This thesis is about determining the risks of positioning swimming pools on top of high-rise buildings.Pursuing this determination, computational simulations of constructed structural models in a finiteelement model software called RFEM have been analyzed. In further pursuit of wanted results comingfrom the computational software, the models have acquired relevant theory regarding both swimmingpools and high-rise buildings respectively to obtain realistic approximations of equivalent results if themodels were real life structures. Thence analytical observations and measures of each structural modelcontaining different positions of the swimming pools are generated, in several degrees, differentpossibilities of risks of failure are possible. Results have been compared out of design of swimmingpools and high-rise buildings in an initial stage of background and thereafter set as input values for themodeling where following perspectives have been analyzed:• Structural deformations,• Internal forces,• Utilization ratios, and• Mode shapes.Further analysis of social-, economic-, and environmental sustainability have been deliberated. Thus,in conclusion of this thesis, swimming pools positioned on top of the structure core or at center of theplan section tend to harm the stability of the structure likewise if the positioning of the swimming poolare cantilevered completely over the edge of the rooftop. More suitable design would either bepositioning the swimming pool attached to the core of the structure meanwhile cantilevered over theedge or integrated entirely along the edge.The results showed that some of the overhanging swimming pools pass the requirements of theEurocode. This will result in the columns experiencing a utilization which exceed its capacity. Thecolumn utilization was shown to behave differently depending on where the swimming pool was placedon the top floor. Furthermore, it was also a difference between the structures studied as dimensions ofthe members required either more or less depending on the form the structure had. The reaction of theswimming pool could be observed to behave as a stiff part of the structures with the deformation mostlybeing located at the slabs. The internal forces developed in the members due to the swimming poolaffected the columns at the bottom floors the most. The thesis finally shows how much is needed forthe worst case of each structure to pass the requirements. This resulted in different dimensions for themembers where the smaller structure (structure model 1) needed bigger dimensions and the largerstructure (structure model 2) needed smaller dimensions compared to the originally based dimensions.The social, economic, and environmental impact of the structures showed that the larger structureswould release more carbon dioxide than the smaller structures. The social aspect was treated moreregarding the safety and the experience of the user of the facility of swimming pool. The reinforcementvaried the most between the structures with the concrete being mostly the same for the two differentstructures made, in which an impact was made for both the economic and the environmental. Here itwas shown that in order to pass the requirements of the Eurocodes the impact on the climate needed tobe considerable different.

After only two years of service, extensive cracking was found in the webs of two light-rail commuter line bridges in Stockholm, the Gröndal and Alvik bridges. Due to this incident it was found necessary to study the means available for analysing shear cracking in concrete structures subjected to in-plane stresses. The aim of this PhD project is to study shear cracking with these two bridges as reference. In this thesis, the first part aims to study the possibility of using finite element analysis as a tool for predicting shear cracking for plane state stresses. The second part is concerning how the shear cracks are treated in the concrete design standards. Shear cracking in reinforced beams has been studied with non-linear finite element analyses. In these analyses the shear cracking behaviour was compared to experiments conducted to analyse the shear failure behaviour. Finite element analyses were performed with two different FE programs Abaqus and Atena. The material model used in Atena is a smeared crack model based on damage and fracture theory with either fixed or rotated crack direction. The material model used in Abaqus is based on plasticity and damage theory. The fixed crack model in Atena and the model in Abaqus gave good results for all studied beams. For the two studied deep beams with flanges the results from the rotated crack model were almost the same as obtained with the fixed crack model. The rotated crack model in Atena gave though for some beams a rather poor estimation of the behaviour. The calculation of crack widths of shear cracks has been studied for the long-term load case in the serviceability state for the Gröndal and Alvik bridges, with the means available in the design standards. The methods based on the crack direction corresponding to the principal stress and do not include the effect of aggregate interlocking seems to be too conservative. Two of the studied methods included the effect of aggregate interlocking, it was made either by introducing stresses in the crack plane or implicitly by changing the direction of the crack so that it no longer coincide with the direction of principal stress. For calculations based on probable load conditions, these methods gave estimations of the crack widths that were close to the ones observed at the bridges. Continuous measurements of cracks at the Gröndal and the Alvik bridges have also been included. Monitoring revealed that the strengthening work with post-tensioned tendons has, so far, been successful. It also revealed that the crack width variations after strengthening are mainly temperature dependent where the daily temperature variation creates movements ten times greater than those from a passing light-rail vehicle. Monitoring a crack between the top flange and the webs on the Gröndal Bridge showed that the top flange was moving in a longitudinal direction relative to the web until the strengthening was completed. The crack widths in the sections strengthened solely by carbon fibre laminates seem to increase due to long-term effects. / QC 20101119

