• Journal of the Korea Organic Resources Recycling Association
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• v.29 no.4
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• pp.47-54
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• 2021

In this study, the performance of a honeycomb-type hydrogen oxidation catalyst to remove hydrogen in a hydrogen economy society to secure leaking hydrogen. The Pd/TiO₂ catalyst was prepared based on a liquid phase reduction method that is not exposed to a heat source, and it was showed through H₂-chemisorption analysis that it existed as very small active particles of 2~4 nm. In addition, it was found that the metal dispersion decreased and the active particle size increased as the reduction reaction temperature increased. It was meant that the active metal particle size and the hydrogen oxidation performance were in a proportional correlation, so that it was consistent with the hydrogen oxidation performance reduction result. The prepared catalyst was coated on a support in the form of a honeycomb so that it could be applied to the hydrogen industrial process. When 20 wt% or more of the AS-40 binder was coated, oxidation performance of 90% or more was observed under low-concentration hydrogen conditions. It was showed through SEM analysis that long-term catalytic activity can be expected by enhancing the adhesion strength of the catalyst and preventing catalyst desorption. It is a basic research that can secure safety in a hydrogen society such as gasification, organic resource, and it can be utilized as a system that can respond to unexpected safety accidents in the future.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.1
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• pp.78-82
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• 2020

In this study, MOSFETs fabricated on Si-doped, MBE-grown β-Ga₂O₃ are demonstrated. A Si-doped Ga₂O₃ epitaxial layer was grown on a Fe-doped, semi-insulating 1.5 cm × 1 cm Ga₂O₃ substrate using molecular beam epitaxy (MBE). The fabricated devices are circular type MOSFETs with a gate length of 3 ㎛, a source-drain spacing of 20 ㎛, and a gate width of 523 ㎛. The device exhibited a good pinch-off characteristic, a high on-off drain current ratio of approximately 2.7×10⁹, and a high breakdown voltage of 1,080 V, which demonstrates the potential of Ga₂O₃ for power device applications including electric vehicles, railways, and renewable energy.

• Laser Solutions
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• v.1 no.1
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• pp.24-29
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• 1998

A new wide laser beam optical system for the laser materials processing has been developed with a polygonal mirror. It consists of polygonal mirror and cooling part that prevents the surface of rotating polygonal mirror from damage by heat. The polygonal minors have been designed and made as 24 and 30 facets in pyramid type. This system provides a uniform linear laser heat source with the surface scanning width from 15 to 50mm according to the scanning height To examine the wide laser beam, He-Ne laser is used. Also, Acryl is used to confirm the laser beam pattern by bum-pattern print To analyze the energy distribution of the wide laser ben empirical values and theoretical values are compared and discussed. To improve the efficiency of the wide laser beam optical system, methods are suggested by the optical theories. For larger area processing like turbine blade, drawing blade, cold roller and guide plate, optimal overlapping locations have been calculated and analyzed by geometric and optical theories.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.57-60
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• 2008

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 single cells 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 after pre-treatment process, 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.

• Korean Journal of Microbiology
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• v.23 no.2
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• pp.90-100
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• 1985

The present study was designed to investigate cellular regulation of phosphate metabolism between catabolically repressed and derepressed states in yeast (Saccharomyces uvarum). The activities of various phospatases and the contents of phosphate compounds were detected according to the culture phase and various phosphate concentrations. As the results, Saccharomyces uvarum derepressed many phosphate metabolizing enzymes such as alkaline phosphatase, acid phosphatase and ATPase more than ten fold simultaneously during catabolic repression (phospgate and sugar starvation). At the same state, the amounts of orthophosphate, nucleotidic labile phosphate and acid soluble polypgosphate were increased, compared to basal levels of normally cultivated cells. $Mg^{++}-stimulated$ type among all phospatases was appeared to have most of the enzyme activity. It could be postulated that $K^+ -stimulated$ alkaline phosphatase was directly or indirectly correlated with the synthesis of acid insoluble polyphosphate $Mg^{++}-stimulated$ phosphatase with the degradation of polyphosphates. In case of cultivation in the medium supplemented with sugar and phosphate (catabolic derepression), phospgatase activities except for alkaline phosphatase were decreased rapidly through the progressive batch culture, After 12 hrs culture, at early exponential phase, the cellular accumulation of acid insoluble polyphosphate increased about 5 fold, compared to those of the starved cells. Under catabolic repression, it could be postulated that intracellular phosphate metabolism was regulated by derepressions of phosphatases. The function of polyphosphate system was shown to compensate the ATP/ADP system as phosphate donor and energy source especially during catabolic repression.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.590-595
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• 2004

