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Search Results: 1 - 10 of 808 matches for " Shigeru Ohtsuka "
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A Micromixer Using the Chaos of Secondary Flow: Rotation Effect of Channel on the Chaos of Secondary Flow  [PDF]
Yasutaka Hayamizu, Shinichiro Yanase, Shinichi Morita, Shigeru Ohtsuka, Takeshi Gonda, Kazunori Nishida, Kyoji Yamamoto
Open Journal of Fluid Dynamics (OJFD) , 2012, DOI: 10.4236/ojfd.2012.24A021
Abstract: The micromixer, which has a rotor with a curved channel, is studied experimentally. The secondary flow in a curved channel of rectangular cross-section is investigated using PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) methods. Two walls of the channel (the inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction of the exit of the channel. The non-dimensional channel curvature δ=a/R is taken to be about 0.1, where 2a is the width of the channel, R the curvature radius of the channel. Other non-dimensional parameters concerned are the Dean number De=Reδ1/2, the Reynolds number Re=qdh/v, where q is the mean flow velocity in the channel axis direction, ν the kinematic viscosity, dh the hydraulic diameter of the channel, and the Taylor number Tr=2(2δ)1/2Ωa2/(δv), where Ω is the angular velocity of the rotor. Photographs of the flow in a cross-section at 180° downstream from the curved channel entrance are taken by changing the flux (De) at a constant rotational speed (Tr) of the channel walls. It is found that good mixing performance is obtained in the case of De≤0.1|Tr| and for that case secondary flows show chaotic behaviors. And then we have confirmed the occurrence of reversal of the mean axial flow.
Behavior of Motile Sperm in Taylor-Couette Flow: Effect of Shear Stress on the Behavior of Motile Sperm  [PDF]
Yasutaka Hayamizu, Toru Hyakutake, Koji Matsuura, Shinichiro Yanase, Shinichi Morita, Shigeru Ohtsuka, Takeshi Gonda
Open Journal of Fluid Dynamics (OJFD) , 2013, DOI: 10.4236/ojfd.2013.32A002
Abstract:

Infertility is often cited as one of the causes of a declining birthrate, which has become a serious social problem in recent years. Processes by which motile sperm can be safely and easily sorted are therefore important for infertility treatment. Therefore, as a new sorting method, microfluidic sperm sorter using the microfluidic system has been developed. To improve more separation efficiency of this device, it is necessary to know the behaviors of motile sperm in the microchannel where the sperm undergo shear flow. The previous study implied the necessity of the modeling of motile sperm in the shear flow. In the present study, therefore, we experimentally investigated the behavior of the motile sperm in the Taylor-Couette flow using PTV (Particle Tracking Velocimetry) method. The experimental results showed that the ascent of the shear stress led to the increase in the sperm velocity, and the direction of the sperm velocity was opposite to that of the flow.

A Micromixer Using the Taylor-Dean Flow: Effect of Inflow Conditions on the Mixing  [PDF]
Toshihiko Kawabe, Yasutaka Hayamizu, Shinichiro Yanase, Takeshi Gonda, Shinichi Morita, Shigeru Ohtsuka, Kyoji Yamamoto
Open Journal of Fluid Dynamics (OJFD) , 2014, DOI: 10.4236/ojfd.2014.45037
Abstract: Chaotic mixing in a curved-square channel flow is studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flows. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In the present paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental and numerical results. We produced a micromixer model of the curved channel several centimeters long with square cross section of a few millimeters side. The secondary flow was measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. We also performed three-dimensional numerical simulations for the exactly same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is achieved for the case of De ≤ 0.1Tr, and that mixing efficiency changes according to the difference in inflow conditions. The flow is studied both experimentally and numerically, and both results agree with each other very well.
A Micromixer Using the Taylor-Dean Flow: Effects of Aspect Ratio and Inflow Condition on the Mixing  [PDF]
Yasutaka Hayamizu, Toshihiko Kawabe, Shinichiro Yanase, Takeshi Gonda, Shinichi Morita, Shigeru Ohtsuka, Kyoji Yamamoto
Open Journal of Fluid Dynamics (OJFD) , 2015, DOI: 10.4236/ojfd.2015.53027
Abstract: Chaotic mixing in three different types of curved-rectangular channels flow has been studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient are imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flow. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In this paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental results and numerical ones. We produced three micromixer models of the curved channel, several centimeters long, with rectangular cross-section of a few millimeters side. The secondary flow is measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. Also we performed three-dimensional numerical simulations with the open source CFD solver, OpenFOAM, for the same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is obtained in the case of De ≤ 0.1 Tr, and it becomes more remarkable when the aspect ratio tends to large. And it is found that the mixing efficiency changes according to the aspect ratio and inflow condition.
Comparison of the Sampling Efficiency in Spatial Autoregressive Model  [PDF]
Yoshihiro Ohtsuka, Kazuhiko Kakamu
Open Journal of Statistics (OJS) , 2015, DOI: 10.4236/ojs.2015.51002
Abstract: A random walk Metropolis-Hastings algorithm has been widely used in sampling the parameter of spatial interaction in spatial autoregressive model from a Bayesian point of view. In addition, as an alternative approach, the griddy Gibbs sampler is proposed by [1] and utilized by [2]. This paper proposes an acceptance-rejection Metropolis-Hastings algorithm as a third approach, and compares these three algorithms through Monte Carlo experiments. The experimental results show that the griddy Gibbs sampler is the most efficient algorithm among the algorithms whether the number of observations is small or not in terms of the computation time and the inefficiency factors. Moreover, it seems to work well when the size of grid is 100.
Seismic Damage Estimation of an Actual Reinforced Concrete Structure Using Subset MCMC  [PDF]
Shigeru Kushiyama
Open Journal of Civil Engineering (OJCE) , 2013, DOI: 10.4236/ojce.2013.33016
Abstract:

