• 대한의용생체공학회:의공학회지
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• 제39권2호
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• pp.87-93
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• 2018

The measurement of Heart Rate Variability (HRV) using electrocardiogram (ECG) signals has been used to predict fatigue and stress levels in a clinical environment, yet, owing to the complexity of such ECG systems, a domestic, nonclinical monitoring of HRV has not been a practical possibility. Recently though, Pulse Rate Variability (PRV) has been studied as an alternative to HRV. In this study, we investigated the reliability of measuring PRV by means of a smartwatch. The PRV results were compared to HRV results in similar test conditions, i.e. those obtained under rapid and deep-breathing scenarios. From the results obtained, it transpires that the Bland-Altman ratio and cross-correlation coefficients between several PRV and HRV parameters were highly correlated, thus suggesting that the results of measuring PRV using a smartwatch can be used to predict HRV in nonclinical environments.

• Journal of Acupuncture Research
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• 제23권1호
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• pp.135-143
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• 2006

Objectives : This study was performed to observe effect of acupuncture stimulation on heart rate variability in stroke patients. Methods : Data were obtained from heart rate variability of 29 stroke patients. Heart rate variability was measured total five times(before and after needle insertion, before and after needle removal, and 10 minutes after needle removal) for five minutes each time. Results : Heart rates were continuously decreased until 10 minutes after needle removal. SDNN, Total power, LF, and HF were increased until 5 minutes after needle removal, but deceased between 5 and 10 minutes after needle removal. There was no significant changes between male and female and among age groups. Conclusion : This study showed that acupuncture stimulation could effect on heart rate variability in stroke patients. Heart rate variability could be a objective tool to verify the mechanism of acupuncture effect in various condition.

• 한국환경과학회지
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• 제22권10호
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• pp.1305-1316
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• 2013

A long-term wind resource map was made to provide the key design data for the 2.5 GW Korean West-South Offshore Wind Project, and its reliability was validated. A one-way dynamic downscaling of the MERRA reanalysis meteorological data of the Yeongwang-Gochang offshore was carried out using WindSim, a Computational Fluid Dynamics based wind resource mapping software, to establish a 33-year time series wind resource map of 100 m x 100 m spatial resolution and 1-hour interval temporal resolution from 1979 to 2012. The simulated wind resource map was validated by comparison with wind measurement data from the HeMOSU offshore meteorological tower, the Wangdeungdo Island meteorological tower, and the Gochang transmission tower on the nearby coastline, and the uncertainty due to long-term variability was analyzed. The long-term variability of the wind power was investigated in inter-annual, monthly, and daily units while the short-term variability was examined as the pattern of the coefficient of variation in hourly units. The results showed that the inter-annual variability had a maximum wind index variance of 22.3% while the short-term variability, i.e., the annual standard deviation of the hourly average wind power, was $0.041{\pm}0.001$, indicating steady variability.

• 수산경영론집
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• 제48권2호
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• pp.1-17
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• 2017

This work studies the variability of flatfish sales revenue. The theoretical analysis draws functions for equilibrium price and quantity using expectation hypotheses. The functions include unpredictable phenomenon with dummy variable and GARCH. The equilibrium function, using adaptive expectation hypothesis, contains the independent variables of supply and demand, while the equilibrium function, embodying rational expectation hypothesis, includes only the independent variables of supply side, because the demand side disappears by the information extraction process theoretically, if economic subjects build the expectation rational. The empirical analysis shows: the variability of flatfish production has a spillover effect on the variability of revenue with the adaptive expectation hypothesis. In the case when the model has a rational expectation hypothesis, the variability of flatfish production has a spillover effect on the revenue (the mean equation of GARCH model). This study indicates that there is the variability in flatfish production and sales revenue, and the spillover effect between them. The result can help to build of the rational system for the fishery income stability.

