O presente estudo refere-se a uma das deteriorações mais freqüentes nas estruturas de concreto armado: a ação da carbonatação. Para essa verificação construiu-se uma câmara de carbonatação acelerada, que foi calibrada, com a finalidade de estudar o processo de carbonatação em corpos-de-prova executados em concreto e argamassa com cimentos CP V ARI Plus e CP V ARI RS com e sem adição de sílica ativa, curados em câmara úmida por sete dias e posteriormente expostos à atmosfera agressiva de gás carbônico por 7, 14, 28, 63 e 91 dias. Também foram executados corpos-de-prova semelhantes (controle), os quais foram ensaiados à compressão axial e à compressão diametral para determinação da resistência à compressão, tração e medida da profundidade de carbonatação. A partir destes resultados é ajustado um modelo teórico experimental para previsão da profundidade de carbonatação em função do tempo. Observa-se que para todas as composições estudadas a profundidade de carbonatação é pequena. Analisa-se também, a influência da carbonatação no ganho da resistência mecânica das argamassas e dos concretos, e o efeito da adição de sílica ativa e do tipo de cimento no fenômeno de carbonatação. Finalizando, é apresentada uma justificativa dos resultados com base no banco de dados existente no LMABC-SET-EESC-USP. / The present study refers to one of the most frequent deterioration in reinforced concrete structure: the action of carbonation. For this, an accelerated carbonation chamber was built and gauged in order to study the carbonation process in concrete and mortar specimens with CP V ARI Plus and CP V ARI RS cements, with and without silica fume addition. The specimens were cured in a humidity chamber for seven days and exposed to aggressive atmosphere of carbonic gas for 7, 14, 28, 63 and 91 days. Similar specimens of control were also manufactured and left in humidity chamber during the same periods. These specimens were tested an axial compression and splitting tensile strength to determine the compression and tensile strength and the carbonation depth. From all the obtained results an experimental theoretical model was forecasted to determine the depth carbonation in function of time. It is observed that all the depths carbonation measured is small. The carbonation influence on mechanical resistance gain of the mortar and concrete, as well as the effect addition of both of silica fume and cement type on the phenomenon of carbonation is also analyzed. Finally, it is presented a justification of results based on the existent database at LMABC-SET-EESC-USP.

Roofs are the most vulnerable part of the building envelope that often get damaged when subjected to hurricane winds. Damage to the roofs has a devastating impact on the entire structure, including interior losses and service interruptions. This study aimed at the development of a novel light-weight composite flat roof system for industrial, commercial and multi-story residential buildings to withstand Category 5 hurricane wind effects based on the Florida Building Code requirements for hurricane-prone regions, the strictest wind design code in the United States. The proposed roof system is designed as a combination of two advanced materials: ultra-high performance concrete (UHPC), reinforced with high strength steel (HSS). The novel combination of these two materials in a specially designed cross section led to a lightweight low-profile ultra-thin-walled composite roof deck, with only 17 pounds per square foot self-weight, 4-inch overall depth and only ¾-inch thick flanges and webs, with no shear reinforcement or stirrup. Two groups of specimens, single-cell and multi-cell, were fabricated and tested in four-point flexure to determine the ultimate bending capacity and ductility of the system. Each group of specimens included two short-span (9 ft.) samples (due to the laboratory constraints) -- one specimen subjected to positive bending and the other one subjected to negative bending, representing the critical loading conditions including the effects of wind pressures. All specimens exhibited pure flexural failure in a ductile behavior and with no sign of shear failure. Finite element models of laboratory specimens were also developed and calibrated based on experimental data in order to project the performance of the system for larger and more realistic spans. The experimental work and the finite element analyses showed that the proposed roof system with its given section has adequate flexural and shear strength, and also meets serviceability requirements for a 20-foot long span. Moreover, connections for the roof system were proposed, including panel-to-panel connections and roof-to-wall connections. In addition to safety, the other advantages of the proposed roof system in comparison to the equivalent reinforced concrete roofs include a three-fold reduction in self-weight, a three-fold reduction in overall profile height, and a five-fold reduction of steel reinforcement. Together, these advantages may lead to an increased span length beyond what is typically feasible for the conventional reinforced concrete slabs. All these features translate the proposed deck to a sustainable roof system.

