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The statistical features of distributed cumulative image histograms for their use in the processes of classification and search are researched. To check their similarity on the proposed features are used faces of different intensity. Segmented 2D image histograms give the slightest difference for faces made for experiments.

Analytical solution of the first-order Ornstein–Zernike equation known as the first-order mean spherical approximation (FMSA) theory due to Tang and Lu [J. Chem. Phys. 99, 9828 (1993)] is used to write down a closed equation for the static structure factor of the hard-sphere fluid with a short-range Yukawa attraction. Calculations are performed for a Yukawa decay exponent that corresponds to a range of attraction that does not exceed the first coordination shell of Lennard-Jones-like simple fluids. By comparison with Monte Carlo simulation data it is shown that the analytical FMSA equation for the static structure factor is of the same or even of superior accuracy as that within the seminumerical mean spherical approximation theory.

In this paper an informative distributed cumulative histogram is proposed to analyze a metal and other surfaces having defects. The IDCH is used to illustrate and to measure an intensity and location of defects.

In this paper the clustering algorithm was used to classify the regions of the metal sample with defects to determine their coordinates. The informative distributed cumulative histogram is proposed. To measure sizes and intensity of defects the IDCH image is transformed and clustered.

The method of clouds determination and classification on the basis of satellite images is considered. To detect clouds, a 3-stage image clustering algorithm is used. The cloudiness analysis in Ukraine was carried out using the proposed overall cloudiness estimate and its intensity coefficients.

The method for cloudiness statistical features extraction from intensity columns, rows and rectangles of image is considered. Clustering algorithm was used to classify the regions of Ukraine by cloudiness intensity.

The paper presents a solution to the wind farm structure optimization problem (determination of the optimal set of active wind turbines at a given time). The significance of wind parameters prediction for determining the wind farm active set is justified. The theoretical solution to this problem enables refining control algorithms for the power-dynamic modes of wind farms in order to increase their efficiency by reducing operational losses and electrodynamic overload when switching wind turbines. It can be achieved by estimating the future wind power capacity based on the short-term prediction of wind speed values in combination with other mode parameters. The findings are particularly relevant when electric power storage element is used in a wind farm structure. In this case, the key variables that determine the mode parameters are current and future wind speed, consumer load, current energy capacity of a storage battery, effectiveness and availability of wind turbines (WT). As a result, we receive the optimal number of active (operating at a given time) wind turbines not only for the current, but also the next parameters of power-dynamic modes minimizing switching operations. The effectiveness of the available methods of time series prediction depends on the knowledge and skills of experts, and subjectivity in the development of mathematical models. Hence, the feasibility of artificial neural networks application for prediction is surveyed. The research shows the results of the implementation of such networks as a classical back propagation network, the Elman network and the cascade neural network. The impact of the energy storage element capacity on the number of switching operations in the wind farm structure is investigated. We offer the solution to the problem of optimal choice of the energy storage element capacity which will balance meeting maximum load requirements and the cost of its installation and operation. As a practical result, the algorithm (rules of inference) for minimizing the number of switching operations of the active set of WF is developed taking into account such parameters as current wind speed, archival wind speed, predicted value of wind speed, current load value, next load value, nominal output of a wind farm, types of wind turbines, the number of wind turbines of each type, technical condition of each wind turbine, power capacity of a storage battery, etc. The results of the experimental studies of the developed algorithm efficiency are presented.

