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Réalisation d'un faisceau d'ions-électrons monochromatiques à partir d'atomes refroidis par laser / Realisation of a monochromatic ion/electron beam based on laser-cooled atomsBruneau, Yoann 01 October 2014 (has links)
Cette thèse porte sur l’étude d’une nouvelle source de particules chargées peu dispersive basée sur le refroidissement d’atomes par laser. Les technologies actuelles, basées sur des pointes fines de quelques nanomètres, sont limitées à des faisceaux de hautes énergies (champ d’accélération supérieur à 10 kV) et de fortes dispersions supérieures à 1 eV du fait des fortes interactions entre les particules se retrouvant très proches les unes des autres au moment de leur création. Une nouvelle source, basée sur un jet atomique refroidi transversalement et ionisé par lasers, permet d’étendre la zone de création des particules chargées à des dimensions de quelques centaines de micron et ainsi de limiter les intéractions entre les particules, tout en créant une source refroidie à 100 µK et ainsi très peu dispersive. Un guidage, utilisant la force dipolaire exercée par un laser appliqué le long de la propagation des atomes, est étudié expérimentalement et permet de piéger les atomes au centre du laser piégeur. En jouant sur la forme du laser, il est ainsi possible de concentrer les atomes dans une section de diamètre de l’ordre de 0,4 mm. Il est dès lors envisageable de créer une source de particules chargées avec des courants supérieurs au nA. L’ionisation des atomes du jet refroidi, basée sur l’ionisation d’atomes de Rydberg sous champ, est étudiée et comparée aux récentes expériences de photoionisation d’atomes refroidis dans un MOT-3D. / This thesis presents the creation of charged-particle beam based on a source with a low energy spread. Common sources, based on thin nanometer-size needle, allows to create charged-particles beams with a high energy (electric higher than 10 kV are used) and with a high energy spread (higher than 1 eV) due to interactions between particles created close to each other. A new source, based on an atomic beam cooled transversaly and ionized using lasers, allows to extend the size of the source until 100 µm and limit the interactions between particles while creating a cold source with temperatures as low as few 100 µK and thus with a low energy spread. A guiding laser applied along the propagation axis of the atomic beam uses the dipole force to concentrate the atoms in a area with a size as little as 0,4 mm while keeping the properties of low temperature of the atomic beam. With this kind of source, it is possible to create a charged-particle beam with a current greater than 1 nA. A new process of ionisation based Rydberg ionisation is studied in this thesis and compared to the early experiments based on photoionisation of cold atoms from a 3D-MOT.
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Aspectos da biologia reprodutiva do niquim Lophiosilurus alexandri Steindachner, 1876 (Actinopterygii, Pimelodidae) e crescimento da progênie em diferentes condições ambientaisTENÓRIO, Ruy Albuquerque 20 February 2003 (has links)
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Previous issue date: 2003-02-20 / This work was accomplished at Estação de Piscicultura de Paulo Afonso, belonging to the Hidro-Electric Company of San Francisco (CHESF) (09o 22’38 S and 38o13’58 W), Paulo Afonso, BA, in the period from fevereiro/2001 to fevereiro/2002. It had the objective to study the aspects of reproductive biology of the niquim Lophiosilurus alexandri Steindachner, 1876 and to evaluate the growth performance of its offspring, during the early life phases under different environmental conditions. This work offers subsidies for the propagation of the species in the natural environment, i.e dams and rivers and for the commercial pond-net culture in the reservoirs of CHESF. The growth of the niquim was investigated during the early life phases under different conditions of lightness (100, 50 and 0% of light). In each condition two alimentary approaches were used: plankton + balanced food and branconeta (Dendrocephalus brasiliensis) + food (in the ration of 1:1, in volume), each one with