• Archives of Reconstructive Microsurgery
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• 제2권1호
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• pp.82-92
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• 1993

A comparative study was undertaken to evaluate the contact Neo-dymium : yttrium aluminum garnet(Nd:YAG) laser system for vascular anastomosis of small caliber blood vessels(diameter 0.5-1.2 mm) in the animal model. In this study 40 femoral arteries and 40 femoral veins of Sprague-Dawley rats were anastomosed by contact laser assisted microvascular anastomosis(LAMA) utilizing 3 stay sutures which were placed 120 degrees apart and the intervals welded with contact Nd:YAG laser unit, conventionally sutured anastomosis(CSA) served as controls. The time needed for vascular anastomosis, patency rate(immediate postoperative, postoperative 2nd day, postoperative 1 week, postoperative 4 weeks), gross and microscopic evaluations were compared to conventional microsurgical suture technique. The results are as follows: 1. Postoperative patency rate was 82.5% for femoral artery and 75% for femoral vein by contact LAMA technique compared to 90% and 75% by CSA technique at postoperative 4 weeks. 2. Less time-consumed for arterial anastomosis by 6 minutes 23 seconds and venous anastomosis by 8 minutes 55 seconds with contact LAMA technique compared to CSA technique. 3. Grossly almost complete healing had taken place by postoperative 1 week by contact LAMA technique. 4. Aneurysm formation was 5% for femoral artery and 15% for femoral vein by contact LAMA technique compared to 5% and 10% respectively by CSA technique. 5. Microscopically, re-endothelization was complete by postoperative 7th day by contact LAMA technique. There was less medial hypertrophy and hyperplasia and also less inflammatory response compared to CSA.

• The Korean Journal of Ceramics
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• 제2권1호
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• pp.39-42
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• 1996

${\alpha}-SiC$ powder with or without the addition of 0.1 wt% of large ${\alpha}-SiC$ partices(seeds) was pressureless-sintered at $1950^{\circ}C$ for 0.5, 2, and 4 h using $Y_3Al_5 O_{12}$ (yttrium aluminum garnet, YAG) as a sintering aid. The materials without seeds had an equiaxed grain struture. In contrast, the materials with seeds sintered for 2 and 4 h had a duplex microstructure with large elongated grains and amall equiaxed grains. Addition of large ${\alpha}-SiC$ seeds into ${\alpha}-SiC$ accelerated the grain growth of some ${\alpha}-SiC$ grains during sintering and resulted in the increased fracture toughness of the sintered materials. The fracture toughnesses of materials with or without seeds sintered for 4 h were 6.6 and $5.2 MPa \;m^{12}$, respectively.

• Medical Lasers
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• 제8권2호
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• pp.74-79
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• 2019

Periorbital melasma is often refractory to treatment and highly associated with rebound hyperpigmentation or mottled hypopigmentation after laser treatment in Asian patients. In this report, we describe 2 patients with cluster-1 periorbital melasma and 1 patient with cluster-2 periorbital melasma who experienced remarkable clinical improvements after microwave-generated, atmospheric-pressure, non-thermal nitrogen plasma treatments. All patients exhibited limited clinical responses after combination treatments with topical bleaching agents, systemic oral tranexamic acid, and low-fluenced Q-switched neodymium (Nd):yttrium-aluminum-garnet (YAG) lasers. Low-energy nitrogen plasma treatment at 0.75 J elicited remarkable clinical improvement in the periorbital melasma lesions without post-laser therapy rebound hyperpigmentation and mottled hypopigmentation. We deemed that a single pass of nitrogen plasma treatment at 0.75 J induces mild microscopic thermal tissue coagulation and modification within the epidermis while preserving the integrity of the basement membrane in patients with periorbital melasma. Accordingly, nitrogen plasma-induced dermal tissue regeneration could play a role in the treatment of melasma lesions.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.185-185
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• 2012

