Showing papers by "Nagoya Institute of Technology published in 1990"

Brushless DC motor control without position and speed sensors

Abstract: The control strategy using a DSP-TMS320C25 is developed on the basis of the instantaneous voltage equation of the brushless DC motor. Without a position sensor, the controller has no information about rotor position: therefore, the controller determines the applied voltage according to the hypothetical rotor position, which is not necessarily coincident with the actual rotor position. Since the voltage supplied through the inverter is the actual applied voltage, it can be measured. Under the ideal condition that the hypothetical rotor position is coincident with the actual rotor position, the ideal applied voltage can be calculated by using the instantaneous voltage equation of the motor and the detected current. The difference between the actual and the ideal voltages is proportional to the angular difference of the hypothetical and actual rotor positions. Therefore, self-synchronization is possible by reducing the angular difference to zero. Once the rotor position is estimated, the motor can be operated without position and speed sensors. >

An improved k-e model for boundary layer flows

Abstract: An improvement of the k-e model has been made in conjunction with an accurate prediction of the near-wall limiting behaviour of turbulence and the final period of the decay law of free turbulence. The present improved k-e model has been extended to predict the effects of adverse pressure gradients on shear layers, which most previously proposed models failed to do correctly. The proposed model was tested by application to a turbulent pipe flow, a flat plate boundary layer, a relaminarising flow and a diffuser flow with a strong adverse pressure gradient. Agreement with the experiments was generally very satisfactory.

Method of making an epitaxial gallium arsenide semiconductor wafer using a strained layer superlattice

Abstract: A semiconductor wafer having an epitaxial GaAs layer, including a monocrystalline Si substrate having a major surface which is inclined at an off angle between 0.5° and 5° with respect to (100); and at least one intermediate layer epitaxially grown on the major surface of the monocrystalline Si substrate, as a buffer layer for accommodating a lattice mismatch between the Si substrate and the epitaxial GaAs layer which is epitaxially grown on a major surface of the top layer of the at least one intermediate layer. The at least one intermediate layer may comprise one or mor GaP/GaAsP, GaAsP/GaAs superlattice layers. the wafer may be used to produce a seimconductor light emitting element which has a plurality of crystalline gaAs layers including a light emitting layer epitaxially grown on the GaAs layer on the intermediate layer. The wafer may also be used to produce a compound semiconductor device such as amplifying and switching elements, light emitting and receiving elements and photovolataic elements. Methods for producing the semiconductor wafer, light emitting element and compound semiconductor devices are also disclosed.

Processing and superconducting properties of high-Jc bulk YBaCuO prepared by melt process☆

Abstract: The authors tried to produce high critical current density (Jc) bulk superconducting material by a melt process. It became clear that the grain boundary region acts as a weak-link and causes the low Jc of the sintered material. It was found that highly oriented bulk material can be produced by a melt process in YBaCuO system. The authors obtained samples which contained many fine Y2BaCuO5 (211) phases and no grain boundary throughout a region of several tens of cubic millimeters. By magnetization measurements, it was found that Jc exceeded 104 A/cm2 at 77 K and 1 T, which is a promising value for practical applications.

Electron-density distribution from X-ray powder data by use of profile fits and the maximum-entropy method

Abstract: Following the profile decomposition of CeO2 X-ray powder data into individual structure factors, the maximum-entropy method (MEM) has been used to obtain an electron-density-distribution map. In the profile decomposition process, it is impossible to avoid the problems of overlapping peaks which have the same magnitude of reciprocal vectors, such as d*(511) and d*(333), for a cubic crystal, or very severely overlapping reflections. The formalism to treat such overlapping reflections in the MEM analysis is to introduce combined structure factors. The maximum value of the scattering vector, 4π(sinθ)/λ, which was used in the present analysis is small (about 7.8 A−1) but the resulting electron-density-distribution map is of a high quality and much superior to the conventional map. As a consequence, the ionic charge of Ce and O ions can be obtained with reasonable accuracy from the MEM density map. Furthermore, the map reveals the existence of electrons around the supposedly vacant site surrounded by eight O atoms, which is probably related to the high ionic conductivity of this substance.

