Academic literature on the topic 'Irregular phenomena'
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Journal articles on the topic "Irregular phenomena":
1
Itin, A. P., A. I. Neishtadt, and A. A. Vasiliev. "Resonant Phenomena in Slowly Irregular Rectangular Waveguides." Journal of Mathematical Sciences 128, no. 2 (July 2005): 2778–81. http://dx.doi.org/10.1007/s10958-005-0230-z.
2
HERNÁNDEZ, E. S., A. HERNANDO, R. MAYOL, and M. PI. "HELIUM IN PORES AND IRREGULAR SURFACES." International Journal of Modern Physics B 22, no. 25n26 (October 20, 2008): 4338–45. http://dx.doi.org/10.1142/s0217979208050097.
Abstract:
We report studies of adsorption of helium in translationally invariant polygonal pores at zero temperature, with emphasis on the route to capillary condensation and the appearance of metastable states. We analyze hysteresis and hysterectic-like phenomena associated to the existence of multiple equilibrium states in a rhombic pore and examine the effects of the angular geometry, as opposed to the smooth curvature of cylindrical tubes.
3
Kress, Moshe. "Lanchester Models for Irregular Warfare." Mathematics 8, no. 5 (May 7, 2020): 737. http://dx.doi.org/10.3390/math8050737.
Abstract:
Military operations research and combat modeling apply mathematical models to analyze a variety of military conflicts and obtain insights about these phenomena. One of the earliest and most important set of models used for combat modeling is the Lanchester equations. Legacy Lanchester equations model the mutual attritional dynamics of two opposing military forces and provide some insights regarding the fate of such engagements. In this paper, we review recent developments in Lanchester modeling, focusing on contemporary conflicts in the world. Specifically, we present models that capture irregular warfare, such as insurgencies, highlight the role of target information in such conflicts, and capture multilateral situations where several players are involved in the conflict (such as the current war in Syria).
4
Diirr, Bruna, and Marcos Roberto da Silva Borges. "Decision Support for Plan Adaptation in Unforeseen Situations." International Journal of Decision Support System Technology 14, no. 1 (January 2022): 1–19. http://dx.doi.org/10.4018/ijdsst.286696.
Abstract:
Handling irregular phenomena might bring great complexity for involved teams. Variables considered for undertaking recommended procedures may yield many decision alternatives, challenging to deal with at planning time. Additionally, expectations regarding the phenomena handling may not match those observed. This means that the existing plan’s application may become inappropriate, and teams must be creative in performing actions and decision-making. An approach for on-the-fly adaptation of plans aims to assist teams in identifying and diagnosing unforeseen situations, besides adjusting previously developed plans at runtime. This approach was evaluated through experiments in the emergency management domain, and the initial results indicate its feasibility in dealing with unforeseen situations while handling irregular phenomena in complex environments.
5
Kasatkin, B. A., and N. V. Zlobina. "Resonant phenomena in irregular acoustic waveguides of the coastal wedge type." Doklady Earth Sciences 436, no. 2 (February 2011): 249–52. http://dx.doi.org/10.1134/s1028334x11020024.
6
Higuchi, Mizuki, Shunki Nishida, Yasuo Yoshihashi, Katsuhide Tarada, and Kiyohiko Sugano. "Prediction of coning phenomena for irregular particles in paddle dissolution test." European Journal of Pharmaceutical Sciences 76 (August 2015): 213–16. http://dx.doi.org/10.1016/j.ejps.2015.05.019.
7
Yan, Duokui, and Tiancheng Ouyang. "New Phenomena in the Spatial Isosceles Three-Body Problem." International Journal of Bifurcation and Chaos 25, no. 09 (August 2015): 1550116. http://dx.doi.org/10.1142/s0218127415501163.
Abstract:
In the three-body problem, it is known that there exists a special set of periodic orbits: spatial isosceles periodic orbits. In each period, one body moves up and down along a straight line, and the other two bodies rotate around this line. In this work, we revisit this set of orbits by applying variational method. Two unexpected phenomena are discovered. First, this set is not always spatial. It actually bifurcates from the circular Euler (central configuration) orbit to the Broucke (collision) orbit. Second, one of the orbits in this set encounters an oscillating behavior. By running its initial condition, the orbit stays periodic for only a few periods before it becomes irregular. However, it moves close to another periodic shape in a while. Shortly it falls apart again and starts running close to a third periodic shape after a moment. This oscillation continues as t increases. Actually, up to t = 1.2 × 105, the orbit is bounded and keeps oscillating between periodic shapes and irregular motions.
8
Mimura, Nubuo, Yukinori Otsuka, and Akira Watanabe. "LABORATORY STUDY ON TWO-DIMENSIONAL BEACH TRANSFORMATION DUE TO IRREGULAR WAVES." Coastal Engineering Proceedings 1, no. 20 (January 29, 1986): 102. http://dx.doi.org/10.9753/icce.v20.102.
Abstract:
In the present study, effects of irregular waves on two-dimensional beach transformation and related phenomena were investigated through a series of laboratory experiments. Attempts were made to determine a representative wave of irregular wave trains which controlled individual phenomenon related to the two-dimensional beach profile change. It was found that the representative wave is different for each phenomenon. For the macroscopic beach profile change, it is the mean wave which represents whole incident waves. On the other hand, some of microscopic phenomena, such as initiation of sand movement and sand ripple formation, are controlled by larger waves in the wave train selectively, of which representative wave is the significant wave.
9
Yan, Duokui, Rongchang Liu, Xingwei Hu, Weize Mao, and Tiancheng Ouyang. "New Phenomena in the Spatial Isosceles Three-Body Problem with Unequal Masses." International Journal of Bifurcation and Chaos 25, no. 12 (November 2015): 1550169. http://dx.doi.org/10.1142/s0218127415501692.
Abstract:
This work studies periodic orbits as action minimizers in the spatial isosceles three-body problem with mass [Formula: see text]. In each period, the body with mass [Formula: see text] moves up and down on a vertical line, while the other two bodies have the same mass [Formula: see text], and rotate about this vertical line symmetrically. For given [Formula: see text], such periodic orbits form a one-parameter set with a rotation angle [Formula: see text] as the parameter. [Formula: see text]Two new phenomena are found for this set. First, for each [Formula: see text], this set of periodic orbits bifurcate from a circular Euler (central configuration) orbit to a Broucke (collision) orbit as [Formula: see text] increases from [Formula: see text] to [Formula: see text]. There exists a critical rotation angle [Formula: see text], where the orbit is a circular Euler orbit if [Formula: see text]; a spatial orbit if [Formula: see text]; and a Broucke (collision) orbit if [Formula: see text]. The exact formula of [Formula: see text] is numerically proved to be [Formula: see text]. Second, oscillating behaviors occur at rotation angle [Formula: see text] for all [Formula: see text]. Actually, the orbit with [Formula: see text] runs on its initial periodic shape for only a few periods. It breaks the first periodic shape and becomes irregular in a moment. However, it runs close to a different periodic shape after a while. In a short time, it falls apart from the second periodic shape and runs irregularly again. Such oscillation continues as time [Formula: see text] increases. Up to [Formula: see text], the orbit is bounded and keeps oscillating between periodic shapes and irregular motions. Further study implies that, for each [Formula: see text], the angle between any two consecutive periodic shapes is a constant. When [Formula: see text], similar oscillating behaviors are expected.
