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A dynamic closure modeling framework for large eddy simulation using approximate deconvolution: Burgers equation
Maulik R., San O.
AbstractWe put forth a dynamic closure modeling framework for the large eddy simulations of the Burgers equation based upon the use of the approximate deconvolution (AD) procedure to compute the Smagorinsky constant self-adaptively from the resolved flow quantities. In our proposed framework, the test filtering process of the standard dynamic model is replaced by the AD procedure. The robustness of the model has been tested considering the Burgers equation in its conservative and skew-symmetric forms. Our numerical assessments for solving the single-mode sine wave and the decaying Burgers turbulence problems show that the present framework effectively damps grid-to-grid oscillations and yields an improved shock capturing property for central numerical schemes as underlying discretizations.
Irreversible thermodynamics of ideal plastic deformation
Ogawa K., Ichitsubo T., Ishioka S.
AbstractThermodynamics for ideal plastic deformation causing no disorganization of the structure in the deformed body, which was discussed by P. W. Bridgman studied (1950), revealed that the concept of entropy was still applicable to its irreversible process. Noting that the structural invariability in an ideal plastic body is physically equivalent to the prerequisite of thermodynamics, namely, thermodynamic quantities must be independent of the macroscopic body shape, the generalized concept of entropy can be extended to the other thermodynamic potentials such as internal energy, free energies and so on. Here the extended generalization for ideal plastic deformation is theoretically justified on the basis of the irreversible thermodynamics constructed by Prigogine and his discipline. Thermodynamic state of the ideally deformed body is found to be specified both by the generalized thermodynamic potential (S, U, F, H or G) and by the irreversible potential energy J which drives the plastic deformation.
The interboundary properties and kinematics of N719 dye with titania photoanode framework and spectral responses with different electrolytes
Abodunrin T.J., Boyo A.O., Usikalu M.R.
Titanium oxide is as ancient in age as our planet but its use for photoanode
is more recent. It exists naturally as rutile (the second most abundant), anatase and
brookite ores. The anatase several metastable states trigger diverse spectral responses
with Magnifera Indica Linn. (M.indica L) dye as it is synthesized with an N719 dye grown
on its matrix. Facile doctor blade method and high temperature sintering at 723 Kwere
used in fabrication. Doping of titanium oxide in effect lowers the band gap of TiO2 for
photo-excitation caused by a bathochromic shift and simultaneously decreases the
rate of recombination in photogenerated electron–hole pairs. This study explored the
visible light induced photocatalytic action of doped M.indica L DSSC towards reduction
of titaniumoxide bandgap. The SEMmicrographs reveal themolecular interactions and
the interplay as electrolytes percolate the intricate N719 dye/Titania framework.
Detailed analysis stem from comparison of M.indica L crude faction and the batch
separated faction using FTIR spectroscopy. The absorbance peak, rates of reaction and
% transmittance identify the particular chromophores responsible for the reaction.
Result shows the batch-separated hexane faction approximately 1000 times more
efficient than its crude faction although the ff of the crude was only about twice that of
the hexane faction. The optical study showed that doping ions lead to an increase in
the absorption edge wavelength, and a decrease in the band gap energy of TiO2 nanoparticles. The doped TiO2 nanoparticles in general showed higher photocatalytic
activities than the pure ones.
Acknowledgement of reviewers
Editors S.
Investigation on the influence of LaCl3 concentration on the electrical conduction mechanism of chemical-bath deposited LaF3/porous-silicon structure
Rahman M.H., Ismail A.B.
AbstractEffect of LaCl3 concentration on the electrical conduction mechanism of LaF3/porous silicon (PS) structure has been investigated in this work. LaF3 layers have been deposited by a novel chemical bath deposition (CBD) technique. With this simple technique, LaF3 produced as LaCl3 are made to react with hydrofluoric (HF) acid on the porous silicon substrate. This enables direct deposition of LaF3 on the pore walls of the porous silicon leading to a successful passivation of PS. The compositions of the deposited LaF3 were confirmed by Energy Dispersive of X-ray (EDX) analysis. The electrical conduction study has been done by impedance analyzer (HP4294A). From this study it can be concluded that the conductance increases with LaCl3 concentration but decreases for higher concentration.
Forecasting of the electricity price on the day-ahead electricity market in Russia
Maksimov A.G., Shchurupova D.V.
AbstractAfter analyzing the characteristics and pricing models on the Russian wholesale electricity market, some important features for econometric modeling are introduced. This paper suggests econometric forecasting models developed to predict daily and hourly electricity prices on the day-ahead market for two price zones in Russia: European and Siberian ones. A set of 24 models, which are similar in nature but different in included regressors, are introduced. On the basis of the actual database for 2014, different modifications of price formation are offered and analyzed with the help of the Eviews econometric package. Dynamic forecasts on various distances (day, week, and month) are conducted and the most suitable models from the point of minimizing the norms of the vectors residuals are chosen. Constructed ARMA models have high predictive power and are able to reflect the price trend on the base of exogenous factors and the previous price values.
