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1
Shane, Christopher Koldobsky Alexander. "Uniqueness theorems for non-symmetric convex bodies." Diss., Columbia, Mo. : University of Missouri-Columbia, 2009. http://hdl.handle.net/10355/6785.
Повний текст джерелаАнотація:
The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on March 29, 2010). Thesis advisor: Dr. Alexander Koldobsky. Vita. Includes bibliographical references.
2
Hope, David John. "Bodily symmetry : origins and lifecourse associations with cognition, personality, and status." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/6442.
Повний текст джерелаАнотація:
Symmetry – measured as the size asymmetry of a group of symmetrical body traits such as ear height or elbow circumference – has often been used as an index of the capacity to develop normally despite stress and correlates with a wide range of outcomes including intelligence, health and aspects of behaviour. However, theoretical debate continues over the underlying causes of these associations and outstanding methodological issues – such as the reliance on small sample sizes of college age students – makes the robustness of the findings uncertain. The present work advances the existing empirical literature in six separate domains. It also improves upon past methodology by using novel methods of digital measurement of asymmetry as well as for the first time digitally measuring endogenous asymmetry as indexed by the bones and linking bone asymmetry to intelligence. The research was conducted on four samples. Numbers given are for participants who provided asymmetry measures. Firstly, a sample of elderly participants from the Lothian Birth Cohort 1921 (LBC1921, n = 216) tested around ages 11, 79, 83, and 87. Secondly, the Science Festival Sample (SFS), a group of children recruited at a public science event aged between 4 and 15 (n = 856). Thirdly, a group of Orkney residents aged 18 to 86 (the ORCADES, n = 1200). Fourthly the Berlin Sample (BS), a group of Berlin residents (n = 207) between 20 and 30 years old. In the LBC 1921, men with poorer socioeconomic status in childhood had higher facial asymmetry in old age (β = -.25, p = .03). While investigating issues related to asymmetry in the same sample it was found that relatively more severe digit curvature – a minor physical anomaly – was associated with relatively greater cognitive decline (β = -.19, p = .02). Within the SFS asymmetry decreased across human childhood (β = -.16, p = .01), and more asymmetrical children exhibited slower choice reaction times (β = .0.17, p = .002). In the ORCADES sample, the more asymmetrical participants (as indexed by bone asymmetry) were less intelligent (β = -.24, p = .01). In the Berlin Sample and the LBC 1921 no consistent associations were found between personality traits and asymmetry. Collectively, these findings suggest symmetry functions as a measure of overall well-being as the trend is for higher asymmetry to be associated with a relatively poorer score on a variety of outcome measures. The findings considerably expand the number of existing studies in these empirical areas and in several cases – particularly asymmetry’s association with socioeconomic status in the elderly and reaction times among children – represent the first work on those areas. The present work confirms the finding that asymmetry is linked to adverse outcomes. However, the underlying mechanisms by which symmetry is linked to such outcomes remain underexplored and require clarification.
3
Priyono, Eddy. "An investigation of the transonic pressure drag coefficient for axi-symmetric bodies." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA280990.
Повний текст джерела
4
Fan, Yue Sang. "An investigation of the transonic viscous drag coefficient for axi-symmetric bodies." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA297698.
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5
Carlén, Eriksson Lennie, and Willners Jonatan Scharff. "Body Area Network with Gait Symmetry Analyses." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-28353.
Повний текст джерелаАнотація:
Smart portable devices is increasing in popularity in many fields. In motion tracking many devices have been created in the last years as a help in motivation and observation for training. Most of them is for tracking distance moved, heart-rate and some more basic functions. For deeper analyses in motion tracking a more advanced system is needed. The system needs to be small and light to not influence the movement of the subject in a negative way. It should preferably be cheap. Two other factors is that the system needs to be easy to use, both in the interface and deployment. Symmetry in motion is an key-element to effective use of energy. Measuring the symmetry in gait should then help to improve motion. This could be used as a tool for more efficient training or to faster recover from an injury. For a stroke-patient this could perhaps decrease the time of rehabilitation and remind the patient to move one leg. To create this, a reliable communication between a data sink and sensor nodes has been developed. The sensor nodes is gathering nine dimensions IMU data, accelerometer, gyroscopes and magnetometer, each in three dimensions. The data is saved to a database where it can be extracted for further analyses. Testing of the script language for Bluetooth devices, BGScript for time synchronisation has been done to see if it is able to use for frequencies high enough for a system to measure movement.
6
Scharff, Willners Jonatan. "Body Area Network with Gait Symmetry Analyses." Thesis, Mälardalens högskola, Inbyggda system, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-28306.
Повний текст джерелаАнотація:
Smart portable devices is increasing in popularity in many fields. In motion tracking many devices have been created in the last years as a help in motivation and observation for training. Most of them is for tracking distance moved, heart-rate and some more basic functions. For deeper analyses in motion tracking a more advanced system is needed. The system needs to be small and light to not influence the movement of the subject in a negative way. It should preferably be cheap. Two other factors is that the system needs to be easy to use, both in the interface and deployment. Symmetry in motion is an key-element to effective use of energy. Measuring the symmetry in gait should then help to improve motion. This could be used as a tool for more efficient training or to faster recover from an injury. For a stroke-patient this could perhaps decrease the time of rehabilitation and remind the patient to move one leg. To create this, a reliable communication between a data sink and sensor nodes has been developed. The sensor nodes is gathering nine dimensions IMU data, accelerometer, gyroscopes and magnetometer, each in three dimensions. The data is saved to a database where it can be extracted for further analyses. Testing of the script language for Bluetooth devices, BGScript for time synchronisation has been done to see if it is able to use for frequencies high enough for a system to measure movement.
7
Sivasankaran, Anoop. "The stability of the Caledonian Symmetric Four-Body Problem with close encounters." Thesis, Glasgow Caledonian University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687398.
Повний текст джерелаАнотація:
The central theme of the research presented in this thesis is an investigation of the stability of a symmetrically restricted four-body problem called the Caledonian Symmetric Four-Body Problem (CSFBP) (Steves and Roy, 2001) using a newly developed numerical integration scheme which enables the numerical exploration of the systems as they pass through two-body close encounters. A study of the hierarchical stability of the CSFBP system is made, followed by an empirical stability analysis of hierarchically stable regions in the phase space of the CSFBP. The study of the dynamics and stability of four-body systems like CSFBP is relevant in order to determine stable hierarchical arrangements which will be capable of hosting exoplanetary systems. A comprehensive literature review of the key features of the CSFBP is presented. The collision manifold of the phase space of the CSFBP is explored for a whole range of CSFBP systems and the fundamentallimitatioDs of the existing numerical integration scheme (cf. Szell, Steves and Erdi (2004a); Szell, Erdi: Sandor and Steves (2004)) have been analysed. It was found that, neglecting the collision orbits in the phase space of the CSFBP is a major limitation in the numerical exploration of the global stability features of the CSFBP. A review of regularisation theory is given, highlighting the key stages needed to develop a regularisation method for a gravitational few-body problem. A global regularisation method (cf. Heggie (1974)) is then derived to handle various two-body close encounters. An algebraic optimisation algorithm (Gruntz and Waldvogel, 1997) is adapted for numerically implementing the regularisation scheme. The numerical accuracy and the computational performance of the developed integration scheme were tested for a broad range of CSFBP orbits. Regardless of the nature of the orbits, it was found that the regularised integration scheme outperformed the standard non-regularised integration schemes in terms of computational performance and improved numerical accuracy characterized by stable energy profiles. The hierarchical stability of the CSFBP is investigated using the developed integration schemes. Numerical simulations were conducted for a comprehensive set of CSFBP orbits. It was found that the analytical hierarchical stability criteria was satisfied even after the inclusion of orbits with two-body close encounters. An empirical stability investigation was also made and it identified regions of hierarchical stability in the phase space of the CSFBP for any value of Co < Ccrit.
8
Shibayama, Mitsuru. "Multiple symmetric periodic solutions to the 2n-body problem with equal masses." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136738.
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9
De, Sousa Dias Maria Esmeralda Rodrigues. "Local dynamics of symmetric Hamiltonian systems with application to the affine rigid body." Thesis, University of Warwick, 1995. http://wrap.warwick.ac.uk/107563/.
Повний текст джерелаАнотація:
This work is divided into two parts. The first one is directed towards the geometric theory of symmetric Hamiltonian systems and the second studies the so-called affine rigid body under the setting of the first part. The geometric theory of symmetric Hamiltonian systems is based on Poisson and symplectic geometries. The symmetry leads to the conservation of certain quantities and to the reduction of these systems. We take special attention to the reduction at singular points of the momentum map. We survey the singular reduction procedures and we give a method of reducing a symmetric Hamiltonian system in a neighbourhood of a group orbit which is valid even when the momentum map is singular. This reduction process, which we called slice reduction, enables us to partially reduce the (local) dynamics to the dynamics of a system defined on a symplectic manifold which is the product of a symplectic vector space (symplectic slice) with a coadjoint orbit for the original symmetry group. The reduction represents the local dynamics as a coupling between vibrational motion on the vector space and generalized rigid body dynamics on the coadjoint group orbits. Some applications of the slice reduction are described, namely the application to the bifurcation of relative equilibria. We lay the foundations for the study of the affine rigid body under geometric methods. The symmetries of this problem and their relationship with the physical quantities are studied. The symmetry for this problem is the semi-direct product of the cyclic group of order two Z2 by 50(3) x 50(3). A result of Dedekind on the existence of adjoint ellipsoids of a given ellipsoid of equilibrium follows as consequence of the Z2 symmetry. The momentum map for the Z2 x, (50(3) x 50(3)) action on the phase space corresponds to the conservation of the angular momentum and circulation. Using purely geometric arguments Riemann’s theorem on the admissible equilibria ellipsoids for the affine rigid body is established. The symmetries of different relative equilibria are found, based on the study of the lattice of isotropy subgroups of Z2 x, (50(3) x 50(3)) on the phase space. Slice reduction is applied in a neighbourhood of a spherical ellipsoid of equilibrium leading to different reduced dynamics. Based also on the slice reduction we establish the bifurcation of S-type ellipsoids from a nondegenerate ellipsoidal equilibrium.
10
Tamgho, Ingrid-Suzy. "Synthesis of Ligands and Macrocycles Based on 1,3-Diiminoisoindoline and Study of New Highly Fluorescent and Symmetric Pyrrole-BF2 Chromophores." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1412163224.
