Showing papers by "Nagoya Institute of Technology published in 1991"

Experimental study of turbulent swirling flow in a straight pipe.

Abstract: Swirling flow through a pipe is a highly complex turbulent flow and is still challenging to predict. An experimental investigation is performed to obtain systematic data about the flow and to understand its physics. A free-vortex-type swirling flow is introduced in a long straight circular pipe. The swirling component decays downstream as a result of wall friction. The velocity distributions are continuously changing as they approach fully developed parallel flow. The swirl intensity Ω, defined as a non-dimensional angular momentum flux, decays exponentially. The decay coefficients, however, are not constant as conventionally assumed, but depend on the swirl intensity. The wall shear stresses are measured by a direct method and, except in a short inlet region, are a function only of the swirl intensity and the Reynolds number. The velocity distributions and all Reynolds stress components are measured at various axial positions in the pipe. The structure of the tangential velocity profile is classified into three regions: core, annular and wall regions. The core region is characterized by a forced vortex motion and the flow is dependent upon the upstream conditions. In the annular region, the skewness of the velocity vector is noticeable and highly anisotropic so that the turbulent viscosity model does not work well here. The tangential velocity is expressed as a sum of free and forced vortex motion. In the wall region the skewness of the flow becomes weak, and the wall law modified by the Monin–Oboukhov formula is applicable. Data on the microscale and the spectrum are also presented and show quite different turbulence structures in the core and the outer regions.

Experimental evidence for the Si-Si bond model of the 7.6-eV band in SiO2 glass.

Abstract: We have found a decrease in the intensity of the 7.6-eV band and the appearance of the Si-H band upon heating ${\mathrm{SiO}}_{2}$ glasses, which were prepared by a method involving processes of dehydration with ${\mathrm{Cl}}_{2}$ gas, in ${\mathrm{H}}_{2}$ gas. The absorption cross section of the 7.6-eV band evaluated from these changes is 7.5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}17}$ ${\mathrm{cm}}^{2}$, which is close to that of a band centered at 7.56 eV of the ${\mathrm{Si}}_{2}$${\mathrm{H}}_{6}$ molecule containing a Si-Si bond. These results give experimental evidence for the Si-Si bond model of the 7.6-eV band in unirradiated ${\mathrm{SiO}}_{2}$ glass.

Robust speed control of IM with torque feedforward control

Abstract: The authors present a robust speed control of an induction motor (IM) using a load torque observer and feedforward control. The speed response characteristics using a conventional PI (proportional plus integral) controller are affected by variations of system parameters. With the proposed system, the load torque disturbance and the effects of motor and mechanical parameter variations can be removed. The entire control processing was performed by the software of a digital signal processor within a reasonable period, and experimental results showed the robustness of the control system against the disturbance torque and the variation of motor and mechanical parameters. >

Occurrence of Dielectric 1:1:4 Compound in the Ternary System BaO—Ln2O3—TiO2 (Ln = La, Nd, and Sm): II, Reexamination of Formation of Isostructural Ternary Compounds in Identical Systems

Abstract: To establish the correct composition of a ternary compound having higher TiO2 content in the BaO—Nd2O3—TiO2 system, the phase change of samples with variable controlled compositions, which were prepared by a modified coprecipitation method, was examined by X-ray diffractometry and Raman spectroscopy. Identification of the phases present in the calcined samples and microstructural evidence for the fired product from electron microprobe analysis clearly indicated that the ternary compound having the composition 1:1:4 occurs in the present system. X-ray powder diffraction data of the isostructural 1:1:4 and 1:1:3 compounds in each identical ternary system (Ln = La, Nd, and Sm) were refined and indexed. Partial subsolidus phase relations consisting of different composition triangles were also proposed for the present ternary systems.

Complex form of current pulses in negative corona discharges

Abstract: Current wave forms of the first Trichel pulses and initial stages of negative point-to-plane breakdown in carbon monoxide have been measured at a pressure of 13.33 kPa. The results include a report of the intricate pulse wave form with a step on the pulse leading edge and a current hump on the pulse trailing part, which indicates that the physical mechanism for the Trichel pulse phenomenon is more complex than the generally accepted description in terms of Morrow's theory [Phys. Rev. A 32, 1799 (1985); 32, 3821 (1985)]. A tentative explanation of the observed pulse wave form based on the presumed existence of a cathode-directed ionizing wave is outlined.

