• Journal of Biomedical Engineering Research
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• v.21 no.4
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• pp.391-401
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• 2000

Flow through compliant tubes with linear taper in wall thickness is numerically simulated by finite element analysis. For verification of the numerical method, flow through a compliant stenotic vessel is simulated and the results are compared to the existing experimental data. Steady two-dimensional flow in a collapsible channel with initial tension is also simulated and the results are compared with numerical solutions from the literature. Computational results show that as cross-sectional area decreases with the reduction in downstream pressure, flow rate increases and reaches the maximum when the speed index (mean velocity divided by wave speed) is near the unity at the point of minimum cross-section area, indicating the flow limitation or choking (flow speed equals wave speed) in one-dimensional studies. for further reductions in downstream pressure, flow rate decreases. The flow limitation or choking consist of the main reasons of waterfall effect which occurs in the airways, capillaries of lung, and other veins. Cross-sectional narrowing is significant but localized. When the ratio of downstream-to-upstream wall thickness is 2, the area throat is located near the downstream end. As this ratio is increased to 3, the constriction moves to the upstream end of the tube.

• Journal of the Society of Disaster Information
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• v.13 no.3
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• pp.366-375
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• 2017

Internal factors having effects on compressive strength test results of concrete include size, shape, height-diameter ratio(h/d), section processing method, dryness and wetness, etc. of the specimen. As it is difficult to ensure dimensions of core specimen due to rebar cutting from rebar spacing, wall thickness, effects on the structure, etc. when taking core of the concrete structure, correction of dimensions and h/d of the specimen become important for quality control of the concrete. Thus, in order to review effects of specimen size and height-diameter ratio for the concretes with compressive strength within 40~60MPa, this study has experimentally reviewed compressive strength test values by applying correction factors pursuant to KS F 2422 (Method of obtaining and testing drilled cores and sawed beams of concrete), when changing specimen diameter to ${\emptyset}5{\sim}15cm$, and h/d to 2.0~1.25.

• Composites Research
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• v.20 no.3
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• pp.8-16
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• 2007

Bending collapse of light-weight square tubes used for vehicle structure components is a dominant failure mode in oblique collision and rollover of vehicles. In this paper bending performances of aluminum-GFRP hybrid tube beams were evaluated in relation with bending deformation behavior and energy absorption characteristics. Aluminum/GFRP hybrid tube beams fabricated by inserting adhesive film between prepreg and metal layer were used in the bending test. Failure mechanisms of hybrid tubes under a bending load were experimentally investigated to analyze the bending performance as a function of ply orientation and composite layer thickness. Ultimate bending moments and energy absorption capacity of hybrid tube beams were obtained from the measured load-displacement corves. It was found that aluminum/GFRP hybrid tubes could be converted to rather stable collapse mode showing excellent energy absorption capacity in comparison to the pure aluminum tube beams. In particular, the hybrid tube beam with $[0^{\circ}/90^{\circ}]s$ composite layer showed a large improvement by about 78% in energy absorption capacity and by 29% in specific energy absorption.

• Journal of the Korean Geosynthetics Society
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• v.5 no.2
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• pp.23-30
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• 2006

This paper aims at investigating the material and dimensions of a wall barrier such as installation depth, thickness, and distance from vibration source by means of finite element method (FEM). In this study, various materials such as concrete, EPS, and steel were adopted. The results showed that the efficiency of a wall barrier appears to be more dependent on installation depth than thickness. In addition, a concrete wall barrier is less efficient than any other wall barrier. In contrast, EPS wall barriers seem to be much sensitive to the wall thickness than the depth.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.5
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• pp.584-590
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• 2012

The structural and functional disorder of a detrusor induces a bladder hypertrophy and degenerates a bladder muscle gradually by preventing normal urination. Thus, the thickness of the bladder wall has been increased in proportion to the degree of bladder outlet obstruction. In this study, the mechanical characteristics of the detrusor is analyzed for the physical properties and the thickness changes of the bladder muscle using a mathematically analytic method. In order to obtain the mechanical property of the bladder muscle, the tensile test of porcine bladder tissue is performed because its property is similar to that of human. The result of tensile test is applied to the mathematically model as Mooney Rivlin coefficients which represent the hyperelastic material. The model of the bladder is defined as the spherical shape with the initial volume of 50ml. The principal stress and strain according to the thickness are analyzed. Also, computer simulations for three types of the material property for the model of the bladder are performed based on the fact that the stiffness of the bladder is weakened as the progress of the benign prostatic hyperplasia. As a result, the principal stress is 341kPa at the initial thickness of 2.2mm, and is 249kPa at 6.5mm. As the bladder wall thickness increases, the principal stress decreases. The principal stress and strain decrease as the stiffness of the bladder decreases under the same thinkness.

