Search results for "dispersion"
showing 10 items of 1101 documents
Convection and thermodiffusion of colloidal gold tracers by laser light scattering
1999
In a dynamic light scattering experiment, we have investigated the time intensity correlation function and the profile of the transmitted laser beam for organic dispersions of light absorbing colloidal particles containing tiny gold clusters. The correlation functions have been found to show a superposition of an exponential decay, corresponding to Brownian motion of the tracers, and well-defined oscillations. These oscillations are caused by convection due to local heating of the sample by the incident laser beam, which has been confirmed independently via measurements of the local temperature within the sample. It will be shown how the particle convection velocity, which is the order of 1…
Onset of convection in a vertical porous cylinder with a permeable and conducting side boundary
2015
Abstract The onset of natural convection in a vertical porous cylinder saturated by a fluid is studied. The lateral confinement of the porous cylinder is due to an external porous medium having a permeability much smaller than that of the cylinder. Thus, the vertical side boundary of the cylinder is permeable and constrained by given pressure and temperature distributions. The lower and upper plane boundaries of the cylinder are impermeable walls. The lower wall is subject to a uniform heat flux, while the upper wall has a uniform temperature. The basic motionless state displays a uniform and vertical temperature gradient oriented downward. The linear stability analysis is carried out by us…
R Code for Hausdorff and Simplex Dispersion Orderings in the 2D Case
2010
This paper proposes a software implementation using R of the Hausdorff and simplex dispersion orderings. A copy can be downloaded from http://www.uv.es/~ayala/software/fun-disp.R . The paper provides some examples using the functions exactHausdorff for the Hausdorff dispersion ordering and the function simplex for the simplex dispersion orderings. Some auxiliary functions are commented too.
The ALHAMBRA survey: Estimation of the clustering signal encoded in the cosmic variance
2015
[Aims]: The relative cosmic variance (σv) is a fundamental source of uncertainty in pencil-beam surveys and, as a particular case of count-in-cell statistics, can be used to estimate the bias between galaxies and their underlying dark-matter distribution. Our goal is to test the significance of the clustering information encoded in the σv measured in the ALHAMBRA survey. [Methods]: We measure the cosmic variance of several galaxy populations selected with B-band luminosity at 0.35 ≤ z< 1.05 as the intrinsic dispersion in the number density distribution derived from the 48 ALHAMBRA subfields. We compare the observational σv with the cosmic variance of the dark matter expected from the theory…
The effect of triple excitations in coupled cluster calculations of frequency-dependent polarizabilities
1998
Abstract Frequency-dependent polarizabilities have been implemented within the CC3 model. Comparison with full configuration interaction results shows that the triple excitation effects included in CC3 lead to a significantly improved treatment for the dispersion of the polarizability of CH+. For the refractivity and polarizability anisotropy of N2, better agreement with experiment is found for the CC3 results than for those obtained with the coupled cluster singles and doubles model.
The energy dependence of Zweig-rule-violating couplings. A dynamical calculation of ϕ → ρπ
1978
It has been argued that the violation of the Zweig rule is strongly dependent on the kinematical region, especially that it should decrease for large timeliket (asymptotic planarity). We have calculated thet-dependence of the vertex ϕρπ with two different methods, the first one using partial-wave dispersion relations and unitarity and the second one based on FESR and duality. The decrease in the timelike region is confirmed by both calculations. In the spacelike region the energy dependence of the Zweig-rule-violating coupling depends on the method of continuation to off-shell values. We only find an energy dependence if the full amplitude πρ → K $$\bar K$$ is taken into account.
Beam matching with space charge in energy recovery linacs
2019
Abstract Matching with space charge of an Energy-Recovery Linac (ERL) arc into the subsequent RF structure is essential to preserve beam quality. We show how to match beam envelopes and dispersion along the bends and recirculation arcs of an ERL, including space charge forces, in order to adjust the beam to the parameters of the subsequent RF structure. For a qualitative analysis, we show that one can use a beam matrix approach together with the smooth focusing approximation but with longitudinal–transverse coupling. It is also shown that the space-charge-modified dispersion plays a key role for the adjustment of the momentum compaction R 56 required for both the isochronous and the non-iso…
Kerr Optical Frequency Combs With Multi-FSR Mode Spacing in Silica Microspheres
2021
We experimentally demonstrate Kerr optical frequency combs (OFCs) with mode spacing of 1, 2, 3, 5, 6, and 8 free spectral ranges (FSRs) corresponding to 0.4, 0.8, 1.2, 2, 2.4, and 3.2 THz, respectively, in silica microspheres pumped by CW C-band lasers in the anomalous dispersion range. Experimental realizations are based on using standard telecom equipment and components such as SMF-28e fiber for producing microspheres and fiber tapers for pump coupling and OFC outcoupling. Numerical simulation is performed to support the experimental results and explain the observed spectral asymmetry in OFCs by the influence of the 3rd-order dispersion.
Inelastic and quasi-elastic light scattering in (NaCN)1?x(KCN)x quadrupolar glasses
1990
The elastic constantsc11 andc44, and the attenuation of longitudinal phonons along (100)-direction in (NaCN)1−x(KCN)x mixed crystals have been determined by brillouin spectroscopy in the temperature range fromT=10K−300K. Minima inc44 (T) which determine the freezing tempratureTF in these orientational glasses appear at lower temperatures compared to neutron scattering results. The coupling of molecular reorientations to longitudinal phonons in NaCN-rich smaples shows up in dispersion effects inc11 (T) and the appearence of a dynamical central peak nearTF.
Herding in the cryptocurrency market: CSSD and CSAD approaches
2018
Abstract We analyse the existence of herding in the cryptocurrency market through the cross-sectional standard (absolute) deviation of returns. Our results show that extreme dispersion of returns is explained by rational asset pricing models although it is possible to observe herding during down markets, which highlights the inefficiency and risk of cryptocurrencies. We also observe that the smallest digital currencies are herding with the largest ones, thus traders base their decisions on the performance of the main cryptocurrencies. However, the herding phenomenon cannot be solely attributed to Bitcoin, since the rest of the market is not herding with the main cryptocurrency.