• KOREAN JOURNAL OF CROP SCIENCE
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• v.67 no.4
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• pp.285-295
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• 2022

The trapping efficacy of five commercially available sex pheromones manufactured in Korea, the Netherlands, North America, China, and Costa Rica was evaluated to determine the population dynamics of Spodoptera frugiperda and Mythimna loreyi and their relationships with the weather parameters of maize fields in Miryang, Gyeongnam Province, Korea in 2019. The results show that the sex pheromone manufactured in Costa Rica were more efficient at capturing S. frugiperda and M. loreyi than those manufactured in other countries. The lowest number of S. frugiperda moths were captured using sex pheromones manufactured in the Netherlands. We noted that more than four population peaks of both the moth species and weather parameters influenced the moth population dynamics in Miryang. A positive relationship was observed between the population of S. frugiperda and weather parameters, such as mean temperature, rainfall, and relative humidity, for sex pheromones manufactured in Korea. Furthermore, a positive relationship was recorded between the population of M. loreyi and wind speed for the sex pheromone manufactured in Korea. The results of this study suggest that the sex pheromones manufactured in Costa Rica are the best solution for the efficient capture of S. frugiperda and M. loreyi under typical weather conditions in the southern parts of Korea. In addition, the outcomes of this study are discussed in terms of population dynamics and integrated pest management for S. frugiperda and M. loreyi as alternatives to chemical management by maize producers. Further studies related to the continuous improvement in the capture efficiency of both moth species using sex pheromones are now needed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.347-354
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• 2003

The dynamics of fluid flow through nanomachines is completely different from that of continuum. In this study, molecular dynamics simulations were performed for the flow of helium, neon, argon inside carbon(graphite) nanotubes of several sizes. The fluid was introduced into the nanotube at a given initial velocity according to given temperature. Diffusion coefficients were evaluated by Green-Kubo equation derived from Einstein relationship. The behaviour of the fluid was strongly dependent on the density of fluid and tube diameter, not on the tube length. It was found that the diffusion Coefficients increased With decreasing the density of molecules and increasing the diameter and temperature.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1584-1589
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• 2003

This work applies the equilibrium molecular dynamics simulation method to study a Lennard-Jones liquid thin film suspended in the vapor and calculates diffusion coefficients by Green-Kubo equation derived from Einstein relationship. As a preliminary test, the diffusion coefficients of the pure argon fluid are calculated by equilibrium molecular dynamics simulation. It is found that the diffusion coefficients increase with decreasing the density and increasing the temperature. When both argon liquid and vapor phases are present, the effects of the system temperature on the diffusion coefficient are investigated. It can be seen that the diffusion coefficient significantly increases with the temperature of the system.

• Korean System Dynamics Review
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• v.15 no.4
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• pp.85-100
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• 2014

We propose a composite make or buy decision model considering both the transaction cost theory and the resource based view in the Korean defense industry using System Dynamics. We analyze relationship between core variables(transaction frequency, technological uncertainty, the level of technological dependency, technological level and acquisition ability for market information) and 'Make or Buy decision' focused on technological innovation capability. Based on the result, we propose the implications as follows : First, the defence industry needs more R&D investment. Second, it needs a balance between domestic(Make) and overseas(Buy) to increase the technological capability rapidly.

• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.1
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• pp.113-126
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• 2016

This study investigates the effect of power dynamics on R&D and market performances. Various types of relationships in a supply chain are considered. An R&D company offering new technology for product quality and a manufacturer responsible for both production and sales are utilized as subjects. The company with bargaining power differs with respect to the supply chain situation in practice, and no fixed single relationship and supply chain structure exist. However, only a few studies have considered the various relationships among players in a supply chain and their effects on performance. Therefore, we propose three models with different supply chain structures and power dynamics among players. This study contributes to the academia and supply chain practice by revealing the different characteristics of supply chain models.

• Korean System Dynamics Review
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• v.1 no.2
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• pp.61-89
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• 2000

The purpose of this study is first, to find out what factors affect the cooperation and trust within the functions in the policy implementation network and in what mechanism these factors interact, second to investigate the whys to manage trust and cooperation successfully in the dynamic situation such as the network setting. For these purpose, this study reviews the concept and characteristics of policy implementation organizations, second, extracts the various factors affecting trust and cooperation in the network situation, third applies and analyzes the relationship among factors to system dynamics model based on the game theory. The results of this study could be summarized as follows: It was found that the utility change within the participants by persuasion ＆ mutual understanding and change of rule would be leading to success in policy implementation network. Also bureaucratic management such as power enforcement does not have any good impact in the managing network. In this study, system simulation method tried to analyze the hypothesis. Quantitative and case analyses were not accompanied and analysis was limited to two-person game theory. So there is some doubt this results could be generalized to actual situation which is N-person game.

