检索结果-南通市图书馆

Vibration-assisted material damage mechanism:From indentation cracks to scratch cracks

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第8期37卷 527-546页

作者： Bingrui LV Bin LIN Tianyi sui Chunyan LIU Jinshuo ZHANG Longfei WANG Xuhui CHEN Jingguo ZHOU Key Laboratory of Advanced Ceramics and Machining Technology Ministry of EducationTianjin UniversityTianjin 300072China Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education Tianjin UniversityTianjin 300072China Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials and Processing TechnologyBeijing 100076China

Vibration-assisted grinding is one of the most promising technologies for manufacturing optical components due to its efficiency and quality ***,the damage and crack propagation mechanisms of materials in vibration-assisted grinding are not well *** order to elucidate the mechanism of abrasive scratching during vibration-assisted grinding,a kinematic model of vibration scratching was *** influence of process parameters on the evolution of vibration scratches to indentation or straight scratches is revealed by displacement metrics and velocity ***,scratch and vibration scratch experiments were performed on quartz glass,and the results showed that the vibration scratch cracks are a combination of indentation cracks and scratch *** scratch cracks change from indentation cracks to scratch cracks as the indenter moves from the entrance to the exit of the workpiece or as the vibration frequency changes from high to low.A vertical vibration scratch stress field model is established for the first time,which reveals that the maximum principal stress and tensile stress distribution is the fundamental cause for inducing the transformation of the vibration scratch cracking *** model provides a theoretical basis for understanding of the mechanism of material damage and crack propagation during vibration-assisted grinding.

关键词： Vibration assisted grinding Indentation Vibration scratch Material removal mechanism Stress field model Crack propagation mechanism

Effect of Ball Milling Time on Microstructure and Hydrogen Storage Properties of Nd5Mg41Ni Alloy

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2024年第7期37卷 1201-1214页

作者： Zeming yuan Chenxu Liu Xiaoming Li Yongqi sui Zhonggang Han Tingting Zhai Dianchen Feng Yanghuan Zhang Instrumental Analysis Center Inner Mongolia University of Science and TechnologyBaotou014010China Department of Functional Material Research Central Iron and Steel Research InstituteBeijing100081China

Mg-based alloys must be dehydrogenated at high pressure and temperatures, limiting their practical application. In this paper, Nd_(5)Mg_(41)Ni alloy was prepared by vacuum melting, and the as-cast alloy was ball milled for 5 h, 10 h, 15 h, and 20 h. The effect of ball milling time on the microstructure and hydrogen storage properties of the alloy was systematically studied. The alloy comprises Nd_(5)Mg_(41), NdMg_(12), NdMg_(3), and Mg_(2)Ni phases. The Nd_(5)Mg_(41)Ni alloy milling for 10 h can reach 95% of the saturated hydrogen absorption at 553 K by 40 s, and the alloy can desorb hydrogen only by 20 min. The dehydrogenation activation energy is only 99.9 kJ/mol H_(2). Ball milling makes the alloy produce many nanocrystalline and amorphous structures. The nano-grain boundary provides a channel for the diffusion of hydrogen atoms, and the high energy at the grain boundary provides energy for the phase deformation nucleus. Ball milling leads to the refinement of alloy particles and shortens the diffusion distance of hydrogen atoms to the interior of alloy particles. Defects such as twins and dislocations generated by milling provide energy for the phase deformation nucleus during the hydrogen absorption and desorption.

关键词： Hydrogen storage materials Magnesium-base alloy Ball milling Nanocrystal Kinetics

Real-time Rescue Target Detection Based on UAV Imagery for Flood Emergency Response

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Geodesy and Geoinformation Science 2024年第1期7卷 74-89页

作者： ZHAO Bofei sui Haigang ZHU Yihao LIU Chang WANG Wentao State Key Laboratory of Information Engineering in Surveying Mapping and Remote SensingWuhan UniversityWuhan 430079China

Timely acquisition of rescue target information is critical for emergency response after a flood *** Aerial Vehicles(UAVs)equipped with remote sensing capabilities offer distinct advantages,including high-resolution imagery and exceptional mobility,making them well suited for monitoring flood extent and identifying rescue targets during ***,there are some challenges in interpreting rescue information in real time from flood images captured by UAVs,such as the complexity of the scenarios of UAV images,the lack of flood rescue target detection datasets and the limited real-time processing capabilities of the airborne on-board ***,we propose a real-time rescue target detection method for UAVs that is capable of efficiently delineating flood extent and identifying rescue targets(i.e.,pedestrians and vehicles trapped by floods).The proposed method achieves real-time rescue information extraction for UAV platforms by lightweight processing and fusion of flood extent extraction model and target detection *** flood inundation range is extracted by the proposed method in real time and detects targets such as people and vehicles to be rescued based on this *** experimental results demonstrate that the Intersection over Union(IoU)for flood water extraction reaches an impressive 80%,and the IoU for real-time flood water extraction stands at a commendable 76.4%.The information on flood stricken targets extracted by this method in real time can be used for flood emergency rescue.

