The thesis considers the Ginzburg-Landau process on the lattice $\Z^d$ whose potential is a bounded perturbation of the Gaussian potential. For such processes the thesis establishes the decay rate to equilibrium in the variance sense is $C_g t^{-d/2} + o\left(t^{-d/2}\right)$, for any local function $g$ that is bounded, mean zero, and having finite triple norm; $\triplenorm{g}=\sum_{x \in \Z^d} \norm{\partial_{\eta(x)}g}_\infty.$ The constant $C_g$ is computed explicitly. This extends the decay to equilibrium result of Janvresse, Landim, Quastel, and Yau [JLQY99] for zero-range process, and the related result of Landim and Yau [LY03] for Ginzburg-Landau processes. The thesis also considers additive functionals $\int_{0}^{t} g(\eta_s) ds$ of Ginzburg-Landau processes, where $g$ is a bounded, mean zero, local function having finite triple norm. A central limit is proven for $a^{-1}(t)\int_{0}^{t} g(\eta_s) ds$ with $a(t)= \sqrt{t}$ in $d \ge 3$, $a(t)=\sqrt{t \log{t}}$ in $d=2$, and $a(t)= t^{3/4}$ in $d=1$ and an explicit form of the asymptotic variance in each case. Corresponding invariance principles are also obtained. Standard arguments of Kipnis and Varadhan [KV86] are employed in the case $d \ge 3$. Martingale methods together with $L^2$ decay estimates for the semigroup associated with the process are employed to establish the result in the cases $d=1$ and $d=2$. This extends similar results for noninteracting random walks (see[CG84]), the symmetric simple exclusion processes (see [Kip87]), and the zero-range process (see [QJS02]).

The thesis considers the Ginzburg-Landau process on the lattice $\Z^d$ whose potential is a bounded perturbation of the Gaussian potential. For such processes the thesis establishes the decay rate to equilibrium in the variance sense is $C_g t^{-d/2} + o\left(t^{-d/2}\right)$, for any local function $g$ that is bounded, mean zero, and having finite triple norm; $\triplenorm{g}=\sum_{x \in \Z^d} \norm{\partial_{\eta(x)}g}_\infty.$ The constant $C_g$ is computed explicitly. This extends the decay to equilibrium result of Janvresse, Landim, Quastel, and Yau [JLQY99] for zero-range process, and the related result of Landim and Yau [LY03] for Ginzburg-Landau processes. The thesis also considers additive functionals $\int_{0}^{t} g(\eta_s) ds$ of Ginzburg-Landau processes, where $g$ is a bounded, mean zero, local function having finite triple norm. A central limit is proven for $a^{-1}(t)\int_{0}^{t} g(\eta_s) ds$ with $a(t)= \sqrt{t}$ in $d \ge 3$, $a(t)=\sqrt{t \log{t}}$ in $d=2$, and $a(t)= t^{3/4}$ in $d=1$ and an explicit form of the asymptotic variance in each case. Corresponding invariance principles are also obtained. Standard arguments of Kipnis and Varadhan [KV86] are employed in the case $d \ge 3$. Martingale methods together with $L^2$ decay estimates for the semigroup associated with the process are employed to establish the result in the cases $d=1$ and $d=2$. This extends similar results for noninteracting random walks (see[CG84]), the symmetric simple exclusion processes (see [Kip87]), and the zero-range process (see [QJS02]).

Directional selection is prevalent in nature yet phenotypes tend to remain relatively constant, suggesting a limit to trait evolution. The genetic basis of evolutionary limits in unmanipulated populations, however, is generally not known. Given widespread pleiotropy, opposing selection on a focal trait may arise from the effects of the underlying alleles on other fitness components, generating net stabilizing selection on trait genetic variance and thus limiting evolution. Here, I look for the signature of stabilizing selection for a suite of cuticular hydrocarbons (CHCs) in Drosophila serrata. Despite strong directional sexual selection on CHCs, genetic variance differed between high and low fitness individuals and was greater among the low fitness males for seven of eight CHCs. Univariate tests of a difference in genetic variance were non-significant but have low power. My results implicate stabilizing selection, arising through pleiotropy, in generating a genetic limit to the evolution of CHCs in this species.

