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弹性各向同性介质一次散射波场高斯束Born正演
一次散射 高斯束 Born近似 弹性各向同性介质
2019/2/27
本文提出了一种弹性波一次散射波场的正演方法——弹性波高斯束Born正演.该方法以线性散射理论为基础，通过Born近似建立起地下散射点处不同波型的反射率同弹性波主分量波场之间的数据映射关系，利用高斯束所包含的走时、振幅和极性信息进行不同波型的局部平面波的合成，进而通过逆倾斜叠加将所合成的局部平面波转化为时空域的多分量地震记录.该方法不但保持了射线类方法高效的优点，还具备了处理多次走时波场的能力，从而...
声波介质一次散射波场高斯束Born正演
一次散射 高斯束 Born近似 声波介质
2019/2/27
Born正演是一种常用的地震波场正演模拟方法，也是线性化地震反演的理论基础.在实际应用时，Born正演通常结合常规的地震射线方法进行实现.为了克服常规地震射线方法的弊端，并且保证地震波场的模拟精度和计算效率，本文提出了一种基于高斯束的一阶散射波场Born正演方法.该方法分为两个环节：首先，我们利用高斯束的走时和振幅信息将地下散射点处的反射率映射为地表束中心位置处的局部平面波；然后，我们利用逆倾斜叠...
How Ice In Clouds Is Born（图）
Ice Clouds Born
2017/11/24
Something almost magical happens when you put a tray full of sloshing, liquid water into a freezer and it comes out later as a rigid, solid crystal of ice. Chemists at the University of Utah have pull...
Into a competitive world,guppies are born not just bigger,but more mature（图）
competitive world guppies born not just bigger more mature
2017/9/1
Throughout nature, moms engage in a trade-off: Churn out a bevy of offspring and hope for the best, or have fewer kids but invest more in their survival.Trinidadian guppies provide a model example of ...
Follow-up of a randomized trial on postdischarge nutrition in preterm-born children at age 8 y
preterm-born infants postdischarge nutrition follow-up growth body composition bone metabolic health
2018/11/15
Background: Early nutritional interventions may modulate health risks in preterm-born infants. Previously, we showed that preterm-born infants fed an isocaloric protein- and mineral-enriched postdisch...
Nonviolent civil insecurity is negatively associated with subsequent height-for-age in children aged <5 y born between 1998 and 2014 in rural areas of Africa
civil insecurity stunting Africa community and international nutrition height-for-age
2018/11/12
Background: Civil wars and wars between states have occurred less frequently since the start of the 21st century, but civil insecurity outside the contexts of official wars continues to plague many pa...
The saying ”what doesn’t kill you makes you stronger” may not hold up to scientific scrutiny. Baboons born in times of famine are more vulnerable to food shortages later in life, finds a new study.The...
Dreier Männer Arbeit in der frühen Bundesrepublik. Max Born,Werner Heisenberg und Pascual Jordan als politische Grenzgänger
Dreier Mä nner Arbeit der frühen Bundesrepublik Max Born Werner Heisenberg Pascual Jordan politische Grenzgä nger
2015/3/26
Dreier Männer Arbeit in der frühen Bundesrepublik. Max Born,Werner Heisenberg und Pascual Jordan als politische Grenzgänger.
A ‘STAR’ is born: Engineers devise genetic 'on' switch
STAR is born Engineers devise genetic switch
2015/3/4
All life processes depend on genes turning on and off. Cornell scientists have created a new “on” switch to control gene expression – a breakthrough that could revolutionize genetic engineering.Synthe...
Dynamics of the Dirac-Born-Infeld spike soliton
Oscillation the horizon transverse scalar field model system the dynamic degree of freedom
2014/12/22
We compare oscillations of a fundamental string ending on a D3-brane in two different settings: (1) a test string radially threading the horizon of an extremal black D3-brane and (2) the spike s...
Analysis of the Time Reversible Born-Oppenheimer Molecular Dynamics
Ab initio molecular dynamics self-consistent field iteration time reversibility
2014/9/26
We analyze the time reversible Born-Oppenheimer molecular dynamics
(TRBOMD) scheme, which preserves the time reversibility of the Born-Oppenheimer
molecular dynamics even with non-convergent self-co...
Washington, D.C.—New modeling studies from Carnegie’s Alan Boss demonstrate that most of the stars we see were formed when unstable clusters of newly formed protostars broke up. These protostars are b...
本文基于VTI介质拟声波方程,利用散射积分原理,在Born近似下导出了速度与各向异性参数的敏感核函数,同时结合作者前期研究提出的矩阵分解算法实现了一种新的VTI介质多参数全波形反演方法.矩阵分解算法通过对核函数-向量乘进行具有明确物理含义的向量-标量乘分解累加运算实现目标函数一阶方向或二阶方向的直接求取,从而避免了庞大核函数矩阵与Hessian矩阵的存储,该方法同时可以大大降低常规全波形反演在计算...
为了提高表层速度反演精度，本文提出了一种新的波形反演方法.该方法只利用初至波波形信息以减少波形反演对初始模型的依赖性，降低反演多解性与稳定性.由于只利用初至波波形信息，所以该方法利用高斯束计算格林函数和正演波场，以减少正演计算量.为了避免庞大核函数的存储，该方法基于Born波路径，利用矩阵分解算法实现方向与步长的累加计算.将此基于Born波路径的初至波波形反演方法应用于理论模型实验，并与声波方程全...
People born in the Middle East but residing in the Netherlands: Invariant population size estimates and the role of active and passive covariates
Population size estimation capture-Crecapture collapsbility multiple record-systems estimation missing data structural zeros
2012/11/23
Including covariates in loglinear models of population registers improves population size estimates for two reasons. First, it is possible to take heterogeneity of inclusion probabilities over the lev...