Showing papers by "University of Electro-Communications published in 1994"
TL;DR: A formula for the capacity of arbitrary single-user channels without feedback is proved and capacity is shown to equal the supremum, over all input processes, of the input-output inf-information rate defined as the liminf in probability of the normalized information density.
Abstract: A formula for the capacity of arbitrary single-user channels without feedback (not necessarily information stable, stationary, etc.) is proved. Capacity is shown to equal the supremum, over all input processes, of the input-output inf-information rate defined as the liminf in probability of the normalized information density. The key to this result is a new converse approach based on a simple new lower bound on the error probability of m-ary hypothesis tests among equiprobable hypotheses. A necessary and sufficient condition for the validity of the strong converse is given, as well as general expressions for /spl epsiv/-capacity. >
907 citations
TL;DR: In this article, the temperature dependence of chromatic dispersion at any wavelength from UV to 1.7 nm/m was investigated for fused silica (SiO/sub 2/), aluminosilicate, and Vycor glasses.
Abstract: Temperature-dependent Sellmeier coefficients are necessary to optimize optical design parameters of the optical fiber transmission system. These coefficients are calculated for fused silica (SiO/sub 2/), aluminosilicate, and Vycor glasses for the first time to find the temperature dependence of chromatic dispersion at any wavelength from UV to 1.7 /spl mu/m. The zero dispersion wavelength /spl lambda//sub 0/ (1.273 /spl mu/m for SiO/sub 2/, 1.393 /spl mu/m for aluminosilicate, and 1.265 /spl mu/m for Vycor glasses at 26/spl deg/C) varies linearly with temperature, and d/spl lambda//sub 0//dT is 0.03 nm/K for aluminosilicate and Vycor glasses, whereas for SiO/sub 2/ it is 0.025 nm/K. This study interprets the recently observed experimental value of d/spl lambda//sub 0//dT for two dispersion shifted optical fibers; and the dominantly material origin of d/spl lambda//sub 0//dT is confirmed here as a fundamental property of the optical fiber glasses. >
307 citations
TL;DR: Experimental results are presented that demonstrate the validity of the principle and Unlike conventional moiré techniques the proposed technique permits the objects to have discontinuous height steps and/or surfaces spatially isolated from one another.
Abstract: An interferometric technique for automated profilometry of diffuse objects has been proposed. It is based on the Fourier-fringe analysis of spatiotemporal specklegrams produced by a wavelength-shift interferometer with a laser diode as a frequency-tunable light source. Unlike conventional moire techniques the proposed technique permits the objects to have discontinuous height steps and/or surfaces spatially isolated from one another. Experimental results are presented that demonstrate the validity of the principle.
227 citations
TL;DR: The results suggest that the magnetic moments in the doped compound freeze into a spin-glass state at low temperature, indicating that the high-temperature transition is not dominantly magnetic in origin.
Abstract: ${\mathrm{LaCoO}}_{3}$ exhibits two magnetic-electronic transitions, one near 90 K and a second near 500 K. A previous study of the paramagnetic scattering using polarized neutrons demonstrated that the low-temperature transition is associated with the thermal excitation of ${\mathrm{Co}}^{3+}$ ions from the low-spin to the high-spin state. In the present work, we extend the paramagnetic-scattering measurements up to a temperature of 700 K. We find that the magnetic-scattering intensity decreases monotonically for temperatures above 300 K, indicating that the high-temperature transition is not dominantly magnetic in origin. Furthermore, the anomalous thermal expansion associated with the low-temperature transition is measured and shown to be consistent with a simple theoretical model for the spin-state transition. For comparison, paramagnetic-scattering measurements for ${\mathrm{La}}_{0.92}$${\mathrm{Sr}}_{0.08}$${\mathrm{CoO}}_{3}$ are also presented. In this material the ferromagnetic correlations are substantially stronger than in the undoped compound, and no transition to the low-spin state is observed. Instead, the paramagnetic scattering increases steadily with decreasing temperature until saturating below 24 K, the same temperature at which the magnetization of the zero-field-cooled specimen shows a sharp cusp. These results suggest that the magnetic moments in the doped compound freeze into a spin-glass state at low temperature.
