294 research outputs found
Editorial Introduction on Proceedings of the 2015 International Congress on Ultrasonics, 2015 ICU Metz
No full textAbstractA brief summary of the 2015 International Congress on Ultrasonics is presented. The 2015 ICU has taken place in Metz, France, at the Arsenal and was hosted by Georgia Tech Lorraine in collaboration with the French Acoustical Society. The congress hosted a record number of 700 participants. The report focuses on the awards presented during the congress, the invited speakers and some statistics. Other details can be found in reports available on the congress website. The author N. F. Declercq, president of 2015 ICU and Editor of the congress proceedings, wishes to publish the congress proceedings in loving memory of his father Maurice Alois who suddenly passed away 5 weeks after the end of the congress
Numerical study of beam shape adaptation by anisotropic disk covering transducer or metamaterial
No full textMetamaterials are intensely explored for their capabilities to modify sound beams. In addition to frequency filtering, acoustic lenses offer intriguing possibilities for shaping sound beams. For the time being, the versatility of metamaterials remains limitless. In beam-shape adaptation, however, their complexity suggests that manufacturers of transducers could benefit from combining metamaterials with more conventional materials. This paper investigates the transmission of a circumscribed beam through a stratum of anisotropic material to examine the change in beam shape after transmission. The incident sound is presumed to originate from a conventional transducer, possibly coated with a metamaterial to modify the sound field, before being transmitted through the anisotropic layer. Different incident beam shapes, such as conical-like, Gaussian, and pillar beams, are investigated. While the results are not exhaustive, they demonstrate the beam shape’s adaptability
Damage detection in a PA 66,6/Glass woven fabric composite material using ultrasonic techniques towards durability prediction of automotive parts
No full textCes travaux de thèse portent sur l'étude expérimentale approfondie d'un composite à base polyamide 66/6 renforcé par des fibres de verres tissés suivant un motif sergé 2/2. L’objectif est de proposer des solutions de Contrôle Non Destructif (CND) basées sur les ultrasons afin de détecter différents niveaux d’endommagement induis. Pour cela, une étude approfondis des mécanismes d’endommagement apparaissant lors de sollicitations en traction suivant l’axe des fibres et hors axes est réalisé. Le cas d’impact induis par poids tombant est également étudiés. En effet, ces différents cas de sollicitions entraînent l’apparition de différent mécanismes d’endommagement. Ces derniers, ainsi que leur ordre d’apparition, sont caractérisés par Microscopie Electronique à Balayage (MEB) et tomographie à rayons X principalement. L’évaluation de la réduction du module élastique pré et post chargement ainsi que la fraction volumique de vide montrent une évolution de l’endommagement plus importante lors de chargement en traction hors axes des fibres que lors de chargement suivant l’axe. Lors des essais d’impact par poids tombant différents niveaux d’énergie sont considérés en restant proche du domaine des BVID en vue d’éprouver la sensibilité des méthodes de CND. Deux méthodes de CND par ultrasons étudiées durant ce projet peuvent être mises en avant. Premièrement, par mesure de la vitesse de propagation des ondes dans plusieurs directions du composites, le tenseur de rigidité est estimé dans tous ces cas de sollicitation mécanique pour différents niveaux d’endommagement. Des indicateurs d’endommagement basés sur ces mesures montrent une évolution de l’état d’endommagement similaire à celle discutée précédemment. Deuxièmement, une étude de la détection de l’endommagement par ondes guidées est menée. Aucun changement des modes transmit n’est visible lors de l’augmentation de l’état d’endommagement. L’évolution de l’énergie du signal transmis est alors proposée et validée comme indicateur d’endommagement efficace pour des chargements en traction mais pas pour l’impact. La mesure du décalage temporel à en revanche permis une localisation et une quantification de l’endommagement induit par impact.The present study is focused on the experimental study of a polyamide 66/6 based composite reinforced by a 2/2 twill weave glass fabric. The aim is to propose Non Destructive Evaluation (NDE) methods based on ultrasound that can efficiently distinguish different damage state. In order to do so, an investigation of the damage mechanisms induced by different type of mechanical solicitations. Tension along and off the axis of the fibers was considered as well as the case of drop weight impact. Those solicitations were shown to induce different damage mechanisms. The latter were characterized by means of Scanning Electronic Microscopy (SEM) and X-Ray tomography mostly. The decreasing of the elastic modulus and the void volume fraction evolution were shown to be more significant for the samples loaded in tension off-axis. During the drop weight impact tests, the energies were considered in order to remain close to the Barely Visible Impact Damage (BVID) regime in order to experience the capability of the ultrasound based NDE methods. Two NDE methods investigated during this study deserve to be highlighted. Firstly, the stiffness tensor was estimated by means of phase velocities measurements in different propagation direction. Damage indicators based on results from this method were proposed. They were found to give results similar with the one from the evaluation of damage discussed earlier on. Secondly, a study of the damage detection using guided waves was performed. No mode conversion effect was observed from this investigation. Consequently, the signal energy was proposed as damage indicator and was found to be suitable to detect damage induced by tension but not by impact. The measure of time shift allowed obtaining a localization and evaluation of the damage induced by impact
