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We investigated the radiative properties of InGaN/GaN heterostructures with multiple quantum wells (MQWs) grown on silicon substrates with different thicknesses of quantum wells at optical excitation. The correlation of laser and photoluminescent properties with the surface morphology of the gallium nitride coating layers and the density of V-defects has been established. It is shown that, with a growth in the density of V-defects, the threshold power density of the excitation of the generation of InGaN/GaN heterostructures with MQWs increases.

The structural features of aggregation in magnetic fluids based on solutions of the surfactant polysorbate-80 (tween-80) were investigated. Using small-angle X-ray and neutron scattering and dynamic light scattering the fractional distributions of magnetite and cobalt ferrite nanoparticles in a liquid carrier were obtained, for which a comparative analysis was carried out. In the case of neutron scattering, to analyze the contributions from different components of the solutions, a contrast variation based on mixtures of light and heavy water was additionally applied. As a result, it was shown that the studied systems have a more complex structure than classical magnetic fluids, when magnetic nanoparticles form “core-shell” complexes with surfactant molecules, and represent solutions of large associates (size of about 100 nm). Nevertheless, the dispersions show colloidal stability for a long (at least one year) time.

—This article discusses the results of parallel measurements with two-coordinate position-sensitive He3 detectors with a delay line, which are installed on REFLEX and GRAINS neutron spectrometers of the IBR-2 pulsed reactor with the simultaneous use of three data acquisition systems: DeLiDAQ-1, DeLiDAQ-2, and a system based on the N6730 digitizer produced by CAEN.

The article is devoted to studying prerequisites for the formation of the institutional environment of the economy of joint consumption in the current digital environment. From the standpoint of institutional theory, the institutional environment is understood as an ordered set of institutions that determine the constraints for economic agents in making innovative managerial decisions. The peculiarities of the institutional environment functioning are determined by the mutual support of the institutions, which is ensured by performing their respective functions. It is proved that the development of the relationship between formal and informal institutions is one of the key factors of institutional dynamics. It needs not only the formation but also the perception of the rules and norms accepted in society. Formal constraints, rules, and institutions emerge for the most part from the principles of already existing informal rules and mechanisms that enforce them. The functions of the institutional environment, which generally represent the activities aimed at streamlining the actions to maintain stability in society, are highlighted.

The development of the sharing economy results in the transformation of the social and economic institutions capable of both fostering and hindering the development of the economic system. Such institutions function as a means of reducing transaction costs. The economic effect of the digital revolution lies in slashing the transaction costs whereas all the previous industrial revolutions made for technology cost reduction and transaction cost escalation. At the same time, the total costs decreased and the transaction costs increased at an accelerating pace. The reduction in transaction costs is possible due to the transformation of business models and institutions. The sharing digital economy is a complex of technologies based on the artificial intelligence (AI) that allows transaction costs reduction accompanied by the emergence of a set of institutions. The article studies the functions of the institutional environment subject to the transformation in the sharing economy. The functions of the institutes this research accounts for are attributable to the fundamental regulatory relations between the economic agents which concern the changing character of the shared enjoyment of the property rights. Another promising area of the research is believed to be the analysis of the sharing economy’s effect on the transformation of the economic institution of property triggered by the new challenges originating from the inferiority of the traditional economic institutions.

Structural aspects of powders containing magnetic nanoparticles Fe3O4/CoFe2O4 with the anticipated “core-shell” structure are considered by means of comparative analysis with individual particles of Fe3O4, CoFe2O4 in accordance of data obtained from X-ray powder diffraction and small-angle scattering of X-ray (synchrotron) radiation and neutrons. It is shown that magnetic particles in the powders under study have a strong polydispersity and form complex aggregates. Characteristic sizes of the crystallites, as well as a ratio of magnetite to cobalt-ferrite in the composition of the Fe3O4/CoFe2O4 particles were evaluated from the analysis of the diffraction peaks. Аnalyzing the data on small-angle scattering, the dimensional characteristics of particles and aggregates, as well as the volume fraction of the last ones in the powders, have been obtained. Fractal dimensions of aggregates are determined. A significant difference is observed in the scattering on Fe3O4/CoFe2O4 particles and the total scattering consisting of partial contributions to scattering on individual magnetite (Fe3O4) and cobalt-ferrite (CoFe2O4) powders, which does not exclude the formation of the “core-shell” structure.

