• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 266
  • 70
  • 67
  • 51
  • 19
  • 16
  • 14
  • 9
  • 8
  • 5
  • 4
  • 4
  • 3
  • 3
  • 3
  • Tagged with
  • 694
  • 89
  • 82
  • 74
  • 71
  • 70
  • 69
  • 64
  • 51
  • 50
  • 49
  • 47
  • 45
  • 42
  • 40
  • 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.
331

[en] STUDIES OF THE INTERACTION OF THE ANTIBIOTIC NORFLOXACIN AND ITS COPPER COMPLEXES WITH MICELLES OF IONIC SURFACTANTS BY UV-VISIBLE ABSORPTION SPECTROSCOPY AND FLUORESCENCE / [pt] ESTUDOS DA INTERAÇÃO DO ANTIBIÓTICO NORFLOXACINA E DE SEUS COMPLEXOS DE COBRE COM MICELAS DE SURFACTANTES IÔNICOS POR ESPECTROSCOPIA DE ABSORÇÃO UV-VISÍVEL E FLUORESCÊNCIA

GABRIEL SILVA VIGNOLI MUNIZ 03 May 2019 (has links)
[pt] A norfloxacina é um antibiótico de amplo espectro bacteriano, amplamente utilizado na medicina. É membro da família das fluorquinolonas e, como a maioria dos membros dessa família, é naturalmente fluorescente. Isso torna técnicas espectroscópicas ideais para o seu estudo. Ademais, tem sido relatado que, quando complexada com metais de transição, como o cobre, pode apresentar maior ação microbiana e também ação antitumoral. Surfactantes são usualmente utilizados em formulações para transporte de fármacos, com o objetivo de acurar a ação dos mesmos em regiões específicas. Este trabalho teve por finalidade estudar, através de técnicas espectroscópicas como absorção, fluorescência estacionária e resolvida no tempo, a interação de norfloxacina com micelas dos surfactantes iônicos dodecilsulfato de sódio (SDS) e brometo de cetil trimetilamônio (CTAB). Esse estudo foi realizado em diferentes pHs, pois o equilíbrio iônico da norfloxacina depende do pH, e diversos trabalhos demonstram que o seu estado de carga é extremamente importante para a interação com alvos biológicos. Através das técnicas utilizadas foi possível mensurar as constantes de associação da norfloxacina às micelas, como também foi notório que, no caso do SDS, a concentração micelar crítica do surfactante sofre uma considerável redução, diminuindo em até seis vezes o valor usual em solução aquosa. Em pH 7,4 também foram avaliados os efeitos da complexação de norfloxacina com cobre e com os complexos cobre piridina, cobre bipiridina e cobre fenentrolina na interação com micelas de SDS. / [en] Norfloxacin is a broad-spectrum antibacterial drug widely used in medicine. It is a member of the family of fluoroquinolones and is naturally fluorescent, as the majority of the members of this family. This makes spectroscopic techniques ideal for its study. Moreover, it has been reported that complexation with transition metals such as copper can result in a higher antimicrobial and antitumor action. Surfactants are commonly used in formulations for drug delivery, with the purpose of improving the action in a specific region. This paper aims at studying the interaction of norfloxacin with ionic micelles of sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB) using spectroscopic techniques such as UV-Visible absorption, steady state and time resolved fluorescence. This study was carried out at different pH, since the ionic state of norfloxacin is modified by the pH, and several studies have shown that the ionic state of the molecule is extremely important for the interaction with biological targets. The techniques allowed obtaining the association constants of norfloxacin to the micelles. It was also noticed that in the case of SDS, the critical micelle concentration of the surfactant undergoes a considerable reduction, reducing six times the usual value in aqueous solution. At pH 7.4 the effects of norfloxacin complexation with copper and with the copper complexes with pyridine, bipyridine and phenanthroline on the interaction with SDS and CTAB micelles were also evaluated.
332

Avaliação econômica de clientes: um estudo exploratório sobre modelos na prática e a capacidade de geração de valor para a empresa e/ou acionistas / Customers\' economical evaluation: an exploratory study on models in practice and the value generation capacity for the company and/or shareholders

