• Journal of Advanced Marine Engineering and Technology
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• 제28권1호
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• pp.109-115
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• 2004

The spatter and porosity could be occurred during$CO_2$CW laser welding of Primer- coated steel for shipbuilding. This study has suggested an alternative idea by examining of weld-defect formation mechanism. The primer-coated plate induced the spatter humping bead and porosity and these are main part of the welding defect. attributed to the powerful vaporizing pressure of primer attached on the base metal The zinc of Primer has a boiling point that is the lower temperature than melting point of steel zinc vapor will build up at the interface between the two sheets and this tends to deteriorate the quality of the weld by ejecting weld material from lap position or leaving porosity. Therefore introducing a small gap clearance in the lap position. the zinc vapor could escape through it and sound weld beads can be acquired. In conclusion, we suggested the occurred and prevented mechanism of weld defects with searching the factor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 G
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• pp.3048-3050
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• 1999

This paper suggests a position estimating algorithm using mono vision system with projective geometry method. Generally, 3-D information can not be easily extracted from mono vision system which is taken by a camera at a specific point. But this defect is overcome by adopting model-based image analysis and selecting lines and points on the ground as natural landmarks. And this paper suggests a method that estimates position from many natural landmarks by distance error weight function.

• 비파괴검사학회지
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• 제15권2호
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• pp.378-385
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• 1995

초음파검사는 초음파 펄스가 한 방향으로 진행한다고 하는 지향성을 이용하고 있다. 초음파의 지향성은 전파 방향과 음압 분포의 관계를 나타내고 있으며 탐촉자의 배치, 탐상 감도 및 주사 간격, 결함의 위치 및 특성의 결정에 밀접한 관계가 있다. 본 논문은 초음파가시화법을 이용하여 pyrex glass로 만든 가상 맞대기 용접부내의 용접 금속부에 위치한 인공 결함으로부터 산란한 반사 횡파의 지향성을 측정하였다. 2 MHz와 4 MHz의 사각탐촉자가 인공 결함에서의 반사파의 지향성 조사에 사용되었다. 인공 결함으로부터 반사된 횡파의 지향성은 사각탐촉자의 위치 및 가상 용접부의 형상에 따라 달랐으며 2 MHz와 4 MHz의 사각 탐촉자에 따라 반사파의 지향성은 큰 차이를 나타내고 있었다. 또한 가상 용접부의 높이가 커짐에 따라 반사각과 입사각은 비슷하게 되었다.

• 대한족부족관절학회지
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• 제11권2호
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• pp.232-237
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• 2007

Introduction: To report the result of the thigh perforator free flap for the reconstruction of the soft tissue defect of the lower extremities and usefulness of this flap. Materials and Methods: We have performed 23 cases of thigh perforator free flap to reconstruct the soft tissue defect of the lower extremities between February 2004 and July 2005. The anterior aspect of the legs were 9 cases, the ankle joints were 4 cases, the dorsal aspect of the feet were 6 cases, the sole of the feet were 4 cases as recipient sites. The anterolateral thighs were 13 cases, the anteromedial thighs were 10 cases as donor sites. The size of the flap ranged from $4{\times}5\;cm$ to $12{\times}18\;cm$. The mean flap area was $73.2\;cm^2$. The length of the pedicle ranged from 5 cm to 15 cm. Every patient except children was operated under the spinal anesthesia. Results: 21 flaps (91.3%) survived, 2 flaps (8.7%) failed. In the 21 flaps that had survived, there were partial necrosis in 4 cases, which healed without any additional operation. In the 13 anterolateral thigh perforator flaps, 9 cases survived totally, 3 cases had the partial necrosis, 1 case failed. In the 10 anteromedial thigh perforator flaps, 8 cases survived totally, 1 case had the partial necrosis, 1 case failed. Conclusion: The authors had a good result with the thigh perforator free flap and believe that this flap is a good option for the reconstruction of the soft tissue defect of the lower extremities, because this flap has a thin thickness and it is easy to dissect the vessels. Moreover the patients can be operated with supine position.

• 한국안전학회지
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• 제30권1호
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• pp.144-149
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• 2015

This study aims to quantitatively evaluate failure pressure of wall-thinned elbow under combined load along with internal pressure, by conducting real-scale burst test and finite element analysis together. For quantitative evaluation, failure pressure data was extracted from the real-scale burst test first, and then finite element analysis was carried out to compare with the test result. For the test, the wall-thinning defect of the extrados or intrados inside the center of 90-degree elbow was considered and the loading modes to open or close the specimen maintaining a certain load or displacement were applied. Internal pressure was applied until failure occurred. As a result, when the bending load was applied under the load control condition, the intrados of the defect was more affected by failure pressure than the extrados, and the opening mode was more vulnerable to failure pressure than the closing mode. When the bending load was applied under the displacement control, it was hardly affected by failure pressure though it was slightly different from the defect position. The result of the finite element analysis showed a similar aspect with the test. Moreover, when major factors such as material properties and pipeline thickness were calibrated to accurate values, the analytical results was more similar to the test results.

