• Journal of Information Processing Systems
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• 제17권1호
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• pp.28-36
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• 2021

This paper proposes two novel methods to model and simulate a mobile Internet of Things (IoT) system using the discrete event system specification (DEVS) formalism. In traditional simulation methods, it is advantageous to partition the simulation area hierarchically to reduce simulation time; however, in this case, the structure of the model may change as the IoT nodes to be modeled move. The proposed methods reduce the simulation time while maintaining the model structure, even when the IoT nodes move. To evaluate the performance of the proposed methods, a prototype mobile IoT system was modeled and simulated. The simulation results show that the proposed methods achieve good performance, even if the number of IoT nodes or the movement of IoT nodes increases.

• Corrosion Science and Technology
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• 제18권6호
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• pp.285-291
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• 2019

In this study, the corrosion characteristics of T22 and T92 steel were investigated in 6O₂ + 16CO₂ + 2SO₂ gas environment at 650 ℃. Corrosion characteristics were characterized by weight gain, oxide layer thickness, scanning electron microscope, optical microscope, energy dispersive X-ray spectroscopy, and X-ray diffraction. T22 and T92 steel tended to stagnate oxide layer growth over time. Oxidation kinetics were analyzed using the data of oxide layer thickness, and a regression model was presented. The regression model was significantly acceptable. The corrosion rate between the two steels through the regression model showed significant difference. The T92 steel was approximately twice as large as the time exponent and showed very good corrosion resistance compared to the T22 steel. In both steels, the oxide layer mainly formed a Fe-rich oxide layer composed of hematite (Fe₂O₃), magnetite (Fe₃O₄), and spinel (FeCr₂O₄). Sulfide segregation occurred in the oxide layer due to SO₂ gas. However, the locations of segregation for the T22 and T92 steel were different.

• Journal of the Korean Data and Information Science Society
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• 제14권2호
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• pp.393-403
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• 2003

In this paper, various replacement policies for the general failure model are considered. There are two types of failure in the general failure model. One is Type I failure (minor failure) which can be removed by a minimal repair and the other is Type II failure (catastrophic failure) which can be removed only by a complete repair. In this model, when the unit fails at its age t, Type I failure occurs with probability 1-p(t) and Type II failure occurs with probability p(t), $0{\leq}p(t){\leq}1$. Under the model, optimal replacement policies for the long-run average cost rate and the limiting efficiency are considered. Also taking the cost and the efficiency into consideration at the same time, the properties of the optimal policies under the Cost-Priority-Criterion and the Efficiency-Priority-Criterion are obtained.

• 한국농공학회지
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• 제44권5호
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• pp.106-115
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• 2002

The objective of this study was to evaluate the GLEAMS-PADDY model by applying it to estimate nutrients loading from paddy-field areas. Field data from Soro region of Chungbuk province during May to September 1999 were used for model application. Field data collected include the amounts of rainfall, irrigation water, drainage water, ET, and Percolation in hydrology Part. T-N and T-P concentrations in the rain water, irrigation water, ponded water, drainage water and percolated water were measured. The comparisons of observed and simulated water balance components and nutrient concentrations showed reasonably good agreements and the GLEAMS-PADDY model may be used to simulate nutrients loading from paddy fields. Futher research was suggested to include the erosion submodel in the GLEAMS-PADDY model to better simulate the nutrient behavior. In addition, the pesticide submodel also recommended to be included in order to simulate the various pesticide applied in paddy fields.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1423-1424
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• 2013

• 한국농공학회논문집
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• 제52권1호
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• pp.1-11
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• 2010

Generation and transportation of runoff and pollutant loads within watershed generated eutrophication at Daecheong reservoir. To improve water quality at Daecheong reservoir, the best management practices should be developed and applied at upper watersheds for water quality improvement at downstream areas. In this study, two small watersheds of upper Daecheong reservoir were selected. The Long-Term Hydrologic Impact Assessment (L-THIA) model has been widely used for the estimation of the direct runoff worldwide. To apply the L-THIA ArcView GIS model was evaluated for direct runoff and water quality estimation at small watershed. And the Web-based Hydrograph Analysis Tool (WHAT) was used for direct runoff separating from total flow. As a result, the $R^2$ (Coefficient of determination) value and Nash-Sutcliffe coefficient value for direct runoff comparison at An-nae watershed were 0.81 and 0.71, respectively. And the $R^2$ value and Nash-Sutcliffe coefficient value at Wol-oe were 0.95 and 0.93. The $R^2$ value of BOD, TOC, T-N and T-P at An-nae watershed were BOD 0.94, TOC 0.81, T-N 0.94 and T-P 0.89. And the $R^2$ value of BOD, TOC, T-N and T-P at Wol-oe watershed were BOD 0.80, TOC 0.93, T-N 0.86 and T-P 0.65. The result that estimated pollutant loadings using the L-THIA ArcView GIS model reflected well the measured pollutant loadings except for T-P in Wol-oe watershed. With L-THIA ArcView GIS model, the direct runoff and non-point pollutant (NPS) loadings in the watershed could be analyzed through simple input data such as daily rainfall, land uses, and hydrologic soil group.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2002년도 학술발표회 발표논문집
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• pp.461-464
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• 2002

