• The Korean Journal of Applied Statistics
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• v.11 no.1
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• pp.185-192
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• 1998

A bivariate extension of the two-parameter exponential distribution is proposed as a model for certain problems in system level life testing. In particular, it applies to two-component shared parallel systems having a minimum guarantee time. Various statistical properties of the model are investigated, including maximum likelihood estimators (MLEs), modified MLEs, and unbiased estimators of the parameters and their distributions.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.1
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• pp.1-5
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• 2011

We furnished some properties of fuzzy testing of independence for correlation in a bivariate normal distribution by agreement index. First we present some restriction of the fuzzy data, define fuzzy sample correlation coefficient and agreement index for testing hypothesis with acceptance or rejection degree. Also, we show that UMP unbiased fuzzy test and drawing conclusions the fuzzy test.

• Journal of Korea Society of Industrial Information Systems
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• v.4 no.2
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• pp.51-56
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• 1999

In this paper, we study the estimation of system reliability for the parallel system based on Spurrier and Weier 〔9〕 bivariate Weibull distribution. We assume that when one component fails, the workload of the remaining component becomes proportional to ψλ, where ψ〉0. We obtain the maximum likelihood estimators for the parameters of system reliability, and by using the numerical method, study the effects of reliability for the parallel system.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.5
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• pp.25-34
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• 2021

Increase in avian species richness is one of the important issues of urban biodiversity policies, since it can promote diverse ecosystem services such as seed dispersal, education, and pollination. However, though human disturbance can significantly affect avian species richness, there are limited studies on the way to reflect the dynamics of floating population. Therefore, this study analyzed the spatial relationship between avian species richness, floating population, and vegetation cover using telecommunications information to identify the areas that requiring targeted monitoring and restoration action. Bivariate Local Moran's I was applied to identify LISA cluster map that showing representative biotopes, which reflect significant spatial relationship between species richness and population distribution. Edge density and distribution of ndvi were identified for evaluating relative adequacy of selected biotopes to strengthen the robust biodiversity network. This study offers insight to consider human disturbance in spatial context using innovative big data to increase the effectiveness of urban biodiversity measures.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.151-151
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• 2019

Because drought is a complex and stochastic phenomenon in nature, statistical approaches for drought assessment receive great attention for water resource planning and management. Generally drought characteristics such as severity, duration and intensity are modelled separately. This study aims to develop a relationship between drought characteristics using a bivariate copula model. To achieve the objective, we calculated the Standardized Precipitation Index (SPI) using rainfall data at 6 rain gauge stations for the period of 1961-1999 in Jehlum River Basin, Pakistan, and investigated the drought characteristics. Since there is a significant correlation between drought severity and duration, they are usually modeled using different marginal distributions and joint distribution function. Using exponential distribution for drought severity and log-logistic distribution for drought duration, the Galambos copula was recognized as best copula to model joint distribution of drought severity and duration based on the KS-statistic. Various return periods of drought were calculated to identify time interval of repeated drought events. The result of this study can provide useful information for effective water resource management and shows superiority against univariate drought analysis.

• Communications for Statistical Applications and Methods
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• v.15 no.5
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• pp.775-781
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• 2008

It is developed that a family of the semicircular Laplace distributions for modeling semicircular data by simple projection method. Mathematically it is simple to simulate observations from a semicircular Laplace distribution. We extend it to the l-axial Laplace distribution by a simple transformation for modeling any arc of arbitrary length. Similarly we develop the l-axial log-Laplace distribution based on the log-Laplace distribution. A bivariate version of l-axial Laplace distribution is also developed.

• 한국방재학회:학술대회논문집
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• 2009.02b
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• pp.153.2-153.2
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• 2009

• Journal of Korea Water Resources Association
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• v.45 no.2
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• pp.191-201
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• 2012

This study reviewed the parameter estimation procedure of the Freund bivariate exponential distribution for the decision of the annual maximum rainfall event. The method of moments was reviewed first, whose results were compared with those from the method of maximum likelihood. Both methods were applied to the hourly rainfall data of the Seoul rain gauge station measured from 1961 to 2010 to select the annual maximum rainfall events, which were also compared each other. The results derived are as follows. First, when applying the method of moments for the parameter estimation, it was found necessary to consider the correlation coefficient between the two variables as well as the mean and variance. Second, the method of maximum likelihood was better to reproduce the mean, but the method of moments was better to reproduce the annual variation of the variance. Third, The annual maximum rainfall events derived were very similar in both cases. Among differently selected annual maximum rainfall events, those with the higher rainfall amount were selected by the method of maximum likelihood, but those with the higher rainfall intensity by the method of moments.

• Korean Journal of Organic Agriculture
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• v.27 no.3
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• pp.271-288
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• 2019

It has continuously promoted to scale up the agricultural management body in order to cope with the market-opening pressure such as the UR negotiation, the DDA negotiation, and more conclusions of FTAs and to enhance the competitiveness of our agriculture. This study evaluated the factors associated with production organization participation centered on environmentally-friendly agriculture farmers in order to improve the production efficiency of environmentally-friendly agriculture in the aspect of production. In order to achieve this objective, this study evaluated the factors that contributed to participating in an organization using the bivariate probit model focusing on environmentally-friendly agriculture farmers in Chungnam. This study examined the validity and reliability of the study model through exploratory factor analysis. The results of factor analyses identified four factors: "distribution", "production", "organization operation", and "social capital". The results of the bivariate probit model showed that distribution significantly affected production activities and distribution, organization operation, agricultural income, and gender significantly influenced sale activities. Environmentally-friendly production organization had not been able to provide the productive support that was needed for local farmers to produce environmentally-friendly agricultural products in a region. Additionally, farming education did not provide the information needed by the farmers. Although producers had a network within a production organization, it was operated mainly for administrators. Therefore, participants felt somewhat lacking. This study identified the level of organization of producer organizations in Chungnam area, where environmentally-friendly agriculture is well activated. This study suggested implications for future production organization participation by evaluating factors affecting participation quantitatively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2B
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• pp.155-162
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• 2009

Univariate frequency analyses are widely used in practical hydrologic design. However, a storm event is usually characterized by amount, intensity, and duration of the storm. To fully understand these characteristics and to use them appropriately in hydrologic design, a multivariate statistical approach is necessary. This study applied a Gumbel mixed model to a bivariate storm frequency analysis using hourly rainfall data collected for 46 years at the Seoul rainfall gauge station in Korea. This study estimated bivariate return periods of a storm such as joint return periods and conditional return periods based on the estimation of joint cumulative distribution functions of storm characteristics. These information on statistical behaviors of a storm can be of great usefulness in the analysis and assessment of the risk associated with hydrologic design problems.