냉간성형강재 벽체 패널의 한계높이 산정

이영기,토마스 밀러,Lee, Young ki,Miller, Thomas H. 한국강구조학회 2003 韓國鋼構造學會 論文集 Vol.15 No.1

본 연구의 목적은 서고보드로 둘러 싸여진 냉간성형강재 벽체패널의 실험에 근거한 한계높이를 산정하는 것이다. 이 패널은 내장 비내력벽으로서 등분포하중이 측면으로 작용된다고 가정한다. 한계높이는 처짐공식 뿐만 아니라 휨, 전단, 그리고 복부판 압착을 고려한 강도에도 기초하여 산정한다. 3가지 처짐제한(L/360, L/240, L/120)에 대한 한계높이는 전형적인 설계압력 범위에 걸쳐 산정된다(여기서 L은 벽체의 높이임). This study aimed to develop experiment-based limiting heights for interior, nonload-bearing, cold-formed steelwall panels sheathed with gypsum board and subjected to uniformly distributed lateral loadings. Th e limiting heightswere evaluated by their strength (for flexure, shear, and web crippling) and deflection. Limiting heights for deflectionlimits of L/360, L/240, and L/120 (where L is the height of the wall) were developed over the range of typical designpressures.

상호확산법에 의한 (Ti , Al)N계 복합질화물의 합성

이영기,김정열,김동건,손용운 ( Young Ki Lee,Jung Yeul Kim,Dong Kun Kim,Yong Un Sohn ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.2

TiN and AlN are ceramic materials with extensive applications due to its excellent mechanical and chemical properties at elevated temperature. The purpose of this research is to develop the method for the synthesis of ternary nitride powder, titanium-aluminum-nitrogen system, which have an excellent property of both TiN and AlN. The ternary nitride such as Ti₃AlN, Ti₂AlN and Ti₃Al₂N₂can be synthesized by the interdiffusion nitriding method in Ar gas, however, the ternary nitride coexist with TiN, AlN, Ti₃Al and α-Ti. The ternary nitride are stable below 1400℃ but these are gradually decomposed into TiN, Ti₃Al and AlN above 1400℃. The thermal oxidation characteristics of the Ti-Al-N compound synthesized by the interdiffusion nitriding method is superior to that of the TiN+AlN mixed powder, and the oxidation for both materials show the differential behaviors.

혼승 및 시간대별 학생들의 동적유입을 고려한 스쿨버스 경로 문제

이영기,정석재,윤호영,김경섭,Lee, Young-Ki,Jeong, Suk-Jae,Yun, Ho-Young,Kim, Kyung-Sup 한국시뮬레이션학회 2013 한국시뮬레이션학회 논문지 Vol.22 No.1

스쿨버스 경로문제는 학생들을 다수의 승차지점으로부터 학생들의 해당 학교까지 안전하고 효율적으로 수송할 수 있는 방법을 찾는 문제이다. 일반적인 스쿨버스 경로문제의 제약 조건으로는 차량의 용량, 학생의 최대 수송 시간, 학교의 도착 시간 제약 등이 있다. 본 연구에서는 기존의 혼승을 허용한 스쿨버스 경로 문제를 확장한 모델을 구축하고, 국내의 대학교 스쿨버스 운영 형태를 고려하여 학생들이 승차지점에 유동적으로 유입이 되는 상황을 고려한다. 본 연구에서 제시하는 모델에 대한 실험을 하기 위하여, 첫 단계로 Sweep Algorithm을 이용하여 초기 경로를 구성한다. 두 번째 단계에서는 전역탐색 능력이 있는 메타 휴리스틱 방법인 Genetic Algorithm을 이용하여 최선해을 도출 한다. 또한, 기존의 스쿨버스 경로문제에 적용되었던 현실 가능성 있는 제약들을 완화하여 다양한 시나리오를 구성하고 시나리오별 비교우위 평가를 한다. The School Bus Routing Problem(SBRP) seeks to plan an efficient schedule of a fleet of school buses that must pick up student from various bus stops and deliver them by satisfying various constraints; maximum capacity of the bus, maximum riding time of students, arrival time between a school's time window. By extending the existing SBRP, we consider a case study of SBRP with allowance of mixed-loading and dynamic arrivals reflecting the school bus operation of university in Korea. Our solution procedure is based on constructing the initial solution using sweep algorithm and then improving solution within the framework of the evolutionary approach known as efficient meta-heuristics. By comparing the various scenarios through the constraints relaxation for reflecting the real operational strategies, we assess the merit of our proposed procedure.

