Curriculum Vitaes
Profile Information
- Affiliation
- Professor, Faculty of Science and Technology, Department of Information and Communication Sciences, Sophia University
- Degree
- 博士(工学)(上智大学)
- Researcher number
- 90407338
- J-GLOBAL ID
- 201301073146868965
- researchmap Member ID
- 7000004362
- External link
Research Areas
1Papers
152-
Computer Networks, 288 112670-112670, Oct, 2026
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Zorig Melong | A Technical Journal of Science, Engineering and Technology, 9(1) 165-173, Aug 18, 2026
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Drones, 10(8) 616-616, Aug 12, 2026The Traveling Salesman Problem (TSP) and the Vehicle Routing Problem (VRP) are two classical combinatorial optimization problems. In recent years, their drone-assisted variants, the Traveling Salesman Problem with Drones (TSP-D) and the Vehicle Routing Problem with Drones (VRP-D) have attracted growing attention. Generally, these problems are solved using exact algorithms or metaheuristic algorithms. However, as the problem complexity increases and the scale of instances grows, these approaches often become less efficient. In this paper, we propose a reinforcement learning method with a shared attention encoder and a hierarchical dual-decoder architecture, where truck–drone coordination is achieved by first decoding the truck’s next node and then conditionally decoding the drone action. To further explore the solution space of large-scale instances, the proposed method adopts a multi-rollout learning strategy. We conducted experiments on large-scale TSP-D and VRP-D instances, and the results show that this model outperforms traditional metaheuristic algorithms in terms of both solution quality and computational efficiency.
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Frontiers in Artificial Intelligence, 9, Mar 13, 2026The two-tier vehicle routing problem (2T-VRP) represents a novel variant differing from the traditional VRPs. It can be applied to urban logistics operations system, offering significant potential for mitigating last-mile traffic congestion and reducing delivering costs. Distinct from traditional VRPs, this scenario contains a hierarchical two-tier structure, with trucks operating on the first tier and drones at stations on the second tier. In this study, we first extend the 2T-VRP framework by relaxing the hierarchical constraints, enabling trucks to transport goods not only to robot stations but also directly to customers. This new variant is referred to as the flexible two-tier vehicle routing problem with drone stations (F2T-VRP-DS). Then we formulate the problem as a mixed-integer linear programming (MILP) model. Finally, given the complexity of this problem, an improved adaptive large neighborhood search heuristic algorithm (IALNS) is proposed. The algorithm incorporates an adapted Clark and Wright saving algorithm as the initial solution, and a simulated annealing scheme is employed as the acceptance criterion. The experimental results show that our algorithm can provide high-quality solutions. In particular, compared with the MILP method, our algorithm demonstrates strong competitiveness on large-scale instances, offering smaller time consumption and better solution quality compared to commercial solver like Gurobi. In addition, based on the results of the sensitivity analysis, we further assessed the influence of several key parameters within the F2T-VRP-DS framework.
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ICCS (Workshops 1), 281-294, 2026
Misc.
6-
Sep 18, 2025Large Language Models (LLMs) are gaining popularity and improving rapidly. Tokenizers are crucial components of natural language processing, especially for LLMs. Tokenizers break down input text into tokens that models can easily process while ensuring the text is accurately represented, capturing its meaning and structure. Effective tokenizers enhance the capabilities of LLMs by improving a model's understanding of context and semantics, ultimately leading to better performance in various downstream tasks, such as translation, classification, sentiment analysis, and text generation. Most pre-trained tokenizers are suitable for high-resource languages like English but perform poorly for low-resource languages. Dzongkha, Bhutan's national language spoken by around seven hundred thousand people, is a low-resource language, and its linguistic complexity poses unique NLP challenges. Despite some progress, significant research in Dzongkha NLP is lacking, particularly in tokenization. This study evaluates the training and performance of three common tokenization algorithms in comparison to other popular methods. Specifically, Byte-Pair Encoding (BPE), WordPiece, and SentencePiece (Unigram) were evaluated for their suitability for Dzongkha. Performance was assessed using metrics like Subword Fertility, Proportion of Continued Words, Normalized Sequence Length, and execution time. The results show that while all three algorithms demonstrate potential, SentencePiece is the most effective for Dzongkha tokenization, paving the way for further NLP advancements. This underscores the need for tailored approaches for low-resource languages and ongoing research. In this study, we presented three tokenization algorithms for Dzongkha, paving the way for building Dzongkha Large Language Models.
