• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.59-59
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• 2009

The influences of B and Si in the filler metals on microstructure and isothermal solidification during transient liquid-phase (TLP) bonding of a nitrogen-containing duplex stainless steel with MBF-30 (Ni-4.5wt.%Si-3.2wt.%B) and MBF-35 (Ni-7.3wt.%Si-2.2wt.%B), were studied at the temperature range of $1030-1090^{\circ}C$ with various times from 60 s to 3600 s under a vacuum of approximately $10^{-5}$ Torr. In case of the former, BN, $Ni_3B$ and $Ni_3Si$ precipitates were formed in the bonding region. BN and $Ni_3Si$ secondary phases were present in the joint for the latter case. The formation of $Ni_3B$ within the joint centerline is dependent on B content. The morphology of $Ni_3Si$ is dominated by Si concentration. A difference between the times for complete isothermal solidification obtained by the experiments and the conventional TLP bonding diffusion model was observed when using MBF-35. According to the simulated results, the isothermal solidification completion time for MBF-35 case was smaller than that in MBF-30. However, this experimental value obtained using MBF-35 was notably larger than that obtained using MBF-30. Isothermal solidification of liquid MBF-30 is controlled by the first isothermal solidification regime dependent on B diffusion model, whereas that of liquid MBF-35 experiences two isothermal solidification regimes and is mainly controlled by the second isothermal solidification dependent on Si diffusion model. In addition, only if Si content exceeds a critical value, the slower 2nd solidification regime will commence.

• Journal of Welding and Joining
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• 제21권4호
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• pp.69-74
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• 2003

The mechanical properties of STD11 Joints by using TLP (Transient Liquid Phase Diffusion) bonding method employing MBF-30 and MBF-80 insert metals were investigated with concerning to the microstructural change. TLP bonding of STD 11 was carried out at 1323∼1423K for 0.6ks∼3.6ks in vacuum. The microstructure and the element distribution of the interlayer between tool steels and insert metals showed specific feature with bonding conditions. It was found that the width of the interlayer increased at initial bonding stage. However, the width of interlayer showed nearly constant value during the isothermal solidification. After isothermal solidification was completed, the joint showed homogeneous element distribution and similar microstructure with base metal because of the grain boundary migration to the bonded interlayer. The bonding strength measured by a tensile test has been varied with the bonding conditions. The maximum joint strength, 760MPa, was obtained with the condition of 1423K for 1.2ks using MBF30 insert metal in this experiment.

• Journal of Welding and Joining
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• 제30권6호
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• pp.106-112
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• 2012

This study was carried out to investigate the effect of bonding temperature and holding time on microstructure and mechanical properties in brazing joints of Ni-base superalloy using MBF-30 (Ni-4.5Si-3.2B [wt.%]). The heating rate was $20^{\circ}C$/min to the bonding temperatures $1050^{\circ}C$, $1070^{\circ}C$, $1090^{\circ}C$ under high vacuum condition. The holding times were 100s, 400s, 900s and 1600s. $Ni_3B$ phases and proeutectic Ni were observed in the interlayer of Ni-201. Then, Ni3B and Ni3Si were found in the middle region of brazing joint. Cr-boride phase appeared in the interlayer of Inconel-625. Tensile strength and elongation were decreased at $1050^{\circ}C$-1600s, $1070^{\circ}C$-900s and $1090^{\circ}C$-400s. After observation the fracture specimens, There was Ni3B which is very brittle phase in the grain boundary of Ni201.

