Browsing by Author "Hsu, Hung-Wei"

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Effect of the cord pretension of the Dynesys dynamic stabilisation system on the biomechanics of the lumbar spine: a finite element analysis
(2011-11-01)
Liu, Chien-Lin
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Zhong, Zheng-Cheng
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Hsu, Hung-Wei
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Shih, Shih-Liang
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Wang, Shih-Tien
The Dynesys dynamics stabilisation system was developed to maintain the mobility of motion segment of the lumbar spine in order to reduce the incidence of negative effects at the adjacent segments. However, the magnitude of cord pretension may change the stiffness of the Dynesys system and result in a diverse clinical outcome, and the effects of Dynesys cord pretension remain unclear. Displacement-controlled finite element analysis was used to evaluate the biomechanical behaviour of the lumbar spine after insertion of Dynesys with three different cord pretensions. For the implanted level, increasing the cord pretension from 100 to 300 N resulted in an increase in flexion stiffness from 19.0 to 64.5 Nm/deg, a marked increase in facet contact force (FCF) of 35% in extension and 32% in torsion, a 40% increase of the annulus stress in torsion, and an increase in the high-stress region of the pedicle screw in flexion and lateral bending. For the adjacent levels, varying the cord pretension from 100 to 300 N only had a minor influence on range of motion (ROM), FCF, and annulus stress, with changes of 6, 12, and 9%, respectively. This study found that alteration of cord pretension affects the ROM and FCF, and annulus stress within the construct but not the adjacent segment. In addition, use of a 300 N cord pretension causes a much higher stiffness at the implanted level when compared with the intact lumbar spine.
Performance Model And Deployment Strategy For Mm-wave Multi-Cellular Systems
(2016)
Lu, Youyi
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Hsu, Hung-Wei
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Wang, Li-Chun
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電信工程研究所
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Institute of Communications Engineering
The next generational wireless system require ubiquitous access to the huge volume of data. An interesting observation is that small cells, mm-Wave, and massive MIMO can orchestrate a blueprint of a high-capacity wireless system. We will propose a new cellular system architecture, in which mm-Wave small cells with massive MIMO for the 5G use case of broadband access providing Gbps data rate. The millimeter-wave band, is very attractive for the bandwidth-hungry 5G system. However, since different mm-Wave frequencies have different propagation conditions, how many small cells should be deployed is an issue. In this paper, we use ray-tracing based model to analyze the performance of mm-wave multicellular systems in a real scenario and give suggested number of small cells for guaranteeing different QoS. In addition, the directive property and high absorption by blockage of mmWave reveal the importance of LoS propagation conditions. Hence, we propose a grid strategy for mm-Wave small cell deployment to ensure the LoS scenario available for most of users. Simulation results show that this deployment strategy is especially effective when small cells are not-so-ultra dense.