Yaghoob Naimi
Abstract
A B S T R A C TWe present a comparative study based on Density Functional Theory (DFT), of the effect that different approximations such as exchange-correlation (XC) functional, effect of Hubbard U, TB-mBJ correction and optimized lattice constant strain have on the structural and electronic properties ...
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A B S T R A C TWe present a comparative study based on Density Functional Theory (DFT), of the effect that different approximations such as exchange-correlation (XC) functional, effect of Hubbard U, TB-mBJ correction and optimized lattice constant strain have on the structural and electronic properties of NaTiAs compound. At first, by using DFT based full-potential WIEN2k package we compare the total energy vs volume of ferromagnetic, antiferromagnetic and non-magnetic half-Heusler structures to obtain the more stable configuration phase and magnetic state. Calculations show that our compound is more stable in the half-Heusler beta-phase and the ferromagnetic state. Then, we investigate the structural and electronic properties of NaTiAs-beta by using LDA, PBEsol, WC and PBE XC functionals. Our results show that different XC functionals cannot lead to half metallicity. But when we use the GGA+U and TB-mBJ schemes with PBE parameterization, results indicate that the Fermi level cuts through the partially occupied band in majority spin channel while it is located in the gap between valence and conduction bands in the minority spin direction thus it demonstrates the half-metallic behavior of this compound, and the amount of a total magnetic moment is equal to . Furthermore, by applying at least optimized lattice constant strain, NaTiAs-beta becomes half metal. Examination of the elastic constants shows that the compound is stable. These types of compounds are candidates for making spintronic devices.
Zeinab Hajijamali-Arani; Tymaz Fatolahi-Khalkhali
Abstract
In this research, the photonic structure of an inverse linear tapered waveguide made of silicon nitride is investigated. This structure serves as a connector between a few micron-sized waveguides and sub-micrometer waveguides in photonic integrated circuits. Since the propagation of electromagnetic modes ...
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In this research, the photonic structure of an inverse linear tapered waveguide made of silicon nitride is investigated. This structure serves as a connector between a few micron-sized waveguides and sub-micrometer waveguides in photonic integrated circuits. Since the propagation of electromagnetic modes in the structure of waveguides, especially in tapered waveguides, depends on the shape, dimensions, and material of the waveguide, the investigations of various aspects of the mentioned geometric structure are analyzed. The distribution of electromagnetic field for guided modes in this structure is also studied. Considering the importance of the transmission spectrum of a waveguide for the design of integrated photonic circuits, this will be simulated using the 3D finite-difference time-domain (FDTD) method. Among the selected single-mode structures, an optimized structure with improved efficiency is obtained. This structure has a length of 100 μm, an output width of 1 μm, and an input width of 0.3 μm.
Mina shiri; Mehrdad Ghominejad; Mohammad Reza Pourkarimi
Abstract
In this paper, we model a two-qubit system of identical superconducting charge qubits, where Josephson junctions are coupled via a fixed capacitor. In this model, the effects of temperature, Josephson energy, and mutual coupling energy between the two qubits under increase or decrease of coherence and ...
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In this paper, we model a two-qubit system of identical superconducting charge qubits, where Josephson junctions are coupled via a fixed capacitor. In this model, the effects of temperature, Josephson energy, and mutual coupling energy between the two qubits under increase or decrease of coherence and dense coding capacity (DCC) are examined. The results indicate that increasing temperature leads to a reduction in coherence and DCC, while mutual coupling energy contributes to an increase in these two quantities. On the other hand, Josephson energy has an effect opposite to mutual coupling energy, reducing both coherence and DCC.
Parisa Mahmoudi
Abstract
Effective mixing of samples is a critical requirement in many biochemical processes. However, achieving fast and homogeneous mixing in microfluidic channels presents significant challenges due to the low Reynolds number characteristic of microscale fluid flows. This study introduces an active micromixer ...
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Effective mixing of samples is a critical requirement in many biochemical processes. However, achieving fast and homogeneous mixing in microfluidic channels presents significant challenges due to the low Reynolds number characteristic of microscale fluid flows. This study introduces an active micromixer with a non-symmetric lateral geometry that facilitates the application of electroosmotic flow, particularly near the inlet and, most notably, at the outlet of the mixing chamber. In this proposed configuration, input fluids are more rapidly and precisely subjected to efficient mixing, under very low applied voltages. As a result, a higher quality of fluid mixture is achieved throughout the mixing chamber, driven by vortices generated through electroosmotic stimulation as well as the sharp edges within the chamber. Additionally, the mixing quality is further modified by the electric field at the outlet of the mixing chamber. This performance reduces the effective mixing time, minimizes the required voltage amplitude, improves the Mixing Index, and ensures consistent and stable operation over time. According to the finite element simulation results, at an applied voltage of 0.1 volts, the mixing time is less than 2 seconds, and the Mixing Index is 0.98. Consequently, this design is highly safe and efficient for lab-on-a-chip microfluidic applications, where the integrity of the samples within the mixers must remain unchanged.