Showing papers by "University of Electro-Communications published in 1993"
01 May 1993
TL;DR: The notion of resolvability of a channel is introduced, defined as the number of random bits required per channel use in order to generate an input that achieves arbitrarily accurate approximation of the output statistics for any given input process, and a general formula is obtained which holds regardless of the channel memory structure.
Abstract: Given a channel and an input process we study the minimum randomness of those input processes whose output statistics approximate the original output statistics with arbitrary accuracy. We introduce the notion of resolvability of a channel, defined as the number of random bits required per channel use in order to generate an input that achieves arbitrarily accurate approximation of the output statistics for any given input process. We obtain a general formula for resolvability which holds regardless of the channel memory structure. We show that, for most channels, resolvability is equal to Shannon capacity. By-products of our analysis are a general formula for the minimum achievable (fixed-length) source coding rate of any finite-alphabet source, and a strong converse of the identification coding theorem, which holds for any channel that satisfies the strong converse of the channel coding theorem.
749 citations
22 Jun 1993
TL;DR: The authors proposed a new indicator of text structure, called the lexical cohesion profile (LCP), which locates segment boundaries in a text, and measured the mutual similarity of words in a sequence of text using a semantic network.
Abstract: This paper proposes a new indicator of text structure, called the lexical cohesion profile (LCP), which locates segment boundaries in a text. A text segment is a coherent scene; the words in a segment are linked together via lexical cohesion relations. LCP records mutual similarity of words in a sequence of text. The similarity of words, which represents their cohesiveness, is computed using a semantic network. Comparison with the text segments marked by a number of subjects shows that LCP closely correlates with the human judgments. LCP may provide valuable information for resolving anaphora and ellipsis.
205 citations
TL;DR: This article showed that the Choquet integral can represent some useful quantities such as supremum, infimum, essential supremum and essential infimum for the L-estimators including α-trimmed mean.
166 citations
21 Apr 1993
TL;DR: The authors proposed a method for measuring semantic similarity between words as a new tool for text analysis, which is measured on a semantic network constructed systematically from a subset of the English dictionary, LDOCE (Longman Dictionary of Contemporary English).
Abstract: This paper proposes a method for measuring semantic similarity between words as a new tool for text analysis. The similarity is measured on a semantic network constructed systematically from a subset of the English dictionary, LDOCE (Longman Dictionary of Contemporary English). Spreading activation on the network can directly compute the similarity between any two words in the Longman Defining Vocabulary, and indirectly the similarity of all the other words in LDOCE. The similarity represents the strength of lexical cohesion or semantic relation, and also provides valuable information about similarity and coherence of texts.
129 citations
TL;DR: In particular, the authors showed that subtraction is hard for the closure properties of #P, SpanP, OptP, and MidP, which is a general theory of complexity of closure properties.
95 citations
TL;DR: In this paper, a nonlinear optical generation using electromagnetically induced transparency is demonstrated with atomic hydrogen as a test medium, where the generated sum-frequency Lyman-β radiation at 103 nm can continue to grow without suffering resonant absorption and phase mismatching.
Abstract: Nonlinear optical generation using electromagnetically induced transparency is demonstrated with atomic hydrogen as a test medium. With the application of a strong-coupling laser field to the 3p-2s transition, the resonant Lyman-β (3p-1s) transition becomes transparent. The generated-sum-frequency Lyman-β radiation at 103 nm can continue to grow without suffering resonant absorption and phase mismatching
94 citations
01 Sep 1993-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: A highly efficient focusing device which uses a RF multipole field (sextupole-ion-beam guide (SPIG) has been developed for the ion guide isotope separator on-line (IGISOL) in this article, which consists of six circular rods uniformly distributed on a circle in the plane perpendicular to the axis of symmetry.
Abstract: A highly efficient focusing device which uses a RF multipole field (sextupole-ion-beam guide (SPIG)) has been developed for the ion guide isotope separator on-line (IGISOL) The SPIG, placed after the nozzle, consists of six circular rods uniformly distributed on a circle in the plane perpendicular to the axis of symmetry Under the combined action of the sextupole RF electric field produced by the rods and helium gas flow, well focused ion beams with low energy spread can be transmitted efficiently by use of the SPIG The experimental results, using a discharge ion source, show that almost nearly 90% of the ions which leave the nozzle can be transported through the SPIG, and that the width of the kinetic energy distribution after the SPIG is about 08 eV (FWHM) These experimental results agree with the results of Monte Carlo simulations; the simulation studies also indicate that the size of the spatial distribution in the plane perpendicular to the symmetry axis is less than 1 mm in diameter at the end of the SPIG
92 citations
TL;DR: In this paper, the general structure of carbon tubules and fullerenes projected in a two-dimensional hexagonal lattice sheet with +12 defects representing the pentagonal faces is summarized.
