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排序方式: 共有274条查询结果,搜索用时 135 毫秒
1.
Joannie W. Chin Eric Byrd Ned Embree Jonathan Martin J. D. Tate 《Journal of Coatings Technology》2002,74(929):39-44
Laboratory ultraviolet (UV) chambers are widely used to obtain weathering data for a wide range of commercial polymer products
including coatings, textiles, elastomers, plastics, and polymeric composites. Although numerous improvements have been made
in the design of UV chambers over the last 80 years, the reproducibility of the exposure results from these chambers has remained
elusive. This lack of reproducibility is attributed to systematic errors in their design, operation, and control which prevent
direct comparisons of the performance of materials exposed in the same environment, comparisons of the performance of the
same material exposed in different laboratories, and the comparison of field and laboratory results. This paper describes
an innovative UV chamber design based on integrating sphere technology that greatly reduces the magnitude of these errors,
as well as provides additional experimental capabilities.
Presented at the 79th Annual Meeting of the Federation of Societies for Coatings Technology, on November 4–7, 2001, in Atlanta,
GA.
Building Materials Division. Gaithersburg, MD.
Freeport, TX. 相似文献
2.
A time-limited lease is a set of rights that expires after a specified duration. We analyze ways to use leases to facilitate innovation in radio devices and wireless communication. In our vision, manufacturers include in their devices a simple, secure subsystem that contains a clock and disables specific transmit capabilities if no extension message is received by the end of the lease period. When devices provide this support, regulators may use certification leases rather than permanent grants to accelerate deployment of innovative radios. Spectrum rights holders may use leases to reduce risk in secondary spectrum market transactions. Firms collaborating in innovative wireless service business models can better retain control of their respective rights. We examine both the technical and policy issues associated with leases. 相似文献
3.
COGNITIVE RADIOS FOR DYNAMIC SPECTRUM ACCESS - The Path to Market Success for Dynamic Spectrum Access Technology 总被引:2,自引:0,他引:2
Rapid progress is being made in the technology for dynamic spectrum access (DSA) radio systems. However, the structure and dynamics of the wireless services market must also evolve for DSA to succeed. This article examines the interlinked technical and economic issues associated with markets for DSA-based wireless services. We use this analysis to make technical and policy recommendations supporting the commercial success of DSA technology 相似文献
4.
Advanced oxidation processes are defined as those which involve the generation of hydroxyl radicals in sufficient quantity to affect water purification. The theoretical and (practical yield of OH from O3 at high pH, 03/H202, O3/UV and H2O2/UV systems is reviewed. New data is presented which illustrates the importance of direct photolysis in the O3/UV process, the effect of the H202:03 ratio in the O3/H2O2 process, and the impact of the low extinction coefficient of H2O2 in the H202/UV process. 相似文献
5.
Marc Secanell Ron Songprakorp Ned Djilali Afzal Suleman 《Structural and Multidisciplinary Optimization》2010,40(1-6):563-583
A computational framework for fuel cell analysis and optimization is presented as an innovative alternative to the time consuming trial-and-error process currently used for fuel cell design. The framework is based on a two-dimensional through-the-channel isothermal, isobaric and single phase membrane electrode assembly (MEA) model. The model input parameters are the manufacturing parameters used to build the MEA: platinum loading, platinum to carbon ratio, electrolyte content and gas diffusion layer porosity. The governing equations of the fuel cell model are solved using Netwon’s algorithm and an adaptive finite element method in order to achieve near quadratic convergence and a mesh independent solution respectively. The analysis module is used to solve the optimization problem of finding the optimal MEA composition for maximizing performance. To solve the optimization problem a gradient-based optimization algorithm is used in conjunction with analytical sensitivities. By using a gradient-based method and analytical sensitivities, the framework presented is capable of solving a complete MEA optimization problem with state-of-the-art electrode models in approximately 30 min, making it a viable alternative for solving large-scale fuel cell problems. 相似文献
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8.
F. Stuart Chapin Jr. 《Journal of the American Planning Association. American Planning Association》2013,79(2):120-125
This article is the outgrowth of a long period of experimentation with models of residential and other development which focus on the individual decision-maker—the householder in search of a home, and the builder attempting to cater to his desires. The first part of the paper describes the means by which this process is simulated in a computer. Later parts of the paper indicate how this view of consumer behavior has led naturally into a consideration of households' activity patterns and into research on these patterns. In conclusion the author indicates by implication that the integration of these two approaches may lead in the direction of measurements of accessibility and of taking account of the competition fm desirable sites, of consequent increases in the intensity of utilization, and of the rents of these sites. Thus this article, in conjunction with others, illustrates a remarkable convergence between research starting at the level of individual decision units and coming to consider the larger framework, and research starting from gross changes in the metropolitan configuration and coming to give increasing consideration to the actual decision process. 相似文献
9.
Robert Goldston Mohamed Abdou Charles Baker Michael Campbell Vincent Chan Stephen Dean Amanda Hubbard Robert Iotti Thomas Jarboe John Lindl B. Grant Logan Kathryn McCarthy Farrokh Najmabadi Craig Olson Stewart Prager Ned Sauthoff John Sethian John Sheffield Steven Zinkle 《Journal of Fusion Energy》2002,21(2):61-111
This is the final report of a panel set up by the U.S. Department of Energy (DOE) Fusion Energy Sciences Advisory Committee (FESAC) in response to a charge letter dated September 10, 2002 from Dr. Ray Orbach, Director of the DOE's Office of Science. In that letter, Dr. Orbach asked FESAC to develop a plan with the end goal of the start of operation of a demonstration power plant in approximately 35 years. This report, submitted March 5, 2003, presents such a plan, leading to commercial application of fusion energy by mid-century. The plan is derived from the necessary features of a demonstration fusion power plant and from the time scale defined by President Bush. It identifies critical milestones, key decision points, needed major facilities and required budgets. The report also responds to a request from DOE to FESAC to describe what new or upgraded fusion facilities will best serve our purposes over a time frame of the next twenty years. 相似文献
10.
Boutaba Raouf Ren Ned Ning Rasheed Yasser Leon-Garcia Alberto 《Multimedia Tools and Applications》2002,16(1-2):99-136
In this paper, we apply a top-down approach to describe the architecture components of Distributed video production (DVP) systems. We first introduce the concept of a Distributed video production environment and describe typical DVP tasks involved. We then propose a generic layered functional model that captures the characteristics of the DVP architecture. Subsequently, we identify system and network performance parameters and discuss possible network protocol stack realizations for the transport of DVP traffic. Finally, we propose a quality of service-sensitive model for resource allocation and optimization. 相似文献