Letteratura scientifica selezionata sul tema "Signal externe"
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Articoli di riviste sul tema "Signal externe":
1
Jödden, Bernd. "Induktive Weg- und Winkelsensoren". Konstruktion 69, n. 05 (2017): 46–47. http://dx.doi.org/10.37544/0720-5953-2017-05-46.
Abstract (sommario):
In der Messtechnik werden seit vielen Jahren induktive Weg- und Winkelaufnehmer eingesetzt. Die Technik dieser Sensoren basiert auf dem Prinzip der Differentialdrossel. Innerhalb eines Spulenkörpers wird ein NiFe-Kern axial bewegt. Die jeweilige Position des Kerns bewirkt dabei eine entsprechende Induktivitätsverteilung in den beiden Spulenhälften, die durch eine externe oder integrierte Elektronik in ein wegproportionales, analoges Signal umgewandelt wird (Bild 1).
2
Behar-Cohen, Francine, Emmanuelle Gelizé, Laurent Jonet e Patricia Lassiaz. "Anatomie de la rétine". médecine/sciences 36, n. 6-7 (giugno 2020): 594–99. http://dx.doi.org/10.1051/medsci/2020094.
Abstract (sommario):
La neurorétine est une unité fonctionnelle du système nerveux central assurant la conversion d’un signal lumineux en un influx nerveux. D’origine neuroectodermique, dérivée du diencéphale, la neurorétine est un tissu stratifié, composé de six types de cellules neuronales (deux types de photorécepteurs : les cônes et les bâtonnets ; les cellules horizontales, bipolaires, amacrines et ganglionnaires) et de trois types de cellules gliales (les cellules gliales de Müller, les astrocytes et les cellules microgliales). La neurorétine repose sur l’épithélium pigmentaire rétinien, l’ensemble constituant la rétine. L’existence des barrières hémato-rétiniennes interne et externe et des jonctions intra-rétiniennes rend compte de la finesse de la régulation des échanges de la rétine avec la circulation et au sein de la rétine elle-même. La zone centrale de la rétine humaine, la macula, zone hautement spécialisée pour assurer l’acuité visuelle, présente des spécificités anatomiques. Les méthodes d’imagerie récentes permettent d’enrichir nos connaissances sur les caractéristiques anatomiques et fonctionnelles de la rétine, qui restent encore imparfaitement décrites.
3
Zech, Roland. "A permafrost glacial hypothesis – Permafrost carbon might help explaining the Pleistocene ice ages". E&G Quaternary Science Journal 61, n. 1 (11 maggio 2012): 84–92. http://dx.doi.org/10.3285/eg.61.1.07.
Abstract (sommario):
Abstract. Während der letzten ~100 ka Glazial-Interglazial-Zyklen war die Konzentration des Treibhausgases CO2 in der Atmosphäre eng mit der globalen Temperatur gekoppelt. Die Gründe fuür die CO2 Konzentrationsschwankungen wurden bislang vor allem im Ozean vermutet, bleiben aber rätselhaft. Darüberhinaus gibt es nur spekulative Erklärungsansätze für den mittelpleistozänen Übergang von den 41 ka Eiszeitzyklen im Frühpleistozän vor ~0.7 Ma zu den ~100 ka Eiszeitzyklen danach. Die klassische Milankovitch Theorie der Sommerinsolation in hohen nördlichen Breiten kann die Abfolge der pleistozänen Eiszeiten nicht vollständig erklären. Basierend auf jüngsten Erkenntnissen, dass die Menge des organischen Bodenkohlenstoffs in Permafrostgebieten massiv unterschätzt wurde, und der simplen Logik, dass Permafrostgebiete und die entsprechende Kohlenstoffspeicherung in den Eiszeiten vermutlich wesentlich größer waren als in den Warmzeiten, soll hier eine „Permafrost Hypothese“ vorgestellt werden: (i) Langsame Anreicherung von Kohlenstoff in Permafrostböden während Abkühlungsphasen, sowie rasche Freisetzung von CO2 und Methan während Erwärmungsphasen, sind entscheidende positive Rückkopplungsprozesse für das Klima. (ii) Änderungen der integrierten annuellen Insolation an der südlichen, und damit sensitiven Permafrostgrenze könnten als externe Auslöser für globale Klimaveränderungen fungieren. (iii) Der mittelpleistozäne Wechsel der Eiszeitzyklen könnte implizit damit erklärt werden, dass Permafrostgebiete im Laufe der langfristigen pleistozänen Abkühlung Breiten von ~45°N erreichten. Dort verschwindet das für höhere nördliche Breiten charakteristische aus der Schiefe der Ekliptik resultierende ~41 ka Signal der annuellen Insolation, und es dominiert allein das ~100 ka Signal der orbitalen Ekzentrizität.
4
Lacefield, Soni, e Nicholas Ingolia. "Signal Transduction: External Signals Influence Spore-Number Control". Current Biology 16, n. 4 (febbraio 2006): R125—R127. http://dx.doi.org/10.1016/j.cub.2006.02.005.
5
Abeysekera, Indra. "Signalling external capital disclosure in annual reports". Corporate Ownership and Control 11, n. 4 (2014): 193–202. http://dx.doi.org/10.22495/cocv11i4c1p4.
Abstract (sommario):
Much of the discussion of voluntary disclosure of external capital in annual reports entails only limited examination as signals for capital accumulation. Using the method of content analysis, this paper examines the signalling of external capital disclosure practices, the most disclosed category of intellectual capital, in annual reports of a sample of listed firms in Sri Lanka, a developing nation. Eleven case study interviews from the sample firms explore the role of signal for capital accumulation. Findings reveal that signals differ between industry sectors in convincing stakeholders to advance capital accumulation
6
Chatterjee, Shre Kumar, Saptarshi Das, Koushik Maharatna, Elisa Masi, Luisa Santopolo, Stefano Mancuso e Andrea Vitaletti. "Exploring strategies for classification of external stimuli using statistical features of the plant electrical response". Journal of The Royal Society Interface 12, n. 104 (marzo 2015): 20141225. http://dx.doi.org/10.1098/rsif.2014.1225.
Abstract (sommario):
Plants sense their environment by producing electrical signals which in essence represent changes in underlying physiological processes. These electrical signals, when monitored, show both stochastic and deterministic dynamics. In this paper, we compute 11 statistical features from the raw non-stationary plant electrical signal time series to classify the stimulus applied (causing the electrical signal). By using different discriminant analysis-based classification techniques, we successfully establish that there is enough information in the raw electrical signal to classify the stimuli. In the process, we also propose two standard features which consistently give good classification results for three types of stimuli—sodium chloride (NaCl), sulfuric acid (H 2 SO 4 ) and ozone (O 3 ). This may facilitate reduction in the complexity involved in computing all the features for online classification of similar external stimuli in future.
7
Aditya, K., Ganesha Udupa e Yongkwun Lee. "Development of Bio-Machine Based on the Plant Response to External Stimuli". Journal of Robotics 2011 (2011): 1–7. http://dx.doi.org/10.1155/2011/124314.
Abstract (sommario):
In the area of biorobotics, intense research work is being done based on plant intelligence. Any living cell continuously receives information from the environment. In this paper, research is conducted on the plant nameddescoingsiixhaworthioides(Pepe) obtaining the action potential signals and its responses to stimulations of different light modes. The plant electrical signal is the reaction of plant’s stimulation owing to various environmental conditions. Action potentials are responsible for signaling between plant cells and communication from the plants can be achieved through modulation of various parameters of the electrical signal in the plant tissue. The modulated signals are used for providing information to the microcontroller’s algorithm for working of the bio-machine. The changes of frequency of action potentials in plant are studied. Electromyography (EMG) electrodes and needle-type conductive electrodes along with electronic modules are used to collect and transform the information from the plant. Inverse fast Fourier transform (IFFT) is used to convert signal in frequency domain into voltage signal for real-time analysis. The changes in frequency of the plant action potentials to different light modes are used for the control of the bio-machine. This work has paved the way for an extensive research towards plant intelligence.
8
HOLZHÜTTER, HERMANN-GEORG, e JÖRN QUEDENAU. "MATHEMATICAL MODELLING OF CELLULAR RESPONSES TO EXTERNAL SIGNALS". Journal of Biological Systems 03, n. 01 (marzo 1995): 127–38. http://dx.doi.org/10.1142/s0218339095000125.
