• 연구논문집
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• s.31
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• pp.127-133
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• 2001

In chromium electrodeposition, crack is inevitably accompanied by chromium layer. Behavior of crack formation and crack density were different from the plating conditions such as current density, temperature, waveform of applied current and so on. And cracks have an influence on the corrosion resistance of chromium deposit, because corrosion occurs through the network of cracks between deposit and substrate. Therefore, many researches have been achieved in order to remove the cracks in chromium deposit. Formation of double layers, Cr/Cr and Ni/Cr were investigated to increase corrosion resistance of chromium deposit in this study. As pretreatment prior to outer chromium coating, acid pickling and current control method were examined. Cracks in cross-section of each sample were observed with SEM and CASS(Copper modified acetic acid salt spray) test was performed to evaluate corrosion resistance. It was found that corrosion resistance of Cr/Cr and Ni/Cr double layers were superior to Cr or Ni single layer from the results of CASS test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.304-307
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• 2003

In this paper, stacked piezoelectric ceramics were used for obtaining a large vibration for a small ultrasonic motor which is useable for the both linear drive and rotational drive. We studied this motor through the finite element analysis method and the simulated driving characteristics were presented. As results, the displacement of the tip of the stator was increased when the layers of the ceramics were increased. Also, by inserting additional aluminum plates between the ceramics and the aluminum bar, the displacement were amplified. In this model, two voltages which have 90 degree phase difference were applied for the bi-directional movement.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.273-275
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• 1998

This paper presents a method of determining the minimum amount of reactive power capacity installation and minimizing transmission line losses. It deals with maintaining voltage profile within an acceptable range with respect to the increase in load demand. Our approach provides three-different stages to power system planner. First stage considers existing capacitors. Second stage considers expanding the size of the installed capacitors. Third stage considers existing capacitors and newly installed capacitors whose locations are irrelevant to the locations of existing ones. Validity and effectiveness of the proposed algorithm are confirmed by results on modified New England 30 bus test system.

• International Journal of Highway Engineering
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• v.15 no.5
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• pp.57-64
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• 2013

PURPOSES : It is to evaluate lightweight soil as a subgrade material based on mechanical tests and calculation of pavement performance. METHODS : In this research, various contents of cement and air foam are used to make lightweight soil using wasted dredged soil. Uniaxial compressive strength test is conducted to evaluate strength of 7 and 28 day cured specimens. Secant modulus was calculated based on the stress and strain relationship of uniaxial compressive strength test. Resilient modulus test was measured using by repeated triaxial compression test. The measured resilient modulus was used in layered elastic program to predict fatigue and rutting life at a given pavement structure. RESULTS : Uniaxial compressive strength increases as cement content increases but decrease as air foam content increases. Resilient modulus also increases as cement content increases and decrease as air foam content decrease. CONCLUSIONS : It is concluded that dredge clay soil can be used as subgrade layer material using by lightweight treated soil method.

• Journal of the Korean Vacuum Society
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• v.8 no.3A
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• pp.213-217
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• 1999

Fe/MnO multilayers with different bilayer thicknesses were grown by pulsed laser deposition method. Grazing incidence X-ray reflectivity results showed obvious multilayer Bragg peaks implying highly layered samples and, through their analysis, some structural parameters were quantiatively estimated. From the X-ray diffraction peak corresponding to MnO(111), Mn-oxide turned out to be dominantly MnO. To characterize the magnetic properties of $Mn^{+2}$, XMCD were carried out. Magnetic moments of MnO near interfaces were ordered in the opposite direction to those of Fe.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.28-28
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• 2010

Photoelectrochemical solar cells such as dye-sensitized cells (DSSCs), which exhibit high performance and are cost-effective, provide an alternative to conventional p-n junction photovoltaic devices. However, the efficiency of such cells plateaus at 11-12%, in contrast to their theoretical value of 33%. Improvements in efficiency can only occur through a fundamental understanding of the underlying physics, materials, and device designs of DSSCs. A photoelectrode consisting of semiconducting oxide nanoparticles and a transparent conducting oxide electrode (TCO) is a key component of DSSC and design of photoelectrode materials is one of promising strategies to improving energy conversion efficiency. We introduce monodisperesed $TiO_2$ nanoparticles prepared by forced hydrolysis method and their superiority as photoelectrode materials was characterized with aids of optical and electrochemical analysis. Multi-layered TCO materials are also introduced and their feasibility for use as photoelectrodes is discussed in terms of optical absorption and charge collecting properties.

• Asia pacific journal of information systems
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• v.1 no.1
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• pp.63-86
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• 1991

In this paper, our concern is the artificial neural network-based patten classification, when can resolve the difficulties in the Autoregressive Moving Average(ARMA) model identification problem To effectively classify a time series into an approriate ARMA model, we adopt the Multi-layered Backpropagation Network (MLBPN) as a pattern classifier, and Extended Sample Autocorrelation Function (ESACF) as a feature extractor. To improve the classification power of MLBPN's we suggest an integrated neural network system which consists of an AR Network and many small-sized MA Networks. The output of AR Network which will gives the MA order. A step-by-step training strategy is also suggested so that the learned MLBPN's can effectively ESACF patterns contaminated by the high level of noises. The experiment with the artificially generated test data and real world data showed the promising results. Our approach, combined with a statistical parameter estimation method, will provide a way to the automation of ARMA modeling.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2089-2095
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• 2002

Ceramic/metal composites have many attractive properties and great potential fur applications. Interfacial fracture properties of different layered composites are important in material integrity. Therefore, evaluation of fracture toughness at interface is required in essence. In this study, the mechanical characteristics for interface of ceramic/metal composites were investigated by indentation test of micro-hardness method. Apparent interfacial toughness of TBC system could be determined with a relation between the applied load and the length of the crack formed at the interface by indentation test.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.180-187
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• 2003

The purpose of this study is to investigate the seismic behavior of reinforced concrete shear wall subjected to earthquake motions. A computer program, named RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology), was used for the analysis of reinforced concrete structures. A 4-node flat shell element with drilling rotational stiffness is used for spatial discretization. The layered approach is used to discretize behavior of concrete and reinforcement through the thickness. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. Solution of the equations of motion is obtained by numerical integration using Hither-Hughes-Taylor(HHT) algorithm. The proposed numerical method for the seismic analysis of reinforced concrete shear wall is verified by comparison of analysis results with reliable experimental results.

• Structural Engineering and Mechanics
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• v.27 no.3
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• pp.365-391
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• 2007

The vibration and stability analysis is investigated for composite cylindrical shells that composed of ceramic, FGM, and metal layers subjected to various loads. Material properties of FG layer are varied continuously in thickness direction according to a simple power distribution in terms of the ceramic and metal volume fractions. The modified Donnell type stability and compatibility equations are obtained. Applying Galerkin's method analytic solutions are obtained for the critical parameters. The detailed parametric studies are carried out to study the influences of thickness variations of the FG layer, radius-to-thickness ratio, lengths-to-radius ratio, material composition and material profile index on the critical parameters of three-layered cylindrical shells. Comparing results with those in the literature validates the present analysis.