• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.161-168
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• 2011

Cerebral aneurysm mostly occurs at a bifurcation of the circle of Willis. When the cerebral aneurysm is ruptured a disease like subarachnoid hemorrhage and stroke is caused and this can be even deadly for patients. Generally it is known that causes of the intracranial aneurysm are a congenital deformity of the artery and pressure or shear stress from the blood flow. A blood flow pattern and the geometry of the blood vessel are important factors for the aneurysm formation. Research for several hemodynamic indices has been performed and these indices can be used for the prediction of aneurysm initiation and rupture. Therefore, the numerical analysis was performed for hemodynamic characteristics of the blood flow through the cerebral artery applying the various bifurcation angle and flow rate ratio. We analyze the flow characteristics using indices from the results of the numerical simulation. In addition, to investigate the flow pattern in the aneurysm according to the bifurcation angle and the flow rate ratio, we performed the numerical simulation on the supposition that the aneurysm occurs.

• Journal of Pharmaceutical Investigation
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• 제19권2호
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• pp.99-107
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• 1989

In order to develop a pediatric liquid preparation with sustained release properties, dextromethorphan hydrobromide (DEXT) was complexed with strong cation exchange resin (CG 120) and the-complex was coated with Eudragit RS using a phase separation method by non-solvent addition. The effect of pH, ionic strength of the release medium and drug/resin ratio on the release rate of DEXT was studied. The release rate of free drug from the uncoated complex, and coated complexes with 9.5 and 18.5% Eudragit RS in artificial gastric juice were measured. The release rate from the uncoated complex was faster with higher pH, higher ionic strength of the release medium and higher drug/resin ratio. The release rate from the coated complex could be controlled by the amount of coating material, and the surface after release did not rupture into.

• Geomechanics and Engineering
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• 제29권4호
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• pp.451-461
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• 2022

The roadways surrounded by rock and coal will lose their stability or even collapse under rock burst. Rock burst mainly involves an evolution of dynamic loading which behaves quite differently from static or quasi-static loading. To compare the dynamic response of coal and rocks with different static strengths, three different rocks and bituminous coal were selected for testing at three different dynamic loadings. It's found that the dynamic compression strength of rocks and bituminous coal is much greater than the static compression strength. The dynamic compression strength and dynamic increase factor of the rocks both increase linearly with the increase of the strain rate, while those of the bituminous coal are irregular due to the characteristics of multi-fracture and heterogeneity. Moreover, the absorbed energy of the rocks and bituminous coal both increase linearly with an increase in the strain rate. And the ratio of absorbed energy to the total energy of bituminous coal is greater than that of rocks. With the increase of dynamic loading, the failure degree of the sample increases, with the increase of the static compressive strength, the damage degree also increases. The static compassion strength of the bituminous coal is lower than that of rocks, so the number of small-scale fragments was the largest after bituminous coal rupture.

• Journal of Chest Surgery
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• 제37권5호
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• pp.401-409
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• 2004

