对于自由振动问题,基于单元能量投影(element energy projection, EEP)技术,对频率和模态同时进行误差控制的自适应有限元分析已建立,并被证明可靠且高效。在实际应用中,也存在另一类需求,即只需保证频率的精度,而并不关心模态误差大小...对于自由振动问题,基于单元能量投影(element energy projection, EEP)技术,对频率和模态同时进行误差控制的自适应有限元分析已建立,并被证明可靠且高效。在实际应用中,也存在另一类需求,即只需保证频率的精度,而并不关心模态误差大小。该研究提出了频率超收敛计算方案,继而建立了整体频率误差和局部模态误差的转换关系,从而在整体上以频率误差估计控制算法停机,在局部上以模态误差估计驱动网格更新,最终建立了以频率误差控制为目标的自由振动问题自适应有限元分析策略。该方法的有效性在二阶Sturm-Liouville问题及弹性薄膜自由振动问题上得到了应用验证。展开更多
By taking the urban greenland as testing objective,the GeoEye-1 fusion image as background, and using Moran’s index,the correlativity of greenland units has been measured.Then,the presampling was conducted based on t...By taking the urban greenland as testing objective,the GeoEye-1 fusion image as background, and using Moran’s index,the correlativity of greenland units has been measured.Then,the presampling was conducted based on the measured correlativity,the systematic sampling design has been carried out at the precision 95%and 85%.By using of Kriging interpolation method,the weight of different type of greenland has been divided into the stratifications.Through the stratified sampling,the estimation of greenland coverage has been obtained. The results show that the urban greenland coverage area is 14.81 km^2,accounting for 27.73%of all urban land areas.Compared with the common sampling method,the precision of that increased about 3%. This method can also be utilized in monitoring dynamic variation of urban greenland with the real time images.展开更多
文摘对于自由振动问题,基于单元能量投影(element energy projection, EEP)技术,对频率和模态同时进行误差控制的自适应有限元分析已建立,并被证明可靠且高效。在实际应用中,也存在另一类需求,即只需保证频率的精度,而并不关心模态误差大小。该研究提出了频率超收敛计算方案,继而建立了整体频率误差和局部模态误差的转换关系,从而在整体上以频率误差估计控制算法停机,在局部上以模态误差估计驱动网格更新,最终建立了以频率误差控制为目标的自由振动问题自适应有限元分析策略。该方法的有效性在二阶Sturm-Liouville问题及弹性薄膜自由振动问题上得到了应用验证。
文摘By taking the urban greenland as testing objective,the GeoEye-1 fusion image as background, and using Moran’s index,the correlativity of greenland units has been measured.Then,the presampling was conducted based on the measured correlativity,the systematic sampling design has been carried out at the precision 95%and 85%.By using of Kriging interpolation method,the weight of different type of greenland has been divided into the stratifications.Through the stratified sampling,the estimation of greenland coverage has been obtained. The results show that the urban greenland coverage area is 14.81 km^2,accounting for 27.73%of all urban land areas.Compared with the common sampling method,the precision of that increased about 3%. This method can also be utilized in monitoring dynamic variation of urban greenland with the real time images.
