published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 1998 / However, studies were also conducted for the buckling of composite laminates involving temperature distribution. Chen and Chen (1991) studied thermal buckling of laminated plates under uniform and nonuniform temperature distribution using the eight-node Serendipity finite element. Mathew, Singh and Rao (1992) investigated thermal buckling of antisymmetric cross-ply composite laminates with a onedimensional furite element having two nodes and six degrees of freedom. Chandrashekhara (1992) accounted for transverse shear flexibility by using the thermo-elastic version of the first-order shear deformation theory. This will also be the case in this report. Literature on buckling and laminated composites abounds. Brush and Aimroth (1975) published a book on Buckling of Bars, Plates, and Shells, while Bushnell (1985) surveyed the Methods and Modes of Behaviour in Static Collapse. The foundation for the study of composite materials was based on the references [8], [10], [15] and [18]. The use of the Finite Element Method to analyse the buckling behaviour of laminated structures comes from references [I], [4]. [I2]. [16], [24] and [32]. Reference [14] provided the basis for the formulation of the variation of the governing equations. Most of the ideas in this report are based on these publications and references. Chapter I of this report introduces the concept of a composite. the formation of a composite and a brief overview of the elements of a composite material. This chapter also presents the concept of buckling that will form the basis of the development of this project. At the end of this chapter the choice of the element that is used in this study is justified. Chapter 2 provides the fundamentals of elasticity that relate to the deformation of a loaded body. In this Chapter the stresses and strains are defined and the temperature terms are introduced. In Chapter 3 the Mindlin plate theory is presented with a view to laying the foundation for the analysis of laminated plates, and as a starting point in the formulation of thermal buckling behaviour of laminated plates. In Chapter 4 the elements of a composite material are discussed and the constitutive equations of a laminated composite plate are built. Also the idea of lamination is introduced and the various simplifications that can be introduced as a result of lamination are discussed. The non-linear equilibrium equations and the stability analysis of a composite plate are formulated in Chapter 5 using the conventional anal}1ical method. The resulting equations justify the use of the Finite Element Method as introduced in Chapter 6 and it is the method by which the governing equations will be solved in ABAQUS computer analysis. The results for various computer runs are presented for a normal plate, a plate with a square hole, and the plate ""ith a circular cut-out in Chapter 7. Also in chapter 7 a comparison is made between the laminate "ith a central hole and a normal plate to study the effect of a cut-out on a critical buckling temperature. Appendices A deals the transverse shear in plates, and Appendix B deals with the transformation of the laminate elastic constants form the principal material direction to the general Cartesian co-ordinates. Also in Appendix B the laminate stiffness matrices and these matrices are briefly evaluated analytically. Appendix C is about the governing equations of laminated composites, while Appendix D gives a full representation of the abbreviated finite element equations of Chapter 6. Appendix E presents the list of ABAQUS input files that were used in the computer simulation of Chapter 7.

