Showing papers by "University of Electro-Communications published in 2000"
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01 Jan 20002,534 citations
TL;DR: In this article, the effect of trigonal warping on the energy dispersion relations near the Fermi energy splits the peaks of the density of states for metallic nanotubes, and the magnitude of this effect depends on the chiral angle of the carbon nanotube.
Abstract: Chirality-dependent van Hove singularities (vHs) of the one-dimensional electronic density of states (DOS) are discussed in connection with resonant Raman spectroscopy. The effect of trigonal warping on the energy dispersion relations near the Fermi energy splits the peaks of the density of states for metallic nanotubes, and the magnitude of this effect depends on the chiral angle of the carbon nanotube. The width of the peak splitting has a maximum for metallic zigzag nanotubes, and no splitting is obtained for armchair nanotubes or semiconducting nanotubes. We also find an additional logarithmic singularity in the electronic DOS for carbon nanotubes that is related to a two-dimensional singularity, which does not depend on either the diameter or the chirality.
631 citations
TL;DR: A new inequality is shown between the errors of the first kind and the second kind, which complements the result of Hiai and Petz (1991) to establish the quantum version of Stein's lemma and yields the strong converse in quantum hypothesis testing.
Abstract: The hypothesis testing problem for two quantum states is treated. We show a new inequality between the errors of the first kind and the second kind, which complements the result of Hiai and Petz (1991) to establish the quantum version of Stein's lemma. The inequality is also used to show a bound on the probability of errors of the first kind when the power exponent for the probability of errors of the second kind exceeds the quantum relative entropy, which yields the strong converse in quantum hypothesis testing. Finally, we discuss the relation between the bound and the power exponent derived by Han and Kobayashi (1989) in classical hypothesis testing.
384 citations
01 Oct 2000
TL;DR: In this article, a polycrystalline Nd-doped Y3Al5O12 ceramics was used for the first time to achieve highly efficient laser oscillation at 1064 nm.
Abstract: Optical absorption, emission spectra have been measured for polycrystalline Nd-doped Y3Al5O12 ceramics. Fluorescence lifetimes of 257.6 μs, 237.6 μs, 184.2 μs and 95.6 μs have been obtained for 0.6%, 1%, 2% and 4% neodymium-doped YAG ceramics, respectively. For the first time, highly efficient laser oscillation at 1064 nm has been obtained with this kind of ceramics. Slope efficiency of 53% has been achieved on a uncoated 4.8-mm thick 1% Nd:YAG ceramics sample. Optical to optical conversion efficiency is 47.6%. Laser oscillation has also been obtained with a 2% Nd:YAG ceramics. The optical properties and laser output results have been compared with that of Nd:YAG single crystal grown by the Czochralski method. Almost identical results have been achieved including laser experiments results. But fabrication of Nd:YAG ceramics is much easier compared to the single-crystal growth method. And also large size (now of about 400 mm diameter×5 mm is available) and high-concentration (>1%) Nd:YAG ceramics can be fabricated. The results show that this kind of Nd:YAG ceramics is a very good alternative to Nd:YAG single crystal.
361 citations
TL;DR: A new parallel distributed compensation, the so-called "twin parallel distributed compensations" (TPDC) to realize the nonlinear model following control, is proposed and a design technique based on the TPDC is presented.
Abstract: This paper defines a fuzzy descriptor system by extending the ordinary Takagi-Sugeno (T-S) fuzzy model. Several kinds of stability conditions for the fuzzy descriptor system are derived and represented in terms of linear matrix inequalities (LMIs). We illustrate an example of defining the fuzzy descriptor system instead of the ordinary T-S fuzzy model. An LMI design approach is employed to find stable feedback gains and a common Lyapunov function. In addition, this paper presents a nonlinear model following control for the fuzzy descriptor system. A new parallel distributed compensation, the so-called "twin parallel distributed compensations" (TPDC) to realize the nonlinear model following control, is proposed. We present a design technique based on the TPDC. The proposed method is a unified approach to nonlinear model following control. It contains the regulation and servo control problems as special cases.
