• 한국작물학회지
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• 제50권4호
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• pp.268-275
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• 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.

• 해양환경안전학회지
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• 제19권6호
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• pp.561-569
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• 2013

본 연구에서는 우리나라 연안의 2003~2009년 해수면자료로 조위편차를 산출하고, 일평균조위편차의 시공간적 변동을 EOF 분석, 해면기압과 바람이 조위편차 변동에 얼마나 영향을 미치는지를 상관성 분석을 통해 알아보았다. 일평균조위편차는 전체 변동량의 68 %(제1모드)가 동시승강하였고, 전체 변동량의 21 %(제2모드)는 서해안이 상승할 때 남해안과 동해안이 하강하는 교차승강을 하였다. 해역별로 조위편차에 영향을 주는 주요 요인을 보면, 서해안은 남-북 방향의 바람 성분이었고, 남해안은 동해안으로 갈수록 해면기압의 영향이 우세하였다.

• 한국지구과학회지
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• 제26권3호
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• pp.199-217
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• 2005

TOMS 월별 오존전량의 전구 자료를 이용하여, 두 기간(전기: 1979-1992년, 후기: 1997-2002년)에 대한 오존전량 추세 및 시공간 변동을 지역과 해륙 분포에 따라 상호 비교하였다. 전기에 비하여 후기의 오존전량이 0-20 N 일부 지역을 제외하고 전지구적으로 10 DU 정도 감소하였다. 오존전량의 추세는 전구적으로 전자기간에 감소(-6.30 DU/decade)를 나타냈다. 후자 기간의 오존 증가 경향은 열대 지역에서 현저하였다. 1997-2002년 기간의 오존전량에 대한 경험직교함수 분석은 준2년 진동(QBO), 준3년 진동(QTO), 엘니뇨(ENSO), 그리고 화산폭발과 관련된 시공간 변동을 반영하였다. 열대 지역에서 대류권 오존의 연직 분포는 동서방향에서 파수 1의 형태를 보였다. 본 연구는 기후 및 환경변화와 관련된 성층권과 대류권 오존 변화의 원인 규명에 도움을 줄 수 있다.

• 생태와환경
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• 제42권4호
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• pp.452-464
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• 2009

The objectives of this study were to evaluate spatial and temporal variability of water quality in 10 reservoirs and identify the key nutrients (N, P) influencing chlorophyll-a (CHL) along with analysis of empirical models and zonal patterns of total phosphorus (TP) and CHL. We analyzed total nitrogen (TN), TP, CHL, water clarity (Secchi depth, SD), and evaluated potential limiting nutrient using ambient N:P ratios and previous criteria of ambient nutrients. Water clarity and CHL varied largely depending on the seasonal monsoon and type of reservoir, but trophic state was diagnosed as eutrophy, base on mean CHL in most reservoirs. The peak of TP did not match the contents of CHL due to rapid flushing during the high run-off period. In the reservoir of DR, regression coefficient in the $P_r$ was 0.510 but was 0.159 in the $M_o$, while the TP-CHL relation in the YR increased during the monsoon compared to the premonsoon. The regression coefficient in the $P_r$ was not statistically significant but the value of $M_o$ was 0.250. TP showed similar longitudinal zonal gradients among the reservoirs of DR, YR and JR. Empirical models of TP-CHL, based on overall data, showed that CHL was determined by phosphorus($R^2=0.244$, p=0.0019). Regression analysis of CHL-SD showed a stronger linear fit ($R^2=0.638$, p<0.001) than the TP-CHL model.