A variable resolution x-ray (VRX) computed tomography (CT) scanner can image objects of various sizes with greatly improved spatial resolution. The scanner employs an angulated discrete detector and achieves the resolution boost by matching the detector angulation to the scanner field of view (FOV) determined by the size of an object being imaged. A comprehensive evaluation of spatial resolution in an experimental version of the VRX CT scanner is presented in this dissertation. Two components of this resolution were evaluated – the pre-reconstruction spatial resolution, described by the detector presampling modulation transfer function (MTF), and the post-reconstruction spatial resolution, given by the scanner reconstruction MTF. The detector presampling MTF was modeled by the Monte Carlo simulation and measured by the moving-slit method. The modeled results showed the increase in the maximum cutoff frequency (in the detector plane) from 1.53 to 53.64 cycles per mm (cy/mm) as the scanner FOV decreased from 32 to 1 cm. The measured results supported the modeling, except for the small FOVs (below 8 cm), where the MTF could not be measured up to the cutoff frequency due to the focalspot limitation. The scanner reconstruction MTF was measured by the special-phantom method. The measured results demonstrated the increase in the average cutoff frequency (in the object plane) from 2.44 to 4.13 cy/mm as the scanner FOV decreased from 16 to 8 cm. The MTF could not be measured at the FOVs other than 8 and 16 cm, due to the calibration-reconstruction inaccuracies and, again, the focal-spot limitation. Overall, the evaluation confirmed the potential value of the VRX CT scanner and produced results important for its further development.

An approach for decomposition of visual images by clustering and pattern classification by structure features is considered. Multilevel hierarchical clusters such as rectangles, closed regions and integrated areas are proposed. Hierarchically constructed fragments are material to form pattern structure features. To reduce the clustering algorithm complexity the tolerance coefficient and quality criteria for merging process are proposed. The results of pattern classification by structure features for some image groups by hand and automatic regimes are presented in the article. Hierarchical trees are got for different number of structure coefficients as well as for absolute and relative merging functions.

The paper contains research results of graphic file format influence on image structure, quantitative changes in structuring coefficients of clustered images, influence of deformation changes caused by destruction processes on image quality. Clustering package for visual black-white and grey patterns was taken as the main instrument for investigation.

Photoluminescence (PL) spectroscopy has been used to characterize neutron-irradiated cubic silicon carbide crystals. The effects of thermal annealing (600-1100OC) on the PL bands have been studied. Several PL bands consisting of a sharp line and its phonon replicas have been observed in the 9-80 K temperature range. Certain of them like the D1 spectrum doublet with 1.975 eV and 1.977 eV zero-phonon lines (ZPL) at 9 K and the L2 spectrum with ZPL at 1.121 eV were reported previously for ion-implanted and electron irradiated 3C-SiC crystals, respectively. Besides, some new bands with ZPL at 2.027, 1.594, 0.989 and 0.844 eV and a broad band at 1.360 eV have been found. A correlation of PL and EPR spectra intensities of these neutron-irradiated and annealed cubic SiC crystals is briefly discussed.

EPR spectroscopy has been used to characterize neutron-irradiated cubic SiC samples after thermal annealing in the 200-1100OC temperature range. Three new paramagnetic defects named Ky6, Ky7 and Ky8 have been revealed. Based on the present results, these defects have been tentatively attributed to the negatively charged carbon vacancy-carbon antisite pair, negatively charged divacancy and neutral carbon split interstitial, respectively. Furthermore, the finding of practically isotropic hyperfine splitting for EPR lines of the T6 center confirms its assignment as a carbon vacancy-interstitial pair.

The method for pattern statistical features extraction and simplification is considered. Learning the artificial network by images from database allows to retrieve the nature images.

In this study, Boltzmann inversion is applied in conjunction with molecular dynamics simulations to derive inter-molecular potential for protein lysozyme in aqueous solution directly from experimental static structure factor. The potential has a soft repulsion at short distances and an attraction well at intermediate distances that give rise to the liquid-liquid phase separation. Moreover, Gibbs ensemble Monte Carlo simulations demonstrate that a non-spherical description of lysozyme is better suited to correctly reproduce the experimentally observed properties of such a phase separation. Our findings shed new light on the common problem in molecular and cell biology: “How to model proteins in their natural aqueous environments?”

