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We study the problem of moving Chaplygin sleigh along an arbitrary surface. Motion equations for the sleigh are represented as Appel equations. We consider the case when the sleigh moves along a surface of rotation, in particular, along a plane, sphere, and cylinder. We show several cases when the sleigh’s motion equations can be fully integrated. 相似文献
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Development of Saturable Absorbers for Laser Passive Q‐Switching near 1.5 μm Based on Transparent Ceramic Co2+:MgAl2O4 下载免费PDF全文
Adrian Goldstein Pavel Loiko Zeev Burshtein Nikolai Skoptsov Ilya Glazunov Ehud Galun Nikolai Kuleshov Konstantin Yumashev 《Journal of the American Ceramic Society》2016,99(4):1324-1331
We describe the development of a reasonable cost Co2+:MgAl2O4 transparent ceramic plates fabrication technology that allows the producing of parts functioning as passive laser Q‐switches in the 1.3–1.7 μm domain. The main relevant material characteristics were measured. The absorption band, positioned between 1.2 and 1.7 μm, is typical of the 4A2 (4F) → 4T1 (4F) transition of Co2+ substituting Mg2+ ions in their Td symmetry sites. The measured ground‐state absorption cross section σgs = 2.9 × 10?19 cm2, saturation contrast γ = 0.12, and depleted ground‐state recovery time τ2 = 110–430 ns render such parts suitable for the intended application. The radiative lifetime was estimated as . The spin‐orbit splitting constant was estimated as ξSL??150 cm?1 for the 4F parent ground state, and ξSL ? –575 cm?1 for the 4P parent excited state. Obtained specimens had a transmission of ~80% (t = 2 mm, λ = 600 nm) and included some opaque, white spots. Further improvement of host optical transmission and resistance to laser damage are necessary. 相似文献
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A. A. Kuleshov N. M. Hidalgo Dias G. M. Makhviladze S. E. Yakush 《Mathematical Models and Computer Simulations》2010,2(6):691-703
Modeling of industrial accidents with liquefied toxic and flammable gases is considered. Propagation of nonreacting heavy
gas clouds over complex terrains is described by a two-dimensional model with averaging over the cloud height. A numerical
simulation of a toxic accident initiated by the release of chlorine in the urban environment has been performed and the number
of injured people has been computed. A two-dimensional axisymmetric model based on the Favre-averaged Navier-Stokes equations
is used to model the fireballs occurring upon combustion of hydrocarbon fuel-air clouds. Zones of various thermal hazards
for people have been obtained. 相似文献
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A detailed kinetic model of propane ignition and combustion in air is developed. The model includes 599 reactions with 92 species and involves both the high-temperature and low-temperature mechanisms of oxidation. The model is tested against experimental data on the ignition delay time, on propane conversion during low-temperature oxidation, on changes in species concentrations during propane pyrolysis, and on laminar flame propagation velocity. The model is tested in wide ranges of the initial temperature T 0 = 680–1900 K, pressure p 0 = 0.17–30 atm, and fuel-air equivalence ratio ϕ = 0.13–2. 相似文献
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A. N. Ermilov A. Yu. Kovalenko Yu. A. Kovalenko V. S. Kuleshov D. N. Novichkov T. M. Sapronova 《High Temperature》2008,46(4):535-541
Various breadboard models of Hall thrusters are analyzed with a view to optimizing the output parameters which characterize the degree of processing of the working medium and the energy efficiency of the device. It is demonstrated that the channel geometry with the magnetic field uniform along the channel affects only slightly the efficiency of acceleration of ion flow. In a number of working modes, the formation of accelerated ion flow is accompanied by the emergence of pulsations of discharge current, this leading to destructive processes of acceleration and formation of ion flow. The development of a breadboard model with a nonuniform magnetic field along the channel significantly decreasing in the direction of anode with cylindrical space makes possible the elimination of discharge current pulsations in a wide range of parameters. The increase in the density of the flow of working medium by a factor of 1.7 results in a 30% increase in the energy efficiency and provides for the working medium utilization factor of the order of 1.2. 相似文献