The Thin Slab Cast Direct Rolling (TSCDR) process offers several economic and environmental advantages. The elimination of slab reheating and roughing deformation, however, leave fewer opportunities for grain refinement and some large grains persist in the microstructure. To solve this problem, a new chemistry which leads to a two-phase mixture of ferrite and austenite over a wide temperature range was introduced by Zhou et al. The two phase mixture is highly resistant to grain coarsening leading to a small initial grain size compared with the grain size of conventional TSCDR slab. In addition, ferrite and austenite co-exist over wide range of temperature in many third generation steels, making it extremely important to understand the hot deformation behavior of these materials, which have traditionally received less attention in the literature. In order to investigate the microstructure evolution of ferrite-austenite mixtures during thermomechanical processing, an Al containing model alloy, for which the two phases co-exist over a wide temperature range, was designed. Two types of experiments were carried out: the first involved single hit hot compression tests; and the second involved stress relaxation tests. According to the microstructure observation the main change of austenite microstructure under deformation conditions was a decrease in the spacing of the austenite particles within the ferrite matrix. In other words the austenite phase behaved as hard particles inside a soft ferrite matrix. Hot deformation led to the static recrystallization of the ferrite matrix. The most favourable nucleation sites were in the vicinity of the old grain boundaries and the around austenite particles. The recovery and recrystallization kinetics of ferrite were analyzed using the stress relaxation test. Based on analysis of the stress relaxation tests, more than 95% of stored energy was consumed by recovery, while static recrystallization consumed less than 5% of the stored energy. The retardation of recrystallization in the model alloy is attributed to both the high rate of recovery in BCC materials and texture effects. / Thesis / Master of Applied Science (MASc) / The Thin Slab Cast Direct Rolling (TSCDR) process offers several economic and environmental advantages. The elimination of slab reheating and roughing deformation, however, leave fewer opportunities for grain refinement and some large grains persist in the microstructure. To solve this problem, a new chemistry which leads to a two-phase mixture of ferrite and austenite over a wide temperature range was introduced by Zhou et al. The two phase mixture is highly resistant to grain coarsening leading to a small initial grain size compared with the grain size of conventional TSCDR slab. In addition, ferrite and austenite co-exist over wide range of temperature in many third generation steels, making it extremely important to understand the hot deformation behavior of these materials, which have traditionally received less attention in the literature. In order to investigate the microstructure evolution of ferrite-austenite mixtures during thermomechanical processing, an Al containing model alloy, for which the two phases co-exist over a wide temperature range, was designed. Two types of experiments were carried out: the first involved single hit hot compression tests; and the second involved stress relaxation tests. According to the microstructure observation the main change of austenite microstructure under deformation conditions was a decrease in the spacing of the austenite particles within the ferrite matrix. In other words the austenite phase behaved as hard particles inside a soft ferrite matrix. Hot deformation led to the static recrystallization of the ferrite matrix. The most favourable nucleation sites were in the vicinity of the old grain boundaries and the around austenite particles. The recovery and recrystallization kinetics of ferrite were analyzed using the stress relaxation test. Based on analysis of the stress relaxation tests, more than 95% of stored energy was consumed by recovery, while static recrystallization consumed less than 5% of the stored energy. The retardation of recrystallization in the model alloy is attributed to both the high rate of recovery in BCC materials and texture effects.