Performance of the SAFT-VR equation of state developed for the hard sphere based simple fluids, namely the square-well, Sutherland and Yukawa fluids, is examined by comparing its results with simulation data and an augmented van der Waals (vdW) equation based on a Yukawa (Y) reference. Its shown that both for the equilibrium vapor–liquid data and data along selected isotherms in the liquid and supercritical fluid phases the vdW(Y) equation provides better results, particularly when going to lower temperatures.

The vapour–liquid phase diagram of long-range Yukawa fluids with the decay parameter zσ ≤ 1 is calculated by means of an augmented van der Waals theory based on the reference system that includes both the repulsive and short-range attractive interaction. Comparison with Monte Carlo simulation data, as well as with the traditional van der Waals approach based on a purely repulsive hard-sphere reference system and other semi-analytical theoretical approaches, is made.

A novel approach to perturbed equations of state for simple fluids is presented and its advantages over the traditional perturbed hard sphere equations are demonstrated by its application to several model fluids. The approach is based on a short range Yukawa reference which incorporates, in addition to repulsive interactions, also attractive interactions at short separations. The considered models of common interest are the Sutherland, Lennard-Jones, and EXP6 fluids. It is shown that using the proposed approach the reference system captures a good deal of properties of the studied fluids and that an accurate equation of state can be obtained using only the crude mean field (augmented van der Waals) approach.

In this study, we show that the inclusion of a short-range part of the total attractive interaction into a reference system allows a natural extension of the traditional first-order perturbation theory of simple fluids to practically all thermodynamic states. This theory is applied to the thermodynamic functions and the liquid–vapor coexistence curve of the Lennard-Jones-like medium range Yukawa fluid and to the Sutherland fluid. Comparison with computer simulation data and the second-order Barker–Henderson perturbation theory is discussed.

The detector presampling modulation transfer function (MTF) of a 576-channel variable resolution x-ray (VRX) computed tomography (CT) scanner was evaluated in this study. The scanner employs a VRX detector, which provides increased spatial resolution by matching the scanner's field of view (FOV) to the size of an object being imaged. Because spatial resolution is the parameter the scanner promises to improve, the evaluation of this resolution is important. The scanner's pre-reconstruction spatial resolution, represented by the detector presampling MTF, was evaluated using both modeling (Monte Carlo simulation) and measurement (the moving slit method). The theoretical results show the increase in the cutoff frequency of the detector presampling MTF from 1.39 to 43.38 cycles/mm as the FOV of the VRX CT scanner decreases from 32 to 1 cm. The experimental results are in reasonable agreement with the theoretical data. Some discrepancies between the measured and the modeled detector presampling MTFs can be explained by the limitations of the model. At small FOVs (1-8 cm), the MTF measurements were limited by the size of the focal spot. The obtained results are important for further development of the VRX CT scanner.

Scatter is a significant source of image artifacts in wide-cone CT. Scatter management includes both scatter rejection and scatter correction. The common scatter rejection approach is to use an anti-scatter grid (ASG). Conventional CT scanners (with detector coverage not exceeding 40mm along the patient axis) typically employ one-dimensional (1D) ASGs. Such grids are quite effective for small cone angles. For larger cone angles, however, simply increasing the aspect ratio of a 1D ASG is not sufficient. In addition, a 1D ASG offers no scatter rejection along the patient axis. To ensure adequate image quality in wide-cone CT, a two-dimensional (2D) ASG is needed. In this work, we measured the amount of scatter and the degree of image artifacts typically attributable to scatter for four prototype 2D ASG designs, and we compared those to a 1D ASG. The scatter was measured in terms of the scatter-toprimary ratio (SPR). The cupping and ghosting artifacts were assessed through quantitative metrics. For the 2D ASGs, when compared to the 1D ASG, the SPR decreased by up to 66% and 75% for 35cm water and 48cm polyethylene, respectively, phantoms, at 80-160mm apertures (referenced to isocenter), as measured by the pinhole method. As measured by the two-aperture method, the SPR reduction was 59%-68% at isocenter for the 35cm water phantom at 160mm aperture. The cupping artifact was decreased by up to ~80%. The ghosting artifact was reduced as well. The results of the evaluation clearly demonstrate the advantage of using a 2D ASG for wide-cone CT.

