• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 11
  • 7
  • 5
  • 3
  • 3
  • 1
  • Tagged with
  • 30
  • 9
  • 7
  • 7
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 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.
1

Flame retardancy of EVM-based polymers with low smoke emission / Procédé de polymères EVM ignifugés à faible émission de fumées

Hoffendahl, Carmen 11 July 2014 (has links)
Cette étude est dédiée aux matériaux élastomères à base d’éthylène acétate de vinyle (EVM) ignifugés à l'aide de trihydroxide d’aluminium (ATH) et de mélamine ou de ses dérivés. Les différents types de formulations sont testés concernant leurs propriétés mécaniques, vieillissement, ignifugation et libération de fumée. La combinaison d’ATH et borate de mélamine dans l’EVM (EVM-ATH-MB) présente une plus faible libération de fumées et une meilleure stabilité pendant les tests vieillissement. En conséquence les mécanismes de la décomposition sont étudiées en utilisant entre autres des nouvelles approches comme le pyrolyzeur chromatographie en phase gazeuse couplée à la spectrométrie de masse (py-GCMS) et calorimètre à cône couplé à la spectroscopie infrarouge à transformée de Fourier (MLC-FTIR). L’effet de refroidissement ainsi que la formation d’une couche protectrice à la surface protège le matériau principalement. / This work deals with new elastomeric ethylene-vinyl acetate (EVM) materials containing aluminum trihydroxide (ATH) in combination with melamine or its derivatives are evaluated regarding mechanical properties, hydrothermal aging, fire retardancy and smoke release. The decomposition mechanism of EVM containing ATH and melamine borate (MB) (EVM-ATH-MB) is analyzed in details because of its high stability during hydrothermal aging and its low smoke release. Decomposition reactions EVM-ATH-MB are studies using amongst others new approaches such as pyrolysis-gas chromatography-mass spectrometry (py-GCMS) and mass loss calorimeter coupled with Fourier transform infra-red (MLC-FTIR). It is found that EVM-ATH-MB is mainly protected by the mode of action of ATH diluting the fuel and forming a protective layer that reduces mass and heat transfer.
2

USER GENERATED CONTENT IN THE DESTINATION IMAGE PRESENTATION : THE DESTINATION VIENNA

Lindgren, Natalie January 2021 (has links)
UGC has become an important part of traveling both for the companies and for the travellers themselves. The topic is currently at its forefront of research, which makes the area of study even more relevant. Followed by the development of social media in the corporate world and especially its major part in the everyday life of Generation Y. The competition has become tougher among the destinations since social media, a positive online image has, therefore, become essential on these platforms due to the new ways of obtaining information in a previsiting setting. Instagram is an attractive platform for generation Y and the main channel for tourist to publish their visual word-of-mouth experience after a travel. The concept has its own name called, UGC which together with the consumers perceptions of it has been studied in this thesis. The purpose of the study was to see a comparison between the differences of perceived -usefulness, - credibility and -authenticity based on DMOC and UGC. Moreover, how the participants respond concerning the intention to visit Vienna based on an illustrated destination image of UGC or DMOC. The conceptual S-O-R-model was implemented to illustrate how the input of destination image, became a process of perceptions and outcome of intentions belongs together like a common thread. A quantitative study approach was applied with the strategy of Experimental vignette methodology (EVM), to formulate and illustrated the experiment also, to obtain empirical data which later was analyzed and defined the result. Additionally, the study found that there is no significant difference between USG and DMOC in perceived -usefulness, -credibility, and visiting intention. However, findings of perceived authenticity of the destination image demonstrated that UGC communicates a more positive destination image compared to the DMOC regarding perceived authenticity. Moreover, the practical contributions of this study suggest in accordance with previous studies DMO to cooperate with the users and in that way combine UGC with DMOC in the destination presentation.
3

Modélisation et caractérisation linéaire et non linéaire des filtres RF en technologie BAW et CRF et méthode pseudo-temporelle de test industriel / Modelling and characterization of RF filters in BAW and CRF technology and industrial test using pseudo-time domain method

