• Journal of the Korea Society for Simulation
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• v.28 no.4
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• pp.21-32
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• 2019

Inspired by the social behavior models of a bird flock or fish school, particle swarm optimization (PSO) is a popular metaheuristic optimization algorithm and has been widely used from solving a complex optimization problem to learning a artificial neural network. However, PSO is difficult to apply to many real-life optimization problems involving stochastic noise, since it is originated in a deterministic environment. To resolve this problem, this paper incorporates a resampling method called the uncertainty evaluation (UE) method into PSO. The UE method allows the particles to converge on the accurate optimal solution quickly in a noisy environment by selecting the particles' global best position correctly, one of the significant factors in the performance of PSO. The results of comparative experiments on several benchmark problems demonstrated the improved performance of the propose algorithm compared to the existing studies. In addition, the results of the case study emphasize the necessity of this work. The proposed algorithm is expected to be effectively applied to optimize complex systems through digital twins in the fourth industrial revolution.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.2
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• pp.38-45
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• 1997

In this paper, the three-dimensional stress effect of thermal oxide is simulated. We developed a three-dimensional finite element numerical simulator including three-dimensional adaptive mesh generator that is able to refine and eliminate nearby moving boundary of oxide, and oxidation solver with stress model. To investigate the behavior of thermal oxidation the simulations of thermal oxidation for island and hole structures are carried out assuming silicon wafer of <100> direction, temperature of $1000^{\circ}C$, oxidation time of 60min, wet ambient, initial oxide thickness of $300\AA$, and nitride thickness of $2, 000\AA$. The main effect of deformation at the corner area of oxide is due to distribution of oxidant, but the deformation of oxide is affected by the stressin theoxide. In the island structure which is the structure mostly covered with nitride and a coner is opended to oxidation, oxidation is reduced at the coner by compressive stress. In the hole structure which is the structure mostly opedned to oxide and a coner is convered with nitride, however, oxidation is increased at the coner by tensile stress.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.279-286
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• 2019

In this study, a numerical investigation is conducted for the shock deceleration prediction of a conical impactor in gas-gun tests. With the development of weapon systems, gas-gun tests are required to validate the survivability and structural reliability of devices under test (DUT) in high-G shock environments, such as those over ten thousand Gs or more. As shock endurance is highly influenced by various bird parameters, such as mass, velocity, and pressure, it is important to determine the appropriate test conditions to generate a high-G shock environment. However, experimental repetitive studies are inefficient to validate test conditions in terms of economic aspects. Therefore, a numerical technique is required to replace experimental gas-gun tests. Here, a numerical investigation is conducted with ANSYS AUTODYN using explicit code. Through this investigation, the dynamic behavior of DUT is presented. In addition, the results of numerical studies are verified through a comparison with the experimental results of a gas-gun test.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.2
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• pp.65-74
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• 2013

A research program for the roe deer (Capreolus pygargus) has been set up at the Jeju Experimental Forest of Warm-temperate and Subtropical Forest Research Center in Jeju Island. To explore the home range size and habitat environment, 3 males and 3 females have been captured and released with GPS-CDMA based telemetry since 24th April 2012. Among them 2 females were captured at Hannam Forest of Seoguipo, were pregnant and monitored by the tracking system. There are significantly different patterns in behavior around the parturition. After parturition they show recurrence behavior toward one point in the forest, while they have irregular patterns in moving before. To calculate the home range size, the MCP (minimum convex polygon) and Kernel Method are applied through the extension of ESRI ArcView GIS 3.2a. The pregnant female captured 9th May 2012 has the size of MCP=67ha and Kernel 95%=0.5ha and the pregnant female captured 12th July 2012 has the size of MCP=82ha and Kernel 95%=0.9ha. Although a fawn could move immediately just after the birth likely others to avoid any risks, they stay at very narrow space significantly, and the size become wider when more time goes by. Furthermore, they mainly have a home range away from human activity area such as forest tracking roads. The habitat environment for the parturition is summarized as 40years old cryptomeria forests with new sprouting shrubs for foods, which are the controlled forest through the thinning and removing shrubs 2 years ago. This means that forest works could cause positive results for the parturition and survival of young. The period of parturition is earlier than highland in Jeju Island, the size of home range is narrower than other countries, and the habitat environment of the shelter for a fawn is similar to previous research in other countries.

• Korean Journal of Environment and Ecology
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• v.32 no.3
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• pp.256-260
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• 2018

Cannibalism is a widely observed phenomenon in the animal kingdom. However, it is rarely found among birds outside nests in the wild because it occurs irregularly and it is almost impossible to monitor animal behavior constantly. On 17 January 2017, this behavior was directly observed from a group of vultures feeding on a conspecific in a paddy field near Lake Geumho in Haenam-gun ($34^{\circ}35^{\prime}58.25^{{\prime}{\prime}}N$, $126^{\circ}26^{\prime}57.64^{{\prime}{\prime}}E$). It was observed and recorded with the binoculars and a camera with a telephoto lens in a car approximately 20 m (or 60 m) away from the site. The observer approached the feeding site after the last vulture had finished feeding and flown away and found remains of a vulture, including body feathers, skull, sterna keel, and both legs. It was the first report of cannibalism in Cinereous vulture Aegypius monachus in its overwintering grounds. The remaining skeleton was very fleshy, and the surrounding grass was wet with the blood of vulture. No other traces of a mammal or bird that could have been the vultures' prey were found. This report provides a detailed account of the events related to this rare observation and the causes that might have led to it.

• Journal of Environmental Impact Assessment
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• v.24 no.5
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• pp.532-548
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• 2015

The winter ecology of individual yellow-throated martens(Martes flavigula) intemperate region of Korea were studied through snow-tracking. The study was performed across 3 winter seasons, from January 2011 to February 2013. Total distance of 49.8km was snow tracked (comprising 13 snow-tracking routes) to determine winter foraging habits, general behavior and movement paths of solitary and small groups (1-6 individuals; $mean=2.9{\pm}1.6$) of yellow-throated martens. The martens in the current study were omnivorous, with their winter diet including 9 animal and 5 plant species. Yellow-throated martens searched for food near and under the fallen logs and branches, root plates of fallen trees, around the roots of growing trees, and in small holes in the ground. They also climbed trees to search inside the tree holes and vacant bird nests. Foraging activity was estimated to occur at a frequency of 1.20 times/km, while territory marking occurred 1.42 times/km on average. Of the 60 documented foraging activities we observed, 17 were successful (28.3%). Moving activity and territory marking mainly occurred along ridges, whereas foraging activity was recorded in valleys, slopes, and forest edges. To protect the habitat of this species, the entire forest should be preserved, including the valleys, slopes, and even forest edges as well as main ridges.