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135 results on '"Umemoto, Kazuki"'

5. GAN-based Multiple Adjacent Brain MRI Slice Reconstruction for Unsupervised Alzheimer's Disease Diagnosis

Author

Han, Changhee, Rundo, Leonardo, Murao, Kohei, Milacski, Zoltán Ádám, Umemoto, Kazuki, Sala, Evis, Nakayama, Hideki, and Satoh, Shin'ichi

Subjects
Electrical Engineering and Systems Science - Image and Video Processing, Computer Science - Computer Vision and Pattern Recognition
Abstract

Unsupervised learning can discover various unseen diseases, relying on large-scale unannotated medical images of healthy subjects. Towards this, unsupervised methods reconstruct a single medical image to detect outliers either in the learned feature space or from high reconstruction loss. However, without considering continuity between multiple adjacent slices, they cannot directly discriminate diseases composed of the accumulation of subtle anatomical anomalies, such as Alzheimer's Disease (AD). Moreover, no study has shown how unsupervised anomaly detection is associated with disease stages. Therefore, we propose a two-step method using Generative Adversarial Network-based multiple adjacent brain MRI slice reconstruction to detect AD at various stages: (Reconstruction) Wasserstein loss with Gradient Penalty + L1 loss---trained on 3 healthy slices to reconstruct the next 3 ones---reconstructs unseen healthy/AD cases; (Diagnosis) Average/Maximum loss (e.g., L2 loss) per scan discriminates them, comparing the reconstructed/ground truth images. The results show that we can reliably detect AD at a very early stage with Area Under the Curve (AUC) 0.780 while also detecting AD at a late stage much more accurately with AUC 0.917; since our method is fully unsupervised, it should also discover and alert any anomalies including rare disease., Comment: 10 pages, 4 figures, Accepted to Lecture Notes in Bioinformatics (LNBI) as a volume in the Springer series

Published
2019

6. Synthesizing Diverse Lung Nodules Wherever Massively: 3D Multi-Conditional GAN-based CT Image Augmentation for Object Detection

Author

Han, Changhee, Kitamura, Yoshiro, Kudo, Akira, Ichinose, Akimichi, Rundo, Leonardo, Furukawa, Yujiro, Umemoto, Kazuki, Li, Yuanzhong, and Nakayama, Hideki

Subjects
Computer Science - Computer Vision and Pattern Recognition, Electrical Engineering and Systems Science - Image and Video Processing
Abstract

Accurate Computer-Assisted Diagnosis, relying on large-scale annotated pathological images, can alleviate the risk of overlooking the diagnosis. Unfortunately, in medical imaging, most available datasets are small/fragmented. To tackle this, as a Data Augmentation (DA) method, 3D conditional Generative Adversarial Networks (GANs) can synthesize desired realistic/diverse 3D images as additional training data. However, no 3D conditional GAN-based DA approach exists for general bounding box-based 3D object detection, while it can locate disease areas with physicians' minimum annotation cost, unlike rigorous 3D segmentation. Moreover, since lesions vary in position/size/attenuation, further GAN-based DA performance requires multiple conditions. Therefore, we propose 3D Multi-Conditional GAN (MCGAN) to generate realistic/diverse 32 X 32 X 32 nodules placed naturally on lung Computed Tomography images to boost sensitivity in 3D object detection. Our MCGAN adopts two discriminators for conditioning: the context discriminator learns to classify real vs synthetic nodule/surrounding pairs with noise box-centered surroundings; the nodule discriminator attempts to classify real vs synthetic nodules with size/attenuation conditions. The results show that 3D Convolutional Neural Network-based detection can achieve higher sensitivity under any nodule size/attenuation at fixed False Positive rates and overcome the medical data paucity with the MCGAN-generated realistic nodules---even expert physicians fail to distinguish them from the real ones in Visual Turing Test., Comment: 9 pages, 6 figures, accepted to 3DV 2019

Published
2019

8. GAN-Based Multiple Adjacent Brain MRI Slice Reconstruction for Unsupervised Alzheimer’s Disease Diagnosis

Author

Han, Changhee, Rundo, Leonardo, Murao, Kohei, Milacski, Zoltán Ádám, Umemoto, Kazuki, Sala, Evis, Nakayama, Hideki, Satoh, Shin’ichi, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Cazzaniga, Paolo, editor, Besozzi, Daniela, editor, Merelli, Ivan, editor, and Manzoni, Luca, editor

Published
2020
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12. Response Characteristics of Pressure-Sensitive Conductive Elastomer Sensors Using OFC Electrode with Triangular Wave Concavo-Convex Surfaces.

