• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.109-114
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• 2013

In underwater wireless sensor networks, sensing data such temperature and salinity can be merged by averaging them. Data aggregation is a good choice to reduce the amount of packets and save energy in underwater wireless sensor networks. However, data aggregation could bring about packet delay and non-directional transmission to the sink. In this paper, we propose a new path building algorithm based on data aggregation to mitigate these problems. The paper reduces the delay without wireless interferences and maximizes the energy efficiency by removing the non-directional transmission to the sink. Experimental results show that the proposed algorithm outperforms in terms of the energy efficiency and the packet delay.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.108-116
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• 2001

In this paper, statistical properties of waves in the sea area of Mara-do, Korea are examined based on 1998-1999's wave data from a directional wave buoy which is located in Mara-do. Wave data aquisition rate, monthly maximium, minimum and mean wave heights, frequency of wave direction are summarized. Wave height and period scatter diagrams and n-year return period wave heights are estimated. Wave periods of maximum wave heights are also estimated.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.309-316
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• 2003

In this paper, The statistical properties of ocean waves in the sea area of Hong-do, Korea are examined based on 1998-2002's wave data from a directional wave buoy. Wave data aquisition rate, mean wave heights, frequency of wave direction are summarized. Wave height and period scatter diagrams and n-years return period wave heights are estimated. Wave periods of maximum wave heights are also estimated. Large amplitude wave characteristics during the typhoon Prapiroon in 2000, Rusa in 2002 are also examined.

• Proceedings of the Korea Contents Association Conference
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• 2004.11a
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• pp.296-301
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• 2004

The Wireless Sensor Network is technology that makes possible utilize the information collected from rescue, the agricultural and livestock management system, and the home automation system by using an ultra-small sized, ultra-lightweight sensor module. This study proposes the routing protocol with directional nature that can improve the utilization by higher energy efficiency and reliability than those of existing studies on data transmission, and we also analyze the current studies, make a comparison of them in performance.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.2
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• pp.268-274
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• 2010

A steganographic method using three directional data embedding for gray images is presented in this paper. Cover image is divided into non-overlapping $2\times2$ sub-blocks and the basis pixel is selected to calculate the three different values of each sub-block. Difference values are replaced by embedding the number of secret bits that is referenced by the range table. For the three pixel pairs in the sub-block, the optimal pixel adjustment is preceded to reduce the distortion of visual quality. The experimental results show that the proposed method achieves a good visual quality and high capacity.

• International Journal of Internet, Broadcasting and Communication
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• v.10 no.1
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• pp.61-64
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• 2018

In this paper, a pixel value prediction algorithm using edge components in three directions is proposed. There are various directional edges and similarity between adjacent pixels in natural images. After detecting the edge components in the x-axis direction, the y-axis direction, and the diagonal axis direction, the pixel value is predicted by applying the detected edge components and similarity between neighboring pixels. In particular, the predicted pixel value is calculated according to the intensity of the edge component in the diagonal axis direction. Experimental results show that the proposed algorithm can effectively predict pixel values. The proposed algorithm can be used for applications such as reversible data hiding, reversible watermarking to increase the number of embedded data.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.469-471
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• 2005

802.11 기반의 DCF 모드 상에서 하나의 패킷 전송을 위해서는 RTS-CTS-DATA-ACK 의 4가지 단계의 프레임 전송 과정이 이루어져야한다. 다중 홉 상태에서의 패킷 전송 또한 위 4단계를 거쳐서 종단 간에 패킷 전송이 이루어진다. 다중 홉 상태의 패킷 전송 단계에서는 전송 도중 패킷간의 충돌이 발생 할 수 있다. 이와 같은 충돌을 최소화 시키고 종단 간 패킷전송의 성능을 향상시키기 위한 연구가 진행되고 있다. 본 논문에서는 이러한 연구 중에 하나인 DCMA(Data-driven Cut-through Medium Access) 프로토콜[1]의 기능을 파악하고 이에 대한 보완 방법을 제안하여 이를 발전시킨 BCTMA (Bi-directional Cut-Through Medium Access) 프로토콜을 제안 한다.

• Journal of Information Technology Applications and Management
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• v.27 no.6
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• pp.141-151
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• 2020

The job mismatch between job seekers and SMEs is becoming more and more intensifying with the serious difficulties in youth employment. In this study, a bi-directional content-based metric learning model is proposed to recommend suitable jobs for job seekers and suitable job seekers for SMEs, respectively. The proposed model not only enables bi-directional recommendation, but also enables HR matching without relearning for new job seekers and new job offers. As a result of the experiment, the proposed model showed superior performance in terms of precision, recall, and f1 than the existing collaborative filtering model named NCF+GMF. The proposed model is also confirmed that it is an evolutionary model that improves performance as training data increases.

• The Journal of the Korea Contents Association
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• v.7 no.4
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• pp.39-48
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• 2007

Ad hoc network is a wireless network without fixed base stations or any wired backbone infrastructure. In the DUDMAC protocol, ORTS and OCTS in control channel solve the problem of deafness and DDATA and DACK in data channel improve spatial reuse by using the efficient blocking algorithm for directional antennas. In this paper, we propose the PCDUDMAC (Power Controlled DUDMAC) protocols. In the PCDUDMAC protocol, the power control of DATA/DACK in data channel saves transmission power and improves spatial reuse. We confirm the throughput performance of the proposed MAC protocol by computer simulations using Qualnet ver.3.8 simulator.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.95-102
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• 2016

Geomagnetic sensors are widely utilized for sensing heading direction of quadrotors. However, measurement from a geomagnetic sensor is easily corrupted by environmental magnetic field interference and roll/pitch directional motion. In this paper, a measurement method of a quadrotor heading direction is proposed for application to yaw attitude control. In order to eliminate roll/pitch directional motion effect, the geomagnetic sensor data is compensated using the roll/pitch angles measured for stabilization control. In addition, yaw-directional angular velocity data from a gyroscope sensor is fused with the geomagnetic sensor data using a complementary filter which is a simple and intuitive sensor fusion method. The proposed method is applied to experiments, and the results are presented to prove validity and effectiveness of the proposed method.