• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.78-83
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• 2014

In this research, we evaluated the performance and characteristics of carbon supported PtM (M = Ni and Y) alloy catalysts (PtM/Cs) synthesized by a modified polyol method. With the PtM/Cs employed as a catalyst for the oxygen reduction reaction (ORR) of cathodes in proton exchange membrane fuel cells (PEMFCs), their catalytic and ORR activities and electrical performance were investigated and compared with those of commercial Pt/C. Their particle sizes, particle distributions and electrochemically active surface areas (EAS) were measured by TEM and cyclic voltammetry (CV), while their ORR activity and electrical performance were explored using linear sweeping voltammetries with rotating disk electrodes and rotating ring-disk electrodes as well as PEMFC single cell tests. TEM and CV measurements show that PtM/Cs have the compatible particle size and EAS with Pt/C. When it comes to ORR activity, PtM/C showed the equivalent or better half-wave potential, kinetic current density, transferred electron number per oxygen molecule and $H_2O_2$ production(%) to or than commerical Pt/C. Based on results gained by the three electrode tests, when the PEMFC single cell tests were carried out, the current density measured at 0.6 V and maximum power density of PEMFC single cell adopting PtM/C catalysts were better than those adopting Pt/C catalyst. It is therefore concluded that PtM/C catalysts synthesized by modified polyol can result in the equivalent or better ORR catalytic capability and PEMFC performance to or than commercial Pt/C catalyst.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.313-331
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• 2022

Natural or native abiotic molecular hydrogen (H₂) is a major component in natural gas, however yet its importance in the global energy sector's usage as clean and renewable energy is underestimated. Here we review the occurrence and geological settings of native hydrogen to demonstrate the much widesprease H₂ occurrence in nature by comparison with previous estimations. Three main types of source rocks have been identified: (1) ultramafic rocks; (2) cratons comprising iron (Fe²⁺)-rich rocks; and (3) uranium-rich rocks. The rocks are closely associated with Precambrian crystalline basement and serpentinized ultramafic rocks from ophiolite and peridotite either at mid-ocean ridges or within continental margin(Zgonnik, 2020). Inorganic geological processes producing H₂ in the source rocks include (a) the reduction of water during the oxidation of Fe²⁺ in minerals (e.g., olivine), (b) water splitting due to radioactive decay, (c) degassing of magma at low pressure, and (d) the reaction of water with surface radicals during mechanical breaking (e.g., fault) of silicate rocks. Native hydrogen are found as a free gas (51%), fluid inclusions in various rock types (29%), and dissolved gas in underground water (20%) (Zgonnik, 2020). Although research on H₂ has not yet been carried out in Korea, the potential H₂ reservoirs in the Gyeongsang Basin are highly probable based on geological and geochemical characteristics including occurrence of ultramafic rocks, inter-bedded basaltic layers and iron-copper deposits within thick sedimentary basin and igneous activities at an active continental margin during the Permian-Paleogene. The native hydrogen is expected to be clean and renewable energy source in the near future. Therefore it is clear that the origin and exploration of the native hydrogen, not yet been revealed by an integrated studies of rock-fluid interaction studies, are a field of special interest, regardless of the presence of economic native hydrogen reservoirs in Korea.

• Korean Journal of Agricultural Science
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• v.8 no.2
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• pp.195-202
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• 1981

