Proceedings of the National Academy of Sciences of Belarus. Series of Physical-Mathematical Sciences / Известия Национальной академии наук Беларуси. Серия физико-математических наук
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ПОЛУЧЕНИЕ И РЕНТГЕНОГРАФИЧЕСКИЕ ИССЛЕДОВАНИЯ ТВЕРДЫХ РАСТВОРОВ Cu2CdSn(SxSe1–x)4
Get PDFThe quaternary semiconductors Cu2CdSnS4, Cu2CdSnSe4 and Cu2CdSn(SxSe1–x)4 solid solutions were synthesized by the one-temperature method from the elementary components. The X-ray diffraction method showed that the obtained polycrystalline samples are single-phased. The unit cell parameters of the synthesized compounds and Cu2CdSn(SxSe1–x)4 solid solutions were determined from diffraction spectra by the full-profile analysis using the Rietveld method with the Fullprof software package. It has been established that with an increase in sulfur concentration, the unit cell parameters decrease smoothly linearly in accordance with the Vegard rule, which indicates the formation of a continuous series of solid solutions in the Cu2CdSn(SxSe1–x)4 system within the range 0 ≤ x ≤ 1. The parameter of crystal lattice tetragonal distortions h of the investigated compounds is calculated. The h values are close to 1 for all the compositions studied, which indicates a small crystal lattice distortion of the obtained samples.Методом однотемпературного синтеза из элементарных компонентов синтезированы четверные полупроводниковые соединения Cu2CdSnS4, Cu2CdSnSe4 и твердые растворы Cu2CdSn(SxSe1–x)4. Рентгенографическим методом показано, что полученные поликристаллические образцы являются однофазными. Из дифракционных спектров полнопрофильным анализом по методу Ритвельда с использованием программного пакета Fullprof опре- делены параметры элементарной ячейки синтезированных соединений и твердых растворов Cu2CdSn(SxSe1–x)4. Установлено, что с ростом концентрации серы параметры элементарной ячейки плавно уменьшаются по линейному закону в соответствии с правилом Вегарда, что свидетельствует об образовании в системе Cu2CdSn(SxSe1–x)4 непрерывного ряда твердых растворов в области 0 ≤ x ≤ 1. Рассчитан параметр тетрагональных искажений кристаллической решетки исследованных соединений h. Значения h близки к единице для всех изученных составов, что свидетельствует о малых искажениях кристаллической решетки полученных образцов
ПОИСК И ИДЕНТИФИКАЦИЯ ЭФФЕКТОВ ДОПОЛНИТЕЛЬНЫХ ПРОСТРАНСТВЕННЫХ ИЗМЕРЕНИЙ В ПРОЦЕССЕ РОЖДЕНИЯ ПАР ЛЕПТОНОВ НА БОЛЬШОМ АДРОННОМ КОЛЛАЙДЕРЕ LHC
Get PDFN. Arkani-Hamed, S. Dimopoulous, and G. Dvali have proposed a model (ADD) of low-scale quantum gravity featuring large extra dimensions. In this model, the exchange of Kaluza – Klein towers of gravitons can enhance a production rate of lepton pairs at high invariant mass in proton-proton collisions at LHC. By considering the present and future LHC energy regimes, we have again analyzed the LHC potential to discover the effects of large extra dimensions and to discriminate between various theoretical models. Specifically, in the latter case we explore the LHC capability to distinguish spin-2 Kaluza – Klein towers of gravitons exchange from other new physics effects which might be conveniently parametrized by the four-fermion contact interactions. We find that LHC with planned energy of 14 TeV and luminosity of 100 fb–1 will be capable of discovering (and identifying) graviton exchange effects in the large extra dimensions with the cutoff parameter of the order MS = 6.2 TeV (4.8 TeV) for d = 6 and MS = 8.8 TeV (6.8 TeV) for d = 3.
