Dissertations / Theses on the topic 'Cycle binaire'

Introduction. Comptage des mots circulaires de longueur n. Recherche d'une fonction de comptage. Généralisation du problème aux cycles. Définitions et propriétés des suites binaires périodiques de période 2 h. Cycles antisymétriques. Etude de la loi croisée du couple (i. J. ) Lorsque le nombre d'itérations est supérieur à 1.

L'approche théorique de systèmes modèles a permis de mettre en évidence (1) le caractère d'ultrasensitibilité d'ordre zéro, dans un cycle fermé dont les deux enzymes ont un comportement michaélien, (2) des comportements bistables réversibles (hystérésis) et irréversibles (transitions), lorsque l'une des deux enzymes d'inter conversion est soumise à un facteur déstabilisant (inhibition par le substrat). L'étude a été généralisée à ces mêmes cycles, ouverts aux transferts de masses (diffusion, convection). Les études expérimentales effectuées sur des cycles binaires fermés ont permis de vérifier l'existence de l'ultrasensitibilité d'ordre zéro (NAD+/NADH avec la formate et la lactate déshydrogénase d'une part) et de transitions irréversibles (ATP/ADP, avec la phosphofructokinase et la pyruvate kinase, d'autre part)<br>A theoretical approach to model systems showed (1) zero-order ultra sensitivity in a closed system, in which both enzymes exhibited Michaelis-Menten behaviours, and (2) reversible (hysteresis) and irreversible (transitional) bistability when one of the two interconverting enzymes was subjected to a destabilizing factor, such as substrate inhibition. The study was extended to the same cycles when opened to mass transfer by diffusion and/or convection. Experimental studies carried out on closed binary cycles demonstrated on the one hand, the occurrence of zero-order uItrasensitivity (NAD+/NADH, with the enzymes formate and Iactate deshydrogenases) and, on the other hand, irreversible transitions (ATP / ADP, with the enzymes phosphofructokinase and pyruvate kinase)

On a testé l'aptitude de molécules organiques variées à s'insérer dans les composés d'intercalation binaires graphite-alcalin. Le furanne est capable de ternariser pratiquement tous les G/M (M = K, Rb, Cs) donnant par exemple KFU 0,75C8 et KFU2,2Cn (n = 24, 36, 48, 72). On a fait une étude critique de ce processus de ternarisation : cinétique, stoechiométrie limite, changements de stade, cycles intercalation-vidage, mobilité de la molécule organique. Le processus n'est pas entièrement réversible, accompagné de réactions chimiques plus complexes que la simple solvatation de l'alcalin. Le rôle du transfert de charge entre l'alcalin, les plans graphitiques et la molécule organique est analysé<br>The possibility of ternarization of binary alkali metal-graphite intercalation compounds by numerous organic molecules was studied. Furan (Fu) will combine with practically all the M-GIC (M = K, Rb, Cs), thus yielding for instance, KFu0 ,75C8 or KFU2 ,2cn (n = 24, 36, 48, 72). Critical studies of the kinetics of ternarization, stoechiometries, stage of the ternary compounds and of the intercalation -desintercalation process were perfomed. This process is not fully reversible because of chemical reactions more complex than mere solvation of alkali metal. The role of charge transfer between the organic molecule and the other components is analysed

Ce travail est une contribution à l'étude de la dynamique de cycles de substrats, un trait d'union entre l'empirisme et la théorie. Les modèles proposés représentent ou prédisent les faits expérimentaux mais dans un langage non empirique. Le choix des modèles expérimentaux tient compte de cette démarche. Dans une première partie, nous avons fait une approche théorique et expérimentale des systèmes cycliques binaires simples. Le système modèle comporte deux enzymes ayant une cinétique Michaelienne et le phénomène à mettre en évidence est l'amplification. Dans la deuxième partie, nous avons couplé un cycle binaire comportant une non-linéarité avec un transfert de masse. Une des deux enzymes présente une cinétique avec inhibition par excès de substrat. Nous avons mis en évidence l'existence d'états stationnaires multiples présentant des phénomènes de bistabilité ou de transitions irréversibles. Dans la troisième partie, nous avons étudié notre deuxième modèle selon la théorie du contrôle métabolique. Notre but n'était pas de trouver des comportements nouveaux, sinon de faire par une méthode l'étude d'un cycle de substrats. Dans ce cas, l'évolution des coefficients de contrôle est comparée à l'évolution des différents états stationnaires.

The present work addresses the thermodynamic optimization of small binary-cycle geothermal power plants. The optimization process and entropy generation minimization analysis were performed to minimize the overall exergy loss of the power plant, and the irreversibilities associated with heat transfer and fluid friction caused by the system components. The effect of the geothermal resource temperature to impact on the cycle power output was studied, and it was found that the maximum cycle power output increases exponentially with the geothermal resource temperature. In addition, an optimal turbine inlet temperature was determined, and observed to increase almost linearly with the increase in the geothermal heat source. Furthermore, a coaxial geothermal heat exchanger was modeled and sized for minimum pumping power and maximum extracted heat energy. The geofluid circulation flow rate was also optimized, subject to a nearly linear increase in geothermal gradient. In both limits of the fully turbulent and laminar fully-developed flows, a nearly identical diameter ratio of the coaxial pipes was determined irrespective of the flow regime, whereas the optimal geofluid mass flow rate increased exponentially with the Reynolds number. SeveORCs were observed to yield maximum cycle power output. The addition of an IHE and/or an Oral organic Rankine Cycles were also considered as part of the study. The basic types of the FOH improved significantly the effectiveness of the conversion of the available geothermal energy into useful work, and increased the thermal efficiency of the geothermal power plant. Therefore, the regenerative ORCs were preferred for high-grade geothermal heat. In addition, a performance analysis of several organic fluids was conducted under saturation temperature and subcritical pressure operating conditions of the turbine. Organic fluids with higher boiling point temperature, such as n-pentane, were recommended for the basic type of ORCs, whereas those with lower vapour specific heat capacity, such as butane, were more suitable for the regenerative ORCs.<br>Dissertation (MEng)--University of Pretoria, 2013.<br>Mechanical and Aeronautical Engineering<br>unrestricted

