检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

CFRP砂轮高速外圆磨削稳定性分析

航空制造技术 2024年第8期67卷 76-84页

作者：秦鹏冯伟刘斐张霖杨淮文曹乐张国建河南工业大学郑州450001 河南省超硬磨料磨削装备重点实验室郑州450001 白鸽磨料磨具有限公司郑州450199

为分析不同影响因素对CFRP砂轮高速外圆磨削稳定性的影响,采用铁木辛柯梁理论对具有阶梯特征的工件进行动力学分析,结合锤击试验测得砂轮动态特性,对高速磨削过程中的砂轮-工件两自由度系统进行了磨削稳定性分析。在对阶梯工件进行动力... 详细信息

为分析不同影响因素对CFRP砂轮高速外圆磨削稳定性的影响,采用铁木辛柯梁理论对具有阶梯特征的工件进行动力学分析,结合锤击试验测得砂轮动态特性,对高速磨削过程中的砂轮-工件两自由度系统进行了磨削稳定性分析。在对阶梯工件进行动力学分析的过程中,发现阶梯特征对于动态特性的影响较小,误差小于2%。在稳定性分析中发现,不同的砂轮转速和不同的工件磨削位置均会影响磨削稳定性。磨削位置越靠近工件中心,工件刚度越弱,磨削稳定性降低易诱发颤振;而在靠近顶尖支撑的位置,由于工件刚度增强,该位置的磨削稳定性将同时受到工件和砂轮的动力学性能的影响。通过磨削试验验证了分析方法的有效性,试验结果表明,工件磨削位置的刚度差异将会影响加工表面质量,由磨削失稳导致的粗糙度增幅可达51.6%。

关键词： CFRP砂轮高速磨削阶梯工件铁木辛柯梁理论磨削稳定性分析

Mechanism of slope failure in loess terrains during spring thawing

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2018年第4期15卷 845-858页

作者： XU jian WANG Zhang-quan REN jian-wei WANG Song-he JIN Long School of Civil Engineering Xi'an University of Architecture and Technology Xi'an 710055 China Institute of Geotechnical Engineering Xi'an University of Technology Xi'an 710048 China State Key Laboratory of Road Engineering Safety and Health in Cold and High-altitude Region CCCC First Highway Consultants Co. Ltd. Xi'an 710075 China

Slope failure in loess terrains of Northern China during spring thawing period is closely related to the freeze-thaw cycling that surface soils inevitably experienced. Field surveys were carried out on natural and artificial slopes in thirteen surveying sites located in the Northern Shaanxi, the center of Loess Plateau, covering five characteristic topographic features including tablelands, ridges, hills, gullies and valleys. Based on the scale that is involved in freeze-thaw cycling, the induced failures can be classified into three main modes, i.e., erosion, peeling and thaw collapse, depending on both high porosity and loose cementation of loess that is easily affected. Model tests on loess slopes with gradients of 53.1°, 45.0° and 33.7° were carried out to reveal the heat transfer, water migration and deformation during slope failure. The surface morphology of slopes was photographed, with flake shaped erosion and cracks noted. For three slope models, time histories for the thermal regime exhibit three obvious cycles of freeze and thaw andthe maximum frost depth develops downwards as freeze-thaw cycling proceeds. Soil water in the unfrozen domain beneath was migrated towards the slope surface, as can be noticed from the considerable change in the unfrozen water content, almost synchronous with the variation of temperature. The displacement in both vertical and horizontal directions varies over time and three obvious cycles can be traced. The residual displacement for each cycle tends to grow and the slopes with higher gradients are more sensitive to potentially sliding during freeze-thaw cycling.

关键词： Freeze and thaw Loess Slope failure Water migration Heat transfer

在线全文

学校读者我要写书评

暂无评论

罕见的胃底腺型胃癌69例内镜特征分析

临床消化病杂志 2024年第3期36卷 168-171页

作者：文峰周昊程建国朱杰伦陈兰徐维田中部战区总医院消化科湖北武汉430010 江汉大学附属武汉市六医院湖北武汉430015

[目的]分析罕见的胃底腺型胃癌(GA-FG)内镜下特征,提高其诊治能力。[方法]在中国知网、万方医学、PubMed、Springer等数据库中检索相关文献,收集我国学者公开报道的GA-FG病例共68例(69处病灶),分别对“病变部位、大小、表面形态、色调... 详细信息

