931 research outputs found
Nanoskyrmion engineering with -electron materials: Sn monolayer on SiC(0001) surface
Materials with -magnetism demonstrate strongly nonlocal Coulomb
interactions, which opens a way to probe correlations in the regimes not
achievable in transition metal compounds. By the example of Sn monolayer on
SiC(0001) surface, we show that such systems exhibit unusual but intriguing
magnetic properties at the nanoscale. Physically, this is attributed to the
presence of a significant ferromagnetic coupling, the so-called direct
exchange, which fully compensates ubiquitous antiferromagnetic interactions of
the superexchange origin. Having a nonlocal nature, the direct exchange was
previously ignored because it cannot be captured within the conventional
density functional methods and significantly challenges ground state models
earlier proposed for Sn/SiC(0001). Furthermore, heavy adatoms induce strong
spin-orbit coupling, which leads to a highly anisotropic form of the spin
Hamiltonian, in which the Dzyaloshinskii-Moriya interaction is dominant. The
latter is suggested to be responsible for the formation of a nanoskyrmion state
at realistic magnetic fields and temperatures.Comment: 4 pages, supplemental materia
Kalman filtering in the problem of noise reduction in the absorption spectra of exhaled air
We examined possibilities of the Kalman filter for reducing the noise effects in the analysis of absorption spectra of gas samples, in particular, for samples of the exhaled air. It has been shown that when comparing groups of patients with broncho-pulmonary diseases on the basis of the absorption spectra analysis of exhaled air samples the data preprocessing with the Kalman filtering can improve the classification sensitivity using a support vector kernel with mpl
Backtracking algorithms for constructing the Hamiltonian decomposition of a 4-regular multigraph
We consider a Hamiltonian decomposition problem of partitioning a regular
multigraph into edge-disjoint Hamiltonian cycles. It is known that verifying
vertex nonadjacency in the 1-skeleton of the symmetric and asymmetric traveling
salesperson polytopes is an NP-complete problem. On the other hand, a
sufficient condition for two vertices to be nonadjacent can be formulated as a
combinatorial problem of finding a Hamiltonian decomposition of a 4-regular
multigraph. We present two backtracking algorithms for verifying vertex
nonadjacency in the 1-skeleton of the traveling salesperson polytope and
constructing a Hamiltonian decomposition: an algorithm based on a simple path
extension and an algorithm based on the chain edge fixing procedure. According
to the results of computational experiments for undirected multigraphs, both
backtracking algorithms lost to the known general variable neighborhood search
algorithm. However, for directed multigraphs, the algorithm based on chain edge
fixing showed comparable results with heuristics on instances with the existing
solution and better results on instances of the problem where the Hamiltonian
decomposition does not exist.Comment: In Russian. Computational experiments are revise
Applications of principal component analysis to breath air absorption spectra profiles classification
The results of numerical simulation of application principal component analysis to absorption spectra of breath air of patients with pulmonary diseases are presented. Various methods of experimental data preprocessing are analyzed
Алгоритмы поиска с возвратом для построения гамильтонова разложения 4-регулярного мультиграфа
We consider a Hamiltonian decomposition problem of partitioning a regular graph into edge-disjoint Hamiltonian cycles. It is known that verifying vertex non-adjacency in the 1-skeleton of the symmetric and asymmetric traveling salesperson polytopes is an NP-complete problem. On the other hand, a suffcient condition for two vertices to be non-adjacent can be formulated as a combinatorial problem of finding a Hamiltonian decomposition of a 4-regular multigraph. We present two backtracking algorithms for verifying vertex non-adjacency in the 1-skeleton of the traveling salesperson polytope and constructing a Hamiltonian decomposition: an algorithm based on a simple path extension and an algorithm based on the chain edge fixing procedure. Based on the results of the computational experiments for undirected multigraphs, both backtracking algorithms lost to the known heuristic general variable neighborhood search algorithm. However, for directed multigraphs, the algorithm based on chain fixing of edges showed comparable results with heuristics on instances with existing solutions, and better results on instances of the problem where the Hamiltonian decomposition does not exist.Рассматривается задача построения гамильтонова разложения регулярного мультиграфа на гамильтоновы циклы без общих рёбер. Известно, что проверка несмежности вершин в полиэдральных графах симметричного и асимметричного многогранников коммивояжёра является NP-полной задачей. С другой стороны, достаточное условие несмежности вершин можно сформулировать в виде комбинаторной задачи построения гамильтонова разложения 4-регулярного мультиграфа. В статье представлены два алгоритма поиска с возвратом для проверки несмежности вершин в полиэдральном графе коммивояжёра и построения гамильтонова разложения 4-регулярного мультиграфа: алгоритм на основе последовательного расширения простого пути и алгоритм на основе процедуры цепного фиксирования рёбер. По результатам вычислительных экспериментов для неориентированных мультиграфов оба переборных алгоритма проиграли известному эвристическому алгоритму поиска с переменными окрестностями. Однако для ориентированных мультиграфов алгоритм на основе цепного фиксирования рёбер показал сопоставимые результаты с эвристиками на экземплярах задачи, имеющих решение, и лучшие результаты на экземплярах задачи, для которых гамильтонова разложения не существует
Millimetre-wave range optical properties of BIBO
We present the thorough studies of optical properties of BiB3O6 (BIBO) crystal in the millimeter-wave (subterahertz) range. We observe a large birefringence Δn = nZ −nX = 1.5 and the values of absorption coefficients of all three axes to be less than 0.5 cm−1 at the frequency of 0.3 THz. The difference from visible range in angle ϕ between the dielectric axis z and crystallophysical axis X is found to be more than 6°. The simulated phase-matching curves in the xz plane of the crystal show the optimal value of the angle θ to be around 25.5°±1° for an efficient millimeter-wave generation under the pump of 1064 nm laser radiation
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