Patterned-based time series segmentation (PTSS) is an important task for many time series data mining applications. In this paper, according to the characteristics of PTSS, a generalized model is proposed for PTSS. Fi...Patterned-based time series segmentation (PTSS) is an important task for many time series data mining applications. In this paper, according to the characteristics of PTSS, a generalized model is proposed for PTSS. First, a new inter-pretation for PTSS is given by comparing this problem with the prototype-based clustering (PC). Then, a novel model, called clustering-inverse model (CI-model), is presented. Finally, two algorithms are presented to implement this model. Our experimental results on artificial and real-world time series demonstrate that the proposed algorithms are quite effective.展开更多
Liver Segmentation is one of the challenging tasks in detecting and classifying liver tumors from Computed Tomography(CT)images.The segmentation of hepatic organ is more intricate task,owing to the fact that it posses...Liver Segmentation is one of the challenging tasks in detecting and classifying liver tumors from Computed Tomography(CT)images.The segmentation of hepatic organ is more intricate task,owing to the fact that it possesses a sizeable quantum of vascularization.This paper proposes an algorithm for automatic seed point selection using energy feature for use in level set algorithm for segmentation of liver region in CT scans.The effectiveness of the method can be determined when used in a model to classify the liver CT images as tumorous or not.This involves segmentation of the region of interest(ROI)from the segmented liver,extraction of the shape and texture features from the segmented ROI and classification of the ROIs as tumorous or not by using a classifier based on the extracted features.In this work,the proposed seed point selection technique has been used in level set algorithm for segmentation of liver region in CT scans and the ROIs have been extracted using Fuzzy C Means clustering(FCM)which is one of the algorithms to segment the images.The dataset used in this method has been collected from various repositories and scan centers.The outcome of this proposed segmentation model has reduced the area overlap error that could offer the intended accuracy and consistency.It gives better results when compared with other existing algorithms.Fast execution in short span of time is another advantage of this method which in turns helps the radiologist to ascertain the abnormalities instantly.展开更多
红树林是重要的碳汇生态系统。激光雷达LiDAR (Light Detection And Ranging)是获取林木三维结构参数进行生物量估算的重要技术手段。针对仅利用机载LiDAR难以完整描述红树林三维结构的问题,本文以广东省湛江市英罗港和广西壮族自治区...红树林是重要的碳汇生态系统。激光雷达LiDAR (Light Detection And Ranging)是获取林木三维结构参数进行生物量估算的重要技术手段。针对仅利用机载LiDAR难以完整描述红树林三维结构的问题,本文以广东省湛江市英罗港和广西壮族自治区茅尾海红树林保护区为研究区,利用无人机载和手持式LiDAR获取的点云数据,提出了一种红树冠层下部约束聚类分割方法,对木榄、红海榄、桐花树等不同类型红树的单木分割以及树高、冠幅的进行提取,并与传统单木分割算法进行了对比和分析。结果表明:本文提出的结合空地LiDAR数据的单木分割算法,在不同类型红树单木分割中均取得了较高的单木检出率,与传统的冠层高度模型分割法相比较,单木检出率提升了13.4%—26.7%。其次,有效提高了红树树高的提取精度。3种红树树高参数提取值与实测值之间的R2提高了1.8%—42.2%,RMSE降低了3.4%—55.3%。此外,由于红树冠幅分割结果存在提取值偏小的规律,本研究将能够表征红树冠层交叠密集程度的点云密度变量作为修正因子,经修正后的RMSE降低了45.25%—53.33%。因此,本文提出的联合空地LiDAR的红树林单木生长参数提取方法,可以实现精确的红树单木点云分割并有效提升红树生长参数提取精度,为红树林生物量估算及碳汇能力评估提供了技术和数据支撑。展开更多
Efficient parameterization of point-sampled surfaces is a fundamental problem in the field of digital geometry processing. In order to parameterize a given point-sampled surface for minimal distance distortion, a diff...Efficient parameterization of point-sampled surfaces is a fundamental problem in the field of digital geometry processing. In order to parameterize a given point-sampled surface for minimal distance distortion, a differentialslbased segmentation and parameterization approach is proposed in this paper. Our approach partitions the point-sampled geometry based on two criteria： variation of Euclidean distance between sample points, and angular difference between surface differential directions. According to the analysis of normal curvatures for some specified directions, a new projection approach is adopted to estimate the local surface differentials. Then a k-means clustering （k-MC） algorithm is used for partitioning the model into a set of charts based on the estimated local surface attributes. Finally, each chart is parameterized with a statistical method -- multidimensional scaling （MDS） approach, and the parameterization results of all charts form an atlas for compact storage.展开更多
Accurate panoptic segmentation of 3D point clouds in outdoor scenes is critical for the success of applications such as autonomous driving and robot navigation.Existing methods in this area typically assume that the d...Accurate panoptic segmentation of 3D point clouds in outdoor scenes is critical for the success of applications such as autonomous driving and robot navigation.Existing methods in this area typically assume that the differences between instances are greater than the differences between points belonging to the same instance and use heuristic techniques for segmentation.However,this assumption may not hold in real scenes with occlusion and noise.In addition,most of the previous methods formulate point-wise embedding learning and instance clustering as two decoupled steps for separate optimization,making it a challenging task to learn discriminative embeddings.To address these issues,we introduce a framework for modeling points belonging to the same instance using learnable Gaussian distributions and formulate the point cloud as a Gaussian mixture model.Based on this formulation,we introduce a unified loss function that links the embedding learning and instance clustering in an end-to-end manner.Our framework is generic and can be seamlessly incorporated with existing panoptic segmentation networks.By explicitly modeling intra-instance variance and leveraging end-to-end optimization,our framework improves the discrimination capability of point embeddings with higher accuracy and robustness.Extensive experiments on two large-scale benchmarks demonstrate the effectiveness of the proposed method.展开更多
文摘Patterned-based time series segmentation (PTSS) is an important task for many time series data mining applications. In this paper, according to the characteristics of PTSS, a generalized model is proposed for PTSS. First, a new inter-pretation for PTSS is given by comparing this problem with the prototype-based clustering (PC). Then, a novel model, called clustering-inverse model (CI-model), is presented. Finally, two algorithms are presented to implement this model. Our experimental results on artificial and real-world time series demonstrate that the proposed algorithms are quite effective.
