• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.109-120
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• 2018

Sidestream in domestic wastewater treatment plants contains high concentration of ammonium, which increases nitrogen loading rate in the mainstream. The process for deammonification consisting of partial nitritation-anaerobic ammonium oxidation (ANAMMOX) and heterotrophic denitrification is an economical method of solving this problem. Currently, about 130 full-scale deammonification plants are fully operating around the world, but none is in Korea. In order to transfer the principal information about sidestream deammonification processes to researchers and operators, we summarized basic concepts, processes type, and key influence factors (e.g., concentration of nitrogen compounds, dissolved oxygen (DO), temperature, and pH). This review emphasis on the processes of single-stage sequencing batch reactor (SBR) deammonification, which are widely used as full-scale plants. Since simultaneous processes of partial nitritation, ANAMMOX and heterotrophic denitrification occur in a single reactor, the single-stage SBR deammonification requires appropriate control/monitoring strategies for several operating factors (DO and pH mostly) to achieve efficient and stable operation. In future, AB-process consisting of A-stage (energy harvesting from organics) and B-stage (ammonium removal without organics) will be applied to the wastewater treatment process. Thus, we suggest mainstream deammonification for B-stage connected with the sidestream deammonification as seeding source of ANAMMOX. We expect that many researchers will become more interested in the sidestream deammonification.

• International Journal of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.70-77
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• 2017

Where there are all the flowers, the songs of all kinds of insects and birds are put in, the sunshine and shadows flicker The forest through which the water sound flows is an optimum resting space. All living creatures in these spaces will awaken the five senses of humans and perhaps turn the sensibility index (EQ). The forest meditation in the forest, which can be an optimal shelter for the people who need it, needs to feel the reverence of nature, to refine emotions, to be a self-reflection, to have a mind to respect, Have an important meaning. In this paper, we tried to consider the cause of the influence of forest sounds on human hearing from the acoustical aspect. The type of sound source of forest was divided into four seasons of spring, summer, autumn, winter. And the change in the duration of the sound during the four seasons, so that the general characteristics of the sounds of the four seasons are as follows: It can be seen that the change in the ratio of sub-band energy is almost equal to the change in dB in frequency of the equal-light curve. To compare this phenomenon, the criterion for changing the sound duration of each forest is natural The main forms of the luminance curve, such as the change in the duration of the white signal in the sound, are determined by the minimum, maximum audible frequency and the most sensitive frequency band, and the auditory characteristics of the other three inflection points Determines the overall shape of the equal-light curve.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1B
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• pp.21-27
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• 2012

The HLLL scheme, proposed by T. Linde, determines all the wave speeds from the initial states because the middle wave is evaluated by the introduction of a generalized entropy function. The scheme is considered a genuine successor to the original HLL scheme because it is completely separated form the Roe's linearization scheme unlike the HLLE scheme and does not rely on the exact solution unlike the HLLC scheme. In this study, a numerical model was configured by the HLLL scheme with the total energy as a generalized entropy function to solve governing equations, which are the one-dimensional shallow water equations without source terms and with an additional conserved variable relating a concentration. Despite the limitations of the first order solutions, results to three cases with the exact solutions were generally accurate. The HLLL scheme appeared to be superior in comparison with the other HLL-type schemes. In particular, the scheme gave fairly accurate results in capturing the front of wetting and drying. However, it revealed shortcomings of more time-consuming calculations compared to the other schemes.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.634-637
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• 2005

