• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 448
  • 167
  • 17
  • 16
  • 12
  • 11
  • 8
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 4
  • Tagged with
  • 772
  • 573
  • 528
  • 309
  • 179
  • 172
  • 108
  • 106
  • 88
  • 82
  • 62
  • 49
  • 43
  • 42
  • 39
  • 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.
301

Elastohydrodynamic Analysis of a Rotary Lip Seal Using Flow Factors

Rocke, Ann H. 30 July 2004 (has links)
An elastohydrodynamic analysis of a rotary lip seal is performed numerically, incorporating both the fluid mechanics of the lubricating film and the elastic deformation of the lip, by solving the Reynolds equation with flow factors. Asperities on the lip surface dominate the behavior of the flow field in the lubricating film and the elastic deformation of the lip. Since previous analyses treated those asperities deterministically, they required very large computation times. The present approach is much less computationally intensive because the asperities are treated statistically. Since cavitation and asperity orientation play important roles, these are taken into account in the computation of the flow factors. An asperity distortion analysis is introduced to obtain a more realistic model of the complex variations in the asperity distribution on the surface of the seal. Results of the analysis show how the operating parameters of the seal and the characteristics of the asperities affect such seal characteristics as the thickness of the lubricating film, reverse pumping rate, power dissipation and load carrying capacity.
302

Central auditory impairment in children with nonsyndromic cleft lip and/or palate

Yang, Feng, Frank., 杨峰. January 2011 (has links)
Auditory impairment in patients with craniofacial clefts has been well studied for decades. However, most previous research has only focused on middle ear disorders and related auditory consequences in this group. Studies of higher level auditory status and central auditory processing abilities of this group—particularly in children—have been unsystematic and have significant limitations, while the potentially negative impact of central auditory impairment on children should not be ignored. One important area which needs further research is the status of the central auditory nervous system (CANS) in children with non-syndromic cleft lip and/or palate (NSCLP). In order to objectively investigate possible central auditory impairment in children with NSCLP, the present research programme was initiated. Firstly, two major studies aimed to provide anatomical structural analysis and functional evaluation of the auditory structures of CANS in a group of infants with NSCLP, and compare the results to those of normal controls (Studies 1 and 2). Secondly, a pilot study (Study 3) was conducted to provide preliminary data and suggest methodology to support a major, future research programme to comprehensively investigate central auditory processing abilities in children with NSCLP. A multi-disciplinary approach that included brain magnetic resonance image (MRI) scanning, auditory evoked potentials (AEP) recording, and a central behavioural auditory test battery assessment protocol, was applied in the present research programme. Based on the results of the studies and data analysis, it was concluded that: (1) Structural abnormalities of CANS in infants with NSCLP may be primarily located in the left cerebral hemisphere and cortical abnormalities were more marked compared with those in other subcortical locations. The development and maturation of the auditory cortex in infants with NSCLP may be abnormal, compared with that in normal children; (2) Infants with NSCLP might have normal auditory sensory function at brain stem and subcortical levels, yet this group may have significant impaired auditory discriminatory function at cortical level; (3) Children with NSCLP may show normal auditory processing abilities in a quiet listening environment. However, they may be more vulnerable to background noise and have impaired auditory processing abilities in areas such as monaural low redundancy and temporal resolution ability. In summary, combining the results of MRI, AEP and behavioural measurements in the present research programme, it is suggested that children with NSCLP are at potential risk of both structural abnormalities and functional disorders of the CANS, particularly at auditory cortical level. In addition, this group might also be at risk of auditory processing impairments to some degree, particularly in noisy environments. The present research programme has made a contribution to our understanding of the central auditory status of children with NSCLP, which was not systematically investigated in previous studies, and provided information on which to base further research. The research findings should draw the attention of researchers and clinicians to improving auditory assessment and intervention for patients with craniofacial cleft disorders. Further efforts in this field in the long-term may help to develop a more sophisticated audiological evaluation and intervention approach for this population. / published_or_final_version / Speech and Hearing Sciences / Doctoral / Doctor of Philosophy
303

