• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1686-1704
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• 2021

This study addresses the numerical simulation of the shield building of an AP1000 nuclear power plant (NPP) subjected to a large commercial aircraft impact. First, a simplified finite element model (F.E. model) of the large commercial Boeing 737 MAX 8 aircraft is established. The F.E. model of the AP1000 shield building is constructed, which is a reasonably simplified reinforced concrete structure. The effectiveness of both F.E. models is verified by the classical Riera method and the impact test of a 1/7.5 scaled GE-J79 engine model. Then, based on the verified F.E. models, the entire impact process of the aircraft on the shield building is simulated by the missile-target interaction method (coupled method) and by the ANSYS/LS-DYNA software, which is at different initial impact velocities and impact heights. Finally, the laws and characteristics of the aircraft impact force, residual velocity, kinetic energy, concrete damage, axial reinforcement stress, and perforated size are analyzed in detail. The results show that all of them increase with the addition to the initial impact velocity. The first four are not very sensitive to the impact height. The engine impact mainly contributes to the peak impact force, and the peak impact force is six times higher than that in the first stage. With increasing initial impact velocity, the maximum aircraft impact force rises linearly. The range of the tension and pressure of the reinforcement axial stress changes with the impact height. The perforated size increases with increasing impact height. The radial perforation area is almost insensitive to the initial impact velocity and impact height. The research of this study can provide help for engineers in designing AP1000 shield buildings.

• Applied Biological Chemistry
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• 제34권4호
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• pp.379-385
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• 1991

12품종의 쌀로 부터 분리 정제한 전분의 2.5% (w/v) 현탁액을 각각 $65^{\circ}C$에서 $95^{\circ}C$까지 $5^{\circ}C$ 간격으로 30분간 가열 조리한 후, 전분 입자들의 형태학적 변화를 주사현미경으로 관찰 하였다. 품종에 관계없이 쌀 전분 입자들은 온도가 증가함에 따라 점진적인 형태학적 변화를 보여주었다. 이들 형태학적 변화는 전분의 팽윤도, 용해도 및 아밀로그라프점성 특성등과 밀접한 연관성을 보였다. 전분 입자로 부터 가용성 물질이 용출되는 것과 팽윤된 전분 입자가 그 자체의 독특한 형태를 잃고 서로 망상구조로 연결되면서 이들 리올로지 특성들의 급격한 증가를 가져왔다. 초기 팽윤 단계에서 전분 입자들의 독특한 구조손실 시기는 각각의 호화온도에 영향을 받았다. 호화 온도 이상의 높은 온도에서 전분 입자들이 삼차원적 망상구조를 형성하는 정도는 아밀로오스 함량이 감소할 수록 망상구조가 더 세밀해지며, 증가하는 경향을 보였다.

• 대한기관식도과학회지
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• 제9권1호
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• pp.30-38
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• 2003

Cancers of the cervical esophagus occur uncommonly, but treatment is remaining a challenging problem and surgery demands special knowledge of abdominal, thoracic, and neck surgery. The primary risk factor is chronic heartburn, leading to a sequence of esophagitis, Barrett's esophagus, reflux esophagitis and etc. Among the various treatment modalities, Surgery is still a mainstay of treatment. The main aim of surgery is not only oncologically adequate resection but also preservation or restoration of physiologic functions, such as deglutition and phonation. Surgical treatment of cervical esophageal cancer is influenced by special problems arising from tumor factors, patient factors and surgeon factors. Complete clearance of loco-regional disease and prevention of postoperative complications are of particular importance for the improvement of long-term survival in patients with these cancers. So the cervical and thoracic extension of these tumors usually required an extensive lymphadenectomy with primary resection. Radical resection of the primary site almostly include sacrifice of the larynx, but the voice could be rehabilitated with various methods, such as tracheoesophageal prosthesis or tracheoesophageal shunts, etc. Restoration of the esophageal conduit can be performed using gastric or colon interposition, radial forearm free flap or jejunum free flap, etc. Recently, the advances of radiation therapy and chemotherapy will enable less extended resections with greater rates of laryngeal preservation. At initial presentation, up to 50％ to 70％ of patients will have advanced locoregional or distant disease with virtually no chance for cure. Patients with advanced but potentially resectable esophageal cancer are generally treated by surgery with some form of neoadjuvant chemotherapy, radiotherapy, or both, with 5-year survivals in the 20％ to 30％ range. So the significant adverse factors affecting survival should be taken into account to select the candidates for surgery.

