• The Korean Journal of Physiology
• /
• v.29 no.2
• /
• pp.225-232
• /
• 1995

The present study was conducted to evaluate the effect of phorbol 12,13-dibutyrate (PDBu) on the contraction of rabbit jugular vein in vitro. PDBu concentrations of greater than 10 nM induced a periodic contraction which was composed of rapid contraction, plateau and slow relaxation. The frequency of periodic contraction increased as PDBu concentration increased. The PDBu-induced contraction was inhibited by staurosporine (100 nM), it was not changed by tetrodotoxin $(1\;{\mu}M).$ In $Ca^{2+}$-free medium, PDBu induced a sustaining contraction, but not periodic contraction. Addition of $Ca^{2+}$ to medium evoked periodic contraction which was inhibited by nifedipine, PDBu concentrations of greater than $0.1\;{\mu}M$ increased ^{45}Ca^{2+}$ uptake without changing $^{45}Ca^{2+}$ efflux. Charybdotoxin and apamin, $Ca^{2+}$-activated K^{+}$ channel blockers, did not affect the PDBu-induced periodic contraction, whereas tetraethylammonium (TEA) abolished the periodicity. Pinacidil $(10\;{\mu}M).$, a potassium channel activator, blocked PDBu induced periodic contraction, which was recovered by glybenclamide $(10\;{\mu}M).$. In high potassium solution, PDBu did not produce the periodic contraction. These results suggest that the PDBu-induced periodicity of contraction is modulated by voltage dependent $Ca^{2+}$ channel and ATP-sensitive $K^{+}$ channel.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.05a
• /
• pp.31.2-31.2
• /
• 2011

We have investigated frequency dependant conductivity (or permittivity) of low dimensional oxide structures represented by [($Sr_{0.75}$, $La_{0.25}$)$TiO_3$]$_1$/1$[SrTiO_3]_n$ superlattices. The low dimensional oxide superlattice was made by cumulative stacking of one unit cell thick La doped $SrTiO_3$ and $SrTiO_3$ with variable thickness from 1 to 6 unit cell, i,e, [($Sr_{0.75}$, $La_{0.25}$)$TiO_3$]$_1$/$[SrTiO_3]_n$ (n=1, 2, 3, 4, 5, 6). We found two kinds of relaxation when n is 3 and 4, while, inductance component was observed at n=1. This behavior can be explained by electron modulation in ($Sr_{0.75}$, $La_{0.25}$)$TiO_3/SrTiO_3$ superlattices. When n is 1, electrons by La doping well extend to un-doped layer. Therefore, the transport of superlattices follows bulk-like behavior. On the other hand, as n increased, the doped electrons became two types of carrier: one localized and the other extended. These results in two kinds of transport phase. At further increase of n, most of doped electrons are localized at the doped layer. This result shows that dimensionality of the oxide structure significantly affect the transport of oxide nanostructures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.11
• /
• pp.895-899
• /
• 2011

Multiferroic BFO/PZT(5/95) multilayer films were fabricated by spin-coating method on the Pt/Ti/$SiO_2$/Si substrate alternately using BFO and PZT(9/95) alkoxide solutions. The structural and dielectric properties were investigated with variation of the solvent and the number of coatings. All films showed the typical XRD patterns of the perovskite polycrystalline structure without presence of the second phase such as $Bi_2Fe_4O_3$. BFO/PZT multilayer thin films showed the typical dielectric relaxation properties with increase an applied frequency. The average thickness of 6-coated BFO/PZT multilayer film was about 600 nm. The dielectric properties such as dielectric constant, dielectric loss and remnant polarization were superior to those of single composition BFO film, and those values for BFO/PZT multilayer film were 1199, 0.23% and 12 ${\mu}C/cm^2$.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.10
• /
• pp.127-136
• /
• 2004

This paper is the first of two companion papers concerning the analysis and design of a pneumatic vibration isolation system. The design optimization of the pneumatic vibration isolation system is required for the reduction of cost, endeavor and time, and it needs modeling and calculation algorithm. The nonlinear models are devised from the fluid mechanical expression for components of the system and the calculation algorithm is derived from the mathematical relationship between the models. It is shown that the orifice makes the nonlinear property of the transmissibility curve that the resonant frequency changes by the amplitude of excited vibration. Linearization of the nonlinear models is tried to reduce elapsed time and truncation error accumulation and to enable the transmissibility calculation of the system with multi damping chambers. The equivalent mechanical models generated by linearization clarify the function of each component of the system and lead to the linearized transfer function that can give forth to the transmissibility exactly close to that of nonlinear models. The modified successive under-relaxation method is developed to calculate the linearized transfer function.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.34 no.12
• /
• pp.2062-2072
• /
• 2010

