Confinement and electron correlation effects in photoionization of atoms in endohedral anions: Ne@C60^{z-}

Trends in resonances, termed confinement resonances, in photoionization of atoms A in endohedral fullerene anions A@C60^{z-} are theoretically studied and exemplified by the photoionization of Ne in Ne@C{60}^{z-}. Remarkably, above a particular nl ionization threshold of Ne in neutral Ne@C60 (I_{nl}^{z=0}), confinement resonances in corresponding partial photoionization cross sections sigma_{nl} of Ne in any charged Ne@C60^{z-} remain almost intact by a charge z on the carbon cage, as a general phenomenon. At lower photon energies, omega < I_{nl}^{z=0}, the corresponding photoionization cross sections develop additional, strong, z-dependent resonances, termed Coulomb confinement resonances, as a general occurrence. Furthermore, near the innermost 1s ionization threshold, the 2p photoionization cross section sigma_{2p} of the outermost 2p subshell of thus confined Ne is found to inherit the confinement resonance structure of the 1s photoionization spectrum, via interchannel coupling. As a result, new confinement resonances emerge in the 2p photoionization cross section of the confined Ne atom at photoelectron energies which exceed the 2p threshold by about a thousand eV, i.e., far above where conventional wisdom said they would exist. Thus, the general possibility for confinement resonances to resurrect in photoionization spectra of encapsulated atoms far above thresholds is revealed, as an interesting novel general phenomenon.Comment: 6 pages, 4 figures, Latex2e, jpconf.cls styl

Diffuse versus square-well confining potentials in modelling AA@C60_{60} atoms

Attention: this version-$2$ of the manuscript differs from its previously uploaded version-$1$ (arXiv:1112.6158v1) and subsequently published in 2012 J. Phys. B \textbf{45} 105102 only by a removed typo in Eq.(2) of version-$1$; there was the erroneous factor "2" in both terms in the right-hand-side of the Eq.(2) of version-$1$. Now that the typo is removed, Eq.(2) is correct. A perceived advantage for the replacement of a discontinuous square-well pseudo-potential, which is often used by various researchers as an approximation to the actual C$_{60}$ cage potential in calculations of endohedral atoms $A$@C$_{60}$, by a more realistic diffuse potential is explored. The photoionization of endohedral H@C$_{60}$ and Xe@C$_{60}$ is chosen as the case study. The diffuse potential is modelled by a combination of two Woods-Saxon potentials. It is demonstrated that photoionization spectra of $A$@C$_{60}$ atoms are largely insensitive to the degree $\eta$ of diffuseness of the potential borders, in a reasonably broad range of $\eta$'s. Alternatively, these spectra are found to be insensitive to discontinuity of the square-well potential either. Both potentials result in practically identical calculated spectra. New numerical values for the set of square-well parameters, which lead to a better agreement between experimental and theoretical data for $A$@C$_{60}$ spectra, are recommended for future studies.Comment: 11 pages, 4 figure

Development and research of data transmission system using M-sequence

В исследовании синтезируется система передачи данных высокой помехозащищенности. Разработаны передающее и приемное устройства, реализующие метод расширения спектра, осуществляющие кодирование и декодирование передаваемого сообщения М-последовательностью. Схемы синтезированы в среде SysGen, эксперимент проведен на ПЛИС фирмы XILINX семейства Kintex7. Получение данных передатчиком осуществлялось с помощью стандарта «UART» со скоростью передачи 1,5 Мб/с. Эксперимент установил, что работоспособность системы ограничивается отношением мощности сигнала и помехи равной -14 дБ.A data transmission system with high noise immunity is synthesized. Transmitting and receiving devices, implementing the spread spectrum and carrying out transmitted message encoding and decoding by m‑sequence, are designed. Schemes are synthesized by using the SysGen software. The experiment is performed with Kintex7 PLD developed by XILINX. The system is based on the use of the standard «UART» with a rate of 1.5 Mbit/s. The experiment found that the system performance is limited by the signal-to-noise ratio equaled to -14 dB

Secure radio communication systems using encoded signal in time, frequency and phase

The original algorithm of transfer 8-bit digital data with use of signal, discretely-encoded in the timing, frequency and phase using the matrix of Costas and of Walsh functions, providing high reserve of work and security from broadband and narrow-band interferences is developed. The algorithms of generation and processing of signals on the receiving side is realized in FPGA of type XC7k325T (Xilinx).A radio communication system on the SDR technology (software defined radio) on the basis of the AD 9361 transceiver (Analog Devices).Разработан оригинальный алгоритм передачи 8-бит цифровых данных с использованием сигнала, дискретно-кодированного по времени, частоте и фазе с помощью матрицы Костаса и функций Уолша. Обеспечивается высокая скрытность работы и защищенность от широкополосных и узкополосных помех. Алгоритмы формирования сигналов и обработки их на приемной стороне реализованы в ПЛИС типа XC7k325T (Xilinx). Система радиосвязи реализована по технологии SDR (программно определяемое радио) на основе трансивера AD 9361 (Analog Devices)

