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Rotational stretched exponential relaxation in random trap–barrier model

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Chinese Physics B 2015年第7期24卷 149-154页

作者： ekrem Aydiner Department of Physics Faculty of Sciencestanbul University

The relaxation behavior of complex-disordered systems, such as spin glasses, polymers, colloidal suspensions, structural glasses,and granular media, has not been clarified. Theoretical studies show that relaxation in these systems has a topological origin. In this paper, we focus on the rotational stretched exponential relaxation behavior in complex-disordered systems and introduce a simple phase space model to understand the mechanism of the non-exponential relaxation of these systems. By employing the Monte Carlo simulation method to the model, we obtain the rotational relaxation function as a function of temperature. We show that the relaxation function has a stretched exponential form under the critical temperature while it obeys the Debye law above the critical temperature.

关键词： random walks rotational relaxation slow dynamics Kohlrausch–William–Watts(KWW) relaxation

A NOTE ON GENERALIZED ABSOLUTE SUMMABILITY FACTORS FOR A TRIANGULAR MATRIX

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Acta Mathematica Scientia 2011年第4期31卷 1513-1516页

作者： ekrem savas Department of Mathematics Istanbul Ticaret Universityskdar

In this paper, a general theorem on ｜ A, δ ｜k -summability factors of infinite series is proved under different conditions.

关键词： absolute summability summability factors triangular matrix

Current and efficiency optimization under oscillating forces in entropic barriers

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Chinese Physics B 2016年第9期25卷 227-234页

作者： Ferhat Nutku ekrem Aydiner Theoretical Physics Research Group Department of PhysicsFaculty of ScienceIstanbul University

The transport of externally overdriven particles confined in entropic barriers is investigated under various types of oscillating and temporal ***,load,and amplitude dependence of the particle current and energy conversion efficiency are investigated in three *** oscillating forces,the optimized temperature–load,amplitude–temperature,and amplitude–load intervals are determined when fixing the amplitude,load,and temperature,*** using three-dimensional plots rather than two-dimensional ones,it is clearly shown that oscillating forces provide more efficiency compared with a temporal one in specified optimized parameter ***,the dependency of efficiency to the angle between the unbiased driving force and a constant force is investigated and an asymmetric angular dependence is found for all types of ***,it is shown that oscillating forces with a high amplitude and under a moderate load lead to higher efficiencies than a temporal force at both low and high temperatures for the entire range of contact angle.

关键词： entropic barrier Brownian motion Fick–Jacobs equation efficiency of Brownian motor

Entanglement in Ising Chain with Inhomogeneous Magnetic Field

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Chinese Physics Letters 2008年第5期25卷 1557-1560页

作者： Cenk Akyfiz ekrem Aydlner Theoretical and Computational Physics Research Group Department of Physics Dokuz Eyliil University Faculty of Arts and Sciences 35160-izmir Turkey

We have numerically calculated the thermal entanglement of a two-qubit system at low temperatures in a isotropic Ising chain under an inhomogeneous magnetic field. It is shown that in the homogeneous magnetic field, the two- qubit system has entangled states. It is concluded that the presence of the inhomogeneity in the magnetic field plays an effective role on the entangled states. Finally, it is suggested that the inhomogeneity in the magnetic field can be used to create two separated entangled formations in a two-qubit system.

关键词： THERMAL ENTANGLEMENT QUANTUM COMPUTER BELL THEOREM CRYPTOGRAPHY SYSTEM COMPUTATION COUPLINGS MODELS STATE DOTS

Thermal entanglement in the mixed three-spin XXZ Heisenberg model on a triangular cell

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Chinese Physics B 2014年第5期23卷 73-79页

作者： Seyit Deniz Han ekrem Aydiner Department of Physics Istanbul University

We numerically investigate the thermal entanglements of spins （1/2, 1） and spins （1/2, 1/2） in the three-mixed （1/2, 1, 1/2） anisotropic Heisenberg XXZ spin system on a simple triangular cell under an inhomogeneous magnetic field. We show that the external magnetic field induces strong plateau formation in the pairwise thermal entanglement for fixed parame-ters of the Hamiltonian in the cases of ferromagnetic and antiferromagnetic interactions. We also .observe an unexpected critical point at finite temperature in the thermal entanglement of spins （1/2, 1） for the antiferromagnetic case, while the entanglement of spins （1/2, 1） in the ferromagnetic case and the entanglement of spins （1/2, 1/2） in both ferromagnetic and antiferromagnetic cases almost decay exponentially to zero with increasing temperature. The critical point in the en-tanglement of spins （1/2, 1） in the antiferromagnetic case may be a signature of the quantum phase transition at finite temperature.

