• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2014-2016
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• 2004

In order to obtain a low-loss ferroelectric phase shifter, the reflection-type phase shifter with ferroelectric defected ground structure (DGS) resonators has been designed in this paper. The proposed phase shifter is consist of a 3-dB $90^{\circ}$ branch-line hybrid coupler and terminated reflective circuit with tunable ferroelectric DGS resonator. The ferroelectric DGS unit structure can provide high Q resonator characteristic at high frequencies. The design parameters of equivalent circuit for the tunable DGS resonator are derived by using simple circuit analysis method and three-dimensional full wave finite element method. The fabricated phase shifter has an insertion loss of better than 3.4dB at 13.5GHz.

• Journal of electromagnetic engineering and science
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• v.14 no.1
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• pp.15-24
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• 2014

A compact dual-band three-way metamaterial power divider is proposed that has three in-phase outputs. Fully printed composite rightand left-handed (CRLH) unequal and equal power dividers are first implemented for 900-MHz and 2.4-GHz bands with the power-division ratios of 2:1 and 1:1, respectively. An initial 1:1:1 power divider is then achieved by incorporating the input of the two-way equal block into an output of the unequal block, and trimming the interconnection parameters. The condition of an identical phase at the three outputs of the power divider is then met by devising a hybrid CRLH phase-shift line to compensate for the different phase errors at the two frequencies. This scheme is confirmed by predicting the performance of the power divider with circuit analysis and full-wave simulation and measuring the fabricated prototype. They results show agreement; the in-phase outputs as well as the desirable power-division are accomplished and outdo the conventional techniques.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.4
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• pp.209-215
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• 2001

In this paper a method for analysis and modelling of coplanar transmission interconnect lines that are placed on top of silicon-silicon oxide substrates is presented. The potential function is expressed by series expansions in terms of solutions of the Laplace equation for each homogeneous region of layered structure. The expansion coefficients of different series are related to each other and to potentials applied to the conductors via boundary conditions. In the plane of conductors, boundary conditions are satisfied at $N_d$ discrete points with $N_d$ being equal to the number of terms in the series expansions. The resulting system of inhomogeneous linear equations is solved by matrix inversion. No iterations are required. A discussion of the calculated line admittance parameters as functions of width of conductors, thickness of the layers, and frequency is given. The interconnect capacitance and conductance per unit length results are given and compared with those obtained using full wave solutions, and good agreement have been obtained in all the cases treated

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.79-86
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• 2005

The role of the injector as an acoustic resonator is studied for the high performance rocket engine adopting the gas-liquid scheme injector. Acoustic behavior in the combustor with single injector is investigated numerically adopting linear acoustic analysis for cold condition. Acoustic-damping effect of the injector is evaluated by damping factor as a function of the injector length. From the numerical results, it is found that the injector can play a significant role in acoustic damping and the optimum length of the injector corresponds to half of a full wavelength of the longitudinal mode with the acoustic frequency to be damped in the chamber. In baffled chamber, the optimum lengths of the injector are calculated as a function of baffle length for both cold and hot conditions.

• Geotechnical Engineering
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• v.13 no.3
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• pp.53-62
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• 1997

Analytical studies were conducted to develop the Spectral-Analysis-of-Surface-Waves (SASW) method for underwater use. For the precise estimation of the in-situ soil stiffness profile from SASW measurements, it is essential to determine economical and reasonable theoretical dispersion curves reflecting various experimental conditions. In this paper, therefore, analytical methods are mainly discussed, which were developed to determine theoretical dispersion curves of surface waves propagated along the soil-water interface. Application of the analytical methods is then illustrated by an example involving estimation of a stiffness profile through a forward modeling process of SASW measurements. Applicabilities of the SASW method as well as the developed analytical methods are evaluated, respectively, from the example.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.62-67
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• 2002

It has been shown that the vibrational response of a tire can be represented by a set of decaying waves, each associated with a particular cross-sectional mode shape in the region near the contact patch. Thus, it can be concluded that tires can be effectively modeled as lossy waveguides. It has also been shown that the sound radiation from tires is mainly from the region close to the contact patch. In consequence, it may be computationally efficient to analyze tire vibration and sound radiation in the region close to the contact patch by using a hybrid finite element model in which the cross-section of a tire is approximated by 2-D finite elements while an analytical wave solution is assumed in the circumferential direction of the tire. In this article. a hybrid finite element was formulated based on a composite shell model. The dispersion relations for sample structures obtained by using the hybrid FE model were then compared with those obtained by using a full, three-dimensional FE model. It has been shown that the FE analysis made using the hybrid 2-D finite elements yields results in close agreement with the three-dimensional model.

