Image flow is the velocity field in the image plane caused by the motion of the observer, objects in the scene, or apparent motion, and can contain discontinuities due to object occlusion in the ...scene. An algorithm that can estimate the image flow velocity field when there are discontinuities due to occlusions is described. The constraint line clustering algorithm uses a statistical test to estimate the image flow velocity field in the presence of step discontinuities in the image irradiance or velocity field. Particular emphasis is placed on motion estimation and segmentation in situations such as random dot patterns where motion is the only cue to segmentation. Experimental results on a demanding synthetic test case and a real image are presented. A smoothing algorithm for improving the velocity field estimate is also described. The smoothing algorithm constructs a smooth estimate of the velocity field by approximating a surface between step discontinuities. It is noted that the velocity field estimate can be improved using surface reconstruction between velocity field boundaries.< >
A two-stage algorithm for visual surface reconstruction from scattered data while preserving discontinuities is presented. The first stage consists of a robust local approximation algorithm (the ...moving least median of squares (MLMS) of error) to clean the data and create a grid from the original scattered data points. This process is discontinuity preserving. The second stage introduces a weighted bicubic spline (WBS) as a surface descriptor. The WBS has a factor in the regularizing term that adapts the behavior of the spline across discontinuities. The weighted bicubic approximating spline can approximate data with step discontinuities with no discernible distortion in the approximating surface. The combination of robust surface fitting and WBSs removes outliers and reduces Gaussian noise. Either stage by itself would not effectively remove both kinds of noise. Experimental results with the two-stage algorithm are presented.< >
Dynamic stereo with self-calibration Tirumalai, A.P.; Schunck, B.G.; Jain, R.C.
IEEE transactions on pattern analysis and machine intelligence,
12/1992, Letnik:
14, Številka:
12
Journal Article
Recenzirano
An approach for incremental refinement of disparity maps obtained from a dynamic stereo sequence of a static scene is presented. The approach has been implemented using a binocular stereo vision ...system mounted on a mobile robot. A robust least median of squares based algorithm is given for recovering the camera motion between successive viewpoints, which provides a self-calibration mechanism. The recovered motion is utilized for recursive disparity prediction and refinement using a robust Kalman filter model.< >
A polymerase chain reaction (PCR) assay is described for the detection of parvovirus in feces of dogs and cats. A touch-down protocol was used which enabled the specific amplification of virion DNA ...from feces after a fast and simple boiling pretreatment. The sensitivity of PCR was as high as ten infectious particles per reaction which corresponds to a titer of about 103 infectious particles per gram of unprocessed feces. This renders the PCR about 10- to 100-fold more sensitive than electron microscopy, the standard method for parvovirus diagnosis. The very rapid and simple sample preparation recommends this PCR assay as an alternative technique for routine parvovirus diagnosis.
The immunogenicity, reactogenicity, and safety of an inactivated hepatitis A vaccine were assessed in anti-HIV positive homosexual men. Fourteen anti-HIV positive (group 1) and 20 anti-HIV negative ...(group 2) men received vaccine (containing 720 ELISA units of hepatitis A antigen per dose) intramuscularly at 0, 1, and 6 months. Twelve unvaccinated anti-HIV positive men (group 3) were included as controls to evaluate disease progression. Seroconversion (anti-hepatitis V virus (HAV) > or = 20 mlU/ml) was higher in group 2 than group 1 at months 2 (100% vs. 73%) and 7 (100% vs. 77%). Group 2 had higher antibody titres than group 1 at months 1 (201 vs. 92 mlU/ml) and 7 (1,687 vs. 636 mlU/ml). The decline in CD4+ cells between months 0 and 7 was similar in groups 1 and 3 (6.4% vs. 16.2%), showing no evidence for harmful effect of the vaccine on the course of HIV infection. This hepatitis A vaccine appears safe, well tolerated, but less immunogenic in HIV positive homosexual men.
Evidential reasoning for building environment maps Tirumalai, A.P.; Schunck, B.G.; Jain, R.C.
IEEE transactions on systems, man, and cybernetics,
1995-Jan., 1995, 1995-01-00, Letnik:
25, Številka:
1
Journal Article
We address the problem of building a map of the environment utilizing sensory depth information obtained from multiple viewpoints. The desired representation of the environment is in the form of a ...finite-resolution three-dimensional grid of voxels. Each voxel within the grid is assigned a binary value corresponding to its occupancy state. We present an approach for multi-sensory depth information assimilation based on the Dempster-Shafer theory for evidential reasoning. This approach provides a mechanism to explicitly model ignorance which is desirable when dealing with an unknown environment. We present results obtained from this approach on a laboratory stereo sequence and contrast these with results obtained from the traditional Bayesian approach.< >
PDF
