• Journal of the Korea Society for Simulation
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• v.33 no.1
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• pp.27-34
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• 2024

This study aims to propose an optimal asset allocation that minimizes the risk of insufficient realized replacement rates compared to the OECD average replacement rate. To do this, we set the shortfall risk of replacement rates and calculates an asset allocation plan to minimize this risk based on the period of enrollment, the income level and additional contribution. We consider stocks and deposits as investment assets, using Monte Carlo simulation with a GBM model to generate return distributions for stocks. Our result show that, for individuals with a enrollment period of less than 30 years, participants should invest a minimum of 70-80% of their funds in risky assets to minimize the shortfall risk. However, the proportion of funds that need to be invested in risky assets declines significantly when participants contribute an additional premiums. This effect is particularly pronounced among low-income individuals. Therefore, to achieve OECD average replacement rates, the government needs to incentivize participants to invest more in risky assets, while also providing policies to encourage additional contributions, especially for the low-income population.

• Korean Journal of Agricultural and Forest Meteorology
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• v.10 no.4
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• pp.121-131
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• 2008

This study was conducted to delineate temporal and spatial patterns of potential risk of cold injury by combining the short-term cold hardiness of Campbell Early grapevine and the IPCC projected climate winter season minimum temperature at a landscape scale. Gridded data sets of daily maximum and minimum temperature with a 270m cell spacing ("High Definition Digital Temperature Map", HD-DTM) were prepared for the current climatological normal year (1971-2000) based on observations at the 56 Korea Meteorological Administration (KMA) stations using a geospatial interpolation scheme for correcting land surface effects (e.g., land use, topography, and elevation). The same procedure was applied to the official temperature projection dataset covering South Korea (under the auspices of the IPCC-SRES A2 and A1B scenarios) for 2071-2100. The dormancy depth model was run with the gridded datasets to estimate the geographical pattern of any changes in the short-term cold hardiness of Campbell Early across South Korea for the current and future normal years (1971-2000 and 2071-2100). We combined this result with the projected mean annual minimum temperature for each period to obtain the potential risk of cold injury. Results showed that both the land areas with the normal cold-hardiness (-150 and below for dormancy depth) and those with the sub-threshold temperature for freezing damage ($-15^{\circ}C$ and below) will decrease in 2071-2100, reducing the freezing risk. Although more land area will encounter less risk in the future, the land area with higher risk (>70%) will expand from 14% at the current normal year to 23 (A1B) ${\sim}5%$ (A2) in the future. Our method can be applied to other deciduous fruit trees for delineating geographical shift of cold-hardiness zone under the projected climate change in the future, thereby providing valuable information for adaptation strategy in fruit industry.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.1
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• pp.174-192
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• 2021

The LIDAR sensor, which provides higher cognitive performance than cameras and radar, is difficult to apply to ADAS or autonomous driving because of its high price. On the other hand, as the price is decreasing rapidly, expectations are rising to improve existing autonomous driving functions by taking advantage of the LIDAR sensor. In level 3 autonomous vehicles, when a dangerous situation in the cognitive module occurs due to a sensor defect or sensor limit, the driver must take control of the vehicle for manual driving. If the driver does not respond to the request, the system must automatically kick in and implement a minimum risk maneuver to maintain the risk within a tolerable level. In this study, based on this background, a LIDAR-based LKS MRM algorithm was developed for the case when the normal operation of LKS was not possible due to troubles in the cognitive system. From point cloud data collected by LIDAR, the algorithm generates the trajectory of the vehicle in front through object clustering and converts it to the target waypoints of its own. Hence, if the camera-based LKS is not operating normally, LIDAR-based path tracking control is performed as MRM. The HAZOP method was used to identify the risk sources in the LKS cognitive systems. B, and based on this, test scenarios were derived and used in the validation process by simulation. The simulation results indicated that the LIDAR-based LKS MRM algorithm of this study prevents lane departure in dangerous situations caused by various problems or difficulties in the LKS cognitive systems and could prevent possible traffic accidents.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.759-768
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• 2019

