非对称振荡并联扑翼能量采集特性数值模拟研究

针对目前并联扑翼装置采集性能优化手段单一、提升效果不佳的问题,提出并联扑翼非对称振荡模式。采用动网格技术,建立一套非对称振荡模式下并联扑翼振荡控制与仿真程序,实现对多种复杂非对称俯仰振幅振荡过程的准确模拟,揭示多种非对称冲程下并联扑翼的能量采集性能及气动特性变化规律,阐明并联扑翼附近的涡结构与压力场演变规律。研究表明,随着俯仰振幅增大,扑翼平均功率系数及采集效率均呈现先增大后减小的趋势,验证了通过非对称振荡模式有效提升并联扑翼装置性能的可行性。

基于广域信息的振荡中心实时定位及保护闭锁方法研究

针对电力系统发生振荡时振荡中心难以追踪,以及振荡过程中发生对称性故障时保护开放延时长、不准确等问题,提出了一种基于广域信息的振荡中心实时定位及保护闭锁方法。根据本地电压、电流相量及广域电压幅值信息,构造基于电压幅值比的振荡中心位置函数,提出了振荡中心实时定位方法。在此基础上引入能够体现振荡与故障差异特征的电气距离系数,据此构造振荡识别判据,并提出了相应的保护振荡闭锁与再开放判据。PSCAD仿真验证表明,该方法能够实时定位电力系统振荡中心位置,有效减少距离保护在振荡初期不必要的闭锁时间。

新型光电振荡器(特邀)

光电振荡器是拥有闭合光电反馈回路的微波光子信号源。借助微波光子学大带宽、低损耗等优势,光电振荡器可实现高中心频率、超低相位噪声的微波信号产生,从而克服传统电学信号源面临的频率和相位噪声瓶颈,应用于雷达、通信、测量和电子对抗等现代电子信息系统。综述近些年来涌现的新型光电振荡器,介绍可实现无滤波器单模振荡的宇称-时间对称光电振荡器、快速扫频的傅里叶域锁模光电振荡器、参量锁相的光电参量振荡器、频率随机变化的宽带随机光电振荡器、自发跳频的孤子光电振荡器、脉冲型的主动和被动锁模光电振荡器以及小型化的集成光电振荡器等,并探讨这些新型光电振荡器的应用和未来发展趋势。

稠密颗粒射流倾斜撞击颗粒膜特征

采用高速摄像仪对稠密颗粒射流倾斜撞击形成的类液体颗粒膜特征进行实验研究,考察了颗粒粒径、射流速度以及射流含固率等因素对颗粒膜形态及动态特征的影响.结果表明:随着颗粒粒径增大,稠密颗粒倾斜撞击流由颗粒膜向散射模式转变;随着射流速度增加,气固不稳定增强,射流流量出现脉动,正面与侧面分别表现为颗粒膜的非轴对称振荡和表面波纹结构;颗粒膜非轴对称振荡的振荡频率和振荡幅度随射流速度的增大而增大;表面波纹速度和波长沿传播方向增大,波纹间存在叠加现象.颗粒膜出现非轴对称振荡主要是因为喷嘴出口由气固不稳定性引起的射流流量脉动,射流流量脉动频率与撞击面振荡频率基本相当.

A 2.4GHz CMOS Quadrature Voltage-Controlled Oscillator Based on Symmetrical Spiral Inductors and Differential Diodes

A voltage controlled oscillator (VCO) which can generate 2 4GHz quadrature local oscillating (LO) signals is reported.It combines a LC VCO,realized by on chip symmetrical spiral inductors and differential diodes,and a two stage ring VCO.The principle of this VCO is demonstrated and further the phase noise is discussed in detail.The fabrication of prototype is demonstrated using 0 25μm single poly five metal N well salicide CMOS digital process.The reports show that the novel VCO is can generate quadrature LO signals with a tuning range of more than 300MHz as well as the phase noise--104 33dBc/Hz at 600KHz offset at 2 41GHz (when measuring only one port of differential outputs).In addition,this VCO can work in low power supply voltage and dissipate low power,thus it can be used in many integrated transceivers.

关于无穷积分收敛的必要性探讨

分析了无穷积分收敛的一些性质,给出了三个具有典型代表意义的函数,用以认识无穷积分收敛的本质,并给出了能得出被积函数趋于零的一个简明条件。

N = 4 Supersymmetric Morse Oscillator and Its Spectrum-Generating Algebra

In this paper N = 4 supersymmetry of generalized Morse oscillators in one dimension is studied. Both bound states and scattering states of its four superpartner Hamiltonians are analyzed by using unitary irreducible representations of the noncompact Lie algebra su(1,1). The spectrum-generating algebra governing the Hamiltonian of the N = 4 supersymmetric Morse oscillator is shown to be connected with the realization of Lie superalgebra osp(1,2)or B(0,1) in terms of the variables of a supersymmetric two-dimensional harmonic oscillator.

Constraints on Non-Radial Oscillation Modes by Symmetry Energy Slope

The effect of the nuclear symmetry energy slope on the non-radial oscillation f-modes in neutron stars is calculated and discussed. Based on a conservative range of the symmetry energy slope constrained by the experiment and theoretical analysis, a constraint on the frequency and damping time of the gravitational radiation from the f-mode in neutron star is obtained. It is also shown that a higher symmetry energy slope corresponds with a smaller frequency and a longer damping time. Meanwhile, a new set of parameters is given to present the universal properties of the scaled frequency and damping time.

