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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.
41

Non-intrusive condition monitoring of power cables within the industrial sector / Johannes Hendrik van Jaarsveldt

Van Jaarsveldt, Johannes Hendrik January 2015 (has links)
Condition monitoring (CM) of electrical equipment is an important field in electrical engineering and a considerable amount of research is dedicated to this field. Power cables are one of the most important parts of any electrical network and the variety of techniques available for CM of electrical cables is therefore no surprise. Electrical cables are exposed to operational and environmental stressors which will cause degradation of the insulation material. The degradation will continue to the point where the cable fails. Blackouts caused by failing cables will have an effect on the safety, efficiency and production of an electrical network. It is therefore important to constantly monitor the condition of electrical cables, in order to prevent the premature failure of cables. The research presented in this dissertation sets out to investigate CM techniques for power cables and to design and implement a basic cable CM technique based on the principles of partial discharge (PD) measurements. A comprehensive literature study introduces the fundamental concepts regarding the CM of power cables. The basic construction of electrical cables, as well as the variety of different types is researched in order to lay a foundation for the research that follow. CM techniques for electrical equipment are investigated, with the emphasis on techniques used on cables. Conducted research led to the decision to focus on CM by means of PD measurements. PD as a phenomenon is investigated to be able to better understand the origins and effects of discharge activity. From there the focus shifts to the available techniques for monitoring the condition of electrical cables by means of PD measurements. The research conducted in the literature study chapter forms the basis from which the rest of the study is conducted. Simulation models were used to study PD characteristics. The models are derived from engineering and mathematical principles and are based on the well-known three-capacitor model of PD. The simulations were performed in order to study the effects of discharge activity. The designed simulation models allows for a variety of PD characteristics to be studied. The simulations were performed in the MATLAB® Simulink® environment. The research conducted in the dissertation was used to design an elementary CM technique which can be used to detect the presence of PD within electrical cables. The designed CM technique was used for the practical measurement of PD data. MATLAB® programs were designed in order to analyse the PD data in both the time- and frequency-domain. The analysis of the measured data revealed PD characteristics of the test specimen used for the measurements. The designed CM is used for the detection of PD activity within electrical cables and in combination with other techniques, may be used for complete CM of electrical cables. The experimental setup which was used to take practical PD measurements adds another dimension to the work presented in this dissertation. / MIng (Electrical and Electronic Engineering), North-West University, Potchefstroom Campus, 2015
42

Non-intrusive condition monitoring of power cables within the industrial sector / Johannes Hendrik van Jaarsveldt

Van Jaarsveldt, Johannes Hendrik January 2015 (has links)
Condition monitoring (CM) of electrical equipment is an important field in electrical engineering and a considerable amount of research is dedicated to this field. Power cables are one of the most important parts of any electrical network and the variety of techniques available for CM of electrical cables is therefore no surprise. Electrical cables are exposed to operational and environmental stressors which will cause degradation of the insulation material. The degradation will continue to the point where the cable fails. Blackouts caused by failing cables will have an effect on the safety, efficiency and production of an electrical network. It is therefore important to constantly monitor the condition of electrical cables, in order to prevent the premature failure of cables. The research presented in this dissertation sets out to investigate CM techniques for power cables and to design and implement a basic cable CM technique based on the principles of partial discharge (PD) measurements. A comprehensive literature study introduces the fundamental concepts regarding the CM of power cables. The basic construction of electrical cables, as well as the variety of different types is researched in order to lay a foundation for the research that follow. CM techniques for electrical equipment are investigated, with the emphasis on techniques used on cables. Conducted research led to the decision to focus on CM by means of PD measurements. PD as a phenomenon is investigated to be able to better understand the origins and effects of discharge activity. From there the focus shifts to the available techniques for monitoring the condition of electrical cables by means of PD measurements. The research conducted in the literature study chapter forms the basis from which the rest of the study is conducted. Simulation models were used to study PD characteristics. The models are derived from engineering and mathematical principles and are based on the well-known three-capacitor model of PD. The simulations were performed in order to study the effects of discharge activity. The designed simulation models allows for a variety of PD characteristics to be studied. The simulations were performed in the MATLAB® Simulink® environment. The research conducted in the dissertation was used to design an elementary CM technique which can be used to detect the presence of PD within electrical cables. The designed CM technique was used for the practical measurement of PD data. MATLAB® programs were designed in order to analyse the PD data in both the time- and frequency-domain. The analysis of the measured data revealed PD characteristics of the test specimen used for the measurements. The designed CM is used for the detection of PD activity within electrical cables and in combination with other techniques, may be used for complete CM of electrical cables. The experimental setup which was used to take practical PD measurements adds another dimension to the work presented in this dissertation. / MIng (Electrical and Electronic Engineering), North-West University, Potchefstroom Campus, 2015
43

