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The Global ETD Search service is a free service for researchers
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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.
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Showing 21 to 28 of 28 (0.02 seconds)| 21 |
Aplica??o de t?cnicas de espalhamento a sistemas coloidais destinados ? extra??o de petr?leoMorais, Wildson Arcanjo de 18 August 2015 (has links)
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Previous issue date: 2015-08-18 / A ind?stria de petr?leo necessita de v?rias subst?ncias qu?micas em seus processos de extra??o e investe em novas tecnologias a todo o momento. Os sistemas micelares do tipo-minhoca-WLM e os complexos polieletrol?ticos-PECs est?o sendo estudados para ingressar como novas tecnologias na extra??o de ?leo. Esta tese objetiva obter, caracterizar e identificar esses sistemas coloidais utilizando t?cnicas de espalhamento de luz como principais ferramentas; possibilitando o conhecimento de base para poss?veis aplica??es na ind?stria petrol?fera. Os par?metros obtidos no DLS, b, GC e n sofreram transi??es na concentra??o tensoativo/co-tensoativo 200g/L. A adi??o da fase ?leo, xileno, dificulta a transi??o de micelas esf?ricas para micelas minhoca. No SAXS, a rela??o RG,O/ RG,S atinge um m?ximo que corrobora com a transi??o no DLS. b aumenta bruscamente, n se torna mais homog?neo, GC,2 e a contribui??o para o segundo processo, f2, foram visualizados para raz?es poli?nion/polic?tion WAC pr?ximas de 2. Essa regi?o, no SAXS, aglomerados de PECs se adsorvem nas part?culas prim?rias, que contribuiu para o comportamento dos gr?ficos de Kratky. As fun??es P(r) perdem seu formato ?sino? e se alargam. As contribui??es de ?rea S17 e S29 foram maiores para menores valores de WAC e S37 foi influente em valores maiores. / The oil industry needs various chemicals compounds in their extraction processes and
invests in new technologies all the time. Worm-like micelles-WLM and polyelectrolyte
complexes-PECs have been studied to join as new technologias in oil extraction processes. This
thesis aims to obtain, characterize and identify these colloidal systems using as a tool light
scattering experiments; enabling the required knowledge to applied them in oil industry. To the
surfactants systems, the parameters from DLS, b, GC and n in a function of surfactant/co-surfactant
concentrations suffered transitions around 200 g/L. The addition of oil phase, xylene, hinders the
transition from spherical micelles to worm-like micelles. In SAXS, the ratio RG,O/ RG,S reaches a
maximum value which corroborates with the transition in DLS. To PECs, b increases sharply, n
becomes more homogeneous, GC,2 and second contribution to the process, f2, were visualized for
polyanion/polycation ratio with WAC next 2. This region in SAXS, PECs clusters adsorb in primary
particles, which contributed to the behavior of Kratky graphics. The pair distribution functin, P(r),
lose its bell shape and widen. The S17 and S29 were higher for lower values of WAC ratio. S37 was
influential in higher values.
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An experimental analysis of opportunity and communication response form in a child with autism and hearing impairments.Dempsey, Donna Jean 12 1900 (has links)
An alternating treatment design was used to systematically evaluate the communication response forms, picture exchange communication system (PECS) or sign language, selection for a child with pervasive developmental disorder-not otherwise specified, profound hearing loss, and cochlear implants. The child had a limited pool of high preference items and very few functional skills. Key factors for this child included a structured environment that created a verbal community and contingent access to high preference items. No preference in communication response form was observed. The child successfully used four response forms to communicate: gestures, PECS, sign language, and vocalization. The results are discussed in terms of decision making factors in the selection of response forms.
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Effects of Picture Exchange Training on Communication TopographiesHaray, Aimee H. 05 1900 (has links)
The Picture Exchange Communication System (PECS) has been used with children with autism and other developmental disabilities as an alternative to vocal communication. Some researchers have reported rapid acquisition of picture-exchange requesting as well as increased vocal speech and increased spontaneous social interactions following PECS training. Earlier research has found that although 3 children with autism learned to exchange pictures for preferred items during PECS training, requesting topographies did not change and vocal speech did not increase after PECS training. The present study evaluated the effects of PECS training on requesting topographies, especially vocal speech, with 3 participants with autism and mental retardation. Only one participant maintained picture-exchange requesting, and none of the participants showed an increase in vocal speech during probe sessions conducted after each PECS training phase.
