• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.4
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• pp.491-505
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• 2018

As an alternative to deep geological disposal technology, which is considered as a reference concept, the domestic applicability of deep borehole disposal technology for high level radioactive waste, including spent fuel, has been preliminarily evaluated. Usually, the environment of deep borehole disposal, at a depth of 3 to 5 km, has more stable geological and geo-hydrological conditions. For this purpose, the characteristics of rock distribution in the domestic area were analyzed and drilling and investigation technologies for deep boreholes with large diameter were evaluated. Based on the results of these analyses, design criteria and requirements for the deep borehole disposal system were reviewed, and preliminary reference concept for a deep borehole disposal system, including disposal container and sealing system meeting the criteria and requirements, was developed. Subsequently, various performance assessments, including thermal stability analysis of the system and simulation of the disposal process, were performed in a 3D graphic disposal environment. With these analysis results, the preliminary evaluation of the domestic applicability of the deep borehole disposal system was performed from various points of view. In summary, due to disposal depth and simplicity, the deep borehole disposal system should bring many safety and economic benefits. However, to reduce uncertainty and to obtain the assent of the regulatory authority, an in-situ demonstration of this technology should be carried out. The current results can be used as input to establish a national high-level radioactive waste management policy. In addition, they may be provided as basic information necessary for stakeholders interested in deep borehole disposal technology.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.414-421
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• 2022

Subsea oil and gas exploration is increasingly moving into deeper water depths, and typically, subsea pipelines operate under high pressure and temperature conditions. Owing to the difference in these components, the axial force in the pipe is accumulated. When a pipeline is operated at a high internal pressure and temperature, it will attempt to expand and contract for differential temperature changes. Typically, the line is not free to move because of the plane strain constraints in the longitudinal direction and soil friction effects. For a positive differential temperature, it will be subjected to an axial compressive load, and when this load reaches a certain critical value, the pipe may experience vertical (upheaval buckling) or lateral (snaking buckling) movements that can jeopardize the structural integrity of the pipeline. In these circumstances, the pipeline behavior should be evaluated to ensure the pipeline structural integrity during operation in those demanding loading conditions. Performing this analysis, the correct mitigation measures for thermal buckling can be considered either by accepting bar buckling but preventing the development of excessive bending moment or by preventing any occurrence of bending.

• 한국유가공학회:학술대회논문집
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• 2002.04a
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• pp.59-60
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• 2002

