• Economic and Environmental Geology
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• v.44 no.6
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• pp.513-523
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• 2011

We estimated geothermal power generation potential in Korea through Enhanced Geothermal System (EGS) technology following the recently proposed protocol which was endorsed by international organizations. Input thermal and physical data for estimation are density, specific heat and thermal conductivity measurements from 1,516 outcrop samples, 180 heat production, 352 heat flow, and 52 mean surface temperature data. Inland area was digitized into 34,742 grids of $1'{\times}1'$ size and temperature distribution and available heat were calculated for 1 km depth interval from 3 km down to 10 km. Thus estimated theoretical potential reached 6,975 GW which is 92 times total generation capacity of Korea in 2010. Technical potential down to 6.5 km and considering land accessibility, thermal recovery ratio of 0.14 and temperature drawdown factor of $10^{\circ}C$ was 19.6 GW. If we disregard temperature drawdown factor, which can be considered in estimating economic potential, the technical potential increases up to 56 GW.

• Journal of Soil and Groundwater Environment
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• v.10 no.4
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• pp.54-61
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• 2005

An aquifer thermal energy storage (ATES) system can be very cost-effective and renewable energy sources, depending on site-specific parameters and load characteristics. In order to develop the ATES system which has certain hydrogeological characteristics, understanding the thermohydraulic process of an aquifer is necessary for a proper design of an aquifer heat storage system under given conditions. The thermohydraulic transfer for heat storage was simulated according to two sets of simple pumping and waste water reinjection scenarios of groundwater heat pump system operation in a two-layered aquifer model. In the first set of the scenarios, the movement of the thermal front and groundwater level was simulated by changing the locations of injection and pumping wells in a seasonal cycle. However, in the second set the simulation was performed in the state of fixing the locations of pumping and injection wells. After 365 days simulation period, the shape of temperature distribution was highly dependent on the injected water temperature and the distance from the injection well. A small temperature change appeared on the surface compared to other simulated temperature distributions of 30 and 50 m depths. The porosity and groundwater flow characteristics of each layer sensitively affected the heat transfer. The groundwater levels and temperature changes in injection and pumping wells were monitored and the thermal interference between the wells was analyzed to test the effectiveness of the heat pump operation method applied.

• Korean Journal of Materials Research
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• v.19 no.1
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• pp.28-32
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• 2009

Silicon carbide (SiC) is a promising material for power device applications due to its wide band gap (3.26 eV for 4H-SiC), high critical electric field and excellent thermal conductivity. The Schottky barrier diode is the representative high-power device that is currently available commercially. A field plate edge-terminated 4H-SiC was fabricated using a lift-off process for opening the Schottky contacts. In this case, Ni/Ti dual-metal contacts were unintentionally formed at the edge of the Schottky contacts and resulted in the degradation of the electrical properties of the diodes. The breakdown voltage and Schottky barrier height (SBH, ${\Phi}_B$) was 107 V and 0.67 eV, respectively. To form homogeneous single-metal Ni/4H-SiC Schottky contacts, a deposition and etching method was employed, and the electrical properties of the diodes were improved. The modified SBDs showed enhanced electrical properties, as witnessed by a breakdown voltage of 635 V, a Schottky barrier height of ${\Phi}_B$=1.48 eV, an ideality factor of n=1.04 (close to one), a forward voltage drop of $V_F$=1.6 V, a specific on resistance of $R_{on}=2.1m{\Omega}-cm^2$ and a power loss of $P_L=79.6Wcm^{-2}$.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.1-13
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• 2014

