• Korean Journal of Agricultural and Forest Meteorology
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• v.15 no.4
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• pp.219-233
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• 2013

We employed the ecological niche modeling framework using GARP (Genetic Algorithm for Ruleset Production) to model the current and future geographic distribution of Pinus densiflora based on environmental predictor variable datasets such as climate data including the RCP 8.5 emission climate change scenario, geographic and topographic characteristics, soil and geological properties, and MODIS enhanced vegetation index (EVI) at 4 $km^2$ resolution. National Forest Inventory (NFI) derived occurrence and abundance records from about 4,000 survey sites across the whole country were used for response variables. The current and future potential geographic distribution of Pinus densiflora, one of the tree species dominating the present Korean forest was modeled and mapped. Future models under RCP 8.5 scenarios for Pinus densiflora suggest large areas predicted under current climate conditions may be contracted by 2090 showing range shifts northward and to higher altitudes. Area Under Curve (AUC) values of the modeled result was 0.67. Overall, the results of this study were successful in showing the current distribution of major tree species and projecting their future changes. However, there are still many possible limitations and uncertainties arising from the select of the presence-absence data and the environmental predictor variables for model input. Nevertheless, ecological niche modeling can be a useful tool for exploring and mapping the potential response of the tree species to climate change. The final models in this study may be used to identify potential distribution of the tree species based on the future climate scenarios, which can help forest managers to decide where to allocate effort in the management of forest ecosystem under climate change in Korea.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.501-505
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• 2017

Due to the rapid urbanization and increased population, there is an increase in airtight nature of buildings which causes serious indoor air pollution. Among several indoor air pollutants, volatile organic compounds (VOCs) emitted from paint are of major concern. Therefore, there is an urge for the development of environmental friendly paint products. In this wok, a natural wall paint (NWP) was prepared by utilizing a natural clay material "sericite" as a main component. A small chamber test was carried out to identify the toxic substances release from NWP and the results were compared with two eco-friendly commercial paints. The total VOCs were detected in trace level inside the test chamber and their concentrations were below the recommended indoor air quality standards. Toluene was not detected for NWP, whereas formaldehyde was observed in trace level. The toxicity index results were compared with two commercial paints and found that NWP exhibited less harmful gas emission. Based on certification rating of building materials, NWP can be classified as the first grade of building materials. Due to the above advantages, the use of sericite as a major component in NWP will be a useful technique to maintain the indoor air quality.

• Spatial Information Research
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• v.20 no.3
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• pp.15-25
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• 2012

In order to resolve transportation system focused on vehicles which have led to all sorts of problems such as traffic congestion, air pollution and so on, Korea recently have tended to center around Transit Oriented Development(TOD) which is capable of initiating public traffic demands. It is imperative to develop objective evaluation method which is able to measure pedestrian environment and amenity in order to facilitate green transit. The purpose of this paper is to present evaluation indices and measurement framework of pedestrian environment by analyzing effect on TOD major planning factors such as diversity, density, design, and supply etc. For this, we applied evaluation index with regard to TOD planning factors, investigating connection to pedestrian and employed AHP (Analytic Hierarchy Process) so as to quantify the result of measurement in Jongro 3ga and Hangangjin station. As a result, we presented relationship between travel patterns of pedestrian and each TOD planning factor. More importantly, the proposed framework is expected to make the best of the visualization as well as evaluation method for the pedestrian accessibility, convenience of public transportation, and the mixed land-use patterns in subway area and transit center.

• Journal of the Korean Society of Safety
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• v.24 no.6
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• pp.63-71
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• 2009

In order to improve flame retardancy, the halogen free organic melamine phosphate(M-P) flame retardant was synthesized from melamine and phosphoric acid by the reaction of precipitation. The ignition test was carried out preparing hybrid flame retardant compound($H_bFRC$) consisting of organic M-P and inorganic Mg$(OH)_2$ as a flame retardant in the polyolefin resins. The flame retardancy and mechanical properties of flame retardant aluminum composite panel($H_bFRC$-ACP) were performed to investigate the possibility of the composite material, which was contained M-P, as a inner core for $H_bFRC$-ACP. For this study, the results of ignition test indicate that a char formation and drip suppressing effect, and combustion time reduced as the content of M-P increased. The limited oxygen index(LOI) values were measured 17.4vol% and 31.5vol% for LDPE only and $H_bFRC$-3(M-P content: 15wt%), respectively. And it was verified that the $H_bFRC$-3 was needed more oxygen quantity with the increase of M-P content when it combustion. Also, the results from thermogravimetric analysis were observed endothermic peak at $350^{\circ}C$ and $550^{\circ}C$, it was confirmed predominant thermal stability though the wide temperature range by the mixture of M-P and Mg$(OH)_2$. The LDPE-ACP (using only LDPE as a inner core), $35.13kW/m^2$ of heat release rate(HRR) and 13.43MJ/m2 of total heat release(THR) were measured while the $H_bFRC$-ACP, $10.44kW/m^2$ of HRR and 1.84MJ/m2 of THR were measured by results of cone calorimeter test. In case of $H_bFRC$-ACP, the average gas emission amount of CO and $CO_2$ could be decreased down to 25% and 20%, respectively, in comparison with LDPE-ACP. The mechanical properties such as tensile strength, bending strength and adhesion strength of $H_bFRC$-ACP were revealed slightly high values $54N/mm^2$, $152N/mm^2$ and 120N/25mm, respectively, compared with LDPE-ACP. It was confirmed that flame retardancy was improved with the synergy effect because of char formation by M-P and hydrolysis by Mg$(OH)_2$. The result of this study suggest that $H_bFRC$ can be applied for an adequate halogen free flame retardant composite material as a inner core for ACP.

