409 research outputs found
Specialized Web Portal for Solving Problems on Multiprocessor Computing Systems
A system for remote calculations called “Specialized web portal for solving problems on multiprocessor computing systems” has been developed and installed at the Department of Ill-Posed Problems of Analysis and Applications of the Institute of Mathematics and Mechanics UrB RAS. The parallel algorithms have been incorporated into this system to solve the inverse gravity problem of lateral density reconstruction, the structural inverse gravity and magnetic problem of the contact surfaces reconstruction, and solving SLAEs with block-tridiagonal matrices in geoelectrics problems
The Problem of Scheduling for the Linear Section of a Single-Track Railway with Independent Edges Orientations
The paper is devoted to the problem of scheduling for the linear section of a single-track railway: how to organize the ow in both directions in the most efficient way. In this paper, the authors propose an algorithm for scheduling with independent edges orientations, examine the properties of this algorithm and perform the computational experiments
Algorithms for solving inverse geophysical problems on parallel computing systems
For solving inverse gravimetry problems, efficient stable parallel algorithms based on iterative gradient methods are proposed. For solving systems of linear algebraic equations with block-tridiagonal matrices arising in geoelectrics problems, a parallel matrix sweep algorithm, a square root method, and a conjugate gradient method with preconditioner are proposed. The algorithms are implemented numerically on a parallel computing system of the Institute of Mathematics and Mechanics (PCS-IMM), NVIDIA graphics processors, and an Intel multi-core CPU with some new computing technologies. The parallel algorithms are incorporated into a system of remote computations entitled "Specialized Web-Portal for Solving Geophysical Problems on Multiprocessor Computers." Some problems with "quasi-model" and real data are solved. © 2013 Pleiades Publishing, Ltd
Proton configurations in the hydrogen bonds of KH2PO4 as seen by resonant x-ray diffraction
KH2PO4 (KDP) belongs to the class of hydrogen-bonded ferroelectrics, whose
paraelectric to ferroelectric phase transition is driven by the ordering of the
protons in the hydrogen bonds. We demonstrate that forbidden reflections of
KDP, when measured at an x-ray absorption edge, are highly sensitive to the
asymmetry of proton configurations. The change of average symmetry caused by
the "freezing" of the protons during the phase transition is clearly evidenced.
In the paraelectric phase, we identify in the resonant spectra of the forbidden
reflections a contribution related to the transient proton configurations in
the hydrogen bonds, which violates the high average symmetry of the sites of
the resonant atoms. The analysis of the temperature dependence reveals a change
of relative probabilities of the different proton configurations. They follow
the Arrhenius law, and the activation energies of polar and Slater
configurations are 18.6 and 7.3 meV, respectively
Fine structure of perturbed Laguerre-Gaussian beams: Hermite-Gaussian mode spectra and topological charge
We found that small perturbations of the optical vortex core in the
Laguerre-Gaussian (LG) beams generate a fine structure of the Hermite-Gauss
(HG) mode spectrum. Such perturbations can be easily simulated by weak
variations of amplitudes and phases of the HG modes in the expansion of the LG
beam field. We also theoretically substantiated and experimentally implemented
a method for measuring the topological charge of LG beams with an arbitrary
number of ring dislocations. Theoretical discussion and experimental studies
were accompanied by simple examples of estimating the orbital angular momentum
and the topological charge of perturbed LG beams.Comment: 16 pages, 7 figure
Memory efficient algorithm for solving the inverse gravimetry problem of finding several boundary surfaces in multilayered medium
For solving the inverse gravimetry problem of finding several boundary surfaces in a multilayered medium, the parallel algorithm was constructed and implemented for multicore CPU using OpenMP technology. The algorithm is based on the modified nonlinear conjugate gradient method with weighting factors previously proposed by authors. To reduce the memory requirements and computation time, the modification was constructed on the basis of utilizing the Toeplitz-block-Toeplitz structure of the Jacobian matrix of the integral operator. The model problem of reconstructing three surfaces using the quasi-real gravitational data was solved on a large grid. It was shown that the proposed implementation reduces the computation time by 80% in comparison with the earlier algorithm based on calculating the entire matrix. The parallel algorithm shows good scaling of 94% on 8-core processor. © 2019 Author(s).Ministry of Education and Science of the Republic of Kazakhstan: AP 05133873This work was financially supported by the Ministry of Education and Science of the Republic of Kazakhstan (project AP 05133873)
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