In large loop transient electromagnetic method(TEM),the late time apparent resistivity formula cannot truly reflect the geoelectric model,thus it needs to define the all-time apparent resistivity with the position inf...In large loop transient electromagnetic method(TEM),the late time apparent resistivity formula cannot truly reflect the geoelectric model,thus it needs to define the all-time apparent resistivity with the position information of measuring point.Utilizing very fast simulated annealing(VFSA) to fit the theoretical electromagnetic force(EMF) and measured EMF could obtain the all-time apparent resistivity of the measuring points in rectangular transmitting loop.The selective cope of initial model of VFSA could be confirmed by taking the late time apparent resistivity of transient electromagnetic method as the prior information.For verifying the correctness,the all-time apparent resistivities of the geoelectric models were calculated by VFSA and dichotomy,respectively.The results indicate that the relative differences of apparent resistivities calculated by these two methods are within 3%.The change of measuring point position has little influence on the tracing pattern of all-time apparent resistivity.The first branch of the curve of all-time apparent resistivity is close to the resistivity of the first layer medium and the last branch is close to the resistivity of the last layer medium,which proves the correctness of the arithmetics proposed.展开更多
A convenient numerical calculation method (inverse spline interpolation) for all-time apparent resistivity intransient electromagnetic method (TEM) is proposed in this paper. Characteristic of early and late normalize...A convenient numerical calculation method (inverse spline interpolation) for all-time apparent resistivity intransient electromagnetic method (TEM) is proposed in this paper. Characteristic of early and late normalized inductiveelectromotive force was investigated. According to the turning point, the transient process is divided into the earlyphase, the turning point, and the late phase. Afterwards, apparent resistivity is obtained through inverse spline interpo-lation in the early and the late phases, respectively. Finally, the resistivities of the early-time and the late-time wereconnected together by the turning point. The result shows that the inverse spline method is feasible and the method alsolays a foundation for initial model construction in the TEM automatic inversion.展开更多
简要介绍变系数模型,并以变系数Cox模型为例,通过实际数据分析展示其在医学和公共卫生领域的应用,为相关研究提供方法学参考。实例基于某疾病预防控制中心部分慢病管理数据,拟合变系数Cox模型,探索高血压人群中体重指数(body mass index...简要介绍变系数模型,并以变系数Cox模型为例,通过实际数据分析展示其在医学和公共卫生领域的应用,为相关研究提供方法学参考。实例基于某疾病预防控制中心部分慢病管理数据,拟合变系数Cox模型,探索高血压人群中体重指数(body mass index,BMI)与死亡风险之间的时变关联。结果显示,体重过低(BMI<18.5 kg/m^(2))与较高的死亡风险相关,但其关联程度随着随访时间的延长而逐渐减弱;超重(23 kg/m^(2)≤BMI<25 kg/m^(2))与较低的死亡风险相关,其关联程度随着随访时间的延长而逐渐减弱。变系数模型能够捕捉到暴露因素对于结局的影响如何随着其他变量的改变而变化,有助于更为全面地理解变量间的复杂关系,在医学和公共卫生研究中有很好的应用和推广价值。展开更多
挖掘时间序列中的全链集是一个新兴领域。据了解,当前并无多尺度最近时间序列的全链集挖掘算法存在。对多尺度最近时间序列下全序链集的挖掘问题进行研究,在现有LRSTOMP和ALLC算法的基础上提出了一种具有增量计算特性的挖掘算法MTSC(Min...挖掘时间序列中的全链集是一个新兴领域。据了解,当前并无多尺度最近时间序列的全链集挖掘算法存在。对多尺度最近时间序列下全序链集的挖掘问题进行研究,在现有LRSTOMP和ALLC算法的基础上提出了一种具有增量计算特性的挖掘算法MTSC(Mining Time Series All-Chain Sets over Multi-scale Nearest Time Series,MTSC)。该算法依次使用LRSTOMP与ALLC算法对第一个最近时间序列成员内容进行处理,得到该成员上的全序链集挖掘结果,同时保留该成员相关的PL和PR结构。从第二个最近时间序列成员开始,MTSC算法中的LRSTOMP过程只需要处理当前最近时间序列成员相对于前一个最近时间序列成员的新增部分,进一步结合前一个最近时间序列成员上的PL和PR,可以增量获得当前最近时间序列成员上的PL和PR结构,在此基础上使用ALLC算法得到该成员上的全序链集挖掘结果。相较于对每一个最近时间序列成员内容都使用LRSTOMP和ALLC算法处理的Naive方式,MTSC算法利用增量计算的思想,避免了对全部数据进行重复性计算,从而加快了算法的执行速度,具有更高的时间效率。基于公有数据样本Penguin和TiltABP的仿真实验验证了该算法的有效性,实验结果表明其性能与Naive算法完全一致,且对于以上数据样本,在空间开销增加1.1%~9.7%的情况下,可以实现时间效率80%~88.3%的提升。展开更多