Perini, Aline Araujo 17 September 2010 (has links)
A configuração do capitalismo atual, a globalização de mercados, o acirramento da concorrência, a velocidade de mudança e os gerentes cada vez mais cobrados por resultados e sustentabilidade das tomadas de decisão têm impelido as empresas a investir cada vez mais em sistemas de relacionamento para conhecer clientes. Os clientes são a mola propulsora de qualquer empresa e sem eles a empresa não possui valor algum. O objetivo desse trabalho foi explorar os fatores que impactam e determinam o valor do cliente para a empresa e/ou acionistas. Com base em fundamentação teórica, foram evidenciadas as principais pesquisas, destacando as contribuições empíricas de cada caso e a contemplação dos vetores de valor para a empresa e/ou acionistas. Resultados sugerem que o advento da tecnologia da informação nas empresas tem proporcionado a produção de conhecimento para a tomada de decisão mais estruturada em relação à gestão de clientes por valor. Foram evidenciadas (9) nove pesquisas sobre análise de padrão de lucratividade, (8) oito sobre otimização de alocação de recursos, (5) cinco sobre aquisição, retenção e efeitos sociais e (4) quatro sobre avaliação de empresas por meio de clientes. Cliente é definido como ativo intangível na medida em que otimiza a utilização dos recursos para a cocriação de valor para a empresa e/ou acionistas. / The current capitalism configuration, markets globalization, tight competitiveness, the change speed, managers more and more called by results and account for their decision have been forcing companies to invest more and more in customer relationship systems. The customers are the bottom line of any company and without them the company doesn\'t possess any value. The objective of this work was to explore the factors that impact and determine the customer\'s value for the company and/or shareholders. Based on theoretical, it was evidenced the mainly researches, dealing with empirical contribution of each case and the value vectors contemplation for company and/or shareholders. Results suggest that the introducing information technology in the companies has been providing the knowledge production for decision models more structured for managing customers by value. Nine researches were evidenced on profitability pattern analysis, eight on optimize resources allocation, five on acquisition and retention and social effects and four about firm evaluation through customers. Customer is defined as in-tangible assets as long as optimizes the utilization of resources for the co-creation of value for the company and/or shareholders.
333

Collectivité des noyaux de Zinc riches en neutrons par mesure de temps de vie avec le démonstrateur AGATA. Développement d'une cible d'hydrogène et physique aux énergies relativistes / Collectivity of neutron rich Zn nuclei by lifetime measurement with the AGATA Demonstrator. Development of a Hydrogen target and Physics at relativistic energies.

Louchart-Henning, Corinne 17 September 2012 (has links)
L’étude de la spectroscopie et de la structure des noyaux exotiques a permis ces dernières années de nombreuses découvertes par rapport à ce qu’on connaissait sur les noyaux stables : les noyaux peuvent être déformés et certains nombres magiques ne sont pas persistants lorsque l’on s’approche des drip line. Autour du 68Ni, qui présente des signes de fermeture de sous couche à N=40 (énergie d’excitation du 2+1 élevée et B(E2 ;2+->0+) faible), les noyaux exotiques tels les isotopes de Cr, Fe, Zn et Ge, présentent des déformations et les expériences récemment menées indiquent un développement rapide de la collectivité. L’expérience menée au LNL (Laboratori Nazionali di Legnaro) sur les isotopes 70,72,74Zn a conclu à la mesure d’une durée de vie étonnamment longue pour l’état 4+ du 74Zn, menant à un rapport entre B(E2; 4+ -> 2 +) et B(E2; 2+ -> 0+) très faible, non expliqué par les calculs au-delà du champ moyen ou de modèle en couche. Cette expérience a été l’une des premières de la campagne du démonstrateur AGATA.Deux types de réactions directes sont utilisées pour extraire les facteurs spectroscopiques, quantités reliées au nombre d’occupation des couches. Les valeurs trouvées expérimentalement ne sont pas consistantes entre elles dans le cas d’arrachage d’un nucléon très lié au noyau. Cette différence entre les deux mesures expérimentales pourrait provenir du fait qu’on ne modélise pas correctement le mécanisme de réaction des réactions d’arrachage d’un nucléon. Des calculs basés sur une approche d’une cascade intra-nucléaire suivie d’une phase d’évaporation tendent à montrer les insuffisances dans la modélisation actuelle des réactions. / The study of exotic nuclei spectroscopy and structure allowed, in the last years, numerous discoveries in respect to what is known from stable nuclei: nuclei can be deformed and the magic numbers are not persistent when moving toward the drip lines. Around 68Ni, which presents signs of shell closures at N=40 (high excitation energy of the 2+1 and low B(E2)), exotic nuclei, like Cr, Fr, Zn and Ge, present deformation and recent experiments point to rapid development of collectivity. The experiment done at LNL (Laboratori Nazionali di Legnaro) on 70,72,74Zn isotopes concluded a surprisingly long life time for the 4+ states of 74Zn, leading to a ratio of B(E2; 4+ -> 2 +) to B(E2; 2+ -> 0+) very low, not explicated by calculations beyond ,mean field or shell models. This experiment was one of the first of the AGATA demonstrator. Two types of direct reactions are used to extract spectroscopic factors, quantity linked to the shell occupation number. The experimental values are not consistent between the cases for the removal of one deeply bound nucleon in the nuclei. This difference between the two experimental measures could come from an incorrect modelization of the reaction mechanism or nucleon removal. Calculations based on intra-nuclear cascade followed by an evaporation phase show shortcomings in the current reaction models.
334

