A novel algorithm for a continuous and fast 3D projection of points on triangulated surfaces for CAM/CAD/CAE applications

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A novel algorithm for a continuous and fast 3D projection of points on triangulated surfaces for CAM/CAD/CAE applications

In the present work, a novel algorithm for the continuous projection of point triangles belonging to a triangle mesh is presented. The algorithm uses the normals defined at the vertices of the triangle to perform the projection. The direction of projection is not chosen a priori but depends on the point to be projected: the proposed algorithm, named Fast Continuous Projection method (FCP) lets the projection direction vary continuously on the mesh. Moreover, the direction is coherent with the original surface that is approximated with the triangle mesh. An optimized version of the algorithm is also presented: this uses pre-evaluated matrices to reduce the calculation time. This algorithm can be effectively used when a large set of points has to be projected on a coarse mesh as, for example, to generate the scanning vectors for laser engraving/milling

Isotopic Analysis of Purple Sulfur Bacteria and the Environmental Conditions of Lakes in Indiana and the Pacific Northwest: Water Column Characterizations for Use in Developing a Water Column Profiling Device

poster abstractA better understanding of purple sulfur bacterial geochemical signatures within natural anoxic lakes will provide essential information for the fabrication of a device to isolate and sample the biomass. Purple sulfur bacteria are sulfide (H2S) oxidizing phototropic organisms. They utilize the process of anoxygenic photosynthesis, the reaction of a reducing agent other than water (H2O) and light energy, to produce chemical energy. Dissolved oxygen inhibits the anaerobic respiration of the bacteria causing blooms, or clusters of cellular mass, to form in very restricted conditions. Sulfide is produced by another class of microorganisms called sulfate reducing bacteria. Purple sulfur bacteria must form near the transitional layer between aerobic and anaerobic water (known as the chemocline); at a depth light can reach (photic zone); and in the presence of reduced sulfur. Environments conducive to the development of purple sulfur bacteria can be further understood by isotopic analysis. Samples of lake water from various depths were taken and filtered to isolate the bacteria, and preserve the dissolved sulfate and sulfide. Sulfate was precipitated as BaSO4, and sulfide was extracted using acid volatile extraction (AVS) to trap Ag2S for analysis using mass spectrometry. Sulfur and oxygen isotopes in the samples allow for a comparison between Northern Indiana and Pacific Northwest lakes. Research is ongoing, but the lakes in Indiana have higher lower concentrations of sulfate (~10mM) compared to the Pacific Northwestern lakes (20 to 100mM). Sulfide concentrations are extremely high in the Pacific Northwest lakes (up to 30 mM), possibly reflecting high rates of sulfate reduction and high concentrations of sulfate. Combined, this research will give insight on the nature of anoxic bacterial systems and how they change sulfur isotope composition. The research also provides the opportunity to understand the sedimentary record of the geologic past

First Order Description of D=4 static Black Holes and the Hamilton-Jacobi equation

In this note we discuss the application of the Hamilton-Jacobi formalism to the first order description of four dimensional spherically symmetric and static black holes. In particular we show that the prepotential characterizing the flow coincides with the Hamilton principal function associated with the one-dimensional effective Lagrangian. This implies that the prepotential can always be defined, at least locally in the radial variable and in the moduli space, both in the extremal and non-extremal case and allows us to conclude that it is duality invariant. We also give, in this framework, a general definition of the ``Weinhold metric'' in terms of which a necessary condition for the existence of multiple attractors is given. The Hamilton-Jacobi formalism can be applied both to the restricted phase space where the electromagnetic potentials have been integrated out as well as in the case where the electromagnetic potentials are dualized to scalar fields using the so-called three-dimensional Euclidean approach. We give some examples of application of the formalism, both for the BPS and the non-BPS black holes.Comment: A clarifying discussion on the existence of the prepotential and a comment on multiple attractors are added; typos corrected, references adde

The April-May 2006 volcano-tectonic events at Stromboli volcano (Southern Italy) and their relation with the magmatic system.