two replications. In the first experimental trials twelve incubators were used (capacity of 80 liters), for the photoperiod treatments associated to the diet type. Each incubator receaved 200 offsprings. Soon after, the growth was evaluated in pond-nets, with those fingerlings that presented better growth in the in the previous experimental conditions. One treatment was done with three repetitions. Here, it were used three pond-nets of 1m3, in which each were placed l30 juveniles, for 248 days of cultivation. In order to verify the statistical difference among the growth of the niquins in the different conditions of brightness and food, it was used the Analysis of Variance (ANOVA), with the significance level of 5%. Informations on the aspects of the reproductive biology of the niquim were obtained from bibliographical references and from the experimental results caried out along the present work. The results indicate that the mainly period of reproductive activity of the niquim happens between September to March (83,24% of the spawnings total number). In SL treatment (without light) it was observed the best length performance, with averages of 71.25 + 8.10 mm and 74.70+5.95 mm, for the alimentary approaches plankton+food and (food+branconeta), respectively. In the present work, niquim reached the average weight of 101.77+ 20.70 g, in248 culture days. According to the results, it was concluded that the brightness influences the growth of the niquim during the embryological early phases, and with 10 cm of length , (around 20 grams), it can be realeased safely in large reservoirs and starting hight densities cultivation in pond-net, with meshes up to 12 mm. / O presente trabalho foi realizado na Estação de Piscicultura de Paulo Afonso da Companhia Hidro-Elétrica do São Francisco (CHESF) (09o 22’38’’S e 38o13’58’’W), Paulo Afonso, BA, no período de fevereiro/2001 a fevereiro/2002, e teve como objetivo estudar aspectos da biologia reprodutiva e avaliar o crescimento da progênie durante as fases ontogênicas iniciail do niquim Lophiosilurus alexandri Steindachner, 1876, em diferentes condições ambientais.Esse trabalho oferece subsídios que viabilizam a sua propagação no ambiente natural, ou seja, nos reservatórios das hidrelétricas do rio São Francisco e na piscicultura comercial.Investigou-se o crescimento do niquim durante as fases ontogênicas iniciais, em diferentes condições de luminosidade (100, 50 e 0% de luz). Em cada condição, utilizaram-se dois critérios alimentares: plâncton + ração balanceada e branconeta (Dendrocephalus brasiliensis) + ração (na proporção de 1:1, em volume), com duas réplicas, cada uma. Nessa primeira etapa experimental, foram utilizadas 12 incubadoras (com capacidade de 80 litros), para os tratamentos com fotoperíodo associado ao tipo de dieta. Cada incubadora foi estocada com 200 larvas. Em seguida, avaliou-se em tanques-rede o crescimento (mm) e o peso (g), dos alevinos que obtiveram melhor desempenho na etapa anterior. Nessa etapa, utilizaram-se três tanques-rede de 1m3, cada um deles contendo l30 alevinos, durante o período de 248 dias de cultivo. Para avaliar o crescimento dos niquins nas diferentes condições de luminosidade e alimento, utilizou-se a Análise de Variância (ANOVA) ao nível de significancia de 5%. Os dados sobre aspectos da biologia reprodutiva do niquim foram obtidos por meio de levantamentos bibliográficos e dos resultados experimentais realizados ao longo do presente trabalho. Os resultados indicam que o período de maior atividade reprodutiva do niquim ocorre entre setembro e março (83,24% das desovas). No tratamento “SL” (0% de luminosidade), houve a melhor performance de comprimento, com médias de 71,25±8,10 mme 74,70±5,95 mm, para os critérios alimentares 1 (plâncton+ração) e (ração+braconeta), respectivamente. No presente trabalho, o niquim alcançou o peso médio de 101,77+ 20,70 g, em 248 dias de cultivo. De acordo com os resultados, conclui-se que a luminosidade influencia o crescimento do niquim durante as fases ontogênicas iniciais, e que com 10 cm de comprimento (aprox. 20g), pode-se com segurança realizar o peixamento nos reservatórios e iniciar o cultivo em tanques-rede com malhas de até 12 mm, em densidades maiores.
