33 research outputs found
Modelos de producción de madera sólida en plantaciones de Eucalyptus globulus de Galicia
El objetivo de este trabajo es establecer las
interacciones existentes entre crecimiento diametral,
crecimiento en altura y la dinámica de poda natural
de Eucalyptus globulus con el objetivo de evaluar la
eficiencia de distintas opciones de gestión forestal
para producir madera de alta calidad. Para ello se ha
desarrollado un modelo de crecimiento basados en el
árbol individual. La toma de muestras comprende
más de 900 Eucalyptus globulus medidos en
diferentes localizaciones de Galicia (España). En
esos árboles se ha encontrado una elevada
correlación significativa entre el diámetro normal y
el diámetro de la copa. El modelo basado en el
ancho de copa permite calcular el espacio vital
requerido por un árbol para alcanzar un diámetro
predefinido a una cierta edad. Una vez conocido, es
también posible calcular el número de árboles por
hectárea así como el momento y la intensidad de las
claras. Se ha podido comprobar que los eucaliptos
orientados a la producción de madera aserrada en
rotaciones cortas tienen que podarse y, dada la
tendencia de los árboles a incluir el tocón de las
ramas muertas, es recomendable realizar la poda
mientras las ramas todavía están verdes. Para
optimizar la producción de madera limpia, es
esencial conocer el impacto de los tratamientos
silvícolas y condiciones de crecimiento en el proceso
de formación de la base de la copa. Se ha encontrado
que la altura de la base de copa viva muestra una
buena correlación con el diámetro normal, la altura
del árbol y la edad. Empleando estas tres variables
se ha desarrollado un modelo multivariable para
predecir la altura de la primera rama viva, que puede
ser de utilidad para optimizar el momento y la
intensidad de las claras para producir madera de
sierra de eucalipto en plantaciones de corta rotación._________________________________The study aims to point out the interactions between
diameter and height growth and the self-pruning
dynamics of Eucalyptus globulus in order to
evaluate different management regimes according to
their efficiency for high value timber production.
Therefore a growth model for individual trees has
been developed. The database contains over 900
trees of Eucalyptus globulus measured at different
sites in Galicia / Spain. For these trees a significant
relationship between diameter at breast height (d1,3)
and crown diameter calculated from this area was
found. The crown width model enables us to
calculate the growing space needed by a tree to get a
pre-defined diameter at a given age. Knowing this, it
is also possible to calculate the number of trees/ha as
well as time and intensity of thinning interventions.
It could be shown that eucalypt grown for sawlogs in
short rotations have to be pruned. Since the trees
tend to include dead branches partly into the bole, it
is recommendable to prune branches when still
green. In order to optimize production of knot free
timber, it is essential to know the impact of
silvicultural treatments and growth conditions on the
process of living crown base recession. It was found
that height of living crown base shows good
correlations with d1,3, tree height and age. Using
these 3 variables a multivariate model for predicting
height of the first living branch has been developed,
which may be helpful to optimize time and intensity
of pruning for eucalypt sawlog production in short
rotation plantations
The UNSW Extrasolar Planet Search: Methods and First Results from a Field Centred on NGC 6633
We report on the current status of the University of New South Wales
Extrasolar Planet Search project, giving details of the methods we use to
obtain millimagnitude precision photometry using the 0.5m Automated Patrol
Telescope. We use a novel observing technique to optimally broaden the PSF and
thus largely eliminate photometric noise due to intra-pixel sensitivity
variations on the CCD. We have observed 8 crowded Galactic fields using this
technique during 2003 and 2004. Our analysis of the first of these fields
(centred on the open cluster NGC 6633) has yielded 49 variable stars and 4
shallow transit candidates. Follow-up observations of these candidates have
identified them as eclipsing binary systems. We use a detailed simulation of
our observations to estimate our sensitivity to short-period planets, and to
