• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.195.1-195.1
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• 2011

This paper presents an experimental study on a new potential geothermal energy source obtained from tunnel structures. An "energy textile", which is a textile-type ground heat exchanger, was fabricated between a shotcrete layer and a guided drainage geotextile in the tunnel lining system. To examine the long-term thermal behavior of the energy textile, the difference in temperatures of the inlet and outlet fluid circulating through the heat exchange pipe within the energy textile was monitored using a constant-temperature water bath. Daily heat exchange rate of the energy textile during cooling operation was estimated from the measured temperatures of the inlet and outlet fluid through the energy textile. The air and ground temperature was also continuously monitored. The operation of the energy textile as a ground heat exchanger was simulated using a 3D numerical CFD model (Fluent). The thermal conductivity of shotcrete and concrete lining components and temperature variation of air in the tunnel were incorporated in the model. The numerical analysis shows a good agreement with the long-term monitoring result.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.3
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• pp.219-228
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• 2003

Numerical and experimental studies were conducted on the temperature distribution of a buried steel pipe and surrounding granite frozen soils in the closed system. The relationship between unfrozen water content and temperatures was analysed by laboratory test. The thermal conductivity measurements were made to compare the results with a formula presented by Lachenbruch. A steel container model that consists of a freezing chamber and a buried circular steel pipe was built for the laboratory temperature measurements. The time temperature records were measured experimentally, and those records were compared with numerical results obtained from FEM analysis in order to verify the feasibility. The latent heat effect on the granite frozen soils in the numerical study was considered.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1110-1119
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• 2006

If water flows through a narrow passage into a medium that keeps the equilibrium of temperature, it causes small temperature difference and makes a temperature anomaly. The seepage or leakage often observed at old dams is a representative example of bringing about a temperature anomaly. Therefore, temperature measurements have been regarded as one of excellent methods that can detect the situation of seepage or leakage. However, because existing temperature measurement methods are based on a single sensor, the application of the method to the whole structure is nearly not possible in technical and economical phases. This paper introduces a temperature monitoring system using a thermal sensor cable that is comprised of addressable thermal sensors connected in parallel at many positions within a single cable. Through various laboratory and field experiments, it has been proved that the temperature monitoring technique can give an useful information about permeability of a medium or connectivity of fractures which have been regarded as difficult problems.

• Tunnel and Underground Space
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• v.5 no.3
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• pp.251-265
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• 1995

One of the most important matters in stress measurement by hydraulic fracturing technique is the determination of the breakdown pressure, reopening pressure, and shut-in pressure, since these values are the basic input data for the calculation of the in-situ stress. The control of the fracture propagation is also important when the hydraulic fracturing technique is applied to the development of groundwater system, geothermal energy, oil, and natural gas. In this study, a laboratory scale hydraulic fracturing device was built and a series of model tests were conducted with cube blocks of Machon gabbro. A new method called 'flatjack method' was adopted to determine shut-in pressure. The initial stress calculated from the shut-in pressure measured by flatjack method showed much higher accuracy than the stress determined by the conventional method. The dependency of the direction of fracture propagation on the state of the initial stresses was measured by introducin g artificial slots in the borehole made by water jet system. Numerical modeling by BEM was also performed to simulate the fracture propagation process. Both results form numerical and laboratory tests showed good agreement. From this study which provides the extensive results on the determination of shut-in pressure and the control of fracture propagation which are the critical issue in the recent hydraulic fracturing, it is conclued that in-situ stress measurement and the control of fracture propagation could be achived more accurately.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.594-599
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• 2009

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Apart from wind and solar, ocean holds tremendous amount of untapped energy in forms such as geothermal vents, tides and waves. The current study looks at generating power using waves and the focus is on the primary energy conversion (first stage conversion) of incoming waves for different models. Observation of flow characteristics and the velocity in the augmentation channel as well as the front guide nozzle are presented in the paper. A numerical wave tank was used to simulate the waves and after obtaining the desired wave properties; the augmentation channel plus the front guide nozzle and rear chamber were integrated to the numerical wave tank. The waves in the numerical wave tank were generated by a piston type wave maker which was located at the wave tank inlet. The inlet which was modeled as a plate wall moved sinusoidally with the general function, x=asin$\omega$t The augmentation channel consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. The analysis was performed using the commercial CFD code ANSYS-CFX.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.12a
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• pp.87-100
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• 2007

