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Articles 1 - 11 of 11
Full-Text Articles in Physics
Optimal Site-Centered Electronic Structure Basis Set From A Displaced-Center Expansion: Improved Results Via A Priori Estimates Of Saddle Points In The Density, Aftab Alam, Duane D. Johnson
Optimal Site-Centered Electronic Structure Basis Set From A Displaced-Center Expansion: Improved Results Via A Priori Estimates Of Saddle Points In The Density, Aftab Alam, Duane D. Johnson
Duane D. Johnson
Site-centered, electronic-structure methods use an expansion inside nonoverlapping “muffin-tin” (MT) spheres plus an interstitial basis set. As the boundary separating the more spherical from nonspherical density between atoms, the “saddle-point” radii (SPR) in the density provide an optimal spherical region for expanding in spherical harmonics, as used in augmented plane wave, muffin-tin orbital, and multiple-scattering [Korringa, Kohn, and Rostoker (KKR)] methods. These MT-SPR guarantee unique, convex Voronoi polyhedra at each site, in distinction to Bader topological cells. We present a numerically fast, two-center expansion to find SPR a priori from overlapping atomic charge densities, valid also for disordered alloys. We …
Research On Fractal Mathematics And Some Application In Mechanics, Yang Xiaojun
Research On Fractal Mathematics And Some Application In Mechanics, Yang Xiaojun
Xiao-Jun Yang
Since Mandelbrot proposed the concept of fractal in 1970s’, fractal has been applied in various areas such as science, economics, cultures and arts because of the universality of fractal phenomena. It provides a new analytical tool to reveal the complexity of the real world. Nowadays the calculus in a fractal space becomes a hot topic in the world. Based on the established definitions of fractal derivative and fractal integral, the fundamental theorems of fractal derivatives and fractal integrals are investigated in detail. The fractal double integral and fractal triple integral are discussed and the variational principle in fractal space has …
Quantitative Prediction Of Twinning Stress In Fcc Alloys: Application To Cu-Al, Sandeep A. Kibey, Lin-Lin Wang, J. B. Liu, H. T. Johnson, H. Sehitoglu, Duane D. Johnson
Quantitative Prediction Of Twinning Stress In Fcc Alloys: Application To Cu-Al, Sandeep A. Kibey, Lin-Lin Wang, J. B. Liu, H. T. Johnson, H. Sehitoglu, Duane D. Johnson
Duane D. Johnson
Twinning is one of most prevalent deformation mechanisms in materials. Having established a quantitative theory to predict onset twinning stress τcrit in fcc elemental metals from their generalized planar-fault-energy (GPFE) surface, we exemplify its use in alloys where the Suzuki effect (i.e., solute energetically favors residing at and near planar faults) is operative; specifically, we apply it in Cu-xAl (x is 0, 5, and 8.3 at. %) in comparison with experimental data. We compute the GPFE via density-functional theory, and we predict the solute dependence of the GPFE and τcrit, in agreement with measured values. We show that τcrit correlates …
Bcc-To-Hcp Transformation Pathways For Iron Versus Hydrostatic Pressure: Coupled Shuffle And Shear Modes, J. B. Liu, Duane D. Johnson
Bcc-To-Hcp Transformation Pathways For Iron Versus Hydrostatic Pressure: Coupled Shuffle And Shear Modes, J. B. Liu, Duane D. Johnson
Duane D. Johnson
Using density-functional theory, we calculate the potential-energy surface (PES), minimum-energy pathway (MEP), and transition state (TS) versus hydrostatic pressure σhyd for the reconstructive transformation in Fe from body-centered cubic (bcc) to hexagonal closed-packed (hcp). At fixed σhyd, the PES is described by coupled shear (ϵ) and shuffle (η) modes and is determined from structurally minimized hcp-bcc energy differences at a set of (η,ϵ). We fit the PES using symmetry-adapted polynomials, permitting the MEP to be found analytically. The MEP is continuous and fully explains the transformation and its associated magnetization and volume discontinuity at TS. We show that σhyd (while …
Effect Of Salts On The Electrospinning Of Poly(Vinyl Alcohol), Jonathan J. Stanger, Nick Tucker, Mark P. Staiger, Kerry Kirwan, Stuart Coles, Daniel Jacobs, Nigel Larsen
Effect Of Salts On The Electrospinning Of Poly(Vinyl Alcohol), Jonathan J. Stanger, Nick Tucker, Mark P. Staiger, Kerry Kirwan, Stuart Coles, Daniel Jacobs, Nigel Larsen
Jonathan J Stanger
Fibres with a diameter in the nanometer range were electrospun from aqueous poly(vinyl alcohol) (PVOH). In order to improve the mass deposition rate and decrease the final fibre diameter salts (NaCl, LiCl, LiBr and LiF) were added to the solution. The aim was to increase the charge density and hence increase the electrostatic forces on the fluid. It was found that with increasing salt concentration the charge density did increase. However the mass deposition rate was found to decrease and the final fibre diameter was found to increase. The decrease in mass deposition rate is explained by considering the concept …
