检索结果-内蒙古大学图书馆

ARFTG Conference

作者： Charles Baylis Buford Randall Jean Josh Martin Loria Wang Matthew Moldovan Hunter Miller Wireless and Microwave Circuits and Systems Program Department of Electrical and Computer Engineering Baylor University Waco TX USA

With the widespread use of high-voltage GaN devices and other high-power transistors, understanding the heating of a device during large-signal excitation and measurement is critical, both to ensure efficient operation and to prevent destruction of devices during measurement. Device self-heating during RF excitation is directly dependent upon the power-added efficiency of operation. All DC and RF power that is not converted to output RF power is dissipated in the device as heat. When properly applied, the traditional electrothermal model used in circuit simulators adequately calculates this self heating and yields some interesting results. In this paper, it is demonstrated that the load impedance providing maximum power-added efficiency also results in the lowest average dissipated power, and hence the lowest channel temperature, of the device. The variation in average dissipated power (and hence channel temperature) is also examined for different loading conditions; it is shown that some loading conditions produce a dissipated power that is actually higher than the DC power, a situation which often can lead to device failure during load-pull measurements.

关键词： Radio frequency Power dissipation Temperature measurement Mathematical model Heating Microwave measurements Equations

来源：评论

学校读者我要写书评

暂无评论

LINC power amplifiers for reducing out-of-band spectral re-growth: A comparative study

LINC power amplifiers for reducing out-of-band spectral re-g...

引用

IEEE Annual Conference on Wireless and Microwave Technology (WAMICON)

作者： Charles Baylis Matthew Moldovan Loria Wang Josh Martin Wireless and Microwave Circuits and Systems Program Department of Electrical and Computer Engineering Baylor University Waco TX USA

ISBN: (纸本)9781424466887;9781424466890

The Linear Amplification with Nonlinear Components (LINC) power amplifier structure combiner implementation has an effect on the linearity and efficiency of the design. Understanding and using this tradeoff is helpful to radar and communication designers and can be used to assist in operating with optimum efficiency while meeting spectral mask requirements instituted by regulatory agencies. In this paper, a simulation-based investigation is performed into implementations with a 180-degree coupler and with a Chireix outphasing network. In general, the overall efficiency in both designs is a function of the amplitude modulation of the message signal in the LINC configuration; however, the 180-degree coupler has a potential to obtain higher linearity in many cases due to the isolation of its two input ports. In certain cases of amplitude modulation, however, much of the output power in the 180-degree coupler design is delivered to an unused termination rather than to the network output.

关键词： Power amplifiers Linearity Amplitude modulation Radar Phase modulation Signal design Voltage Interference Microwave amplifiers Circuits and systems

来源：评论

学校读者我要写书评

暂无评论

Accelerating the Shuffled Frog Leaping algorithm by parallel implementations in FPGAs

Accelerating the Shuffled Frog Leaping algorithm by parallel...

引用

2010 IEEE 5th International Conference on Bio-Inspired Computing: Theories and Applications, BIC-TA 2010

作者： Muñoz, Daniel M. Llanos, Carlos H. Dos S. Coelho, Leandro Ayala-Rincón, Mauricio Department of Mechanical Engineering Automation and Control Group/GRACG University of Brasilia Brasilia D.F. Brazil Industrial and Systems Engineering Graduate Program Pontifical Catholic University of Parana Curitiba Parana Brazil Department of Computer Science and Mathematics University of Brasilia Brasilia D.F. Brazil

