Yayınlar
Koleksiyondaki öğeler
- MakaleYalnız künye2017Scopus SJRQ2Existence of one weak solution for p(X)-biharmonic equations involving a concave-convex nonlinearity
Mashiyev, Rabil Ayazoglu; Alisoy, Gülizar; Ekincioglu, Ismail
In the present paper, using variational approach and the theory of the variable exponent Lebesgue spaces, the existence of nontrivial weak solutions to a fourth order elliptic equation involving a p(x)-biharmonic operator and a concave-convex nonlinearity the Navier boundary conditions is obtained.
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İncele - MakaleYalnız künye2014Scopus SJRQ2Simple procedure for robust and accurate complex permittivity measurements of low-loss materials over a broad frequency band
Hasar, U.C.; Barroso, J.J.; Kaya, Y.; Bute, M.; Ertugrul, M.
In this research paper, we propose a simple procedure for accurate, stable and broadband measurements of complex permittivity of low-loss dielectric samples with considerable lengths. We identify and demonstrate by numerical and analytical analyses the main ill-behaved factor that gives rise to inaccurate peaks for measurements of electrical properties of low-loss samples in the well-known Nicolson-Ross-Weir method. Without using this factor in the expressions and combining better features of the methods available in the literature, the proposed procedure allows highly accurate permittivity measurements over a broad band. We have validated the proposed method by permittivity measurements of a low-loss sample by different methods.
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İncele - MakaleYalnız künye2015Scopus SJRQ3Conformational and spectroscopic behaviors of 2,4-xylyl isothiocyanate
Cinar, Mehmet; Karabacak, Mehmet; Chand, Satish; Shukla, Vikas K.; Sinha, Leena; Prasad, Onkar; Singh, Manoj Pratap; Asiri, Abdullah M.
This study aims to identify the conformational and spectroscopic characteristics of 2,4-xylyl isothiocyanate (C9H9NS) compound via experimental and computational methods. To accomplish this, density functional theory (DFT), with the B3LYP functional was used to determine ground state conformation, vibrational wavenumbers and also isotropic chemical shifts of the title molecule. Experimentally, vibrational features of the compound were evaluated by FT-IR and FT-Raman spectroscopic analysis in the solid phase. On the basis of these studies, the conformational and spectroscopic behaviors of 2,4-xylyl isothiocyanate were interpreted. The fundamental vibrational wavenumbers as well as their intensities were computed, and a good correlation between experimental and scaled calculated wavenumbers was observed. The polarizability, first hyperpolarizability and dipole moment values of 2,4-xylyl isothiocyanate were calculated at the same level of theory and basis set. The results show that 2,4-xylyl isothiocyanate molecule possesses nonlinear optical (NLO) behavior with non-zero values. Stability of the molecule arising from hyper-conjugative interactions and charge delocalization was analyzed using natural bond orbital (NBO) analysis.
AtıfScopus7WoS5OpenAlex5İncele - MakaleYalnız künye2019Scopus SJRQ1The effectiveness of the monetary transmission mechanism channel in Turkey
Okur, Fatih; Akkuş, Ömer; Durmaz, Atakan
This study investigates on which channels the monetary transmission mechanism works effectively. In this context, quarterly data for the period 2005-2017 is used for Turkey and the variables used to determine the efficiency of the monetary transmission mechanism are analyzed by the VAR method. The obtained results indicate that the loans and reserves have a more effective role on the inflation as a channel of the monetary transmission mechanism. According to the long run results, while the exchange rate and reserves channel have a negative effect on the real GDP, it is revealed that loans have a positive effect on the real GDP in the long run stabilization.