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Image Processing Using the Least-Squares Approximation for Quality Improvement of Underwater Laser RangingWu, Chen-Mao 29 June 2003 (has links)
This paper attempts to use image processing methods to reduce the influences of ambient
light and scattering effect on the performance of an underwater range finder. The Taguchi method, as well, is employed to increase the repeatability of underwater range finding. In this study, the image processing methods of the least-squares approximation, brightness and contrast adjustment, and primary color processing are presented. The illumination center is also used to estimate the position of the laser spot in the image. In addition, a bandpass optical filter at the receiving end is used to investigate the effects of filters on the quality of range finding. To verify the effectiveness of the proposed image processing methods, a series of DOE process runs are carried out to study effects of the design parameters on quality of range finding. For each image processing method, its corresponding control factors and levels are assigned to an inner orthogonal array. To make the proposed image processing methods robust against noises, both environmental illumination and turbidity are forced into the experiments by utilizing an outer orthogonal array. Images for processing are then captured under different noise conditions in accordance with the allocation of the outer noise array. And, according to the layout of the inner array, the S/N ratio of each treatment combination is calculated. After that, the optimum combination of control factors is predicted through the analysis of variance. Then, the confirmation experiments are carried out to verify that the combination of control factors at the perceived best levels is valid. Based on the results of experiments and analyses, it is found that the least-squares approximation is better than other proposed image processing methods for increasing the quality of range finding. Moreover, the effect
of increasing quality of range finding by using the least-squares approximation is superior to that of using a bandpass optical filter. Even though a range finding system has incorporated a bandpass optical filter for filtering out unwanted noises, the quality of range finding can still be increased distinctly while the algorithm of the least-squares approximation is employed. As well, the least-squares approximation is feasible to reduce the scattering effects in the laser images if the size of the sparse backscattering light spot is smaller than that of the target light spot.
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Intrasexual selection and warning color evolution in an aposematic poison dart frogCrothers, Laura Rose 04 September 2015 (has links)
Flamboyant colors are widespread throughout the animal kingdom. While many of these traits arise through sexual selection, bright coloration can also evolve through natural selection. Many aposematic species, for example, use conspicuous warning coloration to communicate their noxiousness to predators. Recent research suggests these signals can also function in the context of mate choice. Studies of warning color evolution can therefore provide new insights into how the interplay of natural and sexual selection impact the trajectory of conspicuous signal evolution. For my dissertation, I investigated the potential for male-male competition to impact the warning color evolution of a species of poison frog. I focused my work on an exceptionally bright and toxic population of the strawberry poison frog (Oophaga pumilio) where males are brighter than females, a classic signature of sexual selection. In Chapter 1, I used theoretical models of predator and frog visual systems to determine which can see the variation in bright warning coloration within this population. I found that birds, the presumed major predator, likely cannot see this variation, indicating that sexual selection can work under the radar of predators in this species. In Chapter 2, I tested the aggressive responses of males using a two-way choice paradigm that manipulated the perceived brightness of stimulus males. I found that males directed more of their behaviors to bright stimulus frogs, and brighter focal frogs more readily approached stimuli and directed more of their attention to the brighter rival. In Chapter 3, I tested the outcomes of dyadic interactions between males of varying brightness and observed male reactions to simulated intruders in their territories. I found that brighter males initiated aggressive interactions with rivals more readily, and brightness asymmetries between males settled interactions in a way that is consistent with classic hypotheses about male sexual signals. In Chapter 4 I sought to describe physiological correlates of male warning color brightness. While male brightness did not co-vary with classic measures of body condition (circulating testosterone and skin carotenoids), it did correlate with toxins sequestered from the diet and thus appears to be a reliable signal of toxicity in this population. / text
