Made available in DSpace on 2014-10-09T12:53:57Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:29Z (GMT). No. of bitstreams: 0 / No presente trabalho foi desenvolvida uma técnica radiográfica para a inspeção de amostras finas, que emprega feixes de partículas - ? como radiação penetrante e, detectores de traços nucleares de estado sólido para o registro da imagem. O feixe é gerado em uma tela de boro natural quando irradiada com nêutrons térmicos e o detector utilizado foi o CR-39. A interação das partículas - ? com o detector geram danos, os quais sob a ação de uma solução química adequada transformam-se em traços, as unidades básicas formadoras da imagem. Foi desenvolvido um sistema digital próprio para a aquisição, análise e processamento dos dados e das imagens registradas nos detectores. As condições ótimas de irradiação e de revelação para a obtenção de uma radiografia são 1,3 horas e 25 minutos a 70°C, respectivamente. Nestas condições a técnica é capaz de analisar amostras com até 10?m de espessura, com uma resolução espacial de 32?m. O emprego do sistema digital permitiu uma redução significativa no tempo despendido para a aquisição e análise de dados e, uma melhoria na visualização das imagens radiográficas registradas. Além disto permitiu acesso a novos dados referentes aos traços registrados, o que abriu novas perspectivas de pesquisa pois, tem-se acesso aos parâmetros fundamentais que norteiam a teoria da formação da imagem em detectores de traços nucleares utilizada neste trabalho. São apresentadas algumas radiografias que demonstram a potencialidade da técnica desenvolvida. Quando comparada com as outras técnicas radiográficas usuais, empregadas para inspecionar amostras finas, a desenvolvida no presente trabalho permite um menor tempo para a obtenção da imagem, não é necessário a manipulação de materiais radioativos líquidos e, o filme empregado é praticamente insensível às radiações ?, ?, raios - X e luz visível. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

This master's thesis introduces the areas of approximate computing, image filtering in hardware and evolutionary algorithms. It proposes a new design solution to the problem of the evolutionary approximation of median filters, where the objective is to reduce computational and implementation requirements and simultaneously minimize the error of filtering. Based on the gained knowledge and proposals, the necessary programs have been implemented. Experimental evaluation shows that the proposed method can provide good tradeoffs between the quality of filtering and the implementation cost for median filters.

Companies have undergone a process of digitalization and automation of their work processes across various levels. Consequently, this transformation has had a significant impact on the HR departments functions and way of working, where certain parts have been automated and is not outcarried manually anymore. However, the adequacy of the training provided to recruiting personnel in utilizing these digital tools can be questioned. Enterprises did provide different training options to their personnel, and conclusions can be drawn on different trainingmethods, where some were more suitable for specific contexts. The present study has collected empirical research through interviews with companies, showing that companies did consider factors at various levels before implementing digital tools. The findings revealed that organizations with larger HR departments did devote greater resources to training personnel to effectively utilize new digital tools, in contrast to smaller HR departments. / Företag har digitaliserat och automatiserat arbetsprocesser till olika nivåer. Följaktligen har denna omvandling haft en betydande inverkan även på HR-avdelningarnas funktioner och arbetssätt, där vissa delar har automatiserats och utförs därmed inte längre manuellt. Det kan dock ifrågasättas om den utbildning som ges till rekryteringspersonal för att använda digitala verktyg är tillräcklig. Intervjuade företagen tillhandahöll olika utbildningsalternativ till sin personal och slutsatser kan dras gällande olika utbildningsmetoder, där vissa var mer lämpade för specifika företagskontexter. Den presenterade studien har samlat in empirisk forskning genom intervjuer med företag, som visar att företag beaktade essentiella faktorer på olika nivåer inför implementering av digitala verktyg. Resultaten visade att organisationer med större HR-avdelningar tillägnade större resurser till att utbilda personal för att effektivt använda nya digitala verktyg, i kontrast mot vad mindre HR-avdelningar gjorde.

