Littérature scientifique sur le sujet « Sensory distortion »
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Articles de revues sur le sujet "Sensory distortion"
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Suranthiran, Sugathevan, et Suhada Jayasuriya. « Signal Conditioning With Memory-Less Nonlinear Sensors ». Journal of Dynamic Systems, Measurement, and Control 126, no 2 (1 juin 2004) : 284–93. http://dx.doi.org/10.1115/1.1766030.
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Proposed in this paper is an off-line signal conditioning scheme for memoryless nonlinear sensors. In most sensor designs, a linear input-output response is desired. However, nonlinearity is present in one form or another in almost all real sensors and therefore it is very difficult if not impossible to achieve a truly linear relationship. Often sensor nonlinearity is considered a disadvantage in sensory systems because it introduces distortion into the system. Due to the lack of efficient techniques to deal with the issues of sensor nonlinearity, primarily nonlinear sensors tend to be ignored. In this paper, it is shown that there are certain advantages of using nonlinear sensors and nonlinear distortion caused by sensor nonlinearity may be effectively compensated. A recursive algorithm utilizing certain characteristics of nonlinear sensor functions is proposed for the compensation of nonlinear distortion and sensor noise removal. A signal recovery algorithm that implements this idea is developed. Not having an accurate sensor model will result in errors and it is shown that the error can be minimized with a proper choice of a convergence accelerator whereby stability of the developed algorithm is established.
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Hwang, Alex D., et Eli Peli. « Stereoscopic Three-dimensional Optic Flow Distortions Caused by Mismatches Between Image Acquisition and Display Parameters ». Journal of Imaging Science and Technology 63, no 6 (1 novembre 2019) : 60412–1. http://dx.doi.org/10.2352/j.imagingsci.technol.2019.63.6.060412.
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Abstract We analyzed the impact of common stereoscopic three-dimensional (S3D) depth distortion on S3D optic flow in virtual reality environments. The depth distortion is introduced by mismatches between the image acquisition and display parameters. The results show that such S3D distortions induce large S3D optic flow distortions and may even induce partial/full optic flow reversal within a certain depth range, depending on the viewer’s moving speed and the magnitude of S3D distortion. We hypothesize that the S3D optic flow distortion may be a source of intra-sensory conflict that could be a source of visually induced motion sickness.
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Cui, Bliss, et Peter Bex. « Facing Distortion ». Journal of Vision 22, no 14 (5 décembre 2022) : 3356. http://dx.doi.org/10.1167/jov.22.14.3356.
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Gardner, Rick M., Renee Martinez et Yvonne Sandoval. « Obesity and body image : an evaluation of sensory and non-sensory components ». Psychological Medicine 17, no 4 (novembre 1987) : 927–32. http://dx.doi.org/10.1017/s0033291700000738.
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SynopsisBody image in 38 obese and normal weight subjects was measured using a video TV monitor. Tasks included a continuous task where subjects manipulated the size of their body image on a TV screen, and a discrete task, where they judged the accuracy of their TV image which was presented as either too heavy or too thin. Subjects viewed their images in both regular street clothes and with minimal clothing.Results from the continuous task revealed that obese subjects overestimated body size. All subjects were more accurate on trials in which the initial image was adjusted in the heavier direction.On the discrete task, a signal detection analysis revealed sensory sensitivity differences between obese and normal weight subjects. Obese subjects were better at detecting distortion caused by a too thin image, but were inferior in detecting a too heavy distortion. No significant differences were obtained in response criteria or between clothing conditions.
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Саркисян, Н. В., et А. Ю. Сорокин. « Information and cybernetic model of the human sensory system ». International Journal of Medicine and Psychology 7, no 2 (28 mars 2024) : 208–16. http://dx.doi.org/10.58224/2658-3313-2024-7-2-208-216.
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в настоящей статье рассматривается работа сенсорно-перцептивной системы в ключе проблемы искажения информации при коммуникации. Обоснована информационно-кибернетическая модель сенсорной системы, а также приведены подпроцессы при обработке информацией сенсорной системы, в которых возможно искажение информации. Приведены три составляющие на примере разговора двух людей в шумном торговом центре. В статье раскрывается вопрос соответствия информации озвученной первым субъектом и информации услышанной вторым. Подразумевается также информация в виде электрического сигнала, дошедшая до соответствующего отдела мозга второго субъекта. Поскольку все информативные сигналы внутри организма имеют электрическую природу, предлагается рассмотреть работу сенсорно-перцептивной системы с позиции информатики и кибернетики. Предполагается, что сенсорно-перцептивная система является прежде всего кибернетической системой и содержит все ее признаки. Проверке данной гипотезы, а также определению возможных механизмов искажения информации в сенсорной системе и посвящается настоящая статья. Применен системный анализ, предполагающий рассмотрение сенсорной системы и создание ее модели как взаимосвязанных структурных элементов, обрабатывающих информацию. Сравнительный анализ применен для сопоставления особенностей получившейся модели сенсорной системы с принципами кибернетики. Гипотетико-дедуктивный метод применен для анализа модели сенсорной системы в целях определения возможных механизмов искажения информации. Было установлено, что сенсорная система работает в полном соответствии с принципами кибернетики, а потому может справедливо рассматриваться как кибернетическая система. Сделан вывод о том, что сенсорно-перцептивною систему можно рассматривать как систему кибернетическую. Установлено междисциплинарное сопряжение между психофизикой, социальной психологией и кибернетикой. this article examines the work of the sensory-perceptual system in the context of the problem of information distortion during communication. The information-cybernetic model of the sensory system is substantiated, and subprocesses in the processing of sensory system information in which information distortion is possible are given. Three components are given using the example of a conversation between two people in a noisy shopping center. The article reveals the issue of correspondence between the information voiced by the first subject and the information heard by the second. This also means information in the form of an electrical signal that has reached the corresponding part of the brain of the second subject. Since all informative signals inside the body are of an electrical nature, it is proposed to consider the operation of the sensory-perceptual system from the perspective of computer science and cybernetics. It is assumed that the sensory-perceptual system is primarily a cybernetic system and contains all its characteristics. This article is devoted to testing this hypothesis, as well as identifying possible mechanisms of information distortion in the sensory system. System analysis was applied, which involves considering the sensory system and creating its model as interconnected structural elements that process information. Comparative analysis is used to compare the features of the resulting sensor system model with the principles of cybernetics. The hypothetico-deductive method was used to analyze the sensory system model in order to determine possible mechanisms of information distortion. It was found that the sensor system operates in full accordance with the principles of cybernetics, and therefore can rightly be considered as a cybernetic system. It is concluded that the sensory-perceptual system can be considered as a cybernetic system. An interdisciplinary connection has been established between psychophysics, social psychology and cybernetics.