Temporal Processing in the Visual System

Aghdaee, Seyed Mehdi 18 March 2013 (has links)
Encoding time is one of the most important features of the mammalian brain. The visual system, comprising almost half of the brain is of no exception. Time processing enables us to make goal-directed behavior in the optimum “time window” and launch a ballistic eye movement, reach/grasp an object or direct our processing resources (attention) from one point of interest to another. In addition, encoding time is critical for higher cognitive functions, enabling us to make causal inferences. The limitations of temporal individuation in the visual stream seem to vary across the visual field: the resolution gradually drops as objects become farther away from the center of gaze, where little differences were found in terms of resolution for objects in the upper versus lower visual field. This resolution of temporal individuation is vastly different from the resolution ascribed to spatial individuation. If individuation is mediated through attention, as some researchers have proposed, the general term ”attention” seems to possess different properties, at least regarding temporal and spatial processing. Next we looked at another aspect of encoding time: Temporal Order Judgments (TOJ), where animals had to judge the relative timing onset of two visual events. After training two monkeys on the task, we recorded from neurons in the lateral intraparietal area (LIP), while the animals reported the perceived order of two visual stimuli. We found that LIP neurons show differential activity based on the animal’s perceptual choice: when the animal reports the stimulus inside the receptive field of the neuron as first, the cells show an increased level of activity compared to when the animal reports he same stimulus as second. This differential activity was most reliable in the tonic period of the response \((\sim100 ms\) after stimulus onset). However, no difference in visual response latencies was observed between the different perceptual choices. The parietal cortex has previously been implicated in temporal processing based on patient studies as well as neuroimaging investigations. Physiological studies have also suggested the involvement of parietal area in encoding elapsed time. However, our study is the first to demonstrate parietal neurons encoding relative timing. / Psychology
304

Développement de techniques de métallisation innovantes pour cellules photovoltaïques à haut rendement

Boulord, Caroline 11 April 2011 (has links) (PDF)
Cette thèse s'est focalisée sur le développement et l'optimisation de techniques de métallisation électrochimique permettant le dépôt de métaux conducteurs, l'argent et le cuivre, par voie électrolytique ou par la technique dite LIP (Light-Induced Plating). Deux approches ont été abordées pour l'élaboration des contacts en face avant : l'épaississement de contacts sérigraphiés d'une part, et la réalisation de contacts entièrement par voie électrochimique sans recours à la sérigraphie. Pour cette dernière solution, le dépôt d'une couche d'accroche avant l'étape d'épaississement est nécessaire afin d'assurer une résistivité de contact faible, une bonne adhérence et une bonne sélectivité au travers de la couche anti-reflet. Ces objectifs ont été atteints grâce à la mise en œuvre et l'optimisation de dépôts electroless de nickel-phosphore (NiP), y compris sur émetteur peu dopé. Les investigations menées ont également permis une meilleure compréhension des mécanismes de formation du contact NiP/Si. La faisabilité des techniques de dépôt électrochimique a été démontrée pour diverses applications: cellules avec contacts électrochimiques NiP/Ag en face avant, cellules de type n, épaississement de contacts fins sérigraphiés... Des résultats très prometteurs d'amélioration de facteur de forme FF et de rendement η ont été obtenus et permettent d'envisager une ouverture potentielle vers de nouvelles structures de cellules photovoltaïques à haut rendement : cellules à émetteur peu dopé, cellules à émetteur sélectif avec ouverture laser de la couche anti-reflet, cellules à contacts arrières....
305

