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Step-by-Step Numerical Prediction of Aerodynamic Noise Generated by High Speed Trains

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Chinese Journal of Mechanical Engineering 2022年第2期35卷 251-264页

作者： Tian Li deng qin Ning Zhou Weihua Zhang State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

In this paper,the unsteady flow around a high-speed train is numerically simulated by detached eddy simulation method(DES),and the far-field noise is predicted using the Ffowcs Williams-Hawkings(FW-H)acoustic *** reliability of the numerical calculation is verified by wind tunnel *** superposition relationship between the far-field radiated noise of the local aerodynamic noise sources of the high-speed train and the whole noise source is *** the aerodynamic noise of high-speed trains is derived from its different components,a stepwise calculation method is proposed to predict the aerodynamic noise of high-speed *** results show that the local noise sources of high-speed trains and the whole noise source conform to the principle of sound source energy *** the head,middle and tail cars of the high-speed train as noise sources,different numerical models are established to obtain the far-field radiated noise of each aerodynamic noise *** far-field total noise of high-speed trains is predicted using sound source superposition.A step-by-step calculation of each local aerodynamic noise source is used to obtain the superimposed value of the far-field *** is consistent with the far-field noise of the whole train model’s aerodynamic *** averaged sound pressure level of the far-field longitudinal noise measurement points differs by 1.92 *** step-by-step numerical prediction method of aerodynamic noise of high-speed trains can provide a reference for the numerical prediction of aerodynamic noise generated by long marshalling high-speed trains.

关键词： High-speed train Aerodynamic noise Sound source superposition Numerical prediction

On Generic Extensions of Representations of a Dynkin Quiver of Type D

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Acta Mathematica Sinica,English Series 2005年第3期21卷 613-622页

作者： Xiao qin deng Jiang Rong CHEN School of Sciences Beijing Jiaotong University Beijing 100044 P. R. China Department of Mathematics Beijing Normal University Beijing 100875 P. R. China

The notion of generic extensions of representations of a Dynkin quiver plays a big role in the study of the structure of the corresponding quantum group. In this paper, we describe the generic extensions of a simple representation by any representation and that of any representation by a simple representation of a Dynkin quiver Q of type D.

关键词： Dynkin quiver Representation Generic extension

Automated identification of retinopathy of prematurity by image-based deep learning

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Eye and Vision 2020年第4期7卷 379-390页

作者： Yan Tong Wei Lu qin-qin deng Changzheng Chen Yin Shen Eye Center Renmin Hospital of Wuhan UniversityWuhan 430060HubeiChina Medical Research Institute Wuhan UniversityWuhanHubeiChina

Background:Retinopathy of prematurity(ROP)is a leading cause of childhood blindness worldwide but can be a treatable retinal disease with appropriate and timely *** study was performed to develop a robust intelligent system based on deep learning to automatically classify the severity of ROP from fundus images and detect the stage of ROP and presence of plus disease to enable automated diagnosis and further ***:A total of 36,231 fundus images were labeled by 13 licensed retinal experts.A 101-layer convolutional neural network(ResNet)and a faster region-based convolutional neural network(Faster-RCNN)were trained for image classification and *** applied a 10-fold cross-validation method to train and optimize our *** accuracy,sensitivity,and specificity were assessed in a four-degree classification task to evaluate the performance of the intelligent *** performance of the system was compared with results obtained by two retinal ***,the system was designed to detect the stage of ROP and presence of plus disease as well as to highlight lesion regions based on an object detection network using ***:The system achieved an accuracy of 0.903 for the ROP severity ***,the accuracies in discriminating normal,mild,semi-urgent,and urgent were 0.883,0.900,0.957,and 0.870,respectively;the corresponding accuracies of the two experts were 0.902 and ***,our model achieved an accuracy of 0.957 for detecting the stage of ROP and 0.896 for detecting plus disease;the accuracies in discriminating stage I to stage V were 0.876,0.942,0.968,0.998 and 0.999,***:Our system was able to detect ROP and differentiate four-level classification fundus images with high accuracy and *** performance of the system was comparable to or better than that of human experts,demonstrating that this system could be used to support clinical decisions.

