Refik Kayali

Theoretical and Experimental Analysis of a Salt Gradient Solar Pond with Insulated and Reflective Covers

Abstract In this study, a salt gradient solar pond having a surface area of 3.5 × 3.5 m2 and depth of 2 m has been built for supplying hot water to a leather workshop on the campus area of Vocational College of Isparta/Yalvaç. A cover system was used on the surface of the pond to reduce the thermal losses from the top to air and to increase the thermal efficiency of the pond. Such an arrangement is used for the very first time. The system is composed of two covers that can be rotated between 0 and 180 degrees by a controlled electric motor and has insulation and reflection properties, i.e., the covers function as insulators when closed and as reflectors when opened. The ponds thermal analysis has been carried out theoretically and experimentally for different operating conditions. Results obtained from this study show that salt gradient solar ponds can be used as a source of warm water required at the leather workshop and for suitable domestic applications. The covers were effective both for reducing the night thermal losses and for increasing the daytime performance, although the former effect is negligible.

Temperature and Thickness Effects on Electrical Properties of InP Films Deposited by Spray Pyrolysis

InP film samples are prepared by spray pyrolysis technique using aqueous solutions of InCl3 and Na2HPO4, which are atomized with compressed air as carrier gas onto glass substrates at 500° C with different thicknesses of the films. The structural properties of the samples are determined by x-ray diffraction (XRD). It is found that the crystal structure of the InP films is polycrystalline hexagonal. The orientations of all the obtained films are along the c-axis perpendicular to the substrate. The electrical measurements of the samples are obtained by dc four-probe technique on rectangular-shape samples. The effects of temperature on the electrical properties of the InP films are studied in detail.

Simulation of astrophysical jet using the special relativistic hydrodynamics code

Abstract This paper describes a multi-dimensional hydrodynamic code which can be used for the studies of relativistic astrophysical flows. The code solves the special relativistic hydrodynamic equations as a hyperbolic system of conservation laws based on high resolution shock capturing (HRSC) scheme. Two standard tests, one of which is the relativistic blast wave tested in our previous paper [O. Donmez, Astrophys. Space Sci. 293 (2004) 323–354], and the other is the collision of two ultra-relativistic blast waves tested in here, are presented to demonstrate that the code captures correctly and gives solution in the discontinuities, accurately. The relativistic astrophysical jet is modeled for the ultra-relativistic flow case. The dynamics of jet flowing is then determined by the ambient parameters such as densities, and velocities of the jets and the momentum impulse applied to the computational surface. We obtain solutions for the jet structure, propagation of jet during the time evolution, and variation in the Mach number on the computational domain at a fixed time.

Investigation of Antibacterial Properties of Ag Doped TiO2 Nanofibers Prepared by Electrospinning Process

Abstract In this study, undoped and 1, 2,3, 4, and 5 wt % Ag-doped TiO2 nanofibers have been fabricated by the electrospinning method applying 20 kV voltages at 8 cm height with a flow rate 0.1 mL/h. The antibacterial properties of undoped and doped Ag/TiO2 nanofibers were tested on Staphylococcus aureus bacteria. The antibacterial effect of these fabricated nanofibers has been determined by disc diffusion and Baird parker methods. The results have shown that Ag/TiO2 nanofibers have an excellent antibacterial effect on this bacterium compared to pure TiO2 nanofibers. As a result, developed nanofibers can easily be applied in various fields such as biomedical sector and tissue engineering. In addition, the chemical components, morphology, and crystal structure of the nanofibers have been performed by scanning electron microscopy energy dispersive analysis (SEM-EDX), differential thermal analysis/thermal gravimetric analysis (DTA/TG), and X-ray diffraction (XRD) methods.

Investigation of Structural and Optical Properties of InP Thin Films Developed by Using Spraying Method

Structural and optical properties of InP films developed with the solutions prepared with InCl3 and Cl2HPO4 salts having different rates by using spraying method have been investigated using the data obtained from UV spectrometer and XRD (x‐ray difractometer). Band gap energy values of all samples obtained by using UV spectrometer are found in 1.60–1.85 eV range. It was observed that basic piks of all samples are in (200) plane and have a fcc structure in the XRD analysis. In addition, grain size of the samples increases with the rate of indium included in samples and it is seen that the crystallization in surface structure tends to become more homogenity.