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11
Philipson, Joshua Benjamin Julius. "Near- to Far-Field Transformation for Arbitrarily-Shaped Rotationally-Symmetric Antenna Measurement Surfaces." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41434.
Повний текст джерелаАнотація:
The wireless industry is such that suppliers of antennas have to adapt their designs to requirement changes over a period of just a few months. In these short design cycles time is crucial. Radiation pattern testing of the antennas at various points in this design cycle are nowadays mostly done using spherical near-field techniques, where the tangential electric field is acquired over an imaginary sphere close to, and surrounding, the antenna under test, and this data then transformed into a far-zone radiation pattern. There are some applications where acquisition over a rotationally symmetric surface other than a spherical one would not only reduce test times, but allow equipment cost reductions as well. However, near-field to far-field transformations for finite non-spherical measurement surface shapes are not available. Such a transformation is proposed, implemented and validated in this thesis. It uses the method of moments, customized to a rotationally symmetric surface (body of revolution) to effect this transformation.
12
Crawford, Emily Anne. "The relevance of the Goldsmith Index of Body Symmetry to functional seated posture." University of Western Australia. School of Human Movement and Exercise Science, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0007.
Повний текст джерелаАнотація:
Whilst literature exists describing prevalence and theories about mechanisms of development of deformity, there is a distinct lack of research that examines how deformity can be measured despite it being an area of identified need. This study established the inter- and intra-rater reliability of the Goldsmith Index of Body Symmetry and examined the relevance of the information it provides within the context of a comprehensive postural assessment for individuals with cerebral palsy in conjunction with a commonly used clinical assessment ... Results demonstrated that high index levels were not exclusively associated with people with windswept deformity. Postural patterns of windsweeping, frog leg (abducting) and scissor (adducting) postures and hip extension were found to occur in all categories, suggesting that asymmetry is not confined to one particular postural pattern. Clinically observable changes were identified through comparison of the supine evaluation and index scores. The flexibility of postural components (or the ability to correct asymmetry) in a supine position for the SD categories demonstrated wide variation. However, subjects in the 3+SD groupings had fixed scoliosis and the majority (83%) also had fixed pelvic obliquity and rotation. All other subjects up to the 3SD category had flexible pelvic obliquity and rotation. No definitive differences in postural components between groups were identified in sitting positions, which was attributed to the influence of gravity on the body in an upright posture. Examination of sitting ability and index level did not demonstrate any relationship, suggesting that greater independence in sitting is not necessarily associated with a lower Goldsmith Index. The study highlighted that assessment of posture is complex, and that no single tool provides the answers required to manage a person’s posture. It demonstrates the need for clinicians to be aware that subjective clinical assessment may not be sufficient to adequately assess and detect changes in posture, and that the Goldsmith Index of Body Symmetry provides objective data that can be used as a powerful adjunct in interpreting clinical assessment and supporting the evaluation of clinical interventions.
13
Crawford, Emily Anne. "The relevance of the Goldsmith Index of Body Symmetry to functional seated posture /." Connect to this title, 2004. http://theses.library.uwa.edu.au/adt-WU2006.0007.
Повний текст джерела
14
Robertson, Alan Iain. "Observation of the charmless two-body decay B → ′K∗ using data collected by the BABAR experiment." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7860.
Повний текст джерелаАнотація:
A search for B decays to quasi two-body charmless final states involving a pseudoscalar η′ meson recoiling against a K∗ vector meson is described. This thesis primarily describes the analysis of two of the six possible decay channels, with the other four channels necessarily included as the subdecay modes are combined to give an overall branching fraction measurement. The method of analysis is a multivariate maximum likelihood fit for each subdecay channel. The likelihood curves for both modes are then combined, firstly with two other charged modes to yield an overall charged result, and finally the four charged modes are combined with two neutral modes to give an overall branching fraction and significance for the decay channel B → η′K∗. All results use the full Run 1 to Run 4 datasets, comprising 210.5 fb−1 of data, equivalent to 232 million BB pairs, gathered by the BABAR detector at Stanford Linear Accelerator Center in Menlo Park, California. The measured branching fractions and upper limits at 90% confidence limit (CL) are: B(B+ → η′ηππK∗+ K+π0) < 9.5 × 10−6B(B+ → η′ργK∗+ K+π0) < 22 × 10−6.The four-mode combined fit determined the branching fraction for the decay B+ → η′K∗+: B(B+ → η′K∗+) < 7.9 × 10−6. The six-mode combined fit determined the branching fraction for the decay B → η′K∗: B(B → η′K∗) = (4.1 ± 1.0 ± 0.5) × 10−6 at a significance of 5.6 standard deviations.
15
Choudhury, Anshuman. "Statistics of dislocations at low temperature in pure metals with body centered cubic symmetry." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS569/document.
Повний текст джерелаАнотація:
Les observations de microscopie électronique in situ effectuées par Daniel Caillard (CEMES, Toulouse) au cours de la déformation de cristaux de symétrie cubique centrée ont montré que les dislocations vis effectuaient des sauts de plusieurs distances inter-atomiques alors que la théorie standard de Peierls prédit des sauts de une seul distance inter-atomique. Nous avons étudié par simulation atomique le glissement d'une dislocation vis dans un cristal de fer pure. Nous montrons que la propagation de décrochement le long de la dislocation induit un échauffement local qui favorise la nucléation de décrochements supplémentaires. L'accumulation de ces décrochements permet à la dislocation de parcourir plusieurs distances inter-atomiques. Ces simulations nous permettent de proposer une théorie pour l'explication des observations de D. CaillardIn situ straining tests in high purity α-Fe thin-foils at low temperatures have demonstrated that crystalline defects, called dislocations, have a jerky type of motion made of intermittent long jumps of several nanometers. Such an observation is in conflict with the standard Peierls mechanism for plastic deformation in bcc crystals, where the screw dislocation jumps are limited by inter-reticular distances, i.e. of a few Angstroms. Employing atomic-scale simulations, we show that although the short jumps are initially more favorable, their realization requires the propagation of a kinked profile along the dislocation line which yields coherent atomic vibrations acting as traveling thermal spikes. Such local heat bursts favor the thermally assisted nucleation of new kinks in the wake of primary ones. The accumulation of new kinks leads to long dislocation jumps like those observed experimentally. Our study constitutes an important step toward predictive atomic-scale theory for materials deformation
16
Douguet, Nicolas. "Symmetry in the dissociative recombination of polyatomic ions and in ultra-cold few body collisions." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4654.
Повний текст джерелаАнотація:
We discuss the role of symmetries in the dissociative recombinations (DR) of three polyatomic ions, namely the linear HCO+ (formyl) ion and the two highly symmetric H+3 and H3O+ (hydronium) molecular ions. Regarding the HCO+ ion, we apply a quantum mechanical treatment using the Multi-channel Quantum Defect Theory (MQDT) formalism to describe the ion-electron scattering process. Our study takes into account the Renner-Teller effect in order to model the non Born-Oppenheimer vibronic coupling in linear polyatomic ions. The coupling has shown to represent the main mechanism responsible for electronic capturing in highly excited Rydberg states associated with excited vibrational levels of the ionic core. We consider all internal degrees of freedom of HCO+ and obtain the dissociative cross section as a function of the incident electron kinetic energy. We have also improved the theoretical approach by including the large permanent dipole moment of HCO+ using a generalization of the MQDT formalism. To our knowledge, this is the rst time the permanent dipole moment of an ion is included in a DR study. The obtained results are in good agreement with experimental data. We also study the DR of H+3 and H3O+ symmetric ions using a simpli ed theoretical treatment, which focuses on the key ingredient of the DR process, the electron capture in the rst excited degenerate vibrational normal mode of the ions through non Born-Oppenheimer Jahn-Teller coupling. For both ions the obtained cross sections are in very good agreement with the available experimental data. Moreover, in the case of H+3 , the results reproduce previous calculations from two independent theoretical studies. Finally, we investigate the role of symmetries in few body ultra-cold collisions by considering both three and four identical atoms systems. We derive allowed rearrangements of different fragments of the system, satisfying the complete symmetry of the molecular Hamiltonian. For that purpose we establish a correspondence between constants of motion of the system in di erent large-distance con gurations and irreducible representations of the total symmetry group. Selection rules (forbidden transitions) and allowed states, which depend on the fermionic or bosonic nature of the atoms, can be derived from these results.ID: 029050862; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2010.; Includes bibliographical references (p. 226-232).
Ph.D.
Doctorate
Department of Physics
Sciences
17
Persson, Anders. "Platform development of body area network for gait symmetry analysis using IMU and UWB technology." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-39498.
Повний текст джерелаАнотація:
Having a device with the capability of measure motions from gait produced by a human being, could be of most importance in medicine and sports. Physicians or researchers could measure and analyse key features of a person's gait for the purpose of rehabilitation or science, regarding neurological disabilities. Also in sports, professionals and hobbyists could use such a device for improving their technique or prevent injuries when performing. In this master thesis, I present the research of what technology is capable of today, regarding gait analysis devices. The research that was done has then help the development of a suggested standalone hardware sensor node for a Body Area Network, that can support research in gait analysis. Furthermore, several algorithms like for instance UWB Real-Time Location and Dead Reckoning IMU/AHRS algorithms, have been implemented and tested for the purpose of measuring motions and be able to run on the sensor node device. The work in this thesis shows that a IMU sensor have great potentials for generating high rate motion data while performing on a small mobile device. The UWB technology on the other hand, indicates a disappointment in performance regarding the intended application but can still be useful for wireless communication between sensor nodes. The report also points out the importance of using a high performance micro controller for achieving high accuracy in measurements.
18
Sadoudi, Jérémy. "Constraints on the nuclear energy density functional and new possible analytical forms." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00653740.
