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Search Results: 1 - 10 of 474 matches for " Shintaro Kawahara "
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Immersive VR Visualizations by VFIVE. Part 2: Applications
Akira Kageyama,Nobuaki Ohno,Shintaro Kawahara,Kazuo Kashiyama,Hiroaki Ohtani
Physics , 2013,
Abstract: VFIVE is a scientific visualization application for CAVE-type immersive virtual reality systems. The source codes are freely available. VFIVE is used as a research tool in various VR systems. It also lays the groundwork for developments of new visualization software for CAVEs. In this paper, we pick up five CAVE systems in four different institutions in Japan. Applications of VFIVE in each CAVE system are summarized. Special emphases will be placed on scientific and technical achievements made possible by VFIVE.
Super-Droplet Method for the Numerical Simulation of Clouds and Precipitation: a Particle-Based Microphysics Model Coupled with Non-hydrostatic Model
Shin-ichiro Shima,Kanya Kusano,Akio Kawano,Tooru Sugiyama,Shintaro Kawahara
Physics , 2007, DOI: 10.1002/qj.441
Abstract: A novel simulation model of cloud microphysics is developed, which is named Super-Droplet Method (SDM). SDM enables accurate calculation of cloud microphysics with reasonable cost in computation. A simple SDM for warm rain, which incorporates sedimentation, condensation/evaporation, stochastic coalescence, is developed. The methodology to couple SDM and a non-hydrostatic model is also developed. It is confirmed that the result of our Monte Carlo scheme for the coalescence of super-droplets agrees fairly well with the solution of stochastic coalescence equation. A preliminary simulation of a shallow maritime cumulus formation initiated by a warm bubble is presented to demonstrate the practicality of SDM. Further discussions are devoted for the extension and the computational efficiency of SDM to incorporate various properties of clouds, such as, several types of ice crystals, several sorts of soluble/insoluble CCNs, their chemical reactions, electrification, and the breakup of droplets. It is suggested that the computational cost of SDM becomes lower than spectral (bin) method when the number of attributes $d$ becomes larger than some critical value, which may be $2\sim4$.
MovieMaker: A Parallel Movie-Making Software for Large Scale Simulations
Hitoshi Uehara,Shintaro Kawahara,Nobuaki Ohno,Mikito Furuichi,Fumiaki Araki,Akira Kageyama
Physics , 2006, DOI: 10.1017/S0022377806004995
Abstract: We have developed a parallel rendering software for scientific visualization of large-scale, three-dimensional, time development simulations. The goal of this software, MovieMaker, is to generate a movie, or a series of visualization images from totally one TB-scale data within one night (or less than 12 hours). The isocontouring, volume rendering, and streamlines are implemented. MovieMaker is a parallel program for the shared memory architecture with dynamic load balancing and overlapped disk I/O.
Deterministic Parsing Model of the Compound Biological Effectiveness (CBE) Factor for Intracellular 10Boron Distribution in Boron Neutron Capture Therapy  [PDF]
Shintaro Ishiyama
Journal of Cancer Therapy (JCT) , 2014, DOI: 10.4236/jct.2014.514140

Purpose: In defining the biological effects of the 10B(n, α)7Li neutron capture reaction, we have previously developed a deterministic parsing model to determine the Compound Biological Effectiveness (CBE) factor in Borono-Phenyl-Alanine (BPA)-mediated Boron Neutron Capture Therapy (BNCT). In present paper, we demonstrate that the CBE factor is directly and unambiguously derivable by the new formula for any case of intracellular 10Boron (10B) distribution, which is founded on this model for tissues and tumor. Method: To determine the

Simulation of Human Phonation with Vocal Nodules  [PDF]
Shinji Deguchi, Yuki Kawahara
American Journal of Computational Mathematics (AJCM) , 2011, DOI: 10.4236/ajcm.2011.13022
Abstract: The geometric and biomechanical properties of the larynx strongly influence voice quality and efficiency. A physical understanding of phonation natures in pathological conditions is important for predictions of how voice disorders can be treated using therapy and rehabilitation. Here, we present a continuum-based numerical model of phonation that considers complex fluid-structure interactions occurring in the airway. This model considers a three-dimensional geometry of vocal folds, muscle contractions, and viscoelastic properties to provide a realistic framework of phonation. The vocal fold motion is coupled to an unsteady compressible respiratory flow, allowing numerical simulations of normal and diseased phonations to derive clear relationships between actual laryngeal structures and model parameters such as muscle activity. As a pilot analysis of diseased phonation, we model vocal nodules, the mass lesions that can appear bilaterally on both sides of the vocal folds. Comparison of simulations with and without the nodules demonstrates how the lesions affect vocal fold motion, consequently restricting voice quality. Furthermore, we found that the minimum lung pressure required for voice production increases as nodules move closer to the center of the vocal fold. Thus, simulations using the developed model may provide essential insight into complex phonation phenomena and further elucidate the etiologic mechanisms of voice disorders.
The Phonetics of Multiple Vowel Lengthening in Japanese  [PDF]
Shigeto Kawahara, Aaron Braver
Open Journal of Modern Linguistics (OJML) , 2013, DOI: 10.4236/ojml.2013.32019
Abstract: Many languages exploit a short vs. long lexical contrast in vowels. In most, if not all of these languages, the contrast is binary. In Japanese, however, speakers can lengthen vowels to express emphasis, and multiple degrees of lengthening can be used to express different degrees of emphasis. This paper offers the first experimental documentation of this emphatic vowel lengthening phenomenon. The current results demonstrate that, among the seven speakers recorded, at least a few speakers show six-levels of distinction in duration, and all but one speaker showed a steady linear correlation between duration and level of emphasis. We conclude that Japanese speakers have articulatory control that allows them to make very fine-grained durational distinctions, which go beyond mere binary short vs. long distinctions.
Object-Spatial Imagery Types of Japanese College Students  [PDF]
Masahiro Kawahara, Kazuo Matsuoka
Psychology (PSYCH) , 2013, DOI: 10.4236/psych.2013.43024

