• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.846-856
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• 1998

In this paper, we have applied Berenger's perfectly matched layer(PML) absorbing boundary conditition(ABC) with three dimension at the propagation direction of field, side boundary and upper boundary in which evanescent and radiation field is exist. Even though the same computationaal domain is used, PML is superior to other ABC in the absorbing ability that is obtained reflective coefficient about $10^{-4}$ unit for the propagation wave, but PML is ineffective in absorbing evanescent field. Also we have compared dispersive characteristics of the microstrip with Kobayashi's emprical method, and obtaind very similar result, but 0.8% error is generated at the dc or near.

• Earthquakes and Structures
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• v.3 no.3_4
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• pp.383-411
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• 2012

The objective of the present paper is to review and implement the most recent developments in the Spectral Element Method (SEM), as well as improve aspects of its implementation in the study of wave propagation by numerical simulation in elastic unbounded domains. The classical formulation of the method is reviewed, and the construction of the mass matrix, stiffness matrix and the external force vector is expressed in terms of matrix operations that are familiar to earthquake engineers. To account for the radiation condition at the external boundaries of the domain, a new absorbing boundary condition, based on the Perfectly Matched Layer (PML) is proposed and implemented. The new formulation, referred to as the Multi-Axial Perfectly Matched Layer (M-PML), results from generalizing the classical Perfectly Matched Layer to a medium in which damping profiles are specified in more than one direction.

• Journal of the Korean Ceramic Society
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• v.37 no.3
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• pp.263-270
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• 2000

The Pt/copper oxide/n-Si electrodes were fabricated by depositing copper oxide thin film of 500${\AA}$ and very thin Pt layer on the n-type (100) Si substrate. hotoelectrochemical properties and stability profiles of the electrodes were investigated as a function of deposition time of Pt layer. As the deposition time of Pt layer increased up to 10 seconds, the photocurrent and quantum efficiency were increased and then decreased with further depositing time. The better cell stability was observed for the electrode with longer deposition time. The improvements in above photoelectrochemical properties indicate that Pt layer acts as a catalyst layer at electrode/electrolyte interface as well as a protective layer. The decreasing tendency of the photocurrent and efficiency for the electrode with Pt layer deposited above 20 seconds was explained as an increases in probbility of electron-hole pair recombination and also the absorbing photon loss at electrode surface due to the excessive thickness of Pt layer. The results were confirmed by impedance spectroscopy, mutiple cycle voltammograms and microstructural analyses.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.87-95
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• 2018

PURPOSES : A geo-grid pavement, e.g., a stress-absorbing membrane interlayer (SAMI), can be applied to an asphalt-overlay method on the existing surface-pavement layer for pavement maintenance related to reflection cracking. Reflection cracking can occur when a crack in the existing surface layer influences the overlay pavement. It can reduce the pavement life cycle and adversely affect traffic safety. Moreover, a failed overlay can reduce the economic value. In this regard, the objective of this study is to evaluate the bonding properties between the rigid pavement and a SAMI by using the direct shear test and the pull-off test. The predicted fractural energy functions with the shear stress were determined from a numerical analysis of the moving average method and the polynomial regression method. METHODS : In this research, the shear and pull-off tests were performed to evaluate the properties of mixtures constructed using no interlayer, a tack-coat, and SAMI with fabric and without fabric. The lower mixture parts (describing the existing pavement) were mixed using the 25-40-8 joint cement-concrete standard. The overlay layer was constructed especially using polymer-modified stone mastic asphalt (SMA) pavement. It was composed of an SMA aggregate gradation and applied as the modified agent. The sixth polynomial regression equation and the general moving average method were utilized to estimate the interlayer shear strength. These numerical analysis methods were also used to determine the predictive models for estimating the fracture energy. RESULTS : From the direct shear test and the pull-off test results, the mixture bonded using the tack-coat (applied as the interlayer between the overlay layer and the jointed cement concrete) had the strongest shear resistance and bonding strength. In contrast, the SAMI pavement without fiber has a strong need for fractural energy at failure. CONCLUSIONS : The effects of site-reflection cracking can be determined using the same tests on cored specimens. Further, an empirical-mechanical finite-element method (FEM) must be done to understand the appropriate SAMI application. In this regard, the FEM application analy pavement-design analysis using thesis and bonding property tests using cored specimens from public roads will be conducted in further research.

