• Journal of Korean Society of Environmental Engineers
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• v.37 no.11
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• pp.636-641
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• 2015

Waste energy conversion to SRF (Solid Refuse Fuel) has the effects not alternative fossil fuel usage but also the reduction of greenhouse gas. But the direct burning of the SRF including a plastic waste generates air pollution problem like soot, dioxin, etc. so that an application of pyrolysis and gasification treatment should be needed. The purpose of this study is to supply a basic thermal data of the pyrolysis gasification characteristics in the plastic-rich SRF which are needed for developing the novel pyrolyser or gasifier. To do so, a bench-scale test rig was newly engineered, and then experiments were achieved for the production characteristics of gas, tar, and char. While SRF sample, gasification air ratio, holding time changed as 2 g, 0.691, 32 min respectively, the $H_2$ 1.36%, $CH_4$ 2.18%, CO 1.88%, $Cl_2$ 15.9 ppm, HCl 6.4 ppm were composed. Also light tar benzene $4.03g/m^3$, naphthalene $0.39g/m^3$, anthracene $0.11g/m^3$, pyrene $0.06g/m^3$, gravimetric tar $18g/m^3$, and char 0.29 g was formed.

• Clean Technology
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• v.23 no.1
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• pp.73-79
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• 2017

Recently usage of biomass is increased in pulverized coal power plants for reduction of $CO_2$ emission. Many problems arise when thermal share of the biomass is increased, and milling of the biomasses is one of the most important problems due to their low grindability when existing coal pulverizer is used. Grindability of coal can be measured through the HGI (Hardgrove grindability index) equipment as a standard, but method of measuring biomass grindability has not been established yet. In this study, grinding experiment of coal and biomass was performed using a lab-scale ball mill. One type of coal (Adaro coal) and six biomasses (wood pellet (WP), empty fruit bunch (EFB), palm kernel shell (PKS), walnut shell (WS), torrefied wood chip (TBC) and torrefied wood pellet (TWP)) were used in the experiment. Particle size distributions of the fuels were measured after being milled in various pulverization times. Pulverization characteristics were evaluated by portion of particles under the diameter of $75{\mu}m$. As a result, about 70% of the TBC and TWP were observed to be pulverized to sizes of under $75{\mu}m$, which implies that they can be used as alternative biomass fuels without modification of the existing mill. Other biomass was observed to have low grindability compared with torrefied biomass. Power consumption of the mill for various fuels was measured as well, and the results show that lower power was consumed for torrefied biomasses. This result can be used for characterization of biomass as an alternative fuel for pulverized coal power plants.

• Journal of the Korean Electrochemical Society
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• v.12 no.3
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• pp.203-218
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• 2009

The development of lithium-ion battery (LIB) technologies and their application in the field of large-scale power sources, such as electric vehicles (EVs), hybrid EVs, and plug-in EVs require enhanced reliability and superior safety. The main components of LIBs should withstand to the inevitable heating of batteries during high current flow. Carbonate solvents that contribute to the dissociation of lithium salts are volatile and potentially combustible and can lead to the thermal runaway of batteries at any abuse conditions. Recently, an interest in nonflammable materials is greatly growing as a means for improving battery safety. In this review paper, novel approaches are described for designing highly safe electrolytes in detail. Non-flammability of liquid electrolytes and battery safety can be achieved by replacing flammable organic solvents with thermally resistive materials such as flame-retardants, fluorinated organic solvents, and ionic liquids.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1119-1127
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• 2010

In this paper, the design and nonlinear simulation of a multistable electromagnetic microactuator, which provides four stable equilibrium positions within its operating range, have been discussed. Quadstable actuator motion has been made possible by using both X- and Y-directional bistable structures with snapping curved beams. Two pairs of the curved beams are attached to an inner frame in both X- and Y-directions to realize independent bistable behavior in each direction. For the actuation of the actuator at the micrometer scale, an electromagnetic actuation method in which Lorentz force is taken into consideration was used. By using this method, micrometer-stroke quadstability in a plane parallel to a substrate was possible. The feasibility of designing an actuator that can realize quadstable motion by using the electromagnetic actuation method has been thoroughly clarified by performing nonlinear static and dynamic analyses and electrothermal coupled-field analysis of the multistable microactuator.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.5
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• pp.389-397
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• 2014

An absorption chiller-heater using only a natural refrigerant hardly causes any environmental pollution. In an absorption chiller-heater, the performance of its high-temperature generator, which uses exhaust gases, is essential to achieving superior system performance. To investigate the performance of such a high-temperature generator, a laboratory-scale high-temperature generator working with exhaust gases was designed and tested. Changes in the performance of the high-temperature generator as a function of inlet conditions of the absorbing solution, such as air inlet temperature and mass flow, were investigated. It was observed that when the air mass flow rate ratio was increased from 80% to 120%, the heat capacity was increased by 30%, 33%, 34%, and 37%, respectively. Additionally, when the air inlet temperature was elevated from $170^{\circ}C$ to $210^{\circ}C$ for absorption solution concentrations of 56%, 55%, 545, and 53%, the heat capacity increased by 140%, 160%, 220%, and 224%, respectively.

