• 한국지반공학회논문집
• /
• 제26권12호
• /
• pp.71-79
• /
• 2010

설계지반정수의 합리적인 결정과 확률론적 방법에 의한 지반구조물의 설계를 위해서는 지반정수의 변동계수에 대한 신뢰성 있는 추정이 필요하다. 본 논문에서는 인천 송도지역의 지반조사자료를 이용하여 Three-Sigma Rule 및 통계적인 방법과 같은 표준편차 추정방법의 적용성을 평가해 보았다. 무작위성을 보이는 지반 물성값 중, 변동성이 작은 ${\gamma}_t$, ${\gamma}_b$, $e_0$는 $N_o=6$을, 상대적으로 변동성이 큰 $C_{\alpha}/C_c$, $C_c(1+e_0)$, $c_v$, $k_v$의 경우 $N_{\sigma}$=4.2~5.3을 사용하여 Three-Sigma Rule을 적용하면 통계학적 방법과 유사한 결과를 얻는 것이 관찰되었다. 또한 깊이에 따라 경향성을 보이는 비배수전 단강도는 약 40%의 변동계수를 보이는 것으로 관찰되었으며 $N_{\sigma}$=4를 사용하면 Three-Sigma Rule로 얻는 것으로 나타났다. 본 논문에서 추정한 변동계수를 이용하여 지반정수의 신뢰구간, 특성값을 결정할 수 있었다.

• 한국조경학회지
• /
• 제30권4호
• /
• pp.28-36
• /
• 2002

The main purpose of this study was to estimate a new regression model to explain the relationship between urban forest and air temperature in summer, 2001. This study consists of two parts: correlation coefficient analysis and regression analysis. According to correlation coefficient analysis, thermal infra-red radiations of the major land use categories found significant difference in each category. However there were no significant relationship between the data (thermal infra-red radiation and NDVI) derived from Landsat-7 ETM+ image and air temperature at Automatic Weather Stations(AWSs). After estimating various regression models for summer air temperature, the final models were chosen. The final regression models consisted of two variables such as forest m and traffic facilities area. The regression models explained over 78% of the variability in air temperatures. The regression models with variables of forest area and traffic facilities area showed that the coefficient of the first variable was even more significant than the second one. However, the negative impact of the traffic facilities area was slightly greater than the positive impact of the forest area. Consequently, the effects of forest area and traffic facilities area were apparent to explain summer air temperature in Seoul. Therefore two policies have the most important implications to mitigate the summer air temperature in Seoul: to expand and to conserve the urban forest; and to change the Oafnc facilities'characteristics. The results from this study are expected to be useful not merely in informing the public that urban forest mitigates summer air temperahne, but in urging the necessity of budgets for trees and managing urban forests. It is recommended that field swey of summer air temperature be Performed for the vadidation of the models. The main purpose of this study was to estimate a new regression model to explain the relationship between urban forest and air temperature in summer, 2001. This study consists of two parts: correlation coefficient analysis and regression analysis. According to correlation coefficient analysis, thermal infra-red radiations of the major land use categories found significant difference in each category. However there were no significant relationship between the data (thermal infra-red radiation and NDVI) derived from Landsat-7 ETM+ image and air temperature at Automatic Weather Stations(AWSs). After estimating various regression models for summer air temperature, the final models were chosen. The final regression models consisted of two variables such as forest m and traffic facilities area. The regression models explained over 78% of the variability in air temperatures. The regression models with variables of forest area and traffic facilities area showed that the coefficient of the first variable was even more significant than the second one. However, the negative impact of the traffic facilities area was slightly greater than the positive impact of the forest area. Consequently, the effects of forest area and traffic facilities area were apparent to explain summer air temperature in Seoul. Therefore two policies have the most important implications to mitigate the summer air temperature in Seoul: to expand and to conserve the urban forest; and to change the traffic facilities'characteristics. The results from this study are expected to be useful not merely in informing the public that urban forest mitigates summer air temperature, but in urging the necessity of budgets for trees and managing urban forests. It is recommended that field survey of summer air temperature be Performed for the vadidation of the models.

