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OPTICAL PROPERTIES OF LOWEST-ENERGY CARBON ALLOTROPES FROM FIRST-PRINCIPLES CALCULATIONS
стр.476-483
V.A. Saleev, A.V. Shipilova
We study optical properties of lowest-energy carbon allotropes in the infrared, visible and ultraviolet spectral ranges in the general gradient approximation of the density functional theory. In our calculations we use an all-electron approach as well as a pseudo-potential approximation. In the infrared range, complex dielectric functions, infrared and Raman spectra have been calculated using a CRYSTAL14 program. Electronic properties and energy-dependent dielectric functions in
the visible and ultraviolet spectral ranges are calculated using a VASP program. We describe with good accuracy the experimentally known optical properties of a cubic diamond crystal. Using the obtained set of relevant calculation parameters, we predict the optical constants, dielectric functions and Raman spectra of the lowest-energy hypothetical carbon allotropes and lonsdaleite.
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ASYMMETRIC APODIZATION FOR THE COMMA ABERRATED POINT SPREAD FUNCTION
стр.484-488
A.N.K. Reddy, D.K.Sagar, S.N. Khonina
This paper deals with the study of light flux distributions in the point spread function formed by an optical system with a one-dimensional aperture under the influence of the coma aberration. The traditional design of an asymmetric optical filter improves the resolution of a diffraction-limited optical imaging system. In this approach we explore the control of monochromatic aberrations through
pupil engineering with asymmetric apodization. This technique employs the amplitude and phase apodization for the mitigation of the effects of third-order aberrations on the diffracted image. On introducing the coma wave aberration effect, the central peak intensity in the field of diffraction is a function of the edge strips width and the amplitude apodization parameter of a one-dimensional pupil
filter, whereas the magnitude of the reduction of optical side-lobes is a function of the degree of phase apodization at the periphery of the aperture. The analytically computed results are illustrated graphically in terms of point spread function curves under various considerations of the coma aberrations and a different degree of amplitude and phase apodization. Hence, for the optimum values of
apodization, the axial resolution has been analyzed using well-defined quality criteria.
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SIMULATION OF A LONG-HAUL FIBER OPTIC LINK WITH A TWO-MODE OPTICAL FIBER
стр.489-493
V.A. Burdin, A.V. Bourdine
Modern telecommunication networks approach the capacity crunch, which is associated with the so-called nonlinear Shannon limit. So, the passage to fiber optic links with few-mode optical fibers is considered as an alternative solution of the described problem concerned with high nonlinearity of conventional commercial single-mode optical fibers. Presently, various designs of fewmode
optical fibers have been known, with the recently published works presenting experimental results demonstrating their potentialities for long-haul fiber optic links. A lot of models of longhaul fiber optic links with few-mode optical fibers have been developed based on which features of a few-mode optical fiber transport network were numerically simulated. This work presents the
results of simulation of a 6000-km long-haul fiber optic link with a two-mode optical fiber and 100-km-per-span Erbium doped fiber optic amplifiers system under 100 Gbps DP-DQPSK data transmission. We studied the use of particular linearly polarized modes and optical vortices for signal transmission. The computation results were compared with the simulation of the same fiber optic link with a single-mode optical fiber under the identical conditions.
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CONDITIONS OF A SINGLE-MODE RIB CHANNEL WAVEGUIDE BASED ON DIELECTRIC TIO2/SIO2
стр.494-498
M.A. Butt, E.S. Kozlova, S.N. Khonina
In this paper, we propose conditions for the design of a single-mode rib channel waveguide based on dielectric materials such as titanium dioxide (TiO2) and silicon dioxide (SiO2) for the 0.633-μm visible light. We also design Y-splitter structures, which show high-degree optical confinement and low bend losses at various radii of curvatures. Small radii of curvatures are extremely desirable in integrated photonics as they permit decreasing the dimensions but can also potentially reduce power consumption in the active devices.
