Analysis of the impact responses in a degenerated spinal motion segment FE model

A three-dimensional non-linear poroelastic finite element model of an L3/L4 motion segment was used to analyze the biomechanical effects of degeneration under impact loading on the spinal segment. A previously developed degeneration algorithm was applied to generate a degenerated disc model. Regional variation in intact vertebral body bone morphology was simulated by assigning different void ratios of 4.0–5.02, which were assessed for 27 regions of vertebral cancellous bone. For the osteoporotic structure of the vertebral body, the body was divided into 5 regions with 10–24 void ratios. Different material properties were assigned to the annulus fibers; hereupon our annulus model reflected variation in tensile behavior of multiple layer annulus samples. The impact load applied to the top of the L3 vertebral body was assumed to be a triangular impulsive force with a maximum compressive impact load of 3 kN and 20ms impact duration time. Calculated results indicated that the effect of the degeneration was predominant at the center of the vertebral body. The maximum von Mises stress was found at the region of near the endplate. The degeneration increased the averaged stress at the center of the vertebral body of L3 from 1.54 MPa to 1.69 MPa, the stress remaining relatively small at L4. Decreased fluid volume ratio of the degenerated nucleus tended to increase pressure slightly at the nucleus, and the averaged stress at the nucleus was almost doubled compared to the intact case. The innermost layers of the anterior annulus showed the highest stress concentration, followed by outermost anterior and posterior regions, for both the degenerated and the intact models. Despite an irregular stress distribution in the degenerated model, pore pressure showed relatively uniform distribution. This paper was recommended for publication in revised form by Associate Editor Young Eun Kim YoungEun Kim received a B.S. degree in Mechanics and Design from Seoul National University in 1978. He then went on to receive his M.S. from KAIST in 1986 and Ph.D. degrees from U. of Iowa 1988. Dr. Kim is currently a Professor at the Dept. of Mechanical Engineering at Dankook University in Yongin, Korea. He is currently serving as an Editor of the Open Orthopedic Research Journal. He was also served as a division chair of KSPE. Dr. Kim’s research interests are in the area of biomechanics, and occupant dynamics.     

金属材料疲劳损伤与力学性能退化机制研究

研究了中碳钢光滑试样在经历了不同程度的疲劳损伤以后,其力学性能退化机制与试样表面短裂纹之间的关系。结果表明,疲劳损伤会引起材料力学性能产生一定程度的退化,这一退化现象与试样表面短裂纹的演化过程密切相关,同时也对力学性能退化机制进行了讨论。     

适合背板信号传输的连续时间均衡器

介绍了一种适用于背板信号传输的连续时间均衡器(EQ),给出了电路的增益表达式。该电路数据传输速率可达到1.25Gb/s。采用0.18μm CMOS工艺对电路进行仿真,结果表明,电路自举因子为6dB和12dB,分别支持50mm和100mm的FR4背板信号传输。     

基于Radon变换的运动模糊方向估计的改进算法研究

运动模糊图像的复原在天文,军事,工业控制,道路监控和刑侦方面具有重要的现实意义。在研究运动模糊图像复原中,对点扩散函数PSF（point spread function）的估计是关键点也是难点。通过对运动模糊图像进行傅里叶变化,得到其明暗相间条纹的频谱图。基于亮条纹的方向和运动模糊方向垂直的原理,利用Radon变化求解频谱图中亮条纹的方向,从而得到PSF中的运动模糊方向。由于模糊图像频谱图中十字亮线的存在,直接影响了实验结果的准确性,因此对于十字亮线产生的原因进行了分析,提出一种简单有效的去除十字亮线干扰的算法。实验结果表明：该算法简单、有效,能准确测量出模糊方向,误差控制在1°之内。     

多值逻辑函数与其变元的几种无关性的谱分析

多值逻辑函数与它们的变元之间有许多种特殊关系,单从它们的表达式是较难判断的。本文给出了多值逻辑函数与其变元无关和统计无关的一些充分必要条件;给出了多值逻辑函数与其某些变元代数无关(也称为退化)的一些条件和最大程度地退化一个函数的方法;指出了这些结果在实际中的应用。所有这些结果都是Chrestenson谱方法来研究的。     

跨阻放大器的带宽扩展技术

提出了一种针对CMOS跨阻放大器的带宽扩展技术.基于此技术,采用应用于0.18μm 1.8V CMOS工艺,设计了一个RGC结构的跨阻放大器.仿真结果表明,该放大器具有66dB的跨阻增益,4.49GHz的带宽,输入等效噪声电流平均值为11.5pA/(Hz)～(1/2),该电路的功耗仅为15.4mW.     

Thermal modes of bimolecular exothermic reactions: Concentration limits of ignition

In the present work, the analytical investigation of the phase trajectories structures on the plane: heating rate-temperature for bimolecular exothermic reactions was carried out. This gave a possibility to divide the parametric plane Todes parameter–Semenov parameter into five characteristic regions with various modes of self-heating. It was established that all regions converge at a single point which determines the thermal explosion degeneration conditions. The correlation between Todes parameter, Semenov parameter and concentration ratio of initial reactants at the limit of the thermal explosion degeneration was found. The critical conditions for thermal explosion at any ratio of concentrations of initial reactants were determined. The approach proposed is a general one and allows analyzing both first and second order reactions.     

Y06108 ZQ铁型覆砂曲轴产生灰化的原因及解决办法

对YC6108ZQ曲轴灰化原因进行了分析,通过采用铁型覆砂铸造工艺和工艺过程的控制等几方面的结合,明显提高曲轴整体质量水平,按此工艺生产,基本解决了灰化问题。     

纳米氧化锌的制备及光催化性能研究进展

纳米氧化锌作为一种具有优良光催化性能的半导体材料,其制备方法及光催化性能研究受到广泛关注。对近几年来纳米氧化锌的合成工艺、光催化降解有机污染物方面的应用研究做一综述,并展望其未来发展。     

太阳漫反射板衰减监测辐射计的设计及性能评估

论述了太阳漫射板星上定标原理,研究了太阳漫射板衰减监测方法。针对星上太阳漫反射板双向反射分布函数(BRDF)的衰变,设计了以太阳为参照,通过与星上漫反射板反射辐射量比对测量实现监测功能的多波段星上漫反射板衰减监测辐射计(SDDM)。介绍了星上定标与漫射板监测的关系,设计了SDDM积分球两开口入光+挡板的光机结构,消除了入射光角度变化与探测器响应的相关性。根据光机结构设置的监测过程,给出了SDDM的监测物理模型,并对SDDM滤光片探测器动态范围设置及信噪比进行了验证和分析。在实验室模拟了太阳照射SDDM太阳观测端口的角度变化,对其透过率模型进行了多次重复测量,结合漫射板相对双向反射比因子(BRF)测量不确定度、卫星姿态及漫射板安装误差进行分析,得到SDDM测量的漫射板监测不确定度优于0.88%。