检索结果-南通市图书馆

A New Sparse Reco.ery Method for the Inverse Aco.stic Scattering Problem

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2020年第1期36卷 49-66页

作者： Chang-long WANG Jun-xiong JIA Ji-gen PENG Shou-jin LIN Ministry Key Laboratory of Electronic Information co.ntermeasure and Simulation Xidian UniversityXi'an 710049China School of Mathematics and Statistics Xi’an Jiaotong UniversityXi’an 710049China School of Mathematics and Information Science Guangzhou UniversityGuangzhou 510006China lmtor intellignet equipment co. LtdNo.5 Fengsheng RoadZhongshanChina

Based on sparse information reco.ery,we develop a new method for locating multiple multiscale aco.stic ***,with the prior information of the scatterers’shape,we reformulate the location identification problem into a sparse information reco.ery model which brought the power of sparse reco.ery method into this type of inverse scattering ***,the new model can advance the judgment of the existence of alternative scatterers and,in the meantime,co.clude the number and locating of each existing ***,as well known,the co.e model(l0-minimization)in sparse information reco.ery is an NP-hard *** to the characteristics of the proposed sparse model,we present a new substitute method and give a detailed theoretical analysis of the new substitute *** on the properties of the new model,we co.struct a basic algorithm and an improved ***,we verify the validity of the proposed method through two numerical experiments.

关键词： sparse reco.ery aco.stic scatterer l0-minimization substitute function

Enhanced Beam-forming Technique

在线全文

学校读者我要写书评

暂无评论

China co.munications 2009年第2期6卷 144-149页

作者： Rakesh Tamrakar Datang Mobile Teleco.munications equipment co. Ltd

Beam-forming technique with small-spaced-array is based on the antenna （e.g. 0.5A）, known as smart antenna. The smart antenna array can generate directional beam towards the designated user more effectively than the antenna with largespaced-array （e.g. lOA） and thus obtain significant array gain. In network deployment and the testing, we observed that smart antenna enlarged the co.- erage, increased system capacity thus lowering the initial investment for operators, and at the same time flexible network co.figuration,

关键词：通信技术波束智能天线网络配置安全技术

Prefix co.e Translation by Mapping

在线全文

学校读者我要写书评

暂无评论

Journal of co.puter Science & Technology 1994年第2期9卷 175-181页

作者：蒋贤春 Beijing Stone Office equipment Technology co. LTD. Beijing

This paper introduces a new way of prefix co.e translation. It helps to finish the whole translation by mapping once (only one co.parison instruction is needed for getting the length of prefix co.e), and returns the original data and the length of prefix co.e element. The deco.ing time is only about four times as many as the time accessing original data directly.

关键词： Prefix co.e R-optimum-tree deco.e Huffman algorithm

A Novel Vibration-Based Self-Adapting Method to Acquire Real-Time Following Distance for Virtually co.pled Trains

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2025年第1期 27-39页

作者： Qinglai Zhang Jianmin Gao Qing Wu Qinglie He Libin Tie Wanming Zhai Shengyang Zhu State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong University IEEE Centre for Railway Engineering Central Queensland University National Energy Railway equipment co. LTDNational Energy Group

Virtual co.pling(VC) is an emerging technology for addressing the shortage of rail transportation capacity. As a crucial enabling technology, the VC-specific acquisition of train information, especially train following distance(TFD), is *** this paper, a novel method is proposed to acquire real-time TFD by analyzing the vibration response of the front and following trains, during which only onboard accelerometers and speedometers are required. In co.trast to the traditional arts of train positioning, this method targets a relative position between two adjacent trains in VC operation, rather than the global positions of the trains. For this purpose, an adaptive system co.taining three strategies is designed to co.e with possible adverse factors in train operation. A vehicle dynamics simulation of a heavy-haul railway is implemented for the evaluation of feasibility and performance. Furthermore, a validation is co.ducted using a set of data measured from in-service Chinese high-speed trains. The results indicate the method achieves satisfactory estimation accuracy using both simulated and actual data. It has favorable adaptability to various uncertainties possibly enco.ntered in train operation. Additionally, the method is preliminarily proven to adapt to different loco.otive types and even different rail transportation modes. In general, such a method with good performance, low-co.t, and easy implementation is promising to apply.

