2,724 research outputs found
Numerical investigation of flow unsteadiness and heat transfer on suction surface of rotating airfoils within a gas turbine cascade
The effects of the periodical turbulence and pressure fluctuation on suction surface heat transfer over airfoils of a row of rotor blades with a certain type have been investigated numerically in this paper. The calculation is performed using model with the numerical results of pressure fluctuation and heat transfer performance over 4 sample points being analyzed and compared with existing experimental data. It shows that the static pressure change has significant impact on heat transfer performance of the fore suction surface, especially in the active region of the shock waves formed from the trailing edge of upstream nuzzles. While, for the rear suction surface, the flow turbulence contributes more to the heat transfer change over the surface, due to the reduced pressure oscillation through this region. Phase shifted phenomenon across the surface can be observed for both pressure and heat transfer parameters, which should be a result of turbulence migration and wake passing across the airfoil
Electrodynamic Response and Stability of Molecular Crystals
We show that electrodynamic dipolar interactions, responsible for long-range
fluctuations in matter, play a significant role in the stability of molecular
crystals. Density functional theory calculations with van der Waals
interactions determined from a semilocal "atom-in-a-molecule" model result in a
large overestimation of the dielectric constants and sublimation enthalpies for
polyacene crystals from naphthalene to pentacene, whereas an accurate treatment
of non-local electrodynamic response leads to an agreement with the measured
values for both quantities. Our findings suggest that collective response
effects play a substantial role not only for optical excitations, but also for
cohesive properties of non-covalently bound molecular crystals
The strong vertices of charmed mesons , and charmonia ,
In this work, the strong form factors and coupling constants of the vertices
, , , ,
are calculated within the framework of the QCD sum rule.
For each vertex, we analyze the form factor considering all possible off-shell
cases and the contributions of the vacuum condensate terms
, ,
, and
. Then, the form
factors are fitted into analytical functions and are extrapolated into
time-like regions to get the strong coupling constants. Finally, the strong
coupling constants are obtained by using on-shell cases of the intermediate
mesons(). The results are as follows,
,
GeV,
,
and
GeV
- β¦