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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Commande sans capteur mécanique de la machine asynchrone pour la variation de vitesse industrielle / Sensorless induction machine control for industrial speed variation

Solvar, Sébastien 21 December 2012 (has links)
La machine asynchrone présente un intérêt majeur par rapport aux autres types de machines(courant continu, synchrone, ...), sa robustesse, son faible coût de fabrication etd'entretien en sont les principales raisons. Cependant ces avantages ont longtemps été inhibés par la complexité de la commande de celle-ci.De nos jours de nombreux industrielles proposent des variateurs de vitesse pour la machine asynchrone offrant à la fois la souplesse de contrôle, et la qualité de la conversion électromagnétique,naturellement obtenues jusqu'alors avec la machine à courant continu et de la machine synchrone.Depuis quelques années les industrielles font face à une nouvelle problématique, qui est la suppression du capteur mécanique dans le processus de régulation de vitesse de la machine asynchrone. Les travaux de cette thèse, effectués dansle cadre d'un support CIFRE entre l'entreprise GS Maintenance et le laboratoire ECS-Lab EA 3649, ont été orientésvers la réalisation d'un système de contrôle commande d'un variateur industrieldédié aux machines asynchrones sans capteur mécanique. De ce point de vue, l'objectifpremier du travail de thèse, est la conception des techniques de détermination des grandeursmécaniques (vitesse) de la machine asynchrone en utilisant comme seules mesuresles grandeurs électriques. Ces techniques, utilisées pour remplacer l'informationdonnée par les capteurs mécaniques, sont parfois appelées capteurs logiciels.Une attention particulière est donnée au fonctionnement de la machine asynchrone sanscapteur mécanique à basse vitesse. Dans un second temps l'objectif étant d'illustrer lesintérêts technologiques d'un observateur basé sur la technique des modes glissants dansle but d'intégrer celui-ci dans le système contrôle commande d'un variateur industriel. / Induction machine includes main interests compared with others electricals machines like brushed DC Motor,or synchronus electric Motor.Its robustness, its low cost manufacture, and maintenance are major reason of its success.However, for long time this advantages inhibited because of induction machine control complexity.Nowadays,many industrial propose speed drives for induction machine giving both control flexibility, and electromagnetic qualited conversion, naturally obtained with DC motor, and synchronus electric Motor.For several years now, many manufacturers face to a new problematic, wich is sensorless induction machine control.This thesis work, carried out in concert with the firm GS Maintenance and ECS-Lab EA 3649 laboratory under CIFRE financement.This work focused on conception plant dedicated to sensorless industrial speed drive control for induction machine.From this point of view, at first glance this work proposes technical strategies to identify mechanical induction machine variables, by using only electrical measurements.This strategies used to stand in for informations from a mechanical sensor, are the so called software sensor.Specific attention has been paid to induction machine sensorless working at very low speed. Secondly, we propose to illustrate the interest of a second order Sliding Mode Observer with final aim to be integrated into an industrial speed drive


Ziegler, Alexander H. 01 January 2019 (has links)
This dissertation consists of two essays that discuss the influence of embarrassment on consumers. In the first essay, I examine consumers’ coping responses to embarrassment in a meta-analytic review. In essay two, I utilize an experimental approach to investigate the impact of embarrassing encounters on unrelated consumers who merely observe the situation. In the first essay, the meta-analysis is guided by findings in the literature that demonstrate embarrassment can both promote and detract from consumer well-being. However, despite being investigated for decades, little is known about how consumers cope with embarrassing situations, and when and why consumers respond in positive and negative ways. The meta-analysis draws on the transactional framework of appraisals and coping to analyze the extant literature, construing positive responses as problem-focused coping, and negative responses as emotion-focused coping. I examine both situational and trait factor moderators to explain variance in these divergent outcomes and to resolve competing findings. A meta-analysis of 93 independent samples (N = 24,051) revealed that embarrassment leads to both problem-focused coping (r = 0.21), which can promote consumer well-being, and emotion-focused coping (r = 0.23), which can detract from consumer well-being. The relationship between embarrassment and emotion-focused coping was particularly strong in emotionally intense situations that were out of a transgressor’s control, for female consumers, and for consumers with an individualist orientation. The relationship between embarrassment and problem-focused coping was particularly strong in emotionally intense situations for male and young consumers. The second essay investigates the influence of embarrassing situations on neutral observers of the situation. The extant literature suggests that a consumer who commits a social transgression will experience embarrassment if real or imagined others are present to witness the transgression. However, the parallel embarrassment experienced, in turn, by those observers lacks a theoretical account, since observers have committed no transgression and are not the subject of appraisal by others. I label this phenomenon observer embarrassment, and introduce perspective taking as the underlying process that leads to observer embarrassment. Across six studies, I use physiological, behavioral, and self-report measures to validate the presence of observer embarrassment, as well as the underlying perspective-taking mechanism. Specifically, the results demonstrate that observers are more likely to experience embarrassment when they imagine themselves as the transgressor (versus experience empathy for the transgressor), something more likely to occur when the observer and actor share a common identity. Thus, observer embarrassment is not an empathetic response to witnessing a social transgression, but rather an experience parallel to personal embarrassment of others.

