449 research outputs found
A Unit Commitment Model with Demand Response for the Integration of Renewable Energies
The output of renewable energy fluctuates significantly depending on weather
conditions. We develop a unit commitment model to analyze requirements of the
forecast output and its error for renewable energies. Our model obtains the
time series for the operational state of thermal power plants that would
maximize the profits of an electric power utility by taking into account both
the forecast of output its error for renewable energies and the demand response
of consumers. We consider a power system consisting of thermal power plants,
photovoltaic systems (PV), and wind farms and analyze the effect of the
forecast error on the operation cost and reserves. We confirm that the
operation cost was increases with the forecast error. The effect of a sudden
decrease in wind power is also analyzed. More thermal power plants need to be
operated to generate power to absorb this sudden decrease in wind power. The
increase in the number of operating thermal power plants within a short period
does not affect the total operation cost significantly; however the
substitution of thermal power plants by wind farms or PV systems is not
expected to be very high. Finally, the effects of the demand response in the
case of a sudden decrease in wind power are analyzed. We confirm that the
number of operating thermal power plants is reduced by the demand response. A
power utility has to continue thermal power plants for ensuring supply-demand
balance; some of these plants can be decommissioned after installing a large
number of wind farms or PV systems, if the demand response is applied using an
appropriate price structure.Comment: submitted to 2012 IEEE Power & Energy Society General Meetin
Report on the method for determining the location of the polar vortex boundary region
To determine the boundary region of the polar vortex objectively using the PV distribution on isentropic surfaces, the equivalent latitude(Eql) of the polar vortex boundary was calculated using a slightly modified form of the technique of E.R. Nash et al.(J. Geophys. Res., 101D, 9471, 1996). Using the NCEP/NCAR reanal- ysis data, the Eql of the polar vortex boundary region in the winter of 1999/2000 was calculated, and compared with the ozone mixing ratio in the lower stratosphere over Eureka observatory(80°N , 86°W ). The results indicate that this method determines the boundary region of the polar vortex well
Single crystal growths and magnetic properties of hexagonal polar semimetals RAuGe (R = Y, Gd-Tm, and Lu)
We study structural and magnetic properties of rare-earth based semimetals
RAuGe (R = Y, Gd-Tm, and Lu) using flux-grown single crystals. These compounds
belong to the noncentrosymmetric polar space group P63mc. We confirm the
systematic structural evolution at room temperature as a function of ionic
radius of rare earths to clarify the isopointal crossover between two polar
structures: three-dimensional LiGaGe-type and quasi-two-dimensional
NdPtSb-type. Magnetism shows a characteristic anisotropy in reasonable
agreement with the crystal electric field (CEF) theory; the easy-plane-type
anisotropy for R = Tb and Dy turns into the Ising-type anisotropy for R = Er
and Tm. We evaluate the CEF parameters based on the Stevens operators to
reasonably reproduce the temperature dependence of magnetic susceptibilities
and specific heat for RAuGe (R = Tb-Tm). The estimated energy scale of the
Ising gap (~ 11 meV) in TmAuGe is consistent with an excitation observed in an
inelastic neutron scattering experiment. These findings suggest an opportunity
for interplay between conduction electrons and nontrivial spin structures in
the family of magnetic polar semimetals RAuGe.Comment: 10 pages, 7 figures, 1 tabl
Ycf12 is a core subunit in the photosystem II complex
AbstractThe latest crystallographic model of the cyanobacterial photosystem II (PS II) core complex added one transmembrane low molecular weight (LMW) component to the previous model, suggesting the presence of an unknown transmembrane LMW component in PS II. We have investigated the polypeptide composition in highly purified intact PS II core complexes from Thermosynechococcus elongatus, the species which yielded the PS II crystallographic models described above, to identify the unknown component. Using an electrophoresis system specialized for separation of LMW hydrophobic proteins, a novel protein of ∼5 kDa was identified as a PS II component. Its N-terminal amino acid sequence was identical to that of Ycf12. The corresponding gene is known as one of the ycf (hypothetical chloroplast reading frame) genes, ycf12, and is widely conserved in chloroplast and cyanobacterial genomes. Nonetheless, the localization and function of the gene product have never been assigned. Our finding shows, for the first time, that ycf12 is actually expressed as a component of the PS II complex in the cell, revealing that a previously unidentified transmembrane protein exists in the PS II core complex
Ectopic Cervical Thymoma:A Case Report with 18F-fluorodeoxyglucose Positron Emission Tomography Findings
Ectopic thymoma is considered to arise from ectopic thymus tissue deposited as a result of the abnormal
mislocalization of thymus tissue during the embryonic stage. An 86-year-old man visited our hospital
with chief complaints of hoarseness and a mass in his anterior neck. A preoperative needle biopsy of the mass did not yield a definitive diagnosis. A positron emission tomography (PET) study revealed heterogeneous accumulation of 18F-fluorodeoxyglucose (FDG) in the tumor. The tumor, affecting the left sternocleidomastoid muscle, the recurrent laryngeal nerve, the internal carotid vein, and the brachiocephalic vein, was resected using a combination of a collar incision in the neck and a median incision in the sternum. Immunohistochemically, the tumor was diagnosed as an ectopic thymoma
of the neck. To date, only a few cases of ectopic thymoma presenting with FDG accumulation have been reported. Our experience indicates that ectopic thymoma should be kept in mind during the differential diagnosis of neck tumors with FDG accumulation appearing on PET images
- …