• Tunnel and Underground Space
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• v.32 no.6
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• pp.411-434
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• 2022

In deep geological disposal concept for spent nuclear fuel, it is well-known that rock mass at near-field experiences the thermal-hydraulic-mechanical (THM) coupled behavior. The mechanical properties of rock changes during the coupled process, and it is important to consider the changes into the analysis of numerical simulation and in-situ tests for long-term stability evaluation of nuclear waste disposal repository. This report collected the previous studies on indirect coupled behaviors of rock. The effects of water saturation and temperature on some mechanical properties of rock was considered, while the change in hydraulic conductivity of rock due to stress was included in the indirect coupled behavior.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2019.04a
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• pp.44-44
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• 2019

This study aimed to develop a suitable method for inducing the proliferation of prothallus and producing sporophytes of rock polypody (Polypodium vulgare L.). The prothalli used in all experiments were obtained from spore germination and sub-cultured for 8-week intervals. The most appropriate media for prothallus propagation were investigated by culturing 300 mg of prothallus in MS ($1/4{\times}$, $1/2{\times}$, $1{\times}$, and $2{\times}$ strength) medium and in Knop medium for 8 weeks. Cultures were maintained at a temperature of $25{\pm}1^{\circ}C$, light intensity of $30{\pm}1.0{\mu}mol-m-2{\cdot}s-1$, and a photoperiod of 16/8 h (light/dark). Fresh weight of prothalli was 4.8 g on $1{\times}$ MS, 4.5 g on $1/2{\times}$ MS and 4.3 g on 1/4 MS medium. To select a suitable soil combination for sporophyte formation, 1.0 g of prothallus was ground with distilled water, spread in five combinations onto different soil substrates (decomposed granite, horticultural substrates, peat moss, and perlite), and then cultivated for 13 weeks. The sporophyte cultures were maintained at a temperature of $25{\pm}1^{\circ}C$, light intensity of $43{\pm}2.0{\mu}mol-m-2{\cdot}s-1$, humidity of $84{\pm}1.4%$, and a photoperiod of 16/8 h (light/dark). The results showed that a mixture containing a 2:1 (v:v) ratio of horticultural substrate and perlite, increased sporophyte formation to 462.5 sporophytes per pot (7.5 cm2). The other soil substrates produced from 314.5 to 405.3 sporophytes per pot. Therefore, our results will provide conditions suitable for mass production of Polypodium vulgare L.

• Microbiology and Biotechnology Letters
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• v.27 no.1
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• pp.1-7
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• 1999

A fungus, Penicillium sp. PS-113, isolated from soil showed the high phosphate-solubilizing activity in patato dextrose broth-rock phosphate to produce free phosphates to the culture broth with the concentrations of 585 ppm against rock phosphate. In this medium, the optimum temperature and initial pH to solubilize rock phosphate were 30$^{\circ}C$ and pH 7.5, respectively. In order to make the mass production of the conidia from this fungus, we cultured in on various solid-based media like barley, corn, wheat, rice, rice bran, and compost. As a result, the fungus highly produced conidia ranging from 2.1 to $5.1{\times}10_9$ conidia/g${\cdot}$media on these solid media except compost-based medium, which was 0 times less than others. Effects of inoculation of the phosphate solubilizing fungus as a biofertilizer were studied in perlite-based pot cropped with Zea mays Suwon 19. Inoculation of Penicillium sp. PS-113 increased in plant height (1.4 times), plant weight (5.2~8.1 times) and root length (1.1~1.2 times) at 60-day cultivation, compared to Hogland solution either without $NH_4H_2PO_4$ or displace $NH_4H_2PO_4$ to powdered rock phosphate, a phosphorus source for plant growth.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.5
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• pp.399-405
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• 2010

The accumulated displacements and fatigues of rock are increased by the stress-hysteresis, induced from repeated frost-thawing. Also the shear strength is decreased by them continuously. The stress-hysteresis is affected by the atmospheric temperature changes, whose behavior is visco-elasticity, usually. Therefore, to do ideal body analysis, Kelvin model could be used to analyze the frost-thawing behavior in winter. In general, rock slope failure occurs by the deterioration of rocks, which is caused by the repetition of freezing-thawing process. In order to keep the safety of such rock mass structures the deterioration process of rock needs to be described quantitatively using some meaningful parameters. In this work, the deterioration process in freezing-thawing cycle of tuff, which is a famous soft porous rock, is investigated through laboratory tests and successfully described as a differential equation for the change of porosity. And then, the deterioration of the mechanical properties of rock, such as Young's modulus and uniaxial compressive strength, are quantitatively described as a function of the porosity.

