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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.
171

Modelling of tilt rotor mission performance to assess environmental impact

Ruge Montilla, Jhonn Hamberth 01 1900 (has links)
New technologies and new rotorcraft operations are being developed in order to meet new environmental requirements such as noise reduction and less pollutant emissions. In this project a parametric study was developed over a tilt rotor model in order to assess the environmental impact in terms of operational parameter and fuel burned looking at pollutant emission released into the air such as NOx, CO, UHC, PM, CO2 & H2O In order to perform the study previously stated, a computational tool build on Simulink titled tilt rotor mission performance was developed to run a single mission profile as a base line making different operational variations on every mission segment looking at deviations over fuel burned and pollutant emissions. The contribution of pollutant emissions during the cruise segment was compared to other phases obtaining 80% of CO2 and H2O, 75% of CO and UHC, 77% of NOx, and 78% of PM. Also, comparing the distance flown of the tilt rotor with some turboprop aircraft, it was found that the fuel burned and levels of CO2 are higher using tilt rotor rather than turboprop aircraft. On the other hand this is much better than helicopters.
172

Transferability of community-based macro-level collision prediction models for use in road safety planning applications

Khondaker, Bidoura 11 1900 (has links)
This thesis proposes the methodology and guidelines for community-based macro-level CPM transferability to do road safety planning applications, with models developed in one spatial-temporal region being capable of used in a different spatial-temporal region. In doing this. the macro-level CPMs developed for the Greater Vancouver Regional District (GVRD) by Lovegrove and Sayed (2006, 2007) was used in a model transferability study. Using those models from GVRD and data from Central Okanagan Regional District (CORD), in the Province of British Columbia. Canada. a transferability test has been conducted that involved recalibration of the 1996 GVRD models to Kelowna, in 2003 context. The case study was carried out in three parts. First, macro-level CPMs for the City of Kelowna were developed using 2003 data following the research by GVRD CPM development and use. Next, the 1996 GVRD models were recalibrated to see whether they could yield reliable prediction of the safety estimates for Kelowna, in 2003 context. Finally, a comparison between the results of Kelowna’s own developed models and the transferred models was conducted to determine which models yielded better results. The results of the transferability study revealed that macro-level CPM transferability was possible and no more complicated than micro-level CPM transferability. To facilitate the development of reliable community-based, macro-level collision prediction models, it was recommended that CPMs be transferred rather than developed from scratch whenever and wherever communities lack sufficient data of adequate quality. Therefore, the transferability guidelines in this research, together with their application in the case studies, have been offered as a contribution towards model transferability to do road safety planning applications, with models developed in one spatial-temporal region being capable of used in a different spatial-temporal region.
173

(Bort)förklaringar till varför reflexer inte används : Ålder, kön och Construal Level Theory

Lyytikäinen, Maria January 2013 (has links)
Genom att använda reflex kan gångtrafikanten i mörkret upptäckas 100 meter tidigare av bilisten. Ändå används de inte. CLT rör hur mentala konstruktioner formas och hur individen rör sig mellan psykologiska distanser på abstrakta eller konkreta nivåer. Kognitiv dissonans innebär att beteenden ligger i konflikt vilket leder till obehag som behöver reduceras. En enkätundersökning med 120 deltagare genomfördes med syftet att se om individer inomhus i dagsljus förklarade sin frånvaro av reflexer abstrakt medan individer utomhus i mörker förklarade konkret. Resultatet visade inget stöd för detta men däremot att män hade en tendens att förklara sig mer abstrakt än kvinnor samtidigt som de använde reflexer mer sällan och ansåg dem vara mindre viktiga för säkerheten. Resultatdiskussionen gällde om frågorna i indelningarna av abstrakt och konkret är alltför olika. Dessutom diskuteras om den psykologiska distansen var för liten eller om kön avgör mer för typ av förklaring än miljön.
174

Developing Innovative Designs with Manufacturing Capability Using the Level Set Method

