• 한국통계학회:학술대회논문집
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• 한국통계학회 2003년도 춘계 학술발표회 논문집
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• pp.281-286
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• 2003

The stationarity is one of the most important properties of a time series. We propose robust sign tests for seasonal autoregressive process to determine whether or not a time series is stationary. The tests have an exact binomial null distribution and are robust to the outliers and the heteroscedastic errors. Monte-Carlo simulation shows that the sign test is locally more powerful than the OLSE-based tests for heavy-tailed and/or heteroscedastic error distributions.

• The Korean Journal of Ecology
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• 제13권1호
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• pp.25-32
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• 1990

The vertical distribution and seasonal fluctuation of soil microarthropods in the forests with different flora were investigated in this study. soil micrarthropods were concentrated as much as 71.8% in the first layer subsoil (0-5cm), 22.3% in the second layer subsoil (5-10cm), and 5.9% in the third layer subsoil (10-15cm) in the decreasing order. The population density in the first layer decreased slightly in winter while that of the second layer increased. However, the density in the first layer bounced back in the following spring. Seasonal fluctuations of population density were revealed "Two peak-Two valley type", that is, the densities were high in fall and spring, and low in winter and summer.nd summer.

• The Korean Journal of Ecology
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• 제23권2호
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• pp.169-173
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• 2000

Seasonal distribution of ectomycorrhizal associations in various types of forest in a boreal forest in Manitoba. Canada was investigated. Alsohe relationship between ectomycorrhizal growth and pine pollen nutrients was examined. In four different forest stands, ectomycorrhizas tended to be lower in the spring than in the summer and fall samples. In addition. a mature jack pine (Pinus banksiana) stand showed higher mycorrhizal activities than a young jack pine stand. Growth of Suillus brevipes hyphae wa ts stimulated by additions of pollen representing mean pollen deposition in Mistik Creek study area after 30 and 70 days of growth with dextrose availability. This result suggests that the peak ectomycorrhizal activity is followed by pollen deposition in the study region and therefore, addition of pine and spruce pollen in early or middle of June in the boreal forest can be an important seasonal nutrient source for ectomycorrhizal growth.

• The Journal of Asian Finance, Economics and Business
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• 제7권12호
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• pp.627-633
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• 2020

The study attempts to analyze the impact of firm's risk on capital structure in the context of seasonal and non-seasonal businesses. We use two independent variables namely credit risk and systematic risk and one dependent variable to explore this connection. Sugar sector is taken as seasonal while the textile sector as non-seasonal businesses. The panel data of twenty-five firms from each sector are taken ranging for the period of 2012 to 2019 which has been retrieved from their annual reports for empirical analysis of the study. The results reveal the negative impact of credit risk on capital structure in both types of businesses. Increasing (decreasing) one point of credit risk causes a decrease (increase) leverage ratio by 0.27 points for seasonal while increasing (decreasing) one point of credit risk causes to decrease (increase) leverage by 0.15 points for non-seasonal businesses. Furthermore, the study shows positive impact of systematic risk on leverage ratio in non-seasonal business and no impact in seasonal business. Any increase (decrease) in the systematic risk causes an incline (decline) leverage ratio by 2.68 units for non-seasonal businesses. The study provides a guideline to managers for risk management in businesses. The research focusses on theoretical as well as managerial and policy implications on risk management in businesses.

• 한국양식학회지
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• 제19권4호
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• pp.236-241
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• 2006

남해안에 서식하는 왕우럭의 공생성 요각류 3종의 감염률에 대한 계절 변동을 연구하였다. 계절에 따라서 감염률과 출현량의 차이를 보였으며, 겨울철에 높게 출현하였다. 요각류의 출현 양상에 따른 생산력은 성숙한 요각류의 비율이 높아지면서 초가을과 봄에 높게 나타났다. 공생성 요각류 3종의 출현 빈도는 숙주의 개체군이 성장할 수 있는 서식 조건에 따른 적합한 환경이 되어야 높아지는 것으로 나타났다. 공생성 요각류의 계절에 따른 감염률, 상대 감염강도, 평균 감염밀도는 수온과 그들의 생활사에 기인한 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제37권5호
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• pp.503-510
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• 2005

