• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.104-107
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• 2000

High quality BSCCO thin films have been fabricated by means of an ion beam sputtering at various substrate temperatures, T$\_$sub/, and ozone gas pressures, PO$_3$. The correlation diagrams of the BSCCO Phases appeared against T$\_$sub/ and PO$_3$ are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 phases as well as Bi2212 one come out as stable phases depending on T$\_$sub/ and PO$_3$. From these results, the thermodynamic evaluations of ΔH and ΔS which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase are performed.

• Water Engineering Research
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• 제5권4호
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• pp.195-206
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• 2004

This paper deals with oxygen transfer by air entrainment and energy dissipations by flow characteristics at the stepped drop structure. Nappe flow occurred at low flow rates and for relatively large step height. Dominant flow features included an air pocket, a free-falling nappe impact and a subsequent hydraulic jump on the downstream step. Most energy was dissipated by nappe impact and in the downstream hydraulic jump. Skimming flow occurred at larger flow rates with formation of recirculating vortices between the main flow and the step comers. Oxygen transfer was found to be proportional to the flow velocity, the flow discharge, and the Froude number. It was more related to the flow discharge than to the Froude number. Energy dissipations in both cases of nappe flow and skimming flow were proportional to the step height and were inversely proportional to the overflow depth, and were not proportional to the step slope. The stepped drop structure was found to be efficient for water treatment associated with substantial air entrainment and for energy dissipation.

• 천문학회지
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• 제55권6호
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• pp.215-220
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• 2022

To seek an atmospheric heating mechanism operating on the Sun we investigated a heating source generated by a downflow, both of which may arise in a magnetic loop dynamically formed on the Sun via flux emergence. Since an observation shows that the illumination of evolving magnetic loops under the dynamic formation occurs sporadically and intermittently, we performed a magnetohydrodynamic simulation of flux emergence to obtain a high-cadence simulated data, where temperature enhancement was identified at the footpoint of an evolving magnetic loop. Unlike a rigid magnetic loop with a confined flow in it, the evolving loop in a low plasma β atmosphere is subjected to local compression by the magnetic field surrounding the loop, which drives a strong supersonic downflow generating an effective footpoint heating source in it. This may introduce an energy conversion system to the magnetized atmosphere of the Sun, in which the free magnetic energy causing the compression via Lorentz force is converted to the flow energy, and eventually reduced to the thermal energy. Dynamic and thermodynamic states involved in the system are explained.

• 한국자기학회지
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• 제12권1호
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• pp.34-40
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• 2002

고에너지 Nd-Fe-B 소결자석 제조용 strip-cast 합금의 미세조직 개선을 위하여, Nd-Fe-B 합금을 다양한 조건하에서 strip casting법으로 제조한 후, 제조 조건이 상 형성, 상 분포 및 조직 형성에 미치는 영향을 조사하였다. 냉각속도 즉, wheel speed가 5 m/s 이하일 때 고특성 소결자석 제조에 적합한 미세조직을 갖는 Strip 합금들을 제조할 수 있었으며, 이때의 한계 조성은 Nd$_{14}$Fe$_{79}$B$_{7}$ 정도로 추정되었다. 또한 조성에 상관없이 5 m/s 이하에서는 strip 표면에 수직한 방향으로 <001> preferred orientation이 발생하였는데, 이것은 궁극적으로 합금의 분쇄.성형시 결정립 배향도 향상에 유리하게 작용할 것으로 보인다. 한편 냉각속도가 증가할수록 Nd$_2$Fe$_{14}$B 결정립의 미세화로 인하여 보자력이 증가하였으나, Nd 함량이 감소할 경우 $\alpha$-Fe 정출의 증가로 인하여 보자력이 감소하였다.

• Bulletin of the Korean Chemical Society
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• 제30권8호
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• pp.1845-1850
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• 2009

We have performed replica-exchange molecular dynamics (REMD) simulations on the dimer formation of fibrilforming segments of $\alpha$-Synuclein (residues 71 - 82) using implicit solvation models with two kinds of force fields- AMBER parm99SB and parm96. We observed spontaneous formation of dimers from the extensive simulations, demonstrating the self-aggregating and fibril forming properties of the peptides. Secondary structure profile and clustering analysis showed that dimers with antiparallel $\beta$-sheet conformations, stabilized by well-defined hydrogen boding, are major species corresponding to global free energy minimum. Parallel dimers with partial $\beta$-sheets are found to be off-pathway intermediates. The relative instability of the parallel arrangements is due to the repulsive interactions between bulky and polar side chains as well as weaker backbone hydrogen bonds.

• 한국미생물·생명공학회지
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• 제28권1호
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• pp.26-32
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• 2000

Electrostatic forces contribute to the high degree of enzyme transition state complementarity in enzyme catalyzed reaction and such forces are modified by the solvent through its dielectric constant and polar properties. The contributions of electrostatic interaction to the formation of ES complex and the stabilization of transition state of the trypsin catalyzed reaction were probed by kinetic studied with high pressure and solvent dielectric constant. A good correlation has been observed between the increase of catalytic efficiency of trypsin and the decrease of solvent dielectric constant. Activation volume linearly decreased as the dielectric constant of solvent decreased, which means the increase in the reaction rae. Moreover, the decrease of activation volume by lowering the solvent dielectric constant implies a solvent penetration of the active with and a reduction of electrostatic energy for the formation of dipole of the active site oxyanion hole. When the 야electric constant of the solvents was lowered to 4.7 unit, the loss of activation energy and that of free energy of activation were 2.262 KJ/mol and 3.169 KJ/mol, respectively. The results of this study indicate that the high pressure kinetics combined with solvent effects can provide unique information on enzyme reaction mechanisms, and the controlling the solvent dielectric constant can stabilize the transition state of the trypsin-catalyzed reaction.