• Fire Science and Engineering
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• v.24 no.5
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• pp.32-38
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• 2010

Multi-dimensional fire dynamics were studied numerically with the change in ventilation conditions in a full-scale ISO 9705 room. Fire Dynamic Simulator (FDS) was used for the identical conditions conducted in previous experiments. Flow rate and doorway width were changed to create over-ventilated fire (OVF) and under-ventilated fire (UVF). From the numerical simulation, it was found that the internal flow pattern rotated in the opposite direction for the UVF relative to the OVF so that a portion of products recirculated to the inside of compartment. Significant change in flow pattern with ventilation conditions may affect changes in the complex process of CO and soot formation inside the compartment due to increase in the residence time of high-temperature products. The fire behavior in the UVF created complex 3D characteristics of species distribution as well as thermal and flow structures. In particular, additional burning near the side wall inside the compartment significantly affected the flow pattern and CO production. The distribution of CO inside the compartment was explained with 3D $O_2$ distribution and flow patterns. It was observed that gas sampling at local positions in the upper layer were insufficient to completely characterize the internal structure of the compartment fire.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.187-194
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• 2012

The strength of particle-reinforced metal matrix composites is, in general, known to be increased by the geometrically necessary dislocations punched around a particle that form during cooling after consolidation because of coefficient of thermal expansion (CTE) mismatch between the particle and the matrix. An additional strength increase may also be observed, since another type of geometrically necessary dislocation can be formed during extensive deformation as a result of the strain gradient plasticity due to the elastic-plastic mismatch between the particle and the matrix. In this paper, the magnitudes of these two types of dislocations are calculated based on the dislocation plasticity. The dislocations are then converted to the respective strengths and allocated hierarchically to the matrix around the particle in the axisymmetric finite-element unit cell model. The proposed method is shown to be very effective by performing finite-element strength analysis of $SiC_p$/Al2124-T4 composites that included ductile failure in the matrix and particlematrix decohesion. The predicted results for different particle sizes and volume fractions show that the length scale effect of the particle size obviously affects the strength and failure behavior of the particle-reinforced metal matrix composites.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.362-362
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• 2014

Atomic layer deposition (ALD) can be regarded as a special variation of the chemical vapor deposition method for reducing film thickness. ALD is based on sequential self-limiting reactions from the gas phase to produce thin films and over-layers in the nanometer scale with perfect conformality and process controllability. These characteristics make ALD an important film deposition technique for nanoelectronics. Tantalum pentoxide ($Ta_2O_5$) has a number of applications in optics and electronics due to its superior properties, such as thermal and chemical stability, high refractive index (>2.0), low absorption in near-UV to IR regions, and high-k. In particular, the dielectric constant of amorphous $Ta_2O_5$ is typically close to 25. Accordingly, $Ta_2O_5$ has been extensively studied in various electronics such as metal oxide semiconductor field-effect transistors (FET), organic FET, dynamic random access memories (RAM), resistance RAM, etc. In this experiment, the variations of chemical and interfacial state during the growth of $Ta_2O_5$ films on the Si substrate by ALD was investigated using in-situ synchrotron radiation photoemission spectroscopy. A newly synthesized liquid precursor $Ta(N^tBu)(dmamp)_2$ Me was used as the metal precursor, with Ar as a purging gas and $H_2O$ as the oxidant source. The core-level spectra of Si 2p, Ta 4f, and O 1s revealed that Ta suboxide and Si dioxide were formed at the initial stages of $Ta_2O_5$ growth. However, the Ta suboxide states almost disappeared as the ALD cycles progressed. Consequently, the $Ta^{5+}$ state, which corresponds with the stoichiometric $Ta_2O_5$, only appeared after 4.0 cycles. Additionally, tantalum silicide was not detected at the interfacial states between $Ta_2O_5$ and Si. The measured valence band offset value between $Ta_2O_5$ and the Si substrate was 3.08 eV after 2.5 cycles.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.409-409
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• 2014