The return of water to the atmosphere from water, soil and vegetation surface is one of the most important aspects of hydrological cycle, and the seasonal trend of variation of river basin evaporation is also meaningful in the longterm runoff analysis for the irrigation and water resources planning. This paper has been prepared to show some imformation to estimate the monthly river basin evaporation from pan evaporation, potential evaporation, regional evaporation and temperature through the comparison with river basin evaporation derived from water budget method. The analysis has been carried out with the observation data of Yongdam station in the Geum river basin for five year. The results are summarized as follows and these would be applied to the estimation of river basin evaporation and longterm runoff in ungaged station. 1. The ratio of pan evaporation to river basin evaporation ($E_w/E_{pan}$) shows the most- significant relation at the viewpoint of seasonal trend of variation. River basin evaporation could be estimated from the pan evaporation through either Fig. 9 or Table-7. 2. Local coefficients of cloudness effect and wind function has been determined to apply the Penman's mass and energy transfer equation to the estimation of river basin evaporation. $R_c=R_a(0.13+0.52n/D)$ $E=0.35(e_s-e)(1.8+1.0U)$ 3. It seems that Regional evaporation concept $E_R=(1-a)R_C-E_p$ has kept functional errors due to the inapplicable assumptions. But it is desirable that this kind of function which contains the results of complex physical, chemical and biological processes of river basin evaporation should be developed. 4. Monthly river basin evaporation could be approximately estimated from the monthly average temperature through either the equation of $E_w=1.44{\times}1.08^T$ or Fig. 12 in the stations with poor climatological observation data.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.4
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• pp.243-252
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• 2006

Influence of the increasing carbon dioxide concentration in seawater on various marine organisms is assessed in this article with regard to the impacts of anthropogenic $CO_2$ introduced into surface or deep oceans. Recent proposals to sequester $CO_2$ in deep oceans arouse the concerns of adverse effects of increased $CO_2$ concentration on deep-sea organisms. Atmospheric introduction of $CO_2$ into the ocean can also acidify the surface water, thereby the population of some sensitive organisms including coral reefs, cocolithophorids and sea urchins will be reduced considerably in near future (e.g. in 2100 unless the increasing trend of $CO_2$ emission is actively regulated). We exposed bioluminescent bacteria and benthic amphipods to varying concentrations of $CO_2$ and also pH for a short period. The ${\sim}l.5$ unit decrease of pH adversely affected test organisms. However, amphipods were not influenced by decreasing pH when HCl was used for the seawater acidification. In this article, we reviewed the biological adverse effects of $CO_2$ on various marine organisms studied so for. Theses results will be useful to predict the potential risks of the increase of $CO_2$ concentrations in seawater due to the increase of atmospheric $CO_2$ emission and/or sequestration of $CO_2$ in deep oceans.

• Geophysics and Geophysical Exploration
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• v.11 no.4
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• pp.279-285
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• 2008

Korea Institute of Geoscience & Mineral Resources (KIGAM) carried out 2 dimensional multi-channel seismic surveys for Domi-Basin of east-southern part of Jeju Island, South Sea, Korea in 2007. The purpose of this survey is to investigate the structure of acoustic basement and the potential of energy resources in the Korean shelf. It is essential to produce fine stack and migration section to understand the structure of basement. However a basement can not be clearly defined where multiples exist between sea surface and seafloor. This study aimed at designing the optimal data processing parameter, especially to eliminate the peg-leg multiples. Main data processing procedure is composed of minimum phase predictive deconvolution, velocity analysis and Radon filter. We tested the efficiency of processing parameter from stack sections of each step. Our results confirmed that processing parameters are suitable for the seismic data of Domi-Basin.

• Journal of the Society of Disaster Information
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• v.14 no.2
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• pp.130-140
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• 2018

Purpose: In this paper, we propose a design technique for the safety characterization grounding in the construction of the photovoltaic power generation complex which can be useful and useful as an alternative power energy source in our society. In other words, we will introduce the application of safety grounding for each application, which can improve and optimize the reliability of the internal grid from the cell module to the electric room in the photovoltaic power generation complex. Method: We analyze the earth resistivity of the soil in the solar power plant and use the computer program (CDEGS) to analyze the contact voltage and stratospheric voltage causing the electric shock, and propose the calculation and calculation method of the safety ground. In addition, we will discuss the importance of semi-permanent ground electrode selection in consideration of soil environment. Results: We could obtain the maximum and minimum value of ground resistivity for each of the three areas of the data measured by the Wenner 4 - electrode method. The measured data was substituted into the basic equation and calculated with a MATLAB computer program. That is, it can be determined that the thickness of the minimum resistance value is the most favorable soil environment for installing the ground electrode. Conclusion: Through this study, we propose a grounding system design method that can suppress the potential rise on the ground surface in the inner grid of solar power plant according to each case. However, the development of smart devices capable of accumulating big data and a monitoring system capable of real-time monitoring of seismic changes in earth resistances and grounding systems should be further studied.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.663-666
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• 2005

