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Search Results: 1 - 10 of 527 matches for " Tomohito Okumura "
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Comparison of Developmental Stages in Relation to Way Finding Behavior in an Immersive Virtual Reality Space  [PDF]
Hiroshi Watanabe, Tomohito Okumura, Eiji Wakamiya
Health (Health) , 2016, DOI: 10.4236/health.2016.85052
Abstract: To establish a proper evaluation method for spatial cognitive deficits and a form of developmental disorder, we have used an immersive virtual reality (VR) device to develop a game that involves actually walking through a VR space to search for a target object. In this paper, we presented the results of control experiment with 22 healthy elementary school students as participants. The complexity of the VR space was controlled according to the number of pillars present and whether an overall view was possible (controlled by the height of the pillars). For each set of conditions, 24 trials were performed, and the route and time taken to search for the target were recorded. The starting point was changed in each subsequent trial. Results showed that the search time decreased as the number of trials increase, suggesting a process whereby a cognitive map was formed. We also compared the present results to results from our previous experiment with university students using the same experimental conditions, and we discussed the influence of developmental stage on spatial cognition.
Study on Non-Uniqueness of Taylor Vortex Flow Changing Inner Cylinder Acceleration Time  [PDF]
Hiroyuki Furukawa, Tomohito Suzuki
World Journal of Mechanics (WJM) , 2018, DOI: 10.4236/wjm.2018.88023
Abstract: In concentrically rotating double cylinders consisting of a stationary outer cylinder a rotating inner cylinder, Taylor vortex flow appears. Taylor vortex flow occurs in journal bearings, various fluid machineries, containers for chemical reaction, and other rotating components. Therefore, the analysis of the flow structure of Taylor vortex flow is highly effective for its control. The main parameters that determine the modes of Taylor vortex flow of a finite length are the aspect ratio, Reynolds number Re. Aspect ratio is defined as the ratio of the cylinder length to the gap length between cylinders, and Re is determined on the basis of the angular speed of the inner cylinder. Aspect ratio was set to be 4.0, and Re to be values in the range from 100 to 1000 at intervals of 100. Thus far, a large number of studies on Taylor vortex flow have been carried out; however, the effects of the differences in initial conditions have not yet been sufficiently clarified. In this study, we changed the acceleration time of the inner cylinder in a numerical analysis, and examined the resulting changes in the mode formation and bifurcation processes. The acceleration time was changed from 1.0 s to 10.0 s. As a result, a difference was observed in the final mode depending on the difference in the acceleration time. From this finding, non-uniqueness, which is a major characteristic of Taylor vortex flow, was confirmed. However, no regularities regarding the difference in mode formation were found and the tendency of the mode formation process was not specified. Moreover, the processes of developing the vortex resulting in different final modes were monitored over time by visual observation. Similar flow behaviors were initially observed after the start of the calculation. Then, a bifurcation point, at which the flow changed to a mode depending on the acceleration time observed, and finally the flow became steady. In addition, there was also a difference in the time taken for the well-developed flow to reach the steady state. Both EFD (Experimental Fluid Dynamics) and CFD (Computational Fluid Dynamics) results show good agreement qualitatively.
Hilbert schemes of finite abelian group orbits and Grobner fans
Tomohito Morita
Mathematics , 2007,
Abstract: Let $G$ be a finite abelian subgroup of $PGL(r-1,K)=\mathrm{Aut}(\P^{r-1}_K)$. In this paper, we prove that the normalization of the $G$-orbit Hilbert scheme $\Hilb^G(\P^{r-1})$ is described as a toric variety, which corresponds to the Gr\"obner fan for some homogeneous ideal $I$ of $K[x_1, ..., x_r]$.
