研究者業績
基本情報
- 所属
- 上智大学 理工学部情報理工学科 教授
- 学位
- 博士(工学)(上智大学)
- 研究者番号
- 90407338
- J-GLOBAL ID
- 201301073146868965
- researchmap会員ID
- 7000004362
- 外部リンク
研究分野
1論文
152-
Computer Networks 288 112670-112670 2026年10月
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Zorig Melong | A Technical Journal of Science, Engineering and Technology 9(1) 165-173 2026年8月18日
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Drones 10(8) 616-616 2026年8月12日The 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 2026年3月13日The 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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2025 IEEE Conference on Cloud and Big Data Computing (CBDCom) 112-119 2025年10月21日
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2025 International Workshop on Artificial Intelligence and Education (WAIE) 362-366 2025年9月27日
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2025 International Workshop on Artificial Intelligence and Education (WAIE) 207-211 2025年9月27日
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Egyptian Informatics Journal 31 100752-100752 2025年9月
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2025 International Conference on Advanced Machine Learning and Data Science (AMLDS) 612-616 2025年7月19日
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Electronics 14(4) 676-676 2025年2月10日Automatic medical segmentation is crucial for assisting doctors in identifying disease regions effectively. As a state-of-the-art (SOTA) approach, generative AI models, particularly diffusion models, have surpassed GANs in generating high-quality images for tasks like segmentation. However, most diffusion-based architectures rely on U-Net designs with multiple residual blocks and convolutional layers, resulting in high computational costs and limited applicability on general-purpose devices. To solve this issue, we propose an enhanced denoising diffusion implicit model (DDIM) that incorporates lightweight depthwise convolution layers within residual networks and self-attention layers. This approach significantly reduces computational overhead while maintaining segmentation performance. We evaluated the proposed DDIM on two distinct medical imaging datasets: X-ray and skin lesion and polyp segmentation. Experimental results demonstrate that our model achieves, with reduced resource requirements, accuracy comparable to standard DDIMs in both visual representation and region-based scoring. The proposed lightweight DDIM offers a promising solution for medical segmentation tasks, enabling easier implementation on general-purpose devices without the need for expensive high-performance computing resources.
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Connection Science 37(1) 2025年1月17日
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Advances in Artificial Intelligence and Machine Learning 5(1) 3216-3235 2025年
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IEEE Access 13 103405-103416 2025年 査読有り責任著者
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Lengua y Sociedad 23(2) 1047-1068 2024年12月30日 査読有り責任著者La rápida globalización y la creciente necesidad de comunicación interlingüística requieren corpus modernos y en tiempo real para ayudar a los estudiantes de idiomas. Los métodos tradicionales para crear dichos corpus, especialmente en español, son inadecuados debido a su incapacidad para procesar la gran cantidad de datos no estructurados disponibles en internet. En este estudio se exploran las metodologías de inteligencia artificial (IA) para la adquisición automática de documentos en español de la web, preprocesándolos y clasificándolos con el fin de construir un corpus vasto y flexible para el aprendizaje del español. La investigación aplica el rastreo web mediante el framework Scrapy para recopilar datos, que luego se limpian y clasifican utilizando modelos avanzados de procesamiento del lenguaje natural (PLN). En concreto, el estudio emplea el algoritmo BERT (Bidirectional Encoder Representations from Transformers) y su variante mejorada RoBERTa para lograr la clasificación de documentos. Mediante una combinación de técnicas de aumento de datos y modelos de aprendizaje profundo, el estudio logra una alta precisión en la clasificación de texto en español, lo que demuestra el potencial del uso de la IA para superar las limitaciones de los enfoques tradicionales de creación de corpus.