Author

Katagiri, Takeru, Kodama, Sogo, Kawahara, Kotaro, Umemoto, Kazuki, Miyoshi, Takanori, and Nakayama, Tadachika

Subjects
ELASTOMERS, DETECTORS, ELECTRODES, SURFACE roughness, PRESSURE sensors, SURFACE potential
Abstract

The sensor response of pressure-sensitive conductive elastomers using polymeric materials can be adjusted by altering the type and quantity of fillers used during manufacturing. Another method involves modifying the surface shape of the elastomer. This study investigates the sensor response by altering the surface shape of an electrode using a readily available pressure-sensitive conductive elastomer. By employing an oxygen-free copper electrode with a flat surface (with surface roughness parameters Ra = 0.064 μm and Rz = 0.564 μm) as a baseline, we examined the sensor system's characteristics. Electrodes were fabricated with triangular wave concavo-convex surfaces, featuring tip angles of 60, 90, and 120°. Improved sensor responses were observed with electrodes having tip angles of 60 and 90°. Additionally, even with varying conductive properties of elastomers, the conductance of the elastomer sensor increased similarly when using an electrode with a 90° tip angle. This study demonstrates the potential for expanding the applications of conductive elastomer sensors, highlighting the noteworthy improvement in sensor response and performance achieved by altering the surface shape of electrodes used with commercially available conductive elastomers. [ABSTRACT FROM AUTHOR]

Published
2024
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17. Investigation of Contact Surface Changes and Sensor Response of a Pressure-Sensitive Conductive Elastomer.

Author

Katagiri, Takeru, Ngo, Nguyen Chi Trung, Togawa, Yuki, Kodama, Sogo, Kawahara, Kotaro, Umemoto, Kazuki, Miyoshi, Takanori, and Nakayama, Tadachika

Subjects
ELASTOMERS, SURFACE resistance, DETECTORS, PRESSURE sensors
Abstract

The pressure-sensing mechanisms of conductive elastomers, such as conductive networks, and tunneling effects within them have been extensively studied. However, it has become apparent that external pressure can significantly impact the contact area of polymeric materials. In this study, we will employ a commercially available conductive elastomer to investigate changes in resistance and contact surface under external pressure. Resistance measurements will be taken with and without applying conductive grease to the surface of the elastomer. This allows us to observe changes in resistance values associated with pressure variations. Furthermore, as pressure is applied to the conductive elastomer, the contact area ratio increases. Such an increase in the contact area and its correlation to changes in conductance values will be assessed. [ABSTRACT FROM AUTHOR]

Published
2023
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21. Li@C-60 thin films : characterization and nonlinear optical properties

Author

Wolf, Mathias, Toyouchi, Shuichi, Walke, Peter, Umemoto, Kazuki, Masuhara, Akito, Fukumura, Hiroshi, Takano, Yuta, Yamada, Michio, Hirai, Kenji, Fron, Eduard, Uji-i, Hiroshi, Wolf, Mathias, Toyouchi, Shuichi, Walke, Peter, Umemoto, Kazuki, Masuhara, Akito, Fukumura, Hiroshi, Takano, Yuta, Yamada, Michio, Hirai, Kenji, Fron, Eduard, and Uji-i, Hiroshi

Abstract

Organic materials have attracted considerable attention in nonlinear optical (NLO) applications as they have several advantages over inorganic materials, including high NLO response, and fast response time as well as low-cost and easy fabrication. Lithium-containing C-60 (Li@C-60) is promising for NLO over other organic materials because of its strong NLO response proven by theoretical and experimental studies. However, the low purity of Li@C-60 has been a bottleneck for applications in the fields of solar cells, electronics and optics. In 2010, highly purified Li@C-60 was finally obtained, encouraging further studies. In this study, we demonstrate a facile method to fabricate thin films of Li@C-60 and their strong NLO potential for high harmonic generation by showing its comparatively strong emission of degenerate-six-wave mixing, a fifth-order NLO effect.

Published
2022

27. Li@C60 thin films: characterization and nonlinear optical properties

Author

Wolf, Mathias, primary, Toyouchi, Shuichi, additional, Walke, Peter, additional, Umemoto, Kazuki, additional, Masuhara, Akito, additional, Fukumura, Hiroshi, additional, Takano, Yuta, additional, Yamada, Michio, additional, Hirai, Kenji, additional, Fron, Eduard, additional, and Uji-i, Hiroshi, additional

Published
2022
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28. Local robust stability on compact set for nonlinear systems with continuous time controller against to aperiodic sampling and disturbance.