Sahyoun, Walaa 14 October 2011 (has links)
Les systèmes de télécommunications actuels nécessitent des filtres passe bande fonctionnant à des fréquences comprises entre 1 GHz et 10 GHz pour les systèmes les plus répandus, notamment la téléphonie mobile. Les filtres actuels sont reportés, donc non intégrés sur silicium. Ils présentent certains inconvénients : coût, place occupée, incompatibilité avec les technologies silicium…Une solution consiste à utiliser des résonateurs à ondes de volume, plus communément appelés BAW (Bulk Acoustic Waves). Ils présentent l'avantage d'être intégrables sur silicium. De nouvelles architectures nommées CRF (Coupled Resonator Filter) font appel à des résonateurs à ondes de volume (BAW) mais aussi à des structures utilisant des couplages acoustiques entre différentes couches. L'objectif du travail proposé est de modéliser les structures actuelles et en cours d'études pour obtenir des modèles de type circuits électriques. Ces modèles seront validés par des mesures effectuées au laboratoire sur des résonateurs BAW et sur des filtres qui sont réalisés par nos partenaires. La première partie des études portait sur le comportement RF sous faible et forte puissances, suivi du développement d’un modèle large bande simulé sous ADS décrivant le comportement des filtres BAW sous faible et forte puissances. Une optimisation du temps de mesure en fréquence est effectuée pour réduire le temps du test RF. La seconde partie de la thèse est orientée vers le développement d'une nouvelle méthode de test pseudo-temporelle des filtres hyperfréquences qui consiste à mesurer directement leur impact sur un signal numérique grâce au paramètre «EVM» (Error Vector Magnitude). Ce paramètre est relié au BER et nos travaux montrent qu’il permet également de retrouver en partie les paramètres S et détecter les filtres défaillants à partir d’une seule mesure. Cette nouvelle technique permettant le test de filtres à partir d’un seul point de mesure permet de réduire le temps et le coût de caractérisation à des fins industrielles. Ce travail s'est déroulé dans un cadre de collaborations avec le LETI et STMicroelectronics au sein du projet FAST labellisé par le pôle MINALOGIC. / The telecommunication systems require pass band filters operating between 1 GHz and 10 GHz for most of the popular radio communication system including the mobile phones. The current filters that are not integrated on silicon present some inconveniences such as cost, surface occupied and incompatibility with silicon technology. The solution consists on using Bulk Acoustic Wave resonator called BAW that has the advantage of being integrated on silicon. Innovative architectures called CRF (Coupled Resonator Filter) are based on BAW resonator and use acoustic coupling between different layers. To understand the design and the functioning of these structures, finite element software can be used which requires significant computing time. The objective of our work is modelling the existing and coming structures with models made of electrical circuits. These models will be validated on BAW filters designed by our partners (CEA-LETI) and measured in our laboratory. In the first part, we develop an electro-acoustical wide band model of BAW and CRF filters simulated with ADS software for low and high RF powers. Optimization of measurement in the frequency domain is made to reduce the time of RF test. The second part of the thesis is directed towards the development of a new method of pseudo-time domain test of RF filters, which consists on measuring directly their impact on a digital signal with the parameter «EVM» (Error Vector Magnitude) that is related to BER. Our work shows that we can also find some of S parameters and detect the defected filters from a single measurement extraction. This new technique of filter testing with a single measurement point allows reducing time and cost of test for industrial purposes. This work takes place within collaboration with CEA-LETI and STMicroelectronics in the project FAST labelled by MINALOGIC pole
4

