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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.
121

The ghosts in the nursery : the maternal representations of a woman who killed her baby

Gous, Ansie 25 August 2005 (has links)
The aim of this study is to give an in-depth understanding of the representations of a depressed woman who killed her baby. The representations under study is based on “The motherhood constellation” by Stern (1995) and focus on the woman’s representation of her mother as mother-of-herself-as-child, herself-as-mother and her representations of her children. Pregnancy is an important phase in a woman’s life. Parent-infant psychotherapies are a rapidly growing field of infant mental health as many psychological problems have their roots in infancy. Neglect, trauma and abuse and prolonged maternal depression can cause a child to develop a range of problems. The work of Winnicott (1965a) and Bion (1988) put the mother’s fantasy life about her infant as one of the major building blocks of the infant’s construction of a sense of identity (Stern, 1995). Fraiberg (Fraiberg, Adelson&Shapiro, 1980) with her “ghosts in the nursery” revolutionised this perception by placing the maternal representation at the core of the parent-infant clinical situation (Stern, 1995). The way the research developed and the nature of the research problem necessitated a pure qualitative mode of enquiry. A single case study was done about the representations (of self-as-mother, mother-as –mother–of–self-as-child- and of the children) in an extreme case where the mother’s depression led to her murdering her baby. Data collection was done through semi-structured interviews and documents from the psychiatric hospitals she attended. Data was also obtained from field notes, before and after the interviews and also while transcribing the audio-taped interviews. Data analysis was done by the procedures of data reduction and organising it into categories on the basis of themes as described by Neuman (2000). Coding and analytic memo writing were done. The relationships between concepts were examined and linked to each other and interweaved into theoretical statements. The researcher argues that not enough is done to enhance the relationship between a mother and her foetus, and later her baby. The concept of maternal representations is the only approach that opens the possibility to start working at the earliest point of prevention, because intervention can start during pregnancy. Intervention during pregnancy is ideal because defence mechanisms are less rigid during pregnancy and women are more in touch with their entire life cycle and the whole system is more open for change. The ghosts can be chased out of the nursery by helping the mother to see the repetition of the past in the present. The affective link, recognising and remembering the feelings help a parent not to repeat the past in the present - “…it is the parent who cannot remember his childhood feelings of pain and anxiety who will need to inflict his pain upon his child” (Fraiberg, Adelson&Shapiro, 1980, p. 182). / Thesis (PhD (Psychotherapy))--University of Pretoria, 2006. / Psychology / unrestricted
122

Digitální pozemní televizní vysílání DVB-T/H a DVB-T2 / Digital terrestrial television broadcasting DVB-T/H and DVB-T2

Pospíchal, Martin January 2011 (has links)
Master's thesis compares the standard for digital terrestrial television broadcasting of the first generation DVB-T/H and the second generation DVB-T2 with particular emphasis on the modulator, a security channel interference, the signal from the transmitting environment itself and the modulation signal. The following description of specific models of transmission channels for fixed, portable and mobile reception of digital terrestrial signal. Comparison with the particular relates of the transmission parameters for different types of reception of digital terrestrial television with achieving efficiency and effectiveness of transmission at the level of laboratory measurements and computer simulation.
123

GNSS Inter-Constellation Time Offset Determination in Low Earth Orbit

Peters, Brian C. 03 June 2021 (has links)
No description available.
124

MULTIPLE SIGNALS OF OPPORTUNITY FOR LAND REMOTE SENSING

Seho Kim (8820074) 27 July 2023 (has links)
<p>Multiple Signals of Opportunity (multi-SoOp) across different frequencies and polarizations</p> <p>offer a potential breakthrough for remote sensing of root-zone soil moisture (RZSM). Deeper penetration depths of existing communication transmissions in the frequency ranges of 137–138, 240–270, and 360–380 MHz enable the estimation of RZSM by complementing global navigation satellite system reflectometry (GNSS-R) in L-band. The small form factor of the multi-SoOp observatory allows for high spatiotemporal coverage of RSZM by a satellite constellation in a cost-effective manner. This study aims to develop models and tools to define mission requirements for various system parameters that affect observation accuracy and coverage, for the advancement of spaceborne multi-SoOp remote sensing. These parameters include frequency and polarization combinations, observation error, inter-frequency temporal coincidence, and configuration of the satellite constellation. We present the development of a retrieval algorithm and the sensitivity analysis of retrieval accuracy. The retrieval algorithm was evaluated using synthetic observations generated from multiyear time series of in-situ soil moisture (SM) and satellite-based vegetation data. The combined use of both high and low frequencies improves retrieval accuracy by limiting uncertainties from vegetation and surface SM and providing sensitivity to deeper layers. A bivariate model, derived from the sensitivity analysis, facilitates error prediction for future science missions. We introduce a framework for tradespace exploration of the multi-SoOp satellite constellation. A constellation design study indicates that a Walker constellation comprising 24 satellites with 3 orbital planes at 500 km and 50° inclination optimizes the coverage and mission cost under mission requirements. A tower-based field experiment validated the performance of a prototype antenna for multi-SoOp using the interference pattern technique. More field experiments with improved instruments are required to further advance the multi-SoOp technique.</p>
125