This study was conducted to estimate the mean annual extreme minimum temperature raster and predict the potential distribution of the invasive plant, Ipomoea triloba, on the Korean peninsula. We collected annual extreme minimum temperature and mean coldest month minimum temperature data from 129 weather stations on the Korean peninsula from 1990-2019 and used this data to create a linear regression model. The min temperature of the coldest month raster from Worldclim V2 were used to estimate a 30 second spatial resolution, mean annual extreme minimum temperature raster of the Korean peninsula using a regression model. We created three climatic rasters of the Korean peninsula for use with the Proto3 species distribution model and input the estimated mean annual extreme minimum temperature raster, a Köppen-Geiger climate class raster from Beck et al. (2018), and we also used the mean annual precipitation from Worldclim V2. The potential distribution of I. triloba was estimated using the Proto3 model with 117 occurrence points. As a result, the estimated area for a potential distribution of I. triloba was found to be 50.7% (111,969 ㎢) of the Korean peninsula.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.618-622
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• 2017

Gasoline is a widely used product as a source for energy in homes, the automotive industry, and for industrial power generation, and it is also a product with a high risk of fire and explosion. In this study, to examine the risk for explosion for gasoline, PG, MG and RG, which are categorized according to octane number, were used as test specimens to measure their explosion limit according changes in oxygen concentration. The explosion limit for 21% oxygen concentration in air were confirmed to be 1.5~10.9%, 1.4~8.1%, and 1.3~7.6%, respectively, and the MOC for each of the test sample were confirmed to be 10.9%. The explosion limit measured in the test performed in this study confirmed between a 1.2%~7.6% wider explosion limit for the currently accepted MSDS for gasoline, and therefore it is considered that the results of this study can provide significant reference for preventing fires and explosions for process used gasoline.

• Journal of the Korean Society of Safety
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• v.25 no.4
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• pp.13-18
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• 2010

To investigate electrostatic ignition hazards of commercial gasoline used in the gas station, experiments were conducted dealing with the minimum ignition energy(MIE) of several kinds of gasoline under the various temperature. The conductivity of gasoline that was required for an accurate risk assessment as well as the MIE were also examined. The solvent ignitability apparatus which can heat up the inside of the vessels up to $210^{\circ}C$ was used in this study. Four kinds of premium gasoline and four kinds of regular gasoline, differing with respect to the companies, were used as test specimens. The following results were obtained: (1) all gasoline specimens were so sensitive that even an electrostatic discharge with a very low energy, such as about 0.5mJ, could ignite them. The ignitability of premium gasoline was constant irrespective of the companies. On the other hand, the ignitability of regular gasoline was variable depending on the company. (2) The MIE of all specimens depended markedly on the temperature; in other words, an increase in temperature decreases the ignition energy value. (3) The conductivity values of all specimens were low. Those must be taken into consideration in electrostatic risk assessment.

• Child Health Nursing Research
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• v.24 no.2
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• pp.148-156
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• 2018

Purpose: The aim of this study was to evaluate the influence of the mothers' native country on influenza vaccinations in adolescents in multicultural families. Methods: Data were gathered from the 13th (2017) Youth Risk Behavior Web-Based Survey. Logistic regression analyses were conducted using a complex sample data analysis method. The participants in this study had a father who was born in Korea and a mother born outside of Korea. The sample included 481 adolescents. Results: The analysis of non-adjusted confounding variables showed that influenza vaccination was higher in multicultural adolescents whose mother's native country had an annual minimum temperature less than $21^{\circ}C$ (odds ratio [OR]: 1.81, 95% confidence interval [CI]: 1.20~2.74). Furthermore, when the analysis was adjusted for confounding variables, an annual minimum temperature less than $21^{\circ}C$ in the mother's native country had a statistically significant association with influenza vaccination (OR: 2.12, 95% CI: 1.36~3.29). Conclusion: Multicultural adolescents belong to a socioeconomically vulnerable class, and their health promotion behaviors are influenced by their mothers' culture. Thus, healthcare providers and school nurses should provide adolescents with appropriate information related to influenza vaccination depending on their mothers' culture and their family's cultural background.

