Na engenharia em geral existem técnicas consagradas de construção e materiais com comportamentos exaustivamente estudados para um melhor aproveitamento de suas características a favor do engenheiro. Pode-se dizer que uma construção está cada vez mais integrada com o meio ambiente, tanto na economia de materiais quanto no reaproveitamento dos mesmos. O uso mais racional dos materiais também é uma importante alternativa para minimizar custos em uma obra, tais como transporte, escolha do material mais adequado a ser utilizado, tanto por suas características quanto por sua disponibilidade de uso. Já foram realizadas e ainda hoje têm sido realizadas inúmeras pesquisas sobre solos artificialmente cimentados na Universidade Federal do Rio Grande do Sul, visando seu emprego como camada de suporte para fundações superficiais, no encapsulamento de solos contaminados e como barreiras de contenção de contaminação. Analisando as características mecânicas de areia fina artificialmente cimentada, o objetivo desta pesquisa é verificar a validade do uso do fator vazios/cimento na estimativa da resistência à compressão simples, rigidez inicial, resistência à compressão triaxial em condições drenadas com medidas de G0, comportamento tensão-dilatância e comportamento tensão-deformação da areia de Osório. Para tanto foi verificado que o fator vazios/cimento mostrou-se ser um parâmetro muito eficaz e confiável no que diz respeito à previsão de comportamento do material para dosagem de solo-cimento, em projetos geotécnicos que utilizem a areia de Osório. / In traditional engineering, there are special construction techniques and exhausted studies in materials behavior, for a better employment of it due to the characteristics by the engineer. Today, constructions are increasingly integrated in the environment, both in the economy as in the reuse of materials from them. The more rational use of materials is also important alternative to minimize costs in a work such as transportation, choice of the most appropriate material to be used, either by their characteristics, or their availability for use. Many researches have been made until today on artificially cemented soils in the Federal University of Rio Grande do Sul, targeting their employment as layer of support for foundations surface in the encapsulation of contaminated soil and barriers of contamination containment. Analyzing the mechanical characteristics of fine artificially cemented sand, the objective of this research is to verify the validity of the use of the void/cement ratio in the estimation of the unconfined compressive strength, initial stiffness, triaxial compressive strength in drained conditions with measures of shear modulus (G0), stress-dilatancy behavior and stress-strain behavior of the Osório sand. Thus was verified that the void/cement ratio has proven to be a very effective and reliable parameter regarding prediction of material behavior for soil-cement, dosage in geotechnical projects that use the sand of Osório.