Baradaran Nakhjavani, Omid 05 September 2012 (has links)
This thesis discusses how to use topology and shape optimization, specifically the level set method, for innovative design. The level set method is a numerical algorithm that simulates the expansion of dynamic implicit surfaces. In this research, the equations for manufacturability are generated and solved through use of the level set method joined with the COMSOL multi-physics package. Specific constraints are added to make the optimization practical for engineering design. The resulting method was applied to design the best underlying support structure, conforming to both curvature and manufacturability constraints, for the longerons used with the International Space Station solar panels.
175

High Level Control for an Unmanned Aerial Vehicle

Söderman, Johan January 2011 (has links)
This thesis work was undertaken to develop a new high level command for an unmanned aerial vehicle. The command is assumed to make the UAV follow a reference position that is placed on a certain distance to an object. At the same time the UAV is assumed to move more smoothly than the reference position and the UAV is allowed to follow the reference position with margin. The problem was solved with an automatic control system that takes the reference position as input signal and has a fictitious position as output signal. The fictitious position moves smoothly inside the margin and irregular behavior of the reference position is smoothed out by the automatic control system. The fictitious position is affected by strong feedback outside the margin and weak feedback inside the margin. This makes the fictitious position to stay inside the margin and moves smoothly inside the margin. The UAV follows the fictitious position instead of the reference position. In this way the UAV holds a certain distance to an object and at the same time moves smoother than the object.
176

Corporate and business strategy at MNEs : A managerial practice view

Machulskyi, Ievgen, Bogomyagkov, Yury January 2012 (has links)
Corporate strategy is a foundation for companies operations, processes and  the ways in which its various businesses  work together to achieve particular goals.  Scholars and managers  recognize different levels of strategy for organizations. One of  the  differentiations  is  based  on  governance structure of the organization, and divides  corporate strategy on two levels: corporate strategy  and business-unit strategy. In many cases, some might think that business and corporate dimensions are the same. However,  when divided into strategies, there is a difference. This especially relates to MNEs (multinational enterprises), with their massive and sometimes complicated structure  and business units all over the world.  This study intends to find out whether and how corporate strategy as whole is employed and engineered in terms of this differentiation at MNEs, as well as to explore the additional factors   to well-known ones, affecting strategy development on both levels. Even though, a decent amount of studies have been done on a field,  the views on which questions should be answered by corporate level  strategies or business unit strategies are significantly differ. Hence, in order to develop understanding and contribute to the further research, this study has been undertaken.
177

Improving expertise-sensitive help systems

Masarakal, Mangalagouri 18 March 2010 (has links)
Given the complexity and functionality of todays software, task-specific, system-suggested help could be beneficial for users. Although system-suggested help assists users in completing their tasks quickly, user response to unsolicited advice from their applications has been lukewarm. One such problem is lack of knowledge of system-suggested help about the users expertise with the task they are currently doing. This thesis examines the possibility of improving system-suggested help by adding knowledge about user expertise into the help system and eventually designing an expertise-sensitive help system. An expertise-sensitive help system would detect user expertise dynamically and regularly so that systems could recommend help overtly to novices, subtly to average and poor users, and not at all to experts.<p> This thesis makes several advances in this area through a series of four experiments. In the first experiment, we show that users respond differently to help interruptions depending on their expertise with a task. Having established that user response to helpful interruptions varies with expertise level, in the second experiment we create a four-level classifier of task expertise with an accuracy of 90%. To present helpful interruptions differently to novice, poor, and average users, we need to design three interrupting notifications that vary in their attentional draw. In experiment three, we investigate a number of options and choose three icons. Finally, in experiment four, we integrate the expertise model and three interrupting notifications into an expertise-sensitive system-suggested help program, and investigate the user response. Together, these four experiments show that users value helpful interruptions when their expertise with a task is low, and that an expertise-sensitive help system that presents helpful interruptions with attentional draw that matches user expertise is effective and valuable.
178

Chief Executive Officer’s (CEO’s) Educational Background and Firm Performance : An empirical study on Manufacturing and IT listed firms in the Stockholm Stock Exchange

