6,587 research outputs found
Structural Analysis and Control of a Model of Two-site Electricity and Heat Supply
This paper introduces a control problem of regulation of energy flows in a
two-site electricity and heat supply system, where two Combined Heat and Power
(CHP) plants are interconnected via electricity and heat flows. The control
problem is motivated by recent development of fast operation of CHP plants to
provide ancillary services of power system on the order of tens of seconds to
minutes. Due to the physical constraint that the responses of the heat
subsystem are not necessary as fast as those of the electric subsystem, the
target controlled state is not represented by any isolated equilibrium point,
implying that stability of the system is lost in the long-term sense on the
order of hours. In this paper, we first prove in the context of nonlinear
control theory that the state-space model of the two-site system is non-minimum
phase due to nonexistence of isolated equilibrium points of the associated zero
dynamics.Instead, we locate a one-dimensional invariant manifold that
represents the target controlled flows completely. Then, by utilizing a virtual
output under which the state-space model becomes minimum phase, we synthesize a
controller that achieves not only the regulation of energy flows in the
short-term regime but also stabilization of an equilibrium point in the
long-term regime. Effectiveness of the synthesized controller is established
with numerical simulations with a practical set of model parameters
`Island Surfing' Mechanism of Electron Acceleration During Magnetic Reconnection
One of the key unresolved problems in the study of space plasmas is to
explain the production of energetic electrons as magnetic field lines
`reconnect' and release energy in a exposive manner. Recent observations
suggest possible roles played by small scale magnetic islands in the
reconnection region, but their precise roles and the exact mechanism of
electron energization have remained unclear. Here we show that secondary
islands generated in the reconnection region are indeed efficient electron
accelerators. We found that, when electrons are trapped inside the islands,
they are energized continuously by the reconnection electric field prevalent in
the reconnection diffusion region. The size and the propagation speed of the
secondary islands are similar to those of islands observed in the magnetotail
containing energertic electrons.Comment: 5 pages, 4 figures, submitted to J. Geophys. Res
Mass singularity and confining property in
We discuss the properties of the position space fermion propagator in three
dimensional QED which has been found previouly based on Ward-Takahashi-identity
for soft-photon emission vertex and spectral representation.There is a new type
of mass singularity which governs the long distance behaviour.It leads the
propagator vanish at large distance.This term corresponds to dynamical mass in
position space.Our model shows confining property and dynamical mass generation
for arbitrary coupling constant.Since we used dispersion retation in deriving
spectral function there is a physical mass which sets a mass scale.For finite
cut off we obtain the full propagator in the dispersion integral as a
superposition of different massses.Low energy behaviour of the proagator is
modified to decrease by position dependent mass.In the limit of zero infrared
cut-off the propagator vanishes with a new kind of infrared behaviour.Comment: 22pages,4figures,revtex4,Notational sloppiness are crrected.Submitted
to JHE
3D Measurement of Water and Bed Surface Shapes During the Formation of Sand Waves Using the Moving Optical Cutting Method
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive
High statistics calculations of quenched QCD spectrum using various quark sources
We present the results for the hadron spectrum calculated on 400
configurations using point source, wall source and 8-cubic sources, in quenched
QCD with Wilson fermions at and on a
lattice. The results for the ground state masses obtained with three types of
quark sources agree well with each other. Masses of the first excited states
appear consistent with experimental values within large errors.Comment: 3 pages, 2 postscript figures, to appear in the Proceedings of
LATTICE 93, Dallas, USA; preprint UTHEP-26
First study on parasites of Hemibrycon surinamensis (Characidae), a host from the eastern Amazon region.
This study was the first investigation of communities and infracommunities of parasites of Hemibrycon surinamensis. All the fish collected in a tributary of the Amazon river were parasitized by one or more parasite species. The Brillouin diversity index (HB) was 0.46 ± 0.28 and the mean species richness was 3.5 ± 1.2 parasites per host. A total of 14,734 parasites were collected, including Ichthyophthirius multifiliis and Piscinoodinium pillulare (Protozoa); Jainus hexops and Tereancistrum sp. (Monogenoidea); Ergasilus turucuyus and Argulus sp. (Crustacea); metacercariae of Derogenidae gen. sp.; metacercariae and adults of Genarchella genarchella (Digenea); and Cucullanus larvae and Contracaecum larvae (Nematoda). The dominant parasite was I. multifiliis, followed by P. pillulare. The parasites showed aggregated dispersion, except for E. turucuyus, which had random dispersion. The condition factor (Kn) indicated that the parasitism levels had not affected host body condition. The high levels of infection observed were due to host behavior, and this was discussed. This was the first report of I. multifiliis, P. pillulare, Argulus sp., E. turucuyus, G. genarchella, J. hexops and Tereancistrum sp. in H. surinamensis, and it expanded the occurrence of E. turucuyus and G. genarchella to the eastern Amazon region
X-Ray Study of the Outer Region of Abell 2142 with Suzaku
We observed outer regions of a bright cluster of galaxies A2142 with Suzaku.
Temperature and brightness structures were measured out to the virial radius
() with good sensitivity. We confirmed the temperature drop from 9 keV
around the cluster center to about 3.5 keV at , with the density
profile well approximated by the model with . Within
0.4\r_{200}, the entropy profile agrees with , as predicted by the
accretion shock model. The entropy slope becomes flatter in the outer region
and negative around . These features suggest that the intracluster
medium in the outer region is out of thermal equilibrium. Since the relaxation
timescale of electron-ion Coulomb collision is expected to be longer than the
elapsed time after shock heating at , one plausible reason of the low
entropy is the low electron temperature compared to that of ions. Other
possible explanations would be gas clumpiness, turbulence and bulk motions of
ICM\@. We also searched for a warm-hot intergalactic medium around
and set an upper limit on the oxygen line intensity. Assuming a line-of-sight
depth of 2 Mpc and oxygen abundance of 0.1 solar, the upper limit of an
overdensity is calculated to be 280 or 380, depending on the foreground
assumption.Comment: 14 pages, 8 figure
Relativistic particle acceleration in developing Alfv\'{e}n turbulence
A new particle acceleration process in a developing Alfv\'{e}n turbulence in
the course of successive parametric instabilities of a relativistic pair plasma
is investigated by utilyzing one-dimensional electromagnetic full particle
code. Coherent wave-particle interactions result in efficient particle
acceleration leading to a power-law like energy distribution function. In the
simulation high energy particles having large relativistic masses are
preferentially accelerated as the turbulence spectrum evolves in time. Main
acceleration mechanism is simultaneous relativistic resonance between a
particle and two different waves. An analytical expression of maximum
attainable energy in such wave-particle interactions is derived.Comment: 15 pages, 9 figures, 1 tabl
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