Precise, automatic and fast method for vanishing point detection

A new automated approach for vanishing point detection in images of urban scenes is described. This method is based on the theorem of Thales. The main contribution of this paper is the automatic and simultaneous detection of all vanishing points of the image, achieved by converting this problem into the detection of circles in a complex cloud of points, in which each point corresponds to a segment and is associated with an uncertainty. This extraction of circles uses a RANSAC method, modified to improve its speed by using accumulation techniques (Hough transform or otherwise). This robust estimation is then refined by least squares error propagation using the individual variances of each segment. The algorithm is robust, its accuracy is optimised and it is entirely automatic. Its successful operation has been tested on a large number of images of varied urban scenes.     

基于噪声随机模型的加权观测融合方法

信息融合技术中,在各局部传感器的有色观测噪声为一阶AR模型的情况下,可以利用观测扩增方法消除有色噪声的影响,得到最优加权观测融合方程,从而实现状态的最优滤波解。对于有色观测噪声为MA或ARMA模型的情况,观测扩增方法不再适用。提出了基于有色观测噪声随机模型级数展开的方法,求解出各局部传感器有色观测噪声的方差,并利用该方差对加权观测融合滤波器进行了构造。通过计算实例证明,该方法不仅适用于观测噪声为AR模型,同时适用于噪声MA或ARMA模型。     

Cascaded image analysis for dynamic crack detection in material testing

Concrete probes in civil engineering material testing often show fissures or hairline-cracks. These cracks develop dynamically. Starting at a width of a few microns, they usually cannot be detected visually or in an image of a camera imaging the whole probe. Conventional image analysis techniques will detect fissures only if they show a width in the order of one pixel. To be able to detect and measure fissures with a width of a fraction of a pixel at an early stage of their development, a cascaded image analysis approach has been developed, implemented and tested. The basic idea of the approach is to detect discontinuities in dense surface deformation vector fields. These deformation vector fields between consecutive stereo image pairs, which are generated by cross correlation or least squares matching, show a precision in the order of 1/50 pixel. Hairline-cracks can be detected and measured by applying edge detection techniques such as a Sobel operator to the results of the image matching process. Cracks will show up as linear discontinuities in the deformation vector field and can be vectorized by edge chaining. In practical tests of the method, cracks with a width of 1/20 pixel could be detected, and their width could be determined at a precision of 1/50 pixel.     

轨道平顺性与测量精度

从轨道平顺性验收标准性切入,提出轨道平顺性对控制网的精度要求;指出轨道平顺性与控制点间的相对精度相关,与控制测量网垂直于线路的的横向误差及高程相关。     

基于模糊理论的时空数据模型及算法解决

针对当前时空数据模型中存在的主要问题,本文提出了一种基于模糊理论的时空数据模型.该模型从时空对象演化的角度出发,结合模糊隶属度的概念,力求精确表达对象演化的整个过程及对象之间的相互关系.在此基础上,进一步分析了该模型的数据结构以及算法解决,为时空数据模型的研究提供了新的思路.     

Partially standing wave measurement in the presence of steady current by use of coincident velocity and/or pressure data

In recent years, instrumentation for field flow measurements has become more and more sophisticated. In particular, local pressure and velocity are measured at frequency rates up to at least 2 Hz, which gives information on wave energy. The present work describes the methods for partially standing wave measurement in the presence of current by use of coincident measurements of both horizontal velocity and pressure, or vertical velocity. Reflection calculated from either coincident horizontal and vertical velocities or three-gauge methods are compared. They are based on existing experiments carried out in an ocean wave basin for both regular and irregular waves in the presence of current. Applications to field measurements, out of and in the breaking zones are then presented. In the nearshore, coincident horizontal and vertical velocities far from the bottom, and coincident horizontal velocity and pressure close to the bottom give relevant information concerning partially standing waves.     

Short-term temperature and salinity variations in the Tsushima Strait in 2004: Behavior of the surface low-salinity water in the strait

Temporal variations in temperature and salinity observed in 2004 were investigated on a short time scale in the Tsushima Strait. The data were obtained by long-term in situ measurements at Mitsushima and Futaoi Island using an instrument equipped with a piston-type wiper to avoid biofouling. In addition, the temperature and salinity values of the surface layer obtained by a commercial ferryboat between Hakata and Busan were used to investigate their spatiotemporal variations. Temperature and salinity variations with a time scale of several days had a negative correlation in the summer. This evidence suggests that a warm and less saline water mass, which is considered to be mainly the Changjiang Diluted Water (CDW), flowed intermittently through the Tsushima Strait in summer. In late July 2004, a large low-salinity water mass was detected in the Tsushima Strait. At that time, the freshwater transport through the Tsushima Strait transiently reached about 12 × 10⁴ m³s⁻¹, which is estimated from observed acoustic Doppler current profiler (ADCP) data along a ferryboat line and inferred salinity profiles. This estimated value is more than double the maximum of the climatological monthly mean of the Changjiang discharge. Furthermore, salinity and surface current data obtained by high frequency ocean radar (HF radar) indicate that water properties at Mitsushima may occasionally represent part of the water flowing through the western channel via a countercurrent, although Mitsushima is geographically located in the eastern channel.