scholarly journals К вопросу о влиянии неоднородного диэлектрического покрытия на характеристики металлической поверхности

2022 ◽  
Vol 64 (1) ◽  
pp. 125
Author(s):  
В.В. Погосов
Keyword(s):  
Work Function ◽  
Continuous Medium ◽  
Flat Surface ◽  
Unit Area ◽  
Ritz Method ◽  
Uniform Coating ◽  
Inhomogeneous Dielectric ◽  
Interacting Electrons ◽  
Inhomogeneous Coating ◽  
Quantum Statistical

Within the framework of the quantum-statistical functional and the Ritz method, the the problem of finding the surface energy per unit area and work function electrons of a metal flat surface with a inhomogeneous dielectric coating, taken into account in the approximation of a continuous medium. For a uniform coating, the calculated values are insensitive to the selection one-parameter functions for an electronic profile, but sensitive to the gradient series of kinetic energy non-interacting electrons. Calculations are performed for Al, Na and the comparison with the calculations by the Kohn-Shem method is made. Analytically the connection between the theory of the Ritz method for inhomogeneous coatings and calculations by the Kohn-Shem method work function of electrons for metal-dielectric nanosandwiches. As it turned out, the influence inhomogeneous coating on the characteristics of the metal surface can be scaled down to a uniform coverage case. The possibility of using the obtained results in various experimental situations are discussed.

scholarly journals Designing bioinspired surfaces for water collection from fog

2018 ◽  
Vol 377 (2138) ◽  
pp. 20180269 ◽  
Author(s):  
Dev Gurera ◽  
Bharat Bhushan
Keyword(s):  
Flat Surface ◽  
Unit Area ◽  
Water Repellency ◽  
Vertical Axis ◽  
Collection Rate ◽  
Flat Surfaces ◽  
Single Cone ◽  
Water Collection ◽  
The Difference ◽  
Conical Surfaces

A systematic study is presented on various water collectors, bioinspired by desert beetles, desert grass and cacti. Three water collecting mechanisms including heterogeneous wettability, grooved surfaces, and Laplace pressure gradient, were investigated on flat, cylindrical, conical surfaces, and conical array. It is found that higher water repellency in flat surfaces results in higher water collection rate and inclination angle (with respect to the vertical axis) has little effect. Surfaces with heterogeneous wettability have higher water collection rate than surfaces with homogeneous wettability. Both cylindrical and conical surfaces resulted in comparable water collection rate. However, only the cone transported the water droplets to its base. Heterogeneity, higher inclination and grooves increased the water collection rate. A cone has a higher collection rate per unit area than a flat surface with the same wettability. An array of cones has higher collection rate per unit area than a single cone, because droplets in a conical array coalesce, leading to higher frequency of droplets falling. Adding heterogeneity further increases the difference. Based on the findings, scaled-up designs of beetle-, grass- and cactus-inspired surfaces and nets are presented. This article is part of the theme issue ‘Bioinspired materials and surfaces for green science and technology’.

Modeling of a Rolling Flexible Circular Ring

2015 ◽  
Vol 82 (11) ◽  
Author(s):  
François Robert Hogan ◽  
James Richard Forbes
Keyword(s):  
Numerical Simulations ◽  
Dynamic Model ◽  
Lagrange Multipliers ◽  
Flat Surface ◽  
Ritz Method ◽  
Free Vibrations ◽  
Circular Ring ◽  
Ring Rolling ◽  
Motion Equations ◽  
Out Of Plane

The motion equations of a rolling flexible circular ring are derived using a Lagrangian formulation. The in-plane flexural and out-of-plane twist-bending free vibrations are modeled using the Rayleigh–Ritz method. The motion equations of a flexible circular ring translating and rotating in space are first developed and then constrained to roll on a flat surface by introducing Lagrange multipliers. The motion equations developed capture the nonholonomic nature of the circular ring rolling without slip on a flat surface. Numerical simulations are performed to validate the dynamic model developed and to investigate the effect of the flexibility of the circular ring on its trajectory. The vibrations of the circular ring are observed to impact the ring's motion.

The Mechanisms of the Phenomenon of Tornado-Like Jets Self-Organization in the Flow Along the Dimples on the Initially Flat Surface

2012 ◽  
Author(s):  
G. I. Kiknadze ◽  
I. A. Gachechiladze ◽  
T. T. Barnaveli
Keyword(s):  
Continuous Medium ◽  
Flat Surface ◽  
Three Dimensional ◽  
Self Organization ◽  
Double Curvature

The mechanisms of the phenomenon of the tornado-like jets self-organization are described. Tornado-like jets are incorporated into a continuous medium stream and induced by three-dimensional reliefs of double curvature indented on surfaces.

scholarly journals Thermal Fluctuations and Electromagnetic Noise Spectra in Quantum Statistical Mechanics

2021 ◽  
Author(s):  
Ladislaus Alexander Bányai ◽  
Mircea Bundaru ◽  
Paul Gartner
Keyword(s):  
Wave Vector ◽  
Quantum Statistical Mechanics ◽  
Field Operator ◽  
Thermal Fluctuations ◽  
Noise Spectrum ◽  
Complex Frequency ◽  
Occupation Numbers ◽  
Interacting Electrons ◽  
Quantum Statistical ◽  
The Fourier Transform