중공 발광 나노 물질은 특유의 구조적 특성(낮은 밀도, 높은 비표면적, 다공성 물질, 낮은 열팽창계수 등)과 광학적 성질을 이용하여 디스플레이 패널, 광결정, 약물전달체, 바이오 이미징 라벨 등의 다양한 적용이 가능하다. 이러한 적용에 있어 균일한 크기와 형태의 중공 입자는 필수 조건으로 여겨진다. 지금까지 합성된 중공 발광 입자에는 BaMgAl10O17 : Eu2+-Nd3+, Gd2O3 : Eu3+, $EuPO_4{\cdot}H_2O$과 같은 것들이 있으나 크기 조절이 어렵고, 그 균일성이 확보되지 못하였다. 균일한 크기의 중공 발광 입자를 만들기 위해 SiO2나 emulsion을 템플릿으로 이용하여 황화카드뮴, 카드뮴 셀레나이드 중공 입자를 합성한 예가 있으나, 양자점의 독성으로 인하여 바이오분야 응용에는 적합하지 않다. YAG는 모체로써 형광체에서 가장 많이 이용되는 물질로, 화학적 안정성과 낮은 독성, 높은 양자 효율 등 많은 장점을 갖고 있다. 특히 세륨이 도핑된 YAG형광체의 경우 WLED, 신틸레이터, 바이오산업에 적용이 가능하다. 그러나 지금까지 중공 YAG:Ce3+형광체를 합성한 예가 없었다. 본 연구에서는 단분산 수화 알루미늄 (Al(OH)3) 입자 위에 세륨이 도핑 된 이트륨 베이직 카보네이트 ($Y(OH)CO_3$)를 균일하게 코팅한 후 열처리를 하여 균일한 크기의 Y3Al5O12:Ce3+(YAG) 중공 입자를 합성하였다. 열처리 온도에 따른 고분해능 투과 전자 현미경(HRTEM), X-선 회절(XRD), 고분해능 에너지 분광법(HREDX) 분석결과, 중공 YAG: Ce3+입자는 Kirkendall 효과에 의해 형성됨을 확인하였다. 전계방사형 주사 전자 현미경(FE-SEM) 측정을 통해, 열처리 후에도 입자의 크기와 형태가 균일함을 확인하였으며, 공초점 현미경 관찰을 통해 중공 형태를 명확히 확인 할 수 있었다. Photoluminescence (PL) 분광법과 형광 수명 이미징 현미경(FLIM)을 이용한 광 특성 분석결과, 합성된 입자는 400-500 nm에서 흡수 파장 (456 nm에서 최대 강도)과 500-700 nm 범위의 발광 파장(544 nm에서 최대 강도)을 나타냈고, 상용 YAG: Ce3+(70 ns)에 준하는 74 ns의 잔광 시간(decay time)이 측정되었다. 단분산 수화 알루미늄 입자의 크기를 조절하여 최종 합성된 YAG: Ce3+의 크기를 조절할 수 있었다. 지름 약 600 nm의 Al(OH)3를 사용한 경우, $1,300^{\circ}C$에서 열처리를 한 후 평균 지름 590 nm의 중공입자를 합성하였고, 약 170 nm의 Al(OH)3를 이용하여, 더 낮은 온도인 $1,100^{\circ}C$에서의 열처리를 통해 평균지름 140 nm의 중공 YAG: Ce3+입자를 합성하였다. 본 연구를 통하여 합성된 균일한 크기의 YAG 중공입자는 LED와 같은 광전변환 소자 및 다기능성 바이오 이미징 등의 나노바이오 소자 분야에 활용될 수 있음이 기대된다.

• 한국세라믹학회지
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• 제41권7호
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• pp.541-547
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• 2004

