M. Baeva

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Charalampos Vasilatos

National & Kapodistrian University of Athens

Thomas Cramer

Universidad Nacional de Colombia (National University of Colombia)

Dr. Matrika Prasad Koirala

Tribhuvan University

Tohid N.Borhani

University of Wolverhampton

Paulo Emanuel T F Fonseca

Universidade de Lisboa

Vasilios Melfos

Aristotle University of Thessaloniki

Abdellah Boushaba

Sidi Mohamed Ben Abdellah University Morocco

K Sudhakar

Maulana Azad National Institute of Technology

Pandian M S

Pondicherry university

Mahmoud Abdel-Aty

Zewail City of Science and Tech.

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Papers by M. Baeva

$Research paper thumbnail of Microstructural Investigation of Fe-Ni-Mn-Mo-V-C-N Ferritic Steels by Neutron Diffraction$

Microstructural Investigation of Fe-Ni-Mn-Mo-V-C-N Ferritic Steels by Neutron Diffraction

AIP Conference Proceedings, 2010

The design of alloys, that economize strategic element as chromium requires detailed physical inv... more The design of alloys, that economize strategic element as chromium requires detailed physical investigations of their structure and phase composition. In the search for new materials in the last two decades a new class of Fe alloys was composed-the so-called nitrogen steels. The contemporary achievements in the casting technology-the use of nitrogen under high preasure above the melt-made possible the production of Fe alloys with nitrogen concentration even above 0.4 wt%. The wide application of investigated alloy system is connected with creation of alloys without presence of strong carbides-forming elements. The microstructure and phase formation of these new materials are insufficiently studied. The aim of this work is to characterize the microstructure and phase composition of two series Fe-alloys casted with and without nitrogen pressure above the melt. The so cast steels appear as experimental ones and they are directed to demonstrate the possibility for nitrogen doping of steels without presence of Chromium in them. The latter is technologically difficult to fulfil at usual conditions. Six samples [with lower nitrogen, N = 0.0111 wt%] are cast at normal pressure, and six samples [with higher nitrogen, N0.2121 wt%] are cast at pressure of 10.106 Pa. The results of Rietveld structure analysis of Time-Of-Flight neutron diffraction data show that studied steels consist of purely ferritic crystal phase (Body Centered Cubic crystal lattice).

Grundlegende Untersuchungen zu ausgewaehlten Phaenomenen der gepulsten Plasmen. Einkopplung gepulster Mikrowellenfelder durch dielektrische Fenster und Vermessung des Plasmazustands im Plasma-Wand-Bereich Abschlussbericht

Available from TIB Hannover: F99B354+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technis... more

Spectroscopic investigations on high pressure discharge lamps

Light Sources 2004 Proceedings of the 10th International Symposium on the Science and Technology of Light Sources, 2004

... Constants for resonance, Stark and van der Waals broadening are derived. The data serve as in... more

Determination of spectral line-broadening data in high pressuredischarge lamps

3D Monte Carlo simulation of radiation transfer for HID lamps

Mercury free HID-lamps

Experimental and theoretical study on high-pressure Hg-Xe discharge lamps

Adaption of a nuclear fusion radiation transport Monte Carlo Code for HID lamp modelling

Mercury-Free Automotive Discharge Lamps

ABSTRACT Mercury-free HID lamps are currently under investigation for front lighting application ... more ABSTRACT Mercury-free HID lamps are currently under investigation for front lighting application in the automotive industry. Besides European legislation aiming at a total removal of hazardous components - such as mercury - in cars, environmentally friendly products are requested by the market. The work presented here is based upon a collaboration between industrial and university partners aiming at a characterisation of properties of mercury-free metal halide lamps in quartz envelopes. The physical and chemical aspects of such lamps, i.e. light technical and electrical lamp data, are studied. The results show that a replacement of mercury in automotive headlight lamps is possible using standard reflectors without significant changes in beam patterns. The main difference to mercury containing lamps observed up to now is a lower lamp voltage in the order of 40-50 V instead of 80-90 V. Light technical data of standard Na/Sc lamps are realised in mercury-free discharges. The project is supported by the German government (BMBF) under contract no. 13N8072 and 13N8264.

The effect of oxygen admixture on the properties of microwave generated plasma in Ar–O2: a modelling study

Journal of Physics D: Applied Physics

This work presents results of a self-consistent modelling analysis on microwave plasma generated ... more This work presents results of a self-consistent modelling analysis on microwave plasma generated in Ar–O2 mixtures at a frequency of 2.45 GHz at atmospheric pressure. The study focuses on how the plasma properties are influenced by the increase of the oxygen fraction in the gas mixture. The oxygen admixture is increased from 1% up to 95% in mass for values of the input microwave power of 1 and 1.5 kW. The results show that for a power of 1 kW and gradually increasing the oxygen admixture from 1% to 25% the electron density drops by a factor of more than four due to the energy lost by the electrons due to dissociation of oxygen molecules and the gas heating. An analysis of the number densities of species produced in the Ar–O2 plasma is presented. Oxygen admixtures of above 50% are considered along with an increase of the input microwave power in order to supply the discharge with electron number density values of the order of 1019 m−3. Gas temperatures above 3700 K are obtained in th...

