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Samuel Park,Nakkyu Chae,Pilhyeon Ju,Seongkoo Hong,Taehoon Park,Sungyeol Choi 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
Since 1992, various numerical codes, such as TOUGH-FLAC and ROCMAS, have been developed and validated to dispose of Spent Nuclear Fuel (SNF) safely through a series of DEvelopment of COupled models and their VALidation against EXperiments (DECOVALEX) projects. These codes have been developed using different approaches, such as general two-phase flow and Richards’ flow which is an approximated approach neglecting gas pressure change, to implement the same multiphysics behaviors. However, the quantitative analysis for numerical results, which originated from different fundamental approaches, has not been conducted accurately. As a result, improper utilization of the approach to analyze certain conditions occurring such as dramatic gas pressure change may result in erroneous outcomes and systemic problem pertaining to TH analysis. In this study, the quantitative analysis of the two approaches, in terms of TH behavior, was conducted by comparing them with a 1D simulation of the CTF1 experiment carried out by laboratory experiment. The results calculated by different approaches show agreement in terms of TH behaviors and material properties change until 120°C. The results verify the applicability of Richards’ flow approach in a high temperature environment above the current thermal criteria, set as 100°C, and gas pressure change does not have a significant impact until 120°C. Therefore, although further studies for applicability of Richards’ flow are needed to suggest the appropriate temperature range, these quantitative analyses may contribute to the performance assessment of a compact repository using the high-temperature bentonite concept, which is currently gaining attention.
효모의 종류를 달리하여 제조한 동결 농축 청수 와인의 품질 특성
박혜진,박의광,최성열,신혜림,김민자,박정미,Park, Hyejin,Park, Eui Kwang,Choi, Sungyeol,Shin, Hyerim,Kim, Min-Ja,Park, Jung-Mi 한국식품영양학회 2020 韓國食品營養學會誌 Vol.33 No.5
The objective of this study was to investigate the quality characteristics of Cheongsoo wine using freeze concentration fermented with 5 kinds of yeast strains (Saccharomyces cerevisiae EJ18, EJ30, HK22, HK32 and Fermivin). We compared the characteristics, volatile flavor component and physiological activity of 5 wines. The freeze concentration can increase the sugar concentration in grape juice by reducing its water content and the alcohol content of freeze-cententrated Cheongsoo wines ranged between 15.0~15.8%. The pH of wines ranged from 2.92 to 2.94 and the total acidity and soluble solid of wines ranged from 12.40~13.27. °Brix. The major organic acid in the wines was tartaric acid (4.49~5.11 mg/mL) and malic acid (7.00~7.97 mg/mL). It contains higher functional compounds in wine fermented with yeast (EJ18, EJ30, HK22, HK32) than wine fermented with fermivin. α-glucosidase and tyrosinase inhibitory activity had the highest values (78.87% and 62.25%) in wine fermented with HK22 and EJ18 yeast, respectively. 16 volatile flavor compounds (alcohols, esters, ketones, acids, and others) were detected in the Cheongsoo wines by freeze concentration. These results provide useful information that the quality characteristics of wine developed by the freeze-concentration method using grapes cultivated in Korea.
박혜진,박은하,박의광,최성열,신혜림,김민자,Park, Hyejin,Park, Eunha,Park, Eui Kwang,Choi, Sungyeol,Shin, Hyerim,Kim, Min-Ja 한국식품영양학회 2021 韓國食品營養學會誌 Vol.34 No.5
In this study, vin chaud were manufactured with eight types of vin chaud-bomb containing different amounts of ingredients, and Campbell Early wine. Samples were analyzed for pH, total acidity, volatile acidity, ethanol content, total polyphenol, and anthocyanins, and radical scavenging activities for antioxidant effect. Based on the results of this study the pH of the samples ranged from 3.34 to 3.41 and the total acidity of wines ranged from 0.55 to 1.00%. The alcohol contents of the vin chaud samples ranged from 3.8~5.8% to and the color intensity of the vin chaud samples was higher than that of the wine. Total polyphenol content was 145.90~262.98 mg% and the tannin content of the C-1 (236.90 mg%) was the highest among the samples. The ABTS and DPPH radical scavenging activity of the samples were 57.39~75.10% and 63.71~80.00% respectively. α-Glucosidase inhibitory activity ranged from 21.54 to 33.49%, on the other hand, wine was not detected and tyrosinase inhibitory activity had the highest values (39.26%) in the C-1 sample. The findings of the present study provide insightful scientific information on vin chaud, and forms a basis for further innovations in the food and wine industry.