This study is to application the TANK modle for Ponding depth and discharge, T-N, T-P simulation from paddy field area. Simulation coefficient of correlation for Ponding depth and discharge, T-N, T-P were 0.89, 0.60, 0.99, 0.91 respectively. advanced purposes are development of agriculture runoff character modeling and application of best management practice with this study model.

• 대한수학회보
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• 제41권2호
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• pp.337-345
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• 2004

In allelic model X = ($\chi_1\chi$_2ㆍㆍㆍ, \chi_d$), M_f(t) = f(p(t)) - ${{\int^t}_0}\;Lf(p(t))ds$ is a P-martingale for diffusion operator L under the certain conditions. In this note, we can show existence and uniqueness of solution for stochastic differential equation and martingale problem associated with mean vector. Also, we examine that if the operator related to this martingale problem is connected with Markov processes under certain circumstance, then this operator must satisfy the maximum principle.

• STI Policy Review
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• 제6권1호
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• pp.85-110
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• 2015

Science and technology diplomacy has become an important policy agenda because of its diplomatic utility and enhancing of international science networks. However, different countries possess different objectives and governance of S&T diplomacy. In this context, this paper seeks to answer the following questions: what are the similarities and differences of S&T diplomacy in countries and what shapes these characteristics? To answer these questions, this paper conducts a comparative case study with five countries - Switzerland, Germany, Japan, the United Kingdom, and the United States - whose S&T diplomatic programs are highly recognized and benchmarked by other countries. A useful typology is devised to conduct a systematic comparison. For S&T diplomatic objectives, this paper suggests five types by elaborating concepts from the previous literature: access diplomacy, promotion diplomacy, public aid diplomacy, functional diplomacy, and global leadership diplomacy. Also, in terms of a governance model for S&T diplomacy, three models - a sciencecentered model, a science-outsourcing model and a top-down coordinating model - are suggested based on leadership organization. This paper reveals the different characteristics of the selected countries in S&T diplomacy. While the selected countries pursue almost every type of S&T diplomatic objective, the US and the UK tend to conduct influence-based diplomacy more than other countries do. In addition, different countries each have unique governance models for S&T diplomacy. While more research is necessary for vigorously testing the causes of different objectives and their relationship with governance models, this paper suggests more general policy implications throughout. The strength of the country's S&T base is fundamentally important for the success of S&T diplomacy. However, domestic S&T assets need to be transferred to its diplomatic capabilities. In this sense, the appropriate governance that fits best with the country's S&T mission should be established, while S&T communities should increasingly play a leadership role in evolving global S&T networks.

• 산업융합연구
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• 제18권2호
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• pp.69-75
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• 2020

산업용 IoT는 비용 효율적이고 넓은 커버리지를 제공하는 무선 메쉬 네트워크에 관심이 많았다. 하지만, 무선 메쉬 네트워크는 멀티홉 환경의 심각한 성능 절하를 겪는다. 이를 극복하기 위해 메쉬 라우터에 캐시를 장착하는 연구가 많았으나 캐시 파워 소모 모델 연구는 적었다. 최근 캐시 파워 효율 기반 모델은 캐시까지 콘텐츠 전달 파워를 모두 측정했기 때문에 무선 메쉬 네트워크에서 쓰기에 부적절합니다. 본 논문은 CPU의 동작속도가 캐시 크기에 비례한다는 사실을 이용하여 캐시 적중률 기반 파워 소모 모델을 제안하고, 기존 캐시 파워 효율 기반 소모 모델과 비교하여 정확하게 측정되었다. 제안된 캐시 적중률 기반 파워 소모 모델은 산업용 IoT에서 무선 메쉬 네트워크를 구성할 시 에너지 효율적인 캐시 운용을 위한 참조 모델로 활용되길 기대합니다.