Search

Paddy fields in the agricultural landscape have become alternative habitats for natural wetland species. Habitat degradation, including habitat loss and fragmentation, is a major threat to members of Amphibia, which is a good indicator species for the Satoyama landscape. Recently, linear artificial structures, such as roads and railways, were recognized as factors inhibiting amphibian population persistence. Thus, irrigation canals and cement-walled streams may also affect amphibian movement and dispersal in the rural agricultural landscape termed Satoyama, which is now the main habitat for lowland wetland amphibians. However, there is limited information on such effects. Here, we focused on the Japanese brown frog (Rana japonica), which is an indicator species of the ecosystem health of the Satoyama landscape, to investigate the effects of irrigation canals on population structure. The barrier effects of roads and irrigation canals on gene flow between breeding sites were evaluated. We constructed a resistance map of the limiting factors to gene flow based on land use and frog movement and tested for correlations between cost and genetic distances. The habitat resistance values alone were insufficient to explain the genetic distances among breeding sites. Thus, we hypothesize that irrigation canals and roads have barrier effects on gene flow among amphibians in the Japanese Satoyama landscape.

The active gate drive (AGD) technique is payed attention as a switching technique which can reduced both of switching loss and surge voltage. So far, only switching loss and surge voltage of main switch have been discussed, and the reverse recovery characteristic of rectification diode has not been discussed. In addition, the mechanism of loss and surge reduction has not been clarified. In this paper, the influence of AGD on reverse recovery characteristics, and the mechanism of loss and surge reduction are discussed for system reliability improvement. As a result, the mechanism of loss and surge reduction is clarified.

This paper presents a concept of a power module with multiple series-connected power devices controlled by fully digital active gate drivers. The performance of series-connected power devices with lower voltage ratings is expected to be higher than the case of using only one device with higher voltage ratings. The required voltage balance of each power device to prevent an overvoltage issue can be achieved by a fine adjustment of the switching speed using the active gate control. As a first design example, a prototype module configured mainly by two series Si-MOSFETs, active gate drive circuits, and a fully digital controller was designed and developed. It was experimentally verified that suitable active gate control can realize the voltage balance in two series-connected MOSFETs under continuous operation.

Power-SoC, which integrates MCU, power device, control circuits and passive devices on the same chip has been attracted attention. In this paper, we discuss the impact of passive component structure for high efficiency and fast response POL using 3D Power-SoC (Supply on Chip). We propose the optimal structure according to the switching frequency based on simulations.

In this paper, we propose a new control algorithm for a novel fully digital-controlled H-bridge DC-DC converter, which can output the power in both boost and buck mode by only rewriting three digital codes: input voltage, output voltage, and maximum load current. In addition, the proposed algorithm improves the transient response.

Every year, exhaust gas regulations are getting stricter with the intention to solve the average air pollution problem, however, local roadside pollution is still a pressing issue. In order to solve this local roadside pollution problem, it is necessary to evaluate and/or predict “where” and “how much” pollutants such as NOx are emitted. To predict the local roadside pollution, it is necessary to collect emissions data from various kinds of vehicles driving on realworld and analyze them. In recent years, Real Driving Emission regulations using PEMS (Portable Emission Measurement System) have been introduced mainly in Europe. A typical PEMS configuration can weigh close to 100 kg however, and its weight affects the driving conditions of vehicles running on actual roads. In this study, we focused on the analysis of real-world emissions using SEMS (Sensorbased Emission Measurement System). Whereas PEMS is a method of sampling and analyzing exhaust gas, SEMS directly attaches a NOx sensor and PM sensor to the exhaust pipe and measures the concentration. Although SEMS has a limited number of items that can be measured compared to PEMS, other analysis is possible by devising the analysis method. This paper focuses on the analysis method of real-world emissions using SEMS and aims to examine the analysis method of CO2 emission concentration, exhaust gas flowrate, and local roadside emissions from the measured value of SEMS. In addition, an example of applying this analysis method using on-road test data of a diesel passenger car equipped with SEMS is shown. The NOx sensor can measure not only the NOx concentration but also the O2 concentration and air-fuel ratio. It is clarified that the CO2 concentration at wet condition can be calculated with high accuracy by using the measured values of the O2 concentration. Also, the exhaust flowrate is obtained by combining the intake air flow rate acquired through the vehicle's OBD and the air-fuel ratio measured by the NOx sensor. At that time, the exhaust gas density is also calculated based on the air-fuel ratio, so that the exhaust flowrate can be calculated with higher accuracy.

