Image based visual servoing using algebraic curves applied to shape alignment

Visual servoing schemes generally employ various image features (points, lines, moments etc.) in their control formulation. This paper presents a novel method for using boundary information in visual servoing. Object boundaries are modeled by algebraic equations and decomposed as a unique sum of product of lines. We propose that these lines can be used to extract useful features for visual servoing purposes. In this paper, intersection of these lines are used as point features in visual servoing. Simulations are performed with a 6 DOF Puma 560 robot using Matlab Robotics Toolbox for the alignment of a free-form object. Also, experiments are realized with a 2 DOF SCARA direct drive robot. Both simulation and experimental results are quite promising and show potential of our new method

Turbulent transport by diffusive stratified shear flows: from local to global models. III. A closure model

Being able to account for the missing mixing in stellar radiative zones is a key step toward a better understanding of stellar evolution. Zahn (1974) argued that thermally diffusive shear-induced turbulence might be responsible for some of this mixing. In Part I and Part II of this series of papers we showed that Zahn's (1974, 1992) mixing model applies when the properties of the turbulence are local. But we also discovered limitations of the model when this locality condition fails, in particular near the edge of a turbulent region. In this paper, we propose a second-order closure model for the transport of momentum and chemical species by shear-induced turbulence in strongly stratified, thermally diffusive environments (the so-called low P\'eclet number limit), which builds upon the work of Garaud \& Ogilvie (2005). Comparison against direct numerical simulations (DNSs) shows that the model is able to predict the vertical profiles of the mean flow and of the stress tensor (including the momentum transport) in diffusive shear flows, often with a reasonably good precision, and at least within a factor of order unity in the worst case scenario. The model is sufficiently simple to be implemented in stellar evolution codes, and all the model constants have been calibrated against DNSs. While significant limitations to its use remain (e.g. it can only be used in the low P\'eclet number, slowly rotating limit), we argue that it is more reliable than most of the astrophysical prescriptions that are used in stellar evolution models today

Different approaches on the implementation of implicit polynomials in visual tracking /

Visual tracking has emerged as an important component of systems in several application areas including vision-based control, human-computer interfaces, surveillance, agricultural automation, medical imaging and visual reconstruction. The central challenge in visual tracking is to keep track of the pose and location of one or more objects through a sequence of frames. Implicit algebraic 2D curves and 3D surfaces are among the most powerful representations and have proven very useful in many model-based applications in the past two decades. With this approach, objects in 2D images are described by their silhouettes and then represented by 2D implicit polynomial curves. In our work, we tried different approaches in order to efficiently apply the powerful implicit algebraic 2D curve representation to the phenomenon of visual tracking. Through the proposed concepts and algorithms, we tried to reduce the computational burden of fitting algorithms. Besides showing the usage of this representation on boundary data simulations, use of the implicit polynomial as a representative of the target region is also experimented on real videos

ＶＲ/ＭＲ技術を用いた歴史観光のＩＴ活用に関する研究

観光の新しい形が求められている．わが国の経済を支える大きな産業の一つとして，観光業に大きな期待が集まっている．観光地の魅力を高めるために，観光資源を抱える各地の自治体では様々な模索を続けており，観光のIT 活用はその目玉となっている．インターネットを利用した観光案内は広く普及し，すでに多くの旅行者が使用する社会インフラとなっている．差別化のために新しい技術が積極的に試まれており，バーチャルリアリティ(VR)やミックストリアリティ(MR)はその一つである．観光の心理学的分析によれば，観光が動機づけ・学習・訪問・感動・再訪のサイクルで成り立つとされている．各段階をIT 活用によって魅力的にしようという提案がなされており，スマートツーリズム構想として知られている．とくに訪問先の現地の魅力をよりよく伝えて感動を深めるための手段が課題となっている．文化財をデジタルデータ化する技術はデジタルアーカイビングと呼ばれ，VR/MR 技術を用いてデジタル化された文化財を鑑賞する試みがなされており，感動深化のために観光への融合が標榜されている．本研究では，VR/MR を使ったデジタルアーカイブの展示の観光応用を試み，実用化へ向けた提案を行う．古代飛鳥京があった奈良県高市郡明日香村において，飛鳥時代を題材にして往時の建物や街並みをCG を用いて仮想復元したVR コンテンツを制作し用意した．遺跡が存在したとされる場所においてVR コンテンツを鑑賞できるように，屋外で使用できる歴史体験端末を開発し実証実験を行った．とくに観光応用における課題の一つが移動にあると見定めて，移動中にVR/MR コンテンツを楽しむことのできる運用を試みた．VR/MR の観光応用は実例が少ないため，大小さまざまな課題が残されている．そこで次の2 つの形式の運用を試みた．・ガイドツアーのサポートツールとしてモバイル型VR/MR 装置を用いる運用・多人数が同時に移動しながら体験できるMR モビリティシステムとしての運用観光イベントとして一般の訪問客から参加者を募り，体験終了後にアンケート調査の協力をお願いし，観光応用の可能性を調査した．その結果，VR/MR の観光応用の有用性と課題を確認できた．VR/MR を観光に導入する大きな目的は観光地の魅力を深めて観光客に現地に足を運んでもらうことであり，歴史観光体験の感動の深化をVR/MR技術で実現するための課題と要件を検討していく．VR/MR の観光応用に関する課題は，運用面における課題および技術面における課題の2 つの側面がある．運用面における課題は，環境を壊さない導入方法，従来のサービスを壊さない導入方法，現地における運用，コミュニケーションの促進，移動の有効活用が重要であると考え，2 つの試行の結果を基に解決方法の検討をおこなった．ガイドツアーのサポートツールとしてモバイル型VR/MR 装置を用いる運用では，特に運用者が現地のボランティアガイドであることに留意して，システムを受け入れてもらいやすいように近いしやすく使いやすいようにすることに配慮した．技術優先とせずに，従来の観光サービスを後押しするようにVR/MR システムを導入することが重要であると考える．技術面での課題は，現時点では特に音による臨場感の向上，VR/MR 特有のコンテンツ編集コストの削減手法が重要であると考えた．MR モビリティシステムを用いた運用において，移動に伴い場面が転換していくようなストーリー仕立ての演出を行うことでエンターテイメント性の向上が期待できる．観光においてエンターテイメント性は重要な要件の一つである．移動中のユーザーの位置・姿勢に伴って，映像とともに音も空間を持った表現にすると臨場感を向上できる．また，映像を360 度任意の方向に眺める自由が与えられている多くのMRシステムのようにユーザーの行動の自由の幅が広すぎると，コンテンツ制作者の意図とは合わずに体験者が視線を送っていない方向で演出されているイベントに気が付かないという問題がある．演出についても，音声により気配を感じさせることによって，ユーザーの視線方向を暗に誘導することができ，その幅を広げることができる．VR/MR のコンテンツ制作は，通常のCG やアニメーションコンテンツの制作と異なり，実際に存在した事物の復元をするためわずかな記録や現存する事物の情報を基にして，最大限史実に近い形で仮想復元する必要がある点に難しさがある．特に日本の古代建造物は多くが木造であり，災害等で失われ現存していないことが多い．しかしながら，礎石や石敷きなど石でできた構造物の一部は残されている史跡が多い．そこで，現存する石敷きの情報を基にして簡単な操作によって自然に石敷きの編集をできる手法を開発した．このようにデジタルアーカイブの情報の欠落部分を容易に自然に復元するための編集手法は今後重要になってくるだろう．電気通信大学201

