Time filter

Source Type

Ku K.H.,Korea Advanced Institute of Science and Technology | Shin J.M.,Korea Advanced Institute of Science and Technology | Kim M.P.,Korea Advanced Institute of Science and Technology | Lee C.-H.,Korea Advanced Institute of Science and Technology | And 4 more authors.
Journal of the American Chemical Society | Year: 2014

The tuning of interfacial properties at selective and desired locations on the particles is of great importance to create the novel structured particles by breaking the symmetry of their surface property. Herein, a dramatic transition of both the external shape and internal morphology of the particles of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) was induced by precise positioning of size-controlled Au nanoparticle surfactants (Au NPs). The size-dependent assembly of the Au NPs was localized preferentially at the interface between the P4VP domain at the particle surface and the surrounding water, which generated a balanced interfacial interaction between two different PS/P4VP domains of the BCP particles and water, producing unique convex lens-shaped BCP particles. In addition, the neutralized interfacial interaction, in combination with the directionality of the solvent-induced ordering of the BCP domains from the interface of the particle/water, generated defect-free, vertically ordered porous channels within the particles. The mechanism for the formation of these novel nanostructures was investigated systemically by varying the size and the volume fraction of the Au NPs. Furthermore, these convex lens-shaped particles with highly ordered channels can be used as a microlens, in which the light can be concentrated toward the focal point with enhanced near-field signals. And, these particles can possess additional optical properties such as unique distribution of light scattering as a result of the well-ordered Au cylinders that filled into the channels, which hold great promise for use in optical, biological-sensing, and imaging applications. © 2014 American Chemical Society.

Wi Y.-M.,Korea University | Lee J.-U.,Korea Electric Power Research Institute | Joo S.-K.,Korea University
IEEE Transactions on Consumer Electronics | Year: 2013

Due to the increased penetration of electric vehicles (EVs) and photovoltaic (PV) systems, additional application for home/building energy management system (EMS) is needed to determine when and how much to charge an electric vehicle in an individual home/building. This paper presents a smart EV charging method for smart homes/buildings with a PV system. The paper consists of two parts: EV charging scheduling algorithm for smart homes/buildings and implementation of prototype application for home/building EMS. The proposed EV charging algorithm is designed to determine the optimal schedules of EV charging based on predicted PV output and electricity consumption. The implemented prototype application for home/building EMS can provide EV charging schedules according to user preferences. Numerical results are provided to demonstrate the effectiveness of the proposed smart EV charging method. © 2011 IEEE.

Choi J.C.,KAIST | Lee S.R.,KAIST | Lee D.S.,Korea Electric Power Research Institute
Computers and Geotechnics | Year: 2011

The effect of varying the thermal properties of inhomogeneous unsaturated soil on the intermittent operation of a vertical ground heat exchanger (GHE) was simulated by a conjugate heat transfer simulation using a transient conductive heat transfer model. A three-phase soil model was used to introduce soil properties that vary with depth. The performance during the first few hours was significantly different from that of an analytical infinite line source model that assumes steady-state borehole conditions, although relatively good agreement was obtained thereafter. Unsaturated soil conditions afforded a 40% lower mean heat exchange rate than saturated conditions. This demonstrates the importance of considering unsaturated conditions in the design and performance evaluation of GHEs. © 2011 Elsevier Ltd.

Lee H.P.,Korea Electric Power Research Institute
Nuclear Engineering and Design | Year: 2011

This paper describes a 9-node degenerated shell finite element (FE), an analysis program developed for ultimate pressure capacity evaluation and nonlinear analysis of a nuclear containment building. The shell FE developed adopts the Reissner-Mindlin (RM) assumptions to consider the degenerated shell solidification technique and the degree of transverse shear strain occurring in the structure. The material model of the concrete determines the level of the concrete stress and strain by using the equivalent stress-equivalent strain relationship. When a crack occurs in the concrete, the material behavior is expressed through the tension stiffening model that takes adhesive stress into account and through the shear transfer mechanism and compressive strength reduction model of the crack plane. In addition, the failure envelope proposed by Niwa is adopted as the crack occurrence criteria for the compression-tension region, and the failure envelope proposed by Yamada is used for the tension-tension region. The performance of the program developed is verified through various numerical examples. The analysis based on the application of the shell FE developed from the results of verified examples produced results similar to the experiment or other analysis results. © 2010 Elsevier B.V. All rights reserved.