Abstract (sommario):
An empirical mathematical model is proposed to describe the response (growth rate, metabolic activity etc.) of a cell population to various intensities of an external signal (hormone, antibody, pharmacon etc.). The model is based on the assumption that the signal causes the target system to pass consecutively through i=1, …, N distinct population states having response coefficients Ri. Describing the interaction of the system with the signal according to the rules of chemical kinetics by two phenomenological parameters (k - sensitivity, n - cooperativity index) one arrives at a series expansion for Ri which is linear in the Ri’s but nonlinear with respect to k and n (“R-decomposition”). The pattern of expansion coefficients Ri is characteristic of a given signal and can be used to reveal similarities in the responses of the cell population to various signals. A user-friendly microcomputer program has been developed to fit the model equation to experimental data by means of constraint nonlinear regression analysis and to determine all characteristic curve parameters (number and location of extremal values, inflection points etc.). The robustness and benefit of the model is demonstrated by applications to various types of “exotic” dose-reponse-curves obtained from a neutral-red assay of fibroblasts. Similarities between response curves are studied.
9
STELMASIAK, Zdzisław, e Mariusz RUDNICKI. "Impact of external interferences on vibroacoustic signals coming from combustion engine during cold test". Combustion Engines 160, n. 1 (1 febbraio 2015): 26–35. http://dx.doi.org/10.19206/ce-116899.
Abstract (sommario):
In the paper is presented impact of external interferences on vibroacoustic signals coming from a spark ignition engine’s vibrations in cold test performed on engine assembly line. As the basis to the analysis were used signals of piezoelectric sensor mounted on cylinder block of the engine driven by electric motor. In course of the testing it has been used the order tracking analysis of the vibrations during the cold test, while experimental results were used to statistic analysis of significance of influence with use of the MiniTab computer program. The main objective of the investigations was to verify actually obtained vibroacoustic signals and to minimize interferences coming from the measuring system. It should contribute to reduction of tolerance limits and improved detection of faulty engines with use of vibroacoustic methods. The investigations have shown significant impact of contact surface of the cylinder block with the sensor and impact of deformations of compression spring on results of recorded vibroacoustic signal. Such impact should be taken into considerations in numerical analysis of the signal. It has been proposed to perform activities to reduce influence of the interferences on recorded signals. Results of the investigations have been already utilized in production cold tests of spark ignition engines.
10
Yang, Lifeng, Chulin Chen, Zhaojiang Zhang e Xin Wei. "Glucose Determination by a Single 1535 nm Pulsed Photoacoustic Technique: A Multiple Calibration for the External Factors". Journal of Healthcare Engineering 2022 (19 settembre 2022): 1–10. http://dx.doi.org/10.1155/2022/9593843.
Abstract (sommario):
Photoacoustic spectroscopy has been proved to be a potential method for noninvasive blood glucose detection. We used 1535 nm pulsed laser to excite photoacoustic signal in glucose solution and then explored the influence of different glucose concentration on photoacoustic signal to analyze the sensitivity of photoacoustic signal to glucose at this wavelength. We designed a simple photoacoustic cell structure, which used a focused ultrasonic transducer to receive signals, so as to reduce signal attenuation. In terms of the results, we have found that for high-concentration glucose solutions, the results have strong linearity and discrimination, and when the concentration is close to the human body level, the signal difference is not so obvious. Therefore, we explore the external factors affecting the photoacoustic signal in detail and propose a calibration method. Through calibration, the signal generated by the low-concentration glucose solution also has a good linearity.
Tesi sul tema "Signal externe":
1
Rondelet, Arnaud. "Caractérisation d'une nouvelle voie d'adressage des protéines à la membrane externe des bactéries à Gram négatif". Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00833222.
Abstract (sommario):
Le système Tat (pour Twin Arginine Translocation) exporte des protéines repliées depuis le cytoplasme vers le périplasme des bactéries. L'adressage des protéines à exporter au système Tat repose sur une séquence signal spécifique amino terminale clivée après exportation. Chez le phytopathogène Dickeya dadantii, l'homologue de pectine lyase PnlH possède une séquence signal Tat qui assure son adressage au système Tat mais qui n'est pas clivée après exportation et ancre la protéine dans la membrane externe. Chez les protéobactéries, la majorité des protéines de membrane externe sont soit des lipoprotéines soit des protéines intégrales de membrane en tonneau β. L'adressage de ces protéines à la membrane externe repose sur des voies spécifiques du type de protéine : la voie Lol pour les lipoprotéines et la combinaison des chaperons périplasmiques SurA, Skp et DegP et du complexe de membrane externe Bam (β barrel assembly machinery) pour les protéines en tonneau β. Au cours de ce travail, l'étude de l'adressage de PnlH à la membrane externe a montré que SurA se liait à la séquence signal hydrophobe de PnlH pour la protéger de l'environnement hydrophile au cours de son transit dans le périplasme. La séquence signal de PnlH (41 acides aminés) porte l'intégralité de l'information nécessaire à son adressage à la membrane externe. La nature de l'information adressant les protéines au système Tat est bien connue et dans ce travail nous nous sommes efforcés d'identifier les informations requises pour les deux dernières étapes de l'adressage de PnlH à la membrane externe : la traversée du périplasme et l'insertion dans la membrane externe. La délétion d'une région conservée comprise entre les résidus 28 et 41 de la séquence signal de PnlH affecte l'adressage de cette dernière à la membrane externe. Des substitutions des acides aminés conservés de cette région ne semblent pas affecter l'adressage de PnlH, indiquant que l'information nécessaire à l'adressage de PnlH à la membrane externe après exportation ne réside pas dans la séquence en acides aminés de la séquence signal de PnlH. En revanche, nos données suggèrent que la présence d'une hélice α hydrophobe dans la séquence signal de PnlH est importante pour son adressage à la membrane externe. Cette observation est particulièrement intéressante puisqu'une telle structure est généralement considérée comme une caractéristique des protéines de membrane interne.
2
Djilas, Milan. "Interprétation des informations sensorielles des récepteurs du muscle squelettique pour le contrôle externe". Phd thesis, Montpellier 2, 2008. http://www.theses.fr/2008MON20092.
Abstract (sommario):
Le sujet de cette thèse se situe dans le cadre général de la restauration du mouvement de membres paralysés à travers la stimulation électrique fonctionnelle (FES) implantée. L'objectif du projet était d'explorer la faisabilité d'utiliser les informations issues des fibres nerveuses sensorielles des récepteurs musculaires comme information de retour d'une commande en boucle fermée d'un système FES à travers des électrodes nerveuses périphériques intra fasciculaires. Des expérimentations animales aigues ont été réalisées pour mesurer les réponses afférentes des fuseaux neuromusculaires muscle à des étirements passifs du muscle. Les enregistrements ont été réalisés en utilisant une nouvelle électrode Intra-fasciculaire (tfLIFE), développées par le Dr. Ken Yoshida à l'université d'Aalborg au Danemark. Un modèle du premier ordre de la réponse des fuseaux neuromusculaires à des étirements passifs a été proposé. Ce modèle prend en compte les propriétés non linéaires des activités neurales afférentes. De plus, l'estimation de l'état du muscle à partir d'un enregistrement ENG multicanaux a fourni des résultats plus robustes comparés à un enregistrement monocanal. Pour que le modèle ci-dessus puisse être utilisé pour l'estimation de l'état du muscle, le taux de variation de la longueur du muscle pendant le mouvement doit avoir un effet négligeable sur les paramètres du modèle. Nous avons proposé dans cette thèse une approche pour la détection et la classification de pics dans l'enregisrement neural dans l'objectif d'isoler les activités neurales sensorielles des récepteurs musculaires ayant une sensibilité minimale à la vitesse de l'élongation musculaire. L'algorithme est basé sur la transformée en ondelettes continue multi-échelle utilisant des ondelettes complexes. Le système de détection utilise une simple détection par seuillage, couramment utilisé, particulièrement avec les enregistrements ayant un faible rapport signal sur bruit. Les résultats de classification des unités montrent que la classification développée est capable d'isoler l'activité ayant une relation linéaire avec la longueur du muscle. Ceci constitue une étape vers une estimation, en ligne basée modèle, de la longueur du muscle qui pourra être utilisée dans un système FES en boucle fermée utilisant des informations sensorielles naturelles. Un des principaux problèmes limitant l'interprétation des données ENG est le faible niveau du signal neural par rapport à celui du bruit dans l'enregistrement. Nos hypothèses ont été que le blindage de l'implant aiderait à améliorer le rapport signal sur bruit. Des résultats expérimentaux, issus d'une étude préliminaire que nous avons réalisée, montrent que le placement d'électrodes standards à manchon placées autour du site d'implantation de la tfLIFE augmentait le niveau du signal ENG dans les enregistrementsThe topic of this thesis was the rehabilitation of movement of paralyzed limbs through functional electrical stimulation (FES). The objective of the project was to explore the possibility of using information from sensory nerve fibers of muscle receptors as feedback of the closed-loop control of FES systems using intrafascicular peripheral nerve electrodes. Acute animal experiments were performed to record afferent muscle spindle responses to passive stretch. The recordings were performed using the new thin-film Longitudinal Intra-Fascicular Electrode (tfLIFE), developed by Dr. Ken Yoshida at Aalborg University in Denmark. A first-order model of muscle spindle response to passive muscle stretch was proposed that manages to capture the non-linear properties of the afferent neural activity. Moreover, estimation of muscle state from the recorded multi-channel ENG provided more robust results compared to using single-channel recordings. For the abovementioned model to be usable in a estimator of muscle state, the rate of change of muscle length during movement must have negligible effect on model parameters. A neural spike detection and classification scheme was developed for the purpose of isolating sensory neural activity of muscle receptors having minimal sensitivity to the velocity of muscle motion. The algorithm was based on the multi-scale continuous wavelet transform using complex wavelets. The detection scheme outperformes the commonly used simple threshold detection, especially with recordings having low SNR. Results of classification of units indicate that the developed classifier is able to isolate activity having linear relationship with muscle length, which is a step towards on-line model-based estimation of muscle length that can be used in a closed-loop FES system with natural sensory feedback. One of the main issues limiting the interpretation of ENG data is the low level of the neural signal compared to the level of noise in the recordings. Our hypothesis was that shielding the implant site would help improve signal-to-noise level. Experimental results from a preliminary study we had performed indicate that placing a standard cuff electrode around the tfLIFE active sites increases the level of ENG signal in the recordings
3
Djilas, Milan. "Interprétation des informations sensorielles des récepteurs du muscle squelettique pour le contrôle externe". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2008. http://tel.archives-ouvertes.fr/tel-00333530.
