• 한국시스템다이내믹스연구
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• 제11권1호
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• pp.27-57
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• 2010

This article deals with an ecological-economic analysis of the 'Pasture Project of Kum River', which is the farming plan of mitten crabs using Jichun, a stream of the River Kum where the natural propagation of mitten crabs are blocked because of the estuary dam constructed in 1990. Toward analyzing the ecological and economic effects of the crab releasing and harvesting activities in Jichun, a two-stage cohort model of population dynamics with cannibalistic behaviors and density restrictions in biomathematics is adopted, despite of the current infertility in Kum, considering the opportunity of establishing dam fishways in the near future. This study moreover presents a method of parameter estimation especially with assuming a steady state of the ecosystem, and performs various analyses such as the risk measurement of climate change and the economic value of such fishways.

• Journal of the Korean Physical Society
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• 제73권9호
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• pp.1219-1224
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• 2018

We investigate the evolutionary dynamics and the phase transitions of the island model which consists of subdivided populations of individuals confined to two islands. In the island model, the population is subdivided so that migration acts to determine the evolutionary dynamics along with selection and genetic drift. The individuals are assumed to be haploid and to be one of two species, X or Y. They reproduce according to their fitness values, die at random, and migrate between the islands. The evolutionary dynamics of an individual based model is formulated in terms of a master equation and is approximated by using the diffusion method as the multidimensional Fokker-Planck equation (FPE) and the coupled non-linear stochastic differential equations (SDEs) with multiplicative noise. We analyze the infinite population limit to find the phase transitions from the monomorphic state of one type to the polymorphic state to the monomorphic state of the other type as we vary the ratio of the fitness values in two islands and complete the phase diagram of our island model.

• 한국측량학회지
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• 제38권1호
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• pp.57-67
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• 2020

최근 스마트도시는 교통, 환경, 안전, 에너지 등 다양한 도시문제를 해결하기 위한 대안으로 주목받고 있다. 그러나 스마트도시의 개념, 동향, 정책 및 법제도에 관한 연구는 활발히 이루어지는데 비해서, 도시의 성장·정체·쇠퇴 과정 등 전 단계를 고려한 동태적 관점에서 스마트도시 서비스가 실제로 도시에 어떠한 영향을 미치는지에 대한 연구는 미흡한 실정이다. 따라서 도시를 인구, 산업, 교통, 환경, 주택, 토지 등의 하위 구성요소들이 상호간에 밀접하게 상호작용 하는 하나의 전체 시스템으로 보는 시각을 바탕으로, 도시가 시간의 흐름에 따라 어떻게 변화하는지 파악할 필요가 있다. 이에 본 연구는 시스템 다이내믹스 기법을 활용하여 안양시의 도시동태성이 장기적으로 어떠한 행태로 나타나는지 규명하고, 안양시의 스마트도시계획 등 관련 사업예산 투자가 도시동태성에 어떠한 영향을 미치는지를 분석하였다. 분석결과, 안양시는 성숙·안정형 도시에 해당되며 2040년까지 인구가 서서히 감소하는 것으로 나타났다. 구체적으로 안양시 인구는 2030까지 55만3천명 수준으로 감소하고 2040년까지 54만3천명 수준으로 감소하는 것으로 나타났다. 안양시 스마트도시계획(안)에 따라 스마트도시 사업예산을 투입하면 투자하지 않을 경우에 비해서 인구감소 완화, 사업체수 증가, 도시안전지수 개선, 평균 주행속도 개선 등의 효과가 있는 것으로 나타났다. 인구는 2040년 기준으로 예산 투입 이전보다 4000명 정도 증가하고 사업체수는 761개 증가하는 것으로 나타났다. 이러한 연구결과는 장기적인 관점에서 스마트도시 관련 정책의 효과를 파악하고 예측하는데 활용될 수 있다.