A structural turbulence model for triple products of velocity and scalar

Abstract: The statistical characteristics of third-order moments of velocity and scalar have been investigated from both experimental and theoretical points of view. The third-order moments have a highly intermittent nature and are dominated by coherent motions in shear-generated turbulence. Using a previously developed statistical method the similarity between the Reynolds stress and scalar flux transport was analysed. On the basis of the experimental results, an new approach to the modelling of triple products was developed. A 'structural' turbulence model for triple velocity and scalar products was constructed. The model has a simple form and universal applicability and its effectiveness has been tested by application to various types of flow.

Reconstructing shape from shading images under point light source illumination

Abstract: A photometric method called point source illuminating stereo is proposed for determining the 3D shape of an object from multiple shading images under point light source illumination. When the surface is a perfect diffuser with uniform reflectance, an algorithm for the determination of 3D shape with positions is developed by using the method of least squares and relying on the principle of the monocular vision and the inverse square law for illuminance. In the proposed method, the number of the necessary images is four for the general surface, and can be reduced to three for the continuous surface. >

Determination of combined water in glasses by infrared spectroscopy

Abstract: Presentation et commentaire des resultats obtenus au cours de differentes etudes realisees sur ce sujet

Data compression of the ECG using neural network for digital Holter monitor

Abstract: A data-compression algorithm for digital Holter recording using artificial neural networks (ANNs) is described A three-layer ANN that has a hidden layer with a few units is used to extract features of the ECG (electrocardiogram) waveform as a function of the activation levels of the hidden layer units The number of output and input units is the same The backpropagation algorithm is used for learning The network is tuned with supervised signals that are the same as the input signals One network (network 1) is used for data compression and another (network 2) is used for learning with current signals Once the network is tuned, the common waveform features are encoded by the interconnecting weights of the network The activation levels of the hidden units then express the respective features of the waveforms for each consecutive heartbeat >

Sintering and Properties of Monazite‐Type CePO4

Abstract: This paper reports on Monazite-type CePO{sub 4} powder (average grain size 0.3 {mu}m) dry-pressed to disks or bars. The green compacts began to sinter above 950{degrees} C. Relative density {ge} 99% and apparent porosity {lt}1% were achieved when the specimens were sintered at 150{degrees} C for 1 h in air. The linear thermal expansion coefficient and thermal conductivity of the CePO{sub 4} ceramics were 9 {times} 10{sup {minus}6}/{degrees} C to 11 {times} 10{sup {minus}6}/{degrees} C (200{degrees} to 1300{degrees} C) and 1.81 W/(m {center dot} K) (500{degrees} C), respectively. Bending strength of the ceramics (average grain size 4 {mu}m) was 174 {plus minus} 28 MPa (room temperature). The CePO{sub 4} ceramics were cracked or decomposed by acidic or alkaline aqueous solutions at high temperatures.

Electron Collision Cross-Sections Determined from Beam and Swarm Data by Boltzmann Analysis

Abstract: Whenever free electrons collide with atoms and molecules, a wide variety of kinetic processes may take place. Electron collision cross-sections, of interest in plasma processing of VLSI production, carbonization of surfaces and so on, modeling of gas lasers, physics of gaseous dielectrics, analysis of high current discharge switches, applications for space science and radiation physics and chemistry, have been determined from available electron beam and electron swarm data utilizing the Boltzmann analysis. The goal of electron collision studies is to provide absolute values of cross-sections for all processes involved, from elastic to inelastic scattering, as a function of incident electron energy and scattering angle. In spite of many experimental and theoretical studies, electron impact cross-sections for atoms and molecules have not been systematically quantified.