Abstract (sommario):
Le sujet de cette thèse se situe dans le cadre général de la restauration du mouvement de membres paralysés à travers la stimulation électrique fonctionnelle (FES) implantée. L'objectif du projet était d'explorer la faisabilité d'utiliser les informations issues des fibres nerveuses sensorielles des récepteurs musculaires comme information de retour d'une commande en boucle fermée d'un système FES à travers des électrodes nerveuses périphériques intra fasciculaires. Des expérimentations animales aigues ont été réalisées pour mesurer les réponses afférentes des fuseaux neuromusculaires à des étirements passifs du muscle. Les enregistrements ont été réalisés en utilisant une nouvelle électrode Intra-fasciculaire (tfLIFE), développées par le Dr. Ken Yoshida à l'université d'Aalborg au Danemark. Un modèle du premier ordre de la réponse des fuseaux neuromusculaires à des étirements passifs a été proposé. Ce modèle prend en compte les propriétés non linéaires des activités neurales afférentes. De plus, l'estimation de l'état du muscle à partir d'un enregistrement ENG multicanaux a fourni des résultats plus robustes comparés à un enregistrement monocanal.Pour que le modèle ci-dessus puisse être utilisé pour l'estimation de l'état du muscle, le taux de variation de la longueur du muscle pendant le mouvement doit avoir un effet négligeable sur les paramètres du modèle. Nous avons proposé dans cette thèse une approche pour la détection et la classification de pics dans l'enregisrement neural dans l'objectif d'isoler les activités neurales sensorielles des récepteurs musculaires ayant une sensibilité minimale à la vitesse de l'élongation musculaire. L'algorithme est basé sur la transformée en ondelettes continue multi-échelle utilisant des ondelettes complexes. Le système de détection utilise une simple détection par seuillage, couramment utilisée, particulièrement avec les enregistrements ayant un faible rapport signal sur bruit. Les résultats de classification des unités montrent que la classification développée est capable d'isoler l'activité ayant une relation linéaire avec la longueur du muscle. Ceci constitue une étape vers une estimation, en ligne basée modèle, de la longueur du muscle qui pourra être utilisée dans un système FES en boucle fermée utilisant des informations sensorielles naturelles.
Un des principaux problèmes limitant l'interprétation des données ENG est le faible niveau du signal neural par rapport à celui du bruit dans l'enregistrement. Nos hypothèses ont été que le blindage de l'implant aiderait à améliorer le rapport signal sur bruit. Des résultats expérimentaux, issus d'une étude préliminaire que nous avons réalisée, montrent que le placement d'électrodes standards à manchon placées autour du site d'implantation de la tfLIFE augmentait le niveau du signal ENG dans les enregistrements.
4
David, Etienne. "Time series forecasting models applied on large datasets with inclusion of external signals". Electronic Thesis or Diss., Institut polytechnique de Paris, 2024. http://www.theses.fr/2024IPPAS002.
Abstract (sommario):
La prévision de séries temporelles est un problème mathématique répandu dans de nombreux secteurs, devenant un véritable défi pour les méthodes existantes de la littérature lorsque de grands ensembles de données rassemblant des milliers de séries temporelles et des signaux externes sont considérés. Une illustration concrète de ce problème peut être trouvée dans l'industrie de la mode où ses acteurs tentent d'anticiper l'évolution de milliers de vêtements pour créer leurs collections, analysant les comportements des influenceurs pour proposer la mode de demain.En utilisant cette application comme fil conducteur, nous présentons trois contributions explorant différentes réponses concernant le problème de prévision de séries temporelles où de grands ensembles de données et des signaux externes sont considérés. Une première réponse est proposée avec l'introduction d'un nouveau modèle hybride et la publication d'un large ensemble de données rassemblant 10000 séries temporelles de mode et des signaux externes d'influenceurs. Une seconde approche est ensuite étudiée avec un travail théorique sur les modèles de Markov cachés à signaux externes. Enfin, une dernière réponse est proposée avec l'introduction d'une nouvelle méthode mélangeant le fonctionnement interne des modèles de Markov cachés avec des réseaux de neurones.Les résultats présentés dans ces trois contributions ont mis en évidence plusieurs éléments de réponse. Premièrement, les réseaux de neurones sont décisifs pour traiter de grands ensembles de données et sont particulièrement bien conçus pour exploiter des signaux externes. Deuxièmement, les modèles de Markov cachés avec signaux externes sont également des méthodes efficaces, capables de capturer des dépendances complexes entre des séries temporelles et leurs signaux externes. Cependant, ils ne parviennent pas à gérer de grands ensembles de données car un modèle doit être entraîné pour chaque nouvelle série temporelle. Enfin, inspirés par les résultats frappants des modèles de Markov cachés avec des signaux externes, nous montrons que l'introduction de processus cachés dans des modèles basés sur des réseaux neuronaux peut les aider à explorer plus profondément les grands ensembles de données, à modéliser une plus grande variété de comportements et à exploiter plus finement les signaux externesTime series forecasting is a widespread mathematical problem in numerous sectors becoming a real challenge for existing methods of the literature where large datasets gathering thousands of time series and external signals are considered. A concrete illustration of this issue can be find in the fashion industry where its actors try to anticipate the evolution of thousands of garments to create their collections, analysing influencers and early adopters behaviours to propose the fashion of tomorrow.Using this application as a common thread, we present three contributions exploring different answers regarding the time series forecasting problem where large datasets and external signals are considered. A first answer is proposed with the introduction of a new hybrid model and the publication of a large dataset gathering 10000 fashion time series and influencers external signals. A second approach is then studied with theoretical work done on hidden Markov models with external signals. Finally, a last answer is proposed with the introduction of a new method mixing the inner workings of hidden Markov model and neural networks.Results presented in this three contribution highlighted several elements of answer. Firstly, neural networks are decisive to deal with large datasets and they are particularly well designed to leverage external signals. Secondly, hidden Markov models with external signals are also strong methods that can capture complex dependencies between time series and their external signals. However, they fail at handling large datasets as a model has to be trained for each new time series. Finally, inspired by the striking results of hidden Markov models with external signals, we reveal that introducing hidden processes in neural-network-based models can help them explore large datasets more deeply, model a richer variety of behaviour and leverage more finely external signals
5
Ghebrebrhan, Ogubazghi. "Amelioration des performances d'un systeme radar vhf par des techniques de codage et de pretraitement : analyse et mise en oeuvre". Toulon, 1987. http://www.theses.fr/1987TOUL0002.
Abstract (sommario):
Le systeme radar st operant dans le bas gamme radioelectrique vhf est etudie du point de vue du traitement du signal. Etude des moyens permettant d'augmenter la resolution en distance pour une detectabilite optimale. Le codage d'impulsion offre une solution dans certaines conditions et trois types de code sont consideres. Pour des radars a emetteurs a tubes, les resultats optimaux sont obtenus par utilisation d'un processeur rapide et d'un generateur d'impulsions. Presentation d'observations geophysiques avec le systeme ameliore
6
Perret, Stéphanie. "Imagerie confocale du signal calcique dans un modèle de cellules non-excitables de la prostate humaine". Bordeaux 2, 1999. http://www.theses.fr/1999BOR28659.
7
Denux, Francis. "Diffusion du signal isotopique dans le névé et dans la glace : Implication pour l'échantillonnage". Grenoble 1, 1996. http://www.theses.fr/1996GRE10254.
