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Search Results: 1 - 10 of 117891 matches for " T. Ebisuzaki "
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Hands-On TAROT: Intercontinental use of the TAROT for Education and Public Outreach
M. Boer,C. Thiebaut,A. Klotz,G. Buchholtz,A. L. Melchior,C. Pennypacker,T. Ebisuzaki
Physics , 2001,
Abstract: The TAROT telescope has for primary goal the search for the prompt optical counterpart of Cosmic Gamma-Ray Bursts. It is a completely autonomous 25cm telescope installed near Nice (France), able to point any location of the sky within 1-2 seconds. The control, scheduling, and data processing activities are completely automated, so the instrument is completely autonomous. In addition to its un-manned modes, we added recently the possibility to remotely control the telescope, as a request of the "Hands-On Universe" (HOU) program for exchange of time within automatic telescopes for the education and public outreach. To this purpose we developed a simple control interface. A webcam was installed to visualize the telescope. Access to the data is possible through a web interface. The images can be processed by the HOU software, a program specially suited for use within the classroom. We experienced these feature during the open days of the University of California Berkeley and the Astronomy Festival of Fleurance (France). We plan a regular use for an astronomy course of the Museum of Tokyo, as well as for French schools. Not only does Hands-On TAROT gives the general public an access to professional astronomy, but it is also a more general tool to demonstrate the use of a complex automated system, the techniques of data processing and automation. Last but not least, through the use of telescopes located in many countries over the globe, a form of powerful and genuine cooperation between teachers and children from various countries is promoted, with a clear educational goal.
Hands-On Universe: A Global Program for Education and Public Outreach in Astronomy
M. Boer,H. Pack,C. Pennypacker,A. L. Melchior,S. Faye,T. Ebisuzaki
Mathematics , 2001,
Abstract: Hands-On Universe (HOU) is an educational program that enables students to investigate the Universe while applying tools and concepts from science, math, and technology. Using the Internet, HOU participants around the world request observations from an automated telescope, download images from a large image archive, and analyze them with the aid of user-friendly image processing software. This program is developing now in many countries, including the USA, France, Germany, Sweden, Japan, Australia, and others. A network of telescopes has been established among these countries, many of them remotely operated, as shown in the accompanying demo. Using this feature, students in the classroom are able to make night observations during the day, using a telescope placed in another country. An archive of images taken on large telescopes is also accessible, as well as resources for teachers. Students are also dealing with real research projects, e.g. the search for asteroids, which resulted in the discovery of a Kuiper Belt object by high-school students. Not only Hands-On Universe gives the general public an access to professional astronomy, but it is also a more general tool to demonstrate the use of a complex automated system, the techniques of data processing and automation. Last but not least, through the use of telescopes located in many countries over the globe, a form of powerful and genuine cooperation between teachers and children from various countries is promoted, with a clear educational goal.
Algorithm for Linear Response Functions at Finite Temperatures: Application to ESR spectrum of s=1/2 Antiferromagnet Cu benzoate
Toshiaki Iitaka,Toshikazu Ebisuzaki
Physics , 2002, DOI: 10.1103/PhysRevLett.90.047203
Abstract: We introduce an efficient and numerically stable method for calculating linear response functions $\chi(\vec{q},\omega)$ of quantum systems at finite temperatures. The method is a combination of numerical solution of the time-dependent Schroedinger equation, random vector representation of trace, and Chebyshev polynomial expansion of Boltzmann operator. This method should be very useful for a wide range of strongly correlated quantum systems at finite temperatures. We present an application to the ESR spectrum of s=1/2 antiferromagnet Cu benzoate.
Calculating response functions in time domain with non-orthonormal basis sets
Toshiaki Iitaka,Toshikazu Ebisuzaki
Physics , 2000, DOI: 10.1103/PhysRevE.61.R3314
Abstract: We extend the recently proposed order-N algorithms (cond-mat/9703224) for calculating linear- and nonlinear-response functions in time domain to the systems described by nonorthonormal basis sets.
Astrophysical ZeV acceleration in the relativistic jet from an accreting supermassive blackhole
Toshikazu Ebisuzaki,Toshiki Tajima
Physics , 2013, DOI: 10.1016/j.astropartphys.2014.02.004
Abstract: An accreting supermassive blackhole, the central engine of active galactic nucleus (AGN), is capable of exciting extreme amplitude Alfven waves whose wavelength (wave packet) size is characterized by its clumpiness. The pondermotive force and wakefield are driven by these Alfven waves propagating in the AGN (blazar) jet and accelerate protons/nuclei to extreme energies beyond Zetta-electron volt (ZeV$=10^{21}$ eV). Such acceleration is prompt, localized, and does not suffer from the multiple scattering/bending enveloped in the Fermi acceleration that causes excessive synchrotron radiation loss beyond $10^{19}$ eV. The production rate of ZeV cosmic rays is found to be consistent with the observed gamma-ray luminosity function of blazars and their time variabilities.
