火山灰質粗粒土の内部浸食に関する安定性評価

Japan has a variety of volcanic ash soils that cause complicated geotechnical engineering problems in all the regions of the islands, i.e., in Hokkaido, Tohoku, Kanto, Chubu, Chugoku and Kyushu. The distribution of volcanic ground was widespread and each volcanoes has acted numerously over geological time. In Hokkaido, Japan, there are over forty Quaternary volcanoes, and pyroclastic materials cover over 40 % of its area. Sedimentary structure, components, distributional area and degrees of the weathering greatly differ with the depositional environment. Therefore, it is anticipated that the mechanical property of volcanic soil grounds will be diverged. Such volcanic soils have been also used as useful construction materials, especially man-made earth structures (embankments and cut slopes, etc.). However, a large number of earthquake- and rainfall-induced failures of artificial slopes such as cut slopes or embankments have been reported in Hokkaido, Japan. Examples include embankment slope failures due to the 2003 Tokachi-oki earthquake, cut slope failure on the Hokkaido Expressway (1999) due to rainfall and snow-thaw water in the spring. Therefore, volcanic soils have been classified as “problematic soils” in Japan engineering researches. Notwithstanding, the research on volcanic soils from the engineering standpoint is extremely superficial in comparison with cohesion and cohesionless soils. Internal erosion is one of the major causes of failures and accidents for soil structures such as embankments. Examples include slope failure of the Hokkaido heavy rainfalls in 2016 and collapses of dykes around Kinugawa River (2015) due to internal erosion such as piping phenomenon by heavy rainfall. Therefore, this paper aims at clarifying destabilization of volcanic coarse grained soils caused by internal erosion in which soil particles within soil structures are outflowed by seepage flow. In order to accomplish the purposes, field observation of a full-scale embankment was firstly carried out. Thereafter, a series of upward seepage test was conducted to grasp features of seepage behavior in volcanic soils and to investigate effects of differences in compaction conditions and the shapes of grain distribution curve on its behavior. Additionally, internal stability of volcanic soils under several geotechnical conditions was elucidated by empirical criteria such as Kenny & Lau’s, Kezdi’s and Li & Fannin’s criteria, etc. In this study, a volcanic coarse grained soil erupted from the Shikotsu caldera in Sapporo city, Hokkaido was used in the seepage tests. The sample was specified into pumice flow deposits (the notation is Spfl), and was referred to as Komaoka volcanic soils. In the experiments, the movement of soil particles in seepage flow tests was observed using an X-ray CT scanner in detail. The test results showed that destabilization of soil structures due to seepage flow is changed depending on an increase of amount of finer soil particles, and that internal erosion is induced by loss of fine particles with the changes in void ratio. As a result, a significant variation in hydraulic conductivity was generated. In the consideration of the results, it was shown that volcanic coarse grained soil including pumice particles with a low specific gravity is internally unstable. Finally, a new evaluation method on internal erosion was proposed for the stability of soil structures constructed by volcanic coarse grained soils by taking index properties and mechanical behavior of materials into account.近年の豪雨災害，例えば2016年8月に発生した北海道豪雨での切土・盛土の斜面崩壊や2015年9月の鬼怒川の堤防決壊では，一部パイピングに起因すると考えられる浸食ならびに崩壊が報告されている。このような土構造物の内部浸食に起因する安定性評価は，現在もなお工学1級の問題として扱われている。実際，このような土構造物の構築の際には，現地の土質材料を利用する場合が多い。そのため，全面積の約40％を火山灰質土で覆われている北海道では，多くの土構造物において火山灰質粗粒土が利用されている。このような火山灰粗粒土は排水性が高く，良質な地盤材料として，今まで多くの土構造物に採用されてきた。しかしながら，その透水・通水特性について詳細に検討された事例は少ないのが現状である。一連の研究では，火山灰質粗粒土で構築された実大盛土斜面の降雨時・浸透時の崩壊挙動が調査されているが，崩壊後に解体した本盛土断面においてパイピングの痕跡が確認されており，パイピング現象が崩壊を助長した可能性があることを指摘している。このような内部浸食に関する既往の研究ではKenny and Lau, Kezdi, Li and Fanninの評価式などを代表するように，礫質土や砂質土の通常の土質材料に対する検討は行われているものの，粒子破砕性や非塑性かつ低土粒子密度を有する火山灰質土（特殊土）に対する検討および評価は行われていない。本研究では，北海道内に分布する代表的な火山灰質粗粒土（支笏を噴出源とする火山灰質土：Spfl）を用いて，パイピング，ボイリング現象に代表される内部浸食現象について工学的な検討を行っている。なお，この火山灰質粗粒土は，旧河川域を埋め立てて住宅盛土として使用した土質材料であり，1968年と2003年に発生した十勝沖地震で液状化した試料と同噴出源の試料である。本研究では，はじめに内部浸食に関する過去の研究事例を整理している。すなわち，従来より提案されている各評価式の火山灰質粗粒土への適用を調査し，地盤工学的な評価を行っている。次いで，火山灰盛土への浸透特性が力学的安定性に及ぼす影響をパイピング試験により明らかにしている。一連の実験では，X線CTスキャンの画像解析より浸透流にともなう土粒子個々の移動量を定量化し，パイピング現象のプロセスと土構造物の不安定化を導く要因を把握している。本研究の総括として，物性評価（示標特性）と力学的評価（浸透流による有効応力の評価）を取り入れた，火山灰質土の内部浸食に対する安定性評価手法を新たに提案している。室蘭工業大学 (Muroran Institute of Technology)博士（工学

