In this paper we experimentally studied the influence of geometrical parameters of the planar O-ring resonators on its Q-factor and losses. We systematically changed the gap between the bus waveguide and the ring, as well as the width of the ring. We found the highest Q= 5× 105 for gap 2.0 μm and the ring width 2 μm. This work is important for further on-chip SFWM applications since the generation rate of the biphoton field strongly depends on the quality factor as Q 3
Lattice Boltzmann method is a mesoscopic method used for solving hydrodynamics problems of both incompressible and compressible fluids. Although the method is widely used, reliability of the results is unclear. Therefore, we use the method to solve a fundamental problem with a known analytical solution, the Couette flow. We estimate the accuracy of the simulation results obtained by setting different types of spatial grids, boundary conditions, and equilibrium distribution functions. However, the method imposes restrictions on a large number of simulation parameters such as Reynolds and Mach numbers. During simulation we discovered an unexpected behavior of the solution using classical lattice Boltzmann method. In these simulations we find that the conservation law is violated due to an unexpected inflow in the upper corners of the computational domain.
We present data of quantum detector tomography for the samples specifically optimized for this problem. Using this method, we take results of hot-spot correlation length of 17 ± 2 nm. 1.
The increasing luminosities of future Large Hadron Collider runs and next generation of collider experiments will require an unprecedented amount of simulated events to be produced. Such large scale productions are extremely demanding in terms of computing resources. Thus new approaches to event generation and simulation of detector responses are needed. In LHCb, the accurate simulation of Cherenkov detectors takes a sizeable fraction of CPU time. An alternative approach is described here, when one generates high-level reconstructed observables using a generative neural network to bypass low level details. This network is trained to reproduce the particle species likelihood function values based on the track kinematic parameters and detector occupancy. The fast simulation is trained using real data samples collected by LHCb during run 2. We demonstrate that this approach provides high-fidelity results.
Modern experiments in high-energy physics require an increasing amount of simulated data. Monte-Carlo simulation of calorimeter responses is by far the most computationally expensive part of such simulations. Recent works have shown that the application of generative neural networks to this task can significantly speed up the simulations while maintaining an appropriate degree of accuracy. This paper explores different approaches to designing and training generative neural networks for simulation of the electromagnetic calorimeter response in the LHCb experiment.
Supercomputing of the exascale era is going to be inevitably limited by power efficiency. Nowadays different possible variants of CPU architectures are considered. Recently the development of ARM processors has come to the point when their floating point performance can be seriously considered for a range of scientic applications. In this work we present the analysis of the flooating point performance of the latest ARM cores and their efficiency for the algorithms of classical molecular dynamics.
An analysis is presented of experimental data where fluid–fluid phase transitions are observed for different substances at high temperatures with triple points on melting curves. Viscosity drops point to the structural character of the transition, whereas conductivity jumps remind of both semiconductor-to-metal and plasma nature. The slope of the phase equilibrium dependencies of pressure on temperature and the consequent change of the specific volume, which follows from the Clapeyron–Clausius equation, are discussed. P(V, T ) surfaces are presented and discussed for the phase transitions considered in the vicinity of the triple points. The cases of abnormal P(T ) dependencies on curves of phase equilibrium are in the focus of discussion. In particular, a P(V, T ) surface is presented when both fluid–fluid and melting P(T ) curves are abnormal. Particular attention is paid to warm dense hydrogen and deuterium, where remarkable contradictions exist between data of different authors. The possible connection of the P(V, T ) surface peculiarities with the experimental data uncertainties is outlined.
We studied silver nanoparticles combined with periodic gratings on a glass surface. The gratings were fabricated by selective etching of the glass slide patterned by thermal poling. The nanoparticles were grown on the bottom of the gratings’ grooves by out-diffusion technique. Obtained nanostructures supported both plasmonic and grating optical resonances and demonstrated SERS enhancement two times higher than one of the pure plasmonic structure.
Recently found quasi-two dimensional metalloorganic compound (C4H12N2)(Cu2Cl6) (abbreviated PHCC) is an example of a spin-gap magnet. Its ground state is a nonmagnetic singlet separated from the triplet excitations by an energy gap of approximately 1 meV. This compound allows partial substitution of chlorine ions by bromine, which results in the modulation of the affected exchange bonds. We have found by means of electron spin resonance spectroscopy that this doping results in the formation of the gapless S = 1 paramagnetic centers. These centers can be interpreted as triplet excitations trapped in a potential well created by doping.
