scholarly journals Phonon Density of States and Debye Temperatures of BCC Transition Metals

1985 ◽  
Vol 40 (8) ◽  
pp. 834-842
Author(s):  
A. R. Jani
Keyword(s):  
Transition Metals ◽  
Phonon Frequency ◽  
Theoretical Data ◽  
Phonon Density ◽  
Frequency Spectra ◽  
Fine Mesh ◽  
Debye Temperatures ◽  
Density Of Phonon States ◽  
Theoretical Results ◽  
Better Than

A screened shell phenomenological model is applied to determine the density of phonon states and Debye temperatures of six bcc transition metals. The theoretical results are discussed in the light of existing experimental and other theoretical data. It has been found that the results obtained in the present study are better than those reported previously on the basis of phenomenological models. Moreover, it should be emphasized that in the present work a fine mesh of 64 000 evenly spaced vector has been employed to generate the phonon frequency spectra.

ELECTRONIC STATE CALCULATION OF MANGANESE DIOXIDE ELECTRODE WITH ADDITIVE TRANSITION METALS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4255-4260 ◽  
Author(s):  
BONG-SEO KIM ◽  
SU-DONG PARK ◽  
HEE-WOONG LEE ◽  
DONG-YOON LEE ◽  
WON-SUB CHUNG
Keyword(s):  
Electrical Conductivity ◽  
Transition Metals ◽  
Theoretical Calculation ◽  
Manganese Dioxide ◽  
Cluster Model ◽  
Electronic States ◽  
Deposition Method ◽  
Energy Band Gap ◽  
Anodic Deposition ◽  
Better Than

The electronic states of manganese dioxide substituted with transition metals were theoretically calculated by DV-Xα method, cluster model was Mn 15 O 56 and Mn 14 XO 56 (X = transition metal). The energy band gap of manganese-X oxides is lower than that of manganese dioxide from theoretical calculation. Also it is identified that the electrical conductivity of manganese-tungsten oxide is better than that of manganese dioxide from experiment of anodic deposition method. It is confirmed that the theoretical calculation coincides with experimental results.

scholarly journals Simulation and Measurement Studies of The Vdes System’s Terrestrial Component

2019 ◽  
Vol 26 (1) ◽  
pp. 95-106 ◽  
Author(s):  
Krzysztof Bronk ◽  
Patryk Koncicki ◽  
Adam Lipka ◽  
Dominik Rutkowski ◽  
Błażej Wereszko
Keyword(s):  
Data Transmission ◽  
Data Exchange ◽  
Technical Information ◽  
Theoretical Data ◽  
Current Version ◽  
Coding Gain ◽  
Exchange System ◽  
Measurement Results ◽  
Simulation Results ◽  
Theoretical Results

Abstract In the paper, the measurement and simulation results of the VDES (VHF Data Exchange System) terrestrial component are discussed. It is anticipated that VDES will be one of the major solutions for maritime communications in the VHF band and its performance will be sufficient to fulfill the requirements of the e-navigation applications. The process of the VDES standardization (ITU R, IALA) has not been officially completed yet, but substantial amount of technical information about the future system’s terrestrial component (VDE-TER) is already available. The paper is divided into three general parts: (a) theoretical presentation of the system’s physical layer and the radio channels applicable to VDES, (b) simulation results (BER, BLER, channel delay between two propagation paths and its influence on bit rates) and (c) measurement results (useful ranges, BER). It turned out that in real maritime conditions, the VDES system can offer ranges between 25 and 38 km for the configurations assumed during the measurement campaign. Those results are generally compliant with the theoretical data in the line-of-sight conditions. In the NLOS scenarios, where fading becomes the dominant phenomenon, the discrepancies between the measurements and the theoretical results were more significant. The obtained results confirmed that VDES provides a large coding gain, which significantly improves the performance of data transmission and increases the bit rate compared to the existing maritime radiocommunication solutions. It should be noted that the results presented in the article were used by the IALA while developing the current version of the VDES specification.

Parallel Molecular Dynamics Code Validation Through Bulk Silicon Thermal Conductivity Calculations

2003 ◽  
Author(s):  
Carlos J. Gomes ◽  
Marcela Madrid ◽  
Cristina H. Amon
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Single Crystals ◽  
Phonon Frequency ◽  
Interatomic Potential ◽  
Dispersion Relations ◽  
Bulk Silicon ◽  
Ghost Cell ◽  
Frequency Spectra ◽  
Parallel Molecular Dynamics

We have implemented a parallel molecular dynamics algorithm, which incorporates the Stillinger-Weber interatomic potential. The code was parallelized using a ghost cell atomic division approach, ensuring scaling with the number of processors and a significant increase in speed with respect to the serial version. The methodology is validated by computing the thermal conductivity and phonon frequency spectra of bulk silicon single crystals for different domain sizes at 1000K. The predicted thermal conductivities are consistent with the experimental value at that temperature. In addition, the phonon frequency spectra capture the properties expected from the dispersion relations for silicon.

