关于磁悬浮陀螺稳定悬浮条件的探讨

利用牛顿力学中的稳定性理论对磁悬浮陀螺稳定悬浮的条件进行了分析,在实验上对磁悬浮陀螺底座磁场的空间分布进行了测量,将理论分析和测量的数据结合起来从理论上预测陀螺稳定悬浮的区域范围,再将实验上实际观察到的稳定悬浮区域与之对比,得到了一致性的结论,由此得出了磁悬浮陀螺稳定悬浮的条件.     

Levy stability for anisotropic dynamical fluctuation in high energy multiparticle production

The behaviour of Levy index 7 in various phase space dimensions is studied. The reason for the violation of Levy stable condition at three-dimension observed in experiment is investigated. It is shown that the apparent violation of Levy stable condition may be due to the wrong isotropic analysis for the highly anisotropic phase space of multiparticle production.     

Levy stability for anisotropic dynamical fluctuation in high energy multiparticle production

The behaviour of Levy index?? in various phase space dimensions is studied. The reason for the violation of Levy stable condition at three-dimension observed in experiment is investigated. It is shown that the apparent violation of Levy stable condition may be due to the wrong isotropic analysis for the highly anisotropic phase space of multiparticle production.     

Levy stability for anisotropic dynamical fluctuation in high energy multiparticle production

The behaviour of Levy indexμ in various phase space dimensions is studied. The reason for the violation of Levy stable condition at three-dimension observed in experiment is investigated. It is shown that the apparent violation of Levy stable condition may be due to the wrong isotropic analysis for the highly anisotropic phase space of multiparticle production.     

Topology change without any pathology

A class of (noncompact) singularity-free spacetimes is found, where topology changes without violating the weak energy condition (wec) or the stable causality condition.     

Stability in linear response and clustering properties

We derive a necessary and sufficient asymptotic condition assuring that a quantum dynamical system in equilibrium is stable in linear response. We prove, in particular, that if the Hamiltonian has no singular-continuous spectrum and zero is the only eigenvalue, the dynamical system is stable. Finally we prove that a dynamical system is strongly clustering, if and only if, it is weakly clustering and stable in linear response.     

Approximate solution of optical soliton in lossless fibres with third-order dispersion

A near zero-dispersion regime, fundamental soliton with third-order dispersion is considered. There are three different waves radiated from the soliton. We find a threshold condition for the radiated waves. Below the threshold condition a stable soliton exists; an approximate soliton solution is obtained.     

二维R—N型声光光学双稳态

本文在理论上给出了对二维R-N(喇曼-奈斯)型声光作用的光学双稳系统普遍适用的动态方程,并由此导出了该声光光学双稳系统的稳态解,借助于计算机给出了取(1,0)级作为反馈级次情况下的几个级次输入～输出关系曲线,并对此进行了稳定性分析;在实验上对该理论进行了验证,实验结果与理论相符.     

Proof that the hydrogen-antihydrogen molecule is unstable

In the framework of nonrelativistic quantum mechanics we derive a necessary condition for four Coulomb charges (m1(+), m2(-), m3(+), m4(-)), where all masses are assumed finite, to form the stable system. The obtained stability condition is physical and is expressed through the required minimal ratio of Jacobi masses. In particular, this provides the rigorous proof that hydrogen-antihydrogen and muonium-antimuonium molecules and hydrogen-positron-muon systems are unstable. It also proves that replacing hydrogen in the hydrogen-antihydrogen molecule with its heavier isotopes does not make the molecule stable. These are the first rigorous results on the instability of these systems.     

On the onset condition of fast-time instability in Liñán's premixed-flame regime

The fast-time instability of Liñán's premixed-flame regime is revisited in order to resolve the unrealistic result, previously obtained by Peters, that the inner reaction zone becomes unstable under all subadiabatic conditions. The problem is posed as that of finding the stable range of the heat-loss parameter, defined as the ratio of the downstream heat loss to the total chemical energy influx, near the adiabatic condition. Central to the analysis is rescaling near the adiabatic condition by employing a distinguished limit that the heat-loss parameter is of the order of the inverse of the Zel'dovich number, which enables us to take into account the stabilizing effect of the outer diffusive layers on the inner reaction zone. For a general diffusion flamelet model, the critical value of the heat-loss parameter at the neutral-stability condition is obtained to form a bound for the stable subadiabatic range of the heat–loss parameter.     

