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Chinese Physics B 2021年第11期30卷 268-273页

作者： Guang-Tai Xue Xiao-Hui Tian Chi Zhang Zhenda Xie Ping Xu Yan-Xiao Gong Shi-Ning Zhu National Laboratory of Solid State Microstructures School of PhysicsSchool of Electronic Science and EngineeringCollege of Engineering and Applied Sciencesand Collaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China Institute for Quantum Information and State Key Laboratory of High Performance Computing College of ComputingNational University of Defense TechnologyChangsha 410073China

We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric downconversion in the periodically-poled lithium niobate on insulator(LNOI)*** analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum,such as narrowing,broadening,and *** also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad *** study may promote the development of on-chip photon sources in the LNOI platform,as well as opens up a way to engineer photon frequency state.

关键词： lithium niobate on insulator spontaneous parametric down-conversion waveguide thickness variation frequency spectrum

Target tracking based on frequency spectrum amplitude

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Journal of Systems Engineering and Electronics 2006年第3期17卷 473-476页

作者： Guo Huidong Zhang Xinhua Xia Zhijun Research Center on Signal and Information Dalian Navy Academy Dalian 116018 P. R. China

The amplitude of frequency spectrum can he integrated with prohabilisfic data association （PDA） to distinguish the target with clutter echoes, especially in low SNR underwater environment. A new target-tracking algorithm is presented which adopts the amplitude of frequency spectrum to improve target tracking in clutter. The prohabilisfic density distribution of frequency spectrum amplitude is analyzed. By simulation, the results show that the algorithm is superior to PDA. This approach enhances stability for the association probability and increases the performance of target tracking.

关键词： target tracking amplitude frequency spectrum probabilistic data association.

Bandwidth Scale for frequency spectrum of Sea Waves

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China Ocean Engineering 2000年第2期15卷 203-210页

作者：王伟钱成春邓拥军孙孚 Physical Oceanography Laboratory Ocean University of Qingdao Qingdao 266003 China

It is well known that energy spectrum bandwidth should be able to reflect the degree of energy concentration. However, the commonly used bandwidth factors defined by Longuet-Higgins could not fit the concept satisfactorily. A new kind of spectrum bandwidth scale factor with a clear physical meaning is given in the present paper and a constant is obtained which reveals the intrinsic characteristics of sea waves. Thereby a universal relationship between significant wave height of sea waves and spectrum bandwidth is established.

关键词： sea waves frequency spectrum spectrum bandwidth

Composite Type Wind Wave frequency spectrum

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China Ocean Engineering 1992年第4期7卷 437-444页

作者： Fu Yuhua Senior Engineer, Structural Engineering Department, China Offshore Oil Development & Engineering Corporation, 100027 Beijing

Based on the P-M spectrum and improved theoretical wind wave frequency spectrum, this paper presents the composite type wind wave frequency spectrum, which is given by 2 pieces and satisfies 4 conditions: the spectrum peak passes through a given point; spectral area m0 and significant wave height H have the relationship H = 4.0 ; at the piecewise point, the values of spectrum and slope are contin-

关键词： wind wave frequency spectrum composite piecewise expression

Limb-Angle-Dependent frequency spectrum of Electrical Conductance for 12 Yuan Acupuncture Points

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Limb-Angle-Dependent Frequency Spectrum of Electrical Conduc...

