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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.
11

Cross-Sectional Stiffness Properties of Complex Drone Wings

Muthirevula, Neeharika 05 January 2017 (has links)
The main purpose of this thesis is to develop a beam element in order to model the wing of a drone, made of composite materials. The proposed model consists of the framework for the structural design and analysis of long slender beam like structures, e.g., wings, wind turbine blades, and helicopter rotor blades, etc. The main feature consists of the addition of the coupling between axial and bending with torsional effects that may arise when using composite materials and the coupling stemming from the inhomogeneity in cross-sections of any arbitrary geometry. This type of modeling approach allows for an accurate yet computationally inexpensive representation of a general class of beam-like structures. The framework for beam analysis consists of main two parts, cross-sectional analysis of the beam sections and then using this section analysis to build up the finite element model. The cross-sectional analysis is performed in order to predict the structural properties for composite sections, which are used for the beam model. The thesis consists of the model to validate the convergence of the element size required for the cross-sectional analysis. This follows by the validation of the shell models of constant cross-section to assess the performance of the beam elements, including coupling terms. This framework also has the capability of calculating the strains and displacements at various points of the cross-section. Natural frequencies and mode shapes are compared for different cases of increasing complexity with those available in the papers. Then, the framework is used to analyze the wing of a drone and compare the results to a model developed in NASTRAN. / Master of Science
12

Grönskans betydelse i den täta staden

Kleverman, Johanna, Sjölin, Jenny January 2018 (has links)
I samband med förtätning av städer minskar andelen grönska per invånare, vilket ställer krav på att städer planerar för miljöer med grönska som främjar mental återhämtning och andra ekosystemtjänster. Med underlag av att Malmö stad är en av de städer i Sverige som har minst grönska per invånare, och att torg är potentiella offentliga rum för att öka grönska, innehåller följande studie en analys av Nobeltorget och Masttorget med inriktning på grönska och mental återhämtning. Syftet med studien har varit att analysera hur två torg som nyligen byggts eller byggts om är utformade utifrån målet att uppnå ökad grönska i staden.Studien består av två separata undersökningar, där resultatet har använts för analys av de mål som formulerats i Malmö stads Grönplan och Översiktsplan. Planeringsinstrumentet grönytefaktorn har använts som verktyg för att skapa kvalitativa värden genom att kvantitativt beräkna andelen grönska på torgen. En enkätstudie har utformats med Perceived Restoration Scale, för att undersöka upplevelsen av Nobeltorget och Masttorget genom en värdering utifrån fotografier av torgen. Resultatet av fältstudien visar att andelen grönska skiljer sig betydligt mellan torgen, där Nobeltorget har mer grönska i förhållande till den totala ytan, jämfört med Masttorget. Resultatet av enkätstudien visade på mindre skillnader i upplevelsen av torgen, där Nobeltorget värderas något högre enligt kategorierna fascination, att vara borta, sannolikhet för återhämtning och preferens. / In conjunction with urban densification, the proportion of greenery per inhabitant decreases, requiring cities to plan for environments with greenery promoting mental recovery and other ecosystem services. Based on the fact that Malmö is one of the cities in Sweden with the least greenery per inhabitant, and that squares are potential public spaces to increase greenery, the following study contains an analysis of Nobeltorget and Masttorget with focus on greenery and mental recovery. The purpose of the study has been to analyze how two squares, recently built or rebuilt, are designed based on the goal of achieving increased greenness in the city.The study consists of two separate studies, where the results have been used for analyzing the goals formulated in the Malmö City Green Plan (Grönplan) and General Plan (Översiktsplan). The planning tool Biotope Area Factor has been used as a tool for creating qualitative values ​​by quantitatively calculating the proportion of greenery on the squares. A survey has been designed with Perceived Restoration Scale, to investigate the experience of Nobeltorget and Masttorget by valuation based on photographs of the squares. The result of the field study shows that the proportion of greenery differs significantly between the squares, where Nobeltorget has more greenery in relation to the total area, compared to Masttorget. The results of the survey showed minor differences in the experience of the squares, where Nobeltorget was evaluated slightly higher according to fascination, being away, restoration likelihood and preference.
13