Structure characterization of magnetic fluids (MFs) synthesized by three different methods in aqueous solutions of agarose was done by means of small-angle neutron (SANS) and synchrotron X-ray scattering (SAXS). The differences in the complex aggregation observed in the studied magnetic fluids were related to different stabilizing procedures of the three kinds of MFs. The results of the analysis of the scattering (mean size of single polydisperse magnetic particles, fractal dimensions of the aggregates) are consistent with the data of transmission electron microscopy (TEM).

In the article, using the example of earthquakes that occurred in Japan in 2003 and 2011, the results of the method verification proposed by the author for destructive earthquakes prediction are given. The method involves the identification of zones with a seismic signal level higher in relation to the surrounding areas, the construction of a seismic signals total trend registered at each of the seismic stations located in this zone. The total trend is approximated by the trend model. The model is designed in such a way that the predicted parameters: the time of the earthquake and the coordinates of its epicenter are included in its mathematical structure. These parameters are determined in the parametric identification process of the model based on the results of seismic signals regular monitoring performed on each of the reference seismic stations. Further, on the basis of these data and the known strength of the reference earthquake, the strength of the future earthquake is determined. Verification showed that the prediction of earthquakes, carried out in accordance with the method considered in the article, has a high degree of reliability and stable repeatability of the forecast throughout the entire period of observation of the developing earthquake. This property of the technique is explained by the fact that it is based on the study of the dynamics of the change in the prognostic trait, and not on the generally accepted current consideration of the current (static) value of the trait. Positive results of verification served as the basis for the approbation of the method, which allowed predicting the time, coordinates of the epicenter and the strength of the ripening earthquakes in the Nanking Valley area., На примере землетрясений, произошедших в Японии, в 2003 и 2011 гг., Приведены результаты верификации предложенной автором методики прогнозирования разрушительных землетрясений. Методика предполагает выявление зон с повышенным относительно окружающих территорий уровнем сейсмического сигнала, построение суммарного тренда сейсмических сигналов, зарегистрированных на каждой из размещенных в этой зоне опорных сейсмостанций. Суммарный тренд аппроксимированы моделью тренда. Модель составлена таким образом, что прогнозируемые параметры: время наступления землетрясения и координаты его эпицентра, включенные в ее математическую структуру. Эти параметры определяют в процессе параметрической идентификации модели по результатам регулярного мониторинга сейсмических сигналов, выполняется на каждой из опорных сейсмостанций. Далее на основании этих данных и известной силы эталонного землетрясения определяют силу будущего землетрясения. Верификация показала, что прогнозирование землетрясений, осуществляемое в соответствии с рассматриваемой в статье методики, имеет высокую степень достоверности и устойчивую повторяемость прогноза течение всего периода наблюдения за землетрясением, зреет. Это свойство методики объясняется тем, что она основывается на изучении динамики изменения прогностической признаки, а не на общепринятом в настоящее время рассмотрении текущего (статического) значение признака. Положительные результаты верификации стали основанием для апробации методики, в результате чего было прогнозируемо время, координаты эпицентра и силу землетрясения, зреет в районе Нанкинской впадины., На прикладі землетрусів, що сталися в Японії, в 2003 і 2011 рр., наведено результати верифікації запропонованої автором методики прогнозування руйнівних землетрусів. Методика передбачає виявлення зон з підвищеним відносно оточуючих територій рівнем сейсмічного сигналу, побудову сумарного тренду сейсмічних сигналів, зареєстрованих на кожній з розміщених у цій зоні опорних сейсмостанцій. Сумарний тренд апроксимовано моделлю тренду. Модель складена таким чином, що прогнозовані параметри: час настання землетрусу і координати його епіцентру, включені в її математичну структуру. Ці параметри визначають в процесі параметричної ідентифікації моделі за результатами регулярного моніторингу сейсмічних сигналів, що виконується на кожній з опорних сейсмостанцій. Далі на підставі цих даних і відомої сили еталонного землетрусу визначають силу майбутнього землетрусу. Верифікація показала, що прогнозування землетрусів, здійснюване відповідно до розглянутої в статті методики, має високий ступінь достовірності і стійку повторюваність прогнозу протягом усього періоду спостереження за землетрусом, що зріє. Ця властивість методики пояснюється тим, що вона ґрунтується на вивченні динаміки зміни прогностичної ознаки, а не на загальноприйнятому в даний час розгляді поточного (статичного) значення ознаки. Позитивні результати верифікації стали підставою для апробації методики, в результаті чого було прогнозовано час, координати епіцентру і силу землетрусу, що зріє в районі Нанкінської западини.