The shape and size variations of the nanopatterns produced on a positive photoresist using a near-field scanning optical microscope(NSOM) are investigated with respect to the process variables. A cantilever type nanoprobe having a 100nm aperture at the apex of the pyramidal tip is used with the NSOM and a He-Cd laser at a wavelength of 442nm as the illumination source. Patterning characteristics are examined for different laser beam power at the entrance side of the aperture( $P_{in}$ ), scan speed of the piezo stage(V), repeated scanning over the same pattern, and operation modes of the NSOM(DC and AC modes). The pattern size remained almost the same for equal linear energy density. Pattern size decreased for lower laser beam power and greater scan speed, leading to a minimum pattern width of around 50nm at $P_{in}$ =1.2$\mu$W and V=12$\mu$m/. Direct writing of an arbitrary pattern with a line width of about 150nm was demonstrated to verify the feasibility of this technique for nanomask fabrication. Application on high-density data storage using azopolymer is discussed at the end.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.10
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• pp.667-673
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• 2017

We investigated the temperature uniformity in an anode-supported solid oxide fuel cell, using the open source computational fluid dynamics (CFD) toolbox, OpenFOAM. Numerical simulation was performed in three different flow paths, i.e., co-flow, counter-flow, and cross-flow paths. Gas flow in a porous electrode was calculated using effective diffusivity while considering the effect of interconnect rib. A lumped internal resistance model derived from a semi-empirical correlation was implemented for the calculation of electrochemical reaction. The result showed that the counter-flow path displayed the most uniform temperature distribution.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.686-695
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• 1993

A flywheel-type, inclined axis chopper for small-area rice and livestock farmers, has been developed at IRRI Agricultural Engineering, The prototype is belt-driven by a 2.6kW engine and uses four angled blades rotating below a fixed counteredge. Manual feeding is facilitated by a convenient spout presenting the crop to the inclined blade housing and also suction created by the rotating blades . The distance between the rotating blades and the bottom of the housing determines the length of chops, set here for 25 cm. The unit would cost $200 without the engine. Tests with napier grass, corn stalks , and rice straw showed satisfactory performance within the acceptable clearance, speed and moisture content ranges of the material presented. Highest capacities were 1186, 1148 and 744kg/hr for napier grass, corn stalks and rice straw, respectively. Corn stalks required the highest power demand at 2.3kW engine would be adequate as power source. The chopper performance was comparable to higher cost commercial chippers in terms of capacity and specific energy.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.11
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• pp.1609-1618
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• 2000

Thin stillage and distillers' grains are byproducts remaining after alcohol distillation from a fermented cereal grain mash. Both byproducts are used as energy and protein sources for ruminants. Due to its liquid nature, more than 50% of thin stillage bypasses the rumen. Thin stillage can be fed alone or in combination with distillers' grains. However, a better utilization by beef cattle is anticipated when thin stillage replaces water as a fluid source. Ruminal undegraded protein content of distillers' grains is greatly affected by type of cereal grain and by drying. Corn distillers' grains have a higher ruminal undegraded protein content than wheat distillers' grains while dried distillers' grains have a higher ruminal undegraded protein content than the wet distillers' grains. Wet and dried distillers' grains can replace up to 50% of corn grain in beef cattle diets without affecting animal performance. The estimated NEg of corn distillers' grains for beef cattle ranges from 100 to 169% of that of corn. In general, wet corn distillers' grains have a higher NEg value than dried corn distillers' grains and the addition of thin stillage improves the NEg of distillers' grains. Improved performance of ruminats fed distillers' byproducts can be attributed to high digestible fiber content, improved rumen environment and a shift in organic matter digestion from the rumen to the small intestine.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.696-698
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• 2001

This paper considers the research of the hybrid interrupter which adopts both rotating arc and thermal expansion technology. The operating principle of this device depends on rapid arc rotation due to the magnetic field created by the fault current through a coil which is mounted on contacts and also relies on the principle of thermal expansion created by arc energy in extinguishing chamber and finally causes pressure rise in expansion volume. To develope this type of interrupter, we introduced analytical analysis including electromagnetic and arc fluid simulation and experimental analysis including construction of current source generation facility and arc behavior measurements. In this research, the principle of the interrupting techniques are given and analytical and experimental results of hybrid interrupter which is developed by new technology is introduced.