• Journal of Korean Society of Forest Science
• /
• v.112 no.1
• /
• pp.23-31
• /
• 2023

Predicting forest productivity is essential to evaluate sustainable forest management or to enhance forest ecosystem services. Ordinary least squares (OLS) and partial least squares (PLS) regression models were used to develop predictive models for forest productivity (site index) from the site characteristics and soil profile, along with soil physical and chemical properties, of 112 Quercus mongolica stands. The adjusted coefficients of determination (adjusted R²) in the regression models were higher for the site characteristics and soil profile of B horizon (R²=0.32) and of A horizon (R²=0.29) than for the soil physical and chemical properties of B horizon (R²=0.21) and A horizon (R²=0.09). The PLS models (R²=0.20-0.32) were better predictors of site index than the OLS models (R²=0.09-0.31). These results suggest that the regression models for Q. mongolica can be applied to predict the forest productivity, but new variables may need to be developed to enhance the explanatory power of regression models.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.5
• /
• pp.776-778
• /
• 2006

• Bulletin of the Korean Chemical Society
• /
• v.26 no.12
• /
• pp.2044-2046
• /
• 2005

• 한국경영정보학회:학술대회논문집
• /
• 2007.11a
• /
• pp.466-471
• /
• 2007

현재 국내 이동통신 단말기 시장은 디지털 컨버젼스라는 사회적 트랜드 아래 다양한 기능을 가진 단말기가 출시되고 있다. 본 연구의 목적은 $2005{\sim}2007$년에 제조된 약 300개의 이동통신 단말기 중 에 대한 데이터에 근거하여 이동통신 단말기에 대한 가격지수를 도출하여 측정하는 것으로서 이를 위한 방법으로서 Hedonic price analysis을 이용하고자 한다.

• Journal of the Korean Statistical Society
• /
• v.23 no.1
• /
• pp.33-38
• /
• 1994

The OLS-estimator of the distribance variance in the linear regression model is shown to be asymptotically unbiased when the disturbances are MA(1)-process or particular s-th autocorrelated AR(s)-process.

• Communications for Statistical Applications and Methods
• /
• v.2 no.1
• /
• pp.1-12
• /
• 1995

An estimator of coefficients of polynomial measurement error model with vector predictor and first-order interaction terms is derived using Hermite polynomial. Asymptotic normality of estimator is provided and some simulation study is performed to compare the small sample properties of derived estimator with those of OLS estimator.

• Proceedings of the Korean Nutrition Society Conference
• /
• 2003.05a
• /
• pp.267.1-267.1
• /
• 2003

• Bulletin of the Korean Chemical Society
• /
• v.26 no.7
• /
• pp.1107-1108
• /
• 2005

• Bulletin of the Korean Chemical Society
• /
• v.4 no.5
• /
• pp.200-203
• /
• 1983

1,1,1-Trifluoro-4-substituted-3-buten-2-ols and 1,1,1-trifluoro-5-phenyl-4-penten-2-ol were prepared by hydromagnesation and palladium catalyzed phenylation in high stereoselectivity.

• The Journal of Asian Finance, Economics and Business
• /
• v.7 no.6
• /
• pp.379-385
• /
• 2020

The effect of research and development (R&D) expenditure on firm output is an interesting topic, but hardly explored in developing countries due to the unavailability of data. This study investigates this topic in the context of Vietnam by utilizing a novel dataset of 343 firms listed on the Vietnam Stock Exchange in the 2010-2018 period. The effect of R&D expenditure is examined under the production function framework. In order to obtain the robustness of the quantitative results, we estimate the production function with two coherent techniques including the OLS and 2-SLS. An instrumental variable regression technique is adopted to avoid the endogeneity problem between R&D expenditure and other variables. In our empirical analysis, we find that R&D expenditure has a positive and significant impact on output growth. The finding is robust in both OLS and 2-SLS frameworks. Besides, the output elasticity to R&D expenditure of our result is much higher than the estimated elasticity of other countries. The results imply that a 1% increase in R&D expenditure in Vietnam will help to expand the output more than a 1% increase in R&D investment in other countries. The findings from our paper provide important implications for firm managers, investors, and policymakers in Vietnam.