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Now showing items 33 - 48 of 136

  • Square-Wave Operation for a Single-Phase-PFC Three-Phase Motor Drive System Without a Reactor

    Itoh, Jun-ichi   Ohtani, Nobuhiro  

    This paper proposes a square-wave control strategy for a single-phase power factor correction with a new boost-up converter which uses the leakage inductance of a motor instead of a boost-up reactor. Since the power supply is connected to the neutral point of the motor, the current distortion in the power supply occurs when the inverter outputs square waveforms. First, this paper describes the characteristic of the proposed circuit and the problems in the square-wave operation. Next, a current control method for the square waveform is proposed to suppress the current distortion. Finally, the validity of the proposed converter and its control strategy are demonstrated by experimental results.
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  • Control Strategy for Modular Multilevel Converter based on Single-phase Power Factor Correction Converter

    Nakanishi, Toshiki   Itoh, Jun-ichi  

    This paper proposes a novel control strategy for a step-down rectifier that applies a modular multilevel converter (MMC). This paper first discusses the circuit configuration and the proposed control method. The main part of the control system is based on the control method for the single-phase power factor correction converter (PFC converter), which means that the conventional control techniques of the single-phase PFC converter can be simply applied to the MMC. The control elements which achieve step-down rectification and capacitor voltage balancing are added to the main part. Besides, in capacitor voltage balancing of the proposed control method, it is not necessary to design the control parameters. In addition, the operation of the proposed step-down rectifier is confirmed by the simulation. The simulation results show that the proposed converter achieves step-down rectification from the grid voltage of 6.6 kV to the DC voltage of 400V. Moreover, the step-down rectifier maintains all capacitor voltages constant. Finally, a fundamental operation is confirmed by experiments using a miniature model. As the results, the step-down rectifier converts from the input grid voltage of 200V to the output DC voltage of 75V. Besides, the proposed step-down rectifier maintains the capacitor voltage of each cell to the voltage command of 130V. The maximum error between the voltage command of the cell capacitor and the measured voltage is less than 2%.
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  • The small interfering RNA production pathway is required for shoot meristern initiation in rice

    Nagasaki, Hiroshi   Itoh, Jun-Ichi   Hayashi, Katsunobu   Hibara, Ken-Ichiro   Satoh-Nagasawa, Namiko   Nosaka, Misuzu   Mukouhata, Motohiro   Ashikari, Motoyuki   Kitano, Hidemi   Matsuoka, Makoto   Nagato, Yasuo  

    The shoot apical meristem (SAM) is a group of stem cells that are responsible for plant development. Mutations in rice SHOOTLESS2 (SHL2), SHL4/SHOOT ORGANIZATION2 (SHO2), and SHO1 cause complete deletion or abnormal formation of the SAM. In this study we showed that defects in SAM formation in shl mutants are associated with the loss of expression of the homeodomain-leucine zipper (HD-ZlPIII) family genes. Rice SHL2, SHL4/SHO2, and SHO1 encoded orthologues of Arabidopsis RNA-dependent RNA polymerase 6, ARGONAUTE (AGO) 7, and DICER-like 4, respectively, whose mutations affect leaf development through the trans-acting siRNA (ta-siRNA) pathway. This suggested that the ta-siRNA pathway regulates the critical step of SAM formation during rice embryogenesis. The gain-of-function experiment by the ectopic expression of SHL4 resulted in reduced accumulation of an microRNA, miR166, and partial adaxialization of leaves, supporting a role for the ta-siRNA pathway in the maintenance of leaf polarity as previously reported in maize. Analysis of the spatiotemporal expression patterns of HD-ZIPIII and miR166 in wild-type and shl mutant embryos suggested that the loss of HD-ZIPIII expression in the SAM region of the developing embryo is the result of ectopic expression of miR166. Our analysis of shl mutants demonstrated that HD-ZIPIII expression regulated by miR166 is sensitive to the ta-siRNA pathway during SAM formation in rice embryogenesis.
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  • Rice PLASTOCHRON genes regulate leaf maturation downstream of the gibberellin signal transduction pathway