Analysis of structural elements' integrity after thermomechanical loading

Brevus, Vitaly 26 February 2014 (has links)
Cette thèse a été réalisée en cotutelle entre l'Université Technique Nationale Ivan Pul'uj de Ternopil (TNTU, Ukraine) et l’Université Blaise Pascal (Clermont-Ferrand, France). Les travaux ont été effectués au sein de l'Institut Pascal de l’Université Blaise Pascal - Clermont II, de l’IFMA et du CNRS, dans le thème scientifique Matériaux actifs et intelligents, modélisation multi-échelle de l'axe Mécanique, Matériaux et Structures, et au sein de l'Institut Français de Mécanique Avancée. La thèse présentée appartient au domaine scientifique de la mécanique de la rupture et la science des matériaux. L'objectif de la thèse est de développer la méthodologie analytique et expérimentale pour la durée de vie résiduelle des collecteurs du surchauffeur dans les centrales thermiques, en tenant compte des caractéristiques de fonctionnement de chargement thermomécanique. La prédiction de la durée de vie est une tâche cruciale pour un fonctionnement continu des éléments structuraux très chargés et fait partie d'un problème plus large, couvert dans la recherche de la résistance et la durabilité des éléments structurels à haute température dans les équipements d'énergie générateur. Le mémoire décrit l'influence de la température de fonctionnement sur la vitesse de propagation des fissures de fatigue et micromécanismes de rupture dans le matériau du collecteur de surchauffeur. / This thesis was performed under the cotutelle agreement between Ternopil Ivan Pul’uj National Technical University (TNTU, Ukraine) and Blaise Pascal University (Clermont Ferrand, France). The thesis was carried out within Pascal Institute of the Blaise Pascal University - Clermont II, the IFMA and the CNRS, in the Scientific Theme “Active and Smart Materials and Multiscale Modeling” of the Mechanics, Materials and Structures Department, and within the French Institute for Advanced Mechanics. The presented thesis belongs to the scientific field of fracture mechanics and material science. The aim of the thesis is to develop the analytical and experimental methodology for the residual lifetime estimation of the superheater collectors at thermal power stations (TPS), taking into account the operational features of thermomechanical loading. Prediction of lifetime is crucial task for continuous operation of heavy loaded structural elements and is a part of a broader problem, covered in the research of the strength and durability of high temperature structural elements in power-generating equipment. The thesis describes the influence of operating temperature on the fatigue crack growth rate and fracture micromechanisms in the material of the superheater collector.
335

