Milcho Kirilov Tsvetkov

Milcho Kirilov Tsvetkov
Bulgarian Academy of Sciences | BAS · Institute of Mathematics and Informatics

PhD

About

195
Publications
5,295
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511
Citations
Additional affiliations
January 2012 - November 2016
Bulgarian Academy of Sciences
Position
  • Associare member

Publications

Publications (195)
Article
Cobalt ferrite CoFe2O4 with spinel-like structure, modified with different contents of Hf(IV), was synthesized by a sol-gel method using propylene oxide as a gelating agent. The impact of the Hf(IV) content on the physicochemical characteristics of the catalysts and on the oxidation of ethyl acetate used as model molecule was studied. The phase hom...
Article
In order to study the possibilities for the incorporation of lanthanide ions in the spinel crystal lattice, cobalt ferrite CoFe2O4 modified by the lanthanide ions Ce(III), Nd(III), аnd Dy(III) was prepared using the sol-gel method, and two diffraction techniques, XRD and neutron diffraction, were applied to detect the position of the lanthanide ion...
Article
The spinel-type ferrites NiFe2O4 and Zn0.5Ni0.5Fe2O4 modified by lanthanide ions Eu³⁺ and Tb³⁺ were prepared by a sol-gel process with propylene oxide as a gelating agent. The phase homogeneity of the samples was tested by XRD and Mössbauer spectroscopy. Transmission electronic microscopy used for characterisation of the morphology of the samples r...
Article
Full-text available
Представљамо рад Симона Мариуса - математичара и астронома који је 1610. открио четири највећа сателита Јупитера помоћу телескопа направљеног у Белгији, отприлике у исто време кад и Галилео Галилеј, али је своја открића објавио четири године касније. Године 2014. астрономска заједница обележава 400 година од објављивања књиге Симона Мариуса Mundus...
Article
Nanosized copper ferrite-type materials (CuxFe3–xO4, 0 ≤ x ≤ 1) have been prepared by combination of co-precipitation and mechanochemical activation and/or thermal treatment. The crystalline structure and morphology of the obtained ferrite nanopowders have been characterized by different instrumental methods, such as Powder X-ray diffraction (PXRD)...
Article
Full-text available
Nickel ferrites with different Ni content, NixFe3–xO4, 0 ≤ × ≤ 1, are technologically important materials for microwave, electronic, and magnetic storage devices. They are members of solid-solution series of spinel-type materials (Fe3O4–NiFe2O4) having specific magnetic properties and different degree of electron delocalization. They demonstrate go...
Article
Series of nanostructured zinc ferrite-type materials ZnxFe3-xO4 (x= 0.25, 0.5, 1) with average crystallite size about 8 nm prepared by co-precipitation or co-precipitation and mechanochemical treatment were tested for photocatalytical degradation of Malachite green oxalate as model contaminant in aqueous solution under UV-light. The performed exper...
Article
Full-text available
We want to approximate the mxn image A from scanned astronomical photographic plates (from the Sofia Sky Archive Data Center) by using far fewer entries than in the original matrix. By using rank of a matrix, k we remove the redundant information or noise and use as Wiener filter, when rank k<m or k<n. With this approximation more than 98% compress...
Article
The aim of presented paper was to study preparation of catalytic materials for water purification. Iron oxide (Fe3O4) samples supported on activated carbon were prepared by wet impregnation method and low temperature heating in an inert atmosphere. The as-prepared, activated and samples after catalytic test were characterized by Mössbauer spectrosc...
Data
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Keywords: Gold catalysts Ceria doped with Co 3 O 4 Complete benzene oxidation Reduction behavior Very high catalytic activity in complete benzene oxidation (CBO) was observed over gold catalyst on pre-pared by mechanochemical mixing CeO 2 –Co 3 O 4 (10 wt.% of dopant). It was significantly higher compared with gold catalysts supported on ceria dope...
Article
Full-text available
The purpose of this article is to study the influence of gamma irradiation on the sorption capacity and photocatalytic activity of commercially available TiO2 Degussa P25. The photocatalyst was gamma-irradiated at ambient temperature with doses 8–60 kGy (137Cs, dose rate 2 kGy/24 h) and then stored until analysis/tests in liquid N2. X-ray diffracti...
Article
Full-text available
We present new results from optical photometric and spectroscopic observations of the eruptive pre-main sequence star V2493 Cyg (HBC 722). The object has continued to undergo significant brightness variations over the past few months and is an ideal target for follow-up observations. We carried out CCD BVRI photometric observations in the field of...
