13,079 research outputs found
Identify Critical Branches with Cascading Failure Chain Statistics and Hypertext-Induced Topic Search Algorithm
An effective way to suppress the cascading failure risk is the branch
capacity upgrade, whose optimal decision making, however, may incur high
computational burden. A practical way is to find out some critical branches as
the candidates in advance. This paper proposes a simulation data oriented
approach to identify the critical branches with higher importance in cascading
failure propagation. First, a concept of cascading failure chain (CFC) is
introduced and numerous samples of CFC are generated with an AC power flow
based cascading failure simulator. Then, a directed weighted graph is
constructed, whose edges denotes the severities of branch interactions. Third,
the weighted hypertext-induced topic search (HITS) algorithm is used to rate
and rank this graph's vertices,through which the critical branches can be
identified accordingly. Validations on IEEE 118bus and RTS96 systems show that
the proposed approach can identify critical branches whose capacity upgrades
suppress cascading failure risk more greatly. Moreover, it is also shown that
structural importance of a branch does not agree with its importance in
cascading failure, which indicates the effectiveness of the proposed approach
compared with structure vulnerabilities based identifying methods
Bounds for Odd -Perfect Numbers
Let be an integer. A natural number is called -perfect if
For any integer we prove that the number of odd
-perfect numbers with at most distinct prime factors is bounded by
.Comment: 6 page
Odd Multiperfect Numbers
A natural number is called {\it multiperfect} or {\it-perfect} for
integer if , where is the sum of the positive
divisors of . In this paper, we establish the structure theorem of odd
multiperfect numbers analogous as Euler's theorem on odd perfect numbers. We
prove the divisibility of the Euler part of odd multiperfect numbers and
characterize the forms of odd perfect numbers such that
. We also present some examples to show the
nonexistence of odd perfect numbers as applications.Comment: 10 page
Tunable and switchable multi-wavelength erbium-doped fiber ring laser based on a modified dual-pass Mach-Zehnder interferometer
A tunable and switchable multi-wavelength erbium-doped fiber ring laser based
on a new type tunable comb filter is proposed and demonstrated. By adjusting
the polarization controllers, dual-function operation of the channel spacing
tunability and the wavelength switching (interleaving) can be readily achieved.
Up to 29 stable lasing lines with 0.4 nm spacing and 14 lasing wavelengths with
0.8 nm spacing in 3 dB bandwidth were obtained at room temperature. In
addition, the lasing output, including the number of the lasing lines, the
lasing evenness and the lasing locations, can also be flexibly adjusted through
the wavelength-dependent polarization rotation mechanism.Comment: 11 pages, 6 figure
Multipath interference analysis of IR-UWB systems in indoor office LOS environment
Bit error rate (BER) performance of impulse radio Ultra-Wideband (UWB)
systems in the presence of intrasymbol interference, inter-symbol interference,
multiuser interference and addictive white Gaussian noise (AWGN) is presented
in this paper. By analyzing the indoor office LOS channel model defined by IEEE
802.15.4a Task Group and deducing the variance for intra-symbol interference
(IASI), inter-symbol interference (ISI) and multiuser interference (MUI), the
system BER expression is obtained and verified by MATLAB simulations. Through
comparing the simulation results with and without intra-symbol interference,
the conclusion that intra-symbol interference cannot be neglected is
drawn-moreover, such interference will significantly decrease performance of
UWB based wireless sensor networks (WSN). Then, the BER performance of UWB
systems in multiuser environment is also analyzed and analysis results show
that multiuser interference will further worsen the transmission performance of
UWB systems.Comment: 5 pages, 2 figures, Communications and Networking in China
(CHINACOM), 2011 6th International ICST Conference o
Partial Template Based Receiver in Impulse Radio Ultra-Wideband Communication Systems
For high speed ultra-wideband (UWB) communication systems, the multipath
interference exhibits a primary obstacle to improve transmission performance.
In order to enhance the signal to interference plus noise ratio (SINR) in the
receiver, a partial template receiver is proposed in this paper. Instead of
using the conventional template, the model in this paper adopts a partial
template to demodulate signals. To analyze the performance of the proposed
receiver, bit error rate (BER) formulation of IR-UWB systems in the presence of
multipath interference, multiuser interference and addictive white Gaussian
noise (AWGN) is derived in IEEE 802.15.4a channel models. Simulation results
show that, compared with the conventional correlation receiver, the proposed
receiver can achieve a better BER performance for high Eb/N0, which falls in
the conventional used Eb/N0 range.Comment: 4 pages, 5 figures, Communications and Networking in China
(CHINACOM), 2011 6th International ICST Conference o
Placement of EV Charging Stations --- Balancing Benefits among Multiple Entities
This paper studies the problem of multi-stage placement of electric vehicle
(EV) charging stations with incremental EV penetration rates. A nested logit
model is employed to analyze the charging preference of the individual consumer
(EV owner), and predict the aggregated charging demand at the charging
stations. The EV charging industry is modeled as an oligopoly where the entire
market is dominated by a few charging service providers (oligopolists). At the
beginning of each planning stage, an optimal placement policy for each service
provider is obtained through analyzing strategic interactions in a Bayesian
game. To derive the optimal placement policy, we consider both the
transportation network graph and the electric power network graph. A simulation
software --- The EV Virtual City 1.0 --- is developed using Java to investigate
the interactions among the consumers (EV owner), the transportation network
graph, the electric power network graph, and the charging stations. Through a
series of experiments using the geographic and demographic data from the city
of San Pedro District of Los Angeles, we show that the charging station
placement is highly consistent with the heatmap of the traffic flow. In
addition, we observe a spatial economic phenomenon that service providers
prefer clustering instead of separation in the EV charging market.Comment: 10 pages, 10 figure
Ricci-flat graphs with girth four
Lin-Lu-Yau introduced an interesting notion of Ricci curvature for graphs and
obtained a complete characterization for all Ricci-flat graphs with girth at
least five [1]. In this paper, we propose a concrete approach to construct an
infinite family of distinct Ricci-flat graphs of girth four with edge-disjoint
4-cycles and completely characterize all Ricci-flat graphs of girth four with
vertex-disjoint 4-cycles
Generation of large-scale magnetic fields from inflation in teleparallelism
We explore the generation of large-scale magnetic fields from inflation in
teleparallelism, in which the gravitational theory is described by the torsion
scalar instead of the scalar curvature in general relativity. In particular, we
examine the case that the conformal invariance of the electromagnetic field
during inflation is broken by a non-minimal gravitational coupling between the
torsion scalar and the electromagnetic field. It is shown that for a power-law
type coupling, the magnetic field on 1 Mpc scale with its strength of G at the present time can be generated.Comment: 18 pages, no figure, version accepted for publication in JCA
Interpretable Charge Predictions for Criminal Cases: Learning to Generate Court Views from Fact Descriptions
In this paper, we propose to study the problem of COURT VIEW GENeration from
the fact description in a criminal case. The task aims to improve the
interpretability of charge prediction systems and help automatic legal document
generation. We formulate this task as a text-to-text natural language
generation (NLG) problem. Sequenceto-sequence model has achieved cutting-edge
performances in many NLG tasks. However, due to the non-distinctions of fact
descriptions, it is hard for Seq2Seq model to generate charge-discriminative
court views. In this work, we explore charge labels to tackle this issue. We
propose a label-conditioned Seq2Seq model with attention for this problem, to
decode court views conditioned on encoded charge labels. Experimental results
show the effectiveness of our method.Comment: To appear in NAACL 2018, Long pape
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