Bakgrund: Under de senaste decennierna har det skett en förändring med minskad svårighetsgrad av symtom och en minskad dödlighet vid stroke. Termen ”minor stroke” används för patienter med milda neurologiska handikapp. Inom hälso- och sjukvården görs bedömningen att dessa patienter inte har funktionsnedsättningar och förväntningarna är att de ska återhämta sig snabbt. Detta är den vanligaste stroke diagnosen men ändå den som får minst uppmärksamhet både kliniskt och vetenskapligt. Syfte: Syftet med undersökningen var att beskriva patienters erfarenhet efter minor stroke. Metod: Kvalitativ ansats med intervju som insamlingsmetod. Urvalet bestod av 10 in remitterade patienter till strokemottagningen Länssjukhuset Kalmar. Data analyserades med innehållsanalys. Resultat: I studiens resultat framkommer tre teman: det var inte som vanligt i kroppen, det fungerade inte som förr och det var inte lätt att återta kontrollen . Informanterna beskrev en bristande delaktighet från sjukvården, generell information och en oklar utskrivning. Först då de kom hem till sin vardag började de förstå vilka svårigheter som stroke hade fört med sig. Deras största svårigheter var dolda funktionshinder såsom kognitiva symtom framför allt hjärntrötthet. De hade svårt att acceptera situationen och till en början negligerade de allvaret. Allt eftersom började de att återta kontrollen i sin vardag, de skapade copingstrategier och hitta en ny livsstil på egen hand. Konklusion: Patienter med minor stroke beskriver svårigheter efter insjuknandet som de behöver fortsatt stöd i att hantera. Tidig uppföljning och fortsatt stöd från sjukvården är viktig. / Background: In recent decades there has been a change with reduced severity of symptoms and reduced mortality of stroke. The term “minor stroke” is used for patients with mild neurological disabilities. In the health care field, it is considered that these patients do not have disabilities, and are expected to recover quickly. This is the most common stroke diagnosis, yet the one who gets the least attention, both clinically and scientifically. Aim: The aim of the study was to describe patients experience after minor stroke. Method: Qualitative approach with interview data collection method. The sample consisted of 10 patients with minor stroke at stroke clinic Länssjukhuset Kalmar. Data were analyzed by content analysis. Results: The result of the study reveals three themes: it was not as before in the body, it did not work as before and it was not easy to regain control. The informants describe a lack of participation from the health care field, no specific information’s and a lack of participation. When the patients came home to their everyday lives, they began to understand the difficulties that stroke had brought them. Their greatest difficulty was hidden disabilities such as cognitive symptoms, especially brain fatigue. They found it difficult to accept the situation and initially ignored the gravity. As they began to regain control in their everyday lives, they created coping strategies and find a new life on their own. Conclusion: Patients suffering from minor stroke that has had onset of difficulties need continued support to manage. Early follow-up and continued support of health care field is important.

Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: A continuous comfort analysis of the whole-body vibration level aboard the S.A. Agulhas II during the 2013-2014 Antarctic voyage was conducted ac- cording BS ISO 2631-1:1997, assuming a standing posture. Just noticeable difference in magnitude testing was conducted on nine subject in the standing posture on a man-rated shaker in the laboratory environment. Two stimuli, a 5 Hz sinusoidal stimulus with a magnitude of 0,5 m.s-2 and a slamming event recoded during the voyage with a magnitude of 0,2 m.s-2 where selected as the stimuli on which to investigate the just noticeable difference thresh-old. The study shows that the vibration level for the duration of the voyage can be considered to be not uncomfortable. The results of the just notice-able difference threshold obtained for the sinusoidal stimulus concur with that found in literature for seated subjects. The just noticeable difference threshold obtained for the ship stimulus does not correlate with the results for the sinu-soidal vibration, implying that there may be an error in the vertical weighting filter provided by the standard or that Webers law does not hold for the just noticeable difference threshold of standing subjects. / AFRIKAANSE OPSOMMING: 'n Deurloopnede gemakanalise van volliggaam vibrasievlakke aanboord die S.A. Agulhas II is uitgevoer. Die analise tydens die 2013-2014 Antarktiese reis is gedoen volgens BS ISO 2631-1 : 1997 vir 'n staande postuur. 'n Net-opmerkbare-verskildrempel toets is uitgevoer op nege vrywillers in 'n staande postuur deur vibrasieherkonstruksie op 'n platform in die laboratorium. Twee stumuli, 'n 5 Hz sinusvorminge stimulus (0,5 m.s-2 r.m.s.) en 'n branderim-pak stimulus (wat tydens die reis opgeneem is, 0,2 m.s-2 r.m.s. is gebruik) om die net-opmerkbare-verskildrempel to ondersoek. Die studie toon dat die vibrasievlakke gedeurende die reis as `nie ongemaklik' geklassifiseer kan word. Die resulte van die net-opmerkbare-verskildrempel verkry vir die sinusvormige stimulus stem saam met bevindinge vir sittende vrywilligers uit die literatuur. Die net-opmerkbare-verskildrempel verkry vir die skip stimulus stem egter nie 'n moonlike onakkuraatheid weegfunksie is wat deur die standard is aanbeveel word of datWeber se wet nie toepaslik is vir die net-opmerkbare-verskildrempel van staande vreywilligers nie.