344 citations
TL;DR: Polarized Raman spectra of high purity aligned arrays of multiwalled carbon nanotubes, prepared on silica substrates from the thermal decomposition of a ferrocene-xylene mixture, show a strong dependence of the graphitelike G band and the disorder-induced D band on the polarization geometry employed in the experiments.
Abstract: Polarized Raman spectra of high purity aligned arrays of multiwalled carbon nanotubes, prepared on silica substrates from the thermal decomposition of a ferrocene-xylene mixture, show a strong dependence of the graphitelike G band and the disorder-induced D band on the polarization geometry employed in the experiments. The experimental G-band intensity exhibits a minimum at straight theta(m) = 55 degrees in the VV configuration, in good agreement with theoretical predictions of a characteristic minimum at 54.7 degrees for A(1g) modes in single wall nanotubes, where straight theta(m) denotes the angle between the polarization direction and the nanotube axis.
322 citations
TL;DR: Polarized Raman spectra were obtained from a rope of aligned semiconducting single-wall nanotubes (SWNTs) in the vicinity of the D band and the G band based on group theory analysis and related theoretical predictions.
Abstract: Polarized Raman spectra were obtained from a rope of aligned semiconducting single-wall nanotubes (SWNTs) in the vicinity of the D band and the G band. Based on group theory analysis and related theoretical predictions, the G-band profile was deconvolved into four intrinsic SWNT components with the following symmetry assignments: 1549 cm(-1) [E-2(E-2g)], 1567 cm(-1) [A(A(1g)) + E-1(E-1g)], 1590 cm(-1) [A(A(1g)) + E-1(E-1g)] and 1607 cm(-1) [E-2(E-2g)]. The frequency shifts of the tangential G modes from the 2D graphitelike E-2g2 frequency are discussed in terms of the nanotube geometry.
206 citations
TL;DR: TiO2 powder seemed to be a broad potential matrix for low molecular mass polar or non-polar analytes, and can be readily applied to obtain the low background noise MALDI-TOF mass spectra of small-sized compounds.
Abstract: Fine metal or metal oxide powder as an alternative to conventional organic matrices in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) has been utilized successfully for lower molecular mass analytes, poly(ethylene glycol) 200 (PEG 200) and methyl stearate. Eleven kinds of particle, Al, Mn, Mo, Si, Sn, SnO2, TiO2, W, WO3, Zn and ZnO, were evaluated. The analyte was mixed with a metal or metal oxide powder (inorganic matrix) with particle diameter of tens of micrometers and liquid dispersant, followed by application to the sample target. Using a commercial MALDI-TOFMS instrument equipped with an internal 337 nm pulsed nitrogen laser, the analytes, PEG 200 and methyl stearate, were ionized as the alkali metal ion adducted molecules [M+Na]+ or [M+K]+ when the inorganic matrices Mn, Mo, Si, Sn, TiO2, W, WO3, Zn or ZnO were used. In the case of an Al matrix, PEG 200 was ionized as [M+K]+, whereas methyl stearate was ionized as [M+H]+ and [M+Al]+. These particles have potential as the matrix for MALDI. During our examination, however, only SnO2 particles did not ionize either PEG 200 or methyl stearate. Based on our protocol, when TiO2 powder was suspended with liquid paraffin, PEG 200 and methyl stearate gave their MALDI-TOF mass spectra with the lowest background noise and highest intensity. TiO2 powder seemed to be a broad potential matrix for low molecular mass polar or non-polar analytes. The results suggested that bulk particles caused rapid heating/vaporization processes and ionized analyte molecules under irradiation with a pulsed UV laser. The present method can be readily applied to obtain the low background noise MALDI-TOF mass spectra of small-sized compounds.
194 citations
26 Mar 2000
TL;DR: A fast and robust method for tracking positions of the centers and the fingertips of both right and left hands, which makes use of infrared camera images for reliable detection of a user's hands, and uses a template matching strategy for finding fingertips.