• Journal of Welding and Joining
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• 제21권3호
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• pp.78-84
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• 2003

The changes of microstructure and hardness of TLP bonds of directionally solidified Ni base superalloy, GTD-111, with variation of homogenizing and aging treatment were investigated. The specimens were bonded at 1403K for 7.2ks using different insert metals such as MBF-50, MBF-80 and MBF-90 and they were homogenized at 1393K with various holding time. At center of bonded interlayer homogenized for hold time 30h, the contents of aluminum and titanium were approximately 90% and 95% of base metal, respectively. In this study, aging was performed at three different kinds : one step aging ; 1113K $\times$ 16h, two step aging ; 1113K $\times$ 10h ⇒ 1103K $\times$ 10h, three step aging ; 1113K $\times$ 10h ⇒ 1103K $\times$ 8h ⇒ 922K $\times$ 24h. ${\gamma}$' volume fraction and hardness of joints were high in the sequence of one step, two step and three step aging, whereas ${\gamma}$' volume fraction and hardness of joints obtained by three step aging treatment were higher than those of raw material. Tensile properties of joints bonded with MBF-80 and MBF-90, homogenized at 1393K for 30h and then three step aged became excellent than those of raw material, however, joint bonded with MBF-50 was poor.

• Korean Journal of Radiology
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• 제22권1호
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• pp.97-105
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• 2021

Objective: The present study aimed to investigate the association between myocardial blood flow (MBF) quantified by dynamic CT myocardial perfusion imaging (CT-MPI) and the increments in heart rate (HR) after stress in patients without obstructive coronary artery disease. Materials and Methods: We retrospectively included 204 subjects who underwent both dynamic CT-MPI and coronary CT angiography (CCTA). Patients with more than minimal coronary stenosis (diameter ≥ 25%), history of myocardial infarction/revascularization, cardiomyopathy, and microvascular dysfunction were excluded. Global MBF at stress was measured using hybrid deconvolution and maximum slope model. Furthermore, the HR increments after stress were recorded. Results: The median radiation dose of dynamic CT-MPI plus CCTA was 5.5 (4.5-6.8) mSv. The median global MBF of all subjects was 156.4 (139.8-180.4) mL/100 mL/min. In subjects with HR increment between 10 to 19 beats per minute (bpm), the global MBF was significantly lower than that of subjects with increment between 20 to 29 bpm (153.3 mL/100 mL/min vs. 171.3 mL/100 mL/min, p = 0.027). This difference became insignificant when the HR increment further increased to ≥ 30 bpm. Conclusion: The global MBF value was associated with the extent of increase in HR after stress. Significantly higher global MBF was seen in subjects with HR increment of ≥ 20 bpm.

• 구강회복응용과학지
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• 제26권1호
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• pp.69-75
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• 2010

A형 보툴리눔 독소(botulinum toxin type A, BTX-A)는 교근 비대의 치료에 성공적으로 적용되어 왔지만 주사 부위 근육의 약화를 초래한다. 이 연구는 BTX-A를 사람 교근에 주사한 후 최대 교합력(Maximum Bite Force, MBF) 의 변화를 측정하고, 반복 주사의 효과를 평가하기 위해 시행되었다. 30명의 자원자들을 18주간 추적 관찰하고, 최대 교합력을 측정하였다. 1차 주사로부터 18주가 경과한 후 시술에 만족한 16명은 제외하고 나머지 14명에게 반복 주사를 시행하였고, 다시 18주간 측정하였다. 평균 최대 교합력은 주사 2주 후 20% 감소하였다가 4주부터 점차 회복되었으며, 12주 뒤에는 주사 이전 수준으로 회복되었다. 최대 교합력은 주사 전과 주사 2주, 4주, 8주 후에서 유의한 차이를 보였다(p<.05). 반복 주사군(n=14)의 최대 교합력은 6주에 두드러진 감소를 보였다가(p<.05) 12주간 점차 회복되었다. 실험군이 경험한 불편감의 수준은 일반적인 저작에는 거의 영향을 미치지 않았다.

