• Nuclear Engineering and Technology
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• 제29권4호
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• pp.269-279
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• 1997

The errors associated with incorrect sampling and transport of radioactive aerosol from radwaste thermal process off-gas are analyzed and the conditions of representative sampling and correct transport of radioactive aerosol for off-gas system evaluation are discussed. An estimation method of sampling errors for individual radionuclides is proposed and applied to simulated vitrification melter aerosols. Prediction methods for particle deposition in sample transport tube under laminar as well as turbulent flow conditions are also described by example calculations with simulated incinerator off-gas From the results of example calculations and plots, instrumental and operational conditions of radioactive aerosol sampling system with minimized errors and correction methods for nonideal sampling and transport are recommended.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 춘계학술발표회논문집(2)
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• pp.769-774
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• 1995

In this study, a transport model was developed in order to analyze and predict the transport behaviors of radionuclides mediated by pseudo-colloid in the fractured rock media. It was resulted that the transport of Pu-239 was faster than Ni-63 because pseudo-colloid formation constant of Pu-239 was greater than that of Ni-63. Also, the effect of pseudo-colloid formation on the transport of a radionuclide was shown to be very significant when the apparent pseudo colloid formation constant, $K_{ap}(m^{3}/kg)$, was greater than 100. Thus, it can be concluded that acceleration of radionuclide migration may be occurred because the pseudo-colloid formation of radionuclides increases the amount of mobile components in the solution and consequently decreases the amount of radionuclides adsorbed on the stationary solid medium.

• International Journal of Air-Conditioning and Refrigeration
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• 제12권1호
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• pp.1-9
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• 2004

The purpose of the present study is to examine the heat transport limitations in a screen mesh heat pipe for electronic cooling by theoretical analysis. Diameter of pipe was 6mm, and mesh numbers were 50, 100, 150, 200 and 250, and water was investigated as working fluid. According to the change of mesh number, wick layer, inclination and saturation temperature, the maximum heat transport limitations by capillary, entraintment, sonic and boiling were analyzed by a theoretical design method of heat pipe, including capillary pressure, pumping pressure, liquid friction coefficient in wick, vapor friction coefficient, etc. Based on the results, the capillary limitation in a small diameter of heat pipe is largely affected by mesh number and wick layer. Mesh number of 250 is desirable not to be used in pipe diameter of 6 mm, because capillary heat transport limitation decreases by the abrupt increase of liquid friction pressure due to the small liquid flow area. For the heat transport of 15 watt in 6mm diameter pipe, mesh number of 100 and one layer is an optimum wick condition, which thermal resistance is the smallest.

• E2M - 전기 전자와 첨단 소재
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• 제8권6호
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• pp.685-692
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• 1995

The electron transport coefficients in argon gas is studied over the range of E/N values from 85 to 566 Td by the Monte Carlo method considering the latest cross section data. The result of the Monte Carlo method analysis shows that the value of the electron transport coefficients such as the electron drift velocity, the ratio of the longitudinal and transverse diffusion coefficients to the mobility. It is also found that the electron transport coefficients calculated by the two-term approximation analysis agree well with those by Monte Carlo calculation. The electron energy distributions function were analysed in argon at E/N=283, and 566 Td for a case of the equilibrium region in the mean electron energy. A momentum transfer cross section for the argon atom which was consistent with both of the present electron transport coefficients was derived over the range of mean electron energy from 10.3 to 14.5 eV, also suggested as a set of electron cross section for argon atom. The validity of the results obtained has been confirmed by a Monte Carlo simulation method.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2084-2094
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• 2021

Delta-form-based methods for solving high order spatial discretization schemes are introduced into the reactor S_N transport equation. Due to the nature of the delta-form, the final numerical accuracy only depends on the residuals on the right side of the discrete equations and have nothing to do with the parts on the left side. Therefore, various high order spatial discretization methods can be easily adopted for only the transport term on the right side of the discrete equations. Then the simplest step or other robust schemes can be adopted to discretize the increment on the left hand side to ensure the good iterative convergence. The delta-form framework makes the sweeping and iterative strategies of various high order spatial discretization methods be completely the same with those of the traditional S_N codes, only by adding the residuals into the source terms. In this paper, the flux limiter method and weighted essentially non-oscillatory scheme are used for the verification purpose to only show the advantages of the introduction of delta-form-based solving methods and other high order spatial discretization methods can be also easily extended to solve the S_N transport equations. Numerical solutions indicate the correctness and effectiveness of delta-form-based solving method.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.442-454
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• 2021

The porous transport layer (PTL) is essential to effectively remove oxygen and hydrogen gas from the electrode surface at high current density operation conditions. In this study, the effect of PTL with different characteristics such as pore size, pore gradient, interfacial coating was investigated by multi-layered sintered mesh. A water electrolysis single cell of active area of the 34.56 cm² was constructed, and IV performance and impedance analysis were conducted in the range of 0 to 2.0 A/cm². It was confirmed that the multi-layered sintered mesh PTL, which have an average pore size of 25 to 57 ㎛ and a larger pore gradient, removed bubbles effectively and thus seemed to improve IV performance. Also, it was confirmed that the catalytic metals such as Ni, NiMo coating on the PTL reduced activation overpotential, but increased mass transport overpotential.

