• Proceedings of the Korea Information Processing Society Conference
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• 2002.04a
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• pp.779-782
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• 2002

영상 압축 분야에서 데이터의 압축이 필수적인데, 이때 가장 많은 중복성을 가지고 있는 시간적 중복성은 이전 프레임의 데이터를 이용하여 움직임 추정과 움직임 보상을 수행하고 추정된 움직임 벡터에 의해서 보상된 영상과 원 영상과의 차 신호를 부호화하여 데이터를 압축한다. 움직임 추정과 움직임 보상 기법은 비디오 영상압축에서 중요한 역할을 하지만 많은 계산량으로 인하여 실시간 응용 및 고해상도 응용에 많은 어려움을 가지고 있다. 만일 움직임 추정을 하기 전에 블록의 움직임을 예측할 수 있다면 이를 바탕으로 탐색 영역에서 초기 탐색점의 위치 및 탐색 패턴을 결정할 수 있다. 본 논문에서는 움직임 벡터의 높은 공간적 상관성을 이용하여 초기 탐색점의 위치와 탐색 패턴을 결정함으로써 적응적으로 움직임 벡터를 추정하는 새로운 기법을 제안하고 성능을 평가한다. 실험을 통하여 제안된 알고리즘은 계산량의 감소에 있어서 높은 성능 향상을 보였다.

• The KIPS Transactions:PartB
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• v.11B no.2
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• pp.199-206
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• 2004

This paper proposes a hybrid independent component analysis(ICA) of fixed-point(FP) algorithm and robust algorithm. The FP algorithm is applied for improving the analysis speed and performance, and the robust algorithm is applied for preventing performance degradations by means of very small kurtosis and temporal correlations between components. And the adaptive adaptation of temporal correlations has been proposed for solving limits of the conventional robust algorithm dependent on the maximum time delay. The proposed ICA has been applied to the problems for separating the 4-mixed signals of 500 samples and 10-mixed images of $512\times512$pixels, respectively. The experimental results show that the proposed ICA has a characteristics of adaptively adapting the maximum time delay, and has a superior separation performances(speed, rate) to conventional FP-ICA and hybrid ICA of heuristic correlation. Especially, the proposed ICA gives the larger degree of improvement as the problem size increases.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.1
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• pp.13-24
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• 2013

Various elastic wave-based site investigation methods have been used to characterize subsurface ground because the dynamic properties can be correlated with various geotechnical parameters. Although the inherent spatial variability of the geotechnical parameters affects the P-wave propagation characteristics, ground heterogeneity has not been considered as an influential factor. Thus, the effect of heterogeneous ground on the travel-time shift and wavefront characteristics of elastic waves through stochastic numerical analyses is investigated in this study. The effects of the relative correlation lengths and relative propagation distances on the travel-time shift of P-waves considering various intensities of ground heterogeneity were investigated. Heterogeneous ground fields of stiffness (e.g., the coefficient of variation = 10 ~ 40%) were repeatedly realized in numerical finite difference grids using the turning band method. Monte Carlo simulations were undertaken to simulate P-wave propagation in heterogeneous ground using a finite difference method-based numerical approach. The results show that the disturbance of the wavefront becomes more significant with stronger heterogeneity and induces travel-time delays. The relative correlation lengths and propagation distances are systematically related to the travel-time shift.

• The Korean Journal of Financial Studies
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• v.10 no.1
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• pp.231-248
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• 2004

본 연구는 주식간 상관관계 속성을 검증하고자 하는 연구의 일환으로, 한국주식시장에서 1980년 1월부터 2003년 5월까지 기간동안에 수익률 측정기간단위 변화에 따라 주식수익률간 상관관계에 어떤 영향이 관찰되는지를 검증하고자 하였다. 즉, 주식수익률간 상관관계가 시간의 함수(시간종속성)인지를 관찰하고자 하였다. 또한, 수익률의 측정기간단위에 따라 영향을 받는 주식수익률간 상관관계가 주식수익률에 영향을 미치는 요인의 어떤 변화에 기인하는 것인지를 시장모형을 이용하여 개별주식수익률 변동성의 구성요소로 분해 및 분석함으로써 그 원인을 찾고자 하였다. 검증결과에 의하면, 수익률의 측정기간단위가 증가함에 따라 주식수익률간 상관관계는 증가하는 경향을 나타냄에 따라 시간의 함수임을 부정할 수 없었고, 또한 측정기간단위가 단기에서 장기로 변화함에 따라 개별주식수익률의 변동성 구성요소에서 개별기업요인에 기인하는 부분은 감소되고 시장요인에 기인하는 부분은 증가하는 것을 알 수 있었다. 즉, 수익률 측정기간단위는 주식수익률간 상관관계에 유의적인 영향을 미치고, 이러한 영향은 주식수익률에 영향을 미치는 요인 중, 시장요인의 변화를 야기하는 것에서 원인을 찾을 수 있었다.

