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Objective: To compare the characteristics of hydraulic potential in worn steel pipes with internal deposits subjected to cleaning by mechanical and chemical methods. Methods: Calculated dependencies are used for hydraulic calculation of new metal pipes and pipes with internal deposits. Results: A calculated dependence was obtained to determine the value of the inner diameter of pipes with any thickness of the layer of internal deposits. The concept of an efficient pipeline is introduced and a comparison made of the values of head losses in new pipes and in pipes with internal deposits. A specific practical example is considered. For the given example, compare the values of energy consumption of pumping equipment for two methods of cleaning the inner surface of pipes. Measures are indicated to ensure the efficiency of operation of water supply networks. Practical importance: It is shown that the chemical method of technical regulation of the hydraulic characteristics of new steel pipes provides an extension of the period of their further use.

We demonstrate a new method for a systematic, dynamic, high-speed, spatio-temporal control of femtosecond light filamentation in BK7 as a particular example of nonlinear medium. This method is based on using coherent conjugate asymmetric Bessel-Gaussian beams to control the far-field intensity distribution and in turn control the filamentation location. Such spatio-temporal control allows every femtosecond pulse to have a unique intensity distribution that results in the generation of structured filamentation patterns on demand. The switching speed of this technique is dependent on the rise time of the acousto-optic deflector, which can operate in the MHz range while having the ability to handle high peak power pulses that are needed for nonlinear interactions. The proposed and demonstrated spatio-temporal control of structured filaments can enable generation of large filament arrays, opto-mechanical manipulations of water droplets for fog clearing, as well as engineered radiofrequency plasma antennas.

In this paper, we investigate the applications of Higher Order Bessel Beams with temporal modulation of Orbital Angular Momentum (OAM) for maritime applications. Examples include the creation and detection of HOBBIT beams at unprecedented time scales and power densities. Results are also presented for sensing of rotating fog clouds and nonlinear interactions in water.

We demonstrate a new route for a systematic, dynamical, high-speed, spatio-temporal control of femtosecond light filamentation in water and, more generally, other maritime environments that can be precisely controlled on a pulse by pulse basis.

Dielectric nanophotonics became a hot topic during the last decade. Particularly, a lot of relevant studies were devoted to metasurfaces and their optical properties. Here we propose and numerically study the quadrumerbased silicon metasurface supporting magnetic octupole response. Specific meta-atoms allow to excite magnetic octupole moment in optical range without going beyond the diffraction limit. Comparing to a metasurface based on solid blocks of similar size, the quadrumer-based metasurface feature significant absorption enchantment and strong change of a reflection spectrum. Obtained results can be exploited in development of novel sensors, optical elements and energy harvesting devices.

Bound states in the continuum (BIC) attracted great attention in the photonics community. The existence of such states has led to numerous applications, including optical sensors and filters. Here we report on the approach to externally tune a magnitude and spectral position of high-Q resonances, associated with not symmetry-protected BIC state in silicon nitride (Si3N4) photonic crystals. We show that BIC properties can be controlled by the external thermal impact. These results can be used to construct compact and thermally stable optical sensors immune to harsh environmental conditions.

In this work, we investigated the possibility of creating various multipole combinations in conical silicon nanoparticles. It was found that in conical silicon particles it seems possible to create key effects for nanophotonics, such as various kinds of Kerker effects (Generalized Kerker, Transverse Kerker), Hybrid anapole state, Bound states in the continuum. This greatly simplifies the manufacturing process of photonic devices due to the easier production of nanocones in practice. Also, conical particles allow an additional degree of freedom, which opens up new horizons for obtaining previously unknown effects.

Tuning electric and magnetic response of dielectric structures at the nanoscale is a very important task nowadays. Multipole decomposition is a useful instrument to analyze and then control an opical response. Here we show the way to excite magnetic octupole moment by nanostructuring dielectric scatterer in near-IR spectral range. This response leads to magnetic hot-spots generations and a eresonant peak in scattering cross-section. Our results can be widely used to design novel metasurfaces avoiding diffraction limit, for particle trapping and imaging applications.