First Principles Calculation of Elastic Properties of Solid Argon at High Pressures
Toshiaki Iitaka,Toshikazu Ebisuzaki
Physics , 2001, DOI: 10.1103/PhysRevB.65.012103
Abstract: The density and the elastic stiffness coefficients of fcc solid argon at high pressures from 1 GPa up to 80 GPa are computed by first-principles pseudopotential method with plane-wave basis set and the generalized gradient approximation (GGA). The result is in good agreement with the experimental result recently obtained with the Brillouin spectroscopy by Shimizu et al. [Phys. Rev. Lett. 86, 4568 (2001)]. The Cauchy condition was found to be strongly violated as in the experimental result, indicating large contribution from non-central many-body force. The present result has made it clear that the standard density functional method with periodic boundary conditions can be successfully applied for calculating elastic properties of rare gas solids at high pressures in contrast to those at low pressures where dispersion forces are important.
Non-degenerate Two Photon Absorption Spectra of Si Nanocrystallites
Toshiaki Iitaka,Toshikazu Ebisuzaki
Physics , 1999,
Abstract: We propose an efficient linear-scaling time-dependent method for calculating nonlinear response function, and study the size effects in non-degenerate two photon absorption spectra of Si nanocrystallites by using semi-empirical pseudopotentials.
Random phase vector for calculating the trace of a large matrix
Toshiaki Iitaka,Toshikazu Ebisuzaki
Physics , 2004, DOI: 10.1103/PhysRevE.69.057701
Abstract: We derive an estimate of statistical error in calculating the trace of a large matrix by using random vector, and show that {\em random phase vector} gives the results with the smallest statistical error for a given basis set. This result supports use of random phase vectors in the calculation of density of states and linear response functions of large quantum systems.
Methane Hydrate under High Pressure: Searching for Centering of Hydrogen Bonds
Toshiaki Iitaka,Toshikazu Ebisuzaki
Physics , 2003, DOI: 10.1103/PhysRevB.68.172105
Abstract: The structural, electronic, and spectroscopic properties of a high-pressure phase of methane hydrate (MH-III) are studied by first principles electronic structure calculations. A detailed analysis of the atomic positions suggests that {\it ionization} of hydrogen-bonded water molecules occurs around 40GPa and {\it centering} or symmetrization of hydrogen-bonds occurs around 70 GPa. These pressures are much lower compared with ioninzation around 55 GPa and centering around 100 GPa in pure ice. The transition may be observed with low-temperature IR/Raman spectroscopy of OH stretching modes or neutron diffraction.
The focal surface of the JEM-EUSO instrument
Y. Kawasaki, M. Casolino, P. Gorodetzky, A. Santangelo, M. Ricci, F. Kajino, T. Ebisuzaki,the JEM-EUSO collaboration
Astrophysics and Space Sciences Transactions (ASTRA) , 2011, DOI: 10.5194/astra-7-167-2011
Abstract: The Extreme Universe Space Observatory on JEM/EF (JEM-EUSO) is a space mission to study extremely high-energy cosmic rays. The JEM-EUSO instrument is a wide-angle refractive telescope in the near-ultraviolet wavelength region which will be mounted to the International Space Station. Its goal is to measure time-resolved fluorescence images of extensive air showers in the atmosphere. In this paper we describe in detail the main features and technological aspects of the focal surface of the instrument. The JEM-EUSO focal surface is a spherically curved surface, with an area of about 4.5 m2. The focal surface detector is made of more than 5000 multi-anode photomultipliers (MAPMTs). Current baseline is Hamamatsu R11265-03-M64. The approach to the focal surface detector is highly modular. Photo-Detector-Modules (PDM) are the basic units that drive the mechanical structure and data acquisition. Each PDM consists of 9 Elementary Cells (ECs). The EC, which is the basic unit of the MAPMT support structure and of the front-end electronics, contains 4 units of MAPMTs. In total, about 1 200 ECs or about 150 PDMs are arranged on the whole of the focal surface of JEM-EUSO.
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