检索结果-南通市图书馆

Generation of high-quality electron beams by ionization injection in a single acceleration stage

在线全文

学校读者我要写书评

暂无评论

High Power Laser Science and Engineering 2016年第3期4卷 39-45页

作者： Nasr A.M.Hafz Song li guangyu li Mohammad Mirzaie Ming Zeng Jie Zhang Key Laboratory for Laser Plasmas(MOE) and Department of Physics and Astronomy Collaborative Innovation Center of IFSAShanghai Jiao Tong University

Ionization-induced electron injection in laser wakefield accelerators, which was recently proposed to lower the laser intensity threshold for electron trapping into the wake wave, has the drawback of generating electron beams with large and continuous energy spreads, severely limiting their future applications. Complex target designs based on separating the electron trapping and acceleration stages were proposed as the only way for getting small energy-spread electron beams. Here, based on the self-truncated ionization-injection concept which requires the use of unmatched laser–plasma parameters and by using tens of TW laser pulses focused onto a gas jet of helium mixed with low concentrations of nitrogen, we demonstrate single-stage laser wakefield acceleration of multi-hundred MeV electron bunches with energy spreads of a few percent. The experimental results are verified by PIC simulations.

关键词： ionization injection laser–plasma acceleration PIC simulations self-truncation wakefield

Losses of Ecosystem Service Values in the Taihu Lake Basin from 1979 to 2010

在线全文

学校读者我要写书评

暂无评论

Frontiers of Earth Science 2017年第2期11卷 310-320页

作者： Hui ZHANG Qiao WANG guangyu li Hanpei ZHANG Jue ZHANG College of Geographical Sciences Nanjing Normal University Nanjing 210023 China Nanjing Institute of Environmental Science Ministry of Environmental Protection Nanjing 210042 China Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET) Nanjing University of Information Science & Technology Nanjing 210044 China Environmental Satellite Application Center Ministry of Environmental Protection Beijing 100029 China

The Taihu Lake Basin, an east-coastal developed area, is one of the fastest-growing metropolitan areas in China. Ecosystem services in the Taihu Lake Basin have been overexploited and jeopardized. Based on land-use and land-cover change （LUCC） data from 1979, 1984, 2000, and 2010, in conjunction with the adjusted ecosystem service values （ESV）, changes in ESV were analyzed in detail. Results revealed that LUCC resulted in a substantial decrease in total ESV from S3.92 billion in 1979 to S2.98 billion in 2010. The ESV of cropland decreased from $1.64 billion in 1979 to S1.34 billion in 2010, which represented a 20.28% reduction. The ESV of water areas decreased from S1.08 billion in 1979 to $0.36 billion in 2010, which represented a 65.62% reduction mainly because of a decline in water quality. In terms of annual change rate, cropland and water areas showed a sustained downward trend. Spatially, ESV declines were mainly observed in Suzhou, Wuxi, Changzhou, and Shanghai, probably due to a combination of economic progress, population growth, and rapid urbanization. The research results can be a useful reference for policymakers in mitigating ESV decline.

关键词： ecosystem service values land use/land cover,water quality Taihu Lake Basin

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

弱刚性构件双机器人协同加工振动抑制方法

振动．测试与诊断 2024年第1期44卷 147-152,203页

作者：崔光裕李波乐毅田威廖文和李明伟南京航空航天大学机电学院南京210016 上海宇航系统工程研究所上海201109 北京卫星制造厂有限公司北京100094

针对弱刚性航天器舱体壁板多任务并行加工的振动抑制需求,研究了弱刚性构件在切削激励作用下的振动产生、传播与耦合机理,提出了基于双加工激励相位差控制的弱刚性构件双机器人协同加工振动抑制方法,并以薄壁舱体壁板为对象进行了仿真... 详细信息

针对弱刚性航天器舱体壁板多任务并行加工的振动抑制需求,研究了弱刚性构件在切削激励作用下的振动产生、传播与耦合机理,提出了基于双加工激励相位差控制的弱刚性构件双机器人协同加工振动抑制方法,并以薄壁舱体壁板为对象进行了仿真与试验研究。结果表明,该方法能够有效实现振动抑制,验证了其正确性与有效性,为多机器人协同原位加工的复杂振动抑制难题提供了一种新思路。

关键词：振动抑制双机器人相位差弱刚性构件协同加工

在线全文

学校读者我要写书评

暂无评论

广州航空轮胎大科学装置主体结构设计

建筑结构 2024年第5期54卷 15-24页

作者：李光雨刘宁高峰深圳市建筑设计研究总院有限公司深圳518031

广州航空轮胎大科学装置作为科学试验、产业吸引的重要建筑,方案新颖奇特,为竖向及水平圆组合的造型。结构设计时,通过设置防震缝将其分割成两个独立的结构主体,同时考虑建筑造型、试验设备、超高大跨吊车等的相关需求。竖向圆为中部通... 详细信息