Повний текст джерелаАнотація:
The theoretical tool of choice for the microscopic description of all medium- and heavy-mass nuclei is the Energy Density Functional (EDF) method. Such a method relies on the concept of spontaneous symmetry breaking and restoration. In that sense, it is intrinsically a two-step approach. However, the symmetry restoration procedure is only well-defined in the particular case where the energy functional derives from a pseudo-potential. Thereby and as it has been recently shown, existing parameterizations of the energy functional provides unphysical results. Such a problem as well as the lack of predictive power call for developing new families of functionals. The first part of the present work is devoted to a study of the symmetry restoration problem and to the identification of properties that could constrain the analytic form of energy functionals that do not derive from a pseudo-potential. The second part deals with the construction of an energy functional that derives from a pseudo potential. The difficulties of such work are (i) the identification of the minimal complexity of the pseudo-potential necessary to obtain an energy functional that is flexible enough to provide high-quality EDF parameterizations, (ii) the tedious analytical derivation of the functional and of the associated one-body fields, (iii) the implementation of the latter in existing codes, and (iv) the development of an efficient fitting procedure. Eventually, it seems possible to generate a parameterization that strictly derives from a pseudo-potential and that provides as good results as state-of-the-art (quasi) bilinear functionals.
19
Kasparek, Alexander J. "Secure Key Agreement for Wearable Medical Devices." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-theses/1333.
Повний текст джерелаАнотація:
In this thesis we explore if a proposed random binary sequence generation algorithm can be combined with a separately proposed symmetric key agreement protocol to provide usable security for communications in Wireless Body Area Networks (WBAN). Other previous works in this area fall short by only considering key generation between two of the same signals or allowing for key generation between two different types of signals but with the cost of a significant signal collection time requirement. We hoped to advance this area of research by making secure key generation more efficient with less signal collection time and allowing keys to be generated between two sensors that measure two different physiological signals. However, while the binary sequence generation algorithm and key agreement protocol perform well separately, they do not perform well together. The combined approach yields keys that have good properties for use in a WBAN, but the generation rate is low.
20
Lin, Ting. "Poincaré-invariant three-nucleon scattering." Ohio : Ohio University, 2008. http://www.ohiolink.edu/etd/view.cgi?ohiou1210773278.
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21
Hirose, Toru. "The reduction of quantum many-body systems with symmetry and the boundary behavior of wave functions at singular configurations." 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/148782.
Повний текст джерела
22
Sadoudi, Jeremy. "Constraints on the nuclear energy density functional and new possible analytical forms." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112151/document.
Повний текст джерелаАнотація:
La méthode dite de la fonctionnelle de la densité d'énergie (EDF) est l'outil théorique de référence pour l'étude systématique de la structure des noyaux atomiques de masse A>20. La méthode EDF est formulée en deux étapes successives consistant à briser puis à restaurer les symétries du Hamiltonien nucléaire sous-jacent. La technique de restauration des symétries n'est cependant rigoureusement formulée que si la fonctionnelle d'énergie dérive explicitement d'une interaction effective, i.e. d'un pseudo-potentiel, ce qui constitue un cas particulier de la méthode EDF plus générale. Ainsi, et comme cela a été démontré récemment, l'utilisation des paramétrisations existantes des fonctionnelles d'énergie conduit à l'obtention de résultats non physiques. Le pouvoir prédictif limité des fonctionnelles d'énergie existantes et leur inocuité relative à la restauration des symétries, nécessitent aujourd'hui de repenser leur méthode de construction. La première partie de ce travail a été dédié à l'analyse approfondie du problème associé à la restauration de symétrie et à l'identification de pistes permettant de contraindre la forme analytique des fonctionnelles d'énergie ne dérivant pas d'un pseudo-potentiel indépendant du système. La seconde partie a consisté à développer un pseudo-potentiel rendant la restauration des symétries automatiquement bien définie. Les difficultés de ce travail ont résidé dans (i) l'identification de la complexité minimale du pseudo-potentiel nécessaire à l'obtention d'une fonctionnelle d'énergie assez flexible pour égaler, et si possible améliorer, les performances des paramétrisations existantes, (ii) la dérivation analytique de la fonctionnelle et des champs à un corps découlant de celle ci, (iii) l'implémentation de ces derniers dans les codes de calculs, et dans (iv) le développement d'un protocole d'ajustement des paramètres adapté à la nouvelle fonctionnelle d'énergie ainsi développée. Les premiers résultats obtenus ont permis de valider l'approche en démontrant la flexibilité suffisante du pseudo-potentiel au niveau des calculs réalisés sans restauration des symétriesThe theoretical tool of choice for the microscopic description of all medium- and heavy-mass nuclei is the Energy Density Functional (EDF) method. Such a method relies on the concept of spontaneous symmetry breaking and restoration. In that sense, it is intrinsically a two-step approach. However, the symmetry restoration procedure is only well-defined in the particular case where the energy functional derives from a pseudo-potential. Thereby and as it has been recently shown, existing parameterizations of the energy functional provides unphysical results. Such a problem as well as the lack of predictive power call for developing new families of functionals. The first part of the present work is devoted to a study of the symmetry restoration problem and to the identification of properties that could constrain the analytic form of energy functionals that do not derive from a pseudo-potential. The second part deals with the construction of an energy functional that derives from a pseudo potential. The difficulties of such work are (i) the identification of the minimal complexity of the pseudo-potential necessary to obtain an energy functional that is flexible enough to provide high-quality EDF parameterizations, (ii) the tedious analytical derivation of the functional and of the associated one-body fields, (iii) the implementation of the latter in existing codes, and (iv) the development of an efficient fitting procedure. Eventually, it seems possible to generate a parameterization that strictly derives from a pseudo-potential and that provides as good results as state-of-the-art (quasi) bilinear functionals
23
Ripoche, Julien. "Projected Bogoliubov Many-Body Perturbation Theory : Overcoming formal and technical challenges." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS325.
Повний текст джерелаАнотація:
Étant donnée l’interaction entre les nucléons,la résolution de l’équation de Schrödinger à A corps permet d’accéder aux propriétés des états quantiques des noyaux. La théorie des perturbations à N corps (MBPT) basée sur un état de champ moyen d’Hartree-Fock permet de traiter les corrélations dynamiques mises en jeu dans les noyaux à doubles couches fermées. Au-delà des fermetures de couches, la brisure spontanée de la symétrie U(1)associée à la conservation du nombre de protons et de neutrons permet en sus l’inclusion des corrélations statiques au niveau du champ moyen et la formulation de la théorie des perturbations à N corps de Bogoliubov (BMBPT). Néanmoins, les résultats des calculs BMBPT présentent des contaminations du fait que la brisure de symétrie n’est qu’émergente dans les systèmes quantiques finis tels que le noyau atomique. Ainsi, la restauration de la symétrie U(1) au-delà du champ moyen est nécessaire pour une description correcte et donne lieuà la formulation de la méthode BMBPT projetée(PBMBPT). Le but est d’implémenter PBMBPTafin d’effectuer des calculs ab initio pour les noyaux à couche ouverte et de masse intermédiaire. Le présent travail apporte des solutions systématiques aux problèmes formels et techniques qui se posent lorsde l’implémentation numérique de PBMBPT : une méthode automatique et sûre permettant de générer les diagrammes PBMBPT ainsi que les expressions correspondantes, un formalisme permettant de calculer d’autres observables que l’énergie, une extension de l’approximation en produit normal aux méthodes avec brisures de symétries ainsi qu’un outil automatique et sûr de réduction sphérique de réseaux de tenseursGiven elementary inter-nucleon interactions,the resolution of the A-body Schrödinger equation gives access to the properties of the nuclear eigenstates. Many-body perturbation theory (MBPT) based on a Hartree-Fock mean field allows one to treat the dynamical correlations at play in doubly-closed-shell nuclei. Beyond shell closures,breaking U(1) symmetry associated with the conservation of neutron and proton numbers further permits to capture static correlations at the meanfield level and to formulate the well-behaved Bogoliubov many-body perturbation theory (BMBPT).Nevertheless, BMBPT results show contaminations associated with the broken symmetry that is only emergent on finite quantum system such as theatomic nucleus. Thus, the restoration of U(1) symmetry beyond the mean field is necessary for acorrect description and gives rise to the projected BMBPT method (PBMBPT). The goal is to implement PBMBPT in order to perform ab initio calculations of singly-open-shell mid-mass nuclei.The present work provides systematic solutions to the formal and technical problems arising during the implementation of PBMBPT: an automatic and safe method to generate PBMBPT diagrams and associated expressions, a framework to calculate other observables than the energy, an extension of the normal ordering approximation to symmetry breaking methods as well as an automatic and safe tool for spherical reduction of tensor networks
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Juršėnas, Rytis. "Algebraic development of many-body perturbation theory in theoretical atomic spectroscopy." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20101223_153004-84982.
Повний текст джерелаАнотація:
The principal goals of the thesis are subjected to general methods and forms of effective operators by the nowadays demands of theoretical application of many-body perturbation theory to atomic physics. The present theoretical research follows up step by step by systematic observation of various possibilities to restrict the Fock space operators to their irreducible subspaces and the classification of irreducible tensor operators which represent the physical as well as the effective interactions. To ground the results of the thesis, the symbolic preparation of obtained expressions is strictly proved mathematically. Most of the main results are listed in theorems. The doctoral dissertation contains 101 pages, 5 sections, 4 appendices, 40 tables and 9 figures. The main results described in the present dissertation have been published in journals of physical and mathematical sciences.Šis darbas yra skirtas šiuolaikinės atomo trikdžių teorijos matematinio aparato, paremto efektinių operatorių formalizmu, plėtojimui. Darbe nuosekliai ir sistemingai, pradedant nuo pačių bendriausių principų, nagrinėjami Foko erdvės apribojimo į redukavimo grupių neredukuotinus poerdvius metodai bei pateikiama neredukuotinų tenzorinių operatorių, charakterizuojančių fizikines ir efektines sąveikas, klasifikacija bendrais ir tam tikrais atskirais atvejais. Gautos išraiškos ir iš jų išplaukiančios išvados yra grindžiamos matematine kalba. Dauguma esminių rezultatų yra suformuluoti teoremų pavidalu. Disertaciją sudaro 101 puslapis, 5 skyriai, 4 priedai, 40 lentelių ir 9 paveikslėliai. Pagrindiniai rezultatai, pateikti disertacijoje, yra publikuoti fizikos ir matematikos mokslų žurnaluose.
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Alam, Muhammad Faiz, and Muhammad Faiz Alam. "Dielectric Resonator Antennas (DRA) for satellite and body area network applications." Phd thesis, Université Paris-Est, 2012. http://tel.archives-ouvertes.fr/tel-00795292.
