Jute and luffa fiber-reinforced biocomposites: Effects of sample thickness and fiber/resin ratio on sound absorption and transmission Loss Performance

The acoustic properties of natural fiber-reinforced composites should be identified before using these materials in various engineering applications including sound and vibration isolation. This study investigates the effects of sample thickness and fiber/resin ratio on the acoustic performance of jute and luffa fiber-reinforced biocomposites. For this purpose, jute and luffa composite samples with different thicknesses and fiber/epoxy ratios are manufactured and their sound absorption coefficients (SACs) and transmission losses (TLs) are determined using impedance tube method. Thickness-dependent tendencies of the SACs and TLs of jute and luffa composites for low-, medium-, and high-frequency ranges are identified. The effect of fiber/epoxy ratio on the acoustic properties of jute and luffa composites as a function of frequency are determined. Furthermore, the SACs and TLs of some natural fiber-based samples with different thicknesses are predicted using mathematical models and the theoretical and experimental results are compared and evaluated.TUBITAK (The Scientific and Technological Research Council of Turkey) under Grant 119M115.WOS:000638569100001Scopus - Affiliation ID: 60105072Science Citation Index ExpandedQ1Article; Early AccessUluslararası işbirliği ile yapılmayan - HAYIRNisan2021YÖK - 2020-2

Symmetric Teleparallel Gravity: Some exact solutions and spinor couplings

In this paper we elaborate on the symmetric teleparallel gravity (STPG) written in a non-Riemannian spacetime with nonzero nonmetricity, but zero torsion and zero curvature. Firstly we give a prescription for obtaining the nonmetricity from the metric in a peculiar gauge. Then we state that under a novel prescription of parallel transportation of a tangent vector in this non-Riemannian geometry the autoparallel curves coincides with those of the Riemannian spacetimes. Subsequently we represent the symmetric teleparallel theory of gravity by the most general quadratic and parity conserving lagrangian with lagrange multipliers for vanishing torsion and curvature. We show that our lagrangian is equivalent to the Einstein-Hilbert lagrangian for certain values of coupling coefficients. Thus we arrive at calculating the field equations via independent variations. Then we obtain in turn conformal, spherically symmetric static, cosmological and pp-wave solutions exactly. Finally we discuss a minimal coupling of a spin-1/2 field to STPG.Comment: Accepted for publication in the International Journal of Modern Physics

Propiedades antioxidantes de algunas plantas que crecen salvajes en Turquía

In this study, the antioxidant activity of 50% aqueous methanol extracts of 38 plants growing in the Afyonkarahisar province of Turkey were evaluated by various antioxidant assay, including free radical scavenging, hydrogen peroxide (H2O2) scavenging and metal (Fe2+) chelating activities. The methanolic fruit extracts of the Cornus and Morus species (H2O2 and DPPH scavenging activities, Fe2+ chelating activity) and the methanolic leaf extracts of the Mentha species (DPPH scavenging activities) examined in the assay showed the strongest activities. These antioxidant properties depended on the concentration of samples.En este estudio, la actividad antioxidante de extractos metanólicos al 50% en agua de 38 plantas que crecen en la provincia turca de Afyonkarahisar fueron evaluados con algunos ensayos antioxidantes, incluyendo la actividad capta-dora de radicales libres y de peróxido de oxígeno (H2O2) y la actividad quelatante de metales (Fe2+). Los extractos metanólicos de frutas de las especies Cornus y Morus (actividades captadoras de H2O2 y DPPH y actividad quelatante de Fe2+) y los extractos metanólicos de hojas de especies de Mentha (actividad captadora de DPPH) son los que mostraron una actividad mayor. Estas propiedades antioxidantes dependieron de la concentración de la muestra

Scalar Casimir Effect on a D-dimensional Einstein Static Universe

We compute the renormalised energy momentum tensor of a free scalar field coupled to gravity on an (n+1)-dimensional Einstein Static Universe (ESU), RxS^n, with arbitrary low energy effective operators (up to mass dimension n+1). A generic class of regulators is used, together with the Abel-Plana formula, leading to a manifestly regulator independent result. The general structure of the divergences is analysed to show that all the gravitational couplings (not just the cosmological constant) are renormalised for an arbitrary regulator. Various commonly used methods (damping function, point-splitting, momentum cut-off and zeta function) are shown to, effectively, belong to the given class. The final results depend strongly on the parity of n. A detailed analytical and numerical analysis is performed for the behaviours of the renormalised energy density and a quantity `sigma' which determines if the strong energy condition holds for the `quantum fluid'. We briefly discuss the quantum fluid back-reaction problem, via the higher dimensional Friedmann and Raychaudhuri equations, observe that equilibrium radii exist and unveil the possibility of a `Casimir stabilisation of Einstein Static Universes'.Comment: 37 pages, 15 figures, v2: minor changes in sections 1, 2.5, 3 and 4; version published in CQ

