The first through ninth radial derivatives of a harmonic function and gravity anomaly are derived in this paper. These derivatives can be used in the analytical continuation application. For the downward continuation ...The first through ninth radial derivatives of a harmonic function and gravity anomaly are derived in this paper. These derivatives can be used in the analytical continuation application. For the downward continuation of gravity anomaly, the Taylor series approach developed in the paper is equivalent theoretically to but more efficient and storage-saving computationally than the well-known gradient operator approach. Numerical simulation shows that Taylor series expansion constructed by the derived formulas for the radial derivatives of gravity disturbance is still convergent for height up to 4 km.展开更多
为提高电力系统暂态稳定分析效率,本文提出了多维阶数控制的多步Taylor级数暂态稳定快速计算方法。该方法基于多步Taylor级数展开理论,针对不同时间常数的机组及不同积分时刻的机组转角状态量,根据时域仿真计算精度建立了转角状态量的...为提高电力系统暂态稳定分析效率,本文提出了多维阶数控制的多步Taylor级数暂态稳定快速计算方法。该方法基于多步Taylor级数展开理论,针对不同时间常数的机组及不同积分时刻的机组转角状态量,根据时域仿真计算精度建立了转角状态量的高阶导数阶数差异化控制策略,并从理论上分析了忽略部分高阶导数对转角轨迹的影响。所提方法可实现状态变量时间和空间上的动态多维导数阶数控制,消除常规Taylor级数法暂态稳定分析的计算冗余。New England 10机39节点算例仿真验证了所提方法可灵活方便地实现Taylor级数法的时空多维阶数控制,能有效提高暂态稳定分析效率。展开更多
The conventional gravity gradient method to plot the geologic body location is fuzzy. When the depth is large and the geologic body is small, the Vzz and Vzx derivative errors are also large. We describe that using th...The conventional gravity gradient method to plot the geologic body location is fuzzy. When the depth is large and the geologic body is small, the Vzz and Vzx derivative errors are also large. We describe that using the status distinguishing factor to optimally determine the comer location is more accurate than the conventional higher-order derivative method. Thus, a better small geologic body and fault resolution is obtained by using the gravity gradient method and trial theoretical model calculation. The actual data is better processed, providing a better basis for prospecting and determination of subsurface geologic structure.展开更多
目的 :验证从MRI灰度图像及其高阶偏导图像中提取的三维纹理特征,表征出膀胱肿瘤和壁组织之间的纹理差异,从而实现对膀胱肿瘤与壁组织的鉴别。方法:从62名临床确诊的膀胱癌患者的T2加权MRI数据中提取出感兴趣区容积(volume of interest,...目的 :验证从MRI灰度图像及其高阶偏导图像中提取的三维纹理特征,表征出膀胱肿瘤和壁组织之间的纹理差异,从而实现对膀胱肿瘤与壁组织的鉴别。方法:从62名临床确诊的膀胱癌患者的T2加权MRI数据中提取出感兴趣区容积(volume of interest,VOI)的62例癌和62壁体积。从每个VOI中计算出三维高阶偏导映射(梯度和曲度图),然后从每个VOI提取基于灰度及其高阶偏导图的三维Haralick特征及基于灰度图的Tamura特征,以更好地反映肿瘤组织的异质性分布。结果:每个VOI共提取出58个纹理特征,其中37个特征显示出显著的组内差异(P≤0.01)。结论:从灰度及其高阶偏导图像提取的三维纹理特征可以更好地反映癌组织的异质分布。展开更多
文摘The first through ninth radial derivatives of a harmonic function and gravity anomaly are derived in this paper. These derivatives can be used in the analytical continuation application. For the downward continuation of gravity anomaly, the Taylor series approach developed in the paper is equivalent theoretically to but more efficient and storage-saving computationally than the well-known gradient operator approach. Numerical simulation shows that Taylor series expansion constructed by the derived formulas for the radial derivatives of gravity disturbance is still convergent for height up to 4 km.
文摘为提高电力系统暂态稳定分析效率,本文提出了多维阶数控制的多步Taylor级数暂态稳定快速计算方法。该方法基于多步Taylor级数展开理论,针对不同时间常数的机组及不同积分时刻的机组转角状态量,根据时域仿真计算精度建立了转角状态量的高阶导数阶数差异化控制策略,并从理论上分析了忽略部分高阶导数对转角轨迹的影响。所提方法可实现状态变量时间和空间上的动态多维导数阶数控制,消除常规Taylor级数法暂态稳定分析的计算冗余。New England 10机39节点算例仿真验证了所提方法可灵活方便地实现Taylor级数法的时空多维阶数控制,能有效提高暂态稳定分析效率。
基金support by the "Eleventh Five-Year" National Science and Technology Support Program (No. 2006BAB01A02)the Pivot Program of the National Natural Science Fund (No. 40930314)
文摘The conventional gravity gradient method to plot the geologic body location is fuzzy. When the depth is large and the geologic body is small, the Vzz and Vzx derivative errors are also large. We describe that using the status distinguishing factor to optimally determine the comer location is more accurate than the conventional higher-order derivative method. Thus, a better small geologic body and fault resolution is obtained by using the gravity gradient method and trial theoretical model calculation. The actual data is better processed, providing a better basis for prospecting and determination of subsurface geologic structure.
文摘目的 :验证从MRI灰度图像及其高阶偏导图像中提取的三维纹理特征,表征出膀胱肿瘤和壁组织之间的纹理差异,从而实现对膀胱肿瘤与壁组织的鉴别。方法:从62名临床确诊的膀胱癌患者的T2加权MRI数据中提取出感兴趣区容积(volume of interest,VOI)的62例癌和62壁体积。从每个VOI中计算出三维高阶偏导映射(梯度和曲度图),然后从每个VOI提取基于灰度及其高阶偏导图的三维Haralick特征及基于灰度图的Tamura特征,以更好地反映肿瘤组织的异质性分布。结果:每个VOI共提取出58个纹理特征,其中37个特征显示出显著的组内差异(P≤0.01)。结论:从灰度及其高阶偏导图像提取的三维纹理特征可以更好地反映癌组织的异质分布。