Study on frequency spectrum of Air Electrostatic Discharge

第十八届中国科协年会——分16 针灸大科学研究学术高峰论坛

作者： Jingjing XU Hongbin HAN Shengyong XU Peking University

With a long history of thousand years, conventional Chinese acupuncture treatment has been used worldwide as an important alternative treatment in daily clinical practice. However, the actual physical structures of various meridians, the networks along which acupuncture points are distributed, and how do electrical signals propagate along the meridian networks, still remain as controversial and open issues to date. Electrical conductance measurement is one of the approaches that have been extensively applied to address the above two open issues [1-3]. In this work, we reported twodimensional(2D) mapping of electrical conductance in the range of 40 Hz to 10 k Hz for a number of acupuncture points on hands and feet, with respect to universal electrodes wrapped on upper arm(or leg), by means of a high-accurate impedance analyzer. We repeatedly observed that for some acupuncture points showed dominant conductance peak in the 2D mapping, while others did not. The results were consistent with previous reports [1]. For the first time, we examined the change in conductance spectrum of each acupuncture point when the limb(arm or leg) angle was changed during the measurements. For the bending angle increases from zero degree to more than 90 degree, the measured electric conductance of 12 Yuan acupuncture points behaved differently, that some increased but some decreased, and the left side could play opposite direction with the right side. The results suggested that each meridian should have its own unique pathway in the limbs, and simple R-C circuits as discussed in the review Ref. 1 might not be applicable. Based on our model of soft-material waveguide, we presented a new vision for the 3D structure of meridian network.

关键词： meridian acupuncture points electrical conductance frequency spectrum limb angle softmaterial waveguide

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Study on frequency spectrum of Air Electrostatic Discharge

The analysis of complex behaviours of a novel three dimensional autonomous system

The Fourth Asia-Pacific Conference on Environmental Electromagnetics

作者： He Qiyuan Liu Shanghe Chen Jingping Institute of Electrostatic and Electromagnetic Protection Mechanical Engineering College Shijiazhuang Hebei Province China

＜正＞Derivation for the frequency spectrum expressions of air Electrostatic Discharge （ESD） electromagnetic fields was performed with postponed potential equations of radiated fields. Using Electrostatic discharge simulation and measurement set-up and home-made metal semi-circle loop, the peak currents of air discharge and peak-peak voltages induced on the loop were measured, and the waveforms of them were recorded by a digital memory oscilloscope. spectrum characteristic of air ESD was investigated with the measured data and by calculation. Amplitude and power spectrum for different discharge voltages were compared. It is shown that the energy of air ESD is dominated in the low frequencies. The spectrum research for air ESD can provide reference and guide for electrostatic prevention technology.

关键词： ESD Coupling FFT frequency spectrum

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Chinese Physics B 2010年第7期19卷 156-166页

作者：董高高郑松田立新杜瑞瑾孙梅 Research Center for Nonlinear Science Faculty of ScienceJiangsu University

This paper introduces a new three dimensional autonomous system with five equilibrium points. It demonstrates complex chaotic behaviours within a wide range of parameters, which are described by phase portraits, Lyapunov exponents, frequency spectrum, etc. Analysis of the bifurcation and Poincar@ map is used to reveal mechanisms of generating these complicated phenomena. The corresponding electronic circuits are designed, exhibiting experimental chaotic attractors in accord with numerical simulations. Since frequency spectrum analysis shows a broad frequency bandwidth, this system has perspective of potential applications in such engineering fields as secure communication.

关键词： three dimensional autonomous system chaotic attractor electronic circuit frequency spectrum

Alleviation of spike stall in axial compressors utilizing grooved casing treatment

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Chinese Journal of Aeronautics 2015年第3期28卷 649-658页

作者： Reza Taghavi-Zenouz Sarallah Abbasi School of Mechanical Engineering Iran University of Science and Technology School of Mechanical Engineering Arak University of Technology

Abstract This article deals with application of grooved type casing treatment for suppression of spike stall in an isolated axial compressor rotor blade row. The continuous grooved casing treatment covering the whole compressor circumference is of 1.8 mm in depth and located between 90% and 108% chord of the blade tip as measured from leading edge. The method of investigation is based on time-accurate three-dimensional full annulus numerical simulations for cases with and without casing treatment. Discretization of the Navier Stokes equations has been carried out based on an upwind second-order scheme and k-a-SST （Shear Stress Transport） turbulence modeling has been used for estimation of eddy viscosity. Time-dependent flow structure results for the smooth casing reveal that there are two criteria for spike stall inception known as leading edge spillage and trailing edge backftow, which occur at specific mass flow rates in near-stall conditions. In this case, two dominant stall cells of different sizes could be observed. The larger one is caused by the spike stall covering roughly two blade passages in the circumferential direction and about 25% span in the radial direction. Spike stall disturbances are accompanied by lower frequencies and higher amplitudes of the pressure signals. Casing treatment causes flow blockages to reduce due to allevi- ation of backflow regions, which in turn reduces the total pressure loss and increases the axial veloc- ity in the blade tip gap region, as well as tip leakage flow fluctuation at higher frequencies and lower amplitudes. Eventually, it can be concluded that the casing treatment of the stepped tip gap type could increase the stall margin of the compressor. This fact is basically due to retarding the movement of the interface region between incoming and tip leakage flows towards the rotor leading edge Diane and suttressing the reversed flow around the blade trailing edee.