Aquesta tesi es situa en el marc de la teoria qualitativa dels sistemes diferencials en el pla. Cada capítol conté un aspecte diferent. A la introducció, es dóna un resum dels resultats més coneguts i s'hi introdueix la notació que es fa servir al llarg de la tesi. En particular, descrivim el problema de la integrabilitat i alguns resultats sobre la determinació de l'estabilitat d'un punt singular o d'una òrbita periòdica a fi de presentar els darrers capítols. El problema de la integrabilitat es defineix com el problema de trobar la integral primera d'un sistema d'equacions diferencials en el pla i determinar la classe funcional a la qual pertany. Els Capítols 2 i 3 tracten el problema de la integrabilitat.En el Capítol 2 donem un resultat que permet trobar una expressió explícita per a una integral primera d'un cert tipus de sistemes polinomials. Mitjançant un canvi racional de variables, fem correspondre a una equació diferencial lineal homogènia de segon ordre: A2(x) w'(x) + A1(x) w'(x) + A0(x) w(x) = 0, els coeficients de la qual són polinomials, a un sistema diferencial polinomial pla. Provem que aquest sistema té un invariant per a cada solució arbitrària no nul·la w(x) de l'edo de segon ordre, que, quan w(x) és un polinomi, dóna lloc a una corba algebraica invariant. A més, donem una expressió explícita per a una integral primera del sistema construïda a partir de dues solucions independents de l'edo de segon ordre. Aquesta integral primera no és, en general, una funció Liouvilliana. Finalment, verifiquem que tots els exemples coneguts de famílies de sistemes quadràtics amb una corba algebraica invariant de grau arbitràriament alt es poden descriure mitjançant aquesta construcció (mòdul transformacions birracionals).En el Capítol 3, les corbes algebraiques invariants d'un sistema diferencial polinomial pla juguen el paper fonamental. Si un sistema diferencial polinomial pla té una corba algebraica invariant irreductible, aleshores els valors del seu cofactor en cadascun dels punts singulars no degenerats estan determinats. De fet, aquest valor es una combinació lineal a coeficients naturals dels valors propis associats al punt singular no degenerat. Aquests coeficients naturals es poden determinar completament en alguns casos depenent de la natura del punt singular. Així mateix, els punts de l'infinit també es poden tenir en compte. Un cop considerem el sistema en el pla projectiu complex, el grau d'una corba algebraica invariant esdevé un paràmetre del seu cofactor. Si considerem un sistema de grau d, aleshores té d^2 + d + 1 punts singulars (comptats amb la seva multiplicitat) i el cofactor d'una corba algebraica invariant té grau pel cap alt d-1. Procedim de la manera següent: prenem un polinomi de grau d-1 amb els seus d(d+1)/2 coeficients arbitraris i suposem que és el cofactor d'una corba algebraica invariant irreductible de grau n. Aleshores, imposem totes les condicions que ens donen els punts singulars no degenerats. En el cas general, imposem d^2 + d +1 condicions i, així, podem determinar completament el cofactor i el grau de la corba, l'existència de la qual es pot determinar resolent un sistema d'equacions lineal, o trobem una condició d'incompatibilitat. D'aquesta manera, en general, podem determinar l'existència de totes les corbes algebraiques invariants d'un sistema.El Capítol 4 tracta sobre l'estabilitat d'una òrbita periòdica d'un sistema diferencial pla. Suposem que f(x,y)=0 és una corba invariant irreductible amb cofactor que conté l'òrbita periòdica. Provem que les integrals sobre l'òrbita periòdica de la divergència i del cofactor coincideixen. Així, podem decidir sobre l'estabilitat de l'òrbita periòdica mitjançant la integració del cofactor sobre aquesta. En el Capítol 5, donem una aplicació dels resultats descrits en els Capítols 3 i 4. Considerem els sistemes quadràtics amb un cicle límit algebraic coneguts fins al moment de la redacció d'aquesta tesi. Aquest cicles límit algebraics estan continguts en corbes algebraiques invariants de graus 2, 4, 5 i 6 i algunes d'aquestes famílies de sistemes quadràtics son birracionalment equivalents. Aplicant el mètode descrit en el Capítol 3, mostrem que la corba algebraica invariant que conté el cicle límit es l'única corba algebraica invariant del sistema. Aprofitem aquest resultat per provar que aquests sistemes no tenen integral primera Liouvilliana. I aplicant la formula donada en el Capítol 4, provem que aquests cicles límit algebraics son hiperbòlics. El Capítol 6 tracta sobre l'estudi i les propietats de la funció període associada a un punt singular amb part lineal de tipus