    Mimura, Manaki   Nagato, Yasuo   Itoh, Jun-Ichi  

    Rice PLASTOCHRON 1 (PLA1) and PLA2 genes regulate leaf maturation and plastochron, and their loss-of-function mutants exhibit small organs and rapid leaf emergence. They encode a cytochrome P450 protein CYP78A11 and an RNA-binding protein, respectively. Their homologs in Arabidopsis and maize are also associated with plant development/organ size. Despite the importance of PLA genes in plant development, their molecular functions remain unknown. Here, we investigated how PLA1 and PLA2 genes are related to phytohormones. We found that gibberellin (GA) is the major phytohormone that promotes PLA1 and PLA2 expression. GA induced PLA1 and PLA2 expression, and conversely the GA-inhibitor uniconazole suppressed PLA1 and PLA2 expression. In pla1-4 and pla2-1 seedlings, expression levels of GA biosynthesis genes and the signal transduction gene were similar to those in wild-type seedlings. GA treatment slightly down-regulated the GA biosynthesis gene GA20ox2 and up-regulated the GA-catabolizing gene GA2ox4, whereas the GA biosynthesis inhibitor uniconazole up-regulated GA20ox2 and down-regulated GA2ox4 both in wild-type and pla mutants, suggesting that the GA feedback mechanism is not impaired in pla1 and pla2. To reveal how GA signal transduction affects the expression of PLA1 and PLA2, PLA expression in GA-signaling mutants was examined. In GA-insensitive mutant, gid1 and less-sensitive mutant, Slr1-d1, PLA1 and PLA2 expression was down-regulated. On the other hand, the expression levels of PLA1 and PLA2 were highly enhanced in a GA-constitutive-active mutant, slr1-1, causing ectopic overexpression. These results indicate that both PLA1 and PLA2 act downstream of the GA signal transduction pathway to regulate leaf development.
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  • Experimental Verification of Self-Supplying Power Circuit using One-Turn Transformer for Gate Drive Unit

    Orikawa, Koji   Kinomae, Takeshi   Itoh, Jun-ichi  

    This paper proposes a power supply circuit for gate drive units (GDUs) that uses a one-turn transformer, which gives advantages in terms of cost and loss reduction. The structure of the proposed one-turn transformer consists of a primary winding in which the number of turns is one and a secondary winding in which there are multiple number of turns. The proposed one-turn transformer is connected in series with a switching device of the main circuit in order to obtain power for the GDUs. The proposed power supply circuit can be applied to all types of main circuit topologies such as a multilevel converter topology or matrix converters, in addition to a conventional six-arm inverter. In this paper, the design method of the one-turn transformer and its characteristics are described based on an equivalent circuit and fundamental experimental results with a step-down chopper. Besides, the proposed power supply circuit for GDUs is tested in a two-level three-phase inverter. Secondly, the obtained power for GDUs from the proposed one-turn transformer with three connection points is investigated by harmonics analysis from the viewpoint of core size and other parameters. Finally, experimental results confirm that the GDU in the two-level three-phase inverter with switching frequencies of 12.5 kHz and 16 kHz is operated by the proposed self-supplying gate power supply circuit without an external power source.
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  • Experimental Verification of Self-Supplying Power Circuit using One-Turn Transformer for Gate Drive Unit

    Orikawa, Koji   Kinomae, Takeshi   Itoh, Jun-ichi  

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  • Optical Properties and X-ray Absorption Fine Structure Analysis of ZnS:Cu,Cl Thin-Film Phosphors

    Ichino, Kunio   Kato, Haruki   Sakai, Yuichiro   Ohmi, Koutoku   Honma, Tetsuo   Itoh, Jun-ichi   Sasakura, Asuka  

    ZnS Cu,Cl thin-film phosphors have been studied for possible application to resin-free white light-emitting diodes (LEDs) The ZnS Cu,Cl polycrystalline films grown by a molecular-beam deposition technique at relatively high substrate temperatures exhibit strong blue-green photoluminescence (PL) The films with a relatively high (similar to 1%) Cu concentration exhibit an enhanced near-UV excitation band as well as strong PL, making them suitable for excitation by UV LEDs. however, the transmission in the visible spectral range decreases The X-ray absorption fine structure analysis of the phosphor films suggests that Cu atoms substitute for Zn sites at low Cu concentrations, whereas excess Cu atoms exist in a different form, possibly as CuS-like precipitates, at high Cu concentrations The addition of Al donors to the phosphor films enhances the PL intensity and transparency, resulting from a reduction in the amount of the precipitates (C) 2010 The Japan Society of Applied Physics
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  • BLADE-ON-PETIOLE genes temporally and developmentally regulate the sheath to blade ratio of rice leaves

