Survey on Benchmarks for a GPU Based Multi Camera Stereo Matching Algorithm

Stereo matching algorithms and multi camera reconstruction algorithms are usually compared using benchmarks. These benchmarks compare the quality of the resulting depth map or reconstructed surface mesh. We describe the differences between several known stereo and multi-view stereo benchmarks and their various datasets. Also the modifications that are necessary to use our own GPU based multi camera stereo matching algorithm with the data from these benchmarks are discussed

Triangular Gk-splines

In this paper a new approach is presented to construct piecewise polynomial G^k-surfaces of arbitrary topology and smoothness order k>= 1 of degree O(k). This approach generalizes some results presented in 1997 in CAGD and in 1999 at the St. Malo conference, respectively. In our construction only 4n polynomial patches are needed to fill an n-sided hole in a generalized C^k-(half)-boxspline surface. This is achieved by coalescing certain control points while at the same time maintaining a regular parametrization

Finite Element Analysis for Linear Elastic Solids Based on Subdivision Schemes

Finite element methods are used in various areas ranging from mechanical engineering to computer graphics and bio-medical applications. In engineering, a critical point is the gap between CAD and CAE. This gap results from different representations used for geometric design and physical simulation. We present two different approaches for using subdivision solids as the only representation for modeling, simulation and visualization. This has the advantage that no data must be converted between the CAD and CAE phases. The first approach is based on an adaptive and feature-preserving tetrahedral subdivision scheme. The second approach is based on Catmull-Clark subdivision solids

Triangular G2-splines

We introduce curvature continuous regular free-form surfaces with triangular control nets. These surfaces are composed of quartic box spline surfaces and are piecewise polynomial multisided patches of total degree 8 which minimize some energy integral. The Bezier nets can be computed efficiently form the spline control net by some fixed masks, i.e. matrix multiplications

A Hand-held Laser Scanner based on Multi-camera Stereo-matching

Most laser scanners in engineering are extended versions of tactile measuring machines. These high precision devices are typically very expensive and hardware modifications are not possible without impairing the precision of the device. For these reasons we built our own laser-scanner system. It is based on a multi-camera reconstruction system developed for fast 3D face reconstructions. Based on this camera system, we developed a laser-scanner using GPU accelerated stereo-matching techniques and a hand-held line-laser probe. The resulting reconstruction is solely based on the known camera positions and parameters. Thus, it is not necessary to track the position and movement of the line-laser probe. This yields an inexpensive laser-scanner system where every hardware component can be modified individually for experiments and future extensions of the system

Comparison of Monitoring Approaches for Selected Priority Pollutants in Surface Water - An Initiative in support to the Water Framework Directive Chemical Monitoring Activity

Laboratories from seven EU Member States under the coordination of the Joint Research Centre and in collaboration with the Provincia di Ferrara participated in a technical on-site project during which sampling and analytical methodologies for chemical monitoring according to proposed WFD provisions have been compared. Laboratories had been invited to take samples from a river according to their standard protocols and to analyse them for PAHs, PBDE and Nonyl-, Octylphenol. It was shown that it is possible to analyse contaminants at relevant levels. Results showed also that currently only experienced laboratories can achieve the required performance, indicating the need for improvement at European level.JRC.H.5-Rural, water and ecosystem resource

Tribological system for cold sheet metal forming based on volatile lubricants and laser structured surfaces

AbschlussberichtA novel tribological system has been developed, in which volatile lubricants (carbon dioxide - CO2 or nitrogen- N2) are used as a substitute for mineral oil-based lubricants in deep drawing processes. This process enables the introduction of an intermediate medium under high pressure through flow-optimized, laser-drilled micro holes into the contact surfaces. This eliminates the need for subsequent, cost-intensive cleaning processes, as the volatile lubricants evaporate without leaving any residue during expansion to ambient pressure. The design of initial micro hole geometries was based on simulations of the flow behaviour of the lubricants passing through, which in turn were validated using pressure reactor tests. In addition, the wetting behaviour of CO2 on relevant surfaces (tool surface and sheet material surface) was investigated experimentally using the captive-bubble-method. Thus, the optimal design of the micro holes (diameter, hole geometry and number of micro holes) could be determined using flat strip drawing tests. The optimal micro hole geometry determined in this way is suited for the use of both CO2 and N2 as volatile lubricant. Furthermore, extensive investigations for the production of the required micro hole geometry by laser drilling were carried out. The fundamentals for drilling micro holes in steel with high aspect ratios could be developed using an ultrashort pulsed research laser with very high pulse energy. Further experiments were conducted using an ultrashort pulsed prototype laser of the kW-class specially developed to increase productivity when drilling a multitude of micro holes with higher average laser power. The novel tribological system has been characterised by means of strip drawing tests and stretch bending tests. For both, CO2 (liquid) and N2 (gaseous), relatively low friction values could be achieved compared to conventional lubricants. It could be shown that deep drawing with both CO2 and N2 as dry lubricants is possible. Here, usage of the volatile lubricants not only allows the replacement of mineral oil based lubricants, but even improves the tribological system with regard to frictional forces in sheet metal forming. The feasibility of the new tribological system has been proven by performing deep drawing tests of rectangular cups. These tests showed a significantly enlarged process window of the forming process, which emphasise the tremendous potential of this new tribological system.12816

Grundlagenuntersuchungen zur Herstellung von Lasermikrobohrungen in Stahl und dem Ausströmverhalten von CO2 als Trockenschmiermedium

Technische, wirtschaftliche und gesetzliche Vorgaben führen zu gesteigerten Anforderungen an Schmierstoffe der Blechumformung. Auch die Auswirkungen auf die Umwelt werden immer relevanter. Langfristig ist das Ziel, die verwendete Schmierstoffmenge zu reduzieren, um zukünftig Blechbearbeitungen ohne Schmierstoffe durchführen zu können. Ausgehend vom Bestreben der Trockenumformung wird ein neuartiges Verfahren zur Schmierung von Tiefziehprozessen mit flüssigem CO als Schmierstoffersatz entwickelt. Dieses Verfahren ermöglicht das Einbringen eines Zwischenmediums in das tribologische System mit Verzicht auf nachfolgende, kostenintensive Reinigungsprozesse, da das flüssige CO bei der Entspannung auf Umgebungsdruck seinen Aggregatszustand ändert und rückstandslos verdampft. Die Zuführung erfolgt dabei direkt in der Wirkfuge über lasergebohrte Mikrolöcher. Es wird gezeigt, dass mit La- serpulsen mit Pulsenergien von bis zu 2,3 mJ und einer Pulsdauer von 8 ps 12 mm dicker, nichtrostender Stahl in weniger als 50 Sekunden (pro Loch) gebohrt werden kann. Erst durch diese relativ kurzen Prozesszeiten wird es möglich sein, ausreichend viele Löcher für Werkzeuge für industrielle Anforderungen zu erzeugen und anschließend im Modellversuch â Streifenziehen mit Flachbahnâ auf ihre grundsätzliche Eignung zu verifizieren. Zur Verteilung des CO werden in die Oberfläche von Umformwerkzeugen lasergenerierte Strukturen eingebracht. Zur Beurteilung der ablaufenden Prozesse und zur Beschreibung des tribologischen Systems wurden Untersuchungen zum Benetzungsverhalten von Werkzeug und Blech in einem Druckreaktor durchgeführt.Volume