Implementation of a High-speed Sinusoidal Encoder Interpolation System

Lepple, Charles 25 February 2004 (has links)
In order to meet higher performance demands on brushless motor controllers, motor feedback signals must meet correspondingly higher standards. Brushless motor controllers require angular feedback for motor commutation, and generally for one or more of the following: torque, velocity or position regulation. These feedback categories impose different requirements on the control system. In many brushless motor applications, sinusoidal encoders have significant advantages over square-wave encoders. Signal processing techniques for sinusoidal encoder feedback signals are considered in the context of a brushless motor positioning system. In particular, a method is presented for correcting gain and offset measurement errors based on ellipse-fitting techniques. / Master of Science

Pozorování času: Odvozování ve statických světech / Pozorování času: Odvozování ve statických světech

Švarný, Petr January 2019 (has links)
The topic of this thesis is temporal logical inference in atemporal models of time. The thesis presents a branching logic with observers for the purpose of this investigation. A series of theorems rigorously demonstrate that temporal reasoning is possible also in an atemporal world. 1

Evaluation of a Computer-Based Observer-Effect Training on Mothers' Vocal Imitation of Their Infant

Shea, Kerry A. 01 December 2019 (has links)
Infants begin to learn important skills, such as contingency learning, social referencing, and joint attention through everyday interactions with their environment. When infants learn that their behavior produces a change in the environment (e.g., attention from others), infants engage in behavior that produces that effect (e.g., increases in smiling sustained engagement. When mothers and other caregivers respond immediately to infant behavior, they help their infant learn that the infant’s own behavior is effective, producing a change in the environment. The current investigation evaluated the effect of a computer-based training that aimed at teaching mothers to play a vocal-imitation contingency-learning game. The training included observer-effect methodology, meaning the mothers engaged in observation and evaluation of other mothers engaging in vocal imitation but did not themselves receive any direct coaching or feedback. All mothers completed the training during one session and in less than 45 min. Results indicate that all mothers increased their use of vocal imitation post training and maintained their performance at a two-week follow-up. Results are discussed in terms of how computer training may facilitate dissemination of responsive caregiver training.

Intra- and inter-observer agreement in the visual interpretation of interim 18F-FDG PET/CT in malignant lymphoma: influence of clinical information / 悪性リンパ腫の早期治療効果判定18F-FDG PET/CTの視覚的評価における読影者内・読影者間一致率:臨床情報の影響をふまえて

Arimoto, Maya 23 July 2018 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21294号 / 医博第4383号 / 新制||医||1030(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 佐藤 俊哉, 教授 今中 雄一, 教授 増永 慎一郎 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Renal stone detection using a low kilo-voltage paediatric CT protocol – A porcine phantom study

