다점 확률분포 모델을 이용한 초임계 압력 액체질소 제트 해석

정기영,김남수,김용모,Jung, Kiyoung,Kim, Namsu,Kim, Yongmo 한국액체미립화학회 2017 한국액체미립화학회지 Vol.22 No.3

This paper describes numerical modeling of transcritical and supercritical fluid flows within a liquid propellant rocket engine. In the present paper, turbulence is modeled by standard $k-{\varepsilon}$ model. A conserved scalar approach in conjunction with multi-environment probability density function model is used to account for the turbulent mixing of real-fluids in the transcritical and supercritical region. The two real-fluid equations of state and dense-fluid correction schemes for mixtures are used to construct thermodynamic data library based on the conserved scalar. In this study, calculations are made on two cryogenic nitrogen jets under different chamber pressures. Sensitivity analysis for two different real-fluid equations of sate is particularly emphasized. Based on numerical results, precise structures of cryogenic nitrogen jets are discussed in detail. Numerical results show that the current real-fluid model can predict the essential features of the cryogenic liquid nitrogen jets.

CFD를 이용한 항공기 공기 흡입구 주위 결빙 예측

정기영(K.Y. Jung),안국빈(G.B. Ahn),정성기(S.K. Jung),명노신(R.S. Myong),조태환(T.H. Cho),신훈범(H.B. Shin),정주현(J.H. Jung),최영호(Y.H. Choi),김정훈(J.H. Kim) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5

Ice accretion on aircraft surface can greatly deteriorate the safety of aircraft. In particular, it can be a cause of impediment for aircraft performances such as aerodynamic characteristics, control, and engine. Numerical simulation of icing accretion based on the state-of-art CFD techniques can be alternative to expensive icing wind tunnel test or flight test. In this study, icing conditions are defined in order to predict the ice accretions around the air intake of aircraft. Then the range and amount of ice accretion on the intake in icing wind tunnel were investigated. In addition, a study on the size effect of icing wind tunnel was conducted in order to check the compatibility with the real in-flight test environment.

Al6061S 합금의 고속엔드밀 절삭시 치수오차와 표면정도 추이에 관한 연구

정기영(Ki-Young Jung) 산업기술교육훈련학회 2011 산업기술연구논문지 (JITR) Vol.16 No.4

High speed machining aims to raise the productivity and efficiency by making more precise and higher value-added products than other machining method by means of the high speediness of spindle and feed drive system. The purpose of this study is to investigate the effects of the run-out of endmill on the dimension precision of workpiece and to obtain the fundamental data on high speed machining, which is available by machining the side of Al-alloy with solid carbide endmills in high speed machining center and by measuring dimensions and surface roughness. From the results of experimentations followings are obtains; if spindle speed is ultrahigh in conditions that radial depth of cut and feed per tooth are very small, highly precise and accurate products are to be made efficiently with feed rate and so we can raise productivity.

스텐레스 메쉬 전극을 이용한 금속전극 태양전지 제작

정기영(Ki-Young Jung),성열문(Youl-Moon Sung),곽동주(Dong-Joo Kwak),지종국(Jong-Gook Ji) 한국조명·전기설비학회 2010 한국조명·전기설비학회 학술대회논문집 Vol.2010 No.5월

본 연구에서는 염료태양전지의 제작 시 고가의 TCO전극을 사용하지 않고 간단히 광전극을 대체할 수 있는 방법으로 메쉬전극을 이용하는 TCO-less 염료태양전지를 제작하였다. 메쉬전극을 이용한 염료태양전지의 구조는 “Glass / 메쉬전극(TiO₂를 딥코팅 한 후 염료를 흡착시킴) / 전해질 / 멤브레인 필터 / 상대전극(Pt-coated TCO) / Glass”로 구성된다. 제작된 샘플의 광전변환 효율은 약 1.5%였으며 fill factor는 0.55로 나타났다. 향후 계획으로 효율을 향상 시킬 수 있는 방법을 도입하여 광전류밀도와 fill factor를 개선하는 연구를 진행할 예정이다.