Partial Composite Action of Gypsum-Sheathed Cold-Formed Steel Wall Stud Panels

이영기,Lee, Young Ki Korean Society of Steel Construction 2001 韓國鋼構造學會 論文集 Vol.13 No.4

본 연구에서는 벽 패널의 부분 합성거동 해석에 대하여 거론한다. 기 발표된 목재 바닥 시스템으로부터 유도된 처짐공식을 소개하고, 이 공식을 적용하여 석고보드와 강재 샛기둥으로 결합된 합성벽 패널의 중앙지점 처짐값을 산정한다. 나사연결부의 불완전성(미끄럼), 국부좌굴, 샛기둥 복부의 개구부, 그리고 인접 석고보드간의 불연속으로 야기 될 수 있는 강성의 감소 등을 처짐공식에 적절히 반영하는데 그 목적을 두었다. 적용된 처짐공식으로 산정된 처짐 기대치와 실험 관측치간의 비교에서는, 나사연결부의 상한 강성치를 사용한 처짐 기대치가 실험 관측치와 가장 근접한 결과를 보였다. The problem addressed in this study is how to analytically treat the partial composite action for wall panels. An equation, derived for wood-joist floor systems, which determines deflections for beams with partial composite action is introduced. The equation is applied to the calculation of the mid-span deflection for gypsum-sheathed, cold-formed steel was stud panels. The objective of this study is to properly reflect the influence of the following factors in the calculation of mid-span deflection for the panel: connection slip, local buckling, perforations in the stud web, and effects from joints in the sheathing. Predicted deflections based on an upper bound for connection rigidity were closest to experimental deflections.

SrAl₂O₄:Eu⁺², Dy⁺³ 장잔광 형광체 합성에 있어서 알루미늄 화합물에 따른 열적거동 및 발광특성 변화

이영기,이유기,Lee, Young-Ki,Lee, You-Kee 한국재료학회 2007 한국재료학회지 Vol.17 No.11

Both photoluminescence and thermal characteristics for $SrAl_2O_4:Eu^{+2},\;Dy^{+3}$ phosphors synthesized with various aluminum compounds (${\alpha}-Al_2O_3$, ${\gamma}-Al_2O_3$, amorphous-$Al_2O_3$ and $Al(OH)_3)$ were investigated in this study. The formation temperature of the host $SrAl_2O_4$ crystal is changed by these various aluminum compounds, as a result of the different thermal decomposition temperature of $SrCO_3$ phase. Among these compounds, the amorphous-$Al_2O_3$ phase shows the lowest formation temperature of the host $SrAl_2O_4$ crystal. The PL emission and excitation spectra of $SrAl_2O_4:Eu^{+2},\;Dy^{+3}$ phosphor are not affected by these aluminum compounds. After the removal of the Xenon lamp excitation (360 nm), however, the excellent longphosphorescent property of the phosphor is obtained by the amorphous-$Al_2O_3$ phase, although the decay time for all phosphors decrease exponentially.

흰쥐 자궁에서 스테로이드호르몬에 의한 c-Fos, CREB, ATF 및 HSP70의 발현에 관한 연구

이영기,김성례,Lee, Young-Ki,Kim, Sung-Rye 대한생식의학회 1998 Clinical and Experimental Reproductive Medicine Vol.25 No.3