<p> Aluminum is usually added to the zinc bath to form an Fe-Al interfacial layer which retards the formation of a series of Fe-Zn intermetallic compounds during the hot-dip galvanizing process. However, experimentally exploring the inhibition layer formation and obtaining useful experimental data to understand the mechanisms is quite challenging due to short times involved in this process. In this study, a galvanizing simulator was used to perform dipping times as short as O.ls and rapid spot cooling techniques have been applied to stop the reaction between the molten zinc coating and steel substrate as quickly as possible. In addition, the actual reaction time has been precisely calculated through the logged sample time and temperature during the hot-dipping process. The kinetics and formation mechanism of the inhibition layer was characterized using SEM, ICP and EBSD based on the total reaction time. For bath containing 0.2wt% dissolved AI, the results show that FeA13 nucleates and grows during the initial stage of the inhibition layer formation and then Fe2Als forms by a diffusive transformation. The evolution of the interfacial layer formed in a zinc bath with 0.13wt% dissolved AI, including Fe-Aland Fe-Zn intermetallic compounds, was a result of competing reactions. In the initial period, the Fe-Al reaction dominated due to high thermodynamic driving forces. After the zinc concentration reached a critical composition in the substrate grain boundaries, formation of Fe-Zn intermetallic compounds was kinetically favoured. Fe-Zn intermetallic compounds formed due to zinc diffusing to the substrate via short circuit paths and continuously grew by consuming Fe-Al interfacial layer after samples exited the zinc bath due to the limited Al supply. A mathematical model to describe the formation kinetics as a function of temperature for the 0.2wt% Al zinc bath was proposed. It indicated that the development of microstructure of the interfacial layer had significant influence on the effective diffusion coefficient and growth of this layer. However, the model underestimates the AI uptake by the interfacial layer, particularly at higher temperatures. This is thought to be due to the effect of the larger number of triple junctions in the inhibition layer leading to an underestimation of the effective diffusivity. </p> / Thesis / Master of Science (MSc)

No description available.

En esta tesis, se analiza la relación entre el envejecimiento y la evolución microestructural en las aleaciones refractarias conocidas como HP40-Nb y ET45 micro. Se presentan resultados obtenidos por microscopía óptica y electrónica de barrido con microanálisis por rayos X, así como ensayos isotérmicos de dilatometría. Además, se aplicó el modelo cinético de Johnson-Mehl-Avrami-Kolmogorov para estudiar la nucleación y crecimiento de la precipitación secundaria de carburos del tipo Cr23C6. Estas aleaciones, de microestructura dendrítica, presentan una red de carburos primarios de tipo NbC y Cr7C3 en el caso de la ET45 micro, y de tipo NbC y Cr23C6 en el caso de la aleación HP40-Nb. En ambas aleaciones, se observa una zona de deplexión libre de precipitados secundarios adyacente a la red de carburos eutécticos primarios y que presenta menor dureza que la matriz austenítica. En la aleación HP40-Nb, se encontraron zonas ricas en silicio y níquel en los bordes de los carburos primarios de niobio, mientras que no se halló presencia de estos átomos en las zonas centrales de estas partículas. Ensayos isotérmicos de dilatometría indicaron que, a 1073 y 1098 K, la aleación sufre una contracción, la cual se estima que está asociada a la diferencia entre coeficientes de dilatación térmica entre la matriz y los carburos eutécticos primarios, mientras que a 1123 y 1148 K la aleación experimenta una expansión térmica. La transformación del carburo de niobio en el siliciuro rico en níquel y niobio, induce un cambio de volumen significativo en la celda unitaria, lo que se manifiesta en aquellos ensayos de dilatometría para temperaturas en las cuales la muestra se expande. Se encontraron indicios de la presencia de un siliciuro coincidente con la fase G para muestras envejecidas a 1123 K a tiempos equivalentes a la duración del ensayo de dilatometría a dicha temperatura. La transformación del carburo de niobio hacia el siliciuro rico en níquel y niobio, comienza en la interfaz de los carburos de niobio con la matriz, progresando hacia el interior de los mismos con el desarrollo del envejecimiento. Luego de tratamientos térmicos de envejecimiento a temperaturas de 1073, 1173 y 1273 K por cortos períodos de tiempo, se halló que la precipitación secundaria de carburos de tipo Cr23C6 en la matriz ocurre en una sola etapa. En el caso de la aleación HP40-Nb, este fenómeno presentó una energía de activación de 194 kJ/mol. Análogamente, para la aleación ET45 micro, se encontró que dicha energía es de 188 kJ/mol. / In this thesis, the relationship between exposure to high temperatures and microstructural evolution in centrifugal cast alloys HP40-Nb and ET45 micro is analysed. Results obtained by optical and scanning electron microscopy with X-ray microanalysis are presented, as well as isothermal dilatometry tests. In addition, the Johnson-Mehl-Avrami-Kolmogorov kinetic model was applied to study the nucleation and growth of secondary precipitation of Cr23C6 carbides. These alloys, of dendritic-type microstructure strengthened by a network of NbC and Cr7C3 primary carbides of type in the case of the ET45 micro, and of NbC and Cr23C6 primary carbides in the case of the HP40-Nb alloy. In both alloys, there is a depleted zone which is free of secondary precipitates adjacent to the network of primary eutectic carbides and presenting lower hardness than the austenitic matrix. In the HP40-Nb alloy, areas rich in silicon and nickel were found at the edges of primary niobium carbides, while no presence of these atoms was found in the central areas of these particles. Isothermal dilatometry tests showed that at 1073 and 1098 K, the alloy undergoes a contraction, which is estimated to be associated with the difference between thermal expansion coefficients between the matrix and primary eutectic carbides, while at 1123 and 1148 K alloy undergoes thermal expansion. The transformation of niobium carbide into nickel and niobium-rich silicide induces a significant change in volume in the unit cell. Such effect is manifested during those dilatometry tests for temperatures in which the sample expands. Indications of the presence of a silicide coinciding with the G phase were found for samples aged at 1123 K at times equivalent to the duration of the dilatometry test at said temperature. It has been found that the transformation of niobium carbide into silicon rich in nickel and niobium begins at the interface of niobium carbides with the matrix, progressing inwards with the development of aging. After thermal aging treatments at temperatures of 1073, 1173 and 1273 K for short periods of time, it was found that secondary precipitation of Cr23C6 carbides in the matrix occurs in a single stage. In the case of the HP40-Nb alloy, this phenomenon had an activation energy of 194 kJ/mol. Similarly, for the ET45 micro alloy, the activation energy was found to be 188 kJ/mol. / TEXTO PARCIAL en período de teletrabajo

