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https://hdl.handle.net/20.500.12428/3542

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Sol-gel derived ZnO:Sn thin films and fabrication of n-ZnO:Sn/p-Si heterostructure
(Elsevier B.V., 2021) Sarıca, Emrah; Güneş, İbrahim; Akyüz, İdris; Bilgin, Vildan; Ertürk, Kadir
In this work ZnO:Sn thin films were deposited onto glass and p-Si substrates by spin coating of prepared sols which contains different amounts of Zn(CH3COO)2·2H2O and SnCl2 (0, 5, 10 and 15%). Physical properties of ZnO films were examined as a function of SnCl2 in prepared sols. In addition to that, heterostructure examinations were also carried out by depositing all films on p-Si substrates as well. XRD studies revealed that all films have c-axis orientation with crystallite sizes between 38 and 47 nm. AFM and SEM images showed that morphology of the films remarkably deteriorated with the increase in amount of SnCl2 in sol. Optical transmittance and absorbance spectra showed that films have high transmittance and low absorbance in the visible region. Besides, optical band gap increased from 3.27 eV to 3.37 eV. Additional band gap energies were determined for 10% and 15% Sn doped ZnO films. Room temperature photoluminescence spectra for all films were deconvoluted for the evaluation of all emission bands and it was noted that incorporation of SnCl2 into sol led to enhancement of UV-blue emission bands and caused emission bands related to oxygen vacancies to diminish. Four-point-probe measurements revealed that electrical resistivity of ZnO:Sn films increased from 3.20 × 100 Ωcm to 2.82 × 104 Ωcm and diode ideality factor of Ag/ZnO:Sn/p-Si/Au heterostructure was calculated to be in the range of 2.14–4.59 while zero-bias barrier height is in the range of 0.63–0.78 eV.
Türkiye’de COVID-19 Salgınının Tüketici ve Üretici Davranışları Üzerindeki Etkisi
(Çanakkale Onsekiz Mart Üniversitesi, 2021) Can, Gülistan; Kılıç, Figen
İnsanlar olağanüstü bir durumla karşılaştığında, oluşan yeni durumdan daha az etkilenebilmek hatta avantaj sağlayabilmek için davranışlarını değiştirebilmektedirler. COVID-19 salgını bugün insanoğlunun içinde bulunduğu olağanüstü bir durumu yansıtmaktadır. Salgın bütün dünyayı sosyo-ekonomik, kültürel ve politik çapta etkilemektedir. Etkilerin şiddetini azaltmak ve hastalığın yayılmasını kontrol etmek adına karantina ve sosyal uzaklaşma zorunlulukları gibi çeşitli önlemler alınmıştır. Halk sağlığı için alınan önlemler ekonominin tüm unsurları ile bağlantılı olması nedeniyle ekonomik konjonktürü olumsuz yönde etkilenmiştir. Hükümetlerin makro düzeyde aldığı önlemler yanında her bir tüketici ve üreticinin bu salgın sürecinden daha az etkilenmek adına davranışlarında ve tutumlarında meydana getirdikleri değişimler de mikro düzeydeki önlemleri yansıtmaktadır. Üretici ve tüketicilerin davranışları ve tutumlarında meydana gelen değişim ekonomik dönüşümünde en önemli faktörleridir. Buradan hareketle yapılan bu araştırmada COVID-19 salgını sürecinde tüketici ve üreticilerin değişen karar ve davranışları incelenmiş ve gelecek adına öngörüler belirlenmiştir.
Domain wall with quark matters cosmological models in f(R,T) theory
(Springer, 2024) Çag̃lar, Halife; Taşer, Dog̃ukan; Aygün, Sezgin
In this article, Ruban universe has been investigated in presence strange quark matter and normal matter coupled with domain wall for f(R, T) alternative gravitation theory. One of the classifying of f(R, T) has been used as f(R, T) = f(R) + 2 μ(T) to obtain modified Einstein field equations (MEFE’s). The solutions of MEFE’s have been attained with help of relationship between metric potentials. The model has been constructed with domain wall matter distribution in form perfect fluid and then strange quark matter and normal matter (NM) have been attached by using equations of states. Also, all solutions have been reduced from f(R, T) theory to General Relativity (GR) by assuming μ= 0 . In last section, all solutions have been concluded with physical and geometrical perspective for f(R,T) and GR theories.
