• Composites Research
• /
• v.14 no.1
• /
• pp.30-38
• /
• 2001

As fiber reinforced composite materials are widely used in aircraft, space structures and robot arms, the on-line cure monitoring during the cure process of the composite materials has become an important research area for the better quality and productivity. In this paper, the dielectric circuit of the Wheatstone bridge type for measuring the dissipation factor during cure of thermsetting resin matrix composite materials was designed and manufactured. Also, the dielectric sensor for the cure monitoring of high temperature cure composites was developed and tested. The residual thermal stresses of the dielectric sensor during high temperature cure were analyzed by the finite element method and its dielectric characteristics at high temperature cure were analyzed by the finite element method and its dielectric characteristics at high temperature were evaluated. The on-line cure monitoring of the BMI(Bismaleimide) resin was performed using the developed Wheatstone bridge type circuit and the high-temperature dielectric sensor.

• Journal of the Korean Ceramic Society
• /
• v.32 no.3
• /
• pp.295-304
• /
• 1995

Stabilization of the perovskite phase and sequence of reactions occuring during calcination were studied with solid solutions formed between Pb(Zn1/3Nb2/3)O3 and Pb(Fe1/2Nb1/2)O3. In the PZN-PFN composition of equal molar ratio, rhombohedral type pyrochlore phase (Pb2Nb2O7) and PbO-rich distorted cubic type pyrochlore phase (Pb3Nb2O8) were coexisted as intermediate phases at temperatures below 85$0^{\circ}C$, and these phases transformed to a stable cubic type pyrochlore phase, Pb3Nb4O13 solid solution and a perovskite solid solution at temperatures above 85$0^{\circ}C$. The major stable phase as increasing sintering temperatures was a perovskite phase in this binary system and prominent suppression of the pyrochlore phase was achieved by substituting Zn2+ with Fe3+ or by increasing sintering temperature. The composition containing 20mol% PZN possessed the best dielectric properties, and the dissipation factor was lower than 5% in all compositions.

• Journal of Ocean Engineering and Technology
• /
• v.20 no.5 s.72
• /
• pp.49-56
• /
• 2006

In this thesis, centrifuge model experiments and numerical analyses were carried out to investigate the behavior of an excavated slope in soft clay ground. Centrifuge model tests were performed with various slopes for the excavated ground, such as 1:1.5 and 1:2. Pore pressuresthe model ground were measured to find their effects on the stability of the excavated slope. These experiments showed that the model with 1:2.5 maintained its stability within a short period of time and failed gradually. Therefore, anexcavated slope of soft soil with this slope might maintain stable conditions within a certain time. The mode1 with a 1:3 slope was observed to maintain a very stable condition, showing insignificant deformation in the ground after being excavated. Numerical analyses with PLAXIS, a commerciallyavailable software implemented with the finite element numerical technique, were performed to find the pore pressure distribution within the ground mass and the deformation of the soil. From the results of numerical analysis, a negative pore pressure was developed after the excavation and thus the stability of the slope was maintained. The safety factor for slope failure was found to decrease with time because of the dissipation of negative pore pressure with time.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.6
• /
• pp.2425-2433
• /
• 2018

This study investigates a new organic based material and its dielectric and mechanical properties. It is a comprehensive nanocomposite comprising a combination of various types of nanofillers with hydrophobic silica nanoparticles (AEROSIL R 974) as a matrix modifier and a polyamide nano nonwoven textile, Ultramid-Polyamide 6, pulped in the electrostatic field as a dielectric barrier. The polymer matrix is an epoxy network based on diglycidyl ether of bisphenol A (DGEBA) and cycloaliphatic diamine (Laromine C260). The designed nanocomposite material is an alternative to the conventional three-component composites containing fiberglass and mica with properties that exceed current electroinsulating systems (volume resistivity on the order of $10^{16}{\Omega}{\cdot}m$, dissipation factor tan ${\delta}=4.7{\cdot}10^{-3}$, dielectric strength 39 kV/mm).

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.142-147
• /
• 2007

A series of styrene-butadiene-styrene/aluminium (SBR/Al) composites have been compounded with different weight ratios of Al. The prepared SBR-Al systems have been characterized for different mechanical properties such as tensile strength, tensile modulus and surface hardness have improved with the increase in content of Al in SBR matrix. This may is because of the increase in polymer-filler interaction. The electrical properties such as volume conductivity, surface resistivity, dielectric constant, dissipation factor (tan delta), and break down voltage of SBR/Al composites have been measured with reference to volume fraction $(V_{f}),$ frequency and temperature. The resistance of the SBR-Al composites is found to be ohmic. The voltage-current (V-I) characteristics for SBR-Al also exhibit a linear relationship indicating the ohmic behavior.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.2
• /
• pp.87-94
• /
• 2007

