距骨的交互式快速图像分割算法

距骨的图像分割是对其进行三维可视化及运动学研究的基础.提出一种距骨的交互式图像分割算法,由三部分组成:(1)提出一种改进的迭代阈值法,从一组足部CT图像序列中分割出所有骨骼.(2)提出一种加速的live-wire分割算法,断开距骨与其他骨骼的连接线,该方法与原Live-wire算法相比,代价计算量大为减小且缩短了最优路径搜索时间.(3)用形态学操作提取距骨.实验结果表明,该算法能以较少的交互次数快速地进行距骨图像分割,也可用于其他骨骼的分割.     

距下关节三维可视化研究

提出基于活体后足CT序列图像的距下关节三维可视化及主分量描述方法编程重建距下关节表面,并计算出距骨和跟骨的旋转方向,为足部的诊断和治疗提供理论依据.     

一种基于改进分水岭算法的图像分割方法

使用分水岭方法对图像进行分割引起了人们的重视,但是在图像分割中,分水岭变换使用的是梯度图像,容易造成过度分割。因此首先对原始图像进行平滑,将平滑后的图像使用分水岭变换,同一标号的像素属于同一贮水盆地,而将距不同贮水盆地距离相等的像素标为分水岭点,这样就得到了图像的初始分割结果;最后应用灰度齐次性准则和边界强度准则进行区域的融合,从而解决了过度分割问题。实验结果表明,该方法得到了精确的、有意义的分割结果。     

一种基于改进分水岭算法的图像分割方法

使用分水岭方法对图像进行分割引起了人们的重视,但是在图像分割中,分水岭变换使用的是梯度图像,容易造成过度分割.因此首先对原始图像进行平滑,将平滑后的图像使用分水岭变换,同一标号的像素属于同一贮水盆地,而将距不同贮水盆地距离相等的像素标为分水岭点,这样就得到了图像的初始分割结果;最后应用灰度齐次性准则和边界强度准则进行区域的融合,从而解决了过度分割问题.实验结果表明,该方法得到了精确的、有意义的分割结果.     

基于图像检测的双绞线绕距测量方法

针对双绞线绕距测量,提出了一种图像检测框架。此框架通过图像分割、修复、细化、拟合以及比例尺的设置,可实时计算出双绞线绕距值。在此框架下,针对传统二维最大类间方差法--Otsu运行时间较长的问题,提出了一种新的基于区域斜分的快速算法。快速算法通过对二维直方图区域重新划分,结合快速查找表以及递推算法,大大减少了分割时间。针对图像缺失的问题,采用了基于边缘检测的算法对其特定区域进行填充修复,并对修复后的图像进行细化。通过最小二乘法,拟合细化图像中的单像素点,得到拟合曲线。通过计算拟合曲线交点间的距离可得双绞线绕距的图像距离。最后将图像距离按比例尺转换为绕距的测量值。实验结果表明,基于区域斜分的快速算法其分割时间约为传统算法的0.22%,且两种算法的分割效果基本一致。将图像检测方法测得的绕距值与其真实值进行比较,结果表明测量值与真实值的绝对误差为0.48%。通过使用图像检测方法测量双绞线绕距,可以准确测得绕距值,提高绕距测量的效率。     

手腕骨X线片兴趣区域图像分割的研究

提出了一种准确分割骨骺兴趣区域边缘位置的方法。针对手腕骨X线片图像的特征,采用Gibbs 随机场对兴趣区域进行初始分割,将骨从图像中分割出来;针对骨与软组织的灰度值相差不大,Gibbs 随机场正确分割困难的问题,再进一步利用主动轮廓法对初始轮廓进行改善,将软骨与软组织准确分割开,从而得到了正确的骨的边缘位置。实验验证了该方法对分割出的底部区域骨的轮廓线有较大的改善,同时这种联合的方法具有较强的抗噪声能力。     

基于小波神经网络的脑图像分割研究

随着影像学的发展,医学影像设备极大地提高了人类获取自身信息的能力,推动了现代医学的发展.为了更好地获得脑部图像的信息,对脑部图像进行分割研究.首先介绍了脑图像的分割研究背景,然后详细研究了脑图像的分割方法.在分割算法中,给出了脑图像预处理模型,然后通过将小波理论和神经网路相结合提出一种脑部图像分割算法,并将将该算法在脑部图像处理中实现.脑图像分割实验表明算法能够有效地对图像进行分割.实验评估结果显示算法对于脑图像的分割足高效的.     