To estimate seismic damage of structures under strong motions is very important to know true safety of structures. However, we have to deal with very small failure probability issue to investigate quantitatively. If we use standard MCS (Monte Calro Simulation) to discuss failure probability, e.g., 1 × 10-6 order, since we have to execute nonlinear dynamic response analyses of approximate 107 times, it is not realistic. Recently, a subset simulation, which reduces the computation time by replacing small failure probability into the product of conditional failure probabilities, was proposed. In this study, the subset simulation is applied to estimate failure probability of an actual reinforced concrete building with 11 stories, and discuss the safety of the structure by checking with design criteria.

Spin-Magnetic Moment of Dirac Electron, and Role of Zitterbewegung  [PDF]
Shigeru Sasabe
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.57064
Abstract:

The spin-magnetic moment of the electron is revisited. In the form of the relativistic quantum mechanics, we calculate the magnetic moment of Dirac electron with no orbital angular-momentum. It is inferred that obtained magnetic moment may be the spin-magnetic moment, because it is never due to orbital motion. A transition current flowing from a positive energy state to a negative energy state in Dirac Sea is found. Application to the band structure of semiconductor is suggested.

Statistical Survey of Deaths from Nonmelanoma Skin Cancer in Japan during 54 Years
Hisashi Ohtsuka
Journal of Skin Cancer , 2011, DOI: 10.1155/2011/293926
Abstract: The author analyzed the annual trends in the number of deaths from nonmelanoma skin cancer (NMSC) from 1955 to 2008 in Japan on the basis of the data from the Vital Statistics of Japan. The general trends in the number of deaths from NMSC were downward between 1979 to 1994, but upward after 1995. The general trends in age-standardized death rates were roughly downward, although the death rates plateaued after 1995. The recent annual increased ratio of deaths from NMSC was 3.8% (95% confidence interval: 2.7?~?4.9%). The number and proportion of deaths from NMSC among the elderly were increasing in Japan. For females, more than 50% of the deaths occurred recently at or after 85?years of age, whereas, for males, this proportion was at or after 75?years of age, nearly reaching at or after 80?years of age. 1. Introduction The incidence of nonmelanoma skin cancer (NMSC) has been increasing during the past half century in many countries [1–6]. Authors performed the analysis of changing trends in the number of deaths from NMSC in Japan from 1955 to 2000 [7]. This time, the author expanded the period of survey to 2008 and revised the analysis, using the new WHO standard population which is effective for the period 2000–2025 [8]. 2. Material and Methods The annual trends in the number of deaths from NMSC in Japan from 1955 to 2008, those in age-standardized death rates, those in 3-year moving average, those by 5-year age group, those by sex and age group, and those in the proportion of deaths by sex and age group were investigated on the basis of the data from the Vital Statistics of Japan, Statistics and Information Department, Minister's Secretariat, Ministry of Health, Labor and Welfare. The corresponding revisions of the International Classification of Diseases (ICD) and codes were ICD-6 code 191 in 1955–1957, ICD-7 code 191 in 1958–1967, ICD-8 code 173 in 1968–1978, ICD-9 code 173 in 1979–1994, and ICD-10 code C44 in 1995–2008, respectively. The author, however, treated the results continuously from 1955 to 1967, because there was no difference between ICD-6 and ICD-7 concerning NMSC. The author treated the remaining revisions as discontinuous, because there was a minor difference between ICD-6/-7, ICD-8, ICD-9, and ICD-10. The author judged that it would be possible to obtain the general annual trends in the number of deaths from NMSC in Japan for 54 years, although, strictly speaking, there were four times minor changes of ICD classifications concerning NMSC between these periods. The death rates were adjusted every year using the new WHO world standard
Corrosion Protection of Steels by Conducting Polymer Coating
Toshiaki Ohtsuka
International Journal of Corrosion , 2012, DOI: 10.1155/2012/915090
