RESUMEN
This paper characterizes the correlation of simultaneous measurements with different fast-ion H-alpha (FIDA) spectroscopy sightlines on Wendelstein 7-X. Using a collisionless guiding-center code, it is shown that, for two investigated volumes in the bulk of the plasma, some regions of phase space are correlated and the magnetic configuration has little influence on this correlation. For the sightlines of the FIDA system, the correlation between these is explained well by the magnetic configuration. Sightlines with measurement volumes at the same spatial locations have the highest correlation, and sightlines with measurement volumes near the same flux surface but on different sides of the magnetic axis have a high correlation. The correlation between the blueshifted signal in the starting sightline and redshifted signal in the detection sightline is investigated, demonstrating that it is possible to investigate any finite interval of detection wavelengths. Due to the different shapes of the weight functions for the toroidal and oblique sightlines, the blue-redshift correlation is very different from the total-spectrum correlation. The correlation between the toroidal and oblique sightline fans is relatively much larger than the internal correlation in the oblique sightlines, which is however, much larger than the internal correlation in the toroidal sightlines. This is a result of the dependence of the weight functions on the angle between the sightline and magnetic field, illustrating how important it is for the FIDA sightlines to cover different angles with the magnetic field.
RESUMEN
Shark skin has for many years inspired engineers to produce biomimetic structures reducing surface drag or acting as an anti-fouling layer. Both effects are presumed to be consequences of the structure of shark skin that is composed of arrays of so-called dermal denticles. However, the understanding of the full functional role of the dermal denticles is still a topic of research. We report optical microscopy and scanning electron microscopy of dermal denticles from three slowly swimming shark species for which the functional role of the dermal denticles is suggested as one of defense (possibly understood as anti-fouling) and/or abrasion strength. The three species are Greenland shark (Somnosius microcephalus), small-spotted catshark (Scyliorhinus canicula) and spiny dogfish (Squalus acanthias). Samples were taken at over 30 different positions on the bodies of the sharks. In addition, we demonstrate that the flow pattern near natural shark skin can be measured by micro-PIV (particle image velocimetry). The microfluidic experiments are complemented by numerical flow simulations. Both visualize unsteady flow, small eddies, and recirculation bubbles behind the natural dermal denticles.
RESUMEN
Translational, rotational, vibrational and electron temperatures of a gliding arc discharge in atmospheric pressure air were experimentally investigated using in situ, non-intrusive optical diagnostic techniques. The gliding arc discharge was driven by a 35 kHz alternating current (AC) power source and operated in a glow-type regime. The two-dimensional distribution of the translational temperature (Tt) of the gliding arc discharge was determined using planar laser-induced Rayleigh scattering. The rotational and vibrational temperatures were obtained by simulating the experimental spectra. The OH A-X (0, 0) band was used to simulate the rotational temperature (Tr) of the gliding arc discharge whereas the NO A-X (1, 0) and (0, 1) bands were used to determine its vibrational temperature (Tv). The instantaneous reduced electric field strength E/N was obtained by simultaneously measuring the instantaneous length of the plasma column, the discharge voltage and the translational temperature, from which the electron temperature (Te) of the gliding arc discharge was estimated. The uncertainties of the translational, rotational, vibrational and electron temperatures were analyzed. The relations of these four different temperatures (Te>Tv>Tr >Tt) suggest a high-degree non-equilibrium state of the gliding arc discharge.
RESUMEN
In this paper, we present a design and measurements of a five-section bandpass filter with a passband from 96 to 106 GHz. The insertion loss is less than 1.4 dB in the passband, and the rejection is better than 40 dB in the range from 115 to 142 GHz. We use transmission line coupling theory based on Tchebyscheff's synthesis in order to provide an initial guess for the geometrical parameters of the filter such as cavity lengths and coupling widths. The filter is manufactured from brass in two halves in the E-plane cut topology. The S-parameters of the filter are measured and compared with the simulations. The measured passband insertion loss is approximately 0.4 dB worse than in the simulation, and the measured passband width is approximately 3.4% narrower. The measured filter attenuation roll-off corresponds well to the simulation. We also compare our S-parameter measurements of the E-plane filter with corresponding measurements of a very similar H-plane filter. The transmission and reflection characteristics of the E-plane filter are better than those of the H-plane filter.