Occurrence of Dielectric 1:1:4 Compound in the Ternary System BaO—Ln2O3—TiO2 (Ln = La, Nd, and Sm): I, An Improved Coprecipitation Method for Preparing a Single-Phase Powder of Ternary Compound in the BaO—La2O3—TiO2 System

Abstract: An improved coprecipitation method for incorporating three different cations quantitatively in a precursor was developed to prepare a single-phase powder of a ternary compound in the system BaO—La2O3—TiO2. The preparation technique consisted of a preliminary introduction of a specified single component as a preformed binary compound powder. This was followed by the quantitative deposition of the remaining unlike cations as coprecipitated particles in a solution containing a suspension of the preformed compound powder. X-ray fluorescence and electron microprobe analyses showed that the stoichiometric incorporation of the constituent cations was completed for the powder samples thus prepared. From a detailed examination of the phases produced in the composition-controlled powders, it was evident that a ternary compound having the composition BaO · La2O3· 4TiO2 occurs in the present system, for which the X-ray diffraction data were refined and indexed. In addition, the single-phase 1:1:4 compound was found to be synthesized from different precursors through different formation processes.

Auto-compensation of torque ripple of DD motor by torque observer

Abstract: A torque control system for DDM (direct drive motor) with a permanent magnet rotor equipped with a torque observer implemented by software of a digital signal processor is proposed. The speed fluctuation against a disturbance can be fully removed with a torque feedforward loop. It is shown that the direct motor control system with a torque observer gives a superior speed control characteristics. Furthermore, the system has a robustness against disturbing torque and a variation of mechanical parameters. >

A large scale neural network 'CombNET-II'

Abstract: Summary form only given. The authors propose a large-scale neural network model, CombNET-II, which consists of a four-layered network with a comb structure. A vector quantizing network forms the first layer as a stem and many three-layered networks form layers two through four as branches. As input data flows into the stem network, one of the category groups is selected according to the activation level of the neuron. Then the input data flows into one of the branch networks, which classifies the input data into a specified category. CombNET-II employs a self-growing procedure for learning the stem network and back propagation for branch networks. CombNET-II was applied to implement a network to classify 2965 printed Kanji characters (Japanese Industrial Standard, JIS first-level set). Recognition rates of 99.8 approximately 99.9% have been achieved for test data sets. This network consists of more than 10000 neurons and nearly 1 million connections. >

Ammonia and lactate in the blood after short-term sprint exercise

Abstract: Nine well-trained subjects performed 15-, 30-and 45-s bouts of sprint exercise using a cycle ergometer. There was a significant difference in the mean power between a 15-s sprint (706.0 W, SD 32.5) and a 30-s sprint (627.0 W, SD 27.8;P<0.01). The mean power of the 30-s sprint was higher than that of the 45-s sprint (554.7 W, SD 29.8;P<0.01). Blood ammonia and lactate were measured at rest, immediately after warming-up, and 2.5, 5, 7.5, 10, 12.5 min after each sprint. The peak blood ammonia content was 133.8 μmol·1−1, SD 33.5,- for the 15-s sprint, 130.2 μol·1−1, SD 44.9, for the 30-s sprint, and 120.8 μmol ·1−1, SD 24.6, for the 45-s sprint. Peak blood lactates after the 15-, 30- and 45-s sprints were 8.1 mmol · 1−1, SD 1.7, 11.2 mmol · 1−1, SD 2.4, and 14.7 mmol ·1−1, SD 2.1, respectively. There was a significant linear relationship between peak blood ammonia and lactate in the 15-s (r, 0.709;P< 0.05), 30-s (r, 0.797;P<0.05) and 45-s (r, 0.696;P<0.05) sprints. Though the peak blood lactate content increased significantly with increasing duration of the sprints (P<0.01), no significant difference was found in peak blood ammonia content among the 15-, 30- and 45-s sprints. These results suggest that the peak value of ammonia in the blood appears in sprints within 15-s and that the blood ammonia level is linked to the lactate in the blood.

High field magnetoresistance and de Haas - van Alphen effect in UGe2

Abstract: We have measured the magnetoresistance and de Haas-van Alphen (dHvA) effect in the ferromagnetic compound UGe 2 . It is found that UGe 2 is a compensated metal whose Fermi surface supports open orbits, along the b - and c -axes of the orthorhombic crystal structure. From the dHvA experiment, we have detected carriers with heavy cyclotron masses, ranging from 2.3 m 0 to 24.5 m 0 .