Performance Evaluation of Buffer Mangement Schemes for Implementing ATM Cell Reassembly Mechanism
Park, Gwangman,Kang, Sungyeol,Lie, Changhoon 한국경영과학회 1997 한국경영과학회지 Vol.22 No.2
An ATM switching system may be designed so that communications between processors of its control part can be performed via its switching network rather than a separate inter-processor communications (IPC) network. In such a system, there should be interfaces to convert IPC traffic from message format to cell format and vice versa, that is, mechanisms to perform the SAR (Segmentation And Reassembly) sublayer functions. In this paper, we concern the cell reassembly mechanism among them, mainly focused on buffer management schemes. We consider a few alternatives to implement cell reassembly function block, namely, separated buffering, reserved buffering and shared buffering in this paper. In case of separated and reserved buffering, we employ a continuous time Markov chain for the performance evaluation of cell reassembly mechanism, judicially defining the states of the mechanism. Performance measures such as message loss probability, mean number of messages queued in buffer and average reassembly delay are obtained in closed forms. In case of shared buffering, we compare the alternatives for implementing cell reassembly function block using simulation because it is almost impossible to analyze the mechanism of shared buffering by analytical modeling. Some illustrations are given for the performance analysis of the alternatives to implement cell reassembly function block.
Meso-scale multi-physics full coupling within porous CRUD deposits on nuclear fuel
Park, Byung Gi,Seo, Seungjin,Kim, Sung Joong,Kim, Ji Hyun,Choi, Sungyeol Elsevier 2018 Journal of Nuclear Materials Vol.512 No.-
<P><B>Abstract</B></P> <P>A 2D dimensional model was developed to simulate boron hideout within a porous Chalk River Unidentified Deposits (CRUD) on nuclear fuel in PWR. All thermal, fluid, transport, chemical, and radiolysis phenomena were fully coupled at meso-scale. A wick boiling structure with heat conduction was adopted, while Darcy's flow was solved for fluid dynamics in the porous medium. The diffusion and convection of soluble species were coupled with various chemical and radiolysis reactions. These reactions include water ionization, interaction of boric acid, adsorption of boron, precipitation of <I>LiBO</I> <SUB>2</SUB>, and distribution of volatile species at chimney surfaces. Results showed that boron hideout resulted from adsorption of boron in the lower side of CRUD and precipitation of <I>LiBO</I> <SUB>2</SUB> in the upper side. Precipitation is a dominating mechanism. The precipitation of <I>LiBO</I> <SUB>2</SUB> was shown to be dependent on the pH at the given temperature. Precipitated boron at CRUD close to bulk coolant might be an explanation why boron is easily re-dissolved into bulk coolant during shutdown chemistry. Also, this study compares thermal properties used in many models to compare differently predicted superheated liquid in the porous medium.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A single chimney model at meso-scale CRUD is newly developed for boron hideout. </LI> <LI> Thermal, fluid, transport, chemistry, and radiolysis phenomena are fully coupled. </LI> <LI> Boron hideout is dominated by precipitation than adsorption by a factor of 10<SUP>6</SUP>. </LI> <LI> Precipitated boron is located near coolant, favorable to dissolve during shutdown. </LI> <LI> Physical explanations and predictions of superheated liquid in CRUD are provided. </LI> </UL> </P>
Park, Jaeyeong,Choi, Sungyeol,Sohn, Sungjune,Kim, Kwang-Rag,Hwang, Il Soon The Electrochemical Society 2014 Journal of the Electrochemical Society Vol.161 No.3
<P>This study examines zirconium electrochemical redox behaviors in LiCl-KCl-ZrCl4 at 500 degrees C. Cyclic voltammetries are conducted with tungsten working and counter electrode. Four oxidation peaks and three reduction peaks are observed and redox reactions which could contribute to each peak are determined based on electrolysis results and peak height changes of cyclic voltammogram according to scan rates and ranges. Zr(IV) could be reduced into ZrCl when cathode potential is more negative than -1.1 V (vs. 1 wt% Ag/AgCl) and ZrCl would be reduced into Zr metal if cathode potential become more negative than -1.2 V. ZrCl and Zr metal could be oxidized into mainly Zr(IV) in LiCl-KCl-ZrCl4(1 wt%). Zr(II) could exist in the molten salt but the concentration might be small because heights of cyclic voltammogram peaks related to redox reactions of Zr(II) are relatively small. Based on cyclic voltammetry results, suggestions for the electrorefining of irradiated Zircaloy-4 cladding are proposed. High cathodic current density is preferred to recover zirconium as a metal state and low anodic current density is required to prevent dissolution of elements which are more reductive than zirconium. (C) 2013 The Electrochemical Society. All rights reserved.</P>
Park, Jaeyeong,Choi, Sungyeol,Sohn, Sungjune,Hwang, Il Soon The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.12
<P>To achieve a better understanding of Zircaloy-4 electrorefining in LiCl-KCl at 500 degrees C, redox behaviors of Zr, Sn, Cr, Fe and Co, were examined by cyclic voltammetry using tungsten working and counter electrode. Zr metal can be produced from Zr4+ through two step reduction and ZrCl is generated as an intermediate product. As ZrCl4 concentration decreases, ZrCl would be easily reduced into Zr metal. In addition, Zr2+ formation would be unlikely at low ZrCl4 concentration. The redox reactions of the other elements are much simpler than Zr. The reduction of Zr4+ into ZrCl was close to irreversible but the reduction reactions of the other elements are close to reversible. The diffusion coefficients and apparent reduction potentials were calculated using equations for a reversible or irreversible reaction. The diffusion coefficients are in the order of 10(-9) m(2)/s and Zr is less reductive than other elements. (C) 2017 The Electrochemical Society. All rights reserved.</P>