為城市環境設計之微型風力發電機系統

風力發電擁有巨大潛力，可廣泛在許多國家發展以減少化石燃料之使用。傳統的三葉片風力發電機常用於風能密度高的地方，小型風力發電機則專為風量低的地點而設計，例如市區及面積較小的平地等。本項研究專為風速通常較低的都市環境開發一部創新的微型風力發電機。傳統的風力發電機可直接連接到輸電網，這個系統則可連接到小型發電機和蓄電池並主要在設置系统的地方使用。微型風力發電機的優點包括低成本和低切入風速，並可靈活調節大小。這項研究進行了計算流體動力學（CFD）的模擬分析和實驗，以幫助評估設有不同配置的個別微型風力發電機的性能，以及多個微型風力發電機系統的發電特性。關鍵詞：發電，空氣動力學，功率係數。published_or_final_versio

Micro-wind turbine system in urban environment

Wind power is identified to be of great potential for extensive development in many countries to reduce the fossil fuel based power generation. Conventional three blades wind turbines are commonly used in locations with high wind energy density, while small wind turbines are developed for less windy locations such as urban areas and flat lands. An innovative micro wind turbine was developed to generate power in urban environment where wind speed is usually low. Differing from the traditional wind turbine that can be connected directly to the grid, this system is linked to a small generator and batteries, and mainly used for local applications. The advantage of the micro wind turbine is that, apart from its low cost, it can be propelled by a very low wind speed. Computation fluid dynamics (CFD) simulations have been conducted to help evaluate the performance of a single micro wind turbine.published_or_final_versio

An experimental study on a motion sensing system for sports training

In sports science, motion data collected from athletes is used to derive key performance characteristics, such as stride length and stride frequency, that are vital coaching support information. The sensors for use must be more accurate, must capture more vigorous events, and have strict weight and size requirements, since they must not themselves affect performance. These requirements mean each wireless sensor device is necessarily resource poor and yet must be capable of communicating a considerable amount of data, contending for the bandwidth with other sensors on the body. This paper analyses the results of a set of network traffic experiments that were designed to investigate the suitability of conventional wireless motion sensing system design � which generally assumes in-network processing - as an efficient and scalable design for use in sports training

Interplay between multiple scattering, emission, and absorption of light in the phosphor of a white light-emitting diode

We study light transport in phosphor plates of white light-emitting diodes (LEDs). We measure the broadband diffuse transmission through phosphor plates of varying YAG:Ce$^{3+}$ density. We distinguish the spectral ranges where absorption, scattering, and re-emission dominate. Using diffusion theory, we derive the transport and absorption mean free paths from first principles. We find that both transport and absorption mean free paths are on the order of the plate thickness. This means that phosphors in commercial LEDs operate well within an intriguing albedo range around 0.7. We discuss how salient parameters that can be derived from first principles control the optical properties of a white LED.Comment: 14 pages, 9 figure

Valid Inequalities and Facets of the Capacitated Plant Location Problem

Recently, several successful applications of strong cutting plane methods to combinatorial optimization problems have renewed interest in cutting plane methods, and polyhedral characterizations, of integer programming problems.In this paper, we investigate the polyhedral structure of the capacitated plant location problem. Our purpose is to identify facets and valid inequalities for a wide range of capacitated fixed charge problems that contain this prototype problem as a substructure.The first part of the paper introduces a family of facets for a version of the capacitated plant location problem with constant capacity K for all plants. These facet inequalities depend on K and thus differ fundamentally from the valid inequalities for the uncapacitated version of the problem. We also introduce a second formulation for a model with indivisible customer demand and show that it is equivalent to a vertex packing problem on a derived graph. We identify facets and valid inequalities for this version of the problem by applying known results for the vertex packing polytope