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1.
For the detailed investigation of the 3D unsteady incompressible viscous separated fluid flows around a sphere (for 200≤Re≤700) and a circular cylinder (for 200≤Re≤400) the direct numerical simulation and 3D visualization are used. For 3D visualization of the fluid flows around a sphere
the definition of vortex core as a connected region containing two negative eigenvalues of theS
2+Ω
2 tensor is used (whereS
i,j andΩ
ij
are the rate of strain and the rate of rotation tensors). The formation mechanism of vortices in the sphere wake for Re=500
is described in detail. For 3D visualization of the fluid flows around a circular cylinder the 3D isosurfaces of the streamwise
component of vorticity ω
x
are used. 相似文献
2.
Abstract
Classic examples of low-Reynolds recirculating cavity flows are typically generated from lid-driven boundary motion at a solid–fluid interface, or alternatively may result from shear flow over cavity openings. Here, we are interested in an original family of boundary-driven cavity flows occurring, in contrast to classic setups, at fluid–fluid interfaces. Particle image velocimetry (PIV) is used to investigate the structure of internal convective flows observed in thin liquid shells. Under the specific configuration investigated, the soap bubble’s liquid shell is in fact in motion and exhibits sporadic local “bursts”. These bursts induce transient flow motion within the cavity of order Re ∼ O(1). The combination of PIV and proper orthogonal decomposition (POD) is used to extract dominant flow structures present within bubble cavities. Next, we show that thermally induced Marangoni flows in the liquid shell can lead to forced, (quasi) steady-state, internal recirculating flows. The present findings illustrate a novel example of low-Reynolds boundary-driven cavity flows. 相似文献3.
Rigorous estimates for the total – (kinetic) energy plus pressure – flux in
\mathbbR3{\mathbb{R}^3} are obtained from the three dimensional Navier-Stokes equations. The bounds are used to establish a condition – involving
Taylor length scale and the size of the domain – sufficient for existence of the inertial range and the energy cascade in
decaying turbulence (zero driving force, non-increasing global energy). Several manifestations of the locality of the flux
under this condition are obtained. All the scales involved are actual physical scales in
\mathbbR3{\mathbb{R}^3} and no regularity or homogeneity/scaling assumptions are made. 相似文献
4.
Yuri Bakhtin 《Journal of statistical physics》2006,122(2):351-360
We consider the 3D Navier–Stokes system in the Fourier space with regular forcing given by a stationary in time stochastic
process satisfying a smallness condition. We explicitly construct a stationary solution of the system and prove a uniqueness
theorem for this solution in the class of functions with Fourier transform majorized by a certain function h. Moreover we prove the following “one force—one solution” principle: the unique stationary solution at time t is presented as a functional of the realization of the forcing in the past up to t. Our explicit construction of the solution is based upon the stochastic cascade representation. 相似文献
5.
Yu. M. Smirnov 《Journal of Applied Spectroscopy》1998,65(1):5-9
The excitation cross-sections of transitions of a ruthenium atom from the3
S
0−,3
P
0−, and3
D
0-levels are measured by the method of extended crossed beams. Based on the results of measurements, the excitation cross-sections
of the states are calculated (ignoring cascade contribution).
Moscow Power Engineering Institute, 14, Krasnokazarmennaya St., Moscow, E-250, 111250, Russia. Translated from Zhurnal Prikladnoi
Spektroskopii, Vol. 65, No. 1, pp. 9–13, January–February, 1998. 相似文献
6.
The magnetic hyperfine field of Se in nickel was measured by means of the time-differential perturbed angular correlation
(DPAC) technique, using the 755–250 keV γ-ray cascade fed in the decay of77Br. A value ofB
hf(NiSe)=+15.11(35) T was obtained at room temperature. The half-life of the 250 keV state and the anisotropy of the 755–250 keV
cascade were found to beT
1/2=9.68(6) ns andA
22=−0.454(9), respectively. 相似文献
7.
