• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.49-60
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• 2022

Motivated by the high-resolution properties of high-order Weighted Essentially Non-Oscillatory (WENO) and flux limiter (FL) for steep-gradient problems and the robust convergence of Jacobian-free Newton-Krylov (JFNK) methods for nonlinear systems, the preconditioned JFNK fully implicit high-order WENO and FL schemes are proposed to solve the transient two-phase two-fluid models. Specially, the second-order fully-implicit BDF2 is used for the temporal operator and then the third-order WENO schemes and various flux limiters can be adopted to discrete the spatial operator. For the sake of the generalization of the finite-difference-based preconditioning acceleration methods and the excellent convergence to solve the complicated and various operational conditions, the random vector instead of the initial condition is skillfully chosen as the solving variables to obtain better sparsity pattern or more positions of non-zero elements in this paper. Finally, the WENO_JFNK and FL_JFNK codes are developed and then the two-phase steep-gradient problem, phase appearance/disappearance problem, U-tube problem and linear advection problem are tested to analyze the convergence, computational cost and efficiency in detailed. Numerical results show that WENO_JFNK and FL_JFNK can significantly reduce numerical diffusion and obtain better solutions than traditional methods. WENO_JFNK gives more stable and accurate solutions than FL_JFNK for the test problems and the proposed finite-difference-based preconditioning acceleration methods based on the random vector can significantly improve the convergence speed and efficiency.

• Journal of Environmental Science International
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• v.17 no.6
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• pp.689-698
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• 2008

Numerical study is conducted to predict effects of radiative heat loss and fuel composition in synthetic gas diffusion flame diluted with $CO_2$. The existing reaction models in synthetic gas flames diluted with $CO_2$ are evaluated. Numerical simulations with and without gas radiation, based on an optical thin model, are also performed to concrete impacts on effects of radiative heat loss in flame characteristics. Importantly contributing reaction steps to heat release rate are compared for synthetic gas flames with and without $CO_2$ dilution. It is also addressed that the composition of synthetic gas mixtures and their radiative heat losses through the addition of $CO_2$ modify the reaction pathways of oxidation diluted with $CO_2$.

• Journal of Environmental Health Sciences
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• v.22 no.1
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• pp.99-106
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• 1996

The purpose of this study is to observe a specific removal efficiency of synthethetic wastewater which is managed by upflow submerged type at porous media which was sinteringed on a comparative low temperature 600$\circ$C, was annexed slag and humus soil with main material kaolinite. Observing removal efficiency quality of each media, a mixed media of kaolinite and humus soil by gravity percent 60, 40% respectively showed the most excellent removal utility, and applied predictive models for suspended culture kinetics without consideration diffusion limitation, and when analyzed kinetic which had been processed by this study the removal efficiency accompanied by carbon, nitrogen, phosphorous volumetric loading rate variation standed for a comparative large change rate 61~71%, it means the selection of the most proper load factor had a great effect on the highly removal efficiency, yield coefficient(Y) and specific microbial attach equation showed 1.53 mgVSS/mgCOD, $m_p=10039.4\times ((S_0)/(6.75+S_0))$ repectively.

• Nuclear Engineering and Technology
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• v.29 no.2
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• pp.99-109
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• 1997

A dynamic model for hydrogen generation by Fuel-Coolant Interactions(FCI) is developed with separate models for each FCI stage, coarse mixing and stratification. The model includes the physical concept of FCI, semi-empirical heat and mass transfer correlation and the concentration diffusion equation with the general non-zero boundary condition. The calculated amount of hydrogen, which is mainly generated in stratification, is compared with the FITS experiments. The model developed in this study shows a good agreement within a range of 10 % fuel oxidation rate and predicts the controlled mechanism of the chemical reaction very well. And this model predicts more accurately than the previous works. It is shown from the sensitivity study that the higher initial temperature of fuel particle is, the larger the reaction rate is. Up to 2700 K of temperature of the particle, the reaction rate increases rapid, which can lead to metal ignition.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.8
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• pp.1451-1459
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• 2011

Recently, low energy houses have become an essential issue globally and various subsidy programs are ongoing to penetrate. All-electric houses which are another type of low energy houses or zero carbon houses are being developed. These houses consider new & renewable energy and demand side management programs in the construction and the diffusion process because these programs are essential policies to use energy resources reasonably. This paper shows a simulation methodology to control home appliances in all-electric houses considering the electricity consumption pattern of residents. The simulation is a first step to estimate energy saving of the house in a practical manner.

