Ognyan Ivanov

Dr. Ognyan Ivanov

Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences

Research Focus & Metrics

Academic Career Length

42Years (1985-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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20 October 2017 in Water
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Journal Article
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JPJose Luis Perez-Diaz
Jose Luis Perez-Diaz
OIOgnyan Ivanov
Ognyan Ivanov
ZPZahari Yordanov Peshev
Zahari Yordanov Peshev
MÁMarco A. Álvarez-Valenzuela
Marco A. Álvarez-Valenzuela
IVIgnacio Valiente-Blanco
Ignacio Valiente-Blanco
Ashok VaseashtaAshok Vaseashta
Ashok Vaseashta
This work presents a selective overview of natural fogs in terms of fog types, forms and states of occurrence, physical, micro-physical, chemical and dynamic properties, basic characterizing parameters, etc. In focus are related achievements and contributions reported mainly during the last decade and a half, as a result of both laboratory studies and field observations. Processes of homogeneous and heterogeneous nucleation are analyzed in the aspects of condensation, nuclei diversity and specifics, as related to the activation, growth and deposition of fog droplets. The effect is highlighted of the water vapor’s partial pressure on the surface tension of the liquid water–air interface and the freezing point of the water droplets. Some problems and aspects of fog modeling, parameterization, and forecasting are outlined and discussed on the examples of newly developed relevant 1D/3D theoretical models. Important issues of fog impacts on the air quality, ecosystems, water basins, societal life, and human health are also addressed and discussed, particularly in cases of anthropogenically modified (chemical, radioactive, etc.) fogs. In view of reducing the possible negative effects of fogs, conclusions are drawn concerning the new demands and challenges to fog characterization imposed by the changing natural and social environment and the needs for new data on and approaches to more adequate observations of fog-related events.

30 November 1989 in Solid State Communications
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Journal Article
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VPV.I. Pustovoit
V.I. Pustovoit
MBM. Borisov
M. Borisov
OIOgnyan Ivanov
Ognyan Ivanov

6 February 1989 in Physics Letters A
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Journal Article
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VPV.I. Pustovoit
V.I. Pustovoit
MBM. Borissov
M. Borissov
OIOgnyan Ivanov
Ognyan Ivanov

1 January 1995 in Optics Communications
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Journal Article
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OIOgnyan Ivanov
Ognyan Ivanov
VMV. Mihailov
V. Mihailov
VPV.I. Pustovoit
V.I. Pustovoit
AAA. Abbate
A. Abbate
PDP. Das
P. Das

1 May 1992 in IEEE Electron Device Letters
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PDP. Das
P. Das
VMV. Mihailov
V. Mihailov
OIOgnyan Ivanov
Ognyan Ivanov
VGV. Gueorgiev
V. Gueorgiev
SAS. Andreev
S. Andreev
VPV.I. Pustovoit
V.I. Pustovoit
A technique for evaluating electrical properties of semiconductor wafers and devices using the surface photocharge effect caused by laser radiation is proposed. The measurement setup used in the experiments is presented along with some preliminary results. In particular, experimental results are presented for MOS devices on silicon under bias. It is possible to distinguish from the experimental plots the depletion, accumulation, and inversion regions of the device. Information could be obtained from these curves in a manner analogous to CV plots.

26 February 2020 in Atmosphere
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OIOgnyan Ivanov
Ognyan Ivanov
Petar TodorovPetar Todorov
Petar Todorov
Ismail GultepeIsmail Gultepe
Ismail Gultepe
Lab experiments related to artificial fog studies are limited due to instrument sensitivity to small fog and aerosol particles; therefore, the goal of this work is to evaluate aerosol solute effects on fog physical properties in a lab environment. To reach the goal, an automated fog-generating system was designed and that includes controlled chemical compounds dissolved in pure water. In the analysis, the impact of changing the mass concentration of potassium dihydrogen phosphate—KH2PO4, urea-CO(NH2)2, and potassium hexacyanoferrate trihydrate-K3(Fe(CN)6) on fog droplet size spectra is studied, because visibility is directly related to fog droplet spectra and aerosol composition. In the experiment, various microphysical conditions, including fog droplet size and volume concentration, were analyzed as a function of changing aerosol composition/spectra and fixed thermodynamic conditions. The results showed that fog droplet size spectra vary with the addition of chemical impurities to the pure water volume. For example, increasing KH2PO4 concentration compared to distilled water volume resulted in a higher mean particle size, which led to faster droplet settlement, and that resulted in cleaning air more efficiently compared to pure water fog. Overall, both issues and challenges of the experimental fog generating system with respect to water and aerosol solutions resembling CRBN (chemical, radiological, biological, and nuclear agents) characteristics are provided and evaluated.