• Journal of Ginseng Research
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• v.14 no.3
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• pp.437-441
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• 1990

The investigation of UV absorbing compounds in saponin fraction of Pnm.1. Kiairnk root was carried out by thin layer chromatography, semipreparative HVLC. l3C, 1H-NMR, mass spectrometry and chemical characteristics in searching plant for growth regulatony substances such as phenolic glycoside. Drying of fresh ginseng at 15 $^{\circ}C$ decreased not only number but also size of UV absorbing sports on TLC. One of the relatively large spots in fresh ginseng was isolated and identified as adenosine, which is subjected for growth stimulatory activity Detection of phenolic glycosides failed in dried root bolt was highly probable in fresh ginseng even with the insufficient amount of sample.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.1
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• pp.70-78
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• 1995

In order to implement broadband RAM's(Radar Absorbing Materials) made up of multiple dielectricl layers, the design variables such as the dielectrci constaints, the depths and the loss tangents of dielectric are optimized. The wave impedances regarding the reflective wave are found in dielectrics, input impedances and reflection coefficients with multiple dielectric layers are derived from the transmission line circuit theory. Finally, minimum average reflective power and optimum design variables are obtained by applying the numerical technique, called modified Powell method. In case of four dielectric layers with inequality constraints in design variables, a quite favourable and feasible result with the total depth of 1.1 cm, the average reflective power of 0.85% over the bradband frequency range is obtained for a specific example.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.17-24
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• 1997

Broad-band RAM's (Radar absorbing materials) are designed by multi-layered lossy dielectrics. The depth, the relative permittivity and the loss tangent of each layer are optimized in order to meet the required reflective power over the specified frequency range using a genetic algorithm. The reflection coefficients are calculated by the continued fraction method. A new population model of the partial initialization method during iterations is applied for the multi-modal functions to enhance the performance of the genetic algorithm. The optimal RAN's are designed by setting the relative permittivity and the loss tangent of the dielectrics as a funtion of the frequency over 5~20GHz.

• Journal of the Korean Institute of Navigation
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• v.23 no.1
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• pp.15-22
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• 1999

In this paper, ferrite-rubber composite has been studied in order to apply to RF-A-PF in a super wideband electromagnetic absorber in RF-A-PF type, which can be used for a general purpose anechoic chamber. $Ni_x - Mn_0.1 - Zn_{(1-x-0.1)}ㆍFe_2O_4$ ferrite powder has been fabricated, then, using this, 〔$Ni_x - Mn_0.1 - Zn_{(1-x-0.1)}ㆍFe_2O_4$〕-Rubber composite for RF-layer in the RF-A-PF type absorber has been fabricated and it's characteristics have been analyzed. As a result, it has been clearly shown that the 〔$Ni_x - Mn_0.1 - Zn_{(1-x-0.1)}ㆍFe_2O_4$〕-Rubber composite has excellent electromagnetic wave absorbing properties.

• Korean Journal of Crystallography
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• v.7 no.2
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• pp.133-146
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• 1996

Morphology and infrared absorbing characteristics of Pt-black prepared by electroplating have been investigated with XRD, SEM, and IR spectrophotometer. The Pt later was coated on Au-coated alumina/glass substrates for 1-5 min at pH 1.0-1.5, where a solution of platinum chloride and lead acetate was used as the electrolyte. At the electrical current density of 20-50 mA/㎠, the Pt-black showed a dendritic growth which was characterized by a "tree" shape. Absorptivity of above 90% at IR radiation of 10 m was observed for the Pt absorbing layer with an area density of ≥1.3mg/㎠.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.1
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• pp.35-42
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• 1999

This paper describes the characteristics of the complex isotropic ferrite-rubber composite for a super wideband electromagnetic absorber in RP-A-PF type, which can be used for an anechoic chamber, wall material to prevent TV ghost, etc. The $Ni_x-A_{0.1}-ZN_{(1-x0.1)}$. $Fe{_2}O_4$ ferrite powder has been fabricated. Using this, then, [$Ni_x-A_{0.1}-ZN_{(1-x0.1)}$. $Fe{_2}O_4$]-Rubber composite for RF-layer in the RF-A-PF type absorber has been fabricated and it's characteristics has been analyzed. As a result, it has been shown that the [$Ni_x-A_{0.1}-ZN_{(1-x0.1)}$. $Fe{_2}O_4$].Rubber composite has excellent electromagnetic wave absorbing properties.