Abstract: The corrosion protection of steels by conducting polymer coating is reviewed. The conducting polymer such as polyaniline, polypyrrole, and polythiophen works as a strong oxidant to the steel, inducing the potential shift to the noble direction. The strongly oxidative conducting polymer facilitates the steel to be passivated. A bilayered PPy film was designed for the effective corrosion protection. It consisted of the inner layer in which phosphomolybdate ion, (PMo), was doped and the outer layer in which dodecylsulfate ion (DoS) was doped. The inner layer stabilized the passive oxide and the outer possessed anionic perm-selectivity to inhibit the aggressive anions such as chloride from penetrating through the PPy film to the substrate steel. By the bilayered PPy film, the steel was kept passive for about 200?h in 3.5% sodium chloride solution without formation of corrosion products. 1. Introduction Since the investigation of Shirakawa et al. on conducting polyacetylene, various applications of conducting polymer have been reported [1]. Utilization of the conducting polymer for corrosion protection coating is one of these applications, and many papers have been presented in the last decade. Preparation of polyacetylen was made by oxidation in gaseous phase; however, at present, the conducting polymers such as polyaniline (PAni), polypyrrole (PPy), and polythiophen (Pthio) in Figure 1 for the corrosion protection have been prepared by electrochemical oxidation in liquid phase. Figure 1: Typical conducting polymers: (a) polypyrrole (PPy), (b) polythiophen (PThio), and (c) polyaniline (PAni). For application of the conducting polymer to corrosion protection, DeBerry was firstly reported in 1985, who presented that the stainless steel covered by PAni was kept in the passive state for relatively long period in sulfuric acid solution [2]. Wessling then pointed out that the conducting polymer coating of polyaniline and polypyrrole possibly possessed self-healing properties, in which the passive oxide between the substrate metal and the conducting polymer could be spontaneously reformed at a flawed site by oxidative capability of the conducting polymer [3]. When anodic potentials are applied to electrodes covered by the conducting polymers shown in Figure 1 after the polymerization, the oxidative property is provided in addition to the conductivity. The ability of the conducting polymer to oxidize the substrate steels allows potential of steels to be shifted to the passive state, in which the steels are protected by the passive oxide formed beneath the
Views on luck and winning, self-control, and gaming service expectations of culturally and linguistically diverse Australian poker machine gamblers
Keis Ohtsuka
Asian Journal of Gambling Issues and Public Health , 2013, DOI: 10.1186/2195-3007-3-9
Abstract: Despite an increase in social diversity in recent years, the role of culture in gambling cognition and behaviour is not fully understood. Qualitative interviews examined subjective views of Australian poker machine (electronic gaming machine) gamblers from culturally and linguistically diverse (CALD) backgrounds. A total of 49 Australian poker machine gamblers from CALD backgrounds (20 Chinese, 15 Vietnamese and 14 Greek Australians) were interviewed regarding their views on the concept of luck and winning, self control, subjective meanings of gambling and gaming venue service expectations. The current findings showed that the majority of poker machine gamblers from CALD backgrounds believed that the payout of poker machines occurred randomly. Luck was defined, therefore, as being at the right place at the right time when the poker machine pays out. However, a small number of interviewees maintained an optimistic view about achieving gambling wins by using a certain system. While experienced gamblers and those with secondary school qualification or lower regarded poker machine gambling as a random potluck, a few young players with university education subscribed to a more elaborate endorsement in favour of their own systems to win on the poker machine. Australian CALD gamblers valued friendly professional service from gaming venue staff (e.g., courteous customer service, affordable, quality food and drink, personal greetings using first names) but disliked intrusive or over-friendly interactions. Implications of the findings on the role of superstition and cognition on gamblers' beliefs are discussed.
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