Operando detection and quantification of damage in the automotive components made of polyamide based composite reinforced with continuous fibres submitted to the fatigue-pre and/or post-impact by advanced ultrasonic techniques
No full textLa détection et la caractérisation des endommagements dans des composantes automobiles fabriquées en matériaux composites restent un souci majeur que les constructeurs automobiles cherchent à confronter. Le projet de thèse s'inscrit dans cette thématique et a comme but l'analyse qualitative et quantitative des endommagements induits par différentes sollicitations dans un composite à matrice polyamide 66/6 renforcé de fibres de verre tissées sergé 2/2. Pour cela, des essais d’impact à faible vitesse à différents niveaux d’énergie, des essais de fatigue en traction-traction ainsi que des essais d’impact post-fatigue, sont réalisés. Une méthodologie expérimentale qui repose sur l'utilisation des méthodes de contrôle non-destructif est établit et a pour but l’évaluation de l’endommagement induit par différents chargements. Différents outils sont utilisés dans cette étude, à savoir : la microscopie optique, la microscopie électronique, la tomographie aux rayons X, les ondes guidées (les ondes de Lamb), l'imagerie C-Scan par propagation des ondes de volumes et d'autres outils ultrasonores. En effet, les mécanismes d’endommagement liés aux multiples sollicitations sont observés et leurs degrés de propagation en fonction du type et du niveau de chargement sont examinés. Les propriétés résiduelles sont estimées par le biais de la vitesse de propagation des ondes de volume. En outre, une investigation basée sur la propagation des ondes de Lamb est menée. A l'issu de cette étude, des indicateurs d'endommagement, permettant de quantifier l'état d'endommagement induit dans chaque échantillon inspecté, sont proposés. Finalement, des essais de traction quasi-statique sont réalisés pour la prédiction des propriétés résiduelles post-chargement.The detection and characterization of damage in automotive components made of composite materials remains a major concern that automotive manufacturers are seeking to address. The aim of this thesis project is to qualitatively and quantitatively analyze the damage induced by different solicitations in a polyamide 66/6 based composite reinforced with 2/2 woven glass fibers intended for automotive applications. For this purpose, low-velocity impact tests at different energy levels, tensile-tensile fatigue tests as well as impact post-fatigue tests are conducted. An experimental methodology relying on the use of non-destructive testing methods (NDT) is established and aims at the assessment of the damage induced by different types of loads. Several tools are used in this study, namely: optical microscopy, X-ray tomography, guided waves (Lamb waves), C-Scan imaging and other ultrasonic tools. The damage mechanisms associated with the multiple loading are observed and their degrees of propagation as a function of the type and level of loading are examined. The stiffness matrix components are estimated by means of the velocity of propagation of the bulk waves. Furthermore, a Lamb waves-based investigation is conducted. By estimating the velocity of propagation of the waves, velocity profiles as a function of the angle of emission/reception are obtained. As a result of this study, several damage indicators are proposed to quantify the damage state induced in each inspected specimen. A good correlation between all experimental results is found indicating the efficiency of the developed Lamb waves-based method. Finally, quasi-static tensile tests are carried out to estimate the post-loading residual properties
Towards Comparison of Ultrasound Dose Measurements - Current Capabilities and Open Challenges
No full textThe aim of this work is to evaluate measurement methods for dosimetry and exposimetry quantities that were developed in the EMRP project “Dosimetry for Ultrasound Therapy -DUTy” by comparing the measurement results for three common quantities from three national laboratories. It further aims to investigate the general feasibility of possible future (key) comparisons for dosimetry and exposimetry quantities and to identify possible open challenges towards this goal. The general format is similar to a metrological comparison, with which the National Metrological Institutes, NMIs, are already familiar. The first step involved the agreement of the protocol that was to specify the set of transducers to be circulated and the measurement conditions. Two transducers were circulated and different drive voltage levels and pulsing regimes were defined and tissue mimicking materials (TMMs) characteristics were specified. Each lab was asked to prepare the TMMs for their own measurements with the inclusion of formulations and preparation instructions specified in the protocol. Uncertainties of the input data were to be declared by the participating laboratories
Ultrasone beeldvorming van microschade gebruik makend van technieken gebaseerd op tijdsomkering en niet-lineaire elastische golfspectroscopie.