Steroid hormone is known to cause the dynamic changes of mammalian uterus during reproductive cycle. However there is little information about the effect of estrogen (E) and progesterone (P) on the expression of various transcription factors involved in gene expression. Thus the present study was designed to demonstrate E and/or P-induced expression of c-Fos, CREB, ATF and HSP70 in rat uterus. Rats, ovariectomized (OVX) for two weeks, were divided into 6 experimental groups, 1) OVX, 2) OVX+V, 3) OVX+E, 4) OVX+P, 5) OVX+E+V, 6) OVX+E+P, and western blotting assay for nuclear extract and immunohistochemical staining were carried out for each experimental group. Treatment of E $(10{\mu}g)$ showed to increase the expression of c-Fos, CREB, ATF, and HSP70, and maximal expression was occured at $3\sim6$ hr after E administration. P (1mg) also increased, but much less than E, the expression of c-Fos, ATF, and HSP70. However, P did not reveal any effect on the expression CREE. P treatment 4 hr after E injection decreased c-Fos, CREB, and ATF expression, but did not show any change in the E-induced HSP70 expression. In immunohistochemical study c-Fos-, CREB-, and ATF-immunoreactivities were confined to the cells of luminal epithelium of uterine endometrium. These results suggest that proliferation and differentiation of rat uterus during reproductive cycle may mediated via expression of transcription factors, such as c-Fos, CREB, ATF, and HSP70.

${\beta}-Galactosidase$ 생산 유산균 선별 및 특성 조사

이영기,최수산나,박용일,박찬선,윤병대,황윤식,김희식,Lee, Young-Ki,Choi, Susanna,Park, Young-Il,Park, Chan-Sun,Yoon, Byung-Dae,Hwang, Yun-Sik,Kim, Hee-Sik 한국미생물학회 2006 미생물학회지 Vol.42 No.3

[ ${\beta}-Galactosidase$ ] (lactase)를 생산하는 유산균을 선별하고 그들이 생산하는 ${\beta}-galactosidase$의 특성을 조사하였다. X-gal이 포함된 MRS배지에서 푸른색을 나타내는 약 100여개의 콜로니를 김치로부터 분리하였다. 그들 중 ET-1과 LA-12 두 균주를 최종 선별하였으며, 16S rDNa 염기서열 분석을 통해 각 각 Lactobacillus fermentum과 L. acidophilus와 상동성이 높은 Lactobacillus 속으로 동정되었다. 선별된 두 균주는 높은 ${\beta}-galactosidase$ activeity와 우수한 생존력을 나타내었으며, 이들이 생산하는 ${\beta}-galactosidase$의 최적 활성조건을 조사한 결과, 반응온도 $55^{\circ}C$에서 가장 높은 활성을 나타내었으며, 반응 pH의 경우 ET-1은 pH 5.5에서 최고 활성을 나타내었고, LA-12는 pH7.0에서 가장 높은 활성을 보였다. 선별 유산균 ET-1과 LA-12는 위액과 담즙산액에 대해 우수한 내성을 나타내었다. 두 개의 선별 균주는 인공위액에 3시간 배양 후 초기 생균수와 비교하여 생균수 변화가 거의 없었고, 담즙산액으로 사용한 0.3% oxgall에서 24시간 반응 후에도 1 log cycle 정도 감소된 $10^8CFU/ml$의 생균수를 유지하였다. 이러한 결과를 바탕으로 유산균 ET-1과 LA-12는 유제품 산업에 이용 가능성이 크다고 판단된다. This study was carried out to select the lactic acid bacteria producing ${\beta}-galactosidase$ (lactase) and investigate the properties of the ${\beta}-galactosidase$. About 100 strains of lactic acid bacteria showing blue colony on the MRS agar medium containing X-gal were isolated from several kinds of Kimchi. Among them, 2 strains were selected as potential ${\beta}-galactosidase$ producers. The selected strains, ET-1 and LA-12, were identified as Lactobacillus fermentum and L. acidophilus, respectively by the analysis of 16S rDNA sequences. They showed relatively high ${\beta}-galactosidase$ activity and cellular viability. Their ${\beta}-galactosidase$ showed the highest activity at $55^{\circ}C$. And the optimum pHs of the enzymes produced by ET-1 and LA-12 were pH 5.5 and pH 7.0, respectively. They were also highly resistant to artificial gastric juice and bile. Two selected strains showed little change of viable cell number for 3 hr incubation in artificial gastric juice, and maintained the viable cell number at $10^8CFU/ml$ for 24 hr in 0.3% oxgall after incubation for 2 hours in artificial gastric juice. Based on these results, ET-1 and LA-12 are expected to be applied in dairy industry.

