• Journal of the Korea Society of Computer and Information
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• v.26 no.4
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• pp.39-46
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• 2021

In this paper, we propose a method for the motion recognition method required in the industrial field in mixed reality. In industrial sites, movements (grasping, lifting, and carrying) are required throughout the upper full-body, from trunk movements to arm movements. In this paper, we use a method composed of sensors and wearable devices that are not vision-based such as Kinect without using heavy motion capture equipment. We used two IMU sensors for the trunk and shoulder movement, and used Myo arm band for the arm movements. Real-time data coming from a total of 4 are fused to enable motion recognition for the entire upper body area. As an experimental method, a sensor was attached to the actual clothes, and objects were manipulated through synchronization. As a result, the method using the synchronization method has no errors in large and small operations. Finally, through the performance evaluation, the average result was 50 frames for single-handed operation on the HoloLens and 60 frames for both-handed operation.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.797-802
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• 2023

In an environment where English is a foreign language, English learners can use AI voice chatbots in English-speaking practice activities to enhance their speaking motivation, provide opportunities for communication practice, and improve their English speaking ability. In this study, we propose a teaching-style AI voice chatbot that can be easily utilized by lower elementary school students and enhance their learning. To apply the Teachable Agent system to language learning, which is an activity based on tense, context, and memory, we proposed a new method of TA by applying the Teachable Agent to reflect the learner's English pronunciation and level and generate the agent's answers according to the learner's errors and implemented a Teachable Agent AI chatbot prototype. We conducted usability evaluations with actual elementary English teachers and elementary school students to demonstrate learning effects. The results of this study can be applied to motivate students who are not interested in learning or elementary school students to voluntarily participate in learning through role-switching.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.10
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• pp.1264-1274
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• 1999

본 논문에서는 분산된 클록들을 주기적으로 동기화 시키는 분산 실시간 시스템에서 시간적 제약을 만족시키기 위한 정적/동적 시간 제약(timing constraint) 변환 기법을 제안한다. 전형적인 이산클록동기화(discrete clock synchronization) 알고리즘은 클록의 값을 순간적으로 조정하여 클록의 시간이 불연속적으로 진행한다. 이러한 시간상의 불연속성은 시간적 이벤트를 잃어버리거나 다시 발생시키는 오류를 범하게 한다.클록 시간의 불연속성을 피하기 위해 일반적으로 연속클록동기화(continuous clock synchronization) 기법이 제안되고 있지만 소프트웨어적으로 구현되면 많은 오버헤드를 유발시키는 문제점이 있다. 본 논문에서는 시간적 제약을 동적으로 변환시키는 DCT (Dynamic Constraint Transformation) 기법을 제안하였으며, 이를 통해 기존의 이산클록동기화 알고리즘을 수정하지 않고서도 클록 시간의 불연속성에 의한 문제점들을 해결할 수 있도록 하였다. 아울러 DCT에 의해 이산클록동기화 하에서 생성된 태스크 스케쥴이 연속클록동기화에 의해 생성된 스케쥴과 동일함을 증명하여 DCT의 동작이 이론적으로 정확함을 증명하였다.또한 분산 실시간 시스템에서 지역 클록(local clock)이 기준 클록과 완벽하게 일치하지 않아서 발생하는 스케쥴링상의 문제점을 다루었다. 이를 위해 먼저 두 가지의 스케쥴링 가능성, 지역적 스케쥴링 가능성(local schedulability)과 전역적 스케쥴링 가능성(global schedulability)을 정의하고, 이를 위해 시간적 제약을 정적으로 변환시키는 SCT (Static Constraint Transformation) 기법을 제안하였다. SCT를 통해 지역적으로 스케쥴링 가능한 태스크는 전역적으로 스케쥴링이 가능하므로, 단지 지역적 스케쥴링 가능성만을 검사하면 스케쥴링 문제를 해결할 수 있도록 하였고 이를 수학적으로 증명하였다.Abstract In this paper, we present static and dynamic constraint transformation techniques for ensuring timing requirements in a distributed real-time system possessing periodically synchronized distributed local clocks. Traditional discrete clock synchronization algorithms that adjust local clocks instantaneously yield time discontinuities. Such time discontinuities lead to the loss or the gain of events, thus raising serious run-time faults.While continuous clock synchronization is generally suggested to avoid the time discontinuity problem, it incurs too much run-time overhead to be implemented in software. We propose a dynamic constraint transformation (DCT) technique which can solve the problem without modifying discrete clock synchronization algorithms. We formally prove the correctness of the DCT by showing that the DCT with discrete clock synchronization generates the same task schedule as the continuous clock synchronization.We also investigate schedulability problems that arise when imperfect local clocks are used in distributed real-time systems. We first define two notions of schedulability, global schedulability and local schedulability, and then present a static constraint transformation (SCT) technique. The SCT ensures that it is sufficient to check the schedulability of a task locally in a node with a local clock, since the global schedulability of the task is derived from its local schedulability through SCT. We formally prove the correctness of SCT.