Power supply on chip (power-SoC) has been caught attentions because ultimately miniaturize the power supplies. Especially, the 3D power-SoC is attractive and is fabricated using LSI and MEMS process. It is important to meet the various electrical requirements for expanding applications because they are fabricated using mass production process. In such situations, series and/or parallel connections of them is attractive. However, we generally use transformers as power supplies for floating gate driver circuits when we connect DC-DC converters series. Transformers are not suitable for power-SoC because they disturb miniaturization. In this paper, we propose a transformer-less floating gate driver circuit for 3D power SoC., The IEEE International 3D Systems Integration Conference (3DIC 2019), October 8-10, 2019, Sendai, Japan

Habitat fragmentation is one of the major threats to amphibian species. In a previous study, population genetic analyses of the Japanese brown frog Rana japonica were conducted using a mitochondrial DNA (mtDNA) marker in a typical Japanese agricultural landscape (known as satoyama) in Chiba, Japan. This previous study revealed that gene flow was restricted by the roads and cement-walled urban river that divide this site. In the present study, we reanalyzed the genetic structure of the same meta-population using microsatellite markers in comparison with the mtDNA results and elucidated fine-scale gene flow. The genetic structure derived from the microsatellite clustering analysis was almost identical to that of the mtDNA results, although some important details differed. We recognized boundaries of genetic structure are consistent with the major roads and cement-walled river, however, we also detected gene flow across those artificial barriers. We concluded that the current genetic structure was formed in the past when gene flow was strongly restricted. Gene flow among breeding populations is now being restored by the maintenance of breeding sites, although it is not sufficient to erase the signature of historical isolation.

The shoot-through fault in inverters results from a gate noise voltage of power semiconductor switches including IGBTs. Testing the gate voltage under the high-speed switching event is important to evaluate immunity to the fault as well as to analyze the mechanism of the fault. This paper presents a testing method of shoot-through immunity in a PWM inverter consisting of IGBTs because the conventional double-pulse test can miss the shoot-through fault in the inverter. Theoretical analysis reveals that the N-base charge has influence on the gate-emitter voltage in the IGBT, which disturbs evaluating the shoot-through immunity in the inverter. This implies that IGBTs have a different characteristic from MOSFETs when the double-pulse test is carried out. The testing method introduces an additional pulse into the off-state IGBT to release the N-base charge, the circuit operation of which is the same as the inverter. Experimental results confirmed that the method did not affected by the N-base voltage, so that it is applicable to testing the shoot-through immunity of IGBTs in an inverter.

The shoot-through phenomenon has not been fully discussed for high-power inverters with IGBTs. This is because a negative gate voltage is applied to IGBTs during off states. Recently, attention is paid to an improved gate driver with only a positive gate voltage in order to meet demands for simplification, integration, and reduction in power consumption as well as in cost of the gate driver. Moreover, the threshold voltage of the next-generation IGBT will decrease with microfabrication techniques of the gate structure. This will make the shoot-through phenomenon severer and degrade the inverter reliability with the next-generation IGBTs. The influence of the parasitic parameters in both the IGBT and circuit on the shoot-through mechanism has not been investigated so far. This paper clarifies the shoot-through mechanism and investigates the impact of the next generation IGBTs on the inverter reliability. The influence of the internal capacitance of IGBT including stray inductance on inverter reliability is experimentally confirmed.

A general-purpose clocked gate driver integrated circuit (IC) to generate an arbitrary gate waveform is proposed to provide a universal platform for fine-grained gate waveform optimization handling various power transistors. The fabricated IC with a 0.18 μm Bipolar-CMOS-DMOS process has 63 P-type MOS (PMOS) and 63 N-type MOS (NMOS) driver transistors on a chip whose activation patterns are controlled by 6-bit digital signals and 40 ns time step control. In the 500 V switching measurements with a manual gate waveform optimization, the proposed gate driver reduces the IC overshoot by 25% and 41%, and the energy loss by 38% and 55% for Si-insulated-gate bipolar transistor and SiC-MOSFET, respectively, which demonstrate the feasibility of driving various power devices with the same driver. An automatic optimization by simulated annealing algorithm is introduced to fully utilize the benefit of the gate driver, and the further reduction of IC overshoot by 26% and the energy loss by 18% are achieved over the manual optimization.