广州航空轮胎大科学装置作为科学试验、产业吸引的重要建筑,方案新颖奇特,为竖向及水平圆组合的造型。结构设计时,通过设置防震缝将其分割成两个独立的结构主体,同时考虑建筑造型、试验设备、超高大跨吊车等的相关需求。竖向圆为中部通高的六层钢框架-中心支撑结构,充分利用吊车支撑做成强支撑框架,减少中部30m高跃层柱的长度系数,同时充分利用建筑形体,在30m以上做成半圆柱面单层网壳结构,实现建筑效果的同时也节约了材料;水平圆为钢框架结构,针对屋面大跨楼盖,采用单向密肋实腹钢梁,钢梁截面最大高度为1.9m,以满足建筑净空和结构挠度等要求;幕墙与主体间采用桁架式铰接支座,实现外鼓幕墙造型;10台半埋式试验台基础采用灌注桩基础,并设置隔振沟以减轻动力试验对主体结构的影响。设计最终很好地实现了建筑功能及结构安全性和适用性。

关键词：航空轮胎防震缝钢框架-中心支撑结构钢框架结构跃层柱网壳结构

Enhanced mechanical properties of 6082 aluminum alloy via SiC addition combined with squeeze casting

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2021年第29期88卷 119-131页

作者： Wenming Jiang Junwen Zhu guangyu li Feng Guan Yang Yu Zitian Fan State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan430074China State Key Laboratory of High Performance Complex Manufacturing Central South University410083 ChangshaChina

In order to improve mechanical properties of 6082 aluminum alloy,the SiC_(p)/Al 6082 composites were prepared by the addition of the micron-sized SiC_(p)articles combined with the squeeze casting.The effects of the SiC_(p)content and squeeze casting on the microstructure and mechanical properties of the 6082 aluminum alloy were investigated by SEM,EDS,TEM,tensile testing and hardness testing analysis methods.Research results exhibited that the SiC_(p)content and squeeze casting had a significant impact on the microstructure and mechanical properties of the 6082 aluminum alloy.The addition of the SiC_(p)refined the grain size of the 6082 aluminum alloy while caused the increase of the porosity with increasing the SiC_(p)content,especially in the permanent mold casting condition.Compared to the permanent mold casting,the squeeze casting obviously reduced pore defects,refined grain size and made the SiC_(p)distribute evenly as well as bond tightly with the Al matrix.The tensile strength,yield strength,elongation,elastic modulus and hardness of the 6082 aluminum alloy obtained with the SiC_(p)and squeeze casting were remarkably improved,and the optimal mechanical properties were obtained with a 2 wt.%SiC_(p),and they increased 10.73%,72.7%,193.9%,23.5%and 25.2%,respectively,compared to those of the6082 aluminum alloy obtained without SiC_(p)and squeeze casting.The fracture surface of the SiC_(p)/Al 6082 composites obtained with the squeeze casting was dense and exhibited a ductile fracture mode.

关键词： 6082 aluminum alloy SiC_(p) Aluminum matrix composites Squeeze casting Microstructure Mechanical properties

2D-SiC/SiC复合材料的弹丸冲击损伤及冲击后拉伸性能

在线全文

学校读者我要写书评

暂无评论

无机材料学报 2024年第5期39卷 494-500页

作者：李广宇岳一凡王波张程煜索涛李玉龙西北工业大学航空学院西安710072 陕西省冲击动力学及工程应用重点实验室西安710072 强度与结构完整性全国重点实验室西安710065 西北工业大学材料学院西安710072 西北工业大学民航学院西安710072

连续纤维增韧陶瓷基复合材料以其良好的高温性能而被广泛应用在航空发动机等高温部件处,但服役过程中容易受到异物碎片冲击,这受到了广泛关注。研究采用轻气炮对化学气相渗透(CVI)技术制备的2D-SiC/SiC试样进行弹丸冲击,利用高速摄像机... 详细信息

连续纤维增韧陶瓷基复合材料以其良好的高温性能而被广泛应用在航空发动机等高温部件处,但服役过程中容易受到异物碎片冲击,这受到了广泛关注。研究采用轻气炮对化学气相渗透(CVI)技术制备的2D-SiC/SiC试样进行弹丸冲击,利用高速摄像机记录冲击过程,使用光学显微镜和CT观察异物损伤(FOD)的表面和内部结构,探讨了2D-SiC/SiC复合材料的高速冲击损伤特性。结果表明,2D-SiC/SiC复合材料的高速冲击损伤形式包括锥形裂纹、层间分层、纤维断裂以及基体压溃等。通过表征损伤发现,试件背部损伤和边缘处分层损伤由反射拉伸波造成,随着冲击速度提升,弹丸与拉伸波共同作用会造成试件穿透,试件边缘分层损伤减弱。对高速冲击后的试件进行准静态拉伸试验,明确了剩余力学性能与冲击速度、弹丸直径的关系,表明剩余拉伸强度是表征冲击损伤程度的有效参数。同时,采用数字图像相关(DIC)方法获得拉伸过程中的应变分布,并结合不同弹丸直径、冲击速度冲击后的剩余拉伸强度,进一步对比探究不同变量对冲击损伤的影响。研究结果表明弹丸直径是高速冲击损伤程度的主要影响因素。