Gas hydrates are ice-like compounds that form at the low temperature and high pressure conditions common in shallow marine sediments at water depths greater than 300-500 m when concentrations of methane and other hydrocarbon gases exceed saturation. Estimates of the total mass of methane carbon that resides in this reservoir vary widely. While there is general agreement that gas hydrate is a significant component of the global near-surface carbon budget, there is considerable controversy about whether it has the potential to be a major source of fossil fuel in the future and whether periods of global climate change in the past can be attributed to destabilization of this reservoir. Also essentially unknown is the interaction between gas hydrate and the subsurface biosphere. ODP Leg 204 was designed to address these questions by determining the distribution, amount and rate of formation of gas hydrate within an accretionary ridge and adjacent basin and the sources of gas for forming hydrate. Additional objectives included identification of geologic proxies for past gas hydrate occurrence and calibration of remote sensing techniques to quantify the in situ amount of gas hydrate that can be used to improve estimates where no boreholes exist. Leg 204 also provided an opportunity to test several new techniques for sampling, preserving and measuring gas hydrates. During ODP Leg 204, nine sites were drilled and cored on southern Hydrate Ridge, a topographic high in the accretionary complex of the Cascadia subduction zone, located approximately 80km west of Newport, Oregon. Previous studies of southern Hydrate Ridge had documented the presence of seafloor gas vents, outcrops of massive gas hydrate, and a pinnacle' of authigenic carbonate near the summit. Deep-towed sidescan data show an approximately $300\times500m$ area of relatively high acoustic backscatter that indicates the extent of seafloor venting. Elsewhere on southern Hydrate Ridge, the seafloor is covered with low reflectivity sediment, but the presence of a regional bottom-simulating seismic reflection (BSR) suggests that gas hydrate is widespread. The sites that were drilled and cored during ODP Leg 204 can be grouped into three end-member environments basedon the seismic data. Sites 1244 through 1247 characterize the flanks of southern Hydrate Ridge. Sites 1248-1250 characterize the summit in the region of active seafloor venting. Sites 1251 and 1252 characterize the slope basin east of Hydrate Ridge, which is a region of rapid sedimentation, in contrast to the erosional environment of Hydrate Ridge. Site 1252 was located on the flank of a secondary anticline and is the only site where no BSR is observed.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.342-343
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• 2013