Abstract (sommario):
Un modèle amélioré de diffusion du signal isotopique dans le névé est établi après étude de l'influence du coefficient de diffusion de la vapeur d'eau, de la variabilité de la densité, de la tortuosité, de la température et de son gradient. Ce nouveau modèle est testé depuis la surface jusqu'a la profondeur du close-off en antarctique et au Groenland. Pour la plupart des sites du Groenland, les variations saisonnières de la composition en isotope survivent a la diffusion dans le névé. Les résultats du modèle de diffusion dans le névés sont ensuite utilisés dans un modèle de diffusion dans la glace pour estimer la profondeur de disparition des cycles saisonniers pour le Groenland et des cycles présents au close-off pour les sites d'Antarctique. Le couplage des modèles de diffusion dans le névé et dans la glace permet alors une interprétation des fortes variations de courtes longueurs d'ondes observées dans le névé profond de Pôle Sud et dans la glace pour Dôme C et Vostok. Enfin, l'étude de la diffusion de signaux synthétiques comprenant des cycles à différentes longueurs d'ondes permet d'estimer, en fonction de la profondeur, les longueurs d'ondes susceptibles de survivre à la diffusion et de déterminer des consignes d'échantillonnage des carottes de glace
8
Leprettre, Benoit. "Reconnaissance de signaux sismiques d'avalanches par fusion de données estimées dans les domaines temps, temps-fréquence et polarisation". Université Joseph Fourier (Grenoble ; 1971-2015), 1996. http://www.theses.fr/1996GRE10182.
Abstract (sommario):
L'estimation de l'activite avalancheuse naturelle d'une portion de massif repose actuellement sur l'observation visuelle. Pour s'affranchir des contraintes de visibilite qui lui sont liees, une solution est de detecter les ondes sismiques produites par les avalanches au cours de leur chute. Cependant, 90 pour cent des signaux enregistres ne sont pas des avalanches et doivent etre elimines. Nous proposons une approche pluridisciplinaire de ce probleme de reconnaissance. Dans le domaine temps, le module du signal est utilise comme un premier critere de reconnaissance. Dans le domaine temps-frequence, la methode hybride arcap fournit une representation temps-frequence du signal avec une bonne reduction d'information. Dans le domaine de polarisation, nous proposons d'utiliser le filtre de capon pour ameliorer le rapport signal a bruit des signaux avant d'estimer un critere de linearite. Cela permet d'estimer la repartition dans le plan temps-frequence des mouvements lineaires contenus dans le signal. Le filtre de capon est etudie en detail et compare a un filtre de fourier. Les resultats de l'analyse sont reduits a environ 25 descripteurs qui, combines a l'aide d'une base de regles, permettent l'identification des signaux. Les regles sont inspirees principalement par des considerations sur les phenomenes physiques generateurs d'ondes sismiques et sur les lois de propagation. Un test sur un ensemble de signaux identifies permet d'evaluer le taux de reussite de notre systeme a environ 90 pour cent. Un prototype autonome est propose ; il sera installe sur site pour l'hiver 96/97. Une comparaison entre l'information fournie par notre systeme et d'autres donnees relatives a l'activite avalancheuse confirme l'interet de notre systeme pour des applications concretes
9
Guédon, Stéphane. "Système à base de connaissances pour l'aide à la surveillance océanique à partir d'un réseau de magnétomètres". Grenoble INPG, 1994. http://www.theses.fr/1994INPG0132.
Abstract (sommario):
Cet ouvrage etudie la faisabilite d'un systeme a base de connaissances pour l'aide a la surveillance oceanique a partir d'un reseau de magnetometres. La detection de la signature magnetique au passage d'une cible sous le reseau necessite un savoir faire qui releve de la connaissance experte du systeme de mesure, des proprietes des phenomenes naturels perturbateurs et des methodes de traitement specifiques. L'objectif a terme est de fournir a l'operateur, une assistance informatique lui communiquant les elements utiles pour l'aider a prendre des decisions optimales, en prenant en compte toute l'information a priori disponible, meme imparfaite et en pilotant les codes de calcul. L'etude s'effectue en trois etapes. La premiere repertorie l'ensemble des connaissances: l'environnement des mesures (phenomenes, sources, proprietes) ; les methodes de traitement des signaux (mono et bidimensionnels) pour l'extraction de caracteristiques et leur interpretation (en temps et frequences) ; les strategies pour la detection magnetique sous-marine. La seconde propose une architecture distribuee (blackboard) pour l'integration et la modelisation des connaissances expertes. Une base de donnees orientee objet symbolise l'etat de la resolution et l'organisation de l'environnement des mesures. Un controleur reactif a l'environnement planifie le declenchement de codes de calcul declares par les sources de connaissances. La decision dans le controle est realisee par une methode a base de regles floues. Elle associe les informations numeriques et symboliques. L'operateur communique avec la machine sur une base lexicale de qualificatifs. La troisieme etape presente un demonstrateur. Il fournit des avis directement interpretables par l'operateur en adequation avec le manque d'information. Il prend en compte l'acquisition des informations, l'apprentissage des bruits, la surveillance de la zone, la reduction des bruits et la detection d'une cible mobile
10
Fargeas, Aureline. "Classification, feature extraction and prediction of side effects in prostate cancer radiotherapy". Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S022/document.
Abstract (sommario):
Le cancer de la prostate est l'un des cancers les plus fréquents chez l'homme. L'un des traitements standard est la radiothérapie externe, qui consiste à délivrer un rayonnement d'ionisation à une cible clinique, en l'occurrence la prostate et les vésicules séminales. Les objectifs de la radiothérapie externe sont la délivrance d'une dose d'irradiation maximale à la tumeur tout en épargnant les organes voisins (principalement le rectum et la vessie) pour éviter des complications suite au traitement. Comprendre les relations dose/toxicité est une question centrale pour améliorer la fiabilité du traitement à l'étape de planification inverse. Des modèles prédictifs de toxicité pour le calcul des probabilités de complications des tissus sains (normal tissue complication probability, NTCP) ont été développés afin de prédire les événements de toxicité en utilisant des données dosimétriques. Les principales informations considérées sont les histogrammes dose-volume (HDV), qui fournissent une représentation globale de la distribution de dose en fonction de la dose délivrée par rapport au pourcentage du volume d'organe. Cependant, les modèles actuels présentent certaines limitations car ils ne sont pas totalement optimisés; la plupart d'entre eux ne prennent pas en compte les informations non-dosimétrique (les caractéristiques spécifiques aux patients, à la tumeur et au traitement). De plus, ils ne fournissent aucune compréhension des relations locales entre la dose et l'effet (dose-espace/effet relations) car ils n'exploitent pas l'information riche des distributions de planification de dose 3D. Dans un contexte de prédiction de l'apparition de saignement rectaux suite au traitement du cancer de la prostate par radiothérapie externe, les objectifs de cette thèse sont : i) d'extraire des informations pertinentes à partir de l'HDV et des variables non-dosimétriques, afin d'améliorer les modèles NTCP existants et ii) d'analyser les corrélations spatiales entre la dose locale et les effets secondaires permettant une caractérisation de la distribution de dose 3D à l'échelle de l'organe. Ainsi, les stratégies visant à exploiter les informations provenant de la planification (distributions de dose 3D et HDV) ont été proposées. Tout d'abord, en utilisant l'analyse en composantes indépendantes, un nouveau modèle prédictif de l'apparition de saignements rectaux, combinant d'une manière originale l'information dosimétrique et non-dosimétrique, a été proposé. Deuxièmement, nous avons mis au point de nouvelles approches visant à prendre conjointement profit des distributions de dose de planification 3D permettant de déceler la corrélation subtile entre la dose locale et les effets secondaires pour classer et/ou prédire les patients à risque de souffrir d'un saignement rectal, et d'identifier les régions qui peuvent être à l'origine de cet événement indésirable. Plus précisément, nous avons proposé trois méthodes stochastiques basées sur analyse en composantes principales, l'analyse en composantes indépendantes et la factorisation discriminante en matrices non-négatives, et une méthode déterministe basée sur la décomposition polyadique canonique de tableaux d'ordre 4 contenant la dose planifiée. Les résultats obtenus montrent que nos nouvelles approches présentent de meilleures performances générales que les méthodes prédictives de la littératureProstate cancer is among the most common types of cancer worldwide. One of the standard treatments is external radiotherapy, which involves delivering ionizing radiation to a clinical target, in this instance the prostate and seminal vesicles. The goal of radiotherapy is to achieve a maximal local control while sparing neighboring organs (mainly the rectum and the bladder) to avoid normal tissue complications. Understanding the dose/toxicity relationships is a central question for improving treatment reliability at the inverse planning step. Normal tissue complication probability (NTCP) toxicity prediction models have been developed in order to predict toxicity events using dosimetric data. The main considered information are dose-volume histograms (DVH), which provide an overall representation of dose distribution based on the dose delivered per percentage of organ volume. Nevertheless, current dose-based models display limitations as they are not fully optimized; most of them do not include additional non-dosimetric information (patient, tumor and treatment characteristics). Furthermore, they do not provide any understanding of local relationships between dose and effect (dose-space/effect relationship) as they do not exploit the rich information from the 3D planning dose distributions. In the context of rectal bleeding prediction after prostate cancer external beam radiotherapy, the objectives of this thesis are: i) to extract relevant information from DVH and non-dosimetric variables, in order to improve existing NTCP models and ii) to analyze the spatial correlations between local dose and side effects allowing a characterization of 3D dose distribution at a sub-organ level. Thus, strategies aimed at exploiting the information from the radiotherapy planning (DVH and 3D planned dose distributions) were proposed. Firstly, based on independent component analysis, a new model for rectal bleeding prediction by combining dosimetric and non-dosimetric information in an original manner was proposed. Secondly, we have developed new approaches aimed at jointly taking advantage of the 3D planning dose distributions that may unravel the subtle correlation between local dose and side effects to classify and/or predict patients at risk of suffering from rectal bleeding, and identify regions which may be at the origin of this adverse event. More precisely, we proposed three stochastic methods based on principal component analysis, independent component analysis and discriminant nonnegative matrix factorization, and one deterministic method based on canonical polyadic decomposition of fourth order array containing planned dose. The obtained results show that our new approaches exhibit in general better performances than state-of-the-art predictive methods
Libri sul tema "Signal externe":
1
Acharya, Sankarshan. Sovereign debt buybacks as a signal of creditworthiness. Washington, D.C. (1818 H Street NW, Washington DC 20433): International Economics Department, World Bank, 1989.