Proton collective flows in heavy-ion collisions from AGS ((2–11) A GeV) to SPS ((40,158) A GeV) energies are investigated
in a nonequilibrium transport model with nuclear mean-field (MF). Sideward (p
x), directedv
1, and ellipticv
2 flows are systematically studied with different assumptions on the nuclear equation of state (EoS). We find that momentum
dependence in the nuclear MF is important for understanding the proton collective flows at AGS and SPS energies. Calculated
results with momentum-dependent MF qualitatively reproduce the experimental data of proton sideward, directed, and elliptic
flows in an incident energy range of (2–158) A GeV
This talk is based on ref. [1] 相似文献
8.
Subordinating regular diffusion – namely, Brownian motion – to random time flows generated by Lévy noises may result in anomalous
diffusion. Motivated by this phenomena, and by the recent interest in the phenomena of blinking in various physical systems, we explore the subordination of regular stochastic pulsation – namely, Poisson process – to
random time flows generated by Lévy noises. We show that such subordination may yield, analogous to the case of diffusion,
anomalous pulsation. Anomalous pulsation displays the following anomalous behaviors, which are impossible in the case of regular pulsation: (i)
simultaneous emission of multiple pulses; (ii) non-linear local pulsation rates; (iii) clustering of pulsation epochs. 相似文献
9.
Zhiyuan Tian Yazhou Zhang Yanli Zhang Aidong Peng Ying Ma Yu Chen Wensheng Yang Yalin Tang Jiannian Yao 《Journal of nanoparticle research》2006,8(1):65-77
Nanostructures with well-defined shape and highly monodisperse size were fabricated from model stilbazolium-like dyes with specific molecular structural and conformational characteristics. With the help of absorption and fluorescence optical spectroscopy, the correlated spectroscopy (COSY) and two- dimensional nuclear Overhauser effect spectroscopy (2D NOESY) techniques, along with X-ray diffraction (XRD) measurement, distinctively different aggregation processes of the model molecules are demonstrated. For model dye molecule with linear donor–π system–acceptor (D–π–A) structure, strong D–A pair, and planar conformation, specific intermolecular interaction was identified and special crystal structures as well as spectral properties were observed. For model dye molecules bearing nonlinear D–π–A–π–D structure, weak D–A pair but actual amphiphilic characteristics, a special aggregation process was confirmed and a focused size distribution of the produced nanostructures was obtained. 相似文献
10.
Flake-built 3D β-In2S3 nanostructures were synthesized by thermolysis of S-methyl dithiocarbazate–indium(III) complex precursor in hexamethylenediamine (HMDA). XRD patterns showed that the cubic phase
of 3D β-In2S3 remained unchanged but the crystallinity was increased after annealing at 400 °C for 20 min. The products were also characterized
by SEM, TEM, and EDS. Based on the experimental results, we propose that the growth of 3D nanostructures is controlled by
the stability of the intermediate chelate complex made by indium(III) and solvent. The optical properties of the 3D β-In2S3 nanostructures were also investigated by UV–Vis and PL spectroscopy, which indicated strong quantum confinement effect. 相似文献
11.
The Klein–Fock–Gordon equation is solved for a 2D pion moving in a constant uniform magnetic field. A relativistic energy
spectrum is calculated for fixed values of the angular momentum and magnetic field Н. An analysis of the results of these calculations allows us to conclude that the Klein–Fock–Gordon equation, unlike the Schr?dinger
equation, cannot describe the energy of the particle s-state in the magnetic field. It is elucidated that a correction for
the relativistic energy level caused by the constant magnetic field is noticeable for the magnetic field H > 100.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 91–96, March, 2009. 相似文献
12.
Surface acoustic wave (SAW) delay lines without gas-sensitive coatings are used as thermal sensors for the thermoconductometric
detection of gases and gas flows. The forced convection of 13 gases is analyzed in the linear approximation without regard
for their interaction with the environment. Quartz, LiNbO3, Bi12GeO20, and Bi12SiO20 delay lines are used to detect H2, He, Ar, CH4, NH3, N2, and O2 at frequencies f=21–263 MHz and temperatures T=25–165 °C. The SAW “response” is measured as a function of the gas concentration n, the flow rate U, the temperature coefficient of the SAW velocity (TCV), and the working temperature T
p
. The feasibility of controlling the level of the gas “response” and imparting selectivity to the choice of TCV and T
p
is demonstrated. The threshold gas concentrations are 0.35% for CH4 and 0.1% for H2 and NH3 in nitrogen. A linear response is obtained in the interval U=20–200 ml/min.
