• 열처리공학회지
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• 제20권6호
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• pp.311-317
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• 2007

This study examined the phase changes, nitride precipitation and variation in mechanical properties of STS 304, STS 321 and STS 316L austenitic stainless steels after high temperature gas nitriding (HTGN) at temperature ranges from $1050^{\circ}C\;to\;1150^{\circ}C$. Fine round type of $Cr_2N$ nitrides were observed in the surface layers of 304 and 316L steels, even more in STS 321. Additionally, square type of TiN was found in STS 321 austenitic matrix too. As a result of many precipitates in the surface layer of the STS 321, it was seen $370{\sim}470Hv$ hardness variation depending on the HTGN treatment conditions, and interior region of austenite represented 150Hv. The surface hardness value of STS 304 and STS 316L showed $255{\sim}320Hv$, respectively. The nitrogen content was shown 0.27, 1.7 and 0.4% respectively at the surface layers of the STS 304, STS 321 and STS 316L. After the HTGN it was shown the improvement of corrosion resistance of the STS 321 and STS 316L compared with solution annealed steels in the solution of 1N $H_2SO_4$ whereas the STS 304 was not.

• 한국추진공학회지
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• 제20권5호
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• pp.51-59
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• 2016

STS 321 스테인리스강은 액체 로켓 엔진을 비롯한 고온 고압의 시스템의 재료로서 많이 사용된다. 321 스테인리스강의 고온에서의 변형 거동을 예측하기 위해 Kocks의 전위 장벽 모델을 근거로 유동응력에 대한 구성 방정식을 열적 응력 요소와 비열적 응력 요소를 사용하여 제안하였다. 제안한 모델은 321 스테인리스강의 상온부터 $500^{\circ}C$의 넓은 온도 영역에서 재료의 변형 거동들을 잘 예측하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2001년도 춘계학술발표대회 개요집
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• pp.112-113
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• 2001

• Journal of Welding and Joining
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• 제20권6호
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• pp.106-106
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• 2002

This study investigated variations of micro-structures and mechanical properties of Ti / STS321L joint with various bonding temperature and time using brazing method. According to increasing bonding temperature and time, it was observed that the thickness of their reaction layer increased due So increasing diffusion rate and time. From the EPMA results, Ti diffused to the STS321L substrate according to increasing bending time to 30min. Hardness of bonded interface increased with increasing bonding temperature and time due to increasing their oxides and intermetallic compounds. XRD data indicated that Ag, Ag-Ti intermetallic compounds, TiAg and Ti₃Ag and titanium oxide, TiO₂were formed in interface. In tensile test, it was found that the tensile strength had a maximum value at the bonding temperature of 900℃ and time of 5min, and tensile strength decreased over bonding time of 5min. The critical thickness of intermetallic compounds was observed to about 30㎛, because of brittleness from their excessive intermetallic compounds and titanium oxide, and weakness from void.

• Journal of Welding and Joining
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• 제20권6호
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• pp.830-837
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• 2002

This study investigated variations of micro-structures and mechanical properties of Ti / STS321L joint with various bonding temperature and time using brazing method. According to increasing bonding temperature and time, it was observed that the thickness of their reaction layer increased due So increasing diffusion rate and time. From the EPMA results, Ti diffused to the STS321L substrate according to increasing bending time to 30min. Hardness of bonded interface increased with increasing bonding temperature and time due to increasing their oxides and intermetallic compounds. XRD data indicated that Ag, Ag-Ti intermetallic compounds, TiAg and $Ti_3Ag$ and titanium oxide, $TiO_2$ were formed in interface. In tensile test, it was found that the tensile strength had a maximum value at the bonding temperature of $900^{\circ}C$ and time of 5min, and tensile strength decreased over bonding time of 5min. The critical thickness of intermetallic compounds was observed to about $30\mu\textrm{m}$, because of brittleness from their excessive intermetallic compounds and titanium oxide, and weakness from void.

• Corrosion Science and Technology
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• 제9권3호
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• pp.122-128
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• 2010

The corrosion of the flexible tube in the automobile exhaust system is caused by the ambient water and chloride ions. Since welding is one of the key processes for the flexible tube manufacturing, it is required to select a proper welding method to prevent the flexible tube corrosion and to increase its lifetime. There are many studies about the efficiency of the welding method, but no systematic study is performed for the effect of welding method on the corrosion property of the austenitic stainless weldment. The aim of the present study is to provide information on the effect of two different welding methods of TIGW (tungsten inert gas welding) and PAW (plasma arc welding) on the corrosion property of austenitic stainless steel weldment. Materials used in this study were two types of the commercial austenitic stainless steel, STS321 and XM15J1, which were used for flexible tube material for the automotive exhaust system. Microstructure was observed by using optical microscopy (OM) and scanning electron microscopy (SEM). To evaluate the corrosion behavior, potentiodynamic and potentiostatic tests were performed. The chemical state of the passive film was analyzed in terms of XPS depth profile. Metallurgical analysis show that the ferrite content in fusion zone of both STS321 and XM15J1 is higher when welded by PAW than by TIGW. The potentiodynamic and potentiostatic test results show that both STS321 and XM15J1 have higher transpassive potential and lower passive current density when welded by PAW than by TIGW. XPS analysis indicates that the stable $Cr_2O_3$ layer at the outermost layer of the passive film is formed when welded by PAW. The result recommends that PAW is more desirable than TIGW to secure corrosion resistance of the flex tube which is usually made of austenitic stainless steel.

