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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Baggy paper webs : Effect of uneven moisture and grammage profiles in different process steps

Land, Cecilia January 2010 (has links)
One of the problems encountered in paper converting is caused by the occurrence of "baggy webs", which essentially is when the tension profile of the paper web is uneven. In an area with low tension the paper is longer, which results in bagginess. The baggy parts can not usually be stretched to even out the tension of the paper web in a converting machine, with the result that runnability problems are likely to occur. The aim of the work described in this thesis was to investigate three particular stages in papermaking, namely drying, calendering and storage, and rank them according to their propensity for inducing baggy webs. The focus was placed on investigating the effects of uneven moisture and grammage profiles on the machine-direction strain difference profile. The largest strain difference occurred when there were systematic thick streaks throughout a reel that formed ridges. Stress relaxation during storage then gave rise to a difference in strain of 0.14% when the ridge height was around 2-3 mm. Thickness variations due to variations in grammage is also a source of moisture variation. A difference in moisture of 5% in the calendering stage resulted in strain differences of about 0.05-0.08%. These strain differences resulted in creases being formed as early on as in the calender nip when differences in both grammage and moisture content were present. Most creases appeared when the moisture difference was 2-8%. The difference in grammage could be large without creases being formed when no differences in moisture content were present. A moisture difference of about 5-6% during drying resulted in a strain difference of 0.1% measured on isotropic samples. The moist area turned into a tight streak when the moisture difference appeared at moisture contents higher than 25%. At moisture contents lower than 20%, on the contrary, the moist area turned into a slack streak. The conclusion drawn is that papermakers should concentrate first and foremost on eliminating variations in grammage, especially if these are systematic. This would also eliminate some variations in moisture content, which would solve more problems.
2

Characterization of MBE Grown Metal, Semiconductor and Superconductor Films and Interfaces by Concurrent Use of In Situ Reflection High Energy Electron Diffraction (RHEED) and Reflection Electron Energy Loss Spectroscopy (REELS)

January 2012 (has links)
abstract: This work is an investigation into the information provided by the concurrent use of in situ reflection high energy electron diffraction (RHEED) and reflection electron energy loss spectroscopy (REELS). The two analytical methods were employed during growth of metal, semiconductor and superconductor thin films by molecular beam epitaxy (MBE). Surface sensitivity of the REELS spectrometer was found to be less than 1 nm for 20 KeV electrons incident at a 2 degree angle to an atomically flat film surface, agreeing with the standard electron escape depth data when adjusted incident angle. Film surface topography was found to strongly influence the REELS spectra and this was correlated with in situ RHEED patterns and ex situ analysis by comparison with atomic force microscopy (AFM). It was observed in all the experimental results that from very smooth films the plasmon peak maxima did not fall at the predicted surface plasmon values but at slightly higher energies, even for nearly atomically flat films. This suggested the REELS plasmon loss spectra are always a combination of surface and bulk plasmon losses. The resulting summation of these two types of losses shifted the peak to below the bulk plasmon value but held its minimum to a higher energy than the pure surface plasmon value. Curve fitting supported this conclusion. / Dissertation/Thesis / Ph.D. Engineering Science 2012
3

Marknadsförares attityd av marknadsföringstrenderna händelser, reels och Tiktok : En kvalitativ undersökning av marknadsföringstrender

