347 research outputs found
Spatial aerodynamics of blunted cones in the presence of complicating factors in approach supersonic flow
The results of problem solution on blunted cone interaction with spherical heated region in approach at nonzero attack angle in supersonic flow in the absence and at the presence of strong localized blowing from surface as well as from falling at attack angle plane blast wave are presented
Systematic NLTE study of the -2.6 < [Fe/H] < 0.2 F and G dwarfs in the solar neighbourhood. I. Stellar atmosphere parameters
We present atmospheric parameters for 51 nearby FG dwarfs uniformly
distributed over the -2.60 < [Fe/H] < +0.20 metallicity range that is suitable
for the Galactic chemical evolution research. Lines of iron, Fe I and Fe II,
were used to derive a homogeneous set of effective temperatures, surface
gravities, iron abundances, and microturbulence velocities. We used
high-resolution (R>60000) Shane/Hamilton and CFHT/ESPaDOnS observed spectra and
non-local thermodynamic equilibrium (NLTE) line formation for Fe I and Fe II in
the classical 1D model atmospheres. The spectroscopic method was tested with
the 20 benchmark stars, for which there are multiple measurements of the
infrared flux method (IRFM) Teff and their Hipparcos parallax error is < 10%.
We found NLTE abundances from lines of Fe I and Fe II to be consistent within
0.06 dex for every benchmark star, when applying a scaling factor of S_H = 0.5
to the Drawinian rates of inelastic Fe+H collisions. The obtained atmospheric
parameters were checked for each program star by comparing its position in the
log g-Teff plane with the theoretical evolutionary track in the Yi et al.
(2004) grid. Our final effective temperatures lie in between the T_IRFM scales
of Alonso et al. (1996) and Casagrande et al. (2011), with a mean difference of
+46 K and -51 K, respectively. NLTE leads to higher surface gravity compared
with that for LTE. The shift in log g is smaller than 0.1 dex for stars with
either [Fe/H] > -0.75, or Teff 4.20. NLTE analysis is
crucial for the VMP turn-off and subgiant stars, for which the shift in log g
between NLTE and LTE can be up to 0.5 dex. The obtained atmospheric parameters
will be used in the forthcoming papers to determine NLTE abundances of
important astrophysical elements from lithium to europium and to improve
observational constraints on the chemo-dynamical models of the Galaxy
evolution.Comment: 18 pages, 14 figures, accepted for publication in Ap
Quantum Size Effect transition in percolating nanocomposite films
We report on unique electronic properties in Fe-SiO2 nanocomposite thin films
in the vicinity of the percolation threshold. The electronic transport is
dominated by quantum corrections to the metallic conduction of the Infinite
Cluster (IC). At low temperature, mesoscopic effects revealed on the
conductivity, Hall effect experiments and low frequency electrical noise
(random telegraph noise and 1/f noise) strongly support the existence of a
temperature-induced Quantum Size Effect (QSE) transition in the metallic
conduction path. Below a critical temperature related to the geometrical
constriction sizes of the IC, the electronic conductivity is mainly governed by
active tunnel conductance across barriers in the metallic network. The high 1/f
noise level and the random telegraph noise are consistently explained by random
potential modulation of the barriers transmittance due to local Coulomb
charges. Our results provide evidence that a lowering of the temperature is
somehow equivalent to a decrease of the metal fraction in the vicinity of the
percolation limit.Comment: 21 pages, 8 figure
Predicting Multiple ICD-10 Codes from Brazilian-Portuguese Clinical Notes
ICD coding from electronic clinical records is a manual, time-consuming and
expensive process. Code assignment is, however, an important task for billing
purposes and database organization. While many works have studied the problem
of automated ICD coding from free text using machine learning techniques, most
use records in the English language, especially from the MIMIC-III public
dataset. This work presents results for a dataset with Brazilian Portuguese
clinical notes. We develop and optimize a Logistic Regression model, a
Convolutional Neural Network (CNN), a Gated Recurrent Unit Neural Network and a
CNN with Attention (CNN-Att) for prediction of diagnosis ICD codes. We also
report our results for the MIMIC-III dataset, which outperform previous work
among models of the same families, as well as the state of the art. Compared to
MIMIC-III, the Brazilian Portuguese dataset contains far fewer words per
document, when only discharge summaries are used. We experiment concatenating
additional documents available in this dataset, achieving a great boost in
performance. The CNN-Att model achieves the best results on both datasets, with
micro-averaged F1 score of 0.537 on MIMIC-III and 0.485 on our dataset with
additional documents.Comment: Accepted at BRACIS 202
Analysis of the application of the optical method to the measurements of the water vapor content in the atmosphere - Part 1: Basic concepts of the measurement technique
We retrieved the total content of the atmospheric water vapor (or Integrated
Water Vapor, IWV) from extensive sets of photometric data obtained since 1995
at Lindenberg Meteorological Observatory with star and sun photometers.
