Dense 3-D Reconstruction of an Outdoor Scene by Hundreds-Baseline Stereo Using a Hand-Held Video Camera

Three-dimensional (3-D) models of outdoor scenes are widely used for object recognition, navigation, mixed reality, and so on. Because such models are often made manually with high costs, automatic 3-D reconstruction has been widely investigated. In related work, a dense 3-D model is generated by using a stereo method. However, such approaches cannot use several hundreds images together for dense depth estimation because it is difficult to accurately calibrate a large number of cameras. In this paper, we propose a dense 3-D reconstruction method that first estimates extrinsic camera parameters of a hand-held video camera, and then reconstructs a dense 3-D model of a scene. In the first process, extrinsic camera parameters are estimated by tracking a small number of predefined markers of known 3-D positions and natural features automatically. Then, several hundreds dense depth maps obtained by multi-baseline stereo are combined together in a voxel space.So, we can acquire a dense 3-D model of the outdoor scene accurately by using several hundreds input images captured by a hand-held video camera.     

Proteinase and phospholipase activities and development at different temperatures of yeasts isolated from bovine milk

The presence of yeasts in milk may cause physical and chemical changes limiting the durability and compromising the quality of the product. Moreover, milk and dairy products contaminated by yeasts may be a potential means of transmission of these microorganisms to man and animals causing several kinds of infections. This study aimed to determine whether different species of yeasts isolated from bovine raw milk had the ability to develop at 37°C and/or under refrigeration temperature. Proteinase and phospholipase activities resulting from these yeasts were also monitored at different temperatures. Five genera of yeasts (Aureobasidium sp., Candida spp., Geotrichum spp., Trichosporon spp. and Rhodotorula spp.) isolated from bovine raw milk samples were evaluated. All strains showed one or a combination of characteristics: growth at 37°C (99·09% of the strains), psychrotrophic behaviour (50·9%), proteinase production (16·81% of the strains at 37°C and 4·09% under refrigeration) and phospholipase production (36·36% of the isolates at 37°C and 10·9% under refrigeration), and all these factors may compromise the quality of the product. Proteinase production was similar for strains incubated at 37°C (16·81% of the isolates) and room temperature (17·27%) but there was less amount of phospholipase-producing strains at room temperature (15·45% of the isolates were positive) when compared with incubation at 37°C (36·36%). Enzymes production at 37°C by yeasts isolated from milk confirmed their pathogenic potential. The refrigeration temperature was found to be most efficient to inhibit enzymes production and consequently ensure better quality of milk. The viability of yeasts and the activity of their enzymes at different temperatures are worrying because this can compromise the quality of dairy products at all stages of production and/or storage, and represent a risk to the consumer.     

Image segmentation schema for low-level computer vision

This paper describes two distinct approaches to image-segmentation, both of which take the form of so-called region-growing algorithms. This kind of algorithms begin with a seed location and attempt to join neighboring pixels to this growing seed until no neighbors can be joined to it.

In the first approach, each pixel is linked to the nearest neighbor in the sense of the gray level. The second approach is based on a binary relation named relative similarity relation which reflects relative properties in an image. The combined segmentation scheme of these approaches is also presented.     

Design of a polarized positron source for linear colliders

We propose a design of a polarized positron source for linear colliders. The design is based on electron–positron pair creation from polarized γ-rays which are produced by Compton scattering of circularly polarized laser light off a high-energy electron beam. Polarized positrons are created from those γ-rays incident on a thin conversion target. A future linear collider of the TeV-energy region requires an extraordinary large number of positrons (1×10¹⁰ positrons/bunch) in a multi-bunch time structure. To meet these requirements, our design employs a high-current, low-emittance electron beam of 5.8 GeV, 10 CO₂ lasers, and 200 laser–electron collision-points. At each collision point, a pair of specially designed parabolic mirrors is installed to achieve efficient head-on collisions. This system allows us to produce high-intensity polarized γ-rays, which effectively generate high-intensity polarized positrons with the magnitude of polarization greater than 50%.     