关键词： Deep learning Retinopathy of prematurity Artificial intelligence Fundus image

Effect of streamlined nose length on aerodynamic performance of high-speed train with a speed of 400 km/h

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第7期25卷 525-540页

作者： Nianxun LI Tian LI Zhiyuan DAI deng qin Jiye ZHANG State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu 610031China

The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed *** appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces,but also improve the performance of the high-speed train in tunnel passing and crosswind *** this study,a numerical simulation of the aerodynamic performance of high-speed trains at a speed of 400 km/h,with varying SNLs,is conducted using the k-ωshear stress transport(SST)turbulence *** different SNLs include 6.0,7.0,8.0,9.0,9.8,12.0,15.0,and 18.0 *** order to validate the accuracy of the numerical simulation,its results are compared with wind tunnel test data obtained from the *** simulation is carried out using compressible and incompressible gases to determine the effect of gas compressibility on *** impact of SNL on the aerodynamic performance of the trains is analyzed in terms of aerodynamic forces,velocity,and pressure *** comparison to the original train,the train with a 6.0 m SNL experienced a 10.8%increase in overall aerodynamic ***,the lift forces on the head and tail cars increased by 35.7%and 75.5%,*** the other hand,the train with an 18.0 m SNL exhibited a 16.5%decrease in aerodynamic ***,the lift forces on the head and tail cars decreased by 21.9%and 49.7%,*** aerodynamic drag force of the entire train varies linearly with the SNL,while the aerodynamic lift of the tail car follows a quadratic function in relation to the SNL.

关键词： Streamlined nose length(SNL) High-speed train Aerodynamic performance Numerical simulation Flow structures

Numerical Study on Reduction in Aerodynamic Drag and Noise of High-Speed Pantograph

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 2155-2173页

作者： deng qin Xing Du Tian Li Jiye Zhang State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu610031China School of Electrical Engineering Southwest Jiaotong UniversityChengdu610031China

Reducing the aerodynamic drag and noise levels of high-speed pantographs is important for promoting environmentally friendly,energy efficient and rapid advances in train *** computational fluid dynamics theory and the K-FWH acoustic equation,a numerical simulation is conducted to investigate the aerodynamic characteristics of high-speed pantographs.A component optimization method is proposed as a possible solution to the problemof aerodynamic drag and noise in high-speed *** results of the study indicate that the panhead,base and insulator are the main contributors to aerodynamic drag and noise in high-speed ***,a gradual optimization process is implemented to improve the most significant components that cause aerodynamic drag and *** optimizing the cross-sectional shape of the strips and insulators,the drag and noise caused by airflow separation and vortex shedding can be *** aerodynamic drag of insulator with circular cross section and strips with rectangular cross section is the *** insulators and optimizing the chamfer angle and height of the windward surface of the strips can improve the aerodynamic performance of the *** addition,the streamlined fairing attached to the base can eliminate the complex flow and shield the radiated *** contrast to the original pantograph design,the improved pantograph shows a 21.1%reduction in aerodynamic drag and a 1.65 dBA reduction in aerodynamic noise.

关键词： High-speed pantograph aerodynamic drag aerodynamic noise reduction optimizing

Dependence of Conductance of Corrugated Graphene Quantum Dot on Geometrical Features

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Communications in Theoretical Physics 2009年第11期52卷 960-964页

作者： LI Gui-qin deng Jing-Kang CAI Jun Department of Physics Tsinghua University Beijing 100084 China

Dependence of conductance of corrugated graphene quantum dot(CGQD)on geometrical features includinglength,width,connection and edge is investigated by the first principles *** results demonstrate that theconductance of CGQD with different geometrical features is different from each *** positions and amplitudesof discrete levels in densities of states and transmission coefficients are sensitive to geometrical *** I-Vcharacteristics of graphene are modified by size and edge,it is surprise the current does not change monotonously butoscillatory with *** they are slight change for different connections.

关键词： corrugated graphene conductance first principles calculations geometrical features

LCH:A local clustering H-index centrality measure for identifying and ranking influential nodes in complex networks

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Chinese Physics B 2021年第8期30卷 566-574页

作者： Gui-Qiong Xu Lei Meng deng-qin Tu Ping-Le Yang Department of Information Management School of ManagementShanghai UniversityShanghai 200444China Business School University of Shanghai for Science and TechnologyShanghai 200093China School of Electrical and Information Engineering Jiangsu University of Science and Technology Zhangjiagang 215600China

Identifying influential nodes in complex networks is one of the most significant and challenging issues,which may contribute to optimizing the network structure,controlling the process of epidemic spreading and accelerating information *** node importance ranking measures based on global information are not suitable for large-scale networks due to their high computational ***,they do not take into account the impact of network topology evolution over time,resulting in limitations in some *** on local information of networks,a local clustering H-index(LCH)centrality measure is proposed,which considers neighborhood topology,the quantity and quality of neighbor nodes *** proposed measure only needs the information of first-order and second-order neighbor nodes of networks,thus it has nearly linear time complexity and can be applicable to large-scale *** order to test the proposed measure,we adopt the susceptible-infected-recovered(SIR)and susceptible-infected(SI)models to simulate the spreading process.A series of experimental results on eight real-world networks illustrate that the proposed LCH can identify and rank influential nodes more accurately than several classical and state-of-the-art measures.

