• Journal of Korean Society of Forest Science
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• v.90 no.2
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• pp.217-226
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• 2001

This study estimated the impacts of the building permit area change on the forest products import quantities in Korea. The first objective of this dissertation is to analyze whether there is any causal relationship between change in the building permit area and changes in the import quantities of forest products in Korea. Assuming that there is any causal relationship, the second objective is to evaluate the dynamics of the impacts of the building permit area change on the forest products import quantities in Korea. The relationship between the building permit area and the import quantity was represented by bivariate vector autoregressive or vector error correction model. Whether there is any causal relationship between change in the building permit area and changes in the import quantities of forest products was analyzed by the causality test of Granger. And the dynamics of the impacts of the building permit area change on the forest products import quantities were evaluated by variance decomposition analysis and impulse response analysis. The import quantity of forest products can be explained by the lagged building permit area variables and the lagged import quantity variables in Korea. Change in the building permit area causes change in the high-density fiberboard import quantity in Korea. In the bivariate model of the high-density fiberboard import quantity, after six months, the building permit area change accounts for about ten percent of variation in the import quantity, and its own change accounts for about ninety percent of variation in the import quantity. On the other hand, the impact of a shock to the building permit area is significant for about six months on the import quantity of high-density fiberboard in Korea. That is, if the building permit area change indeed had an impact on the import quantity of high-density fiberboard in Korea, it was only of a short-term nature.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.18-18
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• 2011

Climate change is impacting and will increasingly impact both the quantity and quality of the world's water resources in a variety of ways. In some areas warming climate results in increased rainfall, surface runoff, and groundwater recharge while in others there may be declines in all of these. Water quality is described by a number of variables. Some are directly impacted by climate change. Temperature is an obvious example. Notably, increased atmospheric concentrations of $CO_2$ triggering climate change increase the $CO_2$ dissolving into water. This has manifold consequences including decreased pH and increased alkalinity, with resultant increases in dissolved concentrations of the minerals in geologic materials contacted by such water. Climate change is also expected to increase the number and intensity of extreme climate events, with related hydrologic changes. A simple framework has been developed in New Zealand for assessing and predicting climate change impacts on water resources. Assessment is largely based on trend analysis of historic data using the non-parametric Mann-Kendall method. Trend analysis requires long-term, regular monitoring data for both climate and hydrologic variables. Data quality is of primary importance and data gaps must be avoided. Quantitative prediction of climate change impacts on the quantity of water resources can be accomplished by computer modelling. This requires the serial coupling of various models. For example, regional downscaling of results from a world-wide general circulation model (GCM) can be used to forecast temperatures and precipitation for various emissions scenarios in specific catchments. Mechanistic or artificial intelligence modelling can then be used with these inputs to simulate climate change impacts over time, such as changes in streamflow, groundwater-surface water interactions, and changes in groundwater levels. The Waimea Plains catchment in New Zealand was selected for a test application of these assessment and prediction methods. This catchment is predicted to undergo relatively minor impacts due to climate change. All available climate and hydrologic databases were obtained and analyzed. These included climate (temperature, precipitation, solar radiation and sunshine hours, evapotranspiration, humidity, and cloud cover) and hydrologic (streamflow and quality and groundwater levels and quality) records. Results varied but there were indications of atmospheric temperature increasing, rainfall decreasing, streamflow decreasing, and groundwater level decreasing trends. Artificial intelligence modelling was applied to predict water usage, rainfall recharge of groundwater, and upstream flow for two regionally downscaled climate change scenarios (A1B and A2). The AI methods used were multi-layer perceptron (MLP) with extended Kalman filtering (EKF), genetic programming (GP), and a dynamic neuro-fuzzy local modelling system (DNFLMS), respectively. These were then used as inputs to a mechanistic groundwater flow-surface water interaction model (MODFLOW). A DNFLMS was also used to simulate downstream flow and groundwater levels for comparison with MODFLOW outputs. MODFLOW and DNFLMS outputs were consistent. They indicated declines in streamflow on the order of 21 to 23% for MODFLOW and DNFLMS (A1B scenario), respectively, and 27% in both cases for the A2 scenario under severe drought conditions by 2058-2059, with little if any change in groundwater levels.

• Journal of Korean Society of Forest Science
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• v.90 no.5
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• pp.663-671
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• 2001

This study estimated the impacts of the interest rate change on the forest products import quantities in Korea. The first objective is to analyze whether there is any causal relationship between change in the interest rate and changes in the import quantities of forest products in Korea. And the second objective is to evaluate the dynamics of the impacts of the interest rate change on the forest products import quantities in Korea. The relationship between the interest rate and the import quantity was represented by bivariate vector autoregressive model. Whether there is any causal relationship between change in the interest rate and changes in the import quantities of forest products was analyzed by the causality test. And the dynamics of the impacts of the interest rate change on the forest products import quantities were evaluated by variance decomposition analysis and impulse response analysis. The import quantity of forest products can be explained by the lagged interest rate variables and the lagged import quantity variables in Korea. Change in the interest rate causes change in the plywood import quantity in Korea. In the bivariate model of the plywood import quantity, after three months, the interest rate change accounts for about twenty percent of variation in the import quantity, and its own change accounts for about eighty percent of variation in the import quantity. On the other hand, the impact of a shock to the interest rate is significant for about six months on the import quantity of plywood in Korea. That is, if the interest rate change had an impact on the import quantity of plywood in Korea, it was only of a short-term nature.

