Immersed boundary method for unsteady kinetic model equations

Predicting unsteady flows and aerodynamic forces for large displacement motion of microstructures requires transient solution of Boltzmann equation with moving boundaries. For the inclusion of moving complex boundaries for these problems, three immersed boundary method flux formulations (interpolation, relaxation, and interrelaxation) are presented. These formulations are implemented in a 2‐D finite volume method solver for ellipsoidal‐statistical (ES)‐Bhatnagar‐Gross‐Krook (BGK) equations using unstructured meshes. For the verification, a transient analytical solution for free molecular 1‐D flow is derived, and results are compared with the immersed boundary (IB)‐ES‐BGK methods. In 2‐D, methods are verified with the conformal, non‐moving finite volume method, and it is shown that the interrelaxation flux formulation gives an error less than the interpolation and relaxation methods for a given mesh size. Furthermore, formulations applied to a thermally induced flow for a heated beam near a cold substrate show that interrelaxation formulation gives more accurate solution in terms of heat flux. As a 2‐D unsteady application, IB/ES‐BGK methods are used to determine flow properties and damping forces for impulsive motion of microbeam due to high inertial forces. IB/ES‐BGK methods are compared with Navier–Stokes solution at low Knudsen numbers, and it is shown that velocity slip in the transitional rarefied regime reduces the unsteady damping force. Copyright © 2015 John Wiley & Sons, Ltd.     

Novel derivatives of 3,5-di-tert-butylpyrocatechol with pharmacophore substituents

Russian Chemical Bulletin - New potentially bioactive derivatives comprising spatially hindered pyrocatechol linked to hydrazine, acid hydrazides (including isoniazid), and acetylcysteine by a...     

Synthesis,structure, and properties of 2-[(4,6-di-tert-butyl-2,3-dihydroxyphenyl)thio]acetic acid amides

Russian Chemical Bulletin - New potential biologically active derivatives, in which the sterically hindered pyrocatechol moiety is linked through a 2-thioacetyl covalent bridge to a number of...     

Entropy considerations in numerical simulations of non-equilibrium rarefied flows

Non-equilibrium rarefied flows are encountered frequently in supersonic flight at high altitudes, vacuum technology and in microscale devices. Prediction of the onset of non-equilibrium is important for accurate numerical simulation of such flows. We formulate and apply the discrete version of Boltzmann’s H-theorem for analysis of non-equilibrium onset and accuracy of numerical modeling of rarefied gas flows. The numerical modeling approach is based on the deterministic solution of kinetic model equations. The numerical solution approach comprises the discrete velocity method in the velocity space and the finite volume method in the physical space with different numerical flux schemes: the first-order, the second-order minmod flux limiter and a third-order WENO schemes. The use of entropy considerations in rarefied flow simulations is illustrated for the normal shock, the Riemann and the two-dimensional shock tube problems. The entropy generation rate based on kinetic theory is shown to be a powerful indicator of the onset of non-equilibrium, accuracy of numerical solution as well as the compatibility of boundary conditions for both steady and unsteady problems.     

Sol-Gel Derived Silica Films with Ultrafine Copper, Copper Sulfide and Copper Selenide Particles

A development of the silica-based sol-gel materials in the form of films containing ultrafine copper compounds and metallic copper is presented. Semiconductor nanoparticles with new optical features due to size effects and unique chemical properties of copper are produced. The chemical state of copper-containing dopants was manipulated by the sequence of chemical transformations monitored with XRD and optical absorption spectroscopy and discussed together with other recent data (XPS, TEM). A number of nanocrystalline phases of sulfides and selenides controllable by preparation conditions were detected in the films. The chemical composition of the dopants controls optical absorption both in the visible and near IR ranges.     

Copper clusters and small particles stabilized within nanoporous materials

Copper was incorporated into mordenites with variable SiO₂/Al₂O₃ molar ratio, porous silica xerogels, natural pumice, and -alumina. The UV/Visible spectroscopy of the copper species produced as the result of hydrogen reduction and catalytic runs is presented. Different spectral features were detected assignable to nanoparticles, few-atomic clusters, oxide forms and Cu(II) compounds. The significant effect of support upon the redox-behavior of copper is discussed on the basis of experimental data.     

Cygnus X-3 observation in gamma-ray energy range >1014 eV

Summary We present experimental data on observations of Cygnus X-3 using an air shower array. The angular resolution of the array is of the order of 1 degree and the median energy of showers isE ₀≿10¹⁴ eV. During one year of observation there was no absolute excess of the number of showers from the source region and a small peak at the phase plot has only limited statistical significance. The value of UHE gammaray flux (if there exists any) seems to be in contradiction with values previously reported by Kiel and Haverah Park groups. We have analysed separately a sample of experimental data covering the short period in October 1985, when a radioburst from Cygnus X-3 was observed. Considerable excess of showers from the source was found in this sample: it lasted for three days with the maximal effect (40% excess) in the first one, 14th of October 1985.

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Riassunto Presentiamo i risultati sperimentali di osservazioni di Cygnus X-3 condotte mediante un apparato sciami. La risoluzione angolare dell'apparato è dell'ordine di 1 grado e l'energia mediana degli eventiE ₀≿10¹⁴ eV. Durante un anno di osservazioni non si è rivelato alcun eccesso assoluto di conteggi dalla regione della sorgente; un debole picco nel diagramma di fase ha una limitata significatività statistica. Il limite superiore al flusso di raggi gamma di altissima energia sembra essere in contraddizione con i valori riportati dai gruppi di Kiel ed Haverah Park. Abbiamo analizzato separatamente i dati dell'Ottobre 1985 in coincidenza con il burst osservato da Cygnus X-3 a frequenze radio. Si è trovato, in questo campione, un notevole eccesso di conteggi dalla sorgente della durata di tre giorni, il massimo effetto (40%) è osservato il 14 ottobre 1985.

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Резюме Мы приводим эксперементальные данные наблюдений излучения Лебедь X-3, использыя антенную решетку для детектирования атмосферных ливней. Угловое разрешение антенной решетки имеет порядок одного градуса, а медианная энергия ливней составляетE≿10¹⁵ эВ. В течение одного года наблюдений не было обнаружено абсолютного увеличения числа ливней из области источника, а небольшой пик на фазовой диаграмме имеет только ограниченную статистическую значимость. Верхний предел потока гамма-лучей сверхвысоких энергий, по-видимому, находится в противоречии с ранее опубликованными величннами. Мы анализируем отдельно выборку экспериментальных данных, полученных в течение короткого периода октября 1985, когда наблюдалаць радиовспышка из Лебедя X-3. В этой выборке обнаружен значительный избытол ливней из источнка в течение трех дней, причем максимальный эффект (40%) наблюдался 14 октября.

     

Formation and Properties of Sol-Gel Films and Glasses with Ultrafine Metal and Semiconductor Particles

A novel method of fabrication of silica-based sol-gel films and glasses containing small semiconductor particles was developed. A series of films and glasses with nanoparticles of copper chalcogenides (CuS, Cu₂Se, CuInS₂) and metal particles (Cu) were fabricated through the chemical transformation of precursors incorporated into a sol-gel derived matrix. The properties of the nanoparticles studied by means of XRD, XPS, TEM and optical spectroscopy are provided both by size effects and the chemical nature of surface states and can be controlled at different steps of chemical treatment.     

Uncommon condensations of 1,2,3-triketone 2-oximes with o-phenylenediamine

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