Coloma Johansson, Alexandra, Neugebauer, Melinda January 2023 (has links)
I takt med digitaliseringen tillförs ständigt nya marknadsföringsmöjligheter där tidigare forskning betraktar sociala medier som en aktuell marknadsföringsstrategi, där främst videobaserade funktioner uppmärksammats och blivit en marknadsföringstrend. Därför är det vanligt att se marknadsföring som ofta sker genom online videos där händelser, reels och Tiktok identifieras som starka marknadsföringsverktyg som är aktuella och trendar. Marknadsförare måste därför agera för att hålla sig uppdaterade på de marknadsföringstrender som skapas för att bidra till en ökad kunskapskompetens, som främjar ett organisatoriskt lärande och som leder företaget framåt. Denna studie ämnar därför att skapa en djupare förståelse för marknadsförares attityd till marknadsföringstrenderna händelser, reels samt Tiktok för att främja ett organisatoriskt lärande. Detta genom att tillhandahålla insikter som kan tillämpas för vidare användning och implementering av trenderna, vilket berikar organisationers kunskapskompetens.  Studien baseras utifrån tidigare forskning där en teoretisk referensram ligger till grund för studiens empiri vilket består av fyra olika teorier och modeller. Social penetrationsteori och teorin medierikedomens roll används för att ge en förklaring kring hur nära relationer och förbättrad kommunikation kan uppstå mellan företag och kunder. Teorin om triggers och val av tjänsteleverantör ger studien en beskrivning kring hur digitala triggers kan användas för att påverka kunder, där till sist teknikacceptansmodellen används för att kunna tolka marknadsförares attityder till händelser, reels och Tiktok. Studien använder sig av en kvalitativ metod där datainsamlingen genomfördes via semi-strukturerade intervjuer där analysmetoden baseras utifrån ett hermeneutiskt och abduktivt förhållningssätt. Den slutsats studien kommer fram till beskriver attityden marknadsförare har gentemot händelser, reels och Tiktok, vilket visar sig vara positiv. Slutsatsen visar att majoriteten av de intervjuade marknadsförarna har en positiv attityd gentemot marknadsföringstrenderna, även ifall några uttryckte funktionernas utmaningar och svårigheter. Följaktligen besvaras därmed studiens problemformulering som lyder: Hur ser marknadsförares attityd ut gentemot marknadsföringstrenderna händelser, reels och Tiktok? / In step with digitization, new marketing opportunities are constantly being added where previous research considers social media as a current marketing strategy, where mainly video-based functions have been noticed and become a marketing trend. Therefore, it is common to see marketing that often takes place through online videos where stories, reels and Tiktok are identified as strong marketing tools that are current and trending. Marketers must therefore act to stay up-to-date on the marketing trends that are created to contribute to an increased knowledge competence that promotes organizational learning and that leads the company forward. This study therefore intends to create a deeper understanding of marketers attitude to the marketing trends stories, reels and Tiktok in order to promote organizational learning. This is by providing insights that can be applied for further use and implementation of the trends, which enriches the knowledge competence of organizations. The study is based on previous research where a theoretical frame of reference is the basis for the study's empirical work, which consists of four different theories and models. Social penetration theory and the theory of the role of media richness are used to provide an explanation for how close relationships and improved communication can arise between companies and customers. The theory of triggers and choice of service provider gives the study a description of how digital triggers can be used to influence customers, where finally the technology acceptance model is used to be able to interpret marketers attitudes towards stories, reels and Tiktok. The study uses a qualitative method where the data collection was carried out via semi-structured interviews where the analysis method is based on a hermeneutic and abductive approach. The conclusion reached by the study describes the attitude marketers have towards stories, reels and Tiktok, which turns out to be positive. The conclusion shows that the majority of the interviewed marketers have a positive attitude towards the marketing trends, even if some expressed the challenges and difficulties of the functions. Consequently, the study's problem formulation is answered, which reads: What do marketers attitude look like towards the marketing trends events, reels and Tiktok?
4