Title: EMG analysis of lower limb muscles in dependence on growing muscle fatigue Objectives: The main objective of this thesis is monitor and evaluate changes in EMG parameters of muscles of low extremities depending on the level of local muscle fatigue (during exercise on legpress. Methods: Study included 8 subjects who completed the exercise on weight lifting machine legpress, while we were measuring 6 muscles on lower extremities by using surface EMG. The measuremets was at level 75 % of maximum weight, when probands doing exercises until he had complete muscle fatigue. Data from electromyography was processed and through them we could watched the spectral distribution of the EMG signal and changes of EMG amplitude, which we relate to maximal voluntary contraction. Results: After analysis of all 48 measured muscles, increased of EMG amplitude occured in 45 of them. There was 67 % statistically significant, another 6 % was really close to significant level and remaining 23 % was insignificant. We have 144 time series in analysis of quartile milestones (Q25, Q50 and Q75). From this number decrease of frequency occured 135 times. There was 75 % statistically significant. Then we found out that biggest decreased was in median and mainly in Q75, it was in 82 %. Conclusions: Study proved that during...

Title: EMG analysis of lower limb muscles in dependence on growing muscle fatigue Objectives: The main objective of this thesis is monitor and evaluate changes in EMG parameters of muscles of low extremities depending on the level of local muscle fatigue (during exercise on legpress). Methods: Study included 8 subjects who completed the exercise on weight lifting machine legpress, while we were measuring 6 muscles on lower extremities by using surface EMG. The measuremets was at level 75 % of maximum weight, when probands doing exercises until he had complete muscle fatigue. Data from electromyography was processed and through them we could watched the spectral distribution of the EMG signal and changes of EMG amplitude. Key words: amplitude analysis, spectral analysis, surface polyelectromyography, muscle fatigue

ABSTRACT The negative impacts of trauma on clients are well known. However, the negative impact of working with traumatized clients on the counselor or helper has received less attention in the literature. Similarly, the contributions of certain work environments to experiences of compassion fatigue and the role of personality characteristics have gone unnoticed, especially in the South African context. The aim of this research is to examine the relationships between compassion fatigue, sense of coherence and work environment variables (job control, workload and collegial support), and to determine whether sense of coherence moderates the relationship between work environment and compassion fatigue on a sample of Employee Assistance Programme (EAP) practitioners in the South African organisational context (both public and private sectors). The current study adopted a non-experimental research design, categorised as cross-sectional and correlational. A non-probability sampling procedure was utilised. A sample of ninety-nine (99) EAP practitioners was obtained. A 10-items Job Control Scale (Wall, Jackson and Mullarkey, 1995), Workload and Collegial Support Scale by Dewe (1987) 11-items each, a 30- items Compassion Fatigue Self-Test Scale (Figley, 1995), and 13-items Orientation to Life Questionnaire (QLQ-13/SOC-13) by Antonovsky (1987; 1993) were administered. Results indicate that the sample in the current study were at higher risk of experiencing compassion fatigue. There was a positive significant relationship between workload, collegial support and compassion fatigue, a negative insignificant correlation between job control and compassion fatigue, and positive insignificant relationship between sense of coherence and compassion fatigue. The results between sense of coherence and the work environment variables were insignificant. Finally, sense of coherence was only found to moderate the relationship between workload and compassion fatigue and the relationship between collegial support and compassion fatigue.