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NANOPHOTONIC STRUCTURE FORMATION BY DRY E-BEAM ETCHING OF THE RESIST: RESOLUTION LIMITATION ORIGINS
стр.499-503
A. Rogozhin, M. Bruk, E. Zhikharev, F. Sidorov
A wide range of structures for nanophotonics and optoelectronics can be formed by dry e-beam etching of the resist (DEBER). High resist sensitivity due to chain depolymerization reaction provides efficient etching with high throughput of the method. The structures obtained by the DEBER in this research are well-rounded diffraction gratings, binary gratings and staircase profiles. The major disadvantage of DEBER is poor lateral resolution, which may be caused by different physical
mechanisms. Four groups of possible mechanisms leading to the resolution limitation are determined and the influence of some mechanisms is estimated
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FEATURES OF CHANGES IN THE NANOSTRUCTURE AND COLORIZING OF COPPER DURING SCANNING WITH A FEMTOSECOND LASER BEAM
стр.504-509
G. Liedl, R. Pospichal, S.P. Murzin
We have studied the nanostructuring and colorizing of the copper surface by scanning with a femtosecond laser beam with a near-Gaussian beam profile. The experimental studies were conducted using a femtosecond laser comprising a Ti:Sapphire oscillator and a multi-pass amplifier with the maximum pulse energy of 0.7 mJ, pulse frequency of 1 kHz, and pulse duration
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INTEGRATED FIBER-BASED TRANSVERSE MODE CONVERTER
стр.510-514
A.V. Gavrilov, V.S. Pavelyev
A transverse mode converter based on a binary microrelief implemented directly on the endface of a few-mode fiber was numerically investigated. The results of numerical simulation demonstrated the converter to form LP-11 and LP-21 modes with high efficiency, providing a more-than 92% mode purity. Transformations of modes excited by a fiber microbending were also numerically investigated. The excited beams were shown to save their mode purity even in a strong bending as the arising parasitical modes were mostly unguided by the fiber. The resulting
beam power and mode content were also demonstrated to depend on the beam and bending mutual orientation for beams with strong rotational symmetry.
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FOCAL-PLANE FIELD WHEN LIGHTING DOUBLE-RING PHASE ELEMENTS
стр.515-520
The focal-plane field amplitude is calculated when lighting double-ring phase elements by flat and Gaussian beams. Emerging conditions in the minimum or maximum centers, including flat-top maxima, are given. For the field amplitude, we obtain equations that define the radius of the first zerointensity ring based on the deduced expressions. The root values are listed for several parameters of optical
elements and incident beams due to the lack of analytical solutions. Numerical simulation results are given for flat incident beams; they are fully consistent with the theoretical calculations.
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AN EFFICIENT BLOCK-BASED ALGORITHM FOR HAIR REMOVAL IN DERMOSCOPIC IMAGES
стр.521-527
Hair occlusion in dermoscopy images affects the diagnostic operation of the skin lesion. Segmentation and classification of skin lesions are two major steps of the diagnostic operation required by dermatologists. We propose a new algorithm for hair removal in dermoscopy images that includes two main stages: hair detection and inpainting. In hair detection, a morphological bottom-hat operation is implemented on Y-channel image of YIQ color space followed by a binarization
operation. In inpainting, the repaired Y-channel is partitioned into 256 nonoverlapped blocks and for each block, white pixels are replaced by locating the highest peak, using a histogram function and a morphological close operation. The proposed algorithm reports a true positive rate (sensitivity) of 97.36%, a false positive rate (fall-out) of 4.25%, and a true negative rate (specificity) of 95.75%. The diagnostic accuracy achieved is recorded at a high level of 95.78%.
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MAPPING AND EVALUATING URBAN DENSITY PATTERNS IN MOSCOW, RUSSIA
стр.528-534
K. Choudhary, M.S. Boori, A. Kupriyanov
The defense of the notion of ‘compact city’ as a strategy to reduce urban sprawl to support greater utilization of existing infrastructure and services in more compact areas and to improve the connectivity of employment hubs is actively discussed in urban research. Using the urban residential density as a surrogate measure for urban compactness, this paper empirically examines a cadaster database that contains details of every property with a view of capturing changes in urban residential density patterns across Moscow using geospatial techniques. The policy of densification in chase of a more compact city has produced mixed results. Findings of this study signal that the urban densities across the buffer zones around Moscow city are significantly different. The Landsat images from 1995, 2005 and 2016 are classified based on the maximum likelihood to expand the land use/cover maps and identify the land cover. Then, the area coverage for all the land use/cover types at different points in time is combined
with the distance from the city center. After that, urbanization densities from the city center toward the outskirts for every 1-km distance from 1 to 60 km are calculated. The city density on the distance of 1 to 35 km is found to be very high in the years 1995 to 2016. As usual, the population, traffic conditions,
industrialization and government policy are the major factors that influenced the urban expansion.