centre-focus. Com que el punt singular és sempre monodròmic, donada una secció transversal al flux amb el punt singular com a extrem, podem definir l'aplicació de Poincaré i la funció període associades a la secció. Diem que el punt és isòcron si podem trobar una secció tal que la seva funció període associada és constant. Aquesta definició generalitza la definició usual donada per centres a punts singulars qualssevol amb part lineal de tipus centre-focus. Caracteritzem aquesta propietat mitjançant simetries de Lie i formes normals, tot generalitzant els procediments coneguts per centres. Així mateix, donem un exemple d'una família de sistemes depenent d'un paràmetre real, tals que el seu origen és un punt singular amb part lineal de tipus centre-focus i que mai no és un punt isòcron. / Esta tesis se sitúa en el marco de la teoría cualitativa de los sistemas diferenciales en el plano. Cada capítulo contiene un aspecto distinto. En la introducción, se da un resumen de los resultados conocidos y se presenta la notación usada durante el resto de la tesis. En particular, se describe el problema de la integrabilidad y algunos resultados referentes a la determinación de la estabilidad de un punto singular o una órbita periódica con el fin de introducir los últimos capítulos. Definimos el problema de la integrabilidad como el problema de encontrar una integral primera para un sistema diferencial plano y determinar la clase funcional a la cual ésta debe pertenecer. Los Capítulos 2 y 3 tratan sobre el problema de la integrabilidad. En el Capítulo 2, obtenemos un resultado que permite encontrar una expresión explícita para una integral primera para un cierto tipo de sistema polinomial. Mediante un cambio racional de variable, hacemos corresponder una ecuación diferencial lineal homogénea de segundo orden: A2 (x) w'(x) + A1(x) w'(x) + A0(x) w(x) = 0, cuyos coeficientes son polinomios, a un sistema diferencial polinomial en el plano. Probamos que dicho sistema tiene un invariante para cada solución arbitraria no nula w(x) de la edo de segundo orden, que, en caso que w(x) sea un polinomio, da lugar a una curva algebraica invariante. Además, damos una expresión explícita de una integral primera para el sistema construida a partir de dos soluciones independientes de la edo de segundo orden. Esta integral primera no es, en general, una función Liouvilliana. Finalmente, verificamos que todos los ejemplos conocidos de familias de sistemas cuadráticos con una curva algebraica invariante de grado arbitrariamente alto se pueden describir mediante esta construcción (módulo transformaciones birracionales).En el Capítulo 3, las curvas algebraicas invariantes de un sistema diferencial plano polinomial juegan un papel fundamental. Si una curva algebraica invariante e irreducible existe para un sistema polinomial plano, entonces los valores de su cofactor en cada punto singular no degenerado están determinados. De hecho, este valor es una combinación lineal a coeficientes naturales de los valores propios asociados al punto singular no degenerado. Estos coeficientes naturales se pueden determinar completamente según la naturaleza del punto singular. Además, también podemos considerar los puntos del infinito. Una vez que el sistema se considera en el plano proyectivo complejo, el grado de una curva algebraica invariante deviene un parámetro de su cofactor. Si consideramos un sistema de grado d, entonces tiene d^2 + d + 1 puntos singulares (contados con su multiplicidad) y el cofactor de una curva algebraica invariante es un polinomio de grado a lo sumo d-1. Procedemos de la manera siguiente: tomamos un polinomio de grado d-1 con sus d(d+1)/2 coeficientes arbitrarios y suponemos que es el cofactor de una curva algebraica invariante e irreducible de grado n. Entonces, imponemos todas las condiciones dadas por los puntos singulares no degenerados. En el caso general, imponemos d^2 + d + 1 condiciones y, en consecuencia, determinamos completamente el cofactor y el grado de la curva, cuya existencia puede ser determinada resolviendo un sistema lineal de ecuaciones, o mostramos una condición de incompatibilidad. Por tanto, podemos determinar la existencia de todas las curvas algebraicas invariantes para un sistema general. El Capítulo 4 trata sobre la estabilidad de una órbita periódica de un sistema diferencial plano. Suponemos que f(x,y)=0 es una curva invariante e irreducible con cofactor que contiene la órbita periódica. Probamos que las integrales sobre la órbita periódica de la divergencia y del cofactor coinciden. De aquí que podamos deducir la estabilidad de una órbita periódica mediante la