检索结果-南通市图书馆

The Journal of China Universities of Posts and Telecommunications 2016年第1期23卷 55-59页

作者： Kang Hongbo shen yu Institute of Electrical and Control Engineering Chang'an University College of Automation Xi'an University of Posts Communications School of Computer and Information Science Southwest University

In this paper, the influence of sampling intervals on the chattering in sliding mode （SM） control systems is considered. The describing function （DF） approach is employed to analyze the chattering characteristics in the sampling SM control. By the DF calculations and limit cycle existence conditions, an unstable limit cycle and two stable limit cycles are found in the SM control system. The frequencies and amplitudes of the two limit cycles can also be estimated by graphical calculations. The estimation accuracy of chattering parameters is evaluated by the simulations. The results of simulations show that the system could converge to a large and a small limit cycle from different initial conditions.

关键词： sampling interval chattering parameters describing function approach multiple limit cycle analysis

基于普适型GNSS的数据质量评估与水汽反演研究

在线全文

学校读者我要写书评

暂无评论

测绘通报 2024年第S1期 79-85页

作者：浦彦彦朱雪健刘世焕沈煜郜旭辉中交绿建(厦门)科技有限公司福建厦门361000 长安大学地质工程与测绘学院陕西西安710054

为确保普适型全球卫星导航系统(GNSS)接收机所在监测站的合理布设及数据处理结果的可靠性,需对普适型GNSS观测数据质量进行评估。为此,本文以安置在西安市不同环境下的普适型GNSS接收机实测数据为例,分别利用TEQC、ANUBIS和RINGO软件对... 详细信息

为确保普适型全球卫星导航系统(GNSS)接收机所在监测站的合理布设及数据处理结果的可靠性,需对普适型GNSS观测数据质量进行评估。为此,本文以安置在西安市不同环境下的普适型GNSS接收机实测数据为例,分别利用TEQC、ANUBIS和RINGO软件对观测数据质量进行了可视化对比分析;基于预处理后的普适型GNSS数据获取了大气可降水量(PWV)信息,并结合西安强降雨事件分析GNSS-PWV与降雨量的相关变化和内在联系。研究结果表明:普适型GNSS接收机所采集的观测数据质量较好,且北斗数据在遮挡环境下具有较好的抗干扰性。此外,利用普适型GNSS观测数据反演的PWV具有较好的精度,PWV在强降雨发生前会出现快速抬升的现象,在降雨期呈现随降雨量的增加而抬升,后随降雨量的减少而下降的趋势,PWV与强降雨事件具有较强的内在联系。

关键词：普适型GNSS TEQC软件 ANUBIS软件 RINGO软件数据质量大气可降水量

等级孔结构协同Fe改性提升ZSM-5分子筛催化苯甲醇烷基化性能

在线全文

学校读者我要写书评

暂无评论

高等学校化学学报 2024年第5期45卷 28-37页

作者：宋宇航刘湛吕佳敏余申李小云孙明慧陈丽华苏宝连武汉理工大学材料复合新技术国家重点实验室武汉430070 武汉理工大学硅酸盐建筑材料国家重点实验室武汉430070 那慕尔大学无机材料化学实验室那慕尔B-5000比利时

针对ZSM-5分子筛微孔扩散限制和催化活性位单一的问题,使用有序大孔-介孔碳模板为硬模板并结合原位引入金属策略,一步晶化合成了具有高结晶度、高比表面积的有序贯通大孔-介孔-微孔等级结构的Fe/ZSM-5分子筛单晶.通过X射线衍射(XRD)、紫... 详细信息

针对ZSM-5分子筛微孔扩散限制和催化活性位单一的问题,使用有序大孔-介孔碳模板为硬模板并结合原位引入金属策略,一步晶化合成了具有高结晶度、高比表面积的有序贯通大孔-介孔-微孔等级结构的Fe/ZSM-5分子筛单晶.通过X射线衍射(XRD)、紫外-可见光谱(UV-Vis)、H_(2)程序升温还原实验(H2-TPR)和X射线光电子能谱(XPS)等手段对催化剂中活性Fe的存在形式进行了表征.结果表明,该材料中位于离子交换位及铁氧八面体(六配位)的孤立Fe(III)是主要的氧化还原活性中心,当Fe负载量(质量分数)为1%时,苯甲醇转化率最高为59.3%,产物选择性为83.2%,最终收率达到49.3%,在循环使用5次后仍保持高催化活性.

