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A comprehensive research on wear resistance of GH4169 superalloy in longitudinal-torsional ultrasonic vibration side milling with tool wear and surface quality

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Chinese Journal of Aeronautics 2024年第4期37卷 556-573页

作者： Baoqi chang Zhaoxi yi Fen ZHANG Lian DUAN Ji-an DUAN School of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China State Key Laboratory of High Performance and Complex Manufacturing Central South UniversityChangsha 410083China School of Physics and Electronics Central South UniversityChangsha 410083China

To improve the service and machining performance of the workpiece, the tool wear mechanisms, surface machining quality, and wear resistance in conventional side milling(CSM)and longitudinal-torsional ultrasonic vibration side milling(LTUVSM) of GH4169 superalloy at different cutting lengths are investigated systematically. Tool wear mechanisms are revealed and the correlation between machined surface quality with tool wear is analyzed correspondingly. Tool wear patterns mainly include adhesive wear, diffusion wear, abrasive wear, and chipping *** surface quality is achieved in LTUVSM due to a maximum reduction of flank wear bandwidth and wear rate by 71.9% and 71.5%, respectively, compared to CSM. The friction coefficient,initial wear stage time, and wear volume of dry sliding wear were measured to evaluate the workpiece wear resistance. The maximum reductions in friction coefficient and wear volume in LTUVSM are 18.2% and 15.8% compared to CSM. The regular ultrasonic vibration textures suppress the friction and the growth of contact nodes in the contact area, decreasing the degree of surface wear, which is demonstrated by a 38.8% increase in initial wear stage time compared to *** conclusion, the workpiece in LTUVSM exhibits higher wear resistance because of the improvement of tool wear and the guarantee of surface quality.

关键词： Dry sliding wear Surface quality Tool wear Ultrasonic vibration Wear resistance

Efficient coupling of evanescent waves in rectangular waveguides based on ultrathin planar capacitive metasurfaces

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Science China(Information Sciences) 2021年第8期64卷 182-194页

作者： Da yi Ming-Chun TANG Mei LI Xing-chang WEI College of Microelectronics and Communication Engineering Chongqing University Zhejiang Provincial Key Laboratory of Advanced Microelectronic Intelligent Systems and Applications College of Information Science and Electronic Engineering Zhejiang University

This work proposes an approach to enable efficient coupling of evanescent waves below the cutoff frequency of a standard rectangular waveguide(RWG) system based on ultrathin planar capacitive metasurfaces(CMSs). It is demonstrated that the CMS at the RWG’s cross-section can couple the evanescent wave from one port to the other, and thus enable an efficient frequency-selective transmission below the cutoff frequency. Theoretical formulas, together with the equivalent circuit, are presented to quantitatively illustrate the operational mechanism of the proposed approach. The performance characteristics, including out-of-band suppression, Q-factor, transmission loss, and coupling bandwidth, are studied in a comprehensive manner. Three CMS samples with different surface impedance values are designed, fabricated, and *** measurement results show good agreement with the numerical values, validating their highly efficient evanescent wave coupling performance characteristic at selected frequencies below the cutoff frequency, with approximately 100% transmission efficiency. Benefiting from the admirable low-frequency coupling performance,this approach has potential applications in many miniaturized and high-performance transmission components, such as compact evanescent wave resonators, filters, and antennas.

关键词： cutoff frequency capacitive metasurface evanescent wave miniaturized components rectangular waveguide

Migration of hepatic stellate cells in fibrotic microenvironment of diseased liver model

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Hepatobiliary & Pancreatic Diseases International 2008年第4期7卷 401-405页

作者： chang, yi-Zhong Yang, Li Yang, chang-Qing Tongji Univ Tongji Hosp Div Gastroenterol Shanghai 200065 Peoples R China

