A new homeostat

Homeostasis concepts, and design of simple adaptive controlle

Free flight determination of boundary layer transition on small scale cones in the presence of surface ablation

To assess the possibility of achieving extensive laminar flow on conical vehicles during hyperbolic entry, the Ames Research Center has had an ongoing program to study boundary-layer transition on ablating cones. Boundary layer transition results are presented from ballistic range experiments with models that ablated at dimensionless mass transfer rates comparable to those expected for full scale flight at speeds up to 17 km/sec. It was found possible to measure the surface recession and hence more accurately identify regions of laminar, transitional, and turbulent flow along generators of the recovered cones. Some preliminary results using this technique are presented

Probing the geometry and motion of AGN coronae through accretion disc emissivity profiles

To gain a better understanding of the inner disc region that comprises active galactic nuclei it is necessary to understand the pattern in which the disc is illuminated (the emissivity profile) by X-rays emitted from the continuum source above the black hole (corona). The differences in the emissivity profiles produced by various corona geometries are explored via general relativistic ray tracing simulations. Through the analysis of various parameters of the geometries simulated it is found that emissivity profiles produced by point source and extended geometries such as cylindrical slabs and spheroidal coronae placed on the accretion disc are distinguishable. Profiles produced by point source and conical geometries are not significantly different, requiring an analysis of reflection fraction to differentiate the two geometries. Beamed point and beamed conical sources are also simulated in an effort to model jet-like coronae, though the differences here are most evident in the reflection fraction. For a point source we determine an approximation for the measured reflection fraction with the source height and velocity. Simulating spectra from the emissivity profiles produced by the various geometries produce distinguishable differences. Overall spectral differences between the geometries do not exceed 15 per cent in the most extreme cases. It is found that emissivity profiles can be useful in distinguishing point source and extended geometries given high quality spectral data of extreme, bright sources over long exposure times. In combination with reflection fraction, timing, and spectral analysis we may use emissivity profiles to discern the geometry of the X-ray source.Comment: 15 pages, 12 figures. Accepted for publication in MNRA

Language in Context : Text-based Language Learning

本指導ユニットは、「話す」、「書く」ことに関わる二つのテキストをベースとしている。本ユニットは言語学習とわれわれが行う言語選択におけるコンテクストの影響への体系的機能文法的アプローチを探求できるように作成されている。両テキストの領域は基本的に言語学習と二カ国語使用をベースとしている。本論文では、第一に、このユニットのコンテクスト、つまり、学習者のタイプと彼らの必要とすること、この独特な一連の授業の脈絡、作業とその継続の目的について論ずる。第二に、筆者のテキスト選択の根拠、文法的側面を含むテキストの主要な特徴について説明する。最後に、ユニット全体の目的・目標を達成するための一連の教室での活動について述べる