• KIPS Transactions on Software and Data Engineering
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• v.7 no.5
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• pp.195-204
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• 2018

In this paper, we propose both a new loss function and an online hard example mining scheme for improving the performance of single-stage object detectors which use deep convolutional neural networks. The proposed loss function and the online hard example mining scheme can not only overcome the problem of imbalance between the number of annotated objects and the number of background examples, but also improve the localization accuracy of each object. Therefore, the loss function and the mining scheme can provide intrinsically fast single-stage detectors with detection performance higher than or similar to that of two-stage detectors. In experiments conducted with the PASCAL VOC 2007 benchmark dataset, we show that the proposed loss function and the online hard example mining scheme can improve the performance of single-stage object detectors.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.6
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• pp.221-229
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• 2004

We present new digital watermarking scheme that embeds a watermark according to the characteristics of the image or video. The scheme is compatible with established image compression standard. We define a weighting function using a parent-child structure of the DCT coefficients in a block to embed a maximum watermark. The spatio-frequency localization of the DCT coefficients can be achieved with this structure. In the detection stage, we present an optimum a posteriori threshold with a given false detection error probability based on the statistical analysis. Simulation results show that the proposed algorithm is efficient and robust against various signal processing techniques. Especially, they are robust against widely used coding standards, such as JPEG and MPEG.

• Journal of Broadcast Engineering
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• v.2 no.1
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• pp.65-73
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• 1997

This paper propose a new triangular mesh approximation method using wavelet coefficients for large terrain data. Using spatio-freguency localization characteristics of wavelet coefficients, we determine the complexity of terrain data and approximate the data according to the complexity. This proposed algorithm is simple and requires low computational cost due to its top-down approach. Because of the similarity between the mesh approximation and data compression procedures based on wavelet transform, we combine the mesh approximation scheme with the Embedded Zerotree Wavelet (EZW) coding scheme for the effective management of large terrain data. Computer simulation results demonstrate that the proposed algorithm is very prospective for the 3-D visualization of terrain data.

• Journal of KIISE:Computing Practices and Letters
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• v.5 no.5
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• pp.611-618
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• 1999

An efficient and effective access to needed information becomes an important factor in the modern information society. Many people have developed information retrieval (IR) systems that retrieve needed information from a large amount of data at a given time. However, most freely available IR systems have been developed for English text rather than for Korean text. In this research, we have analyzed the IR system freeWAIS-sf, and localized it with the Korean morphological analyzer, namely HAM. The localized freeWAIS-sf can handle both English text and Korean text simultaneously. We have also modified the weighting scheme of freeWAIS-sf. The experimental result shows that the modified weighting scheme outperforms the original one in terms of retrieval effectiveness.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.2
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• pp.45-53
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• 2019

RGB-D SLAM (Simultaneous Localization and Mapping) refers to the technology of using deep camera as a visual sensor for SLAM. In view of the disadvantages of high cost and indefinite scale in the construction of maps for laser sensors and traditional single and binocular cameras, a method for creating three-dimensional map of indoor environment with deep environment data combined with RGB-D SLAM scheme is studied. The method uses a mobile robot system equipped with a consumer-grade RGB-D sensor (Kinect) to acquire depth data, and then creates indoor three-dimensional point cloud maps in real time through key technologies such as positioning point generation, closed-loop detection, and map construction. The actual field experiment results show that the average error of the point cloud map created by the algorithm is 0.0045m, which ensures the stability of the construction using deep data and can accurately create real-time three-dimensional maps of indoor unknown environment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.878-883
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• 2018

A jamming design scheme to disturb target position estimation of a bistatic multiple-input multiple-output(MIMO) radar system is presented. The proposed method exploits the received signals from distributed multiple electronic sensors and combines them to produce a jamming signal. The proposed algorithm can eliminate the target by transmitting the delayed sum or the weighted sum of the received senor signals. Simulation results confirm the performance of the proposed method.

• Structural Monitoring and Maintenance
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• v.9 no.3
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• pp.237-258
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• 2022

This paper studies detecting and locating loose bolts using nonlinear guided waves. The 3D Finite Element (FE) simulation is used for the prediction of guided waves' interactions with loose bolted joints. The numerical results are verified by experimentally obtained data. The study considers bolted joints consisting of two bolts. It is shown that the guided waves' interaction with surfaces of a loose bolted joint generates Contact Acoustic Nonlinearity (CAN). The study uses CAN for detecting and locating loose bolts. The processed experimentally obtained data show that the CAN is able to successfully detect and locate loose bolted joints. A 3D FE simulation scheme is developed and validated by experimentally obtained data. It is shown that FE can predict the propagation of guided waves in loose bolts and is also able to detect and locate them. Several numerical case studies with various bolt sizes are created and studied using the validated 3D FE simulation approach. It is shown that the FE simulation modeling approach and the signal processing scheme used in the current study are able to detect and locate the loose bolts in imperfect bolted joints. The outcomes of this research can provide better insights into understanding the interaction of guided waves with loose bolts. The results can also enhance the maintenance and repair of imperfect joints using the nonlinear guided waves technique.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.3
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• pp.81-86
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• 2014

According to the development of streaming services with P2P and mobile network technologies, researches to enhance the service quality in mobile environment have been proposed. However, streaming services considering high-speed mobile environment and characteristics of heterogenous terminals have been hindered from being provided with the required quality from user because of bandwidth congestion between selfish peers of existing P2P system. It is also prone to long delay and loss in accordance with the repeated traffic amounts because there are no optimized solution for traffic localization. The structure to enhance peer contribution for service differentiation and peer selection with clustering scheme with location information of terminal can satisfy both users and service providers with service quality and efficiency. In this paper, we propose an incentive mechanism and resource distribution scheme with user contribution and traffic cost information based on user location, which make mobile users increase the satisfaction of service quality in LTE environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11C
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• pp.957-964
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• 2010

In this paper, we propose an indoor positioning algorithm based on 3 points near field angle-of-arrival estimation without side information. The conventional angle-of-arrival based positioning scheme requires the distance between the listener and the center of two points which is obtained by a received signal strength based range estimation. However, a received signal strength is affected by structure of room, placement of furniture, and characteristic of signal, these effects cause a large error to estimation of angle. In this paper, the proposed positioning scheme based on near field angle-of-arrival estimation can be used to estimate the position of listener without a prior distance information, just using time-difference-of-arrival information given from 3 points microphones. The performance of the proposed scheme is shown by cumulative distribution function of root mean squared error.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.31-33
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• 2006

센서 네트워크를 구성함에 있어서 센서 노드들의 자기위치 인식은 가장 기본이 되며 중요한 부분 중 하나이다. 이런 자기 위치 인식 기법 중에서도 소리를 이용한 기법은 정확도가 높은 장점이 있어 많은 연구가 있어 왔지만 기존의 방법들은 추가적으로 고가의 하드웨어를 이용하거나 중앙 집중식 연산을 함으로써 시스템의 부하가 크며 소리의 발생시간을 미리 계획하여야 한다는 단점이 있었다. 본 논문에서는 일반 음원감지 센서를 장착한 노드들을 이용하여 임의의 시간에 소리를 발생시키고 이를 감지한 각 개별 노드들이 독립적으로 자기위치 인식의 연산을 수행함으로써 에너지 소모를 줄이고, 시스템 설계의 비용은 낮추며 소리의 특성 또한 사용자의 요구에 맞게 설계하여 실용성을 높이는 자기 위치 인식 기법을 제안하고, 실제 구현을 통한 성능 분석을 제시한다.