• The Journal of the Korea Contents Association
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• v.14 no.11
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• pp.355-361
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• 2014

The aim of the present study was to evaluate a relative emission of image plate (IP) in computed radiography (CR) system by using relative sensitivity in film/screen methods. The characteristic curve was obtained by using the uniform aluminum 11-step wedge penetrometer. X-ray exposure factors on radiographic digital image were 50 kVp, 10 mAs. We adjusted zero of all parameter of algorithms (MUSICA) so proximate to raw data and applied to 200 of exposure class. Modeling on relative emission of IP are used IP without fading time and IP after 4 hours, 8 hours, 12 hours, 24 hours in the respective storage after X-ray exposure. The results of this study showed that the sensitivity point density at the measuring of relative sensitivity in CR was suited pixel values of the 2000 easy to relatively measure the characteristic curve and when relative sensitivity is decreased, the amount of light emitted from the image signal for generating was also decreased. In conclusion, the proposed method of measurement of relative sensitivity can be utilized to evaluate the quantity of relative emission of IP in CR system.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.10
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• pp.889-895
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• 2014

Machine parts and structures of a change in the displacement and strain can be evaluated safety is one of the important factors. Typically the strain gauge has been employed to measure the displacement and strain. However, this contact-type measurement method has disadvantages that are not measured under condition of specific object shape, surface roughness and temperature. In particularly, 3 point bending and 4 point bending test not use strain gauge. So its test used cross head displacement and deflect meter. Digital Image Correlation measurement methods have many advantages. It is non contact-type measurement method to measure the object displacements and strain. In addition, it is possible to measure the Map of full field displacements and strain. In this paper, measured the 3 point bending deflection using the Digital Image Correlation methods. In order to secure the reliability, Digital Image Correlation method and universal test machine were compared.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.2
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• pp.163-168
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• 2001

Due to aging, adhesively bonded and riveted aircraft lap joints can contain distends, cracks around rivet holes, fatigue induced flaws, and corrosion. It is required for the safety of aircraft to inspect these defects through the whole region of mint in rapid speed. Bond quality or adhesively bonded and riveted aluminum lap splice joints is investigated using non-contact remote ultrasonic nondestructive evaluation (NDE). Non-contact ultrasonic tests are performed using laser generation and air-coupled transducer detection. A Q-switched Nd:YAG laser and a periodic transmission mask are used to generate a selected Lamb mode. The Lamb wave is generated on one side of the lap splice joint, propagates along the plate, interacts with the joint and is detected on the other side by a micromachined air-coupled capacitance transducer. Analysis of recorded signals allows to evaluate the condition of the bond.

• Steel and Composite Structures
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• v.36 no.2
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• pp.119-141
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• 2020

In this paper, wavy square absorbers were experimentally and numerically investigated. Numerical simulations were performed with LS-Dyna software on 36 wavy absorbers and their crushing properties were extracted and compared with the simple one. The effect of different parameters, including wave height, wave depth, and wave type; either internal or external on the crushing characteristics were also investigated. To experimentally create corrugation to validate the numerical results, a set of steel mandrel and matrix along with press machines were used. Since the initial specimens were brittle, they were subjected to heat treatment and annealing to gain the required ductility for forming with mandrel and matrix. The annealing of aluminum shells resulted in a 76%increase in ultimate strain and a 60% and 56% decrease in yield and ultimate stresses, respectively. The results showed that with increasing half-wave height in wavy square absorbers, the maximum force was first reduced and then increased. It was also found that in the specimen with constant diameter and half-wave depth, an increment in the half-wave height led to an initial increase in efficiency, followed by a decline. According to the conducted investigations, the lowe maximum force can be observed in the specimen with zero half-wave depth as compared to those having a depth of 1 cm.

• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.415-424
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• 2020

Recently, many structural damage detection (SDD) methods have been proposed to monitor the safety of structures. As an important modal parameter, mode shape has been widely used in SDD, and the difference of vectors was adopted based on sensitivity analysis and mode shapes in the existing studies. However, amplitudes of mode shapes in different measured points are relative values. Therefore, the difference of mode shapes will be influenced by their amplitudes, and the SDD results may be inaccurate. Focus on this deficiency, a multi-strategy SDD method is proposed based on the included angle of vectors and sparse regularization in this study. Firstly, inspired by modal assurance criterion (MAC), a relationship between mode shapes and changes in damage coefficients is established based on the included angle of vectors. Then, frequencies are introduced for multi-strategy SDD by a weighted coefficient. Meanwhile, sparse regularization is applied to improve the ill-posedness of the SDD problem. As a result, a novel convex optimization problem is proposed for effective SDD. To evaluate the effectiveness of the proposed method, numerical simulations in a planar truss and experimental studies in a six-story aluminum alloy frame in laboratory are conducted. The identified results indicate that the proposed method can effectively reduce the influence of noises, and it has good ability in locating structural damages and quantifying damage degrees.

