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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.
91

Estimativas de parâmetros genéticos e análise dialélica de cruzamentos de trigo (Triticum aestivum L.) envolvendo a cultivar BH-1146 e linhagens irradiadas / Estimates of genetic parameters and diallel analysis of wheat crossings (Triticum aestivum L.) with cultivar BH-1146 and irradiated strains

Mary Túlia Vargas Lobato 29 July 2010 (has links)
Visando avaliar o potencial de populações segregantes de trigo obtidas de parentais portadores de características agronômicas contrastantes, quanto ao comprimento da raiz primária, produção de grãos e caracteres agronômicos; estimar a herdabilidade no sentido amplo e restrito para populações F2 obtidas, além das associações das características em estudo; confirmar os genitores mais promissores para utilização em programas de melhoramento de trigo e estimar a capacidade geral e específica de combinação dos genótipos de trigo, foram efetuados cruzamentos, em forma dialélica, entre quatro genótipos de trigo: BH-1146, Anahuac M-1, IAC-287/IAC-24 M-1 e MONS/ALDS// IAC-24 M-3. Foram obtidos híbridos em geração F1 e F2 e os retrocruzamentos RC1 e RC2, que foram avaliados quanto ao comprimento da raiz em solução nutritiva, conforme Camargo e Ferreira Filho (2005a). Após a medição das raízes, as plântulas foram transplantadas para telado do Centro de Grãos e Fibras do IAC sob delineamento de blocos ao acaso, com 28 tratamentos (os 4 parentais, os 6 F1s, F2s, RC1s e RC2s), com 6 repetições. Avaliaram-se os caracteres comprimento da raiz primária, altura das plantas, comprimento da espiga, número de espiguetas por espiga, grãos por espiga, grãos por espigueta, massa de cem grãos, comprimento do internódio da raque, número de espigas por planta, produção de grãos por planta e florescimento. Para análise dialélica foi utilizado o Modelo de Griffing (1956) Os valores estimados para a herdabilidade em sentido amplo, para os seis cruzamentos, foram altas para altura de plantas; médios, na maioria dos cruzamentos, para comprimento da raiz, comprimento da espiga, números de espigas por planta e grãos por espiga, produção de grãos por planta e florescimento; de médios a altos para comprimento do internódio da raque e número de espiguetas por espiga e de médios a baixos para massa de cem grãos e número de grãos por espigueta. Esses valores indicaram que grande parte das variações encontradas foi de origem genética. As estimativas de herdabilidade no sentido restrito (h2r) mostraram grande variação de magnitude nos diferentes cruzamentos para todos os caracteres avaliados. Ressaltou-se o cruzamento P1/P4, com parentais divergentes, com elevados valores de herdabilidade no sentido restrito. Altos valores de h2r foram estimados para altura de plantas em todos os cruzamentos, indicando que a seleção será efetiva nas primeiras gerações segregantes. As correlações fenotípicas revelaram haver uma tendência da seleção de plantas com maior comprimento da raiz primária estar associada com maior produção de grãos por planta e maior precocidade para o florescimento. BH-1146 demonstrou ser fonte genética de tolerância à seca no estádio inicial da cultura do trigo. As análises dialélicas corroboraram os resultados dos ensaios de genótipos, destacando os genótipos P4 como fonte de redução de altura das plantas e o P1 como fonte de aumento do comprimento da raiz; para produção de grãos evidenciaram-se P1 e P2 com elevados valores de capacidade geral de combinação. Detectaram-se efeitos significativos da CEC e CGC, evidenciando a ação de genes preponderantemente aditiva e de dominância na manifestação dos na maioria dos caracteres estudados / Diallel crossing was made with four wheat genotypes: BH-1146, Anahuac M-1, IAC-287/IAC-24 M-1 and MONS/ALDS// IAC-24 M-3, bearing agronomically contrasting characteristics, to evaluate the potential of segregating populations of wheat obtained from parents bearing contrasting agronomic characteristics for primary root length, grain yield and agronomic characteristics; to estimate the herdability, in the broad and narrow senses, for F2 obtained populations in addition to the association of the traits under study; to confirm the more promising parents for use in wheat improvement programs and to estimate the general and specific combining abilities of wheat genotypes. Hybrid were obtained in F1 and F2 generation of RC1 and RC2 backcrossing, which were evaluated for their root length in nutrient solution, according to Camargos and Ferreira Filhos method (2005a). After root measuring, plantules were transplanted to screens of the IAC Center for Grain and Fibers in blocks at random, with 28 treatments (4 parents, the 6 F1s, the 6 F2s, the 6 RC1s and the 6 RC2s), with 6 repetitions. Characteristics such as primary root length, plant length, and spike length, number of spikelet per spike, grains per spike, grains per spikelet, 100 grain weight, length of the rachis internode heigth, number of spike per plant, grain yield per plant and flowering were evaluated. The Griffing Model (1956) was used for the diallel analysis. Herdability estimates were obtained. The herdability estimates in the broad sense for the six crossings were high for plant height in all of them; moderate, in most of the crossings for root growth, spike heigth, number of spikes per plant and grain per spike, grain yield per plant and flowering; were moderate to high for rachis internode height and the number of spikelet per spike and moderate to low for 100 grain weight per spikelet. These values indicated that a large part of the variability found was of genetic origin. Herdability estimates in the narrow sense showed large variability in magnitude in the different crossings for the studied traits. P1/P4 crossing with different parents showed high herdability in the narrow sense. High herdability values in the narrow sense were estimated for plant heigth in all crossings, indicating that the selection will be effective for the first segregating generations. Phenotype correlations showed a tendency for the selection of plants with larger heigth for the primary root being associated with a higher grain yield per plant and higher early flowering. BH-1146 proved to be a genetic source of tolerance to drought in the initial stage of the wheat breeding. Diallel analysis confirm the results of experiments with genotypes, showing high values in the combining ability of P4 genotypes as being the source of reduction of plant heigth, and P1 as source of the increase in root length; P1 and P2 were found with high values of gi for the production of grain. CEC and CGC, showed the action of genes of major aditive effects and prevalence of the traits studies
92