关键词： complex networks influential nodes local structure susceptible infected recovered model susceptible infected model

Determination of gross α and β activities in Zouma River based on online HPGe gamma measurement system

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Nuclear Science and Techniques 2020年第12期31卷 65-76页

作者： Xian Guan Liang-Quan Ge Guo-Qiang Zeng Xiao-qin deng Li-Peng Xu Sheng-Liang Guo Key Laboratory of Applied Nuclear Techniques in Geosciences of Sichuan Province Chengdu University of TechnologyChengdu 610059China Sichuan Management&Monitoring Center Station of Radioactive Environment Chengdu 610031China Chengdu New Nuclear Tyco Technology Co. LtdChengdu 610052China

This paper describes a low-cost and fast method to evaluate gross α and β^(-) radioactivities in natural water based on an online high-purity germanium detector gamma measurement *** major gamma activities in natural water are provided by natural and artificial radionuclides such as ^(40) K,^(137)Cs,and radionuclides belonging to ^(238)U and ^(232)Th *** main a emitters related to gamma emissions in natural water are ^(224)Ra(240.98 keV)and ^(226)Ra(186.21 keV),and the β^(-) emitters are ^(40) K(1460.85 keV),^(214)Bi(609.31 keV),^(208)Tl(583.19 keV),and ^(214)Pb(351.93 keV).The formula for gross α and β^(-) activity concentration is based on these radionuclides,and the short half-life decay products are considered in the *** detection efficiency of the device across energy region(0–3 MeV)is obtained through Monte Carlo simulation,and a calibration experiment is conducted to verify the simulation *** radioactivity is measured continuously for 114 d in Pixian County and Dongfeng Canal located in the Zouma River,Chengdu,Sichuan Province,China.A comparison of the calculation results and monitoring data from the Sichuan Management and Monitoring Center Station of Radioactive Environment indicates that the percentage and absolute error of a activity concentration is lower than 53%and 0.02 Bq/L,respectively,and that of β-activity concentration is lower than 33.2%and 0.016 Bq/L,*** method can rapidly determine gross α and β^(-) activity concentrations in natural water online.

关键词： Grossαandβ^(-)activity HPGe gamma spectrometer Online radioactivity level measurement for natural water Natural radioactivity Water sources of Chengdu

Theoretical Calculations on the Second-order Nonlinear Optical Property of Chiral Bis-corroles

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Chinese Journal of Structural Chemistry 2007年第8期26卷 955-961页

作者： YING Xiao deng qin LIAO Shi-Jun HU Xi-Ming LIU Hai-Yang CHANG Chi-Kwong Department of Applied Physics South China University of Technology Guangzhou 510641 China Department of Applied Chemistry South China University of Technology Guangzhou 510641 China Department of Chemistry The Hongkong University of Science and Technology Hongkong China

The second-order nonlinear optical （NLO） properties of 5,10,15-triphenylcorrole （TPC）, 5,10,15,20-tetraphenylporphyrin （TPP） and L-amino acid bridged bis-corroles 1,2,3 and 4 have been calculated by using TDHF/PM3 method based on the RHF/6-31G （TPC and TPP） or semiempirical PM3 （1, 2, 3, 4） optimized geometries. Calculation results showed TPC and TPP have C1 and D2h symmetry, respectively when N-H protons are localized on the nitrogen atoms. TPC is the second-order NLO active chromophore due to the cancellation of centrosymmetrical structure and its first hyperpolarizability β increases to 11.524×10^-30 esu. Under electrical dipole approximation, βvalues of bis-corroles 1, 2, 3 and 4 vary from 9.831×10^-30 to 14.221×10^-30 esu, and no much improvement in the first hyperpolarizability was observed as compared to TPC ***, β values of bis-corroles 1, 2, 3 and 4 are improved by about 4 times as compared to their bis-porphyrin counterparts. The analysis of β components indicates that β of this kind of bis-corroles is mainly contributed from its radial component βr. With the variation of amino acid side chains, βHRS, β,βxyz, βr and βa of bis-corroles change remarkably. Chiral L-amino acid bridged bis-corroles 2, 3 and 4 have a right-handed helix structure, and their chiral component βxyz matches βxyz ∝ r^2 ζ/L^4 （helix parameters）, showing the second-order chiral NLO response of these bis-corroles could be described by one-electron helical model theory. It was found that the radial component βr of chiral helix bis-corroles also matches βr ∝ r^2 ζ/L^4.

关键词： corrole amino acid chiral bis-corrole the second-order NLO TDHF/PM3