In one step inverse finite element approach, an initial blank shape is normally predicted from the final deformed shape. The final deformed shape needs to be trimmed into a final part after stamping, the trimmed area,...In one step inverse finite element approach, an initial blank shape is normally predicted from the final deformed shape. The final deformed shape needs to be trimmed into a final part after stamping, the trimmed area, therefore, needs to be compensated manually before using one step inverse approach, which causes low efficiency and in consistency with the real situation. To solve this problem, one step positive approach is proposed to simulate the sheet metal stamping process. Firstly the spatial initial solution of one step positive method is preliminarily obtained by using the mapping relationship and area coordinates, then based on the deformation theory the iterative solving is carried out in three-dimensional coordinate system by using quasi-conjugate-gradient method. During iterative process the contact judgment method is introduced to ensure that the nodes on the spatial initial solution are not separated from die surface. The predicted results of sheet metal forming process that include the shape and thickness of the stamped part can be obtained after the iterative solving process. The validity of the proposed approach is verified by comparing the predicted results obtained through the proposed approach with those obtained through the module of one step inverse approach in Autoform and the real stamped part. In one step positive method, the stamped shape of regular sheet can be calculated fast and effectively. During the iterative solution, the quasi-conjugate-gradient method is proposed to take the place of solving system of equations, and it can improve the stability and precision of the algorithm.展开更多
We have derived and tested several relations between geoid （N） and quasi-geoid （~） with model validation. The elevation correction consists of the first-term （Bouguer anomaly） and second-term （vertical gradient...We have derived and tested several relations between geoid （N） and quasi-geoid （~） with model validation. The elevation correction consists of the first-term （Bouguer anomaly） and second-term （vertical gradient of gravity anomaly）. The vertical gradient was obtained from direct measurement and terrain calcula- tion. The test results demonstrated that the precision of geoid can reach centimeter-level in mountains less than 5000 meters high.展开更多
The main purpose of this paper is to provide a restarting direction for improving on the standard conjugate gradient method.If a drastic non-quadratic behaviour of the objective function is observed in the neighbour o...The main purpose of this paper is to provide a restarting direction for improving on the standard conjugate gradient method.If a drastic non-quadratic behaviour of the objective function is observed in the neighbour of xk,then a restart should be done.The scaling symmetric rank-one update with Davidon’s optimal criterion is applied to generate the restarting direction.It is proved that the conjugate gradient method with this strategy retains the quadratic termination.Numerical experiments show that it is successful.展开更多
Embelia ribes Burm f., also known as Vidanga or Baibidanga, belonging to the family of Myrsinaceae, is an important but vulnerable medicinal woody climber. Recent survey and observations of E. ribes in different aspec...Embelia ribes Burm f., also known as Vidanga or Baibidanga, belonging to the family of Myrsinaceae, is an important but vulnerable medicinal woody climber. Recent survey and observations of E. ribes in different aspects like distribution, population structure, growth habit, climate, natural regeneration and seedling ecology in Karnataka have been thoroughly discussed. This is the first report on artificial regeneration through seeds of diverse origins in ex-situ and in situ conditions and field planting of them in its natural environment. Field planting of in vitro and nursery raised seedlings showed better field performance in terms of survival and growth in its natural growing areas only. Current studies and observations have shown that this species has low ecological gradient and is a “habitat specialist”. E. ribes being a threatened species with small populations coupled with low ecological gradient and virtually no natural regeneration, a modified approach of quasi in situ conservation where in in-situ raising of seedlings of diverse origin with an aim to enrich the diversity of existing population was attempted with considerable success.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 51075187)
文摘In one step inverse finite element approach, an initial blank shape is normally predicted from the final deformed shape. The final deformed shape needs to be trimmed into a final part after stamping, the trimmed area, therefore, needs to be compensated manually before using one step inverse approach, which causes low efficiency and in consistency with the real situation. To solve this problem, one step positive approach is proposed to simulate the sheet metal stamping process. Firstly the spatial initial solution of one step positive method is preliminarily obtained by using the mapping relationship and area coordinates, then based on the deformation theory the iterative solving is carried out in three-dimensional coordinate system by using quasi-conjugate-gradient method. During iterative process the contact judgment method is introduced to ensure that the nodes on the spatial initial solution are not separated from die surface. The predicted results of sheet metal forming process that include the shape and thickness of the stamped part can be obtained after the iterative solving process. The validity of the proposed approach is verified by comparing the predicted results obtained through the proposed approach with those obtained through the module of one step inverse approach in Autoform and the real stamped part. In one step positive method, the stamped shape of regular sheet can be calculated fast and effectively. During the iterative solution, the quasi-conjugate-gradient method is proposed to take the place of solving system of equations, and it can improve the stability and precision of the algorithm.
文摘We have derived and tested several relations between geoid （N） and quasi-geoid （~） with model validation. The elevation correction consists of the first-term （Bouguer anomaly） and second-term （vertical gradient of gravity anomaly）. The vertical gradient was obtained from direct measurement and terrain calcula- tion. The test results demonstrated that the precision of geoid can reach centimeter-level in mountains less than 5000 meters high.
基金The Project Supported by National Natural Foundation of China
文摘The main purpose of this paper is to provide a restarting direction for improving on the standard conjugate gradient method.If a drastic non-quadratic behaviour of the objective function is observed in the neighbour of xk,then a restart should be done.The scaling symmetric rank-one update with Davidon’s optimal criterion is applied to generate the restarting direction.It is proved that the conjugate gradient method with this strategy retains the quadratic termination.Numerical experiments show that it is successful.
文摘Embelia ribes Burm f., also known as Vidanga or Baibidanga, belonging to the family of Myrsinaceae, is an important but vulnerable medicinal woody climber. Recent survey and observations of E. ribes in different aspects like distribution, population structure, growth habit, climate, natural regeneration and seedling ecology in Karnataka have been thoroughly discussed. This is the first report on artificial regeneration through seeds of diverse origins in ex-situ and in situ conditions and field planting of them in its natural environment. Field planting of in vitro and nursery raised seedlings showed better field performance in terms of survival and growth in its natural growing areas only. Current studies and observations have shown that this species has low ecological gradient and is a “habitat specialist”. E. ribes being a threatened species with small populations coupled with low ecological gradient and virtually no natural regeneration, a modified approach of quasi in situ conservation where in in-situ raising of seedlings of diverse origin with an aim to enrich the diversity of existing population was attempted with considerable success.