• 신재생에너지
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• 제7권4호
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• pp.18-29
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• 2011

Biofuls are considered as an option to reduce greenhouse gases emission, increase energy supply diversity and security of supply, as well as an opportunity for job creation and rural development. First of all, biofuls technologies have been promoted as a means for reducing the carbon intensity of the transport sector. Hence, in the last decade biofuels production has been driven by governmental policies. The key instruments widely adopted to foster production and increase consumption have been mandatory blending targets, tax exemptions and sibsidies. As one of the most powerful instruments, biofuel mandates require fuel producers to produce a pre-defined amount (or share) of biofuels and blend them with petroleum fuel. National biofuels mandates are in place 35 countries and partially in place in 6 countries. In this study, we reviewed status of global biofuels policies to reduce greenhouse gases in the European Union, United States and other countires worldwide. Especially, we discussed representative biofuels mandates policies same as Renewable Fuel Standard (RFS, US), Renewable Transport Fules Obligation (RTFO, UK) in transport sector.

• Journal of Electrochemical Science and Technology
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• 제12권1호
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• pp.1-20
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• 2021

In-depth knowledge of electrode processes is crucial for determining the electrochemical performance of lithium-ion batteries (LIBs). In particular, the conduction mechanisms of charged species in the electrodes, such as lithium ions (Li+) and electrons, are directly correlated with the performance of the battery because the overall reaction is dependent on the charge transport behavior in the electrodes. Therefore, it is necessary to understand the different electrochemical processes occurring in electrodes in order to elucidate the charge conduction phenomenon. Thus, it is essential to conduct fundamental studies on electrochemical processes to resolve the technical challenges and issues arising during the ionic and electronic conduction. Furthermore, it is also necessary to understand the transport of charged species as well as the predominant factors affecting their transport in electrodes. Based on such in-depth studies, potential approaches can be introduced to enhance the mobility of charged entities, thereby achieving superior battery performances. A clear understanding of the conduction mechanism inside electrodes can help overcome challenges associated with the rapid movement of charged species and provide a practical guideline for the development of advanced materials suitable for high-performance LIBs.

• 한국포장학회지
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• 제28권3호
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• pp.193-199
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• 2022

Sustainable energy supplies without the recharging and replacement of charge storage device have become increasingly important. Among various energy harvesters, the triboelectric nanogenerator (TENG) has attracted considerable attention due to its high instantaneous output power, broad selection of available materials, eco-friendly and inexpensive fabrication process, and various working modes customized for target applications. The TENG harvests electrical energy from wasted mechanical energy in the ambient environment. TENG devices are very likely to be used in next-generation renewable energy and energy harvesting. TENG devices have the advantage of being able to manufacture very simple power devices. In this experiment, various organic dielectrics and inorganic dielectrics were used to improve the open voltage of TENG, Among the various organic dielectrics, Teflon-based FEP, which has the highest electron affinity, showed the highest open voltage and Al electrode was fabricated on Teflon substrate by sputtering deposition process. And AAO (Anodized Aluminum Oxide) nanostructures were applied to maximize the specific surface area of the TENG device. The power generation of TENG within the acceleration level (0.25, 0.5, 1.0, 1.5 and 2 G) and the frequency range (5-120 Hz) of the domestic transport environment was up to 4 V.

• 방사성폐기물학회지
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• 제20권4호
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• pp.455-468
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• 2022

Colloid Formation and Migration (CFM) project is being carried out within the Grimsel Test Site (GTS) Phase Ⅵ. Since 2008, the Korea Atomic Energy Research Institute (KAERI) has joined CFM to investigate the behavior of colloid-facilitated radionuclide transport in a generic Underground Research Laboratory (URL). The CFM project includes a long-term in-situ test (LIT) and an in-rock bentonite erosion test (i-BET) to assess the in-situ colloid-facilitated radionuclide transport through the bentonite erosion in the natural flow field. In the LIT experiment, radionuclide-containing compacted bentonite was equipped with a triple-packer system and then positioned at the borehole in the shear zone. It was observed that colloid transport was limited owing to the low swelling pressure and low hydraulic conductivity. Therefore, a postmortem analysis is being conducted to estimate the partial migration and diffusion of radionuclides. The i-BET experiment, that focuses more on bentonite erosion, was newly designed to assess colloid formation in another flow field. The i-BET experiment started with the placement of compacted bentonite rings in the double-packer system, and the hydraulic parameters and bentonite erosion have been monitored since December 2018.