AtıfScopus3İncele - MakaleAçık Erişim2013Scopus SJRQ2Time-dependent effect of salicylic acid on alleviating cold damage in two barley cultivars differing in cold tolerance
Mutlu, Salih; Karadaǧoǧlu, Ömer; Atici, Ökkeş; Taşǧin, Esen; Nalbantoǧlu, Barbaros
The time-dependent effect of salicylic acid (SA) on alleviating cold damage in the Tokak (tolerant) and Akhisar (sensitive) varieties of barley (Hordeum vulgare) was investigated. Seedlings subjected to 0.0, 0.1, and 1 mM SA for 7 days were transferred to cold (7/5 °C) on days 7, 14, 21, and 28 for 3 days. It was found that 0.1 mM SA had a greater alleviating effect, decreasing the freezing injury in both varieties for at least 10 days after the application. Moreover, 0.1 mM SA had a greater effect on alleviation in Tokak by increasing the ice nucleation activity of apoplastic proteins extracted from the leaves. SA was effective for at least 24 days in decreasing the effect of freezing temperature by regulating apoplastic proteins in the leaves after the application. Furthermore, 0.1 and 1 mM SA had an alleviating effect by decreasing the lipid peroxidation level in both varieties for at least 24 days after the application. It can be seen that SA treatment can play a positive role in alleviating cold damage in barley. Therefore, it is suggested that results from SA treatments may contribute to research related to diminishing cold damage in agricultural applications.
AtıfScopus21WoS8OpenAlex23İncele - MakaleAçık Erişim2016Scopus SJRQ4Karyotype analyses of the genus Matthiola (Brassicaceae) in Turkey
Martin, Esra; Ünal, Murat; Doǧan, Bekir; Altinordu, Fahim; Sefali, Abdurrahman; Kaya, Ayla
In the present paper, karyotype analyses are reported for 12 taxa of Matthiola from Turkey. Matthiola trojana Dirmenci, Satil & Tümen, M. odoratissima (Pall.) R.Br., M. anchonifolia Hub.-Mor., M. montana Boiss., M. fruticulosa (L.) Maire ssp. fruticulosa and M. ovatifolia (Boiss.) Boiss. counted 2n=12 chromosomes, and M. incana (L.) R.Br., M. longipetala (Vent.) DC. ssp. bicornis (Sibth. et Smith) P. W. Ball, M. longipetala (Vent.) DC. ssp. longipetala, M. longipetala (Vent.) DC. ssp. pumilio (Sibth. & Smith) P. W. Ball, M. sinuata (L.) R.Br., and M. tricuspidata (L.) R.Br. showed 2n=14 chromosomes. The idiograms and karyomorphometric data obtained by using Image Analysis System (Bs200Pro). The chromosome number of M. montana was determined for the first time. Also, karyotype asymmetry index such as MCA, CVCL and CVCL were measured for the reconstruction of karyological relationships.
AtıfScopus9WoS7OpenAlex7İncele - MakaleAçık Erişim2019Scopus SJRQ1Electrospraying method for fabrication of essential oil loaded-chitosan nanoparticle delivery systems characterized by molecular, thermal, morphological and antifungal properties
Yilmaz, Mustafa Tahsin; Yilmaz, Azime; Akman, Perihan Kubra; Bozkurt, Fatih; Dertli, Enes; Basahel, Abdulrahman; Al-Sasi, Basil; Taylan, Osman; Sagdic, Osman
Fabrication of essential oil loaded-chitosan nanoparticles using electrospraying technique appears to be a novel strategy to develop thermally stable nanoparticles possessing higher encapsulation efficiency and particle stability. This study aims to fabricate chitosan nanoparticles (CNPs) loaded with Origanum vulgare essential oil (OEO, Origanum vulgare L.) at different proportions (OEO/CH proportions of 0:1, 0.0625:1, 0.125:1, 0.25:1 and 0.5:1 mL/g) using electrospraying technique. The CNPs were characterized in term of their particle size and stability (dynamic light scattering), encapsulation efficiency (spectrophotometry), and molecular (Fourier transform infrared spectroscopy), thermal (differential scanning calorimetry/thermogravimetric analysis), morphological (scanning electron microscopy) and antifungal (agar dilution method) and fungistatic activity properties. The average particle sizes of the CNPs ranged between 290 and 483 nm with a spherical morphology. Positively charged surface characteristics were observed to increase with the increment of OEO concentration in CNPs. The encapsulation efficiency values were determined in the range of 70.1 and 79.6%. The molecular and thermal analyses exposed very decent encapsulation of OEO into thermally stable chitosan nanoparticles. Morphological analysis verified the spherical shapes of these nanoparticles. Above