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Search Results: 1 - 10 of 107 matches for " Yasuhisa Kuzuha "
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Simulation of a Daily Precipitation Time Series Using a Stochastic Model with Filtering  [PDF]
Chieko Gomi, Yasuhisa Kuzuha
Open Journal of Modern Hydrology (OJMH) , 2013, DOI: 10.4236/ojmh.2013.34025
Abstract: After we modified raw data for anomalies, we conducted spectral analysis using the data. In the frequency, the spectrum is best described by a decaying exponential function. For this reason, stochastic models characterized by a spectrum attenuated according to a power law cannot be used to model precipitation anomaly. We introduced a new model, the e-model, which properly reproduces the spectrum of the precipitation anomaly. After using the data to infer the parameter values of the e-model, we used the e-model to generate synthetic daily precipitation time series. Comparison with recorded data shows a good agreement. This e-model resembles fractional Brown motion (fBm)/fractional Lévy motion (fLm), especially the spectral method. That is, we transform white noise Xt to the precipitation daily time series. Our analyses show that the frequency of extreme precipitation events is best described by a Lévy law and cannot be accounted with a Gaussian distribution.
Performance Prospects of Fully-Depleted SOI MOSFET-Based Diodes Applied to Schenkel Circuit for RF-ID Chips  [PDF]
Yasuhisa Omura, Yukio Iida
Circuits and Systems (CS) , 2013, DOI: 10.4236/cs.2013.42024

The feasibility of using the SOI-MOSFET as a quasi-diode to replace the Schottky-barrier diode in the Schenkel circuit is examined by device simulations primarily and experiments partly. Practical expressions of boost-up efficiency for d. c. condition and a. c. condition are proposed and are examined by simulations. It is shown that the SOI-MOSFET-based quasi-diode is a promising device for the Schenkel circuit because high boost-up efficiency can be gained easily. An a. c. analysis indicates that the fully-depleted condition should hold to suppress the floating-body effect for GHz-level RF applications of a quasi-diode.

Proposal of High-Temperature-Operation Tolerant SOI MOSFET and Preliminary Study on Device Performance Evaluation
Yasuhisa Omura
Active and Passive Electronic Components , 2011, DOI: 10.1155/2011/850481
Abstract: We propose a high-temperature-operation (HTOT) SOI MOSFET and show preliminary simulation results of its characteristics. It is demonstrated that HTOT SOI MOSFET operates safely at 700?K with no thermal instability because of its expanded effective bandgap. It is shown that its threshold voltage is higher than that of the conventional SOI MOSFET because its local thin Si regions offer an expanded effective band gap. It is shown that HTOT SOI MOSFET with 1-nm-thick local-thin Si regions is almost insensitive to temperature for (427?C). This confirms that HTOT SOI MOSFET is a promising device for future high-temperature applications. 1. Introduction The long-term goal in integrated circuits is to lower the dimensionality of MOS transistors in order to increase the function-density and also the speed of extremely large-scale silicon-integrated circuits [1]. The necessity of the silicon-on-insulator (SOI) MOSFET is clear, given its merits of high-speed operation and low-power operation with fewer short-channel effects [2]. However, its off-leakage current is significant, even in thin SOI MOSFETs in the sub-100-nm regime [3]. The author recently proposed the tunneling barrier junction (TBJ) SOI MOSFET that offers suppressed off-leakage current [4, 5]. It has been shown that the TBJ SOI MOSFET suffers from low drive current if used at low temperatures as intended [6]. It has been demonstrated, however, that the thin SOI MOSFET is a promising device for applications that work at 300?C [1]. Its off-leakage current is still a serious problem and prevents its use at higher temperatures. When analyzing high-temperature-operation, it is anticipated that we do not need full quantum-mechanical simulations even for a thin SOI MOSFET because the influence of various carrier scattering events on the transport in the channel region is crucial; so-called thermalization is dominant in the Si material. This paper applies the semiclassical transport model to assess the feasibility of SOI MOSFET in achieving high-temperature operation. This paper introduces the High-Temperature-Operation Tolerant (HTOT) SOI MOSFET and shows preliminary simulation results of its characteristics. A commercial 2D device simulator [7] is used to simulate the drain current characteristics throughout the study. 2. Device Structure and Simulations A schematic of HTOT SOI MOSFET is shown in Figure 1(a). The device has an n+-Si gate, a thin n-type body, two thin p-type bodies, and two local-thin Si regions; it is assumed that the top SOI layer surface has (001) orientation. The gate oxide layer is