• Journal of the Korean Geotechnical Society
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• v.37 no.4
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• pp.19-26
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• 2021

The high-level radioactive waste (HLW) produced from nuclear power plants is disposed in a rock-mass at a depth of hundreds meters below the ground level. Since HLW is very dangerous to human being, it must be disposed of safely by the engineered barrier system (EBS). The EBS consists of a disposal canister, backfill material, buffer material, and so on. When the components of EBS are installed, gaps inevitably exist not only between the rock-mass and buffer material but also between the canister and buffer material. The gap can reduce water-retarding capacity and heat release efficiency of the buffer material, so it is necessary to investigate properties of gap-filling materials and to analyze gap spacing effect. Furthermore, there has been few researches considering domestic disposal system compared to overseas researches. In this reason, this research derived the peak temperature of the bentonite buffer material considering domestic disposal system based on the numerical analysis. The gap between the canister and buffer material had a minor effect on the peak temperature of the bentonite buffer material, but there was 40% difference of the peak temperature of the bentonite buffer material because of the gap existence between the buffer material and rock mass.

• The Journal of Engineering Geology
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• v.19 no.1
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• pp.63-70
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• 2009

The optical fiber cable acting as a sensor was embedded in the underground research tunnel and portal area in order to monitor their stability and the spatial temperature variation. This system includes two types of sensing function to monitor the distributed strain and temperature along the line, where sensor cable is installed, not a point sensing. According to the results of one year monitoring around the KURT, there is no significant displacement or movement at the tunnel wall and portal slope. However, it would be able to aware of some phenomena as an advance notice at the tunnel wall which indicates the fracturing in rockmass and shotcrete fragmentation before rock falls accidently as well as movement of earth slope. The measurement resolution for rock mass displacement is 1 mm per 1 m and it covers 30 km length with every 1m interval in minimum. In temperature, the cable measures the range of $-160{\sim}600^{\circ}C$ with $0.01^{\circ}C$ resolution according to the cable types. This means that it would be applicable to monitoring system for the safe operation of various kinds of facilities having static and/or dynamic characteristics, such as chemical plant, pipeline, rail, huge building, long and slim structures, bridge, subway and marine vessel. etc.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.630-633
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• 2005

Some gases can be formed into hydrate by physical combination with water under appropriate temperature and pressure condition. Besides them, it was found that the pore size of the sediments can affect the formation and dissociation of hydrate. In this study, formation temperatures of carbon dioxide and methane hydrate have been measured using isobaric method to investigate the effects of flow rates of gases on formation condition of hydrate in porous rock samples. The flow rates of gases were controlled using a mass flow controller. To minimize Memory effect, system temperature increased for the dissociation of gas hydrates and re-established the initial saturation. The results show that the formation temperature of hydrate decreases with increasing the injection flow rate of gas. This indicates that the velocity of gas in porous media may act as kinds of inhibitor for the formation of hydrate.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.238-243
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• 2003

As there are many advantages on underground caverns, such as safety and operation, they can also be used for gas storage purpose. When liquefied gas is stored underground, the cryogenic temperature of the gas will affect the stability of the storage cavern. In order to store the liquefied gas successfully, it is essential to estimate the exact temperature distribution of the rock mass around the cavern. In this study, an analytic solution and a conceptual model that can estimate three-dimensional temperature distribution around the storage cavern are suggested. When calculating the heat transfer within a solid, it is likely to consider the solid as the intersection of two or more infinite or semi-infinite geometries. Therefore heat transfer solution for the solid is expressed by the product of the dimensionless temperatures of the geometries, which are used to form the combined solid. Based on the multi-dimensional transient heat transfer theory, the analytic solution is successfully derived by assuming the cavern shape to be of simplified geometry. Also, a conceptual model is developed by using the analytic solution of this study. By performing numerical experiments of this multi-dimensional model, the temperature distribution of the analytic solution is compared with that of numerical analysis and theoretical solutions.

• Tunnel and Underground Space
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• v.22 no.4
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• pp.243-256
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• 2012

Developing efficient and reliable energy storage system is as important as exploring new energy resources. Energy storage system can balance the periodic and quantitative mismatch between energy supply and energy demand and increase the energy efficiency. Industrial waster heat and renewable energy such as solar energy can be stored by the thermal energy storage (TES) system at high and low temperatures. TES system using underground rock carven is considered as an attractive alternative for large-scale storage, because of low thermal conductivity and chemical safety of surrounding rock mass. In this report, the development of available thermal energy storage methods and the characteristics of storage media were introduced. Based on some successful applications of cavern storage and high-temperature storage reported in the literature, the applicabilities and practicabilities of storage media and technologies for large-scale cavern thermal energy storage (CTES) were reviewed.

• Journal of Energy Engineering
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• v.18 no.3
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• pp.203-211
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• 2009

Vapor pressure of HFC-404a and polyol ester system were measured at 56 points from 263.15 to 323.15 K and from 0 to 90 mass %polyol ester. It was found that below 273.15 K, the effect of the polyol ester on the vapor pressure was negligible up to 30 mass % polyol ester. The vapor pressure of the system significantly decreased as the mass fraction of polyol ester increased over 50 percent. Raoult's model and Flory-Huggins model were tested for data reduction. Empirical vapor pressure equations were obtained in terms of temperature and mass fraction of polyol ester.