1,484 research outputs found
Characteristics of Deforestation in the Democratic People’s Republic of Korea (North Korea) between the 1980s and 2000s
There has been a significant lack of land cover change studies in relation to deforestation in the Democratic People’s Republic of Korea (North Korea). The purpose of this study is to characterise deforestation in North Korea through land cover change trajectory and spatial analysis. We used three 30-m gridded land cover data sets for North Korea representing the conditions of the late 1980s, 1990s, and 2000s, respectively, as well as a digital elevation model. We examined the land cover trajectories during the two decades, i.e. which land cover became which at the pixel level. In addition, we calculated topographic characteristics of deforested pixels. Major findings from the study are summarised as follows: (1) net forest loss in North Korea slowed since the 1990s, whereas land cover changes were active; (2) as a result of deforestation, forest land cover became mostly agricultural and grassland; (3) expansion of agricultural land cover continued during the time; and (4) elevation and slope of deforested areas decreased slightly in the latter decade. The key contribution of the study is that it has demonstrated which land cover became which at the 30-m pixel level, complementing existing studies that examined overall forest stock in North Korea
The Globular Cluster System of NGC 1399 IV. Some noteworthy objects
We present 8 bright globular clusters and/or objects of less familiar nature
which we found in the course of scrutinizing the globular cluster system of NGC
1399. These objects are morphologically striking, either by their sizes or by
other structural properties. Some of them may be candidates for stripped dwarf
galaxy nuclei, emphasizing the possible role of accretion in the NGC 1399
cluster system. They are all highly interesting targets for further deep
spectroscopy or HST-imaging. Since these objects have been found within an area
of only 42 arcmin**2, we expect many more still to be detected in a full census
of the NGC 1399 cluster system.Comment: 6 pages, 3 figures, accepted by A&A (Research Note
Thermodynamics of Exotic Black Holes, Negative Temperature, and Bekenstein-Hawking Entropy
Recently, exotic black holes whose masses and angular momenta are
interchanged have been found, and it is known that their entropies depend only
on the horizon areas. But a basic problem of these entropies is that
the second law of thermodynamics is not guaranteed, in contrast to the
Bekenstein-Hawking entropy. Here, I find that there is another entropy formula
which recovers the usual Bekenstein-Hawking form, but the characteristic
angular velocity and temperature are identified with those of the inner
horizon, in order to satisfy the first law of black hole thermodynamics. The
temperature has a value, due to an upper bound of mass as in spin
systems, and the angular velocity has a bound. I show that one can
obtain the same entropy formula from a conformal field theory computation,
based on classical Virasoro algebras. I also describe several unanswered
problems and some proposals for how these might be addressed.Comment: Explicit discussuin of the remanining open questions added, enlarged
references accordingly, accepted in Phys. Lett.
Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood
We estimated the dynamical surface mass density Sigma at the solar position
between Z=1.5 and 4 kpc from the Galactic plane, as inferred from the
kinematics of thick disk stars. The formulation is exact within the limit of
validity of a few basic assumptions. The resulting trend of Sigma(Z) matches
the expectations of visible mass alone, and no dark component is required to
account for the observations. We extrapolate a dark matter (DM) density in the
solar neighborhood of 0+-1 mM_sun pc^-3, and all the current models of a
spherical DM halo are excluded at a confidence level higher than 4sigma. A
detailed analysis reveals that a small amount of DM is allowed in the volume
under study by the change of some input parameter or hypothesis, but not enough
to match the expectations of the models, except under an exotic combination of
non-standard assumptions. Identical results are obtained when repeating the
calculation with kinematical measurements available in the literature. We
demonstrate that a DM halo would be detected by our method, and therefore the
results have no straightforward interpretation. Only the presence of a highly
prolate (flattening q>2) DM halo can be reconciled with the observations, but
this is highly unlikely in LambdaCDM models. The results challenge the current
understanding of the spatial distribution and nature of the Galactic DM. In
particular, our results may indicate that any direct DM detection experiment is
doomed to fail, if the local density of the target particles is negligible.Comment: Accepted for publication in the Astrophysical Journa
Dynamical population synthesis: Constructing the stellar single and binary contents of galactic field populations
[abridged] The galactic field's late-type stellar single and binary
population is calculated on the supposition that all stars form as binaries in
embedded star clusters. A recently developed tool (Marks, Kroupa & Oh) is used
to evolve the binary star distributions in star clusters for a few Myr so that
a particular mixture of single and binary stars is achieved. On cluster
dissolution the population enters the galactic field with these
characteristics. The different contributions of single stars and binaries from
individual star clusters which are selected from a power-law embedded star
cluster mass function are then added up. This gives rise to integrated galactic
field binary distribution functions (IGBDFs) resembling a galactic field's
stellar content (Dynamical Population Synthesis). It is found that the binary
proportion in the galactic field of a galaxy is larger the lower the minimum
cluster mass, the lower the star formation rate, the steeper the embedded star
cluster mass function and the larger the typical size of forming star clusters
in the considered galaxy. In particular, period-, mass-ratio- and eccentricity
IGBDFs for the Milky Way are modelled. The afore mentioned theoretical IGBDFs
agree with independently observed distributions. Of all late-type binaries, 50%
stem from M<300M_sun clusters, while 50% of all single stars were born in
