Evaluation of the Performance of Polished Mirror Surfaces for the TAMA Gravitational Wave Detector by Use of a Wave-Front Tracing Simulation

We evaluated the performance of polished mirror surfaces for the TAMA interferometric gravitational wave detector by comparing the experimental results with a wave-front tracing simulation. The TAMA mirror surfaces were polished to a roughness of a few nanometer rms. We confirmed that these polished mirrors do not limit the present TAMA sensitivity and that the target shot-noise sensitivity will be achieved with these mirrors, even if a power-recycling technique is introduced in the next stage of the TAMA

8 kbit/s オンセイ フゴウカ ITU-T ヒョウジュン ノ エンザンリョウ サクゲンバン Annex A カンコク ノ ケイイ ト ヒンシツ ヒョウカ ジョウホウ ヒョウゲン ガッカ

ITU-Tの8 kbit/s音声符号化方式G.729の演算量削減版がAnnex Aとして勧告された経緯とのアルゴリズムの特徴、及び、品質評価について述べる。Annex Aは、電話網上でモデムを介して、PC等の端末装置間でディジタルデータと音声とを同時に送受する方式DSVD (Digital Simultaneous Voice and Data)のITU-T勧告V.70に使われることを主目的として、G.729の演算量削減により開発された。DSVD用音声符号化式は、低ビットレート、商用電話品質、短遅延時間、低演算量が望まれ、また、伝送効率の要請からVAD(voice Activity Detection)機能の併用が必須である。G.729 CS-ACELPは、演算量を除いてほぼすべて要求を満たしていたが、Annex Aは演算量を大幅に削減し、DSVDの要求に合致させたものである。品質評価は、日本語ほか複数国語で行われ、G.729本体とAnnex Aが相互に接続可能であり、かつ、所定の品質条件を満たすことが明らかとなった。DSVD方式はその後、インターネット上のバケット音声通信にとって代わられるが、音声符号化標準は広くVoIP(Voice over Internet Protocol)などに使用されその用途が拡大している。This paper presents the history of recommending Annex A to G.729 in ITU-T (international Telecommunication Union, Telecommunication Standerdization Sector) and quality assessment of the coder. The requirements for this system were toll speech quality, low complexity, and short delay time at low bit-rate less than 12 kbit/s, and were not met by existing speech coding standards. Rreduced complexity CS-ACELP was selected from among 5 candidates as the coding algorithm after extensive subjective selection tests and was recommended as Annex A to G.729. The subjective test in Japanese shows that this Annex is compatible with G.729 and meets all the requirements

Development of a Gas-Cylinder-Free Plasma Desorption/Ionization System for On-Site Detection of Chemical Warfare Agents

A gas-cylinder-free plasma desorption/ionization system was developed to realize a mobile on-site analytical device for detection of chemical warfare agents (CWAs). In this system, the plasma source was directly connected to the inlet of a mass spectrometer. The plasma can be generated with ambient air, which is drawn into the discharge region by negative pressure in the mass spectrometer. High-power density pulsed plasma of 100 kW could be generated by using a microhollow cathode and a laboratory-built high-intensity pulsed power supply (pulse width: 10–20 μs; repetition frequency: 50 Hz). CWAs were desorbed and protonated in the enclosed space adjacent to the plasma source. Protonated sample molecules were introduced to the mass spectrometer by airflow through the discharge region. To evaluate the analytical performance of this device, helium and air plasma were directly irradiated to CWAs in the gas-cylinder-free plasma desorption/ionization system and the protonated molecules were analyzed by using an ion-trap mass spectrometer. A blister agent (nitrogen mustard 3) and nerve gases [cyclohexylsarin (GF), tabun (GA), and <i>O</i>-ethyl <i>S</i>-2-<i>N</i>,<i>N</i>-diisopropylaminoethyl methylphosphonothiolate (VX)] in solution in <i>n</i>-hexane were applied to the Teflon rod and used as test samples, after solvent evaporation. As a result, protonated molecules of CWAs were successfully observed as the characteristic ion peaks at <i>m</i>/<i>z</i> 204, 181, 163, and 268, respectively. In air plasma, the limits of detection were estimated to be 22, 20, 4.8, and 1.0 pmol, respectively, which were lower than those obtained with helium plasma. To achieve quantitative analysis, calibration curves were made by using CWA stimulant dipinacolyl methylphosphonate as an internal standard; straight correlation lines (<i>R</i>² = 0.9998) of the peak intensity ratios (target per internal standard) were obtained. Remarkably, GA and GF gave protonated dimer ions, and the ratios of the protonated dimer ions to the protonated monomers increased with the amount of GA and GF applied