• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1756-1768
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• 2021

The containment filtered venting system (CFVS) filters the atmosphere of the containment building and discharges a part of it to the outside environment to prevent containment overpressure during severe accidents. The Korean CFVS has a tank that filters fission products from the containment atmosphere by pool scrubbing, which is the primary decontamination process; however, prediction of its performance has been done based on researches conducted under mild conditions than those of severe accidents. Bubble behavior in a pool is a key parameter of pool scrubbing. Therefore, the bubble behavior in the pool was analyzed under various injection flow rates observed at the venturi nozzles used in the Korean CFVS using a wire-mesh sensor. Based on the experimental results, void fraction model was modified using the existing correlation, and a new bubble size prediction model was developed. The modified void fraction model agreed well with the obtained experimental data. However, the newly developed bubble size prediction model showed different results to those established in previous studies because the venturi nozzle diameter considered in this study was larger than those in previous studies. Therefore, this is the first model that reflects actual design of a venturi scrubbing nozzle.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 디스플레이 광소자분야
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• pp.83-85
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• 2004

MOCVD(metalorganic chemical vapor deposition)에 의해 성장된 InGaAs/AlGaAs 물질을 이용하여 V-형 양자선 (V-groove quantum-wire) 어레이(array) 구조에서 이득 결합(gain-coupling)에 의한 분포 광귀환(distributed optical feedback) 특성을 조사하였다. 분포 귀환형 (distributed feedback, DFB) 구조를 제작하는 동안 격자 재성장(grating overgrowth)을 피하기 위하여, 새롭게 개발된 constant MOCVD 성장 방법을 적용하였고, Bragg 파장에서 DFB 방향으로 광귀환의 결과인 스펙트럼의 이득 이방성(gain asymmetry)을 실험적으로 관찰하였다.

• 한국전기전자재료학회논문지
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• 제16권9호
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• pp.833-837
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• 2003

The spectral and temporal characteristics of a V-groove AIGaAs-GaAs quantum wire (QWR) laser were investigated with varying the cavity length. At cavity lengths shorter than 300 ${\mu}{\textrm}{m}$, a discrete shift in tile wavelength occurred from the n=1 to the n=2 subband due to the increased cavity losses. Utilizing this characteristic, ultrafast lasing characteristics at each subband were investigated by tile gain switching method.

• 한국진공학회지
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• 제10권2호
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• pp.262-266
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• 2001

GaAS/AlGaAS 이종접합구조 위에 Split gate로 양자세선을 제작하여 Shubnikov de Haas 진동 및 양자 Hall 효과 측정으로 1DEG의 전기적 특성을 관측하였다. Gate 전압이 증가할수록 채널폭이 좁아짐에 따라 ID 특성이 나타났다. Edge state 수송 이론인 Landauer-Butikker formula로부터 QHE plateau와 SdH 진동의 최소값이 나타나는 자기장 영역이 일치하지 않고 있는 현상을 명확히 규명하였다.

• 한국전기전자재료학회논문지
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• 제14권12호
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• pp.1027-1031
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• 2001

A new constant growth technique to conserve an initial grating height of V-groove AlGaAs/InGaAs quantum nanostructures above 1.0 $\mu\textrm{m}$ thickness has been successfully embodied on submicron gratings using low pressure metalorganic chemical vapor deposition. A GaAs buffer prior to an AlGaAs barrier layer on submicron gratings plays an important role in overcoming mass transport effects and improving the uniformity of gratings. Transmission electron microscopy (TEM) image shows that high-density V-groove InGaAs quantum wires (QWRs) are well confined at the bottom of gratings. The photoluminescence (PL) peak of the InGaAs QWRs is observed in the temperature range from 10 to 280 K with a relatively narrow full width at half maximum less than 40 meV at room temperature PL. The constant growth technique is an important step to realize complex optoelectronic devices such as one-step grown distributed feedback lasers and two-dimensional photonic crystal.

