A recursive coupling-decoupling approach to improve experimental frequency based substructuring results

Substructure decoupling techniques allow identifying the dynamic behavior of a substructure starting from the dynamic behavior or the assembled system and a residual subsystem. Standard approaches rely on the knowledge of all FRFs at the interface DOFs between the two substructures. However, as these typically include also rotational DOFs which are extremely difficult and most of the time impossible to measure, several techniques have been investigated to overcome these limitations. A very attractive solution consists in defining mixed or pseudo interfaces, that allow to substitute unmeasurable coupling DOFs with internal DOFs on the residual substructure. Additionally, smoothing/denoising techniques have been proposed to reduce the detrimental effect of FRF noise and inconsistencies on the decoupling results. Starting from these results, some recent analysis on the possibility of combining coupling and decoupling FBS to validate the results and compensate for inconsistencies will be presented in this paper. The proposed method relies on errors introduced in the substructuring process when assuming that the interface behaves rigidly, while it is generally known that this assumption is seldom verified. Consequently, a recursive coupling-decoupling approach will be used to improve the estimation of the dynamic response of either the residual structure (for decoupling) or the assembly (for coupling). The method, validated on analytical data, will be here analyzed on a numerical example inspired by an experimental campaign used to validate the finite element models and on which standard substructuring techniques showed some limitations. The results discussed in this paper will be then used as guidelines to apply the proposed methodologies on experimental data in the future

Non-functional properties in the model-driven development of service-oriented systems

Systems based on the service-oriented architecture (SOA) principles have become an important cornerstone of the development of enterprise-scale software applications. They are characterized by separating functions into distinct software units, called services, which can be published, requested and dynamically combined in the production of business applications. Service-oriented systems (SOSs) promise high flexibility, improved maintainability, and simple re-use of functionality. Achieving these properties requires an understanding not only of the individual artifacts of the system but also their integration. In this context, non-functional aspects play an important role and should be analyzed and modeled as early as possible in the development cycle. In this paper, we discuss modeling of non-functional aspects of service-oriented systems, and the use of these models for analysis and deployment. Our contribution in this paper is threefold. First, we show how services and service compositions may be modeled in UML by using a profile for SOA (UML4SOA) and how non-functional properties of service-oriented systems can be represented using the non-functional extension of UML4SOA (UML4SOA-NFP) and the MARTE profile. This enables modeling of performance, security and reliable messaging. Second, we discuss formal analysis of models which respect this design, in particular we consider performance estimates and reliability analysis using the stochastically timed process algebra PEPA as the underlying analytical engine. Last but not least, our models are the source for the application of deployment mechanisms which comprise model-to-model and model-to-text transformations implemented in the framework VIATRA. All techniques presented in this work are illustrated by a running example from an eUniversity case study

Effects of Trade Cost on the Textile and Apparel Market: Evidence from Asian Countries

Global textile and apparel industry has since the 1950s been subjected to various forms of trade policy measures. Well noted among these are tariffs and non-tariff barriers (NTB)/policy indicators. Understanding the dynamics in such relevant policy indicators and the implications they yield for trade is a vital step toward informing relevant policy formulation and agribusiness investment decisions. With the textile and apparel industry being the primary grounds on which development in most Asian countries is founded, we for the first time in literature assess effects of various trade cost indicators on global textile and apparel imports from 37 Asian countries using a ‘cost-incorporated’ gravity model for the period 1988–2004. Estimates from this study affirm theory-based associations between trade, distance, cultural linkage, tariffs, and non-tariffs barriers. We however discovered quite interesting associations regarding effects of tariff increments and existence of NTB. Although both are primarily imposed/instilled to restrict trade flow, effect of tariff increments was consistently negative across all models, but that for NTB was consistently positive, although significant only in the case of apparel imports. Plausible reasons behind the implications for tariffs and NTB are elaborated on in this article. A keen discovery from this study, however, is that imports of apparels are more responsive than textile imports to dynamics in various trade-related cost, geographic and economic indicators

A BPMN extension to support discrete-event simulation for healthcare applications:an explicit representation of queues, attributes and data-driven decision points

