检索结果-南通市图书馆

同方期刊数据库

P-and SV-wave dispersion and attenuation in saturated microcracked porous rock with aligned penny-shaped fractures

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2024年第1期21卷 143-161页

作者： Sheng-Qing Li Wen-Hao Wang Yuan-da.Su Jun-Xin Guo Xiao-Ming Tang School of Geosciences China University of Petroleum(East China)Qingdao 266580ShandongChina Laoshan National Laboratory Qingdao 266071ShangdongChina Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology Southern University of Science and TechnologyShenzhen 518055GuangdongChina Department of Earth and Space Sciences Southern University of Science and TechnologyShenzhen 518055GuangdongChina

P-and SV-wave dispersion and attenuation have been extensively investigated in saturated poroelastic media with aligned ***,there are few existing models that incorporate the multiple wave attenuation mechanisms from the microscopic scale to the macroscopic ***,in this work,we developed a unified model to incorporate the wave attenuation mechanisms at different scales,which includes the microscopic squirt flow between the microcracks and pores,the mesoscopic wave-induced fluid flow between fractures and background(FB-WIFF),and the macroscopic Biot's global flow and elastic scattering(ES)from the *** Tang's modified Biot's theory and the mixed-bounda.y conditions,we derived the exact frequency-dependent solutions of the scattering problem for a single penny-shaped fracture with oblique incident P-and *** then developed theoretical models for a set of aligned fractures and randomly oriented fractures using the Foldy *** results indicated that microcrack squirt flow considerably influences the dispersion and attenuation of P-and SV-wave *** coupling effects of microcrack squirt flow with the FB-WIFF and ES of fractures cause much higher velocity dispersion and attenuation for P waves than for SV *** oriented fractures substantially reduce the attenuation caused by the FB-WIFF and ES,particularly for the ES attenuation of SV *** a comparison with existing models in the limiting cases and previous experimental measurements,we valida.ed our model.

关键词： Aligned fractures P-and SV-wave Dispersion and attenuation Microcracked porous background FB-WIFF Elastic scattering Squirt flow

Analysis and Optimization of the Electrohydraulic Forming Process of Sinusoida. Corrugation Tubes

在线全文

学校读者我要写书评

暂无评论

Fluid Dynamics & Materials Processing 2024年第4期20卷 873-887页

作者： da.Cai Yinlong Song Hao Jiang Guangyao Li Junjia Cui State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle Hunan UniversityChangsha410082China

Aluminum alloy thin-walled structures are widely used in the automotive industry due to their advantages related to light weight and *** can be produced at room temperature by the electrohydraulic forming *** the present study,the influence of the related parameters on the forming quality of a 6063 aluminum alloy sinusoida. corrugation tube has been *** particular,the orthogonal experimental design(OED)and central composite design(CCD)methods have been *** the range analysis and variance analysis of the experimental da.a,the influence degree of wire diameter(WD)and discharge energy(DE)on the forming quality was *** regression analysis was performed using the response surface methodology.A prediction model for the attaching-die state coefficient was established *** following optimal arrangement of parameters was obtained(WD=0.759 mm,DE=2.926 kJ).The attaching-die state coefficient reached the peak value of *** optimized wire diameter and discharge energy for a better attaching-die state could be screened by CCD compared with *** response surface method in CCD was more suitable for the design and optimization of the considered process parameters.

关键词： Electrohydraulic forming aluminum alloy tube process parameters attaching-die state 1 Introduction

Multi-gait snake robot for inspecting inner wall of a pipeline

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Biomimetic Intelligence & Robotics 2024年第2期4卷 32-41页

作者： Jingwei Liu Man Li Yahui Wang da.Zhao Rui Deng School of Electrical and Information Engineering Beijing University of Civil Engineering and ArchitectureBeijing 100044China Bejing Key Laboratory of Robot Bionics and Function Research Bejing 100044China

In the field of pipeline inner wall inspection,the snake robot demonstrates significant advantages over other inspection *** a simple traveling wave or meandering motion will suffice for inspecting the inner wall of small-diameter pipes,comprehensively and meticulously inspecting the inner wall of large-diameter pipes requires the snake robot to adopt a helical gait that closely adheres to the inner *** review of existing literature indicates that most research and development on the helical gait of snake robots has focused on the outer surface of cylinders,with very few studies dedicated to developing a helical gait specifically for the inspection of the inner wall of ***,in this study,we propose a helical gait that is suitable for the inner wall of pipes and meets the requirements of gas pipeline *** helical gait is designed using the backbone curve ***,we create a mathematical model for a circular helix curve with constant curvature and torsion,ensuring it is applicable to a snake robot prototype in a laboratory *** calculate the joint angles required for two conical spiral curves with variable curvature and torsion,establish a new model,and define the physical significance of the specific *** ensure the feasibility of the proposed gait,we conduct experiments involving meandering and traveling wave motions to verify the communication and control between the host computer and the snake *** upon this founda.ion,we further valida.e the mathematical model of the complex helical motion gait through simulation *** findings provide a theoretical basis for realizing helical movement with a real snake robot.