No full textDuring the last decade, Nonlinear techniques based on Time Reversed Acoustics (NLTRA) have proven their efficiency and extreme sensitivity for Nondestructive Testing (NDT) of materials containing damage with a nonlinear behavior. NLTRA-techniques combine Nonlinear Elastic Wave Spectroscopy (NEWS), which is a collective term for techniques aiming to detect various kinds of nonlinear behavior in response signals, with the principle of Time Reversal (TR). This combination results in more efficient and sensitive techniques to localize and image incipient damage in the form of microcracks, delaminations, etc.Despite the success of NLTRA, these techniques share an important shortcoming. In a purely experimental application, only near-surface defects can be localized, since it is required to position a detector near the defect region. Detection of embedded defects is therefore only possible in a hybrid experimental/numerical approach. The main obstacle is to achieve a reliable numerical model, with a high accuracy on the material parameters such that the propagation of multiple reverberating signals that are typical for NLTRA can be calculated without losing the focus quality in the TR-process. Apart from the density and the geometry, it is critical to know the velocities and/or velocity distribution of the sample under consideration.In view of future hybrid ultrasonic NDT applications, we first developed a new automatic procedure for the determination of the (isotropic) longitudinal and shear material velocities, based on traditional TR-principles, and the signal dilatation and contraction method developed by Scalerandi et al. The method requires a single recorded signal as input, together with a (crude) estimation of the longitudinal velocity. Density and geometry are assumed to be known exactly, as well as the position of excitation and recording. Iteration of this TR based procedure allows to determine the longitudinal and shear velocities of the sample material with an accuracy better than 0.5%. Results are presented for a 3D numerical 'blind' test case and for two applications involving experimentally recorded data.Further, a NLTRA-technique was investigated that consists of the following two steps. In the first step, TR is used to focus high levels of energy in a small area of a medium in order to activate possible defects, and in a second postprocessing step, information regarding the nonlinear contribution is extracted from the reponse signals. Numerical simulations are reported showing the potential of a combination consisting of dual energy reciprocal time reversal and nonlinearity filtering using the scaling subtraction method. The method is applied to the detection of planar near-surface defects parallel to the surface in a 2D domain. The results are evaluated for sweep excitation at different frequency ranges; for point-like receivers as well as extended transducers, and for in-plane as well as out-of-plane focusing. The observable nonlinear response at the surface is linked to an effective nonlinearitywithin the medium based on the defect geometry and the distribution of the local stresses.The final problem that is considered in this thesis deals with the difficulty of imaging multiple masked scatterers. Inherent limitations of the traditional time reversal process in the case of multiple sources or scatterers make it difficult to distinguish the scattering sources individually. The selective source reduction (SSR) method employs a subtraction technique to selectively suppress in amplitude (and ideally eliminate) a time reversed focal signal that is masking another focus. In previous work, Scalerandi et al. and Anderson et al. successfully applied the SSR method to identify masked primary sources in a fully linear medium. Here, we extend the capabilities of the SSR method to deal with scattering caused by embedded defects. We call this new method SSR-NLTRA (Selective Source Reduction based on Nonlinear Time Reversed Acoustics). In the extended approach, the contribution of all primary and linear sources is first eliminated by means of the scaling subtraction method. Subsequently, the SSR(-TRA) method is applied to the remaining nonlinear content of the signals. We show by means of 2D wave propagation simulations that the new method can be applied iteratively to successfully image multiple masked nonlinear defects.status: Publishe
Pulsed ultrasonic comb filtering effect and its applications in the measurement of sound velocity and thickness of thin plates
No full textInternational audienceAn analytical and experimental study of the pulsed ultrasonic comb filtering effect is presented in this work intending to provide a fundamental tool for data analysis and phenomenon understanding in pulsed ultrasonics. The basic types of comb filter, feedforward and feedback filters, are numerically simulated and demonstrated. The characteristic features of comb filters, which include the formula for determining the locations of the spectral peaks or notches and the relationship between its temporal characteristics (relative time delay between constituent pulses) and its spectral characteristics (frequency interval between peaks or notches), are theoretically derived. To demonstrate the applicability of the comb filtering effect, it is applied to measuring the sound velocities and thickness of a thin plate sample. It is proven that the comb filtering effect based method not only is capable of accurate measurements, but also has advantages over the conventional time-of-flight based method in thin plate measurements. Furthermore, the principles developed in this study have potential applications in any pulsed ultrasonic cases where the output signal shows comb filter features