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May 17, 2021Unpaired image-to-image translation using Generative Adversarial Networks (GAN) is successful in converting images among multiple domains. Moreover, recent studies have shown a way to diversify the outputs of the generator. However, since there are no restrictions on how the generator diversifies the results, it is likely to translate some unexpected features. In this paper, we propose Style-Restricted GAN (SRGAN) to demonstrate the importance of controlling the encoded features used in style diversifying process. More specifically, instead of KL divergence loss, we adopt three new losses to restrict the distribution of the encoded features: batch KL divergence loss, correlation loss, and histogram imitation loss. Further, the encoder is pre-trained with classification tasks before being used in translation process. The study reports quantitative as well as qualitative results with Precision, Recall, Density, and Coverage. The proposed three losses lead to the enhancement of the level of diversity compared to the conventional KL loss. In particular, SRGAN is found to be successful in translating with higher diversity and without changing the class-unrelated features in the CelebA face dataset. To conclude, the importance of the encoded features being well-regulated was proven with two experiments. Our implementation is available at https://github.com/shinshoji01/Style-Restricted_GAN.
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Proceedings of the Annual Conference of JSAI, JSAI2019 3B3E204-3B3E204, 2019Developing deep learning models has a great potential in assisting human tasks involving design and creativity. This study deals with generating handwritten characters using deep learning techniques. The task is not simply generating images randomly, but generating them conditionally, making a distinction according to the UI designates. To solve this task, we constructed the Conditional DCGAN model which includes the techniques from DCGAN and Conditional GAN. We tried training the models to be able to generate conditional images by adding label information as input to the Generator. Deep learning experiments were performed using 141319 training data consisting of 96 kinds of characters including digits, Roman alphabets and Katakana. The Generator trained by inputting random noise concatenated with the 96 kinds of characters, could generate each kind of character by just adding the appropriate label information.
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Technical report of IEICE. KBSE, 103(604) 1-6, Dec, 2004In this paper we propose a composite-server model and make use of the knowledge of the intrinsic composition of its service providing units (personnel or equipment) to derive Qualitative knowledge-based rules for its performance evaluation. The composite server model that takes into account the composite nature of service has wider scope in its applications and can be used to represent a variety of system classes. We use this novel concept in the performance design and improvement of collaborative engineering systems. System modeling is done by Multi-Context Map (MCM) technique. MCM is a descriptive model that expresses the collaborative activity performed through the exchange of token, material and information; bottlenecks primarily arise due to the non-uniformity in the flow of token, material and information. Another source of bottlenecks in collaborative engineering systems is the lack or surplus of service-providing units, known as "Perspectives" in the MCM terminology. Bottlenecks due to inappropriate Perspective allocation are resolved by the Qualitative Reasoning approach. We have found this method successful in the performance design, evaluation and improvement of a practical collaborative engineering system presented at the end of this paper.
Books and Other Publications
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CRC Press, 2021 (ISBN: 9780367638368)
Presentations
73-
13th International Conference on Awareness Science and Technology (iCAST), Yog Jakarta, Nov, 2025 Invited
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NPO Mental Health Care Research Group Chiba (NPO), Jun 12, 2025 Invited
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International Conference on Artificial Intelligence and Data Analytics for Business, Gedu College of Business, Royal University of Bhutan, Bhutan, Apr 25, 2025 Invited
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International Conference on Smart Technologies in Electrical & Communication Engineering, Andhra Loyola Institute of Engineering and Technology, Vijayawada, India, Mar 9, 2025 Invited
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ICCI 25,Kristu Jayanti University, Bangalore,, Mar, 2025 Invited
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Baraka Agriculture College, Molo, Kenya, Aug, 2024 Invited
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National Health Service (NHS) clinic, Mar 26, 2024 Invited
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The 2nd International Conference on Innovative and Creative Information Technology 2021, Sep, 2021 Invited
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University of South-Eastern Norway, 2018 Invited
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SDPS2017, Dec, 2017
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Proceedings of the 13th IASTED International Conference on on Artificial Intelligence and Soft Computing, September 7-9, 2009, Palma de Mallorca, Spain, Nov, 2009
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The Second International Conference on the Applications of Digital Information and Web Technologies : ICADIWT 2009 : London Metropolitan Business School, London Metropolitan University, UK, August 4-6, 2009, Sep, 2009
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2009 International Conference on Artificial Intelligence and Pattern Recognition (AIPR-09), Aug, 2009
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Proceedings of the International MultiConference of Engineers and Computer Scientists 2009 : IMECS 2009, Jul, 2009
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2008 IEEE 32nd International Computer Software and Applications Conference (COMPSAC) (3rd IEEE International Workshop on Engineering Semantic Agent Systems ESAS 2008), Sep, 2008