Because of restriction of workspace of parallel kinematics Machine (PKM), 6 DOF PKM can’t finish machining of workpiece with complicated surfaces under only once locating. It is necessary to fit workpiece beyond twic...Because of restriction of workspace of parallel kinematics Machine (PKM), 6 DOF PKM can’t finish machining of workpiece with complicated surfaces under only once locating. It is necessary to fit workpiece beyond twice and to lead to low machining precision. Therefore the seven-axis linkage PKM is implemented by fixing a turntable on the worktable of the six-axis linkage PKM. However, the turntable angle decomposing problem from the CL file should be well considered. If the traditional decomposing methods are adopted, the nutation angle usually goes beyond the workspace of the machine. Therefore, according to the relation of the machine coordinate system and the workpiece coordinate system, the turntable angle decomposition algorithmic of the consistent coordinate system and the turntable angle decomposition algorithmic of the non-consistent coordinate system are developed to resolve the problem mentioned above. The turntable angle decomposition of the non-consistent coordinate system processes the decomposition which is based on the consistent coordinate system again. It calculates the initial angle of the locating workpiece, and the decomposed angle of the turntable at the machine coordinate system results in the nutation angle not going beyond workspace of the machine, thereby the decomposition process can be simplified.展开更多
The combination of deep wet etching and a magneto-rheological finishing （MRF） process is investigated to simultaneously improve laser damage resistance of a fused-silica surface at 355 nm. The subsequently deposited...The combination of deep wet etching and a magneto-rheological finishing （MRF） process is investigated to simultaneously improve laser damage resistance of a fused-silica surface at 355 nm. The subsequently deposited SiO2 coatings are researched to clarify the impact of substrate finishing technology on the coatings. It is revealed that a deep removal proceeding from the single side or double side had a significant impact on the laser-induced damage threshold （LIDT） of the fused silica, especially for the rear surface. After the deep etching, the MRF process that followed does not actually increase the LIDT, but it does ameliorate the surface qualities without additional LIDT degradation. The combination guarantee both the integrity of the surface＇s finish and the laser damage resistance of the fused silica and subsequent SiO2 coatings.展开更多
It is demonstrated that spectral methods can be used to improve the accuracy of numerical solutions obtained by some lower order methods.More precisely,we can use spectral methods to postprocess numerical solutions of...It is demonstrated that spectral methods can be used to improve the accuracy of numerical solutions obtained by some lower order methods.More precisely,we can use spectral methods to postprocess numerical solutions of initial value differential equations.After a few number of iterations(say 3 to 4),the errors can decrease to a few orders of magnitude less.The iteration uses the Gauss-Seidel type strategy,which gives an explicit way of postprocessing.Numerical examples for ODEs,Hamiltonian system and integral equations are provided.They all indicate that the spectral processing technique can be a very useful way in improving the accuracy of the numerical solutions.In particular,for a Hamiltonian system accuracy is only one of the issues;some other conservative properties are even more important for large time simulations.The spectral postprocessing with the coarse-mesh symplectic initial guess can not only produce high accurate approximations but can also save a significant amount of computational time over the standard symplectic schemes.展开更多
The post-processing procedure is given by a interpolant postprocessing of the finit element solution by appropriately-define finite dimensional subspaces, The corresponding superconvergence are established on general ...The post-processing procedure is given by a interpolant postprocessing of the finit element solution by appropriately-define finite dimensional subspaces, The corresponding superconvergence are established on general quasi-regular finite element partitions.展开更多
目的探讨C臂CT引导下经皮三叉神经半月节球囊压迫术治疗三叉神经痛的应用价值。方法回顾性分析采用C臂CT(Xper-CT)引导下经皮三叉神经半月节球襄压迫术治疗三叉神经痛患者40例,所有患者均进行C臂CT程序扫描,并通过X-travision工作站进...目的探讨C臂CT引导下经皮三叉神经半月节球囊压迫术治疗三叉神经痛的应用价值。方法回顾性分析采用C臂CT(Xper-CT)引导下经皮三叉神经半月节球襄压迫术治疗三叉神经痛患者40例,所有患者均进行C臂CT程序扫描,并通过X-travision工作站进行颅骨后处理重建,引导穿刺针进入卵圆孔及球囊到位,确定球囊头端位于Meckel’s腔,充盈球囊。术后记录手术剂量面积乘积(dose area product,DAP)、空气比释动能(cumulative air kerma,CAK)、曝光时间(fluo time,FT),分析辐射剂量。结果40例患者均通过C臂CT后处理重建技术引导卵圆孔穿刺成功(其中小卵圆孔2例);40例患者中通过C臂CT后处理重建技术确定球囊一次性到位并获得满意梨形21例(52%),通过C臂CT后处理重建技术分析后多次调整球囊位置及方向,使球囊头端位于岩骨切迹,并获得满意梨形12例(30%),7例(18%)患者未获得满意梨形。术后40例患者疼痛完全消失17例(42%),疼痛满意缓解21例(53%);疼痛缓解不满意2例(5%);总有效率95%。术后伴面部麻木26例(65%),咀嚼肌无力9例(23%)。40例患者DAP、CAK、FT分别为(79.39±23.15)Gycm^(2)、(245.07±84.04)mGy、(5.20±1.30)min。结论C臂CT引导下经皮三叉神经半月节球囊压迫术直观准确显示穿刺针、卵圆孔、球囊、岩骨脊的三维结构及其相互位置关系,尤其对解剖变异或异常增生的显示更具优势。展开更多
文摘Because of restriction of workspace of parallel kinematics Machine (PKM), 6 DOF PKM can’t finish machining of workpiece with complicated surfaces under only once locating. It is necessary to fit workpiece beyond twice and to lead to low machining precision. Therefore the seven-axis linkage PKM is implemented by fixing a turntable on the worktable of the six-axis linkage PKM. However, the turntable angle decomposing problem from the CL file should be well considered. If the traditional decomposing methods are adopted, the nutation angle usually goes beyond the workspace of the machine. Therefore, according to the relation of the machine coordinate system and the workpiece coordinate system, the turntable angle decomposition algorithmic of the consistent coordinate system and the turntable angle decomposition algorithmic of the non-consistent coordinate system are developed to resolve the problem mentioned above. The turntable angle decomposition of the non-consistent coordinate system processes the decomposition which is based on the consistent coordinate system again. It calculates the initial angle of the locating workpiece, and the decomposed angle of the turntable at the machine coordinate system results in the nutation angle not going beyond workspace of the machine, thereby the decomposition process can be simplified.
