检索结果-南通市图书馆

Fuzzy tracking control design for hypersonic vehicles via T-S model

在线全文

学校读者我要写书评

暂无评论

science china(information sciences) 2011年第3期54卷 521-528页

作者： GAO DaoXiang 1 & SUN ZengQi 2 1 School of technology, beij.ng Forestry University, beij.ng 100083, china 2 State Key laboratory of Intelligent technology and System, Department of Computer science and technology, tsinghua University, beij.ng 100084, china 1. School of technology Beijing Forestry University Beijing 100083 China2. State Key Laboratory of Intelligent Technology and System Department of Computer Science and Technology Tsinghua University Beijing 100084 China

The main focus of this paper is on designing a T-S fuzzy controller for the hypersonic vehicle. The longitudinal dynamics of the vehicle are studied using time-scale decomposition to reduce the complexity of T-S modeling. The dynamic inversion with PI control technique is applied for the slow dynamics to derive the flight path angle command and throttle setting by taking the pilot altitude and velocity command as its inputs. The T-S fuzzy controller is designed for the fast dynamics to derive the elevator deflection to track the flight path angle command. The discrepancy between the T-S model and real vehicle model is considered by using sliding mode control for the system stability. Simulation results are included to show the effectiveness of the controller.

关键词： fuzzy control T-S model sliding mode control hypersonic vehicle

Bionic Design and Finite Element Analysis of Elbow in Ice Transportation Cooling System

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 Bionic Engineering 2010年第3期7卷 301-306页

作者： Dejun Miao~(1,2), Xiuhua Sui~3, Linjing Xiao~3 1. Key laboratory of Mine Hazard Prevention and Control (Ministry of Education, china), Shandong University of science and technology, Qingdao 266510, P. R. china 2. School of Architecture, tsinghua University, beij.ng 100084, P. R. china 3. College of Mechanical and Electronic Engineering, Shandong University of science and technology, Qingdao 266510, P. R. china [a] Key laboratory of Mine Hazard Prevention Control (Ministry of Education China) Shandong University of Science technology Qingdao 266510 P. R. China [b] School of Architecture Tsinghua University Beijing 100084 P. R. China [c] College of Mechanical Electronic Engineering Shandong University of Science technology Qingdao 266510 P. R. China

With the increase in mining depth, mine heat harm has appeared to be more prominent. The mine heat harm could be resolvedor reduced by ice refrigeration. Thus, ice transportation through pipeline becomes a critical problem; typically flowresistance occurs in the elbow. In the present study, according to the analysis of the surface morphology of fish scale, abiomimetic functional surface structure for the interior wall of elbow is designed. Based on the theory of liquid-solid two phaseflow, a CFD numerical simulation of ice-water mixture flowing through the elbow is carried out using finite element *** experiments of pressure drop and flow resistance for both bionic and common elbows are conducted to test theeffect of the bionic elbow on flow resistance reduction. It is found that with the increase in the ice mass fraction in the ice-watermixture, the effect of bionic elbow on resistance reduction becomes more obvious.

关键词： bionic elbow two phase flow ice transportation flow resistance reduction pressure loss

Dense coding scheme using superpositions of Bell-states and its NMR implementation

在线全文

学校读者我要写书评

暂无评论

science china(Physics,Mechanics & Astronomy) 2005年第1期48卷 57-67页

作者： ZHAng Jingfu, XIE Jingyi, DEng Zhiwei & LU Zhiheng Key laboratory for Quantum information and Measurements, Department of Physics, tsinghua University, beij.ng 100084, china Center for Quantum information, tsinghua University, beij.ng 100084, china Department of Materials science and Engineering, beij.ng Normal University, beij.ng 100875, china Testing and Analytical Center, beij.ng Normal University, beij.ng 100875, china Department of Physics, beij.ng Normal University, beij.ng 100875, china 1. Key laboratory for Quantum information and Measurements Department of Physics Tsinghua University 100084 Beijing China 2. Center for Quantum information Tsinghua University 100084 Beijing China 3. Department of Materials science and Engineering Beijing Normal University 100875 Beijing China 4. Testing and Analytical Center Beijing Normal University 100875 Beijing China 5. Department of Physics Beijing Normal University 100875 Beijing China

Dense coding using superpositions of Bell-states is proposed. The generalized Grover's algorithm is used to prepare the initial entangled states, and the reverse process of the quantum algorithm is used to determine the entangled state in the decoding measurement. Compared with the previous schemes, the superpositions of two Bell-states are exploited. Our scheme is demonstrated using a nuclear magnetic resonance (NMR)quantum computer. The corresponding manipulations are obtained. Experimental results show a good agreement between theory and experiment. We also generalize the scheme to transmit eight messages by introducing an additional two-state system.

