• 한국결정성장학회지
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• 제8권4호
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• pp.550-554
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• 1998

Bridgman-Stockbarger법에서 thermal screen의 역할을 하는 새로운 방법을 6inch 형석(CaF2) 단결정성장을 위하여 고안하였다. 본 방법으로 poly-grain으로의 성장과 내부 cavity, 그리고 solid-liquid(SL) interface를 제어할 수 있었다. Graphite pipe와 ceramic warmer를 사용하여 성장한 6inch의 CaF2 결정은 완전한 단결정으로 성장하였다. 이때의 조건은 2mm/hr의 성장속도, 성장구역에서의 $14^{\circ}C$/cm의 온도구배, 그리고 도가니의 conical tip에서 $1324^{\circ}C$의 온도를 나타내었다. 내부 cavity에 의해 발생되는 light scattering 현상은 성장속도를 감소시키거나 융액을 회전함으로써 제어할 수 있었다.

• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.716-721
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• 2016

A single-and dual-wavelength switchable polarized Yb-doped double-clad fiber laser around 1120 nm based on a pair of fiber Bragg gratings (FBGs) is demonstrated. The polarization-maintaining (PM) linear cavity is composed of a double clad PM Yb-doped fiber (YDF) and a pair of PM FBGs. The laser can operate in stable dual-wavelength or wavelength-switching modes due to the polarization hole burning (PHB) and the spatial hole burning (SHB) enhanced by the PM linear cavity. In dual-wavelength operation, the two orthogonally polarized wavelengths are centered at 1118.912 nm and 1119.152 nm, with an interval of 0.24 nm and a signal to noise ratio (SNR) of 35 dB. The maximum output power is 14.67 W when the launched LD pump is 24 W corresponding to an optical efficiency of 61.1%. The lasing lines switchover may be realized by adjusting the polarization controller (PC) fitted in the cavity. The two single-wavelengths are 1118.912 nm and 1119.152 nm. When the injected LD pump is 24 W, the highest output powers are 7.68 W and 8.64 W corresponding to optical efficiencies of 32% and 36% respectively. The spectral linewidth of the lasing lines are 0.075 nm and 0.07 nm, and the average numerical values of PER aredB and 19.9 dB, respectively.

• Restorative Dentistry and Endodontics
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• 제20권2호
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• pp.527-537
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• 1995

The effect of calcitonin gene-related peptide (CGRP), substance P (SP) and electrical stimulation of the tooth on the intradental nerve activtiy (INA) was investigated in anesthetized cats. The INA was recorded from single pulp nerve units dissected from the inferior alveolar nerve under stereomicroscope. The INA elicited by 3 minute application of 4M NaCl in deep dentinal cavity was compared before and after stimulation at 10 minute intervals. The magnitude of INA was calculated as the total number of nerve impulses produced in given period, and the changes of INA are expressed as % of control INA. The results obtained were as follows. 1. 16 single pulp nerve units were classified as 14 $A{\delta}$-fibers (3.4~19.4m/sec) and 2-fibers (1.5~1.7m/sec) according to the conduction velocity. 2. 4M NaCl evoked an irregular bursts of spikes which continued until washing out. Isotonic saline did not affect INA to subsequent applications of the hypertonic NaCl solution (P>0.05). 3. Local application of CGRP ($200{\mu}g$/ml) in deep dentinal cavity reduced the INA induced by 4M NaCl in $A{\delta}$-fiber units (P<0.01) and some units of those responded to CGRP during application. 4. Local application of SP ($100{\mu}g$/ml) in deep dentinal cavity reduced the INA induced by 4M NaCl in AS-fiber units (p<0.05), but increased the INA in C-fiber unit coincided with large reduction of the INA of $A{\delta}$-fiber units. 5. Monopolar electrical stimulation applied to the crown at intensities high enough to excite C-fibers (12V, 5ms, 10Hz, 10~30min) decreased the INA in $A{\delta}$-fiber units (P<0.01) and systemic pretreatment with phenoxybenzamine (3mg/kg, i.v.) enhanced this inhibitory effect (P<0.01). On the contrary, electrical stimulation increased the INA in C-fiber unit.

