Solving Grid Equations Using the Alternating-triangular Method on a Graphics Accelerator

The paper describes a parallel-pipeline implementation of solving grid equations using the modified alternating-triangular iterative method (MATM), obtained by numerically solving the equations of mathematical physics. The greatest computational costs at using this method are on the stages of solving a system of linear algebraic equations (SLAE) with lower triangular and upper non-triangular matrices. An algorithm for solving the SLAE with a lower triangular matrix on a graphics accelerator using NVIDIA CUDA technology is presented. To implement the parallel-pipeline method, a three-dimensional decomposition of the computational domain was used. It is divided into blocks along the y coordinate, the number of which corresponds to the number of GPU streaming multiprocessors involved in the calculations. In turn, the blocks are divided into fragments according to two spatial coordinates — x and z. The presented graph model describes the relationship between adjacent fragments of the computational grid and the pipeline calculation process. Based on the results of computational experiments, a regression model was obtained that describes the dependence of the time for calculation one MATM step on the GPU, the acceleration and efficiency for SLAE solution with a lower triangular matrix by the parallel-pipeline method on the GPU were calculated using the different number of streaming multiprocessors.The paper describes a parallel-pipeline implementation of solving grid equations using the modified alternating-triangular iterative method (MATM), obtained by numerically solving the equations of mathematical physics. The greatest computational costs at using this method are on the stages of solving a system of linear algebraic equations (SLAE) with lower triangular and upper non-triangular matrices. An algorithm for solving the SLAE with a lower triangular matrix on a graphics accelerator using NVIDIA CUDA technology is presented. To implement the parallel-pipeline method, a three-dimensional decomposition of the computational domain was used. It is divided into blocks along the y coordinate, the number of which corresponds to the number of GPU streaming multiprocessors involved in the calculations. In turn, the blocks are divided into fragments according to two spatial coordinates — x and z. The presented graph model describes the relationship between adjacent fragments of the computational grid and the pipeline calculation process. Based on the results of computational experiments, a regression model was obtained that describes the dependence of the time for calculation one MATM step on the GPU, the acceleration and efficiency for SLAE solution with a lower triangular matrix by the parallel-pipeline method on the GPU were calculated using the different number of streaming multiprocessors

SAMPLE TRASFORMATION AT TWO-STAGE PROBE ATOMIZATION IN GRAPHITE FURNACE FOR ATOMIC ABSORPTION SPECTROMETRY

The surface of the U-shaped tungsten probe for a graphite furnace atomic absorption analysis with two-stage probe atomization was studied using scanning electron microscopy. The aim of the work was investigation of morphology of the sample after vapor phase transfer from the tube furnace to the tungsten probe and additional thermal treatment on the probe. It is shown for the sample having complex matrix (the slurry of milled up to 80 µm gold ore) that a polycrystalline layer of agglomerated particles of size less than 1 µm is formed on the surface of the probe after primary vaporization. After additional pyrolysis on the probe at the furnace temperature1500°Cthe deposit is modified into an amorphous film and drops of reduced metals with diameter up to 1 µm. In the case of simple matrix (water solution of palladium nitrate) a solid film with clots and flakes of 50 – 100 nm micro drops of palladium is deposited on the probe. The two stage treatment leads to the simplification of chemical and phase composition of the deposit and its localization on the probe tip within2 mm. This caused substantial improvement of analytical signal associated with atomization of the deposit from the probe inserted into the graphite furnace.Keywords: atomic absorption analysis, two-stage probe atomization, graphite furnace, ore, suspension, electron microscopy.(Russian)DOI:http://dx.doi.org/10.15826/analitika.2015.19.1.008Y.А. Zakharov, D.S. Irisov1, R.R. Haibullin, I.B. Chistyakov2Kazan (Volga region) Federal University, Kazan`, Russian Federation1LLC «Atzond», Kazan`, Russian Federation2LLC «Interlab», Moscow, Russian Federatio

Free-space subcarrier wave quantum communication

We experimentally demonstrate quantum communication in 10 dB loss outdoor atmospheric channel with 5 kbit/s bitrate using subcarrier wave coding method. Free-space link was organized by telescoping system with symmetric fiber-optic collimators

Electric field of a pointlike charge in a strong magnetic field and ground state of a hydrogenlike atom

In an external constant magnetic field, so strong that the electron Larmour length is much shorter than its Compton length, we consider the modification of the Coulomb potential of a point charge owing to the vacuum polarization. We establish a short-range component of the static interaction in the Larmour scale, expressed as a Yukawa-like law, and reveal the corresponding "photon mass" parameter. The electrostatic force regains its long-range character in the Compton scale: the tail of the potential follows an anisotropic Coulomb law, decreasing away from the charge slower along the magnetic field and faster across. In the infinite-magnetic-field limit the potential is confined to an infinitely thin string passing though the charge parallel to the external field. This is the first evidence for dimensional reduction in the photon sector of quantum electrodynamics. The one-dimensional form of the potential on the string is derived that includes a delta-function centered in the charge. The nonrelativistic ground-state energy of a hydrogenlike atom is found with its use and shown not to be infinite in the infinite-field limit, contrary to what was commonly accepted before, when the vacuum polarization had been ignored. These results may be useful for studying properties of matter at the surface of extremely magnetized neutron stars.Comment: 45 pages, 6 figures, accepted to Phys. Rev.