A Mutant of SWAP-70, a Phosphatidylinositoltrisphosphate Binding Protein, Transforms Mouse Embryo Fibroblasts, Which Is Inhibited by Sanguinarine
Yasuhisa Fukui,Sayoko Ihara
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0014180
Abstract: SWAP-70, a phosphatidylinositol trisphosphate (PtdIns(3,4,5)P3) binding protein, has been suggested to be involved in transformation of mouse embryo fibroblasts (MEFs) as well as membrane ruffling after growth factor stimulation of the cells. A mutant, SWAP-70-374, was found to be able to bind to F-actin in vitro, whereas wild-type SWAP-70 failed to do so. This mutant was present at the plasma membrane without any stimulation while the wild-type protein was present only in the cytosol unless cells were stimulated with EGF. Expression of this mutant in MEFs resulted in morphologic transformation, fast growth, and loss of contact inhibition, suggesting that SWAP-70 with this mutation can transform the cells. ERK1/2 was activated in SWAP-70-374-transformed cells. Use of MEK inhibitors revealed that the ERK1/2 pathway does not affect the cell growth of MEFs but is responsible for loss of contact inhibition. To investigate the function of SWAP-70 further, drugs that can inhibit SWAP-70-dependent cell responses were screened. Among various drugs, sanguinarine was found to inhibit transformation of MEFs by SWAP-70-374. This drug was able to inhibit SWAP-70-mediated membrane ruffling as well, suggesting that its effect was closely related to the SWAP-70 signaling pathway. These results suggest that SWAP-70-374 can activate some signaling pathways, including the ERK1/2 pathway, to transform MEFs.
Mitochondrial genomes of acrodont lizards: timing of gene rearrangements and phylogenetic and biogeographic implications
Yasuhisa Okajima, Yoshinori Kumazawa
BMC Evolutionary Biology , 2010, DOI: 10.1186/1471-2148-10-141
Abstract: Acrodontan mitogenomes were found to be less conservative than iguanid counterparts with respect to gene arrangement features and rates of sequence evolution. Phylogenetic relationships were constructed with the mitogenomic sequence data and timing of gene rearrangements was inferred on it. The result suggested highly lineage-specific occurrence of several gene rearrangements, except for the translocation of the tRNAPro gene from the 5' to 3' side of the control region, which likely occurred independently in both agamine and chamaeleonid lineages. Phylogenetic analyses strongly suggested the monophyly of Agamidae in relation to Chamaeleonidae and the non-monophyly of traditional genus Chamaeleo within Chamaeleonidae. Uromastyx and Brookesia were suggested to be the earliest shoot-off of Agamidae and Chamaeleonidae, respectively. Together with the results of relaxed-clock dating analyses, our molecular phylogeny was used to infer the origin of Acrodonta and historical biogeography of its descendant lineages. Our molecular data favored Gondwanan origin of Acrodonta, vicariant divergence of Agamidae and Chamaeleonidae in the drifting India-Madagascar landmass, and migration of the Agamidae to Eurasia with the Indian subcontinent, although Laurasian origin of Acrodonta was not strictly ruled out.We detected distinct modes of mitogenomic evolution among iguanian families. Agamidae was highlighted in including a number of lineage-specific mitochondrial gene rearrangements. The mitogenomic data provided a certain level of resolution in reconstructing acrodontan phylogeny, although there still remain ambiguous relationships. Our biogeographic implications shed a light on the previous hypothesis of Gondwanan origin of Acrodonta by adding some new evidence and concreteness.Acrodonta is a group of squamate lizards that have the characteristic acrodont dentition. Acrodonta consists of two families, Agamidae and Chamaeleonidae, while Pleurodonta having the pleurodont dentition i
Yuya Takahashi,Yasuhisa Ikeda
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809045930
Abstract: In the title compound, [Pd(NO3)2(C10H17NO)2], the PdII centre is located on an inversion center and is coordinated in a square-planar geometry by two O atoms of the monodentate nitrate groups and two carbonyl O atoms of the 1-cyclohexylpyrrolidin-2-one ligands.
