• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2953-2959
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• 2021

A new practical modeling of the Norton's power law creep is proposed and implemented to analyze the high temperature behaviors of Alloy 690 SG tube material. In the model, both the stress exponent n and the rate constant B are simply treated as the temperature dependent parameters. Based on the two-step optimization procedure, the temperature function of the rate constant B(T) was determined for the data set of each B value after fixing the stress exponent n value by using the prior optimized function at each temperature. This procedure could significantly reduce the numerical errors when using the power law creep equations. Based on the better description of the steady-state creep rates, the experimental rupture times could also be well predicted by using the Monkman-Grant relationship. Furthermore, the difference in tensile strengths at high temperatures could be very well estimated by assuming the imaginary creep stress related to the given strain rate after correcting the temperature effects on the elastic modulus.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.3
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• pp.167-176
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• 2005

Demand on the nuclear energy in East Asian countries has been grown rapidly to support economic development. After 9.11, nuclear security has become the world wide issue. In addition, unlike to other region, some countries are considering the introduction of nuclear power plants. To meet the challenges a new regional multilateral nuclear approach is proposed aiming at assurance of supply and non -proliferation. The new proposal is based on the principles of confidence building, volunteering, and incentives. The step wise approach is recommended to implement the multilateral system in East Asia.

• Nuclear Engineering and Technology
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• v.40 no.6
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• pp.489-496
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• 2008

Ferrocyanide-anion exchange resin was prepared and the prepared ion exchange resins were tested on the ability to uptake $Cs^+$ ion. The prepared ion exchange resins were resin-KCoFC, resin-KNiFC, and resin-KCuFC. The three tested ion exchange resins showed ion exchange selectivity on the $Cs^+$ ion of the surrogate soil decontamination solution, and resin-KCoFC showed the best $Cs^+$ ion uptake capability among the tested ion exchange resins. The ion exchange behaviors were explained well by the modified Dubinin-Polanyi equation. A regeneration feasibility study of the spent ion exchange resins was also performed by the successive application of hydrogen peroxide and hydrazine. The desorption of the $Cs^+$ ion from the ion exchange resin satisfied the electroneutrality condition in the oxidation step; the desorption of the $Fe^{2+}$ ion in the reduction step could also be reduced by adding the $K^+$ ion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1906-1913
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• 2004

A new method has been proposed for the calibration of frictional forces in atomic force microscopy. Angle conversion factor is defined using the relationship between torsional angle and frictional signal. Once the factor is obtained from a cantilever, it can be applied to other cantilevers without additional experiments. Moment balance equations on the flat surface and top edge of a commercial step grating are used to obtain angle conversion factor. Proposed method is verified through another step grating test and frictional behavior of Mica.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.460-465
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• 2004

Hydrofluoric acid has been used as a novel stripping agent for molybdenum(VI) after its extraction with Cyanex 301. In the extraction step, the effects of parameters such as type and initial concentration of acid, type of diluent, extractant concentration, metal concentration and temperature have been studied. In the stripping step, the effects of various stripping agents on stripping efficiency have been investigated. Hydrofluoric acid has been chosen as an effective stripping agent, and the effects of concentration of hydrofluoric acid, stripping time, volume of hydrofluoric acid and the number of stages of stripping have been studied. Molybdenum(VI) has been effectively separated from a large number of elements in binary mixtures, with a very high tolerance limit. Finally, the optimized method has been extended for the analysis of Mo(VI) in spent molybdenum catalysts.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.846-851
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• 2004

A new method has been proposed for the calibration of frictional forces in atomic force microscopy. Angle conversion factor is defined using the relationship between torsional angle and frictional signal. Once the factor is obtained from a cantilever, it can be applied to other cantilevers without additional experiments. Moment balance equations on the flat surface and top edge of a commercial step grating are used to obtain angle conversion factor. Proposed method is verified through another step grating test and frictional behavior of Mica.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.169-169
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• 2003

실리콘 절연막은 반도체 및 디스플레이 소자의 gate 절연막과 보호막으로, 그리고 배선공정에서는 층간절연막(ILD, Inter Layer Dielectric)으로 사용하는데, 주로 IPCVD, PECVD, APCVD법에 의하여 증착되고 있다. 그러나 이러한 방법들은 반도체 소자의 고집적화가 진행됨에 따라 증착온도와 step coverage 및 물성 이 문제점으로 대두되고 있다. 이러한 문제점들을 해결할 수 있는 원자층 증착(ALD, Atomic Layer Deposition)기술은 기판 표면에서의 self-limiting reaction을 통해 매우 얇은 박막을 형성할 수 있고, 두께 및 조성 제어를 정확히 할 수 있으며, 복잡한 형상의 기판에서도 우수한 step coverage를 얻을 수 있어 초미세패턴의 형성과 매우 얇은 두께에서 균일한 물리적, 전기적 특성이 요구되는 초미세 반도체 공정에 적합하다. 또 저온에서 증착이 가능해 유리를 기판으로 사용하는 TFT-LCD소자의 gate 절연막에 적용이 가능하다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.31-35
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• 2000

A cantilever deflection measurement system for AFM(atomic force microscope) was constructed by the laser deflection method using LEP type PSD. Design process including sensitivity analysis was presented and the performance of the system was demonstrated by several experiments using a sample specimen with 50nm-step on the surface. The measured displacement-amplification-factor showed good agreement with the expected one with about 8% deviation. The step height measurement data were compared to what were acquired by commercial AFM, and the result showed that there were about 5nm-deviation between the two data. These results satisfies our expectation in the stage of system design.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.989-992
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• 2004

PEMBE(plasma enhanced molecular beam epitaxy)방법으로 성장된 GaN 박막의 초기 거동현상을 실시간 X-선 산란을 이용하여 관찰하였다. 표면이 원자 계단(atomic step)을 이루고 있는 사파이어 기판 위에 성장하는 GaN 박막은 layer-by-layer 모드로 성장 후 3D 모드로 성장을 하였다. 거친 표면을 가진 사파이어 기판 위에 성장하는 GaN 박막은 성장 초기는 표면을 평평하게 만든 후, 3D 모드로 성장하였다. 플라즈마로 생성된 이온화된 질소는 표면의 에너지를 변화시켜 GaN 박막의 증착을 증진시키고, 표면의 coverage를 증가시킨다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.125-125
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• 2012

Graphene was epitaxially grown on a 6H-SiC(0001) substrate by thermal decomposition of SiC under ultrahigh vacuum conditions. Using scanning tunneling microscopy (STM), we monitored the evolution of the graphene growth as a function of the temperature. We found that the evaporation of Si occurred dominantly from the corner of the step rather than on the terrace. A carbon-rich $(6{\sqrt{3}}{\times}6{\sqrt{3}})R30^{\circ}$ layer, monolayer graphene, and bilayer graphene were identified by measuring the roughness, step height, and atomic structures. Defect structures such as nanotubes and scattering defects on the monolayer graphene are also discussed. Furthermore, we confirmed that the Dirac points (ED) of the monolayer and bilayer graphene were clearly resolved by scanning tunneling spectroscopy (STS).