• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.4
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• pp.178-185
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• 2007

A study is improvement of power and emission in a inline-pump Dr diesel engine by using Dimethyl ether Fuel. Dimethyl ether (DME) is an oxygenated fuel with a cetane number higher than that of diesel oil. It meets the ULEV emission regulation and reduces the smoke to almost zero when used in a diesel engine. But NOx emission is almost same and CO, THC emissions are lower than that of diesel engine. The emissions aren't satisfied the stronger emission regulation in the further. Generally DOC (Diesel Oxidation Catalyst) is used to reduce CO & THC emissions and EGR (Exhaust Gas Recirculation) system is used to reduce NOx emission. Test results showed that the torque and the power with DME were almost same as those of pure diesel oil, but the brake thermal efficiency increased a little. also the BSEC (Brake Specific Energy Consumption) with DME was similar that of diesel. The test results showed that the DOC was the vary effective method to reduce the CO emission in case of Dimethyl Ether Fuel in diesel engine. But, THC emission is showed a little reduction rates. Also EGR system was the very effective method to reduce the NOx emission in case of Dimethyl Ether Fuel in diesel engine.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.725-728
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• 2002

A series of fabric filters including P-84, Nomex and PTFE were coated with a commercial $V_2O_5/TiO_2$ catalyst as an effort to develop a functional fabric filter of simultaneous removal of dust and NOx. The coating methods employed are sol-gel coating method, spray coating method and dip coating method, and the effects of coating method on NOx removal performance of functional fabric filter were investigated. Experimental conditions are as follows: the temperatures of $100-250^{\circ}C$ which are the normal operating temperature range of fabric filters, the space velocity of $5,000hr^{-1}$, the oxygen concentration of 6%, and the $NH_3/NO$ ratio of 1.0. Results showed that the sol-gel coating method gave the best NOx removal performance mainly due to its ability in controlling the amount of catalyst and uniform coating.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.989-996
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• 2011

An understanding of the concentrated solar flux is critical for the analysis and design of solar-energy-utilization systems. The current work focuses on the development of an algorithm that uses the Monte Carlo ray-tracing method with excellent flexibility and expandability; this method considers both solar limb darkening and the surface slope error of reflectors, thereby analyzing the solar flux. A comparison of the modeling results with measurements at the solar furnace in Korea Institute of Energy Research (KIER) show good agreement within a measurement uncertainty of 10%. The model evaluates the concentration performance of the KIER solar furnace with a tracking accuracy of 2 mrad and a maximum attainable concentration ratio of 4400 sun. Flux variations according to measurement position and flux distributions depending on acceptance angles provide detailed information for the design of chemical reactors or secondary concentrators.

• Journal of the Korean Electrochemical Society
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• v.14 no.1
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• pp.9-15
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• 2011

The composite membranes comprising of sulfonated polymers as matrix and ionic liquids as ion-conducting medium in replacement of water are studied to investigate the effect of annealing of the sulfonated polymers. The polymeric membranes are prepared on recast Nafion containing the ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate ($EMIBF_4$). The composite membranes are characterized by thermogravitational analyses, ion conductivity and small-angle X-ray scattering. The composite membranes annealed at $190^{\circ}C$ for 2 h after the fixed drying step showed better ionic conductivity, but no significant increase in thermal stability. The mean Bragg distance between the ionic clusters, which is reflected in the position of the ionomer peak (small-angle scattering maximum), is larger in the annealed composite membranes containing $EMIBF_4$ than the non-annealed ones. It might have been explained to be due to the different level of ion-clustering ability of the hydrophilic parts (i.e., sulfonic acid groups) in the non- and annealed polymer matrix. In addition, the ionic conductivity of the membranes shows higher for the annealed composite membranes containing $EMIBF_4$. It can be concluded that the annealing of the composite membranes containing ionic liquids due to an increase in ion-clustering ability is able to bring about the enhancement of ionic conductivity suitable for potential use in proton exchange membrane fuel cells (PEMFCs) at medium temperatures ($150-200^{\circ}C$) in the absence of external humidification.

• Journal of the Korean Ceramic Society
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• v.40 no.3
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• pp.317-321
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• 2003

The grain-boundary microcracking materials in the system A1$_2$Ti $O_{5}$ -ZrTi $O_4$(ZAT) is influenced by the thermal expansion anisotropy. The range of ZAT compositions investigated had showed very low thermal expansions of 0.3~1.3$\times$10$^{-6}$K compared to 8.29$\times$10$^{-6}$K of pure ZrTi $O_4$and 0.68$\times$10$^{-6}$K of polycrystalline A1$_2$Ti $O_{5}$ , respectively, compared with the theoretical thermal expansion coefficient for a single crystal of A1$_2$Ti $O_{5}$ , 9.70$\times$10$^{-6}$K. The low thermal expansion and microcraking temperature are apparently due to a combination of thermal contraction and expansion caused by the large thermal expansion anisotropy of the crystal axes of the A1$_2$Ti $O_{5}$ phase.