This thesis presents the author's contribution <p>to the design and implementation of COOLFluiD,<p>an object oriented software platform for <p>the high performance simulation of multi-physics phenomena on unstructured grids. In this context, the final goal has been to provide a reliable tool for handling high speed aerothermodynamic <p>applications. To this end, we introduce a number of design techniques that have been developed in order to provide the framework with flexibility<p>and reusability, allowing developers to easily integrate new functionalities such as arbitrary mesh-based data structures, numerical algorithms (space discretizations, time stepping schemes, linear system solvers, ),and physical models. <p>Furthermore, we describe the parallel algorithms <p>that we have implemented in order to efficiently <p>read/write generic computational meshes involving <p>millions of degrees of freedom and partition them <p>in a scalable way: benchmarks on HPC clusters with <p>up to 512 processors show their effective suitability for large scale computing. <p>Several systems of partial differential equations, <p>characterizing flows in conditions of thermal and <p>chemical equilibrium (with fixed and variable elemental fractions)and, particularly, nonequilibrium (multi-temperature models) <p>have been integrated in the framework. <p>In order to simulate such flows, we have developed <p>two state-of-the-art flow solvers: <p>1- a parallel implicit 2D/3D steady and unsteady cell-centered Finite Volume (FV) solver for arbitrary systems of PDE's on hybrid unstructured meshes; <p>2- a parallel implicit 2D/3D steady vertex-centered Residual Distribution (RD) solver for arbitrary systems of PDE's on meshes with simplex elements (triangles and tetrahedra). <p>The FV~code has been extended to handle all <p>the available physical models, in regimes ranging from incompressible to hypersonic. <p>As far as the RD code is concerned, the strictly conservative variant of the RD method, denominated CRD, has been applied for the first time in literature to solve high speed viscous flows in thermochemical nonequilibrium, yielding some preliminary outstanding results on a challenging double cone flow simulation. <p>All the developments have been validated on real-life testcases of current interest in the aerospace community. A quantitative comparison with experimental measurements and/or literature has been performed whenever possible. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

The overall objective of this study was to develop an optimised Ultra-High-Performance Concrete (UHPC) matrix based on the modified Andreasen and Andersen optimum particle packing model by using available South African materials. The focus of this study was to determine the optimum combined fibre and superplasticiser content for UHPC by using a response surface design. The UHPC was appropriately designed, produced and tested. Various changes in mechanical properties resulting from different combinations of steel fibre and superplasticiser contents was investigated. The flowability, density and mechanical properties of the designed UHPC were measured and analysed. Both the fibre and superplasticiser content play a significant role in the flowability of the fresh concrete. The addition of fibres significantly improved the strength of the concrete. The results show that the superplasticiser content can be increased if a more workable mix is required without decreasing the strength significantly. The statistical analysis of the response surface methodology confirms that the designed models can be used to navigate the design space defined by the Central Composite Design. The optimum combined fibre and superplasticiser content depend on the required mechanical properties and cost. Using the modified Andreasen and Andersen particle packing model and surface response design methodology, it is possible to efficiently produce a dense Ultra-High-Performance Fibre Reinforced Concrete (UHPFRC) with a relatively low binder amount, low fibre content and good workability. The effect of heat curing on the mechanical properties was investigated. It was concluded that heat curing is not recommended when considering the long-term strength development. The estimated strength development of concrete obtained by using the fib Model Code 2010 (2013) does not incorporate the detrimental effect of high curing temperatures on long-term strength and therefore overestimate the long-term strengths. The strength estimates for both early and long-term ages can be improved by considering this effect in the strength development functions obtained from fib Model Code 2010 (2013). The effect of specimen size on the compressive and flexural tensile strength of UHPFRC members were established. It was found that the specimen size has a significant effect on the measured cube compressive strength. Smaller beam specimens showed higher ductility compared to those of the larger beam specimens. The crack width decreased as the beam’s depth decreased. A lower variability was experienced in the beams with limited depth (< 45 mm). Further testing is required to determine whether a span-to-depth ratio of 10 would yield optimum results. The utilisation of by-products, such as undensified silica fume and fly ash, as cement replacement materials makes UHPFRC sustainable, leading to a reduced life-cycle cost. The calculated Embodied Energy per unit strength (EE/unit strength) and Embodied Carbon per unit strength (EC/unit strength) values for the UHPFRC mixture yield lower values compared to that of the 30 MPa concrete mixture, indicating that UHPFRC can be used to reduce the environmental footprint of the concrete industry. The inverse analysis method used was successful in providing an improved simplified stress-strain response for the UHPFRC. The analysis provided valuable information into the stress-strain, load-deflection and moment-curvature responses of the UHPFRC. Standard material test results were used to theoretically calculate moment-curvature responses and were then compared to the experimental results obtained. The study demonstrated that it is possible to efficiently produce a dense and workable UHPFRC with relatively low binder amount and low fibre content. This can result in more cost-effective UHPFRC, thus improving the practical application thereof. / Dissertation (MEng)--University of Pretoria, 2020. / Civil Engineering / MEng (Structural engineering) / Unrestricted