BACKGROUND: In liver fibrosis, alterations within the space of Disse microenvironment facilitate the progression of chronic liver disease. The normal basement membranelike matrix in the space of Disse converts to a matrix rich in fibril-forming collagens during the fibrosis. This study aimed to investigate the impact of alterations in the space of Disse microenvironment on the migration of hepatic stellate cells (HSCs) in the process of liver fibrosis, and to explore the novel mechanism ofliver fibrosis from the viewpoint of cell migration. METHODS: A modified in vitro Boyden chamber system was employed to partially mimic the in vitro microenvironment of the Disse space in normal liver and in fibrosis. The effects of fibrogenetic growth factors on the migration of HSCs in simulated liver fibrosis were assessed by cell migration and cell proliferation experiments. RESULTS: Enhanced platelet-derived growth factor (PDGF)-BB, transforming growth factor-beta 1 (TGF-beta 1) and/or epithelial growth factor (EGF) in liver fibrosis resulted in an increase in migratory capacity of activated HSCs. The enhanced migration of HSCs, induced by PDGF-BB was proliferation -independent. The elevation of basic fibroblast growth factor (bFGF) or vascular endothelial growth factor (VEGF) during liver fibrosis had no effect on the migration of HSCs. CONCLUSIONS: The study provides valuable insights into the role of the space of Disse microenvironment in regulating the migratory behavior of HSCs. TGF-beta 1, PDGF-BB and EGF, which increase in liver fibrosis, induce the migration of activated HSCs. However, bFGF and VEGF have no effect although they also increase during liver fibrosis.

关键词： liver fibrosis hepatic stellate cells migration

A new ventilation mode of air conditioning in subway vehicles and its air distribution performance

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Energy and Built Environment 2021年第1期2卷 94-104页

作者： Zhiyuan chang Ke yi Weiwei Liu School of Energy Science&Engineering Central South UniversityChangshaHunanChina CRRC Zhuzhou Electric Locomotive Co. Ltd.ZhuzhouHunanChina

The traditional ventilation mode of subway vehicles adopts the form that the inlets and outlets are placed on the upper part of the *** air distribution formed in this mode often cause serious problems of thermal comfort and energy *** order to solve these problems caused by the traditional ventilation mode,a new hybrid ventilation mode was *** hybrid ventilation mode uses both upper and underside air supply inlets.A method for evaluating the air distribution performance of subway air conditioning was *** method applies non-uniformity coefficients,maximum temperature difference,air diffusion performance index,modified energy utilization coefficient and Air short-circuit comprehensive *** short-circuit comprehensive coefficient was a new index to evaluate the degree of air short-circuit of supply *** on the airflow simulation,the air distribution performance for the hybrid ventilation mode was evaluated using these indexes,and compared with the traditional ventilation *** results show that compared with the traditional ventilation mode,the hybrid ventilation mode has more uniform temperature distribution,better thermal comfort,higher energy utilization efficiency and lower degree of air short-circuit of supply air.

关键词： Air conditioning supply Air distribution performance Air short-circuit Subway

Stress and fabric in granular material

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Theoretical & Applied Mechanics Letters 2013年第2期3卷 10-15页

作者： ching S. chang Yang Liu Department of Civil Engineering University of Massachusetts Amherst Department of Civil Engineering University of Science and TechnologyBeijing

It has been well recognized that, due to anisotropic packing structure of granular material, the true stress in a specimen is different from the applied stress. However, very few research efforts have been focused on quantifying the relationship between the true stress and applied stress. In this paper, we derive an explicit relationship among applied stress tensor, material-fabric tensor, and force-fabric tensor; and we propose a relationship between the true stress tensor and the applied stress tensor. The validity of this derived relationship is examined by using the discrete element simulation results for granular material under biaxial and triaxial loading con- ditions.

关键词： stress tensor force fabric tensor material fabric tensor granular material discrete elementmethod

Voice Response Questionnaire System for Speaker Recognition Using Biometric Authentication Interface

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Intelligent Automation & Soft Computing 2023年第1期35卷 913-924页

作者： chang-yi Kao Hao-En Chueh Soochow University Taipei City100TaiwanChina Chung Yuan Christian University Taoyuan City32023TaiwanChina

