128 research outputs found

    Résistance à la torsion de poutres-caissons en béton armé avec des barres d'armature longitudinale et d'armature tranversale constituée de cadres ou de spirales en PRFV

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    Les poutres-caissons en béton armé sont utilisées dans de nombreuses applications de génie civil incluant des ponts suspendus, des ponts piétonniers, des ponts courbes et des structures surélevées modernes pour le transport léger sur rail. L'utilisation de poutres-caissons en béton armé présente des avantages économiques et structurels, tels qu'un faible poids propre et une rigidité à la torsion plus élevée. Cependant de telles structures en béton armé sont généralement exposées à des environnements agressifs et/ou marins, entraînant la corrosion de l'armature en acier. Les barres d'armature en polymère renforcé de fibres (PRF) peuvent être utilisées comme alternative à l'armature d’acier pour éliminer ce problème de corrosion, ce qui permet de réduire les coûts de maintenance et rallonge la durée de vie des ouvrages. À ce jour, le comportement à la torsion de poutres-caissons en béton armé d’armature longitudinale et d’armature transversale en polymère renforcé de fibre de verre (PRFV) n’a pas été traité. Dans la cadre de cette thèse de doctorat, un programme expérimental a été conçu pour étudier le comportement à la torsion de poutres-caissons en béton armé avec des barres d’armature longitudinale et d’armature transversale constituée de cadres ou de spirales en PRFV. Dix-neuf poutres-caissons en béton armé de grandeur nature ayant une largeur de 380 mm, une profondeur de 380 mm, une longueur totale de 4 000 mm et une épaisseur de paroi de 100 mm ont été fabriquées et testées sous un moment de torsion jusqu'à la rupture. Les paramètres d'essai comprenaient la résistance en compression du béton, le taux d’armature longitudinale et le type d’armature (PRFV et acier), ainsi que le taux d’armature transversale et le type d’armature transversale (PRFV et acier sous forme de cadres et spirales). Les résultats des essais ont été analysés en termes de réseau de fissuration, de mode de rupture, de réponse moment-torsion, de déformations de l’armature, de contraintes du béton, et de résistance à la torsion. Un modèle analytique dit «softened membrane model» a été développé pour prédire le comportement en torsion (avant et après la fissuration) des poutres-caissons en béton armé avec des barres d’armature longitudinale et d’armature transversale constituée de cadres ou de spirales en PRFV. L'applicabilité de ce modèle analytique a été vérifiée à l’aide des résultats expérimentaux obtenus dans cette étude. De plus, un modèle Rahal non itératif a été modifié pour prédire la résistance à la torsion de poutres en béton armé, y compris les poutres à section pleine et les poutres-caissons.Abstract: Reinforced concrete (RC) box girders can be found in many civil-engineering applications. The most notable are cable-supported bridges, pedestrian bridges, curved bridges, and modern elevated structures for light rail transport. There are economic and structural benefits of using concrete box girders such as low self-weight of structures and higher torsional stiffness. Such structures are usually exposed to aggressive and/or harsh marine environments, leading to corrosion of the steel reinforcement. This type of corrosion in concrete structures is a prime cause of structural deterioration, particularly in North America, resulting in costly repairs, rehabilitation, and a considerable reduction in service life span. Fiber-reinforced polymer (FRP) reinforcing bars, on the other hand, can be used as an alternative to steel reinforcement to combat corrosion, thereby lowering maintenance costs and extending service life. In recent years, the torsional behavior of RC solid rectangular members reinforced with FRP bars has been the focus of many studies. Accordingly, all available FRP code standards and design guidelines that include torsional provisions were developed based on experimental work on solid rectangular members reinforced with FRP bars and tie stirrups. So far, the torsional behavior and strength of the concrete box girders reinforced with glass-FRP (GFRP) bars, ties, and spirals have not been discussed. In this research study, an experimental program was designed to investigate the torsional behavior of concrete box girders reinforced with GFRP bars, ties, and spiral. Nineteen full-scale RC box girders with a width of 380 mm, a depth of 380 mm, a total length of 4000 mm, and a wall thickness of 100 mm were designed, cast, and examined under pure torsional moment until failure. The torsion span was maintained constant at 2000 mm to ensure that each specimen developed at least one complete helical crack. The test parameters included the concrete strength, the longitudinal reinforcement ratio, and type (GFRP and steel), and the web reinforcement ratio, type (GFRP and steel), and configuration (ties and spirals). The test results were carefully analyzed in terms of cracking patterns, failure modes, torque-twist response, reinforcement strains, concrete strains, torsional strength, and twist capacity. The test results indicated that the stirrup's capacity strongly influenced the torsional strength of the GFRP and steel RC box girders, however, the stirrup stiffness did not affect the ultimate torque. The web reinforcement ratio and configuration had a significant effect on the torsional strength, post-cracking stiffness, and the distribution of diagonal cracks. Compared with normal-strength concrete (NSC), high-strength concrete (HSC) substantially improved the overall torsional performance of the tested specimens. An analytical softened membrane model was developed for predicting the entire torsional behavior (pre-and-post cracking) of concrete box girders reinforced with GFRP bars, ties, and spirals. The applicability of using this model was verified with the experimental results. In addition, a noniterative Rahal model was modified to predict the ultimate torsional strength of FRP-RC members, including solid and hollow members. Moreover, an analytical model was presented to estimate the post-cracking torsional stiffness of GFRP-RC members. Finally, the experimental test results were compared against the current FRP torsional design equations in the design guidelines, codes, and literature