Multichannel seismic data acquired in Ulleung Basin of East Sea for gas hydrate exploration. The seismic sections of this area show strong BSR(bottom simulating reflections) associated with methane hydrate occurrence in deep marine sediments. Very limited information is available from deep sea drilling as the risk of heating and destabilizing the initial hydrate conditions during the processing of drilling is considerably high. Not so many advanced status of gas hydrate exploration in Korea, the most of information of gas hydrate characteristics and properties are inferred from seismic reflection data. In this study, The AVO analysis using the long offset seismic data acquired in Ulleung Basin used to explain the characteristics and structure of gas hydrate. It is used primarily P-wave velocity accessible from seismic data. To make a good quality of AVO analysis input data, seismic preprocessing including 'true gain correction', 'source signature deconvolution', twice velocity analysis and some kinds of multiple rejection and enhancing the signal to noise ratio processes is carried out very carefully. The results of AVO analysis, the eight kinds of AVO attributes are estimated basically and some others of AVO attributes are evaluated for interpretation of AVO analysis additionally. The impedance variation at the boundary of gas hydrate and free gas is estimated for investing the BSR characteristics and properties. The complex analysis is performed also to verifying the amplitude variation and phase shift occurrence at BSR. Type III AVO anomaly appearance at saturated free gas area is detected on BSR. It can be an important evidence of gas hydrate deposition upper the BSR.

• Progress in Superconductivity
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• v.13 no.2
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• pp.105-110
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• 2011

SQUID sensor-based ultra low-field magnetic resonance apparatus with ${\mu}T$-level measurement field requires a strong prepolarization magnetic field ($B_p$) to magnetize its sample and obtain magnetic resonance signal with a high signal-to-noise ratio. This $B_p$ needs to be ramped down very quickly so that it does not interfere with signal acquisition which must take place before the sample magnetization relaxes off. A MOSFET switch-based $B_p$ coil driver has current ramp-down time ($t_{rd}$) that increases with $B_p$ current, which makes it unsuitable for driving high-field $B_p$ coil made of superconducting material. An energy cycling-type current driver has been developed for such a coil. This driver contains a storage capacitor inside a switch in IGBT-diode bridge configuration, which can manipulate how the capacitor is connected between the $B_p$ coil and its current source. The implemented circuit with 1.2 kV-tolerant devices was capable of driving 32 A current into a thick copper-wire solenoid $B_p$ coil with a 182 mm inner diameter, 0.23 H inductance, and 5.4 mT/A magnetic field-to-current ratio. The measured trd was 7.6 ms with a 160 ${\mu}F$ storage capacitor. trd was dependent only on the inductance of the coil and the capacitance of the driver capacitor. This driver is scalable to significantly higher current of superconducting $B_p$ coils without the $t_{rd}$ becoming unacceptably long with higher $B_p$ current.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.361-364
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• 2009

KEPRI has studied planar type SOFC stacks using anode-supported single cells and kW class co-generation systems for residential power generation. A 1kW class SOFC system consisted of a hot box part, a cold BOP part and a water reservoir. A hot box part contains a SOFC stack made up of 48 cells with $10{\times}10cm^2$ area and ferritic stainless steel interconnectors, a fuel reformer, a catalytic combustor and heat exchangers. Thermal management and insulation system were especially designed for self-sustainable operation. A cold BOP part was composed of blowers, pumps, a water trap and system control units. When a 1kW class SOFC system was operated at $750^{\circ}C$ with hydrogen, the stack power was 1.2kW at 30 A and 1.6kW at 50A. Turning off an electric furnace, the SOFC system was operated using hydrogen and city gas without any external heat source. Under self-sustainable operation conditions, the stack power was about 1.3kW with hydrogen and 1.2kW with city gas respectively. The system also recuperated heat of about 1.1kW by making hot water. Recently KEPRI developed stacks using $15{\times}15cm^2$ cells and tested them. KEPRI will develop a 5 kW class CHP system using $15{\times}15cm^2$ stacks by 2010.

