Diğer Yayınlar / Other Publications
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Browsing Diğer Yayınlar / Other Publications by Subject "chemical engineering"
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Article A computational study on 4,7-di(furan-2-yl)benzo[c][1,2,5] thiadiazole monomer and its oligomers(Journal of Molecular Modeling, 2014) Kayı, Hakan; Chemical EngineeringThe energy gap, Eg, between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molec ular orbital (LUMO) energy levels that determines the elec tronic and optical properties of 4,7-di(furan-2- yl)benzo[c][1,2,5]thiadiazole (FSF) polymer is calculated by performing quantum chemical calculations. First, we theoret ically investigated the most stable conformers of FSF mono mer and its corresponding oligomers at the B3LYP/6-31G(d) and B3LYP/LANL2DZ levels of theory. We reveal the theoret ical molecular structure of this very recently synthesized novel monomer and its oligomers for the first time in the literature. Our results from the B3LYP/6-31G(d) calculations indicated that FSF polymer has a low HOMO-LUMO gap of 1.55 eV to be in good agreement with the experiments. Experimental design and synthesis of novel conjugated polymers require time-consuming and expensive procedures. The findings from this study are promising for the use of computational methods in the design of the novel conjugated polymers, and help to narrow the materials to be used in design and synthesis of conjugated polymers with desired properties.Article A theoretical investigation of 4,7-di(furan-2-yl)benzo[c][1,2,5]selenadiazole-based donor–acceptor type conjugated polymer(Computational and Theoretical Chemistry, 2014) Kayi, Hakan; Elkamel, Ali; Chemical EngineeringQuantum chemical calculations are performed using density functional theory (DFT) to investigate the HOMO–LUMO energy gap of the 4,7-di(furan-2-yl)benzo[c][1,2,5]selenadiazole-based (FSeF) donor– acceptor type conjugated polymer which ascertains the optoelectronic properties and plays a crucial role, especially in polymeric solar cell applications. In this paper, the most stable conformers of the FSeF monomer and its corresponding oligomers are investigated at the B3LYP/Def2TZV and B3LYP/LANL2DZ levels of theory, and their molecular structures are revealed. The band gap of the polymer is determined by linear-fitting and extrapolation of the DFT data. This gap is found to be 1.44 eV and 1.45 eV by the B3LYP/Def2TZV, and B3LYP/LANL2DZ with PCM calculations, respectively. Our theoretical findings related to the band gap of the FSeF polymer (PFSeF) are in good agreement with other experimental stud ies in the literature and, hence, the theoretical methods used in this study are promising for the design of similar donor–acceptor type novel conjugated polymers.Article Az bilinen fakat potansiyeli yüksek sürdürülebilir bir enerji türü: Mavi Enerji(Herkese Bilim Teknoloji, 2017) Güler, Enver; Chemical Engineering21. yüzyılda insanoğlunun karşılaştığı ve ileride ziyadesiyle sözkonusu olacak en temel durum enerji, su ve gıdaya olan taleptir. Bu talebin karşılanmasında ise sürdürülebilirlik şimdiki ve gelecek kuşakların temel sorunu olmaya devam edecektir. Su, enerji ve gıda arasındaki sıkı bağ açıkça gösteriyor ki; su ve enerji gıda üretiminde, su enerji üretiminde ve enerji su temini ve üretiminde en temel faktörlerdir [1]. Bunun neticesinde bu üçlü bağlam, 2035 yılında enerjiye olan talebin en fazla değer olarak % 50 olacağını öngörmektedir (Şekil 1). Enerjiye olan bu yüksek talebin yakın gelecekte fosil yakıtlar ile sürdürülebilir şekilde karşılanamayacağı aşikardır. Bu durum, enerjinin sürdürülebilir olarak üretimini sağlayacak alternatif teknikler geliştirilmesini bir öncelik haline getirmiştir.Article Conformational behaviors of trans-2,3- and trans-2,5-dihalo 1,4-diselenanes. A complete basis set, hybrid-density functional theory study and natural bond orbital interpretations(Journal of Molecular Modeling, 2014) Nori-shargh, Davood; Mousavı, Seiedeh Negar; Kayı, Hakan; Chemical EngineeringComplete basis set CBS-4, hybrid-density func tional theory (hybrid-DFT: B3LYP/6-311+G**) based methods and natural bond orbital (NBO) interpretations have been used to examine the contributions of the hyperconjugative, electrostatic, and