• 대한치과의사협회지
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• 제56권10호
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• pp.567-571
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• 2018

Obturation is a important procedure of root canal treatment. Canal filling should be both provide a hermetic seal for the root canal system and eliminate leakage channel from the oral cavity. Gutta-percha have been the standard material of choice for root canal obturation. Canal filling has been aimed at maximizing the amount of gutta-percha and minimizing the amount of sealer. However recently, single cone technique has been introduced that include calcium silicate-based sealer and single gutta-percha cone. It is important to select an obturation technique that offers consistency and is easy to use. From the standpoint of appropriate technology, the single cone technique is thought to be useful for general dentist.

• Journal of the Optical Society of Korea
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• 제18권2호
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• pp.167-173
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• 2014

A novel multi-oxide layer structure for vertical cavity surface emitting laser (VCSEL) structures is proposed to achieve higher single mode output power. The structure has four oxide layers with different aperture sizes and thicknesses. The oxide layer thicknesses are optimized simultaneously to reach the highest single mode output power. A heuristic method is proposed for plotting the influence of these variable changes on the operation of optical output power. A comprehensive optical-electrical thermal-gain self-consistent VCSEL model is used to simulate the continuous-wave operation of the multi-layer oxide VCSELs. A comparison between optimized VCSELs with different structures is presented. The results show that by using multi-oxide layers with different thicknesses, higher single-mode optical output power could be achieved in comparison with multi-oxide layer structures with the same thicknesses.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권6호
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• pp.260-264
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• 2002

We developed LD Pumped Nd:$VVO_4$ microchip laser with the cavity length of 1mm. The microchip laser output was 87.5㎽ at the wavelength of 1063.9nm with the input power of 241㎽ at the wavelength of 809nm. The slope efficiency was 40.7% and the threshold input power was 31.1㎽. We have also defined input power limit for the single longitudinal mode operation theoretically. It was 2.5 times larger than that of threshold input intensity. According to the results of simulation, the Nd:YVO$_4$ microchip laser can be operated with the maximum output of 15㎽ for the single longitudinal mode up to the input power of 77.75㎽.

• 한국전자파학회논문지
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• 제16권4호
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• pp.366-372
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• 2005

본 논문에서는 $2,630\;\cal{MHz}\~2,655\;\cal{MHz\$의 위성 DMB(Digital Multimedia Broadcasting)의 지상 중계기 시스템에 적합한 낮은 부엽레벨과 높은 전후방 비를 갖는 슬롯배열 안테나를 제안하였다. 중계기용 안테나는 시스템의 특성상 고이득과 시스템간의 신호 간섭을 줄이기 위해 충분한 격리도가 확보되어야 하며, 이를 위해서는 안테나의 부엽레벨을 억제시키고, 전후방 비는 증대시켜야 한다. 제안된 안테나는 도파관 구조의 직접급전이 가능한 CBSA(Cavity-Backed Slot Array) 안테나이다. 일반적인 마이크로 스트립 급전라인을 이용한 구조와는 달리 유전체 손실이나 급전라인의 손실이 없는 공기를 매질로 하므로, 고출력에 적합하며, 고효율을 가진다. 또한 tapered 배열 방식과 최적화된 수직 반사판을 이용하여 부엽레벨 및 전후방 비를 개선하고 이득을 증대시켰다. 제작 및 측정을 통하여 부엽레벨은 수평 및 수직면에서 각각 $-33.24\;\cal{dB}$ 이하, $-35.78\;\cal{dB}$ 이하를 얻었고 전후방비는 $37.84\;\cal{dB}$ 이상, 이득은 전 대역에서 $17\;\cal{dBi}$ 이상을 얻었다.