关键词： UAV flood extraction target rescue detection real time

在线全文

学校读者我要写书评

暂无评论

黑土区耕作措施对春季耕层温度的影响

农业现代化研究 2009年第1期30卷 113-117页

作者：张少良张兴义于同艳刘晓冰隋跃宇中国科学院东北地理与农业生态研究所黑龙江省黑土生态重点实验室黑龙江哈尔滨150081 中国科学院研究生院北京100049

本文通过长期定位试验,分析了免耕、少耕和旋松三种耕作措施下耕层黑土土壤容积热容量、土壤热通量、净辐射的变化,进而阐明了耕作措施对耕层土壤温度日变化的影响。研究表明:各处理0cm和5cm处土壤温度变化与净辐射通量变化存在极显著... 详细信息

本文通过长期定位试验,分析了免耕、少耕和旋松三种耕作措施下耕层黑土土壤容积热容量、土壤热通量、净辐射的变化,进而阐明了耕作措施对耕层土壤温度日变化的影响。研究表明:各处理0cm和5cm处土壤温度变化与净辐射通量变化存在极显著相关关系。5cm处土壤热通量日变化各处理均表现为"S"型波动曲线,日变化相对较大,10cm处相对较小。免耕秸秆覆盖日净辐射平均值为0.58MJ/m2,比少耕和旋松小0.04MJ/m2,受净辐射、容积热容量和5cm处热通量影响,0cm和5cm处土壤温度日变化较大,且有波动现象;受深层较低地温、容积热容量和10cm处热通量影响,10cm和15cm处土壤温度变化较小,且较平稳。所有耕作措施土壤温度随深度的增加出现滞后现象。免耕秸秆覆盖措施各耕层相对于其他处理地温均较低,影响春季地温的升高。

关键词：地温容积热容量净辐射通量土壤热通量

Effect of Phase Separation Size on the Properties of Self-healing Elastomer

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2024年第6期42卷 798-804页

作者： Jun Xu Lei Zhu Xian-Qi Feng Cong sui Wen-Peng Zhao Shou-Ke Yan School of Chemical Engineering Qingdao University of Science&TechnologyQingdao266042China College of Engineering Yanching institute of TechnologyLangfang065210China Key Laboratory of Rubber-plastics Qingdao University of Science&TechnologyQingdao266042China State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing100029China

Regulation of phase structure has been recognized as one of the most effective ways to fabricate self-healing polymers with high mechanical *** mechanical properties of the resultant polymers are certainly affected by the size of separated phase ***,the study on this aspect is absence,because it can hardly exclude the influence of variation in monomer proportion required for tuning the separated phase ***,we report the first study on tuning the phase size through reversible addition-fragmentation chain transfer(RAFT)polymerization without changing the proportion of *** expected,the size of separated phase has been successfully mediated from 15 nm to 9 nm by tuning the molecular weight of the chain transfer *** is found that the mechanical strength and the self-healing efficiency of the resultant polymers increase simultaneously with the decrease of phase *** study on the formation kinetics of hydrogen bonds reveals that the decrease of phase size can facilitate the re-bonding rate of hydrogen bonds,even if the migration of polymer chains is restricted.

关键词： Self-healing polymers Phase separation Reversible addition-fragmentation chain transfer

Emission and capture characteristics of deep hole trap in n-GaN by optical deep level transient spectroscopy

在线全文

学校读者我要写书评

暂无评论

Journal of Semiconductors 2024年第3期45卷 58-63页

作者： Jin sui Jiaxiang Chen Haolan Qu yu Zhang Xing Lu Xinbo Zou School of Information Science and Technology ShanghaiTech UniversityShanghai 201210China Shanghai Institute of Microsystem and Information Technology Chinese Academy of SciencesShanghai 200050China School of Microelectronics University of Chinese Academy of SciencesBeijing 100049China School of Electronics and Information Technology Sun Yat-sen UniversityGuangzhou 510275China

Emission and capture characteristics of a deep hole trap(H1)in n-GaN Schottky barrier diodes(SBDs)have been investigated by optical deep level transient spectroscopy(ODLTS).Activation energy(Eemi)and capture cross-section(σ_(p))of H1 are determined to be 0.75 eV and 4.67×10^(−15)cm^(2),*** of apparent trap concentration in space charge region is ***-enhanced emission process is revealed by decrease of emission time ***-boosted trap emission kinetics are analyzed by the Poole−Frenkel emission(PFE)*** addition,H1 shows point defect capture properties and temperature-enhanced capture *** both hole capture and emission processes into account during laser beam incidence,H1 features a trap concentration of 2.67×10^(15)cm^(−3).The method and obtained results may facilitate understanding of minority carrier trap properties in wide bandgap semiconductor material and can be applied for device reliability assessment.

