• Journal of Korean Society for Geospatial Information Science
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• v.6 no.2 s.12
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• pp.133-141
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• 1998

Terrain modelling is composed of a method using the rectangular grid and another using the triangulated irregular network. The method using the triangulated irregular network is most widely used because it can express the characteristics of the terrain well with only a small amount of information on the terrain and also reduces the rendering time. The process of extracting the surface-specific point and a triangular process is needed to construct such triangulated irregular network. This paper concentrates on the process of extracting the surface-specific point. The 8-direction neighborhood method and other transformed methods of the former method are frequently used to extract the surface-specific point. Another method which eliminates the unnecessary points using the Polygon reduction method is also suggested However, the 8-direction neighborhood method has a big fault of also drawing out some unnecessary points. To resolve such problem, we suggest a method of extracting the surface-specific point using the cross section of the terrain. This method reduces the time to extract the surface-specific point and enables a more precise extraction with less terrain information.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.1
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• pp.20-30
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• 2010

In this paper, a new tomographic scan method with fixed installed detectors and rotating source from gamma projector was presented to diagnose the industrial plants which were impossible to be examined by conventional tomographic systems. Weight matrix calculation method which was suitable for volumetric detector and statistical iterative reconstruction method were applied for reconstructing the simulation and experimental data. Monte Carlo simulations had been performed for two kinds of phantoms. Lab scale experiment with a same condition as one of phantoms, had been carried out. Simulation results showed that reconstruction from photopeak counting measurement gave the better results than from the gross counting measurement although photopeak counting measurement had large statistical errors. Experimental data showed the similar result as Monte Carlo simulation. Those results appeared to be promising for industrial tomographic applications, especially for petrochemical industries.

• The KIPS Transactions:PartB
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• v.10B no.5
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• pp.509-514
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• 2003

The virtual bronchoscopy was implemented using chest CT images to visualize inside of tracheo-bronchial wall. The optical endoscopy procedures are invasive, uncomfortable for patients and sedation or anesthesia may be required. Also, they have serious side effects such as perforation, infection and hemorrhage. In order to determine the navigation path, we segmented the tracheo-bronchial wall from the chest CT image. We used the coordinates as a navigation path for virtual camera that were calculated from medial axis transformation. We used the perspective projection and marching cube algorithm to render the surface from volumetric CT image data. The tracheobronchial disease was classified into tracheobronchial stenosis causing from inflammation or lung cancer, bronchiectasis and bronchial cancer. The virtual bronchoscopy is highly recommended as a diagnosis tool with which the specific place of tracheobronchial disease can be identified and the degree of tracheobronchial disease can be measured qualitatively, Also, the virtual bronchoscopy can be used as an education and training tool for endoscopist and radiologist.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.2
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• pp.108-113
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• 2009

MFL(magnetic flux leakage) inspection is a general method of non-destructive evaluation(NDE) of underground gas pipelines. Pipelines are magnetized by permanent magnets when MFL PIG(pipeline inspection gauge) gets through them. If defects or corrosions exist in pipelines, effective thickness is changed and thus variation of leakage flux occurs. The leakage flux signals detected by hall-sensors are analyzed to characterize defect's geometries such as length, width, depth, and so on. This paper presents several methods for estimating defect's length using MFL signals and their performances are compared for real defects carved in KOGAS pipeline simulation facility. It is found that 80% and 90% of minimum values for axial and peak values for radial signals respectively show the best performance in the point of length estimation error.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.5
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• pp.442-448
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• 2007

The ultrasonic inspection system for the expansion/transition area of steam generator tube was successfully developed. Variety of artificial flaw and real track specimen was tested using the UT system to verify the performance of the system. All artificial flaws of which through-wall depth larger than 10% was clearly detected by UT system. Measurement results of through-wall depth of flaws larger than 20% had good linearity and reproducibility with 3.27 of standard deviation. Results of real crack specimen test suggested that the detection limit of real crack strongly depends on the track morphology. A potential for measurement of PRL(percentage of remaining ligament) was recognized by the real crack specimen test.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.661-668
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• 2020

One of the causes of death for pregnant female is embolism, when a chest PA examination is performed. In addition, due to small doses, the examinations are performed for the purpose of preparing for pre-delivery emergency surgery or basic examination for pregnant female. Evaluating fetal doses through actual measurements is subject to ethical problems, Monte Carlo simulations assesses the organ and fetal doses of pregnant females according to week of pregnancy. The results of the simulations showed that the fetal dose decreased according to weeks of pregnancy and it showed a dose of about 0.1 mGy. The higher the density and thickness of the shielding material, the better the shielding effect. In addition, the dose reduction effect for each shielding material is between 40 and 98%. Afterwards, it is deemed necessary to study the reduction of fetal doses through various shielding characteristics and methods.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.229-237
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• 2005

