88 research outputs found
Numerical methods and time-dependent physical models for the design and diagnostic of pulsed-dc magnetrons
No full textPulsed DC operation of magnetrons is a relatively new sputtering technique that significantly improves the properties of deposited layers. The understanding and control of phenomena taking place during pulsed DC sputtering requires new time-resolved methods of investigation.
This thesis presents a comprehensive development of new methods for magnetron design and time-resolved plasma diagnostic, based on Monte Carlo simulations and timeresolved plasma physical models derived for a pulsed DC opposed target magnetron discharge with rectangular geometry.
The numerical methods have been developed and benchmarked by the author through extensive numerical experiments. A representative set of application examples is included. The time-resolved physical models for the pulse-on and pulse-off time discharge are based on the experimental data obtained by the author, which are presented as a basis for the interpretation.
The experimental data are obtained using new time-dependent diagnostic methods combining: I-V characteristics and waveforms, time and space-resolved Optical Emission Spectroscopy (OES) and time and space-resolved Ion Energy Spectra (IBS).
The following original algorithms and new time-resolved plasma diagnostic methods arc
presented:
• Algorithm and method for Monte Carlo simulation of ion transport in the magnetron discharge, based on an original non-Runge-Kutta routine developed for calculating charged particles’ trajectories in complex, position dependent, magnetic and electric fields. The Monte Carlo simulation is used for evaluating the intensity of the pre-sheath electric field through calculations of the travel time to targets of Ar ions. The time-scale for the sputtering and selfsputtering processes is also evaluated.
A new method for time-resolved plasma diagnostic in pulsed DC discharges based on time and space-resolved OES using an acousto-optic spectrometer. The described method indicates the applicability conditions for electron temperature evaluations based on timeresolved OES. the procedure and interpretation of results. Based on time and space-resolved OES evaluations of electron temperatures, a model of the physical phenomena taking place in the pulsed DC discharge during the pulse-on time is developed.
A new method for time-resolved analysis of the Ion Energy Spectra at the substrate region in pulsed DC discharges using a mass-energy analyser. Experimental results and data analysis are presented and an original physical model for plasma behaviour during the pulse-off time is developed, explaining the mechanism for the observed increase in the ion flux and energy at substrate during pulsed DC discharges. The described model explains for the first time the above effects and allows the control of the ion flux and energy at the substrate from the choice of the pulsed DC duty cycle.
The developed plasma models and time-resolved diagnostic methods are discussed for nonferromagnetic(copper) and ferromagnetic (iron) targets and the observations are correlated in order to infer a global understanding of phenomena taking place in the pulsed DC discharge and at the substrate region
H1N1 influenza virus interaction with a porous layer of silicon nanowires
No full textHere, the non-specific interaction of the H1N1 influenza virus with a porous layer of silicon nanowires (PSi NWs) was studied by transmission and scanning electron microscopy (TEM, SEM, respectively) and optical spectroscopy. PSi NW layer with a thickness of about 200 nm was fabricated by metal-assisted chemical etching of p-type highly doped crystalline silicon wafers, and consist of porous nanowires with a diameter of 50-200 nm, and a distance between the nanowires of 100-200 nm. It was shown that during the adsorption of viruses, viral particles with a diameter of about 100 nm bind to the porous surface of the nanowires. This interaction was revealed using TEM, SEM, and causes wavelength shifts in the Fabry-Perot fringes in the reflection spectrum of visible light from the PSi NW layer. The results show that thin layers of PSi NWs are a promising nanomaterial for creating filters and sensors for binding and detection of viruses. © 2020 The Author(s). Published by IOP Publishing Ltd
To the topic of the analytical definition of the cog of the wheel having an elliptic profile
No full textAnalytical dependence for the estimation of coordinates of a concave cog side having an elliptic profile, which take into account the limitation of it's height by the value of internal circle radius of the wheel, is presented. An algorithm for the calculation of profile coordinates of elliptic cog is presented
To the topic of the analytical definition of the cog of the wheel having an elliptic profile
No full textAnalytical dependence for the estimation of coordinates of a concave cog side having an elliptic profile, which take into account the limitation of it's height by the value of internal circle radius of the wheel, is presented. An algorithm for the calculation of profile coordinates of elliptic cog is presented
Forecasting oil tanker shipping market in crisis periods: Exponential smoothing model application
No full textThis paper fills the gap in the literature of applying an exponential smoothing model in the oil shipping market forecasting. The author refines the adaptive combined model with B-criterion based on Brown's model with modification by Trigg and Leach. Forecasting the values of the average time-charter equivalent of a tanker along 6 different routes of oil transportation in the world ocean during the crisis period 2015–2019. The accuracy of the proposed method is superior to naive, autoregression methods and machine learning models in all used error metrics. The obtained accuracy in 71% of cases is available for commercial use by operators and charterers of the tanker fleet
VERIFICATION OF GLOBAL HYDRODYNAMIC MODEL REGIONAL CONFIGURATION FOR THE SEA OF AZOV WITH IN SITU DATA
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