• 한국멀티미디어학회논문지
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• 제18권9호
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• pp.997-1007
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• 2015

In this paper, we propose a method for automatically analyzing the bone formation in a mouse model of frontal bone defect. We perforate two holes of 0.8mm diameter in the frontal bone and observe the bone formation process using a micro CT. Because the conventional analysis software of the micro CT does not support automatic analysis of the bone formation status, we have to use a manual analysis method. However the manual analysis is very cumbersome and requires a lot of time, we propose an automatic analysis method. It rotates the image around three axes directions so that the mouse's skull come into regular position. It calculates the cumulative image of the voxel values for the perforated bone surface. It estimates the hole location by finding the darkest point in the cumulative image. The proposed method was applied to 24 CT images of saline administration group and PTH administration group and hole location was estimated. BV/TV index was calculated for the estimated hole to evaluate the bone formation status. Experimental results showed that bone formation process is more active in PTH administration group. The method proposed in this paper could replace successfully the cumbersome and time consuming manual job.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권4호
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• pp.161-164
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• 2006

In this thesis we designed the vision system to inspect the defect of a back light unit of plat panel display device. The vision system is divided into hardware and inspection algorithm of defect. Hardware components consist of illumination part, robot-arm controller part and image-acquisition part. Illumination part is made of acrylic panel for light diffusion and five 36W FPL's(Fluorescent Parallel Lamp) and electronic ballast with low frequency harmonics. The CCD(Charge-Coupled Device) camera of image-acquisition part is able to acquire the bright image by the light coming from lamp. The image-acquisition part is composed of CCD camera and frame grabber. The robot-arm controller part has a role to let the CCD camera move to the desired position. To take inspections of surface images of a flat panel display it can be controlled and located every nook and comer. Images obtained by robot-arm and image-acquisition board are saved on the hard-disk through windows programming and are tested whether there are defects by using the image processing algorithms.

• 한국정밀공학회지
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• 제17권12호
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• pp.107-114
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• 2000

Rollers and rolls in the continuous process systems are noes of key components that determine the quality of web products. The condition of rollers and rolls(ex. eccentricity wear) should be consistently monitored in order to maintain the process conditions (ex. tension, edge position) within a required specification. In this paper, a new diagnosis technique is suggested to detect the defect of rollers/rolls (ex. eccentricity, wear) based on frequency domain analysis of web tension signal. The kernel of this technique is to use the spectrum amplitude of tension signal which allows to identify the fault rollers/rolls and to also diagnose the degree of fault in corresponding rollers and rolls. The experimental results proved that the suggested diagnosis technique can be successfully used to identify the defect rollers and rolls as well as to diagnose the degree of the defect of those rollers. The suggested technique can be applied to monitor and diagnose the shape of rollers and rolls in various multi-span web transport systems.

• Structural Engineering and Mechanics
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• 제28권5호
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• pp.525-548
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• 2008

This article deals the theory for solving an inverse problem of plate structures using the frequency-domain information instead of classical time-domain delays or free vibration eigenmodes or eigenvalues. A reduced set of output parameters characterizing the defect is used as a regularization technique to drastically overcome noise problems that appear in imaging techniques. A deconvolution scheme from an undamaged specimen overrides uncertainties about the input signal and other coherent noises. This approach provides the advantage that it is not necessary to visually identify the portion of the signal that contains the information about the defect. The theoretical model for Quantitative nondestructive evaluation, the relationship between the real and ideal models, the finite element method (FEM) for the forward problem, and inverse procedure for detecting the defects are developed. The theoretical formulation is experimentally verified using dynamic responses of a steel plate under impact loading at several points. The signal synthesized by FEM, the residual, and its components are analyzed for different choices of time window. The noise effects are taken into account in the inversion strategy by designing a filter for the cost functional to be minimized. The technique is focused toward a exible and rapid inspection of large areas, by recovering the position of the defect by means of a single accelerometer, overriding experimental calibration, and using a reduced number of impact events.

• Journal of Welding and Joining
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• 제32권5호
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• pp.50-57
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• 2014

Friction Stir Welding (FSW) is a complex process with several mutually interdependent parameters. A slight difference from known settings may lead to imperfections in the stirred zone. These inhomogeneities affect on the mechanical properties of the FSWed joints. In order to prevent the failure of the welded joint it is necessary to detect the most critical defects non-destructive. Especially critical defects are wormhole and lack of penetration (LOP), because of the difficulty of detection. Online thermography is used process-accompanying for defect detecting. A thermographic camera with a fixed position relating to the welding tool measures the heating-up and the cool down of the welding process. Lap joints with sound weld seam surfaces are manufactured and monitored. Different methods of evaluation of heat distribution and intensity profiles are introduced. It can be demonstrated, that it is possible to detect wormhole and lack of penetration as well as surface defects by analyzing the welding and the cooling process of friction stir welding by passive online thermography measurement. Effects of these defects on mechanical properties are shown by tensile testing.