源于颤动时空相对论中曲率动力学的确定性核结构、裂变与聚变: 一种无概率隧穿、无壳层闭合、无配对拟合的统一描述
No full textKonventionelle Kernmodelle — von flüssigkeitstropfenbasierten Parametrisierungen über Schalenmodelle bis hin zu Dichtefunktionaltheorien — beschreiben viele globale Trends der Bindung und des Zerfalls, bleiben jedoch probabilistisch und stark parameterabhängig. Sie liefern keine erstprinzipielle Erklärung für anhaltende Anomalien wie die tiefe Unterdrückung der Fusion unterhalb der Barriere, die ungerade-gerade-Staggering-Struktur der Spaltungserträge oder die lange Halbwertszeit von ¹⁴C.Diese Arbeit erweitert die Trembling Spacetime Relativity Theory (TSRT) in den nuklearen Bereich als deterministisches geometrisches Rahmenwerk für Struktur, Stabilität und Transformation der Kerne. In TSRT ist jeder Kern ein lokalisierter Eigenmodus vibrierender Krümmung, dessen Stabilität aus einer anhaltenden Unterdrückung der intrinsischen Raumzeitkrümmung resultiert. Zerfall ist eine kausale Relaxation dieser Unterdrückung und wird als Krümmungsreorganisation modelliert, nicht als stochastischer Übergang. Bindung, Spaltung, Fusion und Zerfall entstehen somit aus derselben geometrischen Dynamik.Mit einer einzigen globalen Normierung, einmalig anhand von ⁶⁰Co festgelegt, reproduziert TSRT experimentelle Halbwertszeiten für β-Zerfall, α-Zerfall und spontane Spaltung über mehr als zwanzig Größenordnungen mit einer mittleren logarithmischen Abweichung unter einer Millionstel. Weder Schalenschließungen, Paarungskorrekturen, empirische Präformationsfaktoren noch kernspezifische Feinjustierungen werden benötigt. Die ¹⁴C-Anomalie ergibt sich unmittelbar aus seiner geometrischen β-Pfad-Krümmung, ohne anpassbare Hindernisfaktoren.Alle Q-Werte, Barriereaktionen und Emissionsraten folgen deterministisch aus der Raumzeitmetrik und ihrer Krümmungsenergie; zudem liefert TSRT einen kausalen Mechanismus der Masse–Energie-Umwandlung als Krümmungsumverteilung. TSRT reproduziert ebenfalls das Auftreten der Neutronen-magischen Zahlen als geometrische Minima der Krümmungs-Steifigkeits-Karte und stimmt damit mit der konventionellen magischen Sequenz überein — ohne quantentheoretische Postulate.Die starke Unterdrückung der Fusion im tiefen Unterbarriereregime entsteht aus einer geometrischen Reduktion der Überlappung vibrierender Modi; das ungerade-gerade-Staggering der Spaltungserträge geht auf phasenverriegelte Nackeneigenmoden beim Scission-Punkt zurück; und Elektronenscreening-Verschiebungen spiegeln eine Renormalisierung der elektromagnetischen Nahfeldkrümmung wider. Diese Effekte sind konsistent mit der vibrierenden Raumzeitgeometrie, die auch der Atomstruktur, der Photonenausstrahlung und der gravitativen Rotverschiebung zugrunde liegt.Quantitativ reproduziert TSRT absolute Halbwertszeiten vom Millisekundenbereich bis zu etwa zehn Quintillionen Jahren mit einer mittleren logarithmischen Abweichung unter einer Millionstel — unter Verwendung von nur drei globalen Konstanten, die einmal pro Modus festgelegt werden. Diese Genauigkeit übertrifft konventionelle mikroskopische und empirische Modelle — mit typischen Abweichungen zwischen einem Zehntel und einem Hundertstel — um etwa vier Größenordnungen und zeigt, dass der radioaktive Zerfall ein deterministisches geometrisches Phänomen ist, kein stochastischer Prozess.Alle physikalischen Größen werden in absoluten SI- und nuklearen Einheiten angegeben; die TSRT-Kalibrationskonstanten sind an fundamentale Krümmungs- und Lebensdaueranker gebunden und enthalten keine empirischen Skalierungen. TSRT reproduziert außerdem die absolute Spaltungsenergetik und ergibt eine Gesamtfreisetzung von 170,0 MeV für thermische-Neutronen-induzierte ²³⁵U(n,f)-Spaltung — ohne observable-spezifische Anpassungen.Indem TSRT Kernbindung, Zerfall, Reaktionszeitskalen und die Masse–Energie-Umwandlung aus einem einzigen geometrischen Prinzip herleitet, etabliert die Theorie eine einheitliche, vorhersagende und reproduzierbare Beschreibung der nuklearen Stabilität und Transformation. Sie verbindet mikroskopische Kernstruktur mit makroskopischer relativistischer Konsistenz und zeigt, dass Masse–Energie-Bilanz und Zerfallskinetik natürliche Manifestationen der Krümmungsumverteilung in einer vibrierenden Raumzeit sind.Conventional nuclear models, from liquid-drop parametrizations to shell and density-functional theories, describe many global trends in binding and decay but remain probabilistic and heavily parameterized. They do not explain, from first principles, persistent anomalies such as deep sub-barrier fusion hindrance, odd-even staggering in fission yields, or the long half-life of 14C. This work extends Trembling Spacetime Relativity Theory (TSRT) into the nuclear domain as a deterministic geometric framework for structure, stability, and transformation. In TSRT, each