Experimental study and analysis of shock train self-excited oscillation in an isolator with background waves

A study of shock train self-excited oscillation in an isolator with background waves was implemented through a wind tunnel experiment.Dynamic pressure data were captured by high-frequency pressure measurements and the flow field was recorded by the high-speed Schlieren technique.The shock train structure was mostly asymmetrical during self-excited oscillation,regardless of its oscillation mode.We found that the pressure discontinuity caused by background waves was responsible for the asymmetry.On the wall where the pressure at the leading edge of the shock train was lower,a large separation region formed and the shock train deflected toward to the other wall.The oscillation mode of the shock train was related to the change of wall pressure in the oscillation range of its leading edge.The oscillation range and oscillation intensity of the shock train leading edge were affected by the wall pressure gradient induced by background waves.When located in a negative pressure gradient region,the oscillation of the leading edge strengthened;when located in a positive pressure gradient region,the oscillation weakened.To find out the cause of self-excited oscillation,correlation and phase analyses were performed.The results indicated that the instability of the separation region induced by the leading shock was the source of perturbation that caused self-excited oscillation,regardless of the oscillation mode of the shock train.

Meridional movement of northern and southern equatorial ionization anomaly crests in the East-Asian sector during 2002-2003SSW

The present paper investigates the asymmetrical variability of the location of the north and the south equatorial ionization anomaly(EIA) crests in the East-Asian sector,along with their association with simultaneous observations of equatorial electrojet(EEJ) strength,geomagnetic activity index,and solar flux index during the 2002-2003 sudden stratospheric wanning(SSW) event.Analysis of these observations indicates the existence of a large-scale quasi 16-day periodic meridional movement in both EIA crests,and also reveals a strong correlation between the quasi 16-day oscillation in geomagnetic latitudes of the EIA crest and EEJ strength.The latitude of the northern/southern EIA crest and the EEJ strength indicate that obvious synchronous periodic oscillations were in-phase in the northern and southern hemisphere when the SSW occurred.In addition,it is also found that both the EIA crest location and amplitude of the periodic movement of the EIA locations exhibit hemispheric asymmetry.The amplitude of the periodic movement of the EIA location in the southern hemisphere is larger than that of the northern hemisphere,and the southern EIA crest is further off from the equator than the north one.Understanding these asymmetries requires a combination of mechanisms that involve at least trans-equator meridional winds and the position of a sub-solar point;however,potential disturbances in neutral winds associated with the SSW may additionally complicate the equatorial ionospheric dynamics.

A Four-Element Sensor Array Consisting of Asymmetric Distributed-Feedback Fiber Lasers

A sensor array system formed by arranging four asymmetric distributed-feedback fiber lasers （DFB-FL） in ascending order according to their slope efficiencies was proposed. The output flatness could be effectively improved with the application of asymmetric DFB-FLs. The last element had almost the same output with the others although it obtained the smallest pump power. The relative intensity noise （RIN） and relaxation oscillation frequency of the sensor array were also analyzed. It is found that the relaxation oscillation frequency of a certain DFB-FL was relevant to its relative position in the array. And the RIN of a certain DFB-FL was always affected by the other elements in the array, which was not dependent on the order of their arrangement.

Dynamic cavitations in incompressible hyperelastic pre-strained circular sheets

A class of dynamic cavitations is examined for an isotropic incompressible hyperelastic circular sheet under a pre-strained state caused by an initially applied finite radial tension.The solutions that describe the radially symmetric motion of the pre-strained sheet are obtained.The conditions of cavitated bifurcation that describe cavity formation and motion with time at the axial line of the pre-strained sheet are proposed,that is to say,a circular cavity will form if the suddenly applied radial tensile load exceeds a certain critical value;dynamically,it is proved that the formed cavity will present a nonlinearly periodic oscillation,which is essentially different from the singular periodic oscillation of the formed cavity in an incompressible hyperelastic solid sphere.Numerical simulations show the effects of prescribed radial tension,material parameter and tensile load on critical ten-sile load describing cavity formation and periodic oscillation of the pre-strained circular sheet.

On symmetry-breaking bifurcation in the periodic parameter-switching Lorenz oscillator

By introducing the periodic parameter-switching signal to the Lorenz oscillator, a switched dynamic model is established. In order to investigate the mechanism of the behaviors of the whole system, bifurcation sets of the subsystems are derived and the Poincar6 map of the switched system is defined by suitable local sections and local maps. Under certain parameter conditions, symmetric periodic oscillations may be observed. With the variation of parameter, the symmetry-breaking bifurcation mecha- nisms of the symmetric periodic oscillations can be understood by calculating the associated maximal Lyapunov exponent and Floquet multiplies. Meanwhile, the parameter values of the related local bifurcations, such as saddle-node, pitchfork and peri- od-doubling bifurcations are calculated based on the Floquet multiplies.

θ_(13) and the Higgs Mass from High Scale Supersymmetry

In the framework in which supersymmetry is used for understanding fermion masses rather than stabilizing the electroweak scale, we elaborate on the phenomenological analysis for the neutrino physics. A relatively large sin θ13= 0.13 is naturally obtained. The model further predicts vanishingly small CP violation in neutrino oscillations. While the high scale supersymmetry generically results in a Higgs mass of about 141 GeV, our model reduces this mass to 126 CeV via introducing SU（2）L triplet fields which make the electroweak vacuum metastable （with a safe lifetime） and also contribute to neutrino masses.