Effect of grid system on finite element calculation

Detailed parametric studies of the effect of grid system on finite element calculation for potential flows were made. These studies led to the formulation of a design criteria for optimum mesh system and the development of two methods to generate the optimum mesh system. The guidelines for optimum mesh system are: (1) the mesh structure should be regular; (2) the element should be as regular and equilateral as possible; (3) the distribution of size of element should be consistent with that of flow variables to insure maximum uniformity in error distribution; (4) for non-Dirichlet boundary conditions, smaller boundary elements or higher order interpolation functions should be used; and (5) the mesh should accommodate the boundary geometry as accurately as possible. The results of the parametric studies are presented

GaAs-GaAlAs distributed-feedback diode lasers with separate optical and carrier confinement

Remarkable reduction of the threshold current density is achieved in GaAs-GaAlAs distributed-feedback diode lasers by adopting a separate-confinement heterostructure. The diodes are lased successfully at temperatures up to 340 °K under pulsed operation. The lowest threshold current density is 3 kA/cm^2 at 300 °K

Liquid phase epitaxy of GaAlAs on GaAs substrates with fine surface corrugations

Liquid phase epitaxy of GaAlAs was performed on GaAs fine surface corrugations. By optimizing the growth conditions, GaAlAs layers were grown successfully with only minimal meltback

Artifacts with uneven sampling of red noise

The vast majority of sampling systems operate in a standard way: at each tick of a fixed-frequency master clock a digitizer reads out a voltage that corresponds to the value of some physical quantity and translates it into a bit pattern that is either transmitted, stored, or processed right away. Thus signal sampling at evenly spaced time intervals is the rule: however this is not always the case, and uneven sampling is sometimes unavoidable. While periodic or quasi-periodic uneven sampling of a deterministic signal can reasonably be expected to produce artifacts, it is much less obvious that the same happens with noise: here I show that this is indeed the case only for long-memory noise processes, i.e., power-law noises $1/f^\alpha$ with $\alpha > 2$. The resulting artifacts are usually a nuisance although they can be eliminated with a proper processing of the signal samples, but they could also be turned to advantage and used to encode information.Comment: 5 figure

Strangeness counting in high energy collisions

The estimates of overall strange quark production in high energy e+e-, pp and ppbar collisions by using the statistical-thermal model of hadronisation are presented and compared with previous works. The parametrization of strangeness suppression within the model is discussed. Interesting regularities emerge in the strange/non-strange produced quark ratio which turns out to be fairly constant in elementary collisions while it is twice as large in SPS heavy ion collision.Comment: talk given at Strangeness in Quark Matter 98, submitted to J. Phys.

Postmortem imaging of blood and its characteristics using MSCT and MRI

The rapid development of computed tomography (CT) and magnetic resonance imaging (MRI) led to the introduction and establishment in postmortem investigations. The objectives of this preliminary study were to describe the imaging appearances of the early postmortem changes of blood after cessation of the circulation, such as sedimentation, postmortem clotting, and internal livores, and to give a few first suggestions on how to differentiate them from other forensic findings. In the Virtopsy project, 95 human corpses underwent postmortem imaging by CT and MRI prior to traditional autopsy and therefore 44 cases have been investigated in this study. Postmortem alterations as well as the forensic relevant findings of the blood, such as internal or subcutaneous bleedings, are presented on the basis of their imaging appearances in multislice CT and MR

Observation of sub-Poisson photon statistics in the cavity-QED microlaser

We have measured the second-order correlation function of the cavity-QED microlaser output and observed a transition from photon bunching to antibunching with increasing average number of intracavity atoms. The observed correlation times and the transition from super- to sub-Poisson photon statistics can be well described by gain-loss feedback or enhanced/reduced restoring action against fluctuations in photon number in the context of a quantum microlaser theory and a photon rate equation picture. However, the theory predicts a degree of antibunching several times larger than that observed, which may indicate the inadequacy of its treatment of atomic velocity distributions.Comment: 4 pages, 4 figure

Second Cluster Integral and Excluded Volume Effects for the Pion Gas

The quantum mechanical formula for Mayer's second cluster integral for the gas of relativistic particles with hard-core interaction is derived. The proper pion volume calculated with quantum mechanical formula is found to be an order of magnitude larger than its classical evaluation. The second cluster integral for the pion gas is calculated in quantum mechanical approach with account for both attractive and hard-core repulsive interactions. It is shown that, in the second cluster approximation, the repulsive pion-pion-interactions as well as the finite width of resonances give important but almost canceling contributions. In contrast, an appreciable deviation from the ideal gas of pions and pion resonances is observed beyond the second cluster approximation in the framework of the Van der Waals excluded-volume model.Comment: 29 pages, Latex, 9 PS-figure