9,679 research outputs found
Efficient Authentication of Outsourced String Similarity Search
Cloud computing enables the outsourcing of big data analytics, where a third
party server is responsible for data storage and processing. In this paper, we
consider the outsourcing model that provides string similarity search as the
service. In particular, given a similarity search query, the service provider
returns all strings from the outsourced dataset that are similar to the query
string. A major security concern of the outsourcing paradigm is to authenticate
whether the service provider returns sound and complete search results. In this
paper, we design AutoS3, an authentication mechanism of outsourced string
similarity search. The key idea of AutoS3 is that the server returns a
verification object VO to prove the result correctness. First, we design an
authenticated string indexing structure named MBtree for VO construction.
Second, we design two lightweight authentication methods named VS2 and EVS2
that can catch the service provider various cheating behaviors with cheap
verification cost. Moreover, we generalize our solution for top k string
similarity search. We perform an extensive set of experiment results on real
world datasets to demonstrate the efficiency of our approach
Frequency-hiding Dependency-preserving Encryption for Outsourced Databases
The cloud paradigm enables users to outsource their data to computationally
powerful third-party service providers for data management. Many data
management tasks rely on the data dependencies in the outsourced data. This
raises an important issue of how the data owner can protect the sensitive
information in the outsourced data while preserving the data dependencies. In
this paper, we consider functional dependency FD, an important type of data
dependency. We design a FD-preserving encryption scheme, named F2, that enables
the service provider to discover the FDs from the encrypted dataset. We
consider the frequency analysis attack, and show that the F2 encryption scheme
can defend against the attack under Kerckhoff's principle with provable
guarantee. Our empirical study demonstrates the efficiency and effectiveness of
F2
Integrity Authentication for SQL Query Evaluation on Outsourced Databases: A Survey
Spurred by the development of cloud computing, there has been considerable
recent interest in the Database-as-a-Service (DaaS) paradigm. Users lacking in
expertise or computational resources can outsource their data and database
management needs to a third-party service provider. Outsourcing, however,
raises an important issue of result integrity: how can the client verify with
lightweight overhead that the query results returned by the service provider
are correct (i.e., the same as the results of query execution locally)? This
survey focuses on categorizing and reviewing the progress on the current
approaches for result integrity of SQL query evaluation in the DaaS model. The
survey also includes some potential future research directions for result
integrity verification of the outsourced computations
Time-varying Bang-bang Property of Minimal Controls for Approximately Null-controllable Heat Equations
In this paper, optimal time control problems and optimal target control
problems are studied for the approximately null-controllable heat equations.
Compared with the existed results on these problems, the boundary of control
variables are not constants but time varying functions. The time-varying
bang-bang property for optimal time control problem, and an equivalence theorem
for optimal control problem and optimal target problem are obtained.Comment: 13 page
Magnetic dipole-dipole interaction induced by the electromagnetic field
We give a derivation for the indirect interaction between two magnetic
dipoles induced by the quantized electromagnetic field. It turns out that the
interaction between permanent dipoles directly returns to the classical form;
the interaction between transition dipoles does not directly return to the
classical result, yet returns in the short-distance limit. In a finite volume,
the field modes are highly discrete, and both the permanent and transition
dipole-dipole interactions are changed. For transition dipoles, the changing
mechanism is similar with the Purcell effect, since only a few number of nearly
resonant modes take effect in the interaction mediation; for permanent dipoles,
the correction comes from the boundary effect: if the dipoles are placed close
to the boundary, the influence is strong, otherwise, their interaction does not
change too much from the free space case.Comment: 8 pages, 2 figure
Long-Term Stability Analysis of Power Systems with Wind Power Based on Stochastic Differential Equations: Model Development and Foundations
In this paper, the variable wind power is incorporated into the dynamic model
for long-term stability analysis. A theory-based method is proposed for power
systems with wind power to conduct long-term stability analysis, which is able
to provide accurate stability assessments with fast simulation speed.
