Showing papers by "University of Electro-Communications published in 1991"

Wavelength-shift interferometry for distance measurements using the Fourier transform technique for fringe analysis

Abstract: The Fourier transform technique, originally developed for spatial fringe pattern analysis, has been applied to the analysis of a temporal fringe signal obtained by a wavelength-shift interferometer used for absolute distance measurements. It has been shown that the error caused by the nonlinear and time-varying current-wavelength characteristic of the laser diode can be removed by combining the Fourier transform technique with the reference technique. A novel technique for distance measurement based on multiple-beam interferometry has been proposed, and an experimental demonstration is given for a three-beam interferometer that includes a reference reflector as an integral part of the system. Error sources and the limitation of the technique are discussed.

High-resolution spectra of the 3.29 micron interstellar emission feature - A summary

Abstract: High spectral resolution observations of the 3.29-micron interstellar emission feature show two types of profiles. Type 1 has a central wavelength of 3.289-micron and is observed in extended objects such as planetary nebulae and H II regions. Type 2 has a central wavelength of 3.296 microns and is observed around a small number of stellar sources. Type 2 has a full width at half-maximum of 0.020 micron; Type 1 has a broader FWHM, perhaps as much as 0.042 micron, but this is uncertain because of contamination by Pf(delta) emission. These profiles are tabulated for comparison to laboratory data. It is found that no proposed identification for the 3.29-micron emission feature definitely matches the observational spectra, although amorphous aromatic materials and heated polycyclic aromatic hydrocarbons tend to fit the best.

Four-beam laser trap of neutral atoms

Abstract: An efficient spontaneous-force laser trap of neutral atoms without standing waves is demonstrated by using the Ne 1s5 metastable state. The metastable Ne beam is decelerated by a laser by using Zeeman tuning and is trapped in a trap consisting of a quadrupole magnetic field and four laser beams in a tetrahedral configuration. The dynamics of atomic motion from the deceleration stage to the trap is discussed.

Parametric loudspeaker—characteristics of acoustic field and suitable modulation of carrier ultrasound

Abstract: Due to the inherent nonlinearity of the medium, finite amplitude ultrasound interacts with itself and generates some secondary waves in the sound beam. The parametric loudspeaker, making use of this phenomenon, has a sharp directivity and might be applied to a speech transmission system under the limited environment. In this paper, a numerical analysis method available for high sound pressure levels, where the nonlinear interactions of ultrasound become greatly active, can be used successfully to theoretically design the parametric loudspeaker. It is reported that the numerical computations agree well with the experiments by a circular aperture projector of radius 21 cm and carrier frequency 27 kHz. To develop the parametric loudspeaker for practical uses, the problems on harmonic distortions and the physiological effect on human being must be solved. Based on the theoretical prediction, the reasonable solutions for such problems are considered in accordance with appropriate primary wave modulations.

On polynomial-time truth-table reducibility of intractable sets to P-selective sets

Abstract: The existence of setsnot being ≤ttP-reducible to low sets is investigated for several complexity classes such as UP, NP, the polynomial-time hierarchy, PSPACE, and EXPTIME. The p-selective sets are mainly considered as a class of low sets. Such investigations were done in many earlier works, but almost all of these have dealt withpositive reductions in order to imply the strongest consequence such as P=NP under the assumption that all sets in NP are polynomial-time reducible to low sets. Currently, there seems to be some difficulty in obtaining the same strong results undernonpositive reducibilities. The purpose of this paper is to develop a useful technique to show for many complexity classes that if each set in the class is polynomial-time reducible to a p-selective set via anonpositive reduction, then the class is already contained in P. The following results are shown in this paper.

A Relationship between Difference Hierarchies and Relativized Polynomial Hierarchies.