• 한국농공학회지
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• 제39권4호
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• pp.106-113
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• 1997

Dynamic loading of structures often causes excursions of stresses well into the inelastic range, and the influence of the geometric changes on the dynamic response is also significant in many cases. Therefore, both material and geometric nonlinearity effects should be considered in case that a dynamic load acts on the structure. A structure in a nuclear power plant is a structure of importance which puts emphasis on safety. A nuclear container is a pressure vessel subject to internal pressure and this structure is constructed by a reinforced concrete or a pre-stressed concrete. In this study, the material nonlinearity effect on the dynamic response is formulated by the elasto-viscoplastic model highly corresponding to the real behavior of the material. Also, the geometrically nonlinear behavior is taken into account using a total Lagrangian coordinate system, and the equilibrium equation of motion is numerically solved by a central difference scheme. The constitutive relation of concrete is modeled according to a Drucker-Prager yield criterion in compression. The reinforcing bars are modeled by a smeared layer at the location of reinforcements, and the steel layer model under Von Mises yield criteria is adopted to represent an elastic-plastic behavior. To investigate the dynamic response of a nuclear reinforced concrete containment structure, the steel-ratios of 0, 3, 5 and 10 percent, are considered. The results obtained from the analysis of an example were summarized as follows 1. As the steel-ratio increases, the amplitude and the period of the vertical displacements in apex of dome decreased. The Dynamic Magnification Factor(DMF) was some larger than that of the structure without steel. However, the regular trend was not found in the values of DMF. 2. The dynamic response of the vertical displacement and the radial displacement in the dome-wall junction were shown that the period of displacement in initial step decreased with the steel-ratio increases. Especially, the effect of the steel on the dynamic response of radial displacement disapeared almost. The values of DMF were 1.94, 2.5, 2.62 and 2.66, and the values increased with the steel-ratio. 3. The characteristics of the dynamic response of radial displacement in the mid-wall were similar to that of dome-wall junction. The values of DMF were 1.91, 2.11, 2.13 and 2.18, and the values increased with the steel-ratio. 4. The amplitude and the period of the hoop-stresses in the dome, the dome-wall junction, and the mid-wall were shown the decreased trend with the steel-ratio. The values of DMF were some larger than those of the structure without steel. However, the regular trend was not found in the values of DMF.

• 한국구조물진단유지관리공학회 논문집
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• 제8권1호
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• pp.183-194
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• 2004

연약점토지반의 압밀거동 예측시, 압축성과 투수성에 대한 비선형 물질함수 특성을 규명하는 것은 가장 중요하며 기본적인 선행 연구내용이라 할 수 있다. 본 연구에서는 압축성과 투수성에 대한 물질함수 특성을 파악하기 위해 해성점토를 이용한 실내 시험을 실시하였다. 실내시험은 수직배수조건 및 수평배수조건, 수직 수평배수조건으로 구분하되 표준압밀 시험과 로우셀 시험등을 실시하였다. 수평배수조건에 대한 물질함수 특성을 파악하기위한 개량 표준압밀 시험장치를 개발하였으며, 시료교랸영항을 최소화하기위한 별도의 시료추출장치를 고안하였다. 또한 로우셀 시험결과와의 비료를 통해, 시험법에 있어 비교적 간편한 개량 표준압밀 시험결과의 신뢰도를 확인할 수 있었다. 모든 시험결과를 통한 유효응력-간극비-투수계수등에 관한 물질함수 특성을 분석한 결과, 유효응력 단계별 간극비 분포는 누승함수의 형태로 표현될 수 있으며, 간극비 단계별 투수계수는 지수함수의 형태로 표현됨을 확인할 수 있었다. 초기함수비가 높고 전단강도가 작은 연약점토의 경우, 유효응력단계별 압축성과 투수성의 비선형성이 매우 크게 나타났으며, 연약 점토지반의 압밀현상 예측에 있어 이러한 비선형성은 무시할 수 없는 큰 영향요소임을 알 수 있었다.