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Sauer, Yannick, Siegfried Wahl et Katharina Rifai. « Interocular transfer of distortion adaptation ». Journal of Vision 20, no 11 (20 octobre 2020) : 663. http://dx.doi.org/10.1167/jov.20.11.663.
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Aloimonos, Y., et C. Fermuller. « Chromatic induction and perspective distortion ». Journal of Vision 5, no 8 (1 septembre 2005) : 1026. http://dx.doi.org/10.1167/5.8.1026.
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Adamian, Nika, Stuart Anstis et Patrick Cavanagh. « Motion-induced distortion of shape ». Journal of Vision 23, no 12 (30 octobre 2023) : 10. http://dx.doi.org/10.1167/jov.23.12.10.
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Martin, Glen K., Barden B. Stagner, Wei Dong et Brenda L. Lonsbury-Martin. « Comparing Distortion Product Otoacoustic Emissions to Intracochlear Distortion Products Inferred from a Noninvasive Assay ». Journal of the Association for Research in Otolaryngology 17, no 4 (26 mai 2016) : 271–87. http://dx.doi.org/10.1007/s10162-016-0552-1.
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Morgan, M. J., I. Mareschal, C. Chubb et J. A. Solomon. « Perceived pattern regularity computed as a summary statistic : implications for camouflage ». Proceedings of the Royal Society B : Biological Sciences 279, no 1739 (21 mars 2012) : 2754–60. http://dx.doi.org/10.1098/rspb.2011.2645.
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Why do the equally spaced dots in figure 1 appear regularly spaced? The answer ‘because they are’ is naive and ignores the existence of sensory noise, which is known to limit the accuracy of positional localization. Actually, all the dots in figure 1 have been physically perturbed, but in the case of the apparently regular patterns to an extent that is below threshold for reliable detection. Only when retinal pathology causes severe distortions do regular grids appear perturbed. Here, we present evidence that low-level sensory noise does indeed corrupt the encoding of relative spatial position, and limits the accuracy with which observers can detect real distortions. The noise is equivalent to a Gaussian random variable with a standard deviation of approximately 5 per cent of the inter-element spacing. The just-noticeable difference in positional distortion between two patterns is smallest when neither of them is perfectly regular. The computation of variance is statistically inefficient, typically using only five or six of the available dots.
Thèses sur le sujet "Sensory distortion"
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Lin, Jiun-Shian. « Applying sensory distortion devices in artistic production : practice-based studies of creating artefacts with perceptual devices which confuse artists' vision and kinesthesis ». Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3760.
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When I was an art school student, I was trained to pursue the likeness of subjects in all my artworks. This practice-based research explores alternative forms of self-expression in art practice. The exploration starts by questioning the relationship between perceptual devices, artists’ perceptions and artistic production. Most perceptual devices are designed to enhance artists’ sensory capabilities and facilitate the creation of art. Their success is often based on enabling artists to achieve a likeness of the subject drawn or making the creation of artefacts easier. My research focuses on investigating the consequences and artistic potential of applying sensory distortion devices that confuse, mislead and distort artists’ vision and kinesthesis, increasing the difficulty of making art, and exploring the productive potential of such devices to engender new creative forms. In this research three visual distortion devices and two kinaesthetic distortion devices are prototyped and used in experimental calligraphy, painting and drawing exercises. After analysing the artists’ experience of using these devices, the influence and artistic potential of applying them are examined. It is discovered that distorted vision and kinesthesis can greatly influence the making of art by disrupting habitual eye-hand coordination and control over producing artefacts. Besides which, the use of visual and kinaesthetic distortion devices can be a technique for new forms of artistic expression. It can also be an effective technique for creating serendipitous opportunities in the visual arts and a way of exploring and provoking reflection upon artistic methodologies. Consideration of the attributes of visual and kinaesthetic distortion devices and distorted perceptions during the process of prototyping can benefit the generation of ideas, methods of production and the contents of artworks. Some practical implications for creating art with visual and kinaesthetic distortion devices are also explored. They are discussed in relation to theories of human performance, such as flow theory, and attitudes toward the conflict between habitual and unfamiliar perceptual experience. Keeping an open and uncritical mind toward unfamiliarity, chaos and the accidents caused by distorted perceptions and reduced control of drawing instruments is suggested to working artists. Finally, this research contributes to art education by demonstrating a possible way of achieving self-exploration through art making.
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Dumas, Louise-Émilie. « Les cognitions sensorielle, émotionnelle et sociale dans les troubles de perception et le trouble de stress post traumatique ». Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ6021.
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Introduction : Les cognitions sensorielle, émotionnelle et sociale représentent le traitement des informations nécessaires à l'adaptation du sujet dans son environnement. Un psycho traumatisme est un évènement menaçant l'intégrité physique et psychique d'un individu et agit comme une « effraction » soudaine et intense de son système cognitif exposé au danger. Cette « effraction » entraine des atteintes cognitives provoquées par des altérations du système de neuromodulation des structures cérébrales impactées. Ces séquelles cognitives provoquent les symptômes qui constituent le trouble de stress post traumatique (TSPT) dont des troubles de perception. Le TSPT est associé à d'autres troubles psychiatriques comorbides dont le trouble psychotique. Notre travail propose l'hypothèse d'une compréhension clinique en « cascade » du psycho traumatisme. Il soutient l'idée que les cognitions sensorielle, émotionnelle et sociale s'articulent entre elles et avec l'environnement et participent à l'évolution du continuum entre psycho traumatisme et trouble psychotique.Méthodes : Nos travaux étudient la place des cognitions sensorielles, émotionnelles et sociales dans les troubles de perception post traumatiques illustrée par deux études de recherche clinique prospectives et longitudinales sur 6 mois. PROJET 1 : Identification des marqueurs de cognitions émotionnelle et sociale associés aux hallucinations acoustico-verbales (HAV) en population pédiatrique générale et en population pédiatrique clinique avec TSPT. PROJET 2 : Impact des troubles olfactifs persistants post Covid-19 sur la qualité de vie, l'expérience hédonique et les dimensions anxieuse et dépressives en population adulte.Résultats : PROJET 1 : L'étude réalisée en population pédiatrique générale a inclus 40 patients d'âge moyen 12,8 ans. Les émotions négatives (tristesse, peur colère) étaient significativement retrouvées dans le groupe avec des HAV persistantes à 6 mois. Les HAV persistantes étaient significativement associées au diagnostic de TSPT (p=0,01). L'étude réalisée en population pédiatrique clinique avec TSPT a inclus 31 patients d'âge moyen 12,9 ans. Les émotions négatives (culpabilité et malveillance des HAV) étaient significativement associées et corrélées à la persistance des HAV. Les émotions négatives (dégout, peur