Two solar eclipses observations in Turkey

In thispap er, the changesin the ionosphere over Turkey due to two solar eclipses are reported. TEC on the eclipse day (26 April 1976) and the intensity of an HF radio wave during itspropagation over 567 km between Ankara and Elazıˇg on the eclipse day (11 August 1999) exhibited a very marked decrease

The Synthesis of Styrene-Oligoester Copolymer and Investigation of Their Physico-mechanical Properties

The copolymerization reaction of commercial propylene oxide with glycidylmethacrilate in the presence of BF3·O(C2H5)2 catalyst have been investigated. The composition and structure of copolymerization products and anchored functional groups have been determined using IR and gel chromatographic methods. The physico-mechanical properties and utility of polyfunctional unsaturated oligoester were investigated. The obtained thermoset product via the reaction of the oligoester with both styrene and oligostyrene obtained from the bottom of column as a waste material during the rectification operation of styrene in the presence of radicalic initiator has a good adhesion capability, hardness and high heat and water resistance. Thus the waste material was converted to the high valuable polymeric material

Late Acceptance Selection Hyper-heuristic for Wind Farm Layout Optimisation Problem

Wind is a promising source of renewable energy which can be harvested using wind turbines placed on farms. An efficient wind farm layout achieving various engineering and financial objectives is crucial to ensure the sustainability and continuity of energy production. In this study, a high-level search technique, namely late acceptance selection hyper-heuristic is applied to optimise the layout of wind farms. This approach aims to find the best placement of turbines at a given site, maximising the energy output while minimising the cost at the same time. The computational experiments indicate that the late acceptance selection hyper-heuristic improves upon the performance of a previously proposed genetic algorithm across all scenarios and an iterated local search over the majority of scenarios considering the best solutions obtained by each algorithm over the runs

An Automatic Digital Terrain Generation Technique for Terrestrial Sensing and Virtual Reality Applications

The identification and modeling of the terrain from point cloud data is an important component of Terrestrial Remote Sensing (TRS) applications. The main focus in terrain modeling is capturing details of complex geological features of landforms. Traditional terrain modeling approaches rely on the user to exert control over terrain features. However, relying on the user input to manually develop the digital terrain becomes intractable when considering the amount of data generated by new remote sensing systems capable of producing massive aerial and ground-based point clouds from scanned environments. This article provides a novel terrain modeling technique capable of automatically generating accurate and physically realistic Digital Terrain Models (DTM) from a variety of point cloud data. The proposed method runs efficiently on large-scale point cloud data with real-time performance over large segments of terrestrial landforms. Moreover, generated digital models are designed to effectively render within a Virtual Reality (VR) environment in real time. The paper concludes with an in-depth discussion of possible research directions and outstanding technical and scientific challenges to improve the proposed approach

Vitamin e treatment enhances erythrocyte deformability in aged rats

The harmful effects of aging on blood rheology have been well known. These effects in the aging have been found to be associated with an increase in oxidative stress. The aim of this study was to seek whether treatment of vitamin E as a potent antioxidant could improve the age-related haemorheological abnormalities. For this purpose, male Wistar rats at the age of 3 and 24 months were used. The following parameters were evaluated: red blood cell (RBC) deformability, aggregation, plasma viscosity, vitamin E level, total oxidant status (TOS), total antioxidant status (TAS) and oxidative stress index (OSI), and the following results were obtained. First, aging was associated with a decrease in RBC deformability and increase in RBC aggregation and plasma viscosity. Second, compared with the young group, while plasma TOS levels and OSI were found to be significantly increased in aged rats, there was no significant change in their plasma TAS level. Third, vitamin E administration produced significant improvement in RBC deformability and decrement in TOS and OSI values in aged rats with respect to young and aged control groups. We did not find any significant effect of vitamin E treatment on RBC aggregation in both young and aged rats and finally, we found a significantly lower plasma vitamin E level in aged rats than in young rats. In conclusion, these findings suggest that blood rheology impairs with age and vitamin E has ameliorating effects on age-induced haemorheological abnormalities especially in RBC deformability, probably by reducing the increased oxidative stress in old age