El articulo busca brindar un enfoque acerca de la aplicación del artículo cinco de la Ley N° 30313, Ley de Oposición al Procedimiento de Inscripción Registral en Trámite y cancelación del Asiento Registral por Suplantación de Identidad o Falsificación de Documentación y Modificatoria de los Artículos 2013 y 2014 del Código Civil y de los artículos 4 y 55 y la quinta y sexta Disposiciones complementarias, transitorias y finales del decreto legislativo 1049, su contexto histórico y la esencia de la mencionada Ley. Se brinda al lector una opinión acerca de las implicancias de la entrada en vigencia de la Ley N° 30313 y al mismo tiempo se otorga una serie de críticas que son relevantes para entender porque se considera que es Ley no es la solución idónea para los problemas de fraudes inmobiliarios.

Yes / Cerium (Ce3+) substituted Ni-Co ferrites with composition Ni0.3Co0.7CexFe2−xO4 (x = 0.0–0.20, with step size 0.05) were synthesized by sol-gel method. Face-centered cubic (FCC) spinel structure was revealed by X-ray analysis. The crystalline size was calculated ranging between 17.1 and 18.8 nm, lattice constant showed a decreasing trend with increase of Ce3+ contents, furthermore, X-ray density was calculated between 5.30 and 5.69 g/cm3. The two characteristic spinel ferrites absorption bands were seen around 550 (cm−1) and 415 (cm−1) in Fourier transform infra-red (FTIR) spectroscopy. The microstructural and elemental studies were carried out by field emission transmission electron microscopy (FE-TEM) and energy dispersive X-ray (EDX) respectively, the average particle size was calculated around 21.83 nm. Magnetic studies were per- formed by vibrating sample magnetometer (VSM), which showed that saturation magnetization Ms and remanence Mr decreased with substitution up to x = 0.10 due to small magnetic moment of Ce3+ than Fe3+. The coercivity Hc increased with substitution up to 908.93 Oe at x = 0.05, then it decreased following the trend of anisotropy constant. The dielectric studies exhibited decrease in dielectric parameters with fre- quency due to decreasing polarization in material. The dielectric loss was significantly decreased in material at high frequency. The Cole-Cole interpretation exhibited conduction mechanism being caused by grain boundary density. These attributes of Ce3+ substituted Ni-Co ferrites suggest their possible use in memory storage, switching and high frequency devices like antenna and satellite systems. / The authors would like to acknowledge the Researcher's Supporting Project Number (RSP-2021/269) King Saud University, Riyadh, Saudi Arabia, for their support in this work. / The full-text of this article will be released for public view at the end of the publisher embargo on 28 Dec 2023.