Author

Umemoto, Kazuki, Endo, Takahiro, and Matsuno, Fumitoshi

Subjects
*CONTINUOUS time systems, *LIPSCHITZ continuity, *NONLINEAR systems
Abstract

In this study, the stability of a sampled‐value control system with time‐ and state‐dependent disturbance and aperiodic sampling is investigated. To expand the application class of the sampled‐value controller, the local stability on a compact set is considered under the assumption of local Lipschitz continuity on the compact set. Because the assumption is weaker than the global Lipschitz continuity, the proposed stability analysis is applicable to a wider class of controlled systems. Global stability under the assumption of global Lipschitz continuity is also considered. The effectiveness of the derived stability condition is verified by conducting numerical simulations with some control parameters variations such as the disturbance magnitude and sample interval. [ABSTRACT FROM AUTHOR]

Published
2023
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30. Modeling and Control of a Quadrotor UAV Equipped With a Flexible Arm in Vertical Plane

Author

70432185, 00190489, Wang, Tiehua, Umemoto, Kazuki, Endo, Takahiro, Matsuno, Fumitoshi, 70432185, 00190489, Wang, Tiehua, Umemoto, Kazuki, Endo, Takahiro, and Matsuno, Fumitoshi

Abstract

In the field of unmanned aerial vehicles (UAVs), aerial manipulations are receiving considerable attention because of their potential application to tasks such as pick and place, detection, and inspection. However, short flight endurance times and concerns about the safety to surroundings during interacting heavily limit the expansion of aerial manipulations in real implementations. To overcome these challenges, this paper focuses on a system in which a quadrotor UAV is equipped with a lightweight and flexible arm. Based on the infinite-dimensional dynamics, the mathematic model of system is described by a hybrid partial differential equation-ordinary differential equation (PDE-ODE). An easily implementable controller is derived from a Lyapunov functional construction related to the energy of the system. The proposed controller ensures global Lyapunov stability for nonlinear system and local asymptotic stability for the linearized system. Further, it is shown that the proposed controller realizes stable motion of the aerial manipulator as well as vibration control of the flexible arm. Finally, numerical simulations are conducted to investigate the validity of the proposed controller.

Published
2021

34. Simple Production of Highly Luminescent Organometal Halide Perovskite Nanocrystals Using Ultrasound-Assisted Bead Milling

Author

Umemoto, Kazuki, primary, Ebe, Hinako, additional, Sato, Ryota, additional, Enomoto, Junya, additional, Oshita, Naoaki, additional, Kimura, Taisei, additional, Inose, Tomoko, additional, Nakamura, Takahiro, additional, Chiba, Takayuki, additional, Asakura, Satoshi, additional, Uji-i, Hiroshi, additional, and Masuhara, Akito, additional

Published
2020
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38. Facile-controlling of the coating amount of poly(acrylic acid)-b-polystyrene coated on silica nanoparticles for polymer electrolyte membrane

Author

Tabata, Keisuke, primary, Nohara, Tomohiro, additional, Koseki, Kazuki, additional, Umemoto, Kazuki, additional, Sato, Ryota, additional, Rodbuntum, Sasiphapa, additional, Suzuki, Yukina, additional, Shimada, Ryuichiro, additional, Asakura, Satoshi, additional, Arita, Toshihiko, additional, and Masuhara, Akito, additional

Published
2020
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39. Synthesis of highly luminescent CH3NH3PbBr3 perovskite nanocrystals via a forced thin film reactor

Author

Takeda, Masaki, primary, Yokoyama, Masaaki, additional, Umemoto, Kazuki, additional, Lyu, Bozhang, additional, Takahashi, Yoshihito, additional, Rodbuntum, Sasiphapa, additional, Enomoto, Junya, additional, Tozawa, Keitaro, additional, Nohara, Tomohiro, additional, Tabata, Keisuke, additional, Sato, Ryota, additional, Chiba, Takayuki, additional, Asakura, Satoshi, additional, Uji-i, Hiroshi, additional, and Masuhara, Akito, additional

Published
2020
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43. Effects of alkylamine chain length on perovskite nanocrystals after washing and perovskite light-emitting diodes

Author

Tezuka, Yuki, primary, Umemoto, Kazuki, additional, Takeda, Masaki, additional, Takahashi, Yoshihito, additional, Ebe, Hinako, additional, Enomoto, Junya, additional, Rodbuntum, Sasiphapa, additional, Nohara, Tomohiro, additional, Fontecha, Daniela, additional, Asakura, Satoshi, additional, Chiba, Takayuki, additional, Furis, Madalina Ioana, additional, Yoshida, Tsukasa, additional, Uji-i, Hiroshi, additional, and Masuhara, Akito, additional

Published
2019
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46. Photoconductive Properties of Dibenzotetrathiafulvalene-Tetracyanoquinodimethane (DBTTF-TCNQ) Nanorods Prepared by the Reprecipitation Method

Author

Takeda, Masaki, primary, Hojo, Kenta, additional, Umemoto, Kazuki, additional, Scharber, Markus Clark, additional, Stadler, Philipp, additional, Yumusak, Cigdem, additional, Sariciftci, Niyazi Serdar, additional, White, Matthew Shuette, additional, Furis, Madalina, additional, Okada, Shuji, additional, Yoshida, Tsukasa, additional, Matsui, Jun, additional, and Masuhara, Akito, additional

Published
2019
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