Abstract: Chang and Kadin have shown that if the difference hierarchy over NP collapses to level $k$, then the polynomial hierarchy (PH) is equal to the $k$th level of the difference hierarchy over $\Sigma_{2}^{p}$. We simplify their proof and obtain a slightly stronger conclusion: If the difference hierarchy over NP collapses to level $k$, then PH = $\left(P_{(k-1)-tt}^{NP}\right)^{NP}$. We also extend the result to classes other than NP: For any class $C$ that has $\leq_{m}^{p}$-complete sets and is closed under $\leq_{conj}^{p}$and $\leq_{m}^{NP}$-reductions, if the difference hierarchy over $C$ collapses to level $k$, then $PH^{C} = $\left(P_{(k-1)-tt}^{NP}\right)^{C}$. Then we show that the exact counting class $C_{=}P$ is closed under $\leq_{disj}^{p}$and $\leq_{m}^{co-NP}$-reductions. Consequently, if the difference hierarchy over $C_{=}P$ collapses to level $k$ then $PH^{PP}$ is equal to $\left(P_{(k-1)-tt}^{NP}\right)^{PP}$. In contrast, the difference hierarchy over the closely related class PP is known to collapse. Finally, we consider two ways of relativizing the bounded query class $P_{k-tt}^{NP}$: the restricted relativization $P_{k-tt}^{NP^{C}}$, and the full relativization $\left(P_{k-tt}^{NP}\right)^{C}$. If $C$ is NP-hard, then we show that the two relativizations are different unless $PH^{C}$ collapses.

An upwind finite element scheme for high‐Reynolds‐number flows

Abstract: A new upwind finite element scheme for the incompressible Navier-Stokes equations at high Reynolds number is presented. The idea of the upwind technique is based on the choise of upwind and downwind points. This scheme can approximate the convection term to third-order accuracy when these points are located at suitable positions. From the practical viewpoint of computation, the algorithm of the pressure Poisson equation procedure is adopted in the framework of the finite element method

Cobalt-59 Nuclear Magnetic Resonance Spectroscopy in Coordination Chemistry

Abstract: The current status of cobalt-59 NMR spectroscopy is reviewed including historical perspectives and application to various areas of coordination chemistry. Chemical shift data are summarized and tabulated for about 800 complexes from values in the literature and our experimental data. Spin-spin coupling constants are also collected for 20 nuclear pairs.

Spontaneous Emission in a Very Short Optical Cavity with Plane-Parallel Dielectric Mirrors

Abstract: A detailed account of the calculation on the spontaneous emission rate in a very short optical cavity with plane-parallel dielectric mirrors is given. A cavity model consisting of a pair of plane dielectric slabs is used. Guided modes as well as outgoing modes are considered. The emission rate from a two-level atom is calculated under quantum-mechanical perturbation approximation. The enhancement factor for the rate is found to be of the order of unity except for extremely short cavities. The concept of quasimodes in a very short cavity and their effective area are discussed in relation to the enhancement factor. The coupling ratios into various quasimodes are derived.

On one query, self-reducible sets

Abstract: The authors study one-word-decreasing self-reducible sets, which are the usual self-reducible sets with the peculiarity that the self-reducibility machine makes at most one query to a word lexicographically smaller than the input. It is first shown that for all counting classes defined by a predicate on the number of accepting paths there exist complete sets which are one-word-decreasing self-reducible. Using this fact it is proved that, for any class K chosen from a certain set of complexity classes, it holds that (1) if there is a sparse polynomial-time bounded-truth-table-hard set for K, then K=P, and (2) if there is a sparse strongly nondeterministic bounded-truth-table-hard set for K, then K contained in NP intersection co-NP. The main result also shows that the same facts hold for the class PSPACE. >

Study on Frictional Loss of Spur Gears (Concerning the Influence of Tooth Form, Load, Tooth Surface Roughness, and Lubricating Oil)©

Abstract: Nowadays, reducing frictional loss of gears to save energy is a big concern. There are many sources of printed information on this problem for gears, but most of them are practical specialized information and are not developed to give a generalized basic consideration. Since this kind of research has not been brought beyond such, a practical and specialized range, experiments were carried out to study the influences of tooth form, sliding velocity, load, tooth surface roughness, and viscosity of lubricating oils, and kinds of oils on the frictional loss of gears. The frictional loss of spur gears decreases with sliding velocity and the viscosity of lubricating oils, and increases with surface roughness. The frictional loss is very low when using a synthetic oil of the SHF type. The organic molybdenum friction modifier (FM) is also quite effective for reducing frictional loss. Finally, empirical formulas for calculating frictional loss were expressed in terms of tooth form, sliding velocity, tooth surface ...

