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Research on the estimation and reduction measures of antenna mode RCS of airborne phased array

Research on the estimation and reduction measures of antenna...

2011 4th IEEE International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications, MAPE 2011

作者： Liu, Yun You, Lizhi Aviation Key Laboratory of Science and Technology on Avionics Integrated Sensor System Simulation Radar and Avionics Institute of AVIC Wuxi China

ISBN: (纸本)9781424482665

In this paper, the scattering principium of airborne phased array antenna is discussed, and the antenna mode RCS of the two-dimensional array is estimated. Based on theoretical calculations, broadband matching, incline, manufacturing tolerances and other RCS reduction measures are researched. The results show that these stealth approaches have an obviously effect on the RCS reduction. © 2011 IEEE.

关键词： Antenna arrays Antenna radiation patterns Arrays Phased array RCS reduction measures Radar antennas Reflector antennas Scattering airborne phased array antenna airborne radar antenna mode RCS estimation antenna mode scattering antenna mode scattering antenna phased arrays broadband antennas broadband matching electromagnetic wave scattering manufacturing tolerances phased array radar radar cross-sections reduction two-dimensional array

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Existence and stability of multiple solutions to the gap equation

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Physical Review D 2012年第11期86卷 114001-114001页

作者： Kun-lun Wang Si-xue Qin Yu-xin Liu Lei Chang Craig D. Roberts Sebastian M. Schmidt Department of Physics Center for High Energy Physics and State Key Laboratory of Nuclear Physics and Technology Peking University Beijing 100871 China Institut für Kernphysik Forschungszentrum Jülich D-52425 Jülich Germany Argonne National Laboratory Physics Division Argonne Illinois 60439 USA Department of Physics Illinois Institute of Technology Chicago Illinois 60616-3793 USA Institute for Advanced Simulation Forschungszentrum Jülich and JARA D-52425 Jülich Germany

We argue by way of examples that, as a nonlinear integral equation, the gap equation can and does possess many physically distinct solutions for the dressed-quark propagator. The examples are drawn from a class that is successful in describing a broad range of hadron physics observables. We apply the homotopy continuation method to each of our four exemplars and thereby find all solutions that exist within the interesting domains of light current-quark masses and interaction strengths; and simultaneously provide an explanation of the nature and number of the solutions, many of which may be associated with dynamical chiral symmetry breaking. Introducing a stability criterion based on the scalar and pseudoscalar susceptibilities we demonstrate, however, that for any nonzero current-quark mass only the regular Nambu solution of the gap equation is stable against perturbations. This guarantees that the existence of multiple solutions to the gap equation cannot complicate the description of phenomena in hadron physics.

关键词： NONLINEAR integral equations HOMOTOPY equivalences HADRON interactions PARTICLES (Nuclear physics) -- Chirality STABILITY criterion

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Twin boundary spacing-dependent friction in nanotwinned copper

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Physical Review B 2012年第5期85卷 054109-054109页

作者： Junjie Zhang Yujie Wei Tao Sun Alexander Hartmaier Yongda Yan Xiaodong Li Center for Precision Engineering Harbin Insitute of Technology Harbin 150001 China State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China Interdisciplinary Centre for Advanced Materials Simulation (ICAMS) Ruhr University Bochum Stiepeler Strasse 129 (UHW) D-44801 Bochum Germany Department of Mechanical Engineering University of South Carolina 300 Main Street Columbia South Carolina 29208 USA

The deformation mechanisms of nanotwinned Cu subjected to nanoscratching are investigated by means of molecular dynamics simulations. Scratching simulations on nanotwinned single-crystalline Cu with the twin planes parallel and perpendicular to the scratching direction are performed. Since the detwinning mechanism is completely suppressed in the former case, no apparent correlation between frictional coefficient and the twin spacing is observed. In samples where the twin planes are perpendicular to the scratching direction, the friction increases as the twin spacing decreases, and then decreases as the twin spacings become even smaller. It results from the competitive plastic deformation between the inclined dislocations and the detwinning mechanism. Subsequent simulations for nanotwinned polycrystalline Cu unveil that in addition to the grain-boundary-associated deformation mechanism, dislocation-mediated detwinning plays a significant role in the plastic deformation of nanotwinned Cu. The twin boundary spacing in turn affects nanotwinned materials to resist scratching via plastic deformation. We demonstrate via the nanoscratching tests that there exists a critical twin boundary spacing for which the friction coefficient is maximized and that this transition results from the competing deformation mechanisms in those nanotwinned materials.