• Journal of the Korean Society for information Management
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• v.8 no.2
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• pp.125-138
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• 1991

This paper focuses on issues in the relat~onshlp of library and information science with a closely allied chsciphne, communication studies. It is obvious that researchers in both fields study topics similar in focus, such as information theory, information-seeking behavior includ~ng user studies, systems theory, invisible colleges, the diffusion of knowledge, human interaction with information /communication technologies and the information society. In order to discuss the comparison of theoretical

• Journal of Korean Library and Information Science Society
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• v.20
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• pp.471-495
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• 1993

This paper focuses on issues in the convergence of library and information science and communication studies. Common research topics in both fields include scholarly communication, knowledge gaps, invisible colleges, diffusion of innovations, human interaction with communication technologies, information-seeking behavior, information theory, and the information society. To consider these two disciplines in this broader context, this paper compares these two discipline's paradigms, suggests four models of convergence, and traces bibliometric studies performed. This study may be of use to those studying scholarly communication or bibliometrics, to faculty constructing curricula in either of the disciplines, to communication and information science scholars seeking new areas of research, and to collection development librarians in drawing the boundaries of these disciplines.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2008.10a
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• pp.147-151
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• 2008

신제품 또는 신기술이 도입되는 시장에서는 보통 선두 진출자가 먼저 시장을 개척하고 나중에 후발 기업이 시장에 진출한다. 시장 진출자는 생산능력이 과한 경우 과투자의 위험이 존재하는 반면, 부족한 경우 잠재고객의 수요에 적절히 대응하지 못하여 고객을 유치하지 못하게 된다. 또한 신규 시장에서 선두 진출자의 광고효과는 시장 규모를 키움으로써 자신의 입지뿐 아니라 후발 주자의 몫까지 키워주는 양날의 칼과 같은 역할을 한다. 그렇다면, 선두 진출자가 취할 수 있는 최적의 생산능력 확장 정책과 광고 정책은 어떻게 결정할 수 있을까? 본 연구에서는 신제품이 도입되는 시장에서 선두 진출자가 경쟁자의 시장 진입을 예상하는 경우, 기존 시장 진출자가 취할 수 있는 생산 능력 확장 정책과 광고 수준에 대한 의사 결정모형을 수립하기 위해 Bass의 확산 모형을 확장하여 적용하였다.

• Advances in environmental research
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• v.1 no.2
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• pp.143-151
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• 2012

Nitrate removal from aqueous solution was investigated using $ZnCl_2$ and phosphoric acid activated carbon developed from pomegranate peel with particle size 0.4 mm. Potassium nitrate solution was used in batch adsorption experiments for nitrate removal from water. The effects of activated carbon dosage, time of contact, and pH were studied. The equilibrium time was fond to be 45 min. Two theoretical adsorption isotherms namely Langmuir and Freundlich were used to describe the experimental results. The Langmuir fit the isotherm with the theoretical adsorption capacity ($q_t$) was fond 78.125 mg g-1. Adsorption kinetics data were modeled using the pseudo-first, pseudo-second order, and intraparticle diffusion models. The results indicate that the second-order model best describes adsorption kinetic data. Results show activated carbon produced from pomegranate is effective for removal of nitrate from aqueous solution.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.10
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• pp.42-48
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• 1992

RoA is an important figure of merits for estimating the performance of p-n junction infrared detectors. This paper presents the tunneling current contribution to RoA of $Hg_{1-x}Cd_{x}$Te n$^{+}$-p juction photodiodes. Then, a diffusion model, a thermal generation-recombination model, an indirect tunneling model via trap, and a band-to-band direct tunneling model are considered to calculate RoA. Using these models, RoA depending on temperature, doping concentration, and mole fraction is calculated. Also from these results, under various operating conditions the dominant dark current mechanisms cna be understood.