A flexible and adaptable design method for the tooth crown is presented based on the direct manipulation of free-form deformation （FFD）. The correct shape of the tooth crown can be obtained by adding, modifying, and...A flexible and adaptable design method for the tooth crown is presented based on the direct manipulation of free-form deformation （FFD）. The correct shape of the tooth crown can be obtained by adding, modifying, and deleting constraint points or load points based on stretching and compressing operation. Finally, an example is given to illustrate the method to be efficient.展开更多
Based on the Latin square design of statistics, the thickness of first boundary layer, the turbulence model and the cell number were taken as the three main factors of uncertainty in CFD （computational fluid dynamics...Based on the Latin square design of statistics, the thickness of first boundary layer, the turbulence model and the cell number were taken as the three main factors of uncertainty in CFD （computational fluid dynamics）. Total resistance of hull was calculated and the flow field around the hull was simulated by CFD method. Then, the influence of uncertainty factors on the hull resistance was discussed by regression analysis with trimmed mesh and overset mesh. Through a series of calculation and analysis, the optimal calculation method was put forward, and the relevant parameters of the calculation were determined. Thirdly, the total resistance of different speed was calculated by using these two kinds of grids, which were in good agreement with the experimental results. Finally, according to the ITTC recommended procedures, uncertainty analysis in CFD was carried out with the numerical results of the total resistance by three sets of grids with uniform refinement ratio rG = √2. Then the modified resistance was compared with the experimental result, which improved the accuracy of the resistance prediction.展开更多
Studying the interaction of components is basic for a railroad project, which is also very important for creating maintenance procedures based on predictions from a model that assumes adequate performance. To determin...Studying the interaction of components is basic for a railroad project, which is also very important for creating maintenance procedures based on predictions from a model that assumes adequate performance. To determine these interactions, which can have a great number of combinations, the use of a computational model is of vital importance, in this case, the program FERROVIA 1.0 （RAILROAD 1.0） was used. A critical study developed the program FERROVIA 1.0, and its variables were characterized based on values observed in the literature. After initial characterization was carried out, a comparative study was performed on the sensitivity between these variables and the indications of significant behavior for a railway deformed by the known load of a wheel. A statistical program was used to correlate the elements. The intention was to launch the program FERROVIA 1.0 and later use it for 2,187 combinations. The data used in these correlations corresponded to the normal values for the elements used in railroad engineering practice. Our main goal is to understand the behavior of the track vertical deflection according to the variation of the scaling of the various elements of the railway,展开更多
Objective： To study whether the range of knee flexion （ROF） is affected by geometrical mismatch of the femoral component and the resultant change in the pos- terior condylar offset （PCO） after high-flexion poster...Objective： To study whether the range of knee flexion （ROF） is affected by geometrical mismatch of the femoral component and the resultant change in the pos- terior condylar offset （PCO） after high-flexion posterior-sta- bilized total knee arthroplasty （TKA）. Methods： One hundred osteoarthritic patients （50 males and 50 females） underwent femoral osteotomy by the ante- rior referencing technique. The PCO for each patient was measured from lateral radiographs before, during and 2 years after TKA. The thickness of the joint cartilage was mea- sured by magnetic resonance imaging before TKA and added onto the radiographic measurement. The relationship between changes in the PCO and improvements in the ROF before, during and 2 years after TKA were statistically analyzed. Results： Compared with the preoperative value, the PCO was reduced by （3.45±3.28） mm after TKA, with a significantly larger reduction observed in female patients than male patients （P〈0.05）. When examining the subject popu- lation as a whole, there was a significant positive correla- tion between PCO and ROF improvement during TKA （P〈 0.05）, but this improvement was not maintained 2 years after TKA （P〉0.05）. However, when male and female patients were analyzed separately, there was a significant positive correlation between PCO change and ROF improvement for both sexes at both time points （all P〈0.05）. Conclusions： Restoration of PCO plays an important role in the optimization of knee flexion even after posteriorstabilized TKA. Femoral components based on Caucasian anatomic characteristics could not match the native anatomy of distal femurs in Chinese population especially female Chinese. Rotated resection of distal femur with anterior referencing technique usually leads to a decreased PCO and therefore reduces maximal obtainable flexion.展开更多
文摘A flexible and adaptable design method for the tooth crown is presented based on the direct manipulation of free-form deformation （FFD）. The correct shape of the tooth crown can be obtained by adding, modifying, and deleting constraint points or load points based on stretching and compressing operation. Finally, an example is given to illustrate the method to be efficient.
