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RISS 인기검색어
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- 저자 : Nobuo Nakajima (검색결과 7 건)
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WIDEBAND DS - CDMA FOR 3RD GENERATION MOBILE COMMUNICATION SYSTEMS
Nobuo Nakajima,Fumiyuki Adachi 에스케이텔레콤 (주) 1997 Telecommunications Review Vol.7 No.2
This paper describes the features and technology of the wideband DS-CDMA system for next generation mobile communication system. The wider the bandwidth, the more the capacity increases. In addition, wide range of data rates from as low as about 4kbps to 2 Mbps can be accommodated by the wideband system, In order to flexibly offer data services with a variety of rates multi-rate codes are employed and four different bandwidths of 1.25, 5, 10, and 20 Mcps are adopted. The system operates in an inter cell asynchronous mode to allow flexible and continuous system deployment from outdoors into indoors. New technologies are developed to enhance the capacity and quality of the wideband DS-CDMA. They are the interference canceler and adaptive antenna array. Exensive measurements and evaluations of a 2-㎓ band DS-CDMA system were carried out under real multipath fading environments.
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Kiyohiko Hattori,Nobuo Nakajima,Tetuya Fujii,Youiti Kado,Bing Zhang,Takahiro Hazugawa,Kieiki Takadama 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
The positional estimate system which is represented in GPS is applied from the convenience to various fields, and to be used as a navigation system for pedestrians in recent years. However, GPS has a weak point that it is not possible to use in indoors such as underground stations, buildings, etc. This is because GPS needs a radio wave from GPS space satellites. To tackle this subject, a lot of method with RFID and radio wave of wireless LAN is proposed. Those systems have a large error of accuracy about position estimation. Thus, to supplement the estimating error margin of the radio base methods, we purpose a hybrid indoor positioning system that uses a wireless adhoc communication and two dimension marker for the position and direction estimation in this research. To verify the effectiveness of proposed methods by simulations, it was clarifed to be able to improve the positional estimation accuracy by using two dimension markers and adhoc communication.
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X-ray Absorption Study of the Local Dipole Moment in SrTiO3 under Uniaxial Pressure
Chisato Temba,Shuhei Kawakami,Nobuo Nakajima,Naoki Ishimatsu,Hiroshi Maruyama 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.9
X-ray absorption spectra under uniaxial pressure were measured at the Ti K-edge of a SrTiO3 single crystal in order to obtain direct evidence for the ferroelectric transition that is expected on the basis of second harmonic generation studies. A uniaxial pressure was applied perpendicular to the ab-plane. The pre-edge peak, which corresponds to Ti 3d eg-O 2pσ bonding, shows little change across the transition temperature of 40 K at 1 GPa. This indicates that a local electric dipole moment is not induced under uniaxial pressure, as opposed to the macroscopic ferroelectric moments that are predicted to be induced along the ab-plane.
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Aerosol model evaluation using two geostationary satellites over East Asia in May 2016
Goto, Daisuke,Kikuchi, Maki,Suzuki, Kentaroh,Hayasaki, Masamitsu,Yoshida, Mayumi,Nagao, Takashi M.,Choi, Myungje,Kim, Jhoon,Sugimoto, Nobuo,Shimizu, Atsushi,Oikawa, Eiji,Nakajima, Teruyuki Elsevier 2019 Atmospheric research Vol.217 No.-
<P><B>Abstract</B></P> <P>This study newly applies measurements from two geostationary satellites, the Advanced Himawari Imager (AHI) onboard the geostationary satellite Himawari-8 and the Geostationary Ocean Color imager (GOCI) onboard the geostationary satellite COMS, to evaluate a unique regional aerosol-transport model coupled to a non-hydrostatic icosahedral atmospheric model (NICAM) at a high resolution without any nesting technique and boundary conditions of the aerosols. Taking advantage of the unique capability of these geostationary satellites to measure aerosols with unprecedentedly high temporal resolution, we focus on a target area (115°E-155°E, 20°N-50°N) in East Asia in May 2016, which featured the periodic transport of industrial aerosols and a very heavy aerosol plume from Siberian wildfires. The aerosol optical thickness (AOT) fields are compared among the AHI, GOCI, MODIS, AERONET and NICAM data. The results show that both AHI- and GOCI-retrieved AOTs were generally comparable to the AERONET-retrieved ones, with high correlation coefficients of approximately 0.7 in May 2016. They also show that NICAM successfully captured the detailed horizontal distribution of AOT transported from Siberia to Japan on the most polluted day (18 May 2016). The monthly statistical metrics, including correlation between the model and either AHI or GOCI, are estimated to be >0.4 in 42–49% of the target area. With the aid of sensitivity model experiments with and without Siberian wildfires, it was found that a long-range transport of aerosols from Siberian wildfires (from as far as 3000 km) to Japan influenced the monthly mean aerosol levels, accounting for 7–35% of the AOT, 26–49% of the surface PM2.5 concentrations, and 25–66% of the aerosol extinction above 3 km in height over Japan. Therefore, the air pollutants from Siberian wildfire cannot be ignored for the spring over Japan.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A high resolution model generally produces an observed aerosol distribution. </LI> <LI> Next-generation geostationary satellites are applied for aerosol model evaluation. </LI> <LI> Multiple measurement helped to understand the 4-dimensional aerosol structure. </LI> <LI> Siberian wildfires strongly affected the aerosol levels over Japan in May 2016. </LI> </UL> </P>
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