Eco-friendly and multifunctional aluminum flake/carbon fiber/cellulose composite papers with electromagnetic interference shielding
(SAGE Publications Ltd, 2023) Yıldırım, Ferhat
Recycling every viable material to produce new value-added products not only reduces waste, but also provides an opportunity to create sustainable and innovative solutions while preserving our natural resources. With this motivation, electrically conductive one-dimensional carbon fibers and two-dimensional aluminum flakes reinforced cellulose matrix composite papers were manufactured using recycled materials with a scalable, eco-friendly, and low-cost papermaking process. The designed composite paper showed 36.1 dB electromagnetic interference shielding efficiency (EMSE) with an absorbance-dominated performance by absorbing 98.85% of electromagnetic waves. An efficient impedance matching was obtained on the composite paper surface using reinforcements with different morphologies. Cellulose paper samples were converted to electrically conductive composites (0.415 S/cm), and the electrical conductivity was altered by tailoring the reinforcement ratios. Thermo-mechanical test results revealed that the cellulose matrix’s storage modulus was increased from 1.44 to 2.1 GPa with a 46.5% improvement. The composite cellulose paper represented increased hydrophilicity with higher porosity. The environmentally friendly composite paper responses to the escalating environmental worries and possesses a tremendous possibility of being utilized as an electromagnetic shielding material.
Evaluation of Anti-Cytotoxicity and Anti-Genotoxicity of Raphanus sativus L. Tuber on Allium cepa L. Root Tips
(Pleiades Publishing, 2023) Kaya, Nergis
Abstract: Raphanus sativus (radish) tuber extracts stock solutions were prepared by dissolving radish extracts prepared with certain solvents (distilled water, ethanol and methanol) in dimethyl sulfoxide. Negative control (dimethyl sulfoxide, DMSO), positive control mutagen (ethyl methanesulfonate) and R. sativus extracts (10 and 20 mg/mL doses) were applied to Allium cepa root tips at for 24 and 48 h. For examination under the light microscope, the root tips were placed in fixative, then hydrolyzed and treated with acetocarmine. Chromosomal aberration index (CAI%) was increased as compared with the negative control, but decreased as compared with the positive control after the application of three different extracts. It was put forward that mitotix index decreased with increasing extract concentration applications. In this way, it has been determined that these extracts have an inhibitory effect on cell division at high doses. It has been found that CAI% was an increase with increasing extract concentration. It has been revealed that distilled water, ethanol and methanol extracts have more inhibitory effect on cell division and an increasing frequency of chromosomal anomalies, respectively. As a result of this research, R. sativus tuber might cause damage to cells genetic material and spindle formation when used incorrectly.
Coating graphene nanoplatelets onto carbon fabric with controlled thickness for improved mechanical performance and EMI shielding effectiveness of carbon/epoxy composites
(Elsevier Ltd, 2023) Mutlu, Gökhan; Yıldırım, Ferhat; Ulus, Hasan; Eskizeybek, Volkan
Coating nanostructures on fiber reinforcement is a facile and scalable technique to manufacture next-generation fiber-reinforced polymer composites with tailored physical properties. Optimizing the nanomaterial coating thickness on fibers is vital in tailoring the multifunctionality of fiber-reinforced composites without sacrificing the mechanical performance since it relies on the fiber–matrix interface, where interlaminar and other physical properties are governed. This paper investigates the impact of graphene nanoparticle (GNP) coating thickness on the mechanical properties, fracture behavior, thermo-mechanical, and electromagnetic interference (EMI) shielding effectiveness (SE) of composite structures. We grafted GNPs on carbon fabrics using a solution coating method with various thicknesses (10, 20, and 30 µm), and GNPs grafted fabrics were impregnated with an epoxy resin. The 20 µm GNPs coating thickness exhibited the highest mechanical performance, increasing the tensile and interlaminar shear strength by 32% and 26%, respectively, compared to pristine samples. Storage modulus and transition (Tg) temperature values increased by 18.6% and 13.6% for 20 µm coating thickness, respectively. Besides, the unstable crack growth at the fiber–matrix interface was stabilized when the GNPs coating thickness reached 20 µm according to delamination toughness tests. While mode-I fracture toughness increased up to 22%, an improvement of 13.5% was obtained in mode-II fracture toughness. The underlying toughening mechanisms at the interfacial region were identified using scanning electron microscopy. The EMI-SE was slightly increased by the GNPs grafting, whereas thinner GNPs coatings exhibited higher shielding efficiency.