Abstract: A one-dimensional electronic band structure model for carbon tubules is summarized. The general structure of carbon tubules and fullerenes projected in a two-dimensional hexagonal lattice sheet with +12 defects representing the pentagonal faces. The possible caps which are fitted smoothly to a tubule can be generated by this projection method. Growth of the tubule can occur by absorbing C2 clusters at such topological defects (i.e. pentagonal faces) on generalized fullerenes. The tubule electronic structure is obtained from a simple tight-binding model for a single-layer carbon tubule. The model shows that approximately one-third of the tubules are metallic and two-thirds are semiconducting, depending on the tubule diameter and chirality. Metallic one-dimensional electronic energy bands are stable under a Peierls distortion. As the tubule diameter, d increases, the semiconductor energy gap decreases approximately as 1/d . The calculation of the electronic structure of two concentric tubules shows that pairs of concentric metal—semiconductor (orsemiconductor—metal) and metal—metal tubules are stable under the weak turbostratic interlayer interaction. Possible applications of concentric carbon tubules to semiconductor—metal devices are discussed.
87 citations
TL;DR: In this paper, a review of auroral hiss emissions observed at ground-based stations and in the magnetosphere is presented, and different approaches to modelling of these emissions are discussed.
84 citations
TL;DR: An architecture for the copy network that is an integral part of multicast ATM switches that makes use of the property that the broadcast banyan network (BBN) is nonblocking if the active inputs are cyclically concentrated and the outputs are monotone is described.
Abstract: An architecture for the copy network that is an integral part of multicast ATM switches is described. The architecture makes use of the property that the broadcast banyan network (BBN) is nonblocking if the active inputs are cyclically concentrated and the outputs are monotone. In the architecture, by employing a token ring reservation scheme, the outputs of the copy network are reserved before a multicast cell is replicated. By the copy principle, the number of copies requested by a multicast call is not limited by the size of the copy network so that very large multicast switches can be configured in a modular fashion. The sequence of cells is preserved in the structure. Though physically separated, buffers within the copy network are completely shared, so that the throughput can reach 100%, and the cell delay and the cell loss probability can be made to be very small. The cell delay is estimated analytically and by computer simulation, and the results of both are found to agree with each other. The relationship between the cell loss probability under various traffic parameters and buffer sizes is studied by computer simulation. >
83 citations
TL;DR: The final results obtained by the sum of three amplitudes do not depend on the choice of the dipole formula at photon energies above 1 keV and are in excellent agreement with recent experimental results at energies 2--12 keV.
Abstract: Cross sections for double photoionization of He are calculated using the lowest-order many-body perturbation theory. There are three amplitudes contributing in the present calculation. They represent the three mechanisms for double ionization, namely, two-step-1, shake off, and ground-state correlation. It is explicitly shown that the cross section for each of these mechanisms depends strongly on the adopted form of the dipole interaction as indicated by Dalgarno and Sadeghpour [Phys. Rev. A 46, 3591 (1992)]. Our final results obtained by the sum of three amplitudes do not depend on the choice of the dipole formula at photon energies above 1 keV. The ratios of the cross sections for double ionization to single ionization are in excellent agreement with recent experimental results at energies 2--12 keV.
TL;DR: In this paper, the authors reported that a density of diamond nuclei as high as 10 10 cm −2 was attained on a mirror-polished silicon surface by pretreating the substrate surface in a hydrogen plasma containing a high concentration of methane and applying a negative bias.
TL;DR: Spin-restricted and unrestricted post-Hartree-Fock calculations were carried out for clusters of triplet methylene and nitroxide radicals in this paper, where the UHF-based methods such as UMP and QCISD followed by approximate spin projection provided reasonable energy differences between the high and low-spin states of these species.
TL;DR: A new type of mobile robot that has a spherical wheel, an arched body, and motion-controlling mech anisms installed inside the wheel is described, which provides great possibility to the mobile robots in the manufacturing and nonmanufacturing environments.
