• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.517-519
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• 2015

A large-scale neutral hydrogen ($H\small{I}$) ring serendipitously found in the Leo I galaxy group is 200 kpc in diameter with $M_{H\small{I}}{\sim}1.67{\times}10^9M_{\odot}$, unique in size in the Local Universe. It is still under debate where this $H\small{I}$ ring originated - whether it has formed out of the gas remaining after the formation of a galaxy group (primordial origin) or been stripped during galaxy-galaxy interactions (tidal origin). We are investigating the optical and $H\small{I}$ gas properties of the dwarf galaxies located within the gas ring in order to probe its formation mechanism. In this work, we present the photometric properties of the dwarfs inside the ring using the CFHT MegaCam $u^{\ast}$, $g^{\prime}$, $r^{\prime}$ and $i^{\prime}$-band data. We discuss the origin of the gas ring based on the stellar age and metal abundance of dwarf galaxies contained within it.

• Environmental Engineering Research
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• v.24 no.3
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• pp.521-528
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• 2019

Electrochemical method was used for the fracturing flow-back fluid treatment in Guangyuan oilfield. After performing electrolysis, we found that the amount of $H_2$ gas produced by electrode was closely related to the combination mode of electrodes and electrode materials. Using an aluminium electrode resulted in a large $H_2$ production of each electrode combination, whereas inert anode and cathode materials resulted in low $H_2$ production. Then, the relationship between the gas production of $H_2$ and the treatment efficiency of fracturing flow-back fluid in Guangyuan oilfield was studied. Results showed that the turbidity removal and decolourisation rates of fracturing flow-back fluid were high when $H_2$ production was high. If the $H_2$ production of inert electrode was large, the energy consumption of this inert electrode was also high. However, energy consumption when an aluminium anode material was used was lower than that when the inert electrode was used, whereas the corresponding electrode combination production of $H_2$ was larger than that of the inert electrode combination. When the inert electrode was used as anode, the gas production type was mainly $O_2$, and $Cl_2$ was also produced and dissolved in water to form $ClO^-$. $H_2$ production at the cathode was reduced because $ClO^-$ obtained electrons.

• Clean Technology
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• v.21 no.4
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• pp.271-277
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• 2015

A photocatalyst which mixed by the commercialized P25-TiO₂ and a synthesized Ag_xO was used in an appropriate weight ratio to effectively produce hydrogen gas in this study. The Ag_xOs were synthesized with the conventional sol-gel method, and tetramethylammonium hydroxides were added at the synthesis process in order to stabilize the solutions, and then the solutions were heat-treated at the temperatures of -5, 25, and 50 ℃, resulted to obtain the three types of silver oxides. Physicochemical properties of the synthesized Ag_xOs were identified through X-ray diffraction analysis (XRD), scanning emission microscopy (SEM), ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). In the photolysis results of water/methanol (weight ratio 1:1) solution, the mixture of P25-TiO₂/Ag_xO exhibited a significantly higher hydrogen gases evolution, compared to that of pure P25-TiO₂. Additionally, the addition of H₂O₂ as an supplement oxidant and in Ag_xO synthesized at 50 ℃ improved the hydrogen production efficiency. In particular, the emitted hydrogen gases reached to 13,000 μmol during 8 hours when a mixed catalyst, Ag_xO of 0.1 g and P25-TiO₂ of 0.9 g, were used.

• Corrosion Science and Technology
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• v.6 no.2
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• pp.37-43
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• 2007

Iodine sulfur (IS) process is one of the promising processes for a hydrogen production by using a high temperature heat generated by a very high temperature gas cooled reactor(VHTR) in the nuclear power industries. Even though the IS process is very efficient for a hydrogen production and it is not accompanied by a carbon dioxide evolution, the highly corrosive environment of the process limits its application in the industry. Corrosion tests of selected materials were performed in sulfuric acid to select appropriate materials compatible with the IS process. The materials used in this work were Fe-Cr alloys, Fe-Ni-Cr alloys, Fe-Si alloys, Ni base alloys, Ta, Ti, Zr, SiC, Fe-Si, etc. The test environments were 50 wt% sulfuric acid at $120^{\circ}C$ and 98 wt% at $320^{\circ}C$. Corrosion rates were measured by using a weight change after an immersion. The surface morphologies and cross sectional areas of the corroded materials were examined by using SEM equipped with EDS. Corrosion behaviors of the materials were discussed in terms of the chemical composition of the materials, a weight loss, the corrosion morphology, the precipitates in the microstructure and the surface layer composition.