integración del cofactor sobre ésta. En el Capítulo 5, describimos una aplicación de los resultados dados en los Capítulos 3 y 4. Consideramos los sistemas cuadráticos con un ciclo límite algebraico conocidos hasta la redacción de esta tesis. Estos ciclos límite algebraicos están contenidos en curvas algebraicas invariantes de grados 2, 4, 5 y 6 y algunas de estas familias de sistemas cuadráticos son birracionalmente equivalentes. Aplicando el método descrito en el Capítulo 3, mostramos que no existe ninguna curva algebraica invariante excepto la que contiene el ciclo límite. Aprovechamos este resultado para mostrar que estos sistemas no tienen integral primera Liouvilliana. Y, aplicando la formula dada en el Capítulo 4, probamos que estos ciclos límite algebraicos son hiperbólicos. El Capítulo 6 trata sobre el estudio de las propiedades de la función periodo asociada a un punto singular con parte lineal de tipo centro-foco. Dada una sección transversal al flujo con dicho punto singular por extremo, podemos definir la aplicación de Poincaré y la función periodo asociadas a esta sección puesto que este punto es siempre monodrómico. Decimos que este punto es isócrono si podemos encontrar una sección tal que la función periodo asociada a ella sea constante. Esta definición generaliza la definición usual dada para centros a cualquier punto singular con parte lineal de tipo centro-foco. Caracterizamos esta propiedad mediante simetrías de Lie y formas normales, generalizando los procedimientos conocidos para centros. Además, damos un ejemplo de una familia de sistemas que dependen de un parámetro real, tales que el origen es un punto singular con parte lineal de tipo centro-foco y que nunca es un punto isócrono. / This thesis is situated in the framework of the qualitative theory of differential systems in the plane. Each chapter contains a different topic. In the introduction, a summary of known results is given and the notation used through the rest of the memory is presented. In particular, we describe the integrability problem and some results concerning the determination of the stability of a singular point or a periodic orbit in order to introduce the latest chapters. We define the integrability problem as the problem of finding a first integral for a planar differential system and determining the functional class it must belong to. Chapters 2 and 3 are concerned with the integrability problem. In Chapter 2, we obtain a result which allows to find an explicit expression for a first integral of a certain type of polynomial system. By means of a rational change of variable, we make correspond the homogenous second order linear differential equation: A2 (x) w'(x) + A1(x) w'(x) + A0(x) w(x) = 0, whose coefficients are polynomials, to a planar polynomial differential system. We prove that this system has an invariant for each arbitrary nonnull solution w(x) of the second-order ode, which, in case w(x) is a polynomial, gives rise to an invariant algebraic curve. In addition, we give an explicit expression of a first integral for the system constructed from two independent solutions of the second order ode. This first integral is not, in general, a Liouvillian function. Finally, we verify that all the known examples of families of quadratic systems with an invariant algebraic curve of arbitrarily high degree can be described by this construction (modulus birrational transformations). In Chapter 3, invariant algebraic curves of a planar polynomial differential system play the fundamental role. If an irreducible invariant algebraic curve for a planar polynomial differential system exists, then the values of its cofactor at each non-degenerate singular point are determined. In fact, this value is a linear combination with natural coefficients of the eigenvalues associated to the non-degenerate singular point. These natural coefficients can be completely determined in some cases depending on the nature of the singular point. Moreover, the points at infinity can also be taken into account. Once the system is considered in the projective complex plane, the degree of an invariant algebraic curve becomes a parameter of its cofactor. If we consider a system of degree d, then it has d^2 + d + 1 singular points (counted with multiplicity) and the cofactor of an invariant algebraic curve is a polynomial of degree at most d-1. We proceed as follows: we take a polynomial of degree d-1 with its d(d+1)/2 arbitrary coefficients and we assume that it is the cofactor of an irreducible invariant algebraic curve of degree n. Then, we impose all the conditions given by the non-degenerate singular