• Geophysics and Geophysical Exploration
• /
• v.22 no.4
• /
• pp.177-185
• /
• 2019

Ground roll is a surface wave which is usually observed in the land seismic data. It is one of the typical coherent noise. During the reflection data processing, ground roll is removed because it is considered as noise. This removal process often causes the loss of reflection signals if the ground roll overlaps reflection signals. In this study, we look over Karhunen-Loeve Transform (KLT) and analyze its effects to suppress the ground roll appropriately while reducing the reflection loss. Numerical tests in homogeneous elastic media show that the ground roll has been properly rejected. However, the field data application reveals that there is no significant suppression of ground roll when compared to band-pass filtering. This can be considered that it is hard to calculate horizontally aligned gathers in the field data because the ground roll contains a wide range of frequency bands. On the contrary, the result of singular value decomposition (SVD) filtering shows that the ground roll has been significantly reduced. It is thought that the SVD filtering performs better in the ground roll suppression than KLT because it is easy to calculate the horizontally aligned gathers in the SVD filtering.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.12C
• /
• pp.1133-1143
• /
• 2005

In this paper, we propose an enhanced two-step search scheme for rapid and reliable signal acquisition in UWB systems under multipath channels. The proposed TSS-LS (Two-Step Search scheme with the Linear search based Second step) achieves rapid acquisition performance comparable to the conventional TSS-BS (Two-Step Search scheme with the Bit reversal search based Second step) already proposed by the authors, based on the single-dwell search with two-step thresholds and search windows. However, unlike the TSS-BS which employs the bit reversal search in the second step, the proposed TSS-LS utilizes the linear search in the second step to improve the reliability of signal acquisition. Simulation results with multipath channel models by IEEE 802.15.3a show that the two-step search schemes for the UWB signal acquisition can achieve sig nificant reduction of the required mean acquisition time as compared to general search schemes. In addition, we observe that the proposed TSS-LS achieves quite good bit error rate performance for large signal-to-noise ratios, which is favorably comparable to the case of ideal perfect timing.

• Korean Journal of Social Welfare
• /
• v.61 no.1
• /
• pp.323-357
• /
• 2009

This study illuminates the mechanism of life course on labor status of old age complementing the limits of labor status hypothesis of old age and model of statues attainment and combining them. The main results from this analysis are summarized in four points. Firstly, older men mostly engaged in agriculture, forestry and fishing industry or low-class occupations. A very small portion held high level or professional occupations. Regular full-time employees or employers were only 4.4% while, about 70% of older employees were temporal employees or self-employed. This shows that the elderly affluence hypothesis which alleges that most older men maintain high level occupations, applies to only a few. The second finding is that wealth differentials are sizable: about 20% of older workers own less than 50 million won, while 9.3% possess more than 600 million won. Therefore, it is not safe to claim that most people have accumulated enough wealth for old age according to the elderly affluence hypothesis. This gap being mainly reflected by education level, suggests that the model of status attainment is appropriate as wealth accumulation hypothesis. Thirdly, educational level determined not only lifetime careers, but also labor status of old age. Fourthly, using path analysis, the last finding is that education had effect on labor status of old age through lifetime career and wealth. That is, old men who have low education level had unstable lifetime career and own less wealth. They work in low income job, low social occupations and unstable occupation type in old age. This shows that life inequality continues until old age. Therefore, the inequality of education opportunity, spread of part-time work and small scale self employees should be discouraged. Furthermore, related policy should be provided in order to prevent being caught in unstable work.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.2
• /
• pp.27-34
• /
• 2001

