Chaotic Vibrations in a Buckled Beam Induced by a Galloping Phenomenon

Chaos theory has spectacularly evolved since the pioneering work by E. Lorenz on chaotic motion in a simple, deterministic system. Since then, the chaotic behavior of many other deterministic, low-dimensional systems in a large variety of fields has been developed. In the particular field of aeroelasticity of aircraft structures several reports of chaos have been documented. However, we are unaware of any report of chaotic systems of civil (non-aeronautical) use induced by an aeroelastic phenomenon. In this paper a well defined civil, aeroelastic system, susceptible to exhibit chaotic behavior is presented. The system consists of a buckled beam from which a second beam is suspended. This last beam (hereafter, galloping beam) has a square cross- section and can undergo transverse galloping. The system is subjected to an uniform wind flow and, as it will be shown in the paper, for wind velocities larger than a threshold value, the galloping beam begins to oscillate and induces, for a determined set of parameter values, a chaotic motion in the buckled bea

Multi-Party Coordination in the Context of MOWS

Separation of concerns has been presented as a promising tool to tackle the design of complex systems in which cross-cutting properties that do not fit into the scope of a class must be satisfied. In this paper, we show that interactions amongst a number of objects can also be described separately from functionality, which enhances reusability of functional code and interaction patterns. We present our proposal in the context of Multi-Qrganisational Web-Based Systems (MOWS) and also present a framework that provides the infrastructure needed to implement multiparty coordination as an independent aspect

Aspect-oriented interaction in multi-organisational web-based systems

Separation of concerns has been presented as a promising tool to tackle the design of complex systems in which cross-cutting properties that do not fit into the scope of a class must be satisfied. Unfortunately, current proposals assume that objects interact by means of object-oriented method calls, which implies that they embed interactions with others into their functional code. This makes them dependent on this interaction model, and makes it difficult to reuse them in a context in which another interaction model is more suited, e.g., tuple spaces, multiparty meetings, ports, and so forth. In this paper, we show that functionality can be described separately from the interaction model used, which helps enhance reusability of functional code and coordination patterns. Our proposal is innovative in that it is the first that achieves a clear separation between functionality and interaction in an aspect-oriented manner. In order to show that it is feasible, we adapted the multiparty interaction model to the context of multiorganisational web-based systems and developed a class framework to build business objects whose performance rates comparably to handmade implementations; the development time, however, decreases significantly.Comisión Interministerial de Ciencia y Tecnología TIC2000-1106-C02-0

Fractional Integration and Structural Breaks in U.S. Macro Dynamics

This paper identifies structural breaks in the post-World War II joint dynamics of U.S. inflation, unemployment and the short-term interest rate. We derive a structural break-date procedure which allows for long-memory behavior in all three series and perform the analysis for alternative data frequencies. Both long-memory and short-run coefficients are relevant for characterizing the changing patterns of U.S. macroeconomic dynamics. We provide an economic interpretation of those changes by examining the link between macroeconomic events and structural breaks.Fractional integration, structural breaks, multivariate analysis, inflation dynamics

Tools for managing knowledge in SMEs and laggard regions

As the biggest producers and employers of the system, in general SMEs in laggard regions need to keep pace with the expanding rate of technological change that is taking place. To achieve that goal, adequate tools must be developed to generate sufficient transfer of knowledge to those regions and SMEs. The paper will analyze past development and the current situation of Technological Institutes (TI) as a feasible tool for transfering and managing technical change in SMEs. Analyzing their characteristics and proposing how they should be related to the industrial fabric of the region will be the main output of the paper.

Technology Shocks and Hours Worked: A Fractional Integration Perspective

Previous research has found that the response of hours worked to a technology shock crucially depends on whether the variable hours is assumed to be an I(0) or an I(1) variable ex-ante. In this paper we employ a multivariate fractionally integrated model which allows us to determine simultaneously the order of integration of hours worked and the response of hours to a technology shock. We find that hours fall on impact in response to a positive technology shock.