2
Carroll, Anya A. Safety of highway-railroad grade crossings: Use of auxiliary external alerting devices to improve locomotive conspicuity. Washington, DC: U.S. Dept. of Transportation, Federal Railroad Administration, Office of Research and Development, 1995.
3
Ismail, Ayman Farouk. Higher Order Repetitive Control for External Signals with Uncertain Periods. [New York, N.Y.?]: [publisher not identified], 2022.
4
Jockers, Matthew L. Style. University of Illinois Press, 2017. http://dx.doi.org/10.5406/illinois/9780252037528.003.0006.
Abstract (sommario):
This chapter shows how stylistic signals can be derived from high-frequency features and how the usage, or nonusage, of those features was susceptible to influences that are external to the so-called “authorial style,” external influences such as genre, time, and gender. These aspects of style were explored using a controlled corpus of 106 British novels where genre was a key point of analysis. The chapter first provides an overview of statistical or quantitative authorship attribution before discussing the author's project, in which he analyzed the degree to which novelistic genres express a distinguishable stylistic signal by focusing on the distribution of novels in a corpus based on their genres and decades of publication. Through a series of experiments, he demonstrates the use of the classification methodology as a way of measuring the extent to which factors beyond an individual author's personal style may play a role in determining the linguistic usage and style of the resulting text.
5
and, Bruno. Attention and Learning. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198725022.003.0009.
Abstract (sommario):
Attention can be defined as a multifaceted gateway to consciousness. We use attention to focus on specific sensory signals (selective attention), to allocate resources to concurrent relevant sources (divided attention), to switch between tasks (alternate attention), to maintain focus on a task for a prolonged period (sustained attention), to ready ourselves for a quick response to sudden novel information (alertness); and all these processes, to some extent, control what sensory signals are processed up to the level of conscious awareness. The multifarious functions of attention often involve multisensory interactions, and in this chapter, will we discuss three broad issues in studying multisensory attention. We will start by considering multisensory spatial attention to signals within different sensory channels in a goal directed manner, in comparison to conditions whereby attention is automatically engaged by external multisensory signals. Next, we will discuss multisensory non-spatial attention. In conclusion, we will discuss the implications for multisensory learning and memory.
6
Millikan, Ruth Garrett. Markers of Identity and Grounded Infosigns. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198717195.003.0015.
Abstract (sommario):
Some ways that identity of the referents of two signs may be marked is by recurrence of the same sign design (“duplicates markers”), by use of the same sign token over again (“Strawson markers”), and by various anaphorical relations (anaphors). Strawson markers, of which “mental files” are an example, are of particular interest, their occurrence or use very significantly reducing the number of separate signs needed to represent complex states of affairs, hence, the number of inferences that must be drawn to extract the consequences of a set of premises. What a sign gives information about, however, is sometimes shown not just in elements of its sign design but in an external relation of the sign to its signified. Thus, a volt meter shows the voltage between the terminals to which its leads are connected.
7
Sheldon, Donald. Lean Materials Planning and Execution: Guide to Internal and External Supply Management Excellence. J. Ross Publishing, 2007.
8
Cary, Phillip. Outward Signs: The Powerlessness of External Things in Augustine's Thought. Oxford University Press, 2008.
9
Cary, Phillip. Outward Signs: The Powerlessness of External Things in Augustine's Thought. Oxford University Press, Incorporated, 2008.
10
Payne, Russell A., e Elias B. Rizk. Axillary Nerve Injury. A cura di Meghan E. Lark, Nasa Fujihara e Kevin C. Chung. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190617127.003.0024.
Abstract (sommario):
Axillary nerve injury has been associated with sports injuries, especially those involving anterior shoulder dislocation. The nerve injury leads to weakness of the deltoid and teres minor muscles, which impairs abduction and external rotation of the arm at the shoulder. Electrodiagnostic studies are helpful for determining extent of reinnervation and recovery after injury. In the absence of clinical or electrodiagnostic signs of recovery 3 to 6 months after injury, it is appropriate to offer surgical exploration. The options for surgical repair include direct nerve repair, nerve grafting, and nerve transfer. In appropriately selected individuals, outcomes are favorable.
Capitoli di libri sul tema "Signal externe":
1
Devasahayam, Suresh R. "External Stimulation of Nerves in Tissue: From Theory to Practice". In Signals and Systems in Biomedical Engineering: Physiological Systems Modeling and Signal Processing, 297–319. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-3531-0_10.
2
Nayyeri, Keyvan. "How to Extend and Customize SignalR Functionality". In Pro ASP.NET SignalR, 155–92. Berkeley, CA: Apress, 2014. http://dx.doi.org/10.1007/978-1-4302-6320-3_7.
3
Devasahayam, Suresh R. "External Stimulation of Excitable Tissue". In Signals and Systems in Biomedical Engineering, 211–24. Boston, MA: Springer US, 2012. http://dx.doi.org/10.1007/978-1-4614-5332-1_9.
4
Korte, Monika, Stephen C. Constable e Catherine G. Constable. "Separation of External Magnetic Signal for Induction Studies". In First CHAMP Mission Results for Gravity, Magnetic and Atmospheric Studies, 315–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-540-38366-6_46.
5
Zhang, Zhenya, Jie An, Paolo Arcaini e Ichiro Hasuo. "Online Causation Monitoring of Signal Temporal Logic". In Computer Aided Verification, 62–84. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-37706-8_4.
Abstract (sommario):
AbstractOnline monitoring is an effective validation approach for hybrid systems, that, at runtime, checks whether the (partial) signals of a system satisfy a specification in, e.g., Signal Temporal Logic (STL). The classic STL monitoring is performed by computing a robustness interval that specifies, at each instant, how far the monitored signals are from violating and satisfying the specification. However, since a robustness interval monotonically shrinks during monitoring, classic online monitors may fail in reporting new violations or in precisely describing the system evolution at the current instant. In this paper, we tackle these issues by considering the causation of violation or satisfaction, instead of directly using the robustness. We first introduce a Boolean causation monitor that decides whether each instant is relevant to the violation or satisfaction of the specification. We then extend this monitor to a quantitative causation monitor that tells how far an instant is from being relevant to the violation or satisfaction. We further show that classic monitors can be derived from our proposed ones. Experimental results show that the two proposed monitors are able to provide more detailed information about system evolution, without requiring a significantly higher monitoring cost.
6
Bonchi, Filippo, Robin Piedeleu, Paweł Sobociński e Fabio Zanasi. "Contextual Equivalence for Signal Flow Graphs". In Lecture Notes in Computer Science, 77–96. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45231-5_5.
Abstract (sommario):
AbstractWe extend the signal flow calculus—a compositional account of the classical signal flow graph model of computation—to encompass affine behaviour, and furnish it with a novel operational semantics. The increased expressive power allows us to define a canonical notion of contextual equivalence, which we show to coincide with denotational equality. Finally, we characterise the realisable fragment of the calculus: those terms that express the computations of (affine) signal flow graphs.
7
Weiland, Siep. "Balancing General Quadratic Measures on External Signals". In Realization and Modelling in System Theory, 133–40. Boston, MA: Birkhäuser Boston, 1990. http://dx.doi.org/10.1007/978-1-4612-3462-3_13.
8
Dey, Arnab. "COV-XDCNN: Deep Learning Model with External Filter for Detecting COVID-19 on Chest X-Rays". In Computer, Communication, and Signal Processing, 174–89. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-11633-9_14.