nucleus is a localized trembling-curvature eigenmode whose stability results from sustained suppression of intrinsic spacetime curvature. Decay is a causal relaxation of this suppression and is modeled as curvature reconfiguration rather than a stochastic transition. Binding, fission, fusion, and decay thus emerge from the same geometric dynamics. Using a single global normalization fixed once on 60Co, the TSRT formulation reproduces experimental half-lives across beta decay, alpha decay, and spontaneous fission over more than twenty orders of magnitude, with a mean logarithmic deviation below one part in a million. No shell closures, pairing corrections, empirical preformation factors, or per-nucleus tuning are invoked. The 14C anomaly follows from its geometric beta-path curvature without adjustable hindrance. All Q-values, barrier actions, and emission rates follow deterministically from the spacetime metric and its curvature energy, and TSRT provides a causal mechanism for mass–energy conversion as curvature redistribution. TSRT also reproduces the emergence of neutron magic numbers as geometric minima of the curvature–stiffness map, matching the conventional magic sequence without quantum postulates. Deep sub-barrier fusion hindrance arises from geometric suppression of trembling-mode overlap; odd-even staggering in fission yields originates from phase-locked neck eigenmodes at scission; and electron-screening shifts reflect renormalization of near-field electromagnetic curvature. These effects are consistent with the trembling-spacetime geometry that also underlies atomic structure, photon emission, and gravitational redshift. Quantitatively, TSRT reproduces absolute nuclear half-lives from milliseconds up to about ten quintillion years, with mean logarithmic deviation below one millionth, using only three global constants fixed once per mode. This accuracy surpasses conventional microscopic and empirical models—which typically yield mean logarithmic deviations between one tenth and one hundredth—by roughly ten thousand times, showing that nuclear decay is a deterministic geometric phenomenon rather than a stochastic process. All physical quantities are expressed in absolute SI and nuclear units, with TSRT calibration constants tied to fundamental curvature and lifetime anchors without empirical scaling. TSRT also reproduces absolute fission energetics, yielding a total energy release of 170.0 MeV for thermal-neutron-induced U-235 (n,f) without any per-observable tuning. By deriving nuclear binding, decay, reaction timescales, and mass–energy conversion from a single geometric principle, TSRT establishes a unified, predictive, and reproducible description of nuclear stability and transformation. It bridges microscopic nuclear structure with macroscopic relativistic consistency, showing that mass–energy balance and decay kinetics are natural manifestations of curvature redistribution in trembling spacetime.Los modelos nucleares convencionales —desde las parametrizaciones de gota líquida hasta los modelos de capas y las teorías funcionales de la densidad— describen muchas tendencias globales del enlace y del decaimiento, pero siguen siendo probabilísticos y fuertemente parametrizados. No explican, desde primeros principios, anomalías persistentes como la inhibición de fusión profunda bajo barrera, el staggering par–impar en los rendimientos de fisión o la larga vida media del ¹⁴C.Este trabajo extiende la Trembling Spacetime Relativity Theory (TSRT) al dominio nuclear como un marco geométrico determinista para la estructura, la estabilidad y la transformación. En TSRT, cada núcleo es un modo propio localizado de curvatura temblorosa cuya estabilidad resulta de una supresión sostenida de la curvatura intrínseca del espaciotiempo. El decaimiento es una relajación causal de esta supresión y se modela como una reconfiguración de la curvatura, no como una transición estocástica. Así, el enlace, la fisión, la fusión y el decaimiento emergen de la misma dinámica geométrica.Usando una única normalización global fijada una sola vez en ⁶⁰Co, el formalismo TSRT reproduce las vidas medias experimentales en decaimientos β, α y fisión espontánea a lo largo de más de veinte órdenes de magnitud, con una desviación logarítmica media inferior a una parte por millón. No se introducen cierres de capas, correcciones de emparejamiento, factores empíricos de preformación ni ajustes específicos por núcleo. La anomalía del ¹⁴C surge directamente de su curvatura geométrica a lo largo del camino β, sin necesidad de factores de inhibición ajustables.Todos los valores Q, las acciones de barrera y las tasas de emisión siguen de manera determinista a partir de la métrica del espaciotiempo y su energía de curvatura; además, TSRT proporciona un mecanismo causal para la conversión masa–energía como redistribución de curvatura. TSRT también reproduce la aparición de los números mágicos de neutrones como mínimos geométricos del mapa curvatura–rigidez, concordantes con la secuencia mágica convencional —sin postulados cuánticos.La inhibición de la fusión profunda bajo barrera surge de la supresión geométrica de la superposición de modos temblorosos; el staggering par–impar en los rendimientos de fisión se origina en modos propios del cuello