Koichiro Takao,Yasuhisa Ikeda
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810013449
Abstract: In the crystal structure of the title compound, [U2(NO3)2O4(O2)(C4H7NO)4], two UO22+ ions are connected by a μ-η2:η2-O2 unit. The O2 unit shows `side-on' coordination to both U atoms. An inversion center is located at the midpoint of the O—O bond in the O2 unit, affording a centrosymmetrically expanded dimeric structure. The U—O(axial) bond lengths are 1.777 (4) and 1.784 (4) , indicating that the oxidation state of U is exclusively 6+, i.e., UO22+. Furthermore, the O—O distance is 1.492 (8) , which is typical of peroxide, O22–. The U atom is eight-coordinated in a hexagonal-bipyramidal geometry. The coordinating atoms of the nitrate and pyrrolidine-2-one ligands and the μ-η2:η2-O22– unit are located in the equatorial plane and form an irregular hexagon. An intermolecular hydrogen bond is found between N—H of the pyrrolidine-2-one ligand and the coordinating O of the same ligand in a neighboring complex. A second intermolecular hydrogen bond is found between the N—H of the other pyrrolidine-2-one ligand and one of the uranyl oxido atoms.
Koichiro Takao,Yasuhisa Ikeda
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536807065865
Abstract: In the title compound, [U(C4F9O3S)O2(C4H8O)3], each UVI ion is located on a twofold rotation axis and is seven-coordinated by two terminal O atoms in the axial positions [U—O = 1.737 (5) ] and five O atoms from two monodentate nonafluorobutanesulfonate (NfO ) and three tetrahydrofuran ligands in the equatorial plane [U—O = 2.388 (5)–2.411 (4) ] in a pentagonal–bipyramidal geometry. The crystal packing exhibits weak intermolecular C—H...O hydrogen bonds involving the non-coordinated O atoms of the NfO ligands.
Koichiro Takao,Yasuhisa Ikeda
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536807063799
Abstract: In the title compound, [U(C15H11O2)2O2(C2H6O)], the UVI atom has a pentagonal–bipyramidal coordination geometry. The two so-called `-yl' O atoms occupy the axial positions whereas four O atoms from the two chelating dibenzoylmethanate ligands and the O atom from the ethanol molecule are situated in the equatorial plane. Intermolecular hydrogen bonds between one of the `-yl' O atoms and the ethanol OH group assemble molecules into a centrosymmetric dimer.
Di-μ-chlorido-bis[chloridobis(dimethyl sulfoxide)dioxidouranium(VI)]
Koichiro Takao,Yasuhisa Ikeda
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536807064264
Abstract: In the crystal structure of the title compound, [U2Cl4O4(C2H6OS)4], the compound has a centrosymmetric dimeric structure bridged by two chloride anions. Each UVI atom is seven-coordinate in a pentagonal-bipyramidal geometry. In the equatorial plane of the uranyl unit there are two O atoms from non-adjacent dimethyl sulfoxides and three chloride ions (of which two chlorides are bridging). The compound is of interest as an anhydrous starting material of the uranyl(VI) ion.
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