• 한국항공우주학회지
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• 제33권9호
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• pp.48-55
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• 2005

본 논문에서는 비등방성 멤브레인의 주름 거동을 조사하였다. 해석시 멤브레인에 발생하는 주름은 벌칙매개변수법을 사용하여 물성치를 수정하는 방법으로 하였으며, ABAQUS 내 사용자 서브루틴으로 구현하였다. 모서리에 인장하중이 걸린 사각형 멤브레인 문제에 적용하여 주름 거동을 해석한 결과, 핀의 지름이 미치는 영향은 매우 작으며, 잘라낸 모서리의 길이와 전단계수의 크기에 상당한 영향을 받고 있음을 알 수 있었다.

• 한국안광학회지
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• 제18권3호
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• pp.347-356
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• 2013

목적: 비구면 다초점 인공수정체인 ReSTOR$^{(R)}$ SN6AD3 삽입안의 시력과 시기능 변화를 분석하였다. 방법: 양안 또는 단안에 비구면 다초점 인공수정체(ReSTOR$^{(R)}$ SN6AD3)를 삽입한 백내장 환자 19명의 30안을 대상으로 하였다. 수술 전, 수술 후 1주일, 1개월 및 3개월 후에 시력과 객관적인 시기능을 측정하였고 수술 3개월 후 인공수정체 삽입안의 시기능 측정값을 동일 연령대의 정상안 20명(38안)과 비교하였다. 원거리 시력은 2 m 거리에서 LCD chart ETDRS 시력표를 이용하여 측정하였고, 중간거리(50 cm)과 근거리(30 cm) 시력은 Jaeger chart를 이용하였다. 객관적인 시기능은 OQAS 장비를 이용하여 OSI (objective scatter index, 객관적 산란지수), MTF (modulation transfer function, 변조전달함수) cut off, Strehl ratio를 4 mm 동공크기에서 측정하여 수술 후 경과기간에 따른 측정값을 비교 평가하였다. 수술 3개월 째 시력 및 시기능은 객관적 평가와 주관적인 평가를 통해 동일 연령대의 정상안과 비교하였다. 결과: 나안 원거리 시력과 OSI, MTF와 Strehl ratio는 다초점 인공수정체 삽입 1개월까지 유의하게 향상되었다(p<0.05). 수술 3개월 후 다초점 인공수정체 삽입안의 MTF와 Strehl ratio는 정상 대조군의 수준으로 회복되었지만, OSI는 대조군보다 높은 값으로 측정되었다(p<0.001). 자각적인 원거리 및 근거리 시력에 대한 만족도는 높았지만, 중간거리 시력에 대한 만족도가 낮으며 눈부심과 빛 번짐 증상이 나타났다. 결론: 비구면 다초점 인공수정체 삽입안의 시기능은 수술 1개월 후부터 안정화되며 동일 연령대의 정상안의 수준으로 개선되지만 만족스러운 중간거리 시력을 제공하지 못하며 눈부심과 빛 번짐의 시각적 불편감이 나타나는 것으로 사료된다.

• Korean Journal of Radiology
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• 제19권6호
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• pp.1042-1052
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• 2018

Objective: To determine the utility of computed tomography (CT) ventricular volumes and morphometric parameters for deciding the treatment strategy in children with a hypoplastic left ventricle (LV). Materials and Methods: Ninety-four consecutive children were included in this study and divided into small LV single ventricle repair (SVR) (n = 28), small LV biventricular repair (BVR) (n = 6), disease-matched control (n = 19), and control (n = 41) groups. The CT-based indexed LV volumes, LV-to-right-ventricular (LV/RV) volume ratio, left-to-right atrioventricular valve (AVV) area ratio, left-to-right AVV diameter ratio, and LV/RV long dimension ratio were compared between groups. Proportions of preferred SVR in the small LV SVR group suggested by the parameters were evaluated. Results: Indexed LV end-systolic (ES) and end-diastolic (ED) volumes in the small LV SVR group ($6.3{\pm}4.0mL/m^2$ and $14.4{\pm}10.2mL/m^2$, respectively) were significantly smaller than those in the disease-matched control group ($16.0{\pm}4.7mL/m^2$ and $37.7{\pm}12.0mL/m^2$, respectively; p < 0.001) and the control group ($16.0{\pm}5.5mL/m^2$ and $46.3{\pm}10.8mL/m^2$, respectively; p < 0.001). These volumes were $8.3{\pm}2.4mL/m^2$ and $21.4{\pm}5.3mL/m^2$, respectively, in the small LV BVR group. ES and ED indexed LV volumes of < $7mL/m^2$ and < $17mL/m^2$, LV/RV volume ratios of < 0.22 and < 0.25, AVV area ratios of < 0.33 and < 0.24, and AVV diameter ratios of < 0.52 and < 0.46, respectively, enabled the differentiation of a subset of patients in the small LV SVR group from those in the two control groups. One patient in the small LV biventricular group died after BVR, indicating that this patient might not have been a good candidate based on the suggested cut-off values. Conclusion: CT-based ventricular volumes and morphometric parameters can suggest cut-off values for SVR in children with a hypoplastic LV.