Preparation and Characterization of YBa 2 Cu 3 O 2−δ Films Containing an Excess Amount of Cu by Chemical Vapor Deposition

Abstract: YBa2Cu3O7-δ films containing an excess amount of Cu were prepared on MgO(001) at 650-750°C by chemical vapor deposition using β-diketone metal chelates. In the films prepared at the low temperatures of 650°C and 700°C, the degree of c-axis orientation was enhanced with increase of the Cu content from Y:Ba:Cu=1:2:3 to 1:2:4, and the films with Cu-rich content showed higher Tc values than the films close to the stoichiometric composition. At the higher temperature of 750°C, a supplied excess of the Cu element affected the in-plane alignment of the grains and critical current density.

Effects of coimplantation of silicon and nitrogen on structural defects and Si-N bond formation in silica glass.

Abstract: Effects of coimplantation of Si and N ions on structural defects in ${\mathrm{SiO}}_{2}$ glass are reported. Silicon-silicon bonds are formed as the predominant defect and their concentrations are almost the same as those of the implanted ions in Si-implanted samples but only about 1/10 those in the case of N-implanted samples. The bond concentrations in the coimplanted samples are approximately 50% of the sum of the concentrations in samples implanted with either Si or N. No difference was observed in the concentrations between specimens coimplanted in two different sequences. Paramagnetic nitrogen dioxide molecules are found to be formed in N-implanted samples but are not detected in the coimplanted samples. These results show that coimplantation is highly effective in combining implanted silicon with nitrogen, resulting in the formation of Si-N bonds. The importance of a Si-Si bond is suggested as an active reaction intermediate in coimplantation in ${\mathrm{SiO}}_{2}$.

Gas transport properties of annealed polyimide films

Abstract: La sorption et la permeation de CO 2 dans des films de polypyromellitimide recuit dans differentes conditions est analysee avec les modeles de sorption en mode binaire et d'immobilisation partielle. La trempe du polymere a partir d'une temperature superieure a Tg augmente la sorption du CO 2 alors que le refroidissement lent la diminue. La trempe ameliore aussi la permeabilite selective de l'oxygene par raport a l'azote

Room-temperature continuous-wave operation of AlGaAs-GaAs single-quantum-well lasers on Si by metalorganic chemical-vapor deposition using AlGaAs-AlGaP intermediate layers

Abstract: The heterointerfaces of single quantum wells and the characteristics of single-quantum-well lasers on Si substrates grown with Al/sub 05/Ga/sub 05/As-Al/sub 055/Ga/sub 045/P intermediate layers entirely by metalorganic chemical-vapor deposition are reported The effects of thermal cycle annealing on the crystallinity and lasing characteristics of GaAs-Si are also reported Thermal cycle annealing is found to improve the crystallinity of GaAs-Si, and to contribute to room-temperature continuous-wave operations of lasers on Si substrates By using the Al/sub 05/Ga/sub 05/As-Al/sub 055/Ga/sub 0/ intermediate layers, single quantum wells with a specular surface morphology and a smoother heterointerface can be grown on an Si substrate >

Mechanical Properties of Copoly(N-hydroxyethyl L-glutamine-co-N-hydroxypentyl L-glutamine) Hydrogels.

Abstract: Random copolymers, poly(N-hydroxyethyl L-glutamine-co-N-hydroxypentyl L-glutamine) (PHPeEG) as well as the corresponding homopolymers, poly(N-hydroxyethyl L-glutamine) (PHEG) and poly(N-hydroxypentyl L-glutamine) (PHPeG), were prepared by aminolysis with a mixture of 2-amino-1-ethanol (EA) and 5-amino-1-pentanol (PeA) in the presence of crosslinking agent, octamethylenediamine (OMDA), on membranes of poly(γ-benzyl L-glutamate) The properties of the resultant membranes, such as the degree of swelling Qw, conformational properties and mechanical properties were studied in the pseudo-extracellular fluid (PECF) Qw and helix content are dependent on the composition of the random copolymers The mechanical strength of PHEG hydrogel was improved largely by introducing HPeG residues, while low Young’s modulus, high swelling and low helix content were found to remain unchanged The transition from the elastomer-type mechanical behavior to the skin-type mechanical behavior was observed at 82–90% of helix content and 110–160% of Qw for the copolymers from tensile tests The difference in mechanical behavior was investigated in detail by creep, stress relaxation and hysteresis experiments

An Infinite-stiffness Aerostatic Bearing with an Exhaust-control Restrictor

Abstract: The aerostatic bearing is a crucial element for ultra-precision machine tools, and its stiffness should be as high as possible. To obtain an infinite bearing stiffness, we propose a new type of active restrictor. Differing from conventional inflow passive and active restrictors [1], the proposed restrictor controls the air volume exhausted from the bearing surface. Therefore, we have called this active restrictor an exhaust-control restrictor (ECR). Main advantage of the ECR is its stability for the occurrence of pneumatic hammer.