• Korean Journal of Radiology
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• 제20권5호
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• pp.709-718
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• 2019

Objective: To investigate the association of myocardial blood flow (MBF) quantified by dynamic computed tomography (CT) myocardial perfusion imaging (MPI) with troponin level and left ventricle (LV) function in patients with ST-segment elevated myocardial infarction (STEMI). Materials and Methods: Thirty-five STEMI patients who successfully had undergone reperfusion treatment within 1 week of their infarction were consecutively enrolled. All patients were referred for dynamic CT-MPI. Serial high-sensitivity troponin T (hs-TnT) levels and left ventricular ejection fraction (LVEF) measured by echocardiography were recorded. Twenty-six patients with 427 segments were included for analysis. Various quantitative parameters derived from dynamic CT-MPI were analyzed to determine if there was a correlation between hs-TnT levels and LVEF on admission and again at the 6-month mark. Results: The mean radiation dose for dynamic CT-MPI was 3.2 ± 1.1 mSv. Infarcted territories had significantly lower MBF (30.5 ± 7.4 mL/min/100 mL versus 73.4 ± 8.1 mL/min/100 mL, p < 0.001) and myocardial blood volume (MBV) (2.8 ± 0.9 mL/100 mL versus 4.2 ± 1.1 mL/100 mL, p = 0.044) compared with those of reference territories. MBF showed the best correlation with the level of peak hs-TnT (r = -0.682, p < 0.001), and MBV showed a moderate correlation with the level of peak hs-TnT (r = -0.437, p = 0.026); however, the other parameters did not show any significant correlation with hs-TnT levels. As for the association with LV function, only MBF was significantly correlated with LVEF at the time of admission (r = 0.469, p = 0.016) and at 6 months (r = 0.585, p = 0.001). Conclusion: MBF quantified by dynamic CT-MPI is significantly inversely correlated with the level of peak hs-TnT. In addition, patients with lower MBF tended to have impaired LV function at the time of their admission and at 6 months.

• Nuclear Medicine and Molecular Imaging
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• 제41권3호
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• pp.194-200
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• 2007

목적: $^{13}N$-암모니아는 심근혈류 측정에 유용한 방사성의 약품으로 최근 국내에 도입된 PET/CT를 이용하여 비침습적으로 정량적인 검사를 시행 할 수 있다. 이 연구에서는 $^{13}N$-암모니아를 이용한 동적 영상으로부터 얻은 심근혈류정보와 정적 영상으로부터 얻은 심근관류정보의 상관관계를 살펴봄으로써 심장핵의학 검사의 유용성을 알아보고자 하였다. 방법: 심혈관질환이 의심되어 핵의학 심근관류 검사를 시행한 12명(남 11명, 여 1명, 평균나이 $57.9{\pm}8.6$세)을 대상으로 $^{13}N$-암모니아 검사를 시행하였다. 휴식기와 부하기에서 영상획득을 위하여 $^{13}N$ 암모니아 0.3 mCi/kg를 15초간 순간주사하면서 동시에 동적영상을 6분간(5초씩 12회, 10초씩 6회, 20초씩 3회, 30초씩 6회) 획득하고 이어서 게이트 영상을 13분간 각각 획득하였다. 심근혈류의 측정은 기저부 4분절, 중간부 4분절, 그리고 심첨부로 구성된 9분절 모델을 이용하였으며, 추출한 시간-방사능곡선과 추적자 모델을 사용하여 정량화 하였다. 심근관류는 정량화 분석 소프트웨어를 사용하여 구하였다. 20분절 모델을 9분절 모델과 비교하기 위하여 최기저부 6분절은 제외하고 인접분절의 값을 평균하여 사용하였다. 결과: 심근혈류량(휴식기, 0.18-2.38 ml/min/g; 부하기, 0.4-4.95 ml/min/g)과 심근섭취율(휴식기, 22-91%; 부하기, 14-90%) 간에는 약한 상관관계가 있었으며, 휴식기 보정된 심근관류와 혈류의 상관이 부하기에서보다 더 컸다(휴식기 r=0.59, 부하기 r=0.80). 수축기 심근두꺼워짐이 좋을수록 보정된 관상동맥 혈류예비능과 심근관류 예비능이 상관관계를 보였다. 결론: $^{13}N$-암모니아를 이용한 관류값을 특성에 따라 보정하고 해석하였을 때, 동적영상에서 절대값으로 구한 심근혈류와 좋은 상관관계를 보였다. 따라서 심근관류가 심근혈류를 잘 반영하는 지표임을 보였으므로 심장질환에서의 PET-CT 검사를 유용하게 활용할 수 있을 것으로 기대한다.

