LEDs are being developed as the next generation lighting source due to their high efficiency and long life time, with a potential to save $15 billion per year in energy cost by 2020. State of the art LEDs are capable of emitting light at ~115 lm/W and have lifetime over 50,000 hours. It has already surpassed the efficiency of incandescent light sources, and is even comparable to that of fluorescent lamps. Since the total luminous flux generated by a single LED is considerably lower than other light sources, to be competitive the total light output must be increased with higher forward currents and packages of multiple LEDs. However, both of these solutions would increase the junction temperature, which degrades the performance of the LED--as the operating temperature goes up, the light intensity decreases, the lifetime is reduced, and the light color changes. The word "junction" refers to the p-n junction within the LED-chips. Critical to the temperature rise in high powered LED sources is the very large heat flux at the die level (100-500 W/cm2) which must be addressed in order to lower the operating temperature in the die. It is possible to address the spreading requirements of high powered LED die through the use of power electronic substrates for efficient heat dissipation, especially when the die are directly mounted to the power substrate in a chipon- board (COB) architecture. COB is a very attractive technology for packaging power LEDs which can lead improved price competiveness, package integration and thermal performance. In our work high power LED-chips (>1W/die) implementing COB architectures were designed and studied. Substrates for these packaging configurations include two types of power electronic substrates; insulated-metal-substrates (IMS) and direct-bonded-copper (DBC). To lower the operating temperature both the thermal impedance of the dielectric layer and the heat spreading in the copper circuit layers must be studied. In the analysis of our architectures, several lead free solders and thermal interface materials were considered. We start with the analysis of single-chip LED package and extend the result to the multi-chip arrays. The thermal resistance of the system is only a function of geometry and thermal conductivity if temperature-independent properties are used. Thus through finite element analysis (ANSYS) the effect of geometry and thermal conductivity on the thermal resistance was investigated. The drawback of finite element analysis is that many simulations must be conducted whenever the geometry or the thermal conductivity is changed. To bypass same of the computational load, a thermal resistance network was developed. We developed analytical expressions of the thermal resistance, especially focusing on the heat spreading effect at the substrate level. Finally, multi-chip LED arrays were analyzed through finite element analysis and an analytical analysis; where die-spacing is another important factor to determine the junction temperature. With this thermal analysis, critical design considerations were investigated in order to minimize device temperatures and thereby maximizing light output while also maximizing device reliability.

Les développements technologiques en télécommunication et microondes tendent depuis plusieurs années vers la miniaturisation des circuits, une réduction des coûts, des masses et des pertes dans ces dispositifs. Les circuits SIW (Substrate Integrated Waveguide) s'inscrivent tout à fait dans cette mouvance et font à l'heure actuelle l'objet de nombreux sujets de recherche avec des applications directes dans l'industrie. Les circuits SINRD (Substrate Integrated Non Radiative Dielectric), utilisent eux les propriétés du substrat usiné (insertion de trous) pour la propagation du signal et des fonctions de l'électronique peuvent également être développées avec cette technologie. La conception de ces circuits passe généralement par des outils peu performants car non dédiés. Dans ce travail de thèse, une méthode numérique dédiée à ces circuits est développée. Elle est validée par comparaison à d'autres méthodes numériques et des mesures. Elle présente des temps de calcul très faibles. De nouveaux dispositifs pour des applications en télécommunications spatiales bas coût et faibles pertes peuvent ainsi être développés grâce à elle.