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Fabrication and analysis of carbon nanotube based emittersMancevski, Vladimir 28 October 2011 (has links)
We have advanced the state-of-the-art for nano-fabrication of carbon nanotube (CNT) based field emission devices, and have conducted experimental and theoretical investigations to better understand the reasons for the high reduced brightness achieved. We have demonstrated that once the CNT emitter failure modes are better understood and resolved, such CNT emitters can easily reach reduced brightness on the order of 10⁹ A m⁻² sr⁻¹ V⁻¹ and noise levels of about 1%. These results are about 10% better than the best brightness results from a nanotip emitter archived to date. Our CNT emitters have order of magnitude better reduced brightness than state-of-the-art commercial Schottky emitters. Our analytical models of field emission matched our experimental results well. The CNT emitter was utilized in a modified commercial scanning electron microscope (SEM) and briefly operated to image a sample. We also report a successful emission from a lateral CNT emitter element having a single suspended CNT, where the electron emission is from the CNT sidewall. The lateral CNT emitters have reduced brightness on the order of 10⁸ A m⁻² sr⁻¹ V⁻¹, about 10X less than the vertical CNT emitters we fabricated and analyzed. The characteristics of the lateral field emitter were analyzed for manually fabricated and directly grown CNT emitters. There was no significant difference in performance based on the way the CNT emitter was fabricated. We showed that the fabrication technique for making a single CNT emitter element can be scaled to an array of elements, with potential density of 10⁶-10⁷ CNT emitters per cm². We also report a new localized, site selective technique for editing carbon nanotubes using water vapor and a focused electron beam. We have demonstrated the use of this technique to cut CNTs to length with 10s of nanometers precision and to etch selected areas from CNTs with 10s of nanometers precision. The use of this technique was demonstrated by editing a lateral CNT emitter. We have conducted investigations to demonstrate the effects of higher local water pressure on the CNT etching efficiency. This was achieved by developing a new method of localized gas delivery with a nano-manipulator. / text
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Prediction of wood species and pulp brightness from roundwood measurementsNilsson, David January 2005 (has links)
This thesis presents a number of studies, where a multivariate approach was taken to construct models that predict wood species and thermo mechanical pulp brightness from roundwood of Norway spruce and Scots pine. The first and second studies produced multivariate prediction models for wood species from the bark of spruce and pine. These models can be used for wood species classification and would replace the manual log assessment that takes place today. Principal Component Analysis, PCA, and Partial least squares projections to Latent Structures, PLS, were used to predict the wood species from multivariate measurements recorded from the bark of spruce and pine. Two different kinds of measurements were employed, near-infrared spectroscopy and digital imaging. Both methods showed that it was possible to predict the wood species with a high accuracy. The third and fourth studies of the thesis are related to the wood storage of roundwood and the deterioration of wood that occurs during the storage. The third study used an experimental design with five storage factors that provided different conditions for the analysed wood. The experimental design made it possible to identify the factors and the interaction between factors, which were important for the ISO brightness of peroxide and dithionite bleached thermo mechanical pulp, TMP. The final study of the thesis used NIR spectroscopy for predicting the ISO brightness of bleached TMP. Spectra recorded from stored wood were used to construct PLS prediction models.
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Parental effort in the Northern Flicker (Colaptes auratus) and the trade-off between quantity and quality of offspring2014 September 1900 (has links)
The two main goals of my thesis were to further our understanding of how parental effort is related to life-history trade-offs and to see how parental investment is reflected in various potential measures of nestling quality. I looked at how fitness is maximized by examining (1) the trade-off between current and future reproduction, and (2) the trade-off between quantity and quality of offspring. To see how parents responded to energetic demands and whether each sex reacted in a similar way, I experimentally manipulated brood sizes and quantified provisioning rates. Both male and female parents with enlarged broods increased their feeding rates, but provisioning on a per nestling basis declined, so that parents fledged lighter nestlings with shorter wings. Although the incidence of mortality did not differ between control and enlarged broods, nestlings from enlarged broods were lighter than those from control broods with the same brood size, suggesting that clutch size may be individually optimized.