광전기화학셀용 나노구조 산화물 박막제작에 관한 연구

정기영(Ki-Young Jung),박선희(Sun-Hee Park),곽동주(Dong-Joo Kwak),성열문(Youl-Moon Sung) 한국조명·전기설비학회 2010 한국조명·전기설비학회 학술대회논문집 Vol.2010 No.9월

In this study, used simplest sandwich cells containing Ru2? liquid electrolytes in order to clarify the role of nanoporous ITO electrodes. And, the cell structure is as follow: F:SnO₂ glass/ nanoporous ITO/ tris(2,2'-bipyridy)ruthenium(Ⅱ) colplex [Ru(bpy)₃(PF?)₂] in propylene carbonate! F:SnO₂ glass. Nanoporous indium tin oxide (ITO) powder was synthesized employing a new route sol-gel combustion hybrid method using Ketjen Black as a fuel. The nano porous ITO powder was composed of SnCl₄~98.0% (aqueous solution) and In (NO₃)₃ · 5H₂O-99.999% (aqueous solution), produce with a NH₄OH (aqueous solution) with sol-gel method as a catalyst. The result, we found that ECL intensities increased rapidly by use of cathodes with nanoporous ITO layers. And, porous ITO electrodes were confirmed to be efficient for ECL devices as well as solar cell devices. It is thought that the increases in the ECL intensities may be associated with both formation of Ru? in porous ITO electrodes and the process taking place after reduction of Ru? which occurs in the nanoporous electrodes.

MCT에서 볼 엔드밀가공으로 고능률 고정밀도 제고를 위한 절삭 조건

정기영(Ki-Young Jung) 산업기술교육훈련학회 2012 산업기술연구논문지 (JITR) Vol.17 No.2

The curved surface machined by plate end mill causes a excess non-cutting volume, in these cases ball end mill is used for the curved surfaces. This study is aimed to obtain the optimum cutting condition by measuring the surface roughness on the conditions of various cutting speed, table speed, tool diameter, radius of curvature when machining the curved surface using the ball and mill. The cutting condition were the same as follow, velocity; 15, 20, 25, 30m/min, feed; 40, 60, 80, 100m/min amd radius of curvature; 30, 40, 50, 60mm, tool diameters; ∅8, ∅12, ∅16, ∅20mm. Analizing the working results, we can acquire the optimum cutting condition of curved specimen at the cutting velocity of 20∼25m/min and the feed rate of 80mm/min. As the same cutting condition, the best surface roughness was showed at ∅16mm of the tool diameter. But the tool diameter was smaller than ∅8mm, we could improve for the surface roughness by controlling the cusp.

이동 접속망에서 마이크로 이동성을 고려한 자원예약 경로 설정 방법

정기영(Ki-Young Jung),전찬호(Chan-Ho Jun),김정준(Jung-Joon Kim) 한국통신학회 2008 한국통신학회 학술대회논문집 Vol.2008 No.7

나노조작기 및 집속이온빔을 이용한 정밀 나노튜브 탐침의 제작

정기영(Jung Ki Young),박병천(Park Byong Chon),안상정(Ahn Sang Jung),최진호(Choi Jinho) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11

Precision carbon nanotube tip for atomic force microscope was fabricated where carbon nanotube orientation is controlled within the precision of 1 degree. The orientation, diameter and length of carbon nanotube tip are crucial factors for faithful profiling of surface patterns. With a nano-manipulation while viewing scanning electron microscope live image followed by focused ion beam process, precision carbon nanotube tip could be made. Precision carbon nanotube tip acts as a normal nanotube tip without Focused ion beam process. Further it maintains the elasticity. Precision tip can, in principle, enter the trench or hole less than 70 ㎚, which is impossible with the current state of the art silicon tip for critical dimension atomic force microscope.

