• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.1
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• pp.156-163
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• 2010

A nonequilibrium molecular dynamics(NEMD) simulation method is developed and applied to study shock waves propagating through argon gas. In this simulation method, shock waves are generated by pushing a piston at a constant speed from one side of a simulation box filled with argon molecules. A linear relationship between piston speeds and shock speeds is observed. Thermodynamic properties including density, temperature, and pressure before and after the shock front are obtained from the simulations and compared with the well-known Rankine-Hugoniot equations based on ideal gases. The comparison shows an excellent agreement, indicating that this NEMD simulation method can be employed to investigate various physical properties of shock waves further.

• International Journal of Advanced Culture Technology
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• v.5 no.1
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• pp.1-8
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• 2017

The purpose of the present study is to examine the effect of civic cooperation with the police on the number of crime that the police must solve by conducting simulation based on system dynamics. The study sets police oriented-policing model and police-citizen cooperative model to investigate the effect of civic cooperation with the police. As a result of the simulation, the police oriented-policing model shows that the number of crime that police must solve is increasing over time, while the police-citizen cooperative model shows that the number of crime that must be solved by the police is keeping it stable in the increase of crimes. Comparing both models, civic cooperation with the police is more effective in reducing or deterring crime than police oriented-policing activity. The study proves that building cooperative relationship between citizens and the police can become a strategic method for controlling crime effectively without a rapid increase in police finance. It is meaningful in terms of presenting a dynamic change of interaction for reducing crimes between civic cooperation with the police and policing activity of the police over time.

• Korean System Dynamics Review
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• v.14 no.2
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• pp.31-53
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• 2013

This article deals with a Causal-Loop analysis of the characteristics of Ouroboros effects. The meaning of the effects is that solutions to problems are usually intended as final fixes, but more often than not, while solving one problem, they generate more problems. It means 'to worsen through attempts to make better.' The Ouroboros effects are very dangerous because they are regarded as a kind of self-destructive mechanisms. While existing researchers recognize the risks of the effects, they are not able to solve the systematic problem but only to describe the symptom. Such a way to deal with the effects results in difficulty to clarify the cause-and-effect relationship within the system. Thus the authors are focusing on explaining the effects by SD (System Dynamics), which are considered as the sole methodology to do effectively so far since SD is a great tool to discover structural causes. To solve the self-destructive problem of the effects, the authors analyze the characteristics of several cases of the effects in elaborating the CLD (Causal Loop Diagram) for each case. The analysis reveals the structural characteristics of the effects and how to correct them towards maintaining the sustainability of systems.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.12
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• pp.181-188
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• 2019

The maintenance of school building is pivotal issue. However, it is difficult to obtain basic analysis data for LCC(Lifecycle Cost) analysis and maintenance planning of school building. Therefore, this study proposed System Dynamics(SD) techniques to make maintenance decisions for school building. The interaction between the major parameters related to the aging of a building, maintenance activities, and cost were expressed in Causal Loop Diagram. Based on this, the formula for the relationship between causal maps was defined and converted to Stock and Flow Diagram. Through the completed SD model the 50-year plan of 214 educational building were tested by considered in account budget, maintainability, and budget allocation opinions. As a result, the integrated SD model demonstrated that it can support strategic decision making by identifying the status class and LCC behavior of school buildings by scenario. According to the scenario analysis, the rehabilitation action of preventive maintenance that primarily repairs the buildings in condition grade C showed the best performance improvement effect relative to the cost. Therefore, if the proposed SD model is expanded to consider the effects of other educational policies, the crucial performance improvement budget can be estimated in the long-term perspective.

• Journal of Ecology and Environment
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• v.30 no.3
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• pp.209-223
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• 2007

Twenty-four wetlands located in Higashi-Hiroshima City in West Japan were selected for this study in order to investigate both the relationship between aquatic plant composition and environmental conditions; and the relationship between changing land use patterns in the catchments and the concentration of different forms of nitrogen in the wetlands. The dominant and subdominant species which comprised the principal vegetation were determined based on a vegetation census conducted in each wetland during the growing season from June to August, 2006. The seasonal variations of water quality factors (pH, electrical conductivity, turbidity, dissolved oxygen, total dissolved solid, and temperature) and different forms of nitrogen such as nitrite, nitrate, ammonium, total nitrogen, dissolved organic nitrogen and dissolved inorganic nitrogen concentrations were analyzed as important indicators of water quality for the surface water of the wetlands. The surveyed wetlands were classified into three types (non-disturbed wetlands, moderately-disturbed wetlands and highly-disturbed wetlands), based on the degree of human disturbance to their catchment areas. An analysis of variance indicated that there was a significant difference among the wetland groups in the annual mean values of electrical conductivity, total dissolved solids, total nitrogen, nitrite, dissolved inorganic nitrogen and dissolved organic nitrogen. Classification of the wetlands into three groups has revealed a pattern of changes in the composition of plant species in the wetlands and a pattern of changes in nitrogen concentrations. A majority of the non-disturbed wetlands were characterized by Brasenia schrebi and Trapa bispinosa as dominant; with Potamogeton fryeri and Iris pesudacorus as sub-dominant species. For most of the moderately-disturbed wetlands, Brasenia schrebi were shown to be a dominant species; Elocheriss kuriguwai and Phragmites australis were observed as sub-dominant species. For a majority of the highly-disturbed wetlands, Typha latifolia and T. angustifolia were observed as dominant species, and Nymphea tetragona as the sub-dominant species in the study area. An analysis of land use and water quality factors indicated that forest area played a considerable role in reducing the concentration of nutrients, and can act as a sink for surface/subsurface nutrient inputs flowing into wetland water, anchor the soil, and lower erosion rates into wetlands.

