• Journal of the Institute of Convergence Signal Processing
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• v.18 no.1
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• pp.13-20
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• 2017

In this paper, we evaluate the basic test results of the 32 Gbps observational equipment introduced as the back-end system for the wideband VLBI (Very Long Baseline Interferometry) observation of KVN (Korean VLBI Network). Radio astronomers want to make a large radio telescope that has excellent performance in order to observe the superfine structure of a celestial body, but a lot of money is needed. Therefore, in order to increase the sensitivity, the performance improvement of the receiving system and the method of observing the wide frequency bandwidth are introduced. To do this, we adopted a wideband sampling method for converting analog signals to digital with ultra-fast speeds and a wideband sampler for performing digital filtering in order to observe a wide observational frequency bandwidth. The wideband sampler (OCTAD-K) supports up to 16 Gsps-2bits sampling and supports a variety of observational bandwidth using digital filtering techniques. In particular, it is designed to support KVN's 4-frequency simultaneous observation system and VERA(VLBI Exploration of Radio Astrometry)'s 2-beam observation system. It can also support polKVN(Korean VLBI Network), KaVA(KVN and VERA Array), 32Gbps Direct Sampler, Digital Filter, Widebandarization observations and supports the standard VDIF(VLBI Data Interchange Format) format of observed data. In this paper, the performance of the system and the problem solving are described in detail after performing the factory inspection and field test before the system is introduced.

• Journal of Convergence for Information Technology
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• v.12 no.4
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• pp.260-269
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• 2022

In this paper, We propose an anomaly detection model using deep neural network to automate the identification of outliers of the national air pollution measurement network data that is previously performed by experts. We generated training data by analyzing missing values and outliers of weather data provided by the Institute of Environmental Research and based on the BeatGAN model of the unsupervised learning method, we propose a new model by changing the kernel structure, adding the convolutional filter layer and the transposed convolutional filter layer to improve anomaly detection performance. In addition, by utilizing the generative features of the proposed model to implement and apply a retraining algorithm that generates new data and uses it for training, it was confirmed that the proposed model had the highest performance compared to the original BeatGAN models and other unsupervised learning model like Iforest and One Class SVM. Through this study, it was possible to suggest a method to improve the anomaly detection performance of proposed model while avoiding overfitting without additional cost in situations where training data are insufficient due to various factors such as sensor abnormalities and inspections in actual industrial sites.

• Journal of Digital Convergence
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• v.20 no.2
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• pp.339-344
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• 2022

It is about how much fine dust can be efficiently removed with respect to the electric dust collector used in factories and large facilities. The results of evaluating the fine dust removal efficiency are as follows. At 10,000 V, Efficiency method I showed 68.1 %, and Efficiency method II was 58.6 %, which was lower than that of Efficiency method I. At 5,000 V, Efficiency method I showed 57.6%, and Efficiency method II showed 51.6%, which was lower than Efficiency method I. At 2,500 V, Efficiency method I showed 50.3%, and Efficiency method II showed 24.4%, which was lower than Efficiency method I. In case of Efficiency method I, it is the efficiency calculated by using the dust concentration before and after passing through the filter. Efficiency method II calculated Efficiency method II to measure the efficiency a little more accurately in the environment where the air after the filter and the polluted air are mixed. Efficiency method II showed lower efficiency than Efficiency method I. As a result of the electrostatic precipitator test, the dust collecting performance was highest at 10,000 V, followed by 5,000 V and 2,500 V in that order.

• Journal of Digital Convergence
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• v.15 no.4
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• pp.285-293
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• 2017

They are rapidly evolving malicious attacks on smart devices, and to timely protect the smart devices from these attacks has become a very important issue. In particular, smishing attack has emerged as one of the most important threats on the smartphone. In this paper, we propose the cloud service that can fundamentally protect the user from the risk of smishing attack. The proposed scheme provides cloud messaging service that can filter text messages including URLs in the user's smart device, view and manage them through a virtual machine provided by a cloud server. The existing techniques for preventing smshing attacks protect only malicious code of a known pattern and there is the possibility of error such as FP(False Positive) or FN(False Negative). However, since the proposed method automatically filters all text messages including URLs, storing, viewing, and managing them in their own storage space on the cloud server, it can completely block the installation of malwares(malicious codes) on the user's smart device through smishing attacks.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.465-469
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• 2000