배경 : 승모판막 폐쇄부전증의 원인 중 건삭이나 유두근 파열이 원인이 되는 예가 증가됨에 따라 승모판막에 대한 수술, 특히 판막 재건술의 임상적 역할이 중요시되고 있다. 이에 본원에서 시행한 승모판막 폐쇄부전증의 수술적 치료에 따른 임상결과 및 술 후 조기 성적을 분석해 보았다. 대상 및 방법: 1991년 8월부터 2002년 4월까지 승모판막 건삭 및 유두근 파열로 인해 본원에서 수술한 승모판막 폐쇄부전증 환자 49명(남 26명, 여 23명, 나이 49.0$\pm$16.5세)을 대상으로 시행하였다. 수술적 방법에 있어서는 22명(44.9%)에서 판막성형술을, 나머지 27명(59.2%)에서는 판막치환술을 시행하였다 결과: 전체수술예에서 승모판막 전엽의 건삭파열은 23예, 후엽의 건삭파열은 31예였으며 전외(Anter-olateral)유두근의 파열이 2예, 후외(Posteromedial)유두근파열이 1예였다 승모판막 건삭 및 유두근 파열의 병리조직학적 원인은 비특이적 변성이 25예(51.0%), 점액성 변성이 11예(22.4%), 아급성세균성 심내막염이 7예(14.3%)였다. 특발성 퇴행성 변성에 의한 건삭 파열의 경우 전엽보다는 후엽에 많았으며 전엽에서는 A3 구역, 후엽에서는 P3 구역에서 빈발하였다. 수술사망은 3명(6.1%)이었으며 1명의 환자에서 판막재건술 시행 후 잔존 승모판막 폐쇄부전으로 인해 판막치환술을 재시행하였다. 전체 승모판막 폐쇄부전환자의 술 후 5년 생존율은 81.4%였다. 승모판막 폐쇄부전의 원인이 퇴행성 병변이었던 환자 36명에 대해서 판막재건술을 시행한 군과 판막치환술을 시행한 군 사이의 수술결과를 비교 분석한 결과, 수술사망률은 각각 0%와 14.3%였고 술 후 5년 생존율은 90.2%와 64.3%로 판막재건술을 시행했던 환자에서 높게 나타났으나 두 군 사이의 통계학적 의의는 보이지 않았다. 결론: 건삭파열 및 유두근 파열로 인한 승모판막 폐쇄 부전의 가장 많은 병리조직학적 원인은 비특이적 변성이었다. 또한 판막 폐쇄 부전의 원인이 승모판막의 퇴행성 병변일 경우에 수술적 방법으로서 승모판막 재건술은 그 장기 성적이 양호하고 수술적 결과가 승모판막 치환술과 비교적 우월한 차이를 보이므로 승모판막 폐쇄 부전의 수술적 치료에 있어서 가장 좋은 방법이라 생각한다.

• 콘크리트학회논문집
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• 제23권5호
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• pp.551-558
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• 2011

경량 골재 콘크리트의 역학적 특성에 대한 천연모래 치환율과 경량 굵은 골재 최대 크기의 영향을 평가하기위해 15배합의 실험이 진행되었다. 경화된 경량 골재 콘크리트의 공극률 및 기건 단위 질량, 재령에 따른 압축강도 발현, 인장저항성능, 탄성계수, 파괴계수 및 응력-변형률 관계를 측정하였다. 측정된 역학적 특성들은 ACI 318-08, EC2 및 CEB-FIP 기준 또는 Slate 등, Yang 등 및 Wang 등의 제안모델들과 비교하였다. 실험 결과 경량 골재 콘크리트의 압축강도는 굵은 골재 최대 크기가 클수록 그리고 경량 잔골재 양이 증가할수록 감소하였다. 경량 골재 콘크리트의 압축강도 발현에 대한 상수는 굵은 골재의 비중과 천연모래 치환율의 함수로서 제시될 수 있었다. 한편, 측정된 경량 콘크리트의 파괴계수 및 인장강도는 설계기준 및 제안모델들에 비해 일반적으로 낮았는데, 이는 경량 콘크리트의 인장저항성은 압축강도뿐만 아니라 기건 단위 질량에 의해서도 영향을 받기 때문이다.

• Structural Engineering and Mechanics
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• 제89권6호
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• pp.617-626
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• 2024

The study investigated the behavior of plain and fibered Ultra-High Performance Concrete (UHPC) beams under varying loading conditions using integrated analysis of the flexure and acoustic emission tests. The loading rate of testing is -0.25 -2 mm/min. It is observed that on increasing loading rate, flexural strength increases, and toughness decreases. The acoustic emission testing revealed that higher loading rates accelerate crack propagation. Fiber effect and matrix cracking are identified as significant contributors to the release of acoustic emission energy, with fiber rupture/failure and matrix cracking showing rate-dependent behavior. Crack classification analysis indicated that the rise angle (RA) value decreased under quasi-static loading. The average frequency (AF) value increased with the loading rate, but this trend reversed under rate-dependent conditions. K-means analysis identified distinct clusters of crack types with unique frequency and duration characteristics at different loading rates. Furthermore, the historic index and signal strength decreased with increasing loading rate after peak capacity, while the severity index increased in the post-peak zone, indicating more severe damage. The sudden rise in the historic index and cumulative signal strength indicates the possibility of several occurrences, such as the emergence of a significant crack, shifts in cracking modes, abrupt failure, or notable fiber debonding/pull-out. Moreover, there is a distinct rise in the number of AE knees corresponding to the increase in loading rate. The crack mapping from acoustic emission testing aligned with observed failure patterns, validating its use in structural health monitoring.

