239 research outputs found
A comparative study between wmms and tls for the stability analysis of the San Pedro church barrel vault by means of the finite element method
Stability of masonry constructions is highly conditioned by the geometric disposition of its elements due to its low tensile strength and great compressive mechanical properties. Under this framework, this paper attempts to evaluate the suitability of a wearable mobile mapping solution, equipped in a backpack and based on the well-known simultaneous location and mapping paradigm, for the structural diagnosis of historical constructions. To evaluate the suitability of this device, the structural analysis obtained is compared with a high precision terrestrial laser scanner, which is considered as ground truth. The Romanesque church of San Pedro (Becerril del Carpio, Spain) was selected as a study case. This construction, initially conceived in the XIIIth century, has experimented in the past a soil settlement promoting the leaning of the north wall, several plastic hinges in its barrel vault and a visible geometrical deformation. The comparison of both techniques was carried out at different levels: i) an evaluation of the time needed to obtain the point cloud of the church; ii) an accuracy assessment based on the comparison of a terrestrial network using artificial spheres as checkpoints and; iii) an evaluation of the discrepancies, in terms of safety factor and collapse topology, found during the advance numerical evaluation of the barrel vault by means of the finite element method. This comparison places this wearable mobile mapping solution as an interesting tool for the creation of advanced numerical simulations to evaluate the structural stability of historical constructionsJunta de Castilla y León | Ref. SA075P17FEDER | Ref. SOE1/P5/P025
EVALUATION OF A SLAM-BASED POINT CLOUD FOR DEFLECTION ANALYSIS IN HISTORIC TIMBER FLOORS
This paper aims at evaluating the possibility of using wearable mobile mapping solutions as a tool for detecting deflections in timber floors. These construction systems are prone to present this type of damage due to the mechanical properties of the wood (relatively low flexural stiffness and creep behaviour). During this study we have evaluated the chance of introducing an additional stage to the general workflow. This stage is devoted to reduce the noise of the 3D point cloud by using the Statistical Outlier Removal filter in combination with a noise-reduction filter such as the Anisotropic filter, the PointCleannet or the Scored-based denoised networks (Deep Learning methods). According with our results, the use of this strategies improves the quality of the 3D point cloud form a qualitative and quantitative point of view. However, these improvements seem to be not sufficient for using this product as a universal source of information for deflection analysis. In this sense, and according with the sensor and study case exploited, this type of point clouds could be used in floors with 5-8-meter length and a relative deflection of about L/200 or higher
The Recent Star Formation History of NGC 5102
We present Hubble Space Telescope photometry of young stars in NGC 5102, a
nearby gas-rich post-starburst S0 galaxy with a bright young stellar nucleus.
We use the IAC-pop/MinnIAC algorithm to derive the recent star formation
history in three fields in the bulge and disk of NGC 5102. In the disk fields,
the recent star formation rate has declined monotonically and is now barely
detectable, but a starburst is still in progress in the bulge and has added
about 2 percent to the mass of the bulge over the last 200 Myr. Other studies
of star formation in NGC 5102 indicate that about 20 percent of its stellar
mass was added over the past Gyr. If this is correct, then much of the stellar
mass of the bulge may have formed over this period. It seems likely that this
star formation was fueled by the accretion of a gas-rich system with HI mass of
about 2 x 10^9 Msol which has now been almost completely converted into stars.
The large mass of recently formed stars and the blue colours of the bulge
suggest that the current starburst, which is now fading, may have made a
significant contribution to build the bulge of NGC 5102.Comment: 36 pages, 16 figures, accepted in A
The ALHAMBRA photometric system
This paper presents the characterization of the optical range of the ALHAMBRA
photometric system, a 20 contiguous, equal-width, medium-band CCD system with
wavelength coverage from 3500A to 9700A. The photometric description of the
system is done by presenting the full response curve as a product of the
filters, CCD and atmospheric transmission curves, and using some first and
second order moments of this response function. We also introduce the set of
standard stars that defines the system, formed by 31 classic spectrophotometric
standard stars which have been used in the calibration of other known
photometric systems, and 288 stars, flux calibrated homogeneously, from the
Next Generation Spectral Library (NGSL). Based on the NGSL, we determine the
transformation equations between Sloan Digital Sky Survey (SDSS) ugriz
photometry and the ALHAMBRA photometric system, in order to establish some
relations between both systems. Finally we develop and discuss a strategy to
calculate the photometric zero points of the different pointings in the
ALHAMBRA project.Comment: Astronomical Journal on the 14th of January 201
Search for blue compact dwarf galaxies during quiescence II: metallicities of gas and stars, ages, and star-formation rates
We examine the metallicity and age of a large set of SDSS/DR6 galaxies that
may be Blue Compact Dwarf (BCD) galaxies during quiescence (QBCDs).The
individual spectra are first classified and then averaged to reduce noise. The
metallicity inferred from emission lines (tracing ionized gas) exceeds by ~0.35
dex the metallicity inferred from absorption lines (tracing stars). Such a
small difference is significant according to our error budget estimate. The
same procedure was applied to a reference sample of BCDs, and in this case the
two metallicities agree, being also consistent with the stellar metallicity in
QBCDs. Chemical evolution models indicate that the gas metallicity of QBCDs is
too high to be representative of the galaxy as a whole, but it can represent a
small fraction of the galactic gas, self enriched by previous starbursts. The
luminosity weighted stellar age of QBCDs spans the whole range between 1 and 10
Gyr, whereas it is always smaller than 1 Gyr for BCDs. Our stellar ages and
metallicities rely on a single stellar population spectrum fitting procedure,
which we have specifically developed for this work using the stellar library
MILES.Comment: Accepted for publication in ApJ. 20 pages. 16 figures (corrected
typos
Herschel FIR counterparts of selected Ly-alpha emitters at z~2.2. Fast evolution since z~3 or missed obscured AGNs?
