• Journal of the Microelectronics and Packaging Society
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• v.21 no.3
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• pp.7-17
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• 2014

Power electronics modules are semiconductor components that are widely used in airplanes, trains, automobiles, and energy generation and conversion facilities. In particular, insulated gate bipolar transistors(IGBT) have been widely utilized in high power and fast switching applications for power management including power supplies, uninterruptible power systems, and AC/DC converters. In these days, IGBT are the predominant power semiconductors for high current applications in electrical and hybrid vehicles application. In these application environments, the physical conditions are often severe with strong electric currents, high voltage, high temperature, high humidity, and vibrations. Therefore, IGBT module packages involves a number of challenges for the design engineer in terms of reliability. Thermal and thermal-mechanical management are critical for power electronics modules. The failure mechanisms that limit the number of power cycles are caused by the coefficient of thermal expansion mismatch between the materials used in the IGBT modules. All interfaces in the module could be locations for potential failures. Therefore, a proper thermal design where the temperature does not exceed an allowable limit of the devices has been a key factor in developing IGBT modules. In this paper, we discussed the effects of various package materials on heat dissipation and thermal management, as well as recent technology of the new package materials.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.2
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• pp.258-262
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• 2001

The study was conducted to evaluate the effects of chromium picolinate (CrP) on growth, carcass characteristics and serum metabolites in growing-finishing pigs. A total of 96 Landrace$\times$Yorkshire$\times$Duroc hybrid pigs, initial live weight about $38.12{\pm}00kg$, were randomly assigned to 2 groups (16 pigs per pen, 3 pens per group), each group had 48 pigs with an equal number of barrows and gilts. The pigs were fed the diet with or without $200{\mu}g/kg$ Cr from CrP. The results indicated that the addition of $200{\mu}g/kg$ CrP increased ADG by 3.58% and decreased feed conversion rate (FCR) by 3.00% compared to the control group. Pigs fed CrP had 7.58% (p<0.05) higher carcass lean percentage, 15.55% (p<0.05) larger longissimus muscle area (LMA) and 10.90% (p<0.05) lower back fat thickness, 15.17% (p<0.05) lower carcass fat percentage. In addition, the IGF-I level in serum was elevated by 79.20% (p<0.05), the Insulin and cortisol level decreased by 27.35% (p<0.05) and 34.58% (p<0.05) respectively with supplementation of CrP. Analysis of subcutaneous fat (10th rib) showed that the activity of hormone sensitive lipase (HSL) increased by 79.58% (p<0.05) and the activities of isocitrate dehydrogenase (ISD) and malate dehydrogenase (MDH) decreased significantly by 15.06% (p<0.05) and 54.53% (p<0.05) respectively in the $200{\mu}g/kg$ CrP group. The concentration of RNA, RNA/DNA in LMA increased by 31.89% (p<0.05) and 5.41% (p<0.05) respectively with the addition of CrP. These results suggest that CrP reduced fat deposits by decreasing lipogenic enzyme activities and increasing HSL activity and may have promoted muscle anabolic metabolism through elevated IGF-I levels.

• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.7
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• pp.881-886
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• 2005

This paper presents intelligent digital redesign method of global approach for hybrid state space fuzzy-model-based controllers. For effectiveness and stabilization of continuous-time uncertain nonlinear systems under discrete-time controller, Takagi-Sugeno(TS) fuzzy model is used to represent tile complex system. And global approach design problems viewed as a convex optimization problem that we minimize the error of the norm bounds between nonlinearly interpolated linear operators to be matched. Also, by using the power series, we analyzed nonlinear system's uncertain parts more precisely. When a sampling period is sufficiently small, the conversion of a continuous-time structured uncertain nonlinear system to an equivalent discrete-time system have proper reason. Sufficiently conditions for the global state-matching of tile digitally controlled system are formulated in terms of linear matrix inequalities (LMIs). Finally, a TS fuzzy model for the chaotic Lorentz system is used as an example to guarantee the stability and effectiveness of the proposed method.

• Journal of Korea Port Economic Association
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• v.28 no.1
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• pp.105-122
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• 2012

This paper proposes a fuzzy-based AHP model by which the greenhouse gas reduction for container terminal problem was systematically structured and then evaluated. The model was established by exploiting a fuzzy theory and AHP for capturing the inexactness and vagueness of information. In this study, measurement areas were selected for equipment aspect, operating aspect, and energy aspect. The greenhouse gas reduction is the number one priority in the equipment aspect, operating aspect, energy aspect in order. The analysis result of equipment aspect reveals that the most important element is electrical T/C. The most important element of operating and energy aspect were a container rehandling and a LED lighting. As for the whole priority which conversion weight was applied, the results were shown as follows: an electrical T/C(16.2%) as the first rank: a hybrid Y/T(14.4%) as the second rank: a AMP(10.6%) as the third rank. The result of this study suggests some guidelines for deciding priority of greenhouse gas reduction for container terminal.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.33-38
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• 2013

In the past, a very popular method for reducing the corrosion on zinc involved the use of chemical conversion layer coatings based on $Cr^{+6}$. However, there is an important problem with using chromium salts as a result of restrictive environmental protection legislation. This study investigated the optimum condition for galvanized steel using an organic/inorganic solution with a Ti composition. In the case of a fixed heat treatment time, the corrosion resistance values of LR-0727(1) and LR-0727(2) were improved as the heat treatment temperature increased, and the optimum minimum temperature decreased with the heat treatment time. At the optimum heat treatment condition of two coating solutions, the heat treatment time of the LR-0727(1) solution was shorter than LR-0727(2) for the same heat treatment temperature. LR-0727(1) coated specimens did not show desquamation, and all of the specimens showed a good adhesive property. In contrast, in the case of the LR-0727(2) coated specimens, desquamation arose. Therefore, the adhesive property of LR-0727(1) was superior to that of LR-0727(2). The pencil hardness had a 3H average for all of the coating solutions and heat treatment conditions. In the case of a corrosion resistance test with boiling water, the coated specimens of LR-0727(1) were discolored, but LR-0727(2) was not. Finally, LR-0727(1) was more moisture proof than LR-0727(2).

