The influence of dimension parameters on the performance of Body-surface Laplacian electrodes is studied in this paper. Some rules about the parameter optimization design are presented. The investigation suggests that...
详细信息
The development of the World Wide Web (or Internet) has provided the ability to connect the entire world together. Thousands of web servers located around the world allow users to connect and communicate with one anot...
详细信息
ISBN:
(纸本)0769523870
The development of the World Wide Web (or Internet) has provided the ability to connect the entire world together. Thousands of web servers located around the world allow users to connect and communicate with one another. Additionally, a huge transaction based product sales business has evolved, via the Internet. For many, the next generation of the Internet needs to focus on collections of servers and users working collectively together to solve problems. Grids and the Global Information Grid (GIG) are terms associated with enabling technologies that provide the framework for collections of servers and users to work together. Network Centric Operations and/or Network Centric Warfare are terms that refer to the actual concepts, applications, and processes that will execute on the GIG and solve real world problems. Moving to this "next generation Internet" provides many exciting opportunities as well as many difficult challenges. This year's panel will explore these opportunities and challenges from several different perspectives: government, defense industry, commercial industry and academia.
Broadband wireless access (BWA) systems offer a solution for broadband access and high data rate transmission of multimedia services with distinct quality-of-service (QoS) requirements through a wireless medium, IEEE ...
详细信息
Broadband wireless access (BWA) systems offer a solution for broadband access and high data rate transmission of multimedia services with distinct quality-of-service (QoS) requirements through a wireless medium, IEEE 802.16 standard specifies the PHY and MAC layers for BWA systems. However, in spite of including the possibility for QoS support, the standard does not define how to schedule different types of traffic. This article propose a new MAC protocol for BWA systems that incorporates a traffic scheduling mechanism based on messages and/or stations priorities. An analytical model to evaluate the performance of the proposed protocol is also developed and results obtained for the messages waiting times of different traffic classes are presented.
With the rapid development of high-power white light-emitting diodes (LEDs), advances in packaging are required to further improve the device performance. In this work, an optimized packaging configuration for high po...
详细信息
ISBN:
(纸本)1424400848
With the rapid development of high-power white light-emitting diodes (LEDs), advances in packaging are required to further improve the device performance. In this work, an optimized packaging configuration for high power LED lamps with enhanced phosphorescence efficiency is presented based on ray-tracing simulations and experimental results. Figure 1 shows two phosphor arrangements, namely a "proximate phosphor" and a "remote phosphor" arrangement. The surface of the reflector cup is assumed to be either specular or diffuse. Three different encapsulant geometries, i.e., a "flat" (no cap), "convex" (spherical cap with height h = r/2), and "hemispherical" (h = r) top surface, are used in the simulations. Figure 2 shows phosphorescence efficiency with different packaging configurations obtained by ray-tracing simulation. The packaging configuration with remote phosphor, diffuse reflector cup and hemispherical encapsulation shows a 50% enhancement of phosphorescence efficiency compared to conventional packaging configuration. This improvement is attributed to reduced absorption of the phosphorescence by the LED chip and the reduction of deterministic optical modes trapped inside the encapsulant of remote-phosphor and diffuse reflector cup configuration. The angular dependence of the reflectivity for a diffuse Ag reflector and a specular Ag reflector is measured and shown in Figure 3. The roughened Ag reflector has a more than two orders of magnitude higher diffusely reflected power compared with the specular Ag reflector, which leads to the extraction of the trapped optical modes occurring in packaging structures with specular reflector cups. Dichromatic LED lamps comprising an ultraviolet GaN LED (λ = 400 nm) with a blue phosphor and a blue GaInN LED (λ = 470 nm) with a yellow phosphor are fabricated with different phosphor arrangements and reflector cups. The emission spectra of the reference primary LED emitters and of the dichromatic lamps operating at 20 mA are mea
in this paper, we consider the problem of dynamically regulating the timing of traffic light controllers in busy cities. We use a Stochastic Fluid Model (SFM) to model the dynamics of the queues formed at an intersect...
详细信息
Microkernel based systems tend to depend heavily on IPC. This paper addresses the problem of a system response spanning more than one task in an embedded real-time system. The approach is based on a mix of classical r...
详细信息
Microkernel based systems tend to depend heavily on IPC. This paper addresses the problem of a system response spanning more than one task in an embedded real-time system. The approach is based on a mix of classical response time analysis equations and a graph based approach to estimate the impact of different parts of the system on the time needed by the system to respond. This approach has the major advantage of being intuitive.
Enhancement of light extraction in GaN light-emitting diodes (LEDs) employing omnidirectional reflectors (ODRs) is presented. The ODR consists of GaN, ITO nanorod low-refractive-index layer, and an Ag layer. An array ...
详细信息
Enhancement of light extraction in GaN light-emitting diodes (LEDs) employing omnidirectional reflectors (ODRs) is presented. The ODR consists of GaN, ITO nanorod low-refractive-index layer, and an Ag layer. An array of ITO nanorods is deposited by oblique-angle deposition using e-beam evaporation. The refractive index of the ITO nanorods is 1.34 at 461 nm, significantly lower that that of dense ITO, which is n = 2.06 at 461 nm. It is experimentally shown that the GaN LED with GaN/ITO nanorods/Ag ODR show much better electrical properties and higher light-extraction efficiency than LEDs with Ag contact. This is attributed to enhanced reflectivity of the ODR by using an ITO low-refractive-index layer with high transparency, high conductivity, and low refractive index.
In this paper, we consider the problem of dynamically regulating the timing of traffic light controllers in busy cities. We use a Stochastic Fluid Model (SFM) to model the dynamics of the queues formed at an intersect...
详细信息
In this paper, we consider the problem of dynamically regulating the timing of traffic light controllers in busy cities. We use a Stochastic Fluid Model (SFM) to model the dynamics of the queues formed at an intersection. Based on this model, we derive gradients of the queue lengths with respect to the green/red light lengths within a signal cycle. We report preliminary numerical results comparing the performance of the estimates with finite-difference and smoothed perturbation analysis estimates. Then all estimators are used to optimize the traffic system via Stochastic Approximation.
作者：
De Brito, Halisson MatosStrauch, JuliaDe Souza, Jano MoreiraOsthoff, CarlaCOPPE/UFRJ
Systems Engineering and Computer Science Program Federal University of Rio de Janeiro PO Box 68511 ZIP Code: 21945-970 Rio de Janeiro RJ Brazil ENCE /IBGE
National School of Statistical Sciences 106 S. 401 ZIP Code: 20231-050 R. André Cavalcanti Rio de Janeiro RJ Brazil LNCC
National Laboratory for Scientific Computing Av. Getulio 333 Quitandinha Vargas Petrópolis RJ Brazil IM/UFRJ
Institute of Mathematics Federal University of Rio de Janeiro PO Box 68511 ZIP Code: 21945-970 Rio de Janeiro RJ Brazil
This paper presents MODENA, an architecture for scientific models management using Computational Grid platform. This architecture is comprised of two systems: ModManager and ModRunner. ModManager deals with knowledge ...
详细信息
This paper presents MODENA, an architecture for scientific models management using Computational Grid platform. This architecture is comprised of two systems: ModManager and ModRunner. ModManager deals with knowledge management about scientific models, acting as a scientific models library allowing for cataloguing, searching, reutilization and generation of new models. To achieve this, a metamodel is proposed to classify models, in order to support the organization, searching and retrieving of models. ModRunner manages the execution of models in a Grid environment allowing for model composition to generate a scientific Grid Workflow to be executed by distributed services offered by Grid Services. An initial prototype of ModManager is presented.
暂无评论