• 한국물환경학회지
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• 제37권6호
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• pp.520-530
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• 2021

Multivariate statistical analysis and an environmental hydrological model were applied for investigating the causes of water pollution and providing best management practices for water quality improvement in urban and agricultural watersheds. Principal component analysis (PCA) and cluster analysis (CA) for water quality time series data show that chemical oxygen demand (COD), total organic carbon (TOC), suspended solids (SS) and total phosphorus (T-P) are classified as non-point source pollutants that are highly correlated with river discharge. Total nitrogen (T-N), which has no correlation with river discharge and inverse relationship with water temperature, behaves like a point source with slow and consistent release. Biochemical oxygen demand (BOD) shows intermediate characteristics between point and non-point source pollutants. The results of the PCA and CA for the spatial water quality data indicate that the cluster 1 of the watersheds was characterized as upstream watersheds with good water quality and high proportion of forest. The cluster 3 shows however indicates the most polluted watersheds with substantial discharge of BOD and nutrients from urban sewage, agricultural and industrial activities. The cluster 2 shows intermediate characteristics between the clusters 1 and 3. The results of hydrological simulation program-Fortran (HSPF) model simulation indicated that the seasonal patterns of BOD, T-N and T-P are affected substantially by agricultural and livestock farming activities, untreated wastewater, and environmental flow. The spatial analysis on the model results indicates that the highly-populated watersheds are the prior contributors to the water quality degradation of the river.

• 농촌지도와개발
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• 제10권1호
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• pp.57-76
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• 2003

This study examined th socioeconomic returns to agricultural research in Korea, using multivariate time series technique and Akino-Hyami formula. Results showed that the socioeconomic returns were quite competitive with internal rates of 49.18% and 56.04% for agricultural research and horticultural research respectively. The lagged response to the investment in research varied according to the type of production: agricultural production responded to agricultural research shock about three tears after the shock, while horticultural and livestock productions responded only after abort seven, and ten years, respectively. The magnitudes of the impacts of investment, however, showed a similar pattern for the three types of production: after responding to the shock, the impact increased until a peak was reached and then declined and got down to zero after some years. The peak was reached within five, seventeen, and twenty tears after the intial expenditures for agricultural, horticultural, and livestock productions, respectively. Moreover, the impacts disappeared about thirty tears after the initial expenditures for all three types of production. These findings were consistent with the results from previous literature on agricultural research, which indicated that the lag lengths of the response to investments on research were between seven and thirty years.

• The Journal of Asian Finance, Economics and Business
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• 제6권3호
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• pp.151-162
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• 2019

The paper examines the effects of Foreign Direct Investment (FDI) on the economic growth of Lao People's Democratic Republic (Lao PDR) between 1993 and 2015. The investigation is based on the influence of growth and economic absorptive capability determinants such as human capital, trade openness, and institutional quality. The methodological analysis uses a multivariate framework accounting capital stock, labor stock, FDI, human capital, trade openness, and institutional quality in regression of the Vector Autoregressive model. Augmented Dickey-Fuller unit root test, Johansen Cointegration test, and Granger Causality test were applied as parts of the econometric time-series analysis approach. The empirical results demonstrate the positive effects of FDI and trade openness, and the negative effects of human capital and institutional quality on the economic growth of the Lao PDR over the 1993 to 2015 period. The findings confirm that trade openness complemented by a sufficient level of infrastructure, education, quality institutions, and transparency significantly influence economic growth and attract more FDI. Research results lend credence to the need for the Lao PDR's government to focus on improving its economic absorptive capability and economic competitiveness regionally and globally by improving wealth and resource management strategies, as failure to take this course of action could lead to the Dutch Disease effects.