Abstract: We introduce a fast and robust method for tracking positions of the centers and the fingertips of both right and left hands. Our method makes use of infrared camera images for reliable detection of a user's hands, and uses a template matching strategy for finding fingertips. This method is an essential part of our augmented desk interface in which a user can, with natural hand gestures, simultaneously manipulate both physical objects and electronically projected objects on a desk, e.g., a textbook and related WWW pages. Previous tracking methods which are typically based on color segmentation or background subtraction simply do not perform well in this type of application because an observed color of human skin and image backgrounds may change significantly due to protection of various objects onto a desk. In contrast, our proposed method was shown to be effective even in such a challenging situation through demonstration in our augmented desk interface. This paper describes the details of our tracking method as well as typical applications in our augmented desk interface.
185 citations
TL;DR: In this paper, a simple analysis of magnetic field intensity (horizontal and vertical magnetic field components) at both stations was found to be closely correlated with geomagnetic ΣKp activity, a detailed analysis of the difference of H and Z components at the two stations, the polarization analysis (Z/H) and fractal analysis (frequency spectrum slope) at these two stations has yielded that the ULF emissions (in the frequency range from 5 mHz to 30 mHz) about 1.5-1.0 months before the quake are likely to be a precurs
Abstract: ULF electromagnetic emissions associated with a large earthquake occurred at Biak Island, Indonesia at 5h 59m UT on February 17, 1996 (magnitude (Mw) = 8.2 and depth = 20 km from USGS catalog), have been investigated on the basis of ULF magnetic observations at two stations, Biak and Darwin in Australia (about 1,200 km apart). Though a simple analysis of magnetic field intensity (horizontal and vertical magnetic field components) at both stations was found to be closely correlated with geomagnetic ΣKp activity, a detailed analysis of the difference of H and Z components at the two stations, the polarization analysis (Z/H) and fractal analysis (frequency spectrum slope) at these two stations has yielded that the ULF emissions (in the frequency range from 5 mHz to 30 mHz) about 1.5–1.0 months before the quake are likely to be a precursory signature of the quake with its intensity on the order of 0.2–0.3 nT.
176 citations
TL;DR: In this article, a linear and ring Raman oscillator based on PbWO 4 was demonstrated in lead tungstate in the nanosecond regime, where the resonators were pumped by the fundamental and second harmonic wavelengths, respectively, of a Q-switched Nd 3+ :Y 3 Al 5 O 12 laser.
24 Apr 2000
TL;DR: This paper introduces the RoboCup-Rescue Simulation Project, a contribution to the disaster mitigation, search and rescue problem, a comprehensive urban disaster simulator constructed on distributed computers that provides a virtual reality training function for the public.
Abstract: This paper introduces the RoboCup-Rescue Simulation Project, a contribution to the disaster mitigation, search and rescue problem. A comprehensive urban disaster simulator is constructed on distributed computers. Heterogeneous intelligent agents such as fire fighters, victims and volunteers conduct search and rescue activities in this virtual disaster world. A real world interface integrates various sensor systems and controllers of infrastructures in the real cities with the virtual world. Real-time simulation is synchronized with actual disasters, computing complex relationship between various damage factors and agent behaviors. A mission-critical man-machine interface provides portability and robustness of disaster mitigation centers, and augmented-reality interfaces for rescue parties in real disasters. It also provides a virtual reality training function for the public. This diverse spectrum of RoboCup-Rescue contributes to the creation of the safer social system.
TL;DR: A unified systematic framework for designing dynamic feedback controllers for nonlinear systems described by Takagi–Sugeno (T–S) models is presented, which can be applied to hybrid or switching systems.
TL;DR: In this article, the Dirichlet eigenvalue optimization problem was studied and the existence and properties of the optimal solutions were investigated. But their qualitative properties and numerical results were not discussed.
Abstract: We consider the following eigenvalue optimization problem: Given a bounded domain Ω⊂ℝ and numbers α > 0, A∈[ 0, |Ω|], find a subset D⊂Ω of area A for which the first Dirichlet eigenvalue of the operator −Δ+αχ
D
is as small as possible. We prove existence of solutions and investigate their qualitative properties. For example, we show that for some symmetric domains (thin annuli and dumbbells with narrow handle) optimal solutions must possess fewer symmetries than Ω on the other hand, for convex Ω reflection symmetries are preserved. Also, we present numerical results and formulate some conjectures suggested by them.