Particularly, the theoretical foundation for the proposed approximation
approach is presented. The accuracy and efficiency of the method are
illustrated by several numerical examples.Comment: The paper has been submitted to IEEE Transactions on Sustainable
Energ
A Framework for Dynamic Stability Analysis of Power Systems with Volatile Wind Power
We propose a framework employing stochastic differential equations to
facilitate the long-term stability analysis of power grids with intermittent
wind power generations. This framework takes into account the discrete dynamics
which play a critical role in the long-term stability analysis, incorporates
the model of wind speed with different probability distributions, and also
develops an approximation methodology (by a deterministic hybrid model) for the
stochastic hybrid model to reduce the computational burden brought about by the
uncertainty of wind power. The theoretical and numerical studies show that a
deterministic hybrid model can provide an accurate trajectory approximation and
stability assessments for the stochastic hybrid model under mild conditions. In
addition, we discuss the critical cases that the deterministic hybrid model
fails and discover that these cases are caused by a violation of the proposed
sufficient conditions. Such discussion complements the proposed framework and
methodology and also reaffirms the importance of the stochastic hybrid model
when the system operates close to its stability limit.Comment: The paper has been accepted by IEEE Journal on Emerging and Selected
Topics in Circuits and System
How isolated is enough for an "isolated" system in statistical mechanics?
Irreversible processes are frequently adopted to account for the entropy
increase in classical thermodynamics. However, the corresponding physical
origins are not always clear, e.g. in a free expansion process, a typical model
in textbooks. In this letter, we study the entropy change during free expansion
for a particle with the thermal de Broglie wavelength () in a
one-dimensional square trap with size . By solely including quantum
dephasing as an irreversible process, we recover classical result of entropy
increase in the classical region (), while predict prominent
discrepancies in the quantum region () because of
non-equilibrium feature of trapped atoms after expansion. It is interesting to
notice that the dephasing, though absent in classical system, is critical to
clarify mysteries in classical thermodynamics.Comment: 5 pages, 4 figure
Cost-efficient Data Acquisition on Online Data Marketplaces for Correlation Analysis
Incentivized by the enormous economic profits, the data marketplace platform
has been proliferated recently. In this paper, we consider the data marketplace
setting where a data shopper would like to buy data instances from the data
marketplace for correlation analysis of certain attributes. We assume that the
data in the marketplace is dirty and not free. The goal is to find the data
instances from a large number of datasets in the marketplace whose join result
not only is of high-quality and rich join informativeness, but also delivers
the best correlation between the requested attributes. To achieve this goal, we
design DANCE, a middleware that provides the desired data acquisition service.
DANCE consists of two phases: (1) In the off-line phase, it constructs a
two-layer join graph from samples. The join graph consists of the information
of the datasets in the marketplace at both schema and instance levels; (2) In
the online phase, it searches for the data instances that satisfy the
constraints of data quality, budget, and join informativeness, while maximize
the correlation of source and target attribute sets. We prove that the
complexity of the search problem is NP-hard, and design a heuristic algorithm
based on Markov chain Monte Carlo (MCMC). Experiment results on two benchmark
datasets demonstrate the efficiency and effectiveness of our heuristic data
acquisition algorithm
Tensor effects on gap evolution of N=40 from non-relativistic and relativistic mean-field theory
Tensor effects on the N=40 gap evolution of N=40 isotones are studied by
employing the Skyrme-Hartree-Fock-Bogoliubov (SHFB) and relativistic
Hartree-Fock-Bogoliubov (RHFB) theories. The results with and without the
inclusion of the tensor component are compared with the experimental data. When
the tensor force is included, both of the two different approaches are found to
give the same trend and agree with the experimental one, which indicates the
necessity of introducing the tensor force in the evolution of N=40 subshell and
on the other hand the reliability of the methods. Furthermore, it is shown that
the gap evolution is primarily determined by the corresponding tensor
contributions from and -tensor coupling in the relativistic
framework.Comment: 4 pages, 3 figure
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