Byggprojektstyrning med Earned Value Management

Liljegren, Emma, Rydlund, Anna January 2011 (has links)
Abstract Today, too many construction projects are delayed and deviates from the budget. A good project management is the basis for successful construction project. The most common planning methods in the construction industry is currently Gantt chart and CPM. The problem with these is that focus is only at the time of the project and doesn’t handle the budget. A project management method which connects the time and cost is Earned Value Management. Earned Value Management enables calculations of different metrics for cost and time that can be used early to see trends in project implementation. The aim of our study is to describe the project managenment in the construction industry and to explain the criteria needed to implement project management methodology Earned Value Management in a construction company. The EVM is unproved at the construction company we chose to do a case study about. We have in a completed building projects in ByggSjögren in Halmstad, Sweden, examined the criteria that exist, and are required to apply Earned Value Management. Through interviews with Annarell Malmberg and Martin Bengtsson, responsible for calculations and purchase of ByggSjögren, and Insa Ostendorf, project manager at Ramböll, we were using the information they gave us to do our study. Based on empirical evidence and data we collected, we have made estimates and proposals for ByggSjögren could proceed at an implementation of Earned Value Management. We have from a completed project studied the criteria that exist today, and what is missing to be able to use Earned Value Management. Finally, we concluded that the criteria that are important to implement Earned Value Management in construction industry is particularly close monitoring. Much of what is included in the Earned Value Management is already being done today in many construction companies, but they have no name for it. / Idag blir alltför många byggprojekt försenade och håller inte budget. Därför är en bra projektstyrning grunden för lyckade byggprojekt. De vanligaste planeringsmetoderna inom byggbranschen är idag Gantt-schema och Critical Path Method. Problemet med dessa är att fokus endast ligger på tiden för projektet och hanterar inte budgeten. En projektstyrningsmetod som kopplar samman tid och kostnad är Earned Value Management. Earned Value Management möjliggör beräkningar av olika nyckeltal för kostnad och tid som kan användas för att i ett tidigt skede kunna se trender i projektgenomförandet. Syftet med vår studie är att beskriva projektstyrning inom byggbranschen samt att förklara vilka kriterier som krävs för att implementera projektstyrningsmetoden Earned Value Management på ett byggföretag. I och med att Earned Value är oprövad på byggföretag valde vi att göra en fallstudie. Vi har utifrån ett avslutat byggprojekt på ByggSjögren i Halmstad undersökt vilka kriterier som finns, och krävs för att tillämpa Earned Value Management. Genom intervjuer med Annarell Malmberg och Martin Bengtsson, ansvariga för kalkyler och inköp på ByggSjögren, och Insa Ostendorf, projektledare på Ramböll kunde vi med hjälp av den information de gav oss utföra vår studie. Utifrån den empiri och data vi samlat har vi gjort beräkningar och förslag på hur ByggSjögren skulle kunna gå till väga vid en implementering av Earned Value Management. Vi har utifrån ett avslutat projekt studerat vilka kriterier som idag finns, och vilka som saknas för att kunna använda sig av Earned Value Management. Slutligen kom vi fram till att de kriterier som är viktiga för att kunna implementera Earned Value Management i byggbranschen är framförallt en noggrann uppföljning. Metoden består av tio viktiga steg, vilka utgör de kriterier som krävs för en implementering. Mycket av det som ingår i Earned Value Management görs redan idag på många byggföretag fast de har inget namn på det.
5

Low Cost Analytical Techniques for Transceiver Characterization

January 2013 (has links)
abstract: Radio frequency (RF) transceivers require a disproportionately high effort in terms of test development time, test equipment cost, and test time. The relatively high test cost stems from two contributing factors. First, RF transceivers require the measurement of a diverse set of specifications, requiring multiple test set-ups and long test times, which complicates load-board design, debug, and diagnosis. Second, high frequency operation necessitates the use of expensive equipment, resulting in higher per second test time cost compared with mixed-signal or digital circuits. Moreover, in terms of the non-recurring engineering cost, the need to measure complex specfications complicates the test development process and necessitates a long learning process for test engineers. Test time is dominated by changing and settling time for each test set-up. Thus, single set-up test solutions are desirable. Loop-back configuration where the transmitter output is connected to the receiver input are used as the desirable test set- up for RF transceivers, since it eliminates the reliance on expensive instrumentation for RF signal analysis and enables measuring multiple parameters at once. In-phase and Quadrature (IQ) imbalance, non-linearity, DC offset and IQ time skews are some of the most detrimental imperfections in transceiver performance. Measurement of these parameters in the loop-back mode is challenging due to the coupling between the receiver (RX) and transmitter (TX) parameters. Loop-back based solutions are proposed in this work to resolve this issue. A calibration algorithm for a subset of the above mentioned impairments is also presented. Error Vector Magnitude (EVM) is a system-level parameter that is specified for most advanced communication standards. EVM measurement often takes extensive test development efforts, tester resources, and long test times. EVM is analytically related to system impairments, which are typically measured in a production test i environment. Thus, EVM test can be eliminated from the test list if the relations between EVM and system impairments are derived independent of the circuit implementation and manufacturing process. In this work, the focus is on the WLAN standard, and deriving the relations between EVM and three of the most detrimental impairments for QAM/OFDM based systems (IQ imbalance, non-linearity, and noise). Having low cost test techniques for measuring the RF transceivers imperfections and being able to analytically compute EVM from the measured parameters is a complete test solution for RF transceivers. These techniques along with the proposed calibration method can be used in improving the yield by widening the pass/fail boundaries for transceivers imperfections. For all of the proposed methods, simulation and hardware measurements prove that the proposed techniques provide accurate characterization of RF transceivers. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013
6

Caractérisation de l’environnement électromagnétique transport pour la reconnaissance de conditions électromagnétiques critiques / Characterization of the electromagnetic railway environment for the recognition of critical electromagnetic conditions