La dégradation du béton associée à l’exposition en ambiance hivernale rigoureuse est une problématique connue en Amérique du Nord en raison de la sévérité du climat en période hivernale. Un des types de dégradation, la fissuration interne, se manifeste par l'apparition d'une intense microfissuration du béton en surface, mais aussi à l'intérieur de la masse. Celle-ci peut conduire à une perte de cohésion du matériau, réduisant ses caractéristiques mécaniques et sa perméabilité. Dans un souci de développement durable et de recherche performancielle, des liants ternaires, comprenant des ajouts minéraux autre que la fumée de silice ont été développés. Les études scientifiques portant sur l’influence du facteur d’espacement à ce type de dégradation sont peu nombreuses, voire inexistantes. Il est par conséquent important de vérifier si les spécifications actuelles permettent d’assurer la confection d’un matériau durable au gel. Dans ce mémoire, nous avons étudié l’influence du facteur d’espacement, du paramètre E/L, de l’influence du type de superplastifiant et d’un granulat marginal sur la résistance à la fissuration interne des bétons en utilisant l’essai accéléré normalisé ASTM C666, procédure A lors de l’utilisation de liants ternaires. Une grande partie de cette recherche a porté sur l’étude de la relation entre le facteur d’espacement et la tenue aux cycles gel-dégel des bétons. Le projet s’est divisé en 4 phases, la première a permis de déterminer un intervalle contenant le facteur d’espacement critique pour chacun des liants étudiés. Il est ainsi établi qu’il est nécessaire d’avoir un facteur d’espacement inférieur à 340 µm pour assurer la durabilité des bétons V-S formulés à partir de liants ternaires. La deuxième phase a montré que le type de superplastifiant n’influe pas sur le facteur d’espacement critique, mais change les caractéristiques du réseau d’air à l’état frais. La troisième phase a porté sur l’analyse de l’influence d’une variation du rapport E/L sur la durabilité au gel-dégel. Il en résulte qu’une variation dans les limites permises n’a pas d’incidence sur le facteur d’espacement critique tant que les hypothèses restent dans l’intervalle prescrit par le tome VII de la norme 3101. La dernière et quatrième phase a permis de montrer que le granulat marginal sélectionné n’a pas d’incidence particulière sur la résistance au gel-dégel en fissuration interne.

Les séquences binaires pseudo-aléatoires sont couramment employées par les systèmes de transmissions numériques ou des mécanismes de chiffrement. On les retrouve en particulier dans les transmissions par étalement de spectre par séquence direct (e.g. 3G ou GPS)) ou pour construire des séquences d'apprentissage pour faciliter la synchronisation ou l'estimation du canal (e.g. LTE). Un point commun à toutes ces applications est la nécessité de se synchroniser avec la séquence émise. La méthode conventionnelle consiste à générer la même séquence au niveau du récepteur et la corréler avec le signal reçu. Si le résultat dépasse un seuil pré-défini, la synchronisation est déclarée acquise. On parle alors de détection par corrélation.Cette thèse aborde une autre voie : la détection des séquences binaires pseudo-aléatoire par des techniques de décodage canal. Ceci permet par exemple de détecter des séquences longues (e.g. de période 242), contrairement aux techniques par corrélation qui sont trop complexes à implémenter. Cela nécessite néanmoins que le récepteur connaisse au préalable le polynôme générateur de la séquence.Nous avons montré que le décodage d'une séquence pseudo-aléatoire est une problématique du type 'détecte et décode'. Le récepteur détecte la présence de la séquence et simultanément estime son état initial. Ceci correspond dans la théorie classique de la détection à un détecteur de type GLRT qui ne connaît pas la séquence émise, mais qui connaît sa méthode de construction. L'algorithme implémente alors un GLRT qui utilise un décodeur pour estimer la séquence reçue. Ce dernier est implémenté avec un algorithme de décodage par passage de messages qui utilise une matrice de parité particulière. Elle est construite avec des équations de parités différentes, chacune ayant un poids de Hamming valant t.Il correspond au nombre de variables participants à l'équation.Les équations de parité sont un constituant indispensable du décodeur. Nous avons donné leur nombre pour les m-séquences et les séquences de Gold. Pour le cas particulier des séquences de Gold, nous avons calculé le nombre d'équations de parité de poids t=5 lorsque le degré du polynôme générateur r est impair. Ce calcul est important car il n'y a pas d'équations de parité de poids t &lt; 5 lorsque r est impair. Le nombre d'équations de parité est aussi utilisé pour estimer le degré minimal des équations d'un poids t donné. Nous avons montré que le modèle de prédiction estime correctement la valeur moyenne du degré minimal de l'ensemble des séquences de Gold. Nous avons néanmoins mis en évidence une grande variabilité du degré minimal des séquences autour de cette valeur moyenne.Nous avons ensuite identifié les ensembles absorbants complets de plus petite taille lorsque le décodeur emploie plusieurs polynômes de parité. Ces ensembles bloquent la convergence du décodeur lorsque celui-ci est alimenté avec du bruit. Ceci évite les fausses alarmes lors du processus de détection. Nous avons montré que des cycles 'transverses' détruisent ces ensembles absorbants, ce qui génère des fausses alarmes. Nous en avons déduit un algorithme qui minimise le nombre de cycles transverses de longueur 6 et 8, ce qui minimise la probabilité de fausse alarme lorsque le poids des équations de parité vaut t=3. Notre algorithme permet de sélectionner les équations de parité qui minimisent la probabilité de fausse alarme et ainsi réduire notablement le temps d'acquisition d'une séquence de Gold.Nous avons enfin proposé deux algorithmes de détection du code d'embrouillage pour les systèmes WCDMA et CDMA2000. Ils exploitent les propriétés des m-séquences constituant les séquences de Gold, ainsi que les mécanismes de décodage par passage de messages. Ces algorithmes montrent les vulnérabilités des transmissions par étalement de spectre<br>Pseudo-random binary sequences are very common in wireless transmission systems and ciphering mechanisms. More specifically, they are used in direct sequence spread spectrum transmission systems like UMTS or GPS, or to construct preamble sequences for synchronization and channel estimation purpose like in LTE. It is always required to synchronize the receiver with the transmitted sequence. The usual way consists in correlating the received signal with a replica of the sequence. If the correlation exceeds a predefined threshold, the synchronization is declared valid.This thesis addresses a different approach: the binary sequence is detected with a forward error correction decoding algorithm. This allows for instance to detect very long sequences.In this thesis, we show that decoding a pseudo-random sequence is a problematic of the kind ‘detect and decode'. The decoder detects the presence of the transmitted sequence and simultaneously estimates its initial state. In conventional detection theory, this corresponds to a GLRT detector that uses a decoder to estimate the unknown parameter which is the transmitted sequence. For pseudo-random sequences, the decoder implements an iterative message-passing algorithm. It uses a parity check matrix to define the decoding graph on which the algorithm applies. Each parity check equation has a weight t, corresponding to the number of variables in the equation.Parity check equations are thus an essential component of the decoder. The decoding procedure is known to be sensitive to the weight t of the parity check equations. For m-sequences, the number of parity check equations is already known. It is given by the number of codewords of weight t of the corresponding Hamming dual code. For Gold sequences, the number of parity check equations of weight t = 3 and 4 has already been evaluated by Kasami. In this thesis we provide an analytical expression for the number of parity check equations of weight t = 5 when the degree of the generator polynomial r is odd. Knowing this number is important because there is no parity check equation of weight t &lt; 5 when r is odd. This enumeration is also used to provide an estimation of the least degree of parity check equations of weight t.We have then addressed the problem of selecting the parity check equations used by the decoder. We observed the probability of false alarm is very sensitive to this selection. It is explained by the presence or absence of absorbing sets which block the convergence of the decoder when it is fed only with noise. These sets are known to be responsible for error floor of LDPC codes. We give a method to identify these sets according to the parity check equations used by the decoder. The probability of false alarm can increase dramatically if these absorbing sets are destroyed. Then we propose an algorithm for selecting these parity check equations. It relies on the minimization of the number of cycles of length 6 and 8. Simulation show that the algorithm allows to improve significantly the probability of false alarm and the average acquisition time.Eventually, we propose 2 algorithms for the detection of the scrambling codes used in the uplink of UMTS-FDD and CDMA2000 systems. They highlights a new vulnerability of DSSS transmission systems. It is now conceivable to detect these transmission if the sequence's generator is known