We present a novel optical effect where the scattered light on dielectric particles is suppressed simultaneously in the forward and backward directions. In contrary to the quadrupolar generalized Kerker conditions, this effect requires the coherent dipoles to be with pi phase with their quadruple counterparts. Electric dipole Fano profile and quadruples long-wavelength characteristics together set the physical environment to satisfy these conditions at a certain spectral position. The metasurface constructed from transverse scatterers is extraordinary transparent for the incident light where neither the phase nor the amplitude is perturbed.

All-dielectric nanophotonics attracts more and more attention nowadays due to the possibility to control and configure light scattering on high-index semiconductor nanoparticles. It opens a room of opportunities for designing novel types of nanoscale elements and devices, paving the way to advanced technologies of light energy manipulation. One of the most pespective and interesting effects is directive light scattering provided by the so-called Kerker and anti-Kerker effects giving a possibility to realize Huygens light sources, fully transparent metasurfaces, different types of nanoantennae etc. Another one corresponds to the realization of so-called “anapole states” providing near-zero scattering accompanied with strong near-fields. Here we briefly review some new results on the induced invisibility regarding fully transparent metasurfaces based on the simultaneous cancellation of the forward and backward scatteringvia particular optical responses of multipoles (similar to Kerker effect), and invisible objects and structures governed by the novel type of anapoles - hybrid anapole states.

Light scattering by all-dielectric nanoparticles attract significant attention of photonics community. Single nanoparticles can be used both as nanoantennas and as building blocks to construct 2D and 3D meta-structures. In this work we study scattering effect when silicon nanoparticles are embedded in different media. To analyze the evolution of multipole moments and their contributions to the scattering cross-sections of the nanoparticles in media, we use semi-analytical multipole decomposition approach. Explicitly, we investigate the behavior of electric and magnetic multipoles, up to third order, while dielectric nanoparticle made of silicon is embedded in a media. We found that electric and magnetic multipoles experience different red shift as refractive index increases. Due to this behavior separated high-order multipole resonances overlap with each other; thereby, scattering cross section peaks, which could be observed when a particles are in air, merge to the joint scattering cross section peaks. Such resonances overlap also affect both far-field radiation diagrams and field distribution inside the nanoparticle. Importantly, we noticed that when index of a surrounding media increases, the cubical nanoparticles provide spectral broadening of forward scattering effect. Our results provide fundamental information for understanding the scattering effect in all-dielectric nanoantennas or metasurfaces embedded in different dielectric media and operating in wide spectral range. For practical utilization, explored here dielectric nanoparticles could be used in broad range of applications such as in-vitro and in-vivo biomedical devices for sensing and drug delivering, sub-wavelength nano-amplifiers, and many other emerging applications.

In the compound feedstuff production, one of the main problems is the dust emission at all stages of production. The most significant dust emission occurs at the raw materials acceptance stage, where the concentration of dust can be many times higher than the maximum permissible values. The impact of dusts and their capture depends on the dispersed dust composition, and since the raw materials come in different types (bran, wheat, corn, sunflower meal, etc.), the dispersed dust composition is complex. For this reason, it becomes necessary to study their dispersed composition. The article presents the analysis results on some types of the dispersed dust, which generated in the air of the working area on feed mill reception center.

An effective semianalytical method for analyzing the Cartesian multipole contributions in light transmission and reflection spectra of flat metasurfaces composed of identical nanoparticles is developed and demonstrated. The method combines numerical calculation of metasurface reflection and transmission coefficients with their multipole decompositions. The developed method is applied for the multipole analysis of reflection and transmission spectra of metasurfaces composed of silicon nanocubes or nanocones. In the case of nanocubes, we numerically demonstrate a ``lattice invisibility effect,'' when light goes through the metasurface almost without amplitude and phase perturbations with the simultaneous excitation of nanoparticles' multipole moments. The effect is realized due to destructive interference between the fields generated by the basic multipole moments of nanoparticles in the backward and forward directions. For metasurfaces composed of conical nanoparticles, we show that their transmission coefficient does not depend on illumination direction. In contrast, the reflection and absorption can be different for the illumination from different metasurface sides, which is associated with the excitation of different multipoles. We believe our results could be useful for analysis and understanding of the electromagnetic properties of nanoparticle arrays and pave the way for the design of novel metasurfaces for various optical applications.