Al-Ti 혼합 분말 슬러리를 이용한 강의 알루미나이징처리 방법

이영기,김정열,이유기,Lee, Young-Ki,Kim, Jung-Yeul,Lee, You-Kee 한국재료학회 2009 한국재료학회지 Vol.19 No.4

In this study, we attempted to develop a convenient aluminizing process, using Al-Ti mixed slurry as an aluminum source, to control the Al content of the aluminized layer as a result of a one-step process and can be widely adopted for coating complex-shaped components. The aluminizing process was carried out by the heat treatment on disc and rod shaped S45C steel substrates with Al-Ti mixed slurries that were composed of various mixed ratios (wt%) of Al and Ti powders. The surface of the resultant aluminized layer was relatively smooth with no obvious cracks. The aluminized layers mainly contain an Fe-Al compound as the bulk phase. However, the Al concentration and the thickness of the aluminized layer gradually decrease as the Ti proportion among Al-Ti mixed slurries increases. It has also been shown that the Al-Ti compound layer, which formed on the substrate during heat treatment, easily separates from the substrate. In addition, the incorporation of Ti into the substrate surface during heat treatment was not observed.

금속티타늄분말의 질화반응과 산화반응에 관한 연구

이영기,손용운,조영수,김용석,김석윤 ( Young Ki Lee,Yong Un Sohn,Young Soo Cho,Yong Seog Kim,Suk Yoon Kim ) 한국열처리공학회 1995 熱處理工學會誌 Vol.8 No.2

The nitridation kinetics of titanium powder were studied by isothermal and non-isothermal (dynamic) methods in high purity nitrogen under 1 atm pressure. For the comparison with nitridation, the oxidation kinetics of titanium powder were also studied in dry oxygen at 1 atm pressure. An automatic recording electrobalance was used to measure the weight gain as a function of time and temperature. For the reaction with nitrogen, the nitride was formed at over 700℃. The reaction with nitrogen followed the parabolic rate law, and the activation energy was calculated to be 31 ㎉/㏖ in the isothermal method (above 900℃). The non-stoichiometric TiNx has been synthesized by the nitridation at a proper temperature and time, followed by the homogenizing treatment above 1100℃. In comparison with the stoichiometric TiN_(1.0) and the non-stoichiometric TiNx(TiN_(0.5) and TiN_(0.65)), the hot oxidation characteristics of the former is superior to that of the latter. However, both non-stoichiometric nitrides make little difference in the hot oxidation characteristics.

냉간성형강 벽체패널의 연결부실험

이영기,Lee, Young-Ki 대한토목학회 2014 대한토목학회논문집 Vol.34 No.3

본 연구의 대상은 석고보드와 냉간성형강 스터드로 구성된 벽체용 합성패널이다. 양면의 석고보드 사이에 위치한 스터드는 나사로 연결되어 있고, 이와 같은 연결부의 부분합성거동을 정량화하여 나사접합부의 단위미끄럼을 유발하는 단위길이 당 전단하중($S_{slip}$)을 산정하는 것이 목적이었다. 실험방법은 1962 AISI규준을 기초로 하여 실시하였다. 본 연구에서 산정한 $S_{slip}$값을 이용한 이론적 추정치와 기 발표된 공칭축강도의 실험값과의 비교에서 만족할 만한 결과를 도출하였다. 그러므로 본 연구의 결과는 연구범위와 유사한 냉간성형강 부재의 해석과 설계에 있어 구조 기술자에게 가치가 있는 정보를 제공할 것이다. The objective of this test series was to determine shear load per unit length which causes a unit slip in the fastener joint. The shear load is one of major factors which reflect partial composite action for cold-formed steel wall stud panels. Test method used were based on the methods presented in the 1962 AISI Specification. According to the comparison with experimental strength, it is seen that the shear loads used in nominal axial strength predictions made acceptable results.