检索结果-南通市图书馆

低温切削7075铝合金鳞刺形成规律及抑制措施

在线全文

学校读者我要写书评

暂无评论

中国机械工程 2022年第3期33卷 261-269页

作者：刘枭邓文君陈海涛张保玉华南理工大学机械与汽车工程学院广州510641

针对干切削铝合金工件表面易产生鳞刺、表面完整性较差的问题,采用液氮冷却方式在不同切削参数下对7075铝合金进行了正交切削试验,使用扫描电子显微镜和3D光学轮廓仪分别表征了已加工表面形貌、鳞刺分布和鳞刺尺寸,分析了切削速度、进... 详细信息

针对干切削铝合金工件表面易产生鳞刺、表面完整性较差的问题,采用液氮冷却方式在不同切削参数下对7075铝合金进行了正交切削试验,使用扫描电子显微镜和3D光学轮廓仪分别表征了已加工表面形貌、鳞刺分布和鳞刺尺寸,分析了切削速度、进给量、刀具前角和冷却方式(干切削、液氮冷却、切削液)对已加工表面鳞刺分布和尺寸的影响,并基于鳞刺形成理论讨论了切削参数和液氮冷却对鳞刺形成过程的影响。金属层积是鳞刺形成的充分必要条件,通过改善刀屑接触摩擦特性能够抑制鳞刺的形成。试验结果表明,较高切削速度、小进给量和大刀具前角能减小金属层积厚度,抑制鳞刺的形成。低温切削下已加工表面鳞刺分布密度和尺寸均小于常温切削,可得到较为光整的已加工表面。

关键词：低温切削鳞刺 7075铝合金表面质量

维普期刊数据库博看期刊

在线全文

学校读者我要写书评

暂无评论

限制接触切削过程力热特性仿真及试验研究

航空制造技术 2023年第5期66卷 36-46页

作者：李梓钊邓文君庞学勤华南理工大学广州510641

316L奥氏体不锈钢因其优良的力学性能和耐腐蚀性在航空航天领域被广泛应用,但其加工硬化现象严重,刀–屑接触环境恶劣,导致刀具寿命严重缩短,影响加工效率。本文将通过有限元仿真与试验相结合的方法研究限制接触刀具对切削过程中力与热... 详细信息

316L奥氏体不锈钢因其优良的力学性能和耐腐蚀性在航空航天领域被广泛应用,但其加工硬化现象严重,刀–屑接触环境恶劣,导致刀具寿命严重缩短,影响加工效率。本文将通过有限元仿真与试验相结合的方法研究限制接触刀具对切削过程中力与热特性的影响。通过建立限制接触切削的有限元仿真模型,探究加工参数和限制接触参数对切削性能的影响,并阐明了变限制接触结构在切削过程中的作用机理。结果表明,变限制接触结构能有效减小切削力与切削温度,并改善奥氏体钢的切削性能。其中梯形限制接触结构改善切削性能效果最好。该结果在切削试验中得到验证,并证明了有限元仿真的可靠性,为新型限制接触刀具结构的优化提供理论基础。

关键词：限制接触切削变限制接触长度刀具有限元仿真 316L奥氏体不锈钢力热特性

Lateral root elongation in maize is related to auxin synthesis and transportation mediated by N metabolism under a mixed NO_(3)^(–) and NH_(4)^(+) supply

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2024年第3期23卷 1048-1060页

作者： Peng Wang Lan Yang Xichao Sun wenjun Shi Rui Dong Yuanhua Wu Guohua Mi Key Laboratory of Tobacco Biology and Processing of Ministry of Agriculture and Rural Affairs Tobacco Research InstituteChineseAcademy of Agricultural SciencesQingdao 266101China Department of Plant Nutrition College of Resources and Environmental SciencesChina Agricultural UniversityBeijing 100193China College of Resources Hunan Agricultural UniversityChangsha 410128China Agro-Environmental Protection Institute Ministry of Agriculture and Rural AffairsTianjin 300191China

