• Korean Journal of Environmental Biology
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• v.35 no.4
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• pp.566-572
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• 2017

For four times, zooplankton collection were conducted seasonally in October 2015-July 2016 at five sites located in the wet lands of the lower Han River, ie., Si-am, Sung-dong, Gong-reung stream, San-nam and Jang-hang. A total of 46 species of zooplankton were collected, which comprise 25 species of rotifers, seven cladocerans, ten copepods, and one species of nematod, ostracod and decapod, respectively. No brackish and marine species were distributed except for two species of brackish water copepods. Prosperity in the species number of 15 species was observed in October at Sung-dong and Jang-hang. The maximum abundance was recorded in March at Si-am with $8,000indiv.\;L^{-1}$ with the explosion of Brachionus calyciflorus. Other sites also showed high abundances in March with the abundance higher than $5,000indiv.\;L^{-1}$. Except in March, the abundance levels were recorded as less than some hundred $indiv.\;L^{-1}$ throughout the study. Species diversity varied between 0.4-1.8. The gut contents of the copepodite showed that various diatoms might be their major food items, and lots of unidentified materials were also observed. The environmental conditions of water temperature, pH and dissolved oxygen content showed to vary $10.1-28.2^{\circ}C$, 7.1-8.6 and $4.5-11.0mg\;L^{-1}$, respectively.

• Korean Journal of Remote Sensing
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• v.25 no.5
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• pp.399-409
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• 2009

Many researches have shown that NDVI provides a potential methods to derive meaningful metrics that describe ecosystem functions. In this paper we investigated the use of the MODIS NDVI (Normalized Difference Vegetation Index) to monitor vegetation phenology dynamics of Northern plateau region, North Korea, during last 9-years (2000~2008). The findings of this paper can be summarized as follows. First, the length of growing season ranged from a low of 128 days in 2003 to a high of 176 days in 2000 and 2005. On the average of the last 9 years, the highest NDVI of 0.86 was marked on 28 July. Greenup onset occurs at the start of May, while the senescence begins between late September and October. Second, these annual vegetation cycles were compared with Seorak and Jiri Mountain regions of South Korea which have similar vegetation condition. Greenup onsets in South Korea were observed earlier than those of North Korea and the average time lag between the South and North Korea in Greenup was about 16 days which is a time-resolution of remotely sensed data. Sub-alpine conifers of such areas may be severely affected by the large of phenological characteristics due to the global warming trend.

• International Area Studies Review
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• v.20 no.2
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• pp.113-140
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• 2016

This paper first extracts the main basis for the Middle-Income Trap(MIT) to apply these grounds to reality of the Chinese economy. And then confirmed crisis factors of China economy. Also discussed then the economic reforms of China in order to not fall into the MIT. After reviewing previous research extracted six factors the results will correspond to comply with the Chinese economy. Those are 'Over-investment', 'excess capacity' 'reduction of TFP continued,' 'disappearance and the aging of the population bonus', 'excessive debt and structural adjustment and financial instability of the company', 'income unequal expansion', 'low financial and information infrastructure accessibility', and 'low transparency index'. China's policy direction to avoid the MIT generally set properly, but proof that implementation process not easy, was appearing everywhere. After all, China economy should be modified now to a reforms of 'government failure' and promotion of function for ongoing restructuring system in the market. Because of the SDR incorporation from 2015, it is inevitable to face major constraints in the external aspects.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2014.10a
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• pp.25-48
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• 2014

Increased frequency of climate extremes is another face of climate change confronted by humans, resulting in catastrophic losses in agriculture. While climate extremes take place on many scales, impacts are experienced locally and mitigation tools are a function of local conditions. To address this, agrometeorological early warning systems must be place and location based, incorporating the climate, crop and land attributes at the appropriate scale. Existing services often lack site-specific information on adverse weather and countermeasures relevant to farming activities. Warnings on chronic long term effects of adverse weather or combined effects of two or more weather elements are seldom provided, either. This lecture discusses a field-specific early warning system implemented on a catchment scale agrometeorological service, by which volunteer farmers are provided with face-to-face disaster warnings along with relevant countermeasures. The products are based on core techniques such as scaling down of weather information to a field level and the crop specific risk assessment. Likelihood of a disaster is evaluated by the relative position of current risk on the standardized normal distribution from climatological normal year prepared for 840 catchments in South Korea. A validation study has begun with a 4-year plan for implementing an operational service in Seomjin River Basin, which accommodates over 60,000 farms and orchards. Diverse experiences obtained through this study will certainly be useful in planning and developing the nation-wide disaster early warning system for agricultural sector.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.559-566
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• 2021

