151,142 research outputs found
Optimization of micromachined relex klystrons for operation at terahertz frequencies
New micromachining techniques now provide us
with the technology to fabricate reflex klystron oscillators with dimensions suitable for operation in the terahertz region of the electromagnetic spectrum. For the success of these devices, accurate designs are required since the optimization of certain parameters is critical to obtaining useful amounts of ac power. Classical models for device design have long been in existence,
but these are no longer valid at terahertz frequencies. For this reason, we have developed a simulation tool, specifically aimed at the design of terahertz frequency reflex klystrons. The tool, based on the Monte Carlo algorithm, includes loss mechanisms and takes into account the main peculiarities expected for device
operation at terahertz frequencies. In this study, the tool is used to study the influence of the electron beam aperture angle and cavity dimensions (particularly the grid spacing) on ac power generation. The results demonstrate that aperture angles of less than 10 are necessary for the optimization of output power. It is
also found that the power output is highly sensitive to the distance between the grids
Little Higgs searches at LHC
A new method of solving the hierarchy problem in the SM has been proposed.
This method leads to the so-called "Little Higgs" models. The ATLAS experiment
at LHC has undertaken studies of the new particles predicted by these model: a
heavy top quark, heavy gauge bosons and additional Higgs bosons. Simulations of
their decays have been carried out. The sensitivity of the ATLAS experiment to
discover these new particles is discussed.Comment: 8 pages, 8 figures, XXXIXth Rencontres de Moriond, La Thuile(2004
Towards Loop-Free Forwarding of Anonymous Internet Datagrams that Enforce Provenance
The way in which addressing and forwarding are implemented in the Internet
constitutes one of its biggest privacy and security challenges. The fact that
source addresses in Internet datagrams cannot be trusted makes the IP Internet
inherently vulnerable to DoS and DDoS attacks. The Internet forwarding plane is
open to attacks to the privacy of datagram sources, because source addresses in
Internet datagrams have global scope. The fact an Internet datagrams are
forwarded based solely on the destination addresses stated in datagram headers
and the next hops stored in the forwarding information bases (FIB) of relaying
routers allows Internet datagrams to traverse loops, which wastes resources and
leaves the Internet open to further attacks. We introduce PEAR (Provenance
Enforcement through Addressing and Routing), a new approach for addressing and
forwarding of Internet datagrams that enables anonymous forwarding of Internet
datagrams, eliminates many of the existing DDoS attacks on the IP Internet, and
prevents Internet datagrams from looping, even in the presence of routing-table
loops.Comment: Proceedings of IEEE Globecom 2016, 4-8 December 2016, Washington,
D.C., US
A metric property of umbilic points
In the space of cubic forms of surfaces, regarded as a
-space and endowed with a natural invariant metric, the ratio of the volumes
of those representing umbilic points with negative to those with positive
indexes is evaluated in terms of the asymmetry of the metric, defined here. A
connection of this ratio with that reported by Berry and Hannay (1977) in the
domain of Statistical Physics, is discussed.Comment: 8 pages, 1 figur
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