The Album de Colbert compiled by an anonymous author in the second half of the seventeenth century is among the most important illustrated testimonies of the art of shipbuilding. Probably ...commissioned by Jean-Baptiste Colbert, Minister of Finance and Minister of the Navy of the kingdom of France, the Album was composed to make Louis XIV understand the complexity of shipbuilding. It was also made to support the creation of a navy with the ambition of being competitive with the Royal Navy and with the intent of modernising and expanding the French shipbuilding industry. The fifty plates that make up this illustrated treatise unravel the story of the construction of a first-rank 80-gun line vessel, from the laying of the keel to the launch. It is a unique document that has no contemporaries or precursors because it is not a didactic collection of boats, like the previous treaties that had a completely different methodological approach, more technical-descriptive than illustrative, but it wants to go beyond the scientific treatise. Its purpose was instead to measure itself with representation, showing through the strength of drawing and images the peculiar aspects of the reality of shipbuilding, using iconography as a means of transmitting knowledge related to the world of shipyards and shipbuilding in the 17th century.
ABSTRACT We present the discovery of a 3h5m orbital-period binary star at the heart of the planetary nebula M 3-1 – the shortest period photometrically variable central star known and second only to ...V458 Vul, in general. Combined modelling of light and radial velocity curves reveals both components to be close to Roche lobe filling, strongly indicating that the central star will rapidly evolve to become a cataclysmic variable, perhaps experiencing a similar evolution to V458 Vul resulting in a nova eruption before the planetary nebula has fully dissipated. While the short orbital period and near Roche lobe filling natures of both components make the central binary of M 3-1 an important test case with which to constrain the formation processes of cataclysmic variables, novae, and perhaps even supernovae type Ia.
We present a study of Hen 2-155 and Hen 2-161, two planetary nebulae which bear striking morphological similarities to other planetary nebulae known to host close-binary central stars. Both central ...stars are revealed to be photometric variables while spectroscopic observations confirm that Hen 2-155 is host to a double-eclipsing, post-common-envelope system with an orbital period of 3h33m making it one of the shortest period binary central stars known. The observations of Hen 2-161 are found to be consistent with a post-common-envelope binary of period ~1 day. A detailed model of the central star of Hen 2-155 is produced, showing the nebular progenitor to be a hot, post-AGB remnant of approximately 0.62 M⊙, consistent with the age of the nebula, and the secondary star to be an M dwarf whose radius is almost twice the expected zero age main sequence radius for its mass. In spite of the small numbers, all main-sequence companions, of planetary nebulae central stars, to have had their masses and radii constrained by both photometric and spectroscopic observations have also been found to display this “inflation”. The cause of the “inflation” is uncertain but is probably related to rapid accretion, immediately before the recent common-envelope phase, to which the star has not yet thermally adjusted. The chemical composition of both nebulae is also analysed, showing both to display elevated abundance discrepancy factors. This strengthens the link between elevated abundance discrepancy factors and close binarity in the nebular progenitor.
This paper describes an experimental programme which examines the reinforcement in flexure of timber beams with composite materials based on natural fibers in the form of fabrics made from hemp, ...flax, basalt and bamboo fibers. The industrial use of natural fibers has been continuously increasing since 1990s due to their advantages in terms of production costs, pollution emissions and energy consumption for production and disposal. The technique allows the reinforcement of the intrados of beams, avoiding the dismantling of the overlying part of the structure with significant savings in terms of costs and work time. The test program consists of three phases incorporating 45beams. The bending tests on the wooden elements made it possible to measure the increase in capacity and stiffness resulting from the composite reinforcement. This was applied to beams, creating different arrangements and using different quantities (number of layers). Despite the diversity of the various tests carried out, the results obtained in some cases showed significant increases in terms of load-carrying capacity and in deflection ductility.
Stars are generally spherical, yet their gaseous envelopes often appear nonspherical when ejected near the end of their lives. This quirk is most notable during the planetary nebula phase, when these ...envelopes become ionized. Interactions among stars in a binary system are suspected to cause the asymmetry. In particular, a precessing accretion disk around a companion is believed to launch point-symmetric jets, as seen in the prototype Fleming 1. Our finding of a post-common-envelope binary nucleus in Fleming 1 confirms that this scenario is highly favorable. Similar binary interactions are therefore likely to explain these kinds of outflows in a large variety of systems.
This paper presents an experimental study on the strengthening of wood beams under bending loads through the use of very high strength steel cords. The study also presents the results of 21 double ...shear push-out tests conducted to determine the strength of Steel fiber Reinforced Polymers (SRP) bonded to wood prisms. An experimental programme based on a four-point bending test configuration is proposed to characterize the stiffness, ductility and strength response of strengthened wood beams. Mechanical tests on the strengthened wood showed that external bonding of steel fibers produce high increases in flexural stiffness and capacity. Finally experiment results are used to calibrate existing analytical formulations for capacity prediction. This economic and effective technique may be an interesting alternative to glass or carbon fibers or other expensive retrofitting methods.
On the most luminous planetary nebulae of M 31 Galera-Rosillo, Rebeca; Mampaso, Antonio; Corradi, Romano L. M. ...
Astronomy and astrophysics (Berlin),
01/2022, Letnik:
657
Journal Article
Recenzirano
Odprti dostop
Context.
The planetary nebula luminosity function (PNLF) is a standard candle that comprises a key rung on the extragalactic distance ladder. The method is based on the empirical evidence that the ...luminosity function of planetary nebulae (PNe) in the O
III
λ
5007 nebular emission line reaches a maximum value that is approximately invariant with population age, metallicity, or host galaxy type. However, the presence of bright PNe in old stellar populations is not easily explained by single-star evolutionary models.
