• 비파괴검사학회지
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• 제21권2호
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• pp.163-168
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• 2001

접착제와 리벳으로 접합된 항공기 판재의 접합부는 접합 불량, 크랙, 피로 결함이나 부식등에 의해 손상되고 열화될 수 있으며 이런 결함을 전 영역에 걸쳐서 신속하고도 신뢰성 있게 검사하는 것은 항공기 안전을 위해 매우 중요하다. 본 연구에서는 이를 위해 항공기용 알루미늄 판재의 랩 스플라이스 접합 연결부의 접합 품질을 비접촉 방식으로 수행할 수 있는 초음파 비파괴 평가법을 제안한다. 여기서는 레이저를 이용해 램파를 발생시키고 비접촉식 트랜스듀서 (공기정합 용량형 트랜스듀서)를 이용해 피치-캐치 방식으로 검사한다. 레이저 소스로는 Q-스위치된 Nd:YAG 레이저가 이용되며 배열 형태의 직선 슬릿을 갖는 마스크를 이용해 특정 모드의 램파를 발생시켜 이용하였다. 접합부의 한 쪽에서 발생된 레이저 여기 초음파는 판을 따라 전파하여 접합부를 지나 반대편에서 수신되고 수신된 신호의 특성과 접합부의 품질과의 관련성을 조사하였다.

• Journal of the Optical Society of Korea
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• 제7권4호
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• pp.230-233
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• 2003

This study describes the conceptual design of a soft x-ray microscope system based on a laserbased source for biomedical application with high resolution (${\leq}$50nm). The laboratory scale soft x-ray microscope consists of high power laser plasma x-ray source and grazing incidence mirrors with high reflectivity. The laser plasma source used for developing this system employs Q-switched Nd-YAG pulsed laser. The laser beam is focused on a tantalum (Ta) target. The Wolter type I mirror was used as condenser optics for sample illumination and as objective mirror for focusing on a detector. The fabrication of the Wolter type I mirror was direct internal cutting using ultraprecision DTM. A hydrated biological specimen was put between the two silicon wafers, the center of which was $Si_3N_4$ windows of 100㎚ thickness. The main issues in the future development work are to make a stable, reliable and reproducible x-ray microscope system.

• JSTS:Journal of Semiconductor Technology and Science
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• 제4권3호
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• pp.217-221
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• 2004

[ $CO_2$ ]laser ablation rates for bulk 4H-SiC substrates and GaN/AIN/SiC templates in the range 229-870 ${\mu}m.min^{-1}$ were obtained for pulse energies of 7.5-30 mJ over diameters of 50·500 ${\mu}m$ with a Q-switched pulse width of ${\sim}30$ nsec and a pulse frequency of 8 Hz. The laser drilling produces much higher etch rates than conventional dry plasma etching (0.2 - 1.3 ${\mu}m/min$) making this an attractive maskless option for creating through-wafer via holes in SiC or GaN/AlN/SiC templates for power metal-semiconductor field effect transistor applications. The via entry can be tapered to facilitate subsequent metallization by control of the laser power and the total residual surface contamination can be minimized in a similar fashion and with a high gas throughput to avoid redeposition. The sidewall roughness is also comparable or better than conventional via holes created by plasma etching.

• Clinical and Experimental Pediatrics
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• 제54권4호
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• pp.179-182
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• 2011

Transient neonatal diabetes mellitus (TNDM) is a rare form of diabetes mellitus that presents within the first 6 months of life with remission in infancy or early childhood. TNDM is mainly caused by anomalies in the imprinted region on chromosome 6q24; however, recently, mutations in the ABCC8 gene, which encodes sulfonylurea receptor 1 (SUR1), have also been implicated in TNDM. Herein, we present the case of a male child with TNDM whose mutational analysis revealed a heterozygous c.3547C>T substitution in the ABCC8 gene, leading to an Arg1183Trp mutation in the SUR1 protein. The parents were clinically unaffected and did not show a mutation in the ABCC8 gene. This is the first case of a de novo ABCC8 gene mutation in a Korean patient with TNDM. The patient was initially treated with insulin and successfully switched to sulfonylurea therapy at 14 months of age. Remission of diabetes had occurred at the age of 16 months. Currently, the patient is 21 months old and is euglycemic without any insulin or oral hypoglycemic agents. His growth and physical development are normal, and there are no delays in achieving neurological and developmental milestones.