• Economic and Environmental Geology
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• v.24 no.3
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• pp.261-276
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• 1991

The main aspect of this study are to clarify igneous activity of igneous rocks, which is a member of various intrusives and volcanics exposed in Naju-Namchang area of southern central zone of Ogcheon Geosynclinal Belt, southern part of Youngdong-Kwangju depression zone of tectonic provinces in Korea. Naju-Namchang area are subdivided into three rock belts based on occuring of Cretaceous granites. Three rock belts consist of foliated granites, Jurassic granites and Cretaceous granites in central granitic rock belt (C-C), and acidic tuff and lavas in northwest volcanic rock belt(C-NW) and southeast volcanic rock belt(C-SE). Chemical composition of these igneous rocks show mostly similar trend to the Daly's values on Harker diagram and correspond to VAG + Syn-COLG region on Pearce's discrimination diagram. These igneous rocks vary wide range in total REE amount(37.4-221.3ppm) characterized by enriched LREE content and steep negative slope in Eu(-) anomaly. It is concluded each synchronous granites which composed of serveral rock facies is considered to formed by differentiation of co-magma at continental margin, and igneous activity of study area are two more Pre-Cambrian Orogenies, Songrim Disturbance, Daebo Orogeny and Bulkuksa Disturbance.

• Membrane Journal
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• v.29 no.1
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• pp.61-65
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• 2019

Anisotropic particles have been issued in various fields due to their unique physical properties. Herein, a novel dynamic phase separation method (DPS) is introduced to fabricate anisotropic acorn-like nanoparticles. DPS consists of two dynamic conditions; solvent evaporation and nonsolvent induced precipitation. The bottom layer is controlled by feeding the water as a non-solvent diluent, and the phase separation of the upper layer relies on the diffusion and evaporation of a volatile good solvent. At this condition, the acorn-like particles were fabricated. Under a closed box filled with water (spontaneous phase separation), monodisperse polystyrene (PS) particles were synthesized. At the coexistence between DPS and spontaneous phase separation, the sizes of cap and particle were changed. Also, the volume of PS solutions influences on the particle shape. Since the unique structures could be utilized into various applications, if advanced techniques such as membrane-based controlled water feeding is developed, monodisperse acorn-like particles could be tuned.

• Journal of Ceramic Processing Research
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• v.21 no.2
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• pp.170-191
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• 2020

As interest in environmental pollution has increased, research in the field of filtration has been concentrated. While various types of filters have been developed, research on nanomaterial filtration has been limited. Since then, the development of new materials such as carbon nanotubes (CNTs) has accelerated the study of new filters. Especially, CNTs have been among the most attractive materials ever synthesized for the development of nano-technologies. However, there are fundamental technical problems to be solved the development of new CNT composites. One of these problems is the development of a CNTs filter with excellent adsorption behavior and a filter that is capable of filtering a specific substance. In addition, it is necessary to develop a technology to increase the uniform distribution of CNTs, and to reduce the high processing cost of CNT composite production. In general, the chemical pathways for the production of CNTs include hydrocarbon gases, such as methane (CH4) and acetylene (C2H2), through metal nanoparticle catalysts. However, nano-metal particles have a strong coagulation phenomenon at high temperature by catalytic chemical vapor deposition (CCVD) method. In this review, attempts were made by applying three different reaction techniques to form CNTs on biomorphic carbon materials (BCM) coated with catalyst materials to control the shape and size of CNTs. Hierarchical carbon substrates with pore size of 100 ~ 300 ㎛ were developed using carbonization reaction. Linde type A (LTA) zeolite, silicalite-1, and mesoporous SiO2 template crystals were simultaneously synthesized and coated on the BCM by an in-situ hydrothermal process to synthesize high-yield CNTs composites.

• Clean Technology
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• v.30 no.2
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• pp.134-144
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• 2024

In this study, the mechanical stability of red mud was improved for its commercial use as a catalyst to effectively decompose HFC-134a, one of the seven major greenhouse gases. Red mud is an industrial waste discharged from aluminum production, but it can be used for the decomposition of HFC-134a. Red mud can be manufactured into a catalyst via the crushing-preparative-compression molding-firing process, and it is possible to improve the catalyst performance and secure mechanical stability through calcination. In order to determine the optimal heat treatment conditions, pellet-shaped compressed red mud samples were calcined at 300, 600, 800 ℃ using a muffle furnace for 5 hours. The mechanical stability was confirmed by the weight loss rate before and after ultra-sonication after the catalyst was immersed in distilled water. The catalyst calcined at 800 ℃ (RM 800) was found to have the best mechanical stability as well as the most catalytic activity. The catalyst performance and durability tests that were performed for 100 hours using the RM 800 catalyst showed thatmore than 99% of 1 mol% HFC-134a was degraded at 650 ℃, and no degradation in catalytic activity was observed. XRD analysis showed tri-calcium aluminate and gehlenite crystalline phases, which enhance mechanical strength and catalytic activity due to the interaction of Ca, Si, and Al after heat treatment at 800 ℃. SEM/EDS analysis of the durability tested catalysts showed no losses in active substances or shape changes due to HFC-134a abasement. Through this research, it is expected that red mud can be commercialized as a catalyst for waste refrigerant treatment due to its high economic feasibility, high decomposition efficiency and mechanical stability.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.3
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• pp.147-152
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• 2002

When a liquid is supplied through a nozzle onto a relatively non-wetting inclined solid surface, a narrow rivulet forms. There exist several regimes of rivulet flow depending on various flow conditions. In this paper, the fundamental mechanism behind the transition of a linear rivulet to a droplet flow is investigated. The experiments show that the droplet flow emerges due to the necking of a liquid thread near the nozzle. Based on the observation, it is argued that when the retraction velocity of a liquid thread exceeds its axial velocity, the bifurcation of the liquid thread occurs, and this argument is experimentally verified.