研究課題　「成長するネットワーク型知能と人間中心システム」
工学部 科学技術交流センター内

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スタンフォード大学との間で、１９９８年からネットワークを介して実施してきている大学院の設計のグローバルPBLの活動と、そこから得た経験と知見を紹介する。とくにチームワーキングと設計の意図の理解について述べる。

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は,1998年以来,スタンフォード大学の大学院の設計授業にネットワークを介して参加してきた.この授業は,企業から課題提供を受け,学生がチームを組んで主体的に設計を行うプロジェクトベーストラーニング(PBL)方式である.最近,遠隔教育への関心が急速に高まり,多くのシステムが開発されている.しかし,その多くは,講義形式であり,十分にPBLのチームワークを支援できない.そこで,では,PBL方式の設計授業について,長い経験のあるスタンフォード大学と,ネットワークを介して,同大学が実施している,PBLのチームワークの設計授業を実施できるかどうかを検討するために,1998年から同授業ME310に参加をしてきた.また,企業としては,トヨタ自動車から,課題の提供を受け,日米で,チームを組んで取り組める課題をスタンフォード大学の教員,の教員,トヨタの関係者で検討して,学生に提示してPBL設計授業を実施している.本論文では,この経験から,遠隔で,チームで,PBLを行う場合,とくに外国との場合,どのような問題が生じ,それらをいかに解決したかを述べる.私達の経験が,今後,創成教育,遠隔PBL実施の環境開発に役立つことを期待している.

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Scale model experiments were made to investigate the steady and unsteady airflow characteristics in an underground railway station. The experimental apparatus consists of a scale model of a two-layer underground railway station and train wind generators that simulate the steady and unsteady airflow caused by trains. The steady and unsteady airflows were measured with hotwire anemometers at several points of the station for several cases. The unsteady airflow patterns were almost identical to the estimated airflow patterns obtained from steady values. The method of reducing the train wind effect in a station by means of tunnel ventilation dynamic control was considered and its effectiveness was confirmed through experimentation.

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The present paper describes a new design of a fluid driven microactuator which comprises a planar piston, a four-way control valve, and a mechanical feedback system that controls the output in accordance with an input displacement. Fabrication processes of the microactuator include bulk micromachining of two sheets of silicon substrate and their assembly by electrostatic bonding to glass plates. The output characteristics were measured supplying the compressed air. Generated output force was partially linear to supplied pressure and to valve displacement. However, the magnitude was asymmetric in terms of driven directions, which results from geometrical configuration essentially introduced by an anisotropic etching of the silicon. The position of the output shaft was sufficiently controlled with a designed magnification factor multiplied to the input displacement in both static and dynamic senses.

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事故が発生すると,警察による責任の追求が行われるのが通常であるが,責任を追求しても,事故はなくならないことが多いので,最近は事故調査委員会による調査が優先するようになってきた.しかし,死者が100人を超えるような巨大事故に対しては,事故の直接原因を追求するだけでは不十分なことも判ってきた.即ち,事故の原因だけでなく,事故が拡大した原因を研究し,その対策を検討する必要がある.この場合には,直接原因とは異なった原因が考えられるようになるので,科学技術でなく,社会技術として対策を検討しなければならない.この点を事例により,考察してみた.

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In this study, flow fields around idealized conical waveriders as well as aerodynamic characteristics are examined experimentally in TMIT hypersonic wind tunnel. Flow fields are observed with a schlieren system and aerodynamic forces are measured by a three-component balance. From the force measurement, the L/D ratio of on-design-/off-design- waveriders are found. The result shows that for waveriders with fins, value of L/D ratio drops as the decrease of angle of attack rapidly, whereas for a half cone, not so suddenly. Moreover from schliren photographs, shock shapes of attach/dettach condition are examined. The these photographs show that for planform-, small- and on designfins, shock shapes are conical, and for a large-fin, the shape is not conical.

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We consider an inspection system consisting of two inspection stations, numbered 1 and 2, arranged in tandem, in which station i, i=1, 2, inspects m_i jobs (at a time) as a batch with constant inspection time T_i. An infinite number of jobs always waits in front of station 1. After station 1 inspects one batch, information on whether the inspection operation was (a) successful or (b)unsuccessful can be obtained. In the case of (a), it is decided whether each job in the batch is defective or nondefective. The nondefective jobs are transferred to station 2 but the defective jobs are removed. In the case of (b), the batch is inspected again at station 1 for time T₁. Station 2 operates in the same manner except that the batch size and inspection time differ from those at station 1, and that jobs determined to be nondefective after inspection at station 2 are considered to be perfect products. There is a finite number of waiting positions (buffer) between stations 1 and 2 so that 'production blocking' occurs. We propose an approximation method for the production rate of the system. Through a series of numerical experiments we show that the method not only gives a good estimate of the rate, but is very useful for overcoming design problems in such inspection systems.

