Enhanced exfoliation technique for the separation of graphene nanosheets

Graphene sheets are carbon-based materials which combine exceptional electron conductivity, mechanical strength and optical transparency. Graphene nanosheets were fabricated by an enhanced, safer and mild technique in a shortened processing time. Samples were characterized by SEM, XRD, TGA, AFM and Raman Spectroscopy

Modal identification of a reduced-scale masonry arch bridge with experimental measurements and finite element method

This study aims to investigate modal parameters such as mode shapes, natural frequencies and damping ratios of a reduced scale one-span historical masonry arch bridge constructed in laboratory conditions by performing numerical and experimental analysis. Sarp Dere historical masonry bridge, in Ordu, Ulubey, has 15.5m in length and 4.75m in width was chosen as a prototype model. The reduced-scale bridge model and structural details were carried out in the scale of 1:12.5. Operational Modal Analysis (OMA) technique was used for experimental study. The experimental modal parameters of the bridge model were figured out by using Enhanced Frequency Domain Decomposition (EFDD). ANSYS software was used to create 3D finite element (FE) model and to expose the analytical modal parameters of the reduced-scaled bridge model. Moreover, FE model of the reduced-scale bridge model was calibrated based on the experimental results by using the Response Surface based FE model calibration technique to obtain more accurate results. The analysis results of experimental, initial and calibrated FE model were compared. It is noted that there are significant differences between the modal parameters obtained from experimental and initial FE model. Model calibration techniques are beneficial to get a more reasonable FE model

THE EVALUATION OF THE CONNECTION BETWEEN MOTOR PERFORMANCE SKILLS AND BODY COMPOSITION OF THE GIRLS

The Purpose: This study was done for evaluating the connection between motor performance skills and body composition of the girls between 6-10 ages. The Method: 57 schoolgirls between 6-10 ages were included to the study. Weight, Age, Height, Body Mass Index (BMI), Free Fat Mass (FFM), Lean Muscle Mass (LMM), Body Fat Mass (BFM) and Body Fat Percentage (BFP) values were measured with (Inbody 230) branded tanita. Long jump, right hand and left hand strength, back strength, 20 meters speed test, sit & reach test, 1 minute pull-up and flamingo balance tests were applied to the participants. Results: Pearson Correlation Test was applied for the analysis by using SPSS 23.0 program. According to the results, the average age is (8,00±,926) years, the average height is (128,7±6,64) cm and the average weight is (28,6±6,67) kg. There is a statistically meaningful relation between long jump, right hand, left hand, back strength, flamingo balance test and BFM, FFM, LMM, BMI and BFP at the (p<0.01) level. However, there is no relation found between 20 meters speed test, sit & reach test, 1 minute pull-up test and body composition parameters. Discussion and Conclusion: At the end of our study, we can say that there is a meaningful relation in a positive way between some motor performance skills and body composition of the girls.  Article visualizations

Graphene manufacture and utilization

An improved, safer and mild method was proposed for the exfoliation of graphene like sheets from graphite to be used in fuel cells. The major aim in the proposed method is to reduce the number of layers in the graphite material and to produce large quantities of graphene bundles to be used as catalyst support in polymer electrolyte membrane fuel cells. Graphite oxide was prepared using potassium dichromate/sulfuric acid as oxidant and acetic anhydride as intercalating agent. The oxidation process seemed to create expanded and leafy structures of graphite oxide layers. Heat treatment of samples led to the thermal decomposition of acetic anhydride into carbondioxide and water vapor which further swelled the layered graphitic structure. Sonication of graphite oxide samples created more separated structures. Morphology of the sonicated graphite oxide samples exhibited expanded the layer structures and formed some tullelike translucent and crumpled graphite oxide sheets. The mild procedure applied was capable of reducing the average number of graphene sheets from 86 in the raw graphite to nine in graphene-based nanosheets. Raman spectroscopy analysis showed the significant reduction in size of the in-plane sp2 domains of graphene nanosheets obtained after the reduction of graphite oxide

Utilization of multiple graphene nanosheets in fuel cells: 2. The effect of oxidation process on the characteristics of graphene nanosheets

Structural properties of graphene nanosheets that will be used as electrode material in fuel cells were investigated at different oxidation times. As the oxidation time was increased, the strong bonding between graphene layers in graphite was reduced and graphene layers started to exfoliate forming clusters with a few number of graphene layers. The variations in interplanar spacings, layer number and percent crystallinity indicated how stepwise chemical procedure influenced the morphology of graphite. It was possible to produce relatively flat graphene clusters with definite number of layers by controlling the oxidation time. Graphene nanosheets were characterized in detail by scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy, and thermal gravimetric analyzer

Experimental modal investigation of scaled minaret embedded in different soil types

The influence of various types of foundation soil on dynamic behaviour of reinforced-concrete minarets is analysed in the paper. A 1:20 RC scale model was constructed in laboratory for the testing. The gravel, sand, and clay-gravel mixture, were used as foundation soil types to determine differences in dynamic behaviour as related to the type of foundation soil. Experimental measurements were conducted using the Operational Modal Analysis (OMA), taking into account ambient vibrations due to wind action and traffic. Test results show that the dynamic behaviour of RC minaret is strongly influenced by the type of foundation soil

ZİÇEV'in tarihçesi ve zihinsel engelli bireylerin Türk toplumundaki yeri

Ankara : İhsan Doğramacı Bilkent Üniversitesi İktisadi, İdari ve Sosyal Bilimler Fakültesi, Tarih Bölümü, 2016.This work is a student project of the The Department of History, Faculty of Economics, Administrative and Social Sciences, İhsan Doğramacı Bilkent University.by Emiroğlu, Kudret

An improved technique for the exfoliation of graphene nanosheets and utilization of their nanocomposites as fuel cell electrodes

Graphene nanosheets (GNS) were separated from graphite by an improved, safer and mild method including the steps of oxidation, thermal expansion, ultrasonic treatment and chemical reduction. Graphene nanosheets (GNS) were exfoliated by following two ways. 1st way, the longest exfoliation technique, contained these steps: graphite oxidation, ultrasonic treatment, thermal exfoliation, ultrasonic treatment and chemical reduction. 2nd way, the shortest exfoliation technique, included graphite oxidation, ultrasonic treatment and chemical reduction. Both the reaction procedures with thermal expansion and without thermal expansion led to the formation of GNS