Kalbančiojo lūpų formos registravimas / Speaker lip shape registration

Kubickas, Egidijus 16 August 2007 (has links)
Kubickas E., Kalbančiojo lūpų formos registravimas: Elektronikos inžinerijos magistro darbas/mokslinis vadovas doc. dr. G. Daunys; Šiaulių universitetas, Technologijos fakultetas, Elektronikos katedra, – Šiauliai, 2007. – 67p. Magistro darbo tema yra aktuali, kadangi lūpos yra vienas svarbiausių vizualinės kalbos dalių. Komunikuojant žmonėms svarbiausi informacijos kanalai yra kalbos ir vizualiniai ženklai. Norint suprasti vartotojo instrukcijas triukšmingoje aplinkoje kompiuteris turi pasikliauti vizualiniais vartotojo ženklais. Šiame darbe atliekamas lūpų formos registravimas pasitelkus OpenCV ir Matlab 7.0 paketą. Pagrindinis tikslas yra sudaryti ir išanalizuoti algoritmą tiksliam lūpų formos registravimui. Ištyrinėta 4 žmonių lūpų forma (kontūrai). Remiantis gautais rezultatais matyti, kad lūpų registravimas susijęs su keletu problemų – sudėtingas lūpų registravimas dėl panašios veido spalvos, taip pat sudėtingas vidinių kontūrų radimas dėl matomų artikuliatorių. Tiksliausiai lūpų forma registruojama naudojant žalios spalvos komponentę (G). Gauti rezultatai gali būti panaudoti tolesniems tyrinėjimams, tokiems kaip neuroninių tinklų apmokymas lūpų padėčiai ar raidėms atpažinti. / Kubickas E. Speaker lip shape registration: Master thesis of electronics engineer/research advisor Assoc. Dr. G. Daunys; Šiaulių University, Technological Faculty, Electronics Department. – Šiauliai, 2007. – 67 p. The theme of Master Project of Electronics engineer is actual, because the lip is the one of the principal visual speech part. For better users instruction‘s understanding in the noisy environment, computer must rely on the visual users signs. In the theory section there is described the most important channels for communication - speech and visual signs. There is performing lip shape registration by using OpenCv and Matlab 7.0 package in this work. The approach proposed to make and to analize algorithm for more accurate lip registration. The main task is to investigate how to detect speaker lip shape robustly, when their location is different. There is presented research of four people lip‘s shape (contours). The results showed that there are few problems, related with lip registration – difficult lip extraction because of the similar skin colour, problematic lips inner contours extraction, because of the visible articulators such as teeth, tongue. Above all, that the main task was reached – there was received the robust lip registration by green colours component. Received results can be used for the further investigations such as different expression pictures research, the neural network for lip position or letters recognizing training.
306

UV-LITHOGRAPHIC PATTERNING OF MICRO-FEATURES ON A CONICAL MOLD INSERT

Huber, Justin P. 01 January 2010 (has links)
In past studies, several techniques have been employed to create microscopic features on relatively simple surfaces. Of these, lithography-based techniques have proven effective at manufacturing large fields of deterministic microasperities and microcavities on planar and cylindrical substrates. The present study focuses on adapting UV-lithography to a more complex substrate. Machined from stainless steel, a conical mold insert introduces an interesting geometry designed for the injection molding of radial lip seal elastomer. The distinct shape of this mold insert poises unique challenges to a conventional lithography procedure. Spray application is investigated as a feasible means to deposit layers of photoresist on the surface. An appropriate masking element is designed and created to facilitate transfer of a particular pattern via UV exposure. A clamping technique is implemented to align and secure the photomask. These techniques are incorporated into a three-day process, and results are obtained through optical microscopy and light interferometry. By applying Design of Experiments (DOE) and Analysis of Variance (ANOVA), significant process variables are indentified. Based on these findings, refinements to the process are enabled and future considerations are made evident.
307

DETAILED SURFACE ANALYSIS OF LIP SEAL ELASTOMERS RAN AGAINST SHAFTS MANUFACTURED WITH TRIANGULAR CAVITIES

Kanakasabai, Vetrivel 01 January 2009 (has links)
Previous experimental and theoretical results indicate that the keys to successful radial lip seals are the surface characteristics of the shaft and the microasperity pattern that develops due to wear on the elastomer. In this study, the lip seal was tested against five different patterns of shaft surface: plain stainless steel, triangular cavities oriented towards air, triangular cavities oriented towards oil, triangular cavities leading and triangular cavities lagging. Using Zygo optical profilometer and scanning electron microscope, a thorough surface characterization of the micro-asperities and microcavities is done on the lip seal elastomer. Correlation coefficients were calculated between the surface parameters of the final shaft surface and elastomer. Although both the surface characteristics of the shaft and the micro-asperities that develop on the elastomer sealing zone are responsible for a successful operation of the lip seal, the deterministic triangular micro-cavity patterns created on the shaft surface dominated the pumping direction with a large variability in the pumping rate. This variability is due to the elastomer wear in. This study also finds a significant correlation between the axial position of minimum roughness on the sealing zone of the elastomer and the pumping rate of the lip seals.
308

