• Smart Structures and Systems
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• v.13 no.1
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• pp.111-135
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• 2014

Based on the Reissner mixed variational theorem (RMVT), finite rectangular layer methods (FRLMs) are developed for the three-dimensional (3D) linear buckling analysis of simply-supported, fiber-reinforced composite material (FRCM) and functionally graded material (FGM) sandwich plates subjected to bi-axial compressive loads. In this work, the material properties of the FGM layers are assumed to obey the power-law distributions of the volume fractions of the constituents through the thickness, and the plate is divided into a number of finite rectangular layers, in which the trigonometric functions and Lagrange polynomials are used to interpolate the in- and out-of-plane variations of the field variables of each individual layer, respectively, and an h-refinement process is adopted to yield the convergent solutions. The accuracy and convergence of the RMVT-based FRLMs with various orders used for expansions of each field variables through the thickness are assessed by comparing their solutions with the exact 3D and accurate two-dimensional ones available in the literature.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.54.3-55
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• 2016

We model the spectral energy distribution (SED) of the Class 0 protostar L1527 IRS using a dust continuum radiative transfer code RADMC-3D to study the initial condition of gravitational collapse. To constrain the envelope structure, we use the data obtained by Herschel /PACS, which covers the far-infrared regime ($55-190{\mu}m$) where the SED of L1527 IRS peaks. According to our modeling, a more flattened density profile fits the far-infrared SED of L1527 IRS better than the density profile of a rotating and infalling envelope. Thus, we employ the density structure of a Bonnor-Ebert sphere, which consists of the inner flat-topped and the outer power-law regions and is often used for describing the density structure of the youngest sources in the low mass star formation process. A Bonnor-Ebert sphere fits very well the observed SED at ${\lambda}$ > $10{\mu}m$, suggesting that L1527 IRS might collapse from an unstable Bonnor-Ebert sphere rather than a singular isothermal sphere.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.5
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• pp.430-436
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• 2008

This paper proposes a way to predict electrical lifetime of a relay using Accelerated Life Testings (ALTs). The relay of interest mounting on printed circuit boards is usually under an inrush current stress. The inrush current is generated and accelerated through controlling a lamp switching device in the ALT. We find that the dominant failure mechanism under high levels of inrush current would be contact welding in the contact surface of the relay and the contact welding process is accelerated according to increase in inrush current. The electrical lifetime model based on Inverse Power Law in term of inrush current is proposed, and parameters characterizing relay's lifetime distribution are statistically estimated using ALTA 6 PRO software.

• Korean Journal of Materials Research
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• v.25 no.12
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• pp.678-682
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• 2015

The electrical property of polymer matrix composites with added carbon powder is studied based on the temperature dependency of the conduction mechanism. The temperature coefficient of the resistance of the polymer matrix composites below the percolation threshold (x) changed from negative to positive at 0.20 < x < 0.21; this trend decreased with increasing of the percolation threshold. The temperature dependence of the electrical property(resistivity) of the polymer matrix composites below the percolation threshold can be explained by using a tunneling conduction model that incorporates the effect of the thermal expansion of the polymer matrix composites into the tunneling gap. The temperature coefficient of the resistance of the polymer matrix composites above the percolation threshold has a positive value; its absolute value increased with increasing volume fraction of carbon powder. By assuming that the electrical conduction through the percolating paths is a thermally activated process and by incorporating the effect of thermal expansion into the volume fraction of the carbon power, the temperature dependency of the resistivity above the percolation threshold can be well explained without violating the universal law of conductivity.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.70-73
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• 2002

Using a simple compression test, the viscosity measurement experiment is carried out with the grain-refined Al-Si alloy(A356). The measured rheological data are expressed with power-law(Ostwald-de Waele) model and using commercial package, MAGMAsoft, coefficients of Ostwald-de Waele model and Carreau-Yasuda model are calculated. To verify the viscosity data, the die is designed to be applicable to the semi-solid die casting of automotive component and filling test is carried out. The filling test and the simulation result are compared and in good agreement. Hereafter, these data are considered to be usefully allied other product in the semi-solid die casting.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.3
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• pp.115-119
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• 2001

