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Gurbuz R.,Adiyaman University | Birgin O.,Usak University
Computers and Education | Year: 2012

The aim of this study is to determine the effects of computer-assisted teaching (CAT) on remedying misconceptions students often have regarding some probability concepts in mathematics. Toward this aim, computer-assisted teaching materials were developed and used in the process of teaching. Within the true-experimental research method, a pre- and post-test control group study was carried out with 37 seventh-grade students-18 in the experimental group (CAT) and 19 in the control group (traditional teaching). A 12-item instrument, made up of 4 items related to each of the concepts "Probability Comparisons (PC)," "Equiprobability (E)," and "Representativeness (R)," was developed and implemented with the participants. After the teaching intervention, the same instrument was again administered to both groups as a post-test. In light of the findings, it can be concluded that computer-assisted teaching was significantly more effective than traditional methods in terms of remedying students' misconceptions. © 2011 Published by Elsevier Ltd. All rights reserved.

An experimental study has been carried out to investigate the bearing strength behavior of pinned joints of glass fiber reinforced composite filled with different proportions of Al2O3 particles, as a function of filler loading and joint geometry. The weight fractions of the filler in the matrix were 7.5, 10, and 15%. Single-hole pin-loaded specimens of each composite material were tested in tension. The results show that the bearing strength of glass fiber reinforced epoxy composites pinned joints is associated with the filler content and geometric parameters. The increase of the Al2O3 particle loading in the matrix improved the bearing strength of the composites. The highest bearing strengths were obtained for composite specimens with 10 wt.% Al2O3 particle content. Further increases in the Al2O3 particle content in the matrix resulted in a decrease of the bearing strength, but remains above that of the unfilled glass reinforced epoxy composites. © 2009 Elsevier Ltd. All rights reserved.

This study focuses on the mineralogical, chemical, thermal and physical characterization of Afyon and Istanbul clays from Turkey and evaluation of the potential of the Afyon clay to manufacture traditional ceramic products with industrial processing. The suitability of the raw clay material from Afyon region to produce floor tiles was not tested yet. The effect of partial substitution of the clay from Istanbul-Sile deposit (one of the main clay producing areas of Turkey) by Afyon clay on ceramic properties was studied. The studied samples were kaolinite (Istanbul clay) and illite (Afyon clay) based materials. While there were no major differences in water absorption, the bending strength decreased slightly when the kaolinitic Istanbul clay was substituted by the illitic Afyon clay for floor tile production. Almost all technological properties of the Afyon clay deposit demonstrated the industrial suitability of Afyon clay as a potential ceramic raw material for the growing Turkish ceramic tile industry. © 2010 Elsevier B.V.

In this study, the response of a FG (functionally graded) coated truncated conical shell subjected to an axial load is investigated by means of non-linear equations governing the finite deformations of the shell. In the solution of non-linear basic equations in the finite deflection the Superposition and Galerkin methods have been used. The effects of material property of FG composite coatings and geometrical parameters on the non-linear critical axial load are discussed in detail through a parametric study. The results are verified by comparing the obtained values with those in the existing literature. © 2013 Elsevier Ltd.

Kandilli C.,Usak University
Energy Conversion and Management | Year: 2013

In the present study, a novel Concentrating Photovoltaic Combined System (CPVCS) based on the spectral decomposing approach is introduced, modeled, tested experimentally and evaluated thermodynamically and economically. In this study, energy and exergy analyses of the system have been evaluated, economical analysis has been performed and the experimental results have been compared to data obtained by the control system. As a result, energy efficiencies of concentrator, vacuum tube and overall CPVCS have been determined to be 15.35%; 49.86%; and 7.3% respectively. Similarly the second law (exergy) efficiencies of concentrator, vacuum tube and overall CPVCS are 12.06%; 2.0%; and 1.16% respectively. The cost of energy production has been stated as 6.37 $/W and it is predicted that this value could be decreased by improving the system performance. © 2012 Elsevier Ltd. All rights reserved.

Caliskan H.,Usak University
Energy Conversion and Management | Year: 2013

The energy and exergy analyses are performed to the human body for the summer season of the Izmir city in Turkey. It is found that the metabolism energy and exergy rates are the major part of the human body's energy generation. However, metabolism energy rate (58.326 W/m2) is much higher than corresponding exergetic one (1.661 W/m2). The maximum energy loss of the human body (70.59%) occurs due to heat exchange such as radiation, convection, and conduction. On the other hand, the maximum exergy loss of the human body happens due to exhaled humid air (6.393%), while the most of the total exergy is consumed by the human body (90.786%). Thermal comfort condition is also calculated. The Predicted Mean Vote (PMV) rate is found as 0.028 which means that the thermal sensation of the human body is called as comfortable. Furthermore, the Predicted Percentage Dissatisfied (PPD) rate is determined to be 5.017% which is low and shows the thermally dissatisfied people percentages. © 2013 Elsevier Ltd. All rights reserved.