On the sets of real vectors recognized by finite automata in multiple bases

Brusten, Julien 08 June 2011 (has links)
This thesis studies the properties of finite automata recognizing sets of real vectors encoded in positional notation using an integer base. We consider both general infinite-word automata, and the restricted class of weak deterministic automata, used, in particular, as symbolic data structures for representing the sets of vectors definable in the first order additive theory of real and integer numbers. <br><br> In previous work, it has been established that all sets definable in the additive theory of reals and integers can be handled by weak deterministic automata regardless of the chosen numeration base. In this thesis, we address the reciprocal property, proving that the sets of vectors that are simultaneously recognizable in all bases, by either weak deterministic or Muller automata, are those definable in the additive theory of reals and integers. <br><br> Precisely, for weak deterministic automata, we establish that the sets of real vectors simultaneously recognizable in two multiplicatively independent bases are necessarily definable in the additive theory of reals and integers. For general automata, we show that the multiplicative independence is not sufficient, and we prove that, in this context, the sets of real vectors that are recognizable in two bases that do not share the same set of prime factors are exactly those definable in the additive theory of reals and integers. <br><br> Those results lead to a precise characterization of the sets of real vectors that are recognizable in multiple bases, and provide a theoretical justification to the use of weak automata as symbolic representations of sets. <br><br> As additional contribution, we also obtain valuable insight into the internal structure of automata recognizing sets of vectors definable in the additive theory of reals and integers.
5

Étude de films ultra-minces de PTCDI et Pd(Pc)<br />déposés sur les surfaces Pt(001), Pt(111) et Au(001) :<br />application à l'hétérostructure métal/PTCDI/Pd(Pc)/métal

Guillermet, Olivier 24 October 2006 (has links) (PDF)
Nous avons étudié la croissance de films organiques de pérylène tetracarboxylique diimide (PTCDI) et de phthalocyanine de palladium (Pd(Pc)) sur les surfaces métalliques Pt(001), Pt(111) et Au(001). Une étude de l'hétérostructure Au/PTCDI/Pd(Pc)/Au ayant précédemment conclu à un effet redresseur, nous nous sommes plus particulièrement intéressés à la réalisation de cette hétérostructure pour des épaisseurs nanométriques par dépôt en phase vapeur sous ultravide, ainsi qu'à sa caractérisation par différentes techniques d'analyse des surfaces (AES, LEED, REELS, UHV-STM et STS). Il était important de réaliser des couches organiques ordonnées afin d'optimiser le transport de charges dans ces couches.<br /> A l'aide des cinétiques de dépôt réalisées par spectroscopie d'électrons Auger (AES) et de la microscopie à effet tunnel (STM), nous avons identifié les modes de croissance des deux types de molécule en films minces. Nous montrons que PTCDI et Pd(Pc), déposés sur un substrat de platine (Pt(111) et Pt(001)) à différentes températures, croissent suivant le mode Stransky-Krastanov : après la formation d'une première couche désordonnée, les molécules se regroupent dans des îlots cristallins. Les propriétés électroniques de films moléculaires de différentes épaisseurs déposés sur Pt(001) ont pu être déduites par spectroscopie de pertes d'énergie d'électrons lents en mode réflexion (REELS) montrant une lente ouverture du gap. Nous observons la formation de monocouches désordonnées en raison d'une forte interaction molécule-platine comparativement à l'interaction molécule-molécule. Ce résultat étant en opposition avec notre critère initial d'obtention de couches ultraminces ordonnées, nous nous sommes donc intéressés au substrat Au(001). Dans ce cas, il a été démontré que les couches déposées donnent généralement des surstructures organisées.<br />Nous avons utilisés les vitesses de dépôt précédemment déterminées dans le cadre des dépôt sur platine afin d'étudier par AES et STM les monocouches de PTCDI et Pd(Pc) sur la face (001) de l'or. La monocouche de Pd(Pc) déposée à température ambiante s'ordonne en fonction de la quantité adsorbée en une maille carrée ou rectangulaire, orientée suivant les directions <110> et < 10> du substrat. Le film de PTCDI forme une maille rectangulaire dont les paramètres sont proches de ceux obtenus par diffraction des rayons X sur des monocristaux de PTCDI.<br /> Finalement, le dépôt d'une fraction de monocouche de PTCDI sur la surstructure carrée de Pd(Pc) adsorbée sur Au(001) conduit à la formation d'une maille de PTCDI commensurable avec la maille de Pd(Pc). Les courbes I-V obtenues par STS pour le système W / PTCDI / Pd(Pc) / Au(100) sont semblables à une caractéristique de diode (coefficient redresseur compris entre 13 et 24), mais l'origine de cet effet reste pour le moment à déterminer.
6

