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Phase Transition in Ferroelectric SrBi$_2$Ta$_2$O$_9$ Single Crystal
K. Yoshio,A. Onodera,A. Yamada,A. Sakai,H. Yamashita,I. Matsubara 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
Single plate-like crystal of Bi-layered ferroelectric perovskite SrBi2Ta2O9 was prepared by self- ux method. Temperature dependence of the lattice constant c, specic heat, Raman scattering were measured to study phase transitions in SrBi2Ta2O9. There are clear anomalies at 613 K (Tc) and 850 K (T) in the c-axis. The mechanism of this phase transition was discussed in terms of Dzialoshinsky-Moriya-type interaction.
K.Izaki,I.hirota,H.Yamashita,H.Omon,K.Matsumoto,K.Nishida,J.M.Sun,M.Nakaoka 전력전자학회 1998 ICPE(ISPE)논문집 Vol.- No.-
This paper describes an advanced prototype of voltage-fed zero voltage soft-switching PWM resonant inverter with an active voltage clamped capacitor, which is put into practice for high-frequency high-power induction-heated appliances This application-specific quasi-resonant inverter using the latest generation IGBTs for soft-switching can regulate its output power under a principle of a fixed frequency ZVS-PWM strategy. Its operating principle and unique features are presented as compared with a conventional quasi-resonant ZVS inverter for induction-heated cooker, together with its power regulation characteristics on the basis of its simulation and experimental results. The steady-state performances of this inverter developed for mutli-bumer type induction-heated food cooking appliance are evaluated and discussed from a practical point of view.<br/>
Search for dark matter in the form of hidden photons and axion-like particles in the XMASS detector
Abe, K.,Hiraide, K.,Ichimura, K.,Kishimoto, Y.,Kobayashi, K.,Kobayashi, M.,Moriyama, S.,Nakahata, M.,Ogawa, H.,Sato, K.,Sekiya, H.,Suzuki, T.,Takachio, O.,Takeda, A.,Tasaka, S.,Yamashita, M.,Yang, B.S Elsevier 2018 Physics letters: B Vol.787 No.-
<P><B>Abstract</B></P> <P>Hidden photons and axion-like particles are candidates for cold dark matter if they were produced non-thermally in the early universe. We conducted a search for both of these bosons using 800 live-days of data from the XMASS detector with 327 kg of liquid xenon in the fiducial volume. No significant signal was observed, and thus we set constraints on the <SUP> α ′ </SUP> / α parameter related to kinetic mixing of hidden photons and the coupling constant <SUB> g A e </SUB> of axion-like particles in the mass range from 40 to 120 keV/ <SUP> c 2 </SUP> , resulting in <SUP> α ′ </SUP> / α < 6 × <SUP> 10 − 26 </SUP> and <SUB> g A e </SUB> < 4 × <SUP> 10 − 13 </SUP> . These limits are the most stringent over this mass range derived from both direct and indirect searches to date.</P>
Abe, K.,Hiraide, K.,Ichimura, K.,Kishimoto, Y.,Kobayashi, K.,Kobayashi, M.,Moriyama, S.,Nakahata, M.,Norita, T.,Ogawa, H.,Sato, K.,Sekiya, H.,Takachio, O.,Takeda, A.,Tasaka, S.,Yamashita, M.,Yang, B.S Elsevier 2018 Nuclear Instruments & Methods in Physics Research. Vol.884 No.-
<P><B>Abstract</B></P> <P>We established a method to assay <SUP>210</SUP>Pb and <SUP>210</SUP>Po contaminations in the bulk of copper samples using a low-background alpha particle counter. The achieved sensitivity for the <SUP>210</SUP>Pb and <SUP>210</SUP>Po contaminations reaches a few mBq/kg. Due to this high sensitivity, the <SUP>210</SUP>Pb and <SUP>210</SUP>Po contaminations in oxygen free copper bulk were identified and measured for the first time. The <SUP>210</SUP>Pb contaminations of our oxygen free copper samples were 17–40 mBq/kg. Based on our investigation of copper samples in each production step, the <SUP>210</SUP>Pb in oxygen free copper was understood to be a small residual of an electrolysis process. This method to measure bulk contaminations of <SUP>210</SUP>Pb and <SUP>210</SUP>Po could be applied to other materials.</P>
Direct dark matter search by annual modulation with 2.7 years of XMASS-I data
Abe, K.,Hiraide, K.,Ichimura, K.,Kishimoto, Y.,Kobayashi, K.,Kobayashi, M.,Moriyama, S.,Nakahata, M.,Norita, T.,Ogawa, H.,Sato, K.,Sekiya, H.,Takachio, O.,Takeda, A.,Tasaka, S.,Yamashita, M.,Yang, B. American Physical Society 2018 Physical Review D Vol.97 No.10
<P>An annual modulation signal due to the Earth orbiting around the Sun would be one of the strongest indications of the direct detection of dark matter. In 2016, we reported a search for dark matter by looking for this annual modulation with our single-phase liquid xenon XMASS-I detector. That analysis resulted in a slightly negative modulation amplitude at low energy. In this work, we included more than one year of additional data, which more than doubles the exposure to 800 live days with the same 832 kg target mass. When we assume weakly interacting massive particle (WIMP) dark matter elastically scattering on the xenon target, the exclusion upper limit for the WIMP-nucleon cross section was improved by a factor of 2 to 1.9 x 10(-41) cm(2) at 8 GeV/c(2) at 90% confidence level with our newly implemented data selection through a likelihood method. For the model-independent case, without assuming any specific dark matter model, we obtained more consistency with the null hypothesis than before with a p-value of 0.11 in the 1-20 keV energy region. This search probed this region with an exposure that was larger than that of DAMA/LIBRA. We also did not find any significant amplitude in the data for periodicity with periods between 50 and 600 days in the energy region between 1 to 6 keV.</P>
Search for sub-GeV dark matter by annual modulation using XMASS-I detector
Kobayashi, M.,Abe, K.,Hiraide, K.,Ichimura, K.,Kishimoto, Y.,Kobayashi, K.,Moriyama, S.,Nakahata, M.,Ogawa, H.,Sato, K.,Sekiya, H.,Suzuki, T.,Takeda, A.,Tasaka, S.,Yamashita, M.,Yang, B.S.,Kim, N.Y.,K North-Holland Pub. Co 2019 Physics letters. Section B Vol.795 No.-
<P><B>Abstract</B></P> <P>A search for dark matter (DM) with mass in the sub-GeV region (0.32–1 GeV) was conducted by looking for an annual modulation signal in XMASS, a single-phase liquid xenon detector. Inelastic nuclear scattering accompanied by bremsstrahlung emission was used to search down to an electron equivalent energy of 1 keV. The data used had a live time of 2.8 years (3.5 years in calendar time), resulting in a total exposure of 2.38 ton-years. No significant modulation signal was observed and 90% confidence level upper limits of 1.6 × <SUP> 10 − 33 </SUP> cm<SUP>2</SUP> at 0.5 GeV was set for the DM-nucleon cross section. This is the first experimental result of a search for DM mediated by the bremsstrahlung effect. In addition, a search for DM with mass in the multi-GeV region (4–20 GeV) was conducted with a lower energy threshold than previous analysis of XMASS. Elastic nuclear scattering was used to search down to a nuclear recoil equivalent energy of 2.3 keV, and upper limits of 2.9 × <SUP> 10 − 42 </SUP> cm<SUP>2</SUP> at 8 GeV was obtained.</P>