This paper describes a single-chip full-custom implementation of pipelined adaptive decision-feedback equalizer (PADFE) using a 0.25-${\mu}{\textrm}{m}$ CMOS technology for wide-band wireless digital communication systems. To enhance the throughput rate of ADFE, two pipeline stage are inserted into the critical path of the ADFE by using delayed least-mean-square (DLMS) algorithm Redundant binary (RB) arithmetic is applied to all the data processing of the PADFE including filter taps and coefficient update blocks. When compared with conventional methods based on two's complement arithmetic, the proposed approach reduces arithmetic complexity, as well as results in a very simple complex-valued filter structure, thus suitable for VLSI implementation. The design parameters including pipeline stage, filter tap, coefficient and internal bit-width and equalization performance such as bit error rate (BER) and convergence speed are analyzed by algorithm-level simulation using COSSAP. The singl-chip PADFE contains about 205,000 transistors on an area of about 1.96$\times$1.35-$\textrm{mm}^2$. Simulation results show that it can safely operate with 200-MHz clock frequency at 2.5-V supply, and its estimated power dissipation is about 890-mW.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.29-35
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• 2006

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference(ISI) or Multiple Access Interference(MAI) to degrade the performance of CDMA(Code Division Multiple Access) system. Constant Modulus Algorithm which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.3
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• pp.95-101
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• 2006

A face detection plays an important role in face recognition, video surveillance, and human computer interaction. In this paper, we propose a progressive threshold method to detect human faces in real time. The consecutive face images are acquired from camera and transformed into YCbCr color space images. The skin color of the input images are separated using a skin color filter in the YCbCr color space and some candidated face areas are decided by connected component analysis. The intensity equalization is performed to avoid the effect of many circumstances and an arbitrary threshold value is applied to get binary images. The eye area can be detected because the area is clearly distinguished from others in the binary image progressive threshold method searches for an optimal eye area by progressively increasing threshold from low values. After progressive thresholding, the eye area is normalized and verified by back propagation algorithm to finalize the face detection.

• Journal of the Korea Convergence Society
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• v.11 no.2
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• pp.271-279
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• 2020

Squats and lunges are important exercises for strengthening the trunk and lower body among various free weight exercises. It should be achieved safe and effective excise through establishing of theoretical basis for exercise posture and standard movement. Therefore, it's necessary to develop the exercise model in order to prepare the scientific countermeasures for the prevent injuries and error movement through optimal exercise movement. For this purpose, it is effective to use appropriate instruments for motion compensation according to the optical motion and error motion. In this paper, we develop a motion model analysis system based on dynamic motion through the four-point load cell for dynamic motion analysis. Proposed analytical method, the optimal and the error motion numerical data is obtained through the dynamic motion analysis. And we verified that dynamic movement is simplified to establish the motion modeling according to the classification motion and the numerical quantification data for analyzing.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.7 no.1
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• pp.15-22
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• 2007

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference(ISI) or Multiple Access Interference(MAI) to degrade the performance of CDMA(Code Division Multiple Access) system. Constant Modulus Algorithm which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye- pattern obtained from algorithm are compared.

• The Journal of the Acoustical Society of Korea
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• v.22 no.4
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• pp.261-268
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• 2003

Conventional acoustic echo cancellers using ES algorithm have simple structure and fast convergence speed compared with those using NLMS algorithm, but they are very weak to external noise because ES algorithm updates the adaptive filter taps based on average energy reduction rate of room impulse response in specific acoustical condition. To solve this problem, in this paper, a new update algorithm for acoustic echo canceller with stepsize matrix generator is proposed. A set of stepsizes is determined based on residual error energy which is estimated by two moving average operators, and applied to the echo canceller in matrix from, resulting in improved convergence speed. Simulations in various noise condition show that the proposed algorithm improves the robustness of acoustic echo canceller to external noise.