Chung H.-S.,Korea Electric Power Research Institute
Nuclear Engineering and Technology | Year: 2010

Flow Accelerated Corrosion is an active degradation mechanism of CANDU feeder. The tight bend downstream to Gray loc weld connection, close to reactor face, suffers significant wall thinning by FAC. Extensive in-service inspection of feeder wall thinning is very difficult because of the intense radiation field, complex geometry, and space restrictions. Development of a knowledge-based inspection program is important in order to guarantee that adequate wall thickness is maintained throughout the whole life of feeder. Research results and plant experiences are reviewed, and the plant inspection databases from Wolsong Units One to Four are analyzed in order to support developing such a knowledge-based inspection program. The initial thickness before wall thinning is highly non-uniform because of bending during manufacturing stage, and the thinning rate is non-uniform because of the mass transfer coefficient distributed non-uniformly depending on local hydraulics. It is obvious that the knowledge-based feeder inspection program should focus on both fastest thinning locations and thinnest locations. The feeder wall thinning rate is found to be correlated proportionately with QV of each channel. A statistical model is proposed to assess the remaining life of each feeder using the QV correlation and the measured thicknesses. W-1 feeder suffered significant thinning so that the shortest remaining life barely exceeded one year at the end of operation before replacement. W-2 feeder showed far slower thinning than W-1 feeder despite the faster coolant flow. It is believed that slower thinning in W-2 is because of higher chromium content in the carbon steel feeder material. The average Cr content of W-2 feeder is 0.051%, while that value is 0.02% for W-1 feeder. It is to be noted that FAC is reduced substantially even though the Cr content of W-2 feeder is still very low.

Lee H.-I.,Korea Electric Power Research Institute | Noh M.D.,Chungnam National University
IEEE Transactions on Industrial Electronics | Year: 2011

Toroidally wound brushless dc (BLDC) machines are compact, economical, and can operate across large air gaps. In this paper, we provide analytical design equations for a radial-flux toroidally wound BLDC machine. The validity of the design equations is checked against finite-element analyses (FEAs) and experiments. It is found that the motor constant calculated by the design equations is off only by 5% from the results by the FEAs or experiments. We also provide an optimization metric that corresponds to the maximization of machine torque while maintaining minimum power loss. Two optimal design cases are presented. © 2011 IEEE.

Kim M.H.,Daegu University | Ham S.-W.,Kyungil University | Lee J.-B.,Korea Electric Power Research Institute
Applied Catalysis B: Environmental | Year: 2010

CuCl2/TiO2-based catalysts were examined to investigate the role of copper chloride for the oxidation of gaseous elemental mercury in selective catalytic reduction (SCR) process. CuCl2 on CuCl2/TiO2 catalyst was decomposed releasing Cl by calcination at high temperatures and restored to its original form by being exposed to gas phase HCl, reversibly. The activity for mercury oxidation was significantly increased with the increase of CuCl2 loading and HCl concentration. CuCl2/TiO2 catalysts revealed high activity for mercury oxidation even in the absence of HCl. This suggests that mercury oxidation could occur via a Mars-Maessen mechanism by which adsorbed or weakly bound Hg0 would react with Cl in CuCl2 that is replenished from gas phase HCl. However, the activity of CuCl2-loaded catalysts for NO removal considerably decreased with the increase of temperature above 300-350°C, which may be due to the ability of CuCl2 for NH3 oxidation in SCR reaction. © 2010 Elsevier B.V.