A mixed nitrate (NO_(3)^(–)) and ammonium (NH_(4)^(+)) supply can promote root growth in maize (Zea mays),however,the changes in root morphology and the related physiological mechanism under different N forms are still ***,maize seedlings were grown hydroponically with three N supplied in three different forms (NO_(3)^(–)only,75/25 NO_(3)^(–)/NH_(4)^(+)and NH_(4)^(+)only).Compared with sole NO_(3)^(–)or NH_(4)^(+),the mixed N supply increased the total root length of maize but did not affect the number of axial *** main reason was the increased total lateral root length,while the average lateral root (LR) length in each axle was only slightly *** addition,the average LR density of 2nd whorl crown root under mixed N was also *** with sole nitrate,mixed N could improve the N metabolism of roots (such as the N influx rate,nitrate reductase (NR) and glutamine synthase (GS)enzyme activities and total amino content of the roots).Experiments with exogenously added NR and GS inhibitors suggested that the increase in the average LR length under mixed N was related to the process of N assimilation,and whether the NR mediated NO synthesis participates in this process needs further ***,an investigation of the changes in root-shoot ratio and carbon (C) concentration showed that C transportation from shoots to roots may not be the key factor in mediating lateral root elongation,and the changes in the sugar concentration in roots further proved this ***,the synthesis and transportation of auxin in axial roots may play a key role in lateral root elongation,in which the expression of ZmPIN1B and ZmPIN9 may be involved in this *** study preliminarily clarified the changes in root morphology and explored the possible physiological mechanism under a mixed N supply in maize,which may provide some theoretical basis for the cultivation of crop varieties with high N efficiency.

关键词： maize NO_(3)^(–)/NH_(4)^(+)ratio lateral root elongation N assimilation indole-3-acetic acid

Prediction of the thermal conductivity of Mg–Al–La alloys by CALPHAD method

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 129-137页

作者： Hongxia Li wenjun Xu Yufei Zhang Shenglan Yang Lijun Zhang Bin Liu Qun Luo Qian Li State Key Laboratory of Advanced Special Steels&Shanghai Key Laboratory of Advanced Ferrometallurgy&School of Materials Science and Engineering Shanghai UniversityShanghai 200444China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing 400044China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China College of Materials Science and Engineering Chongqing UniversityChongqing 400044China National Key Laboratory of Advanced Casting Technologies Chongqing UniversityChongqing 400044China

Mg-Al alloys have excellent strength and ductility but relatively low thermal conductivity due to Al *** accurate prediction of thermal conductivity is a prerequisite for designing Mg-Al alloys with high thermal ***,databases for predicting temperature-and composition-dependent thermal conductivities must be *** this study,Mg-Al-La alloys with different contents of Al2La,Al3La,and Al11La3phases and solid solubility of Al in the α-Mg phase were *** influence of the second phase(s) and Al solid solubility on thermal conductivity was *** results revealed a second phase transformation from Al_(2)La to Al_(3)La and further to Al_(11)La_(3)with the increasing Al content at a constant La *** degree of the negative effect of the second phase(s) on thermal diffusivity followed the sequence of Al2La>Al3La>Al_(11)La_(3).Compared with the second phase,an increase in the solid solubility of Al in α-Mg remarkably reduced the thermal *** the basis of the experimental data,a database of the reciprocal thermal diffusivity of the Mg-Al-La system was established by calculation of the phase diagram (CALPHAD)*** a standard error of±1.2 W/(m·K),the predicted results were in good agreement with the experimental *** established database can be used to design Mg-Al alloys with high thermal conductivity and provide valuable guidance for expanding their application prospects.

