• Macromolecular Research
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• v.12 no.3
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• pp.311-315
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• 2004

We have prepared new polyelectrolytes containing trialkoxysilyl groups by copolymerizing 3-(trimethoxysilyl)propyl methacrylate (TSPM) with either [2-(methacryloyloxy)ethyl]trimethyl ammonium chloride (METAC), [2-(methacryloyloxy)ethyl]dimethyl propyl ammonium bromide (MEDPAB), or [2-(acryloyloxy)ethyl]trimethyl ammonium chloride (AETAC). The copolymers TSPM/METAC, TSPM/MEDPAB, and TSPM/METAC having compositions of 15/85, 10/90, and 5/95, respectively, were self-crosslinkable polyelectrolytes that possess humidity-sensitive properties. We measured the impedances of the copolymers at various relative humidities (RHs) and found that the resistance was dependent on the content of METAC, MEDPAB, or AETAC. The impedance changed from 10$\^$7/ $\Omega$ at 20% RH to 10$^3$ $\Omega$ at 95% RH, which is quite a suitable range for a humidity sensor that is to be utilized at ambient humidity. We also performed tests of the materials temperature dependence, hysteresis, response time, and water durability.

• Journal of electromagnetic engineering and science
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• v.16 no.2
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• pp.67-73
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• 2016

This paper presents simple expressions for the effective permeability of bulk metamaterial consisting of ring resonators (RRs) or split ring resonators (SRRs) based on the convenient geometrical factors of the structure compared with wavelength. The resonant frequency dependence of the medium permeability, including loss effects, is analyzed in detail. Inverting the analysis equations, useful design (or synthesis) equations are derived for a systematic design process with some examples. This paper may particularly be useful for the design of a bulk metamaterial with a specific negative relative permeability at a desired frequency. The loss of metamaterials consisting of RRs (or SRRs) is also analyzed over a wide frequency band from 10 MHz to 10 THz.

• Journal of the Korean Home Economics Association
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• v.40 no.9
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• pp.17-33
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• 2002

This study was to investigate the relationships of personal resources, individual psychological variables, and relational characteristics with marital instability of wives who experienced physical and/or psychological abuse from their husbands, and to analyze the relative significance of related variables on marital instability. Self-administered questionnaire method was used to collect data from 500 wives residing in Chonbuk-do province, and data from 306 wives who reported to be psychologically and/or physically abused during last three years were used in the final analyses. Results showed that there were significant differences in the levels of marital instability according to wives' employment status, number of children, and occupational status of husbands. Correlational analyses indicated that wives' economic dependence, all individual psychological variables, and three relational variables were significantly correlated with marital instability of abused wives. Finally, multiple regression analyses showed that marital comparison level and degree of abuse from husband were the most powerful predictors on marital instability, and all these variables accounted for 61% of the total variance of abused wives' marital instability.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.243-246
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• 2006

This study investigates the improvement in the theoretical success rate of the integer ambiguity resolution in GPS/GNSS carrier-phase positioning by using many visible satellites. It estimates the dependence of the rate on the baseline length in relative positioning under the condition of the use of double/triple-frequency navigation signals. The calculation results show that the use of 14 navigation satellites (i.e., seven GPS and seven Galileo ones) remarkably improves the success rate under the condition of very short baseline length, compared with the use of seven GPS ones. The numerical reliability of the calculated success rates is strictly tested by examining the tightness of the union and minimum-distance bounds to the rate. These bounds are also shown to be effective to investigate the realization of the high success rates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.149-152
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• 2000

AC impedance measurements on poly-p-phenylenevinylene (PPV) LEDs in the frequency range between 10 Hz and 10$\^$6/ Hz were carried out. The complex-plane impedance spectra indicate that PPV devices can be represented by equivalent circuits that corresponds to the bulk and interfacial regions at high and low frequencies, respectively. As a result of complex impedance analysis through the separation of bulk and interfacial region impedances, increase of forward bias in Al/PPV/ITO devices gave rise to relative decrease of the interfacial region impedance. Above the electric field of 10$\^$6/ V/cm the PPV device showed a space charge limited current (SCLC) conduction. The dependence of the transport mechanism and dielectric properties on the applied bias voltage is discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.129-132
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• 1992

