• Journal of Welding and Joining
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• 제27권4호
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• pp.67-72
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• 2009

In this paper, arc characteristics of V groove joints using pulsed GMA welding were found out. The bevel angles of $22.5^{\circ}$ and $30.0^{\circ}$ were chose to make the V groove configuration with the groove angles of $45^{\circ}$ and $60.0^{\circ}$, respectively. In the experiment, the arc current waveform measurement and the high speed photography were taken to investigate the arc characteristics for a single-beveled asymmetric workpiece. Consequently, the welding current was changed abnormally around the edge of groove. As the arc moved close to the groove face, the welding current was increased rapidly because the welding arc was affected by the inclined surface. Also the welding current waveforms were measured for the double-sided symmetric workpiece to verify the previous measurements for the single-beveled workpiece, and similar current waveforms were found.

• 한국CDE학회논문집
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• 제22권1호
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• pp.44-58
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• 2017

The inspection for building occupancy authorization has lacked objectivity due to manual measurement methods. This is why connivance of the illegal buildings has been rampant, which has led to so many incidents. Consequently, this law has lost its intent to protect people's lives and property. In this study, for the purpose of improvement of this law, the research was conducted by the utilization of unmanned aerial vehicle for automated inspection for building occupancy authorization. Theoretical considerations about building occupancy authorization and the trend of UAV technology were accomplished. Secondly, a series of reverse engineering was conducted including digital photography, network RTK-VRS surveying and post-processing data. Thirdly, the resultant spatial information was used for building occupancy inspection authorization in a BIM platform and the effectiveness and applicability of UAV-based inspection was analyzed. As a result, methodology for UAV-based automated building occupancy inspection authorization was derived. And it was found that eleven items would be possible to be automated among thirty total items for building occupancy authorization. Also it was found that UAV-based automated inspection could be valid in inspecting building occupancy authorization due to authentic accuracy, effectiveness and applicability with government policy.

• Advanced Composite Materials
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• 제16권2호
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• pp.151-166
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• 2007

High-cycle fatigue characteristics of quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates [-45/0/45/90]s up to $10^8$ cycles were investigated. To assess the fatigue behavior in the high-cycle region, fatigue tests were conducted at a frequency of 100 Hz, since it is difficult to investigate the fatigue characteristics in high-cycle at 5 Hz. Then, the damage behavior of the specimen was observed with a microscope, soft X-ray photography and a 3D ultrasonic inspection system. In this study, to evaluate quantitative characteristics of both transverse crack propagation and delamination growth in the high-cycle region, the energy release rate associated with damage growth in the width direction was calculated. Transverse crack propagation and delamination growth in the width direction were evaluated based on a modified Paris law approach. The results revealed that transverse crack propagation delayed under the test conditions of less than ${\sigma}_{max}/{\sigma}_b$ = 0.3 of the applied stress level.

• 한국해양공학회지
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• 제2권2호
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• pp.104-111
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• 1988

This paper deals with the micro-surface-cracks behavior on the unnotched smooth specimens of Type 304 stainless steel at $593^{\circ}C$ in air under creep and creep-fatigue conditions that have 10 mim and 1 min load holding times respectively. The behaviors of the micro-surface-cracks have been visualized by means of surface replica method and optical micro-photography. The quantitative characteristics of initiation, growth and coalescence of micro-surface-cracks have been investigated by observing and measuring the crack growth behaviors. some of the important results are as follows: Main crack initiates at grain boundary in the early stage(10 to 20%)of its life time and grows through coalescence and finally leads to fracture. The distribution of micro-surface-crack length, 2a, can be plotted against the composite Weibull distribution. The growth rate of the main crack can be plotted against the stress intensity factor, crack tip opering displacement and J integral.

• 대한토목학회논문집
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• 제7권2호
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• pp.89-98
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• 1987

X-Ray 사진측량(寫眞測量)은 인체에 대한 해부학적(解剖學的) 또는 생리학적(生理學的) 자료를 사진형태로 기록하여 해석하는 방법이다. 본 연구는 X-Ray를 이용하여 모델이 되는 피사체(被寫體)에 변형(變形)을 준 각 경우와, 인체 부분을 모델로 할 경우의 3 차원 좌표에 대한 정확도를 분석하므로써, X-Ray 사진(寫眞)에 의한 3 차원 위치결정의 정확도(正確度)를 향상시키고, 실용성을 높이는데 그 목적을 두고 있다. X-Ray를 이용하여 인체부분의 실제 피사체(被寫體)를 관측(觀測)한 결과, 높은 정확도(正確度)로 실제응용을 할 수 있었으며, X-Ray 사진을 이용하여 피사체(被寫體) 모든 면에 대한 삼차원(三次元) 좌표(座標)를 결정 할 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2076-2081
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• 2004