A feasibility study for a satellite VHF Data Exchange System (VDES) / En förstudie för ett satellit väldigt högfrekvent datautbytessystem (VDES)

Grujicic, Julian January 2019 (has links)
Transportation across the globe's oceans increases every year and is expected to keep increasing in the following decades. Consequently, there is a need to establish communication over the horizon through the Automatic Identification System (AIS) and the Very High Frequency (VHF) Data Exchange System (VDES), still in development, to track and communicate with vessels all over the globe regardless of the distance from shore. In this Master thesis a feasibility study for the development of a system that fulfils that need is proposed consisting of a Low Earth Orbit (LEO) constellation providing VDES communication continuously all over the globe. A system engineering approach has been followed, identifying stakeholders and producing system requirements setting up a framework for the system. The key stakeholders were found to be the customers/users, the satellite provider, the satellite operator, the service provider and the payload provider. Furthermore, possible use-cases were presented and a system architecture was defined to outline the system, dividing the system into three segments: the space segment, the ground segment and the launch segment. In addition, design proposals for a satellite constellation and a typical satellite in such a constellation were implemented. The satellite constellation was proposed to consist of 91 satellites at an orbit altitude of around 550 km in polar orbits of common inclination, this was regarding a minimum elevation angle of 10 degrees. The satellite is recommended to consist of a 6 U CubeSat using as payload the existing airborne transponder R5A from Saab TransponderTech, it builds on the Software Defined Radio (SDR) technology and is to be further developed for VDES applications. Moreover, a link- and a data budget were implemented. Different launch options were addressed concluding that launching as secondary payload on a ride-share mission or as primary payload on a small satellite launch vehicle are the preferable options. A market analysis has been made providing details on how many AIS/VDES satellites that have been launched into LEO and by which service provider, as well as further details on small/nano satellites of extra interest to this work. A short risk evaluation was also done, identifying the most evident risks with developing, operating and disposing the system. In addition, Saab's potential role in the development of satellite VDES is discussed.  In conclusion to this work it has been shown that it is possible to build a global continuous satellite constellation in LEO utilising as payload an SDR-platform to provide VDES services to vessels at open seas. / Transport globalt till havs ökar varje år och förväntas fortsätta att öka de följande årtiondena. Följaktligen finns ett behov av att etablera över horisonten kommunikation genom det automatiska identifieringssystemet (AIS) och det väldigt högfrekventa datautbytessystemet (VDES), under utveckling, för att spåra och kommunicera med fartyg över hela världen oberoende av avståndet från land. I detta examensarbete har en förstudie utförts för utvecklingen av ett system som uppfyller detta behov. Systemet föreslås bestå av en låg jordbana satellitkonstellation som kontinuerligt tillhandahåller VDES-kommunikation över hela världen. Ett systemtekniskt tillvägagångssätt har följts, intressenter har identifierats och utifrån dessa har systemkrav tagits fram. De viktigaste intressenterna befanns vara användare/kunder, satellitleverantören, satellitoperatören, tjänsteleverantören och nyttolastleverantören. Vidare lyftes olika möjliga användningsområden för systemet fram och en systemarkitektur framställdes vari systemet delades in i tre segment: rymdsegmentet, marksegmentet och uppskjutningssegmentet. Dessutom genomfördes designförslag för en satellitkonstellation samt en typisk satellit i en sådan konstellation. Satellitkonstellationen föreslogs bestå av 91 satelliter på en altitud på omkring 550 km i polära banor med gemensam inklination, detta var gällande för en minimum elevationsvinkel på 10 grader. Satelliten rekommenderades bestå av en 6 U CubeSat med den befintliga luftburna transpondern R5A från Saab TransponderTech som nyttolast, vilken bygger på mjukvaruradioteknik och är tänkt att vidareutvecklas för VDES-applikationer.  Vidare, implementerades en länk- och data budget. Olika uppskjutningsmöjligheter undersöktes, varav slutsatsen att uppskjutning som sekundär nyttolast på ett delningsuppdrag eller som primär nyttolast medhjälp av ett mindre uppskjutningsfordon anpassat för små satelliter var de föredragna alternativen. Även en marknadsanalys har genomförts, där det redogjorts för hur många AIS / VDES - satelliter som har uppskjutits i LEO och av vilken tjänsteleverantör, samt ytterligare detaljer om små / nano satelliter av extra intresse för arbetet. En kort riskbedömning har också gjorts, där de mest uppenbara riskerna med utveckling, drift och undanröjande av systemet identifierats. Dessutom diskuteras Saabs möjliga roll i utvecklingen av satellit VDES. Slutsatsen av detta arbete har visat att det är möjligt att bygga en global kontinuerlig satellitkonstellation i låg jordbana med en mjukvaruradio som nyttolast som tillhandahåller VDES-tjänster till fartyg på öppna hav.
126