We derive the thermal noise spectrum of the Fourier transform of the electric field operator of a given wave vector starting from the quantum-statistical definitions and relate it to the complex frequency and wave vector dependent complex conductivity in a homogeneous, isotropic system of electromagnetic interacting electrons. We analyze separately the longitudinal and transverse case with their peculiarities. The Nyquist formula for vanishing frequency and wave vector, as well as its modification for non-vanishing frequencies and wave vectors follow immediately. Furthermore we discuss also the noise of the photon occupation numbers. It is important to stress that no additional assumptions at all were used in this straightforward proof.

scholarly journals A new approach to the problem of removal of soluble gaseous pollutants from the atmosphere and its correspondence with the existing approach

1994 ◽  
Vol 17 (1) ◽  
pp. 165-172
Author(s):  
Soumitra Chattopadhyay ◽  
A. K. Mukherjee
Keyword(s):  
Air Pollutants ◽  
Continuous Medium ◽  
Unit Area ◽  
Mass Transfer Process ◽  
Gaseous Pollutants ◽  
Cloud Droplets ◽  
New Approach ◽  
Rate Of Dissolution ◽  
The Mean ◽  
Gas Molecules

A new approach has been developed using the kinetic theory for the dissolution of gaseous pollutants in cloud droplets. The existing theory, using the diffusion approach, assumes dissolving gas to be a continuous medium. This approach may not always be suitable; especially, as the mean free paths of the pollutant gases at the existing concentrations available at the atmosphere are of the same order as the diameter of the cloud droplets. We develop an equation by considering the mass of the gas molecules striking per unit area of the droplets. Equations are also developed for the rate of dissolution of gaseous air pollutants and an attempt has been made to find out the correspondence with the classical approach and the mass transfer process.

scholarly journals Thermal Fluctuations and Electromagnetic Noise Spectra in Quantum Statistical Mechanics.

2022 ◽  
Author(s):  
Ladislaus Bányai
Keyword(s):  
Wave Vector ◽  
Transverse Electric ◽  
Quantum Statistical Mechanics ◽  
Field Operator ◽  
Thermal Fluctuations ◽  
Noise Spectrum ◽  
Complex Frequency ◽  
Occupation Numbers ◽  
Interacting Electrons ◽  
Quantum Statistical

We derive the thermal noise spectrum of the of the longitudinal and transverse electric field operator of a given wave vector starting from the quantum-statistical definitions and relate it to the complex frequency and wave vector dependent complex conductivity in a homogeneous, isotropic system of electromagnetic interacting electrons. No additional assumptions were used in the proof. We analyze separately the longitudinal and transverse case with their peculiarities. The Nyquist formula for vanishing frequency and wave vector, as well as its modification for non-vanishing frequencies and wave vectors follow immediately. Furthermore we discuss also the noise of the photon occupation numbers.

scholarly journals Effects of Surface Defects on the Local Electric Field in Inhomogeneous Media

1992 ◽  
Vol 291 ◽  
Author(s):  
Kim F. Ferris ◽  
Steven M. Risser
Keyword(s):  
Electric Field ◽  
Surface Defects ◽  
Flat Surface ◽  
Dielectric Film ◽  
Element Model ◽  
Local Fields ◽  
Local Electric Field ◽  
Effective Medium Approximation ◽  
Inhomogeneous Dielectric ◽  
The Relationship

ABSTRACTSurface defects both focus the local electric field and enhance its intensity in the vicinity of the defect. Using a finite element model of an inhomogeneous dielectric film, we have examined the relationship between the defect shape and local electric field in the film and defect. We find that raised defect regions that are peaked have the largest local fields while the slope of removed regions has little effect on the field in raised defects. Both peaked and flat surface defects can lead to large enhancements of the local electric field above that predicted by effective medium approximation (EMA) methods.

Quantum-Statistical Calculations on the Work Function of Metals

1966 ◽  
Vol 16 (2) ◽  
pp. 399-404 ◽  
Author(s):  
M. Dubejko ◽  
S. Olszewski
Keyword(s):  
Work Function ◽  
Quantum Statistical

scholarly journals The modification of apparent thermionic constants for oxygenated tungsten by the temperature variation of adsorptive equilibrium

1937 ◽  
Vol 158 (893) ◽  
pp. 55-68 ◽  
Keyword(s):  
Work Function ◽  
Temperature Variation ◽  
Unit Area ◽  
The Other ◽  
Electronic Data ◽  
Electronic Work Function ◽  
Other Hand ◽  
Adsorptive Equilibrium ◽  
High Degree

When the temperature variation of a saturated thermionic current i per unit area is represented by plotting log ( i /T 2 ) against 1/T, it has been customary to identify the slope and the vertical intercept of the graph with the electronic work function ϕ and the logarithm of the emission constant A, respectively, in Richardson’s equation i = AT 2 e - ϕ /k T . This identification has been reasonably successful for materials of a high degree of homogeneity, since they exhibit straight “Richardson plots” whose measurement offers values of A and ϕ not inconsistent with electronic data from other sources. On the other hand, certain materials exhibit curved plots, indicating at once that no fixed A and ϕ can be recorded. Others, with which we are here concerned, give plots which appear straight over an observed range but suggest values of A and ϕ , disagreeing so radically with established theory or with indirect experiments that they have been regarded as anomalous. We prove in one instance that an extension of the range reveals such a plot as part of a curve, and that the curve contains implicit quantities not solely electronic and therefore not expressed by even a sequence of simple Richardson equations. Hence the slopes and intercepts of tangents to this curve are not identifiable with values of ϕ and log A.

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