Problem - Problemet som den här studien utgår ifrån är den kunskapslucka som finns om hur ett digitalt system kan underlätta samverkan mellan högskolor och studenter inom ramen för högskolestudier. Forskningsfrågan - Forskningsfrågan som formulerades lyder: vilka förväntningar har studenter på ett digitalt system för samverkan med företag inom ramen för högskolestudier?. Bakgrund - Den litterära bakgrunden målar en bild av samverkan mellan högskolor och företag som fördelaktig för alla parter. Den tidigare forskningen pekar också på att samverkan mellan högskolor och företag är utmanande att utföra på ett bra sätt. Det finns med andra ord många hinder och framgångsfaktorer för utvecklarna av digitala system att ta i beaktande. Metod - I studien användes en mixed methods approach där 17 studenter från Stockholms universitet fick genomföra användartester och System usability scale för att först mäta användarupplevelsen av ett digitalt system för samverkan mellan högskolor och företag. Sedan genomfördes fokusgrupper med samma studenter för att ta fram mer djupgående och förklarande kvalitativa data om deras tankar om systemet i frågan och det övergripande ämnet. Resultat - Det undersökta systemet fick ett SUS-värde på 73,4 vilket är “Bra”. Det kvalitativa resultatet visade i likhet med SUS att studenterna tyckte systemet var bra , men att det fanns utrymme för förbättring. Studenterna sa att de tyckte designen var snygg och att systemet var relativt enkelt att använda. Resultatet visade att studenterna efterlyser enkelhet, vägledande design och goda kommunikationskanaler hos ett digitalt system för samverkan mellan högskolor och företag. Datainsamlingens kvalitativa del gav också studenterna möjlighet att komma med flera förbättringsförslag. Diskussion och slutsats - I likhet med flera tidigare studier gjorda inom ämnet samverkan mellan högskolor och företag, visade resultatet att studenterna inte uppfattar samverkan som något självklart eller enkelt. Studenterna upplever några av de system som finns idag som undermåliga och är positiva till att testa nya, mer specialiserade system. Resultatet pekade även på det intressanta faktumet att det saknades en enighet i hur studenterna går tillväga för att hitta ett företag att samverkan med. Man kan argumentera för att det finns en möjlighet för ett specialiserat system att hjälpa till att föra samma studenter och företag som vill samverka. Om systemet i fråga också möjliggör samverkan baserat på kursämne istället för personliga kontakter kan man tänka sig att fler studenter kan få chansen att samverka oavsett bakgrund och kontaktnät. / Problem - The problem this study addresses is the knowledge gap that exists about how a digital system can facilitate collaboration between universities and students within the framework of higher education studies. Research question - The research question that was formulated reads: what expectations do students have of a digital system for collaboration with companies within the framework of higher education? Background - The literary background paints a picture of industry-university collaboration as beneficial for all parties. Earlier studies also point to industry-university collaboration as being challenging to execute well. There are many obstacles and success factors for the developers of digital systems to consider. Methodology -The study used a mixed methods approach where 17 students from Stockholm University had to complete user tests and the System usability scale to first measure the user experience of a digital system for industry-university collaboration. Focus groups were then conducted with the same students to elicit more in-depth and explanatory qualitative data on their thoughts about the system in question and the overall topic. Findings - The investigated system received a SUS-score of 73.4 which is "Good". The qualitative result showed, similarly to the SUS score, that the students thought the system was good, but that there was room for improvement. The students said they thought the design was neat and that the system was relatively easy to use. The result showed that the students call for simplicity, guiding design, and good communication channels in a digital system for industry-university collaboration. The qualitative part of the data collection also gave the students the opportunity to come up with several suggestions for improvement. Discussion and conclusion - Similar to several previous studies carried out on the subject of industry-university collaboration, the results showed that the students do not perceive industry-university collaboration as something obvious or simple. The students feel that some of the systems that exist today are substandard and are positive towards testing new, more specialized systems. The result also pointed to the interesting fact that there was a lack of agreement on how the students in this study go about finding a company to collaborate with. One could argue that there is an opportunity for a specialized system to help bring together students and businesses that want to collaborate. If the system in question also enables collaboration based on course subjects instead of personal contacts, one can imagine that more students can get the chance to collaborate regardless of background and contact network.

The purpose of this study was to examine how middle managers experience their workload and work relief in relation to the use of digital systems in the work life. Seven people has participated, three women and four men. The interviews were conducted with a semi structured interview guide and the collected data was analyzed with a thematic analysis. The information that emerged from the analysis of the collected data was that almost all the participants have experienced stress when using the digital systems. It also shows that when using the digital systems most of the participants have gotten more tasks and expectations from the management to complete. Some of them also thought that the educations were inadequate for some of the digital systems and there was a desire for more and better educations. This might indicate that they are experiencing more demands due to the increase of tasks but not as high support because of the inadequate educations. Almost all participants said that their knowledge in some of the digital systems were good. Which can indicate that they have a good control when using them. Almost all participants used the digital systems outside of work daily for example to read their email and to reduce the risk of having an overflowing inbox for the next workday. This can indicate that they at some extent have a high workload due to that they check their email daily after work.