文摘Liver Segmentation is one of the challenging tasks in detecting and classifying liver tumors from Computed Tomography(CT)images.The segmentation of hepatic organ is more intricate task,owing to the fact that it possesses a sizeable quantum of vascularization.This paper proposes an algorithm for automatic seed point selection using energy feature for use in level set algorithm for segmentation of liver region in CT scans.The effectiveness of the method can be determined when used in a model to classify the liver CT images as tumorous or not.This involves segmentation of the region of interest(ROI)from the segmented liver,extraction of the shape and texture features from the segmented ROI and classification of the ROIs as tumorous or not by using a classifier based on the extracted features.In this work,the proposed seed point selection technique has been used in level set algorithm for segmentation of liver region in CT scans and the ROIs have been extracted using Fuzzy C Means clustering(FCM)which is one of the algorithms to segment the images.The dataset used in this method has been collected from various repositories and scan centers.The outcome of this proposed segmentation model has reduced the area overlap error that could offer the intended accuracy and consistency.It gives better results when compared with other existing algorithms.Fast execution in short span of time is another advantage of this method which in turns helps the radiologist to ascertain the abnormalities instantly.
文摘红树林是重要的碳汇生态系统。激光雷达LiDAR (Light Detection And Ranging)是获取林木三维结构参数进行生物量估算的重要技术手段。针对仅利用机载LiDAR难以完整描述红树林三维结构的问题,本文以广东省湛江市英罗港和广西壮族自治区茅尾海红树林保护区为研究区,利用无人机载和手持式LiDAR获取的点云数据,提出了一种红树冠层下部约束聚类分割方法,对木榄、红海榄、桐花树等不同类型红树的单木分割以及树高、冠幅的进行提取,并与传统单木分割算法进行了对比和分析。结果表明:本文提出的结合空地LiDAR数据的单木分割算法,在不同类型红树单木分割中均取得了较高的单木检出率,与传统的冠层高度模型分割法相比较,单木检出率提升了13.4%—26.7%。其次,有效提高了红树树高的提取精度。3种红树树高参数提取值与实测值之间的R2提高了1.8%—42.2%,RMSE降低了3.4%—55.3%。此外,由于红树冠幅分割结果存在提取值偏小的规律,本研究将能够表征红树冠层交叠密集程度的点云密度变量作为修正因子,经修正后的RMSE降低了45.25%—53.33%。因此,本文提出的联合空地LiDAR的红树林单木生长参数提取方法,可以实现精确的红树单木点云分割并有效提升红树生长参数提取精度,为红树林生物量估算及碳汇能力评估提供了技术和数据支撑。
基金This work is supported by the National Grand Fundamental Research 973 Program of China under Grant No.2002CB312101National Natural Science Foundation of China(NSFC)under Grant Nos. 60503056,60333010the Natural Science Foundation of Zhejiang Province under Grant No.R106449.
文摘Efficient parameterization of point-sampled surfaces is a fundamental problem in the field of digital geometry processing. In order to parameterize a given point-sampled surface for minimal distance distortion, a differentialslbased segmentation and parameterization approach is proposed in this paper. Our approach partitions the point-sampled geometry based on two criteria： variation of Euclidean distance between sample points, and angular difference between surface differential directions. According to the analysis of normal curvatures for some specified directions, a new projection approach is adopted to estimate the local surface differentials. Then a k-means clustering （k-MC） algorithm is used for partitioning the model into a set of charts based on the estimated local surface attributes. Finally, each chart is parameterized with a statistical method -- multidimensional scaling （MDS） approach, and the parameterization results of all charts form an atlas for compact storage.
文摘Accurate panoptic segmentation of 3D point clouds in outdoor scenes is critical for the success of applications such as autonomous driving and robot navigation.Existing methods in this area typically assume that the differences between instances are greater than the differences between points belonging to the same instance and use heuristic techniques for segmentation.However,this assumption may not hold in real scenes with occlusion and noise.In addition,most of the previous methods formulate point-wise embedding learning and instance clustering as two decoupled steps for separate optimization,making it a challenging task to learn discriminative embeddings.To address these issues,we introduce a framework for modeling points belonging to the same instance using learnable Gaussian distributions and formulate the point cloud as a Gaussian mixture model.Based on this formulation,we introduce a unified loss function that links the embedding learning and instance clustering in an end-to-end manner.Our framework is generic and can be seamlessly incorporated with existing panoptic segmentation networks.By explicitly modeling intra-instance variance and leveraging end-to-end optimization,our framework improves the discrimination capability of point embeddings with higher accuracy and robustness.Extensive experiments on two large-scale benchmarks demonstrate the effectiveness of the proposed method.