• 한국표면공학회지
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• 제49권3호
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• pp.301-306
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• 2016

The effects of nanotexturing and post-etching on the reflection and quantum efficiency properties of diamond wire sawn (DWS) multicrystalline silicon (mc-Si) solar cell have been investigated. The chemical solutions, which are acidic etching solution (HF-$HNO_3$), metal assisted chemical etching (MAC etch) solutions ($AgNO_3$-HF-DI, HF-$H_2O_2$-DI) and post-etching solution (diluted KOH at $80^{\circ}C$), were used for micro- and nano-texturing at the surface of diamond wire sawn (DWS) mc-Si wafer. Experiments were performed with various post-etching time conditions in order to determine the optimized etching condition for solar cell. The reflectance of mc-Si wafer texturing with acidic etching solution showed a very high reflectance value of about 30% (w/o anti-reflection coating), which indicates the insufficient light absorption for solar cell. The formation of nano-texture on the surface of mc-Si contributed to the enhancement of light absorption. Also, post-etching time condition of 240 s was found adequate to the nano-texturing of mc-Si due to its high external quantum efficiency of about 30% at short wavelengths and high short circuit current density ($J_{sc}$) of $35.4mA/cm^2$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.211-211
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• 2012

Using spin-polarized density-functional theory calculations, we find that the existence of either Peierls instability or antiferromagnetic spin ordering is sensitive to hydrogen passivation near the step. As hydrogens are covered on the terrace, the dangling bond electrons are localized at the step, leading to step-induced states. We investigate the competition between charge and spin orderings in dangling-bond (DB) wires of increasing lengths fabricated on an H-terminated vicinal Si(001) surface. We find antiferromagnetic (AF) ordering to be energetically much more favorable than charge ordering. The energy preference of AF ordering shrinks in an oscillatory way as the wire length increases. This oscillatory behavior can be interpreted in terms of quantum size effects as the DB electrons fill discrete quantum levels.

• ETRI Journal
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• 제26권1호
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• pp.1-6
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• 2004

The photonic quantum ring (PQR) laser is a three dimensional whispering gallery (WG) mode laser and has anomalous quantum wire properties, such as microampere to nanoampere range threshold currents and ${\sqrt{T}}$-dependent thermal red shifts. We observed uniform bottom emissions from a 1-kb smart pixel chip of a $32{\times}32$ InGaAs PQR laser array flip-chip bonded to a 0.35 ${\mu}m$ CMOS-based PQR laser driver. The PQR-CMOS smart pixel array, now operating at 30 MHz, will be improved to the GHz frequency range through device and circuit optimization.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1994년도 제7회 학술발표회 및 한·일 CVD 심포지움 논문개요집
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• pp.98-99
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• 1994

• Advances in nano research
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• 제2권3호
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• pp.157-172
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• 2014

The three-dimensional Nano-Electronic Modeling toolkit (NEMO 3-D) is an open source software package that allows the atomistic calculation of single-particle electronic states and optical response of various semiconductor structures including bulk materials, quantum dots, impurities, quantum wires, quantum wells and nanocrystals containing millions of atoms. This paper, first, describes a software module introduced in the NEMO 3-D toolkit for the calculation of electronic bandstructure and interband optical transitions in nanowires having wurtzite crystal symmetry. The energetics (Hamiltonian) of the quantum system under study is described via the tight-binding (TB) formalism (including $sp^3$, $sp^3s^*$ and $sp^3d^5s^*$ models as appropriate). Emphasis has been given in the treatment of surface atoms that, if left unpassivated, can lead to the creation of energy states within the bandgap of the sample. Furthermore, the developed software has been validated via the calculation of: a) modulation of the energy bandgap and the effective masses in [0001] oriented wurtzite nanowires as compared to the experimentally reported values in bulk structures, and b) the localization of wavefunctions and the optical anisotropy in GaN/AlN disk-in-wire nanowires.