The Vickers residual stress field (VRSF) in soda-lime glass results from the elastic-plastic contact event that takes place when a Vickers diamond pyramid is loaded onto the surface of the material in an indentation cycle. The importance of elastic-plastic indentation lies in the contact damage that it gives rise to in the surface of the glass. Since such surface flaws can be characterised, with respect to shape and size, they offer the opportunity to study naturally occurring flaws in glass and brittle materials in general. The residual stress field is not passive; rather it exerts a crack opening force on the associated crack system during subsequent strength testing of a Vickers-indented sample through a residual stress field coefficient, c. Besides the strength-controlling properties, the elastic-plastic contact residual stress field is also important as a region where the influence of mechanical excitation on material properties such as hardness, H, and elastic modulus, E, can be studied. This thesis concerns studies that were made to characterise the Vickers residual stress field by first measuring the magnitude and distribution of stresses around it, using nanoindentation with a cube corner tip. With a Berkovich tip in nanoindentation, experiments were conducted in the VRSF to study the dependence of hardness, H and elastic modulus, E, on stresses in soda-lime glass: a strong E dependence on stress was observed, while H was not affected unless the stresses were high. In the process, a method was developed to determine the true contact area during elastic-plastic nanoindentation when the Oliver-Pharr method is used for the data analysis. The observed elastic modulus dependence on stress was then utilised in a study where it was shown that the VRSF responds differently to relaxation annealing on either side of the glass transition temperature. This result was then used to explain strength recovery trends in annealed Vickers-indented glass specimens.

Comprehensive studies are needed to better understand the original acoustical features of historical baths in order to uncover the historical technologies that enabled the acoustical performance for which they are renowned and to ensure they retain this performance with time. In this study, acoustic performances of Seng&uuml / l Hamami and Kadi Hamami, two 15th century historical baths belonging to the Ottoman period, were examined to discover their original acoustical features and to assess their present situation by taking into consideration the recent incompatible repair work. The analyses were done by using 3D computer modeling and acoustical simulation methods supported by laboratory analyses. The results were evaluated in terms of sound absorption characteristics of historical lime-based plasters, the original acoustical features of historical Turkish baths and acoustical failures related to recent repairs. The study showed that these baths had originally well-designed acoustical features provide for a proper environment for musical performances. This success was attributed to the conscious use of historical materials having high sound absorption characteristics. It was seen that these original acoustical features had been destroyed by wrong repairs using cement-based plasters. These plasters demonstrated incompatible acoustical properties, such as less porosity and lower sound absorption coefficients. This study also helped to define acoustical specifications for such historical baths to be maintained in restoration work.

<p>The Vickers residual stress field (VRSF) in soda-lime glass results from the elastic-plastic contact event that takes place when a Vickers diamond pyramid is loaded onto the surface of the material in an indentation cycle. The importance of elastic-plastic indentation lies in the contact damage that it gives rise to in the surface of the glass. Since such surface flaws can be characterised, with respect to shape and size, they offer the opportunity to study naturally occurring flaws in glass and brittle materials in general. The residual stress field is not passive; rather it exerts a crack opening force on the associated crack system during subsequent strength testing of a Vickers-indented sample through a residual stress field coefficient, c. Besides the strength-controlling properties, the elastic-plastic contact residual stress field is also important as a region where the influence of mechanical excitation on material properties such as hardness, H, and elastic modulus, E, can be studied.</p><p>This thesis concerns studies that were made to characterise the Vickers residual stress field by first measuring the magnitude and distribution of stresses around it, using nanoindentation with a cube corner tip. With a Berkovich tip in nanoindentation, experiments were conducted in the VRSF to study the dependence of hardness, H and elastic modulus, E, on stresses in soda-lime glass: a strong E dependence on stress was observed, while H was not affected unless the stresses were high. In the process, a method was developed to determine the true contact area during elastic-plastic nanoindentation when the Oliver-Pharr method is used for the data analysis.</p><p>The observed elastic modulus dependence on stress was then utilised in a study where it was shown that the VRSF responds differently to relaxation annealing on either side of the glass transition temperature. This result was then used to explain strength recovery trends in annealed Vickers-indented glass specimens.</p>

No description available.