This study investigated the object-spatial imagery types found among Japanese college students. First, we examined the descriptive statistics of the Japanese version of the Object-Spatial Imagery Questionnaire object-spatial imagery scales, which measure respondents’ tendencies with respect to object-spatial imagery types. Although the means of these subscales were lower than those of the original versions, the raw score distributions and gender differences were similar to those obtained using the original version. Additionally, we compared imagery types among students in seven different academic departments. Specifically, the results showed specific patterns of imagery type among students in each department, indicating that the object-spatial imagery type model is applicable to Japanese college students and that individual imagery type data would be helpful for career guidance.

Computation of Greeks Using Binomial Tree  [PDF]
Yoshifumi Muroi, Shintaro Suda
Journal of Mathematical Finance (JMF) , 2017, DOI: 10.4236/jmf.2017.73031
Abstract: This paper proposes a new efficient algorithm for the computation of Greeks for options using the binomial tree. We also show that Greeks for European options introduced in this article are asymptotically equivalent to the discrete version of Malliavin Greeks. This fact enables us to show that our Greeks converge to Malliavin Greeks in the continuous time model. The computation algorithm of Greeks for American options using the binomial tree is also given in this article. There are three advantageous points to use binomial tree approach for the computation of Greeks. First, mathematics is much simpler than using the continuous time Malliavin calculus approach. Second, we can construct a simple algorithm to obtain the Greeks for American options. Third, this algorithm is very efficient because one can compute the price and Greeks (delta, gamma, vega, and rho) at once. In spite of its importance, only a few previous studies on the computation of Greeks for American options exist, because performing sensitivity analysis for the optimal stopping problem is difficult. We believe that our method will become one of the popular ways to compute Greeks for options.
The Effect of Participants' Stress Manipulation on Experimenters’ Mood States  [PDF]
Hirotsune Sato, Jun I. Kawahara
Psychology (PSYCH) , 2017, DOI: 10.4236/psych.2017.88079
Abstract: This study examined whether experimenters’ mood states vary as a function of participants’ mood states. Thirty unacquainted “Experimenter”-“Participant” pairs participated. Participants delivered an unscripted speech in front of an experimenter while being videotaped. The stress levels of experimenters and participants were measured using a questionnaire and salivary cortisol measurements prior to and following the stress induction. A strong negative relationship was found between changes in the stress indices of the experimenters and those of the participants; a smaller increase in stress among participants was associated with a greater increase in stress among experimenters. This result suggests that stress induction can produce negative side effects among experimenters.
MicroRNAs in Neural Stem Cells and Neurogenesis
Hironori Kawahara
Frontiers in Neuroscience , 2012, DOI: 10.3389/fnins.2012.00030
Abstract: MicroRNA (miRNA) is a type of short-length (~22 nt) non-coding RNA. Most miRNAs are transcribed by RNA polymerase II and processed by Drosha-DGCR8 and Dicer complexes in the cropping and dicing steps, respectively. miRNAs are exported by exportin-5 from the nucleus to the cytoplasm after cropping. Trimmed mature miRNA is loaded and targets mRNA at the 3′ or 5′ untranslated region (UTR) by recognition of base-pairing in the miRNA-loaded RISC, where it is involved in gene silencing including translational repression and/or degradation along with deadenylation. Recent studies have shown that miRNA participates in various biological functions including cell fate decision, developmental timing regulation, apoptosis, and tumorigenesis. Analyses of miRNA expression profiles have demonstrated tissue- and stage-specific miRNAs including the let-7 family, miR-124, and miR-9, which regulate the differentiation of embryonic stem cells and/or neurogenesis. This review focuses on RNA-binding protein-mediated miRNA biogenesis during neurogenesis. These miRNA biogenesis-relating proteins have also been linked to human diseases because their mutations can cause several nervous system disorders. Moreover, defects in core proteins involved in miRNA biogenesis including Drosha, DGCR8, and Dicer promote tumorigenesis. Thus, the study of not only mature miRNA function but also miRNA biogenesis steps is likely to be important.
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