227 citations
TL;DR: Every comonotonically additive, positively homogeneous functional of bounded variation can be represented as a Choquet integral with respect to a non-monotonic fuzzy measure of boundedVariation.
199 citations
TL;DR: In this paper, a new electrochemical method for incorporating high concentration Er ions deep into porous silicon layers and its intense photoluminescence at ∼1.54 μm at room temperature was presented.
Abstract: We present a new electro‐chemical method for incorporating high concentration Er ions deep into porous silicon layers and its intense photoluminescence at ∼1.54 μm at room temperature. Porous silicon layers prepared by anodic etching of p‐type silicon substrates in HF/H2O are immersed in ErCl3/ethanol solution. Then the negative bias relative to a counter platinum electrode is applied to the samples. Er3+ ions are drawn into fine pores of the porous silicon layers by the electric field. After thermal annealing at ∼1300 °C in an O2/Ar atmosphere, the samples show sharp and intense Er3+‐related photoluminescence at ∼1.54 μm at room temperature upon excitation with an Ar ion laser.
150 citations
22 Oct 1994
TL;DR: Based on experimental results, the following were determined to be the system requirements to support spatial workspace collaboration: independency of a field of view, predictability, confidence in transmission and sympathy toward the system.
Abstract: An approach supporting spatial workspace collaboration via a video-mediated communication system is described. Based on experimental results, the following were determined to be the system requirements to support spatial workspace collaboration: independency of a field of view, predictability, confidence in transmission and sympathy toward the system. Additionally, a newly developed camera system, the GestureCam System, is introduced. A camera is mounted on an actuator with three degrees of freedom. It is controlled by master-slave method or by a touch-sensitive CRT. Also, a laser pointer is mounted to assist with remote pointing. Preliminary experiments were conducted and the results are described herein.
148 citations
27 Jun 1994
TL;DR: A general class of algebraic geometry codes is treated and it is shown how to decode these up to half the Feng-Rao bound, using an extension and modification of the Sakata algorithm.
Abstract: Summary form only given, as follows. Efficient decoding of BCH- and Reed-Solomon codes can be done using the Berlekanp-Massey (1969) algorithm, and it is natural to try to use the extension of this to N dimensions of Sakata (see Inform. Computat., vol.84, no.2, p.207, 1990) to decode algebraic geometry codes. We treat a general class of algebraic geometry codes and show how to decode these up to half the Feng-Rao (see IEEE Trans. Inform. Theory, vol.IT 39, no.1 p.37-45, 1993) bound, using an extension and modification of the Sakata algorithm. >
97 citations
TL;DR: Given an arbitrary position of the Othello game played on an n × n board, the problem of determining the winner is shown to be PSPACE-complete.
88 citations
TL;DR: A protocol, Virtual Internet Protocol (VIP), that allows hosts to move transparently within the Internet and is scalable to the total number of mobile hosts and the scale of the Internet, is free from routing loops, and tolerant of loss of control packets.
Abstract: \Mobile Computing" has been a buzzword in the area of computer communications. A technology vital to mobile computing is how to communicate with mobile hosts. This paper proposes a protocol, Virtual Internet Protocol (VIP), that allows hosts to move transparently within the Internet. VIP is de ned as an instance of the virtual network protocol, the general protocol supporting mobile hosts. The virtual network protocol is based on the concept of a virtual network and the propagating cache method. VIP is scalable to the total number of mobile hosts and the scale of the Internet, is free from routing loops, and tolerant of loss of control packets. VIP is currently running on operating systems based on 4.3BSD UNIX. The VIP overhead is negligible when compared with IP.