Les cycles d’hysteresis des binaires X lors de leurs sursauts restent inexpliqués a ce jour. Dans ce travail, nous avons développé les idées du paradigme propose par Ferreira et al. (2006), ou la matière dans le disque accrète de deux manières différentes. Dans le mode standard (SAD, Shakura et Sunyaev 1973), le couple turbulent transporte le moment cinétique radialement vers l’extérieur du disque. Dans le mode éjectant (JED, Ferreira et Pelletier 1995), le disque magnetise produit des jets qui emporte la matière, l’énergie et le moment angulaire verticalement. Dans ce cadre, la transition entre les deux modes est liée a la distribution de champ magnétique dans le disque, une inconnue. Pendant cette thèse, j’ai développé un code capable de résoudre a chaque rayon dans un disque l’équilibre thermique a deux températures pour de multiples jeu de paramètres. Ce code utilise Belm (Belmont et al. 2008 ; Belmont 2009) pour traiter le refroidissement radiatif et créer les spectres de manière auto-cohérente. Les processus de chauffage sont analytiques, ainsi que les processus d’advection, qui sont calcules de l’interieur vers l’exterieur.Grace a ce code, nous avons pu montrer que des solutions de JED reproduisaient très bien les états hard jusqu’à 0.5 luminosités d’Eddington (Marcel et al. 2018a). Il a aussi été démontré que le JED subit un cycle d’hysteresis. En revanche, la luminosité de ce cycle est bien trop faible et la présence inévitable de jets dans la configuration nous pousse a l’utilisation d’un SAD pour la reproduction d’états soft.Fort de ces résultats, j’ai adapte le code a la résolution de configuration de disque hybride, compose d’un JED interne et d’un SAD externe, séparé en un rayon de transition rJ. En jouant sur ce paramètre rJ et sur le taux d’accrétion mdot, nous avons pu montrer que les observations X de cycles typiques pouvaient être pavée. Après des calculs similaires a Heinz et Sunyaev (2003), nous pouvons estimer quel est le flux radio associe a chaque jeu de paramètres. Cela nous a permis de montrer 2 choses. (1) tous les flux radios sont reproductibles a l’aide d’un seul facteur de normalisation commun. (2) le flux radio et la forme du spectre en rayons X sont cohérents : les jeux de paramètres qui reproduisent le mieux chaque forme spectral sont associes aux bon flux radios. Afin d’illustrer ce résultat, 5 états canoniques de l’évolution de GX 339-4 ont ete reproduits : forme spectrale en X et flux radios (Marcel et al. 2018b). Pour finir, en utilisant une simple procédure d’ajustement sur la forme spectrale en X, le cycle de 2010-2011 de GX 339-4 a pu être reproduit. De manière bluffante, les évolutions de rJ et mdot semblent être en accord avec les prédictions théoriques (Esin et al. 1997). De plus, les estimations de flux radio étant cohérentes avec les observations, nous avons décidé de les ajouter directement dans la procédure d’ajustement. L’ajout de cette composante a permis une excellente reproduction simultanée de la radio et des spectres X de manière. C’est, a notre connaissance, la première fois que les phénomènes d’accrétion et d’éjection sont utilisés simultanément. Ces résultats, ainsi que les discussions et implications seront bientôt soumis<br>The hysteresis behavior of X-ray binaries during their outbursts remains a mystery. In this work, we developed the paradigm proposed in Ferreira et al. (2006) where the disk material accretes in two possible, mutually exclusive, ways. In the standard accretion disk (SAD, Shakura et Sunyaev 1973) mode, the dominant local torque is due to MHD turbulence that transports radially the disk angular momentum. In the jet-emitting disk (JED, Ferreira et Pelletier 1995) mode, magnetically-driven jets carry away mass, energy and all the angular momentum from the disk. Within our framework, the transition from one mode to another is related to the magnetic field distribution, an unknown yet.In this thesis, I have developped a two-temperature plasma code able to compute the thermal balance at each radius for a large ensemble of disk parameters, as well as the self- consistent global emitted spectrum. The radiative cooling term and related spectrum (comptonized bremsstrahlung and synchrotron emission) are obtained using the Belm code (Belmont et al. 2008 ; Belmont 2009). Heating processes are analytical and due only to accretion, while advection is properly taken into account, carrying outside-in the memory of the outer thermal states.Using this code, we have shown that a JED extending along the entire disk nicely repro- duces hard states up to 0.5 Eddington luminosities (Marcel et al. 2018a). It was also shown that JEDs produce a natural hysteresis cycle. However, the global luminosity of the cycle is insufficient and the inevitable presence of jets in JEDs advocates for an inner SAD configuration in soft states.Based on these results, the code was enhanced to solve hybrid configurations with an internal JED and an external SAD, separated by a given transition radius rJ. Playing on both rJ and the accretion rate mdot, we have shown that X-ray observations of typical cycles can be completely covered. Using a simple synchrotron model similar to that of Heinz et Sunyaev (2003), the radio flux produced by the jets can be estimated, showing two important features. First, all radio observations can be covered by our model. Second, the radio flux and X- ray spectral coverages are consistents : parameter sets that reproduce best each spectral state also account for a consistent associated radio flux. For illustration, 5 canonical states from GX 339-4 have been reproduced in X-ray spectral shape and associated radio fluxes (Marcel et al. 2018b).Finaly, using a simple fitting procedure on X-ray spectral shape, the 2010-2011 cycle from GX 339-4 has been reproduced. Strikingly, the co-evolution of rJ and mdot seems to be in adequacy with initial theoretical expectations (Esin et al. 1997). Moreover, the estimated radio flux evolution being close to observations, we decided to use those within the fitting procedure. Adding radio fluxes constraints in the procedure allowed us to reproduce both the associated X-ray spectral shape and radio fluxes with excellent agreement. This is, to our knowledge, the first time that such an accretion-ejection cycle is reproduced. Those results, as well as discussions and implications will be soon submitted

