10 research outputs found
Soft capacitor fibers using conductive polymers for electronic textiles
A novel, highly flexible, conductive polymer-based fiber with high electric
capacitance is reported. In its crossection the fiber features a periodic
sequence of hundreds of conductive and isolating plastic layers positioned
around metallic electrodes. The fiber is fabricated using fiber drawing method,
where a multi-material macroscopic preform is drawn into a sub-millimeter
capacitor fiber in a single fabrication step. Several kilometres of fibers can
be obtained from a single preform with fiber diameters ranging between 500um
-1000um. A typical measured capacitance of our fibers is 60-100 nF/m and it is
independent of the fiber diameter. For comparison, a coaxial cable of the
comparable dimensions would have only ~0.06nF/m capacitance. Analysis of the
fiber frequency response shows that in its simplest interrogation mode the
capacitor fiber has a transverse resistance of 5 kOhm/L, which is inversely
proportional to the fiber length L and is independent of the fiber diameter.
Softness of the fiber materials, absence of liquid electrolyte in the fiber
structure, ease of scalability to large production volumes, and high
capacitance of our fibers make them interesting for various smart textile
applications ranging from distributed sensing to energy storage
Violent solar events of October-November 2003 as recorded by IZMIRAN radio observations
The extreme solar activity of October-November 2003 was recorded at IZMIRAN with digital radiospectrographs at 25-270 MHz and fixed-frequency radiometers at 169, 204 and 3000 MHz. An outstanding metre-wavelength noise storm took place during the fist passage of the grandiose evolving active complex across the disc which testifies to permanent electron acceleration over the complex with energy of up to tens of kiloelectronvolts. Against this background, intense metric and microwave radio bursts were recorded in association with several outstanding flare and huge coronal mass ejection (CME) events. The dynamic spectra of these events display multiband and sometimes fine-structure type II bursts, initiated by coronal shocks, and various continuum emissions. In some cases, a corresponding microwave burst at 3000 MHz includes not only an impulsive component coinciding with a flare maximum but also a predominating delayed long-duration component with a smooth time profile. The latter component is thought to be linked with a post-eruptive energy release and particle acceleration when the magnetic field, strongly disturbed by a CME, relaxes to a new quasi-equilibrium configuration via reconnection in high coronal levels
Fine Structure of Solar Radio Bursts Observed at Decametric and Hectometric Waves
International audienceThe analysis of WIND/WAVES RAD2 spectra with fine structure in the form of different fibers in 14 events covering 1997 2005 is carried out. A splitting of broad bands of the interplanetary (IP) type II bursts into narrow band fibers of different duration is observed. The instantaneous-frequency bandwidth of fibers is stable: 200 300 kHz for slow-drifting fibers in type II bursts, and 700 1000 kHz for fast-drifting fibers in type II + IV (continuum). Intermediate drift bursts (IDB or fiber bursts) and zebra patterns with variable frequency drift of stripes, typical for the metric range, were not found. Comparison of spectra with the Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph (SOHO/LASCO C2) images shows a connection of the generation of the fiber structures with the passage of shock fronts through narrow jets in the wake of Coronal Mass Ejections (CME). Therefore the most probable emission mechanism of fibers in IP type II bursts appears to be resonance transition radiation (RTR) of fast particles at the boundary of two media with different refractive indices. The same mechanism is also valid for striae in the type III bursts. Taking into account a high-density contrast in the CME wake and the actually observed small-scale inhomogeneities, the effectiveness of the RTR mechanism in IP space must be considerably higher than in the meter or decimeter wavelengths. For the most part the fibers in the type IV continuum at frequencies of 14 8 MHz were seen as the direct expansion of similar fine structure (as fibers or ``herringbone'' structure) in the decametric range observed with the Nançay and IZMIRAN spectrographs