Värdering av Kundrelation

Blohm, Helena, Engdahl, Petter January 2010 (has links)
<p>Studien har genomförts i Kista Galleria med syftet att utvärdera Ryals (2005) formel för värde­ring av kundrelationer. Med hjälp av formeln beräknas Customer Lifetime Value (CLV) för ett antal kundrelationer det undersökta företaget har. Huruvida formeln är funktionell för ändamålet kundvärdering är den centrala frågeställningen. Resultaten som framkommer ty­der på att en utgångspunkt för värdering av kundrelationer med hjälp av enbart monetära faktorer kan resultera i kortsiktiga strategiska beslut. Mindre butiker uppvisade generellt bättre Customer Lifetime Value per kvadratmeter än välkända butiker med stora butiksytor. Viktiga ickemonetära faktorer är ekonomisk styrka vid förhandlingsbordet och kund­attraktion. För att på lång sikt skapa ett framgångsrikt koncept krävs det att såväl monetära som ickemonetära faktorer tas med i beräkningarna för att kunna göra en korrekt bedömning av en kundrelations verkliga värde.</p>
336

Lifetime value modelling / Frederick Jacques van der Westhuizen

Van der Westhuizen, Frederick Jacques January 2009 (has links)
Given the increase in popularity of Lifetime Value (LTV), the argument is that the topic will assume an increasingly central role in research and marketing. As such, the decision to assess the state of the field in Lifetime Value Modelling, and outline challenges unique to choice researchers in customer relationship management (CRM). As the research has argued, there are an excess of issues and analytical challenges that remain unresolved. The researcher hopes that this thesis inspires new answers and new approaches to resolve LTV. The scope of this project covers the building of a LTV model through multiple regression. This thesis is exclusively focused on modelling tenure. In this regard, there are a variety of benchmark statistical techniques arising from survival analysis, which could be applied, to tenure modelling. Tenure prediction will be looked at using survival analysis and compared with "crossbreed" data mining techniques that use multiple regression in concurrence with statistical techniques. It will be demonstrated how data mining tools complement the statistical models, and show that their mutual usage overcomes many of the shortcomings of each singular tool set, resulting in LTV models that are both accurate and comprehensible. Bank XYZ is used as an example and is based on a real scenario of one of the Banks of South Africa. / Thesis (M.Sc. (Computer Science))--North-West University, Vaal Triangle Campus, 2009.
337

Collaborative beamforming for wireless sensor networks

Ahmed, Mohammed 11 1900 (has links)
Collaborative Beamforming (CB) has been introduced in Wireless Sensor Networks (WSNs) context as a long-distance and power-efficient communication scheme. One challenge for CB is the randomness of sensor node locations where different network realizations result in different CB beampatterns. First, we study the effect of sensor node spatial distribution on the CB beampattern. The characteristics of the CB beampattern are derived for circular Gaussian distributed sensor nodes and compared with the case of uniform distributed sensor nodes. It is shown that the mainlobe behavior of the CB beampattern is essentially deterministic. This suggests that the average beampattern characteristics are suitable for describing the mainlobe of a sample beampattern. However, the CB beampattern sidelobes are random and highly depends on the particular sensor node locations. Second, we introduce the multi-link CB and address the problem of random sidelobes where high level sidelobes can cause unacceptable interference to unintended Base Stations or Access Points (BSs/APs). Centralized sidelobe control techniques are impractical for distributed sensor nodes because of the associated communication overhead for each sensor node. Therefore, we propose a node selection scheme as an alternative to the centralized sidelobe control which aims at minimizing the interference at unintended BSs/APs. Our algorithm is based on the use of the inherent randomness of the channels and a low feedback that approves/rejects tested random node combinations. The performance of the proposed algorithm is analyzed in terms of the average number of trials and the achievable interference suppression and transmission rate. Finally, we study CB with power control aiming at prolonging the lifetime of a cluster of sensor nodes in the WSN. The energy available at different sensor nodes may not be the same since different sensor nodes may perform different tasks and not equally frequently. CB with power control can be used to balance the individual sensor nodes' lifetimes. Thus, we propose a distributed algorithm for CB with power control that is based on the Residual Energy Information (REI) at each sensor node while achieving the required average SNR at the BS/AP. The effectiveness of the proposed CB with power control is illustrated by simulations. / Communications
338

Lifetime Performance Assessment of Thermal Systems : Studies on Building, Solar and Disctrict Heating Applications