Das Verständnis magnetisch verursachter Aktivität auf Sternen sowie der zugrundeliegenden Dynamoprozesse ist von fundamentaler Bedeutung für das Verständnis von Entstehung und Entwicklung von Sternen sowie des Lebens im Universum. Sichtbare Erscheinungen dieser stellaren Aktivität sind u.a. Sternflecken, welche als Indikatoren des zugrundeliegenden Magnetfeldes dienen. Solche Flecken können auf anderen Sternen als der Sonne nicht direkt beobachtet werden, zumal mit den heutigen technischen Mitteln eine Auflösung der Oberfläche selbst der benachbarten Sterne unmöglich ist. Eine indirekte Rekonstruktionsmethode namens 'Doppler Imaging' erlaubt es jedoch, auf die Temperaturverteilung auf der Sternoberfläche zu schließen. Für diese Arbeit wurden elf Jahre kontinuierlicher spektroskopischer Beobachtungen des aktiven Doppelsterns EI Eridani herangezogen, um insgesamt 34 Dopplerkarten zu erstellen. In der Folge wird versucht, eine Grundlage zu schaffen für die Analyse des zweidimensionalen Informationsgehalts dieser Karten. Drei Oberflächenkartenparameter werden vorgeschlagen: gemittelte Temperatur, getrennt für verschiedenen stellare Breitenbänder; relative Fleckenhäufigkeit; und, zum Zwecke der Auswertung der strukturellen Temperaturverteilung, Längen- und Breiten-Ortsfunktion der Sternfleckenhäufung. Die resultierenden Werte zeigen deutlich, daß kein zeitlicher Zusammenhang mit dem photometrischen Aktivitätszyklus besteht. Die Morphologie der Fleckenverteilung bleibt während des kompletten Beobachtungszeitraums im wesentlichen konstant. Im Gegensatz zur Sonne gibt es also, im beobachteten Zeitraum und innerhalb der bestehenden Genauigkeit, keinen Fleckenzyklus auf dem aktiven Stern EI Eri. Darüberhinaus wurde eine ausführliche Studie der stellaren Parameter von EI Eri und eine vorläufige Abschätzung der differentiellen Rotation auf EI Eri durchgeführt, die eine anti-solare Ausrichtung aufzuweisen scheint, d.h. der Pol rotiert schneller als der Äquator.<br>Understanding stars, their magnetic activity phenomena and the underlying dynamo action is the foundation for understanding 'life, the universe and everything' - as stellar magnetic fields play a fundamental role for star and planet formation and for the terrestrial atmosphere and climate. Starspots are the fingerprints of magnetic field lines and thereby the most important sign of activity in a star's photosphere. However, they cannot be observed directly, as it is not (yet) possible to spacially resolve the surfaces of even the nearest neighbouring stars. Therefore, an indirect approach called 'Doppler imaging' is applied, which allows to reconstruct the surface spot distribution on rapidly rotating, active stars. In this work, data from 11 years of continuous spectroscopic observations of the active binary star EI Eridani are reduced and analysed. 34 Doppler maps are obtained and the problem of how to parameterise the information content of Doppler maps is discussed. Three approaches for parameter extraction are introduced and applied to all maps: average temperature, separated for several latitude bands; fractional spottedness; and, for the analysis of structural temperature distribution, longitudinal and latitudinal spot-occurrence functions. The resulting values do not show a distinct correlation with the proposed activity cycle as seen from photometric long-term observations, thereby suggesting that the photometric activity cycle is not accompanied by a spot cycle as seen on the Sun. The general morphology of the spot pattern on EI Eri remains persistent for the whole period of 11 years. In addition, a detailed parameter study is performed. Improved orbital parameters suggest that EI Eri might be complemented by a third star in a wide orbit of about 19 years. Preliminary differential rotation measurements are carried out, indicating an anti-solar orientation.

Thesis (M.S.) -- University of Maryland, College Park, 2009.<br>Thesis research directed by: Reliability Engineering Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Dans cette thèse, nous abordons tout d'abord le problème de reconnaissance de codes. Il consiste à retrouver la structure d'un code correcteur d'erreurs utilisé lors d'une transmission de données seulement à partir de la séquence bruitée interceptée. Nous donnons ici des méthodes efficaces pour la reconnaissance d'un code connu, pour la reconstruction de codes appartenant à une famille tels que les codes cycliques et pour la détection des paramètres de codes convolutifs. Ensuite, nous étudions la structure des codes quasi-cycliques parallèlement aux résultats connus pour les codes cycliques. Nous donnons une construction d'une sous-famille de codes quasi-cycliques annulés par un polynôme à coefficients matriciels. Cette construction permet de trouver des codes ayant de bonnes distances minimales. Finalement, nous nous intéressons aux permutations laissant invariante la quasi-cyclicité d'un code<br>In this thesis, we first deal with the problem of recognition of codes. It consists in recovering the structure of an error-correcting code used during a data transmission only from the noisy intercepted sequence. We give efficient methods for the recognition of a known code, for the reconstruction of codes belonging to a family like cyclic codes and for the detection of parameters of convolutional codes. Then, we study the structure of quasi-cyclic codes in parallel of the results known for cyclic codes. We give a construction of a sub-family of quasi-cyclic codes cancelled by a polynomial with matricial coefficients. Some of these codes reach large minimum distances. Finally, we deal with permutations keeping the quasi-cyclicity of a code