La transglutaminase microbienne (Microbial transglutaminase : MTG) est fortement exploitée dans l’industrie textile et alimentaire afin de modifier l’apparence et la texture de divers produits. Elle catalyse la formation de liaisons iso-peptidiques entre des protéines par l’entremise d’une réaction de transfert d’acyle entre le groupement γ-carboxamide d’une glutamine provenant d’un substrat donneur d’acyle, et le groupement ε-amino d’une lysine provenant d’un substrat accepteur d’acyle. La MTG est tolérante à un large éventail de conditions réactionnelles, ce qui rend propice le développement de cette enzyme en tant que biocatalyseur. Ayant pour but le développement de la MTG en tant qu’alternative plus soutenable à la synthèse d’amides, nous avons étudié la réactivité d’une gamme de substrats donneurs et accepteurs non-naturels. Des composés chimiquement diversifiés, de faible masse moléculaire, ont été testés en tant que substrats accepteurs alternatifs. Il fut démontré que la MTG accepte une large gamme de composés à cet effet. Nous avons démontré, pour la première fois, que des acides aminés non-ramifiés et courts, tels la glycine, peuvent servir de substrat accepteur. Les α-acides aminés estérifiés Thr, Ser, Cys et Trp, mais pas Ile, sont également réactifs. En étendant la recherche à des composés non-naturels, il fut observé qu’un cycle aromatique est bénéfique pour la réactivité, bien que les substituants réduisent l’activité. Fait notable, des amines de faible masse moléculaire, portant les groupements de forte densité électronique azidure ou alcyne, sont très réactives. La MTG catalyse donc efficacement la modification de peptides qui pourront ensuite être modifiés ou marqués par la chimie ‘click’. Ainsi, la MTG accepte une variété de substrats accepteurs naturels et non-naturels, élargissant la portée de modification des peptides contenant la glutamine. Afin de sonder le potentiel biocatalytique de la MTG par rapport aux substrats donneurs, des analogues plus petits du peptide modèle Z-Gln-Gly furent testés; aucun n’a réagi. Nous avons toutefois démontré, pour la première fois, la faible réactivité d’esters en tant que substrats donneurs de la MTG. L’éventuelle amélioration de cette réactivité permettrait de faire de la MTG un biocatalyseur plus général pour la synthèse d’amides. Mots clés: Lien amide, biocatalyse, biotransformation, transglutaminase, arrimage moléculaire, criblage de substrats, ingénierie de substrats. / Microbial transglutaminase (MTG) is used extensively in the food and textile industry to alter the appearance and texture of products. MTG catalyses the formation of isopeptide linkages between proteins by an acyl transfer reaction between the γ-carboxamide group of a glutamine ‘acyl-donor’ substrate, and the ε-amino group of a lysine ‘acyl-acceptor’ substrate. MTG is tolerant to a broad range of reaction conditions and is therefore suitable for further development as a biocatalyst. Toward developing MTG as a “green” alternative for amide synthesis, we have investigated a range of non-native donor and acceptor substrates to probe the scope of MTG reactivity. Small, chemically varied compounds were tested as alternative acyl-acceptor substrates. We observed a broad acceptor specificity. We show, for the first time, that very short-chain alkyl-based amino acids such as glycine can serve as acceptor substrates. The esterified α-amino acids Thr, Ser, Cys and Trp – but not Ile – also show reactivity. Extending the search to non-natural compounds, an aromatic ring was observed to be beneficial for reactivity, although ring substituents reduced reactivity. Overall, bonding of the amine to a less hindered carbon increases reactivity. Importantly, very small amines carrying either the electron-rich azide or the alkyne groups required for click chemistry were highly reactive as acceptor substrates, providing a ready route to minimally modified, ‘clickable’ peptides. These results demonstrate that MTG is tolerant to a variety of chemically varied natural and non-natural acceptor substrates, which broadens the scope for modification of glutamine-containing peptides. To further probe the biocatalytic potential of MTG in terms of the donor substrate, smaller analogues of the model substrate Z-Gln-Gly were tested. We did not find product formation with substrates smaller than the model substrate. We observed, for the first time, trace esterase activity with MTG. Future improvement of this activity would render MTG a more attractive, general biocatalyst for amide bond formation.