文摘Based on the Latin square design of statistics, the thickness of first boundary layer, the turbulence model and the cell number were taken as the three main factors of uncertainty in CFD （computational fluid dynamics）. Total resistance of hull was calculated and the flow field around the hull was simulated by CFD method. Then, the influence of uncertainty factors on the hull resistance was discussed by regression analysis with trimmed mesh and overset mesh. Through a series of calculation and analysis, the optimal calculation method was put forward, and the relevant parameters of the calculation were determined. Thirdly, the total resistance of different speed was calculated by using these two kinds of grids, which were in good agreement with the experimental results. Finally, according to the ITTC recommended procedures, uncertainty analysis in CFD was carried out with the numerical results of the total resistance by three sets of grids with uniform refinement ratio rG = √2. Then the modified resistance was compared with the experimental result, which improved the accuracy of the resistance prediction.
文摘Studying the interaction of components is basic for a railroad project, which is also very important for creating maintenance procedures based on predictions from a model that assumes adequate performance. To determine these interactions, which can have a great number of combinations, the use of a computational model is of vital importance, in this case, the program FERROVIA 1.0 （RAILROAD 1.0） was used. A critical study developed the program FERROVIA 1.0, and its variables were characterized based on values observed in the literature. After initial characterization was carried out, a comparative study was performed on the sensitivity between these variables and the indications of significant behavior for a railway deformed by the known load of a wheel. A statistical program was used to correlate the elements. The intention was to launch the program FERROVIA 1.0 and later use it for 2,187 combinations. The data used in these correlations corresponded to the normal values for the elements used in railroad engineering practice. Our main goal is to understand the behavior of the track vertical deflection according to the variation of the scaling of the various elements of the railway,
文摘Objective： To study whether the range of knee flexion （ROF） is affected by geometrical mismatch of the femoral component and the resultant change in the pos- terior condylar offset （PCO） after high-flexion posterior-sta- bilized total knee arthroplasty （TKA）. Methods： One hundred osteoarthritic patients （50 males and 50 females） underwent femoral osteotomy by the ante- rior referencing technique. The PCO for each patient was measured from lateral radiographs before, during and 2 years after TKA. The thickness of the joint cartilage was mea- sured by magnetic resonance imaging before TKA and added onto the radiographic measurement. The relationship between changes in the PCO and improvements in the ROF before, during and 2 years after TKA were statistically analyzed. Results： Compared with the preoperative value, the PCO was reduced by （3.45±3.28） mm after TKA, with a significantly larger reduction observed in female patients than male patients （P〈0.05）. When examining the subject popu- lation as a whole, there was a significant positive correla- tion between PCO and ROF improvement during TKA （P〈 0.05）, but this improvement was not maintained 2 years after TKA （P〉0.05）. However, when male and female patients were analyzed separately, there was a significant positive correlation between PCO change and ROF improvement for both sexes at both time points （all P〈0.05）. Conclusions： Restoration of PCO plays an important role in the optimization of knee flexion even after posteriorstabilized TKA. Femoral components based on Caucasian anatomic characteristics could not match the native anatomy of distal femurs in Chinese population especially female Chinese. Rotated resection of distal femur with anterior referencing technique usually leads to a decreased PCO and therefore reduces maximal obtainable flexion.
