• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.60-68
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• 2003

Tension tests of six half-thickness concrete containment wall elements were conducted as a part of Korea Atomic Energy Research Institute (KAERI) program. The aim of the KAERI test program is to provide a test-verified analytical method for estimating capacities of concrete reactor containment buildings under internal overpressurization from postulated degraded core accidents. The data from the tests reported herein should be useful for benchmarking analytical method that require modeling of material behavior including concrete cracking behavior and reinforcement/concrete interaction exhibited by the test. Major test variable is compressive strength of concrete, and its effect on the behavior of prestressed concrete panel subjected to biaxial tension is investigated.

• Journal of the Korean Geotechnical Society
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• v.30 no.10
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• pp.5-18
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• 2014

Many regions around the world are vulnerable to rainfall-induced slope failures. A variety of methods have been proposed for revealing the mechanism of slope failure initiation. Current analysis methods, however, do not consider the effects of non-homogeneous soil profiles and variable hydraulic responses on rainfall-induced slope failures. In this study, probabilistic stability analyses were conducted for weathered residual soil slopes with different soil thickness overlying impermeable bedrock to study the rainfall-induced failure mechanisms depending on the soil thickness. A series of seepage and stability analyses of an infinite slope based on one-dimensional random fields were performed to consider the effects of uncertainty due to the spatial heterogeneity of hydraulic conductivity on the failure of unsaturated slopes due to rainfall infiltration. The results showed that a probabilistic framework can be used to efficiently consider various failure patterns caused by spatial variability of hydraulic conductivity in rainfall infiltration assessment for a infinite slope.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.21.2-21.2
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• 2011

$Fe_3O_4$ having half metallic property is one of the efficient spin filtering materials which are widely used in spintronic research field and ZnO is wide band gap semiconductor which can be used by tunnel barrier or semiconductor channel in spin MOSFET. We investigated the magnetic and the electric properties of $Fe_3O_4$/ZnO multilayer fabricated on c-$Al_2O_3$ substrate by pulsed laser deposition (PLD). For multilayer films, PLD was performed at variable temperatures such as $200{\sim}750^{\circ}C$ and at target distance from 40 to 80 mm, KrF eximer laser of 1.5 $J/cm^2$ and a reputation rate of 2Hz. $Fe_3O_4$/ZnO multilayers were deposited at $4{\times}10^{-6}$ Torr. After fabricating $Fe_3O_4$/ZnO multilayers, $Fe_3O_4$/ZnO multilayers were treated by RTA(Rapid Thermal Annealing) at various temperature to change magnetic phase. The magnetism of the multilayer is changed by thickness of the ZnO tunnel barrier. Magnetic phase of FexOy showed a very small magnetism due to $Fe_2O_3$ ${\alpha}$-phase, but large magnetism from $Fe_3O_4$ or $Fe_2O_3$ ${\gamma}$-phase was observed. In the present study, effect of the ZnO thickness on the MR (magnetoresistance) ratio was investigated in detail.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.476-484
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• 2010

Recently, as the piezoelectric transformer technology develops, piezoelectric transformer may become a variable alternative to magnetic transformers in various applications. Because it was have to favorable characteristics such as electromagnetic-noise free, compact size, higher efficiency, and superior power density, linkage flux, noiseless, etc. its resonance frequency was used to output waveform of a sine wave. In this paper, the switching mode power supply of about 87.2[KHz] is driven by the multilayer thickness vibration mode piezoelectric transformer and the DC to DC converter drive circuit using an electrical equivalent circuit is proposed. Also, it was possible to drive power source device of the high-luminance LED by propose circuits.

