检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

心怀星辰大海不负法治人生

人民司法 2024年第12期 94-96页

作者：徐飞云(文/图) 江苏省苏州市中级人民法院

今年,是我进入法院工作的第13个年头,也是我人生中成长飞快、浓墨重彩的时光。这些年,我共计参与审理了2000多起知识产权案件,我时常问自己:这些数字后面,到底是什么?

关键词：知识产权案件法院人生

MODIFIED LAPLACIAN EIGENMAP ETHOD FOR FAULT DIAGNOSIS

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2008年第3期21卷 90-93页

作者： JIANG Quansheng JIA Minping HU Jianzhong xu feiyun School of Mechanical Engineering Southeast University Nanjing 211189 China Department of Physics Chaohu UniversityChaohu 238000 China

A novel method based on the improved Laplacian eigenmap algorithm for fault pattern classification is proposed. Via modifying the Laplacian eigenmap algorithm to replace Euclidean distance with kernel-based geometric distance in the neighbor graph construction, the method can preserve the consistency of local neighbor information and effectively extract the low-dimensional manifold features embedded in the high-dimensional nonlinear data sets. A nonlinear dimensionality reduction algorithm based on the improved Laplacian eigenmap is to directly learn high-dimensional fault signals and extract the intrinsic manifold features from them. The method greatly preserves the global geometry structure information embedded in the signals, and obviously improves the classification performance of fault pattern recognition. The experimental results on both simulation and engineering indicate the feasibility and effectiveness of the new method.

关键词： Laplacian eigenmap Kernel trick Fault diagnosis Manifold learning

Improved adaptive filter and its application in acoustic emission signals

在线全文

学校读者我要写书评

暂无评论

Journal of Southeast University(English Edition) 2019年第1期35卷 43-50页

作者： Wang Jiajun xu feiyun School of Mechanical Engineering Southeast UniversityNanjing 211189China

In order to de-noise and filter the acoustic emission(AE) signal, the adaptive filtering technology is applied to AE signal processing in view of the special attenuation characteristics of burst AE signal. According to the contradiction between the convergence speed and steady-state error of the traditional least mean square(LMS) adaptive filter, an improved LMS adaptive filtering algorithm with variable iteration step is proposed on the basis of the existing algorithms. Based on the Sigmoid function, an expression with three parameters is constructed by function translation and symmetric *** for the error mutation, e(k) and e(k-1) are combined to control the change of the iteration step. The selection and adjustment process of each parameter is described in detail, and the MSE is used to evaluate the performance. The simulation results show that the proposed algorithm significantly increases the convergence speed, reduces the steady-state error, and improves the performance of the adaptive filter. The improved algorithm is applied to the AE signal processing, and the experimental signal is demodulated by an empirical mode decomposition(EMD) envelope to obtain the upper and lower envelopes. Then, the expected function related to the AE signal is established. Finally, the improved algorithm is substituted into the adaptive filter to filter the AE signal. A good result is achieved, which proves the feasibility of adaptive filtering technology in AE signal processing.

关键词： acoustic emission adaptive filtering envelope demodulation least mean square(LMS)algorithm variable iteration step

A fault feature extraction method of gearbox based on compound dictionary noise reduction and optimized Fourier decomposition

在线全文

学校读者我要写书评

暂无评论

Journal of Southeast University(English Edition) 2021年第1期37卷 22-32页

作者： Mao Yifan xu feiyun School of Mechanical Engineering Southeast UniversityNanjing 211189China

Aimed at the problem that Fourier decomposition method(FDM)is sensitive to noise and existing mode mixing cannot accurately extract gearbox fault features,a gear fault feature extraction method combining compound dictionary noise reduction and optimized FDM(OFDM)is ***,the characteristics of the gear signals are used to construct a compound dictionary,and the orthogonal matching pursuit algorithm(OMP)is combined to reduce the noise of the vibration ***,in order to overcome the mode mixing phenomenon occuring during the decomposition of FDM,a method of frequency band division based on the extremum of the spectrum is proposed to optimize the decomposition ***,the OFDM is used to decompose the signal into several analytic Fourier intrinsic band functions(AFIBFs).Finally,the AFIBF with the largest correlation coefficient is selected for Hilbert envelope spectrum *** fault feature frequencies of the vibration signal can be accurately *** proposed method is validated through analyzing the gearbox fault simulation signal and the real vibration signals collected from an experimental gearbox.

