• Bulletin of the Korean Chemical Society
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• v.12 no.4
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• pp.429-433
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• 1991

The photoinduced electron transfer reactions of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) in various polar solvents were studied by measuring time-resolved fluorescence. The temperature dependence on the fluorescence decay rate in acetonitrile, methanol, ethanol and buthanol was carried out to obtain the activation energy and Arrehnius factor for the photoinduced electron transfer reaction. It was found that as the dielectric constant of the solvent increases, the activation energy and the reaction rate increase. This implys that the Arrehnius factor is important in controlling the photoinduced electron transfer reaction rate. In water, TMPD exists in three forms (cationic, protonated and neutral forms) due to the high dielectric constant and strong proton donating power of water. The photoinduced electron transfer reaction was found to be very fast (< 50 ps) and also the long liverd component in the fluorescence decay profile attributable to the photoexcited protonated form of TMPD was observed. Probably, the reaction pathway and the reaction coordinate seem to be different depending on the solvents studied here.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.6
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• pp.10-18
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• 1995

Diffraction patterns of the electromagnetic field scattered by a circular cylindrical cavity embedded in a dielectric medium are analyzed. When the wavelength of the incident wave is comparable to the radius of the cavity, strong double dips occur at the locations corresponding to the top and the bottom of the cavity. Furthermore, the phase changes abruptly about the dip points. The changes of the amplitude and the phase patterns are observed as the measuring distance and the signal frequency varies. The effects of the change of the medium dielectric constant on the diffraction pattern is also presented.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.267-271
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• 1987

The test cell for preventing the edge effect reducing the intrinsic breakdown strength of polypropylene film and measuring the intrinsic breakdown strength of the film was developed. The new approach was to develope an electrode system with an edge region which is carefully graded over an extended distance. The new test arrangement employed a central circular electrode at high voltage and a set of nine concentric surrounding rings each controlled in potential by external grading resistors to be at decreasing potentials from that at the center in 10% increments. Two different size structures using the same basic principle were tried and were both found to be successful. The test electrodes were manufactured using standard printed circuit technology and were chosen to be copper on high dielectric constant GIO board.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2196-2201
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• 2007

Materials used at microwave are usually used as a dielectric with a manufacturing purpose of printed circuit boards, etc. Complex permittivity of them can be measured from attenuation constant or propagation constant of a transmission line using a microstrip line with bulk type. But as the technique recently which can manufacture to have complex permittivity and permeability demanded using nonferrous metals for powder-type grows up, we need sensors and methods which can measure characteristics of powder-type materials. So far measuring methods of permittivity and permeability with waveguide or coaxial cable are used but they have faults which have a complex measurement method and are difficult to simultaneously measure permittivity and permeability. In this paper, a simultaneous measuring method of permittivity and permeability with 2-port coaxial cable and a new proposed calculation. The proposed 2-port coaxial cable is designed to be easy to insert materials and to have a wideband. We measure permittivity and permeability of magnetic powder(Ni-Fe-Mo, Ni-Fe) which reveal its characteristic at $0.3{\sim}1.3GHz$ to identify the proposed sensor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.689-692
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• 2001

In this paper, the pizoelectric and dielectric properties of 0.95Pb(ZrxTil-x)O$_3$- 0.05Pb(Mn$\_$0.2/Fe$\_$0.4/W$\_$0.4/)O$_3$piezoelectric ceramics is investigated as a function of Zr/Ti mole ratio. Also, MPB(Morphotropic Phase Boundary) and optimal sintering temperature is studied using XRD and SEM. As a results, when Zr/Ti mole ratio is 52/48, electromechanical coupling factor, k$\_$p/, is 58[%], permittivity, $\varepsilon$$\^$T/$\_$33//$\varepsilon$0, is 1360 and piezoelectric strain constant, d$\_$33/ is 265[pC/N] and the piezoelectric and dielectric properties become maximum. Phase transition temperature of its ternary piezoelectric system is about 350[$^{\circ}C$]. From the XRD analysis, when Zr/Ti mole ratio is 52/48, tetragonal phase transits to rhombohedral phase. Also, From measuring results of the sintering density, when sintering temperature is 1050[$^{\circ}C$], sintering density become maximum and is about 7930[kg/㎥], and average grain size is about 2-3[$\mu\textrm{m}$].