ISBN: (纸本)9781424464388

Meta-heuristics are efficient techniques for solving large scale optimization problems in which traditional mathematical techniques are impractical or provide sub-optimal solutions. The Shuffled Frog Leaping algorithm (SFLA) is a stochastic iterative method, bio-inspired on the memetic evolution of a group of frogs when seeking for food, which combines the social behavior-based of the particle swarm optimization technique (PSO) and the global information exchange of memetic algorithms. However, the SFLA algorithm suffers on large execution times, being this problem clearly evident when solving complex optimization problems for embedded applications. This drawback can be overcome by exploiting the parallel capabilities of the SFLA. This paper proposes a hardware parallel implementation of the SFLA algorithm (HPSFLA) using FPGAs (Field programmable gate Arrays) and the efficient floating-point arithmetic. The proposed architecture allows the SFLA to improve the functionality of the algorithm as well as to decrease the execution times by implementing parallel frogs and parallel memeplexes. Three well-known benchmark problems have been used to validate the implemented algorithm and simulation results demonstrate that the HPSFLA speeds-up by factors of 362, 727 and 211 a C-code implementation using an embedded microprocessor for the Sphere, Rastrigin and Rosenbrock benchmarks problems, respectively. Synthesis, simulation and execution time results demonstrate the effectiveness of the proposed HPSFLA architecture for embedded optimization systems. © 2010 IEEE.

关键词： Global optimization

来源：评论

学校读者我要写书评

暂无评论

Comparison between two FPGA implementations of the particle swarm optimization algorithm for high-performance embedded applications

Comparison between two FPGA implementations of the particle ...

引用

2010 IEEE 5th International Conference on Bio-Inspired Computing: Theories and Applications, BIC-TA 2010

作者： Muñoz, Daniel M. Llanos, Carlos H. Dos S. Coelho, Leandro Ayala-Rincón, Mauricio Department of Mechanical Engineering Automation and Control Group/GRACO University of Brasilia Brasilia D.F. Brazil Industrial and Systems Engineering Graduate Program LAS/PPGPES Pontifical Catholic University of Parana Curitiba Parana Brazil Department of Computer Science and Mathematics University of Brasilia Brasilia D.F. Brazil

ISBN: (纸本)9781424464388

Particle Swarm Optimization (PSO) algorithms have been proposed to solve engineering problems that require to find an optimal point of operation. There are several embedded applications which requires to solve online optimization problems with a high performance. However, the PSO suffers on large execution times, and this fact becomes evident when using Reduced Instruction Set computer (RISC) microprocessors in which the operational frequencies are low in comparison with the high operational frequencies of traditional personal computers (PCs). This paper compares two hardware implementations of the parallel PSO algorithm using an efficient floating-point arithmetic which perform computations with large dynamic range and high precision. The full-parallel and the partially-parallel PSO architectures allow the parallel capabilities of the PSO to be exploited in order to decrease the running time. Three well-known benchmark test functions have been used to validate the hardware architectures and a comparison in terms of cost in logic area, quality of the solution and performance is reported. In addition, a comparison of the execution time between the hardware and two C-code software implementations, based on a Intel Core Duo at 1.6GHz and a embedded Microblaze microprocessor at 50MHz, are presented. © 2010 IEEE.

关键词： Global optimization

来源：评论

学校读者我要写书评

暂无评论

Modeling GaN: Powerful but challenging

Modeling GaN: Powerful but challenging

引用

作者： Dunleavy, Lawrence Baylis, Charles Curtice, Walter Connick, Rick Modelithics Inc. Tampa FL United States Department of Electrical Engineering Center for Wireless and Microwave Information Systems University of South Florida Tampa United States Department of Electrical and Computer Engineering Wireless and Microwave Circuits and Systems Program Baylor University Waco TX United States W.R. Curtice Consulting Washington Crossing PA United States Triquint Semiconductor Apopka FL United States

Gallium nitride transistor-based power amplifiers (PA) which are currently among the most important technologies impacting high-power transmitter design at microwave frequencies are discussed. GaN HEMTs also allow high-power operation at much higher frequencies than silicon laterally diffused metal oxide semiconductor field-effect transistors (LDMOS FETs), currently a staple for the cellular base station industry. The significant attention placed on nonlinear models is in step with the growing community of designers who are using nonlinear circuit simulators with good success to design and optimize high-power amplifiers. The use of pulsed measurements as part of the modeling process, along with sufficiently flexible modeling equations and topologies, is critical for obtaining reliable electrothermal GaN models. The successful modeler will be aware of the need for accurate data, carefully applied extraction methodologies, along with the strengths and limitations of available models to obtain the best results for circuit designers.