An instrumental neutron activation analysis was used to measure the concentrations of about 24 elements associated with airborne particulates (PM10) that were collected in the most polluted urban region of Daejeon city, Korea from 2000 to 2002. Using the measurement data for various elements, both the extent of elemental pollution in the study area and the seasonality in their distribution characteristics were examined. Examinations of their distribution patterns indicated that most elements with crustal origin tend to exhibit seasonal peaks during spring, while most elements with anthropogenic origin tend to exhibit seasonal peaks during fall or winter. In order to explain the factors regulating their mobilization properties, the data were processed by a factor analysis. Results of the factor analysis suggested competing roles of both industrial and natural source processes, despite that the study site is located at a downwind position of the industrial complex. Based on the overall results of this study, it is concluded that the site may be strongly impacted by man-made sources but the general patterns of elemental distributions in the study area inspected over a seasonal scale are quite consistent with those typically observed from natural environment.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2000년도 정기총회 및 봄 학술발표회
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• pp.251-254
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• 2000

In this study, we investigated vertical distribution and seasonal changes of phytophlankton community in the Hae-Dong Reservoir from March 1999 to Feburary 2000. This reservoir is relativly small (surface area, 2.7 $km^2$) and is the source of drinking water supply to the eastern part of Pusan City. Samples were collected at 2 sites (1, 3, and 6 m; site 1, in front of the dam; site 2, inlet). The dominant group was Bacillriophyceae at both sites (over 63%), and other groups exhibited seasonal changes (high cyanobacterial density in summer; green algal communities in winter). Chrysophyceae and Dinophyceae were maintained lower level during the study period. Along the water depth, all classess of phytoplankton did not show distintive vertical distribution at both sites except during the blue-green algal bloom in the middle of July and late September. The phytoplankton community dynamics in the Hoe-Dong Reservoir was strongly affected by the hydrological factors such as concentrated precipitation and short retention time.

• 한국환경과학회지
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• 제28권12호
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• pp.1123-1131
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• 2019

In this study, we investigated the spatial range, distribution pattern, temporal appearance, sex ratio, seasonal pattern, and size of the population of Leptalina unicolor locally inhabiting the wetland protection area in the Jaeyaksan Mountain. We found that the butterfly was distributed across four areas at 750 m above sea level and in an area of 96,000 ㎡. in the southeastern slope of the mountain. The discontinuous distribution of the butterflies in the meadow. According to our survey conducted from 2012 to 2014, L. unicolor occurred in May (spring) and July (summer) each year, with the male population more than three times higher than that of the female population. The population size estimated using the mark and recapture method on the back of the hind wing in the two years was as follows: 877±502 and 1243±800 individuals in the spring and summer of 2012, respectively, and 783±429 and 506±365 individuals in the spring and summer of 2014, respectively, suggesting no specific seasonal pattern. The findings of this study are expected to be useful for the conservation of the populations and habitats of L. unicolor, which are currently distributed locally due to a decrease in population size.

• 한국환경보건학회지
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• 제26권2호
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• pp.108-115
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• 2000

The mass fraction of PM10 had a bimodal distribution in the middle of between 2.1 ${\mu}{\textrm}{m}$, and the average mass fraction of particles less than 2.1~3.1 ${\mu}{\textrm}{m}$ was 54.1% for Pb and 890.8 ng/㎥ for Fe, respectively. For the concentration of PM10 and metallic elements by seasonal variation, PM10 showed bimodal distribution, while metallic elements showed different distributions by their sources. The ratios of fine particles to total mass were 0.45 for PM10, 0.41 for Cr, and 0.20 for Fe, 0.57 for Zn, 0.68 for Cd and 0.63 for Pb, respectively. That facts indicated that PM10, Zn, Cd, Cr and Pb were from anthropogenic sources, and Fe was from natural source. The geometric means and geometric standard deviations by seasonal variations were 3.6 ${\mu}{\textrm}{m}$ , 2.31 ${\mu}{\textrm}{m}$ in winter, 3.0 ${\mu}{\textrm}{m}$ , 2.49 ${\mu}{\textrm}{m}$ in spring, 2.7 ${\mu}{\textrm}{m}$ , 2.03 ${\mu}{\textrm}{m}$ in summer respectively. And, total efficiency of cascade impactor by seasonal variations were 49.6% in winter, 45.9% in spring and 44.5% in summer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.450-453
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• 2003

This paper presents the estimation on Load Characteristic Factor(k) which is considered to load pattern and seasonal characteristic of consumer. We can calculate the loss of distribution networks through the equation composing of Load Factor(LF), Loss Load Factor(LLF) and load characteristic factor(k). This equation is similar to the method of Regulator-General Victoria, Australia. Generally, the conventional method for calculating the distribution losses uses k with a constant value from 0.1 to 0.3. However, the k which is a relationship between LF and LLF can be varied by load pattern and seasonal characteristics. It is necessary to estimate the k according to load characteristics. This paper shows the result for recalculating k using the KEPCO's SOMAS data measured in distribution networks.