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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.
251

Gaze strategies in perception and action

Desanghere, Loni January 2011 (has links)
When you want to pick up an object, it is usually a simple matter to reach out to its location, and accurately pick it up. Almost every action in such a sequence is guided and checked by vision, with eye movements usually preceding motor actions (Hayhoe & Ballard, 2005; Hayhoe, Shrivastava, Mruczek, & Pelz, 2003). However, most research in this area has been concerned about the sequence of movements in complex “everyday” tasks like making tea or tool use. Less emphasis has been placed on the object itself and where on it the eye and hand movements land, and how gaze behaviour is different when generating a perceptual response to that same object. For those studies that have, very basic geometric shapes have been used such as rectangles, crosses and triangles. In everyday life, however, there are a range of problems that must be computed that go beyond such simple objects. Objects typically have complex contours, different textures or surface properties, and variations in their centre of mass. Accordingly, the primary goals in conducting this research were three fold: (1) To provide a deeper understanding of the function of gaze in perception and action when interacting with simple and complex objects (Experiments 1a, 1b, 1c); (2) To examine how gaze and grasp behaviours are influenced when you dissociate important features of an object such as the COM and the horizontal centre of the block (Experiments 2a, 2c); and (3) To explore whether perceptual biases will influence grasp and gaze behaviours (Experiment 2b). The results from the current series of studies showed the influence of action (i.e., the potential to act) on perception in terms of where we look on an object, and vice versa, the influence of perceptual biases on action output (i.e. grasp locations). In addition, grasp locations were found to be less sensitive to COM changes than previously suggested (for example see Kleinholdermann, Brenner, Franz, & Smeets, 2007), whereas fixation locations were drawn towards the ‘visual’ COM of objects, as shown in other perceptual studies (for example see He & Kowler, 1991; Kowler & Blaser, 1995; McGowan, Kowler, Sharma, & Chubb, 1998; Melcher & Kowler, 1999; Vishwanath & Kowler, 2003, 2004; Vishwanath, Kowler, & Feldman, 2000), even when a motor response was required. The implications of these results in terms of vision for Perception and vision for Action are discussed.
252

Exposure of welders to manganese in welding fumes / Miriska Ferreira

Ferreira, Miriska January 2012 (has links)
Aims and objectives: The general aim of this study was to determine the personal respiratory exposure and biological monitoring of manganese (Mn) present in welding fumes as well as its neurological influence on welders. The objectives of this study were: (i) to assess the respiratory exposure of welders to Mn present in welding fumes; (ii) to assess the biological Mn load of welders via the use of nail clippings; (iii) to establish possible correlations between respiratory exposure to Mn and its presence in nail clippings, and (iv) to determine the possible difference in finger dexterity and coordination between Mn exposed welders and a control group. Methods: A gravimetrical method was used to determine the respiratory exposure of welders. A cassette containing a 0.8-μm, cellulose ester membrane filter, attached to the side of a welding helmet provided, was connected via a stainless steel fitting to the inside (respiratory zone) of the helmet. Chemical analysis (metal content) of the welding fumes was done according to the NIOSH 7300 method, using Inductively Coupled Argon Plasma, Atomic Emission Spectroscopy (ICP-AES). Nail clippings were collected at the beginning and end of the study to determine the Mn level in the nails in both welders as well as paired controls. The nails were deposited into small, plastic vials and also analysed according to the NIOSH 7300 method. A Perdue pegboard and mirror drawing test was also conducted to determine the influence of Mn exposure on finger dexterity and hand-eye coordination of welders. Results: Mn exposure in the welding fumes did not exceed the occupational exposure limit – recommended limit (OEL-RL) (1 mg/m3) of the Regulations for Hazardous Chemical Substances (RHCS), although two of these exposures exceeded the action level (0.5 mg/m3). No statistical significant correlations were found between the Mn respiratory exposure and the Mn found in the nails of the welders. Mn in the nails of exposed welders was statistical significantly higher (p = 0.003) than that of controls. The only statistical significant differences found in the motor function tests between the controls and welders were the test which was done by using their non-dominant hand in the beginning of the study (p = 0.016) and when the non-dominant hand values were pooled (p = 0.012). The usage of both hands simultaneously showed results that leaned toward statistical significant decrease of the welders compared to the control subjects (p = 0.090). In all these cases the controls inserted more pins than the welders. Only one moderately positive correlation (r = 0.612; p = 0.02) was found between Mn in the welding fumes and the number of errors made in the mirror drawing coordination test done by the welders. Discussion and Conclusions: The Mn in the nails of the control group was significantly lower than the Mn in the nails of the welders. This indicates that Mn respiratory exposure may influence Mn body burden although no correlation between Mn in welding fumes and Mn in nails were found. Nail Mn may serve as a biomarker to determine Mn body burden. Only the use of the non-dominant hand of the control subjects compared to the welders showed a significant decrease in finger dexterity of the welders. The moderately positive association between the Mn in the welding fumes and the number of errors made in the mirror drawing coordination test done by the welders indicates that with an increase in Mn in welding fumes, a decrease in hand-eye coordination will occur. It can be concluded that welders’ finger dexterity and hand-eye coordination may be influenced by the exposure to Mn in the welding fumes. / Thesis (MSc (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2013
253