• Journal of Radiation Protection and Research
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• v.25 no.1
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• pp.3-9
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• 2000

The Korea Atomic Energy Research Institute acquired the Lawrence Livermore National Laboratory phantom for calibration of germanium detectors used for in vivo measurement of radionuclides deposited in human lungs. The manufacturer inscribed concentric circles as a phoswich detector positioning guides on the phantom's torso plate and its overlay plates, and provided the effective thickness of the chest wall for each plate measured at locations over the circles. However, since the germanium detectors are of different sizes, the areas considered for phoswich detectors were no. longer applicable for the locations of the germanium detectors on the phantom. Therefore, we re-evaluated the effective thickness of the phantom to determine if the manufacturer' s data are valid for germanium detectors in use for in vivo lung counting or if new values must be implemented. Differences no more than 3% in effective thickness were found between the germanium detector regions to be used at the Korea Atomic Energy Research Institute and the phoswich detector regions prescribed by the manufacturer.

• Journal of Chest Surgery
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• v.35 no.1
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• pp.1-10
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• 2002

Background: Despite the relatively high mortality rates in the chronic heart failure model induced by coronary artery ligation are relatively high, this model has been a subject of continuos research because of its clinical correlation. Chronic heart failure model of large-sized animals is very useful to analyse mechanical or biological effects on circulatory system which is difficult in small-sized animals. The purpose of this study is to establish the heart failure model by coronary artery ligation in sheep. Material and Method: Among 9 Corridale sheep, the homonymous artery and the diagonal branch were ligated simultaneously in 2 sheep and remaining 7 sheep were assigned to successive ligation of both arteries at an interval of 1 hour. Both coronary arteries were ligated from the point 40% proximal to the apex of the heart. Hemodynamic and echocardiographic parameters were analyzed before the ligation of the coronary artery, after the ligation of the homonymous artery, and after additional ligation of the diagonal branch. The experimental animals were sacrificed after 2 or 3 months of growth and histopathologic studies were performed Result: Immediate postoperative death occurred in the 2 sheep that had received simultaneous ligation of the homonymous artery and diagonal branch. On the other hand, all the 7 sheep that were lifated in succession were survived up to 3 months. Arterial pressure was sifnificantly decreased immediately after ligation of the homonymous artery(p<0.05), and the cardiac output was decreased and pulmonary capillary wedge pressure was increased after further ligation of the diagonal branch(p<0.05). Central venous pressure, pulmonary artery pressure, pulmonary capillary wedge pressure, left ventricular end-diastolic dimension and end-systolic dimension were markedly increased 3 months after ligation of coronary arteries. Anteroseptal akinesia or dyskinesia was developed after the ligation of coronary arteries. Histopathologic study revealed we]1-demarcated ischemic area of fibrosis. Conclusion: Using methods of successive ligation of the homonymous artery and diagonal branch, chronic heart failure model could be reliably established in sheep.

• Journal of Chest Surgery
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• v.39 no.9 s.266
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• pp.659-667
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• 2006

Background: Experimental studies of vascular remodeling in the pulmonary arteries have been performed actively. These models required a persistent vascular insult for intimal injury induced by chronic hypoxia, monocrotaline intoxication or chronic air embolism and characterized medial hypertrophy and neointimal formation by active synthesis of the extracellular matrix protein. The purpose of this study was to determine the pattern of pulmonary vascular remodeling after obstruction of the pulmonary vein. Material and Method: Obstruction of the right pulmonary vein with a metal clip was performed in Sprague-Dawley rats $(352{\pm}18g,\;n=10)$ to cause pulmonary vascular disease. Fifteen days later, experimental studies were done and finally the both lungs and hearts were extirpated for experimental measurement. Pulmonary arterial pressure, weight ratio of right ventricle (RV) to left ventricle (LV) and ventricular septum (S) (RV/LV +S weight ratio), and pulmonary artery morphology (percent wall thickness, %WT) were evaluated and compared with normal control groups. Result: Pulmonary hypertension $(38{\pm}12mmHg\;vs\;13{\pm}4mmHg;\;p<0.05)$ and right ventricular hypertrophy (right ventricular/left ventricular and septal weight ratio, $0.52{\pm}0.07\;vs\;0.35{\pm}0.04;\;p<0.05$) with hypertrophy of the muscular layer of the pulmonary arterial wall (percent wall thickness, $22.4{\pm}6.7%\;vs\;6.7{\pm}3.4%;\;p<0.05$) were developed by 15 days after obstruction of the pulmonary vein. Conclusion: Obstruction of the pulmonary vein developed elevation of pulmonary blood pressure and medial hypertrophy of the pulmonary artery. These results are a part of the characteristic vascular remodeling. Theses results demonstrate that obstruction of the pulmonary vein can develope not only high pulmoanry blood flow of contralateral lung but also intima injury inducing vascular remodeling.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.37-39
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• 2001