Article
We present the Wide-Field Plate Database, a basic source of data and meta-data for astronomy's more than 2.4 million wide-field photographic images obtained with professional telescopes worldwide. The technology developed in Sofia for plate digitization with commercial high-quality flatbed scanners yields low-resolution digital images for quick vis...
Article
Full-text available
In progress is a process of cataloguing and digitization of direct observation astro-plates archives stored in the National Astronomical Observatory Rozhen, Bulgaria. This is a part of a project aimed to develop the Wide-Field Plate Database from direct astronomical observations archives of all astronomical institutions over the world being in poss...
Article
Full-text available
The results of the plate cataloging and digitization in the Zvenigorod Observatory are described. The observational material was obtained in the period 1972 - 2005 with the 40 cm Carl Zeiss astrograph (F=200 cm, field size 8x8 sq. deg., scale 100 arcsec/mm). The archive includes at present 3703 plates observations in the northern hemisphere mainly...
Article
Sol-gel produced TiO2 is gamma-irradiated at ambient temperature (Cs-137, dose rate 2 kGy/24 h) with doses 8-60 kGy and stored up to the analysis/tests in liquid N-2. Phase composition, crystal cell parameters, crystallites size, textural properties (morphological grains size, specific surface area), EPR behaviour and UV-vis. reflectance spectra of...
Article
Full-text available
The wide-field plate archives at disposal in Rozhen Observatory (9332 plates obtained in the period 1979 – 1994) and Belgrade Observatory (14500 plates obtained in the period 1936 -1996) are presented. The plate archives, made in the frames of differ-ent observing programmes, reflect the tendencies in the development of astronomy in these countries...
Article
Full-text available
Saturated stellar images on digitized photographic plates are many times greater in area than the `seeing disk' seen in unsaturated CCD images. Indeed the flux profile of a bright star can be traced out for several degrees from the star's centre. The radius of the saturated stellar image can often be directly related to the magnitude of the star, a...
Article
The latest version of the Wide-Field Plate Database Catalogue of Wide-Field Plate Archives (April 2008) contains 43 archives stored at some Ukrainian observatories, namely, at the Main Astronomical Observatory of the National Academy of Sciences of Ukraine (Golosiiv, Kyiv), at the Crimean Astrophysical Observatory (Nauchnyi and Simeiz), at the Kyiv...
Article
Full-text available
We present an inventory ofthe Carte du Ciel (CdC) plates stored in the Astrophysical Institute Potsdam. The Potsdam CdC zone (+32° to +39°) was divided into 1232 areas and about 2200 plates from the first and second epochs were obtained within the framework of the CdC project. At present, only 977 plates (45% of all) are stored in AIP, the others g...
Chapter
Full-text available
The wide-field plates are the basic source for information on the astronomical objects back in time. Their archiving in the context of repeated use for different tasks requires cataloging and storage of plate information in digitized form. We consider here the status of archiving of the wide-field plate astronomical observations in Serbia done in c...
Article
The Catalogue of Wide-Field Plate Archives (CWFPAs, version 5.2 from July 2008) contains the information for 440 plate archives stored in astronomical observatories and institutions all over the world. It is an integrated part of the Wide-Field Plate Database (WFPDB) aiming to store the valuable astronomical plate observations (more than 2,200,000...
Article
This paper is dedicated to the first comparative study concerning position determinations of selected small bodies in the solar system observed with the Bucharest Observatory equatorial PRIN-MERTZ refractor (d = 0.38m, f = 6.0m) by means of the Carl-Zeiss ASCORECORD measurements and the processing of 5 photographic plates dating from 1971, digitize...
Article
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Aims. The main purpose of our investigation is to construct the long-time light curve of the PMS star V 1184 Tau. We consider the study of the photometrical variability of PMS stars as very important for understanding stellar evolution. The unusual photometric variability of V 1184 Tau was reported in previous studies as well, but the nature of the...
Article
Full-text available
The last version of the Wide-Field Plate Database Catalogue of Wide-Field Plate Archives (April 2008) contains 43 archives stored in observatories located in Ukraine -Crimean Astrophysical Observatory (Nauchny and Simeiz), Kyiv University Observatory, L'viv University Observatory, Main Astronomical Observatory of the National Academy of Sciences of...
