人工全髋关节置换术后髋臼假体初始不稳定原因分析及处理

目的探讨初次人工全髋关节置换术后髋臼假体初始不稳定的原因及处理方法。方法回顾性分析2003年1月-2010年6月初次人工全髋关节置换术后出现髋臼假体初始不稳定行髋臼翻修术的19例患者临床资料。男11例,女8例;年龄55～79岁,平均67.2岁。左髋9例,右髋10例。应用骨水泥型髋臼假体7例,非骨水泥型12例。初次置换术后3周～6个月行翻修术,平均4.5个月。分析髋臼假体初始不稳定的原因,比较翻修术前后髋臼假体骨覆盖率及髋关节功能Harris评分。结果髋臼假体初始不稳定与髋臼的处理、假体的选择及放置角度、骨水泥操作技术不当等有关。翻修术后l例出现坐骨神经麻痹,7周后自行恢复;1例髋臼前壁轻微骨折,3个月后骨折愈合。术后切口均Ⅰ期愈合,无关节假体周围感染、血管损伤、假体脱位、下肢深静脉血栓形成等并发症发生。术后患者均获随访,随访时间11～73个月,平均28个月。患者均未出现髋臼假体初始不稳定。髋臼假体骨覆盖率由初次置换时的67.9%±5.5%提高至翻修术后87.7%±5.2%,差异有统计学意义(t=11.592,P=0.003)。末次随访时Harris评分为(84.4±4.6)分,较术前的(56.5±9.3)分显著提高(t=11.380,P=0.005)。结论术前详细计划、选择合适的假体、妥善处理髋臼、按合理角度植入髋臼假体有助于获取良好的髋臼假体初始稳定性。

具有不稳定初始状态的连续时间系统辨识

针对传统辨识方法不适用于具有不稳定初始状态的连续时间系统的问题,提出一种全新的状态估计辨识法.首先,用状态空间模型中状态变量的初始值表征系统初始状态,并将状态变量的初始值看作待辨识参数的一部分.然后,用粒子群优化算法获得所有参数的最优估计.该方法在测试开始前不需要任何过程数据,对测试信号无任何要求,可直接用于闭环辨识.仿真实验证明该算法是有效的.

Effects of porosity heterogeneity on chemical dissolution-front instability in fluid-saturated rocks

Homogeneity and heterogeneity are two totally different concepts in nature.At the particle length scale,rocks exhibit strong heterogeneity in their constituents and porosities.When the heterogeneity of porosity obeys the random uniform distribution,both the mean value and the variance of porosities in the heterogeneous porosity field can be used to reflect the overall heterogeneous characteristics of the porosity field.The main purpose of this work is to investigate the effects of porosity heterogeneity on chemical dissolution front instability in fluid-saturated rocks by the computational simulation method.The related computational simulation results have demonstrated that:1) since the propagation speed of a chemical dissolution front is inversely proportional to the difference between the final porosity and the mean value of porosities in the initial porosity field,an increase in the extent of the porosity heterogeneity can cause an increase in the mean value of porosities in the initial porosity field and an increase in the propagation speed of the chemical dissolution front.2) An increase in the variance of porosities in the initial porosity field can cause an increase in the instability probability of the chemical dissolution front in the fluid-saturated rock.3) The greater the mean value of porosities in the initial porosity field,the quicker the irregular morphology of the chemical dissolution front changes in the supercritical chemical dissolution systems.This means that the irregular morphology of a chemical dissolution front grows quicker in a porosity field of heterogeneity than it does in that of homogeneity when the chemical dissolution system is at a supercritical stage.

Primary instabilities and bicriticality in fiber suspensions between rotating cylinders

The linear stability of fiber suspensions between two concentric cylinders rotating independently is studied. The modified stability equation is obtained based on the fiber orientation model and Hinch-Leal closure approximation. The primary instabilities and bicritical curves have been calculated numerically. The critical Reynolds number,wavenumber and wave speeds of fiber suspensions as functions of the aspect ratio,volume concentration of the fibers and the gap width of cylinders are obtained.

一种李萨如图形的作法

本文介绍了使李萨如图形稳定、准确的一种作法，即频率比与相位差的控制。