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OPTIMAL CALIBRATION OF A PRISM-BASED VIDEOENDOSCOPIC SYSTEM FOR PRECISE 3D MEASUREMENTS
стр.535-544
A.V. Gorevoy, A.S. Machikhin
Modern videoendoscopes are capable of performing precise three-dimensional (3D) measurements of hard-to-reach elements. An attachable prism-based stereo adapter allows one to register images from two different viewpoints using a single sensor and apply stereoscopic methods. The key condition for achieving high measurement accuracy is the optimal choice of a mathematical model
for calibration and 3D reconstruction procedures. In this paper, the conventional pinhole camera models with polynomial distortion approximation were analyzed and compared to the ray tracing model based on the vector form of Snell’s law. We, first, conducted a series of experiments using an industrial videoendoscope and utilized the criteria based on the measurement error of a segment
length to evaluate the mathematical models considered. The experimental results confirmed a theoretical conclusion that the ray tracing model outperforms the pinhole models in a wide range of working distances. The results may be useful for the development of new stereoscopic measurement tools and algorithms for remote visual inspection in industrial and medical applications.
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AERIAL VEHICLES DETECTION AND RECOGNITION FOR UAV VISION SYSTEM
стр.545-551
V.S. Muraviev, S.A. Smirnov, V.V. Strotov
This article focuses on aerial vehicle detection and recognition by a wide field of view monocular vision system that can be installed on UAVs (unmanned aerial vehicles). The objects are mostly observed on the background of clouds under regular daylight conditions. The main idea is to create a multi-step approach based on a preliminary detection, regions of interest (ROI) selection,
contour segmentation, object matching and localization. The described algorithm is able to detect small targets, but unlike many other approaches is designed to work with large-scale objects as well. The suggested algorithm is also intended to recognize and track the aerial vehicles of specific kind using a set of reference objects defined by their 3D models. For that purpose a computationally
efficient contour descriptor for the models and the test objects is calculated. An experimental research on real video sequences is performed. The video database contains different types of aerial vehicles: airplanes, helicopters, and UAVs. The proposed approach shows good accuracy in all case studies and can be implemented in onboard vision systems.
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FOOD VULNERABILITY ANALYSIS IN THE CENTRAL DRY ZONE OF MYANMAR
стр.552-558
M.S. Boori, K. Choudhary, R.A. Paringer, M. Evers
The central dry zone of Myanmar is the most water stressed and also one of the most food insecure regions in the country. In the Dry Zone, the total population is 10.1 million people in 54 townships, in which approximately 43% of people live below the poverty line and 40 – 50% of the rural population is landless. Agriculture is the most important economic sector in Myanmar as it is essential
for the national food security and a major source of livelihood of the people. In this region the adverse effects of climate change such as a late or early onset of the monsoon season, longer dry spells, erratic rainfall, increasing temperatures, heavy rains, stronger typhoons, extreme spatialtemporal variability of rainfall, high intensities, limited rainfall events in the growing season, heat stress, drought, flooding, sea water intrusion, land degradation, desertification, deforestation, and
other natural disasters are believed to be major constraints to food security. Theses extreme climatic events are likely to increase in frequency and magnitude, leading to serious drought periods and extreme floods. Food insecurity is an important thing that must be reviewed because it affects the lives of many people. For food vulnerability, we use the following indicators: slope, precipitation, vegetation, soil, erosion, land degradation and harvest failure in ArcGIS software. The erosion is influenced by rainfall and slope, while land degradation is directly related to vegetation, drainage and soil. In the meantime, the harvest failure can be generated by rainfall and flood potential zones. The results show that around 45% of the area studied comes under a very high erosion danger level, 70% are in the
average harvest failure zone, 59% are in the intermediate land degradation area, and overall around 45% of the studied area comes under the insecure food vulnerability zone. Our analysis shows that an increase in the alluvial farming by 1745.33 km2 since 1988 has helped reduce the insecure food vulnerability. The food vulnerability map is also relevant to increased population and low income areas. This paper is helpful for identifying the areas of food needs in central dry zone of Myanmar.
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CONFORMING IDENTIFICATION OF THE FUNDAMENTAL MATRIX IN THE IMAGE MATCHING PROBLEM
стр.559-563
V.A. Fursov, A.V. Gavrilov, Ye.V. Goshin, K.G. Pugachev
The article considers the conforming identification of the fundamental matrix in the image matching problem. The method consists in the division of the initial overdetermined system into lesser dimensional subsystems. On these subsystems, a set of solutions is obtained, from which a subset of the most conforming solutions is defined. Then, on this subset the resulting
solution is deduced. Since these subsystems are formed by all possible combinations of rows in the initial system, this method demonstrates high accuracy and stability, although it is computationally complex. A comparison with the methods of least squares, least absolute deviations, and the RANSAC method is drawn.
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HYPERSPECTRAL IMAGE SEGMENTATION USING DIMENSIONALITY REDUCTION AND CLASSICAL SEGMENTATION APPROACHES
стр.564-572
Unsupervised segmentation of hyperspectral satellite images is a challenging task due to the nature of such images. In this paper, we address this task using the following three-step procedure. First, we reduce the dimensionality of the hyperspectral images. Then, we apply one of classical segmentation algorithms (segmentation via clustering, region growing, or watershed transform).
