Papers by İbrahim BELENLİ
Journal of Alloys and Compounds, 2011
ABSTRACT
Pamukkale University Journal of Engineering Sciences, 2006
The main energy sources which are natural, clean, environmentally friendly, and renewable are win... more The main energy sources which are natural, clean, environmentally friendly, and renewable are wind power, solar energy, biomass energy, hydro energy, and wave energy. The wave energy has no cost except for the first investment and maintenance. There is also no cost for input energy. Besides these, it has no pollution effect on the environment, it is cheap and there is a huge potential all around the world. Wave energy is a good opportunity to solve the energy problem for Turkey which is surrounded by seas. Concerning all these facts, it has been conducted some studies which included five years of observation in the Western Black Sea Region (Akçakoca). The wave energy potential has also been calculated. From this sutdy results, it can be concluded that the wave energy potential of this region is inefficient. It is believed that by the improvement of the new energy converter devices in future, this low potential can be used more efficiently and as a result this study might be used as ...
Bulletin of the American Physical …, 2007
In polycrystalline high-T$_{c}$ compounds the critical current densities are mostly limited by th... more In polycrystalline high-T$_{c}$ compounds the critical current densities are mostly limited by the grain boundaries. Their characterization is of significant importance to understand and improve the superconducting properties. In our work, superconducting Bi$_{1.8}$Pb$_{0.35}$Sr$_ ...
Bulletin of the American …, 2007
The effect of the addition of hBN (x = 0.005, 0.015, 0.025, 0.035 and 0.05 g.) in the \textit{Bi-... more The effect of the addition of hBN (x = 0.005, 0.015, 0.025, 0.035 and 0.05 g.) in the \textit{Bi-2223} superconducting samples have been investigated in terms of magnetoresistivity, T$_{c}$, $J_{c}^{trans}$, and ac susceptibility. The samples were ...
Journal of Higher Education and Science, 2011
Bu çalışmada dünyadaki mevcut kalite güvence sistemleri incelenerek, ülkemizdeki mevzuat, mevcut ... more Bu çalışmada dünyadaki mevcut kalite güvence sistemleri incelenerek, ülkemizdeki mevzuat, mevcut yapı ve yükseköğretim sisteminin gözönünde bulundurulması suretiyle geliştirilen bir model önerisi sunulmaktadır. Türkiye'nin yükseköğretim alanında önde gelen ülkelerden biri olabilme potansiyeli, iyi işleyen bir kalite güvence sistemi oluşturularak değerlendirilebilir. Kalite güvence sisteminin önemli bir bileşeni olan akreditasyon işleminin bağımsız akreditasyon kuruluşları tarafından icra edilmesi hayati önem taşır. Diğer yandan, birçok batı ülkesinden farklı olarak ülkemizde üniversitelerin yasayla kurulması ve hemen hemen tamamen merkezi hükümet tarafından finanse edilmesi, merkezi bir yapının da bulunmasını gerekli kılmaktadır. Bu çalışmada sunulan model, dengeli bir çözüme ulaşmak ve dinamik bir yapı oluşturmak amacını gütmektedir. Model, daha çok yükseköğretimin eğitim faaliyetlerinin kalite güvencesini sağlamaya yönelik olmakla birlikte, yükseköğretim kurumlarının işleyişini doğrudan etkileyeceği için aynı zamanda araştırma ve hizmet alanlarında da önemli ilerleme ve gelişme sağlayacaktır.
Journal of Alloys and Compounds, 2009
We have investigated the effect of the gold diffusion on the crystal structure and superconductin... more We have investigated the effect of the gold diffusion on the crystal structure and superconducting properties of Bi-2223 superconducting samples employing X-ray diffraction (XRD), scanning electron microscopy (SEM), critical transition temperature, critical current density, and room temperature resistivity measurements. Doping of Bi-2223 was carried out by means of gold diffusion from an evaporated gold film on pellets during sintering. XRD patterns and SEM micrographs are used to obtain information about Bi-2223 phase ratio, lattice parameters and grain size, respectively. Au doping of the samples increased the critical transition temperature and the critical current density from 100 ± 0.2 to 104 ± 0.2 K and from 40 to 125 A cm −2 , in comparison with those of undoped samples. The gold diffusion in Bi 1.8 Pb 0.35 Sr 1.9 Ca 2.1 Cu 3 O y has been studied over the temperature range of 500-830 • C using the technique of successive removal of thin layers and measurement of the sample's conductivity at room temperature. The temperature dependence of the Au diffusion coefficient in the range of 500-830 • C was described by the relation D = 5 × 10 −4 exp (−1.09 eV/k B T). The possible reasons for the observed improvements in microstructure and superconducting properties due to Au diffusion were discussed.
