33,862 research outputs found
Scattering of Bunched Fractionally Charged Quasiparticles
The charge of fractionally charged quasiparticles, proposed by Laughlin to
explain the fractional quantum Hall effect (FQHE), was recently verified by
measurements. Charge q=e/3 and e/5 (e is the electron charge), at filling
factors nu=1/3 and 2/5, respectively, were measured. Here we report the
unexpected bunching of fractional charges, induced by an extremely weak
backscattering potential at exceptionally low electron temperatures (T<10 mK) -
deduced from shot noise measurements. Backscattered charges q=nu e,
specifically, q=e/3, q=2e/5, and q<3e/7, in the respective filling factors,
were measured. For the same settings but at an only slightly higher electron
temperature, the measured backscattered charges were q=e/3, q=e/5, and q=e/7.
In other words, bunching of backscattered quasiparticles is taking place at
sufficiently low temperatures. Moreover, the backscattered current exhibited
distinct temperature dependence that was correlated to the backscattered charge
and the filling factor. This observation suggests the existence of 'low' and
'high' temperature backscattering states, each with its characteristic charge
and characteristic energy.Comment: 4 pages, 3 figure
Compressed Air Energy Storage-Part I: An Accurate Bi-linear Cavern Model
Compressed air energy storage (CAES) is suitable for large-scale energy
storage and can help to increase the penetration of wind power in power
systems. A CAES plant consists of compressors, expanders, caverns, and a
motor/generator set. Currently used cavern models for CAES are either accurate
but highly non-linear or linear but inaccurate. Highly non-linear cavern models
cannot be directly utilized in power system optimization problems. In this
regard, an accurate bi-linear cavern model for CAES is proposed in this first
paper of a two-part series. The charging and discharging processes in a cavern
are divided into several virtual states and then the first law of
thermodynamics and ideal gas law are used to derive a cavern model, i.e., model
for the variation of temperature and pressure in these processes. Thereafter,
the heat transfer between the air in the cavern and the cavern wall is
considered and integrated into the cavern model. By subsequently eliminating
several negligible terms, the cavern model reduces to a bi-linear (linear)
model for CAES with multiple (single) time steps. The accuracy of the proposed
cavern model is verified via comparison with an accurate non-linear model.Comment: 8 page
Reliability assessment of microgrid with renewable generation and prioritized loads
With the increase in awareness about the climate change, there has been a
tremendous shift towards utilizing renewable energy sources (RES). In this
regard, smart grid technologies have been presented to facilitate higher
penetration of RES. Microgrids are the key components of the smart grids.
Microgrids allow integration of various distributed energy resources (DER) such
as the distributed generation (DGs) and energy storage systems (ESSs) into the
distribution system and hence remove or delay the need for distribution
expansion. One of the crucial requirements for utilities is to ensure that the
system reliability is maintained with the inclusion of microgrid topology.
Therefore, this paper evaluates the reliability of a microgrid containing
prioritized loads and distributed RES through a hybrid analytical-simulation
method. The stochasticity of RES introduces complexity to the reliability
evaluation. The method takes into account the variability of RES through Monte-
Carlo state sampling simulation. The results indicate the reliability
enhancement of the overall system in the presence of the microgrid topology. In
particular, the highest priority load has the largest improvement in the
reliability indices. Furthermore, sensitivity analysis is performed to
understand the effects of the failure of microgrid islanding in the case of a
fault in the upstream network
Compressed Air Energy Storage-Part II: Application to Power System Unit Commitment
Unit commitment (UC) is one of the most important power system operation
problems. To integrate higher penetration of wind power into power systems,
more compressed air energy storage (CAES) plants are being built. Existing
cavern models for the CAES used in power system optimization problems are not
accurate, which may lead to infeasible solutions, e.g., the air pressure in the
cavern is outside its operating range. In this regard, an accurate CAES model
is proposed for the UC problem based on the accurate bi-linear cavern model
proposed in the first paper of this two-part series. The minimum switch time
between the charging and discharging processes of CAES is considered. The whole
model, i.e., the UC model with an accurate CAES model, is a large-scale mixed
integer bi-linear programming problem. To reduce the complexity of the whole
model, three strategies are proposed to reduce the number of bi-linear terms
without sacrificing accuracy. McCormick relaxation and piecewise linearization
are then used to linearize the whole model. To decrease the solution time, a
method to obtain an initial solution of the linearized model is proposed. A
modified RTS-79 system is used to verify the effectiveness of the whole model
and the solution methodology.Comment: 8 page
Impact of edge-removal on the centrality betweenness of the best spreaders
The control of epidemic spreading is essential to avoid potential fatal
consequences and also, to lessen unforeseen socio-economic impact. The need for
effective control is exemplified during the severe acute respiratory syndrome
(SARS) in 2003, which has inflicted near to a thousand deaths as well as
bankruptcies of airlines and related businesses. In this article, we examine
the efficacy of control strategies on the propagation of infectious diseases
based on removing connections within real world airline network with the
associated economic and social costs taken into account through defining
appropriate quantitative measures. We uncover the surprising results that
removing less busy connections can be far more effective in hindering the
spread of the disease than removing the more popular connections. Since
disconnecting the less popular routes tend to incur less socio-economic cost,
our finding suggests the possibility of trading minimal reduction in
connectivity of an important hub with efficiencies in epidemic control. In
particular, we demonstrate the performance of various local epidemic control
strategies, and show how our approach can predict their cost effectiveness
through the spreading control characteristics.Comment: 11 pages, 4 figure
Designing Geotextile Support for Submarine Power Cables
Six 36 cm diameter submarine pipe-cables were buried in a 1.2 km long, fabric-lined trench in the soft river mud under 17 m average water head across the Hudson River about 4.8 km north of the Newburgh Bridge, New York. This paper describes the design considerations based on geotechnical point of view of using geotextile to support submarine power cables
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