• 한국연소학회:학술대회논문집
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• 2001.06a
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• pp.17-22
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• 2001

The flow induced by a circular jet vertically impinging under a horizontal plate is investigated by visualization technique, using kerosene smoke in nitrogen gas to visualize the flow in the vortex as well as under the plate. The light source was the sheet beam of Ar-Ion laser. The vertical and 3-dimensional images of vortices were recorded by the digital video camera.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.355-358
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• 2003

The strengthening method with CFS(Carbon Fiber Sheet) to reinforced concrete structures has a fatal defect. Strengthened beams have been almost failed far below their ultimate strength due to interface debonding failure between the surface of concrete and CFS. The purpose of this study is to investigate the failure mechanism and failure behavior of strengthened RC beam using CFS.

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.108-111
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• 2004

Laser induced incandescence and laser induced fluorescence techniques have been investigated to measure the concentrations of soot and PAH, respectively. The Nd:YAG and dye lasers were used to form a sheet beam, and its wavelength were modulated to obtain a optimized signals of soot and PAH. Results showed that the relative size groups of soot and PAH can be measured by using our laser techniques.

• Journal of Ocean Engineering and Technology
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• v.13 no.1 s.31
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• pp.105-112
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• 1999

This research is an experimental investigation of the region of the Biased Flow. This experiment was carried out in a circulating water channel, and the results are analyzed by using the PIV technique. The results are presented in velocity vector field, velocity contour and vorticity contour. The results were compared with those of Zdravkovich which were carried out in a wind tunnel. These results will be very useful to verify numerical codes.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.385-392
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• 2011

In this study, experimental research was carried out to evaluate and improve the seismic performance of reinforced concrete beam-column joint regions using strengthening materials (steel plate, carbon fiber sheet, and embedded carbon fiber rod) in existing reinforced concrete buildings. Six specimens of retrofitted beam-column joints are constructed using various retrofitting materials and tested for their retrofit performances. Specimens designed by retrofitting the beam-column joint regions (LBCJ series) of existing reinforced concrete building showed a stable mode of failure and an increase in load-carrying capacity due to the effect of crack control at the time of initial loading and confinement from retrofitting materials during testing. Specimens of LBCJ series, designed by the retrofitting of FRP in reinforecd beam-column joint regions increased its maximum load carrying capacity by 26~50% and its energy dissipation capacity by 13.0~14.4% when compared to standard specimen of LBCJC with a displacement ductility of 4.

• Steel and Composite Structures
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• v.34 no.1
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• pp.91-105
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• 2020

Steel-concrete composite beam with profiled steel sheet has gained its popularity in the last two decades. Due to the ageing of these structures, retrofitting in terms of flexural strength is necessary to ensure that the aged structures can carry the increased traffic load throughout their design life. The steel ribs, which presented in the profiled steel deck, limit the use of shear connectors. This leads to a poor degree of composite action between the concrete slab and steel beam compared to the solid slab situation. As a result, the shear connectors that connects the slab and beam will be subjected to higher shear stress which may also require strengthening to increase the load carrying capacity of an existing composite structure. While most of the available studies focus on the strengthening of longitudinal shear and flexural strength separately, the present work investigates the effect of both flexural and longitudinal shear strengthening of steel-concrete composite beam with composite slab in terms of failure modes, ultimate load carrying capacity, ductility, end-slip, strain profile and interface differential strain. The flexural strengthening was conducted using carbon fibre reinforced polymer (CFRP) or steel plate on the soffit of the steel I-beam, while longitudinal shear capacity was enhanced using post-installed high strength bolts. Moreover, a combination of both the longitudinal shear and flexural strengthening techniques was also implemented (hybrid strengthening). It is concluded that hybrid strengthening improved the ultimate load carrying capacity and reduce slip and interface differential strain that lead to improved composite action. However, hybrid strengthening resulted in brittle failure mode that decreased ductility of the beam.

• Laser Solutions
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• v.9 no.2
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• pp.1-9
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• 2006

In this paper, we investigated the characteristics of fatigue fracture on TB(Tailored Blank) weldment by comparing the fatigue crack propagation characteristics of base metal with those of TB welded sheet used for vehicle body panels. We also investigated the influence of center crack on the fatigue characteristic of laser weld sheet of same thickness. We conducted an experiment on fatigue crack propagation on the base metal specimen of 1.2mm thickness of cold-rolled metal sheet(SPCSD) and 2.0mm thickness of hot-rolled metal sheet(SAPH440) and 1.2+2.0mm TB specimen. We also made an experiment on fatigue crack propagation on 2.0+2.0mm and 1.2+1.2mm thickness TB specimen which had center crack. The characteristics of fatigue crack growth on the base metal were different from those on 1.2+2.0mm thickness TB specimen. The fatigue crack growth rate of the TB welded specimens is slower in low stress intensity factor range $({\Delta}K)$ region and faster in high${\Delta}K$ region than that of the base metal specimens. The slant crack angle slightly influenced the crack propagation of the TB specimen of 2.0+2.0mm thinkness.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.380-383
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• 2006