Mussmann, B., Hardy, Maryann L., Jung, H., Ding, M., Osther, P.J., Fransen, M.L., Greisen, P.W., Graumann, O. 18 June 2021 (has links)
yes / Introduction: Reducing tube voltage is an effective dose saving method in computed tomography (CT) assuming tube current is not concurrently increased. Recent innovations in scanner technology now enable CT tube voltage reduction to 70 kV thereby increasing opportunities for dose reduction in paediatric patients, but it is unclear if the increased image noise associated with 70 kV impacts on ability to visualise renal stones accurately. The purpose was to assess detectability of nephrolithiasis using a bespoke paediatric phantom and low kV, non-contrast CT and to assess inter-observer agreement. Methods: Forty-two renal stones of different size and chemical composition were inserted into porcine kidneys and positioned in a bespoke, water-filled phantom mimicking a 9-year-old child weighing approximately 33kg. The phantom was scanned using 120 and 70 kV CT protocols, and the detectability of the stones was assessed by three radiologists. Absolute agreement and Fleiss’ kappa regarding detectability were assessed. Results: The mean diameter of renal stones as measured physically was 4.24 mm ranging from 1 to 11 mm. Four stones were missed by at least one observer. One observer had a sensitivity of 93 and 95% at 70 and 120 kV, respectively, while the sensitivity for observers 2 and 3 was 98% at both kV levels. Specificity was 100% across readers and kV levels. Absolute agreement between the readers at 70 kV was 92% (kappa = 0.86) and 98% (kappa = 0.96) at 120 kV indicating a strong agreement at both kV levels. Conclusions: The results suggest that lowering the kV does not affect the detection rate of renal stones and may be a useful dose reduction strategy for assessment of nephrolithiasis in children.

Adaptive Feedforward Control of Sinusoidal Disturbances with Unknown Parameters: AnExperimental Investigation

Bassford, Marshall R., Mr. 21 July 2022 (has links)
No description available.

The impact of image test bank construction on radiographic interpretation outcomes: A comparison study.

Hardy, Maryann L., Flintham, K., Snaith, Beverly, Lewis, Emily F. 22 October 2015 (has links)
Assessment of image interpretation competency is commonly undertaken through review of a defined image test bank. Content of these image banks has been criticised for the high percentage of abnormal examinations which contrasts with lower reported incidences of abnormal radiographs in clinical practice. As a result, questions have been raised regarding the influence of prevalence bias on the accuracy of interpretive decision making. This article describes a new and novel approach to the design of musculoskeletal image test banks. Three manufactured image banks were compiled following a standard academic menu in keeping with previous studies. Three further image test banks were constructed to reflect local clinical workload within a single NHS Trust. Eighteen radiographers, blinded to the method of test bank composition, were randomly assigned 2 test banks to review (1 manufactured, 1 clinical workload). Comparison of interpretive accuracy was undertaken. Inter-rater agreement was moderate to good for all image banks (manufactured: range k = 0.45–0.68; clinical workload: k = 0.49–0.62). A significant difference in mean radiographer sensitivity was noted between test bank designs (manufactured 87.1%; clinical workload 78.5%; p = 0.040, 95% CI = 0.4–16.8; t = 2.223). Relative parity in radiographer specificity and overall accuracy was observed. This study confirms the findings of previous research that high abnormality prevalence image banks over-estimate the ability of observers to identify abnormalities. Assessment of interpretive competency using an image bank that reflects local clinical practice is a better approach to accurately establish interpretive competency and the learning development needs of individual practitioners.

Nonlinear Adaptive Estimation Andits Application To Synchronization Of Lorenz System

Jin, Yufang 01 January 2004 (has links)
Synchronization and estimation of unknown constant parameters for Lorenz-type transmitter are studied under the assumption that one of the three state variables is not transmitted and that transmitter parameters are not known apriori. An adaptive algorithm is proposed to estimate both the state and system parameters. Since Lorenz system shows the property of sensitivity to initial conditions and evolves in different mode with parameter variation, an equivalent system is introduced. The adaptive observer is designed based on this equivalent system without any requirement on initial conditions of the observer. It is shown by Lyapunov arguments and persistent excitation analysis that exponential stability of state and parameter estimation is guaranteed. Simulation results are included to demonstrate properties of the algorithm. In a practical communication system, the received signals presented at the receiver part differ from those which were transmitted due to the effects of noise. The proposed synchronization scheme is robust with regard to external bounded disturbance. When an additive white gaussian noise (AWGN) channel model is considered, estimates of state and parameter converge except for small errors. The results show promise in either coherent detection or the message decoding in telecommunication systems.

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