• ETRI Journal
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• 제37권6호
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• pp.1096-1107
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• 2015

This paper presents a dynamic retry adaptation scheme for H.264 HD video, called DRAS.264, which dynamically adjusts the retry limits of frames at the medium access control (MAC) layer according to the impact those frames have on the streamed H.264 HD video. DRAS.264 is further improved with a bandwidth estimation technique, better prediction of packet delays, and expanded results covering multi-slice video. Our study is performed using the Open Evaluation Framework for Video Over Networks as a simulation environment for various congestion scenarios. Results show improvements in average peak signal-to-noise ratios of up to 4.45 dB for DRAS.264 in comparison to the default MAC layer operation. Furthermore, the ability of DRAS.264 to prioritize data of H.264 bitstreams reduces error propagation during video playback, leading to noticeable visual improvements.

• Journal of Power Electronics
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• 제1권2호
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• pp.107-116
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• 2001

Two AC-DC PWM full-bridge converters that can input current to improve input power factor while performing dc-dc conversion are investigated in this paper. Both converters are simple in that they are similar to the standard PWM full-bridge converter with a diode rectifier/LC low-pass filter input, and both can operate with a simple method of PWM control. In the paper, the operation of the converters is explained and their steady-state characteristics are discussed. The feasibility of the converters and their ability to meet EN61000-3-2 Class D Standards for electrical equipment are shown with results obtained from experimental prototypes. The performance of both converters in terms of dc bus voltage level, input power factor and efficiency is compared and discussed.

• International Journal of Computer Science & Network Security
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• 제22권10호
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• pp.201-206
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• 2022

The main purpose of the study is to analyze the features of innovation and project management in the system of improving the performance of personnel as a factor in ensuring competitiveness and investment security. For the successful operation of enterprises, regardless of their form of ownership and field of activity, in order to carry out effective activities, they turn to innovative methods related to the formation of the potential of the workforce, and increasing the level of education and qualifications of staff and establishing their potential ability to make independent decisions. Based on the results of the study, the key features of innovation and project management in the system of improving the performance of personnel as a factor in ensuring competitiveness and investment security are characterized.

• 융합정보논문지
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• 제11권5호
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• pp.23-29
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• 2021

최근 글로벌 플랫폼 서비스사업자가 제공하는 플랫폼 서비스의 장애로 전 세계적으로 특정 콘텐츠 서비스가 불가한 상황이 발생하고, 글로벌 서비스 시장에 사회 경제적으로 상당히 큰 문제를 초래하고 있다. 플랫폼 서비스의 안정성 확보를 위해서는 지능화된 플랫폼 운용 관리가 요구된다. 또한, 플랫폼 장애를 사전에 예방하고 대응할 수 있는 지능형 관리 기술이 필요하다. 본 연구에서는 플랫폼 운용 환경에서 비정상적인 서비스 상태 및 장애를 신속하게 감지 대응하기 위한 플랫폼 빅데이터 플로우 관리 기법 및 관리 모듈 구현 방안을 제안하였다. 서비스 및 장애 상황 감시 특성 분석 결과 빅데이터 플로우 관리 기법이 장애 감시 측면에서 전통적인 네트워크 관리 방법에 비하여 비정상적인 장애 상황 감지 및 장애 대응 특성이 30%이상 개선됨을 확인하였다. 빅데이터 플로우 관리 방법의 경우 플랫폼 시스템 장애 및 비정상적인 서비스 상태를 신속하게 감지할 수 있는 장점이 있으며 AI 기반 기술과 연계시 플랫폼 관리를 지능적으로 수행하고 장애 예방보전 능력은 크게 향상될 수 있을 것으로 기대된다.

• International Journal of Computer Science & Network Security
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• 제22권2호
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• pp.232-240
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• 2022

To fulfill user expectations, the rapid evolution of software techniques and approaches has necessitated reliable and flawless software operations. Aging prediction in the software under operation is becoming a basic and unavoidable requirement for ensuring the systems' availability, reliability, and operations. In this paper, an improved evolutionary computing-driven extreme learning scheme (ECD-ELM) has been suggested for object-oriented software aging prediction. To perform aging prediction, we employed a variety of metrics, including program size, McCube complexity metrics, Halstead metrics, runtime failure event metrics, and some unique aging-related metrics (ARM). In our suggested paradigm, extracting OOP software metrics is done after pre-processing, which includes outlier detection and normalization. This technique improved our proposed system's ability to deal with instances with unbalanced biases and metrics. Further, different dimensional reduction and feature selection algorithms such as principal component analysis (PCA), linear discriminant analysis (LDA), and T-Test analysis have been applied. We have suggested a single hidden layer multi-feed forward neural network (SL-MFNN) based ELM, where an adaptive genetic algorithm (AGA) has been applied to estimate the weight and bias parameters for ELM learning. Unlike the traditional neural networks model, the implementation of GA-based ELM with LDA feature selection has outperformed other aging prediction approaches in terms of prediction accuracy, precision, recall, and F-measure. The results affirm that the implementation of outlier detection, normalization of imbalanced metrics, LDA-based feature selection, and GA-based ELM can be the reliable solution for object-oriented software aging prediction.