Ofe, Hosea Ayaba January 2012 (has links)
In this thesis I examine the impact of the educational background of Chief Executive Officers (CEOs) on firm performance of listed firms in the Stockholm stock exchange. This area of research is important given that researchers in the area of behavioral finance and in management argue that CEO characteristics such as educational orientation, age and functional background influence the way business problems are perceived and the decision making process. The numerous and growing challenges which businesses face, particularly in the area of operations,cost-cutting and production efficiency makes the need to examine how CEO educational background could be beneficial for firm performance very relevant. Particular attention is on listed firms in the manufacturing, oil and gas, energy sector characterized by low instability (turbulence) and the IT industry characterized by rapid growth and high turbulence. Educational background information for 100 CEOs is examined between 2008-2010. The information gathered from the annual reports of these companies, shows that the educational path way for most CEOs in these industries has been an engineering degree. The regression analysis on CEO educational background and firm performance show no significant relationship. More specifically the regression analysis show no support for the assertion that firms controlled by CEOs with an educational background in engineering have a firm performance advantage or outperformed firms controlled by CEOs with other backgrounds such as law ,marketing and finance. In addition, the finding shows no significant relationship between CEO educational level (undergraduate or postgraduate) and firm performance. The analysis thus showed no support for the claim that firms controlled by CEO with a higher level of education (postgraduate degree) had a superior firm performance over firms controlled by a CEO who had an undergraduate degree.
179

Level-set RANS method for sloshing and green water simulations

Yu, Kai 15 May 2009 (has links)
An interface-preserving level set method is incorporated into the Reynolds- Averaged Navier-Stokes (RANS) numerical method for the time-domain simulation of green water effects. This generalized method can be used to evaluate two- and three-dimensional, laminar and turbulent, free surface flows in moving non-orthogonal grids. In the method, free surface flows are modeled as immiscible two-phase (air and water) flows. A level set function is used to mark the individual fluids and the free surface itself is represented by the zero level set function. The level set evolution equation is coupled with the conservation equations for mass and momentum, and solved in the transformed plane. Chimera domain decomposition technique is employed to handle embedding, overlapping, or matching grids. To demonstrate the feasibility of the method, calculations are performed in several bench mark free surface flows including dam break flows, free jets, solitary wave propagations and the impingement of dam break flow on a fixed structure. The comparisons between the simulations and the experimental data provide a thorough validation of the present method. The results also show the potential capability of level-set RANS method in much more complicated free surface flow simulations. After validations, the method is applied to simulate sloshing flows in LNG tank and green water over the platform. In sloshing flows, the level-set RANS method captures the large impact pressure accurately on LNG tank walls. It also generates a plunging breaker successfully in front of a platform in the numerical wave tank. The good agreements between numerical and experimental results prove the level set RANS method is a powerful and accurate CFD methodology in free surface flow simulations.
180

Computational Fluid Dynamics Simulation of Green Water Around a Two-dimensional Platform

Zhao, Yucheng 2009 December 1900 (has links)
An interface-preserving level set method is incorporated into the Reynolds-Averaged Navier-Stokes (RANS) numerical method to simulate the application of the green water phenomena around a platform and the breaking wave above the deck. In the present study, this method is used to evaluate the laminar in two dimension plane with fixed orthogonal grids. In this method, it is assumed that the free surface is modeled as immiscible two-phase flow (air and water). A level set function can present the individual fluids, and the interface between two-phase is represented by the zero level set. In addition, the level set evolution equation is coupled with the conservation equations for mass and momentum, which will be solved in the transformed plane. For different purposes, there are several block domains in the application grid. Chimera domain decomposition technique is employed to handle such embedding, overlapping, or matching grids. Several simple test cases were performed to demonstrate the feasibility of this method. The comparisons between the ENO scheme and the WENO scheme will be illustrated in the Zalesak's disk case and will further prove that the WENO scheme is superior to the ENO scheme. The propagation of continuous wave case will validate some properties of wave and determine the importance of some parameters in code. Moreover, the method will be applied in simulation of green water around a two dimensional platform. By configuring different deck heights, some distinct phenomena can be represented. Lastly, it is crucial to observe the green water phenomena around the platform deck by applying the velocity-extrapolation routine.

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