Hakkari, Turkey

Time filter

Source Type

Kurt E.,Gazi University | Gor H.,Hakkari University | Demirtas M.,Gazi University
Energy Conversion and Management | Year: 2014

A new single phase generator has been designed and preliminary experimental results have been reported. The effects of two types of alternator cores have been explored. The proposed generator has one stator and two rotors with rare-earth-element-made permanent magnets (PMs). The physical and electromagnetic features of this PM generator are presented. The electromagnetic analyses are realized by the finite element method (FEM). The proposed machine has a combined type of flux directing mechanism, namely with axial and radial directions. The flux orientations are provided by 12 cores at the double-sided stator. The design has 2 rotors with totally 24 permanent magnets, which are positioned at different radial distances. It has been found that this design reduces the cogging torque values compared to the simple axial flux machine with 2 rotors having cylindrical cores. Thus a new cogging torque reduction technique is also proposed beside the new design. The electromagnetic simulations have been realized at different rotor speeds. The analyses also include the waveforms of currents, voltages, magnetic fluxes and cogging torque calculations. The maintenance and control of the machine is easier in operation, since the output power increases smoothly and become nearly constant up to the rotor speeds 1000 rpm. Preliminary results indicate that peak-to-peak voltage Up = 34 V is generated at the rotor speed ω = 200 rpm and it increases linearly with ω. The rated speed is expected to be 1000 rpm and 95% of efficiency is measured in the preliminary tests. © 2013 Elsevier B.V. All rights reserved.


Korucu D.,Hakkari University | Turut A.,Istanbul Medeniyet University | Altindal S.,Gazi University
Current Applied Physics | Year: 2013

Capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements of the Au/n-GaAs Schottky barrier diodes (SBDs) in the wide frequency range of 10 kHz-10 MHz at room temperature were carried out in order to evaluate the reason of negative capacitance (NC). Experimental results show that C and G/ω are strong functions of frequency and bias voltage especially in the accumulation region. NC behavior was observed in the C-V plot for each frequency and the magnitude of absolute value of C increases with decreasing frequency in the forward bias region. Contrary to C, G/ω increases with decreasing frequency positively in this region. NC behavior may be explained by considering the loss of interface charges at occupied states below Fermi level due to impact ionization processes. Such behavior of the C and G/ω values can also be attributed to the increase in the polarization especially at low frequencies and the introduction of more carriers in the structure. The values of Rs decrease exponentially with increasing frequency according to literature. In addition, the values of C and G/ω at 1 MHz were corrected to obtain the real diode capacitance by taking the effect of Rs into account. © 2013 Elsevier B.V. All rights reserved.


Atli G.,Hakkari University | Canli M.,Cukurova University
Ecotoxicology and Environmental Safety | Year: 2010

Antioxidant systems are known to be sensitive to metal exposures and are suggested to use in predicting sublethal metal toxicity. In this study, several antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPX) and glutathione reductase (GR) were measured in the liver and kidney of Oreochromis niloticus exposed to sublethal concentrations of metals (Cd, Cu, Cr, Zn and Fe), using an acute (20 μM, 48. h) or subchronic (10 μM, 20. d) protocol. Beside the several increases of antioxidant enzyme activities, general inhibition was recorded after acute and chronic metal exposures. Results indicated that there were variations in responses of the enzymes to metal exposures, depending upon tissues, metals and exposure types. This study emphasized that the antioxidant enzymes are very sensitive to metals as their activities altered significantly, suggesting they could be helpful in predicting sublethal metal toxicity and useful as an early warning tool in natural monitoring studies. © 2010 Elsevier Inc.


Freshwater fish, Oreochromis niloticus, were individually exposed to 0, 0.1, 0.5, 1.0, and 1.5 96 h (acute) and 0.05 μg/mL concentrations of the same metals for 0, 5, 10, 20, and 30 days (chronic). Following each period, metal accumulation and ion levels (Na +, K +, Ca +2, and Mg +2) were measured in the gills, kidneys, and muscles. Except for Ag +, none of the metals killed the fish within 30 days. Silver killed all the fish within 16 days. With the exceptions of Ag + and Cr 6+, as their levels were below detection limits, metal accumulation occurred in the tissues following both acute and chronic exposures. Ion levels in the tissues were altered by metal exposure, the general tendency being a decrease in Na + and K + levels and an increase in Mg 2+ and Ca 2+ levels. Acute exposure to heavy metals seemed to be more effective in altering ion levels of the tissues than chronic exposure. Na + was the most affected ion while Mg 2+ was the least affected. Results of this study emphasize that ion levels in the tissues of O. niloticus can be altered by heavy metals, both in acute and chronic exposures. This suggests that heavy metals should be monitored carefully in ecotoxicological studies in the field due to their importance in fish physiology. © TÜBİTAK.


Stigmaeus pulchellus Kuznetzov, 1978, reported for the first time from Turkey, is described and illustrated based on females. In addition to the male and nymphal stages of this species, the male of Stigmaeus kumalariensis Akyol and Koç, 2007 is also described and illustrated in this article for the first time. The males and females presented differences in chaetotaxy, notably the absence of seta h3in the male of S. pulchellus. © 2015, Les Amis d'Acarologia. All rights reserved.