The effective multipole decomposition approach is applied to study the optical features of the silicon metasurface in the near-infrared. The spectral regions of perfect transmission and reflection have been analyzed using the Cartesian multipole decomposition. It is shown that transmission peaks appear due to the mutual interaction of multipole moments up to the third order, while reflection peaks are due to the dominant contribution of one of the multipole moments. The results of this work can be broadly applied to design novel metasurfaces, sensors, and optical filters. © 2019 SPIE.

The ability of all-dielectric nanostructures to perform exotic photonics effects is with superior efficiency compared to their metallic counterparts. Free from joules losses, high-index dielectrics support comparable excitation of electric and magnetic resonances and pave a way to advanced technologies of light energy manipulation. One of the most important effects is directive light scattering provided by the Kerker and anti-Kerker effects giving the potential to realize Huygens source of light, transparent metasurfaces, router nanoantennas etc. Here we study an effect where most of the scattered power is redirected to the side directions rather than to the forward and/or backward directions. This kind of scattering on isotropic scatterer requires at least the presence of the first two orders of multipoles to enable simultaneous forward and back-scattering suppressions. Electric dipole Fano resonance profile and quadrupoles off-resonance characteristics provide the required phase and amplitude conditions to obtain such an optical signature. We find the individual scatterers sustain the transverse scattering conditions when assembled into a metasurface so exhibit invisibility effect. We investigate this phenomenon analytically and numerically in the visible and microwave domains and provide the proof-of-the-concept experiment in the gigahertz frequency and showing very good agreement with the theoretical predictions.

Here we use multipole decomposition approach to study optical properties of a silicon nanocylinder in different lossless media. We show that resonant peaks of multipole moments experience red shift, smoothing and broadening. Worth noting that electric multipoles experience bigger red shift than their magnetic counterparts. Our results can be applied to design optical devices within a single framework.

Dielectric nanophotonics is the modern and very relevant field of optics. In this work we use the recently reported Cartesian multipole decomposition approach for all-dielectric metasurfaces [1] to study optical properties of the silicon metasurface at the nanoscale. This metasurface consists of crystalline silicon cubes rotated by 45° around the axis perpendicular to the surface plane. We use numerical modeling and semi-analytical approach to find origins of the scatering by the considered metasurface. Results obtained with the multipole approach are in the good agreement with the direct calculations of transmission and reflection spectra. Insights from our study can be widely used to design novel metasurfaces and metadevices and tune their optical properties to achieve a needed functionality.

All-dielectric nanophotonics attracts more and more attention nowadays due to the possibility to control and configure light scattering on high-index semiconductor nanoparticles. It opens a room of opportunities for the designing novel types of nanoscale elements and devices, and paves a way to advanced technologies of light energy manipulation. One of the most perspective and interesting effects is directive light scattering provided by the so-called Kerker and anti-Kerker effects giving a possibility to realize Huygens source of light, fully transparent metasurfaces, different types of nanoatennae etc. Another one corresponds to the realization of so-called “anapole states” providing near-zero scattering accompanied with strong near-fields. Here we briefly review some new results on the induced invisibility regarding fully transparent metasurfaces based on the simultaneous cancellation of the forward and backward scattering via particular optical responses of multipoles (similar to Kerker effect), and invisible objects and structures governed by the novel type of anapoles – hybrid anapole states.

In this work we theoretically study spectral multipole resonances of parallelepiped- and pyramid- silicon nanoparticles excited by linearly polarized light waves. We apply the numerical finite element method to calculate the scattering cross-sections as a function of the nanoparticles geometrical parameters. We use the multipole decom- position approach to explore optical resonances in silicon nanoparticles and the influence of second and third order multipoles to scattering diagrams. In contradistinction to our previous investigations, now we explore effects in near-IR spectral range. Apart from basic study we also obtained non-symmetrical combination of multipole contributions due to illumination from top and bottom sides of pyramids. Our work provides important information about the role of high-order multipoles in the light scattering by non-spherical and non-symmetrical nanoparticles. Our results can be applied, for example, for development of metasurfaces and metamaterials in near-IR spectral range.

