579 research outputs found
A mixed formulation for the direct approximation of the control of minimal -norm for linear type wave equations
No full textThis paper deals with the numerical computation of null controls for the wave equation with a potential. The goal is to compute approximations of controls that drive the solution from a prescribed initial state to zero at a large enough controllability time. In [\textit{Cindea, Fernandez-Cara \& Münch, Numerical controllability of the wave equation through primal methods and Carleman estimates, 2013}], a so called primal method is described leading to a strongly convergent approximation of boundary controls : the controls minimize quadratic weighted functionals involving both the control and the state and are obtained by solving the corresponding optimality condition. In this work, we adapt the method to approximate the control of minimal square-integrable norm. The optimality conditions of the problem are reformulated as a mixed formulation involving both the state and his adjoint. We prove the well-posedeness of the mixed formulation (in particular the inf-sup condition) then discuss several numerical experiments. The approach covers both the boundary and the inner controllability. For simplicity, we present the approach in the one dimensional case
A mixed formulation for the direct approximation of the control of minimal -norm for linear type wave equations
No full textThis paper deals with the numerical computation of null controls for the wave equation with a potential. The goal is to compute approximations of controls that drive the solution from a prescribed initial state to zero at a large enough controllability time. In [\textit{Cindea, Fernandez-Cara \& Münch, Numerical controllability of the wave equation through primal methods and Carleman estimates, 2013}], a so called primal method is described leading to a strongly convergent approximation of boundary controls : the controls minimize quadratic weighted functionals involving both the control and the state and are obtained by solving the corresponding optimality condition. In this work, we adapt the method to approximate the control of minimal square-integrable norm. The optimality conditions of the problem are reformulated as a mixed formulation involving both the state and his adjoint. We prove the well-posedeness of the mixed formulation (in particular the inf-sup condition) then discuss several numerical experiments. The approach covers both the boundary and the inner controllability. For simplicity, we present the approach in the one dimensional case
Controllability of the linear 1D-wave equation with inner moving forces
No full textThis paper deals with the numerical computation of distributed null controls for the 1D wave equation. We consider supports of the controls that may vary with respect to the time variable. The goal is to compute approximations of such controls that drive the solution from a prescribed initial state to zero at a large enough controllability time. Assuming a geometric optic condition on the support of the controls, we first prove a generalized observability inequality for the homogeneous wave equation. We then introduce and prove the well-posedness of a mixed formulation that characterizes the controls of minimal square-integrable norm. Such mixed formulation, introduced in [\textit{Cindea and Münch, A mixed formulation for the direct approximation of the control of minimal -norm for linear type wave equations}], and solved in the framework of the (space-time) finite element method, is particularly well-adapted to address the case of time dependent support. Several numerical experiments are discussed
Implementarea programului Dspace-CRIS în Repozitoriul Instituțional IRMS - Nicolae Testemițanu SUMPh
No full textBackground. Institutional Repository IRMS - Nicolae Testemitanu SUMPh is an archive of scientific
publications by university staff based on Dspace. For further development and expansion, new
opportunities are needed, namely, obtaining relevant information about the studies conducted and their
results. Objective of the study. The work aims to describe the experience of implementing the free
open-source extension DSpace-CRIS in the current IRMS repository - Nicolae Testemitanu SUMPh.
Material and Methods. It was made an analysis of scientific publications and technical literature on
the use of the DSpace-CRIS extension, to further introduce the extension into the repository. It has been
identified the best and acceptable criteria which can be used to implement this extension. The research
was based on a comparison and analysis of the repositories of educational institutions using DSpaceCRIS. Results. Implementation of the CRIS-Dspace extension in the institutional repository IRMS
Nicolae Testemitanu SUMPh will allow to monitor, systematize and keep records of the results of
research activities of Nicolae Testemitanu SUMPh university employees. Create profiles of researchers,
department pages, project grants and awards, research results reports; establish the relationship between
the author, unit and the result of scientific activity. Conclusion. The implementation of the extension
DSpace-CRIS will allow to monitor and record the results of the research activities of Nicolae
Testemitanu SUMPh university employees. Will ensure the availability and improve the ranking of the
university.
