Experimental damage localization in beam by using natural frequency distribution and modal strain energy change ratio based methods

Two methods for a beam like structures damage identification using frequencies distribution and Modal Strain Energy Change Rate (MSECR) are presented in this paper. Firstly, the measured frequencies sensitivity is improved, and the frequency distribution is used to determine the suspected damage location. Secondly, the change of modal strain energy before and after the occurrence of damage is employed to locate the damage location. To conduct these studies, an experimental modal analysis program was carried out on a cantilever Bernoulli-Euler beams subjected to a controlled crack levels and the first seven modes (natural frequencies and mode shapes) were extracted and used to localize the damage. The effect of crack sizing in the local stiffness and in the frequency fluctuation was evaluated. The localization magnitude of the damage by the frequency distribution was predicted within an acceptable error range. The experimental MSECR was computed and the location of the damage was accurately identified especially for crack sizing as small as 10 % of the beam height. Finally, finite elements models were built and validated, MSECR method was applied and the results demonstrate that the method is capable of localizing damage for beam structure

Experimental damage localization in beam by using natural frequency distribution and modal strain energy change ratio based methods

Two methods for a beam like structures damage identification using frequencies distribution and Modal Strain Energy Change Rate (MSECR) are presented in this paper. Firstly, the measured frequencies sensitivity is improved, and the frequency distribution is used to determine the suspected damage location. Secondly, the change of modal strain energy before and after the occurrence of damage is employed to locate the damage location. To conduct these studies, an experimental modal analysis program was carried out on a cantilever Bernoulli-Euler beams subjected to a controlled crack levels and the first seven modes (natural frequencies and mode shapes) were extracted and used to localize the damage. The effect of crack sizing in the local stiffness and in the frequency fluctuation was evaluated. The localization magnitude of the damage by the frequency distribution was predicted within an acceptable error range. The experimental MSECR was computed and the location of the damage was accurately identified especially for crack sizing as small as 10 % of the beam height. Finally, finite elements models were built and validated, MSECR method was applied and the results demonstrate that the method is capable of localizing damage for beam structure

PCI-SS: MISO dynamic nonlinear protein secondary structure prediction

<p>Abstract</p> <p>Background</p> <p>Since the function of a protein is largely dictated by its three dimensional configuration, determining a protein's structure is of fundamental importance to biology. Here we report on a novel approach to determining the one dimensional secondary structure of proteins (distinguishing α-helices, β-strands, and non-regular structures) from primary sequence data which makes use of Parallel Cascade Identification (PCI), a powerful technique from the field of nonlinear system identification.</p> <p>Results</p> <p>Using PSI-BLAST divergent evolutionary profiles as input data, dynamic nonlinear systems are built through a black-box approach to model the process of protein folding. Genetic algorithms (GAs) are applied in order to optimize the architectural parameters of the PCI models. The three-state prediction problem is broken down into a combination of three binary sub-problems and protein structure classifiers are built using 2 layers of PCI classifiers. Careful construction of the optimization, training, and test datasets ensures that no homology exists between any training and testing data. A detailed comparison between PCI and 9 contemporary methods is provided over a set of 125 new protein chains guaranteed to be dissimilar to all training data. Unlike other secondary structure prediction methods, here a web service is developed to provide both human- and machine-readable interfaces to PCI-based protein secondary structure prediction. This server, called PCI-SS, is available at <url>http://bioinf.sce.carleton.ca/PCISS</url>. In addition to a dynamic PHP-generated web interface for humans, a Simple Object Access Protocol (SOAP) interface is added to permit invocation of the PCI-SS service remotely. This machine-readable interface facilitates incorporation of PCI-SS into multi-faceted systems biology analysis pipelines requiring protein secondary structure information, and greatly simplifies high-throughput analyses. XML is used to represent the input protein sequence data and also to encode the resulting structure prediction in a machine-readable format. To our knowledge, this represents the only publicly available SOAP-interface for a protein secondary structure prediction service with published WSDL interface definition.</p> <p>Conclusion</p> <p>Relative to the 9 contemporary methods included in the comparison cascaded PCI classifiers perform well, however PCI finds greatest application as a consensus classifier. When PCI is used to combine a sequence-to-structure PCI-based classifier with the current leading ANN-based method, PSIPRED, the overall error rate (Q3) is maintained while the rate of occurrence of a particularly detrimental error is reduced by up to 25%. This improvement in BAD score, combined with the machine-readable SOAP web service interface makes PCI-SS particularly useful for inclusion in a tertiary structure prediction pipeline.</p

A simple and compact model of defects and non-linear dynamic stiffness of a ball bearing

This paper presents a modelling study of a ball bearing dynamic behaviour with different defects types, which is part of an investigation related to the modelling of machinery rotating components. Our contribution in this work is a proposition of a five-degree of freedom model describing the nonlinear dynamic behaviour of a ball bearing. The aim is a parametric formulation of the ball bearing stiffness which allows the introduction of the defects characteristics. This approach is a result of an intrinsic structural behaviour making it different from methods which introduce external impulsion to simulate defects. Hence, a more realistic dynamic ball bearing defect simulation is obtained for better use in design and maintenance domain. This simulation can be formulated by two methods. The first, partial contact method, is based on elimination of some ball stiffness. The second one imposes displacement in the system response. Obtained results give response forms similar to standards and to different author’s results (theoretical and experimental) found in the literature. The developed model is simple, compact as compared to existing ones and we can express our satisfaction about this promising model