Mode mixing in asymmetric double trench photonic crystal waveguides

e investigate both experimentally and theoretically the waveguiding properties of a novel double trench waveguide where a conventional single-mode strip waveguide is embedded in a two dimensional photonic crystal (PhC) slab formed in silicon on insulator (SOI) wafers. We demonstrate that the bandwidth for relatively low-loss (50dB/cm) waveguiding is significantly expanded to 250nm covering almost all the photonic band gap owing to nearly linear dispersion of the TE-like waveguiding mode. The flat transmission spectrum however is interrupted by numerous narrow stop bands. We found that these stop bands can be attributed to anti-crossing between TE-like (positive parity) and TM-like (negative parity) modes. This effect is a direct result of the strong asymmetry of the waveguides that have an upper cladding of air and lower cladding of oxide. To our knowledge this is the first demonstration of the effects of cladding asymmetry on the transmission characteristics of the PhC slab waveguides.Comment: 7 pages, 6 figure

Electroslag remelting of wares at solid start with the use of exothermic fluxes

Експериментальними методами встановлено, що розроблений спосіб твердого старту з використанням екзотермічних флюсів, що проводять електричний струм у твердому стані, істотно знижує час наведення шлакової ванни необхідного обсягу, підвищуючи продуктивність процесу. Запропонований спосіб старту електрошлакового процесу із використанням екзотермічних електропровідних флюсів не здійснює негативного впливу на якість донної частини злитка. Розроблені технологічні процеси прискореного наведення шлакової ванни на твердому старті як за монофілярною, так і біфілярною, або трифазною схемою ведення процесу. Властивості литої електрошлакової сталі 5ХНМ задовольняють вимоги, які пред’являються до механічних властивостей кованого металу відкритої виплавки. Гранулометричний склад екзотермічного флюсу в основному впливає тільки на процес наведення шлакової ванни витратним електродом.The authors established that an effective way to improve performance of such electroslag processes as casting and remelting was the use of exothermic fluxes containing such components as: slag, ferro alloys and aluminum powder in quantities sufficient for exothermic reactions. In particular, the experimental techniques revealed that the presence of electrically conductive layer of exothermic flux allowed for electroslag process being carried out according to the monofilar, as well as bifilar or three-phase schemes at «solid» start. The conducted research testified that the use of exothermic alloyed flux does not result in lower quality of the metal on the bottom of an ingot. The macro-structural analysis revealed that the cast metal of the ingot-bottom was dense; cracks, cavities and other defects did not occur, and columnar crystals were directed almost in parallel to the center line of a templet; in the middle and upper parts a zone of columnar crystals is clearly revealed; in the central part there was a zone of equiaxed crystals; besides the content of sulfur in the bottom of the ingot under the proposed method of start was smaller than that in its middle and upper part. The micro- structural study of pollution of the stamping dice metal by nonmetallic inclusions demonstrated that the metal had low content of non-metallic inclusions, while the pollution of wrought metal was significantly higher than the pollution of electroslag cast metal. The authors proved that the properties of electroslag cast steel 5HNM met the requirements for mechanical properties of openly melted wrought metal. The component of exothermic flux was found to be worthy being used, which is a waste of rolling or forging and pressing industry with particle size of 0.1 ... 2.5 mm and alloying elements with particle size of 0.1 ... 6.0 mm. It has been determined experimentally that granulometric composition of exothermic flux mainly affected only the process of restoring the slag bath in the application of consumable electrode. As a result of comparative tests of the effective option of the developed method of start and the applied methods of solid and liquid starts of the electroslag remelting, the parameters were obtained, which testify that the developed method of start of electroslag remelting can improve the performance of electroslag remelting process and increase the production of useful metal by 2...7 %. In addition, the authors found that the melting of exothermic flux the component of slug is formed: aluminum oxide (Al2O3), the mass of which can contain up to 20% of the required mass of the working flux being melted

Image of Russian Pan-Slavism in German Official Press at End of 19th Century

The aim of the research is to reconstruct the image of Russian Pan-Slavism in the German official press during the Bismarck era. The study examines the characteristic features of this image and its evolution over time, with particular attention given to the relationship between the image of Russian Pan-Slavism and the development of Russiangerman relations. The key source for this research is official newspapers, which were used by the German government to influence public opinion within the country and to transmit unofficial messages to ruling circles in other European states. The relevance of this research lies in the significant impact that historically established images and perceptions have on international relations in the modern world. The study concludes that the official press referred to the stereotypical image of Russian Pan-Slavism as a dangerous threat to the European world, which existed in German society, and contributed to its further strengthening. This image was widely used in the second half of the 1880s during a serious crisis in Russiangerman relations

Effect of particle size on the diffuse reflection coefficient of titanium dioxide powder

In the present work a model of light scattering is shown which explains the result about effect of particle size on the diffuse reflection coefficient of initial titanium dioxide powders. The diffuse reflection coefficient depending on particle size for TiO2 pigment varies on the curve with maximum. The experimental results and the model can be used for technology development of manufacturing pigment for light-reflecting temperature-control coatings of spacecraft

Derivation of the particle dynamics from kinetic equations

We consider the microscopic solutions of the Boltzmann-Enskog equation discovered by Bogolyubov. The fact that the time-irreversible kinetic equation has time-reversible microscopic solutions is rather surprising. We analyze this paradox and show that the reversibility or irreversibility property of the Boltzmann-Enskog equation depends on the considered class of solutions. If the considered solutions have the form of sums of delta-functions, then the equation is reversible. If the considered solutions belong to the class of continuously differentiable functions, then the equation is irreversible. Also, we construct the so called approximate microscopic solutions. These solutions are continuously differentiable and they are reversible on bounded time intervals. This analysis suggests a way to reconcile the time-irreversible kinetic equations with the time-reversible particle dynamics. Usually one tries to derive the kinetic equations from the particle dynamics. On the contrary, we postulate the Boltzmann-Enskog equation or another kinetic equation and treat their microscopic solutions as the particle dynamics. So, instead of the derivation of the kinetic equations from the microdynamics we suggest a kind of derivation of the microdynamics from the kinetic equations.Comment: 18 pages; some misprints have been corrected, some references have been adde

Vlasov Equation In Magnetic Field

The linearized Vlasov equation for a plasma system in a uniform magnetic field and the corresponding linear Vlasov operator are studied. The spectrum and the corresponding eigenfunctions of the Vlasov operator are found. The spectrum of this operator consists of two parts: one is continuous and real; the other is discrete and complex. Interestingly, the real eigenvalues are infinitely degenerate, which causes difficulty solving this initial value problem by using the conventional eigenfunction expansion method. Finally, the Vlasov equation is solved by the resolvent method.Comment: 15 page

Fractional Systems and Fractional Bogoliubov Hierarchy Equations

We consider the fractional generalizations of the phase volume, volume element and Poisson brackets. These generalizations lead us to the fractional analog of the phase space. We consider systems on this fractional phase space and fractional analogs of the Hamilton equations. The fractional generalization of the average value is suggested. The fractional analogs of the Bogoliubov hierarchy equations are derived from the fractional Liouville equation. We define the fractional reduced distribution functions. The fractional analog of the Vlasov equation and the Debye radius are considered.Comment: 12 page