Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Teber, Ahmet(2)
- Akçadirci, Esra(1)
- Celikbicak, Omur(1)
- Dikmen, Fatih(1)
- Ecem Bayram, Nesrin(1)
- Gencay Celemli, Omur(1)
- Gokce, H. Suleyman(1)
- Güneş, Sibel(1)
- Kahya, Volkan(1)
- Manay, Eyüphan(1)
- Ozenirler, Cigdem(1)
- Simsek, Osman(1)
- Sorkun, Kadriye(1)
- Turan, Muhittin(1)
- Zare, Golshan(1)
- Çakir, Ǔur(1)
- Çomakli, Ömer(1)
- Özceyhan, Veysel(1)
Yayınlar
- MakaleAçık Erişim2024Scopus SJRQ2Reflective Polarization Conversion with Multi-Functional, Ultrathin Metasurface for Ku-and K-Band Applications
Teber, Ahmet
Reflective polarization conversions with a simplistic design of an ultrathin, single-layered, and multi-functional anisotropic metasurface as a polarization converter is utilized for Ku-and K-band applications. The designs with two substrate thicknesses (0.095λ0 and 0.069λ0, respectively) are capable of a cross-polarization converter (CPC) and a linear-to-circular (LTC) polarization conversion. The design with 0.095λ0 thickness achieves a CPC between 17.96 and 26.90GHz with the efficiency of more than 90% and a relative bandwidth of 40% under normal incidence. It maintains angular stability by altering the oblique incidence angles up to 300 with greater than 80% of the PCR in the K-band. Meanwhile, an LTC in two frequency bands, 10.30-10.53GHz and 28.65-29.70GHz, is also numerically demonstrated. The second design with 0.069 λ0 thickness provides a CPC above the PCR value of 87% in the frequency range from 10.46-23.05GHz (covering the entire Ku-and part of the K-band) with angular stability of 40 above the PCR value of 80%. In the meantime, an LTC with relative bandwidth of 75% in the frequency range from 9.53-9.79&24.74-25.27GHz is numerically revealed. These polarization converters exhibit relatively good performances of facile structure and multi-functional properties, which can be useful in Ku-and K-band applications.
AtıfScopus5WoS3OpenAlex5TR Dizin1
İncele - MakaleAçık Erişim2021Scopus SJRQ2Free vibration and buckling analysis of functionally graded sandwich beams by Navier's method; [Fonksiyonel derecelendirilmiş sandviç kirişlerin Navier yöntemiyle serbest titreşim ve burkulma analizi]
Turan, Muhittin; Kahya, Volkan
In this study, free vibration and buckling analyses of functionally graded (FGM) sandwich beams is investigated by Navier's method. Displacement field is defined according to the first order shear deformation theory, and the equations of motion are derived by the Lagrange's principle. Volumetric ceramic ratio is defined by a power-law rule. In the analytical solution, different trigonometric series functions are used for each end conditions considered. Two cases of functionally graded sandwich beams are considered: a) Homogeneous ceramic core and FGM faces (Type A), and b) FGM core and homogeneous faces (Type B). Natural frequencies and buckling loads are obtained for different boundary conditions, power-law indices and slenderness. Numerical results are compared with the available literature, and a good agreement are obtained between the results.
AtıfScopus24WoS21OpenAlex16TR Dizin7İncele - MakaleAçık Erişim2021Scopus SJRQ3Aggressive environment performance of low energy cements containing fly ash
Gokce, H. Suleyman; Simsek, Osman
In this study, compressive strength performance of boron active belite cement containing fly ash at the ratios of 0, 10, 20, and 30% (by weight of cement) is researched against aggressive environments; sea water, 5% sodium sulphate solution, and 5% ammonium nitrate solution in addition to tapping water. Alternative low energy cement i.e., Portland-composite cement was used and its results were compared with those of boron active belite cement. Early strength losses (reaching up to 40%) of the boron active belite cement with incorporation of fly ash up to 30% were found to be less pronounced than those (reaching up to 51%) of Portland-composite cement in tapping water. Although, the losses were highly compensated with the prolonged curing period (90 days), boron active belite cement and Portland-composite cement kept their losses up to 14% and 36%, respectively. Residual mechanical properties (reaching up to 67%) of boron active belite cement against aggressive environments were found almost similar to those of Portland-composite cement in presence of 30% fly ash. In conclusion, the study shows that belite cements with low fly ash contents can be a reasonable alternative for specific applications such as mass concrete, hot weather concreting especially in aggressive environments.
