• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.05a
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• pp.391-392
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• 2018

• Journal of Broadcast Engineering
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• v.21 no.3
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• pp.341-348
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• 2016

HEVC is the next compression standard and is expected to be used widely replacing the conventional H.264/AVC standard. The compression ratio of the HEVC is twice times than H.264/AVC, whereas its computational complexity is increased by up to 40%. Many research efforts have been made to reduce the computational complexity and to speed up encoding. For intra coding, the rough mode decision (RMD) is commonly applied. The rate-distortion optimization (RDO) process to decide the best mode is too complex so that RMD chooses the candidate modes with a simple process and sends the candidates to RDO process. However, for large-size blocks, the RMD also requires considerable computations. In this paper, a down-sampling scheme is proposed for the RMD process. The reference pixel loading, predicted pixel generation are performed using the down-sampled pixel data. When the proposed scheme is applied to the RMD, the computational complexity is reduced by 70% with a marginal bitrate increase of 0.04%. In terms of area of hardware-based RMD, the gate count and the buffer size is reduced 33% and 66%, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12C
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• pp.1249-1256
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• 2006

This paper proposes, based on a bandpass sampling theory, a novel method to find valid sampling frequency range and minimum sampling rate with low computational complexity for downconversion of multiple bandpass radio frequency (RF) signals. Guard-bands or spacing between adjacent downconverted signal spectrums are also taken into consideration in determining sampling frequency for practical implementation. Moreover, we verify through comparison with other method that the proposed method has more advantageous properties.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.7
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• pp.1247-1251
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• 2016

This study aims to investigate the effect of sampling frequency to the time domain and frequency domain analysis of pulse rate variability (PRV). Typical time domain variables - AVNN, SDNN, SDSD, RMSSD, NN50 count and pNN50 - and frequency domain variables - VLF, LF, HF, LF/HF, Total Power, nLF and nHF - were derived from 7 down-sampled (250 Hz, 100 Hz, 50 Hz, 25 Hz, 20 Hz, 15 Hz, 10 Hz) PRVs and compared with the result of heart rate variability of 10 kHz-sampled electrocardiogram. Result showed that every variable of time domain analysis of PRV was significant at 25 Hz or higher sampling frequency. Also, in frequency domain analysis, every variable of PRV was significant at 15 Hz or higher sampling frequency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.8
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• pp.1805-1812
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• 2011

Bandpass sampling technique has an advantage that it uses lower sampling frequency than Nyquist criterion. But special care is required in choosing sampling frequency to avoid self-image overlapping in the first Nyquist region. Recently, the second-order BPS techniques which can suppress possible self-image by using an additional ADC and by employing digital signal processing have been proposed. This paper addresses a complex BPS based SDR front-end. Unlike general second-order BPS, it needs simple FIR filter to compensate delay in the second ADC. We show a method to find proper sampling frequencies to down convert RF signals selected by tunable RF filter operating in arbitrary frequency range.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1418-1423
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• 2016

The purpose of this research is to investigate the effect of sampling frequency on the photoplethysmography (PPG) and to evaluate the performance of interpolation methods for under-sampled PPG. We generated down-sampled PPG using 10 kHz-sampled PPG then evaluated waveshape changes with correlation coefficient. Correlation coefficient was significantly decreased at 50 Hz or below sampling frequency. We interpolated the down-sampled PPG using four interpolation method-linear, nearest, cubic spline and piecewise cubic Hermitt interpolation polynomial - then evaluated interpolation performance. As a result, it was shown that PPG waveform that was sampled over 20 Hz could be reconstructed by interpolation. Among interpolation methods, cubic spline interpolation showed the highest performance. However, every interpolation method has no or less effect on 5 Hz sampled PPG.

• Journal of Sensor Science and Technology
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• v.21 no.5
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• pp.352-358
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• 2012

A sensor network system can be an efficient tool for healthcare telemetry for multiple users due to its power efficiency. One drawback is its limited data size. This paper proposed a real-time application of data compression/decompression method in u-Health monitoring system in order to improve the network efficiency. Our high priority was given to maintain a high quality of signal reconstruction since it is important to receive undistorted waveform. Our method consisted of down sampling coding and differential Huffman coding. Down sampling was applied based on the Nyquist-Shannon sampling theorem and signal amplitude was taken into account to increase compression rate in the differential Huffman coding. Our method was successfully tested in a ZigBee and WLAN dual network. Electrocardiogram (ECG) had an average compression ratio of 3.99 : 1 with 0.24% percentage root mean square difference (PRD). Photoplethysmogram (PPG) showed an average CR of 37.99 : 1 with 0.16% PRD. Our method produced an outstanding PRD compared to other previous reports.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.11a
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• pp.29-32
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• 2020

Due to the lack of improper image acquisition process, noise induction is an inevitable step. As a result, objective image quality assessment (IQA) plays an important role in estimating the visual quality of noisy image. Plenty of IQA methods have been proposed including traditional signal processing based methods as well as current deep learning based methods where the later one shows promising performance due to their complex representation ability. The deep learning based methods consists of several convolution layers and down sampling layers for feature extraction and fully connected layers for regression. Usually, the down sampling is performed by using max-pooling layer after each convolutional block. We reveal that this max-pooling causes information loss despite of knowing their importance. Consequently, we propose a better IQA method that replaces the max-pooling layers with strided convolutions to down sample the feature space and since the strided convolution layers have learnable parameters, they preserve optimal features and discard redundant information, thereby improve the prediction accuracy. The experimental results verify the effectiveness of the proposed method.

• The Korean Journal of Applied Statistics
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• v.28 no.3
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• pp.495-509
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• 2015

We study a classification problem of significant differences in the proportion of two groups known as the unbalanced classification problem. It is usually more difficult to classify classes accurately in unbalanced data than balanced data. Most observations are likely to be classified to the bigger group if we apply classification methods to the unbalanced data because it can minimize the misclassification loss. However, this smaller group is misclassified as the larger group problem that can cause a bigger loss in most real applications. We compare several classification methods for the unbalanced data using sampling techniques (up and down sampling). We also check the total loss of different classification methods when the asymmetric loss is applied to simulated and real data. We use the misclassification rate, G-mean, ROC and AUC (area under the curve) for the performance comparison.

• Clinical and Experimental Reproductive Medicine
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• v.21 no.2
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• pp.201-206
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• 1994

Down syndrome is one of the major chromosomal anomalies in Korea. To decrease incidence of Down syndrome, antenatal diagnosis is essential. At present, antenatal diagnosis of Down syndrome is done by karyotyping from chorionic villus sampling, amniocentesis, and cordocentsis. All these methods have some problems such as a risk of abortion, a long waiting time, difficulties in sampling, and so on. The aim of study was to confirm that PCR(Polymerase Chain Reaction) using D21S11 primer could be a diagnostic tool for Down syndrome. PCR using D21S11 primers with $^{32}P$ labeling at 5' end was done in 21 cases of DNA from 21 Trisomy and 20 cases of DNA from normal karyotype. PCR product was running for 10 hours on the 6% polyacrylamide gel under 1,000 V or for 8 hours under 1,500 V. After X-ray film exposure, it was read by densitometry. Normal group showed 1: 1 band or single band. 21 Trisomy group showed 1.3-2: 1 band or 2.3 times of density compared to normal single band or 3 bands. This method gave the result within 24 hours. It can be an useful diagnostic tool to detect 21 Trisomy antenatally, especially in late pregnancy, and in preimplantation diagnosis.