• 대한핵의학회지
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• 제39권4호
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• pp.231-238
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• 2005

목적: 비소세포성폐암(NSCLC)의 FDG-PET 판독 시 SUV만 진단기준으로 사용하면 우리나라와 같이 만성 염증성 폐질환이 호발하는 지역에서는 폐문 및 종격동 림프절에 대한 위양성률이 높다. 이에 최근 국내에 도입된 CT-보정 FDG-PET (PET/CT)을 이용하여 SUV 외에 FDG 섭취양상 및 CT영상에서 림프절 석회화 등의 다른 기준을 어떻게 적용하면 림프절의 악성 유무 판정 및 N 병기 결정에 있어 검사의 정확도가 높아질 수 있는지 전향적으로 알아보았다. 대상 및 방법 : 림프절 절제술을 받기 전에 PET/CT를 시행한 91명의 NSCLC 환자를 대상으로 하였다(남/여: 62/29, 평균나이: $60{\pm}9$ yr). 종격동 대혈관보다 FDG 섭취가 증가되어 있는 폐문과 종격동 림프절의 최대 SUV (maxSUV)와 단경을 측정하고, FDG 섭취증가 병변의 경계 및 석회화 유무를 파악하였다. 이 기준들을 이용하여 PET/CT 소견을 세 단계로 나누어 각각의 진단 성적을 병리결과와 비교하였다. 1단계에서는 maxSUV만을 진단기준으로 사용하였다. 2단계 에서는 1단계에서 정한 cut-off 보다 낮은 maxSUV를 가지는 림프절 또는 높은 maxSUV를 가지더라도 CT 영상에서 석회화가 있거나 높은 attenuation을 보이는 림프절을 양성으로 분류하였다. 3단계에서는 2단계에서 양성으로 분류한 림프절 및 2단계에서 악성으로 분류된 림프절 중 FDG 섭취증가의 경계가 명확하지 않은 림프절을 양성으로 하였다. 결과: 수술로 절제된 총 432개의 림프절 중 28개가 악성, 404개가 양성이었다. 71개가 비정상적인 FDG 섭취증가를 보였다. ROC 곡선 분석을 이용해 구한 cut-off는 maxSUV=3.5였다. 악성 림프절 판정에 대한 민감도, 특이도, 정확도는 각각 1단계에서 64.3%, 86.9%. 85.4%. 2단계 64.3%, 95.0%, 93.1%, 그리고 3단계 57.1%, 98.0%, 95.4%였다. N 병기 일치율은 1단계 64.8%, 2단계 80.2%, 3단계 85.7%였다. 결론: NSCLC 환자의 PET/CT 판독 시 림프절의 FDG 섭취증가 정도뿐만 아니라 병변의 석회화 유무 및 FDG 섭취증가의 경계부분 모양을 함께 고려하면 폐문 및 종격동 림프절의 악성 여부 평가 및 N 병기 결정에 있어 더 탁월한 진단성적을 기대할 수 있을 것으로 생각된다.

• 한국전산유체공학회지
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• 제13권4호
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• pp.72-79
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• 2008

This study is to investigate the air flow around a sirocco fan which is used in a range hood. The main object of the study is to improve the flow rate of the fan by analysis of unsteady 3-dimensional incompressible flow. Overall analysis is carried out using CFD method. For this, we used a commercial code, SC/Tetra, and used a sliding mesh method to give the same condition as an actual state. First, verification of the CFD results is done by comparing the experimental data with the numerical data for the suction flow rate. It is confirmed that two results are well consistent. Then for the improvent of flow rate, the effect of shape factors such as diameter ratio of fan, geometry of case, cut-off aperture and guide angle of case exit on the suction flow rate was considered. Especially, for a new design of housing, the principle of Archimedes spiral was used. The overall analysis was applied to a new design of housing, and the result showed an increase of flow rate by 10.7%.