Schémas pratiques pour la diffusion (sécurisée) sur les canaux sans fils / (Secure) Broadcasting over wireless channels practical schemes

Mheich, Zeina 19 June 2014 (has links)
Dans cette thèse, on s'est intéressé à l'étude des canaux de diffusion avec des contraintes de transmission pratiques. Tout d'abord, on a étudié l'impact de la contrainte pratique de l'utilisation d'un alphabet fini à l'entrée du canal de diffusion Gaussien avec deux utilisateurs. Deux modèles de canaux de diffusion sont considérés lorsqu'il y a, en plus d'un message commun pour les deux utilisateurs, (i) un message privé pour l'un des deux utilisateurs sans contrainte de sécurité (ii) un message confidentiel pour l'un des deux utilisateurs qui doit être totalement caché de l'autre utilisateur. On a présenté plusieurs stratégies de diffusion distinguées par leur complexité d'implémentation. Plus précisément, on a étudié les régions des débits atteignables en utilisant le partage de temps, la superposition de modulation et le codage par superposition. Pour la superposition de modulation et le cas général du codage par superposition, les régions des débits atteignables maximales sont obtenues en maximisant par rapport aux positions des symboles dans la constellation et la distribution de probabilité jointe. On a étudié le compromis entre la complexité d'implémentation des stratégies de transmission et leurs efficacités en termes de gains en débits atteignables. On a étudié aussi l'impact de la contrainte de sécurité sur la communication en comparant les débits atteignables avec et sans cette contrainte. Enfin, on a étudié les performances du système avec des schémas d'accusés de réception hybrides (HARQ) pour un canal à écoute à évanouissement par blocs lorsque l'émetteur n'a pas une information parfaite sur l'état instantané du canal mais connait seulement les statistiques. On a considéré un schéma adaptatif pour la communication sécurisée en utilisant des canaux de retour à niveaux multiples vers l'émetteur pour changer la longueur des sous mots de code à chaque retransmission afin que le débit utile secret soit maximisé sous des contraintes d'"outages". / In this thesis, we aim to study broadcast channels with practical transmission constraints. First, we study the impact of finite input alphabet constraint on the achievable rates for the Gaussian broadcast channel with two users. We consider two models of broadcast channels, when there is in addition of a common message for two users, (i) a private message for one of them without secrecy constraint (ii) a confidential message for one of them which should be totally hidden from the other user. We present several broadcast strategies distinguished by their complexity of implementation. More precisely, we study achievable rate regions using time sharing, superposition modulation and superposition coding. For superposition modulation and superposition coding strategies, maximal achievable rate regions are obtained by maximizing over both symbol positions in the constellation and the joint probability distribution. We study the tradeoff between the complexity of implementation of the transmission strategies and their efficiency in terms of gains in achievable rates. We study also the impact of the secrecy constraint on communication by comparing the achievable rates with and without this constraint. Finally, we study the system performance using HARQ schemes for the block-fading wiretap channel when the transmitter has no instantaneous channel state information but knows channel statistics. We consider an adaptive-rate scheme for the secure communication by using multilevel feedback channels to change sub-codeword lengths at each retransmission, in order to maximize the secrecy throughput under outage probabilities constraints.
127

Time-window optimization for a constellation of earth observation satellite

Oberholzer, Christiaan Vermaak 02 1900 (has links)
Thesis (M.Com.(quantitative Management)) / Satellite Scheduling Problems (SSP) are NP-hard and constraint programming and metaheuristics solution methods yield mixed results. This study investigates a new version of the SSP, the Satellite Constellation Time-Window Optimization Problem (SCoTWOP), involving commercial satellite constellations that provide frequent earth coverage. The SCoTWOP is related to the dual of the Vehicle Routing Problem with Multiple Timewindows, suggesting binary solution vectors representing an activation of time-windows. This representation fitted well with the MatLab® Genetic Algorithm and Direct Search Toolbox subsequently used to experiment with genetic algorithms, tabu search, and simulated annealing as SCoTWOP solution methods. The genetic algorithm was most successful and in some instances activated all 250 imaging time-windows, a number that is typical for a constellation of six satellites. / Quantitative Management
128

