• Journal of Korea Multimedia Society
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• v.16 no.10
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• pp.1189-1195
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• 2013

In this paper, we are going to describe the performance characteristic of very high resolution image processing with WebCL on the web environment. In order to evaluate the variance of the execution time by WebCL, we modified the Pixastic library, one of the most representative image processing libraries written in JavaScript, by using WebCL. We achieved a speedup of up to 4.2 times and 2.8 times on average against the original one for the image of 8K Ultra HD with the WebCL-based library.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.2
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• pp.59-70
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• 2017

Since GPS signals are vulnerable to interference and obstruction, many alternate aiding systems have been proposed to integrate with an inertial navigation system. Among these alternate systems, the vision-aided method has become more attractive due to its benefits in weight, cost and power consumption. This paper proposes a loosely-coupled vision/INS integrated navigation method which can work in GPS-denied environments. The proposed method improves the navigation accuracy by correcting INS navigation and sensor errors using position and attitude outputs of a landmark based vision navigation system. Furthermore, it has advantage to provide redundant navigation output regardless of INS output. Computer simulations and the van tests have been carried out in order to show validity of the proposed method. The results show that the proposed method works well and gives reliable navigation outputs with better performance.

• Journal of Communications and Networks
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• v.15 no.5
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• pp.538-542
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• 2013

This paper proposes a broadcast software download (BSD) scheme for a 10-gigabit-capable passive optical network (XG-PON), which dramatically reduces the time required to update a remotely-located user terminal's software. The performance of the proposed BSD is examined by numerical analysis and demonstrated by experimental verification on our XG-PON test platforms. The results show that the BSD takes less than 5 minutes to update 45 user-terminal software, while the conventional unicast software download scheme normally takes more than one and half hours.

• Phonetics and Speech Sciences
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• v.8 no.3
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• pp.31-38
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• 2016

Speech inversion (acoustic-to-articulatory mapping) is not a trivial problem, despite the importance, due to the highly non-linear and non-unique nature. This study aimed to investigate the performance of Deep Neural Network (DNN) compared to that of traditional Artificial Neural Network (ANN) to address the problem. The Wisconsin X-ray Microbeam Database was employed and the acoustic signal and articulatory pellet information were the input and output in the models. Results showed that the performance of ANN deteriorated as the number of hidden layers increased. In contrast, DNN showed lower and more stable RMS even up to 10 deep hidden layers, suggesting that DNN is capable of learning acoustic-articulatory inversion mapping more efficiently than ANN.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.5
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• pp.337-345
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• 2016

Recently, as the number of cores in computer systems has increased, the need for larger memory capacity has also increased. Unfortunately, dynamic random access memory (DRAM), popularly used as main memory for decades, now faces a scalability limitation. Phase change memory (PCM) is considered one of the strong alternatives to DRAM due to its advantages, such as high scalability, non-volatility, low idle power, and so on. However, since PCM suffers from short write endurance, direct use of PCM in main memory incurs a significant problem due to its short lifetime. To solve the lifetime limitation, many studies have focused on reducing the number of bit flips per write request. In this paper, we describe the PCM operating principles in detail and explore various bit flip reduction schemes. Also, we compare their performance in terms of bit reduction rate and lifetime improvement.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.302-303
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• 2015

이 논문은 빅데이터 활용을 위한 Cloud computing 기반 전력 시스템 해석을 위한 조류계산 알고리즘을 개발하고자 한다. 하지만 컴퓨터 연산 속도의 빠른 발전으로 이미 기존 조류계산 알고리즘을 이용하여 전력 시스템을 해석하는데 많은 시간이 소요되지 않는다. 그럼에도 불구하고 우리는 계통이 안전하게 운영될 수 있도록 하기 위해 다양한 상정고장을 고려하여 계통 해석을 해야 하며 또한 해석 결과와 그 원인과의 상관관계를 분석하기에는 많은 어려움이 있는 실정이다. 이에 본 논문에서는 Cloud computing을 이용하여 빅데이터 기반 조류계산 알고리즘을 구현하고자 한다. 본 논문에서 제안하는 빅데이터 기반 조류게산 알고리즘 기반 계통 해석시 중간에 파생되는 결과나 최종 결과 등의 분석을 통해 보다 효율적이고 안정한 계통 운영에 기여할 수 있을 것이다.

• Journal of Applied Reliability
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• v.15 no.3
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• pp.181-191
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• 2015

Change in labor time is affecting occupational safety and health. Recently reduction in labor time brought innovational operation method, investment in plant and equipment, and flexible labor time in some companies, thereby affecting working conditions for labourers. However, working conditions for some vulnerable social groups have deteriorated. As a result, they are becoming more exposed to risk factors such as injury and emotional stress. In this study we use 2014 KWCS data in order to find the social and demographic characteristics in Korean working conditions. To this end, we use exploratory data analysis approach to find the relationship between some of the important variables in the KWCS data. We also use Press-State-Response model to find which group of people are vulnerable to Press and State. We find that women, people over age 50 and business owners are more vulnerable to Press and State than men, people below age 50 and wage workers.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.113-116
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• 2000

Phase noise of oscillator gives the performance degradation significantly when a high carrier frequency and low transmission rate are used. The BER(Bit Error Rates) degradation of QPSK(Quadrature Phase Shift Keying) transmission is analyzed with the oscillator phase noise level specified in downstream physical interface of LMDS(Local Multipoint Distribution Services) which is described in DAVIC(Digital Audio Visual Council). The model used for the phase noise is a power-law model. We also investigated the effects of the various transmission rates on system performance. For the transmission rate below 0.5 Mbps, the BER performance is severely degraded and we verified that the transmission rate, 20 Mbps, is adequate for the downstream of LMDS systems.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1681-1684
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• 2002

A multilevel modulation with selectable constellations is adopted in the downlink subframe modulation of the IEEE 802.16 standard to increase the total throughput. One of the decision factors of the modulation is the location of SS(Subscriber Station) . Also, for the 802.16, low phase noise of local oscillator is needed due to high operating frequency and severe loss in the propagation channel. We investigate the BER of down-link subframe with the phase jitter under the standard's specified LOS(line of sight) and multipath environment with randomly generated SS locations. Simulation results show BER performance degradation for the modulation corresponding to selected constellations and additionally required SNR to achieve 10$\^$-3/ BER under various phase jitter.

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.07a
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• pp.167-170
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• 2012

본 연구에서는 언플러그드를 활용한 컴퓨터 과학 교육의 연구 동향을 파악하고, 앞으로의 연구 방향을 제시하고자 한다. 이를 위해 2012년 5월까지 발행된 석사학위논문과 학술지 논문, 총 33편을 대상으로 연도별 논문 발행 수, 연구 대상, 연구 영역에 따라 분석을 실시하고, 연구주제에 따라 구체적인 연구 사례를 살펴보았다. 그 결과, 연도별 논문 발행 수는 증가 추세에 있으며, 초등학생을 대상으로 한 연구가 집중적으로 이루어졌다. 연구 영역에서 알고리즘에 대한 연구가 많았으며, 연구 주제로는 언플러그드 학습의 교육적 효과, 언플러그드 수업 설계 등이 있었다. 지금까지 연구 결과를 바탕으로, 향후 다양한 학교급과 학생유형을 대상으로 컴퓨터 과학의 여러 영역에서 그 교육적 목적을 효과적으로 반영할 수 있는 연구가 이루어져야 할 것이다.