• 전기학회논문지
• /
• 제61권9호
• /
• pp.1340-1349
• /
• 2012

Increasing the oxidation of fat through exercise is the recommendable method for weight control. Preceding researches have proposed increase in the usage of fat during exercise in stabilized state and under maximum exertion through aerobic training. However, such researches require additional equipment for gas analysis in order to measure the caloric value or gas exchange of subjects during exercise. Such equipments become highly restrictive for those exercise and cause substantially higher cost. According to this, we have presented the method of estimating the maximal fat oxidation point through changes in LF & HF which reflects changes in heart rate and the autonomic nervous system in order to induce exercise for a less restrictive and efficient fat oxidation than existing methods. We have conducted exercise stress test on subject with similar exercise abilities, and have detected the changes in heart rate and changes in LF & HF by measuring changes in fat oxidation and measuring ECG signals at the same time through a gas analyzer. Changes in heart rate and HRV of the subjects during exercising was detected through only the electrocardiographic signals from exercising and detected the point of maximum fat oxidation that differs from person to person. The experiment was carried out 16 healthy males, and used Modified Bruce Protocol, which is one of the methods of exercise stress test methods that use treadmill. The fat oxidation amount during exercise of all the subjects showed fat oxidation of more than 4Fkcal/min in the exercise intensity from about 5 minutes to 10 minutes. The correlation between the maximal fat oxidation point obtained through gas analysis and the point when 60% starts to be relevant in the range from -0.01 to 0.01 seconds for values of R-R interval from changes in heart rate had correlation coefficients of 0.855 in Kendall's method and in Spearman's rho, it showed significant results of it being p<0.01 with 0.950, respectively. Furthermore, in the changes in LF & HF, we have determined the point where the normalized area value starts to become the same as the maximal fat oxidation point, and the correlation here showed 0.620 in Kendall and 0.780 in Spearma of which both showed significant results as p<0.01.

• Journal of Ecology and Environment
• /
• 제32권2호
• /
• pp.67-73
• /
• 2009

Soil $CO_2$ efflux can vary markedly in magnitude over both time and space, and understanding this variation is crucial for the correct measurement of $CO_2$ efflux in ecological studies. Although considerable research has quantified temporal variability in this flux, comparatively little effort has focused on its spatial variability. To account for spatial heterogeneity, we must be able to determine the number of sampling points required to adequately estimate soil $CO_2$ efflux in a target ecosystem. In this paper, we report the results of a study of the number of sampling points required for estimating soil $CO_2$ efflux using a closed-dynamic chamber in young and old Japanese cedar plantations in central Japan. The spatial heterogeneity in soil $CO_2$ efflux was significantly higher in the mature plantation than in the young stand. In the young plantation, 95% of samples of 9 randomly-chosen flux measurements from a population of 16 measurements made using 72-$cm^2$ chambers produced flux estimates within 20% of the full-population mean. In the mature plantation, 20 sampling points are required to achieve means within $\pm$ 20% of the full-population mean (15 measurements) for 95% of the sample dates. Variation in soil temperature and moisture could not explain the observed spatial variation in soil $CO_2$ efflux, even though both parameters are a good predictor of temporal variation in $CO_2$ efflux. Our results and those of previous studies suggest that, on average, approximately 46 sampling points are required to estimate the mean and variance of soil $CO_2$ flux in temperate and boreal forests to a precision of $\pm$ 10% at the 95% confidence level, and 12 points are required to achieve a precision of $\pm$ 20%.

