在光学加工领域,采用功率谱密度(power spectral density,PSD)对误差频谱方面信息进行表征,但是功率谱密度是表面误差统计信息,不如峰谷值(peak-valley,PV)和均方根值(root mean square,RMS)直观。为了分析功率谱密度与工艺参数之间的关...在光学加工领域,采用功率谱密度(power spectral density,PSD)对误差频谱方面信息进行表征,但是功率谱密度是表面误差统计信息,不如峰谷值(peak-valley,PV)和均方根值(root mean square,RMS)直观。为了分析功率谱密度与工艺参数之间的关系,该文从PSD定义出发,分析了随机面形轮廓不同参数对光学PSD的影响规律,总结了PSD控制的要点,在平面玻璃上对数控抛光典型路径下加工的PSD曲线进行分析。分析结果表明:PSD与随机轮廓幅值、频率分布有关,相位对它几乎无影响;在RMS接近情况下,PSD线性拟合斜率和RMS Slope随随机轮廓的自相关长度增加而下降;短程加工路径相较于长程有序路径能够有效抑制PSD曲线峰值,使得光学元件符合频谱抑制要求。展开更多
This paper aims to establish a 3D evaluation method for cutting surface topography of C/C composites. The cutting surface is measured by Talyscan 150, using 3D non-contact measurement. By evaluating 2D and 3D roughnes...This paper aims to establish a 3D evaluation method for cutting surface topography of C/C composites. The cutting surface is measured by Talyscan 150, using 3D non-contact measurement. By evaluating 2D and 3D roughness of C/C composite and Duralumin, the 2D evaluation method of the cutting surface topography of C/C composite loses a lot of information, and the characteristics of the surface topography of C/C composite can be comprehensively and authentically evaluated only by the 3D evaluation method. Furthermore, 3D amplitude and spatial parameters are adopted to evaluate the surface and the results show that： the topography of the C/C composite is anisotropy and there are no obvious feeding textures but abrupt peaks and valleys on surface of the C/C composite, which indicates that the machining mecha- nism is different from that of the metal. In conclusion, The C/C composite surface is evaluated using a 3D evaluation method, the roughness error is small, and the unique topography characteristics earl be au- thentically evaluated.展开更多
Objective： To retrospectively evaluate the early results of anatomic double-bundle anterior cruci- ate ligament （ACL） reconstruction and compare with the results of native ACL of the contralateral knee. Methods： ...Objective： To retrospectively evaluate the early results of anatomic double-bundle anterior cruci- ate ligament （ACL） reconstruction and compare with the results of native ACL of the contralateral knee. Methods： The results of a consecutive series of 118 patients receiving arthroscopic ACL reconstruction were evaluated. Eight patients were lost to the latest follow-up, leaving a total of 110 patients available for study within at least 3 years＇ clinical follow-up. Among them, 63 patients underwent postoperative MRI and CT scan, as well as clini- cal evaluation. Results： After reconstruction, the knees were stable and pain-free. Mean postoperative Lysholm score was 95.54 in 110 patients after 3 years. CT and MRI assessment showed that the reconstruction centered in the femoral footprint of ACL （n=63）. The sagittal ACL angle in the reconstructed ACL （52.16°±2.45°） was much close to that in the contralat- eral intact ACL （51.31 °±2.18°, P〉0.05）. By ACL-Blumensaat line angle analysis, there was no difference between doublebundle reconstructed knees and their contralateral normal knees （4.67°±0.43° vs. 4.62°±＊0.60°, P〉0.05）. Conclusion： Anatomic double-bundle ACL reconstruction can place grafts more precisely in the anatomic foot- print of the ACL and better restore knee kinematics.展开更多
基金Supported by the National Natural Science Foundation of China (No. 50875036)
文摘This paper aims to establish a 3D evaluation method for cutting surface topography of C/C composites. The cutting surface is measured by Talyscan 150, using 3D non-contact measurement. By evaluating 2D and 3D roughness of C/C composite and Duralumin, the 2D evaluation method of the cutting surface topography of C/C composite loses a lot of information, and the characteristics of the surface topography of C/C composite can be comprehensively and authentically evaluated only by the 3D evaluation method. Furthermore, 3D amplitude and spatial parameters are adopted to evaluate the surface and the results show that： the topography of the C/C composite is anisotropy and there are no obvious feeding textures but abrupt peaks and valleys on surface of the C/C composite, which indicates that the machining mecha- nism is different from that of the metal. In conclusion, The C/C composite surface is evaluated using a 3D evaluation method, the roughness error is small, and the unique topography characteristics earl be au- thentically evaluated.
文摘Objective： To retrospectively evaluate the early results of anatomic double-bundle anterior cruci- ate ligament （ACL） reconstruction and compare with the results of native ACL of the contralateral knee. Methods： The results of a consecutive series of 118 patients receiving arthroscopic ACL reconstruction were evaluated. Eight patients were lost to the latest follow-up, leaving a total of 110 patients available for study within at least 3 years＇ clinical follow-up. Among them, 63 patients underwent postoperative MRI and CT scan, as well as clini- cal evaluation. Results： After reconstruction, the knees were stable and pain-free. Mean postoperative Lysholm score was 95.54 in 110 patients after 3 years. CT and MRI assessment showed that the reconstruction centered in the femoral footprint of ACL （n=63）. The sagittal ACL angle in the reconstructed ACL （52.16°±2.45°） was much close to that in the contralat- eral intact ACL （51.31 °±2.18°, P〉0.05）. By ACL-Blumensaat line angle analysis, there was no difference between doublebundle reconstructed knees and their contralateral normal knees （4.67°±0.43° vs. 4.62°±＊0.60°, P〉0.05）. Conclusion： Anatomic double-bundle ACL reconstruction can place grafts more precisely in the anatomic foot- print of the ACL and better restore knee kinematics.
