• ETRI Journal
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• 제32권5호
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• pp.687-694
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• 2010

Breaks in presence (BIP) are those moments during virtual environment (VE) exposure in which participants become aware of their real world setting and their sense of presence in the VE becomes disrupted. In this study, we investigate participants' experience when they encounter technical anomalies during game play. We induced four technical anomalies and compared the BIP responses of a navigation mode game to that of a combat mode game. In our analysis, we applied a linear mixed model (LMM) and compared the results with those of a conventional regression model. Results indicate that participants felt varied levels of impact and recovery when experiencing the various technical anomalies. The impact of BIPs was clearly affected by the game mode, whereas recovery appears to be independent of game mode. The results obtained using the LMM did not differ significantly from those obtained using the general regression model; however, it was shown that treatment effects could be improved by consideration of random effects in the regression model.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.1524-1524
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• 2001

A previous paper(Ito et al., 2000) has described the improvement of the standard error(SEC and SEP) of the predicted soluble solids(Brix) in a melon cultivar by non-contact mode with a fiber optic probe. Then we examined the immature and mature fruits. The objective of this study was to determine if non-contact mode could improve the standard error of the predicted Brix of matured melon fruits from cross progeny as well as the contact mode(usual method). The optical absorption spectrum was measured using a NIR Systems model 6500 spectrophotometer. A commercial spectral program(NSAS ver. 3.27) was used for multiple linear regression analysis. Absorbances of 902 and in the vicinity of 877 nm were included as the independent variables in both multiple regression equations. These wavelengths are key wavelengths for non-destructive Brix determination. When the results for the contact mode and non-contact mode are compared, the latter mode improved the former standard error(SEP and RMS).

• 부모자녀건강학회지
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• 제13권2호
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• pp.95-101
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• 2010

Purpose: This study is intended to identify difference postpartum depression according to delivery mode in the postpartum women. Methods: The subjects were 239 postpartum women in D and A city. Data collected from June 9, 2006 to August 6, 2007 using structured questionnaire surveys and convenience sampling. Measuring instrument was BDI (Beck Depression Inventory) translated By Lee and Song (1991). Collected data was analyzed by $x^2$-test, ANCOVA, Stepwise Multiple Regression with SPSS/PC 14.0. Results: There were significant differences in postpartum period ($x^2$=12.40, p = .002) and sleeping hours ($x^2$=9.09, p = .011) as analysed distribution of the subjects according to delivery mode. As result of analyzing the difference of postpartum depression according to delivery mode using ANCOVA, C-sec women's postpartum depression was higher than vaginal delivery women statistically (F=6.32, p = .013). As a result of Multiple Regression, income was a influencing factor of postpartum depression in vaginal delivery women and support of spouse and sleeping hours were influencing factors in C-sec women. Conclusion: There were differences in postpartum depression and their influencing factors according to delivery mode. Therefore it is necessary to develop and study a concrete nursing intervention and strategies for reducing the postpartum depression according to delivery mode.

• 대한교통학회지
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• 제28권3호
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• pp.145-155
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• 2010

녹색교통으로서 자전거 이용활성화가 사회적으로 큰 조명을 받고 있으나 효과적인 성과를 내기 위해서는 자전거 이용특성에 대한 구체적이고 치밀한 분석이 선행되어야 한다. 이는 1995년 이래 2007년까지 자전거도로를 9,170km나 정비하였음에도 불구하고 동기간동안 자전거 수단분담률이 오히려 감소(국토해양부, 2009)한 점을 통해 알 수 있다. 본 연구는 2006년 조사된 '수도권 가구통행실태조사' 자료(303,308개)를 이용하여 통행 주체별 자전거 수단분담률을 구체적으로 분석하였다. 그 결과 학원 수강목적과 오피스텔 거주자의 자전거 수단분담률이 각각 3.75%, 3.13%로 통행 주체 중 가장 높은 것으로 나타났다. 아울러 로지스틱 회귀분석을 통한 서울시의 자전거 수단분담률 추정모형을 구축하였다. 동시에 로지스틱 회귀계수에 대한 승산비(odds ratio)의 산출을 통해 자전거 수요에 영향을 미치는 관련 요인과 영향 정도를 분석하였다. 그 결과 단거리 통행, 학원가와 공원, 오피스텔 주택가 중심의 자전거 이용활성화가 효과적인 것으로 판명되었다.

• Wind and Structures
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• 제38권5호
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• pp.381-398
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• 2024

This study presents a mode analysis of 3D turbulent velocity data around a square-section building model to identify the dynamic system for Kármán-type vortex shedding. Proper orthogonal decomposition (POD) was first performed to extract the significant 3D modes. Magnitude-squared coherence was then applied to detect the phase consistency between the modes, which were roughly divided into three groups. Group 1 (modes 1-4) depicted the main vortex shedding on the wake of the building, with mode 2 being controlled by the inflow fluctuation. Group 2 exhibited complex wake vortexes and single-sided vortex phenomena, while Group 3 exhibited more complicated phenomena, including flow separation. Subsequently, a third-order polynomial regression model was used to fit the dynamics system of modes 1, 3, and 4, which revealed average trend of the state trajectory. The two limit cycles of the regression model depicted the two rotation directions of Kármán-type vortex. Furthermore, two characteristic periods were identified from the trajectory generated by the regression model, which indicates fast and slow motions of the wake vortex. This study provides valuable insights into 3D mode morphology and dynamics of Kármán-type vortex shedding that helps to improve design and efficiency of structures in turbulent flow.