• Ocean Science Journal
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• 제41권1호
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• pp.1-10
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• 2006

Total sea surface temperature (SST) in a coupled GCM is diagnosed by separating the variability into signal variance and noise variance. The signal and the noise is calculated from multi-decadal simulations from the COLA anomaly coupled GCM and the interactive ensemble model by assuming both simulations have a similar signal variance. The interactive ensemble model is a new coupling strategy that is designed to increase signal to noise ratio by using an ensemble of atmospheric realizations coupled to a single ocean model. The procedure for separating the signal and the noise variability presented here does not rely on any ad hoc temporal or spatial filter. Based on these simulations, we find that the signal versus the noise of SST variability in the North Pacific is significantly different from that in the equatorial Pacific. The noise SST variability explains the majority of the total variability in the North Pacific, whereas the signal dominates in the deep tropics. It is also found that the spatial characteristics of the signal and the noise are also distinct in the North Pacific and equatorial Pacific.

• 음성과학
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• 제12권4호
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• pp.95-112
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• 2005

We investigate Korean learners' speech-timing of English before and after instruction in comparison with native speech, in an attempt to resolve disagreements in the literature as to whether speech-timing is measurable (Lehiste, 1977; Roach, 1982; Dauer, 1983 vs. Low et al., 2000; Yun 2002; Jian, 2004). We measured the pair-wise variability between the adjacent stressed and unstressed syllables within a foot as well as that among adjacent feet in approximately 555 English sentences, which were read by 29 native speakers and 41 Korean learners in the intermediate proficiency level. The results show that in comparison with native American English, Korean learner speech is before instruction significantly (p<.001) smaller for the pair-wise variability between the adjacent stressed and unstressed syllables within a foot; and significantly (p=.01) bigger for the variability among adjacent feet within the utterance. The learner speech after instruction showed significant (p=.01) improvement in the pair-wise variability of syllable sequence toward native speech values. The variability among adjacent feet was progressively smaller for learner speech before and after instruction and for native speech (p=.03). We thus conclude that the speech timing difference between Korean English and American English is measurable in terms of the duration. of stressed and unstressed syllables and that the latter is stress-timed and the former is syllable-timing interfered.

• 대한원격탐사학회지
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• 제17권2호
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• pp.111-119
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• 2001

This study analyzes time variability of the normalized difference vegetation index (NDVI), the leaf area index (LAI) and surface temperature (Ts) estimated from AVHRR data collected from across the Korean peninsula from 1981 to 1994. In the present study, LAI defined as vegetation density, as a function of NDVI applied for the vegetation types and Ts defined by the split-window formulation of Becker and Li (1990) with emissivity of a function of NDVI, are used. Results of the inter-annual, intra-annual and intra-seasonal variabilities in Korea show: (1) Inter-annual variability of NDVI is generally larger in the southem and eastern parts of the peninsula than in the western part. This large variability results from the significant mean variation. (2) Inter-annual variability of Ts is larger in the areas of smaller NDVI. This result shows that the NDVI play a small role in emissivity. (3) Inter-annual variability of LAI is larger in the regions of higher elevation and urban areas. Changes in LAI are unlikely to be associated with NDVI changes. (4) Changes in NDVI and Ts are likely dominant in July and are relatively small in spring and fall. (5) Urban effect would be obvious on the time-varying properties of NDVI and Ts in Seoul and the northern part of Taejon, where NDVI decreases and Ts increases with a significant magnitude.

• 한국임상약학회지
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• 제30권1호
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• pp.36-43
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• 2020

Background: Tacrolimus, a calcineurin inhibitor, is an immunosuppressant used in post-transplantation maintenance therapy. The drug has a narrow therapeutic range and requires periodic therapeutic drug monitoring. Although many studies have reported the effects of intrapatient variability of tacrolimus on survival, rejection, and complications in renal transplant recipients, very few studies have reported these effects in liver transplant recipients. The purpose of this study was to evaluate the effect of intrapatient variability of tacrolimus on clinical outcomes after liver transplantation. Methods: Intrapatient variability was calculated using individual, averaged tacrolimus concentrations. Patients were divided into two groups according to their median variability value: high-variability and low-variability groups. The rate of deviation from the therapeutic range, incidence of acute rejection, post-transplant diabetes, incidence of infection, and estimated glomerular filtration rate (eGFR) after transplantation were compared between the groups. Results: Of the total patients (n=82), the high-variability group (n=41) exhibited significantly greater deviation from the therapeutic range (65.92% vs. 56.84%; p<0.001). There was no significant difference in acute rejection or post-transplantation diabetes incidence or eGFR; however, the number of infection in the first 6 months was significantly lower in the low-variability group (0.4 vs. 0.9 times; p=0.039). Multiple linear regression analysis showed that the number of infection significantly increased as intrapatient variability increased (p=0.015). Conclusion: High intrapatient variability in tacrolimus concentrations was strongly associated with an increased frequency of deviation from the suggested therapeutic range and an increased number of infection.