This paper presents an efficient and simple method for analyzine maximum simultaneous switching noise (SSN) on ground interconnection networks in CMOS systems. For the derivation of maximum SSN expression, we use ${\alpha}$-power law MOS model and Taylor's series approximation. The accuracy of the proposed method is verified by comparing the results with those of previous researches and HSPICE simulations under the contemporary process parameters and environmental conditions. The proposed method predicts the maximum SSN values more accurately when compared to existing approaches even in most practical cases such that exist some output drivers not in transition.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.377-382
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• 2008

For stator winding protection of AC generator, KCL(Kirchhoff's Current Law) is widely applied. Actually a CRDR(Current Ratio Differential Relay) based on DFT(Discrete Fourier Transform) has been used for protecting generator. It has been pointed out that defects can occur during the process of transforming a time domain signal into a frequency domain one which can lead to loss of time domain information. Wavelets techniques are proposed for the analysis of power system transients. This paper introduces an algorithm to choose a suitable Mother Wave1et for generator stator fault detection. For optimal selection, we analyzed db(Daubechies), sym(Symlets), and coif(Coiflects) of Mother Wavelet. And we compared with performance of the choice algorithm using detail coefficients energy and RMS(root mean square) error. It can be improved the reliability of the conventional DFT based CRDR. The feasibility and effectiveness of the proposed scheme is proved with simulation using collected data obtained from ATP (Alternative Transient Program) package.

• Journal of the Korean institute of surface engineering
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• v.14 no.4
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• pp.221-233
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• 1981

Section 102(2) (c) of the National Environmental Policy Act of 1969 of the United States requires an environmental assessment of the major federal actions that could significantly a-ffect environmental quality. The review is known as the NEPA assessment process, and the resulting document is called an Environmental Impact Assessment (EIS). Article 5 of the En-vironmental Preservation Law of ROK also introduced this system to a cereain extent. The purpose of this paper is, therefore, to review the general impacts of environmental pollution caused by newly proposed actions on air quality, water resources, and land use as well as specific impacts from the disposal of radiation wastes, operation of petroleum and ru-bber industries, construction of highways and dams, location of power plants and industrial co-mplexes, etc., in order to fully understand the importance of this system. Differences between American and Korean system are also briefly studied and reached to a conclusion that this important system should be understood in such a way as to link and uti-lize all conceivable disciplines and human knowledge in order to protect our environment by all means for ourselves and our coming generations as well.

• The Korean Journal of Air & Space Law and Policy
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• v.18
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• pp.385-444
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• 2003

Current Military Airbase Law, in an effort to promote safety of military aircraft and security of military airbase, requires an administrative agency or its empowered branch to consult with the Secretary of Defense or the commander of the airbase before they issue a certain administrative approval or decision related to the installation. Although this consultation process purports itself in simplifying what can be an protracted administrative procedure, and in unifying objectives of the military and the administrative services, such procedural requirement is vulnerable inevitability of various legal problems whenever there is a conflict of interests among civil, military, government services. Nor is there sufficient studies done by academian in the area of bureaucratic issues of administrative resolution, and certainly not in the area of the military consultation procedure. This article, with such reality in mind attempts to constructively examine 1) when a consultation application is submitted, whether the discretionary power of the commander of the affected airbase is acknowledged at the outset; 2) if the content of the consultation is deemed unlawful, whether a civilian can institute an administrative lawsuit against it; 3) problems about the subject matters of the consultation requirement within the framework of military airbase law; 4) whether the issuing administrative agency must abide by and issue approval or decision in accordance with the opinion proposed by the said commander; 5) the legal problems of the remedial measure such as an order of removal, appellate review, notion to challenge authority, and etc. in cases such as administrative agency ignoring the commanders proposal or issuing final approval or decision that is inconsistent with what was consulted and agreed upon between both parties.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.6
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• pp.683-691
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• 2011

In order to develop technology for an equipment qualification (EQ) test, which is an important process in localizing solenoid-operated valves used in nuclear power plants, we analyzed related regulations, test procedures, conditions, equipment, and acceptance criteria. EQ regulations for the solenoid-operated valve are classified as law, guide, and standard, and are subdivided according to test specimens and contents. The EQ test is composed of functional, normal-, and accident- condition tests. The solenoid-operated valve is aged under normal and accident conditions, which are predicted in the design conditions of a nuclear power plant, and the performance of the valve is measured by a functional test. The test method and procedure analyzed in this paper might be very useful for manufacturers as well as EQ testers.