• 한국발생생물학회지:발생과생식
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• 제7권1호
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• pp.29-34
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• 2003

이 연구는 자주복의 개체발생 단계에 따른 소화관 외부형태의 변화와 소화관의 발달 양상을 조직학적으로 조사하였다. 부화 직전 수정란의 소화관은 난황낭과 배체의 척추 사이에 위치하였고, 형태는 거의 직선상 이었다. 입은 부화 후 2일째, 항문은 부화 후 4일째 열렸다. 부화 후 4일째 소화관은 식도, 전장, 중장 그리고 직장으로 구분이 되었고, 전장과 중장이 괄약근에 의해 구분되었다. 부화 후 5일째 자어는 전장과 중장 사이가 배측으로 굴곡되었고, 식도상피에 점액세포가 분포하였다. 이 시기에 난황은 대부분 흡수되었다 부화 후 6일째 자어의 소화관은 전장이 두부 쪽으로 팽창하면서 U자형으로 분화하였다. 부화 후 10일 째에 팽창한 전장은 더욱 커져서 구형을 형성하였다. 부화 후 15일째 전장의 배측 부위 중간에서 함입되기 시작하여 전장이 두 부분으로 나누어졌다. 부화 후 21일째 전장의 앞부분이 팽창낭으로 분화하였다. 부화 후 24일째에 후장의 앞부분이 배측으로 다시 회전하였다. 부화 후 30일째 팽창낭은 두부 쪽과 항문 쪽으로 길게 신장되어 어미의 소화관 형태로 발달하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제8권1호
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• pp.203-210
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• 2004

1994년 Northridge 지진 이후 내진보강한 콘크리트 교량의 손상도 곡선을 유도하였고, 이 곡선을 사용하여 교각과 신축이음장치에 설치한 강재 재킷과 구속부재의 내진보강 효과를 고찰하였다. 손상도 곡선을 2변수(중간값과 대수 표준편차) 대수정규분포함수의 형태로 가정하였고, 최대지반가속도의 함수로 나타냈다. 여기서 Maximum likelihood 방법을 사용하여 대수정규분포함수의 2변수를 구하였고, FEMA SAC 프로젝트의 60개 Los Angeles 지진 시간이력을 지진해석에 사용하였다. 교각의 강재 재킷은 교량의 전반적 손상등급에서 내진보강 효과를 나타냈고, 구속부재는 낙교 등 교량의 심한 손상등급에서 효과적이었다. 여기서, 교각은 Dutta & Handel이 제시한 5개 손상등급으로 손상을 정의하였고, 신축이음장치에서는 구속부재의 파괴 및 낙교를 교량의 심각한 손상으로 규정하였다.

• 마이크로전자및패키징학회지
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• 제18권3호
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• pp.67-74
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• 2011

Keys to high wiring density semiconductor packages include flip-chip bonding and build-up substrate technologies. The current issues are the establishment of a fine pitch flip-chip bonding technology and a low coefficient of thermal expansion (CTE) substrate technology. In particular, electromigration and thermomigration in fine pitch flipchip joints have been recognized as a major reliability issue. In this paper, electromigration and thermomigration in Cu/Sn-3Ag-0.5Cu (SAC305)/Cu flip-chip joints and electromigration in Cu/In/Cu flip chip joints are investigated. In the electromigration test, a large electromigration void nucleation at the cathode, large growth of intermetallic compounds (IMCs) at the anode, a unique solder bump deformation towards the cathode, and the significantly prolonged electromigration lifetime with the underfill were observed in both types of joints. In addition, the effects of crystallographic orientation of Sn on electromigration were observed in the Cu/SAC305/Cu joints. In the thermomigration test, Cu dissolution was accelerated on the hot side, and formation of IMCs was enhanced on the cold side at a thermal gradient of about $60^{\circ}C$/cm, which was lower than previously reported. The rate of Cu atom migration was found comparable to that of electromigration under current conditions.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 추계 학술발표회논문집
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• pp.319-325
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• 2003

The fragility curves of seismic retrofitted bridges by steel jacketing of bridge columns and restrainers at expansion joints after the 1994 Northridge earthquake are developed. Fragility curves are represented by lognormal distribution functions with two parameters(fragility parameters consisting of median and log-standard deviation) and developed as a function of peak ground acceleration (PGA). Two parameters in the lognormal distribution are estimated by the maximum likelihood method. The sixty ground acceleration time histories for Los Angeles area developed for FEMA SAC project are used for the dynamic analysis of the bridges and a computer code is developed to calculate hysterestic parameters of bridge columns before and after steel jacketing. The effect of retrofit is expressed in terms of the increase of the median value of the fragility curve for the retrofitted bridge from that of the bridge before retrofit. The comparison of fragility curves of the bridges before and after column retrofit demonstrates that the improvement of the bridges with steel jacketing on the seismic performance is excellent for the damage states defined in this study. The comparison of fragility curves of the bridges before and after restrainers at expansion joints also shows the improvement in the seismic performance of restrained bridges for the severe damage states.

• 대한치과의사협회지
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• 제21권12호통권175호
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• pp.991-995
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• 1983

A radicular cyst is a slowly-growing epithelial sac lining a pathologic cavity in the bone at the apex of a tooth. Large radicular cyst revealed by radiographic examination almost always appear to involved several teeth. The author observed a 31 year old woman with a labial swelling and palatal mucosal expansion of the maxillary anterior region. Radiographic examination indicated that the lesion extended from the left maxillary lateral incisor to the right lateral incisor. Cyst consisted of tan to gray yellow slightly firm to partly hard plaque like tissue measuring 3.4 x 2.2 x 0.3㎝. The author has treated the cyst by means of enucleation with apicoecomies of the involved teeth except the right central incisor. Recovery proceed satisfactorily and there were no clinical or radiologic signs of recurrence 8 months later.