关键词： dense coding, superpositions of Bell-states, generalized Grover's algorithm, nuclear magnetic res-onance, quantum computer.

Spin electromagnetic field and dipole:A localized and quantized field

在线全文

学校读者我要写书评

暂无评论

science Bulletin 2011年第14期 1472-1481页

作者： FEng ZhengHe national laboratory of information science and technology,Department of Electronic Engineering,tsinghua University,beij.ng 100084,china

This paper investigates the structure of a spin electromagnetic (EM) field and its various physical properties.A spin EM field is an intrinsic mode of free space,which satisfies the spin equations derived from Maxwell equations.A spin mode has two basic properties:the spin along its axis and the localization of electromagnetic *** source and EM structure of this electric and magnetic mode are described in detail in this *** distributed charge and current of a spin mode can be integrated to obtain the electric and magnetic moment,and they can be treated as the electromagnetic dipole.A spin mode possesses both wave and particle properties:a wave number,angular frequency and characteristic speed are its wave parameters;an intrinsic radius,energy and angular momentum are its dynamic *** former is analogous to an EM resonant mode;the latter is similar to the behavior of a particle with intrinsic *** are two kinds of electric modes present,one can be expressed through a pair of charges,and the other can be expressed by a magnetic *** both have the same electric moment,but have different divergence properties.

关键词： spin electromagnetic field spin equation distribution source dipole moment intrinsic radius quantized Plank constant

Orthogonally linear polarized lasers (I)——principle and devices

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural science:Materials International 2005年第7期15卷 586-595页

作者： ZHAng Shulian and XU Ting (State Key laboratory of Precision Measurement technology and Instruments, Department of Precision Instruments, tsinghua University, beij.ng 100084, china) State Key laboratory of Precision Measurement technology and Instruments Department of Precision Instruments Tsinghua University Beijing 100084 China

Two kinds of orthogonally polarized lasers, i. e. Zeeman dual-frequency lasers and four-frequency ring lasers (laser gyros) have been developed since the invention of lasers, in which circularly polarized lights oscillate. This paper summarizes recent progress of the study on orthogonally linear polarized lasers with the standing wave cavity. Firstly, the expression of producing orthogonally linear polarized lights in standing wave cavity, i. e. laser frequency splitting, is given. Almost all the birefringence effects made in laser cavity are used to produce orthogonally linear polarized lights. The effect includes quartz crystal birefringence effect, calcite birefringence effect, stress (photo-elastic) birefringence effect and electro-optical birefringence effect. Secondly, several physical phenomena of orthogonally linear polarized lasers are discovered such as aberrance of frequency splitting curves caused by optical activity of quartz crystal, order-passing of longitudinal modes with frequency splitting and strong modes competition. Finally, because the traditional Zeeman dual frequency laser cannot output frequency difference larger than 3 MHz, the approaches of obtaining larger frequency difference are studied. The sequential results, several kinds of orthogonally polarized lasers, are described, such as birefringence dual frequency lasers outputting a frequency difference from 40 MHz to hundreds of megahertz, birefringence-Zeeman dual frequency lasers outputting a frequency difference from 1 MHz to hundreds of megahertz, the LD pumped YAG birefringence dual frequency laser outputting frequency difference of several gigahertz, and the lasers whose longitudinal mode spacing is c/4L instead of c/2L .

关键词： orthogonally polarized laser dual frequency laser intra-cavity birefringence Zeeman effect photo-elastic birefringence electro-optical birefringence frequency splitting.

A Feedback Scheme for Fountain Codes Based Transport Protocol in Space Communications

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

china Communications 2015年第8期12卷 62-72页

作者： XIng Yanling GE Ning tsinghua national laboratory for information science and technology Department of Electronic Engineering Tsinghua University Aerospace Communications and Terminal Application Technologies Engineering laboratory in Shenzhen

This paper proposed a practical- feedback scheme for fountain codes based transportprotocol in space communications. In the proposed scheme, the sender is signaled by two types of acknowledgment （ACK） *** decoding, packet loss probability isestimated on the receiver side and encapsulated intoa soft ACKand sent to the *** decoding,decoding results are encapsulated into hard ACKsandsent to the sender. There are two contributionsin the proposed scheme： 1. Empl layer calculation instead layer statistics to estimate oying physical of application the packet loss probability of space channel, which can improvethe accuracy and practicality. 2. A cascade overhead-failure probability relationship between the sender and the receiver has been analyzed to help determine the exact numberof packetsneeded byfountain *** show that for space communications,compared with the existing space transport protocols, fountain codes based transport protoeolwith the proposed schemecan not only ensure transmission reliability, but also greatly improvelink utilization.

