109,683 research outputs found
Dynamic Provable Data Possession Protocols with Public Verifiability and Data Privacy
Cloud storage services have become accessible and used by everyone.
Nevertheless, stored data are dependable on the behavior of the cloud servers,
and losses and damages often occur. One solution is to regularly audit the
cloud servers in order to check the integrity of the stored data. The Dynamic
Provable Data Possession scheme with Public Verifiability and Data Privacy
presented in ACISP'15 is a straightforward design of such solution. However,
this scheme is threatened by several attacks. In this paper, we carefully
recall the definition of this scheme as well as explain how its security is
dramatically menaced. Moreover, we proposed two new constructions for Dynamic
Provable Data Possession scheme with Public Verifiability and Data Privacy
based on the scheme presented in ACISP'15, one using Index Hash Tables and one
based on Merkle Hash Trees. We show that the two schemes are secure and
privacy-preserving in the random oracle model.Comment: ISPEC 201
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Robust optimization for energy transactions in multi-microgrids under uncertainty
Independent operation of single microgrids (MGs) faces problems such as low self-consumption of local renewable energy, high operation cost and frequent power exchange with the grid. Interconnecting multiple MGs as a multi-microgrid (MMG) is an effective way to improve operational and economic performance. However, ensuring the optimal collaborative operation of a MMG is a challenging problem, especially under disturbances of intermittent renewable energy. In this paper, the economic and collaborative operation of MMGs is formulated as a unit commitment problem to describe the discrete characteristics of energy transaction combinations among MGs. A two-stage adaptive robust optimization based collaborative operation approach for a residential MMG is constructed to derive the scheduling scheme which minimizes the MMG operating cost under the worst realization of uncertain PV output. Transformed by its KKT optimality conditions, the reformulated model is efficiently solved by a column-and-constraint generation (C&CG) method. Case studies verify the effectiveness of the proposed model and evaluate the benefits of energy transactions in MMGs. The results show that the developed MMG operation approach is able to minimize the daily MMG operating cost while mitigating the disturbances of uncertainty in renewable energy sources. Compared to the non-interactive model, the proposed model can not only reduce the MMG operating cost but also mitigate the frequent energy interaction between the MMG and the grid
Ferroelectricity in perovskite and
Ferroelectricity is observed in orthorhombic and at the
magnetic lock-in transitions into an E-type structure or an incommensurate
phase with a temperature independent wave vector, respectively. In
the ferroelectric polarization strongly depends on the external magnetic field
indicating the involvement of the rare earth moment order in this compound. The
results are discussed within the framework of recent theoretical models, in
particular the double exchange driven polar displacements predicted for E-type
magnetic structures.Comment: 5 pages, 3 figure
Construction of a surface air temperature series for Qingdao in China for the period 1899 to 2014
Abstract. We present a homogenized surface air temperature (SAT) time series at 2 m height for the city of Qingdao in China from 1899 to 2014. This series is derived from three data sources: newly digitized and homogenized observations of the German National Meteorological Service from 1899 to 1913, homogenized observation data of the China Meteorological Administration (CMA) from 1961 to 2014 and a gridded dataset of Willmott and Matsuura (2012) in Delaware to fill the gap from 1914 to 1960. Based on this new series, long-term trends are described. The SAT in Qingdao has a significant warming trend of 0.11 ± 0.03 °C decade−1 during 1899–2014. The coldest period occurred during 1909–1918 and the warmest period occurred during 1999–2008. For the seasonal mean SAT, the most significant warming can be found in spring, followed by winter. The homogenized time series of Qingdao is provided and archived by the Deutscher Wetterdienst (DWD) web page under overseas stations of the Deutsche Seewarte (http://www.dwd.de/EN/ourservices/overseas_stations/ueberseedoku/doi_qingdao.html) in ASCII format. Users can also freely obtain a short description of the data at https://doi.org/https://dx.doi.org/10.5676/DWD/Qing_v1 And the data can be downloaded at http://dwd.de/EN/ourservices/overseas_stations/ueberseedoku/data_qingdao.txt
Rank-frequency relation for Chinese characters
We show that the Zipf's law for Chinese characters perfectly holds for
sufficiently short texts (few thousand different characters). The scenario of
its validity is similar to the Zipf's law for words in short English texts. For
long Chinese texts (or for mixtures of short Chinese texts), rank-frequency
relations for Chinese characters display a two-layer, hierarchic structure that
combines a Zipfian power-law regime for frequent characters (first layer) with
an exponential-like regime for less frequent characters (second layer). For
these two layers we provide different (though related) theoretical descriptions
that include the range of low-frequency characters (hapax legomena). The
comparative analysis of rank-frequency relations for Chinese characters versus
English words illustrates the extent to which the characters play for Chinese
writers the same role as the words for those writing within alphabetical
systems.Comment: To appear in European Physical Journal B (EPJ B), 2014 (22 pages, 7
figures
Abell 2111: An Optical and Radio Study of the Richest Butcher-Oemler Cluster
We present an in-depth analysis of the Butcher-Oemler cluster A2111,
including new optical spectroscopy plus a deep Very Large Array (VLA) radio
continuum observation. These are combined with optical imaging from the Sloan
Digital Sky Survey (SDSS) to assess the activity and properties of member
galaxies. Prior X-ray studies have suggested A2111 is a head-on cluster merger,
a dynamical state which might be connected to the high level of activity
inferred from its blue fraction. We are able to directly assess this claim,
using our spectroscopic data to identify 95 cluster members among 196 total
galaxy spectra. These galaxy velocities do not themselves provide significant
evidence for the merger interpretation, however they are consistent with it
provided the system is viewed near the time of core passage and at a viewing
angle >~30 degrees different from the merger axis. The SDSS data allow us to
confirm the high blue fraction for A2111, f_b = 0.15 +/- 0.03 based on
photometry alone and f_b = 0.23 +/- 0.03 using spectroscopic data to remove
background galaxies. We are able to detect 175 optical sources from the SDSS in
our VLA radio data, of which 35 have redshift information. We use the SDSS
photometry to determine photometric redshifts for the remaining 140
radio-optical sources. In total we identify up to 26 cluster radio galaxies, 14
of which have spectroscopic redshifts. The optical spectroscopy and radio data
reveal a substantial population of dusty starbursts within the cluster. The
high blue fraction and prevalence of star formation is consistent with the
hypothesis that dynamically-active clusters are associated with more active
member galaxies than relaxed clusters.Comment: To appear in AJ; 53 pages including 10 figures and several long
table
Laser Mode Bifurcations Induced by -Breaking Exceptional Points
A laser consisting of two independently-pumped resonators can exhibit mode
bifurcations that evolve out of the exceptional points (EPs) of the linear
system at threshold. The EPs are non-Hermitian degeneracies occurring at the
parity/time-reversal () symmetry breaking points of the threshold
system. Above threshold, the EPs become bifurcations of the nonlinear
zero-detuned laser modes, which can be most easily observed by making the gain
saturation intensities in the two resonators substantially different. Small
pump variations can then switch abruptly between different laser behaviors,
e.g. between below-threshold and -broken single-mode operation.Comment: 4 pages, 3 figure
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