膝关节内侧半月板径向移位的影像学进展

膝关节由髌骨、股骨、胫骨三部分构成,是人体最大的关节部分之一。位于胫骨与股内中间的膝关节内侧半月板具有缓冲和稳定功能,当膝关节内侧半月板出现径移位时,易导致关节功能出现异常,进而对患者生活质量造成较大的影响。膝关节内侧半月板径向移位是临床较为普遍的膝关节病变情况,易引起膝关节疼痛、失稳等多种症状。本文就膝内侧半月板径向移位进行综合分析,进而分析该疾病的影像学进展,旨在探索各种成像手段对膝内侧半月板的诊断与评价的优点与限制,从而为临床上更为精准的诊治及手术选择提供依据。

半月板径向移位的MRI研究及临床意义

目的:观察半月板移位的特点及相关临床表现,从而判断其与骨关节炎影像学征象的相关性,探讨其临床意义。方法:对未行半月板切除术的半月板径向移位通过MRI加以测量,以MDI和LDI(内、外半月板移位指数)作为半月板移位与半月板宽度的比率,用以量化径向移位。将年龄、性别、骨关节炎影像表现等参照研究。结果:有径向移位和无径向移位年龄分别为40.7±16.7岁和27.2±12.5岁;有径向移位的女性与男性年龄分别为43.9±17.3与33.6±16.0岁;年龄匹配分组中有、无骨关节炎征象的MDI分别为0.28±0.05与0.10±0.12;LDI分别为0.13±0.15与0.06±0.07(x±s),差别显著。有意义的是有骨关节炎征象时必然伴有半月板移位。结论:半月板径向移位与年龄、骨性关节炎影像学表现等有明显相关性。

膝骨性关节炎与半月板径向移位的研究进展

膝关节骨性关节炎是临床上的常见疾病,其发生机制尚不明确。近年来不断有国内外学者报道半月板径向移位可能是膝骨性关节炎发生、发展的重要因素。本文对半月板径向移位现象的国内外研究进行总结,并对目前存在的相关问题进行了综述,以期提高临床医师对此现象的认识。

抽水蓄能机组推力轴承径向移位研究

本文针对单波纹弹性油箱支撑推力轴承瓦出现的径向移位进行了分析,研究了最大径向力的计算方法,并利用高速推力轴承试验台和试验推力轴承进行了推力瓦所受径向力的测量,试验结果表明,推力瓦在停机后存在较大的径向力,推力瓦的径向力最大约为单瓦最小受力的0.11倍;停机2h内,瓦面油膜厚度约0.01mm降到约0.005mm,推力瓦所受径向力变化不明显;对于正在运行的机组,停机后定时起动高压油顶起系统,有助于减小推力瓦所受的径向力;推力瓦的径向限位应有足够的强度,此项核算应作为设计的核算指标。

Vertical vibration of a large diameter pipe pile considering transverse inertia effect of pile

Considering the transverse inertia effect of pile, the vertical soil layer is studied. The wave propagations in the outer and inner soil dynamic response of a large diameter pipe pile in viscoelastic are simulated by three-dimensional elastodynamic theory and those in the pile are simulated by Rayleigh-Love rod theory. The vertical and radial displacements of the outer and inner soil are obtained by utilizing Laplace transform technique and differentiation on the governing equations of soils. Then, based on the continuous conditions between the pile and soils, the displacements of the pile are derived. The frequency domain velocity admittance and time domain velocity response of the pile top are also presented. The solution is compared to a classical rod model solution to verify the validity. The influences of the radii and Poisson ratio of pile on the transverse inertia effect of pile are analyzed. The parametric study shows that Poisson ratio and outer radius of pile have significant influence on the transverse inertia effect of large diameter pipe piles, while the inner radius has little effect.

Dynamic responses of deep underground explosions based on improved Grigorian model

It is important to investigate the dynamic behaviors of deep rocks near explosion cavity to reveal the mechanisms of deformations and fractures. Some improvements are carried out for Grigorian model with focuses on the dilation effects and the relaxation effects of deep rocks, and the high pressure equations of states with Mie-Grüneisen form are also established. Numerical calculations of free field parameters for deep underground explosions are carried out based on the user subroutines which are compiled by means of the secondary development functions of LS-DYNA9703 D software. The histories of radial stress, radial velocity and radial displacement of rock particles are obtained, and the calculation results are compared with those of U.S. Hardhat nuclear test. It is indicated that the dynamic responses of free field for deep underground explosions are well simulated based on improved Grigorian model, and the calculation results are in good agreement with the data of U.S. Hardhat nuclear test. The peak values of particle velocities are consistent with those of test, but the waveform widths and the rising times are obviously greater than those without dilation effects. The attenuation rates of particle velocities are greater than the calculation results with classic plastic model, and they are consistent with the results of Hardhat nuclear test. The attenuation behaviors and the rising times of stress waves are well shown by introducing dilation effects and relaxation effects into the calculation model. Therefore, the defects of Grigorian model are avoided. It is also indicated that the initial stress has obvious influences on the waveforms of radial stress and the radial displacements of rock particles.