Caliskan H.,Usak University
Energy Conversion and Management | Year: 2014

In this study, novel approaches to exergy and economy based enhanced environmental analyses for energy systems are explained. The methods are named as "exergoenvironment" (EXEN) and "exergoenviroeconomic" (EXENEC). These two analyses are also performed to the three conventional (fuel-oil, coal, natural gas) and two renewable (solar PV, wind turbine) energy options based electricity generation systems used for a building heating to show the reliability of the analyses. The EXEN analysis gives information relating to CO2 emission over time considering exergetic point of view. According to the EXEN results, greenhouse gas management can be achieved and CO2 reduction procedures can be prepared. On the other hand, EXENEC analysis presents the released CO2 price exergetically in a given period of time, while its unit is created to be $/time. EXENEC analysis can be helpful for the economic management of the greenhouse gases. Among the conventional energy options, the natural gas is the best choice, when the exergy based environmental & economical situations are considered. But, wind turbine energy option, which is one of the renewable energy options, is the best exergoenvironmental and exergoenviroeconomic choice among the all energy options. Because, the EXEN and EXENEC results are found minimum for this energy option to be 60 kg CO2/month and 0.87 $/month, respectively. So, these methods can be applied to the various energy options effectively, and the methods are useful for policy makers, researchers, decision makers and investors due to the enhanced methods' comprehensive environmental and exergetic approaches. © 2014 Elsevier Ltd. All rights reserved.

Gun H.,Usak University
International Journal of Mechanical Sciences | Year: 2014

In this paper, a quadratic meshless boundary element formulation for isotropic damage analysis of contact problems with friction is presented. To evaluate domain-related integrals due to the damage effects, the radial integration method (RIM) based on the use of the approximating the normalized displacements in the domain integrals by a series of prescribed radial basis functions (RBF) is employed. An exponential evolution equation for the damage variable is adopted. The details of coupling the different systems of equations for each body in contact under the several contact conditions are given to obtain the overall system of equations. Numerical examples covering shrink-fit and frictional punch problems are given to demonstrate the efficiency of the present meshless BEM. © 2014 Elsevier Ltd.

Genotoxic effects of Bismuth (III) oxide nanoparticles (BONPs) were investigated on the root cells of Allium cepa by Allium and Comet assay. A. cepa roots were treated with the aqueous dispersions of BONPs at five different concentrations (12.5, 25, 50, 75, and 100. ppm) for 4. h. Exposure of BONPs significantly increased mitotic index (MI) except 12.5. ppm, total chromosomal aberrations (CAs) in Allium test. While stickiness chromosome laggards, disturbed anaphase-telophase and anaphase bridges were observed in anaphase-telophase cells, pro-metaphase and c-metaphase in other cells. A significant increase in DNA damage was also observed at all concentrations of BONPs except 12.5. ppm by Comet assay. The results were also analyzed statistically by using SPSS for Windows; Duncan's multiple range test was performed. These results indicate that BONPs exhibit genotoxic activity in A. cepa root meristematic cells. © 2013 Elsevier Ltd.

The dimensional, some physical and thermal comfort properties of the plain knitted fabrics having modal viscose microfibers in three different stitch lengths are investigated in comparison with the similar fabrics having conventional modal viscose fibers. The fabrics made from microfibers and conventional fibers exhibit different dimensional properties. The stitch density results and the dimensional constants calculated at the fully relaxed state reveal that the fabrics with microfibers tend to have lower shrinkage tendency than those with conventional fibers. The statistical results show that the fiber type (or fiber fineness) and the stitch length affect the some physical properties and all of the thermal comfort properties of the fabrics significantly. The bursting strength values of the fabrics with microfibers are observed to be slightly higher than those of the fabrics with conventional fibers. However, the difference between the bursting strength values of these fabrics is found to be statistically unimportant. The fabrics with microfibers reveal lower thickness and air permeability and, higher pilling tendency than those with conventional fibers. It is also observed from the thermal comfort results that the fabrics made from microfibers have higher thermal conductivity, thermal absorptivity and maximum heat flux values and, lower thermal resistance and thermal diffusivity values. Because of the higher thermal absorptivity and maximum heat flux values, the fabrics from microfibers provide cooler feeling when compared with those from conventional fibers. © 2011 The Korean Fiber Society and Springer Netherlands.

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