• 전자공학회논문지A
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• 제31A권10호
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• pp.79-86
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• 1994

Gain-guided broad-area single quantum well separate confinement heterostructure diode lasers have been fabricated from structures grown by metal organic vapor phase epitaxy. The active layer of the epi-structure is InGaAs emitting 962-965nm and the guiding layer GaAs. The channel width is fixed to 150${\mu}$m and the cavity length varys within the range of 300~800${\mu}$m. For uncoated LD's, the output power of 0.7W has been obtaained at a pulsed current level of 2A, which results about 60% external quantum efficiency. The threshold current density is 200A/cm$^{2}$ for the cavity lengths of 800.mu.m LD's. The stain effect upon the transparent current density has been observed. The internal quantum efficiency is expected to be 88% and the internal loss to be 18$cm^{-1}$. The beam divergence has been measured to be 7$^{\circ}$to lateral and 40$^{\circ}$to transverse direction. finally, 1.2W continuous-wave output power has been obtained at a current level of 2A for AR/HR coated LD's die-bonded on Cu heat-sink and cooled by TEC.

• 대한기계학회논문집
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• 제16권4호
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• pp.803-810
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• 1992

본 연구에서는 서산등과 Nishiyama등이 제시한 특이점 분포법에 의한 기초식 을 비선형으로 해석하기 위하여 익과 유한한 길이의 캐비티의 자유유선에 용출, 와, 이중용출 등의 특이점을 분포시켜서 수퍼캐비테이션을 발생시키는 익열의 유동장을 지 배하는 비선형의 적분방정식을 복소포텐셜로 나타내고 경계 요소법을 이용하여 수치계 산함으로써 수퍼비테이션익열의 유동에서의 수력특성을 구하는 데 있다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.365-366
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• 2002

A novel TEM resonator coil was developed for the imaging of small animals. The functional elements of the TEM resonator were 8 inner conductors, distributed in a cylindrical pattern and connected at the ends with capacitors to the cylindrical outer shield. The TEM resonator coil with cavity elements was robust to the surrounding influences due to the self-shielding structure. The TEM resonator coil with high Q factor could provide high quality MR images at 3.0T MRI system. Also, the TEM resonator coil has an advantage for a fine tune with length adjustment of each cavity elements. Thus, The TEM resonator coil at 3.0T, even higher field could be used in the research studies.

• 한국광학회지
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• 제15권4호
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• pp.337-342
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• 2004

본 연구에서는 opto-Hertzian 효과를 이용하여 고주파 여기식 슬랩형 $CO_2$ 레이저의 출력을 안정화하였다. 슬랩레이저 공진기속의 복사선 세기가 변화할 때 opto-Hertzian 효과에 의해서 공진기의 방전 임피던스도 함께 변화한다. 이에 따라 공진기로 입사 또는 반사되는 고주파 에너지 값도 변화한다. 이 같은 변화를 결합 루프를 통해 검출하여 고주파 성분을 제거한 후 록인 안정기에서 발생시킨 오차신호를 기준신호로 사용하여 슬랩 레이저의 출력을 안정화하였다. 본 방법으로 안정화된 레이저의 출력 변동률이 0.2%로 개선됨을 확인하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권1호
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• pp.153-155
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• 2015

Background: The aim of this study was to establish the feasibility and efficiency of different pelvic drainage routes after laparoscopic abdominoperineal resection (LAPR) for rectal cancer by assessing short-term outcomes. Materials and Methods: Clinicopathological data of 76 patients undergoing LAPR for very low rectal cancer were reviewed retrospectively between June 2005 and June 2014. Outcomes were evaluated considering short-term results. Results: Of 76 relevant patients at our institution in the period of study, trans-perineal drainage of the pelvic cavity was performed in 17 cases. Compared with the trans-perineal group, the length of hospital stay was shorter in the trans-abdominal group, while the duration of drainage and the infection rates of the perineal wounds between two groups showed no significant differences. Conclusions: The outcomes of this study suggest that trans-abdominal drainage of pelvic cavity is a reliable and feasible procedure, the duration of drainage, infection rates and the healing rates of the perineal wounds being acceptable. Trans-abdominal drainage has a more satisfactory effect after laparoscopic abdominoperineal resection for rectal carcinoma.

