192 research outputs found
Resource requirements and speed versus geometry of unconditionally secure physical key exchanges
The imperative need for unconditional secure key exchange is expounded by the
increasing connectivity of networks and by the increasing number and level of
sophistication of cyberattacks. Two concepts that are information theoretically
secure are quantum key distribution (QKD) and Kirchoff-law-Johnson-noise
(KLJN). However, these concepts require a dedicated connection between hosts in
peer-to-peer (P2P) networks which can be impractical and or cost prohibitive. A
practical and cost effective method is to have each host share their respective
cable(s) with other hosts such that two remote hosts can realize a secure key
exchange without the need of an additional cable or key exchanger. In this
article we analyze the cost complexities of cable, key exchangers, and time
required in the star network. We mentioned the reliability of the star network
and compare it with other network geometries. We also conceived a protocol and
equation for the number of secure bit exchange periods needed in a star
network. We then outline other network geometries and trade-off possibilities
that seem interesting to explore.Comment: 13 pages, 7 figures, MDPI Entrop
The Highly Dynamic Behavior of the Innermost Dust and Gas in the Transition Disk Variable LRLL 31
We describe extensive synoptic multi-wavelength observations of the
transition disk LRLL 31 in the young cluster IC 348. We combined four epochs of
IRS spectra, nine epochs of MIPS photometry, seven epochs of cold-mission IRAC
photometry and 36 epochs of warm mission IRAC photometry along with multi-epoch
near-infrared spectra, optical spectra and polarimetry to explore the nature of
the rapid variability of this object. We find that the inner disk, as traced by
the 2-5micron excess stays at the dust sublimation radius while the strength of
the excess changes by a factor of 8 on weekly timescales, and the 3.6 and
4.5micron photometry shows a drop of 0.35 magnitudes in one week followed by a
slow 0.5 magnitude increase over the next three weeks. The accretion rate, as
measured by PaBeta and BrGamma emission lines, varies by a factor of five with
evidence for a correlation between the accretion rate and the infrared excess.
While the gas and dust in the inner disk are fluctuating the central star stays
relatively static. Our observations allow us to put constraints on the physical
mechanism responsible for the variability. The variabile accretion, and wind,
are unlikely to be causes of the variability, but both are effects of the same
physical process that disturbs the disk. The lack of periodicity in our
infrared monitoring indicates that it is unlikely that there is a companion
within ~0.4 AU that is perturbing the disk. The most likely explanation is
either a companion beyond ~0.4 AU or a dynamic interface between the stellar
magnetic field and the disk leading to a variable scale height and/or warping
of the inner disk.Comment: Accepted to ApJ. 10 pages of text, plus 11 tables and 13 figures at
the en
A System Design Approach for Unattended Solar Energy Harvesting Supply
Remote devices, such as sensors and communications devices, require continuously available power. In many applications, conventional approaches are too expensive, too large, or unreliable. For short-term needs, primary batteries may be used. However, they do not scale up well for long-term installations. Instead, energy harvesting methods must be used. Here, a system design approach is introduced that results in a highly reliable, highly available energy harvesting device for remote applications. First, a simulation method that uses climate data and target availability produces Pareto curves for energy storage and generation. This step determines the energy storage requirement in watt-hours and the energy generation requirement in watts. Cost, size, reliability, and longevity requirements are considered to choose particular storage and generation technologies, and then to specify particular components. The overall energy processing system is designed for modularity, fault tolerance, and energy flow control capability. Maximum power point tracking is used to optimize solar panel performance. The result is a highly reliable, highly available power source. Several prototypes have been constructed and tested. Experimental results are shown for one device that uses multicrystalline silicon solar cells and lithium-iron-phosphate batteries to achieve 100% availability. Future designers can use the same approach to design systems for a wide range of power requirements and installation locations
A Two-loop Test of Buscher's T-duality I
We study the two loop quantum equivalence of sigma models related by
Buscher's T-duality transformation. The computation of the two loop
perturbative free energy density is performed in the case of a certain
deformation of the SU(2) principal sigma model, and its T-dual, using
dimensional regularization and the geometric sigma model perturbation theory.
We obtain agreement between the free energy density expressions of the two
models.Comment: 28 pp, Latex, references adde
On Accelerated Aging of Mechanical Assets in Distribution Systems with Renewable Generation
The integration challenges associated with the widespread adoption of the photovoltaic generation can be divided into operational and the maintenance issues. Work done in recent years has addressed issues like voltage rise and unbalance. Less attention was directed to the maintenance challenges like accelerated aging of mechanically controlled voltage support assets under rapidly changing conditions. In particular, there is need for analysis on the mechanism of accelerated wear and tear of devices such as on-load tap changers and capacitor banks exposed to rapid voltage fluctuations. Such an analysis relies on development of lifetime models of switching devices to study the impact of increased stress, whether electrical or mechanical, on operational life. This article focuses on developing such models and proposes the framework to study the impact of non-scheduled distributed generation on aging of mechanically-switched devices commonly used in distribution feeders
Capacity usage determination of a Capacitor-less D-STATCOM considering Power System Uncertainties
The increasing adoption of distributed energy resources (DERs), particularly solar generation and the use of unconventional loads such as plug-in electric vehicles (PHEVs), has a profound impact on the planning and operation of electric distribution systems. In particular, PHEV charging introduces stochastic peaks in energy consumption, while solar generation is fraught with variability during intermittent clouds. The stochastic nature of such DERs renders the operation of mechanical assets such as on-load tap changers and switched capacitor banks ineffective. A possible solution to mitigate the undesirable effects of DERs is using solid-state-based devices such as a distribution static synchronous compensator (D-STATCOM). This paper examines the capacity usage of a capacitor-less D-STATCOM in distribution systems while considering the uncertainties associated with using the aforementioned DERs. We propose a Monte Carlo simulation to study the capacity usage problem with DER inputs sampled from the proposed underlying distributions
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