We propose a microscopic approach for investigating the behavior of a symmetric binary fluid mixture in the vicinity of the vapor-liquid critical point. The problem can be reduced to calculating the partition function of a 3D Ising model in an external field. For a square-well symmetric binary mixture, we express the parameters of the critical point as functions of the microscopic parameter r measuring the relative strength of interactions between the particles of dissimilar and similar species. The calculations are performed at intermediate (λ=1.5) and moderately long (λ=2) intermolecular potential ranges. The obtained results agree well with the results of computer simulations.

A two-Yukawa representation of the EXP6 fluids at supercritical temperatures and high pressures has been developed and examined using molecular simulations. A uniquely defined mapping of the repulsive part of the EXP6 potential curve onto the two-Yukawa potential is used. Two ranges of temperatures, one encountered in geochemical applications (T(geo) range) and the other at conditions of detonations (T(det) range), are considered and it is shown that the local structures of both fluids are practically identical. Deviations between the EXP6 and two-Yukawa potential functions at intermediate separations lead to differences in the thermodynamic properties of the two fluids at lower temperatures of the T(geo) range; at higher temperatures and in the high T(det) temperature range both the structural and thermodynamic properties of the EXP6 and two-Yukawa fluids are practically identical.

An oblique 2D variable resolution x-ray (VRX) detector is a new approach aimed to increase spatial resolution of volumetric CT imaging. The resolution increase results from rotating a 2D planar detector about two axes. In the initial phase of the development of such a detector, the increase in its projection spatial resolution and the side effects of its rotations were analyzed theoretically. The results of the analysis confirmed the feasibility of the proposed approach.

One of the possible ways of decompose and formalize visual images is to break them down into correct geometric figures and integrating the latter into fragments of the image. The article is dedicated to development and study of the algorithm for covering images with rectangles and region of rectangles for criteria, the parameters of which can be managed by user. Possible practical applications of these parameters management are also considered.

The detector presampling modulation transfer function (MTF) of a 576-channel variable resolution x-ray (VRX) computed tomography (CT) scanner was evaluated in this study. The scanner employs a VRX detector, which provides increased spatial resolution by matching the scanner's field of view (FOV) to the size of an object being imaged. Because spatial resolution is the parameter the scanner promises to improve, the evaluation of this resolution is important. The scanner's pre-reconstruction spatial resolution, represented by the detector presampling MTF, was evaluated using both modeling (Monte Carlo simulation) and measurement (the moving slit method). The theoretical results show the increase in the cutoff frequency of the detector presampling MTF from 1.39 to 43.38 cycles/mm as the FOV of the VRX CT scanner decreases from 32 to 1 cm. The experimental results are in reasonable agreement with the theoretical data. Some discrepancies between the measured and the modeled detector presampling MTFs can be explained by the limitations of the model. At small FOVs (1-8 cm), the MTF measurements were limited by the size of the focal spot. The obtained results are important for further development of the VRX CT scanner.

The test examples with the experimental software package based on the cluster approach are presented. The problem to cover some visual patterns by rectangles and more complex integrated areas is considered.

The basic VRX technique boosts spatial resolution of a CT scanner in the scan plane by two or more orders of magnitude by reducing the angle of incidence of the x-ray beam with respect to the detector surface. A four-arm Variable-Resolution X-ray (VRX) detector has been developed for CT scanning. The detector allows for "target imaging" in which an area of interest is scanned at higher resolution than the remainder of the subject, yielding even higher resolution for the focal area than that obtained from the basic VRX technique. The new VRX-CT detector comprises four quasi-identical arms each containing six 24-cell modules (576 cells total). The modules are made of individual custom CdWO4 scintillators optically-coupled to custom photodiode arrays. The maximum scan field is 40 cm for a magnification of 1.4. A significant advantage of the four-arm geometry is that it can transform quickly to the two-arm, or even the single-arm geometry, for comparison studies. These simpler geometries have already been shown experimentally to yield in-plane CT detector resolution exceeding 60 cy/mm (