et colère et les diagnostics de dépression et d'anxiété) étaient associées à la persistance du TSPT à 6 mois. La persistance des HAV était significativement associée à l'émergence du diagnostic de trouble psychotique à 6 mois (p=0,01). PROJET 2 : L'étude a inclus 56 patients d'âge moyen 39 ans. Les troubles olfactifs étaient significativement associées à des émotions négatives (qualité de vie, perte de plaisir). Les patients avec une distorsion sensorielle (parosmie, phantosmie) étaient significativement impactés sur le plan émotionnel comparé aux patients qui présentaient une perte sensorielle (anosmie). Bien qu'ils aient retrouvés l'odorat au test psychophysique, les patients qui percevaient d'un trouble olfactif persistant répondaient aux symptômes de TSPT et étaient émotionnellement impactés (qualité de vie, perte de plaisir, anxiété et dépression).Conclusion : Les cognitions sensorielles et émotionnelles, après un évènement traumatique, sont significativement liées entre elles. Leur articulation participent à l'installation et au maintien des troubles de perception. Elles interviennent dans l'évolution de la clinique post traumatique, du TSPT et des troubles psychiatriques associés dont le trouble psychotique. L'évolution des symptômes post traumatiques nécessite une lecture dimensionnelle pour une meilleure compréhension clinique, un suivi préventif des facteurs de risques de mauvaise évolution psychiatrique et une proposition thérapeutique ciblée sur les cognitions sensorielles et émotionnellesIntroduction: Sensory, emotional and social cognition represent the processing of internal and external information required by the subject to adapt to the environment. A psycho-trauma is defined as an event that threatens the physical and psychological integrity of an individual, and acts as a sudden and intense intrusion of the cognitive system exposed to danger. This psycho-traumatic intrusion leads to sensory, emotional and social cognitive damage, caused by alterations in the neuromodulation system of the brain structures affected. These cognitive sequelae give rise to the post-traumatic symptoms that constitute post-traumatic stress disorder (PTSD), including perceptual disorders. PTSD is also associated with other comorbid psychiatric disorders, including psychotic disorders. Our work proposes the hypothesis of a "cascade" clinical understanding of psycho-trauma. It supports the idea that sensory, emotional and social cognition articulate with each other and with the environment, and participate in the evolution of the continuum between psycho-trauma and psychotic disorder.Methods: The aim of our research is to study the role of sensory, emotional and social cognition in post-traumatic perceptual disorders. This work is illustrated by two prospective, longitudinal 6-month clinical research studies. PROJECT 1: Identification of markers of emotional and social cognition associated with acoustic-verbal hallucinations (AVH) in the general pediatric population, then in the clinical pediatric population with PTSD. PROJECT 2: Impact of persistent post-Covid-19 olfactory disorders on quality of life, hedonic experience and anxiety and depression dimensions in an adult population.Results: PROJECT 1: The study, carried out in a general pediatric population, included 40 patients (30 girls, 10 boys) with a mean age of 12.8 years. Negative emotions (sadness, fear, anger) were significantly found in the group with persistent AVH at 6 months. Persistent AVH were significantly associated with the diagnosis of PTSD (p=0.01). The study conducted in a clinical pediatric population with PTSD included 31 patients (25 girls, 6 boys) with a mean age of 12.9 years. Negative emotions (patient guilt and maliciousness of HAV) were significantly associated and correlated with persistence of HAV. Negative emotions (disgust, fear and anger, and diagnoses of depression and anxiety) were also associated with PTSD persistence at 6 months. The persistence of HAV was significantly associated with the emergence of a diagnosis of psychotic disorder at 6 months (p=0.01). PROJECT 2: The study included 56 patients with a mean age of 39 (33 women, 23 men). Olfactory disorders were significantly associated and correlated with negative emotions (quality of life, loss of pleasure). Patients with sensory distortion (parosmia, phantosmia) were more significantly impacted emotionally than patients with no sensory perception (anosmia). Although they "objectively" recovered their sense of smell on the psychophysical test, patients who "subjectively" perceived the persistence of an olfactory disorder responded to PTSD symptoms and were more emotionally impacted (quality of life, loss of pleasure, anxiety and depression).Conclusion: Sensory and emotional cognitions are significantly linked after a traumatic event. Their articulation contributes to the onset and maintenance of perceptual disorders. They are also involved in the development of post-traumatic clinical symptoms, PTSD and other associated psychiatric disorders, including psychotic disorders. The evolution of post-traumatic symptoms requires a dimensional reading for a better clinical understanding, preventive monitoring of risk factors for poor psychiatric evolution, and a therapeutic proposal targeting sensory and emotional cognition
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Karaaslan, Ibrahim. « Anti-sensor Network : Distortion-based Distributed Attack In Wireless Sensor Networks ». Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609276/index.pdf.
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In this thesis, a novel anti-sensor network paradigm is introduced against wireless sensor networks (WSN). Anti-sensor network (ASN) aims to destroy application reliability by adaptively and anonymously introducing adequate level of artificial distortion into the communication of the event features transported from the sensor nodes (SN) to the sink. ASN is composed of anti-sensor nodes (aSN) randomly distributed
over the sensor network field. aSNs pretend to be SNs tomaintain anonymity and so improve resiliency against attack detection and prevention mechanisms. Performance
evaluations via mathematical analysis and simulation experiments show that ASN can effectively reduce the application reliability of WSN.
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King, Bradley R. « Sensory integration during de-adaptation to visuomotor distortions ». College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3946.
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Thesis (M.A.) -- University of Maryland, College Park, 2006.Thesis research directed by: Dept. of Kinesiology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Aguirre, Jurado Ricardo. « Resilient Average and Distortion Detection in Sensor Networks ». ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/962.
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In this paper a resilient sensor network is built in order to lessen the effects of a small portion of corrupted sensors when an aggregated result such as the average needs to be obtained. By examining the variance in sensor readings, a change in the pattern can be spotted and minimized in order to maintain a stable aggregated reading. Offset in sensors readings are also analyzed and compensated to help reduce a bias change in average. These two analytical techniques are later combined in Kalman filter to produce a smooth and resilient average given by the readings of individual sensors. In addition, principal components analysis is used to detect variations in the sensor network. Experiments are held using real sensors called MICAz, which are use to gather light measurements in a small area and display the light average generated in that area.
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Ioakim, Panagiotis. « A high precision accelometer-based sensor unit for the acquisition of ultra low distortion seismic signals ». Thesis, City, University of London, 2017. http://openaccess.city.ac.uk/19360/.
