• 반도체디스플레이기술학회지
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• 제6권4호
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• pp.1-4
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• 2007

Carbon nanotube oscillators encapsulating copper nanowire were investigated by molecular dynamics simulations. The excess forces due to the carbon-carbon van der Waals interactions are higher than the excess force due to carbon-copper interactions. And the masses of copper atoms are higher than those of carbon atoms. So, the carbon atoms are easier accelerated than the copper atoms. When the encapsulated copper nanowire deforms the encapsulating nanotube, the frequency can not be estimated by the mass-frequency dependence in classical oscillation theory.

• 폴리머
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• 제25권1호
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• pp.98-107
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• 2001

팬텀 모델 제작을 위해 도전체로서 전도성 카본블랙을, 유전체로서 (Ba, Ca)$(Sn, Ti)O_3$ 와 $SrTiO_3$를 적용한 SBS 복합재료의 유전 특성과 형상 회복 특성을 조사하였다. 카본블랙만을 첨가한 복합재료는 카본블랙 함량이 증가함에 따라 복소유전율과 도전율이 증가하였으며, 주파수가 증가함에 따라 유전율이 감소하고 도전율은 증가하는 주파수 의존 특성을 보였다. 카본블랙과 유전체를 동시에 적용한 3상 복합재료는 동일한 카본블랙 함량에 대해서 유전체의 함량이 증가할수록 복소유전율과 도전율이 증가하는 특성을 나타냈으며, 카본블랙의 영향으로 주파수가 증가함에 따라 유전율이 감소하였고 도전율은 증가하였다. 유전체/SBS 복합재료의 유전성질과 도전체/SBS 복합재료의 주파수 의존도를 조절하여 현재 이동전화 사용 주파수 대역인 775 MHz~2 GHz 범위에서 인체의 뇌와 두개골 조직의 유전율, 도전율과 상응하는 비흡수율 측정용 팬텀 모델 재료를 제작할 수 있었다. 열기계적 반복시험에서는 충전재의 함량이 증가함에 따라 잔류변형량이 증가하였으나, 인체 조직을 모사한 SBS 복합재료는 우수한 형상 회복 성능을 보였다.

• Applied Microscopy
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• 제47권3호
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• pp.121-125
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• 2017

This study deals the prediction of temperature effect on low-frequency dispersion of alternating current (AC) conductivity spectra of composite materials based on copolymer reinforced with carbon black (CB) particles. A sample of ethylene butylacrylate loaded with 13% of CB particles were prepared and investigated using the impedance spectroscopy representation in the frequency range from 40 Hz to 0.1 MHz and temperature range from $20^{\circ}C$ to $125^{\circ}C$. The dielectric constant, ${\varepsilon}^{\prime}$, and dielectric losses, ${\varepsilon}^{{\prime}{\prime}}$, were found to decrease with increasing frequency. The frequency dependence of the AC conductivity follows the universal power law with a large deviation in the high frequency region, the positive temperature coefficient in resistivity effect has been observed below the melting temperature which makes this composite potentially remarkable for industrial applications.

• 한국수산과학회지
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• 제53권2호
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• pp.209-217
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• 2020

The purpose of this study was to compare the model-predicted and experimentally measured target strength (TS) of golden cuttlefish Sepia esculenta cuttlebones. Ultrasonic signals used to estimate frequency-dependent TS and the speed of sound in cuttlebones were measured by pulse-echo and through-transmission techniques, using a chirp sonar system and an ultrasonic pulser/receiver system under controlled laboratory conditions. The model appeared to slightly underestimate the predicted TS values in the frequency range of 100-160 kHz. However, there was good agreement between the predicted and measured TS values in the frequency range of 160-200 kHz. The significant similarity between the model-predicted and experimentally measured TS values supports the use of the Kirchhoff-ray mode (KRM) model for acoustic scattering analysis of cuttlebones. Accordingly, we concluded that the KRM model can be used as a tool to evaluate the frequency-dependent variability of TS due to changes in golden cuttlefish swimming depth.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.550-553
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• 2001

In this study, unity current gain frequency f$\_$T/ of GaAs MESFET is predicted with different temperatures up to 400 $^{\circ}C$. Temperature dependence parameters of the device including intrinsic carrier concentration n$\_$i/ effective mass, depletion width are considered to be temperature dependent. Small signal parameters such as gate-source, gate dran capacitances C$\_$gs/ C$\_$gd/ are correlated with transconductance g$\_$m/ to predict the unity current gain frequency. The extrinsic capacitance which plays an important roles in high frequency region has been taken into consideration in evaluating total capacitance by using elliptic integral through the substrate. From the results, f$\_$T/ decreases as the temperature increases due to the increase of small signal capacitances and the mobility degradation. Finally the extrinsic elements of capacitances have been proved to be critical in deciding f$\_$T/ which are originated from the design rule of the device.

