• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제40회 동계학술대회 초록집
• /
• pp.21-21
• /
• 2011

A series of Quasi-Elastic Neutron Scattering (QENS) experiments helps us to understand the single-particle (hydrogen atom) dynamics of a globular protein and its hydration water and strong coupling between them. We also performed Molecular Dynamics (MD) simulations on a realistic model of the hydrated hen-egg Lysozyme powder having two proteins in the periodic box. We found the existence of a Fragile-to-Strong dynamic Crossover (FSC) phenomenon in hydration water around a protein occurring at TL=$225{\pm}5K$ by analyzing Intermediate Scattering Function (ISF). On lowering of the temperature toward FSC, the structure of hydration water makes a transition from predominantly the High Density Liquid (HDL) form, a more fluid state, to predominantly the Low Density Liquid (LDL) form, a less fluid state, derived from the existence of a liquid?liquid critical point at an elevated pressure. We showed experimentally and confirmed theoretically that this sudden switch in the mobility of the hydration water around a protein triggers the dynamic transition (so-called glass transition) of the protein, at a temperature TD=220 K. Mean Square Displacement (MSD) is the important factor to show that the FSC is the key to the strong coupling between a protein and its hydration water by suggesting TL${\fallingdotseq}$TD. MD simulations with TIP4P force field for water were performed to understand hydration level dependency of the FSC temperature. We added water molecules to increase hydration level of the protein hydration water, from 0.30, 0.45, 0.60 and 1.00 (1.00 is the bulk water). These confirm the existence of the FSC and the hydration level dependence of the FSC temperature: FSC temperature is decreased upon increasing hydration level. We compared the hydration water around Lysozyme, B-DNA and RNA. Similarity among those suggests that the FSC and this coupling be universal for globular proteins, biopolymers.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
• /
• pp.70-70
• /
• 2011

The prospects of current and coming solar-photovoltaic (PV) technologies are envisioned, arguing this solar-electricity source is beyond a tipping point in the complex worldwide energy outlook. Truly, a revolution in both the technological advancements of solar PV and the deployment of this energy technology is underway; PV is no longer an outlier. The birth of modern photovoltaics (PV) traces only to the mid-1950s, with the Bell Telephone Laboratories' development of an efficient, single-crystal Si solar cell. Since then, Si has dominated the technology and the markets, from space through terrestrial applications. Recently, some significant shift toward technology diversity have taken place. Some focus of this presentation will be directed toward PV R&D and technology advances, with indications of the limitations and relative strengths of crystalline (Si and GaAs) and thin-film (a-Si:H, Si, Cu(In,Ga)(Se,S)2, CdTe). Recent advances, contributions, industry growth, and technological pathways for transformational now and near-term technologies (Si and primarily thin films) and status and forecasts for next-generation PV (nanotechnologies and non-conventional and "new-physics" approaches) are evaluated. The need for R&D accelerating the now and imminent (evolutionary) technologies balanced with work in mid-term (disruptive) approaches is highlighted. Moreover, technology progress and ownership for next generation solar PV mandates a balanced investment in research on longer-term (the revolution needs revolutionary approaches to sustain itself) technologies (quantum dots, multi-multijunctions, intermediate-band concepts, nanotubes, bio-inspired, thermophotonics, ${\ldots}$ and solar hydrogen) having high-risk, but extremely high performance and cost returns for our next generations of energy consumers. This presentation provides insights to the reasons for PV technology emergence, how these technologies have to be developed (an appreciation of the history of solar PV)-and where we can expect to be by this mid-21st century.

• 한국재료학회지
• /
• 제16권2호
• /
• pp.106-110
• /
• 2006

We have investigated the effect of the experimental variables such as temperature and pressure on conformality of Co films deposited over high aspect ratio trenches using $Co_2(CO)_8$ as a precursor. The results show that the conformality of Co films is a strong function of temperature and process pressure. Lowering the pressure and temperature significantly improves the conformality. As the pressure decreases from 0.6 Torr to 0.2 Torr at $50^{\circ}C$, the bottom coverage of Co films over $0.2{\mu}m$ width trenches with an aspect ratio of 13 to 1 significantly increases to 85%. However, further increasing the temperature from 50 to $60^{\circ}C$ at the pressure of 0.2 Torr degrades the bottom coverage to 14%. In contrast, the extremely low pressure of 0.03 Torr allows the excellent conformal deposition of Co films up to $70^{\circ}C$. This can be attributed to the suppression of homogeneous reaction in the gas phase, which can create the intermediate products with high sticking coefficient. In addition, the Co films deposited at $50^{\circ}C$ show the low resistivity with negligible contamination. As a result, the newly developed Co process using MOCVD can be implemented into the next generation devices with complex shapes.