일반적으로 혼합분말의 소결에서 작은 입자에 큰 입자의 첨가는 소결성의 저하를 가져온다. 본 연구에서는 이러한 원리를 이용하여 작은 SiC 입자에 큰 SiC 휘스커 또는 큰 SiC 입자를 첨가하여 소결성을 저하시키고, YAG(Y$_3$A1$_{5}$O$_{12}$)상을 소결 첨가제로 사용함으로서 다공질 SiC 세라믹스를 제조하였다. 제조된 다공질 SiC 세라믹스의 기공율은 큰 입자의 함량과 소결 압력을 제어함으로서 0.3-39% 범위에서 제어할 수 있었다. 기공율은 큰 입자의 함량이 증가함에 따라 증가하였고, SiC 휘스커를 첨가하는 것이 큰 SiC 입자를 첨가하는 것 보다 기공율을 높이는데 효과적이었다. 제조된 다공질 세라믹스에서 기체의 통기성은 기공율이 증가함에 따라 증가하였고, 굽힘강도는 기공율이 증가함에 따라 감소하였다. 기공율이 18% 이상인 다공질 SiC 세라믹스의 경우에 주목할 만한 변형율이 관찰되었다.

• The Journal of Advanced Prosthodontics
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• 제11권4호
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• pp.223-231
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• 2019

PURPOSE. The purpose of this study was to evaluate the shear bond strength (SBS) of an indirect resin composite (IRC) to the various resin matrix ceramic (RMC) blocks using different surface treatments. MATERIALS AND METHODS. Ninety-nine cubic RMC specimens consisting of a resin nanoceramic (RNC), a polymer-infiltrated hybrid ceramic (PIHC), and a flexible hybrid ceramic (FHC) were divided randomly into three surface treatment subgroups (n = 11). In the experimental groups, untreated (Cnt), tribochemical silica coating (Tbc), and Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser irradiation (Lsr) with 3 W (150 mJ/pulse, 20 Hz for 20 sec.) were used as surface treatments. An indirect composite resin (IRC) was layered with a disc-shape mold ($2{\times}3mm$) onto the treated-ceramic surfaces and the specimens submitted to thermal cycling (6000 cycles, $5-55^{\circ}C$). The SBS test of specimens was performed using a universal testing machine and the specimens were examined with a scanning electron microscope to determine the failure mode. Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tukey HSD test (${\alpha}=.05$). RESULTS. According to the two-way ANOVA, only the surface treatment parameter was statistically significant (P<.05) on the SBS of IRC to RMC. The SBS values of Lsr-applied RMC groups were significantly higher than Cnt groups for each RMC material, (P<.05). Significant differences were also determined between Tbc surface treatment applied and untreated (Cnt) PIHC materials (P=.039). CONCLUSION. For promoting a reliable bond strength during characterization of RMC with IRC, Nd:YAG laser or Tbc surface treatment technique should be used, putting in consideration the microstructure and composition of RMC materials and appropriate parameters for each material.

• Medical Lasers
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• 제8권1호
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• pp.7-12
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• 2019

Background and Objectives Skin and soft tissue defects can be treated according to a range of strategies, such as local flap, skin graft, biological dressing, or free flap. On the other hand, free tissue transfer usually leaves a distinct scar with an inconsistency of color or hypertrophy. This problem is highlighted if the defect is located on the face, which could have devastating effects on a patient's psychosocial health. Materials and Methods The authors used an erbium : yttrium-aluminum-garnet (Er:YAG) laser to resurface the free flap skin and match the color with the surrounding facial skin. This study evaluated the effectiveness of laser skin resurfacing on the harmonious color matching of transferred flap. Patients who had undergone laser resurfacing on facial flap skin between January 2014 and December 2018 were reviewed retrospectively. An ablative 2,940-nm fractional Er:YAG laser treatment was delivered to the entire flap skin at 21 J/cm² with the treatment end-point of pinpoint bleeding. Several months later, the clinical photographs were analyzed. The L^*a^*b^* color co-ordinates of both the flap and surrounding normal skin were measured using Adobe Photoshop. The L^*a^*b^* color difference (ΔE) for the scar and normal surrounding skin were calculated using the following equation: ${\Delta}E=\sqrt{({\Delta}L)^2+({\Delta}a)^2+({\Delta}b)^2}$ Results All five patients were satisfied with the more natural appearance of the flaps. The ΔE values decreased significantly from the pre-treatment mean value of 19.64 to the post-treatment mean value of 11.39 (Wilcoxon signed-rank test, p = 0.043). Conclusion Ablative laser resurfacing can improve the aesthetic outcome of free tissue transfer on the face.