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1861-1866
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• 2012

The new semiconducting copolymers with 4,4-dialkyl-$4H$-cyclopenta[2,1-$b$:3,4-$b^{\prime}$]dithiophene and 2,2-dimethyl-$2H$-benzimidazole units were synthesized. The fused aromatic rings, such as cyclopentadithiophene (CPDT) unit, can make the polymer backbone more rigid and coplanar, which induces long conjugation length, narrow band gap, and strong intermolecular ${\pi}-{\pi}$ interaction. The stacking ability was controlled through attaching of linear or branched alkyl side chains. The spectra of PEHCPDTMBI and PHCPDTMBI in the solid films show absorption bands with maximum peaks at 401, 759 and 407, 768 nm, and the absorption onsets at 925 and 954 nm, corresponding to band gaps of 1.34 and 1.30 eV, respectively. The devices comprising PHCPDTMBI with $TiO_X$ showed a $V_{OC}$ of 0.39 V, a $J_{SC}$ of 1.14 $mA/cm^2$, and a $FF$ of 0.34, giving a power conversion efficiency of 0.15%. The PHCPDTMBI with linear alkyl chain on CPDT shows good solubility in organic solvent with higher PCE value than that of PEHCPDTMBI.

• Polymer(Korea)
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• v.37 no.4
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• pp.470-477
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• 2013

Multi-walled carbon nanotube (MWCNT) based nano-composite pastes having a high filler content are prepared for the facile fabrication of a counter electrode (CE) of dye-sensitized solar cell (DSSC). A polystyrene-based functional block copolymer is prepared through a controlled "living" radical polymerization technique, affording a surface modifier for the dispersion control of MWCNT in the paste. Physical dispersion through a ball-milling method additionally confirms the importance of the dispersion control, providing DSSC with enhanced processibility and improved solar-to-electricity energy conversion efficiency (${\eta}$) values. The performances of the DSSCs are further improved through the incorporation of minor amount of platinum (Pt) nanoparticles into the MWCNT pastes. The DSSC with the Pt/MWCNT hybrid CE exhibits very high ${\eta}$ values, which is superior to that of DSSC with the standard Pt CE.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.2
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• pp.138-143
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• 2006

This paper presents intelligent digital redesign method for hybrid state space fuzzy-model-based controllers. For effectiveness and stabilization of continuous-time uncertain nonlinear systems under discrete-time controller, Takagi-Sugeno(TS) fuzzy model is used to represent the complex system. And global approach design problems viewed as a convex optimization problem that we minimize the error of the norm bounds between nonlinearly interpolated linear operators to be matched. Also, by using the bilinear and inverse bilinear approximation method, we analyzed nonlinear system's uncertain parts more precisely. When a sampling period is sufficiently small, the conversion of a continuous-time structured uncertain nonlinear system to an equivalent discrete-time system have proper reason. Sufficiently conditions for the global state-matching of the digitally controlled system are formulated in terms of linear matrix inequalities (LMIs). Finally, a TS fuzzy model for the chaotic Lorentz system is used as an . example to guarantee the stability and effectiveness of the proposed method.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.262-267
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• 2016

In this study, we present an excellent approach for easily and uniformly immobilizing Pt, Au and bimetallic PtAu nanoparticles (NPs) on a multi-walled carbon nanotube (MWNT)-coated layer through dry plasma reduction. The NPs are stably and uniformly immobilized on the surface of MWNTs and the nanohybrid materials are applied to counter electrode (CE) of dye-sensitized solar cells (DSCs). The electrochemical properties of CEs are examined through cyclic voltammogram, electrochemical impedance spectroscopy, and Tafel measurements. As a result, both electrochemical catalytic activity and electrical conductivity are highest for PtAu/MWNT electrode. The DSC employing PtAu/MWNT CE exhibits power conversion efficiency of 7.9%. The efficiency is better than those of devices with MWNT (2.6%), AuNP/MWNT (2.7%) and PtNP/MWNT (7.5%) CEs.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.129-139
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• 2010

Coal gasification process, which had developed originally to convert coal from hydrogen and carbon monoxide, has used and developed in many countries because of environmental advantages such as carbon dioxide storage, decrease of pollutants and so on. Generally entrained-flow gasification process using pulverized coal under $75{\mu}m$ is used in Integrated Gas Combined Cycle(IGCC) because of easy scale up and high efficiency of energy conversion. Especially entrained-flow gasifers with coal water slurry have been used in many applications due to its fully developed technologies. In this paper, several technologies for coal-water slurry gasification that involves slurry preparation, burner, gasifier, slag melting and numerical simulation for plant design and operation were investigated. Entrained-flow gasification with coal water slurry can be used for synfuel production, SNG, chemicals as well as IGCC. To develop hybrid gasification process and use different types of coal, it is necessary to develop new technologies that will increase efficiency of the process.