As orações de tempo e condição na fala da criança : uma perspectiva socio-funcionalista

Rodrigues, Angelica Terezinha Carmo 22 February 2001 (has links)
Orientador: Maria Luiza Braga / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Estudos da Linguagem / Made available in DSpace on 2018-07-27T19:14:12Z (GMT). No. of bitstreams: 1 Rodrigues_AngelicaTerezinhaCarmo_M.pdf: 3730027 bytes, checksum: ef1d6083270ff884218582dc219c17b5 (MD5) Previous issue date: 2001 / Resumo: Neste trabalho, investigo as orações hipotáticas de tempo e condição presentes na fala de crianças em fase de aquisição de primeira língua. Na literatura consultada, há um consenso de que as orações temporais emergem na fala da criança primeiro do que as condicionais. Como sugere Slobin (1975), algumas noções, por serem mais salientes psicologicamente do que outras, são primeiramente desenvolvidas na infância. Os dados, no entanto, permitem afirmar apenas que as primeiras ocorrem em maior número do que as segundas. A justificativa, nesse caso, remete tanto a Givón quanto a Heine et alii. Tomando por base os pressupostos de Givón (1995), pode se dizer que as temporais representam estruturas não-marcadas, uma vez que são menos freqüentes. Nesse caso, é provável que tendam a ser, ao contrário das condicionais, menos complexas. Uma outra hipótese remete ao continuum de categorias cognitivas proposto por Heine et alii (1991), que defende que entidades mais concretas, como as que se referem a TEMPO, podem ser recrutadas para expressar noções mais abstratas, como CONDIÇÃO. Mostro, entre outros aspectos que, em algumas orações, é possível identificar uma superposição de significados temporais e condicionais, e que, em outras, essa possibilidade é, senão bloqueada, pelo menos, mais difícil. A correlação modo-temporal e o grau de hipoteticidade explicam, parcialmente, a intercambialidade entre noções temporais e condicionais. Para aferir o grau de integração dessas orações, utilizei as variáveis correlação modo-temporal, explicitude, correferencialidade e formas de expressão dos sujeitos. Em relação ao primeiro parâmetro, os resultados empíricos sugerem que as construções de tempo, por apresentarem tempos e modos idênticos tanto na núcleo quanto na temporal, estão mais integradas, e, portanto, mais gramaticalizadas. No que concerne aos outros parâmetros, parece haver uma inversão nos resultados. Casos de anáfora zero, que indicam um grau forte de entrelaçamento, foram registrados mais nas orações condicionais do que nas temporais. Todavia, em ambas estruturas, os sujeitos apresentaram os traços [- correferencialidade] e [+ explicitude], que indicam relações sintáticas mais frouxas / Abstract: This study investigates the hypotactic temporal and conditional clausespresent in the speech pattems of children who are in the language acquisition phase. According to the literature researched there is consensus that temporal clauses emerge in children speech patterns before conditional clauses. Like Slobin (1975) suggests, some notions, being more visible than others frem a psychological perspective, are the first to be developed in childhood. In my data, however, I verified to a certain extent that the first occur in greater number than the latter. In this case, the justification points to the hypotheses of both Givón and Heine et aloTaking Givón's pressupositions as a basis, I can say that the temporal clauses are unmarked structures, once they are less frequent. In this case, it is possible that they tend to be, contrary to condicional clauses,less complex. Another hypotheses alludes to the continuum of cognitive categories proposed by Heine et al (1991), which defends that concrete entities are recruited to express more abstract notions, such as condition. I emphasize, among other aspects, that in some sentences it is possible to identify a superposition of temporal and conditional meanings and that, in other sentences, this possibility is, if not blocked, at least less apparent. The modus-temporal correlation and hypothetical explanation ratio partially explain the interchangeability of temporal and conditional notions. In order to assess the integration degree of these sentences I used the sharing of tenses and moods, co-reference and expressions forros of subject variables. As regards the first parameter, empiric outcomes suggest that temporal constructions, because identical tenses and modes are presented in both the nucleus and the temporal clause, are more integrated and therefore characterized by more marked grammaticalization. Conceming the other parameters there seems to be an inversion of results. Cases of total absence of anaphora, which indicate a strong degree of interchange, were found more frequently in conditional than in temporal clauses. However, in both structures the subjects presented signs that indicate looser syntactic relationships [- co-reference] e [+ explicitness] / Mestrado / Mestre em Linguística
93

Amplification fibrée multivoie avec décomposition spectrale pour la synthèse d’impulsions femtosecondes / Multichannel fiber amplification with spectral splitting for femtosecond pulse synthesis

