• The Journal of Information Systems
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• v.29 no.1
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• pp.75-91
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• 2020

Purpose Retrofit, defined to be addition of new technologies or features to the old system to increase efficiency or to abate GHG emissions, is considered as an important alternative for the old coal-fired power plant. The purpose of this study is to propose mathematical method to model multiple alternative retrofit in Generation Capacity Expansion Planning(GCEP) problem, and to get insight to the retrofit patterns from realistic case studies. Design/methodology/approach This study made a multi-alternative retrofit GECP model by adopting some new variables and equations to the existing GECP model. Added variables and equations are to ensure the retrofit feature that the life time of retrofitted plant is the remaining life time of the old power plant. We formulated such that multiple retrofit alternatives are simultaneously compared and the best retrofit alternative can be selected. And we found that old approach to model retrofit has a problem that old plant with long remaining life time is retrofitted earlier than the one with short remaining life time, fixed the problem by some constraints with some binary variables. Therefore, the proposed model is formulated into a mixed binary programming problem, and coded and run using the GAMS/cplex. Findings According to the empirical analysis result, we found that approach to model the multiple alternative retrofit proposed in this study is comparing simultaneously multiple retrofit alternatives and select the best retrofit satisfying the retrofit features related to the life time. And we found that retrofit order problem is cleared. In addition, the model is expected to be very useful in evaluating and developing the national policies concerning coal-fired power plant retrofit.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.16.1-16.1
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• 2011

$TiO_2$ is a promising material for gas sensors. To achieve high sensitivities, the material should exhibit a large surface-to-volume ratio and possess the high accessibility of the gas molecules to the surface. Accordingly, a wide variety of porous $TiO_2$ nanomaterials synthesized by wet-chemical methods have been reported for gas sensor applications. Nonetheless, achieving the large-area uniformity and comparability with well-established semiconductor production processes of the methods is still challenging. An alternative method is soft-templating which utilizes nanostructured inorganic or organic materials as sacrificial templates for the preparation of porous materials. Fabrication of macroporous $TiO_2$ films and hollow $TiO_2$ tubes by soft-templating and their gas sensing applications have been reported recently. In these porous materials composed of assemblies of individual micro/nanostructures, the form of links or necks between individual micro/nanostructures is a critical factor to determine gas sensing properties of the material. However, a systematic study to clarify the role of links between individual micro/nanostructures in gas sensing properties of a porous metal oxide matrix is thoroughly lacking. In this work, we have demonstrated a fabrication method to prepare highly-ordered, embossed $TiO_2$ films composed of anatase $TiO_2$ hollow hemispheres via soft-templating using polystyrene beads. The form of links between hollow hemispheres could be controlled by $O_2$ plasma etching on the bead templates. This approach reveals the strong correlation of gas sensitivity with the form of the links. Our experimental results highlight that not only the surface-to-volume ratio of an ensemble material composed of individual micro/nanostructures but also the links between individual micro/nanostructures play a critical role in evaluating the sensing properties of the material. In addition to this general finding, the facileness, large-scale productivity, and compatability with semiconductor production process of the proposed fabrication method promise applications of the embossed $TiO_2$ films to high-quality sensors.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.23-27
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• 1998

To protect the underground pipeline from the mechanical damage and to enhance the cathodic protection effect, the river sand has been backfilled traditionally around the buried pipeline. However, river sand became depleted and expensive. One has to seek for the economic alternative materials. Crashed stone is a good candidate for the backfill material. In this study, how much the particle size and shape of the crashed stone can effect on the gas pipeline coating was examined. A series of laboratory and field test was performed. In the Lab, the increasing loads were applied to the coated pipeline surrounded by the crashed stone, where no significant damage was observed.

• Journal of the Korean Institute of Gas
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• v.15 no.2
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• pp.1-8
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• 2011

In this research, the safety trends and technologies of HCNG, a mixture of hydrogen and natural gas, are analyzed. This is an attracting alternative fuels to meet the strengthened automotive exhaust gas emission standards. HCNG is very important opportunities and challenges in that it is available the existing CNG infrastructures, meets the strengthened emission standards, and the technical, social bridge of the coming era of hydrogen. It is essential for the commercialization of HCNG that hydrogen - compressed natural gas blended fuel for use in preparation of various safety considerations included accidents scenario, safety distance, hydrogen attack, ignition sources and fire detectors are examined. Risk assessments also are suggested as one of permission procedure for HCNG filling station.

• Journal of the Korean Institute of Gas
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• v.19 no.6
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• pp.8-14
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• 2015

Synthetic natural gas(SNG), acquired from coal, is regarded as an alternative to natural gas since a rise in natural gas due to high oil price can be coped with it. In the present study, 11-liter heavy duty compressed natural gas(CNG) engine was employed in order to examine the combustion and emission characteristics of SNG. The simulated SNG, made up 90.95% of methane, 6.05% propane and 3% hydrogen was used in the experiment. Power output, thermal efficiency, combustion stability and emission characteristics were compared to those with CNG at the same engine operating conditions. Knocking phenomenon was also analyzed at 1260 rpm, full load condition. Combustion with SNG was more stable than CNG. Nitrogen oxides emissions increased while Carbon dioxides emissions decreased. Anti-knocking characteristics were improved with SNG.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1277-1281
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• 2020

A novel ceramic Gas Electron Multiplier (GEM) has been developed to meet the demand of high counting rate for the neutron detection which is an alternative to ³He-based detector at China Spallation Neutron Source (CSNS). An experiment was performed to measure the neutron transmittance of ceramic-GEM and FR4-GEM at the small angle neutron scattering (SANS) instrument. The result showed the ceramic-GEM has higher transmittance and less self-scattering especially for cold neutrons. One single ceramic GEM could give a gain of 10²-10⁴ in the mixture gas of Ar and CO₂ (90%:10%) and its energy resolution was about 27.7% by using ⁵⁵Fe X ray of 5.9 keV. A prototype has been developed in order to investigate the performances of the ceramic GEM-based neutron detector. Several neutron beam tests, including detection efficiency, spatial resolution, two-dimensional imaging, and wavelength spectrum, were carried out at CSNS and China Mianyang Research Reactor (CMRR). The results show that the ceramic GEM-based neutron detector is a good candidate to measure the high intensity neutrons.

