論文 - 島田 沢彦
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Nomadic responses to rainfall: Nighttime light evidence from wadis in Djibouti 査読あり 国際共著 国際誌
Bouh Omar Ali, Yutaka Ito, Shuichi Oyama, Sawahiko Shimada & Yuki Yamamoto
Scientific African 25 e02337 2024年09月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Elsevier B.V.
This study examined how precipitation affects human activity in dry areas, focusing on Djibouti's nomads. Using satellite data, researchers found increased nighttime light brightness near wadis after rainfall, indicating higher nomadic activity. This effect decreased with distance from wadis and was absent in urban areas. The findings highlight water's crucial role in nomadic settlements and resource management, providing valuable insights for policymakers in African countries.
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Pandit S, Shimada S & Dube T
Environmental Challenges 15 100920 2024年04月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Elsevier
The study focuses on analyzing land use changes in Djibouti from 1990 to 2023 using remote sensing and machine learning techniques. We identified seven major land cover classes shows declines in mangroves and farmland, and highlights expansions in built-up areas, water bodies, and barren lands over time.
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Abdul Basir Mahmoodzada, Pragyan Das, Divyesh Varade, Mohd Arslaan Akhtar, Sawahiko Shimada
Acta Geophysica 71 ( 6 ) 2024年01月
担当区分：最終著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Springer Link
This study proposes a framework to develop high-resolution snow cover area (SCA) products using freely available Sentinel-1 and MODIS data. Various Sentinel-1 parameters sensitive to snow are integrated with resampled MODIS normalized difference snow index (NDSI) data to estimate an equivalent NDSI for determining 15m resolution SCA. Equivalent NDSI is derived using machine learning regression with support vector machines (SVMs) and multilayer perceptron (MLP). Experiments were performed for northern Hindu Kush mountain regions in February and March 2019. SCA evaluation used thresholded NDSI from Landsat-8. SVM regression showed better SCA performance over MLP. Both SVM and MLP improved snow classification accuracy over resampled MODIS NDSI alone, with higher mean conditional kappa coefficients.
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Quantification of Amu River Riverbank Erosion in Balkh Province of Afghanistan during 2004–2020 査読あり 国際誌
Abdul Basir Mahmoodzada, Divyesh Varade, Sawahiko Shimada, Hiromu Okazawa, Shafiqullah Aryan, Gulbuddin Gulab, Abd El-Zaher M. A. Mustafa, Humaira Rizwana, Yogesh K. Ahlawat and Hosam O. Elansary
land 12 ( 10 ) 1890 2023年10月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：MDPI
This study quantifies riverbank erosion along the Amu River in Afghanistan's Kaldar District from 2004-2020 using modeled river discharge data. A framework integrating multi-source data models erosion area based on: river discharge, river width, and erosion area. Discharge was modeled using ECMWF and ground data. River width was manually determined from Landsat imagery. Erosion area was calculated through shoreline analysis. From 2008-2020, average annual erosion was 5.4 km2, totaling 86.3 km2 during 2004-2020 due to flooding. Peak erosion occurred in 2008-2009, 2011-2012 and 2015-2016. Erosion area correlated linearly with discharge intensity and stream power (R2=0.84).
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FRACTURE-FAULT DETECTION USING DEEP LEARNING WITH STEPWISE ELIMINATION FROM SATELLITE IMAGES IN DJIBOUTI 査読あり 国際共著 国際誌
Rubanga DP, May-Cuevas SA, Arvelyna Y & Shimada S
International Journal of GEOMATE 25 ( 108 ) 241 - 248 2023年08月
担当区分：最終著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
This study focuses on accurately detecting fracture-fault structures in Djibouti using WV-3 high resolution imagery. A deep learning approach using a deep convolutional neural network (Deep-CNN) model is proposed. The model successfully identifies fracture-fault lines, contributing to sustainable water management and improving water security in Djibouti.
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THE CHARACTERISTICS AND DISTRIBUTION OF DEEP GROUNDWATER IN DJIBOUTI 査読あり 国際誌
Asakura Y, Shimada S, Hinokidani K, & Nakanishi Y
International Journal of GEOMATE 24 ( 104 ) 93 - 100 2023年04月
記述言語：英語 掲載種別：研究論文（学術雑誌）
This study examines the characteristics of groundwater quality in Djibouti using ion chromatography, stable isotope ratios of hydrogen and oxygen, and tritium concentrations. The results show that most groundwater samples are mixed with seawater or hot spring water and fossil seawater, and the concentration of NO3- is high at some sites.