Size dependence of the thermo-electrodynamics states of composite high-Tc superconductors and its effect on the current instability conditions

The effect of transverse geometries of the slab of composite high-T_c superconductors on their stable and unstable thermal and electrodynamics transient states in the incomplete and complete penetration modes during the current charging are discussed. The transient period when the electric field that is induced by the charged current becomes more homogeneous during the initial stage of the complete penetration mode in the sub-critical voltage range is studied. In the over-critical voltage range, the cross-section shape of the slab affects its stable and unstable temperature variation. As a result, the current instability condition is not identical for high-T_c superconducting composite tapes that have the same cross-sectional area with various shapes of the cross-section. The condition depends on their thickness: the less thickness, the more stable the current distribution in the composite superconductors with the same cross-sectional area. This feature is a result of the unavoidable reduction of the current-carrying capacity of a high-T_c superconducting composite by the temperature increase. This reduction is caused by the relevant temperature dependence of electrodynamics states of the composite. This temperature dependence happens even during a stable stage of the current charging. These mechanisms must be considered during experiments at which the critical or quenching currents are defined.     

基于uClinux的嵌入式水声信号采集存储系统设计

为了减少水声学研究和水声工程设计试验的时间、成本等,针对水声信号和系统工作环境的特点,设计并实现了一种基于嵌入式uClinux操作系统的水声信号采集存储系统。发挥了处理器对外部设备优秀的控制能力和uClinux操作系统出色的稳定性两大优势,使系统稳定、可靠、低功耗、便捷地工作。通过海试验证了数据的有效性,证明系统具有实用价值。     

Stochastic Resonance in a Simple Threshold Sensor System with Alpha Stable Noise

We investigate the effect of alpha stable noise on stochastic resonance in a single-threshold sensor system by analytic deduction and stochastic simulation. It is shown that stochastic resonance occurs in the threshold system in alpha stable noise environment, but the resonant effect becomes weakened as the alpha stable index decreases or the skewness parameter of alpha stable distribution increases. In particular, for Cauchy noise a nonlinear relation among the optimal noise deviation parameter, the signal amplitude and the threshold is analytically obtained and illustrated by using the extreme value condition for the output signal-to-noise ratio. The results presented in this communication should have application in signal detection and image restoration in the non-Gaussian noisy environment.     

Theory of passively mode-locked lasers with self-frequency shift and saturable absorber response

A general theoretical model for passively mode-locked lasers is presented, in which both the self-frequency shift and either a fast or a slow saturable absorber response are taken into account. An exact soliton-like solution and condition for its existence are obtained under a definite compatible condition. The stability of the solution is analyzed by using a variational method, and a parameter region, in which the solution is linearly stable, is acquired theoretically. To verify the theoretical predictions, a typical example is given for stable pulse propagation over a long distance. The numerical results show that the soliton-like solution is stable under some perturbations within the linearly stable region and an arbitrary Gaussian pulse converges to the exact soliton-like solution after evolution in a distance.     

连续简并量子拍频激光器的工作特性

采用饰缀(dressed)原子方法,讨论了被共振微波场驱动的三能级原子系统简并量子拍频激光器的增益系数,小信号增益系数、饱和光强、阈值条件和稳态光强.     

数值研究含有负折射率材料的一维光子晶体的带隙特性

由修正后的传输矩阵理论研究了由单负材料构成的一维光子晶体的带隙特性。发现了此结构的光子晶体中同时存在着全方位带隙和布拉格带隙,且发现A、B层厚度等比例变化时全方位带隙非常稳定;当引入缺陷时,全方位带隙里的缺陷态将随入射角度、A层和B层同比例缩放的变化相对稳定,而布拉格带隙里的缺陷态在频谱域内变化很大。     

Two-slab all-optical spring

It is demonstrated that a waveguide consisting of two dielectric slabs may become an all-optical spring when guiding a superposition of two transverse evanescent modes. Both slabs are transversally trapped in stable equilibrium due to the optical forces developed. A condition for stable equilibrium on the wavenumbers of the two modes is expressed analytically. The spring constant characterizing the system is shown to have a maximal value as a function of the equilibrium distance between the slabs and their width.     

Analysis of global exponential stability for a class of bi—directional associative memory networks

In real-time applications of bi-directional associative memory (BAM) networks.a global exponentially stable equilibrium is highly desired.The existence,uniqueness and global exponential stability for a class of BAM networks are studied in this paper,the signal function of neurons is assumed to be piece-wise linear from the engineering point of view.A very concise condition for the equilbrium of such a network being globally exponentially stable is derived.which makes the pactical design of this kind of networks an easy job.     

One-step alternating direction implicit FDTD algorithm

In this paper, a novel unconditionally stable alternating direction implicit finite-different time-domain method(ADI-FDTD) called the one-step ADI-FDTD method is presented, where the calculation for one discrete time step is performed using only one procedure, but not the original two sub-updating procedures. Consequently, the proposed one-step ADI-FDTD methods have consumed less computer memory and computation resources and have been faster than the conventional ADI-FDTD methods. We analytically and numerically verified that the new algorithm is unconditionally stable and free from the Courant condition.