points. In the general case, we impose d^2 + d + 1 conditions and, hence, we completely determine the cofactor and the degree of the curve, whose existence can be determined by solving a linear system of equations, or we show an incompatibility condition. Therefore, we can determine the existence of all the invariant algebraic curves of a general system.Chapter 4 is about the stability of a periodic orbit of a planar differential system. We assume that f(x,y)=0 is a real irreducible invariant curve with cofactor which contains the periodic orbit. We prove that the integrals over the periodic orbit of the divergence and the cofactor coincide. Hence, we can decide the stability of a periodic orbit by means of the integration of the cofactor over it. In Chapter 5, we describe an application of the results given in Chapters 3 and 4. We consider the quadratic systems with an algebraic limit cycle known until the composition of this thesis. These algebraic limit cycles are contained in invariant algebraic curves of degrees 2, 4, 5 and 6 and there are some of these families of quadratic systems which are birrationally equivalent one to the other. Applying the method given in Chapter 3, we show that there is no other irreducible invariant algebraic curve that the one which contains the limit cycle. We take profit from this result to show that these systems have no Liouvillian first integral. And applying the formula given in Chapter 4, we prove that these algebraic limit cycles are hyperbolic.Chapter 6 is devoted to the study of the properties of the period function associated to a singular point with linear part of centre-focus type. Given a section through the flow with such a singular point as endpoint, we can define the Poincaré map and the period function associated to this section since this point is always monodromic. We say that this point is isochronous if we can find a section such that the period function associated to it is constant. This definition generalizes the usual definition given for centres to any singular point with linear part of centre-focus type. We characterize this property by means of Lie symmetries and normal forms, generalizing the known procedures for centres. Moreover, we provide an example of a family of systems depending on a real parameter, such that the origin is a singular point with linear part of centre-focus type and which is never an isochronous point. / Cette thèse de doctorat traite sur la théorie qualitative des systèmes différentiels planaires. Chaque chapitre contient un sujet différent. Dans l'introduction, un sommaire des résultats connus est donné et la notation utilisée dans le reste du mémoire est présentée. En particulier, nous décrivons le problème de l'intégrabilité et quelques résultats concernant la détermination de la stabilité d'un point singulier ou d'une orbite périodique afin de présenter les derniers chapitres. Nous définissons le problème de l'intégrabilité comme le problème de trouver une intégrale première pour un système différentiel planaire et de déterminer la classe fonctionnelle à la quelle elle doit appartenir. Les Chapitres 2 et 3 traitent du problème de l'intégrabilité. Au Chapitre 2, nous obtenons un résultat permettant de trouver une expression explicite pour une intégrale première d'un certain type de système polynomial. Au moyen d'un changement rationnel de variables, nous faisons correspondre l'équation linéaire du deuxième degré: A2(x) w''(x) + A1(x) w'(x) + A0(x) w(x) = 0, dont les coefficients sont des polynômes, à un système différentiel polynomial planaire. Nous montrons que ce système a un invariant pour chaque solution arbitraire w(x) différent de zéro de l'équation considérée, qui, dans le cas où le w(x) serait un polynôme, est une courbe algébrique invariante. De plus, nous donnons une expression explicite d'une intégrale première pour le système construite à partir de deux solutions indépendantes de l'edo du deuxième degré. Cette intégrale première n'est pas, en général, une fonction de Liouville. En conclusion, nous vérifions que tous les exemples connus des familles des systèmes quadratiques avec une courbe algébrique invariante de degré arbitrairement élevé peuvent être décrits par cette construction (modulo des transformations birationnelles). Au Chapitre 3, les courbes algébriques invariantes d'un système différentiel polynomial planaire jouent le rôle fondamental. Si une courbe algébrique invariante et irréductible existe pour un système différentiel polynomial planaire, alors les valeurs de son cofacteur à chaque point singulier non dégénéré sont déterminées. En fait, cette valeur