• Nuclear Engineering and Technology
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• v.15 no.4
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• pp.236-247
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• 1983

Analyzed are the the DNBR(Departure from Nucleate Boiling Ratio) sensitivities to variations in various PWR operating parameters utilizing the Korea Nuclear Unit 1(KNU-1) design and operating data. Studied parameters in the analysis are core power level, system pressure, core inlet flow rate, core inlet temperature, enthalpy rise hot channel factor, and axial power peaking factor and axial offset. The calculations are performed using the steady state and transient thermal-hydraulics computer program, COBRA-IV-K, which is the revised version of COBRA-IV-i that has been adapted, partially modified and verified at KAERI. A reference case is established based on the design and operating condition of the KNU-1 reactor core, and this provides a basis for the subsequent sensitivity analysis. From the calculation results it is concluded that the most sensitive parameter in the DNBR thermal design is the coolant core inlet temperature while the axial power peaking factor is the least sensitive.

• Journal of the Korean Institute of Gas
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• v.22 no.1
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• pp.1-8
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• 2018

FCV is installed with a automatic valve attached in an high pressure cylinder to control the hydrogen flow. The supply of hydrogen from the cylinder into the fuel cell stack is controlled via the on/off operation of a solenoid attached to the automatic valve. The solenoid needs to provide the necessary attraction force even at any saturation temperature caused by drive of the vehicle. In this study, the simplified prediction equations for the saturation temperature are suggested. The finite element analysis was performed by steady state technique, according to the boundary condition in order to predict the saturation temperature and attraction force. Finally, the saturation temperature was validated through comparison between the analysis results and measurement results. From the results, the measured saturation temperature $5.9^{\circ}C$ lower with respect to the analysis results. And the error of attraction force ranged from 1.0 to 2.1 N at testing conditions.

• Journal of Pharmaceutical Investigation
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• v.30 no.4
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• pp.247-252
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• 2000

The advantages of transdermal administration are avoiding hepatic first pass effect, minimizing inter- and intra-patient variation, maintaining steady-state plasma level to provide long-term therapy from a single dose, and allowing a rapid termination of drug input. Clenbuterol, a selective ${\beta}_2-adrenergic$ receptor stimulant, has been introduced as a potent bronchodilator for patients with bronchial asthma, chronic obstructive bronchial disease. For the development of transdermal systems containing clenbuterol, two limiting factors - long lag time and low flux - must be overcome. In this study, we attempted to select optimal formulation for preparation of clenbuterol patch using hairless mouse skin and flow-through diffusion cell. The flux of clenbuterol increased as the percent of clenbuterol dose dependently in the concentration range of 5-15%. Based on this result, we fixed the concentration of clenbuterol as 15%. The effect of various penetration enhancers on percutaneous absorption of clenbuterol through hairless mouse skin was investigated. Labrafil was the most effective enhancer, which increased the permeability of clenbuterol approximately 4-fold compared with the control without penetration enhancer. Optimal enhancer concentration was 3%. The effect of various adhesives on penetration of clenbuterol was also investigated. Among the adhesives studied, MA-31 was the most effective adhesive. Furthermore, the clenbuterol patch composed of 15% clenbuterol, 3% Labrafil and 82% MA-31, which gave most excellent penetration of drug in in vitro penetration study, maintained therapeutic plasma levels in in vivo study using S.D. rats. These studies demonstrated a good feasibility of clenbuterol administration through the intact skin using a transdermal patch, and show a possibility of the development of clenbuterol patches.

• Journal of Korean Institute of Industrial Engineers
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• v.39 no.3
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• pp.172-182
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• 2013

In this study we consider a flow line CONWIP system in which two types of product are produced. The processing times of each product type at each station follow an independent exponential distribution and the demands for the finished products of each type arrive according to a Poisson process. The demands that are not satisfied instantaneously are either backordered or lost according to the number of unsatisfied demands that exist at their arrival instants. For this system we develop an approximation method to obtain the performance measures such as steady state probabilities of the number of parts of each product type at each station, mean waiting times of backordered demands and the proportion of backordered demands. For the analysis of the proposed CONWIP system, we model the CONWIP system as a two class closed queueing network with a synchronization station and analyze the closed queueing network using a product-form approximation method for multiple classes developed by Baynat and Dallery. In the approximation method, each subsystem is analyzed using a matrix geometric method. Comparisons with simulation show that the approximation method provides fairly good results for all performance measures.

• Molecules and Cells
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• v.43 no.9
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• pp.813-820
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• 2020