Multipath propagation and mobility in wireless communication systems give rise to variations in the amplitude and phase of the transmitted signal, commonly referred to as fading. Many wireless applications are affected by slowly varying fading, where the channel is non-ergodic, leading to non-reliable transmission during bad channel realizations. These communication scenarios are well modeled by the block-fading channel, where the reliability is quantatively characterized by the outage probability. This thesis focuses on the analysis and design of adaptive transmission schemes to improve the outage performance of both single- and multiple-antenna transmission over the block-fading channel, especially for the cases where discrete input constellations are used. Firstly, a new lower bound on the outage probability of non-adaptive transmission is proposed, providing an efficient tool for evaluating the performance of non-adaptive transmission. The lower bound, together with its asymptotic analysis, is essential for efficiently designing the adaptive transmission schemes considered in the thesis. Secondly, new power allocation rules are derived to minimize the outage probability of fixed-rate transmission over block-fading channels. Asymptotic outage analysis for the resulting schemes is performed, revealing important system design criteria. Furthermore, the thesis proposes novel suboptimal power allocation rules, which enjoy low-complexity while suffering minimal losses as compared to the optimal solution. Thus, these schemes facilitate power adaptation in low-cost devices. Thirdly, the thesis considers incremental-redundancy automatic-repeat-request (INR-ARQ) strategies, which perform adaptive transmission based on receiver feedback. In particular, the thesis concentrates on multi-bit feedback, which has been shown to yield significant gains in performance compared to conventional single-bit ARQ schemes. The thesis proposes a new information-theoretic framework for multi-bit feedback INR-ARQ, whereby the receiver feeds back a quantized version of the accumulated mutual information. Within this framework, the thesis presents an asymptotic analysis which yields the large gains in outage performance offered by multi-bit feedback. Furthermore, the thesis proposes practical design rules, which further illustrates the benefits of multi-bit feedback in INR-ARQ systems. In short, the thesis studies the outage performance of transmission over block-fading channels. Outage analysis is performed for non-adaptive and adaptive transmission. Improvements for the existing adaptive schemes are also proposed, leading to either lower complexity requirements or better outage performance. Still, further research is needed to bring the benefits offered by adaptive transmission into practical systems. / Thesis (PhD)--University of South Australia, 2010

Opportunistic communication techniques have shown to provide significant performance improvements in centralised random access wireless networks. The key mechanism of opportunistic communication is to send back-to-back data packets whenever the channel quality is deemed "good". Recently there have been attempts to introduce opportunistic communication techniques in distributed wireless networks such as wireless ad hoc networks. In line of this research, we propose a new paradigm of medium access control, called Channel MAC based on the channel randomness and opportunistic communication principles. Scheduling in Channel MAC depends on the instance at which the channel quality improves beyond a threshold, while neighbouring nodes are deemed to be silent. Once a node starts transmitting, it will keep transmitting until the channel becomes "bad". We derive an analytical throughput equation of the proposed MAC in a multiple access environment and validate it by simulations. It is observed that Channel MAC outperforms IEEE 802.11 for all probabilities of good channel condition and all numbers of nodes. For higher number of nodes, Channel MAC achieves higher throughput at lower probabilities of good channel condition increasing the operating range. Furthermore, the total throughput of the network grows with increasing number of nodes considering negligible propagation delay in the network. A scalable channel prediction scheme is required to implement the practical Channel MAC protocol in practice. We propose a mean-value based channel prediction scheme, which provides prediction with enough accuracy to be used in the Channel MAC protocol. NS2 simulation result shows that the Channel MAC protocol outperforms the IEEE 802.11 in throughput due to its channel diversity mechanism in spite of the prediction errors and packet collisions. Next, we extend the Channel MAC protocol to support multi-rate communications. At present, two prominent multi-rate mechanisms, Opportunistic Auto Rate (OAR) and Receiver Based Auto Rate (RBAR) are unable to adapt to short term changes in channel conditions during transmission as well as to use optimum power and throughput during packet transmissions. On the other hand, using channel predictions, each source-destinations pair in Channel MAC can fully utilise the non-fade durations. We combine the scheduling of Channel MAC and the rate adaptive transmission based on the channel state information to design the 'Rate Adaptive Channel MAC' protocol. However, to implement the Rate adaptive Channel MAC, we need to use a channel prediction scheme to identify transmission opportunities as well as auto rate adaptation mechanism to select rates and number of packets to transmit during those times. For channel prediction, we apply the scheme proposed for the practical implementation of Channel MAC. We propose a "safety margin" based technique to provide auto rate adaptation. Simulation results show that a significant performance improvement can be achieved by Rate adaptive Channel MAC as compared to existing rate adaptive protocols such as OAR.

