• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 82
  • 44
  • 28
  • 20
  • 9
  • 7
  • 6
  • 5
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 242
  • 43
  • 41
  • 39
  • 30
  • 29
  • 26
  • 22
  • 20
  • 18
  • 17
  • 17
  • 16
  • 16
  • 16
  • 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.
31

DBS multi-variables pour des problèmes de coordination multi-agents

Monier, Pierre 12 March 2012 (has links) (PDF)
Le formalisme CSP (Problème de Satisfaction de Contraintes) permet de représenter de nombreux problèmes de manière simple et efficace. Cependant, une partie de ces problèmes ne peut être résolue de manière classique et centralisée. Les causes peuvent être diverses : temps de rapatriement des données prohibitif, sécurité des données non garantie, etc. Les CSP Distribués(DisCSP), domaine intersectant celui des SMA et des CSP, permettent de modéliser et de résoudre ces problèmes naturellement distribués. Les raisonnements intra-agent et inter-agents sont alors basés sur un ensemble de relations entre différentes variables. Les agents interagissent afin de construire une solution globale à partir des solutions locales. Nous proposons, dans ce travail, un algorithme de résolution de DisCSP nommé Distributed Backtracking with Sessions (DBS) permettant de résoudre des DisCSP où chaque agent dispose d'un problème local complexe. DBS a la particularité de ne pas utiliser de nogoods comme la majorité des algorithmes de résolution de DisCSP mais d'utiliser à la place des sessions. Ces sessions sont des nombres permettant d'attribuer un contexte à chaque agent ainsi qu'à chaque message échangé durant la résolution du problème. Il s'agit d'un algorithme complet permettant l'utilisation de filtres sur les messages échangés sans remettre en cause la preuvede complétude. Notre proposition est évaluée, dans les cas mono-variable et multi-variables par agents, sur différents benchmarks classiques (les problèmes de coloration de graphes distribués et les DisCSP aléatoires) ainsi que sur un problème d'exploration en environnement inconnu.
32

Är det lönsamt att investera i CSR? : Förhållandet mellan Corporate Social Performance och Corporate Financial Performance

Bergquist, Gustav, Sandström, Pelle January 2018 (has links)
Denna studie undersöker det finansiella värdeskapandet av CSR-aktiviteter genom att studera förhållandet mellan Corporate Social Performance (CSP) och Corporate Financial Performance (CFP). I enlighet med The CSP-CFP multilevel framework studeras ett avgränsat CSP-CFP samband med utgångspunkt i svenska konsumenter. Vidare undersöker studien den modererande effekten av företagsstorlek på det undersökta CSP-CFP sambandet. Av resultatet framkommer ett signifikant positivt CSP-CFP förhållande för CSR-aktiviteter riktade mot svenska konsumenter. Av resultatet framkommer även ett signifikant starkare positivt CSP-CFP samband för små svenska företag jämfört med för stora svenska företag. Resultatet bidrar till en ökad förståelse av CSP-CFP förhållandet på den svenska marknaden avgränsat för intressentgruppen konsumenter. Framtida forskning kan med fördel, genom kvalitativa metoder, undersöka de underliggande faktorerna som påverkar det finansiella värdeskapandet av CSR-aktiviteter riktade mot konsumenter.
33

Reconstrução tomográfica de imagens SPECT a partir de poucos dados utilizando variação total / Tomographic reconstruction of SPECT images from few data using total variation

