29,345 research outputs found
Common approach to solving SGEMP, DEMP, and ESD survivability
System Generated Electromagnetic Pulse (SGEMP) and Dispersed Electromagnetic Pulse DEMP) are nuclear generated spacecraft environments. Electrostatic discharge (ESD) is a natural spacecraft environment resulting from differential charging in magnetic substorms. All three phenomena, though differing in origin, result in the same problem to the spacecraft and that is Electromagnetic Interference (EMI). A common design approach utilizing a spacecraft structural Faraday Cage is presented which helps solve the EMI problem. Also, other system design techniques are discussed which minimize the magnitude of these environments through control of materials and electrical grounding configuration
Supersymmetric KdV equation: Darboux transformation and discrete systems
For the supersymmetric KdV equation, a proper Darboux transformation is
presented. This Darboux transformation leads to the B\"{a}cklund transformation
found early by Liu and Xie \cite{liu2}. The Darboux transformation and the
related B\"{a}cklund transformation are used to construct integrable super
differential-difference and difference-difference systems. The continuum limits
of these discrete systems and of their Lax pairs are also considered.Comment: 13pages, submitted to Journal of Physics
I Know Why You Went to the Clinic: Risks and Realization of HTTPS Traffic Analysis
Revelations of large scale electronic surveillance and data mining by
governments and corporations have fueled increased adoption of HTTPS. We
present a traffic analysis attack against over 6000 webpages spanning the HTTPS
deployments of 10 widely used, industry-leading websites in areas such as
healthcare, finance, legal services and streaming video. Our attack identifies
individual pages in the same website with 89% accuracy, exposing personal
details including medical conditions, financial and legal affairs and sexual
orientation. We examine evaluation methodology and reveal accuracy variations
as large as 18% caused by assumptions affecting caching and cookies. We present
a novel defense reducing attack accuracy to 27% with a 9% traffic increase, and
demonstrate significantly increased effectiveness of prior defenses in our
evaluation context, inclusive of enabled caching, user-specific cookies and
pages within the same website
Singlet and Triplet Superfluid Competition in a Mixture of Two-Component Fermi and One-Component Dipolar Bose Gases
We consider a mixture of two-component Fermi and (one-component) dipolar Bose
gases in which both dipolar interaction and s-wave scattering between fermions
of opposite spins are tunable. We show that in the long wavelength limit, the
anisotropy in the Fermi-Fermi interaction induced by phonons of the dipolar
condensate can strongly enhance the scattering in the triplet channel. We
investigate in detail the conditions for achieving optimal critical temperature
at which the triplet superfluid begins to compete with the singlet superfluid.Comment: 5 pages, 2 figure
A charging model for three-axis stabilized spacecraft
A charging model was developed for geosynchronous, three-axis stabilized spacecraft when under the influence of a geomagnetic substorm. The differential charging potentials between the thermally coated or blanketed outer surfaces and metallic structure of a spacecraft were determined when the spacecraft was immersed in a dense plasma cloud of energetic particles. The spacecraft-to-environment interaction was determined by representing the charged particle environment by equivalent current source forcing functions and by representing the spacecraft by its electrically equivalent circuit with respect to the plasma charging phenomenon. The charging model included a sun/earth/spacecraft orbit model that simulated the sum illumination conditions of the spacecraft outer surfaces throughout the orbital flight on a diurnal as well as a seasonal basis. Transient and steady-state numerical results for a three-axis stabilized spacecraft are presented
Polar codes and polar lattices for the Heegard-Berger problem
Explicit coding schemes are proposed to achieve the rate-distortion function of the Heegard-Berger problem using polar codes. Specifically, a nested polar code construction is employed to achieve the rate-distortion function for doublysymmetric binary sources when the side information may be absent. The nested structure contains two optimal polar codes for lossy source coding and channel coding, respectively. Moreover, a similar nested polar lattice construction is employed when the source and the side information are jointly Gaussian. The proposed polar lattice is constructed by nesting a quantization polar lattice and a capacity-achieving polar lattice for the additive white Gaussian noise channel
Weyl points and line nodes in gapless gyroid photonic crystals
Weyl points and line nodes are three-dimensional linear point- and
line-degeneracies between two bands. In contrast to Dirac points, which are
their two-dimensional analogues, Weyl points are stable in the momentum space
and the associated surface states are predicted to be topologically
non-trivial. However, Weyl points are yet to be discovered in nature. Here, we
report photonic crystals, based on the double-gyroid structures, exhibiting
frequency-isolated Weyl points with intricate phase diagrams. The surface
states associated with the non-zero Chern numbers are demonstrated. Line nodes
are also found in similar geometries; the associated surface states are shown
to be flat bands. Our results are readily experimentally realizable at both
microwave and optical frequencies.Comment: 6 figures and 8 pages including the supplementary informatio
Stability analysis of event-triggered anytime control with multiple control laws
To deal with time-varying processor availability and lossy communication
channels in embedded and networked control systems, one can employ an
event-triggered sequence-based anytime control (E-SAC) algorithm. The main idea
of E-SAC is, when computing resources and measurements are available, to
compute a sequence of tentative control inputs and store them in a buffer for
potential future use. State-dependent Random-time Drift (SRD) approach is often
used to analyse and establish stability properties of such E-SAC algorithms.
However, using SRD, the analysis quickly becomes combinatoric and hence
difficult to extend to more sophisticated E-SAC. In this technical note, we
develop a general model and a new stability analysis for E-SAC based on Markov
jump systems. Using the new stability analysis, stochastic stability conditions
of existing E-SAC are also recovered. In addition, the proposed technique
systematically extends to a more sophisticated E-SAC scheme for which, until
now, no analytical expression had been obtained.Comment: Accepted for publication in IEEE Transactions on Automatic Contro
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