AtıfScopus3WoS1OpenAlex5TR Dizin1İncele - MakaleAçık Erişim2020Scopus SJRQ3Beamforming radiation properties of absorbing/transparent zones-added horn antenna
Teber, Ahmet
In this study, we present beamforming of radiation patterns on a transmitter horn antenna by mounting an electromagnetic wave absorber, in which electromagnetic wave absorber is fabricated as concentric zones. The concentric zones consist of an absorbing material of manganese soft spinel ferrite blended with multi-walled carbon nanotubes with the thickness of 1 mm installed on the aperture of the antenna working in Ku-band. We have experimentally measured scattering parameter of transmission, S21, using a vector network analyser to perform radiation patterns in polar coordinates. As compared to the radiation properties of air horn antenna and absorbing/transparent zone-added horn antenna produces an appreciable effect to concentrate radiation beam in the main, side and back lobes with reducing side and back lobe levels for each frequency in H-plane. For the radiation pattern in E-plane, we have observed the suppressed side lobes at three frequencies of 15 GHz, 17 GHz and 18 GHz. The results indicate that the absorbing/transparent zone keeps an important role for further development of the applications of directional antennas so that the effective radiation is to be significantly concentrated.
AtıfScopus1OpenAlex2İncele - MakaleYalnız künye2019Scopus SJRQ3Physicochemical and palynological characterization of the onobrychis miller (fabaceae) honey
Ozenirler, Cigdem; Gencay Celemli, Omur; Ecem Bayram, Nesrin; Dikmen, Fatih; Zare, Golshan; Celikbicak, Omur; Sorkun, Kadriye
The purpose of this study was to contribute toward characterizing the general properties of the Onobrychis Miller (sainfoin) honey.We analyzed 21 samples of Onobrychis honeys, which were collected in 2013, from Northeast Anatolia according to their microscopic and physicochemical features (fructose/glucose (F/G) ratio, 5-(hydroxymethyl) furan-2-carbaldehyde (HMF) value, and volatile compounds). The relationships were examined between these variables with statistical methods such as principal component, regression, and correlation analyses. Statistical analyses revealed certain correlation patterns between several parameters. Onobrychis radiata (Desf.) M. Bieb., O. tournefortii (Willd.) Desv., O. oxyodonta Boiss. and Onobrychis spp. pollens were identified.TPN-10 ranged from 6532 to 481157 while the HMF values were between 0.1-7.5 mg/kg and F/G ratios were between 0.8-1.3. Alcohols, aldehydes, aliphatic acids and their esters, carboxylic acids and their esters, hydrocarbons, flavonoids, ketones, sugars and vitamins were identified in the honey samples within ranges of 0-11.95%, 0-16.76%, 0-24.72%, 0-1.86%, 0-14.71%, 2.74-7.09%, 0-27.02%, 5.12-51.39%, and 0-21.36%, respectively.Although it was not significant, a positive correlation between flavonoids and Onobrychis pollen number was calculated via correlation analysis. There was no meaningful correlation between Onobrychis pollen number and other parameters. Although a negative trend between flavonoids and sugars was observed, it was not significant. F/G ratio was found to be positively correlated with sugars, HMF, and TPN-10 of which the latter two parameters had significant values. Furthermore, a significant positive correlation between TPN-10 and HMF was also detected.
AtıfScopus3İncele - MakaleYalnız künye2012Scopus SJRQ3The prediction of heat transfer and fluid characteristics for equilateral triangular bodies in tandem arrangement by artificial neural networks
Manay, Eyüphan; Güneş, Sibel; Akçadirci, Esra; Özceyhan, Veysel; Çakir, Ǔur; Çomakli, Ömer
The objective of this study is to investigate the effect of the spacing between equilateral dual triangular bodies symmetrically placed into the channel axis under steady state conditions on heat transfer and fluid characteristics by using artificial neural networks (ANN). The Back Propagation (BP) training algorithm was applied to train the model. The successful application proved that ANN model can be used for predicting the Nusselt number and skin friction coefficient as a convenient and effective method. The distribution of local Nusselt number, skin friction coefficient along the channel wall and overall enhancement ratio of all investigated cases are presented.
AtıfScopus5İncele - DergiJournal of the Faculty of Engineering and Architecture of Gazi University
- DergiGazi University Journal of Science