ПЕРСПЕКТИВЫ ИДЕНТИФИКАЦИИ НОВЫХ ФИЗИЧЕСКИХ СЦЕНАРИЕВ НА КОЛЛАЙДЕРЕ LHC В ЦЕРНе
Get PDFThe signatures of the spin-2 graviton excitations predicted by the Randall – Sundrum model with one warped extra dimension, in dilepton and diphoton production at LHC were studied. By using the center – edge asymmetry, we evaluate the ranges of mass and coupling constant where such gravitons can be discriminated against competitor spin-1 and spin-0 objects that could potentially manifest themselves in these processes. Depending on the value of coupling constants, the numerical results allow one to obtain graviton identification mass ranges of the order of 2.4 TeV and 3.2 TeV for LHC nominal energy of 14 TeV and time-integrated luminosity of 100 fb–1. Исследованы эффекты возбужденных состояний гравитонов со спином 2, предсказываемых моделью Рендалл – Сандрума с одним искаженным дополнительным измерением, в процессах дилептонного и дифотонного рождения на Большом адронном коллайдере LHC. С помощью асимметрии центр-край мы оцениваем интервал масс и констант связи, где такие гравитоны могут отличаться от конкурирующих объектов со спином 1 и 2 в исследуемых процессах. В зависимости от величины констант связи численный анализ позволяет определить область идентификации масс гравитона, верхняя граница которого составляет 2,4 и 3,2 ТэВ для LHC с номинальной энергией 14 ТэВ и интегральной светимостью 100 фб–1.
МЕТОДЫ ПОСТРОЕНИЯ ОБУЧАЮЩЕГО НАБОРА ДЛЯ КАЛИБРОВКИ С ПОМОЩЬЮ ФЛУОРЕСЦЕНТНОЙ СПЕКТРОСКОПИИ НЕБОЛЬШИХ ВЫБОРОК ОБРАЗЦОВ
Get PDFA limited number of samples and an impossible a priori control of a desired parameter value stipulate how it is important to solve the problem of selecting a training set for calibration by the multivariate spectral analysis in order to reduce a calibration error. Possible variants of a training subset selection from small data sets are shown for temperature calibration with fluorescence spectra of Yb3+:CaF2 recorded in the range of 880–1120 nm with a resolution of about 0.2 nm for the temperature range from 66 to 150 °C and at a step of 2 °C. The methods applied are the uniform distribution, the Kennard and Stone algorithm and the cluster analysis in principal component space. The effect of the method choice on the calibration accuracy has been evaluated. The application of the principal component analysis gives the possibility to select spectra without a priori knowledge of a temperature, to which the fluorescence spectra correspond. The root-mean-square error of the predicted temperature value is shown to be 3.98 ° C for the uniform distribution of the training subset samples over the space of the first principal component and 1.07 ° C for the Kennard and Stone algorithm. The minimum root-mean-square prediction error of 0.98 °C is shown to be achieved with the training subset selection by the hierarchical cluster analysis in the space of the principal components of the spectra studied
Распределение ИК-излучения от нелокального источника внутри биологической ткани
Get PDFNon-invasive thermographic methods are based on the measurement of IR radiation from human tissue and, by which using Kirchhoff’s law, it restores the temperature of the examined body region. The disadvantage of this method is that the temperature image is noisy due to the thermal influence of the tissue layer between the organ under study inside the medium and the thermal imager. This degrades the quality of the image under consideration. Using the data on the temperature distribution inside the biological medium from a point source, the expression for the temperature from different-shape sources was obtained. The influence of various factors on the brightness increment distribution at the medium surface from a source shaped as a cylinder is studied. These include the source depth in the medium, the radiation wavelength, the absorption index, the heat transfer parameter, the cylinder height and diameter. The brightness increment from the source and the natural brightness of the skin surface are compared. It is shown how the source brightness changes the full brightness of the surface in a wide spectral interval
ОБОБЩЕННЫЕ ИНТЕРПОЛЯЦИОННЫЕ МНОГОЧЛЕНЫ ЭРМИТА – БИРКГОФА ДЛЯ ДИФФЕРЕНЦИАЛЬНЫХ ОПЕРАТОРОВ ПРОИЗВОЛЬНОГО ПОРЯДКА В ЧАСТНЫХ ПРОИЗВОДНЫХ
