• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.990-991
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• 2006

• Journal of Drive and Control
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• v.14 no.4
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• pp.17-22
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• 2017

In this study, the back-drivability of the single-rod and double-rod type EHAs (Electro-Hydrostatic Actuators) was compared by computer simulation and experiments. The back-drivability of EHAs exhibit non-linear behavior like their force tracking performance. In case of the double-rod type EHA, the back-drivability was mostly influenced by the bulk modulus of oil that changes with the working pressure due to entrapped air. The back-drivability of the single-rod type EHA was directly affected by the operation states of its pilot-operated check valves, while the asymmetrical piston geometry and the non-linear bulk modulus of oil also made the dynamic response in building up the cylinder pressure dependent on the operating conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.187-197
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• 2004

This paper presents the effects of cylinder shell elasticity on effective bulk modulus of oil $K_e$ in automotive hydraulic dampers. A theoretical model of cylinder shell bulk modulus $K_c$ based on the elasticity theory of thick-walled cylinder incorporating not only radial but longitudinal deformation is proposed. In a cylinder, values of $K_c$ by the new model and traditional models are computed and the discrepancies among them are discussed. In a twin-tube type automotive damper, the variation of $K_e$ under different pressure values in chambers of the damper cylinder, based on different theoretical models for $K_c$ is computed. Through these computations, it is shown that remarkable discrepancies in computed values of $K_e$ might occur according to the $K_e$ models in connection with $K_c$ models.

• Tribology and Lubricants
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• v.26 no.1
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• pp.37-43
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• 2010

Precise prediction of rotordynamic coefficients for annular type seal of turbomachinery is necessary for enhancing their vibrational stability and various prediction methods have been developed. As the seal passage is designed complicatedly, the analysis based on Bulk-flow concept which has been mainly used in predicting seal dynamics is limited. In order to improve the seal rotordynamic prediction, full Navier-Stokes Equations with turbulent model derived in the seal flow passage have to be solved. In this study, 3D CFD(Computational Fluid Dynamics) analysis has been performed for predicting rotordynamic coefficients of non-contact type annular plain seal using FLUENT. Comparing with the results of Bulk-flow model analysis, the result of 3D CFD analysis shows good agreement.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.43-46
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• 2006

일반적으로 전기강의 특성측정에는 Epstein frame과 Single sheet tester를 이용한 측정법이 사용된다. 그러나 위의 방법은 시료 규격이 매우 제한적이며 Sheet 형태의 시료를 요구하기 때문에 측정이 용이하지 못한 경우가 많다. 이러한 경우를 위한 측정법이 Ring test 측정법으로 시료에 제한이 적기 때문에 그 활용도가 매우 높으며 특히 Bulk 형태의 시료에 대해서는 거의 유일한 측정법이라 하겠다. 본 논문에서는 0.2Hz의 교번자계 여자를 통해 Bulk형 전기강의 특성 측정을 하였으며, 정현파 자속밀도 조건과 정현파 여자 전류 조건에서의 B-H특성과 철손을 측정, 비교하였다.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.75-76
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• 2006

New PM route via bulk mechanical alloying is developed to fabricate the solid solution semi-conductive materials with $Mg_2Si_{1-x}Ge_x$ and $Mg_2Si_{1-y}Sn_y$ for 0 < x, y < 1 and to investigate their thermoelectric materials. Since $Mg_2Si$ is n-type and both $Mg_2Ge$ and $Mg_2Sn$ are p-type, pn-transition takes place at the specified range of germanium content, x, and tin content, y. Through optimization of chemical composition, solid-solution type thermoelectric semi-conductive materials are designed both for n-and p-type materials.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.67-71
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• 2009

In this treatise, presented module choice plan that analyze relation with meteorological condition (work trillion amounts, mean air temperature, precipitation, cloudiness, wind speed etc.) because diagnoses June output amount of 247.5kW bulk type module and a-Si type module that is established in equal environment in our country and is the high effectiveness enemy more by climate fluctuation by latest global warming back.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.75-82
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• 2009

In this thesis, presented module choice plan that analyze relation with weather condition (work trillion amounts, mean air temperature, precipitation, cloudiness, wind speed etc.) because diagnoses June output amount of 247.5[kW] bulk type module and a-Si type module that is established in equal environment in our country and is the high effectiveness enemy more by climate fluctuation by latest global warming back.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.177-184
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• 2012

An optical defect detection method using ESPI(electronic speckle pattern interferometry) is proposed. ESPI is widely used as a non-contact measurement system which show deformation and phase map in real time. ESPI can be divided as the in-plane, out-of-plane and shearography by operation principle and target object and also divided with bulk type and optic fiber type by the optic configurations. This paper is focused on optic fiber type out-of-plane ESPI, which has the following advantages: (1) low cost; (2) reduction of the unreliable factors generated by separated optic components; (3) simplification of the optic configuration; (4) great reduction of volume; (5) flexibility, to be easily designed into different structures to adapt to inaccessible environments such as pipeline cavity and so on.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.185-191
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• 2003

In this study, We measured transmittance and color change of various photochromic lens as a function of temperature(6, 12, $28^{\circ}C$), irradiation time of UVA lamp and the types of materials(plastic and glass) and distribution of photochromic ingredients(coated and bulk type). The coated-type photochromic lens showed higher saturated value than bulk-type lens without regard to temperature. And darkening rate of smoke color lenses were higher compare to brown lens in case of glass photochromic lens. All of photochromic lens passed ANSI Z80.3 regulation in transmittance and color independent of temperature. The saturated values of plastic photochromic lens excluded coated-type and glass photochromic lens were ranked as cosmetic use. The saturated value of coated-type. Tbr and TMs were general applications in $6^{\circ}C$ and $12^{\circ}C$, but cosmetic purpose in $28^{\circ}C$. The darkening rate was increased with decreasing temperature, whereas the fading rate became higher with increasing temperature.