87 citations
TL;DR: In this article, positionally coincident maser emission from the J = 1 → 0 rotational transition of the first two vibrational levels in the SiO masers in VY Canis Majoris and W Hydrae was analyzed.
Abstract: ALTHOUGH SiO masers (lasing systems at microwave frequencies) have been detected in many old red-giant stars1,2, several fundamental questions, such as what drives the masers and where in the stars' environment they are located3, remain unresolved. Evolved stars are known to have winds, which distribute enriched material throughout the interstellar medium, but the acceleration mechanism and the point in the stellar atmosphere at which the winds are initiated, are unknown4. SiO masers have high brightness temperatures, which allows them to be studied with high spatial and spectral resolution using very-long-baseline interferometry (VLSI) techniques, and thereby potentially determine how the stellar winds are generated. This will only be possible, however, once the physical conditions giving rise to the maser emission are known. Here we present images of positionally coincident maser emission from the J = 1 → 0 rotational transition of the first two vibrational levels in the SiO masers in VY Canis Majoris and W Hydrae. These results clearly demonstrate that the maser emission is collisionally pumped in distinct regions, rather than radiatively pumped. This means that SiO maser emission can be used to follow the clumps of gas as they are accelerated in the stellar atmosphere.
TL;DR: Landau quantization of the energy bands of a carbon nanotube is calculated within the tight-binding approximation and shows oscillations with a period that is scaled by a cross section of the unit cell of the tubule, which is specified by the symmetry of the nanotubes.
Abstract: Landau quantization of the \ensuremath{\pi} energy bands of a carbon nanotube is calculated within the tight-binding approximation The energy bands do not show explicit Landau levels, but they do have energy dispersion for all values of magnetic field The energy bandwidth shows oscillations with a period that is scaled by a cross section of the unit cell of the tubule, which is specified by the symmetry of the nanotube
TL;DR: It is shown that any rooted tree ofn vertices can be straight-line embedded into any setS ofn points in the plane in general position so that the image of the root is arbitrarily specified.
Abstract: In this paper we show that any rooted tree ofn vertices can be straight-line embedded into any setS ofn points in the plane in general position so that the image of the root is arbitrarily specified.
TL;DR: A review of periodic and quasiperiodic VLF emissions observed at ground-based stations and in the Earth's magnetosphere is presented in this paper, where emissions with periods below 10 s are divided into three main groups: periodic emissions, hisslers and pulsing hiss.
TL;DR: This paper considers a linear constant-coefficient system of DDEs with a constant delay, and shows that anA-stable method preserves the asymptotic stability property of the analytical solutions of the system.
Abstract: A natural Runge-Kutta method is a special type of Runge-Kutta method for delay differential equations (DDEs); it is known that any one-step collocation method is equivalent to one of such methods. In this paper, we consider a linear constant-coefficient system of DDEs with a constant delay, and discuss the application of natural Runge-Kutta methods to the system. We show that anA-stable method preserves the asymptotic stability property of the analytical solutions of the system.
TL;DR: In this paper, nonlinear coefficient measurements for dispersion shifted fibres (DSFs) using the self-phase modulation (SPM) method at 1.55 mu m are presented for the first time.
Abstract: Nonlinear coefficient measurements for dispersion shifted fibres (DSFs) using the self-phase modulation (SPM) method at 1.55 mu m are presented for the first time. The nonlinear Kerr refractive index n/sub 2/ for various DSFs is found to be approximately 2.31*10/sup -20/m/sup 2//W (+or-5%) for random polarisation states at 1.55 mu m. >
TL;DR: In this article, the authors studied the non-physical increase of kinetic energy observed in electrostatic particle simulations, defined as the relative magnitude of the kinetic energy increment in unit time to the initial energy.
TL;DR: The isotopic composition of molybdenum in a shelf reagent standard (MoO 3, 99.99%) was determined with a thermal ionization mass spectrometer.
TL;DR: In this paper, the authors measured the spin polarization P as a function of the fragment momentum and showed that P does not vanish at the momentum corresponding to the beam velocity, indicating an important effect which has not been considered in the previously proposed model.