• The Journal of the Acoustical Society of Korea
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• v.31 no.7
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• pp.427-434
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• 2012

The overlap-add technique based on waveform similarity (WSOLA) method is known to be an efficient high-quality algorithm for time scaling of speech signal. The computational load of WSOLA is concentrated on the repeated normalized cross-correlation (NCC) calculation to evaluate the similarity between two signal waveforms. To reduce the computational complexity of WSOLA, this paper proposes a fast NCC computation method, in which NCC is obtained through pre-calculated sum tables to eliminate redundancy of repeated NCC calculations in the adjacent regions. While the denominator part of NCC has much redundancy irrespective of the time-scale factor, the numerator part of NCC has less redundancy and the amount of redundancy is dependent on both the time-scale factor and optimal shift value, thereby requiring more sophisticated algorithm for fast computation. The simulation results show that the proposed method reduces about 40%, 47% and 52% of the WSOLA execution time for the time-scale compression, 2 and 3 times time-scale expansions, respectively, while maintaining exactly the same speech quality of the conventional WSOLA.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.4
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• pp.138-150
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• 2012

The purpose of this study was to examine the regional disparity of ambulatory health care utilization considering spatio-temporal variation in South Korea during 1996-2008(precisely, in 1996, 1999, 2002, 2005, and 2008) using bayesian hierarchial spatio-temporal model. The spatial pattern uses an intrinsic gaussian conditional autoregressive (CAR) error component. Ornstein-Uhlenbeck method was applied to detect the temporal patterns. The results showed that substantial temporal-geographical variation depending on diseases exists in Korea. On the Contrary to the pattern of total outpatient utilizations, for example, the areas that chronic diseases distributed relatively high were most in rural where the proportion of elderly population was higher than in the urban. Chungcheongnam-do, Junlabuk-do, and Kyeongsangbuk-do had higher risks in hypertension, whereas arthritis was higher risk in the Kyeonggi-do, Chungcheongbuk-do, Junlanam-do, and Junlabuk-do. The results of this study suggested that the effective health intervention programmes needed to alleviate the regional variation of health care utilization. These outcomes also provided the foundation for further investigation of risk factors and interventions in these high-risk areas.

• Journal of KIISE:Information Networking
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• v.37 no.1
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• pp.27-34
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• 2010

In this paper, we examine a long-range dependence in an active measurement of a network traffic which has been a well known characteristic from analyses of a passive network traffic measurement. To this end, we utilize RTT(Round Trip Time), which is a typical active measurement measured by PingER project, and perform a relevant analysis to a time series of both RTT and its volatilities. The RTT time series exhibits a long-range dependence or a 1/f noise. The volatilities, defined as a higher-order variation, follow a log-normal distribution. Furthermore, volatilities show a long-range dependence in relatively short time intervals, and a long-range dependence and/or 1/f noise in long time intervals. From this study, we find that the long-range dependence is a characteristic of not only a passive traffic measurement but also an active measurement of network traffic such as RTT. From these findings, we can infer that the long-range dependence is a characteristic of network traffic independent of a type of measurements. In particular, an active measurement exhibits a 1/f noise which cannot be usually found in a passive measurement.

• Journal of Chest Surgery
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• v.31 no.10
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• pp.952-963
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• 1998