The use of voice to perform biometric authentication is an importanttechnological development,because it is a non-invasive identification methodand does not require special hardware,so it is less likely to arouse user *** study tries to apply the voice recognition technology to the speech-driveninteractive voice response questionnaire system aiming to upgrade the traditionalspeech system to an intelligent voice response questionnaire network so that thenew device may offer enterprises more precise data for customer relationshipmanagement(CRM).The intelligence-type voice response gadget is becominga new mobile channel at the current time,with functions of the questionnaireto be built in for the convenience of collecting information on local preferencesthat can be used for localized promotion and *** of this study propose a framework using voice recognition and intelligent analysis models to identify target customers through voice messages gathered in the voice response questionnaire system;that is,transforming the traditional speech system to anintelligent voice *** speaker recognition system discussed hereemploys volume as the acoustic feature in endpoint detection as the computationload is usually low in this *** correct two types of errors found in the endpoint detection practice because of ambient noise,this study suggests ways toimprove the ***,to reach high accuracy,this study follows a dynamictime warping(DTW)based method to gain speaker ***,it isdevoted to avoiding any errors in endpoint detection by filtering noise from voicesignals before getting recognition and deleting any test utterances that might negatively affect the results of *** is hoped that by so doing the recognitionrate is *** to the experimental results,the method proposed inthis research has a high recognition rate,whether it is on personal-level or industrial-level computers,and can reach the pract

关键词： Biometric authentication customer relationship management speaker recognition questionnaire

Missing Data Imputation for Traffic Flow Based on Improved Local Least Squares

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Tsinghua Science and Technology 2012年第3期17卷 304-309页

作者： Gang chang yi Zhang Danya Yao Tsinghua National Laboratory for Information Science and Technology Department of AutomationTsinghua UniversityBeijing 100084China

Complete and reliable field traffic data is vital for the planning, design, and operation of urban traf- fic management systems. However, traffic data is often very incomplete in many traffic information systems, which hinders effective use of the data. Methods are needed for imputing missing traffic data to minimize the effect of incomplete data on the utilization. This paper presents an improved Local Least Squares （LLS） ap- proach to impute the incomplete data. The LLS is an improved version of the K Nearest Neighbor （KNN） method. First, the missing traffic data is replaced by a row average of the known values. Then, the vector angle and Euclidean distance are used to select the nearest neighbors. Finally, a regression step is used to get weights of the nearest neighbors and the imputation results. Traffic flow volume collected in Beijing was analyzed to compare this approach with the Bayesian Principle Component Analysis （BPCA） imputation ap- proach. Tests show that this approach provides slightly better performance than BPCA imputation to impute missing traffic data.

关键词： Local Least Squares (LLS) vector angle missing value imputation traffic flow

Stability analysis of n-species Lotka-Volterra almost periodic competition models with grazing rates and diffusions

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International Journal of Biomathematics 2014年第2期7卷 1-11页

作者： yi-Jin Zhang chang-You Wang Institute of Applied MathematicsChongqing University of Posts and Telecommunications Chongqing 400065 P. R. China Key Laboratory of Industrial Internet of Things and Networked Control Ministry of Education Chongqing 400065 P. R. China

In this pape, almost periodic solution of a n-species Lotka-Volterra competition system with grazing rates and diffusions is investigated. By using the method of upper and lower solutions anti Schauder fixed point theorem as well as Lyapunov stability theory, we give sufficient conditions under which the strictly positive space homogeneous almost perilodic solution of the system is globally asymptotically stable. Moreover, some numerical simulations are given to validate our theoretical analysis.

关键词： Grazing rate competition model diffusion almost periodic solution stability.

Microstructure,Tensile Properties and Heat Treatment Process of Spray Formed FGH95 Superalloy

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Journal of Iron and Steel Research International 2013年第4期20卷 59-63页

作者： XU yi GE chang-chun SHU Qin School of Materials Science and Engineering Southwest Jiaotong University Institute of Special Ceramics and Powder Metallurgy University of Scienceand Technology Beijing

The potential of spray forming for microstructural refining can be attractive to the production of superalloys.A200mm spray formed FGH95superalloy round billet that was produced using a single atomizer has considerably homogeneous,small,equiaxed *** measured oxygen content is 2×10-5,and the measured porosity is only 0.6%.The achieved yield of deposit is in a good range of about 73.6%.The microstructure and tensile properties of nickel-based spray formed FGH95superalloy are ***,effects of heat treatment on microstructure were *** results show that the spray formed FGH95superalloy has higher isotropy in tensile property due to itsγ′phase homogeneous distribution and less defects in the *** processing procedures,the different heat treatment processes affect the microstructure andγ′phase homogeneous distribution of spray formed FGH95superalloy.

关键词： spray forming FGH95superalloy isotropy γ′