• Journal of KIISE:Software and Applications
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• v.30 no.11
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• pp.1072-1079
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• 2003

This study is purported for suggesting a new clustering algorithm that enables incremental categorization of numerous documents. The suggested algorithm adopts the natures of the spherical k-means algorithm, which clusters a mass amount of high-dimensional documents, and the fuzzy ART(adaptive resonance theory) neural network, which performs clustering incrementally. In short, the suggested algorithm is a combination of the spherical k-means vector space model and concept vector and fuzzy ART vigilance parameter. The new algorithm not only supports incremental clustering and automatically sets the appropriate number of clusters, but also solves the current problems of overfitting caused by outlier and noise. Additionally, concerning the objective function value, which measures the cluster's coherence that is used to evaluate the quality of produced clusters, tests on the CLASSIC3 data set showed that the newly suggested algorithm works better than the spherical k-means by 8.04% in average.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.69-76
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• 2020

The sound signal radiated from an underwater source is received by the hydrophone of the system, including multi-path time-delay and multi-path signal by sea surface and bottom reflection. The system using a time-delay between received signals for the source localization shows performance degradation due to incoherence by the multi-path propagation environment and the disturbance of a marine environment. Various types of array and signal processing have been used for robust source range and bearing estimation in this environment. In this paper, we use a line array composed of doublet array and an estimated time-delay correction method for robust localization performance in a multi-path propagation environment. Three doublet arrays are located on the same line, and the time-delay between signals received on each doublet array is estimated in a two-step procedure. The estimated time-delay value is obtained by the cross-correlation function and corrected by the interaction formula between the center-frequency of received signal and the geometry of the array with respect to aperture. By this proposed procedure, the range and bearing of source from array were calculated. In order to confirm the validity of the proposed method and array, we simulated localization and estimation using the Monte-Carlo method.

• The Journal of the Acoustical Society of Korea
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• v.41 no.3
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• pp.326-334
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• 2022

In this paper, we propose speech enhancement algorithm as a pre-processing for robust speech recognition in noisy environments. Auxiliary-function-based Independent Vector Analysis (AuxIVA) is performed with weighted covariance matrix using time-varying variances with scaling factor from target masks representing time-frequency contributions of target speech. The mask estimates can be obtained using Neural Network (NN) pre-trained for speech extraction or diffuseness using Coherence-to-Diffuse power Ratio (CDR) to find the direct sounds component of a target speech. In addition, outputs for omni-directional noise are closely chained by sharing the time-varying variances similarly to independent subspace analysis or IVA. The speech extraction method based on AuxIVA is also performed in Independent Low-Rank Matrix Analysis (ILRMA) framework by extending the Non-negative Matrix Factorization (NMF) for noise outputs to Non-negative Tensor Factorization (NTF) to maintain the inter-channel dependency in noise output channels. Experimental results on the CHiME-4 datasets demonstrate the effectiveness of the presented algorithms.

• International Journal of Highway Engineering
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• v.18 no.6
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• pp.123-130
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• 2016

OBJECTIVES : The objective of this research is to determine the moisture resistance of the freeze-thaw process occurring in low-noise porous pavement using either hydrated-lime or anti-freezing agent. Various additives were applied to low-noise porous asphalt, which is actively paved in South Korea, to overcome its disadvantages. Moreover, the optimum contents of hydrated-lime and anti-freezing agent and behavior properties of low-noise porous asphalt layer are determined using dynamic moduli via the freeze-thaw test. METHODS : The low-noise porous asphalt mixtures were made using gyratory compacters to investigate its properties with either hydrated-lime or anti-freezing agent. To determine the dynamic moduli of each mixture, impact resonance test was conducted. The applied standard for the freeze-thaw test of asphalt mixture is ASTM D 6857. The freeze-thaw and impact resonance tests were performed twice at each stage. The behavior properties were defined using finite element method, which was performed using the dynamic modulus data obtained from the freeze-thaw test and resonance frequencies obtained from non-destructive impact test. RESULTS : The results show that the coherence and strength of the low-noise porous asphalt mixture decreased continuously with the increase in the temperature of the mixture. The dynamic modulus of the normal low-noise porous asphalt mixture dramatically decreased after one cycle of freezing and thawing stages, which is more than that of other mixtures containing additives. The damage rate was higher when the freeze-thaw test was repeated. CONCLUSIONS : From the root mean squared error (RMSE) and mean percentage error (MPE) analyses, the addition rates of 1.5% hydrated-lime and 0.5% anti-freezing agent resulted in the strongest mixture having the highest moisture resistance compared to other specimens with each additive in 1 cycle freeze-thaw test. Moreover, the freeze-thaw resistance significantly improved when a hydrated-lime content of 0.5% was applied for the two cycles of the freeze-thaw test. Hence, the optimum contents of both hydrated-lime and anti-freezing agent are 0.5%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.644-652
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• 2017

