Preconditioned fully implicit PDE solvers for monument conservation

Mathematical models for the description, in a quantitative way, of the damages induced on the monuments by the action of specific pollutants are often systems of nonlinear, possibly degenerate, parabolic equations. Although some the asymptotic properties of the solutions are known, for a short window of time, one needs a numerical approximation scheme in order to have a quantitative forecast at any time of interest. In this paper a fully implicit numerical method is proposed, analyzed and numerically tested for parabolic equations of porous media type and on a systems of two PDEs that models the sulfation of marble in monuments. Due to the nonlinear nature of the underlying mathematical model, the use of a fixed point scheme is required and every step implies the solution of large, locally structured, linear systems. A special effort is devoted to the spectral analysis of the relevant matrices and to the design of appropriate iterative or multi-iterative solvers, with special attention to preconditioned Krylov methods and to multigrid procedures. Numerical experiments for the validation of the analysis complement this contribution.Comment: 26 pages, 13 figure

Seismic reliability assessment of classical columns subjected to near-fault ground motions

A methodology for the performance-based seismic risk assessment of classical columns is presented. Despite their apparent instability, classical columns are, in general, earthquake resistant, as proven from the fact that many classical monuments have survived many strong earthquakes over the centuries. Nevertheless, the quantitative assessment of their reliability and the understanding of their dynamic behavior are not easy, because of the fundamental nonlinear character and the sensitivity of their response. In this paper, a seismic risk assessment is performed for a multidrum column using Monte Carlo simulation with synthetic ground motions. The ground motions adopted contain a high- and low-frequency component, combining the stochastic method, and a simple analytical pulse model to simulate the directivity pulse contained in near source ground motions. The deterministic model for the numerical analysis of the system is three-dimensional and is based on the Discrete Element Method. Fragility curves are produced conditional on magnitude and distance from the fault and also on scalar intensity measures for two engineering demand parameters, one concerning the intensity of the response during the ground shaking and the other the residual deformation of the column. Three performance levels are assigned to each engineering demand parameter. Fragility analysis demonstrated some of the salient features of these spinal systems under near-fault seismic excitations, as for example, their decreased vulnerability for very strong earthquakes of magnitude 7 or larger. The analysis provides useful results regarding the seismic reliability of classical monuments and decision making during restoration process

The Monumental Cemeteries of Northern Pictland

Peer reviewedPublisher PD

Characterization of site-specific GPS errors using a short-baseline network of braced monuments at Yucca Mountain, southern Nevada

We use a short-baseline network of braced monuments to investigate site-specific GPS effects. The network has baseline lengths of ∼10, 100, and 1000 m. Baseline time series have root mean square (RMS) residuals, about a model for the seasonal cycle, of 0.05–0.24 mm for the horizontal components and 0.20–0.72 mm for the radial. Seasonal cycles occur, with amplitudes of 0.04–0.60 mm, even for the horizontal components and even for the shortest baselines. For many time series these lag seasonal cycles in local temperature measurements by 23–43 days. This could suggest that they are related to bedrock thermal expansion. Both shorter-period signals and seasonal cycles for shorter baselines to REP2, the one short-braced monument in our network, are correlated with temperature, with no lag time. Differences between REP2 and the other stations, which are deep-braced, should reflect processes occurring in the upper few meters of the ground. These correlations may be related to thermal expansion of these upper ground layers, and/or thermal expansion of the monuments themselves. Even over these short distances we see a systematic increase in RMS values with increasing baseline length. This, and the low RMS levels, suggests that site-specific effects are unlikely to be the limiting factor in the use of similar GPS sites for geophysical investigations

Numerical Analysis of the Tetrapylon Roman's Triumphal Arch of Tebessa: A Case Study.

The Tetrapylon  Roman Triumphal Arch or commonly called  'Caracalla Gate', located  in Tebessa City (Northern Algeria), is considered as one of the most distinctive type of arches associated with the ancient Roman's architecture. This historical monument, erected in the 3rd century, was dedicated to the Roman Emperor Caracalla. In the 6th Century the Caracalla gate was enclosed in the Byzantine old city, built by the General Salomon. Although the monument is still standing, over time, it suffered apparent damages. The conservation and restoration of this monument is actually a major preoccupation for the concerned authorities. In this paper a 3D numerical analysis of the deformations and global stability of the gate are presented. The numerical results obtained were compared to previous site survey and measurements, and were found to be in good agreement. The results revealed that part of the monument damages and deformations occurred following the construction of the Byzantine walls.  In its actual state, the monument was found sufficiently stable, and the restoration would not affect its firmness, if appropriate materials and techniques are deployed

2012: The End of the World as We Know It?

Many so-called “2012 doomsayers theorists,” such as John Major Jenkins and Jose Arguelles successfully convinced a portion of the modern Western world that the ancient Maya had predicted the end of the world. They swayed many into believing that the world was supposed come to a violent end on December 21, 2012. This important date is referred to as the end of the “Great Cycle” of 13 Bak’tuns, according to translations of the ancient Maya hieroglyphic texts. But what evidence, if any, in the archaeological recorded suggested a cataclysmic collapse in support of these doomsday predictions? Here, I explore the root of these concepts of violent collapse. Although we now know their predictions were false, they seem to have gotten a good deal of the Western world worried about what was to come this past winter. What exactly did these doomsayers like Jenkins and Arguelles predict and how do their predictions compare with what the ancient and contemporary Maya say? The archaeological evidence that survives suggests the ancient Maya would not have feared this time but would have celebrated it as a time of renewal. Although the ancient Maya mythology suggests destruction of the world at the end of the 13th Bak’tun, a new world would no doubt have been anticipated by the ancient Maya who would have celebrated this period as a time of rebirth and renewal, much like other important period endings in their calendar. Below I review the doomsayers’ theories and present evidence from several archaeological contexts that suggest the predictions of December 21st, 2012 do not accurately reflect the thinking of the ancient Maya

Writing with Pictures: Immersive Technology and 21st Century Professional Development

In The Language of New Media, Lev Manovich asks, “What kind of space is virtual space?” (254). This seemingly simple question will pose a number of challenges for writing centers as they develop services that transcend physical space. As writing center administrators integrate new media and technology into their operations, they must continue to invent and articulate theory that informs the development of virtual spaces. In Heuretics, Gregory Ulmer poses a related question: “What will research be like in an electronic apparatus?” (32). Ulmer explains that the notion of spatiality has changed since the development and widespread adoption of the computer (Heuretics 36). Indeed, it has, and the cultural and political landscape of the university has changed as well, as educational technology and virtual spaces are often at the heart of many academic institutions.University Writing Cente