Recurrent ovarian cancer presenting in the right supraclavicular lymph node with isolated metastasis: a case report
Tomohito Tanaka, Masahide Ohmichi
Journal of Medical Case Reports , 2012, DOI: 10.1186/1752-1947-6-176
Abstract: A 69-year-old Japanese woman had recurrent ovarian cancer presenting with isolated right supraclavicular lymph node metastasis. After surgical resection and combination chemotherapy with carboplatin and paclitaxel, her right supraclavicular lymph node completely regressed.Peripheral isolated lymph nodes, including right supraclavicular lymph node, can recur without a macroscopic abdominal lesion. Clinicians should carefully examine peripheral lymph nodes for recurrence.
Giant nonlinear conduction and thyristor-like negative derivative resistance in BaIrO3 single crystals
Tomohito Nakano,Ichiro Terasaki
Physics , 2005, DOI: 10.1103/PhysRevB.73.195106
Abstract: We synthesized single-crystalline samples of monoclinic BaIrO3 using a molten flux method, and measured their magnetization, resistivity, Seebeck coefficient and nonlinear voltage-current characteristics. The magnetization rapidly increases below a ferromagnetic transition temperature TC of 180 K, where the resistivity concomitantly shows a hump-type anomaly, followed by a sharp increase below 30 K. The Seebeck coefficient suddenly increases below TC, and shows linear temperature dependence below 50 K. A most striking feature of this compound is that the anomalously giant nonlinear conduction is observed below 30 K, where a small current density of 20 A/cm2 dramatically suppresses the sharp increase in resistivity to induce a metallic conduction down to 4 K.
Association of festival observance with psychological distress in a rural Japanese community  [PDF]
Tomohito Minamizono, Yoshihiro Kaneko, Sachiko Minamizono, Yutaka Motohashi
Open Journal of Preventive Medicine (OJPM) , 2013, DOI: 10.4236/ojpm.2013.35050
Abstract: Introduction: A growing body of evidence suggests that social capital improves mental health. However, the association between the observance of festivals and mental health has not yet been investigated in depth by public health researchers. The purpose of this study is to examine whether festival observance is associated with psychological distress. Methods: We conducted a cross-sectional survey of 17,525 residents aged 40 to 79 who lived in a rural town in northern Japan. We assessed each participant’s psychological distress level, social capital and festival observance via a questionnaire. We performed multiple logistic regression analyses to examine the association of festival observance with psychological distress. Results: A total of 11,649 residents responded to this survey (a response rate of 66.5%). The group who responded that their community did not hold festivals was negatively associated with psychological distress, even after adjusting for socio-demographic characteristics (OR = 1.71, 95% CI 1.49-1.97). After adjusting for both socio-demographics and social capital, the association became weaker, but was still significant (OR = 1.27, 95% CI 1.10-1.48). Conclusions: Festival observance was associated with psychological distress in a rural Japanese community. It seems that festival observance is a factor to be taken into consideration in mental health promotion in the community.

Determination of inspection schedules of equipment by variational method
Susumu Okumura
Mathematical Problems in Engineering , 2006, DOI: 10.1155/mpe/2006/95843
Abstract: Maintained equipment can be subject to random failures. If failures are evident, they can be detected immediately when they occur. On the other hand, hidden failures that are not revealed during the performance of regular duties may be detected by inspection process. If concerned equipment has hidden failures, loss is assumed to incur from the moment its failure until the time when it is detected. Optimal inspection schedule should be considered when inspection is costly. In this study, optimal inspection schedules for equipment are derived by the variational method employing the inspection density function. For the case in which the time-to-failure distribution of equipment is given, a conditional equation that optimal inspection schedules should satisfy is derived. Furthermore, when the time-to-failure distribution is unknown, an ordinary differential equation that optimal inspection schedules should satisfy is obtained. Optimal inspection schedules in a closed form and numerical examples are shown for some potential loss rate functions.
Inductively Coupled Plasma Sources and Applications
Tomohiro Okumura
Physics Research International , 2010, DOI: 10.1155/2010/164249
Abstract: The principle of inductively coupled plasma (ICP) and perspective of ICP development are reviewed. Multispiral coil ICP (MSC-ICP), which has the advantages of low inductance, high efficiency, and excellent uniformity, is discussed in detail. Applications to thin film processing technologies and the future prospects of ICP are also described.