The media transport system is used in a printer, a ATM(Automated Tellor Machine), and so on. The media transport system has many problems through miniaturization and rapid transportation of these machines. In the paper feeding mechanism, it is important to feed the sheet without jamming under any conditions. To avoid sheet jamming, first we need to predict the behavior of the sheet exactly. In this paper, the analysis of media behavior is based on J. Stolte's studies. In all of OA machines, a flexible beam or plate is pushed from the channel. The motion may be constrained by guides. This leads to a transient and geometrically nonlinear problem. The behavior of paper is simulated by dynamic elastica theory. The shape of guide is represented by parametric cubic curve. But J. Stolte's studies did not considered contact condition between sheet and guide. So Klarbring's Model. will be applied. And the analysis of flexible media has to include aerodynamic effect for more exact behavior analysis, because the flexible media can be deformed drastically by a little force. Therefore aerodynamic force must be applied to the governing equation. Lastly, the simulation of this model is performed, and the experiment is performed for verification of this model. The experimental results of low exit velocity are consistent with the simulation results, however experimental results of high exit velocity do not agree well with analytical results. The reason is that there may be other effects like nip Phenomena

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.403-403
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• 2011

결정질 태양전지는 태양전지 시장에 큰 서막을 장식하였다. 현재 여러 종류의 태양전지 기술들이 많이 나오고 있지만 결정질 태양전지는 변환 효율이 좋고 신뢰성이 높아서 높은 시장 점유율을 차지하고 있다. 하지만 응용 분야가 적고 기판 가격이 비싸다는 단점이 있다. 현재에는 응용분야 개선을 위하여 Flexible solar cell에 대한 연구가 활발하다. Flexible solar cell에 상부전극은 결정질 태양전지에서 사용되는 Ag나 Al 전극 대신 TCO 종류의 일종인 ITO를 많이 사용한다. Flexible Solar cell은 Organic Solar cell과 Amorphous Solar Cell 두 가지 범주를 가지고 있다. 본 연구에서는 Amorphous Solar Cell의 전극에 사용되는 ITO의 온도 Stress에 따른 특성을 연구함으로써 Engineer의 근본적인 이슈인 저비용, 고효율에 초점을 맞추어 소자특성을 확인해 보도록 한다. Glass에 E-beam evaporation 장비를 이용하여 ITO를 증착하였고 제작된 소자를 200, 250, 300, 350$^{\circ}C$의 온도변수를 두어 1시간동안 Annealing 하였다. 각 Annealing 온도에 따른 Sheet resistivity,와 visible 영역의 transmittant를 측정하였다. visible영역에서의 transmittant는 Annealing 200$^{\circ}C$에서 300$^{\circ}C$로 온도가 증가함에 따라 transmittant는 증가하다가 350$^{\circ}C$에서 감소하였다. Sheet resistivity의 경우 Annealing 200$^{\circ}C$에서 300$^{\circ}C$로 온도가 증가함에 따라 ITO의 Sheet resistivity가 줄어들다가 350$^{\circ}C$에서 증가하였다. 300$^{\circ}C$로 Annealing한 ITO가 가시광선 영역에서 transmittant가 가장 높은 80%로 측정 되었다. Sheet resistivity역시 300$^{\circ}C$로 Annealing한 ITO가 8${\Omega}/{\Box}$로 가장 낮았다. Annealing 온도가 ITO의 electrical 특성과 optical 특성에 변화를 주었음을 알 수 있었다. Resistivity가 낮은 ITO 전극으로 박막 셀을 제작한다면 좋은 효율을 얻을 수 있을 거라 생각된다.

• Journal of the Korean Society of Radiology
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• v.15 no.7
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• pp.965-973
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• 2021

Since radiation therapy is irradiated with high-energy X-rays in a variety of at least 20 Gy to 80 Gy, a high dose is administered to the local area where the tumor is located, and various side effects of some normal tissues are expected. Currently, in clinical practice, lead, a representative material, is used as an effort to shield normal tissues, but lead is classified as a heavy metal harmful to the human body, and a large amount of skin contact can cause poisoning. Therefore, this study intends to manufacture a measurement sheet that can compensate for the limitations of lead using the materials Tungsten, Brass, and Copper of the 3D printer of the FDM (Fused Deposition Modeling) method and to investigate the penetration performance. Tungsten mixed filament transmission measurement sheet size was 70 × 70 mm and thickness 1, 2, 4 mm using a 3D printer, and a linear accelerator (TrueBeam STx, S/N: 1187) was measured by irradiating 100 MU at SSD 100 cm and 5 cm in water using a water phantom, an ion chamber (FC-65G), and an elcetrometer (PTW UNIDOSE), and the permeability was evaluated. As a result of increasing the measurement sheet of each material by 1 mm, in the case of Tungsten sheet at 3.8 to 3.9 cm in 6 MV, the thickness of the lead shielding body was thinner than 6.5 cm, and in case of Tungsten sheet at 4.5 to 4.6 cm in 15 MV. The sheet was thinner than the existing lead shielding body thickness of 7 cm, and equivalent performance was confirmed. Through this study, the transmittance measurement sheet produced using Tungsten alloy filaments confirmed the possibility of transmission shielding in the high energy region. It has been confirmed that the usability as a substitute is also excellent. It is thought that it can be provided as basic data for the production of shielding agents with 3D printing technology in the future.