Exposure of welders to manganese in welding fumes / Miriska Ferreira

Ferreira, Miriska January 2012 (has links)
Aims and objectives: The general aim of this study was to determine the personal respiratory exposure and biological monitoring of manganese (Mn) present in welding fumes as well as its neurological influence on welders. The objectives of this study were: (i) to assess the respiratory exposure of welders to Mn present in welding fumes; (ii) to assess the biological Mn load of welders via the use of nail clippings; (iii) to establish possible correlations between respiratory exposure to Mn and its presence in nail clippings, and (iv) to determine the possible difference in finger dexterity and coordination between Mn exposed welders and a control group. Methods: A gravimetrical method was used to determine the respiratory exposure of welders. A cassette containing a 0.8-μm, cellulose ester membrane filter, attached to the side of a welding helmet provided, was connected via a stainless steel fitting to the inside (respiratory zone) of the helmet. Chemical analysis (metal content) of the welding fumes was done according to the NIOSH 7300 method, using Inductively Coupled Argon Plasma, Atomic Emission Spectroscopy (ICP-AES). Nail clippings were collected at the beginning and end of the study to determine the Mn level in the nails in both welders as well as paired controls. The nails were deposited into small, plastic vials and also analysed according to the NIOSH 7300 method. A Perdue pegboard and mirror drawing test was also conducted to determine the influence of Mn exposure on finger dexterity and hand-eye coordination of welders. Results: Mn exposure in the welding fumes did not exceed the occupational exposure limit – recommended limit (OEL-RL) (1 mg/m3) of the Regulations for Hazardous Chemical Substances (RHCS), although two of these exposures exceeded the action level (0.5 mg/m3). No statistical significant correlations were found between the Mn respiratory exposure and the Mn found in the nails of the welders. Mn in the nails of exposed welders was statistical significantly higher (p = 0.003) than that of controls. The only statistical significant differences found in the motor function tests between the controls and welders were the test which was done by using their non-dominant hand in the beginning of the study (p = 0.016) and when the non-dominant hand values were pooled (p = 0.012). The usage of both hands simultaneously showed results that leaned toward statistical significant decrease of the welders compared to the control subjects (p = 0.090). In all these cases the controls inserted more pins than the welders. Only one moderately positive correlation (r = 0.612; p = 0.02) was found between Mn in the welding fumes and the number of errors made in the mirror drawing coordination test done by the welders. Discussion and Conclusions: The Mn in the nails of the control group was significantly lower than the Mn in the nails of the welders. This indicates that Mn respiratory exposure may influence Mn body burden although no correlation between Mn in welding fumes and Mn in nails were found. Nail Mn may serve as a biomarker to determine Mn body burden. Only the use of the non-dominant hand of the control subjects compared to the welders showed a significant decrease in finger dexterity of the welders. The moderately positive association between the Mn in the welding fumes and the number of errors made in the mirror drawing coordination test done by the welders indicates that with an increase in Mn in welding fumes, a decrease in hand-eye coordination will occur. It can be concluded that welders’ finger dexterity and hand-eye coordination may be influenced by the exposure to Mn in the welding fumes. / Thesis (MSc (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2013
254