Bulletin of Materials Science, 2002
We have investigated Bi 2 O 3-Eu 2 O 3 binary system by doping with Eu 2 O 3 in the composition r... more We have investigated Bi 2 O 3-Eu 2 O 3 binary system by doping with Eu 2 O 3 in the composition range from 1 to 10 mole% via solid state reactions and succeeded to stabilize β β-Bi 2 O 3 phase which is metastable when pure. Stability of β β-Bi 2 O 3 polymorph was influenced by heat treatment temperature. Tetragonal type solid solution was obtained in 3-6 mole% addition range when annealed at 750°C and the range was 2-7 mole% when annealed at 800°C. We have also carried out investigations on lattice parameters, microstructural properties and elemental compositions of this β β type solid solution for each doping ratio. Lattice parameters increased with amount of Eu 2 O 3 addition. Our experimental observations strongly suggested that oxygen deficiency type non-stoichiometry is present in doped β β type solid solutions. Keywords. Bismuth trioxide polymorphs; solid solution; Bi 2 O 3-Eu 2 O 3 binary system.
Materials, 2021
Our results show that a lower density of unreacted Mg + B material during an Mg solid-state synth... more Our results show that a lower density of unreacted Mg + B material during an Mg solid-state synthesis reaction leads to a significant reduction in the quantity of the superconducting phase and lowers the homogeneity of the superconducting material. It also significantly reduces the irreversible magnetic field (Birr), critical temperature (Tc), upper magnetic field (Bc2), engineered critical current density (Jec), and n-value, despite high isostatic pressure (HIP) treatment and the use of nanoboron in the sample. Our measurements show that samples with large boron grains with an 8% higher density of unreacted Mg + B material allow better critical parameters to be achieved. Studies have shown that the density of unreacted material has little effect on Birr, Tc, Bc2, Jec, and the n-value for an Mg liquid-state synthesis reaction. The results show that the critical parameters during an Mg liquid-state synthesis reaction depend mainly on grain size. Nanoboron grains allow for the highest...
Cerâmica, 2011
Electrical conductivity of tetragonal β-phase (Bi2O3)1-x(Eu2O3)x (0.01 ≤ x ≤ 0.10 %mol) ceramic s... more Electrical conductivity of tetragonal β-phase (Bi2O3)1-x(Eu2O3)x (0.01 ≤ x ≤ 0.10 %mol) ceramic systems were investigated. The temperature and doping concentration dependences of the electrical conductivity were studied by four-point probe technique. The electrical conductivity increases with the increasing doping concentration and temperature. The highest value of the electrical conductivity is 0.013 Ω-1cm-1 (x = 0.05, 750 ºC) for the β-phase at 670 ºC and 0.57 Ω-1cm-1 (x=0.05, 800 ºC) in binary systems at 690 ºC. The phase transition which manifests itself by the jump in the conductivity curves was seen and verified by differential thermal analysis measurements. The activation energies of the samples were found to be about 0.71-1.57 eV.
Physica C: Superconductivity and its Applications
The present study was on the sound of a traditional instrumentQanun and investigated the effects ... more The present study was on the sound of a traditional instrumentQanun and investigated the effects of soundboards of different thicknesson tone characteristics. Changes in sound level were observed. Theacoustic envelopes contained three regions were drawn for all of pitches.The changes in the sound levels were studied on this graphic. FourierAnalysis was made on recordings. Frequency distribution curves werealso drawn. Fundamental and overtone level distributions were shownon these graphics. The levels of harmonics were compared tofundamental level on these graphics. The structures of upper partialtones were studied. Frequency ranges of the graphics were limited to 100-10000 Hz. The numeric values on the all of graphics were analysed; andthe differences between all overtones were noted. A typical sound levelcurve for the Qanun was shown. In 3.0 mm thickness, due to theirregular resonances resulting from the thin body, too many harmonicsand long decay periods were observed. In higher t...