steric effects on the con formational behaviors of trans-2,3-dihalo-1,4-diselenane [halo=F (1), Cl (2), Br (3)] and trans-2,5-dihalo-1,4- diselenane [halo = F (4), Cl (5), Br (6)]. Both levels of theory showed that the axial conformation stability, compared to its corresponding equatorial conformation, decreases from com pounds 1→3 and 4→6. Based on the results obtained from the NBO analysis, there are significant anomeric effects for compounds 1-6. The anomeric effect associated with the electron delocalization is in favor of the axial conformation and increases from compounds 1→3 and 4→6. On the other hand, dipole moment differences between the axial and equa torial conformations [Δ(μeq - μax)] decrease from compounds 1→3. Although Δ(μeq-μax) parameter decreases from com pound 1 to compound 3, the dipole moment values of the axial conformations are smaller than those of their corresponding equatorial conformations. Therefore, the anomeric effect as sociated with the electron delocalizations (for halogen-C-Se segments) and the electrostatic model associated with the dipole-dipole interactions fail to account for the increase of the equatorial conformations stability on going from com pound 1 to compound 3. Since there is no dipole moment for the axial and equatorial conformations of compounds 4-6, consequently, the conformational preferences in compounds 1-6 is in general dictated by the steric hindrance factor asso ciated with the 1,3-syn-axial repulsions. Importantly, the CBS-4 results show that the entropy difference (ΔS) between the equatorial axial conformations increases from compounds 1→3 and 4→6. This fact can be explained by the anomeric effect associated with the electron delocalization which affects the C2-Se bond orders and increase the rigidity of the corre sponding rings. The Gibbs free energy difference values be tween the axial and equatorial conformations (i.e. ΔGax-ax and ΔGeq-eq) of compounds 1 and 4, 2 and 5 and also 3 and 6 have been calculated. The correlations between the anomeric effect, electrostatic model, ΔGeq-ax, ΔGax-ax, ΔGeq-eq, bond orders, dipole-dipole interactions, structural parameters and confor mational behaviors of compounds 1-6 have been investigated.Article İlaç Araştırmalarında Yeni Nesil Uygulamalar: Kontrollü İlaç Salımı(Bilim ve Teknoloji, 2012) İşgör, Belgin S.; Korkmaz Özkan, Filiz; Physics Group16.yüzyılda yaşamış olan ve bugünkü Modern tıbbın kurucularından sayılan Paracelsus’un “Her şey zehirdir. Zehirle ilacı ayıran dozudur” sözü, bugünkü modern toksikolojinin temeli olan doz-cevap ilişkisine dikkat çekmesi açısından son derece önemlidir. Günümüzde ilaç olarak sunulan sentetik ve doğal kaynaklı kimyasal bileşiklerin vücuda alımı genel olarak ağızdan (oral) katı veya sıvı formlarda, damar ve kas içerisine sıvı enjeksiyonuyla, nazal yol aracılığıyla sprey veya toz formunda inhalatör yardımıyla, veya deriden lokal uygulamalarla gerçekleşmektedir. Vücuda verilen ilaç ilk olarak dolaşım sistemine alınır ve tedavi için hedeflenen dokuya kan damarları ile taşınır. Hedef dokulara ise bu dokulara nüfuz etmiş kılcal damarlar yoluyla ulaşır. İlacın vücuda alımından hedef dokuya taşınması sürecinde, damar yolu üzerinde bulunan tüm dokularca alınıp hücresel mekanizmalarca işlenmesi mümkündür.Article Natural bond orbital, nuclear magnetic resonance analysis and hybrid-density functional theory study of σ-aromaticity in Al2F6, Al2Cl6, Al2Br6 and Al2I6(Journal of Molecular Modeling, 2013) Norı-shargh, Davood; Yahyaeı, Hooriye; Mousevı, Seiedeh Negar; Maasoomı, Akram; Kayı, Hakan; Chemical EngineeringNatural bond orbital (NBO), nuclear magnetic res onance (NMR) analysis and hybrid-density functional theory based method (B3LYP/Def2-TZVPP) were used to investigate the correlation between the nucleus-independent chemical shifts [NICS, as an aromaticity criterion], σAl(1)-X2(b) → σ*Al(3)-X4(b) electron delocalizations and the dissociation ener gies of Al2F6, Al2Cl6, Al2Br6 and Al2I6 to 2AlX3 (X=F, Cl, Br, I). The results obtained showed that the dissociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6 decrease from Al2F6 to Al2I6. Like aromatic molecules, these compounds have relatively significant negative NICSiso(0) values. Clearly, based on mag netic criteria, they exhibit aromatic character and