How do gender separation and the transition to wind pollination happen in temperate trees? What does the reproductive ecology in the crowns of temperate forest trees look like? These connected questions intrigued researchers before and since Darwin but it is only in the last years that a direct study of the latter question has been enabled. A research crane was used to study the flowering ecology of Fraxinus excelsior, Acer platanoides, Acer pseudoplatanus and Tilia cordata in Leipzig’s floodplain forest. These species originate from hermaphrodite insect pollinated plant families and exhibit different grades of gender separation and different stages between insect and wind pollination. As they are typical elements of temperate deciduous forests, an ecological comparison of their flowering ecology may shed new light on the evolution of gender separation and wind pollination in this habitat. Using the crane, gender distribution, flowering phenology in relation to microclimate, pollination levels (including pollen tubes in the styles) and fruit set were studied in ca. 200 trees over 2-4 years. Main results are a new appreciation of the sexual system of Fraxinus excelsior as dioecy, of Tilia cordata as andromonoecy and a detailed description of the intricacies of the heterodichogamous sexual system of Acer pseudoplatanus. Several flowering phenological patterns are described in Fraxinus excelsior and Acer platanoides in relation to microclimate in early spring. The role of small arthropods is underlined as gall mites may play a role in gender specialisation in Fraxinus excelsior, gall midges are related to maleness in T. cordata and thrips are probably the pollinators of Acer pseudoplatanus in the stand. Thrips pollination is suggested to be a possible stepping-stone between insect pollination and wind pollination, which may drive the transition in Acer pseudoplatanus and possibly in intensively flowering dominant species in other habitats. The study presents the complexity of the reproductive systems and the strong interdependencies among their elements.

A técnica de estabilização de solos através da incorporação de agentes cimentantes é uma opção eficaz e amplamente utilizada em obras de engenharia geotécnica. Portanto, são relevantes os estudos que contemplam aspectos ainda não bem compreendidos relativos aos efeitos causados pela adição de agentes cimentantes na porosidade dos materiais obtidos e, por consequência, nas propriedades de desempenho destas misturas. Neste sentido, o presente trabalho pretende contribuir no que tange ao conhecimento da estrutura de poros de solos compactados tratados com cal e cimento e sua relação com o comportamento hidráulico destes materiais. Os solos utilizados têm granulometria arenosa e areno-siltosa. As variáveis de controle envolvidas nas análises são os teores dos agentes de cimentação empregados (cal e cimento), densidades de compactação e tempos de cura (para amostras com cal). Para a caracterização dos sistemas de poros empregou-se porosimetria por intrusão de Mercúrio e, de forma complementar, na quantificação das porosidades globais, microtomografia computadorizada de raios x. Um permeâmetro de parede flexível foi utilizado para as determinações das condutividades hidráulicas das amostras estudadas através de ensaios de carga constante. Para as amostras de matriz arenosa pura, os volumes de intrusão indicaram maior refinamento da rede porosa, sob efeito da cimentação, para as condições mais densas de moldagem. Para as amostras de matriz areno-siltosa, ao se variarem as condições de cimentação, e fixando-se o peso específico aparente seco, os volumes intrudidos indicaram o refinamento dos poros quando da adição de cal ou cimento em comparação à condição não cimentada. Com respeito à análise da influência do tempo de cura para as amostras moldadas com cal, os resultados sugeriram que a adição de cal (aos 7 dias de cura) não causou variação da porosidade, comparada à condição sem cimentação, mas aos 28 dias foi possível perceber o aumento da porosidade global e, com o passar do tempo (180 dias) verificou-se a redução da porosidade. O refinamento dos poros se tornou cada vez mais pronunciado conforme a evolução do tempo. Para a matriz arenosa, foi identificado que a adição de cimento e a variação da porosidade de moldagem não implicaram em mudanças mensuráveis no valor da condutividade hidráulica, quando comparadas às condições com e sem cimento. Para as amostras da