João Guilherme Vicente de Araujo 13 April 2017 (has links)
Para realizar a correção de atenuação em uma tomografia computadorizada por emissão de fóton único (SPECT, em inglês) é necessário medir e reconstruir o mapa dos coeficientes de atenuação utilizando uma leitura de um tomógrafo de transmissão, feita antes ou simultaneamente à leitura de emissão. Essa abordagem encarece a produção da imagem e, em alguns casos, aumenta consideravelmente a duração do exame, sendo a imobilidade do paciente um fator importante para o sucesso da reconstrução. Uma alternativa que dispensa a leitura de transmissão é reconstruir tanto a imagem de atividade quanto o mapa de atenuação somente através dos dados de uma leitura de emissão. Dentro dessa abordagem propusermos um método baseado no algoritmo criado por Censor, cujo objetivo é resolver um problema misto de viabilidade côncavo-convexo para reconstruir simultaneamente as imagens. O método proposto é formulado como um problema de minimização, onde a função objetivo é dada pela variação total das imagens sujeita à viabilidade mista de Censor. Os teste foram feitos em imagens simuladas e os resultados obtidos na ausência de ruídos, mesmo para uma pequena quantidade de dados, foram satisfatórios. Na presença de dados ruidosos com distribuição de Poisson o método foi instável e a escolha das tolerâncias, nesse caso, ainda é um problema aberto. / In order to perform attenuation correction in single photon emission computed tomography (SPECT), we need to measure and reconstruct the attenuation coefficients map using a transmission tomography scan, performed either sequentially or simultaneously with an emission scan. This approach increases the cost required to produce the image and, in some cases, increases considerably the scanning time, therefore the patient immobility is an important factor to the reconstruction success. An alternative that dispense the transmission scan is reconstruct both the activity image and the attenuation map only from emission scan data. In this approach we proposed a method based on the Censors algorithm, which objective is to solve a mixed convex-concave feasibility problem to reconstruct simultaneously all images. The method proposed is formulated as a minimization problem, where the objective function is given by the total variation of the images subject to Censors mixed feasibility. In the simulations, artificial images were used and the obtained results without noised data, even for small amount of data, were satisfactory. The method was unstable in the presence of Poisson distributed noise and the tolerance choice, in this case, is an open problem yet.
34

OPTIMAL EEG CHANNELS AND RHYTHM SELECTION FOR TASK CLASSIFICATION

Adikarapatti, Vikramvarun Kannan 11 June 2007 (has links)
No description available.
35

Optimization of hydraulic drives for parabolic troughs

Nocker, Andreas 03 May 2016 (has links) (PDF)
HAWE Hydraulic SE, Munich, engineers and manufactures hydraulic drives (CSP-drives) for parabolic trough plants consisting of a compact power pack, directional and control valves, over-center valves, two cylinders and the fittings/hoses for connecting these components. Optional, but this is depending on the system and the control philosophy, also a hydralic accumulator. An optimized hydraulic drive for a parabolic trough field makes the power plant operator profit from savings at components, higher system efficiency, lower operational energy supply needs, less time spent on commissioning and first start-up, lower maintenance effort and increased life span of the drive and finally also savings on peripheral and safety devices. Many of shown proposals are even combining two or more of above mentioned advantages.
36

Modelling CPV

Cole, Ian R. January 2015 (has links)
A methodology for the simulation of CPV systems is presented in four distinct sections: input, optics, uncertainty and electrical output. In the input section, existing methods of describing the solar irradiation that is incident at the primary optical element of a CPV system are discussed, the inadequacies of the existing methods are explored and conditions of validity for their use drawn. An improved and spectrally extended model for a variable, spatially resolved solar image is arrived at. The model is used to analyse losses at the primary concentration device stage under varying solar profiles and air masses. A contextual analysis of an example Seattle based CPV system operating with constant solar tracking errors of 0.3-0.4° show a corresponding loss in isolation available to the optical system of 5-20%, respectively. In the optics section, an optical ray trace model is developed specifically for this work. The optical ray trace model is capable of the spectrally resolved ray tracing of all insolation input models discussed above. Plano-convex and Fresnel lenses are designed, investigated and compared using each of the insolation models described in the input section. Common CPV component material samples for the plano-convex and Fresnel lenses are analysed for their spectrally resolved optical properties. The computational expense of high resolution spatial and spectral modelling is addressed by means of a spectrally weighted banding method. The optical properties parameter spectral weighting method can be applied to any arbitrary spectral band. The bands used herein correspond to the active ranges of a typical triple-junction solar cell. Each band shows a different spectral dependency. Banded beam irradiation proportions are shown to change by as much as 10% in absolute terms within the air mass range of 1 to 3. Significant variations in spectrally banded illumination profiles are found with the extended light source insolation model. These banded variations are mostly unaccounted for with the use of approximated insolation models, further compounding the argument for extended light source Sun models in CPV system simulations. In the uncertainty section, the limitations of the manufacturing process are explored. Manufacturing tolerance errors from manufacturer datasheets are presented. These production uncertainties are used in the design of an erroneous plano-convex lens which is then analysed with the optical modelled presented in the optics section and compared to the ideal design specification. A 15% variation in maximum intensity value is found alongside a linear shift in the focal crossover point of approximately 0.2mm, although the optical efficiency of the lens remains the same. Framing manufacture errors are investigated for a square Fresnel lens system resulting in a linear shift of the focal centre of approximately 0.85mm. A process for the calculation of wind loading force on a CPV array is also presented. The process uses real 2 second resolution wind data and highlights the chaotic nature of loading force. A maximum force of 1.4kN was found on an example day for a 3m by 3m by 0.1m cuboid (i.e. CPV array); corresponding to a wind speed of approximately 13m/s, which is well within the typical operating range of a CPV tracking system. In the electrical output section, a spatially resolved solar cell model is identified and used for the investigation of solar cell performance under the inhomogeneous cell illumination profiles produced in the uncertainty section. Significant differences in the maximum power point of the cell IVs are found for the ideal and erroneous system illumination profiles. Approximately, a 15% variation is found in the plano-convex lens example, with a relative difference of 4% attributable to illumination profile distortion, and a 6% variation in the module framing component example. These results further highlight the need for the consideration of production uncertainties in CPV system simulation.
37