Rigaud, Philippe 28 November 2014 (has links)
Les impulsions femtosecondes (fs) sont employées pour réaliser des interactions lumière matière athermiques intéressant aussi bien les mondes industriel, médical que scientifique.Des lasers avec toujours plus de puissance crête (P c ) à des cadences toujours plus élevées sont requis. Les sources à fibre dopée ytterbium ont pour cela un potentiel important. Or, la durée des impulsions amplifiées demeure élevée (~ 300 fs) en raison du rétrécissement du spectre amplifié pour de forts niveaux de gain, limitant la valeur de P c accessible. L’amplification avec division spectrale à travers un réseau d’amplificateurs fibrés et la synthèse d’impulsions fs par recombinaison spectrale cohérente est proposée comme solution. Les composantes spectrales sont amplifiées séparément en parallèle avant d’être réassemblées en un seul faisceau. La gestion des relations de phase entre les rayonnements issus des voies assurent la reconstruction de l’impulsion après amplification. Différentes architectures sont considérées.Après avoir choisi et dimensionné l’une d’entre elles, nous avons réalisé l’amplification et la synthèse d’impulsions de 280 fs à travers 12 guides non couplés d’une fibre multicœur, sans étireur/compresseur. Nous avons mis en évidence le gain en puissance de cette architecture par rapport à un amplificateur monovoie, proportionnel au carré du nombre de voies mises enjeu. La compatibilité de ce montage avec l’amplification d’impulsions large bande (≈ 40 nm)a été prouvée. En perspective, les performances énergétiques accessibles et la transposition du schéma d’amplification aux oscillateurs en vue de produire des impulsions fs large bande à haute énergie sont discutées. / Femtosecond pulses (fs) are used to produce no thermal light matter interactions which areinteresting for industrial, medical, or scientific activities. Lasers producing higher peak powerat a higher repetition rate are required. Ytterbium doped fiber sources are good candidates.However, pulse duration is still high (~ 300 fs) owing to spectral narrowing at high gainlevels. Peak power is also limited. Amplification in an array of amplifiers with spectralsplitting and fs pulse synthesis by coherent spectral combining is proposed as a solution.Spectral components are separately amplified before to coherently recombine the amplifieroutputs in a single beam. Phase management of the radiations from different amplifiers leadsto short pulse synthesis. Different setups are considered. After the choice and the gauging ofone of them, we amplified and synthesized 280 fs pulses through 12 uncoupled cores of amulticore fiber, without stretcher/compressor devices. We demonstrated the powerenhancement of this setup compared to a single amplifier, proportional to the square of thenumber of amplifier used. Compatibility of the setup with broadband amplification (≈ 40 nm)was demonstrated. In prospects, performance scaling in terms of peak power are in a first timedevelopped. The conception of an oscillator based of this amplification scheme to produce fsbroadband and energetic pulses is proposed in a second time.
94

Montée en brillance des réseaux de lasers à fibre : Nouvelle approche par diagnostic à contraste de phase dans une boucle d’optimisation / Brightness enhancement in tilled-aperture laser systems : Innovative method associating a phase-contrast like filter with an optimization loop

