检索结果-南通市图书馆

Broadband and perfect terahertz absorber based on multilayer metamaterial with cross-ring patterned structures

在线全文

学校读者我要写书评

暂无评论

Optoelectronics Letters 2025年第1期21卷 1-6页

作者： WEN jin LIU Zhanzhi WU Zhengwei PAN Yu ZHANG Ying School of Science Xi'an Shiyou University Shaanxi Key Laboratory of Measurement and Control Technology for Oil and Gas Wells

Broadband and perfect terahertz absorber based on multilayer metamaterial using cross-ring patterned structures is proposed and investigated. The structure of the absorber is double absorption layers consisting of a chromium cross ring and eight isosceles right triangles. The unique structure of the double absorbing layers excites the electric dipole multimode resonance, giving rise to high absorption performance. Meanwhile, the influence of construal parameters on absorber behavior is also discussed. The numerical results show that the absorption achieves over 90% ranging from 2.45 THz to 6.25 THz and 99% absorption in the range of 3.7—5.3 THz. The realization of broadband and perfect absorber is described using the impedance matching principle. It is obviously found that the absorber is insensitive to the high angle of incidence for both transverse electric(TE) and transverse magnetic(TM) polarizations. Compared with the former reports, this absorber has remarkable improved absorption efficiency and smaller period. The terahertz absorber may be found applications in the fields of energy capture and thermal detection.

关键词： Metamaterials

A Hierarchical Ensemble Learning Framework for Energy-Efficient Automatic Train Driving

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2019年第2期24卷 226-237页

作者： Guohua xi xibin Zhao yan Liu jin Huang yangdong Deng CRRC Corporation Limited School of Software and Key Laboratory for Information System Security Ministry of Education (KLISS)/Beijing National Research Center for Information Science and Technology (BNRist) Tsinghua University

Railway transportation plays an important role in modern society. As China's massive railway transportation network continues to grow in total mileage and operation density, the energy consumption of trains becomes a serious concern. For any given route, the geographic characteristics are known a priori, but the parameters(e.g., loading and marshaling) of trains vary from one trip to another. An extensive analysis of the train operation data suggests that the control gear operation of trains is the most important factor that affects the energy consumption. Such an observation determines that the problem of energy-efficient train driving has to be addressed by considering both the geographic information and the trip parameters. However, the problem is difficult to solve due to its high dimension, nonlinearity, complex constraints, and time-varying characteristics. Faced with these difficulties, we propose an energy-efficient train control framework based on a hierarchical ensemble learning approach. Through hierarchical refinement, we learn prediction models of speed and gear. The learned models can be used to derive optimized driving operations under real-time requirements. This study uses random forest and bagging – REPTree as classification algorithm and regression algorithm, respectively. We conduct an extensive study on the potential of bagging, decision trees, random forest, and feature selection to design an effective hierarchical ensemble learning framework. The proposed framework was testified through simulation. The average energy consumption of the proposed method is over 7% lower than that of human drivers.

关键词： machine learning energy efficiency train driving system feature selection ensemble learning

Preparation and Performance of HGM/PPENK-based High Temperature-resistant Thermal Insulating Coatings

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2021年第6期39卷 770-778,I0008页

作者： Lei Song Li-Shuai Zong jin-yan Wang xi-Gao Jian State Key Laboratory of Fine Chemicals Department of Polymer Science and MaterialsSchool of Chemical EngineeringDalian University of TechnologyDalian 116024China

Novel high temperature-resistant coatings with high mechanical strength and thermal-insulating performance were prepared with poly(ether nitrile ketone)(PPENK)resin as matrix and hollow glass microspheres(HGMs)as thermal-insulating *** corresponding mechanical and thermal-insulating study indicated that the mechanical properties of the coatings decreased with the increase of HGM content,and were improved after surface modification of HGM by KH570 resulting in enhancement of interaction between HGM and PPENK *** thermal conductivity of HGM/PPENK thermal-insulating coating decreased with the increase of HGM content and coating thickness,along with the decrease of the true *** also showed slight increase trend due to HGMs surface *** HGM/PPENK coating filled with modified HGMs showed better thermal resistance than that of unmodified HGM/PPENK *** thermal decomposition temperature at 5%weight loss of the coating containing modified HGMs was 10°C lower than that of pure PPENK,and 40°C higher than that of neat HGM/PPENK *** coating exhibited commendable appearance after 400°C for 30 *** merits of HGM/PPENK-based thermal coatings obviously demonstrated promising prospect in thermal protection fields.