Na engenharia geotécnica o principal material utilizado, o solo, é complexo e muito variável, sendo que nem sempre satisfaz as necessidades da obra a ser realizada. Com a constante busca de soluções que proporcionem melhoria no solo, redução de custos e preservação dos recursos naturais, o aproveitamento de resíduos vem se destacando, como é o caso da utilização da cinza volante na estabilização de solos com cal. Contudo, ainda não existem metodologias de dosagem dessas misturas baseadas em critérios mais racionais, como a relação água/cimento para o concreto. Assim, esta pesquisa tem como objetivo quantificar a influência das variáveis de interesse quantidade de cal, quantidade de cinza volante, porosidade e do tempo de cura sobre a resistência de um solo estabilizado com cal e cinza volante, verificando a adequação do uso da relação vazios/cal na estimativa da resistência à compressão simples destas misturas. Para isso foram realizados ensaios de compressão simples e medidas de sucção matricial. Os resultados demonstram que o aumento da quantidade de cal e cinza volante, do peso específico aparente seco e do tempo de cura provoca o aumento da sua resistência à compressão simples. Sendo que, a resistência à compressão simples cresce linearmente com o aumento da quantidade de cal e exponencialmente com a redução da sua porosidade. Assim, verifica-se que, a relação vazios/cal, definida pela razão entre a porosidade da mistura compactada e o teor volumétrico de cal, ajustado por um expoente, demonstra ser um parâmetro adequado na estimativa da resistência à compressão simples das misturas estudadas. Além disso, a existência de relações únicas e distintas no controle da resistência à compressão simples do solo estudado em função da porosidade, do teor volumétrico de cal e da quantidade de cinza volante para 28, 60 e 90 dias de cura mostrou-se muito eficiente para relações de dosagem. Contudo, a análise estatística dos dados obtidos em um experimento é de extrema importância. Uma metodologia utilizada para analisar estes dados é a metodologia de Projeto de Experimentos, que é apoiada fortemente em conceitos estatísticos, destinada a otimizar o planejamento, a execução e análise de um experimento. Assim, a análise a ser realizada neste experimento baseia-se em um projeto fatorial completo que investiga todas as combinações de níveis dos fatores controláveis quantidade de cal, quantidade de cinza volante, porosidade e tempo de cura. Os resultados demonstram, a partir da análise da variância, que todos os fatores controláveis escolhidos no experimento são significativos, bem como todas as interações entre eles. A metodologia de Projeto de Experimentos mostrou-se eficiente na determinação de quais fatores intervenientes são importantes para o fenômeno em estudo. / The main material used in the geotechnical engineering, the soil, is complex and highly variable, and does not always meet the needs of the work to be performed. With the constant search for solutions that provide soil improvement, costs reduction and natural resources preservation, the waste recovery has been increasing, such as the use of fly ash in the soils stabilization with lime. However, there are still no dosage methods of these mixtures based on more rational criteria such as the water/cement ratio for the concrete. Thus, this research aims to quantify the influence of variables of interest lime amount, the fly ash quantity, porosity and curing time on the strength of soil stabilized with lime and fly ash, verifying the adaptation of the use of the voids/lime ratio in the estimation of unconfined compression strength of these mixtures. Unconfined compression strength tests and measurement of matric suction were carried out in present work. The results show that increasing lime and/or fly ash amount, dry unit weight and curing time has as consequence the increase of unconfined compression strength. Unconfined compression strength increases linearly with the increase of lime amount and exponentially with the reduction of its porosity. The voids/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 unconfined compression strength of the soil-ash-lime studied. Furthermore, the existence of unique and distinct relationships in the control of unconfined compression strength of the soil studied as a function of porosity, lime volumetric content and fly ash quantity for 28, 60 and 90 days of curing was very efficient for dosage relationships. However, the statistical analysis of data from an experiment is utmost importance. A methodology to analyze these data is the methodology of Design of Experiments, which is strongly supported by statistical concepts, designed to optimize the planning, the implementation and analysis of an experiment. The analysis to be performed in this experiment is based on a complete factorial design to investigate all combinations of levels of controllable factors lime amount, fly ash quantity, porosity, and time curing. The results show, from the analysis of variance, that all controllable factors chosen in the experiment and all interactions between them are significant. The methodology of Design of Experiments was efficient in determining which involved factors are important for the phenomenon under study.

Following chemo-mechanical cleaning of the root canal system, the provision of a fluid-tight seal is one of the main requirements for successful endodontic treatment. Gutta percha with a sealer has been considered as the gold standard root canal filling for many years. However, it does not have all the properties of an ideal root canal filling. A resin-based root filling, Resilon, has been introduced which has the advantage of bonding to the root canal dentine forming a “monoblock”. Different properties of Resilon have been investigated, but some properties using different obturation techniques and in retreatment need further investigation. The aim of this project was to investigate selected properties of Resilon in primary endodontic treatment (quality of obturation using either cold lateral condensation or thermal compaction, and push-out bond strength following the use of different intracanal medicaments) and secondary endodontic treatment (removability using a combination of hand and rotary instrumentation, fracture resistance and leakage resistance following different removal techniques).Using micro-CT, the volume of voids in root canals obturated with Resilon in comparison with gutta percha using either cold lateral condensation or thermal compaction was investigated. The results showed that there was no significant difference between the two materials regardless of the obturation technique. The use of Vitapex and iodoform was found to significantly reduce the bond strength of Resilon to dentine in comparison with calcium hydroxide and its aqueous combination with iodoform (Calcipast1). The effectiveness of the combined use of hand K-files and ProTaper retreatment files in removal of Resilon using either cold lateral condensation or thermal compaction was compared to that of gutta percha. Micro-CT assessment showed that Resilon resulted in significantly more remaining material than gutta percha when thermal compaction was used. Fracture resistance of retreated roots filled with Resilon was found to be not significantly different from those filled with gutta percha irrespective to the removal technique (either hand K-files or ProTaper retreatment files). Using the same retreatment techniques, dye leakage resistance of root canals re-filled with Resilon was compared with that of primarily treated root canals. The results showed that there was no significant difference in leakage resistance between re-treated and primarily treated root canals. Obturation with Resilon was shown to have no significant advantage over gutta percha in terms of quality of obturation and fracture resistance in retreated roots. More investigation of the clinical performance of Resilon is required before it can be considered as a replacement for gutta percha.

