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A Hybrid Signal Processing Method Combining Mathematical Morphology and Walsh Theory for Power Quality Disturbance Detection and classification

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 584-592页

作者： Zhi Ding Tianyao ji Mengshi Li Q.H.Wu School of Electric Power Engineering South China University of Technology(SCUT)Guangzhou 510641China

In this paper, a novel signal processing method combining mathematical morphology (MM) and Walsh theory is proposed, which uses Walsh functions to control the structuring element (SE) and MM operators. Based on the Walsh-MM method, a scheme for power quality disturbances detection and classification is developed, which involves three steps: denoising, feature extraction and morphological clustering. First, various evolution rules of Walsh function are used to generate groups of SEs for the multiscale Walsh-ordered morphological operation, so the original signal can be denoised. Next, the fundamental wave of the denoised signal is suppressed by Hadamard matrix;thus, disturbances can be extracted. Finally, the Walsh power spectrum of the waveform extracted in the previous step is calculated, and the parameters of which are taken by morphological clustering to classify the disturbances. Simulation results reveal the proposed scheme can effectively detect and classify disturbances, and the Walsh-MM method is less affected by noise and only involves simple calculation, which has a potential to be implemented in hardware and more suitable for real-time application.

关键词： Hadamard matrix mathematical morphology morphological clustering power quality disturbance Walsh theory

Pyrolysis Empirical Modeling of Polyester Glass Fiber Reinforced Plastics Using Sestak-Berggren Model Method

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Journal of Thermal Science 2024年第2期33卷 725-738页

作者： NAN Wei ji Wenhui YUAN Yanping YUAN Zhongyuan SUN Yong School of Mechanical Engineering Southwest Jiaotong UniversityChengdu610031China CRRC Changchun Railway Vehicles Co. LtdChangchun130062China

Polyester Glass Fiber Reinforced Plastic(Polyester GFRP),a thermosetting plastic comprised of glass fiber and polyester polymer compounds,is extensively utilized in high-speed *** its pyrolysis mechanism is crucial as it significantly influences the combustion characteristics and fire safety ***,kinetic research on polyester GFRP primarily focuses on employing the Coats-Redfern method to derive a theoretical kinetic ***,the pyrolysis process of polyester GFRP is complex and the aforementioned theoretical model fails to accurately describe the pyrolysis ***,this study seeks to utilize the Sestak and Berggren(SB) model as a methodological approach to reveal the complex reaction mechanism during the pyrolysis *** on thermogravimetric analysis,the entire pyrolysis process of polyester GFRP is divided into two primary ***,model-free methods are employed to ascertain the activation energy and pre-exponential *** results show that the fitted empirical models of the two main pyrolysis stages are f(α)=(1-α)^(1.47)[-ln(1-α)]^(1.50) and f(α)=(1-α)^(1.77)[-ln(1-α)]^(1.72),*** predicted results are in good agreement with experimental data under different heating rates,which indicates that the empirical model can sufficiently describe the pyrolysis process of polyester GFRP.

关键词： polyester GFRP model-fitting methods empirical models pyrolysis

Microstructure and Internal Friction Behavior of Laser 3D Printed Fe-Based Amorphous Composites

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Acta Metallurgica Sinica(English Letters) 2024年第1期37卷 196-204页

作者： Shuilong Huang Qingjun Chen Li ji Kan Wang Guosheng Huang School of Material Science and Engineering Nanchang Hangkong UniversityNanchang330063China State Key Laboratory for Marine Corrosion and Protection Luoyang Ship Material Research Institute(LSMRI)Qingdao266237China

Laser 3D printing,also known as laser additive manufacturing(LAM),is favored for its ability to form bulk metallic glass(BMG)and its composite materials(BMGcs)with freeform *** this work,two different kinds of Fe_(41)Co_(7)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2)amorphous coatings(A and B)were prepared by using LAM technology under air-and water-cooled conditions,respectively;meanwhile,to reduce the cracks generated due to the residual thermal stresses,coating C obtained by air-sweep annealing of B with a low energy-density *** morphology and amorphous content and microstructure of the coatings were investigated,the results show many cracks in coating B deposited under water-cooled conditions,and its microstructure shows an amorphous-crystal-nanocrystalline mixed *** was suppressed in coating C,obtained by air-sweep annealing based on coating B,but the amorphous content was reduced from 32.6 to 13.4%.And the hardness and corrosion resistance of the coating will increase with the increase in the amorphous ***,the internal friction behavior of a BMGcs was prepared on the basis of the process of sample C is compared with that of as-cast amorphous *** results show that the low temperature internal friction behavior of BMGcs is affected by the defects produced during printing,and the high temperature internal friction behavior is affected by the precipitated hard phase.

