The purpose of this study was to compare ankle joint loads (Linear and Angular Impulses) while descending the stairs and ramp. Ten young male subjects participated in this study. Stairs and ramp of identical slope (30 degrees) were custom-made to include force plates in the middle of pathways. Subjects descended the stairs and ramp at a comfortable speed and posture. The stance period was divided into three phases, weight acceptance (WA), single limb stance, and pre-swing. Three-directional impulses and their sum were derived from the reaction forces and moments at the ankle joint. Differences in impulse sums (Both Linear and Angular) between stairs and ramp were significant only in the early (WA) phase, whereas those of stairs were greater than the ramp. All subjects adopted forefoot strike strategy for the stairs and 80% of the subjects adopted rearfoot strike strategy for the ramp. An increase in the GRF and moment arm of the GRF at the ankle joint in case of forefoot strike may have contributed to the increase in the linear and angular impulse in the early phase of stair descent compared to ramp descent. The results are in agreement with the preference of ramp in the elderly.

In this paper, topology optimization of a main roller for Multi-wire saws is conducted for the purpose of reducing mass of the main roller. Modal analysis is carried out to evaluate whether the resonance could have occurred, or not. The pressure from the cutting wires are modelled mathematically. Topology optimization analysis with the pressure model developed is conducted to derive optimal solution of the sectional shape of the roller. As a result, the cross section of the main roller manifests as an arch shape. The mass of the final optimal model is reduced by 14%, while the deflection and natural frequencies of the roller is same as those of the base model.