It is necessary to quickly detect and respond to ship accidents that occur continuously due to the influence of the recently increased maritime traffic. For this purpose, ship detection research is being actively conducted based on satellite images that can be monitored in real time over a wide area. However, there is a possibility that the wake may be falsely detected as a ship because the wake removal is not performed in previous studies that performed ship detection using spectral characteristics. Therefore, in this study, ship detection was performed using SDI (Ship Detection Index) based on the Sentinel-2A satellite image, and the wake was removed by utilizing the difference in the spectral characteristics of the ship and the wake. Probability of detection (POD) and false alarm rate (FAR) indices were used to verify the accuracy of the ship detection algorithm in this study. As a result of the verification, POD was similar and FAR was improved by 6.4% compared to the result of applying only SDI.

• Korean Journal of Remote Sensing
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• v.38 no.3
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• pp.311-326
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• 2022

The Compact Advanced Satellite 500-4 (CAS500-4) is under development to efficiently manage and monitor forests in Korea and is scheduled to launch in 2025. The National Institute of Forest Science is developing 36 types of forestry applications to utilize the CAS500-4 efficiently. The products derived using the remote sensing method require validation with ground reference data, and the quality monitoring results for the products must be continuously reported. Due to it being the first time developing the national forestry satellite, there is no official calibration and validation site for forestry products in Korea. Accordingly, the author designed a calibration and validation site for the forestry products following international standards. In addition, to install calibration and validation sites nationwide, the authors selected appropriate sensors and evaluated the applicability of the sensors. As a result, the difference between the ground observation data and the Sentinel-2 image was observed to be within ±5%, confirming that the sensor could be used for nationwide expansion.

• Economic Analysis
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• v.25 no.2
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• pp.96-131
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• 2019

Initially entering into the job market during hard times with unfavorable market institutions has a persistent, negative effect on young workers' subsequent employment. This paper analyzes hysteresis in youth unemployment by using a composite fixed-effect panel data model. Data sets for the age-cohort unemployment rate and for labor market institutions are constructed from OECD statistics from 21 advanced economies, including Korea, from 1985 to 2017, and are then readjusted to match with the peculiarities of the Korean market. In Korea, with a less-aggressive stance on active labor market policy spending, a male worker who experiences a one percentage point higher youth unemployment rate when he was 20- to 29-years-old has a 0.146 percentage point higher unemployment rate at the ages of 30-to 34-years-old and a 0.035 percentage point higher unemployment rate at the age of 35- to 39-years-old. These figures are larger than those in most countries that have more aggressive spending schemes. These findings point out that hysteresis in the Korean labor market can be mitigated by expanding active labor market policy spending more aggressively and more effectively.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.542-549
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• 2023

Since the growing interest in surrogate modeling, there has been continuous research aimed at simulating nonlinear chemical processes using data-driven machine learning. However, the opaque nature of machine learning models, which limits their interpretability, poses a challenge for their practical application in industry. Therefore, this study aims to analyze chemical processes using Explainable Artificial Intelligence (XAI), a concept that improves interpretability while ensuring model accuracy. While conventional sensitivity analysis of chemical processes has been limited to calculating and ranking the sensitivity indices of variables, we propose a methodology that utilizes XAI to not only perform global and local sensitivity analysis, but also examine the interactions among variables to gain physical insights from the data. For the ammonia synthesis process, which is the target process of the case study, we set the temperature of the preheater leading to the first reactor and the split ratio of the cold shot to the three reactors as process variables. By integrating Matlab and Aspen Plus, we obtained data on ammonia production and the maximum temperatures of the three reactors while systematically varying the process variables. We then trained tree-based models and performed sensitivity analysis using the SHAP technique, one of the XAI methods, on the most accurate model. The global sensitivity analysis showed that the preheater temperature had the greatest effect, and the local sensitivity analysis provided insights for defining the ranges of process variables to improve productivity and prevent overheating. By constructing alternative models for chemical processes and using XAI for sensitivity analysis, this work contributes to providing both quantitative and qualitative feedback for process optimization.