关键词：

Effects of Bending-torsional Duct-induced Swirl Distortion on Aerodynamic Performance of a Centrifugal co.pressor

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Thermal Science 2017年第2期26卷 97-106页

作者： HOU Hongjuan WANG Leilei WANG Rui YANG Yanzhao co.lege of Mechanical and equipment Engineering Hebei University of Engineering Kangyue Technology co. Ltd

A turbocharger co.pressor working in co.mercial vehicles, especially in some passenger cars, often works together with some pipes with co.plicated geometry as an air intake system, due to limit of available space in internal co.bustion engine co.partments. These pipes may generate various distortions of physical parameters of the air at the inlet of the co.pressor and therefore the co.pressor aerodynamic performance deteriorates. Sometimes, the turbocharging engine fails to work at some operation points. This paper investigates the effects of various swirl distortions induced by different bending-torsional intake ducts on the aerodynamic performance of a turbocharger co.pressor by both 3D numerical simulations and experimental measurements. It was found that at the outlet of the pipes the different inlet ducts can generate different swirl distortions, twin vortices and bulk-like vortices with different rotating directions. Among them, the bulk-like vortices not only affect seriously the pressure distribution in the impeller domain, but also significantly deteriorate the co.pressor performance, especially at high flow rate region. And the rotating direction of the bulk-like vortices is also closely associated with the efficiency penalty. Besides the efficiency, the transient flow rate through a single impeller channel, or the asymmetric mass flow crossing the whole impeller, can be influenced by two disturbances. One is from the upstream bending-torsional ducts; other one is from the downstream volute.

关键词： bending-torsional duct centrifugal co.pressor swirl distortion relative flow angle

Vision, application scenarios, and key technology trends for 6G mobile co.munications

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2022年第5期65卷 5-31页

作者： Zhiqin WANG Ying DU Kejun WEI Kaifeng HAN Xiaoyan XU Guiming WEI Wen TONG Peiying ZHU Jianglei MA Jun WANG Guangjian WANG Xueqiang YAN Jiying XIANG He HUANG Ruyue LI Xinhui WANG Yingmin WANG Shaohui SUN Shiqiang SUO Qiubin GAO Xin SU China Academy of Information and co.munications Technology Huawei Technologies Canada co. Ltd. Huawei Technologies co. Ltd.(Hangzhou) Huawei Technologies co. Ltd.(Chengdu) Huawei Technologies co. Ltd.(Shanghai) ZTE co.poration Datang Mobile co.munications equipment co. Ltd.

With the global co.mercialization of the fifth-generation(5G) network, many co.ntries, including China, USA, European co.ntries, Japan, and Korea, have started exploring 6G mobile co.munication network, following the tradition of “planning the next while co.mercializing one generation”. Currently,studies on 6G networks are at the infancy stage. Research on the vision and requirements for 6G is still ongoing, and the industry is yet to clarify the key enabling technologies for 6G. However, 6G will certainly build on the success of 5G. Therefore, developing high-quality 5G networks and seamlessly integrating 5G with verticals are the priorities before 2030, when 6G is projected to be co.mercialized. Also, global 5G standards will keep evolving to better support vertical applications. As a milestone, the Third-Generation Partnership Project(3GPP) published Release 16 in July 2020, which co.tinuously enhanced the capabilities of mobile broadband service based on Release 15 and realized the support for low-delay and high-reliability applications, such as Internet of Vehicles and industrial Internet. Currently, 3GPP is working on Releases 17 and 18, focusing on meeting the demands of medium-and high-data-rate machine co.munication with low-co.t and high-precision positioning, which will be published in June 2022. Thus, 6G networks will further expand the application fields and sco.e of the Internet of Things to acco.modate those services and applications that are beyond the capabilities of 5G networks. Herein, we present our vision, application scenarios,and key technological trends for 6G networks. Furthermore, we propose several future research opportunities in 6G networks with regard to industrialization and standardization.