Opportunistic communication techniques have shown to provide significant performance improvements in centralised random access wireless networks. The key mechanism of opportunistic communication is to send back-to-back data packets whenever the channel quality is deemed "good". Recently there have been attempts to introduce opportunistic communication techniques in distributed wireless networks such as wireless ad hoc networks. In line of this research, we propose a new paradigm of medium access control, called Channel MAC based on the channel randomness and opportunistic communication principles. Scheduling in Channel MAC depends on the instance at which the channel quality improves beyond a threshold, while neighbouring nodes are deemed to be silent. Once a node starts transmitting, it will keep transmitting until the channel becomes "bad". We derive an analytical throughput equation of the proposed MAC in a multiple access environment and validate it by simulations. It is observed that Channel MAC outperforms IEEE 802.11 for all probabilities of good channel condition and all numbers of nodes. For higher number of nodes, Channel MAC achieves higher throughput at lower probabilities of good channel condition increasing the operating range. Furthermore, the total throughput of the network grows with increasing number of nodes considering negligible propagation delay in the network. A scalable channel prediction scheme is required to implement the practical Channel MAC protocol in practice. We propose a mean-value based channel prediction scheme, which provides prediction with enough accuracy to be used in the Channel MAC protocol. NS2 simulation result shows that the Channel MAC protocol outperforms the IEEE 802.11 in throughput due to its channel diversity mechanism in spite of the prediction errors and packet collisions. Next, we extend the Channel MAC protocol to support multi-rate communications. At present, two prominent multi-rate mechanisms, Opportunistic Auto Rate (OAR) and Receiver Based Auto Rate (RBAR) are unable to adapt to short term changes in channel conditions during transmission as well as to use optimum power and throughput during packet transmissions. On the other hand, using channel predictions, each source-destinations pair in Channel MAC can fully utilise the non-fade durations. We combine the scheduling of Channel MAC and the rate adaptive transmission based on the channel state information to design the 'Rate Adaptive Channel MAC' protocol. However, to implement the Rate adaptive Channel MAC, we need to use a channel prediction scheme to identify transmission opportunities as well as auto rate adaptation mechanism to select rates and number of packets to transmit during those times. For channel prediction, we apply the scheme proposed for the practical implementation of Channel MAC. We propose a "safety margin" based technique to provide auto rate adaptation. Simulation results show that a significant performance improvement can be achieved by Rate adaptive Channel MAC as compared to existing rate adaptive protocols such as OAR.

Multipath propagation and mobility in wireless communication systems give rise to variations in the amplitude and phase of the transmitted signal, commonly referred to as fading. Many wireless applications are affected by slowly varying fading, where the channel is non-ergodic, leading to non-reliable transmission during bad channel realizations. These communication scenarios are well modeled by the block-fading channel, where the reliability is quantatively characterized by the outage probability. This thesis focuses on the analysis and design of adaptive transmission schemes to improve the outage performance of both single- and multiple-antenna transmission over the block-fading channel, especially for the cases where discrete input constellations are used. Firstly, a new lower bound on the outage probability of non-adaptive transmission is proposed, providing an efficient tool for evaluating the performance of non-adaptive transmission. The lower bound, together with its asymptotic analysis, is essential for efficiently designing the adaptive transmission schemes considered in the thesis. Secondly, new power allocation rules are derived to minimize the outage probability of fixed-rate transmission over block-fading channels. Asymptotic outage analysis for the resulting schemes is performed, revealing important system design criteria. Furthermore, the thesis proposes novel suboptimal power allocation rules, which enjoy low-complexity while suffering minimal losses as compared to the optimal solution. Thus, these schemes facilitate power adaptation in low-cost devices. Thirdly, the thesis considers incremental-redundancy automatic-repeat-request (INR-ARQ) strategies, which perform adaptive transmission based on receiver feedback. In particular, the thesis concentrates on multi-bit feedback, which has been shown to yield significant gains in performance compared to conventional single-bit ARQ schemes. The thesis proposes a new information-theoretic framework for multi-bit feedback INR-ARQ, whereby the receiver feeds back a quantized version of the accumulated mutual information. Within this framework, the thesis presents an asymptotic analysis which yields the large gains in outage performance offered by multi-bit feedback. Furthermore, the thesis proposes practical design rules, which further illustrates the benefits of multi-bit feedback in INR-ARQ systems. In short, the thesis studies the outage performance of transmission over block-fading channels. Outage analysis is performed for non-adaptive and adaptive transmission. Improvements for the existing adaptive schemes are also proposed, leading to either lower complexity requirements or better outage performance. Still, further research is needed to bring the benefits offered by adaptive transmission into practical systems. / Thesis (PhD)--University of South Australia, 2010