Ferroelectric (piezoelectric) and ferromagnetic materials have extensively permeated in modern industry. (Na1/2Bi1/2)TiO3-BaTiO3 (NBT-x%BT) single crystals and K1/2Na1/2NbO3 (KNN) textured ceramics are top environment-friendly candidates which have potential to replace the commercial lead zirconate titanate or PZT. High magnetostrictive strain (up to 400 ppm) of Fe-xat.%Ga makes this alloys promising alternatives to existing magnetostrictive materials, which commonly either contain costly rare-earth elements or have undesirable mechanical properties for device applications. These systems have common characteristics: compositional/thermal/ electrical dependent structural heterogeneity and chemical disorder on sub-micron or nano scale, resulting in diverse local structures and different physical properties. In this work, I have investigated domain and local structures of NBT-x%BT crystals, KNN ceramics and Fe-xat.%Ga alloys under various conditions, mainly by scanning probe and electron transmission techniques. In NBT-x%BT single crystals, polarized light, piezo-response force (PFM) and transmission electron (TEM) microscopies were used to study domain structures and oxygen octahedral tiltings. Hierarchical domain structures were found in NBT: a high-temperature tetragonal ferroelastic domain structure is elastically inherited into a lower temperature rhombohedral ferroelectric phase. Nanoscale domain engineering mechanism was found to still work in NBT-x%BT system and a modified phase diagram was proposed based on domain observations. An increased intensity of octahedral in-phase tilted reflections and a decrease in the anti-phase ones was observed, with increasing x as the morphotropic phase boundary (MPB) is approached. It was also found that Mn substituents favor the formation of long range ordered micro-sized ferroelectric domains and octahedral in-phase tilted regions near the MPB. Nano-size heterogeneous regions were observed within submicron domain structure, indicating that the nanoscale polarization dynamics are not confined by domain boundaries, and the high piezoelectricity of NBT-x%BT is due to a polarization dynamics with high sensitivity to electric field and a broadened relaxation time distribution. In KNN textured ceramics, an aging effect was found to exist in the orthorhombic single phase field, not only in the orthorhombic and tetragonal two-phase field as previously reported. No variation of phase structure was revealed between before and after aging states. However, pronounced changes in domain morphology were observed by both PFM and TEM: more uniform and finer domain structures were then found with aging. These changes were even more pronounced after poling the aged state. A large number of sub-micron lamellar domains within micron-domains were observed: suggesting a domain origin for improved piezoelectric properties. In Fe-xat.%Ga alloys, an underlying inhomogeneity from Ga atoms embedded into the α-Fe matrix was believed to be the origin of giant magneostrictive properties. I have systematically investigated the phase structure and nano-size heterogeneity of Fe-xat.%Ga alloys subjected to different thermal treatments using standard TEM and high resolution TEM for 10<x<30. Nano-precipitates were observed in all specimens studied: A2, D03 and B2 phases were found depending on x. Nano-precipitates of D03 were observed to be dominant for compositions near the magnetostriction peaks in the phase diagram. Quenching was found to increase the volume fraction of nanoprecipitates for x=19, near the first magnetostriction peak. With increasing x to 22.5, nanoprecipitates were observed to undergo a D03 – B2 transformation. A high density of D03 precipitates of nanoscale size was found to be the critical factor for the first maximum in the magnetostriction. / Ph. D.

The adsorption behavior of silicic acid and arsenite alone and competitively on goethite over a broad pH range (3-11) at environmentally relevant concentrations was investigated utilizing pH adsorption data and zeta potential measurements. Both addition scenarios (Si before As(III) and As(III) before Si) were examined. The results of the adsorption experiments and zeta potential measurements were then used to model the single ion and competitive ion adsorption on goethite with the CD-MUSIC model implemented in the FITEQL 4.0 computer program. Silicic acid adsorption was reduced by the presence of arsenite for all but one of the adsorption scenarios examined, while in contrast silicic acid had little effect upon arsenite adsorption. However, the presence of silicic acid, regardless of the addition scenario, dramatically increased the arsenite equilibrium solution concentration over the entire pH range investigated. The CD-MUSIC model was able to predict the single ion adsorption behavior of silicic acid and arsenite on goethite. The modeled zeta potential data provided further evidence of the CD-MUSIC model's ability to describe the single anion adsorption on goethite. Our model was also able to collectively describe adsorption and zeta potential data for the low Si-arsenite adsorption scenario quite well however, our model under-predicted silicic acid adsorption for the high Si-arsenite competitive scenario. / Master of Science