616 research outputs found

    Dynamic and Static Behavior of Hollow-Core FRP-Concrete-Steel and Reinforced Concrete Bridge Columns under Vehicle Collision

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    This paper presents the difference in behavior between hollow-core fiber reinforced polymer-concrete-steel (HC-FCS) columns and conventional reinforced concrete (RC) columns under vehicle collision in terms of dynamic and static forces. The HC-FCS column consisted of an outer FRP tube, an inner steel tube, and a concrete shell sandwiched between the two tubes. The steel tube was hollow inside and embedded into the concrete footing with a length of 1.5 times the tube diameter while the FRP tube stopped at the top of footing. The RC column had a solid cross-section. The study was conducted through extensive finite element impact analyses using LS-DYNA software. Nine parameters were studied including the concrete material model, unconfined concrete compressive strength, material strain rate, column height-to-diameter ratio, column diameter, column top boundary condition, axial load level, vehicle velocity, and vehicle mass. Generally, the HC-FCS columns had lower dynamic forces and higher static forces than the RC columns when changing the values of the different parameters. During vehicle collision with either the RC or the HC-FCS columns, the imposed dynamic forces and their equivalent static forces were affected mainly by the vehicle velocity and vehicle mass

    Concrete-Filled-Large Deformable FRP Tubular Columns under Axial Compressive Loading

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    The behavior of concrete-filled fiber tubes (CFFT) polymers under axial compressive loading was investigated. Unlike the traditional fiber reinforced polymers (FRP) such as carbon, glass, aramid, etc., the FRP tubes in this study were designed using large rupture strains FRP which are made of recycled materials such as plastic bottles; hence, large rupture strain (LRS) FRP composites are environmentally friendly and can be used in the context of green construction. This study performed finite element (FE) analysis using LS-DYNA software to conduct an extensive parametric study on CFFT. The effects of the FRP confinement ratio, the unconfined concrete compressive strength (ƒc\u27), column size, and column aspect ratio on the behavior of the CFFT under axial compressive loading were investigated during this study. A comparison between the behavior of the CFFTs with LRS-FRP and those with traditional FRP (carbon and glass) with a high range of confinement ratios was conducted as well. A new hybrid FRP system combined with traditional and LRS-FRP is proposed. Generally, the CFFTs with LRS-FRP showed remarkable behavior under axial loading in strength and ultimate strain. Equations to estimate the concrete dilation parameter and dilation angle of the CFFTs with LRS-FRP tubes and hybrid FRP tubes are suggested

    Use of Phenols, Peroxidase and Polyphenoloxidase of Seed to Quantify Resistance of Cotton Genotypes to Damping-off Incited by Fusarium oxysporum

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    A greenhouse test was conducted in 2011 and 2012 growing seasons at Giza Agricultural Research Station to evaluate the reaction of six cotton genotypes to damping-off incited by Fusarium oxysporum. Damping-off incidence on the genotypes ranged from 70-88%. In general, the genotypes could be divided into highly susceptible, susceptible, and moderately susceptible. Data for damping-off incidence and level or activity of some biochemical components (phenols, peroxidase, and polyphenoloxidase) were entered into a computerized linear regression analysis. The analysis contrasted seven predictive models by using the biochemical components, singly or in combination, as biochemical predictors. It was evident that models nos. 2 and 6 were the best models for predicting incidence of damping-off. The superiority of these models was attributed to their high RІ values (0.748 and 0.902, respectively) and the significance of their F. values (P = 0.026 and P = 0.031, respectively). The results of the present study suggest that peroxidase alone or both peroxidase and polyphenoloxidase, which may or may not parts of damping-off resistance mechanisms, can be used as biochemical markers to predict resistance to damping-off incited by F. oxysporum

    An Investigation of Inference of the Generalized Extreme Value Distribution Based on Record

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    In this article, the maximum likelihood and Bayes estimates of the generalized extreme value distribution based on record values are investigated. The asymptotic confidence intervals as well as bootstrap confidence are proposed. The Bayes estimators cannot be obtained in closed form so the MCMC method are used to calculate Bayes estimates as well as the credible intervals. A numerical example is provided to illustrate the proposed estimation methods developed here. Keywords: Generalized extreme value distribution, Record values, Maximum likelihood estimation, Bayesian estimation

    Some Features of Joint Confidence Regions for the Parameters of the Inverse Weibull Distribution

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    In this paper, we will study the joint confidence regions for the parameters of inverse Weibull distribution in the point of view of record values. One of the applications of the joint confidence regions of the parameters is to find confidence bounds for the functions of the parameters. Joint confidence regions for the parameters of extreme value distribution are also discussed. In this way we will discus some numerical examples with real data set and simulated data, to illustrate the proposed method. A simulation study is performed to compare the proposed joint confidence regions. Keywords: The joint confidence regions, confidence bounds; inverse Weibull distribution, extreme value distribution