Diese Arbeit basiert auf der Untersuchung von hochfesten und ultrahochfesten Betonen mit und ohne Fasern unter zwei- und dreiaxialer Druckbeanspruchung. Die Auswirkung der unterschiedlichen Betonzusammensetzung ist für verschiedene Beanspruchungen nicht gleich ausgeprägt, dennoch konnten grundlegende Zusammenhänge herausgearbeitet werden. Anhand der Bruchbilder konnten die drei Versagensmechanismen Druck-, Spalt- und Schubbruch identifiziert werden, deren Charakteristik über die Kalibrierung an vier speziellen Versuchswerten direkt in das Bruchkriterium einfließen. Dieses stellt eine Erweiterung der Formulierung von OTTOSEN dar, so dass das spröde und z. T. anisotrope Verhalten von Hochleistungsbeton berücksichtigt wird. Die beobachteten Spannungs-Dehnungs-Verläufe korrelieren mit den Versagensformen. Deshalb wird ein Stoffgesetz getrennt für den Druck- und den Zugmeridian aufgestellt, dessen Parameter sich mit zunehmendem hydrostatischen Druck verändern. In die Anfangswerte fließen die Betonzusammensetzung und herstellungsbedingte Anisotropien ein. Die lastinduzierte Anisotropie infolge einer gerichteten Mikrorissbildung wird in dem vorgestellten Stoffgesetzt über richtungsabhängige Parameter ebenfalls berücksichtigt.

Der GDSW-Vorkonditionierer ist ein zweistufiges überlappendes Schwarz-Gebietszerlegungsverfahren mit einem energieminimierenden Grobraum, dessen parallele Skalierbarkeit durch das direkt gelöste Grobproblem begrenzt ist. Zur Verbesserung der parallelen Skalierbarkeit wurde hier eine mehrstufige Erweiterung eingeführt. Für den Fall skalarer elliptischer Probleme wurde eine Konditionierungszahlschranke aufgestellt. Die parallele Implementierung wurde in das quelloffene ShyLU/FROSch Paket der Trilinos-Softwarebibliothek (http://trilinos.org) integriert und auf mehreren der leistungsstärksten Supercomputern der Welt (JUQUEEN, Forschungszentrum Jülich; SuperMUC-NG, LRZ Garching; Theta, Argonne Leadership Computing Facility, Argonne National Laboratory, USA) für Modellprobleme (Laplace und lineare Elastizität) getestet. Das angestrebte Ziel einer verbesserten parallelen Skalierbarkeit wurde erreicht, der Bereich der Skalierbarkeit wurde um mehr als eine Größenordnung erweitert. Die größten Rechnungen verwendeten mehr als 200000 Prozessorkerne des Theta Supercomputers. Zudem wurde die Anwendung des GDSW-Vorkonditionierers auf ein vollständig gekoppeltes nichtlineare Deformations-Diffusions Problem in der Chemomechanik betrachtet.