Повний текст джерелаАнотація:
Technologies such as direct broad cast satellite system (DBSS), Geosynchronous Earth Orbit (GEO) and Low Earth Orbit (LEO) satellite communications , global positioning system (GPS), high accuracy airborne navigation system and a large variety of radar systems demand for high level of antenna performance. Similar is the requirement for upcoming land based wireless systems such as cellular and indoor communication systems that is needed some more specific and additional features added to the antenna to compensate for the deficiencies encountered in system's performance. Though metallic antennas are capable enough to fulfil all the operational requirements, however at very high frequencies and under hostile temperature conditions they are constrained to face certain limitations. To avoid these constraints the performance of Dielectric Resonator Antennas (DRAs) is evaluated and their new applications are proposed. In the thesis, two types of antenna applications are sought :-First is for tracking and satellite applications that needs a larger aperture coverage in elevation plane. This coverage is realized with a good CP purity by proposing two ports dual linearly polarized DRA working at X-band. The DRA is excited by two orthogonal H-shaped aperture slots yielding two orthogonal polarizations in the broadside direction. A common impedance bandwidth of 5.9% and input port isolation of -35 dB are obtained. The broadside radiation patterns are found to be highly symmetric and stable with cross polarization levels -15dB or better over the entire matching frequency band. The maximum measured gain is found to be 2.5dBi at 8.4 GHz.- The 2nd type of antenna is a dual pattern diversity antenna to be used in the Body Area Network (BAN) context. This antenna combines a slot loop and DRA yielding broadside and end-fire radiation patterns respectively. Based upon the feeding techniques, the DG antenna is further divided into two categories one with planar feeds and the other with non-planar feeds (slot loop excited by planar CPW but DRA excited by vertical monopole) .Both types are successfully designed and measured upon body when configured into different propagation scenarios. The non-planar feeds antenna allows wider common impedance bandwidths than the planar feeds (4.95% vs 1.5%).In both cases, a maximum value of DG=9.5dB was achieved when diversity performance tests were carried out in rich fading environments. This value is close to the one (10 dB) theoretically reached in a pure Rayleigh environment and was obtained with efficiencies of 70% and 85% for the slot loop and the DRA respectively. Therefore, we conclude that these antennas could be used on the shoulders or the chest of professional clothes (firemen, policemen, soldier) where full planar integration is not a key issue but where the communication must be efficient in harsh environments and for various gestures, positions and scenarios
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González, Merino Bernardo. "Los radios sucesivos de un cuerpo convexo = Successive radii of convex bodies." Doctoral thesis, Universidad de Murcia, 2013. http://hdl.handle.net/10803/116860.
Повний текст джерелаАнотація:
La Tesis Doctoral está dedicada al estudio de ciertas propiedades de los radios sucesivos de los cuerpos convexos (funcionales definidos a partir de circunradios e inradios de proyecciones o secciones del cuerpo). Comenzamos estableciendo las nociones básicas necesarias para el desarrollo de los contenidos. A continuación calculamos los radios sucesivos de familias particulares de conjuntos (p-bolas, anchura constante, cuerpos tangenciales), y estudiamos la conexión existente entre estos funcionales y los números de Gelfand y Kolmogorov. En el tercer capítulo consideramos el problema de Pukhov-Perel'man sobre la mejor cota superior para un cierto cociente de radios, determinando desigualdades para problemas de este tipo que van a permitir mejorar los resultados existentes en ciertos casos. Finalmente, estudiamos cómo se relacionan los radios sucesivos de la suma de Minkowski (Firey) de dos cuerpos convexos con los correspondientes funcionales de los conjuntos, obteniendo los resultados óptimos en todos los casos.The Doctoral Thesis is focused in the study of some properties of the successive radii of convex bodies (functionals defined by means of circumradii and inradii of projections or sections of the set). We start establishing the basic notions that will be needed further on. Next, we compute the successive radii of particular families of sets (p-balls, constant width sets and tangential bodies), and study the connection between these functionals and the Gelfand and Kolmogorov numbers. In the third chapter we consider the Pukhov-Perel'man problem on the best upper bound for a particular ratio of radii, determining inequalities for some problems of this type which will allow to improve the known results in particular cases. Finally we study how the successive radii of the (Firey)-Minkowski addition of two convex bodies are related with the corresponding functionals of the sets, obtaining the optimal results in all cases.
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Alam, Muhammad Faiz. "Dielectric Resonator Antennas (DRA) for satellite and body area network applications." Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST1057/document.
Повний текст джерелаАнотація:
Dans cette thèse, on vise deux types d'applications de l’antenne à résonateur diélectrique (DRA): 1) La réalisation d’un élément rayonnant pour un réseau phasé embarqué sur un véhicule terrestre ou un avion. Cet élément de base requiert une couverture en élévation supérieure à celle des éléments imprimés pour permettre une poursuite typique comprise entre ±70°. La couverture dans un cône large est assurée avec une bonne pureté de polarisation circulaire en alimentant l’antenne à travers deux ouvertures à fente en H orthogonales parfaitement découplées en bande X. 2) La deuxième structure est destinée à la diversité d’antennes dans le contexte des réseaux corporels embarqués ou Body Area Network (BAN). L’antenne à diversité combine une antenne fente en boucle avec un DRA ce qui permet dans un espace compact de réaliser des diagrammes de type “broadside” et “endfire” respectivement. Les alimentations considérées sont de 2 types; Soit purement planaire (microruban et coplanaire) soit mixte en combinant une alimentation coaxiale et une alimentation coplanaire. Caractéristiques principales des antennes à résonateur diélectrique (DRA): Pour répondre aux attentes des utilisateurs en termes de débit, les systèmes de communication sans fils se tournent vers des fréquences de plus en plus élevées. La conséquence de cette montée en fréquence est notamment l’augmentation des pertes au niveau des éléments conducteurs et donc une diminution de l’efficacité globale des systèmes de communication. Dans ces circonstances, les DRA offre de meilleurs résultats par rapport à d'autres familles d'antennes à base d’éléments métalliques. De plus, les DRA offrent des pertes diélectriques négligeables, elles sont peu sensibles aux variations de température et s’intègrent facilement sur des technologies de fabrication planairesTechnologies such as direct broad cast satellite system (DBSS), Geosynchronous Earth Orbit (GEO) and Low Earth Orbit (LEO) satellite communications , global positioning system (GPS), high accuracy airborne navigation system and a large variety of radar systems demand for high level of antenna performance. Similar is the requirement for upcoming land based wireless systems such as cellular and indoor communication systems that is needed some more specific and additional features added to the antenna to compensate for the deficiencies encountered in system's performance. Though metallic antennas are capable enough to fulfil all the operational requirements, however at very high frequencies and under hostile temperature conditions they are constrained to face certain limitations. To avoid these constraints the performance of Dielectric Resonator Antennas (DRAs) is evaluated and their new applications are proposed. In the thesis, two types of antenna applications are sought :-First is for tracking and satellite applications that needs a larger aperture coverage in elevation plane. This coverage is realized with a good CP purity by proposing two ports dual linearly polarized DRA working at X-band. The DRA is excited by two orthogonal H-shaped aperture slots yielding two orthogonal polarizations in the broadside direction. A common impedance bandwidth of 5.9% and input port isolation of -35 dB are obtained. The broadside radiation patterns are found to be highly symmetric and stable with cross polarization levels -15dB or better over the entire matching frequency band. The maximum measured gain is found to be 2.5dBi at 8.4 GHz.- The 2nd type of antenna is a dual pattern diversity antenna to be used in the Body Area Network (BAN) context. This antenna combines a slot loop and DRA yielding broadside and end-fire radiation patterns respectively. Based upon the feeding techniques, the DG antenna is further divided into two categories one with planar feeds and the other with non-planar feeds (slot loop excited by planar CPW but DRA excited by vertical monopole) .Both types are successfully designed and measured upon body when configured into different propagation scenarios. The non-planar feeds antenna allows wider common impedance bandwidths than the planar feeds (4.95% vs 1.5%).In both cases, a maximum value of DG=9.5dB was achieved when diversity performance tests were carried out in rich fading environments. This value is close to the one (10 dB) theoretically reached in a pure Rayleigh environment and was obtained with efficiencies of 70% and 85% for the slot loop and the DRA respectively. Therefore, we conclude that these antennas could be used on the shoulders or the chest of professional clothes (firemen, policemen, soldier) where full planar integration is not a key issue but where the communication must be efficient in harsh environments and for various gestures, positions and scenarios
28
Arthuis, Pierre. "Bogoliubov Many-Body Perturbation Theory for Nuclei : Systematic Generation and Evaluation of Diagrams and First ab initio Calculations." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS304/document.
Повний текст джерелаАнотація:
Les dernières décennies ont donné lieu à un développement rapide des théories ab initio visant à décrire les propriétés des noyaux à partir de l'interaction nucléonique. Un tel développement a été rendu possible à la fois par la très importante croissance de la puissance de calcul et de nouveaux développements formels. Le présent travail se consacre au développement de la théorie de perturbation à N corps de Bogolioubov récemment proposée, qui repose sur l'usage d'un état de référence brisant la symétrie associée au nombre de particules pour permettre une description des noyaux à simple couche ouverte. Le formalisme est tout d'abord décrit en détails, son lien avec la théorie de perturbation à N corps standard est établi, tout comme sa connexion avec la théorie de cluster couplés de Bogolioubov. L'extension du formalisme à des ordres plus élevés à partir de méthodes de théorie des graphes est ensuite présentée ainsi que le programme ADG qui génère et évalue les diagrammes BMBPT à un ordre quelconque. Les implications de ce développement formel dépassent le cadre du présent travail, les méthodes développées pouvant être appliqués à d’autres méthodes à N corps. Pour terminer, de premiers résultats numériques pour les isotopes de l'oxygène, du calcium et du nickel sont présentés. Ces résultats établissent la théorie de perturbation à N corps de Bogolioubov comme une méthode de premier intérêt pour des calculs à grande échelle sur les chaînes isotopiques et isotoniques de masse moyenneThe last few decades in nuclear structure theory have seen a rapid expansion of ab initio theories, aiming at describing the properties of nuclei starting from the inter-nucleonic interaction. Such an expansion relied both on the tremendous growth of computing power and novel formal developments. This work focuses on the development of the recently proposed Bogoliubov Many-Body Perturbation Theory that relies on a particle-number-breaking reference state to tackle singly open-shell nuclei. The formalism is first described in details, and diagrammatic and algebraic contributions are derived up to second order. Its link to standard Many-Body Perturbation Theory is made explicit, as well as its connexion to Bogoliubov Coupled-Cluster theory. An automated extension to higher orders based on graph theory methods is then detailed, and the ADG numerical program generating and evaluating BMBPT diagrams at arbitrary order is introduced. Such a formal development carries implications that are not restricted to the present work, as the developed methods can be applied to other many-body methods. Finally, first numerical results obtained for oxygen, calcium and nickel isotopes are presented. They establish BMBPT as a method of interest for large-scale computations of isotopic or isotonic chains in the mid-mass sector of the nuclear chart
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Juršėnas, Rytis. "Algebrinis daugiadalelės trikdžių teorijos plėtojimas teorinėje atomo spektroskopijoje." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20101223_152955-40113.