10
Yugay, Klimentiy, Nikolay Blinov, and Igor Shirokov. "Dynamical chaos and macroscopic quantum phenomena in long Josephson junctions." Izvestiya VUZ. Applied Nonlinear Dynamics 9, no. 2 (2001): 51–59. http://dx.doi.org/10.18500/0869-6632-2001-9-2-51-59.
Abstract:
It is shown, that the quantum number characterizing the flux in asymptotic stationary states of a long Josephson junction is integer. The quantum number is both integer and half-integer in nonstationary states. Transitions between states and lifetime of any states have an irregular character in dynamical chaos states.
Dissertations / Theses on the topic "Irregular phenomena":
1
Teixeira, Nicácio De Messias Alan. "Stochastic Analysis of non-Markovian irregular phenomena." Electronic Thesis or Diss., Institut polytechnique de Paris, 2022. http://www.theses.fr/2022IPPAE006.
Abstract:
Cette thèse se concentre sur certains aspects d'analyse stochastique de modèles non-markoviens irréguliers. On formule existence et unicité pour certains problèmes de martingales impliquant deux types de dérive irrégulière perturbée par des fonctionnelles dépendant de la trajectoire. Dans le premier cas, on considère le cas où la dérive est la dérivée d'une fonction continue: le modèle correspondant est celui de milieux aléatoires irréguliers dépendant de la trajectoire. Le second concerne le cas où la dérive est celui d'un processus de Bessel en basse dimension: dans ce cas il est bien connu qu'en général les processus ne sont pas des semimartingales. Enfin la thèse explore également des relations et des analogies entre la théorie des chemins rugueux et le calcul stochastique via régularisationThis thesis focuses on some particular stochastic analysis aspects of non-Markovian irregular phenomena. It formulates existence and uniqueness for some martingale problems involving two types of irregulat drifts perturbed by path-dependant functionals: the first one is related to the case which is the derivative of continuous function and it models irregular path-dependent media; the second one concerns the case when the drift is of Bessel type in low dimension. Finally the thesis also focuses on rough paths techniques and its relation with the stochastic calculus via regularization
2
Roche, Jean-Marie. "Tendances d'un phenomene irregulier ; definition et caracterisation." Reims, 1995. http://www.theses.fr/1995REIMS006.
Abstract:
L'etude de phenomenes evoluant au cours du temps de facon chaotique (turbulence, meteotologie, fluctuations de la bourse) implique tot ou tard la recherche d'une tendance, c'est-a-dire d'une courbe moyenne representant l'allure generale de leur evolution. Si l'homme sait tracer a main levee et de facon intuitive une telle courbe, sa determination objective est beaucoup plus delicate. Les methodes mises a la disposition du physicien ou de l'economiste sont nombreuses et variees, mais elles sont toutes plus ou moins arbitraires dans la mesure ou elles laissent a l'utilisateur le choix d'un ou de plusieurs parametres. Ces remarques ont conduit a la recherche d'une methode autoadaptative, objective, ne laissant pas a l'experimentateur la possibilite de faire prevaloir ses souhaits dans le resultat final. Le principe retenu consiste a definir un parametre, l'indice de non linearite (inl) decrivant l'allure plus ou moins tourmentee du graphe representatif du fichier dont on cherche a determiner la tendance. Apres application d'un operateur de lissage de type passe-bas symetrique, on suit l'evolution de l'inl en fonction du degre de lissage effectue. Un critere, base sur le principe de moindre action, permet la quantification de celui-ci et la determination d'une echelle d'observation. A chaque valeur de l'echelle d'observation est associee une tendance partielle. La tendance ultime, correspondant a la plus grande valeur de l'echelle, traduit l'evolution globale du phenomene. La methode proposee a ete testee avec succes sur des fichiers de mesures de natures tres diverses. Elle est applicable sans reserve au cas des fichiers bruites. L'utilisation d'un echantillonnage par linearisation n'affecte pas l'echelle d'observation
3
Neto, Apiano Ferreira de Morais. "Escoamento de fluidos complexos e transporte de partÃculas em geometrias irregulares." Universidade Federal do CearÃ, 2011. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=5889.
Abstract:
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoNeste trabalho, foram estudados vÃrios tipos de escoamentos laminares de fluidos incompressÃveis Newtonianos e nÃo-Newtonianos. Isto foi feito atravÃs do estudo da interaÃÃo destes escoamentos com geometrias complexas atravÃs de modelagem computacional e da soluÃÃo numÃrica das equaÃÃes de conservaÃÃo do momento e continuidade de massa. Numa primeira etapa, a modelagem computacional de uma rede de poros foi usada para a gerar padrÃes de agregados granulares resultando de mecanismos de erosÃo-deposiÃÃo de grÃos leves. A geometria da rede de poros foi alterada dinamicamente de acordo com a transferÃncia de momento do escoamento para as partÃculas localizadas em cada vÃrtice da rede de poros. Os resultados mostraram que, para esse processo irreversÃvel, o modelo foi capaz de reproduzir padrÃes tÃpicos de processos de erosÃo bem-conhecidos. Numa segunda etapa, um separador de partÃculas semelhante à estrutura pulmonar foi proposto com base nas propriedades de escoamento em uma estrutura ramificada e nas propriedades de transporte inercial das partÃculas, quantificadas atravÃs do nÃmero de Stokes. Os resultados indicaram que a variaÃÃo dos parÃmetros de construÃÃo da estrutura ramificada leva a um regime eficiente do processo de separaÃÃo em um amplo espectro de valores do nÃmero de Stokes. Por Ãltimo, o escoamento de vÃrios fluidos nÃo-Newtonianos atravÃs de meios porosos desordenados em trÃs-dimensÃes foi estudado. Os resultados mostraram, para fluidos do tipo lei-de-potÃncia, que o escoamento pode ser descrito como uma curva universal se o nÃmero de Reynolds e a permeabilidade hidrÃulica forem redefinidos de maneira apropriada. Fluidos de Bingham tambÃm foram estudados atravÃs do modelo de Herschel-Bulkley. Neste caso, as simulaÃÃes revelaram que as interaÃÃes entre a geometria complexa do espaÃo poroso, as propriedades reolÃgicas do fluido e os efeitos inerciais do escoamento sÃo responsÃveis por uma melhora substancial da permeabilidade hidrÃulica do sistema em valores intermediÃrios do nÃmero de Reynolds.
