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Unsupervised phase mapping of X-ray diffraction data by nonnegative matrix factorization integrated with custom clustering

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npj Computational Materials 2018年第1期4卷 295-304页

作者： valentin Stanev velimir v.vesselinov A.Gilad Kusne Graham Antoszewski Ichiro Takeuchi Boian S.Alexandrov Department of Materials Science and Engineering University of MarylandCollege ParkMD 20742USA Center for Nanophysics and Advanced Materials University of MarylandCollege ParkMD 20742USA Joint Quantum Institute University of MarylandCollege ParkMD 20742USA Los Alamos National Laboratory Earth Science DivisionLos AlamosNM 87545USA National Institute of Standards and Technology GaithersburgMD 20899USA Department of Mathematics University of MarylandCollege ParkMD 20742USA Los Alamos National Laboratory Theoretical DivisionLos AlamosNM 87545USA

Analyzing large X-ray diffraction(XRD)datasets is a key step in high-throughput mapping of the compositional phase diagrams of combinatorial materials *** and automating this task can help accelerate the process of discovery of materials with novel and desirable ***,we report a new method for pattern analysis and phase extraction of XRD *** method expands the Nonnegative Matrix Factorization method,which has been used previously to analyze such datasets,by combining it with custom clustering and cross-correlation *** new method is capable of robust determination of the number of basis patterns present in the data which,in turn,enables straightforward identification of any possible peak-shifted ***-shifting arises due to continuous change in the lattice constants as a function of composition and is ubiquitous in XRD datasets from composition spread *** identification of the peak-shifted patterns allows proper quantification and classification of the basis XRD patterns,which is necessary in order to decipher the contribution of each unique single-phase structure to the multi-phase *** process can be utilized to determine accurately the compositional phase diagram of a system under *** presented method is applied to one synthetic and one experimental dataset and demonstrates robust accuracy and identification abilities.

关键词： properties. phase nonnegative

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Absolute parameters of the three totally-eclipsing W UMa stars NSvS 2443858,NSvS 780649 and v1098 Her

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Research in Astronomy and Astrophysics 2021年第9期21卷 124-134页

作者： velimir Popov Francesco Acerbi Carlo Barani Department of Physics and Astronomy Shumen University115 Universitetska str.9700 ShumenBulgaria via Zoncada 51 26845 Codogno(LO)Italy via Molinetto 35 26845 Triulza di Codogno(LO)Italy

We present the first photometric analysis of three totally-eclipsing W UMa binaries,NS vS2443858,NSvS 780649 and v1098 *** absolute astrophysical parameters of the stellar components were determined by means of Gaia distances and light curve *** results show that:(ⅰ)Two of the systems,NSvS 2443858 and v1098 Her,are of A subtype while the obtained temperature of the secondary component of NSvS 780649 indicates that it is a W-subtype system;(ⅱ)The estimated mass ratios approach the lower limit of the mass ratio assumed by researchers in recent years so our targets could be classified as extreme mass ratio binary(EMRB)systems;(ⅲ)All the systems have deep contact configurations,so they also are deep low mass ratio(DLMR)systems;(ⅳ)The components of our systems are stars of F and G spectral type and undergo total eclipses;(ⅴ)The sum 0.871 M⊙of the component masses of NSvS 780649 is below the mass limit of 1.0-1.2 M⊙assumed for the known contact binary stars.

关键词： techinques:photometric binaries:eclipsing stars:fundamental parameters stars:individual

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v2551 Cyg:a pulsating star with enigmatic peculiarities

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Research in Astronomy and Astrophysics 2017年第7期17卷 57-66页

作者： Diana P.Kjurkchieva velimir A.Popov Dragomir v.Marchev Kenneth T.Menzies Nikola I.Petrov Department of Physics Shumen University IRIDA Observatory Rozhen NAO Tigh Speuran Observatory Institute of Astronomy and NAO Bulgarian Academy of Sciences

Intensive photometric and spectral observations of the variable star v2551 Cyg are *** light curve shape reveals that the target is a pulsating star, contrary to its previous classification as an eclipsing binary. The period and amplitude of the light curve, the amplitudes of color changes and the radial velocity curve of v2551 Cyg are similar to those of a high-amplitude δ Scuti variable. The target seems to pulsate with the fundamental mode. However, v2551 Cyg exhibits several important peculiarities：（i） the decreasing branch of its light curve is steeper than the increasing one;（ii） the radial velocity curve has a flat section in the phase range 0.7-1.2 and short increase of the negative radial velocity at phase 0.7;（iii） the rotational velocity is quite big for a HADS star;（iv） the Fourier coefficients of v2551 Cyg are quite different from those of HADS stars. The target classification is difficult due to these peculiarities.