以用户地理位置为中心的兴趣点标签云

以基于位置的服务(Location-Based Service,LBS)为研究场景,针对常规地图表达兴趣点的局限,结合标签云的表达优势,设计了一种以用户地理位置为中心、面向兴趣点可视化的“LBS标签云”,并初步实现了一种基于标签径向移位的布局方法。LBS标签云的主要创新是将一个布局中心点引入常规标签云,并根据标签与中心点的空间关系来确定标签的摆放位置。本文设计的布局方法如下:首先,将LBS用户的地理位置作为布局中心点;然后,基于兴趣点名称生成文字标签,并根据兴趣点属性确定标签的字号、字色及其他视觉变量;最后,在极坐标下根据标签与中心点的关系计算标签的初始摆放位置及布局优先级,并按优先级将标签从初始摆放位置依次向外径向移位至与其他标签无压盖的位置。在标签移位过程中,着重考虑角度相邻关系以确保标签距离远近的顺序关系,利用四叉树剖分字形轮廓提高了标签碰撞检测的效率。实验以景点类兴趣点为例,探讨了LBS标签云在3个场景下的可用性及可扩展性。结果表明,相比常规地图,LBS标签云不仅可以展示更多的兴趣点,而且可以有效突出用户关注的信息,如兴趣点的热度、评分及通行时间等。虽然LBS标签云包含一定的距离变形,但多种视觉变量的协同有效缓解了距离变形导致的认知误差。综上,LBS标签云可完整、直观地表达兴趣点的空间分布、多维属性及其与用户位置的关系,是一种新型的、适宜用户高效认知周边环境的可视化形式。

The Topic of Contact Zone Problems in the Shaft and Hole Joint, Taking into Account Component Form Errors

In assemblies constructed from components manufactured with radial deviations, cross-section deviations and deviations being combination of both, there occur variable values of local stresses and displacements. Both the types of shape deviations and their values need to be taken into account in the designing process and play an important role during machine operation. They have a crucial effect on the value and scatter of maximum reduced von Mises stresses and contact stresses. Axisymmetric joints were examined, in which shafts in selected shape variants and in variable angular positions were associated with a non-deformable hole. The aspects of contact zone problems are presented using the example of numerical simulation of contact between an elliptical saddle-shaped shaft placed in a rigid, non-deformable hole in different angular positions. Occurrence of both variable relative stresses and contact stresses as well as shaft＇s axial shift and rotary movement resistance were demonstrated.

Unified analytical solutions for a circular opening based on non-linear unified failure criterion

Unified analytical solutions are presented for the predictions of the stresses and displacements around a circular opening based on nonqinear unified failure criterion and the elastic-brittle-plastic softening model. Unified analytical solutions not only involve generally traditional solutions which are based on the Hock-Brown （H-B） failure criterion or the non-linear twin-shear failure criterion, but also involve other new results. The results of the radius of plastic zone, radial displacements and stresses are obviously different using three rock masses when different values of the unified failure criterion parameter or different material behavior models are used. For a given condition, the radius of plastic zone and radial displacements are reduced by increasing the unified failure criterion parameter. The latent potentialities of rock mass result from considering the effect of intermediate principal stress. It is shown that proper choices of the failure criterion and the material behavior model for rock mass are significant in the tunnel design.

Deformation analysis of the flexspline of harmonic drive gears considering the driving speed effect using laser sensors

Accurate description of the elastic deformation of the flexspline is the foundation for optimization design of the structure and conjugate profiles of the harmonic drive gear. This paper proposed an experimental method to investigate the effect of the driving speed on the deformation characteristics of the flexspline. First, an experimental apparatus that integrates a special-fabricated micro-displacement platform and a pair of laser displacement sensors is developed, and the radial displacement of the flexspline is measured in vertical and horizontal directions. Next, the deformation analyses of the flexspline at different driving speeds are performed with our method and the conventional method, and the comparison results reveal that the radial displacement of the flexspline is actually composed of both harmonic and random components, and the amplitude decreases and tends to zero with the increase of the driving speed, especially near the closed end of the flexspline. Last, the mechanisms of the inherent multi-frequency and amplitude attenuation characteristics of the radial displacement of the flexspline are discussed. It is indicated that the impact and friction existing in the flexible bearing of the wave generator is likely responsible for the existence of the random component, and the assumption of linear distribution of the ftexspline deformation along the rotating axis is invalid under high speed condition. Our research promotes the further study on the contact-impact problem of the flexible bearing of the wave generator and the transfer characteristic of the elastic deformation of the flexspline.