Ce travail contribue aux efforts de l'Union Européenne pour réduire les émissions de CO2. Son objectif est d'aider les industries produisant de la chaleur fatale à récupérer cette énergie perdue, d'augmenter sa température et de la réutiliser in situ. Les transformateurs de chaleur (Absorption Heat Transformers ou AHT), machines à absorption consommant très peu d'électricité, sont alors ici étudiés. Les AHTs existants rencontrent des problèmes comme la corrosion, la cristallisation, la toxicité et les niveaux de pression éloignés de la pression atmosphérique. Ceux-ci sont causés par les fluides conventionnels (Eau/LiBr et Ammoniaque/Eau) et s'aggravent à des températures supérieures à 120°C. Des modèles de conception ainsi que des solutions techniques, applicables avec tous mélanges de fluides organiques, sont alors proposés dans cette thèse. Ces modèles sont validés avec des données de la littérature et implémentés dans des outils d'aide à la décision.Tout d'abord, un modèle de sélection de paires de fluides organiques (parmi une liste de fluides) est développé. Les contraintes prises en compte sont, entre autres, les types et les profils de températures des sources et puits de chaleur, et les propriétés du fluide. Pour chaque type de fluide, la méthode la plus adaptée au calcul des propriétés physiques des fluides est choisie.En second lieu, pour effectuer la séparation des 2 constituants du mélange de fluides organiques, le générateur (composant recevant la chaleur fatale) et le condenseur de l'AHT sont fusionnés pour former une colonne de distillation. Un modèle d'une colonne de distillation nommée « hybride » est alors développé en adaptant la méthode de Ponchon-Savarit et en la combinant avec la méthode ETD (Equal Thermodynamic Distance). Cette colonne associe les avantages des 2 types de colonnes adiabatiques et diabatiques. Elle allie réduction de production d'entropie et meilleure exploitation des sources de chaleur à températures glissantes. La conception mécanique de la colonne hybride est aussi incluse.Troisièmement, pour atteindre la température théorique maximale du mélange de fluide déjà choisi, l'absorbeur de l'AHT (où la chaleur à haute température est libérée) est divisé en sections adiabatiques suivies par des sections diabatiques. De plus, les modèles détaillés des colonnes à bulles (fonctionnant en co-courant ou en contre-courant) ainsi que de la colonne à garnissage sont présentés et comparés entre eux.Les principaux résultats de ces travaux consistent en une nouvelle méthodologie de choix de fluides organiques pouvant remplacer les mélanges classiques surtout à températures élevées (supérieures à 130 °C). En ce qui concerne la colonne de distillation, il est montré que la colonne adiabatique constitue un meilleur choix lorsqu'une source de chaleur latente est disponible tandis qu'avec une source de chaleur sensible, la colonne hybride engendre moins de pertes exergétiques. En passant à l'absorbeur, le nouveau mode d'opération de celui-ci permet à l'utilisateur d'atteindre des températures plus élevées que celles réalisées avec les technologies actuellement disponibles. Enfin, les modèles développés permettent de choisir les technologies de distillation (adiabatique, diabatique ou hybride) et d'absorption (colonne à bulles ou à garnissage) les plus appropriées en s'adaptant à différentes problématiques industrielles<br>This work is part of the European union efforts to reduce its CO2 emissions. It aims to assist any waste heat producing industry in recuperating this lost thermal energy, pumping it to higher temperature levels and reusing it on site. Absorption Heat Transformers (AHT), that consume little electricity, are used for this task. Current AHT problems such as corrosion, crystallization, toxicity and inconvenient pressure levels are caused by conventionally used H2O/LiBr and NH3/ H2O working fluids and get worse at temperatures exceeding 120°C. Potential solutions are thus suggested. According to them, models are developed; they are all able to operate with any organic mixture and are customized to accompany the industrialist from start to finish. These solutions were validated by comparing them with literature data and are implemented into several tools.Firstly, a model selects the optimal organic binary mixture -among a list of fluids- in terms of the real case application's constraints: Heat transfer fluids used, Heat source's and heat sink's types and temperature profiles, mixtures transport properties among other parameters. Suitable thermodynamic model is selected for different fluid group types.Secondly, in order to separate the 2 components of the chosen mixture of organic compounds, the AHT generator (component which receives waste heat) is merged with the AHT condenser thus forming a distillation column. A “hybrid column” is designed by modifying the Ponchon-Savarit method and combining it with the Equal Thermodynamic Distance (ETD) method. This new column associates the best features of the two columns. It reduces entropy production rates and best exploits temperature gliding heat sources. Mechanical design for the hybrid column is also included.Thirdly, to ensure that the maximum theoretical temperature of the working fluid is reached, the AHT absorber (where high temperature heat is released) is divided into consecutive adiabatic parts followed by diabatic ones. Detailed Models for co-current and counter-current bubble columns as well as packing columns are presented and compared.Main results consist in a selection methodology of organic compounds mixtures, capable of replacing conventional ones specially at temperatures higher than 130 °C. It's also shown that adiabatic columns are better options when latent type heat sources are available while hybrid columns lose less exergy when used with sensible heat sources. As for the absorber, the new operating mode provides the user with higher temperatures than currently reached by available technologies. Finally, using the developed models, tailored and most suitable distillation (adiabatic, diabatic or hybrid columns) and absorber (bubble or packing columns) technologies can be proposed depending on the industrial specific cases and requirements

Submitted by Arthur Moreira Saude (arthur-moreira@hotmail.com) on 2017-04-27T16:03:53Z No. of bitstreams: 1 Dissertacao Final.pdf: 947767 bytes, checksum: ca50219ab757930a6d88422c06d48234 (MD5)<br>Approved for entry into archive by GILSON ROCHA MIRANDA (gilson.miranda@fgv.br) on 2017-04-28T19:14:36Z (GMT) No. of bitstreams: 1 Dissertacao Final.pdf: 947767 bytes, checksum: ca50219ab757930a6d88422c06d48234 (MD5)<br>Made available in DSpace on 2017-05-02T19:31:50Z (GMT). No. of bitstreams: 1 Dissertacao Final.pdf: 947767 bytes, checksum: ca50219ab757930a6d88422c06d48234 (MD5) Previous issue date: 2017-03-31<br>This paper aims to create an econometric model capable of anticipating recessions in the United States economy, one year in advance, using not only monetary market variables that are already used by economists, but also capital market variables. Using a data span from 1959 to 2016, it was observed that the yield spread continues to be an explanatory variable with excellent predictive power over recessions. Evidence has also emerged of new variables that have very high statistical significance, and which offer valuable contributions to the regressions. Out-of-sample tests have been conducted which suggest that past recessions would have been predicted with substantially higher accuracy if the proposed Probit model had been used instead of the most widespread model in the economic literature. This accuracy is evident not only in the predictive quality, but also in the reduction of the number of false positives and false negatives in the regression, and in the robustness of the out-of-sample tests.<br>Este trabalho visa desenvolver um modelo econométrico capaz de antecipar, com um ano de antecedência, recessões na economia dos Estados Unidos, utilizando não só variáveis dos mercados monetários, que já são indicadores antecedentes bastante utilizados por economistas, mas também dos mercados de capitais. Utilizando-se dados de 1959 a 2016, pode-se observar que o spread de juros de longo e curto prazo continua sendo uma variável explicativa com excelente poder preditivo sobre recessões. Também surgiram evidências de novas variáveis que possuem altíssimas significâncias estatísticas, e que oferecem valiosas contribuições para as regressões. Foram conduzidos testes fora da amostra que sugerem que as recessões passadas teriam sido previstas com acurácia substancialmente superior, caso o modelo Probit proposto tivesse sido utilizado no lugar do modelo mais difundido na literatura econômica. Essa acurácia é evidente não só na qualidade preditiva, mas também na redução do número de falsos positivos e falsos negativos da regressão, e na robustez dos testes fora da amostra.

