Optimizing the Cross Section of Cold-Rolled Steel Beams Using a Genetic Algorithm: Avoiding Local Optima Using Adaptive Mutation Control, Flexible Restriction Handling and Inbreed Avoiding Mating Strategies

In modern mechanical engineering and steelwork the use of cold-rolled steel sections is a standard method. These sections should be mechanically stable on the one hand and cost efficient on the other hand. To decide what profile suits for a certain case is a constrained optimization problem which is in general non convex, i.e. several local optima exist. To solve this non trivial problem we used genetic algorithms, search heuristics that mimic the process of natural evolution. For the specific application some additional problems had to be solved:First, an adaptive mutation control was implemented. Second, a mixed asexual and sexual reproduction was applied with an inbreed avoiding method based on the genetic distance of the individuals. Third, the restrictions were handled flexible, dependent on the mutation strength. This means that under the conditions of strong mutations (r-strategy), violations of the restrictions are allowed within some limits corresponding to reduced evolutionary pressure. Later on when approaching an optimum and the algorithm changes eventually to K-strategy, the restrictions become more severe corresponding to stabilising selection.The presented algorithm was tested on some cases; we found that significant improvement of cost efficiency was reached while mechanical stability was still granted. In comparison to hard restriction implementations like constant penalty functions or Lagrange-multipliers due to the flexible restrictions the algorithm tends significantly less to sustain in local optima. This approach could help to find cost efficient and light weight steel structures for mechanical engineering in the near future.</p

The Impact of a Flexible Stern on Canoe Boat Maneuverability and Speed

Paddle boats like canoes and kayaks draw a sinusoidal path when a linear movement is intended. The reason for this behavior is that each paddle stroke induces a lateral movement of the boat. In this study, we sought to reduce the so-called yawing motion. We therefore replaced the stiff stern by a flexible stern, which is based on the Fin Ray Effect&reg;. We built down-scaled boat models and tested them in a water channel. The similarities between experimental and original setup were evaluated by means of a dimensional analysis. (Thermoplastic) elastomers with various flexibility were used for the stern construction. In the experiments conducted in the water channel, we determined the forces acting on the boat with different stern models. The results reveal that the flexible stern induced a torque counteracting the boat&rsquo;s deflection, while the stiff stern caused a torque enhancing it. A paddle boat with a flexible stern could hence be a promising new method to reduce the boat&rsquo;s yawing movement

MCAD-Deficiency with Severe Neonatal Onset, Fatal Outcome and Normal Acylcarnitine Profile

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is an autosomal recessively inherited disorder of fatty acid oxidation with a potentially fatal outcome in undiagnosed patients. The introduction of tandem mass spectrometry into newborn screening (NBS) has led to the inclusion of MCADD in NBS in many countries, which has resulted in a significant reduction of morbidity and mortality. We report a child with MCADD presenting neonatally with apnoea and heart arrest. Despite intensive efforts to rescue the child, including reanimation for 90 min, the child died at the second day of life. Autopsy revealed fatty liver and also fat storage in heart muscle, which was suggestive of a fatty acid oxidation defect. However, acylcarnitines determined from stored EDTA blood were not suggestive of MCADD. Nevertheless, a subsequent whole exome sequencing analysis revealed homozygosity for the ACADM gene c.1084A&gt;G/p.Lys362Glu mutation