• Journal of the Korean Association of Geographic Information Studies
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• v.25 no.4
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• pp.136-150
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• 2022

In this study, a comparative review was conducted on how to use RGB images to obtain river topographic information, which is one of the most essential data for eco-friendly river management and flood level analysis. In terms of the topographic information of river zone, to obtain the topographic information of flow section is one of the difficult topic, therefore, this study focused on estimating the river topographic information of flow section through RGB images. For this study, the river topography surveying was directly conducted using ADCP and RTK-GPS, and at the same time, and orthomosiac image were created using high-resolution images obtained by drone photography. And then, the existing developed regression equations were applied to the result of channel topography surveying by ADCP and the band values of the RGB images, and the channel bathymetry in the study area was estimated using the regression equation that showed the best predictability. In addition, CCHE2D flow modeling was simulated to perform comparative verification of the topographical informations. The modeling result with the image-based topographical information provided better water depth and current velocity simulation results, when it compared to the directly measured topographical information for which measurement of the sub-section was not performed. It is concluded that river topographic information could be obtained from RGB images, and if additional research was conducted, it could be used as a method of obtaining efficient river topographic information for river management.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.731-734
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• 2004

본 논문은 입력영상의 화질 향상을 위하여 기존의 스트레칭 알고리즘을 이용하여 개선된 콘트라스트 알고리즘을 제안하였다. 입력영상의 픽셀(pixel)을 DR(Difference Range)의 범위에 따라 정해진 가중치를 적용하여 새로운 픽셀을 출력한다. 특별한 사용자 정의(User Define)없이 실시간적으로 화질을 개선할 수 있는 장점이 있다. 또한, 하드웨어 적인 측면에서 곱셈 과 나눗셈 연산을 배럴쉬프트(Barrel Shift)를 이용하여 하드웨어 복잡도를 감소 시켰다. 제안한 방식의 알고리즘의 검증을 위하여 C를 이용한 시각적 검증과 하드웨어 측면에서의 검증을 VHDL을 이용한 컴퓨터 시뮬레이션을 통해 확인하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.11a
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• pp.82-84
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• 2022

최근 자율주행에서 안전한 주행을 위해 영상 기반 다중객체 검출 기술이 활발히 연구되고 있다. 이때, 저해상도 영상은 객체 검출 단계에서 정확도가 떨어지는 한계가 있다. 본 논문에서는 이러한 문제점을 해결하기 위해 초해상화와 객체 검출을 위한 방법을 함께 사용하는 기법을 제안한다. 더 나아가 초해상화 단계에서 하나의 구분자만 사용하는 기존의 방법과 다르게 이미지 생성 과정 중간에서 추가의 구분자를 사용하여 총 두 개의 구분자를 사용하여 성능을 향상하고자 하였다. 본 논문은 한국 고속도로 교통 데이터를 사용하여 실험하였으며, 그 결과 제안된 방법의 성능이 mAP@0.5 및 F1 점수 측면에서 기존 방법보다 우수하다는 것을 확인하였다.

• The korean journal of orthodontics
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• v.39 no.1
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• pp.6-17
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• 2009

Objective: The purpose of this study was to evaluate the possibility of using a digital model and cone beam computed tomograph(CBCT) image for model analysis. Methods: Model analyses of CBCT images, plaster models, and digital models of 20 orthodontic patients with a permanent dentition with no proximal metal restorations, were compared. Results: The average differences of tooth size measurements were 0.01 to 0.20 mm, and the average difference of arch length discrepancy measurements were 0.41 mm in the maxilla and 0.82 mm in the mandible. The difference in Bolton discrepancy measurements was 0.17 mm for the anterior region and 0.44 mm overall but with no statistically significant difference. When comparing CBCT images with plaster models, the average differences in tooth size measurements were -0.22 to 0.01 mm, and the average differences in arch length discrepancy measurements were 0.43 mm in the maxilla and 0.32 mm in the mandible. Difference in Bolton discrepancy measurements were 0.35 mm in the anterior region and 1.25 mm overall. CBCT images showed significantly smaller overall Bolton discrepancy measurements. Conclusions: Although there were statistically significant differences in some model analysis measurements, the ranges of measurement errors of the digital model and CBCT images were clinically acceptable. Therefore, a digital model and CBCT image can be used for model analysis.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.1
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• pp.17-24
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• 2020

The purpose of this study was to evaluate the accuracy and precision of the three-dimensional (3D) imaging system of children's facial soft tissue by comparing linear measurements. The subjects of the study were 15 children between the ages of 7 and 12. Twenty-three landmarks were pointed on the face of each subject and 16 linear measurements were directly obtained 2 times using an electronic caliper. Two sets of 3D facial images were made by the 3D scanner. The same 16 measurements were obtained on each 3D image. In the accuracy test, the total average difference was 0.9 mm. The precision of 3D photogrammetry was almost equivalent to that of direct measurement. Thus, 3D photogrammetry by the 3D scanner in children had sufficient accuracy and precision to be used in clinical setting. However, the 3D imaging system requires the subject's compliance for exact images. If the clinicians provide specific instructions to children while obtaining 3D images, the 3D device is useful for investigating children's facial growth and development. Also the device can be a valuable tool for evaluating the results of orthodontic and orthopedic treatments.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.123-130
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• 2014

