Berry phase and persistent current in disordered mesoscopic rings

A novel quantum interference effect in disordered quasi-one-dimensional rings in the inhomogeneous magnetic field is reported. We calculate the canonical disorder averaged persistent current using the diagrammatic perturbation theory. It is shown that within the adiabatic regime the average current oscillates as a function of the geometric flux which is related to the Berry phase and the period becomes half the value of the case of a single one-dimensional ring. We also discuss the magnetic dephasing effect on the averaged current.Comment: 6 pages, RevTeX, 2 figures. To appear in Phys. Rev. B Rapid Communications Vol.60 No.12 (1999

Recognition of nonmanual markers in American Sign Language (ASL) using non-parametric adaptive 2D-3D face tracking

This paper addresses the problem of automatically recognizing linguistically significant nonmanual expressions in American Sign Language from video. We develop a fully automatic system that is able to track facial expressions and head movements, and detect and recognize facial events continuously from video. The main contributions of the proposed framework are the following: (1) We have built a stochastic and adaptive ensemble of face trackers to address factors resulting in lost face track; (2) We combine 2D and 3D deformable face models to warp input frames, thus correcting for any variation in facial appearance resulting from changes in 3D head pose; (3) We use a combination of geometric features and texture features extracted from a canonical frontal representation. The proposed new framework makes it possible to detect grammatically significant nonmanual expressions from continuous signing and to differentiate successfully among linguistically significant expressions that involve subtle differences in appearance. We present results that are based on the use of a dataset containing 330 sentences from videos that were collected and linguistically annotated at Boston University

A multi-projector CAVE system with commodity hardware and gesture-based interaction

Spatially-immersive systems such as CAVEs provide users with surrounding worlds by projecting 3D models on multiple screens around the viewer. Compared to alternative immersive systems such as HMDs, CAVE systems are a powerful tool for collaborative inspection of virtual environments due to better use of peripheral vision, less sensitivity to tracking errors, and higher communication possibilities among users. Unfortunately, traditional CAVE setups require sophisticated equipment including stereo-ready projectors and tracking systems with high acquisition and maintenance costs. In this paper we present the design and construction of a passive-stereo, four-wall CAVE system based on commodity hardware. Our system works with any mix of a wide range of projector models that can be replaced independently at any time, and achieves high resolution and brightness at a minimum cost. The key ingredients of our CAVE are a self-calibration approach that guarantees continuity across the screen, as well as a gesture-based interaction approach based on a clever combination of skeletal data from multiple Kinect sensors.Preprin

Automatic polishing process of plastic injection molds on a 5-axis milling center

The plastic injection mold manufacturing process includes polishing operations when surface roughness is critical or mirror effect is required to produce transparent parts. This polishing operation is mainly carried out manually by skilled workers of subcontractor companies. In this paper, we propose an automatic polishing technique on a 5-axis milling center in order to use the same means of production from machining to polishing and reduce the costs. We develop special algorithms to compute 5-axis cutter locations on free-form cavities in order to imitate the skills of the workers. These are based on both filling curves and trochoidal curves. The polishing force is ensured by the compliance of the passive tool itself and set-up by calibration between displacement and force based on a force sensor. The compliance of the tool helps to avoid kinematical error effects on the part during 5-axis tool movements. The effectiveness of the method in terms of the surface roughness quality and the simplicity of implementation is shown through experiments on a 5-axis machining center with a rotary and tilt table

Back to the edge: relative coordinate system for use-wear analysis

Use-wear studies rely heavily on experiments and reference collections to infer the function of archeological artifacts. Sequential experiments, in particular, are necessary to understand how use-wear develops. Consequently, it is crucial to analyze the same location on the tool's surface during the course of an experiment. Being able to relocate the area of interest on a sample is also essential for reproducibility in use-wear studies. However, visual relocation has limited applicability and there is currently no easy and efficient alternative. Here we propose a simple protocol to create a coordinate system directly on the sample. Three ceramic beads that serve as reference markers are adhered onto the sample, either with epoxy resin or acrylic polymer. The former is easier to work with but the latter is reversible so it can be applied to archeological samples too. The microscope's software then relocates the position(s) of interest. We demonstrate the feasibility of this approach and measure its repeatability by imaging the same position on an experimental flint blade 10 times with two confocal microscopes. Our results show that the position can be relocated automatically with a horizontal positional repeatability of approximately 14% of the field of view. Quantitative surface texture measurements according to ISO 25178 vary due to this positional inaccuracy, but it is still unknown whether this variation would mask functional differences. Although still perfectible, we argue that this protocol represents an important step toward repeatability and reproducibility in experimental archeology, especially in use-wear studies.Funding Agency Romisch-Germanisches Zentralmuseum - Leibniz Research Institute for Archeology by German Federal and Rhineland Palatinate funding (Sondertatbestand "Spurenlabor")info:eu-repo/semantics/publishedVersio