134 research outputs found
Relativistic quantum model of confinement and the current quark masses
We consider a relativistic quantum model of confined massive spinning quarks
and antiquarks which describes leading Regge trajectories of mesons. The quarks
are described by the Dirac equations and the gluon contribution is approximated
by the Nambu-Goto straight-line string. The string tension and the current
quark masses are the main parameters of the model. Additional parameters are
phenomenological constants which approximate nonstring short-range
contributions. Comparison of the measured meson masses with the model
predictions allows one to determine the current quark masses (in MeV) to be
. The chiral
model[23] makes it possible to estimate from here the - and -quark masses
to be ~ Mev and Mev.Comment: 15 pages, LATEX, 2 tables. (submitted to Phys.Rev.D
Heuristic Models of Two-Fermion Relativistic Systems with Field-Type Interaction
We use the chain of simple heuristic expedients to obtain perturbative and
exactly solvable relativistic spectra for a family of two-fermionic bound
systems with Coulomb-like interaction. In the case of electromagnetic
interaction the spectrum coincides up to the second order in a coupling
constant with that following from the quantum electrodynamics. Discrepancy
occurs only for S-states which is the well-known difficulty in the bound-state
problem. The confinement interaction is considered too.
PACS number(s): 03.65.Pm, 03.65.Ge, 12.39.PnComment: 16 pages, LaTeX 2.0
Experimental and theoretical study of swept-wing boundary-layer instabilities. Three-dimensional Tollmien-Schlichting instability
Extensive combined experimental and theoretical investigations of the linear evolution of three-dimensional (3D) Tollmien-Schlichting (TS) instability modes of 3D boundary layers developing on a swept airfoil section have been carried out. The flow under consideration is the boundary layer over an airfoil at 35 degrees sweep and an angle of attack of +1.5 degree. At these conditions, TS instability is found to be the predominant one. Perturbations with different frequencies and spanwise wavenumbers are generated in a controlled way using a row of elastic membranes. All experimental results are deeply processed and compared with results of calculations based on theoretical approaches. Very good quantitative agreement of all measured and calculated stability characteristics of swept-wing boundary layers is achieved
Experimental and theoretical study of swept-wing boundary-layer instabilities: Unsteady crossflow instability
Extensive combined experimental and theoretical investigations of the linear evolution of unsteady (in general) Cross-Flow (CF) and threedimensional (3D) Tollmien-Schlichting (TS) instability modes of 3D boundary layers developing on a swept airfoil section have been carried
out. CF-instability characteristics are investigated in detail at an angle of attack of −5○ when this kind of instability dominates in the laminarturbulent transition process, while the 3D TS-instability characteristics are studied at an angle of attack of +1.5○ when this kind of instability is predominant in the transition process. All experimental results are deeply processed and compared with results of calculations based on several theoretical approaches. For the first time, very good quantitative agreement of all measured and calculated stability characteristics of swept-wing boundary layers is achieved both for unsteady CF- and 3D TS-instability modes for the case of a boundary layer developing on a real swept airfoil. The first part of the present study (this paper) is devoted to the description of the case of CF-dominated transition, while the TS-dominated case will be described in detail in a subsequent second part of this investigation
Verification and characterization of predominant instabilities of swept-wing boundary layers
The problem of identification and verification of the most important linear stability mechanisms of initial stages of laminar-turbulent transition in three-dimensional (3D) swept-wing boundary layers is discussed based on experimental and theoretical investigations performed, in particular, for real swept airfoil sections. Detailed analysis of all main boundary-layer stability characteristics with respect to the cross-flow (CF) instability modes and 3D Tollmien-Schlichting (TS) instability modes is carried out based on experimental data, as well as on computations within the framework of linear stability theories and the Parabolized Stability Equation (PSE) approach. The possibility of a very good agreement between all main measured and calculated stability characteristics is shown. Role of surface curvature and base-flow non-parallelism is discussed
Quantitative study of localized mechanisms of excitation of cross-flow instability modes in a swept-wing boundary layer
An experimental study of two efficient receptivity mechanisms of excitation of cross-flow (CF) instability modes is carried out in a boundary layer of a real airfoil section of a swept wing due to: (i) action of localized surface vibrations, and (ii) scattering of 2D freestream vortices on them. It is found that the two mechanisms lead to rather efficient excitation of CF-modes both at surface vibration frequency and at combination 'vortex-vibration' frequencies. First estimations of the corresponding localized receptivity coefficients are obtained. Direct comparison of the experimental amplification curves of the excited CF-modes with those calculated based on the linear stability theory (LST) has shown that the experimental data obtained at vibration frequency are in excellent agreement with the LST. At the same time, growth rates of the CF-modes excited at combination frequencies are found to be completely inconsistent with the LST. A possible explanation of this phenomenon via action of a new efficient distributed receptivity mechanism is suggested. This mechanism is associated with scattering of freestream vortices on rather high-amplitude CF-modes excited by surface vibrations
New superstructural thermoplastics and carbon composite materials based on them
New superconstructional polyarylates with glass transition temperatures from 216 to 280°C and polyethersulfones with glass transition temperatures from 230 to 255°C have been developed. On the basis of these polymers, industrial polysulfone PSFF-30, PSF-150, polyethersulfone E-3010, polyetherimide Ultem 1000, PEEK and PEKK, and two types of carbon fabrics, thermoplastic prepregs and consolidated carbon composite plates were obtained, and their mechanical properties under compression and three-point bending were determined
Production technology of heat-resistant high-strength syntactic carbon foams for operation in extreme conditions
© Published under licence by IOP Publishing Ltd. Production technology of products based on the syntactic carbon foams designed to operate in extreme conditions is proposed. The components and regime parameters for the production of foams of an open-pore cellular structure with specified thermophysical and strength characteristics for manufacturing the large-sized products of complex shape are determined
Probing Anomalous Quartic Couplings in e-gamma and gamma-gamma Colliders
We analyze the potential of the e+e- Linear Colliders, operating in the
e-gamma and gamma-gamma modes, to probe anomalous quartic vector--boson
interactions through the multiple production of W's and Z's. We examine all
chiral operators of order p^4 that lead to new
four--gauge--boson interactions but do not alter trilinear vertices. We show
that the e-gamma and gamma-gamma modes are able not only to establish the
existence of a strongly interacting symmetry breaking sector but also to probe
for anomalous quartic couplings of the order of 10^{-2} at 90% CL. Moreover,
the information gathered in the e-gamma mode can be used to reduced the
ambiguities of the e+e- mode.Comment: Revtex, 18 pages, 6 figure
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