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パルス型プラズマスラスタ（Pulsed Plasma Thruster : PPT）は固体推進剤を用いた電気推進機の一種で，軽量・低コスト・高信頼性などの特徴をもつため，超小型衛星に適した推進機の1つである．本研究室では長年にわたりPPTの研究開発に取り組み，PPTの性能向上や構成要素が性能に与える影響の評価，様々な用途に対応が可能なPPTのラインナップ化などを行ってきた．その成果をまとめ，超小型衛星搭載に向けたミッション検討を行ったので報告する．

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This paper proposes a movement model of a human walking behavior in order to investigate walking behavior of crowd humans. This model contains functions of the collision avoidance and the trajectory decision of each human taking one’s own inertia into account. The trajectory decisition is realized as a servo system.
Collision avoidance is attained by quasi Coulomb force generated among humans and also between a human and a wall. Simulation results that humans simultaneously advance to the destination are shown.

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Lean premixed combustion may reduce NO_x emission of gas turbines. On the basis of this concept, a micro gas turbine test combustor using a lean premixed swirling hydrogen flame has been developed. To attain experimental understanding of combustion characteristics of the combustor, stability limits, temperature and flow fields, and exhaust emissions were measured. The measurements showed that a stable swirling hydrogen flame attached to a flame holder was formed even in high-velocity premixed streams at low equivalence ratios. The combustor had the high rate of volumetric heat release of 2.5×10³ W/(m³·Pa), and attained high combustion efficiencies of over 99.98%. Hydrogen combustion in the combustor resulted in extremely low NO-x emission levels of under 1 ppm, in comparison with a hydrogen-burning diffusion combustor.

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In this paper we analyze a two-stage inspection system. There are two stations numbered 1 and 2, in tandem. An infinite number of jobs always waits in front of station 1 and there is a finite buffer space between stations 1 and 2. If a processed (inspected) job at station 1 is defective, it is rejected ; otherwise it proceeds to station 2. Station 2 in operates the same manner. Both stations process m jobs at a time and there may be failures during each processing time. In this mode of operation station 1 will at any time be busy or blocked and station 2 will be busy or idle. An important problem for such a system is how to improve the production rate by increasing the buffer space. We attempt to formulate this problem as a Markov chain. It is shown that the buffer size should be larger than the batch service size, m. Futhermore, we propose an approximation formula for the production rate. Numerical examples are presented which support the usefulness of the approximation.

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Aerodynamic configuration of a cone-derived waverider is designed according to the Taylor-Maccoll equation. Flow fields are numerically calculated at an on-design flow condition of the Mach number of 5.5, and the aerodynamic characteristics are estimated. The on-design model is manufactured using a numerical controled machine. In a hypersonic wind tunnel testing at the free stream Mach number 5.5 and the unit Reynolds number of 4.34×10⁶(/m), flow fields are observed with Schlieren photographs and oil flow pattern; also aerodynamic characteristics are measured by a three-component balance. As a comparison, a off-design model with a flat lower surface is made and used for tests at the same flow conditions. The results show that shock wave is well attach to the leading edge of the on-design model at zero angle of attack; streamline on the lower surface is conical and cross flow is not observed. The maximum L/D ratio is found to be about 4.0 at the angle of attack of around -1°, which is higher than that of the off-design model.

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The initial state of controllers is discussed in terms of improving the transient. We derive an optimal value of the initial state, which attains favorable transient of the closed loop system.

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An experimental investigation was conducted to determine the mechanism and conditions of governing the boundary-layer transition phenomena which were induced by a circular cylinder placed at some distance apart from a plate. The cylinder of 1.0 mm in diameter was placed 0.25 m downstream from the leading edge of the plate, and gap to diameter ratios were selected to be 0.3, 0.5 and 0.6. These ratios were chosen because they were found to have different characteristics on the boundary-layer transition in the former experiments. Mean velocity distribution, intensity of turbulence and distribution spectra in the wake flow were measured for each gap condition under the unit Reynolds number of U₀/ν=3.5×10⁵ (m<-1>). The results obtained are as follows. In the case of the gap ratio of 0.6, boundary-layer transition occurs by the direct interference between the wake of the cylinder and the laminar boundary-layer of the plate. On the contrary, the transition at the ratio of 0.5 is observed to be shed from the cylinder. In the case of the ratio of 0.3, no vortices were observed and the mechanism of transition was similar to that of a tripping wire which has no gap with the plate.

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