Ab-initio study of C15-type Laves phase superconductor LaRu2
Kholil M.I., Islam M.S., Rahman M.A.
AbstractStructural, elastic, electronic, optical, thermodynamic, and superconducting properties of the Laves phase superconductor LaRu2 with Tc ~ 1.63 K were investigated using the first-principles calculations for the first time. The corresponding evaluated structural parameters are in good agreement with the available theoretical values. The different elastic properties like as, elastic constants, bulk modulus B, shear modulus G, Young’s modulus E, and Poisson ratio ν were calculated using the Voigt–Reuss–Hill approximation. The ductility nature appears in both values of Cauchy pressure and Pugh’s ratio. The band structure and Cauchy pressure shows that the material behaves metallic nature. The calculated total density of state is 6.80 (electrons/eV) of LaRu2. The optical properties such as reflectivity, absorption spectrum, refractive index, dielectric function, conductivity, and energy loss spectrum are also calculated. The photoconductivity reveals the metallic nature of LaRu2 and absorption coeffici...
Closed form solutions of complex wave equations via the modified simple equation method
Hossain A.K., Akbar M.A., Wazwaz A.
AbstractThe Kundu–Eckhaus equation and the derivative nonlinear Schrodinger equation describe various physical processes in nonlinear optics, plasma physics, fluid mechanics, magneto-hydrodynamic equation in the presence of the Hall Effect. Thus, closed form solutions of these equations are very important to realize the obscurity of the phenomena. The modified simple equation (MSE) method is highly effective and competent mathematical tool to examine closed form wave solutions of nonlinear evolution equations (NLEEs) arising in mathematical physics, applied mathematics and engineering. In this article, the MSE method is suggested and executed to construct closed form wave solutions of the above-mentioned equations involving parameters. When the parameters receive special values, impressive solitary wave solutions are derived from the exact solutions.
RT-TDDFT study of hole oscillations in B-DNA monomers and dimers
Tassi M., Morphis A., Lambropoulos K., Simserides C.
We employ Real-Time Time-Dependent Density Functional Theory to study hole oscillations within a B-DNA monomer (one base pair) or dimer (two base pairs). Placing the hole initially at any of the bases which make up a base pair, results in THz oscillations, albeit of negligible amplitude. Placing the hole initially at any of the base pairs which make up a dimer is more interesting: For dimers made of identical monomers, we predict oscillations with frequencies in the range $f \approx$ 20-80 THz, with a maximum transfer percentage close to 1. For dimers made of different monomers, $f \approx$ 80-400 THz, but with very small or small maximum transfer percentage. We compare our results with those obtained recently via our Tight-Binding approaches and find that they are in good agreement.
Tailoring the electronic structure and optical properties of cadmium-doped zinc oxides nanosheet
Ayaz Khan S., Azam S., Kanoun M.B., Murtaza G., Rani M., Goumri-Said S.
High-pressure structural parameters and equation of state of osmium to 207 GPa
Perreault C.S., Velisavljevic N., Vohra Y.K.
Electronic origin of melting T–P curves of alkali metals with negative slope and minimum
Degtyareva V.F.
Group I elements - alkali metals Li, Na, K, Rb and Cs - are examples of simple metals with one s electron in the valence band. Under pressure these elements display unusually complex structural behaviour transforming from close-packed to low symmetry open structures. Unexpectedly complex form was found for melting curves of alkalis under compression with initial increasing in accordance to Lindemann criterion and further decreasing to very low melting point. To understand complex and low symmetry structures in compressed alkalis a transformation of the electron energy levels was suggested which involves an overlap between the valence band and outer core electrons. Within the model of the Fermi sphere - Brillouin zone interaction one can understand the complex melting curve of alkalis.
Synthesis and characterization of high-quality cobalt vanadate crystals and their applications in lithium-ion batteries
Bhuiyan M.T., Rahman M.A., Rahman M.A., Sultana R., Mostafa M.R., Tania A.H., Sarker M.A.
AbstractHigh-quality cobalt vanadate crystals have been synthesized by solid-state reaction route. Structure and morphology of the synthesized powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. The XRD patterns revealed that the as prepared materials are of high crystallinity and high quality. The SEM images showed that the crystalline CoV2O6 material is very uniform and well separated, with particle (of) area ~252 μm. The electronic and optical properties were investigated by impedance analyzer and UV–visible spectrophotometer. Temperature-dependent electrical resistivity was measured using four-probe technique. The crystalline CoV2O6 material is a semiconductor and its activation energy is 0.05 eV.
Ab-initio study on structural, elastic, electronic and optical properties of iron-based superconductor
Chowdhury U.K., Rahman M.A., Rahman M.A., Bhuiyan M.T.
