Anisotropic deformation for local shape control

Computational Visual Media - We present a novel approach to mesh deformation that enables simple context sensitive manipulation of 3D geometry. The method is based on locally anisotropic...     

Uplink–downlink duality with regard to constraints imposed in practice

The uplink–downlink duality is reviewed with regard to constraints imposed on the transmission schemes in practice. In particular, the effects of non-Gaussian signaling, the use of implementable precoding schemes, and the availability of only imperfect channel state information at the central base-station are analyzed and discussed. The sources for violating the uplink–downlink duality in practical schemes are identified, and it is shown under which setting still the same (but not optimum) performance of both transmission directions can be achieved. Besides treating signal-to-interference plus noise ratios, as usually done, the duality is studied with respect to bit error rate, a parameter more relevant in practical applications.     

An augmented reality human–computer interface for object localization in a cognitive vision system

The European Cognitive Vision project VAMPIRE uses mobile AR-kits to interact with a visual active memory for teaching and retrieval purposes. This paper describes concept and technical realization of the used mobile AR-kits and discusses interactive learning and retrieval in office environments, and the active memory infrastructure. The focus is on 3D interaction for pointing in a scene coordinate system. This is achieved by 3D augmented pointing, which combines inside-out tracking for head pose recovery and 3D stereo human–computer interaction. Experimental evaluation shows that the accuracy of this 3D cursor is within a few centimeters, which is sufficient to point at an object in an office. Finally, an application of the cursor in VAMPIRE is presented, where in addition to the mobile system, at least one stationary active camera is used to obtain different views of an object. There are many potential applications, for example an improved view-based object recognition.     

Apparent fracture toughness of low-carbon steel CSN 411353 as related to stress corrosion cracks

The occurrence of cracks in structural components indicates a certain threat to their reliable operation, because these cracks can grow during operation and reach critical sizes, leading to fracture. The fracture resistance of a structural component is given by the fracture toughness of the material, determined on standardized specimens with a precycled fatigue crack, and the constraint. The fracture toughness itself depends also on the environment. There is enough evidence that in the conditions of the environment assisted cracking the fracture toughness can be significantly reduced by hydrogen mechanism. Our research results have confirmed this and have demonstrated a considerable reduction in the stress corrosion fracture toughness as compared to that related to fatigue cracks. This should be taken into account when assessing the integrity of structural components with stress corrosion cracks. This paper presents experimental results concerned with the stress corrosion fracture toughness of specimens from a DN150 gas line pipe made of low-C steel CSN 411353.     

Phase stability and grain boundary structure in the Cu-Bi system

Cu-Bi system is a model system for studies of interfacial phenomena, such as segregation and segregation induced faceting. In previous studies it was found that there is a strong preference for Σ = 3}111{-}111{ type facets, and their atomic structure was successfully resolved by combining high-resolution electron microscopy and computer simulation using Finnis-Sinclair type interatomic potential. The resolved grain-boundary structure was examined usingab initio full-potential linear muffin-tin orbital method by calculating formation enthalpies of several (hypothetical) Cu-Bi compounds under pressure. It was found that there is no driving force for the ordered alloy formed at the boundary to grow into a three-dimensional phase and thus specific interfacial phases are formed in this system. The range of applicability of Finnis-Sinclair potential used in the previous studies was also investigated by comparison withab initio calculations, and it was shown that the potential is entirely appropriate when Cu concentration is higher than about 66 at. %. In those cases the Cu-Bi system exhibits metallic behavior.     

Performance of peak-to-average power ratio reduction in single- and multi-antenna OFDM via directed selected mapping

Selected mapping (SLM) is a popular scheme for peak power reduction in orthogonal frequency-division multiplexing (OFDM) systems. In this letter, the performance of various versions of SLM, among them ordinary and directed SLM, in single- and multi-antenna point-to-point OFDM systems is assessed. Analytic expressions for the distribution of the PAR are derived. Numerical results cover that significant gains over conventional SLM can be achieved by directed SLM.     

Biocompatibility of ultra-high molecular weight polyethylene (UHMW-PE) stabilized with α-tocopherol used for joint endoprostheses assessed in vitro

Adding the natural antioxidant α-tocopherol to ultra-high molecular weight polyethylene (UHMW-PE) can remarkably delay the oxidation of hip cups made thereof. However, α-tocopherol is likely to undergo different chemical transformations during manufacturing and sterilization of hip cups than in human metabolism. Therefore, the biocompatibility of the putative transformation products has to be investigated. In-vitro tests with L929 mice fibroblast-cells gave no evidence for cytotoxicity. To further ensure the biocompatibility, in-vitro tests with human cells were carried out in this study. Two different human cell lines, one adherent cell line, HF-SAR, and one suspension culture, GSJO, were tested on UHMW-PE-tablets (diameter: 15 mm; thickness: 2 mm; processed according to standard procedures for artificial hip-cups) with and without α-tocopherol with respect to cell viability, proliferation and morphology by means of cell counting, WSt-1 proliferation assay and scanning electron microscopy. Similar proliferation rates were found with both polyethylene samples. Further, we found intact morphology in light and electron microscopy on each substrate. The morphologic characteristics of skin fibroblasts were not changed by any material. Normal adherence and spreading of the fibroblasts was found on controls of glass, as well as on polystyrene and on stabilized and unstabilized polyethylene. The characteristic behaviour as suspension of the GSJO cells remained unchanged. The mitochondrial activity, as studied by WST-1 cell proliferation reagent, was identical on each substrate during the whole observation period of 7 days. Christian Wolf—in partial fulfillment of a Ph.D. (Dr.mont.) thesis at the University of Leoben     

Mechanical properties and fracture behavior of high-strength steels

Typical thicknesses of high-strength steels (HSS) sheets used in the car industry are inapplicable for standardized testing procedures. The aim of this study is to propose an appropriate methodology for testing and comparing of thin HSS sheets. Microstructures were observed by means of light and scanning electron microscopy. The modified Charpy impact tests and fracture toughness tests were used in order to compare the fracture properties of three different HSS sheets (Docol 1200 M, Multiphase 1200 and BTR 165). Ductile-to-brittle transition curves and tearing resistance (J − Δa) curves were measured. From the fracture toughness linked to the specimen thicknesses the value of fracture toughness K_Ic was estimated. Fractographic analysis of broken specimens has revealed that due to the fine microstructure of mixed ferrite-martensite fracture mechanism remains ductile even at low temperatures (down to −100°C). __________ Translated from Problemy Prochnosti, No. 1, pp. 155–158, January–February, 2008.     

Optical signature of RF arcs in the ICRH frequency range

RF arc detection is a key operational and safety issue for ICRF systems. Dedicated measurements on a RF test-stand were made in order to characterize the optical signature of RF arcs (time and spectrum) to assess the potential of optical arc detection on ICRF systems. Time-resolved intensity measurements were carried out using high-speed Si photodetectors with different bandpass filters. The rise time of the arc emission, the light intensity and the time evolution of the arc under different pressure conditions are discussed. Spectral signature of the arcs was obtained using spectrometers in the visible and UV range. It is shown that the arc emission spectrum is independent of the gas pressure and that it is mainly dominated by the stainless steel components of the test bench. The results of the RF arc optical characterization is discussed with a view on the implementation of an optical arc detection system for an ICRF antenna on a fusion machine, both for sections viewing the plasma light as for private vacuum sections.