est une combinaison linéaire avec des coefficients naturels des valeurs propres associées au point singulier non dégénéré. Ces coefficients naturels peuvent être complètement déterminés dans certains cas selon la nature du point singulier. De plus, les points à l'infini peuvent également être pris en considération. Une fois que le système est considéré dans le plan projectif complexe, le degré d'une courbe algébrique invariante devient un paramètre de son cofacteur. Si nous considérons un système de degré d, alors il y a d^2 + d + 1 points singuliers (comptés avec sa multiplicité) et le cofacteur d'une courbe algébrique invariante est un polynôme de degré au plus d-1. Nous opérons comme suit: nous prenons un polynôme de degré d-1 avec ses d(d+1)/2 coefficients arbitraires et nous supposons que c'est le cofacteur d'une courbe algébrique invariante et irréductible de degré n. Nous imposons alors toutes les conditions données par les points singuliers non dégénérés. Dans le cas général, nous imposons d^2 + d + 1 conditions et, par conséquent, nous déterminons complètement le cofacteur et le degré de la courbe, dont l'existence peut être déterminée en résolvant un système linéaire d'équations, ou bien nous prouvons l'incompatibilité d'une condition. Par conséquent, nous pouvons déterminer l'existence de toutes les courbes algébriques invariantes d'un système général. Le sujet du Chapitre 4 est la stabilité d'une orbite périodique d'un système différentiel planaire. Nous supposons que f(x,y)=0 est une courbe invariante irréductible réelle avec cofacteur qui contient l'orbite périodique. Nous montrons que les intégrales sur l'orbite périodique de la divergence et le cofacteur coïncident. Par conséquent, nous pouvons déterminer la stabilité d'une orbite périodique en intégrant le cofacteur sur celle-ci.Dans le Chapitre 5, nous décrivons une application des résultats donnés aux Chapitres 3 et 4. Nous considérons les systèmes quadratiques avec un cycle limite algébrique connus jusqu'alors. Ces cycles limites algébriques sont contenus dans des courbes algébriques invariantes de degrés 2, 4, 5 et 6 et il existe certaines de ces familles de systèmes quadratiques qui sont birationnellement équivalentes. Appliquant la méthode exposée au Chapitre 3, nous prouvons qu'il n'y a aucune autre courbe algébrique invariante et irréductible différente à celle qui contient le cycle limite. Ceci nous permet de prouver que ces systèmes n'ont aucune intégrale première de Liouville. En appliquant la formule donnée au Chapitre 4, nous montrons que ces cycles limites algébriques sont hyperboliques. Le Chapitre 6 est consacré à l'étude des propriétés de la fonction de période associée à un point singulier dont la partie linéaire est de type centre-foyer. Etant donnée une section du flux avec tel point singulier comme point final, nous pouvons définir l'application de Poincaré et la fonction de période associée à cette section puisque ce point est toujours monodromique. Nous disons que ce point est isochronique si nous pouvons trouver une section telle que la fonction de période associée à elle est constante. Cette définition généralise la définition habituelle donnée pour des centres à n'importe quel point singulier dont la partie linéaire est de type centre-foyer. Nous caractérisons cette propriété au moyen des symétries de Lie et des formes normales, généralisant les procédures connues pour des centres. De plus, nous donnons un exemple d'une famille de systèmes avec un paramètre réel, telle que l'origine est un point singulier dont la partie linéaire est de type centre-foyer et qui n'est jamais un point isochronique.

We investigate spectral properties of limit-periodic Schrödinger operators in [cursive l] 2 ([Special characters omitted.] ). Our goal is to exhibit as rich a spectral picture as possible. We regard limit-periodic potentials as generated by continuous sampling along the orbits of a minimal translation of a procyclic group. This perspective was first proposed by Avila and further exploited by the author, which allows one to separate the base dynamics and the sampling function. Starting from this point of view, we conclude that all the spectral types (i.e. purely absolutely continuous, purely singular continuous, and pure point) can appear within the class of limit-periodic Schrödinger operators. We furthermore answer questions regarding how often a certain type of spectrum would occur and discuss the corresponding Lyapunov exponent. In the regime of pure point spectrum, we exhibit the first almost periodic examples that are uniformly localized across the hull and the spectrum.