• 인지과학
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• 제25권3호
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• pp.233-257
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• 2014

범주기반 귀납추론은 인간이 사용하는 주요한 추론방법중 하나이다. 본 연구는 지각된 범주내 변산성이 범주기반 귀납적 일반화에 미치는 효과를 검증하기 위해 실시되었다. 실험 1에서는 범주 예시를 직접 제시하여 범주 변산성 지각을 조작하였다. 조건에 따라 범주내 변산성이 낮은 예시들 (낮은 변산 조건) 혹은 높은 예시들 (높은 변산 조건)을 범주의 예로 제시한 후, 해당 범주에 대한 귀납적 일반화 과제를 실시하였다. 그 결과 지각된 범주 변산성이 낮은 조건이 지각된 변산성이 높은 조건보다 귀납적 일반화에 대한 확신이 더 높다는 것을 확인하였다. 실험 2에서는 범주의 예시를 직접 제시하지 않고, 다양한 예시들 중 특정 범주에 속하는 예들을 참가자들이 변별하는 범주화 과제를 실시함으로써 범주 변산성을 지각하도록 한 후, 귀납추론 과제를 실시하였다. 그 결과, 실험 1과 마찬가지로 지각된 범주 변산성이 낮은 조건이 높은 조건보다 귀납적 일반화에 대한 확신이 더 강해지는 경향을 확인할 수 있었다. 본 연구의 결과는 기존 연구에서 보여준 다양성 효과와 차이점을 보이며 또한 Osherson과 동료들 (1990)이 제안한 귀납추론 모형으로는 설명하기 어렵다. 종합논의에서 범주기반 귀납추론에서 지각된 변산성 효과의 검증에 대해 간략히 논의하였다.

• 인터넷정보학회논문지
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• 제9권1호
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• pp.115-127
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• 2008

다양한 도메인의 요구사항을 만족시켜 주기 위한 컴포넌트는 내부에 다양성을 제공할 수 있도록 개발되어야 한다. 그러나 컴포넌트 개발 시에 다양한 요구사항을 분석하여 설계하더라도 컴포넌트가 이용될 때 또 다른 다양한 요구 사항들이 발생한다. 따라서 다양한 요구 사항들을 완전하게 만족시켜 주기 위한 컴포넌트의 설계는 매우 어려우며 또한 도메인의 특정 화된 업무 로직을 완전하게 수용하는 것은 불가능하다. 이와 같은 문제들로 인해 컴포넌트가 블랙박스가 아닌 화이트 박스로 제공해야 하는 문제가 발생한다. 따라서 본 논문에서는 컴포넌트에 다양성을 제공하기 위해 다양한 도메인을 분석하여 컴포넌트를 설계하기 위한 기법보다는 다양한 도메인의 요구사항을 수용할 수 있는 장치를 제공하기 위해 컴포넌트의 가변성 설계 기법과 이런 설계 기법을 이용하여 컴포넌트를 특화(커스터마이제이션)하기 위한 기법을 제안한다. 컴포넌트의 가변성은 컴포넌트 개발(CD : Component Development)과정에서 초기 가변성이 설계되며 가변성 적용을 위해 특화기법을 이용한다. 가변성이 적용된 컴포넌트를 이용하여 어플리케이션을 개발하는 과정에서 가변성이 재 설계될 수 있으며 이러한 과정을 통해 컴포넌트의 가변성이 진화되고 컴포넌트의 일반성이 더욱 향상될 수 있다. 일반적으로 컴포넌트의 가변성 범위는 컴포넌트 내부의 기능 변경과 컴포넌트 외부의 요구사항에 따라 컴포넌트 내부 구조가 변경되는 것으로 구분될 수 있다. 여기서는 이러한 가변성 범위에 따라 컴포넌트 내의 메시지 호출 변경을 위한 메시지 흐름(Message Flow) 설계 기법을 제안한다.