基于改进分水岭的CTA去骨技术①

为避免快速分水岭在CTA图像去骨中存在的过分割现象,采用一种改进的可交互分水岭算法对CTA图像进行去骨研究。改进算法建立在快速分水岭的排序操作基础上,排序完成后,采用侧重于像素空间关系的方法对像素进行溢流标记,同时采用树结构组织水盆及其合并关系,最后通过用户给定标记和合并阈值对集水盆合并过程进行干预,从而影响分割结果以抑制过分割。实验结果表明,改进算法有效地解决了分水岭变换中的过分割问题,并较好地去除骨骼结构。     

基于机器视觉的蟋蟀体态测量

设计一套基于机器视觉的蟋蟀体态测量装置,初步研究用图像处理和图像测量的方法实现对蟋蟀躯干长宽的测量.该装置构建一个PC-Based的机器视觉系统,利用VisuaI Basic开发工具编写图像处理算法和图像测量算法的程序.应用惯性主轴的方法实现蟋蟀图片位置的归一化,应用数学形态学分割算法实现了蟋蟀躯干与足和触角的分割,将分割后的躯干进行边缘提取,从而进行蟋蟀体态的测量.     

一种应用于身份证字符精确切分的算法

针对身份证图像的特点：干扰强烈、信息排列有规律，本文提出了一种分割算法，该算法利用Sobel算子进行局部阈值化，结合投影法与平均字符中心距对字符进行精确切分。实验结果表明，该方法定位效果好、分割精度高、适用于身份证图像的自动识别。     

Mathematical modeling of talus development

A new mathematical model for talus development and retreat of cliff behind the talus was constructed. This model includes both the rate of declining retreat of cliff (v_θ) and the rate of parallel retreat of cliff (v_a) independently. It can, therefore, reproduce diverse topographic changes having various ratios of v_θ to v_a. The model was applied to the result of a field experiment for talus development at a cliff composed of chalk. The calculated form by the model was in good agreement with the field observations. This agreement validates the model.     

Effects of lichens on the reflectance spectra of granitic rock surfaces

The objective of this study was to determine the effect of lichen cover on the spectral reflectance characteristics of granitic rocks. Rock samples collected from bedrock exposures and talus slopes were granodiorite, tonalite, granite, and quartz-diorite. The lichens found on these rocks varied in color, i.e., black, dark brown, medium gray, olive-green, yellow-green, green, orange, and orange-red. The visible and near infrared reflectance spectra (400–1100 nm) of the rock and lichen samples show that lichens can affect the rock's spectra. These changes are dependent on the reflectance contrast between the rock surface and the lichen covering.     

Geomorphic evolution of the Piedmont Zone of the Ganga Plain,India: a study based on remote sensing,GIS and field investigation

The geomorphic evolution of the Piedmont Zone of the Ganga Plain is not well understood, since the identification of various morpho-tectonic features in the field is very difficult because of the thick forest cover, extensive anthropogenic modifications in the landscape and easily reworkable gravels. Interpretation of satellite imagery, Digital Terrain Models (DTMs) and field data has helped in identification and mapping of various morpho-tectonic features in a hitherto unstudied part of the Piedmont Zone and the adjoining areas in north-western Ganga Plain, India. The Piedmont Zone has formed as a result of laterally coalescing alluvial fans of variable dimensions and talus deposits, and is traversed by active faults and thrusts. The variable subsidence rates along the basin margin (i.e. the Himalayan Frontal Thrust) and climatic events have controlled the accommodation space and basinward progradation of alluvial fans. The landscape of the Piedmont Zone is presently being continuously modified by the ongoing tectonic movements and seasonal climatic variations.     

Variations of anatomical elements contributing to subtalar joint stability: intrinsic risk factors for post-traumatic lateral instability of the ankle?

Ankle sprains are frequently followed by chronic lateral instability, often with talar hypermobility. This might be due to subtalar instability. Among intrinsic risk factors, anatomical variants are generally overlooked. In the subtalar region, anatomical variation is particularly frequent. On the talus as well as on the calcaneus, the anterior articular facets may be missing or fused with the medial facets, giving rise to three subtalar joint configurations: a three-joint configuration, a fused configuration with a relatively large anteromedial joint, and a twojoint configuration without anterior joint. Osteometry was performed on these joint facets (134 calcanei, 122 tali), demonstrating significant differences in the surface of these configurations and the existence of a supplementary supporting surface with grossly transverse orientation in the three-joint configuration. There are also several variants of stabilizing ligaments within the sinus tarsi. Some of these configurations might expose to increased risk of associated subtalar lesions, resulting in subtalar instability. A systematic look for these variants is recommended in order to evaluate the associated risk factors, eventually resulting in a better understanding, prevention and cure of sequellae.     