9
Papesh, Megan H., e Stephen D. Goldinger. "Pupillometry and Memory: External Signals of Metacognitive Control". In Handbook of Biobehavioral Approaches to Self-Regulation, 125–39. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-1236-0_9.
10
Gerwin, Johanna, e Melanie Röthlisberger. "Dialectal ditransitive patterns in British English". In Ditransitives in Germanic Languages, 195–225. Amsterdam: John Benjamins Publishing Company, 2023. http://dx.doi.org/10.1075/sigl.7.06ger.
Abstract (sommario):
The present study weighs the effect of well-established language-internal factors of the dative alternation such as animacy or pronominality of the object phrases against language-external factors such as origin of the speaker. For that purpose, the study samples three types of dative variants (N = 7,070) from six regional dialects in the UK, namely the canonical prepositional and double object constructions as well as the alternative double object construction (e.g. Give it me), using the Freiburg English Dialect Corpus (FRED) and the British National Corpus (BNC). By applying a novel dialectometric approach that uses conditional random forests, we compare the importance of well-known predictors across these six regions and highlight two (political) clusters that contrast England with Wales. Our study advances current knowledge on regional variation in probabilistic grammars and highlights the importance of including non-canonical variable patterns in the analysis.
Atti di convegni sul tema "Signal externe":
1
Feng, Shangting, e Eugene A. Irene. "External switching of reflection from InSb surface". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.tua4.
Abstract (sommario):
We demonstrate a novel InSb optical switch that relies on an increasing absorption mechanism and uses only surface reflection. We have observed of external switching of the reflectivity of the InSb surface using a pump beam from a pulsed CO2 laser. The polarity of the switched-out signal was found to depend on the wavelength of the probe beam. For the same samples and the same experimental setup, all reflected signals from the visible probe beam were positive, whereas the signals switched out from near-infrared light were negative. We propose that this potentially useful effect is based on positive feedback in which the increasing absorption increases the local InSb temperature. The thermal coefficient of the refractive index also depends on the wavelength of radiation. This spectral-dependence effect has been applied to demonstrate optical AND, NAND, and NOR gates by using configurations of one probe with both one and two pump beams. The external switching of the surface reflection also exhibits the potential for parallel optical processing. Based on one pump beam, two probe beams with different wavelengths have been modulated simultaneously.
2
Wang, Changting, e Robert X. Gao. "Sensor Module for Integrated Bearing Condition Monitoring". In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0098.
Abstract (sommario):
Abstract To obtain bearing fault signals with high signal-to-noise ratio, an appropriate sensor module needs to be designed and implemented that can be placed in the vicinity of the bearing to be monitored. This paper presents several design issues related to the sensor module, the build-in electronics, and the scheme of wireless signal communication. Advantages of using an integrated sensor over an external sensor for acquiring bearing signals are presented. Experimental studies have been conducted under various loading and speed conditions, using a commercially available ball bearing that has a seeded defect on its inner ring. The defect was detected using power spectrum analysis techniques. The results provided useful input to the further development of signal processing algorithms for bearing defect feature extraction.
3
Ishihara, S., e H. Yajima. "Concept of Array Processing with Optical Integrated Circuits Controlled by External Optical Signals". In Optical Computing. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/optcomp.1985.tub2.
Abstract (sommario):
The application of optical integrated circuits to optical computing has been discussed in the literature; for logic operations[1~3], for residue arithmetics[4~6], for polynomial processors[7], and so on. The optical integrated circuits are suitable particularly for optical array processing because the elementary devices can be easily duplicated and arranged in regular way with so-called step-and-repeat process. Until recently, those integrated circuits are usually controlled by external electric signals (Fig.1 a); which cause the input bottleneck problem as well as electro-magnetic interferences from both the environment and control signal wires themselves. In this paper, the concept and advantages of optical array processing with optical integrated circuits whose functions can be controlled by external ‘optical’ signals[8](Fig.1 b) are discussed.
4
Xu, Lushuai, Shaohua Dong, Donghua Peng, Haotian Wei e Yundong Ma. "Prediction of Depth Defects During Pipeline Magnetic Flux Leakage Detection Based on the AVOA-BPNN". In ASME 2023 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/pvp2023-106300.
Abstract (sommario):
Abstract The complex operational conditions of in-service pipelines and the extended service time make them susceptible to metal loss, which can lead to pipeline failure. However, quantifying the defect depth presents a challenge to current research. The depth quantification accuracy of pipeline defects can be improved, and the defect state of long-distance pipelines can be accurately controlled by building a model based on the internal magnetic flux signal. This study performed a pulling experiment for internal magnetic flux leakage detection in pipelines and extracted the triaxial leakage signals of 60 internal and external pipeline defects. Firstly, Pearson correlation coefficient is used to extract the seven main influencing factors affecting the depth of pipeline leakage defects, namely axial signal peak-valley value, axial signal waveform area, axial signal waveform energy, circumferential signal peak-valley value, radial signal peak-valley value, axial integral signal peak-valley value, and radial integral signal peak-valley value. Secondly, the initial weights and thresholds of the backpropagation neural network (BPNN) were optimized using the African Vulture Optimization Algorithm (AVOA). Furthermore, an AVOA-BPNN-based defect depth prediction model for pipe leakage detection was established to address the problem challenge of the BPNN algorithm easily falling into the local optimum. The magnetic triaxial leakage signals of the internal and external pipeline defects collected via 60 sets of drafting experiments were used as examples, while a particle swarm optimized BPNN (PSO-BPNN), genetic algorithm optimized BPNN (GA-BPNN), and an unoptimized BPNN were used as models for comparative analysis. The results showed that optimizing the BPNN using AVOA substantially improved the prediction accuracy of the BPNN model. The AVOA-BPNN model predicted 12 sets of pipe defect depths with an average relative error (MRE) of only 2.67% and a determination coefficient (R2) of 0.99800, which exceeded the values of the BPNN, PSO-BPNN, and GA-BPNN models. The AVOA-BPNN uses the internal leakage detection signal to predict the depth of pipe defects, supporting effective decision-making regarding pipe inspection and maintenance.
5
FAN, YIMING, e FOTIS KOPSAFTOPOULOS. "EXPLAINABLE MACHINE LEARNING FRAMEWORK FOR GUIDED WAVES SIGNAL RECONSTRUCTION AND STRUCTURAL HEALTH MONITORING UNDER VARYING OPERATING AND ENVIRONMENTAL STATES". In Structural Health Monitoring 2023. Destech Publications, Inc., 2023. http://dx.doi.org/10.12783/shm2023/37019.
Abstract (sommario):
Lamb Wave (LW) signal has been widely used as a technique for damage identification and localization in Structural Health Monitoring (SHM) due to its sensitivity to varying types of state changes. Analyzing and constructing the guided wave signals then become a critical step in damage detection and assessment. Researchers have discovered features in both temporal and frequency domains for signal description and reconstruction. Yet the related features are challenging to be manually developed as the stochastic acoustic signals captured by sensors can be complex and are determined by various factors such as complex boundary conditions and material properties. Recently, neural network has exhibited the capability for time series reconstruction yet lacking of interpretability. In this study, a convolutional autoencoder (CAE) network has been developed to compress the information of the collected signals along with parameters such as damage levels and external loads into time-invariant and time-variant latent spaces at the bottleneck layer which can be easier to analyze and more efficiently used for state estimation and signal reconstruction. The power of estimating signal and its corresponding conditions has been examined by combining a feed forward neural network (FFNN) with the encoder or decoder extracted from the CAE network so that states of raw signals can be predicted and signals under known states can be reconstructed. The proposed framework has been applied in two test cases to verify its capability and stability in terms of different latent space types. The experiment was conducted on an Al plate under different damage states with PZTs serving as actuators and receivers. It is shown that the state parameters can be estimated with high accuracy and the signals can be generated with low error and thus alleviate the requirements of time-consuming experiments.
6
Lennie, Peter. "Central pathways for color vision". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/oam.1986.tuf1.
Abstract (sommario):
Psychophysical evidence suggests that signals from cones are later transformed to yield an achromatic signal and two chromatically opponent ones. Although physiological observations on the lateral geniculate nucleus (LGN) of the macaque monkey have confirmed the existence of opponent transformations, these differ in important respects from the kind inferred from psychophysical evidence. In particular, the red-green chromatic pathway appears also to carry an achromatic signal, to an extent determined by the spatial properties of the stimulus. The characteristics of the yellow-blue pathway also differ from those inferred from psychophysical observations. Although signals that arise in the LGN do not meet the requirements of the psychophysical model, a linear transformation of these signals could do the required job. Analysis of the chromatic properties of neurons in striate cortex (the recipient of information from the LGN) shows that signals from the LGN are transformed substantially, so as to resemble more closely those expected on psychophysical grounds. The second-stage mechanisms inferred from psychophysical observations therefore seem to reflect the action of at least two distinct physiological transformations.