Introducere. Repozitoriul instituțional IRMS Nicolae Testemițanu SUMPh reprezintă o arhivă de
publicații științifice a angajaților Universității, bazată pe platforma DSpace. Diversificarea
funcționalității Repozitoriului presupune dezvoltarea și extinderea acestuia prin implementarea unor
noi programe, cum ar fi Dspace -CRIS-ul etc. Acest fapt este confirmat de bunele practici ale
repozitoriilor instituționale de peste hotarele țarii. Scopul lucrării. Scopul lucrării este de a analiza,
descrie și a scoate în evidență specificul implementării programului DSpace-CRIS în repozitoriul IRMS
- Nicolae Testemițanu SUMPh. Material și Metode. În vederea atingerii scopului a fost realizată
analiză publicațiilor științifice și tehnice privind aplicarea sistemului DSpace-CRIS. A fost efectuată o
analiză comparativă a repozitoriilor care funcționează în baza acestei extensii în vederea identificării și
aplicării celor mai bune practici de aplicare și funcționare. Rezultate. Aplicarea sistemului DspaceCRIS- în repozitoriul instituțional IRMS - SUMPh Nicolae Testemițanu va permite o organizare și
monitorizare mai eficientă a rezultatelor activității de cercetare a angajaților USMF „Nicolae
Testemițanu”. Concluzii. Implementarea suplimentului DSpace-CRIS va avea un impact pozitiv asupra
managementului științific, vizibilității Universității și a fiecărui cercetător în parte
Painful syndrome and microcirculation impairments in lumbosacral region at children with vertebral etiologies dorsopathies
No full textCentrul Naţional Ştiinţifico-Practic de Chirurgie Pediatrică „Natalia Gheorghiu”, Catedra de Chirurgie Pediatrică a USMF „ Nicolae Testemiţanu”, laboratorul „Infecţii chirurgicale la copii”, Conferinţa a XI-a Naţională a ortopezilor-tramatologi din Republica Moldova “Politraumatisme – concepţii contemporane de diagnostic şi tratament”, 21 mai 2009, Chișinău, Republica MoldovaAu fost analizate rezultatele investigaţiei stării microcirculaţiei între anii 2003-2007 la 61 pacienţi cu lombalgii cu vârstă de la 9 la 18 ani,
cu diferite displazii în regiunea lombo-sacrată a coloanei vertebrale,complicate cu proces degenerativ -distrofic. Din lotul studiat: băieţi
- 33 (53,9%), fete - 28 (46,1%), a predominat vîrsta 13-15ani - 43 (69,8%). Printre pacienţii examinaţi au predominat cei cu sindrom algic
„moderat” şi „grav”. Dereglări microcirculatorii au fost depistate la toate loturile de pacienţi cu sindrom algic. Intensitatea sindromului
algic depinde direct de gradul insuficienţei microcirculatorii.According to the Higher Health Care Service, the vertebral etiologies painful syndromes reach the epidemical sizes - together with cardiovascular
pathology they take the first and second place. The reasons capable to cause a painful syndrome are various, therefore in west
medical literature it is defined, how a “low pain back syndrome”. The author investigated features of a painful syndrome at 61 children at
the age from 9 to 18 with vertebral dorsopathy. He objectified these dates with using visual and verbal estimated scales and confronted
their results with microcirculation state dates, which were got with dopler fluometry using
Inverse problems and controllability with applications to elasticity and MRI
No full textLe but de cette thèse est d'étudier, du point de vue théorique, la contrôlabilité exacte de certaines équations aux dérivées partielles qui modélisent les vibrations élastiques, et d'appliquer les résultats ainsi obtenus à la résolution des problèmes inverses provenant de l'imagerie par résonance magnétique (IRM). Cette thèse comporte deux parties. La première partie discute la problématique de la contrôlabilité exacte, respectivement de l'observabilité exacte, de l'équation des plaques perturbées avec des termes linéaires ou non linéaires. Ainsi, dans le Chapitre 2 de cette thèse nous avons démontré l'observabilité interne exacte de l'équation des plaques perturbées par des termes linéaires d'ordre un et dans le Chapitre 3 la contrôlabilité exacte locale d'une équation des plaques non linéaire attribuée à Berger. Le Chapitre 4 introduit une méthode numérique pour l'approximation des contrôles exactes dans des systèmes d'ordre deux en temps. La deuxième partie de la thèse est dédiée à l'imagerie par résonance magnétique. Plus précisément, on s'intéresse aux méthodes de reconstruction des images pour des objets en mouvement. Dans le Chapitre 6, nous avons formulé la reconstruction d'images cardiaques acquises en respiration libre comme un problème des moments dans un espace de Hilbert à noyau reproductif. L'existence d'une solution pour un tel problème des moments est prouvée par des outils bien connus dans la théorie du contrôle. La connexion entre les deux parties de la thèse est réalisée par le Chapitre 7 où l'on présente le problème inverse d'identification d'un terme source dans l'équation des ondes à partir d'une observation correspondante à un enregistrement IRM.The aim of this thesis is to study the exact controllability and exact observability of some partial differential equations, modeling elastic vibrations of structures and to apply the results obtained in this way to solve some inverse problems provided by magnetic resonance imaging (MRI). This thesis has two parts. In the first part we study the exact controllability and exact observability of Euler-Bernoulli equation perturbed with linear or non-linear terms. Therefore, in Chapter 2 of this work we prove the internal exact observability of the Euler-Bernoulli