Kim J.K.,Korea Electric Power Research Institute | Lee H.D.,Korea Electric Power Research Institute
Journal of Industrial and Engineering Chemistry | Year: 2010

Combustion possibility of three dry sludges as pulverized fuel of coal power plant like sub-bituminous Minco coal was studied by thermogravimetric analysis (TGA) and Drop Tube Furnace (DTF). TGA results showed that the fixed carbon contained with minor content in dry sludge was slowly burned than it of Minco coal. The linear regression for the Arrhenius plot to the experimental data is very good, and activation energies for overall combustion of Minco coal and DDSS are 64.382 and 26.799. kJ/mol, respectively. But, combustion patterns of KDSS and SDSS divided into devolatilization and oxidation reaction. It was derived that activation energies for the devolatilization of KDSS and SDSS are 27.127 and 12.571. kJ/mol in reciprocal proportion to volatile matter content, the fixed carbon combustion derives to 45.289. kJ/mol for KDSS, 33.777. kJ/mol for SDSS. Test results show that the volatile content in sludge significantly improved the combustion reactivity whereas the time for the combustion completion delayed. The conversion behavior of the coals and sludge observed in DTF was similar to that reflected in TGA. DTF studies showed that the individual sludge was lower conversion than the Minco coal, but the combustion of most sludge was completed at residence time of around 1. s, set temperature range of 1200°C similar to commercial coal fired plant. These high IDT of sludge ashes with minimum 1214°C are not expected to be associated with slagging and fouling in pulverized coal fired systems. © 2010.

Baek S.H.,Korea Electric Power Research Institute | Park H.Y.,Korea Electric Power Research Institute | Ko S.H.,Chungnam National University
Fuel | Year: 2014

This paper describes the numerical investigations of the influence of the blending method on the combustion characteristics and NOx emission in a 500 MW, tangentially coal-fired boiler. The in-furnace and out-furnace blending methods are simulated with the blend of 60% bituminous and 40% subbituminous coals on a weight basis. The simulation shows the blending method has a great effect on carbon in ash, but a little effect on NOx emission. The in-furnace blending method which burns bituminous coal at lower burners and subbituminous coal at upper burners gives the least carbon in ash. For two blending methods, carbon in ash is mainly attributed to the middle burner sets in the furnace. The field tests at a 500 MW coal-fired power plant showed that the in-furnace blending method substantially reduces in NOx and carbon in ash, compared with the out-furnace blending method. © 2014 Published by Elsevier Ltd.

Kang D.W.,Inha University | Kim T.S.,Inha University | Hur K.B.,Korea Electric Power Research Institute | Park J.K.,Korea Electric Power Research Institute
Applied Energy | Year: 2012

We investigated the influence of firing biogas on the performance and operating characteristics of gas turbines. Combined heat and power systems based on two different gas turbines (simple and recuperative cycle engines) in a similar power class were simulated. A full off-design analysis was performed to predict the variations in operations due to firing biogas instead of natural gas. A wide range of biogas compositions differing in CH4 content was simulated. Without consideration of operating restrictions on the compressor and turbine, using biogas was predicted to augment the power output in both engines. Power output increased as CH4 content decreased. The main reason is the increase in turbine power due to increased fuel flow. Gas turbine efficiency increased with decreasing CH4 content in the simple cycle engine, but decreased in the recuperative cycle engine. Net efficiency including the fuel compression power consumption decreased with decreasing CH4 content even in the simple cycle engine. The heat recovery also increased by firing biogas. However, the increased turbine flow was accompanied by a surge margin reduction of the compressor and overheating of the turbine blade. These two problems were more severe in simple cycle gas turbines and as the ambient temperature increased. The turbine blade temperature and the compressor surge margin could be recovered to the reference values by either under-firing or compressor air bleeding, which are effective for blade temperature control and surge margin control, respectively. However, satisfaction of both restrictions by a single modulation caused excessive power and efficiency losses. An optimal combination between under-firing and air bleeding would minimize the performance penalty. © 2011 Elsevier Ltd.

Loading Korea Electric Power Research Institute collaborators
Loading Korea Electric Power Research Institute collaborators