In this study, a vision-based displacement measurement system is developed to accurately measure the displacement of a structure with locating the camera at arbitrary position. The previous vision-based system brings error when the optical axis of a camera has an angle with the measured structure, which limits the applicability at large structures. The developed system measures displacement by processing the images of a target plate that is attached on the measured position of a structure. To measure displacement regardless of the angle between the optical axis of the camera and the target plate, planar homography is employed to match two planes in image and world coordinate systems. To validate the performance of the present system, a laboratory test is carried out using a small 2-story shear building model. The result shows that the present system measures accurate displacement of the structure even with a camera significantly angled with the target plate.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.146-149
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• 2006

Spray characteristics of an injector employed in mono-propellant hydrazine thrusters were investigated by PIV(particle image velocimetry) and LDA/PDA(laser/phase Doppler anemometry) techniques. The instanteneous plane image data captured by PIV measurement were examined in order to judge a pass-fail criteria of spray injection performance according to the specific pressure supplied. LDA/PDA technique were also applied to measure the velocity and droplet size of spray were not obtained from PIV measurement. The objective of this experimental study was the clear understanding of spray characteristics as well as the derivation of injector performance to understand clearly the spray characteristics by comparing the both results.

• The korean journal of orthodontics
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• v.32 no.5 s.94
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• pp.313-325
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• 2002

Three-dimensional CT imaging is efficient in examining specific structures in the craniofacial area by reproducing actual measurements through minimization of errors from patient movement and image magnification. Due to the rapid development of digital image technology and the expansion of treatment range a need for developing three -dimensional analysis has become urgent. Therefore the purpose of this study was to evaluate the percentage of error and magnification of three-dimensional CT using a dried skull and Vworks $program^{TM}$ (Cybermed Inc., Seoul, Korea) and also to obtain landmarks that are easy to designate and reproduce in three-dimensional images using the Vmorph-proto $program^{TM}$ (Cybermed Inc., Seoul, Korea). The following conclusions were obtained, 1. In the comparison of actual measurements from the dried skull and the three-dimensional image obtained from the Vworks program, the mean error was 0.99mm and the magnification was 1.04%. 2. Clinically useful hard tissue landmarks from three-dimensional images were Supraorbitale, Lateral orbital margin, Infraorbitale, Nasion, ANS, A point, Zygomaticomaxilla, Upper incisor, Lower incisor, B point, pogonion, Menton, PNS, Condylar inner margin, Condylar outer margin, Porion, Condylion, Gonionl, Gonion2, Gonion3, Sigmoid notch and Basion. 3. Clinically useful soft tissue landmarks from three-dimensional images were Endocanthion, Exocanthion, Soft tissue Nasion, Pronasale, Alare lateralis, Upper nostril point, Lower nostril point, Subnasale, Upper lip point, Cheilion, Stomion, Lower lip center, Soft tissue B, Pogonion, Menton and Preaurale. The Vworks program can be considered a clinically efficient tool to produce and measure three-dimensional images. Most of the hard and soft tissue landmarks proposed above are anatomically important points which are also easily reproducible and designated. These landmarks can be beneficial in three-dimensional diagnosis and the prediction of changes before and after surgery.

• The korean journal of orthodontics
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• v.32 no.1 s.90
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• pp.59-69
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• 2002

The purpose of this study was to evaluate the reproducibility of lateral cephalometric landmarks according to radiographic image enhancement, and to contribute to the identification of cephalometric landmarks. Lateral cephalograms of ten individuals were taken and stored into computer. The images were then enhanced up to four grades by Quick Ceph Image Pro$^{TM}$ on condition that the gray-scale equalization number was 50 and the detail enhancement number was 50. After thirty two landmarks were identified on monitor images by five observers, the deviations from the mean, the distances estimated between identified points and the mean point of five identified points, were evaluated for each landmark at each enhancement grade. Through the statistical analysis, following results were obtained. 1. In case of unenhanced radiographic images, the inter-observer reproducibility of the landmarks showed a large variation. 2. The comparison of deviation from the mean according to the degree of radiographic image enhancement for each landmark showed that the inter-observer reproducibility was significantly different at 5 landmarks. 3. The landmark of pterygomaxillary fissure showed higher reproducibility at enhancement grade 1 and 2 images than at unenhanced images. So did the landmark of posterior nasal spine at enhancement grade 1 images, and the landmark of menton at enhancement grade 2, 3 and 4 images respectively. The above results suggest that the reproducibility of some landmarks can be increased by radiographic image enhancement during the identification of the lateral cephalometric landmarks on the monitor.

• Water for future
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• v.56 no.2
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• pp.8-14
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• 2023