• Economic and Environmental Geology
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• v.37 no.1
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• pp.73-86
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• 2004

In order to estimate the post-ingestion bioavailability of heavy metals and to assess the risk of adverse health effects on human exposure to toxic heavy metals, environmental geochemical surveys were undertaken around the Dogok Au-Ag-Cu and the Hwacheon Au-Ag-Pb-Zn mine sites. Human risk assessment of toxic heavy metals was performed with the results of the SBET(simple bioavailability extraction test) analysis for soil and chemical analytical data for crop plant and water. Arsenic and other heavy metals were highly elevated in tailings from the Dogok(218 As mg/kg, 90.2 Cd mg/kg, 3,053 Cu mg/kg, 9,473 Pb mg/kg, 14,500 Zn mg/kg) and the Hwacheon(72 As mg/kg, 12.4 Cd mg/kg. 578 Pb mg/kg, 1,304 Zn mg/kg) mines. These significant concentrations can impact on soils and waters around the tailing dumps. The quantities of As, Cd and Zn extracted from paddy soils in the Hwacheon mine using the SBET analysis were 55.4%, 20.8% and 26.4% bioavailability, respectively, and for farmland soils in the Dogok mine, 40.8%, 37.6% and 33.0% bioavailability, respectively. From the results of human risk assessment, HI(Hazard Index) value exceeded 1.0 for As in the Hwacheon mine and for Cd in the Dogok mine. Thus, toxic risks for As and Cd exist via exposure(ingestion) of contaminated soil, water and rice grain in these mine sites. The cancer risk for As by the consumption of rice and groundwater in the Hwacheon mine area was 8E-4 and 1E-4, respectively. This risk level exceeds the acceptable risk(1 in 100,000) for regulatory purpose. Therefore, regular ingestion of locally grown rice and ground-water by the local population can pose a potential health threat due to long-term arsenic exposure.

• 한국사회정책
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• v.20 no.3
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• pp.77-115
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• 2013

The purpose of this study is to present empirical evidence for discussion of financing social welfare via estimating optimal tax burden in the main member countries of the OECD by using Hausman-Taylor method considering endogeneity of explanatory variables. Also, the author produced an international tax comparison index reflecting theoretical hypotheses on revenue-expenditure nexus within a model to compare real tax burden by countries and to examine feasibility of tax increase in Korea. As a result of the analysis, the higher the level of tax burden was, the higher the level of welfare expenditure was, indicating the connection between high burden and high welfare from the aspect of scale. The results also indicated that the subject countries recently entered into the state of low tax burden. Meanwhile, Korea had maintained low burden until the late 1990s but the tax burden soared up since the financial crisis related to the IMF. However, due to the impact of foreign economy and the tax reduction policy, it reentered into the low-burden state after 2009. On the other hand, the degree of social welfare expenditure's reducing tax burden has been gradually enhanced since the crisis. In this context, the current optimal tax burden ratio of Korea as of 2010 may be 25.8%~26.5% of GDP based on input of welfare expenditure variables, a percent that Korea was investigated to be a 'high tax burden-low ITC' country whose tax increase of 0.7~1.4%p may be feasible and that the success of tax system reform for tax increase might be higher probability when compare to others. However, measures of increasing social security contributions and consumption tax were analyzed to be improper from the aspect of managing finance when compared to increase in other tax items, considering the relatively higher ITC. Tax increase is not necessarily required though there may be room for tax increase; the optimal tax burden ratio can be understood as the level that may be achieved on average when compared to other nations, not as the "proper" level. Thus, discussion of tax increase should be accompanied with comprehensive understanding of models of economic developmental difference from nations and institutional & historical attributes included in specific tax mix.