Accommodating a High Penetration of Plug-in Electric Vehicles in Distribution Networks

Shaaban, Mostafa January 2014 (has links)
The last few decades have seen growing concern about climate change caused by global warming, and it now seems that the very future of humanity depends on saving the environment. With recognition of CO2 emissions as the primary cause of global warming, their reduction has become critically important. An effective method of achieving this goal is to focus on the sectors that represent the greatest contribution to these emissions: electricity generation and transportation. For these reasons, the goal of the work presented in this thesis was to address the challenges associated with the accommodation of a high penetration of plug-in electric vehicles (PEVs) in combination with renewable energy sources. Every utility must consider how to manage the challenges created by PEVs. The current structure of distribution systems is capable of accommodating low PEV penetration; however, high penetration (20 % to 60 %) is expected over the next decades due to the accelerated growth in both the PEV market and emission reduction plans. The energy consumed by such a high penetration of PEVs is expected to add considerable loading on distribution networks, with consequences such as thermal overloading, higher losses, and equipment degradation. A further consideration is that renewable energy resources, which are neither exhaustible nor polluting, currently offer the only clean-energy option and should thus be utilized in place of conventional sources in order to supply the additional transportation-related demand. Otherwise, PEV technology would merely transfer emissions from the transportation sector to the electricity generation sector. As a means of facilitating the accommodation of high PEV penetration, this thesis proposes methodologies focused on two main themes: uncontrolled and coordinated charging. For uncontrolled charging, which represents current grid conditions, the proposal is to utilize dispatchable and renewable distributed generation (DG) units to address the high PEV penetration in a way that would not be counterproductive. This objective is achieved through three main steps. First, the benefits of allocating renewable DG in distribution systems are investigated, with different methodologies developed for their evaluation. The benefits are defined as the deferral of system upgrade investments, the reduction in the energy losses, and the reliability improvement. The research also includes a proposal for applying the developed methodologies for an assessment of the benefits of renewable DG in a planning approach for the optimal allocation of the DG units. The second step involves the development of a novel probabilistic energy consumption model for uncontrolled PEV charging, which includes consideration of the drivers’ behaviors and ambient temperature effect associated with vehicle usage. The final step integrates the approaches and models developed in the previous two steps, where a long-term dynamic planning approach is developed for the optimal allocation of renewable and dispatchable DG units in order to accommodate the rising penetration of PEV uncontrolled charging. The proposed planning approach is multi-objective and includes consideration of system emissions and costs. The second theme addressed in this thesis is coordinated PEV charging, which is dependent on the ongoing development of a smart grid communication infrastructure, in which vehicle-grid communication is feasible via appropriate communication pathways. This part of the work led to the development of a proposed coordinated charging architecture that can efficiently improve the performance of the real-time coordinating PEV charging in the smart grid. The architecture is comprised of two novel units: a prediction unit and an optimization unit. The prediction unit provides an accurate forecast of future PEV power demand, and the optimization unit generates optimal coordinated charging/discharging decisions that maximize service reliability, minimize operating costs, and satisfy system constraints.
255

MITIGATION OF SYNCHRONOUS MACHINE BASED DISTRIBUTED GENERATION INFLUENCES ON FUSE-RECLOSER PROTECTION SYSTEMS IN RADIAL DISTRIBUTION NETWORKS USING SUPERCONDUCTING FAULT CURRENT LIMITERS

2015 February 1900 (has links)
Distributed generation (DG) is increasingly employed in modern utility grids to address the growing complexity and size of consumer energy demands. The obstacles associated with DG integration are related to the additive effect the DG has on the short circuit current characteristics of power systems during short circuit conditions. This thesis proposes a novel mitigation technique for synchronous machine based DG integration effects on existing radial fuse-recloser protection infrastructure. The mitigation method provides a comparative analysis of the utilization of resistive (R), inductive (L) and resonant (LC) type superconducting fault current limiters (FCLs) for prevention of excessive fault current contribution from DG sources. Within the frame of reference of this thesis is an interrogation into the effects of synchronous machine based DG sources, in conjunction with mitigation capabilities of FCL integration in the context of fuse-recloser coordination, recloser sensitivity and recloser directionality behavior during radial distribution short circuit conditions. For validation purposes, the proposed methods are demonstrated on a suburban test benchmark using the PSCAD/EMTDC program.
256

