Details of a Researcher - Yakoh, Takahiro

Papers - Yakoh, Takahiro

Division display 1 - 20 of about 107 ／ All the affair displays >>

Real-Time Survey of Vaccine Safety of the mRNA-1273 SARS-CoV-2 Vaccine in Workplace Vaccination at Keio University

Okumura K., Hara A., Inada I., Sugiyama D., Hoshino T., Yakoh T., Yokoyama H., Urushihara H.

Vaccines (Vaccines) 10 ( 9 ) 2022.09

ISSN 2076-393X

The mRNA-1273 Moderna COVID-19 vaccine was introduced to combat the COVID-19 global pandemic in 2020. Although the safety of the vaccine has been investigated worldwide, real-world safety data is scarce in Japan. An online, real-time survey of adverse events following immunization (AEFIs) with mRNA-1273 was conducted in the setting of a workplace vaccination program at the School of Pharmacy, Keio University from 26 June 2021, to 11 June 2022. Participants were requested to take four surveys during a seven-day follow-up period after each of the first, second, and third booster doses. The maximum number of responses, from 301 respondents, was obtained on day 0 (vaccination date) for the first dose. 98% of respondents reported local and systemic AEFIs for the second dose on day 1. No noticeable difference in local reactions was seen among the three doses. Females reported more AEFIs than males, and the young group (18–29 years) reported a higher rate than the middle age group (≥30 years) after the first dose. Age and gender differences in rates decreased at the second and third doses. This survey confirmed that the safety profile of mRNA-1273 in a real-world setting was similar to that derived from the clinical trials, and that the agent was well-tolerated.

Access to Document (DOI)

Re-shooting Resistant Blind Watermarking Framework Based on Feature Separation With Gaussian Mixture Model

Yakoh T., Oi M.

IEEJ Transactions on Electrical and Electronic Engineering (IEEJ Transactions on Electrical and Electronic Engineering) 17 ( 4 ) 556 - 565 2022.04

ISSN 19314973

Watermarking is a technology to embed digital data into a digital image. In particular, blind watermarking is expected to ensure the authenticity and/or accountability of digital images without compromising the visual impression of viewing. A re-shooting resistant blind watermarking method is proposed in this study. This method uses the features of a given image to select regions, which are modified to embed digital data. As the proposed embedding process preserves these image features, no markers are required to extract the embedded data from the watermarked image. Furthermore, based on the estimation of the watermarked image region, the method crops the re-shot image before the extraction. Therefore, the proposed method works, even if the re-shot image includes the outer area surrounding the watermarked image region. Moreover, the proposed method compensates for the geometric transformation of the re-shot image based on the definition of the coordinate system, which is based on the distribution of the image feature points. Therefore, the proposed method works when the re-shot image is taken diagonally in front of the watermarked image. Experimental results validated that the proposed method can extract the embedded digital data from re-shot images of a watermarked image under considerable conditions of re-shooting. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Access to Document (DOI)

An NLP-Inspired Data Augmentation Method for Adverse Event Prediction Using an Imbalanced Healthcare Dataset

Ishikawa T., Yakoh T., Urushihara H.

IEEE Access (IEEE Access) 10 81166 - 81176 2022

This paper proposes a data augmentation method for imbalanced healthcare datasets. This method was inspired by a data augmentation method in natural language processing (NLP) that generates synthetic sentences for training by replacing some words with similar words. The proposed method generates synthetic patient records by replacing patient backgrounds with similar backgrounds. In this paper, the cosine similarity of the distributed representations was used as the similarity metric between patient backgrounds. The distributed representations of the patient backgrounds were generated by the skip-gram model. To confirm the performance improvement with the proposed data augmentation method, the prediction performance of adverse events (AEs) caused by drug administration was experimentally evaluated on a real-world medical dataset with 1,510,137 records. The combination of the proposed data augmentation method and a conventional undersampling method resulted in an 80.0% improvement in accuracy and a 40.0% improvement in the precision and F1-score. The multifaceted evaluation demonstrated that the proposed method is effective, especially for predicting AEs with positive ratios ranging from 1.0% to 2.1%, which are difficult to predict with conventional machine learning methods but should be predictable in the medical field.

Access to Document (DOI)

Saliency Prediction based on Object Recognition and Gaze Analysis

Ishikawa T., Yakoh T.