Wireless Sensor System for Airborne Applications

Pellarin, Steve, Grossman, Hy, Musteric, Steven 10 1900 (has links)
ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / Adding an instrumentation / telemetry system to a test article has historically required an intrusive installation. Power, wiring, and available space typically present significant challenges. There has been a long-standing need in the test and training community for a non-intrusive, flexible and modular instrumentation and telemetry system that can be installed on an aircraft or other test article without the need for permanent modifications. In addition, as available space in aircraft weapon bays, small weapons, and unmanned vehicles becomes a premium, the miniaturization of remote sensors and telemetry units becomes critical. This paper describes the current status of the Advanced Subminiature Telemetry System (ASMT) Initial Test Capability Project. It discusses the progress to date in fielding an operational, wireless sensor system that may be installed on the aircraft skin using an Electro-Cleavable adhesive as an alternative to conventional mounting methods. The wireless sensor utilizes the Wireless Communications Standard for Wireless Personal Area Network™ (WPAN™) IEEE 802.15 Working Group standard (commonly referred to as Bluetooth) to establish communication between the sensor and controller modules. Results of aircraft ground testing for EMI compatibility with aircraft systems will be presented. It is also expected that actual flight test results will be available by the time the paper goes to publication.
44

WIRELESS SENSOR SYSTEM FOR AIRBORNE APPLICATIONS

Pellarin, Steve, Musteric, Steven 10 1900 (has links)
ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Adding an instrumentation / telemetry system to a test article has historically required an intrusive installation. Power, wiring, and available space typically present significant challenges. There has been a long-standing need in the test and training community for a non-intrusive, flexible and modular instrumentation and telemetry system that can be installed on an aircraft or other test article without the need for permanent modifications. In addition, as available space in aircraft weapon bays, small weapons, and unmanned vehicles becomes a premium, the miniaturization of remote sensors and telemetry units becomes critical. This paper describes the current status of the Advanced Subminiature Telemetry System (ASMT) Initial Test Capability Project. It discusses the challenges that have been overcome in developing a wireless sensor network system for use in an airborne test environment. These include wireless sensor packaging design, selection of operating frequencies, COTS wireless devices, batteries, system synchronization and data bandwidth calculations. The paper will also document the progress to date including preliminary test results.
45

Intrusive thoughts, mindfulness and dissociation in self-harm

Batey, Helen Elizabeth January 2011 (has links)
This thesis presents four studies that examine the potential role that intrusive thoughts, dissociation and mindfulness in self-harming behaviours in young people and adults. A large online study was conducted with students and staff at a UK university. This examined a range of risk factors for self-harm derived from the literature, including dissociation, family background/trauma history and intrusive thoughts. This study was followed up with a qualitative study investigating triggers of self-harm, and the role of intrusive thoughts. A third study then looked at these factors in young people who were inpatients in an American psychiatric hospital, and who had all expressed intent to self- harm or commit suicide. This study also introduced a measure of trait mindfulness in order to investigate this potential way of dealing with intrusive thoughts. Finally, the risk factors identified in these studies were further investigated with an online survey with undergraduate students at a second UK university, dissociation, mindfulness and thought suppression. Intrusive thoughts were found to differ in content, frequency and effect between people with experience of self-harm and those without. A subgroup of potentially maladaptive behaviours were found to be associated with high scores on the predictors of self-harm, and therefore potentially predictive of self-harm. In the young people in hospital, the extent to which they reacted to their intrusive thoughts was inversely associated with the extent to which they were naturally mindful. Trait mindfulness scores were lower for those individuals with a history of childhood trauma, and for those meeting diagnostic criteria for Borderline Personality Disorder, in which self-harm is a key feature. These findings together suggest that mindfulness skills may play an important role in both dealing with intrusive thoughts and for protecting against self-harm. Overall, intrusive thoughts and dissociation were associated with experience of self- harming behaviours, while mindfulness skills were negatively associated with self-harm. Some potentially maladaptive behaviours (including smoking and eating pathology) represent risk factors for self-harm, and therefore may provide professionals with a way of identifying people for early intervention, if further longitudinal research shows evidence of progression. Alternatively, the differences in mindfulness between this group and the self-harmers may indicate that mindfulness training could benefit people who self-harm.
46