scholarly journals Piecewise Legendre spectral-collocation method for Volterra integro-differential equations

2015 ◽  
Vol 18 (1) ◽  
pp. 231-249 ◽  
Author(s):  
Zhendong Gu ◽  
Yanping Chen
Keyword(s):  
Differential Equations ◽  
Collocation Method ◽  
Spectral Collocation Method ◽  
Piecewise Polynomial ◽  
Spectral Collocation ◽  
Numerical Errors ◽  
Piecewise Polynomial Collocation Method ◽  
Theoretical Results ◽  
Polynomial Collocation ◽  
Better Than

Our main purpose in this paper is to propose the piecewise Legendre spectral-collocation method to solve Volterra integro-differential equations. We provide convergence analysis to show that the numerical errors in our method decay in$h^{m}N^{-m}$-version rate. These results are better than the piecewise polynomial collocation method and the global Legendre spectral-collocation method. The provided numerical examples confirm these theoretical results.

Energies, wavelengths, lifetimes, E1, M1, E2, and M2 transitions rates for the sulfur isoelectronic sequence Fe XI, Nb XXVI–In XXXIV

2017 ◽  
Vol 95 (4) ◽  
pp. 393-401 ◽  
Author(s):  
K. Wang ◽  
S. Li ◽  
R. Si ◽  
C.Y. Chen ◽  
J. Yan ◽  
...  
Keyword(s):  
Quantum Electrodynamics ◽  
Energy Levels ◽  
Theoretical Data ◽  
Electric Quadrupole ◽  
Oscillator Strengths ◽  
Transition Rates ◽  
Isoelectronic Sequence ◽  
Fusion Plasma ◽  
Magnetic Quadrupole ◽  
Theoretical Results

Energies, wavelengths, lifetimes, oscillator strengths, electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2) transition rates among the 42 fine structure levels belonging to the 3s23p4, 3s23p33d, and 3s3p5 configurations for S-like Fe and S-like ions with 41 ≤ Z ≤ 49 are calculated using the fully relativistic multiconfiguration Dirac–Fock (MCDF) method. In the calculations, contributions from correlations within the n = 6 complex, Breit interaction, and quantum electrodynamics effects are included. Detailed comparisons are made between the present results and the available experimental and other theoretical data. We found that our calculated energy levels generally agree within ≤0.5% with the experimentally compiled results, and the transition rates agree within ≤12% with other theoretical results for a majority of the transitions. These accurate theoretical data should be beneficial in fusion plasma research and astrophysical applications.

Time and Price Dependent Demand with Varying Holding Cost Inventory Model for Deteriorating Items

2013 ◽  
Vol 4 (4) ◽  
pp. 75-95 ◽  
Author(s):  
Diwakar Shukla ◽  
Uttam Kumar Khedlekar ◽  
Raghovendra Pratap Singh Chandel
Keyword(s):  
Simulation Study ◽  
Demand Function ◽  
Inventory Model ◽  
Time Parameter ◽  
Suggested Model ◽  
Open Problems ◽  
Holding Cost ◽  
Theoretical Results ◽  
Dependent Demand ◽  
Better Than

This paper presents an inventory model considering the demand as a parametric dependent linear function of time and price both. The coefficient of time-parameter and coefficient of price-parameter are examined simultaneously and proved that time is dominating variable over price in terms of earning more profit. It is also proved that deterioration of item in the inventory is one of the most sensitive parameter to look into besides many others. The robustness of the suggested model is examined using variations in the input parameters and ranges are specified on which the model is robust on most of occasions and profit is optimal. Two kinds of doubly-demand function strategies are examined and mutually compared in view of the two different cases. Second strategy found better than first. Holding cost is treated as a variable. Theoretical results are supported by numerical based simulation study with robustness. Some recommendations are given at the end for the inventory managers and also open problems are discussed for researchers. This model is more realistic than considered by earlier author.

