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Dielectric properties of epoxy nanocomposites containing TiO2, Al2O3 and ZnO fillers
The paper presents results of dielectric spectroscopy and space charge (PEA) measurements on epoxy resin filled with 10% w/w micro- and nano- sized particles of TiO2, Al3O2 and ZnO. The results appear to show that the material from which the nano-particle is made is not highly significant in influencing these results. The results support the proposition that the dielectric properties of such nano-filled composites are controlled by Stern-Gouy-Chapman layers (“interaction zones”) around the particles
Improving the Dielectric Properties of Polymers by Incorporating Nano-particles.
The paper presents a brief review of the promise of nanotechnology applied to polymeric insulation materials and discusses the electrical properties found. For a variety of nanocomposites, the dielectric behaviour has shown that the interface between the embedded particles and host matrix holds the key to the understanding of the bulk phenomena being observed. Dielectric spectroscopy verified the motion of carriers through the interaction zones that surround the particles. The obvious improvements in endurance and breakdown strength of nanocomposites may be due to a reduction of charge accumulation. PEA space charge tests confirm this charge dissipation. By examining the onset field of space charge accumulation, it may be possible to determine whether a system is likely to be useful
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The influence of physical and chemical linkage on the properties of nanocomposites
It has been shown by several groups that the mechanical and electrical behavior of composites changes quite substantially, and often beneficially, when the filler particle size is less than 100 nm in diameter. There is also good reason to believe that the interface between the embedded particulates and the polymer matrix holds the key to understanding the bulk phenomena observed. Materials based on an SiO2-polyolefin system have been formulated with functionalized particulates so as to affect the physical and chemical linkages. The agents used to achieve this include amino-silane, hexamethyl-disilazane and triethoxyvinylsilane. The emerging picture of the interface is supported by detailed dielectric spectroscopy and internal space charge assessment. The nature of the internal structure has been related to the bulk properties observed such as the breakdown strength, voltage endurance, and the measurement of internal charges resulting from interfacial polarization
Competition and cooperation in one-dimensional stepping stone models
Cooperative mutualism is a major force driving evolution and sustaining
ecosystems. Although the importance of spatial degrees of freedom and number
fluctuations is well-known, their effects on mutualism are not fully
understood. With range expansions of microbes in mind, we show that, even when
mutualism confers a distinct selective advantage, it persists only in
populations with high density and frequent migrations. When these parameters
are reduced, mutualism is generically lost via a directed percolation process,
with a phase diagram strongly influenced by an exceptional DP2 transition.Comment: 8 pages, 4 figure
The 1980 solar maximum mission event listing
Information is contained on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1980 pointed observations. Data from the following SMM experiments are included: (1) Gamma Ray Spectrometer, (2) Hard X-Ray Burst Spectrometer, (3) Hard X-Ray Imaging Spectrometer, (4) Flat Crystal Spectrometer, (5) Bent Crystal Spectrometer, (6) Ultraviolet Spectrometer and Polarimeter, and (7) Coronagraph/Polarimeter. Correlative optical, radio, and Geostationary Operational Environmental Satellite (GOES) x ray data are also presented. Where possible, bursts or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observations. Spacecraft pointing coordinates and flare site angular displacement values from Sun center are also included
Symbiotic stars in X-rays III: Suzaku observations
We describe the X-ray emission as observed with Suzaku from five symbiotic
stars that we selected for deep Suzaku observations after their initial
detection with ROSAT, ASCA and Swift. We find that the X-ray spectra of all
five sources can be adequately fit with absorbed, optically thin thermal plasma
models, with either single- or multi-temperature plasmas. These models are
compatible with the X-ray emission originating in the boundary layer between an
accretion disk and a white dwarf. The high plasma temperatures of kT keV
for all five targets were greater than expected for colliding winds. Based on
these high temperatures, as well as previous measurements of UV variability and
UV luminosity, and the large amplitude of X-ray flickering in 4 Dra, we
conclude that all five sources are accretion-powered through predominantly
optically thick boundary layers. Our X-ray data allow us to observe a small,
optically thin portion of the emission from these boundary layers. Given the
time between previous observations and these observations, we find that the
intrinsic X-ray flux and the intervening absorbing column can vary by factors
of three or more on a time scale of years. However, the location of the
absorber and the relationship between changes in accretion rate and absorption
are still elusive.Comment: 14 pages, 3 figures and 3 tables. Accepted to published 04/15/2016.
arXiv admin note: substantial text overlap with arXiv:1505.0063
Statistical Analysis of Small Ellerman Bomb Events
The properties of Ellerman bombs (EBs), small-scale brightenings in the
H-alpha line wings, have proved difficult to establish due to their size being
close to the spatial resolution of even the most advanced telescopes. Here, we
aim to infer the size and lifetime of EBs using high-resolution data of an
emerging active region collected using the Interferometric BIdimensional
Spectrometer (IBIS) and Rapid Oscillations of the Solar Atmosphere (ROSA)
instruments as well as the Helioseismic and Magnetic Imager (HMI) onboard the
Solar Dynamics Observatory (SDO). We develop an algorithm to track EBs through
their evolution, finding that EBs can often be much smaller (around 0.3") and
shorter lived (less than 1 minute) than previous estimates. A correlation
between G-band magnetic bright points and EBs is also found. Combining SDO/HMI
and G-band data gives a good proxy of the polarity for the vertical magnetic
field. It is found that EBs often occur both over regions of opposite polarity
flux and strong unipolar fields, possibly hinting at magnetic reconnection as a
driver of these events.The energetics of EB events is found to follow a
power-law distribution in the range of "nano-flare" (10^{22-25} ergs).Comment: 19 pages. 7 Figure
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