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2024 6th International Workshop on Artificial Intelligence and Education (WAIE) 379-383 2024年9月28日 査読有り責任著者
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2024 6th International Workshop on Artificial Intelligence and Education (WAIE) 353-357 2024年9月28日 査読有り責任著者
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2024 4th Asian Conference on Innovation in Technology (ASIANCON) 1-6 2024年8月23日 査読有り責任著者
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Soft Computing 28(17-18) 9905-9919 2024年7月20日 査読有り
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Algorithms 17(5) 180-180 2024年4月28日 査読有りResource Constraint Project Scheduling Problems with Discounted Cash Flows (RCPSPDC) focuses on maximizing the net present value by summing the discounted cash flows of project activities. An extension of this problem is the Payment at Event Occurrences (PEO) scheme, where the client makes multiple payments to the contractor upon completion of predefined activities, with additional final settlement at project completion. Numerous approximation methods such as metaheuristics have been proposed to solve this NP-hard problem. However, these methods suffer from parameter control and/or the computational cost of correcting infeasible solutions. Alternatively, approximate dynamic programming (ADP) sequentially generates a schedule based on strategies computed via Monte Carlo (MC) simulations. This saves the computations required for solution corrections, but its performance is highly dependent on its strategy. In this study, we propose the hybridization of ADP with three different metaheuristics to take advantage of their combined strengths, resulting in six different models. The Estimation of Distribution Algorithm (EDA) and Ant Colony Optimization (ACO) were used to recommend policies for ADP. A Discrete cCuckoo Search (DCS) further improved the schedules generated by ADP. Our experimental analysis performed on the j30, j60, and j90 datasets of PSPLIB has shown that ADP–DCS is better than ADP alone. Implementing the EDA and ACO as prioritization strategies for Monte Carlo simulations greatly improved the solutions with high statistical significance. In addition, models with the EDA showed better performance than those with ACO and random priority, especially when the number of events increased.
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IEEE Open Journal of the Computer Society 5 624-635 2024年 査読有り
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IEEE Access 12 190445-190453 2024年 査読有り責任著者
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AITI 20(2) 125-134 2023年8月25日 査読有り
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Connection Science 35(1) 2023年3月8日 査読有り
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2023 International Conference on Intelligent Data Communication Technologies and Internet of Things (IDCIoT) 53 524-530 2023年1月5日 査読有り責任著者
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Proceedings of the 2022 5th Artificial Intelligence and Cloud Computing Conference 53 66-72 2022年12月17日 査読有り
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Indian Journal of Computer Science and Engineering 13(5) 1483-1496 2022年10月20日 査読有り
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The Chinese Journal of Artificial Intelligence 1(2) 2022年9月 査読有りBackground: Examination Timetabling Problem which tries to find an optimal examination schedule for schools, colleges, and universities, is a well-known NP-hard problem. This paper presents a Genetic Algorithm variant approach to solve a specific examination timetabling problem common in Japanese colleges and universities. Methods: The proposed algorithm uses direct chromosome representation Genetic Algorithm and implements constraint-based initialization and constraint-based crossover operations to satisfy the hard and soft constraints. An Island model with varying crossover and mutation probabilities and an improvement approach called pre-training are applied to the algorithm to further improve the result quality. Results: The proposed model is tested on synthetic as well as real datasets obtained from Sophia University, Japan and shows acceptable results. The algorithm was fine-tuned with different penalty points combinations and improvement combinations. Conclusion: The comparison results support the idea that the initial population pre-training and the island model are effective approaches to improve the result quality of the proposed model. Although the current island model used only four islands, incorporating greater number of islands, and some other diversity maintenance approaches such as memetic structures are expected to further improve the diversity and the result quality of the proposed algorithm on large scale problems.
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International Conference on Unmanned Aircraft Systems 2022年6月 査読有り
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2022 10th International Conference on Information and Education Technology (ICIET) 14 409-414 2022年4月9日 査読有り
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10th International Conference on Information and Education Technology (ICIET) 2022年4月 査読有り
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International Journal of Big Data Intelligence and Applications 2(1) 21-38 2022年3月9日 査読有り<p>In this paper, the authors have proposed a computationally efficient, robust, and lightweight system for gait recognition. The proposed system contains two main stages: In the first stage, a classification network identifies optical flow corners in the normalized silhouette and calculates the distances traveled in every viewpoint which is further used by a regression model to identify the viewing angle. In the second stage, a feature extraction network computes the gait energy image (GEI) for every viewpoint and then uses principal component analysis (PCA) to extract low dimensional feature vectors from these GEI images. Finally, a multi-layer perceptron model is trained using the extracted principal components for every viewing angle. The performance of a system is comprehensively evaluated on the CASIA B and OULP gait dataset. The experimental results demonstrate the superior performance of a proposed system in viewing angle classification (100% accuracy), gait recognition (100% accuracy in normal walk), computational efficiency, robustness to clothing, and viewing angle variation.</p>