关键词： FRICTION COPPER MOLECULAR dynamics PLASTICITY POLYCRYSTALS DEFORMATIONS (Mechanics) DISLOCATIONS in crystals CRYSTALLOGRAPHY

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Visualization of signalized intersections in driving simulator and validity of driving behaviors in virtual environments

Advances in Transportation Studies

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Advances in Transportation Studies 2012年第26期 17-28页

作者： Yan, X. Abdel-Aty, M. Guo, D. Radwan, E. MOE Key Laboratory for Transportation Complex Systems Theory and Technology Beijing Jiaotong University Beijing 100044 China Department of Civil and Environmental Engineering University of Central Florida Orlando FL 32816-2450 United States Computer Science Program College of Business Florida Gulf Coast University 10501 FGCU Boulevard South Fort Myers FL 33965-6565 United States Center for Advanced Transportation Systems Simulation University of Central Florida Orlando FL 32816-2450 United States

Visualization of highway traffic environments in virtual reality plays a key role on fidelity of simulation and validity of driving behaviors in driving simulator studies. This paper describes a procedure to replicate a signalized intersection with many complex features into a driving simulator's 3-D databases through building a graphical visual database, constructing a road motion database, and creating simulated traffic. The validity of the visualization was assessed via the comparison of the drivers' speeds in the simulator and the speed data at the real intersection. It was found that both speed data follow normal distributions and have equal means for each intersection approach;however, that the speeds measured in the driving simulator have a larger variability than those measured in the field. The users' subjective evaluation results indicated that 92% subjects could recognize the simulated intersection in the driving simulator experiment. Therefore, the strategy of geo-specific environment modeling would be useful for studying driving behaviors in virtual environments.

关键词： Visualization

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Research on the estimation and reduction measures of antenna mode RCS of airborne phased array

Research on the estimation and reduction measures of antenna...

引用

International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications (MAPE)

作者： Yun Liu Lizhi You Aviation key Laboratory of Science and Technology on Avionics Integrated Sensor System Simulation Radar and Avionics Institute of AVIC Wuxi China

ISBN: (纸本)9781424482658

关键词： Arrays Scattering Reflector antennas Antenna arrays Antenna radiation patterns Radar antennas

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Ground clutter censoring for airborne weather radar employing DEM

Ground clutter censoring for airborne weather radar employin...

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6th International Conference on Radar, RADAR 2011

作者： Qin, Juan Wu, Renbiao Su, Zhigang Lu, Xiaoguang School of Electronic Information Engineering Tianjin University Tianjin 300072 China School of Electronic Information Engineering Tianjin University of Technology Tianjin 300384 China Tianjin Key Laboratory for Advanced Signal Processing Civil Aviation University of China Tianjin 300300 China

ISBN: (纸本)9781424484416

A ground clutter rejection method based on Digital Elevation Model (DEM) is proposed, which can be used to censor the clutter when airborne weather radar operates in weather mode. The theory of visibility analysis is used to identify the ranges with clutter. The terrain altitude in DEM and the height of points at the line-of-sight is compared, and the ranges where the beam crosses the surface or mountain are identified. Then these ranges with clutter are edited and rejected, so the suppression is implemented directly in time domain. In virtue of the proposed algorithm, the ranges where the clutter exists can be computed accurately using radar parameters and DEM. Finally, the validity and effectivity of the presented method is verified by processing the measured airborne data. © 2011 IEEE.

关键词： Visibility

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Application of associate rules mining on CGF's behavior modeling

Application of associate rules mining on CGF's behavior mode...