关键词： Gallium nitride

来源：评论

学校读者我要写书评

暂无评论

A parallel architecture for Ray-Tracing

A parallel architecture for Ray-Tracing

引用

IEEE Latin American Symposium on Circuits and systems (LASCAS)

作者： Alexandre S. Nery Nadia Nedjah Felipe M.G. França LAM - Computer Architecture and Microeletronics Laboratory Systems Engineering and Computer Science Program COPPE Universidade Federal do Rio de Janeiro Department of Electronics Engineering and Telecommunications Universidade do Estado do Rio de Janeiro

Real time rendering of three-dimensional scenes in high photorealistic detail is a hard task, such as in the Ray Tracing rendering algorithm. However, parallel implementations of Ray Tracing have been enabling real time performance, as the algorithm is embarrassingly parallel. Thus, a custom parallel design in hardware is likely to achieve an acceptable performance. In this paper, we propose a hardware parallel architecture capable of dealing with the main desirable features of Ray Tracing, such as shadows and reflection effects, imposing low area cost and acceptable rendering performance.

关键词： computer architecture Interrupters computers Light sources Process control Real-time systems Telecommunications

来源：评论

学校读者我要写书评

暂无评论

An agent-based architecture for knowledge management in context-aware business processes

An agent-based architecture for knowledge management in cont...

引用

International Conference on computer Supported Cooperative Work in Design

作者： De C. Gatti, Leonardo A. Santoro, Flávia Maria Nunes, Vanessa T. NP2TEC - Research and Practice Group in Information Technology Department of Applied Informatics Federal University of the State of Rio de Janeiro UNIRIO Rio de Janeiro Brazil COPPE - Systems Engineering and Computer Science Program Federal University of Rio de Janeiro UFRJ Rio de Janeiro Brazil

ISBN: (纸本)9781424467631

The main knowledge management challenges are to capture, store and reuse contextual knowledge generated during interactions that occur daily in an organization. In this paper, we propose an activity context-aware architecture to support knowledge management in working processes. The required features for this architecture are processing, reasoning and sharing contextual knowledge involving information about activities performed. We also present results from evaluation of our proposal - A-CoBrA - for a specific domain. © 2010 IEEE.

关键词： Knowledge management

来源：评论

学校读者我要写书评

暂无评论

Support for flight trajectories and video capture: Initial results using a free open source flight simulator

Support for flight trajectories and video capture: Initial r...

引用

12th International Conference on engineering, Science, Construction, and Operations in Challenging Environments - Earth and Space 2010

作者： Durham, Jayson Mehrubeoglu, Mehrube McLauchlan, Lifford Carter, David McBee, Ross Capabilities Branch SPA WAR Systems Center - Pacific United States Dept. of Computing Sciences Engineering Technology Program Texas A and M University Corpus Christi TX United States Dept. of Electrical Engineering and Computer Science Texas A and M University Kingsville TX United States University of Texas Austin TX United States Regents School of Austin United States