• Journal of the Korean Society for Railway
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• v.8 no.6 s.31
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• pp.520-524
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• 2005

It is consequential to reduce the environmental impact of a product for sustainable development in 21st Century. In the field of transportation, especially, the technological market concerned about reduction and assessment of greenhouse gas emission is expected to be extended. The LCA gas been esteemed and utilized as a realistic alternative greenhouse gas emission is expected to be extended. The LCA has been esteemed and utilized as a realistic alternative to improve the environment by the assessment of environmental impacts. In this study, simplified life cycle assessment(S-LCA), was performed to analyze the environmental impacts quantitatively, which were produced through the life cycle of a electric motor unit(EMU). The object of the present work is rth investigate main parameters of environmental impacts and to establish the plans to improve the environment impact of EMU. As a result of quantitative assessment for environmental impact and manufacturing, the EMU carbody made of SUS showed acidification(AD) and marine water aquatic ecotoxicity(MAET) the most, while that made of Mild showed high impact of global warning(GW) and abiotic resources depletion(ARD). For the SUS EMU, the high AD and MAET impact is occurred by the discharged pollutants during acid-washing process. Also, high value of GW and ARD for Mild EMU is resulted from the consumption of iron ore, coal and crude oil during manufacturing. Therefore, the environment impact of carbody would be decreased by enhancing of energy efficiency and the lightening the weight of it.

• Journal of the Korea Convergence Society
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• v.12 no.2
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• pp.193-200
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• 2021

As the degree of environmental pollution caused by the use of fossil fuels intensifies, many countries continue to invest in the development of alternative energy. PEMFC, one of the alternative energies, consists of four main components: bipolor plate, electrolyte, gas diffusion layer, and electrode. Among them, bipolor plate, the gas diffusion layer, and electrode are generally manufactured using carbon materials such as carbon black and carbon fiber. These carbon materials are expensive in manufacturing process or have disadvantages such as corrosion, and research is being conducted in many fields to improve this. This paper collects several research results conducted to improve the shortcomings of these three components and examines the trends of PEMFC by grasping what problems have been and how they have improved.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.988-995
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• 2020

Air gun shock systems are commonly used as alternative explosion energy sources for underwater explosion (UNDEX) shock tests owing to their low cost and environmental impact. The airbag inflator of automotive airbag systems is also very useful to generate extremely rapid underwater gas release in labscale tests. To overcome the restrictions on the very small computational time step owing to the very fine fluid mesh around the nozzle hole in the explicit integration algorithm, and also the absence of a commercial solver and software for gas UNDEX of airbag inflator, an idealized airbag inflator and fluid mesh modeling technique was developed using nozzle holes of relatively large size and several small TNT charges instead of gas inside the airbag inflator. The objective of this study is to validate the results of an UNDEX response analysis of one and two idealized airbag inflators by comparison with the results of shock tests in a small water tank. This comparison was performed using the multi-material Arbitrary Lagrangian-Eulerian formulation and fluid-structure interaction algorithm. The number, size, vertical distance from the nozzle outlet, detonation velocity, and lighting times of small TNT charges were determined. Through mesh size convergence tests, the UNDEX response analysis and idealized airbag inflator modeling were validated.

• Journal of the Korean institute of surface engineering
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• v.34 no.5
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• pp.403-408
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• 2001

In this work, the cyclic perfluorinated ether (c-C$_4$F$_{8}$O) with very high destructive removal efficiency (DRE) than other alternative gases, such as $C_3$F$_{8}$, c-C$_4$F$_{8}$ and NF$_3$ was used as an alternative process chemical. The plasma cleaning of silicon nitride using gas mixtures of c-C$_4$F$_{8}$O/O$_2$ and c-C$_4$F$_{8}$O/O$_2$+ $N_2$ was investigated in order to evaluate the effects of adding $N_2$ to c-C$_4$F$_{8}$O/O$_2$ on the global warming effects. Under optimum condition, the emitted net perfluorocompounds (PFCs) during cleaning of silicon nitride were quantified and then the effects of additive $N_2$ by obtaining the destructive removal efficiency (DRE) and the million metric tons of carbon equivalent (MMT-CE) were calculated. DRE and MMTCE were obtained by evaluating the volumetric emission using. Fourier transform-infrared spectroscopy (FT-IR). During the cleaning using c-C$_4$F$_{8}$O/O$_2$+$N_2$, DRE values as high as (equation omitted) 98% were obtained and MMTCE values were reduced by as high as 70% compared to the case of $C_2$F$_{6}$O$_2$. Recombination characteristics were indirectly investigated by combining the measurements of species in the chamber using optical emission spectroscopy (OES), before and after the cleaning, in order to understand any correlation between plasma and emission characteristics as well as cleaning rate of silicon nitride.silicon nitride.