Two different chemical methods (co-precipitation from solution of diethylene glycol and cryogenic method) for the synthesis and dispersing of magnetic nanoparticles into water with coating by double layer of sodium oleate are compared with respect to the final structural organization of magnetic fluids obtained. Basing on the data of X-ray diffraction (XRD), transmission electron microscopy (TEM), small-angle X-ray (SAXS) and neutron (SANS) scattering it was shown that both methods result in stable in time solutions of polydisperse magnetite particles with the average size of about 10 nm, which are partially aggregated. The aggregation rate is different for the two types of the systems, which correlates with the aggregate density and surfactant content in them determined by the SANS contrast variation (H/D substitution in solvent).

Structure characterizations of concentrated water-based magnetic fluids stabilized by oleic and lauric acids were done by means of small-angle neutron scattering (SANS) and complemented by dynamic light scattering and magnetization analysis. Stability of ferrofluids with time against sedimentation was concluded despite the presence of aggregates in solutions. Differences in the average sizes of individual polydisperse magnetite nanoparticles coated with surfactants and their aggregates were revealed. Structural parameters obtained from SANS have been confirmed by magnetogranulometry data. The comparative analysis of the aggregation and its change upon dilution is made basing on the data of SANS and dynamic light scattering techniques.

The understanding of stabilization mechanisms for ferrofluids (which are presented as fine dispersions of magnetic nanoparticles coated with surfactants) is an important favorable circumstance in the synthesis of highly stable magnetic colloids with specific properties. The presented work reviews principal results that were obtained in thorough investigations of ferrofluid’s stability regarding changes in the structure at nanoscale under various conditions, including the determination and analysis of the agglomeration regimes in biocompatible ferrofluids for biomedical applications. The structural features of the ferrocolloids and concomitant surfactant solutions were revealed and further analyzed principally relying on the data of Small-Angle Neutron Scattering (SANS). Thereby, for magnetic fluids prepared on the basis of nonpolar liquids (benzene, decalin) with magnetite nanoparticles covered by a single-layer shell of monocarboxylic acids, the studying of the effect of surfactant excess showed a tendency to a significant enhancement of the effective attraction between free (non-adsorbed) acid molecules. This explains the sharp and sudden loss of a ferrofluid’s stability that occurs because of the liquid crystal transition when exceeding some critical concentration of an acid. This transition depends strongly on an interparticle solvent-acid interaction and peculiarity of the different critical concentrations is for different solvents. For an aqueous ferrofluid (nanomagnetite stabilized with a double-layered shell of sodium oleate (SO)) that is used as a precursor for a biocompatible modification with polyethylene glycol (PEG), the fraction of micelles of non-adsorbed surfactant and its change under modification were found by SANS. The comparison with another kinds of water-based ferrocolloids showed the different rate of surfactant adsorption on magnetite particles surface depending on the surfactant type. The aggregate reorganization and its growth in the ferrofluid after ‘PEGylation’ were observed. In order to illuminate the possible influence of the micelle formation with free surfactants on this process in the presence of polymer, the SANS study was performed on mixed SO/PEG aqueous solutions. SANS results revealed drastic morphological and interacting changes of micelles due to addition of PEG. In particular, it was concluded the screening of the micelle interaction due to the formation of an effective PEG shell around micelles at high (about 10 vol%) concentration of the polymer.

Structural parameters of the magnetite-oleic acid-decalin magnetic fluid at various excesses of oleic acid (up to 25 vol %) have been determined using small-angle neutron scattering. Based on the comparison of the behavior of oleic acid in the magnetic fluid and in the pure solvent (decalin), it has been concluded that the interaction between the molecules of free (unadsorbed) surfactant changes in the presence of magnetic nanoparticles. However, the system remains stable and does not form aggregates of magnetic particles or free oleic acid. These results are compared with the previously presented data for similar benzene-based magnetic fluids.