关键词： Fourier decomposition compound dictionary mode mixing gearbox fault feature extraction

Design of Reflective Concentrator Model with Application for Concentrator Photovoltaic System

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2011年第6期24卷 1007-1012页

作者： SU Zhongyuan ZHANG Yaoming JIA Minping SUN Liguo xu feiyun WANG Jun School of Energy ＆ Environment Southeast University Nanjing 210096 China School of Mechanical Engineering Southeast University Nanjing 210096 China

The nonuniform irradiation in the standard photovoltaic（PV） cells causes their relatively high series resistance,which results in a considerably lowered efficiency of PV *** the concentrator of uniform irradiation designed for concentrator photovoltaic is rare in China and lack sufficient theoretical *** this paper,a systematic research on the solar reflective concentrator is conducted.A novel structure for a solar reflective concentrator is designed with the application of a flat mirror matrix to concentrate the sunlight for concentrator photovoltaic（CPV） *** beams are focused through the reflection of the mirror array on the solar cell to generate *** concentrator is capable of producing much more uniform sunlight with a certain concentration *** design scheme includes laying out the flat mirrors,optimizing the optical pathway and the parameters of each *** prototype of the CPV system was installed at Nanjing,*** the configuration of the prototype,it is composed of 24 pieces parallelogram flat mirrors,which are arranged into a total reflective array of 5 rows and 5 *** comparison with the parabolic trough concentrator,the experimental measurements verify such design has high *** concentrator model of a flat mirror matrix and the proposed new design method will lay a solid foundation for designing the concentrator of uniform irradiation.

关键词： concentrator uniform concentration concentrator photovoltaic sun tracking

Roughness evaluation of three-dimensional asphalt pavement based on two-dimensional power spectral density

在线全文

学校读者我要写书评

暂无评论

Journal of Southeast University(English Edition) 2022年第4期38卷 401-407页

作者： Ding Zhike xu feiyun Zhao xun School of Mechanical Engineering Southeast UniversityNanjing 211189China

To solve the problem of the lack of comprehensive evaluation of three-dimensional(3D)asphalt pavement roughness,a method for evaluating the asphalt pavement roughness is proposed based on two-dimensional(2D)power spectral density(PSD).By calculating the 2D PSD of a 3D asphalt pavement and converting it into the longitudinal average asphalt pavement PSD,the relationship between the evaluation method of the 3D asphalt pavement roughness and the current evaluation standard of roughness is *** with the road-fitting formula used in international standards,the elevation data of the A,B,C,and D grades of the 3D asphalt pavement are simulated by the harmonic superposition *** to the proposed method,the longitudinal PSD of each level of simulated asphalt pavement is calculated and compared with the standard spectral line of each pavement *** approach verifies the effectiveness of the proposed method in evaluating the roughness of the 3D asphalt *** with the PSD of a certain horizontal profile elevation,it is verified that the fluctuation amplitude of the spectral line calculated by the proposed method is greatly *** results show that the proposed method can evaluate the roughness of asphalt pavements more comprehensively and accurately and has strong practicability.

关键词： roughness power spectral density three-dimensional asphalt pavement

Bispectrum Feature Extraction of Gearbox Faults Based on Nonnegative Tucker3 Decomposition with 3D Calculations

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2013年第6期26卷 1182-1193页

作者： WANG Haijun xu feiyun ZHAO Jun’ai JIA Minping HU Jianzhong HUANG Peng School of Mechanical Engineering Southeast University