关键词： fountain code feedback spacecommunication packet loss probabilityestimation transport protocol

Optimizing write operation on replica in data grid

在线全文

学校读者我要写书评

暂无评论

science china(information sciences) 2011年第1期54卷 1-11页

作者： XU PengZhi,WU YongWei,HUAng XiaoMeng, YAng GuangWen & ZHEng WeiMin Department of Computer science and technology,tsinghua University,beij.ng 100084,china 1. Department of Computer science and technology Tsinghua University Beijing 100084 China

Replication technique can improve access performance and data availability of data grid systems. So far,most related work on data replication in data grid systems focuses on read-only *** write operations have been widely used in practice,its optimization problem has not been suciently *** this paper,we show that write requests from users can be processed by a nearest site,regardless of the location of latest written *** policy of write nearby instead of write to the latest replica can improve the performance of write operations,while inconsistency is caused between multiple ***,we propose two metadata management algorithms to make sure that users can retrieve up-to-date datasets at any *** extend OptorSim to support the implementation and evaluation of our *** results of simulation show that our scheme achieves performance gains up to 3.3 compared with WriteMaster scheme.

关键词： replication data grid simulation access latency

Effect of carbon source on the denitrification in constructed wetlands

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 Environmental sciences 2009年第8期21卷 1036-1043页

作者： LU Songliu, HU Hongying, SUN Yingxue, YAng Jia ESPC State Key Joint laboratory, Department of Environmental science and Engineering, tsinghua University, beij.ng 100084, china. [a]ESPC State Key Joint laboratory Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China

The ability of constructed wetlands with different plants in nitrate removal were investigated. The factors promoting the rates of denitrification including organic carbon, nitrate load, plants in wetlands, pH and water temperature in field were systematically investigated. The results showed that the additional carbon source （glucose） can remarkably improve the nitrate removal ability of the constructed wetland. It demonstrated that the nitrate removal rate can increase from 20% to more than 50% in summer and from 10% to 30% in winter, when the nitrate concentration was 30-40 rag/L, the retention time was 24 h and 25 mg/L dissolved organic carbon （DOC） was ploughed into the constructed wetland. However, the nitrite in the constructed wetland accumulated a little with the supply of the additional carbon source in summer and winter, and it increased from 0.15 to 2 mg/L in the effluent. It was also found that the abilities of plant in adjusting pH and temperature can result in an increase of denitrification in wetlands. The seasonal change may also impact the denitrification.

关键词： constructed wetland carbon source denitrification nitrate nitrite

Heuristic for no-wait flow shops with makespan minimization based on total idle-time increments

在线全文

学校读者我要写书评

暂无评论

science in china(Series F) 2008年第7期51卷 896-909页

作者： LI XiaoPing1,2 & WU Cheng3 1 School of Computer science & Engineering, Southeast University, Nanjing 210096, china 2 Key laboratory of Computer Network and information Integration (Southeast University), Ministry of Education, Nanjing 210096, china 3 Department of Automation, tsinghua University, beij.ng 100084, china 1. School of Computer science & Engineering Southeast University Nanjing 210096 China 2. Key laboratory of Computer Network and information Integration (Southeast University) Ministry of Education Nanjing 210096 China 3. Department of Automation Tsinghua University Beijing 100084 China

No-wait flow shops with makespan minimization are classified as NP-hard. In this paper, the optimization objective is equivalently transformed to total idle-time minimization. The independence relationship between tasks is analyzed, and objective increment properties are established for the fundamental operators of the heuristics. The quality of the new schedules generated during a heuristic is judged only by objective increments and not by the traditional method, which computes and compares the objective of a whole schedule. Based on objective increments, the time complexity of the heuristic can be decreased by one order. A seed phase is presented to generate an initial solution according to the transformed objective. Construction and improvement phases are introduced by experimental analysis. The FCH （fast composite heuristic） is proposed and compared with the most effective algorithms currently available for the considered problem. Experimental results show that the effectiveness of the FCH is similar to that of the best methods but requires far less computation time. The FCH can also be efficient in real time scheduling and rescheduling for no-wait flow shops.

关键词： no-wait flow shops heuristic makespan Tabu search