Marine controlled source electromagnetics (CSEM) or sea bed logging (SBL) is an emerging technology which can provide quantitative information on hydrocarbon reservoir embedded in marine sediment. Electromagnetic responses to the resistive formation saturated with a certain amount of hydrocarbon can be characterized by less attenuated profile otherwise exponentially attenuated fields in conductive sea water or through sediments, and thus can be regarded as a direct indicator of hydrocarbon. In this paper, we introduce the technology of marine CSEM in terms of its physical characteristics and in comparison of typical three-dimensional (3-D) seismic method. History and evolution of commercial marine CSEM are also briefly summarized. We then introduce a representative case history showing how marine CSEM works in reality. Outlook of future applications and technical advances to be made are discussed. Finally, we demonstrate a test example of 2.5-D inversion of synthetic data as the groundwork of 3-D inversion of field data that is to be the ultimate goal of technical development.

• Journal of the Korean Solar Energy Society
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• v.33 no.1
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• pp.57-65
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• 2013

The temperatures with the ground depth, the positions of circulation water in ground heat exchanger were measured and thermal diffusion characteristics with the distances of the direction normal to the borehole was analysed. The deeper the depth of ground, the less the influences of outdoor temperature, but below 10m of ground, there was no influences of ground temperature. When the depth of trench pipe was below the depth of 2m, there was no influence. In the ground of 10m when the distances between the pipe and the other places were above 0.5m, the variations of temperature were less than $1.6^{\circ}C$ and above 2.5m they were less than $0.1^{\circ}C$. When the distances of bore hole were above 5m, there were no. influences of the nearest ground heat exchanger.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.833-844
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• 2008

Bio-energy offers the opportunity to lessen fossil fuel consumption. Energy derived from solar, wind, hydroelectric, geothermal, and biomass sources are considered renewable. Because most forms of bio-energy are derive deither directly or indirectly from the sun, there is an abundant supply of renewable energy available, unlike fossil fuels. The use of bio-energy also provides environmental, economic and political benefits. Bio-energy can be produced from a marine source such as biomass provides a $CO_2$ neutral, non-polluting form of energy. In this paper, the potential of marine biomass is increasingly discussed, given the size of the resource in that more than three quarters of the surface of planet earth is covered by water.

• Advances in Energy Research
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• v.6 no.2
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• pp.103-129
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• 2019

While global demand for energy increases annually, at the same time the demand for carbon-free, sulphur-free and NO_x-free energy sources grows considerably. This state poses a challenge in the research for newer sources like biomass and shale gas as well as renewable energy resources such as solar, wind, geothermal and hydraulic energy. Although wave energy also is a form of renewable energy it has not fully been exploited technically and economically so far. This study tries to explain those reasons in which it is beyond doubt that the demand for wave energy will soon increase as fossil energy resources are depleted and environmental concerns gain more importance. The electrical energy supplied to the grid shall be produced from wave energy whose conversion devices can basically work according to three different systems. i. Systems that exploit the motions or shape deformations of their mechanisms involved, being driven by the energy of passing waves. ii. Systems that exploit the weight of the seawater stored in a reservoir or the changes of water pressure by the oscillations of wave height, iii. Systems that convert the wave motions into air flow. One of the aims of this study is to present the classification deficits of the wave energy converters (WECs) of the "wave developers" prepared by the European Marine Energy Center, which were to be reclassified. Furthermore, a new classification of all WECs listed by the European Marine Energy Center was arranged independently. The other aim of the study is to assess the technological state of the art of these WECs designed and/or produced, to obtain an overview on them.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.28-30
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• 2003

Hot Spring Law of Taiwan was passed in legislative assembly on 3 June 2003. Hot springs would become one of the most important natural resources for recreation purposes. Both public and private sectors will invest large amount of capital in this area in the near future. The value of remote sensing technology is to give a critical tool for observing the landscape to find out mega-scaled geological structures, which may not be able to be found by conventional approaches. The occurrences of the hot springs in Taiwan are mostly in metamorphic and sedimentary rocks , other than in volcanic environments. Local geothermal anomaly or heat of springs transfer by liquid convection other than conduction or radiation. The deeply -seated fractures of hard rocks are the conduit of the convection of hot water, which could be as deep as 3000 meters in a hypothetical model of Taiwan. Clues to find outcrops of hot spring can be obtained by a structure-controlled model deduced by geological lineaments observed by satellite images and stereoscopic interpretation of aerial photographs. A case study conducted in Eastern Taiwan will be demonstrated.