• Journal of applied mathematics & informatics
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• v.29 no.5_6
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• pp.1097-1115
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• 2011

We consider the global stability of a general tuberculosis model with two differential infectivity, n classes of latent individuals and mass action incidence. This system exhibits the traditional threshold behavior. There is always a globally asymptotically stable equilibrium state. Depending on the value of the basic reproduction ratio $\mathcal{R}_0$, this state can be either endemic ($\mathcal{R}_0$ > 1), or infection-free ($\mathcal{R}_0{\leq}1$). The global stability of this model is derived through the use of Lyapunov stability theory and LaSalle's invariant set theorem. Both the analytical results and numerical simulations suggest that patients should be strongly encouraged to complete their treatment and sputum examination.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.870-875
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• 2004

Current trend of design technologies shows engineers to objectify or automate the given decision-making process. The numerical optimization is an example of such technologies. However, in numerical optimization, the uncertainties are uncontrollable to efficiently objectify or automate the process. To better manage these uncertainties, Taguchi method, reliability-based optimization and robust optimization are being used. To obtain the target performance with the maximum robustness is the main functional requirement of a mechanical system. In this research, the robust design strategy is developed based on the DACE and the global optimization approaches. The DACE modeling, known as the one of Kriging interpolation, is introduced to obtain the surrogate approximation model of the system. The robustness is determined by the DACE model to reduce the real function calculations. The simulated annealing algorithm of global optimization methods is adopted to determine the global robust design of a surrogated model. The mathematical problems and the MEMS design problem are investigated to show the validity of the proposed method.

• Journal of the Korean Solar Energy Society
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• v.31 no.6
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• pp.86-94
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• 2011

For accurate dayligh tsimulation, accurate exterior illuminance is necessary. But, Korea Meteorological Agency provides only the solar irradiance data. Thus, there is a need for the research on luminous efficacy. In this study, global horizontal irradiance, diffuse horizontal irradiance, global horizontal illuminance, and diffuse horizontal illuminance were measured to calculate the luminous efficacy in SEOUL. And, we evaluated the applicability of the Perez's model by comparing the measured data and calculated data. As a result, measured global luminous efficacy is 126(110~129)lm/W and diffuse luminous efficacy is 127(115~133)lm/W in Seoul. Perez's model was relatively accurate with 5% difference in the diffuse luminous efficacy. But, it can be predicted about 15% lower in the global luminous efficacy.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.486-490
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• 2015

SWOT model was used to develop strategies for the Korean construction firms in entering the global construction market. Literature review, official statistics survey and other research methods were utilized in order to extract internal and external environmental factors of both the firm and local area. By extracting strength, weakness, opportunity and threat factors, a total of 12 strategies were produced: SO (Strengths-Opportunities), ST (Strengths-Threats), WT (Weaknesses-Threats), and WO (Weaknesses-Opportunities). The result of the study can be utilized as a basic data in developing a strategy for the Korean construction firms to penetrate into the global construction market.

• Journal of Korea Water Resources Association
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• v.43 no.12
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• pp.1063-1074
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• 2010

The objective of this study is to evaluate the application of Land Surface Model (LSM) and global spatial and weather data. After selecting the appropriate LSM, we evaluated the calculation ability of the model for dam basins. Based on the global meteorological and topography data, the accuracy of runoff results were analysed to assess the uncertainty of global data. Period analysis was performed to suggest the global data utilization. The model results by using local data are within the acceptable range reflecting the local complex meteorological and topographical characteristics. Although the accuracy of the simulated results from global data is not good by the uncertainty of meteorological data, it indicated that the accuracy can be improved with increasing duration of runoff analysis over 10 days.