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Teachers' experiences of teaching learners diagnosed with autismMacIntosh, Jolene January 2013 (has links)
The purpose of the study was to explore teachers’ experiences of teaching learners diagnosed with autism. In particular, information was obtained regarding the assets that learners with ASD have and how these assets can be utilised within classrooms. Teachers also gave insight about the challenges that they encounter while teaching learners with ASD. Current classroom practices were investigated and information obtained about the type of support that teachers provide to learners with ASD. This was done in an attempt to provide guidelines on how to improve classroom practices within various educational settings to best support learners with ASD. Furthermore, I explored whether learners with ASD can be included within mainstream or remedial schools and what assistance they will need if they can be accommodated within these school environments.
A case study design was utilized. A total of six participants participated in the study. Data was collected by means of a focus group interview as well as one-on-one interviews. Two research sites were used and the information obtained from these sites was used to establish similarities and differences between teachers’ experiences in the respective school environments. The findings of the studies indicate that teacher training programmes need to be revisited in order to achieve the ideal of authentic inclusive school environments. / Dissertation (MEd)--University of Pretoria, 2013. / gm2014 / Educational Psychology / unrestricted
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Ecological risk assessment of pesticide use in rice farming in the Mekong Delta , VietnamDirikumo, Bubaraye Ohiosimuan January 2023 (has links)
Pesticide use in rice farming is a common practice in the Mekong Delta and poses ecological risks to aquatic organisms, the environment, and human health. This study focused on the ecological risk assessment of pesticide use in rice farming using the PRIMET model as a decision support tool to evaluate the risks of pesticide exposure, ecotoxicity, and risk characterization, as well as employing the species sensitivity distribution (SSD) assessment model to calculate the potentially affected fraction (PAF) of species based on the computed predicted environmental concentrations (PECs) from PRIMET. The study involved collating and analyzing data on pesticide inventories and the application of 138 farmers, which formed the basis for pesticide use, farming practices,environmental variables, and ecological indicators from two provinces in the Mekong Delta: Dong Thap and Hau Giang. This study showed that pesticide use was high with a wide range of pesticide types. The ecotoxicity assessment indicated that some pesticides pose a potential acute and chronic risk to non-target organisms. The active ingredient identified as posing acute toxicity risk with an ETR >100 is the insecticide indoxacarb, which belongs to the chemical class of oxadiazine of which Arthropods were seen to be highly sensitive to when exposed making them more at risk even at very low concentrations. In contrast, fish generally exhibit moderate tolerance and are sensitive to certain chemicals. The risk characterization revealed that the ecological risks of pesticide use were higher in Dong Thap than in Hau Giang due to differences in ecological conditions, pesticide practices, and farming systems. Overall, this study highlights the need for improved pesticide management practices in rice farming in the Mekong Delta region to reduce ecological risks and protect the environment and human health. The practical and theoretical implications of this study are discussed.
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Analyse critique de cinq interventions éducatives proposées pour les enfants (5-12 ans) qui ont des troubles envahissants du développementPapazian, Any January 2005 (has links)
Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.
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Densification Mechanisms for Spark Plasma Sintering in Alumina and Alumina Based SystemsChakravarty, Dibyendu January 2013 (has links) (PDF)
The densification mechanisms of polycrystalline α-alumina by spark plasma sintering are highly contradictory, with different research groups suggesting diffusion to dislocation controlled mechanisms to be rate controlling. The specific objective of this work was to investigate densification mechanisms of α-alumina during the intermediate and final stages of sintering by SPS, analyze the microstructural development and establish sintering trajectories. In addition, zirconia and yttria were added in different weight percentages to study the effect of solute concentration on the densification kinetics of spark plasma sintered alumina. The present work adopts a different approach from the classical method adopted previously to analyze the sintering kinetics and densification mechanisms of alumina in SPS, although existing models for hot pressing were adopted for the basic analysis.
The densification behavior was investigated in the temperature range 1223-1573 K under applied stresses of 25, 50 and 100 MPa and grain sizes between 100 and 250 nm. The SEM micrographs reveal equiaxed grains with no abnormal grain growth in the dense samples. The ‘master sintering curve’ shows grain size to be primarily dependent on density, irrespective of the applied stresses or temperature. The stress exponent of 1 along with an inverse grain size exponent of 3 and activation energy of 320-550 kJ mol-1 suggests Al3+ grain boundary diffusion as the rate controlling densification mechanism in alumina.