Behcet L.,Bingöl University | Rustemoglu M.,Hakkari University
Turkish Journal of Botany | Year: 2012

Allium shirnakiense L.Behçet & Rüstemoǧlu sp. nova (sect. Melanocrommyum Webb & Berth.) is described as a species new to science on the basis of material collected from Şi{dotless}rnak Province. Morphologically, it is related to A. rhetoreanum Nab., which is an species endemic to South-eastern Turkey. A diagnosis, a taxonomic description, and some illustrations are given.


Bayrakdar H.,Hakkari University
Progress In Electromagnetics Research M | Year: 2012

We have synthesis ferrite-polymer nanocomposite structures, theoretically and experimentally investigated electromagnetic propagation, absorption properties of these nanocomposite materials at 8-20 GHz in microwave guides. The microwave properties of the samples were investigated by transmission line method, and reflection loss of -59.60 dB was found at 12 GHz for an absorber thickness of 2 mm. These nanocomposites may be attractive candidates for microwave absorption materials.


Korucu D.,Hakkari University | Turut A.,Istanbul Medeniyet University | Efeoglu H.,Atatürk University
Physica B: Condensed Matter | Year: 2013

The current-voltage (I-V) characteristics of Au/n-GaAs contacts prepared with photolithography technique have been measured in the temperature range of 80-320 K. The ideality factor and barrier height (BH) values have remained almost unchanged between 1.04 and 1.10 and at a value of about 0.79 eV at temperatures above 200 K, respectively. Therefore, the ideality factor values near unity say that the experimental I-V data are almost independent of the sample temperature, that is, contacts have shown excellent Schottky diode behavior above 200 K. An abnormal decrease in the experimental BH Φb and an increase in the ideality factor with a decrease in temperature have been observed below 200 K. This behavior has been attributed to the barrier inhomogeneity by assuming a Gaussian distribution of nanometer-sized patches with low BH at the metal-semiconductor interface. The barrier inhomogeneity assumption is also confirmed by the linear relationship between the BH and the ideality factor. According to Tung's barrier inhomogeneity model, it has been seen that the value of σT=7. 41×10-5 cm2/3 V1/3from ideality factor versus (kT)-1 curve is in close agreement with σT=7. 95×10-5 cm2/3 V1/3 value from the Φeff versus (2kT)-1 curve in the range of 80-200 K. The modified Richardson ln(J0/T2)-(qσT) 2(Vb/η)2/3/[2(kT)2] versus (kT)-1 plot, from Tung's Model, has given a Richardson constant value of 8.47 A cm-2 K-2which is in very close agreement with the known value of 8.16 A cm-2 K-2 for n-type GaAs; considering the effective patch area which is significantly lower than the entire geometric area of the Schottky contact, in temperature range of 80-200 K. Thus, it has been concluded that the use of Tung's lateral inhomogeneity model is more appropriate to interpret the temperature-dependent I-V characteristics in the Schottky contacts. © 2013 Elsevier B.V. All rights reserved.


Korucu D.,Hakkari University | Duman S.,Atatürk University
Thin Solid Films | Year: 2013

In order to evaluate current conduction mechanism in the Au/p-InP Schottky barrier diode (SBD), some electrical parameters such as the barrier height (Φbo) and ideality factor (n) have been obtained from the forward bias current-voltage (I-V) characteristics. The I-V measurements show that n is close to unity at room temperature, indicating that the main mechanism of current flow through the SBD is thermionic emission (TE).On the other hand, the particular contact fabrication process produces a relatively high value of barrier height (0.78 eV) at room temperature. The variation of Φbo with temperature has been obtained as 4 × 10 - 4 eV K- 1, which is close to the temperature coefficient of the band-gap of InP. It has been found that Φbo and n values of the SBD are temperature dependent below room temperature by using TE theory. Φbo increases and n decreases with increasing temperature. The assumption of a double Gaussian distribution of the Schottky barrier height has been applied due to barrier inhomogeneities that prevail at the metal-semiconductor interface giving mean barrier heights of 0.98 and 0.84 eV and standard deviations of 88 and 53 mV for 80-180 K and 180-320 K temperature regions, respectively. The values of mean barrier height and Richardson constant (A*) using the modified Richardson ln(I0/T 2) - (q2σs 2/2k 2T2) plot have been found as 1.00 eV, 77.52 A/cm 2 K2 for 80-180 K and 0.83 eV, 56.76 A/cm2 K2 for 180-320 K, respectively. A*values are in close agreement with the value of 60 A/cm2 K2 known for p-type InP. © 2013 Elsevier B.V.


A new species of Stigmaeus berwariensis sp. nov. from eastern Turkey is described and illustrated. Eryngiopus coheni Vacante & Gerson 1987 is a new record for Turkish fauna. © 2015 Taylor & Francis.

Loading Hakkari University collaborators
Loading Hakkari University collaborators