• International Commerce and Information Review
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• v.8 no.2
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• pp.141-162
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• 2006

This paper focuses on the phenomenon that international payment system is essential as reverse action of delivery or supply of digital goods in global transactions. In order to impose the customs duties on imported goods in global on-line transactions, the imposition of tariff by tracing the payment process when business transaction is occurring is recommended. The purpose of this study is to review the countermeasures for effective tariff imposition system by using the model of the main payment tools in global transactions. Some models reviewed in this paper are as follows : i) a model of withholding taxes at the source by the credit company ii) a model of self declaration by the importer iii)a model of registering by overseas company iv) a model of negotiating after the taxation at the export country This study is different from existing preceding research at the point of view of presenting 4 models and doing appraisal by each model. It should be done more in depth and various study on the model of the tariff imposition system about the models reviewed at this paper. Systematic and reasonable alternatives which are actually adoptable at the system should also be studied and examined carefully. Because it is required that tariff imposition system on the digital goods should be harmonized with that of traditional business in order to obtain effectiveness and rightfulness, and especially, in order to get justness for the imposition a tariff on digital goods, the process of tax imposition should be predictable and be sure to get the fairness by enhancing the equilibrium, impartiality and transparency.

• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.9-17
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• 2013

Hourly horizontal global solar radiation has been used as one of significant parameters in a weather file for building energy simulations, which determines the quality of building thermal performance. However, as about twenty two weather stations in Korea have actually measured the horizontal global sola radiation, the weather files collected in other stations requires solar data simulation from the other meteorological parameters. Thus, finding the reliable complicated method that can be used in various weather conditions in Korea is critically important. In this paper, three solar simulation models were selected and evaluated through the reliability test with the simulated hourly horizontal global solar radiation against the actually measured solar data to find the most suitable model for the south east area of Korea. Three selected simulation models were CRM, ZHM, and MRM. The first two models are regression type models using site-fitted coefficients which are derived from the correlation between measured solar data and local meteorological parameters from the previous years, and the last model is a mechanistic type model using the meteorological data to calculate conditions of atmospheric constituents that cause absorption and scattering of the extraterrestrial radiation on the way to the surface on the Earth. The evaluation results show that ZHM is the most reliable model in this area, yet a complicated hybrid simulation methods applying the advantages of each simulation method with the monthly-based weather data is needed.

• Bulletin of the Korean Mathematical Society
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• v.49 no.2
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• pp.319-327
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• 2012

The equations of a multifluid interpenetration mix model are analyzed. The model is an intermediate mix model in the sense that it is defined by partial pressures but only a single global pressure and a single global temperature. It none-the-less avoids the stability difficulty. It is shown that the model is hyperbolic so that it is mathematically stable.

• Bulletin of the Korean Mathematical Society
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• v.57 no.4
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• pp.891-907
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• 2020

In this paper, we consider the Cauchy problem to the tropical climate model. We establish the global regularity for the 2D tropical climate model with generalized nonlocal dissipation of the barotropic mode and obtain a multi-logarithmical vorticity blow-up criterion for the 2D tropical climate model without any dissipation of the barotropic mode.

• Journal of Astronomy and Space Sciences
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• v.28 no.1
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• pp.71-77
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• 2011

Ionospheric error modeling is necessary to create reliable global navigation satellite system (GNSS) signals using a GNSS simulator. In this paper we developed algorithms to generate Klobuchar coefficients ${\alpha}_n$, ${\beta}_n$ (n = 1, 2, 3, 4) for a GNSS simulator and verified accuracy of the algorithm. The eight Klobuchar coefficients were extracted from three years of global positioning system broadcast (BRDC) messages provided by International GNSS service from 2006 through 2008 and were fitted with Fourier series. The generated coefficients from our developed algorithms are referred to as Fourier Klobuchar model (FOKM) coefficients, while those coefficients from BRDC massages are named as BRDC coefficients. The correlation coefficient values between FOKM and BRDC were higher than 0.97. We estimated total electron content using the Klobuchar model with FOKM coefficients and compared the result with that from the BRDC model. As a result, the maximum root mean square was 1.6 total electron content unit.