Since last two decades researches have been working on developing systems that can assistsdrivers in the best way possible and make driving safe. Computer vision has played a crucialpart in design of these systems. With the introduction of vision techniques variousautonomous and robust real-time traffic automation systems have been designed such asTraffic monitoring, Traffic related parameter estimation and intelligent vehicles. Among theseautomatic detection and recognition of road signs has became an interesting research topic.The system can assist drivers about signs they don’t recognize before passing them.Aim of this research project is to present an Intelligent Road Sign Recognition System basedon state-of-the-art technique, the Support Vector Machine. The project is an extension to thework done at ITS research Platform at Dalarna University [25]. Focus of this research work ison the recognition of road signs under analysis. When classifying an image its location, sizeand orientation in the image plane are its irrelevant features and one way to get rid of thisambiguity is to extract those features which are invariant under the above mentionedtransformation. These invariant features are then used in Support Vector Machine forclassification. Support Vector Machine is a supervised learning machine that solves problemin higher dimension with the help of Kernel functions and is best know for classificationproblems.

During last decades, the Internet teleobotics has been growing at an enormous ratedue to the rapid improvement of Internet technology. This paper presents theinternet-based remote control of mobile robot. To face unpredictable Internet delaysand possible connection rupture, a direct continuous control based teleoperationarchitecture with “Speed Limit Module” (SLM) and “Delay Approximator” (DA) isproposed. This direct continuous control architecture guarantees the path error of therobot motion is restricted within the path error tolerance of the application.Experiment results show the feasibility and effectiveness of this direct Internet controlarchitecture in the real Internet environment.

This work was carried out to study the effect of shot-peening on the fatigue behaviour of carbon steels. Differently heat treated medium and high carbon steel specimens were selected. Medium carbon steels, AISI 1141 and AISI 1151, were respectively air cooled and quenched-tempered. A high carbon steel, C70S6 (AISI 1070), was air cooled. The other material was a powder metal (0.5% C) steel. Each group of steels was divided into two. One was shot-peened. The other half remained in their original conditions. All were fatigue tested under fully reversed (R=-1) tension-compression loading conditions. Microhardness tests were carried out on both the grip and gage sections of selected non shot-peened and shot-peened specimens to determine the hardness profile and effect of cycling. Shot-peening was found to be deeper on one side of each specimen. Compressive residual stress profiles and surface roughness measurements were provided. Shot-peening increased the surface roughness from 0.26±0.03µm to 3.60±0.44µm. Compressive residual stresses induced by shot-peening reached a maximum of -463.9MPa at a depth of 0.1mm.The fatigue limit (N≈106 cycles) and microhardness profiles of the non shot-peened and shot-peened specimens were compared to determine the material behaviour changes after shot-peening and cycling. Also their fatigue properties were related to the manufacturing process including heat and surface treatments. Comparing the grip and gage microhardness profiles of each steel showed that neither cyclic softening nor hardening occurred in the non shot-peened condition. Cyclic softening was apparent in the shot-peened regions of all steels except powder metal (PM) steel. The amount of softening in the shot-peened region was 55.0% on the left side and 73.0% on the right in the AISI 1141 steel , 46.0% on the left side and 55.0% on the right in the C70S6AC steel and 31.0% on the right side in AISI 1151QT steel. Softening was accompanied by a decrease in the depth of surface hardness. It is suggested that although the beneficial effects of shot peening, compressive residual stresses and work hardening, were offset by surface roughness, crack initiation was more likely to occur below the surface. Surface roughness was not a significant factor in controlling the fatigue lives of AISI 1141AC and C70S6 steels, since they were essentially the same for the non shot-peened and shot-peened conditions. Shot-peening had very little effect on the push-pull fatigue limit of C70S6 steel (-2.1%), and its effect on AISI 1141AC steel was relatively small (6.0%). However, the influence of shot-peening on the AISI 1151QT and PM steels was more apparent. The fatigue limit of the PM steel increased 14.0% whereas the fatigue limit of the AISI 1151QT steel decreased 11.0% on shot peening.