IEEJ Transactions on Electronics, Information and Systems (IEEJ Transactions on Electronics, Information and Systems) 141 ( 1 ) 76 - 84 2021.01

ISSN 03854221

Predicting the human visual attention in an image is called saliency prediction, and is an active research area in the field of neuroscience and computer vision. Early works on saliency prediction was performed by using low-level features. In recent years, convolutional neural networks (CNN) have been adapted for saliency prediction and achieved the state-of-the-art performance. However, the eye-gaze depends on the personality of each viewer and conventional methods did not take into account such individual properties of the viewer. Therefore, this paper proposes a novel saliency prediction method considering the influence of eye-gaze. Assuming that personality can be expressed as the degree of attention to an object, our proposed method considers the personality by learning which objects are likely to be perceived by each viewer, and weighting the universal saliency map with the generated mask based on the object detection results. The experimental results show that the proposed universal saliency map achieves higher accuracy than conventional methods on the public dataset, and the proposed weighted saliency map can reflect the variation of the eye-gaze influences among viewers. (1)

Access to Document (DOI)

Saliency prediction based on object recognition and gaze analysis

Ishikawa T., Yakoh T.

Electronics and Communications in Japan (Electronics and Communications in Japan) 2021

ISSN 19429533

Predicting the human visual attention in an image is called saliency prediction and is an active research area in the field of neuroscience and computer vision. Early works on saliency prediction was performed by using low-level features. In recent years, convolutional neural networks have been adapted for saliency prediction and achieved the state-of-the-art performance. However, the eye-gaze depends on the personality of each viewer and conventional methods did not take into account such individual properties of the viewer. Therefore, this paper proposes a novel saliency prediction method considering the influence of eye-gaze. Assuming that personality can be expressed as the degree of attention to an object, our proposed method considers the personality by learning which objects are likely to be perceived by each viewer and weighting the universal saliency map with the generated mask based on the object detection results. The experimental results show that the proposed universal saliency map achieves higher accuracy than conventional methods on the public dataset, and the proposed weighted saliency map can reflect the variation of the eye-gaze influences among viewers.

Access to Document (DOI)

A precise time synchronization method for real-time schedulers

Kikutani T., Yakoh T.

Electronics and Communications in Japan (Electronics and Communications in Japan) 101 ( 12 ) 21 - 29 2018.12

ISSN 19429533

This paper proposed a precise time synchronization method between schedulers of real-time operating systems by communicating time stamps over a network. An NTP-based communication protocol was used to measure the time offset between nodes. To minimize the measurement error, a light-weight network stack called RT-Messenger was used instead of common transmission control protocol/Internet protocol (TCP/IP) stack. Also, a Kalman filter was introduced to eliminate such error and to estimate time offset and drift. Furthermore, a real-time scheduler in RTAI/Linux (where RTAI is real-time application interface) was modified to compensate the time difference using the estimated offset and drift. The time compensation of a scheduler clock affects the next resume times for real-time tasks. Therefore, a recalculation process of next resume times for all real-time tasks and a reordering process of real-time task queue were added to the real-time scheduler. To validate the proposed method, time differences of resume times for two real-time tasks on different nodes were measured under various experimental conditions. The results confirm that the resume time differences were successfully kept lower than 400 ns with 300 ns standard deviation under the condition of observation period at 1 s and correction period at 10 s.

Access to Document (DOI)

Frame transmission time control for TDMA-based ethernet

Hagino N., Yamamoto M., Yakoh T.

IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS (IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS) 2018-June 1 - 8 2018.07

Processes of network-based control system require accurate timing control of frame transmission. A special network interface card (NIC) was proposed and implemented to adjust the timing accurately based on a dual queue structure and precise time synchronization mechanism in this paper. A high resolution measurement tool for frame transmission latency was also developed to validate the implementation. The measured results verified that the proposed NIC achieved the latency shorter than 790 ns and the deviation of it less than 49 ns while a commercial off-the-shelf NIC showed the latency longer than 9700 ns and the deviation of it more than 300 ns.

Access to Document (DOI)

Position and Velocity Measurement Method from a Single Image using Modulated Illumination

Kentaro Matsuo, YAKOH TAKAHIRO

International Workshop on Advanced Motion Control, AMC (Proceedings - 2018 IEEE 15th International Workshop on Advanced Motion Control, AMC 2018) 353 - 358 2018.03

Research paper (international conference proceedings), Joint Work, Accepted

Visual feedback systems utilize position and velocity information estimated from frames captured by a camera. Since the velocity information is derrived through pseudo differential with two consecutive frames, the information must be delayed essentially, and the delay often limits the performance of visual feedback systems. To eliminate the delay, this paper proposed a novel technique to estimate position and velocity information from a single image. By detecting the start and end points of the motion blur of a target object in an image, the velocity information during the exposure time of the image can be estimated fundamentally. To tag such a temporal information on motion blurs, a modulated illumination was employed. This tagging method aimed to make motion blur detection robust against various background scenery. Some simulation results validated the feasibility of the proposed method.