TL;DR: The PrBa 2 Cu 4 O 8 compound with a trace of BaCuO 3 and PrBaO 3 was synthesized for the first time by annealing at the temperature or 957°C under 5 atm oxygen pressure as discussed by the authors.
Abstract: The PrBa 2 Cu 4 O 8 compound with a trace of BaCuO 3 and PrBaO 3 was synthesized for the first time by annealing at the temperature or 957°C under 5 atm oxygen pressure. The content of the PrBaO 3 is estimated to be less than 0.2%. The superconducting transition was not detected down to 2 K. The magnitude of the resistivity and its temperature dependence are consistent with the possession of a metallic character in this compound in contrast to the semiconducting behavior reported previously for the PrBa 2 Cu 3 O 7- δ compound. The effective magnetic moment, μ eff , estimated from the Curie-Weiss fitting to the magnetic susceptibility data, turns out to be 2.67 μ B .
TL;DR: In this article, Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry was used to study the Coulomb force between two charged particles, and it was found that there is an oscillating force acting between the two ions and when the force is resonant with the oscillating radius, the two ion packets are decoupled and appears as two separate peaks in the spectrum.
Abstract: When two ions with very small mass difference are analyzed by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry, the two peaks in the mass spectrum approach to each other by increasing the number of ions and finally merge into a single peak, even though the width of the peaks is sufficiently small compared to the distance between the peaks. It seems that Coulomb force between the two ion packets modulates their cyclotron motions produced by an rf electric field in the FT-ICR trap. We studied the phenomenon theoretically using a model of two charged particles which are confined in a plane perpendicular to a uniform magnetic field. In the case that the two ions appear as a single peak the two ion packets are coupled and rotate around the center of mass with oscillating radius and the position of the peak in the spectrum is determined by the frequency of rotation of the center of mass which corresponds to the weighted average of the mass of the two ion packets. It is found that there is an oscillating force acting between the two ion packets and when the force is resonant with the oscillating radius, the two ion packets are decoupled and appears as two separate peaks in the spectrum. Various factors which affect the phenomenon are discussed.
TL;DR: Isotope ratios of Ce, Nd and Sr, and light rare-earth elements (La, Ce, nd and Sm) concentrations were measured for sixteen N-type MORB samples from DSDP Sites 420, 421, 429, 597 B and 597 C (East Pacific Rise), 504 B (Costa Rica Rift), and 395, 519 A, 522 B, 562 and 564 (Mid Atlantic Ridge).
TL;DR: In this article, a new upwind finite element scheme for the three-dimensional incompressible Navier-Stokes equations at high Reynolds numbers is presented, which has a potential to approximate the convection term in third-order accuracy.
TL;DR: In this article, the Fourier coefficients of the periodic port power ratios corresponding to the sliding load positions are closely related to the six-port system parameters, and the unknown reflection coefficient of the sliding loads as well as the eleven system parameters at each frequency is determined in the procedure.
Abstract: A novel method is presented for calibrating a six-port reflectometer using only one sliding load of unknown reflection coefficient and one short as a calibration standard. The calibration procedure is derived from the fact that the Fourier coefficients of the periodic port power ratios corresponding to the sliding load positions are closely related to the six-port system parameters. The unknown reflection coefficient of the sliding load as well as the eleven system parameters at each frequency is determined in the procedure. The validity and utility of the proposed method are confirmed by experiments over the frequency range 8.5-12.0 GHz in 0.5 GHz steps with a rectangular waveguide sliding load and a polished metal standard short. >
TL;DR: It is demonstrated that rod-type or cone-type visual pigments are contained in both typical and modified pineal photoreceptors, and whether iodopsin and serotonin immunoreactivities are colocalized in one and the same cell.