Magnesium, with a Hexagonal Close-Packed (HCP) structure, is the eighth most abundant element in the earth’s crust and the third most plentiful element dissolved in the seawater. Magnesium alloys exhibit the attractive characteristics of low densities and high strength-to-weight ratios along with good castability, recyclability, and machinability. Replacing the steel and/or aluminum sheet parts with magnesium sheet parts in vehicles is a great way of reducing the vehicles weight, which results in great savings on fuel consumption. The lack of magnesium sheet components in vehicle assemblies is due to magnesium’s poor room-temperature formability. In order to successfully form the sheets of magnesium at room temperature, it is necessary to understand the formability of magnesium at room temperature controlled by various plastic deformation mechanisms. The plastic deformation mechanisms in pure magnesium and some of its alloys at room temperature are crystallographic slip and deformation twinning. The slip systems in magnesium at room temperature are classified into primary (first generation), secondary (second generation), and tertiary (third generation) slip systems. The twinning systems in magnesium at room temperature are classified into primary (first generation) and secondary (second generation, or double) twinning systems. A new comprehensive rate-dependent elastic-viscoplastic Crystal Plasticity Constitutive Model (CPCM) that accounts for all these plastic deformation mechanisms in magnesium was proposed. The proposed model individually simulates slip-induced shear in the parent as well as in the primary and secondary twinned regions, and twinning-induced shear in the primary and secondary twinned regions. The model also tracks the texture evolution in the parent, primary and secondary twinned regions. Separate resistance evolution functions for the primary, secondary, and tertiary slip systems, as well as primary and secondary twinning systems were considered in the formulation. In the resistance evolution functions, the interactions between various slip and twinning systems were accounted for. The CPCM was calibrated using the experimental data reported in the literature for pure magnesium single crystals at room temperature, but needs further experimental data for full calibration. The partially calibrated model was used to assess the contributions of various plastic deformation mechanisms in the material stress-strain response. The results showed that neglecting secondary slip and secondary twinning while simulating plastic deformation of magnesium alloys by crystal plasticity approach can lead to erroneous results. This indicates that all the plastic deformation mechanisms have to be accounted for when modelling the plastic deformation in magnesium alloys. Also, the CPCM in conjunction with the Marciniak–Kuczynski (M–K) framework were used to assess the formability of a magnesium single crystal sheet at room temperature by predicting the Forming Limit Diagrams (FLDs). Sheet necking was initiated from an initial imperfection in terms of a narrow band. A homogeneous deformation field was assumed inside and outside the band, and conditions of compatibility and equilibrium were enforced across the band interfaces. Thus, the CPCM only needs to be applied to two regions, one inside and one outside the band. The FLDs were simulated under two conditions: a) the plastic deformation mechanisms are primary slip systems alone, and b) the plastic deformation mechanisms are primary slip and primary twinning systems. The FLDs were computed for two grain orientations. In the first orientation, primary extension twinning systems had favourable orientation for activation. In the second orientation, primary contraction twinning systems had favourable orientation for activation. The effects of shear strain outside the necking band, rate sensitivity, and c/a ratio on the simulated FLDs in the two grain orientations were individually explored.

Dynamic compressors are susceptible to aerodynamic instabilities while operating at low mass flow rates. These instabilities, rotating stall and surge, are detrimental to engine life and operational safety, and are thus undesirable. In order to prevent stability problems, a passive technique, involving fuel flow scheduling, is currently employed on gas turbines. The passive nature of this technique necessitates conservative stability margins, compromising performance and/or efficiency. In the past, model based active control has been proposed to enable reduction of margin requirements. However, available compressor stability models do not predict the different stall inception patterns, making model based control techniques practically infeasible. This research presents active stability management as a viable alternative. In particular, a limit detection and avoidance approach has been used to maintain the system free of instabilities. Simulations show significant improvements in the dynamic response of a gas turbine engine with this approach. A novel technique has been developed to enable real-time detection of stability limits in axial compressors. It employs a correlation measure to quantify the chaos in the rotor tip region. Analysis of data from four axial compressors shows that the value of the correlation measure decreases as compressor loading is increased. Moreover, sharp drops in this measure have been found to be relevant for stability limit detection. The significance of these drops can be captured by tracking events generated by the downward crossing of a selected threshold level. It has been observed that the average number of events increases as the stability limit is approached in all the compressors studied. These events appear to be randomly distributed in time. A stochastic model for the time between consecutive events has been developed and incorporated in an engine simulation. The simulation has been used to highlight the importance of the threshold level tosuccessful stability management. The compressor stability management concepts have also been experimentally demonstrated on a laboratory axial compressor rig. The fundamental nature of correlation measure has opened avenues for its application besides limit detection. The applications presented include stage load matching in a multi-stage compressor and monitoring the aerodynamic health of rotor blades.