all, the antifungal effectiveness of OEO against the Alternaria alternata AY1 could be significantly (p < 0.05) increased by its encapsulation into chitosan nanoparticles fabricated by the electrospraying technique. Consequently, it can be stated that the electrospraying technique developed is able to fabricate thermally stable nanoparticles owning higher encapsulation efficiency and particle stability. The results and findings suggest that the electrospraying technique would be a promising method to fabricate chitosan-based nanoparticles as an antimicrobial agent to control their release in a prolonged preservative effect in cosmetic, pharmaceutical and food applications for adjustable dosage forms. Industrial relevance: The fungal agents such as Alternaria alternata cause great damages on post-harvest fresh fruits and vegetables, thus leading to a great economical lose. Therefore, a great variety of methods in struggling with disease have been previously proposed. Nowadays, the most effective leading methods to struggle against plant diseases are those applied with synthetic fungicides to minimize such lose in post-harvest fruit and vegetables. However, intensive and unconscious use of the fungicides leads the pathogens to develop resistance against these agents as well as to accumulation of chemical residues in soil, water and air and finally to formation of carcinogenic effects on human health. Nowadays, a great effort is being exerted to develop novel biodegradable and natural antimicrobial agents for struggling fungal spoilage in postharvest products. Essential oils are among the most widely used natural struggling methods. Essential oils obtained from plants have been extensively used since they are natural antimicrobial agents. However, they cannot be effectively used in spite of their extensive applications. Recently, some researches in the field of nanotechnology have demonstrated that the effectiveness of active substances could be increased by using some techniques. In this respect, we aimed at developing essential-oil-loaded-chitosan-nanoparticle delivery systems using an electrospraying deposition system to prevent fungal colonization on food and plant materials. By increasing antifungal effectiveness of essential oils by their encapsulation into nanoparticles, it will be possible to decrease the levels of regularly applied dose and reflect the obtained outcomes to the food and agriculture industry. This study is the first example of production of essential oil loaded nanoparticles using the electrospraying-hydrodynamic process and showed that encapsulation of oregano essential oil into chitosan based nanoparticles (CNPs) by using the electrospraying deposition technique considerably increased the antifungal effectiveness of the Origanum vulgare essential oil. Our results highlight the potential use of the chitosan nanoparticles (CNPs) loaded with different amounts of Origanum vulgare in food and agriculture industry as an effective fungicidal material against Alternaria alternata, suggesting that the CNPs can be promising tools to compete with synthetic fungicide counterparts and limit use of synthetic ones for struggling of food and plant pathogens. Therefore, the results of this study should be of great importance to industrial applications in terms of development of natural, but effective preservatives as alternative to synthetic ones. In this respect, the CNPs would find a great industrial application area in the food and agriculture industry which seek natural preservatives due to the recent health concerns.
AtıfScopus119WoS101OpenAlex118İncele - MakaleAçık Erişim2019Scopus SJRQ3A functional bleeding test apparatus for concrete
Gökçe, H. Süleyman; Andiç-Çakır, Özge
Bleeding is one important indicator that is related to the physical and mechanical properties of fresh and hardened concrete. Standards generally prefer methodologies that are similar to one another to measure the bleeding of fresh concrete. The preferred test apparatus used in the standards is troublesome because it requires a manual test procedure and repeated measurements until final setting of the fresh concrete. The functional bleeding test apparatus presented in this study will ease test performance and eliminate the faults caused by the test procedure and the experimenter.