Sac Malzeme Yüzey Pürüzlülüğünün Fiber-Metal Tabakalı Kompozitlerin Mekanik Özelliklerine Olan Etkisi
(TUBITAK, 2021) Kaçal, Alaattin; Yıldırım, Ferhat; Koyunbakan, Murat
Fiber-metal tabakalı kompozitlerin kullanımının özellikle havacılık gibi endüstrilerde giderek yaygınlaşmasıyla bu tür malzemelerin mekanik performanslarının incelenmesi de oldukça önemli hale gelmiştir. Matris ve takviye malzemesinin özelliklerinin, operatör tecrübesinin ve üretim yönteminin nihai ürünün kullanım performansı üzerinde doğrudan etkisinin olduğu bilinmektedir. Bu çalışmada yüzeyi 60, 220 ve 600 kum zımpara ile mekanik olarak farklı pürüzlülük değerlerinde işlenen 1050 serisi alüminyum sac malzeme, cam elyaflarla tabakalı kompozit olarak üretilmiş ve mekanik özellikleri incelenmiştir. Buna göre numunelerin çekme, üç nokta eğilme ve tabakalar arası kayma gerilmesi değerleri ölçülmüş ve hasar durumları makro görüntüler üzerinden değerlendirilmeye çalışılmıştır. Elde edilen sonuçlara göre en yüksek çekme ve eğilme gerilmesi değerleri sırasıyla 301.272 MPa ve 760.200 MPa ile 220 kum zımparada elde edilmiştir. En yüksek tabakalar arası kayma gerilmesi ise 17.804 MPa ile 60 kum zımparada elde edilmiştir. En yüksek ve en düşük sonuçlar arasındaki fark çekme, eğilme ve tabakalar arası kayma gerilmesi değerleri için sırasıyla, %10, %4 ve %7 olarak hesaplanmıştır. Bu çalışma ile fiber-metal tabakalı kompozitlerin tasarım parametrelerine ilişkin önemli çıktılar elde edilmiştir.
Improved mechanical performance of three-dimensional woven glass/epoxy spacer composites with carbon nanotubes
(SAGE Publications, 2021) Yıldırım, Ferhat; Aydın, Mustafa; Avcı, Ahmet
Three-dimensional polymer composites offer various features and design options due to their hollow structure and lightweight. However, to exploit their advantages, it is a must to improve their structural features and mechanical performances including out-plane direction. Although introducing thermoplastic fillers between the plies or multilayered design addresses on this critical issue, the benefits offered by the nanoparticles with superior mechanical properties come a step forward as an another engineering solution. Based on this motivation, the goal of this study is to investigate the impact of multiwalled carbon nanotubes on the mechanical and thermomechanical performances of three-dimensional woven glass/epoxy spacer composites. Therefore, multiwalled carbon nanotubes at various content were introduced into epoxy matrix, and the multiwalled carbon nanotubes–epoxy mixture was infused to three-dimensional woven fabric with the vacuum-assisted resin transfer method. The obtained results indicated that the three-point bending strength and modulus were enhanced up to 25 and 80% for warp direction and enhanced up to 44 and 85% for weft direction with carbon nanotube addition, respectively. Tensile strength developed in the warp direction by 7%, while the strength value in the weft direction did not change. The tensile strain values for warp and weft directions enhanced up to 19 and 12% with carbon nanotube addition, respectively. In addition, thermomechanical analysis has revealed that the glass transition temperature and storage modulus were also improved. Particle dispersion detection with color measurement and scanning electron microscopy analyses revealed the effectiveness of the ultrasonic mixing on the dispersion of carbon nanotubes in the epoxy matrix. The consequences of carbon nanotube addition on microscale morphology were discussed based on the fracture morphologies to nanoscale and microscale toughening mechanisms in the existence of carbon nanotube reinforcement.
Impact response of nanoparticle reinforced 3D woven spacer/epoxy composites at cryogenic temperatures
(SAGE Publications, 2021) Yıldırım, Ferhat; Tatar, Ahmet Caner; Eskizeybek, Volkan; Avcı, Ahmet; Aydın, Mustafa
Fiber-reinforced polymer composites serving in harsh conditions must maintain their performance during their entire service. The cryogenic impact is one of the most unpredictable loading types, leading to catastrophic failures of composite structures. This study aims to examine the low-velocity impact (LVI) performance of 3D woven spacer glass-epoxy composite experimentally under cryogenic temperatures. LVI tests were conducted under various temperatures ranging from room temperature (RT) to −196°C. Experimental results reveal that the 3D composites gradually absorbed higher impact energies with decreasing temperature. Besides, the effect of multi-walled carbon nanotube and SiO2 nanofiller reinforcements of the matrix on the impact performance and the damage characteristics were further assessed. Nanofiller modification enhanced the impact resistance up to 30%, especially at RT. However, the nanofiller efficiency declined with decreasing temperature. The apparent damages were visually examined by scanning electron microscopy to address the damage formation. Significant outcomes have been achieved with the nanofiller modification regarding the new usage areas of 3D woven composites.