关键词： magnesium alloy thermal conductivity thermodynamic calculations materials computation

Transient synthesis of carbon-supported high-entropy alloy sulfide nanoparticles via flash Joule heating for efficient electrocatalytic hydrogen evolution

在线全文

学校读者我要写书评

暂无评论

Nano Research 2024年第4期17卷 3379-3389页

作者： Yuntian Liao Rongtao Zhu wenjun Zhang Haiyang Zhu Yang Sun Jiale Chen Zhenhua Dong Ronghuan Lv School of Chemical Engineering and Technology China University of Mining and TechnologyXuzhou 221116China

High entropy alloys(HEA)are frequently employed as catalysts in electrocatalytic hydrogen ***,the traditional high entropy alloy synthesis methods are time-consuming,energy-intensive,and environmentally polluting,which limits their application in the hydrogen evolution reaction(HER).This study leveraged the capabilities of flash Joule heating(FJH)to synthesize carbon-supported high-entropy alloy sulfide nanoparticles(CC-S-HEA)on carbon cloth(CC)with good self-standing properties within 300 *** carbon thermal shock generated by the Joule heating could pyrolyze the sulfur source into gas,resulting in numerous pore structures and defects on CC,forming an S-doped carbon substrate(CC-S).Then the S atoms were used to stably anchor the metal atoms on CC-S to form high-density uniformly dispersed HEA *** electrochemical test results demonstrated that CC-S-HEA prepared at 60 V flash voltage had HER performance comparable to Pt/*** density functional theory(DFT)calculation indicated that the S atoms on CC-S accelerated the electron transfer between the carbon substrate and HEA ***,the unique electronic structure of CC-S-HEA was beneficial to H*adsorption and promoted catalytic *** simplicity and versatility of FJH synthesis are of great significance for optimizing the synthesis of HEA and improving the quality of HEA products,which provides a broad application prospect for the synthesis of nanocatalysts with efficient HER performance.

关键词： high entropy alloy flash Joule heating carbon thermal shock hydrogen evolution reaction density functional theory

A First-principles Study on the Adhesion Strength,Interfacial Stability,and Electronic Properties of Mg/Mg_(2)Y Interface

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3期37卷 537-550页

作者： Yunxuan Zhou wenjun Tian Quan Dong Hailian Wang Jun Tan Xianhua Chen Kaihong Zheng Fusheng Pan College of Materials Science and Engineering National Engineering Research Center for Magnesium AlloysChongqing UniversityChongqing 400044China State Key Laboratory of Mechanical Transmission Chongqing UniversityChongqing 400044China Institute of New Materials Guangdong Academy of SciencesGuangzhou 510650China

The interfacial microstructures and configurations directly affect the comprehensive properties of the composites,but their interfacial adhesion mechanism is complicated to expound by experimental *** this work,based on the stacking sequence of the Mg/Mg_(2)Y interface models,nine different Mg/Mg_(2)Y interface configurations with top site,bridge site,and hollow site(HCP)under Mg1,Mg_(2),and Y terminations were successfully constructed and systematically explored by first-principles *** results showed that the Mg_(2)Y(0001)surface with Y termination is the most stable when the yttrium chemical potential()is less than-1.09 eV;otherwise,Mg_(2)Y(0001)surface with Mg1 termination is the most *** seven-layer Mg(0001)and eleven-layer Mg_(2)Y(0001)slabs are employed to reflect the bulk-like interior ***,the Mg(0001)/Mg_(2)Y(0001)with the Y-HCP stacking has the largest interface thermodynamic stability with the value of 2.383 J/m^(2) in all interface configurations owing to its largest work of *** addition,the interfacial energy of Y-HCP stacking is significantly smaller than those of Mg1-HCP when is approximately less than-0.55 eV,showing that it is more *** thermodynamic stability of Mg/Mg_(2)Y with Y-HCP is due to Mg-Y chemical bonds formed between Mg and Y ***,the Mg/Mg_(2)Y interfaces are strong interfaces based on the Griffith fracture theory.

关键词： Mg/Mg_(2)Y interface Interface stability Work of adhesion Electronic structure First-principles calculations

Defining the We-map Reference Frames and Providing Mathematical Expressions for Transformation Relations

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3期7卷 76-88页

作者： WANG Xiaolong YAN Haowen WANG Zhuo MA wenjun YU Yitao College of Earth and Environmental Sciences Lanzhou UniversityLanzhou 730000China Key Laboratory of Western China’s Environmental Systems Ministry of EducationLanzhou 730000China Faculty of Geomatics Lanzhou Jiaotong UniversityLanzhou 730070China National-Local Joint Engineering Research Center of Technologies and Applications for National Geographic State Monitoring Lanzhou 730070China Gansu Provincial Key Laboratory of Science and Technology in Surveying&Mapping Lanzhou 730070China School of Resource and Environmental Sciences Wuhan UniversityWuhan 430072China