In this work many types of incompressible laminar Newtonian and Non-Newtonian flows are studied. The interplay of these flows with complex geometries was investigated using computational modeling and numerical solution of the conservation of momentum and mass continuity equations. As a first step, the computational modeling of a network of pores was adopted to reveal the formation patterns caused by the mechanism of erosion-deposition of light grains. The geometry of the pore network was changed dynamically according to the flow momentum transfer for particles located on each vertex of the pore network. The results showed that, for this irreversible processes, the model is capable of reproducing patterns of formation of well-known erosion processes. In a second step, a particle separator inspired on the lung structure was proposed based on the flow properties in a branched structure and transport of inertial particles, quantified in terms of the Stokes number. The results indicated that the variation of construction parameters of the branched structure leads to an efficient design of the separation process in a wide range of values of the Stokes number. Finally, the flow of non-Newtonian fluids through three-dimensional disordered porous media has been studied. The results showed, for power-law fluids that the flow can de described as a universal curve if the Reynolds number and the hydraulic permeability are redefined properly. The flow of Bingham fluids was also studied using the model of Herschel-Bulkley. In this case, the simulations showed that the interaction between the complex geometry of the pore space, the rheological properties of the fluid and the inertial effects of the flow is responsible for a substantial improvement of the hydraulic permeability of the system at intermediate values of the Reynolds number.
4
Stamenova, Teodora Lachezarova. "Uma Diretiva de Exclusão numa disfarçada política de harmonização- Diretiva 2008/115/CE." Master's thesis, 2019. http://hdl.handle.net/10316/86463.
Abstract:
Dissertação de Mestrado em Ciências Jurídico-Forenses apresentada à Faculdade de DireitoA crescente atenção em torno do direito migratório, nos últimos vinte anos, em função da complexidade da gestão de uma política migratória eficaz pelos EM, num espaço europeu sem fronteiras internas e com uma fronteira externa comum, teve como consequência a transferência da competência sobre vários domínios da imigração para a União Europeia. As exigências de funcionamento de um mercado interno comum e o estabelecimento de um direito à livre circulação, dos cidadãos europeus e dos cidadãos do espaço Schengen, ditou a necessidade, estipulada pelo Tratado de Lisboa, de criar uma política de imigração comum. Foi, pois, com base nas atribuições que decorrem da execução dessa política, que foi aprovada pelo Parlamento Europeu e pelo Conselho a Diretiva 2008/115/UE, de 16 de dezembro de 2018.A referida Diretiva, conhecida como “Diretiva Retorno”, é o objeto do presente estudo.A crescente atenção em torno do direito migratório, nos últimos vinte anos, em função da complexidade da gestão de uma política migratória eficaz pelos EM, num espaço europeu sem fronteiras internas e com uma fronteira externa comum, teve como consequência a transferência da competência sobre vários domínios da imigração para a União Europeia. As exigências de funcionamento de um mercado interno comum e o estabelecimento de um direito à livre circulação, dos cidadãos europeus e dos cidadãos do espaço Schengen, ditou a necessidade, estipulada pelo Tratado de Lisboa, de criar uma política de imigração comum. Foi, pois, com base nas atribuições que decorrem da execução dessa política, que foi aprovada pelo Parlamento Europeu e pelo Conselho a Diretiva 2008/115/UE, de 16 de dezembro de 2018.A referida Diretiva, conhecida como “Diretiva Retorno”, é o objeto do presente estudo.
The growing focus on migration law, over the last twenty years, because of the complexity of managing an effective migration policy by MS, in a European area without internal borders and with a common external border, has resulted in the transfer of competence over a number of areas of immigration to the European Union.The exigencies or demands for an operative common internal market and the establishment of a right to freedom of movement, for European citizens and for the citizens of the Schengen area, have dictated the need for a common immigration policy, laid down in the Treaty of Lisbon. It was therefore on the basis of the powers resulting from the implementation of this policy that Directive 2008/115 / EU of 16 December 2018 was approved by the European Parliament and the Council.This Directive, known as the "Return Directive", is the subject of the present study.The growing focus on migration law, over the last twenty years, because of the complexity of managing an effective migration policy by MS, in a European area without internal borders and with a common external border, has resulted in the transfer of competence over a number of areas of immigration to the European Union.The exigencies or demands for an operative common internal market and the establishment of a right to freedom of movement, for European citizens and for the citizens of the Schengen area, have dictated the need for a common immigration policy, laid down in the Treaty of Lisbon. It was therefore on the basis of the powers resulting from the implementation of this policy that Directive 2008/115 / EU of 16 December 2018 was approved by the European Parliament and the Council.This Directive, known as the "Return Directive", is the subject of the present study.
5
Gagnon, Jean-François. "Caractère intrinsèque des matrices de Stokes." Thèse, 2015. http://hdl.handle.net/1866/13444.
Abstract:
Il est connu qu’une équation différentielle linéaire,
x^(k+1)Y' = A(x)Y,
au voisinage d’un point singulier irrégulier non-résonant est uniquement déterminée
(à isomorphisme analytique près) par :
(1) sa forme normale formelle,
(2) sa collection de matrices de Stokes.
La définition des matrices de Stokes fait appel à un ordre sur les parties réelles
des valeurs propres du système, ordre qui peut être perturbé par une rotation en
x. Dans ce mémoire, nous avons établi le caractère intrinsèque de cette relation :
nous avons donc établi comment la nouvelle collection de matrices de Stokes obtenue
après une rotation en x qui change l’ordre des parties réelles des valeurs
propres dépend de la collection initiale.
Pour ce faire, nous donnons un chapitre de préliminaires généraux sur la forme
normale des équations différentielles ordinaires puis un chapitre sur le phénomène
de Stokes pour les équations différentielles linéaires. Le troisième chapitre contient
nos résultats.It is well known that a linear differential equation, x^(k+1)Y' = A(x)Y, near a non-resonant irregular singular point is uniquely determined (up to analytic isomorphism) by : (1) its formal normal form, (2) the collection of its Stokes matrices. By definition, the Stokes matrices depend on an order defined on the real parts of the eigenvalues of the system which can be perturbed by a rotation in the x coordinate. In this paper, we have established the intrinsic character of the dependency : we have described how the new Stokes collection is obtained from the first collection after a rotation in x which changes the order on the real parts of the eigenvalues. The first chapter contains preliminaries concerning the normal form of an ordinary differential equation and a chapter on the Stokes phenomenon for linear differential equations. The third chapter contains our results.