Time-window optimization for a constellation of earth observation satellite

Oberholzer, Christiaan Vermaak 02 1900 (has links)
Thesis (M.Com.(quantitative Management)) / Satellite Scheduling Problems (SSP) are NP-hard and constraint programming and metaheuristics solution methods yield mixed results. This study investigates a new version of the SSP, the Satellite Constellation Time-Window Optimization Problem (SCoTWOP), involving commercial satellite constellations that provide frequent earth coverage. The SCoTWOP is related to the dual of the Vehicle Routing Problem with Multiple Timewindows, suggesting binary solution vectors representing an activation of time-windows. This representation fitted well with the MatLab® Genetic Algorithm and Direct Search Toolbox subsequently used to experiment with genetic algorithms, tabu search, and simulated annealing as SCoTWOP solution methods. The genetic algorithm was most successful and in some instances activated all 250 imaging time-windows, a number that is typical for a constellation of six satellites. / Quantitative Management
129

Dynamics of corporate strategy from a value chain perspective : A study of the Swedish telecom and construction industries during the 90’s

de Paula, Andes January 2006 (has links)
<p>Changes in sectors and industries have brought new challenges to corporations as well as been important driving forces for the dynamics in strategy at the corporate level. With the dramatic developments of the 1990’s in mind, such as multilateral free-trade agreements, liberalization, privatization, sharp industry growth/decline, increased competition and globalization, in particular within the telecom and the construction industry, this study contributes to describing and understanding strategic change at the corporate level as well as changes in the division of work within value chains. Strategy is defined as intentions, decisions and actions that relate to bundling and unbundling at different strategic levels, aiming to establish and reestablish a value chain position. Thus, outsourcing, M&As, modularization and systems development and sales are important strategic components which are examined from a value chain perspective. From a value chain perspective, the purpose of this study is to describe and understand strategic change at the corporate level in the telecom and construction industries during the 1990’s. More specifically this study shall contribute to describing and understanding (i) the dynamics of and between M&As, outsourcing, modularization and systemization, as well as (ii) industrial and financial drivers to strategic change.</p><p>The conclusions describe strategic change from a value chain perspective using three descriptive patterns, including an increasing degree of specialization and need for interorganizational coordination across the value chain. In addition, outsourcing and modularization of systems and an increased scope of offering through systemization and BOT-projects, result in the fact that due to M&As the horizontal boundary of the firm sometimes goes beyond the industry scope while the vertical scope is often narrowed through outsourcing. The conclusions also focus on understanding the content of strategic change, that is to say the dynamics of and between mergers and acquisitions, outsourcing, modularization and system sales. These findings are summarized in nine explanatory patterns. These patterns show that the strategic decisions of bundling and unbundling at the corporate and functional level through mergers and acquisitions, outsourcing, systemization and modularization are guided by an industrial as well as a financial logic. By considering the descriptive and explanatory patterns found this study, the conclusions also include what to expect during the next decade with regard to corporate strategy from a value chain perspective in five predictive patterns.</p>
130

Dynamics of corporate strategy from a value chain perspective : A study of the Swedish telecom and construction industries during the 90’s

de Paula, Andes January 2006 (has links)
Changes in sectors and industries have brought new challenges to corporations as well as been important driving forces for the dynamics in strategy at the corporate level. With the dramatic developments of the 1990’s in mind, such as multilateral free-trade agreements, liberalization, privatization, sharp industry growth/decline, increased competition and globalization, in particular within the telecom and the construction industry, this study contributes to describing and understanding strategic change at the corporate level as well as changes in the division of work within value chains. Strategy is defined as intentions, decisions and actions that relate to bundling and unbundling at different strategic levels, aiming to establish and reestablish a value chain position. Thus, outsourcing, M&amp;As, modularization and systems development and sales are important strategic components which are examined from a value chain perspective. From a value chain perspective, the purpose of this study is to describe and understand strategic change at the corporate level in the telecom and construction industries during the 1990’s. More specifically this study shall contribute to describing and understanding (i) the dynamics of and between M&amp;As, outsourcing, modularization and systemization, as well as (ii) industrial and financial drivers to strategic change. The conclusions describe strategic change from a value chain perspective using three descriptive patterns, including an increasing degree of specialization and need for interorganizational coordination across the value chain. In addition, outsourcing and modularization of systems and an increased scope of offering through systemization and BOT-projects, result in the fact that due to M&amp;As the horizontal boundary of the firm sometimes goes beyond the industry scope while the vertical scope is often narrowed through outsourcing. The conclusions also focus on understanding the content of strategic change, that is to say the dynamics of and between mergers and acquisitions, outsourcing, modularization and system sales. These findings are summarized in nine explanatory patterns. These patterns show that the strategic decisions of bundling and unbundling at the corporate and functional level through mergers and acquisitions, outsourcing, systemization and modularization are guided by an industrial as well as a financial logic. By considering the descriptive and explanatory patterns found this study, the conclusions also include what to expect during the next decade with regard to corporate strategy from a value chain perspective in five predictive patterns.

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