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91.
The results of an experimental investigation of the hydraulic resistance of a circular pipe for turbulent flow with periodic flow rate fluctuations are presented. The presence of resonance phenomena in the pipe is revealed. It is established that, for hydrodynamic nonstationarity, the pipe resistance is a nonmonotonous function of the frequency of the imposed flow rate fluctuations and differs from the pipe resistance in the stationary flow regime. Under the conditions considered, to find the pipe resistance it is necessary to take into account the variation of the flow kinetic energy with respect to the phase of the imposed flow rate fluctuations due to the deformation of the velocity profile. 相似文献
92.
V. I. Bukreev E. M. Romanov N. P. Turanov 《Journal of Applied Mechanics and Technical Physics》1998,39(2):205-210
Experimental data on gravity shallow-water waves generated by a vertical plate moving in a predetermined manner are given.
The plate completely covers the cross section of the channel. It is found that with when the wave speed exceeds the first
critical value known in hydraulics, the wave retains smoothness. Breaking of the waves begins at the second critical speed
(which is about 1.3 times as high), whose value coincides with the limiting propagation speed of a solitary wave.
Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from
Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 2, pp. 52–58, March–April, 1998. 相似文献
93.
Alexander S. Romanov Tatiana V. Timofeeva Mikhail Yu. Antipin 《Journal of organometallic chemistry》2011,696(23):3822-3825
Novel radial tetra(ferrocenyl)- and tetra(cymantrenyl)cyclobutadienecobalt complexes were prepared by metal carbonyls free protocol of [2 + 2] cycloaddition reaction of 1,2-diferrocenyl- or 1,2-dicymantrenylethynes with chlorotris(triphenylphospine)cobalt(I) and carboethoxycyclopentadienide sodium with good yields. The molecular structure of these products was confirmed with X-ray analysis, and their electrochemical behavior was studied. 相似文献
94.
I. V. Romanov 《Moscow University Mathematics Bulletin》2011,66(2):53-59
The problem of control over plate vibrations is considered for the case when absolute values of controlling forces are bounded.
The aim of the control is to get the plate into the so-called “ɛ-neighborhood” of the rest state in finite time. 相似文献
95.
Romanov AN Gularyan SK Polyak BM Sakovich RA Dobretsov GE Sarkisov OM 《Physical chemistry chemical physics : PCCP》2011,13(20):9518-9524
Quantum-chemical calculations of ground and excited states for membrane fluorescent probe 4-dimethylaminochalcone (DMAC) in vacuum were performed. Optimized geometries and dipole moments for lowest-lying singlet and triplet states were obtained. The nature of these electronic transitions and the relaxation path in the excited states were determined; changes in geometry and charge distribution were assessed. It was shown that in vacuum the lowest existed level is of (n, π*) nature, and the closest to it is the level of (π, π*) nature; the energy gap between them is narrow. This led to an effective (1)(π, π*) →(1)(n, π*) relaxation. After photoexcitation the molecule undergoes significant transformations, including changes in bond orders, pyramidalization angle of the dimethylamino group, and planarity of the molecule. Its dipole moment rises from 5.5 Debye in the ground state to 17.1 Debye in the (1)(π, π*) state, and then falls to 2 Debye in the (1)(n, π*) state. The excited (1)(n, π*) state is a short living state; it has a high probability of intersystem crossing into the (3)(π, π*) triplet state. This relaxation path explains the low quantum yield of DMAC fluorescence in non-polar media. It is possible that (3)(π, π*) is responsible for observed DMAC phosphorescence. 相似文献
96.
Victor A. Soltamov Ivan V. Ilyin Alexandra A. Soltamova Daniel O. Tolmachev Nikolai G. Romanov Alexandr S. Gurin Vladimir A. Khramtsov Eugene N. Mokhov Yurii N. Makarov Georgy V. Mamin Sergei B. Orlinskii Pavel G. Baranov 《Applied magnetic resonance》2013,44(10):1139-1165
The results of studies of shallow donors and deep-level color centers in bulk AlN crystals are presented. Two shallow donors (presumably oxygen located on the nitrogen site and carbon located on the aluminum site) are suggested to exhibit the DX-relaxation. Third shallow donor (presumably silicon on the Al site) shows the shallow donor behavior up to the room temperature and can be observed without light excitation at temperatures above 200 K. The values of the Bohr radius of the shallow donors are estimated. The structure of deep-level color centers (neutral nitrogen vacancy V N) in bulk AlN crystals is determined and analyzed by electron paramagnetic resonance, electron-nuclear double resonance, optical absorption and thermoluminescence induced by X-ray irradiation. Spin-dependent recombination processes in AlN crystals are studied by means of optically detected magnetic resonance. 相似文献
97.
98.
V. N. Romanov 《Acoustical Physics》2002,48(4):467-472
Expressions are obtained for determining the noise immunity of a receiving antenna with a planar aperture under the action of different types of inhomogeneous acoustic fields. The inhomogeneity of these fields is shown to considerably affect the noise immunity of the antenna, which should be taken into account in estimating the antenna efficiency. 相似文献
99.
100.
A simple model is proposed which makes it possible to obtain correctly the boundary conditions on the envelope wave functions
in the case of contact of materials with substantially different electron spectra (presence or absence of a side valley or
substantial difference in its position). The passage of an electron through such a boundary is considered, and analytical
expressions for the transmission coefficient and intervalley transition coefficient are found. The dependence of these coefficients
on the parameters of the bounding materials and on the nature of the boundary turn out to be decisive for vertical transport
phenomena. Possible consequences of efficient conversion at the boundaries in multilayer structures are discussed.
Fiz. Tverd. Tela (St. Petersburg) 39, 839–843 (May 1997) 相似文献