Institution
University of Electro-Communications
Education•Tokyo, Japan•
About: University of Electro-Communications is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Laser & Robot. The organization has 8041 authors who have published 16950 publications receiving 235832 citations. The organization is also known as: UEC & Denki-Tsūshin Daigaku.
Topics: Laser, Robot, Ion, Mobile robot, Fiber laser
Papers published on a yearly basis
Papers
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National Institutes of Natural Sciences, Japan1, Leiden University2, Ames Research Center3, Harvard University4, Chinese Academy of Sciences5, Ibaraki University6, University of Electro-Communications7, Max Planck Society8, University of Chile9, University of Cologne10, IBM11, Chalmers University of Technology12
TL;DR: In this paper, the authors used the minimum spanning tree (MST) technique to characterize the separation between cores and their spatial distribution, and to derive mass segregation ratios, and they test several theoretical conditions and conclude that overall, competitive accretion and global hierarchical collapse scenarios are favored over the turbulent core accretion scenario.
Abstract: © 2019. The American Astronomical Society. All rights reserved. The ALMA Survey of 70 μm dark High-mass clumps in Early Stages (ASHES) is designed to systematically characterize the earliest stages and constrain theories of high-mass star formation. Twelve massive (>500 M⊙ ), cold (≤15 K), 3.6-70 μm dark prestellar clump candidates, embedded in infrared dark clouds, were carefully selected in the pilot survey to be observed with the Atacama Large Millimeter/submillimeter Array (ALMA). We have mosaicked each clump (∼1 arcmin2) in continuum and line emission with the 12 m, 7 m, and Total Power (TP) arrays at 224 GHz (1.34 mm), resulting in ∼1.″2 resolution (∼4800 au, at the average source distance). As the first paper in the series, we concentrate on the continuum emission to reveal clump fragmentation. We detect 294 cores, from which 84 (29%) are categorized as protostellar based on outflow activity or "warm core" line emission. The remaining 210 (71%) are considered prestellar core candidates. The number of detected cores is independent of the mass sensitivity range of the observations and, on average, more massive clumps tend to form more cores. We find a large population of low-mass ( 30 M⊙) prestellar cores (maximum mass 11 M⊙). From the prestellar core mass function, we derive a power-law index of 1.17 ± 0.10, which is slightly shallower than Salpeter. We used the minimum spanning tree (MST) technique to characterize the separation between cores and their spatial distribution, and to derive mass segregation ratios. While there is a range of core masses and separations detected in the sample, the mean separation and mass per clump are well explained by thermal Jeans fragmentation and are inconsistent with turbulent Jeans fragmentation. Core spatial distribution is well described by hierarchical subclustering rather than centrally peaked clustering. There is no conclusive evidence of mass segregation. We test several theoretical conditions and conclude that overall, competitive accretion and global hierarchical collapse scenarios are favored over the turbulent core accretion scenario.
117 citations
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TL;DR: In this paper, high-power laser experiments yield an optical-to-optical conversion efficiency of 30% for Nd (0.6 at%):YAG ceramic as compared to 34% for an Nd single crystal.
Abstract: Nd: YAG ceramic materials have been synthesized using vacuum sintering technique with the raw materials prepared by the nano-crystalline methods. The spectroscopic studies suggest overall improvement in absorption and emission and reduction in scattering loss. Judd-Ofelt analysis has been employed to compute the relevant spectroscopic and radiative parameters of the material. The SEM and TEM measurements reveal the excellent optical quality of the ceramic with low pore volume and narrow grain boundary. Fluorescence and Raman measurements reveal that the Nd/sup 3+/-doped YAG ceramic is almost equivalent to its single-crystal counterpart in its radiative and nonradiative properties. Individual Stark levels for /sup 2s+1/L/sub J/ manifolds are obtained from the absorption and fluorescence spectra and are analyzed to identify the stimulated emission channels possible in the Nd: YAG ceramic. Laser performance studies favor the use of high-concentration Nd: YAG ceramics in the design of an efficient microchip laser. With 4 at% Nd: YAG ceramic acting as a microchip laser, we obtained a slope efficiency of 40%. High-power laser experiments yield an optical-to-optical conversion efficiency of 30% for Nd (0.6 at%):YAG ceramic as compared to 34% for an Nd (0.6 at%):YAG single crystal. The oscillation experiments at 1.3 mm gives a slope efficiency of 35%. Optical gain measurements conducted in these materials also show values comparable to single crystal, supporting that these materials could be suitable substitutes to single crystals in solid-state laser applications.
116 citations
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TL;DR: A double-slit interference of ultracold neon atoms in the 1$ s3 metastable state is studied, and because of gravity acceleration the atom changes its velocity as much as 2 m/s during the passage of the interference.
Abstract: A double-slit interference of ultracold neon atoms in the 1${\mathit{s}}_{3}$ metastable state is studied. The interferometer is aligned vertically, and because of gravity acceleration the atom changes its velocity as much as 2 m/s during the passage of the interference. The interference fringes are observed for the initial atomic velocity between 0 and 2 m/s.
116 citations
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TL;DR: It is demonstrated that the structural information, in particular the differential elastic scattering cross sections of the target ion by free electrons, can be accurately extracted from the intensity distributions of photoelectrons on the ridges, thus effecting a first step toward laser-induced self-imaging of thetarget, with unprecedented spatial and temporal resolutions.
Abstract: We have measured two-dimensional photoelectron momentum spectra of Ne, Ar, and Xe generated by 800-nm, 100-fs laser pulses and succeeded in identifying the spectral ridge region (back-rescattered ridges) which marks the location of the returning electrons that have been backscattered at their maximum kinetic energies. We demonstrate that the structural information, in particular the differential elastic scattering cross sections of the target ion by free electrons, can be accurately extracted from the intensity distributions of photoelectrons on the ridges, thus effecting a first step toward laser-induced self-imaging of the target, with unprecedented spatial and temporal resolutions.
116 citations
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TL;DR: In this article, the authors measured photoluminescence (PL) excitation spectra of TiO 2 powders with various rutile phase contents, and found a correlation between the energy level of the PL excitation band (E PLE ) and the RUTile phase content.
116 citations
Authors
Showing all 8079 results
Name | H-index | Papers | Citations |
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Mildred S. Dresselhaus | 136 | 762 | 112525 |
Matthew Nguyen | 131 | 1291 | 84346 |
Juan Bisquert | 107 | 450 | 46267 |
Dapeng Yu | 94 | 745 | 33613 |
Riichiro Saito | 91 | 502 | 48869 |
Shun-ichi Amari | 90 | 495 | 40383 |
Shigeru Nagase | 76 | 617 | 22099 |
Ingrid Verbauwhede | 72 | 575 | 21110 |
Satoshi Hasegawa | 69 | 708 | 22153 |
Yu Qiao | 69 | 484 | 29922 |
Yukio Tanaka | 68 | 744 | 19942 |
Zhijun Li | 68 | 614 | 14518 |
Iván Mora-Seró | 67 | 235 | 23229 |
Kazuo Tanaka | 63 | 535 | 27559 |
Da Xing | 63 | 624 | 14766 |