Vůz pro transport odlitků / Transport truck for castings

Krbeček, Petr January 2015 (has links)
The diploma thesis deals with the construction design of rail mounted transfer cars. The first of the designed cars is equipped with the electrical drive and the second is non-driven and must be towed or pushed. This thesis contains description of main components of the transfer cars and their implementation. The next section deals with original construction design of the transfer cars. The thesis includes functional calculation of travel wheels, the design and check of the travel unit and the strength calculation of the connecting pin. Conclusion of the thesis deals with the strength analysis of the transfer car frame using the finite element method. The required technical drawings are attached to the thesis.
7

Abstract Numeration Systems: Recognizability, Decidability, Multidimensional S-Automatic Words, and Real Numbers

Charlier, Emilie 07 December 2009 (has links)
In this doctoral dissertation, we studied and solved several questions regarding positional and abstract numeration systems. Each particular problem is the focus of a chapter. The first problem concerns the study of the preservation of recognizability under multiplication by a constant in abstract numeration systems built on polynomial regular languages. We obtained several results generalizing those from P. Lecomte and M. Rigo. The second problem we considered is a decidability problem, which was already studied, most notably, by J. Honkala and A. Muchnik. For our part, we studied this problem for two new cases: the linear positional numeration systems and the abstract numeration systems. Next, we focused on the extension to the multidimensional setting of a result of A. Maes and M.~Rigo regarding S-automatic infinite words. We obtained a characterization of multidimensional S-automatic words in terms of multidimensional (non-necessarily uniform) morphisms. This result can be viewed as the analogous of O. Salon's extension of a theorem of A. Cobham. Finally, generalizing results of P. Lecomte and M. Rigo, we proposed a formalism to represent real numbers in the general framework of abstract numeration systems built on languages that are not necessarily regular. This formalism encompasses in particular the rational base numeration systems, which have been recently introduced by S. Akiyama, Ch. Frougny, and J. Sakarovitch. Finally, we ended with a list of open questions in the continuation of this work./Dans cette dissertation, nous étudions et résolvons plusieurs questions autour des systèmes de numération abstraits. Chaque problème étudié fait l'objet d'un chapitre. Le premier concerne l'étude de la conservation de la reconnaissabilité par la multiplication par une constante dans des systèmes de numération abstraits construits sur des langages réguliers polynomiaux. Nous avons obtenus plusieurs résultats intéressants généralisant ceux de P. Lecomte et M. Rigo. Le deuxième problème auquel je me suis intéressée est un problème de décidabilité déjà étudié notamment par J. Honkala et A. Muchnik et ici décliné en deux nouvelles versions : les systèmes de numération de position linéaires et les systèmes de numération abstraits. Ensuite, nous nous penchons sur l'extension au cas multidimensionnel d'un résultat d'A. Maes et de M. Rigo à propos des mots infinis S-automatiques. Nous avons obtenu une caractérisation des mots S-automatiques multidimensionnels en termes de morphismes multidimensionnels (non nécessairement uniformes). Ce résultat peut être vu comme un analogue de l'extension obtenue par O. Salon d'un théorème de A. Cobham. Finalement, nous proposons un formalisme de la représentation des nombres réels dans le cadre général des systèmes de numération abstraits basés sur des langages qui ne sont pas nécessairement réguliers. Ce formalisme englobe notamment le cas des numérations en bases rationnelles introduits récemment par S. Akiyama, Ch. Frougny et J. Sakarovitch. Nous terminons par une liste de questions ouvertes dans la continuité de ce travail.

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