• 대한화학회지
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• 제36권5호
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• pp.632-637
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• 1992

물-아세틸아세톤 용매계에서 과염소산나트륨과 과염소산구리의 표준이동 자유에너지는 갈바니전지의 기전력을 측정하여 구하였으며, 이 용매계에서 나트륨이온과 구리이온의 표준이동 자유에너지는 extrathermodynamic procedure로서 테트라페닐붕산 테트라부틸암모늄 가정을 써서 계산하였다. 물로부터 아세틸아세톤 용매로 나트륨이온과 구리이온이 이동할 때의 표준자유에너지값은 25${\circ}C$에서 각각 5.09 및 4.16 kcal/mol이었다. 이 값은 아세틸아세톤이 물보다 나트륨이온과 구리이온에 대하여 약한 donor solvent임을 뜻한다. 물로부터 소량의 아세틸아세톤을 포함하는 혼합용매로 구리이온이 이동할 때의 표준자유에너지값은 이상하게 (-)값을 나타내는데, 이것은 아세틸아세톤이 구리이온과 반응하여 킬레이트를 생성하는 효과 때문이다.

• 분석과 대안
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• 제5권2호
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• pp.77-105
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• 2021

Потребление природного газа в Азии растет быстрыми темпами из-за различных факторов, таких как экономический рост в регионе, урбанизация, переход с угля на газ в секторах производства электроэнергии и промышленности. Из-за географических особенностей и отсутствия международных трубопроводных соединений между странами в АТР большая часть природного газа, экспортируемого азиатским потребителям, транспортируется танкерами по морю в виде сжиженного природного газа. Поскольку азиатский рынок является наиболее прибыльным рынком с самым быстрым ростом спроса, конкуренция между продавцами сжиженного природного газа (СПГ) за долю азиатского рынка усиливается. Конкуренция ускорилась, особенно после того, как на рынок были выведены большие объемы дополнительных поставок со стороны новых экспортеров из США, Австралии и России. Cheniere Energy, первый экспортер СПГ в континентальной части США, не приняла традиционный механизм ценообразования и бизнес-модель. Традиционно цены по долгосрочным контрактам на СПГ индексируются к ценам на конкурирующие виды топлива, такие как сырая нефть. Компания приняла механизм ценообразования и бизнесмодель по системе «кост-плюс». Cheniere Energy выбрала более безопасную и безрисковую систему ценообразования, которая ежегодно гарантирует продавцу фиксированную сумму дохода. Компания зарабатывает одинаковую сумму денег, независимо от динамики цен на природный газ на внутреннем и международном рынке, возможно с меньшим доходом. Однако, успешно внедрив более безопасную и безрисковую бизнес-модель, Cheniere Energy, компания относительно меньшего размера по сравнению с крупными нефтегазовыми компаниями, стала примером для других небольших компаний в стране. Бизнес-модель компании продемонстрировала, как войти и управлять бизнесом СПГ в США в условиях растущей конкуренции между продавцами на внутреннем и международном рынке.

• 마이크로전자및패키징학회지
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• 제10권3호
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• pp.37-42
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• 2003

전자 패키징에 사용되는 솔더합금에 납을 함유됨으로써 인하여 야기되는 환경적 문제와 인체 유해성 때문에 Pb-Sn 합금계를 대체할 수 있는 새로운 무연 솔더 재료의 필요성이 대두되고 있다. 새로운 솔더합금의 개발에 있어서 솔더 조인트의 신뢰성이 가장 중요한 문제라고 할 수 있는데, 솔더 조인트의 신뢰성은 솔더와 기판 사이의 계면 반응 형태와 그 정도에 의해서 크게 영향을 받기 때문에 솔더와 기판 사이의 계면 현상에 관한 더 깊은 이해가 필요하게 된다 솔더링 동안 기판/솔더 계면에서 가장 먼저 생성되는 금속간 화합물의 상을 예측하기 위한 열역학적인 방법이 제안되었다. 계면 에너지와 석출 구동력의 함수로 표현되는 각각의 금속간 화합물에 대한 핵생성 활성화 에너지를 비교함으로써 활성화 에너지가 가장 낮은 금속간 화합물이 가장 먼저 생성된다고 예측하였다. 거기에 더해 에너지를 기반으로 한 계산을 통하여 솔더 조인트에서 금속간 화합물의 입자 형상을 설명하였다. 울퉁불퉁한 계면을 가진 금속간 화합물의 Jackson의 parameter 값은 2보다 작은 반면 평평한 입자의 경우 2보다 크게 된다.

• Journal of Mechanical Science and Technology
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• 제18권8호
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• pp.1271-1287
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• 2004

In this article, vapor bubble nucleation in liquid and the evaporation process of a liquid droplet at its superheat limit were discussed from the viewpoint of molecular clustering (molecular cluster model for bubble nucleation). For the vapor bubble formation, the energy barrier against bubble nucleation was estimated by the molecular interaction due to the London dispersion force. Bubble nucleation by quantum tunneling in liquid helium under negative pressure near the absolute zero temperature and bubble nucleation on cavity free micro heaters were also presented as the homogenous nucleation processes.