• Steel and Composite Structures
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• v.23 no.3
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• pp.273-283
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• 2017

In this paper, it is aimed to present a detail investigation related to structural behavior of laterally unrestrained steel cantilever roof of tribune with slender cross section. The structure is located in Tutak town in $A{\breve{g}}r{{\i}}$ and collapsed on October 25, 2015 at eastern part of Turkey is considered as a case study. This mild sloped roof structure was built from a variable I beam, and supported on steel columns of 5.5 m height covering totally $240m^2$ closed area in plan. The roof of tribune collapsed completely without any indication during first snowfall after construction at midnight a winter day, fortunately before the opening hours. The meteorological records and observations of local persons are combined together to estimate the intensity of snow load in the region and it is compared with the code specified values. Also, the wide/thickness and height/thickness ratios for flange and web are evaluated according to the design codes. Three dimensional finite element model of the existing steel tribune roof is generated considering project drawings and site investigations using commercially available software ANSYS. The displacements, principal stresses and strains along to the cantilever length and column height are given as contour diagrams and graph format. In addition to site investigation, the numerical and analytical works conducted in this study indicate that the unequivocal reasons of the collapse are overloading action of snow load intensity, some mistakes made in the design of steel cantilever beams, insufficient strength and rigidity of the main structural elements, and construction workmanship errors.

• Journal of Plant Biology
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• v.13 no.2
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• pp.1-10
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• 1970

This experiment surveys ecological and morphological phase on Prasiola sp. in the mountain torrent of Chodang-ri, Keunduck-myon, Samchuck-gun, Kangwon-do, Korea from November 1968 through January 1970 and the results obtained were summarized as follows. 1. The temperature of the surface water was 12.4$\pm$2.3$^{\circ}C$, and pH was 7.25$\pm$0.2. 2. The external forms of thallus are very variable, but its basic form likely lanceolated and ovated. 3. The length of thallus is 0.6cm-8.8cm (3.6$\pm$1.72cm), and the width, 0.2cm-5.5cm(1.7$\pm$0.92cm). (The inside of the parentheses the average for 500 individuals). 4. It is observed that thallus at the time of formation of a monospore is a monostratum cell whose thickness is 21$\pm$3.2$\mu$. 5. Thickness of thallus at the transveres section at the time of heteroplanogametes formation is 29.9$\pm$2.2$\mu$, and that of the female gametes cell is 6.3$\pm$1.7$\times$6.3$\pm$0.8$\mu$, and that of the male gametes cell is 2.8$\pm$0.6$\times$28.1$\pm$1.1$\mu$. 6. As for growth, it begins with apical growth, followed by marginal growth. It seems to grow, through cell division when microsopical papillae are produced in growth line cell of marginal rigion thus by fusioning microscopical papillae. 7. The two kinds of thallus, one produced from a monospore and other from a planozygotes, are both haplonts and observed as n-3. 8. It seems that a thallus sprouts in April and increases its number through a asexual reproduction by a monospore and begins a sexual reproduction in November by forming gametes. 9. Female gametes are produced 16 from one thallus cell, whose structure shows 8 cells in the surface view and 4 layers in transverse section. Male gametes are produced 128 from one thallus cell, 16 cells surface, 8 layers in transverse section.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.71-79
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• 2002

A new rapid prototyping process, Variable Lamination Manufacturing using a 4-axis-controlled hotwire cutter and expandable polystyrene foam sheet as a laminating material of the part (VLM-S), has been developed to reduce building time and to improve the surface finish of parts. The objective of this study is to reconstruct the surface of the original 3D CAD model in order to generate mid-slice data using the advancing front technique. The generation of 3D layers by a 4 axis-controlled hot-wire cutter requires a completely different procedure to generate toolpath data unlike the conventional RP CAD systems. The cutting path data for VLM-S are created by VLM-Slicer, which is a special CAD/CAM software with automatic generation of 3D toolpath. For the conventional sheet type system like LOM, the STL file would be sliced into 2D data only. However, because of using the thick layers and a sloping edge with the firstorder approximation between the top and bottom layers, VLM-Slicer requires surface reconstruction, mid-slice, and the toolpath data generation as well as 2D slicing. Surface reconstruction demands the connection between the two neighboring cross-sectional contours using the triangular facets. VLM-S employs thick layers with finite thickness, so that surface reconstruction is necessary to obtain a sloping angle of a side surface and the point data at a half of the sheet thickness. In the process of the toolpath data generation the surface reconstruction algorithm is expected to minimize the error between the ruled surface and the original parts..