关键词：陶瓷基复合材料高速冲击异物损伤剩余拉伸强度数字图像相关技术

在线全文

学校读者我要写书评

暂无评论

基于分层网络的电能表运行状态评价

电测与仪表 2024年第5期61卷 218-224页

作者：吴宇赵莉冉光宇李竹国网重庆市电力公司营销服务中心重庆400000 重庆广汇供电服务有限责任公司客户服务分公司重庆400000

现有的电能表状态评价大都从孤立微观的角度对电能表运行状态进行评估,没有从更大的视角对台区电能表进行整体评价。孤立地对单个电能表进行状态评价,有可能造成对整个台区运行风险的误判。为了更加全面细致掌握电能表及台区的运行状态... 详细信息

现有的电能表状态评价大都从孤立微观的角度对电能表运行状态进行评估,没有从更大的视角对台区电能表进行整体评价。孤立地对单个电能表进行状态评价,有可能造成对整个台区运行风险的误判。为了更加全面细致掌握电能表及台区的运行状态,文章提出了一种分层网络模型。方法是基于用电采集系统和计量生产调度平台的历史数据,根据各指标的状态对电能表质量,预期寿命和故障率进行评分,依据评分将电能表状态划分为稳定、正常、关注、严重和预警五个等级。基于台区终端记录的电能表异常事件数据,利用深度决策森林(Deep Neural Decision Forests)模型将台区中的异常事件等级程度划分为严重、重要、较重要和一般四个等级,模型分类正确率达到86.58%。实验结果表明,方法能够准确判断电能表的运行状态和整个台区的运行风险情况,为实现电网可靠稳定运行创造了条件。

关键词：分层模型状态评价 DNDF 运行风险

In Vivo Corrosion Resistance of Ca-P Coating on AZ60 Magnesium Alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2013年第2期10卷 156-161页

作者： Xing Xiao Haiying Yu Qingsan Zhu guangyu li Yang Qu Rui Gu First Hospital of Jilin University Changchun 130021 P. R. China Shandong Qianfoshan Hospital Jinan 250014 P. R. China Shandong Tumour Hospital Jinan 250117 P. R. China College of Materials Science and Engineering Jilin University Changchun 130022 P. R. China China Japan Union Hospital of Jilin University Changchun 130033 P. R. China

Magnesium-based alloys are frequently reported as potential biodegradable orthopedic implant materials. Controlling the degradation rate and mechanical integrity of magnesium alloys in the physiological environment is the key to their applications. In this study, calcium phosphate （Ca-P） coating was prepared on AZ60 magnesium alloy using phosphating technology. AZ60 samples were immersed in a phosphating solution at 37 ± 2 ℃ for 30 min, and the solution pH was adjusted to 2.6 to 2.8 by adding NaOH solution. Then, the samples were dried in an attemperator at 60 ℃. The degradation behavior was studied in vivo using Ca-P coated and uncoated magnesium alloys. Samples of these two different materials were implanted into rabbit femora, and the corrosion resistances were evaluated after 1, 2, and 3 months. The Ca-P coated samples corroded slower than the uncoated samples with prolonged time. Significant differences （p 〈 0.05） in mass losses and corrosion rates between uncoated samples and Ca-P coated samples were observed by micro-computed tomography. The results indicate that the Ca-P coating could slow down the degradation of magnesium alloy in vivo.

关键词： Ca-P coating mass loss micro-computed tomography corrosion resistance magnesium 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

基于集成学习算法的可持续模块划分方法

机床与液压 2024年第11期52卷 87-92页

作者：邹光宇李中凯中国矿业大学机电工程学院江苏徐州221000

随着客户对可持续产品需求的增加,针对产品功能和结构属性的传统模块化设计,正逐步转向可持续模块化设计。然而当前的模块划分方法更注重于对模块化指数的优化迭代,忽略了产品多组件间的信息传递和反馈。为此,提出一种集成学习算法的可... 详细信息

随着客户对可持续产品需求的增加,针对产品功能和结构属性的传统模块化设计,正逐步转向可持续模块化设计。然而当前的模块划分方法更注重于对模块化指数的优化迭代,忽略了产品多组件间的信息传递和反馈。为此,提出一种集成学习算法的可持续模块划分方法。首先,面向组件间的回收性、材料和寿命因素,构建产品的综合DSM模型。其次,提出集成学习算法的弱分类器构建规则和强分类器结合策略。最后,通过颚式破碎机案例验证了所提模块划分方法的可行性,集成学习算法同直接聚类和遗传算法的模块划分结果对比,表明所提方法各模块组件更接近DSM的对角线。

关键词：模块划分可持续设计集成学习算法信息回路