Konsten att förmedla online-annonser : En studie om vilken typ av online-annonser som används för att nå ut till internetanvändare på ett mindre påträngande sätt

Wallin, Clas, Wisseng, Sara January 2016 (has links)
Påträngande och störande annonser har blivit alltmer vanligt på internet vilket har medfört att konsumenter fått en alltmer negativ inställning till online-annonser. Därmed har användningen av mjukvaror för blockering av annonser på senare tid blivit alltmer vanligt. Detta har medfört minskningar i reklamintäkter för företag som använder sig av webbaserad marknadsföring, vilket har lagt för handen att de måste anpassa sina online-annonser till konsumenten för att kunna hålla verksamheten lönsam. Syftet med denna studie är att undersöka vilken typ av online-annonser som används för att nå ut till användare på internet på ett mindre påträngande och irriterande sätt samt vilken inställning de har till annonsblockerare. Uppsatsen har en triangulär ansats i form av kvalitativa semi-strukturerade intervjuer som stärks och jämförs med en kvantitativ enkätundersökning. Av slutsatsen framkommer det att native advertising är det mest effektfulla annonsformatet för att nå ut till konsumenter på ett mer accepterat sätt. Samtidigt börjar fler företag som använder sig av online-annonser att införa betalväggar på sina hemsidor där konsumenter på internet tvingas stänga av sin annonsblockerare, bli nekade innehållet eller betala för att få tillgång till det. / Intrusive and annoying ads have become increasingly common on the internet, which has led to that consumers have a more negative attitude to online ads. Thus, using softwares for blocking ads have lately become more common. This has led to reductions in advertising revenues for companies that use web-based marketing which have forced them to customize their ads to the consumers in order to keep the business profitable.     The aim of this paper is to examine what type of online ads that is used to reach out to internet users in a less intrusive way and to see their opinion about adblockers. From a consumer perspective the study examines the view of the consumer on this development and if they fulfil their purpose. The thesis has a triangular approach with semi-structured interviews that is strengthened and compared with a quantitative questionnaire. The conclusion of the research have showed that native advertising is the most effective ad format to reach out to consumers in a more acceptable manner. At the same time more companies that are using online ads choose to introduce paywalls on their webpages where consumers on the internet are forced to deactivate their adblockers, to be denied the content or to pay to gain access to it.
47

Sleep and sleep timing in relation to light and emotional processing

Porcheret, Kate L. January 2012 (has links)
Sleep is a complex process: the timing of sleep is regulated by two systems (the sleep homeostat and the circadian clock) and there are many potential functions of sleep. The aim of this thesis was to investigate: the impact of light on the regulation of sleep timing (study 1) and the role of sleep in emotional processing (study 2). Study 1 used natural variations in environmental light levels at different geographical locations, to examine the influence of daily light irradiance on sleep timing and chronotype using the Munich chronotype questionnaire (MCTQ). 6443 students were included in this study from six universities from the northern and southern hemispheres. Students in southern hemisphere cities had earlier sleep timings than those in the northern cities. Daily irradiance was higher in the southern hemisphere cities. The amount of time spent outside, age and sex, but not daily irradiance, influenced sleep timings. Study 2 explored the impact of an analogue traumatic event (trauma film) in students who were either sleep deprived or not sleep deprived on intrusive memories ("flashbacks"), sleep physiology and the impact of an increased risk of a mood disorder on this relationship. In this study the sleep deprived participants (n=19) reported fewer intrusive memories to the trauma film than those not sleep deprived (n=22). A change in sleep physiology was observed in the first sleep period following the trauma film, which was more pronounced in the sleep deprived group: increased levels of arousal, REM density and activity in the occipital region. Only three participants at-risk of a mood disorder completed study 2: their data are presented as case studies. In conclusion this research has demonstrated that differences in sleep timings exist between cities in the southern and northern hemispheres and has confirmed that many factors can influence sleep timing. It has also been demonstrated that following a highly emotional event not sleeping may have a beneficial effect, which has implications for the treatment of people after trauma.
48

Évaluation et dépendance angulaire de l'estimateur Lagrangien en élastographie vasculaire non-intrusive

Mercure, Élizabeth January 2006 (has links)
Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.
49