    Toriba, Taiyo   Tokunaga, Hiroki   Shiga, Toshihide   Nie, Fanyu   Naramoto, Satoshi   Honda, Eriko   Tanaka, Keisuke   Taji, Teruaki   Itoh, Jun-Ichi   Kyozuka, Junko  

    Axis formation is a fundamental issue in developmental biology. Axis formation and patterning in plant leaves is crucial for morphology and crop productivity. Here, we reveal the basis of proximal-distal patterning in rice leaves, which consist of a proximal sheath, a distal blade, and boundary organs formed between these two regions. Analysis of the three rice homologs of the Arabidopsis BLADE-ON-PETIOLE1 (BOP1) gene indicates that OsBOPs activate proximal sheath differentiation and suppress distal blade differentiation. Temporal expression changes of OsBOPs are responsible for the developmental changes in the sheath: blade ratio. We further identify that the change in the sheath: blade ratio during the juvenile phase is controlled by the miR156/SPL pathway, which modifies the level and pattern of expression of OsBOPs. OsBOPs are also essential for differentiation of the boundary organs. We propose that OsBOPs, the main regulators of proximal-distal patterning, control temporal changes in the sheath: blade ratio of rice leaves.
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  • BLADE-ON-PETIOLE genes temporally and developmentally regulate the sheath to blade ratio of rice leaves

    Toriba, Taiyo   Tokunaga, Hiroki   Shiga, Toshihide   Nie, Fanyu   Naramoto, Satoshi   Honda, Eriko   Tanaka, Keisuke   Taji, Teruaki   Itoh, Jun-Ichi   Kyozuka, Junko  

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  • A Novel Single-Phase Buck PFC AC-DC Converter With Power Decoupling Capability Using an Active Buffer

    Ohnuma, Yoshiya   Itoh, Jun-Ichi  

    This paper discusses a new circuit configuration and a new control method for a single-phase ac-dc converter with power factor (P.F.) correction and a power pulsation decoupling function. The proposed converter can achieve low total harmonic distortion (THD) on the input current and the power pulsation decoupling function between the input and output sides, which allows low output voltage ripple even on a small output energy buffer at the same time using an active buffer. Therefore, the proposed converter does not require large smoothing capacitors or large smoothing inductors. The buffering energy is stored by a small capacitor, which controls the variation of the capacitor voltage through the active buffer. In this paper, the fundamental operations of the proposed converter are investigated experimentally. The experimental results reveal that the input current THD is 1.44%, the rate of the output voltage ripple is 6.33%, and the input P. F. is over 99%. In addition, a maximum efficiency of over 96% is obtained for a 750-W prototype converter.
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  • Circuit-Parameter-Independent Nonlinearity Compensation for Boost Converter Operated in Discontinuous Current Mode

    Le, Hoai Nam   Orikawa, Koji   Itoh, Jun-Ichi  

    This paper proposes a current control method for discontinuous current mode (DCM) in order to achieve the same control performance as continuous current mode (CCM) in a boost converter. By utilizing the duty ratio at the previous calculation period to compensate for a DCM nonlinearity, the controller, which is designed for CCM, can also be used in DCM. In the frequency analysis, the cutoff frequency of the proposed DCM current control agrees exactly to the design value, which is 2 kHz, whereas the cutoff frequency of the conventional DCM current control results in high error of 47.5%. In the current step response experiment with a 360-W prototype and the switching frequency of 20 kHz, the experimental DCM current response almost agrees with the conventional CCM current response, which are 380-mu s rise time for both CCM and DCM, 9% and 8% overshoot for CCM and DCM, respectively. Furthermore, the computation time of the proposed DCM current control is shorter 35% than the conventional DCM current control.
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  • The SHOOT ORGANIZATION2 gene coordinates leaf domain development along the central-marginal axis in rice