• Structural Engineering and Mechanics
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• 제53권5호
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• pp.867-880
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• 2015

Mechanical fastening is still one of the main methods used for joining components. Different techniques have been applied to reduce the effect of stress concentration of notches like fastener holes. In this work we evaluate the feasibility of combining laser shock peening (LSP) and cold expansion to improve fatigue crack initiation and propagation of open hole specimens made of 6061-T6 aluminum alloy. LSP is a new and competitive technique for strengthening metals, and like cold expansion, induces a compressive residual stress field that improves fatigue, wear and corrosion resistance. For LSP treatment, a Q-switched Nd:YAG laser with infrared radiation was used. Residual stress distribution as a function of depth was determined by the contour method. Compact tension specimens with a hole at the notch tip were subjected to LSP process and cold expansion and then tested under cyclic loading with R=0.1 generating fatigue cracks on the hole surface. Fatigue crack initiation and growth is analyzed and associated with the residual stress distribution generated by both treatments. It is observed that both methods are complementary; cold expansion increases fatigue crack initiation life, while LSP reduces fatigue crack growth rate.

• Journal of the Optical Society of Korea
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• 제11권4호
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• pp.192-195
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• 2007

A high-conversion efficiency, nanosecond pulsed optical parametric generation and amplification with repetition rate of 20 kHz based on a periodically poled MgO-doped stoichiometric lithium tantalate was presented. Pumped by a Q-switched $Nd:YVO_4$ laser at 1064 nm with a pumping power of 4.8W, the generated output power was 1.6W for the signal and idler waves, achieving a slope efficiency of 50%. Using a seed source at signal wave the amplified signal output-pulse energy reached $65{\mu}J$. The obtained maximum gain was 72.4 dB.

• E2M - 전기 전자와 첨단 소재
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• 제9권6호
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• pp.593-599
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• 1996

Laser scribing of silicon plays an important role in metallization including the grid pattern and the front surface geometry which means aspect ratio of metal contacts. To make a front metal electrode of buried contact solar cell, we used ND:YAG lasers that deliver average 3-4W at TEM$\_$00/ mode power to sample stage. The Q-switched Nd:YAG laser of 1.064 gm wavelength was used for silicon scribing with 20-40.mu.m width and 20-200.mu.m depth capabilities. After silicon slag etching, the groove width and depth for buried contact solar cell are -20.mu.m and 30-50.mu.m respectively. Using MEL 40 Nd:YAG laser system, we can scribe the silicon surface with 18-23.mu.m width and 20-200.mu.m depth controlled by krypton arc lamp power, scan speed, pulse frequency and beam focusing. We fabricated a buried contact Silicon Solar Cell which had an energy conversion efficiency of 18.8 %. In this case, the groove width and depth are 20.mu.m and 50.mu.m respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.598-602
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• 2004

Organic light entitling diode panel was fabricated using pulsed laser deposition (PLD) method Nd-YAG laser with Q-Switched and 355 nm pulse was used for the PLD. While TPD(N,N'-Di-[naphthaleny]-N, N'-diphenyl-benzidine) was used as a HTL(Hole transport layer), $Alq_3$(8-Hydroxyquinoline, Aluminum Salt) was used as EML/ETL(Emitting Layer/Electron Transport Layer) Organic pellet was fabricated and employed for the PLD method. The absorbances of the organic films were investigated and the measured absorbance values of TPD and $Alq_3$ films was 362 nm and 399 nm, respectively. The turn-on voltage of the OLED panel was 7.5 V and its luminance was $90\;cd/m^2$

• 한국전기전자재료학회논문지
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• 제29권11호
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• pp.707-711
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• 2016

ITO/Ag/ITO conductive films on PET (polyethylene terephthalate) was etched by a Q-switched diode-pumped neodymiun-doped yttrium vanadate (Nd:YVO4, ${\lambda}=1064nm$) laser. During the laser direct etching, the laser beam was incident on the two different directions of PET and the etching patterns were investigated and analyzed. At a lower repetition rate of laser pulse, the larger laser etched patterns were obtained by laser beam incident on reverse side of PET substrate. On the contrary, at a higher repetition rate, it was possible to find the larger etched patterns in case of the laser beam incidence on forward side of PET substrate. For the laser beam incidence on reverse side, the laser beam is expected to be transferred and scattered through the PET substrate and the laser beam energy is thought to be dependent on the etch laser pulse beam energy.

• The Journal of Korean Physical Therapy
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• 제22권4호
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• pp.83-89
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• 2010

Purpose: The goal of this study was to investigate the feasibility for the early diagnosis of inflammatory arthritis by the reconstruction of three-dimensional photoacoustic imaging with a tissue phantom. Methods: Q-switched Nd:YAG laser (l = 532 nm) was applied to a tissue phantom to generate photoacoustic waves, and the acquired photoacoustic signals at different positions around the sample were used to recombine the distribution of the optical absorption and the images were subsequently generated through a reconstruction algorithm. Results: From the acquired photoacoustic signals, the surface andinner core of the phantom was clearly distinguished. Furthermore, the back-projection algorithm was able to reconstruct two-dimensional and three-dimensional photoacoustic images that contained the optical absorption property information of the tissue phantom. Conclusion: The results indicate that the photoacoustic imaging technique has many advantages such as high optical contrast and high acoustic resolution. The acquired images can be used for the early diagnosis of inflammatory arthritis by the structural information obtained from the region of interest.