The theory of stellar evolution and stellar structure relies on the observation of stars in di erent phases of their evolutionary cycle. The relation between observations and theory can be strengthened by obtaining observational data of a large sample of stars in a particular evolutionary phase. The search for Cephei stars, as conducted in this study, can contribute to the sample of known Cephei stars, where these interesting stars are massive non-supergiant early B-type stars, displaying pulsating behaviour which is not well understood. Stars tend to form in clusters where it can therefore be expected that young massive stars can be found in open clusters. For this reason two young southern open clusters were observed in order to search for B-type pulsating stars. The region of NGC 6204 and Hogg 22 was observed over a period of thirteen nights in Johnson B, V and I bands. NGC 6204 is believed to be the oldest cluster of the two at a distance of 0.8 kpc while the much younger Hogg 22 is more distant at 2.8 kpc. These two open clusters are located 6 arcminutes apart which made it possible to observe them simultaneously with a 12.8 12.8 arcminute eld of view. The observations were done with the newly installed 1600 telescope of the North-West University, South Africa. In order to do a variability search, periodic stars need to be identi ed from the cluster data, where a typical data set may contain thousands of scienti c images. In addition to the main motivation for this study, a pipeline was created in order to automate the photometry and data reduction processes. A Lomb-Scargle transform was applied to the stellar light curves in order to identify periodic sources. 354 signi cantly periodic stars were identi ed from the 3182 observed stars. Amongst them, two new possible Cephei stars were found together with a possible slowly pulsating B star (SPB), and numerous eclipsing binary systems. By using photometry of this region obtained by Forbes & Short (1996), instrumental magnitudes were transformed to a standard system in order to compare photometry results. From the constructed colour magnitude diagram of the two clusters, it could be seen that some stars, indicated by Forbes & Short (1996) to be cluster members, were in fact eld stars belonging to neither cluster. The reduction and photometry pipeline was implemented successfully on the data set, which also highlighted the importance of instrumentation and correct data analysis procedures. Possible improvements were identi ed in order to overcome di culties experienced during this study.<br>Thesis (MSc (Space Physics))--North-West University, Potchefstroom Campus, 2013

碩士<br>國立臺灣大學<br>機械工程學研究所<br>87<br>The purpose of this dissertation is to improve the efficiency of a binary-cycle refrigeration system that combines a compression system with a heat driven ejector cooling system. This paper will introduce the theoretical analysis of the binary-cycle refrigeration system , reformulate the frame design of the binary hardware , estimate its performance , and draw conclusions from the real applications of the binary-cycle refrigeration system . This study advances the theory for the binary-cycle refrigeration system developed by the Jet Empirical Correlation . (According to the literature , the jet empirical correlation predicts the system entrainment ratio ω with an error range between -10﹪and +14﹪) The theoretical prediction and the experiment shows that the ejector cooling system can enhance COP by 10﹪or more (which is 2.6﹪more than 7.4﹪recorded in the literature) in comparison with the single-compressor system at the design point of the air condition system( =+5℃) and the ice-storage condition system( = - 5℃) . In addition , the experiment successfully increases the critical condensing temperature ( )of the ejector cooling system , making the integration of the ice-storage condition system possible . To put the binary-cycle refrigeration system - the ice-storage condition system into practice , this study investigates the possibility of operation in the binary-cycle ice-storage condition system in a new coil-type ice-storage tank . This new combination is tested in a real and unsteady environment to provide as a groundwork for future studies . This study has successfully applied the ejector technology to the binary-cycle refrigeration system , and makes a significant contribution to this field of studies .

In this thesis we consider two classes of binary matroids, even cycle matroids and even cut matroids. They are a generalization of graphic and cographic matroids respectively. We focus on two main problems for these classes of matroids. We first consider the Isomorphism Problem, that is the relation between two representations of the same matroid. A representation of an even cycle matroid is a pair formed by a graph together with a special set of edges of the graph. Such a pair is called a signed graph. A representation for an even cut matroid is a pair formed by a graph together with a special set of vertices of the graph. Such a pair is called a graft. We show that two signed graphs representing the same even cycle matroid relate to two grafts representing the same even cut matroid. We then present two classes of signed graphs and we solve the Isomorphism Problem for these two classes. We conjecture that any two representations of the same even cycle matroid are either in one of these two classes, or are related by a local modification of a known operation, or form a sporadic example. The second problem we consider is finding the excluded minors for these classes of matroids. A difficulty when looking for excluded minors for these classes arises from the fact that in general the matroids may have an arbitrarily large number of representations. We define degenerate even cycle and even cut matroids. We show that a 3-connected even cycle matroid containing a 3-connected non-degenerate minor has, up to a simple equivalence relation, at most twice as many representations as the minor. We strengthen this result for a particular class of non-degenerate even cycle matroids. We also prove analogous results for even cut matroids.

