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Daejeon, South Korea

Kim D.-K.,GFTEK Corporation | Oh Y.-J.,GFTEK Corporation | Kim S.-H.,ITC Ltd | Hong K.-J.,Gwangju University | And 3 more authors.
Transactions on Electrical and Electronic Materials | Year: 2013

In this paper, silicon solar cells are analyzed regarding power conversion efficiency by changed capacitance in the depletion region. For the capacitance control in the depletion region of silicon solar cell was applied for 10, 20, 40, 80, 160 and 320 Hz frequency band character and alternating current(AC) voltage with square wave of 0.2~1.4 V. Academically, symmetry formation of positive and negative change of the p-n junction is similar to the physical effect of capacitance. According to the experiment result, because input of square wave with alternating current(AC) voltage could be observed to changed capacitance effect by indirectly method through non-linear power conversion (Voltage- Current) output. In addition, when input alternating current(AC) voltage in the silicon solar cell, changed capacitance of depletion region with the forward bias condition and reverse bias condition gave a direct effect to the charge mobility. © 2013 KIEEME. All rights reserved.

Beamish S.,KIER | El-Belbol S.,Structures Delivery | Ngala V.,KIER
Proceedings of the Institution of Civil Engineers: Forensic Engineering | Year: 2016

Cathodic protection has been applied to reinforced concrete structures in the UK as a reinforcement corrosion protection technique since the 1980s. It is now well established in the toolbox of repair techniques available for chloride-contaminated reinforced concrete structures. Cathodic protection is an ‘active’ technique and includes an ongoing operation and performance-monitoring commitment. The technique works by introducing an anode through which a small direct current is applied to protect the reinforcement. Monitoring is required to ensure that the current is maintained at the correct level to maintain the reinforcement adequately. This paper provides a brief history of the use of cathodic protection on reinforced concrete in the UK, including the trials and subsequent wholesale use of the technique on the Midland Links motorway viaducts. Also described are the operating and performance-monitoring requirements for cathodic protection systems, including the sensors and monitoring and control equipment used. The paper also discusses the use of monitoring data in the management of cathodic protection systems, and the structures to which they are applied, to predict future performance and life, allowing future maintenance interventions to be planned and providing best value for structure owners. © 2016, Thomas Telford Services Ltd. All Rights Reserved.

Ju H.,Gwangju Institute of Science and Technology | Eom J.,Gwangju Institute of Science and Technology | Lee J.K.,Institute for Research In Catalysis | Choi H.,Korea Institute of Energy Research | And 4 more authors.
Electrochimica Acta | Year: 2014

We have investigated the comparable performance of raw and ash-free coal in the operation of a direct carbon fuel cell (DCFC). The various structural and morphological analyses using SEM, TEM, EDX, XPS, XRD, and TGA are carried out to study the distinct physicochemical properties of coals. Due to contained volatile organic compounds, raw coal generates about a two-fold higher fuel cell performance compare to ash-free coal below a reaction temperature of 750 C. However, over a cell temperature of 900 C, both of them reach a similar power density of 170 mW cm-2. In the long-term operation of a DCFC, we observe a distinctly more durable power performance using ash-free coal than that of raw coal. © 2013 Elsevier Ltd. All rights reserved.

Jeong J.H.,University of Ulsan | Jung D.W.,University of Ulsan | Lim O.T.,University of Ulsan | Pyo Y.D.,KIER | Lee Y.J.,KIER
International Journal of Automotive Technology | Year: 2014

This work experimentally investigates how the dwell time between pilot injection and main injection influences combustion and emissions characteristics (NOx, CO, THC and smoke) in a single-cylinder DI diesel engine. The experiments were conducted using two fuel injection systems according to the fuel type, diesel or dimethyl ether (DME), due to the different fuel characteristics. The injection strategy is accomplished by varying the dwell time (10°CA, 16°CA and 22°CA) between injections at five main injection timings (−4°CA aTDC, −2°CA aTDC, 0°CA aTDC, 2°CA aTDC and 4°CA aTDC). Results from pilot-main injection conditions are compared with those shown in single injection conditions to better demonstrate the potential of pilot injection. It was found that pilot injection is highly effective for lowering heat-release rates with smooth pressure traces regardless of the fuel type. Pilot injection also offers high potential to maintain or increase the BMEP; even the combustion-timing is retarded to suppress the NOx emission formation. Overall, NOx emission formation was suppressed more by the combustion phasing retard effect, and not the pilot injection effect considered in this study. Comparison of the emissions for different fuel types shows that CO and HC emissions have low values below 100 ppm for DME operation in both single injection and pilot-main injection. However, NOx emission is slightly higher in the earlier main injection timings (−4°CA aTDC, −2°CA aTDC) than diesel injections. Pilot injection was found to be more effective with DME for reducing the amount of NOx emission with combustion retardation, which indicates a level of NOx emission similar to that of diesel. Although the diesel pilot-main injection conditions show higher smoke emission than single-injection condition, DME has little smoke emission regardless of injection strategy. © 2014, The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg.

Woo Y.,KIER | Lee Y.J.,KIER
International Journal of Automotive Technology | Year: 2014

Free piston engine generators which utilize a free piston engine and a linear generator are under investigation by a number of research groups around the world. Free piston engines give power output in a more efficient way when compared to conventional crankshaft engines, because the former do not have a crank mechanism which brings about additional mechanical loss. However, for the reliable and stable operation of the free piston engine generators, it is required to have a viable control system to address the uncertainty of piston motion. In this paper, most of the successful free piston engine generator developments were reviewed and a recent experimental result on a prototype free piston system was also presented with regard to engine performance with different mixture preparation strategies. © 2014 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg.

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