matriz areno-siltosa, sob diferentes condições analisadas (adição de cal aos diferentes tempos investigados e adição de cimento), foi evidenciado que o peso específico aparente seco de moldagem causou influência significativa sobre a condutividade hidráulica. Foram obtidos bons ajustes para as correlações condutividade hidráulica versus relação porosidade/teor volumétrico do agente cimentante ao se aplicar a potência de 0,032 sobre o parâmetro teor volumétrico do agente cimentante. As curvas obtidas apresentaram relações distintas e sinalizaram aspectos do comportamento do material: aumento da condutividade hidráulica para 28 dias de cura da cal, em relação a 7 dias; para 180 dias e amostras nas condições menos densas, não ocorreu modificação em relação à idade de 28 dias, mas na condição mais densa o parâmetro investigado tornou-se sensível às modificações promovidas por efeitos do tempo de cura; ainda, para as amostras moldadas com cimento, ocorreu redução mais pronunciada da condutividade hidráulica relacionada às condições mais densas de moldagem. / The soil stabilization technique which incorporates cementing agents is an effective alternative and widely used in geotechnical engineering works. Therefore, research on the aspects not well understood related to the effects caused by the addition of cementing agents on the porosity of the obtained materials and, consequently, on the performance properties of cemented blends, are relevant. In this sense, this study aims to contribute improving the knowledge on the pore structure of compacted soils treated with lime and cement, as well as to the relationship between pore structure and the hydraulic behavior of these materials. The used soils have a sandy and sandy-silty grain size distribution. The studied variables involved in the analysis are: the cement and lime contents; compaction density; and curing time (for samples with lime). To characterize the pore systems it was employed the Mercury intrusion porosimetry test and, additionally, in order to quantify the global porosities, it was used x-ray computed microtomography tests. A flexible wall permeameter was used to determinate the hydraulic conductivity of the samples through constant head tests. For sandy samples, the intrusion volumes indicated a more significant reduction of the porous media, under the effect of the cementation, when compacted in denser conditions. For the sandy-silt samples, it was observed that by maintaining the specific dry unit weight constant and by varying the cementation conditions, the intruded volumes indicated a reduction of the pores after the addition of lime or cement compared to the uncemented samples. With regards to the influence of the curing time for samples treated with lime, the results suggested that the addition of lime after 7 days of curing did not cause variation in porosity, compared to condition without cementing additions; however, after 28 days of curing it was observed a slight increase on the overall porosity and, after 180 days of curing, it was observed a reduction of the porosity. The reduction of the pores became more significant with the curing time. Related to the sandy soil, the results indicated that addition of cement to the soil and variations on the molding porosity did not result in measurable changes in the hydraulic conductivity, when compared the conditions with and without cement. For the sandy-silt samples, which were analyzed under different conditions (addition of lime and different curing times, and addition of cement), it was shown that the specific dry unit weight caused significant influence on the hydraulic conductivity. It was observed a satisfactory correlation between hydraulic conductivity and porosity/cementing agent ratio when the volumetric cementing agent content is to the power of 0,032. The obtained curves showed distinct relationships and indicated the following aspects of the material behaviour: the increasing of the hydraulic conductivity after 28 days of curing of the sample with lime, compared to 7 days of curing; after 180 days of curing and under low compaction conditions, it was observed no changes when compared to the samples tested after 28 days of curing; however, in the densest condition the investigated parameter became dependent on the curing time; moreover, for the samples molded with cement, it was observed a more significant reduction of the hydraulic conductivity related to denser molded conditions.

