563 research outputs found
The Pantano Longarini shipwreck: a reanalysis
No full textA late antique shipwreck was excavated in the Pantano Longarini marsh in the southeastern corner of Sicily in the 1960s. Despite its excellent preservation, problematic circumstances surrounding its excavation and publication have resulted in scholars ignoring or misinterpreting it. The majority of the data, including original field notes and documentation, are lost, and the drawings, plans, and photographs that remain are sometimes inconsistent and incomplete. My research reanalyzes the remains of this ship to determine how the Sicilians adapted to their marine and economic conditions within the turbulent socio-economic and political climate of late antiquity. The Pantano Longarini shipwreck demonstrates early stages in a shift from the tradition of plank-based construction to the modern system of reliance on an internal framework for structural support. Contemporary wrecks provide parallels, but unique elements distinguish this ship from those typically studied. Extremely thick timbers, a relatively flat bottom and bow and stern ramps argue that the Pantano Longarini ship was designed to carry bulk loads. Although the ship was originally reported as an extremely advanced ship, the present analysis points to a different type of watercraft: a coastal barge. Correctly identifying the Pantano Longarini ship allows us to gather information about the needs of its builders, as well as extends our knowledge of shipping and ship construction in the seventh century
Beam-induced background identification with image vision techniques at ATLAS
No full textAt the LHC the interaction between the proton beam and the
residual gas in the beam pipes originates secondary particles which, in the case of
high-energy muons, are able to cross longitudinally the ATLAS detector and leave
jet-like signatures in the calorimeter. Many new physics searches are affected by
this beam-induced background. This study shows new ideas, based on image vision
techniques, to suppress this source of background
The behaviour of eccentric sub-pc massive black hole binaries embedded in massive discs
No full textUsing the 3D smoothed-particle hydrodynamics code PHANTO
Longarini, Cristian Ezequiel y otros c/ Ministerio de la Producción y otros s/ amparo. Recurso extraordinario de inaplicabilidad de ley
No full textEl siguiente fallo investigado genera un precedente jurídico relevante en el campo de
la jurisprudencia. La Suprema Corte de Justicia de la Provincia de Buenos Aires en el caso
“Longarini, Cristian Ezequiel y otros c/ Ministerio de la Producción y otros s/ amparo.
Recurso extraordinario de inaplicabilidad de ley”, muestra la protección ambiental y el
derecho a su acceso, en un sentido de naturaleza expansiva, de difícil restricción, el cual no
puede ser desvirtuado por ninguna norma inferior, ni forma procesal. Dando una importancia
notable al acceso a la información pública “Se entiende por información ambiental toda
aquella información en cualquier forma de expresión o soporte relacionada con el ambiente,
los recursos naturales o culturales y el desarrollo sustentable” (Ley n 25831 Regimen de libre
acceso a la informacion publica ambiental, 2003), a su continuo seguimiento, y
principalmente a la tutela del hombre en su medio ambiente
LE CENERI VOLANTI NEL CONFEZIONAMENTO DI CALCESTRUZZI AD ALTA RESISTENZA
No full textAlla luce delle nuove conoscenze sulla confezione delle miscele per calcestruzzi ad alta resistenza (High Strenght Concrete, HSC), i calcestruzzi strutturali per la realizzazione delle gallerie del “Progetto Adriatico” (argomento già trattato presso AICAP nel Novembre 2010) sono stati rivisti e studiati considerando idoneo per essi l’utilizzo di cenere volante. In particolare, affinché la progettazione del “Canale Adriatico” sia anche orientata verso la Sostenibilità, l’utilizzo della cenere volante in parziale sostituzione del Cemento Portland sembra essere una valida soluzione, sia da un punto di vista prestazionale, che economico. I vantaggi ivi illustrati possono essere estesi dal caso in oggetto (strutture interrate del progetto Adriatico) ad altre costruzioni fuori terra. Nella memoria vengono citate le principali normative tecniche sull’utilizzo delle ceneri volanti e si spiega come, con tali ceneri, migliorino non solo le prestazioni del calcestruzzo in termini di resistenza meccanica, ma anche in termini di resistenza all’ attacco degli agenti chimici (quali si solfati) ad ai cicli di gelo e disgelo. Inoltre, è affrontato il tema legato ai benefici inerenti il minore rapporto a/c a parità di lavorabilità del calcestruzzo fresco. Ulteriori considerazioni sono fatte circa l’idratazione, durante la quale, con le ceneri volanti, la miscela sviluppa minore calore per l’abbassamento delle percentuali di C3A e C3S presenti in essa. Infine, in questa sede, si analizza la maggiore impermeabilità del materiale ottenuta grazie alla cenere volante, per la quale si ha un minore tenore di calce di idrolisi che, essendo idrosolubile, porta ad un aumento della porosità della pasta cementizia. Il complesso dei suddetti benefici dimostra come l’aggiunta delle ceneri volanti nel confezionamento di calcestruzzi ad alta resistenza rappresenti una valida soluzione nei confronti di molte problematiche che normalmente affliggono il materiale calcestruzzo in importanti opere strutturali ed infrastrutturali
Dynamical dust traps in misaligned circumbinary discs: analytical theory and numerical simulations