Esta dissertação investiga a aplicação dos algoritmos evolucionários inspirados na computação quântica na síntese de circuitos sequenciais. Os sistemas digitais sequenciais representam uma classe de circuitos que é capaz de executar operações em uma determinada sequência. Nos circuitos sequenciais, os valores dos sinais de saída dependem não só dos valores dos sinais de entrada como também do estado atual do sistema. Os requisitos cada vez mais exigentes quanto à funcionalidade e ao desempenho dos sistemas digitais exigem projetos cada vez mais eficientes. O projeto destes circuitos, quando executado de forma manual, se tornou demorado e, com isso, a importância das ferramentas para a síntese automática de circuitos cresceu rapidamente. Estas ferramentas conhecidas como ECAD (Electronic Computer-Aided Design) são programas de computador normalmente baseados em heurísticas. Recentemente, os algoritmos evolucionários também começaram a ser utilizados como base para as ferramentas ECAD. Estas aplicações são referenciadas na literatura como eletrônica evolucionária. Os algoritmos mais comumente utilizados na eletrônica evolucionária são os algoritmos genéticos e a programação genética. Este trabalho apresenta um estudo da aplicação dos algoritmos evolucionários inspirados na computação quântica como uma ferramenta para a síntese automática de circuitos sequenciais. Esta classe de algoritmos utiliza os princípios da computação quântica para melhorar o desempenho dos algoritmos evolucionários. Tradicionalmente, o projeto dos circuitos sequenciais é dividido em cinco etapas principais: (i) Especificação da máquina de estados; (ii) Redução de estados; (iii) Atribuição de estados; (iv) Síntese da lógica de controle e (v) Implementação da máquina de estados. O Algoritmo Evolucionário Inspirado na Computação Quântica (AEICQ) proposto neste trabalho é utilizado na etapa de atribuição de estados. A escolha de uma atribuição de estados ótima é tratada na literatura como um problema ainda sem solução. A atribuição de estados escolhida para uma determinada máquina de estados tem um impacto direto na complexidade da sua lógica de controle. Os resultados mostram que as atribuições de estados obtidas pelo AEICQ de fato conduzem à implementação de circuitos de menor complexidade quando comparados com os circuitos gerados a partir de atribuições obtidas por outros métodos. O AEICQ e utilizado também na etapa de síntese da lógica de controle das máquinas de estados. Os circuitos evoluídos pelo AEICQ são otimizados segundo a área ocupada e o atraso de propagação. Estes circuitos são compatíveis com os circuitos obtidos por outros métodos e em alguns casos até mesmo superior em termos de área e de desempenho, sugerindo que existe um potencial de aplicação desta classe de algoritmos no projeto de circuitos eletrônicos. / This thesis investigates the application of quantum inspired evolutionary algorithms in the synthesis of sequential circuits. Sequential digital systems represent a class of circuit that is able to execute operations in a particular sequence. In sequential circuits, the values of output signals not only depend on the values of input signals but also on the current state of the system. The increasingly high requirements regarding the functionality and performance of digital systems demand more efficient designs. The design of these circuits, when implemented manually, became slow and thus the importance of tools for automatic synthesis of circuits grew rapidly. These tools known as ECAD (Electronic Computer-Aided Design) are computer programs usually based on heuristics. Recently, evolutionary algorithms also began to be used as a basis in ECAD tools developing. These applications are referenced in literature as evolutionary electronics. The algorithms most commonly used in evolutionary electronics are genetic algorithms and genetic programming. This work presents a study of the application of quantum inspired evolutionary algorithms as a tool for automatic synthesis of sequential circuits. This class of algorithms uses the principles of quantum computing to improve the performance of evolutionary algorithms. Traditionally, the design of sequential circuits is divided into five main steps: (i) State machine specification; (ii) Reduction of states; (iii) State assignment; (iv) Control logic synthesis and (v) Implementation of the state machine. The proposed algorithm AEICQ is used in the state assignment design step. The choice of an optimal state assignment is treated in the literature as an issue still unresolved. The state assignment chosen for a particular state machine has a direct impact on the complexity of its control logic. The results show that the state assignment obtained by AEICQ in fact leads to the implementation of circuits of less complexity when compared with the ones generated from assignments obtained by other methods. The AEICQ is also used in the control logic synthesis of the state machine. The circuits evolved by AEICQ are optimized according to the area occupied and the propagation delay. These circuits are compatible with the circuits obtained by other methods and in some cases even higher in terms of area and performance, suggesting that there is a potential for application of this class of algorithms in the design of electronic circuits.