Kabeya, David 12 December 2016 (has links)
Les méthodes de combinaison cohérente sont rapidement apparues comme très prometteuses dans la course à la puissance des sources lasers. Cela s’explique par le fait que la puissance autour de l’axe de propagation évolue selon une loi quadratique avec le nombre de faisceaux combinés. Mes premiers travaux ont porté sur la montée en puissance de pompage dans les systèmes de mise en phase passive par auto-organisation. Pour la première fois, nous avons mis en évidence à la fois expérimentalement et numériquement, qu’au-delà du seuil laser, le filtrage spectral intracavité dû à la structure interférométrique du système laser, est un des principaux facteurs limitant l’obtention de qualités de phasage élevées. L’augmentation du nombre d’émetteurs accentue la dégradation de l’efficacité de combinaison avec la montée en puissance, montrant l’incapacité de ce type de méthode à combiner efficacement un grand nombre d’émetteurs lasers de forte puissance. Par la suite, mes travaux ont porté sur l’étude d’une méthode innovante de phasage actif, mise au point à XLIM. Le principe de cette méthode associe un filtrage optique de type contraste de phase, à un algorithme d’optimisation réduisant les écarts de phases entre émetteurs. Les calculs et expériences ont mis en évidence la très faible sensibilité de la méthode au nombre d’émetteurs mis en jeu. Les démonstrations de combinaison cohérente de 7 à 37 émetteurs fibrés délivrant jusqu’à 5W chacun ont été faites. Ce dernier résultat constitue aujourd’hui un record en termes de nombre d’émetteurs combinés de manière active. L’efficacité de combinaison en champ lointain a été estimée à une valeur élevée de 94%, correspondant à une erreur de phase résiduelle d’environ λ/25. Le faible nombre d’itérations d’algorithme nécessaires pour converger a permis de corriger les fluctuations de phase sur une bande d’environ 1kHz. / Coherent laser beam combining techniques rapidly appeared highly promising in the field of ultra-high power laser sources. Indeed, the combined intensity around the propagation axis follows a quadratic law with the number of combined emitters. The first part of my work has been focused on passive phasing techniques, based on self-organization properties of coupled lasers. We have shown, both numerically and experimentally, that the intracavity filtering function due to the interferometric nature of the set-up, is an intrinsic reason for combining efficiency decrease far above laser threshold. The decrease goes steeper when the number of combined laser increases, making that kind of system inappropriate for coherently combining a large number of lasers delivering high power. The second part of my work consisted in studying an innovative active phasing method that associates a phase-contrast like filter with an optimization algorithm reducing phase errors between emitters. Both simulations and experiments showed the weak sensitivity of this method to the number of combined emitters. We demonstrated the phasing of 7 to 37 fiber lasers, delivering up to 5W each. To the best of our knowledge, this last result is the highest number of fiber lasers combined with an active phasing method. The combining efficiency has been estimated around 94%, corresponding to a residual phase error of λ/25. The weak number of algorithm iterations needed to reach the in-phase regime offered a bandwidth of approximately 1kHz.
95