关键词： ZSM-5分子筛等级结构过渡金属铁芳烃烷基化

Computational fluid dynamics simulations of respiratory airflow in human nasal cavity and its characteristic dimension study

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2008年第2期24卷 223-228页

作者： Jun Zhang Yingxi Liu Xiuzhen Sun shen yu Chi yu State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian 116024 China Department of Otorhinolaryngology the Second Affiliated Hospital of Dalian Medical University Dalian 116027 China

To study the airflow distribution in human nasal cavity during respiration and the characteristic parameters of nasal structure, three-dimensional, anatomically accurate representations of 30 adult nasal cavity models were recons- tructed based on processed tomography images collected from normal people. The airflow fields in nasal cavities were simulated by fluid dynamics with finite element software ANSYS. The results showed that the difference of human nasal cavity structure led to different airflow distribution in the nasal cavities and variation of the main airstream passing through the common nasal meatus. The nasal resistance in the regions of nasal valve and nasal vestibule accounted for more than half of the overall resistance. The characteristic model of nasal cavity was extracted on the basis of characteristic points and dimensions deduced from the original models. It showed that either the geometric structure or the airflow field of the two kinds of models was similar. The characteristic dimensions were the characteristic parameters of nasal cavity that could properly represent the original model in model studies on nasal cavity.

关键词： Nasal cavity Characteristic dimension Three-dimensional reconstruction Numerical simulation of flowfield Computational fluid dynamic Finite element method

Manufacture and Performance of Ionic Polymer-Metal Composites

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2007年第3期4卷 143-149页

作者： Min yu Hui shen Zhen-dong Dai Institute of Bio-inspired Structure and Surface Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 P. R. China

Ion-exchange Polymer Metal Composites （IPMC） are a new class of intelligent material that can be used effectively as actuators and artificial muscles. IPMC was fabricated and its displacement and force characteristics were investigated with respect to voltage, frequency and waveform of the controlling signal. A square waveform input generated slightly larger displacement and force than sinusoidal or triangular waveform. When the voltage was increased and the frequency was decreased, displacement and force were both increased. However, although the bending deformation of IPMC was large, the output force was much lower than we expected. Improvement of the force output is key and is the main obstacle to be overcome in order to make IPMC of practical use.

关键词： IPMC artificial muscle

在线全文

学校读者我要写书评

暂无评论

基于上转换纳米材料的免疫检测技术应用

生物化学与生物物理进展 2024年第2期51卷 355-368页

作者：黄惠威李丽华罗林沈玉栋雷红涛徐振林华南农业大学食品学院广东省食品质量安全重点实验室广州510642 华南师范大学未来科技研究院广州510631

免疫分析法具有简便、快速、准确等特点,广泛应用于医学、食品、环境等领域检测,将免疫分析方法与纳米材料相结合可以提高免疫分析的性能。与传统纳米材料相比,上转换纳米颗粒(upconversion nanoparticles,UCNPs)具有光稳定性好、发光... 详细信息

免疫分析法具有简便、快速、准确等特点,广泛应用于医学、食品、环境等领域检测,将免疫分析方法与纳米材料相结合可以提高免疫分析的性能。与传统纳米材料相比,上转换纳米颗粒(upconversion nanoparticles,UCNPs)具有光稳定性好、发光寿命长和狭窄及可调整的发射带等优秀的光学性质,与免疫分析相结合可显著降低背景噪声,提高分析灵敏度。本文简要介绍了UCNPs的发光机制,对UCNPs的合成和表面修饰方法进行了总结,并详细论述荧光共振能量转移、内滤效应、磁分离技术、上转化连接免疫吸附技术和上转换免疫层析技术五种基于UCNPs的免疫检测技术,最后对该技术所面临的挑战和前景进行总结和展望,以期为UCNPs免疫检测技术的发展提供理论指导。

关键词：上转换纳米颗粒合成方法表面修饰方法免疫检测技术

DEM/CFD modelling of the deposition of dilute granular systems in a vertical container

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2009年第23期54卷 4318-4326页

作者： yu shen GUO yu WU Chuan-yu School of Chemical Engineering University of Birmingham Edgbaston Birmingham B15 2TT UK

Deposition of granular materials into a container is a general industrial packing process. In this study, the deposition behaviour of dilute granular mixtures consisting of two types of particles that were of the same particle size but different particle densities in the presence of air was numerically analyzed using a coupled discrete element method (DEM) and computational fluid dynamics (CFD). Bilayer granular mixtures with light particles at bottom and heavy particles at top were first simulated. It was found that the presence of air significantly affected the flow behaviour of the bilayer mixtures. For the system with a relatively low initial void fraction, the air entrapped inside the container escaped through the dilated zones induced due to the friction between the powder bed and wall surfaces. The escaping air streams entrained light particles that were originally located at the bottom of the granular system. Consequently, these light particles were migrated to the top of the granular bed at the end of deposition process. More light particles were migrated when the deposition distance was increased. For the system with a high initial void fraction, some light particles penetrated into the top layer of heavy particles and created a mixing zone. Deposition of random mixtures with different initial void fractions was also investigated and the influence of initial void fraction on the segregation behaviour was explored as well. It was found that the increase of void fraction promoted segregation during the deposition in air. It was demonstrated that, for granular mixtures consisting of particles of different air sensitivities, the presence of air had a significant impact on the mixing and segregation behaviour during the deposition.