• Journal of the Korean Society of Radiology
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• v.13 no.6
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• pp.825-830
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• 2019

A detector module measuring a depth of interaction was developed using silicon photomultiplier (SiPM) and two layers of scintillation crystal array treated with multiple reflectors. When reconstructing an image based on a signal obtained by using different types of reflector of each layer, the interaction positions of scintillation pixels and gamma rays could be tracked by utilizing the feature that all scintillation pixels were recorded at different positions. The bottom layer uses a specular reflector, and the top layer uses a diffuse reflector to differently process the size of the signal obtained from the SiPM. The optical grease was used to recude the sharp refractive index change between the layers of scintillator and the SiPM. The signals obtained from the 16 SiPMs were reduced to four signals using the Anger equations, and the images were reconstructed using them. All the scintillation pixels composed of the two layers appeared in the reconstructed image, which distinguished the layer where the scintillation pixels and gamma rays interacted. If the detectors, which measure the interaction depth of two layers using different reflectors, will be applied to preclinical positron emission tomography, the degradation of spatial resolution appearing outside the field of interest could be solved.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1307-1319
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• 2018

As interests in the air pollution increases, many kinds of researches are underway on the reduction of air pollutants. The removal of nitrogen oxides from the emission gas of diesel vehicles using urea solution has shown a great effect. The quality of urea solution is strictly defined by domestic law, but the increase of impurities in urea solution reduces the effect of reducing nitrogen oxides. Therefore, in this study, the change of physical properties of urea solution was analyzed after heating the urea solution for a certain temperature and time. Also, the changes of physical properties of urea solution were analyzed according to kinds of storage container and temperature for storing the urea solution. After heating the urea solution for a certain period of time, the biuret content in urea solution increased and the content of urea decreased. As the urea content decreased, both density and refractive index decreased. In the storage stability test carried out at a constant temperature with iron and PET containers, no change in physical properties was observed.

• Fire Science and Engineering
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• v.33 no.2
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• pp.30-38
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• 2019

Tracking, which is one of the main causes of electrical fires, is perceived as a physical phenomenon of electrical discharge. Hence tracking should be explained based on electric field analysis, conduction path by electron generation, and gas discharge physics. However, few papers have considered these details. This paper proposes a tracking mechanism including their effects on tracking progress. In order to prove this mechanism, a tracking experiment, an electric field analysis for the carbonization evolution model, and an explanation of the tracking process by gas discharge physics were conducted. From the tracking experiment, the current waveforms were measured at each stage of the tracking progress from corona discharge to tracking breakdown. The electric field analysis was carried out in order to determine the electric field on the surface of a dry-band and the high electric field region for electron generation during the generation and progress of carbonization. In this paper, the proposed tracking mechanism consisted of six stages including electron avalanche by corona discharge, accumulation of positive ions, expansion of electron avalanche, secondary electron emission avalanche, streamer, and tracking by conductive path. The pulse current waveforms measured in the tracking experiment can be explained by the proposed tracking mechanism. The results of this study will be used as the technical data to detect tracking phenomenon, which is the cause of electric fire, and to improve the proof tracking index.

• Korean Journal of Biological Psychiatry
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• v.27 no.2
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• pp.94-100
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• 2020

Objectives Amyloid β positron emission tomography (Aβ PET) is widely used as a diagnostic tool in patients who have symptoms of cognitive impairment, however, this diagnostic examination is too expensive. Thus, predicting the positivity of Aβ PET before patients undergo the examination is essential. We aimed to analyze clinical predictors of patients who underwent Aβ PET retrospectively, and to develop a predicting model of Aβ PET positivity. Methods 468 patients who underwent Aβ PET with cognitive impairment were recruited and their clinical indicators were analyzed retrospectively. We specified the primary outcome as Aβ PET positivity, and included variables such as age, sex, body mass index, diastolic blood pressure, systolic blood pressure, education, dementia family history, Mini Mental Status Examination (MMSE), Clinical Dementia Rating (CDR), Clinical Dementia Rating-Sum of Box (CDR-SB), hypertension (HTN), diabetes mellitus (DM) and presence of apolipoprotein E (ApoE) E4 as potential predictors. We developed three final models of amyloid positivity prediction for total subjects, mild cognitive impairment (MCI) and Alzheimer's disease (AD) dementia using a multivariate stepwise logistic regression analysis. Receiver operating characteristic (ROC) curve analysis was performed and the area under curve (AUC) value was calculated for the ROC curve. Results Aβ PET negative patients were 49.6% (n = 232), and Aβ PET positive patients were 50.4% (n = 236). In the final model of all subjects, older age, female sex, presence of ApoE E4 and lower MMSE are associated with Aβ PET positivity. The AUC value was 0.296. In the final model of MCI subjects (n = 244), older age and presence of ApoE E4 are associated with Aβ PET positivity. The AUC value was 0.725. In the final model of AD subjects (n = 173), lower MMSE scores, the presence of ApoE E4 and history of HTN are associated with Aβ PET positivity. The AUC value was 0.681. Conclusions The cerebral amyloid positivity model, which was based on commonly available clinical indicators, can be useful for prediction of amyloid PET positivity in MCI or AD patients.