Computational Analysis of Elastic Moduli of Covalently Functionalized Carbon Nanomaterials, Infinitesimal Elastostatic Deformations of Doubly Curved Laminated Shells, and Curing of Laminates

Shah, Priyal 05 April 2017 (has links)
We numerically analyze three mechanics problems described below. For each problem, the developed computational model is verified by comparing computed results for example problems with those available in the literature. Effective utilization of single wall carbon nanotubes (SWCNTs) and single layer graphene sheets (SLGSs) as reinforcements in nanocomposites requires their strong binding with the surrounding matrix. An effective technique to enhance this binding is to functionalize SWCNTs and SLGSs by covalent attachment of appropriate chemical groups. However, this damages their pristine structures that may degrade their mechanical properties. Here, we delineate using molecular mechanics simulations effects of covalent functionalization on elastic moduli of these nanomaterials. It is found that Young's modulus and the shear modulus of an SWCNT (SLGS), respectively, decrease by about 34% (73%) and 43% (42%) when 20% (10%) of carbon atoms are functionalized for each of the four functional groups of different polarities studied. A shell theory that gives results close to the solution of the corresponding 3-dimensional problem depends upon the shell geometry, applied loads, and initial and boundary conditions. Here, by using a third order shear and normal deformable theory and the finite element method (FEM), we delineate for a doubly curved shell deformed statically with general tractions and subjected to different boundary conditions effects of geometric parameters on in-plane and transverse stretching and bending deformations. These results should help designers decide when to consider effects of these deformation modes for doubly curved shells. Composite laminates are usually fabricated by curing resin pre-impregnated fiber layers in an autoclave under prescribed temperature and pressure cycles. A challenge is to reduce residual stresses developed during this process and simultaneously minimize the cure cycle time. Here, we use the FEM and a genetic algorithm to find the optimal cycle parameters. It is found that in comparison to the manufacturer's recommended cycle, for a laminate with the span/thickness of 12.5, one optimal cycle reduces residual stresses by 47% and the total cure time from 5 to 4 hours, and another reduces the total cure time to 2 hours and residual stresses by 8%. / Ph. D.
14

The Effect of the COVID-19 Pandemic on Loneliness, Life Meaning, and Resilience among Indigenous and Non-Indigenous Post-Secondary Students: Improving Academic Success, Inclusion, and Stress Recovery