Aims.
To gain information about the progenitors of PNe at the tip of the PNLF, we obtained the deepest existing spectra of a sample of PNe in the galaxy M 31 to determine their physico-chemical properties and infer the post-asymptotic giant branch (AGB) masses of their central stars (CSs). Precise chemical abundances allow us to confront the theoretical yields for AGB stellar masses and metallicities expected at the bright end of the PNLF. Central star masses of the sampled PNe provide direct information on the controversial origin of the universal cutoff of the PNLF.
Methods.
Using the OSIRIS instrument at the 10.4 m Gran Telescopio Canarias (GTC), optical spectra of nine bright M 31 PNe were obtained: four of them at the tip of the PNLF, and the other five some 0.5 mag fainter. A control sample of 21 PNe with previous GTC spectra from the literature is also included. We analyze their physical properties and chemical abundances (He, N, O, Ar, Ne, and S), searching for relevant differences between bright PNe and the control samples. The CS masses are estimated with Cloudy modeling using the most recent evolutionary tracks.
Results.
The studied PNe show a remarkable uniformity in all their nebular properties, and the brightest PNe show relatively large electron densities. Stellar characteristics also span a narrow range: ⟨
L
*
/
L
⊙
⟩ = 4300 ± 310, ⟨
T
eff
⟩ = 122 000 ± 10 600 K for the CSs of the four brightest PNe, and ⟨
L
*
/
L
⊙
⟩ = 3300 ± 370, ⟨
T
eff
⟩ = 135 000 ± 26 000 K for those in the control set. This groups all the brightest PNe at the location of maximum temperature in the post-AGB tracks for stars with initial masses
M
i
= 1.5
M
⊙
.
Conclusions.
These figures provide robust observational constraints for the stellar progenitors that produce the PNLF cutoff in a star-forming galaxy such as M 31, where a large range of initial masses is in principle available. Inconsistency is found, however, in the computed N/O abundance ratios of five nebulae, which are 1.5 to 3 times larger than predicted by the existing nucleosynthesis models for stars of these masses.
► The paper deals with a specific type of masonry largely used in Central Italy. ► We test unreinforced walls to characterize the behavior of historical masonry walls. ► We test reinforced walls to ...study the effectiveness of existing methods of repair.
Approach to safety evaluations issued by modern codes is clearly based on quantitative assessment of performances. As a consequence, validated mechanical parameters and numerical models should be made available on large scale for practical applications. This is the background of the present paper that deals with a specific type of masonry largely used in Central Italy and particularly in Umbria and Abruzzo region, whose territory exhibits a relevant seismic risk. A research project focused on the shear behavior of masonry panels subjected to in situ diagonal compression tests has been issued. The project consists of two parts: tests were performed on unreinforced and reinforced panels. As to the unreinforced panels, focusing attention on the diagonal cracking failure mode, the experimental research allowed to provide representative values of the mechanical parameters adopted to define the limit strength domain of some typical masonry walls in old buildings of Umbria and Abruzzo. Conversely, reinforced panels were tested aimed at investigating the effectiveness of existing methods of repair. A comparison between traditional and innovative seismic-upgrading techniques has been made in order to characterize the behavior of historical masonry walls under different strengthening configurations.
We address the general problem of the luminosity-specific planetary nebula (PN) number, better known as the ‘α’ ratio, given by α=NPN/Lgal, and its relationship with the age and metallicity of the ...parent stellar population. Our analysis relies on population synthesis models that account for simple stellar populations (SSPs), and more elaborate galaxy models covering the full star formation range of the different Hubble morphological types. This theoretical framework is compared with the updated census of the PN population in Local Group (LG) galaxies and external ellipticals in the Leo group, and the Virgo and Fornax clusters. The main conclusions of our study can be summarized as follows. According to the post-asymptotic giant branch (AGB) stellar core mass, PN lifetime in a SSP is constrained by three relevant regimes, driven by the nuclear (Mcore≳ 0.57 M⊙), dynamical (0.57 M⊙≳Mcore≳ 0.55 M⊙) and transition (0.55 M⊙≳Mcore≳ 0.52 M⊙) time-scales. The lower limit for Mcore also sets the minimum mass for stars to reach the AGB thermal-pulsing phase and experience the PN event. Mass loss is the crucial mechanism to constrain the value of α, through the definition of the initial-to-final mass relation (IFMR). The Reimers mass-loss parametrization, calibrated on Pop II stars of Galactic globular clusters, poorly reproduces the observed value of α in late-type galaxies, while a better fit is obtained using the empirical IFMR derived from white dwarf observations in the Galaxy open clusters. The inferred PN lifetime for LG spirals and irregulars exceeds 10 000 yr, which suggests that Mcore≲ 0.65 M⊙ cores dominate, throughout. The relative PN deficiency in elliptical galaxies, and the observed trend of α with galaxy optical colours, support the presence of a prevailing fraction of low-mass cores (Mcore≲ 0.55 M⊙) in the PN distribution and a reduced visibility time-scale for the nebulae as a consequence of the increased AGB transition time. The stellar component with Mcore≲ 0.52 M⊙, which overrides the PN phase, could provide an enhanced contribution to hotter HB and post-HB evolution, as directly observed in M 32 and the bulge of M 31. This implies that the most UV-enhanced ellipticals should also display the lowest values of α, as confirmed by the Virgo cluster early-type galaxy population. Any blue-straggler population, invoked as progenitor of the Mcore≳ 0.7 M⊙ PNe in order to preserve the constancy of the bright luminosity-function cut-off magnitude in ellipticals, must be confined to a small fraction (a few per cent at most) of the whole galaxy PN population.
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