• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.83-87
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• 2005

In this paper, the combustion characteristics of a hybrid propulsion system were studied with various L/D(length vs diameter) ratio of the single port type solid fuel. Experiments of L/D ratio change were performed for 2 cases with the fixed grain port diameter and fuel length respectively. For the First case, results show that there are no large variation for regression rates as the L/D ratio changes. And as the L/D ratio increases, the O/F ratio and thrust tends to increase. For the Second case, there are no large change for O/F ratio and thrust as L/D ratio changes. On the other hand, as the L/D ratio decreases, only the regression rate tends to increase.

• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.900-906
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• 2004

Solid oxide fuel cells have a limitation in their low-temperature application due to the low ionic conductivity of electrolyte materials and difficulties in thin film formation on porous gas diffusion layer. These problems can be solved by improvement of ionic conductivity through controlled nanostructure of electrolyte and adopting nanoporous electrodes as substrates which have homogeneous submicron pore size and highly flattened surface. In this study, ultra-thin oxide films having submicron thickness without gas leakage are deposited on nanoporous substrates. By oxidation of metal thin films deposited onto nanoporous anodic alumina substrates with pore size of $20nm{\sim}200nm$ using dc-magnetron sputtering at room temperature, ultra-thin and dense ionic conducting oxide films with submicron thickness are realized. The specific material properties of the thin films including gas permeation, grain/gran boundaries formation, change of crystalline structure/microstructure by phase transition are investigated for optimization of ultra thin film deposition process.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.71-78
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• 2007

An experimental investigation was conducted to clarify the combustion characteristics of Polyethylene-GOX(PE-GOX) hybrid motor using a single-port fuel grain configuration. Data from the experiments were analyzed to evaluate the length-averaged regression rate of PE-GOX propellants. Based on the existing theories, the empirical regression rate formulas provided from Marxman[3,4] and Altman[14] showed good concordance with the PE-GOX experiments. The accuracy of the regression rate was then evaluated and compared with the measured one. As a result, Marxman's model was somewhat more precise than Altman's model in these experiments. Moreover, the consideration of the empirical regression rate showed that O/F ratio has minor variation due to the quasi constant inflow of the fuel during motor firing.

• Journal of the Korean Ceramic Society
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• v.45 no.4
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• pp.245-249
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• 2008

The SiC and ZrC are critical and essential materials in TRISO coated fuel particles since they act as protective layers against diffusion of metallic and gaseous fission products and provides mechanical strength for the fuel particle. However, SiC and ZrC have critical disadvantage that SiC loses chemical integrity by thermal dissociation at high temperature and mechanical properties of ZrC are weaker than SiC. In order to complement these problems, we made new combinations of the coating layers that the ZrC layers composed of SiC. In this study, after Silicon carbide(SiC) were chemically vapor deposited on graphite substrate, Zirconium carbide(ZrC) were deposited on SiC/graphite substrate by using Zr reaction technology with Zr sponge materials. The different morphologies of sub-deposited SiC layers were correlated with microstructure, chemical composition and mechanical properties of deposited ZrC films. Relationships between deposition pressure and microstructure of deposited ZrC films were discussed. The deposited ZrC films on SiC of faceted structure with smaller grain size has better mechanical properties than deposited ZrC on another structure due to surface growth trend and microstructure of sub-deposited layer.

• Journal of the Korean Ceramic Society
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• v.44 no.3 s.298
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• pp.182-187
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• 2007

10 mol% $Gd_{2}O_{3}-CeO_{2}$ powder was sintered by microwave in a 2.45 GHz multimode cavity to develop a dense electrolyte layer for intermediate temperature solid oxide fuel cells (IT-SOFCs). Samples were sintered from $1100^{\circ}C$ upto $1500^{\circ}C$ by $50^{\circ}C$ difference and kept for 10 min and 30 min at the maximum temperature respectively. Theoretical density of the sample sintered at $1200^{\circ}C$ for 10 min was 95.4% and increased gradually upto 99% in the sample sintered at $1500^{\circ}C$ for 30 min. All of sintered samples showed very fine microstructures and the maximum average grain size of the sintered sample at $1500^{\circ}C$ for 30 min was $(0.87{\pm}0.42){\mu}m$. Ionic conductvity of the samples were measured by DC 4 probe method.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1317-1321
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• 2007

