• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.268-276
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• 2021

As wireless communication devices become more common, interests in how to control the electromagnetic waves generated from the devices are increasing. One of the most commonly used electromagnetic wave control materials is magnetic one, but due to the features that make the product heavy and thick when applied to the product, it is difficult to use them in curved electronic devices. Therefore, a polymer flexible meta electronic device has been presented to sort out the problem, which is thin and can have various curvatures. However, it requires an additional evaluation of curvature reliability. In this study, we developed a method to predict electromagnetic wave control characteristics through the resistance/length of the conductive ink line patterns of polymer flexible meta electronic devices, which is inversely proportional to the electromagnetic wave control characteristics. As the radius of curvature decreased, the resistance/length increased, and there was little variations with the duration times of curvature. We also found that both permanent and recoverable changes along with the removal of curvature were occurred when the curvature was applied, and that the cause of these changes was newly created vertical cracks in the conductive ink line pattern due to the tensile stress applied by applying curvature.

• Journal of Conservation Science
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• v.28 no.3
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• pp.235-245
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• 2012

Nondestructive deterioration diagnosis has been carried out for the former ore dressing plant of the Yongwha mine in Yeongyang (Registered Cultural Property No. 255). Deterioration rates about organic contaminant and soil of the upper part (7 to 13 layer) indicate higher than the lower part (1 to 6 layer) of the ore dressing plants. By contrast, deterioration rates such as crack, break out and discoloration of the lower part indicate very higher than the upper part. It is estimated that the plants of the lower part that mechanical and chemical process had been done for flotation were damaged severely by physicochemical weathering with reaction of concrete and chemical solution. As results of ultrasonic velocity measurement, average p-wave velocity of plants were measured 2,462m/s (compressive strength $529kgf/cm^2$). As for the analytical results of surface contaminants and soil compositions using P-XRF, they were identical with major elements (Cu, Zn, Pb, Fe and As) of ore minerals from the Yongwha mine. Therefore, the ore dressing plant should be treated by phytoremediation with conservation because heavy metals could impinged upon plants and natural environment.

• Journal of the Korean Geophysical Society
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• v.3 no.2
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• pp.127-138
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• 2000

This study was conducted to examine the differences between dynamic and static elastic constants by use of some laboratory tests of cement mortar specimens which have different water/cement mixing ratios. Specific gravity measurement, ultrasonic velocity estimating and uniaxial compression test were adopted to acquire the dynamic and static elastic constants. Digital data acquisition and processing enhanced the accuracy of estimating the velocities of specimens drastically, Also, the method using the gradient of propagation delay time in according to increment of specimen length more enhanced the accuracy than the method using the only one specimen length over total propagation time. The correlation between density and the P and S wave velocity of specimens shows reliable positive relation and the correlation between density and the strength of uniaxial compression has the similar relationship. The dynamic Young's modulus $(E_D)$ is alway greater than the static Young's modulus $(E_S)$ and there is increasing tendency of the ratio $(E_D/E_S)$ according to the increase of density or strength of the specimens. On the other hand, there is no typical relationship between dynamic Poisson's ratio $({\nu}_D)$ and static Poisson's ratio $({\nu}_S)$ and just the ratio of ${\nu}_D/{\nu}_S$ ranges front 69 to 122 %.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.2
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• pp.161-167
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• 2009

Organic insulating materials which are utilized as insulating materials for the low voltage show unique carbonization characteristics when they are carbonized by a leakage current. Therefore the use of the carbonization characteristics makes it possible to examine the electrical fire which is caused by a leakage current flowing on the surface of the organic insulating material. In order to understand such carbonization characteristics, in this paper, experiments have been done to carbonize typical organic insulating materials such as phenol resin, PVC, and acrylic resin, and the carbonization patterns and the IR absorption spectrum of specimens have been analyzed. According to the analysis of the carbonization patterns, the phenol resin shows the so-called 'spider-leg' carbonization pattern due to a thermosetting property. In contrast to the phenol resin, the thermoplastic property makes it difficult to observe a clear carbonization pattern to verify carbonizing causes on the surfaces of PVC and acrylic resins. In this case, the IR absorption spectrum can be analyzed to examine the specimen carbonized by a leakage current. The analysis result shows that absorption peaks appear at the wave numbers of $3,400[cm^{-1}]$ and $1,618[cm^{-1}]$, which can be an important factor to verify the carbonizing causes.