6
Lambert, Caroline. "Classification analytique de systèmes différentiels linéaires déployant une singularité irrégulière de rang de Poincaré 1." Thèse, 2010. http://hdl.handle.net/1866/4430.
Abstract:
Cette thèse traite de la classification analytique du déploiement de systèmes différentiels linéaires ayant une singularité irrégulière. Elle est composée de deux articles sur le sujet: le premier présente des résultats obtenus lors de l'étude de la confluence de l'équation hypergéométrique et peut être considéré comme un cas particulier du second; le deuxième contient les théorèmes et résultats principaux.
Dans les deux articles, nous considérons la confluence de deux points singuliers réguliers en un point singulier irrégulier et nous étudions les conséquences de la divergence des solutions au point singulier irrégulier sur le comportement des solutions du système déployé. Pour ce faire, nous recouvrons un voisinage de l'origine (de manière ramifiée) dans l'espace du paramètre de déploiement $\epsilon$. La monodromie d'une base de solutions bien choisie est directement reliée aux matrices de Stokes déployées. Ces dernières donnent une interprétation géométrique aux matrices de Stokes, incluant le lien (existant au moins pour les cas génériques) entre la divergence des solutions à $\epsilon=0$ et la présence de solutions logarithmiques autour des points singuliers réguliers lors de la résonance. La monodromie d'intégrales premières de systèmes de Riccati correspondants est aussi interprétée en fonction des éléments des matrices de Stokes déployées.
De plus, dans le second article, nous donnons le système complet d'invariants analytiques pour le déploiement de systèmes différentiels linéaires $x^2y'=A(x)y$ ayant une singularité irrégulière de rang de Poincaré $1$ à l'origine au-dessus d'un voisinage fixé $\mathbb{D}_r$ dans la variable $x$. Ce système est constitué d'une partie formelle, donnée par des polynômes, et d'une partie analytique, donnée par une classe d'équivalence de matrices de Stokes déployées. Pour chaque valeur du paramètre $\epsilon$ dans un secteur pointé à l'origine d'ouverture plus grande que $2\pi$, nous recouvrons l'espace de la variable, $\mathbb{D}_r$, avec deux secteurs et, au-dessus de chacun, nous choisissons une base de solutions du système déployé. Cette base sert à définir les matrices de Stokes déployées. Finalement, nous prouvons un théorème de réalisation des invariants qui satisfont une condition nécessaire et suffisante, identifiant ainsi l'ensemble des modules.This thesis deals with the analytic classification of unfoldings of linear differential systems with an irregular singularity. It contains two papers related to this subject: the first paper presents results concerning the confluence of the hypergeometric equation and may be viewed as a particular case of the second one; the second paper contains the main theorems and results. In both papers, we study the confluence of two regular singular points into an irregular one and we give consequences of the divergence of solutions at the irregular singular point for the unfolded system. For this study, a full neighborhood of the origin is covered (in a ramified way) in the space of the unfolding parameter $\epsilon$. Monodromy of a well chosen basis of solutions around the regular singular points is directly linked to the unfolded Stokes matrices. These matrices give a complete geometric interpretation to the well-known Stokes matrices: this includes the link (existing at least for the generic cases) between the divergence of the solutions at $\epsilon=0$ and the presence of logarithmic terms in the solutions for resonant values of $\epsilon$. Monodromy of first integrals of related Riccati systems are also interpreted in terms of the elements of the unfolded Stokes matrices. The second paper goes further into the subject, giving the complete system of analytic invariants for the unfoldings of nonresonant linear differential systems $x^2y'=A(x)y$ with an irregular singularity of Poincaré rank $1$ at the origin over a fixed neighborhood $\mathbb{D}_r$ in the space of the variable $x$. It consists of a formal part, given by polynomials, and an analytic part, given by an equivalence class of unfolded Stokes matrices. For each parameter value $\epsilon$ taken in a sector pointed at the origin of opening larger than $2\pi$, we cover the space of the variable, $\mathbb{D}_r$, with two sectors and, over each of them, we construct a well chosen basis of solutions of the unfolded differential system. This basis is used to define the unfolded Stokes matrices. Finally, we give a realization theorem for the invariants satisfying a necessary and sufficient condition, thus identifying the set of modules.
7
Klimes, Martin. "Unfolded singularities of analytic differential equations." Thèse, 2014. http://hdl.handle.net/1866/11090.
Abstract:
La thèse est composée d’un chapitre de préliminaires et de deux articles sur le sujet
du déploiement de singularités d’équations différentielles ordinaires analytiques dans
le plan complexe.
L’article Analytic classification of families of linear differential systems unfolding
a resonant irregular singularity traite le problème de l’équivalence analytique
de familles paramétriques de systèmes linéaires en dimension 2 qui déploient une
singularité résonante générique de rang de Poincaré 1 dont la matrice principale est
composée d’un seul bloc de Jordan. La question: quand deux telles familles sontelles
équivalentes au moyen d’un changement analytique de coordonnées au voisinage
d’une singularité? est complètement résolue et l’espace des modules des classes
d’équivalence analytiques est décrit en termes d’un ensemble d’invariants formels
et d’un invariant analytique, obtenu à partir de la trace de la monodromie. Des
déploiements universels sont donnés pour toutes ces singularités.
Dans l’article Confluence of singularities of non-linear differential equations via
Borel–Laplace transformations on cherche des solutions bornées de systèmes paramétriques
des équations non-linéaires de la variété centre de dimension 1 d’une singularité
col-noeud déployée dans une famille de champs vectoriels complexes. En
général, un système d’ÉDO analytiques avec une singularité double possède une
unique solution formelle divergente au voisinage de la singularité, à laquelle on peut
associer des vraies solutions sur certains secteurs dans le plan complexe en utilisant
les transformations de Borel–Laplace. L’article montre comment généraliser
cette méthode et déployer les solutions sectorielles. On construit des solutions de
systèmes paramétriques, avec deux singularités régulières déployant une singularité
irrégulière double, qui sont bornées sur des domaines «spirals» attachés aux deux
points singuliers, et qui, à la limite, convergent vers une paire de solutions sectorielles
couvrant un voisinage de la singularité confluente. La méthode apporte une
description unifiée pour toutes les valeurs du paramètre.The thesis is composed of a chapter of preliminaries and two articles on the theme of unfolding of singularities of analytic differential equations in a complex domain. They are both related to the problem of local analytic classification of parametric families of linear systems: When two parametric families of linear systems are equivalent by means of an analytic change of coordinates in a neighborhood of the singularity? The article Analytic classification of families of linear differential systems unfolding a resonant irregular singularity deals with the question of analytic equivalence of parametric families of systems of linear differential equations in dimension 2 unfolding a generic resonant singularity of Poincaré rank 1 whose leading matrix is a Jordan bloc. The problem is completely solved and the moduli space of analytic equivalence classes is described in terms of a set of formal invariants and a single analytic invariant obtained from the trace of the monodromy. Universal unfoldings are provided for all such singularities. The article Confluence of singularities of non-linear differential equations via Borel-Laplace transformations investigates bounded solutions of systems of differential equations describing a 1-dimensional center manifold of an unfolded saddle-node singularity in a family of complex vector fields. Generally, a system of analytic ODE at a double singular point possesses a unique formal solution in terms of a divergent power series. The classical Borel summation method associates to it true solutions that are asymptotic to the series on certain sectors in the complex plane. The article shows how to unfold the Borel and Laplace integral transformations of the summation procedure. A new kind of solutions of parameter dependent systems of ODE with two simple (regular) singular points unfolding a double (irregular) singularity are constructed, which are bounded on certain “spiraling” domains attached to both singular points, and which at the limit converge uniformly to a pair of the classical sectorial solutions. The method provides a unified treatment for all values of parameter.