Education and Economic Growth in Vietnam

The relationship between education and economic growth has always been considered a fundamental concern of many economists as well as governments. This research provides empirical evidence of the education true effects are not well understood, especially in Vietnam. This research provides empirical evidence of the influences of education in Vietnam’s economy, more specifically on Vietnam’s productivity, from the period 2000 to 2015. The paper find that the final findings are supportive to the hypothesis made: education is critical factor of economic enhancement. More specifically, primary and secondary schooling levels better the productivity of the economy estimated by the Total Factor Productivity and the GDP growth. Keywords: GPD growth, social return, TFP DOI: 10.7176/JEP/11-6-02 Publication date: February 29th 202

Performance Analysis of Hybrid ALOHA/CDMA RFID Systems with Quasi-decorrelating Detector in Noisy Channels

In this paper we investigate the performance of a hybrid Aloha/CDMA radio frequency identification (RFID) system with quasi-decorrelating detector (QDD). Motivated by the fact that the QDD outperforms the conventional decorrelating detector (DD) in noisy network scenarios, we study and propose using QDD as one of the most promising candidates for the structure of RFID readers. Performance analysis in terms of bit error rate and the RFID system efficiency is considered considering CDMA code collision and detection error. Computer simulations are also performed, and the obtained results of QDD-based structure are compared with those of DD-based one to confirm the correctness of the design suggestion in different practical applications of tag identification and missing-tag detection

Bacteria associated with soft coral from Mot island - Nha Trang bay and their antimicrobial activities

Microbial communities associated with invertebrates had been considered as a new source of bioactive compounds. The soft coral associated bacteria in Mot island, Nha Trang bay were isolated, extracted and assessed for antagonistic activity against human and coral pathogens, the strongly active strains were identified by 16S rRNA analysis. The soft coral associated bacterium SCN10 had abcd antibacterial pattern which was named for inhibition towards Bacillus subtilis (pattern a), Escherichia coli (pattern b), Salmonella typhimurium (pattern c) and Serratia marcescens (pattern d). It was the nearest strain to the well-known antibiotic producer Bacillus amyloliquefaciens with 99% sequence similarity. Whereas strain SCL19 had abde pattern which means inhibition of the growth of B. subtilis, E. coli, S. marcescens and Vibrio parahaemolyticus (pattern e). This strain SCL19 affiliated with Bacillus sp. strain A-3-23B with 99.8% identity. In addition to antimicrobial activity to the aforementioned tested bacteria, the isolate SCX15 also inhibited Vibrio alginolyticus (pattern f) and Candida albicans (pattern g), so this isolate possessed abcdefg antimicrobial pattern. The coral associated isolate SCX15 was identified as Bacillus velezensis with 99% sequence similarity. Among the 78 screened strains, 25 isolates possessed antibacterial activity against at least one of seven tested microorganisms and exhibited 12 different types of antimicrobial activities, suggesting that they can produce many different natural substances with antibacterial activity

Le portail g-INFO pour surveiller la grippe Influenza A

Le portail g-INFO pour surveiller la grippe Influenza

An Improved MobileNet for Disease Detection on Tomato Leaves

Tomatoes are widely grown vegetables, and farmers face challenges in caring for them, particularly regarding plant diseases. The MobileNet architecture is renowned for its simplicity and compatibility with mobile devices. This study introduces MobileNet as a deep learning model to enhance disease detection efficiency in tomato plants. The model is evaluated on a dataset of 2,064 tomato leaf images, encompassing early blight, leaf spot, yellow curl, and healthy leaves. Results demonstrate promising accuracy, exceeding 0.980 for disease classification and 0.975 for distinguishing between diseases and healthy cases. Moreover, the proposed model outperforms existing approaches in terms of accuracy and training time for plant leaf disease detection