• Current Optics and Photonics
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• 제7권1호
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• pp.28-32
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• 2023

Frequency characteristics of gain-saturated erbium-doped fiber amplifier (EDFA) are experimentally evaluated to mitigate the optical signal fluctuation induced by atmospheric turbulence in terrestrial freespace optical communication systems. Here, an acousto-optic modulator (AOM) is used to emulate optical signal fluctuations induced by atmospheric turbulence. The waveform which is generated in proportion to the refractive-index structural parameters is used to drive the AOM at various periodic frequencies. Thus, the dependence of the signal fluctuation suppression on the frequency is evaluated. The experiment is conducted using a periodic frequency sweep of the AOM driving voltage waveform and signal input power variation of the amplifier. It is observed that a low periodic frequency and high input signal power effectively suppress the optical signal fluctuation. This study evaluates the experimental results from the high-pass filter and gain-saturation characteristics of the EDFA.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.143.2-143.2
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• 2007

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 추계학술대회 논문집
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• pp.12-13
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• 1988

• 한국생활과학회지
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• 제5권2호
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• pp.131-143
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• 1996

The purpose of this study was to investigate clothing involvement and clothing behavior of women and to indentify the relationship between clothing behavior and clothing involvement. The data were analyzed using percentage, frequency, factor analysis, ANOVA, Scheffe test, t-test, and Multiple Regression. The results of the study were as follows: 1. Five dimensions of clothing involvement were derived by factor analysis such as fashion, interest pleasure, symbolism, and perceived buying risk. 2. There were significant relationships between clothing involvement dimensions and demographic characteristics such as age, educational background and family income level. Those who were younger and not married showed positive relationship among fashion, interest and pleasure of clothing involvement dimensions. Those who had higher educational background showed positive relationship with clothing involvement. Those who were empolyed showed higher clothing involvement with symbolism and perceived buying risk. 3. Age, marital status, and educational background showed important variables as factors that exert influence on clothing behavior: Those who were younger and not married attached importance to interest aesthetics, psychological dependence, and fashion. Those who were older and married attached importance to modesty and comfort. The more educated respondents were more concerned about interest aesthetics, symbolism, psychological dependence, and fashion. 4. The fashion of clothing involvement showed positive relationship in fashion, interest, symbolism, and psychological dependence of clothing behavior, and negative relationship in modesty and comfort. The interest of clothing involvement showed positive relationship in aesthetics and interest, and negative relationship in modesty and comfort of clothing behavior. The pleasure of clothing involvement showed positive relationship in psychological dependence, management, interest, and pleasure of clothing behavior. The symbolism of clothing involvement showed positive relationship in symbolism, modesty, conformity, psychological dependence, and fashion of clothing behavior. The perceived buying risk of clothing involvement showed positive relationship in management, conformity, and comfort and negative relationship in symbolism and fashion of clothing behavior.

• 산업융합연구
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• 제22권6호
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• pp.61-71
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• 2024

본 연구의 목적은 아동의 모 애착과 행복감 간의 관계에서 자아탄력성과 스마트폰 의존도의 매개효과를 검증하는 것이다. 이를 위해 육아정책연구소(Korea Institute of Child Care and Education)에서 조사한 한국 아동패널 12차 데이터를 활용하였고, 그 중 1,143명을 연구대상자로 선정했다. 분석 방법은 빈도분석, 기술통계분석, 상관분석을 실시하였고, Process Macro Model Number 4 분석을 활용하여 매개효과를 분석하였다. 스마트폰 의존도와 자아탄력성의 간접효과는 부트스트래핑(Bootstrapping)를 적용하여 검증하였다. 연구결과는 다음과 같다. 첫째, 모 애착은 아동의 행복감을 증가시키는 것으로 나타났다. 둘째, 아동의 모 애착과 행복감 간의 관계에서 자아탄력성의 부분 매개효과를 확인했다. 셋째, 아동의 모 애착이 행복감에 미치는 영향에서 스마트폰 의존도는 부분 매개효과를 보이는 것으로 나타났다. 이러한 연구결과를 바탕으로 아동의 행복감을 증진시킬 수 있는 다양한 실천적 과제들을 제시했다.