Instability of isolated compressible entropy-stratified vortices

The normal mode linear analysis is applied to investigate the stability of a circular isolated compressible vortex with the emphasis on studying the effect of entropy stratification of the basic flow on stability properties. We study a family of vortices that have zero total circulation, with the swirl velocity being presented by a Taylor-type distribution in the radial direction. The stratification of entropy is modeled by a Gaussian two-parametric profile whose parameters control the maximal deviation from the homentropic distribution and the extent of the entropic zone. Results presented concern the effect of these parameters and the vortex intensity on instability characteristics. In particular, in the case of homentropic flow, vortices considered are found to be stable only for sufficiently high intensities and cease to be stable as the intensity weakens. As an example of the situation where unstable normal modes can be excited, the scattering of sound waves by the vortex flow is considered. By simulating this process numerically, we show that the scattered field becomes unstable in the course of time and acquires a typical periodical pattern in polar angle. The characteristics of this instability (viz., the growth rate and the azimuthal phase frequency)coincide with those of the linear analysis very closely. This fact shows conclusively that the instability is caused by the induction of unstable normal modes in the vortex by means of sound irradiation.journal articl

2011 年度子ども国際理解サマースクール ～「多文化共生」教育実践～

一般雑誌記事 / Articlearticl

Investigation about the Continuity of the Sign in a Transit Center (3)

In the public space of the city, the sign is effective as a method to provide the information to users. In this study that we began in 2001, we performed 50 times of investigations in railway stations and the outskirts space. We refer to the space constitution and the space change of the course at three stations (JR Hiroshima Station, JR Okayama Station, JR Kagoshima-Chuo Station) in this article. And we refer to the analysis of signs that there is at those stations. We speak the result that we analyzed as follows. By the place of the station of a streetcar, we understood that the intelligibility of space was different. It is revealed that the signs of three stations were not unified. It will be necessary to think about the space constitution so that people transfers from the railway to the streetcar smoothly. And it is necessary to consider the sign as a system.departmental bulletin pape

Improved measurement of CP-violation parameters sin⁡2ϕ1 and |λ|, B meson lifetimes, and B0-B̅0 mixing parameter Δmd

journal articl

biennis

Artemisia biennis Willdenowbiennial wormwood;biennial sagewortarmoise bisannuelleArtemisia biennisCoteau du Missouri; Entre Valjean et ParkbergRembla

環境の文化特性に関する考察 : 環境の<詩性>に関する研究 その1

The condition of a high-quality environment is showed by a cultural factor which consists of four elements : place, history, climate and poetic-imagery. In poetic-imagery, not only is comfort given, but delight and pleasure as well. Poetic-imagery means a special and environmental element which gives rise to a strong impression and activation of consciousness. It is thought that poetic-imagery is obtained by making the best use of place, history, and climate. In order to create an ideal urban environment, it is necessary to find the way to realize the environment of poetic-imagery.application/pdfjournal articl

ロータリ耕うんにおける直進補助制御に関する基礎研究 : ロータリ取付けヨー角の制御によるトラクタヨー姿勢角変化の抑制

application/pdfIn this study, some basic experiments were carried out for the purpose of constructing the oncoming compensatory rectilinear progress control system that controls the yaw angle of a rotary tiller automatically, to improve the straightness of the tractor path in the rotary tillage work. Primarily, some experiments were carried out to confirm that tractors turn by setting the yaw angle of the rotary tiller largely. Following, the steering wheel of a tractor was manipulated so that the tractor was traveling straight while the rotary tiller was set at a certain angle to the tractor, while the front steering angle was measured simultaneously to investigate the effectiveness of the yaw angle of the rotary tiller. In addition, the compensatory rectilinear progress control system that controlled the yaw angle of the rotary tiller was tried to be constructed with an oscillatory type yaw rate sensor and a telescopic lower link in order to reduce the yaw attitude angle of the tractor. Lastly, some control experiments were carried out. The effectiveness of this system was confirmed using estimations of the potentiality of the compensatory rectilinear progress control derived from the turning characteristics of the tractor obtained in the preliminary experiments by setting the yaw angle of the rotary tiller.本研究では，ロータリ耕うん作業においてトラクタの直進性を改善するために，ロータリのトラクタへの取付け角（ヨー角：以下「ロータリの取り付け角」）を自動制御する直進補助制御系を構成することを将来の目的とし，これに関連するいくつかの基礎実験および考察を行った。まず，ロータリの取付け角を大きく採ることにより，トラクタが旋回運動をすることを確認する実験を行った。次にトラクタの旋回に対し，ロータリの取付け角がどの程度影響するのかを調べるために，ロータリの取付け角を固定した状態で直進するように操舵して走行実験を行い，そのときの前輪舵角を計測した。さらに，トラクタに振動型ヨーレートセンサとテレスコピックロワリンクを搭載し，トラクタのヨー姿勢角の変化を抑制するようにロータリ取付け角の制御を試みる直進補助制御実験系を構成し，実験を行った。また，予備実験により得られたロータリ取付け角によるトラクタの旋回特性から，走行実験における直進補助制御実験系の制御効果を推定する手法も提案した。departmental bulletin pape