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Effect of Highly Pressurized Hydrogen Gas Charging on the Hydrogen Embrittlement of API X70 Steel
Dong-Su Bae,Chi-Eun Sung1,Hyun-Ju Bang,Sang-Pill Lee,Jin-Kyung Lee,In-Soo Son,조영래,Un-Bong Baek,Seung-HoonNahm 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.4
During the use of API X70 steel as a pipeline structural material for the transportation of natural gas,hydrogen embrittlement can occur due to the hydrogen contained in natural gas. The aim of this study is toinvestigate the effects of the hydrogen content under high-pressure hydrogen gas conditions on the hydrogenembrittlement of air-cooled API X70 steel. The air-cooled API X70 steel was manufactured by hot rollingand was then air-cooled to room temperature. Tensile test specimens were held for 0 h, 1000 h, and 2000 hwithin a pressure vessel filled with 100% hydrogen gas at a gas pressure of 10 MPa, with the tensile teststhen performed at room temperature. The microstructure of the API X70 steel consists of coarse polygonalferrite, coarse pearlite, and fine acicular ferrite. The yield and tensile strength increased and elongationdecreased considerably after a holding time of 2000 h compared to those of 0 h and 1000 h within the pressurevessel. The morphology of the fracture surface changed from ductile to brittle upon hydrogen gas charging. Secondary cracks were observed in both of the hydrogen-gas-charged specimens. No external cracks wereformed on the surface of the tensile-tested specimen with a 0 h holding time; however, many external crackswere observed on the specimen surface subjected to hydrogen gas charging.
이기환,구광호,이상용,이규용,유언호,김종숙 ( Ki Whan Lee,Kwang Hoo Koo,Sang Yong Lee,Kyu Yong Lee,Un Ho Ryoo,Chong Sook Kim ) 대한소화기학회 1974 대한소화기학회지 Vol.6 No.1
The measurements of sium amylase and urine amylase for 2-1 and 2 hrs were caried ou normal perso,-s, 118 pat;:enls vith disardei s in the upp r alimentary tract, 184 patie.,ts v, ith h;le- cystopathy and 26 patients ivith acute pancreatitis. The follosving rc.su1ts were drawn: In the normal prsons, the average determination of serum amylas was 5-l. I L 21, 9. Units ' 100 m]. It shov;ed no difference by sex and age. 2 The frequezcy manifesting raise of serum amylase (the value higher than mean+2S.I),,, v,as 5 ] y in the patients with the upper G.I. Disorders, an<l 6, l,jj in the patients of chiIccys'.:>p.ithy v, ith normal features in cholecys.ograms. It, however, showed 2S. 7, of frequeny appeaiing nis:.. of serv,m an.ylase in the patients of cholecystopathy with abnorrnalities in roentgenographic exa!ii- ;iations indicating a mean value of 86. 4 31. 67 units,'l0(l ml. 3, The determination of s rum amylase in the pat,ents of acute pancreatitis was 12a. ] un!ts,'100 ml on the initial day, and it showed ahrupt diminution thereafter. 4. Each dete:mination of urine amylase for 24 and 2 hnurs was 1394. 3 .867. 43 and 15 4 -(j;, Hi units in the normal pers1ns, but there was no significant shift in the group of the uppr:.;- G,I disorders, and a little raise in the group of cholecystopathy. In the group of acute panc:eatili:., ii showed marked rais of urine amylas, ,6562, 9---4526, 3<J units for 24 hours on the se ond cia o!' ailment), revealins: subs quent gradual cle rease, (30i;>. 9 l 1927. 92 units on the sexth day',. It must b emphasized that in picture of urine amylase should be a great help for c!iagnos!.ng tli. Conditions.