Повний текст джерелаАнотація:
Šis darbas yra skirtas šiuolaikinės atomo trikdžių teorijos matematinio aparato, paremto efektinių operatorių formalizmu, plėtojimui. Darbe nuosekliai ir sistemingai, pradedant nuo pačių bendriausių principų, nagrinėjami Foko erdvės apribojimo į redukavimo grupių neredukuotinus poerdvius metodai bei pateikiama neredukuotinų tenzorinių operatorių, charakterizuojančių fizikines ir efektines sąveikas, klasifikacija bendrais ir tam tikrais atskirais atvejais. Gautos išraiškos ir iš jų išplaukiančios išvados yra grindžiamos matematine kalba. Dauguma esminių rezultatų yra suformuluoti teoremų pavidalu. Disertaciją sudaro 101 puslapis, 5 skyriai, 4 priedai, 40 lentelių ir 9 paveikslėliai. Pagrindiniai rezultatai, pateikti disertacijoje, yra publikuoti fizikos ir matematikos mokslų žurnaluose.The principal goals of the thesis are subjected to general methods and forms of effective operators by the nowadays demands of theoretical application of many-body perturbation theory to atomic physics. The present theoretical research follows up step by step by systematic observation of various possibilities to restrict the Fock space operators to their irreducible subspaces and the classification of irreducible tensor operators which represent the physical as well as the effective interactions. To ground the results of the thesis, the symbolic preparation of obtained expressions is strictly proved mathematically. Most of the main results are listed in theorems. The doctoral dissertation contains 101 pages, 5 sections, 4 appendices, 40 tables and 9 figures. The main results described in the present dissertation have been published in journals of physical and mathematical sciences.
30
García, Arregui Aníbal. "La selva tecnológica. Sistemas Sociotécnicos y Antropología Simétrica en Comunidades Ribereñas del Bajo Amazonas." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/104557.
Повний текст джерелаАнотація:
En esta tesis se reinterpreta la idea de “tecnología” partiendo de los ejemplos etnográficos de varias comunidades ribereñas del Bajo Amazonas. La situación híbrida de estos ribereños, que mantienen las técnicas tradicionales indígenas y a la vez se acomodan al influjo de la modernidad, permite establecer un eje de simetría entre la tecnología amazónica y la occidental. El objetivo teórico es demostrar que la idea de “tecnología” se ha definido desde Occidente en términos etnocéntricos, esto es, identificándola con las máquinas y artefactos que han generado el desarrollo industrial a base de dominar un entorno natural opuesto simbólicamente a la cultura humana. La tecnología de los ribereños, sin embargo, no se cifra en esos parámetros, sino que debe rastrearse en sus modos de utilizar el cuerpo, en el conocimiento implícito y en las circunstancias (más sociales que técnicas) de la modernización y la política agraria brasileña. Partiendo de estas cuatro dimensiones sociotécnicas, se verá cómo la perspectiva antropológica puede proporcionar un cuadro interpretativo de la tecnología que la llevaría más allá de su caracterización occidental. Si el pensamiento moderno la ha presentado como el instrumento con el que la sociedad logra emanciparse de la naturaleza, aquí se van a invertir dichos términos, para definirla como una estrategia de relación con el entorno por la que precisamente se refuerza la mímesis entre lo “social” y lo “natural”.This thesis develops a reinterpretation of the idea of “technology” by focusing on the ethnographical examples of several Lower Amazon riverine communities. The hybrid situation of the riverines, who still maintain the indigenous traditional techniques and at the same time are influenced by modernity, allows us to establish an axis of symmetry between native and western technologies. The theoretical objective is to show that technology has been defined by the West in ethnocentric terms, this is, identifying it with the machines and artefacts that generated the industrial development by dominating a natural environment that is symbolically opposed to human culture. Riverines technology, however, can’t be understood through these parameters, but rather through their body uses, their implicit knowledge and the circumstances (more social than technical) of modernization and the Brazilian agrarian politics. Regarding to these four sociotechnical dimensions, it will be seen how anthropology provides an interpretative frame that leads technology beyond its Western characterisation. While modern thought has represented it as the instrument with which society becomes emancipated form nature, here these terms will be reversed, aiming to define technology as a strategy of relation with the environment that precisely reinforces the mimesis between the “social” and the “natural”.
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Ricaud, Julien. "Symétrie et brisure de symétrie pour certains problèmes non linéaires." Thesis, Cergy-Pontoise, 2017. http://www.theses.fr/2017CERG0849.
Повний текст джерелаАнотація:
Cette thèse est consacrée à l'étude mathématique de deux systèmes quantiques décrits par des modèles non linéaires : le polaron anisotrope et les électrons d'un cristal périodique. Après avoir prouvé l'existence de minimiseurs, nous nous intéressons à la question de l'unicité pour chacun des deux modèles. Dans une première partie, nous montrons l'unicité du minimiseur et sa non-dégénérescence pour le polaron décrit par l'équation de Choquard--Pekar anisotrope, sous la condition que la matrice diélectrique du milieu est presque isotrope. Dans le cas d'une forte anisotropie, nous laissons la question de l'unicité en suspens mais caractérisons précisément les symétries pouvant être dégénérées. Dans une seconde partie, nous étudions les électrons d'un cristal dans le modèle de Thomas--Fermi--Dirac--Von~Weizsäcker périodique, en faisant varier le paramètre devant le terme de Dirac. Nous montrons l'unicité et la non-dégénérescence du minimiseur lorsque ce paramètre est suffisamment petit et mettons en évidence une brisure de symétrie lorsque celui-ci est grandThis thesis is devoted to the mathematical study of two quantum systems described by nonlinear models: the anisotropic polaron and the electrons in a periodic crystal. We first prove the existence of minimizers, and then discuss the question of uniqueness for both problems. In the first part, we show the uniqueness and nondegeneracy of the minimizer for the polaron, described by the Choquard--Pekar anisotropic equation, assuming that the dielectric matrix of the medium is almost isotropic. In the strong anisotropic setting, we leave the question of uniqueness open but identify the symmetry that can possibly be degenerate. In the second part, we study the electrons of a crystal in the periodic Thomas--Fermi--Dirac--Von~Weizsäcker model, varying the parameter in front of the Dirac term. We show uniqueness and nondegeneracy of the minimizer when this parameter is small enough et prove the occurrence of symmetry breaking when it is large
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Silva, Madson Rubem Oliveira. "Alguns resultados exatos a Temperatura Finita da Eletrodinâmica CPT-par do Modelo Padrão Estendido." Universidade Federal do Maranhão, 2010. http://tedebc.ufma.br:8080/jspui/handle/tede/721.
Повний текст джерелаАнотація:
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Previous issue date: 2010-04-30Maxwell s electrodynamics is a field theory which contains in its structure three fundamental physical symmetries: The Lorentz symmetry, the CPT-symmetry and the local gauge symmetry. The Lorentz covariance and the CPT-symmetry are fundamental in the construction of any field theory describing elementary (or not elementary) particles. Both together with the local gauge symmetry are the cornerstones in the construction of the Standard Model and of others modern field theories. However, it is cogitate that as much the Lorentz covariance as the CPT-symmetry can be spontaneously broken at Planck energy scale (or in the very early Universe when energies are close to the Planck scale) due to quantum gravity effects. The possible residual effects of such spontaneous symmetry breaking are studied within the structure of the Standard Model Extension (SME). The U(1)-local gauge symmetry sector of the SME describes the effects produced in Maxwell s electrodynamics due to the Lorentz-covariance violation and the spontaneous symmetry breaking of the CPT-invariance. Here, we study the finite temperature properties of the CPT-even electrodynamics of SME, represented by the term (kF )ανρφFανFρφ. First, we construct a well-defined and gauge invariant partition function in the functional integration formalism for an arbitrary tensor (kF ). Then, we specialize for the leading-order-nonbirefringent coefficients of the tensor (kF ) and we study in separate the parityeven and the parity-odd sectors. Consequently, for both sectors, the partition function is exactly caculated by showing that it is a power of Maxwell s partition function. Such power is an explicit function of the respective parameters ruling the Lorentz-covariance violation. This way, Planck s radiation law retains its frequency dependence and the Stefan-Boltzmann law is maintained, except for a change in Stefan-Boltzmann s constant that is multiplied by a global factor containing all the LIV contributions. Nevertheless, in general, it is observed that the LIV coefficients induce an anisotropy in the angular distribution of the black body energy density.