Stakeholder engagement in simulation projects is important, especially in healthcare where there is a plurality of stakeholder opinions, objectives and power. One promising approach for increasing engagement is facilitated modelling. Currently, the complexity of producing a simulation model means that the ‘model coding’ stage is performed without the involvement of stakeholders, interrupting the possibility of a fully-facilitated project. Early work demonstrated that with currently-available software tools we can represent a simple healthcare process using Business Process Model and Notation (BPMN) and generate a simulation model automatically. However, for more complex processes, BPMN currently has a number of limitations, namely the ability to represent queues and data-driven decision points. To address these limitations, we propose a conceptual design for an extension to BPMN (BPMN4SIM) using Model Driven Architecture. Application to an elderly emergency care pathway in a UK hospital shows that BPMN4SIM is able to represent a more-complex business process

A Model transformation framework for the automated building of performance models from UML models

In order to effectively validate the performance of software systems throughout their development cycle it is necessary to continuously build performance models from software models and then use the obtained models to check whether the system is being developed according to its performance requirements. The model building activity is a critical and effort-consuming activity. Several approaches have been envisaged to endow software designers with tools that automatically build ready-to-evaluate performance models from software development models. One essential requirement of such tools, often disregarded by current approaches, is a high degree of interoperability with software development tools, which has the positive effect of reducing both the level of required expertise in performance theory and the burden of learning separate tools. This paper introduces a framework for transforming source software models into target performance models. The transformation requires a clear understanding of the abstract syntax and semantics of both the source and target models, which is obtained by use of metamodeling techniques for defining the abstract syntax of models, the interrelationships between model elements and the model transformation rules. In the paper case, the framework is applied to the transformation of source models of UML type into target models of LQN (layered queueing network) type. The proposed approach is founded on the precepts recently introduced by model-driven development (MDA) and makes use of the set of related standards (MOF, QVT, XMI). This allows to obtain a high degree of automation, so that interoperable model transformation tools can be implemented in a timely and efficient way, leading to improvements in terms of software designers' productivity and system quality

Identificazione parametrica di modelli dinamici agli elementi finiti mediante algoritmi genetici

The parametric identification/correction (updating) of dynamic finite element models is here tackled using genetic algorithms. The main advantage with respect to deterministic approaches is a lower sensitivity to measurement noise: this allows using less precise measurement techniques as well as to avoid sophisticated regularisation procedures. The goal of the formulation is to minimise an appropriate combination of the natural frequency error, the correlation error and the response residual. The method is tested by updating a three dimensional steel structure, fixed at one end, whose frequency response is previously measured

A comparison between the use of physical parameters and correction factors in dynamic model updating

The selection of quantities and/or variables that have to be corrected during the updating process is addressed in this paper. Among quantities, the major alternative is the choice between correction factors and physical parameters. The former represent scale factors used to adjust mass and stiffness submatrices of the analytical model, while the latter include parameters such as the elasticity modulus, mass density, geometrical dimensions, etc. Advantages and limitations in the process of updaring physical parameters instead of correction factors are highlighted: it can be shown that only a limited number of physical parameters can be simultaneously updated for each element. The two approaches are compared using a previously developed updating procedure to solve an experimental test case

A Model-driven approach to describe and predict the performance of composite services

Distributed applications are rapidly converging towards the adoption of a computing paradigm based on service-oriented architectures (SOA), according to which an application results from the composition of a set of services in execution on networked server hosts. In a SOA context, service providers are strategically interested both to describe the performance characteristics of offered services, to better qualify their offer and gain a significant advantage in the global marketplace, and to predict the level of performance that can be offered to service consumers when building composite web services that make use of services managed by various service providers. This paper introduces a model-driven approach for integrating performance prediction into service composition processes carried out by use of BPEL (Business Process Execution Language for Web Services). The proposed approach is founded on P-WSDL (Performance-enabled WSDL), a performance-oriented extension of WSDL, the language for describing the information about service capabilities and invocation mechanisms. P-WSDL is a lightweight WSDL extension for the description of performance characteristics of a web service. The approach is illustrated by use of an example application to a composite web service for travel planning