Zh. Tekh. Fiz. 67, 119–123 (May 1997) 相似文献
13.
V. I. Kadushkin 《Russian Physics Journal》2006,49(3):268-275
The volume (3D), quasi-two-dimentional (Q2D), and two-dimentional (2D) oscillations of degenerated electrons of the Shubnikov-de
Haase reluctance reveal common properties. The region of quantum oscillations is bounded (in the magnetic field) from below
by the weak field condition (ωcτt≤1) and from above by the quantum limit condition (ξF≥ħωc/2). The monotonic oscillation component is saturated for the occupied main conduction Em-subband and excitation Ep-subband of dimensional quantization for the Q2D and 2D electron systems in strong magnetic fields. The reluctance of the
Q2D system in the quantum limit changes according to a law ∼B
α with α ≈ 2.6–2.8. The oscillation amplitude is described by an exponential dependence on the magnetic field strength and
temperature, similarly to the 3D case. This is caused by the identity of physical conditions and the topology of resonant
escape of the Landau levels out of the Fermi surface.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 33–39, March, 2006. 相似文献
14.
A dynamical non-Abelian 2-form gauge theory (with B∧F term) is endowed with the “scalar” and “vector” gauge symmetry transformations. In our present endeavor, we exploit the latter
gauge symmetry transformations and perform the Becchi–Rouet–Stora–Tyutin (BRST) analysis of the four (3+1)-dimensional (4D)
topologically massive non-Abelian 2-form gauge theory. We demonstrate the existence of some novel features that have, hitherto,
not been observed in the context of BRST approach to 4D (non-)Abelian 1-form as well as Abelian 2-form and 3-form gauge theories.
We comment on the differences between the novel features that emerge in the BRST analysis of the “scalar” and “vector” gauge
symmetries. 相似文献
15.
Cubic-stabilized ((DyO1.5)
x
–(WO3)
y
–(BiO1.5)1 − x − y
) electrolytes (DWSB) with much higher conductivity than (ErO1.5)0.2(BiO1.5)0.8, 20ESB, were developed through a double-doping strategy. (DyO1.5)0.08–(WO3)0.04–(BiO1.5)0.88, 8D4WSB, is the highest conductivity composition but underwent the greatest conductivity degradation at 500 °C due to its
low total dopant concentration. The effect of dopant composition on conductivity behavior with time at 500 °C demonstrates
that there is a trade-off between initial conductivity and long-term stability at this temperature. Therefore, it is necessary
to find an optimal total and relative concentration of dopants to provide the enhanced long-term stability needed to make
this DWSB electrolyte system feasible for 500 °C operation. To this end, it was found that (DyO1.5)0.25–(WO3)0.05–(BiO1.5)0.70, 25D5WSB, maintained a conductivity of 0.0068 S/cm without appreciable degradation after annealing at 500 °C for 500 h. Moreover,
since bismuth oxide-based electrolytes do not exhibit any grain boundary impedance, the total conductivity of 25D5WSB is significantly
higher than that of alternate electrolytes (e.g., GDC: Gd0.1Ce0.9O1.95) at this temperature. 相似文献
16.
High-resolution two-dimensional (2D) 1H–13C heteronuclear correlation spectra are recorded for selective observation of interfacial 3–5.5 ? contacts of the uniformly
13C-labeled phycocyanobilin (PCB) chromophore with its unlabeled binding pocket. The experiment is based on a medium- and long-distance
heteronuclear correlation (MELODI–HETCOR) method. For improving 1H spectral resolution, a windowed phase-modulated Lee–Goldburg (wPMLG) decoupling scheme is applied during the t
1 evolution period. Our approach allows for identification of chromophore–protein interactions, in particular for elucidation
of the hydrogen-bonding networks and charge distributions within the chromophore-binding pocket. The resulting pulse sequence
is tested on the cyanobacterial (Cph1) phytochrome sensory module (residues 1–514, Cph1Δ2) containing uniformly 13C- and 15N-labeled PCB chromophore (u-[13C,15N]-PCB-Cph1Δ2) at 17.6 T. 相似文献
17.