Evaluation of cytotoxic and genotoxic effects of hosap stream gumuscay biga canakkale on Allium cepa L.
(Parlar Scientific Publications, 2021) Kaya, Nergis
Since the Hosap Stream is located near the urban settlement area, water pollution might occur. In this study, the cytotoxic and genotoxic effect of Hosap Stream, which is also used in irrigation of agricultural lands, was investigated at the root tip cells of Allium cepa. The EC50 value in A. cepa roots was determined by exposure to different concentrations of the water sample taken from Hosap Stream. Then, the root tips were treated with EC50 values for 24 h, 48 h and 72 h. The root tips were prepared according to the method of preparing the mitotic preparation and examined under a microscope. It was determined that the water sample taken from Hosap Stream had a cytotoxic and genotoxic effect on A. cepa root tip cells. It was evaluated that the chromosomal aberration index increased statistically significantly depending on the dose in all application periods except for the 24 h application. It was determined that the mitotix index and chromosomal aberration index were higher than the control groups. The lowest mitotix index (2,217±0,625) and the highest chromosomal aberration index (53,153±1,642) was observed with EC50X2 dose at 72h. The prevalent chromosome aberration observed in A. cepa root tip cells were -mitosis, laggard chromosome, polar shifting in anaphase and telophase, equatorial plate shifting, chromosome fragment. According to the results of this study, it can be said that Hosap tea has cytotoxic and genotoxic effects on other living organism.
Comparative study on the quality characteristics of yoghurt produced by caw milks with different somatic cells count
(Agricultural Academy in Bulgaria, 2021) Bilgücü, Ertugrul; Ivanov, Galin Y.; Balabanova, Tatyana B.; Ivanova, Ivelina, V
The present study aimed to provide the necessary information for the effect of somatic cells count (SCC) of raw cow milk on the fermentation process and quality characteristics of yoghurt. Test yoghurt samples were produced from three different batches of cow milk with low (< 400 000 cells.cm(-3)), medium (between 500 000 and 600 000 cells.cm(-3)) and high (1 000 000 cells.cm(-3)) SCC, respectively. The main physicochemical parameters as pH, total solids, milk fat, protein, lactose, lactic acid content and microbiological parameters as somatic cells count (SCC) and total viable count (TVC) of raw milk and yoghurt samples were studied. It was found that, the SCC of the raw milk did not have a significant effect on the composition and pH values of the yoghurt. A similar rate of acidification during fermentation of the milks having different SCC, as well as during the cold storage of yoghurt samples was established. The variations in the SCC of the raw milk within the range up to 500 000 cells.cm(-3) had no significant effect on the organoleptic properties of the yoghurt. The increase in the SCC values up to 1 000 000 cells.cm(-3) in the raw cow's milk affected negatively the organoleptic characteristics of the yoghurt made from it.
Lojistik Değer ve Çok Boyutlu Değer Modeliyle Kullanımı
(Çanakkale Onsekiz Mart Üniversitesi, 2009) Akyıldız, Murat
Son yıllarda lojistik hizmetlerin üçüncü parti lojistik hizmet sağlayıcıları olarak tanımlanan lojistik firmalara aktarılması, rakipleri karşısında üstünlük kurmak isteyen lojistik firmaların değer ve değer stratejilerine gösterdikleri önemi giderek daha fazla artırmıştır. Bu nedenle bu çalışmada değer, lojistik değer lojistik katma değer kavramlarının yanı sıra değer modellerini ele alan literatür gözden geçirilerek, çeşitli modelleri bünyesinde barındıran çok boyutlu yeni bir değer modeli oluşturma teşebbüssünde bulunulmuştur. Lojistik hizmetlere uyarlanan çok boyutlu değer modeli, lojistik hizmetler vasıtasıyla müşterilerine üstün değer yaratmak isteyen uygulayıcılara farklı bir bakış açısı kazandırabilir.

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