Physiological and Molecular Characterization of Genetic Competence in Streptococcus sanguinis

Rodriguez, Alejandro 21 July 2008 (has links)
The ability of bacteria to assimilate free DNA from the environment is known as competence. Though many studies have focused on competence regulation in Streptococcus pneumoniae and Streptococcus gordonii, Streptococcus sanguinis has yet to be examined. Physiological characterization of competence in S. sanguinis strain SK36 and its comC mutant, JFP41, led to the genome-wide transcriptional analysis of cells induced to competence via addition of competence-stimulating peptide (CSP). A total of 128 genes were induced at least 2-fold, 74 of which were classified as either “early” or “late” based on their induction patterns. Expression patterns were verified using qRT-PCR. This study identified genes not up-regulated in S. pneumoniae or S. gordonii and lays the foundation for bioinformatic studies to identify conserved binding sites upstream from CSP-regulated genes. These results also shed light on the possible existence and identity of expected CSP exporters in S. sanguinis, which have so far eluded discovery.
38

Electricity Production from Concentrated Solar Power and PV System in Ethiopia

Tefera, Misrak A. January 2019 (has links)
Ethiopia has been facing problems regarding power generation, distribution, balancingbetween demand and supply and access to modern energy service. About 92.4% of energysupply is from biomass (mostly in traditional) 5.7% oil which is not friendly with theenvironment and about 1.6% of energy supply is from renewable energy resource,hydropower plants.Being dependent on hydropower plant causes the country to face many challenges indistribution and balancing demand and supply. This thesis provides another way ofconsidering and implementing renewable energy resource (solar energy resource) throughtechnologies like grid-connected roof mounted solar PV system and CSP plant with the helpof PVGIS, PVWatt and SAM software.This thesis aims to come up with an idea that will work out for current engineering, socialand political issue that is seen in the country. Considering new way in planting PV system onthe roof is strongly recommended and increasing the alternative sites for power generationalong with the appropriate technology is recommended as another way. The possibility andpower generating efficiency is checked through each application.Based on the demonstration in all software’s used, it is clearly visible that the country couldhave been satisfied the needed demand and become the hub of east Africa as mentioned inthe policy and strategy. However, this dependency causes the country to insufficiently supplythe need. Apart from the possibilities and estimation, ideas that might help the country tocome over these challenges are provided in recommendation section.
39

Analysis of parabolic through collector cleaning system under adaptive scheduling policy

Turkoglu, Aykut 10 July 2017 (has links)
The purpose of this study is to investigate the effects of stochastic dust accumulations and rain events on the cleaning schedule of the parabolic trough collectors that are used to generate power at concentrated solar power (CSP) plants. The level of cleanliness is proportional to the power produced, and thus it affects the economic pay off at CSP plants. Current practice to address this dust problem, termed as conventional cleaning, is to follow a periodic cleaning schedule that entails a fixed setup cost for each cleaning event. The frequency of cleaning under such conventional (periodic schedule) policy is selected based upon a tradeoff between the set up cost and the payoff from improving the cleanliness factor. The conventional practice is to have a constant and periodic cleaning schedule over an entire season (e.g. either severe or mild combination of the dust and rain over a 180-day cleaning season, with either 8 or 4 cycles scheduled for the severe and mild seasons respectively). This thesis draws upon evidence from recent literature to show that presence of random rain events improves the cleanliness of parabolic troughs in CSP plants. Upon analyzing such evidence, this study models rain event as a compound Poisson process that replenishes the level of cleanliness. In this scenario, it is possible to establish an adaptive threshold policy for scheduling plant cleaning that analogous to the formulation of a (s,S) inventory management policy, subject to random replenishment of inventory. The study offers a review of related literature to establish that such formulations are not amenable to a close form solution. The second half of the thesis describes a numerical study that has been conducted using Arena Simulation package for characterizing the adaptive cleaning policy. The parameter of interest for assessing system performance is the average payoff over the average cost of cleaning for a 180-day cleaning season. Numerical study shows that adaptive cleaning policy outperforms the conventional (periodic) cleaning policy under reasonable assumptions for dust and rain event distributions. As an extension, the simulation study also examines the use of alternative cleaning system, known as electrodynamic screening (EDS), for different rain scenarios that may be used in conjunction with either conventional or adaptive cleaning policies to improve the overall system performance. / 2019-07-09T00:00:00Z
40