关键词： GaN deep level transient spectroscopy minority carrier trap time constant trap concentration

A harmonic-wave bio-thermal method for continuous monitoring skin thermal conductivity and capillary perfusion rate

在线全文

学校读者我要写书评

暂无评论

Nano Research 2024年第5期17卷 4420-4427页

作者： yuxin Ouyang Jie Lin Jiajing Pei Rui sui Di Liu Yanhui Feng Lin Qiu School of Energy and Environmental Engineering University of Science and Technology BeijingBeijing 100083China Ningbo Institute of Materials Technology and Engineering Chinese Academy of SciencesNingbo 315201China Beijing Synchrotron Radiation Facility Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China Department of Chemistry Tsinghua UniversityBeijing 100084China Institute of Analysis and Testing Beijing Academy of Science and TechnologyBeijing 100089China

The revelation of thermal energy exchange mechanism of human body is challenging yet worthwhile,because it can clearly explain the changes in human symptoms and health ***,the heat transfer of the skin is significant because the skin is the foremost organ for the energy exchange between the human body and the *** order to diagnose the physiological conditions of human skin without causing any damage,it is necessary to use a non-invasive measurement technique by means of a conformal flexible *** harmonic method can minimize the thermal-induced injury to the skin due to its low heat generating properties.A novel type of computational theory assessing skin thermal conductivity,blood perfusion rate of capillaries in the dermis,and superficial subcutaneous tissues was formed by combining the multi-medium thermal diffusion model and the bio-thermal model(Pennes equation).The skins of the hand back of six healthy subjects were *** was found that the results revealed no consistent changes in thermal conductivity were observed across genders and *** measured blood perfusion rates were within the range of human capillary *** was found that female subjects had a higher perfusion rate range(0.0058-0.0061 s^(-1))than male subjects(0.0032-0.0049 s^(-1)),which is consistent with invasive medical studies about the gender difference in blood flow rates and stimulated effects in relaxation situations.

关键词： thermal conductivity blood perfusion rate harmonic method Pennes equation

典型黑土侵蚀区自然植被恢复措施水土保持功效研究

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

水土保持学报 2010年第1期24卷 73-77,81页

作者：张少良张兴义刘晓冰刘爽隋跃宇于同艳中国科学院东北地理与农业生态研究所/黑龙江省黑土生态重点实验室哈尔滨150081 中国科学院研究生院北京100049

利用田间定位实验来分析植被恢复措施的自我恢复能力和其水土保持功效,目的为黑土区土壤侵蚀治理和生态环境建设提供依据。结果表明,植被恢复措施从5月份开始,在4个月的时间内覆盖率可达100%,植物种类丰富。2007年和2008年植被恢复措施... 详细信息

利用田间定位实验来分析植被恢复措施的自我恢复能力和其水土保持功效,目的为黑土区土壤侵蚀治理和生态环境建设提供依据。结果表明,植被恢复措施从5月份开始,在4个月的时间内覆盖率可达100%,植物种类丰富。2007年和2008年植被恢复措施年径流水深分别比传统耕作低64.7%和99.7%,比裸地低98.1和99.9%;2008年植被恢复措施径流系数是2007年的19%。2007和2008年植被恢复措施侵蚀模数都少于传统耕作和裸地。2008年植被恢复措施侵蚀模数比2007年低97.2%。自然植被恢复措施能够有效的抑制土壤侵蚀和地表径流的发生,为植物生长提供更多的有效水分。相关分析表明,3种管理措施径流水深与I30和I60都达到极显著水平,地表径流主要发生在6-9月份,土壤侵蚀主要发生在6-7月份。

关键词：植被恢复径流量侵蚀量土壤储水量

在线全文

学校读者我要写书评

暂无评论

长期培肥对农田暗棕壤土壤微生物量的影响

农业系统科学与综合研究 2010年第4期26卷 484-486页

作者：隋跃宇焦晓光魏丹刘洪家中国科学院东北地理与农业生态研究所黑土区农业生态院重点实验室黑龙江哈尔滨150081 黑龙江省农业科学院土壤肥料与环境资源研究所黑龙江省植物营养与土壤环境重点实验室黑龙江哈尔滨150086 黑龙江大学农业资源与环境学院黑龙江哈尔滨150080

以黑龙江省农业科学院黑河分院"土壤肥力与肥效长期定位试验"的农田暗棕壤为研究对象,测定不同施肥制度下大豆土壤微生物量C、N动态变化,探讨长期不同施肥处理对暗棕壤的培肥效应。结果表明,与不施肥、单施化肥、单施有机肥处理相比,化... 详细信息

以黑龙江省农业科学院黑河分院"土壤肥力与肥效长期定位试验"的农田暗棕壤为研究对象,测定不同施肥制度下大豆土壤微生物量C、N动态变化,探讨长期不同施肥处理对暗棕壤的培肥效应。结果表明,与不施肥、单施化肥、单施有机肥处理相比,化肥配施有机肥能显著增加大豆各生育期土壤微生物量C、N量及qMB值,增强了农田暗棕壤土壤养分容量的供应强度,有利于农田暗棕壤的培肥。

关键词：暗棕壤大豆生育期长期施肥土壤微生物量碳、氮