• Journal of Astronomy and Space Sciences
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• v.29 no.1
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• pp.23-31
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• 2012

Thermal analysis and control design are prerequisite essential to design the satellite. In the space environment, it makes satellite survive from extreme hot and cold conditions. In recent years CubeSat mission is developed for many kinds of purpose. Triplet Ionospheric Observatory (TRIO)-CubeSat for Ion, Neutral, Electron, MAgnetic fields (CINEMA) is required to weigh less than 3 kg and operate on minimal 3 W power. In this paper we describe the thermal analysis and control design for TRIO-CINEMA mission. For this thermal analysis, we made a thermal model of the CubeSat with finite element method and NX6.0 TMG software is used to simulate this analysis model. Based on this result, passive thermal control method has been applied to thermal design of CINEMA. In order to get the better conduction between solar panel and chassis, we choose aluminum 6061-T6 for the material property of standoff. We can increase the average temperature of top and bottom solar panels from $-70^{\circ}C$ to $-40^{\circ}C $ and decrease the average temperature of the magnetometer from $+93^{\circ}C$ to $-4^{\circ}C$ using black paint on the surface of the chassis, inside of top & bottom solar panels, and magnetometer.

• Environmental Engineering Research
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• v.16 no.4
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• pp.219-225
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• 2011

The objective of this study was to investigate the bacterial adhesion to iron (hydr)oxide-coated sand (IHCS) and aluminum oxidecoated sand (AOCS) in the presence of Tween 20 (nonionic surfactant) and lipopeptide biosurfactant (anionic surfactant) through column experiments. Results show that in the presence of Tween 20, bacterial adhesion to the coated sands was slightly decreased compared to the condition of deionized water; the mass recovery (Mr) increased from 0.491 to 0.550 in IHCS and from 0.279 to 0.380 in AOCS. The bacterial adhesion to the coated sands was greatly reduced in lipopeptide biosurfactant; Mr increased to 0.980 in IHCS and to 0.797 in AOCS. Results indicate that the impact of lipopeptide biosurfactant on bacterial adhesion to metal oxide-coated sands was significantly greater than that of Tween 20. Our results differed from those of the previous report, showing that Tween 20 was the most effective while the biosurfactant was the least effective in the reduction of bacterial adhesion to porous media. This discrepancy could be ascribed to the different surface charges of porous media used in the experiments. This study indicates that lipopeptide biosurfactant can play an important role in enhancing the bacterial transport in geochemically heterogeneous porous media.

• Transactions on Electrical and Electronic Materials
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• v.6 no.4
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• pp.154-158
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• 2005

Organic molecules have many properties that make them attractive for electronic applications. We have been examining the progress of memory cell by using molecular-scale switch to give an example of the application using both nano scale components and Si-technology. In this study, molecular electronic devices were fabricated with amino style derivatives as redox-active component. This molecule is amphiphilic to allow monolayer formation by the Langmuir-Blodgett (LB) method and then this LB monolayer is inserted between two metal electrodes. According to the current-voltage (I-V) characteristics, it was found that the devices show remarkable hysteresis behavior and can be used as memory devices at ambient conditions, when aluminum oxide layer was existed on bottom electrode. The diode-like characteristics were measured only, when Pt layer was existed as bottom electrode. It was also found that this metal layer interacts with organic molecules and acts as a protecting layer, when thin Ti layer was inserted between the organic molecular layer and Al top electrode. These electrical properties of the devices may be applicable to active components for the memory and/or logic gates in the future.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.241.1-241.1
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• 2011

Numerous possible applications for $ZrO_2$ nanotubes exist such as for catalyst support structures, for sensing or for applications as a solid state electrolyte. Especially, because of a large specific surface area, high efficiency for solid oxide fuel cell (SOFC) application at low temperature can be expected for nanotublar structures in even small size. A zirconium precursor, Tetrakis (ethylmethylamino) zirconium, TEMAZr and $H_2O$ oxidant were used to deposit$ZrO_2$ thin films on an anodized aluminum oxide (AAO) templates having sub-100nm cylindrical pores by atomic layer deposition (ALD) in the temperature range of 150~250$^{\circ}C$. The crystalline structures of as-prepared and post-annealed $ZrO_2$ nanotubes were characterized by x-ray diffraction and high-resolution transmission electron microscopy. The as-prepared samples at $150^{\circ}C$ and $200^{\circ}C$ were showed amorphous, whereas a mixed phase of tetragonal, monoclinic and amorphous polymorph was observed at $250^{\circ}C$. In the bulk, zirconia remains monoclinic phase up to $1,175^{\circ}C$, however, $ZrO_2$ nanotubes were showed tetragonal phase upon post thermal treatments merely at $400^{\circ}C$. This trend may be indicative of high-curvature surfaces of nanotubes and thereby the presence of intrinsic compressive strain. The amount of amorphous structures in the mixed phase as well as as-grown $ZrO_2$ nanotubes were also gradually decreased by subsequent heat treatment.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.45-53
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• 2011

Recently reinforced retaining walls secure their position as a stabilized method of construction replacing concrete retaining walls gradually. However, in the event of using extensible reinforcement, a bulging phenomenon can be happened in the front of reinforced retaining walls. Bulging of reinforced retaining walls means a phenomenon that, in the height of an arbitrary block, the upper part and the lower part of the block don't secure a relative position in design. Therefore, it is judged that it has the necessity to be examined in design since reinforcement needs metamorphosis to some degree to display tensile force. Therefore, the study examined about how extensibility of reinforcement had an effect on movement of reinforced retaining walls through a small-scale model test with aluminum rods. The study used Changhoji(traditional korean paper made from mulberry bark) as inextensible reinforcement and membrane as extensible reinforcement. As the result of the test, rigidity of reinforcement had a lot of effects on displacement of reinforced retaining walls and generally occurrence point of the maximum horizontal displacement had a tendency transferring to the upper part of walls according to rigidity of reinforcement was increased.