• Journal of Biosystems Engineering
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• v.32 no.4
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• pp.237-246
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• 2007

In this study, the microwave free-space transmission technique was used to measure the dielectric property of powdered food at microwave frequencies. The sample holder was designed and fabricated to transmit the microwave signals ranging from 1 to 15GHz. From the microwave propagation theory the equation expressing the dielectric property of powdered food was derived and validated by standard dielectrics. The dielectric property of powdered food such as wheat flour, coffee powder and milk powder was measured and analyzed. In the uniform range of bulk density of material, the real parts of permittivity of the food samples increased with the increase of moisture content, bulk density and temperature of the samples. The propagation properties such as attenuation and phase shift increased linearly as the moisture density of the food samples increased. As a measuring frequency of the moisture content, the X-band was recommended.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.2
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• pp.132-136
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• 2009

SiOC thin film of hybrid-type that is the limelight as low dielectric material of next generation were deposited by plasma enhanced chemical vapor deposition (PECVD) method with bistrimethylsilylmethane (BTMSM) precursor increased by 2 sccms from 24 sccms to 32 sccm. Manufactured samples are analyzed components by measuring FT/IR absorption lines. It is a tendency that seems to be growing of Si-O-Si(C) bonding group and narrowing of Si-O-$CH_3$ bonding group relative to the increasing flow-rate BTMSM. The chemical shift in the XPS analysis was shown in the specimens between the BTMSM=26 sccm and BTMSM = 28 sccm. The binding energy of Si 2p, C 1s and O 1s electron orbit spectra was the low-est at the specimen of the BTMSM=26 sccm. From the results of electrical Properties using the 1 MHz C - V measurements, the dielectric constant was 2.32 at the specimen with the BTMSM = 26 sccm.

• Journal of the Korean Geosynthetics Society
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• v.13 no.3
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• pp.1-10
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• 2014

Several types of methods such as resistivity survey, ground penetration radar, etc are used for detection of levee leakage and according to the river design guidelines detection of levee leakage is performed by measuring the hydraulic conductivity of levee soil. But, the former can not verify the leakage point and degree of saturation, the latter is an after treatment method. Movable sensor, which is a high-tech TDR system developed since 2000, can obtain directly the dielectric constant profile covering the whole depth of levee. In this study, laboratory and field model experiments were carried out using movable TDR sensor in order to evaluate the applicability as detection system of levee leakage, As the result, movable TDR system has proven to be 3 times more sensitive to water contents than dry unit weight, and the results conclude that the dielectric constant, water contents and density of the ground proved to have a correlation among them, and the dielectric constant is expected to be a basic data on detection of levee leakage.

• Journal of Sensor Science and Technology
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• v.6 no.6
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• pp.491-499
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• 1997

We fabricated the ceramic PLT tablet which was composed of 5, 10 and 15 mol% lanthanum concentration and thin film PLT to develope pyroelectric materials, and investigated their characteristics. Using TG/DTA, we determined calcination and sintering temperature to sinter the PLT completely and to prevent volatilization of the Pb components. The calcination and sintering temperature were $850^{\circ}C$, $1150^{\circ}C$ respectively, and there was a lot of mass loss at higher sintering temperature. By measuring temperature-dielectric constant characteristics of ceramic tablet we investigated dielectric constant characteristics depends on La concentration. The Curie point of PLT with 5, 10 and 15 mol% lanthanum concentration were $330^{\circ}C$, $269^{\circ}C$ and $210^{\circ}C$ respectively. Using PLT ceramic tablet we observed IR detection characteristics, and then deposited PLT thin film by rf magnetron sputtering. We verified that PLT thin film fabricated with completely sintered PLT target had the same structure to target by investigating lattice constant and optical transparency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.326-326
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• 2010

The dielectric properties of continuous composition spreaded (CCS) $BaTiO_3-SrTiO_3$ (BST) thin filmsgrown at room temperature and annealed at different temperature ($350^{\circ}C$ and $550^{\circ}C$) were investigated. Moreover, electrical properties (leakage current and breakdown voltage) of CCS BST thin films were also investigated. The aluminum top-electrode, sized by $200{\times}200\;{\mu}m2$ and apart from each other by $300\;{\mu}m$, were deposited on the CCS BST thin films by the DC sputtering system. The dielectric properties of the CCS BST thin films were significantly influenced depending on the distance from $BaTiO_3$ and $SrTiO_3$ targets which was attributed to the $BaTiO_3-SrTiO_3$ composition ratio. The maps of dielectric constants and loss tangents were plotted via $1500\;{\mu}m$ - step measuring. The specific points showing the dielectric constant (k: ~300) and loss tangent (tand: ~0.008) at 1 MHz were found.