WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394

Browse

Now showing 1 - 15 of 15

Citation - WoS: 35
Citation - Scopus: 40
The Photoionization Cross Section of a Hydrogenic Impurity in a Multi-Layered Spherical Quantum Dot
(Amer Inst Physics, 2012) Sahin, Mehmet; Tek, Firdes; Erdinc, Ahmet
In this study, we have investigated the photoionization cross section of an on-center hydrogenic impurity in a multi-layered spherical quantum dot. The electronic energy levels and their wave functions have been determined fully numerically by shooting method. Also, we have calculated the binding energy of the impurity by using these energy values. The photoionization cross section has also been computed as a function of the layer thickness and normalized photon energies. We have discussed in detail the possible physical reasons behind the changes in the binding energies and photoionization cross section. It is observed that both the binding energies and the photoionization cross sections depend strongly on the layer thickness and photon energies. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4705410]
Citation - WoS: 24
Citation - Scopus: 25
A Model for the Recombination and Radiative Lifetime of Trions and Biexcitons in Spherically Shaped Semiconductor Nanocrystals
(Amer Inst Physics, 2013) Sahin, Mehmet; Koc, Fatih
In this letter, we propose a different model to determine the recombination oscillator strength of trions and biexcitons for bound and unbound cases in the effective mass approximation. The validity of our model has been confirmed by the radiative lifetime of the trion and biexciton in a spherical quantum dot. The results show that the model works with sufficient accuracy in comparison with results of more complex methods such as quantum Monte Carlo techniques and atomistic calculations. (C) 2013 AIP Publishing LLC.
Citation - WoS: 28
Citation - Scopus: 29
Enhanced Transmission and Beaming via a Zero-Index Photonic Crystal
(Amer Inst Physics, 2016) Hajian, Hodjat; Ozbay, Ekmel; Caglayan, Humeyra
Certain types of photonic crystals with Dirac cones at the Gamma point of their band structure have a zero effective index of refraction at Dirac cone frequency. Here, by an appropriate design of the photonic structure, we obtain a strong coupling between modes around the Dirac cone frequency of an all-dielectric zero-index photonic crystal and the guided ones supported by a photonic crystal waveguide. Consequently, we experimentally demonstrate that the presence of the zero-index photonic crystal at the inner side of the photonic crystal waveguide leads to an enhancement in the transmission of some of the guided waves passing through this hybrid system. Moreover, those electromagnetic waves extracted from the structure with enhanced transmission exhibit high directional beaming due to the presence of the zero-index photonic crystal at the outer side of the photonic crystal waveguide. Published by AIP Publishing.
Citation - WoS: 15
Citation - Scopus: 15
The Electronic Properties of a Two-Electron Multi-Shell Quantum Dot-Quantum Well Heterostructure
(Amer Inst Physics, 2013) Aydin, Rasit; Sahin, Mehmet
A detailed investigation of the electronic properties of a double electron in a core/shell/well/shell quantum dot heterostructure has been systematically studied for cases with and without an on-center donor impurity. For this purpose, the Poisson-Schrodinger equations have been solved self-consistently in the frame of the single band effective mass approximation and Hartree treatment. The variation of the binding energies of negatively charged donor impurity (D-) have been examined for different core radii, shell thicknesses, and well widths. The results obtained have been presented comparatively as a function of layer thicknesses and probable physical reasons behind in their behavior have been discussed. (C) 2013 AIP Publishing LLC.
Citation - WoS: 2
Citation - Scopus: 1
The Numerical Solutions for Stiff Ordinary Differential Equations by Using Interpolated Variational Iteration Method With Comparison to Exact Solutions
(Amer Inst Physics, 2018) Ciftci, Cihan; Cayci, Hatice Sinem Sas; Atay, Mehmet Tarik; Toker, Batuhan; Guncan, Berkay; Yildirim, Afsin Talha
Recently proposed Interpolated Variational Iteration Method (IVIM) is used to find numerical solutions of stiff ordinary differential equations for both linear and nonlinear problems. The examples are given to illustrate the accuracy and effectiveness of IVIM method and IVIM results are compared with exact results. In recent analytical approximate methods based studies related to stiff ordinary differential equations, problems were solved by Adomian Decomposition Method and VIM and Homotopy Perturbation Method, Homotopy Analysis Method etc. In this study comparisons with exact solutions reveal that the Interpolated Variational Iteration Method (IVIM) is easy to implement. In fact, this method is promising methods for various systems of linear and nonlinear stiff ordinary differential equations as an initial value problem. Furthermore, IVIM is giving very satisfactory solutions when compared to exact solutions for nonlinear cases depending on the stiffness ratio of the stiff system to be solved.
Citation - WoS: 13
Citation - Scopus: 14
TD-DFTB Study of Optical Properties of Silver Nanoparticle Homodimers and Heterodimers
(Amer Inst Physics, 2020) Liu, Zhen; Alkan, Fahri; Aikens, Christine M.