Flow softening of 7075 aluminum alloy under hot compression

Abstract: Hot deformation of 7075 aluminum alloy was studied in compression in the temperature range of 723 to 803 K and at constant true strain rate from 5.4×lO -6 to O.8s -1 . The flow characteristics were classified into lyzed in each region of testing conditions, as follows; L, M, and H. In region H where flow stresses were above high temperature yield point phenomenon appeared

Polynomial-time learning of very simple grammars from positive data

Abstract: This paper concerns a subclass of simple deterministic grammars, called very simple grammars , and studies the problem of identifying the subclass in the limit from positive data The class of very simple languages forms a proper subclass of simple deterministic languages and is incomparable to the class of regular languages After providing some characterization results for very simple languages, we show that the class of very simple grammars is polynomial-time identifiable in the limit from positive data in the sense of Pitt That is, there is an algorithm that, given the targeted very simple grammar G * , identifies a very simple grammar G equivalent to G * in the limit from positive data, satisfying the property that the time for updating a conjecture is bounded by a polynomial in m , and the total number of prediction errors made by the algorithm is bounded by the cardinality k of the terminal alphabet involved in G * , where m is the maximum of k and the total lengths of all positive data provided

Counting classes are at least as hard as the polynomial-time hierarchy

Abstract: It is shown that many natural counting classes are at least as computationally hard as PH (the polynomial-time hierarchy) in the following sense: for each K of the counting classes, every set in K(PH) is polynomial-time randomized many-one reducible to a set in K with two-sided exponentially small error probability. As a consequence, these counting classes are computationally harder than PH unless PH collapses to a finite level. Some other consequences are also shown. >

Planar-structure focusing lens for acoustic microscope

Abstract: A planar-structure acoustic focusing lens proposed by the authors is applied successfully to the scanning acoustic microscope as a substitute for the conventional concave lens. The lens is composed of a number of concentric annular grooves of uniform depth formed on the radiation plane according to the theory of a Fresnel zone plate. Because of the simple configuration with no spherical surface, the planar lens operating at a very high frequency can be fabricated easily using the conventional photolithographic tech nique.Good focusing capability of the lenses fabricated for operation at 100MHz and 200MHz has been demonstrated through the experimental and theoretical examinations.Images of satisfactory quality have been obtained using the scanning acoustic microscope equipped with the planar lenses.

Control of torque distribution for the BLR-G2 biped robot

Abstract: Human walking is realized by repeating two motions called single-support phase and double-support phase. The authors consider walking control in the double-support phase. During the double-support phase, there are numerous combinations of the joint torques and floor reaction forces which realize the same trajectory of motion since the number of actuators which drive the articular joints is more than the number of degrees of freedom left in the link system. Although this makes control in the double-support phase complicated, it enables sophisticated control by utilizing the redundancy of the input. The authors study the control of the torque distribution, and show that smooth motion during the double-support phase can be achieved by properly distributing the joint torque. >

On the complexity of computing optimal solutions

Abstract: We study the computational complexity of computing optimal solutions (the solutions themselves, not just their cost) for NP optimization problems where the costs of feasible solutions are bounded above by a polynomial in the length of their instances (we simply denote by NPOP such an NP optimization problem). It is of particular interest to find a computational structure (or equivalently, a complexity class) which. captures that complexity, if we consider the problems of computing optimal solutions for NPOP’s as a class of functions giving those optimal solutions. In this paper, we will observe that the class of functions computable in polynomial-time with one free evaluation of unbounded parallel queries to NP oracle sets, captures that complexity. We first show that for any NPOP Π, there exists a polynomial-time bounded randomized algorithm which, given an instance of Π, uses one free evaluation of parallel queries to an NP oracle set and outputs some optimal solution of the instance with very high probability. We then show that for several natural NPOP’s, any function giving those optimal solutions is at least as computationally hard as all functions in . To show the hardness results, we introduce a property of NPOP’s, called paddability, and we show a general result that if Π is a paddable NPOP and its associated decision problem is NP-hard, then all functions in are computable in polynomial-time with one free evaluation of an arbitrary function giving optimal solutions for instances of Π. The hardness results are applications of this general result. Among the NPOP’s, we include MAXIMUM CLIQUE, MINIMUM COLORING, LONGEST PATH, LONGEST CYCLE, 0–1 TRAVELING SALESPERSON, and 0–1 INTEGER PROGRAMMING.

Adiabatic-expansion method applied to diamagnetic Rydberg atoms.

Abstract: We report on a successful implementation of the diabatic-by-sector method as applied to the computation of positive-energy diamagnetic Rydberg spectra of the alkali-metal atoms in a laboratory field (\ensuremath{\sim}6 T). The method provides the quantum-defect parameters directly, and opens up the possibility of accounting for various spectral features quantum mechanically.