Made available in DSpace on 2016-06-02T19:29:56Z (GMT). No. of bitstreams: 1 5136.pdf: 1469178 bytes, checksum: a0809686f5333526f7e5eb0a69d193b3 (MD5) Previous issue date: 2013-03-15 / Financiadora de Estudos e Projetos / With the purpose of elucidating some aspects concerning the importance of substrate spatial complexity to the ecology of Chironomidae (Diptera) family in Cerrado streams, three field experiments were carried out in Ipameri and Mimoso de Goiás Municipalities, Goiás State, Brazil. These experiments are described in three chapters that compose this thesis i) Temporal dynamics of Chironomidae (Diptera) larvae on substrates with different levels of spatial complexity and roughness in a Central Brazil stream; ii) Is substrate complexity important for Chironomidae (Diptera) larvae to resist hydrological disturbance?; iii) Influence of spatial complexity and roughness on Chironomidae (Diptera) assemblages. Artificial substrates with different complexity and roughness levels were fixed in bed streams for colonization of Chironomidae larvae. Samplings were taken after a period of 30 days. Results indicated that: i) Colonization of substrates by larvae was not influenced by substrate spatial complexity and no patterns of colonization were observed, considering the various ecological guilds; ii) Both complexity and roughness were not sufficient to maintain the abundance of these organisms, evidencing their sensibility to sudden rain events; iii) Spatial complexity and roughness of substrate influenced the structure of Chironomidade assemblages and were two important aspects to the diversity of these organisms. / Buscando esclarecer alguns aspectos a respeito da importância da complexidade espacial do substrato sobre a ecologia de Chironomidae (Diptera) em córregos de baixa ordem do Cerrado brasileiro, foram realizados três experimentos aqui apresentados em três capítulos: i) Dinâmica temporal de Chironomidae (Diptera) em substratos com diferentes complexidades e rugosidades em um riacho do Brasil Central; ii) A complexidade do substrato é importante para as larvas de Chironomidae (Diptera) resistirem à perturbação hídrica?; iii) Influência da complexidade espacial e da rugosidade na assembleia de Chironomidae (Diptera). Os experimentos foram realizados nos municípios de Ipameri e Mimoso de Goiás, ambos situados no Estado de Goiás. Para amostragem das larvas de Chironomidae foram utilizados substratos artificiais com diferentes níveis de complexidade e rugosidade fixados no leito dos riachos para colonização. De forma geral os resultados obtidos indicaram que: i) A colonização dos substratos pelas larvas não foi influenciada pela complexidade espacial do substrato, não sendo observados padrões de colonização, considerando as diferentes guildas ecológicas; ii) Tanto a complexidade quanto a rugosidade do substrato não foram suficientes para a manutenção da abundância das larvas de Chironomidae, evidenciando sua sensibilidade a eventos inesperados de chuva; iii) A complexidade espacial e a rugosidade do substrato afetam a estrutura da assembleia de Chironomidae, sendo dois importantes aspectos para a diversidade destes organismos.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Ornamental plants in general are highly susceptive to water deficiency, principally to the elevated soil water level variation that effects at a precarious and uneven final product development. The study was conducted on greenhouse at the Universidade Federal de Santa Maria, RS. It aimed to observe if rice husk ash substrate offers limitation to the pot cultivation of the specie, to evaluate de the root development under different water availability levels and to analyze the effects on the flower stem qualities and pack yields in two different cultivation periods. The studied specie was Gypsophila paniculata Golan . The seedlings were attained from donor plants at the Floriculture Sector of the Phytotecny Department of UFSM. The experiment was conducted in flexible polyethylene pots with 18 liters of capacity, filled with rice husk ash carbonized on a rice drier mill