Development and research characteristics of digital shortwave transceiver

The results of research and development on the SDR (software defined radio) transceiver using direct analogue-digital conversion in the receiver and digital signal conditioning at the transmitter. Algorithms for signal generation and processing them at the receiving end are implemented in FPGA type XC7k325T (Xilinx).Experimental research has shown high quality transceiver sensitivity characteristics of selectivity for all types of noise and spurious. It found a number of features in the noise performance of the main elements of the transceiver: an analog- digital converter (LTC 2208) and a digital signal generator (AD9957).Представлены результаты разработки и исследования трансивера по технологии SDR (программно определяемое радио) с прямым аналого-цифровым преобразованием в приемнике и цифровым формированием сигналов в передатчике. Алгоритмы формирования сигналов и обработки их на приемной стороне реализованы в ПЛИС типа XC7k325T (Xilinx). Экспериментальное исследование трансивера показало высокое качество характеристик по чувствительности, избирательности по всем видам помех и побочным излучениям. Обнаружен ряд особенностей в шумовых характеристиках основных элементов трансивера: аналого-цифрового преобразователя (LTC 2208) и цифрового формирователя сигналов (AD9957)

Vacancy decay in endohedral atoms: the role of non-central position of the atom

We demonstrate that the Auger decay rate in an endohedral atom is very sensitive to the atom's location in the fullerene cage. Two additional decay channels appear in an endohedral system: (a) the channel due to the change in the electric field at the atom caused by dynamic polarization of the fullerene electron shell by the Coulomb field of the vacancy, (b) the channel within which the released energy is transferred to the fullerene electron via the Coulomb interaction. % The relative magnitudes of the correction terms are dependent not only on the position of the doped atom but also on the transition energy \om. Additional enhancement of the decay rate appears for transitions whose energies are in the vicinity of the fullerene surface plasmons energies of high multipolarity. % It is demonstrated that in many cases the additional channels can dominate over the direct Auger decay resulting in pronounced broadening of the atomic emission lines. % The case study, carried out for Sc$^{2+}$@C$_{80}^{6-}$, shows that narrow autoionizing resonances in an isolated Sc$^{2+}$ within the range \om = 30... 45 eV are dramatically broadened if the ion is located strongly off-the-center. % Using the developed model we carry out quantitative analysis of the photoionization spectrum for the endohedral complex Sc$_3$N@C$_{80}$ and demonstrate that the additional channels are partly responsible for the strong modification of the photoionization spectrum profile detected experimentally by M\"{u}ller et al. (J. Phys.: Conf. Ser. 88, 012038 (2008)).Comment: 32 pages, 11 figure

Mechanical activation influence on the morphological properties of La[2]O[3]-TiO[2]-B

The influence of mechanical activation of the powder mixture used to obtain the high-perfomance cathode for accelerating engineering with the SHS-method has been explored. The mechanically processed mixtures have been morphologically analyzed. The optimal modes of mechanical activation have been determined for the mixture

МОДЕЛИРОВАНИЕ ПРОЦЕССА ПОЛУНЕПРЕРЫВНОГО ВЫДАВЛИВАНИЯ ПОРИСТОЙ ЗАГОТОВКИ

Semicontinuous extrusion of the infinite length rods from preliminarily compacted and sintered powder copper is simulated. To minimize the external friction effect, hydrodynamic lubrication mode is used. The dependence of extrusion pressure on the puncheon travel at various die cone angles is presented. A procedure of construction of the grid of finite elements to solve the problems of computer modeling of semicontinuous extrusion of cylindrical samples is proposed. The mechanism of varying the porosity over the bar cross-section at various process stages is investigated. Mathematical models of semicontinuous extrusion are constructed.Осуществлено моделирование процесса полунепрерывного выдавливания прутков неограниченной длины из предварительно спрессованной и спеченной порошкообразной меди. Для минимизации действия внешнего трения применяется гидродинамический режим смазки. Приведена зависимость давления выдавливания от перемещения пуансона при различных углах конуса матрицы. Предложена методика построения сетки конечных элементов для решения задач компьютерного моделирования процесса полунепрерывного выдавливания цилиндрических образцов. Исследован механизм изменения пористости по сечению заготовки на различных стадиях процесса. Построены математические модели процесса полунепрерывного выдавливания

Области энергетической оптимальности схем экстрактивной ректификации смеси метанол - н-пропилацетат - толуол с анилином

This work is devoted for investigation of isocriterial manifolds and isocriterial fields arrangement into initial feed composition simplex. That fields and manifolds dividing of them are formed at methanol - n-propylacetat - toluene with aniline extractive distillation. Initial mixture contains one binary azeotrop with minimum boiling point (in methanol - toluene pair) and one tangential azeotrop in methanol - n-propylacetat pair near the pure n-propylacetat. In the capacity of the optimization criteria was chosen heating capacities on the distillation columns reboilers.Настоящая работа посвящена исследованию расположения изокритериальных много-образий и областей энергетической оптимальности комплексов экстрактивной ректификации смеси метанол-н-пропилацетат-толуол в симплексе исходных сос-тавов питания. Разделяемая смесь содержит один бинарный азеотроп с минимумом температуры кипения (в бинарной паре метанол-толуол) и один тангенциальный азеотроп вблизи чистого н-пропилацетата (в паре метанол - н-пропилацетат)