[目的]分析罕见的胃底腺型胃癌(GA-FG)内镜下特征,提高其诊治能力。[方法]在中国知网、万方医学、PubMed、Springer等数据库中检索相关文献,收集我国学者公开报道的GA-FG病例共68例(69处病灶),分别对“病变部位、大小、表面形态、色调、背景黏膜”等内镜下表现进行归纳,分析其内镜下主要形态特征。[结果]GA-FG好发于中老年,我国平均患病年龄59岁,无明显性别差异。98.6%病灶发生于胃中、上部,97.0%为单发病灶,96.0%无萎缩肠化背景黏膜,88.0%病灶小于1 cm,平均直径7.5 mm。79.7%病灶为隆起型,且以浅表隆起型(Ⅱa)占绝大多数。73.9%病灶表面有血管扩张。52.8%呈褪色调改变。[结论]发生于胃中上部、单个小于1 cm、无萎缩肠化背景黏膜、有表面血管扩张、呈褪色调改变的浅表隆起型病变是国内患者GA-FG内镜下主要形态特征。

关键词：胃癌胃底腺型内镜特征

Two Special Solutions of the Non-ideal Magnetohydrodynamics

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2000年第5期17卷 382-384页

作者： feng Xue-Shang LIU Yong wei feng-Si YE Zhan-Yin Laboratory of Numerical Study for Heliospheric Physics Center for Space Sciences and Applied ResearchChinese Academy of SciencesBeijing 100080

A special transformation is found to solve the Magnetohydrodynamic equations,by which two classes of exactanalytic time-dependent solutions of magnetic annihilation for incompressible magnetic fluid have been *** solutions derived here possesses scaling property with time t as the scale *** find that the currentcan perform the soliton-like behaviour in the case of asymmetric *** relevant evolution characteristics inthe process of magnetic annihilation are also revealed.

关键词： annihilation soliton behaviour

Joining of dissimilar metals between magnesium AZ31B and aluminum A6061-T6 using galvanized steel as a transition joining layer

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 Iron and Steel Research International 2022年第4期29卷 677-686页

作者： wei Li Jing-huan Chang Bao-feng Wen Rui Cao State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metal Lanzhou University of TechnologyLanzhou 730050GansuChina Department of Materials Science and Engineering Lanzhou University of TechnologyLanzhou 730050GansuChina

A galvanized steel is used to join Mg AZ31B alloy and Al A6061-T6 alloy as a joining transition layer by cold metal transfer(CMT)***,to optimize the process variables,extensive welding tests were performed by a design of experiment ***,microstructures,joining mechanisms and tensile properties were characterized and *** indicated that Mg and Al alloys can be joined by using galvanized steel as a joining transition layer and cold metal transfer welding *** formed joint is called as a Mg–steel–Al CMT *** using galvanized steel transition joining layer,Mg–Al brittle intermetallics Al12Mg17 and Al3Mg2 were *** properties of Mg–steel–Al CMT joints have been improved after optimizing the welding *** strength of Mg–steel–Al CMT joint is comparable to those of Al–Al joint and Mg–Mg *** strength of Mg–steel–Al CMT joint can reach 100%that of Al–Al joint and Al–steel joint,and reach 90%that of Mg–Mg joint and Mg–steel *** optimized Mg–steel–Al CMT welded joint with galvanized steel transition layer is fractured at the heat affected zone of Al base metal rather than at the weld-brazed interface,due to softening of Al base metal.

关键词： Cold metal transfer Mg alloy Al alloy Galvanized steel Transition joining layer Dissimilar metal joining

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

基于改进YOLOv5s的无人机图像识别

电光与控制 2024年第4期31卷 22-27,91页

作者：李杰王峰马晨吴国瑞赵伟康智强太原理工大学电子信息与光学工程学院山西晋中030000 中国电子科技集团公司第三十三研究所太原030000

无人机在军事情报、航拍检测等领域能够提供目标相关的图像信息,为处理任务提供目标信息。针对无人机图像背景复杂、检测目标小、可提取特征少等问题,提出基于YOLOv5s的改进无人机图像识别算法。首先,结合CotNet模块对网络结构进行优化... 详细信息

无人机在军事情报、航拍检测等领域能够提供目标相关的图像信息,为处理任务提供目标信息。针对无人机图像背景复杂、检测目标小、可提取特征少等问题,提出基于YOLOv5s的改进无人机图像识别算法。首先,结合CotNet模块对网络结构进行优化,提升模型自学习能力并增强识别精度;其次,对颈部网络进行改进,通过跨层链接和提高特征图分辨率更好地利用浅层特征图中包含的丰富信息来定位目标,并且在检测头部分采用解耦检测头,减少预测过程中定位与分类任务对于特征信息的冲突;最后,为了提高收敛速度和模型精度,在CIoU和EIoU损失函数的基础上对损失函数的宽高纵横比进行优化。在公开数据集VisDrone测试集上进行测试,所提算法相比原始YOLOv5s算法的mAP_(50)与mAP_(50∶95)分别提升了6.1与2.9个百分点,实验结果表明,所提模型能够有效提升无人机图像识别的准确率。

关键词：目标检测无人机图像颈部网络 CotNet 解耦头损失函数

维普期刊数据库博看期刊

Reduction behavior and kinetics of vanadium–titanium sinters under high potential oxygen enriched pulverized coal injection

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2017年第5期24卷 493-503页

作者： Jin-fang Ma Guang-wei Wang jian-liang Zhang Xin-yu Li Zheng-jian Liu Ke-xin Jiao jian Guo School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Plans and Operations Department Wanbao Mining Ltd.