• The Research Journal of the Costume Culture
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• v.17 no.1
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• pp.90-104
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• 2009

If people want to project a successful personal style, hair style might play a big role as well as clothing. The purpose of this study was to observe hair behavior according to demographic variables, and to analyze correlation between desired hair image and clothing image sought. Questionnaires were distributed to 600 females aged $20s{\sim}40s$, using a convenient sampling method. Only 556 reliable questionnaires were selected for statistical analysis. Correlation r, ANOVA and Chi-square were used to analyze the data, using the SPSS program. There was a significant association between hair style and occupation. Career woman preferred roll straight perm treated hair, students preferred general perm treated hair and full time house wives preferred general wave perm treated. The medium layer cut was the most preferred cut style. People want to give different accents in hair styling with occupation and age variable. Certain desired clothing image had a high correlation with desired hair style image. Those who people want to express sexy, and bohemian image through clothing, they also want to create those image in hair styling with a high correlation(r=0.683, r=0.704).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.4
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• pp.29-40
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• 2004

This paper reports the frequency characteristics and the time response of parallel adjacent-transmission lines, crossed adjacent-transmission lines and parallel adjacent-transmission lines which are on the different planes by using FDTD-PML method. In the parallel adjacent-transmission lines, the crosstalks as a function of horizontal distance are calculated and in the crossed adjacent- transmission lines, the crosstalks as a function of vertical distance are simulated. Also, the crosstalks as functions of horizontal and vertical distances are measured and analyzed in the parallel adjacent-transmission lines which are on the different planes.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.142-142
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• 2011

Microwave diagnostics method for plasma science and engineering is vigorous research area for its good characteristics such as high sensitivity, reliability, and broad measurement spectrum from low density plasma to high density. We investigate mechanism of microwave probes (hairpin, impedance and absorbtionf probe) and apply it for interpretation of full transmitted spectrum of cutoff probe. Mechanism of the spectrum having same key roles of I-V curve of Langmuir probe is not exactly revealed yet in spite of its importance. This study elucidates physics behind it using a circuit model and E/M wave simulation. Circuit model reveals exact cut-off peak frequency taking account of a collision frequency and a plasma frequency and it enable precise diagnostics of plasma densty from low pressure to high pressre. Cut-off like peaks have been obstacle for choosing cut-off peak is analyzed by E/M simulation and one of cutoff like peaks made by probe holder used for acquire plasma density with cutoff peak applying the hairpin relation. Furthermore, phase difference method for plasma density is conducted. This method uses a single microwave frequency source and it is low-priced.

• Human Ecology Research
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• v.56 no.5
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• pp.461-472
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• 2018

Using a sample of third grade middle school students from the forth wave of Children and Youth Panel Survey in 2012, the mediation effects of private educational expenditure between parenting styles and children's academic performance were investigated by applying factor, cluster, tobit, and two stage regression analysis. The major results were as follows. First, four types of parenting style were identified. The most frequent parenting style was ambivalent parenting (tiger parenting) which was followed by authoritative parenting. Second, compared to permissive parenting style, ambivalent, authoritative, and authoritarian parenting styles were significantly associated with more private educational expenditures. Third, more private educational expenditures were significantly associated with higher academic performance of children. I found both a full mediation effect of private educational expenditure for ambivalent and authoritarian parenting styles, and a partial mediation effect for authoritative parents. Authoritative parenting style has a negative moderating effect on the relationship between household income and private educational expenditure, along with a positive direct effect on the academic performance of children. The results suggested that an authoritative parenting style was related with higher academic performance of children with less private educational expenditures compared to other parenting styles. The results also implied that the public policies to enhance authoritative parenting style among parents would be effective to reduce household's private educational expenditures.