基于PBGS教学模式的地球物理学专业课程研究

依据PBGS教学的特点,针对地球物理学专业课程展开研究,对教学质量评价体系研究设计了“3+3+X”评价模式。PBGS教学模式让学生加入教师科研项目中,以教学促科研,以科研助教学,及时获得教学反馈,提高学生的创新能力与教师的积极性,从而形成良性循环,成为新的教育改革的推动力。

Studies on quasi-Newton methods in timedomain multiscale full waveform inversion

The time-domain multiscale full waveform inversion(FWI)mitigates the influence of the local minima problem in nonlinear inversion via sequential inversion using different frequency components of seismic data.The quasi-Newton methods avoid direct computation of the inverse Hessian matrix,which reduces the amount of computation and storage requirement.A combination of the two methods can improve inversion accuracy and efficiency.However,the quasi-Newton methods in time-domain multiscale FWI still cannot completely solve the problem where the inversion is trapped in local minima.We first analyze the reasons why the quasi-Newton Davidon–Fletcher–Powell and Broyden–Fletcher–Goldfarb–Shanno methods likely fall into the local minima using numerical experiments.During seismic-wave propagation,the amplitude decreases with the geometric diffusion,resulting in the concentration of the gradient of the velocity model in the shallow part,and the deep velocity cannot be corrected.Thus,the inversion falls into the local minima.To solve this problem,we introduce a virtual-source precondition to remove the influence of geometric diffusion.Thus,the model velocities in the deep and shallow parts can be simultaneously completely corrected,and the inversion can more stably converge to the global minimum.After the virtual-source precondition is implemented,the problem in which the quasi-Newton methods likely fall into the local minima is solved.However,problems remain,such as incorrect search direction after a certain number of iterations and failure of the objective function to further decrease.Therefore,we further modify the process of timedomain multiscale FWI based on virtual-source preconditioned quasi-Newton methods by resetting the inverse of the approximate Hessian matrix.Thus,the validity of the search direction of the quasi-Newton methods is guaranteed.Numerical tests show that the modified quasi-Newton methods can obtain more reasonable inversion results,and they converge faster and entail lesser computational resources than the gradient method.

面向创新能力培养的校内外实践教学平台构建——以勘查技术与工程专业为例

良好的实践教学平台是培养大学生创新能力的关键,勘查技术与工程专业作为应用型较强的专业,构建面向创新能力培养的实践教学平台更是刻不容缓。为此,本文分析了我校勘查技术与工程专业大学生创新能力培养的必要性,结合本专业特点,有机整合了校内实践环节和校外实践环节两个层次的实践教学内容,构建了本专业面向创新能力培养的校内外实践教学平台,并有效探索了平台之间相互运行机制和考核制度,共同提高地方院校大学生的实践与创新能力。