• 대한화학회지
• /
• 제32권6호
• /
• pp.528-535
• /
• 1988

이성분 혼합용매 속에서 $[Mo_2O_3(Ox)_2(OxH)_2(NCS)_2]$의 산소고리화 반응에 대한 속도론적 연구는 분광광도법으로 수행되었다. 이 때 온도는 $20^{\circ}C$ 에서 $40^{\circ}C$, 압력은 1bar에서 1500 bar로 변화시켰다. 관찰된 속도 상수는 수소이온 농도의 증가에 따라 증가하고 티오시안이온 농도의 증가에 따라서는 감소한다. 공용매의 유전상수가 증가할수록 더욱 안정한 중간체가 형성된다. 관찰된 속도상수는 $k_{obs}^{-1} = k^{-1} (1 + K^{-1}[H_2O]^{-1})로 주어진다. 모든 활성화파라미터는 양의 값이다. [Mo_2O_3(Ox)_2(OxH)_2(NCS)_2]$의 산소고리화 반응은 Id 메카니즘에 의해 진행된다.

• Nuclear Engineering and Technology
• /
• 제47권3호
• /
• pp.380-387
• /
• 2015

A lead slowing-down spectrometer (LSDS) system is a promising nondestructive assay technique that enables a quantitative measurement of the isotopic contents of major fissile isotopes in spent nuclear fuel and its pyroprocessing counterparts, such as $^{235}U$, $^{239}Pu$, $^{241}Pu$, and, potentially, minor actinides. The LSDS system currently under development at the Korea Atomic Energy Research Institute (Daejeon, Korea) is planned to utilize a high-flux ($>10^{12}n/cm^2{\cdot}s$) neutron source comprised of a high-energy (30 MeV)/high-current (~2 A) electron beam and a heavy metal target, which results in a very intense and complex radiation field for the facility, thus demanding structural shielding to guarantee the safety. Optimization of the structural shielding design was conducted using MCNPX for neutron dose rate evaluation of several representative hypothetical designs. In order to satisfy the construction cost and neutron attenuation capability of the facility, while simultaneously achieving the aimed dose rate limit (< $0.06{\mu}Sv/h$), a few shielding materials [high-density polyethylene (HDPE)eBorax, $B_4C$, and $Li_2CO_3$] were considered for the main neutron absorber layer, which is encapsulated within the double-sided concrete wall. The MCNP simulation indicated that HDPE-Borax is the most efficient among the aforementioned candidate materials, and the combined thickness of the shielding layers should exceed 100 cm to satisfy the dose limit on the outside surface of the shielding wall of the facility when limiting the thickness of the HDPE-Borax intermediate layer to below 5 cm. However, the shielding wall must include the instrumentation and installation holes for the LSDS system. The radiation leakage through the holes was substantially mitigated by adopting a zigzag-shape with concrete covers on both sides. The suggested optimized design of the shielding structure satisfies the dose rate limit and can be used for the construction of a facility in the near future.

• 한국철도학회논문집
• /
• 제12권4호
• /
• pp.526-534
• /
• 2009

소형궤도차량(PRT)은 무인자동운전으로 중간역 정차 없이 궤도를 따라 운영되는 시스템이다. PRT는 교통체계내에서 철도역, 공항, 업무복합지구, 관광위락시설 및 쇼핑시설 등에서 교통상황에 따라 수요에 부응하는 지선교통체계로서의 역할에 적절하다. 이러한 PRT시스템은 대규모 교통시설간, 지선교통체계와 간선교통체계간, 중심업무지구내 일정 범위 안에서 또는 위락시설간 통행자들을 위한 교통수단으로 적절히 활용될 것으로 전망된다. 본 논문은 신교통시스템으로서 대중교통수단의 다변화에 기여할 수 있는 PRT시스템의 특성을 고려하여 PRT시스템 의 적정 지역 선정을 위한 정책적 검토 사항을 모색하였으며, 지속적인 기술의 발전을 통해 PRT가 대중교통시스템내에서 신뢰성과 효율성을 확보할 것으로 기대한다.