The purpose of this study was to analyze the EEG according to the elderly's tendency to be addicted to smartphone games. We compared the effects of smartphone addiction on mental health such as brain waves, sleep problems and depression through comparative analysis of asymmetry and connectivity in quantitative EEG results. The study participants were two elderly people who were addicted to smartphone game and one elderly person who did not use smartphone (Ed- to confirm: only 3 participants?!). The participant's addiction tendency of smartphone was measured by using the smartphone addiction scale and EEG (QEEG) was used for EEG analysis. The results are as follows. First, the brain waves of elderly people and smartphone non-user elderly who showed symptoms of immersion and smartphone game showed a difference in asymmetry in both opening and closing anisles. Second, there were significant differences in the openness and the anxiety of the elderly who were immersed in the mobile phone and the elderly who did not use the smartphone. Through this, it is also meaningful to explore the relationship between senile cognitive impairment and smartphone use by exploring the effect of smartphone game use on brain cognitive function through comparison of EEG analysis.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.3
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• pp.158-164
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• 1998

We introduce a statistical scheme to classify seabed from acoustic profiling data acquired using Chirp sonar system. The classification is based on grouping of signal traces by similarity index, which is computed using the K-L (Karhunen-Lo$\grave{e}$ve) transform of the Chirp profiling data. The similarity index represents the degree of coherence of bottom-reflected signals in consecutive traces, hence indicating the acoustic roughness of the seabed. The results of this study show that similarity index is a function of homogeneity, grain size of sediments and bottom hardness. The similarity index ranges from 0 to 1 for various types of seabed material. It increases in accordance with the homogeneity and softness of bottom sediments, whereas it is inversely proportional to the grain size of sediments. As a real data example, we classified the seabed off Cheju Island, Korea based on the similarity index and compared the result with side-scan sonar data and sediment samples. The comparison shows that the classification of seabed by the similarity index is in good agreement with the real sedimentary facies and can delineate acoustic response of the seabed in more detail. Therefore, this study presents an effective method for geoacoustic modeling to classify the seafloor directly from acoustic data.

• Journal of the Korea Society of Computer and Information
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• v.16 no.11
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• pp.123-135
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• 2011

The domestic market of database in Korea is estimated to be over 3.663 trillion won. The data migration is getting to be more important along with the continuous growth of the database industry. g-CRM and private recommending function are examples of the service that can be given through coupling among customer database, product database, geographic information database, and others. The core infrastructure is also the database which is integrated, perfect, and reliable. There are not enough researches on efficient way of data migration and integrating process and investigation of migrated data though trends of database in IT environment as above. In connection with this issue, we have made a model for data migration on scientific and technological contents and suggest the result of data migration process adapting that model. In addition, we verified migration's exhaustiveness, migration's consistency, and migration's coherence for investigation of migrated data and database. From the result, we conclude data migration based on proper model has a significant influence on the database consistency and the data values correctness and is essential to maintain high qualified database.

• Journal of Life Science
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• v.20 no.1
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• pp.90-96
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• 2010

Menopause increases the onset of hypertension and heart disease. Whereas it increases the blood LDL-cholesterol, triglyceride and total-cholesterol levels, the HDL-cholesterol concentration is reduced. Accordingly, we examined the effect of internal organs of Todarodes pacificus (IOT) on improvement in blood flow ability and changes in serum lipid content by using ovariectomized rats. For this study, the following four groups of 9-week-old Sprague-Dawley strain female rats were evaluated over 6 weeks: normal rats (SHAM), ovariectomized rats (CON) and ovariectomized rats that were treated with IOT extracts. Ovary removal promoted platelet aggregability. However, IOT administration in the CON group after ovary excision resulted in a hinderance of coherence. The blood vessel passing time of ovariectomized rats was slower than the SHAM group. But the blood flow ability, which was slowed down for ovary removal, was improved by IOT administration. Serum triglyceride levels were significantly reduced by IOT administration. Moreover, blood HDL-cholesterol levels were reduced by ovary removal. However, IOT administration after ovary excision significantly increase HDL-cholesterol levels. The biological activity of IOT could be confirmed from these results. Moreover, IOT can be used in the development of functional foods which are meant to improve blood circulation and anti-platelet aggregation function. According to these results, we could know that IOT improved blood flow and anti-platelet aggregation. Therefore, it is expected that IOT can be used for the development of functional foods.

• Journal of The Korean Ophthalmological Society
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• v.59 no.12
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• pp.1152-1159
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• 2018

Purpose: We prospectively investigated clinical changes and long-term outcomes after administration of the drugs recommended by the Age-Related Eye Disease Study-2 to patients with intermediate age-related macular degeneration (AMD). Methods: This prospective multicenter study enrolled 79 eyes of 55 patients taking lutein and zeaxanthin. The primary endpoint was contrast sensitivity; this was checked every 12 months for a total of 36 months after treatment commenced. The secondary endpoints were visual acuity, central macular thickness, and drusen volume; the latter two parameters were assessed using spectral domain optical coherence tomography. Results: The mean patient age was $72.46{\pm}7.16years$. Contrast sensitivity gradually improved at both three and six cycles per degree. The corrected visual acuity was $0.13{\pm}0.14logMAR$ and did not change significantly over the 36 months. Neither the central macular thickness nor drusen volume changed significantly. Conclusions: Contrast sensitivity markedly improved after treatment, improving vision and patient satisfaction. Visual acuity, central retinal thickness, and drusen volume did not deteriorate. Therefore, progression of AMD and visual function deterioration were halted.