Thesis (M.S.) -- Ohio State University, 2005. / Includes bibliographical references (leaves 49-51). Available online via OhioLINK's ETD Center

A Thesis presented to the Faculty of Science of the University of the Witwatersrand fo r the Degree of Doctor uf Philosophy. January 1979 / Clinical workers in binocular vision , known as o rth o p tis ts , have noticed variations in the binocular performance of patients which appear to have no relation to the ir visual state. Similarly there are some binocular tests, in p a rticu la r stereoscopic tests, which cannot be performed by normal students of the Optometry School. An in it ia l reading of the literature on binocular vision indicated that i t can be divided in to two parts, that concerning the mechanism which produces one visual percept from two visual inputs to the two separate eyes, and the mechanism which produces stereopsis, by evaluating the angular differences between the two re tin a l images and interpreting them as a sense of depth. I t was decided to concentrate on the haploscopic aspect of binocular vision , and to search fo r non-visual variables which determined the operation of th is function. A detailed reading of the lite ra tu re brought to lig h t several sets of experimental results showing marked v a ria b ility between normal subjects on the same te s t. Some of the operators commented on these, but did not look fo r th e ir o rig in . The neurological and neuro-anatomical lite ra tu re indicated that the production of the single visual percept was an on-going process which became more complex as i t was passed to higher neurological levels u n til the fin a l process was controlled by the cortex of the parietal lobe. This suggestion was confirmed by an E.F.G. programme carried out by the w rite r. The existence of neurological a c tiv ity in the parietal cortex involving the in h ib itio n processes which remove an unwanted diplopic image from visual perception suggested very strongly that psychological variables would be found here. This survey of the lite ra tu re also indicated that no previous work had been done in this fie ld and new tests had to be devised to isolate and measure the non-visual variables. This programme was undertaken by the w rite r who had done previous research in orthoptics and in optometry. These tests produced 20 scores, some of which suggested the psychological variable with which the optometric scores might correlate s ig n ific a n tly . The nature of these scores was described to a cross-discipline project team whose members designed a battery of tests, one psychological and the other neuro-psychological. The psychological battery was based on the assumption that the variable appeared to re late to some sort of psychological r ig id ity , but that as th is was not certain, certain other tests such as motivation, fru s tra tio n and suggestion must be adequately covered. The neuro-psychological battery assumed that the binocular variables must be measurable in the a c tiv ity of the central nervous system, and might appear as the muscular control of movement, or in the speeu of perception. A battery of te sts, including the E.E.G., was designed to measure these functions. The to ta l testing programme was now very large, and was given to two p ilo t samples. The battery was reduced in size by a study of the correlations, and by the use of cluster analysis. A study of the selected co rre la tio n between the binocular and the psychological scores indicated a relationship between the psychological results and some of the binocular tests. A reduced battery of both tests was given to a larger sample and a fa cto r analysis of the re su lt selected perseveration as the major psychological variable in binocular performance. During the course of the research work some very valuable discoveries were made fo r c lin ic a l optometry. The possible value of the results to psychology and the avenues of future research opened up by the programme of research are discussed.

This report extends findings (Duffy & Mitchell, 2013) of a dramatic recovery of vision in the deprived eye of amblyopic kittens following a short ‘dark-pulse’ (a 10 day period of darkness) to situations of clinical relevance. To this end, the initial deprivation began at post-natal day 7 rather than post-natal day 30. As before, the dark-pulse was imposed either immediately after the initial monocular deprivation, or was delayed several weeks after stable amblyopia was establsihed. In some animals, this dark-pulse was shortened, or disrupted by short periods of daily binocular visual experience. The effects on the visual acuity and alignment acuity of the two eyes were documented as well as the effects on binocular depth perception. The benefits of a short dark-pulse were identical to those of the prior study. A dark-pulse of 5 days was ineffective as was a dark-pulse interrupted daily by light for 30-minutes.

Diss. (sammanfattning) Göteborg : Göteborgs universitet , 2007. / Härtill 4 uppsatser.

Thesis (Ed. D.)--Illinois State University, 1989. / Title from title page screen, viewed October 13, 2005. Dissertation Committee: Marilyn Newby, Max R. Rennels (co-chairs), Evelyn Rex, Robert Stefl. Includes bibliographical references (leaves 68-72) and abstract. Also available in print.

Thesis (MA)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

No description available.