AtıfScopus2WoS1OpenAlex3İncele - MakaleAçık Erişim2019Scopus SJRQ1Characterization of chemical, molecular, thermal and rheological properties of medlar pectin extracted at optimum conditions as determined by Box-Behnken and ANFIS models
Al-Amoudi, Rami H.; Taylan, Osman; Kutlu, Gozde; Can, Asli Muslu; Sagdic, Osman; Dertli, Enes; Yilmaz, Mustafa Tahsin
In this work, response surface methodology and adaptive neuro-fuzzy inference system approaches were used to predict and model effect of extraction conditions of pectin from medlar fruit (Mespilus germanica L.). The pectin extracted at optimized conditions (89 °C, 4.83 h and 4.2 pH) could be classified as high methoxyl pectin. Sugar composition analysis showed that pectin was mainly composed of D-galacturonic acid, L-arabinose, L-rhamnose, D-galactose and D-glucose. Fourier Transform Infrared Spectroscopy, RAMAN and nuclear magnetic resonance spectra confirmed molecular structure, revealing presence of D-galacturonic acid backbone. X-ray diffraction patterns revealed an amorphous structure. Differential scanning calorimetry showed endothermic (123 °C) and exothermic peaks (192 °C). Thermogravimetric analysis revealed three decomposition regions, 50–225 °C, 225–400 °C and 400–600 °C. Steady and dynamic shear analyses revealed that pectin had a pseudo-plastic behavior with storage (G′) and loss (G″) modulus increasing with increment in frequency, indicating viscoelastic structure more predominantly elastic than viscous.
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İncele - MakaleAçık Erişim2019Scopus SJRQ2A study of gamma attenuation property of UHMWPE/Bi 2 O 3 nanocomposites
Abdalsalam, Alyaa H.; Sayyed, M.I.; Ali Hussein, Thulfiqar; Şakar, Erdem; Mhareb, M.H.A.; Ceviz Şakar, Betul; Alim, Bünyamin; Kaky, Kawa M.
In this study, nanocomposite material made of ultra-high molecular weight and bismuth oxide was developed to be used for protection from nuclear radiation. The traditional hot-pressing technique was used for preparing composite samples. The concentrations of Bi 2 O 3 were selected to be 0.5, 1.0, 1.5, 2.0 wt%. In order to study the changes in surface morphology, we examined all samples by scanning electron microscopic (SEM). We evaluated the semi-quantitative of all elements used to fabricate these samples using EDX. Additionally, all samples including pure Bi 2 O 3 has been examined with X-ray diffraction (XRD). Besides that, Raman spectroscopy of all synthesized polymer matrix was measured to explore the different molecular groups. Also, the photon attenuation ability for the present samples was measured experimentally at eight energies varying from 30.8 keV to 383.9 keV using 133 Ba radioactive point source.
AtıfScopus68WoS64OpenAlex70İncele - MakaleAçık Erişim2014Scopus SJRQ2Impact of antibacterial drugs on human serum paraoxonase-1 (hPON1) activity: An in vitro study
Söyüt, Hakan; Kaya, Elif Duygu; Beydemir, Şükrü
Objective: To investigate the in vitro effects of the antibacterial drugs, meropenem trihydrate, piperacillin sodium, and cefoperazone sodium, on the activity of human serum paraoxonase (hPON1). Methods: hPON1 was purified from human serum using simple chromatographic methods, including DEAE-Sephadex anion exchange and Sephadex G-200 gel filtration chromatography. Results: The three antibacterial drugs decreased in vitro hPON1 activity. Inhibition mechanisms meropenem trihydrate was noncompetitive while piperacillin sodium and cefoperazone sodium were competitive. Conclusions: Our results showed that antibacterial drugs significantly inhibit hPON1 activity, both in vitro, with rank order meropenem trihydrate piperacillin sodium cefoperazone sodium in vitro.
AtıfScopus5OpenAlex7İncele - MakaleYalnız künye2015Scopus SJRQ1An experimental and density functional study on conformational and spectroscopic analysis of 5-methoxyindole-2-carboxylic acid
Cinar, Mehmet; Karabacak, Mehmet; Asiri, Abdullah M.