• Safety and Health at Work
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• 제12권4호
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• pp.445-451
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• 2021

Background: This study aimed to evaluate the reliability and validity of the self-administered questionnaire for Korean radiation workers. Methods: From May 24, 2016, to June 30, 2017, 20,608 participants completed the questionnaire, providing information on sociodemographics, lifestyle, work history and practices, medical radiation exposure, and medical history, which was linked to the National Dose Registry and the National Cancer Registry. The validity of the questionnaire was evaluated using the responses of 20,608 workers, and reliability was evaluated using the responses of 3043 workers who responded to the survey twice. Results: Responses concerning demographic characteristics and lifestyle showed reliability with a moderate-to-high agreement (kappa: 0.43-0.99), whereas responses concerning occupation and medical radiation exposure had a wide range of agreement (kappa: 0.05-0.95), possibly owing to temporal variability during employment. Regarding validity, responses to the question about the first year of employment had an excellent agreement with the national registry (intraclass correlation coefficient = 0.9); however, responses on cancer history had a wide range of agreement (kappa: 0.22-0.85). Conclusion: Although the reliability and validity of the questionnaire were not distinguished by demographic characteristics, they tended to be low among participants whose occupational radiation exposure was minimal. Overall, the information collected can be reliable for epidemiological studies; however, caution must be exercised when using information such as medical exposure and work practices, which are prone to temporal variability.

• 한국기후변화학회지
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• 제7권4호
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• pp.477-484
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• 2016

In general, $CH_4$ concentrations generated in combustion facilities are known to be ppm units. In most cases, $CH_4$ samples are collected in Tedlar bags and transported to laboratories for analysis. Considering this fact, in the present study, an attempt was made to find out how long samples can be stored in cases where they are kept in bags and transported as a preliminary study for sampling. According to the results of the experiment using simulated gases (1 ppm, 5 ppm, 10 ppm) in Tedlar bag, $CH_4$ was safe up to 240 hr which is the full time. In the case of simulated gases are containing 4 kind gases ($N_2$, $CO_2$, $CH_4$, and $N_2O$). Field samples (samples of obtained by collecting combustion facilities' exhaust gases) are known to contain highly reactive substances (for example NOx, SOx, and VOCs) and may affect each other. In the present study, one site sample was secured from each of a bituminous coal combustion facility and an LNG combustion facility and whether the concentrations of $CH_4$ gas would change over time (24 hr, 96 hr, 144 hr, 192 hr) was checked. Since site samples could not be analyzed on the day of collection, an experiment was started 24 hr after the time point of sampling to analyze the samples. As with the results of analysis of the simulated gas (240 hr), the results of analysis using the site sample indicated that it could be stored for the full study period 192 hr. Therefore, it was judged that if 192 hr would be taken after sampling before the sample would be analyzed, the concentration value should be reliable.

• 한국기후변화학회지
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• 제9권1호
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• pp.59-67
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• 2018

In this study, the $N_2O$, emitted from combustion facility, were analyzed by using simulated gas and field samples to find out how long samples can be stored in Tedlar bag. According to the results of the experiment using simulated gases (1 ppm, 5 ppm, 10 ppm) in Tedlar bag, After 144hr, $N_2O$ concentration of simulated gases changed that 1 ppm is 5.3%, 5 ppm is 12.8%, and 10ppm is 10.5%. The higher initial concentration of simulated gas was, the larger rate of $N_2O$ concentration was changed. In case of high concentration samples, it need to be careful when it was analyzed after 144 hr. Stability evaluation in Tedlar bag was carried out through field samples such as combustion facility of bituminous coal, B-C oil and LNG. The concentration rate of field samples, which is under 1 ppm of average initial concentration, was evaluated using statistical method. As a result, $N_2O$ concentrations were changed to field samples in the bag even when 96 hr had passed. And after sampling, it is necessary that sample analysis should be quickly as soon as possible.

• Journal of Ecology and Environment
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• 제44권4호
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• pp.229-240
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• 2020