and kept on 100%, 80%, 60% and 40% of the limit water retention capacity of the pot. The humidity was kept by the weighing method, three times a week (Monday, Wednesday and Friday) the pots were weighted on a decimal precision scale and the difference of the pot weight was added with water to attain the limit established weights to each treatment on the two cultivation periods. The comparison of the production components among the treatments was performed through the variance analyses (ANOVA) significance level of 5% and the regression analyses, because the treatments are quantitative. The comparison between the periods of cultivation was obtained throughout the Tukey Test at the mistake significance level. The results showed that the fine granulometry of the rice husk ash is not a limitation to the cultivation of gypsophila in 18 liters pots. The water consume is higher at the production cycle of spring/summer and it rises with increasing of the water availability, independently the period. The water availability changes the roots spatial distribution in the pot, also changes the length and the dry mass. The commercial quality of the produced stems is not affected importantly by the humidity levels of the substrate or the cultivation cycle. The yield of packs is higher with above 60 % end 80%, humidity for the fall/winter cultivation. However, the 80% of availability provides the best yield. / As plantas ornamentais, de forma geral, são bastante susceptíveis às deficiências hídricas, principalmente às grandes variações do nível de água no solo, refletindo-se num desenvolvimento precário e desuniforme do produto final. O presente trabalho foi realizado em casa de vegetação da Universidade Federal de Santa Maria, RS. Teve como objetivo observar se o substrato casca de arroz carbonizada oferece limitação para o cultivo da espécie em vasos, avaliar o desenvolvimento radicular sob variados níveis de disponibilidade hídrica e analisar sua resposta sob qualidade das hastes florais, e a produtividade de maços, em duas épocas de cultivo. A espécie utilizada foi Gypsophila paniculata variedade Golan . As mudas utilizadas neste experimento foram obtidas a partir de plantas matrizes existentes no Setor de Floricultura do Departamento de Fitotecnia, da UFSM. O ensaio foi conduzido em vasos com capacidade para 18 litros de polietileno flexível, os quais foram preenchidos com substrato de casca de arroz carbonizada, e mantidos em 100%, 80%, 60% e 40% do limite da capacidade de retenção hídrica do vaso. A manutenção da umidade foi realizada pelo método das pesagens, onde três vezes por semana (segunda, quarta e sexta) os vasos eram pesados em balança com precisão decimal, a diferença de peso do vaso, era complementada com água até atingir os limites de peso estipulados para cada tratamento nos dois ciclos de cultivo. O delineamento experimental foi inteiramente casualizado composto por quatro tratamentos e 10 repetições. A comparação dos componentes de produção entre os tratamentos aplicados para os distintos ciclos foi realizada por análise de variância (ANOVA) ao nível de 5% de significância e regressão visto que são tratamentos qualitativos. A comparação entre os ciclos foi feita pelo Teste de Tukey ao nível de 5% de significância de erro. Os resultados obtidos mostram que o tipo de granulometria fina do substrato casca de arroz carbonizada não oferece limitação ao cultivo de gipsofila em vasos de 18 litros. O consumo de água é maior no ciclo de produção correspondente a época primavera/verão e aumenta à medida que a disponibilidade se eleva, independente de época. A disponibilidade hídrica altera a distribuição espacial das raízes no vaso assim como e comprimento e a matéria seca. A qualidade comercial das hastes produzidas não é afetada de modo importante pelos níveis de umidade do substrato ou ciclo de cultivo. A produtividade de maços por m2 é superior com níveis de umidade entre 60 e 80% para os dois ciclos. A disponibilidade de 80% foi aquela que proporcionou a melhor rentabilidade. Palavras-Chave: Flor de corte. Consumo hídrico. Substrato alternativo.

