면섬유와 2-클로로에탄올 반응에 의한 히드록시에틸화 셀룰로스 섬유의 제조 - 반응 조건이 2-클로로에탄올 반응량에 미치는 영향-

박연석,양대혁,김영호,Park, Yeon Seok,Yang, Dae Hyuk,Kim, Young Ho 한국섬유공학회 2017 한국섬유공학회지 Vol.54 No.4

In this study, a one-bath process and a two-step process for the synthesis of hydroxyethylated cellulose (HEC) fibers through the reaction of cotton fibers with 2-chloroethanol (CE) were carried out, and the results of both the processes were compared with each other. A cotton non-woven fabric was treated with a solution containing both sodium hydroxide and CE in water or aqueous isopropyl alcohol (IPA) solutions as a reaction medium in the one-bath process, and the add-ons after reaction and washing were obtained. In the two-step process, the cotton non-woven fabric was padded in a 20% NaOH solution with a constant wet pickup of 300% as the first step of alkali treatment, followed by a CE reaction in a reaction medium of water or aqueous IPA solutions. The effects of reaction conditions, such as IPA concentration of the reaction media, CE concentration, reaction time, washing media, on the reacted amounts, i.e., add-ons of CE of the prepared HEC fibers were analyzed. Results showed that the two-step process is much more effective for obtaining high add-ons of HEC than the one-bath process. Aqueous IPA solution is also more effective than water as a reaction medium. The reacted amounts of the prepared HEC fibers increased on increasing both the IPA concentration in the reaction medium and the CE concentration. However, damage to HEC fibers also increased on increasing the add-ons of the reaction. The reaction for the synthesis of HEC by a two-step process is the most effective when the mol amount of NaOH in the first treatment is similar to that of CE in the second treatment.

2-클로로에탄올을 사용한 면섬유 부직포의 히드록시에틸화 개질 및 특성 분석

박연석,양대혁,김영호,Park, Yeon Seok,Yang, Dae Hyuk,Kim, Young Ho 한국섬유공학회 2018 한국섬유공학회지 Vol.55 No.5

Modification of cotton non-woven fabrics through the hydroxyethylation of cellulose using 2-chloroethanol (CE) was carried out in a two-step process of sodium hydroxide pre-treatment and CE reaction in a reaction medium of isopropyl alcohol (IPA) aqueous solution. The effects of sodium hydroxide concentration in the pre-treatment, IPA and CE concentrations, and treatment conditions of the second step were analyzed, along with washing media after treatment on the reacted amounts (add-ons) of CE and property changes of the fabrics. The add-ons of modified samples pre-treated with sodium hydroxide solution of a constant concentration and reacted with CE of different concentrations increased, reached a maximum, and then decreased with increasing CE concentration. The maximum add-on, i.e., the most effective reaction, was obtained when the molar ratio of NaOH/AGU in the pre-treatment and that of CE/AGU in the second treatment was similar. The moisture regain of the modified fabric increased almost linearly with the add-on of CE, indicating increased hydrophilicity. The hydroxyethylated fibers in the modified fabric with high add-ons were damaged severely and stuck together when the modified fabric was washed with water. However, the modified fibers obtained by washing with IPA solutions maintained their fiber shape with increased diameter even at a high add-on of up to 30%. Although the individual fibers might be deteriorated by hydroxyethylation, the tensile strength of the modified non-woven fabric obtained by washing with IPA solution increased compared to the untreated sample, because of the increase in diameter of the fibers, and thus the increased entanglements of the fibers in the fiber assembly of the non-woven fabric. Apparent dye uptake, as measured by the K/S value, of the hydroxyethylated fabric dyed with a reactive dye also increased linearly with increasing add-on amount. The K/S value of a modified fabric with an add-on of 3.5% was four times higher than that of the untreated sample, indicating that the microstructure of the cotton fiber was affected dramatically by hydroxyethylation.

다관절 해저로봇 'Crabster'에 작용하는 조류하중 산정 및 유동해석

박연석(Yeon-Seok Park),김우전(Wu-Joan Kim),전봉환(Bong-Huan Jun) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6

In this study, numerical simulations were performed for the evaluation of current loads acting on a multi-legged underwater robot 'Crabster' with a variety of incident angles using ANSYS-CFX package. The Reynolds-averaged Navier-Stokes equations were solved to simulate the fluid flow around the Crabster to calculate forces and moments induced by incoming current with angles. In the first, for the assessment of posture stability of the body, forces and moments were calculated with various incident angles when the current acts for vertical and horizontal direction. In the next, two leg forms (box and foil types) were evaluated for the comparison of the hydrodynamic force variation. Finally, the current forces and moments acting on the Crabster body with the legs attached were estimated.