• 한국미생물·생명공학회지
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• 제44권3호
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• pp.376-382
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• 2016

전국에서 수집 또는 직접 제작한 누룩의 전분 분해 효소 활성을 조사하였다. 전분을 액화시키는 효소인 α-amylase 활성은 상대습도 40%, 30℃ 조건에서 제조된 누룩이 24,747.1 ± 777.7 units/mg protein으로 가장 우수하였고, glucoamylase 효소 활성은 상대습도 50%, 25℃ 조건에서 제조된 누룩이 가장 우수하였다. 전분을 분해하는 활성이 가장 우수한 누룩으로부터 곰팡이 98점을 분리하고 동정한 결과, A. oryzae 균주 26점, R. oryzae 균주 18점을 확인하였다. MBF345 명명된 R. oryzae 균주는 α-amylase 활성이 36,724.9 ± 10.2 units/mg protein이었고, glucoamylase 효소활성은 4,911.8 ± 48.1 SP로 대조구 균주 보다 각각 1.7배, 1.4배 효소 활성이 우수한 것으로 나타났으며, 이 균주를 미생물보존센터에 R. oryzae KCTC46312 균주로 기탁하였다.

• Korean Journal of Radiology
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• 제21권1호
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• pp.58-67
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• 2020

Objective: Third-generation dual-source computed tomography (3rd-DSCT) allows dynamic myocardial CT perfusion imaging (dynamic CTP) with a 10.5-cm z-axis coverage. Although the increased radiation exposure associated with the 50% wider scan range compared to second-generation DSCT (2nd-DSCT) may be suppressed by using a tube voltage of 70 kV, it remains unclear whether image quality and the ability to quantify myocardial blood flow (MBF) can be maintained under these conditions. This study aimed to compare the image quality, estimated MBF, and radiation dose of dynamic CTP between 2ndDSCT and 3rd-DSCT and to evaluate whether a 10.5-cm coverage is suitable for dynamic CTP. Materials and Methods: We retrospectively analyzed 107 patients who underwent dynamic CTP using 2nd-DSCT at 80 kV (n = 54) or 3rd-DSCT at 70 kV (n = 53). Image quality, estimated MBF, radiation dose, and coverage of left ventricular (LV) myocardium were compared. Results: No significant differences were observed between 3rd-DSCT and 2nd-DSCT in contrast-to-noise ratio (37.4 ± 11.4 vs. 35.5 ± 11.2, p = 0.396). Effective radiation dose was lower with 3rd-DSCT (3.97 ± 0.92 mSv with a conversion factor of 0.017 mSv/mGy∙cm) compared to 2nd-DSCT (5.49 ± 1.36 mSv, p < 0.001). Incomplete coverage was more frequent with 2nd-DSCT than with 3rd-DSCT (1.9% [1/53] vs. 56% [30/54], p < 0.001). In propensity score-matched cohorts, MBF was comparable between 3rd-DSCT and 2nd-DSCT in non-ischemic (146.2 ± 26.5 vs. 157.5 ± 34.9 mL/min/100 g, p = 0.137) as well as ischemic myocardium (92.7 ± 21.1 vs. 90.9 ± 29.7 mL/min/100 g, p = 0.876). Conclusion: The radiation increase inherent to the widened z-axis coverage in 3rd-DSCT can be balanced by using a tube voltage of 70 kV without compromising image quality or MBF quantification. In dynamic CTP, a z-axis coverage of 10.5 cm is sufficient to achieve complete coverage of the LV myocardium in most patients.