256 research outputs found
KiDS0239-3211: A new gravitational quadruple lens candidate
We report the discovery of a candidate to quadrupole gravitationally lensed
system KiDS0239-3211 based on the public data release 3 of the KiDS survey and
machine learning techniques
Influence of "productive" Impurities (Cd, Na, O) on the Properties of the Cu2ZnSnS4Absorber of Model Solar Cells
The research has been supported by grant of the Ministry of Education and Science of the Republic of Kazakhstan AP09562784. The authors (D. Sergeyev) acknowledges the provision of SCAPS-1D software by Prof. Marc Burgelman. The research of A.I. Popov has been supported by the Institute of Solid State Physics (ISSP), University of Latvia (UL). ISSP UL as the Centre of Excellence is supported through the Framework Program for Euro-pean Universities Union Horizon 2020, H2020-WIDESPREAD-01â2016â2017-TeamingPhase2 under Grant Agreement No. 739508, CAMART2 project.Abstract
The study focuses on the optical properties of the CZTS multicomponent semiconductor absorber with 3 % "production"impurities of Cd, Na, O within the framework of the density functional theory using the generalized gradient approximation and the SCAPS program, as well as investigates their influence on the performance and efficiency of CZTS-solar cells. The results showed that the introduction of Cd, Na, O impurities would lead to a decrease in the intensity of the absorption bands at 2.06 eV and 2.55 eV. The density of states CZTS: (Cd, Na, O) was determined from first principles, and it was revealed that impurities of Cd and O atoms would lead to a decrease in the band gap (to 0.9 eV and 0.79 eV), and an increase in Na impurity absorption (1.2 eV). It was also found that a decrease in the band gap led to a decrease in the open circuit voltage, and it was also shown that "industrial"impurities led to a decrease in the efficiency of energy conversion of solar cells to 2.34 %. © 2021 D. Sergeyev et al., published by Sciendo. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.Ministry of Education and Science of the Republic of Kazakhstan AP09562784; ISSP UL as the Centre of Excellence is supported through the Framework Program for Euro-pean Universities Union Horizon 2020, H2020-WIDESPREAD-01â2016â2017-TeamingPhase2 under Grant Agreement No. 739508, CAMART2 project
Upconversion assisted self-pulsing in a high-concentration erbium doped fiber laser
We report results on experimental and theoretical characterisation of self-pulsing in high concentration erbium doped fibre laser which is free from erbium clusters. Unlike previous models of self-pulsing accounting for pair-induced quenching (PIQ) on the clustered erbium ions, new model has been developed with accounting for statistical nature of the excitation migration and upconversion and resonance-like pumpto-signal intensity noise transfer. The obtained results are in a good agreement with the experimental data
Computer Simulation of the Electric Transport Properties of the FeSe Monolayer
The research has been supported by the grant of the Ministry of Education and Science of the Republic of Kazakhstan AP08052562. In addition, the research of AIP has been supported by the Latvian- Ukrainian Grant LV-UA/2018/2.The paper deals with the model research of electric transport characteristics of stressed and non-stressed FeSe monolayers. Transmission spectra, current-voltage characteristic (CVC) and differential conductivity spectra of two-dimensional FeSe nanostructure have been calculated within the framework of the density functional theory and non-equilibrium Green's functions (DFT + NEGF). It has been shown that the electrophysical properties depend on the geometry of the sample, the substrate, and the lattice constant. On CVC of non-stressed sample in the range from -1.2 V to -1 and from 1.2 V to 1.4 V, a region of negative differential resistance (NDR) has been observed. NDR is at both signs of the applied voltage due to the symmetry of the nanostructure. d2I/dV2 is used to determine the nature of the electron-phonon interaction and the features of quasiparticle tunnelling in stressed and non-stressed samples. The results obtained can be useful for calculating new elements of 2D nanoelectronics. © 2020 D. Sergeyev et al., published by Sciendo 2020. --//-- Published under the CC BY 4.0 license.Ministry of Education and Science of the Republic of Kazakhstan AP08052562, LV-UA/2018/2; The Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART
KiDS-SQuaD: The KiDS Strongly lensed Quasar Detection project
New methods have been recently developed to search for strong gravitational
lenses, in particular lensed quasars, in wide-field imaging surveys. Here, we
compare the performance of three different, morphology- and photometry- based
methods to find lens candidates over the Kilo-Degree Survey (KiDS) DR3
footprint (440 deg). The three methods are: i) a multiplet detection in
KiDS-DR3 and/or Gaia-DR1, ii) direct modeling of KiDS cutouts and iii)
positional offsets between different surveys (KiDS-vs-Gaia, Gaia-vs-2MASS),
with purpose-built astrometric recalibrations. The first benchmark for the
methods has been set by the recovery of known lenses. We are able to recover
seven out of ten known lenses and pairs of quasars observed in the KiDS DR3
footprint, or eight out of ten with improved selection criteria and looser
colour pre-selection. This success rate reflects the combination of all methods
together, which, taken individually, performed significantly worse (four lenses
each). One movelty of our analysis is that the comparison of the performances
of the different methods has revealed the pros and cons of the approaches and,
most of all, the complementarities. We finally provide a list of high-grade
candidates found by one or more methods, awaiting spectroscopic follow-up for
confirmation. Of these, KiDS 1042+0023 is to our knowledge the first confirmed
lensed quasar from KiDS, exhibiting two quasar spectra at the same source
redshift at either sides of a red galaxy, with uniform flux-ratio
over the wavelength range
Comment: 12 pages, 4 figures, 4 tables, accepted for publication in MNRA
Dynamics of transcutaneous oxygen tension at the operations on the aorto-femoral segment distal of the level of aortic compression
Estimation of transcutaneous partial pressure of oxygen is the main noninvasive method of evaluation and study microhaemodynamics and tissue blood supply. Aim of the research: to study the dynamics of transcutaneous partial pressure of oxygen at surgery of aortofemoral segment performed more distally of aortic compression. Material and methods: the survey included 49 patients with arterial sclerotic disease of aortofemoral segment with comorbid Ilb-IV stage chronic lower limb ischemia according to Pokrovsky-Fountain classification, and with II-III stage chronic infrarenal abdominal aortic aneurysm according to Pokrovsky classification. The patients' age was 52-76y.o. For the assessment of peripheral microhaemodynamics we used the technique of estimation of transcutaneous partial pressure of oxygen (ĐąŃĐ Đ2) with application of multichannel monitor of Radiometer TCM-400 system. The suggested method offers the possibility to evaluate the severity degree of microcirculatory disorders in lower limbs and to assess effectiveness of revascularization process
The CRESST Experiment: Recent Results and Prospects
The CRESST experiment seeks hypothetical WIMP particles that could account
for the bulk of dark matter in the Universe. The detectors are cryogenic
calorimeters in which WIMPs would scatter elastically on nuclei, releasing
phonons. The first phase of the experiment has successfully deployed several
262 g sapphire devices in the Gran Sasso underground laboratories. A main
source of background has been identified as microscopic mechanical fracturing
of the crystals, and has been eliminated, improving the background rate by up
to three orders of magnitude at low energies, leaving a rate close to one count
per day per kg and per keV above 10 keV recoil energy. This background now
appears to be dominated by radioactivity, and future CRESST scintillating
calorimeters which simultaneously measure light and phonons will allow
rejection of a great part of it.Comment: To appear in the proceedings of the CAPP2000 Conference, Verbier,
Switzerland, July, 2000 (eds J. Garcia-Bellido, R. Durrer, and M.
Shaposhnikov
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