1,795 research outputs found
Local Cyber-physical Attack with Leveraging Detection in Smart Grid
A well-designed attack in the power system can cause an initial failure and
then results in large-scale cascade failure. Several works have discussed power
system attack through false data injection, line-maintaining attack, and
line-removing attack. However, the existing methods need to continuously attack
the system for a long time, and, unfortunately, the performance cannot be
guaranteed if the system states vary. To overcome this issue, we consider a new
type of attack strategy called combinational attack which masks a line-outage
at one position but misleads the control center on line outage at another
position. Therefore, the topology information in the control center is
interfered by our attack. We also offer a procedure of selecting the vulnerable
lines of its kind. The proposed method can effectively and continuously deceive
the control center in identifying the actual position of line-outage. The
system under attack will be exposed to increasing risks as the attack
continuously. Simulation results validate the efficiency of the proposed attack
strategy.Comment: Accepted by IEEE SmartGridComm 201
Local Cyber-Physical Attack for Masking Line Outage and Topology Attack in Smart Grid
Malicious attacks in the power system can eventually result in a large-scale
cascade failure if not attended on time. These attacks, which are traditionally
classified into \emph{physical} and \emph{cyber attacks}, can be avoided by
using the latest and advanced detection mechanisms. However, a new threat
called \emph{cyber-physical attacks} which jointly target both the physical and
cyber layers of the system to interfere the operations of the power grid is
more malicious as compared with the traditional attacks. In this paper, we
propose a new cyber-physical attack strategy where the transmission line is
first physically disconnected, and then the line-outage event is masked, such
that the control center is misled into detecting as an obvious line outage at a
different position in the local area of the power system. Therefore, the
topology information in the control center is interfered by our attack. We also
propose a novel procedure for selecting vulnerable lines, and analyze the
observability of our proposed framework. Our proposed method can effectively
and continuously deceive the control center into detecting fake line-outage
positions, and thereby increase the chance of cascade failure because the
attention is given to the fake outage. The simulation results validate the
efficiency of our proposed attack strategy.Comment: accepted by IEEE Transactions on Smart Grid. arXiv admin note: text
overlap with arXiv:1708.0320
TEACHING AND PROMOTION ON INQUIRYBASED INSTRUCTIONAL MODULE
The purpose of this study is to design two teaching modules that will enable science teachers to teach laboratory course for students to achieve a meaningful and useful learning. We emphasize students’ self-exploration about science. Each module can be modified for students of different grades (7-12 students) and abilities. The modules greatly enhanced the teacher's own understanding of what he/she wishes the laboratory teaching to achieve. The module contained inquiring activities with explicit teaching of the nature of science. At the same time, these activities can promote their learning motivation; let the students have a better understanding of the science concepts by doing the experiments, and to undergo an experience of learning and reflection by themselves. By observing interesting phenomena and practicing the scientific process skills repeatedly, the modules also efficiently inspired students who lack of learning motivation. This study involves the design of two experimental teaching modules dealing with concepts about animal life, plant life, foraging behavior and social behavior. The designed modules are: 1) Ecosphere experimental teaching module: including photosynthesis, respiration and burning; and 2) Animal behavior ecological observation experimental teaching module: including foraging behavior and social behavior
Using LC-MS with de novo software to fully characterize the multiple methylations of lysine residues in a recombinant fragment of an outer membrane protein from a virulent strain of Rickettsia prowazekii
The outer membrane protein B (OmpB) of the typhus group rickettsiae is an immunodominant antigen and has been shown to provide protection against typhus in animal models. Consequently, OmpB is currently being considered as a potential rickettsiae vaccine candidate to be used in humans. The OmpB from virulent strains are heavily methylated while the attenuated strains are hypomethylated. Western blot analysis of partially digested OmpB revealed that one of the reactive fragments was located at the N-terminus (fragment A, aa 33–272). Recently, we have over expressed, purified, and chemically methylated the recombinant fragment A from Rickettsia prowazekii (Ap). The methylated Ap was thoroughly characterized by LC/MS/MS on the ProteomeX workstation. The protein sequence of Ap with and without methylation was 87.7% and 100% identified, respectively. This high sequence coverage enabled us to determine the sites and extent of methylation on the lysine residues in Ap. All the lysine residues except the C-terminus lysine were either mono-, di- or tri-methylated. In addition, carbamylation on the N-terminus glycine was identified using a combination of denovo sequencing (DeNovoX) and the pattern recognition (SALSA) program with accurate mass measurement. We demonstrated that the use of peptide identification (SEQUEST) in combination with SALSA and denovo sequencing provided a useful means to characterize the sequence and posttranslational modifications of given proteins
DEXON: A Highly Scalable, Decentralized DAG-Based Consensus Algorithm
A blockchain system is a replicated state machine that must be fault
tolerant. When designing a blockchain system, there is usually a trade-off
between decentralization, scalability, and security. In this paper, we propose
a novel blockchain system, DEXON, which achieves high scalability while
remaining decentralized and robust in the real-world environment. We have two
main contributions. First, we present a highly scalable sharding framework for
blockchain. This framework takes an arbitrary number of single chains and
transforms them into the \textit{blocklattice} data structure, enabling
\textit{high scalability} and \textit{low transaction confirmation latency}
with asymptotically optimal communication overhead. Second, we propose a
single-chain protocol based on our novel verifiable random function and a new
Byzantine agreement that achieves high decentralization and low latency
Design And Fabrication of Condenser Microphone Using Wafer Transfer And Micro-electroplating Technique
A novel fabrication process, which uses wafer transfer and
micro-electroplating technique, has been proposed and tested. In this paper,
the effects of the diaphragm thickness and stress, the air-gap thickness, and
the area ratio of acoustic holes to backplate on the sensitivity of the
condenser microphone have been demonstrated since the performance of the
microphone depends on these parameters. The microphone diaphragm has been
designed with a diameter and thickness of 1.9 mm and 0.6 m, respectively,
an air-gap thickness of 10 m, and a 24% area ratio of acoustic holes to
backplate. To obtain a lower initial stress, the material used for the
diaphragm is polyimide. The measured sensitivities of the microphone at the
bias voltages of 24 V and 12 V are -45.3 and -50.2 dB/Pa (at 1 kHz),
respectively. The fabricated microphone shows a flat frequency response
extending to 20 kHz.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
Observational Constraints on Exponential Gravity
We study the observational constraints on the exponential gravity model of
f(R)=-beta*Rs(1-e^(-R/Rs)). We use the latest observational data including
Supernova Cosmology Project (SCP) Union2 compilation, Two-Degree Field Galaxy
Redshift Survey (2dFGRS), Sloan Digital Sky Survey Data Release 7 (SDSS DR7)
and Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP7) in our analysis.
From these observations, we obtain a lower bound on the model parameter beta at
1.27 (95% CL) but no appreciable upper bound. The constraint on the present
matter density parameter is 0.245< Omega_m^0<0.311 (95% CL). We also find out
the best-fit value of model parameters on several cases.Comment: 14pages, 3 figures, accepted by PR
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