The absorption spectra for face-centered cubic nanoparticle dimers at various interparticle distances are investigated using time-dependent density functional tight binding. Both homodimers and heterodimers are investigated in this work. By studying nanoparticles at various interparticle distances and analyzing their vertical excitations, we found that as the interparticle distance decreases, a red shift arises from contributions of the transition dipole moment that are aligned along the z-axis with nondegenerate features; blue shifts occur for peaks that originate from transition dipole moment components in the x and y directions with double degeneracy. When the nanoparticles are similar in size, the features in the absorption spectra become more sensitive to the interparticle distances. The best-fit curves from vertical excitation energy in the form of AR(-b) for Delta E-redshift/Delta E-blueshift vs R are determined. In this way, we determined trends for absorption peak shifts and how these depend on the interparticle distance.
Statistical Approach for Table Tennis Athletes' Success
(Amer Inst Physics, 2018) Goren, Selcuk; Gulbahar, Ibrahim Tumay; Pinar, Muhammed Safak
This report summarizes the statistical modeling and analysis results associated with the athletes' success and athletes' features. Main purpose of this report is to find any relation between athletes' success and their features. As a tool of creating correlation regression is used with SPSS.
Twist-Bend Instability of a Cantilever Beam Subjected to an End Load via Homotopy Perturbation Method
(Amer Inst Physics, 2018) Yucesoy, Ahmet; Coskun, Safa Bozkurt; Atay, Mehmet Tarik
In this article, twist-bend buckling analysis of a cantilever beam subjected to a concentrated end load is conducted using Homotopy Perturbation Method (HPM). Even in the linear stability analysis, obtaining an exact solution for some cases is not an easy task. However, by the use of HPM this difficulty can be overcome easily. This issue is presented with a case study and the results show that HPM can be used successfully in the analysis of twist-bend buckling of beams.
Statistical Analysis of Vehicle Driver Behaviors
(Amer Inst Physics, 2018) Saracli, Sinan; Gazeloglu, Cengiz
Purpose of this study is to examine the drivers' attitudes and behaviors in traffic via statistical techniques. With this purpose, the reactions of the motor vehicle drivers in traffic, correlations between negative reactions and personality characteristics and how they describe themselves and how they feel while they are driving have been examined. The participants of this study are composed of 500 drivers in Afyonkarahisar Province dates between 01 April - 30 June 2016. To measure the drivers attitudes and behaviors in traffic, a Likert scale type questionnaire, which was used in Cmar 's (2007) study, ranging from 1 'strongly disagree' to 5 'strongly agree' is applied on a face-to-face basis. Because of some unfilled and wrong filled questionnaires, the statistical analyses were applied to over 440 questionnaires. Drivers attitudes and behaviors and the behavior types whether they do or they exposure, on their feelings and determinations of themselves as a driver were examined via CHAID and Multi Dimensional Scaling Analysis. SPSS Software is used to perform the statistical analysis. Some of the important results of the analysis showed that drivers who feel themselves aggressive while driving, determine themselves as drivers since they were born. Physical attack / fighting: as a behavior that they were exposed to was also found significant on the variable of determining themselves as how driver they are.
Citation - WoS: 33
Citation - Scopus: 35
Oscillation Characteristics of Mutually Impinging Dual Jets in a Mixing Chamber
(Amer Inst Physics, 2018) Tomac, Mehmet N.; Gregory, James W.
In this study, we consider the oscillatory behavior of mutually impinging jets in an enclosed, domeshaped mixing chamber. The frequency of the impinging jet oscillations is dictated by the flow rate, with the oscillatory behavior being grouped into three regimes: a low flow rate regime (Re < 1500), a transition regime (1500 < Re < 2000), and a high flow rate regime (Re > 2000). The detailed characteristics of the oscillations in the high flow rate regime (Re = 6800 in the present study) are investigated through simultaneous frequency and refractive-index-matched particle image velocimetry measurements. The oscillation mechanism in the high flow rate regime was found to be similar to that of the other two regimes, where jets collide and interact in an oscillatory manner. However, in the high flow rate regime, there is a distinct and phase-evolving process of saddle point formation and jet bifurcation that is not present at the lower flow rates. The jet bifurcation process is also distinctly related to the balance of vortical structures inside the mixing chamber, and saddle point formation plays a key role in the internal and external flow field of this configuration. The external sweep angle of the exiting jet increases with the flow rate throughout the low and transition flow rate regimes, but a constant sweep angle was found to persist in the high flow rate regime. Thus, formation and location of the internal saddle point is directly linked to the external sweep angle of the jet. (C) 2018 Author(s).