• 대한치과보철학회지
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• 제31권4호
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• pp.482-505
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• 1993

The purpose of this study was to evaluate the fracture characteristics and the effect of resin bonding of laminate porcelain. In order to characterize the indentation-induced crack, Young's moduli and characteristic indentation dimensions were measured. The fatigue life under three point flexure test was measured using the electro-dynamic type fatigue machine, and the crack propagation with thermocycling was investigated on the condition of 15 second dwell time each in $5^{\circ}C\;and\;55^{\circ}C$ bath. The Vickers indentation pattern and the fracture surface were examined by an optical microscope and a scanning electron microscope (SEM). The results obtained were summarized as follows ; 1. Young's moduli(E) of the laminate porcelain and the resin cement used in this experiment were $62.56{\pm}3.79GPa$ and $15.01{\pm}0.12GPa$, respectively. 2. The initial crack size of the laminate porcelain was $69.19{\pm}5.94{\mu}m$ when an indentation load of 9.8N was applied, and the fracture toughness was $1.065{\pm}0.156MPa\;m^{1/2}$. 3. The fatigue life of laminate porcelain showed the constant fracture range at the stress level 27.46-35.30MPa. 4. When a cyclic flexure load was applied, the fatigue life of resin-bonded laminate porcelain was more decreased than that of laminate porcelain. 5. When a thermocycling was conducted, the crack growth rate of resin-bonded laminate porcelain was more increased than that of laminate porcelain. 6. Fracture surface showed the radial crack, the lateral crack, and the macroscopic crack branching region beneath the plastic deformation region when an indentation load of 9.8N was applied.

• Archives of Reconstructive Microsurgery
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• 제22권1호
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• pp.24-28
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• 2013

Purpose: Soft tissue defect of the hand, which cannot be covered with skin graft or local flap, is usually reconstructed using a free flap. Temporoparietal fascial free flap is one of the best alternatives for functional reconstruction of the hand with exposed tendons, bones, and joints. Materials and Methods: We have experienced four cases of reconstruction using a temporoparietal fascial flap with a skin graft and followed up for 20 years. We conducted a retrospective review of the patients' clinical charts and photos. Results: At the time of initial injury, the average age of patients was 50.3 (39~62) years. The radial artery was used for reconstruction of the dorsal side of the hand, whereas the ulnar artery was used for that of the volar side of the wrist. Short term complication such as skin graft loss and donor site alopecia occurred. However, during the long term follow-up period, no change of flap volume was noted, and full range of motion in the adjacent joint was maintained. In addition, hyperpigmentation of the grafted skin on the flap disappeared gradually. Conclusion: Selection of the optimal flap is important for reconstruction of the hand without functional limitation. We obtained satisfactory soft tissue coverage and functional outcomes using a temporoparietal fascial free flap and followed up for 20 years.

• 한국재료학회지
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• 제8권8호
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• pp.678-684
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• 1998

정압분자동역학 시뮬레이션에 의하여 주기경계조건을 지닌 L-J 입자들로 구성된 계의 액체-유리-결정 전이를 연구하였다. 원자체적과 엔탈피는 가열 및 냉각과정에서 온도의 함수로 계산되었다. 반경분포함수로부터 유도된 Wendt-Abraham비와 단거리규칙도를 나타내는 각도분포함수를 분석하여 액체, 유리 및 결정상태를 구분하였다. 초기 fcc 결정을 가열하여 얻은 액체상은 급냉시에 비정질화하나 서냉시엔 결정화하였다. 급냉으로 생긴 유리는 다시 서서히 가열하면 fcc로 결정화하였다. 자유표면을 지닌결정은 표면에서부터 용해가 시작되어 벌크에 비하여 낮은 온도에서 녹고 냉각시에는 빠른 냉각속도에서도 결정화가 쉽게 일어나는 경향을 보였다.