关键词： stars variables delta Scuti - stars variables RR Lyrae - stars individual (v2551 Cyg)

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The W UMa binaries USNO-A2.0 1350-17365531,v471 Cas,v479 Lac and v560 Lac:light curve solutions and global parameters based on Gaia distances

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Research in Astronomy and Astrophysics 2019年第1期19卷 141-148页

作者： Diana P.Kjurkchieva velimir A.Popov Yordanka Eneva Nikola I.Petrov Department of Physics and Astronomy Shumen University Medical University Institute of Astronomy and NAO Bulgarian Academy of Sciences

We present photometric observations in Sloan filters g′, i′of the eclipsing W UMa stars USNOA2.0 1350-17365531, v471 Cas, v479 Lac and v560 Lac. The sinusoidal-like O-C diagram of v471 Cas indicates the presence of a third body with mass 0.12 M_⊙(a red dwarf) at distance 897 R_⊙. The O-C diagram of v479 Lac reveals a period decrease of d P/dt =-1.69 × 10-6d yr-1. The results of the light curve solutions are:(i) the targets are overcontact binaries with small fill-out factors;(ii) their components are F–K stars, comparable in size, whose temperature differences are below 80 K;(iii) all targets undergo partial eclipses and to limit the possible mass ratios we carried out two-step q-search analysis. The target global parameters(luminosities, radii, masses) were obtained on the basis of their Gaia distances and the results of our light curve solutions. The obtained total mass of v560 Lac turns out to be smaller than the lower mass limit for presently known W UMa binaries of 1.0-1.2 M_⊙, i.e. this target is a peculiar overcontact system.

关键词： binaries:close binaries:eclipsing methods:data analysis stars:fundamental parameters stars:individual(USNO-A2.0 1350-17365531,v471 Cas,v479 Lac,v560 Lac)

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Observations and light curve solutions of the W UMa binaries v796 Cep,v797 Cep,CSS J015341.9+381641 and NSvS 3853195

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Research in Astronomy and Astrophysics 2017年第5期17卷 31-38页

作者： Diana Petrova Kjurkchieva velimir Angelov Popov Sunay Ibryamov Ibryamov Doroteya Lyubenova vasileva Nikola Ivanov Petrov Department of Physics Shumen University115 Universitetska Str.9712 ShumenBulgaria IRIDA Observatory Rozhen NAOBulgaria Institute of Astronomy and NAO Bulgarian Academy of Sciences72 Tsarigradsko Shose Blvd.1784 SofiaBulgaria

Photometric observations in Sloan g′and i′bands of four W UMa binaries, v796 Cep,v797 Cep, CSS J015341.9＋381641 and NSvS 3853195, are presented. Our observations showed that CSS J015404.1＋382805 and NSvS 3853195 are the same star. We determined the initial epochs T_0 of all targets and found improved values for the period of NSvS 3853195. The light curve solutions of our data revealed that the components of each target are almost the same in terms of mass, temperature,radius and luminosity. The stellar components are G and K spectral types and undergo partial *** systems have barely-overcontact configurations and can be classified as H subtype W UMa *** established that the relation between the luminosity ratio l_2/l_1 and mass ratio q of our targets is approximately l_2/l_1 = q^（1.5）.

关键词： stars: binaries: eclipsing -- stars: fundamental parameters -- stars: individual (v796 Cep,v797 Cep CSS J015341.9+381641 NSvS 3853195)

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Adenosquamous carcinoma arising within a retrorectal tailgut cyst: Report of a case

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World Journal of Gastroenterology 2005年第39期11卷 6225-6227页

作者： Zoran Krivokapic Ivan Dimitrijevic Goran Barisic velimir Markovic Miodrag Krstic Institute for Digestive Diseases Clinical Center of Serbia BelgradeSerbia and Montenegro

Retrorectal, developmental tail gut cysts, include dermoid cysts, rectal duplication cysts and retrorectal cyst-hamartomas. Retrorectal cyst-hamartomas （RCH） are derived from remnants of the tail gut, the most caudal part of the embryonic hincl gut, which normally involutes by the 8^th wk of embryonic development （3-8 mm stage）. They have specific radiological and histopathological features that distinguish them from other similar formations （dermoid cysts, enteric duplication cysts and teratomas）. We report a patient with adenosquamous carcinoma arising within RCH, who underwent complete resection of the cyst through anterior laparotomy, and reached complete （recurrencefree for 14 mo, so far） functional recovery. The cyst was incidentally discovered during hysterectomy 12 years ago. Diagnostic, therapeutic arid histopathological aspects of this rare case are discussed. The mentioned pedod between diagnosis and surgical treatment suggests that RCH, given enough time, can develop malignant degeneration, and should be resected at the time of diagnosis.

关键词： Tailgut cyst Malignant transformation

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