Stojanovic, Bojan January 2009 (has links)
The main questions today concerning thermal systems are their economical and environmental impacts. These entities are generally, at present, assessed on the basis of operation performances of newly installed/designed systems, during an assumed lifetime period. While this is the common way of perceiving thermal systems, performance-over-time will change as an effect of degradation, and not solely of different operation scenarios. How and to what extent is the question that needs assessing in order to evaluate if these changes will jeopardise the intended system performance requirement, hence service life (SL). The lack of knowledge/approaches and tools for assessing durability and performance-over-time of thermal systems complicates the task of incorporating these aspects in engineering. In turn, this pro-active assessment and analysis is in line with today’s performance based directives, laws and regulations; of which the working life is an essential part. The durability of materials, components and systems is not a topic that is an end in itself, but becomes a vital part in a comprehensive perspective as sustainability. The lifetime performance assessment of thermal systems, as presented in this thesis, shows that it is a vital part of the R&amp;D in the quest of sustainable energy/thermal systems and energy use. This thesis gives knowledge to the thermal (energy) system/technology R&amp;D and engineering sector, regarding durability and lifetime performance assessment methodologies; but also to the durability of construction works sector, regarding the needs for assessing lifetime performance of materials and components in relation to system performance. It also presents descriptions of requirements on construction works. Specifically, the studies presented in the thesis show how durability and lifetime performance assessment of thermal systems may be sought, with knowledge on: methodologies, exposure test set-ups, modelling and the attainment and use of adequate tools. The main focus is on performance-over-time modelling, tying material/component degradation to altered thermal performance, thereby attaining performance-over-time assessment tools to be used in order to incorporate these aspects when engineering thermal systems; hence enabling the forecasting of SL. The presented work was predominantly done in association to the EU project ENDOHOUSING. The project developed a solar-assisted heat pump system solution, with heat storage, to provide the thermal energy to meet space heating, cooling and hot water requirements for domestic houses in different regions of the EU. The project constituted the platform for the work presented in this thesis, thereby outlining the main context with studies on durability and lifetime performance of: flat plate solar collectors ground heat sources/storages and interaction with a heat pump system evaluation of the ENDOHOUSING solar-assisted heat pump system The thesis also presents a study of SL prediction and estimation of district heating distribution networks (an additional thermal system application). In this particular context, the Factor Method is proposed as a methodology. The main issue of lifetime performance of thermal systems is how and to what extent performance reduction in individual materials or components influence the overall system performance, as the essence of energy/thermal system sustainability is system performance. / QC 20100810
339

Värdering av Kundrelation

Blohm, Helena, Engdahl, Petter January 2010 (has links)
Studien har genomförts i Kista Galleria med syftet att utvärdera Ryals (2005) formel för värde­ring av kundrelationer. Med hjälp av formeln beräknas Customer Lifetime Value (CLV) för ett antal kundrelationer det undersökta företaget har. Huruvida formeln är funktionell för ändamålet kundvärdering är den centrala frågeställningen. Resultaten som framkommer ty­der på att en utgångspunkt för värdering av kundrelationer med hjälp av enbart monetära faktorer kan resultera i kortsiktiga strategiska beslut. Mindre butiker uppvisade generellt bättre Customer Lifetime Value per kvadratmeter än välkända butiker med stora butiksytor. Viktiga ickemonetära faktorer är ekonomisk styrka vid förhandlingsbordet och kund­attraktion. För att på lång sikt skapa ett framgångsrikt koncept krävs det att såväl monetära som ickemonetära faktorer tas med i beräkningarna för att kunna göra en korrekt bedömning av en kundrelations verkliga värde.
340

Canadian Advanced Nanospace eXperiment 7 (CanX-7) Mission Analysis, Payload Design and Testing

Shmuel, Barbara 26 November 2012 (has links)
A deorbiting drag device is being designed and built by the University of Toronto Institute for Aerospace Studies/Space Flight Laboratory (UTIAS/SFL) to be demonstrated on the Canadian Advanced Nanospace eXperiment 7 (CanX-7) satellite. CanX-7 will address the growing issue of space debris by designing a drag sail device that will be demonstrated for cubesat-sized satellites. Mission analysis done to ensure the drag device functions properly and deorbits within the required lifetime is performed while varying different properties such as drag coefficient, effective drag area, and solar cycle variations. The design evolution of the device is documented and the chosen design, along with several stages of prototyping, is described. The individual components that make up the device are described as are preliminary numerical analyzes. Finally, the test plan required for the device is described with several deployment experiments and risk reduction tests documented.

Page generated in 0.0563 seconds