Photonic components are superior to electronic ones in terms of operational bandwidth, but the diffraction limit of light poses a significant challenge to the miniaturization and high-density ...integration of optical circuits. The main approach to circumvent this problem is to exploit the hybrid nature of surface plasmon polaritons (SPPs), which are light waves coupled to free electron oscillations in a metal that can be laterally confined below the diffraction limit using subwavelength metal structures. However, the simultaneous realization of strong confinement and a propagation loss sufficiently low for practical applications has long been out of reach. Channel SPP modes—channel plasmon polaritons (CPPs)—are electromagnetic waves that are bound to and propagate along the bottom of V-shaped grooves milled in a metal film. They are expected to exhibit useful subwavelength confinement, relatively low propagation loss, single-mode operation and efficient transmission around sharp bends. Our previous experiments showed that CPPs do exist and that they propagate over tens of micrometres along straight subwavelength grooves. Here we report the design, fabrication and characterization of CPP-based subwavelength waveguide components operating at telecom wavelengths: Y-splitters, Mach–Zehnder interferometers and waveguide–ring resonators. We demonstrate that CPP guides can indeed be used for large-angle bending and splitting of radiation, thereby enabling the realization of ultracompact plasmonic components and paving the way for a new class of integrated optical circuits.
•Heat transfer, temperature and velocity fields have been studied.•Using PIV measurements the liquid velocity fields have been obtained.•The thermal and the solutal Ma have a greater influence on the ...flow than Gr number.
Heat transfer, temperature and velocity fields of droplets of water and aqueous salt solutions have been studied. The initial concentration of salt solutions C01 = 30% in accordance with advanced technological applications. It is shown that the heat flux q for a water droplet is several times higher than for salt solutions. During the droplet evaporation, this difference increases, since q for aqueous salt solutions is many times reduced. While maintaining the wall temperature under the drop quasi-constant (Tw = 83 °C), the heat transfer coefficient α (for the time t < 150 s) for a drop of water 1.5–2 times exceeds α for the salt solution, and is 7 times higher for water than for the salt solution at t = 280 s. Using PIV measurements the liquid velocity fields have been obtained; and for the first time it has been shown that only for very small times and at high ΔT, the important role is played by thermo-gravitational convection in the droplet (the Rayleigh number Ra). But already for t > 10 s, the thermal and solutal Marangoni flows have a greater influence on the flow in a drop of the salt solution.
This work reports an original approach to the synthesis of composite “core-shell” nanoparticles of o-EuFeO3@am-EuFeO3 via solution combustion synthesis (SCS) followed by heat treatment in the air. ...PXRD, 57Fe and 151Eu Mössbauer spectroscopy, FTIR, DSC-TGA, SEM-EDX, TEM-SAED and vibrating-sample magnetometry were used to analyze the as-prepared and heat-treated samples. It was shown that the formation of amorphous am-EuFeO3 “shell” on the surface of crystalline o-EuFeO3 “cores” arises from the partial carbonatization of europium oxide during the solution combustion. It was found that the average crystallite size of o-EuFeO3 “cores” (37–92 nm) and thickness of am-EuFeO3 “shell” (1–10 nm) can be easily varied through the simple temperature change of heat treatment in the range of 500–900 °C. Acquired composite nanoparticles o-EuFeO3@am-EuFeO3 demonstrate uniform isometric morphology with a well distinct core and shell. Magnetometry results indicate the paramagnetic behavior of composite nanoparticles in a wide range of temperatures and applied magnetic fields that contradict the Mössbauer spectroscopy results showing the magnetic ordering of Fe-sublattice of o-EuFeO3 “cores”. Thus, the results of this work confirm the possibility of obtaining a new class of rare earth orthoferrite nanomaterials with the core-shell structure that can have promising functional applications.
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•New approach is proposed to the synthesis of EuFeO3-based core-shell nanoparticles.•Procedure is based on a solution combustion synthesis followed by heat treatment.•Core-shell structure forms due to partial carbonatization of nanoparticle surface.•Core and shell sizes can be controlled by simply varying the treatment temperature.•synthesized composite nanoparticles exhibit unusual magnetic behavior.
The article presents the measuring results of droplet velocity and temperature fields using non-contact optical methods: Particle Image Velocity (PIV), Planar Laser Induced Fluorescence (PLIF) and ...Thermal imager. The novelty of the work is that the influence of free convection in gas and liquid is investigated experimentally and theoretically and that the key criteria affecting heat and mass transfer are determined. The analysis of experimental data has shown that in the initial period of water drop evaporation, the predominant role in the heat exchange is played by the thermal Marangoni convection. However, for an aqueous salt solution, in spite of the strong influence of the surfactant, the dominant role passes to the solutal Marangoni convection (MaC). In the first seconds after the drop falling, convection and heat transfer in liquid are maximal. Under such conditions it is important to realize an accurate numerical simulation to assess the degree of wall cooling and calculate the non-stationary evaporation. When simulating heat transfer, it is incorrect to neglect free convection in gas or liquid due to their strong nonlinear influence on each other. The heat exchange in the drop is extremely conservative to convection in the liquid (the Peclet number Pe = 100 and the Nusselt number Nu = 4).