• 한국멀티미디어학회논문지
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• 제24권4호
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• pp.569-582
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• 2021

Education emphasizes problem-solving skills based on convergent thinking power in an era of rising uncertainty and rapid progress. This paper proactively designed e-Learning team teaching convergence liberal arts courses for prospective teachers by these social needs. It analyzed the empirical effects on the operation of the subjects to foster future talent who can converge and apply knowledge in various fields. The curriculum consisted of professors of mathematics, practical Arts, computer, and education, and was operated to convey convergent knowledge of information technology and humanities, and consisted of 15 liberal arts courses at J University. Besides, textbooks and teaching materials were also developed by the faculty. As a result of the primary research, prospective teachers who took the course generally showed high satisfaction with the class, especially for the faculty. The students' overall convergent thinking ability has increased to a statistically significant level (p<.01), and the students' major has been found to be irrelevant. On the other hand, it can be seen that communication, content convergence, and caring factors, excluding creativity factor, have all risen to a significant level.

• 한국정보처리학회논문지
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• 제7권12호
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• pp.3944-3951
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• 2000

본 논문에서는 비화특성을 가진 새로운 FEC(Forward Error Correction) 부호기법으로 RCNC (Random Connection Node Convolutional) 부호화방식을 소개한다. 최근의 무선통신시스템은 다양한 멀티미디어 데이터 서비스를 하고 있다. 이러한 시스템은 전송 중 발생한 오류에 대한 정정 능력과 더불어 인증 사용자의 접근에 대한 비화 특성이 중요시된다. 이러한 문제를 해결하기 위한 방안으로 RCNC 부호화 방식은 전송 중 발생한 에러에 대한 오류 정정 기능을 가지면서, 전송데이터에 대한 비화성질을 부가하여 허용된 사용자 이외에는 접근이 불가능하도록 하는 암호화 특성을 가진다는 점이다. 본 논문에서는 RCNC 부호화 기법의 동작과 특성을 설명하고 있으며, 또한 컴퓨터 시뮬레이션을 이용하여 에러 정정 능력과 사용자 접근 허용정도를 검증하였다.

• 융합신호처리학회논문지
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• 제22권3호
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• pp.110-115
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• 2021

4차 산업혁명 시대가 도래하면서 인공지능에 대한 교육이 활발하게 진행되고 있다. 그러나 기존의 강의식 교육은 지식의 전달을 목적으로 두고 있어 인공지능 분야에서 요구하는 능동적인 문제해결 능력과 인공지능 활용능력을 기르는 데 어려움을 겪는다. 본 논문에서는 이를 해결하기 위해 학습자가 제시된 문제를 해결하는 과정에서 학습이 이루어지는 문제 중심학습 기반 교육 방안을 제안한다. 학습자들에게 제공되는 문제는 완성된 하나의 프로젝트이다. 이 프로젝트는 3가지 종류로 구성된다. 분류 모델, 분류 모델의 학습 데이터, 분류된 결과에 따라 실행될 블록 코드. 해당 프로젝트는 동작은 하지만 각각의 구성요소들이 낮은 동작 수준을 보이도록 설계되어 있다. 이를 해결하기 위해 학습자들은 테스팅을 통해 프로젝트의 문제점을 찾고 토론을 통해 해결책을 찾아 좀 더 높은 동작 수준으로 개선하는 과정을 거치며 컴퓨팅 사고력 향상을 기대할 수 있다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.625-631
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• 2002

In the previous study, a polishing robot system was developed to automate the polishing process and to cope with the shortage of skilled workers. This polishing robot system has several advantages: reduced time for setting polishing work, decreased labor costs, effective operation, continuous polishing work without an operator, improved machine accuracy, and the ability to polish a free curved surface die. However, still the problem remains that a worker must stay to monitor the polishing process in the poor working conditions for a long time. Nowadays some advanced manufacturing companies need to find a way to check the performance of their production equipments and plants from remote sites. Thus, this study constructed the communication network and developed the monitoring programs (a servo program and a client program) to operate the polishing robot from remote sites. Using these programs, workers are able to monitor and control the polishing robot on the web page, in any place where internet service is possible. To guarantee a stable operation in spite of a variable computer operating environment, the monitoring system is implemented in Java. The experimental results showed that the developed monitoring programs provided a stable communication.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.588-590
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• 1994

This paper describes current controlled PWM technique of IPM synchronous motors for a wide variety of speed control applications. The IPM synchronous motors have a saliency, in which the q-axis inductance is larger than the d-axis inductance. As a consequence, there exists a reluctance torque component Thus when this component is added to the torque component produced by the stator currents and the air-gap flux, IPM motor drives are readily applicable where full torque Is required up to full or base speed. They are however limited in their ability to operate in the power limited regime where the available torque is reduced as the speed is increased above its base value. This paper reviews the operation of the IPMSM drives when they are constrained to be within the permissible envelope of maximum inverter voltage and current to produce the rated power and to provide this with the highest attainable rotor speed. The wide variety of speed control strategy is analyzed and the performance is investigated by the computer simulation using actual parameters of a drive system. Simulation results are given and discussed.