Assessment of localized artificial diffusivity scheme for large-eddy simulation of compressible turbulent flows

The localized artificial diffusivity method is investigated in the context of large-eddy simulation of compressible turbulent flows. The performance of different artificial bulk viscosity models are evaluated through detailed results from the evolution of decaying compressible isotropic turbulence with eddy shocklets and supersonic turbulent boundary layer. Effects of subgrid-scale (SGS) models and implicit time-integration scheme/time-step size are also investigated within the framework of the numerical scheme used. The use of a shock sensor along with artificial bulk viscosity significantly improves the scheme for simulating turbulent flows involving shocks while retaining the shock-capturing capability. The proposed combination of Ducros-type sensor with a negative dilatation sensor removes unnecessary bulk viscosity within expansion and weakly compressible turbulence regions without shocks and allows it to localize near the shocks. It also eliminates the need for a wall-damping function for the bulk viscosity while simulating wall-bounded turbulent flows. For the numerical schemes used, better results are obtained without adding an explicit SGS model than with SGS model at moderate Reynolds number. Inclusion of a SGS model in addition to the low-pass filtering and artificial bulk viscosity results in additional damping of the resolved turbulence. However, investigations at higher Reynolds numbers suggest the need for an explicit SGS model. The flow statistics obtained using the second-order implicit time-integration scheme with three sub-iterations closely agrees with the explicit scheme if the maximum Courant–Friedrichs–Lewy is kept near unity.     

Weissenberg reflection high-energy electron diffraction for surface crystallography

The principle of a Weissenberg camera is applied to surface crystallographic analysis by reflection high-energy electron diffraction. By removing inelastic electrons and measuring hundreds of patterns as a function of sample rotation angle phi, kinematical analysis can be performed over a large volume of reciprocal space. The data set is equivalent to a three-dimensional stack of Weissenberg photographs. The method is applied to analysis of an Si(111)-square root of 3 x square root of 3-Ag surface, and the structural data obtained are in excellent agreement with the known atomic structure.     

Plateaus in the dispersion of two-dimensional magnetoplasmons in GaAs quantum wells: theoretical evidence of an electron reservoir

The filling-factor-dependent plateau-type dispersion of the long-wavelength magnetoplasmon in high-mobility two-dimensional electron system observed by Holland et al. [Phys. Rev. Lett. 93, 186804 (2004)10.1103/PhysRevLett.93.186804] can be explained by the well-established semiclassical dispersion, by adopting the electron reservoir hypothesis previously proposed in order to explain the integer quantum Hall effects.     

Observation of B_(s)(0)-->phigamma and search for B_(s)(0)-->gammagamma decays at Belle

We search for the radiative penguin decays B_{s}{0}-->varphigamma and B_{s}{0}-->gammagamma in a 23.6 fb{-1} data sample collected at the Upsilon(5S) resonance with the Belle detector at the KEKB e{+}e{-} asymmetric-energy collider. We observe for the first time a radiative penguin decay of the B_{s}{0} meson in the B_{s}{0}-->varphigamma mode and we measure B(B_{s}{0}-->varphigamma)=(57_{-15}{+18}(stat)-11+12(syst))x10{-6}. No significant B_{s}{0}-->gammagamma signal is observed and we set a 90% confidence level upper limit of B(B_{s}{0}-->gammagamma)<8.7x10{-6}.     

Observation of anomalous upsilon(1S)pi+pi(-) and upsilon(2S)pi+pi(-) production near the upsilon(5S) resonance

We report the first observation of e;{+}e;{-}-->Upsilon(1S)pi;{+}pi;{-}, Upsilon(2S)pi;{+}pi;{-}, and first evidence for e;{+}e;{-}-->Upsilon(3S)pi;{+}pi;{-}, Upsilon(1S)K+K-, near the peak of the Upsilon(5S) resonance at sqrt[s] approximately 10.87 GeV. The results are based on a data sample of 21.7 fb;{-1} collected with the Belle detector at the KEKB e;{+}e;{-} collider. Attributing the signals to the Upsilon(5S) resonance, the partial widths Gamma(Upsilon(5S)-->Upsilon(1S)pi;{+}pi;{-})=0.59+/-0.04(stat)+/-0.09(syst) MeV and Gamma(Upsilon(5S)-->Upsilon(2S)pi;{+}pi;{-})=0.85+/-0.07(stat)+/-0.16(syst) MeV are obtained from the observed cross sections. These values exceed by more than 2 orders of magnitude the previously measured partial widths for dipion transitions between lower Upsilon resonances.     

Zero frequency shift of an oscillating-rotating liquid droplet

Free-decay oscillations and rotations of a levitated liquid droplet are simulated numerically, and the frequency shift of drop-shape oscillations is studied. It is shown for an oscillating-rotating liquid droplet that the oscillation frequency decreases as the amplitude of drop-shape oscillations increases, while it increases as the rotation rate increases. The pressure difference between the equator and the pole of the droplet is found to correspond to the frequency shift. It is also found that the relation between the amplitude and the rotation rate is linear both for zero frequency shift and for zero pressure difference.     

Experimental determination of orientations for the 17 O electric-field-gradient and chemical shielding tensors in L-alanine

We have presented a solid-state 17 O NMR study of [13C, 17 O]-L-alanine. Using the experimental results for the 13C-17 O dipolar vector and Euler angles, the absolute orientations of 17 O chemical shielding (CS) and electric-field-gradient (EFG) tensors with respect to the molecular frame can be determined for L-alanine. The present results suggest that the intermediate EFG tensor components, VYY, lie in the carboxylate plane and parallel to the C-O bond directions, while the least shielded components, delta11, and the intermediate CS tensor components, delta22, roughly lie in the molecular plane and the direction of delta22 components are approximately 38 degrees and 25 degrees off the C-O bonds for O1 and O2, respectively. These results are in reasonable agreement with those of our quantum chemical calculations reported previously.     

Measurement of branching fractions, isospin, and CP-violating asymmetries for exclusive b-->dgamma modes

We report new measurements of the decays B+-->rho+gamma, B0-->rho0gamma, and B0-->omegagamma using a data sample of 657x10(6) B meson pairs accumulated with the Belle detector at the KEKB e+e- collider. We measure branching fractions B(B+-->rho+gamma)=(8.7_-2.7-1.1;+2.9+0.9)x10(-7), B(B0-->rho0gamma)=(7.8_-1.6-1.0;+1.7+0.9)x10(-7), and B(B0-->omegagamma)=(4.0_-1.7;+1.9+/-1.3)x10(-7). We also report the isospin asymmetry Delta(rhogamma)=-0.48_-0.19-0.09;+0.21+0.08 and the first measurement of the direct CP-violating asymmetry ACP(B+-->rho+gamma)=-0.11+/-0.32+/-0.09, where the first and second errors are statistical and systematic, respectively.     

Analysis of thermal decomposition behaviors with consecutive reactions by TG

Thermal decomposition behaviors of a fluororubber are observed with linear heating mode at constant rate, controlled rate mode and isothermal mode of TG/DTA, and, with isothermal mode of TG/mass-spectrometer. The results suggest that this material decomposes with, at least, three consecutive reactions. From the results of TG/DTA and TGMS in isothermal mode, it is considered that the first reaction is the first-order reaction, the second reaction is chain reaction and the last reaction is vaporization of residue. Supposing these three consecutive reactions, the decomposition behaviors of the rubber is simulated. The observed curves of fraction of mass loss, , against time, t, are well reproduced by the simulation. The relationship between d/dt and is reproduced also, though the differences between observed and the calculated values of d/dt are slightly larger than noise level of d/dt.