Thesis (M.Tech.: Biotechnology)- Dept. of Biotechnology & Food Technology, Durban University of Technology, 2007 xv, 102 leaves / For decades the genus Aspergillus (of fungi) has been classified based on morphological and growth criteria. Members of the Aspergillus section Flavi are economically valuable and methods of differentiating them are thus very important. Several molecular methods have been developed to distinguish these strains. Also, a number of biochemical and genetic studies have been used in order to provide a better means of classification (Lee et al., 2004). Aflatoxins, the most frequently studied mycotoxins, are produced by certain Aspergillus species/strains/isolates of fungi. The aflatoxin biosynthetic pathway studies have led to a number of discoveries. Several structural and regulatory genes (and their enzymes) involved in the biosynthesis of aflatoxins have been discovered and purified (Trail et al., 1995). Aflatoxin production and contamination of agricultural crops are major causes of economic losses in agriculture. Thus, better methods of characterization/differentiation are required for both aflatoxigenic and non-aflatoxigenic isolates. Molecular biology is one of the current tools used to differentiate between these isolates. Polymerase Chain Reaction (PCR)-based randomly amplified polymorphic DNA (RAPD) analysis has been used successfully in the analysis of DNA relatedness of species of fungi, bacteria, plants and animals. Dendograms which evaluate/assess the likeness between different isolates has also been used (Martinez et al., 2001). Restriction fragment length polymorphism (RFLP) analysis has been applied to a number of studies to detect differences between fungi and to establish relationships between them. Therefore, the scope of this study was to investigate RAPD analysis (with dendograms) and detection of RFLPs by hybridization as molecular methods that can distinctly differentiate or characterize the aflatoxigenic and non-aflatoxigenic Aspergillus isolates.

Dissertation submitted in partial compliance with the requirements for the Masters Degree in Technology, 2010. / Water storage dams play an important part in the collection and purification of water destined for human consumption. However, the nutrient rich silt in these dams promotes rapid growth of aquatic plants which tend to block out light and air. Glyphosate is universally used as the effective non-selective herbicide for the control of aquatic plants in rivers and dams. Invariably there is residual glyphosate present in water after spraying of dams and rivers with glyphosate herbicide. The amount of residual glyphosate is difficult to determine on account of high solubility of glyphosate in water. Thus a method of sample preparation and a sensitive HPLC method for the detection of trace amounts of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) in water is required. A crucial step in sample preparation is pre-column derivitization of glyphosate with 9-fluorenylmethyl chloroformate (FMOC-Cl). For sample pretreatment, water samples were derivatized with FMOC-Cl at pH 9, extracted with ethyl acetate and sample clean-up was carried out by passing a sample through the SPE cartridge. For SPE, recovery studies were done to choose a suitable cartridge for glyphosate and AMPA analysis. The following cartridges were compared, namely, C18, Oasis HLB and Oasis MAX SPE cartridges. Best recoveries (101% for glyphosate and 90% for AMPA) were obtained using 500 mg of C18 solid-phase extraction cartridge. The eluent from SPE cartridge was injected into HPLC column. Three types of separation columns (namely; C18 column, silica based amino column and polymeric amino column) were compared for the separation of glyphosate and AMPA. The best separation of glyphosate and AMPA in water samples was achieved using a polymeric amino column and a mobile phase at pH 10 which contained a mixture of acetonitrile and 0.05 M phosphate buffer (pH 10) 55:45, (v/v) respectively. The method was validated by spiking tap water , deionized water and river water at a level of 100 μg/l. Recoveries were in the range of 77% -111% for both analytes. The method was also used in determining the levels of glyphosate and AMPA in environmental samples. This method gave detection limits of 3.2 μg/l and 0.23 μg/l for glyphosate and AMPA respectively. The limits of quantification obtained for this method were 10.5 μg/l and 3.2 μg/l for glyphosate and AMPA respectively. / Eskom Tertiary Education Support Programme (TESP) Durban University of Technology.