Mili, Souheir 21 October 2014 (has links)
Ces dernières années, nombreux travaux dont l’objectif est de conduire à l’interopérabilité ferroviaire ont permis l’émergence d’un système paneuropéen de contrôle-commande ferroviaire. Ce système exploite des radiocommunications sol-trains fonctionnant selon le protocole GSM-R (Global System for Mobile communications – Railways. La bonne marche de l’exploitation ferroviaire dépend, pour une part, du bon acheminement des données entre sol et trains. Il s’avère donc nécessaire d’assurer un fonctionnement efficace de cette radio sol-trains en dépit de perturbations électromagnétiques intentionnelles ou non intentionnelles qui pourraient la perturber. Ce travail de thèse s’intéresse à cette seconde catégorie de perturbations. Nous développons des méthodes de détection de brouilleurs électromagnétiques afin de mettre en oeuvre rapidement des contre-mesures efficaces contre ces brouillages, à différents niveaux de l’architecture radio. Nous mettons en oeuvre un système de détection supervisé permettant de détecter la présence de signaux de brouillage intentionnels, voire de les reconnaître. Fondé sur l’analyse des signaux échangés, nous développons et évaluons deux méthodes distinctes. L’une exploite les signaux en quadrature mis en évidence par le récepteur dans le canal de communication employé. L’autre méthode considère la densité spectrale de puissance des signaux recueillis dans une bande de fréquence plus large, centrée dans la gamme allouée aux communications GSM-R, et s’étendant de part et d’autre de celle-ci. Ces méthodes sont successivement évaluées par simulation, sur des données issues d’un banc de mesure puis, sur un site ferroviaire réel. / In recent years, numerous studies whose ultimate goal is to drive the railway interoperability have allowed the emergence of a pan-European train control system. This system uses ground-to-train radio operating on the GSM-R (Global System for Mobile communications - Railways) protocol, currently being deployed on a large scale along railway lines. The smooth running of railway operations depends, in part, of the proper routing of radio communications between trains and ground. Therefore, it is necessary to ensure the effective operation of this ground to train link in presence of intentional or unintentional electromagnetic interference that could disrupt communication. This thesis focuses on this second category of disturbances. We develop methods for detecting electromagnetic interference superimposing their signals to GSM-R signals. Then, this detection will promptly set off effective countermeasures against such interference at different levels of the radio architecture, the physical layer, the higher protocol layers. We implement a supervised detection system to detect the presence of jamming signals and, for potentially to recognize them. Based on the analysis of signals exchanged, we develop and evaluate two methods. One considers the quadrature signals recovered by the receiver in the used communication channel. The second method exploits the power spectral density of the signals collected in a wider frequency band, centered in the range allocated to the GSM-R communications and extending on either side thereof. These methods are successively evaluated by simulation, on data obtained using a test bench, and on a real railway site.
7

LTE-Advanced/WLAN testbed / LTE-Advanced/WLAN testbed

Plaisner, Denis January 2017 (has links)
This thesis deals with the investigation and assessment of communication standards LTE-Advance and WiFi (IEEE 802.11n/ac). The EVM error parameter is examined for each standard. To work with different standards a universal workplace have been proposed (testbed). This universal workplace serves for adjusting transmitting and receiving means and for processing signals transmitted and interpreted. Matlab was chosen for this work, through which only control devices such as generators and analyzers from Rohde & Schwarz. This workplace also measures the coexistence of these standards. At the conclusion of this thesis, different coexistence scenarios were designed and evaluated through testbed results.
8

Implementering av EVM och Ganttschema,för stålhallsbolag / Implementation of EVM and Ganttchart,for steel halls companies