O solo é base de praticamente todas as obras de Engenharia Civil e em algumas situações este não apresenta condições de suportar o carregamento imposto. Tal problema pode ser solucionado com técnicas de estabilização. A estabilização com cal é uma técnica clássica, porém não apresenta um método racional de dosagem e uma superfície de falha tridimensional conhecida. Entretanto este quadro vem alterando-se por meio de pesquisas que buscam utilizar o coeficiente porosidade/teor volumétrico de cal para dosar solo-cal. Assim, esta pesquisa tem como objetivo avaliar a influencia do coeficiente n/(Liv) na variação de resistência à tração na compressão diametral de misturas solo- cinza volante-cal para diferentes temperaturas e diferentes tempos de cura. Busca-se obter, também, a envoltória de ruptura tridimensional deste material. Para isso foram realizados ensaios de tração por compressão diametral em corpos de prova da mistura areia de Osório e cinza volante com 3, 5 e 7 % de cal (em peso), com peso especifico aparente seco de 14, 15 e 16 kN/m², curados a 20, 27, 35, 50, 65,80 e 90ºC por 1, 3 e 7 dias. Ensaios em Triaxial Verdadeiro e de ondas ultrassônicas foram executadas em amostras com 3 dias de cura a 35º, 3% de cal, peso específico seco de 14kN/m³ e nvariando de 0 até 180º. A relação porosidade/teor volumétrico de cal ajustado por um coeficiente [n/(Liv)0,3] mostrou-se adequada na previsão da resistência à tração para todas as temperaturas e tempos de cura estudados. O uso deste coeficiente permitiu a obtenção de curvas que permitem o cálculo da temperatura máxima que influência na resistência da mistura estudada para cada tempo de tempo. Este coeficiente também permitiu a obtenção de uma equação capaz de determinar a resistência máxima que pode ser obtida em cada tempo de cura independente da temperatura de cura. A envoltória de ruptura encontrada tem formato não circular, logo a resistência do material é dependente do caminho de tensões. A isotropia do material foi confirmada através da comparação entre caminhos de tensão iguais, porém executados em diferentes direções e através da comparação entre o Módulo Oedométrico há pequenas deformações (M0)e o Módulo de Cisalhamento há pequenas deformações (G0) das direções x, y e z da amostra. / Soil is the base of most civil engineering constructions, and when it cannot support the construction loads, such problem can be solved through the use of soil stabilization technique. Lime stabilization is a classical technique, but does not present a rational dosage method and a known three-dimensional failure envelope. This situation has been changed with researches using the porosity/lime ratio to dose soil-lime. Thereby this research aims to evaluate the influence of the quotient n/(Liv) in the assessment of splitting tensile at different temperatures and time of curing and find. It was also looked for the three dimensional rupture envelope of this material. For this research splitting tensile tests were carried out with lime contents varying from 3% to 7%, dry unit weight ranging from 14kN/m³ to 16kN/m³, time curing varying from 1 to 7 days and curing time varying from 20º to 90º. True Triaxial tests and ultrasonic waves tests were carried out with samples with 3% of lime content, 14kN/m³ of dry weight, 3 days of curing at 35º and nangle between nz and the consider stress path) in ranging from 0º to 180º. The porosity/lime ratio, defined as the ratio of the compacted mixture porosity and the lime volumetric content, adjusted by an exponent, proves to be an appropriate parameter to estimate the splitting tensile strength of the soil-fly ash-lime studied in all time and temperature studied. The use of this coefficient allowed obtaining curves that allow the calculation of the maximum temperature that influences the resistance of the studied mixture for each time period. This coefficient also allowed obtaining an equation capable of determining the maximum resistance that can be reached in each curing time independent of curing temperature. The failure envelope found has a non-circular shape, so the strength of the material is dependent on the stress path. The isotropy of the material was confirmed by comparing equal stress paths, but executed in different directions and by comparing the Oedometric Modulus in small strains (M0 ) and Shear Modulus in small strains (G0 ) of the x, y, and z directions the sample.