Factors affecting the determination of the structural parameters of polydisperse particles of typical magnetic fluids (MFs) from small-angle neutron scattering data (SANS), including the possible anisotropy of the particle shape and the residual incoherent background, are analyzed. It is shown that the effect of particle anisotropy on scattering must be considered in combination with the influence of their polydispersity. The relative shift in the MF’s structural parameters caused by particle anisotropy does not exceed 10–20% for particles with an anisotropy parameter which is less than four and becomes insignificant for more anisotropic particles. The main effect of the residual incoherent background of neutron scattering is related to determination of the thickness of the stabilizing shell and the generalized contrast parameter. It is shown that restrictions on the available maximum values of the scattering vector, measured in the experiment, lead to a relative shift in these parameters by up to 10%, while the other structural parameters (the average particle radius and the width of the size distribution) are determined with sufficiently high accuracy (the relative systematic error is 5% or less).

The possibility to conduct the experiment on small-angle neutron scattering on very dilute magnetic fluids (the volume fraction of magnetite is ∼0.1%) is discussed. The aim of these experiments is to determine the structural parameters of these fluids using the Guinier approximation. Primary attention is concentrated on the experimental observation of a nonmagnetic layer on the surfaces of magnetic nanoparticles dispersed in a liquid carrier. Significant parameters are determined, and conditions for the experiment on the contrast variation are chosen in model calculations.

The structural behavior of the liquid system based on a C70 in an N-methyl-2-pyrrolidone–toluene mixture has been analyzed, by using the small-angle neutron scattering method. The experimental results testify to the selective solvation in the system. The corresponding mechanisms have been discussed.

Based on modeling and numerical calculations, the electrophysical principles for development of innovative electrogasdynamic electropneumatic converters using turbulization of gas jets by a unipolar ion flow induced in the external area of a corona discharge within narrow interelectrode gaps and with different electrode configurations are formulated.

Fe(CN)6 3 - and Fe(CN)6 4 - anions are sorbed from aqueous solutions of their potassium and cesium salts on β-Ni(OH)2 by the mechanism of anion exchange with hydroxy groups. Alkali metal cations (K+, Cs+) are also partly sorbed on nickel(II) hydroxide in the form of anionic complexes (K,Cs) z Fe(CN)6 (n - z)-, where n = 3 or 4 (0 < z < n). The chemical composition of the new phase appearing in contact of nickel(II) hydroxide with aqueous potassium and cesium hexacyanoferrates(II, III) was determined by X-ray phase analysis and IR spectroscopy.

Methods of reducing the errors in measuring the chromaticity coordinates of objects using a three-channel photoelectric colorimeter and automatic recognition of the type of light source, with an appropriate zonal correction of the colorimeter readings, are considered. It is shown that the proposed methods enable the error in measuring the chromaticity coordinates of light sources to be reduced several-fold.

Sorption of Hg(II) on β-Ni(OH)2 was studied as influenced by chloride ion concentration and pH of the solutions, affecting the Hg(II) speciation. The sorption mechanism was considered.

The stability of cylindrical composite shells under dynamic external pressure is discussed. A criterion for determining the load-carrying capacity based on Malmeister's equation with respect to bending parts of deformation is proposed. Optimization of the shell mass relative to various structural parameters has been carried out as a nonlinear programming problem. Numerical results are given.

The asymptotic behavior in L p ,where 1 ≤ p ≤ + ∞,of the spectral function of a perturbed discrete operator, defined on an n-dimensional compact manifold, is found.

A classification is obtained of the irreducible representations of the group indicated in the title. It is shown that a description of the complex representations of the general linear group of arbitrary degree over a residue ring modulo a primary number contains the problem of a matrix pair.

We give a description of the properties of the system of irreducible complex representations of classical groups over finite fields without using characters of representations. The description involves a multiplication of irreducible representations that generalizes the multiplication introduced by Green. More precisely, we define the concept of a prime representation and prove some results on the structure of products containing a prime representation of a classical group.

We obtain a description of all irreducible complex representations of the group indicated in the title (p ≠ 2 is a prime). Namely, for each n ≥ 2 we distinguish three series of representations of degrees (p + 1)pn−1, (p2 − 1)pn−2, (p − 1)pn−1. The other representations of\(GL(2,Z_{p^n } )\) are obtained from representations of\(GL(2,Z_{p^{n - 1} } )\) by tensor multiplication by one-dimensional representations.