Umit Kemalettin Terzi

Novel electrospun polycaprolactone/graphene oxide/Fe3O4 nanocomposites for biomedical applications

In this study, one of the most promising methods of tailoring a composite scaffold material in nano sized diameters, electrospinning method were used to produce Polycaprolactone (PCL)/Graphene Oxide (GO)/Iron(II, III) Oxide (Fe3O4) nanocomposite fibers as biocompatible scaffolds for biomedical applications. Products were analyzed by scanning electron microscopy (SEM) for morphological analysis of the electrospun nanocomposites and Fourier Transform Infrared Spectroscopy (FTIR) was used to determine functional groups of the PCL, GO, and Fe3O4 materials in the electrospun nanocomposites. For physical properties, viscosity, density, permittivity, dielectric loss and liquid and solid state alternating current conductivity, measurements were done for each nanocomposite fibers. Effects of concentration percentage of GO on permittivity, dielectric loss and AC conductivity have been analyzed by using measured and calculated data. Trend lines have been drawn for permittivity, dielectric loss and conductivity via concentration percentage of GO. The relation between ac conductivity and frequency have been studied for each concentration percentage of GO and interpretations have been done by using the obtained results.

Use of shape memory alloys as smart materials to harvest energy powered by renewable energy resources

This paper will study heat engines driven by smart metals also named as Shape Memory Alloys (SMA). It presents studies on contribution to energy production by heat engines driven by SMA using underground thermal water, secondary heat resources of combined cycle natural gas power plants and renewable energy resources. It also studies SMA heat engines with regards to energy conversion.

Technical and economic analysis of energy storage systems in smart grids

By managing the processes productively from power production to distribution to end user in smart grid systems, it is possible to store the energy when needed and then make it available for usage at a later time. This study analyses current and potential future electricity storage systems in smart grid technically and economically.

Discrete wavelet transform based approach for current transformer saturation problem

This work is about the possible effects of protection devices and schemes during current transformer saturation. If current transformer specifications are not selected properly, saturation may occur and affect relay response or even fail to trip. Hence, the performance of the protection devices such as differential and impedance relays is mainly based on the operating condition of the current transformers. An accurate knowledge of current signal is essential for protection devices. In this paper, a different approach is represented for current transformer saturation problem. The proposed technique is based on the discrete wavelet transform. The energy levels of the detail coefficients after the transformation present distinctive features during current transformer saturation.

The effect of the heat applied during removal of the burned windings in electric motors to structure of material and magnetic characteristic of (stator) armature

Summary form only given. As is known, electric motors and generators are varnished for insulation after winding. These varnished coils are formed in stiff construction in the slot. Because of heavy-duty conditions, whole or a part of coils could become burned out or broken. There are two main methods to remove the defective coils. These are thermal method and chemical method. In this study, the burning method of varnish in flame burning room is studied. In the thermal method, either a voltage is applied to defective coils by using a high-power autotransformer (variac) and a short-circuit current flows until all varnish is burned, or, if all of the coils are out of order, varnish is burned by putting the stator or armature in a burning room. The effect of the heat applied in this stage to structure of material and magnetic characteristics of the armature have been investigated. The relations between magnetic characteristics and metallurgical structure of material and their solutions have been emphasized under laboratory and service conditions.