    Use of Microorganisms for the Enrichment of Zn and Se by using Solid-state Fermentation

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    Zinc (Zn) and selenium (Se) are essential minerals for human health and naturally found in many food sources. However, the risk of Zn and Se deficiency has been recognized in several countries. As most people throughout the world consume rice, grains, and cereals as staple foods in their daily diet, which contain a certain amount of phytic acid (antinutrients), the phytic acid content inhibits mineral absorption (Zn and Se) by the human body. Moreover, the low levels of Zn and Se content found in the crop\u27s soil also reduce the amount of minerals in the food sources. Therefore, it is crucial to develop an effective method of naturally supplementing Zn and Se that promotes their absorption. There is yeast, bacteria, fungi, or a combination of these fermented products, enriched with Zn and Se, available in the market. In addition, the fermentation process can reduce the phytic acid content. However, there is no research or data on the application of solid-state fermentation (SSF) for the enhancement of Zn and Se. Therefore, in our study, SSF was applied to determine the amount of Zn and Se uptake by Aspergillus oryzae, Bacillus subtilis, and co-culture. The objectives of the study were to [1] determine the amount of Zn and Se uptake by A. oryzae, B. subtilis, and co-culture in sterile coarsely ground and whole sorghum grain by using solid-state fermentation and [2] measure the amount of phytic acid reduction (antinutrients) in the fermented coarsely ground biomass and whole grain samples containing Zn and Se. The sorghum grain (substrate) was treated with these organisms and supplemented with different concentrations of Zn or Se. After SSF, the samples were analyzed with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The dried substrate was used to analyze the amount of phytic acid present in the grain sorghum after the SSF. The quantification of phytic acid in the substrate was determined using UV/VIS spectroscopy. The results showed that the biological efficiency of the organisms was affected by the addition of different concentrations of Zn and Se. Considering all the concentrations, the highest level of Zn absorption was obtained by adding 50 ÎĽg/g of zinc acetate. In the Se absorption, 3.2 ÎĽg/g of selenium aspartate was efficient. The obtained data show that A. oryzae, B. subtilis and Co-culture can grow in the Zn or Se-containing substrate. SSF process with coarsely ground sorghum grain containing A. oryzae and co-culture significantly reduced the phytic acid content. The results showed that the SSF process with A.oryzae and/or Co-culture positively reduced the phytic acid content, which could help in the proper absorption of Zn and Se by the human body. The fermented biomass could be used as a Zn and Se-enriched ingredient for functional food products

    Use of Microorganisms for the Enrichment of Zn and Se by using Solid-state Fermentation

    Get PDF
    Zinc (Zn) and selenium (Se) are essential minerals for human health and naturally found in many food sources. However, the risk of Zn and Se deficiency has been recognized in several countries. As most people throughout the world consume rice, grains, and cereals as staple foods in their daily diet, which contain a certain amount of phytic acid (antinutrients), the phytic acid content inhibits mineral absorption (Zn and Se) by the human body. Moreover, the low levels of Zn and Se content found in the crop\u27s soil also reduce the amount of minerals in the food sources. Therefore, it is crucial to develop an effective method of naturally supplementing Zn and Se that promotes their absorption. There is yeast, bacteria, fungi, or a combination of these fermented products, enriched with Zn and Se, available in the market. In addition, the fermentation process can reduce the phytic acid content. However, there is no research or data on the application of solid-state fermentation (SSF) for the enhancement of Zn and Se. Therefore, in our study, SSF was applied to determine the amount of Zn and Se uptake by Aspergillus oryzae, Bacillus subtilis, and co-culture. The objectives of the study were to [1] determine the amount of Zn and Se uptake by A. oryzae, B. subtilis, and co-culture in sterile coarsely ground and whole sorghum grain by using solid-state fermentation and [2] measure the amount of phytic acid reduction (antinutrients) in the fermented coarsely ground biomass and whole grain samples containing Zn and Se. The sorghum grain (substrate) was treated with these organisms and supplemented with different concentrations of Zn or Se. After SSF, the samples were analyzed with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The dried substrate was used to analyze the amount of phytic acid present in the grain sorghum after the SSF. The quantification of phytic acid in the substrate was determined using UV/VIS spectroscopy. The results showed that the biological efficiency of the organisms was affected by the addition of different concentrations of Zn and Se. Considering all the concentrations, the highest level of Zn absorption was obtained by adding 50 ÎĽg/g of zinc acetate. In the Se absorption, 3.2 ÎĽg/g of selenium aspartate was efficient. The obtained data show that A. oryzae, B. subtilis and Co-culture can grow in the Zn or Se-containing substrate. SSF process with coarsely ground sorghum grain containing A. oryzae and co-culture significantly reduced the phytic acid content. The results showed that the SSF process with A.oryzae and/or Co-culture positively reduced the phytic acid content, which could help in the proper absorption of Zn and Se by the human body. The fermented biomass could be used as a Zn and Se-enriched ingredient for functional food products