关键词： Coatings Temperature-resistant HGM/PPENK Thermal conductivity Mechanical properties

Microstructure and Mechanical Properties of High Manganese TRIP Steel

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2012年第4期19卷 57-62页

作者： ZHAO jin-long xi yan SHI Wen LI Lin College of Material Science and Engineering Shanghai University Shanghai 200072 China

Microstructure evolution and mechanical properties of newly designed 0.1C-6Mn-0.5Si-1Al TRIP-aided steels under different annealing conditions and the effects of matrix microstructure before intercritical annealing on the final microstructure were studied by means of X-ray diffraction（XRD）,scanning electron microcopy（SEM）,dilatometric simulation,optical microstructure（OM） and tensile testing in this *** experimental results indicate that the TRIP steel with Mn of 6% could form a considerable amount of retained austenite with good TRIP effect after a simple intercritical annealing treatment,and the matrix microstructure before intercritical annealing treatment can greatly affect the final *** original microstructure of the ferritic matrix steel was eliminated,while annealed martensite was remained from the martensite matrix steel under the same intercritical annealing conditions

关键词： high manganese TRIP steel intercritical annealing microstructure mechanical properties

河南省新乡市儿童家庭自我药疗行为的潜类别分析

在线全文

学校读者我要写书评

暂无评论

现代预防医学 2021年第7期48卷 1193-1197页

作者：任静朝席金彦张乘鹏郝鹏飞武首熏赵海涛李玉春新乡医学院公共卫生学院新乡市疾病预防与控制中心

目的通过潜类别分析了解河南省儿童家庭自我药疗行为,并分析不同潜类别组的人群特征,为开展有针对性的宣传教育提供依据。方法招募河南省新乡市及其所辖县城、乡镇18岁以上家有儿童的女性作为调查对象。利用分层随机抽样方法,在新乡市... 详细信息

目的通过潜类别分析了解河南省儿童家庭自我药疗行为,并分析不同潜类别组的人群特征,为开展有针对性的宣传教育提供依据。方法招募河南省新乡市及其所辖县城、乡镇18岁以上家有儿童的女性作为调查对象。利用分层随机抽样方法,在新乡市所辖县中,利用抽签随机抽样法随机抽取2个县城,再在这2个县所辖乡镇中利用抽签随机抽样法各随机抽取2乡镇,在市区、县城及乡镇的热闹地方通过拦截方式获得调查对象。共收回有效问卷849份。利用SAS外挂模块Proc LCA进行潜类别分析,不同潜类别组人群特征利用构成比进行描述,利用卡方检验进行不同潜类别组间的差异性分析。结果 27.21%对象的儿童家庭自我药疗行为不良,17.20%对象的儿童家庭自我药疗行为良好,10.60%的对象购药行为不良,44.99%的对象服药行为不良。自我药疗行为良好组与自我药疗行为不良组和购药行为不良组的相关知识得分存在统计学差异（P0.05）。与市区居民相比,县城和农村居民购药行为较差（χ;=13.04,P=0.0045）;祖辈给儿童自我用药行为较差（χ;=9.87,P=0.0197）;初中及以下教育程度者儿童家庭自我药疗行为较差（χ;=11.57,P=0.0090）。结论河南省儿童家庭自我药疗行为不良者较多,尤其是服药行为不良者众多;县城和农村居民、祖辈、受教育程度低者给儿童用药时具有较多不良行为,应加强对这部分人群的健康教育。

关键词：潜类别分析儿童自我药疗

计算机视觉技术赋能大学英语课堂展示中的学习投入研究

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

新疆师范大学学报（哲学社会科学版） 2025年第2期46卷 144-151页

作者：谭苏燕王晋军广州大学外国语学院广东广州510010

学习投入是预测学习者学习效果的重要指标,学术界对其与课堂展示间的相关性研究鲜有涉猎。文本以某综合性大学303名非英语专业本科生为研究对象,采用人工智能与计算机视觉技术模型YOLOv7对大学英语课堂中的课堂展示实录进行学习投入多... 详细信息

学习投入是预测学习者学习效果的重要指标,学术界对其与课堂展示间的相关性研究鲜有涉猎。文本以某综合性大学303名非英语专业本科生为研究对象,采用人工智能与计算机视觉技术模型YOLOv7对大学英语课堂中的课堂展示实录进行学习投入多模态数据分析,并辅以问卷调查,形成双向印证。研究发现,学生课堂展示中的行为投入、认知投入和情感投入值均等于或高于3.78,投入结果均值达4.01,说明学生在课堂展示中的学习投入情况良好。此外,不同时段课堂展示对学生行为投入的影响显著,学生专注度及参与度在课堂前10分钟的课堂展示中效果最佳。文本为课堂展示的有效性提供了智能化、多模态、多维度的实证支持,为课堂教学的数智技术应用提供了新视角。

