Design of a reflection-suppressed all-optical diode based on asymmetric L-shaped nonlinear photonic crystal cavity

A simple design method for suppressing the reflection of the all-optical diode based on the L-shaped photonic crystal (PC) cavity is proposed. Analyzing the linear resonant characteristics of the PC cavity and using the nonlinear coupled-mode theory, the strategy for obtaining reflection-suppressed structure is illustrated. Based on the design rule, a “reflection-suppressed all-optical diode” is presented, and numerical solutions indicate that the designed structure has a small reflection as well as an extremely large nonreciprocal transmission ratio

Probing the Structure of Gamma-Ray Burst Jets with Steep Decay Phase of their Early X-ray Afterglows

We show that the jet structure of gamma-ray bursts (GRBs) can be investigated with the tail emission of the prompt GRB. The tail emission which we consider is identified as a steep-decay component of the early X-ray afterglow observed by the X-ray Telescope onboard Swift. Using a Monte Carlo method, we derive, for the first time, the distribution of the decay index of the GRB tail emission for various jet models. The new definitions of the zero of time and the time interval of a fitting region are proposed. These definitions for fitting the light curve lead us an unique definition of the decay index, which is useful to investigate the structure of the GRB jet. We find that if the GRB jet has a core-envelope structure, the predicted distribution of the decay index of the tail has a wide scatter and has multiple peaks, which cannot be seen for the case of the uniform and the Gaussian jet. Therefore, the decay index distribution tells us the information on the jet structure. Especially, if we observe events whose decay index is less than about 2, both the uniform and the Gaussian jet models will be disfavored according to our simulation study.Comment: 21 pages, 10 figures, the paper with full resolution images is http://theo.phys.sci.hiroshima-u.ac.jp/~takami/research/achievements/papers/003_full.pd

Spatiotemporal neural network dynamics for the processing of dynamic facial expressions.

表情を処理する神経ネットワークの時空間ダイナミクスを解明. 京都大学プレスリリース. 2015-07-24.The dynamic facial expressions of emotion automatically elicit multifaceted psychological activities; however, the temporal profiles and dynamic interaction patterns of brain activities remain unknown. We investigated these issues using magnetoencephalography. Participants passively observed dynamic facial expressions of fear and happiness, or dynamic mosaics. Source-reconstruction analyses utilizing functional magnetic-resonance imaging data revealed higher activation in broad regions of the bilateral occipital and temporal cortices in response to dynamic facial expressions than in response to dynamic mosaics at 150-200 ms and some later time points. The right inferior frontal gyrus exhibited higher activity for dynamic faces versus mosaics at 300-350 ms. Dynamic causal-modeling analyses revealed that dynamic faces activated the dual visual routes and visual-motor route. Superior influences of feedforward and feedback connections were identified before and after 200 ms, respectively. These results indicate that hierarchical, bidirectional neural network dynamics within a few hundred milliseconds implement the processing of dynamic facial expressions

地理教育におけるGISの活用法に関する研究

内容の要約広島大学(Hiroshima University)博士(教育学)Doctor of Philosophy in Educationdoctora

Group chase and escape with some fast chasers

We study group chase and escape with some fast chasers. In our model chasers look for the nearest target and move to one of the nearest sites in order to catch the target. On the other hand, targets try to escape from the nearest chaser. When a chaser catches a target, the target is removed from the system and the number of targets decreases. The lifetime of targets, at which all targets caught, decreases as tα with increasing the number of chasers. When there are no fast chasers and the total number of chasers is small, the exponent α is large. When the total number of chasers is large, α becomes small. There is an optimal number of chasers to minimize the cost used in order to catch all targets. However, when we add a few fast chasers, the region with the large α vanishes. The optimal number of chasers vanishes, and the cost monotonically increases with increasing the number of chasers. © 2012 American Physical Society

Introduction of GIS into Village Research in India : Construction of GIS Database from Census and Field Work

We applied the technique of GIS (Geographic Information System) at an overseas regional investigation to Indian rural village investigation. We analyzed details of the data we have got in fieldwork with the aid of GIS, then we came to acknowledge the validity of GIS utilization at an overseas regional investigation. We investigated, as an example, one rural village that is adjacent to Noida, a new industrial city near Delhi. At some departments of the federal government, we obtained the information about digitized statistical data. Further, we obtained prefectural population data of the whole of India. In India, a population census (Census of India) has been continually conducted, and the latest result of 1991 can be obtained through a floppy-disk. By this, we were enabled to treat nation-wide population data on a computer, and to analyze the regional characteristics of a study area quantitatively. And we obtained Primary Census Abstract data of the whole of India, and, using these data, we have mapped the fundamental data on population of each district, we were easily able to grasp a state of the population of India, such as scheduled castes / scheduled tribes population, literacy rate and workers according to industrial categories. Thus, a site investigation to extend over a wide range was able to point out a validity of GIS utilization at a difficult overseas regional investigation. Next, we mention how we have constructed GIS database of the resident data on R village gained by our field research. Our investigation party conducted the hearing investigations into all households within the village. And we also made a map of village. After returning to Japan with the result of the field investigation, we inputted the result of the hearing investigation to a computer, and we also digitizes the map we made on the spot. Then we took these in GIS software and constructed GIS database on all the households of the village. This makes it possible to map a household and a personal attribute immediately. Moreover, can

樹液流計測に基づく,タイ北部チーク林の蒸散特性に関する研究

学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 鈴木 雅一, 東京大学教授 丹下 健, 東京大学教授 芝野 博文, 東京大学准教授 蔵治 光一郎, 東京大学講師 浅野 友子University of Tokyo(東京大学