This research evaluates the change of the water absorbency and drying speed of a quick-drying knit fabric by repeated laundering and laundering conditions and investigates the influence of laundering conditions on the functional properties of the knit fabric. Four factors of laundering conditions were studied: detergent, water hardness, water temperature, and frequency of rotation. Knit fabrics were washed for 25 laundering cycles in a drum-type washing machine with nine different laundering conditions derived from an orthogonal array. The properties of knit fabrics were measured with a drop absorption test, a strip test, and a drying time test. Relaxation shrinkage pointed to a change in the structural characteristics of the knit fabric. Wetting time was faster and wickability was greater in the knit fabrics that underwent 5 laundering cycles; in addition, there were no obvious changes in wetting time and wickability. The detergent was the most important factor in wetting time (40.4%) and wickability (60% or above). Water hardness, water temperature and RPM had less of an effect on wetting time and wickability. There were no significant differences between the levels of laundering conditions (except for detergent) on wetting time and wickability. Drying times with neutral and alkali were slower by repeated laundering; however, there was no obvious change in drying time. Hardness, water temperature and RPM had less of an impact on drying time.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.11 no.4
• /
• pp.72-81
• /
• 2012

This study investigates structural, fatigue and modal analyses at bicycle suspension seat post. When weight is applied to the saddle, models 1 and 2 have the weakest strength at the part connected with saddle. And model 2 is greater total deformation and equivalent stress than model 1. Among the cases of nonuniform fatigue loads at models 1 and 2, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'Sample history' with the average stress of 0 to $-10^4MPa$ and the amplitude stress of 0 to $10^4MPa$, the possibility of maximum damage becomes 4%. This stress state can be shown with 5 to 7times more than the damage possibility of 'SAE bracket history' or 'SAE transmission'. Model 1 has better impulse relaxation and passenger sensitivity than model 2. The structural result of this study can be effectively utilized with the design of bicycle suspension seat post by investigating prevention and durability against its damage.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2002.08a
• /
• pp.419-422
• /
• 2002

We have studied dielectric properties in the smectic phases of 4-(6-ethoxy-1-trifluoromethyl-hexyloxycarbonyl)-phenyl-4-Nonyloxybiphenyl-4-carboxylat ( TFMEOHPNBC ) having fluorine attached to one of its benzene rings. Homogeneous and homeotropic 1.5 and 5${\mu}m$ thick test cells were prepared to analyze molecular dynamic property. We measured capacitance as a function of temperature in the frequency range between 20 Hz and 100 kHz by using HP4284A LCR meter. We observed that the homogeneous cell has high dielectric constant causing dipole moment in smectic $C^{\ast}$ phase, but we can see the dipole moments are canceled out in antiferroelectric phase. It is found that there are two kind of the relaxation director fluctuation below 100 kHz. The first is ionic or space charge contribution below 10 Hz, and the second is Goldstone mode near 1-2 kHz. We will discuss molecular dynamics in smectic phase from extra information such as x-ray and electrooptic data.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1988.05a
• /
• pp.38-40
• /
• 1988

This paper was a study on dielectic characteristics of polypropylen film which were annealled in air and qunched in nitorgen after aging for 5[Hr]. Dielectric characteristics of specimen were measured in temperature of the range of 15-120[$^{\circ}C$], and in frequency of the range of $30-1{\times}10^6$[Hz.] As the result, for dielectric relaxation $\beta$-peak was observed in 20[$^{\circ}C$], and $\alpha$-peak was observed in 90[$^{\circ}C$]. Also, it was explained that $\alpha$-peak attributed due to armorphous region and $\beta$-peak attributed due to crystalline region and activation energy from dielectric loss spectra was obtained 34.5[kcal/mole] for $\alpha$-peak and 80.5[Kcal/mole] for $\beta$-peak, respectively.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.5
• /
• pp.402-411
• /
• 2000

This study investigates the method to measure the viscoelastic properties of asphalt cement, one of the viscoelastic materials, using the ultrasound. The wave speed and attenuation were measured from $-20^{\circ}C$ to $60^{\circ}C$ at the frequency of 2.25MHz. Then, the storage and loss longitudinal moduli, loss tangent storage and loss longitudinal compliances were found depending on the temperatures based on the linear viscoelastic theory. Stress relaxation, creep, and viscosity were predicted using Maxwell and Voigt-Kelvin viscoelastic models. The validity of superposition principle and shift factor were verified by comparing the present results to the data reported in the literatures.

• Electrical & Electronic Materials
• /
• v.10 no.10
• /
• pp.1041-1047
• /
• 1997

In this paper the dielectric properties of (0.8-x)Pb(Mb$_{1}$3//Nb/2/3)O$_3$/BaTiO$_3$-CaZrO$_3$(x=0.1, 0.15, 0.2, 0.25) ceramics were investigated. Specimens were prepared by the conventional mixed oxide method and sintering temperature and time were 1000~115$0^{\circ}C$ 2hr, respectively. The structural and dielectric properties with variation of sintering temperature and composition were investigated. All the specimens sintered at 115$0^{\circ}C$ for 2hr showed the highest value of 1043. With increasing the contents of CZ and frequency dielectric constant was decreased and which was decreased with increasing temperature from 3$0^{\circ}C$ to 15$0^{\circ}C$.