bloqueados en fase en el punto de escisión; y los desplazamientos debidos al apantallamiento electrónico reflejan una renormalización de la curvatura electromagnética de campo cercano. Estos efectos son coherentes con la geometría del espaciotiempo tembloroso que también fundamenta la estructura atómica, la emisión de fotones y el corrimiento gravitacional al rojo.Cuantitativamente, TSRT reproduce vidas medias nucleares absolutas desde milisegundos hasta alrededor de diez quintillones de años, con una desviación logarítmica media inferior a una millonésima, usando solo tres constantes globales fijadas una vez por modo. Esta precisión supera a los modelos microscópicos y empíricos convencionales —que típicamente muestran desviaciones logarítmicas entre una décima y una centésima— en aproximadamente cuatro órdenes de magnitud, mostrando que el decaimiento nuclear es un fenómeno geométrico determinista y no un proceso estocástico.Todas las magnitudes físicas se expresan en unidades absolutas SI y nucleares, con constantes de calibración TSRT ancladas a referencias fundamentales de curvatura y de tiempos de vida sin escalados empíricos. TSRT también reproduce la energética absoluta de la fisión, obteniendo una liberación total de 170,0 MeV para ²³⁵U(n,f) inducida por neutrones térmicos, sin ajustes por observable.Al derivar el enlace nuclear, el decaimiento, las escalas temporales de las reacciones y la conversión masa–energía a partir de un único principio geométrico, TSRT establece una descripción unificada, predictiva y reproducible de la estabilidad y la transformación nucleares. Conecta la estructura nuclear microscópica con la consistencia relativista macroscópica, mostrando que el balance masa–energía y la cinética del decaimiento son manifestaciones naturales de la redistribución de la curvatura en un espaciotiempo tembloroso.Les modèles nucléaires conventionnels — des paramétrisations de type goutte liquide aux théories de couches et fonctionnelles de densité — décrivent de nombreuses tendances globales de liaison et de désintégration, mais demeurent probabilistes et fortement paramétrés. Ils n’expliquent pas, de manière première, des anomalies persistantes telles que le freinage de la fusion en régime sous-barrière, l’oscillation pair-impair des rendements de fission, ou encore la longue demi-vie du ¹⁴C.Ce travail étend la Théorie de la Relativité de l’Espace-Temps Vibrant (TSRT) au domaine nucléaire, en tant que cadre géométrique déterministe pour la structure, la stabilité et les transformations nucléaires. Dans TSRT, chaque noyau est un auto-mode localisé de courbure vibrante, dont la stabilité résulte d’une suppression soutenue de la courbure intrinsèque de l’espace-temps. La désintégration est une relaxation causale de cette suppression et se modélise comme une reconfiguration de la courbure plutôt qu’une transition stochastique. Ainsi, la liaison, la fission, la fusion et la désintégration émergent de la même dynamique géométrique.À l’aide d’une unique normalisation globale fixée une seule fois sur ⁶⁰Co, la formulation TSRT reproduit les demi-vies expérimentales des désintégrations β, α et de la fission spontanée sur plus de vingt ordres de grandeur, avec une déviation logarithmique moyenne inférieure à une partie par million. Aucune fermeture de couche, correction d’appariement, facteur de préformation empirique, ni ajustement spécifique à un noyau n’est requis. L’anomalie du ¹⁴C découle de sa courbure géométrique de trajectoire β, sans facteur de freinage ajustable.Toutes les valeurs Q, actions de barrière et taux d’émission suivent de manière déterministe à partir du métrique d’espace-temps et de son énergie de courbure, et TSRT fournit un mécanisme causal pour la conversion masse-énergie compris comme une redistribution de la courbure. TSRT reproduit également l’émergence des nombres magiques de neutrons comme minima géométriques de la carte courbure-raideur, correspondant à la séquence magique conventionnelle sans postulat quantique.Le freinage profond de la fusion sous-barrière résulte d’une suppression géométrique du recouvrement des modes vibrants ; l’oscillation pair-impair des rendements de fission provient d’auto-modes de col issés en phase au scissionnement ; et les effets de blindage électronique reflètent une renormalisation de la courbure électromagnétique de champ proche. Ces phénomènes sont cohérents avec la géométrie d’espace-temps vibrant qui sous-tend également la structure atomique, l’émission photonique et le décalage gravitationnel.Quantitativement, TSRT reproduit les demi-vies absolues des noyaux depuis la milliseconde jusqu’à environ dix quintillions d’années, avec une déviation logarithmique moyenne inférieure au millionième, en n’utilisant que trois constantes globales fixées une fois par mode. Cette précision dépasse de quatre ordres de grandeur celle des modèles microscopiques ou empiriques conventionnels — qui présentent généralement des déviations logarithmiques moyennes entre un dixième et un centième — montrant que la désintégration nucléaire est un phénomène géométrique déterministe plutôt qu’un processus stochastique.Toutes les grandeurs physiques sont exprimées en unités SI et nucléaires absolues, les constantes de calibration TSRT étant ancrées à des