We-map is an interactive mobile map that can be easily communicated and applied on personal electronic devices,such as personal computers and mobile ***,the study of direction systems and coordinate systems is critical,and exploring reference frames is essential in direction and coordinate *** its significance,existing research on We-map lacks specific solutions for the exploration of reference frames is indispensable for the establishment of accurate direction and coordinate *** this paper,we endeavor to address this gap by elucidating the significance of We-map reference frames,defining them with mathematical constraints,summarizing their nature and characteristics,deriving their transformation relationships and representing them through mathematical formulars and *** work contributes to the fundamental theory of We-map and provides valuable systems and support for the mathematical foundation of We-map,map production,and platform ***,this research serves to advance the development of We-map.

关键词： We-map reference frames spatial direction relation coordinate system

Biochemistry and transcriptome analysis reveal condensed tannins alleviate liver injury induced by regulating cholesterol metabolism pathway

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

Food Science and Human Wellness 2024年第2期13卷 909-919页

作者： Xiangxin Li Yijing Pu Bangdi Liu Xiaoming Fang wenjun Peng Weibo Jiang Wenli Tian Institute of Apicultural Research Chinese Academy of Agricultural SciencesBeijing 100093China College of Food Science and Nutritional Engineering China Agricultural UniversityBeijing 100083China Academy of Agricultural Planning and Engineering Ministry of Agriculture and Rural AffairsBeijing 100125China

Free cholesterol has been considered to be a critical risk factor of nonalcoholic fatty liver disease(NAFLD).It remains unknown whether dietary intake of condensed tannins(CTs)have distinguishable effects to alleviate liver damage caused by a high cholesterol *** C57BL/6 mice were fed a high cholesterol diet for 6 weeks,and given CTs treatment at a dosage of 200 mg/(kg·day)at the same *** results indicated that compared with mice fed a normal diet,a high cholesterol diet group resulted in significant weight loss,dysregulation of lipid metabolism in blood and liver,and oxidative stress in the liver,but CTs treatment dramatically reversed these negative *** and eosin(H&E)staining and frozen section observation manifested that CTs treatment could effectively reduce the deposition of liver cholesterol and tissue necrosis caused by high cholesterol *** alleviated liver injury mainly by regulating the expression of related genes in cholesterol metabolism pathway and AMPK *** results confirmed that CTs have remarkable cholesterol lowering and anti-liver injury effects in vivo.

关键词： Condensed tannins High cholesterol Liver injury Antioxidants Transcriptomic analysis

Long Short-Term Memory Spiking Neural Networks for Classification of Snoring and Non-snoring Sound Events

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Electronics 2024年第3期33卷 793-802页

作者： Rulin ZHANG Ruixue LI Jiakai LIANG Keqiang YUE wenjun LI Yilin LI Electronics and Information College Hangzhou Dianzi University

Snoring is a widespread occurrence that impacts human sleep *** is also one of the earliest symptoms of many sleep *** is accurately detected,making further screening and diagnosis of sleep problems *** is frequently ignored because of its underrated and costly detection *** a result,this research offered an alternative method for snoring detection based on a long short-term memory based spiking neural network(LSTM-SNN) that is appropriate for large-scale home detection for *** designed acquisition equipment to collect the sleep recordings of 54 subjects and constructed the sleep sound database in the home *** Mel frequency cepstral coefficients(MFCCs) were extracted from these sound signals and encoded into spike trains by a threshold encoding *** were classified automatically as non-snoring or snoring sounds by our LSTM-SNN *** used the backpropagation algorithm based on an alternative gradient in the LSTM-SNN to complete the parameter *** categorization percentage reached an impressive 93.4%,accompanied by a remarkable 36.9% reduction in computer power compared to the regular LSTM model.

关键词： Costs Databases Computational modeling Backpropagation algorithms Sleep apnea Encoding Recording