Future exhaust gas limits for diesel-driven passenger cars will force the automotive industry to significantly improve the performance of engine. Since modern common-rail injection systems deliver more degrees of freedom referring to the injection process, again the optimization of the injection process could offer a possibility to meet the exhaust gas limits. This study describes the characteristic the pilot spray structure of piezo-driven injector for a passenger car common-rail system to be applicable multiple injection caused by fast response rather than solenoid-driven injector. The piezo-driven injector is prototype injector with same needle chamber of solenoid injector and the solenoid-driven one is commercial injector. The pilot spray characteristic such as spray tip penetration, spray speed, spray angle were obtained by spray images, which is measured by the Mie scattering method with optical system for high-speed temporal photography. It was found that piezo-driven injector effected electric change as important factor and showed faster response than solenoid-driven injector.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제40권
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• pp.7.1-7.5
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• 2018

Background: Oroantral communicating defects, characterized by a connection between the maxillary sinus and the oral cavity, are often induced by tooth extraction, removal of cysts and benign tumors, and resection of malignant tumors. The surgical defect may develop into an oroantral fistula, with resultant patient discomfort and chronic maxillary sinusitis. Small defects may close spontaneously; however, large oroantral defects generally require reconstruction. These large defects can be reconstructed with skin grafts and vascularized free flaps with or without bone graft. However, such surgical techniques are complex and technically difficult. A buccal fat pad is an effective, reliable, and straightforward material for reconstruction. Case presentation: This report describes three cases of reconstruction of large oroantral defects, all of which were covered by a pedicled buccal fat pad. Follow-up photography and radiologic imaging showed successful closure of the oroantral defects. Furthermore, there were no operative site complications, and no patient reported postsurgical discomfort. Conclusion: In conclusion, the use of the pedicled buccal fat pad is a reliable, safe, and successful method for the reconstruction of large oroantral defects.

• 대한두개안면성형외과학회지
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• 제16권1호
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• pp.1-10
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• 2015

Facial symmetry is an important component of attractiveness. However, functional symmetry is favorable to aesthetic symmetry. In addition, fluctuating asymmetry is more natural and common, even if patients find such asymmetry to be noticeable. However, fluctuating asymmetry remains difficult to define. Several studies have shown that a certain level of asymmetry could generate an unfavorable image. A natural profile is favorable to perfect mirror-image profile, and images with canting and differences less than $3^{\circ}-4^{\circ}$ and 3-4 mm, respectively, are generally not recognized as asymmetry. In this study, a questionnaire survey among 434 medical students was used to evaluate photos of Asian women. The students preferred original images over mirror images. Facial asymmetry was noticed when the canting and difference were more than $3^{\circ}$ and 3 mm, respectively. When a certain level of asymmetry is recognizable, correcting it can help to improve social life and human relationships. Prior to any operation, the anatomical component for noticeable asymmetry should be understood, which can be divided into hard tissues and soft tissue. For diagnosis, two-and three-dimensional (3D) photogrammetry and radiometry are used, including photography, laser scanner, cephalometry, and 3D computed tomography.

• 한국광학회지
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• 제1권1호
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• pp.12-15
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• 1990

홀로그래피 간섭법과 스펙클 사진법을 결합한 홀로스펙클 간섭법을 이용하여 3차원 변형을 측정하였다. 이 방법은 이중노출된 하나의 사진건판으로부터 종변위와 횡변위를 모두 알아낼 수 있어 3차원 변형측정에 매우 유용하게 사용되고 있다. 본 연구에서는 물체의 일부분에 밀집되어 일어나는 변형을 측정하기 위하여 image holography에 기초를 둔 광학시스템을 구성하였다. 시스템의 배율을 적절히 증가시키고 기준파의 세기를 감소시킴으로써 보통의 홀로그램에 비해 스펙클의 효과를 증대시켰다. 이로써 가시도가 높은 Young의 무늬 뿐만 아니라 확대되고 명확한 홀로 그래피 간섭무늬를 얻을 수 있어 indentor에 의한 3차원 접촉변형을 측정하였다.

• 대한방사선기술학회지:방사선기술과학
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• 제44권6호
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• pp.615-621
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• 2021

In the medical field, radiation provides information for the diagnosis and treatment of diseases. As the use of radiation increases and the risk of exposure increases, interest in radiation protection is also rapidly increasing. Lead shielding material is mainly used, which has a risk of lead poisoning and absorption into the body. Tungsten mixed filament shielding sheets were fabricated with a size of 70 × 70 mm and a thickness of 1, 2, and 4 mm by using a 3D printer. In the general shooting experiment, the thickness of the shielding sheet is 1 ~ 5mm, the tube voltage is 60, 80, 100, 120 kVp and the tube current is 20, 40 mAs. In general photography, Tungsten showed better shielding rate compared to Brass, Copper, and Lead protective tools under all irradiation conditions, and in particular, Tungsten 5 mm showed 100% shielding rate. The 3D-printed tungsten mixed filament shielding is expected to be used as a new shield that can replace the existing lead protection tools as it shows a better shielding rate than the existing lead protection tools in Radiography.