Effect Of Charge Density On The Taylor Cone In Electrospinning, Jonathan J. Stanger, Nick Tucker, Kerry Kirwan, Stuart Coles, Daniel Jacobs, Mark P. Staiger
Effect Of Charge Density On The Taylor Cone In Electrospinning, Jonathan J. Stanger, Nick Tucker, Kerry Kirwan, Stuart Coles, Daniel Jacobs, Mark P. Staiger
Jonathan J Stanger
A detailed understanding of charge density and its origins during the electrospinning process is desirable for developing new electrospinnable polymer-solvent systems and ensuring mathematical models of the process are accurate. In this work, two different approaches were taken to alter the charge density in order to measure its effect on the Taylor cone, mass deposition rate and initial jet diameter. It was found that an increase in charge density results in a decrease in the mass deposition rate and initial jet diameter. A theory is proposed for this behaviour in that an increase in charge density leads to the tip …
The Effect Of Electrode Configuration And Substrate Material On The Mass Deposition Rate Of Electrospinning, Jonathan J. Stanger, Nick Tucker, Andrew Wallace, Nigel Larsen, Mark P. Staiger, Roger Reeves
The Effect Of Electrode Configuration And Substrate Material On The Mass Deposition Rate Of Electrospinning, Jonathan J. Stanger, Nick Tucker, Andrew Wallace, Nigel Larsen, Mark P. Staiger, Roger Reeves
Jonathan J Stanger
Poly(vinyl alcohol) (PVOH) was electrospun using different methods to charge the polymer solution. A positive high voltage relative to the collecting electrode significantly increased the fibre deposition rate. Electron microscopy showed that approximately half of the increase in fibre mass was due to thicker fibres being deposited. The current flowing from the grounded electrode was measured to determine the charge carried on the PVOH jet. This showed that for a positive voltage charging condition there is a much larger current and hence more charge carriers generated in the PVOH solution. As a result, more mass is ejected from the Taylor …
The Fundamentals Of Local Fractional Derivative Of The One-Variable Non-Differentiable Functions, Yang Xiaojun
The Fundamentals Of Local Fractional Derivative Of The One-Variable Non-Differentiable Functions, Yang Xiaojun
Xiao-Jun Yang
Based on the theory of Jumarie’s fractional calculus, local fractional derivative is modified in detail and its fundamentals of local fractional derivative are proposed in this paper. The uniqueness of local fractional derivative is obtained and the Rolle’s theorem, the mean value theorem, the Cauchy’s generalized mean value theorem and the L’Hospital’s rules are proved.
Local Fractional Newton’S Method Derived From Modified Local Fractional Calculus, Yang Xiao-Jun
Local Fractional Newton’S Method Derived From Modified Local Fractional Calculus, Yang Xiao-Jun
Xiao-Jun Yang
A local fractional Newton’s method, which is derived from the modified local fractional calculus , is proposed in the present paper. Its iterative function is obtained and the convergence of the iterative function is discussed. The comparison between the classical Newton iteration and the local fractional Newton iteration has been carried out. It is shown that the iterative value of the local fractional Newton method better approximates the real-value than that of the classical one.
A Neural Network: Family Competition Genetic Algorithm And Its Application In Electromagnetic Optimization, Chien Hsun Chen, P. Y. Chen, H. Weng
A Neural Network: Family Competition Genetic Algorithm And Its Application In Electromagnetic Optimization, Chien Hsun Chen, P. Y. Chen, H. Weng
Chien Hsun Chen
This study proposes a neural network-family competition genetic algorithm (NN-FCGA) for solving the electromagnetic (EM) optimization and other general-purpose optimization problems. The NN-FCGA is a hybrid evolutionary-based algorithm, combining the good approximation performance of neural network (NN) and the robust and effective optimum search ability of the family competition genetic algorithms (FCGA) to accelerate the optimization process. In this study, the NN-FCGA is used to extract a set of optimal design parameters for two representative design examples: the multiple section low-pass filter and the polygonal electromagnetic absorber. Our results demonstrate that the optimal electromagnetic properties given by the NN-FCGA are …
Problems Of Local Fractional Definite Integral Of The One-Variable Non-Differentiable Function, Yang Xiao-Jun
Problems Of Local Fractional Definite Integral Of The One-Variable Non-Differentiable Function, Yang Xiao-Jun
Xiao-Jun Yang
It is proposed that local fractional calculas introduced by Kolwankar and Gangal is extended by the concept of Jumarie’s fractional calculus and local fractional definite integral is redefined. The properties and the theorems of local fractional calculus are discussed in this paper.