Abstract: The aim of this study has been to examine whether iodopsin immunoreaction exists in the photoreceptor cells of the retina of the river lamprey, Lampetra japonica, and whether this immunoreaction also appears in the photoreceptors of the pineal complex. The lamprey retina possesses long and short photoreceptor cells that display iodopsin immunoreactivity and rod-opsin immunoreactivity, respectively. In the pineal organ, iodopsin immunoreaction has been observed in the peripheral region and the dorsal wall of the end-vesicle. Immunoreactivity is also found in the atrium and the pineal stalk. The iodopsin-immunoreactive outer segments are smaller than those displaying rod-opsin immunoreactivity. In the parapineal organ, iodopsin immunoreactivity is distributed in both dorsal and ventral portions. Double immunostaining has been employed to investigate whether iodopsin and serotonin immunoreactivities are colocalized in one and the same cell. This approach has revealed that the iodopsin-immunoreactive outer segments belong to serotonin-immunopositive and to serotonin-immunonegative photoreceptor cells. These results demonstrate that rod-type or cone-type visual pigments are contained in both typical and modified pineal photoreceptors.
TL;DR: In this article, Phthalimidonitrene (:NPhth) generated from H2N-Phth and lead tetraacetate in chlorobenzene was found to add to C60, affording C60(NPHth)n (n=1-4).
TL;DR: Differential cross sections and generalized oscillator strengths have been measured for two optically allowed transitions 2 and 2 for electron kinetic energies 300, 400, and 500 eV at small scattering angles by means of electron-energy-loss spectroscopy.
Abstract: Differential cross sections and generalized oscillator strengths have been measured for two optically allowed transitions 2${\mathit{p}}^{6}$${(}^{1}$${\mathit{S}}_{0}$)\ensuremath{\rightarrow}2${\mathit{p}}^{5}$${(}^{2}$${\mathit{P}}_{1/2,3/2}$)3s and the optically forbidden transition 2${\mathit{p}}^{6}$${(}^{1}$${\mathit{S}}_{0}$)\ensuremath{\rightarrow}2${\mathit{p}}^{5}$${(}^{2}$${\mathit{P}}_{1/2}$)3p in Ne. These measurements are carried out for electron kinetic energies 300, 400, and 500 eV at small scattering angles (\ensuremath{\theta}=2.4\ifmmode^\circ\else\textdegree\fi{}--33.7\ifmmode^\circ\else\textdegree\fi{}) by means of electron-energy-loss spectroscopy. Optical oscillator strengths have been determined by extrapolating the generalized oscillator strengths to zero momentum transfer, as (0.137\ifmmode\pm\else\textpm\fi{}0.018) and (0.0106\ifmmode\pm\else\textpm\fi{}0.0014), for the 2${\mathit{p}}^{5}$${(}^{2}$${\mathit{P}}_{1/2}$)3s and 2${\mathit{p}}^{5}$${(}^{2}$${\mathit{P}}_{3/2}$)3s states, respectively. Integrated cross sections have been calculated by integrating the differential cross sections for each impact energy. The errrors are estimated to be less than 13%.
24 Jul 1994
TL;DR: In this paper, the 1 2 spins of oxovanadium(IV) ions were ferromagnetic coupled with J k B = +1.1∼+2.7 K in the dinuclear complexes L[VO(hfac) 2 ] 2 (hfac = hexafluoroacetylacetonate, L = pyrimidine derivatives).
Abstract: The 1 2 spins of oxovanadium(IV) ions were ferromagnetically coupled with J k B = +1.1∼+2.7 K in the dinuclear complexes L[VO(hfac) 2 ] 2 (hfac = hexafluoroacetylacetonate, L = pyrimidine derivatives). Among them, a ferromagnetic transition was observed at about 0.14 K in PM[VO(hfac) 2 ] 2 (PM = pyrimidine). The polymeric complex QZ[Cu(hfac) 2 ] (QZ = quinazoline) gave a positive Weiss constant (+0.39 K). The ferromagnetic transition was observed at about 0.12 K.