基金supported by the National Natural Science Foundation of China under Grant Nos.11104293 and 61308021
文摘The combination of deep wet etching and a magneto-rheological finishing （MRF） process is investigated to simultaneously improve laser damage resistance of a fused-silica surface at 355 nm. The subsequently deposited SiO2 coatings are researched to clarify the impact of substrate finishing technology on the coatings. It is revealed that a deep removal proceeding from the single side or double side had a significant impact on the laser-induced damage threshold （LIDT） of the fused silica, especially for the rear surface. After the deep etching, the MRF process that followed does not actually increase the LIDT, but it does ameliorate the surface qualities without additional LIDT degradation. The combination guarantee both the integrity of the surface＇s finish and the laser damage resistance of the fused silica and subsequent SiO2 coatings.
基金The research of the first author was supported by Hong Kong Baptist University,the Research Grants Council of Hong Kong.
文摘It is demonstrated that spectral methods can be used to improve the accuracy of numerical solutions obtained by some lower order methods.More precisely,we can use spectral methods to postprocess numerical solutions of initial value differential equations.After a few number of iterations(say 3 to 4),the errors can decrease to a few orders of magnitude less.The iteration uses the Gauss-Seidel type strategy,which gives an explicit way of postprocessing.Numerical examples for ODEs,Hamiltonian system and integral equations are provided.They all indicate that the spectral processing technique can be a very useful way in improving the accuracy of the numerical solutions.In particular,for a Hamiltonian system accuracy is only one of the issues;some other conservative properties are even more important for large time simulations.The spectral postprocessing with the coarse-mesh symplectic initial guess can not only produce high accurate approximations but can also save a significant amount of computational time over the standard symplectic schemes.
基金the Foundation of Natonal Natural Science of China and the Foundation of Aducation of Hunan Province.
文摘The post-processing procedure is given by a interpolant postprocessing of the finit element solution by appropriately-define finite dimensional subspaces, The corresponding superconvergence are established on general quasi-regular finite element partitions.
文摘目的探讨C臂CT引导下经皮三叉神经半月节球囊压迫术治疗三叉神经痛的应用价值。方法回顾性分析采用C臂CT(Xper-CT)引导下经皮三叉神经半月节球襄压迫术治疗三叉神经痛患者40例,所有患者均进行C臂CT程序扫描,并通过X-travision工作站进行颅骨后处理重建,引导穿刺针进入卵圆孔及球囊到位,确定球囊头端位于Meckel’s腔,充盈球囊。术后记录手术剂量面积乘积(dose area product,DAP)、空气比释动能(cumulative air kerma,CAK)、曝光时间(fluo time,FT),分析辐射剂量。结果40例患者均通过C臂CT后处理重建技术引导卵圆孔穿刺成功(其中小卵圆孔2例);40例患者中通过C臂CT后处理重建技术确定球囊一次性到位并获得满意梨形21例(52%),通过C臂CT后处理重建技术分析后多次调整球囊位置及方向,使球囊头端位于岩骨切迹,并获得满意梨形12例(30%),7例(18%)患者未获得满意梨形。术后40例患者疼痛完全消失17例(42%),疼痛满意缓解21例(53%);疼痛缓解不满意2例(5%);总有效率95%。术后伴面部麻木26例(65%),咀嚼肌无力9例(23%)。40例患者DAP、CAK、FT分别为(79.39±23.15)Gycm^(2)、(245.07±84.04)mGy、(5.20±1.30)min。结论C臂CT引导下经皮三叉神经半月节球囊压迫术直观准确显示穿刺针、卵圆孔、球囊、岩骨脊的三维结构及其相互位置关系,尤其对解剖变异或异常增生的显示更具优势。