No full textRecent observations have shown that circumbinary discs can be misaligned with respect to the binary orbital plane. The lack of spherical symmetry, together with the non-planar geometry of these systems, causes differential precession which might induce the propagation of warps. While gas dynamics in such environments is well understood, little is known about dusty discs. In this work, we analytically study the problem of dust traps formation in misaligned circumbinary discs. We find that pile-ups may be induced not by pressure maxima, as the usual dust traps, but by a difference in precession rates between the gas and dust. Indeed, this difference makes the radial drift inefficient in two locations, leading to the formation of two dust rings whose position depends on the system parameters. This phenomenon is likely to occur to marginally coupled dust particles (St ≳ 1) as both the effect of gravitational and drag force are considerable. We then perform a suite of 3D Smoothed Particle Hydrodynamics (SPH) numerical simulations to compare the results with our theoretical predictions. We explore the parameter space, varying stellar mass ratio, disc thickness, radial extension, and we find a general agreement with the analytical expectations. Such dust pile-up prevents radial drift, fosters dust growth and may thus promote the planet formation in circumbinary discs
Seismic vulnerability of bridges of some italian motorway networks
No full textIn recent years, Italian technical-scientific community has increased its interest on the evaluation of the seismic vulnerability of existing structures. Among this wide range of structures, motorway viaducts stand out for their strategic relevance and technical complexity. Most of these structures were built
between ’60 and ’70 years, according to design procedures which ignored nowadays knowledge in seismic engineering. Thus, the necessity to evaluate the real strength capacity of these structures with modern analysis techniques has become essential, leading to the determination of their safety level in case of an earthquake. For the assessment of several bridges of a motorway network, a multi-modal pushover analysis approach has been considered. This analysis technique allows considering the nonlinear behaviour and the complex dynamic response of such a structures without exceeding in high
computational costs. Some basic rules were defined (constitutive laws of materials, finite element type, plastic hinge models, etc.) for the modelling of viaducts in a commercial FEM software, in order to guarantee homogeneous comparable results among the large number of bridges of a network. Furthermore, a specific software routine was implemented. This routine starts from the pushover results of a FEM commercial software and executes the modal combinations and the safety verifications, reducing the time cost and the possibility of errors, following in the evaluation of the seismic vulnerability indexes. These risk indexes are then reported in seismic vulnerability forms collected by the Italian Hazard Management Agency (Italian Civil Protection) for risk management purposes
Constraining protoplanetary disc mass using the GI wiggle
No full textExoplanets form in protoplanetary accretion discs. The total protoplanetary disc mass is the most fundamental parameter, since it sets the mass budget for planet formation. Although observations with the Atacama Large Millimeter/Submillimeter array (ALMA) have dramatically increased our understanding of these discs, total protoplanetary disc mass remains difficult to measure. If a disc is sufficiently massive (≳10 per cent of the host star mass), it can excite gravitational instability (GI). Recently, it has been revealed that GI leaves kinematic imprints of its presence known as the 'GI Wiggle'. In this work, we use numerical simulations to determine an approximately linear relationship between the amplitude of the wiggle and the host disc-to-star mass ratio, and show that measurements of the amplitude are possible with the spatial and spectral capabilities of ALMA. These measurements can therefore be used to constrain disc-to-star mass ratio
The use of fly ash in high strength concrete mix design
No full textIn this paper the use of fly ash for particular High Strength Concrete (HSC) realizations is investigated. The use of fly ash as a partial replacement of Portland cement in HSC seems a valid solution in particular for a sustainable construction design, considering the interesting HSC performances and the economic aspects. Obviously the advantages demonstrated for the underground constructions can be also evaluated for the structures in elevation. In this paper the most important technical regulations about the use of fly ash for the concrete mix design are discussed and it’s shown the increase of the mechanical resistance and the better protection against the chemical agents attacks and against the freezing and thawing cycles using fly ash. Moreover, in comparison to the fresh concrete, it’s presented the benefits related to the minor ratio water/cement (defined by w/c) in the same conditions of workability. Additional considerations are carried out about the hydration process: the mixture produces less heat for the lowering of the C3A and C3S percentages using fly ash. Finally, a greater concrete impermeability obtained using fly ash, due to the presence of a lower hydrolysis content, which leads to an increment of the cement paste porosity, has been evidence
Angular momentum transport via gravitational instability in the Elias 2–27 disc
No full textGravitational instability is thought to be one of the main drivers of angular momentum transport in young protoplanetary discs. The disc around Elias 2−27 offers a unique example of gravitational instability at work. It is young and massive, displaying two prominent spiral arms in dust continuum emission and global non-axisymmetric kinematic signatures in molecular line data. In this work, we used archival ALMA observations of 13CO line emission to measure the efficiency of angular momentum transport in the Elias 2−27 system through the kinematic signatures generated by gravitational instability, known as “GI wiggles”. Assuming the angular momentum is transported by the observed spiral structure and leveraging previously-derived dynamical disc mass measurements, the amount of angular momentum transport we found corresponds to an α-viscosity of α = 0.038 ± 0.018. This value implies an accretion rate onto the central star of log10 Ṁ⋆ = −6.99 ± 0.17 M⊙ yr−1, which reproduces the one observed value of log10 Ṁ⋆,obs = −7.2 ± 0.5 M⊙ yr−1 very well. The excellent agreement we have found serves as further proof that gravitational instability is the main driver of angular momentum transport acting in this system
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