Link analyses and LPD/AJ strategies for IEEE 802.16a

Wong, Yi Jim 12 1900 (has links)
Approved for public release; distribution is unlimited. / In military operations, covertness of operation is of paramount importance. The transmission power of the data link must be kept to the minimum to maintain a low probability of detection (LPD) from the adversary. However, a reduction in the transmitted power implies a reduction in the operating range, though the detection range by the enemy is also reduced. Therefore, to reduce the enemy’s detection range while maintaining operating distance, this thesis explores strategies to discriminate gain against an adversary’s sensor. The strategies involve using processing gain, directional antennas, polarization and the natural environment as a transmission shield. The processing gain strategy analyzed in this thesis uses a diversity technique called Maximal Ratio Combining (MRC) applied to an IEEE 802.16a link. Sinclair D. Smith carried out a study on the possible processing gain derivable from this technique and this thesis will bring his results to practical applications via link analyses. In the event that the link is detected and the enemy decides to carry out jamming, the thesis explores a possible anti-jamming (AJ) strategy by using MRC and a directional antenna. Daniel P. Zastrow carried out a study on the AJ capability of MRC and this thesis brings his results to practical applications via link analyses. / Major, Republic of Singapore Airforce
96

The potential of eliminating the grain sink for enhancing biofuel traits in sweet sorghum hybrids