Avvikelsen mellan faktisk och förväntad CSP och effekten på företagsvärde : En kvantitativ studie på 185 börsnoterade bolag under en tioårsperiod / The deviation between actual and expected CSP and the effect on company value : A quantitative study of 185 public companies over a ten year period

Jakobsson, Moa, Tideman, Anton January 2019 (has links)
Titel: Avvikelsen mellan faktisk och förväntad CSP och effekten på företagsvärde - En kvantitativ studie på 185 börsnoterade bolag under en tioårsperiod   Nivå: Examensarbete på Grundnivå (kandidatexamen) i ämnet företagsekonomi   Författare: Anton Tideman och Moa Jakobsson   Handledare: Jan Svanberg   Datum: 2019 – mars     Syfte: Tidigare forskning har undersökt vilken effekt CSP har på företagsvärde med positiva och negativa resultat. I syfte att finna en mer trovärdig mätvariabel har studien utvecklat FFCSP som är avvikelsen mellan faktisk och förväntad CSP för att finna en lösningen på tidigare forsknings motstridiga resultat. Studien syftar till att ett positivt samband mellan FFCSP och företagsvärde existerar.   Metod: Studien antar en positivistisk forskningsfilosofi med en hypotetisk-deduktiv ansats och longitudinell design över tiden tio år. Det sekundära dataunderlaget är insamlat från Thomson Reuters Datastream och har därefter analyserats i statistikprogrammet SPSS.   Resultat & slutsats: Studiens resultatet ger bevis på att en avvikelse mellan faktiskt CSP och förväntad CSP existerar. Även att FFCSP är ett tillförlitligt och signifikant mått i mätning av CSPs effekt på företagsvärde samt att ett positivt samband uppvisas.   Examensarbetets bidrag: Studiens utformning av variabeln FFCSP har bidragit med en nytt sätt att mäta sambandet mellan CSP och företagsvärde. Även att minska informationsasymmetrin mellan företag och intressenter.   Förslag till fortsatt forskning: Ett förslag till fortsatt forskning är att behandla en kortare tidsperiod för att generera ett större dataunderlag. Ett annat förslag är att använda kvalitativa intervjuer för att minska informationsasymmetrin mellan företag och intressenter.     Nyckelord: CSP, företagsvärde, marknadsvärde, marknadseffektivitet, informationsasymmetri / Abstract   Title: The deviation between actual and expected CSP and the effect on company value - A quantitative study of 185 public companies over a ten year period   Level: Student thesis, final assignment for Bachelor Degree in Business Administration   Author: Anton Tideman and Moa Jakobsson   Supervisor: Jan Svanberg   Date: 2019 – March     Aim: Prior research have studied the effect that CSP has on company value with both positive and negative results. With the purpose to find a more reliable measuring variable the study has developed AECSP which symbolises the deviation between actual and expected CSP to find a solution to the different results earlier research has presented. The study aims to find a positive relationship between AECSP and company value   Method: The study adopt a positivistic research philosophy with a deductive approach and a longitudinal design over ten years. The secondary data is collected from Thomson Reuters Datastream and have therafter been analyzed and processed in the statistical program SPSS.   Result & Conclusions: The results of the study gives evidence that a deviation between actual CSP and expected CSP exists. Also that AECSP is a reliable and significant measurement in the measuring of CSPs effect on company value and that a positive relationship can be proved.   Contribution of the thesis: The study’s development of the variable AECSP has contributed as a new way of measuring the relationship between CSP and company value. The study has also contributed by reducing the information asymmetry between companies and stakeholders.   Suggestions for future research: One suggestion for future research is to treat a short time period to generate a larger amount of data. Another suggestion is through qualitative interviews reduce the information asymmetry between companies and stakeholders.     Key words: CSP, company value, market value, market efficiency, information asymmetry

Page generated in 0.0573 seconds