• Proceedings of the KSR Conference
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• 2011.10a
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• pp.986-993
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• 2011

The role of brake is safely to transport passenger & cargo and stop vehicles at emergency in railway vehicle. Brake system reduces the speed by control command of electricity or air. mechanical methods to perform brake are disk brake & tread brake. This study targeted development of highly efficient sintered alloy brake shoe in railway vehicle whose high frictional coefficient, wear resistance, compatibility of the existing tread brake shoe & minimization of wheel's thermal damage and performed development of friction material's formulation, analysis of pressure distribution in wheel tread & brake shoe, optimum form design through analysis of heat flow.

• ETRI Journal
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• v.31 no.5
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• pp.598-600
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• 2009

A highly efficient and compactly integrated balanced power amplifier (PA) for W-CDMA handset applications is presented. To overcome the size limit of a typical balanced PA, a bulky input divider is integrated into a PA MMIC, and a complex output network is replaced with simple lumped-element networks. For efficiency improvement at the low output power level, one of the two amplifiers in parallel is deactivated and the other is partially operated with corresponding load impedance optimization. The implemented PA shows excellent average current consumption of 34.5 mA in urban and 56.3 mA in suburban environments, while exhibiting very good load-insensitivity under condition of VSWR=4:1.

• ETRI Journal
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• v.30 no.1
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• pp.158-160
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• 2008

A highly linear and efficient GaN HEMT Doherty amplifier for wideband code division multiple access (WCDMA) repeaters is presented. For better performance, the adaptive gate bias control of the peaking amplifier using the power tracking circuit and the shunt capacitors is employed. The measured one-carrier WCDMA results show an adjacent channel leakage ratio of -43.2 dBc at ${\pm}2.5$-MHz offset with a power added efficiency of 40.1% at an average output power of 37 dBm, which is a 7.5 dB back-off power from the saturated output power.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.2965-2969
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• 2011

Highly efficient and rapid aminolysis of epoxides with various amines in water under microwave irradiation in the absence of catalyst was developed. Chiral ${\beta}$-amino alcohols were formed in a short time with excellent yields.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.724-726
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• 2004

Highly efficient blue organic light-emitting devices (OLEDs) utilizing the idea of copper phthalocyanine (CuPc)/N,N'-bis-(1-naphthyl)-N,N'-diphenyl,1,1'-biphenyl- 4,4'-diamine (NPB) composite hole transport layer (CPHTL) have been fabricated. The effect of inserting CPHTL upon the performance of blue OLEDs with 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) as the blue emitter has been investigated. Compared with the luminous efficiency of the standard blue device without CPHTL (1.33 cd/A), that of the device with 40:60 CuPc/NPB CPHTL has been increased by more than twice up to 2.96 cd/A with a Commission Internationale d'Eclairage (CIE) coordinates of(x = 0.15, y = 0.10) and a power efficiency of 1.46 lm/W (20 mA/$cm^2$) at 6.39 V. The increased device efficiency is attributed to an improved balance between hole and electron currents arriving at the recombination zone.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.265-268
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• 2004

We have developed a highly efficient and stable blue organic electroluminescent device (OLED) based on the blue fluorescent p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph) dopant in a morphologically stable high-bandgap host material, 2-methyl-9,10-di(2-naphthyl)anthracene (MADN), which achieved an EL efficiency of 9.7 cd/A and 5.5 lm/W at 20 mA/$cm^2$ and 5.7 V with a Commission Internationale d'Eclairage coordinates of(x = 0.16, y = 0.32). This sky blue device which could also alleviate the problematic current induced quenching at high current achieved a half-decay lifetime ($t_{1\;2}$) of 46,000 h at an initial brightness of 100 cd/$m^2$.

• Korean Journal of Computational Design and Engineering
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• v.9 no.4
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• pp.294-305
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• 2004

Highly detailed geometric models are rapidly becoming commonplace in computer graphics and other applications. These complex models, which is often represented as complex1 triangle meshes, mainly suffer from the vast memory requirement for real-time manipulation of arbitrary geometric shapes without loss of data. Various techniques have been devised to challenge these problems in views of geometric processing, not a representation scheme. This paper proposes the new mesh structure for the compact representation and the efficient handling of the highly complex models. To verify the compactness and the efficiency, the memory requirement of our representation is first investigated and compared with other existing representations. And then we analyze the time complexity of our data structure by the most critical operation, that is, the enumeration of the so-called one-ring neighborhood of a vertex. Finally, we evaluate some elementary modeling functions such as mesh smoothing, simplification, and subdivision, which is to demonstrate the effectiveness and robustness of our mesh structure in the context of the geometric modeling and processing.

• Journal of Power Electronics
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• v.14 no.2
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• pp.265-270
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• 2014

In terms of power loss, a MOSFET has two advantages over an IGBT with an antiparallel diode: purely resistive without an offset voltage in conduction and no tail current at turn-off. However, the reverse recovery characteristic of the body diode is so poor that MOSFETs have not yet been available for high-voltage power converters with bidirectional power flow legs. This paper introduces how MOSFETs can be fully applied to high-voltage power converters with bidirectional power flow legs in order to achieve high efficiency. With a bidirectional DC-DC converter with one leg as the simplest example, the basic circuit topology and operating principle are described in detail. The high efficiency and stable operation of the proposed converter are validated through experiments with a 1.5 kW prototype.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.491-500
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• 2016

This paper presents a highly efficient aeroelastic optimization method based on a surrogate model; the model is verified by considering the case of a high-aspect-ratio composite wing. Optimization frameworks using the Kriging model and genetic algorithm (GA), the Kriging model and improved particle swarm optimization (IPSO), and the back propagation neural network model (BP) and IPSO are presented. The feasibility of the method is verified, as the model can improve the optimization efficiency while also satisfying the engineering requirements. Moreover, the effects of the number of design variables and number of constraints on the optimization efficiency and objective function are analysed in detail. The accuracy of two surrogate models in aeroelastic optimization is also compared. The Kriging model is constructed more conveniently, and its predictive accuracy of the aeroelastic responses also satisfies the engineering requirements. According to the case of a high-aspect-ratio composite wing, the GA is better at global optimization.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.65-68
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• 1995

A slicing method by thin diamond blade is widely usd slicing of hard and brittle materials such as ceramics,glass and ferrite etc.. In this study, a new slicing system which realizes highly efficient and mirror surface slicing was developed by applying ELID-grinding with metallic bond diamond blades and its performance was evaluated. Hard and brittle materials such as ceramics,glass and ferrite were used as workpiece. Metallic bond diamond blades with grit sizes #325 and #2000 were used. Experimental results show that highly efficient slicing and good mirror surface can be successfully obtained using the developed slicing system with ELID features.