In this paper, we propose a novel software defined power supply using the general purpose DSP (Digital Signal Processor) and its control algorithm based on power supply on chip. The proposed power supply can regulate the output voltage only loading a program into the DSP without adjusting the parameters and changing the external parts. Also, it can change the output voltage according to the state of the load by executive instruction from the load. The simulation results show that the transient response depends on the inductance, the capacitance and the internal resistance, and expects sub-μ s. at switching frequency of 30 MHz., 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe), September 2-6, 2019, Genova, Italy

Negative biasing of the gate voltage in a scaled insulated gate bipolar transistor (IGBT) during the off-state was modeled and found to be effective against self-turn-on failures. The required self-turn-on-free criteria were verified experimentally., 31st IEEE International Symposium on Power Semiconductor Devices and ICs (ISPSD 2019), 19-23 May 2019, Shanghai, China

Chlorella kessleri accumulates triacylglycerol usable for biodiesel-fuel production to >20% dry cell weight in three days when cultured in three-fold diluted seawater, which imposes the combinatory stress of hyperosmosis and nutrients limitation. The quantitative behavior of major C-compounds, and related-gene expression patterns were investigated in Chlorella cells stressed with hyperosmosis, nutrients limitation, or their combination, to elucidate the C-metabolism for economical seawater-based triacylglycerol accumulation. Combinatory-stress cells showed repressed protein synthesis with initially accumulated starch being degraded later, the C-metabolic flow thereby being diverted to fatty acid and subsequent triacylglycerol accumulation. This C-flow diversion was induced by cooperative actions of nutrients-limitation and hyperosmosis. Semi-quantitative PCR analysis implied positive rewiring of the diverted C-flow into triacylglycerol in combinatory-stress cells through upregulation of gene expression concerning fatty acid and triacylglycerol synthesis, and starch synthesis and degradation. The information of regulatory C-metabolism will help reinforce the seawater-based triacylglycerol accumulation ability in algae including Chlorella.

Revegetation using native species requires the development of seed transfer zones that capture genetic distinctiveness and adaptive potentials while avoiding potential maladaptation and genetic contamination by exotic genotypes. Delineation based on phylogeographic information has recently been used to establish seed transfer zones; however, only a few herbaceous species that are suitable for revegetation have been investigated in the temperate regions of Japan. We investigated the phylogeography of non-coding regions of chloroplast DNA of ten native species in the temperate regions of Japan. Although no species showed clear-cut geographical distributions of the 2–14 haplotypes identified, spatially constrained Bayesian clustering showed two clusters in five species (Calamagrostis epigejos, Eragrostis ferruginea, Imperata cylindrica, Microstegium japonicum, and Microstegium vimineum) but not for others. Posterior modes of clusters for I. cylindrica and M. vimineum showed delineations at Chubu (the middle of Honshu Island), which divide the study region into northeastern and southwestern regions, indicating that these species had recovered from glacial refugia. Posterior mode of cluster for E. ferruginea showed that one consists of a coastal zone along the Pacific Ocean side of western Japan, while the other consists of the remaining area, indicating range expansion from south coast to north. Delineation of C. epigejos and M. japonicum were unclear. The mixed results indicated that establishing seed transfer zones for herbaceous species in Japan will require phylogeographical studies on a wide range of species that may be suitable for revegetation.

Attention has been paid to the next-generation IGBT toward CMOS compatible wafer processes, which can be driven by a 5-V logic level due to its low threshold gate voltage. This low threshold voltage makes the so-called shoot-through fault severer. Even though the switching speed of the IGBT is intentionally reduced, the shoot-through fault can happen. This paper presents shoot-through protection for an inverter consisting of the next-generation IGBTs with gate impedance reduction. Theoretical analysis reveals the criterion of the gate impedance with taking parasitic parameters of the inverter into account.

The filum terminale (FT) is a potential source of ependymal cells for transplantation. The present study was performed to clarify the characteristics of ependymal cells of the central canal (CC) of the FT in rats. The FT was a thin strand continuous with the conus medullaris (CM), a caudal end of the main spinal cord, situated at the L3-4 level in adult rats. The border between the CM and FT was not visible, but could be defined as the site where the strand was as thin as its more caudal segment. While the CM contained an appreciable amount of white and grey matter associated with the CC at its center, the FT had no or only a negligible amount of such spinal cord parenchymal tissue. The FT was tracked ca. 4 cm from the site defined above to the level of S4-5 in adult rats. The rostral part of the FT (FTI) included within the cauda equina is exposed to cerebrospinal fluid, whereas the more caudal part (FTE) was surrounded by a dense layer of connective tissue. Almost all ependymal cells were immunostained for Sox2, Sox9, FoxJ1, and CD133, generally recognized immunochemical markers for ependymal cells of the CC in the spinal cord. Ependymal cells of the CC of FT exhibited almost the same structural and immunohistochemical characteristics as those of the CC of the main spinal cord. Ependymal cells of FTI covered by a thin layer of connective tissue are considered appropriate for transplantation.