부유식 파력-해상풍력 복합발전시스템의 풍력터빈 후류효과 추정을 위한 CFD 해석

박연석(Yeon-Seok Park),송창용(Chang-Yong Song),김우전(Wu-Joan Kim),김경환(Kyong-Hwan Kim),홍기용(Key-Yong Hong) 한국해양환경·에너지학회 2014 한국해양환경·에너지학회 학술대회논문집 Vol.2014 No.5

해상풍력 하부 지지구조물의 해저면 Scouring 패턴 예측을 위한 Horse-shoe Vortex 시뮬레이션

박연석(Yeon-Seok Park),김우전(Wu-Joan Kim),이대용(Dae-Yong Lee) 한국해양환경·에너지학회 2012 한국해양환경·에너지학회 학술대회논문집 Vol.2012 No.11

본 연구에서는 해상풍력발전장치를 고정하기 위해 설치되는 하부지지구조물에 의해 해저바닥면에서 발생하는 침식현상인 scouring 패턴을 예측하기 위해 점성유동해석을 수행하였다. Scouring 현상의 주 원인이 되는 horse-shoe vortex를 모사하기 위하여 상용 CFD 해석 코드인 ANSYS-CFX를 사용하여 수치해석을 수행하였다. Horse-shoe vortex 형성에 가장 큰 영향을 미치는 조류의 점성경계층 재현을 위해 구조물이 없는 평판에 대한 수치해석을 선행하여 조류 속도는 1㎧를 기준으로 조류에 의한 점성경계층의 두께가 10m가 되는 지점을 기준으로 지지구조물을 위치하여 난류유동해석을 수행하였다. 해상풍력 하부 지지구조물로 거론되고 있는 Jacket과 Multi-pile (Dolphin) 형상의 구조물에 대하여 해저 바닥면과의 접합부에서 발생하는 horse-shoe vortex를 모사하여 해저 접합부 근처의 유선과 해저바닥면에서의 압력분포 및 한계유선을 도시하였으며, 이를 바탕으로 해저 바닥면의 scouring에 의한 침식 패턴 확인을 위한 기초적인 자료를 확보하였다. In the present study, CFD simulations were performed to predict the scouring pattern at the seabed by the substructures for Ocean wind turbine(OWT). The ANSYS-CFX was used to simulate the horse-shoe vortex formation that is the main cause of scouring phenomenon. First of all, the numerical simulations about the flat plate without structures were preceded to realize the viscous boundary layer which affects horse-shoe vortex creation. When the current velocity was 1㎧, the velocity profiles with the viscous boundary layer thickness of 10m was given to the substructures of jacket and multi-pile (dolphin) type. Turbulent flow simulations were carried out to find out streamlines around the juncture of substructure legs and seabed. The pressure distribution and surface friction lines on sea bed were also investigated to predict the scouring pattern.

반잠수식 해상크레인 및 예인선에 작용하는 풍하중 및 조류하중 산정을 위한 점성 유동장 해석

박연석(Yeon-Seok Park),김우전(Wu-Joan Kim),남보우(Bo-Woo Nam),홍사영(Sa-Young Hong) 한국해양환경·에너지학회 2012 한국해양환경공학회 학술대회논문집 Vol.2012 No.5

In this paper, numerical simulations were performed for the evaluation of wind and current loads acting on the semi-submersible crane and transport barge using AMYS-CFX package. The Navier-Stokes equations are solved to simulate the fluid flow around the offshore structures with incoming wind and current. Offshore structures were divided with topside am sub-side on the basis cf draft for wind and current loads acting on the top and sub side of structures, respectively. Computational domain is consist of hexa-triacontagon(36° sides polygon) to calculate the hydrodynamic forces with incident angle of flow. Wind viscous boundary layer developed above the sea surface was actualized for the wind loads acting on the top-side of structures. Velocity responsiveness test was performed for the estimation about variation of drag coefficient by the velocities. In case of current, numerical simulations were carried out for the evaluation of current km由 and moments acting on the sub-side of semi-submersible crane and transport barge with incident angle of fluid flows.