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Over 800,000 people worldwide lost their lives to earthquakes in the last decade and on average 171 people die every day due to earthquake related damage to structures and buildings. Precisely understanding the effects ground motion has on manmade structures is crucial to making them earthquake resistant. This can only be achieved by the precise measurement, recording, and analysis of ground displacement trends during a seismic event. Although there is a vast amount of recorded seismological data available, current technology and processing methods fail to represent accurate ground displacement over time as the considerable technological challenges have yet to be overcome. Raw seismic data has so far been primarily acquired with instruments utilising geophone or accelerometer based sensors. These instruments produce prominent time domain displacement errors due to the various system and sensor inaccuracies, and due to non-linear response. Since accelerometers provide acceleration over time data: whilst geophones are velocimeters, and therefore provide velocity over time data; in order to derive true ground displacement over time, a double, or single numerical integration is required respectively. During this essential numerical integration processes of data from such sensors, even small in magnitude errors accumulate to yield rather large displacement trend offsets over a typical event recording period of 60 to 120 seconds. In addition, the numerical integration process itself poses considerable challenges due to the theoretically infinite number of samples and the accurate determination of initial conditions required for an exact mathematical result to be obtained. The latter, is currently performed by averaging an up to 60 second pre-event data trend stored on the instrument. Most post-integration data from current instruments appears to contain low frequency drifts amongst other noise artefacts, and generally requires baseline correction algorithms in an attempt to correct for these effects. Such corrections, although helpful, only aid to minimise the perceived effects of an assumed and collective source of error, and hence are largely unable to tackle the individual error contribution of each element within the system. Since individual element contribution is of a dynamic nature, the validity of these algorithms is limited by the accuracy of the initial assumptions made about a specific set of data. Faced with such a multivariable and uncertain dynamic behaviour, where even mathematical system modelling is of inadequate long term accuracy, a solution that aims to directly minimise these errors at source, rather than attempt to correct them postacquisition, is of immense importance when it comes to the recording, analysis, and understanding of earthquakes. This thesis describes the design, implementation, and evaluation of a High Precision Active Gyro Stabilised (HPAGS) sensor unit of exceptional performance for the provision of highly accurate ground displacement data. Experimental results demonstrated that the device described herein, was able to diminish the inherent non-linear and environment-dependant effects of current sensors, and thus was able to provide highly improved time domain displacement data.
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Fulcher, Corinne. « The role of sensory history and stimulus context in human time perception : adaptive and integrative distortions of perceived duration ». Thesis, University of Bradford, 2017. http://hdl.handle.net/10454/16063.
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This thesis documents a series of experiments designed to investigate the mechanisms subserving sub-second duration processing in humans. Firstly, duration aftereffects were generated by adapting to consistent duration information. If duration aftereffects represent encoding by neurons selective for both stimulus duration and non-temporal stimulus features, adapt-test changes in these features should prevent duration aftereffect generation. Stimulus characteristics were chosen which selectively target differing stages of the visual processing hierarchy. The duration aftereffect showed robust interocular transfer and could be generated using a stimulus whose duration was defined by stimuli invisible to monocular mechanisms, ruling out a pre-cortical locus. The aftereffects transferred across luminance-defined visual orientation and facial identity. Conversely, the duration encoding mechanism was selective for changes in the contrast-defined envelope size of a Gabor and showed broad spatial selectivity which scaled proportionally with adapting stimulus size. These findings are consistent with a second stage visual spatial mechanism that pools input across proportionally smaller, spatially abutting filters. A final series of experiments investigated the pattern of interaction between concurrently presented cross-modal durations. When duration discrepancies were small, multisensory judgements were biased towards the modality with higher precision. However, when duration discrepancies were large, perceived duration was compressed by both longer and shorter durations from the opposite modality, irrespective of unimodal temporal reliability. Taken together, these experiments provide support for a duration encoding mechanism that is tied to mid-level visual spatial processing. Following this localised encoding, supramodal mechanisms then dictate the combination of duration information across the senses.
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Li, Junlin. « Distributed estimation in resource-constrained wireless sensor networks ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26633.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Ghassan AlRegib; Committee Member: Elliot Moore; Committee Member: Monson H. Hayes; Committee Member: Paul A. Work; Committee Member: Ying Zhang. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Piruska, Aigars. « Studies of Spectral Distortion Under ATR Condition in Spectroelectrochemical Sensor Development of Laser Induced Fluorescence Detection System for Multilane Capillary Electrophoresis Microchips ». University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1163388232.
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Leinonen, M. (Markus). « Distributed compressed data gathering in wireless sensor networks ». Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526220451.
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Abstract Wireless sensor networks (WSNs) consisting of battery-powered sensors are increasingly deployed for a myriad of Internet of Things applications, e.g., environmental, industrial, and healthcare monitoring. Since wireless access is typically the main contributor to battery usage, minimizing communications is crucial to prolong network lifetime and improve user experience. The objective of this thesis is to develop and analyze energy-efficient distributed compressed data acquisition techniques for WSNs. The thesis proposes four approaches to conserve sensors' energy by minimizing the amount of information each sensor has to transmit to meet given application requirements. The first part addresses a cross-layer design to minimize the sensors’ sum transmit power via joint optimization of resource allocation and multi-path routing. A distributed consensus optimization based algorithm is proposed to solve the problem. The algorithm is shown to have superior convergence compared to several baselines. The remaining parts deal with compressed sensing (CS) of sparse/compressible sources. The second part focuses on the distributed CS acquisition of spatially and temporally correlated sensor data streams. A CS algorithm based on sliding window and recursive decoding is developed. The method is shown to achieve higher reconstruction accuracy with fewer transmissions and less decoding delay and complexity compared to several baselines, and to progressively refine past estimates. The last two approaches incorporate the quantization of CS measurements and focus on lossy source coding. The third part addresses the distributed quantized CS (QCS) acquisition of correlated sparse sources. A distortion-rate optimized variable-rate QCS method is proposed. The method is shown to achieve higher distortion-rate performance than the baselines and to enable a trade-off between compression performance and encoding complexity via the pre-quantization of measurements. The