Recently, efforts have been made for self-powering the batteries and portable electronic devices by piezoelectric nanogenerators. The piezoelectric nanogenerators can work as a power source for nano-systems and also as an active sensor. The piezoelectric nanogenerator is a device that converts random mechanical energy into electrical energy by utilizing the semiconducting and piezoelectric properties. Also, the mechanical energy is always available in and around us for powering these nano devices. The aim of the present thesis work is to explore 1D and 2D ZnO nanostructures (nanorods and nanosheets) on metal alloy substrates for the development of piezoelectric nanogenerators in energy harvesting and sensors applications. Hydrothermal synthesis method was adopted for the growth of ZnO nanostructures. The nanogenerators were fabricated by using the optimized synthesis parameters and subsequently studied their performance for power generation and as an active speed sensor. These 1D and 2D nanostructures based nanogenerators have opened up a new window for the energy harvesting applications and sensors development. The thesis is divided into following six chapters. Chapter 1: This chapter gives a general introduction about energy harvesting devices such as nanogenerators, available energy sources, mechanical energy harvesting, ZnO material and the details on hydrothermal synthesis process. A brief literature survey on different applications of piezoelectric nanogenerators is also included. Chapter 2: A novel flexible metal alloy (Phynox) and its properties along with its applications are discussed in this chapter. Details on the synthesis of 1D ZnO nanorods on Phynox alloy substrate by hydrothermal method are presented. Further, the optimization of parameters such as growth temperature, seed layer annealing and substrate temperature effects on the synthesis of ZnO nanorods are discussed in detail. As-synthesized ZnO nanorods have been characterized using XRD, FE-SEM, TEM and XPS. Chapter 3: It reports on the fabrication of piezoelectric nanogenerator on Phynox alloy substrate as power generating device by harvesting the mechanical energy. Initially, the performance of the nanogenerator for power generation due to finger tip impacts was studied and subsequently its switching polarity test was also carried out. Output voltage measurements were carried out using the in-house developed experimental setup. Stability test was also carried out to see the robustness of the nanogenerator. Finally, the output voltage response of the nanogenerator was studied for its use as an active speed sensor. Chapter 4: Synthesis of Al doped 2D ZnO nanorsheets on Aluminum alloy (AA-6061) substrate by hydrothermal method is reported in this chapter. The optimized parameters such as growth temperature and growth time effects on the synthesis of ZnO nanosheets are discussed. As-synthesized ZnO nanosheets were characterized using XRD, FE-SEM, TEM and XPS. The Al doping in ZnO is confirmed by EDXS and XPS analysis. Chapter 5: Cost effective fabrication of Al doped 2D ZnO nanosheets based nanogenerator for direct current (DC) power generation is reported in this chapter. The performance of the nanogenerator for DC power generation due to finger tip impacts was studied and subsequently its switching polarity test was also carried out. Output voltage measurements were carried out using the in-house developed experimental setup. Stability test was also carried out to see the robustness of the nanogenerator. Finally, the DC output voltage response of the nanogenerator was studied for its use as an active speed sensor. Chapter 6: The first section summarizes the significant features of the work presented in this thesis. In the second section the scope for carrying out the further work is given.

Often synthetic graphene requires transfer onto an arbitrary substrate prior to use because the substrate it was originally synthesized on is inappropriate for either electrical measurement or characterization. While a variety of routes have been developed they are substrate dependant and often involve the use of harsh treatments. Here we present a facile and cheap route that can be applied to graphene over any substrate. This universal transfer route is based on a wet chemical reaction producing gaseous species which can intercalate between the substrate and the graphene and thus gently delaminate the two.

Substrate topography can have profound effects on initial bacterial adhesion during biofilm formation. We applied Staphylococcus epidermidis and Escherichia coli cells onto periodically structured substrates with different structure dimensions, structure types and wetting properties. We found a strong dependence of cell retention on the structure dimensions of the applied substrates. Periodicities in the range of the cell size increased, whereas smaller periodicities decreased cell retention, independent of contact time (minutes to hours) and hydrophobicity. These novel insights on the role of surface topography on bacterial retention might facilitate the development of non-fouling surfaces in the future.