반잠수식 해상크레인 및 예인선에 작용하는 풍하중 및 조류하중 산정을 위한 점성 유동장 해석

박연석(Yeon-Seok Park),김우전(Wu-Joan Kim),남보우(Bo-Woo Nam),홍사영(Sa-Young Hong) 대한조선학회 2012 대한조선학회 학술대회자료집 Vol.2012 No.5

In this paper, numerical simulations were performed for the evaluation of wind and current loads acting on the semi-submersible crane and transport barge using ANSYS-CFX package. The Navier-Stokes equations are solved to simulate the fluid flow around the offshore structures with incoming wind and current. Offshore structures were divided with top-side and sub-side on the basis of draft for wind and current loads acting on the top and sub side of structures, respectively. Computational domain is consist of hexa-triacontagon(36 sides polygon) to calculate the hydrodynamic forces with incident angle of flow. Wind viscous boundary layer developed above the sea surface was actualized for the wind loads acting on the top-side of structures. Velocity responsiveness test was performed for the estimation about variation of drag coefficient by the velocities. In case of current, numerical simulations were carried out for the evaluation of current loads and moments acting on the sub-side of semi-submersible crane and transport barge with incident angle of fluid flows.

순차적 설계기법에 의한 DWT 75,000 정유운반선의 선형설계

박연석(Yeon Seok Park),박세라(Sera Bak),정요한(Yohan Jeong),최정규(Jung-Kyu Choi),유재훈(Jaehoon Yoo) 대한조선학회 2016 大韓造船學會 論文集 Vol.53 No.6

Numerical Study on Wave Loads and Dynamic Responses of Fixed Type Offshore Wind Turbine Substructures

박연석(Yeon-Seok Park),김주인(Ju-In Kim),김진성(Jin-Sung Kim),송창용(Chang-Yong Song),김우전(Wu-Joan Kim),이대용(Dae-Yong Lee) 한국해양환경·에너지학회 2012 한국해양환경공학회 학술대회논문집 Vol.2012 No.11

본 연구에서는 고정식 해상풍력하부구조물로 사용되는 Mono-pile, Jacket, Dolphin 그리고 중력식 구조물에 작용하는 파랑하중 산정 및 동적응답 특성을 분석하기 위하여 수치계산을 수행하였다. 먼저, 상용 CFD 소프트웨어인 Fluent를 사용하여 구현된 수치조파수조에서 구조물에 작용하는 파랑하중을 산정하였다. 수면관통 면적이 파랑하중의 크기에 직접적인 형상요소임을 확인하였다. 다음으로 구조해석 프로그램인 ANSYS-ASAS를 통해 각각의 구조물에 파랑조건을 적용하여 동적하중 응답특성을 살펴보았다. 본 논문에서 검토된 구조물 중에서는 파랑하중과 구조응답의 관점에서 Jacket이 가장 유리한 구조물로 평가되었다. This paper presents a series of numerical studies for the evaluation of dynamic responses of fixed type offshore wind turbine substructures such as mono-pile, gravity based structure (GBS), jacket, and multi-piles (dolphin). In the first CFD simulations using Fluent package were carried out to evaluate wave loads on various fixed type OWT substructures with the design wave condition for the west-south region of Korea. Numerical wave tank (NWT) based on computational fluid dynamics (CFD) was adopted to generate a progressive regular wave using a piston type wave maker. It was found that the water-piercing area of piles of the substructure is a key parameter determining the wave load exerted in horizontal direction. In the next the dynamic structural responses of substructure elements under the wave load were calculated using finite element method (FEM). ANSYS-ASAS package was utilized to calculate structural responses when wave load on each element was determined by Morison’s formula. The paper numerically identifies dynamic response characteristics of various fixed type offshore wind substructures. It is likely that the jacket is the most appropriate type among the substructures considered in this paper.

다관절 해저로봇 'Crabster'에 작용하는 조류하중 산정 및 유동해석

박연석(Yeon-Seok Park),김우전(Wu-Joan Kim),전봉환(Bong-Huan Jun) 한국해양공학회 2012 韓國海洋工學會誌 Vol.26 No.5

In this study, numerical simulations were performed to evaluate the current loads acting on the multi-legged underwater robot “Crabster” with variety of incident angles using the ANSYS-CFX package. The Reynolds-averaged Navier-Stokes equations were solved to simulate the fluid flow around Crabster to calculate the forces and moments induced by incoming currents with various angles. First, to assess the posture stability of the body, the forces and moments were calculated with various incident angles when the current acted in the vertical and horizontal directions. Next, two forms of legs (box and foil types) were evaluated to determine the hydrodynamic force variation. Finally, the current forces and moments acting on the Crabster body with legs attached were estimated.