Johansson, Filip, Åkerstedt, Rasmus January 2021 (has links)
I dagens byggprojekt blir många byggen försenade och innehåller avvikelser som gör att budgeten inte kan upprätthållas. Företag inom branschen har inte alltid standardiserade sätt för att planera sina projekt. Det är vanligt att företag idag använder vissa delar av projektstyrningsmetoder, därmed kan de missa viktiga delar som behövs för ett lyckat projekt. Inom byggbranschen arbetar byggföretagen med små marginaler gällande budgeten, det blir viktigare att hålla budgeten för att inga avvikelser ska ske.Syftet med uppsatsen är att undersöka projektstyrning ur perspektivet PMI, inom projekt vid byggnation av stålhallar. Samt undersöka möjligheten med att kombinera metoderna Gantt-schema med EVM för att sedan implementera de vid projekt. Utifrån vår fallstudie med två företag inom stålhallsbranschen, har vi undersökt vad som definierar ett projekt. Vi har även undersökt hur byggprocessen är strukturerad, hur företagen arbetar med sina projekt samt om det finns möjlighet att implementera metoderna Gantt-schemat och EVM i projektstyrningen för stålhallsbyggbolagen. Vid en implementering av Gantt-schema, hade en tydlig strukturering av aktiviteterna kunnat hjälpa företagen med tidsplaneringen. I projektstyrning kan projektledarna inte enbart använda sig av Gantt-schemat som styrningsmetod. Eftersom Gantt-schemat inte kan utföra komplexa uträkningar, krävs det att projektledaren använder sig av andra metoder för budgeten och prestationen. En metod för detta skulle kunna vara Earned Value Manegement (EVM), metoden används för att mäta prestation över utfört arbete. Med EVM kan företagen mäta alla aktiviteter i ett projekt, för att följa upp hur projektet fortlöper. En implementering av både Gantt-schemat och EVM ger möjligheten att tydliggöra alla delar i projektet, från tid- och kostnadsanalys till planering av varje delmoment och mätning av prestation.
9

Strategies for Improved Earned Value Management Use by Defense Business Leaders

Rhodes, Kevin Robert 01 January 2017 (has links)
Project cost and schedule forecasting accuracy in the defense industry has not significantly changed since the 1960s, making it difficult for defense business leaders to implement successful earned value management (EVM) strategies. The purpose of this multiple case study was to explore EVM strategies that Washington, D.C. area defense contractor business leaders used to improve costs and schedule goal accomplishment. The conceptual framework for this study was the earned time theory. Data were collected from semistructured interviews from 5 defense contractor business leaders with demonstrated use of EVM strategy. The review of company documents focused on EVM use with reporting requirements, and archival EVM study analysis supplemented the data from the semistructured interviews. Data were triangulated and inductively analyzed for themes, and member checking was done to ensure credibility of the interpretations. Four themes emerged from the data: the use of EVM data to improve outcomes, the existence of essential strategies, the role of EVM as but a single tool, and the essential engagement of leadership. Findings may contribute to social change because defense business contractor leaders could help improve business performance and return resources for social improvement. Investment in social and environmental improvements can strengthen employee commitment and ultimately ties to the community at large, furthering social improvement.
10

Modélisation et caractérisation linéaire et non linéaire des filtres RF en technologie BAW et CRF et méthode pseudo-temporelle de test industriel

Sahyoun, Walaa 14 October 2011 (has links) (PDF)
Les systèmes de télécommunications actuels nécessitent des filtres passe bande fonctionnant à des fréquences comprises entre 1 GHz et 10 GHz pour les systèmes les plus répandus, notamment la téléphonie mobile. Les filtres actuels sont reportés, donc non intégrés sur silicium. Ils présentent certains inconvénients : coût, place occupée, incompatibilité avec les technologies silicium...Une solution consiste à utiliser des résonateurs à ondes de volume, plus communément appelés BAW (Bulk Acoustic Waves). Ils présentent l'avantage d'être intégrables sur silicium. De nouvelles architectures nommées CRF (Coupled Resonator Filter) font appel à des résonateurs à ondes de volume (BAW) mais aussi à des structures utilisant des couplages acoustiques entre différentes couches. L'objectif du travail proposé est de modéliser les structures actuelles et en cours d'études pour obtenir des modèles de type circuits électriques. Ces modèles seront validés par des mesures effectuées au laboratoire sur des résonateurs BAW et sur des filtres qui sont réalisés par nos partenaires. La première partie des études portait sur le comportement RF sous faible et forte puissances, suivi du développement d'un modèle large bande simulé sous ADS décrivant le comportement des filtres BAW sous faible et forte puissances. Une optimisation du temps de mesure en fréquence est effectuée pour réduire le temps du test RF. La seconde partie de la thèse est orientée vers le développement d'une nouvelle méthode de test pseudo-temporelle des filtres hyperfréquences qui consiste à mesurer directement leur impact sur un signal numérique grâce au paramètre "EVM" (Error Vector Magnitude). Ce paramètre est relié au BER et nos travaux montrent qu'il permet également de retrouver en partie les paramètres S et détecter les filtres défaillants à partir d'une seule mesure. Cette nouvelle technique permettant le test de filtres à partir d'un seul point de mesure permet de réduire le temps et le coût de caractérisation à des fins industrielles. Ce travail s'est déroulé dans un cadre de collaborations avec le LETI et STMicroelectronics au sein du projet FAST labellisé par le pôle MINALOGIC.

Page generated in 0.0401 seconds