碩士<br>國立中正大學<br>通訊工程研究所<br>106<br>The low density parity check (LDPC) codes is a kind of error correction codes. The error correction performance of LDPC codes is close to Shannon limit. Thus, LDPC codes are widely applied to various communication systems. In general, these codes can be described by Tanner graph. Finding and removing cycles are essential, because the cycles are generally considered to affect the performance of LDPC codes in Tanner graph. To extend this study with Galois field, non-binary LDPC codes have better capability of error correction to against noise, especially for short code length. However, the computational complexity and memory requirement are relatively high in the decoding process and code construction. In this paper, we propose a cycle counting algorithm based on cycle check table with less complexity. Basically, the cycle check table records the connection of nodes in Tanner Graph. Each layer in the table contains three rows. The first row has the record of target node. The second row denotes the previous node of the node in the first row, and the third row has the indices of the position of the node in previous row. In cycle searching, there are two conditions needed to be satisfied within cycle check table. The fist condition is that there are two same nodes in the first row of Nth layer. The second condition is that the nodes in previous path of two nodes which satisfy the first condition are different. To evaluate the proposed scheme, the computational complexity of proposed algorithm is , and the memory requirement is , where m is the number of parity check equations, n is the code block length, wr and wc are the row weight and column weight, respectively, wmax is the maximum of wr and wc, and N is the half length of cycles. The proposed algorithm can perform 9.44 times faster than the conventional method while considering the LDPC codes with code length 3000 and girth (g) 6. Besides, we can find the length longer than 2g-2 which is the upper bound of some existing methods. Eventually, the proposed algorithm is applied to the construction of parallelized-decoding LDPC codes over Galois field to improve the capability of LDPC codes.

碩士<br>國立中山大學<br>資訊工程學系研究所<br>106<br>In this thesis, a 10-bit resolution analog-to-digital converter with 100MHz sampling frequency is proposed. In terms of design, in order to improve the conversion speed, the 2b/cycle conversion is adapted in the conversion of the upper bits. Since three comparators are required to perform the 2b/cycle conversion, it may cause the increase of the error probability. Therefore, the proposed architecture adapts the non-binary correction technique in the upper bits to tolerate fault error and hence correct the error. In the lower bit conversion, a 1b/cycle conversion is implmented to increase the accuracy. Moreover, the architecture also adopted the alternate technique in lower bit conversion to improve the conversion efficiency. This technique not only uses the comparators more efficiently, but also relaxing the issue of the longer comparison time in the lower bit conversions. At last, a redundant bit is added in the lower bits to increase the fault tolerance capability of the lower bits. This thesis implements a 10-bit analog-to-digital converter with 100MHz sampling frequency by using the TSMC 90nm process technology. For the static analysis, the DNL and INL are +1.248 / -0.750 LSB and +1.679 / -1.677 LSB, respectively. For the dynamic analysis, the SFDR and SNDR at the Nyquist rate are 62.76 dB and 56.099 dB. The ENOB is 9.026 bit, the power consumption is 2.397 mW and FoM is 45.98 fJ / conv.-step.

碩士<br>淡江大學<br>美洲研究所碩士班<br>102<br>In this paper, we seek to study the relation between data on leading indicators and U.S. business cycle by using binary logit model to examine business cycle index of the National Bureau of Economic Research and compare to the leading indicators of the 50 states of the United States. from 1982-2013. According to Stock and Watson’s theory to determine the variable combination. The use of dynamic factor models and principal components to model the current state of the economy has led to a series of coincident and leading indicators. These indicators are specifically designed to help predict the future movements in the state of the economy. The empirical result shows Kentucky’s leading index using both of the two or three month lags, the predict ability is significant effect. The conclusion that can be drawn is that two and three months prior, predictions made using the Kentucky leading index will generally be more reliable a predictor for NBER recessions than those using the national leading indicator. One month ahead forecasts are not likely to be very reliable since the NBER number is not available within one month and the state and national leading indicator will not also generally be available so early. Finally, this paper also discusses the use of time for quarterly or monthly frequency difference between the two. When the state’s economic activity is similar to the country, it can forecast the future direction of the business cycle more accurately.

博士<br>國立清華大學<br>資訊工程學系<br>87<br>The binary hypercube is a widely used architecture for commercial, message-passing parallel machines. Its popularity is due to its many attractive advantages, such as regular structure, high communication bandwidth, high degree of fault tolerance capabilities. But in some situations (budgetary constraints or node failures), it can be a significant drawback as the number of nodes in the binary hypercubes is restricted to a power of 2. The incomplete hypercube not only overcomes the size restriction of the complete hypercube but also retains its salient advantages. Furthermore, many variations all take the incomplete hypercube as a subgraph. Therefore, among them, incomplete hypercubes show particular importance. Incomplete binary trees and cycles are highly structured topologies frequently demanded by parallel applications. Therefore, it is important to develop efficient embedding techniques that map these two topologies onto the incomplete hypercube. On the other hand, a multiprocessing system may only allocate a part of the whole system for a task. We are therefore motivated to study the problem of how to embed incomplete binary trees and cycles of arbitrary size onto the incomplete hypercube. It has been proved that an incomplete binary tree cannot be embedded onto an incomplete hypercube with both expansion-1 and dilation-1. The existing dilation-1 embedding scheme can not solve the issue of embedding incomplete binary tree of arbitrary size onto an incomplete hypercube. Furthermore, for the quite popular Wormhole routing, the pipelined nature makes the network latency relatively insensitive to path length. And with the increase of multiprocessor nodes, the number of wires needed to interconnect them also increases. We are therefore motivated to release the constraint of dilation-1 and develop another expansion-1 embedding. In the first part of this dissertation, by the aid of some interesting properties of tree in-order traversal, we propose a simple but effective scheme which embeds an incomplete binary tree onto an incomplete hypercube with expansion (N+1)/N, dilation-2 and congestion-2. We also show that for any node in an incomplete hypercube, we can compute its corresponding mapping addresses in constant time, and vice versa. Experimental analysis confirms the effectiveness of our embedding scheme. In the second part of this dissertation, we improve the former result and give an tree embedding scheme with expansion-1, dilation-2 and congestion-2. By combining our expansion-1 scheme with the existing dilation-1 scheme, we have successfully developed an effective way to solve the problem of embedding an incomplete binary tree with arbitrary size onto incomplete hypercubes. In the third part of this dissertation, we investigate the issue of embedding cycles onto incomplete hypercubes. By horizontal decomposition of incomplete hypercubes, we show how to optimally embed a single cycle of arbitrary size onto incomplete hypercubes. It is worth noting that in all cases of dilation-2 embeddings in our algorithm, only one edge in the cycle is embedded in dilation-2. Therefore, the average dilation of our embedding algorithm approaches 1. Finally, we focus on another interesting problem: how do we effectively embed disjoint cycles onto incomplete hypercubes to execute simultaneously on disjoint parts of the network. The same problem has been solved on arrangement graph and star graph. By the aid of generalized Gray codes, we have presented a systematic and simple way to solve this problem. All of the embedding results in this dissertation can also be carried over to various variations of incomplete hypercubes, such as supercube, enhance incomplete hypercube and hamming cube.