NB4 cell, the human acute promyelocytic leukemia (APL) cell line, was treated with various concentrations of arsenic trioxide (ATO) to induce apoptosis, measured by staining with 7-amino-actinomycin D (7-AAD) by flow cytometry. 2', 7'-dichlorodihydro-fluorescein-diacetate (DCF-DA) and MitoSOX™ Red mitochondrial superoxide indicator were used to detect intracellular and mitochondrial reactive oxygen species (ROS). The steady-state level of SO₂ (Cysteine sulfinic acid, Cys-SO₂H) form for peroxiredoxin 3 (PRX3) was measured by a western blot. To evaluate the effect of sulfiredoxin 1 depletion, NB4 cells were transfected with small interfering RNA and analyzed for their influence on ROS, redox enzymes, and apoptosis. The mitochondrial ROS of NB4 cells significantly increased after ATO treatment. NB4 cell apoptosis after ATO treatment increased in a time-dependent manner. Increased SO₂ form and dimeric PRX3 were observed as a hyperoxidation reaction in NB4 cells post-ATO treatment, in concordance with mitochondrial ROS accumulation. Sulfiredoxin 1 expression is downregulated by small interfering RNA transfection, which potentiated mitochondrial ROS generation and cell growth arrest in ATO-treated NB4 cells. Our results indicate that ATO-induced ROS generation in APL cell mitochondria is attributable to PRX3 hyperoxidation as well as dimerized PRX3 accumulation, subsequently triggering apoptosis. The downregulation of sulfiredoxin 1 could amplify apoptosis in ATO-treated APL cells.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.2
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• pp.45-56
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• 1994

A computationally efficient numerical method based on potential flow is developed for time-domain simulation of the nonlinear free-surface flows around a 2-dimensional hydrofoil. This numerical method, namely, spectral/boundary-element method, is a mixed one of the high-order spectral method and the boundary-element method in time-domain. The high-order spectral method is used to calculate the nonlinear evolution of free-surface, and the boundary-element method is used to calculate the effects of the hydrofoil and the shed vortex. As application examples, nonlinear free-surface flows around a 2-dimensional hydrofoil which starts from the rest and translates near the free-surface with or without harmonic oscillations are calculated. Nonlinear/unsteady results of free-surface waves and hydrodynamic farces are shown and discussed. Particularly, the results of steady-state which are obtained as a special case of the present unsteady solution are compared with others' calculated and experimental results, and good agreements are observed.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.38-47
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• 1995

The three-dimensional multi-layer computer simulation technology for tidal current developed in the previous study is updated to a new version. many improvements are achieved by following changes : (1) No-reflection condition is adopted instead of no-gradient condition as an open boundary condition. (2) Time marching algorithm is changed so that velocity and pressure(surface movement) might be salved in turn at different time step (3) Convection term in equation of motion is estimated by upwind differencing scheme instead of central differencing. The stability is improved considerably and the steady state is achieved within 2 tidal periods which is about 3 times shorter than that of the old version. Moreover, fluctuations in time disappeared by introducing the new time marching technique. An application to the real near shore area(near Inchon harbor) is performed by the new version. Simulated results are compared with those by the simulation total developed in the University of Tokyo. Validity and effectiveness of the two simulation technologies are chocked through the comparative research works.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.58-66
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• 2019

In this study, the start-up characteristics of a staged combustion engine were analyzed numerically based on relational equation modeling of the entire engine components. The start-up characteristics were extensively analyzed considering the transient period of the total engine system from the start-up sequence till the steady-state of the engine. The performance characteristics of the engine components such as RPM of engine power-pack, chamber pressure and O/F ratio of pre-burner, and mass flow of propellants in the start-up period were investigated. Furthermore, the calculated engine data were compared satisfactorily with the experimental data. Through the comparison of data, successful validation of present engine start-up analysis has been obtained.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.2
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• pp.123-128
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• 2022

The torque of the SRM((Switched Reluctance Motor)) is proportional to the inductance slope, so it has a non-linear torque characteristic, and has a disadvantage in that the torque pulsation is large and noise is severe. In particular, the biggest obstacle to the commercialization of SRM is the pulsating torque generated from the rotating shaft, which has various adverse effects not only on the device itself but also on the peripheral devices. Therefore, various methods for reducing the pulsating torque have been published by domestic and foreign researchers, and there is a study result that the hysteresis controller has an advantage in that it can flow a smooth current compared to the chopping control. However, in determining the hysteresis band, if the band is too small, it has a disadvantage in that it may cause a switching loss due to many switching and an unstable initial start when the encoder is used. Therefore, in this paper, a variable hysteresis controller that can reduce torque ripple in a steady state while having a more stable and fast speed response through the change of the hysteresis band according to the speed error.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.18-27
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• 2021

This study aims to develop an improved evaluation technology for assessing CANDU-6 safety. For this purpose, the multiple steam generator tube rupture (mSGTR) followed by an unmitigated station blackout (SBO) in a CANDU-6 plant was selected as a hypothetical event scenario and the analysis model to evaluate the plant responses was envisioned into the MARS-KS input model. The model includes logic models for controlling the pressure and inventory of the primary heat transport system (PHTS) decreasing due to the u-tubes' rupture, as well as the main features of PHTS with a simplified model for the horizontal fuel channels, the secondary heat transport system including the shell side of steam generators, feedwater and main steam line, and moderator system. A steady state condition was successfully achieved to confirm the stable convergence of the key parameters. Until the turbine trip, the fuel channels were adequately cooled by forced circulation of coolant and supply of main feedwater. However, due to the continuous reduction of PHTS pressure and inventory, the reactor and turbine were shut down and the thermal-hydraulic behaviors between intact and broken loops got asymmetric. Furthermore, as the conditions of low-flow coolant and high void fraction in the broken loop persisted, leading to degradation of decay heat removal, it was evaluated that the peak cladding temperature (PCT) exceeded the limit criteria for ensuring nuclear fuel integrity. This study is expected to provide the technical bases to the accident management strategy for transient conditions with multiple events.