Get PDFThis article is devoted to the problem of construction and research of the generalized Hermite – Birkhoff interpolation formulas for arbitrary-order partial differential operators given in the space of continuously differentiable functions of many variables. The construction of operator interpolation polynomials is based both on interpolation polynomials for scalar functions with respect to an arbitrary Chebyshev system, and on the generalized Hermite – Birkhoff interpolation formulas obtained earlier by the authors for general operators in functional spaces. The presented operator formulas contain the Stieltjes integrals and the Gateaux differentials of an interpolated operator. An explicit representation of the error of operator interpolation was obtained. Some special cases of the generalized Hermite – Birkhoff formulas for partial differential operators are considered. The obtained results can be used in theoretical research as the basis for constructing approximate methods for solution of some nonlinear operator-differential equations found in mathematical physics
МОДЕЛИРОВАНИЕ ПЕРЕНОСА ЗАРЯДОВ В ТОКОВОМ РЕЖИМЕ В АКТИВНОМ ОБЪЕМЕ ИОНИЗАЦИОННОЙ КАМЕРЫ ДЕЛЕНИЯ1
Get PDFCharge transport in the active volume of the cylindrical ionization fission chamber (FC) in the current mode has been studied. The model is based on the continuity equations for ions and electrons, as well as on Poisson’s equation for the electric field. The source for the continuity equations is calculated taking into account a correct distribution of the initial ionization density in the active volume of the chamber and the charge, mass, and energy dependent distributions of the fission fragments. The distributions of the ion and electron density and electric fields inside the active volume are found for two types of chambers – miniature chambers and “large” chambers with the consideration of the space charge. The correct algorithm for calculation of the beginning of the plateau of the current-voltage characteristic – the minimum voltage on the FC to provide the stationary operation of the chamber is given. It is shown that the often used condition of the electric field absence at the anode E (ra ) = 0 to determine this value is incorrect, since it leads to complex values of the electric field inside the chamber active volume. Neglecting the processes of ion diffusion and recombination, the sensitivity and output current of the chamber in the stationary mode are calculated. Calculations have been carried out for miniature and “large” chambers. It has been shown that the use of the approximation for the generation density of ion pairs by the fission fragment along its track to be constant, often used in practice for “large” chambers, leads to significant errors when estimating the densities of ions, electrons and electric fields inside the FC; at that, the sensitivity may differ by an order of magnitude.
РАСПРЕДЕЛЕНИЕ ТЕМПЕРАТУРЫ В ПОЛУБЕСКОНЕЧНОЙ СРЕДЕ, ОБУСЛОВЛЕННОЕ ИСТОЧНИКАМИ РАЗНОЙ ФОРМЫ
Get PDFThermographic methods based on IR images are actively used in medical practice for the early diagnosis of diseases, in clinical procedures and surgical operations. One of the weak points of the above methods is that the images are noisy due to the thermal influence of a tissue layer located between a human organ under examination and a thermal imager and they therefore carry only indirectly information about the temperature regime of internal organs. In order to improve the accuracy of remote thermographic methods, as applied to the human skin, the method of temperature estimation due to the presence of heat sources of different origin in the tissue has been developed. This method is based on using the linear systems theory approach and the calculation results of a point source. Sources in the shape of a sphere, a cylinder of different orientation, straight lines, and a circle are considered. Specific features of thermal fields from heat sources are indicated. Simple computational models are obtained for a temperature from a spherical source inside and outside it in an infinite medium. Temperatures from a heated line of finite and infinite length are compared. Using the example of a cylindrical heat source, the temperature inside and outside the source is analyzed in detail as a function of thermal physical parameters, occurrence depth and sizes. Particular attention is paid to comparing the results of the temperature distribution on the surface of the skin and its sizes. The given results can be used for temperature correction in thermographic studies
ПЕРЕЧЕНЬ СТАТЕЙ, ОПУБЛИКОВАННЫХ В ЖУРНАЛЕ «ВЕСЦI НАЦЫЯНАЛЬНАЙ АКАДЭМІІ НАВУК БЕЛАРУСI. СЕРЫЯ ФIЗІКА-МАТЭМАТЫЧНЫХ НАВУК» в 2017 году
Get PDFList of Publications for 2017 in “Proceedings of the National Academy of Sciences of Belarus. Physics and Mathematics Series”.Перечень статей, опубликованных в журнале «Весцi Нацыянальнай акадэміі навук Беларусi. Серыя фiзіка-матэматычных навук» в 2017 году