• School Mathematics
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• v.4 no.3
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• pp.495-511
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• 2002

In this paper, we deal with the teaching of parameter in the school mathematics. The roles of letters become different according to the letters-used context. That is, the meaning of letters may change in the course of being used. But specifying the roles of letters without understanding the distinction between the roles is not enough for students to learn the meaning of variables, specifically that of parameters. Therefore, the parameter-learning should focus on the dynamic change of roles. That implies flexible thinking and changing of perspectives.

• The Korean Journal of Emergency Medical Services
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• v.28 no.1
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• pp.21-34
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• 2024

Purpose: This study aimed to observe change in factors over time in the first cohort of the 2018 Children and Adolescent Panel Middle School. In addition, this study attempted to examine the causal relationship and influence between variables by setting a time gap between independent and dependent variables. Methods: Frequency and descriptive statistical analyses were conducted to determine the general characteristics of the study participants. Hierarchical regression analysis was conducted to analyze the effects of smartphone dependence on health, sleep quality, and depression. After inputting the control variables (Model 2), the influence of the variables was identified based on the input model. Results: Smartphone dependence positively impacted depression in both male and female students and negatively impacted sleep and health. Conclusion: Smartphones are closely associated with teenagers' lives. Additionally, as adolescents experience various psychological anxieties owing to rapid physical changes, there are concerns that psychological dependence may increase, considering that adolescence is the most emotionally unstable period. Therefore, the results of this study consistently prove that smartphone dependence has a causal relationship with emotion-related variables, such as emotional stress, depression, and anxiety.

• Journal of Environmental Science International
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• v.8 no.4
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• pp.533-538
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• 1999

Fuzzy algorithm of automatic control for dissolved oxygen(DO) concentration in the aeration tank of an activated sludge process is proposed. Among variables repirometry and air flowrate are selected as significant input factors and the relationship with DO is estimated using a multiple regression model. The DO concentration and the amount of repirometry are fuzzified and the fuzzy rule base are determined. Using the fuzzy algorithm, the change of amount of air flowrate are determined and the change of amount of DO is derived.

• Journal of The Korean Association For Science Education
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• v.21 no.4
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• pp.658-667
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• 2001

In this study, the relationships among students' cognitive/affective variables, cognitive conflict induced by anomalous data, and conceptual change were investigated. Tests regarding background knowledge, field dependence-independence, learning strategy, logical thinking ability, goal orientation, self-efficacy on prior concept and ability, and control belief were administered. Tests of prior conceptions, responses to anomalous data, conception, and retention of conception were also administered. There were no significant correlations of cognitive conflict induced by anomalous data with students' cognitive and affective variables. However, prior knowledge on molecular motion, field dependence-independence, and learning strategy were significantly correlated with students' conception and retention of conception. Logical thinking ability was also correlated with their conception. Multiple regression analysis indicated that learning strategy significantly predicted students' conception and retention of conception. For the affective variables, self-efficacy on ability was significantly correlated with students' conception and retention of conception, and goal orientation was correlated with their conception. Self-efficacy on ability was a significant predictor on students' conception and retention of conception, and goal orientation on their conception.

• Journal of Electrical Engineering and information Science
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• v.1 no.2
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• pp.101-108
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• 1996

A new speed controller based on the fuzzy algorithm with hierarchical structure is presented. The input variables of the controller are speed error and its derivative(change of error), where the output variable is the change of torque current command. Several comparisons were performed with conventional PI (proportional plus integral) controller and proposed controller. These controllers are applied to the laboratory model drive system with 2.2kW induction motor. Some simulation and experimental results show that the speed controller using fuzzy algorithm is more robust than the conventional PI controller.

• Journal of the Korean Data and Information Science Society
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• v.18 no.2
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• pp.345-356
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• 2007

This study deals with an early detection problem of structural change in won/dollar exchange market. A CUSUM algorithm is developed to monitor relevant economic variables indicating structural change in won/dollar exchange market. We applied the CUSUM algorithm to examine whether or not it was possible to alarm the 1997 economic crisis of Korea in advance.

• Korean Journal of Applied Biomechanics
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• v.17 no.1
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• pp.17-27
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• 2007

It is essential for gait analysis to know the distance information. The purpose of this study was to investigate the effects of start and finish distance on the gait variable during walking. Six adolescent participated in this study. Start condition was given by six conditions.: walking forward from (1) one step, (2) three steps, (3) five steps, (4) ten steps, (5) one step after standing walk, and (6) three steps after standing walk, before contacting the force plate. Stop condition was given by four conditions. : stop after (1) one step, (2) two steps, (3) three steps, and (4) ten steps, passing force plate. Repeated measured one-way ANOVA was utilized for data analysis, and the significant level was set at .05. The largest change from the difference of gait velocity exists between the variables of ground reaction force. There were no significant differences in spatio-temporal and posture(angle) variables, as well as ground reaction force variables with walking over the three steps. There were significant differences in gait velocity, knee angle at heel contact, vertical impulse and ankle angle at toe off in short distance.