• 한국결정성장학회지
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• 제7권1호
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• pp.18-26
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• 1997

소결조제로 Y 3Alo012를 첨가한 {3- SiC 분말에 seed로서 1 wt%의 a- SiC 분말을 첨 가한 시편과 첨가하지 않은 시편을 1950$^{\circ}$C, argon 분위기에서 0.5~4시간 동안 소결하였다. S Seed로써 1 wt% a-SiC 분말의 첨가는 소결 도중에 길게 자란 업자틀의 성장을 가속시켰고, a a- SiC seed를 첨가한 시편에서 더 조대한 미세구조가 얻어졌다 .. a-SiC seed를 첨가하여 4시간 동안 소결한 시편의 파괴인성은 7.5 MPa'ml/2이었고, seed를 첨가하지 않은 시편의 파괴인성은 6 6.1 MPa'm1/2이었다 .. Seed를 첨가한 시편의 높은 파괴인성은 조대한 미세구조에 포함된 길게 자란 입자들에 의한 균열가교 기구의 활발한 작용에 기인한다.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• 제26권1호
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• pp.43-58
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• 1998

The Kwinana Shoreline Fumigation Experiment (KSFE) took place at Fremantle, WA, Australia between January 23 and February 8, 1995. The CSIRO DAR LIDAR measured plume sections from near the Kwinana Power Station (KPS) stacks to up to about 5 km downstream. It also measured boundary layer aerosols and the structure of the boundary layer on some occasions. Both stages A and C of KPS were used as tracers at different times. The heart of the LIDAR system is a Neodymium-doped Yttrium-aluminum-garnet (Nd:YAG) laser operating at a fundamental wavelength of 1064 nm, with harmonics of 532 nm and 355 nm. For these experiments the third harmonic was used because the UV wavelength at 355 nm is eye safe beyond about 50 m. The laser fires a pulse of light 6 ns in duration (about 1.8 m long) and with an energy (at the third harmonic) of about 70 mJ. This pulse subsequently scattered and absorbed by both air molecules and particles in the atmosphere. A small fraction of the laser beam is scattered back to the LIDAR, collected by a telescope and detected by a photo-multiplier tube. The intensity of the signal as a function of time is a measure of the particle concentration as a function of distance along the line of the laser shot. The smoke plume was clearly identifiable in the scans both before and after fumigation in the thermal internal boundary layer (TIBL). Both power station plumes were detected. Over the 9 days of operation, 1,568 plumes scans (214 series) were performed. Essentially all of these will provide instantaneous plume heights and widths, and there are many periods of continuous operation over several hours when it should be possible to compile hourly average plume statistics as well. The results of four days LIDAR observations of the dispersion of smoke plume in the TIBL at a coastal site are presented for the case of stages A and C.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.605-610
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• 2004

Solid propellants allow thrusters to be light-weight, com-pact and robust because they require neither tank nor valve, Moreover, the solid propellant will not leak, spill or slosh. Consequently, the solid propellant thruster is one of the potential candidates for the microthruster. On the other hand, the control of the solid propellant combustion is difficult, since the conventional solid propellant continues to bum until all the stored propellant is consumed. Although particular devices like thrust reverser were designed to control the combustion, these devices were rarely used in the practical rocket motors. These devices rise thruster weight as well as complicate the thruster operation. In this study, a solid propellant microthruster using laser sustained combustion was designed in order to develop a high-efficiency microthruster overcoming the previously-mentioned difficulty. This designed thruster has semiconductor lasers and non-self-combustible solid propellants in addition to the conventional solid propellant thruster. In this designed thruster, the semiconductor laser controls the combustion of the non-self-combustible solid propellant. In order to demonstrate that the solid propellant combustion is controllable with laser, some non-self-combustible solid propellants were irradiated with the laser at a back-pressure of about 1㎪. A 40-W class Neodymium Yttrium Aluminum Garnet (ND:YAG) laser was used as a tentative alternate to the semiconductor laser. This experiment has shown that the solid propellant combustion was controllable with 10- W class laser irradiation.