关键词： Laser 3D printing Amorphous coating Microstructure Corrosion resistance Internal friction behavior

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

A study on carbon emission calculation in operation stage of residential buildings based on micro electricity usage behavior:Three case studies in China

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Building Simulation 2024年第1期17卷 147-164页

作者： Menghan Niu Ying ji Miao Zhao jiefan Gu Aonan Li Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology Beijing University of TechnologyBeijing 100124China College of Architecture and Urban Planning Tongji UniversityShanghai 201804China The Bartlett School of Architecture University College LondonWC1E 6BTUK

Along with the improvement of social productivity and living standard,residential buildings generate a growing portion of carbon emissions,especially during the operation ***,energy use behaviors are usually ignored in carbon emission *** study focuses on calculating carbon emissions during the operation stage for residential buildings based on the characteristics of energy use behaviors in different ***,we investigated energy use behaviors in dwellings across three cities in China:Xi'an,Shanghai and ***,we established calibrated carbon emission models and optimization models with different green building measures for residential *** results of this research reveal a significant disparity between the energy usage habits of residents in different climate *** carbon emissions of residential electricity bills in Xi'an,Shanghai and Fuzhou are 13.6 kgCO_(2)/(m^(2)·a)(excluding central heating),29.3 kgCO_(2)/(m^(2)·a)and 17.2 kgCO_(2)/(m^(2)·a),*** carbon emissions account for 32.2%-64.1% of the *** comparison to the model based on internal standard setting,the accuracy of the models using actual internal has improved by 25.9%-37.4%.The three-star green building methods have the highest carbon reduction rate among different star buildings,the emission reduction rates are around 30%.This study's findings are useful for carbon emission calculation and green building design of residential buildings in the future.

关键词： residential building energy usage behavior energy simulation carbon emissions

Influence of Incomplete Soil Plugs on Bearing Capacities of Bucket Foundations in clay

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China Ocean Engineering 2024年第1期38卷 144-155页

作者： LI Hui-shan LIU Run YANG Xu LIAN ji-jian State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation Tianjin UniversityTianjin 300072China School of Civil Engineering Tianjin UniversityTianjin 300072China Institute of Marine Energy and Intelligent Construction Tianjin University of TechnologyTianjin 300384China

Due to the uneven seabed and heaving of soil during pumping,incomplete soil plugs may occur during the installation of bucket foundations,and the impacts on the bearing capacities of bucket foundations need to be *** this paper,the contact ratio(the ratio of the top diameter of the soil plug to the diameter of the bucket)and the soil plug ratio(the ratio of the soil heave height to the skirt height)are defined to describe the shape and size of the incomplete soil ***,finite element models are established to investigate the bearing capacities of bucket foundations with incomplete soil plugs and the influences of the contact ratios,and the soil plug ratios on the bearing capacities are *** results show that the vertical bearing capacity of bucket foundations in homogeneous soil continuously improves with the increase of the contact ***,in normally consolidated soil,the vertical bearing capacity barely changes when the contact ratio is smaller than 0.75,while the bearing capacity suddenly increases when the contact ratio increases to 1 due to the change of failure *** contact ratio hardly affects the horizontal bearing capacity of bucket ***,the moment bearing capacity improves with the increase of the contact ratio for small aspect ratios,but hardly varies with increasing contact ratio for aspect ratios larger than ***,the reduction coefficient method is proposed based on this analysis to calculate the bearing capacities of bucket foundations considering the influence of incomplete soil *** comparison results show that the proposed reduction coefficient method can be used to evaluate the influences of incomplete soil plug on the bearing capacities of bucket foundations.