• 상하수도학회지
• /
• 제29권4호
• /
• pp.469-479
• /
• 2015

This study have been conducted to analyze the feasibility of establishing Contamination Warning System(CWS) that is capable of monitoring early natural or intentional water quality accidents, and providing active and quick responses for domestic C_water supply system. In order to evaluate the water quality data set, pH, turbidity and free residual chlorine concentration data were collected and each statistical value(mean, variation, range) was calculated, then the seasonal variability of those were analyzed using the independent t-test. From the results of analyzing the distribution of outliers in the measurement data using a high-pass filter, it could be confirmed that a lot of lower outliers appeared due to data missing. In addition, linear filter model based on autoregressive model(AR(1) and AR(2)) was applied for the state estimation of each water quality data set. From the results of analyzing the variability of the autocorrelation coefficient structure according to the change of window size(6hours~48hours), at least the window size longer than 12hours should be necessary for estimating the state of water quality data satisfactorily.

• 한국작물학회지
• /
• 제50권4호
• /
• pp.268-275
• /
• 2005

Early predictions of crop yields call provide information to producers to take advantages of opportunities into market places, to assess national food security, and to provide early food shortage warning. The objectives of this study were to identify the most useful parameters for estimating yields and to compare two model selection methods for finding the 'best' model developed by multiple linear regression. This research was conducted in two 65ha corn/soybean rotation fields located in east central South Dakota. Data used to develop models were small temporal variability information (STVI: elevation, apparent electrical conductivity $(EC_a)$, slope), large temporal variability information (LTVI : inorganic N, Olsen P, soil moisture), and remote sensing information (green, red, and NIR bands and normalized difference vegetation index (NDVI), green normalized difference vegetation index (GDVI)). Second order Akaike's Information Criterion (AICc) and Stepwise multiple regression were used to develop the best-fitting equations in each system (information groups). The models with $\Delta_i\leq2$ were selected and 22 and 37 models were selected at Moody and Brookings, respectively. Based on the results, the most useful variables to estimate corn yield were different in each field. Elevation and $EC_a$ were consistently the most useful variables in both fields and most of the systems. Model selection was different in each field. Different number of variables were selected in different fields. These results might be contributed to different landscapes and management histories of the study fields. The most common variables selected by AICc and Stepwise were different. In validation, Stepwise was slightly better than AICc at Moody and at Brookings AICc was slightly better than Stepwise. Results suggest that the Alec approach can be used to identify the most useful information and select the 'best' yield models for production fields.

• 한국지반공학회논문집
• /
• 제24권5호
• /
• pp.27-35
• /
• 2008

신뢰성 설계를 위한 설계변수의 특성치에 대하여 국내 해양토질을 이용하여 연구하였다. 특성치 산정에 대한 연구결과, Student/Ovesen, Schneider 및 EN 1990 방법의 순으로 평균치에 근접한 것으로 나타났고, EN 1990 방법은 지반특성치 산정방법의 신뢰성 차원에서 부적합한 것을 확인하였다. 그리고 제시된 네가지 특성치 산정방법은 토질의 변동성이 커짐에 따라 특성치를 보수적으로 평가하는 경향을 보였다. 또한 이러한 산정된 특성치가 실 설계에 미치는 영향을 파악하기 위하여 방파제에 대하여 임의 하중하에서 미개량 지반의 지지력 및 침하특성을 검토하였다. Schneider 방법을 이용하여 산정한 결과와 토질정수의 산술평균치를 이용한 결과를 비교한 결과, 허용지지력/작용하중비의 경우 전자가 후자의 65%로 나타났고, 침하량의 경우에는 13.6%를 제시하여 과소평가한 결과였다. 그리고 과거 설계사례에서 산술평균치로 결정된 대표치에 의한 것과 본 논문에서 각 지역의 자료로부터 산정한 특성치에 따른 설계결과를 비교한 결과, 산술평균치로 결정된 대표치에 의한 설계는 대부분 과대평가의 결과를 제시하였다.