Rutile was among the first dielectric materials used. However, rutile exhibits a very high temperature coefficient of capacitance (about -750[ppm/$^{\circ}C$]) which resticts its practical application. Since this first use of titania, other materials have also been studied with the object of decreasing the temperature dependence whilst retaining favorable dielectric loss, Q, and relative permittivity. The temperature coefficient of temperature compensation capacitor is +100~750[ppm/$^{\circ}C$], dielectric constant 10~150. Low loss ceramics with dielectric constants in the 10～150 range also found application. Recently, their applications are extended in EMI filter and dielectric materials for microwave. There temperature coefficient of dielectric materials approaches 0[ppm/$^{\circ}C$]. The dielectric preperties of zirconia titanate ceramics prepared by addition of $Ta_2O_{5}$ were investigated.

• Korea-Australia Rheology Journal
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• v.15 no.2
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• pp.75-82
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• 2003

In this study, with the finite element method we numerically investigate the deformation of liquid drops surrounded by Newtonian or non-Newtonian viscous medium in the axisymmetric contraction flow. 1, 2 or 4 Newtonian or non-Newtonian drops are considered and the truncated power-law model is applied In order to describe non-Newtonian viscous behavior for both fluids. In this type of flow the drop exhibits considerably large deformation, and thus techniques of unstructured mesh generation and auto-remeshing are employed to accurately express the fluid mechanical behavior. We examine the deformation pattern of liquid drops with viscosity dependence different from that of the surrounding medium and also explain their interactions by comparing relative position or speed of drop front.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.238-246
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• 2003

By using simulated ground motions, which is sum of earthquake signals and noise, we measured the distortion of response spectra due to noise. We found that the distortion is more closely related to the signal-to-noise (S/N) ratio of root-mean-square (RMS) measurement than that of conventional peak measurement. Given a S/M ratio, the distortion of absolute acceleration response spectra is independent on the earthquake magnitude, while that of relative displacement response spectra has a strong dependence on the earthquake magnitude. This means that, when we calculate response spectra from time histories, we can efficiently predict the distortion of acceleration response spectra simply by measuring the RMS SJN ratios, or the distortion of displacement response spectra by combining the RMS S/N ratios and the earthquake magnitudes.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.663-666
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• 1995

The domain wall motion coercivity, $H_{c}$, of magnetic materials arises from the dependence of the wall energy on localized changes in material parameters (magnetization, anisotropy, exchange energy densities). However, in an otherwise perfectly homogeneous material, the domain wall energy might change due to the change in the volume of the wall versus the wall position. Thus, any surface roughness contributes to the coercivity. Assuming different two-dimensional surface profiles, characterized by average wavelengths ${\lambda}_{x}$ and ${\lambda}_{y}$, and relative thickness variations dh/h, the coercivity due to the surface roughness has been calculated. Compared to the one dimensional case, the 2D coercivity is reduced. Depending on the ratio of ${\lambda}$ to the domain wall width, $H_{c}$ has a maximum around 2, and increasing with dh/h. With the decreasing thickness of the thin film and GMR heads, it might be the domain factor in determining the coercivity.

• Journal of Magnetics
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• v.20 no.1
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• pp.21-25
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• 2015

Fine Nd-Fe-B-type particles were prepared by ball milling of different types of Nd-Fe-B precursor materials, such as die-upset magnet, HDDR-treated material, and sintered magnets. Coercivity dependence on the grain and particle size of the powder was investigated. Coercivity of the milled particles was reduced as the particle size decreased, and the extent of coercivity loss was dependent upon the precursor material. Coercivity loss in the finely milled particles was attributed to the surface oxidation. The extent of coercivity loss in the fine particles was closely linked to grain size of the precursor materials. Coercivity loss was more profound for the fine particles with larger grain size. Contrary to the fine particles from the sintered magnets with larger grain size the fine particles (~10 um) from the die-upset magnet and HDDR-treated material with much finer grain size still retained high coercivity (> 10 kOe for die-upset magnet, > 4 kOe for HDDR-treated material).