We use the first arrival traveltime to correct the phase distortion in a nonlinear wave equation inversion scheme.This improves the precision of tomographic reconstruction of a velocity structure with large variations...We use the first arrival traveltime to correct the phase distortion in a nonlinear wave equation inversion scheme.This improves the precision of tomographic reconstruction of a velocity structure with large variations and helps solve the ill-posed problem of wave equation inversion.When the variation of the velocity distribution is large,general non-linear wave equation inversions are very ill-posed and for such strong nonlinear we can not obtain a correct inversion.One of main reasons is that the calculated and observed phase of the wavefield differs greatly if the initial model is far from the true model.This leads to highly mismatched phase between the calculated and the observed wave field.This is so-called"Cycle Skipping"problem in the full waveform inversion.The phase mismatch is even more pronounced if a high operating frequency is employed in order to increase resolution.To address this problem,we use the first arrival to"demodulate"the wave field in the frequency domain with a goal of restoring the phase of wave field.Then we minimize an objective function consisting of so called"demodulated"wave field to solve wave equation inversion problem.In this way,we find that the inversion is much improved,and when the velocity perturbation in a complicated model reaches 35%,we can still obtain a good inversion.A computer simulation shows that our method is very robust for acoustical wave inversion with good reconstruction precision.展开更多
目的:通过价值链成本控制理论(CVT)开发护理服务项目定价模型,并验证其科学性和合理性。方法:通过对现有定价模型中与护理服务相关的价值链进行全面审查和分析,并实施新的技术难度和风险程度调整算法,开发基于地区平均工资的CVT定价模型...目的:通过价值链成本控制理论(CVT)开发护理服务项目定价模型,并验证其科学性和合理性。方法:通过对现有定价模型中与护理服务相关的价值链进行全面审查和分析,并实施新的技术难度和风险程度调整算法,开发基于地区平均工资的CVT定价模型,以实现成本控制。使用基于护理干预分类(NIC)框架的定价方法作为基准,将CVT模型和文献报道的模型包括仲原模型(ZY)、李利模型(LL)和蒋帅模型(JS)进行一致性和优越性比较。结果:与NIC定价比较,CVT模型与仲原模型&李利模型、蒋帅模型定价比较差异均无统计学意义(P>0.05);但Bland-Altman一致性检验显示,以NIC定价为参考,仲原模型、李利模型、蒋帅模型3个模型的定价偏差分别呈现出负或正的增长趋势(P<0.05)。Mountain图显示,蒋帅模型定价通常表现出高估,只有当成本被高估时,仲原模型&李利模型的定价才比CVT模型定价更激进。经Passing and Bablok回归分析证实,仅在蒋帅模型定价中存在比例差异(95%CI_(slope)为1.290~1.691)和系统差异(95%CI_(intercept)为-14.247~-4.289)。此外,CVT定价的随机差异较小。结论:CVT模型为护理服务项目提供了一种科学、合理、高效的定价方法,可能与CVT模型设计对技术难度和风险程度进行了调整有关。展开更多
基金supported by the Seismic Tomography Project of Stanford University,a research consortium sponsored by companies of the oil and gas industry
文摘We use the first arrival traveltime to correct the phase distortion in a nonlinear wave equation inversion scheme.This improves the precision of tomographic reconstruction of a velocity structure with large variations and helps solve the ill-posed problem of wave equation inversion.When the variation of the velocity distribution is large,general non-linear wave equation inversions are very ill-posed and for such strong nonlinear we can not obtain a correct inversion.One of main reasons is that the calculated and observed phase of the wavefield differs greatly if the initial model is far from the true model.This leads to highly mismatched phase between the calculated and the observed wave field.This is so-called"Cycle Skipping"problem in the full waveform inversion.The phase mismatch is even more pronounced if a high operating frequency is employed in order to increase resolution.To address this problem,we use the first arrival to"demodulate"the wave field in the frequency domain with a goal of restoring the phase of wave field.Then we minimize an objective function consisting of so called"demodulated"wave field to solve wave equation inversion problem.In this way,we find that the inversion is much improved,and when the velocity perturbation in a complicated model reaches 35%,we can still obtain a good inversion.A computer simulation shows that our method is very robust for acoustical wave inversion with good reconstruction precision.
文摘目的:通过价值链成本控制理论(CVT)开发护理服务项目定价模型,并验证其科学性和合理性。方法:通过对现有定价模型中与护理服务相关的价值链进行全面审查和分析,并实施新的技术难度和风险程度调整算法,开发基于地区平均工资的CVT定价模型,以实现成本控制。使用基于护理干预分类(NIC)框架的定价方法作为基准,将CVT模型和文献报道的模型包括仲原模型(ZY)、李利模型(LL)和蒋帅模型(JS)进行一致性和优越性比较。结果:与NIC定价比较,CVT模型与仲原模型&李利模型、蒋帅模型定价比较差异均无统计学意义(P>0.05);但Bland-Altman一致性检验显示,以NIC定价为参考,仲原模型、李利模型、蒋帅模型3个模型的定价偏差分别呈现出负或正的增长趋势(P<0.05)。Mountain图显示,蒋帅模型定价通常表现出高估,只有当成本被高估时,仲原模型&李利模型的定价才比CVT模型定价更激进。经Passing and Bablok回归分析证实,仅在蒋帅模型定价中存在比例差异(95%CI_(slope)为1.290~1.691)和系统差异(95%CI_(intercept)为-14.247~-4.289)。此外,CVT定价的随机差异较小。结论:CVT模型为护理服务项目提供了一种科学、合理、高效的定价方法,可能与CVT模型设计对技术难度和风险程度进行了调整有关。
