• 제어로봇시스템학회논문지
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• 제8권1호
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• pp.21-27
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• 2002

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. A number of visual or optical technologies have been successfully applied to measure three-dimensional surfaces. However, those conventional visual or optical methods have inherent shortcomings such as occlusion and variant surface reflection. X-ray vision system can be a good solution to these conventional problems, since we can extract the volume information including both the surface geometry and the inner structure of any objects. In the x-ray system, the surface condition of an object, whether it is lambertian or specular, does not affect the inherent characteristics of its x-ray images. In this paper, we propose a three-dimensional x-ray imaging method to reconstruct a three dimensional structure of an object out of two dimensional x-ray image sets. To achieve this by the proposed method, two or more x-ray images projected from different views are needed. Once these images are acquired, the simultaneous algebraic reconstruction technique(SART) is usually utilized. Since the existing SART algorithms have several shortcomings such as low performance in convergence and different convergence within the reconstruction volume of interest, an advanced SART algorithm named as USART(uniform SART) is proposed to avoid such shortcomings and improve the reconstruction performance. Because, each voxel within the volume is equally weighted to update instantaneous value of its internal density, it can achieve uniform convergence property of the reconstructed volume. The algorithm is simulated on various shapes of objects such as a pyramid, a hemisphere and a BGA model. Based on simulation results the performance of the proposed method is compared with that of the conventional SART method.

• Structural Engineering and Mechanics
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• 제72권2호
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• pp.217-227
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• 2019

The methodology known as "shape sensing" allows the reconstruction of the displacement field of a structure starting from strain measurements, with considerable implications for structural monitoring, as well as for the control and implementation of smart structures. An approach to shape sensing is based on the inverse Finite Element Method (iFEM) that uses a variational principle enforcing a least-squares compatibility between measured and analytical strain measures. The structural response is reconstructed without the knowledge of the mechanical properties and load conditions but based only on the relationship between displacements and strains. In order to efficiently apply iFEM to the most common structural typologies of civil engineering, its formulation according to the kinematical assumptions of the Bernoulli-Euler theory is presented. Two beam inverse finite elements are formulated for different loading conditions. Depending on the type of element, the relationship between the minimum number of required measurement stations and the interpolation order is defined. Several examples representing common applications of civil engineering and involving beams and frames are presented. To simulate the experimental strain data at the station points and to verify the accuracy of the displacements obtained with the iFEM shape sensing procedure, a direct FEM analysis of the considered structures is performed using the LUSAS software.

• Archives of Plastic Surgery
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• 제38권3호
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• pp.295-299
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• 2011

Purpose: It is generally believed that alopecia is caused by various factors such as scars, stress, genetical factors, androgens, etc. Androgenic alopecia is one of the most common cause of alopecia and found mainly in males. Propecia (Merck & Co., USA) and Minoxidil (McNEIL-PPC, Inc, USA) were the drugs approved from FDA for treatment of androgenic alopecia. Surgical treatments such as flap, tissue expansion, scalp reduction and hair transplantation can be considered if necessary. Hair micrograft techniques were developed for natural hair shapes and minimal adverse effect. There were attempts to measure the length of the forehead of the Korean young adults. However attempts to classify the shape and location of forehead hairline were rare. This study attempted to find out standard hairlines of young adults in their 20s & 30s and the result would be the guideline of the hairline in hair replacement surgery of male patients in their 40s & 50s. Methods: 200 male adults in 20s and 30s were photographed and measured the length of 11 vertical index lines to determine hairline. The indexes are the distances from hairline to intercanthal midpoint (A), to medial canthus (B), to upper eyelid fissure (C), to lower eyelid fissure (D), to lateral canthus (E) and distance from lateral highest point to medial lowest point, if the hairline is M-shape (F). Additionally, we classified the hairlines into 4 groups, M, horizontal, inverted U and irregular shapes. Results: The most common hairline of male adults in their 20s is inverted U-shape (53.3%), followed by horizontal-shape, M-shape, irregular-shape. In their 30s, inverted U-shape (59%) is followed by irregular-shape, M-shape, horizontal-shape. The M-shape is more frequently found in males in 30s than those in 20s. The mean values of the indexes in their 20s are as follows: A (76.14 mm), B (Rt: 75.78 mm, Lt:76.41 mm), C (Rt: 69.43 mm, Lt: 69.92 mm), D (Rt: 76.92 mm, Lt:77.46 mm), E (Rt: 64.16 mm, Lt: 64.73 mm), F (4.09 mm). Those in their 30s are as follows: A (76.13 mm), B (Rt: 76.114 mm, Lt: 76.02 mm), C (Rt: 69.87 mm, Lt: 70.37 mm), D (Rt: 77.37 mm, Lt: 77.58 mm), E (Rt: 69.63 mm, Lt: 69.85 mm), F (6.14 mm). Conclusion: The knowledge about human body measurement is indispensable to plastic surgeons. In this study, inverted U shape is the most common type of hairline in 30s, and similar distribution is found in 20s. The percentage of M shape in their 30s is elevated more than 10% compared to that in their 20s. The study of hairline shapes and 11 indexes of hairlines can be useful for planning of the hair transplantation and postoperative evaluation. This study being based on photogrammetry, there may be differences between actual distance of curved face and projected distance on flat photographs.