Electrical and optical properties of a PtSn 4 single crystal

A topological semimetal PtSn4 single crystal was grown by method of crystallization from a solution in a melt. Then the electrical resistivity and galvanomagnetic properties (magnetoresistivity and the Hall effect) were studied in the temperature range from 4.2 to 80 K and in magnetic fields up to 100 kOe. The optical measurements were carried out at room temperature. The residual resistivity is shown to be low enough and amount to ∼ 0.5 μOhm•cm. The temperature dependence of the electrical resistivity has a metallic type, increasing monotonically with temperature. A sufficiently large magnetoresistance of 750% is observed. The majority carriers are supposed to be holes with a concentration of ∼ 6.8•10 21 cm -3 and mobility of ∼ 1950 cm 2 /Vs at T = 4.2 K as a result of the Hall effect studies. The optical properties of PtSn 4 have features characteristic of "bad" metals. © 2019 Published under licence by IOP Publishing Ltd.This work was partly supported by the state assignment of Russia (theme “Spin” No. АААА-А18-18020290104-2 and theme “Electron” No. АААА-А18-118020190098-5), by the RFBR (project No.17-52-52008) and by the Government of the Russian Federation (state contract No. 02.A03.21.0006)

Особенности формирования ледникового стока на северном макросклоне массива Табын-Богдо-Ола по изотопным данным

This investigation is based on measurements of stable isotopes concentrations (δD and δ18О) in water, snow and ice samples. Glaciers are composed of ice, snow, and fi n of atmospheric origin. The isotopic composition of these components is different, so when melting they form the melted glacial water with different isotope characteristics. Summer precipitation contains the heaviest isotopes, but only a small part of them remains on the glacier. The average isotopic composition of glacier ice represents the average composition of precipitation that accumulates on it. However, snow and fi n of different seasons can occur on the glacier surface, the isotopic composition of which differs from the isotopic composition of glacier ice. At different times of the ablation season different parts of the glacier melt, therefore the isotopic composition of melt waters will be different. Differences in the isotopic composition of the major runoff-forming components on the Northern slopes of the massif Tabyn-Bogdo-Ola had been identified. A part of melting ice in the formation of the runoff on this massif is determined by estimation of the isotopic composition of snow, ice, and fi n on different glaciers of this region. The average δ18О of snow on the glacier surface is −11.9‰, and this snow can be attributed to the precipitation fallen in late spring or early summer. Measured average isotopic composition of precipitation (δ18О = −11.9‰) was compared with the online calculator of the isotope content in precipitation (OIPC). The isotopic composition of glacial melt waters on the Northern macro-slope in the middle of July 2015 (δ18О = −15.3‰) differs from the isotopic composition of the territory of the Mongolian part of the massif (δ18О = −17.4‰) obtained from results of the analysis of eight samples taken at different edges of the glaciers at the beginning of August 2013. Isotopic separation shows important role of summer snow in feeding the glacial rivers of the massif even in the middle of the ablation season, especially for glaciers in the central part of the massif. The role of seasonal snow in feeding the glacier streams depends on the morphological type of glacier. It is maximum for corrie glaciers and minimum for the valley ones.Определены различия изотопного состава основных стокоформирующих компонентов на северном макросклоне массива Табын-Богдо-Ола. По изотопному разделению дана оценка доли ледникового стока в середине сезона абляции для крупнейших ледников массива. Выявлены отличия в изотопном составе талых ледниковых вод российской и монгольской частей массива, отмечена возможная связь между морфологическим типом ледников и долей талых снежных вод в стоке

Optical Properties and Upconversion Luminescence of BaTiO3 Xerogel Structures Doped with Erbium and Ytterbium

Erbium upconversion (UC) photoluminescence (PL) from sol-gel derived barium titanate (BaTiO3:Er) xerogel structures fabricated on silicon, glass or fused silica substrates has been studied. The fabricated structures under continuous-wave excitation at 980 nm and nanosecond laser excitation at 980 and 1540 nm demonstrate room temperature PL with the bands at 410, 523, 546, 658, 800 and 830 nm, which correspond to the 2H9/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, 4F9/2→ 4I15/2 and 4I9/2→ 4I15/2 transitions in Er3+ ions. The intensity of erbium UС PL increases when an additional macroporous layer of strontium titanate is used beneath the BaTiO3 xerogel layer. It is enhanced for BaTiO3 xerogel films codoped with erbium and ytterbium (BaTiO3:Er,Yb). The redistribution of the intensity of the PL bands is observed for the latter and it depends on the excitation conditions. Finally, a Bragg reflector and a microcavity structure comprising of alternating (BaTiO3:Er,Yb) and SiO2 xerogel layers were fabricated with the cavity mode near the red PL band of Er3+ ions. Enhancement of UC PL from the microcavity was observed for the sample annealed from 450°C to 600°C. The fabricated cavity structures annealed at 450°C allow us to tune the cavity mode with 10 nm shift within the temperature range from +20°C to +130°C. Photonic application of BaTiO3 xerogel structures doped with lanthanides is discussed