In this work, the reduction behavior of vanadium–titanium sinters was studied under five different sets of conditions of pulverized coal injection with oxygen enrichment. The modified random pore model was established to analyze the reduction kinetics. The results show that the reduction rate of sinters was accelerated by an increase of CO and H2contents. Meanwhile, with the increase in CO and H2contents, the increasing range of the medium reduction index (MRE) of sinters decreased. The increasing oxygen enrichment ratio played a diminishing role in improving the reduction behavior of the sinters. The reducing process kinetic parameters were solved using the modified random role model. The results indicated that, with increasing oxygen enrichment, the contents of CO and H2in the reducing gas increased. The reduction activation energy of the sinters decreased to between 20.4 and 23.2 kJ/mol. © 2017, The Author(s).

关键词： Activation energy Coal Injection (oil wells) Kinetic parameters Kinetics Oxygen Pulverized fuel Sintering Titanium Vanadium

高压氧治疗对神经病理性疼痛大鼠疼痛行为及脊髓胶质细胞活化的影响

在线全文

学校读者我要写书评

暂无评论

中华航海医学与高气压医学杂志 2024年第2期31卷 229-232页

作者：王万胜奚海艳李伟冯真真滨州医学院附属医院康复医学科滨州256603 滨州医学院附属医院妇科滨州256603

目的探究高压氧(HBO)治疗对坐骨神经慢性压迫性损伤(CCI)所致神经病理性疼痛大鼠疼痛行为及脊髓胶质细胞活化的影响。方法选取36只成年雄性SD大鼠,按照随机数字表法分为假手术组(S组)、CCI组和CCI+HBO组,每组12只。CCI+HBO组大鼠于造模... 详细信息

目的探究高压氧(HBO)治疗对坐骨神经慢性压迫性损伤(CCI)所致神经病理性疼痛大鼠疼痛行为及脊髓胶质细胞活化的影响。方法选取36只成年雄性SD大鼠,按照随机数字表法分为假手术组(S组)、CCI组和CCI+HBO组,每组12只。CCI+HBO组大鼠于造模后第1天开始给予HBO治疗,1 h/d,连续10 d。所有大鼠在造模前1 d及造模后第1、3、7、10天检测机械反射阈值(WMT)和热反射潜伏期(TWL)。第10天HBO治疗结束后,运用免疫荧光技术和RT-qPCR技术检测各组大鼠L4~L5节段脊髓组织胶质纤维酸性蛋白(GFAP)和离子钙结合衔接分子1(Iba-1)的表达水平。结果造模后第10天,与S组比较,CCI组大鼠的MWT明显降低、TWL明显缩短,脊髓GFAP和Iba-1表达水平明显增加(P<0.05);与CCI组比较,CCI+HBO组大鼠的MWT明显增高、TWL值明显延长,脊髓GFAP和Iba1表达水平明显下降(P<0.05或P<0.01)。结论HBO治疗可减轻CCI大鼠的神经病理性疼痛,可能是通过抑制大鼠脊髓胶质细胞的活化来实现的。

关键词：高压氧神经病理性疼痛小胶质细胞星形胶质细胞

Surface polarization enables high charge separation in TiO_(2) nanorod photoanode

在线全文

学校读者我要写书评

暂无评论

Nano Research 2021年第11期14卷 4056-4062页

作者： wei Ma Keke Huang Xiaofeng Wu Meng Wang Shouhua feng State Key Laboratory of Inorganic Synthesis and Preparative Chemistry NMAC International Joint LaboratoryCollege of ChemistryJilin UniversityChangchun130012China

Poor charge separation efficiency of semiconductors often stands in the way of photoelectrochemical (PEC) water splitting realization. In this report, a surface polarized TiO_(2) photoanode is obtained via −OH moiety decoration, which achieves a fundamentally improved charge separation efficiency of about 94% at 1.23 VRHE. Detailed data shows that these hydroxyls with electric dipoles polarize the surface, inducing substantial electric field in the surface region, and elevating band edges so as to form a homojunction within TiO_(2). Such serves as the direct driving force for the photogenerated charge separation and migration. Moreover, these hydroxyls also facilitate water oxidation kinetics. Without typical doping or cocatalyst, surface polarized TiO_(2) photoanode delivers a considerably increased photocurrent density of about 1.41 mA·cm^(−2) at 1.23 VRHE (AM 1.5 G) and a cathodic shift on onset potential over 200 mV. This report highlights new opportunities to modulate charge separation by surface polarization for the construction of robust photoanodes.

关键词： TiO_(2)nanorod hydroxyls surface polarization charge separation photoelectrochemical water splitting