• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 9624
  • 5175
  • 1738
  • 1339
  • 1093
  • 1083
  • 301
  • 273
  • 223
  • 185
  • 173
  • 168
  • 160
  • 141
  • 111
  • Tagged with
  • 26051
  • 3863
  • 3656
  • 3112
  • 2804
  • 2033
  • 1958
  • 1858
  • 1795
  • 1710
  • 1706
  • 1648
  • 1441
  • 1184
  • 1180
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

New Vistas in Solar Concentration with Gradient Index Optics

Kotsidas, Panagiotis Spyros January 2012 (has links)
Four innovations in the fields of optical design and solar concentration are presented: a) the derivation of fundamentally new gradient-index (GRIN) distributions for perfect optical instruments. For the first time, GRIN lenses for visible and solar radiation with refractive index distributions that are amenable to current fabrication techniques are presented. Those lenses perform at nature's cardinal limits (within the geometrical optics approximation - valid for essentially all solar applications), i.e. perfect imaging and ideal nonimaging performance for monochromatic radiation and unprecedented image fidelity and near-ideal flux concentration for the full solar spectrum. Until now, there have been no GRIN solutions (for performance approaching the fundamental limits of flux concentration and image fidelity) that can accommodate an extended constant-index core - especially relevant because the only available fabrication techniques for visible and solar GRIN lenses require a constant-index core. b) The design, for the first time, of a nominally stationary solar concentrator with attainable geometric concentration of the order of 10super suns with high collection efficiency. The burden of tracking is transferred inside the stationary module where mm-scale motion of GRIN perfect imaging lenses tracks the sun. This creates the possibility for rooftop Concentrator Photovoltaics (CPV) with unprecedented optical performance and exceptional optical tolerance. c) The design of a nominally stationary solar concentrator with a modified Simultaneous Multiple Surface technique for nonimaging contoured lenses with flux concentration of the order of tenths of suns. d) The design of planar GRIN lenses able to deliver flux concentrations close to the thermodynamic limit to Solar Concentration with a single, optical element, previously deemed unattainable and particularly suitable to dual-axis tracking CPV.
22

Design of Portable DC Light Bulb for the DC House Project

Macairan, Jan Marvin Perez 01 June 2013 (has links)
This thesis focuses on the design and implementation of the Portable DC Light Bulb system for Cal Poly San Luis Obispo’s DC House Project. The DC Portable Light Bulb highlights the NiMH battery charging circuit, buck converter, and boost converter. The system is intended as a flashlight adaptor placed in between the dimmable DC light bulb and its screw base. The adaptor adds a portability feature to the DC light bulb to provide lighting wherever the user pleases. The Portable DC Light Bulb system is designed to operate with an input range of 24V-60V and regulate an output voltage of 34V for the DC light bulb. Computer simulations, calculations, and hardware results verifies the proposed Portable DC Light Bulb system’s design, function, and purpose.
23

An investigation of the electric power supply for New Sharon, Iowa

Bates, Ferd Homer 01 January 1912 (has links)
No description available.
24

Estuarine tidal hydraulics : one dimensional model and predictive algorithm

Goodwin, Carl R. 13 March 1974 (has links)
A one-dimensional, implicit, finite-difference model is developed, calibrated and verified for three estuaries along the central Oregon coast. The model is used to generate controlled data for a large number of hypothetical estuaries. Two non-dimensional coefficients, K[subscript F], and. K[subscript I], are developed incorporating physical characteristics of the estuary which summarize the effects due to friction and inertia, respectively, These coefficients are used to explain the variability of tidal response throughout the complete range of hypothetical estuaries investigated. A predictive algorithm based on the derived relationships is presented and examples of its application to real estuaries is given. The results of this study can be used to predict modifications in tidal response due to proposed physical changes in an estuary, such as entrance dredging or filling of tidal flats. Field data of velocity, temperature and salinity for the Yaquina, Alsea and Siletz estuaries is included with the paper. / Graduation date: 1974
25

A critical analysis of power in the institutionalization of changes in a new teacher mentoring program: a case study

Ferguson, Phyllis Cavanaugh 15 May 2009 (has links)
The purpose of this case study is to describe the way power, as individual agency, works in the space of institutionalization of a new teacher mentoring program. The space of institutionalization is thought of as a space in which the design of the mentoring program and the actions of participants interact as the program undergoes changes. The participants in this study tell about the way each goes about mentoring in response to the program changes. Their stories are analyzed through critical discourse analysis for workings of power. Two kinds of power or agency emerge through the analysis. Instrumental agency is the physical activities, perceptions, and spoken words of the mentors limited by their subject and structural positionality. Instrumental agency in the space of institutionalization worked to instill differentiation as plurality and normalization as objectification into the mentoring program. When instrumental agency is the dominant power in the space of institutionalization, the legitimacy of the mentoring program is rationalized as legitimization. Legitimization of the program results in an ecology of the space of institutionalization open to vagaries of political expediency. The second kind of power or agency to emerge is operative agency. Operative agency originates in sensings and feelings as expressed in wondering and uncertainty about mentoring roles and the mentoring program. When engaging operative agency as power, differentiation and normalization in the space of institutionalization can be questioned.
26

A critical analysis of power in the institutionalization of changes in a new teacher mentoring program: a case study