• Progress in Superconductivity
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• v.7 no.1
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• pp.6-10
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• 2005

We have studied feasibility of single-layer second-order $high-T_c$ SQUID gradiometers in magnetocardiography. We have measured human cardiomagnetic signals using a short-baseline (5.8 mm) single-layer second-order YBCO gradiometer in partially shielded environments. The gradiometer has an overall size of $17.6\;mm{\times}6\;mm$ and contains three parallel-connected pickup coils which are directly coupled to a step-edge junction SQUID. The gradiometer showed an unshielded gradient noise of $0.84\;pT/cm^2/Hz^{1/2}$ at 1 Hz, which corresponds to an equivalent field noise of $280\;fT/Hz^{1/2}$. The balancing factor was $10^3$. Based on the same design rules as the short-baseline devices, we have studied fabrication of 30 mm-long baseline gradiometers. The devices had an overall size of $70.2\;mm{\times}10.6\;mm$ with each pickup coil of $10\;mm{\times}10\;mm$ in outer size. As Josephson elements we made two types of submicron bridges, which are variable thickness bridge (VTB) and constant thickness bridge (CTB), from $3\;{\mu}m-wide$ and 300 nm-thick YBCO lines with a thin layer of Au on top by using a focused ion beam (FIB) patterning method. VTB was 300 nm wide, 200 nm thick, 30 nm long with Au removed and CTB 100 nm wide and 30 nm long. In temperature-dependent critical currents, $I_c(T)$, VTB showed an nonmetallic barrier-type behavior and CTB an SNS behavior. We believe that those characteristics are ascribed to naturally formed grain boundaries crossing the bridges.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.168-168
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• 1999

Recently, Fe/Si multilayered films (MLF) have been a focus of interest due to the strong antiferromagnetic (AF) coupling observed in such kind of MLF originates from the same nature as in the metal/metal MLF. In particular, a question of whether the spacer layer in the Fe/Si MLF is metallic or semiconducting is of interest. In spite of various experimental techniques envolved in the study, the chemical composition and the properties of the interfacial regions in the MLF exhibiting the AF coupling is still questionable. The nature of the AF coupling and the interfacial properties of Fe/Si MLF are investigated in this study. A series of Fe/Si MLF with a fixed nominal thickness of Fe(3nm) and a variable thickness of Sk(1.0-2.2nm) were deposited by RF-sputtering onto glass substrates at room temperature. The atomic structures and the actual sublayer thicknesses of the Fe/Si MLF are investigated by using x-ray diffraction. The magnetic-field dependence of the equatorial Kerr effect clearly shows an appearance of the AF coupling between Fe sublayers at tsi = 1.5 - 1.8 nm. the drastic discrepancies between the experimental magnetooptical (MO) and optical properties, and based on the assumption of sharp interfaces between Fe and Si sublayers leads to a conclusion that pure si is absent in the AF-coupled Fe/Si MLF. Introducing in the model nonmagnetic semiconducting FeSi alloy layers between Fe and Si sublayers or as spacer between pure Fe sublayers only slightly improves the agreement between model and experiment. A reasonable agreement between experimental and simulated MO spectra was reached with using the fitted optical properties for the spacer with a typical metallic type of behavior. The results of the magnetic properties measured by vibrating sample magnetometer and magnetic circular dichroism are also analyzed in connection with the MO and optical properties.

• Structural Engineering and Mechanics
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• v.64 no.4
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• pp.391-402
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• 2017

In this paper, a new nonlocal trigonometric shear deformation theory is proposed for thermal buckling response of nanosize functionally graded (FG) nano-plates resting on two-parameter elastic foundation under various types of thermal environments. This theory uses for the first time, undetermined integral variables and it contains only four unknowns, that is even less than the first shear deformation theory (FSDT). It is considered that the FG nano-plate is exposed to uniform, linear and sinusoidal temperature rises. Mori-Tanaka model is utilized to define the gradually variation of material properties along the plate thickness. Nonlocal elasticity theory of Eringen is employed to capture the size influences. Through the stationary potential energy the governing equations are derived for a refined nonlocal four-variable shear deformation plate theory and then solved analytically. A variety of examples is proposed to demonstrate the importance of elastic foundation parameters, various temperature fields, nonlocality, material composition, aspect and side-to-thickness ratios on critical stability temperatures of FG nano-plate.