• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.1974-1987
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• 2023

The load-following operation of small modular reactors (SMRs) requires accurate prediction of transient behaviors that can occur in the balance of plants (BOP) and the nuclear steam supply system (NSSS). However, 1-D thermal-hydraulics analysis codes developed for safety and performance analysis have conventionally excluded the BOP from the simulation by assuming ideal boundary conditions for the main steam and feed water (MS/FW) systems, i.e., an open loop. In this study, we introduced a lumped model of BOP fluid system and coupled it with NSSS without any ideal boundary conditions, i.e., in a closed loop. Various methods for coupling boundary conditions at MS/FW were tested to validate their combination in terms of minimizing numerical instability, which mainly arises from the coupled boundaries. The method exhibiting the best performance was selected and applied to a transient simulation of an integrated NSSS and BOP system of a SMART. For a transient event with core power change of 100-20-100%, the simulation exhibited numerical stability throughout the system without any significant perturbation of thermal-hydraulic parameters. Thus, the introduced boundary-condition coupling method and BOP fluid system model can expectedly be employed for the transient simulation and performance analysis of SMRs requiring daily load-following operations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1643-1646
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• 2003

Drawing is a mechanical operation that attenuates thick material to an appropriate thickness for the next processing or end usage. When the input material has the form of a bundle or bundles made of very thin and long shaped wire or fibers, this attenuation operation is called "bundle drawing" or "drafting" Drafting is being used widely in manufacturing staple yarns. which is indispensable for the textile industry. However, the bundle processed by this operation undertake more or less defects in the evenness of linear density. Such irregularities cause many problems not only for the product quality but also for the efficiency of the next successive processes. Since long there have been many researches tying to find out factors affecting the irregularity of linear desity, to obtain optimal drafting conditions, to develop efficient measuring and analysis methods of linear density of bundle, etc., but there exists yet no fundamental equation describing the dynamic behavior of the flowing bundle during processing. In this research a mathematical model for the dynamic behavior of the bundle fluid is to be set up on the basis of general physical lows representing physical variables, i.e. linear density and velocity as the dynamic state of bundle. The conservation of mass and momentum balance was applied to the fluid field of bundle. while the movement of′ individual material was taken into account. The constitutive model relating the surface force and the deformation of bundle was introduced by considering a representative prodedure that stands for the bundle movement. Then a fundamental equations system could be simplified considering a steady state of the process. On the basis of the simplified model, the simulation was performed and the results could be confirmed by the experiments under various conditions.

• Asian-Australasian Journal of Animal Sciences
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• v.5 no.4
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• pp.687-693
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• 1992

The study was conducted to investigate the effect of soybean meal (SBM) supplementation on the voluntary intake of rice straw and ruminal fermentation characteristics. Balance trials were conducted with three Hapanese Corriedale wethers fed a rice straw alone (control), rice straw supplemented with 75 and 150 g of SBM/day in a $3{\times}3$ latin square design. Voluntary intake of rice straw in sheep fed both levels of SBM supplemented diets was significantly higher (p<0.05) than that in sheep fed control diet. Crude protein digestibility was significantly increased (p<0.05), but organic matter, crude fibre, neutral detergent fibre and acid detergent fibre digestibilities were not affected by SBM supplementation. Nitrogen balance was positive in sheep on both levels of SBM supplemented diets, but negative in animals on the control diet. Rumen ammonia and blood urea-nitrogen concentrations increased (p<0.05) as increasing level of SBM. Total volatile fatty acids, acetate, propionate, butyrate and valerate concentrations in rumen fluid were also significantly increased (p<0.01), but ruminal pH was decreased (p<0.05) by SBM supplementation.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.656-665
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• 2004

An Ozone reaction model combined with CFD(Computational Fluid Dynamics) technique was developed in this research, in the simulation of ozonation, hydrodynamic behavior as well as reaction model is important because ozone is supplied to treated water as gas ozone. In order to evaluate hydrodynamic behavior in an ozone contactor, CFD technique was applied. CFD technique elucidated hydrodynamic behavior in the selected ozone contactor, which consisted of three main chambers. Three back-mixing zones were found in the contactor. The higher velocities of water were observed in the second and third compartments than that in the first compartment. The flow of the opposite direction to the main flow was observed near the water surface. Based on the results of CFD simulation, the ozone contactor was divided into small compartments. Mass balance equations were established were established in each compartment with reaction terms. This reaction model was intended to predict dissolved ozone concentration, especially. We concluded that the model could predict favorably the mass balance of ozone, namely absorption efficiency of gaseous ozone, dissolved ozone concentration and ozone consumption. After establishing the model, we discussed the effect of concentration of gaseous ozone at inlet, temperature and organic compounds on dissolved ozone concentration.

