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Wyszukujesz frazę "Dimitrov, A." wg kryterium: Autor


Wyświetlanie 1-5 z 5
Tytuł:
Influence of Well-Width Fluctuations on the Electronic Structure of GaN/Al$\text{}_{x}$Ga$\text{}_{1-x}$N Multiquantum Wells with Graded Interfaces
Autorzy:
Valcheva, E.
Dimitrov, S.
Monemar, B.
Haratizadeh, H.
Persson, P.O.A.
Amano, H.
Akasaki, I.
Powiązania:
https://bibliotekanauki.pl/articles/2047708.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Cr
73.20.-r
73.21.-b
74.40.+k
Opis:
Experimental and computation results based on chemical composition assessment of metal-organic chemical vapour deposition grown undoped GaN/Al$\text{}_{x}$Ga$\text{}_{1-x}$N multiquantum well structures in the low composition limit of x = 0.07 and wide wells demonstrate composition fluctuations in the barrier layers which lead to large-scale nonuniformities and inequivalence of the different wells. As a consequence the experimental photoluminescence spectra at low temperature show a double peak structure indicative of well-width fluctuations by one lattice parameter (2 monolayers).
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 395-400
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground State and Magnetostatic Properties of a Dipole System Arranged in Two-Dimensional Lattice
Autorzy:
Bolcal, E.
Dimitrov, V.
Aktaş, B.
Aslan, H.
Bozkurt, A.
Powiązania:
https://bibliotekanauki.pl/articles/1491456.pdf
Data publikacji:
2012-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.-b
Opis:
A system of nano sized modomain ferromagnetic particle arranged in two-dimensional lattice is theoretically investigated. The basic aim of the investigation is to find the ground state of these types of models where the interaction is long-ranged and anisotropic. The numerical calculations show that for some lattices there is a number of degenerated states near the zero temperature. The ground state of these systems is basically of a complicated antiferromagnetic type.
Źródło:
Acta Physica Polonica A; 2012, 121, 1; 257-261
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Functionalization and characterization of MWCNT produced by different methods
Autorzy:
Tomova, A.
Gentile, G.
Grozdanov, A.
Errico, M.
Paunović, P.
Avella, M.
Dimitrov, A.
Powiązania:
https://bibliotekanauki.pl/articles/1070616.pdf
Data publikacji:
2016-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.De
Opis:
The subject of this study is chemical functionalization as means of structural modification of multiwalled carbon nanotubes. The main goal of the experiments was to create highest density of carboxyl groups on multiwalled carbon nanotubes surface, necessary for further nanocomposite application. Two different types of multiwalled carbon nanotubes (I: outer diameter d=50÷ 100 nm, purity ≈84%, synthesized by pyrolysis and II: outer diameter d=10÷40 nm, purity ≈94%, synthesized by chemical vapor deposition) were treated by concentrated nitric acid (HNO₃) and by alkaline mixture (NH₄OH+H₂O₂). The alkaline medium as "milder" and less aggressive than nitric acid, was expected to be less destructive and cause minimal structural damage on multiwalled carbon nanotubes surface. Structural changes due to oxidation were observed by the Raman analysis, while the ratio of the intensities of the D and G peak was used to estimate the concentration of defects. Pristine and functionalized multiwalled carbon nanotubes were characterized by thermogravimetric analysis, scanning electron microscopy, ultraviolet-visible spectroscopy and zeta (ζ) spectroscopy. The results showed that functionalization initiates changes in carbon nanotubes structure as well as in their density of states. It also results in carbon nanotubes shortening and exfoliation and decreases their agglomeration tendency. Carbon nanotubes functionalized by both acid and alkaline treatment can successfully replace conventional carbon fibers as fillers in polymer composites for sensing application.
Źródło:
Acta Physica Polonica A; 2016, 129, 3; 405-408
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multinanosensors Based on MWCNTs and Biopolymer Matrix - Production and Characterization
Autorzy:
Tomova, A.
Gentile, G.
Grozdanov, A.
Errico, M.
Paunović, P.
Avella, M.
Dimitrov, A.
Powiązania:
https://bibliotekanauki.pl/articles/1030087.pdf
Data publikacji:
2017-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
sensors
actuators
composites
nanotubes
properties and characterization
Opis:
This study presents the results of the design and characterization of a gas sensor with PMMA/CNTs chemiresistor as sensing element for detection of organic vapors. Multi wall carbon nanotubes (MWCNTs) produced at our lab (by method of pyrolysis, outer diameter d=10÷40 nm, purity ≈94%) were incorporated into biocompatible polymer matrix. Poly(methyl methacrylate) - PMMA - and nanocomposite films were obtained using casting solution technique. Produced nanocomposite films were investigated with thermogravimetric analysis, differential scanning calorimetry, X-ray analysis, scanning electron microscopy, and Fourier transform infrared, while the sensors activity was determined by the changes in electrical resistance of the nanocomposite films due to acetone and chloroform exposure. The response to these vapors was evaluated and it was shown that PMMA/MWCNTs composites exhibit changes in electroresistivity. Sensitivity was calculated to be in 0.58-54.6 range (30 min exposed to acetone) and 0.53-10.35 (30 min exposed to chloroform). The results presented in this paper show that CNTs are able to improve the overall performances of polymer based sensors.
Źródło:
Acta Physica Polonica A; 2017, 132, 4; 1251-1255
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Revising the Metacognitive Awareness of Reading Strategies Inventory (MARSI) and testing for factorial invariance
Autorzy:
Mokhtari, Kouider
Dimitrov, Dimiter M.
Reichard, Carla A.
Powiązania:
https://bibliotekanauki.pl/articles/780595.pdf
Data publikacji:
2018
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
metacognition
reading comprehension
metacognitive awareness
reading strategies
Opis:
In this study, we revised the Metacognitive Awareness of Reading Strategies Inventory (MARSI), a self-report instrument designed to assess students’ awareness of reading strategies when reading school-related materials. We collected evidence of structural, generalizability, and external aspects of validity for the revised inventory (MARSI-R). We first conducted a confirmatory factor analysis of the MARSI instrument, which resulted in the reduction of the number of strategy statements from 30 to 15. We then tested MARSI-R for factorial invariance across gender and ethnic groups and found that there is a uniformity in student interpretation of the reading strategy statements across these groups, thus allowing for their comparison on levels of metacognitive processing skills. We found evidence of the external validity aspect of MARSI-R data through correlations of such data with a measure of the students’ perceived reading ability. Given that this journal is oriented to second language learning and teaching, our article also includes comments on the Survey of Reading Strategies (SORS), which was based on the original MARSI and was designed to assess adolescents’ and adults’ metacognitive awareness and perceived use of ESL reading strategies. We provide a copy of the MARSI-R instrument and discuss the implications of the study’s findings in light of new and emerging insights relative to assessing students’ metacognitive awareness and perceived use of reading strategies.
Źródło:
Studies in Second Language Learning and Teaching; 2018, 8, 2; 219-246
2083-5205
2084-1965
Pojawia się w:
Studies in Second Language Learning and Teaching
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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