• 한국산업융합학회 논문집
• /
• 제26권4_2호
• /
• pp.571-576
• /
• 2023

In this study, the harmless crack size(a_hml) according to the residual stress depth was evaluated using the fatigue limit of SCM440 steel by quenching-tempering(QT) and induction hardening(IH), and threshold stress intensity factor of QT steel. Because the residual stress increased rapidly as the crack depth increased, a_hml was determined at the depth of all the crack aspect ratio(As) regardless of Type I-III, and a_hml also increased according to the residual stress depth. a_hml was minimal at As=1.0 and maximal at As=0.1, but was almost similar on each Type. a_hml was small the dependence on As.

• Journal of Microbiology and Biotechnology
• /
• 제15권1호
• /
• pp.131-135
• /
• 2005

Under sulfur deprived conditions, PS II and photosynthetic $O_2$ evolution by Chlamydomonas reinhardtii UTEX 90 are inactivated, resulting in shift from aerobic to anaerobic condition. This is followed by hydrogen production catalyzed by hydrogenase. We hypothesized that the photosynthetic capacity and the accumulation of endogenous substrates such as starch for hydrogen production might be different according to cell age. Accordingly, we investigated (a) the relationships between hydrogen production, induction time of sulfur deprivation, increase of chlorophyll after sulfur deprivation, and residual PS II activity, and (b) the effect of initial cell density upon sulfur deprivation. The maximum production volume of hydrogen was 151 ml $H_2$/l with 0.91 g/l of cell density in the late-exponential phase. We suggest that the effects of induction time and initial cell density at sulfur deprivation on hydrogen production, up to an optimal concentration, are due to an increase of chlorophyll under sulfur deprivation.

• 폴리머
• /
• 제32권5호
• /
• pp.440-445
• /
• 2008

정수압 상태의 선형저밀도 폴리에틸렌 튜빙의 파손 메커니즘과 파손 모폴로지를 연구하였다. 비디오현미경과 주사전자현미경을 이용한 관찰 결과, 선형저밀도 폴리에틸렌 튜빙의 파손모드는 내면에서 외면으로 진전되는 크랙을 수반하는 취성파괴임을 확인하였다. 또한 산화유발시간과 적외선분광분석을 통하여, 파손된 선형저밀도 플리에틸렌 튜빙의 단면상에 열화에 의한 발열 피크와 카르보닐 피크의 증가를 관찰하였다. 열 가속에 의한 음력과 수명특성 사이의 관계를 고려한 선형저밀도 폴리에틸렌 튜빙의 가속수명시험법 및 시험장치를 개발하였다. 선형저밀도 폴리에틸렌 튜빙의 장기 정수압 상태의 수명을 예측하기 위해 아레니우스 모델과 와이블 분포를 적용한 통계학적 기법을 도입하였다. 그 결과, 사용온도 $25^{\circ}C$에서의 선형저밀도 폴리에틸렌 튜빙의 장기수명을 평가/분석하였다.

• Bulletin of the Korean Chemical Society
• /
• 제25권2호
• /
• pp.267-270
• /
• 2004

The bromate-1,4-cyclohexanedione-ferroin oscillating reactions are uncovered to support two types of wave activities, in which spontaneous formation of circular waves has been achieved after the disappearance of initial waves. The induction period of the revival wave is typically above 10 hours and its dependence on the initial concentrations of reactants is qualitatively different from that of initial waves. In addition to their differences in propagating speed and wavelength, the initial waves and the revival patterns have different colors, suggesting that different reaction mechanisms are involved in the formation of these spatiotemporal behaviors. Our experiments further show that the addition of hydroquinone to the reacting system can significantly shorten the induction time of the revival wave, which implicates that hydroquinone is not only a product in the bromate-1,4-cyclohexanedione-ferroin oscillating reaction but also plays a critical role in the following reactions.