Ferguson, Phyllis Cavanaugh 15 May 2009 (has links)
The purpose of this case study is to describe the way power, as individual agency, works in the space of institutionalization of a new teacher mentoring program. The space of institutionalization is thought of as a space in which the design of the mentoring program and the actions of participants interact as the program undergoes changes. The participants in this study tell about the way each goes about mentoring in response to the program changes. Their stories are analyzed through critical discourse analysis for workings of power. Two kinds of power or agency emerge through the analysis. Instrumental agency is the physical activities, perceptions, and spoken words of the mentors limited by their subject and structural positionality. Instrumental agency in the space of institutionalization worked to instill differentiation as plurality and normalization as objectification into the mentoring program. When instrumental agency is the dominant power in the space of institutionalization, the legitimacy of the mentoring program is rationalized as legitimization. Legitimization of the program results in an ecology of the space of institutionalization open to vagaries of political expediency. The second kind of power or agency to emerge is operative agency. Operative agency originates in sensings and feelings as expressed in wondering and uncertainty about mentoring roles and the mentoring program. When engaging operative agency as power, differentiation and normalization in the space of institutionalization can be questioned.
27

Assessment of Generation Cost of Off-shore Islands by Considering Fuzzy Wind Power Generation Model

Huang, Sheng-Lu 14 June 2004 (has links)
This thesis is to investigate the impact of wind power generation to the generation cost of Peng-Hu offshore islands. To find the load characteristics and load composition of Peng-Hu area, the load survey study has been performed to derive the typical load patterns of residential commercial and industrial customer classes. By retriving the power consumption information of all customers from the customer information system (CIS), the load contribution by each customer class during the system peak and off peak periods can be obtained. According to the temperature sensitivity of power consumption, the system load profile can be modified with the temperature change. With the stochastic wind speed and uncertainty of wind power energy, the nonlinear mathematical modeling of wind power generation has been derived by using the fuzzy theory. The wind power generation can therefore be estimated according to the wind speed variation, which will be used to coordinate with the diesel generators to provide electricity of customers served. With the hourly wind power generation and system load profile, the generation cost of diesel generators is therefore obtained. To illustrate the effectiveness of wind power generation for the offshore islands, the actual hourly wind speed for year 2003 is used for computer simulation to solve the avoided generation cost resulted from wind generation. It is found that wind power generators can reduce generation cost of diesel and provide the peak power capability. The cost benefit and incentive of wind power generation for Peng-Hu islands will help Taipower to evaluate the feasibility and effectiveness of wind power generation in Taiwan.
28

Automatic Measurement of Thermoelectric Power

chang, Bor-wei 29 June 2004 (has links)
My main subject is to set up a measuring system of TEP(Thermoelectric Power) which the theory was based on Thomas Seebeck effect, mechanism of the translation between thermal energy and electricity. There are two applications of thermoelectric power. One is temperature dependent measurement which is applied on thermal couple sensor; another one is to study the thermoelectric materials. The Seebeck coeifficient is approached to zero when superconductivity was occurred, also the calibration of the obtained value and offers essential information of carriers. The hardware of thermoelectric power measuring system consists of Digital NanoVoltmeter¡BProgrammable current Source¡BTemperature controller and Cryogenic compressor system. In the software, we use LabView to control the integral system and analyze the obtained data. For the whole system, it is vital to find a suitable compositions of sample holder¡Bheater and pasted way of sample.
29

The study of national security of ROC

Fu, Der 24 June 2004 (has links)
The existence and development of our nation mainly depends on our national security. As Minisrty of Defense mentioned in the report on the national defence, there are three things threatening the national security of ROC---Beijing using force against Taiwan, the dispute of the sovereignty over the South China Sea , and the independence of Taiwan.With the end of the Cold War, bipolar system collapsed, and the world turned out to be dominated by one super-power and several powerful nations(the super-power is refered to The US and the powerful nations are Russia, Japan, PRC, and EU). The above mentioned threats mentioned above are still threatening the security of our nation . In addition, declaration of the ¡§Peaceful Plebiscite¡¨ by President Chen during the 2004 presidential campaign results in the nervousness of PRC and the concern of the US. They both pronounce that they are against the independence of ROC in the name of ¡§Plebiscite¡¨ and ¡§Constitution¡¨. This article attempts to draw a clear picture of what national security strategy and policy should be made and make sure that our nation could solve any problems when facing threats and enjoy a long peaceful time.
30

AC/DC Testing Systems for High Voltage Power Cables

Hsu, Yu-hsiang 08 July 2008 (has links)
This thesis discusses the property of AC/DC testing systems for high voltage power cables and offers improvement to the design of AC/DC testing for high voltage power cables loops. First, the thesis analyzes the structure, and the physical and the electrical properties. The worsening level of the power cables insulation can be tested out through electrification measuring and diagnosed by spectrum analysis. Using established AC/DC testing loops, we perform High-Voltage Tests and AC Partial Discharge Test, as well as calculate Capacitance and Dissipation Factor. Besides , the thesis studies and processes data analysis according to the standard that was presented by the International Electrotechnical Commission. Finally, the thesis focuses on the noise that is produced by the high voltage reactor of the AC Resonance System, performs field measurements, and analyzes the results. Finally, the thesis proposes such as installing to spacers reduce noise to protect the safety, so as to protect the safety for the people in high voltage testing laboratory.

Page generated in 0.0553 seconds