• Polymer(Korea)
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• v.33 no.5
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• pp.420-428
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• 2009

In this study, the composites containing carbon black (CB) or carbon fibers were prepared, and the microwave absorbing properties and the absorption mechanism of them were investigated and discussed in the frequency range of 2-18 GHz, respectively. The optimum mass fraction of CB has been found as 6%, and the carbon fibers were discovered to absorb radar wave either under parallel or vertical polarization, the suitable gap distance between each bundle of which was 5 mm. According to the results of the single constitute absorber samples, the structured composites with the two kinds of absorbers combination were fabricated and studied at 2-18 GHz. The top layer absorbers affect the absorption performance a lot; the maximum reflection loss of composites with CB as top layer absorbers was -31.8 dB with the frequency range of 2.4 GHz below -10 dB, and the other type with CFs as the top layer absorbers obtained the reflection loss peak value of -31.4 dB with 2 GHz below-10 dB.

• Corrosion Science and Technology
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• v.18 no.4
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• pp.129-137
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• 2019

CFRP (Carbon Fiber Reinforced Plastics) is composed of carbon fiber and plastic resin, and is approximately 20 - 50% lighter than metallic materials. CFRP has a low density, higher specific stiffness, specific strength, and high corrosion resistance. Because of these excellent properties, which meet various regulation conditions needed in the industrial fields, CFRP has been widely used in many industries including aviation and ship building. However, CFRP reveals water absorption in water immersion or high humidity environments, and water absorption occurs in an epoxy not carbon fiber, and can be facilitated by higher temperature. Since these properties can induce volume expansion inside CFRP and change the internal stress state and degrade the chemical bond between the fiber and the matrix, the mechanical properties including bond strength may be lowered. This study focused on the effects of NaCl concentration (0.01 - 1% NaCl) and solution temperature ($30-75^{\circ}C$) on the galvanic corrosion between CFRP and A516Gr.55 carbon steel. When NaCl concentration increases 10 times, corrosion rate of a specimen was not affected, but that of galvanic coupled carbon steel increased by 46.9% average. However, when solution temperature increases $10^{\circ}C$, average corrosion rate increased approximately 22%, regardless of single or galvanic coupled specimen.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.951-962
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• 2020

One hundred ninety-five countries reached agreement on a new climate treaty in Paris, France to reduce the carbon emissions. South Korea has been selected as a target country for reducing greenhouse gas (GHG) obligations since 2020. In this context, the Korean government developed several GHG emissions reduction programs using forests called the "Forest carbon offset scheme (FCOS)." The forest management method is one of the tools to implement FCOS. Most of the participants registered forest management as the preferred methodology to participate in the FCOS. For a successful implementation of the FCOS, it is necessary to explore the optimal methods by considering the cost-effective aspect of conducting the forest management as a tool to increase carbon absorption. In this context, this study investigated the value optimized FCOS projects based on the forest management methodology in South Korea. Three forest management scenarios, 1) extending the final age of maturity of Pinus densiflora stands (S1), 2) extending the final age of maturity of Quercus acutissima stands (S2), and 3) reforestation with new species (Pinus densiflora to Quercus acutissima) (S3), were examined and evaluated to identify the optimal carbon absorption and value optimized economic perspective. The results of the scenario-based modelling indicated that S3 showed value optimized from an economical perspective, and S2 was the most effective method to absorb carbon among the scenarios. It is anticipated that this paper will contribute to provide valuable information by presenting innovative approaches as a value optimized FCOS implementing tool in a GHG reduction program in South Korea.

• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.91-96
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• 2021

This study was conducted to improve the operating conditions of an adsorption tower filled with potassium impregnated activated carbon for high hydrogen sulfide capture capacity. Heat treatment modified the surface properties of activated carbon, and ultimately determined its adsorption capacity. The activated carbon doped with potassium showed 57 times more adsorption at room temperature than that of using the raw adsorbent. It is believed that uniform pore formation and strong bonding of the potassium on the surface of carbon contributed to the chemical and physical absorption of hydrogen sulfide. The SEM analysis on the surface structure of various commercial carbons showed that the modification of surface properties through the heat treatment generated the destruction of pore structures resulted in the decrease of the absorption performance. The pressure drop across the activated carbon bed was closely related with the grain size and shape. The optimum size of irregularly shaped activated carbon granules was 2~4 mesh indicating economical feasibility.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.619-626
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• 2023

Primary and secondary amine-based sorbents were synthesized to investigate the operation capacity for the carbon dioxide separation TSA process. (3-Aminopropyl) triethoxysilane was used as a primary amine precursor as a crosslinking agent to synthesize a secondary amine precursor in which amine groups were crosslinked with a crosslinking agent. Carbon dioxide absorbed by primary amines is completely separated above 170 ℃. The working capacity of the primary amine absorbent was less than 2% when regenerated at 130℃. The secondary amine absorbent has a higher carbon dioxide separation capacity at a lower regeneration temperature than the primary amine absorbent. The secondary amine absorbent could predict process operation performance of about 6.5% with 2% carbon dioxide absorption and 100% carbon dioxide regeneration conditions. Therefore, it was found that the working capacity of the secondary amine absorbent was higher than that of the primary amine.

