• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제8권1호
• /
• pp.93-102
• /
• 2004

A model of three trophic level food chain with ratio dependence is considered. The existencem uniqueness and stability of its solutions are investigated.

• 충청수학회지
• /
• 제20권3호
• /
• pp.231-243
• /
• 2007

In this paper, we study a Lotka-Volterra type simple food chain model. We investigate the positive coexistence of the steady states to the model and give some results for the extinction of species under certain assumptions which can be interpreted as Domino effect and Biological control. The methods of a decoupling operator and the fixed point index theory on a positive cone are used as well as the comparison argument. Numerical evidences for our results also are provided.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1997년도 춘계학술발표회논문집(2)
• /
• pp.407-412
• /
• 1997

The predictive results between a dynamic food-chain model (DYNACON) and an equilibrium model (NRC model) were compared to show the physical validity of DYNACON. Although the mathematical formulations and transport processes of radionuclides in the environment are different between two models, the comparative study shows good agreement for deposition events that occur during the growing season of plants.

• 한국환경보건학회지
• /
• 제30권3호
• /
• pp.264-271
• /
• 2004

An aquatic food chain was constructed to provide information of bioaccumulation of DEHP as followed: phytoplankton(Scenedesmus subspicatus) ${\rightarrow}$ zooplankton(Daphnia magna) ${\rightarrow}$ fish(Oryzias latipes). After 10 days of exposure to DEHP, the fish and culture water were analyzed for residual concentration of DEHP and BAF(Bioaccumulation Factor) was determined. In addition, BCF(Bioconcentration Factor) was calculated in exposure tank in which fish were only exposed DEHP by culture water. These experiments provide the relative importance between BAF and BCF. In this study, BCF and BAF did not show any significant difference. Another work in this study was model construction and application to investigate the effect of food chain structure to BAF in higher organism (fish). The model constructed in this study considered the biological characteristics of DEHP such as metabolic parameters, as well as the chemical characteristics such as solubility. This model could be used in prediction of bioaccumulation level in dependent of various food chain structures, when the target organisms or chemicals would be changed.

• Journal of Radiation Protection and Research
• /
• 제16권2호
• /
• pp.67-74
• /
• 1991

육상 섭취 경로에 따른 내부 피폭선량 계산 모델 KFOOD의 파라메터 불착실성 및 민감도를 몬테칼로법을 사용하여 수치 분석하였다. 쌀을 통한 섭취 경로의 경우 KFOOD 코드에 의한 예측치는 아주 보수적인 값을 나타내었다 모델에서 민감도가 큰 입력변수는 방사능의 침적속도와 식물전이제수였다.

• Agribusiness and Information Management
• /
• 제3권1호
• /
• pp.1-10
• /
• 2011

In this exploratory analysis, we investigate the genesis and the evolution of local food-purchasing networks created and operated by consumers. In details, we describe how collecting and sharing information about food-products can become a central activity for some consumers' communities and how these communities are starting to play an active role in the food supply chain. We define this community-based food-purchasing model as collaborative food network (CFN), and we analytically describe its characteristics and differences with respect to the traditional and industrialized agrifood supply chain models. A collaborative food network community in Italy, known as GAS ("Gruppi di Acquisto Solidale" - "Solidarity Purchasing Groups"), is introduced as an example of our analytical model. We will use this empirical example to present the strengths and weaknesses of the CFN model.

• 한국항만경제학회지
• /
• 제29권4호
• /
• pp.55-71
• /
• 2013

국내 농업이 가지고 있는 구조적 문제와 해외시장 진입에 대한 전략과 실행력 부족으로 인해 농식품 수출시장 경쟁력이 향상되지 못하고 있는 실정이다. 이러한 환경에서 본 연구는 우리나라 수출농업 활성화를 위해 농식품 수출부문의 경쟁력을 제고시킬 수 있는 공급사슬관리 관점에서의 현실적이고 전략적인 비즈니스모델을 제안하였다. 제안된 농식품 수출물류 비즈니스모델은 농식품 수출물류센터를 중심으로 공급사슬 상의 구성원들을 효율적으로 통합 관리 할 수 있는 모델이다. 수출물류센터는 수출물류 시스템 구축, 해외시장 개척, 수출을 위한 전략적 상품 발굴과 개발 등 농식품 수출 효율화를 기반으로 대기업의 가공식품과 중소업체의 농식품을 동시에 유통하는 상품믹스, 수출물류 물적 프로세스적 시스템 구축, 해외시장 개척과 목표시장의 접근성 확보 등으로 구성된 농식품 수출증대를 위한 통합모델이다.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제22권3호
• /
• pp.179-199
• /
• 2018

The paper explores a tri-trophic food chain model with density dependent mortality of intermediate predator. To analyze this aspect, we have worked out the local stability of different equilibrium points. We have also derived the conditions for global stability of interior equilibrium point and conditions for persistence of model system. To observe the global behaviour of the system, we performed extensive numerical simulations. Our simulation results reveal that chaotic dynamics is produced for increasing value of half-saturation constant. We have also observed trajectory motions around different equilibrium points. It is noticed that chaotic dynamics has been controlled by increasing value of density dependent mortality parameter. So, we conclude that the density dependent mortality parameter can be used to control chaotic dynamics. We also applied basic tools of nonlinear dynamics such as Poincare section and Lyapunov exponent to investigate chaotic behaviour of the system.

• Nuclear Engineering and Technology
• /
• 제34권5호
• /
• pp.415-420
• /
• 2002

The previous dynamic food chain model was improved for the consideration of the influence of radioactive contamination to agricultural products due to rain during the environmental releases of radionuclides in a nuclear accident Wet interception coefficients for the agricultural plants were derived as a function of radionuclide and rainfall amount, and mathematical formulations of the previous model were modified. As a result, rain during accidental releases was influential in agricultural contamination. The contamination level of agricultural products decreased dramatically according to increasing rainfall amount. It means that predictive concentrations in agricultural products using the previous model, in which dry interception to the agricultural plants is only considered, can be overestimated. The influence of rainfall in agricultural contamination was the most sensitive for $^{131}$ I, and the least sensitive for $^{90}$ Sr among the radionuclides considered in this study.

• Journal of Radiation Protection and Research
• /
• 제27권1호
• /
• pp.21-26
• /
• 2002

원자력 사고로 인해 방사성물질이 환경으로 방출되는 기간동안 강우가 있을 경우 음식물의 오염 영향을 고려하기 위해 개발된 역동학적 섭식경로모델을 개선하였다. 이를 위해 핵종별 강우량에 따른 농작물에 대한 습차단 상수를 유도하였으며, 아울러 개발된 역동학적 섭식경로모델에 대한 수학적 모델을 재정립하였다. 평가결과, 같은 지표위 농도에 대해 강우는 음식물의 오염을 크게 감소시키며 강우량 증가에 따라 오염은 급격히 감소하였다. 이러한 사실은 원자력 사고 기간동아 강우가 있을 경우 농작물의 건차단 만을 고려한 기존 역동학적 섭식경로모델을 사용하여 평가하였을 때 그 결과는 과대 평가될 수 있다는 사실을 나타낸다. 본 연구에서 고려하는 핵종 ($^{137}Cs,\;^{90}Sr,\;^{131}I$) 중에서 강우량에 따른 음식물의 농도 감소는 $^{131}I$에서 가장 뚜렷하게 나타났으며, $^{90}Sr$이 가장 영향이 적었다.