Integral Operators in Crack Problems and their Perturbations in the Direction of the Crack Extension

The perturbation, in the direction of the crack extension, of the elastostatic hypersingular integral operator for crack problems is calculated rigorously. A variational form including this perturbation is written in terms of the energy release rate. The obtained result is applied to Griffith's crack extension

Properties of radio-frequency-sputter-deposited GaN films in a nitrogen/hydrogen mixed gas

GaN films have been deposited by reactive sputtering in nitrogen gas at pressures from 0.08 to 2.70 Pa with and without the addition of hydrogen gas. X-ray diffraction (XRD), Fourier transform infrared (FTIR), optical absorption, and photoluminescence (PL) spectroscopy have been used to characterize the sputter-deposited GaN films. The XRD pattern reveals that the GaN films deposited in nitrogen gas at pressures lower than 0.53 Pa are polycrystals with the (0001) texture (α-GaN), while those deposited at or above 1.07 Pa display mixed crystalline orientations or an amorphous-like nature. The GaN:H films deposited in nitrogen/hydrogen mixed gas, on the other hand, show an amorphous or amorphous-like nature. The FTIR spectra indicate that the GaN:H films show peaks arising from hydrogen-related bonds at ～1000 and ～3200 cm−1, in addition to the GaN absorption band at ,555 cm−1. The optical absorption spectra at 300 K indicate the fundamental absorption edges at ～3.38 and ～3.7 eV for the highly oriented α-GaN and amorphous GaN:H films, respectively. PL emission has been observed from sputter-deposited a-GaN films at temperatures below 100 K. The GaN:H films also show strong band-edge and donor-acceptor pair emissions. The PL emission in the GaN:H film may arise from crystalline GaN particles embedded in the amorphous GaN matrix

Shape Optimization Approach to a Free Boundary Problem

We take a shape optimization approach to solve a free boundary problem of the Poisson equation numerically. A numerical method called traction method invented by one of the authors are applied. We begin by changing the free boundary problem to a shape optimization problem and define a least square functional as a cost function. Then shape derivative of the cost function is derived by using Lagrange multiplier method. Detail structures and profiles of exact solutions to a concrete free boundary problem due to A. Henrot are also illustrated with proofs. They are used to check the efficiency of the traction method.Selected Papers from the International Symposium on Computational Science - International Symposium on Computational Science Kanazawa University, Japa

Fish fauna of shallow waters of Aki Nada, Seto Inland sea, Japan

瀬戸内海安芸灘に位置する大崎上島の沿岸魚類相について，餌釣りと潜水観察による調査を実施した。ガラモ場の存在する桟橋を中心に調査定点を島の南部北部それぞれに設定し，オキアミ類とゴカイ類を餌に約10名が1時間釣りを行う作業を2007年5月から2008年3月まで隔月で実施し，出現魚類の季節変化を検討した。また，2007年5月から7月にかけて，屋代島から竹原までの安芸灘広域に9ゾーン26調査点を設け，同様の調査を実施し，出現魚類の水域ゾーン間の相違を検討した。本調査により総計29科63魚種を記録した。そのうち高水温期にのみ出現する南方系魚種は4種のみであった。記録した魚種の76％（48種）は伊予灘で記録されているものであった。一方，宇和海での魚類相データとの魚種共通率は30％前後に留まり，安芸灘を含む伊予灘以北の水域が生物地理学的に中間温帯区（西村，1981）と定義されていることの妥当性が裏付けられた。大崎上島において周年および冬期を除き常時記録されたのは，カサゴ，メバル，ハオコゼ，クジメ，アサヒアナハゼ，マダイ，ウミタナゴ，スズメダイ，メジナ，コブダイ，ホシササノハベラ，キュウセン，ホンベラ，クラカケトラギス，ホシノハゼ，イトヒキハゼ，ヒガンフグ，コモンフグであった。これら18魚種の多くは安芸灘広域調査においても広く出現が認められ，安芸灘の浅海魚類群集の基本構成種と考えられた。ホシササノハベラは愛媛県中島周辺水域での出現頻度が極めて高く，同種の安芸灘における主要な個体群が安芸灘南西エリアに存在する可能性が示唆された。また，過去に瀬戸内海での記録のないホシノハゼが安芸灘広くに確認され，急速に分布拡大を進めていることが示唆された。We surveyed fish fauna at shallow waters of Aki Nada, Seto Inland Sea by the line fishing census, using small hooks attaching clamworms or krills as baits, during May 2007 - March 2008. We set up survey points at piers with Sargassum belt in Osaki-Kami Shima Island, and conducted the census (ca. 10 person x 60 min at each) bimonthly to analyze seasonal differences of fish fauna. In order to evaluate geographic variation of fish fauna, we also held the census at 26 survey points of nine zones situated a wide area in Aki Nada during May-July, 2007. A total of 63 species of 29 families were recorded. Of 63 species, 76 % were commonly recorded in Iyo Nada region. In contrast, the common species ratio fell to ca. 30% in comparison with data recorded in Uwa Sea region, which strongly supports the validity of the border of biogeographical regions between “Warm temperate region” including Uwa Sea and “intermediate temperate region” including Iyo Nada and Aki Nada (Nishimura, 1981). The almost year-round occurrences in the Osaki-Kami Shima were admitted in the following 18 species, Sebastiscus marmoratus, Sebastes inermis, Hypodytes rubripinnis, Hexagrammos agrammus, Pseudoblennius cottoides, Pagrus major, Ditrema temmincki, Chromis notata notata, Girella punctata, Semicossyphus reticulatus, Pseudolabrus sieboldi, Halichoeres poecilopterus, Halichoeres tenuispinnus, Parapercis sexfasciata, Istigobius hoshinonis, Cryptocentrus filifer, Takifugu pardalis, Takifugu poecilonotus. Most of these species commonly occurred in the survey zones in Aki Nada waters, suggesting that these are core components of fish fauna in shallow waters of Aki Nada