肝癌是常见癌症之一,有着较高的死亡率,精准分割肝癌区域是辅助诊断治疗的重要前提。然而肝脏CT图像需要专业的医师进行标注,有标签数据较少,获取途径单一。针对分割腹部肝脏CT图像需要大量高质量标签并且较难获取的问题,提出了一种采...肝癌是常见癌症之一,有着较高的死亡率,精准分割肝癌区域是辅助诊断治疗的重要前提。然而肝脏CT图像需要专业的医师进行标注,有标签数据较少,获取途径单一。针对分割腹部肝脏CT图像需要大量高质量标签并且较难获取的问题,提出了一种采用协同训练的半监督学习分割方法。首先,将有标签数据输入3D U-Net和3D Res U-Net进行有监督训练,保存训练得到的两个分割模型,在两个分割模型中分别对无标签数据进行预测;然后,挑选预测的结果,再加入全连接条件随机场处理挑选出的伪标签,细化伪标签的边缘信息,提升伪标签的精确度;最后,加入到训练集中,重复上述步骤直到分割结果的Dice相似系数停止提升时结束训练。实验在LiTS2017 Challenge肝脏数据集上进行测试,结果表明,在有标签数据集占总数据集的30%时,该方法的Dice值达到90.22%,几乎与全监督3D Res U-Net分割结果持平,说明该半监督学习方法是有效的。展开更多
本文以汽车运输船(Pure Car and Truck Carrier,PCTC)为研究对象,提出了一种新型的下水方式。在下水的过程中,浮船坞与PCTC存在的变形是不可协调的。通过2种船型之间的支撑系统,采用一种有限元数值模拟的方法,运用试验所测数据,使用有...本文以汽车运输船(Pure Car and Truck Carrier,PCTC)为研究对象,提出了一种新型的下水方式。在下水的过程中,浮船坞与PCTC存在的变形是不可协调的。通过2种船型之间的支撑系统,采用一种有限元数值模拟的方法,运用试验所测数据,使用有限元软件Abaqus中定义仅受压的弹簧单元,对比弹簧单元与实体单元对结构响应的影响,用弹簧等效替代垫木,为后续的强度分析提供便利,将复杂的动力学问题转化为较为简单的静力学问题。展开更多
Field surveys and empirical integrated methods are commonly used in the ecological research to understand the altitudinal pattern of plant diversity of mountains.However,few studies have compared the differences betwe...Field surveys and empirical integrated methods are commonly used in the ecological research to understand the altitudinal pattern of plant diversity of mountains.However,few studies have compared the differences between the two methods on the same scale.Here,we addressed and compared the altitudinal patterns of species richness(SR),phylogenetic diversity(PD),the standardized effect size of phylogenetic diversity(PDses)and mean phylogenetic distance(MPDses)of about 580 angiosperms growing on Mount Kenya from two independent datasets:one is based on our several times field surveys in this mountain and another one is based on empirical data integrated from literatures.We found that the altitudinal diversity patterns of field surveys dataset were consistent with the empirical integrated dataset.Both SR and PD showed hump-shaped patterns along the altitude,and both PDses and MPDses showed monotonically decreasing patterns along the altitude.The ratio of diversity between field surveys dataset and empirical integrated dataset were gradually increase along the altitude.Our research provides new insight for understanding the altitudinal diversity patterns of plants of a tropical mountain.展开更多
文摘肝癌是常见癌症之一,有着较高的死亡率,精准分割肝癌区域是辅助诊断治疗的重要前提。然而肝脏CT图像需要专业的医师进行标注,有标签数据较少,获取途径单一。针对分割腹部肝脏CT图像需要大量高质量标签并且较难获取的问题,提出了一种采用协同训练的半监督学习分割方法。首先,将有标签数据输入3D U-Net和3D Res U-Net进行有监督训练,保存训练得到的两个分割模型,在两个分割模型中分别对无标签数据进行预测;然后,挑选预测的结果,再加入全连接条件随机场处理挑选出的伪标签,细化伪标签的边缘信息,提升伪标签的精确度;最后,加入到训练集中,重复上述步骤直到分割结果的Dice相似系数停止提升时结束训练。实验在LiTS2017 Challenge肝脏数据集上进行测试,结果表明,在有标签数据集占总数据集的30%时,该方法的Dice值达到90.22%,几乎与全监督3D Res U-Net分割结果持平,说明该半监督学习方法是有效的。
文摘本文以汽车运输船(Pure Car and Truck Carrier,PCTC)为研究对象,提出了一种新型的下水方式。在下水的过程中,浮船坞与PCTC存在的变形是不可协调的。通过2种船型之间的支撑系统,采用一种有限元数值模拟的方法,运用试验所测数据,使用有限元软件Abaqus中定义仅受压的弹簧单元,对比弹簧单元与实体单元对结构响应的影响,用弹簧等效替代垫木,为后续的强度分析提供便利,将复杂的动力学问题转化为较为简单的静力学问题。
基金financially supported by National Natural Science Foundation of China(32260046 and 31800176)the Sino-Africa Joint Research Centre(Y323771W07 and SAJC201322)。
文摘Field surveys and empirical integrated methods are commonly used in the ecological research to understand the altitudinal pattern of plant diversity of mountains.However,few studies have compared the differences between the two methods on the same scale.Here,we addressed and compared the altitudinal patterns of species richness(SR),phylogenetic diversity(PD),the standardized effect size of phylogenetic diversity(PDses)and mean phylogenetic distance(MPDses)of about 580 angiosperms growing on Mount Kenya from two independent datasets:one is based on our several times field surveys in this mountain and another one is based on empirical data integrated from literatures.We found that the altitudinal diversity patterns of field surveys dataset were consistent with the empirical integrated dataset.Both SR and PD showed hump-shaped patterns along the altitude,and both PDses and MPDses showed monotonically decreasing patterns along the altitude.The ratio of diversity between field surveys dataset and empirical integrated dataset were gradually increase along the altitude.Our research provides new insight for understanding the altitudinal diversity patterns of plants of a tropical mountain.