Books on the topic "Irregular phenomena":
1
August, Heydte Friedrich. Modern irregular warfare: In defense policy and as a military phenomenon. New York, N.Y: New Benjamin Franklin House, 1986.
2
Plümmer, Franziska. Rethinking Authority in China’s Border Regime. NL Amsterdam: Amsterdam University Press, 2022. http://dx.doi.org/10.5117/9789463726351.
Abstract:
In the 21st century, governments around the globe are faced with the question on how to tackle new migratory mobilities. Governments increasingly become aware of irregular immigration and are forced to re-negotiate the dilemma of open but secure borders. Rethinking Authority in China’s Border Regime: Regulating the Irregular investigates the Chinese government’s response to this phenomenon. Hence, this book presents a comprehensive analysis of the Chinese border regime. It explores the regulatory framework of border mobility in China by analysing laws, institutions, and discourses as part of an ethnographic border regime analysis. It argues that the Chinese state deliberately creates ‘zones of exception’ along its border. In these zones, local governments function as ‘scalar managers’ that establish cross-border relations to facilitate cross-border mobility and create local migration systems that build on their own notion of legality by issuing locally valid border documents. The book presents an empirically rich story of how border politics are implemented and theoretically contributes to debates on territoriality and sovereignty as well as to the question of how authority is exerted through border management. Empirically, the analysis builds on two case studies at the Sino-Myanmar and Sino-North Korean borders to illustrate how local practices are embedded in multiscalar mobility regulation including regional organizations such as the Greater Mekong Subregion and the Greater Tumen Initiative.
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Koser, Khalid. 5. Irregular migration. Oxford University Press, 2016. http://dx.doi.org/10.1093/actrade/9780198753773.003.0005.
Abstract:
‘Irregular migration’ explores migration outside of established legal means. There are many ways for a migrant to be classed as irregular, but their motivations for leaving are the same as other migrants. Irregular migration is often seen as a threat to host nation sovereignty and, as a result, migrants are often subjected to stereotyping and xenophobia. Migrants—particularly women and children—face great hazards in simply entering the country. A multi-billion dollar industry has developed around the desire of people to move despite legal restrictions, in the form of human trafficking and migrant smuggling. These phenomena occur in all regions, and incur massive costs—and dangers—to irregular migrants.
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Succi, Sauro. LBE Flows in Disordered Media. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199592357.003.0019.
Abstract:
The study of transport phenomena in disordered media is a subject of wide interdisciplinary concern, with many applications in fluid mechanics, condensed matter, life and environmental sciences as well. Flows through grossly irregular (porous) media is a specific fluid mechanical application of great practical value in applied science and engineering. It is arguably also one of the applications of choice of the LBE methods. The dual field–particle character of LBE shines brightly here: the particle-like nature of LBE (populations move along straight particle trajectories) permits a transparent treatment of grossly irregular geometries in terms of elementary mechanical events, such as mirror and bounce-back reflections. These assets were quickly recognized by researchers in the field, and still make of LBE (and eventually LGCA) an excellent numerical tool for flows in porous media, as it shall be discussed in this Chapter.
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Barros, Rodrigo José Saraiva de, Tereza Cristina de Brito Azevedo, Carla de Castro Sant’Anna, Marianne Rodrigues Fernandes, Leticia Martins Lamarão, and Rommel Mario Rodríguez Burbano. Grupos sanguíneos e anticorpos anti-eritrocitários de importância transfusional. Brazil Publishing, 2020. http://dx.doi.org/10.31012/978-65-5861-112-7.
Abstract:
Immunohematology is an area dedicated to the study of the interactions of the immune system and blood cells in transfusion practice. Blood transfusion is a therapeutic technique that has been widely used since the 17th century. The transfusion medicine aims to repair the pathological needs of blood components in the living organism, be it red blood cells, plasma, platelets, clotting factors, among others. Despite being a therapeutic means, transfusion of blood components can be considered at risk because it is a biological material and due to the transfusion immunological reactions that can be caused during or after the moment of transfusion. In the surface structure of red blood cells, numerous molecules of a protein, glycoprotein or glycolipid nature are found, which are also called membrane antigens that make up structures and perform transport functions, as receptors, as adhesion, enzymatic and / or complement regulatory molecules. The formation of these antigens occurs by an approximate amount of 39 genes involved in their production, of which 282 different antigens are organized in more than 30 blood group systems. This antigenic diversity is a major cause of the formation of irregular anti-erythrocyte antibodies. Therefore, with the increase in blood transfusions in surgeries, transplants and clinical treatment of cancer and other chronic diseases, a significant increase in the occurrence of alloimmunizations in polytransfused patients began to be observed. Such biological phenomena motivated us to carry out this study and the antigenic diversity motivated us to elaborate this small compendium where we also describe the main blood groups.
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Temperley, David. Melody. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190653774.003.0005.
Abstract:
Like melody in general, rock melody is understood to have a hierarchical “grouping structure,” with sub-phrases combining into phrases and then into larger units. A fundamental issue in rock melody is the alignment of melodic groups with meter; while “beginning-accented” groups are the norm, “end-accented” patterns and more irregular patterns also occur. Patterns of repetition—pitch and rhythmic repetition, as well as rhyme—are also important aspects of rock melody. Rock melody sometimes shows independence from the underlying harmony, a phenomenon known as “melodic-harmonic divorce.” Of particular interest is the use of the 3 and flat-3 scale degrees, which are sometimes used in rock melodies in close proximity; related to this is the issue of “blue notes,” notes which fall between the cracks of conventional chromatic-scale categories.