A new fabrication process of Y1Ba2Cu4O8 superconducting filament by solution spinning method under ambient pressure

Abstract: The Y1Ba2Cu4O8 superconducting filament has successfully been prepared by dry-spinning through a homogeneous aqueous solution containing Y, Ba and Cu acetates, polyvinyl alcohol and other organic acids. After removing volatile components, the 124 filament is obtained by heating at 780 °C for 3 h. A decomposition of the 124 filament is investigated for introducing fine flux-pinning centers into the 123 filament. A high transport JQ value of 1900 A/cm2 at 77 K and at O T is attained for the 123 filament through the decomposition of the 124 filament.

Cutting Experiments in a Computer using Atomic Models of a Copper Crystal and a Diamond Tool

Abstract: In order to analyze the mechanism of nanometer cutting, a method of atomic-scale cutting in an experiment using a computer has been developed based on the nonlinear finite-element formulation which regards atoms and atomic interaction as nodes and elements, respectively. This method can handle discontinuous phenomena due to instantaneous propagation of dislocation in a workpiece during cutting. Experiments carried out using two kinds of assumed potential energy between tool and workpiece atoms have revealed that the process of chip formation as well as the stress distribution on the tool face during cutting is strongly dependent on the type of interaction energy between the tool and workpiece, while the size effect for the specific cutting coefficient and the discontinuity of cutting force variation during cutting are common in both types of potential energy. The experiments have also shown that the intermittent drop of potential energy accumulated in the workpiece during cutting results in heat generation associated with plastic deformation of the workpiece, while the heat generation repeatedly causes impulsive temperature rise on the tool face during cutting.

Jet Mixing of Liquids with a Rotating Nozzle around the Axis of a Cylindrical Vessel

Abstract: Mixing time in a jet mixing vessel with a rotating nozzle around the vessel axis was measured. The observed ratio of mixing time to mean residence time, tM/tR, was well correlated with the dimensionless angular velocity Ω* defined as the ratio of nozzle rotating velocity to jet velocity, where the profile of tM/tR was almost symmetrical with respect to Ω* value depending on nozzle angle. The minimum dimensionless mixing time (tM/tR)min was about 0.2 regardless of the jet nozzle angle for both the nozzle-rotating and the vessel-rotating systems.Baffle plates in the jet mixing vessel had a negative effect on the mixing time.Using the dimensionless variables derived here, it is expected that the mixing time for both the jet mixing vessel and the non-baffled agitated vessel can be correlated with the same equation.

Hybrid emulsion spectrometer for the detection of hadronically produced heavy flavor states

Abstract: A hybrid apparatus consisting of a movable emulsion target and a magnetic spectrometer was used in a fixed target Fermilab Tevatron experiment to study the production of heavy quarks by high-energy hadron beams. High-resolution silicon microstrip detectors were used for precise tracking in the dense particle environment. Details of the experimental apparatus, including the data acquisition system, are described.

Glass transition temperature of glassy polymers plasticized by CO2 gas.

Abstract: Proposition d'une methode de mesure par DSC de la Tg de polymeres sous une pression allant jusqu'a 60 atm. Application au cas de polymeres plastifies par absorption de CO 2 sous 60 atm a 25°C

Peak blood ammonia and lactate after submaximal, maximal and supramaximal exercise in sprinters and long-distance runners