• 한국시스템다이내믹스연구
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• 제16권2호
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• pp.53-74
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• 2015

Nutria(Myocastor coypus) is one of the most notorious invasive species in many countries. The Nutria's original range was South America like Brazil, Chile and Argentina. But it has been introduced to North America, Europe, Africa, and Asia including Korea, by fur ranchers. Like most invasive and disturbing species, nutria not only destroys habitats but also impacts many native species throughout most of its range with destructive feeding behavior. The purpose of this study is to investigate the dynamics of survival mechanism, population increase and spatial distribution, and eradication effect of Nutria on Nakdong River Area with the systems thinking. The result of this study revealed that Nutria can survive during winter with the behavior that the colder the winter was, the more deeply it burrowed. Further, the study uncovered the dynamics that nutria has survived more and more strongly during the extreme cold winter in almost every region and their population has increased dramatically as a result of the uncontrolled reproduction. Finally, the result showed that the action delay in eradicating Nutria, which was originated from the information delay of perception of nutria's survival and reproduction structure, reinforced the spread of Nutria across the nation.

• 한국시스템다이내믹스연구
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• 제7권2호
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• pp.97-120
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• 2006

This paper deals with the extension of and discussion on the System Dynamics model (Jeong & Jeon, 2005) of river crabs in Korea. The previous model has been elaborated to empirically search for the optimal restoration and harvest rates of crabs in the Imjin River, on the basis of theoretical models of population dynamics in the field of bio-mathematics and environmental economics. In this paper, the authors tries to couple a series of new feedback loops related to density restrictions and cannibalistic behaviors with a stage-structured model of the crab ecosystem, and also to endogenize the parameter of baby crabs' survival that is caused by water quality improvement and income increase. Through these extensions and relaxations, the authors are able to argue about the strategic decision of the optimal rates additional considerations as well as the properties of the integrated system that was not covered in the previous paper.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제14권3호
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• pp.163-173
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• 2010

In this work, we consider a nonlinear budworm model by a system of three ordinary differential equations originally created by Ludwig et al. in 1978. The nonlinear system describes the dynamics of the interaction between a budworm and a fir forest. We introduce stability techniques to analyze the dynamical behavior of this nonlinear system. Then we use constant effort harvesting techniques to control the budworm population. We also give numerical simulations of the population model with harvest and without harvest.

• 한국시스템다이내믹스연구
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• 제16권3호
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• pp.31-48
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• 2015

The purpose of this paper is to simulate drinking population, an alcoholic abuser and an alcoholic through therapy programs and system dynamic model. Then we try to research relationship between an alcoholic crime and related therapy programs. The results of the model simulation were consistently increased drinking population and 3 types drinkers until 2020 years. Specially the growth rate of drinking abusers will be passing that of a drinking population. Second, It showed clearly the decreasing effects of drinking crime on therapy programs(clinical treatment, preventive displine and counseling treatment). Finally, it will be positvely necessary the long-term and various alcoholic therapy program for reducing the ratio of drinking abusers and an alcoholic. In the second place, government and medical centers must be established a concrete information systems for collecting alcoholic datum.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제27권2호
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• pp.123-134
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• 2023

Disordered eating behaviors, such as overeating, are known to be contagious in the general population. The objective of our research is to find an optimal control strategy to reduce the social burden of unhealthy overeating behavior by establishing and analyzing a mathematical model for the social transmission dynamics of unhealthy overeating. We consider four compartments in the population: normal weight with normal eating behavior, normal weight with overeating behavior, overweight with normal eating behavior, and overweight with overeating behavior. Simulation results under various control scenarios show that integrated control measures may be necessary to reduce the growth rate of the overeating population.

• Journal of Korean Vacuum Science & Technology
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• 제4권2호
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• pp.41-43
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• 2000

We present a study of exciton relaxation in GaAs/AIGaAs quantum well structures by using time-resolved photoluminescence techniques.03 observed that light-hole exciton has a longer decay time than heavy-hole exciton, which results from the difference of the exciton population factor. We considered the thermal population time to explain the observed exciton dynamics.

• Journal of applied mathematics & informatics
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• 제28권5_6호
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• pp.1185-1202
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• 2010

In this paper, we have studied the dynamical behaviour such as boundedness, local and global stabilities, bifurcation of a single species population affected by environmental toxicant and population toxicant. We have also studied the effect of discrete delay of the environmental toxicant on the instantaneous growth rates of the population biomass and population toxicant due to incubation period. The length of delay preserving the stability is also estimated. Computer simulations are carried out to illustrate our analytical findings.