• 대한관절경학회:학술대회논문집
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• 대한관절경학회 제21차 추계 학술대회
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• pp.153-153
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• 2009

The purpose of this study was to evaluate tibial tunnel widening prospectively after anterior cruciate ligament (ACL) reconstruction with hamstring tendon grafts using Rigidfix (DePuy Mitek, Raynham, MA) femoral fixation and Intrafix (DePuy Mitek) tibial fixation. 56 consecutive patients who underwent ACL reconstruction with a minimum of 2 years' postoperative evaluation were reviewed. On the anterior-posterior (AP) and lateral radiographs, the diameter of the tibial tunnel was measured at proximal, middle, and distal positions and the shape of the tibial tunnels were classified. Tunnel widening was defined as widening of greater than 2 mm. Group I was defined as cases with no tunnel widening and group II defined as cases with tunnel widening. Postoperative laxity evaluations were performed using Lachman test, pivot-shift test, and Instrumented laxity testing using the KT-1000 arthrometer. On the AP radiographs, the average diameter of the tibial tunnel increased 8.8% at 6 months and 8.5% at 12 months postoperatively compared to the immediate postoperative day. On the lateral radiographs, the average diameter of the tibial tunnel increased 7.2% at 6 months and 8.1% at 12 months year postoperatively compared to the immediate postoperative day. The tunnel shape evaluation revealed predominantly linear type in 53 patients (95%). Group I was 42 patients (75%) and group II was 14 (25%). The average KT-1000 measurement was 1.0~1.8 mm in group I and 2.1~2.8 mm in group II (p>0.05) The Lachman and pivot-shift showed tests no significant differences between the two groups. In conclusion, hamstring ACL reconstruction using Rigidfix and Intrafix fixation showed less widening of the tibial tunnels than observed in previously published studies.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.356-361
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• 1996

Nowadays, Electronic Speckle Pattern Interferometry is a well established measuring technique with a wide range of industrial applications, particularly in the fields of deformation measurement and vibration analysis. Comparing with holographic inteferometry, it has some attractive features, which are rapid recording and reconstruction, satisfiable automation etc. Time-average ESPI was used to provide vibration mode shape of an object whose vibration amplitude is given as a fringe pattern. However, it is not possible to determine the direction of motions of a point on the object at any given time, because time-average method does not give any information about the phase of vibration. A better technique is stroboscopic method which can measure the amplitude and phase of vibrating surface. In this paper, loudspeakers were tested by these two methods and the mode shape and amplitude of vibration were visualized. As measured results, we can assume that these techniques will be applied directly in the loudspeaker industry.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.776-779
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• 1987

This paper describes a technique for measuring the volume of a pile of powder in a visual way. The volume of a fragile object whose shape is easily transformed by a slight touch of another object must be measured without any contact with it. This can be achieved by applying a three-dimensional shape reconstruction technique employed in computer vision. We have developed a measurement system that finds the volume of a pile of powder by employing a range finder, and performed an experiment of determining the volume of PVC powder piled on a table. The result of the experiment was satisfactory.

