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  • 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.
51

The inverse determination of aircraft loading using artificial neural network analysis of structural response data with statistical methods

Carn, Cheril, cheril.Carn@dsto.defence.gov.au January 2007 (has links)
An artificial Neural Network (ANN) system has been developed that can analyse aircraft flight data to provide a reconstruction of the aerodynamic loads experienced by the aircraft during flight, including manoeuvre, buffet and distributed loading. For this research data was taken from the International Follow-On Structural Test Project (IFOSTP) F/A-18 fatigue test conducted by the Royal Australian Air Force and Canadian Forces. This fatigue test involved the simultaneous application of both manouevre and buffet loads using airbag actuators and shakers. The applied loads were representative of the actual loads experienced by an FA/18 during flight tests. Following an evaluation of different ANN types an Ellman network with three linear layers was selected. The Elman back-propagation network was tested with various parameters and structures. The network was trained using the MATLAB 'traingdx' function with is a gradient descent with momentum and adaptive learning rate back-propagation algorithm. The ANN was able to provide a good approximation of the actual manoeuvre or buffet loads at the location where the training loads data were recorded even for input values which differ from the training input values. In further tests the ability to estimate distributed loading at locations not included in the training data was also demonstrated. The ANN was then modified to incorporate various methods for the calculation and prediction of output error and reliability Used in combination and in appropriate circumstances, the addition of these capabilities significantly increase the reliability, accuracy and therefore usefulness of the ANN system's ability to estimate aircraft loading.To demonstrate the ANN system's usefulness as a fatigue monitoring tool it was combined with a formulae for crack growth analysis. Results inficate the ANN system may be a useful fatigue monitoring tool enabling real time monitoring of aircraft critical components using existing strain gauge sensors.
52

Identification of extreme load cases for a surface drill rig by means of MBS simulations

Anbo, Anders January 2010 (has links)
<p>This master thesis is Atlas Copco Craelius’ first step in incorporating numericalmethods in load case analysis during the development process. Atlas Copco needs toconstantly evolve and refine their methods in the design process to remain as thenumber one manufacturer of mining and construction equipment. Poor knowledge ofloads results either in structural failures or in oversized structures, both very costlyfor Atlas Copco.The main goal of this thesis is to examine the potential in MBS software by using it toidentify extreme load cases in one of Atlas Copco Craelius’ surface drill rigs, Mustang5. The MBS-software ADAMS View is used to build a model of the Mustang 5 drill rigand evaluate simulation results. The rig model is subject to motions which representreal case scenarios. The feed positioning possibilities are examined thoroughly since it was expected that the positioning has impact on the load levels. 25 different feedpositioning are simulated.The main conclusion is that the load levels are highly dependent on the feedpositioning. For example, the load levels in the boom raising cylinder can increaseseven times, if the rig is operated with the most unfavorable positioning compared tothe recommended. It could also be concluded that not only one positioning isextreme in terms of loads; it depends on which part of the boom system is beingobserved. Thus, several positioning cases have to be taken into consideration in orderto optimize the design of parts in the boom system.</p>
53

Using Trends and Geochemical Analysis to Assess Salinity Sources along the Pecos River, Texas

Hoff, Aaron 2012 May 1900 (has links)
Increasing salinity has been a growing concern for users of waters from the Pecos River and the reservoirs it feeds in the Texas portion of the River's watershed. Irrigation water diverted from the river in the northern reach of this watershed is often only suitable for a limited number of crops, reducing harvesting options for local farmers. In the south, the Pecos feeds into the International Amistad Reservoir along the border with Mexico. During the 1990s, total dissolved solids concentrations in the reservoir rose as much as 10 mg/L per year and often approached the drinking water standard for potable water (1000 mg/L). Since this time, control efforts have focused on reducing the river's salinity, requiring the identification of salt sources. Hydrologic trend analysis and geochemical identification methods were used to determine these sources for the reach of the river between Red Bluff Reservoir and Brotherton Ranch. Between Red Bluff Reservoir and Coyanosa, flow diversions remove much of the flow that carries the salts, resulting in decreased salt loads, but also making the river more sensitive to evapotranspirative concentration. This sensitivity is evident in the river between Coyanosa and Girvin, where salinity begins to increase to the highest levels within the study area. However, salt loads increase here as well, indicating external salt sources as a contributor. The most substantial increase in bromide ions and the Br-/Cl- ratio appears between Grandfalls and Imperial, although no conclusion could be drawn regarding the identity of the source. The ratio continues to increase up to Girvin, where it appears that evapotranspirative concentration again has a significant effect. Here, several points drifted to the right of the groundwater mixing zones, plotting at values that were uncharacteristic of these sources.
54