Utterance verification is used in variable vocabulary word recognition to reject the word that does not belong to in-vocabulary word or does not belong to correctly recognized word. Utterance verification is an important technology to design a user-friendly speech recognition system. We propose a new utterance verification algorithm for no-training utterance verification system based on the minimum verification error. First, using PBW (Phonetically Balanced Words) DB (445 words), we create no-training anti-phoneme models which include many PLUs(Phoneme Like Units), so anti-phoneme models have the minimum verification error. Then, for OOV (Out-Of-Vocabulary) rejection, the phoneme-based confidence measure which uses the likelihood between phoneme model (null hypothesis) and anti-phoneme model (alternative hypothesis) is normalized by null hypothesis, so the phoneme-based confidence measure tends to be more robust to OOV rejection. And, the word-based confidence measure which uses the phoneme-based confidence measure has been shown to provide improved detection of near-misses in speech recognition as well as better discrimination between in-vocabularys and OOVs. Using our proposed anti-model and confidence measure, we achieve significant performance improvement; CA (Correctly Accept for In-Vocabulary) is about 89％, and CR (Correctly Reject for OOV) is about 90％, improving about 15-21％ in ERR (Error Reduction Rate).

• Journal of Korea Water Resources Association
• /
• v.36 no.4
• /
• pp.533-545
• /
• 2003

This study analyzed several storm events observed in the Seolma-chun basin to derive the characteristic velocity of GIUH (Geomophological Instantaneous Unit Hydrograph) as well as its variability. Especially, this study focused on the variation of characteristic velocity due to the change of rainfall characteristics. The IUH of the Seolma-chun basin was derived using the HEC-1, whose peak discharge and time were then compared with those of the GIUH to derive the characteristic velocities. The characteristics velocities were analyzed by comparing with the GcIUH (Geomorphoclimatic IUH) as well as the characteristics of rainfall. Results are summarized as follows. (1) The characteristic velocity of GIUH was estimated higher with higher variability than the GcIUH, but their trends were found similar (2) Total amount of effective rainfall (or, mean effective rainfall) well explains the characteristic velocity of GIUH. This could be assured by the regression analysis, whose coefficient of determination was estimated about 0.6. (3) The duration and the maximum intensity of rainfall were found not to affect significantly on the characteristic velocity of GIUH. The coefficients of determination were estimated less than 0.3 for all cases considered. (4) For the rainfall events used in this study, the characteristic velocities of GIUH were found to follow the Gaussian distribution with its mean and the standard deviation 0.402 m/s and 0.173 m/s, respectively. Most of the values are within the range of 0.4∼0.5 m/s, and its coefficient of variation was estimated to be 0.43, much less than that of the runoff itself (about 1.0).

• Journal of the Korean Geotechnical Society
• /
• v.32 no.9
• /
• pp.17-27
• /
• 2016

Parial drainage characteristics of clayey silt with low plasticity from the west coast (Incheon and Hwaseong) was analyzed using CPTU based existing correlation equations and compulsory replacement method. Generally, the estimated $OCRs={\kappa}{\cdot}((q_t-{\sigma}_{vo})/{\sigma}^{\prime}_{vo})$ using Powell and Quartman(1988) were higher than those obtained by the oeodometer tests. These trends were noticeable for the layers containing a lot of silty and sand soils. The assessment of partial drainage conditions was performed through Schnaid et al. (2004)'s equation; it is based on plotting the normalized cone resistance, $Q_t$ versus the pore pressure parameter, $B_q$ in combination with the strength incremental ratio, $s_u/{\sigma}^{\prime}_{vo}$ to the CPTU data. It is evident that more than half of the data fall in the range where $B_q$ < 0.3, corresponding to the domain in which the partial drainage prevails when testing normally consolidated soils at a standard rate of penetration (2 cm/s). To estimate the replacement depth of clayey silt with low plasticity, back analysis was carried out to evaluate the internal friction angle based on where the design depths are equal to the checked depths using bearing capacity equation. The internal friction angels obtained from the back analysis tended to increase as the plasticity index decreases, which is ranged approximately from ${\varphi}^{\prime}=2^{\circ}$ to ${\varphi}^{\prime}=7^{\circ}$.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.10 no.6
• /
• pp.609-616
• /
• 2017