In this paper, we propose a new control algorithm for a novel full digital control H-bridge DC-DC converter which can output the power in both boost and buck mode only rewriting three digital code such as input voltage, output voltage, and maximum load current. In addition, the proposed algorithm improves the transient response.

Bone marrow stromal cells (BMSCs) have been studied for the treatment of spinal cord injury (SCI). In previous studies, we showed that the transplantation of BMSCs, even though they disappeared from the host spinal cord within 1-3 weeks after transplantation, improved locomotor behaviors and promoted axonal regeneration. This result led to the hypothesis that BMSCs might release some neurotrophic factors effective for the treatment of SCI. The present study examined this by injecting the conditioned medium (CM) of BMSCs to treat SCI in rats. The spinal cord was contusion-injured, followed immediately by continuous injection for 2 weeks of the CM of BMSCs through the cerebrospinal fluid via the 4th ventricle using an Alzet osmotic pump. Locomotor behaviors evaluated by the Basso-Beattie-Bresnahan score were markedly improved in the CM-injection group, compared with the control group, at 1 to 4 weeks post-injection. The contusion-injured site of the spinal cord was identified as an astrocyte-devoid area, which contained no astrocytes but was filled with collagen matrices and empty cavities of various sizes. Collagen matrices contained type I collagen and laminin. Numerous axons extended through the collagen matrices of the astrocyte-devoid area. Axons were surrounded by Schwann cells, exhibiting the same morphological characteristics as peripheral nerve fibers. The density of axons extending through the astrocyte-devoid area was higher in the CM-injection group, compared with the control group. CM injection had beneficial effects on locomotor improvements and tissue repair, including axonal regeneration, meaning that the BMSC-CM stimulated the intrinsic ability of the spinal cord to regenerate. Activation of the intrinsic ability of the spinal cord to regenerate by the injection of neurotrophic factors such as BMSC-CM is considered to be a safe and preferable method for the clinical treatment of SCI.

The realization of wide input voltage and high power density on the conventional current resonant converter such as LLC converter remarkably increases transformer winding loss and its design difficulty. Therefore, it is difficult for the conventional LLC converter to satisfy both requirements. In order to apply the LLC converter with both conditions, this paper investigates the mechanism of the transformer winding loss occurrence in the conventional LLC converter. Moreover, the solution for mentioned above problems is proposed which can removes the transformer design difficulty as well by only changing the resonant operation mode., Power Electronics and Applications (EPE'17 ECCE Europe), 2017 19th European Conference on, 11-14 Sept. 2017, Warsaw, Poland

A current resonant converter including wider input voltage range and higher power density is required for various applications. However, in our study, it has been found that the drastic increasing of the transformer winding loss becomes a severe problem. This paper clarifies the mechanism of transformer winding loss occurrence and proposes the different resonant mode operation which solves the problem of the huge transformer loss., Future Energy Electronics Conference and ECCE Asia (IFEEC 2017 - ECCE Asia), 2017 IEEE 3rd International, 3-7 June 2017, Kaohsiung, Taiwan

This paper describes electrical characteristics of a silicon based multi-tens MHz gate driver IC for GaN power devices. The fabricated gate driver IC can operate 50 MHz and drive the GaN power device when sine wave inputs. We fabricated prototype synchronous back converter using GaN power devices and the fabricated driver IC. The fabricated buck converter can operate at 30 MHz and results show that the most important challenge for high frequency POL is to reduce parasitic impedance. The simulation results show that a 3D stacked power supply on chip effectively reduces the parasitic impedance and improves the efficiency.

The higher current density of IGBTs has made it difficult to achieve high short-circuit withstand capability as well as good conduction characteristics. Therefore, a fast and reliable protection system is required for the safe operation of IGBT. This paper determines the short-circuit safe protection area (SCSPA) for advanced IGBT that has no short-circuit withstand capability and proposes the protection system satisfied this SCSPA. The fast protection is brought by PCB Rogowski coil and digital gate driver using digital circuit (FPGA). Experimental results verify that short-circuit detection time is 70 ns, shut-down time is reduced by controlling the gate resistance at turn-off.