Abstract: This article describes a new type of mobile robot that has a spherical wheel, an arched body, and motion-controlling mech anisms installed inside the wheel. The robot can travel in every direction and perform unique actions by virtue of the wheel and the motion-controlling mechanisms. We call the latter the Inside Wheel Balancing System (IWBS). Postural stability con trol, omnidirectional steering, and locomotion of the robot were achieved by means of the compound gravity center feedback control. Postural stability and traveling control on a slope and on a flat plane were also attained experimentally. The experimental results coincide well with those obtained by the simulation performed on a personal computer. The omnidirec tion traveling robot proposed here provides great possibility to the mobile robots in the manufacturing and nonmanufacturing environments.
02 May 1993
TL;DR: The generation of collision-free control data of a polishing robot with 6 degrees-of-freedom for a workpiece with complicated curve surface is discussed and is found to be effective from experiments in which a work piece with an overhanging curved surface is polished.
Abstract: The generation of collision-free control data of a polishing robot with 6 degrees-of-freedom for a workpiece with complicated curve surface is discussed. The collision between the polishing tool and the workpiece is the problem to be solved in terms of automatically carrying out the polishing process. To obtain the collision-free polishing path, the possibility of a collision is checked, and a collision-free tool axis vector is determined on the basis of the solid model of the workpiece and the tool shape representative points. The generated collision-free polishing path is converted into the actual robot control data taking into account the robot structure. The system is found to be effective from experiments in which a workpiece with an overhanging curved surface is polished. >
TL;DR: A strong recombination resonance having a peak at around 20 eV center-of-mass energy has been found for the first time in addition to the known recombination at around 0 eV centers ofmass energy.
Abstract: Dissociative recombination of ${\mathrm{HeH}}^{+}$ has been studied for the ${\mathrm{HeH}}^{+}$ ion stored in a storage ring. A strong recombination resonance having a peak at around 20 eV center-of-mass energy has been found for the first time in addition to the known recombination at around 0 eV center-of-mass energy. The strength of the recombination rate changes depending on the storage time of ${\mathrm{HeH}}^{+}$ ions.
TL;DR: In this paper, a cyclopropane structure of C60(CCl2) was determined by 13C NMR spectroscopy at the 6-ring/6-ring junction.
TL;DR: In this paper, the ages of molybdenites from Mt. Mulgine, Matasvaara, Preissac, and Climax were determined using isotope dilution-mass spectrometry.
TL;DR: A metastable neon (1S5) atomic beam with a velocity of 394 m/s (373 K) and an intensity of 1.1×1015 s−1 sr−1 is produced with a novel construction using a dc glow discharge as mentioned in this paper.
Abstract: A metastable neon (1S5) atomic beam with a velocity of 394 m/s (373 K) and an intensity of 1.1×1015 s−1 sr−1 is produced with a novel construction using a dc glow discharge.
TL;DR: In this article, a frequency-stabilized laser-diode-pumped Fabry-Perot cavity was used to achieve a high-transmission and high-finesse reference Fabry perot cavity with a resonant linewidth of 380 kHz.
Abstract: We describe frequency-stabilized laser-diode-pumped Nd:YAG ring lasers locked to a high-transmission and high-finesse reference Fabry–Perot cavity The cavity has a resonant linewidth of 380 kHz, a finesse of 19,400, and a transmission efficiency of 794% for the TEM00 mode We measure the frequency stability by locking two lasers one free spectral range apart and observe the heterodyne beat signal As a result, the spectral densities noise are reduced to
10 mHz/Hz, and a beat linewidth of 193 mHz is obtained The linewidth is of frequency 073 times the Schawlow–Townes limit
TL;DR: In this paper, the fissiogenic isotopic composition of Ba isotopes has been investigated and a good correlation between the elemental abundance of Cs and isotopic abundances of excess 135 Ba and 137 Ba suggests that fissileogenic 135 Ba, 137 Ba behaved as Cs rather than Ba.
TL;DR: In this paper, a new chemistry for extracting Ce from the gel formed after decomposition of ∼1-g chondrite sample with Mg content of 20% was developed with a recovery yield of 80%.
25 Feb 1993
TL;DR: This paper focuses on complexity classes of partial functions that are computed in polynomial time with oracles in NPMV, the class of all multivalued partial functions That are computable nondeterministically in poynomial time.
Abstract: This paper focuses on complexity classes of partial functions that are computed in polynomial time with oracles in NPMV, the class of all multivalued partial functions that are computable nondeterministically in polynomial time. Concerning deterministic polynomial-time reducibilities, it is shown that
1.