한국형발사체 3단 과산화수소 추력기시스템 제어장치 아날로그 데이터 취득 스케줄링 변경을 통한 노이즈 측정오류 개선
이상현(Sang-Hyun Lee),송우근(Woo-Keun Song),오현명(Hyun-Myung Oh),이정운(Jung-Un Lee),이종철(Jong-Cheol Lee),박상준(Sang-Joon Park),이상빈(Sang-Bin Lee),이희중(Hee-Joong Lee),오상관(Sang-Gwan Oh),민병주(Byeong-Joo Min) 한국항공우주학회 2020 한국항공우주학회 학술발표회 논문집 Vol.2020 No.11
Effects of aroclor 1254 on the expression of the KAP3 gene and reproductive function in rats
Lee, Chae Kwan,Kang, Han Seung,Kim, Ju Ran,Lee, Byung Ju,Lee, Jong Tae,Kim, Jeong Ho,Kim, Dae Hwan,Lee, Chang Hee,Ahn, Jin Hong,Lee, Chae Un,Yu, Seong Jin,Kang, Sung Goo CSIRO Publishing 2007 Reproduction, fertility, and development Vol.19 No.4
<P> The present study investigated the effects of aroclor 1254 (A1254) on the expression of the kinesin superfamily associated protein 3 (KAP3) gene in F1 rat brain during brain sexual differentiation and puberty. In addition, the effects of A1254 on reproductive function were examined. The KAP3 gene is involved in the neurogenesis and synaptogenesis of sexual differentiation in rats and also during puberty. In the present study, pregnant Sprague-Dawley rats each received a daily dose of A1254 (0, 10, 50 mg kg-1) dissolved in 1.0 mL corn oil by gavage, from gestational Day (GD) 8 to postnatal Day (PD) 21. The mRNA levels of the KAP3 gene in hypothalamic tissues were analysed by northern blot hybridisation during the critical periods of brain sexual differentiation (GD18 and PD5) and puberty (PD28). Variables affecting reproduction in F1 female rats, such as vaginal opening (VO), vaginal oestrus (VE) and oestrous cyclicity, were recorded. Depending on the sex and A1254 exposure (control or 50 mg kg-1 day-1), F1 rats were divided into three mating groups, namely control male-control female, control male-A1254-treated female and A1254-treated male-control female. During the critical periods of brain sexual differentiation (GD18, PD5) and puberty (PD28), KAP3 mRNA levels were significantly reduced in A1254-treated fetal and pubertal rat brains relative to those of control groups. In A1254-treated F1 female rats, VO and VE were delayed, the percentage of irregular oestrous cycles was increased and the duration of the oestrous cycle was extended in a dose-dependent manner compared with control groups. Treatment with a high dose of A1254 significantly impaired the reproductive function of both male and female F1 rats, including mating and pregnancy indices and the number of live fetuses. These data suggest that A1254 disrupts transcriptional regulation of the KAP3 gene in fetal and pubertal rat brains and that these effects may be related to A1254-induced abnormal brain sexual differentiation and lowered reproductive function in F1 rats. </P>
Magnetic Shielding Effect on Halbach Cylinder used in Magnetic Refrigerators
Un Bong Baek,Jong Suk Lee,Seong-Cho Yu,Kwon-Sang Ryu 한국자기학회 2014 Journal of Magnetics Vol.19 No.4
The system for producing magnetic field constitutes an important component of magnetic refrigerator. Many researchers have directed significant effort to increase the magnetic field intensity, because the magnetocaloric effect at the Curie temperature increases with the power of 2/3 of the magnetic field. In this study, we report the simulation of the magnetic field intensity at polar axis of a Halbach cylinder (HC) by i) changing the length and thickness of the HC, ii) having with or without gap of the HC, and iii) surrounding the HC with a soft magnet shell, acting as a shielding. We simulated the field distribution of a HC with a finite size. Furthermore, the detailed numerical results of the magnetic field distribution and its dependence on shielding are presented in this study.
Sang-Un Lee 한국컴퓨터정보학회 2015 韓國컴퓨터情報學會論文誌 Vol.20 No.7
The time slot assignment problem (TSAP) or Satellite Communications scheduling problem (SCSP) for a satellite performs n×n ground station data traffic switching has been known NP-hard problem. This paper suggests O(n²) time complexity algorithm for TSAP of a satellite that performs n²×n² ground station data traffic switching. This problem is more difficult than n×n TSAP as NP-hard problem. Firstly, we compute the average traffic for n -transponder’s basic coverage zone and applies ground station exchange method that swap the ground stations until all of the transponders have a average value as possible. Nextly, we transform the D matrix to DLB traffic matrix that sum of rows and columns all of transponders have LB. Finally, we select the maximum traffic of row and column in DLB, then decide the duration of κth switch mode to minimum traffic from selected values. The proposed algorithm can be get the optimal solution for experimental data.