A eletrodinâmica de Maxwell é uma teoria de campo que contém em sua estrutura três tipos de simetrias fundamentais na física: A simetria de Lorentz, a simetria CPT e a simetria de calibre local. A covariância de Lorentz e a simetria CPT são fundamentais na construção de qualquer teoria de campo que descreva partículas elementares e não elementares. Ambas simetrias juntamente com a simetria de calibre local são os pilares na construção do Modelo Padrão e de outras modernas teorias de campo. No entanto, cogita-se que ambas, a covariância de Lorentz e a simetria CPT, poderiam sofrer uma quebra espontânea de simetria na escala de energia de Planck (ou no Universo primordial quando as energias eram da ordem de magnitude) devido aos efeitos produzidos pelo gravidade quântica. Os possíveis efeitos residuais dessa quebra espontânea, tanto da covariância de Lorentz como da simetria CPT, são estudados dentro da estrutura do Modelo Padrão Estendido (MPE). Assim, o setor de simetria de calibre local U(1) do MPE descreve os efeitos sofridos pela eletrodinâmica de Maxwell devido à violação da covariância de Lorentz e da quebra espontânea da invariância CPT. O intuito da Dissertação é estudarmos as propriedades à temperatura finita da eletrodinãmica CPT-par do MPE representada pelo termo (kF )ανρφFανFρφ. O primeiro passo é construir uma função de partição, bem definida e invariante de gauge, para uma configuração arbitrária do tensor (kF )ανρφ. Como estamos interessados em conhecer efeitos não perturbativos ou exatos da quebra espontânea da simetria de Lorentz, concentramos nossa atenção nas componentes do tensor (kF ) cujas contribuições, em primeira ordem não nula, para as relações de dispersão da eletrodinâmica de Maxwell ainda as mantém não birrefringentes. Para uma maior clareza ou um melhor entendimento, estudamos separadamente esses coeficientes não birrefringentes pertencentes aos setores de paridadepar e de paridade-ímpar do tensor (kF ) . Consequentemente, para ambos os setores, mostramos que a função de partição é calculada exatamente e resulta ser uma potência da função de partição de Maxwell. Tal potência é uma função explícita somente dos respectivos parâmetros que controlam a violação da simetria de Lorentz (VSL). Esse resultado demonstra que as propriedades termodinâmicas, do setor não birrefringente da eletrodinâmica CPT-par do MPE, como densidade de energia, pressão, entropia, etc, sejam as mesmas da eletrodinâmica de Maxwell multiplicadas por uma função que depende somente nos respectivos coeficientes não birrefringentes. Desse modo, a lei de radiação de Planck mantém a mesma dependência funcional na freqüência e a lei de Stefan-Boltzmann conservasse proporcional a T4. Entretanto, a constante de Stefan-Boltzmann usual sofre uma mudança, pois resulta multiplicada justamente por um fator global que contém as contribuições da VSL. No entanto, observa-se que, em geral, os coeficientes do VSL induzem uma anisotropia na distribuição angular da densidade de energia emitida pelo corpo negro.
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Gouveia, Paulo D. F. "Computação de simetrias variacionais e optimização da resistência aerodinâmica newtoniana." Doctoral thesis, Universidade de Aveiro, 2008. http://hdl.handle.net/10198/1571.
Повний текст джерелаАнотація:
Neste trabalho exploram-se alguns dos actuais recursos de computação científica no contexto da optimização estática e dinâmica. Começa-se por propor um conjunto de procedimentos computacionais algébricos que permitem automatizar todo o processo de obtenção de simetrias e leis de conservação, quer no contexto clássico do cálculo das variações, quer no contexto mais abrangente do controlo óptimo. A utilidade do package de funções desenvolvido é demonstrada com a identificação de novas leis de conservação para alguns problemas do controlo óptimo conhecidos na literatura. Estabelece-se depois uma relação entre as simetrias variacionais do controlo óptimo e as simetrias de equações diferenciais ordinárias. A partir dessa relação, deduz-se um método construtivo, alternativo aos já existentes, para obtenção de simetrias nesta segunda classe de problemas. Numa segunda parte do trabalho, investigam-se, com recurso a simulações computacionais, formas de corpos não convexos que maximizem a sua resistência aerodinâmica quando se desloquem em meios rarefeitos e, simultaneamente, exibam um ligeiro movimento rotacional. É obtido um importante resultado original para o caso bidimensional. Trata-se de uma forma geométrica que confere ao corpo uma resistência muito próxima do seu limite teórico (R=1.4965<1.5). In this thesis some of the scientific computational resources are explored in
the context of static and dynamic optimization. A set of analytical computational
tools is proposed in order to allow the identification, in an automatic
way, of variational symmetries and conservation laws in the calculus of variations
and optimal control. The usefulness of the developed routines is
showed with the identification of new conservation laws to concrete optimal
control problems found in the literature. A relationship between the variational
symmetries of optimal control and the symmetries of ordinary differential
equations is established. Based in this relationship, a constructive method
is created for the purpose of getting the symmetries in this second class of
problems. Finally, we investigate, by means of computational simulations,
shapes of nonconvex bodies that maximize resistance to its motion on a rarefied
medium, considering that bodies are moving forward and at the same
time slowly rotating. An important result is obtained for the two-dimensional
case which consists of a geometric shape that confers to the body a resistance
very close to the supremum value (R = 1.4965 < 1.5).
Some results of the thesis are available in the English language in the following
references: the research reports [29, 35, 37, 79], the poster [36], the conference
proceedings with referee [34] and the refereed journals [31, 32, 38, 80].
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Rodrigues, Josberg Silva. "Propriedades termodinâmicas do campo eletromagnético no setor CPT-ımpar do modelo padrão estendido." Universidade Federal do Maranhão, 2009. http://tedebc.ufma.br:8080/jspui/handle/tede/715.
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Previous issue date: 2009-04-30FUNDAÇÃO DE AMPARO À PESQUISA E AO DESENVOLVIMENTO CIENTIFICO E TECNOLÓGICO DO MARANHÃO
In this work we study the effects of the spontaneous breaking of Lorentz symmetry on black body radiation phenomenon in the context of the Maxwell-Caroll-Field-Jackiw (MCFJ) model. The MCFJ model is the electromagnetic CPT-odd sector of the standard model extension and, it presents for a purely space-like background a positive-definite hamiltonian. Firstly, we study the Maxwell electrodynamics by analyzing its hamiltonian structure following the Dirac s procedure for constrained systems. Then, we calculate the partition function via the path integrals formalism and consequently we obtain its thermodynamic properties such as: energy density, radiation pressure and the entropy. Afterwards, we apply the same procedure to find the partition function of the MCFJ model and we observe how the spectrum of black body changes due to the breaking of the CPT and Lorentz symmetries. We show that if the cosmic microwave background (CMB) radiation is described by this model, it shows an angular anisotropy in the energy density distribution. We also give, at leading order in the Lorentz violating parameter, the contributions of the Lorentz breaking for the Planck s radiation and the Stefan-Boltzmann laws. The Lorentz-violating (LV) corrections for the Planck s law is non-linear in the frequency and for the Stefan-Boltzmann law is quadratic in the temperature. Using our results, we set upper limits for the LV parameter by analyzing the Stefan-Boltmann law and the CMB anisotropy but it is shown that they are much less stringents that those obtained by birefringence or polarization analysis of light.
Esta dissertação aborda os efeitos da quebra espontânea da simetria de Lorentz sob a radiação do corpo negro no contexto da eletrodinâmica de Maxwell-Carroll-Field-Jackiw (MCFJ). O modelo MCFJ advém do setor CPT-ìmpar do modelo padrão estendido e apresenta uma hamiltoniana positiva-definida somente para um campo de fundo puramente tipo-espaço. O estudo começa pela eletrodinâmica de Maxwell realizando uma análise de sua estrutura hamiltoniana através do procedimento de Dirac para sistemas vinculados. Após essa análise, calcula-se a função de partição via o formalismo de integração funcional e obtendo consequentemente suas propriedades termodinâmicas relevantes como: densidade de energia, pressão de radiação e a entropia do sistema. Na segunda parte, seguindo um procedimento similar encontramos a função de partição do modelo MCFJ. Observa-se que o espectro de energia do corpo negro sofre alteração devido à quebra da invariância de Lorentz e da simetria CPT. Mostramos que se a radiação cósmica de fundo (RCF) for descrita por esse modelo desponta uma anisotropia na distribuição de densidade de energia. Também, mostramos que a lei de radiação de Planck e a lei de Stefan Boltzmann são afetadas pela introdução do campo externo responsável pela quebra de Lorentz. Tais modificações no caso da lei de Planck são não-lineares na frequência e na lei de Stefan-Boltzmann são quadráticas na temperatura. Usando esses resultados e os dados experimentais da constante de Stefan-Boltzmann e os dados referentes a anisotropia da radiação cósmica de fundo, estipulamos limites superiores para a magnitude do parâmetro da VL. Contudo, os limites obtidos são menos restritivos que os obtidos pela análise do fenômeno da birrefrigência.
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Decamp, Jean. "Symétries et corrélations dans les gaz quantiques fortement interagissants à une dimension." Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4060/document.
Повний текст джерелаАнотація:
L’objectif principal de cette thèse est l’étude théorique de mélanges quantiques fortement interagissants à une dimension et soumis à un potentiel externe harmonique. De tels systèmes fortement corrélés peuvent être réalisés et testés dans des expériences d’atomes ultrafroids. Leurs propriétés de symétrie par permutation non triviales sont étudiées, ainsi que leurs effets sur les corrélations. Exploitant une solution exacte pour des interactions fortes, nous extrayons des propriétés générales des corrélations encodées dans la matrice densité à un corps et dans les distributions des impulsions associées, dans les mélanges fermioniques et de Bose-Fermi. En particulier, nous obtenons des résultats substantiels sur le comportement à courtes distances, et donc les queues à haute impulsions, qui suivent des lois en k^−4 typiques. Les poids de ces queues, dénotés contacts de Tan, sont liés à de nombreuses propriétés thermodynamiques des systèmes telles que les corrélations à deux corps, la dérivée de l’énergie par rapport à la longueur de diffusion unidimensionnelle, ou le facteur de structure statique. Nous montrons que ces contacts universels de Tan permettent également de caractériser la symétrie spatiale des systèmes, et constituent donc une connexion profonde entre les corrélations et les symétries. En outre, la symétrie d’échange est extraite en utilisant une méthode de théorie des groupes, à savoir la méthode de la somme des classes (class-sum method en anglais), qui provient à l’origine de la physique nucléaire. De plus, nous montrons que ces systèmes suivent une version généralisée du fameux théorème de Lieb-Mattis. Souhaitant rendre nos résultats aussi pertinents expérimentalement que possible, nous dérivons des lois d’échelle pour le contact de Tan en fonction de l’interaction, de la température et du confinement transverse. Ces lois présentent des effets intéressants liés aux fortes corrélations et à la dimensionnalitéThe main focus of this thesis is the theoretical study of strongly interacting quantum mixtures confined in one dimension and subjected to a harmonic external potential. Such strongly correlated systems can be realized and tested in ultracold atoms experiments. Their non-trivial permutational symmetry properties are investigated, as well as their interplay with correlations. Exploiting an exact solution at strong interactions, we extract general correlation properties encoded in the one-body density matrix and in the associated momentum distributions, in fermionic and Bose-Fermi mixtures. In particular, we obtain substantial results about the short-range behavior, and therefore the high-momentum tails, which display typical k^−4 laws. The weights of these tails, denoted as Tan’s contacts, are related to numerous thermodynamic properties of the systems such as the two-body correlations, the derivative of the energy with respect to the one-dimensional scattering length, or the static structure factor. We show that these universal Tan’s contacts also allow to characterize the spatial symmetry of the systems, and therefore is a deep connection between correlations and symmetries. Besides, the exchange symmetry is extracted using a group theory method, namely the class-sum method, which comes originally from nuclear physics. Moreover, we show that these systems follow a generalized version of the famous Lieb-Mattistheorem. Wishing to make our results as experimentally relevant as possible, we derive scaling laws for Tan’s contact as a function of the interaction, temperature and transverse confinement. These laws. Display displadisplay display interesting effects related to strong correlations and dimensionality
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Rocha, Eugénio Alexandre Miguel. "Uma Abordagem Algébrica à Teoria de Controlo Não Linear." Doctoral thesis, Universidade de Aveiro, 2003. http://hdl.handle.net/10773/21444.