Background: Cardiopulmonary bypass(CPB)-induced hemostatic defects may result increased possibility of excessive hemorrhage and additional multiple transfusion reactions or reoperation. Particularly, fibrinolytic activation and decreased platelet count and function by CPB were proposed as a predictor of hemorrhage during postoperative periods in several reports. Materials and methods: Present study, which was conducted in 20 adult patients undergoing CPB, was prospectively designed to examine the hematologic changes, including fibrinolytic activation during and after CPB and to clarify the relationships between these changes and the magnitude of the postoperative nonsurgical blood loss. The serial blood samples for measurment of hematologic parameters were taken during operation and postoperative periods. Blood loss was respectively counted via thoracic catheter drainage at postoperative 3, 6, 12, 24, 48 hours and total period. Results: The results were obtained as follows:Platelet count rapidly declined following CPB(p<0.01), which its decreasing rate was an inverse proportion to total bypass time(TBT, r=0.55, p=0.01), And platelet count in postoperative 7th day was barely near to its control value. Fibrinogen degradating product(FDP) and D-dimer level significantly increased during CPB(p<0.0001, p<0.0001, respectively), and both of fibrinogen and plasminogen concentration correlatively decreased during CPB(r=0.57, p<0.01), implying activation of fibrinolytic system. Postoperative bleeding time (BT), postoperative activated partial thromboplastin time(aPTT) and postoperative prothrombin time (PT) were significantly prolonged as compare with each control value (p=0.05, p<0.0001, p<0.0001, respectively). Total blood loss was positively correlated with patient's age, aortic clamping time (ACT) and TBT, while there was negative correlation between platelet count and blood loss at pre-CPB, CPB-off and the 1st postoperative day, and in some periods. Postoperative aPTT and postoperative PTwere positively related to postoperative 6 hr and 48 hr blood loss(r=0.53, p=0.02; r=0.43, p=0.05) but not to total blood loss, whereas there was no relationship between postoperative BT and blood loss at any period. Conclusions: These observations suggest that CPB results various hematologic changes, including fibrinolytic activation and severe reduction in platelet count. Diverse factors such as age, platelet count, ACT, TBT and postoperative aPTT and PT may magnify the postoperative bleeding. This study will be a basic reference in understanding CPB-induced hemostatic injuries and in decreasing the postoperative hemorrhage

• Korean journal of food and cookery science
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• v.12 no.2
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• pp.193-199
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• 1996

Effects of addition of various additives, sucrose fatty acid ester 1170 (SE), carboxymethyl cellulose (CMC) and soy bean oil (SO) on textural characteristics for untreated and defatted corn and mung bean starch gels stored at room temperature for 24 hrs and 72 hrs were studied. In sensory and instrumental characteristics of starch gels with additives (0.5% for starch basis), the acceptability was highly correlated with cohesiveness and bend property of starch gels stored 24 hrs and springiness, cohesiveness, color, smoothness, bend property, hardness and clarity of starch gels stored 72 hrs. Regardless of adding additives, textural characteristics of defatted corn starch gels showed somewhat higher values than that of com starch gels. The acceptability of starch gels with additives was somewhat lowered in all the cases, which showed highly correlated in cohesiveness for 24 hrs and springiness for 72 hrs. Instrumental characteristics were similar to those of sensory evaluation, which showed no significant difference with additives.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.211-211
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• 2018

미해양대기청 기후예측센터(Climate Prediction Center, NOAA)에서 제공하고 있는 기후지수(climate indices)를 예측인자로 하고 금강유역의 5~6월의 강우량을 예측대상으로 하는 원격상관기반 통계모형을 구축하였다. 1988년부터 2017년까지의 30년 자료에 대해 예측인자와 예측대상간의 시간지연상관분석을 수행한 결과 NAO(North Atlantic Oscillation), EP/NP(East Pacific/North Pacific Oscillation), EA(East Atlantic Pattern), WP(Western Pacific Index) 등과 상관성이 높은 것으로 분석되었으며, 이러한 시간지연 기후지수를 이용하여 4개월전에 5,6월 강수량을 예측할 수 있는 다중회귀모형을 개발하였다. 관측 강우량 아노말리가 큰 경우에는 다소 과소 예측되고, 아노말리가 작은 경우에는 다소 과다 예측되는 경향을 보였지만 관측 강우량과 예측 강우량간의 상관계수가 0.75로서 비교적 우수한 예측 결과를 나타내었다. 5~6월 강우량 아노말리의 3분위 예측성을 평가한 결과 평년이상 적중률은 77.8%, 평년수준은 81.8%로서 예측 성공률이 높았으며, 5, 6월 누적강우량이 매우 작았던 92년과 95년을 제외하고는 강우량이 적은 해에도 예측성이 우수하여 평년이하 적중률이 70.0%를 나타내었다. 따라서 본 개발모형은 최소 4개월 이전 선행시간을 가지고 늦봄, 초여름강우량을 예측할 수 있는 저비용의 가뭄 예측 도구로 유용하게 활용될 수 있을 것이다.