• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.536-543
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• 2017

This study developed a new methodology to evaluate the carbon storage using a Mobile Mapping System according to the life cycle of street trees. The system for calculating the carbon storage of a roadside tree using the MMS developed in this study consisted of a database, memory, processor, user interface, and communication module. The carbon storage was calculated for 261 trees in the Cheonan-Asan New Town (distance: 2.1 km, area: $283,698m^2$). The average biomass and carbon storage of Metasequoia glyptostroboides were highest at 34.5 kg and 17.3 kg C and Chionanthus retusa were lowest at 19.5 kg and 9.8 kg C, respectively. The total biomass and total carbon storage of Ginkgo biloba were highest at 5028.8 kg and 17.3 kg C and Chionanthus retusa were lowest at 780.7 kg and 390.3 kg C, respectively. Based on the roadside tree database, the amount of carbon storage in a given area was converted to Google format and visualized in 3D by GIS analysis.

• Journal of Korean Society of Forest Science
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• v.112 no.2
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• pp.188-194
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• 2023

This study aimed to derive the basic wood density, one of several carbon emission factors, for carbon accounting of bamboo forests in Korea. Bamboo is mainly distributed in Jeollanam-do and Gyeongsangnam-do provinces, and 101 sample trees were selected for each of the three species (Phyllostachys nigra var. henonis, P. bambusoides, and P. pubescens). The basic wood density derivation used the KS F 2098 method. The measurements showed that the basic wood density was 0.83 g/cm³ for P. nigra var. henonis, 0.81 g/cm³ for P. bambusoides, and 0.72 g/cm³ for P. pubescens. However, the bamboo distribution area in Korea is not very large, and P. pubescens grows in one area only. Therefore, the basic wood density that can be applied to bamboo was 0.79 g/cm³. Evaluation of the uncertainty of the extracted basic wood density showed a very low value of 1.61%, which confirmed the reliability of the basic wood density derived from this analysis. The basic wood density, biomass expansion factor, and root-to-shoot ratio were used to calculate the carbon storage capacity of one bamboo plant and expanded to calculate the capacity for a hectare of bamboo. Carbon storage and absorption of bamboo were calculated by applying a carbon-emission factor, such as the basic wood density. These study results are expected to contribute to the carbon-neutral policy and forest management direction in Korea.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.260-266
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• 2023

In recent years, excessive emissions of carbon dioxide(CO₂) have become the cause of global climate change. Consequently, there has been significant research activity aimed at both removing and utilizing CO₂. This study assesses the potential utilization of railway tie concrete waste, generated from railway infrastructure, as a CO₂ absorption material and investigates the physicochemical properties before and after CO₂ absorption to understand the CO₂ removal mechanisms. Railway tie concrete waste primarily consists of Si(26.60 %) and contains 9.82 % of Ca. Compared to samples of Cement and Normal concrete waste, it demonstrated superior potential for use as a CO₂ absorption material, with approximately 98 % of the Ca content participating in CO₂ absorption reactions. Through Thermogravimetric Analysis(TGA) and X-ray Diffraction(XRD) analysis, it was confirmed that the carbonate reaction, where the Ca in railway tie concrete waste converts into CaCO₃ through reaction with CO₂ gas, is the primary mechanism for CO₂ removal. Furthermore, Scanning Electron Microscopy(SEM) analysis revealed the formation of numerous CaCO₃ particles with sizes less than 0.1 ㎛ after the CO₂ absorption reaction. This transformation of large internal voids in the CO₂ absorption material into mesopores resulted in an increase in the specific surface area of the material.