    Hannah Arendt’s Conceptual Framework for the Crisis in Modern Education

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    This work analyzes Hannah Arendt s essay The Crisis in Education published in the late 1950s intending to elucidate its central themes through the concepts presented in other works by the author This intention is a valuable initiative not only because of Arendt s qualifications who is one of the most influential thinkers of the 20th century but also because the essay has fostered research in the area of education and is frequently included in the bibliography of teacher training courses both in undergraduate and graduate levels due to the critical reflections it elaborates on the relationships between adults and children in modernity which includes the exchange between teachers and student

    Multi-omics phenotyping of the gut-liver axis reveals metabolic perturbations from a low-dose pesticide mixture in rats.

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    Health effects of pesticides are not always accurately detected using the current battery of regulatory toxicity tests. We compared standard histopathology and serum biochemistry measures and multi-omics analyses in a subchronic toxicity test of a mixture of six pesticides frequently detected in foodstuffs (azoxystrobin, boscalid, chlorpyrifos, glyphosate, imidacloprid and thiabendazole) in Sprague-Dawley rats. Analysis of water and feed consumption, body weight, histopathology and serum biochemistry showed little effect. Contrastingly, serum and caecum metabolomics revealed that nicotinamide and tryptophan metabolism were affected, which suggested activation of an oxidative stress response. This was not reflected by gut microbial community composition changes evaluated by shotgun metagenomics. Transcriptomics of the liver showed that 257 genes had their expression changed. Gene functions affected included the regulation of response to steroid hormones and the activation of stress response pathways. Genome-wide DNA methylation analysis of the same liver samples showed that 4,255 CpG sites were differentially methylated. Overall, we demonstrated that in-depth molecular profiling in laboratory animals exposed to low concentrations of pesticides allows the detection of metabolic perturbations that would remain undetected by standard regulatory biochemical measures and which could thus improve the predictability of health risks from exposure to chemical pollutants

    Big Data Management in Education Sector: an Overview

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    The advancement in technological innovation has given rise to a new trend known as Big Data today. Given the soaring popularity of big data technology, organisations are profoundly attracted to and interested in it to transform their organisation by improving their businesses. Big data is enabling organisations to outpace their competitors and save cost. Similarly, the application of Big Data management in Universities is an essential aspect to institutions that have Big Data to manage; as the use of Big Data in the higher education sector is increasing day by day. Many studies have been carried out on big data and analytics with little interest in its management. Big Data management is a reality that represents a set of challenges involving Big Data modeling, storage, and retrieval, analysis, and visualization for several areas in organizations. This paper introduces and contributes to the conceptual and theoretical understanding of Big Data management within higher education as it outlines its relevance to higher education institutions. It describes the opportunities this growing research area brings to higher education as well as major challenges associated with it

    Big Data Management in Education Sector: an Overview

    Get PDF
    The advancement in technological innovation has given rise to a new trend known as Big Data today. Given the soaring popularity of big data technology, organisations are profoundly attracted to and interested in it to transform their organisation by improving their businesses. Big data is enabling organisations to outpace their competitors and save cost. Similarly, the application of Big Data management in Universities is an essential aspect to institutions that have Big Data to manage; as the use of Big Data in the higher education sector is increasing day by day. Many studies have been carried out on big data and analytics with little interest in its management. Big Data management is a reality that represents a set of challenges involving Big Data modeling, storage, and retrieval, analysis, and visualization for several areas in organizations. This paper introduces and contributes to the conceptual and theoretical understanding of Big Data management within higher education as it outlines its relevance to higher education institutions. It describes the opportunities this growing research area brings to higher education as well as major challenges associated with it

