5,057 research outputs found
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
Synthesis and characterization of selected fused isoxazole and pyrazole derivatives and their antimicrobial activity
New potent antibacterials, fused isoxazole and pyrazole derivatives, were synthesized using 5,5-dimethylcyclohexane-1,3-dione (1) and 3-[(4-chlorobenzylidene)amino]-2-thioxoimidazolidin-4-one (2) as synthons. Aromatic aldehydes on condensation with 1 and 2 gave 2-arylidene-5,5-dimethylcyclohexane-1,3-dione (3) and 5-arylidene-3-[(4-chlorobenzylidene)amino]-2-thioxoimidazolidin-4-one (4), respectively. Compounds 3 and 4 were forced to undergo heterocyclization reaction with nucleophilic reagents to give the title compounds. The newly synthesized heterocyles (5–8) were characterized based on their chemical properties and spectroscopic data, and were found to inhibit Staphylococcus aureus and Corynebacterium diphtheriae
Purification and Characterization of Recombinant Darbepoetin Alfa from Leishmania tarentolae
Darbepoetin alfa is a biopharmaceutical glycoprotein that stimulates erythropoiesis and is used to treat anemia, which associated with renal failure and cancer chemotherapy. We herein describe the structural characterization of recombinant darbepoetin alfa produced by Leishmania tarentolae T7-TR host. The DNA expression cassette was integrated into the L. tarentolae genome through homologous recombination. Transformed clones were selected by antibiotic resistance, diagnostic PCRs, and protein expression analysis. The structure of recombinant darbepoetin alfa was analyzed by isoelectric focusing, ultraviolet–visible spectrum, and circular dichroism (CD) spectroscopy. Expression analysis showed the presence of a protein band at 40 kDa, and its expression level was 51.2 mg/ml of culture medium. Darbepoetin alfa have 5 isoforms with varying degree of sialylation. The UV absorption and CD spectra were analogous to original drug (Aranesp), which confirmed that the produced protein was darbepoetin alfa. Potency test results revealed that the purified protein was biologically active. In brief, the structural and biological characteristics of expressed darbepoetin alfa were very similar to Aranesp which has been normally expressed in CHO. Our data also suggest that produced protein has potential to be developed for clinical use. © 2016, Springer Science+Business Media New York
Observations of structure in a low-loss radiofrequency-dressed optical lattice
We load a Bose-Einstein condensate into a one-dimensional (1D) optical
lattice altered through the use of radiofrequency (rf) dressing. The rf
resonantly couples the three levels of the Rb manifold and
combines with a spin-dependent "bare" optical lattice to result in adiabatic
potentials of variable shape, depth, and spatial frequency content. We choose
dressing parameters such that the altered lattice is stable over lifetimes
exceeding tens of ms at higher depths than in previous work. We observe
significant differences between the BEC momentum distributions of the dressed
lattice as compared to the bare lattice, and find general agreement with a 1D
band structure calculation informed by the dressing parameters. Previous work
using such lattices was limited by very shallow dressed lattices and strong
Landau-Zener tunnelling loss between adiabatic potentials, equivalent to
failure of the adiabatic criterion. In this work we operate with significantly
stronger rf coupling (increasing the avoided-crossing gap between adiabatic
potentials), observing dressed lifetimes of interest for optical lattice-based
analogue solid-state physics.Comment: 5 pages, 3 figure
Observations of λ/4 structure in a low-loss radio-frequency-dressed optical lattice
We load a Bose-Einstein condensate into a one-dimensional (1D) optical lattice altered through the use of radio-frequency (rf) dressing. The rf resonantly couples the three levels of the Rb87 F=1 manifold and combines with a spin-dependent bare optical lattice to result in adiabatic potentials of variable shape, depth, and spatial frequency content. We choose dressing parameters such that the altered lattice is stable over lifetimes exceeding tens of ms at higher depths than in previous work. We observe significant differences between the BEC momentum distributions of the dressed lattice as compared to the bare lattice, and find general agreement with a 1D band-structure calculation informed by the dressing parameters. Previous work using such lattices was limited by very shallow dressed lattices and strong Landau-Zener tunneling loss between adiabatic potentials, equivalent to failure of the adiabatic criterion. In this work we operate with significantly stronger rf coupling (increasing the avoided-crossing gap between adiabatic potentials), observing dressed lifetimes of interest for optical lattice-based analog solid-state physics
Microlensing towards M31 with MDM data
We report the final analysis of a search for microlensing events in the
direction of the Andromeda galaxy, which aimed to probe the MACHO composition
of the M31 halo using data collected during the 1998-99 observational campaign
at the MDM observatory. In a previous paper, we discussed the results from a
first set of observations. Here, we deal with the complete data set, and we
take advantage of some INT observations in the 1999-2000 seasons. This merging
of data sets taken by different instruments turns out to be very useful, the
study of the longer baseline available allowing us to test the uniqueness
characteristic of microlensing events. As a result, all the candidate
microlensing events previously reported turn out to be variable stars. We
further discuss a selection based on different criteria, aimed at the detection
of short--duration events. We find three candidates whose positions are
consistent with self--lensing events, although the available data do not allow
us to conclude unambiguously that they are due to microlensing.Comment: Accepted for publication in Astronomy and Astrophysic
Full counting statistics of information content
We review connections between the cumulant generating function of full
counting statistics of particle number and the R\'enyi entanglement entropy. We
calculate these quantities based on the fermionic and bosonic path-integral
defined on multiple Keldysh contours. We relate the R\'enyi entropy with the
information generating function, from which the probability distribution
function of self-information is obtained in the nonequilibrium steady state. By
exploiting the distribution, we analyze the information content carried by a
single bosonic particle through a narrow-band quantum communication channel.
The ratio of the self-information content to the number of bosons fluctuates.
For a small boson occupation number, the average and the fluctuation of the
ratio are enhanced.Comment: 16 pages, 5 figure
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