Comparison of constraint-handling techniques for metaheuristic optimization

Many design problems in engineering have highly nonlinear constraints and the proper handling of such constraints can be important to ensure solution quality. There are many different ways of handling constraints and different algorithms for optimization problems, which makes it difficult to choose for users. This paper compares six different constraint-handling techniques such as penalty methods, barrier functions, epsilon-constrained method, feasibility criteria and stochastic ranking. The pressure vessel design problem is solved by the flower pollination algorithm, and results show that stochastic ranking and epsilon-constrained method are most effective for this type of design optimization

Histone methylation marks play important roles in predicting the methylation status of CpG islands

The methylation status of CpG islands is highly correlated with gene expression. Current methods for computational prediction of DNA methylation only utilize DNA sequence features. In this study, besides 35 DNA sequence features, we added four histone methylation marks to predict the methylation status of CpG islands, and improved the accuracy to 89.94%. Also we applied our model to predict the methylation pattern of all the CpG islands in the human genome, and the results are consistent with the previous reports. Our results imply the important roles of histone methylation marks in affecting the methylation status of CpG islands. H3K4me enriched in the methylation-resistant CpG islands could disrupt the contacts between nucleosomes, unravel chromatin and make DNA sequences accessible. And the established open environment may be a prerequisite for or a consequence of the function implementation of zinc finger proteins that could protect CpG islands from DNA methylation. © 2008 Elsevier Inc. All rights reserved

Integrated health monitoring for a steel beam : an experimental study

Civil infrastructures begin to deteriorate once they are built and used. Detecting damages in a structure to maintain its safety is a topic that has received considerable attention in the literature in recent years. Many methods are developed, including global vibration-based methods and local GW-based methods. The global vibration-based method uses changes in modal properties to detect damage. The advantage of this approach is that the vibration properties are straightforward to be measured. The disadvantage of this method is that it might not be sensitive to small damage. On the other hand, local method, such as the guided waves (GW) based method is sensitive to small damage, but its sensing range is small. In this paper, an integrated structural health monitoring test scheme is developed to detect damage in a steel beam. Different saw cuts of various depths are made to simulate crack damage. Vibration tests and guided wave tests are conducted after each cut. The vibration method is used to detect the overall condition change of the beam, whereas the GW method is used to locate and quantify the damage. Experimental results show that the integrated method is efficient to detect and quantify local crack damage in steel structures and its influence on the global structure conditions