    Itoh, Jun-Ichi   Sato, Yutaka   Nagato, Yasuo  

    We describe how rice leaves are regionalized and regulated along the centralmarginal axis. The shoot organization2 (sho2) mutant, a weak allele of SHOOTLESS4 that is a ZIPPY/ARGONAUTE7 homolog in rice, shows a variety of leaf abnormalities; filamentous leaves, bi- or trifurcated leaves, separation of the filamentous structure from the leaf blade or deletion of the margin. All of these phenotypes can be interpreted as combinatorial defects in the growth of the central, lateral and marginal domains along the centralmarginal axis, on the condition that the growth of the central domain is predominant. The leaf founder cells for the lateral and marginal domains are recruited normally in sho2, indicating that sho2 is defective in the growth of leaf domains after the founder cells are recruited. The expression pattern of SHO2 in the outer layer of the shoot apical meristem and the adaxial surface of the leaf, as well as the altered expression of HD-ZIP III and ETTIN homologs in the central domain of sho2 leaves, suggest that normal development of the central domain is a prerequisite for the synchronous growth of the three domains. This synchrony is thought to be mediated by a small interfering RNA-dependent process.
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  • The rice FISH BONE gene encodes a tryptophan aminotransferase, which affects pleiotropic auxin-related processes.

    Yoshikawa, Takanori   Ito, Momoyo   Sumikura, Tsuyoshi   Nakayama, Akira   Nishimura, Takeshi   Kitano, Hidemi   Yamaguchi, Isomaro   Koshiba, Tomokazu   Hibara, Ken-Ichiro   Nagato, Yasuo   Itoh, Jun-Ichi  

    Auxin is a fundamental plant hormone and its localization within organs plays pivotal roles in plant growth and development. Analysis of many Arabidopsis mutants that were defective in auxin biosynthesis revealed that the indole-3-pyruvic acid (IPA) pathway, catalyzed by the TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA) and YUCCA (YUC) families, is the major biosynthetic pathway of indole-3-acetic acid (IAA). In contrast, little information is known about the molecular mechanisms of auxin biosynthesis in rice. In this study, we identified a auxin-related rice mutant, fish bone (fib). FIB encodes an orthologue of TAA genes and loss of FIB function resulted in pleiotropic abnormal phenotypes, such as small leaves with large lamina joint angles, abnormal vascular development, small panicles, abnormal organ identity and defects in root development, together with a reduction in internal IAA levels. Moreover, we found that auxin sensitivity and polar transport activity were altered in the fib mutant. From these results, we suggest that FIB plays a pivotal role in IAA biosynthesis in rice and that auxin biosynthesis, transport and sensitivity are closely interrelated. =C2=A9 2014 The Authors The Plant Journal =C2=A9 2014 John Wiley & Sons Ltd.
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  • Special Issue Ceramics Integration. Oxygen Diffusion and Defect Chemistry in Rare-Earth-Doped BaTiO3.

    ITOH, Jun-ichi   PARK, Dae-Chul   OHASHI, Naoki   SAKAGUCHI, Isao   YASHIMA, Isamu   HANEDA, Hajime   TANAKA, Junzo  

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  • The Effect of Microstructure and Lattice Defect on Electrical Properties of La- and Ho-doped BaTiO3.

    Itoh, Jun-ichi   Park, Dae-Chul   Ohashi, Naoki   Sakaguchi, Isao   Yashima, Isamu   Haneda, Hajime   Tanaka, Junzo  

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  • A New Bidirectional Switch With Regenerative Snubber to Realize a Simple Series Connection for Matrix Converters

    Itoh, Jun-Ichi   Nagayoshi, Ken-Ichi  

    A new bidirectional switch and snubber circuit are proposed for medium-voltage ac/ac converters. The proposed switch can be constructed using 2-in-1 insulated-gate bipolar transistor and 2-in-1 diode modules, and can reduce the voltage stress of the switching device by series connection. The proposed snubber configuration is very simple and can regenerate absorbed energy. On the other hand, timing errors in the switching between the series-connected switches cause a voltage imbalance in the snubber circuit. Therefore, a simple method is proposed for reducing the voltage imbalance that uses one voltage sensor for each switch circuit. This proposed method controls the snubber voltages by adjusting the switch timings. Furthermore, application of the proposed switch circuit to a matrix converter is discussed and is confirmed by experiment.
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