7
Oppo, G. L., A. Politi, G. L. Lippi e F. T. Arecchi. "Frequency Pushing In Lasers With Injected Signal". In Instabilities and Dynamics of Lasers and Nonlinear Optical Systems. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/idlnos.1985.wd7.
Abstract (sommario):
The synchronization of coupled oscillators is a very old problem1; the simplest quantum optical example is, perhaps, offered by laser with injected signal. In fact, the injection technique has important applications, since it offers an efficient way to lock high power lasers to an external frequency reference. On the other hand, the recent studies on laser instabilities and chaotic dynamics2 extend the physical interest to the unlocking parameter region.
8
Bubenik, T. A., J. B. Nestleroth, R. J. Davis e Harvey Haines. "Multiple Magnetization Level MFL for Pipeline Mechanical Damage Characterization". In 2000 3rd International Pipeline Conference. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/ipc2000-206.
Abstract (sommario):
Mechanical damage, caused by externally applied forces, can deform the cylindrical shape of a pipe, scrape away metal, change material properties, and leave residual stresses and plastic strains. Mechanical damage is especially detrimental when it leaves the potential for delayed failure. In-line inspection tools both must detect mechanical damage and characterize parameters such as microstructure changes, residual stresses and extent of removed metal. These are the parameters that determine whether a defect is a candidate for delayed failure. Magnetic flux leakage (MFL) is commonly used for nondestructive detection and sizing of corrosion and metal-loss defects in pipelines, and it is sometimes cited as useful for detecting mechanical damage. Flux leakage from mechanical damage results from geometric and magnetic changes. The geometric part of the flux leakage signal is caused by denting, metal-loss, and wall thinning. The magnetic part of the signal is caused by cold work, plastic deformation and residual stress. At high magnetization levels, MFL signals are due mostly to defect geometry, such as metal-loss length, depth, and shape. At lower magnetization levels, the signals are caused by both geometric and magnetic deformation. To determine the signal due to magnetic deformation only, the geometric MFL signal obtained at high magnetization levels can be scaled and subtracted from the mixed MFL signal obtained at a low magnetization level. In this way, the MFL signal can be decoupled into its geometric and magnetic components. Using the decoupled magnetic signal, information on cold work, plastic deformation, and residual stresses can be gleaned. This paper shows that scaling of high magnetization level signals is possible and differences between signals at multiple magnetization levels provide unique information about the nature of mechanical damage defects. Representative results from hundreds of mechanical damage defect examined are discussed. Included in the analysis are the effects of pipe material and inspection variables, such as pressure and inspection speed. Prospects for tool design and application for in-line inspection are also presented. This work was supported by Department of Transportation, Office of Pipeline Safety.
9
Kikushima, K., E. Yoneda, K. Suto e H. Yoshinaga. "Simultaneous Distribution of AM/FM FDM TV Signals to 65,536 Subscribers Using 4 Stage Cascade EDFAs". In Optical Amplifiers and Their Applications. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oaa.1990.wb1.
Abstract (sommario):
The advantages of erbium-doped fiber amplifiers (EDFAs) have been well reported [1]-[4]. One existing application is in a cascade configuration for TV signal distribution [4]. This paper is an extension of our previous paper and reports the first distribution of multiplexed AM/FM TV signals. The new technique is ideal to support and extend traditional CATV services and area while ensuring support for future CATV services such as FM-NTSC-TV and HDTV signals as shown in Fig. 1.
10
Loker, David R., Yi Wu, Margaret A. Voss, John T. Roth e Stephen A. Strom. "Wireless Nerve Positional Control of Prosthetic Device". In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63891.
Abstract (sommario):
Artificial limb control is an active area of research, and the control of prosthetic devices using electromyographic (EMG) interfaces is well established. The authors have previously performed a feasibility study which demonstrated that wireless nerve control of a prosthetic device is possible. This is critical for injuries that result in the loss of muscle which prevent EMG control. The purpose of this study is to extend the authors’ current research by providing enhancements to the system designed in the feasibility study. The objective of this current study is to take simulated nerve signals and transform them into corresponding positional motion control realized by a servo motor. The system designed has four functioning blocks: artificial nerve signal generation, wireless transmitter, wireless receiver, and servo motor. The artificial nerve generator used a PIC microcontroller to simulate and apply the signals directly to the wireless transmitter. A one-byte message, that indicated when the appropriate signal characteristics were met, was wirelessly transmitted. After receiving the message, the wireless receiver sent a corresponding pulse-width modulated (PWM) signal to the servo motor for positional control. Various input signal combinations were used to test the system.
Rapporti di organizzazioni sul tema "Signal externe":
1
Nuttall, Albert E. Limiting Detection Performance for Random Signals of Unknown Location, Structure, Extent, and Strength. Fort Belvoir, VA: Defense Technical Information Center, marzo 1995. http://dx.doi.org/10.21236/ada292389.
2
Zhao, George, Grang Mei, Bulent Ayhan, Chiman Kwan e Venu Varma. DTRS57-04-C-10053 Wave Electromagnetic Acoustic Transducer for ILI of Pipelines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), marzo 2005. http://dx.doi.org/10.55274/r0012049.
Abstract (sommario):
In this project, Intelligent Automation, Incorporated (IAI) and Oak Ridge National Lab (ORNL) propose a novel and integrated approach to inspect the mechanical dents and metal loss in pipelines. It combines the state-of-the-art SH wave Electromagnetic Acoustic Transducer (EMAT) technique, through detailed numerical modeling, data collection instrumentation, and advanced signal processing and pattern classifications, to detect and characterize mechanical defects in the underground pipeline transportation infrastructures. The technique has four components: (1) thorough guided wave modal analysis, (2) recently developed three-dimensional (3-D) Boundary Element Method (BEM) for best operational condition selection and defect feature extraction, (3) ultrasonic Shear Horizontal (SH) waves EMAT sensor design and data collection, and (4) advanced signal processing algorithm like a nonlinear split-spectrum filter, Principal Component Analysis (PCA) and Discriminant Analysis (DA) for signal-to-noise-ratio enhancement, crack signature extraction, and pattern classification. This technology not only can effectively address the problems with the existing methods, i.e., to detect the mechanical dents and metal loss in the pipelines consistently and reliably but also it is able to determine the defect shape and size to a certain extent.
3
Abbate, Nicolás, Inés Berniell, Joaquín Coleff, Luis Laguinge, Margarita Machelett, Mariana Marchionni, Julián Pedrazzi e María Florencia Pinto. Discrimination Against Gay and Transgender People in Latin America: A Correspondence Study in the Rental Housing Marke. Banco Interamericano de Desarrollo, febbraio 2023. http://dx.doi.org/10.18235/0004753.
Abstract (sommario):
We assess the extent of discrimination against gay and transgender individuals in the rental housing markets of four Latin American countries. We conducted a large-scale field experiment building on the correspondence study methodology to examine interactions between property managers and fictitious couples engaged in searches on a major online rental housing platform. We find evidence of discriminatory behavior against heterosexual couples where the female partner is a transgender woman (trans couples): they receive 19% fewer responses, 27% fewer positive responses, and 23% fewer invitations to showings than heterosexual couples. However, we find no evidence of discrimination against gay male couples. We also assess whether the evidence is consistent with taste-based discrimination or statistical discrimination models by comparing response rates when couples signal high socioeconomic status (high SES). While we find no significant effect of the signal on call-back rates or the type of response for high-SES heterosexual or gay male couples, trans couples benefit when they signal high SES. Their call-back, positive-response, and invitation rates increase by 25%, 36% and 29%, respectively. These results suggest the presence of discrimination against trans couples in the Latin American online rental housing market, which seems consistent with statistical discrimination. Moreover, we find no evidence of heterosexual couples being favored over gay male couples, nor evidence of statistical discrimination for gay male or heterosexual couples.
4
Abbate, Nicolás, Inés Berniell, Joaquín Coleff, Luis Laguinge, Margarita Machelett, Mariana Marchionni, Julián Pedrazzi e María Florencia Pinto. Discrimination against gay and transgender people in Latin America: a correspondence study in the rental housing market. Madrid: Banco de España, giugno 2023. http://dx.doi.org/10.53479/30131.
Abstract (sommario):
We assess the extent of discrimination against gay and transgender individuals in the rental housing markets of four Latin American countries. We conducted a large-scale field experiment based on the correspondence study methodology to examine interactions between property managers and fictitious couples engaged in searches on a major online rental housing platform. We find no evidence of discrimination against gay male couples but we do find evidence of discrimination against heterosexual couples with a transgender woman partner (trans couples). The latter receive 19% fewer responses, 27% fewer positive responses, and 23% fewer invitations to showings than heterosexual couples. We also assess whether the evidence is consistent with taste-based discrimination or statistical discrimination models by comparing response rates when couples signal being professionals with stable jobs (high SES). While we find no significant effect of the signal for high-SES heterosexual or gay male couples, trans couples benefit from this. Their call-back, positive-response, and invitation rates increase by 25%, 36% and 29%, respectively. These results suggest that discrimination against trans couples is consistent with statistical discrimination. Moreover, we find no evidence of heterosexual couples being favored over gay male couples, nor evidence of statistical discrimination for gay male or heterosexual couples.