M>10^4M_sun clusters. Comparison of the G-dwarf and M-dwarf binary population
indicates that the stars formed in mass-segregated clusters. In particular it
is pointed out that although in the present model all M-dwarfs are born in
binary systems, in the Milky Way's Galactic field the majority ends up being
single stars. This work predicts that today's binary frequency in elliptical
galaxies is lower than in spiral and in dwarf-galaxies. The period and
mass-ratio distributions in these galaxies are explicitly predicted.Comment: 14 pages, 9 figures, accepted for publication in MNRA
Evaluation of Preterm Delivery between 32+0-33+6 Weeks of Gestation
Preterm labor after 34 weeks of gestation has shown no great difference from full-term labor in terms of neonatal morbidity and mortality when proper antepartum management (antibiotics or steroids treatment) is done. However, various studies have discussed different views on the risks and safety of preterm delivery at 32+0-33+6 weeks of gestation. We evaluated the complications of different preterm groups that included the neonates born at 32+0-33+6 weeks of gestation (142), stratified randomly selected neonates born at 34+0-36+6 weeks of gestation (267) and neonates born after 37+0 weeks of gestation (356) at our hospital between December 1999 and April 2006. As a result, it was found that neonates born at 34+0-36+6 weeks of gestation showed no great difference from infants born at full term. However, neonates born at 32+0-33+6 weeks were more likely to be admitted to neonatal intensive care unit or develop neonatal complications significantly than the neonates born at 34+0-36+6 weeks and at full term. Therefore, it is suggested that neonates born at 32+0-33+6 weeks have higher risk of neonatal complications following their preterm labor than those born at later than 34+0 weeks. Thus, it would be difficult to accept the idea that preterm labor at 32+0-33+6 weeks is safe
Evolution of Tachyon Kink with Electric Field
We investigate the decay of an inhomogeneous D1-brane wrapped on a with
an electric field. The model that we consider consists of an array of tachyon
kink and anti-kink with a constant electric flux. Beginning with an initially
static configuration, we numerically evolve the tachyon field with some
perturbations under a fixed boundary condition at diametrically opposite points
on the circle . When the electric flux is smaller than the critical value,
the tachyon kink becomes unstable; the tachyon field rolls down the potential,
and the lower dimensional D0- and -brane become thin, which
resembles the caustic formation known for this type of the system in the
literature. For the supercritical values of the electric flux, the tachyon kink
remains stable.Comment: 27 pages, 8 figures, some changes, one reference added, version to
appear in JHE
Planetary Nebulae in Face-On Spiral Galaxies. III. Planetary Nebula Kinematics and Disk Mass
Much of our understanding of dark matter halos comes from the assumption that
the mass-to-light ratio (M/L) of spiral disks is constant. The best way to test
this hypothesis is to measure the disk surface mass density directly via the
kinematics of old disk stars. To this end, we have used planetary nebulae (PNe)
as test particles and have measured the vertical velocity dispersion (sigma_z)
throughout the disks of five nearby, low-inclination spiral galaxies: IC 342,
M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), and M101 (NGC 5457). By using HI
to map galactic rotation and the epicyclic approximation to extract sigma_z
from the line-of-sight dispersion, we find that, with the lone exception of
M101, our disks do have a constant M/L out to ~3 optical scale lengths.
However, once outside this radius, sigma_z stops declining and becomes flat
with radius. Possible explanations for this behavior include an increase in the
disk mass-to-light ratio, an increase in the importance of the thick disk, and
heating of the thin disk by halo substructure. We also find that the disks of
early type spirals have higher values of M/L and are closer to maximal than the
disks of later-type spirals, and that the unseen inner halos of these systems
are better fit by pseudo-isothermal laws than by NFW models.Comment: 18 pages, 15 figures, 5 tables; accepted to Ap
MDM: A Mode Diagram Modeling Framework
Periodic control systems used in spacecrafts and automotives are usually
period-driven and can be decomposed into different modes with each mode
representing a system state observed from outside. Such systems may also
involve intensive computing in their modes. Despite the fact that such control
systems are widely used in the above-mentioned safety-critical embedded
domains, there is lack of domain-specific formal modelling languages for such
systems in the relevant industry. To address this problem, we propose a formal
visual modeling framework called mode diagram as a concise and precise way to
specify and analyze such systems. To capture the temporal properties of
periodic control systems, we provide, along with mode diagram, a property
specification language based on interval logic for the description of concrete
temporal requirements the engineers are concerned with. The statistical model
checking technique can then be used to verify the mode diagram models against
desired properties. To demonstrate the viability of our approach, we have
applied our modelling framework to some real life case studies from industry
and helped detect two design defects for some spacecraft control systems.Comment: In Proceedings FTSCS 2012, arXiv:1212.657
Using XDAQ in Application Scenarios of the CMS Experiment
XDAQ is a generic data acquisition software environment that emerged from a
rich set of of use-cases encountered in the CMS experiment. They cover not the
deployment for multiple sub-detectors and the operation of different processing
and networking equipment as well as a distributed collaboration of users with
different needs. The use of the software in various application scenarios
demonstrated the viability of the approach. We discuss two applications, the
tracker local DAQ system for front-end commissioning and the muon chamber
validation system. The description is completed by a brief overview of XDAQ.Comment: Conference CHEP 2003 (Computing in High Energy and Nuclear Physics,
La Jolla, CA
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