Different methods of determination of the empirical parameters that are
necessary for the retrieval are discussed. The instruments were independently
calibrated using laboratory measurements made at Pulkovo Observatory with the
VKM-100 multi-pass vacuum cell. The empirical parameters were also calculated
by the simulation of the atmospheric absorption by water vapor, using the
MODRAN-4 program package for different model atmospheres. The results are
compared to those presented in the literature, obtained with different
instruments and methods of the retrieval. The reliability of the empirical
parameters, used for the power approximation that links the water vapor content
with the observed absorption, is analyzed. Currently, the total (from
measurements, calibration, and calculations) errors yield the standard
uncertainty of about 10% in the total column water vapor. We discuss the
possibilities for improving the accuracy of calibration to ~1% as indispensable
condition in order to make it possible to use data obtained by optical
photometry as an independent reference for other methods (GPS, MW-radiometers,
lidar, etc).Comment: 28 pages, 8 figures, 3 tables. In submitting to Atmospheric
Measurement Technique
Interstellar absorptions and shocked clouds towards supernova remnant RX J0852.0-4622
We present results of survey of interstellar absorptions towards supernova
remnant (SNR) RX J0852.0-4622. The distribution of KI absorbers along the
distance of the background stars is indicative of a local region (d<600pc)
strongly depopulated by KI line-absorbing clouds. This fact is supported by the
behavior of the interstellar extinction. We find four high-velocity CaII
components with velocities of >100km/s towards three stars and identify them
with shocked clouds of Vela SNR. We reveal and measure acceleration of two
shocked clouds at the approaching and receding sides of Vela SNR along the same
sight line. The clouds acceleration, velocity, and CaII column density are used
to probe cloud parameters. The total hydrogen column density of both
accelerating clouds is found to be similar (~6*10^{17} cm) which
indicates that possibly there is a significant amount of small-size clouds in
the vicinity of Vela SNR.Comment: accepted in MNRA
Longitudinal and transversal piezoresistive response of granular metals
In this paper, we study the piezoresistive response and its anisotropy for a
bond percolation model of granular metals. Both effective medium results and
numerical Monte Carlo calculations of finite simple cubic networks show that
the piezoresistive anisotropy is a strongly dependent function of bond
probability p and of bond conductance distribution width \Delta g. We find that
piezoresistive anisotropy is strongly suppressed as p is reduced and/or \Delta
g is enhanced and that it vanishes at the percolation thresold p=p_c. We argue
that a measurement of the piezoresistive anisotropy could be a sensitive tool
to estimate critical metallic concentrations in real granular metals.Comment: 14 pages, 7 eps figure
Large Anomalous Hall effect in a silicon-based magnetic semiconductor
Magnetic semiconductors are attracting high interest because of their
potential use for spintronics, a new technology which merges electronics and
manipulation of conduction electron spins. (GaMn)As and (GaMn)N have recently
emerged as the most popular materials for this new technology. While Curie
temperatures are rising towards room temperature, these materials can only be
fabricated in thin film form, are heavily defective, and are not obviously
compatible with Si. We show here that it is productive to consider transition
metal monosilicides as potential alternatives. In particular, we report the
discovery that the bulk metallic magnets derived from doping the narrow gap
insulator FeSi with Co share the very high anomalous Hall conductance of
(GaMn)As, while displaying Curie temperatures as high as 53 K. Our work opens
up a new arena for spintronics, involving a bulk material based only on
transition metals and Si, and which we have proven to display a variety of
large magnetic field effects on easily measured electrical properties.Comment: 19 pages with 5 figure
Підсумки інтродукції деревно-чагарникових рослин в арборетумі ботанічного саду Дніпропетровського університету
The results of long-term woods and bushes introduction in the DNU botanical garden’s arboretum are considered. The total quantity of taxa of arboretum collection fund and its present state are given. The condition of largest taxonomic groups is described as well.Приведены результаты многолетней интродукции древесно-кустарниковых растений в арборетуме ботанического сада ДНУ, а также общий перечень таксонов коллекционного фонда дендрария, его состояние в настоящее время. Рассмотрено состояние крупнейших таксономических групп.Наведено результати багаторічної інтродукції деревно-чагарникових рослин в арборетумі ботанічного саду ДНУ, а також загальний перелік таксонів колекційного фонду дендрарію, його стан на цей час. Розглянуто стан найбільших таксономічних груп
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