Papers - OKAZAKI Naonobu
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画像内の反射成分の干渉下でも検出性能を維持できる画像中のプライバシーリスク検出手法 Reviewed
臼崎翔太郎, 油田健太郎, 山場久昭, 朴美娘, 岡崎直宣
情報処理学会論文誌 67 ( 67 ) 588 - 604 2026.3
Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal)
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2010年宮崎県口蹄疫を事例とした感染リスク評価指標の構築と防疫支援への応用 Reviewed
高塚佳代子, 臼崎翔太朗, 山場久昭, 油田健太郎, 岡崎直宣
化学工学論文集 52 ( 1 ) 15 - 20 2026.1
Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal)
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Usuzaki Shotaro, Takahashi Nobuya, Kamada Taiki, Aburada Kentaro, Yamaba Hisaaki, Park Mirang, Okazaki Naonobu
IEICE Communications Express 14 ( 12 ) 441 - 444 2025.12
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：一般社団法人 電子情報通信学会
In this study, we propose a text-based CAPTCHA that utilizes human visual completion to prevent automated programs from getting through, without affecting human cognition. This CAPTCHA requires users to enter the reading of the kanji strings, whose centers are hidden behind a black bar. This method makes it challenging for machines to recognize the characters, while still allowing humans to identify the original text through their visual completion ability. We evaluate both the usability and security of the proposed CAPTCHA. To assess usability, we observed how humans respond to the CAPTCHA challenge. For the security evaluation, we tested the machine’s ability to read the kanji using a Convolutional Neural Network (CNN). The results showed that the proposed CAPTCHA achieves a success rate comparable to traditional CAPTCHAs, with a slightly shorter response time than a similar type of CAPTCHA. Furthermore, security experiments have shown that it exhibits a certain degree of resistance against simple convolutional neural networks.
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Optimal Weighted Voting-Based Collaborated Malware Detection for Zero-Day Malware: A Case Study on VirusTotal and MalwareBazaar Reviewed
Naonobu Okazaki, Shotaro Usuzaki, Tsubasa Waki, Hyoga Kawagoe, Mirang Park, Hisaaki Yamaba and Kentaro Aburada
Future Internet 16 ( 8 ) 259 2024.7
Authorship：Lead author, Corresponding author Language：English Publishing type：Research paper (scientific journal)
DOI： 10.3390/fi16080259
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Usability improvement in color constancy CAPTCHA Reviewed
Shotaro Usuzaki, Wang Yihan, Kentaro Aburada, Hisaaki Yamaba, Kayoko Takatsuka, Tetsuro Katayama, Mirang Park, and Naonobu Okazaki
IEICE Communications Express 2024.6
Authorship：Last author Language：English Publishing type：Research paper (scientific journal)
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プロジェクト・スケジュールの遅延リスク分析のための手法の開発 Reviewed
高塚佳代子, 佐藤知一, 油田健太郎, 岡崎直宣
化学工学論文集 49 ( 6 ) 159 - 165 2023.11
Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal)
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Takatsuka Kayoko, Nagatomo Yoki, Uchida Noriyuki, Ikeda Takuya, Mukunoki Masayuki, Okazaki Naonobu
Journal of Robotics, Networking and Artificial Life 10 ( 1 ) 17 - 24 2023.10
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：ALife Robotics Corporation Ltd.
This study aimed to reduce the effect of the examining environment on accuracy by using an eye movement detection system, a VR head-mounted display. We reproduced the inspection environment in a virtual reality environment and performed the cover test, a basic inspection technique for tropia and phoria. We then developed a system that uses eye data collected by eye tracking to detect the directions and magnitudes of eye misalignment. The Maddox method, an existing testing procedure, was used to verify the accuracy. We have confirmed its effectiveness in detecting the directions and magnitudes of horizontal eye misalignment.
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Development of keypads which use colors or shapes to prevent shoulder surfing Reviewed
Ryo Masuzawa, Kentaro Aburada, Hisaaki Yamaba, Tetsuro Katayama, Naonobu Okazaki
Artificial Life and Robotics 2023.8
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Artificial Life and Robotics
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Tsunami evacuation simulation considering road width in Aoshima district Reviewed
Keita Nabeyama, Shotaro Usuzaki, Kentaro Aburada, Hisaaki Yamaba, Tetsuro Katayama & Naonobu Okazaki
Artificial Life and Robotics 2023.7
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Artificial Life and Robotics
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Isakwisa Gaddy Tende, Kentaro Aburada, Hisaaki Yamaba, Tetsuro Katayama and Naonobu Okazaki
Agriculture 13 ( 3 ) 627 - 645 2023.3
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Artificial Life and Robotics
Most of the small-scale farmers in Tanzania can’t afford to buy quality agricultural inputs (fertilizers and seeds), therefore the Tanzanian government issues paper-based subsidy vouchers to farmers for buying the inputs at half price. However, challenges like misuse of the vouchers by some government officials (stealing and favoritism in allocation) and lack of trust (difficulty of verifying vouchers’ authenticity) have resulted into low crop productivity for the farmers and loss of government funds. To address this, we have developed agricultural input voucher system which stores and allocates digital subsidy vouchers to farmers in the Hyperledger Fabric blockchain network whose features like hashing and digital signature prevent misuse and ensure trust of the vouchers. Farmers access the digital vouchers through Short Message Service (SMS) in their mobile phones. Evaluation reveals that, the developed system is effective and meets performance demands of Tanzanian farmers. Also, Raft has better performance than Kafka consensus protocol.