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International Conference on Computer Application and System Modeling

作者： Gong, Jianglei Gong, Guanghong Song, Xiao Advanced Simulation Technology Aviation Science and Technology Key Laboratory Beihang University Beijing China

ISBN: (纸本)9781424472369

In this paper, Computer Generated Forces (CGF) behavior modeling was studied from the viewpoint of associate data mining, for the large quantity of data, rules and models in its process. Because CGF behavior models data source was the combination of staticDB and dynamic data stream, the paper advanced the methods of item truncation and aim-pattern restriction. Through pretreatment, coding, searching frequent pattern, generating associate rules of the CGF behavior modeling data, then decision could be made according as these rules. Application of the two methods improves on the classical aprior algorithm, also improves efficiency of searching frequent items and credibility of CGF's decision. Finally, the application of associate rules mining in air-combat is studied in detail. As the simulation shows, comparing with the traditional matching-rule decision, associate rule mining has higher efficiency on condition with guaranteeing reliability of decision. © 2010 IEEE.

关键词： Data mining

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A fast predictive-Corrective Mass Spring method in cloth simulation

A fast predictive-Corrective Mass Spring method in cloth sim...

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International Conference on Computer Application and System Modeling

作者： Zhuang, Qing Hong Ding, Ying Gong, Guang Hong Aviation Key Laboratory for Advanced Simulation Technology Beijing University of Aeronautics and Astronautics Beijing China

ISBN: (纸本)9781424472369

Physically-based cloth animation has been a hot topic to the graphics community for more than a decade. Among the physically-based models used in cloth animation, elastically deformable models have been used successfully in order to give a representation of the behavior. We present a novel PCMS (Predictive-Corrective Mass-Spring) algorithm in cloth simulation which combines the advantages of both BMS and an advanced numerical integration method, namely low computational costs and large time steps. The numerical and rendering results show that a speed-up of more than an order of magnitude over the commonly used mass-spring method while the simulation results are in agreement with real cloth behavior. In addition, the super-elastic effect will be effectively controlled without dynamic inverse constraints on deformation rates. © 2010 IEEE.

关键词： Numerical methods

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Researches on modeling and simulation of airplane infrared characteristic

Researches on modeling and simulation of airplane infrared c...

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International Conference on Computer Application and System Modeling

作者： Liu, Juan Gong, Guanghong Han, Liang Gao, Dongdong Aviation Key Laboratory for Advanced Simulation Technology Beijing University of Aeronautics and Astronautics Beijing China

ISBN: (纸本)9781424472369

One of the most important problems of airplane infrared simulation is to establish the simulation model accurately based on real-time status. This paper analyses the three main sources of infrared signatures in airplane: airplane-skin, nozzle components and exhaust plume. By reckoning environment radiation, aerodynamic heating, heat transferring and hot engine casing principle, a synthetic simulation method was used, especially a new infrared engine model for airplane was firstly proposed with airplane's working status as the input. Then atmospheric transmittance is analyzed through Modetran4 with various influential factors such as atmospheric aerosol and geometric path considered. Finally the simulation results obtained have been analyzed with respect to different work status and view angle parameters, which will have an important effect on infrared image simulation system in military simulation system. © 2010 IEEE.

关键词： Engines

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The nonlinear control of simulator of hexapod parallel mechanism

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Journal of Harbin Institute of technology(New Series) 2010年第3期17卷 393-397页

作者：潘春萍管欣卢颖梁建民 State Key Laboratory of Automobile Dynamic Simulation Jilin University Military Simulation Technology Research Institute Aviation University of Air Force

In order to enhance the innervation fidelity of simulators,a nonlinear controller is developed,which guarantees parallel mechanisms closed loop system global asymptotical stability and the convergence of posture tracking error in Cartesian space. The problems of rapid tracking under the condition of the wide range,nonlinear and variable load are solved. After the nonlinear controller is actually applied to the hexapod parallel mechanisms of simulator,the dynamic-static capabilities of motion system are tested by amplitude-frequency response and posture precision. The experimental results show that the static precision improves ten times and system output amplitude increases and the phase lag reduces with respect to the same input signal in Cartesian space in comparison with the traditional proportional and derivative (i.e. PD) controlling method in joint space. Therefore the nonlinear controller can effectively improve the dynamic-static response performance of the hexapod parallel mechanisms of simulators in Cartesian space.

关键词： simulators hexapod parallel mechanisms dynamics model nonlinear control irmervation＇ s fidelity

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