Made available in DSpace on 2014-06-11T19:33:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-11-01Bitstream added on 2014-06-13T19:23:51Z : No. of bitstreams: 1 fonseca_im_dr_jabo.pdf: 887619 bytes, checksum: 496442407236f6e4d0dd60cbc133778e (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Os tecidos vegetais tendem a ficar mais tenros em sistemas de produção onde maior fertilização com nitrogênio (N) é exigida, favorecendo o auto-sombreamento das plantas; entretanto, com aplicação de silício (Si), há melhoria na arquitetura foliar, reduzindo tal fenômeno. Objetivou-se, com este estudo, avaliar os efeitos da adubação nitrogenada e sua interação com a adição de Si na forma de escória de siderurgia nos atributos químicos do solo, na nutrição e na produtividade da cana-planta. O experimento foi instalado em condições de campo no município de Jaboticabal, SP, Brasil. Os tratamentos foram dispostos em esquema fatorial 5x2, sendo cinco doses de N (0, 30, 60, 90 e 120 kg ha-1) com Si (escória de siderurgia) e sem adição de Si (calcário), em delineamento em blocos ao acaso, com quatro repetições. Os atributos químicos do solo não diferiram com a aplicação de calcário ou de escória após 99 dias da aplicação dos materiais corretivos tampouco não houve mobilidade das bases no perfil do solo. A adubação nitrogenada com ou sem adição de Si não afetou as variáveis de desenvolvimento da cana-planta. Os maiores acúmulos de N, P, K, Mg, S, Cu e Zn ocorreram no colmo, ao passo que os maiores acúmulos de Ca, B, Fe, Mn e Si apresentaram-se nas folhas. Os elementos mais extraídos pela cana-planta (variedade RB855156) foram Si, K e N. Houve efeito da adubação nitrogenada na produtividade da cana-planta quando associada à adição de Si na forma de escória, ocorrendo aumento de 15 t ha-1 na produção de colmos industrializáveis. O uso da adubação nitrogenada incrementou o teor de sacarose e fibra de forma linear, entretanto, não houve efeito da escória nas variáveis tecnológicas da cana-planta. De modo geral, a adubação nitrogenada associada à adição de Si na forma de escória mostra-se adequada ao cultivo da cana-planta / In cases where more N fertilization is applied, plant tissues are tender and self-shading of the plants may result. Moreover, Si is important because it promotes improved leaf architecture and reduces self-shading. The objective of this study was to evaluate the effect of nitrogen with addition of Si as slag in soil chemical properties, nutrition and cane plant yield. The experiment was carried out in Jaboticabal, Sao Paulo State, Brazil with five N rates: 0, 30, 60, 90, and 120 kg ha-1 with Si (slag) and without Si (lime), in a randomized block with four replications. The soil chemical properties did not differ with the application of lime or slag in 99 days after application neither any mobility of bases in the soil profile was verified. Nitrogen fertilization with or without addition of Si did not affect the growth parameters of the cane plant. Accumulation of N, P, K, Mg, S, Cu and Zn mostly occurred in the stalk, while the highest Ca, B, Fe, Mn and Si accumulation were found in the leaves. Si, K and N were the most elements extracted by the cane plant (variety RB855156). No significant effects of N fertilization on cane plant yield; however, when associated with Si as slag, there was an increase of 15 t ha-1 of stalks. Nitrogen fertilizer increased the sucrose content and fiber linearly, however, no effect of adding slag in the technological variables of the cane plant. In general, nitrogen associated with Si added in the form of slag proved to be adequate for the cultivation of cane plant

abstract: Chloride solutions have historically been used to stabilize roads and to prevent dust; however, very little work has been done on investigating the soil stabilizing benefits from interactions between salt solutions and different soil types. The primary goal of this research was to analyze the feasibility of utilizing a salt waste product as an economically and environmentally responsible means of dust control and/or soil stabilization. Specifically, this study documents an investigation leading to the understanding of how the addition of saline based waste products, when using a soil stabilizer, modifies the strength behavior of soils. The scope of work included the evaluation of current literature, examination of the main challenges meeting relevant governmental regulations, and exploring the possibility of using saline waste to improve roadways. Three soils were selected, treated with varying amounts of salt (calcium chloride, CaCl2), and tests included soil composition and classification, correlation of soil characteristics and salt, and obtaining strength parameters that are typically used in pavement design and analysis. The work effort also included the determination of the optimum dosage of salt concentration for each soil. Because Lime treatment is also commonly used in soil stabilization, one of the soils in this study included a treatment with Lime for comparison purposes. Results revealed that when salt concentration was increased, a decrease in the plasticity index was observed in all soils. A modest to considerable strength gain of the treated material was also observed for two of the soils; however, a strength loss