Thesis (MOccTher (Interdisciplinary Health Sciences. Occupational Therapy))--University of Stellenbosch, 2005. / According to the Occupational Therapy Practice Framework (2002), the objective of occupational therapy is to help people to participate in activities of daily life which are purposeful and meaningful to them and in which they are expected to participate. According to educators, learners are increasingly experiencing problems with performing academic tasks, and learning barriers, especially with regard to visual perception, are on the increase. Various external factors, such as educational policy pertaining to inclusive education and a younger age for school admission, as well as internal factors, such as learning readiness, may contribute to the occurence of learning barriers that can restrict the academic progress of learners. Learners are increasingly being referred to occupational therapists. Occupational therapists also provide guidance to learner supporters. Occupational therapists refer learners with visual perception problems with possible eye tracking problems for vision therapy, after which occupational therapy is resumed. Meanwhile, learners still have to function in the school environment, which means that incorrect capturing of information processing can take place. According to literature, the promotion of eye movements is regarded as part of occupational therapy services in the USA. In South Africa the proposed model by Fishman-Hellerstein and Fishman (1999: 148) of cooperation between optometrists and occupational therapists is followed. In this approach eye movements are regarded as underlying building blocks of visual perception and the effect of eye movements on the academic performance of learners is clearly described (Green, 2001). There is a shortcoming in the literature where eye movements are promoted as integral to a visual perception programme. Occupational therapy needs to investigate effective methods of intervention that are time and cost effective in order to address the growing problem, especially in South Africa. A clinical experimental field trial with a convenience sample was used to investigate the effect of occulomotor exercises in combination with a visual perception programme on the visual perception of seven-year-old learners with visual perception problems. The study population was seven-year-old learners with visual perception learning barriers from neighbouring schools with foundation phase education. Inclusion and exclusion criteria were applied. Sifting procedures included questionnaires to parents and educators, “Beery-Buktenica Developmental Test of Visual-Motor Integration” 4th edition of Beery (1997) for visio-motor integration, and a screening test by an optometrist. A visual perception programme was presented to the control groups and the experimental groups over ten sessions. An eye exercise of 15 minutes was included with the experimental groups. The Developmental Test of Visual Perception, 2nd edition, by Hammill, Pearson and Voress (1993) was used as measuring instrument in the pre-test and post-test to determine effectiveness, which was statistically indicated by using the repeated measures ANOVA. The results indicated no significant difference between the visual perception programme with eye exercises and the one without. Two tests of the sub-ability of visual perception showed a tendency towards improvement. The educators indicated that the learners benefited functionally from the programme and that it made a difference in academic performance. Behaviour and emotional events may have influenced the results of the study because of external factors. It is recommended that the study be repeated with a larger sample and a longer programme presented over six months to a year. Occupational therapists can include eye exercises integral to activity participation by adapting activities and through the optimal use of space for activities so that the learner would have to adapt to it visually.