• Journal of the Korean Vacuum Society
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• v.6 no.4
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• pp.337-342
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• 1997

We have investigated Mossbauer effect and emission properties of the Fe-doped GaAs grown by liquid phase epitaxy (LPE). The powder type of isotope $^{57}Fe$ was used as a dopant source in LPE-GaAs. From the analysis of Mossbauer effect the value of isomer shift, 0.303$\pm$0.018 mm/sec, is calculated at low temperature. This means that charge state of Fe ion in GaAs is 3+. The results of double crystal x-ray rocking curve (DCRC) and low temperature photoluminescence (PL) show the crystal quality of the epitaxial layers are good. Unusual luminescence peaks from the Fe-GaAs epitaxial layers appeared at emission energy of 0.99 eV and 1.15 eV. We attribute these emissions to Fe-acceptor related two deep radiative centers.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.4
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• pp.440-448
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• 2007

Although the anthracite power plant is an important source of greenhouse gas, research on this type of power plant has not been conducted much. The present study investigated the entire anthracite power plants in Korea and analyzed the emitted gas in connection with GC/FD and a methanizer in order to develop $CO_2$ emission factors. The study also sampled the anthracite to analyze the amount of carbon and hydrogen using an element analyzer, and to measure the calorie using an automatic calorie analyzer. The emission factors computed through the fuel analysis was 30.45 kg/GJ and that computed through the $CO_2$ gas analysis was 26.48 kg/GJ. The former is approximately about 15% higher than the latter. When compared the carbon content factors of anthracite with that of bituminous coal, the value of anthracite was 24% higher Compared with IPCC values, the emission factors by the fuel was 14% higher, and that by the emitted $CO_2$ gas was about 1.2% lower. More research is needed on our own emission factors of various energy-consuming facilities in order to stand on a higher position in international negotiations regarding the treaties on climate changes.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.6
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• pp.562-570
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• 2009

Although anthracite power plant acts as the important source of greenhouse gas emissions, relatively little is known about its emission potentials. Especially, because the emissions of Non-$CO_2$ greenhouse gas $CH_4$ and $N_2O$ are strongly dependent on fuel type and technology available, it is desirable to obtain the information concerning their emission pattens. In this study, the anthracite power plants in Korea were investigated and the emission gases were analyzed using GC/FID and GC/ECD to develop Non-$CO_2$ emission factors. The anthracite samples were also analyzed to quantity the amount of carbon and hydrogen using an element analyzer, while calorie was measured by an automatic calorie analyzer. The emission factor of $CH_4$ and $N_2O$ computed through the gas analysis corresponded to 0.73 and 1.98 kg/TJ, respectively. Compared with IPCC values, the $CH_4$ emission factor in this study was about 25% lower, while that of $N_2O$ was higher by about 40%. More research is needed to extend our database for emission factors of various energy-consuming facilities in order to stand on a higher position.

• Journal of Microbiology and Biotechnology
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• v.20 no.7
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• pp.1092-1100
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• 2010

Bacteria, fungi, and protozoa inhabiting the rumen, the largest chamber of the ruminants' stomach, release large quantities of hydrogen during the fermentation of carbohydrates. The hydrogen is used by coexisting methanogens to produce methane in energy-yielding processes. This work shows, for the first time, a fundamental possibility of using a hydrogen-rich fermentation gas produced by selected rumen ciliates to feed a low-temperature hydrogen fuel cell. A biohydrogen fuel cell (BHFC) was constructed consisting of (i) a bioreactor, in which a hydrogen-rich gas was produced from glucose by rumen ciliates, mainly of the Isotrichidae family, deprived of intra- and extracellular bacteria, methanogens, and fungi; and (ii) a chemical fuel cell of the polymer-electrolyte type (PEFC). The fuel cell was used as a tester of the technical applicability of the fermentation gas produced by the rumen ciliates for power generation. The average estimated hydrogen yield was ca. 1.15 mol $H_2$ per mole of fermented glucose. The BHFC performance was equal to the performance of the PEFC running on pure hydrogen. No fuel cell poisoning effects were detected. A maximum power density of $1.66\;kW/m^2$ (PEFC geometric area) was obtained at room temperature. The maximum volumetric power density was $128\;W/m^3$ but the coulombic efficiency was only ca. 3.8%. The configuration of the bioreactor limited the continuous operation time of this BHFC to ca. 14 h.