265 research outputs found
Shadows of Relic Neutrino Masses and Spectra on Highest Energy GZK Cosmic Rays
The Ultra High Energy (UHE) neutrino scattering onto relic cosmic neutrinos
in galactic and local halos offers an unique way to overcome GZK cut-off. The
UHE nu secondary of UHE photo-pion decays may escape the GZK cut-off and travel
on cosmic distances hitting local light relic neutrinos clustered in dark
halos. The Z resonant production and the competitive W^+W^-, ZZ pair production
define a characteristic imprint on hadronic consequent UHECR spectra. This
imprint keeps memory both of the primary UHE nu spectra as well as of the
possible relic neutrino masses values, energy spectra and relic densities. Such
an hadronic showering imprint should reflect into spectra morphology of cosmic
rays near and above GZK 10^{19}-10^{21}eV cut-off energies. A possible neutrino
degenerate masses at eVs or a more complex and significant neutrino mass split
below or near Super-Kamiokande \triangle m_{\nu_{SK}}= 0.1 eV masses might be
reflected after each corresponding Z peak showering, into new twin unexpected
UHECR flux modulation behind GZK energies: E_{p} sim 3(frac{triangle
m_{\nu_{SK}}}/m_{\nu}10^{21}),eV.
Other shadowsof lightest, nearly massless, neutrinos m_{nu_{2K} simeq 0.001eV
simeq kT_{\nu}, their lowest relic temperatures, energies and densities might
be also reflected at even higher energies edges near Grand Unification: E_{p}
\sim 2.2(m_{\nu_{2K}/E_{\nu}})10^{23}, eV .Comment: 14 pages, 6 Figures,Invited Talk Heidelberg DARK 200
On the Learning Behavior of Adaptive Networks - Part I: Transient Analysis
This work carries out a detailed transient analysis of the learning behavior
of multi-agent networks, and reveals interesting results about the learning
abilities of distributed strategies. Among other results, the analysis reveals
how combination policies influence the learning process of networked agents,
and how these policies can steer the convergence point towards any of many
possible Pareto optimal solutions. The results also establish that the learning
process of an adaptive network undergoes three (rather than two) well-defined
stages of evolution with distinctive convergence rates during the first two
stages, while attaining a finite mean-square-error (MSE) level in the last
stage. The analysis reveals what aspects of the network topology influence
performance directly and suggests design procedures that can optimize
performance by adjusting the relevant topology parameters. Interestingly, it is
further shown that, in the adaptation regime, each agent in a sparsely
connected network is able to achieve the same performance level as that of a
centralized stochastic-gradient strategy even for left-stochastic combination
strategies. These results lead to a deeper understanding and useful insights on
the convergence behavior of coupled distributed learners. The results also lead
to effective design mechanisms to help diffuse information more thoroughly over
networks.Comment: to appear in IEEE Transactions on Information Theory, 201
Adore: Differentially Oblivious Relational Database Operators
There has been a recent effort in applying differential privacy on memory
access patterns to enhance data privacy. This is called differential
obliviousness. Differential obliviousness is a promising direction because it
provides a principled trade-off between performance and desired level of
privacy. To date, it is still an open question whether differential
obliviousness can speed up database processing with respect to full
obliviousness. In this paper, we present the design and implementation of three
new major database operators: selection with projection, grouping with
aggregation, and foreign key join. We prove that they satisfy the notion of
differential obliviousness. Our differentially oblivious operators have reduced
cache complexity, runtime complexity, and output size compared to their
state-of-the-art fully oblivious counterparts. We also demonstrate that our
implementation of these differentially oblivious operators can outperform their
state-of-the-art fully oblivious counterparts by up to .Comment: VLDB 202
Computational Study of Ionic Polymers: Multiscale Stiffness Predictions and Modeling of the Electromechanical Transduction
Ionic polymer transducers (IPTs) represent a relatively new class of active (¡®smart¡¯) materials, which can function as highly sensitive mechanical sensors as well as actuators. An IPT is made of an ionic polymer membrane sandwiched between two conductive electrodes. They generate controllable strain when applying a low voltage (<5 V) across their thickness and generate measurable currents due to extremely small mechanical strain. IPTs are cost effective and often have superior sensing capabilities compared to other active materials such as piezoelectrics. However, this novel class of transducers has not been widely employed mainly because the mechanism of IPT sensing is not clearly understood. In this dissertation, the mechanical properties of ionic polymers, the ionomer morphology, and the fundamental mechanism responsible for the electromechanical sensing responses of IPTs are studied. A multiscale model for the prediction of material stiffness is presented. The results give access to a fundamental material parameters currently inaccessible via experimentation, namely local stiffness. Subsequently the sensing mechanism of stream potential is hypothesized. It is argued that the mechanism of streaming potential, unlike prior hypotheses, is able to systematically explain generalized experimentally observed sensing phenomena, such as the observation of an optimum conductive particulate volume fraction in the interpenetrating electrode region of the transducer. Moreover, it is argued that coupling the exploration of local stiffness and streaming potential is prerequisite to gaining insight into subtler experimental sensing phenomena such as experimentally observed variations in sensing due to variations in IPT architecture
Practical Volume-Based Attacks on Encrypted Databases
Recent years have seen an increased interest towards strong security
primitives for encrypted databases (such as oblivious protocols), that hide the
access patterns of query execution, and reveal only the volume of results.
However, recent work has shown that even volume leakage can enable the
reconstruction of entire columns in the database. Yet, existing attacks rely on
a set of assumptions that are unrealistic in practice: for example, they (i)
require a large number of queries to be issued by the user, or (ii) assume
certain distributions on the queries or underlying data (e.g., that the queries
are distributed uniformly at random, or that the database does not contain
missing values).
In this work, we present new attacks for recovering the content of individual
user queries, assuming no leakage from the system except the number of results
and avoiding the limiting assumptions above. Unlike prior attacks, our attacks
require only a single query to be issued by the user for recovering the
keyword. Furthermore, our attacks make no assumptions about the distribution of
issued queries or the underlying data. Instead, our key insight is to exploit
the behavior of real-world applications.
We start by surveying 11 applications to identify two key characteristics
that can be exploited by attackers: (i) file injection, and (ii) automatic
query replay. We present attacks that leverage these two properties in concert
with volume leakage, independent of the details of any encrypted database
system. Subsequently, we perform an attack on the real Gmail web client by
simulating a server-side adversary. Our attack on Gmail completes within a
matter of minutes, demonstrating the feasibility of our techniques. We also
present three ancillary attacks for situations when certain mitigation
strategies are employed.Comment: IEEE EuroS&P 202
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