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Forrest, Stephen R. Organic Electronics. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198529729.001.0001.
Abstract:
Organic electronics is a platform for very low cost and high performance optoelectronic and electronic devices that cover large areas, are lightweight, and can be both flexible and conformable to irregularly shaped surfaces such as foldable smart phones. Organics are at the core of the global organic light emitting device (OLED) display industry, and also having use in efficient lighting sources, solar cells, and thin film transistors useful in medical and a range of other sensing, memory and logic applications. This book introduces the theoretical foundations and practical realization of devices in organic electronics. It is a product of both one and two semester courses that have been taught over a period of more than two decades. The target audiences are students at all levels of graduate studies, highly motivated senior undergraduates, and practicing engineers and scientists. The book is divided into two sections. Part I, Foundations, lays down the fundamental principles of the field of organic electronics. It is assumed that the reader has an elementary knowledge of quantum mechanics, and electricity and magnetism. Background knowledge of organic chemistry is not required. Part II, Applications, focuses on organic electronic devices. It begins with a discussion of organic thin film deposition and patterning, followed by chapters on organic light emitters, detectors, and thin film transistors. The last chapter describes several devices and phenomena that are not covered in the previous chapters, since they lie outside of the current mainstream of the field, but are nevertheless important.
Book chapters on the topic "Irregular phenomena":
1
Jurčák, J., M. Sobotka, and V. Martínez-Pillet. "Velocity Fields in an Irregular Sunspot." In Solar Magnetic Phenomena, 227–30. Dordrecht: Springer Netherlands, 2005. http://dx.doi.org/10.1007/1-4020-2962-4_22.
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Unno, W., and D. R. Xiong. "One Zone Modeling of Irregular Variability of Stellar Convective Envelope." In Nonlinear Phenomena in Stellar Variability, 77–81. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1062-4_7.
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Kim, Hyung Ick, Yong Huh, and Chang Sung Seok. "Fatigue Life Evaluation of an Actual Structure under the Irregular Loading Using an Acceleration Test." In Solid State Phenomena, 9–14. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/3-908451-29-9.9.
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Jayanti, Sreenivas. "Dealing with Irregular Flow Domains and Complex Physical Phenomena." In Computational Fluid Dynamics for Engineers and Scientists, 271–345. Dordrecht: Springer Netherlands, 2018. http://dx.doi.org/10.1007/978-94-024-1217-8_6.
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Mendil, Samir, and Taoufik Aguili. "Global Modelling of Diffraction Phenomena by Irregular Shapes with Hybrid MOM-GTD Method." In Ubiquitous Networking, 110–21. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-58008-7_9.
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Jaroszewicz, Leszek R., Anna Kurzych, Zbigniew Krajewski, Jerzy K. Kowalski, and Krzysztof P. Teisseyre. "FOSREM: Fibre-Optic System for Rotational Events and Phenomena Monitoring: Construction, Investigation and Area of Application." In Seismic Behaviour and Design of Irregular and Complex Civil Structures II, 49–64. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-14246-3_5.
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Spencer, Sarah, and Anna Triandafyllidou. "Irregular Migration." In IMISCOE Research Series, 191–204. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92377-8_12.
Abstract:
AbstractIrregular migration is a multifaceted, dynamic phenomenon that has attracted disproportionate media and political attention since the early 2000s. It has been at the forefront of the political debate in most of the European Union’s Member States since the outbreak of the so-called ‘migration crisis’ of 2015. Indeed, the political attention paid to irregular migration is disproportionate to its volume. Migrants are estimated to represent 3.3% of the world’s population (IOM, 2017, from UNDESA, 2017) with migrants in an irregular situation between 15% and 20% of them. This is approximately 1% of the global population, some 30–40 million individuals worldwide (UN OHCHR, 2014; ILO, 2015). In the USA, the undocumented population was estimated in 2015 to be 11 million (Rosenblum & Ruiz Soto, 2015); while in Europe it was estimated to be 1.9–3.8 million in 2008 (Kovacheva & Vogel, 2009); and between 2.9 and 3.8 million in 2018 (Pew Research Centre, 2019).
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Ambrosini, Maurizio, and Minke H. J. Hajer. "Defining and Explaining Irregular Migration." In IMISCOE Research Series, 15–37. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-30838-3_2.
Abstract:
AbstractInternational migration has become a crucial issue on the political agenda around the world. Yet it is still difficult to define the phenomenon of irregular migration precisely and to determine which immigrants exactly fall within this definition. Therefore, this chapter will discuss the issue of defining irregular migration. Moreover, it will provide various explanations for irregular migration and why it is so difficult to eradicate it in democratic states with market economies. We will identify six main reasons for the presence of irregular migrants in receiving countries, concluding that irregular migration mirrors several societal contradictions rather than being an effect of external pressure.
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Gustavsson, M., Hideaki Nagai, and Takeshi Okutani. "Characterization of Anisotropic and Irregularly-Shaped Materials by High-Sensitive Thermal Conductivity Measurements." In Solid State Phenomena, 1641–44. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/3-908451-31-0.1641.
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Ambrosini, Maurizio, and Minke H. J. Hajer. "Conclusion: Envisioning Better Governance of Irregular Migration." In IMISCOE Research Series, 141–51. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-30838-3_7.
Abstract:
AbstractIrregular migration is a multifaceted phenomenon that comprises various perspectives, policies, and actors. This concluding chapter sums up some key findings of research on such a contentious issue. It will discuss a narrative for irregular migration beyond the idea of ‘invasion’, so frequently employed by anti-immigrant actors in developed countries, and elaborate on why implementing policies that categorically exclude migrants is difficult. We argue in the chapter that the main reason for this difficulty is that irregular immigration is not only a force stemming from the outside; it is also deeply embedded in the internal dynamics of receiving societies. From this perspective, the fight against irregular migration is not a categorical exclusion; instead, it is a tacit selection which targets some cases with fierce determination while implicitly but systematically condoning others. Moreover, we show that irregular migration finds a way to carve out a place in receiving societies, circumventing controls or enjoying tolerance, because it is situated at the intersection among different societal factors. Among them, together with labour market’s demand, solidarity by civil societies warrants attention. We use the concept of ‘debordering solidarity’ to indicate the solidarity that overcomes the distinction between citizens and non-citizens, authorised and non-authorised migrants, and that gives priority to human rights and people’s needs.
Conference papers on the topic "Irregular phenomena":
1
ANDRADE, J. S., H. F. DA SILVA, E. A. HENRIQUE, and B. SAPOVAL. "ON THE ACTIVITY OF ABSORBING IRREGULAR INTERFACES." In Fractals and Related Phenomena in Nature. WORLD SCIENTIFIC, 2004. http://dx.doi.org/10.1142/9789812702746_0003.
