Motion of a random walker in a quenched power law correlated velocity field

We study the motion of a random walker in one longitudinal and d transverse dimensions with a quenched power law correlated velocity field in the longitudinal x-direction. The model is a modification of the Matheron-de Marsily (MdM) model, with long-range velocity correlation. For a velocity correlation function, dependent on transverse co-ordinates y as 1/(a+|{y_1 - y_2}|)^alpha, we analytically calculate the two-time correlation function of the x-coordinate. We find that the motion of the x-coordinate is a fractional Brownian motion (fBm), with a Hurst exponent H = max [1/2, (1- alpha/4), (1-d/4)]. From this and known properties of fBM, we calculate the disorder averaged persistence probability of x(t) up to time t. We also find the lines in the parameter space of d and alpha along which there is marginal behaviour. We present results of simulations which support our analytical calculation.Comment: 8 pages, 4 figures. To appear in Physical Review

A Laser System for Counting Cloth Filaments

A simple high speed and high accuracy counter system for cloth filament has been constructed. The principle is based on the laser light attenuation through the cloth. The system is composed of semiconductor laser, objective lens, focusing lens PIN photodiode and processing system including amplifier, ΔV detector, counter, comparator, presser and marker. The counting accuracy is above 99% and the maximum counting speed is beyond 5 kHz, which will be enough for practical use

Bleaching of sol-gel glass film with embedded gold nanoparticles by thermal poling

Gold clusters embedded in glass are expected to be hard to dissolve in the form of ions since gold is essentially a nonreactive metal. In spite of that, bleaching of Au-doped nanocomposite sol-gel glass film on a soda-lime glass substrate is demonstrated in which electric-field thermal poling is employed to effectively dissolve randomly distributed gold nanoparticles (15 nm in diameter) embedded in a low conductivity sol-gel glass film with a volume filling factor as small as 2.3%. The surface plasmon absorption band at 520 nm is suppressed in the region covered by the anodic electrode. The phenomenon is explained by the ionization of the gold nanoparticles and the redistribution of gold ions in the glass matrix due to the action of the extremely high electrostatic field locally developed during poling

Random Walks in Random Environments

Random walks provide a simple conventional model to describe various transport processes, for example propagation of heat or diffusion of matter through a medium. However, in many practical cases the medium is highly irregular due to defects, impurities, fluctuations etc., and it is natural to model this as random environment. In the random walks context, such models are referred to as Random Walks in Random Environments (RWRE). This is a relatively new chapter in applied probability and physics of disordered systems, initiated in the 1970s. Early interest was motivated by some problems in biology, crystallography and metal physics, but later applications have spread through numerous areas. After 30 years of extensive work, RWRE remain a very active area of research, which has already led to many surprising discoveries. The goal of this article is to give a brief introduction to the beautiful area of RWRE. The principal model to be discussed is a random walk with nearest-neighbor jumps in independent identically distributed (i.i.d.) random environment in one dimension, although we shall also comment on some extensions and generalizations. The focus is on rigorous results; however, heuristics is used freely to motivate the ideas and explain the approaches and proofs. In a few cases, sketches of the proofs have been included, which should help the reader to appreciate the flavor of results and methods.Comment: A review article in the Encyclopedia of Mathematical Physics (Elsevier, 2006). http://www.elsevier.com/wps/find/bookdescription.cws_home/705128/descriptio

1-ナフトエ酸部分水素添加体とその関連化合物の植物生長素性

京都大学0048新制・課程博士農学博士農博第30号新制||農||12(附属図書館)学位論文||S36||N12(農学部図書室)240京都大学大学院農学研究科農芸化学専攻(主査)教授 三井 哲夫, 教授 今村 駿一郎, 教授 中島 稔学位規則第5条第1項該当Kyoto UniversityDA