나노 다공질 ITO전극 기반 전기화학형 발광셀 제작

정기영(Ki-Young Jung),곽동주(Dong-Joo Kwak),성열문(Youl-Moon Sung) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7

In this study, used simplest sandwich cells containing Ru2? liquid electrolytes in order to clarify the role of nanoporous ITO electrodes. And, the cell structure is as follow: F:SnO₂ glass/nanoporous ITO/ tris(2,2'-bipyridy)ruthenium(Ⅱ) colplex [Ru(bpy)₃(PF?)₂] in propylene carbonate/ F:SnO₂ glass. Nanoporous indium tin oxide (ITO) powder was synthesized employing a new route sol-gel combustion hybrid method using Ketjen Black as a fuel. The nano porous ITO powder was composed of SnCl4-98.0% (aqueous solution) and In (NO₃)₃ · 5H₂O-99.999% (aqueous solution), produce with a NH₄OH (aqueous solution) with sol-gel method as a catalyst. The result, we found that ECL intensities increased rapidly by use of cathodes with nanoporous ITO layers. And, porous ITO electrodes were confirmed to be efficient for ECL devices as well as solar cell devices. It is thought that the increases in the ECL intensities may be associated with both formation of Ru? in porous ITO electrodes and the process taking place after reduction of Ru? which occurs in the nanoporous electrodes.

한일 다문화 원격교육의 사례와 성과

정기영 ( Gi Young Jung ),( Suwa Akihiro ) 한국일어교육학회 2011 일본어교육연구 Vol.0 No.20

오늘날 글로벌 사회 그리고 다문화 공생 사회는 이미 우리의 일상사가 되고 있다. 이러한 시대의 일본어교사는 일본어를 가르치는 것만으로는 학습자의 사회적 수요를 충족시킬 수 없으므로 문화를 도입한 종합적인 일본어교육이 필요 불가결하다고 판단된다. 이러한 시대 배경을 기초로 본고는 2009년도 2 학기에 시작한 세계 7대학 합동 프로젝트 「다언어·다문화 사이버 컨소시엄」의 일환으로 TV 회의 시스템을 이용한 한일다문화 원격 교육의 사례와 성과에 대해 논한 것이다. 본 프로젝트는 상대국이 자신의 나라에 가지는 스테레오타이프에 관해 클래스 내에서 조사, 분석, 토론을 실시하여 작성한 발표 자료를 토대로 TV회의 시스템을 이용해 양국의 학생이 교류하면서 토론을 실시했다. 그리고 실시간 원격교육과 동시에 BLOG를 이용해 온라인상에서 질의응답 장소를 마련함으로써 상호교류의 확대를 도모했다. 그 결과 본 원격교육을 통하여 「학습 동기 유발」, 「협동 학습에 의한 협조성 육성」, 「일본어 4 기능 및 아카데믹 스킬의 향상」, 「자문화·타문화에 대한 이해 촉진」, 「자신감 획득 」등과 같은 여러 가지 효과를 얻을 수 있었다. 한편, 본 연구에서는 심층적인 분석과 객관적 데이터에 의한 근거자료 제시, 질의응답의 질을 향상시키는 아카데믹 스킬 교육의 필요성, 원격 수업 후의 계속적인 교류의 가능성 모색, 원격 수업시의 교수법 확립, 문화 리터러시 획득연구의 필요성 등 과제도 부각되었다. 今日のグロ―バル社會·多文化共生社會において、日本語敎師は、日本語を敎えるだけでは不十分であり、文化を取り入れた總合的な敎育が必要不可欠となっている。このような時代背景をもとに、本稿は、2009年度2學期に始まった世界7大學合同プロジェクト「多言語·多文化サイバ―コンソ―シアム」における、テレビ會議システムを利用した韓日多文化遠隔敎育の事例と成果について論じたものである。相手國が自分の國に持つステレオタイプに關し、クラス內で調査、分析、討論を行い、作成した發表資料をもとに、TV會議システムを用いて兩國の學生が交流、討論を行った。同時に、BLOGを利用し、オンライン上での質疑應答の場を設け、交流の擴大を狙った。その結果、「學習動機の誘發」、「協동學習による協調性育成」、「日本語4技能及びアカデミックスキルの向上」、「自文化·他文化の理解促進」、「自信獲得」といった樣樣な效果が得られたことが分かった。一方で、發表內容においては、さらに深い分析と客觀的デ―タによる裏づけ、質疑應答の質向上といったアカデミックスキルの敎育の必要性、遠隔授業後の繼續的な交流の可能性模索、遠隔授業における敎授法の確立、文化リテラシ―獲得の硏究の必要性など課題も浮き彫りになった。