• Nuclear Engineering and Technology
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• v.36 no.1
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• pp.64-72
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• 2004

The purpose of this study is to develop a system dynamics model for the assessment of the organizational and human factors in a nuclear power plant which contribute to nuclear safety. Previous studies can be classified into two major approaches. One is the engineering approach using tools such as ergonomics and Probability Safety Assessment (PSA). The other is the socio-psychology approach. Both have contributed to find organizational and human factors and to present guidelines to lessen human error in plants. However, since these approaches assume that the relationship among factors is independent they do not explain the interactions among the factors or variables in Nuclear Power Plants. To overcome these restrictions, a system dynamics model, which can show cause and effect relationships among factors and quantify the organizational and human factors, has been developed. Handling variables such as the degree of leadership, the number of employees, and workload in each department, users can simulate various situations in nuclear power plant organization. Through simulation, users can get insights to improve safety in plants and to find managerial tools in both organizational and human factors.

• Korean System Dynamics Review
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• v.12 no.2
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• pp.95-126
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• 2011

This paper aims at developing a System Dynamics model with an augmented predator-prey interaction structure to deal with the population management of roe deer in Jeju, Korea. Although people still regard the creature as one of the important tourist attractions, there has been much debate on the issues of the appropriateness of the population size of roe deers because they have been stigmatized as crop damagers, and roadkill/poaching victims due to their natural habit to move around from the top mountain to the lowland of the island. The model is therefore to incorporate these migrating and grazing behaviors into an augmented Lotka-Volterra model coupling roe deer population in both parts of the island to that of predators and preys of the species. The authors also provide a comprehensive set of dynamic hypotheses and relevant CLD/SFD to understand the population dynamics of roe deer and co-evolving species and perform the steady-state analysis of the proposed equation system to verify the model behavior of the numerical example lastly presented in this paper.

• Wind and Structures
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• v.22 no.1
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• pp.89-106
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• 2016

With an aim to assess the wind damage to urban trees in more realistic conditions, the nonlinear dynamics of structured trees subjected to strong winds with different levels is investigated in the present paper. For the logical treatment of dynamical behavior of trees, material nonlinearities of green wood associated with tree biomechanics and geometric nonlinearity of tree configuration are included. Applying simulated fluctuating wind velocity to the numerical model, the dynamical behavior of the structured tree is explored. A comparative study against the linear dynamics analysis usually involved in the previous researches is carried out. The failure wind velocity of urban trees is then defined, whereby the failure percentages of the tree components are exposed. Numerical investigations reveal that the nonlinear dynamics analysis of urban trees results in a more accurate solution of wind-induced response than the classical linear dynamics analysis, where the nonlinear effect of the tree behavior gives rise to be strengthened as increasing of the levels of wind velocity, i.e., the amplitude of 10-min mean wind velocity. The study of relationship between the failure percentage and the failure wind velocity provides a new perspective towards the vulnerability assessment of urban trees likely to fail due to wind actions, which is potential to link with the practical engineering.

• Korean System Dynamics Review
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• v.13 no.3
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• pp.47-66
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• 2012

This paper aims at investigating and identifying the factor that has led the back and forth relationship between China and the United States since 1989. Previous studies on this subject addressed the issue by taking either of two approaches: one with the micro view that interprets the back and forth relationship in the context of the end of the Cold war, on other hand, with the macro view that interprets the fragile relationship in the context of the rise of China. However, neither of the approaches explains with sufficiency the question at hand. Hence for the inquiry, this article suggests a fresh view by exploring alternative method of using a cognitive map of each nation's leader, Jiangzemin and Bill Clinton. This article provides an empirical analysis through the Selected works of Jiangzemin and the speeches of Bill Clinton in 1998 for the first time in the field of Sino-US relationship studies in Korea. With the results of the cognitive map analysis, we can reach the following four points. Firstly, indicators of the forth relationship between China and the US are: i) the recognition by Bill Clinton on the importance of China's economic growth and; ii) the US's cooperation of science technology with China. Second, the conflict between China and the US results from the discordance of opinions on the matter of human rights and military power. Second, the conflict will inevitably arise on environmental issues around the globe including a global warming. Third, while China has yet to find a legitimate reason to agree upon these issues with the US, the US urges China of its cooperation. Lastly, Both China and the US attach great importance to the alliance with Japan. This implicates that relatively, issues involving Japan take more control in the China-US relationship, than those of Korea Peninsula.