• 대한화학회지
• /
• 제30권1호
• /
• pp.57-62
• /
• 1986

HCr$O_4^-$에 의한 $[Mo_3O_4(C_2O_4)_3(H_2O)_3]^{2-}$의 산화는 몰리브덴(IV)화합물, $[Mo_2O_5(C_2O_4)_2(H_2O)_2]^{2-}$를 생성한다. HCr$O_4^-$와 $[Mo_3O_4(C_2O_4)_3(H_2O)_3]^{2-}$의 반응에 대한 화학양론은 $2Mo_3^{IV} + 4Cr^{VI} {\to} 3Mo_2^{VI} + 4Cr^{III}$와 같다. 관찰된 속도상수는 수소이온농도에 의존한다.$Cr^{VI}$는 $Cr^V$와 $Cr^{IV}$를 거쳐서 $Cr^{III}$로 일전자씩 연속적으로 변화한다. 상세한 메카니즘이 논의된다.

• Bulletin of the Korean Chemical Society
• /
• 제24권3호
• /
• pp.350-356
• /
• 2003

The mechanism of the decomposition of a bronchodilator, S-nitroso-N-acetyl-D,L-penicillamine (SNAP) by a bronchoconstrictor, aqueous sulfite, has been investigated in detail. The decomposition was studied using a conventional spectrophotometer at 336 nm over the ranges: 0.010 ≤ $[S^{IV}]_T$ ≤ 0.045 mol $dm^{-3}$, 3.96 ≤ pH ≤ 6.80 and 15.0 ≤ θ≤ 30.0 ℃, 0.60 ≤ I ≤ 1.00 mol $dm^{-3}$, and at ionic strength 1.00 mol $dm^{-3}$ (NaCl). The rate of reaction is dependent on the total sulfite concentration and pH in a complex manner, i.e., $k_{obs}\;=\;k_1K_2[S^{IV}]_T/ ([H^+]\;+\;K_2)$. At 25.0 ℃, the second order rate constant, $k_1$, was determined as $12.5\;{\pm}\;0.15\;mol^{-1}\;dm^3\;s^{-1}$. ${\Delta}H^{neq}\;=\;+32\;{\pm}\;3 kJ\;mol^{-1}\;and\;{\Delta}S^{\neq}\;=\;-138\;{\pm}\;13\;J\;mol^{-1}K^{-1}$. The N-nitrosohydroxylamine-N-sulfonate ion was detected as an intermediate before the formation of any of the by-products, namely, N-acetyl-D,L-penicillamine. The effect of concentration of aqueous copper(Ⅱ) ions on this reaction was also examined at pH 4.75, but there was no dependence on $[Cu^{2+}]$. In addition, the $pK_a$ of SNAP was determined as 3.51 ± 0.06 at 25.4 ℃ [I = 1.0 mol $dm^{-3}$ (NaCl)].

• 대한조선학회논문집
• /
• 제50권5호
• /
• pp.355-363
• /
• 2013

Panel methods are essential tools for analyzing a fluid-flow problem around complex three dimensional bodies, but they lack ability to solve viscous effects. On the other hand, CFD methods are considered as powerful tools for analyzing fluid-flow characteristics including viscosity. However, they also have short falls, requiring more computing time and showing different results depending on the selection of turbulence models and grid systems. In this paper a hybrid scheme combining a panel method and a CFD method is suggested. The scheme adopts a panel method for far-field solution where viscous effects are negligible and a CFD method for the solution of RANS equations in near-field where viscous effects are relatively strong. The intermediate region between the far-field and near-field is introduced where the calculated field point velocities by the panel method are given as boundary velocities for the CFD method. To verify the scheme, calculated results, by a panel method, a CFD method and the hybrid scheme, for a two dimensional foil section are compared. The suggested hybrid scheme gives reasonable results, while computation time and memory can be dramatically reduced. By using the hybrid scheme efforts can be concentrated for the local flow near the leading and trailing edges, by providing more dense grid system, where detailed flow characteristics are required.

• 대한화학회지
• /
• 제37권10호
• /
• pp.903-909
• /
• 1993

팔라듐(0, II)-포스핀계 착물을 촉매로 하여 crotonic acid, methacrylic acid 및 3-butenoic acid 같은 불포화가크복실산의 카르보닐화 고리반응에서 생성가능한 물질의 구조를 확인하고, 그 반응메카니즘을 MM2 와 EHMO 계산에 의해서 추정하였다. 이 반응은 ${\pi}$ -착물을 거쳐 금속 함유 고리화합물을 만든 다음 산화성 첨가반응과 환원성 제거반응이 일어나 진행된다. ${\pi}$ -착물을 안정화시키는 crotonic acid, methacrylic acid 등은 카르보닐화 고리반응이 진행되지 않고, 3-butenoic acid는 무수카르복실산 유도체로서 glutaric anhydride와 3-methylsuccinic anhydride 및 이중결합이 자리옮김된 crotonic acid가 얻어졌다.