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Kenji OHNO,Hiroki MATSUMOTO,Kenji MURAO 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
As the chip integration advances toward the CMOS VLSI integrated systems, on-chip Digital-to-Analog Converter (DAC) becomes more important building blocks. Key technologies in DAC is fabrication at low-cost and operation on high-performance. Highresolution and Low-Voltage DAC is required in many fields. Their advantage extends to mixed-signal systems where both frequency higher, the device shrinks into deep sub-micrometer. However the shrinking device dimensions also imply proportional scalling of power supply voltage. Advantages of alogorithmic DAC using Switched-Capacitor (SC) are suitable to the above requirement. SC operates on small chip area, low consumption of electoric power, and is compatible to MOS IC. To operate under low supply voltage, terminal of NMOS analog switch should connect to ground or virtual ground.[1] However, major performance of conventional algolithmic DAC is limited by offset voltage and spike.[2] In this paper, they shows two Low-Voltage SC cyclic DACs. They are proposed which consists of a switch, capacitor, MOSFET and operational amplifier (op-amp). Circuit operation is evaluated on SIMetrix.
Spike-compensated Low-Voltage Unity-Gain-Reset Switched-Capacitor Cyclic Digital-to-Analog Converter
Kenji OHNO,HirokiMATSUMOTO,Kenji MURAO 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
As the chip integration advances toward the CMOS VLSI integrated systems, on-chip Digital-to-Analog Converter (DAC) becomes more important building blocks. Key technologies in DAC is fabrication at low-cost and operation on high-performance. Highresolution and Low-Voltage DAC is required in many fields. Their advantage extends to mixed-signal systems where both frequency higher, the device shrinks into deep sub-micrometer. However the shrinking device dimensions also imply proportional scalling of power supply voltage. Advantages of Alogorithmic DAC using Switched-Capacitor (SC) are suitable to the above requirement. SC are small chip area, low consumption of electoric power, and compatibility to MOS IC. To operate under low supply voltage, terminal of NMOS analog switch should connect to ground or virtual ground. However, major performance of conventional algolithmic DAC is limited by offset voltage and spike. In this paper, it shows a Low-Voltage SC cyclic DAC. It is proposed which consists of a switch, capacitor, MOSFET and op-amp. Circuit operation is evaluated on SIMetrix.
NMR Study of Magnetic Properties of Eu1−xSrxMnO3 (0 ≤ x ≤ 0.5)
Kenji Shimizu,Masanori Yamaguchi,Shujuan Yuan,Shixun Cao 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
The perovskite manganite EuMnO3 is known to be a compound with a narrow eg-band width due to small ionic radius of Eu3+ compared to La3+. The Eu1−xSrxMnO3 compounds show complex magnetic properties, depending on the Sr concentration x. We have carried out 55Mn spin-echo nuclear magnetic resonance (NMR) measurements on polycrystalline Eu1−xSrxMnO3 (0 ≤ x≤ 0.5) compounds at 4.2 or 1.4 K in order to clarify the microscopic local magnetic state of the Mn ions. NMR spectra have been observed in the frequency range from 250 MHz to 400 MHz. For the A-type antiferromagnetic EuMnO3, the resonance frequency is about 260 MHz, which is much lower than that observed for Mn3+ in La1−xSrxMnO3. For 0.1 ≤ x ≤ 0.4, the resonance lines corresponding to Mn4+ and Mn3+ have been observed at about 315 MHz and 390 MHz, respectively. Furthermore, the spectra originating from Mn2+ have been observed around 590 MHz for 0.1 ≤ x ≤ 0.4. For Eu0.5Sr0.5MnO3, the NMR spectrum spreads widely with several distinct peaks in the frequency range from 250 MHz to 410 MHz, which shows that the compound is in an inhomogeneous state due to competition between the antiferromagnetic and the ferromagnetic states.
Kenji Ohwada,Tatsuo Fukuda,Jun’ichiro Mizuki,Kazuma Hirota,Hikaru Terauchi,Satoshi Tsutsui,Alfred Q. R. Baron,Hidehiro Ohwa,Naohiko Yasuda 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.31
Pb(In_(1/2)Nb_(1/2))O_3 (PIN) can be antiferroelectric (AFE), ferroelectric (FE) or a relaxor depending upon the perovskite B-site randomness. In order to clarify the effect of B-site randomness, we studied the dynamics of ordered PIN without B-site randomness (O-PIN, AFE), which will give us a clear picture of the AFE/relaxor nature of the ground state due to B-site randomness. The quasielastic (QE) scattering shows a critical slowing down near the Γ-point and the transverse acoustic (TA) mode shows a softening trend at a finite wavenumber position (not at the Γ-point) towards the AFE phase transition temperature (T_N ∼ 450 K). On the other hand, the transverse optic (TO) mode shows a softening near the Γ-point toward low temperature with no clear anomaly at T_N. These results indicate that the AFE phase transition is associated with the TA mode and the origin of the QE scattering while a ferroelectric correlation exists behind the AFE ordering. The effect of B-site randomness is finally discussed on the basis of the results.
Comparative study among Asian Oribatid Fauna. -Is oribatid fauna rich in tropical zone?-
Kenji Fukuyama 한국응용곤충학회 2008 한국응용곤충학회 학술대회논문집 Vol.2008 No.10
It is widely believed that diversity of soil animals are poorer in the tropical zone than in the temperate zone. Is this right? Then, I compared Asian oribatid faunae of the following localities: a tropical lowland rain forest in Pasoh Forest Reserve (Peninsular Malaysia), a subtropical forest in Yunnan Province (China), warm temperate forest in Chiba, a cool temperate forest in Sapporo (Japan), and in a taiga in arctic zone in Siberia (Russia). Samplings in a primary forest and in a 40-year secondary forest, which were 2 ha each and adjacent to each other, showed about 100 oribatid species there. Total species number was estimated at 135 to 150 with Jackknife method. This shows that the species diversity of oribatids are rich in tropics as compared with that in the temperate Japan. Oribatid species richness was even lower in Siberia (Yakutsk) than in Japan. These indicate that oribatid diversity in tropics is higher than in other areas of higher latitudes. Analyses based on Motomura's geometric series rule showed that the inclination became steeper with latitude, also suggesting that a high species diversity in the tropics. Although the number of families did not change greatly with latitude, a DCA analysis showed that composition of families was related with latitude. It was shown that a low latitude area has many winged oribatid mites, such as Haplozetidae, Protoribatidae, and Galumnidae, with many primitive groups in a high latitude area, such as Brachychthoniidae and Hypochthoniidae.