关键词： quantum entanglement quantum phase transition negativity

Current and efficiency of Brownian particles under oscillating forces in entropic barriers

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Chinese Physics B 2015年第4期24卷 82-89页

作者： Ferhat Nutku ekrem Aydιner Theoretical Physics Research Group Department of Physics Faculty of Sciencestanbul University

In this study, considering the temporarily unbiased force and different forms of oscillating forces, we investigate the current and efficiency of Brownian particles in an entropic tube structure and present the numerically obtained results. We show that different force forms give rise to different current and efficiency profiles in different optimized parameter intervals. We find that an unbiased oscillating force and an unbiased temporal force lead to the current and efficiency, which are dependent on these parameters. We also observe that the current and efficiency caused by temporal and different oscillating forces have maximum and minimum values in different parameter intervals. We conclude that the current or efficiency can be controlled dynamically by adjusting the parameters of entropic barriers and applied force.

关键词： entropic barrier Brownian motion Fick-Jacobs equation efficiency of Brownian motor stochastic processes

Magnetic and Thermal Behaviour of One-Dimensional Antiferromagnetic Spin-1 Ising Chain at Low Temperatures

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Chinese Physics Letters 2005年第9期22卷 2382-2385页

作者： ekrem Aydmer Cenk Akyüz Department of Physics Dokuz Eylül University TR-35160 Izmir Turkey

We investigate magnetic and thermal behaviours of one-dimensional antiferromagnetic spin-i Ising chain with single-ion anisotropy at very low temperatures using the classical transfer matrix technique. Magnetic plateaus, phase diagram, specific heat, susceptibility of the spin chain have been evaluated numerically from the free energy. The results are in good agreement with the experimental data for the spin-1 compounds [Ni2 （Medpt）2 （μ- ox）（H2O）2]（ClO4）22H2O, [Ni2（Medpt）2（μ-ox）（μ-N3）]（ClO4）0.5H2O, Ni（C2H8N2）Ni（CN）4 and Ni（C10H8N2）2 Ni（CN）4·H2O.

关键词： GROUND-STATE MAGNETIZATION SINGLE-ION-ANISOTROPY HEISENBERG CHAIN BONDALTERNATION PHASE-DIAGRAM PLATEAUS FIELD LADDERS CURVES

Quadratic interaction effect on the dark energy density in the universe

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Chinese Physics B 2017年第10期26卷 533-538页

作者： Derya G Deveci ekrem Aydiner Department of Physics Faculty of ScienceIstanbul University Department of Opticianry Alt?nbas University

In this study, we deal with the holographic model of interacting dark components of dark energy and dark matter quadratic case of the equation of state parameter （EoS）. The effective equations of states for the interacting holographic energy density are derived and the results are analyzed and compared with the solution of the linear form in the literature. The result of our work shows that the value of interaction term between dark components affects the fixed points at far future in the DE-dominated universe in the case of quadratic EoS parameter; it is a different result from the linear case in the theoretical results in the literature, and as the Quintom scenario the equations of state had coincidence at the cosmological constant boundary of - 1 from above to below.

关键词： dark energy dark matter

Experimental and computational analysis of the coolant distribution considering the viscosity of the cutting fluid during machining with helical deep hole drills

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Advances in Manufacturing 2022年第2期10卷 235-249页

作者： ekrem Oezkaya Sebastian Michel Dirk Biermann Institute of Machining Technology Dortmund University of Technology(TU Dortmund)Dortmund 44227Germany

An experimental analysis regarding the distribution of the cutting fluid is very difficult due to the inaccessibility of the contact zone within the bore ***,suitable simulation models are necessary to evaluate new tool designs and optimize drilling *** this paper the coolant distribution during helical deep hole drilling is analyzed with high-speed *** particles are added to the cutting fluid circuit bya developed high-pressure mixing *** the evaluation of suitable particle size,particle concentration and coolant pressure,a computational fluid dynamics(CFD)simulation is validated with the experimental *** comparison shows a very good model quality with a marginal difference for the flow velocity of 1.57%between simulation and *** simulation considers the kinematic viscosity of the *** results show that the fluid velocity in the chip flutes is low compared to the fluid velocity at the exit of the coolant channels of the tool and drops even further between *** velocity and the flow pressure directly at the cutting edge decrease to such an extent that the fluid cannot generate a sufficient cooling or *** the CFD simulation a deeper understanding of the behavior and interactions of the cutting fluid is *** on these results further research activities to improve the coolant supply can be carried out with great potential to evaluate new tool geometries and optimize the machining process.

关键词： Computational fluid dynamics(CFD)analysis:Viscosity-Tracermicro particles Fluidbehavior Helical deep hole drilling