A multivalued partial function is polynomial-time computable with k adaptive queries to NPMV if and only if it is polynomial-time computable via 2k — 1 nonadaptive queries to NPMV.
2.
A characteristic function is polynomial-time computable with k adaptive queries to NPMV if and only if it is polynomial-time computable with k adaptive queries to NP.
3.
Unless the Boolean hierarchy collapses, k adaptive (nonadaptive) queries to NPMV is different than k+1 adaptive (nonadaptive) queries to NPMV for every k.
TL;DR: In this paper, a multipoint detection network around Tokyo region and the Izu peninsula has been used to detect impulsive noise bursts of seismogenic emissions at 82 kHz, 1525 Hz and 36 Hz.
TL;DR: The quadratic collisional loss rate coefficient β of a 7 Li trap is measured as a function of the trap potential in a range covering the energy of the fine-structure splitting 2 P 3/2 - 2 P 1/2.
Abstract: We report a measurement of the quadratic collisional loss rate coefficient \ensuremath{\beta} of a $^{7}\mathrm{Li}$ trap as a function of the trap potential in a range covering the energy of the fine-structure splitting $^{2}$${\mathit{P}}_{3/2\mathrm{\ensuremath{-}}}^{2}$${\mathit{P}}_{1/2}$. The value of \ensuremath{\beta} decreases an order of magnitude when the trap potential is increased beyond 0.24 K, and reaches the minimum value of 3\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ at 0.45 K. At a higher trap potential the \ensuremath{\beta} increases proportionally to the trap potential.
TL;DR: In this paper, the multiplet structures of C 60 ions were calculated by the semi-empirical procedure, MOPAC, using the calculation library, and the ground states for C n − ions (0⩽ n ⩽5) were consistent with group theory which predicts that the symmetry breaking will be caused by the addition of electrons.
TL;DR: In this paper, the sliding friction and wear tests of sintered titanium boride were conducted in air from room temperature to 1000°C and the coefficient of friction was about 0.8 independent of both the applied load and the sliding speed.
Abstract: Sliding friction and wear tests of sintered titanium boride were conducted in air from room temperature to 1000°C. At room temperature, the coefficient of friction was about 0.8 independent of both the applied load and the sliding speed. It increased at intermediate temperatures around 400°C, particularly at lower applied loads. The wear loss decreased with increasing temperature up to 600°C. The coefficient of friction abruptly decreased at 600°C and exhibited a minimum value of about 0.3 at 800°C. A weight gain was observed after the tests at 800°C and above. X-ray diffraction analysis of the wear surfaces revealed that titanium boride oxidizes even at lower temperatures. Since the oxidation yields B2O3 of low melting point, it would exist as a liquid at the friction interfaces and therefore should have a critical effect on the friction and wear characteristics. High viscosity of liquidized oxides increased the coefficient of friction but decreased the wear loss at intermediate temperatures. The dependence of friction coefficient on both the applied load and the sliding speed suggests that the sliding is in a hydrodynamic lubrication regime because of the presence of a substantial amount of melted oxides at 800°C and above, resulting in a low coefficient of friction.
TL;DR: In this paper, a method for designing digital all-pass filters with equiripple phase responses based on the eigenvalue problem is presented, and the optimal filter coefficients can be easily obtained by computing the maximum eigenvector and applying an iteration procedure.
Abstract: A novel method is presented for designing digital allpass filters with equiripple phase responses based on the eigenvalue problem, and shows that the optimal filter coefficients can be easily obtained by computing the maximum eigenvector and applying an iteration procedure.
TL;DR: In this article, a finite element analysis for the sloshing motion of liquid-filled axisymmetric tanks during lateral excitation, for a circumferential mode number, m = 1, antisymetric, was presented.
Abstract: A finite element analysis is presented for the sloshing motion of liquid-filled axisymmetric tanks during lateral excitation, for a circumferential mode number, m=1, antisymmetric. The system of finite element equations concerned is derived by means of variational principle. Linear basis functions associated with the regular triangulation of Friedrichs-Keller type was used. The analytical expressions of the mass and stiffness matrices for a finite element were obtained. Numerical results of the free vibration for cases of annular and cylindrical tanks were obtained, and compared with existing experiments and other predicted results, showing a good agreement between the experiment and numerical results.
TL;DR: In this article, the authors examined the possible seismic influence on the propagation of magnetospheric whistlers at low latitudes on the basis of long-term data observed at Sugadaira (geomagnetic latitude 25°N) during 1970-1978 and at Sakushima (24°) during 1980-1982.