Повний текст джерелаАнотація:
Doutoramento em MatemáticaNesta tese de Doutoramento desenvolve-se principalmente uma abordagem algébrica à teoria de sistemas de controlo não lineares. No entanto, outros tópicos são também estudados. Os tópicos tratados são os seguidamente enunciados: fórmulas para sistemas de controlo sobre álgebras de Lie livres, estabilidade de um sistema de corpos rolantes, algoritmos para aritmética digital, e equações integrais de Fredholm não lineares. No primeiro e principal tópico estudam-se representações para as soluções de sistemas de controlo lineares no controlo. As suas trajetórias são representadas pelas chamadas séries de Chen. Estuda-se a representação formal destas séries através da introdução de várias álgebras não associativas e técnicas específicas de álgebras de Lie livres. Sistemas de coordenadas para estes sistemas são estudados, nomeadamente, coordenadas de primeiro tipo e de segundo tipo. Apresenta-se uma demonstração alternativa para as coordenadas de segundo tipo e obtêm-se expressões explícitas para as coordenadas de primeiro tipo. Estas últimas estão intimamente ligadas ao logaritmo da série de Chen que, por sua vez, tem fortes relações com uma fórmula designada na literatura por “continuous Baker-Campbell- Hausdorff formula”. São ainda apresentadas aplicações à teoria de funções simétricas não comutativas. É, por fim, caracterizado o mapa de monodromia de um campo de vectores não linear e periódico no tempo em relação a uma truncatura do logaritmo de Chen. No segundo tópico é estudada a estabilizabilidade de um sistema de quaisquer dois corpos que rolem um sobre o outro sem deslizar ou torcer. Constroem-se controlos fechados e dependentes do tempo que tornam a origem do sistema de dois corpos num sistema localmente assimptoticamente estável. Vários exemplos e algumas implementações em Maple°c são discutidos. No terceiro tópico, em apêndice, constroem-se algoritmos para calcular o valor de várias funções fundamentais na aritmética digital, sendo possível a sua implementação em microprocessadores. São também obtidos os seus domínios de convergência. No último tópico, também em apêndice, demonstra-se a existência e unicidade de solução para uma classe de equações integrais não lineares com atraso. O atraso tem um carácter funcional, mostrando-se ainda a diferenciabilidade no sentido de Fréchet da solução em relação à função de atraso.
In this PhD thesis several subjects are studied regarding the following topics: formulas for nonlinear control systems on free Lie algebras, stabilizability of nonlinear control systems, digital arithmetic algorithms, and nonlinear Fredholm integral equations with delay. The first and principal topic is mainly related with a problem known as the continuous Baker-Campbell-Hausdorff exponents. We propose a calculus to deal with formal nonautonomous ordinary differential equations evolving on the algebra of formal series defined on an alphabet. We introduce and connect several (non)associative algebras as Lie, shuffle, zinbiel, pre-zinbiel, chronological (pre-Lie), pre-chronological, dendriform, D-I, and I-D. Most of those notions were also introduced into the universal enveloping algebra of a free Lie algebra. We study Chen series and iterated integrals by relating them with nonlinear control systems linear in control. At the heart of all the theory of Chen series resides a zinbiel and shuffle homomorphism that allows us to construct a purely formal representation of Chen series on algebras of words. It is also given a pre-zinbiel representation of the chronological exponential, introduced by A.Agrachev and R.Gamkrelidze on the context of a tool to deal with nonlinear nonautonomous ordinary differential equations over a manifold, the so-called chronological calculus. An extensive description of that calculus is made, collecting some fragmented results on several publications. It is a fundamental tool of study along the thesis. We also present an alternative demonstration of the result of H.Sussmann about coordinates of second kind using the mentioned tools. This simple and comprehensive proof shows that coordinates of second kind are exactly the image of elements of the dual basis of a Hall basis, under the above discussed homomorphism. We obtain explicit expressions for the logarithm of Chen series and the respective coordinates of first kind, by defining several operations on a forest of leaf-labelled trees. It is the same as saying that we have an explicit formula for the functional coefficients of the Lie brackets on a continuous Baker-Campbell-Hausdorff-Dynkin formula when a Hall basis is used. We apply those formulas to relate some noncommutative symmetric functions, and we also connect the monodromy map of a time-periodic nonlinear vector field with a truncation of the Chen logarithm. On the second topic, we study any system of two bodies rolling one over the other without twisting or slipping. By using the Chen logarithm expressions, the monodromy map of a flow and Lyapunov functions, we construct time-variant controls that turn the origin of a control system linear in control into a locally asymptotically stable equilibrium point. Stabilizers for control systems whose vector fields generate a nilpotent Lie algebra with degree of nilpotency · 3 are also given. Some examples are presented and Maple°c were implemented. The third topic, on appendix, concerns the construction of efficient algorithms for Digital Arithmetic, potentially for the implementation in microprocessors. The algorithms are intended for the computation of several functions as the division, square root, sines, cosines, exponential, logarithm, etc. By using redundant number representations and methods of Lyapunov stability for discrete dynamical systems, we obtain several algorithms (that can be glued together into an algorithm for parallel execution) having the same core and selection scheme in each iteration. We also prove their domains of convergence and discuss possible extensions. The last topic, also on appendix, studies the set of solutions of a class of nonlinear Fredholm integral equations with general delay. The delay is of functional character modelled by a continuous lag function. We ensure existence and uniqueness of a continuous (positive) solution of such equation. Moreover, under additional conditions, it is obtained the Fr´echet differentiability of the solution with respect to the lag function.
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Brenot, Dominique. "Transmission du son à l'intérieur d'une structure axisymétrique." Paris 6, 1986. http://www.theses.fr/1986PA066022.
Повний текст джерелаАнотація:
Problème de la transmission du son sur l'axe d'une structure élastique fermée à symétrie de révolution. Problème de Neumann, associé à la pression acoustique par la méthode de la phase stationnaire et problème de structure par une méthode d'éléments finis.
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Fujdiak, Radek. "Analýza a optimalizace datové komunikace pro telemetrické systémy v energetice." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-358408.
Повний текст джерелаАнотація:
Telemetry system, Optimisation, Sensoric networks, Smart Grid, Internet of Things, Sensors, Information security, Cryptography, Cryptography algorithms, Cryptosystem, Confidentiality, Integrity, Authentication, Data freshness, Non-Repudiation.
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Chang, Ke Ming, and 張格銘. "Symmetric co-circular five-body central configurations." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/87070340930249122915.
Повний текст джерелаАнотація:
碩士國立清華大學
數學系
104
In this paper, we study co-circular five-body central configurations with their center of mass at the center of the circumscribed circle. We shall show that in the symmetric case, the only central configuration satisfying these conditions is the regular pentagon with equal masses.
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Liu, Yu-Hsuan, and 劉雨瑄. "Studies on Potential Flow Pattern for Axially Symmetric Body." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/67490840391484276961.
Повний текст джерелаАнотація:
碩士中原大學
土木工程研究所
91
Abstract This thesis aims to study the three-dimensional, axially symmetric, potential flow. By using the symmetric quality of the three-dimensional flow as our theoretical foundation, Stokes’ stream function can be used to infer the relationship among streamline, stream function and velocity potential. Then we use the result to design the arrangement of line sources and sinks in conjunction with a uniform flow. It is possible to develop approximate solution for flows about bodies of revolution. In this research, the mathematic calculation, resulting from using Matlab to resolve polyinomial , is used to analyze the flow. When the mathematic calculation is used, one would come across some strange situations, which one is unable to give an answer to. Thus, this thesis tried to find out an explanation to those situations.
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Łukaszewicz, Tomasz. "Posturographic methods for body posture symmetry assessment." Rozprawa doktorska, 2018. https://repolis.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=47452.
Повний текст джерела
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Łukaszewicz, Tomasz. "Posturographic methods for body posture symmetry assessment." Rozprawa doktorska, 2018. https://delibra.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=47452.
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Lewis, Mark. "Unstable Brake Orbits in Symmetric Hamiltonian Systems." Thesis, 2013. http://hdl.handle.net/1974/8313.
Повний текст джерелаАнотація:
In this thesis we investigate the existence and stability of periodic solutions of Hamiltonian systems with a discrete symmetry. The global existence of periodic motions can be proven using the classical techniques of the calculus of variations; our particular interest is in how the stability type of the solutions thus obtained can be determined analytically using solely the variational problem and the symmetries of the system -- we make no use of numerical or perturbation techniques. Instead, we use a method introduced in [41] in the context of a special case of the three-body problem. Using techniques from symplectic geometry, and specifically the Maslov index for curves of Lagrangian subspaces along the minimizing trajectories, we verify conditions which preclude the existence of eigenvalues of the monodromy matrix on the unit circle.
We study the applicability of this method in two specific cases. Firstly, we consider another special case from celestial mechanics: the hip-hop solutions of the 2N-body problem. This is a family of Z_2-symmetric, periodic orbits which arise as collision-free minimizers of the Lagrangian action on a space of symmetric loops [14, 53]. Following a symplectic reduction, it is shown that the hip-hop solutions are brake orbits which are generically hyperbolic on the reduced energy-momentum surface.
