Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 3Citation - Scopus: 3The Electronic and Optical Properties of a Triexciton in CdSe/ZnS Core/Shell Quantum Dot Nanocrystals(Taylor & Francis Ltd, 2016-02-21) Akturk, Abdurrahman; Tas, Hatice; Koksal, Koray; Sahin, MehmetIn the study, we aim to investigate the electronic and optical properties of single excitons, biexcions and triexcitons in a CdSe/ZnS core/shell quantum dot nanocrystal. The electronic structure has been determined by solving of the Poisson-Schrodinger equations self-consistently. In calculations, the exchange-correlation effects between identical particles have been taken into account in the frame of the local density approximation. We have demonstrated that the optical properties of triexciton systems are remarkably different from the single and biexciton systems. Absorption peaks or transition energies of the triexciton system are well separated from those of single- and bi-exciton systems. We have observed that the core-radius dependent transition energy variations of triexcitons are higher when compared with single- and bi-excitonic systems. The transition energy shifts of double and triple excitons with respect to the single exciton have been calculated as a function of the core radius and we have shown that the energy shifts are inversely proportional with the radius. We have also investigated the radius-dependent changes in binding energies and lifetimes of the structures and the comparative results have been discussed in a detail manner.Article Citation - WoS: 11Citation - Scopus: 13The Effect of Seed Sludge Type on Aerobic Granulation via Anoxic-Aerobic Operation(Taylor & Francis Ltd, 2014-06-17) Ersan, Yusuf Cagatay; Erguder, Tuba HandeThe effects of two seed sludge types, namely conventional activated sludge (CAS) and membrane bioreactor sludge (MBS), on aerobic granulation were investigated. The treatment performances of the reactors were monitored during and after the granulation. Operational period of 37 days was described in three phases; Phase 1 corresponds to Days 1-10, Phase 2 (overloading conditions) to Days 11-27 and Phase 3 (recovery) to Days 28-37. Aerobic granules of 0.56 +/- 0.23 to 2.48 +/- 1.28mm were successfully developed from both MBS and CAS. First granules appeared on Day 9 in both reactors, indicating that there was no difference between two seed sludge types in terms of the time period for granulation initiation. The results revealed that the granules developed from MBS performed better than CAS in terms of settleability, stability, biomass retention, adaptation, protection of granular structure at high loading rates (0.86 gN/L d and 3.92 gCOD/Ld) and low COD/TAN ratio (5). Granules of MBS were also found to be capable of providing better protection for nitrifiers at toxic free-ammonia concentrations (38-46 mg/L NH3-N), thus showing better treatment recovery than those of CAS.Article Citation - WoS: 3Citation - Scopus: 3Phase Transition of ZrN Under Pressure(Taylor & Francis Ltd, 2019-01-14) Durandurdu, MuratA first principles constant pressure approach is carried out to probe the high-pressure behaviour of the rocksalt (RS) structured zirconium nitride (ZrN). The existence of first order reconstructive phase transition from the RS crystal to a CsCl-type crystal is, for the first time, established throughout the simulations. Upon decompression, the CsCl type phase converts back to the original RS structure by following the same transformation mechanism, suggesting a reversible phase transformation in ZrN. The RS-to-CsCl phase change is additionally considered through the thermodynamic theorem and projected to take place at around 225 GPa in experiments. The structural parameters and mechanical properties computed are found to be comparable with some of the previous findings. Additionally, we investigate the response of ZrN to uniaxial compression and tension stresses. The uniaxial stresses initially lead to a tetragonal modification of the simulation box having an I4/mmm symmetry and subsequently structural failure that is expected to occurs at about -10 and 15 GPa in experiments.Article Citation - WoS: 4Citation - Scopus: 6One-Pot Conjugated Linoleic Acid Production From Castor Oil by Rhizopus Oryzae Lipase and Resting Cells of Lactobacillus Plantarum(Taylor & Francis Ltd, 2017-10-03) Khaskheli, Abid Ali; Talpur, Farah Naz; Aydin, Aysun Cebeci; Jawaid, Sana; Surhio, Muhammad Ali; Afridi, Hassan ImranConjugated linoleic acid (CLA) has attracted as novel type of fatty acids having unusual health-promoting properties such as anticarcinogenic and antiobesitic effects. The present work employed castor oil as substrate for one-pot production of CLA using washed cells of Lactobacillus plantarum (L. plantarum) and lipases as catalysts. Among the screened lipases, the lipase Rhizopus oryzae (ROL) greatly assisted resting cells to produce CLA. Mass spectral analysis of the product showed that two major isomers of CLA were produced in the reaction mixture i.e. cis-9, trans-11 56.55% and trans-10, cis-12 43.45%. Optimum factors for CLA synthesis were found as substrate concentration (8mg/mL), pH (6.5), washed cell concentration (12% w/v), and incubation time of 20h. Hence, the combination of ROL with L. plantarum offers one pot production of CLA selectively using castor oil as a cost-effective substrate.Article Citation - WoS: 3Citation - Scopus: 4Nanosegregated