Lithium ion batteries (LIBs) are the state-of-the-art technology among electrochemical energy storage and conversion cells, and are still considered the most attractive class of battery in the future due to their high specific energy density, high efficiency, and long cycle life. Rapid development of power-hungry commercial electronics and large-scale energy storage applications (e.g. off-peak electrical energy storage), however, requires novel anode materials that have higher energy densities to replace conventional graphite electrodes. Germanium (Ge) and silicon (Si) are thought to be ideal prospect candidates for next generation LIB anodes due to their extremely high theoretical energy capacities. For instance, Ge offers relatively lower volume change during cycling, better Li insertion/extraction kinetics, and higher electronic conductivity than Si. In this focused review, we briefly describe the basic concepts of LIBs and then look at the characteristics of ideal anode materials that can provide greatly improved electrochemical performance, including high capacity, better cycling behavior, and rate capability. We then discuss how, in the future, Ge anode materials (Ge and Ge oxides, Ge-carbon composites, and other Ge-based composites) could increase the capacity of today's Li batteries. In recent years, considerable efforts have been made to fulfill the requirements of excellent anode materials, especially using these materials at the nanoscale. This article shall serve as a handy reference, as well as starting point, for future research related to high capacity LIB anodes, especially based on semiconductor Ge and Si.

• Korean Journal of Food Science and Technology
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• v.49 no.4
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• pp.369-376
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• 2017

Maturation of distilled spirit can generate diverse flavors and tastes. Rice Soju was matured in oak casks (MSO) and stainless steel containers (MSS) for one year at ambient temperature. Ipguk (Aspergillus luchuensis) and Saccharomyces cerevisiae Y88-4 were used, and reduced pressure ($110{\pm}20Torr$) distillation was applied to brew Soju. Acidity and conductivity were increased in both MSO and MSS. MSO reduced alcohol content (from 43 to 40%) and volume (from 18,000 to 12,730 mL), and significantly altered yellowness (from 0.2 to 30.2). Furthermore, MSO increased the isoamyl alcohol (from 276.7 to $339.2{\mu}g/mL$) and isobutyl alcohol (from 122.3 to $144.2{\mu}g/mL$) content. Gas chromatography-mass spectrometry was used to detect volatile compounds in Soju, which included 20 esters, 7 alcohols, 2 acids, and 5 miscellaneous compounds. Oak lactone was detected only in MSO and was considered as a specific flavor component associated with oak maturation. Thus, maturation materials contribute to the physicochemical property of distilled spirits.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.861-867
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• 2019

$Li_4Ti_5O_{12}$ is a promising next-generation anode material for lithium-ion batteries due to excellent cycle life, low irreversible capacity, and little volume expansion during charge-discharge process. However, it has poor charge capacity at high current density due to its low electrical conductivity. To improve this weakness, porous $Li_4Ti_5O_{12}$ was synthesized by sol-gel method with P123 as chelating agent. The physical characteristics of as-prepared sample was investigated by XRD, SEM, and BET analysis, and electrochemical properties were characterized by cycle performance test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS). $Li_4Ti_5O_{12}$ synthesized by 0.01mol ratio of P123/Ti showed most unified particle size, high specific surface area, and relatively high porosity. EIS analysis showed that depressed semicircle size was remarkably reduced, which suggested resistance value in electrode was decreased. Capacity in rate performance showed 178 mAh/g at 0.2C, 170 mAh/g at 0.5C, 110 mA/h at 5C, and 90 mAh/g at 10C. Capacity retention also showed 99% after rate performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.1-9
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• 2021

A60 class deck penetration piece is a fire-resistance apparatus installed on the deck compartment to protect lives and prevent flame diffusion in fire accidents. In case that the A60 piece is newly developed or its initial design is revised, it is important to verify the fire resistance performance using a fire test procedure (FTP) code. In this paper, transient heat transfer analysis was carried out to evaluate the fire resistance design compatibility of the newly devised A60 piece. The analysis results were verified via a fire test. The heat transfer characteristics were also investigated by comparing design specifications, such as diameter, internal configuration, and material type. The analysis was performed using ABAQUS/Implicit, and the fire test was performed according to the FTP code. The fire resistance performance of the A60 pieces satisfied the safety of life at sea convention regulation. The material type was the most important design specification for the A60 piece. Based on the maximum test temperature, the measured temperature of SUS316L material was 25% lower than that of S45C on average. The differences between thermal conductivity and specific heat of each material were 17% and 58%, respectively.