• 대한치과교정학회지
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• 제51권2호
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• pp.77-85
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• 2021

Objective: To evaluate the accuracy of a multi-stage convolutional neural network (CNN) model-based automated identification system for posteroanterior (PA) cephalometric landmarks. Methods: The multi-stage CNN model was implemented with a personal computer. A total of 430 PA-cephalograms synthesized from cone-beam computed tomography scans (CBCT-PA) were selected as samples. Twenty-three landmarks used for Tweemac analysis were manually identified on all CBCT-PA images by a single examiner. Intra-examiner reproducibility was confirmed by repeating the identification on 85 randomly selected images, which were subsequently set as test data, with a two-week interval before training. For initial learning stage of the multi-stage CNN model, the data from 345 of 430 CBCT-PA images were used, after which the multi-stage CNN model was tested with previous 85 images. The first manual identification on these 85 images was set as a truth ground. The mean radial error (MRE) and successful detection rate (SDR) were calculated to evaluate the errors in manual identification and artificial intelligence (AI) prediction. Results: The AI showed an average MRE of 2.23 ± 2.02 mm with an SDR of 60.88% for errors of 2 mm or lower. However, in a comparison of the repetitive task, the AI predicted landmarks at the same position, while the MRE for the repeated manual identification was 1.31 ± 0.94 mm. Conclusions: Automated identification for CBCT-synthesized PA cephalometric landmarks did not sufficiently achieve the clinically favorable error range of less than 2 mm. However, AI landmark identification on PA cephalograms showed better consistency than manual identification.

• Journal of Astronomy and Space Sciences
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• 제26권1호
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• pp.89-98
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• 2009

이 연구에서는 SLR(Satellite Laser Ranging) NP (Normal Point) 데이터를 이용하는 인공위성 정밀궤도 결정 시스템 YLPODS(Yonsei Laser-ranging Precision Orbit Determination System)를 개발하였다. 먼저, 개발된 YLPODS의 성능 검증을 위해서 저궤도 위성인 TOPEX/POSEIDON과 CHAMP의 SLR NP 데이터를 사용한 궤도결정 시험을 수행하였다. JPL에서 배포하는 정밀궤도력을 참값으로 가정하고, 거리측정잔차(range residual)의 RMS(Root Mean Square) 및 결정된 궤도의 반경(radial), 진행(along-track), 교차(cross-track) 방향 오차를 확인하였다. 그리고 거리측정잔차 확인을 통해 검증된 YLPODS의 거리계산 정밀도와 SLR NP 데이터의 높은 거리측정 정밀도를 이용하여, 관측된 값(O)과 계산된 값(C)을 비교하는 방법으로 GPS(Global Positioning System) 데이터를 이용하는 GPS 기반 POD 시스템 결과의 정밀도 검증을 수행하였다. 검증을 위한 GPS 기반 POD 시스템 결과는 YGPODS(Yonsei GPS-based Precision Orbit Determination System)의 TOPEX/POSEIDON위성 POD 결과가 사용되었다. 관측된 값과 계산된 값의 비교(O-C)를 위해서 GPS 기반 POD 시스템 결과로부터 획득된 궤도 정보를 YLPODS의 초기 궤도로 사용하고, 첫 번째 반복 후 얻어진 거리측정잔차를 확인해 보았다. YLPODS의 궤도결정 수행 결과 TOPEX/POSE)DON과 CHAMP 위성 모두 거리측정잔차가 10cm 미만, 각 방향 오차가 1m 수준의 정밀도를 가지는 것을 확인하였다. GPS 기반 POD 시스템 결과에 대한 정밀도 검증 결과 TOPEX/POSEIDON위성의 경우 거리측정잔차가 10cm 미만으로 나오는 것을 확인하였다. YLPODS의 궤도결정 수행 결과에 비추어볼 때 GPS 기반 POD시스템 결과의 각 방향 궤도 정밀도가 1m 수준이 될 것을 예상해볼 수 있고, 실제로 JPL 정밀궤도력과 비교했을 때 1m 수준의 궤도 정밀도를 가지는 것을 확인할 수 있었다. 결과적으로 이 연구를 통해서 개발된 YLPODS는 향후 수행될 과학기술위성 2호와 다목적 실용위성 5호와 같은 SLR 데이터 획득이 가능한 위성의 SLR 기반 POD 및 GPS 기반 POD 결과 검증에 활용될 수 있을 것이다.