Untersuchung zum Gesichtswachstum von Patienten mit Lippen-Kiefer-Gaumenspalten operiert nach dem Leipziger Konzept zur funktionellen Rehabilitation von Lippen-Kiefer-Gaumenspalten

Tzeuschner, Dominique 06 May 2014 (has links) (PDF)
In der vorliegenden Dissertation wurde anhand von 1042 extraoralen Fotos im Profil und en face untersucht, wie sich das Wachstum longitudinal bei 166 gesunden Kindern, je zehn Kindern mit isolierter Gaumenspalte, einseitiger Lippen-Kiefer-Gaumenspalte sowie doppelseitiger Lippen-Kiefer-Gaumenspalte operiert nach dem Leipziger Konzept entwickelt, sowie inwiefern sich die einzelnen Gruppen in verschiedenen Altersstufen voneinander unterscheiden. Dazu wurden pro Gruppe jeweils fünf Jungen und fünf Mädchen kaukasischer Herkunft, geboren in den Jahren 1994 bis 2001, mit einer nichtsyndromalen Spalte ausgewählt, die ab der Geburt über mehrere Jahre hinweg fotografiert wurden. Diese Fotos wurden digitalisiert und denen von Kontrollpatienten gegenüber gestellt. Anhand von Winkeln der klassischen Morphometrie und Grafiken und Statistiken der geometrischen Morphometrie wurden die Veränderungen im Wachstum analysiert und die Kontrollpatienten mit dem Leipziger OP-Konzept verglichen. Es konnte gezeigt werden, dass die geometrische Morphometrie durchaus geeignet ist, das Gesichtswachstum anhand von extraoralen Fotos zu beurteilen. Weiterhin konnte bestätigt werden, dass mit dem Leipziger Konzept zur funktionellen Rehabilitation von Patienten mit Lippen-Kiefer-Gaumenspalten sehr gute Operationsergebnisse und vor allem Langzeitergebnisse erzielt werden können.
309

Spatial image of school environment in children with cleft lip and/or palate

Kasuya, Masayo, Sawaki, Yoshihiro, Ueda, Minoru 05 1900 (has links)
No description available.
310

Cleft Size and Maxillary Arch Dimensions in Unilateral Cleft Lip and Palate and Cleft Palate

Reiser, Erika January 2011 (has links)
The wide variation in infant maxillary morphology and cleft size of children with unilateral cleft lip and palate (UCLP) and isolated cleft palate (CP) raise concerns about their possible influences on treatment outcome. The studies in this thesis aimed to investigate the relation between cleft size in infancy and crossbite at 5 years of age (Paper I); the impact of primary surgery on cleft size and maxillary arch dimensions from infancy to 5 years of age (Paper II); associations between cleft size, maxillary arch dimensions and facial growth in both UCLP and CP children (Paper III); and, to evaluate the relation between infant cleft size and nasal airway size and function in adults treated for UCLP (Paper IV). In homogenously treated groups of children with UCLP and CP, dental casts were used to measure cleft size and maxillary arch dimensions from infancy up to 5 years of age, and for crossbite recording at 5 years. Serial lateral cephalometric radiographs taken between 5 and 19 years of age in the same groups were used to study facial growth. Nasal airway size and function were evaluated by acoustic rhinometry, rhinomanometry, peak nasal inspiratory flow and odour test in a group of adults treated for UCLP. The main findings were: crossbite was a frequent malocclusion at 5 years of age in children with UCLP and large cleft widths at the level of the cuspid points in infancy were associated with less anterior and posterior crossbite in this group (Paper I). Cleft widths decreased after lip closure and/or soft palate closure in both UCLP and CP children. Initially, UCLP children had wider maxillary arch dimensions, but after hard palate closure, the transverse growth was reduced, and at 5 years, they had smaller maxillary arch widths than CP children had (Paper II). Maxillary arch depths and cleft widths in infancy were correlated with maxillary protrusion and sagittal jaw relationships in both UCLP and CP children (Paper III), but cleft width in infancy was not correlated with nasal airway size and function in adults treated for UCLP (Paper IV).

Page generated in 0.0308 seconds