Abstract: The purpose of this study was to elucidate the difference in peak blood ammonia concentration between sprinters and long-distance runners in submaximal, maximal and supramaximal exercise. Five sprinters and six long-distance runners performed cycle ergometer exercise at 50% maximal, 75% maximal, maximal and supramaximal heart rates. Blood ammonia and lactate were measured at 2.5, 5, 7.5, 10 and 12.5 min after each exercise. Peak blood ammonia concentration at an exercise intensity producing 50% maximal heart rate was found to be significantly higher compared to the basal level in sprinters (P < 0.01) and in long-distance runners (P < 0.01). The peak blood ammonia concentration of sprinters was greater in supramaximal exercise than in maximal exercise (P < 0.05), while there was no significant difference in long-distance runners. The peak blood ammonia content after supramaximal exercise was higher in sprinters compared with long-distance runners (P < 0.01). There was a significant relationship between peak blood ammonia and lactate after exercise in sprinters and in long-distance runners. These results suggest that peak blood ammonia concentration after supramaximal exercise may be increased by the recruitment of fast-twitch muscle fibres and/or by anaerobic training, and that the processes of blood ammonia and lactate production during exercise may be strongly linked in sprinters and long-distance runners.

Brownian motion in a rotating flow

Abstract: The Langevin equations for a particle of an arbitrary shape and the correlation functions for the fluctuating forces, torques, or force-torque acting on the particle in a rotating flow are derived from the semimicroscopic level of coarse graining by using fluctuating hydrodynamics. In order to obtain the solution of the Navier-Stokes Langevin equation valid over the entire flow region, use is made of the method of matched asymptotic expansions in (Ω f a2/v)1/2≪ 1. The cases of slow and rapid rotation are analyzed. It is shown that the fluctuation-dissipation theorems hold up to the order of (Ω f a2/v)1/2 in both slow and rapid rotation, and that the diffusivity tensor depends on the angular velocity of the fluid and becomes anisotropic.

Relation between Sulfur Pressure and Sticking of Fine Iron Ores in Fluidized Bed Reduction

Abstract: Fourteen kinds of iron ore fines (0015-0021 cm diameter) were reduced to iron in a laboratory batch fluidized bed with a 90%CO-10%CO2 mixture (flow rate: 8 times the minimum fluidization velocity Umf) at 700-900°C to investigate the relation between sticking behavior and sulfur activity in gas phase of bed during metallization (aS), which could be evaluated from chemical analysis of sulfur species in exhausted gas, relative to iron/iron sulfide equilibriumValues of aS obtained in all of tests were in the range of 001-1 The tests showing middle sulfur activities around 01, fell into sticking state soon after initial metallization, accompanied with long iron whiskers at higher temperatures The tests showing activities other than the above conditions, induced short iron whiskers and porous or plain irons, indicating fluidized state until higher reduction degrees at lower temperatures These temperature and sulfur activity dependences of product morphologies, which were in nearly agreement with authors' previous researches about abnormal swelling during reduction of iron oxide pellets prepared from reagent, corresponded to a sticking tendency of bed These results give one reasonable idea by which the ore kind dependence of sticking can be interpreted

Precision Lattice-Parameter Determination of (Mg,Fe)SiO3 Tetragonal Garnets

Abstract: The tetragonal garnet (Mg,Fe)SiO3 is a high-pressure phase of pyroxene that is thought to be a major constituent of the earth9s upper mantle. Its crystal structure is similar to that of cubic garnet, but it is slightly distorted to tetragonal symmetry so that its x-ray powder diffraction pattern shows a very small line splitting. A suite of tetragonal garnets with different compositions in the MgSiO3-rich portion of the MgSiO3-FeSiO3 system was synthesized at about 20 gigapascals and 2000°C. The lattice parameters a and c of quenched samples were determined by whole-powder-pattern decomposition analysis of Fe Kα x-ray powder diffraction data, which has the capacity to resolve to a high degree heavily overlapping reflections. It was found that the lattice parameters can be obtained from the following equations; a (in angstroms) = 11.516 + 0.088x and c (in angstroms) = 11.428 + 0.157x, where x, teh mole fraction of FeSiO3, is 0.0 ≤ x ≤ 0.2.