• Asia-Pacific Journal of Atmospheric Sciences
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• 제54권4호
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• pp.611-622
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• 2018

Observed climate data are processed under the assumption that their time series are stationary, as in multi-step temperature and precipitation prediction, which usually leads to low prediction accuracy. If a climate system model is based on a single prediction model, the prediction results contain significant uncertainty. In order to overcome this drawback, this study uses a method that integrates ensemble prediction and a stepwise regression model based on a mean-valued generation function. In addition, it utilizes empirical mode decomposition (EMD), which is a new method of handling time series. First, a non-stationary time series is decomposed into a series of intrinsic mode functions (IMFs), which are stationary and multi-scale. Then, a different prediction model is constructed for each component of the IMF using numerical ensemble prediction combined with stepwise regression analysis. Finally, the results are fit to a linear regression model, and a short-term climate prediction system is established using the Visual Studio development platform. The model is validated using temperature data from February 1957 to 2005 from 88 weather stations in Guangxi, China. The results show that compared to single-model prediction methods, the EMD and ensemble prediction model is more effective for forecasting climate change and abrupt climate shifts when using historical data for multi-step prediction.

• 한국철도학회논문집
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• 제12권5호
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• pp.656-662
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• 2009

일반적으로 교통수단선택 모형은 이용자의 인구 및 개인통행특성 등을 반영한 수단별 선호도를 효용함수로 구축하여 분석하고 있다. 본 연구에서는 이용자의 출발지에 대한 공간적 연관성을 수단선택모형에 고려한 방법을 제시하였다. 이를 위하여 공간적 연관성을 포함하는 공간로지스틱 회귀모형을 고려하였다. 신뢰성있는 추정값을 얻기 위해 베이지안 기법을 적용하였으며 이 연구에서 제시한 방법론은 수단선호도 조사가 이루어지지 않은 지역에 대해서도 수단분담률을 추정할 수 있을 것으로 기대된다.

• 대한토목학회논문집
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• 제26권6D호
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• pp.935-943
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• 2006

본 연구는 노선 조정을 통하여 현재의 낮은 수송 분담률을 개선할 수 있도록 개선안을 적용한 결과에 대한 효과 분석을 주된 내용으로 하되, 교통수단선택과 대중교통 네트워크 분석의 복잡한 반복 계산이 없이 네트워크 속성을 집약적으로 반영하며 분담률을 집합적 개념으로 추정하는 방법을 통해 기존의 수집 가능한 자료를 이용하여 Network Reshuffling에 의한 분담률 변화 효과를 빠르게 분석할 수 있는 기법을 제안하고 그 사례연구를 제시하였다. 그 결과 현재의 낮은 도시철도 분담률의 가장 근본적인 원인은 첫째 노선의 과도한 굴곡 및 우회가 포함된 불합리한 도시철도 노선설계, 둘째 잦은 환승과 수직 환승으로 인해 초래되는 긴 환승길이로 나타났으며, 이러한 원인 및 문제 해결에 대한 방안으로 단거리 링크 건설을 통한 기존 노선 간 직결 서비스 창출 개념의 Network Reshuffling과 서울시 도시철도에 포함되어 있는 51개 환승역에서의 환승 불편 해소를 위한 수직 환승에서 동일 승강장 환승으로의 전환 등을 제시하였다.

• 천문학회보
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• 제38권2호
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• pp.89.2-89.2
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• 2013

Solar energetic transients, e.g., flares, CMEs, etc., release large amount of energy which is expected to excite acoustic waves (p-modes) by exerting mechanical impulse of the thermal expansion of the flare on the photosphere. We study the p-mode properties of flaring and dormant active regions (ARs) to find association between flare and p-mode parameters. We compute the magnetic and flare activity indices of ARs using the line-of-sight magnetograms and GOES X-ray fluxes, respectively. The p-mode parameters are computed from the ring-diagram analysis. We correct p-mode parameters for magnetic field, filling factors and foreshortening by multiple linear-regression analysis. Our analysis of several flaring and dormant ARs observed during the Carrington rotations 1980-2109, showed strong association of mode parameters with magnetic and flare activities. We find that the mode parameters are contaminated by the geometrical effect. Mode amplitude decreases with angular distance from the solar disc centre. The mode width increases with magnetic activity while amplitude showed opposite relation due to mode absorption by the sunspot. After correcting modes due to all geometrical effects, magnetic activity and filling factor, we find that the modes amplitude, and mode energy increases with flare energy while width shows opposite relation.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.524-527
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• 2004

Hybrid rocket had many advantage with compared to solid and liquid rockets. However, the engines have not yet been used in practical rocket systems, due mainly to the disadvantage of hybrid combustion, such as low fuel regression rate. In this study, lab-scale hybrid motor was designed and manufactured. And the methods of regression rate improvement were considered. Test firings with thrusts up to 300 N were conducted with GOX and transparent PMMA. Thrust was calculated with the pressure of the combustion chamber and the regression rate was measured in with variation of oxidizer flow rate. The regression rates showed a strong dependency on GOX mass flux. The frequency analysis technique of the bulk-mode oscillation of motor was applied to a hybrid rocket motor and was based on the principle that this frequency was inversely proportional to the square root of the chamber volume. Several problems and solutions of operating hybrid rocket were presented.