Purpose -To compare slip surface and moving band techniques for modelling movement in 3D with FEM. Design/methodology/approach -The slip surface and moving band techniques are used to model the rotation of electrical machines in 3D with FEM. The proposed techniques are applied to a permanent magnet synchronous machine. The comparison is carried out at no-load for the electromotive force (EMF) and the cogging torque. The torque is also compared for the short circuit case. Findings -For both the locked-step and moving band approaches there is no difficulty in establishing the scalar potential and potential vector formulations. However, if step displacement is not equal to the mesh step, the results can show numerical irregularities. Some improvements have been proposed in order to limit this problem. Originality/value -The results of the EMF and the cogging torque are improved.
In model storage systems, the multilevel buffer caches hierarchy is widely used to improve the I/O performance of disks. In the hierarchy, the referenced pages in second-level buffer cache have larger reuse distance that is the number of accesses between two references to the same block in a reference sequence. These reuse distances have close value with their lifetime-the time they are conserved in buffer cache. Therefore, this tiny difference can be more easily eliminated by the prefetched (not yet accessed) data that reduces the lifetime of referenced pages. This leads more pages than those replaced by prefetching to lose their re-access opportunity. This anomaly influence can significantly reduce the overall hit ratio of buffer cache and, unfortunately, it is ignored by traditional sequential prefetching algorithms. To address this problem, we propose an Adaptive SEquential Prefetching (named ASEP) that uncovers this anomaly influence and adaptively adjusts the prefetching depth by considering the access characteristics in second-level buffer cache. We extensively evaluate ASEP by conducting trace driven experiments with a prototype implements in Linux (software RAID-MD). The experiments' results, under varied workloads from transaction processing applications to Web searching applications, show that ASEP outperforms the default sequential prefetching scheme in Linux kernel and other heuristic schemes, with the response time improvement by up to 49.7% and the cache hit ratio improvement ranging from 0.2~ 8.5%.
Patients suffering from paraplegia are special disabled groups in society. In order to help them with lower-limb rehabilitation, a kind of power-assisted gait orthosis is designed. In consideration of the crutches that are rather necessary to keep balance when walking, the effects of crutches on analysis of mechanism cannot be ignored. Based on the gait characteristics, this gait orthosis mechanism is designed, of which the structure is optimized by genetic algorithm and the dynamical model is generated. The periodic movement of hip joints, knee joints, and ankle joints in corrected gait are achieved and the torque can be transferred to the driving force of the back motor and the pushrod according to the orthosis structure. Finally, a verification test shows this design is reasonable and practical.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.