• Korea Trade Review
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• v.48 no.4
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• pp.189-208
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• 2023

This paper analyzed the dynamic conditional correlation between the Korean ETS market, energy market and stock market. This paper conducted an empirical analysis using daily data of Korea's carbon credit trading price, WTI crude oil futures price, and KOSPI index from February 2, 2015 to December 30, 2021. First, the volatility of the three markets was analyzed using the GARCH model, and then the dynamic conditional correlations between the three markets were studied using the bivariate DCC-GARCH model. The research results are as follows. First, it was found that the Korean ETS market has a higher rate of return and higher investment risk than the stock market. Second, the yield volatility of the Korean ETS market was found to be most affected by external shocks and least affected by the volatility information of the market itself. Third, the correlation between the Korean ETS market and the stock market was stronger than that of the WTI crude oil futures market. This paper analyzed the correlation between the Korean ETS market, energy market, and stock market and confirmed that the level of financialization in the Korean ETS market is quite low.

• Atmosphere
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• v.21 no.4
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• pp.429-438
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• 2011

The climatology of surface UV radiation for Seoul, presented in Cho et al. (1998; 2001), has been updated using measurement of surface erythemal ultraviolet (EUV) and total ultraviolet (TUV) irradiance (wavelength 286.5~363.0 nm) by a Brewer Spectrophotometer (MK-IV) for the period 2004~2010. The analysis was also carried out together with the broadband total (global) solar irradiance (TR ; 305~2800 nm) and cloud amount to compare with the UV variations, measured by Seoul meteorological station of Korean Meteorological Agency located near the present study site. Under all-sky conditions, the day-to-day variability of EUV exhibits annual mean of 98% in increase and 31% in decrease. It has been also shown that the EUV variability is 17 times as high as the total ozone in positive change, whereas this is 6 times higher in negative change. Thus, the day to day variability is dominantly caused rather by the daily synoptic situations than by the ozone variability. Annual mean value of daily EUV and TUV shows $1.62kJm^{-2}$ and $0.63MJm^{-2}$ respectively, whereas mean value of TR is $12.4MJm^{-2}$ ($143.1Wm^{-2}$). The yearly maximum in noon-time UV Index (UVI) varies between 9 and 11 depending on time of year. The highest UVI shows 11 on 20 July, 2008 during the period 2004~2010, but for the period 1994~2000, the index of 12 was recorded on 13 July, 1994 (Cho et al., 2001). A 40% of daily maximum UVI belongs to "low (UVI < 2)", whereas the UVI less than 5% of the maximum show "very high (8 < UVI < 10)". On average, the maximum UVI exceeded 8 on 9 days per year. The values of Tropospheric Emission Monitoring Internet Service (TEMIS) EUV and UVI under cloud-free conditions are 1.8 times and 1.5 times, respectively, higher than the all-sky measurements by the Brewer. The trend analysis in fractional deviation of monthly UV from the reference value shows a decrease of -0.83% and -0.90% $decade^{-1}$ in the EUV and TUV, respectively, whereas the TR trend is near zero (+0.11% $decade^{-1}$). The trend is statistically significant except for TR trend (p = 0.279). It is possible that the recent UV decrease is mainly associated with increase in total ozone, but the trend in TR can be attributed to the other parameters such as clouds except the ozone. Certainly, the cloud effects suggest that the reason for the differences between UV and TR trends can be explained. In order to estimate cloud effects, the EUV, TUV and TR irradiances have been also evaluated for clear skies (cloud cover < 25%) and cloudy skies (cloud cover ${\geq}$ 75%). Annual mean values show that EUV, TUV and TR are $2.15kJm^{-2}$, $0.83MJm^{-2}$, and $17.9MJm^{-2}$ for clear skies, and $1.24kJm^{-2}$, $0.46MJm^{-2}$, and $7.2MJm^{-2}$ for cloudy skies, respectively. As results, the transmission of radiation through clouds under cloudy-sky conditions is observed to be 58%, 55% and 40% for EUV, TUV and TR, respectively. Consequently, it is clear that the cloud effects on EUV and TUV are 18% and 15%, respectively lower than the effects on TR under cloudy-sky conditions. Clouds under all-sky conditions (average of cloud cover is 5 tenths) reduced the EUV and TUV to about 25% of the clear-sky (cloud cover < 25%) values, whereas for TR, this was 31%. As a result, it is noted that the UV radiation is attenuated less than TR by clouds under all weather conditions.