关键词： sixth-generation (6G) mobile co.munication holographic radio technology 6G vision application scenarios of 6G terahertz co.munication integrated sensing and co.munication integrated intelligence and co.munication ultra-massive MIMO reco.figurable intelligent surface co.frequency co.time full-duplex

Numerical simulation and structure improvement of double throttling in a high parameter pressure reducing valve

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第2期14卷 137-146页

作者： Zhi-jiang JIN Lin WEI Li-long CHEN Jin-yuan QIAN Ming ZHANG Institute of Chemical Machinery and Process equipment Zhejiang University Hangzhou Worldwides Valve co. Ltd.

In this paper, a new pressure reducing valve （PRV） with an orifice plate is proposed. The main objective is to explain the mechanisms of pressure reduction and energy co.version in the new PRV. A numerical simulation method was used to investigate the PRV internal flow field and to analyze the throttling effects of the orifice plate and the transform of thermal parameters as outlet pressure, outlet temperature, velocity, and superheat. A structure improvement method for the valve body and orifice plate is put forward to reduce energy loss. The governing equations for internal flow numerical simulation are co.posed of the co.tinuity, momentum, energy and k-e transport equations, based on isotropic eddy visco.ity theory. Different valve plug displacement models were built to describe the double throttling process. Our analysis shows that the steam pressure drops twice and the degree of superheat increases. There are also lots of eddies which clog the flow channel and disturb the steam flow in the valve cavity after the valve plug and the outlet cavity. After modifying the structure, the numerical results show a better performance of steam flow.

关键词： Numerical simulation Pressure and temperature reducing system Pressure reducing valve (PRV) Double throttling Structural improvement

Evolution of insoluble eutectic Si particles in anodic oxidation films during adipic–sulfuric acid anodizing processes of ZL114A aluminum alloys

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2015年第3期22卷 302-308页

作者： Lei Hua Jian-hua Liu Song-mei Li Mei Yu Lei Wang Yong-xin Cui School of Materials Science and Engineering Beihang University Beijing Xinghang Mechanical-electrical equipment co. LTD.

The effects of insoluble eutectic Si particles on the growth of anodic oxide films on ZL114A aluminum alloy substrates were in- vestigated by optical microsco.y （OM） and scanning electron microsco.y （SEM）. The anodic oxidation was performed at 25℃ and a co.- stant voltage of 15 V in a solution co.taining 50 g/L sulfuric acid and 10 g/L adipic acid. The thickness of the formed anodic oxidation film was approximately 7.13 μm. The interpore distance and the diameters of the major pores in the porous layer of the film were within the ap- proximate ranges of 10~20 nm and 5-10 nm, respectively. Insoluble eutectic Si particles strongly influenced the morphology of the anodic oxidation films. The anodic oxidation films exhibited minimal defects and a uniform thickness on the ZL114A substrates; in co.trast, when the front of the oxide oxidation films enco.ntered eutectic Si particles, defects such as pits and non-uniform thickness were observed, and pits were observed in the films.

关键词： aluminum alloys anodizing anodic oxidation thin films eutectic silico. particles

Pressure Angle in Parallel Mechanisms: From Planar to Spatial

在线全文

学校读者我要写书评

暂无评论

Transactions of Tianjin University 2016年第5期22卷 411-418页

作者： Zhao Qing Mei Jiangping Song Tao Liu Songtao Key Laboratory of Mechanism Theory and equipment Design of Ministry of Education Tianjin University Chenxing Automation & equipment co. Ltd

This paper presents the evolution process of pressure angles from planar parallel mechanisms to spatial parallel mechanisms. Manipulability and co.dition number, which are frequently used in the optimum design of parallel mechanisms, are introduced from serial robots at first. Then, both theoretical analysis and practical experiences demonstrate that these co.cepts seem imperfect when they are used in parallel mechanisms. For this reason, this paper introduces the pressure angles in planar 4-bar mechanisms to spatial parallel mechanisms, which include redundant parallel mechanisms. Two kinds of pressure angles extracted from the determinant of direct and indirect Jaco.ian matrices are investigated. Moreover, two co.prehensive and visible global performance indices are defined, showing the advantages in evaluating the workspace, singularity and motion/force transmission capabilities. With a 2-DOF planar and a 3-DOF spatial parallel mechanism as examples, the application of the performance indices is investigated and co.pared with the co.dition number at last. The proposed co.cept can be extended to other spatial parallel mechanisms.

关键词： pressure angle performance evaluation global performance index parallel mechanism