• Clean Technology
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• v.18 no.4
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• pp.355-359
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• 2012

For effectively photochemical hydrogen production, Ti ions (0.01, 0.10, 0.50 mol%) impregnated $WO_3$ ($Ti/WO_3$) nanometer sized particles were prepared using a impregnation method as a photocatalyst. The characteristics of the synthesized $Ti/WO_3$ photocatalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectra (PL), atomic force microscope (AFM), and electrostatic force microscope (EFM). The evolution of $H_2$ from methanol/water (1/1) photo-splitting over $Ti/WO_3$ photocatalysts was enhanced compared to those over pure $TiO_2$ and $WO_3$ photocatalysts; 3.02 mL of $H_2$ gas was evolved after 8 h when 0.5 g of a 0.10 mol% $Ti/WO_3$ catalyst was used.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.383-383
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• 2010

Gas-phase hydrogen atoms create a variety of chemical and physical phenomena on Si surfaces: adsorption, abstraction of pre-adsorbed H, Si etching, Si amorphization, and penetration into the bulk lattice. Thermal desorption/evolution analyses exhibited three distinct peaks, including one from the crystalline bulk. It was previously found that thermal-energy gaseous H(g) atoms penetrate into the Si(100) crystalline bulk within a narrow substrate temperature window(centered at ~460K) and remain trapped in the bulk lattice before evolving out at a temperature as high as ~900K. Developing and sustaining atomic-scale surface roughness, by H-induced silicon etching, is a prerequisite for H absorption and determines the $T_s$ windows. Issues on the H(g) absorption to be further clarified are: (1) the role of the detailed atomic surface structure, together with other experimental conditions, (2) the particular physical lattice sites occupied by, and (3) the chemical nature of, absorbed H(g) atoms. This work has investigated and compared the thermal H(g) atom absorptivity of Si(100), Si(111) and Si(110) samples in detail by using the temperature programmed desorption mass spectrometry (TPD-MS). Due to the differences in the atomic structures of, and in the facility of creating atom-scale etch pits on, Si(100), (100) and (110) surfaces, the H-absorption efficiency was found to be larger in the order of Si(100) > Si(111) > Si(110) with a relative ratio of 1 : 0.22 : 0.045. This intriguing result was interpreted in terms of the atomic-scale surface roughening and kinetic competition among H(g) adsorption, H(a)-by-H(g) abstraction, $SiH_3(a)$-by-H(g) etching, and H(g) penetraion into the crystalline silicon bulk.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.102-102
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• 2016

Water, which is most abundant in Earth surface and very closely related to all forms of living organisms, has a simple molecular structure but exhibits very unique physical and chemical properties. Even though tremendous effort has been paid to understand this nature's core substance, there amazingly still lefts much room for scientist to explore its novel behaviors. Especially, as the scale goes down to nano-regime, water shows extraordinary properties that are not observable in bulk state. One of such interesting features is the formation of nanoscale bubbles showing unusual long-term stability. Nanobubbles can be spontaneously formed in water on hydrophobic surface or by decompression of gas-saturated liquid. In addition, the nanobubbles can be generated during electrochemical reaction at normal hydrogen electrode (NHE), which possibly distorts the standard reduction potential at NHE as the surface nanobubble screens the reaction with electrolyte solution. However, the real-time evolution of these nanobubbles has been hardly studied owing to the lack of proper imaging tools in liquid phase at nanoscale. Here we demonstrate, for the first time, that the behaviors of nanobubbles can be visualized by in situ transmission electron microscope (TEM), utilizing graphene as liquid cell membrane. The results indicate that there is a critical radius that determines the long-term stability of nanobubbles. In addition, we find two different pathways of nanobubble growth: i) Ostwald ripening of large and small nanobubbles and ii) coalescence of similar-sized nanobubbles. We also observe that the nucleation and growth of nanoparticles and the self-assembly of biomolecules are catalyzed at the nanobubble interface. Our finding is expected to provide a deeper insight to understand unusual chemical, biological and environmental phenomena where nanoscale gas-state is involved.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.495-497
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• 2015