This thesis concerns various aspects of the durability offibre optic sensors embedded in composite. Since repair orreplacement of embedded sensors is not generally possible, thefunctional reliability of embedded sensors is one of the mostimportant prerequisites for successful use. The main researchobjective was to investigate the interaction between the sensorand the composite, and how this is affecting the mechanical andoptical sensor response. Fibre optic sensors embedded incomposite structures induce local stress concentrations whenthe composite is subjected to mechanical loads andenvironmental changes such as temperature and moisture. Acomplex transfer of stresses through the interfaces between theembedded sensor and the composite occurs and can result inlarge local stresses in the composite and a significant changein the response of the embedded sensor. These stressconcentrations make the interfaces susceptible todebonding. The sensor performance was studied experimentally andnumerically. Some basic results were generated for the EFPI andBragg grating sensors. The phase-strain response was determinedduring static and fatigue loading. The results showed that thesensors were more reliable in compression than in tensilestatic and fatigue loading. Generally, the sensor reliabilityduring loading was significantly improved for the Bragg gratingsensors over that of the EFPI sensor, as an effect of thesensor geometry. This was also demonstrated in theinvestigations on impacts. Impacts do not necessarily result indamage in the composite, but might cause debonding or otherfailure modes in the sensor area. Large, local stressconcentrations occur at several positions in the EFPI sensor,which pointed out that this sensor type was not suitable forembedded applications. The shift in focus from the sensor concept based on the EFPIsensor to that based on the Bragg grating sensor manifesteditself in several studies. The calculated deformation fieldaround an embedded optical fibre was verified in experimentsusing a high-resolution moiré interferometric technique.Furthermore, the improvement in the coating technology wasverified. A significant higher interfacial strength wasobtained with the silane-treated glass surface. The resultsindicated that at least a twofold improvement of the shearstrength was obtained. To simultaneously measure the in-plane strain components andthe temperature change, embedded Bragg grating sensors werearranged in a rosette configuration. The relationship betweenthe optical response from each sensor and the strains in thelaminate was numerically and analytically established. Damage lead to stress redistribution in the sensor region,which may influence the output from the embedded Bragg gratingsensor. The effect was numerically evaluated for interfacialdamage, and was compared to that of a sensor with undamagedinterface. The results showed that debonding might have asignificant influence, in particular for combined thermal andmechanical loading. <b>Keywords</b>: composites, fibre optic sensor, embedded, EFPIsensor, Bragg grating sensor, durability, fatigue, impact,strain measurement, interface, stress analysis

<p>This thesis concerns various aspects of the durability offibre optic sensors embedded in composite. Since repair orreplacement of embedded sensors is not generally possible, thefunctional reliability of embedded sensors is one of the mostimportant prerequisites for successful use. The main researchobjective was to investigate the interaction between the sensorand the composite, and how this is affecting the mechanical andoptical sensor response. Fibre optic sensors embedded incomposite structures induce local stress concentrations whenthe composite is subjected to mechanical loads andenvironmental changes such as temperature and moisture. Acomplex transfer of stresses through the interfaces between theembedded sensor and the composite occurs and can result inlarge local stresses in the composite and a significant changein the response of the embedded sensor. These stressconcentrations make the interfaces susceptible todebonding.</p><p>The sensor performance was studied experimentally andnumerically. Some basic results were generated for the EFPI andBragg grating sensors. The phase-strain response was determinedduring static and fatigue loading. The results showed that thesensors were more reliable in compression than in tensilestatic and fatigue loading. Generally, the sensor reliabilityduring loading was significantly improved for the Bragg gratingsensors over that of the EFPI sensor, as an effect of thesensor geometry. This was also demonstrated in theinvestigations on impacts. Impacts do not necessarily result indamage in the composite, but might cause debonding or otherfailure modes in the sensor area. Large, local stressconcentrations occur at several positions in the EFPI sensor,which pointed out that this sensor type was not suitable forembedded applications.