基金Projects(40804027,41074085) supported by the National Natural Science Foundation of ChinaProject(09JJ3048) supported by the Natural Science Foundation of Hunan Province,ChinaProject(200805331082) supported by the Research Fund for the Doctoral Program of Higher Education,China
文摘In large loop transient electromagnetic method(TEM),the late time apparent resistivity formula cannot truly reflect the geoelectric model,thus it needs to define the all-time apparent resistivity with the position information of measuring point.Utilizing very fast simulated annealing(VFSA) to fit the theoretical electromagnetic force(EMF) and measured EMF could obtain the all-time apparent resistivity of the measuring points in rectangular transmitting loop.The selective cope of initial model of VFSA could be confirmed by taking the late time apparent resistivity of transient electromagnetic method as the prior information.For verifying the correctness,the all-time apparent resistivities of the geoelectric models were calculated by VFSA and dichotomy,respectively.The results indicate that the relative differences of apparent resistivities calculated by these two methods are within 3%.The change of measuring point position has little influence on the tracing pattern of all-time apparent resistivity.The first branch of the curve of all-time apparent resistivity is close to the resistivity of the first layer medium and the last branch is close to the resistivity of the last layer medium,which proves the correctness of the arithmetics proposed.
基金Project 40344022 supported by National Natural Science Foundation of China
文摘A convenient numerical calculation method (inverse spline interpolation) for all-time apparent resistivity intransient electromagnetic method (TEM) is proposed in this paper. Characteristic of early and late normalized inductiveelectromotive force was investigated. According to the turning point, the transient process is divided into the earlyphase, the turning point, and the late phase. Afterwards, apparent resistivity is obtained through inverse spline interpo-lation in the early and the late phases, respectively. Finally, the resistivities of the early-time and the late-time wereconnected together by the turning point. The result shows that the inverse spline method is feasible and the method alsolays a foundation for initial model construction in the TEM automatic inversion.
文摘挖掘时间序列中的全链集是一个新兴领域。据了解,当前并无多尺度最近时间序列的全链集挖掘算法存在。对多尺度最近时间序列下全序链集的挖掘问题进行研究,在现有LRSTOMP和ALLC算法的基础上提出了一种具有增量计算特性的挖掘算法MTSC(Mining Time Series All-Chain Sets over Multi-scale Nearest Time Series,MTSC)。该算法依次使用LRSTOMP与ALLC算法对第一个最近时间序列成员内容进行处理,得到该成员上的全序链集挖掘结果,同时保留该成员相关的PL和PR结构。从第二个最近时间序列成员开始,MTSC算法中的LRSTOMP过程只需要处理当前最近时间序列成员相对于前一个最近时间序列成员的新增部分,进一步结合前一个最近时间序列成员上的PL和PR,可以增量获得当前最近时间序列成员上的PL和PR结构,在此基础上使用ALLC算法得到该成员上的全序链集挖掘结果。相较于对每一个最近时间序列成员内容都使用LRSTOMP和ALLC算法处理的Naive方式,MTSC算法利用增量计算的思想,避免了对全部数据进行重复性计算,从而加快了算法的执行速度,具有更高的时间效率。基于公有数据样本Penguin和TiltABP的仿真实验验证了该算法的有效性,实验结果表明其性能与Naive算法完全一致,且对于以上数据样本,在空间开销增加1.1%~9.7%的情况下,可以实现时间效率80%~88.3%的提升。