The evolution of European Union conflict prevention policy

Stewart, Emma J. January 2005 (has links)
This thesis focuses on a particular aspect of the international role of the European Union (EU), examining the evolution of EU conflict prevention policy in the post- Cold War period. In recent years the EU has extended its range of external relations policies, and conflict prevention has emerged as a prominent objective on the agenda, particularly as the Union faced political and economic instability on its borders. After introducing conflict prevention and analysing the EU's external relations and the post- Cold War security context, the thesis examines the EU's institutional set-up for conflict prevention. The incremental development and institutional structure of the EU renders the formulation and implementation of conflict prevention by the EU a particular challenge. The thesis then proceeds to an investigation of EU cooperation and conflict prevention policy coordination with the security organisations identified as the EU's key partners: the United Nations (UN), the Organisation for Security and Cooperation in Europe (OSCE) and the North Atlantic Treaty Organisation (NATO). While post-Cold War conflict prevention requires a multilateral approach, the proliferation of European security organisations and the increasing overlap in their objectives makes policy coordination between the EU and other organisations particularly important. It is concluded that the EU faces fundamental internal coordination problems and institutional divisions in its elaboration of conflict prevention policy. Conflict prevention is underdeveloped by the EU and is in danger of being marginalised in favour of shorter-term crisis management. Furthermore, internal coordination problems have a detrimental impact on the organisation's ability to cooperate externally with other security organisations. EU external priorities in conflict prevention focus on cooperation in crisis management with the UN and NATO, and fail to capitalise on the advantages of cooperation with the OSCE. The failure of the EU to fully adopt conflict prevention as an external relations priority and to coordinate its activities with other organisations could have implications for future stability in, and on the borders of, the EU.
257

Model driven coordination framework for concurrency programming

Zimmerman, John Dean January 2008 (has links)
Ensembles of distributed, autonomous and heterogenous entities that are situated in an environment, interacting over both space and time, and striving to uphold some global system coherence, mission, and goal characterize a new class of systems coined Open Computational Systems (OCS). OCS are materializing as a result of various enabling Internet technologies and examples include: ubiquitous computing, proactive computing, autonomic computing, network-centric computing, and network-centric warfare. OCS require a fundamental shift in the way we think about software development. In order to address these issues we advocate a holistic approach where models and tools come together to provide a platform for the building, understanding and monitoring of software based on the notion of these type of systems. In this research project, this was investigated by adopting the generative communication paradigm, a framework for entity communication and collaboration that will allow us to construct systems with characteristics of an OCS. Model-Driven Engineering (MDE) technologies (Domain Specific Modelling Languages and Transformation Engines) were used to provision a modelling environment for the construction, visualization and transformation of systems based on the notion of OCS. An initial mechanism was then established, and a prototype built for system understanding, verification and validation.
258

Analysis of visually-guided reaching performance in neurologically healthy young and elderly adults and adults with Alzheimer's disease /

Tippett, William John. January 2006 (has links)
Thesis (Ph.D.)--York University, 2006. Graduate Programme in Kinesiology and Health Science. / Typescript. Includes bibliographical references (leaves 138-152). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:NR19851
259

Synthesis and self-assembly of coordination lipid polymers

Gorlamari, Kranthikkumarreddy, January 2008 (has links)
Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.
260

Structural aspects of bis(quadridentate)zirconium(IV) complexes. Ligand motion and ligand exchange behavior of bis(N, N'-disalicylidene-1,2-phenylenediamino)zirconium(IV) and the two new complexes bis(N, N'-disalicylidene-cis-1,2-diamino-cyclohexane)-zirconium(IV) and bis(N, N''-disalicylidene-trans-1,2-diaminocyclhexane)zirconium(IV) /

Cleary, Brian P. January 1989 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 1989. / "Reference": leaves 224-227.

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