• Bulletin of the Korean Chemical Society
• /
• 제34권8호
• /
• pp.2317-2320
• /
• 2013

Thiourea and vinyl sulfoxide derivatives were designed based on the structures of sulforaphane and gallic acid, prepared and tested for HO-1 inducing activity as a measure of Nrf2 activation, and inhibitory effect on NO production as a measure of anti-inflammatory activity. Both series of compounds showed moderate activity on HO-1 induction, and no inhibitory effect on NO production. Interestingly the thiourea compound 6d showed better HO-1 induction (71% SFN) than the corresponding isothiocyanate compound 6a (55% SFN). Overall, it seemed that more efficient electrophile is needed to get more effective Nrf2 activator.

• Bulletin of the Korean Chemical Society
• /
• 제18권1호
• /
• pp.18-23
• /
• 1997

Data from structure/activity studies in vir gene induction system have led to evaluate the working hypothesis of interaction between phenolic inducers and phenol binding proteins. The primary specificity in the association of a phenolic inducer with its receptor in our system is hypothesized to be the hydrogen bonding interactions through the ortho methoxy substituents as well as the proton transfer between the inducer and the binding protein. In this paper the proposed working model for phenol-mediating signal transduction was evaluated in several ways. The importance of the general acid-base catalysis was first addressed by the presence of an acidic residue and a basic residue in the phenol binding protein. Series of compounds were tested for vir gene expression activity to confirm the generation of a strong nucleophile by an acidic residue and an involvement of a basic residue as a proton acceptor. An attempt was made to correlate the pKa values of the phenolic compounds with vir gene induction activities as inducers to further support the proposed proton transfer mechanism. Finally, it was also observed that the regioselectively attached methoxy group on phenol compounds is required as the proper hydrogen bond acceptor.

• 한국독성학회:학술대회논문집
• /
• 한국독성학회 2001년도 International Symposium on Signal transduction in Toxicology
• /
• pp.120-120
• /
• 2001

Exposure of testis to 2-BP is known to cause degeneration of male germ cells. However, the mechanism underlying this process is poorly understood. The objective of this study was to determine whether 2-BP induces apoptosis during onset of toxicity in germ cells of male Sprague-Dawley rats.(omitted)

• 한국분말재료학회지
• /
• 제8권3호
• /
• pp.207-209
• /
• 2001

Nano particles have recently been a major research interest, motivated by their unusual physical and chemical properties. Such particles can be synthesized using physical and chemical methods. The physical methods need expensive installation like vacuum induction furnace, whereas in chemical methods the process in generally very simple and low cost. In this study, simple and new fabrication process by using ultrasound was investigated to prepare the nano-sized metal particles on various powders at room temperature.

• 한국동물학회:학술대회논문집
• /
• 한국동물학회 1994년도 한국생물과학협회 학술발표대회
• /
• pp.215.2-215
• /
• 1994

No Abstract, See Full Text

• 한국화재소방학회논문지
• /
• 제22권3호
• /
• pp.234-238
• /
• 2008

수소의 연소과정 중 하나인 자연발화에 대해 HFP를 첨가하였을 때 발화 지연을 수치해석을 통하여 조사하였다. 단열 밀폐시스템에서 대기압 하에서의 비정상 상태를 가정하였으며, 수소/공기/헵타플루오르헵탄(HFP)의 반응기구는 93개의 화학종과 817개의 화학반응식을 고려하였다. 먼저 이론당량비의 순수한 수소/공기 혼합기 계산결과로부터 연료와 산화제만 존재하는 혼합기에서는 자연발화시간을 결정하는 판별방법의 선택은 그리 중요하지 않고, 대부분의 판별방법이 잘 일치하는 결과를 얻을 수 있었다. 또한 수소/공기의 자연발화시간은 기존문헌의 실험결과와 잘 일치함을 알 수 있어 사용된 수소반응기구를 검증할 수 있었다. HFP를 수소/공기 혼합기에 섞었을 경우에는 각 순간적 화학적 반응에 의해 OH농도의 변곡점이 다양한 시각에 나타나므로 온도의 변곡점으로 발화시간을 판단하는 것이 보다 타당하다는 결과를 얻었다. 그리고 HFP의 농도가 10% 이상인 경우 큰 발화지연효과를 볼 수 있는데, 이 때, HFP 농도가 증가할수록 희석효과에 비해 화학적 효과가 발화시간 지연에 보다 크게 기여함을 알 수 있다.