The Experts below are selected from a list of 3630 Experts worldwide ranked by ideXlab platform
Rui Zhao - One of the best experts on this subject based on the ideXlab platform.
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2 d 3 d irregular shortest path ray tracing for multiple arrivals and its applications
Geophysical Journal International, 2010Co-Authors: Guojiao Huang, Rui ZhaoAbstract:SUMMARY The purpose of this study is to introduce a Multistage irregular shortest-path method (ISPM) for tracking multiple seismic arrivals including any combinations of transmissions, reflections (or refractions) and mode conversions in complex 2-D/3-D layered media, incorporating irregular interfaces (or subsurface in 3-D) and velocity discontinuities. The basic principle is to first divide the model into several different layers (using irregular cells near each interface, discontinuity and the Earth's undulating surface topography) and then to apply the Multistage technique to trace the multiple arrivals. It is possible to realize the multiple arrival tracking with the Multistage Scheme because the multiple arrivals are just different combinations or conjugations of the simple incident, transmitted, reflected (or refracted) and mode converted waves via the velocity discontinuities and the interfaces. Benchmark tests against the popular Multistage fast marching method (FMM) and the Multistage MSPM (modified shortest path method) are undertaken to assess the solution accuracy and the computational efficiency. The results show that the Multistage ISPM is advantageous over both the Multistage FMM and the Multistage MSPM in both solution accuracy and CPU time. Several examples (including the Marmousi model) are used to demonstrate the viability and versatility of the Multistage ISPM in heterogeneous media, even in the presence of high-velocity contrasts involving interfaces of relatively high curvature. Applications to the seismological problems, such as traveltime tomography and earthquake location, indicate that it is possible to improve the spatial resolution in traveltime tomography and solution accuracy in earthquake location if later arrival information is combined with the first arrivals.
Guojiao Huang - One of the best experts on this subject based on the ideXlab platform.
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2 d 3 d irregular shortest path ray tracing for multiple arrivals and its applications
Geophysical Journal International, 2010Co-Authors: Guojiao Huang, Rui ZhaoAbstract:SUMMARY The purpose of this study is to introduce a Multistage irregular shortest-path method (ISPM) for tracking multiple seismic arrivals including any combinations of transmissions, reflections (or refractions) and mode conversions in complex 2-D/3-D layered media, incorporating irregular interfaces (or subsurface in 3-D) and velocity discontinuities. The basic principle is to first divide the model into several different layers (using irregular cells near each interface, discontinuity and the Earth's undulating surface topography) and then to apply the Multistage technique to trace the multiple arrivals. It is possible to realize the multiple arrival tracking with the Multistage Scheme because the multiple arrivals are just different combinations or conjugations of the simple incident, transmitted, reflected (or refracted) and mode converted waves via the velocity discontinuities and the interfaces. Benchmark tests against the popular Multistage fast marching method (FMM) and the Multistage MSPM (modified shortest path method) are undertaken to assess the solution accuracy and the computational efficiency. The results show that the Multistage ISPM is advantageous over both the Multistage FMM and the Multistage MSPM in both solution accuracy and CPU time. Several examples (including the Marmousi model) are used to demonstrate the viability and versatility of the Multistage ISPM in heterogeneous media, even in the presence of high-velocity contrasts involving interfaces of relatively high curvature. Applications to the seismological problems, such as traveltime tomography and earthquake location, indicate that it is possible to improve the spatial resolution in traveltime tomography and solution accuracy in earthquake location if later arrival information is combined with the first arrivals.
Antonio Ruiz - One of the best experts on this subject based on the ideXlab platform.
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a Multistage fe updating procedure for damage identification in large scale structures based on multiobjective evolutionary optimization
Mechanical Systems and Signal Processing, 2008Co-Authors: Ricardo Perera, Antonio RuizAbstract:This study aims to develop a Multistage Scheme for damage detection for large structures based on experimental modal data and on finite element (FE) model updating methods applied on simple FE models. In the first stage, occurrence and approximate location of damage is performed by using damage functions in order to decrease the number of parameters to be updated. The goal in the second stage is to identify the specific damaged members and damage extent by considering only the members belonging to the regions detected as damage in the first stage. To improve identification, the optimization procedure is formulated in a multiobjective context solved by using evolutionary algorithms. Modal flexibilities and a damage location criterion dependent on frequencies and mode shapes are used as two objective functions of the multiobjective problem. The proposal is implemented in simulated case studies and in a case study of a real bridge experimentally tested with successful results.
Ricardo Perera - One of the best experts on this subject based on the ideXlab platform.
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a Multistage fe updating procedure for damage identification in large scale structures based on multiobjective evolutionary optimization
Mechanical Systems and Signal Processing, 2008Co-Authors: Ricardo Perera, Antonio RuizAbstract:This study aims to develop a Multistage Scheme for damage detection for large structures based on experimental modal data and on finite element (FE) model updating methods applied on simple FE models. In the first stage, occurrence and approximate location of damage is performed by using damage functions in order to decrease the number of parameters to be updated. The goal in the second stage is to identify the specific damaged members and damage extent by considering only the members belonging to the regions detected as damage in the first stage. To improve identification, the optimization procedure is formulated in a multiobjective context solved by using evolutionary algorithms. Modal flexibilities and a damage location criterion dependent on frequencies and mode shapes are used as two objective functions of the multiobjective problem. The proposal is implemented in simulated case studies and in a case study of a real bridge experimentally tested with successful results.
Rodney Long - One of the best experts on this subject based on the ideXlab platform.
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automatic detection of anatomical landmarks in uterine cervix images
IEEE Transactions on Medical Imaging, 2009Co-Authors: Hayit Greenspan, Shiri Gordon, G Zimmerman, Shelly Lotenberg, Jose Jeronimo, Sameer Antani, Rodney LongAbstract:The work focuses on a unique medical repository of digital cervicographic images (ldquoCervigramsrdquo) collected by the National Cancer Institute (NCI) in longitudinal multiyear studies. NCI, together with the National Library of Medicine (NLM), is developing a unique Web-accessible database of the digitized cervix images to study the evolution of lesions related to cervical cancer. Tools are needed for automated analysis of the cervigram content to support cancer research. We present a Multistage Scheme for segmenting and labeling regions of anatomical interest within the cervigrams. In particular, we focus on the extraction of the cervix region and fine detection of the cervix boundary; specular reflection is eliminated as an important preprocessing step; in addition, the entrance to the endocervical canal (the ldquoosrdquo), is detected. Segmentation results are evaluated on three image sets of cervigrams that were manually labeled by NCI experts.