Analysis of foot shape variation based on the medial axis of foot outline

The variations in foot outline forms are analyzed by using flexion angles of the medial axis of foot outline. Foot outline and 12 conventional measurements taken on the right foot of 443 male and 297 female subjects with no visible pathological deformation of the foot were used for analyses. The results indicate that the foot is outflared in most of the subjects. Medial bulge and lateral concavity of foot outline are responsible for the foot outflare, and they are not correlated with each other. Medial bulge is due to the overhang of navicular bone that is caused by the pronation of the foot. Its intensity is negatively correlated with dorsal arch height. Lateral concavity is partly due to the abduction of talus and calcaneus relative to the tarsometatarsal bones anterior to them. These three-dimensional morphological characteristics of outflared feet intimately relate to the fit and comfort of the shoe. The flexion angles of medial axis of foot outline provide a useful tool in morphological analysis of the foot for the following reasons; (1) they carry the information on the three-dimensional foot shape that cannot be represented by conventional measurements; and (2) the data is easily obtained and calculations are easily made with minimum expense.     

Variations of anatomical elements contributing to subtalar joint stability: intrinsic risk factors for post-traumatic lateral instability of the ankle?

Ankle sprains are frequently followed by chronic lateral instability, often with talar hypermobility. This might be due to subtalar instability. Among intrinsic risk factors, anatomical variants are generally overlooked. In the subtalar region, anatomical variation is particularly frequent. On the talus as well as on the calcaneus, the anterior articular facets may be missing or fused with the medial facets, giving rise to three subtalar joint configurations: a three-joint configuration, a fused configuration with a relatively large anteromedial joint, and a two-joint configuration without anterior joint. Osteometry was performed on these joint facets (134 calcanei, 122 tali), demonstrating significant differences in the surface of these configurations and the existence of a supplementary supporting surface with grossly transverse orientation in the three-joint configuration. There are also several variants of stabilizing ligaments within the sinus tarsi. Some of these configurations might expose to increased risk of associated subtalar lesions, resulting in subtalar instability. A systematic look for these variants is recommended in order to evaluate the associated risk factors, eventually resulting in a better understanding, prevention and cure of sequellae.     

Spatial variations of rain-use efficiency along a climate gradient on the Tibetan Plateau: A satellite-based analysis

Understanding the spatial relationship between rain-use efficiency (RUE) and climate conditions is crucial for predicting the steady-state responses of an ecosystem to climate variations. We clarified the spatial variations of RUE in different ecosystems along both mean annual precipitation (MAP) and mean annual temperature (MAT) gradients in the Three-river Headwaters Region (THR) of China. RUE displayed a unimodal pattern along a MAP gradient across different ecosystems, with a higher value in forest, shrub, and less-arid alpine meadow than in alpine steppe, alpine talus vegetation, and more-arid alpine meadow. RUE followed an increasing trend along the MAT gradient both in a given ecosystem and across various ecosystems. The varying maximum RUE (RUE_max) with temperature suggested that no common spatial RUE_max existed across different ecosystems in the driest pixels. With the mutual interference between precipitation and temperature excluded, RUE increased both with precipitation at a given temperature level and with temperature at a given precipitation level in cold and dry ecosystems, while RUE probably decreased both with precipitation at a given temperature level and with temperature at a given precipitation level in warm and humid ecosystems. Our study illuminates the response of RUE to climate variations in alpine areas based on the spatial model, aiming to improve our understanding of the interactions between vegetation and climate conditions and the potential trade-offs between the ecosystem’s carbon and water.     

中心刚体-柔性梁刚柔耦合动力学模型降阶研究

有限单元法被广泛的采用来描述柔性体的弹性变形,然而有限元节点坐标数目庞大,将会给动力学方程求解带来巨大的计算负担.如何降低柔性体的自由度,是当前柔性多体系统动力学研究的一个重要命题.本文以中心刚体-柔性梁系统为例,采用Krylov方法和模态方法进行降价.然后分别采用有限元全模型、Krylov降阶模型和模态降阶模型,对中心刚体-柔性梁进行刚-柔耦合动力学仿真.仿真结果表明,与采用模态降阶方法相比,采用Krylov模型降阶方法只需要较低的自由度,就可以得到与采用有限元方法完全一致的结果.说明Krylov模型降阶方法能够有效的用于柔性多体系统的模型降价研究.