• Journal of applied mathematics & informatics
• /
• 제29권3_4호
• /
• pp.529-546
• /
• 2011

A deterministic tuberculosis model for theoretically assessing the potential impact of the combined effects of case detection in the presence of treatment is formulated. The qualitative features of its equilibria are analyzed and it is found that the disease-free equilibrium may not be globally asymptotically stable when the reproduction number is less than unity. This disease threshold number is further used to assess the impact of active TB case finding alone and in conjunction with treatment. A critical threshold parameter ${\Theta}$ say for which case detection will have a positive impact is derived. Using the Centre Manifold theory, the model may exhibit the phenomenon of backward bifurcation (coexistence of a locally stable endemic equilibrium with a stable disease-free equilibrium) when the reproduction number is less than unity. It is shown that the possibility of backward bifurcation occurring decreases with increase case detection. Graphical representations suggest that increase in case finding accompanied by treatment of detected TB cases, result in a marked decrease of TB cases (both latent and active TB).

• Environmental Engineering Research
• /
• 제11권1호
• /
• pp.33-44
• /
• 2006

The objective of this study was to develop and assess a method for estimating the rain scavenging ratios (RSRs) of particle-bound PAHs and PCBs using measured scavenging ratio of particulate matters (PM) and routinely available data of physico-chemical properties of PM. Paired atmospheric and rainwater sampling was conducted for a total of 4 rain events. Assuming equilibrium partitioning in rainwater-gas-PM system, an equation was derived for estimating the RSR of particle-bound chemicals as a function of RSR of PM and three equilibrium partition constants (i.e. dimensionless Henry's law constant, gas-particle partition coefficient, and water-particle partition coefficient). For all PAHs, the model significantly under-predicted the RSR while the model prediction for PCBs agreed with observation mostly within a factor of 5. The RSR model for the chemicals is of limited use as its accuracy critically depends on how close the observed partitioning of the chemicals in the gas-PM-rainwater system is to that estimated under the equilibrium assumption.

• Nuclear Engineering and Technology
• /
• 제47권3호
• /
• pp.306-314
• /
• 2015

This paper examines the difference in the value of the nuclear fuel cycle cost calculated by the deterministic and probabilistic methods on the basis of an equilibrium model. Calculating using the deterministic method, the direct disposal cost and Pyro-SFR (sodium-cooled fast reactor) nuclear fuel cycle cost, including the reactor cost, were found to be 66.41 mills/kWh and 77.82 mills/kWh, respectively (1 mill = one thousand of a dollar, i.e., $10^{-3}$ $). This is because the cost of SFR is considerably expensive. Calculating again using the probabilistic method, however, the direct disposal cost and Pyro-SFR nuclear fuel cycle cost, excluding the reactor cost, were found be 7.47 mills/kWh and 6.40 mills/kWh, respectively, on the basis of the most likely value. This is because the nuclear fuel cycle cost is significantly affected by the standard deviation and the mean of the unit cost that includes uncertainty. Thus, it is judged that not only the deterministic method, but also the probabilistic method, would also be necessary to evaluate the nuclear fuel cycle cost. By analyzing the sensitivity of the unit cost in each phase of the nuclear fuel cycle, it was found that the uranium unit price is the most influential factor in determining nuclear fuel cycle costs.

• 사회경제평론
• /
• 제38호
• /
• pp.51-83
• /
• 2012

다수의 상품이 생산되는 경제에서 스라파(Sraffa) 균형가격 조건과 균제성장 및 상품시장 균형 조건이 성립하는 경우를 생각하자. 이 모형에서 임금율 결정식과 투자함수를 동시에 부여하면 전체 경제는 과잉결정 되며 균형이 존재하지 않는다. 본 연구는 이 과잉결정 현상을 불균형 상태로 해석하고, 불균형상태에서 실현되는 임금율과 자본축적률이 각각의 동학식을 따라 결정되는 것으로 해석한다. 그리고 이 해석의 유효성을 주장하기 위하여 전체 경제에 대한 단순한 동학모형을 구축하고, 임금율과 자본축적률의 동학경로를 분석한다. 본 연구의 동학모형은 로카-볼테라 식체계의 구성조건을 만족하며, 따라서 전체 경제의 성장경로는 내생적으로 순환변동하는 경로를 따라 결정된다.

• 반도체디스플레이기술학회지
• /
• 제17권1호
• /
• pp.76-83
• /
• 2018

The electron energy probability function (EEPF) is of significant importance since the plasma chemistry such as the rate of ionization is determined by the electron energy distribution function. It is usually assumed to be Maxwell distribution for 0-D global model. Meanwhile, it has been observed experimentally that the form of EEPF of Ar plasma changes from being two-temperature to Druyvesteyn like as the gas pressure increases. Thus, to apply the 0-D global model of Maxwellian distribution to the non-Maxwellian plasma, we investigated the relative contribution of two distinct electrons with different temperatures. The contributions of cold/hot electrons to the equilibrium state of the plasma have attracted interest and been researched. The contributions to the power and particle balance of cold/hot electrons were studied by comparing the result of the global model considering all combinations of electron temperatures with that of 1-D Particle-in-Cell and Monte Carlo collision (PIC-MCC) simulation and the results of studies were analyzed physically. Furthermore, comparisons term by term for variations of the contribution of cold/hot electrons at different driving currents are presented.