Recently hexagonal boron nitride (h-BN), III-V compound of boron and nitrogen with strong covalent $sp^2$ bond, is a 2 dimensional insulating material with a large direct band gap up to 6 eV. Its outstanding properties such as strong mechanical strength, high thermal conductivity, and chemical stability have been reported to be similar or superior to graphene. Because of these excellent properties, h-BN can potentially be used for variety of applications such as dielectric layer, deep UV optoelectronic device, and protective transparent substrate. Ultra flat and charge impurity-free surface of h-BN is also an ideal substrate to maintain electrical properties of 2 dimensional materials such as graphene. To synthesize a single or a few layered h-BN, chemical vapor deposition method (CVD) has been widely used by using an ammonia borane as a precursor. Ammonia borane decomposes into hydrogen (gas), monomeric aminoborane (solid), and borazine (gas) that is used for growing h-BN layer. However, very active monomeric aminoborane forms polymeric aminoborane nanoparticles that are white non-crystalline BN nanoparticles of 50~100 nm in diameter. The presence of these BN nanoparticles following the synthesis has been hampering the implementation of h-BN to various applications. Therefore, it is quite important to grow a clean and high quality h-BN layer free of BN particles without having to introduce complicated process steps. We have demonstrated a synthesis of a high quality h-BN monolayer free of BN nanoparticles in wafer-scale size of $7{\times}7cm^2$ by using CVD method incorporating a simple filter system. The measured results have shown that the filter can effectively remove BN nanoparticles by restricting them from reaching to Cu substrate. Layer thickness of about 0.48 nm measured by AFM, a Raman shift of $1,371{\sim}1,372cm^{-1}$ measured by micro Raman spectroscopy along with optical band gap of 6.06 eV estimated from UV-Vis Spectrophotometer confirm the formation of monolayer h-BN. Quantitative XPS analysis for the ratio of boron and nitrogen and CS-corrected HRTEM image of atomic resolution hexagonal lattices indicate a high quality stoichiometric h-BN. The method presented here provides a promising technique for the synthesis of high quality monolayer h-BN free of BN nanoparticles.

• KSBB Journal
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• v.27 no.6
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• pp.352-360
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• 2012

Bacillus clausii I-52 which produced SDS- and $H_2O_2$-tolerant extracellular alkaline protease (BCAP) was isolated from heavily polluted tidal mud flat of West Sea in Incheon, Korea and stable strain (transformant C5) of B. clausii I-52 harboring another copy of BCAP gene in the chromosome was developed using the chromosome integration vector, pHPS9-fuBCAP. When investigated the production of BCAP using B. clausii transformant C5 through pilot-scale submerged fermentation (500 L) at $37^{\circ}C$ for 30 h with an aeration rate of 1 vvm and agitation rate of 250 rpm, protease yield of approximately 105,700 U/mL was achieved using an optimized medium (soybean meal 2%, wheat flour 1%, sodium citrate 0.5%, $K_2HPO_4$ 0.4%, $Na_2HPO_4$ 0.1%, NaCl 0.4%, $MgSO_4{\cdot}7H_2O$ 0.01%, $FeSO_4{\cdot}7H_2O$ 0.05%, liquid maltose 2.5%, $Na_2CO_3$ 0.6%). The enzyme stability of BCAP was increased by addition of polyols (10%, v/v) and also, the stabilities of BCAP towards not only the thermal-induced inactivation at $50^{\circ}C$ but also the SDS and $H_2O_2$-induced inactivation at $50^{\circ}C$ were enhanced. Among the polyols examined, the best result was obtained with propylene glycol (10%, v/v). The BCAP supplemented with propylene glycol exhibited extreme stability against not only the detergent components such as ${\alpha}$-orephin sulfonate (AOS) and zeolite but also the commercial detergent preparations. The granulized enzyme of BCAP was prepared with approximately 1,310,000 U/g of granule. Wash performance analysis using EMPA test fabrics revealed that BCAP granule exhibited high efficiency for removal of protein stains in the presence of anionic surfactants as well as bleaching agents. When compared to Savinase 6T$^{(R)}$ and Everlase 6T$^{(R)}$ manufactured by Novozymes, BCAP under this study probably showed similar or higher efficiency for the removal of protein stains. These results suggest that the alkaline protease produced from B. clausii transformant C5 showing high stability against detergents and high wash performance has significant potential and a promising candidate for use as a detergent additive.