SiO2-grafted dinuclear molybdenum catalyst derived from Mo2(OAc)4 ; highly active for alkene metathesis reaction

Abstract: SiO2-grafted dinuclear molybdenum species derived from Mo2(OAc)4, e.g.[Mo[graphic omitted]Mo]V, which are characterized by ESR and EXAFS spectroscopy, exhibit marked catalytic activity for propene metathesis reaction, but are inactive for ethane homologation

Iodopsin, a red-sensitive cone visual pigment in the chicken retina.

Abstract: The vertebrate retina contains two kinds of visual cells: rods, responsible for twilight (scotopic) vision (black and white discrimination); and cones, responsible for daylight (photopic) vision (color discrimination). Here we attempt to explain some of their functional differences and similarities in terms of their visual pigments. In the chicken retina there are four types of single cones and a double cone; each of the single cones has its own characteristic oil droplet (red, orange, blue, or colorless) and the double cone is composed of a set of principal and accessory members, the former of which has a green-colored oil droplet. Iodopsin, the chicken red-sensitive cone visual pigment, is located at outer segments of both the red single cones and the double cones, while the other single cones and the rod contain their own visual pigments with different absorption spectra. The diversity in absorption spectra among these visual pigments is caused by the difference in interaction between chromophore (11-cis retinal) and protein moiety (opsin). However, the chromophore-binding pocket in iodopsin is similar to that in rhodopsin. The difference in absorption maxima between both pigments could be explained by the difference in distances between the protonated Schiff-bases at the chromophore-binding site and their counter ions in iodopsin and rhodopsin. Furthermore, iodopsin has a unique chloride-binding site whose chloride ion serves for the red-shift of the absorption maximum of iodopsin. Visual pigment bleaches upon absorption of light through several intermediates and finally dissociates into all-trans retinal and opsin. That the sensitivity of cones is lower than rods cannot be explained by the relative photosensitivity of iodopsin to rhodopsin, but may be understood to some extent by the short lifetime of an enzymatically active intermediate (corresponding to metarhodopsin II) produced in the photobleaching process of iodopsin. The rapid formation and decay of the meta II-intermediate of iodopsin compared with metarhodopsin II are not contradictory to the rapid generation and recovery of cone receptor potential compared with rod receptor potential. The rapid recovery of the cone receptor potential may be due to a more effective shutoff mechanism of the visual excitation, including the phosphorylation of iodopsin. The rapid dark adaptation of cones compared with rods has been explained by the rapid regeneration of iodopsin from 11-cis retinal and opsin. One of the reasons for the rapid regeneration and susceptibility to chemicals of iodopsin compared with rhodopsin may be a unique structure near the chromophore-binding site of iodopsin.

Realization of Dynamic Quadruped Locomotion in Pace Gait by Controlling Walking Cycle

Abstract: In this study, a control method of pace gait which is often observed in middle or high-speed walking of animals is discussed. The motion in pace gait can be divided into the motion in the sagittal plane (plane vertical to the floor including the walking direction) and the motion in the lateral plane (plane vertical to the walking direction). As for the lateral motion control, a dead beat control is adopted for the purpose of adjusting the walking cycle. As for the sagittal motion control, a trajectory of the leg is designed by considering the control algorithm of the lateral plane. The effectiveness of the proposed control method was confirmed by means of computer simulation and also in walking experiments using the quadruped walking robot. Our robot COLT-3 achieved the pace walking at speed of 0.25 m/s.

A method of measuring the vibration level dependence of impedance-type equivalent circuit constants

Abstract: In piezoelectric transducers with high electromechanical coupling and finite dielectric loss angle, the mechanical quality factor of the transducer resonating under the short-circuit condition of the electric terminal is usually lower than that under the open-circuit condition. This fact is well explained by the impedance-type improved equivalent circuit including the effect of dielectric loss. This circuit is available for design of high power ultrasonic devices. A method of measuring the vibration level dependence of the impedance-type circuit constants is described and some experimental results are shown.

Effect of Uniaxial Stress on Central Peaks in the 1q and 3q Incommensurate Phase of Quartz

Abstract: The effects of uniaxial stress σ y y on the incommensurate (INC) phase transition of quartz have been investigated by light scattering spectroscopy. The 1q INC phase is induced between β and the 3q INC phase and its region becomes wider with the increase of stress. Anomalies of the central peak in the Rayleigh-Brillouin spectra are observed at three temperatures, corresponding to T i 1 (β to 1q INC phase), T i 3 (1q to 3q INC phase) and T c (3q to α phase). Only at T i 1 , is the central peak found to have a dynamical component.