Degradation of adhesive composites

Composite materials consisting of natural leather and polyurethane elastomers, and bonded together by polyurethan adhesives, were submitted to accelerated ageing at various testing conditions. The extent of the degradation of these composites was evaluated through the determination of mechanical strength reduction and through the insight into the structural and chemical transformations of the adhesive polymeric materials. Founded data correlations indicate to the mechanism and to the relevant factors that influence of ageing processes.     

Cost-optimized switched reluctance motor drive with bipolar currents

The manufacturing cost of switched reluctance motors (SRM) are low due to concentrated stator windings and extremely simple and robust rotor construction, having neither permanent magnets nor the rotor windings. Therefore, the SRM drives have been considered as a promising solution for cost-critical applications where the electronic speed control is needed, such as the appliance drives, HVAC blowers and compressors, drives in commercial and residential buildings and similar. One of the reasons that hindered the SRM drives expansion was the lack of standardized power converters produced in volume. Advantageous SRM power converter topologies have been proposed over the years, however, some of them were utilizing a large number of discrete power components, while the others were leading to a poor utilization of the DC-bus voltage. In this article, a novel SRM drive is proposed, entirely based on standard industrial inverter modules, fully utilizing bus voltage. Besides, due to the pulse polarity alteration, the dwell period can be arbitrarily chosen and can freely overlap defluxing interval in the adjacent phase. Therefore, the applicable voltage reaches theoretical maximum for the given bus voltage, extending in such way the torque-speed region up to the motor-related limits. Proposed topology is functional in the four quadrants and in the field weakening as well. This article includes the operation principles of the proposed solution and continues with practical application on a three-phase SRM. Also, design considerations and experimental results are included, as well as the consideration of the drive cost.     

Enrichment of eggs in n-3 polyunsaturated fatty acids by feeding hens with different amount of linseed oil in diet

The production of n-3 polyunsaturated fatty acid enriched eggs by addition of linseed oil to the laying hens' diet has been evaluated in terms of production parameters and n-6/n-3 ratio. A total of 150 18weeks old Lohmann Brown laying hens were housed in cages and fed with basal diet and four experimental diets containing 1%, 2%, 3% or 4% of linseed oil added to the basal diet. The effect of the altered level of linseed oil on hens laying performance, fatty acid content and composition and cholesterol content in egg yolk has been evaluated during 13weeks of experiment. Egg weight, yolk fat content, yolk weight, yolk percentage and shape index were not influenced by dietary treatment. The ratio between n-6 and n-3 polyunsaturated fatty acids in eggs decreased in first 5weeks and then remained stable until the end of the experiment for all experimental groups. Different contents of linseed oil in feed highly influenced the n-6/n-3 ratio (P<0.0001). Addition of linseed oil did not influence the cholesterol content in yolks (P=0.5200) while the only factor affecting the cholesterol content was the hens age (P<0.0001).