Edible films such as wax coatings, sugar and chocolate covers, and sausage casings, have been used in food applications for years$^{(1)}$ However, interest in edible films and biodegradable polymers has been renewed due to concerns about the environment, a need to reduce the quantity of disposable packaging, and demand by the consumer for higher quality food products. Edible films can function as secondary packaging materials to enhance food quality and reduce the amount of traditional packaging needed. For example, edible films can serve to enhance food quality by acting as moisture and gas barriers, thus, providing protection to a food product after the primary packaging is opened. Edible films are not meant to replace synthetic packaging materials; instead, they provide the potential as food packagings where traditional synthetic or biodegradable plastics cannot function. For instance, edible films can be used as convenient soluble pouches containing single-servings for products such as instant noodles and soup/seasoning combination. In the food industry, they can be used as ingredient delivery systems for delivering pre-measured ingredients during processing. Edible films also can provide the food processors with a variety of new opportunities for product development and processing. Depends on materials of edible films, they also can be sources of nutritional supplements. Especially, whey proteins have excellent amino acid balance while some edible films resources lack adequate amount of certain amino acids, for example, soy protein is low in methionine and wheat flour is low in lysine$^{(2)}$. Whey proteins have a surplus of the essential amino acid lysine, threonine, methionine and isoleucine. Thus, the idea of using whey protein-based films to individually pack cereal products, which often deficient in these amino acids, become very attractive$^{(3)}$. Whey is a by-product of cheese manufacturing and much of annual production is not utilized$^{(4)}$. Development of edible films from whey protein is one of the ways to recover whey from dairy industry waste. Whey proteins as raw materials of film production can be obtained at inexpensive cost. I hypothesize that it is possible to make whey protein-based edible films with improved moisture barrier properties without significantly altering other properties by producing whey protein/lipid emulsion films and these films will be suitable far food applications. The fellowing are the specific otjectives of this research: 1. Develop whey protein/lipid emulsion edible films and determine their microstructures, barrier (moisture and oxygen) and mechanical (tensile strength and elongation) properties. 2. Study the nature of interactions involved in the formation and stability of the films. 3. Investigate thermal properties, heat sealability, and sealing properties of the films. 4. Demonstrate suitability of their application in foods as packaging materials. Methodologies were developed to produce edible films from whey protein isolate (WPI) and concentrate (WPC), and film-forming procedure was optimized. Lipids, butter fat (BF) and candelilla wax (CW), were added into film-forming solutions to produce whey protein/lipid emulsion edible films. Significant reduction in water vapor and oxygen permeabilities of the films could be achieved upon addition of BF and CW. Mechanical properties were also influenced by the lipid type. Microstructures of the films accounted for the differences in their barrier and mechanical properties. Studies with bond-dissociating agents indicated that disulfide and hydrogen bonds, cooperatively, were the primary forces involved in the formation and stability of whey protein/lipid emulsion films. Contribution of hydrophobic interactions was secondary. Thermal properties of the films were studied using differential scanning calorimetry, and the results were used to optimize heat-sealing conditions for the films. Electron spectroscopy for chemical analysis (ESCA) was used to study the nature of the interfacial interaction of sealed films. All films were heat sealable and showed good seal strengths while the plasticizer type influenced optimum heat-sealing temperatures of the films, 130$^{\circ}$C for sorbitol-plasticized WPI films and 110$^{\circ}$C for glycerol-plasticized WPI films. ESCA spectra showed that the main interactions responsible for the heat-sealed joint of whey protein-based edible films were hydrogen bonds and covalent bonds involving C-0-H and N-C components. Finally, solubility in water, moisture contents, moisture sorption isotherms and sensory attributes (using a trained sensory panel) of the films were determined. Solubility was influenced primarily by the plasticizer in the films, and the higher the plasticizer content, the greater was the solubility of the films in water. Moisture contents of the films showed a strong relationship with moisture sorption isotherm properties of the films. Lower moisture content of the films resulted in lower equilibrium moisture contents at all aw levels. Sensory evaluation of the films revealed that no distinctive odor existed in WPI films. All films tested showed slight sweetness and adhesiveness. Films with lipids were scored as being opaque while films without lipids were scored to be clear. Whey protein/lipid emulsion edible films may be suitable for packaging of powder mix and should be suitable for packaging of non-hygroscopic foods$^{(5,6,7,8,)}$.

• Journal of Applied Biological Chemistry
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• v.61 no.3
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• pp.297-304
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• 2018

Coptis chinensis is used in oriental medicine for soothing, anti-inflammation, antimicrobial and antipyretic properties, and its main ingredient berberine is known to have strong antibacterial activity. In this study, we investigated the anti-microbial effect of hot water extract of Coptis chinensis (CW) on skin related microorganism and the airborne microbe, the antifungal effects of fungi, which are frequently detected in residential environments. CW showed antibacterial effect against Propionibacterium acnes, Staphylococcus aureus and Staphylococcus epidermidis, against the airborne microbe, which was collected in four different places. At the concentration of 100 mg/mL, the antimicrobial activity continued for 42 days, showed heat stability without change in the antimicrobial activity even after heat treatment. The MIC and MBC of CW against S. aureus was 0.03, 0.05 mg/mL, against S. epidermidis was 0.50, 0.75 mg/mL and against P. acne was 0.10, 0.15 mg/mL. As a result of measuring the MIC of four kinds of fungi with high detection frequency in the surrounding environment, Gliocladium virens was 65 mg/mL by determined as MIC which can inhibit one hundred percent of mycelial growth. The concentration 90 mg/mL was determined as MIC against Aureobasidium pullulans and 100 mg/mL against Penicilium pinophilum and Chaetomium globosum. CW was considered a safe extract that showed no irritation even in the ocular mucous membrane irritation evaluation test, a patch test. Therefore, these results suggest that Coptis chinensis has antimicrobial, antifungal and safety on human body and can be applied to the development of materials for cosmetic and residential environment industries.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.23-30
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• 2007