The Diagnosis and Treatment of Neonatal Seizures
Akihisa Okumura
Chang Gung Medical Journal , 2012,
Abstract: The occurrence of neonatal seizures is an important clinical sign indicating brain disorder in neonates. An identification of neonatal seizures is critical in the management of high risk neonates. However, the diagnosis and management of neonatal seizures are challenging, because electroclinical dissociation is an outstanding feature of neonatal seizures. Neonatal seizures are frequently not accompanied by any identifiable clinical symptoms even on close observation, whereas motor phenomena which have been considered to be seizures are not associated with ictal electroencephalography (EEG) correlates. For this reason, neonatal seizures should be diagnosed based on ictal EEG findings and the efficacy of treatment should be evaluated using continuous EEG monitoring. EEG is also useful diagnosing the underlying etiology of neonatal seizures. Although conventional EEG is the gold standard for the diagnosis of neonatal seizures, amplitude-integrated EEG (aEEG) can be considered an option. However, aEEG has substantial limitations. In treatment two aspects must be considered. First, neonatal seizures themselves require emergency therapy and second, etiology-specific therapy is important in order to prevent further brain injury. At present, evidence is limited on the treatment of neonatal seizures. In order to establish effective treatment, studies using continuous EEG/aEEG monitoring and long-term follow-up are necessary. Widespread use of EEG/aEEG is desirable in order to solve several problems in the diagnosis and treatment of neonatal seizures.
Inductively Coupled Plasma Sources and Applications
Tomohiro Okumura
Physics Research International , 2010, DOI: 10.1155/2010/164249
Abstract: The principle of inductively coupled plasma (ICP) and perspective of ICP development are reviewed. Multispiral coil ICP (MSC-ICP), which has the advantages of low inductance, high efficiency, and excellent uniformity, is discussed in detail. Applications to thin film processing technologies and the future prospects of ICP are also described. 1. Introduction In the 1990s, thin-film processing technologies using low-pressure high-density plasma (HDP) sources rapidly improved as manufacturing techniques for electronic devices such as semiconductors and liquid crystal displays (LCDs). Progress in these areas continues today. Plasma generation in a low-pressure etching chamber decreases the probability that ions will collide with one another or with neutral gas particles in an ion sheath, which is formed near the substrate surface, with the result that ions are uniformly directed toward the substrate. The use of highly ionized HDP increases the ratio of ions to neutral radicals reaching the substrate, enhancing etching anisotropy. Microprocessing with a high aspect ratio is therefore possible. In plasma chemical vapor deposition (CVD), a fine pattern is filled flat, owing to the sputtering effect of ions, thus achieving deposition with a high aspect ratio. Moreover, there is an advantage of independent controllability of plasma density and bias energy in the HDP process, in which it is possible to control the plasma density by adjusting the source power, and the self bias voltage by the bias power. Self bias voltage is a key parameter related to ion energy radiated on the substrate. These features of HDP are well known from the past. Electron cyclotron resonance plasma (ECRP), invented in 1970s, had been only one practical HDP and occupied an important position for a long time. However, the strong magnetic field needed by ECRP and the resulting separation of charged particles can cause electrostatic damage to devices. ECRP has the disadvantage of a complex chamber configuration. It was clear that a simply configured HDP without a static magnetic field was strongly needed. Inductively coupled plasma (ICP) sources meeting these demands started to be investigated in the 1990s, eventually becoming widely used in semiconductor manufacturing. In this paper, the principle of ICP and perspective of ICP development are reviewed by presenting various ICPs. Also discussed in detail is multispiral coil ICP (MSC-ICP), invented by the authors. Lastly, applications to thin-film processing technologies and finally the future prospects of ICP are examined. 2. Principle of
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