An Integrated Voltage Optimization Approach For Industrial Loads

Madhavan, Adarsh January 2013 (has links)
Although Voltage Varying (VV) strategies like Conservation Voltage Reduction (CVR) are widely used by utilities to reduce the overall energy consumption and peak power demand of distribution feeders, it is aberrant among industrial customers. This research proposes a Voltage Varying (VV) strategy for industrial customers that takes into account their complex characteristics and unique set of constraints. Unlike VV strategies for Local Distribution Companies (LDC), those for an industrial customers are far more complex, and require specific c load modelling and process estimation to infer the optimal operating voltage for the industrial load. The proposed VV technique referred to as Voltage Optimization (VO), is a generic and comprehensive framework that seeks to reduce the energy consumption of the industrial load vis-~a-vis the bus voltage. It utilizes a Neural Network (NN) model of the industrial load, trained using historical operating data, to estimate the real power consumption of the load, based on the bus voltage and overall plant process. This load model, is incorporated into the proposed VO model, whose objective is the minimization of the energy drawn from the substation and the switching operations of Load Tap Changers (LTC). The proposed VO framework is tested on load models developed using simulated and real data. Results suggest that the proposed technique can be successfully implemented by industrial customers or plant operators to improve their energy savings, in comparison to existing VV techniques.
55

Identification of extreme load cases for a surface drill rig by means of MBS simulations

Anbo, Anders January 2010 (has links)
This master thesis is Atlas Copco Craelius’ first step in incorporating numericalmethods in load case analysis during the development process. Atlas Copco needs toconstantly evolve and refine their methods in the design process to remain as thenumber one manufacturer of mining and construction equipment. Poor knowledge ofloads results either in structural failures or in oversized structures, both very costlyfor Atlas Copco.The main goal of this thesis is to examine the potential in MBS software by using it toidentify extreme load cases in one of Atlas Copco Craelius’ surface drill rigs, Mustang5. The MBS-software ADAMS View is used to build a model of the Mustang 5 drill rigand evaluate simulation results. The rig model is subject to motions which representreal case scenarios. The feed positioning possibilities are examined thoroughly since it was expected that the positioning has impact on the load levels. 25 different feedpositioning are simulated.The main conclusion is that the load levels are highly dependent on the feedpositioning. For example, the load levels in the boom raising cylinder can increaseseven times, if the rig is operated with the most unfavorable positioning compared tothe recommended. It could also be concluded that not only one positioning isextreme in terms of loads; it depends on which part of the boom system is beingobserved. Thus, several positioning cases have to be taken into consideration in orderto optimize the design of parts in the boom system.
56

Full-scale lateral-load tests of a 3x5 pile group in soft clays and silts /

Snyder, Jeffrey L., January 2004 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2004. / Includes bibliographical references (p. 215-220).
57

Reinforced concrete column behavior under cyclic loading /

Xiong, Zhaohui. January 2001 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 226-236).
58

The nature of gustiness of typhoon winds and gust loading on buildings.

Ho, Kar-chung, John. January 1976 (has links)
Thesis--Ph. D., University of Hong Kong.
59

Behavior of steel members with trapezoidally corrugated webs and tubular flanges under static loading /

Wang, Xiaobo. Elgaaly, Mohamed. January 2003 (has links)
Thesis (Ph. D.)--Drexel University, 2003. / Includes abstract and vita. Includes bibliographical references (leaves 186-191).
60

Energy analysis of toplighting strategies for office buildings in Austin

Motamedi, Sara 25 April 2013 (has links)
The purpose of this study is to determine the energy impacts of daylighing through toplights in a hot humid climate. Daylight in the working environment improves the quality of the space, and productivity of employees. In addition, natural light is a free energy resource. On one hand, a proper design of daylight such as distributed toplights can reduce the electrical lighting consumption. On the other hand, in a hot climate like Austin heat gain is a major concern. Therefore, this thesis is shaped around this question: Can toplighting strategies save energy in Austin despite the fact that buildings receive more direct heat gain through toplights? The importance of daylighting is more revealed since electrical lighting takes up a significant portion of the total building energy use (21%). In this thesis I investigated the reduction of lighting electricity and compared that with the total effects of toplights on external conductance, lighting heat gain and solar gain. The results of my thesis show that regarding the site energy a proper toplighting strategy can save electrical lighting up to (70%) with smaller impact on heating and cooling loads. This means that toplights generally can be energy efficient alternatives for a one storey office building. Developing my research I studied which toplights are more efficient: north sawtooth roofs, south sawtooth roofs, monitor roofs or very simple skylights. I compared different toplighting strategies and provided a design guide containing graphs of site energy, source energy, annual cost saving per square feet, as well as light distribution of each toplight. I believe this can accelerate implementation of efficient toplighting strategies in the design process. Concluding how significantly efficient daylighting is over heat gain, I finalized my research by comparison of skylights with different visible transmission (VT) and solar heat gain coefficient (SHGC). The major result of this thesis is that proper toplighting strategies can save energy despite the increased solar gain. It is anticipated that the thesis findings will promote the implementation of toplighting strategies and higher VT glass type in the energy efficient building industry. / text

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