Preconditioning complex symmetric linear systems

A new polynomial preconditioner for symmetric complex linear systems based on Hermitian and skew-Hermitian splitting (HSS) for complex symmetric linear systems is herein presented. It applies to Conjugate Orthogonal Conjugate Gradient (COCG) or Conjugate Orthogonal Conjugate Residual (COCR) iterative solvers and does not require any estimation of the spectrum of the coefficient matrix. An upper bound of the condition number of the preconditioned linear system is provided. Moreover, to reduce the computational cost, an inexact variant based on incomplete Cholesky decomposition or orthogonal polynomials is proposed. Numerical results show that the present preconditioner and its inexact variant are efficient and robust solvers for this class of linear systems. A stability analysis of the method completes the description of the preconditioner.Comment: 26 pages, 4 figures, 4 table

Textile mills in Friuli (XIX-XX century). Building technique analysis and seismic refurbishment

The conservation of industrial architectures and the refurbishment project, must take into account the growing attention to the seismic risk of the built heritage, which the recent events of central Italy have made dramatically current. The different constructive nature and structural behavior of industrial buildings, impose a different approach, combining the new functional needs - and therefore the safety of the building - with its conservation as a testimony for future generations. The work focuses the Friulian textile industry buildings (XIX and XX century), studying their constructive techniques and identyfing some guidelines for the refurbishment

From the CIL Archives: A New Statue Base of Julia Domna from Mustis (Tunisia)

Ananlysis of an unplished statue base bearing a dedication to the Augusta Julia Domna, who is addressed as Fortuna Redux and Fecunditas

The depiction of Livia and Julia Domna by Cassius Dio: Some observations

Among the ancient authors who narrated the reign of Augustus and Tiberius, Cassius Dio is surely the one who dedicated the most space to the influence that Livia Drusilla exercised over both her husband and her son. In this regard, the foremost example is found in a large section where Dio narrates how Livia persuaded Augustus to forgive Cornelius Cinna for having plotted against his regime. Also, according to Dio, after the death of Augustus, Livia considerably increased her authority over the imperial government, trying not only to co-rule with her son, but also to become the sole effective ruler by controlling all his political activities. Some scholars have suggested that Dio probably exaggerated the role played by Livia because of the similar extraordinary power enjoyed by his contemporaries Julia Domna and the other Syrian women who lived during the Severan age. A close examination of Dio’s passages dedicated to Livia reveals no traces of situations that could refer to his contemporary political situation. The statements of the Bithynian historian and senator concerning Livia are normally well detailed because he made use of good sources. Indubitably, Livia’s strong influence was fundamental in shaping the reign of both Augustus and Tiberius. Even two centuries later, while Severus was trying to depict his regime as a new golden era on the model of Augustus, Julia Domna followed the example of Livia on many occasions. Nevertheless, Dio does not seem to be aware of these analogies and his work appears to be characterized by a mere record of facts rather than an investigation of their real power within the imperial court