33,938 research outputs found
Channel Parameters Estimation Algorithm Based on The Characteristic Function under Impulse Noise Environment
Under communication environments, such as wireless sensor networks, the noise observed usually exhibits impulsive as well as Gaussian characteristics. In the initialization of channel iterative decoder, such as low density parity check codes, it is required in advance to estimate the channel parameters to obtain the prior information from the received signals. In this paper, a blind channel parameters estimator under impulsive noise environment is proposed, which is based on the empirical characteristic function in MPSK/MQAM higher-order modulation system. Simulation results show that for various MPSK/MQAM modulations, the estimator can obtain a more accurate unbiased estimation even though we do not know which kind of higher-order modulation is used
An MHD Model For Magnetar Giant Flares
Giant flares on soft gamma-ray repeaters that are thought to take place on
magnetars release enormous energy in a short time interval. Their power can be
explained by catastrophic instabilities occurring in the magnetic field
configuration and the subsequent magnetic reconnection. By analogy with the
coronal mass ejection (CME) events on the Sun, we develop a theoretical model
via an analytic approach for magnetar giant flares. In this model, the rotation
and/or displacement of the crust causes the field to twist and deform, leading
to flux rope formation in the magnetosphere and energy accumulation in the
related configuration. When the energy and helicity stored in the configuration
reach a threshold, the system loses its equilibrium, the flux rope is ejected
outward in a catastrophic way, and magnetic reconnection helps the catastrophe
develop to a plausible eruption. By taking SGR 1806 - 20 as an example, we
calculate the free magnetic energy released in such an eruptive process and
find that it is more than ergs, which is enough to power a giant
flare. The released free magnetic energy is converted into radiative energy,
kinetic energy and gravitational energy of the flux rope. We calculated the
light curves of the eruptive processes for the giant flares of SGR 1806 - 20,
SGR 0526-66 and SGR 1900+14, and compared them with the observational data. The
calculated light curves are in good agreement with the observed light curves of
giant flares.Comment: Accepted to Ap
Photolithographic micropatterning of organic, flexible biomaterials and its applications
A current trend in biodevices has involved a shift from traditional rigid platforms to flexible and stretchable formats. These flexible devices are expected to have a significant impact on future healthcare, disease diagnostics and therapeutics. However, the fabrication of such flexible devices has been limited by the choice of materials. Biomimetic composites of naturally derived and synthetic polymers provide exciting opportunities to develop mechanically flexible, physiologically compliant, and degradable bioelectronic systems. Advantages include the ability to provide conformal contact at non-planar biointerfaces, being able to be degraded at controllable rate, and invoking minimal reactions within the body. These factors present great potential as implantable devices for in-vivo applications, while also addressing concerns with “electronic waste” by being intrinsically degradable. In this work, we present a combination of photo-crosslinkable silk proteins and conductive polymers to precisely fabricate flexible devices and cell culture substrate. A facile and scalable photolithography is applied to fabricate flexible substrates with conductive and non- conductive micropatterns which show tuneable electrical and mechanical properties. We also demonstrate an approach to engineer flexibility in materials through the creation of patterned defects inspired from Kirigami- the Japanese art of paper cutting. Mechanically flexible, free- standing, optically transparent, large-area biomaterial sheets with precisely defined and computationally designed microscale cuts can be formed using a single-step photolithographic process. As composites with conducting polymers, flexible, intrinsically electroactive sheets can be formed. Through this work, the possibility of making next- generation, fully organic, flexible bioelectronics is explored.https://scholarscompass.vcu.edu/gradposters/1099/thumbnail.jp
Criticality in quark-gluon systems far beyond thermal and chemical equilibrium
Experimental evidence and theoretical arguments for the existence of
self-organized criticality in systems of gluons and quarks are presented. It is
observed that the existing data for high-transverse-momentum jet-production
exhibit striking regularities; and it is shown that, together with
first-principle considerations, such regularities can be used, not only to
probe the possible compositness of quarks, but also to obtain {\em direct
evidence} for, or against, the existence of critical temperature and/or
critical chemical potential in quark-gluon systems when hadrons are squeezed
together.Comment: 13 pages, including 1 figure and 1 tabl
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