210 research outputs found
Homogeneous Volatility Bridge Estimators
We present a theory of homogeneous volatility bridge estimators for log-price
stochastic processes. The main tool of our theory is the parsimonious encoding
of the information contained in the open, high and low prices of incomplete
bridge, corresponding to given log-price stochastic process, and in its close
value, for a given time interval. The efficiency of the new proposed estimators
is favorably compared with that of the Garman-Klass and Parkinson estimators.Comment: 25 pages, 9 figure
Применение кластеризации k-means и анализа гистограмм для автоматизации предварительной обработки изображений дискомицетов, полученных в среде обитания
The study of biological diversity requires a thorough inventory of all groups of organisms, including destructors, among which fungi play a significant role. Discomycetes, a group of orders of fungi of the Ascomycota phylum, require close attention from researchers due to their low level of knowledge. The paper proposes an approach to automating the process of inventory of representatives of this group of orders and presents a prototype of a software package that allows one to identify the presence of fruit bodies of discomycetes in photographs taken in the natural habitat. A feature of the proposed solution is the application of the k-means clustering method, the use of scaled histograms to determine the presence of an image of the fruit body of Discomycetes in this image, and the prospects for using this tool in machine learning are described using neural networks
Legibility of Textbooks: A Literature Review
AbstractThe purpose of the study was to analyse findings in the field of the textbooks’ legibility, readability and visual word recognition. The paper focuses on the most significant findings for comprehending the texts’ spatial characteristics during reading, word and letter recognition. The aim of the study was to analyse the factors which have induced inconsistencies between the findings acquired by scientists, as well as to compare findings which continually lead to progression in this field
Directed and Elliptic Flow in Pb+Pb collisions at 40 and 158 AGeV
Directed and elliptic flow are reported for charged pions and protons as a
function of transverse momentum, rapidity, and centrality in 40 and 158 AGeV Pb
+ Pb collisions. The standard method of correlating particles with an event
plane is used. The directed flow of protons is small and shows little variation
near to midrapidity, but rises fast towards projectile rapidity in the 40 AGeV
data. For most peripheral collisions the flat region becomes negative resulting
in changing sign three times. Elliptic flow doesn't seem to change very
much from 40 AGeV to 158 AGeV. The difference is smaller than anticipated from
the overall energy dependence from AGS to RHIC.Comment: Presented at 16th International Conference on Ultrarelativistic
Nucleus-Nucelus Collisions, Quark Matter 2002 (QM 2002), Nantes, France,
18-24 Jul 2002, 4 pages, 3 figure
SEM and AFM studies of two-phase magnetic alkali borosilicate glasses
The morphology and composition of four types of two-phase alkali borosilicate glasses with magnetic atoms prepared by inductive melting have been studied. The results of scanning electron microscopy point to uniform distribution of Na, Si, and O atoms in these samples whilemagnetic iron atoms formball-shaped agglomerates. The magnetic properties of these agglomerates have been confirmed by magnetic force microscopy. Atomic force microscopy had shown that in these samples two different morphological structures, drop-like and dendrite net, are formed. The formation of dendrite-like structure is a necessary condition for production of porous magnetic glasses. The obtained results allowus to optimize the melting and heat treatment processes leading to production of porous alkali borosilicate glasses withmagnetic properties. The first results for nanocompositematerials on the basis ofmagnetic glasses containing the embedded ferroelectrics KH2PO4 demonstrate the effect of applied magnetic field on the ferroelectric phase transition. The morphology and composition of four types of two-phase alkali borosilicate glasses with magnetic atoms prepared by inductive melting have been studied. The results of scanning electron microscopy point to uniform distribution of Na, Si, and O atoms in these samples whilemagnetic iron atoms formball-shaped agglomerates. The magnetic properties of these agglomerates have been confirmed by magnetic force microscopy. Atomic force microscopy had shown that in these samples two different morphological structures, drop-like and dendrite net, are formed. The formation of dendrite-like structure is a necessary condition for production of porous magnetic glasses. The obtained results allowus to optimize the melting and heat treatment processes leading to production of porous alkali borosilicate glasses withmagnetic properties. The first results for nanocompositematerials on the basis ofmagnetic glasses containing the embedded ferroelectrics KH2PO4 demonstrate the effect of applied magnetic field on the ferroelectric phase transition.DAA
Spin-reorientation transitions in the Cairo pentagonal magnet Bi4 Fe5 O13 F
© 2017 American Physical Society. We show that interlayer spins play a dual role in the Cairo pentagonal magnet Bi4Fe5O13F, on one hand mediating the three-dimensional magnetic order, and on the other driving spin-reorientation transitions both within and between the planes. The corresponding sequence of magnetic orders unraveled by neutron diffraction and Mössbauer spectroscopy features two orthogonal magnetic structures described by opposite local vector chiralities, and an intermediate, partly disordered phase with nearly collinear spins. A similar collinear phase has been predicted theoretically to be stabilized by quantum fluctuations, but Bi4Fe5O13F is very far from the relevant parameter regime. While the observed in-plane reorientation cannot be explained by any standard frustration mechanism, our ab initio band-structure calculations reveal strong single-ion anisotropy of the interlayer Fe3+ spins that turns out to be instrumental in controlling the local vector chirality and the associated interlayer order
Magnetron plasma mediated immobilization of hyaluronic acid for the development of functional double-sided biodegradable vascular graft
The clinical need for vascular grafts is associated with cardiovascular
diseases frequently leading to fatal outcomes. Artificial vessels based on
bioresorbable polymers can replace the damaged vascular tissue or create a
bypass path for blood flow while stimulating regeneration of a blood vessel in
situ. However, the problem of proper conditions for the cells to grow on the
vascular graft from the adventitia while maintaining its mechanical integrity
of the luminal surface remains a challenge. In this work, we propose a
two-stage technology for processing electrospun vascular graft from
polycaprolactone, which consists of plasma treatment and subsequent
immobilization of hyaluronic acid on its surface producing thin double-sided
graft with one hydrophilic and one hydrophobic side. Plasma modification
activates the polymer surfaces and produces a thin layer for linker-free
immobilization of bioactive molecules, thereby producing materials with unique
properties. The proposed modification does not affect the morphology or
mechanical properties of the graft and improves cell adhesion. The proposed
approach can potentially be used for various biodegradable polymers such as
polylactic acid, polyglycolide, and their copolymers and blends, with a
hydrophilic inner surface and a hydrophobic outer surface
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