关键词： bucket foundation incomplete soil plug uniaxial bearing capacity contact ratio soil plug ratio

Relaxed Stability Criteria for Time-Delay Systems:A Novel Quadratic Function Convex Approximation Approach

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IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 996-1006页

作者： Shenquan Wang Wenchengyu ji Yulian jiang Yanzheng Zhu jian Sun College of Electrical and Electronic Engineering Changchun University of TechnologyChangchun 130012China the College of Electrical Engineering and Automation Shandong University of Science and TechnologyQingdao 266590China Key Laboratory of Complex Systems Intelligent Control and Decision Beijing Institute of TechnologyBeijing 100081China

This paper develops a quadratic function convex approximation approach to deal with the negative definite problem of the quadratic function induced by stability analysis of linear systems with time-varying *** introducing two adjustable parameters and two free variables,a novel convex function greater than or equal to the quadratic function is constructed,regardless of the sign of the coefficient in the quadratic *** developed lemma can also be degenerated into the existing quadratic function negative-determination(QFND)lemma and relaxed QFND lemma respectively,by setting two adjustable parameters and two free variables as some particular ***,for a linear system with time-varying delays,a relaxed stability criterion is established via our developed lemma,together with the quivalent reciprocal combination technique and the Bessel-Legendre *** a result,the conservatism can be reduced via the proposed approach in the context of constructing Lyapunov-Krasovskii functionals for the stability analysis of linear time-varying delay ***,the superiority of our results is illustrated through three numerical examples.

关键词： Equivalent reciprocal combination technique quadratic function convex approximation approach stability timevarying delay

Towards understanding bogus traffic service in online social networks

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Frontiers of Information Technology & Electronic Engineering 2024年第3期25卷 415-431页

作者： Ping HE Xuhong ZHANG Changting LIN Ting WANG Shouling ji College of Computer Science and Technology Zhejiang UniversityHangzhou 310027China Binjiang Institute of Zhejiang University Hangzhou 310027China College of Information Sciences and Technology Pennsylvania State UniversityUniversity Park 17057-4846USA

Critical functionality and huge infuence of the hot trend/topic page(HTP)in microblogging sites have driven the creation of a new kind of underground service called the bogus traffic service(BTS).BTS provides a kind of illegal service which hijacks the HTP by pushing the controlled topics into it for malicious customers with the goal of guiding public *** hijack HTP,the agents of BTS maintain an army of black-market accounts called bogus trafic accounts(BTAs)and control BTAs to generate a burst of fake trafic by massively retweeting the tweets containing the customer desired topic(hashtag).Although this service has been extensively exploited by malicious customers,little has been done to understand *** this paper,we conduct a systematic measurement study of the *** first investigate and collect 125 BTS agents from a variety of sources and set up a honey pot account to capture BTAs from these *** then build a BTA detector that detects 162218 BTAs from Weibo,the largest Chinese microblogging site,with a precision of 94.5%.We further use them as a bridge to uncover 296916 topics that might be involved in bogus ***,we uncover the operating mechanism from the perspectives of the attack cycle and the attack *** highlights of our findings include the temporal attack patterns and intelligent evasion tactics of the *** findings bring BTS into the *** work will help in understanding and ultimately eliminating this threat.

关键词： Online social networks Measurement Bogus traffic Black market

Detection and analysis of serum bile acid profile in patients with colonic polyps

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World Journal of clinical Cases 2024年第13期12卷 2160-2172页

作者： Xin ji Hong Chen School of Medicine Southeast UniversityNanjing 210009Jiangsu ProvinceChina Department of Gastroenterology Zhongda Hospital Southeast UniversityNanjing 210009Jiangsu ProvinceChina

BACKGROUND Analyzing the variations in serum bile acid(BA)profile can provide a certain biological basis for early warning and prevention of various *** is currently no comprehensive study on the relationship between the serum BA profile and colonic *** To study the serum BA profile detection results of patients with colonic polyps,and analyze the correlation between BA and colonic *** From January 1,2022,to June 1,2023,204 patients with colonic polyps who were diagnosed and treated at Zhongda Hospital Southeast University were chosen as the study subjects,and 135 non-polyp people who underwent physical examination were chosen as the control *** all patients'clinical information,typical biochemical indicators,and BA *** Compared with the control group,the serum levels of taurocholic acid,glycocholic acid,glycochenodeoxycholic acid,and taurochenodeoxycholic acid in the colonic polyp group were significantly higher than those in the control group,while the content of deoxycholic acid(DCA)was lower than that in the control group(P<0.05).When colonic polyps were analyzed as subgroups,it was shown that there was a strong correlation between changes in the BA profile and polyp diameter,location,morphology,pathological kind,*** The serum BA profile showed significant changes in patients with colonic polyps,with a significant increase in primary conjugated BA content and a decrease in secondary free bile acid DCA *** is a certain correlation between primary free BA and pathological parameters of polyps.

关键词： Serum Bile acid profile Colonic polyps Bile acid metabolism