关键词： Pipeline inner wall detection Snake robot Spiral motion Backbone curve Modeling and simulation

Tinea of Vellus Hair Caused by Trichophyton violaceum in a Child:A Case Report

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Dermatology and Venereology 2024年第1期7卷 58-59页

作者： Ge Song Guan-Zhao Liang Wei-da.Liu Department of Medical Mycology Hospital for Skin Diseases(Institute of Dermatology)Chinese Academy of Medical Sciences and Peking Union Medical College&Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIsNanjingJiangsu 210042China Center for Global Health School of Public HealthNanjing Medical UniversityNanjingJiangsu 211166China

Introduction:Tinea of vellus hair is a rare dermatophytosis,caused by dermatophyte infection in the vellus *** clinical symptoms of tinea of vellus hair are more serious and the conventional topical treatment are often ***,we report a case of tinea of vellus hair caused by Trichophyton violaceum in a *** presentation:A 7-year-old boy presented with a localized,scaly,and itchy erythema on his left cheek for two *** once used a topical corticosteroid but without any clinical improvement,the erythema was progressively enlarging and spread to the left *** denied any contact with *** microscopy found abunda.t spores and hyphae on the vellus hair;*** was identified by culture and PCR *** patient was diagnosed with tinea of vellus hair and cured after treating with oral terbinafine 125 mg/da. and topical treatment for two *** was no recurrence during the follow-up ***:The clinical symptoms of tinea of vellus hair are often atypical and easy to be *** fungal examination is necessary for suspicious patients and confirmed patients should be treated with oral antifungal ***:The diagnosis and treatment of tinea of vellus hair need to be paid more attention in clinical works.

关键词： tinea vellus hair case report

Prevalence of visual impairment and estimation of refractive errors among school children in Kakamega,Kenya

在线全文

学校读者我要写书评

暂无评论

International Journal of Ophthalmology(English edition) 2024年第5期17卷 932-939页

作者： Isabel Signes-Soler Alfred ragot Sheilah Nangena Andrew Wekesa raúl Montalbán Llamusí Department of Optics and Optometry and Vision Sciences Universidat de ValènciaBurjassotValencia 46010Spain NGO Vision Without Borders(Visio Sense Fronteres VSF)Calpe 03710AlicanteSpain Masinde Muliro University of Science and Technology P.O Box 190-50100KakamegaKenya Clinica Baviera Alicante C/Ausóy Monzó 16Alicante 03006Spain

AIM:To investigate the prevalence of visual impairment(VI)and provide an estimation of uncorrected refractive errors in school-aged children,conducted by optometry students as a community ***:The study was *** 3343 participants were included in the *** initial examination involved assessing the uncorrected distance visual acuity(UDVA)and visual acuity(VA)while using a+2.00 D *** inclusion criteria for a subsequent comprehensive cycloplegic eye examination,performed by an optometrist,were as follows:a UDVArange 4 to 17y),and 51.3%of the children were female(n=1715).The majority of the children(89.7%)fell within the age range of 8 to *** the ethnic groups,the highest representation was from the Luhya group(60.6%)followed by Luo(20.4%).Mean logMAR UDVA choosing the best eye for each student was 0.29±0.17(range 1.70 to 0.22).Out of the total,246 participants(7.4%)had a full eye *** estimated prevalence of myopia(defined as spherical equivalent≤-0.5 D)was found to be 1.45%of the total *** around 0.18%of the total sample had hyperopia value exceeding+1.75 *** astigmatism(cilibuted to uncorrected refractive *** was detected in 0.66%(22/3343)of the screened *** was no statistically significant correlation observed between age or gender and refractive ***:The primary cause of VI is determined to be uncorrected refractive errors,with myopia being the most prevalent refractive error *** findings underscore the significance of early identification and correction of refractive errors in school-aged children as a means to alleviate the impact of VI.

关键词： visual impairment refractive errors myopia amblyopia sustainable development goals

Efficient privacy-preserving federated learning under dishonest-majority setting

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2024年第5期67卷 323-324页

作者： Yinbin MIAO da.KUANG Xinghua LI Tao LENG Ximeng LIU Jianfeng MA School of Cyber Engineering Xidian University Intelligent Policing Key Laboratory of Sichuan Province Sichuan Police College Institute of Information Engineering Chinese Academy of Sciences School of Cyber Security University of Chinese Academy of Sciences Key Laboratory of Information Security of Network Systems Fuzhou University

Federated learning(FL) is an emerging distributed learning paradigm that solves the problem of isolated da.a by jointly learning the global model through distributed ***, recent studies have shown that FL may not always guarantee sufficient privacy preservation, this is mainly because the model parameters(e.g., weights or gradients)may leak sensitive information to malicious adversaries.

