Extremely Small Energy Gap in the Quasi-One-Dimensional Conducting Chain Compound SrNbO3.41_{3.41}

Resistivity, optical, and angle-resolved photoemission experiments reveal unusual one-dimensional electronic properties of highly anisotropic SrNbO$_{3.41}$. Along the conducting chain direction we find an extremely small energy gap of only a few meV at the Fermi level. A discussion in terms of typical 1D instabilities (Peierls, Mott-Hubbard) shows that neither seems to provide a satisfactory explanation for the unique properties of SrNbO$_{3.41}$.Comment: 4 pages, 3 figure

Effect of pressure on the polarized infrared optical response of quasi-one-dimensional LaTiO3.41_{3.41}

The pressure-induced changes in the optical properties of the quasi-one-dimensional conductor LaTiO$_{3.41}$ were studied by polarization-dependent mid-infrared micro-spectroscopy at room temperature. For the polarization of the incident radiation parallel to the conducting direction, the optical conductivity spectrum shows a pronounced mid-infrared absorption band, exhibiting a shift to lower frequencies and an increase in oscillator strength with increasing pressure. On the basis of its pressure dependence, interpretations of the band in terms of electronic transitions and polaronic excitations are discussed. Discontinuous changes in the optical response near 15 GPa are in agreement with a recently reported pressure-induced structural phase transition and indicate the onset of a dimensional crossover in this highly anisotropic system.Comment: 7 pages, 7 figure

ジョウホウ リュウツウ ノ ゲンジョウ ブンセキ ト コンゴ ノ カダイ

今日のデジタル化とネットワーク化の進展に伴い、メディア上を流通する多様な情報量は急速に増大している。情報通信技術による高度情報ネットワーク、情報端末およびネットワーク上を流れる豊富なコンテンツの開発により、より一層シームレスでスムーズな情報流通の実現が望まれる。 本論文では、情報流通において、個々人の情報行動に密接に関係する情報消費(消費情報量)を、パーソナルメディア及びマスメディアの各メディア毎に、最新の総務省統計局の情報通信統計データベース「情報流通センサス」を基に分析する。また今後の課題として、ブロードバンド環境の整備にともない、リッチなマルチメディア・デジタルコンテンツの情報流通を活性化する鍵ともなる著作権保護について取り上げる。The volumes of diverse information flows and contents distribution have been increasing rapidly due to the recent advance in information communication technology. It is demanded that smooth information flows are realized by the development of the advanced network, information terminals and contents. The present paper reports the analysis of current information flows and contents distribution, especially of the information consumed in the every personal media and mass media in Japan. The information consumed in information flows is closely related with personal activities. In this paper, the volumes of information flows in Japan are based on the latest investigation" Census of Information Flow" conducted by MPHPT(Ministry of Public Management, Home Affairs, Posts and Telecommunications). This paper also reports the copyright protection system to prevent illegal copying digital contents so as to promote production and distribution of digital network contents in the broadband environments

Computer Simulation and Field Experiment for Downlink Multiuser MIMO in Mobile WiMAX System

The transmission performance for a downlink mobile WiMAX system with multiuser multiple-input multiple-output (MU-MIMO) systems in a computer simulation and field experiment is described. In computer simulation, a MU-MIMO transmission system can be realized by using the block diagonalization (BD) algorithm, and each user can receive signals without any signal interference from other users. The bit error rate (BER) performance and channel capacity in accordance with modulation schemes and the number of streams were simulated in a spatially correlated multipath fading environment. Furthermore, we propose a method for evaluating the transmission performance for this downlink mobile WiMAX system in this environment by using the computer simulation. In the field experiment, the received power and downlink throughput in the UDP layer were measured on an experimental mobile WiMAX system developed in Azumino City in Japan. In comparison with the simulated and experimented results, the measured maximum throughput performance in the downlink had almost the same performance as the simulated throughput. It was confirmed that the experimental mobile WiMAX system for MU-MIMO transmission successfully increased the total channel capacity of the system

Signatures of polaronic excitations in quasi-one-dimensional LaTiO3.41_{3.41}

The optical properties of quasi-one-dimensional metallic LaTiO$_{3.41}$ are studied for the polarization along the $a$ and $b$ axes. With decreasing temperature modes appear along both directions suggestive for a phase transition. The broadness of these modes along the conducting axis might be due to the coupling of the phonons to low-energy electronic excitations across an energy gap. We observe a pronounced midinfrared band with a temperature dependence consistent with (interacting) polaron models. The polaronic picture is corroborated by the presence of strong electron-phonon coupling and the temperature dependence of the dc conductivity.Comment: 5 pages, 5 figure