In this article, a brief conformational and spectroscopic characterization of 5-methoxyindole-2-carboxylic acid (5-MeOICA) via experimental techniques and applications of quantum chemical methods is presented. The conformational analysis of the studied molecule was determined theoretically using density functional computations for ground state, and compared with previously reported experimental findings. The vibrational transitions were examined by measured FT-IR and FT-Raman spectroscopic data, and also results obtained from B3LYP and CAM-B3LYP functionals in combination with 6-311++G(d,p) basis set. The recorded proton and carbon NMR spectra in DMSO solution were analyzed to obtain the exact conformation. Due to intermolecular hydrogen bondings, NMR calculations were performed for the dimeric form of 5-MeOICA and so chemical shifts of those protons were predicted more accurately. Finally, electronic properties of steady compound were identified by a comparative study of UV absorption spectra in ethanol and water solution and TD-DFT calculations.
AtıfScopus23WoS22OpenAlex24İncele - MakaleAçık Erişim2013Scopus SJRQ2Biosorption properties of Morus alba L. for Cd (II) ions removal from aqueous solutions
Serencam, Huseyin; Ozdes, Duygu; Duran, Celal; Tufekci, Mehmet
The abundantly available industrial waste product Morus alba L. pomace (MAP) is one of the cost-effective biosorbent for removal of metal ions from aqueous solutions. Hence, in the present study, we aimed to test the ability of MAP to remove Cd(II) ions through batch biosorption process. Firstly, MAP was characterized using several techniques, and then the influence of various experimental parameters such as initial pH of the aqueous solution, initial Cd(II) concentration, contact time, MAP concentration, and temperature were evaluated upon the biosorption process. It was found that the maximum uptake of Cd(II) ions occurred at initial pH 6.0 and optimum contact time was observed as 60 min. Cd(II) ions adsorption on MAP analyzed by the Langmuir and Freundlich isotherm models and the maximum monolayer biosorption capacity of MAP was found to be 21.69 mg g-1 by using the Langmuir isotherm model. The pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models were employed to describe the biosorption kinetics. In order to investigate the thermodynamic properties of the biosorption process, the changes in the Gibbs free energy (â̂†G), enthalpy (â̂†H), and entropy (â̂†S) were also evaluated and it has been concluded that the process was feasible, spontaneous, and endothermic in the temperature range of 5-40 C.
AtıfScopus38WoS36OpenAlex46İncele - MakaleYalnız künye2017Scopus SJRQ1Toward cost-effective and energy-efficient heat recovery systems in buildings: Thermal performance monitoring
Cuce, Pinar Mert; Cuce, Erdem
Recent studies show that it is possible to reduce heating or cooling demand of a building as using heat recovery systems. Heat recovery technology is basically utilised to mitigate the heat loss, and hence energy consumption due to HVAC. Within the scope of this study, thermal comfort analyses of a test house integrated with a novel polycarbonate heat exchanger are conducted. At pre and post-retrofit case, temperature, relative humidity and CO2 measurements are carried out for a test period of one week. The results indicate that the internal CO2 concentration is not at desirable range due to lack of ventilation in the test house at the pre-retrofit case. However, following the integration of the novel ventilation system into the test house, CO2 concentration is found to be varying notably from 350 to 400 ppm which corresponds to the actual comfort conditions for indoor environments. It is also concluded from the results that the average relative humidity inside the test house at the post-retrofit case is found to be 57%, which is in the desired range whereas it is considerably high before retrofitting.
AtıfScopus26WoS25OpenAlex33İncele - BildiriYalnız künye2014Scopus SJRQ1ZnO thin film synthesis by reactive radio frequency magnetron sputtering
Şenay, Volkan; Pat, Suat; Korkmaz, Şadan; Aydoʇmuş, Tuna; Elmas, Saliha; Özen, Soner; Ekem, Naci; Balbaʇ, M. Zafer
In this study, ZnO thin films were deposited on glass substrates by reactive RF magnetron sputtering method at argon-oxygen gas mixing (1:1) atmosphere. Some properties of the synthesized films were investigated by interferometry, UV-vis spectrophotometer, atomic force microscopy, and tensiometer. Tauc method was adopted to estimate the optical band gaps. The band gaps of the deposited films were affected by film thickness. We concluded that the surface composition plays a substantial role in the values of the band gaps. Nanocrystalline structures were detected in all produced samples.