$Research paper thumbnail of Publisher's Note: “Effect of a bidirectional coupling of an LTE arc column to a refractory cathode in atmospheric pressure argon” [Phys. Plasmas 27, 073514 (2020)]$

Publisher's Note: “Effect of a bidirectional coupling of an LTE arc column to a refractory cathode in atmospheric pressure argon” [Phys. Plasmas 27, 073514 (2020)]

Physics of Plasmas, 2021

Chemical non-equilibrium in a free-burning argon arc

Microwave-induced plasma analysis: experiment and modelling

Microwave-induced plasma in argon at a pressure of 20 mbar has been analyzed by means of temporal... more Microwave-induced plasma in argon at a pressure of 20 mbar has been analyzed by means of temporally resolved measurements employing heterodyne reflectometry and spatially resolved measurements employing heterodyne microwave interferometry. A self-consistent two-dimensional fluid model has been developed to describe the flow and heat transfer, the plasma kinetics and the electromagnetic field. The results obtained show good agreement between experimental and predicted values and give a detailed picture of the plasma-microwave interaction during the early stage and the steady-state conditions during the burning phase of the discharge.

Experimental study and modeling of a waveguide-based microwave Plasma source

Advanced Nonequilibrium Modelling of DC Tungsten-Inert Gas Arcs

Plasma Physics and Technology Journal

The paper is concerned with the state-of-the-art nonequilibrium modelling of a DC tungsten-inert ... more The paper is concerned with the state-of-the-art nonequilibrium modelling of a DC tungsten-inert gas arc plasma. The advanced description involves the two-way interaction between the plasma and the electrodes. Results in atmospheric pressure argon demonstrating important features of the arc plasma are presented and discussed. First results in the presence of metal vapour released from the molten anode are presented. Outlook for further developments in nonequilibrium arc modelling are discussed.

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$Research paper thumbnail of Effect of a bidirectional coupling of an LTE arc column to a refractory cathode in atmospheric pressure argon$

Effect of a bidirectional coupling of an LTE arc column to a refractory cathode in atmospheric pressure argon

Physics of Plasmas

Unified modelling of low-current short-length arcs between copper electrodes

Journal of Physics D: Applied Physics

Application of the transferred matrix method to a unified evaluation of the cathodic electron emission

AIP Advances

The work is concerned with the Transfer Matrix Method for solving the steady-state Schrödinger eq... more The work is concerned with the Transfer Matrix Method for solving the steady-state Schrödinger equation applied for a unified evaluation of the emission current density from non-refractory cathodes. The method is applicable to arbitrary shapes of the potential barrier and its transmission probability is obtained without any analytical approximations. The Fermi-Dirac distribution for the free electrons in the metal is considered as a supply function. The results, obtained for a work function of the cathode material of 4.5 eV over a wide range of values of the surface temperature and the electric field strength, clearly show a growing deviation from those obtained by the classical Jeffreys-Wentzel-Kramers-Brillouin approximation with the increase of the electric field strength. Preliminary results are obtained to demonstrate the applicability of the Transfer Matrix method to the evaluation of the ion-assisted electron emission. A significant local enhancement of the emission current density is obtained as a result of the presence of an ion at a fixed position near the metal surface. The effect becomes very strongly pronounced at an appropriate value of the electric field strength, for which a resonant ion contribution appears.

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Comparative Studies of Low-Intensity Short-Length Arcs

Plasma Physics and Technology Journal

We present results obtained by two non-equilibrium modelling approaches and experiments on low-in... more We present results obtained by two non-equilibrium modelling approaches and experiments on low-intensity short-length arcs in argon at atmospheric pressure. The first one considers a quasi-neutral arc column combined with boundary conditions on the electrodes based on the energy balance in the space-charge sheaths. The second approach applies a unified description over the entire gap and solves the Poisson equation for the self-consistent electric field. The experiments provide the arc voltage.

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The electric field and voltage of dc tungsten-inert gas arcs and their role in the bidirectional plasma-electrode interaction

Journal of Physics D: Applied Physics

$Research paper thumbnail of Microstructural Investigation of Fe-Ni-Mn-Mo-V-C-N Ferritic Steels by Neutron Diffraction$

Microstructural Investigation of Fe-Ni-Mn-Mo-V-C-N Ferritic Steels by Neutron Diffraction

AIP Conference Proceedings, 2010

Available from TIB Hannover: F99B354+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technis... more

Spectroscopic investigations on high pressure discharge lamps

Light Sources 2004 Proceedings of the 10th International Symposium on the Science and Technology of Light Sources, 2004

... Constants for resonance, Stark and van der Waals broadening are derived. The data serve as in... more

Determination of spectral line-broadening data in high pressuredischarge lamps

3D Monte Carlo simulation of radiation transfer for HID lamps

Mercury free HID-lamps

Experimental and theoretical study on high-pressure Hg-Xe discharge lamps

Adaption of a nuclear fusion radiation transport Monte Carlo Code for HID lamp modelling

Mercury-Free Automotive Discharge Lamps

The effect of oxygen admixture on the properties of microwave generated plasma in Ar–O2: a modelling study

Journal of Physics D: Applied Physics

$Research paper thumbnail of Publisher's Note: “Effect of a bidirectional coupling of an LTE arc column to a refractory cathode in atmospheric pressure argon” [Phys. Plasmas 27, 073514 (2020)]$

Publisher's Note: “Effect of a bidirectional coupling of an LTE arc column to a refractory cathode in atmospheric pressure argon” [Phys. Plasmas 27, 073514 (2020)]

Physics of Plasmas, 2021

Chemical non-equilibrium in a free-burning argon arc

Microwave-induced plasma analysis: experiment and modelling