Jebril, Jebril January 1900 (has links)
Doctor of Philosophy / Department of Agronomy / Tesfaye Tesso / Sweet Sorghum [Sorghum bicolor (L.) Moench] is a type of cultivated sorghum grown primarily for its sugar-rich stalks. Because of its high fermentable sugar content, the crop is widely recognized as an alternative feedstock source for bio-fuel production. The extent to which stalk sugar accumulation occurs may be determined by several factors including the sink size. Grain is the most important sink in sorghum and other grain crops. Three experiments were conducted in this study to determine the extent to which the grain sink can reduce sugar accumulation in the stalks, to test and validate a genetic system that allows development of sterile sweet sorghum hybrids, and to assess the potential of sugar-rich hybrids to overcome stalk rot diseases. The first experiment, based on 22 sweet sorghum genotypes, was undertaken to study the effect of eliminating the grain sink (removing the head prior to anthesis) on stalk juice yield, sugar accumulation, and biomass. The data showed that the grain sink had a significant effect on all traits measured. Elimination of the grain sink significantly increased oBrix % (17.8%), dry biomass (27.8%), juice yield (23.9%), and total sugar yield (43.5%). The second experiment was aimed at validating the role of A3 genetic male sterility system for producing sterile sweet sorghum hybrids. Ten sweet sorghum pollinator lines of variable sugar content were selected among the entries included in the previous experiment. The lines were crossed to four A1 and A3 cytoplasmic male sterile (CMS) lines using a Design II mating scheme. The A3 females did not have effective restorers so that the hybrids were expected to be sterile. The parental lines and corresponding hybrids were evaluated for biomass production, oBrix, juice and sugar yield using a randomized complete block design. All A3 hybrids were sterile and did not produce seed when heads were covered prior to pollination. The effect of grain sink represented by the A1 vs. A3 CMS were highly significant for Brix%, biomass, juice, and sugar yield. Comparison of parents vs. crosses component was highly significant, indicating marked heterosis effect for the traits. Both general (GCA) and specific (SCA) combining ability effects were also significant for all traits, indicating the role of both additive and dominance genetic effects in the inheritance of the characters. Earlier studies have shown positive relationships between stalk sugar concentration and stalk rot disease resistance in sorghum. Thus, the objective of the third experiment was to study the effects of the CMS mediated differential accumulation of stalk sugar on severity of charcoal rot disease caused by Macrophomina phaseolina. The experiment provided an opportunity to test the effect of variable stalk sugar in the same genetic backgrounds. The data indicated that hybrids produced from A3 cytoplasm were more resistant to charcoal rot (7.1cm lesion length) compared to those produced from the A1 hybrids (9.5 cm lesion length). The enhanced resistance of hybrids with higher sugar yield could have significant agronomic advantage in sugar based bio-fuel feedstock production.
97

Detection and estimation techniques in cognitive radio

Shen, Juei-Chin January 2013 (has links)
Faced with imminent spectrum scarcity largely due to inflexible licensed band arrangements, cognitive radio (CR) has been proposed to facilitate higher spectrum utilization by allowing cognitive users (CUs) to access the licensed bands without causing harmful interference to primary users (PUs). To achieve this without the aid of PUs, the CUs have to perform spectrum sensing reliably detecting the presence or absence of PU signals. Without reliable spectrum sensing, the discovery of spectrum opportunities will be inefficient, resulting in limited utilization enhancement. This dissertation examines three major techniques for spectrum sensing, which are matched filter, energy detection, and cyclostationary feature detection. After evaluating the advantages and disadvantages of these techniques, we narrow down our research to a focus on cyclostationary feature detection (CFD). Our first contribution is to boost performance of an existing and prevailing CFD method. This boost is achieved by our proposed optimal and sub-optimal schemes for identifying best hypothesis test points. The optimal scheme incorporates prior knowledge of the PU signals into test point selection, while the sub-optimal scheme circumvents the need for this knowledge. The results show that our proposed can significantly outperform other existing schemes. Secondly, in view of multi-antenna deployment in CR networks, we generalize the CFD method to include the multi-antenna case. This requires effort to justify the joint asymptotic normality of vector-valued statistics and show the consistency of covariance estimates. Meanwhile, to effectively integrate the received multi-antenna signals, a novel cyclostationary feature based channel estimation is devised to obtain channel side information. The simulation results demonstrate that the errors of channel estimates can diminish sharply by increasing the sample size or the average signal-to-noise ratio. In addition, no research has been found that analytically assessed CFD performance over fading channels. We make a contribution to such analysis by providing tight bounds on the average detection probability over Nakagami fading channels and tight approximations of diversity reception performance subject to independent and identically distributed Rayleigh fading. For successful coexistence with the primary system, interference management in cognitive radio networks plays a prominent part. Normally certain average or peak transmission power constraints have to be placed on the CR system. Depending on available channel side information and fading types (fast or slow fading) experienced by the PU receiver, we derive the corresponding constraints that should be imposed. These constraints indicate that the second moment of interference channel gain is an important parameter for CUs allocating transmission power. Hence, we develop a cooperative estimation procedure which provides robust estimate of this parameter based on geolocation information. With less aid from the primary system, the success of this procedure relies on statistically correlated channel measurements from cooperative CUs. The robustness of our proposed procedure to the uncertainty of geolocation information is analytically presented. Simulation results show that this procedure can lead to better mean-square error performance than other existing estimates, and the effects of using inaccurate geolocation information diminish steadily with the increasing number of cooperative cognitive users.
98