Welch, Brooke Erin 07 September 2022 (has links)
Background Research: The COVID-19 pandemic has likely impacted the resilience of Indigenous and non-Indigenous post-secondary students in Canada. Resilience may be negatively impacted by psychological experiences such as emotional loneliness, social loneliness, and a lack of life meaning. These three psychological experiences are exacerbated by lock down measures, quarantining, and cancelled events such as weddings and funerals. Young adults in post-secondary education must already manage challenging developmental milestones, often with unstable social and familial networks. Furthermore, Indigenous students must manage potentially discriminatory post-secondary environments, as well as school curriculums that challenge Indigenous values. Understanding this, school environments require decolonizing improvements that meet the psychological needs of their students in a changing social, economic, and political climate. Improvements to loneliness and life meaning may subsequently improve resilience, in addition to academic success, inclusion, and stress recovery. Objectives: This thesis aims to provide solution-focused data using Indigenous research methodologies. This thesis specifically explores the statistical relations between emotional loneliness, social loneliness, life meaning, and resilience. Barriers to social support options (i.e., counselling, group therapy, clubs, family, friends, etc.) and university-endorsed activities (i.e., jobs, volunteering, leadership roles, etc.) are also explored for their respective impact on experiences of loneliness and life meaning. Students’ response rates and Indigenous written responses are then analysed (1) to better understand students’ lived experiences, and (2) to uncover decolonizing approaches to improving both on campus social support options and university-endorsed activities. Hypotheses: (H1) Students will report higher scores on measures of emotional loneliness than social loneliness. (H2) Lower scores on measures of emotional loneliness, as well as higher scores on measures of life meaning, will predict higher scores on measures of resilience. (H3) Lower scores on measures of perceived barriers when accessing social support options will predict lower scores on measures of loneliness. (H4) Lower scores on measures of perceived barriers when accessing university-endorsed activities will predict higher scores on measures of life meaning. Method: This thesis incorporates a decolonizing methodology outlined by Hayward et al. (2021). This study utilizes 676 participant responses (3.30% of which identified as Indigenous) from students attending the University of Victoria in a full- or part-time program (Ages: 16-56 years, M = 20.13, SD = 3.84). Data collection occurred between September to December 2021, allowing for responses over the course of one semester. During this period, students were in the process of returning to campus, with daily national COVID-19 cases around roughly 3,000-4000 individuals (Worldometer, n.d.). Online recruitment methods were completed through the Department of Psychology SONA Research Participation System, and through a listserv utilized by the IACE at the University of Victoria. Demographic Questions included employment, financial stability, living situation, social circumstances, school status, workload, and the impact of the COVID-19 pandemic on wellbeing. Standardized Questionnaires included the de Jong Gierveld Loneliness Scale, the Life Engagement Test, and the Brief Resiliency Questionnaire. Additional Questionnaires were created to assess student experiences when accessing both social support options (i.e., the source for support, the method and frequency of contact, and barriers when accessing) and university-endorsed activities (i.e., valued activities, valued aspects of activities, and barriers when accessing). Analysis: At the broadest level, t-tests and hierarchical regression analyses are used to demonstrate a theoretical relation between various predictors and predicted variables. To provide more detail, student response rates for various questionnaires are used to contextualize student experiences when seeking social support options and meaningful activities. For an in-depth account of student experiences, four separate thematic analyses are conducted on Indigenous written responses. Results: All four hypotheses were supported. Scores of emotional loneliness were higher than scores of social loneliness (H1). Scores of resilience were significantly predicted by scores of emotional loneliness and life meaning (H2). These findings justified an exploratory analysis, which demonstrated that only scores of life meaning, and not resilience, emotional loneliness, or social loneliness, predicted scores of school satisfaction. More frequent experiences of barriers to social support options or university-endorsed activities respectively predicted higher scores of loneliness (H3) and lower scores of life meaning (H4). These results are complemented and expanded upon by notable response rates and themes identified from Indigenous student written responses. Discussion: These results suggest the importance of resolving emotional loneliness and a lack of life meaning among post-secondary students, which may be feasible with the use of social support services and university endorsed activities. This may subsequently improve experiences of resilience and school satisfaction. Social Support Options: The Indigenous and general sample both preferred informal, offline, and known sources of support; they also preferred face-to-face, texting, video calling, and phone calling as methods of communication. Common barriers to social support options included issues of cost, the perceived severity of their needs, availability, and a perceived lack of closeness with supports. Across all domains, Indigenous participants were more likely to experience barriers when seeking support. Indigenous written responses specifically identified a need for (1) more considerate services, (2) more culturally and racially specialized services, (3) increased time and availability for each student, and (4) lowered costs. University-Endorsed Activities: The Indigenous and general sample were both more likely to value paid jobs, volunteering, research assistant positions, and off-campus employment, when compared to teaching assistant positions, on-campus employment, or other unpaid positions. They were also most likely to value meeting people with similar interests and gaining knowledge. Students were most likely to face barriers related to a lack of relevant or remote university-endorsed activities. Indigenous written responses suggest an increased need for meaningful, accessible, culturally relevant, and financially rewarding activities. Twenty-one recommendations are offered to decolonize and improve post-secondary settings. / Graduate
15

Psychologické aspekty navigace nevidomých / The Psychological Aspects of Navigation of the Blind

Franc, Jakub January 2014 (has links)
This dissertation thesis addresses the area of spatial navigation of the blind. The author theoretically deals with a complex interplay of psychological functions involved in spatial navigation with respect to the specific conditions of the blind. The empirical part of the thesis presents an experimental study in the population of the blind (N=44). This study focuses on effects of the stress recovery phase from shortly increased stress levels on the process of learning a new route. The experiment is placed in real-world settings and overcomes some of the methodological flaws typical for this research domain. The research evidence suggests that the recovery phase from shortly increased stress levels hinders the development of procedural knowledge of the route. However, this deterioration in route knowledge is not associated with the effects of the strsss phase itself, but affects only the recovery phase part of the route in which stress levels are returning to their original baseline levels (not necessarily the level of the resting conditions). Besides its theoretical conclusions, the value of the presented thesis is in its contribution to the advancements of research methods in the given field. The outcomes of this work are practically applicable to the development of navigation aids for the blind....
16

