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Petroleum Science 2014年第4期11卷 519-525页

作者： Liu Xiaonan Kong Li Zhou Kaibo Zhang Pu School of Automation Huazhong University of Science and Technology

Relaxation time spectra （RTS） derived from time domain induced polarization data （TDIP） are helpful to assess oil reservoir pore structures. However, due to the sensitivity to the signal-to-noise ratio （SNR）, the inversion accuracy of the traditional singular value decomposition （SVD） inversion method reduces with a decrease of SNR. In order to enhance the inversion accuracy and improve robustness of the inversion method to the SNR, an improved inversion method, based on damping factor and spectrum component residual correction, is proposed in this study. The numerical inversion results show that the oscillation of the RTS derived from the SVD method increased with a decrease of SNR, which makes it impossible to get accurate inversion components. However, the SNR has little influence on inversion components of the improved method, and the RTS has high inversion accuracy and robustness. Moreover, RTS derived from core sample data is basically in accord with the pore-size distribution curve, and the RTS derived from the actual induced polarization logging data is smooth and continuous, which indicates that the improved method is practicable.

关键词： Inversion method damping factor relaxation time spectrum time domain inducedpolarization spectrum component residual correction

damping factor Estimation of a Flexible-Matrix-Composite Body Pump

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Journal of Materials Science and Chemical Engineering 2016年第7期4卷 59-66页

作者： N. P. Kumar H. Ghoneim Mechanical Engineering Rochester Institute of Technology Rochester NY USA

Two very important factors which determine the effectiveness of a pump are its volumetric and power efficiencies. Yin and Ghoneim constructed a prototype of a Flexible-Matrix-Composite (FMC) body pump with a very high volumetric efficiency or pumping potential (the relative volume reduction due to a relative input stroke). The high volumetric efficiency is attributed to the geometry of the pump’s structure (hyperboloid) as well as the high negative effective Poisson’s ratio of the 3-layer [θ/β/θ] flexible-matrix-composite (carbon/polyurethane) laminate adopted for the body of the pump. However, the power efficiency of the pump was not evaluated. It is the objective of the current paper to obtain an estimate of the power efficiency of the pump. The viscoelastic properties of the 3-layer FMC (carbon/polyurethane) laminate are evaluated experimentally using the Dynamic Mechanical Analyzer (DMA) as well as analytically by applying the correspondence principle together with the micro-mechanics approach. In order to obtain an estimate of the power efficiency of the FMC body pump, the axial and shear loss factors of a laminated infinitely long cylindrical tube as functions of β and θ fiber orientation angles are determined employing the Adam and Bacon approach. The analysis engenders high loss factors (greater than 0.4), which suggests that the power efficiency of the proposed pump using the 3-layer carbon/polyurethane laminate may be low.

关键词： Flexible-Matrix-Composites Dynamic Mechanical Analyzer Viscoelastic Characteristics damping factor

Rational design of thermoelastic damping in microresonators with phase-lagging heat conduction law

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Applied Mathematics and Mechanics(English Edition) 2022年第11期43卷 1675-1690页

作者： Yu FU Li LI Hongfang CHEN Xuelin WANG Ling LING Yujin HU State Key Laboratory of Digital Manufacturing Equipment and Technology School of Mechanical Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

The design of thermoelastic damping(TED)affected by the phase-lagging non-Fourier heat conduction effects becomes significant but challenging for enlarging the quality factor of widely-used microresonators operating in extreme situations,including ultra-high excitation frequency and ultra-low working temperature.However,there does not exist a rational method for designing the TED in the framework of non-Fourier heat conduction law.This work,therefore,proposes a design framework to achieve low thermoelastic dissipation of microresonators governed by the phase-lagging heat conduction law.The equation of motion and the heat conduction equation for phase-lagging TED microresonators are derived first,and then the non-Fourier TED design problem is proposed.A topology optimization-based rational design method is used to resolve the design problem.What is more,a two-dimensional(2D)plain-strain-based finite element method(FEM)is developed as a solver for the topology optimization process.Based on the suggested rational design technique,numerical instances with various phase lags are investigated.The results show that the proposed design method can remarkably reduce the dissipation of microresonators by tailoring their substructures.

关键词： microresonator non-Fourier damping factor topology optimization

An Impedance-based Parameter Design Method for Active damping of Load Converter Station in MTDC Distribution System

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Journal of Modern Power Systems and Clean Energy 2022年第5期10卷 1423-1436页

作者： Pengwei Chen Wenmeng Zhao Xin Chen Wenwei Jiang IEEE Jiangsu Key Laboratory of New Energy Generation and Power Conversion College of Automation EngineeringNanjing University of Aeronautics and AstronauticsNanjingChina

To achieve the efficient application of impedance analysis in the stability assessment and enhancement of multiterminal DC distribution systems, this paper proposes the DCside reduced-order impedance models with power control and AC voltage control, respectively, by taking the load converter station as the object. By using the DC-side current as the feedforward state, the active compensator applied to the load converter station with two control modes is also derived as well as the corresponding reduced-order impedance models. Combined with the reduced-order impedance models, a method based on damping factor sensitivity is further proposed to design the parameters of the derived active compensators. The verification results in the frequency domain and time domain demonstrate the accuracy of the reduced-order impedance and the effectiveness of the proposed compensator parameter design method.