Preparation of LaNiO3 powder from coprecipitated lanthanum-nickel oxalates

Abstract: Coprecipitation of lanthanum and nickel oxalates in a water-alcohol mixed solution of an oxalic acid resulted in a simultaneous and homogeneous deposition of the respective oxalate particles with a desired cation ratio. The coprecipitated oxalate could be readily converted to a fine powder (5 to 6 m2 g−1) of the desired LaNiO3 by heating at 800 to 850° C. Detailed examination of some precipitation conditions established an optimum procedure needed for the powder synthesis of LaNiO3. Thermal analysis showed that La2NiO4 (high temperature form) is transiently produced prior to the formation of LaNiO3. Mixed valency of the nickel ion in the synthesized powders was quantitatively determined by means of the oxidation-reduction titration, suggesting that the chemical formula of the powders might be LaNiO2.85 to 2.90.

Correlation of Mass Transfer Volumetric Coefficient with Power Input in Stirred Liquid-Liquid Dispersions

Abstract: A continuous-phase mass transfer volumetric coefficient kLa in stirred liquid-liquid dispersions was measured under many stirring conditions by using the hydrolysis reaction of ester with sodium hydroxide. Droplet diameter was also observed with a microscope during the period of reaction progress, allowing the continuous-phase mass transfer coefficient kL to be determined. The resultant kL was correlated with the power input per unit volume and the Sauter mean diameter d32. With the help of the kL correlation equation, d32 was well correlated with the power input per unit volume swept out by the impeller. The kLa values estimated from both the kL correlation equation and the d32 correlation equation agreed well with the observed values.

Structural study of the phase transition of Na4Ca4[Si6O18]

Abstract: Cristallisation a 773 K dans R3m avec a R =7,519 A, α=89,32°, Z=1; a H =10,561, c H =13,199 A, Z=3, affinement jusqu'a R=0,047. Transformation de phase a 748 K. Discussion des deux formes respectivement de haute temperature et de basse temperature

Synthesis and charaterization of new arowmatic polymers containing long alkyl side chains and 1,3,5-triazine rings

Abstract: A series of new aromatic polyamides, polyimides, and polyureas containing 1,3,5-triazine rings in the main chain and two flexible long side chains for each unit, were prepared by the reaction of 2-(N-phenyl-N-octadecylamino)-4-(N-aminophenyl-N-octadecylamino)-6-aminophenyl-1,3,5-triazines with aromatic diacid chlorides, pyromellitic dianhydride, and diisocyanates, respectively. These polymers were soluble in tetrahydrofuran, chloroform, and benzene, but had poor solubility in polar aprotic solvents such as dimethyl sulfoxide and N,N-dimethylformamide. These polymers were stable up to 410°C for polyamides, 430°C for polyimides, and 290°C for polyureas in air. The differntial scanning calorimetric studies of the polymers indicated that the degree of side-chain crystallinity based side chain was 6-10%.

Synthesis and side-chain crystallization of new comb-like polymers from 2-amino-4-(N-alkylanilino)-6-isopropenyl-1,3,5-triazines

Abstract: New isopropenyl-1,3,5-triazines, e.g., 2-amino-4-(N-propyl(N3), hexyl(N6), octyl(N8), decyl(N10), dodecyl(N12), tetradecyl(N14), hexadecyl(N16), octadecyl(N18), and decosyl(N22)anilino)-6-isopropenyl-1,3,5-triazine, were prepared by the reaction of 2-amino-4-anilino-6-isopropenyl-1,3,5-triazine with corresponding alkyl bromides in the presence of sodium hydride in dimethyl sulfoxide. The alkylation reaction proceeded selectively on the imino group, and the products were obtained in high yields. Polymerizations of these monomers were carried out using azobisisobutyronitrile as an initiator. Glass transition temperature of the polymers decreased with increasing the numbers of carbon atoms in alkyl side-chain. The crystallization of the alkyl side-chains in the comb-like polymers was investigated by differential scanning calorimetry (DSC). The crystallization exothermic and the melting endothermic peaks based on the side-chains of the polymers containing long alkyl groups in excess of 14 carbon atoms were observed in DSC thermograms.