통신용 지하 관로는 대부분 내경 100mm인 PVC 재질로 되어 있으며, 지하에 매설한 후 또는 관로를 사용하기 전에 관로 상태의 정상 유무를 확인할 목적으로 맨드릴(직경 90mm)을 이용한 선통 검사로 정상 관로와 불량 관로를 판단 하였다. 그러나 이러한 방법으로는 조사 대상 관로의 불량 원인을 밝힐 수 없을 뿐 아니라, 복수 개소의 불량 지점을 확인하는 것이 불가능하여 관로 보수나 사용을 위한 기본적인 관로 정보를 제공할 수 없었다. 이러한 문제를 해결하기 위해 디지털 관로 조사장비를 개발하였으며, 관로 내부를 따라 관로 카메라를 이동시키면서 관로 내부의 변형 상태를 실시간으로 확인하거나, 관로 벽에 조사된 레이저 빔 영상을 검출하여 관로 단면의 최소 직경을 측정할 수도 있다. 또한, 디지털 맨드릴은 1mm 간격으로 관로의 내경을 측정할 수 있는 게이지가 설치되어 있어, 실시간으로 관로 단면의 최소 직경을 측정할 수 있어 조사 관로의 전반적인 변형 정도를 모니터링 할 수 있다. 이러한 디지털 관로 조사장비를 이용하여 신설 관로의 시공품질을 측정하거나, 기존 관로의 상태를 객관적이고 정확하게 파악하여 관로 상태에 따른 케이블 포설 계획을 수립할 수 있으며, 불량 관로 보수를 위한 정확한 자료를 제공하여 유지관리의 효율성을 높일 수 있다.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.5
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• pp.510-517
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• 2001

This paper describes an initial study for the application of eddy current pattern recognition approaches to more realistic flaw characterization in steam generator tubes. For this purpose, finite-element model-based theoretical eddy current testing (ECT) signals are simulated from 5 types of OD flaws with the variation in flaw size parameters and testing frequency. In addition, three kinds of software are developed for the convenience in the application of steps in pattern recognition approaches such as feature extraction feature selection and classification by probabilistic neural networks (PNNs). The cross point of the ECT signals simulated from flaws with non-symmetric cross-sections shows the deviation from the origin of the impedance plane. New features taking advantages of this phenomenon are added to complete the feature set with a total of 18 features. Then, classification with PNNs are performed based on this feature set. The PNN classifiers show high performance for the identification of symmetry in the cross-section of a flaw. However, they show very limited success in the interrogation of the sharpness of flaw tips.

• Tuberculosis and Respiratory Diseases
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• v.46 no.5
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• pp.628-635
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• 1999

Background : Maximal expiratory flow rate is determined by the size of airway, elastic recoil pressure and the collapsibility of airway in the lung. The obstruction of expiratory flow is one of the major functional impairments of emphysema, which represents COPD. Nevertheless, expiratory narrowing of upper airway may be recruited as a mechanism for minimizing airway collapse, and maintaining lung volume and hyperinflation by an endogenous positive end-expiratory pressure in patients with airflow obstruction. We investigated the physiologic role of trachea in respiration in emphysema. Method : We included 20 patients diagnosed as emphysema by radiologic and physiologic criteria from January to August in 1997 at Seoul Municipal Boramae Hospital. Chest roentgenogram, high resolution computed tomography(HRCT), and pulmonary function tests including arterial blood gas analysis and body plethysmography were taken from each patient. Cross-sectional area of trachea was measured according to the respiratory cycle on the level of aortic arch by HRCT and calibrated with body surface area. We compared this corrected area with such parameters of pulmonary function tests as $PaCO_2$, $PaO_2$, airway resistance, lung compliance and so on. Results : Expiratory cross-sectional area of trachea had significant correlation with $PaCO_2$ (r=-0.61, p<0.05), $PaO_2$ (r=0.6, p<0.05), and minute ventilation (r=0.73, p<0.05), but inspiratory cross-sectional area did not (r=-0.22, p>0.05 with $PaCO_2$, r=0.26, p>0.05 with $PaO_2$, and r=0.44, p>0.05 with minute ventilation). Minute ventilation had significant correlation with tidal volume (r=0.45, p<0.05), but it had no significant correlation with respiratory frequency (r=-0.31, p>0.05). Cross-sectional area of trachea had no significant correlation with other parameters of pulmonary function including $FEV_1$, FVC, $FEV_1$/FVC, peak expiratory flow, residual volume, diffusing capacity, airway resistance, and lung compliance, whether the area was expiratory or inspiratory. Conclusion : Cross-sectional area of trachea narrowed during expiration in emphysema, and its expiratory area had significant correlation with $PaCO_2$, $PaO_2$, and minute ventilation.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.555-561
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• 2000

The remote field eddy current (RFEC) inspection was performed on the ductile cast iron pipes with nominal outer diameter of 100mm, which were machined with various shapes and sizes of defects. Ductile cast iron pipes which are used as water supply pipe have the non-uniform thickness and asymmetric cross section due to relatively high degree of allowable errors during the manufacturing processes. These characteristics of ductile cast in pipes cause the long range background noises in RFEC signals along the pipe. In this study, tile machined defects in pipes were effectively classified by the moving window average (MWA) method which eliminated the long-range noise. The voltage plane polar plots (VPPP) method was used to quantitatively evaluate the depth and circumferential degree of defects. The VPPP signatures showed that the angle between defect signature and the normalized in-phase component on the VPPP is linear to the depth of defects. The nondestructive RFEC technique proved to be capable of quantitatively evaluating the machined defects of underground water supply pipe.