I also looked at how nestlings responded to different levels of nutritional stress in the manipulated broods by quantifying size and body condition, plumage colouration, and the physiological measures of T-cell mediated immune responses, and corticosterone levels in nestling feathers as a long-term integrated measure of stress physiology. The size of melanin ornaments on feathers and the saturation and brightness of carotenoid colouration was associated with nestling mass in such a way that suggested that plumage characteristics reflect nestling quality. The immune function of nestlings was negatively related to brood size and nestlings in better body condition could mount greater immune responses to foreign antigens suggesting that immune responses are energetically costly. Corticosterone levels in the feathers were not related to nestling body condition and were unaffected by the experimental brood manipulation. The
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mass of male nestlings, which are the larger sex, was more compromised by brood size than female mass was. I also found sex-specific relationships between plumage characteristics and measures of physiological performance. These findings help to explain optimal clutch size and the classic trade-off between quality and quantity of offspring. They also offer new insights into the reliability of putative measures of quality in nestlings and relationships between physiological and morphological traits.
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A High-Energy, Ultrashort-Pulse X-Ray System for the Dynamic Study of Heavy, Dense MaterialsGibson, D J January 2004 (has links)
Thesis (Ph.D.); Submitted to Univ. of California, Davis, CA (US); 17 Sep 2004. / Published through the Information Bridge: DOE Scientific and Technical Information. "UCRL-TH-207378" Gibson, D J. 09/17/2004. Report is also available in paper and microfiche from NTIS.
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The design of a two-element correlation interferometer operating at L-bandJansen van Rensburg, Juan-Pierre 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This thesis describes the design and construction of a two-element digital correlation interferometer
operating at 1.42 GHz. This instrument consists of two 92cm off set-parabolic reflectors
arranged in an east-west baseline, with a maximum length of 24m. The reflectors are out-fi tted with helical beam antennas as primary feeds, and are further equipped with low-noise front-ends. A wideband dual-conversion superheterodyne receiver processes the astronomical
signals before digitisation. The receiver is implemented as far as possible using a ffordable off -the-shelf technologies. The cross-correlation between the two antenna signals is measured using
a 256MHz bandwidth digital FX correlator, and is implemented on a Reconfi gurable Open Architecture
for Computing Hardware (ROACH) board. The preliminary observations made with
this interferometer, suggests that it is possible to detect the sun, and some other much weaker
sources such as Taurus A.
The design of an interferometer in general is presented, from the formulation of the underlying
instrumental requirements, to making meridian drift scan observations. The interferometer
developed may serve as a demonstrator for other engineering students to gain a working knowledge
of radio interferometry, which should prove invaluable when addressing the challenges the
Square Kilometre Array (SKA) is faced with. / AFRIKAANSE OPSOMMING: In hierdie tesis word die ontwerp en konstruksie van 'n twee-element digitale korrelasie interferometer
wat by 1.42 GHz ontvang beskryf. Die instrument bestaan uit twee 92 cm afsetparaboliese
re
ektorantennas met 'n oos-wes basislyn, met maksimum lengte 24 m. Heliese
antennas word gebruik as primêre voer vir die reflektors, en verder maak die voorent gebruik
van laeruis versterkers . Die wyeband superheterodineontvanger verwerk die astronomiese seine
in twee stappe voordat dit digitaliseer word. Bekostigbare kommersiëele komponente word gebruik
in die vervaardiging van die ontvanger. Die kruiskorrelasie tussen die twee antenna seine
word digitaal gemeet deur 'n FX korreleerder met 'n 256MHz bandwydte op 'n ROACH bord.
Die resultate toon aan dat dit moontlik is om die son waar te neem, sowel as sommige ander
swakker bronne, soos Taurus A.
Al die kwessies insluitende die instrumentale vereistes betrokke by die ontwerp van 'n interferometer
word bespreek. Verder word die gebruik van interferometers om meridiaan meetings
te doen bespreek. Die interferometer dien as 'n praktiese demonstrasie van radio interferometrie
vir ingenieurstudente. Hierdie demonstrasie is voordelig vir studente om die uitdagings van die
SKA te bestudeer.
