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Design of Reflective Concentrator Model with Application for Concentrator Photovoltaic System

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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

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

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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

OsPHR2-mediated recruitment of Pseudomonadaceae enhances rice phosphorus uptake

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Plant Communications 2024年第8期5卷 137-146页

作者： Jianping Liu Weifeng xu Qian Zhang Wencheng Liao Liang Li Shu Chen Jinyong Yang Zhengrui Wang feiyun xu Center for Plant Water-use and Nutrition Regulation and College of JunCao Science and Ecology Joint International Research Laboratory of Water and Nutrient in CropFujian Agriculture and Forestry UniversityFuzhou 350002China

Plants can shape their root microbiome to promote growth and nutrient *** STARVATION RESPONSE 2(OsPHR2)is a central regulator of phosphate signaling in rice,but whether OsPHR2 can shape the root microbiome to promote phosphorus uptake is ***,we investigate the role of OsPHR2 in recruiting microbiota for phosphorus uptake using high-throughput sequencing and metabolite ***2-overexpressing(OsPHR2 OE)rice showed 69.8%greater shoot P uptake in natural soil compared with sterilized soil under high-phosphorus(HP)conditions,but there was only a 54.8%increase in the wildtype(WT).The abundance of the family Pseudomonadaceae was significantly enriched in OsPHR2 OE roots relative to those of WT *** with the WT,OsPHR2 OE rice had a relatively higher abundance of succinic acid and methylmalonic acid,which could stimulate the growth of Pseudomonas sp.(P6).After inoculation with P6,phosphorus uptake in WT and OsPHR2 OE rice was higher than that in uninoculated rice under low-phosphorus(LP)*** together,our results suggest that OsPHR2 can increase phosphorus use in rice through root exudate-mediated recruitment of *** finding reveals a cooperative contribution of the OsPHR2-modulated root microbiome,which is important for improving phosphorus use in agriculture.

关键词： OsPHR2 rice organic acid phosphorus Pseudomonadaceae

A Novel Acoustic Emission Source Location Method in the Crane Based on EEMD-FastICA

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Journal of Mechanics Engineering and Automation 2017年第1期7卷 17-25页

作者： Yu Jiang feiyun xu College of Intelligent Science and control Engineering Jinling Institute of Technology Nanjing 211169 China School of Mechanical Engineering Southeast University Nanjing 211189 China

The study presents a novel source location method based on EEMD （ensemble empirical mode decomposition） and optimized FastICA （independent component analysis） for determining the position of the AE （acoustic emission） sources in the damage structure of crane. Firstly, The AE signals are self-adaptive decomposed into a number of IMFs （intrinsic mode functions） by using EEMD algorithm. Then, the main feature IMFs signals are extracted as the effective AE source signal by optimized Fast-ICA method, the PSD （power spectral density） of each IMF and the real IMFs are obtained. According to the principle of spectrum similarity, time delay is computed at the different channels in combination with the Cross Correlation time delay estimation principle. Thirdly, a novel source location algorithm based on EEMD-FastICA is proposed and the results of AE source location are obtained. Finally, the three-point bending test for the crane is implemented in order to validate the efficiency of the proposed method. The experimental results indicate that the proposed method has the ability to determinate the position of the AE sources and reduce the interference noises. Moreover, compared with the traditional location algorithm, a considerable improvement is obtained.

关键词： Source location EEMD FastlCA cranet three-point bending test.

Improved adaptive filter and its application in acoustic emission signals

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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

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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

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

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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

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不同含水率云南松声发射信号特征

林业科学 2019年第6期55卷 96-102页

作者：李杨许飞云东南大学机械工程学院

【目的】研究不同含水率条件下云南松试件声发射信号的传播规律,探讨含水率对声发射信号波形的响应,为云南松声发射源定位提供依据,为木材内部缺陷无损检测提供基础数据。【方法】以云南松为试验材料,采用NI高速数据采集设备和LabVIEW... 详细信息

【目的】研究不同含水率条件下云南松试件声发射信号的传播规律,探讨含水率对声发射信号波形的响应,为云南松声发射源定位提供依据,为木材内部缺陷无损检测提供基础数据。【方法】以云南松为试验材料,采用NI高速数据采集设备和LabVIEW软件构建云南松试件声发射信号采集平台,利用铅芯折断模拟声发射源,对绝干、气干、生材和饱水4种含水率状态下的试件表面进行声发射信号采集,通过时差法计算信号在4种含水率状态下的平均传播速率,并运用小波分析对声发射信号波形进行分解和重构,根据软阈值量化方法消除各通道系数和经阈值量化后的各高频层系数,去除非主能量信号以便从噪声中析取微弱的声发射信号。【结果】试验中传感器均以接收表面波信号为主;随着含水率增加,云南松试件表面声发射信号波形和平均声速均大幅度衰减,绝干状态下声发射信号时域波形幅值达到±5.2 V,平均声速可达4 208.77 m·s^-1 ,而饱水状态下信号时域波形幅值仅为±0.6 V,平均声速降至1 414.07 m·s^-1 ,气干和生材状态下信号时域波形幅值和平均声速分别为±4、±2 V和 3 331.79 、 2 328.73 m·s^-1 ,且各含水率状态之间平均声速差在876.98~1 003.06 m·s^-1 范围内;小波变换能有效将“淹没”在噪声中的声发射信号析取出来,4种含水率状态下试件声发射信号频域波形范围在40 ~150 kHz之间,且气干状态下波形峰值出现在110 kHz左右,其余3种均在50 kHz左右达到峰值。【结论】含水率增加可显著改变云南松声发射信号和传播特征,其信号波形和平均声速均与含水率降低呈正比;小波变换在信号降噪处理方面具有明显优势,不仅可去除信号中的大量噪音,而且不会破坏有用信号,保证信号完整性,能更大程度降低对不同含水率云南松试件声发射信号的分析误差,为云南松表面声发射源定位研究及内部无损检测给予试验数据支持;作为一种木材声发射信号采集与分析平台,研究结果可为不同含水率云南松受压变形破坏全过程的声发射特征分析提供必要的基础理论依据。

关键词：云南松含水率平均声速声发射特性小波分析

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

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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