A binary clutter is cycling if its packing and covering linear program have integral optimal solutions for all Eulerian edge capacities. We prove that the clutter of odd st- walks of a signed graph is cycling if and only if it does not contain as a minor the clutter of odd circuits of K5 nor the clutter of lines of the Fano matroid. Corollaries of this result include, of many, the characterization for weakly bipartite signed graphs, packing two- commodity paths, packing T-joins with small |T|, a new result on covering odd circuits of a signed graph, as well as a new result on covering odd circuits and odd T-joins of a signed graft.

碩士<br>國立臺灣科技大學<br>電機工程系<br>98<br>With the progress of the CMOS technologies, the complexity and higher clock signal frequency of memory are increasing day after day. Therefore, the reliability of the clock signal in synchronous system becomes more and more important. How to reduce clock skew will be the most important topic of the clock synchronization circuit. Delay-locked loops (DLLs) are widely used to solve the issue of clock synchronization due to its un-conditionally stable, faster transient response and less jitter accumulation than the phase-locked loops (PLLs). However, the narrow operating frequency range and no supply noise suppression become the major drawbacks for the DLLs. Therefore the variable successive approximation register-controlled (VSAR) algorithm [6] was reported to solve the problems, but the lock time is too long. Thus the subject of this dissertation is to overcome the defects, to break the limitations and to make a flexible use for the conventional DLLs circuit. This paper presents an all-digital implemented delay-locked loop with a fast-lock characteristic using three modified binary search algorithms. First, the phenomenon of repetitive search in the VSAR algorithm is removed by the proposed fast VSAR (FVSAR) algorithm. Second, the recursive SAR (RSAR) algorithm applies the binary search algorithm to the delay length adjustment in the VASR algorithm. However, the phenomenon of repetitive search takes place in the RSAR algorithm as well. Therefore the fast recursive SAR (FRSAR) is proposed to speed up the locking process. Finally, the SAR Algorithm Delay-Lock Loop with Length Detection (LDSAR) resolve the FVSAR and the FRSAR algorithm shortcomings, LDSAR algorithm applies the Length Detection Circuit to speed up the locking time and the wide range phase detector to overcome the Non 50% duty cycle problems.

M.Com. (Financial Economics)<br>The use of the yield curve spread in forecasting future recessions has become popular as it is a simple tool to use, due to the positive relationship between the yield curve spread and economic activity. The inversion or flattening of the yield curve spread usually signals a future recession. This has been the subject of several studies both internationally and in South Africa. This research provides an analysis of the yield curve spread’s ability to accurately forecast future recessions in South Africa through the use of three probit models. Furthermore, the yield curve spread’s ability to estimate is compared to that of share prices, using the JSE All Share Index. This research extends on studies by Khomo and Aziakpono (2006) and Clay and Keeton (2011), who used the static and dynamic probit models to forecast recessions in South Africa. In addition to these models, this research also makes use of the business cycle conditionally independent probit model for estimation. The findings suggest that share prices improve the yield curve spread’s ability to forecast recessions when estimating using the static probit model; however when comparing the results between the financial variables, the yield curve spread continues to produce the best forecast of recessions in South Africa. These results support those of Khomo and Aziakpono (2006) and Clay and Keeton (2011). Of the three probit models, the dynamic probit model estimate using the yield curve spread produced the most accurate forecast of recessions one quarter ahead. Therefore, the yield curve spread continues to provide the most accurate forecast of recessions in South Africa.

Driven by the difficulty to predict the last financial crisis and possible distortion of predictive power of the conventional financial indicators on economic activity, this thesis provides in-sample and out-of-sample analyses whether financial volatility helps in explaining and forecasting economic activity. Several measures of financial volatility were constructed, such as: realized volatility, volatility following a Generalized Autoregressive Conditional Heteroskedasticity (GARCH) process, common long-run component of volatility estimated by Dynamic Factor Model, Principal Component Analysis and cyclical components of financial volatilities filtered out with Baxter-King filter. I find that statistically there are measures of financial volatility that help in explaining economic activity. Moreover, out-of-sample analysis suggests that the model with term-spread and volatility of financial volatility (volatility of value-weighted returns of market portfolio volatility) performs best in forecasting economic activity. The inclusion of a volatility measure reduces the noise in estimated probabilities of expansions and leads to the lowest number of uncertain periods, i.e. periods for which probability of recession is between 16.86% (percentage of recessions in the sample) and 50%, an event that in some studies is already considered as a recession. Thus, a certain financial volatility measure improves forecasts from the conventional financial indicators, especially during less volatile times. Moreover, the most parsimonious measure of volatility predicts business cycles best. On the other hand, industrial production growth seems to be barely affected by financial volatility measures, which tend to be a better predictor for the direction of the future path of the economy than the actual growth rate.

Combinatorial objects can be represented by strings, such as 21534 for the permutation (1 2) (3 5 4), or 110100 for the binary tree corresponding to the balanced parentheses (()()). Given a string s = s1 s2 sn, the right-shift operation shift(s, i, j) replaces the substring si si+1..sj by si+1..sj si. In other words, si is right-shifted into position j by applying the permutation (j j−1 .. i) to the indices of s. Right-shifts include prefix-shifts (i = 1) and adjacent-transpositions (j = i+1). A fixed-content language is a set of strings that contain the same multiset of symbols. Given a fixed-content language, a shift Gray code is a list of its strings where consecutive strings differ by a shift. This thesis asks if shift Gray codes exist for a variety of combinatorial objects. This abstract question leads to a number of practical answers. The first prefix-shift Gray code for multiset permutations is discovered, and it provides the first algorithm for generating multiset permutations in O(1)-time while using O(1) additional variables. Applications of these results include more efficient exhaustive solutions to stacker-crane problems, which are natural NP-complete traveling salesman variants. This thesis also produces the fastest algorithm for generating balanced parentheses in an array, and the first minimal-change order for fixed-content necklaces and Lyndon words. These results are consequences of the following theorem: Every bubble language has a right-shift Gray code. Bubble languages are fixed-content languages that are closed under certain adjacent-transpositions. These languages generalize classic combinatorial objects: k-ary trees, ordered trees with fixed branching sequences, unit interval graphs, restricted Schr oder and Motzkin paths, linear-extensions of B-posets, and their unions, intersections, and quotients. Each Gray code is circular and is obtained from a new variation of lexicographic order known as cool-lex order. Gray codes using only shift(s, 1, n) and shift(s, 1, n−1) are also found for multiset permutations. A universal cycle that omits the last (redundant) symbol from each permutation is obtained by recording the first symbol of each permutation in this Gray code. As a special case, these shorthand universal cycles provide a new fixed-density analogue to de Bruijn cycles, and the first universal cycle for the "middle levels" (binary strings of length 2k + 1 with sum k or k + 1).