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Development of Methods for Project Schedule Delay Risk Analysis Reviewed
Takatsuka Kayoko, Sato Tomoichi, Aburada Kentaro, Okazaki Naonobu
KAGAKU KOGAKU RONBUNSHU 49 ( 6 ) 159 - 165 2023
Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Society of Chemical Engineers, Japan
Since introducing the project management technique “earned value management” in the 1970s, planning and schedule management that balances the three factors of process, resources, and cost are now possible. However, delay risk has increased over the years because of the large-scale scope and changes in the surrounding environment. Therefore, besides the above three factors, preparation and management regarding delay risk are critical. However, many projects rely on the experience and intuition of directors to monitor risk. This study develops a project schedule management mechanism and system that analyzes delay risk besides processes, resources, and costs. A schedule network generation unit with multiple activities and a delay risk evaluation unit are included in the schedule management system to achieve this purpose. As a mechanism for managing delay risk, we propose a method that evaluates the margin (delay risk tolerance) of the total float of the schedule network that has a negative correlation with delay risk and a simple and accurate calculation method.
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Proposal for a blockchain based agricultural input voucher system Reviewed
Isakwisa Gaddy Tende, Kentaro Aburada, Hisaaki Yamaba, Tetsuro Katayama, Naonobu Okazaki
Artificial Life and Robotics 27 461 - 471 2022.1
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Artificial Life and Robotics
Most of the small-scale farmers in Tanzania can’t afford to buy quality agricultural inputs (fertilizers and seeds), therefore the Tanzanian government issues paper-based subsidy vouchers to farmers for buying the inputs at half price. However, challenges like misuse of the vouchers by some government officials (stealing and favoritism in allocation) and lack of trust (difficulty of verifying vouchers’ authenticity) have resulted into low crop productivity for the farmers and loss of government funds. To address this, we have developed agricultural input voucher system which stores and allocates digital subsidy vouchers to farmers in the Hyperledger Fabric blockchain network whose features like hashing and digital signature prevent misuse and ensure trust of the vouchers. Farmers access the digital vouchers through Short Message Service (SMS) in their mobile phones. Evaluation reveals that, the developed system is effective and meets performance demands of Tanzanian farmers. Also, Raft has better performance than Kafka consensus protocol.
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リレーアタック耐性とボット耐性の両立を目指したインタラクティブな動画CAPTCHAの提案と評価 Reviewed
油田健太郎, 臼崎翔太郎, 山場久昭, 片山徹郎, 椋木雅之, 朴美娘, 岡崎直宣
情報処理学会論文誌 62 ( 12 ) 1864 - 1878 2021.12
Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal)
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スマートロックにおける二端末による機械学習を用いた歩行認証に関する研究 Reviewed
朴美娘, 渡辺一樹, 油田健太郎, 岡崎直宣
情報処理学会論文誌 62 ( 12 ) 2011 - 2023 2021.12
Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal)
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Development of a System to Detect Eye Position Abnormality based on Eye-Tracking Reviewed
Noriyuki Uchida, Kayoko Takatuka, Hisaaki Yamaba, Masayuki Mukunoki, Naonobu Okazaki
Journal of Robotics, Networks and Artificial Life, Atlantis Press 8 ( 3 ) 205 - 210 2021.12
Authorship：Last author Language：English Publishing type：Research paper (scientific journal)
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Proposal for a Crop Protection Information System for Rural Farmers in Tanzania Reviewed
Isakwisa Gaddy Tende, Kentaro Aburada, Hisaaki Yamaba, Tetsuro Katayama, Naonobu Okazaki
Agronomy 11 ( 12 ) 1 - 17 2021.11
Authorship：Last author Language：English Publishing type：Research paper (scientific journal)
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Proposal and Evaluation for Color Constancy CAPTCHA Invited Reviewed
Shotaro Usuzaki, Kentaro Aburada, Tetsuro Katayama, Masayuki Mukunoki, Mirang Park, Naonobu Okazaki
Journal of Artificial Life and Robotics, Springer 26 ( 3 ) 291 - 296 2021.3
Authorship：Last author Language：English Publishing type：Research paper (scientific journal)
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主観的輪郭を用いた回転3Dテキスト型CAPTCHAの提案 Reviewed
臼崎翔太郎，油田健太郎，山場久昭，片山徹郎，椋木雅之，朴美娘，岡崎直宣
電子情報通信学会論文誌B J103-B ( 8 ) 332 - 343 2020.8
Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal)
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On a user authentication methods to realize an authentication system using s-EMG Reviewed
Hisaaki Yamaba, Shotaro Usuzaki, Kayoko Takatsuka, Kentaro Aburada, Tetsuro Katayama, Mirang Park, Naonobu Okazaki
International Journal of Grid and Utility Computing 11 ( 5 ) 725 - 734 2020.8
Authorship：Last author Language：English Publishing type：Research paper (scientific journal)
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On a user authentication method to realise an authentication system using s-EMG Reviewed
Yamaba H., Usuzaki S., Takatsuka K., Aburada K., Katayama T., Park M., Okazaki N.
International Journal of Grid and Utility Computing 11 ( 5 ) 725 - 734 2020.8
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：International Journal of Grid and Utility Computing
To prevent shoulder-surfing attacks, we proposed a user authentication method using surface electromyogram (s-EMG) signals, which can be used to identify who generated the signals and which gestures were made. Our method uses a technique called 'pass-gesture', which refers to a series of hand gestures, to achieve s-EMG-based authentication. However, it is necessary to introduce computer programs that can recognise gestures from the s-EMG signals. In this paper, we propose two methods that can be used to compare s-EMG signals and determine whether they were made by the same gesture. One uses support vector machines (SVMs), and the other uses dynamic time warping. We also introduced an appropriate method for selecting the validation data used to train SVMs using correlation coefficients and cross-correlation functions. A series of experiments was carried out to confirm the performance of those proposed methods, and the effectiveness of the two methods was confirmed.