The ultimate objective of this study is to develop oxygen-enriched combustion techniques applicable to the system of practical industrial boiler. To this end the combustion characteristics of lab-scale LNG combustor were investigated as a first step using the method of numerical simulation by analyzing the flame characteristics and pollutant emission behaviour as a function of oxygen enrichment level. Several useful conclusions could be drawn based on this study. First of all, the increase of oxygen enrichment level instead of air caused long and thin flame called laminar flame feature. This was in good agreement with experimental results appeared in open literature and explained by the effect of the decrease of turbulent mixing due to the decrease of absolute amount of oxidizer flow rate by the absence of the nitrogen species. Further, as expected, oxygen enrichment increased the flame temperatures to a significant level together with concentrations of $CO_2$ and $H_2O$ species because of the elimination of the heat sink and dilution effects by the presence of $N_2$ inert gas. However, the increased flame temperature with $O_2$ enriched air showed the high possibility of the generation of thermal $NO_x$ if nitrogen species were present. In order to remedy the problem caused by the oxygen-enriched combustion, the appropriate amount of recirculation $CO_2$ gas was desirable to enhance the turbulent mixing and thereby flame stability and further optimum determination of operational conditions were necessary. For example, the adjustment of burner with swirl angle of $30\sim45^{\circ}$ increased the combustion efficiency of LNG fuel and simultaneously dropped the $NO_x$ formation.

• Journal of the Korean Applied Science and Technology
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• v.34 no.1
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• pp.50-57
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• 2017

Zinc oxide is, one of metal oxide semiconductor, harmless to human and environment-friendly. It has excellent chemical and thermal stability properties. Wurtzite-zinc oxide is a large band gap energy of 3.37 eV and high exciton binding energy of 60 meV. It can be applied to various fields, such as solar cells, degradation of the dye waste, the gas sensor. The photocatalytic activity of zinc oxide is varied according to the particle shape and change of crystallinity. Therefore, It is very important to specify the additives and the experimental variables. In this study, the zinc oxide were synthesized by using a microwave assisted hydrothermal synthesis. The precursor was used as the zinc nitrate, the pH value was controlled as 11 by NaOH. Surfactants are the ethanolamine, cetyltrimethylammonium bromide, sodium dodecyl sulfate, sorbitan monooleate was added by changing the concentration. The composite particles had the shape of a star-like, curcular cone, seed shape, flake-sphere. Physical and chemical properties of the obtained zinc oxide was characterized using x-ray diffractometer, field emission scanning electron microscopy, thermogravimetric analysis and optical properties was characterized using UV-visible spectroscopy, photoluminescence and raman spectroscopy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.583-590
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• 2013

Variable emittance radiators can be used in a thermal management system in space because their total emittance changes depending on the temperature of the system. When the temperature of the system decreased, the emittance also decreased so as to minimize the heat loss to the environment. In contrast, when the temperature of the system increased, the emittance also increased such that radiation cooling could occur. Thermochromic materials, whose emittance is a function of the temperature, are often used in variable emittance radiators because no additional parts are needed. In this study, we fabricated a variable-emittance coating by using a sol-gel method based on LSMO ($La_{1-x}Sr_xMnO_3$) and experimentally characterized the emittance change with respect to temperature. Furthermore, we also examined the stability of LSMO film in space environments by exposing it to extremely low pressure and temperature.

• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.125-134
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• 2022

The Global Expansion Roadmap published by the International Space Exploration Coordination Group, which is organized by space agencies around the world, presents future lunar exploration guidance and stresses a lunar habitat program to utilize lunar resources. The Moon attracts attention as an outpost for deep space exploration. Simulating lunar surface environments is required to evaluate the performances of various equipment for future lunar surface missions. In this paper, an experimental study was conducted to simulate high vacuum pressure and cryogenic temperature of the permanent shadow regions in the lunar south pole, which is a promising candidate for landing and outpost construction. The establishment of an efficient dirty thermal vacuum chamber (DTVC) operation process has never been presented. One-dimensional ground cooling tests were conducted with various vacuum pressures with the Korean Lunar Simulant type-1 (KLS-1) in DTVC. The most advantageous vacuum pressure was found to be 30-80 mbar, considering the cooling efficiency and equipment stability. However, peripheral cooling is also required to simulate a cryogenic for not sublimating ice in a high vacuum pressure. In this study, an efficient peripheral cooling operation process was proposed by applying the frost ratio concept.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.9
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• pp.1013-1019
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• 2007

Electronic wastes have increased tremendously. However, any reliable treatment methodologies have rarely been established. Electronic wastes have posed serious disposal problem due to their physico-chemical stability. This paper investigated the application possibility of pyrolysis for the purpose of recycling the p-CCL(phenol based Copper Clad Laminate). Thermogravimetric analysis(TGA) was used to investigate the thermal decomposition pattern of p-CCL. We elucidated the characteristics of pyrolysis by-products at operating temperatures of 280, 350 and $600^{\circ}C$. GC/MS and FT-IR were used to characterize the liquid by-products along with general characterization methods such as Ultimate Analysis, Proximate Analysis and Heating Value, whereas general characterization methods were only introduced for the solid by-products. At a heating rate of $5^{\circ}C$/min, TGA curves exhibited three decomposition stages: (1) low-temperature decomposition region$(<280^{\circ}C)$, (2) medium temperature region$(280\sim350^{\circ}C)$ and (3) high-temperature region$(>350^{\circ}C)$. The major compounds of liquid by-products at low- and medium-temperatures were accounted for by water and phenol, whereas branched phenols and furans were major compounds at high-temperatures. As the temperature increases, volatile quantities decreased but the fixed carbon increased. High heating values of solid by-products($7,400\sim7,600$ kcal/kg) would suggest that the solid by-products could be applicable as fuel. In addition, high fixed carbon but low ash content of the solid by-products offered an implication that they are capable of being upgradable for adsorbent after applying appropriate activating process.

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.115-124
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• 2020

Sustainable plastics can be mainly categorized into (1) biodegradable plastics decomposed into water and carbon dioxide after use, and (2) biomass-derived plastics possessing the carbon neutrality by utilizing raw materials converted from atmospheric carbon dioxide to biomass. Recently, biomass-derived engineering plastics (EP) and natural nanofiber-reinforced nanocomposites are emerging as a new direction of the industry. In addition to the eco-friendliness of natural resources, these materials are competitive over petroleum-based plastics in the high value-added plastics market. Polyesters and polycarbonates synthesized from isosorbide and 2,5-furandicarboxylic acid, which are representative biomass-derived monomers, are at the forefront of industrialization due to their higher transparency, mechanical properties, thermal stability, and gas barrier properties. Moreover, isosorbide has potential to be applied to super EP material with continuous service temperature over 150 ℃. In situ polymerization utilizing surface hydrophilicity and multi-functionality of natural nanofibers such as nanocellulose and nanochitin achieves remarkable improvements of mechanical properties with the minimal dose of nanofillers. Biomass-derived tough-plastics covered in this review are expected to replace petroleum-based plastics by satisfying the carbon neutrality required by the environment, the high functionality by the consumer, and the accessibility by the industry.