Journal of Materials Science, 2005
ABSTRACT In the present work, tetragonal β type Bi(III)2 − 2x Dy(II)2x O3 − x ■ x (■:,empty oxyge... more ABSTRACT In the present work, tetragonal β type Bi(III)2 − 2x Dy(II)2x O3 − x ■ x (■:,empty oxygen site) solid solutions have been synthesized in the ranges 0.06 ≤ x ≤ 0.08 at 750°C and 0.05 ≤ x ≤ 0.09 at 800°C by doping small amounts of Dy2O3 into monoclinic α -Bi2O3. X-ray powder diffraction (XRD) has been used for characterisation of the doped Dy2O3 powders as well as for calculation of the unit cell parameters. The polymorphic phase transitions, crystallographic properties, particle sizes, the scanning electron microscope (SEM) microprobe analysis and Dy2O3 content dependence of the lattice parameters of the observed β-phase has been reported. The obtained solid solutions had nonstoichiometric character and nonstoichiometry increases with the increasing amount of Dy2O3 addition. The experimental results suggested that oxygen vacancies are present in the crystal structure of Dy2O3 doped β type solid solutions.
Current Applied Physics, 2014
The dielectric loss (ε) properties of MgB 2 composites were investigated by using the conductance... more The dielectric loss (ε) properties of MgB 2 composites were investigated by using the conductance-voltage (G/w-V) measurements in the wide frequency and applied bias voltage range at four different temperature levels. Experimental results show that both G/w and ε are found strong functions of frequency and applied bias voltage for each temperature level. These changes in G/w and ε are considerably high especially at low frequencies and temperatures. The values of ε decrease exponentially with increasing frequency until 100 kHz and then become almost constant. Such behavior of G/w and ε shows that interfacial polarization is more effective especially at low frequencies. In addition, the current-voltage (I-V) characteristics were also evaluated for 100, 200, and 300 K, and the I-V curves for each temperature show linear behavior. Results indicate that the G/w-V measurements may be a useful tool to characterize the dielectric properties and conductivity of MgB 2 .
Brazilian Journal of Medical and Biological Research, 2004
The aim of the present study was to measure full epidermal thickness, stratum corneum thickness, ... more The aim of the present study was to measure full epidermal thickness, stratum corneum thickness, rete length, dermal papilla widening and suprapapillary epidermal thickness in psoriasis patients using a light microscope and computer-supported image analysis. The data obtained were analyzed in terms of patient age, type of psoriasis, total body surface area involvement, scalp and nail involvement, duration of psoriasis, and family history of the disease. The study was conducted on 64 patients and 57 controls whose skin biopsies were examined by light microscopy. The acquired microscopic images were transferred to a computer and measurements were made using image analysis. The skin biopsies, taken from different body areas, were examined for different parameters such as epidermal, corneal and suprapapillary epidermal thickness. The most prominent increase in thickness was detected in the palmar region. Corneal thickness was more pronounced in patients with scalp involvement than in patients without scalp involvement (t =-2.651, P = 0.008). The most prominent increase in rete length was observed in the knees (median: 491 µm, t = 10.117, P = 0.000). The difference in rete length between patients with a positive and a negative family history was significant (t =-3.334, P = 0.03), being 27% greater in psoriasis patients without a family history. The differences in dermal papilla distances among patients were very small. We conclude that microscope-supported thickness measurements provide objective results.
Superconductor Science and Technology, 2022
We report transport, electromechanical, and structural properties of single core MgB2/Fe wire pro... more We report transport, electromechanical, and structural properties of single core MgB2/Fe wire produced using a new fabrication method, called designed IMD process, which relies on the use of non-stoichiometric Mg + B pellets with excess Mg in place of a central Mg rod used in the standard internal Mg diffusion (IMD) method. Structural analysis revealed the successful formation of a porous MgB2 structure in the center and a dense circular MgB2 layer surrounding this structure in the designed-IMD wire. Fast transport I –V measurements showed that the designed IMD method increased engineering critical current density (Je) up to twice that of the IMD wires in self-field. The central porous MgB2 structure shared the applied current and indirectly behaved as an internal stabilizer against quench damage at high applied currents.
Physica B: Condensed Matter, 2020
Abstract A novel method is presented for the production of the in-situ MgB2/Fe mono-core internal... more Abstract A novel method is presented for the production of the in-situ MgB2/Fe mono-core internal magnesium diffusion (IMD) processed wires by using Mg powder instead of Mg rod to accomplish internal diffusion of magnesium into semi-crystalline boron powder. The MgB2/Fe wires were cold drawn to 0.81 mm diameter. The structural investigation of superconducting MgB2 layers was completed using X-ray diffraction and scanning electron microscopy. There are no traces of unreacted magnesium in the central region after Mg/B reaction. The use of magnesium powder increases the reaction rate and provides rapid Mg diffusion. The Mg powder method is also effective in reducing boron-rich regions in MgB2 IMD wires.
Physica C: Superconductivity and its Applications, 2019
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Papers by İbrahim BELENLİ