Published papers

An electro-conjugation fluid (ECF) is a kind of dielectric liquid, which generates a powerful flow when high DC voltage is applied with tiny electrodes. This study deals with the derivation of the governing equations for electro-conjugate fluid flow based on the Korteweg-Helmholtz (KH) equation which represents the force in dielectric liquid subjected to high DC voltage. The governing equations consist of the Gauss's law, charge conservation with charge recombination, the KH equation, the continuity equation and the incompressible Navier-Stokes equations. The KH equation consists of coulomb force, dielectric constant gradient force and electrostriction force. The governing equation gives the distribution of electric field, charge density and flow velocity. In this study, direct numerical simulation (DNS) is used in order to get these distribution at arbitrary time. Successive over-relaxation (SOR) method is used in analyzing Gauss's law and constrained interpolation pseudo-particle (CIP) method is used in analyzing charge conservation with charge recombination. The third order Runge-Kutta method and conservative second-order-accurate finite difference method is used in analyzing the Navier-Stokes equations with the KH equation. This study also deals with the measurement of ECF flow generated with a symmetrical pole electrodes pair which are made of 0.3 mm diameter piano wire. Working fluid is FF-1EHA2 which is an ECF family. The flow is observed from the both electrodes, i.e., the flow collides in between the electrodes. The governing equation successfully calculates mean flow velocity in between the collector pole electrode and the colliding region by the numerical simulation.

This paper presents a novel tactile evaluation method. Although tactile sense is important information for end users to evaluate products, it has not been characterized quantitatively. In order to achieve quantitative characterization of tactile sense, this paper develops a novel tactile evaluation system based on human tactile perception mechanism. In the system, an object, which will be evaluated, is fixed on a sample table rotated with constant speed, and a piezoelectric element is placed in contact with the object surface with constant normal force. Then the piezoelectric element measures the vibration information during experiment. Comparing the vibration information with tactile receptors properties, we could estimate information we are getting during actively touching the object. Comparing the sensory evaluation results with the estimated information, the paper defines three tactile evaluation indexes relating to softness, roughness and preference of the target object. (C) 2013 Elsevier By. All rights reserved.

This paper proposes a novel droplet transportation method for micro total analysis system (mu TAS), which we called as an active flow channel matrix, using an electro-conjugate fluid (ECF). The ECF is a kind of functional fluid, which generates a powerful flow when applying a high voltage across the electrodes. A droplet that is placed into the channel may move in any direction according to the channel flow generated by the ECF. Therefore, in order for the multiple droplets from different channels to be merged, they are moved to reach the desired intersection. According to this concept, we developed a prototype of the active flow channel matrix. Then, we measured two droplets' position and controlled the position of them by using image processing technique. The experimental results demonstrated the possibility of our concept for mu TAS. (C) 2013 Published by Elsevier B.V.

Hydrocarbons are widely used as insulating compounds. However, their fundamental characteristics in conduction phenomena are not completely understood. A great deal of effort is required to determine reasonable ionic behavior from experiments because of their complicated procedures and tight controls of the temperature and the purity of the liquids. In order to understand the conduction phenomena, we have theoretically calculated the ion mobilities of hydrocarbons and investigated their characteristics using the coarse grained model in molecular dynamics simulations. We assumed a molecule of hydrocarbons to be a bead and simulated its dependence on the viscosity, electric field, and temperature. Furthermore, we verified the suitability of the conformation, scale size, and long-range interactions for the ion mobility. The results of the simulations show that the ion mobility values agree reasonably well with the values from Walden's rule and depend on the viscosity but not on the electric field. The ion mobility and self-diffusion coefficient exponentially increase with increasing temperature, while the activation energy decreases with increasing molecular size. These values and characteristics of the ion mobility are in reasonable agreement with experimental results. In the future, we can understand not only the ion mobilies of hydrocarbons in conduction, but also we can predict general phenomena in electrochemistry with molecular dynamics simulations. (C) 2016 Author(s).

The growth rate of vegetables in plant factories can be regulated by environmental factors including light, temperature, and chemicals, which might give rise to mutation in leaf health. Here, we aim to devise a new way that allows for controlling the growth rate of plants in hydroponics as well as maintaining the product quality; we apply underwater ultrasound and dissolved oxygen supersaturation as external stimuli to plants. As an example, we examine the growth of leaf lettuce in hydroponics with exposure to 28-kHz ultrasound and dissolved oxygen supersaturation up to 36 mg/L at 20 °C. Our results show that exposure to the ultrasound of peak-to-peak pressure at 20 kPa or larger works as the growth inhibitor of the leaves and the roots, while the oxygen supersaturation as the growth promoter, without any degradation of chlorophyll in the leaves. This suggests that these external stimuli can be used in the growth control system of plant factories.

Automobile interior is one of the most crucial factors for evaluating products' value. During the evaluation, tactile cue must play an important role in deducing product's quality, however, the regionality of customer's tactile perception is in most cases neglected in previous studies. This study conducted sensory evaluation tests of door armrests in three countries, Japan, USA and Denmark, which are representatives of East Asia, North America and Europe, respectively. Eight samples of door armrests and 29 words expressing tactile sensations were used in the test. 167 participants in total participated in the evaluation test, 53 from Japan, 64 from USA and 50 from Denmark. As results of factor analysis, cluster analysis and multiple regression analysis, the following conclusion can be derived, i.e., although there is no significant difference in preference perception of door armrests, the tactile perception structures are different among three countries.

Electro-conjugate fluid (ECF) is a functional fluid that can generate a high-power flow induced by a high direct-current voltage. While ECF has been used in various fields, including mechanical, chemical, and biomedical systems, its underlying principles have not been sufficiently understood to be applicable to ECF system design, and the lack of theoretical models hampers further applications of ECF. This study aims to investigate underlying principles of ECF flow generation with a rectangular-slit electrode pair. By analyzing the effect of electrode configuration on the flow generation, this paper proposes a theoretical model for electrode design for efficient flow generation. The proposed model has been validated by comparing the simulation results with the visualized characteristics from flow experiments. The results show that the flow rate can be controlled by changing the electrode configuration with the maximum flow rate with the rectangular-slit electrode gap of 1.0 mm and the slit electrode gap of 5.0 mm.