Nouveau procédé dynamique d’analyse et de contrôle du front d’onde synthétique de réseaux de lasers / New dynamical process for analysis and phase control of the synthetic wavefront of a laser beam array

Saucourt, Jérémy 30 September 2019 (has links)
Des projets futuristes tels que la production d’énergie par fusion nucléaire, ou encore la navigation interstellaire par voiles solaires, requièrent l’utilisation d’une source de lumière de luminance extrême. Dans l’objectif d’augmenter la luminance de sources lasers, mes travaux de thèse ont porté sur la combinaison cohérente de réseaux de lasers. Ils ont conduit au développement d’un nouveau procédé de contrôle compact du front d’onde de synthèse formé par le réseau de faisceaux lasers. Ce procédé permet de sculpter à façon la figure intensimétrique du champ lointain et donc de contrôler la distribution angulaire d’énergie émise par le réseau de faisceaux lasers. Le procédé développé utilise un module convertisseur phase/amplitude intégrant un élément diffuseur. Une méthode de mesure de la matrice de transfert d’un système optique a été développée pour caractériser ce module convertisseur de champ. A tout instant, le front d’onde de synthèse est estimé par une boucle numérique de recouvrement de phase basée sur un algorithme à projections alternées. Ce calcul approché permet d’ajuster progressivement les relations de phases du réseau de faisceaux lasers jusqu’au jeu de phases arbitraire souhaité. Le procédé permet le contrôle d’un front d’onde de synthèse en moins de 10 corrections de phases, quasi-indépendamment du nombre de faisceaux lasers à contrôler. Il est robuste aux défauts environnementaux et indépendant du jeu de phases initiales. J’ai démontré la compacité du système étudié en analysant et contrôlant une pupille de synthèse de 4 cm de côté, constituée de 16 faisceaux, à l’aide d’un module d’analyse mesurant seulement 30 cm. J’ai également montré expérimentalement le contrôle des phases de réseaux de 16 à 100 faisceaux lasers avec des erreurs résiduelles valant respectivement λ/30 et λ/20 rms. Les capacités de cette méthode peuvent être étendues au contrôle des ordres de Zernike supérieurs du front d’onde de synthèse, ou bien plus généralement pour mesurer directement le front d’onde d’un rayonnement cohérent. / Futuristic projects such as nuclear fusion power generation, or interstellar navigation by solar sails, require the use of a light source of extreme brightness. In order to increase the brightness of laser sources, my thesis work focused on the coherent beam combination of laser arrays. They led to the development of a new compact control process for the synthetic wavefront formed by the laser beam array. This process makes it possible to tailor the intensity pattern of the far field and thus control the angular distribution of energy emitted by the laser beam array. The process developed uses a phase/amplitude converter module with an integrated diffuser element. A method of measuring the transfer matrix of an optical system has been developed to characterize this field converter module. At any time, the synthetic wavefront is estimated by a phase recovery loop based on an alternating projections algorithm. This approximate calculation makes it possible to gradually adjust the phase relationships of the laser beam array to the desired arbitrary phase set. The process allows the control of a synthetic wavefront in less than 10 phase corrections, almost independently of the number of laser beams to be controlled. It is resistant to environmental defects and independent of the initial phase set. I demonstrated the compactness of the system studied by analyzing and controlling a 4 cm large synthetic pupil, composed of 16 beams, using an analysis module measuring only 30 cm. I also experimentally showed the control of the network phases of 16 to 100 laser beams with residual errors of λ/30 and λ/20 rms respectively. The capabilities of this method can be extended to control the higher Zernike orders of the synthetic wavefront, or more generally to directly measure the wavefront of coherent radiation.
99