In this paper, we propose an algorithm to obtain more stable and high recognition rate by using left and right rotation information of input image in order to obtain a stable recognition rate in face recognition. The proposed algorithm uses the facial image as the input information in the web camera environment to reduce the size of the image and normalize the information about the brightness and color to obtain the improved recognition rate. We apply Principal Component Analysis (PCA) to the detected candidate regions to obtain feature vectors and classify faces. Also, In order to reduce the error rate range of the recognition rate, a set of data with the left and right $45^{\circ}$ rotation information is constructed considering the directionality of the input face image, and each feature vector is obtained with PCA. In order to obtain a stable recognition rate with the obtained feature vector, it is after scattered in the eigenspace and the final face is recognized by comparing euclidean distant distances to each feature. The PCA-based feature vector is low-dimensional data, but there is no problem in expressing the face, and the recognition speed can be fast because of the small amount of calculation. The method proposed in this paper can improve the safety and accuracy of recognition and recognition rate faster than other algorithms, and can be used for real-time recognition system.

• KIPS Transactions on Software and Data Engineering
• /
• v.6 no.10
• /
• pp.465-472
• /
• 2017

In the past, researchers mainly used the supervised learning technique of machine learning to analyze power data and investigated the identification of patterns through the data mining technique. Data analysis research, however, faces its limitations with the old data classification and analysis techniques today when the size of electric power data has increased with the possible real-time provision of data. This study thus set out to propose a clustering architecture to analyze large-sized electric power data. The clustering process proposed in the study supplements the K-means algorithm, an unsupervised learning technique, for its problems and is capable of automating the entire process from the collection of electric power data to their analysis. In the present study, power data were categorized and analyzed in total three levels, which include the row data level, clustering level, and user interface level. In addition, the investigator identified K, the ideal number of clusters, based on principal component analysis and normal distribution and proposed an altered K-means algorithm to reduce data that would be categorized as ideal points in order to increase the efficiency of clustering.

• Korean Journal of Optics and Photonics
• /
• v.13 no.5
• /
• pp.455-459
• /
• 2002

The transport and optical properties of $In_2O_3$:Zn(IZO) thin films grown by DC magnetron sputtering deposition have been studied. The deposition temperatures ($T_s$) were varied from room temperature to $400^{\circ}C$ in $50^{\circ}C$ steps. The IZO films are an amorphous phase for $T_s$<$300^{\circ}C$ and polycrystalline phase for $350^{\circ}C$＜$T_s$. In contrast to ordinary films, amorphous IZO films have lower resistivity and higher optical transmittance than polycrystalline IZO films. The resistivity of amorphous IZO was in the range of 0.29~0.4 m$\Omega$cm and that of polycrystalline IZO was in the range of 1~4 m$\Omega$cm. The carrier type for IZO film was found to be n-type, and the carrier density, was $3~5{\times}10^{20}/cm^3$. The Hall mobility, $({\mu}_H)$, was 20~$50\textrm{cm}^2$/V.sec. The predominant scattering mechanisms in both amorphous and polycrystalline IZO films were believed to be ionized impurity scattering and lattice scattering. The visible transmittance of the IZO films, which decreases with an increase of TS, was above 80%.

• The Journal of Korean Institute of Information Technology
• /
• v.15 no.12
• /
• pp.157-164
• /
• 2017

Mobile ECG signal measurement is a technique to measure small signals of several mV, and many studies have been conducted to remove noise including wandering scheme. Removal of the equipotential line noise caused by shaking or movement of the electrode cable is one of the core research contents for the electrocardiogram measurement. In this study, we proposed a modified step-size of combined NLMS(normalized least squares) and DLMS(delayed least squares) adaptive filter to eliminate baseline noise from ECG signals. The proposed method mainly adjusts initial filter step-size to reduce distortion of original ECG signals characteristic after eliminating baseline noise. The modified filter step-size is scaled by filter order size and distortion minimization factor. This method is suitable for portable ECG device with a small processor and less power consumption. This technique also decreases computation time which is essential for real-time filtering. The proposed filter also increase the signal to noise ratio (SNR) compared to conventional NLMS filter.