Natural Four-Generation Mass Textures in MSSM Brane Worlds

A fourth generation of Standard Model (SM) fermions is usually considered unlikely due to constraints from direct searches, electroweak precision measurements, and perturbative unitarity. We show that fermion mass textures consistent with all constraints may be obtained naturally in a model with four generations constructed from intersecting D6 branes on a T^6/(Z_2 x Z_2) orientifold. The Yukawa matrices of the model are rank 2, so that only the third- and fourth-generation fermions obtain masses at the trilinear level. The first two generations obtain masses via higher-order couplings and are therefore naturally lighter. In addition, we find that the third and fourth generation automatically split in mass, but do not mix at leading order. Furthermore, the SM gauge couplings automatically unify at the string scale, and all the hidden-sector gauge groups become confining in the range 10^{13}--10^{16} GeV, so that the model becomes effectively a four-generation MSSM at low energies.Comment: Accepted for publication in Physical Review

Geometrically designed, variable knot regression splines: variation diminish optimality of knots

A new method for Computer Aided Geometric Design of variable knot regression splines, named GeDS, has recently been introduced by Kaishev et al. (2006). The method utilizes the close geometric relationship between a spline regression function and its control polygon, with vertices whose y-coordinates are the regression coefficients and whose x-coordinates are certain averages of the knots, known as the Greville sites. The method involves two stages, A and B. In stage A, a linear LS spline fit to the data is constructed, and viewed as the initial position of the control polygon of a higher order (n > 2) smooth spline curve. In stage B, the optimal set of knots of this higher order spline curve is found, so that its control polygon is as close to the initial polygon of stage A as possible, and finally the LS estimates of the regression coefficients of this curve are found. In Kaishev et al. (2006) the implementation of stage A has been thoroughly addressed and the pointwise asymptotic properties of the GeD spline estimator have been explored and used to construct asymptotic confidence intervals. In this paper, the focus of the attention is at giving further insight into the optimality properties of the knots of the higher order spline curve, obtained in stage B so that it is nearly a variation diminishing (shape preserving) spline approximation to the linear fit of stage A. Error bounds for this approximation are derived. Extensive numerical examples are provided, illustrating the performance of GeDS and the quality of the resulting LS spline fits. The GeDS estimator is compared with other existing variable knot spline methods and smoothing techniques and is shown to perform very well, producing nearly optimal spline regression models. It is fast and numerically efficient, since no deterministic or stochastic knot insertion/deletion and relocation search strategies are involved

Motion estimation of planar curves and their alignment using visual servoing

Motion estimation and vision based control have been steadily improving research areas recently. Visual motion estimation is the determination of underlying motion parameters by using image data. Visual servoing on the other hand refers to the closed loop control of robotic systems using vision. Solving these problems with objects that have simple geometric features, such as points and lines is rather easy. However, these problems may imply certain challenges when we deal with curved objects that lack such simple features. This thesis proposes novel vision based estimation and control techniques that use object boundary information. Object boundaries are represented by planar algebraic curves. Decomposition of algebraic curves are used to extract features for motion estimation and visual servoing. Motion estimation algorithm uses the parameters of line factors resulting from the decomposition of the curve whereas visual servoing method employs the intersections of lines. Motion estimation algorithm is verified with several simulations and experiments. Visual servoing algorithm developed for the arbitrary alignment of a planar object is tested both with simulations on a 6 DOF Puma 560 robot and experiments on a 2 DOF SCARA robot. Results are quite promising