Environmentálně-psychologická východiska výchovy v přírodě / The Basis of Environmental Psychology for Outdoor Education (The Influence of Nature on Mental and Social Well-Being)

VRBOVÁ, Zuzana January 2012 (has links)
The work deals with theoretical research of basis of Environmental Psychology for Outdoor Education. It answers two questions ? why in the conceptions of Outdoor Education is nature the preferred environment and what are the benefits of nature for physical, mental and social health. The answers to theses questions are in the work described through theories of environmental preference and restorative effects of nature. There are three major sections of the work. The first part discusses the basis, principles and contents of Environmental Psychology and Outdoor Education, the core terminology of the work, and the nodal points of Environmental Psyhcology and the theory of Outdoor Education. Second part describes those theories and concepts of Environmental Psychology which are related to the primary and subsidiary research questions. The third part evaluates the impacts and relevance of environmental-psychological knowledge on concepts of Outdoor Education.
17

Grönstrukturens funktion och betydelse för studenternas återhämtning (under covid-19 restriktioner) / Green structure's function and importance for students' recovery (during Covid-19 restrictions)

Ahmad, Doaa January 2020 (has links)
Tidigare forskning har visat att exponering för grön miljö tillhandahåller hälsofördelar. Dessa fördelar indikerar bland annat återhämtningseffekt av stress, trötthet och uppmärksamhetsutmattning, vilket är särskilt viktigt för universitetsstudenter. Därför syftade denna studie att undersöka om det finns en koppling mellan universitetsstudenters kontakt med grönstruktur i/nära studiemiljö och studenternas upplevelse av sin studiemiljö under covid-19 restriktionerna. Detta med hjälp av en dagbokundersökning som förstudie och telefonintervjuer. Analysverktyget bestod av teoretiska ramverk, Attention Restoration Theory (ART) och Stress Reduktion Theory (SRT). Resultat och analys har bekräftat Attention Restoration Theory (ART), där det uppges att gröna naturliga miljöer ger återhämtningseffekt och väcker uppmärksamhet efter en mental trötthet. Därtill bekräftade den även Stress Recovery Theory (SRT), där det uppges att gröna naturliga miljöer ger positiva effekt på stressminskning, -bearbetning och -återhämtning. Slutsatsen till denna undersökning är att grönstruktur har en stor betydelse för universitetsstudenterna, detta då alla väljer att vistas eller komma i kontakt med gröna naturen på ett eller annat sätt, till exempel gå en promenad i naturen eller åka till en stuga i skogen. Att naturen är en del av studenternas vardag verkar vara framför allt en omedveten upplevelse för de flesta och sker utan erkännande eller bearbetning av miljön. Dock framkommer det att processen kan vara medveten för vissa studenter. / Previous research has shown that exposure to the green environment provides health benefits. These benefits indicate among other things, recovery effect of stress, fatigue and attention-exhaustion, which is especially important for university students. Therefore, this study aimed to investigate whether there is a connection between university students' contact with the green structure in / near the study-environment and the students' experience of their study environment during the covid-19 restrictions. This with the help of a diary-survey as a pilot-study and telephone interviews. The analysis tool consisted of theoretical frameworks, Attention Restoration Theory (ART) and Stress Reduction Theory (SRT). Results and analysis have confirmed Attention Restoration Theory (ART), where it states that green natural environments have a recovery effect and attracts attention after a mental fatigue. In addition, it also confirmed the Stress Recovery Theory (SRT), which states that green natural environments have a positive effect on stress reduction, processing and recovery. The conclusion of this study is that green structure is of great importance to university students, as everyone chooses to reside or get in touch with green nature in one way or another, for example going for a walk in a green environment or staying in a cottage in the forest. That nature is a part of the students' everyday life seems to be above all an unconscious experience for most and takes place without recognition or processing of the environment. However, it appears that the process may be conscious for some students.

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