Galaxies can be "pre-processed" in the low-density outskirts by ambient medium in the filaments or tidal interactions with other galaxies while falling into the cluster. In order to probe how early on and by which mechanisms galaxies can be affected before they enter high-density cluster environments, we are carrying out an atomic hydrogen ($H\small{I}$) imaging study of a sample of galaxies selected from three filamentary structures around the Virgo cluster. Our sample consists of 14 late-type galaxies, which are potentially interacting with their surroundings. The $H\small{I}$ observations have been done using the Westerbork Synthesis Radio Telescope, the Giant Metrewave Radio Telescope, and the Jansky Very Large Array with column density sensitivity of ${\approx}3-5{\times}10^{19}cm^{-2}$ in $3{\sigma}$ per channel, which is low enough to detect faint $H\small{I}$ features in the outer disks of galaxies. In this work, we present the Hi data of two galaxies that were observed with GMRT. We examine the $H\small{I}$ morphology and kinematics to find the evidence for gas-gas and/or tidal interactions, and discuss which mechanism(s) could be responsible for pre-processing in these cases.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.1
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• pp.62-69
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• 1992

A series of laboratory experiment was conducted to find out the effects of physico-chemical, microbiological and commercial inhibitors on the odorous gas evolution in the fermentation of livestock feces. The results obtained were summarized as follows. 1. The rate and amount of evolution of gas were the highest at 7 days after incubation, thereafter gradually decreased until 24 days after incubation. 2. The rate and amount of gases were evolved in order of $CO_2>N_2O>CH_4>NH_3>N_2S$, respectively. 3. The highest amount of methane gas was evolved from the poultry feces, those of carbon dioxide and nitrous oxide were evolved from the pig feces, and that of hydrogen sulfide was dominantly evolved from the cattle feces. 4. Negative correlation were obtained between the total amounts of $NH_3$ and $CH_4$, $CO_2$ and $CH_4$, $N_2O$ and $CH_4$, $N_2O$ and $CH_4$, while positive correlations were obtained between the amounts of $CO_2$ and $N_2O$, $CO_2$ and $NH_3$, and $NH_3$ and $N_2O$, respectively. 5. There was no significantly inhibiting effect obtained that the application of commercial gas inhibitor as VK 88. On the other hand there was significantly inhibiting effect obtained when application of fertile paddy soil and photosynthetic bacteria to the fermentation of livestock feces.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.417-423
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• 2007

Oxy-gasification or oxygen-blown gasification, enables a clean and efficient use of coal and opens a promising way to CO2 capture. The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. The purposes of this study are to develop an evaluation technique for design and performance optimization of coal gasifiers using a numerical simulation technique, and to confirm the validity of the model. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization, mixture fraction model and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The influence of turbulence on the gas properties was taken into account by the PDF (Probability Density Function) model. A numerical simulation with the coal gasification model is performed on the Conoco-Philips type gasifier for IGCC plant. Gas temperature distribution and product gas composition are also presented. Numerical computations were performed to assess the effect of variation in oxygen to coal ratio and steam to coal ratio on reactive flow field. The concentration of major products, CO and H2 were calculated with varying oxygen to coal ratio (0.2-1.5) and steam to coal ratio(0.3-0.7). To verify the validity of predictions, predicted values of CO and H2 concentrations at the exit of the gasifier were compared with previous work of the same geometry and operating points. Predictions showed that the CO and H2 concentration increased gradually to its maximum value with increasing oxygen-coal and hydrogen-coal ratio and decreased. When the oxygen-coal ratio was between 0.8 and 1.2, and the steam-coal ratio was between 0.4 and 0.5, high values of CO and H2 were obtained. This study also deals with the comparison of CFD (Computational Flow Dynamics) and STATNJAN results which consider the objective gasifier as chemical equilibrium to know the effect of flow on objective gasifier compared to equilibrium. This study makes objective gasifier divided into a few ranges to study the evolution of the gasification locally. By this method, we can find that there are characteristics in the each scope divided.