select a new observing strategy to maximise the number of planets detected.Comment: 16 pages, 9 figures, version published in MNRAS Updated figures,
references, and additional discussion in section
Observed Effect of Magnetic Fields on the Propagation of Magnetoacoustic Waves in the Lower Solar Atmosphere
We study Hinode/SOT-FG observations of intensity fluctuations in Ca II H-line
and G-band image sequences and their relation to simultaneous and co-spatial
magnetic field measurements. We explore the G-band and H-line intensity
oscillation spectra both separately and comparatively via their relative phase
differences, time delays and cross-coherences. In the non-magnetic situations,
both sets of fluctuations show strong oscillatory power in the 3 - 7 mHz band
centered at 4.5 mHz, but this is suppressed as magnetic field increases. A
relative phase analysis gives a time delay of H-line after G-band of 20\pm1 s
in non-magnetic situations implying a mean effective height difference of 140
km. The maximum coherence is at 4 - 7 mHz. Under strong magnetic influence the
measured delay time shrinks to 11 s with the peak coherence near 4 mHz. A
second coherence maximum appears between 7.5 - 10 mHz. Investigation of the
locations of this doubled-frequency coherence locates it in diffuse rings
outside photospheric magnetic structures. Some possible interpretations of
these results are offered.Comment: 19 pages, 6 figure
A new detached K7 dwarf eclipsing binary system
We present an analysis of a new, detached, double-lined eclipsing binary
system with K7 Ve components, discovered as part of the University of New South
Wales Extrasolar Planet Search. The object is significant in that only 6 other
binary systems are known with comparable or lower mass. Such systems offer
important tests of mass-radius theoretical models. Follow-up photometry and
spectroscopy were obtained with the 40-inch and 2.3m telescopes at SSO
respectively. An estimate of the radial velocity amplitude from spectral
absorption features, combined with the orbital inclination (83.5 deg) estimated
from lightcurve fitting, yielded a total mass of M=(1.041 +/- 0.06)M_sun and
component masses of M_A=(0.529 +/- 0.035)M_sun and M_B=(0.512 +/- 0.035)M_sun.
The radial velocity amplitude estimated from absorption features (167 +/-
3)kmps was found to be less than the estimate from the H_alpha emission lines
(175 +/- 1.5)kmps. The lightcurve fit produced radii of R_A=(0.641 +/-
0.05)R_sun and R_B=(0.608 +/- 0.06)R_sun, and a temperature ratio of
T_B/T_A=0.980 +/- 0.015. The apparent magnitude of the binary was estimated to
be V=13.9 +/- 0.2. Combined with the spectral type, this gave the distance to
the binary as 169 +/- 14 pc. The timing of the secondary eclipse gave a lower
limit on the eccentricity of the binary system of 0.0025 +/- 0.0005. This is
the most statistically significant non-zero eccentricity found for such a
system, possibly suggesting the presence of a third companion.Comment: 6 pages, published in MNRAS (08/2006
Properties of high-frequency wave power halos around active regions: an analysis of multi-height data from HMI and AIA onboard SDO
We study properties of waves of frequencies above the photospheric acoustic
cut-off of 5.3 mHz, around four active regions, through spatial maps
of their power estimated using data from Helioseismic and Magnetic Imager (HMI)
and Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory
(SDO). The wavelength channels 1600 {\AA} and 1700 {\AA} from AIA are now known
to capture clear oscillation signals due to helioseismic p modes as well as
waves propagating up through to the chromosphere. Here we study in detail, in
comparison with HMI Doppler data, properties of the power maps, especially the
so called 'acoustic halos' seen around active regions, as a function of wave
frequencies, inclination and strength of magnetic field (derived from the
vector field observations by HMI) and observation height. We infer possible
signatures of (magneto-)acoustic wave refraction from the observation height
dependent changes, and hence due to changing magnetic strength and geometry, in
the dependences of power maps on the photospheric magnetic quantities. We
discuss the implications for theories of p mode absorption and mode conversions
by the magnetic field.Comment: 22 pages, 12 figures, Accepted by journal Solar Physic