475 research outputs found
Three-dimensional shape measurement of a transparent object using a rangefinding approach
This paper describes a non-contact optical measuring approach by which to measure the three-dimensional (3D) shape of a transparent object such as a glass panel or an acrylic plate. In conventional approaches to obtain the 3D shape of a transparent object, contact-type sensors have been widely used. However, the measurement accuracy of contact-type sensors is susceptible to the influence of various factors. In this paper, we propose a novel triangulation-based rangefinding approach that can be applied to the 3D shape of a transparent object or to an opaque object. The rangefinder is based on the fact that the light projected onto the surface of a transparent object is in part reflected by the surface, though the majority of the projected light is transmitted through the surface. From the experimental results, the proposed rangefinding approach has the advantage that it can easily measure the 3D-shape of an object if the object reflects or transmits light, depending on its location. As a result, we conclude that the proposed approach has great potential for a wide range of industrial applications.</p
Galactic Rotation from Cepheids with Gaia DR2 and Effects of Non-Axisymmetry
We apply a simple axisymmetric disc model to 218 Galactic Cepheids whose
accurate measurements of the distance and velocities are obtained by
cross-matching an existing Cepheids catalogue with the Gaia DR2 data. Our model
fit determines the "local centrifugal speed", defined as the
rotation speed required to balance the local radial gravitational force at
the Sun's location to be km s and the Sun's
azimuthal and radial peculiar motions to be km s
and km s, respectively. These results are obtained
with strong priors on the solar radius, kpc, and Sun's angular
rotation velocity, km s kpc. We
also applied the axisymmetric model to mock data from an N-body/hydrodynamic
simulation of a Milky Way-like galaxy with a bar and spiral arms. We find that
our axisymmetric model fit to the young stars recovers the local centrifugal
speed reasonably well, even in the face of significant non-axisymmetry.
However, the local centrifugal speed determined from our Cepheid sample could
suffer from systematic uncertainty as large as 6 km s.Comment: 13 pages, 8 figures, 2 tables, accepted for publication in MNRA
Age Dating the Galactic Bar with the Nuclear Stellar Disc
From the decades of the theoretical studies, it is well known that the
formation of the bar triggers the gas funnelling into the central sub-kpc
region and leads to the formation of a kinematically cold nuclear stellar disc
(NSD). We demonstrate that this mechanism can be used to identify the formation
epoch of the Galactic bar, using an N-body/hydrodynamics simulation of an
isolated Milky Way-like galaxy. As shown in many previous literature, our
simulation shows that the bar formation triggers an intense star formation for
~1 Gyr in the central region, and forms a NSD. As a result, the oldest age
limit of the NSD is relatively sharp, and the oldest population becomes similar
to the age of the bar. Therefore, the age distribution of the NSD tells us the
formation epoch of the bar. We discuss that a major challenge in measuring the
age distribution of the NSD in the Milky Way is contamination from other
non-negligible stellar components in the central region, such as a classical
bulge component. We demonstrate that because the NSD is kinematically colder
than the other stellar populations in the Galactic central region, the NSD
population can be kinematically distinguished from the other stellar
populations, if the 3D velocity of tracer stars are accurately measured. Hence,
in addition to the line-of-sight velocities from spectroscopic surveys, the
accurate measurements of the transverse velocities of stars are necessary, and
hence the near-infrared space astrometry mission, JASMINE, would play a crutial
role to identify the formation epoch of the Galactic bar. We also discuss that
the accuracy of stellar age estimation is also crucial to measure the oldest
limit of the NSD stellar population.Comment: accepted for publication in MNRA
A new method for 3-D shape measurement and surface reflectance of an object with rangefinder
An object for computer graphics application requires the following two information: the three dimensional (3D) shape and surface reflectance property of the object. We proposed a 3D shape and surface reflectance measurement system using the new sensor, which can detect the incidence position and the angle of the light simultaneously. Experimental results successfully demonstrate the efficacy of the method.</p
A new method of measuring the 3-D shape and surface reflectance of an object using a laser rangefinder
The present paper describes a newly proposed method for simultaneously measuring 3D shape and surface reflectance of an object using a laser rangefinder. The original work of this method lies in the advantage that the proposed method measures the surface reflectance using the object itself that is used for the 3D shape measurement. Experimental results show that the proposed method was applicable to noncontact industrial inspection, robot vision in automatic assembly, and reverse engineering.</p
Optimization of Emergence Profile of Implant Prosthesis: A Literature Review
In order to achieve esthetically optimal outcome with implant prosthesis, appropriate topography of emergence profile is crucial. The objective of this review is to explorer current evidence regarding this topic and relevant issue. Extent of interproximal papilla is determined not by the shape of emergence profile but the length between interproximal alveolar bone prominence and interproximal contact of crowns. There have been concerned that multiple times of disconnection and reconnection of abutment enhance peri-implant marginal bone loss, but it’s certified not to be a clinically significant level. Current digital workflow makes this step faster and easier, by copying emergence profile of contralateral tooth or extracted teeth
Age distribution of stars in boxy/peanut/X-shaped bulges formed without bar buckling
Some barred galaxies, including the Milky Way, host a boxy/peanut/X-shaped bulge (BPX-shaped bulge). Previous studies suggested that the BPX-shaped bulge can either be developed by bar buckling or by vertical inner Lindblad resonance (vILR) heating without buckling. In this paper, we study the observable consequence of an BPX-shaped bulge built up quickly after bar formation via vILR heating without buckling, using an N-body/hydrodynamics simulation of an isolated Milky Way-like galaxy. We found that the BPX-shaped bulge is dominated by stars born prior to bar formation. This is because the bar suppresses star formation, except for the nuclear stellar disc (NSD) region and its tips. The stars formed near the bar ends have higher Jacobi energy, and when these stars lose their angular momentum, their non-circular energy increases to conserve Jacobi energy. This prevents them from reaching the vILR to be heated to the BPX region. By contrast, the NSD forms after the bar formation. From this simulation and general considerations, we expect that the age distributions of the NSD and BPX-shaped bulge formed without bar buckling do not overlap each other. Then, the transition age between these components betrays the formation time of the bar, and is testable in future observations of the Milky Way and extra-galactic barred galaxies
A Boundary of National Identity Discourse : Karl Florenz’s Strategy for the Historical Writing of Japanese Literature
Interfacial Microstructure of Solid State Diffusion Bonded Silicon Nitride using Niobium Foils(Materials, Metallurgy & Weldability, INTERNATIONAL SYMPOSIUM OF JWRI 30TH ANNIVERSARY)
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