• Korean Journal of Optics and Photonics
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• v.21 no.6
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• pp.254-258
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• 2010

We investigate an optical technique for beam shaping and optical amplification of a pulsed laser diode without variation of its original properties, such as repetition rate and pulse duration. The horizontal and longitudinal sizes of the pulsed laser diode are 300 and $2{\mu}m$, respectively, and its output power is $1.1mW/cm^2$. The multimodal and elliptical pulse shape of the laser diode is converted to the single-modal and Gaussian pulse shape by using a lensed optical fiber. Since the single-modal lensed fiber coupling from the multimodal pulsed laser diode degrades the output power severely, the output power of the pulsed laser diode is dramatically enhanced by using an optical amplification method based on master oscillated power amplification (MOPA). The pulse qualities of the laser diode are not changed after amplifying the pulse power and the output power was finally measured to be $29mW/cm^2$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.712-720
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• 2003

In this paper, a multi-layered metallic disk array structure(MDAS) excited by cross-dipole elements was proposed for efficiently shaping of flat-topped element patterns(FTEP) with circular polarization. The MDAS excited by cross-dipole elements has advantages to decrease in volume and weight of an overall array antenna and so, it is appropriate for the FTEP applications of a ralativlely low frequency band. In order to verify the effectness of this structure, the MDAS breadboard operated at X-band(7.9 ∼ 8.4 GHz) was fabricated, and its design parameters were experimentally optimized on the basis of the previous design experience. The experimental results were shown that the MDAS could shape good FTEPs of ${\pm}$20$^{\circ}$beam width at least within a 6.1 % frequency band.

• Journal of architectural history
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• v.33 no.1
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• pp.45-60
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• 2024

This study aims to examine the cutting traces remaining on the bracket tie beams of Sungnyemun gate, identifying the tools employed during the late Goryeo to early Joseon periods by specific processes, and deliberating on the timber shaping techniques utilized in advanced architectural construction during the late Goryeo to early Joseon eras. Through the research, it was confirmed that in the production of Sungnyemun Gate's bracket tie beams during the 14th to 15th centuries, both the timber splitting and ripsawing methods were used in conjunction. Moreover, the wood finishing process revealed the use of a plane. It can be inferred that the characteristics of the plane used during that time were not significantly different from those observed in the later period of the Joseon dynasty. The ripsawing and plane finishing techniques were evident in various parts of the bracket tie beams of Sungnyemun gate across the reigns of king Taejo and Sejong, indicating that the techniques involving ripsaw and plane were already prevalent in the late Goryeo period. Consequently, it can be inferred that the ripsawing and plane finishing techniques might have been applied in the construction of prominent government buildings in Hanyang(Seoul), including Gyeongbokgung Palace, and in the residences of royalty and nobility after the establishment of the Joseon dynasty.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.4
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• pp.324-328
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• 2014

Aberrant anatomy of mandibular premolars is very rare in Korean, but aberration can contribute the endodontic failure as it makes difficult to remove the irritants during cleaning and shaping procedure. This case report describes the successful root canal treatment of a rare mandibular first premolar with C-shaped root canal as using a cone-beam computed tomography to understand the internal shape of root canal system and a dental operating microscope to improve the magnification and illumination.

• Laser Solutions
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• v.17 no.1
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• pp.1-6
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• 2014

Indium tin oxide (ITO) is an important transparent conducting oxide (TCO). ITO films have been widely used as transparent electrodes in optoelectronic devices such as organic light-emitting devices (OLED) because of their high electrical conductivity and high transmission in the visible wavelength. Finding ways to control ITO micromachining depth is important role in the fabrication and assembly of display field. This study presented the depth control of ITO patterns on glass substrate using a femtosecond laser and slit. In the proposed approach, a gaussian beam was transformed into a quasi-flat top beam by slit. In addition, pattern of square type shaped by slit were fabricated on the surfaces of ITO films using femtosecond laser pulse irradiation, under 1030nm, single pulse. Using femtosecond laser and slit, we selectively controlled forming depth and removed the ITO thin films with thickness 145nm on glass substrates. In particular, we studied the effect of pulse number on the ablation of ITO. Clean removal of the ITO layer was observed when the 6 pulse number at $2.8TW/cm^2$. Furthermore, the morphologies and fabricated depth were characterized using a optical microscope, atomic force microscope (AFM), and energy dispersive X-ray spectroscopy (EDS).