• 한국유기농업학회지
• /
• 제32권2호
• /
• pp.137-159
• /
• 2024

Major crop prices have been raised significantly in recent years by COVID-19, the war in Ukraine, and weather-induced reductions in South American soybean production by unfavoured weather in 2022. Rising international crop prices are likely to destabilize food security in South Korea, which is highly dependent on foreign crops. This study analyzed the impact of soybean import price changes on the domestic soybean market and soybean food self-sufficiency rate from 2024 to 2029 using a dynamic partial equilibrium model. According to the scenario analysis results, if the import prices rise by 10% compared to the baseline, the soybean food self-sufficiency rate would increase by 1.33% in 2024, but it is expected to decrease to -0.58% in 2029 due to the continuous decrease in production. The results of this study are expected to be used as valuable information for policy authorities in establishing policies related to improving food self-sufficiency.

• East Asian Economic Review
• /
• 제28권3호
• /
• pp.277-314
• /
• 2024

This study analyzes the response of economic fundamentals to a misalignment shock of the real effective exchange rate in Korea. The estimation results of the equilibrium exchange rate determination model and time series model show that there is no significant difference in the direction of the deviation from equilibrium and that the won is significantly undervalued during the period before 1988, or during the currency and global financial crises. The cumulative impulse response analysis of the VAR model over the full period shows that an upward shock to the deviation from the equilibrium exchange rate reduces the GDP gap and inflation rate, while the effect on the call rate is not statistically significant. Furthermore, an upward misalignment shock initially worsens the goods and services balance, but the deficit in the goods and services balance shrinks significantly over time. In rolling regressions analysis, the entire sample is divided into two periods to estimate the impulse response function from the first period, and then the same procedure is repeated by moving the sample forward one by one. The cumulative impulse response results show that, as is the case for the full period, a positive exchange rate misalignment shock initially reduces the GDP gap, inflation, and worsens the goods and services balance, but the impact of this upward shock on these variables becomes increasingly weaker in the more recent sample. It also shows that the negative impact of upward shocks on the current account is smoothed out more recently during periods of undervaluation than during periods of overvaluation.

• 한국지반공학회지:지반
• /
• 제11권2호
• /
• pp.121-138
• /
• 1995

여러종류의 화합물질들이 동시에 토양에 유출되었을 때 이들이 토양에 흡착하는 정도를 예측 함에는 Langmuir Competitive Model과 IAS(Ideal Adsorption Model) 등이 널리 사용되고 있 는데, 5개의 유기화합물질(Phenol, 2,4-Dichlorophenol, 2,4,6-Trichlorophenot Brucine, Thiourea)과 2종류의 토양을 이용한 흡착실험을 통해서 이 Model들의 예측도를 비교분석하였다. 흡착실험은 이 화합물질들이 독자적인 상태에서 그리고 혼합상태에서 각각 구분하여 실헙하였다. 일반적으로 IAS Model이 Langmuir Model보다 혼합상태에서 각 구성 화합물질들의 흡착을 더 정확히 예측하였다. Langmuir Model은 Phenol과 함께 섞여있는 다른물질의 농도가 높을 때 Phenol의 흡착을 낮게 예측하였다. 두가지 Model모두 Thiourea가 혼합상태에 있을때 흡착정도를 만족스럽게 예측하지 못했는데 Thiourea는 Aliphatic화합물이고 나머지 4개는 Aromatic화합물이다.

• Earthquakes and Structures
• /
• 제11권4호
• /
• pp.723-740
• /
• 2016

Reinforced concrete corbels are generally used to transfer loads within a structural system, such as buildings, bridges, and facilities in general. They commonly present low aspect ratio, requiring an accurate model for shear strength prediction in order to promote flexural behavior. The model described here, originally developed for walls, was adapted for corbels. The model is based on a reinforced concrete panel, described by constitutive laws for concrete and steel and applied in a fixed direction. Equilibrium in the orthogonal direction to the shearing force allows for the estimation of the shear stress versus strain response. The original model yielded conservative results with important scatter, thus various modifications were implemented in order to improve strength predictions: 1) recalibration of the strut (crack) direction, capturing the absence of transverse reinforcement and axial load in most corbels, 2) inclusion of main (boundary) reinforcement in the equilibrium equation, capturing its participation in the mechanism, and 3) decrease in aspect ratio by considering the width of the loading plate in the formulation. To analyze the behavior of the theoretical model, a database of 109 specimens available in the literature was collected. The model yielded an average model-to-test shear strength ratio of 0.98 and a coefficient of variation of 0.16, showing also that most test variables are well captured with the model, and providing better results than the original model. The model strength prediction is compared with other models in the literature, resulting in one of the most accurate estimates.

• 산학경영연구
• /
• 제20권2호
• /
• pp.1-13
• /
• 2007

The purpose of this study is to investigate a simple present value model Involving earnings (i.e., the earnings discount model) that presumes a relationship between stock prices and earnings. The model suggests a simple linear equilibrium relationship between stock prices and earnings. The tests for cointegration render strong support for the cointegration hypothesis between stock prices (Pt) and earnings (Xt) even at the one-percent significance level. The tests are based on residuals from a cointegrating regression of Pt on Pt+l + Xt. This suggests that there is a stable long-nu equilibrium relationship between stock prices and earnings. The results of the tests lead to the acceptance of the present value model of stock prices involving earnings.