Secondly we consider a class of natural Hamiltonian systems of two degrees of freedom with a homogeneous potential function. The associated action functional is unbounded above and below on the function space of symmetric curves, but saddle points can be located by minimization subject to a certain natural constraint of a type first considered by Nehari [37, 38]. Using the direct method of the calculus of variations, we prove the existence of symmetric solutions of both prescribed period and prescribed energy. In the latter case, we employ a variational principle of van Groesen [55] based upon a modification of the Jacobi functional, which has not been widely used in the literature. We then demonstrate that the (constrained) minimizers are again hyperbolic brake orbits; this is the first time the method has been applied to solutions which are not globally minimizing.Thesis (Ph.D, Mathematics & Statistics) -- Queen's University, 2013-09-25 10:47:53.257
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Gurian, Tyler. "Streamwise Flow-Induced Oscillations of Bluff Bodies - The Influence of Symmetry Breaking." 2018. https://scholarworks.umass.edu/masters_theses_2/646.
Повний текст джерелаАнотація:
The influence of symmetry breaking on the flow induced oscillations of bluff bodies in the steamwise direction is studied. First, a series of experiments is conducted on a one-degree-of-freedom circular cylinder allowed to exhibit pure translational motion in the streamwise direction over a range of reduced velocities, 1.4 < U* < 4.4, corresponding to a Reynolds number range of 970 < Re < 3370. Two distinct regions of displacements were observed in reduced velocity ranges of 1.6 < U* < 2.5 and 2.75 < U* < 3.85. Measured force coefficients in the drag and lift direction were examined, along with the wake visualization, through the range of reduced velocities, to infer the resulting wake modes. A new Alternating Symmetric (AS) mode was found. This transition from symmetric to AS shedding occurred near the end of the first region of response. Similar tests were run with a square prism in the parameter space of 2.4 < U* < 5.8 and 757 < Re < 1900 over angles of incidence of 0° ≤ α ≤ 45°. A distinct region of lock-in is observed for α = 0°, 2.5°, 5°, 7.5° over 3.2 < U* < 5.4 for α = 0°, and decreasing with increasing α. The wake structures were found to be roughly symmetric for α = 0°, but transitioned towards asymmetry with increasing α. For α = 0° and 2.5° a gradual increase in the asymmetry of the fluid forcing was observed with increasing U*, similar to the circular cylinder.
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Bakhtiary, Esmaeel. "Probabilistic Seismic Demand Model and Fragility Estimates for Symmetric Rigid Blocks Subject to Rocking Motions." Thesis, 2013. http://hdl.handle.net/1969.1/149244.
Повний текст джерелаАнотація:
This thesis presents a probability model to predict the maximum rotation of rocking bodies exposed to seismic excitations given specific earthquake intensity measures. After obtaining the nonlinear equations of motion and clarification of the boundaries applied to a rocking body to avoid sliding, a complete discussion is provided on the estimation of approximate period and equivalent damping ratio for the rocking motion. Thereafter, instead of using an iterative solution, which was previously proven defective, a new approximate technique is developed by finding the best representative ground motion intensities. Suitable transformation and normalization are applied to these intensities, and the Bayesian Updating approach is employed to construct a probability model. The proposed probability model is capable of accurately predicting the maximum rotation of a symmetric rocking block given displacement design spectra, peak ground acceleration, peak ground velocity, and arias intensity of an earthquake. This probabilistic model along with the approximate capacity of rocking blocks are used to estimate the fragility curves for rocking blocks with specific geometrical parameters. At the end, a comprehensive and practical form of fragility curves and numerical examples are provided for design purposes.
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Liao, Kuo-Liang, and 廖國良. "A Thermal Image abnormal place search system using human body symmetry compare method." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/83927897508054689388.
Повний текст джерелаАнотація:
碩士國立成功大學
電機工程學系
87
Due to the human body temperature symmetry property, using thermal image to identify abnormal place is possible, we can be able to find out the abnormal place by comparing the difference of base temperature and local temperature. The difference of temperature can be achieved by subtracting the thermal image. Usually Symmetry and asymmetry are two methode is use to find out the abnormal place. In asymmetry method, is subtracting from different timing image. And in symmetry method, due to the symmetry of human body. We first suppose one side of human body is normal, simply by subtracting another side, then we can have the result. Because the result of asymmetry is getting from subtraction of different timing image, it might have very huge error. However, but in symmetry method does not have this weakness, so I recommend the Symmetry Method in this thesis. This thesis proposes the Symmetry Compare method to find out the symmetry axis of Thermal Image. From this symmetry axis, we can be able to find out the abnormal place by using the image process method. Since the noise for Thermal Image is too huge, to be able to remove the noise and keep the edge, this thesis makes some modification on “Adaptive Median Filter”. So that we can be able to reach the better result of remove the noise. To be able to approve and certificate the method, this thesis provides the programs of user interface which contains the windows for viewing the diagrams. Including the Image Detecting, the Edge Testing, and the Symmetry Compare Method that I proposed in this thesis, I also designed a physical information showing method. It will provide the convenience for user to test or analyze the result of image.
47
Mai, Chai-Chi, and 麥家齊. "Model Building and Verification of Body Symmetry feature used in Medical posture analysis Based on SVM." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/38456059884802786581.
Повний текст джерелаАнотація:
碩士國立交通大學
生醫工程研究所
104
Traditionally we set multiple reflective balls on subject’ joints during the gait analysising experiment.But this method takes too much time on setting-up and cost too much as medical diagnosis system.This research solve the problem by using Kinect as free contact sensing system,designing several features to measure subjects’ symmetry and verifying them. In this research, we design set of features to measure body symmetry and dynamic balance ability during the experiment.By using Principal Component Analysis,these features will be projected into new space,and we get several new components combined by the original set of features that include most information.For separating healthy and hemiparesis subject, left and right hemiparesis,we use Support Vector Machine to build several models and get hyperplanes for separating.Finally we use these hyperplanes to build a layered-model and achieve 84.6% accuracy.
48
Uhlířová, Tereza. "Singulární chování Hartreeho-Fockových rovnic." Master's thesis, 2018. http://www.nusl.cz/ntk/nusl-388541.
Повний текст джерелаАнотація:
The non-linear Hartree-Fock (HF) equations are usually solved via the iterative self-consistent field method. However, there is no a priori guarantee of convergence, especially in systems with strong electron correlation where symmetry breaking occurs. This work focuses on closed- shell systems in the HF approximation and the (in)stability of the found solutions, and proposes new deterministic methods for the localization of both symmetry-adapted and broken symmetry solutions. We employ a perturbative method and show how one can always obtain a symmetry-adapted solution of the HF equations. We also determine the radius of convergence, related to the existence of at least one bound state, of the perturbative series. Next, we rederive the matrix of stability and adapt it to spin and orbital symmetry. Calculation of higher energy variations follows, first in terms of spin-orbitals and then orbitals. Motivated by the investigation of the structure of a broken-symmetry solution, we propose a new deterministic method for the localization of a broken-symmetry solution. The general expressions are verified by reformulating the stability conditions for simple cases. The proposed methods are successfully applied to helium-, beryllium- and neon-like systems.
49
Sahoo, Shaon. "Studies Of Electronic, Magnetic And Entanglement Properties Of Correlated Models In Low-Dimensional Systems." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2480.
Повний текст джерелаАнотація:
This thesis consists of six chapters. The first chapter gives an introduction to the field of low-dimensional magnetic and electronic systems and relevant numerical techniques. The recent developments in molecular magnets are highlighted. The numerical techniques are reviewed along with their advantages and disadvantages from the present perspective. Study of entanglement of a system can give a great insight into the system. At the last part of this chapter a general overview is given regarding entanglement, its measures and its significance in studying many-body systems.
Chapter 2 deals with the technique that has been developed by us for the full symmetry adaptation of non-relativistic Hamiltonians. It is advantageous both computationally and physically/chemically to exploit both spin and spatial symmetries of a system. It has been a long-standing problem to target a state which has definite total spin and also belongs to a definite irreducible representation of a point group, particularly for non-Abelian point groups. A very general technique is discussed in this chapter which is a hybrid method based on valence-bond basis and the basis of the z-component of the total spin. This technique is not only applicable to a system with arbitrary site spins and belonging to any point group symmetry, it is also quite easy to implement computationally. To demonstrate the power of the method, it is applied to the molecular magnetic system, Cu6Fe8, with cubic symmetry.
In chapter 3, the extension of the previous hybrid technique to electronic systems is discussed. The power of the method is illustrated by applying it to a model icosahedral half-filled electronic system. This model spans a huge Hilbert space (dimension 1,778,966) and is in the largest non-Abelian point group. All the eigenstates of the model are obtained using our technique.
Chapter 4 deals with the thermodynamic properties of an important class of single-chain magnets (SCMs). This class of SCMs has alternate isotropic spin-1/2 units and anisotropic high spin units with the anisotropy axes being non-collinear. Here anisotropy is assumed to be large and negative, as a result, anisotropic units behave like canted spins at low temperatures; but even then simple Ising-type model does not capture the essential physics of the system due to quantum mechanical nature of the isotropic units. A transfer matrix (TM) method is developed to study statistical behavior of this class of SCMs. For the first time, it is also discussed in detail that how weak inter-chain interactions can be treated by a TM method. The finite size effect is also discussed which becomes important for low temperature dynamics. This technique is applied to a real helical chain magnet, which has been studied experimentally.
In the fifth chapter a bipartite entanglement entropy of finite systems is studied using exact diagonalization techniques to examine how the entanglement changes in the presence of long-range interactions. The PariserParrPople model with long-range interactions is used for this purpose and corresponding results are com-pared with those for the Hubbard and Heisenberg models with short-range interactions. This study helps understand why the density matrix renormalization group (DMRG) technique is so successful even in the presence of long-range interactions in the PPP model. It is also investigated if the symmetry properties of a state vector have any significance in relation to its entanglement. Finally, an interesting observation is made on the entanglement profiles of different states, across the full energy spectrum, in comparison with the corresponding profile of the density of states.
The entanglement can be localized between two noncomplementary parts of a many-body system by performing local measurements on the rest of the system. This localized entanglement (LE) depends on the chosen basis set of measurement (BSM). In this chapter six, an optimality condition for the LE is derived, which would be helpful in finding optimal values of the LE, besides, can also be of use in studying mixed states of a general bipartite system. A canonical way of localizing entanglement is further discussed, where the BSM is not chosen arbitrarily, rather, is fully determined by the properties of a system. The LE obtained in this way, called the localized entanglement by canonical measurement (LECM), is not only easy to calculate practically, it provides a nice way to define the entanglement length. For spin-1/2 systems, the LECM is shown to be optimal in some important cases. At the end of this chapter, some numerical results are presented for j1 −j2 spin model to demonstrate how the LECM behaves.