关键词： Axial compressor Casing treatment frequency spectrum Spike stall inception Tip leakage flow

Connection Between Damping Torque Analysis and Energy Flow Analysis in Damping Performance Evaluation for Electromechanical Oscillations in Power Systems

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Journal of Modern Power Systems and Clean Energy 2022年第1期10卷 19-28页

作者： Yong Hu Siqi Bu Xin Zhang Chi Yung Chung Hui Cai Department of Electrical Engineering and Research Institute for Smart Energy The Hong Kong Polytechnic UniversityHong KongChina Shenzhen Research Institute The Hong Kong Polytechnic UniversityShenzhenChina Centre for Energy Systems and Strategy Cranfield UniversityCranfieldUK Department of Electrical and Computer Engineering University of SaskatchewanSaskatoonCanada State Grid Jiangsu Economic Research Institute NanjingChina

The damping performance evaluation for electromechanical oscillations in power systems is crucial for the stable operation of modern power *** this paper,the connection between two commonly-used damping performance evaluation methods,i.e.,the damping torque analysis(DTA)and energy flow analysis(EFA),are systematically examined and revealed for the better understanding of the oscillatory damping ***,a concept of the aggregated damping torque coefficient is proposed and derived based on DTA of multi-machine power systems,which can characterize the integration effect of the damping contribution from the whole power ***,the pre-processing of measurements at the terminal of a local generator is conducted for EFA,and a concept of the frequency-decomposed energy attenuation coefficient is defined to screen the damping contribution with respect to the interested *** this basis,the frequency spectrum analysis of the energy attenuation coefficient is employed to rigorously prove that the results of DTA and EFA are essentially equivalent,which is valid for arbitrary types of synchronous generator models in multi-machine power ***,the consistency between the aggregated damping torque coefficient and frequency-decomposed energy attenuation coefficient is further verified by the numerical calculation in case *** relationship between the proposed coefficients and the eigenvalue(or damping ratio)is finally revealed,which consolidates the application of the proposed concepts in the damping performance evaluation.

关键词： Electromechanical oscillation damping performance damping torque analysis(DTA) energy flow analysis(EFA) frequency spectrum

Pressure characteristics of hydrodynamic cavitation reactor due to the combination of Venturi tubes with multi-orifice plates

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Journal of Hydrodynamics 2018年第3期30卷 514-521页

作者： Kai Zhang Zhi-yong Dong Rui-hao Yao Research Institute of Hydraulic and Municipal Engineering Zhejiang University of Technology Hangzhou 310014 China

The pressure characteristics in the throats of Venturi tube and behind triangular multi-orifice plates were experimentally investigated by a pressure data acquisition system of SINOCERA-YE6263, and the effect of throat length of Venturi tube, different geometric parameters of multi-orifice plate and their combinations on the time-averaged pressure, cavitation number, and pressure frequency spectrum, correlation function calculated by FFT were analyzed. The experimental results showed that the throat length of L/R= 40 made for improving the fluctuation energy and promoting the uniform energy distribution, appropriately decreasing the size and increasing the number of orifice could accelerate the uniform distribution of the fluctuation energy in frequency domain. In the combination reactors, the cavitation number behind multi-orifice plates was lower and the fluctuation of correlation function was more intense.

关键词： Hydrodynamic cavitation Venturi tube triangular multi-orifice plate pressure characteristics frequency spectrum correlation function