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.225-231
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• 1989

The heterogeneous rate constants for the electrochemical reduction by $trans-[Co(en)_2X_2](ClO_4)_n$(where X is cyanide, nitrite, ammonia, and isothiocyanate) at mercury and glassy carbon electrode were investigated by cyclic voltammetry, DC polarography, and by using rotating disk electrode. The good linear relationship was obtained between the activation energy of reduction and absorption wave number of complexes on glassy carbon electrode. At mercury electrode, $NO_2^-$ ligated complex showed the large deviation from the linear relationship. The difference in the value of rate constants for $NO_2^-$ ligated complex between mercury and glassy carbon electrode was about three order of magnitude which was much larger than the other complexes. It was suggested that $NO_^-$ ligated complex was reduced by inner-sphere mechanism on mercury electrode from the larger value of activation energy and entropy on mercury than carbon electrode.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.297.2-297.2
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• 2016

Photoacoustic generation of ultrasound is an effective approach for development of high-frequency and high-amplitude ultrasound transmitters. This requires an efficient energy converter from optical input to acoustic output. For such photoacoustic conversion, various light-absorbing materials have been used such as metallic coating, dye-doped polymer composite, and nanostructure composite. These transmitters absorb laser pulses with 5-10 ns widths for generation of tens-of-MHz frequency ultrasound. The short optical pulse leads to rapid heating of the irradiated region and therefore fast thermal expansion before significant heat diffusion occurs to the surrounding. In this purpose, nanocomposite thin films containing gold nanoparticles, carbon nanotubes (CNTs), or carbon nanofibers have been recently proposed for high optical absorption, efficient thermoacosutic transfer, and mechanical robustness. These properties are necessary to produce a high-amplitude ultrasonic output under a low-energy optical input. Here, we investigate carbon nanotube (CNT)-polydimethylsiloxane (PDMS) composite transmitters and their nanostructure-originated characteristics enabling extraordinary energy conversion. We explain a thermoelastic energy conversion mechanism within the nanocomposite and examine nanostructures by using a scanning electron microscopy. Then, we measure laser-induced damage threshold of the transmitters against pulsed laser ablation. Particularly, laser-induced damage threshold has been largely overlooked so far in the development of photoacoustic transmitters. Higher damage threshold means that transmitters can withstand optical irradiation with higher laser energy and produce higher pressure output proportional to such optical input. We discuss an optimal design of CNT-PDMS composite transmitter for high-amplitude pressure generation (e.g. focused ultrasound transmitter) useful for therapeutic applications. It is fabricated using a focal structure (spherically concave substrate) that is coated with a CNT-PDMS composite layer. We also introduce some application examples of the high-amplitude focused transmitter based on the CNT-PDMS composite film.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.4
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• pp.201-206
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• 2013

The coal bottom ash and reject ash discharged from a coal-fired power plant are difficult to recycle so most of them are mainly landfill-disposed. In this study, the artificial aggregate were produced using reject ash, bottom ash and dredged soil emitted from the coal-fired power plant in Korea and the effect of experimental factors on the bloating behavior and the properties of the aggregates were analyzed. In particular, a lot of unburned carbon in the reject ash was removed by calcination and the activated carbon was added to batch powders then the dependence of those process upon bloating properties of artificial aggregate were investigated. For this purpose, the specific gravity and water absorption values of artificial aggregates were investigated in conjunction with microstructural observations. This study could contribute to increase the recycling rate of the reject ash.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.9
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• pp.707-711
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• 2013

Carbon nanotubes(CNT) has strength and chemical stability, greatly conductivity characteristics. In particular, MWCNT (multi-walled carbon nanotubes) show rapidly resistance sensitive for changes in the ambient gas, and therefore they are ideal materials to gas sensor. So, we fabricated NOx gas sensors structured MOS-FET using MWCNT (multi-walled carbon nanotubes) material. We investigate the change resistance of NOx gas sensors based on MOS-FET with ultra lean NOx gas concentrations absorption. And NOx gas sensors show sensitivity on the change of gate-source voltage ($V_{gs}=0[V]$ or $V_{gs}=3.5[V]$). The gas sensors show the increase of sensitivity with increasing the temperature (largest value at $40^{\circ}C$). On the other hand, the sensitivity of sensors decreased with increasing of NOx gas concentration. In addition, We obtained the adsorption energy($U_a$), $U_a$ = 0.06714[eV] at the NOx gas concentration of 8[ppm], $U_a$ = 0.06769[eV] at 16[ppm], $U_a$ = 0.06847[eV] at 24[ppm] and $U_a$ = 0.06842[eV] at 32[ppm], of NOx gas molecules concentration on the MWCNT gas sensors surface with using the Arrhenius plots. As a result, the saturation phenomena is occurred by NOx gas injection of concentration for 32[ppm].