    Torsional Behavior of Hollow-Core FRP-Concrete-Steel Bridge Columns

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    This paper presents the behavior of hollow-core fiber reinforced polymer-concrete-steel (HC-FCS) column under pure torsion loading with constant axial load. The HCFCS consists of outer FRP tube and inner steel tube with concrete shell sandwiched between the two tubes. The FRP tube was stopped at the surface of the footing and provided confinement to the concrete shell from outer direction. The steel tube was embedded into the footing to a length of 1.8 times to the diameter of the steel tube. The longitudinal and transversal reinforcements of the column were provided by the steel tube only. A large-scale HC-FCS column with a diameter of 610 mm and height of applied load of 2,438 mm with aspect ratio of 4 was investigated during this study. The study revealed that the torsional behavior of HC-FCS column mainly depended on the stiffness of the steel tube and the interactions among the column components (concrete shell, steel tube, and FRP tube)

    Hollow-Core FRP-Concrete-Steel Bridge Columns under Torsional Loading

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    This paper presents the behavior of hollow-core fiber-reinforced polymer-concrete-steel (HC-FCS) columns under cyclic torsional loading combined with constant axial load. The HC-FCS consists of an outer fiber-reinforced polymer (FRP) tube and an inner steel tube, with a concrete shell sandwiched between the two tubes. The FRP tube was stopped at the surface of the footing, and provided confinement to the concrete shell from the outer direction. The steel tube was embedded into the footing to a length of 1.8 times the diameter of the steel tube. The longitudinal and transversal reinforcements of the column were provided by the steel tube only. A large-scale HC-FCS column with a diameter of 24 in. (610 mm) and applied load height of 96 in. (2438 mm) with an aspect ratio of four was investigated during this study. The study revealed that the torsional behavior of the HC-FCS column mainly depended on the stiffness of the steel tube and the interactions among the column components (concrete shell, steel tube, and FRP tube). A brief comparison of torsional behavior was made between the conventional reinforced concrete columns and the HC-FCS column. The comparison illustrated that both column types showed high initial stiffness under torsional loading. However, the HC-FCS column maintained the torsion strength until a high twist angle, while the conventional reinforced concrete column did not

    Endogenous IFNγ in chronic HCV genotype 4 patients treated with PEG-IFNα and ribavirin

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    Introduction: Hepatitis C virus (HCV) infections remain an increasingly prevalent and emergent health problem worldwide, causing a wide spectrum of liver diseases. Combination therapy with pegylated interferon (PEG-IFN) of peginterferon alfa-2a and oral ribavirinis currently recognized as the standard treatment of chronic HCV infection. Several complex immunological mechanisms are involved during the course of HCV treatment using interferons. The role of endogenous interferon gamma (IFNγ) in Egyptian patients infected with chronic HCV and treated with PEG-IFN/ribavirin is uncertain. The goal of this study was to evaluate the association of IFNγ and chronic HCV infection among patients treated with combination therapy of PEG-IFN/ribavirin. Methodology: Samples from 20 patients infected with HCV genotype-4 (HCV-4) and 20 non-infected individuals as healthy controls were used in this retrospective study. IFNγ levels in peripheral blood monocytes were analyzed, along with liver enzyme alanine aminotransferase (ALT) levels, and single nucleotide polymorphism (SNP) of the myxovirus resistance-A (MxA) gene. Results: The results showed that an increase of IFNγ and a decrease of ALT levels in chronic HCV-infected patients after 12 weeks of treatment with combination therapy. Conclusion: Enhanced IFNγ secretion and decreased liver enzyme ALT production are indicative of HCV clearance and improvement of liver function. In addition, the SNP of the MxA gene is an important host genetic factor that independently influenced the response to IFNα in patients with chronic HCV infection, especially in those with a low viral load

    Facies analysis, glauconite distribution and sequence stratigraphy of the middle Eocene Qarara Formation, El-Minya area, Egypt

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    AbstractThe Qarara Formation consists mainly of shale at the base and overlain by limestone at the top. The formation is Middle Eocene (Lutetian) in age. Three sections located at the eastern bank of the Nile River in El-Minya Province have been measured, described, and sampled. These sections from north to south are: Gebel Qarara, El-Sheikh Fadl, and Gebel El-Ahmar.The main microfacies identified in the studied sections are: silty claystone, silty shale, fossiliferous glauconite, glauconitic (green) sand, glauconitic fossiliferous ironstone, glauconitic bioclastic wacke-packstone, glauconitic bioclastic lime-mudstone-wackestone. These microfacies have been deposited in shallow open marine environment.Collectively the studied rocks contain two principal facies: lower argillaceous facies and upper carbonate facies that separated by glauconitic fossiliferous ironstone bed. The lower argillaceous part represents highstand systems tract (HST), whereas the upper carbonate part represents transgressive systems tract (TST). The glauconitic fossiliferous ironstone bed is recognized as a sequence boundary (SB)
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