The magnetic tunability of ferrites has been studied and applied on many electric components for working in various frequency bands. Filters or resonators loaded by ferrites can thus work for different frequency requirements by tunning external biasing field. However, filters or resonators built by traditional waveguides are large in size. And for tunning with biasing field below the ferroresonance point, dissipation in ferrites will increase rapidly if the working frequency is near the ferroresonance zone. It leads to the drop of Q values of resonators and the tuning range is limited to stay away from ferroresonance. For the filter, remaining high Q values in wide frequency tuning range is the base of good performance and tunability. In industry, demands of cost reduction and integration encourage the miniaturization of electric components. It is always challenging but attractive to find solutions compromising size, performance, and implement ability. In this project, investigation for possible solutions of magnetic bias tunable filter is made and their comparisons are presented. Analysis and simulation are made to a specific ferrites-loaded substrate integrated waveguide resonator. With homogeneous below-resonance biased field, results in the reference are reached again and analyzed. With biasing filed above the ferroresonance, higher Q values and smaller size can be achieved and the drop of Q is avoided. A magnet structure is designed to study how the resonator works in inhomogeneous biasing filed. Biasing of below-resonance field is achieved with the magnets structure, though the performance is not good as homogeneous biasing case. A 3-order filter is then built based on the resonator working in the below-resonance bias. It’s a band-pass filter and tunable. A magnet structure is also built and simulated for the filter to verify its feasibility. / Magnetisk avstämning av ferriter har studerats och applicerats på många elektriska komponenter för arbete i olika frekvensband. Filter eller resonatorer lastade av ferriter kan därmed fungera för olika frekvenskrav genom att tuna externt biasing fält. Filtren eller resonatorerna byggda av traditionella vågledare är dock stora i storlek. Och för tunning med biasing field under ferroresonanspunkten, kommer avledning i ferriter att öka snabbt om arbetsfrekvensen är nära ferroresonanszonen. Det leder till sänkning av Q-värden för resonatorer och inställningsområdet är begränsat för att hålla sig borta från ferroresonans. För filtret är kvarvarande höga Q-värden i brett frekvensinställningsområde grunden för god prestanda och avstämning. Inom industrin uppmuntrar krav på kostnadsminskning och integration till miniatyrisering av elektriska komponenter. Det är alltid utmanande men attraktivt att hitta lösningar som kompromissar med storlek, prestanda och implementerbarhet. I detta projekt undersöks möjliga lösningar av magnetiskt bias tunable filter och deras jämförelser presenteras. Analys och simulering görs till en specifik ferritbelastad substratintegrerad vågledarresonator. Med homogent vinkelfält under resonans nås resultaten i referensen igen och analyseras. Med biasing arkiverad över ferroresonansen, högre Q-värden och mindre storlek kan uppnås och fallet av Q undviks. En magnetstruktur är utformad för att studera hur resonatorn fungerar i inhomogen biasing fil. Biasing av nedanstående resonansfält uppnås med magnetens struktur, men prestandan är inte bra som homogen biasing fall. Ett 3-ordningsfilter byggs sedan baserat på resonatorn som arbetar i nedanstående resonans bias. Det är ett bandpassfilter och kan justeras. En magnetstruktur byggs och simuleras också för filtret för att verifiera dess genomförbarhet.

Microelectronics is heading towards larger and larger systems implemented on a single chip. In wireless communication equipment, e.g., cellular phones, handheld computers etc., both analog and digital circuits are required. If several integrated circuits (ICs) are used in a system, a large amount of the power is consumed by the communication between the ICs. Furthermore, the communication between ICs is slow compared with on-chip communication. Therefore, it is favorable to integrate the whole system on a single chip, which is the objective in the system-on-chip (SoC) approach. In a mixed-signal SoC, analog and digital circuits share the same chip. When digital circuits are switching, they produce noise that is spread through the silicon substrate to other circuits. This noise is known as substrate noise. The performance of sensitive analog circuits is degraded by the substrate noise in terms of, e.g., lower signal-to-noise ratio and lower spurious-free dynamic range. Another problem is the design of the clock distribution net, which is challenging in terms of obtaining low power consumption, sharp clock edges, and low simultaneous switching noise. In this thesis, a noise reduction strategy that focus on reducing the amount of noise produced in digital clock buffers, is presented. The strategy is to use a clock with long rise and fall times. It is also used to relax the constraints on the clock distribution net, which also reduce the design effort. Measurements on a test chip show that the strategy can be implemented in an IC with low cost in terms of speed and power consumption. Comparisons between substrate coupling in silicon-on-insulator (SOI) and conventional bulk technology are made using simple models. The objective here is to get an understanding of how the substrate coupling differs in SOI from the bulk technology. The results show that the SOI has less substrate coupling when no guard band is used, up to a certain frequency that is highly dependent of the chip structure. When a guard band is introduced in one of the analyzed test structures, the bulk resulted in much higher attenuation compared with SOI. An on-chip measurement circuit aiming at measuring simultaneous switching noise has also been designed in a 0.13 µ SOI process. / <p>Report code: LiU-Tek-Lic-2005:33.</p>