Access to Document (DOI)

Implementation of Schedule Management Mechanism for S-TDMA Switch

Syunpei Koyasu, YAKOH TAKAHIRO

International Workshop on Advanced Motion Control, AMC (Proceedings - 2018 IEEE 15th International Workshop on Advanced Motion Control, AMC 2018) 575 - 580 2018.03

Research paper (international conference proceedings), Joint Work, Accepted

Recently, because of the development of industrial systems and network systems, the demands of telehaptics and telesurgery become higher. To realize these systems, a real-time communication which can guarantee deterministic delays and low jitters in a network is required. One of the real-time protocol is Synchronous-Time Division Multiple Access (S-TDMA). S-TDMA makes it possible to coexist of real-time and conventional TCP/IP communications over a multiple-hop network using Ethernet. In previous works, the schedule of real-time combinations was fixed. So this research introduces management mechanism of communication schedules by using the technology of Software Defined Networking (SDN). SDN is a notion to realize a dynamic and centralized control of network configuration by using one controller which can manage all equipments in the network. In this paper, the design and implementation of management mechanism of S-TDMA switches are discussed and performance of the implemented switches is verified. The experiment results confirm that it is possible to change time slot allocation, communication mode and paths dynamically. Results also show that the management system can control multiple switches in the network.

Access to Document (DOI)

A precise time synchronization method for real-time schedulers

Kikutani T., Yakoh T.

IEEJ Transactions on Electronics, Information and Systems (IEEJ Transactions on Electronics, Information and Systems) 138 ( 6 ) 695 - 702 2018

ISSN 03854221

This paper proposed a precise time synchronization method between schedulers of real-time operating systems by communicating timestamps over a network. An NTP based communication protocol was used to measure the time offset between nodes. To minimize the measurement error, a light-weight network stack called RT-Messenger was used instead of common TCP/IP stack. Also, a Kalman filter was introduced to eliminate such error and to estimate time offset and drift. Furthermore, a real-time scheduler in RTAI/Linux was modified to compensate the time difference using the estimated offset and drift. The time compensation of a scheduler clock affects the next resume times for realtime tasks. Therefore, a re-calculation process of next resume times for all real-time tasks and a re-ordering process of reak-time task queue were added into the real-time scheduler. To validate the proposed method, time differences of resume times for two real-time tasks on different nodes were measured under various experimental conditions. The results confirm that the resume time differences were successfully kept lower than 400 ns with 300 ns standard deviation under the condition of observation period at 1 s and correction period at 10 s.

Access to Document (DOI)

A stochastic performance estimation method for wireless multi-hop network

Mori Shizuna, Yakoh Takahiro

IEEJ Transactions on Electronics, Information and Systems 137 ( 5 ) 701 - 708 2017.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 0385-4221

M2M (machine-to-machine) is required and spreads rapidly in recent years. Wireless multi-hop communication is one of the communication styles to construct M2M. However, the performance estimation of such wireless multi-hop communication is not so easy because the bit error ratio and symbol rate adaptation heavily depend on various environmental conditions. Stochastic network calculus (SNC) is a theory for the performance estimation of network. However, current SNC lacks ways to take wireless random errors, branching and joining of traffic flows into calculation, these are necessary to estimate the performance of sink-tree wireless-sensor network. This paper proposed a performance estimation method for sink-tree wireless multi-hop network based on SNC. The proposed method has three attractive points. Firstly, this introduces parameters of hop number and node number considering wireless random error due to packet collision. Secondly, this treats actual sink-tree network model by considering joining of traffic. Thirdly, this separates the service curve and bounding function calculation to avoid double counting. To evaluate the accuracy of the result of the proposed method, conventional estimation methods and simulation evaluation were conducted on a typical wireless multi-hop sensor data collection network. The results validate that the proposed method achieves much higher-accuracy than conventional methods.

Access to Document (DOI)

Integration of Existing Ethernet Devices into Time-Division Multiplexing Ethernet

YAMAMOTO YOSHIAKI, YAKOH TAKAHIRO

Proc. of IEEE International Conference on Industrial Technology 1171 - 1176 2017.03

Research paper (international conference proceedings), Joint Work, Accepted

Performance Evaluation of TCP/IP over Time-Division Multiplexing Ethernet

OTAWARA KANA, MASAAKI YAMAMOTO, YAKOH TAKAHIRO

International Conference on Industrial Electronics, Control and Instrumentation 4695 - 4700 2016.10

Research paper (international conference proceedings), Joint Work

Selective Sending Block Determination Method Based on Quad-Tree Structure for Live Video Streaming System

Ning Zhang, YAKOH TAKAHIRO

情報処理学会第78回全国大会講演論文集 3 279 - 280 2016.03