Article
Full-text available
We present the results of an investigation aimed at characterizing previous eruptions of V1647 Orionis, the illuminating star of McNeil's Nebula. Photographic plates and films from the Asiago Observatory (1960-1998) and Harvard Observatory (1898-1974) collections were inspected for the nebula. We have determined that, to the plate limits, the known...
Article
Full-text available
We used digitised scans of plates from the Bamberg Observatory Southern Photographic Patrol Survey to study the variation of the recently discovered semiregular variable star CPD -80 966 from 1964 to 1976. We present evidence to show that the star was varying during the course of the Bamberg survey, but was apparently overlooked at the time. We als...
Chapter
We present here the inventory of Potsdam CdC plates stored in the Astrophysical Institute Potsdam (AIP). The Potsdam CdC zone ( +32 to +39 degrees) was divided into 1232 fields. The total number of all CdC plates obtained in Potsdam is about 2160. Only 963 plates (45% of all) are now stored in AIP. The first epoch plates had been obtained during th...
Article
The results from five-year work on the Bamberg Observatory plate collection from inventory to digitization are presented. The project supported by the Alexander von Humboldt Foundation, Deutsche Forschung Gemeinschaft, and Bulgarian Academy of Sciences has begun since 2002. At present the information for about 28 000 plates from the Bamberg Souther...
Article
We present the catalogue of the Carte du Ciel plates collected at the Royal Observatory of Belgium (ROB) and incorporated in the Wide-Field Plate Database. The catalogue comprises the descriptive information for 682 plates obtained with the Gautier 0.33-m equatorial telescope in the framework of the Carte du Ciel project in the period 1908-1939. Th...
Article
Full-text available
We present the in the Wide-Field Plate Database (WFPDB) recently incorpo- rated catalogue of the Carte du Ciel plates collected at the Royal Observa- tory of Belgium (ROB). The catalogue comprises the descriptive information for 682 plates obtained with the Gautier 0.33-m equatorial telescope in the framework of the Carte du Ciel project in the per...
Article
The development of the Wide-Field Plate Database (WFPDB) over the last decade, as an initiative of the IAU Working Group on Sky Surveys, hosted by Commission 9, is presented. The latest version of the Catalogue of the Wide-Field Plate Archives (CWFPA) contains descriptive information practically for all of the existing professional wide-field photo...
Article
The Bamberg Observatory Southern Sky Survey provided 93 photographic plates with the FU Orionis object BBW 76, clearly detectable in the time interval 1963-1976. We perform aperture photometry of BBW 76 from the 2 x 2 degrees area near target star scanned with the Epson Expression 1640 XL flatbed scanner. For each plate a transformation of plate ma...
Article
A new program developed for the plate index data pipe line reduction is described. It is a part of the WFPDB (http://www.skyarchive.org). The program is in development stage and is based on the WCSTools (http://tdcwww.harvard.edu/software/wcstools/). It currently converts coordinates from arbitrary year into J2000 and works with the WFPDB maindata...
Article
We present the basic information for archives obtained with the 40 cm Double Wide-angle Astrograph (DWA) of the Main Astronomical Observatory of NAS of Ukraine.
Conference Paper
A great amount of highly valuable information is stored in the photographic archives of many Italian Observatories and in the Specola Vaticana, with approximately 70.000 plates dating from the end of the XIX Century until 1998. This paper presents a large-scale project to digitize these archives of plates. Identical systems, composed by a commercia...
Conference Paper
A great amount of highly valuable information is stored in the photographic archives of many Italian Observatories and in the Specola Vaticana, with approximately 70.000 plates dating from the end of the XIX Century until 1998. This paper presents a large-scale project to digitize these archives of plates. Identical systems, composed by a commercia...
Chapter
HyperLeda (Hyper-Linked Extragalactic Databases and Archives is aimed to study the evolution of galaxies, their kinematics and stellar populations and the structure of Local Universe. HyperLeda is involved in catalogue and software production, data-mining and massive data processing. The products are serviced to the community through web mirrors. T...
Chapter
An updated data collection for UV Cet type stars and their registered flare events in stellar aggregates and in the solar neighbourhood during more than 9580 hours observing time is described. The Flare Stars Database (FSDB) presently includes 3127 entries for 1622 stars.
Article
The basic information for the archives obtained with the 10cm, 11cm and 15cm Three Cameras Astrograph (TCA) of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine in Golosiiv (Kyiv, Ukraine) in the period 1955-1961 is presented. The archives are recently included into the WFPDB installed in the Sofia Sky Archive Data Ce...