Analysis of the Fluid Antenna System

Khammassi, Malek 04 1900 (has links)
Fluid antenna systems (FAS) are an emerging technology that promises a signif icant diversity gain even in the smallest spaces. Motivated by the groundbreaking potentials of liquid antennas, researchers in the wireless communication community are investigating a novel antenna system where a single antenna can freely switch positions along a small linear space to pick the strongest received signal. However, the FAS positions do not necessarily follow the ever-existing rule separating them by at least half the radiation wavelength. Previous work in the literature param eterized the channels of the FAS ports simply enough to provide a single-integral expression of the probability of outage and various insights on the achievable perfor mance. Nevertheless, this channel model may not accurately capture the correlation between the ports, given by Jake’s model. This work builds on the state-of-the-art and accurately approximates the FAS channel while maintaining analytical tractabil ity. The approximation is performed in two stages. The first stage approximation considerably reduces the number of multi-fold integrals in the probability of outage expression, while the second stage approximation provides a single integral represen tation of the FAS probability of outage. Further, the performance of such innovative technology is investigated under a less-idealized correlation model. Numerical results validate our approximations of the FAS channel model and demonstrate a limited performance gain under realistic assumptions. Further, our work opens the door for future research to investigate scenarios in which the FAS provides a performance gain compared to the current multiple antennas solutions.
100

Evaluating Different Genetic Algorithms for a State-machine Combining Assignment Problem

Hillblom, Jonathan January 2020 (has links)
Deep packet inspection (DPI) is useful as a tool for analyzing internet traffic. Regular expressions (regexps) can be used to detect the network traffic patterns that the DPI is able to identify. These regexps can be represented as state-machines, and sometimes combining smaller state-machines into larger state-machines can result in more efficient processing. This thesis looks at how to decide which state-machines used in DPI-classes should be combined with which other state-machines in an efficient manner using genetic algorithms. The goal being to create as few resulting state-machines from the combination while still maintaining a upper limit on the size of the resulting state-machines. The problem is modelled as an assignment problem for which an emulated surrogate problem is used in order to make experimental evaluations. Several genetic algorithms are suggested in an attempt to explore a wide range of parameters. It is also evaluated if different genetic algorithms perform differently depending on if the state-machines represent DPI-classes used to parse UDP or TCP traffic. A 2-dimensional representation is used that allows for a better capture of the underlying assignment problem. Different approaches to fitness are explored and found to have different efficacy in different situations. Several genetic algorithm operators are suggested for different situations and a difference is found between what works for UDP and for TCP. / Deep packet inspection (DPI) ̈ar användbart som ett verktyg f ̈or att analysera internettrafik. Regular expressions (regexps) kan användas för att detektera trafik mönster somDPI:n kan identifiera. De här regexps kan representeras som state-machines, och ibland så kan kombinationen av mindre state-machines till större state-machines resultera i mer effektiv bearbetning. Den här tesen undersöker hur man kan bestämma vilka state-machines som används iDPI-klassen bör bli kombinerade på ett effektivt sätt med genetiska algoritmer. Målet är att skapa så fǻ resulterande state-machines från kombineringen på ett sådant sätt att storleken på alla resulterande state-machines håller sig under en övre gräns. Problemet är modellerat som ett assignment problem för vilket ett emulerat surrogatproblem används för att tillåta experiment att utföras. Ett flertal genetiska algoritmer är föreslagna i ett försök att undersöka en bred räckvidd av parametrar. Det är också undersökt om olika genetiska algoritmer har olika prestanda beroende på om state-machines representerar DPI-klasser använda för UDP eller TCP trafik. En 2-dimensionell representation som fångar det underliggande problemet på ett bras sätt är använd. Olika tillvägagångssätt för att representera fitness är undersökta och är upptäckta att ha olika effektivitet i olika situationer. Ett flertal genetiska algoritm operatorer är föreslagna för olika situationer och en skillnad är hittad mellan vad som fungerar för UDP och vad som fungerar för TCP.

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