fourth part investigates information-theoretic rate-distortion (RD) performance limits of single-sensor QCS. A lower bound to the best achievable compression — defined by the remote RD function (RDF) — is derived. A method to numerically approximate the remote RDF is proposed. The results compare practical QCS methods to the derived limits, and show a novel QCS method to approach the remote RDFTiivistelmä Patterikäyttöisistä antureista koostuvat langattomat anturiverkot yleistyvät esineiden internetin myötä esim. ympäristö-, teollisuus-, ja terveydenhoitosovelluksissa. Koska langaton tiedonsiirto kuluttaa merkittävästi energiaa, kommunikoinnin minimointi on elintärkeää pidentämään verkon elinikää ja parantamaan käyttäjäkokemusta. Väitöskirjan tavoitteena on kehittää ja analysoida energiatehokkaita hajautettuja pakattuja datankeruumenetelmiä langattomiin anturiverkkoihin. Työssä ehdotetaan neljä lähestymistapaa, jotka säästävät anturien energiaa minimoimalla se tiedonsiirron määrä, mikä vaaditaan täyttämään sovelluksen asettamat kriteerit. Väitöskirjan ensimmäinen osa tarkastelee protokollakerrosten yhteissuunnittelua, jossa minimoidaan anturien yhteislähetysteho optimoimalla resurssiallokaatio ja monitiereititys. Ratkaisuksi ehdotetaan konsensukseen perustuva hajautettu algoritmi. Tulokset osoittavat algoritmin suppenemisominaisuuksien olevan verrokkejaan paremmat. Loppuosat keskittyvät harvojen lähteiden pakattuun havaintaan (compressed sensing, CS). Toinen osa keskittyy tila- ja aikatasossa korreloituneen anturidatan hajautettuun keräämiseen. Työssä kehitetään liukuvaan ikkunaan ja rekursiiviseen dekoodaukseen perustuva CS-algoritmi. Tulokset osoittavat menetelmän saavuttavan verrokkejaan korkeamman rekonstruktiotarkkuuden pienemmällä tiedonsiirrolla sekä dekoodausviiveellä ja -kompleksisuudella ja kykenevän asteittain parantamaan menneitä estimaatteja. Työn viimeiset osat sisällyttävät järjestelmämalliin CS-mittausten kvantisoinnin keskittyen häviölliseen lähdekoodaukseen. Kolmas osa käsittelee hajautettua korreloitujen harvojen signaalien kvantisoitua CS-havaintaa (quantized CS, QCS). Työssä ehdotetaan särön ja muuttuvan koodinopeuden välisen suhteen optimoiva QCS-menetelmä. Menetelmällä osoitetaan olevan verrokkejaan parempi pakkaustehokkuus sekä kyky painottaa suorituskyvyn ja enkooderin kompleksisuuden välillä mittausten esikvantisointia käyttäen. Neljäs osa tutkii informaatioteoreettisia, koodisuhde-särösuhteeseen perustuvia suorituskykyrajoja yhden anturin QCS-järjestelmässä. Parhaimmalle mahdolliselle pakkaustehokkuudelle johdetaan alaraja, sekä kehitetään menetelmä sen numeeriseen arviointiin. Tulokset vertaavat käytännön QCS-menetelmiä johdettuihin rajoihin, ja osoittavat ehdotetun QCS-menetelmän saavuttavan lähes optimaalinen suorituskyky
Livres sur le sujet "Sensory distortion"
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Gerbino, Walter. Amodally Completed Angles. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0097.
Texte intégralRésumé :
When the vertex of an occluded angle geometrically belongs to the side of the occluding surface, the occluded angle looks distorted. This characteristic effect of coincidental occlusion—called the Gerbino illusion—is consistent with the phenomenal rounding of angles observed under conditions of symmetrical occlusion. Both effects are robust and appear in static and dynamic displays. The Gerbino illusion differs from distortions observed in Poggendorff-like displays, runs against the tendency to global Prägnanz, and reveals important aspects of amodal completion processes. Alternative explanations based on visual interpolation and visual approximation are discussed. According to the approximation-based explanation, the possible discrepancy between internal models and the sensory input is perceptually represented as a phenomenal distortion.
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Hari, Riitta. Magnetoencephalography. Sous la direction de Donald L. Schomer et Fernando H. Lopes da Silva. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190228484.003.0035.
Texte intégralRésumé :
This chapter introduces magnetoencephalography (MEG), a tool to study brain dynamics in basic and clinical neuroscience. MEG picks up brain signals with millisecond resolution, as does electroencephalography, but without distortion by skull and scalp. The chapter describes current instrumentation based on superconducting quantum interference devices (SQUIDs). It delineates basic characteristics of measured signals: (1) brain rhythms and their reactivity during sensory processing and various tasks and (2) evoked responses elicited by sensory stimuli, and the dependence of these responses on various stimulus characteristics. Signals are described from healthy and diseased brains. The chapter presents studies of the brain basis of cognition and social interaction studied in dual-MEG setups and describes how MEG applications can be broadened by innovative setups, including frequency tagging. Progress in the field is predicted regarding sensor technology, data analysis, and multimodal brain imaging, all of which could strengthen MEG’s role in the study of brain dynamics.
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Barwich, Ann-Sophie. Measuring the World. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198779636.003.0017.
Texte intégralRésumé :
How much does stimulus input shape perception? The common-sense view is that our perceptions are representations of objects and their features and that the stimulus structures the perceptual object. The problem for this view concerns perceptual biases as responsible for distortions and the subjectivity of perceptual experience. These biases are increasingly studied as constitutive factors of brain processes in recent neuroscience. In neural network models the brain is said to cope with the plethora of sensory information by predicting stimulus regularities on the basis of previous experiences. Drawing on this development, this chapter analyses perceptions as processes. Looking at olfaction as a model system, it argues for the need to abandon a stimulus-centred perspective, where smells are thought of as stable percepts, computationally linked to external objects such as odorous molecules. Perception here is presented as a measure of changing signal ratios in an environment informed by expectancy effects from top-down processes.
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Aquino, Frederick D., et Paul L. Gavrilyuk, dir. Perceiving Things Divine. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780198802594.001.0001.
Texte intégralRésumé :
Sensory language is commonly used to describe human encounters with the divine. Scripture, for example, employs perceptual language like ‘taste and see that the Lord is good’, ‘hear the word of the Lord’, and promises that ‘the pure in heart will see God’. Such statements seem to point to certain features of human cognition that make perception-like contact with divine things possible. But how precisely should these statements be construed? Can the elusive notion of ‘spiritual perception’ survive rigorous theological and philosophical scrutiny and receive a constructive articulation? Perceiving Things Divine seeks to make philosophical and theological sense of spiritual perception. Reflecting the results of the second phase of the Spiritual Perception Project, this volume argues for the possibility of spiritual perception. It also seeks to make progress towards a constructive account of the different aspects of spiritual perception while exploring its intersection with various theological and philosophical themes, such as biblical interpretation, aesthetics, liturgy, race, ecology, eschatology, and the hiddenness of God. The interdisciplinary scope of the volume draws on the resources of value theory, philosophy of perception, epistemology, philosophy of art, psychology, systematic theology, and theological aesthetics. However, spiritual perception is often distorted due to the general brokenness of the human condition. The volume explores such distortions as pornographic sensibility and racist prejudice. Since perceiving spiritually involves the whole person, the volume proposes that spiritual perception could be purified by ascetic discipline, healed by contemplative practices, trained in the process of spiritual direction and the pursuit of virtue, transformed by the immersion in the sacramental life, and healed by opening the self to the operation of divine grace.