The densification rates are marginally slower in compositions with 0.1% Y2O3 and ZrO2 content possibly due to the smaller grain sizes used in this study which leads to faster rates compared to earlier reports. However, higher Y2O3 and ZrO2 content led to decrease in densification rate by more than an order of magnitude possibly due to presence of a second phase which increases the effective path length for diffusion, thereby reducing the densification rates. Presence of Y2O3 and ZrO2 in the compositions with 0.1% Y2O3 and ZrO2 were confirmed by TEM studies. The Y3Al5O12 (YAG) phase developed between 1223 and 1273 K and suppressed densification and grain growth in alumina. In spite of higher temperatures required for alumina-YAG and alumina-zirconia composites to attain density ~99%, the alumina grain size in the composites was smaller than that in pure alumina due to the Zener drag effect. The stress exponents obtained for Y2O3 and ZrO2 composites at both the concentrations yield a value of n~ 2, which indicates a change in densification mechanism from pure alumina. The higher stress dependence of these composites could be due to presence of solute and second phase formation, both of which retard densification rates. The inverse grain size exponents obtained are between 1 and 2; both stress exponent and grain size exponent values suggest an interface reaction controlled diffusion mechanism occurring in these composites, independent of the Y2O3 and ZrO2 content. Higher activation energies are obtained with the Y2O3 and ZrO2 composites of higher content, respectively, due to presence of second phase particles at grain boundaries.
The presence of solutes at grain boundaries hinders grain boundary diffusion of alumina, leading to interface reaction controlled process; this is confirmed by superimposing standard aluminum grain boundary and lattice diffusion data on to stress-densification rate data obtained in this work. A comparison of stress exponents using current experimental data adopting the present and the classical approaches show a wide difference in their values indicating a change in the rate controlling diffusion path, necessitating a review of the assumptions made on the basic equations used in previous SPS studies.
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Preventing fatal effects of overworking : Product design solutionAdawi, Rahim January 2018 (has links)
“Overworking to death” is a phenomenon that has been noticeable in developing countries. The cause of death is mainly through ischemic strokes. While the victims’ occupations differed, they all shared a common characteristic, being positioned in a sedentary work, ranging from IT workers to doctors. This project’s aim was to develop a product that prevented or decreased the strokes that derived from sedentary overwork. This was mainly tackled by preventing one of the three causes of developing blood props, slowed blood flow. In order to gather rich data of the phenomenon, a qualitative study was conducted in China, during two months. By doing an extensive structured sampling, information rich data could be gathered during a short period of time. Data were derived from observations, questionnaires and an interview, which then was interpreted to customer needs and the final product specification. The final product became a trouser with an in built dynamic compression mechanic, that can compress the veins mostly during sitting activities, in order to prevent blood stasis. The compression mechanic works like the Chinese finger trap; compressing the calves while sitting and stretching the legs forward. It is made only out of polysaccharides fibres; cotton and corn. / "Guolaosi" eller död från överarbete är ett fenomen som i regel uppkommer bland utvecklingsländer. Dödsorsaken är huvudsakligen genom stroke. Offrens yrken varierar allt från professorer, IT-arbetare till läkare. De delar dock en sak gemensamt; att arbeta under långa perioder stillasittande. Projektets mål var att utveckla en produkt som minskar dödliga följderna av sedentära överarbete, genom att förebygga en av de tre orsakerna för att utveckla blodproppar; saktad blodström. Målgruppen var då kineser av de yrken som hade tidigare drabbats av fenomenet. För att samla informationsrika data om fenomenet genomfördes en kvalitativ studie i Kina under två månader. Genom att göra en omfattande strukturerad provtagning kunde informationsrika data samlas under en kort tidsperiod. Fältstudien bestod av observationer, frågeformulär och en intervju, som då tolkades till kundbehov och eventuellt produktspecifikationen. Den slutliga produkten kom att bli ett par byxor med en inbyggd dynamisk komprimeringsmekanism, som kan komprimera venerna under sittande aktiviteter, för att förhindra saktad blodström. Kompressionsmekanismen fungerar som den kinesiska fingerfällan. Den komprimerar blodkärlen medan personen sitter och sträcker benen framåt. Produkten är konstruerad på så sätt att den kan tillverkas endast av polysackariders tråd, från bomull och majs. Vilket är lämpligt för Kinas lokala resurser.
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