关键词：

Regulation of pseudographitic carbon domain to boost sodium energy storage

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2024年第6期17卷 5188-5196页

作者： Zhidong Hou Mingwei Jiang da.Lei Xiang Zhang Yuyang Gao Jian-Gan Wang State Key Laboratory of Solidification Processing Center for Nano Energy MaterialsSchool of Materials Science and EngineeringNorthwestern Polytechnical University and Shaanxi Joint Lab of Graphene(NPU)Xi’an 710072China

Hard carbon anode has shown extraordinary potentials for sodium-ion batteries(Sibs)owing to the cost-effectiveness and advantaged ***,the widespread application of hard carbon is still hindered by the insufficient sodium storage capacity and depressed rate property,which are mainly induced by the undesirable pseudographitic ***,we develop a molten-salt-mediated strategy to regulate the pseudographitic structure of hard carbon with suitable interlayer spacing and enlarged pseudographitic domain,which is conducive to the intercalation capacity and diffusion kinetics of sodium ***,the optimized hard carbon anode delivers a high reversible capacity of 320 mAh·g^(−1),along with superior rate property(138 mAh·g−1 at 2 A·g^(−1))and stable cyclability over 1800 ***,the in situ raman spectroscopic study and full-cell assembly further investigate the sodium storage mechanism and practical implement of obtained hard *** work pioneers a low-cost and effective route to regulate the pseudographitic structure of hard carbon materials for advanced Sibs.

关键词： pseudographitic structure molten salt hard carbon anode sodium-ion batteries

Understanding the Thermal Impeda.ce of Silicone Rubber/Hexagonal Boron Nitride Composites as Thermal Interface Materials

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 Polymer Science 2024年第3期42卷 352-363,I0008页

作者： Yuan Ji Shi-da.Han Hong Wu Shao-Yun Guo Feng-Shun Zhang Jian-Hui Qiu The State Key Laboratory of Polymer Materials Engineering Sichuan Provincial Engineering Laboratory of Plastic/Rubber Complex Processing TechnologyPolymer Research InstituteSichuan UniversityChengdu 610065China Institute of Chemical Materials China Academy of Engineering PhysicsMianyang 621900China Department of Mechanical Engineering Faculty of Systems Science and TechnologyAkita Prefectural UniversityAkita 015-0055Japan

Silicone rubber(SR) composites are most widely used as thermal interface materials(TIMs) for electronics heat dissipation. Thermal impeda.ce as the main bottleneck limiting the performance of TIMs is usually neglected. Herein, the thermal impeda.ce of SR composites loaded with different levels of hexagonal boron nitride(h-BN) as TIMs was elaborated for the first time by the ASTM D 5470 standa.d test and finite element analysis. It was found that elastic modulus and surface roughness of SR composites increased with the increase of h-BN content, indicating that the conformity was reduced. When the assembly pressure was 0.69 MPa, there existed an optimal h-BN content at which the contact resistance was minimum(0.39 K·cm^(2)·W^(-1)). Although the decreased bond line thickness(BLT) by increasing the assembly pressure was beneficial to reduce the thermal impeda.ce, the proper assembly pressure should be selected to prevent the warpage of the contact surfaces and the increase in contact resistance, according to the compression properties of the SR composites. This study provides valuable insights into fabrication of high-performance TIMs for modern electronic device applications.

关键词： Thermal interface materials Hexagonal boron nitride Thermal impeda.ce Surfaces

da.a-driven casting defect prediction model for sand casting based on random forest classification algorithm

在线全文

学校读者我要写书评

暂无评论

China Foundry 2024年第2期21卷 137-146页

作者： Bang Guan Dong-hong Wang da.Shu Shou-qin Zhu Xiao-yuan Ji Bao-de Sun Shanghai Key Lab of Advanced High-Temperature Materials and Precision Forming School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China State Key Lab of Metal Matrix Composites Shanghai Jiao Tong UniversityShanghai 200240China Hefei Casting and Forging Factory of Anhui Heli Co. LtdHefei 230000China State Key Laboratory of Materials Processing and Die&Mould Technology Huazhong University of Science and TechnologyWuhan 430074China

The complex sand-casting process combined with the interactions between process parameters makes it difficult to control the casting quality,resulting in a high scrap rate.A strategy based on a da.a-driven model was proposed to reduce casting defects and improve production efficiency,which includes the random forest(RF)classification model,the feature importance analysis,and the process parameters optimization with Monte Carlo *** collected da.a includes four types of defects and corresponding process parameters were used to construct the RF *** results show a recall rate above 90% for all *** Gini Index was used to assess the importance of the process parameters in the formation of various defects in the RF ***,the classification model was applied to different production conditions for quality *** the case of process parameters optimization for gas porosity defects,this model serves as an experimental process in the Monte Carlo method to estimate a better temperature *** prediction model,when applied to the factory,greatly improved the efficiency of defect *** show that the scrap rate decreased from 10.16% to 6.68%.

关键词： sand casting process da.a-driven method classification model quality prediction feature importance