27,569 research outputs found
Feature Lines for Illustrating Medical Surface Models: Mathematical Background and Survey
This paper provides a tutorial and survey for a specific kind of illustrative
visualization technique: feature lines. We examine different feature line
methods. For this, we provide the differential geometry behind these concepts
and adapt this mathematical field to the discrete differential geometry. All
discrete differential geometry terms are explained for triangulated surface
meshes. These utilities serve as basis for the feature line methods. We provide
the reader with all knowledge to re-implement every feature line method.
Furthermore, we summarize the methods and suggest a guideline for which kind of
surface which feature line algorithm is best suited. Our work is motivated by,
but not restricted to, medical and biological surface models.Comment: 33 page
Variation propagation of bench vises in multi-stage machining processes
Comunicación presentada a MESIC 2019 8th Manufacturing Engineering Society International Conference (Madrid, 19-21 de Junio de 2019)Variation propagation has been successfully modeled by the Stream of Variation (SoV) approach in multistage machining processes. However, the SoV model basically supports 3-2-1 fixtures based on punctual locators and other workholding systems such as conventional vises are not considered yet. In this paper, the SoV model is expanded to include the fixture- and datum-induced variations on workholding devices such as bench vises. The model derivation is validated through assembly and machining simulations on Computer Aided Design software. The case study analyzed shows an average error of part quality prediction between the SoV model and the CAD simulations of 0.26%
Apparatus for recovering matter adhered to a host surface
The development of an apparatus for removing and recovering matter adhered to a host surface is described. The device consists of a pickup head with an ultrasonic transducer adapted to deliver ultrasonic pressure waves against the material. The ultrasonic waves agitate the material and cause its separation from the surface. A vacuum system recovers the material and delivers it to suitable storage containers
Determining the galactic mass distribution using tidal streams from globular clusters
We discuss how to use tidal streams from globular clusters to measure the
mass distribution of the Milky Way. Recent proper motion determinations for
globular clusters from plate measurements and Hipparcos astrometry provide
several good candidates for Galactic mass determinations in the intermediate
halo, far above the Galactic disk, including Pal 5, NGC 4147, NGC 5024 (M53)
and NGC 5466; the remaining Hipparcos clusters provide candidates for
measurements several kpc above and below the disk. These clusters will help
determine the profile and shape of the inner halo. To aid this effort, we
present two methods of mass determination: one, a generalization of
rotation-curve mass measurements, which gives the mass and potential from
complete position-velocity observations for stream stars; and another using a
simple chi^2 estimator, which can be used when only projected positions and
radial velocities are known for stream stars. We illustrate the use of the
latter method using simulated tidal streams from Pal 5 and find that fairly
accurate mass determinations are possible even for relatively poor data sets.
Follow-up observations of clusters with proper motion determinations may reveal
tidal streams; obtaining radial velocity measurements would enable accurate
measurements of the mass distribution in the inner Galaxy.Comment: 21 pages, 6 figures, published in A
Models of rotating coronae
Fitting equilibrium dynamical models to observational data is an essential
step in understanding the structure of the gaseous hot haloes that surround our
own and other galaxies. However, the two main categories of models that are
used in the literature are poorly suited for this task: (i) simple barotropic
models are analytic and can therefore be adjusted to match the observations,
but are clearly unrealistic because the rotational velocity does
not depend on the distance from the galactic plane, while (ii) models
obtained as a result of cosmological galaxy formation simulations are more
realistic, but are impractical to fit to observations due to high computational
cost. Here we bridge this gap by presenting a general method to construct
axisymmetric baroclinic equilibrium models of rotating galactic coronae in
arbitrary external potentials. We consider in particular a family of models
whose equipressure surfaces in the plane are ellipses of varying axis
ratio. These models are defined by two one-dimensional functions, the axial
ratio of pressure and the value of the pressure along the galaxy's symmetry axis. These models can have a rotation
speed that realistically decreases as one moves away from the
galactic plane, and can reproduce the angular momentum distribution found in
cosmological simulations. The models are computationally cheap to construct and
can thus be used in fitting algorithms. We provide a python code that given
, and returns ,
, , . We show a few examples of these models using
the Milky Way as a case study.Comment: Accepted for publication in MNRA
Effects of jets, wakes, and vortices on lifting surfaces
The interaction of jets, wakes, and vortices on lifting bodies represents a broad spectrum of aerodynamic flow phenomena. A literature survey is presented of 79 research activities in related aerodynamic situations
A comparison of slip, disjoining pressure, and interface formation models for contact line motion through asymptotic analysis of thin two-dimensional droplet spreading
The motion of a contact line is examined, and comparisons drawn, for a
variety of models proposed in the literature. Pressure and stress behaviours at
the contact line are examined in the prototype system of quasistatic spreading
of a thin two-dimensional droplet on a planar substrate. The models analysed
include three disjoining pressure models based on van der Waals interactions, a
model introduced for polar fluids, and a liquid-gas diffuse-interface model;
Navier-slip and two non-linear slip models are investigated, with three
microscopic contact angle boundary conditions imposed (two of these contact
angle conditions having a contact line velocity dependence); and the interface
formation model is also considered. In certain parameter regimes it is shown
that all of the models predict the same quasistatic droplet spreading
behaviour.Comment: 29 pages, 3 figures, J. Eng. Math. 201
Multi-touch 3D Exploratory Analysis of Ocean Flow Models
Modern ocean flow simulations are generating increasingly complex, multi-layer 3D ocean flow models. However, most researchers are still using traditional 2D visualizations to visualize these models one slice at a time. Properly designed 3D visualization tools can be highly effective for revealing the complex, dynamic flow patterns and structures present in these models. However, the transition from visualizing ocean flow patterns in 2D to 3D presents many challenges, including occlusion and depth ambiguity. Further complications arise from the interaction methods required to navigate, explore, and interact with these 3D datasets. We present a system that employs a combination of stereoscopic rendering, to best reveal and illustrate 3D structures and patterns, and multi-touch interaction, to allow for natural and efficient navigation and manipulation within the 3D environment. Exploratory visual analysis is facilitated through the use of a highly-interactive toolset which leverages a smart particle system. Multi-touch gestures allow users to quickly position dye emitting tools within the 3D model. Finally, we illustrate the potential applications of our system through examples of real world significance
Peen plating
A process for metal plating which comprises spraying a mixture of metallic powder and small peening particles at high velocity against a surface is described. The velocity must be sufficient to impact and bond metallic powder onto the surface. In the case of metal surfaces, the process has as one of its advantages providing mechanical working (hardening) of the surface simultaneously with the metal plating
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