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Phylogenetic analysis is the study of evolutionary relationships among organisms. To this end, phylogenetic trees, or evolutionary trees, are used to depict the evolutionary relationships between organisms as reconstructed from DNA sequence data. The likelihood of a given tree is commonly calculated for many purposes including inferring phylogenies, sampling from the space of likely trees and inferring other parameters governing the evolutionary process. This is done using Felsenstein’s algorithm, a widely implemented dynamic programming approach that reduces the computational complexity from exponential to linear in the number of taxa. However, with the advent of efficient modern sequencing techniques the size of data sets are rapidly increasing beyond current computational capability. Parallel computing has been used successfully to address many similar problems and is currently receiving attention in the realm of phylogenetic analysis. Work has been done using data decomposition, where the likelihood calculation is parallelised over DNA sequence sites. We propose an alternative way of parallelising the likelihood calculation, which we call segmentation, where the tree is broken down into subtrees and the likelihood of each subtree is calculated concurrently over multiple processes. We introduce our proposed system, which aims to drastically increase the size of trees that can be practically used in phylogenetic analysis. Then, we evaluate the system on large phylogenies which are constructed from both real and synthetic data, to show that a larger decrease of run times are obtained when the system is used. / AFRIKAANSE OPSOMMING:Filogenetiese analise is die studie van evolusionêre verwantskappe tussen organismes. Filogenetiese of evolusionêre bome word aangewend om die evolusionêre verwantskappe, soos herwin vanuit DNS-kettings data, tussen organismes uit te beeld. Die aanneemlikheid van ’n gegewe filogenie word oor die algemeen bereken en aangewend vir menigte doeleindes, insluitende die afleiding van filogenetiese bome, om te monster vanuit ’n versameling van sulke moontlike bome en vir die afleiding van ander belangrike parameters in die evolusionêre proses. Dit word vermag met behulp van Felsenstein se algoritme, ’n alombekende benaderingwyse wat gebruik maak van dinamiese programmering om die berekeningskompleksiteit van eksponensieel na lineêr in die aantal taxa, te herlei. Desnieteenstaande, het die koms van moderne, doeltreffender orderingsmetodes groter datastelle tot gevolg wat vinnig besig is om bestaande berekeningsvermoë te oorskry. Parallelle berekeningsmetodes is reeds suksesvol toegepas om vele soortgelyke probleme op te los, met groot belangstelling tans in die sfeer van filogenetiese analise. Werk is al gedoen wat gebruik maak van data dekomposisie, waar die aanneemlikheidsberekening oor die DNS basisse geparallelliseer word. Ons stel ’n alternatiewe metode voor, wat ons segmentasie noem, om die aanneemlikheidsberekening te parallelliseer, deur die filogenetiese boom op te breek in sub-bome, en die aanneemlikheid van elke sub-boom gelyklopend te bereken oor verskeie verwerkingseenhede. Ons stel ’n stelsel voor wat dit ten doel het om ’n drastiese toename in die grootte van die bome wat gebruik kan word in filogenetiese analise, teweeg te bring. Dan, word ons voorgestelde stelsel op groot filogenetiese bome, wat vanaf werklike en sintetiese data gekonstrueer is, evalueer. Dit toon aan dat ’n groter afname in looptyd verkry word wanneer die stelsel in gebruik is.

The subject matter of this thesis is governance principles in global management concepts and the application of such principles by managers at a local level. The thesis includes a case study on a foreign-owned Swedish group of companies that has introduced the management concept of High Performance Culture in all of its consolidated group countries. Global management concepts usually originate from the United States and make use of neorational governance principles. High Performance Culture is a management concept that puts increased performance and individualisation in the foreground. In addition, the concept advocates co-determination and self-development. The governance principles further promote employee autonomy orientation and self-development in addition to a leader-centric approach. The case study results indicate a discrepancy in the requirements of the governance principles of the management concept, highlighting the various dimensions of cultural layers and values to which managers in the same organisation are subject. The same values had an effect in different ways on the managers’ interpretation and handling of the management concept. This interpretation and handling of the management concept tools led to an implementation that partially opposed what the French management team and management concept advocated. The managers choosing to oppose the governance principles of the management concept can be seen as an example of modern individualism, according to which people are increasingly questioning rigid and hierarchic authority while showing initiative and assessing one’s own personal work. Hence, the values of modern individualism can act as a counterforce to neorational governance principles. / <p>Akademisk avhandling för avläggande av doktorsexamen i Arbetsvetenskap, som med tillstånd av Fakultetsnämnden vid Fakulteten för humaniora och samhällsvetenskap, vid</p><p>Karlstads universitet framläggs till offentlig granskning fredagen den 25 oktober 2013 kl. 13.00, sal C203, Högskolan i Borås.</p>