Chapitres de livres sur le sujet "Sensory distortion"
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Denkena, Berend, Heinrich Klemme, Eike Wnendt et Matthias Meier. « Thermally Induced Clamping Force Deviations in a Sensory Chuck for Thin-Walled Workpieces ». Dans Lecture Notes in Production Engineering, 192–99. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-34486-2_15.
Texte intégralRésumé :
AbstractDeviations between nominal and actual tolerances are a challenging problem during turning processes of thin-walled workpieces. One main cause of these deviations is the clamping force applied by the turning chuck to hold the workpiece. Due to the low stiffness of thin-walled workpieces, large workpiece deformations can occur even when clamping forces are low. For this reason, the clamping force needs to be precisely adjusted. A possible approach are chucks with integrated actuators. As a result of the more direct power transmission, these chucks have a potentially higher clamping force accuracy compared to conventional external actuation. However, integrated actuators are additional heart sources resulting in thermal loads and thermally induced deformations of the chuck components. Due to the resulting mechanical distortion of the chuck system, the precise adjustment of clamping forces is not possible. Thus, this paper evaluates the thermally induced clamping force deviations on a novel turning chuck with four integrated electric drives. A test bench is used to analyse both a single drive and the combination of all four drives regarding the temperature effect on the clamping force adjustability. A clamping force deviation of up to 26% is observed. Based on the measured chuck temperature, a compensation method is introduced leading to a clamping force accuracy of 96.9%.
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Liaskovitis, Periklis, et Curt Schurgers. « A Distortion-Aware Scheduling Approach for Wireless Sensor Networks ». Dans Distributed Computing in Sensor Systems, 372–88. Berlin, Heidelberg : Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/11776178_23.
Texte intégral
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Li, Wei, Xin’an Yuan, Jianming Zhao, Xiaokang Yin et Xiao Li. « Design and Testing of High-Resolution Probe Arrays Using Alternating Current Field Measurement Technique ». Dans Alternating Current Field Measurement Technique for Detection and Measurement of Cracks in Structures, 67–82. Singapore : Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-7255-1_5.
Texte intégralRésumé :
AbstractFor the large space of sensor array in the alternating current field measurement (ACFM) probe, the spatial resolution of the measured distorted magnetic image is low above defects. As a result, the accurate morphology of defects cannot be reconstructed. In this paper, a novel ACFM probe array and testing system are set up based on the high resolution TMR magnetic field sensor array for the high-resolution imaging of distorted magnetic field. The finite element simulation model of ACFM is established. The induced electromagnetic field distortion law around the different defects is analyzed. The relationship between defect surface profile and magnetic field image is analyzed. The high-resolution sensor array is designed with 1 mm spacing. The range of uniform current field is analyzed by simulation. The multiplexing module is designed to preprocess the signal output from sensor array. The structure of the detection probe is designed. The testing system is set up to carried out defect detection experiment. The results show that Bz (magnetic field perpendicular to specimen) image and Bx (magnetic field parallel to probe scanning direction) image can reflect the information of the end point and edge of the defect respectively. The high-resolution magnetic field image of the distortion around the defect can be obtained by the ACFM probe arrry. The surface profile of the defect can be imaged visually accurately by the image of magnetic field.
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Xu, Liu-Jun, et Ji-Ping Huang. « Theory for Invisible Thermal Sensors : Monolayer Scheme ». Dans Transformation Thermotics and Extended Theories, 149–62. Singapore : Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-5908-0_11.
Texte intégralRésumé :
AbstractIn this chapter, we propose an anisotropic monolayer scheme to prevent thermal sensors from distorting local and background temperature profiles, making them accurate and thermally invisible. We design metashells with anisotropic thermal conductivity and perform finite-element simulations in two or three dimensions for arbitrarily given thermal conductivity of sensors and backgrounds. We further experimentally fabricate a metashell with an anisotropic thermal conductivity based on the effective medium theory, which confirms the feasibility of our scheme. Our results are beneficial to improving the performance of thermal detection and may also guide other diffusive physical fields.
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Rzeszotarski, Dariusz, et Pawel Strumillo. « An Integrated Procedure for Calibrating and Distortion Correction of the Structure Sensor and Stereo-Vision Depth Sensors ». Dans Computer Vision and Graphics, 222–33. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-00692-1_20.
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Davoli, Franco, Mario Marchese et Maurizio Mongelli. « Energy and Distortion Minimization in “Refining” and “Expanding” Sensor Networks ». Dans The Internet of Things, 319–27. New York, NY : Springer New York, 2010. http://dx.doi.org/10.1007/978-1-4419-1674-7_31.
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Li, Guandong, Qiulin Qu et Peiqing Liu. « Experimental Studies on the Load Characteristics of Low-Speed Droplets Impinging onto Surface ». Dans Lecture Notes in Mechanical Engineering, 937–46. Singapore : Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-1876-4_74.
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AbstractDroplet impingement on a wall is a fundamental scientific problem with wide engineering applications. When a droplet impacts the surface of an aircraft, it generates shock waves, airflow disturbances, and splashing phenomena. This not only has a negative impact on the aerodynamic performance and stability of the aircraft but also obstructs the field of view of optical sensors or causes distortion in optical devices. It can also damage the aircraft's structure, thus it’s vital to assess the droplet impact force for flight safety. However, droplets are often treated as rigid spheres for simplicity, but this does not reflect the real physical situation. In this paper, we utilized high-precision force sensors and high-speed imaging technology to experimentally investigate the impact dynamic of droplet impingement on a dry wall. The temporal evolution of force, the associated morphology changes and their relationship during collisions were analyzed systematically, we also elucidated the physical mechanisms underlying flow phenomenon. An unified and accurate mechanical model were established for droplet impingement, providing guidance for related engineering designs.
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Saboktakin, Shekoofeh, et Behzad Kordi. « Time-Domain Distortion Characterization of Electromagnetic Field Sensors Using Hermite–Gauss Subspaces ». Dans Ultra-Wideband, Short-Pulse Electromagnetics 10, 79–87. New York, NY : Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-9500-0_7.
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Wyngaard, J. C. « Flow-Distortion Effects on Scalar Flux Measurements in the Surface Layer : Implications for Sensor Design ». Dans Topics in Micrometeorology. A Festschrift for Arch Dyer, 19–26. Dordrecht : Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-2935-7_3.