• 한국항공우주학회지
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• 제39권5호
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• pp.442-450
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• 2011

회전 블레이드의 모션을 측정하기 위해 스테레오 패턴 인식 (stereo pattern recognition, SPR) 기법을 적용한 측정 시스템을 구성하고 실험을 수행하였다. 시스템 요구사항을 만족시키는 스테레오 카메라를 확보하여 SPR 기반의 측정 시스템을 준비하였다. 시스템의 측정불확도를 계산하기 위한 일련의 실험을 통해, 본 SPR 시스템이 2m~4.2m의 측정 거리에서 0.2mm 이내의 표준불확도를 가짐을 확인하였다. 이를 이용하여 계산한 블레이드 모션의 합성표준불확도는, 리드-래그, 플래핑, 비틀림 운동에 대해 각각 0.296mm, 0.209mm, $0.238^{\circ}$ 이었다. 본 SPR 시스템을 한국항공우주연구원의 소형로터 시험장치에 설치하고 회전속도와 콜렉티브 피치각을 각각 360rpm, 589rpm, 그리고 $0^{\circ}$, $4^{\circ}$, $6^{\circ}$로 바꾸어가며, 지상 제자리비행 조건에서 블레이드의 모션과 탄성 변형을 성공적으로 측정하였다. Higher Harmonic Control Aeroacoustic Rotor Test -II 에서 사용한 측정 시스템과의 비교를 통하여 본 시스템의 장점을 분석하였다.

• 한국생산제조학회지
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• 제6권1호
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• pp.92-99
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• 1997

Nowadays, Electronic Speckle Pattern Interferometry is a well-established measuring technique with a wide range of industrial applications, particularly in the fields of deformation measurement and vibration analysis. Comparing with holographic interferometry, it has some attractive features, which are rapid recording and reconstruction, satisfiable automation etc. The Time-Average ESPI is used to provide vibration mode shape of an object whose vibration amplitude is given as a fringe pattern. Its merit is rapid and simple measurement for vibrating object. However, it is not possible to determine the direction of motions of a point on the object at any given time, because it does not give any information about the phase of vibration. But, Stroboscopic ESPI can measure the amplitude and phase of vibrating surface. In this paper, loudspeakers were tested by these two methods. As a result, we can assume that these techniques will be applied directly in the loudspeaker industry.

• 대한공간정보학회지
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• 제25권1호
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• pp.47-54
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• 2017

최근 unmanned aerial vehicle(UAV)를 이용하여 영상을 취득하고 지도제작 및 3차원 형상을 구축하는 연구들이 활발히 이루어지고 있다. 본 연구에서는 영상정합(image matching) 기술을 이용하여 3차원 형상을 재현하고, 형상 변화가 있을 경우 이를 탐지하여 면적 및 부피를 계산하는 방법론을 제시하는 실험으로 측정 정확도를 평가하였다. 이를 위해 모의 구조물을 구축하여 형상변화 전 후의 UAV 영상을 취득하고, 영상정합 결과물인 포인트 데이터의 비교를 위해 변화 전 데이터는 격자 형태로 변환하여 높이 값을 비교하였다. 실험 결과, 제안된 방법은 가로 세로 30cm 이상의 형상변화는 매우 높은 정확도로 면적 및 부피를 계산하였으나, 그 이하의 형상변화는 아직 영상정합기술의 한계에 기인하여 적용이 어려운 것으로 검증되었다. 하지만 제안한 방법론은 불법건축물 판별, 구조물의 일정규모 이상 피해의 정량적 분석 및 관리 등에 충분히 활용 가능할 것으로 생각된다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1971-1975
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• 2003

This paper describes a technique, which analyzes the functional instability of the ankle using three-dimensional scanner. The technique is based on the structured light pattern projection method, which is performed by using one digital still camera and one LCD projector. This system can be easily realized with the low cost. The measuring result has high accuracy. The measuring error is about 0.2 mm or less. Using this technique the three-dimensional posture of the leg and foot of the target person are measured and analyzed.