• 한국수자원학회논문집
• /
• 제51권2호
• /
• pp.89-98
• /
• 2018

위성자료는 광범위한 지역의 변동성을 관측하기에 매우 유리하다는 특성 때문에 최근 기후변화로 인한 자연재해 등의 연구에서 각광받고 있다. 하지만 위성자료에도 여전히 시 공간적인 해상도의 한계가 있으며, 이를 극복하기 위해 다양한 센서의 융합이나 1차 산출물들을 조합하는 방법을 사용한다. 본 연구에서는 천리안 위성의 GOCI와 MI에서 관측되는 자료를 융합함으로써 500 m 공간 해상도의 지표면 온도 자료를 생산하였고, 정규 식생지수와 함께 사용하여 TVDI를 산정하였다. 산정된 TVDI를 통해 한반도의 토양수분 상태를 모니터링 하고자 하였으며, 이를 비교하기 위해 ASCAT 지표 토양수분 자료를 통해 산정된 SSMI와 비교하였다. 그 결과 천리안 TVDI와 SSMI가 대한민국 전역에서 비슷한 공간 분포를 나타냈으며, 천리안 위성을 활용하여 토양수분을 관측할 수 있는 가능성을 제시하였다. 따라서 본 연구에서 산정 된 한반도의 TVDI가 고해상도의 토양수분을 산정하는 기반이 될 수 있고, 이를 통해 천리안 위성의 활용 범위가 보다 확장되어 다양한 연구의 기반이 될 수 있을 것으로 보인다.

• 한국지반공학회지:지반
• /
• 제3권2호
• /
• pp.17-28
• /
• 1987

본연구에서는 해양토질의 전단강도 산정에 대한 Cone관입시험의 신뇌도를 조사하였다. 사질토에 대하여는 내부마찰각의 불확정성을 조사하였으며, 불확정성에는 자료의 공간적 변화와 해석에 사용 되는 공식의 모텔오차 등이 있고, 그중 해석모텔의 오차가 가장 큰 불확정성이었다. 해석 방법마다 구한 내부마찰각이 서로 다르므로, 해석결과를 종합할 수 있는 주관적 견해개념(subjective opinion) 을 도입하였다. Cone관입시험을 이용하여 잡토지반에서 비배빙전단강도를 산정하기 위해서는 실훈시험이나 현장베인 시험으로 구한 전단강도와 Cone 저항력의 경험적인 관계를 이용하여야 한다. 비배수전단강도의 불확정성은 Cone 계수(Nk)의 자료 산포, Nk의 모델 오차, 이방성과 Cone 저항력의 공간적 변화 등에 기인하며, Nk의 자료산포가 가장 큰 불확정성이었다. Nk값의 산정에 이용되는 비교강도시험은 실내시험보다는 현장베인시험의 신뢰성이 더 큰 것으로 나타났다.

• Journal of Radiation Protection and Research
• /
• 제41권2호
• /
• pp.149-154
• /
• 2016

Background: Any real application of Bayesian inference must acknowledge that both prior distribution and likelihood function have only been specified as more or less convenient approximations to whatever the analyzer's true belief might be. If the inferences from the Bayesian analysis are to be trusted, it is important to determine that they are robust to such variations of prior and likelihood as might also be consistent with the analyzer's stated beliefs. Materials and Methods: The robust Bayesian inference was applied to atmospheric dispersion assessment using Gaussian plume model. The scopes of contaminations were specified as the uncertainties of distribution type and parametric variability. The probabilistic distribution of model parameters was assumed to be contaminated as the symmetric unimodal and unimodal distributions. The distribution of the sector-averaged relative concentrations was then calculated by applying the contaminated priors to the model parameters. Results and Discussion: The sector-averaged concentrations for stability class were compared by applying the symmetric unimodal and unimodal priors, respectively, as the contaminated one based on the class of ${\varepsilon}$-contamination. Though ${\varepsilon}$ was assumed as 10%, the medians reflecting the symmetric unimodal priors were nearly approximated within 10% compared with ones reflecting the plausible ones. However, the medians reflecting the unimodal priors were approximated within 20% for a few downwind distances compared with ones reflecting the plausible ones. Conclusion: The robustness has been answered by estimating how the results of the Bayesian inferences are robust to reasonable variations of the plausible priors. From these robust inferences, it is reasonable to apply the symmetric unimodal priors for analyzing the robustness of the Bayesian inferences.