• The Korean Journal of Applied Statistics
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• v.36 no.6
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• pp.561-571
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• 2023

Volatility of a time series is defined as the conditional variance on the past information. In particular, for financial time series, volatility is regarded as a time-varying measure of risk for the financial series. To capture the intrinsic asymmetry in the risk of financial series, various asymmetric volatility processes including threshold-ARCH (TARCH, for short) have been proposed in the literature (see, for instance, Choi et al., 2012). This paper proposes a volatility function featuring non-zero origin in which the origin of the volatility is shifted from the zero and therefore the resulting volatility function is certainly asymmetric around zero and achieves the minimum at a non-zero (rather than zero) point. To validate the proposed volatility function, we analyze the Korea stock prices index (KOSPI) time series during the Covid-19 pandemic period for which origin shift to the left of the zero in volatility is shown to be apparent using the minimum AIC as well as via parametric bootstrap verification.

• Journal of Food Hygiene and Safety
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• v.30 no.2
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• pp.127-131
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• 2015

This study aimed to calculate the required sample size to monitor food items during risk assessment studies. Based on a data set from a previous study (2,400 data points for heavy metal assessment from 17 food items), the required sample size was estimated by using a single equation with the standard deviation value, error range, and 95%-99% confidence intervals. The required sample size was calculated with each of the heavy metals for the assessment. The results showed that cadmium, lead, and mercury of required sample sizes for further monitoring were range of 7-90, 7-1, 062, and 11-238, respectively. We found that the required sample size varied depending on the standard deviation of the previous monitoring data. This study provides a basic method to determine the minimum sample size required in food monitoring to devise practical sampling strategies.

• Journal of Environmental Impact Assessment
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• v.14 no.5
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• pp.347-353
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• 2005

The risk assessment is the qualitative or quantitative evaluation of the risk posed to human health and the environment by the actual or potential presence or release of hazardous substances, pollutants or contaminants. The environmental impact assessment (EIA) is assessed by the environmental criteria, and risk assessment is assessed by the risk rate. Risk rate based on dose-response values may not be easy to apply on regulatory basis like EIA for uncertainty. Internationally there is an example of OECD program. Risk assessment of High Production Volume (HPV) Chemicals has started since the OECD Program with the 1990 Council Act on the Co-operative Investigation and Risk Reduction of Existing Chemicals. These HPV chemicals include all chemicals produced or imported at levels greater than 1,000 tonnes per year in at least one Member country or in the European Union region. The SIDS called the Screening Information Data Set is regarded as the minimum information needed to assess an HPV chemical to determine whether any further work should be carried out or not. All the data elements of SIDS including assessment for environment and health are prepared as three formats of the full SIDS Dossier, the SIDS Initial Assessment Report (SIAR), and the SIDS Initial Assessment Profile (SIAP) of an HPV chemical. In 1998 the global chemical industry through the International Council of Chemical Associations (ICCA) has joined to work with OECD. The OECD has assessed approximately 1,000 chemicals from 1991 through 2004 with ICCA. Till the February of 2005, 592 chemicals of those chemicals completed SIDS reports. Member countries have been targeted the goal of 1,000 new chemicals from 2005 to 2010 and Korea shared 36 chemicals from the 1,000 new chemicals. Currently Korea has completed SIDS reports of 7 chemicals among sponsored 24 chemicals. In conclusion SIDS project will be linked to national program for outputs application with more reliable production. Both the OECD and industry will carry out their commitment to complete assessments for more and the remaining chemicals assessment. The major outputs will contribute to cope with international chemical management.