• 한국대기환경학회지
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• 제19권1호
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• pp.67-76
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• 2003

Recently consideration of health and interest on bio aerosols have been growing steadily. In this study, inertial impactor, which can be used to collect airborne particles and bio aerosols, was newly devised for real-time observation on the particles collected on impaction plate. and named Visual Impactor. Flow field and particle trajectory in the space between nozzle and impaction plate was analyzed numerically, and the collection effciencies were calculated. Calibration and performance evaluation of the Visual Impactor was conducted with polydisperse aerosols generated from 0.1％ sodium chloride solution. Cut-off diameter from numerical simulation was in good agreement with that from experimental results. Because of particle bounce and particle deposition on nozzle tip due to short jet-to-plate distance, the collection efficiencies from numerical and experimental analyses were different slightly. Visual Impactor was used to collect airborne particles, and the features of collected particles could be seen in real-time. Airborne particles in different weather conditions (fine, cloudy, and rainy) were sampled and compared one another The features of collected airborne particles were dependent strongly upon relative humidity. In addition, with hours elapsing, shapes and colors of collected particles were changed by evaporation and surface tension, etc.

• 대한치과보철학회지
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• 제38권1호
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• pp.108-115
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• 2000

This study was designed to compare the effect of polishing on surface roughness of composite resin. We used Z100(3M) composite resin and placed the composite resin in the hole (4mm thick and 4mm in diameter) of vinyl plate and polymerized it under manufacturer's instructions. Samples were divided into 5 groups by polishing methods. Group 1 was control: resin was polymerized under glass plate, Group 2: resin was polymerized without any polishing procedure, Group 3: resin was polymerized with a polishing procedure of abrasive disc, Group 4: bonding agent was applyed in thin layer and polymerized on the polished polymerized resin surface. Group 5: resin was polymerized under transparent celluloid strip. The surface roughness of each specimen was measured with Sufacoder SEF-30D (Kosaka lab. Ltd) under 0.08mm cut off, 0.05mm/s stylus speed, ${\times}40$ horizontal magnification, ${\times}5000$ vertical magnification. The results were as follows : 1. Group 1 showed the most smooth surface in this study. 2. Group 3 showed more rough surface than Group 2. Considering the surface roughness, it would be better to make the shape completely before polymerize the resin. To finish and polish after the polymerization of resin makes less smooth surface. 3. When we use the transparent celluloid strip, minimum finishing procedures are recommended. Any polishing procedure could not recover the smooth resin surface of celluloid strip. 4. Application and polymerization of the thin layer of bonding agent on the polished surface showed the minimum surface smoothing effect.

• 한국광학회지
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• 제5권2호
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• pp.333-339
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• 1994

단일모드 광섬유를 부착한 고속 광통신용 PIN-전치증폭기 모듈을 GaInAs PIN 광검출기와 GaAs 전치증폭기를 하이브리드로 집적하여 제작하였다. PIN 광검출기의 정전용량은 0.35pF이었으며 이 소자의 수광직경은 $20{\mu}m$였다. 제작된 수광모듈의 -3dB 차단주파수는 2GHz 이상이었으며 2.5Gbps NRZ$(PRBS=2^{23}-1)$ 입력광신호에 대해 비트오율이 $10^{-9}$일 때 -25.2dBm의 수신감도를 보였다.

• 구강회복응용과학지
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• 제22권1호
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• pp.1-10
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• 2006

The purpose of this research was to evaluate ceramics reinforced with thin metal wires, The results could be applied to evaluate the mechanical properties of in fabricating ceramic crowns and bridges. The wires used in the study were Platinum of 0.025 mm, 0.0508 mm, 0.1 mm and Titanium of 0.127 mm diameters. The ingot used was for staining technique. One or two wires were inserted into the ceramics and the specimens were observed with dental X-rays. The results obtained in this study were as follows: 1.The commonly observed phenomenon was that the wires inserted were pushed away to the peripherally, regardless of types diameter, or numbers of wires. 2.In some Empress specimen the wire was observed to be loosed and cut off.

• International Journal of Air-Conditioning and Refrigeration
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• 제17권3호
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• pp.94-99
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• 2009

In the Korean subway station, three types of pre-filters, which include auto filter, electrostatic precipitator (ESP) and auto cleaning demister, are widely used. However, these devices have some problems such as the difficulty of maintenance and high operating cost. In this study, axial-flow cyclone separator was employed as a pre-filter inside a heating, ventilation, and air conditioning (HVAC) system. 3-dimensional computational fluid dynamics (CFD) analysis was performed on a single unit axial-flow cyclone and coupled unit axial-flow cyclone. Calculated and measured pressure drop of the designed axial-flow cyclone were found be comparable to other types of pre-filters and the observed cut-off diameter was less than 10 micron. Considering lower operating and maintenance cost, axial-flow cyclone was proved to be a better solution as a pre-filter.