was observed for the third soil, which was attributed to its low clay content. When comparing the soil corrosive potential, the additional salt treatment showed promise for increasing strength, to an extent; however, it changes the chemical properties of the soil. The soils prior to treatment were corrosive, which could be managed with appropriate techniques, but the salt increases the values to levels that could be potentially cost prohibitive if salt was used by itself to treat the soil. The pavement design and performance investigation revealed that the Vineyard soil treated at 16% CaCl2 had an improvement that is comparable to the Lime treatment. On the other hand, the Eager soil showed very little pavement performance improvement at 8% CaCl2; this goes back to the effect of acid on the clay mineralogy. It was also postulated that using salt by-products to stabilize highway shoulders could be beneficial and save a lot of maintenance money when it comes to cleaning unwanted vegetation. A salt saturated soil structure could help in dust control as well. Future environmental challenges for salt leaching that could affect agriculture in developing countries will still need to be carefully considered. The chlorine levels in the soil would increase, and if not treated, can potentially have corrosive effects on buried structures. Future research is recommended in this area and to also evaluate soil stabilizing properties of varying proportions of Lime and salt using the approach provided in this study. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2017

Métodos de produção eficientes que economizam tempo e energia são sempre exigidos e novos processos de sinterização de baixo custo têm sido desenvolvidos para materiais cerâmicos e implementados por empresas e pesquisadores em todo o mundo. Com este objetivo, uma nova abordagem conhecida como Flash Sintering está atraindo grande interesse. Esta nova técnica de sinterização envolve a aplicação de campo elétrico através de uma amostra durante o aquecimento, gerando assim aceleração abrupta da cinética de densificação, diminuindo o tempo de sinterização de horas para segundos e diminuindo o aquecimento do forno em até centenas de graus Celsius. Frequentemente descritas para cerâmicas policristalinas e compósitos de cerâmica e vidro, a sinterização auxiliada por campo elétrico com apenas vidro não foi encontrado na literatura. A sinterização assistida por campo elétrico foi controlada com sucesso, sem que ocorresse o escoamento da amostra, obtendo uma elevada densidade relativa do vidro comercial. Um vidro de janela soda-cal-sílica não estequiométrica foi usado na pesquisa devido à sua importância comercial, por ser um material de partida de baixo custo, por apresentar condução iônica e haver na literatura dados de propriedades físicas e de cinética de sinterização convencional. O campo elétrico também influencia fortemente a cinética de sinterização do vidro soda-cal-sílica. Os resultados experimentais foram comparados com cálculos analíticos realizados a partir do modelo de Clusters não-isotérmico de sinterização de vidro por fluxo viscoso com cristalização concorrente. O aumento de temperatura nos compactos de pó de vidro durante o aquecimento do forno e aplicação de campo elétrico foi estimado usando um modelo de radiação de corpo negro. Preliminarmente, o aumento da temperatura devido ao efeito Joule pode explicar a diminuição da temperatura de amolecimento em comparação com a temperatura do forno e a sinterização rápida do vidro estudado. / Efficient production methods saving time and energy are always demanded and novel reduced-cost sintering processes have being developed for ceramic materials and implemented by companies and researchers of all over the world. With this aim, a new sintering approach generally known as flash sintering is attracting great interest. This new sintering technique involves the application of electric field through a sample while heating, thereby generating abrupt acceleration of the densification kinetics, decreasing the sintering time from hours to seconds and decreasing the oven heating in up to hundreds of degrees Celsius. Well described for polycrystalline ceramics and ceramic-and-glass composites, the sintering of pure glass aided by electric field is still lacking in the literature. The sintering assisted by electric field, was successfully controlled, without sample flow, achieved a high relative density of a commercial glass. A non-stoichiometric soda-lime-silica window glass was used due to its commercial importance, low cost starting material, ionic conduction, and literature on physical properties and conventional sintering kinetics. Electric field was observed to also strongly influence window glass sintering kinetics. The experimental results were compared with analytical calculations obtained from the non-isothermal Clusters model of glass sintering by viscous flow with concurrent crystallization. The temperature increase in the glass powder compacts during oven heating and electric field application was estimated by using a black-body radiation model. Preliminary, the temperature increase due to Joule effect can explain the softening temperature decrease compared with the oven temperature, and the fast sintering of the studied glass.