier normal-superconducting structures

We study theoretically the current-noise energy (voltage bias and temperature) dependence for a N-N'-S structure, where N and S stand for bulk normal metal and superconductor, respectively, and N' for a short diffusive normal metal. Using quasiclassical theory of current fluctuations we determine the noise for arbitrary distributions of channel transparencies on both junctions. The differential Fano factor turns out to depend on both junction transparencies and the ratio of the two conductances. We discuss analytically the coherent and incoherent regimes and the case when one of the two conductances dominates the other one. Measurement of differential conductance and noise can be used to probe the channel distribution of the interfaces. We discuss recent experiments in the light of our results.     

Parameter-induced stochastic resonance with a periodic signal

In this paper conventional stochastic resonance (CSR) is realized by adding the noise intensity. This demonstrates that tuning the system parameters with fixed noise can make the noise play a constructive role and realize parameter-induced stochastic resonance (PSR). PSR can be interpreted as changing the intrinsic characteristic of the dynamical system to yield the cooperative effect between the stochastic-subjected nonlinear system and the external periodic force. This can be realized at any noise intensity, which greatly differs from CSR that is realized under the condition of the initial noise intensity not greater than the resonance level. Moreover, it is proved that PSR is different from the optimization of system parameters.     

双稳随机共振参数特性的研究

以双稳系统为研究对象，探讨了影响和产生双稳随机共振的参数选择特性.双稳系统参数和二次采样频率参数有着内在的物理联系，它们的改变都会引起势垒、势阱间距和粒子跃迁速率的改变，并使噪声能量相对重新分配，进而影响随机共振效果.根据随机共振的参数选择规律，可通过适当的参数选择来得到最佳的随机共振状态，为后续数据处理奠定基础.