A variable resolution x-ray (VRX) detector provides a great increase in the spatial resolution of a CT scanner. An important factor that limits the spatial resolution of the detector is x-ray cross-talk. A theoretical study of the x-ray cross-talk is presented in this paper. In the study, two types of the x-ray cross-talk were considered: inter-cell and inter-arm cross-talk. Both types of the x-ray cross-talk were simulated, using the Monte Carlo method, as functions of the detector field of view (FOV). The simulation was repeated for lead and tungsten separators between detector cells. The inter-cell x-ray cross-talk was maximum at the 34-36 cm FOV, but it was low at small and the maximum FOVs. The inter-arm x-ray cross-talk was high at small and medium FOVs, but it was greatly reduced when variable width collimators were placed on the front surfaces of the detector. The inter-cell, but not inter-arm, x-ray cross-talk was lower for tungsten than for lead separators. From the results, x-ray cross-talk in a VRX detector can be minimized by imaging all objects between 24 cm and 40 cm in diameter with the 40 cm FOV, using tungsten separators, and placing variable width collimators in front of the detector.

A technique called Variable-Resolution X-ray (VRX) detection greatly increases the spatial resolution in computed tomography (CT) and digital radiography (DR) as the field size decreases. The technique is based on a principle called `projective compression' that allows both the resolution element and the sampling distance of a CT detector to scale with the subject or field size. For very large (40 - 50 cm) field sizes, resolution exceeding 2 cy/mm is possible and for very small fields, microscopy is attainable with resolution exceeding 100 cy/mm. This paper compares the benefits obtainable with two different VRX detector geometries: the single-arm geometry and the dual-arm geometry. The analysis is based on Monte Carlo simulations and direct calculations. The results of this study indicate that the dual-arm system appears to have more advantages than the single-arm technique.

A technique called Variable-Resolution X-ray (VRX) detection that greatly increases the spatial resolution in computed tomography (CT) and digital radiography (DR) is presented. The technique is based on a principle called 'projective compression' that allows the resolution element of a CT detector to scale with the subject or field size. For very large (40 - 50 cm) field sizes, resolution exceeding 2 cy/mm is possible and for very small fields, microscopy is attainable with resolution exceeding 100 cy/mm. Preliminary results from a 576-channel solid-state detector are presented. The detector has a dual-arm geometry and is comprised of CdWO4 scintillator crystals arranged in 24 modules of 24 channels/module. The scintillators are 0.85 mm wide and placed on 1 mm centers. Measurements of signal level, MTF and SNR, all versus detector angle, are presented.

The liquid-vapor phase diagram and surface tension for the Sutherland fluids with a variable range of interaction have been determined by canonical Monte Carlo simulations and compared with the augmented van der Waals analytic theory. The theory, based on a short-range Yukawa reference, performs well for medium-range models but its accuracy deteriorates with the shortening range due to deteriorating accuracy of the underlined analytic mean spherical approximation solution for the reference Yukawa potential. The simulation results are also analyzed from the point of the extended principle of corresponding states and it is shown that the surface tension and also, to a certain degree of accuracy, the vapor-liquid coexistence curve satisfy the principle.

A novel perturbation approach for the structure factor S(k) of the Lennard-Jones-type Yukawa fluid with z=1.8 is presented. An approach is based on a new reference system, that is, the short-range Yukawa model with z0>z=1.8. By choosing for the reference system the value z0=6, it is shown that (i) the proposed approach for S(k) performs much better than the traditional hard-sphere reference perturbation method does; (ii) the use of an approximate mean spherical (MSA) description of the reference structure factor provides the results for S(k) that are more accurate as those obtained from the direct MSA computations; and (iii) the results obtained for S(k) tend to reproduce “exact” simulation results when accurate simulation data for the reference system are used.