TL;DR: In this paper, the magnetic properties of carbon nanotubes are investigated in the presence of disorder and a magnetic field parallel or perpendicular to the nanotube axis. And the effect of disorder on this magnetic-field-related mechanism is considered with a discussion of mean free paths, localization lengths, and magnetic dephasing rate in the context of recent experiments.
Abstract: The electronic properties of carbon nanotubes are investigated in the presence of disorder and a magnetic field parallel or perpendicular to the nanotube axis. In the parallel field geometry, the ${\ensuremath{\varphi}}_{0}$-periodic $({\ensuremath{\varphi}}_{0}=hc/e)$ metal-insulator transition induced in metallic or semiconducting nanotubes is shown to be related to a chirality-dependent shifting of the energy of the van Hove singularities (VHS's). The effect of disorder on this magnetic-field-related mechanism is considered with a discussion of mean free paths, localization lengths, and magnetic dephasing rate in the context of recent experiments.
07 May 2000
TL;DR: Two results concerning the fuzzy modeling and control of nonlinear systems using linear Takagi-Sugeno (T-S) fuzzy models and the approximation of smooth nonlinear state-feedback controllers using the so-called parallel distributed compensation (PDC) controller are presented.
Abstract: We present two results concerning the fuzzy modeling and control of nonlinear systems. The first result is on the approximation of smooth nonlinear dynamical systems using linear Takagi-Sugeno (T-S) fuzzy models. The second result is on the approximation of smooth nonlinear state-feedback controllers using the so-called parallel distributed compensation (PDC) controller. Both results are based on the effectiveness of using linear Takagi-Sugeno systems to approximate nonlinear function, which is also proved in this paper.
TL;DR: Fan filters designed with the proposed method are used to demonstrate that the beam-space adaptive array can suppress interference signals having a wide fractional bandwidth and that the array has fast convergence.
Abstract: We propose a a wideband beamspace adaptive array that uses FIR fan filters to construct a multibeam forming network. We also describe a method for designing such FIR fan filters. Approximation is achieved by combining spectral transformation and the window method such that the beam patterns including the sidelobe characteristics of the resulting fan filters are virtually frequency independent. This is a requirement of beamforming networks used in multibeam forming. Fan filters designed with the proposed method are used to demonstrate that the beam-space adaptive array can suppress interference signals having a wide fractional bandwidth and that the array has fast convergence.
TL;DR: The Raman coherence prepared with two coaxial single-mode lasers beats with multimode laser radiation with very broad bandwidth and efficiently replicates the broadband nature to the Raman sidebands without the restriction of phase matching.
Abstract: Parametric Raman sideband generation is investigated using strongly driven Raman coherence in solid hydrogen We show that the Raman coherence prepared with two coaxial single-mode lasers beats with multimode laser radiation with very broad bandwidth and efficiently replicates the broadband nature to the Raman sidebands without the restriction of phase matching We demonstrate that this efficient replication occurs mainly on the negative side of Raman detuning, where the medium adiabatically follows the antiphased state
TL;DR: By recovering a drawing order of a handwritten script, the temporal information can be recovered from a static 2D image and this method will be used as a bridge from the offline handwriting character recognition problem to the online one.
Abstract: Describes a method to recover a drawing order of a handwritten script from a static 2D image. The script should be written in a single stroke and may include double-traced lines. After the script is scanned in and preprocessed, we apply our recovery method which consists of two phases. In the first phase, we globally analyze the graph constructed from the skeletal image and label the graph by determining the types of each edge. In the second phase, we trace the graph from the start vertex to the end vertex using the labeling information. This method does not enumerate the possible cases, for example, by solving the traveling salesman problem and, therefore, does not cause a combinatorial explosion even if the script is very complex. By recovering a drawing order of a handwritten script, the temporal information can be recovered from a static 2D image. Hence, this method will be used as a bridge from the offline handwriting character recognition problem to the online one.