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The X-ray computed tomography is a technology to investigate air void structure of drilled asphalt cores, which provides a non-destructive alternative to traditional laboratory methods, usually destructive testing.In this work, six in-situ specimens from a double layer porous asphalt pavement in Linköping, Sweden, were taken and analysed using both qualitative and quantitative methods of tomography. The qualitative study focused on identifying different features of the drilled cores, such as densification and air voids in the interface between the two porous layers. In the quantitative study, the air voids contents were quantified from processed tomography images. The tomography results of air voids content in all three directions (X, Y and Z), when increasing the calculated number of slices from 4 to 8, were compared to the measured air voids contents from a standardized laboratory method. Both t-test and F-test were applied to determine if a significant difference was found. Besides, the Evaluation Index (EI) was introduced to determine the most accurate combination slices and directions.The results shown here indicate that a reduced number of tomography slices can give enough accuracy in the determination of air voids content for the porous layers. The results also showed that air voids content determined with tomography gave no significant difference compared to the laboratory results. The most accurate combination found was, in this case, the Y+Z direction. Future development will focus on automatizing the determination of air voids, as well as mastic and aggregate phases using the same methodology of comparing tomography results with laboratory results.

<p dir="ltr">The effects of geometric features on detonation behavior have been well documented and demonstrated through examples spanning large-scale shaped charges to microscale “hot spots”. While extensive research has characterized interactions at either of these extremes – the macroscale (> 1 mm) and the microscale (< 0.1 μm) – the mesoscale (0.1 μm to 1 mm) remains less understood due to historical difficulties associated with producing and studying mesoscale features. Recent advancements in additive manufacturing have begun to change this by enabling the ability to precisely generate structures with such features, generating significant research interest. Experimental studies are hindered, however, by a dependence on diagnostic techniques that have high equipment costs, significant infrastructure requirements, and rely on sophisticated timing techniques, all of which inhibit progress. This work demonstrates the use of witness plates to characterize mesoscale features in a more cost and time-efficient way, speeding up experimentation while maintaining repeatability. The results reveal that mesoscale features cause unique damage that can be easily interpreted with tests conducted at optimal standoff distances. Non-optimal standoff distances can cause this damage to be obscured by the formation of a large underlying crater or significant surface texturing caused by the bulk explosive.</p>

Yes / Much of the existing scholarly works portray institutional voids (IVs) in emerging economies as impeding forces against the development of new ventures. However, little attention has been paid to how such voids generate positive outcomes in emerging market new ventures. Drawing on the institutional theory, we propose IVs as crucial enablers of new venture internationalization. In addition, we investigate both how and when IVs enhance the degree to which new ventures internationalize by examining international learning effort (ILE) as a mediator and two domestic market environmental factors (i.e., environmental dynamism and competitive intensity) as important contingencies. We test our moderated mediation model using primary data gathered from 211 new ventures from Ghana. We found that ILE mediates the relationship between IVs and new venture internationalization and that both environmental dynamism and competitive intensity moderate the indirect relationship between home-country IVs and new venture internationalization. We discuss the theoretical and practical implications of this study.

Yes / This study examines the governance attributes of post-IPO (initial public offering) retained ownership of private equity in business group constituent firms in contrast to their unaffiliated counterparts, in 202 newly listed firms in 22 emerging African economies. We adopt an actor centered institutional-theoretic perspective in rationalizing institutional voids and the advantages of maintained governance by both business angels (BA) and venture capital (VC) private equity. Our findings reveal private equity retain higher post-IPO ownership in business group constituents compared to unaffiliated firms and that this is inversely moderated in the context of improving institutional quality – where this is particularly strong in case of foreign VC as opposed to domestic VC or BA. Our result adds to the literature on multifocal corporate governance mechanisms and the institutional determinants of private equity investment.

Yes / In this conceptual paper, we respond to the calls for broader theoretical approaches that can coherently demonstrate a high degree of conceptual sensitivity to multiple combinations of institutional factors influencing women's informal entrepreneurship (WIE) and related agency. We do so by integrating constructs of gender and gender inequality with those of institutional logics and institutional voids. We find that a refined understanding of institutional voids is required to pave the way for a meaningful theoretical integration and empirical application of the related conceptualizations. We offer such a revised definition by placing formal and informal logics (rather than institutions) at the heart of it. In our theorizing, we propose that gender interplaying with formal and informal institutional logics create varying degrees of obscure and unique institutional voids that shape WIE prevalence. The proposed harmonized theoretical lens provides researchers with flexible yet consistent guidance for conducting context-specific empirical work that can coherently advance understanding of underlying logics shaping WIE and related agency. / Research Development Fund Publication Prize Award winner, Jan 2023.