AlSb is a promising material for optical devices, particularly for high-frequency and nonlinear-optical applications. And AlSb offers significant potential for devices such as quantum-well lasers, laser diodes, and heterojunction bipolar transistors. In this work we study molecular beam epitaxy (MBE) growth of an unstrained AISb film on a GaAs substrate and identify the real-time monitoring capabilities of in situ spectroscopic ellipsometry (SE). The samples were fabricated on semi-insulating (0 0 1) GaAs substrates using MBE system. A rotating sample stage ensured uniform film growth. The substrate was first heated to $620^{\circ}C$ under As2 to remove surface oxides. A GaAs buffer layer approximately 200 nm- thick was then grown at $580^{\circ}C$. During the temperature changing process from $580^{\circ}C$ to $530^{\circ}C$, As2 flux is maintained with the shutter for Ga being closed and the reflection high-energy electron diffraction (RHEED) pattern remaining at ($2{\times}4$). Upon reaching the preset temperature of $530^{\circ}C$, As shutter was promptly closed with Sb shutter open, resulting in the change of RHEED pattern from ($2{\times}4$) to ($1{\times}3$). This was followed by the growth of AlSb while using a rotating-compensator SE with a charge-coupled-device (CCD) detector to obtain real-time SE spectra from 0.74 to 6.48 eV. Fig. 1 shows the real time measured SE spectra of AlSb on GaAs in growth process. In the Fig. 1 (a), a change of ellipsometric parameter ${\Delta}$ is observed. The ${\Delta}$ is the parameter which contains thickness information of the sample, and it changes in a periodic from 0 to 180o with growth. The significant change of ${\Delta}$ at~0.4 min means that the growth of AlSb on GaAs has been started. Fig. 1b shows the changes of dielectric function with time over the range 0.74~6.48 eV. These changes mean phase transition from pseudodielectric function of GaAs to AlSb at~0.44 min. Fig. 2 shows the observed RHEED patterns in the growth process. The observed RHEED pattern of GaAs is ($2{\times}4$), and the pattern changes into ($1{\times}3$) with starting the growth of AlSb. This means that the RHEED pattern is in agreement with the result of SE measurements. These data show the importance and sensitivity of SE for real-time monitoring for materials growth by MBE. We performed the real-time monitoring of AlSb growth by using SE measurements, and it is good agreement with the results of RHEED pattern. This fact proves the importance and the sensitivity of SE technique for the real-time monitoring of film growth by using ellipsometry. We believe that these results will be useful in a number of contexts including more accurate optical properties for high speed device engineering.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.2
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• pp.120-125
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• 2015

With rapid urbanization, the volume of traffic in urban area has been significantly increased. This in turn led to problem which can be described as Road Traffic Noise. Currently, to alleviate the road traffic noise damage, a demand for installation of soundproofing walls is rising. Among different shapes of soundproof walls being installed, the reflection-type acoustical insulation panel is highly drawing attentions of residents due to the fact that it does not obstruct their field of vision in contrast with the opaque acoustical insulation panel. On the other hand, improving the soundproofing wall of the reflection-type acoustical insulation barrier panel needs to be focused on since it has a possibility to cause a secondary damage by reflected sounds. Therefore, in this research, study has been carried out to improve the forms in order to minimize travelling of reflected sounds through changing the frontal surface shape and geometrical shape of the reflection-type soundproofing panel. A result from comparison between the normal reflection-type soundproofing panel and the improved soundproofing panel, with reduction effects in the noise reflection, showed that the curved type of soundproofing panel has an impact on reducing the noise up to 1.5 dB. Furthermore, from the research conducted, it appears that the increase and decrease in the reflected sounds can be changeable depending on various design factors. Thus, it turns out that the study shows a potential possibility to develop a reduction technology of the reflected sounds pertaining to overall condition on the soundproofing walls.

• Membrane Journal
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• v.26 no.1
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• pp.76-85
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• 2016

Fabrication of polysulfone (PSf) hollow fiber membranes was investigated for the separation of $N_2/NF_3$ gas mixtures, which are emitted from the display and the semiconductor industries. A combination of the non-solvent induced phase separation (NIPS) and the vapor-induced phase separation (VIPS) technique was applied to develop high flux hollow fiber membranes. Thin polymer layers were further coated onto the surface of the hollow fiber membranes by using polydimethylsiloxiane (PDMS) or Teflon AF1600(R), which contributes to improve the $N_2/NF_3$ selectivity. The $N_2/NF_3$ separation performances of our PSf hollow fiber membranes were determined by the intrinsic properties of coating materials. Especially, the PSf hollow fiber membrane coated with Teflon AF 1600(R) exhibited a higher $N_2/NF_3$ selectivity (> 14) with a slightly lower $N_2$ permeance (4.5 GPU), as compared to the commercial PSf counterparts. This feature provides a good potential as a membrane structure to separate $N_2/NF_3$.