    Students’ Perceptions of Their Teachers’ Performance in Teaching Engineering Drawing in Nigerian Tertiary Institutions

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    There have been concerns about the performance of Nigerian school teachers’ in delivering occupational related courses. However, there are currently limited empirical data on this phenomenon – in particular with respect to the teaching of engineering drawing – to justify further actions from educational managers and policy makers. The aim of this study was to assess teachers’ performance in teaching engineering drawing using students’ perception as indicator of teachers’ performance. The study utilized a cross-sectional research design method with the target population of technical education students drawn from four (4) Federal Colleges of education (Technical) in Northern Nigeria. Stratified proportionate sampling technique was used to arrive at the study sample of 253 technical education students. A specifically designed instrument, the Students’ Perceptions of Teachers’ Performance Scales (SPTPS) was used to gather data on the three performance dimensions namely contextual, task and adaptability performance. The exploratory factor analysis and confirmatory factor analysis methods were conducted to validate the performance constructs. The instrument has a high reliability of 0.90 based on the Cronbach Alpha method. The result of the analysis using estimation method indicates that students perceive their teachers’ performance to be at a slightly above average level (M= 3.51 ± 0.05 at the 95% confidence level). The teachers’ task performance, in particular, is found to be the least developed among the three dimension of performance while their adaptability performance is the highest while still being less than excellent. The data support the conclusion that there are aspects of teachers’ performance in teaching engineering drawing that is less than excellent and in need of further enhancements

    The evaluation of geochemical analysis techniques for forensic provenance and interpretation

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    This thesis investigates the feasibility of geochemical analysis techniques in forensic investigation, the issues associated with interpreting mixed provenance geochemical evidence and factors that could potentially influence the conclusions drawn. Two forensically relevant locations in the UK were selected for the study. Within these locations three sites were selected with differing land-use characteristics to assess the feasibility of X-ray Fluorescence Spectroscopy, Inductively Coupled Plasma-Atomic Emission Spectroscopy, Inductively Coupled Plasma-Mass Spectroscopy, Isotope Ratio Mass Spectroscopy and Quantitative Evaluation of Materials by Scanning Electron Microscopy techniques in distinguishing between geographically similar samples. The ability of these techniques to provide intelligence from material recovered from exhibits that are pertinent to a forensic investigation, e.g. footwear, was also assessed through the analysis of artificially created mixtures containing material from these sites. Sampling was conducted at quarterly intervals over a 12 month period to monitor the degree of temporal variation between samples from each site. Additionally, differences in the plastic sample bag packaging and storage conditions were explored to identify the optimum packaging, sample state, storage temperature and storage duration for soil/sediment material that is to undergo chemical analysis. Statistical analysis of the geochemical data revealed inter-site variation to be significant while intra-site variation and temporal variance was non-significant at each location and no significant difference was identified between packaging material, storage conditions and storage duration. The interpretation of mixed provenance samples was far more complex and identified the potential for false negative and false positive conclusions to be drawn. This thesis presents the first systematic empirical data set that addresses the issue of mixed and single source sample comparison by geochemical analysis, outlines a procedure for the hand ling of geological evidence, and provides a basis upon which to build future research that addresses the interpretation issues that have been identified

    Students’ Perceptions of Their Teachers’ Performance in Teaching Engineering Drawing in Nigerian Tertiary Institutions

    Get PDF
    There have been concerns about the performance of Nigerian school teachers’ in delivering occupational related courses. However, there are currently limited empirical data on this phenomenon – in particular with respect to the teaching of engineering drawing – to justify further actions from educational managers and policy makers. The aim of this study was to assess teachers’ performance in teaching engineering drawing using students’ perception as indicator of teachers’ performance. The study utilized a cross-sectional research design method with the target population of technical education students drawn from four (4) Federal Colleges of education (Technical) in Northern Nigeria. Stratified proportionate sampling technique was used to arrive at the study sample of 253 technical education students. A specifically designed instrument, the Students’ Perceptions of Teachers’ Performance Scales (SPTPS) was used to gather data on the three performance dimensions namely contextual, task and adaptability performance. The exploratory factor analysis and confirmatory factor analysis methods were conducted to validate the performance constructs. The instrument has a high reliability of 0.90 based on the Cronbach Alpha method. The result of the analysis using estimation method indicates that students perceive their teachers’ performance to be at a slightly above average level (M= 3.51 ± 0.05 at the 95% confidence level). The teachers’ task performance, in particular, is found to be the least developed among the three dimension of performance while their adaptability performance is the highest while still being less than excellent. The data support the conclusion that there are aspects of teachers’ performance in teaching engineering drawing that is less than excellent and in need of further enhancements
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