Reversible and hierarchical composite gels with CdSe nanocrystals

To synthesize composite solid materials of metal salt and CdSe nanocrystals by a simple one-step method has been described. These solids can form stable gel in some organic solvent, such as benzene, cyclohexane and 1-butanol, especial in n-decane even below 0.1 wt/vol.%. Furthermore, these gels appear strong fluorescence which can be easily adjusted by the gel concentration. Temperature-dependent fluorescence spectra of composite gels suggested that the CdSe NCs aggregate together in gel state which would induce the energy transfer between nanocrystals and these aggregates could be reversibly disintegrated when gel was heated to form sol. TEM observations provided the further evidence of the energy transfer and suggested that the CdSe NCs were enchased regularly not only on the surface of self assembly of metal salt, but also embedded inside of self assembly in composite gel with small size nanocrystals. In contrast, in composite organogel with large nanocrystals they were only enchased on the edge of self assembly.     

Efficient hundreds-baseline stereo by counting interest points for moving omni-directional multi-camera system

In this article, we propose an efficient method for estimating a depth map from long-baseline image sequences captured by a calibrated moving multi-camera system. Our concept for estimating a depth map is very simple; we integrate the counting of the total number of interest points (TNIP) in images with the original framework of multiple baseline stereo. Even by using a simple algorithm, the depth can be determined without computing similarity measures such as SSD (sum of squared differences) and NCC (normalized cross correlation) that have been used for conventional stereo matching. The proposed stereo algorithm is computationally efficient and robust for distortions and occlusions and has high affinity with omni-directional and multi-camera imaging. Although expected trade-off between accuracy and efficiency is confirmed for a naive TNIP-based method, a hybrid approach that uses both TNIP and SSD improve this with realizing high accurate and efficient depth estimation. We have experimentally verified the validity and feasibility of the TNIP-based stereo algorithm for both synthetic and real outdoor scenes.     

Surface reflectance modeling of real objects with interreflections for augmented virtuality

In mixed reality, especially in augmented virtuality, in which real objects are virtualized, it is important to estimate object surface reflectance properties in order to render the objects under arbitrary illumination conditions. Although several methods have been explored, faithfully estimating surface reflectance parameters for complex objects having nonuniform surface reflectance properties or interreflections remains difficult. This article describes a new method for densely estimating the nonuniform surface reflectance properties of real objects constructed of convex and concave surfaces with interreflections. Registered range and surface color texture images are obtained using a laser rangefinder. In the proposed method, light source positions are first determined in order to obtain color images for discriminating diffuse and specular reflection components considering the object geometry. Surface reflectance parameters are then estimated based on radiosity and the Torrance–Sparrow model. The usefulness of the proposed method is shown experimentally. © 2005 Wiley Periodicals, Inc. Col Res Appl, 31, 38–47, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20184     

Effect of Nozzle Type and Swirl on Flow Pattern for Initial Filling Conditions in the Mould for Up‐hill Teeming

With increasingly more stringent requirements on steel quality and productivity in uphill teeming production, it is vital to attain more desirable fluid flow conditions in the filling of the mould. In this investigation, physical and mathematical modelling was carried out to study the effects of nozzle type and utilization of a swirl generator in the inlet nozzle on the flow pattern in the ingot mould during the initial filling period. Specific focus was on the effects on the resultant hump and axial velocities. Three cases were considered: 1) a straight nozzle, 2) a divergent nozzle, and 3) a divergent nozzle combined with a swirl generator. It was found that usage of the divergent nozzle, compared to the straight nozzle, resulted in a smaller hump and lower axial velocities in the bath. For the combination of divergent nozzle and swirl generator, these findings were even more pronounced, with the hump practically eliminated, and the axial velocities, as well as the turbulence at the meniscus, significantly lower. The findings of the study suggest that a divergent nozzle combined with a swirling flow generated in the nozzle could be used in the up‐hill teeming process in purpose to get calmer initial filling conditions.