The Ciborium or Lantern Tower of Valencia Cathedral: Geometry, Construction and Stability

Early 18th century treatise writer Tomas Vicente Tosca1 includes in his Tratado de la montea y cortes de Canteria [On Masonry Design and Stone Cutting], what is an important documentary source about the lantern of Valencia Cathedral. Tosca writes about this lantern as an example of vaulting over cross arches without the need of buttresses. A geometrical description is followed by an explanation of the structural behavior which manifests his deep understanding of the mechanics of masonry structures. He tries to demonstrate the absence of buttresses supporting his thesis on the appropriate distribution of loads which will reduce the "empujos" [horizontal thrusts] to the point of not requiring more than the thickness of the walls to stand (Tosca [1727] 1992, 227-230). The present article2 assesses T osca' s appreciation studying how loads and the thrusts they generate are transmitted through the different masonry elements that constitute this ciborium. In order to do so, we first present a geometrical analysis and make considerations regarding its materials and construction methods to, subsequently, analyze its stability adopting an equilibrium approach within the theoretical framework of the lower bound limit analysis

A new framework for large strain electromechanics based on convex multi-variable strain energies: Variational formulation and material characterisation

Following the recent work of Bonet et al. (2015), this paper postulates a new convex multi-variable variational framework for the analysis of Electro Active Polymers (EAPs) in the context of reversible nonlinear electro-elasticity. This extends the concept of polyconvexity (Ball, 1976) to strain energies which depend on non-strain based variables introducing other physical measures such as the electric displacement. Six key novelties are incorporated in this work. First, a new definition of the electro-mechanical internal energy is introduced expressed as a convex multi-variable function of a new extended set of electromechanical arguments. Crucially, this new definition of the internal energy enables the most accepted constitutive inequality, namely ellipticity, to be extended to the entire range of deformations and electric fields and, in addition, to incorporate the electro-mechanical energy of the vacuum, and hence that for ideal dielectric elastomers, as a degenerate case. Second, a new extended set of variables, work conjugate to those characterising the new definition of multi-variable convexity, is introduced in this paper. Third, both new sets of variables enable the definition of novel extended Hu–Washizu type of mixed variational principles which are presented in this paper for the first time in the context of nonlinear electro-elasticity. Fourth, some simple strategies to create appropriate convex multi-variable energy functionals (in terms of convex multi-variable invariants) by incorporating minor modifications to a priori non-convex multi-variable functionals are also presented. Fifth, a tensor cross product operation (de Boer, 1982) used in Bonet et al. (2015) to facilitate the algebra associated with the adjoint of the deformation gradient tensor is incorporated in the proposed variational electro-mechanical framework, leading to insightful representations of otherwise complex algebraic expressions. Finally, under a characteristic experimental setup in dielectric elastomers, the behaviour of a convex multi-variable constitutive model capturing some intrinsic nonlinear effects such as electrostriction, is numerically studied

A mixed variational framework for the design of energy-momentum integration schemes based on convex multi-variable electro-elastodynamics

In Ortigosa et al. (2018), the authors presented a new family of time integrators for large deformation electromechanics. In that paper, definition of appropriate algorithmic expressions for the discrete derivatives of the internal energy and consideration of multi-variable convexity of the internal energy was made. These two ingredients were essential for the definition of a new energy-momentum (EM) time integrator in the context of large deformation electromechanics relying on materially stable (ellipticity compliant) constitutive models. In Betsch et al. (2018), the authors introduced a family of EM time integrators making use of mixed variational principles for large strain mechanics. In addition to the displacement field, the right Cauchy–Green deformation tensor, its co-factor and its Jacobian were introduced as unknown fields in the formulation. An elegant cascade system of kinematic constraints was introduced in this paper, crucial for the satisfaction of the required conservation properties of the new family of EM time integrators. The objective of the present paper is the introduction of new mixed variational principles for EM time integrators in electromechanics, hence bridging the gap between the previous work presented by the authors in References Ortigosa et al. (2018) and Betsch et al. (2018), opening up the possibility to a variety of new Finite Element implementations. The following characteristics of the proposed EM time integrator make it very appealing: (i) the new family of time integrators can be shown to be thermodynamically consistent and second order accurate; (ii) piecewise discontinuous interpolation of the unknown fields (except displacements and electric potential) has been carried out, in order to yield a computational cost comparable to that of standard displacement-potential formulations. Finally, a series of numerical examples are included in order to demonstrate the robustness and conservation properties of the proposed scheme, specifically in the case of long-term simulations