Target Attractor Tracking of Relative Phase in Bosonic Josephson Junction
(Amer Inst Physics, 2016) Borisenok, Sergey
The relative phase of Bosonic Josephson junction in the Josephson regime of Bose-Hubbard model is tracked via the target attractor ('synergetic') feedback algorithm with the inter-well coupling parameter presented as a control function. The efficiency of our approach is demonstrated numerically for Gaussian and harmonic types of target phases.
Citation - WoS: 54
Citation - Scopus: 60
The Electronic Properties of a Core/Shell Spherical Quantum Dot With and Without a Hydrogenic Impurity
(Amer Inst Physics, 2012) Tas, Hatice; Sahin, Mehmet
In this study, we have performed a detailed investigation of the electronic properties of a core/shell/well/shell multilayered spherical quantum dot, such as energy eigenvalues, wave functions, electron probability distribution, and binding energies. The energy eigenvalues and their wave functions of the considered structure have been calculated for cases with and without an on-center impurity. For this purpose, the Schrodinger equation has been numerically solved by using the shooting method in the effective mass approximation for a finite confining potential. The electronic properties have been examined for different core radii, barrier thicknesses, and well widths in a certain potential. The results have been analyzed in detail as a function of the layer thicknesses and their physical reasons have been interpreted. It has been found that the electronic properties are strongly dependent on the layer thicknesses. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3702874]
Citation - WoS: 68
Citation - Scopus: 75
The Inter-Sublevel Optical Properties of a Spherical Quantum Dot-Quantum Well With and Without a Donor Impurity
(Amer Inst Physics, 2012) Tas, Hatice; Sahin, Mehmet
In this study, we have investigated the inter-sublevel optical properties of a core/shell/well/shell spherical quantum dot (QD) with the form of quantum dot-quantum well heterostructure. In order to determine the energy eigenvalues and corresponding wave functions, the Schrodinger equation has been solved full numerically by using shooting method in the effective mass approximation for a finite confining potential. The inter-sublevel optical absorption and the oscillator strength between ground (1 s) and excited (1 p) states have been examined based on the computed energies and wave functions. Also, the effect of a hydrogenic donor impurity, located at the center of the multi-shell spherical quantum dot (MSQD), has been researched for different core radii (R-1), shell thicknesses (T-s), and well widths (T-w) in certain potential. It is observed that the oscillator strengths and the absorption coefficients are strongly depend on the core radii and layer thicknesses of the MSQD. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751483]
Citation - WoS: 40
Citation - Scopus: 40
Linear and Nonlinear Optical Properties of GaAs/AlxGa1-xAs Multi-Shell Spherical Quantum Dot
(Amer Inst Physics, 2013) Kavruk, Ahmet Emre; Sahin, Mehmet; Koc, Fatih
In this work, the optical properties of GaAs/AlxGa1-xAs/GaAs/AlyGa1-yAs multi-shell quantum dot heterostructure have been studied as a function of Al doping concentrations for cases with and without a hydrogenic donor atom. It has been observed that the absorption coefficient strength and/or resonant absorption wavelength can be adjusted by changing the Al content of inner-barrier and/or outer-barrier regions. Besides, it has been shown that the donor atom has an important effect on the control of the electronic and optical properties of the structure. The results have been presented as a function of the Al contents of the inner-barrier x and outer-barrier y regions and probable physical reasons have been discussed. (c) 2013 AIP Publishing LLC.
Citation - WoS: 17
Citation - Scopus: 19
Sol-Gel Applications for Ceramic Membrane Preparation
(Amer Inst Physics, 2017) Erdem, I.
Ceramic membranes possessing superior properties compared to polymeric membranes are more durable under severe working conditions and therefore their service life is longer. The ceramic membranes are composed of some layers. The support is the layer composed of coarser ceramic structure and responsible for mechanical durability under filtration pressure and it is prepared by consolidation of ceramic powders. The top layer is composed of a finer ceramic micro-structure mainly responsible for the separation of components present in the fluid to be filtered and sol-gel method is a versatile tool to prepare such a tailor-made ceramic filtration structure with finer pores. Depending on the type of filtration (e.g. micro-filtration, ultra-filtration, nano-filtration) aiming separation of components with different sizes, sols with different particulate sizes should be prepared and consolidated with varying precursors and preparation conditions. The coating of sol on the support layer and heat treatment application to have a stable ceramic micro-structure are also important steps determining the final properties of the top layer. Sol-gel method with various controllable parameters (e.g. precursor type, sol formation kinetics, heat treatment conditions) is a practical tool for the preparation of top layers of ceramic composite membranes with desired physicochemical properties.

Browse

Browsing WoS İndeksli Yayınlar Koleksiyonu by Publisher "Amer Inst Physics"