TL;DR: In this paper, the authors show that the one-dimensional copper complex [PMCu(NO3)2(H2O)2]n behaves like a uniform S = 1/2 antiferromagnetic Heisenberg chain, characterized by the exchange parameter J/kB = 36 K.
Abstract: Single-crystal magnetic susceptibility and specific heat studies of the one-dimensional copper complex [PMCu(NO3)2(H2O)2]n (PM = pyrimidine) show that it behaves like a uniform S = 1/2 antiferromagnetic Heisenberg chain, characterized by the exchange parameter J/kB = 36 K. Specific heat measurements in the applied magnetic field, however, reveal the formation of a field-induced spin excitation gap, whose magnitude depends on the magnitude and direction of the field. This behaviour is inconsistent with the ideal S = 1/2 Heisenberg chain. In the low-temperature region, a contribution to the susceptibility, approximately proportional to 1/T, is observed which varies strongly with the varying direction of the magnetic field. The field-induced gap and the 1/T contribution are largest for the same field direction. Previous observations of a field-induced gap in the related compounds copper benzoate and Yb4As3 have been explained by the alternating g tensor and alternating Dzyaloshinkii-Moriya interaction, producing an effective staggered magnetic field at the Cu and Yb ions. We apply this model to [PMCu(NO3)2(H2O)2]n and obtain a consistent quantitative explanation of the low-temperature susceptibility, the field-induced gap and their dependence on the magnetic-field direction.
01 Apr 2000
TL;DR: Two interface prototypes which are developed on the authors' augmented desk interface system, EnhancedDesk, are described, which are aimed at providing an effective learning environment and supporting effective information retrieval.
Abstract: This paper describes two interface prototypes which we have developed on our augmented desk interface system, EnhancedDesk. The first application is Interactive Textbook, which is aimed at providing an effective learning environment. When a student opens a page which describes experiments or simulations, Interactive Textbook automatically retrieves digital contents from its database and projects them onto the desk. Interactive Textbook also allows the student hands-on ability to interact with the digital contents. The second application is the Interactive Venn Diagram, which is aimed at supporting effective information retrieval. Instead of keywords, the system uses real objects such as books or CDs as keys for retrieval. The system projects a circle around each book; data corresponding the book are then retrieved and projected inside the circle. By moving two or more circles so that the circles intersect each other, the user can compose a Venn diagram interactively on the desk. We also describe the new technologies introduced in EnhancedDesk which enable us to implement these applications.
TL;DR: In this article, a high power CW (continuous wave) polycrystalline Nd:Y3Al5O12 (Nd: YAG) ceramic rod laser was demonstrated for the first time with a maximum output power of 31 W with a 188% slope efficiency.
Abstract: High power CW (continuous wave) polycrystalline Nd:Y3Al5O12 (Nd:YAG) ceramic rod laser was demonstrated for the first time The maximum output power of 31 W with a 188% slope efficiency was obtained at 1064 nm using 2145 W/808 nm laser diode pumping
TL;DR: In this paper, the effects of strain-induced grain boundaries on the internal stresses and the related lattice distortions evolved in these grain interiors are discussed in detail, and a submicron-scale substructure evolution in a 304 type stainless steel caused by severe warm deformation at 0.5 T{sub m}.
01 Jan 2000
TL;DR: A stable switching fuzzy controller satisfying the smoothness condition is designed by simultaneously solving both of LMIs and is applied to trajectory control of an R/C hovercraft.
Abstract: Describes stability and smoothness conditions for switching fuzzy systems. We first present a switching fuzzy system that has locally Takagi-Sugeno fuzzy models and switches them according to states, external variables and/or time. A switching fuzzy controller is constructed by mirroring the structure of the switching fuzzy system. LMI stability conditions are derived to design the switching fuzzy controller in Tanaka et al. (2000). Switching of several controllers causes non-continuity of control input at switching points. The phenomenon influences important control performance, e.g., ride quality in vehicle control. We derive a smoothness condition to avoid the phenomenon. The smoothness condition is also represented via LMIs. A stable switching fuzzy controller satisfying the smoothness condition is designed by simultaneously solving both of LMIs. The design technique is applied to trajectory control of an R/C hovercraft. The simulation and experimental results far the trajectory control show the validity of the switching fuzzy control.