AtıfScopus55WoS49İncele - MakaleAçık Erişim2016Scopus SJRQ1An experimental study on the ultra-fine grinding of gypsum ore in a dry ball mill
Öksüzoğlu, Bilge; Uçurum, Metin
Gypsum is a crystalline form of hydrated calcium sulfate (CaSO4·2H20) generally used in cements and plasters in the construction industry, though also in paints, fertilizers, medicines, papers, and textiles. For use in these materials, gypsum must be ground finely (<100 μm), if not ultra-finely (<10 μm), for which ball mills are most effective. Despite gypsum's widespread use and the regular need to grind it, studies concerning the grinding of gypsum ore remain scarce. In response, in this study, we have systematically investigated how certain grinding parameters (i.e., mill speed, ball filling ratio, ball size distribution, powder filling ratio, grinding aid ratio, and grinding time) of conventional dry ball mills affect the grindability of gypsum ore. We determined the properties of the micronized gypsum products obtained in optimal grinding conditions, and the results showed that the dry ball mill grinding process can effectively produce ultra-fine gypsum products.
AtıfScopus38WoS32OpenAlex42İncele - MakaleAçık Erişim2017Scopus SJRQ2Prevalence and comparing of some microbiological properties, somatic cell count and antibiotic residue of organic and conventional raw milk produced in Turkey
Ürkek, Bayram; Şengül, Mustafa; Erkaya, Tuba; Aksakal, Vecihi
The aim of this study was to investigate the effects of production systems and milk collection periods on the somatic cell count (SCC), some microbiological properties, total aerobic mesophilic bacteria (TAMB), coliform, Staphylococcus aureus (S. aureus), yeast and mould) and antibiotic residue of milk; in Turkey. Milk samples were collected from 9 conventional farms and 9 organic farms during one year time, at six different months (December 2013 to October 2014), and all farms were selected from the same geographical locations. All organically managed farms had organic production certificates given by the Republic of Turkey Ministry of Food, Agriculture and Livestock. The count of TAMB, coliform, and coagulase positive S. aureus were affected by production systems at the level of p<0.01; yeast and mold, and somatic cell count (SCC) were affected at the level of p<0.05. But, differences according to months were statistically significant only on TAMB (p<0.01) and coliform (p<0.05) counts. The general means of TAMB, coliform and yeast and mould counts of the organic milk (OM) were significantly lower (p<0.05), while the general means of SCC and coagulase positive S. aureus count of the OM was significantly higher (p<0.05) compared to conventional milk (CM). Antibiotic residue was determined in one of the CM sample and in two of the OM samples. Our study is the first research that compared conventional and organic milk in Turkey. This study indicated that the microbiological quality of OM was the higher in terms of TAMB, coliform and yeast and mould, whereas was the lower in relation to SCC and coagulase positive S. aureus counts. But, the quality of both milk types should be improved.