关键词： Impedance modeling order reduction active compensator damping factor sensitivity

High frequency characteristics of (Ni_(75)Fe_2)_x(Zn O)_(1-x) granular thin films with tunable damping coefficient

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Chinese Physics B 2015年第4期24卷 441-444页

作者：李文春左亚路刘晓虹魏清清周雪云姚东升 Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology Faculty of ScienceTianjin University The Key Laboratory for Magnetism and Magnetic Materials Lanzhou University Faculty of Science Jiujiang University

The effect of the volume fraction of ferromagnetic metal （x） in （Ni75Fe25）x（ZnO）1-x nanogranular thin films on microstructural, soft-magnetic, and high-frequency properties was investigated. Good soft-magnetic properties were obtained in a broad x range, with 0.55 〈 x 〈 0.82. High resolution transmission electron microscopy （HRTEM） observations reveal that the grain size of the samples is lower than 14 nm, and that it decreases with decreasing x. Of special interest, our investigation of the permeability spectra indicates that these films exhibit an adjustable frequency linewidth of resonance peak, dependant upon changing x. Correspondingly, large and adjustable damping coefficients （aeff） from 0.023 to 0.043 were achieved by decreasing x from 0.82 to 0.55. Combined with the HRTEM results, the variation of αeff with x was analyzed in detail.

关键词： soft magnetic properties high frequency properties damping factor granular film

Numerical evaluation of acoustic characteristics and their damping of a thrust chamber using a constant-volume bomb model

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Chinese Journal of Aeronautics 2018年第3期31卷 470-480页

作者： Jianxiu QIN Huiqiang ZHANG Bing WANG School of Aerospaee Engineering Tsinghua University Beijing 100084 China

In order to numerically evaluate the acoustic characteristics of liquid rocket engine thrust chambers by means of a computational fluid dynamics method, a mathematical model of an artificial constant-volume bomb is proposed in this paper. A localized pressure pulse with a very high amplitude can be imposed on specified regions in a combustion chamber, the numerical procedure of which is described. Pressure oscillations actuated by the released constant-volume bomb can then be analyzed via Fast Fourier Transformation（FFT）, and their modes can be identified according to the theoretical acoustic eigenfrequencies of the thrust chamber. The damping performances of the corresponding acoustic modes are evaluated by the half-power bandwidth method. The predicted acoustic characteristics and their damping for a special engine combustor agree well with the experimental data, validating the mathematical model and its numerical procedures. A small-thrust liquid rocket engine chamber is then analyzed by the present model. The First Longitudinal（1L） acoustic mode can be excited easily and is hard to be damped. The axial position of the central constantvolume bomb has little influence on the amplitude and damping capacity of the First Radial（1R） and 1L acoustic modes. Tangential acoustic modes can only be triggered by an off-centered constant-volume bomb, among which the First Tangential（1T） mode is the strongest and regarded as the most harmful one. The amplitude of the 1L acoustic mode is smaller, but its damping factor is larger, as a constant-volume bomb is imposed approaching the injector face. These results are contributed to evaluate the acoustic characteristics and their damping of the combustion chamber.

关键词： Acoustic mode Constant-volume bomb damping characteristics damping factor Half-power bandwidth Pressure oscillation

The Effect of Fibre Length on Flexural and Dynamic Mechanical Properties of Pineapple Leaf Fibre Composites

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Journal of Renewable Materials 2020年第7期8卷 833-843页

作者： A.A.Mazlan M.T.H.Sultan S.N.A.Safri N.Saba A.U.M.Shah M.Jawaid Department of Aerospace Engineering Faculty of EngineeringUniversiti Putra MalaysiaSerdangSelangor Darul Ehsan43400 UPMMalaysia Laboratory of Biocomposite Technology Institute of Tropical Forestry and Forest Products(INTROP)SerdangSelangor Darul Ehsan43400 UPMMalaysia Aerospace Malaysia Innovation Centre(944751-A) Prime Minister’s DepartmentMIGHT Partnership HubJalan Impact63000 CyberjayaMalaysia

The present paper deals with the effect of loading different pineapple leaf fibre(PALF)length(short,mixed and long fibres)and their reinforcement for the fabrication of vinyl ester(VE)composites.Performance of PALF/VE composites was investigated through three-point bending flexural testing and viscoelastic(dynamic)mechanical properties through dynamic mechanical analysis(DMA).DMA results revealed that the long PALF/VE composites displayed better mechanical,damping factor and dynamic properties as compared to the short and mixed PALF/VE composites.The flexural strength and modulus of long PALF/VE composites were 113.5 MPa and 14.3 GPa,respectively.The storage(E′)and loss(E″)moduli increased to 2000 MPa and 225 MPa respectively for PALF/VE composites.Overall result analysis indicated that increasing the length of the reinforcement fibre results in satisfactory mechanical performance and dynamic properties of composites.