Ly-alpha emitters (LAEs) are seen everywhere in the redshift domain from
local to z~7. Far-infrared (FIR) counterparts of LAEs at different epochs could
provide direct clues on dust content, extinction, and spectral energy
distribution (SED) for these galaxies. We search for FIR counterparts of LAEs
that are optically detected in the GOODS-North field at redshift z~2.2 using
data from the Herschel Space Telescope with the Photodetector Array Camera and
Spectrometer (PACS). The LAE candidates were isolated via color-magnitude
diagram using the medium-band photometry from the ALHAMBRA Survey, ancillary
data on GOODS-North, and stellar population models. According to the fitting of
these spectral synthesis models and FIR/optical diagnostics, most of them seem
to be obscured galaxies whose spectra are AGN-dominated. From the analysis of
the optical data, we have observed a fraction of AGN or composite over source
total number of ~0.75 in the LAE population at z~2.2, which is marginally
consistent with the fraction previously observed at z=2.25 and even at low
redshift (0.2<z<0.45), but significantly different from the one observed at
redshift ~3, which could be compatible either with a scenario of rapid change
in the AGN fraction between the epochs involved or with a non detection of
obscured AGN in other z=2-3 LAE samples due to lack of deep FIR observations.
We found three robust FIR (PACS) counterparts at z~2.2 in GOODS-North. This
demonstrates the possibility of finding dust emission in LAEs even at higher
redshifts.Comment: 11 pages (including Appendices), 6 figures. Accepted for publication
in Astronomy & Astrophysics Letters (two references added
Lyman break and UV-selected galaxies at z ~ 1: II. PACS-100um/160um FIR detections
We report the PACS-100um/160um detections of a sample of 42 GALEX-selected
and FIR-detected Lyman break galaxies (LBGs) at z ~ 1 located in the COSMOS
field and analyze their ultra-violet (UV) to far-infrared (FIR) properties. The
detection of these LBGs in the FIR indicates that they have a dust content high
enough so that its emission can be directly detected. According to a spectral
energy distribution (SED) fitting with stellar population templates to their
UV-to-near-IR observed photometry, PACS-detected LBGs tend to be bigger, more
massive, dustier, redder in the UV continuum, and UV-brighter than
PACS-undetected LBGs. PACS-detected LBGs at z ~ 1 are mostly disk-like galaxies
and are located over the green-valley and red sequence of the color-magnitude
diagram of galaxies at their redshift. By using their UV and IR emission, we
find that PACS-detected LBGs tend to be less dusty and have slightly higher
total star-formation rates (SFRs) than other PACS-detected UV-selected galaxies
within their same redshift range. As a consequence of the selection effect due
to the depth of the FIR observations employed, all our PACS-detected LBGs are
LIRGs. However, none of them are in the ULIRG regime, where the FIR
observations are complete. The finding of ULIRGs-LBGs at higher redshifts
suggests an evolution of the FIR emission of LBGs with cosmic time. In an
IRX- diagram, PACS-detected LBGs at z ~ 1 tend to be located around the
relation for local starburst similarly to other UV-selected PACS-detected
galaxies at their same redshift. Consequently, the dust-correction factors
obtained with their UV continuum slope allow to determine their total SFR,
unlike at higher redshifts. However, the dust attenuation derived from UV to
NIR SED fitting overestimates the total SFR for most of our PACS-detected LBGs
in age-dependent way: the overestimation factor is higher in younger galaxies.Comment: Accepted for publication in MNRA
Quantic Analysis of Formation of a Biomaterial of Latex, Retinol, and Chitosan for Biomedical Applications
The present work shows the quantum theoretical analysis and practical tests for the formation of a homogeneous mixture with Latex (Lx), Chitosan (Qn) and Retinol (Rl), which work as possible biomaterial for regeneration of epithelial tissue. Lx, Qn, and Rl compounds molecules were designed through Hyperchem to get the coefficient of electrostatic potential calculations. The amounts used to create the biomaterial are minimum depending on the quantities of molecules used in chemical design. A positive calculation was obtained for the reaction of these three compounds and the formation of the biomaterial in physical checking theory etc
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