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•The droplet velocity decreases with a decrease in the Ma number.•The role of convection prevails over conduction for the droplet height above 1 mm.•The solutal Ma has a greater influence on heat transfer than the thermal Ma and Gr.
We report preliminary results on the development of compact (length < 100 microm) fiber-coupled dielectric-loaded plasmonic waveguide components, including Mach-Zehnder interferometers (MZIs), ...waveguide-ring resonators (WRRs) and directional couplers (DCs), whose operation at telecom wavelengths is controlled via the thermo-optic effect by electrically heating the gold stripes of dielectric-loaded plasmonic waveguides. Strong output modulation (> 20%) is demonstrated with MZI- and WRR-based components, and efficient (approximately 30%) rerouting is achieved with DC switches.
We study the solvability of bi-infinite systems of linear equations whose matrices are diagonally dominant. We prove that the estimates of the norm of the solution in terms of the diagonal dominance ...value well-known in the case of finite systems of linear equations are also valid for bi-infinite systems of equations. The estimates are used in interpolation by splines on nonuniform meshes on the real line. Using the estimates, we prove the existence and uniqueness of a cubic spline of linear or quadratic growth interpolating data of linear or quadratic growth, without any constraints on node spacing. The familiar estimates of the interpolation error on a segment are carried over to the case of interpolation on the whole real line.
Archean gneisses cropping out on islands in the White Sea and its coast in northern Karelia host widespread bodies of Early Proterozoic metamorphosed gabbroids. Carbonate–silicate veins hosted in ...these metabasite bodies and constrained to their contacts with the gneisses contain Fe–Cu sulfides, whose concentrations occasionally reach economic levels. The dominant gangue minerals are plagioclase, quartz, carbonates, and chlorite. The formation stages of the veins correspond to the transition from the early quartz–plagioclase to late quartz–carbonate associations with chlorite and sulfides. The early (high-temperature) stage is discernible in the wall-rock amphibolite aureoles, which were formed at temperature of about 550–650°C (estimates by the TWQ method). This stage corresponds to the quartz–plagioclase association in the marginal zones of the veins. The transition to the late stage and the formation of veined quartz–carbonate (±biotite) associations occurred at temperatures of 540°C and lower, judging by the calcite–dolomite associations. The further development of the quartz–chlorite–carbonate and sulfide associations in the veins and wall-rock amphibolites corresponded to a temperature decrease to 350°C and below, as evaluated with the application of chlorite thermometers. The veins and wall-rock amphibolitization may have been induced by metamorphic fluids during the latest retrograde metamorphic stage in the Early Proterozoic.
The effect of impurity particles on the forced convection velocity in a drop is analyzed. The liquid motion in a drop is due to droplet streamlining by the air flow. The experiments are carried out ...in a wide range of air velocities and droplet sizes and compared with approximate numerical solutions. A simple analytical model for determining convection inside the droplet is proposed for the first time. A semi-empirical model is proposed to generalize the experimental data by introducing the function considering the density of impurities (solid particles in the form of contaminants) on the droplet surface. The novelty of the work lies in the newly formulated hypothesis, justifying the 40–50 times underestimation of the experimental data below the theoretical calculation. For the case of motion of a drop of one liquid in another liquid, the experimental data satisfactorily correspond to the obtained analytical expression. The obtained expressions may be used for a wide range of problems related to the interfacial boundary (liquid - gas).
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•Surface and volume concentration of particles (pollution) on a droplet interface are considered.•The experimental studies of convection inside the drops of various liquids are presented.•There is the 40–50 times underestimation of the experimental data below the theoretical calculation.•A semi-empirical model is proposed to generalize the experimental data by introducing impurities.
Abstract
In the present paper we consider the problem to estimate a solution of the system of equations with a circulant matrix in uniform norm. We give the estimate for circulant matrices with ...diagonal dominance. The estimate is sharp. Based on this result and an idea of decomposition of the matrix into a product of matrices associated with factorization of the characteristic polynomial, we propose an estimate for any circulant matrix.
We report on realization of channel plasmon-polariton (CPP) propagation along a subwavelength metal groove. Using imaging with a near-field microscope and end-fire coupling with a tapered fiber ...connected to a tunable laser at telecommunication wavelengths (1425-1620 nm), we demonstrate low-loss (propagation length approximately 100 microm) and well-confined (mode width approximately 1.1 microm) CPP guiding along a triangular 0.6 microm-wide and 1 microm-deep groove in gold. We develop a simple model based on the effective-index method that accounts for the main features of CPP guiding and provides a clear physical picture of this phenomenon.
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