Between April 10th and May 22th 2006, a small seismic swarm of 5 volcano-tectonic events occurred on the volcanic island of Stromboli (Southern Italy). Two of these, having M > 3 and an intensity of about V-VI MCS, were clearly felt causing concern in the population. They were recorded during a period of increased explosive activity and were followed by two major explosions at the summit craters on May 22th, few hours after the last earthquake and on 16th June. The location of such events has been performed using a probabilistic approach based on the Equal Differential Time tecnique. Using this tecnique, we were able to locate all the events, showing how they cluster below the volcanic edifice at a depth of about 5÷6 km. From observed P wave polarities we determined the focal mechanisms of the 4 major events. Using earthquake scaling nlaws, we calculated the fault area and the average slip for the two major events. Finally, assuming an homogeneous half-space model we computed the isotropic stress changes below the volcano edifice. The negative stress variation over the central axis of the volcano suggests that the earthquakes were triggered by a pressurization of the magmatic system

Selectively Tunable Luminescence of Perovskite Nanocrystals Embedded in Polymer Matrix Allows Direct Laser Patterning

Cesium lead halide perovskite nanocrystals (NCs) have gained enormous attention as promising light-emitting and light-converting materials. Most of their applications require embedding NCs in various matrices, which is a challenging task due to their low stability, especially in the case of red-emitting CsPbI3 NCs. In this work, a new approach is proposed allowing the formation of red-emitting perovskite NCs by anion exchange induced directly inside a solid polymer matrix using green-emitting CsPbBr3 NCs as templates and iodododecane as an iodine source. Moreover, a simple and efficient route to photo-assisted termination of the anion exchange reaction in the polymer composite after reaching desired optical properties is demonstrated. The findings allow the authors to pattern a thin composite film with an ultrashort UV laser resulting in a selective generation of green- and red-emitting features with a 15 µm resolution

Effects of anisotropic and isotropic LIPSS on polymer filling flow and wettability of micro injection molded parts

In micro injection molding, the specific cavity surface texture and roughness directly influence the polymer flow and the heat transfer between polymer melt and mold. In this work, two different types of laser-induced periodic surface structures, linear and hexagonal, were generated, and their impact on the flow length in micro injection molding was evaluated. A complete investigation of the surface treatment effect on the polymer flow was carried out, comparing the performance of an untreated cavity surface with surfaces modified by LIPSS. The phenomenon was examined by localizing the weld lines created by the polymer flowing in two parallel channels having different surface treatments. Several cavity inserts were treated by varying the LIPSS process parameters to generate surfaces with different micro-and nanostructures directions and periodicity. Furthermore, the paper addresses the hydro-phobicity achieved on the micro molded surfaces replicated from mold inserts with different LIPSS-based surface topography. Mold surfaces with linear and hexagonal LIPSS and the respective molded parts were analyzed by optical profilometry and scanning electron microscopy to characterize the cavity surfaces replication and localize the weld lines on the micro injection molded parts

The InfraCyrus infrasound sensor

Infrasound sensors are used for a wide range of geophysical applications as the monitoring of volcanic eruptions, the detection of bolides and the recording of infrasounds generated by earthquakes. In 2006 we started the development of cheap infrasound sensors, based on commercial electret microphones. They have been characterized by comparing their response function with existing broadband infrasound sensors. These sensors, called InfraCyrus, have a good response between 1 and 10 Hz, making their application useful for various geophysical purposes. Currently, about a dozen of sensors are deployed in the Neapolitan area showing good performances in the recording of local and regional infrasonic transients

Multi-time delay, multi-point Linear Stochastic Estimation of a cavity shear layer velocity from wall-pressure measurements

Multi-time-delay Linear Stochastic Estimation (MTD-LSE) technique is thoroughly described, focusing on its fundamental properties and potentialities. In the multi-time-delay ap- proach, the estimate of the temporal evolution of the velocity at a given location in the flow field is obtained from multiple past samples of the unconditional sources. The technique is applied to estimate the velocity in a cavity shear layer flow, based on wall-pressure measurements from multiple sensor