• 한국해양공학회지
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• 제6권1호
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• pp.78-86
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• 1992

The creep behaviors of 1%Cr-Mo-V and 12%Cr steam turbine rotor steels under static or cyclic load were examined at 600 and $700^{\circ}C$. The relationship between these two kinds of phenomena was studied and the experimental results were summarized as follows: 1) It is confirmed that the cyclic creep strain dependent on time is more available for creep, behavior analysis according to frequency change than that dependent on number of cycles, and the static creep, the special case of cyclic creep with stress ratio of 1 can be also more effectively analyzed by time-dependence. 2) The steady cyclic creep rate vs. the steady static creep rate, increases according to the increase of stress ratio, and this phenomena may occur on occasion of the decrease of the internal stress. 3) The initial strain affects on all the creep properties of the transient region, the steady state region and the rupture time in cyclic creep as well as static creep, and the quantitative relationships among them exist.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.35-40
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• 2002

In the present study, we examined the influence of prestrain on creep strength of Class M alloy(STS310S) and Class A(STS310J1TB) alloys containing precipitates. Prestrain was given by prior creep at a higher stress than the following creep stresses. Creep behaviour before and after stress change and creep rate of pre-strianed specimens were compared with that of virgin specimens. Pre-straining produced the strain region where the strain rate was lower than that of a virgin specimen both for STS310J1TB and STS310S steels. The reason for this phenomenon was ascribable to the viscous motion of dislocations, the interaction between dislocations and precipitates in a STS310J1TB steel, and the interaction of dislocations with sub-boundaries in a STS310S steel which has the higher dislocation density and smaller subgrain size resulted from pre-straining at higher stress.

• 한국정밀공학회지
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• 제30권8호
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• pp.809-814
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• 2013

The relationship between the small-punch creep test and the conventional creep test was investigated experimentally using a method similar to that of the Monkman-Grant relationship. Uniaxial and small-punch creep rupture tests were carried out on 9Cr-2W ferritic steel (Commercial Grade 92 steel: X10CrWMoVNb 9-2) at elevated temperatures. From the relation derived in the same manner as the Monkman-Grant relation, a correlation between the displacement rate in response to the small-punch creep test and the strain rate in the uniaxial creep test was found, and the creep life was calculated using this relation. Furthermore, the failure modes of the small punch creep test specimens were investigated to show that the fracture was caused by creep.

• Journal of Chest Surgery
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• 제25권1호
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• pp.96-104
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• 1992

The 242 patients were operated due to chronic empyema in Hanyang University Hospital From Jan, 1983 to Aug, 1991, we operated 17 patients by modified.Schede`s thoracoplasty with myoplasty and we concluded to next scentences. 1. The age of patients were varied from 28 to 65[Average 39.1] and male preponderance was seen[more than 3 times]. 2. The preoperative cause of disease were tuberculosis in 14 patients[3 patients were associated with aspergillosis, and 1 patient was associated vrith actinomycosis], lung abscess in 2 patients, and haemophilia in 1 patient. 3. The Preoperative duration of empyema were varied from 1 month to 30 years[Average 49.8 month], and the duration from pulmonary resection to thoracoplasty were 1 month to 13.5 years[Average 55 month] except 3 patients, who were operated pneunectomy with thoracoplasty at the same time. 4. The total number of thoracoplasty were 19, because in 2 patients, we operated 2 steps, and we failed in 6 cases, so the success rate was 68.5%. 5. In failure analysis of 6 cases, the cause were obliteration failure in 3 cases, inadequete drainage in 1 case, and in the other 1 case was mixed type. 6. From 1990 to 1991, there were no death associated with operation and there were 1 failure, so the success rate was greatly improved. 7. The bronchopleural fistula or spontaneous rupture of trachea were seen in 12 cases, and the success rate was high in absent cases.