关键词：大学英语课堂展示学习投入计算机视觉技术展示时段

在线全文

学校读者我要写书评

暂无评论

磁性螯合树脂的悬浮缩聚合成及吸附性能研究

武汉理工大学学报 2004年第11期26卷 1-4页

作者：李曦靳艳巧张超灿武汉理工大学理学院武汉430070

用聚乙烯醇作分散剂 ,以γ- Fe2 O3磁粉为载体、通过聚环氧氯丙烷与己二胺进行悬浮缩聚反应 ,合成了一种新型的磁性螯合树脂 ,并研究了它对过渡金属离子的吸附性能。结果表明 ,该种树脂在 p H=4～ 6的酸度范围内对 Cd2 + 和Pb2 + 等金... 详细信息

用聚乙烯醇作分散剂 ,以γ- Fe2 O3磁粉为载体、通过聚环氧氯丙烷与己二胺进行悬浮缩聚反应 ,合成了一种新型的磁性螯合树脂 ,并研究了它对过渡金属离子的吸附性能。结果表明 ,该种树脂在 p H=4～ 6的酸度范围内对 Cd2 + 和Pb2 + 等金属离子有良好的吸附性。对混合离子的吸附性能也进行了研究 ,各金属离子吸附性能有所不同。

关键词：磁性螯合树脂吸附悬浮缩聚金属离子

沉积温度对氮化铝压电薄膜性能影响及机制分析

在线全文

学校读者我要写书评

暂无评论

光电子·激光 2025年第1期36卷 107-112页

作者：郭燕刘小军王进南京理工大学泰州科技学院天津三安光电有限公司

高频光电通信器件对压电材料特性要求越来越高，氮化铝（AlN）薄膜由于其优异的压电特性而备受关注，高取向高压电AlN薄膜沉积工艺优化成为其应用拓展的瓶颈技术之一，众多制备工艺参数中温度是影响AlN薄膜晶格取向的关键参数之一。本... 详细信息

高频光电通信器件对压电材料特性要求越来越高，氮化铝（AlN）薄膜由于其优异的压电特性而备受关注，高取向高压电AlN薄膜沉积工艺优化成为其应用拓展的瓶颈技术之一，众多制备工艺参数中温度是影响AlN薄膜晶格取向的关键参数之一。本文采用磁控溅射的方法沉积AlN薄膜，研究了沉积温度对AlN薄膜晶体取向及压电性能的影响，X射线衍射（X-ray diffraction, XRD）测试结果表明，250℃下可获得（100）取向AlN,300℃下AlN则优先（002）取向；压电测试结果表明，250℃下压电常数d*33达最大值0.79 V,表现出较优的压电特性。基于原子力显微镜（atomic force microscopy, AFM）结果及温度对价键稳定性影响分析探索了温度对其生长的影响机制。

关键词：氮化铝(AlN) 衬底温度取向生长压电特性

经腹与经会阴超声联合应用诊断前置胎盘的临床价值

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

新疆医科大学学报 2009年第8期32卷 1147-1148页

作者：张喜锦董雁王春霞新疆医科大学第五附属医院超声科武警兵团指挥部医院门诊部新疆乌鲁木齐830000

目的:探讨经腹及经腹联合经会阴超声诊断前置胎盘的临床价值。方法:回顾性分析76例孕妇分娩后临床证实为前置胎盘的超声和临床资料。结果:经腹部超声检查诊断前置胎盘符合率为86.84%,经腹联合经会阴超声诊断前置胎盘符合率为96.05%,2种... 详细信息

目的:探讨经腹及经腹联合经会阴超声诊断前置胎盘的临床价值。方法:回顾性分析76例孕妇分娩后临床证实为前置胎盘的超声和临床资料。结果:经腹部超声检查诊断前置胎盘符合率为86.84%,经腹联合经会阴超声诊断前置胎盘符合率为96.05%,2种诊断方法的诊断符合率比较差异具有统计学意义(X^2=3.84,P<0.05)。结论:经腹与经会阴超声联合应用能明显提高前置胎盘的诊断符合率,给临床提供重要信息,值得推广。

关键词：经腹经会阴超声诊断前置胎盘