• 광물과 암석
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• 제33권3호
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• pp.251-258
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• 2020

Ca²⁺ 이온으로 부분적으로 치환된 제올라이트 A (|Ca₄Na₄|[Si₁₂Al₁₂O₄₈]-LTA) 단결정과 Se을 가는 모세관에 넣은 후 523 K 에서 5일동안 반응을 시켜 Se이 흡착된 제올라이트 A 단결정을 합성 하였다. 이 결정의 구조는 294 K 에서 단결정 X-선 회절 기술을 이용하여 $Pm{\bar{3}}m$ (a = 12.2787(13) Å) 입방 공간군에 속함을 확인 하였고, F_o> 4s(F_o)를 사용하여 최종 오차 인자를 R₁/wR₂= 0.0960/0.3483로 정밀화 하였다. 이 구조에서는 4개의 Na⁺와 4개의 Ca²⁺ 이온이 모든 6-ring 자리에 채워져 있었으며, 이들 이온들은 모두 6-ring 맞은편의 3-fold 축 상의 결정학적 위치에서 발견되었다. Se 원자들은 뚜렷하게 서로 다른 3개의 결정학적 위치에서 발견되었다. 단위 세포당 2개의 Se(1) 원자는 sodalite cavity 내 6-ring 맞은편 (Se(1)-Na(1) = 2.53(5)Å), 1개의 Se(2) 원자는 4-ring 맞은편 (Se(2)-O(1) = 2.76(10) Å), 그리고 1개의 Se(3) 원자는 large cavity 내 6-ring 맞은편 (Se(3)-Na(1) = 2.48(5) Å)에 각각 위치하고 있었다. 2가지 형태의 Se₂ 분자 (Se(1)-Se(1) = 2.37(7) or 2.90(8) Å and Se(2)-Se(3) = 2.91(5)) Å)가 sodalite cavity와 large cavity 내에서 발견되었으며, Se₄와 Se₈과 같은 형태의 클러스터가 large cavity 내에 존재할 수 있었다. 이들 클러스터내 Se 원자들 사이의 거리는 기체상태의 Se₂ 분자내 Se 원자 사이의 거리보다 더 길게 나타났다.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.442-446
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• 2010

Adenosine 3',5'-cyclic monophosphate (cAMP) is a second messenger responsible for a multitude of cellular responses. In this study, we utilized $\beta$-cyclodextrin ($\beta$-CD) as an artificial receptor with a hydrophobic cavity to elucidate the inclusion kinetics of cAMP in a hydrophobic environment using the ultrasonic relaxation method. The results revealed that the interaction of cAMP with $\beta$-CD followed a single relaxation curve as a result of host-guest interactions. The inclusion of cAMP into the $\beta$-CD cavity was found to be a diffusion-controlled reaction. The dissociation of cAMP from the $\beta$-CD cavity was slower than that of adenosine 5'-monophosphate (AMP). The syn and anti glycosyl conformations of adenine nucleotides are considered to play an important role in formation of the inclusion complex. Taken together, our findings indicate that hydrophobic interactions are involved in the inclusion complex formation of cAMP with $\beta$-CD and provide insight into the interactions of cAMP with cAMP-binding proteins.

• 한국전산유체공학회지
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• 제4권1호
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• pp.8-18
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• 1999

In devising a numerical approximation for the convective spatial transport of a fluid mechanical quantity, it is noted that the convective motion of a scalar quantity occurs in one-way, or from upstream to downstream. This consideration leads to a new scheme termed a pure upwind difference scheme (PUDS) in which an estimated value for a fluid mechanical quantity at a control surface is not influenced from downstream values. The formal accuracy of the proposed scheme is third order accurate. Two typical benchmark problems of a wall-driven fluid flow in a square cavity and a buoyancy-driven natural convection in a tall cavity are computed to evaluate performance of the proposed method. for comparison, the widely used simple upwind scheme, power-law scheme, and QUICK methods are also considered. Computation results are encouraging: the proposed PUDS sensitized to the convection direction produces the least numerical diffusion among tested convection schemes, and, notable improvements in representing recirculation of fluid stream and spatial change of a scalar. Although the formal accuracy of PUDS and QUICK are the same, the accuracy difference of approximately a single order is observed from the revealed results.