All-dielectric resonant nanophotonics lies at the heart of modern optics and nanotechnology due to the unique possibilities to control scattering of light from high-index dielectric nanoparticles and metasurfaces. One of the important concepts of dielectric Mie-resonant nanophotonics is associated with the Kerker effect that drives the unidirectional scattering of light from nanoantennas and Huygens' metasurfaces. Here we suggest and demonstrate experimentally a novel effect manifested in the nearly complete simultaneous suppression of both forward and backward scattered fields. This effect is governed by the Fano interference between an electric dipole and off-resonant quadrupoles, providing necessary phases and amplitudes of the scattered fields to achieve the transverse scattering. We extend this concept to dielectric metasurfaces that demonstrate zero reflection with transverse scattering and strong field enhancement for resonant light filtering, nonlinear effects, and sensing.

Spectral multipole resonances of parallelepiped-, pyramid-, and cone-like shaped silicon nanoparticles excited by linearly polarized light waves are theoretically investigated. The numerical finite element method is applied for the calculations of the scattering cross sections as a function of the nanoparticles geometrical parameters. The roles of multipole moments (up to the third order) in the scattering process are analyzed using the semianalytical multipole decomposition approach. The possibility of scattering pattern configuration due to the tuning of the multipole contributions to the total scattered waves is discussed and demonstrated. It is shown that cubic nanoparticles can provide a strong isotropic side scattering with minimization of the scattering in forward and backward directions. In the case of the pyramidal and conical nanoparticles the total suppression of the side scattering can be obtained. It was found that due to the shape factor of the pyramidal and conical nanoparticles their electric toroidal dipole resonance can be excited in the spectral region of the first electric and magnetic dipole resonances. The influence of the incident light directions on the optical response of the pyramidal and conical nanoparticles is discussed. The obtained results provide important information that can be used for the development of nanoantennas with improved functionality due to the directional scattering effects.

We explore the optical multipole resonances in silicon nanoparticles of a conical shape. We use the Finite Element Method (FEM) for solving the Maxwell equations for analysis of optical properties. Harnessing the multipole decomposition technique, we study excited optical resonances in silicon nanoparticles and the influence of high-order multipoles to scattering patterns of considered nanoparticles. Non-symmetrical combination of multipole contributions due to illumination from top and bottom sides of cones is also considered. Our work provides important information about the role of high order multipoles in the light scattering by non-spherical nanoparticles in the non-symmetrical case. Our results could be applied, for example, for development of metasurfaces and metamaterials in optical range, including asymmetrical ones.

In this work we investigate in terms of Cartesian multipoles the Kerker-type effect in high-index dielectric nanoparticles for which the third order multipoles give a considerable contribution to the light scattering process. We show that the Kerker-type effect can be associated with the resonant excitation of toroidal dipole moment (third order multipole) and, namely, with the interference of the scattered waves generated by electric, magnetic and toroidal dipole moments of high-index dielectric nanoparticles. From our theoretical results reveal, that the interplay between these moments with dominating contribution of toroidal dipole moment can provide strong suppression of the backward light scattering and, simultaneously, resonant forward light scattering.

For a long time, light manipulation at the nanoscale has been provided primarily with plasmonic materials. However, recent works show that the light can be controlled with dielectric particles. Here, we exploit the asymmetric shape of silicon nanopyramids to control the far-field scattering pattern and the electric field concentration inside the particles by simply changing the incident light polarization. This effect is considered both in air and lossless optical medium. For an explanation of the demonstrated features, we apply the multipole analysis of the scattering cross sections. We show that the electric and magnetic quadrupole resonances can be switched between them by changing the incident wave polarization providing changes of the scattering diagrams. We also show that the polarization control of the scattering properties of pyramidal nanoparticles strongly depends on the refractive index of the surrounding medium. The obtained results can be used for the development of optical antennas, switchers, and polarization filters composed of silicon materials.