关键词： Pineapple leaf fibre vinyl ester resin flexural strength dynamical mechanical properties damping factor

Control of UPQC Based on Steady State Linear Kalman Filter for Compensation of Power Quality Problems

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Chinese Journal of Electrical Engineering 2020年第2期6卷 52-65页

作者： Sayed Javed Alam Sabha Raj Arya Department of Electrical Engineering Sardar Vallabhai National Institute of TechnologySuart 395007India

A frequency lock loop(FLL)based steady state linear Kalman filter(SSLKF)for unified power quality conditioner(UPQC)control in three-phase systems is introduced.The SSLKF provides a highly accurate and fast estimation of grid frequency and the fundamental components(FCs)of the input signals.The Kalman filter is designed using an optimized filtering technique and intrinsic adaptive bandwidth architecture,and is easily integrated into a multiple model system.Therefore,the Kalman state estimator is fast and simple.The fundamental positive sequence components(FPSCs)of the grid voltages in a UPQC system are estimated via these SSLKF-FLL based filters.The estimation of reference signals for a UPQC controller is based on these FPSCs.Therefore,both active filters of a UPQC can perform one and more functions towards improving power quality in a distribution network.In addition to the SSLKF-FLL based algorithm,a bat optimization algorithm(based on the echolocation phenomenon of bats)is implemented to estimate the value of the proportional integral(PI)controller gains.The bat algorithm has a tendency to automatically zoom into a region where a promising alternative solution occurs,preventing the solution from becoming trapped in a local minima.The complete three-phase UPQC is simulated in the Matlab/Simulink platform and the hardware is tested under various power quality problems.

关键词： damping factor echo-location FPSC harmonics ITSE SSLKF-FLL power quality

Reinforcing Effect of Organo-Modified Fillers in Rubber Composites as Evidenced from DMA Studies

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材料科学与工程（中英文A版） 2022年第1期12卷 13-23页

作者： Raji Vijay A.R.Ravindranatha Menon National Institute for Interdisciplinary Science&Technology Council of Scientific and Industrial ResearchThiruvananthapuram 695019KeralaIndia

The use of organically enhanced kaolin clay as reinforcing filler for NR(natural rubber)and blends of NR with NBR(nitrile-butadiene rubber)and poly BR(butadiene rubber)system were investigated on the basis of DMA(dynamic mechanical analysis).Kaolin clay was modified using a chemical complex of HH(hydrazine hydrate)and SRSO(sodium salt of rubber seed oil).Intercalation of SRSO into kaolin under optimized condition showed an inter-lamellar layer expansion to 4.668 nm,compared to the characteristic d001 XRD(X-ray diffraction)peak of pristine kaolin at 0.714 nm.The morphology,visco-elastic behavior,modulus property,polymer miscibility and Tg(glass transition temperature)of nano-kaolin filled NR and its blend with synthetic rubbers have been studied in detail.DMA showed a diminution in tanδpeak height and a modulus shift in correspondence with increased CLD(crosslink density).Pure NR shows only~1%increase in storage modulus(E′)while adding nanoclay rather than micron sized pristine clay under experimental conditions,because of the feeble interaction between filler and matrix,as compared to blend.An increment of~76%and~117%in E′was recognized by the addition of 4 wt%nanoclay in blends such as BR mK and NBR mK.With loss modulus(E″)pure NR shows only~7%decrease while adding nanoclay,compared to blend.A decrement of~54%and~55%in E″by the addition of 4 wt%nanoclay in BR mK and NBR mK blends were observed.As a whole,DMA was performed to figure out the effect of surface modification enabling to materialize composite.

关键词： Reinforcement rubber cross link density storage modulus loss modulus damping factor surface modification

FREE VIBRATION ANALYSIS OF SIMPLY SUPPORTED BEAM WITH BREATHING CRACK USING PERTURBATION METHOD

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Acta Mechanica Solida Sinica 2010年第5期23卷 459-470页

作者： Mousa Rezaee Reza Hassannejad Department of Mechanical Engineering University of Tabriz

In this paper, a new analytical method for vibration analysis of a cracked simply supported beam is investigated. By considering a nonlinear model for the fatigue crack, the governing equation of motion of the cracked beam is solved using perturbation method. The solution of the governing equation reveals the superhaxmonics of the fundamental frequency due to the nonlinear effects in the dynamic response of the cracked beam. Furthermore, considering such a solution, an explicit expression is also derived for the system damping changes due to the changes in the crack parameters, geometric dimensions and mechanical properties of the cracked beam. The results show that an increase in the crack severity and approaching the crack location to the middle of the beam increase the system damping. In order to validate the results, changes in the fundamental frequency ratios against the fatigue crack severities are compared with those of experimental results available in the literature. Also, a comparison is made between the free response of the cracked beam with a given crack depth and location obtained by the proposed analytical solution and that of the numerical method. The results of the proposed method agree with the experimental and numerical results.

关键词： free vibration cracked beam breathing crack damping factor perturbation method