• Korean Journal of Materials Research
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• v.13 no.3
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• pp.185-190
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• 2003

Titanium dioxide films were prepared by RF sputtering method on glass for various oxygen partial pressures at power 270 W. The crystal structure, photocatalytic property and the hydrophilicity of $TiO_2$thin film the deposition conditions were investigated. Crystallized anatase phase was observed in $TiO_2$film deposited at the ratio of oxygen partial pressure 10% and 20% for 2 hrs. As the increase of deposition time, the grain size and void size of $TiO_2$film have increased and also $V_2$films have been good crystallinity. The ultraviolet-visible light absorption of $TiO_2$films was increased with increasing of deposition time and occured chiefly at the wavelength between 280 and 340 nm. The absorption band was shifted to a longer wave length as deposition time increased. Water contact angle on the X$TiO_2$film of anatase structure was decreased with increasing ultraviolet illumination time and became lower than $11^{\circ}$ from $83^{\circ}$. When hydrophilic $TiO_2$film changed by enough ultraviolet illumination was stored in the dark, the film surface gradually turned to hydrophobic state.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.145-151
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• 1991

The final purpose of this study is to examine the uses of coal ash, by-product from thermal power plant as a type of filling-embankment materials and the reuses of ash ponds. In this time, to investigate the dynamic properties, we made the test piece specimen with coal ashes, and obtained the damping ratio. In place(ash pond), the damping property by underground wall was investigated before and after soil improvements. The damping ratio of coal ash test piece specimen of 12% cement is the highest and that of 9% cement or chemical grout, that of 6% cement is in order. In same coal ash test piece, the damping ratio increases with decreasing the void ratio. In conclusion, it could be said that the damping ratio increases with the stiffness of materials. In the ash pond, the damping effect is the most when trench is set through the vibration wave propagation course, and when soil is improved the higher stiffness of the improved soil is, the more damping effect appeared. It is justified to obtain not only the dropping of permeability and the strength increase, but also the damping effect fairly by soil improvements.

• Tunnel and Underground Space
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• v.25 no.5
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• pp.435-449
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• 2015

Physical and microstructural properties of Pungchon and Maggol limestone were investigated quantitatively during 50 cycles of artificial freezing and thawing test. There were decrease in dry weight and P,S-wave velocity, and increase in absorption rate in both rock types. Porosity, pore volume, equivalent diameter, throat thickness and pore orientation were analyzed using X-ray computed tomography images. Porosity increased, and initiation and expansion of pores were investigated as weathering progresses. Physical and microstructural variation in Maggol limestone was larger than that of Pungchon limestone because Maggol limestone has more pores and microcracks at initial state. As this study analyzes physical and microstructural properties of rock specimens comprehensively, it can be applied to further rock weathering study and can be used as fundamental data of construction and resource development in cold regions.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.4
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• pp.342-348
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• 2003

Ultrasonic backscattering profiles of the Zr plates(with a thickness of 1.32mm) with/without Be-Zr alloy layer(with a thickness of $100{\mu}m$) were measured at various incidence positions to evaluate the characteristics of Be diffusion layer. Four principal subprofiles were observed in the backward ultrasound radiated from leaky Lamb waves. The angles and the intensities of the subprofile peaks decreased by the stiffening effect of Be layer. Generation and change of the subprofiles were explained by the acoustical property, collective group velocity and leaky factor difference of the plates under consideration. Backward radiation subprofiles turned out to be an useful method for evaluating thin diffusion layers on plates.

• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.33-37
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• 2002

The phosphorescence powder, $SrA1_2O_4:Eu^{2+}$, synthesized by a Polymerized Complex Method(PCM), has been compared with that by a Solid-State Reaction(SSR), and their luminescence characteristics have been studied. The PCM powders were synthesized at $900^{\circ}C$ and the SSR powders at $1200^{\circ}C$. The size of PCM powders was about $0.1{\mu}m$ and one tenth of that of the SSR powders, which was due to the lower synthesized temperature. On the other hand, residual carbon in the PCM powders decreased with an increase in the crystallinity of host lattice, which was responsible for the non-white color of the powders. Both powders showed the maximum luminescence peaks around 520nm in the wave length at room temperature. However, the peak position for the PCM powders was shifted to a slightly lower wavelength and the value of half-width of the peak was broad comparing to that of the SSR powders, and the peak intensity decreased significantly. Such a change in the luminescence characteristics was due to the large difference in size for two types of powders and partly the residual carbon in the PCM powders.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.5
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• pp.559-565
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• 2010

In this study we propose noise energy harvesting for green infrastructure development. In this regard, infrastructures such as railroad, subway, and road are taken into consideration as sources of noise which provides energy through certain wave forms. As the need of recycling noise energy became reasonable due to the increase of infrastructure usage, the capacity and property of our noise energy generating device, which uses electromagnetic induction for electricity generation, are analysed in this paper. Consequently, the outcomes of this experiment show the fact that maximum electricity is generated from the device at a specific point of noise frequency, and the relation between air pressure caused by noise and the electricity generated by the device is in a specific proportional form either linear or non-linear. The major points of developing noise energy generating device in order to apply it into social infrastructure are discussed in this paper as well.