• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.3
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• pp.311-318
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• 2015

A nonlinear dynamic response structural optimization process is proposed for the television (TV) packing system that protects the damage from a drop situation using the equivalent static loads (ESLs). Topology optimization using ESLs is carried out for conceptual design, and shape optimization using stress ESLs for a virtual model is performed for detailed design. Stress ESLs are static loads that generate the same displacement as well as the stress fields of linear static analysis as those of nonlinear dynamic analysis. Thus, the response of nonlinear dynamic analysis can be utilized as a constraint in the linear static structural optimization. An actual example is solved to validate the process. The drop test of a television packaging system is analyzed by LS-DYNA, and NASTRAN is used for optimization.

• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.937-945
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• 1999

In an effort to protect a RBSC(reaction -bonded SiC) tube SiC films from methyltrichlorosilane(MTS) by low pressure chemical vapor deposition were deposited in hydrogen atmosphere on the RBSC(reaction-bonded SiC) substrates over a range of input gas ratio(${\alpha}=P_{H2}/P_{MTS}=Q_{H2}/Q_{MTS}$=1 to 10) and deposition temperatures(T=1050~1300$^{\circ}C$). At the temper-ature of 1250$^{\circ}C$ the growth rate of SiC films increased and then decreased with decreasing the input gas ratio. The microstructure of SiC films was changed from granular type structure exhibiting (111) preferred orientation in the high input gas ratios to faceted columnar grain structure showing (220) in the low input gas ratios. The similar microstructure change was obtained by increasing the deposition temperature. These results were closely related to a change of deposition mechanism. Double layer structure having granular type and faceted ciolumnar grain structure from the manipulation of mechanism. Double layer structure having granular type and faceted columnar grain structure from the manipulation of the input gas ratio without changing the deposition temperatue was successfully fabricated through in -site process.

• Korean Journal of Materials Research
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• v.6 no.12
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• pp.1270-1278
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• 1996

고진공하에서 벽개된 GaAs를 대기중 노출시킨후, 결합상태 및 조성의 변화를 정량적으로 연구하여 Ga의 우선적 산화경향 및 결합의 붕괴에 기인한 원소상태 Ga 및 As의 생성을 관찰하였다. 대기중 노출시, 초기 Ga/As 비(=0.01)는 Ga의 우선적 산화에 의해 증가하였으며 원소상태 As의 증가와 더불어 일정값(=1.25)으로 유지되었다. 습식세정된 GaAs와 유황처리된 (S-passivated)GaAs를 각각 대기중에 노출시켜, 각각의 표면상태 변화를 비교, 관찰하였다. 유황처리된 GaAs는 습식세정처리만한 GaAs에 비해 산화막 성장이 크게 억제되었고, 이는 (NH4)2Sx 용액 처리로 형성된 Ga-S 및 As-S 겹합의 표면보호 효과에 기인한 것이다. 특히 대기중 노출에 따른 유황처리된 GaAs 표면조성 및 결합상태 변화의 정량적 관찰을 통하여, 유황보호막(S-passivation layer) 및 GaAs 표면과 대기중 산소와의 반응 기구를 규명할 수 있었다. 대기중 노출에 따라, 표면의 Ga-S 및 As-S 결합은 대기중 산소와 반응하여 점차 붕괴, 감소하는 경향을 나타냈으며, 이와 동시에 unpassivated 상태의 GaAs가 산소와 반응하여 Ga-O 결합을 형성함을 관찰할 수 있었다. 본 연구에서는 X-선 광전자 분광기를 사용하여 GaAs 표면 조성 및 결합상태의 변화를 관찰하였다.

• Journal of the Korean Chemical Society
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• v.37 no.12
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• pp.1068-1075
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• 1993

Catalase activities were assayed on the leaves and roots of Tomato (Lycopersicum esculentum) as a function of age for 1 year after germination. The enzyme activities of root tissue demonstrated to be insignificant through all stages of development. On the other hand, the catalase activities of leaf peroxisomal fractions showed remarkable changes with peak value of 76 ${\mu}mol$/ml/min at germination stage within 2 weeks growth, 7.2 ${\mu}mol$/ml/min at adult stage around 4∼5 months growth and very small activities at aged period around 11∼12 months growth. It is suggested that there may be two factors concerning such catalase activities in relation with age, firstly the glyoxisomal reactions including glyoxylate cycle and $\beta$-oxidation at germination stage and secondly photosynthesis hereafter seemed to affect age dependent changes of catalase activity by producing coincident amount of $H_2O_2$. In addition, NADPH coenzyme was found to have ability to restore catalytic acitivity of inactivated catalase (compound II) at all stages of development except old age, indicating NADPH would play a role as catalase protector against deleterious substrate,$H_2O_2$.

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.187-192
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• 2020

(2S,3R)-3-hydroxyhomoserine lactone (HSL) has been used as a key intermediate for the synthesis of various biologically active compounds. In this study, we demonstrated an efficient synthesis of HSL via anti selective dihydroxylation of a protected vinyl glycine analog with an oxabicyclo[2.2.2]octyl orthoester (OBO) ester group. Because the acyclic conformation of the substrate was efficiently controlled by the bulky OBO ester group, a diastereoselectivity of > 10 : 1 was obtained in the dihydroxylation reaction without the use of a chiral reagent. By using this result, the target compound 1 can be obtained from commercially available N-Cbz-L-serine 2 in seven steps with an overall yeid of 34%. This result could be applied to the stereoselective synthesis of biologically active molecules containing a vicinal amino diol moiety.