5
Nuttall, Albert H. Near-Optimum Detection Performance of Power-Law Processors for Random Signals of Unknown Locations, Structure, Extent, and Arbitrary Strengths,. Fort Belvoir, VA: Defense Technical Information Center, aprile 1996. http://dx.doi.org/10.21236/ada309568.
6
Habib, Ayman, Darcy M. Bullock, Yi-Chun Lin, Raja Manish e Radhika Ravi. Field Test Bed for Evaluating Embedded Vehicle Sensors with Indiana Companies. Purdue University, 2023. http://dx.doi.org/10.5703/1288284317385.
Abstract (sommario):
With the advent of modern sensing technology, mapping products have begun to achieve an unprecedented precision of measurement. Considering their diverse use cases, several factors play a role in what would make the resulting measurements accurate. For light detection and ranging (LiDAR) and photogrammetry-based mapping solutions that implement vehicles outfitted with laser ranging devices, RGB cameras, and global navigation satellite system/inertial navigation system (GNSS/INS) georeferencing units, the quality of the derived mapping products is governed by the combined accuracy of the various sensors. While ranging errors associated with LiDAR systems or the imaging quality of RGB cameras are sensor-dependent and are mostly constant, the accuracy of a georeferencing unit depends on a variety of extrinsic factors, including but not limited to, availability of clear line-of-path to GNSS satellites and presence of radio interferences. The quality of the GNSS signal, in turn, is affected by the grade of hardware components used and, to a great extent, obstructions to signal reception. This document reports some of the major challenges of vehicle-based mobile mapping with regards to GNSS/INS navigation. The background of GNSS/INS positioning is discussed to build a framework for trajectory enhancement as well as improvement of LiDAR mapping products. The focus is put on using available sensor data from LiDAR and/or cameras to enhance their position/orientation quality. Some best practices in light of potential trajectory deterioration are also recommended.
7
Millán-Narotzky, Lucas, Javier García-Bernado, Maïmouna Diakité e Markus Meinzer. Tax Treaty Aggressiveness: Who is Undermining Taxing Rights in Africa? Institute of Development Studies (IDS), novembre 2021. http://dx.doi.org/10.19088/ictd.2021.015.
Abstract (sommario):
Tax avoidance strategies by multinational companies rely heavily on tax treaties. Multinational companies can relocate financial activities across countries to ensure the applicability of the most beneficial tax treaties. This ‘treaty shopping’ can be particularly harmful to African countries, impairing their efforts for domestic resource mobilisation and achieving sustainable development goals. In this paper, we analyse the aggressiveness of tax treaties towards African countries – the extent to which signing tax treaties reduces the taxing rights of African governments. We find that treaties signed with France, Mauritius and the United Arab Emirates reduce withholding tax rates the most, while treaties signed with European countries – and, in particular, the United Kingdom and France – greatly limit other taxing rights, for example, by restricting the scope of permanent establishment definition.
8
Nestleroth. L52298 Augmenting MFL Tools With Sensors that Assess Coating Condition. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), marzo 2009. http://dx.doi.org/10.55274/r0010396.
Abstract (sommario):
External coatings are routinely used to protect transmission pipelines from corrosion; however, coatings may degrade or disbond over time enabling corrosion to occur. Transmission pipeline operators often use magnetic flux leakage (MFL) in-line inspection tools to detect metal loss corrosion defects. Rather than finding the cause of a problem, failure of the coating within a corrosive environment, MFL corrosion surveys only find the result of the problem, corrosion defects that may permanently alter the pressure carrying capacity of the pipeline. Stress corrosion cracking (SCC) can be detected using in-line inspection (ILI) technology, but the availability of tools is limited and the cost of inspection is high compared to MFL inspection. SCC almost always occurs at coating faults; direct coating assessment could indicate future problems that could degrade the serviceability of the pipeline. In this project, a new sensor was developed to assess external coating that could work with currently available ILI tools for minimal additional cost to perform the inspection. The sensors, electromagnetic acoustic transducers (EMATs), generate ultrasonic waves that are guided by the pipe material around the circumference of the pipe. The coating material and adherence can influence the propagation of the ultrasonic waves; changes in ultrasonic signal features were attributed to coating faults. This development used modeling and experiments to establish a more optimal configuration for coating assessment. A multiple feature approach was used. A commonly used feature, signal amplitude, provided good sensitivity to coating condition but was influenced by inspection variables. One unique feature identified in this development is arrival time of the ultrasonic wave. For the wave type and frequency selected, the wave velocity was different for bare and coated pipe. Therefore, disbonded or missing coating can be detected by monitoring arrival time of the ultrasonic wave, a feature that is amplitude independent. Another feature for assessing coating, absorption of selective frequencies, was also demonstrated. Coating assessment capability was experimentally demonstrated using a prototype EMAT ILI tool. All three detection features were shown to perform well in an ILI environment as demonstrated at Battelle"s Pipeline Simulation Facility and BJ Inspection Services pull rigs. Improvement to the prototype occurred between each test; the most significant improvement was the design and construction of a novel set of thick-trace transmitting and receiving Printed Circuit Board (PCB) EMAT coils. Implementation variables such as moisture and soil loading were shown to have a minimal influence on results.
9
Bastawros, Ashraf. DTPH56-16H-CAP01 Mechanochemistry-Based Detection of Early Stage Corrosion Degradation of Pipeline Steels. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), maggio 2020. http://dx.doi.org/10.55274/r0011990.
Abstract (sommario):
The aim of the work is to provide measurable precursor signals associated with the initiation stage of near-surface damage and cracking, as depicted in Fig. 1.1. We have identified many salient features during the early stage of the SCC process (Stages 1, 2 on Fig. 1.1), including residual stress build-up, near-surface (within few microns) defect percolation, and changes of dislocation dynamics and measurable changes of the surface osmic resistance. We developed a model-based prediction of the onset and progression of SCC subsurface damage and assessed the electrochemical impedance spectroscopy (EIS) to measure the extent of surface damage. Such a framework would enable the development of appropriate field-deployable NDE technology with the needed spatial and temporal resolutions.
10
Delmer, Deborah P., Douglas Johnson e Alex Levine. The Role of Small Signal Transducing Gtpases in the Regulation of Cell Wall Deposition Patterns in Plants. United States Department of Agriculture, agosto 1995. http://dx.doi.org/10.32747/1995.7570571.bard.
Abstract (sommario):
The combined research of the groups of Delmer, Levine and Johnson has led to a number of interesting findings with respect to the function of the small GTPase Rac in plants and also opened up new leads for future research. The results have shown: 1) The Rac13 protein undergoes geranylgeranlyation and is also translocated to the plasma membrane as found for Rac in mammals; 2) When cotton Rac13 is highly- expressed in yeast, it leads to an aberrant phenotype reminiscent of mutants impaired in actin function, supporting a role for Rac13 in cytoskeletal organization; 3) From our searches, there is no strong evidence that plants contain homologs of the related CDC42 genes found in yeast and mammals; 4) We have identified a rather unique Rac gene in Arabidopsis that has unusual extensions at both the N- and C-terminal portions of the protein; 5) New evidence was obtained that an oxidative burst characterized by substantial and sustained production of H202 occurs coincident with the onset of secondary wall synthesis in cotton fibers. Further work indicates that the H202 produced may be a signal for the onset of this phase of development and also strongly suggests that Rac plays an important role in signaling for event. Since the secondary walls of plants that contain high levels of lignin and cellulose are the major source of biomass on earth, understanding what signals control this process may well in the future have important implications for manipulating the timing and extent of secondary wall deposition. 6) When the cotton Rac13 promoter is fused to the reporter gene GUS, expression patterns in Arabidopsis indicate very strong and specific expression in developing trichomes and in developing xyelm. Since both of these cell types are engaged in secondary wall synthesis, this further supports a role for Rac in signaling for onset of this process. Since cotton fibers are anatomically defined as trichomes, these data may also be quite useful for future studies in which the trichomes of Arabidopsis may serve as a model for cotton fiber development; the Rac promoter can therefore be useful to drive expression of other genes proposed to affect fiber development and study the effects on the process; 7) The Rac promoter has also been shown to be the best so far tested for use in development of a system for transient transformation of developing cotton fibers, a technique that should have many applications in the field of cotton biotechnology; 8) One candidate protein that may interact with Rac13 to be characterized further in the future is a protein kinase that may be analogous to the PAK kinase that is known to interact with Rac in mammals.