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Evsutin, Oleg, Roman Meshcheryakov, Vladimir Tolmachev, Andrey Iskhakov et Anastasia Iskhakova. « Algorithm for Embedding Digital Watermarks in Wireless Sensor Networks Data with Control of Embedding Distortions ». Dans Communications in Computer and Information Science, 574–85. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-36625-4_46.
Texte intégralActes de conférences sur le sujet "Sensory distortion"
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Carman, Aaron B., Christopher Williams et Changzhi Li. « Gain and Distortion Optimization for Fast-Startup AC-Coupled Baseband Amplifiers in Motion-Sensing Radar ». Dans 2024 IEEE SENSORS, 1–4. IEEE, 2024. https://doi.org/10.1109/sensors60989.2024.10785175.
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Suranthiran, Sugathevan, et Suhada Jayasuriya. « Distortion Analysis of Memory-Less Nonlinear Sensors ». Dans ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41592.
Texte intégralRésumé :
Distortion associated with memory-less nonlinear sensors is analyzed and several distortion compensation techniques are presented. Sensor nonlinearity is considered a defect in sensory systems because it introduces distortion into the system. Due to the fact that no efficient technique is available to deal with the issues related sensor nonlinearity, nonlinear primary sensors tend to be ignored. In this paper, we point out that there are certain advantages of using nonlinear sensor and nonlinear distortion caused by sensor nonlinearity may be completely compensated. A robust and efficient signal recovery procedure is derived to facilitate the design of nonlinear sensors. Not having an accurate sensor will result in errors and it is shown that the error can be minimized with a proper choice of a convergence parameter whereby stability of the developed algorithm is established. Simulation results are presented to validate the algorithms developed.
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Dimitrov, Alexander G., et John P. Miller. « Analyzing sensory systems with the information distortion function ». Dans Proceedings of the Pacific Symposium. WORLD SCIENTIFIC, 2000. http://dx.doi.org/10.1142/9789814447362_0026.
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Farhat, Nabil H., et Haroon Babri. « Cognitive neural networks : collective computing with diverse attractors ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.mii1.
Texte intégralRésumé :
Nearly all neural networks for pattern recognition being dealt with today are associative classifier or identifier networks that are not cognitive. To be cognitive a net must be able to distinguish, on its own, between familiar and unfamiliar or novel sensory signals present at its input, and this can not be done by associative classifiers. It will be argued and shown that, to be truly cognitive, a network must be nonlinear and dynamic and able to manifest bifurcation. This means it should be able to carry out phase space computations with more than one type of attractor and to switch between these depending on whether the sensory input is familiar or novel. Cognition implies, therefore, bifurcation and computing with diverse attractors. Our reasons for adopting this view, which stemmed from known biophysical observations and from our neuromorphic target identification work, are discussed. An example of a cognitive network that computes with both stationary (limit point) and dynamic (periodic) attractors is given to illustrate our thesis. The elements of a neuromorphic radar target identification system which employs these concepts and is capable of distortion invariant recognition of three targets with perfect score is presented. The work presented elucidates the role of periodic attractors in feature binding and cognition and the significance of cognition in autonomous systems.
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Simmons, Harold R., Anthony J. Smalley, Robert W. Frischmuth, Gianluca Lapini et George Robinson. « Tools for Diagnosing Case Deflections and Alignment on a Power Utility Combustion Turbine ». Dans ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-179.
Texte intégralRésumé :
This paper discusses development, installation, and analysis of instrumentation systems for reliably measuring casing, thermal distortion, and alignment deviation on a large combustion turbine in power utility service. A variety of redundant measurement systems were installed to document casing distortion during the cool-down period after firing. The operating principles of each measurement system are described and presented with the rationale developed for installing and locating sensors. A vertical deflection sensor used for casing bow and bearing misalignment measurement is highlighted in the paper to illustrate its potential for use in other investigations. Additional sensors used include an array of shaft proximity probes, blade tip proximity probes, thermocouples, and axial growth probes. A measurement system for casing ovalization was developed using LVDT’s mounted from a thermally stabilized ring. An automated data acquisition system was developed and installed to facilitate the recording of turbine cool-down events over the complete operating season without the need for constant on-site attention. Preliminary results define the turbine cylinder bow and ovalization response during the cool-down event following normal unit operation and correlated casing distortions with thermal gradients.
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Igaki, Seigo, Shin Eguchi, Hiroyuki Ikeda et Takefumi Inagaki. « Real-time fingerprint sensor using a hologram ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.thl1.
Texte intégralRésumé :
We have developed a real-time fingerprint sensor using a flat glass plate with hologram. Personal identification by fingerprint validation will be widely used to maintain security of a computer system because of its high reliability. Such real-time sensors must be distortion free, high contrast, compact, and insensitive to residual fingerprints. The conventional prism-type fingerprint sensors have problems with distortion compensation and compactness.
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Kammerer, Albert, et Reza S. Abhari. « Blade Forcing Function and Aerodynamic Work Measurements in a High Speed Centrifugal Compressor With Inlet Distortion ». Dans ASME Turbo Expo 2009 : Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59911.
Texte intégralRésumé :
Centrifugal compressors operating at varying rotational speeds, such as in helicopters or turbochargers, can experience forced response failure modes. The response of the compressors can be triggered by aerodynamic flow non-uniformities, such as with diffuser-impeller interaction or with inlet distortions. The work presented here addresses experimental investigations of forced response in centrifugal compressors with inlet distortions. This research is part of an ongoing effort to develop related experimental techniques and to provide data for validation of computational tools. In this work measurements of blade surface pressure and aerodynamic work distribution were addressed. A series of pressure sensors were designed and installed on rotating impeller blades and simultaneous measurements with blade-mounted strain gauges were performed under engine representative conditions. To the best knowledge of the authors, this is the first publication which presents comprehensive experimental unsteady pressure measurements during forced response for highspeed radial compressors. Experimental data were obtained for both resonance and off-resonance conditions with uniquely tailored inlet distortion. This paper covers aspects relating to the design of fast response pressure sensors and their installation on thin impeller blades. Additionally, sensor properties are outlined with a focus on calibration and measurement uncertainty estimations. The second part of this paper presents unsteady pressure results taken for a number of inlet distortion cases. It will be shown that the intended excitation order due to inlet flow distortion is of comparable magnitude to the second and third harmonics which are consistently observed in all measurements. Finally, an experimental method will be outlined that enables the measurement aerodynamic work on the blade surface during resonant crossing. This approach quantifies the energy exchange between the blade and the flow in terms of cyclic work along the blade surface. The phase angle between the unsteady pressure and the blade movement will be shown to determine the direction of energy transfer between the blade and the fluid.