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Influência de diferentes tipos de sombreamentos em tanques-rede no desempenho de tilápias do nilo (Oreochromis niloticus) na fase juvenil. / Influence of different types of shading in net tanks on the performance of Nile tilapia (Oreochromis niloticus) in the juvenile phase.OLIVEIRA, Jaene Francisco de Souza. 14 June 2018 (has links)
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JAENE FRANCISCO DE SOUZA OLIVEIRA - DISSERTAÇÃO PPGEA 2010..PDF: 7189495 bytes, checksum: ea2d29073b35fe44ee6f5b7407f4116a (MD5) / Made available in DSpace on 2018-06-14T13:39:33Z (GMT). No. of bitstreams: 1
JAENE FRANCISCO DE SOUZA OLIVEIRA - DISSERTAÇÃO PPGEA 2010..PDF: 7189495 bytes, checksum: ea2d29073b35fe44ee6f5b7407f4116a (MD5)
Previous issue date: 2010-08 / O objetivo desse estudo foi avaliar o crescimento de peixes durante a fase juvenil sob a interferência de diferentes luminosidades, utilizando quatro úpos de sombreamentos. O
experimento foi realizado no setor de piscicultura, pertencente ao Centro de Ciências
Agrárias da Universidade Federal da Paraíba, desenvolvida no período janeiro de 2009 a
maio de 2010. O trabalho foi conduzido em 16 tanques-rede com malhagem de 2mm,
com volume útil de lm3 , a uma profundidade média de 1 m, colocados em viveiro
escavado. Os tanques-rede foram povoados com juvenis de tilápia do Nilo com peso
médio inicial de 17,59±5,53g e comprimento médio total de 9,63±0,95, numa densidade
de 60 peixes/m2, perfazendo um total de 960 peixes, distribuídos em 16 tanques. Durante o cultivo foram analisadas as seguintes variáveis de qualidade de água: transparência, oxigénio dissolvido, pH e temperatura. Foi estudado o desempenho zootécnico: ganho de peso (GP), ganho de peso relativo, ganho em comprimento (GC). O delineamento experimental foi o inteiramente casualizado (DIC), num esquema de parcela subdividida no tempo (Split Plot in Time), onde foram testados quatro tratamentos (100%,80%,70% e 50%), com quatro repetições cada, totalizando dezesseis parcelas. Os resultados demonstraram que os parâmetros físico-químicos da água analisados estavam dentro dos níveis aceitáveis. Foi observado que os melhores índices de desempenho de ganho de peso relativo foram obtidos no tratamento 80% e o tratamento 100% obteve o pior desempenho e o pior ganho de peso relativo (%) foi no o tratamento de 100% de entrada de luz (290,20%), já o tratamento de 80% foi mais satisfatório, pois obteve o melhor ganho de peso relativo (442,29%). / The objective of this study was to evaluate the growth of Nile tilápia (Oreochromis
niloticus, During the juvenile phase in the interference of light using four types of
shaders. The expenment was conducted by the sector of Fish Culture, belonging to the
Centre for Agrarian Sciences, Federal University of Paraíba, was developed in the
period January 2009 to May 2010. The work was conducted in 16 cages with mesh size
of 2mm with a volume of lm3 , the depth average of 1 m, placed in earth pond. The
cages were stocked with juvenile Nile tilápia with average imúal weight of 17.59 ± 5.53
g and average total length of 9.63 ± 0.95. Arriving at the site and after acclimation, fish
were counted, weighed in batches and stored in tanks at a density of 60 peixes/m2, for a
total of 960 fish distributed in 16 tanks. During cultivation, the following variables were
analyzed water quality: transparency, dissolved oxygen, pH and temperature. We
studied the growth performance: weight gain (WG), relative weight gain, gain in length
(CG). The experimental design was completely randomized (CRD), in a split plot
design in time (Split Plot in Time), where four treatments (100%, 80%, 70% and 50%)
with four replicates each, totaling sixteen plots. The results showed that the physicalchemical
parameters of water samples were within acceptable leveis. We observed the
best performance index of relative weight gain was observed in treatment 80% and
already the treatment of 100% had the worst performance. Water temperature values
were similar for ali treatments. The worst relative weight gain (%) was in the treatment
of 100% of incoming light (290.20%), although the treatment of 80% was more
satisfactory because it had the best relative weight gain (442.29%).
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