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Konoshonkin, Alexander V., Natalia V. Kustova, and Anatoli G. Borovoi. "Interference phenomena at backscattering by ice crystals of irregular shape." In XXI International Symposium Atmospheric and Ocean Optics. Atmospheric Physics, edited by Oleg A. Romanovskii. SPIE, 2015. http://dx.doi.org/10.1117/12.2204872.
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Bailey, Sean C. C., Gregory A. Kopp, and Robert J. Martinuzzi. "THE IRREGULAR VORTEX SHEDDING REGIME FOR A SQUARE CYLINDER WAKE NEAR A WALL." In Second Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 2001. http://dx.doi.org/10.1615/tsfp2.1800.
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Haaland, Peter, and James Targove. "Flowing Afterglow Synthesis of Polythiophene Films." In Nonlinear Guided-Wave Phenomena. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/nlgwp.1991.tue4.
Abstract:
Polymers of aromatic heterocycles such as thiophene and pyrrole have been actively investigated for their promising electrical and optical characteristics. However the use of these materials in waveguide structures has been constrained by morphological and synthetic barriers. Specifically, larger oligomers are less soluble causing multiphase chemical kinetics and irregular morphology in the metal-catalyzed coupling syntheses.fi] Electrochemical preparation methods also produce grainy or fibrillar material, most probably because the heterogeneous boundary conditions on film growth change as insulating or semi-conducting material is deposited on the electrodes. [2] We report here a synthetic approach to the polymeric heterocycle polythiophene using electronically excited argon metastables to activate organic precursors. This method is seen to produce dense, uniform films with desirable thiophene linkages and excellent optical properties.
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Chen, Z., Z. Q. Wu, and P. Yu. "Analysis on Critical Phenomena of a Hysteretic System." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-55000.
Abstract:
In this paper, a nonlinear mechanical system with external forcing is investigated to study the critical phenomena of the system. The system involves a von der Pol type damping and a hysteretic damper representing a restoring force. Numerical simulations are used to show that under an external exciting force, the hysteretic restoring force may not follow the routes described by a conventional form of piecewise function, but exhibit some irregular behavior. We call this unusual situation the critical phenomenon of the system. Simulations results suggest that a device with hysteretic property (e.g., the damper considered in this paper) may change its typical characteristics under external forcing. This new finding may enhance the study of nonlinear dynamical systems with hysteretic property under external excitement.
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Tamai, Naoto, Tomoko Yamazaki, Iwao Yamazaki, and Noboru Mataga. "Fractal Behaviors in Two-Dimensional Excitation Energy Transfer on Vesicle Surface." In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/up.1986.thb3.
Abstract:
Excitation energy transport and trapping in molecular assemblies have been the subject in recent theoretical and experimental photophysics. Very little is known about the dynamical characteristics of dipole-dipole energy transfer in restricted geometries of one- and two-dimensional molecular arrangements. The present paper reports on the two-dimensional excitation energy transfer between dye molecules adsorbed on vesicle surface by using a picosecond time-correlated, single-photon counting apparatus [1]. The fluorescence decay curves of the donor are analyzed on the basis of a theoretical framework of "fractal" [2], following a manner of Klafter and Blumen [3]. The fractal denotes a self-similar structure with dilatational symmetry which will have great potential to describe a multitude of irregular structures [2].
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Matheis, Jan, Bernd Budich, and Stefan Hickel. "LARGE EDDY SIMULATION OF THE TRANSITION PROCESS FROM REGULAR TO IRREGULAR SHOCK-WAVE/BOUNDARY-LAYER INTERACTION." In Eighth International Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 2013. http://dx.doi.org/10.1615/tsfp8.110.
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Chen, Y. C., H. G. Winful, and J. M. Liu. "Subharmonic Bifurcations and Irregular Pulsing Behavior of Modulated Diode Lasers." In Instabilities and Dynamics of Lasers and Nonlinear Optical Systems. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/idlnos.1985.wd8.
Abstract:
The problem of existence of lasing regimes characterized by an irregular response of a semiconductor laser to a periodic modulation of the injection current has been of considerable interest recently. Based on coupled nonlinear rate equations for carrier and photon densities, Lee et al (1) predicted a period doubling route to chaos in a directly modulated semiconductor laser as the modulation index increases. Kawaguchi(2) showed a similar route to chaos in the optical response of a directly modulated, self-pulsating semiconductor laser with a saturable absorber. While chaotic behavior has been experimentally observed in other lasers with modulated parameters3,4, chaos in a modulated diode laser still remains to be demonstrated. In this paper we report the observation of a subharmonic bifurcation and erratic behavior in the output of diode lasers subjected to deep modulation of the injection current. The experimentally measured bifurcation sequences differ considerably from the predicted scenarios. Non-deterministic quantum noise sources are believed to play an important role in the observed phenomena.
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Dai, Liming, and Guoqing Wang. "Diagnosing Irregularities of Nonlinear Dynamic Systems With Implementation of Periodicity-Ratio." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-66041.
Abstract:
Among the irregular responses of nonlinear dynamic systems, chaotic responses of nonlinear systems are probably the most attractive phenomena along with the new observations in the last decades. A nonlinear deterministic system may behavior chaotically under regular such as periodic excitations. Regular motion of a system subjected to periodic exertions is usually periodic. In contrast with regular motions, final states of chaotic vibrations are extremely nonperiodic. This research is to analyzing the irregular behavior of dynamic systems with implementation of a newly developed criterion named Periodicity-Ratio. The development of a methodology for diagnosing the irregular motions from the regular motions of a dynamic system is presented. The Periodicity-Ratio describes the degree of periodicity of motion and can be conveniently used to distinguish a nonperiodic motion from a regular vibration or oscillation and to diagnose whether or not a motion is chaotic and the other irregular responses of the nonlinear dynamic systems, without plotting any figures. The analyses on the irregular behavior of nonlinear dynamic systems with the implementation of the Periodicity-Ratio will be demonstrated.
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Glotov, O. G., D. Yu Belyaeva, N. S. Belousova, and M. A. Korchagin. "COMBUSTION CHARACTERISTICS OF LARGE POROUS TITANIUM PARTICLES FALLING FREELY IN AIR." In 9TH INTERNATIONAL SYMPOSIUM ON NONEQUILIBRIUM PROCESSES, PLASMA, COMBUSTION, AND ATMOSPHERIC PHENOMENA. TORUS PRESS, 2020. http://dx.doi.org/10.30826/nepcap9a-28.