No description available.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Over the past 50 years smart materials have made their appearance in many structures. The thermopiezoelectric ceramic is one of these smart materials. When thermal e ects are considered negligible, then the materials are classified as piezo-ceramic and piezoelectric materials. These so called piezo-ceramics are used as actuator and sensor components in many structures. The use of these components with composite materials is significant due to their application in the aerospace and aeronautics fields. The interaction that the piezoelectric material has with a composite body can be improved in order to reduce the energy requirement of the material for deformation. An objective in the optimisation of composite material structures is to minimise compliance or maximise sti ness uT f, with the laminate ply orientations as design variables, where u and f are displacement and force vectors, respectively. Here, the objective is not the maximisation of sti ness but the maximisation of compliance, with typical constraints being failure criteria. These failure criteria can include theories such as the maximum principle stress, the Tsai-Hill or Tsai-Wu failure theories. The compliance is maximised to accentuate any piezoelectric movement and is for theoretical treatment only. Piezoelectric materials once polarized the materials becomes quasi-isotropic. The piezoelectric materials are isotropic in the plane normal to the direction of the voltage being applied and have altered properties normal to this plane. This change in the material properties can be exploited so that the layup can be altered in orientation to improve performance. The idea is to improve the mechanical capabilities of the structure subject to an electrical input or vice versa. In the works by both Carrera et al. and Piefort, First Order Shear Deformation Theory (FSDT) is used in finite element analysis to characterise the structural and electrical behaviour of a plate or shell. FSDT, also known as the Mindlin-Reissner theory, is a plate bending theory that assumes a transverse shear distribution through the thickness of the plate. This theory is considered an improvement on the standard theories such as the Kircho or Timoshenko theories. Many optimisation techniques exist and are classed as either being direct search or gradient based methods. Particle Swarm Optimisation (PSO) is a direct search method. It mimics the behaviour of a flock of birds or school of fish in their attempt to find food. The PSO’s mathematical statement characterises a set of initial unknown particles within a designated search space that are compared to a set of local best particles and a single global best particle. This comparison is used to update the swarm each run cycle. Regression is a procedure whereby a set of testing data is used to fit a pseudo-function that represents the form the data should take in practice. The aim of this work is to optimise the piezoelectric-composite layer interaction to improve the overall compliance of a structure. Extensive modelling is performed and tested with peer reviewed literature to demonstrate its accuracy. / AFRIKAANSE OPSOMMING: Oor die afgelope 50 jaar het slim materiale hulle verskyning gemaak in verskeie strukture. Termopiezo-elektriese keramieke is een van hierdie nuwe materiale. Wanneer termiese e ekte onbeduidend is, word hierdie materiale as piezo-elektriese materiale geklassifiseer. Hierdie sogenaamde piezo-keramieke word gebruik as aandrywers en sensoriese onderdele in verskeie strukture. Die kombinasie van hierdie onderdele met saamgestelde materiale het belangrike toepassings in die ruimte- en lugvaartkunde. Die interaksie van die piezo-elektriese materiale met die saamgestelde materiaal strukture kan verbeter word om die energie-vereistes van die materiaal vir vervorming te verminder. ’n Tipiese doel in die optimering van saamgestelde materiaalstrukture is om styfheid uT f te maksimeer met die gelamineerde laag-oriëntasies as ontwerpsveranderlikes, waar u en f onderskeidelik verplasing en kragvektor voorstel. In teenstelling met die optimering van die samestelling wat voorheen gedoen is, is die doel hier nie die maksimering van styfheid nie, maar die minimering van styfheid, met falingskriteria as tipiese beperkings. Die falingskriteria sluit die volgende in: die maksimum spanningsteorie, en die Tsai-Hill of Tsai-Wu falingsteorieë. Die styfheid word geminimeer om piezo-elektriese verplasing te versterk, maar word hierin net teoreties bekyk. Sodra piezo-elektriese materiale gepolariseer word, word hulle quasi-isotropies. Die piezoelektriese materiale is isotropies in die vlak gelyk aan die rigting van die stroomspanning wat daarop toegepas word en het ander eienskappe normaal tot die vlak. Die verandering in die materiaal se eienskappe kan gebruik word sodat beide die saamgestelde materiaal en die piezoelektriese laag se oriëntasie aangepas kan word vir verbeterde werkverrigting. Die idee is om die meganiese vermoëns te verbeter van ’n struktuur wat onderwerp word aan ’n elektriese inset of vice versa. In die literatuur van beide Carrera et al. en Piefort word Eerste Orde Skuifvervormings Teorie (EOST) gebruik in eindige element analises om die strukturele en elektriese gedrag van ’n plaat of dop te karakteriseer. EOST, ook bekend as Mindlin-Reissner teorie, is ’n plaat buigings-teorie wat ’n dwarsvervormingverspreiding aanneem deur die dikte van die plaat. Hierdie teorie word gesien as ’n verbetering op die standaard teorieë soos bv. Kircho of Timoshenko se teorieë. Daar bestaan baie optimeringstegnieke wat geklassifiseer word as ’direkte soek’ of ’hellinggebaseerde’ metodes. Partikel swerm-optimering (PSO) is ’n direkte soekmetode. Dit boots die gedrag van ’n swerm voëls of ’n skool visse in hulle poging om kos te vind, na. PSO se wiskundige stelling karakteriseer ’n aanvanklike stel onbekende partikels binne ’n afgebakende soekgebied wat vergelyk word met ’n stel van die beste plaaslike partikels sowel as ’n enkele beste globale partikel. Die vergelykings word gebruik om die swerm met elke siklus op te dateer. Regressie is ’n metode waarin toetsdata gebruik word om ’n benaderde funksie te konstrueer wat ongeveer voorspel hoe die regte funksie lyk. Die doel van hierdie werk is om die piezoelektriese saamgestelde laag te optimeer en die interaksie van die totale gedrag van die struktuur te verbeter. Uitgebreide modellering word uitgevoer en getoets met eweknie-beoordeelde literatuur om die akkuraatheid en korrektheid te bewys.