TL;DR: In this article, the spin-spin relaxation rates depend on the resonance peaks split due to the nuclear-electric quadrupole interaction, which is explained by an indirect nuclear spin spin spin interaction through the interacting paramagnetic electron spins.
Abstract: The ${}^{59}\mathrm{C}\mathrm{o}\ensuremath{-}\mathrm{N}\mathrm{M}\mathrm{R}$ on single crystals of ${\mathrm{LaCoO}}_{3}$ has been studied in order to investigate the spin-state transition through the nuclear-spin relaxation in this compound. Below $T\ensuremath{\sim}35\mathrm{K},$ the spin-lattice and spin-spin relaxation rates show a thermal-activation-type temperature dependence with an energy gap of \ensuremath{\sim}180 K. This value is close to the energy difference between the low spin state $(S=0)$ and the intermediate spin state $(S=1)$ predicted in the two-stage spin-state transition model with the intermediate spin state. The apparent spin-spin relaxation rates depend on the resonance peaks split due to the nuclear-electric-quadrupole interaction, which is explained by an indirect nuclear spin-spin interaction through the interacting paramagnetic electron spins. This observation is consistent with the ferromagnetic short-range correlation among the electron spins on ${\mathrm{Co}}^{3+}$ ions confirmed by neutron-scattering experiments.
TL;DR: Pulsed laser action in the novel visible laser channels 4F9/2→6H13/2 (at ≈0.57 µm) and 4F 9/2 →6H11/2, at ≈ 0.66 µm), of Dy3+ ions in monoclinic KGd(WO4)2 single crystals at nitrogen cryogenic temperature under Xeflashlamp pumping is excited for the first time as mentioned in this paper.
Abstract: Pulsed laser action in the novel visible laser channels 4F9/2→6H13/2 (at ≈0.57 µm) and 4F9/2→6H11/2 (at ≈0.66 µm) of Dy3+ ions in monoclinic KY(WO4)2 and KGd(WO4)2 single crystals at nitrogen cryogenic temperature under Xe-flashlamp pumping is excited for the first time. All observed lasing emissions are identified. Some spectroscopic characteristics of the investigated crystals are also presented.
TL;DR: A model equation that describes the propagation of sound beams in a fluid is developed using the oblate spheroidal coordinate system and has a specific application to a theoretical prediction on focused, high-frequency beams from a circular aperture.
Abstract: A model equation that describes the propagation of sound beams in a fluid is developed using the oblate spheroidal coordinate system. This spheroidal beam equation (SBE) is a parabolic equation and has a specific application to a theoretical prediction on focused, high-frequency beams from a circular aperture. The aperture angle does not have to be small. The theoretical background is basically along the same analytical lines as the composite method (CM) reported previously [B. Ystad and J. Berntsen, Acustica 82, 698–706 (1996)]. Numerical examples are displayed for the amplitudes of sound pressure along and across the beam axis when sinusoidal waves are radiated from the source with uniform amplitude distribution. The primitive approach to linear field analysis is readily extended to the case where harmonic generation in finite-amplitude sound beams becomes significant due to the inherent nonlinearity of the medium. The theory provides the propagation and beam pattern profiles that differ from the CM sol...
TL;DR: In this article, the authors demonstrated Cr4+:YAG passively Q-switched Nd:GdVO4 lasers at 1.06 μm with the maximum average output power of 2.1 W and the highest peak power of 625 W were obtained when the initial transmissions of the Cr4 + YAG crystals were 90% and 80%.
Abstract: With a 10-W diode laser to pump Nd:GdVO4 crystal in a folded cavity, we demonstrated Cr4+:YAG passively Q-switched Nd:GdVO4 lasers at 1.06 μm. The maximum average output power of 2.1 W and the highest peak power of 625 W were, respectively, obtained when the initial transmissions of the Cr4+:YAG crystals were 90% and 80%.