• Ecology and Resilient Infrastructure
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• v.7 no.4
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• pp.284-293
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• 2020

We present a quantitative survey of the carbon storage and absorption capacity of tree species in the vegetation conservation and ecological restoration areas of Bulamsan urban nature park in Nowon-gu, Seoul. The density of the sawtooth oak (Quercus acutissima) community in the ecological conservation area is approximately 30 individuals/225 ㎡, while a further 20 species, such as Japanese snowbell (Styrax obassia), galcham oak (Quercus aliena), Asian Sweetleaf (Symplocos chinensis f. pilosa), East Asian ash (Fraxinus rhynchophylla), and Korean rhododendron (Rhododendron mucronulatum) are sparsely distributed. In contrast, the ecological restoration sites typically comprised Mongolian oak (Quercus mongolica), jolcham oak (Quercus serrata), and East Asian ash (Fraxinus rhynchophylla) plantations, with planting densities of 8.3, 7.7, and 14.3 individuals/25 ㎡ , respectively. Approximately 10 species, including Amur maple (Acer tataricum subsp. ginnala), Korean mountain ash (Sorbus alnifolia), Japanese spice bush (Lindera obtusiloba), and Korean rhododendron (Rhododendron mucronulatum) were identified in the ecologically restored area. The total amounts of carbon stored by the trees in the vegetation conservation and ecological restoration sites are 250.77 and 19.3 t C ha-1, respectively, and the total annual carbon uptakes are 10.28 and 2.33 t C ha-1 yr-1, respectively. The survey results are expected to provide important basic data for monitoring the carbon absorption capacity and carbon balance of green areas in the city.

• Carbon letters
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• v.13 no.3
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• pp.161-166
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• 2012

Carbon materials were synthesized by pyrolysis from fibers of Corn-straw (Zea mays), Rice-straw (Oryza sativa), Jute-straw (Corchorus capsularis) Bamboo (Bombax bambusa), Bagass (Saccharum officinarum), Cotton (Bombax malabaricum), and Coconut (Cocos nucifera); these materials were characterized by scanning electron microscope, X-ray diffraction (XRD), and Raman spectra. All carbon materials are micro sized with large pores or channel like morphology. The unique complex spongy, porous and channel like structure of Carbon shows a lot of similarity with the original anatomy of the plant fibers used as precursor. Waxy contents like tyloses and pits present on fiber tracheids that were seen in the inherent anatomy disappear after pyrolysis and only the carbon skeleton remained; XRD analysis shows that carbon shows the development of a (002) plane, with the exception of carbon obtained from bamboo, which shows a very crystalline character. Raman studies of all carbon materials showed the presence of G- and D-bands of almost equal intensities, suggesting the presence of graphitic carbon as well as a disordered graphitic structure. Carbon materials possessing lesser density, larger surface area, more graphitic with less of an $sp^3$ carbon contribution, and having pore sizes around $10{\mu}m$ favor hydrogen adsorption. Carbon materials synthesized from bagass meet these requirements most effectively, followed by cotton fiber, which was more effective than the carbon synthesized from the other plant fibers.

• Journal of the Korean Society of Industry Convergence
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• v.11 no.4
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• pp.195-199
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• 2008

The carbon fiber has low x-ray absorption property and high stiffness. This is the reason why many CT(Computed Tomography) manufacturer use carbon fiber in couch tabletop for CT scanner. In this paper, we design and make the couch tabletop made of carbon fiber composite, and verify the validity in CT scanner. In designing the couch tabletop, to determine the aluminum equivalent thickness of couch tabletop, we evaluate X-ray the transmissivity of aluminum and carbon plate in 80-120kVp X-ray energy range. And we perform structural analysis and mechanical design using determined thickness of carbon sheet. In conclusion, it was evaluated that manufactured couch tabletop satisfies X-ray transmissivity and mechanical requirements in CT scanner.

• Journal of Korean Society of Forest Science
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• v.105 no.1
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• pp.132-138
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• 2016

The objectives of this study were to infer the parameters of forest stand growth functions of STEMS for Cryptomeria japonica stands of Jeju Hannam Experimental Forest, Korea Forest Research Institute, and to investigate the effects of thinning regimes on the patterns of stand growth and carbon absorption. The forest stand growth functions for the potential diameter growth, modifier, crown ratio and mortality are the major ones composing the independent-tree/distance-free forest stand growth simulator, STEMS. The parameters were inferred using the sets of growth data obtained from stem analyses of 39 trees, chosen from 13 sample plots of the forest stands. The effects of thinning regimes on the patterns of stand growth and carbon absorption were investigated by simulating the stand growth patterns of the case study stand with 3 different thinning regimes: no-thinning, early thinning with low intensity and late thinning with high intensity using the simulator. According to the results of the analyses, the different thinning regimes cause significant effects on the growth patterns of average DBH, average height, diameter distribution and stand volume as well as the amount of carbon absorptions.

• Journal of the Korean Institute of Gas
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• v.27 no.1
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• pp.70-77
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• 2023

Air environment regulations have been strengthened due to increasing air pollutant emissions, the target of reducing emissions has increased and interest in gas measurement methods is also increasing. The sampling method is mainly used, but due to the spatial and temporal measurement limitations, the laser absorption spectroscopy which is a real-time and in-situ method is in the spotlight. In this study, we studied the wavelength modulation spectroscopy and described the calibration-free algorithm. The developed algorithm was modified to reflect 46 multi-absorption lines and was applied to light absorption signal analysis in visible and mid-infrared regions. In addition, the difference between the modulation parameters of laser was analyzed. As a result of reviewing the performance through O₂ and NO gas measurement experiments of various concentration conditions, the linearity was R²_O2=0.99999 and R²_NO=0.99967.