• Korean Journal of Culture and Social Issue
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• v.14 no.2
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• pp.63-81
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• 2008

Hasteful behavior means choosing the best suited methods while behaving fast and quickly. We can't conclude whether hasteful behavior is totally bad or good. Striving for achievement of own certain purpose reflects achievement motivation or need for achievement. However, this striving also has potentiality of missing confirmation, therefore the potentiality may cause errors. The aim of this study is to investigate the psychological structure and characteristic of the hasteful behavior. One hundred ninety-one students conducted Hasteful Behavior Questionnaire, Achievement Motivation Measuring Scale, and NEO Personality Inventory. We analyzed data of 188 respondents, because of missing value. The result of factor analysis showed that hasteful behavior consisted of 5 factors- 「Uncomfortableness」, 「Time Pressure」, 「Isolation」, 「Boring Condition」, and 「Expecting Rewards」. According to correlations among the hasteful behavior factors and the relationship between hasteful behavior and achievement motivation, we found that hasteful behavior had two aspects, one was "Missing Confirmation(MC)" and the other was "Need for Achievement(NA)". We also found that 「Time Pressure」 was related to the both aspects. MC had a positive relation to Neuroticism, whereas MC correlated negatively with Conscientiousness. On the other hand, NA had a positive relationship with Extraversion and Achievement Striving.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1329-1340
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• 2016

Recently, Zhang proposed a scheme to hide information in encrypted images using synchronous stream ciphers. After the receiver decrypts the encrypted image and extracts data by calculating the spatial correlation property value using the fluctuation function which is designed to calculate spacial correlation between adjacent pixels in a decrypted image. Then, Hong improved the Zhang's data hiding scheme by introducing the side match technique. In this paper, a novel fluctuation function is proposed to reduce the recovery errors which arise during extracting hidden data. Then, we also demonstrated that the proposed fluctuation function outperforms the previous functions through computer simulations for sample images.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.109-114
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• 2009

An orthogonal frequency division multiplexing(OFDM) system is effective to bandwidth because of orthogonality of subcarriers and robust to multipath fading. However, if there is a frequency offset, we lose the orthogonality of subcarriers and that results in inter-carrier interference(ICI) which increases errors in the system. In this paper, we propose an algorithm that estimates the fine frequency offset using a correlation method in OFDM systems. This scheme compares two correlation values in different frequency offsets with opposite directions. From the difference between two correlation values we can derive a fine frequency offset estimation algorithm. Its performance is verified by computer simulations.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.211-216
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• 2012

Such as disaster rescue in deep water, undersea exploration and monitering for environmental pollution, many applications require the acoustic communication for high data rate over underwater acoustic channel. As underwater channel is very complex and is time-varying, In this paper, The proposed OFDM system with synchronization errors and multipath delay spread is analyzed for high data rate and reliability and rubust service over UWA channels.

• Journal of Korea Society of Industrial Information Systems
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• v.6 no.1
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• pp.15-23
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• 2001

In this paper, we propose a system to cancel the multi-user interference of synchronous BPSK DS/CDMA systems. In this CDMA scheme, the spectrum of the user's signal is directly spread by means of the Simplex code or the phase offsetted PN code. But in arbitrary bit interval, we use the one spreading code of the Simplex code and the phase offsetted PN code. The receiver cancel the multi-user interference and demodulate information bits by using reference correlator. This paper presents a interference cancellation model and analyzes this system mathematically. The suggested system show that the interference resulting from other users are remarkably reduced. In AWGN and Nakagami fading environment we analyze interference generated from other users and compare the resulting performance with that of the conventional receiver in same user side.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.593-596
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• 2007

웹데브(WebDAV)는 분산 저작활동을 지원하기 위한 IETF의 표준 프로토콜로서 원거리 사용자들 간의 비동기적인 저작활동을 지원하며, 웹데브 서버에 등록된 자원에 대하여 속성을 관리하고 접근을 제어할 수 있는 웹데브 메소드와 웹데브 접근제어 프로토콜을 이용하여 웹데브 서버를 다양한 방법으로 확장할 수 있다. 본 논문에서는 웹데브 표준 프로토콜과 접근제어 프로토콜을 이용하여 강좌관리 시스템을 설계한다. 강좌관리 시스템에서 사용되는 웹데브 기반 서버는 Apache 그룹의 Jakarta Slide 서버를 확장하였으며 클라이언트는 KDE 기반의 리눅스에서 동작하도록 설계하였다. 강좌관리 시스템은 HTTP 프로토콜 기반의 응용프로그램으로서 인터넷이 연결되어 있는 어떠한 곳에서라도 사용할 수 있으며 분산저작이 가능한 웹데브 서버의 특성을 살려서 웹상에서 자유로운 자원 교환을 지원한다. 또한 일반적인 강좌관리 시스템에서 사용하는 출석등록, 보고서 제출, 강의 자료 제공 등의 기본 기능을 웹데브 서버가 지원하는 기능을 이용하여 설계하며, 교수와 학생 각자의 역할에 맞는 인터페이스를 제공하여 인터페이스에서 발생할 수 있는 오류를 줄이고 사용자 중심의 인터페이스로 설계하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.3
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• pp.91-98
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• 2015

As one of solutions to obtain efficient use of limited spectrum resource, we suggest a methodology for the co-channel multi-site radar operations with a shifted linear frequency modulation (SLFM) based on GPS clock. The proposed algorithm is that we find a candidate set of SLFM signals with the minimum acceptable level of the correlation from the cross-correlation characteristics among selected SLFM signals. To verify the proposed methodology, numerical analysis has been accomplished for several radars operating in the same channel with a sawtooth or triangle LFM signal. The computational results of detected distances as well as range profiles are also examined for interference, noise, and algorithm limitation including the error of clock synchronization.