10,690 research outputs found
High pressure gas storage capacities. Example of a solution using filament windings
The use of epoxy resin fiber glass and economic factors affecting the choice of materials for gas storage are discussed. The physical nature of the filament windings are described together with the results obtained. It is demonstrated that a substantial reduction in mass and an enhanced level of safety can be assured at a competitive cost by storing gases in this way
A model of an optical biosensor detecting environment
Heller et. Al. (Science 311, 508 (2006)) demonstrated the first DNA-CN
optical sensor by wrapping a piece of double-stranded DNA around the surface of
single-walled carbon nanotubes (CN). This new type of optical device can be
placed inside living cells and detect trace amounts of harmful contaminants by
means of near infrared light. Using a simple exciton theory in nanostructures
and the phenomena of B-Z structural phase transition of DNA, we investigate the
working principle of this new class of optical biosensor from DNA by using the
nanostructure surface as a sensor to detect the property change of DNA as it
responds to the presence of target ions. We also propose some new design models
by replacing carbon nanotubes with graphene ribbon semiconductors.Comment: 4 pages, 4 figures, Accepte
The Yoneda algebra of a graded Ore extension
Let A be a connected-graded algebra with trivial module k, and let B be a
graded Ore extension of A. We relate the structure of the Yoneda algebra E(A)
:= Ext_A(k,k) to E(B). Cassidy and Shelton have shown that when A satisfies
their K_2 property, B will also be K_2. We prove the converse of this result.Comment: 9 page
Precoder design for space-time coded systems over correlated Rayleigh fading channels using convex optimization
A class of computationally efficient linear precoders for space-time block coded multiple-input multiple-output wireless systems is derived based on the minimization of the exact symbol error rate (SER) and its upper bound. Both correlations at the transmitter and receiver are assumed to be present, and only statistical channel state information in the form of the transmit and receive correlation matrices is assumed to be available at the transmitter. The convexity of the design based on SER minimization is established and exploited. The advantage of the developed technique is its low complexity. We also find various relationships of the proposed designs to the existing precoding techniques, and derive very simple closed-form precoders for special cases such as two or three receive antennas and constant receive correlation. The numerical simulations illustrate the excellent SER performance of the proposed precoders
Discovery of a nearby young brown dwarf binary candidate
In near-infrared NaCo observations of the young brown dwarf 2MASS
J0041353-562112, we discovered a companion a little less than a magnitude
fainter than the primary. The binary candidate has a separation of 143 mas, the
spectral types are M6.5 and M9.0 for the two components. Colors and flux ratios
are consistent with the components being located at the same distance
minimizing the probability of the secondary being a background object. The
brown dwarf is known to show Li absorption constraining the age to less than
~200 Myr, and it was suspected to show ongoing accretion, indicating an age as
low as ~10 Myr. We estimate distance and orbital parameters of the binary as a
function of age. For an age of 10 Myr, the distance to the system is 50 pc, the
orbital period is 126 yr, and the masses of the components are ~30 and ~15
MJup. The binary brown dwarf fills a so far unoccupied region in the parameters
mass and age; it is a valuable new benchmark object for brown dwarf atmospheric
and evolutionary models.Comment: 4 pages, 2 figures, accepted by A&
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