Lee, Si Un,Hong, Eun Pyo,Kim, Bong Jun,Kim, Sung-Eun,Jeon, Jin Pyeong Elsevier 2018 World neurosurgery Vol.115 No.-
<P><B>Objective</B></P> <P>To report clinical outcomes of delayed cerebral ischemia (DCI) and vasospasm in angiogram-negative subarachnoid hemorrhage (SAH) according to hemorrhage patterns, perimesencephalic hemorrhage (PMH) and non-PMH.</P> <P><B>Methods</B></P> <P>Online databases from January 1990 to December 2017 were systematically reviewed. A fixed-effects model was used to control heterogeneity. To resolve publication bias, the trim and fill method was used to estimate number of missing studies and adjusted odds ratio (OR). Subgroup analysis of data from studies that defined angiogram-negative subarachnoid hemorrhage by angiography repeated at least twice or computed tomography angiography was performed.</P> <P><B>Results</B></P> <P>Among 24 studies including 2083 patients, 23/985 patients (2.3%) with PMH and 144/1098 patients (13.1%) with non-PMH had DCI, indicating that patients with PMH experienced significantly lower DCI than patients with non-PMH (OR = 0.219; 95% confidence interval [CI], 0.144–0.334). Regarding vasospasm, 99/773 patients (12.8%) with PMH and 231/922 patients (25.1%) with non-PMH exhibited vasospasm, indicating that patients with PMH experienced significantly lower vasospasm than patients with non-PMH (OR = 0.445; 95% CI, 0.337–0.589). Funnel plots show asymmetry indicating possible publication bias. After trimming 10 studies for DCI and 7 for vasospasm, the adjusted ORs remained significant between PMH and lower risks of DCI and vasospasm. Subgroup analysis of 789 patients in 8 studies showed a lower risk of DCI (OR = 0.268; 95% CI, 0.151–0.473) and vasospasm (OR = 0.346; 95% CI, 0.221–0.538) in patients with PMH.</P> <P><B>Conclusions</B></P> <P>PMH showed a significantly lower risk of DCI and vasospasm than non-PMH. Clinical outcomes of angiogram-negative subarachnoid hemorrhage, based on meta-analysis of individual patient data, need to be investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This meta-analysis evaluated differences between PMH and non-PMH. </LI> <LI> Published data analyzed included recent studies that assessed DCI and vasospasm during follow-up. </LI> <LI> Subgroup analysis included studies that defined angiogram-negative SAH. </LI> <LI> PMH was associated with significantly lower incidence of DCI and vasospasm compared with non-PMH. </LI> </UL> </P>
Observation of Rotational Cooling of CN($B^2{\Sigma}^+$) Radical Generated in a Supersonic Expansion
Lee, Sang-Kuk,Choi, Iek-Soon,Kim, Un-Sik Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.5
The $CN(B^2{\Sigma}^+)$ radical was produced in a jet using an electric dc discharge of the precursor $CH_3CN$ with inert carrier gases. The rotationally resolved Fourier transform emission spectra of the 0-0 band of the $(B^2{\Sigma}^+{\to}X^2{\Sigma}^+)$ transition of CN have exhibited different distribution of the intensity for the carrier gases He and Ar, respectively. From the analysis of intensity distribution in the spectra, the mechanism for rotational cooling process of CN radical in a supersonic expansion has been suggested.
Facile Synthesis of Dendritic-Linear-Dendritic Materials by Click Chemistry
Lee, Jae-Wook,Han, Seung-Choul,Kim, Byoung-Ki,Lee, Un-Yup,Sung, Sae-Reum,Kang, Hwa-Shin,Kim, Ji-Hyeon,Jin, Sung-Ho The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.7
General, fast, and efficient stitching methods are presented for the synthesis of Fr$\acute{e}$chet-type dendrimers with linear units at a core, as a preliminary investigation for the synthesis of dendritic-linear-dendritic materials. The synthetic strategy involved an inexpensive, 1,3-dipolar, cycloaddition reaction between an alkyne and an azide in the presence of the Cu(I) species, which is known as the best example of click chemistry. The linear core building blocks, 1,7-octadiyne and 1,6-diazidohexane, were chosen to serve as the alkyne and azide functionalities for dendrimer growth via click reactions with the azide and alkyne-dendrons, respectively. These two building blocks were employed together with the azide- and alkyne-functionalized Fr$\acute{e}$chet-type dendrons in a convergent strategy to synthesize two kinds of Fr$\acute{e}$chet-type dendrimers with different linear core units. This comparative efficiency of the click methodology supports the fast and efficient synthesis of dendritic-linear-dendritic materials with the tailor made core unit.