关键词：模拟系统颗粒沉积差价合约集装箱垂直稀释德国

Parallel Sensing in Metaverses: Virtual-Real Interactive Smart Systems for “6S” Sensing

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2022年第12期9卷 2047-2054页

作者： yu shen yuhang Liu Yonglin Tian Xiaoxiang Na School of Artificial Intelligence University of Chinese Academy of ScienceBeijing 100190China IEEE The State Key Laboratory for Management and Control of Complex Systems Chinese Academy of SciencesBeijing 100190China Department of Engineering University of CambridgeTrumpington StreetCB21PZUnited Kingdom

In the construction of Metaverses,sensors that are referred to as the“bridge of information transmission”,play a key *** functionality and efficiency of today’s sensors,which operate in a manner similar to physical sensing,are frequently constrained by their hardware and *** this research,we proposed the Parallel Sensing framework,which includes background,concept,basic methods and typical application of parallel *** our formulation,sensors are redefined as the integration of real physical sensors and virtual software-defined sensors based on parallel intelligence,in order to boost the performance of the *** sensor will have a parallel counterpart in the virtual world within the framework of parallel *** sensors serve as the brain of sensors and maintain the same properties as physical *** sensing allows physical sensors to operate in discrete time periods to conserve energy,while cloud-based descriptive,predictive,and prescriptive sensors operate continuously to offer compensation data and serve as *** better illustrate parallel sensing concept,we show some example applications of parallel sensing such as parallel vision,parallel point cloud and parallel light fields,both of which are designed by construct virtual sensors to extend small real data to virtual big data and then boost the performance of perception *** results demonstrate the effective of parallel sensing *** interaction between the real and virtual worlds enables sensors to operate actively,allowing them to intelligently adapt to various scenarios and ultimately attain the goal of“Cognitive,Parallel,Crypto,Federated,Social and Ecologic”6S sensing.

关键词： Parallel Sensing Parallel Intelligence CPSS Metaverses Virtual and Real Interaction “6S”Sensing.

基于仿真试验的地铁车站站台宽度设计方法及影响因素分析

在线全文

学校读者我要写书评

暂无评论

城市轨道交通研究 2024年第1期27卷 138-143页

作者：董晓春沈瑜耿天霜杨陶源郑宣传南京地铁建设有限责任公司南京210019 北京城建设计发展集团股份有限公司城市轨道交通绿色与安全建造技术国家工程研究中心北京100037

[目的]当前站台宽度设计计算方法存在客流预测精度较低、客流密度参数取值宽泛、选择依据不明晰、设计裕量缺少量化依据等问题,需对此提出改进,并基于仿真试验标定站台宽度设计的参数取值。[方法]以《地铁设计规范》的标准为依据,给出... 详细信息

[目的]当前站台宽度设计计算方法存在客流预测精度较低、客流密度参数取值宽泛、选择依据不明晰、设计裕量缺少量化依据等问题,需对此提出改进,并基于仿真试验标定站台宽度设计的参数取值。[方法]以《地铁设计规范》的标准为依据,给出站台服务水平分级标准,提出以站台服务水平为基准的单侧站台宽度设计方法。通过仿真试验对关键参数进行标定,对客运量与单侧站台峰值密度关系曲线最小二乘法拟合得到客流密度理论值与实际值的换算系数。考虑站台宽度的影响因素,对乘客滞留比例、乘客携带大件行李比例通过仿真试验进行客流换算测算,并得到相应条件下的站台宽度计算方法。对于考虑多因素影响的计算场景,设计正交试验对参数进行修正,得到最终的单侧站台宽度计算方法。[结果及结论]单侧站台实际峰值密度约为理论值的0.9倍;乘客滞留和乘客携带大件行李对单侧站台峰值密度的影响分别约相当于1.19和1.75倍的普通上下车乘客;当乘客滞留和乘客携带大件行李两个因素同时作用于单侧站台时,造成的影响高于单因素影响的叠加。

关键词：地铁车站站台宽度微观仿真影响因素

维普期刊数据库博看期刊