Background: Genus Quercus is a successful group that has occupied the largest area of forest around the world including South Korea. The acorns are an important food source for both wild animals and humans. Although the reproductive characteristics of this genus are highly variable, it had been rarely studied in South Korea. Therefore, in Seoraksan and Odaesan National Parks (i) we measured the acorn production of Quercus mongolica, an overwhelmingly dominant species in South Korea, for 3 years (2017-2019), (ii) evaluated the spatial-temporal variation of acorn production, and (iii) analyzed the effects of oak- and site-related variables on the acorn production. Results: The annual acorn production of Q. mongolica increased 36 times from 1.2 g m-2 in 2017 to 43.2 g m-2 in 2018, and decreased to 16.7 g m-2 in 2019, resulting in an annual coefficient of variation of 104%. The coefficient of spatial variation was high and reached a maximum of 142%, and the tree size was the greatest influencing factor. That is, with an increase in tree size, acorn production increased significantly (2018 F = 16.3, p < 0.001; 2019 F = 8.2, p < 0.01). Elevation and slope also significantly affected the production in 2019. However, since elevation and tree size showed a positive correlation (r = 0.517, p < 0.001), the increase in acorn production with increasing elevation was possibly due to the effect of tree size. The acorn production of Odaesan for 3 years was 2.2 times greater than that of Seoraksan. This was presumed that there are more distribution of thick oak trees and more favorable site conditions such as deep soil A-layer depth, high organic matter, and slower slopes. Conclusion: As reported for other species of the genus Quercus, the acorn production of Q. mongolica showed large spatial and annual variations. The temporal variability was presumed to be a weather-influenced masting, while the spatial variability was mainly caused by oak tree size.

• 한국운동역학회지
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• 제18권2호
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• pp.49-58
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• 2008

본 연구의 목적은 트레드밀 보행 시, gait dynamics 측면에서 보행의 속도 변화와 인지과제 수행 시 보행 변인의 가변성(variability)을 알아보고자 하는 것이다. 실험은 인지과제의 동시수행 유/무에 따른 5가지 속도(선호속도의 80%, 90%, 100%, 110% and 120%)에 의한 보행 실험으로 구성되었다. 인지과제의 종류는 학습기능이 없는 인지과제(2-back task)를 수행하였다. 인지과제는 피험자의 트레드밀 보행 시, 3m 앞에 놓여진 스크린에 주어지고 무선마우스를 통해 응답하는 형태로 구성되었다. 실험의 모든 과정은 3차원 동작분석기를 통해 동작데이터를 획득하였다. 이를 통해, 5가지 보행 시간 변인과 3가지 공간 변인을 추출하였다. gait dynamics 측면의 분석을 위해, 가변성의 크기를 살펴볼 수 있는 방법인 분산계수(coefficient of variance)와 변동량의 구조적 자기 유사성을 추론할 수 있는 detrended fluctuation analysis (DFA)를 사용하였다. 그 결과 보행 속도 변화에 따라 보행 변인의 평균값과 분산계수에서 통계적 유의한 차이가 발생하였고, 인지과제의 수행 유/무에 따라서는 DFA에서 통계적인 차이가 발생하였다. 이는 인지과제의 수행에 의해 보행의 발생과 조절 능력에 영향을 끼쳤다고 추론할 수 있다. 본 연구 결과를 명백히 하기 위해 더 많은 수의 피험자 실험과 추가 실험이 필요할 것이다.

• 한국지구과학회지
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• 제25권7호
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• pp.604-614
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• 2004

경기도 이천에서 2002년 7월부터 12까지 총 6개월 동안 측정된 지자기 3성분 자료를 이용하여 일별 각 성분의 스펙트럼, 지자기 전달함수의 크기, 위상, 오차 등을 계산하였다. 지자기 스펙트럼은 관측기간 동안 태양활동에 의한 무작위적 강약이 반복되는 형태를 보여주었고, 유의미한 시간적 변동은 존대하지 않았다. 지자기 전달함수의 크기, 위상, 오차의 경우, 주기 100초 이하와 주기 1000초 이상에서 부분적으로 무작위적인 경향을 확인할 수 있었으나, 시간에 따른 증감추세 없이 대체로 안정적인 값을 보였다. 이와 더불어, 전기장의 P$_{1}\;^{0}$ 소스(zonal harmonics) 가정을 통하여 시간에 따른 근사적인 겉보기 전기비저항의 변동을 조사하였는데, 근사된 전기비저항의 변화는 지각의 자체적인 물성 변화보다는 수평 자기장 성분의 시간적 강약에 지배적임을 확인할 수 있었다.