Amorphous AlBN2 Alloy(Taylor & Francis Ltd, 2016-09-14) Durandurdu, MuratWe use ab initio molecular dynamics simulations to create an amorphous AlBN2 model and find that it consists of nanosegregated two-dimensional hexagonal BN-like and tetrahedral AlN-like domains. These domains are somewhat homogenously distributed in the network. There exist no chemical disorder and Al-B bonding. Amorphous AlBN2 is a semiconductor having a theoretical band gap energy of approximate to 2.24eV, larger than that of amorphous AlN and BN systems. This amorphous nitride might find some applications as an electronic material.Article N-Type Conductivity in Si-Doped Amorphous Aln: An Ab Initio Investigation(Taylor & Francis Ltd, 2016-03-11) Durandurdu, MuratWe report the electronic structure and topology of a heavily Si-doped amorphous aluminium nitride (Al37.5Si12.5N50) using ab initio simulations. The amorphous Al37.5Si12.5N50 system is found to be structurally similar to pure amorphous aluminium nitride. It has an average coordination number of about 3.9 and exhibits a small amount of Si-Si homopolar bonds. The formation of Si-Al bonds is not very favourable. Electronic structure calculations reveal that the Si doping has a negligible effect on the band gap width but causes delocalization of the valence band tail states and a shift of the Fermi level towards the conduction band. Thus, amorphous Al37.5Si12.5N50 alloys show n-type conductivity.Article Citation - WoS: 2Citation - Scopus: 2MgCu Metallic Glass(Taylor & Francis Ltd, 2017-12-10) Durandurdu, MuratWe generate an amorphous MgCu model using the rapid solidification of the melt through a first-principles molecular dynamics approach within a generalised gradient approximation and reveal, for the first time, its structural features and mechanical properties in details. The liquid and glassy MgCu are found to acquire slightly distinct local structures. Yet in both forms of MgCu, most Cu atoms have a tendency to form the ideal and defective icosahedrons while Mg atoms are arranged in complex configurations. The mean coordination number of Cu and Mg at 300 K is 11.31 and 13.73, respectively. The short-range order of MgCu glass is projected to be different than the known crystalline MgCu and Mg2Cu phases. The mechanical properties of MgCu glass and the CsCl-type MgCu crystal are computed and compared. On the basis of the enthalpy analyses, a possible pressure-induced crystallisation of the MgCu glass into a CsCl-type structure is proposed to occur at around 11 GPa.Article Irreversible Changes in Amorphous C3n4 Under Pressure: Loss of Chemical Order and Graphite-Like Character(Taylor & Francis Ltd, 2025-04-03) Durandurdu, MuratThe high-pressure behavior of triazine-based amorphous C3N4, initially exhibiting a chemically ordered, graphite-like structure, was investigated using ab initio molecular dynamics simulations. Our study reveals a pressure-induced transition to a high-density amorphous (HDA) phase characterized by increased coordination number for carbon (3.88) and nitrogen (2.93) atoms. This transition occurs gradually over a broad pressure range, initiated by the breakdown of chemical ordering and the formation of homopolar C-C and N-N bonds, which persist in both the HDA and recovered phases. The recovered phase retains elevated coordination numbers (C: 3.25, N: 2.46) but loses its initial graphite-like topology, evolving into a three-dimensional network structure. Electronic structure analysis reveals semiconducting behavior in the HDA phase and n-type semiconductor characteristics in the recovered phase.Article Citation - WoS: 3Citation - Scopus: 3High-Pressure Phase Transitions of TiN: An Ab Initio Constant Pressure Study(Taylor & Francis Ltd, 2015-07-03) Durandurdu, MuratAn ab initio constant pressure molecular dynamics technique is carried out to explore the behaviour of rock salt-structured titanium nitride (TiN) under pressure. Two successive phase transformations are successfully observed in the dynamical simulations. The first one is an isostructural phase transition accompanied by an anomalous volume compression without any symmetry breaking. The second one is a reconstructive phase transformation into a CsCl-type structure. For the first time, the previously proposed two-phase transformations for TiN are confirmed through the simulations.Article Citation - WoS: 3Citation - Scopus: 3Ferromagnetism in Amorphous MgO(Taylor & Francis Ltd, 2017-05-10) Durandurdu, MuratWe report, for the first time, the atomic structure of amorphous MgO based on ab initio molecular dynamics simulations. We find that its main building blocks are four-fold and five-fold coordinated configurations, similar to those formed in the liquid state. Its average coordination is estimated to beabout 4.36. The amorphous form having a perfect stoichiometry has a band gap energy of 2.4eV. On the other hand, Mg vacancies induce an insulator to metal transition and ferromagnetism in amorphous MgO whilst O vacancies do not cause such a transition, implying that the magnetism in amorphous MgO is related to the non-stoichiometry and Mg vacancies. With the application of pressure, the stoichiometric and non-stoichiometric (Mg vacancies) models undergo a phase transformation into a rocksalt state, suggesting that the electronic structure of the initial configurations has no influence on the resulting high-pressure phase in amorphous MgO.