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FAULT DETECTION USING PALSAR-1/2 IMAGE DATA FOR GROUNDWATER ANALYSIS IN CENTRAL AND SOUTHWEST OF DJIBOUTI 査読あり 国際共著 国際誌
Arvelyna Y, Shimada S, May Cuevas S A, & Malow F A
International Journal of GEOMATE 24 ( 104 ) 109 - 116 2023年04月
記述言語：英語 掲載種別：研究論文（学術雑誌）
This study discusses a study that uses fault mapping to observe the possibility of fault-driven groundwater flow in Djibouti using PALSAR-1 and 2 data. The Geology Scoring Index was introduced to analyze the correlation of groundwater data with the geology setting of borehole sites.
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Albertus Sulaiman, Mitsuru Osaki, Hidenori Takahashi, Manabu D. Yamanaka, Raden Dwi Susanto, Sawahiko Shimada, Keiji Kimura, Takashi Hirano, Rahmawati Ihsani Wetadewi, Silsigia Sisva, Tsuyoshi Kato, Osamu Kozan, Hideyuki Kubo, Awaluddin Awaluddin & Nobuyuki Tsuji
scientific reports 13 939 2023年01月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Springer Nature
The condition of Indonesia's peatlands drought and fire can occur before El Niño and after IOD+ peaks. This is attributed to a dropped sea surface temperature anomaly and decreased local rainfall, causing a sharp drop in GWL. The research suggests monitoring GWL variability in peatland to serve as an alert for extreme climate events associated with El Niño and/or moderate IOD+.
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Water resources modeling of the Ali Faren catchment in the Ambouli watershed, Djibouti 査読あり
Hiroyuki TOSAKA, Aurelien HAZART, Toru YORITATE, Sergio Azael MAY CUEVAS, Sawahiko SHIMADA, Yasuhiro NAKANISHI, Fadoumo A. MALOW
Journal of Arid Land Studies 32 ( S ) 313 - 317 2022年12月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
This study explores the potential of groundwater in Djibouti. A numerical hydrological model and field survey technologies were used to analyze the water cycling in Ali Faren catchment.
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Teruaki IRIE, Shuhei SAITO, Sergio Azael MAY CUEVAS, Shinji SUZUKI, Fumio WATANABE, Sawahiko SHIMADA, Hassan A. BARKAD
Journal of Arid Land Studies 32 ( S ) 193 - 197 2022年12月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
The study investigated the meteorological conditions of a farm in Dikhil, Djibouti, and evaluated the windbreak effect of hedgerows to plan a pilot farm in Ali Faren based on wind dynamics simulated using observed meteorological parameters.
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Applicability of farmlands detection in Djibouti from satellite imagery using deep learning 査読あり
Takumi SATO, Ayako SEKIYAMA, Syuhei SAITO, Sawahiko SHIMADA
Journal of Arid Land Studies 32 ( S ) 181 - 185 2022年12月
担当区分：最終著者 記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
The study investigated the use of Mask-R-CNN and SVM for farmland detection in Djibouti using Sentinel-2 data.
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Sergio Azael MAY CUEVAS, Denis Pastory RUBANGA, Shuhei SAITO, Ayako SEKIYAMA, Sawahiko SHIMADA, Dayah Aden GUIRREH, Abdillahi Houssein ABDALLAH
Journal of Arid Land Studies 32 ( S ) 165 - 169 2022年12月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
The study explores the use of Unmanned Aerial Vehicles (UAV) and 3D cloud point data generated in Djibouti. The study found a high accuracy for identifying "Ground" and "High vegetation".
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Preliminary study on improvement of soil water retention characteristics by Spirulina. 査読あり
Shinji SUZUKI, Satoru WATANABE, Abdillahi Ismail OMAR, Fumio WATANABE, Sawahiko SHIMADA
Journal of Arid Land Studies 32 ( S ) 49 - 52 2022年12月
担当区分：最終著者 記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
The study investigates the effect of Spirulina and Extracellular Polymeric Substances (EPS) on the water holding capacity of soil.
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Satoru TANAKA, Shimpei TAKAHASHI, Rikako KIMURA, Sawahiko SHIMADA
Journal of Arid Land Studies 32 ( S ) 19 - 23 2022年12月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
Using of the GBIF database on plant species in Djibouti , a total of 6982 vascular plants from 561 species were found, representing 71.6% of the species reported in the literature.