• Environmental Engineering Research
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• 제22권1호
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• pp.116-124
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• 2017

The study makes an attempt to investigate the causal nexus between carbon dioxide emissions, GDP per capita, industrialization and population with an evidence from Rwanda by employing a time series data spanning from 1965 to 2011 using the autoregressive distributed lag model. Evidence from the study shows that carbon dioxide emissions, GDP per capita, industrialization and population are co-integrated and have a long-run equilibrium relationship. Evidence from the Granger-causality shows a unidirectional causality running from industrialization to GDP per capita, population to carbon dioxide emissions, population to GDP per capita and population to industrialization. Evidence from the long-run elasticities has policy implications for Rwanda; a 1% increase in GDP per capita will decrease carbon dioxide emissions by 1.45%, while a 1% increase in industrialization will increase carbon dioxide emissions by 1.64% in the long-run. Increasing economic growth in Rwanda will therefore reduce environmental pollution in the long-run which appears to support the validity of the environmental Kuznets curve hypothesis. However, industrialization leads to more emissions of carbon dioxide, which reduces environment, health and air quality. It is noteworthy that the Rwandan Government promotes sustainable industrialization, which improves the use of clean and environmentally sound raw materials, industrial process and technologies.

• Journal of the Korean Data and Information Science Society
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• 제25권4호
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• pp.807-817
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• 2014

본 논문은 최근 많은 관심을 받는 미세먼지 (PM10)의 일별 평균농도에 대해서 전국 16개 시도에서 2008년부터 2011년까지 관측한 다변량 시계열 자료에 대한 연구이다. 다변량 시계열 모형을 이용해서 시간 및 공간에 대한 상관관계를 동시에 고려, 일변량 혹은 특정 지역에 국한해서 분석한 기존의 연구와 차별성을 두었다. 또한 Davis 등 (2013)이 제안한 부분 스펙트럼 일관성 (partial spectral coherence)을 통해 다른 지역간의 상호 의존성을 파악하고 이를 토대로 변수 선택을 통해 희박벡터자기회귀모형 (sVAR; sparse vector autoregressive model)을 적합하는 방법론을 적용하여 고차원 자료 분석의 단점 및 한계를 보완하였으며 예측력 비교를 통해서 sVAR 모형 적합의 타당성을 검증하였다.

• The Journal of Asian Finance, Economics and Business
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• 제7권11호
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• pp.117-126
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• 2020

This paper is aimed to explore the co-movement capital market in Southeast Asia and analysis the correlation of conventional and Islamic Index in the regional and global equity. This research become necessary to represent the risk on the capital market and measure market performance, as investor considers the volatility before investing. The time series daily data use from April 2012 to April 2020 both conventional and Islamic stock index in Malaysia and Indonesia. This paper examines the dynamics of conditional volatilities and correlations between those markets by using Multivariate Generalized Autoregressive Conditional Heteroscedasticity (MGARCH). Our result shows that conventional or composite index in Malaysia less volatile than Islamic, but on the other hand, both drive correlation movement. The other output captures that Islamic Index in Indonesian capital market more gradual volatilities than the Composite Index that tends to be low in risk so that investors intend to keep the shares. Generally, the result shows a correlation in each country for conventional and the Islamic index. However, Internationally Indonesia and Malaysia composite and Islamic is low correlated. Regionally Indonesia's indices movement looks to be more correlated and it's similar to Malaysian Capital Market counterparts. In the global market distress condition, the diversification portfolio between Indonesia and Malaysia does not give many benefits.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2010년도 학술발표회
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• pp.571-575
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• 2010

Drought is a natural hazard with different properties that are usually dependent to each other. Therefore, a multivariate model is often used for drought frequency analysis. The Copula based bivariate drought severity and duration frequency analysis is applied in the current study in order to show the effect of tail behavior of drought severity and duration on the selection of a copula function for drought bivariate frequency analysis. Four copula functions, namely Clayton, Gumbel, Frank and Gaussian, were fitted to drought data of four stations in Iran and Canada in different climate regions. The drought data are calculated based on standardized precipitation index time series. The performance of different copula functions is evaluated by estimating drought bivariate return periods in two cases, [$D{\geq}d$ and $S{\geq}s$] and [$D{\geq}d$ or $S{\geq}s$]. The bivariate return period analysis indicates the behavior of the tail of the copula functions on the selection of the best bivariate model for drought analysis.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.29-29
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• 2015