• Economic Analysis
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• v.24 no.3
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• pp.1-36
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• 2018

When it comes to explaining the relationship between inventory investment and business fluctuations, the production smoothing theory and the stock-out avoidance theory take contradictory stances. Decision-making related to inventory investments of corporations is thought to be influenced by both motives, but the relative sizes or directions of their respective influences can differ depending upon the phase of the business cycle. Against this backdrop, this paper differs from existing studies in that it theoretically tests the relative significances of the production smoothing and stock-out avoidance motives in the inventory investment dynamics, while placing its analytical focus on determining the existence and patterns of the asymmetric dynamics of inventory investment over the business cycle phases. To this end this paper sets up a non-linear model that is expanded from the existing linear inventory investment model, and checks whether its predictive power is better than that of the existing model. The results of analysis confirm the nature of the asymmetric dynamics of inventory investment over the business cycle phases. A stock-out avoidance motive appears but there is no significant production smoothing motive in boom times. In downturns, in contrast, the stock-out avoidance motive is insignificant, but a quality of asymmetric dynamics in which changes in inventory cause the deepening of recessions, due to the non-convexity of production costs proposed by Ramey (1991), is detected. This paper confirms that a model considering the asymmetric dynamics of inventory investment can have better predictive power than one that does not consider it, through within-sample and out-of-sample predictions and various predictive power tests. These research results are expected to be useful for economic forecasting, through their enhancement of the understandings of the inventory investment dynamics and of the nature of its business cycle destabilization.

• The Journal of Asian Finance, Economics and Business
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• v.5 no.4
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• pp.149-160
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• 2018

An alternative method for team diversity studies is to examine demographic faultlines. A concept of demographic faultline enables us to better understand team dynamics with multidimensional diversity. This study suggests the demographic faultline as a new situational factorto influence the relationship between leader teamwork behaviors and a climate of support for innovation. When subgroups divided by demographic faultline are homogeneous within them and heterogeneous between them, the homogeneity may increase intimacy in each subgroup while the heterogeneity may increase exclusiveness between those subgroups. We argued that a leader could play an important role to build a cooperative relationship between faultline-based subgroups and highlight positive aspects of developing and maintaining subgroups in organizations. With a sample of 81 teams (558 employees), it was examined how leader teamwork behaviors would affect a team-level climate of support for innovation and how this relationship would be moderated by each team's demographic faultline (gender, age, and educational specialty). As predicted, it was found that there was a significant positive relationship between each leader's teamwork behaviors and each team's climate of support for innovation. In addition, this relationship was stronger for teams with strong faultline than with weak faultline. Our findings and their implications were further discussed.

• Proceedings of the KOSOMBE Conference
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• v.1991 no.05
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• pp.82-85
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• 1991

Cell kinetics and the chemical mass action principle formulate the basis of immune system dynamics which may be synthesized mathematically as cascades of bilinear systems which are connected by nonlinear nondynamical terms. In this manner, a model for cell-mediated immune response (CMI) to tumor antigens and debris is developed. We also consider parametric control variables relevant to the latest experimental data, i.e., sigmoidal dose-response relationship and Michaelis-Menten dynamics. The preliminary results show that the parametric control variable is important in the destruction of tumors. As well as that, the exacerbation theory is a good method for tumor treatment. Finally, tumor control as an application of immunotherapy is analyzed from the basis established above.

• Korean System Dynamics Review
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• v.10 no.3
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• pp.47-79
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• 2009

The paper examines dynamic relationship among 'Limit to Growth' factors in Korea using causal loop diagram. It also aims to explore policy implications for Korea in overcoming current difficulties and future crisis we may face. For this purpose, five factors -economy, population, resource, environment, food- used in the were adopted as an analytical framework. Findings show that Korea is fragile to external shock such as world economic crisis, food price surge, and resource price -including energy price- hike. High dependency of energy, food and resource on foreign market was found to be a major source of limit to growth in Korea. Furthermore, environmental problems like global warming could be a major external shock that could hit Korea harder than the rest of the world. Policy implications and measures for these problems were discussed too.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.93-98
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• 2004

A reasonable analysis of cutting force in end milling may give much advantage to improvement of productivity and cutting tool life. In order to analyze cutting force, the cutting dynamics was modelled mathematically by using chip load, cutting geometry, and the relationship between cutting forces and the chip load. Specific cutting constants of the cutting dynamics model were obtained by average cutting forces, tool diameter, cutting speed, feed, axial depth, and radial depth of cut. The effects of the cutting conditions on the specific cutting force constants in milling were studied. The model is verified through comparisons of model predicted cutting forces with measured culling forces obtained from machining experiments