références fondamentales de courbure et de durée sans mise à l’échelle empirique. TSRT reproduit également l’énergétique absolue de fission, donnant une énergie totale libérée de 170,0 MeV pour la fission induite du ²³⁵U(n,f) sans aucun ajustement observable par observable.En dérivant la liaison nucléaire, les désintégrations, les échelles de temps des réactions et la conversion masse-énergie à partir d’un principe géométrique unique, TSRT établit une description unifiée, prédictive et reproductible de la stabilité et de la transformation nucléaires. Elle relie la structure nucléaire microscopique à la cohérence relativiste macroscopique, montrant que l’équilibre masse-énergie et la cinétique de désintégration sont des manifestations naturelles de la redistribution de la courbure dans un espace-temps vibrant.परम्परागत नाभिकीय मॉडल—तरल-बूँद पैरामीट्रीकरण से लेकर शैल तथा घनत्व-प्रकार्य (density-functional) सिद्धांतों तक—बंधन और क्षय की अनेक वैश्विक प्रवृत्तियों का वर्णन तो करते हैं, परन्तु वे मूलतः प्रायिकत्मक तथा अत्यधिक पैरामीटर-निर्भर बने रहते हैं। वे पहले सिद्धांतों से उन स्थायी विसंगतियों की व्याख्या नहीं कर पाते, जैसे गहरे उप-प्रागतिक ऊर्जा पर संलयन-बाधा (fusion hindrance), विखंडन-खंडों में विषम-सम दाँतेदार पैटर्न, अथवा ¹⁴C की दीर्घ अर्ध-आयु।यह कार्य ट्रेम्बलिंग स्पेसटाइम रिलेटिविटी थ्योरी (TSRT) को नाभिकीय क्षेत्र में विस्तारित करता है, जहाँ संरचना, स्थिरता और रूपांतरण को एक नियतात्मक ज्यामितीय फ्रेमवर्क के रूप में वर्णित किया गया है। TSRT में प्रत्येक नाभिक एक स्थानीयकृत कंपन-वक्रता स्वतं़त्र-मान (eigenmode) होता है, जिसकी स्थिरता मूलभूत स्पेसटाइम वक्रता के निरंतर दमन से उत्पन्न होती है। नाभिकीय क्षय इस दमन का कारणात्मक शिथिलीकरण है, जिसे यादृच्छिक संक्रमण की बजाय वक्रता-पुनर्संयोजन के रूप में मॉडल किया जाता है। इस प्रकार बंधन, विखंडन, संलयन और क्षय सभी एक ही ज्यामितीय गतिकी से उभरते हैं।एकमात्र वैश्विक सामान्यीकरण—⁶⁰Co पर एक बार निर्धारित—के साथ, TSRT β-क्षय, α-क्षय और स्वस्फूर्त विखंडन के प्रयोगात्मक अर्ध-आयुओं को बीस क्रमिकाओं से भी अधिक ऊर्जा-स्तरों पर पुनः उत्पन्न करता है, और औसत लघुगणकीय विचलन दस-लाखवें भाग से भी कम रहता है। इसमें कोई शैल-बन्दी, युग्मन-सुधार, अनुभवजन्य प्रीफॉर्मेशन-कारक अथवा नाभिक-विशिष्ट समायोजन नहीं किया जाता। ¹⁴C विसंगति उसके ज्यामितीय β-पथ-वक्रता से स्वतः प्राप्त होती है, बिना किसी समायोज्य बाधा-कारक के।सभी Q-मान, बाधा-क्रियाएँ और उत्सर्जन-दरें स्पेसटाइम-मेट्रिक तथा उसकी वक्रता-ऊर्जा से नियतात्मक रूप से उत्पन्न होती हैं, और TSRT द्रव्य-ऊर्जा-परिवर्तन (mass–energy conversion) के लिए वक्रता-पुनर्वितरण पर आधारित एक कारणात्मक तंत्र प्रदान करता है। TSRT न्यूट्रॉन-जादुई संख्याओं (magic numbers) के उद्भव को वक्रता-कठोरता मानचित्र के ज्यामितीय निम्नतम बिंदुओं के रूप में पुनः उत्पन्न करता है, जो पारंपरिक जादुई अनुक्रम से बिना किसी क्वांटम उपपत्ति के मेल खाता है।गहरे उप-प्रागतिक संलयन-बाधा कंपित-मोड ओवरलैप के ज्यामितीय दमन से उत्पन्न होती है; विखंडन-उत्पादों में विषम-सम उतार-चढ़ाव विभाजन-गर्दन (neck) पर चरण-लॉक्ड स्वतं़त्र-मानों से आते हैं; और इलेक्ट्रॉन-स्क्रीनिंग शिफ्ट निकट-क्षेत्र विद्युतचुंबकीय वक्रता के पुनर्सामान्यीकरण (renormalization) को दर्शाते हैं। ये सभी प्रभाव उसी ट्रेम्बलिंग-स्पेसटाइम ज्यामिति के साथ संगत हैं जो परमाण्विक संरचना, फोटॉन-उत्सर्जन और गुरुत्वीय रेडशिफ्ट का आधार भी है।मात्रात्मक रूप से, TSRT निरपेक्ष नाभिकीय अर्ध-आयुओं को मिलीसेकंड से लेकर लगभग 10^{18} वर्षों तक पुनः निर्मित करता है, और औसत लघुगणकीय विचलन एक-मिलियनवें से भी कम रहता है—केवल तीन वैश्विक स्थिरांक प्रयोग में लाते हुए, जो प्रतिमोड एक बार तय किए जाते हैं। यह परिशुद्धता परंपरागत सूक्ष्म और अनुभवजन्य मॉडलों (जो सामान्यतः 10^{-1}–10^{-2} के विचलन देते हैं) की तुलना में लगभग चार क्रम बेहतर है, और यह दर्शाती है कि नाभिकीय क्षय एक नियतात्मक ज्यामितीय प्रक्रिया है, न कि एक प्रायिकत्मक घटना।सभी भौतिक राशियाँ SI और नाभिकीय इकाइयों में निरूपित हैं; TSRT-कैलिब्रेशन स्थिरांक मूलभूत वक्रता और जीवनकाल-एंकरों से जुड़े हैं, बिना किसी अनुभवजन्य पैमाना-निर्भरता के। TSRT पूर्ण नाभिकीय विखंडन-ऊर्जा को भी ठीक-ठीक पुनः उत्पन्न करता है—जैसे थर्मल-न्यूट्रॉन-प्रेरित ²³⁵U(n,f) के लिए 170.0 MeV, बिना किसी प्रेक्षण-विशिष्ट समायोजन के।इस प्रकार, नाभिकीय बंधन, क्षय, अभिक्रिया-समयमान और द्रव्य-ऊर्जा-परिवर्तन को एक ही ज्यामितीय सिद्धांत से व्युत्पन्न करके, TSRT नाभिकीय स्थिरता और रूपांतरण का एकीकृत, भविष्यसूचक और पुनरुत्पादक वर्णन स्थापित करता है। यह सूक्ष्म नाभिकीय संरचना को व्यापक सापेक्षतावादी संगति से जोड़ता है और दिखाता है कि द्रव्य-ऊर्जा संतुलन और क्षय-गतिकी कंपित स्पेसटाइम में वक्रता-पुनर्वितरण की स्वाभाविक अभिव्यक्तियाँ हैं।I modelli nucleari convenzionali — dalle parametrizzazioni a goccia liquida ai modelli a guscio fino alle teorie funzionali della densità — descrivono molte tendenze globali di legame e decadimento, ma rimangono probabilistici e fortemente dipendenti dai parametri. Non forniscono una spiegazione di primo principio per anomalie persistenti come l’ostruzione della fusione profonda sotto-barriera, lo “staggering” pari-dispari nei rendimenti di fissione o la lunga vita media del ¹⁴C.Questo lavoro estende la Trembling Spacetime Relativity Theory (TSRT) al dominio nucleare, introducendo un quadro geometrico deterministico per struttura, stabilità e trasformazione del nucleo. In TSRT, ogni nucleo è un modo proprio localizzato di curvatura tremolante, la cui stabilità deriva da una continua soppressione della curvatura intrinseca dello spaziotempo. Il decadimento è una rilassazione causale di questa soppressione