Intrusive advising and its implementation in residence halls

Tennant, Abigail January 1900 (has links)
Master of Science / Department of Special Education, Counseling and Student Affairs / Christy Craft / Abstract Intrusive advising is a concept that developed in the 1970s as a method of working with at-risk students by identifying challenges they faced and solutions to overcome them (Backhus, 1989). Intrusive contacts are those that make early, unsolicited contact with students in the hopes of identifying and resolving academic and social obstacles that would prevent persistence (Frost, 1991). This proactive approach has been experiencing revitalization in the current economic times due to declining funds and changing governmental funding models that would fund higher education on the basis of graduation rather than enrollment. Because 44 percent of first year students do not persist to their second year, this type of governmental funding model has profound implications for administrators (Bushong, 2009). I propose that administrators consider restructuring residence hall personnel responsibilities to include intrusive contacts in an effort to address retention issues. While residence hall personnel will not have the responsibility of scheduling classes, they can begin identifying and addressing issues earlier in the semester. This paper identifies several institutions that currently implement intrusive contacts in their residence halls and the benefits of doing so. These schools have indicated an increase in their students’ grades, commitment and persistence, and overall satisfaction since implementing intrusive contacts (B. Silliman, personal communication, November 1, 2012). The findings also revealed that residence halls with effective intrusive contacts involve collaborative efforts between student affairs personnel and faculty members, engage students in building rapport with staff early in their first semester, and focus on developing students holistically. This report provides a summary of best practices and strategies for implementing these contacts.
50

Metodologia não intrusiva baseada na técnica fotoacústica para o estudo de membranas vítreas porosas / Non-instrusive methodology based on the photoacoustic technique for studying porous vitreous membranes

Yasuda, Márcio Tsuyoshi 25 September 2003 (has links)
A espectroscopia fotoacústica (PA) vem sendo largamente utilizada em diversos ramos de pesquisa, principalmente nas investigações de materiais quanto às suas propriedades ópticas e térmicas, demonstrando a sua vasta versatilidade. No presente trabalho, desenvolveu-se uma câmara fotoacústica de uso geral e uma metodologia baseada na técnica fotoacústica, técnica não intrusiva e não destrutiva, para a determinação da porosidade aberta de membranas vítreas. A porosidade aberta de membranas vítreas está relacionada diretamente à permeabilidade e à eficiência dessas membranas em processos de filtração. Essas membranas foram processadas utilizando-se a técnica de preenchimento e garrafas de vidro, encontradas comercialmente, como matéria-prima. Através da utilização de NaCl como o material inerte, foram processadas membranas com diferentes percentagens de poros. A metodologia fotoacústica desenvolvida neste trabalho teve como base modelos teóricos fotoacústicos tradicionais de análise. Esta metodologia foi capaz de determinar a porosidade aberta das membranas e de distinguí-las quanto as suas superfícies. Os resultados obtidos através da técnica fotoacústica foram comparados com os resultados obtidos por porosimetria de mercúrio (técnica intrusiva e destrutiva) e por ensaios de permeabilidade (técnica intrusiva e não destrutiva) com as mesmas membranas. Estas duas técnicas de análise são as usualmente utilizadas em estudos de estruturas porosas. A comparação entre os dados experimentais comprovou a validade dos resultados obtidos com a nova metodologia. Além desta metodologia fornecer a porosidade aberta com relativa facilidade, ela demonstrou ser rápida, não-destrutiva e de baixo custo para cada ensaio nas análises / The photoacoustic (PA) spectroscopy has been used in several research lines, mainly in the investigation of thermal and optical properties related to different materials, showing in this way high versatility. In this work is described the development of a general-purpose photoacoustic cell, and of a methodology based on photoacoustic technique for the determination of the opened porosity of vitreous membranes. The technique is non-intrusive and non-destructive in relation to the membranes. The opened porosity of vitreous membranes is directly related to the permeability and also directly related to the efficiency of these membranes in the filtration processes. Membranes with different percentage of pores were processed by means of filler principle. For this purpose were used glass bottles found commercially as raw material and NaCl as inert material. The photoacoustic methodology developed in this work was based on classical theoretical models found in the literature. This methodology was capable to determine the open porosity of the membranes and to distinguish membranes with different surfaces. The results obtained with the photoacoustic technique were compared with that obtained by means of mercury porosimetry (intrusive and destructive technique) and permeability measurements (intrusive and non destructive technique) with the same membranes. These two techniques are usually used in studies of porous structures. The comparison between the experimental data showed the validity of the results obtained with this new methodology. Moreover, it supplies the opened porosity with relative easiness, in a faster and non-destructive way, and with low cost in the analyses

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