21세기의 벽두부터 국내외적으로 활발히 논의되고 있는 나노기술에 대한 정의를 생각해보는 것으로부터 우리가 나아갈 방향을 살펴보고자 한다. 나노기술이란, 원자 하나 하나 혹은 분자단위의 조작을 통해 1~100nm정도의 범위 안에서 근본적으로 새로운 물질이나 구조체를 만들어 내는 기술을 말한다. 즉 앞으로 우리는 경험해 보지 못한 새로운 현상에 대한 이해를 할 수 있어야 하고, 새로운 물질 자체를 다룰 수 있는 방법이 우리가 해야 할 구체적인 일이 될 것이란 말이 된다. 뿐만 아니라 나노기술은 종래의 정보.통신.전자 분야에서 주로 추구하던 마이크로화와 달리 재료, 기계, 전자, 의학, 약학, 에너지, 환경, 화학, 생물학, 농학, 정보, 보안기술 등 과학기술 분야 전반을 위시하여 사회분야가지 새로운 인식과 철학적인 이해가 필요하게 되었다. 21세기를 맞은 인류가 나아갈 방향을 나노세계에 대한 도전으로 보아야 하며, 과학기술의 새로운 틀을 제공할 것 임에 틀림 없다. 그러나, 이와 같은 나노기술의 출발점을 살펴보면 VLSI기술로 통칭할 수 있는 마이크로전자소자 기술이란 점이다. 국내의 VLSI기술은 메모리기술이라고 해도 과언이 아닐 것이다. 문제는 종래의 메모리기술은 대규모 투자와 집중적인 인력양성을 통해서 세계 최고 수준에 도달 할 수 있었다. 그러나 여기까지 오는 동안 사식 우리는 선진국의 뒷꽁무니를 혼신의 힘을 다해 뒤쫓아 온 결과라고 보아도 틀리지 않는다. 즉, 앞선자를 보고 뒤쫓는 사람은 갈방향과 목표가 분명하므로 최선을 다하면 따라 잡을 수 있다. 그런데 나노기술은 앞선 사람이 없다는 점이 큰 차이이다 따라서 뒷껑무니를 쫓아가는 습성을 가지고는 개척해 나갈 수 없다는 점을 깨닫지 않으면 안된다. 그런 점에서 이 시간 나노기술의 국내외 현황을 살펴보고 우리가 어떻게 할 것인가를 생각해 보는데 의미가 있을 것이다.하여 분석한 결과 기존의 제한된 RICH-DP는 실시간 서비스에 대한 처리율이 낮아지며 서비스 시간이 보장되지 못했다. 따라서 실시간 서비스에 대한 새로운 제안된 기법을 제안하고 성능 평가한 결과 기존의 RICH-DP보다 성능이 향상됨을 확인 할 수 있었다.(actual world)에서 가상 관성 세계(possible inertia would)로 변화시켜서, 완수동사의 종결점(ending point)을 현실세계에서 가상의 미래 세계로 움직이는 역할을 한다. 결과적으로, IMP는 완수동사의 닫힌 완료 관점을 현실세계에서는 열린 미완료 관점으로 변환시키되, 가상 관성 세계에서는 그대로 닫힌 관점으로 유지 시키는 효과를 가진다. 한국어와 영어의 관점 변환 구문의 차이는 각 언어의 지속부사구의 어휘 목록의 전제(presupposition)의 차이로 설명된다. 본 논문은 영어의 지속부사구는 논항의 하위간격This paper will describe the application based on this approach developed by the authors in the FLEX EXPRIT IV n$^{\circ}$EP29158 in the Work-package "Knowledge Extraction & Data mining"where the information captured from digital newspapers is extracted and reused in tourist information context.terpolation performance of CNN was relatively better than NN.콩과 자연 콩이 성분 분석에서 차이를 나타내지 않았다는 점, 네 번째. 쥐를 통한 다양섭취 실험에서 아무런 이상 반응이 없었다는 점등의 결과를 기준으로 알레르기에 대한 개별 검사 없이 안전한

• Journal of the Korean Society of Radiology
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• v.12 no.3
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• pp.373-379
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• 2018

The purpose of this study was to investigate quantitative data on the difference in breast entrance surface dose with changes in focus-film distance, patient posture (anteroposterior-posteroanterior), thoracic wall thickness, rib bone thickness, lung tissue thickness, tube voltage, and high-voltage rectification method in Whole Spine Scanography, which is necessary for the treatment of scoliosis patients. Given a tube voltage of 90 kVp, kerma of 0.1 mGy, focus-film distance of 260 cm, tube voltage ripple rate of 0, filter thickness of 3.5 mm, and thickness of patient's thoracic wall of 120 mm as an X-ray exposure condition, from the simulation results using the Simulation of X-ray Spectra program to confirm the reduction effect of breast entrance surface dose according to the patient's posture (AP and PA), there was a dose reduction effect in aluminum filter thickness of 2.6 times at 3.5 mm, 25.7 times the thoracic wall thickness at 120 mm, 1.43 times higher tube voltage, and 0 to 1.14 times the tube voltage ripple rate. The total dose reduction effect was about 109 times. In order to confirm the dose reduction effect of RANDO phantom posture (AP and PA), from the results of the measurements taken under the conditions that the focus-film distance was 260 cm, the tube voltage was 90 kVp, the tube current was 270 mA, the exposure time was 0.31 sec, and the tube voltage ripple rate of X-ray generators was 0, the entrance surface dose reduction effect of the breast in the PA position was found to be 20.56 times lower than that of the AP position.