수자원의 지속적인 관리 및 효율적인 활용을 위하여 수문량의 예측과 분석은 필수적인 과정이라 할 수 있으며 이에 따라 다양한 수문 모형이 구축되고 강우, 유량 등 대표적인 수문량의 예측이 수행되어져 왔다. 그 중에서도 수문 시계열 모형은 시간의 흐름에 따라 일정하게 기록되어온 수문 자료를 확률적인 과정을 통하여 모형을 구축하고 이를 바탕으로 미래 수문량을 예측하는 데활용되는 모형으로, 과거에 기록된 수문 패턴이 미래에도 지속된다는 가정 하에 구축된다. 일반적으로 시계열 모형은 하나의 자료계열로 모형을 구축하는 단변량 모형과 원 자료계열 외에 다른 자료계열을 고려하여 모형을 구축하는 다변량 모형이 있으며, 다변량 모형은 원 자료계열에 영향을 미치는 외부변수를 고려함으로써 두 자료계열간의 상관성을 모형에 반영할 수 있는 장점을 가지고 있다. 또한 자료계열의 계절성을 고려하여 시계열 모형을 구축할 경우, 수문 시계열이 가지고 있는 계절적 영향을 잘 반영할 수 있다. 따라서 본 연구에서는 계절성을 고려한 다변량 시계열 모형인 SARIMAX(Seasonal AutoRegressive Integrated Moving Average with eXogenous) 모형을 이용하여 대표적인 수공구조물인 댐의 유입량 예측을 수행하였다. 일반적으로 댐 유입량 예측에는 댐의 유입량과 상관성이 높은 강우가 외부변수로 사용되어져 왔으나, 이 외에도 영향을 미칠 수 있는 지점특성치를 고려하여 모형을 구축한 후 비교하였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제19권4호
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• pp.23-30
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• 2014

Coastal aquifer in Muan, Jeonnam, has experienced heavy seawater intrusion caused by the extraction of a substantial amount of groundwater for the agricultural purpose throughout the year. It was observed that groundwater level dropped below sea level due to heavy pumping during a dry season, which could accelerate seawater intrusion. Therefore, water level needs to be monitored and managed to prevent further seawater intrusion. The purpose of this study is to develop the autoregressive-cross-regressive (ARCR) models that can predict the present or future groundwater level using its own previous values and pumping events. The ARCR model with pumping and water level data of the proceeding five hours (i.e., the model order of five) predicted groundwater level better than that of the model orders of ten and twenty. This was contrary to expectation that higher orders do increase the coefficient of determination ($R^2$) as a measure of the model's goodness. It was found that the ARCR model with order five was found to make a good prediction of next 48 hour groundwater levels after the start of pumping with $R^2$ higher than 0.9.

• The Journal of Asian Finance, Economics and Business
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• 제8권1호
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• pp.327-333
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• 2021

Accounting information disclosure by enterprises is important for third-party entities (suppliers, creditors, banks, regulators, etc.). Voluntary accounting information disclosure (VAID) refers to additional information related to business activities shown on the annual report above and beyond the required information about business results and financial position as well as cash flow. This supports the stakeholders gaining useful information to make proper business decisions. The article examines the influence of ownership structure on the voluntary accounting information disclosure of the top 100 Vietnamese listed companies (VN100). Data collected by authors on regular annual reports totaled 425 observations from 2015 to 2019. The article uses OLS to test multivariate regression models with time-series data. The research results show that there are three variables affecting voluntary accounting information disclosure, of which foreign ownership and institution ownership have a positive impact, while concentration ownership has an opposite impact. Accordingly, the managers of VN100 should raise awareness in order to demonstrate the obligation of information providers to users to ensure clarity and completeness. The state agencies should encourage VN100 to enhance voluntary accounting information disclosure. This contributes to improve the information level of Vietnamese listed companies to embrace the trend of international economic integration.