AtıfScopus10WoS8OpenAlex12İncele - MakaleYalnız künye2018Scopus SJRQ1Thermodynamic and thermoeconomic analyses of an organic Rankine cycle adapted gas turbine cycle using S-CO2 ; [Organik Rankine çevrimi entegre edilmiş S-CO2 kullanılan bir gaz türbin çevriminin termodinamik ve termoekonomik analizi]
Tozlu, Alperen; Özahi, Emrah; Abuşoğlu, Ayşegül
In this study, a model of an organic Rankine cycle (ORC) adopted gas turbine cycle using supercritical CO2 (S-CO2) as working fluid is performed. Thermodynamic analyses of a system are carried out using Aspen Plus and EES programs. As a result of thermodynamic analyses, electricity production capacity, energy and exergy efficiencies of the proposed system are evaluated as 1530.88 kW, 23.30% and 59.60%, respectively. For the thermoeconomic analysis of the system, specific exergy costing method, SPECO, is applied as widely used one among the second law based methods. Unit exergetic cost of electricity production for 1 kWh is found to be 7.28 ¢ and the total cost of electricity production for 1530.88 kWh is found to be 114.43 $. Annual return from the system of ORC adopted gas turbine cycle using S-CO2which has the total investment cost of 3,033,300 $ is evaluated as 741,146 $ taking into account the difference between the cost of electricity production and the sale price of electricity. As a result of the thermoeconomic analysis, the payback period of the system is found to be 4.09 years. Purpose: To propose a model (an organic Rankine cycle (ORC) adopted gas turbine cycle using supercritical CO2: S-CO2) for an existing solid waste power plant in the frame of the heat recovery (Waste-to-energy). Theory and Methods: Thermodynamic and thermoeconomic analyses were utilized for the proposed model in order to evaluate the energy and exergy efficiencies. Results: The energy and exergy efficiencies of the system were calculated as 23.30 % and 61.60 % respectively. 1 kWh of electricity generated from GT-ORC system is produced to 7.28 ¢. The total electricity production cost of 1530.88 kW-hours was calculated as $ 111.43. Conclusion: The total cost of the developed GT-ORC system is $ 3,033,300. The difference between the cost of electricity generated from the GT-ORC system and the cost of the electricity sales is expected to be $ 741,146 annually for the proposed GT-ORC system. As a result of this profit, the payback period of the system was calculated as 4.09 years.
AtıfScopus8İncele - MakaleYalnız künye2018Scopus SJRQ1Vibration and stability analysis of functionally graded sandwich beams by a multi-layer finite element
Kahya, Volkan; Turan, Muhittin
This paper presents a finite element model based on the first-order shear deformation theory for free vibration and buckling analyses of functionally graded (FG) sandwich beams. The present element has 3 N + 7 degrees-of-freedom for an N-layer beam. Lagrange's equations are employed for derivation of the equations of motion. Two types of FG sandwich beams are considered: (a) Type A with FG faces and homogeneous ceramic core, and (b) Type B with homogeneous ceramic and metal faces and FG core. Natural frequencies and buckling loads are calculated numerically for different boundary conditions, power-law indices, and span-to-height ratios. Accuracy of the present element is demonstrated by comparisons with the results available, and discussions are made on the results given in graphs and tables for the sandwich beams considered.
AtıfScopus89WoS81OpenAlex81İncele - MakaleYalnız künye2015Scopus SJRQ2GaN thin film deposition on glass and PET substrates by thermionic vacuum arc (TVA)
Pat, Suat; Korkmaz, Şadan; Özen, Soner; Şenay, Volkan
In this paper, GaN thin film production was realized by thermionic vacuum arc (TVA), a plasma deposition technique, for the first time. We present a new deposition mechanism for GaN thin films with a very short production time. Microstructure properties of samples were analyzed by X-ray diffractometry. The peak at 2θ = 72.88° corresponding to GaN (0004) was detected in XRD spectra. The surface morphology of the deposited GaN films was analyzed using field emission scanning electron microscopy and atomic force microscopy. The surface properties of the produced samples are quite different. The average roughness values were determined to be 0.48 nm for GaN/PET and 1.17 nm for GaN/glass. The optical properties (i.e., refractive index and reflection) were determined using an interferometer. Moreover, the obtained optical data were compared with bulk GaN materials. The refractive indexes were measured as 2.2, 3,0 and 2,5 for the GaN/glass, GaN/PET and bulk GaN, respectively. The transparencies of the different GaN-coated substrates are nearly the same. The obtained band gap values were measured in the energy range of 3.3-3.5 eV. TVA is a novel non-reactive plasma technique for the generation of metal organic thin films. The main advantage of this method is its fast deposition rate without any loss in the quality of the films.
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