32,743 research outputs found
A proposed adjustable RF cable connector
In system that requires negligible loss, it may be necessary to adjust cable length to exact multiple of transmitted wavelength. Adjustable cable connector saves time and cost by eliminating need to add to or cut from cable. Device was especially designed for use with high frequencies. For particular application, connector of suitable dimensions should be used
Causal simulation and sensor planning in predictive monitoring
Two issues are addressed which arise in the task of detecting anomalous behavior in complex systems with numerous sensor channels: how to adjust alarm thresholds dynamically, within the changing operating context of the system, and how to utilize sensors selectively, so that nominal operation can be verified reliably without processing a prohibitive amount of sensor data. The approach involves simulation of a causal model of the system, which provides information on expected sensor values, and on dependencies between predicted events, useful in assessing the relative importance of events so that sensor resources can be allocated effectively. The potential applicability of this work to the execution monitoring of robot task plans is briefly discussed
Highly Optimized Tolerance: Robustness and Power Laws in Complex Systems
We introduce highly optimized tolerance (HOT), a mechanism that connects
evolving structure and power laws in interconnected systems. HOT systems arise,
e.g., in biology and engineering, where design and evolution create complex
systems sharing common features, including (1) high efficiency, performance,
and robustness to designed-for uncertainties, (2) hypersensitivity to design
flaws and unanticipated perturbations, (3) nongeneric, specialized, structured
configurations, and (4) power laws. We introduce HOT states in the context of
percolation, and contrast properties of the high density HOT states with random
configurations near the critical point. While both cases exhibit power laws,
only HOT states display properties (1-3) associated with design and evolution.Comment: 4 pages, 2 figure
Highly Optimized Tolerance: Robustness and Design in Complex Systems
Highly optimized tolerance (HOT) is a mechanism that relates evolving structure to power laws in interconnected systems. HOT systems arise where design and evolution create complex systems sharing common features, including (1) high efficiency, performance, and robustness to designed-for uncertainties, (2) hypersensitivity to design flaws and unanticipated perturbations, (3) nongeneric, specialized, structured configurations, and (4) power laws. We study the impact of incorporating increasing levels of design and find that even small amounts of design lead to HOT states in percolation
Boundary behavior of analytic functions of two variables via generalized models
We describe a generalization of the notion of a Hilbert space model of a
function in the Schur class of the bidisc. This generalization is well adapted
to the investigation of boundary behavior at a mild singularity of the function
on the 2-torus. We prove the existence of a generalized model with certain
properties corresponding to such a singularity and use this result to solve two
function-theoretic problems. The first of these is to characterise the
directional derivatives of a function in the Schur class at a singular point on
the torus for which the Carath\'eodory condition holds. The second is to obtain
a representation theorem for functions in the two-variable Pick class analogous
to the refined Nevanlinna representation of functions in the one-variable Pick
class.Comment: 30 page
Power Laws, Highly Optimized Tolerance, and Generalized Source Coding
We introduce a family of robust design problems for complex systems in uncertain environments which are based on tradeoffs between resource allocations and losses. Optimized solutions yield the “robust, yet fragile” features of highly optimized tolerance and exhibit power law tails in the distributions of events for all but the special case of Shannon coding for data compression. In addition to data compression, we construct specific solutions for world wide web traffic and forest fires, and obtain excellent agreement with measured data
A coronal wave and an asymmetric eruptive filament in SUMER, CDS, EIT, and TRACE co-observations
The objectives of the present study is to provide a better physical
understanding of the complex inter-relation and evolution of several solar
coronal features comprising a double-peak flare, a coronal dimming caused by a
CME, a CME-driven compression, and a fast-mode wave. For the first time, the
evolution of an asymmetric eruptive filament is analysed in simultaneous SUMER
spectroscopic and TRACE and EIT imaging data. We use imaging observations from
EIT and TRACE in the 195A channel and spectroscopic observations from the CDS
in a rastering and SUMER in a sit-and-stare observing mode. The SUMER spectra
cover spectral lines with formation temperatures from logT(K) ~ 4.0 to 6.1.
Although the event was already analysed in two previous studies, our analysis
brings a wealth of new information on the dynamics and physical properties of
the observed phenomena. We found that the dynamic event is related to a complex
flare with two distinct impulsive peaks, one according to the GOES
classification as C1.1 and the second - C1.9. The first energy release triggers
a fast-mode wave and a CME with a clear CME driven compression ahead of it.
This activity is related to, or possibly caused, by an asymmetric filament
eruption. The filament is observed to rise with its leading edge moving at a
speed of ~300 km/s detected both in the SUMER and CDS data. The rest of the
filament body moves at only ~150 km/s while untwisting. No signature is found
of the fast-mode wave in the SUMER data, suggesting that the plasma disturbed
by the wave had temperatures above 600 000 K. The erupting filament material is
found to emit only in spectral lines at transition region temperatures. Earlier
identification of a coronal response detected in the Mg X 609.79 A line is
found to be caused by a blend from the O IV 609.83 A line.Comment: 10 pages, 8 figures, A&A, in pres
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