Aluminized steel sheet that Al coated on low carbon steel has a excellent heat resistance, thermal reflection and corrosion resistance. It has applied to fuel tank, automotive exhaust systems, etc. Laser weldability of the aluminized steel for the full penetration welding will be described in this paper. We focused on the effect of Al coating conditions on weld strength. For these objectives, aluminized steel sheets that has various thickness and coating weight were prepared for laser welding. And then, tensile-shear and hardness test were carried out. At that same time, Al content mixed in weld after laser welding was evaluated and investigated a correlation between the mixed Al and mechanical properties. Besides, as removing partially coating layer, weldability has been investigated according to position of coating layer. As a result of this study, as increasing Al content in weld, tensile-shear strength was decreased. Also it was identified that Al of coating layer caused grain growth.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.980-983
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• 2003

The preparation of ZnS:Mn,Cl phosphor has been carried out by combustion method. Manganese nitrate was decomposed with an organic fuel at $500^{\circ}C$ to give fine sized crystallites in presence of alkali metal halides at a lower temperature than the conventional synthesis. The phosphors thus obtained were then heated at 900 to $1200^{\circ}C$ in an inert atmosphere, for 3hours to get better luminescent properties. The phosphors were prepared at different temperatures and at different doping concentrations of manganese to determine the optimal conditions for synthesizing the phosphors with superior optical properties. Scanning electron microscopy (SEM) investigations have been carried out to observe the particle morphology and the grain size. Powder X-ray diffraction(XRD) was also performed to characterize the phosphors.

• Journal of Plant Biotechnology
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• v.34 no.2
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• pp.103-109
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• 2007

The increasing industrialization of the world has led to precipitous rise for the demand of petroleum-based fuels. The world is presently confronted with the twin crises of fossil fuel depletion and environmental pollution. The search for alternative fuels, which promise a harmonious correlation with sustainable development, energy conservation, efficiency and environmental preservation, has become highly pronounced in the present. Bioenergy is playing an increasingly important role as an alternative and renewable source of energy. Use of Bioenergy has several potential environmental advantages. The most important perhaps is reduction in life cycle greenhouse gases emissions relatives petroleum fuels, since bioenergy is derived from plants which convert Carbon dioxide ($CO_{2}$) into Carbohydrates in their growth. Bioenergy includes solid biomass, biomas and liquid bio-fuels which are fuels derived from crop plants, and include biomass that's directly burned. The two most important bio liquid fuels today are bioethanol from fermenting grain, grass, straw or wood, and biodiesel from plant seed oil.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.5
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• pp.719-725
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• 2004

Mesquite or Vilayati babul (Prosopis juliflora) is a drought resistant, evergreen, spiny tree with drooping branches and a deep laterally spreading root system. It grows in semi-arid and arid tracts of tropical and sub-tropical regions of the world and is spreading because the leaves are unpalatable and animals do not digest its seed. The mesquite has become a major nuisance; cutting or pruning its branches to form a canopy would provide shade for travelers, aid harvesting of pods, as well as make available wood for fuel. An average plant starts fruiting by 3-4 years of age and yields annually 10-50 kg pods/ tree, which can be collected from May-June and September-October. Availability of pods worldwide is estimated to be about 2-4 million metric tonnes. Ripe pods are highly palatable; on dry matter basis they contain 12% crude protein, 15% free sugar, a moderate level of digestible crude protein (7% DCP) with a high level of energy (75% TDN). The pods contain low tannin levels below those toxic to animals. Seeds contain 31-37% protein; pods should be finely ground before feeding to facilitate utilization of the seeds. Mesquite pods could replace costlier feed ingredients such as grain and bran contributing 10-50% of the diet. Phosphorus supplements need to be added when mesquite pod, exceeds 20% of animals' diet.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.11.2-11.2
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• 2010

Photovoltaic devices are promising candidates as affordable and large-area renewable energy sources, which can replace the fossil-fuel-based resources. Especially, thin film solar cells have attracted increasing research attention, since they have a great advantage of low production cost. From the physical point of view, the photovoltaic devices can provide us interesting questions, how to enhance the light absorption and the carrier collection efficiency. A lot of approaches would be possible to address these issues. We have focused on two major topics relevant to photovoltaic device physics; (1) light management using surface plasmons and (2) junction characterizations aiming at proper interface engineering. Regarding the first topic, we have investigated the influences of Ag under-layer morphology on optical properties of ZnO thin films. The experimental results suggested that coupling between the surface plasmon polaritons at the ZnO/Ag interface and excitons in ZnO should play important roles in reflectivity of the ZnO/Ag thin films, which are widely used back reflector structures in thin film solar cells. For the second topic, we have carried out scanning probe microscopy studies of Schottky junctions consisting of photovoltaic materials. Such a research is very helpful to understand the correlation between the defects (e.g., grain boundaries) and local electrical properties. We will introduce some of the recent experimental results and discuss the physical significance.