Multi-parameter numerical optimization of selected thin-walled machine elements using a stigmergic optimization algorithm

This paper presents a method of multi-parameter optimization of shell structures of constant thickness from linearly elastic homogeneous material. Our goal is to present how a relatively complex shape of shell can be optimized in terms of its stiffness only by changing its geometry and at the same time preserve the primary volume. Loading cases are not known exactly and so we use the criterion function which on the basis of arbitrary chosen eigenvalue frequencies, gives a stiffness of the shell structure. The optimization algorithm is based on stigmergy, which is becoming increasingly popular in combinatorial optimization and lately also in multi-parameter optimization. The method was verified on a real industrial problem on an electric motor casing.     

A representation of disjoint sets with fast initialization

A unified formal treatment of simulation and reduction concepts for parallel computation systems is given. A computation homomorphism, a notion introduced by Kasai and Miller (1979), is used to study the correctness properties of parallel computation systems. The concept of reduction induced by a surjective computation of homomorphism is introduced and its relationship with the similar concept of simulation is studied. The use of reduction is combined to verification techniques based on temporal logic. The results of Berthelot et al. (1979), Kasai and Miller (1979) and Kwong (1977) are unified and generalized.     

Mars Soil Mechanical Properties and Suitability of Mars Soil Simulants

Determination of Mars soil mechanical properties will improve future lander mission success and provide narrower constraints for geomorphological modeling. A soil mechanics investigation was conducted wherein soil mechanical properties were determined by computer reconstruction of mass wasting features observed in photographs of Mars Exploration Rover landing sites and analysis of natural slope stability. Mars soil mechanical properties were compared with thermal inertia measurements and a correlation is presented. Tests with rovers and equipment for Mars surface exploration and various past laboratory experiments have incorporated a number of different Mars soil simulants. Standard laboratory measurements were conducted to characterize the shear strength, grain size distribution, and densities of various Mars soil simulants. From these measurements, the ability of a given simulant to appropriately represent the mechanical properties of in situ Mars soils was judged. Specific simulants are recommended for certain regions of Mars.     

Electric arc modeling of the EAF using differential evolution algorithm

?tore Steel Ltd. makes more than 1400 steel grades. The highest costs in steel production from scrap stems from the electric arc furnace electric energy consumption. Electrical energy is used to produce heat energy generated by the burning arc between the graphite electrodes and steel scrap. In general, the balanced heat input of all electrodes is essential. Based on the input of thermal energy from all electrodes, also the possibility of occurrence of hot and cold spots in the electric arc furnace can be determined. Perception of and the elimination of the unequal heat load of electrodes have a major impact on reducing operating costs and increasing the efficiency of the electric arc furnace production. Most authors have modeled the arc furnace as an electrical equivalent circuit, where the electric arc is modeled using the macroscopic approach. In this paper, the microscopic approach to the electric arc model is described, where a set of equations (electrical neutrality, Dalton law, Saha–Eggert) was solved using differential evolution algorithm. The results of modeling were practically confirmed by measuring electric parameters (voltage, current, active power) during the electric arc furnace operation. In November 2016, the investment in a new electrode controller using implemented logic will be carried out.     

Multisensor online 3D view planning for autonomous underwater exploration

This study presents a novel octree‐based three‐dimensional (3D) exploration and coverage method for autonomous underwater vehicles (AUVs). Robotic exploration can be defined as the task of obtaining a full map of an unknown environment with a robotic system, achieving full coverage of the area of interest with data from a particular sensor or set of sensors. While most robotic exploration algorithms consider only occupancy data, typically acquired by a range sensor, our approach also takes into account optical coverage, so the environment is discovered with occupancy and optical data of all discovered surfaces in a single exploration mission. In the context of underwater robotics, this capability is of particular interest, since it allows one to obtain better data while reducing operational costs and time. This study expands our previous study in 3D underwater exploration, which was demonstrated through simulation, presenting improvements in the view planning (VP) algorithm and field validation. Our proposal combines VP with frontier‐based (FB) methods, and remains light on computations even for 3D environments thanks to the use of the octree data structure. Finally, this study also presents extensive field evaluation and validation using the Girona 500 AUV. In this regard, the algorithm has been tested in different scenarios, such as a harbor structure, a breakwater structure, and an underwater boulder.     

Preparation of novel fibre–silica–Ag composites: the influence of fibre structure on sorption capacity and antimicrobial activity

Novel fibre–silica–Ag composites with biocidal activity were successfully produced by chemical modifying cotton (CO), wool (WO), silk (SE), polyamide (PA) and polyester (PES) fabrics and CO/PES and WO/PES fabric blends. A silica–Ag coating was prepared using a two-step procedure that included the creation of a silica matrix on the fibre surface via the application of an inorganic–organic hybrid sol–gel precursor [reactive binder (RB)] using a pad-dry-cure method, followed by the in situ synthesis of AgCl particles within the RB-treated fibres from solutions of 0.10 mM and 0.50 mM AgNO₃ and NaCl. The presence of the coating on the fibres was verified by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The bulk concentration of Ag in the coated fibres was determined using inductively coupled plasma mass spectroscopy. The antimicrobial activity was determined for the bacteria Escherichia coli and Staphylococcus aureus and the fungus Aspergillus niger. The results show that the chemical and morphological structures of the fibres directly influenced their absorptivity and affinity for the Ag compound particles. As the amorphous molecular structure of the fibres and the amount of functional groups available as binding sites for Ag⁺ were increased, both the silver solution uptake and the concentration of the absorbed Ag compound particles increased. The chemical binding of Ag to the fibres significantly reduced the effectiveness of the antimicrobial activity of the Ag compound particles. Accordingly, an increase in the concentration of absorbed Ag was required to achieve a biocidal effect.     

Model for the prediction of bulk temperature changes and pressure losses in rubber compounds flowing through conical dies: An engineering approach

The bulk temperature is a very important parameter for the processing of rubber compounds. Currently, standard injection molding simulation is taking into account just shear heating, while elongational heating is neglected by most available software tools. A new viscous model for the prediction of temperature changes in rubber compounds flowing through conical dies and runner segments was deduced where elongational heating is considered as well. Shear viscosity was directly measured on a Capillary Rheometer and elongational viscosity was calculated from the inlet‐pressure drops using a new approach. To verify the theoretical calculations experiments on a rubber injection molding machine were carried out by means of a specially designed mold. Varying injection speed and the die angle bulk temperature measurements in the purged material were performed. The measured bulk temperature rise showed a dependence on the flow rate and the cone angle with the flow rate being dominant. The results of the temperature measurements showed good correlation with the model results with an average error being <5%. POLYM. ENG. SCI., 55:701–709, 2015. © 2014 Society of Plastics Engineers