Abstract:
The burning of titanium particles in air has recently attracted the serious attention of researchers [1, 2]. This work continues the present authors' studies of large (up to 700 um) titanium particles burning in the free fall in air [3-5]. The particles in [3] were monodisperse agglomerates formed of a large number of small irregular shape particles. In [4,5], a modified approach, which makes it possible to obtain initially monolithic burning titanium particles with a diameter up to 700 yum, was used.
Reports on the topic "Irregular phenomena":
1
Sorenson, T., M. B. Bryndum, and V. Jacobsen. L51522 Hydrodynamic Forces on Pipelines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), December 1986. http://dx.doi.org/10.55274/r0010276.
Abstract:
The aim of this study was to provide hydro-dynamic force coefficients applicable for the determination of forces on pipelines resting on the sea bed when exposed to wave and current flows. This has been achieved through an extensive model test program in which the parameters important for the phenomena have been investigated within wide ranges for a number of flow conditions including irregular waves. The results of the more than 1,000 individual tests have been presented in the form of non-dimensional coefficients determined from three distinctly different types of analysis. These coefficients have been presented as functions of the governing parameters in a series of easily accessible diagrams. The report contains three parts. Part I presents the results of the model test study and the comparison of these results with other data. Part II deals with force calculations in irregular waves, including a statistically based comparison of predictions using traditional and improved force expressions. Part III presents the results of the model tests with a partially buried pipe.
2
Godenau, Dirk, and Daniel Buraschi. Recent trends in irregular maritime immigration in the Canary Islands. Observatorio de la Inmigración de Tenerife. Departamento de Geografía e Historia. Universidad de La Laguna. Tenerife, 2020. http://dx.doi.org/10.25145/r.obitfact.2020.06.
Abstract:
The recent intensification in irregular maritime migrations in the Atlantic route through the Canary Islands, which is employed to reach the European mainland from Africa, coincides in time with the presence of the coronavirus pandemic and incorporates some novelties involving a flow that has been present in the archipelago’s evolution for almost three decades. It also exhibits many similarities with the permanent manifestation of this influx, even though the scant planning and weak response initially implemented in an effort to comprehensively manage this migration has placed the phenomenon at the forefront of the current affairs and debate in the region. As a result, a social context of enormous uncertainty due to the health and economic crisis, the direct and almost real-time knowledge of the outcome of many crossings thanks to social media, together with the confusion sown by how this mobility is being managed, all raise the need to reconsider its analysis in order to ascertain its current characteristics and keys to its understanding.
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Klein. PR-330-063503-R01 Characterization of Stress Corrosion Cracking Using Laser Ultrasonics. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 2008. http://dx.doi.org/10.55274/r0010908.
Abstract:
In-service inspection of gas and oil pipelines is a subject of great current interest.� Issues of safety and fitness for service have driven extensive efforts to develop effective monitoring and inspection techniques.� A number of effective NDT techniques have been developed for screening to identify regions of interest for more detailed evaluation.� The three anomalies of greatest interest are (1) corrosion, (2) mechanical damage and (3) stress corrosion cracking (SCC).� In this paper we will focus on the application of laser ultrasonics to the characterization of SCC. Stress corrosion cracking is the phenomenon in metals wherein the simultaneous presence of tensile stress, a corrosive environment and a susceptible metallurgy leads to the nucleation and propagation of highly irregular and complex cracks, usually found in closely spaced clusters or colonies. In pipelines, SCC has been a particularly elusive and challenging problem. � Several pipeline failures around the world have been attributed to SCC since its discovery in pipelines in the 1960s.� While the number of incidents attributed to SCC is less than those attributed to other threats to pipelines such as corrosion or mechanical damage, it constitutes a formidable challenge due to the following key reasons: ��� �No reliable and accurate inspection tools or predictive modeling based tools exist that are capable of determining what locations along the pipeline are affected by SCC. ��� �No reliable and widely accepted assessment tools exist for evaluation of SCC, once found. ��� �No reliable and widely accepted tools exist that are capable of measuring the depth of these cracks accurately. ��� �No generally accepted method for fitness for service evaluation of SCC exists.
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Tan, Peng, and Nicholas Sitar. Parallel Level-Set DEM (LS-DEM) Development and Application to the Study of Deformation and Flow of Granular Media. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, March 2023. http://dx.doi.org/10.55461/kmiz5819.
Abstract:
We present a systematic investigation of computational approaches to the modeling of granular materials. Granular materials are ubiquitous in everyday life and in a variety of engineering and industrial applications. Despite the apparent simplicity of the laws governing particle-scale interactions, predicting the continuum mechanical response of granular materials still poses extraordinary challenges. This is largely due to the complex history dependence resulting from continuous rearrangement of the microstructure of granular material, as well as the mechanical interlocking due to grain morphology and surface roughness. X-Ray Computed Tomography (XRCT) is used to characterize the grain morphology and the fabric of the granular media, naturally deposited sand in this study. The Level-Set based Discrete Element Method (LS-DEM) is then used to bridge the granular behavior gap between the micro and macro scale. The LS-DEM establishes a one-to-one correspondence between granular objects and numerical avatars and captures the details of grain morphology and surface roughness. However, the high-fidelity representation significantly increases the demands on computational resources. To this end a parallel version of LS-DEM is introduced to significantly decrease the computational demands. The code employs a binning algorithm, which reduces the search complexity of contact detection from O(n2) to O(n), and a domain decomposition strategy is used to elicit parallel computing in a memory- and communication-efficient manner. The parallel implementation shows good scalability and efficiency. High fidelity LS avatars obtained from XRCT images of naturally deposited sand are then used to replicate the results of triaxial tests using the new, parallel LS-DEM code. The result show that both micro- and macro-mechanical behavior of natural material is well captured and is consistent with experimental data, confirming experimental observation that the primary source of peak strength of sand is the mechanical interlocking between irregularly shaped grains. Specifically, triaxial test simulations with a flexible membrane produce a very good match to experimentally observed relationships between deviatoric stress and mobilized friction angle for naturally deposited sand. We then explore the viability of modeling dynamic problems with a new formulation of an impulse based LS-DEM. The new formulation is stable, fast, and energy conservative. However, it can be numerically stiff when the assembly has substantial mass differences between particles. We also demonstrate the feasibility of modeling deformable structures in the rigid body framework and propose several enhancements to improve the convergence of collision resolution, including a hybrid time integration scheme to separately handle at rest contacts and dynamic collisions. Finally, we extend the impulse-based LS-DEM to include arbitrarily shaped topographic surfaces and exploit its algorithmic advantages to demonstrate the feasibility of modeling realistic behavior of granular flows. The novel formulation significantly improves performance of dynamic simulations by allowing larger time steps, which is advantageous for observing the full development of physical phenomena such as rock avalanches, which we present as an illustrative example.