• 대한기계학회논문집B
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• 제20권12호
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• pp.4036-4043
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• 1996

When a high-speed railway train enters a tunnel, a compression wave is generated ahead of the train and propagates along the tunnel, compressing and accelerating the rest air in front of the wave. At the exit of the tunnel, an impulsive wave is emitted outward toward the surrounding, which causes a positive impulsive noise like a kind of sonic boom produced by a supersonic aircraft. With the advent of high-speed train, such an impulsive noise can be large enough to cause the noise problem, unless some attempts are made to alleviate its pressure levels. In the purpose of the impulsive noise reduction, the present study tested the effect of porous walls on the compression wave propagating into a model tunnel. Experimental results were obtained using a shock tube with an open end. The results showed that the cavity/porous wall is very effective for the compression wave with a large nonlinear effect. The porosity of 30% is most effective for attenuation and pressure gradient reduction of the compression wave front. Also the impulsive noise reduction increases with increasing the length and height of the cavity, compared with the tunnel equivalent diameter.

• 한국발생생물학회지:발생과생식
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• 제18권1호
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• pp.51-56
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• 2014

This study describes the developmental process of gonads in chameleon goby, Tridentiger trigonocephalus from the stage of hatching to 100 days after hatching (DAH). Based on histological observation, the primordial germ cells were observed in mesentery between mesonephric duct and gut at 15 DAH (total length, TL: $6.8{\pm}0.2mm$). At 20 DAH (TL: $7.9{\pm}0.1mm$), the primordial gonad began to protrude into peritoneal cavity and developed between mesonephric duct and gut. Initial ovarian differentiation was identified by the presence of ovarian cavity and oogonia in the gonads at 55 DAH (TL: $21.1{\pm}1.3mm$). Testicular differentiation started at 65 DAH (TL: $23.7{\pm}0.9mm$) with appearance of spermatogonial cells in the gonads. These findings indicate that sex differentiation in T. trigonocephalus occurs earlier in females than males, suggesting that this species can be classified as an undifferentiated gonochorist.

• 한국광학회지
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• 제12권4호
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• pp.300-304
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• 2001

압전소자에 전압을 가했을 때 길이가 늘어나며 휘어지는 것을 측정하고 보정하는 방법을 제시한다. 압전소자에 부착된 거울에서 반사되는 레이저빔의 각도 변화를 $0.36\mu$rad의 불확도로 측정하여 압전소자가 휘는 각도와 방향을 알수 있는 장치를 구성하였다. 압전소자의 전극을 세부분을 분할하고 축전기를 직렬 연결하여 하나의 전원으로도 각 전극에 인가되는 전압을 달리 조절할 수 있었다. 압전소자가 휘어지는 크기와 방향에 따라 각 전극에 연결되는 축전기의 용량을 달리함으로써 보정 전에 비해 휨을 6.3%로 줄일수 있었다. 휨이 보정된 압전소를 광자감쇠공동의 길이 변조에 이용하였을 때 압전소자가 휘기 때문에 야기되었던 감쇠시간 요동이 효과적으로 제거되는 것을 확인하였다.

• 한국광학회지
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• 제23권3호
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• pp.103-107
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• 2012

본 논문에서는 반도체 포화 흡수체 거울 (SESAM)에 입사되는 단위 면적당 광세기 변화에 따른 이터븀 첨가 광섬유 레이저의 모드 잠금 출력 특성을 고찰하였다. 단위 면적당 광세기를 변화시키기 위해 공진기 내부에 설치된 렌즈의 초점거리를 조절하여 SESAM에 입사되는 광의 크기를 변화시켰다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.383-390
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• 2008

Flow pattern of cavitation around a plano-convex foil, whose shape is similar to the inducer impeller of the turbo-pumps in the liquid fuel rocket engine, was observed by using a cryogenic cavitation tunnel of blowdown type for visualization. Working fluids were liquid nitrogen and hot water. The parameter range to be varied was between 20 and 60mm for channel width, 20 and 60mm for foil chord, -1.8 and 13.2 for cavitation number, 3.7 and 19.5m/sec for averaged inlet velocity, $8.5{\times}10^4$ and $1.5{\times}10^6$ for Reynolds number, -8 and $8^{\circ}$ for angle of attack, respectively. Especially at positive angle of attack, namely, convex surface being downstream, the whole cavity or a part of the cavity on the foil surface departs periodically. Periodic cavitation occurs only in case of smaller cavitation size than twice foil chord. Cavitation thickness and length in 20mm wide channel are larger than those in 60mm due to the wall confinement effect. Therefore, periodic cavitation in 60mm wide channel easily occurs than that in 20mm. These results suggest that the periodic cavitation is controlled by not only the hydrodynamic effect of vortex shedding but also the channel wall confinement effect.