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Assessment of Three Automated Identification Methods for Ground Object Based on UAV Imagery
Ke Zhang, Sarvesh Maskey, Hiromu Okazawa, Kiichiro Hayashi, Tamano Hayashi, Ayako Sekiyama, Sawahiko Shimada, Lameck Fiwa
Sustainability 14 ( 21 ) 14603 2022年11月
出版者・発行元：MDPI AG
<jats:p>Identification and monitoring of diverse resources or wastes on the ground is important for integrated resource management. The unmanned aerial vehicle (UAV), with its high resolution and facility, is the optimal tool for monitoring ground objects accurately and efficiently. However, previous studies have focused on applying classification methodology on land use and agronomy, and few studies have compared different classification methods using UAV imagery. It is necessary to fully utilize the high resolution of UAV by applying the classification methodology to ground object identification. This study compared three classification methods: A. NDVI threshold, B. RGB image-based machine learning, and C. object-based image analysis (OBIA). Method A was the least time-consuming and could identify vegetation and soil with high accuracy (user’s accuracy > 0.80), but had poor performance at classifying dead vegetation, plastic, and metal (user’s accuracy < 0.50). Both Methods B and C were time- and labor-consuming, but had very high accuracy in separating vegetation, soil, plastic, and metal (user’s accuracy ≥ 0.70 for all classes). Method B showed a good performance in identifying objects with bright colors, whereas Method C showed a high ability in separating objects with similar visual appearances. Scientifically, this study has verified the possibility of using the existing classification methods on identifying small ground objects with a size of less than 1 m, and has discussed the reasons for the different accuracy of the three methods. Practically, these results help users from different fields to choose an appropriate method that suits their target, so that different wastes or multiple resources can be monitored at the same time by combining different methods, which contributes to an improved integrated resource management system.</jats:p>
DOI： 10.3390/su142114603
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都立砧公園における過去30年間の植生変化
上村 隼平, 檜谷 昂, 島田 沢彦
日本森林学会大会発表データベース 133 ( 0 ) 451 2022年05月
記述言語：日本語 出版者・発行元：日本森林学会
<p>〇上村隼平1・檜谷昂1・島田沢彦2 1東京農業大学国際食料情報学部・2東京農業大学地域環境科学部</p><p>東京都世田谷区に位置する都立砧公園(39 万 m2)は，樹林地，草地，ため池，アスレチッ ク広場などから構成される都内最大級の公園緑地であり，生物多様性保全の場のみならず， 地域住民のリラクゼーションの場としても機能している。戦後の高度経済成長期に整備さ れた公園樹木の多くが，巨樹に及ばないまでも大木や古木化しつつある一方，近年の気候変動や外来種の侵入などを背景とする病虫害の被害は，衰退傾向にある樹木や老齢化した樹木でとくに影響を受けやい。こうした背景から，老齢化しつつある公園樹木の維持・管理 は，都市公園が抱える大きな課題となっている。そこで本研究では，都市部における緑地を 保全・再生していくための基盤となる情報の取得を目的とし，1990 年に作成された砧公園樹木台帳を基に，砧公園北西の樹林地において，植栽樹木の生残状況(n = 835)を調査し， 樹種別の生残率を求めた。生存個体については，新たに樹高と DBH を計測し成長量を樹種間で比較した。本発表では，過去 30 年間の植生とバイオマスの変化を GIS で解析したので報告する。</p>
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Capability assessment of Sentinel-1 data for estimation of snow hydrological potential in the Khanabad watershed in the Hindu Kush Himalayas of Afghanistan 査読あり
Mahmoodzada AB, Varade D, Shimada S, Rezazada FA, Mahmoodzada AS, Jawher AN, Toghyan
Remote Sensing Applications: Society and Environment 26 1 - 11 2022年04月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Factors Influencing Farmers’ Adoption of Soil Conservation Development 査読あり
Anissa Gara, Edwin P. Mhede, Sawahiko Shimada, Hiromichi Toyoda
Journal of Social Economics Research 7 ( 2 ) 83 - 90 2020年12月
担当区分：責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Efficiency Evaluation of Solar Pumping System for Wadi Agriculture in Djibouti 査読あり
MAKOTO SHINOZAKI, SAWAHIKO SHIMADA, AYAKO SEKIYAMA, KIYOSHI TAJIMA, HASSAN ALI BARKAD
International Journal of Environmental and Rural Development 11 ( 2 ) 98 - 103 2020年12月
担当区分：責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Early identification of Tuta absoluta in tomato plants using deep learning 査読あり
Lilian Mkonyi, Denis Rubanga, Mgaya Richard, Never Zekeya, Shimada Sawahiko, Baraka Maiseli, Dina Machuve
Scientific African 10 2020年11月
担当区分：責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）