• Restorative Dentistry and Endodontics
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• v.39 no.2
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• pp.132-136
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• 2014

The presence of radix entomolaris (RE) in a mandibular first molar is a common occurrence in certain ethnic groups, but the presence of RE in a mandibular second molar is a rare occurrence. In the present case, RE was identified from preoperative radiographs and confirmed using cone-beam computed tomography (CBCT). The access cavity was modified to locate the RE. Cleaning and shaping were performed with nickel-titanium rotary instruments. Obturation was completed with gutta-percha cones using AH Plus (Dentsply Detrey GmbH) as sealer. From the CBCT axial images, the RE was determined to have a Type III curvature by the De Moor classification, Type B separate RE by the Carlsen and Alexandersen classification, and radiographically, a Type i image by the Wang classification. The presence of RE in the mandibular second molar makes it essential to anticipate and treat the distolingual root canal. This case report highlights the usefulness of CBCT for assessing RE in the mandibular second molar, which can help the clinician in making a confirmatory diagnosis and assessing the morphology of the root canal.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.18-20
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• 2003

Optimal processing and system to produce the laser welded tube for one body formed bumper beam are studied. The calculated size of tube is a thickness of 1.4mm, diameter of 105.4mm and length of 2000mm. The tube is shaped from cool rolled high strength steel sheet(tensile strength: 60kgf/$\textrm{mm}^2$ grade). Two roll bending method is the optimal tube shaping process compared to UO-bending, bending on press brake, multi-step continuous roll forming and 3 roll bending methods. Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are also studied. The longitudinal butt-joint is welded by the $CO_2$ laser welding system equipped with a seam tracker and plasma sensor. The constructed $CO_2$ laser tube welding system can be used for the precision seam tracking and the real-time monitoring of weld quality. Finally, the obtained laser welded tube can be used for one-body formed automobile bumper beam.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.826-831
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• 2008

This paper presents hybrid antenna(HA) design based on shaped reflector for mobile satellite communication. HA is composed of a shaped reflector and a feeder having $1{\times}8$ linear phased array, and reflector shaping method is applied for the performance optimization with minimum aperture size. And, in the feeder design, HA has another merit to minimize the manufacturing cost by optimizing the number of element. Proposed HA is designed at Ka-band and can electrically control a beam pattern within ${\pm}3^{\circ}$ in the basic angle of $+45^{\circ}$ in elevation. This antenna is designed to meet ITU-R S.465-5 for beam pattern including side-lobe level.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.181-184
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• 2009

The hot press farming process, which is the press hardening of steel parts using cold dies, can utilize both ease of shaping and high strength due to the hardening effect of rapid quenching during the pressing. In this study, a thermo-elastoplastic analysis of the hot press forming process using the finite element method was performed in order to investigate the deformation behavior and temperature history during the process and the mechanical properties of the pressed parts.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.111-115
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• 2001

The die design for hot forging was investigated for manufacturing precisely of scroll rotor made with Al-Si alloy. A scroll rotor is a non-symmetric 3-D shape part, having involute wraps. Disk-shaped billet of Al-Si alloy was extruded to wraps and boss simultaneously. Because the involute wraps is not axi-symmetric, the flow velocity and the stress of die is very much different at each portion. Moreover, the die in wraps portion is a cantilever beam and fractured. In this paper, the analysis of forming and die stress is investigated using the FEM tool, DEFORM-3D. The tensile strength of tool material is $250kg/mm^{2}$. From the analysis results, we can find the maximum principal stress of die is over the fracture strength and redesign the die. The prototype forged part is superior in net shaping and microstructure.