Mechanical Systems: Symmetry and Reduction

Reduction theory is concerned with mechanical systems with symmetries. It constructs a lower dimensional reduced space in which associated conservation laws are taken out and symmetries are \factored out" and studies the relation between the dynamics of the given system with the dynamics on the reduced space. This subject is important in many areas, such as stability of relative equilibria, geometric phases and integrable systems

One decade of evolution of corporate governance practices in Brazil

This study presents the evolution of the quality of corporate governance practices of listed Brazilian companies from 2004 to 2013 by means of a broad corporate governance index (CGI). Results indicate that the quality of corporate governance practices improved, notably after the creation of voluntary membership exchange trading lists that require better corporate governance and disclosure practices. The average CGI score of 5.8 (out of 10.0) in 2013 may be considered low and points to the need for further improvement. Moreover, firms score very low in the ethics & conflicts of interest aspects of the CGI, when compared to its disclosure, board composition & functioning, and shareholders rights components. The very small number of firms that ban loans to related parties and that facilitate participation in the shareholder meetings is a concern. The decrease in the use of control enhancement mechanisms, such as non-voting shares and indirect control structures, was a remarkable achievement. Even so, shareholder agreements are increasingly used as instruments to interfere with director independence and leverage the controlling bloc power.Este estudo apresenta a evolução da qualidade das práticas de governança corporativa de empresas brasileiras negociadas em bolsa entre 2004 e 2013 por meio de um índice abrangente de governança corporativa (CGI). Os resultados indicam que a qualidade das práticas de governança corporativa melhorou, especialmente após a criação dos níveis diferenciados de governança corporativa de adesão voluntária na bolsa, que exigem práticas melhores de governança corporativa e transparência. O CGI médio de 5,8 (em um total de 10) em 2013 pode ser considerado baixo e sugere que pode haver mais espaço para melhoria. Além disso, as empresas pontuam muito baixo nos aspectos de ética & conflito de interesse do CGI, quando comparadas com os componentes sobre transparência, composição & funcionamento do conselho e diretos dos acionistas. O número muito pequeno de empresas que proíbem empréstimos a partes relacionadas e que facilitam a participação nas assembleias de acionistas é uma preocupação. A diminuição de mecanismos de aumento do controle, como as ações sem direito de voto e estruturas indiretas de controle, foi um avanço notável. Mesmo assim, os acordos de acionistas são cada vez mais empregados como instrumentos que interferem com a independência dos conselheiros e aumentam o poder do bloco controlador

WATER\u2013BUDGET AS A TOOL TO EVALUATE THE SUSTAINABLE USE OF GROUNDWATER RESOURCES (ISONZO PLAIN, NE ITALY)

Water budget, hydrogeology, Soča/Isonzo River, climate chang

Selection of earthquake ground motions for multiple objectives using genetic algorithms

Existing earthquake ground motion (GM) selection methods for the seismic assessment of structural systems focus on spectral compatibility in terms of either only central values or both central values and variability. In this way, important selection criteria related to the seismology of the region, local soil conditions, strong GM intensity and duration as well as the magnitude of scale factors are considered only indirectly by setting them as constraints in the pre-processing phase in the form of permissible ranges. In this study, a novel framework for the optimum selection of earthquake GMs is presented, where the aforementioned criteria are treated explicitly as selection objectives. The framework is based on the principles of multi-objective optimization that is addressed with the aid of the Weighted Sum Method, which supports decision making both in the pre-processing and post-processing phase of the GM selection procedure. The solution of the derived equivalent single-objective optimization problem is performed by the application of a mixed-integer Genetic Algorithm and the effects of its parameters on the efficiency of the selection procedure are investigated. Application of the proposed framework shows that it is able to track GM sets that not only provide excellent spectral matching but they are also able to simultaneously consider more explicitly a set of additional criteria

Research needs towards a resilient community: Vulnerability reduction, infrastructural systems model, loss assessment, resilience-based design and emergency management

Most of the literature on resilience is devoted to its assessment. It seems time to move from analysis to design, to develop the tools needed to enhance resilience. Resilience enhancement, a close relative of the less fashionable risk mitigation, adds to the latter, at least in the general perception, a systemic dimension. Resilience is often paired with community, and the latter is a system. This chapter therefore discusses strategies to enhance resilience, endorses one of prevention rather than cure, and focuses in the remainder on the role played by systemic analysis, i.e. the analysis of the built environment modelled beyond a simple collection of physical assets, with due care to the associated interdependencies. Research needs are identified and include challenges in network modelling, the replacement of generic fragility curves for components, how to deal with evolving state of information

Synthesis of accelerograms compatible with the Chinese GB 50011-2001 design spectrum via harmonic wavelets: artificial and historic records

A versatile approach is employed to generate artificial accelerograms which satisfy the compatibility criteria prescribed by the Chinese aseismic code provisions GB 50011-2001. In particular, a frequency dependent peak factor derived by means of appropriate Monte Carlo analyses is introduced to relate the GB 50011-2001 design spectrum to a parametrically defined evolutionary power spectrum (EPS). Special attention is given to the definition of the frequency content of the EPS in order to accommodate the mathematical form of the aforementioned design spectrum. Further, a one-to-one relationship is established between the parameter controlling the time-varying intensity of the EPS and the effective strong ground motion duration. Subsequently, an efficient auto-regressive moving-average (ARMA) filtering technique is utilized to generate ensembles of non-stationary artificial accelerograms whose average response spectrum is in a close agreement with the considered design spectrum. Furthermore, a harmonic wavelet based iterative scheme is adopted to modify these artificial signals so that a close matching of the signals’ response spectra with the GB 50011-2001 design spectrum is achieved on an individual basis. This is also done for field recorded accelerograms pertaining to the May, 2008 Wenchuan seismic event. In the process, zero-phase high-pass filtering is performed to accomplish proper baseline correction of the acquired spectrum compatible artificial and field accelerograms. Numerical results are given in a tabulated format to expedite their use in practice

A vector-valued ground motion intensity measure incorporating normalized spectral area

A vector-valued intensity measure is presented, which incorporates a relative measure represented by the normalized spectral area. The proposed intensity measure is intended to have high correlation with specific relative engineering demand parameters, which collectively can provide information regarding the damage state and collapse potential of the structure. Extensive dynamic analyses are carried out on a single-degree-of-freedom system with a modified Clough–Johnston hysteresis model, using a dataset of 40 ground motions, in order to investigate the proposed intensity measure characteristics. Response is expressed using the displacement ductility, and the normalized hysteretic energy, both of which are relative engineering demand parameters. Through regression analysis the correlation between the proposed intensity measure and the engineering demand parameters is evaluated. Its domain of applicability is investigated through parametric analysis, by varying the period and the strain-hardening stiffness. Desirable characteristics such as efficiency, sufficiency, and statistical independence are examined. The proposed intensity measure is contrasted to another one, with respect to its correlation to the engineering demand parameters. An approximate procedure for estimating the optimum normalized spectral area is also presented. It is demonstrated that the proposed intensity measure can be used in intensity-based assessments, and, with proper selection of ground motions, in scenario-based assessments