• Journal of the Korean Ceramic Society
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• v.13 no.1
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• pp.11-19
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• 1976

This study was focused on the improvement of production techniques of small crucibles in relation with the appropriate selection of raw materials, various batch compositions and physical and chemical characteristics of the crucibles. Various tests gave the optimum batch composition for the carbon bond graphite cructble as follows: Pyontaek graphite flake (refractory aggregate) : 40Part Silicon carbide: 15Part Tar pitch (binder) : 11Part Inorganic additives (to improve the oxidation resistance) : 15 Part Cryolite : 3 Part Ferro manganese : 2 Part Ferrosilicon : 25 Part Crucibles pressed with 400kg/$\textrm{cm}^2$ at 12$0^{\circ}C$. and fired in reducing atmosphere at 120$0^{\circ}C$ brought the most favorable results as follows: Bulk density : 2.31 Apparent density : 2.58 Porosity : 15.2% Oxidation loss at 1, 50$0^{\circ}C$. for 3 hrs : below 3.77% Water absorption : 6.01% Compressive strength : 438kg/$\textrm{cm}^2$ Tensile strength : 256kg/$\textrm{cm}^2$.

• Journal of Sensor Science and Technology
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• v.16 no.5
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• pp.331-336
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• 2007

In this study, we have fabricated an infrared optical fiber based sensor which can monitor the respiration of a patient. The design of a chalcogenide optical fiber based sensor is suitable for insertion into a high electro-magnetic field environment because the sensor consists of low cost and compact mid-infrared components such as an infrared light source, a chalcogenide optical fiber and a thermopile sensor. A fiber-optic respiration sensor is capable of detecting carbon dioxide ($CO_{2}$) in exhalation of a patient using the infrared absorption characteristics of carbon gases. The modulated infrared radiation due to the presence of carbon dioxide is guided to the thermopile sensor via a chalcogenide receiving fiber. It is expected that a mid-infrared fiber-optic respiration sensor which can be developed based on the results of this study would be highly suitable for respiration measurements of a patient during the procedure of an MRI.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.16 no.3
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• pp.107-117
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• 2013

Problems in regard of ecological stability of urban ecosystem ensue from climate change and urbanization. Particularly, urban ecological conditions are deteriorating both quantitatively and qualitatively to a great extent. The present study aims to assess the current condition of selected sites (i. e. urban green zones and parks) in terms of preset assessment components; to find out problems and relevant solutions to improve the quality and quantity of parks and green zones; and ultimately to suggest some measures applicable to coping with climate change as well as to securing the ecological attributes of urban green zones and parks. According to the findings of this study, from quantitative perspectives, ecological attributes and responsiveness to climate change are high on account of the large natural-soil area(80%). By contrast, from qualitative perspectives including the planting structure (1 layer: 47%), the percentage of bush area(17%), the connectivity with surrounding green zones (independent types: 44%), the wind paths considered (5.6%), the tree species with high carbon absorption rates (20%), water cycles (17%), energy (8%) and carbon storage capacities(61%), ecological attributes and responsiveness to climate change were found very low. These findings suggest that the ecological values of urban parks and green zones should be improved in the future by conserving their original forms, securing natural-soil grounds and employing multi-layered planting structures and water bodies, and that responsiveness to climate change should be enhanced by planting tree species with high carbon storage capacities and obtaining detention ponds. In sum, robust efforts should be exerted in the initial planning stages, and sustained, to apply the methodology of green-zone development along with securing ecological attributes and responsiveness to climate change.