</p><p>The shift in focus from the sensor concept based on the EFPIsensor to that based on the Bragg grating sensor manifesteditself in several studies. The calculated deformation fieldaround an embedded optical fibre was verified in experimentsusing a high-resolution moiré interferometric technique.Furthermore, the improvement in the coating technology wasverified. A significant higher interfacial strength wasobtained with the silane-treated glass surface. The resultsindicated that at least a twofold improvement of the shearstrength was obtained.</p><p>To simultaneously measure the in-plane strain components andthe temperature change, embedded Bragg grating sensors werearranged in a rosette configuration. The relationship betweenthe optical response from each sensor and the strains in thelaminate was numerically and analytically established.</p><p>Damage lead to stress redistribution in the sensor region,which may influence the output from the embedded Bragg gratingsensor. The effect was numerically evaluated for interfacialdamage, and was compared to that of a sensor with undamagedinterface. The results showed that debonding might have asignificant influence, in particular for combined thermal andmechanical loading.</p><p><b>Keywords</b>: composites, fibre optic sensor, embedded, EFPIsensor, Bragg grating sensor, durability, fatigue, impact,strain measurement, interface, stress analysis</p>

Galvos skausmas yra vienas dažniausių somatinių nusiskundimų vaikų tarpe, kurio priežastys šiandien dar nėra visai aiškios. Manoma, kad už galvos skausmą atsakingi ne tik vidiniai skausmo mechanizmų reguliacijos sutrikimai, bet ir išoriniai aplinkos veiksniai. Galvos skausmas įtakoja vaiko ir jų artimųjų gyvenimo kokybę, dėl galvos skausmo vaikas priverstas praleisti pamokas, mažėja jo socialinis aktyvumas. Galvos skausmas turi neigiamos įtakos vaiko mokymosi rezultatams bei santykiams su bendraamžiais ir dažnai yra lydimas nuovargio. Besiskun¬džian¬čių galvos skausmu vaikų pastaraisiais dešimtmečiais gerokai padaugėjo. Tyrimo tikslas buvo išanalizuoti mokyklinio amžiaus vaikų galvos skausmo paplitimą, įvertinti galvos skausmą sąlygojančius veiksnius, galvos skausmo ypatumus bei besiskundžiančių galvos skausmu vaikų gyvenimo kokybę ir nuovargį. Tyrimo uždaviniai: 1) Ištirti moksleivių galvos skausmo paplitimą Lietuvoje ir galvos skausmą sąlygojančius veiksnius; 2) Išanalizuoti 8-18 m. amžiaus vaikų patiriamo galvos skausmo ypatumus: epizodo trukmę, dažnį, stiprumą ir intensyvumą pagal vizualinių analogų skalę (VAS).; 3) Įvertinti galvos skausmą patiriančių 8-18 m. amžiaus vaikų gyvenimo kokybę bei nuovargio išraiškas jų pačių požiūriu; 4) Įvertinti galvos skausmą patiriančių 8-18 m. amžiaus vaikų gyvenimo kokybę bei nuovargio išraiškas jų tėvų požiūriu; 5) Nustatyti galvos skausmą patiriančių 8-18 m. amžiaus vaikų gyvenimo kokybės bei nuovargio išraiškų vertinimo skirtumus... [toliau žr. visą tekstą] / Headache is a common symptom and complaint in pediatric practice. The etiology and pathogenesis of headache are still under discussion but interplay of physiological and environmental factors are considering. Headache significantly affect lives of children and their relatives and quality of life. Recurrent headache result in school absenteeism and decreased level of social activity. Headache have negative impact on relationships with peers and lead to learning outcomes. Fatigue is common symptom associated with pediatric headache. Recently the number of children who suffer headaches has increased significantly. Aim of the work was to evaluate the prevalence of headache among school age children, causal factors and characteristics of headache, quality of life and fatigue among school age children. Objectives of the work were: 1) To evaluate the headache prevalence and causal factors of headache among school-age children in Lithuania; 2) To analyze characteristics of headaches among 8–18 year olds children (episode duration, frequency, strength and intensity by the visual analog scale (VAS)). 3) To determine patients' own attitude towards quality of life and fatigue in children aged 8–18 years suffering from headaches; 4) To determine parents attitude towards quality of life and fatigue in children aged 8–18 years suffering from headaches; 5) To evaluate assessment differences concerning quality of life and fatigue between children aged 8–18 years suffering from headaches... [to full text]