• Biomolecules & Therapeutics
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• 제25권3호
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• pp.321-328
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• 2017

Steroid sulfatase (STS) is an enzyme responsible for the hydrolysis of aryl and alkyl sulfates. STS plays a pivotal role in the regulation of estrogens and androgens that promote the growth of hormone-dependent tumors, such as those of breast or prostate cancer. However, the molecular function of STS in tumor growth is still not clear. To elucidate the role of STS in cancer cell proliferation, we investigated whether STS is able to regulate the integrin signaling pathway. We found that overexpression of STS in HeLa cells increases the protein and mRNA levels of integrin ${\beta}1$ and fibronectin, a ligand of integrin ${\alpha}5{\beta}1$. Dehydroepiandrosterone (DHEA), one of the main metabolites of STS, also increases mRNA and protein expression of integrin ${\beta}1$ and fibronectin. Further, STS expression and DHEA treatment enhanced phosphorylation of focal adhesion kinase (FAK) at the Tyr 925 residue. Moreover, increased phosphorylation of ERK at Thr 202 and Tyr 204 residues by STS indicates that STS activates the MAPK/ERK pathway. In conclusion, these results suggest that STS expression and DHEA treatment may enhance MAPK/ERK signaling through up-regulation of integrin ${\beta}1$ and activation of FAK.

• Food Science and Biotechnology
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• 제15권2호
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• pp.321-323
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• 2006

A combination of thymol and sodium bisulfate was found to be an effective biocidal agent against strains of Burkholderia cepacia and of Xanthomonas maltophilia that were found in the space shuttle water system. Potassium iodide (KI), the biocidal agent used in the past, had a minimum inhibitory concentration (MIC) of 50,000 ppm against the two B. cepacia (541 STS-81 and 1119 STS-91) strains, whereas that of thymol and sodium bisulfate was 2,400 and 950 ppm, which was 21 and 53 times lower than that of KI for B. cepacia, respectively. The MIC value for the combination of thymol and sodium bisulfate was 4 times lower than that for thymol or sodium bisulfate alone against B. cepacia (541 STS-81, 1119 STS-91) or Pseudomonas cepacia (ATCC 31941). The fractional inhibitory concentration (FIC) of the combination of thymol and sodium bisulfate for all organisms tested was less than 0.5, indicating a strong synergistic effect.

• 대한화학회지
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• 제43권3호
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• pp.321-327
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• 1999

제 6차 교육과정에서 강조하는 STS 교육내용이 중학교 과학교과서(화학단원을 중심으로)에 얼마나 반영되어 있는지를 분석해 보았다. 과학 교과서중 화학부분의 교과서별 STS 내용의 분포를 보면 평균 13.2%로 학문중심 교육과정에 비해 많이 향상된 것을 볼 수 있었 다. STS 내용의 화학 단원별 분포를 보면 물질의 반응 단원이 15.9%로 가장 높았고 물질의 특성과 분리가 12% 그리고 물질의 구성이 10.8% 순서를 보였다. Piel에 따른 교과서별 STS 주제 영역을 비교해 본 결과 7개의 주제 영역 중에서 '과학의 사회학'에 관한 주제가 40.2%로 가장 많았고 이는 5종의 교과서에서 모두 가장 높은 비율을 보였다. 다음으로 환경문제와 천연자원에 관한 주제가 전체 STS의 28.8%이었으며 기술발달의 영향에 관한 것이 약 20.4%이었다. 에너지에 관한 주제는 12.9%가 포함되어 있었으며 인간공학은 한 교과서에만 0.3%가 포함되어 있었고 인구와 우주개발과 국방에 관한 주제는 모든 교과서에서 다루고 있지 않았다. 단원별 STS 주제 영역을 비교해 보면 과학의 사회학, 환경문제와 천연자원, 기술발달의 영향은 '물질의 특성과 분리', '물질의 반응' '물질의 구성' 모두에 포함되어 있으며 에너지에 대한 내용은 물질의 특성과 분리', '물질의 반응' 단원에만 포함되어 있었다. STS 내용의 활동 영역멸 분석에서는 총 71회의 활동 중 문제 해결과 의사 결정'이 22회로 가장 많았고, 모의 실험이 15회, 자료해석이 12회, 현장활동이 9회, 사례연구가 7회,조사연구가 4회, 구조화된 토론이 2회이었으며, 역할 놀이나 연구고안은 전혀 없었다.

• 한국지진공학회논문집
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• 제23권6호
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• pp.321-327
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• 2019

We performed seismic noise level analysis to access the proper functioning of 11 newly established seismic stations in the southeastern region of Korea. One-hour long segments of seismograms were selected from the continuous data of the 3 elements for 61 days from March 1, 2019. For each segment of data, the power spectral density (PSD) was estimated from the continuous back ground noise data of the 3 elements for periods ranging from 0.02~100 s. The median noise levels (NLs) of the stations were compared with the new noise model (NNM) of USGS and NLs of station TJN installed in a tunnel on a granite basement. We observed that the NLs of the newly installed seismometers were between the upper and lower limit of the NNM. In a comparison with the noise level of station TJN, the new seismometers had their own noteworthy features. The NLs from accelerometers (Epi-sensors) were ~ 40 dB higher than the NLs from velocimeters (STS-sensors) for periods > 10 s, which is because the small and light Epi-sensors are sensitive to environmental changes. Daily and weekly variations in spectral noise level were observed clearly in short periods < 1 s, and these are considered to be related to human activities. The seismometers in boreholes showed ~20 dB weaker NLs in the cultural noise band. The NLs of accelerometers at a depth of 30 m were also much lower by 30 dB for long periods > 10 sec. Overall the functioning of the new velocimeter and accelerometer stations was reliable for periods ranging from 0.02~100 s and 0.02~10 s, respectively.