• Journal of Physiology & Pathology in Korean Medicine
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• v.24 no.5
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• pp.848-853
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• 2010

Bone maintains its homeostasis through balance between bone resorbing osteoclasts and bone forming osteoblasts. Thus, unusual balance between osteoclasts and osteoblasts leads to pathological bone diseases, such as osteoporosis, rheumatoid arthritis, autoimmune arthritis, periodontitis. Schisandra chinensis well known traditional herbal has been used for treatment of diseases in China, Korea, Japan, andothers. Recently, research studies have demonstrated that the lignans found in Schisandra chinensis stimulate osteoblasts and suggest that it may be helpful against osteoporosis. However, the inhibitory effect of water extract of Schisandra chinensis on osteoclast differentiation remains largely unknown. In this study, Water extract of Schisandra chinensis markedly suppressed RANKL-induced osteoclast differentiation in cultures of BMMs without cytotoxicity. The mRNA expression of c-Fos, NFATc1, and TRAP induced by RANKL was inhibited by water extract of Schisandra chinensis. It also suppressed c-Fos and NFATc1 protein expression. Taken together, these results suggest that water extract of Schisandra chinensis has the potential to serve as a treatment of bone disease such as osteoporosis.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.82.2-82.2
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• 2011

A channel design which is closely related with the mass transport overpotential is one of the most important procedures to optimize the whole fuel cell performance. In this study, three dimensional results of a numerical study for gas distribution in channels of a molten carbonate fuel cell (MCFC) unit cell for a 1kW class stack was presented. The relationship between the fuel and air distribution in the anode and cathode channels of the unit cell and the electric performance was observed. A charge balance model in the electrodes and the electrolyte coupled with a heat transfer model and a fluid flow model in the porous electrodes and the channels was solved for the mass, momentum, energy, species and charge conservation. The electronic and ionic charge balance in the anode and cathode current feeders, the electrolyte and GDEs were solved for using Ohm's law, while Butler-Volmer charge transfer kinetics described the charge transfer current density. The material transport was described by the diffusion and convection equations and Navier-Stokes equations govern the flow in the open channel. It was assumed that heat is produced by the electrochemical reactions and joule heating due to the electrical currents.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2001.05a
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• pp.45-52
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• 2001

The study on the heat exchanger with catalytic combustion was performed as the development of the catalytic combustion applications. This study tried to achieve the both goals-the mixture preheating and the heat transfer to working fluid simultaneously by using the steady state catalytic combustion. The combustion characteristics were investigated with the quantitative, qualitative experimental variants of the mixture. In addition, the temperature distribution of catalytic layer was investigated to investigate the correlation between the combustion characteristics and the heat balance of the catalytic layer. As a result, the steady state reaction within the appropriate range of temperature is the critical factor in catalytic applications. To get this, the sensible control of both the mixture flow and the heat balance of catalytic layer were required.

• Particle and aerosol research
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• v.5 no.3
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• pp.123-131
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• 2009

This paper presents simulation results of particle transport in low-pressure, low-temperature plasma environment. The size dependent transport of particles in the plasma is investigated with a two-dimensional simulation tool developed in-house for plasma chamber analysis and design. The plasma model consists of the first two and three moments of the Boltzmann equation for ion and electron fluids respectively, coupled to Poisson's equation for the self-consistent electric field. The particle transport model takes into account all important factors, such as gravitational, electrostatic, ion drag, neutral drag and Brownian forces, affecting the motion of particles in the plasma environment. The particle transport model coupled with both neutral fluid and plasma models is simulated through a Lagrangian approach tracking the individual trajectory of each particle by taking a force balance on the particle. The size dependant trap locations of particles ranging from a few nm to a few ${\mu}m$ are identified in both electropositive and electronegative plasmas. The simulation results show that particles are trapped at locations where the forces acting on them balance. While fine particles tend to be trapped in the bulk, large particles accumulate near bottom sheath boundaries and around material interfaces, such as wafer and electrode edges where a sudden change in electric field occurs. Overall, small particles form a "dome" shape around the center of the plasma reactor and are also trapped in a "ring" near the radial sheath boundaries, while larger particles accumulate only in the "ring". These simulation results are qualitatively in good agreement with experimental observation.

• Nuclear Engineering and Technology
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• v.16 no.1
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• pp.1-10
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• 1984

General time-volume averaged conservation equations and jump conditions for two-phase flows are derived here. The time-averaged equations for a single phase region in two-phase flow are obtained from local instant balance equations by a technique often used for single phase turbulent flow equations. The results obtained by integrating the time averaged equations over a flow volume are spatially averaged twice; first, they are averaged over a single phase region of the k-th phase and then averaged over the total volume of the k-th phase, in a flow volume. The mass, momentum, and energy conservation equations are obtained from the general time-volume averaged equations. The advantages of the present model are explained by comparing it with Ishii's model (1) and Banerjee's model (2). Finally, the assumptions and approximate terms of the equations of the THERMIT-6S are clarified.

• Biomedical Science Letters
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• v.16 no.2
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• pp.83-90
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• 2010

Hesperidin, a member of the flavanone group of flavonoids, can be isolated in large amounts from the rinds of some citrus species [e.g., Citrus aurantium L. (bitter orange), Citrus sinensis L. (sweet orange) and Citrus unshiu Marcov. (satsuma mandarin)], and has been reported to have anticarcinogenic, antihypotensive and antimicrobial properties. Despite the efficacy of these polyphenolic compounds as immune modulators, the effects of the flavonoids are poorly understood about allergic effect. In this study, we investigated whether hesperidin could influence on Th1 and Th2 balance. Allergic reactions included an increase in the number of eosinophils in bronchoalveolar lavage (BAL) fluid, an increase in inflammatory cell infiltration into the lung tissue around blood vessels and airways, airway luminal narrowing, the development of airway hyper-responsiveness (AHR). The administration of hesperidin before the last airway OVA challenge resulted in a significant inhibition of all asthmatic reactions. Accordingly, this study may provide evidence that hesperidin plays a critical role in the amelioration of the pathogenetic process of asthma in mice. These findings provide new insight into the immunopharmacological role of hesperidin in terms of its effects in a murine model of asthma, and also broaden current perspectives in our understanding of the immunopharmacological functions of hesperidin.