• Korean Journal of Culture and Social Issue
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• v.12 no.2
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• pp.21-43
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• 2006

This study was conducted to explore college students' implicit identification with others powerful or powerless, and implicit association of self-enhancement & authenticity with their relationships with others powerful or powerless. The study was based on measuring 3 sorts of IAT: an explicit identification test, RWA, & RISC. The results were summed up as follows: Students identified their selves with others more powerful than others powerless; expressed self-enhancement when they were with powerful others; and associated 'true' with relationship with others powerful. Men with high RWA & women with low RWA identified their selves more with others powerful; low RWA & high RISC groups' associated relationship with others powerful to 'true' and others powerless to 'false' more rapidly. These results were discussed in terms of structure of authoritarianism, SEM, relationship with others powerful and powerless.

• Reproductive and Developmental Biology
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• v.39 no.3
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• pp.59-67
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• 2015

Galactose-${\alpha}1,3$-galactose (${\alpha}1,3$-Gal) epitope is synthesized at a high concentration on the surface of pig cells by ${\alpha}1,3$-galactosyltransferase gene (GGTA1). The ${\alpha}1,3$-Gal is responsible for hyperacute rejection in pig-to-human xenotransplantation. The generation of transgenic pigs as organ donors for humans is necessary to eliminate the GGTA1 gene that synthesize $Gal{\alpha}$(1,3)Gal. To prevent hyperacute graft rejection in pig-to-human xenotransplantation, previously, we developed ${\alpha}1,3$-galactosyltransferase gene-knock-out somatic cell by homologous recombination. In this study, we established cell lines of ${\alpha}1,3$-GT knock-out expressing hDAF and hHT gene from minipig fibroblasts to apply somatic cell nuclear transfer. The hDAF and hHT mRNA were expressed in the knock-in somatic cells and ${\alpha}1,3$-GT mRNA was suppressed. However, the knock-in somatic cells were increased resistance to human serum-mediated cytolysis.

• Journal of Applied Biological Chemistry
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• v.62 no.4
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• pp.327-332
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• 2019

Alzheimer's disease (AD) is a common neurodegenerative disease. Oxidative stress by amyloid beta peptide (Aβ) of neuronal cell is the most cause of AD. In the present study, protective effects of several flavonoids such as kaempferol (K), kaempferol-3-O-glucoside (KG), quercetin (Q) and quercetin-3-β-ᴅ-glucoside (QG) from Aβ_25-35 were investigated using C6 glial cell. Treatment of Aβ_25-35 to C6 glial cell showed decrease of cell viability, while treatment of flavonoids such as Q and QG increased cell viability. In addition, treatment of flavonoids declined reactive oxygen species (ROS) production compared with Aβ_25-35-induced control. The ROS production was increased by treatment of Aβ_25-35 to 133.39%, while KG and QG at concentration of 1 μM decreased ROS production to 107.44 and 113.10%, respectively. To study mechanisms of protective effect of these flavonoids against Aβ_25-35, the protein expression related to inflammation under Aβ_25-35-induced C6 glial cell was investigated. The results showed that C6 glial cell under Aβ_25-35-induced oxidative stress up-regulated inflammation-related protein expressions. However, treatment of flavonoids led to reduction of protein expression such as inducible nitric oxide synthase, cyclooxygenase-2 and interleukin-1β. Especially, treatment of KG and QG decreased more effectively inflammation-related protein expression than its aglycones, K and Q. Therefore, the present results indicated that K, Q and its glycosides attenuated Aβ_25-35-induced neuronal oxidative stress and inflammation.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.872-879
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• 2010

Layered copper hydroxides [LCHs, $Cu_2(OH)_3{\cdot}NO_3$] has the agricultural potentials as a fungicide because of its high crystallinity, excellent anion exchange capacity, and its regular layered particle size. The study, for the first time, has synthesized LCHs in highly concentrated solution and evaluated its physicochemical properties including the crystallinity and suspension stability. Optimal synthetic condition of LCHs was determined by crystallinity and stability of suspension as follow; 1) concentrations of $Cu(NO_3)_2$ and NaOH solutions were 3.0 M respectively, 2) reaction temperature and solution pH were $25^{\circ}C$ and 6.0, respectively, and 3) aging time after reaction was 2hr. Crystallinity of LCHs enhanced with increase in pH up to 9.0. Whereas, stability of suspension was decrease by increase in crystal size. Especially, increase in reaction temperature decreased stability of suspension. XRD patterns and SEM images exhibited that LCHs had regular layered particle size with 0.2~0.8 ${\mu}m$ and high crystallinity in optimal synthetic condition. The particle size was increased with increase in reaction temperature and pH. These results showed that LCHs synthesized in highly concentrated solution exhibited high stability of suspension as well as high crystallinity suitable to their potential as a fungicide.

• Korean Journal of Materials Research
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• v.6 no.2
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• pp.188-196
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• 1996

LiOH 용액에서 핵연료피복관용 Zr합금의 부식이 가속되는 현상을 규명하기 위하여 autoclave를 이용하여 순수물, 다른 농도의 Li 용액 및 여러 가지 알카리 수산화물 조건에서 부식시험을 실시하였다. LiOH 용액에서 부식이 가속되는 현상은 용액 내에 Li 농도가 2.2ppm 이상에서부터 일어나기 시작하며 30ppm 이상에서는 급격한 가속 현상이 일어난다. 부식반응 동안에 발생되는 수소 흡수현상은 220ppm Li에서는 물에 비해 약 2배의 높은 수소흡수율을 나타내며 산화막은 주로 수소화물이 모여 있는 지역에서 우선적으로 성장한다. Li가속 부식기구와 관련하여 본 연구 결과는 지금까지 다른 연구자들이 제안한 부식 기구들과는 일치하지 않았다. LiOH 용액 내에서는 수소흡수와 수소화물 형성이 가속되고 이로 인해 산화막의 성질이 비보호성의 산화막으로 변함으로서 부식은 가속된다는 새로운 모델을 제시하였다.