Finally, to overcome the problem of over-segmentation, we use a region merging procedure based on priority queues. To find the parameters of the algorithms and to compare the segmentation approaches, we use known measures of the segmentation quality (global consistency error and rand index) and well-known hyperspectral images.
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VORTEX-FREE LASER BEAM WITH AN ORBITAL ANGULAR MOMENTUM
стр.573-576
V.V. Kotlyar, A.A. Kovalev
We show that if one cylindrical lens is placed in the Gaussian beam waist and another cylindrical lens is placed at some distance from the first one and rotated by some angle, then the laser beam after the second lens has an orbital angular momentum (OAM). An explicit analytical expression for the OAM of such a beam is obtained. Depending on the inter-lens distance, the OAM can be positive, negative, or zero. Such a laser beam has no isolated intensity nulls with a singular
phase and it is not an optical vortex, but has an OAM. By choosing the radius of the beam waist of the source Gaussian beam, the focal lengths of the lenses and the distance between them, it is possible to generate a vortex-free laser beam equivalent to an optical vortex with a topological charge of several hundreds.
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THREE-DIMENSIONAL MODEL OF QUANTUM DOTS' SELF-ASSEMBLY UNDER THE ACTION OF LASER RADIATION
стр.577-580
V.A. Tkachenko, A.S. Tsipotan, A.S. Aleksandrovsky, V.V. Slabko
This study considered a process of quantum dots' self-assembly into nanostructure arrays with predefined geometry, which proceeds in the external resonant laser field. We considered the simplest case of assembling a stable structure of two particles. The problem was solved numerically using a three-dimensional model of Brownian dynamics. The idea of the method is that the attraction of the dots occurs due to the interaction of resonantly induced dipole moments, with the dots being then captured by the Van der Waals force. Finally, a three-dimensional model was considered; the average nanoparticle aggregation time as a function of the laser radiation wavelength was calculated; the probability of such structures' being formed was estimated for the calculated average
aggregation time and for the laser pulse duration used in the experiment. The wavelength of the maximum probability was found to be shifted from the single particle resonance wavelength of 525 nm to the red area of 535 nm, which is in qualitative agreement with the redshift of the resonance wavelength of interacting particles.
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DIFFRACTIVE ELEMENTS FOR IMAGING OPTICS OF MOBILE COMMUNICATION DEVICES
стр.581-584
G.I. Greisukh, E.G. Ezhov, S.V. Kazin, S.A. Stepanov
An estimate of the permissible width of the working spectral range of optical systems with diffractive elements is given. It takes into account the interval of the angles of incidence of the radiation on the microstructure of the element and it proceeds from the requirement that there is no halo in the image that is visualized by the LCD monitor. It is shown that the design parameters of diffractive
elements intended for mobile device cameras are quite achievable for today's technologies of mass production of plastic optics.
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PARALLEL IMPLEMENTATION OF THE INFORMATIVE AREAS GENERATION METHOD IN THE SPATIAL SPECTRUM DOMAIN
стр.585-587
N.S. Kravtsova, R.A. Paringer, A.V. Kupriyanov
This paper proposes a parallel implementation of the image informative segments extraction method. The images are segmented in the spatial spectrum domain. The median energy in each selected segment is viewed upon as an area. For purposes of time savings, a parallel implementation of the algorithm for calculating the areas is developed. The developed approach to the parallel algorithm implementation is tested on a high performance multicore computing system. The experiments have shown that the parallel implementation
of the method allows us to obtain a three-fold speedup, which is a good result.
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PARALLEL IMPLEMENTATION OF A MULTI-VIEW IMAGE SEGMENTATION ALGORITHM USING THE HOUGH TRANSFORM
стр.588-591
Ye. V. Goshin, A.P. Kotov
We report on the parallel implementation of a multi-view image segmentation algorithm via segmenting the corresponding three-dimensional scene. The algorithm includes the reconstruction of a three-dimensional scene model in the form of a point cloud, and the segmentation of the resulting point cloud in three-dimensional space using the Hough space. The developed parallel algorithm
was implemented on graphics processing units using CUDA technology. Experiments were performed to evaluate the speedup and efficiency of the proposed algorithm. The developed parallel program was tested on modelled scenes.
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INDEXING OF COMPUTER OPTICS IN THE EMERGING SOURCES CITATION INDEX DATABASE
стр.592-592
Inclusion of the journal Computer Optics in the Emerging Sources Citation Index database is described in this editorial.
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