make it possible to consider them as σ-delocalized aromatic species, such as Möbius σ-aromatic species. The σ-aromatic character which is demonstrated by their NICSiso(0) values decreases from Al2F6 to Al2I6. The NICSiso values are dominated by the in-plane σ22 (i.e., σyy, the plane containing halogen atoms bridged) chemical shift components. The increase of the NICSiso values explains significantly the decrease of the corre sponding dissociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6. Importantly, the NBO results suggest that in these compounds the dissociation energies are controlled by the stabilization energies associated with σAl(1)-X2(b) →σ*Al(3)- X4(b) electron delocalizations. The decrease of the stabilization energies associated with σAl(1)-X2(b) →σ*Al(3)-X4(b) electron delocalizations is in accordance with the variation of the calculated NICSiso values. The correlations between the dis sociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6, σAl(1)- X2(b) →σ*Al(3)-X4(b) electron delocalizations, natural atomic orbitals (NAOs) and NICSiso values have been investigated.Article Paper-Based versus Computer-Based Testing in Engineering Education(IEEE EDUCON Education Engineering 2010 – The Future of Global Learning Engineering Education, 2010) Çağıltay, Nergiz; Özalp Yaman, Şeniz; Chemical Engineering; Software EngineeringUsing computers for assessment can provide several benefits for educators and test-takers. However, in the literature, there is no consensus on the equivalence of paper-and-pencil and computer-based test environments. Accordingly, more evidences are needed especially for the engineering education. In this study, students’ performance on different test modes was evaluated on 209 first year engineering students of a chemistry course. The results of this study showed that, there is no significant performance difference between paper-and-pencil and computer based tests. By comparing results with the previous studies, this study concludes that, personal characteristics of test takers, the features of computer-based testing systems and the test content are all possible confounding factors when comparing test modes and need to be considered by the implementers. The results of this study show that, once these factors are controlled, students’ performance on computer-based tests and paper-and-pencil tests in chemistry courses for the engineering students will not vary. This finding is encouraging the educators to get benefits of computer-based tests without any affect on students’ performance.Article TÜRKİYE'DE TEMEL BİLİMLERİN ÇÖKÜŞÜ(Bilim ve Teknoloji, 2015) Cihaner, Atilla; Chemical EngineeringÖncelikle Türkiye'nin bugünkü bilim ve teknolojideki konumunu görmek ve kat ettiği mesafeyi anlayabilmek için, Türkiye'nin geçmişten bugüne olan bilim ve teknolojinin üç ayağı olarak nitelendirebileceğimiz, bilim politikalarını, bilim üretimini ve bilim anlayışını kısaca göz atmakta fayda var. Osmanlı'daki Batılılaşma, modernleşme ve yenileşme hareketleri 17. yy'ın sonlarına doğru başlayıp (1683 Viyana bozgunu sonrası) 18. yy'ın ilk yarısına kadar sürer. Lale Devri, ilk matbaa'nın kullanımı, II. Mahmut Devri, III. Selim Devri, Tanzimat, vb. olaylar Osmanlı'ını Batılılaşma ve modernleşme serüvenindeki önemli olaylardan birkaçıdır.Article TÜRKİYE’DE TEMEL BİLİMLERİN ÇÖKÜŞÜ(Bilim ve Teknoloji, 2015) Cihaner, Atilla; Chemical EngineeringÜniversitelerdeki ilk çöküşün habercisi, temel bilimler kontenjanında yaşanan sıkıntılar ve kapanan bölümler olmuştur. Yürütülen bilim politikalarının yanlışlığından kaynaklı olarak son yıllarda boş kontenjanlarla gündemde olan temel bilimler programlarıyla ilgili çalışma başlatan YÖK, 2014 yılında 11’den az öğrenci kaydolan devlet üniversitelerindeki programlara artık kontenjan verilmeyeceğini duyurmuştur. Uygulanan bilim politikasının yanlışlığını 2010 yılında üniversitelerin temel bilimler bölümlerine ayrılan kontenjan sayılarından net olarak anlamak mümkündür. Bir yıl öncesinde mevcut kontenjanlar doldurulmamış olmasına rağmen kontenjan sayıları arttırılırken bu bölümlere yerleşen öğrenci sayılarında dramatik bir düşüş görülmüştür. YÖK’ün kontenjan verilmeyeceğine dair yaptığı açıklama bir domino etkisi yaratmış ve sonraki yıllarda temel bilimler bölümleri bir bir kapanmaya başlamıştır.