ISBN: (纸本)9780784410967

Micro Aerial Vehicles (MAVs) and larger Unmanned Aerial Vehicles (UAVs) constitute a powerful tool for the modern warfighter and first responder. However, every developing technology must first be tested before being exported to the battlefield or hot spot to assure predictable behaviors. In today's digital age, computers give designers and testers unprecedented ability to quickly and easily test virtual models before physical prototypes are created and field tested. We have utilized emerging Free Open Source Software (FOSS) simulators and workbenches (e.g. FlightGear and AUV Workbench) to improve mission-driven MAV/UAV video and imagery capture and analysis capabilities. In this project, use of FlightGear to analyze flight trajectories and video capture capabilities of different UAVs is presented. FlightGear allows the free implementation of changeable flight dynamic models, weather, autopilot, GPS, and multiplayer to be included in the analysis of simulated flights. Another attractive aspect of FlightGear is its extensible and easy-to-modify implementation. Modifications are accomplished by changing or adding human readable XML files in the FlightGear subdirectories. In this effort, existing aerial vehicle models are incorporated into FlightGear to create flight trajectories and analyze video capture capabilities to determine the necessary toolset for analyzing imagery data to meet the mission needs. The limitations of the existing camera systems as well as effects of various flight parameters on mosaicking and georegistration are presented here. Sample analysis of the effect of aerial vehicle speed on the overlap of frames captured at the typical 30 frames/second frame rate, which provides a base for comparison of flight attributes, are demonstrated together with other parameters that affect mission performance. © 2010 ASCE.

关键词： Flight simulators

来源：评论

学校读者我要写书评

暂无评论

Growth and characteristics of GaInN/GaInN multiple quantum well light-emitting diodes

Growth and characteristics of GaInN/GaInN multiple quantum w...

引用

作者： Lee, Wonseok Kim, Min-Ho Zhu, Di Noemaun, Ahmed N. Kim, Jong Kyu Schubert, E.F. Future Chips Constellation and Engineering Science Program Rensselaer Polytechnic Institute Troy NY 12180 United States Samsung LED Suwon 443-743 Korea Republic of Future Chips Constellation Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy NY 12180 United States Future Chips Constellation Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute Troy NY 12180 United States Department of Materials Science and Engineering Pohang University of Science and Technology Pohang 790-784 Korea Republic of

We demonstrate GaInN multiple quantum well (MQW) light-emitting diodes (LEDs) having ternary GaInN quantum barriers (QBs) instead of conventional binary GaN QBs for a reduced polarization mismatch between QWs and QBs and an additional separate confinement of carriers to the MQW active region. In comparison with GaInN LEDs with conventional GaN QBs, the GaInN/GaInN LEDs show a reduced blueshift of the peak wavelength with increasing injection current and a reduced forward voltage. In addition, we investigate the density of pits emerging on top of the MQW layer that are correlated with V-defects and act as a path for the reverse leakage current. The GaInN/GaInN MQW structure has a lower pit density than the GaInN/GaN MQW structure as well as a lower reverse leakage current. Finally, the GaInN/GaInN MQW LEDs show higher light output power and external quantum efficiency at high injection currents compared to the conventional GaInN/GaN MQW LEDs. We attribute these results to the reduced polarization mismatch and the reduced lattice mismatch in the GaInN/GaInN MQW active region. © 2010 American Institute of Physics.

关键词： III-V semiconductors

来源：评论

学校读者我要写书评

暂无评论

Individual-based simulation of sexual selection: A quantitative genetic approach

引用

Procedia computer Science 2010年第1期1卷 2003-2011页

作者： D. van Dijk P.M.A. Sloot J.C. Tay M.C. Schut Computational Science University of Amsterdam Sciencepark 107 1098 XG Amsterdam The Netherlands Evolutionary and Complex Systems Program School of Computer Engineering Nanyang Technological University Singapore 639798 Singapore Department of Artificial Intelligence Vrije Universiteit Amsterdam 1081 HV Amsterdam The Netherlands

Sexual selection has been mathematically modeled using quantitative genetics as well as population genetics. Two-locus simulation models have been used to study the evolution of male display and female preference. We present an individual-based simulation model of sexual selection in a quantitative genetic context. We show that under certain conditions Fisherian self-reinforcing sexual selection takes effect, predicted by Lande’s analytic model of female choice. We also show that the dynamics involved in the co-evolution of male display and female preference is much more complex than mathematics would predict. We therefore argue that the study of sexual selection through individual-based simulation could give new and more realistic insight into a world dominated by overly simplified equations.

关键词： Sexual selection Individual-based modeling Agent-based modeling

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：