Nonnegative Tucker3 decomposition（NTD） has attracted lots of attentions for its good performance in 3D data array analysis. However, further research is still necessary to solve the problems of overfitting and slow convergence under the anharmonic vibration circumstance occurred in the field of mechanical fault diagnosis. To decompose a large-scale tensor and extract available bispectrum feature, a method of conjugating Choi-Williams kernel function with Gauss-Newton Cartesian product based on nonnegative Tucker3 decomposition（NTD_EDF） is investigated. The complexity of the proposed method is reduced from o（nNlgn） in 3D spaces to o（RiR2nlgn） in 1D vectors due to its low rank form of the Tucker-product convolution. Meanwhile, a simultaneously updating algorithm is given to overcome the overfitting, slow convergence and low efficiency existing in the conventional one-by-one updating algorithm. Furthermore, the technique of spectral phase analysis for quadratic coupling estimation is used to explain the feature spectrum extracted from the gearbox fault data by the proposed method in detail. The simulated and experimental results show that the sparser and more inerratic feature distribution of basis images can be obtained with core tensor by the NTD EDF method compared with the one by the other methods in bispectrum feature extraction, and a legible fault expression can also be performed by power spectral density（PSD） function. Besides, the deviations of successive relative error（DSRE） of NTD_EDF achieves 81.66 dB against 15.17 dB by beta-divergences based on NTD（NTD_Beta） and the time-cost of NTD EDF is only 129.3 s, which is far less than 1 747.9 s by hierarchical alternative least square based on NTD （NTD_HALS）. The NTD_EDF method proposed not only avoids the data overfitting and improves the computation efficiency but also can be used to extract more inerratic and sparser bispectrum features of the gearbox fault.

关键词： nonnegative tucker3 decomposition Tucker-product convolution power spectrum density updating algorithm

A modified time domain interpolation method for LS channel estimation in OFDM systems

在线全文

学校读者我要写书评

暂无评论

Journal of Southeast University(English Edition) 2022年第3期38卷 219-226页

作者： Zhang Yenan xu feiyun Jia Minping School of Mechanical Engineering Southeast UniversityNanjing 211189China

A modified time domain interpolation method is proposed for orthogonal frequency division multiplexing(OFDM)systems to address the problem that time domain interpolation in the least square(LS)channel estimation method based on comb-type pilots cannot choose the pilot spacing ***,the estimated channel frequency response(CFR)at pilot positions in the frequency domain is obtained by LS channel estimation based on comb-type pilots,and the estimated channel impulse response(CIR)in the time domain is obtained by linear interpolation and inverse fast Fourier transform(IFFT).Secondly,the error of the estimated CIR obtained by linear interpolation is analyzed by theoretical deduction,and a method for correcting it is ***,an estimated CFR at all subcarrier positions in the frequency domain is obtained by performing zero padding in the time domain and fast Fourier transform(FFT)on the modified *** simulation results suggest that the proposed method gives similar performance to time domain interpolation,yet it does not need to meet the condition of time domain interpolation that the number of subcarriers must be an integral multiple of pilot spacing to use *** proposed method allows for flexible pilot spacing,reducing the number of pilots and the consumption of subcarriers used for channel estimation.

关键词： orthogonal frequency division multiplexing(OFDM) channel estimation linear interpolation time domain interpolation

Research on damage evolution of metal plate based on improved micropolar peridynamic model

在线全文

学校读者我要写书评

暂无评论

Journal of Southeast University(English Edition) 2019年第3期35卷 292-301页

作者： Yang Huichao xu feiyun Zhu Dasheng Liu Yadong School of Mechanical Engineering Southeast UniversityNanjing 211189China School of Mechanical Engineering Nanjing Institute of TechnologyNanjing 211167China

To study the damage evolution of the metal plate in elastic and plastic deformation stages, an improved micropolar peridynamic model is proposed to simulate the deformation process and damage evolution of metal materials with variable Poisson’s ratios in the elastic-plastic stages. Firstly, both the stretching and bending moments of the bonds between the material points are added to peridynamic pairwise force functions, and the coordinate transformation of the micro-beam made up of bonds is deduced. Therefore, the numerical calculation implementation of the improved micropolar peridynamic model is obtained. Then, the strain values are obtained by solving the difference equation based on the displacement values of material points, and the stress values can be calculated according to generalized Hook’s law. The elastic and plastic deformation stages can be estimated based on the von Mises yield criterion, and different constitutive equations are adopted to simulate the damage evolution. Finally, the proposed micropolar peridynamic model is applied to simulate the damage evolution of a metal plate with a hole under velocity boundary conditions, and the effectiveness of the model is verified through experiments. In the experiments, the displacement and strain distributions in the stretching process are analyzed by the digital image correlation(DIC) method. By comparing the results, the proposed model is more accurate than the bond-based peridynamic model and the error of the proposed model is 7.2% lower than that of the bond-based peridynamic model. By loading different velocity boundary conditions, the relationship between the loads and damage evolution is studied.

关键词： micropolar peridynamic model elastic-plastic constitutive equation damage evolution plastic deformation digital image correlation tensile test