Output-inductor-less full-bridge converter for a High-Voltage Direct-Current power distribution system has been proposed. This proposed circuit topology suppresses the surge voltage due to the secondary-side diode's recovery, and miniaturizes the converter because the number of circuit components is reduced. On the other hand, some problems occur, such as the increasing switching-loss of primary switches and another high-frequency noise generation. This paper proposes a novel synchronous rectifier driving for the output-inductor-less full-bridge converter in order to solve these problems, and examines the noise reduction effect, and the relationship between ZVS operation conditions and circuit parameters. The proposed method does not need an external component, and then the smaller size is maintained. Furthermore, the experimental results confirm the power loss reduction of 20W in a wide load range, and also the noise reduction.

In this paper, a high power-density output-inductor-less full-bridge converter for the HVDC power distribution system is proposed. The new reduction techniques of switching loss and noise in the output-inductor-less full-bridge converter by using SiC-MOSFETs are applied. As the result, the power loss is reduced by 20W in a wide load range, and the noise is also reduced. Furthermore, a high power density of 15W/cm3 is achieved by the experimental breadboard with power level of 1kW.

A general-purpose clocked gate driver (CGD) IC to generate an arbitrary gate waveform is proposed to provide a universal platform for fine-grained gate waveform optimization handling various power transistors. The fabricated IC with 0.18µm BCD process has 63 PMOS and 63 NMOS driver transistors on a chip whose activation patterns are controlled by 6-bit digital signals and 25-MHz clock (= 40-ns time step control). In the 500-V switching measurements, the proposed CGD reduces the IC overshoot by 25% and 41% and the energy loss by 38% and 55% for Si-IGBT and SiC-MOSFET, respectively.

This paper proposes an isolated DC-DC converter for Power-Supply on chip (SoC) realized by the couple of air-core coils. The pro-posed isolated DC-DC converter is evaluated by numerical simulations and experimental results. The fabricated prototype DC-DC converter works well and the simulation results are good agreement with experimental results. This paper also discusses the potential of proposed DC-DC converter for power SoC applications based on numerical simulation and experimental results.

We propose a multi input voltage and multiple output voltage DC-DC converter using H-bridge converter for power supply on chip. We analyzed the operation mode of the H-bridge converter and also propose the suitable operation mode for power supply on chip. The proposed POLs realize stable output voltage and high efficiency over the wide range through digital control.

This paper proposes a PFM+PWM hybrid controlled soft-switching half-bridge converter which has both benefit of conventional half-bridge converter and LLC converter. Generally, conventional half-bridge converter has good constant current characteristic due to PWM control, however it has some drawbacks of (1) primary side switches and secondary side diodes operate under hard switching, (2) two magnetic components. Meanwhile, the LLC resonant converter has the benefit of achieving ZVS and ZCS, however it can't realize a constant current (CC) characteristic because of resonant fashion. In order to achieve soft-switching and CC characteristic using half-bridge converter, a DCM operation are employed, which can be controlled by PWM+PFM Hybrid Control. In this paper the operating characteristics of the proposed half-bridge converter are experimentally verified. The experimental results for 48Vin, 16Vo, 80W board achieves 90% efficiency and validated this method is useful practically.

This paper proposes a power-loss reduction technique for a kW-scale isolated dc-dc converter, which installs a novel PWM control to achieve the soft-switching of primary side MOS-FETs. As a result, the efficiency is achieved over 90% in a wide load range. Moreover, the temperature of the primary side MOS-FETs can be reduced by 30 degrees when compared with the conventional method, and the power-density can be improved up to 15W/cm3.

In this paper, we propose a concept of Field Programmable Power supply Array (FPPA), which is a fully digital controlled power supply, based on power supply on chip technology. The FPPA realize multi input voltage and multi output voltage only rewrite digital code of FPGA or DSP.

We investigated the excitation temperature of atmospheric-pressure non-equilibrium (cold) plasma using a line-pair method. An atmospheric cold plasma was intermittently generated using a quartz tube, a rare gas, and a foil electrode by applying high-voltage alternating current. Because the plasma occurred intermittently, an interval appeared between each generated plasma bullet. We assessed the time-averaged effective intensity from the observed intensity at each wavelength measured using a spectrometer. When the exposure time of the spectrometer is longer than the observed period of the plasma emission light, the time-averaged effective intensity at each wavelength decreases because it includes the interval with no plasma emission light. The difference in intensity between wavelengths changes with frequency, because changing the frequency changes the interval between plasma bullets. Consequently, even if the plasma electron temperature does not depend on the frequency of the applied voltage, the excitati...