• 보험의학회지
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• 제3권1호
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• pp.90-102
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• 1986

The gallbladder is a pear-shaped, thin walled sac located on the inferior surface of the liver between the right and quadrate lobe, in a recess called fossa vesicae felleae. It is 7.5cm-12.5 cm in length, 3.5 cm in the largest width, and has a volume of about 45 ml with a remarkable capacity for expansion. There are many kinds of diagnostic methods to evaluate diseases of biliary tract including gallbladder-Plain abdomen, Oral cholecystography. Intravenous cholangiography, Percutaneous transhepatic cholangiography(PTC), Endoscopic retrograde cholangiography(ERCP), Operative or T-tube cholangiography, Ultrasonography, Radioisotope study, Computed tomography, and Angiography. Especially, ultrasonography is the most effective and noninvasive study in these days. Plain abdomen, oral cholecystography, intravenous cholangiography, and ultrasonography have been performed in our clinic. Methods and findings of above mentioned study are discussed with consideration of references.

• 대한소아치과학회지
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• 제25권3호
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• pp.613-618
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• 1998

A dentigerous cyst is an epithelium-lined sac that surrounds the crown of an impacted, embedded, or unerupted tooth. Many surgical procedures have been described for the elimination of dentigerous cyst, but they can be devided into two basic group: enucleation and marsupialization. Marsupialization is a conservative technique which allows the reduction or elimination of a cystic lesion by making it an accessory compartment to the oral cavity and it is the best way to conserve a tooth affected by dentigerous cyst and to permit its eruption, especially in young patient. After using marsupialization to treat dentigerous cyst associated with the crown of unerupted premolar in young patient, the results were as follows: 1. Reduction of bony expansion and rapid bone regeneration without infection and recurrence were observed. 2. Normally spontaneous eruption of involved teeth were permitted, as well as loss of affected tooth was avoided. 3. Follow-up examinations revealed no complication and recurrence.

• 한국초전도ㆍ저온공학회논문지
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• 제14권4호
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• pp.24-27
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• 2012

The measurement of the coefficient of thermal expansion (CTE) of polypropylene laminated paper (PPLP) as electric insulating material is important for its practical superconducting device application. The thermal strain induced to HTS tapes and its insulating material during cooling from room temperature might largely affect the critical current ($I_c$) of HTS tapes. In this study, the thermal contraction of PPLP material was measured during cooling from 300 K to 77 K using double extensometers. Initially, the CTE of a brass tape was measured and it was compared with a reference data. It was found that the measured thermal expansion data of the brass material approaches that of the reference one. Based on the results, it was then confirmed that the measurement technique could be applied to thin and flexible samples. Therefore, the same measurement procedure was applied to PPLP material using double extensometers. As a result, the linear CTE of the PPLP at 77 K has been measured to be ${\sim}15.3{\times}10^{-6}/K$. Also, it was found that the thermal contraction characteristics of PPLP was dominated by polypropylene on the cross direction (higher thermal contraction) while it was dominated by Kraft paper on the machine direction (lower thermal contraction). Overall, this measurement procedure could be adopted for the determination of CTE of flexible materials such as PPLP.

• Journal of Welding and Joining
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• 제32권3호
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• pp.74-80
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• 2014

Due to environmental regulations (RoHS, WEEE and ELV) of the European Union, electronics and automotive electronics have to eliminate toxic substance from their devices and system. Especially, reliability issue of lead-free solder joint is increasing in car electronics due to ELV (End-of-Life Vehicle) banning from 2016. We have prepared engine control unit (ECU) modules soldered with Sn-40Pb and Sn-3.0Ag-0.5Cu (SAC305) solders, respectively. Degradation characteristics of solder joint strength were compared with various conditions of automobile environment such as cabin and engine room. Thermal cycle test (TC, $-40^{\circ}C$ ~ ($85^{\circ}C$ and $125^{\circ}C$), 1500 cycles) were conducted with automotive company standard. To compare shear strength degradation rate with eutectic and Pb-free solder alloy, we measured shear strength of chip components and its size from cabin and engine ECU modules. Based on the TC test results, finally, we have known the difference of degradation level with solder alloys and use environmental conditions. Solder joints degradation rate of engine room ECU is superior to cabin ECU due to large CTE (coefficient of thermal expansion) mismatch in field condition. Degradation rate of engine room ECU is 50~60% larger than cabin room electronics.

• 한국초전도ㆍ저온공학회논문지
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• 제14권3호
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• pp.48-52
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• 2012

This paper describes experimental study on the orientation dependence of GM-type pulse tube refrigerator with helium and neon as working gas. A pulse tube refrigerator generates refrigeration work with gas expansion by gas displacer in the pulse tube. The pulse tube is only filled with working gas and there exists secondary flow due to large temperature difference between cold-end and warm-end. The stability of secondary flow is affected by orientation of cold-head and thus cooling performance is deteriorated by gas mixing due to secondary flow. In this study, a single stage GM-type pulse tube with orifice valve as a phase control device is fabricated and tested. The fabricated pulse tube refrigerator is tested with two different working gases of helium and neon. First, optimal valve opening and operating frequency are determined with experimental results of no-load test. And then, the variation of no-load temperature as orientation angle of cold-head is measured for two different working gases. Effect of orientation dependence of cold-head as working gas is discussed with experimental results.