• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.195-196
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• 2012

In recent years, in an effort to improve the efficiency and the power density of the front-end power factor correction(PFC), the interleaving of multiple converter is employed. The conventional interleaved continuous conduction mode(CCM) boost PFC converter requires input and output voltage sensing and three current sensing to obtain current balancing between modules. In this paper, the interleaved CCM PFC converter based on modulated carrier control is proposed. With the proposed method, two phase interleaved PFC can be realized simply without line voltage sensing resistor and can achieve current balancing without additional current sensing resistor on common return path. The simulation studies are carried out to verify the effectiveness of the proposed control scheme.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.85-88
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• 2006

The transport properties of amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. The effects of As addition on the carrier mobility and recombination lifetime in amorphous selenium (a-Se) films have been studied using the moving photocarrier grating (MPG) technique. We have found an increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with the drift mobilities of holes and electrons obtained by time of flight (TOF) measurement.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.4
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• pp.344-349
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• 2006

A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce thick SiC epitaxial layers for power device applications. We aimed to systematically investigate the dependence of SiC epilayer quality and growth rate during the sublimation growth using the CST method on various process parameters such as the growth temperature and working pressure. The etched surface of a SiC epitaxial layer grown with low growth rate $(30{\mu}m/h)$ exhibited low etch pit density (EPD) of ${\sim}2000/cm^2$ and a low micropipe density (MPD) of $2/cm^2$. The etched surface of a SiC epitaxial layer grown with high growth rate (above $100{\mu}m/h$) contained a high EPD of ${\sim}3500/cm^2$ and a high MPD of ${\sim}500/cm^2$, which indicates that high growth rate aids the formation of dislocations and micropipes in the epitaxial layer. We also investigated the Schottky barrier diode (SBD) characteristics including a carrier density and depletion layer for Ni/SiC structure and finally proposed a MESFET device fabricated by using selective epilayer process.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.4
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• pp.291-297
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• 2019

Polyurethane foam is the most efficient, high-performance insulation material, used for liquefied natural gas carrier (LNGC) insulation. Because LNGC is exposed to sloshing impact load due to ship motion of 6 degrees of freedom, polyurethane foam should be sufficient dynamic properties. The dynamic properties of these polyurethane foam depends on temperature and density. Therefore, this study investigates the dynamic response of polyurethane foam for various temperature($25^{\circ}C$, $-70^{\circ}C$, $-163^{\circ}C$) and density($90kg/m^3$, $113kg/m^3$, $134kg/m^3$, $150kg/m^3$) under drop impact test with impact energy of 20J, 50J, and 80J. For dynamic response was evaluated in terms of peak force, peak displacement, absorb energy, and the mechanical property with minimized density effects. The results show the effect of temperature and density on the polyurethane foam material for the dynamic response.

• Korean Journal of Environmental Biology
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• v.27 no.3
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• pp.244-251
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• 2009

To assess the algicidal effect of a bacterium, Pseudomonas fluorescens HYK0210-SK09 (SK09), attached to activated carbon polyvinyl alcohol (ACPA) and cellulose sponge (CS) carriers against Stephanodiscus hantzschii, the present study was carried out in an indoor-microcosm. As comparing immobilization effects of two carriers, the ACPA carrier allowed for higher packing cell density of SK09 compared to the CS carrier. In the microcosm, immobilized SK09 cells were applied to control S. hantzschii blooms. Immobilized SK09 cells exhibited a species-specific activity towards the diatom, showing an algicidal effect up to 72% attached by ACPA carriers and to 51% attached by CS carriers. In particular, a level of conductivity treated with ACPA carriers was decreased than that of CS carriers. The present study clearly demonstrates that ACPA-immobilized SK09 cells could effectively control S. hantzschii blooms and improve water quality in the microcosm ecosystem.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.8
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• pp.890-894
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• 2014

In this paper, we derive the CRLB (Cramer-Rao Lower Bound) of effective carrier-to-noise power ratio ($C/N_0$) estimation for a GPS (Global Positioning System) L1 C/A (Coarse/Acquisition) signal under band-limited white noise jamming environments. The quality of a received GPS signal is commonly described in terms of its $C/N_0$, implying that the noise is white and thus can be described by scalar noise density. However, if some intentional interference is received to a victim GPS receiver, then the $C/N_0$ is no longer the efficacious performance indicator. The correct and straightforward measurement to analyze the receiving situation is the effective $C/N_0$. In this paper, we consider a band-limited white noise jamming whose bandwidth is 2MHz and is the same as one of the first null-to-null bandwidth of the GPS L1 C/A signal.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.7
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• pp.38-46
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• 1993

Based on the close correlation between the optoelectronic and electrical characteristics of laser diodes, this paper is to present an exact model for electrical characteristics of laser diodes with bulk active layers so that the optoelectronic characteristics may be estimated from the electrical Characteristics. Among the considered models, the most exact model is shown to be one which uses the Fermi-Dirac integral and the bimolecular recombination and takes into account the energy-gap shrinkage with the injected carrier density.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.129-134
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• 2004

The development of fabrication processes of polycrystalline-silicon-thin-film transistors (poly-Si TFTs) at low temperatures is reviewed. Rapid crystallization through laser-induced melt-regrowth has an advantage of formation of crystalline silicon films at a low thermal budget. Solid phase crystallization techniques have also been improved for low temperature processing. Passivation of $SiO_2$/Si interface and grain boundaries is important to achieve high carrier transport properties. Oxygen plasma and $H_2O$ vapor heat treatments are proposed for effective reduction of the density of defect states. TFTs with high performance is reported.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.19-19
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• 1998

Scanning pprobe Microscoppy (SppM) is a ppowerful surface chracterization technology which can measure not only surface toppograpphy but also various ppropperties of the sampple with unpprecedented sensitivity and sppatial resolution. Recent developpment of electrostatic force microscoppe (EFM) and scanning cappacitance microscoppe (SCM) allows us to measure surface ppotential distribution and cappacitance variation n semiconductor devices. The cappacitance image pprovide us valuable information on carrier density and dopping pprofile.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.831-833
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• 2003

BLDC (Blush-Less Direct Current) motors are widely used for machine tools and ODD (Optic Disc Drive). Topology Optimization is applied to the rotor of a BLDC motor to improve in efficiency and save money. Density method and design sensitivity are derived. The result of topology optimization shows better performance.