ed è modellato come una riconfigurazione della curvatura, non come una transizione stocastica. Legame, fissione, fusione e decadimento emergono così dalla stessa dinamica geometrica.Con una singola normalizzazione globale fissata una volta per tutte su ⁶⁰Co, il formalismo TSRT riproduce i tempi di decadimento sperimentali per decadimenti β, α e fissione spontanea su oltre venti ordini di grandezza, con una deviazione logaritmica media inferiore a una parte su un milione. Non vengono introdotte chiusure di guscio, correzioni di pairing, fattori empirici di preformazione o regolazioni specifiche per nucleo. L’anomalia del ¹⁴C risulta direttamente dalla sua curvatura geometrica lungo il percorso β, senza fattori di ostacolo regolabili.Tutti i valori Q, le azioni di barriera e i tassi di emissione derivano in modo deterministico dalla metrica dello spaziotempo e dalla sua energia di curvatura; inoltre TSRT fornisce un meccanismo causale per la conversione massa–energia come ridistribuzione della curvatura. TSRT riproduce anche l’emergere dei numeri magici dei neutroni come minimi geometrici della mappa curvatura–rigidezza, in accordo con la sequenza magica convenzionale
Using Accelerometry to Detect Upper-Extremity Motor Deficits and Delays in Early Childhood
No full textAbstract
Date Presented 3/30/2017
Identifying subtle motor delays in early childhood is challenging. Accelerometry is a novel way to characterize upper-extremity motor patterns in typically developing children. Differences were identified between typically developing children and children with hemiparesis ages 0–5 yr.
Primary Author and Speaker: Catherine Hoyt Drazen
Contributing Authors: Annie Nguyen, Elyse Everet, Melanie Berner, Jonathan Koller, Dustin K. Ragan, Nico U. F. Dosenbach</jats:p
Interaction of ultrasound with periodic structures and composite structures
No full textLa recherche présentée dans cette thèse comporte deux parties : l’interaction des ondes ultrasonores avec des structures périodiques et également l’interaction avec des matériaux composites. La recherche sur l’interaction des ultrasons avec des structures périodiques comporte deux aspects : l’étude du phénomène physique de la diffraction des ultrasons d’une part. Les chapitres II et III représentent l’enquête des deux phénomènes physiques de la diffraction d’ultrasons, c’est-à-dire l’anomalie dites « anomalie de Wood » et le phénomène de diffraction subharmonique. Dans le chapitre IV, le principe de la diffraction de Bragg est appliquée à la caractérisation non destructive de la périodicité des structures périodiques par ondes ultrasonores générées et se propageant dans l’air, tandis qu’une caractérisation géométrique plus générale de surface périodique à l’aide d’une technique ultrasonore à haute fréquence par la technique de imagerie C-scan est présentée au chapitre V. Dans cette thèse, les travaux de recherches sur l’interaction des ultrasons avec des structures composites se concentrent sur la caractérisation des défauts d’impacts des plaques composites. Ce travail comporte deux parties : l’analyse spectrale des défauts d’impact et la comparaison des différentes techniques de caractérisation des défauts d’impact. La première partie de l’ouvrage tente de faire face à la situation où les signaux reçus pour la caractérisation des défauts sont corrompus par le bruit causé par le système d’acquisition. Alors que dans la seconde partie, différentes configurations de test, différents capteurs et différentes méthodes de traitement de données sont comparées, afin d’optimiser la caractérisation des défautsThe research presented in this thesis contains two parts : the interaction of ultrasound with periodic structures and the interaction of ultrasound with composite materials. The investigation in the interaction of ultrasound with periodic structures is made in two aspects : study of the physical phenomenon of ultrasound diffraction and nondestructive characterization of the coorugated structures using ultrasonic techniques. Chapter II and III represent the investigation of two physical phenomena of ultrasound diffraction, i.e. acoustic Wood anomaly and the so-called sub-harmonic diffraction, respectively. In chapter IV the principle of Bragg diffraction is applied to the nondestructive characterization of the periodicity of periodic structures using air-coupled ultrasonic technique; while a more general geometrical characterization of periodic surface using high frequency ultrasonic C-scan imaging technique is presented in chapter V. In this thesis the research work of the interaction of ultrasound with composite structures focuses on the characterization of impact defects of composite plates. This work contains two parts : the spectral analysis of impact defects and the comparison of different techniques in impact defects characterization. The first part of the work tries to deal with the situation where the received signals for defect characterization are corrupted by the avoidable high-level noise caused by the data acquisition system. While in the second part different testing configurations, different transducers and different data processing methods are compared in order to optimize the defect characterizatio
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