In the framework of this paper we apply multifractal formalism to the analysis of statistical behaviour of topic models under variation of the number of topics. Fractal analysis of topic models allows to show that self-similar fractal clusters exist in large textual collections. We provide numerical results for 3 topic models (PLSA, ARTM, LDA Gibbs sampling) on 2 datasets, namely, on an English-language dataset and on a Russian-language dataset. We demonstrate that forming of clusters occurs precisely in the transition regions. Linear regions do not lead to changes in fractals, therefore, it is sufficient to find transition regions for the study of textual collections. Accordingly, the problem of the analysing the evolution of topic models can be reduced to the problem of searching transition regions in topic models.
Abstract. A three-dimensional artistic fractal tomography method that implements a non-glasses 3D visualization of fractal worlds in layered media is proposed. It is designed for the glasses-free 3D vision of digital art objects and films containing fractal content. Prospects for the development of this method in art galleries and the film industry are considered.
In the present work, we introduce a machine learning-based approach for galaxy clustering. It requires to determine clusters to provide further galaxies groups' masses estimation. The knowledge of mass distribution is crucial in dark matter research and study of the large-scale structure of the Universe. State-of-the-art telescopes allow various spectroscopy range data accumulation that highlights the need for algorithms with a substantial generalization property. The data we deal with is a combination of more than twenty different catalogues. It is required to provide clustering of all combined galaxies. We produce a regression on the redshifts with the coefficient of determination R2 equals 0.99992 on the validation dataset with training dataset for 3,154,894 of galaxies (0.0016 < z < 7.0519).
In this report, we study influence of the Si (111) substrate surface preparation on the growth, electronic and optical properties of the GaN nanowires (NWs) obtained via plasmaassisted molecular beam epitaxy. The substrate preparation varied from bare Si (111) surface and its deliberately nitridated counterpart to growth on AlN and Ga2O3 buffer layers and Ga droplets seeding layers. Statistical data on the morphology of the synthesized arrays was obtained and analyzed. The most homogeneous NW array in terms of length distribution was obtained on AlN buffer layer. It was demonstrated that the NWs surface density drastically depends on the surface preparation method. Electrical properties of the arrays were studied via analysis of voltampere characteristics and optical properties were investigated with photoluminescence. The highest conductivity and optical response were obtained with AlN buffer layer.
We investigate the existence and the orthogonality of the generalized Jack symmetric functions which play an important role in the AGT relations. We show their orthogonality by deforming them to the generalized Macdonald symmetric functions.
We consider a dynamic version of the HP model of a linear polymer: a self-avoiding walk on the square lattice, with monomers being either hydrophobic (H) or polar (P). We simulate the model in two dimensions in the grand canonical assemble via the Berretti-Sokal algorithm across the globule-coil transition and map out the phase diagram. Our results are consistent with the universality class of the transition being the same as the universality class of the theta-transition of an interacting self-avoiding walk.
Metal nanoparticles (NPs) serve as important tools for many modern technologies. However, the proper microscopic models of the interaction between ultrashort laser pulses and metal NPs are currently not very well developed in many cases. One part of the problem is the description of the warm dense matter that is formed in NPs after intense irradiation. Another part of the problem is the description of the electromagnetic waves around NPs. Description of wave propagation requires the solution of Maxwell's equations and the finite-difference time-domain (FDTD) method is the classic approach for solving them. There are many commercial and free implementations of FDTD, including the open source software that supports graphics processing unit (GPU) acceleration. In this report we present the results on the FDTD calculations for different cases of the interaction between ultrashort laser pulses and metal nanoparticles. Following our previous results, we analyze the efficiency of the GPU acceleration of the FDTD algorithm.
We consider the Hegselmann-Krause bounded confidence model of opinion dynamics. We assume that the opinion of an agent is influenced not only by other agents, but also by external random noises. The case of independent normally distributed external noises is considered. We perform computer modeling of deterministic and stochastic models. The properties of the models were analyzed and the difference in their behavior was revealed. We study the dependence of the number of a confidence clusters on the parameters of the problem such as the initial profile of opinions, the level of confidence, the variance of noise.
The operation of modern tokamaks is impossible without an effective system for controlling the plasma boundary during the discharge. In this paper, we consider a method for determining the plasma boundary on the basis of integral equations. A high-speed parallel code using GPUs was developed for this purpose. Different methods of parallelization of the algorithm have been considered. The possibility of processing the magnetic measurements in real time during experiments is shown. The effect of the technical parameters of GPUs (the number of cores, the data bus width, the amount of internal memory) on the performance is also shown. The simulation results for the T-15MD tokamak, currently under construction at National Research Center Kurchatov Institute, are presented.
The results of numerical calculations for the mathematical model proposed for describing the magnetization in a thin film of a ferromagnetic semiconductor at temperatures below the Curie temperature in the presence of an external electric field are presented. The theoretical prediction of the existence of a piecewise continuous solution, which describes the presence of the phase transition boundary for magnetization inside the film, is confirmed. The location of this phase transition boundary depends on the external electric field and temperature.