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Rehman, Shafiqur, et Luai M. Al-Hadhrami. « Wind Turbulence Behavior and Study of Tower Distortion and Scatter Factors ». Dans ASME Turbo Expo 2014 : Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-26585.
Texte intégralRésumé :
The performance of wind speed sensors installed at different heights on a 40-meter mast was evaluated during 3 months between July 01, 2006 and April 01, 2009. This evaluation involved estimating the tower distortion factor (TDF) and the scatter factor, and studying the correlation between the co-located wind speed sensors. A total of 23,730 hourly mean wind speed records were used to evaluate each sensor. The overall values of the tower distortion of the wind speed measured by sensors installed at 40 and 30m were found to be 0.025 and 0.021 without tower shading, and 0.047 and 0.035 with tower shading. As indicated by the slightly decreasing TDF values the wind speed measured by the sensors is not distorted with time. Tower shading effect for the wind speed sensor WS5 at 40 meters is pronounced (>1) when wind direction range from 169° to 195°, while that for the wind speed sensors at 30 meters and WS6 at 40 meters, it is less than one when the wind direction is in the 240° to 270° range. The wind speed sensors at 30meters displayed similar behavior and the scatter factor for wind speed sensors at 40meters is higher than that for those at 30meters.
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Peters, Thomas, et Leonhard Fottner. « Effects of Co- and Counter-Rotating Inlet Distortions on a 5-Stage HP-Compressor ». Dans ASME Turbo Expo 2002 : Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30395.
Texte intégralRésumé :
The HP-compressor of a twin-spool aero-engine experiences a rotating inlet distortion if a rotating stall in the upstream LP-compressor occurs. This may lead to HP-compressor instability like rotating stall or surge and has even more serious effects on the performance and behavior of the engine than rotating stall in the LP-compressor alone. Studies on compressor flow instabilities are carried out at the 5-stage HP-compressor Rig212, developed in the TurboUnion RB199 jet engine programme. In order to investigate rotating inlet distortions, the axial compressor test facility is equipped with a distortion generator rotating at high speeds in the compressor inlet duct. A disk with a sectorial total pressure loss screen simulates an upstream rotating stall. It produces a rotating inlet distortion with up to 65% of the compressor’s design speed in co- or counter-rotation direction. This paper extends the presentation of first results by Peters et al. [1] and covers both, co- and counter-rotating inlet distortions and their influence on the compressor surge margin. Hot-wire sensor data are analysed to investigate the stall inception process and the response of the compressor flow field to the excitation by the rotating inlet distortion. The experimental detection of aerodynamic eigenfrequencies of the compressor is compared with numerical results from a compressor model developed by Hu and Fottner [2].
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Zaiss, Curtis, et Swavik Spiewak. « Vibration Rectification and Thermal Disturbances in Ultra Precision Inertial Sensors ». Dans ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-65518.
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Advanced inertial MEMS sensors facilitate achieving superb precision and resolution in measuring translational and rotational displacements, down to femtometers and milli-arcseconds. At present such performance is possible only in measurements of a very short duration, typically below 1 second. As this duration increases, the precision rapidly deteriorates. However, experimental accelerometers indicate the possibility of measurements with sub-micron precision for up to 30 seconds. For longer measurements, e.g., up to 5 minutes, the errors increase. However they still remain below 100 μm. The main cause of errors is a strong amplification of low frequency disturbances and distortions introduced by the sensors. It occurs when acceleration and angular rate are converted to the translational and angular displacement, i.e., during the integration. Thus, the key to maximizing the performance of inertial displacement sensors is a reduction of their low frequency disturbances. In the top tier sensors the key components of the disturbances include (1) the inherent thermodynamic and electrical noise, (2) chaotic mechanical phenomena, and (3) nonlinear distortion. The presented research is concerned with these three areas. It focuses on the identification and correction of errors which deteriorate a stability of the sensors’ bias, in particular on the vibration rectification error (VRE) and temperature variations due to the actuation in servo accelerometers. The investigated accelerometers are high performance sensors, digital and analog, whose total harmonic distortion is in the range from 1% down to a few parts-per-million (i.e., <0.001%). The objective is to develop on-line corrective filters capable of reducing the overall low frequency distortion below 0.00001%.
Rapports d'organisations sur le sujet "Sensory distortion"
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Burks, Thomas F., Victor Alchanatis et Warren Dixon. Enhancement of Sensing Technologies for Selective Tree Fruit Identification and Targeting in Robotic Harvesting Systems. United States Department of Agriculture, octobre 2009. http://dx.doi.org/10.32747/2009.7591739.bard.
Texte intégralRésumé :
The proposed project aims to enhance tree fruit identification and targeting for robotic harvesting through the selection of appropriate sensor technology, sensor fusion, and visual servo-control approaches. These technologies will be applicable for apple, orange and grapefruit harvest, although specific sensor wavelengths may vary. The primary challenges are fruit occlusion, light variability, peel color variation with maturity, range to target, and computational requirements of image processing algorithms. There are four major development tasks in original three-year proposed study. First, spectral characteristics in the VIS/NIR (0.4-1.0 micron) will be used in conjunction with thermal data to provide accurate and robust detection of fruit in the tree canopy. Hyper-spectral image pairs will be combined to provide automatic stereo matching for accurate 3D position. Secondly, VIS/NIR/FIR (0.4-15.0 micron) spectral sensor technology will be evaluated for potential in-field on-the-tree grading of surface defect, maturity and size for selective fruit harvest. Thirdly, new adaptive Lyapunov-basedHBVS (homography-based visual servo) methods to compensate for camera uncertainty, distortion effects, and provide range to target from a single camera will be developed, simulated, and implemented on a camera testbed to prove concept. HBVS methods coupled with imagespace navigation will be implemented to provide robust target tracking. And finally, harvesting test will be conducted on the developed technologies using the University of Florida harvesting manipulator test bed. During the course of the project it was determined that the second objective was overly ambitious for the project period and effort was directed toward the other objectives. The results reflect the synergistic efforts of the three principals. The USA team has focused on citrus based approaches while the Israeli counterpart has focused on apples. The USA team has improved visual servo control through the use of a statistical-based range estimate and homography. The results have been promising as long as the target is visible. In addition, the USA team has developed improved fruit detection algorithms that are robust under light variation and can localize fruit centers for partially occluded fruit. Additionally, algorithms have been developed to fuse thermal and visible spectrum image prior to segmentation in order to evaluate the potential improvements in fruit detection. Lastly, the USA team has developed a multispectral detection approach which demonstrated fruit detection levels above 90% of non-occluded fruit. The Israel team has focused on image registration and statistical based fruit detection with post-segmentation fusion. The results of all programs have shown significant progress with increased levels of fruit detection over prior art.