Dynamic mass generation in 3D quantum electrodynamics (QED3) is considered at T ≠ 0. To solve the Schwinger–Dyson equation for the Matsubara electron Green’s function, the ladder approximation is used
and the corresponding photonic function is taken in the Landau gauge. In this case, the instant approximation is used for
the photonic function. It is established that the process of dynamical mass generation in QED3 at T ≠ 0 is accompanied by a phase transition. Formal analogy of transitions in the coupling constant is revealed at T ≠ 0 in QED3, at T = 0 in QED4, and in graphene theory. Critical values of the coupling constant and temperature, calculated numerically based on an approximate
analytical solution of the Schwinger–Dyson equation are of the same orders of magnitude. 相似文献
18.
Caterina Costa Carmela Cavalcante Francesca Zito Yukio Yokota Valeria Matranga 《Molecular diversity》2010,14(4):653-665
The extracellular matrix protein Pl-nectin, a 210-kDa homodimer originally purified from sea urchin eggs, plays a crucial role in cell adhesion and embryonic
morphogenesis. The compiled cDNA sequence, obtained by RT-PCR primer walking and 3′ RACE, identified a 984aa product containing
a 23aa signal peptide and including all six internal peptides identified by protein microsequencing. The protein is a new
member of the galactose-binding protein superfamily as it consists of six 151–156aa-long tandemly repeated domains (D1–D6),
homologous to the discoidin-like domains, also known as F5/8-type C domains. Based on homology modelling, we present a three-dimensional
structure (3D) for D5, identified as the prototype domain. The molecular modelling of the assembled Pl-nectin homodimer accounts for a Pl-nectin quaternary structure composed of two 105-kDa C-shaped monomers linked by a S–S bridge. The presence of an LDT motif
between the first and the second exposed loops of the D2 domain suggests the binding of Pl-nectin to an integrin receptor. Altogether, the in silico analysis described here is consistent with previous biochemical
reports and offers a basis for predictions to be experimentally tested. 相似文献
19.
A. V. Voitsekhovskii V. V. Vasil’ev D. V. Grigor’ev I. V. Romanov 《Russian Physics Journal》2009,52(5):441-447
The process of reconstuction of the distribution profile of hole concentration in the p
+–n structure by the method of differential Hall measurements upon implantation of ions As+ (Е = 190 keV, D = 3.1014 cm-2, j = 0.025 μA/cm2) into epitaxial films Cd
x
Hg1–x
Te for x ~ 0.2, with the initial electron concentration and mobility n = 1014 cm-3 and μ = 2∙105 cm2∙V–1∙s–1 is numerically simulated. The dependences of degree of reconstruction of the hole-concentration distribution profile on the
depth of a shunting n-layer and magnitude of the magnetic field, at which the electrophysical parameters of the p
+–n structure are measured, are calculated. The dependence of the limiting magnetic field determining the magnetic-field range
for measurements on the n-layer depth is found. It is shown that in calculations one should use the conduction values measured
at the same magnetic fields as the Hall coefficients for determination of the holeconcentration distribution profile using
the Petritz model. 相似文献
20.
E. V. Sedel’nikov 《JETP Letters》1999,69(9):645-649
The results of calculations of 3He, 3H, and D production as a result of the disintegration of primordial 4He by high-energy protons and anti-protons in the early Universe are reported. It is shown that for primary particle energies
E
p
,
p
t-
<0.2 GeV the main role in 3He, 3H, and D production is played by the secondary proton cascade that develops in the cosmological plasma and which destroys
4He most intensively at E~75 MeV. At the current state of the experimental data one can calculate the number of nuclei produced to within 10%, and
investigation of the inelastic p
4He interaction channels at E~75 MeV will make it possible to improve substantially the accuracy of calculations of the additional production of light
elements.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 9, 609–613 (May 1999) 相似文献