equation perturbed by a linear term and in Chapter 3 we prove the local exact controllability of a non-linear plate equation due to Berger. Chapter 4 provide a numerical method to approximate the exact controls of vibrating systems. The second part of the thesis is centered to magnetic resonance imaging. More precisely, we are interested on the image reconstruction methods in magnetic resonance imaging of moving objects. Chapter 6 describe a method to reconstruct cardiac images from MR data acquired in free-breathing, reducing the image reconstruction to a problem of moments in a Hilbert space. The solution of this problem of moments is obtained using the same tools as in control theory. A more direct connexion between the two parts of the thesis is provided by Chapter 7 where we describe the inverse problem of the identification of a source term in the wave equation from a measure corresponding to a magnetic resonance signal
Problèmes inverses et contrôlabilité avec applications en élasticité et IRM
No full textThe aim of this thesis is to study, from a theoretical point of view, the exact controllability of some partial differential equations modeling the vibrations of an elastic structure and to apply the to apply these theoretic results to solve some inverse problems coming from magnetic resonance imaging (MRI). This thesis has two parts. The first one, entitled "Controllability and observability of some plate equations", discuss the controllability and, by duality, the observability of some plate equations perturbed by some linear or nonlinear terms. The second part of the thesis concerns the magnetic resonance imaging. More precisely, we study some methods to reconstruct the magnetic resonance images of a moving object, the typical example being the cardiac imaging reconstruction from MRI data acquired in free-breathing.Le but de cette thèse est d'étudier, du point de vue théorique, la contrôlabilité exacte de certaines équations aux dérivées partielles qui modélisent les vibrations élastiques, et d'appliquer les résultats ainsi obtenus à la résolution des problèmes inverses provenant de l'imagerie par résonance magnétique (IRM). Cette thèse comporte deux parties. La première partie, intitulée ''Contrôlabilité et observabilité de quelques équations des plaques'', discute la problématique de la contrôlabilité, respectivement de l'observabilité, de l'équation des plaques perturbées avec des termes linéaires ou non linéaires. Des résultats récents ont prouvé que l'observabilité exacte d'un système qui modélise les vibrations d'une structures élastique (équation des ondes ou des plaques) implique l'existence d'une solution du problème inverse de la récupération d'un terme source dans l'équation à partir de l'observation. Ainsi, dans le Chapitre 2 de cette thèse nous avons démontré l'observabilité interne exacte de l'équation des plaques perturbées par des termes linéaires d'ordre un et dans le Chapitre 3 la contrôlabilité exacte locale d'une équation des plaques non linéaire attribuée à Berger. Le Chapitre 4 introduit une méthode numérique pour l'approximation des contrôles exactes dans des systèmes d'ordre deux en temps. La deuxième partie de la thèse est dédiée à l'imagerie par résonance magnétique. Plus précisément, on s'intéresse aux méthodes de reconstruction des images pour des objets en mouvement, l'exemple typique étant l'imagerie cardiaque en respiration libre. Dans le Chapitre 6, nous avons formulé la reconstruction d'images cardiaques acquises en respiration libre comme un problème des moments dans un espace de Hilbert à noyau reproductif. L'existence d'une solution pour un tel problème des moments est prouvée par des outils bien connus dans la théorie du contrôle. Nous avons validé cette méthode en utilisant des images simulées numériquement et les images de cinq volontaires sains. La connexion entre les deux parties de la thèse est réalisée par le Chapitre 7 où l'on présente le problème inverse d'identification d'un terme source dans l'équation des ondes à partir d'une observation correspondante à un enregistrement IRM. En conclusion, nous avons montré qu'on peut utiliser les outils de la théorie de contrôle pour des problèmes inverses provenant de l'IRM des objets en mouvement, à la condition de connaître l'équation du mouvement
The course of revolution in the history of the Romanians
No full textTitle: Mersul revoluţiei în istoria Românilor (The course of revolution in the history of the Romanians) Originally published: In the journal România viitoare (Paris, 16 September 1850), vol. I. Language: Romanian The excerpts used are from Nicolae Bălcescu, Opere, vol I/2 (Scrieri istorice, politice şi economice), ed. by G. Zane (Bucharest: Fundaţia pentru literaturăşi artă ‘Regele Carol II,’ 1940), pp. 99–101, 103–108. About the author Nicolae Bălcescu [1819, Bucharest – 1852, Palermo]: his..
Contrôlabilité et problèmes inverses pour quelques équations aux dérivées partielles. Aspects théoriques et numériques
No full textRecommended from our members
MISAME
No full textRecording of Nicolae Brânduș's Kitsch_N. It is an instrumental theatre subscribed to the preoccupation of the author with controlling randomness in a musical action where the sound, attitude and stage gestures are structurally corroborated widening the domain of the performance. It is the second piece of a cycle named Vagues where the author develops similar stochastic principles of composition
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