Article
The plate archives of the Main Astronomical Observatory (Golosyiv, Kyiv) includes about 85 000 plates which were taken for various astronomical projects in the period 1950-2005. Among them there are more than 60 000 plates containing stellar, planetary and active solar formations spectra and more than 20 000 of direct northern sky area plates (most...
Article
We describe a pilot project for creating links between databases (Wide-Field Plate Database, WFPDB) and electronic journals (Information Bulletin on Variable Stars, IBVS). The project aims to create closer links between scientific papers and the data they are based upon. The merits of a paper can be evaluated better (both before and after publicati...
Article
The archives made with the 12 cm Double Short focus Astrograph (DSA) of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine in Golosiiv (Kyiv, Ukraine) in the period 1949-1990 are included recently into the WFPDB (http://www.skyarchive.org). The total number of plates in these archives is 2041 (tube A) and 2142 (tube B)...
Article
Digitization and image processing of the astronomical plates for an astrometric series using flatbed scanners do not preserve high metrological characteristics of the readout information, due to construction features of these devices. The proposed application of the high–precision measuring scale rulers allows to transform a flatbed scanner into a...
Article
We discuss the spectral characteristics of active galaxies Mrk 817 and Mrk 1040, based on observations obtained with the 2 m RCC telescope of Rozhen Observatory and the 2.5 m Isaac Newton telescope at La Palma. Analyzing and modeling their broad and narrow emission lines, as well as studying the narrow band spectrophotometric observations, we inves...
Article
Full-text available
Saturated stellar images on digitised photographic plates are many times greater in area than the `seeing disk' seen in unsaturated CCD images. Indeed the flux profile of a bright star can be traced out for several degrees from the star's centre. The radius of the saturated stellar image can often be directly related to the magnitude of the star, a...
Article
Full-text available
We present a long-term photometric study of the active K subgiant star CF Oct from 1964 to 1976. It is based on over 350 scanned photographic plates from the Bamberg Observatory plate archive. We performed aperture photometry for the target star and 9 field stars for each plate and did a transformation to standard B magnitude for CF Oct using catal...
Article
Full-text available
Here we present an observational program for four Active Galactic Nuclei (AGNs) with the 2-meter telescope of Rozhen observatory (Bulgaria). The aims of the observations are given. Some of the preliminary results for Mrk 1040 are presented.
Article
The Bamberg Northern Sky Survey was part of the observational pro- gramme of the Dr. Remeis-Observatory in Bamberg, started in 1928 by E. Zinner. The aim was to study variable stars in the Northern hemisphere in collaboration with the observatories in Babelsberg (Potsdam, Germany) and Sonneberg (Sonneberg, Germany). The monitoring task was shared a...
Article
Full-text available
The Sy 1 galaxy Mrk 1040 and its close companion LEDA 212995 have been observed in several narrow spectral bands, as well as in the U and I bands, in order to look for possible interaction between them. The analysis of the observations shows a very strong point-like innermost center of Mrk 1040 that is from AGN, an irregular structure of the compan...
Article
New results for the Pleiades Plate Database (PPDB) are presented. The database aims to collect information for the digitized Pleiades plates mainly in the field of 25 square degrees around Alcyone. Using the Wide-Field Plate Database (WFPDB, [http://www.skyarchive.org]) for the Pleiades plate search we found more than 3100 plates existing in the As...
Article
The updated version 5.0 (March 1st, 2005) of the Catalogue of Wide-Field Plate Archives (http://www.skyarchive.org) is presented. This version includes additionally the original name of the telescopes used for observations, which enables the plate search in the observatories. The Catalogue includes information for 414 archives made in the astronomi...
Article
We use the archive of the Bamberg Sky Patrol to obtain light curves of the active K subgiant CF Octantis (HD 196818) for the interval 1964–76. Digitized images of the field near CF Oct were obtained with a flat-bed scanner. Aperture photometry was performed of photo-positives of these images. Using a transformation to second order in plate magnitud...
Conference Paper
Full-text available
The iAstro network is a European action supported by the COST program, to foster coordination in the domain of computational and information infrastructure for the astronomical data grid.
Article
A large-scale national project to digitize the archive of plates of the Italian observatories and Specola Vaticana has started in 2002 following a pilot program funded by the University of Padova in 2001. Identical systems, composed of commercial scanners plus dedicated personal computers and acquisition software have been installed in all particip...