Dielectric photonics platform provides unique possibilities to control light scattering via utilizing high-index dielectric nanoantennas with peculiar optical signatures. Despite the intensively growing field of all-dielectric nanophotonics, it is still unclear how surrounding media affect scattering properties of a nanoantenna with complex multipole response. Here, we report on light scattering by a silicon cubic nanoparticle embedded in lossless media, supporting optical resonant response. We show that significant changes in the scattering process are governed by the electro-magnetic multipole resonances, which experience spectral red-shift and broadening over the whole visible and near-infrared spectra as the indices of media increase. Most interestingly, the considered nanoantenna exhibits the broadband forward scattering in the visible and near-infrared spectral ranges due to the Kerker-effect in high-index media. The revealed effect of broadband forward scattering is essential for highly demanding applications in which the influence of the media is crucial such as health-care, e.g., sensing, treatment efficiency monitoring, and diagnostics. In addition, the insights from this study are expected to pave the way toward engineering the nanophotonic systems including but not limited to Huygens-metasurfaces in media within a single framework.

In this paper, we demonstrate numerically that T1O2 microparticles can exhibit a destructive mode interference in the range 1–3 THz. Resonantly strong destructive interference of the toroidal and electric dipole contributions to the scattered field was achieved by a geometry tuning. An anapole mode can be observed as a composition of electric and toroidal dipole moments.

Electrical, thermal properties, and transport mechanisms in Ge2Sb2Te5 (GST225) thin films were investigated. Crystallization temperature for thin films was estimated. It was established that investigated thin films have p-type conductivity. Temperature dependencies of the resistivity for investigated thin films were studied. Two-channel model of charge carrier transport was used for the modeling of the temperature dependencies of conductivities. Activation energies of conductivity, position of the trap level controlling transport mechanism, and the density of states for this level were estimated.

In this Letter, we demonstrate and investigate the Kerker-type effect in high-index dielectric nanoparticles for which the third-order multipoles give a considerable contribution to the light scattering process. It is shown that the Kerker-type effect (strong suppression of the backward light scattering and, simultaneously, resonant forward light scattering) can be associated with the resonant excitation of a toroidal dipole moment in the system. This effect is realized due to the interference of the scattered waves generated by electric, magnetic, and toroidal dipole moments of high-index nanoparticles.

Problems of optimal approach with two pursuers and one evader are investigated under different assumptions about the player's dynamics. The problem's formulation is the same as in [1]. The duration of the game is fixed. The payoff functional is the distance between the evader and the pursuer, closest to it when the game terminates. Three following problems are solved here. The first is the problem of approach when the motion of all players is caused by the control and friction forces. The second one is the problem with simple motions and different pursuers. The third one is the problem with two inertial pursuers and non-inertial evader.

We obtain formulas for determining the principal values of the thermal-conductivity and electrical-conductivity tensors of materials obtained by the pressing of a powder consisting of anisotropic grains.

A differential game of approach with one evader and two pursuers with a nonconvex payoff function is considered. The duration of the game is fixed. The payoff functional is the distance between the object being pursued and the pursuer closest to it when the game terminates. An explicit form of the game value is found for all possible game positions. The paper is closely related to Refs. 1–12.

Soft apodizing apertures were developed and investigated. They were based on the absorption induced in CaF2:Pr by ionizing radiation and their diameters were 2-5 cm. The transmission profiles of the apertures were determined at the wavelength of 1.06 μ. The optical quality of the apertures was determined, measurements were made of the damage thresholds and their use in high-power laser systems was studied. The damage threshold of CaF2:Pr apertures in focused laser beams was higher than the damage thresholds of laser glasses and these apertures did not bleach right up to the damage threshold. An increase in the efficiency of conversion to the second harmonic was observed when a soft aperture was placed in a laser beam.

Equations are derived to determine the effective thermal and electrical conductivities of anisotropic media of low porosity. The influence of porosity on the thermal and electrical conductivities of anisotropic ternary alloys is established.

A method is proposed for measuring the coefficient of thermal diffusivity of microsections of surface layers and thin films. The coefficient of thermal diffusivity is calculated from the time dependence of the heat flux emitted by the heated surface.

An experimental comparison of two widely employed methods of determining accommodation coefficients is presented; these are the method of free molecular flow and the method of the temperature jump. The values of the coefficients which have to be introduced into the computing relationships of the temperature-jump method in order to obtain the true values of the accommodation coefficient are determined, this method being theoretically the less rigorous. Correction factors are determined for both monatomic and polyatomic gases.

Results are presented of a theoretical and experimental investigation of the dependence of the thermal coefficient of accommodation and emissivity on parameters characterizing surface roughness.