• Design & Manufacturing
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• v.13 no.2
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• pp.17-21
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• 2019

In this study, selective laser sintered 3D printing mold core and metal core were used to investigate the difference of the thickness shrinkage from the gate of the injection molded part at a constant interval. SLS 3D printing mold core was made of nylon-based PA2200 powder and the metal core was manufactured by conventional machining method. As the PA2200 powder material has low strength, thermal conductivity and high specific heat characteristics compared with metal, molding conditions were set with the consideration of molten temperature and injection pressure. Crystalline resin(PP) and amorphous resin(PS) with low melting temperature and viscosity were selected for the injection molding experiment. Cooling time for processing condition was selected by checking the temperature change of the cores with a cavity temperature sensor. The cooling time of the 3D printing core was required a longer time than that of the metal core. The thickness shrinkage of the molded part compared to the core depth was measured from the gate by a constant interval. It was shown that the thickness shrinkage of the 3D printing core was 2.02 ~ 4.34% larger than that of metal core. In additions, in the case of metal core, thickness shrinkage was increased with distance from the gate, on the contrary, in the case of polymer core showed reversed aspect.

• Korean Journal of Environmental Biology
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• v.37 no.1
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• pp.48-59
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• 2019

This study analyzed the water quality characteristics and developed empirical models prior to and after the construction of Baekje Weir, in the Geum River watershed between 2004-2017. The comparative evaluation of the surface water chemistry before and after the four major river projects on the weirs indicated that total phosphorus (TP), based on annual data, rapidly decrease after the construction of the weir while the total nitrogen(TN) decreased. Conversely, chlorophyll-a (CHL) concentration, which is a good indicator of primary productivity, increased after the construction of the weir together with an increase in specific conductivity. Simply put, the construction of the weir led to the decrease in concentrations of N and P due to the increased water residence time (WRT), whereas the CHL :TP ratio greatly increased in magnitude. The regression analysis of the empirical model indicated that CHL had no significant relation (r=0.068, p=0.6102, n=58) with TP before the weir construction, but had a relation with TP after the weir construction (r=0.286, p<0.05, n=56). Therefore, such conditions resulted in an increase in primary productivity on a given unit of phosphorus, resulting in frequent algal blooms. In contrast, seasonal suspended solids (SS) and TP increased during the monsoon period, compared to the pre-monsoon, thereby showing positive correlations (r>0.40, p<0.01, n=163) with precipitation. If the government consistently discharges water from the weir, the phosphorus concentration will be increased due to its reversion to a lotic waterbody from a lentic waterbody hereby reducing algal blooms in the future.

• The Journal of Engineering Geology
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• v.31 no.2
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• pp.187-197
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• 2021

Clay mineral content of weathered zone is a key parameter for landslide studies. Electrical resistivity tomography is usually performed to delineate the geometry of complex landslides and to identify the sliding surface. In clay-bearing weathered zone, parallel resistivity Archie equation is employed to investigate the effect of conductivity added (resistivity reduced) by clay minerals of kaolinite and montmorillonite, which is dependent on their specific surface area and cation exchange capacities (CEC). A decrease of overall resistivity and apparent formation factor is observed with increasing pore-water resistivity, significantly in montmorillonite. Formation factor is found decreased with increasing porosity and decreasing cementation factor. Parallel Archie equation was applied to the electrical resistivity data from the test area (Sinjindo-ri, Taean-gun, Chungcheongnam-do, Korea) which experienced land creeping in the year of 2014. A panel test with varying clay-mineral contents provides the best fit section when the theoretical section constructed with the assumed contents approaches the field section, from which the clay-mineral content of the weathered zone is estimated to be approximately 10%. Resistivity interpretation schemes including the clay mineral contents for land creeping studies explored in this paper can be challenged more when porosity, saturation, and pore-water resistivity are provided and they are included in the numerical resistivity modeling.