Structural, Phonon and Thermodynamic Properties of the Rocksalt Structure LiF from First Principles

2016 ◽  
Vol 850 ◽  
pp. 348-353 ◽  
Author(s):  
Hai Jun Hou ◽  
Hao Guan ◽  
Shun Ru Zhang ◽  
Lin Hua Xie ◽  
Lei Wang
Keyword(s):  
Thermodynamic Properties ◽  
Density Of States ◽  
Phonon Dispersion ◽  
Local Density ◽  
Wide Band ◽  
Present Calculation ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Rocksalt Structure ◽  
Theoretical Results

The structural, electronic, phonon and thermodynamic properties of rocksalt (RS) structure LiF are studied using a plane-wave pseudopotential method within the local density approximation (LDA). The values of lattice constants, elastic constants, and bulk modulus and its pressure derivatives are in well agreement with the available experimental data and other theoretical results. The LiF crystal exhibits a wide band gap of about 8.727 eV. The linear response method is applied to determine the phonon dispersion, phonon density of states and Born effective charge. The phonon frequencies at the Γ, X, L points are analyzed using group theory. We also calculate the thermodynamic functions such as free energy, enthalpy, entropy, specific heat using the phonon density of states. We compare the present calculation results satisfactorily to experimental and previous theoretical results.

ELASTIC CONSTANTS OF d TRANSITION ELEMENTS AND d TRANSITION ALLOYS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 203-206 ◽  
Author(s):  
PER SÖDERLIND ◽  
JOHN WILLS ◽  
OLLE ERIKSSON
Keyword(s):  
Crystal Structure ◽  
Elastic Constant ◽  
Elastic Constants ◽  
First Principles ◽  
Theoretical Data ◽  
Energy Difference ◽  
Transition Elements ◽  
Virtual Crystal Approximation ◽  
Theoretical Results ◽  
Theory And Experiment

The shear elastic constant, C′, is calculated from first principles for the cubic 4d and 5d transition elements. This study also includes calculations for selected alloys using the virtual crystal approximation. The tetragonal shear constant for these elements and alloys is found to follow a trend which can be related to the calculated crystal structure stabilities. In fact, the trend of C′ behaves roughly as the the trend displayed by the energy difference between the fcc and bcc crystal structures. The theoretical results are generally in ~90% agreement with experiment for the tetragonal shear constant and this implies indirectly that the discrepancy between theory and experiment found for the crystal energies do not lie in the theoretical data.

scholarly journals Effective viscosity of puller-like microswimmers: a renormalization approach

2013 ◽  
Vol 10 (89) ◽  
pp. 20130720 ◽  
Author(s):  
Simon Gluzman ◽  
Dmitry A. Karpeev ◽  
Leonid V. Berlyand
Keyword(s):  
Renormalization Group ◽  
Critical Point ◽  
Effective Viscosity ◽  
Collective Motion ◽  
Analytical Determination ◽  
Renormalization Approach ◽  
Theoretical Results ◽  
Better Than ◽  
Passive Suspensions

Effective viscosity (EV) of suspensions of puller-like microswimmers (pullers), for example Chlamydamonas algae, is difficult to measure or simulate for all swimmer concentrations. Although there are good reasons to expect that the EV of pullers is similar to that of passive suspensions, analytical determination of the passive EV for all concentrations remains unsatisfactory. At the same time, the EV of bacterial suspensions is closely linked to collective motion in these systems and is biologically significant. We develop an approach for determining analytical EV estimates at all concentrations for suspensions of pullers as well as for passive suspensions. The proposed methods are based on the ideas of renormalization group (RG) theory and construct the EV formula based on the known asymptotics for small concentrations and near the critical point (i.e. approaching dense packing). For passive suspensions, the method is verified by comparison against known theoretical results. We find that the method performs much better than an earlier RG-based technique. For pullers, the validation is done by comparing them to experiments conducted on Chlamydamonas suspensions.

scholarly journals Damn You, Little h! (Or, Real-World Applications of the Hubble Constant Using Observed and Simulated Data)

2013 ◽  
Vol 30 ◽  
Author(s):  
Darren J. Croton
Keyword(s):  
Data Analysis ◽  
Galaxy Formation ◽  
Real World ◽  
Simulated Data ◽  
Theoretical Data ◽  
Hubble Constant ◽  
Uncertain Parameters ◽  
Modern Age ◽  
Real World Applications ◽  
Better Than

AbstractThe Hubble constant, H0, or its dimensionless equivalent, “little h”, is a fundamental cosmological property that is now known to an accuracy better than a few per cent. Despite its cosmological nature, little h commonly appears in the measured properties of individual galaxies. This can pose unique challenges for users of such data, particularly with survey data. In this paper we show how little h arises in the measurement of galaxies, how to compare like-properties from different datasets that have assumed different little h cosmologies, and how to fairly compare theoretical data with observed data, where little h can manifest in vastly different ways. This last point is particularly important when observations are used to calibrate galaxy formation models, as calibrating with the wrong (or no) little h can lead to disastrous results when the model is later converted to the correct h cosmology. We argue that in this modern age little h is an anachronism, being one of least uncertain parameters in astrophysics, and we propose that observers and theorists instead treat this uncertainty like any other. We conclude with a ‘cheat sheet’ of nine points that should be followed when dealing with little h in data analysis.

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