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1423 57-68 2022年2月26日 査読有り
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Proceedings of the Annual Conference of JSAI 35th Annual Conference 3(1) 37-52 2022年1月24日 査読有り
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Lecture Notes in Networks and Systems 311-322 2021年10月25日 査読有り
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SN Computer Science 2(6) 2021年10月20日 査読有り
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International Conference on Artificial Intelligence and Software Engineering 1-8 2021年9月 査読有り
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2nd International Conference on Innovative and Creative Information Technology 2021 2021年9月 査読有り
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Engineering Applications of Artificial Intelligence 104 104370-104370 2021年9月 査読有り
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AI 2(3) 366-380 2021年8月19日 査読有りResearch on autonomous obstacle avoidance of drones has recently received widespread attention from researchers. Among them, an increasing number of researchers are using machine learning to train drones. These studies typically adopt supervised learning or reinforcement learning to train the networks. Supervised learning has a disadvantage in that it takes a significant amount of time to build the datasets, because it is difficult to cover the complex and changeable drone flight environment in a single dataset. Reinforcement learning can overcome this problem by using drones to learn data in the environment. However, the current research results based on reinforcement learning are mainly focused on discrete action spaces. In this way, the movement of drones lacks precision and has somewhat unnatural flying behavior. This study aims to use the soft-actor-critic algorithm to train a drone to perform autonomous obstacle avoidance in continuous action space using only the image data. The algorithm is trained and tested in a simulation environment built by Airsim. The results show that our algorithm enables the UAV to avoid obstacles in the training environment only by inputting the depth map. Moreover, it also has a higher obstacle avoidance rate in the reconfigured environment without retraining.
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Artificial Intelligence for Future Generation Robotics 93-118 2021年 査読有り
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International Journal of Electrical Power & Energy Systems 124 106295-106295 2021年1月 査読有り
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American Journal of Computer Science and Technology 4(3) 75-75 2021年 査読有り
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Computer Science & Information Technology (CS & IT) 1-12 2020年12月12日 査読有りThis paper presents a Genetic Algorithm approach to solve a specific examination timetabling problem which is common in Japanese Universities. The model is programmed in Excel VBA programming language, which can be run on the Microsoft Office Excel worksheets directly. The model uses direct chromosome representation. To satisfy hard and soft constraints, constraint-based initialization operation, constraint-based crossover operation and penalty points system are implemented. To further improve the result quality of the algorithm, this paper designed an improvement called initial population pre-training. The proposed model was tested by the real data from Sophia University, Tokyo, Japan. The model shows acceptable results, and the comparison of results proves that the initial population pre-training approach can improve the result quality.
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2020 IEEE International Conference for Innovation in Technology (INOCON) 7 1-4 2020年11月6日 査読有り
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IT Professional 22(6) 59-66 2020年11月1日 査読有り
MISC
6-
2025年9月18日Large 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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福音と社会 63(2) 19-41 2024年4月
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2021年5月17日Unpaired 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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人工知能学会全国大会論文集 JSAI2019 3B3E204-3B3E204 2019年新たな手法や技術により発展している深層学習には、人々の仕事効率を助けたり、とある現象をみて予測を立てたり、デザイナーとなって画像を生成するなど様々な可能性に満ちている。本研究では深層学習を用いて"条件付き"の手書き文字を生成を行った。単なる画像生成ではなく、入力者側が生成したい手書き文字を指定する(生成の条件をつける)ことでその文字を生成することを目的とする。目的達成のために、実験では深層学習モデルとしてDCGANとConditional GANを組み合わせたConditional DCGANを構築、ラベル情報の付加で生成条件がつけられた画像生成のトレーニングを行った。141,319のサンプル訓練データにある数字やアルファベット、カタカナなどの総計96種類の手書き文字の書き分けトレーニングを通じて、インプットの要素として含まれるランダムノイズの次元数がその種類数を上回るようにした学習済みのGeneratorは各種類に対応付けたラベルを指定するだけで、その該当文字を生成できたことを紹介する。
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電子情報通信学会技術研究報告. KBSE, 知能ソフトウェア工学 103(604) 1-6 2004年12月In 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 de...
書籍等出版物
2-
CRC Press 2021年 (ISBN: 9780367638368)
講演・口頭発表等
73-
13th International Conference on Awareness Science and Technology (iCAST), Yog Jakarta 2025年11月 招待有り
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NPO Mental Health Care Research Group Chiba (NPO) 2025年6月12日 招待有り
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International Conference on Artificial Intelligence and Data Analytics for Business, Gedu College of Business, Royal University of Bhutan, Bhutan 2025年4月25日 招待有り