Nagoya Institute of Technology

About: Nagoya Institute of Technology is a education organization based out in Nagoya, Japan. It is known for research contribution in the topics: Thin film & Turbulence. The organization has 10766 authors who have published 19140 publications receiving 255696 citations. The organization is also known as: Nagoya Kōgyō Daigaku & Nitech.

Experimental evidence of reaction-driven miscible viscous fingering

Abstract: An experimental demonstration of reaction-driven viscous fingering developing when a more viscous solution of a reactant $A$ displaces a less viscous miscible solution of another reactant $B$ is presented. In the absence of reaction, such a displacement of one fluid by another less mobile one is classically stable. However, a simple $A+B\ensuremath{\rightarrow}C$ reaction can destabilize this interface if the product $C$ is either more or less viscous than both reactant solutions. Using the pH dependence of the viscosity of some polymer solutions, we provide experimental evidence of both scenarios. We demonstrate quantitatively that reactive viscous fingering results from the buildup in time of nonmonotonic viscosity profiles with patterns behind or ahead of the reaction zone, depending on whether the product is more or less viscous than the reactants. The experimental findings are backed up by numerical simulations.

High-precision torque control of reluctance motors

Abstract: A method for the high-precision torque control of a reluctance motor for servo applications is presented. The prototype is a three-phase, eight-pole reluctance motor driven by a MOSFET inverter. The current control as well as the speed control is performed by the software of a digital signal processor. The motor is supplied with sinusoidal current, and two current control methods are proposed. One is based on the vector control principle to achieve linearity between current and torque, and another is developed to obtain the maximum torque/current ratio. Due to the saliency, the instantaneous torque contains a large ripple component. In the case of the test motor, the ripple torque was as much as 26% of the rated torque under the sinusoidal current drive. Experimental results show that the ripple component could be reduced to 6% by superimposing the compensation current component on the current reference. >

Digital PWM-Control-Based Active Vibration Cancellation for Switched Reluctance Motors

Abstract: This paper presents a study on a control strategy for active vibration cancellation (AVC) and noise reduction in switched reluctance (SR) motors. It has been revealed that two-stage commutation control based on the natural frequency of the stator body has been effective in suppressing the vibration occurring on the stator body at the commutation. According to some considerations on the generation mechanism of the vibration, a new AVC control for variable-speed SR motor drives under digital PWM control is proposed. Experimental studies using a 12-kW three-phase 12/8 SR motor demonstrate that the proposed two-step commutation control using negative voltage PWM is much effective as an AVC and noise reduction technique. Moreover, the proposed control is evaluated from the viewpoints of drive performances such as torque ripple and copper loss.

Reticulated Replica Ceramic Foams: Processing, Functionalization, and Characterization

Abstract: Reticulated ceramic foams are used in a wide range of applications such as filters, catalyst supports, lightweight materials, energy absorptions materials, or as scaffolds for tissue engineering as the most common ones. Based on gaseous foaming processes of polymers, a stochastic distribution of closed pores is obtained. By reticulation processing thin foam windows are removed between cells turning a closed cell into an open cell structure. These foams are used as template for porous ceramics manufacturing: With different processing approaches, for example, with dip coating of a ceramic slurry and a subsequent (multistep) thermal treatment ceramic reticulate foams are obtained. A variety of material properties strongly depend on the cell and strut size, as well on material composition. Functionalization of ceramic foam surfaces (outer surface functionalization), for example, with zeolites or nanosized aggregates lead to an increase of the specific surface area or provides catalytic or heat storage functionality. Filling of struts (inner surface functionalization) may lead to improved mechanical stability or may provide functionalities such as electric conductivity. The present work summarizes the processing steps from the template foam to the final cellular ceramic, functionalization strategies, and the most common characterization techniques.

Studies on the Solid Solution of Mn in BaTiO3.

Abstract: BaTi1-xMnxO3 solid solutions with 0≤x≤0.04 were synthesized in reducing atmosphere (PO2<10-9 Pa) and in air at 1350°C for 2 h. The effect of Mn ions with different valences on the crystal structure of BaTiO3 was studied by the room-temperature Raman scattering, electron spin resonance (ESR) and X-ray powder diffraction analyses. The crystal structure of the solid solution was analyzed to determine the change of its lattice parameters. It was found that in a reducing atmosphere, Mn2+ ions promoted the tetragonal-to-cubic transformation, as both a contraction of c-axis and an extension of a-axis were observed with an increase in Mn content. In contrast, Mn ions in the air-synthesized samples promoted the tetragonal-to-hexagonal transformation. The formation of the hexagonal phase was accompanied by a strong extension of the c-axis of the tetragonal phase from 4.032 A to 4.042 A. This was attributed to Jahn-Teller distortions caused by Mn3+ ions.