It has been argued that the use of plastics can cause problems during design and manufacture owing to their low strength, relatively poor thermal conductivity and large thermal expansion. However, the advantages of plastics e.g., corrosion resistance, low cost, curtailment of weight, design flexibility etc., can compensate abundantly for the disadvantages. This study analyzes and compares the heat transfer performance characteristics of automotive compact oil cooler composed of plastic tube bundle with conventional metal oil cooler on the same core area basis as diameter, tube thickness, number of tube or tube arrangement varies. The performance analyses are accomplished by use of computational fluid dynamics program Fluent 6.2, which is verified and compared with the results of performance tests. The result of analyses is coincided with that of experiments. Flow pattern at air side according to tube arrangement is dominant factor which affects heat dissipation in case of similar total heat transfer surface area.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.5
• /
• pp.2105-2119
• /
• 2015

This paper reported the experimental result of dielectric properties of Refined, Bleached and Deodorized Palm Oil (RBDPO) combined with 0-50% of Refined, Bleached and Deodorized Soybean Oil (RBDSO). The dielectric strength and relative permittivity of RBDPO/RBDSO was higher compared to mineral oil at all ranges of ratios and temperatures which indicated a positive sign for its possible use as insulating liquid in a transformer. All ratios of the RBDPO/RBDSO mixture also demonstrated lower dissipation factor compared to mineral oil at 40℃, 70℃ and 90℃. Apart from that, the kinematic viscosity for the oil mixtures shown exceeded the IEC 60296 as well as the mineral oil results. 70%RBDPO/30%RBDSO mixture ratio was chosen as the best mixing percentage after comparison was made with the mineral oil and IEC 60296 standard where the mixture accumulated the most satisfactory of dielectric properties hence making it as the potential candidate for palm and soybean-based transformer oil.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.14 no.3
• /
• pp.38-42
• /
• 2000

Plasma polymerized thin films were manufactured inter-electrode coupled plasma polymerization apparatus. The deposition rate reached its maximum between 40[W] and 100[W]. In the ESCA analysis, peaks revealing -CH2, -CH, -C- were present at 285.4 and 285.5[eV] respectively. The C=O peak at 532.8[eV] and the C-O peak at 533.8[eV], which were grouped with an unignorable amount of oxygen were conformed. In ESR analysis, the curve revealing strong amplification was in saturation, which was affected by weak power. This is considered as a -CH-Ch=Ch- structure containing the Allyl group. The relative permittivity of the plasma polymerized thin films was about 3.5 at a frequency of 100[Hz]∼200[kHz]. The dissipation factor showed allow value of 0.008.

• Steel and Composite Structures
• /
• v.12 no.5
• /
• pp.445-464
• /
• 2012

In order to evaluate the dynamic behavior of passive energy dissipation system, two steps need to be considered for prediction of structural response in the presence of ductile element in an off-centre bracing system. The first is a detailed analysis of the proposed ductile element and the second is the effect of this ductile element on an off-centre bracing system. The use of ductile bracing system is expanding in steel structures in order to increase the force reduction factor. Therefore, regarding the nonlinear behavior of steel material used in an off-centre bracing systems and using ductile element in OBS bracing systems, the seismic evaluation of the mentioned systems seems to be necessary. This paper aims to study linear and nonlinear behavior of steel frames with off-centre bracing system and ductile element, in order to get the best position of these bracing elements. To achieve this purpose, the modeling has been done with ANSYS software. The optimum eccentricity has been obtained by modeling three steel frames with different eccentricities and evaluating the results of them. The analytical results showed that the model OBS-C with 0.3 eccentricities has higher performance among the models.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.186.1-189
• /
• 2001

Ferroelectric $Bi_{4-x}$La$_{x}$Ti$_3$O$_{12}$ (BLT)thin films with various compositions(x=0.65, 0.70, 0.75) were prepared on Pt//Ti/SiO$_2$/Si(100) substrate by metal-organic deposition. The electrical and structural characteristics of BLT thin films were investigated to develop ferroelectric thin films for capacitor layers of FRAM. After spin coating, thin films were annealed at $650^{\circ}C$ for 1hour in oxygen atomosphere. Scanning electron micrographs showed uniform surfaces composed of rod-like grains. The $Bi_{4-x}$La$_{x}$Ti$_3$O$_{12}$ (x=0.70) thin film capacitors with a Pt top electrode showed better ferroelectric properties than other films. At the applied voltage of 5V, the dielectric constant($\varepsilon$$_{r}$), dissipation factor(tan$\delta$),remanent polarization(2Pr), and coercive field(2Ec) of the $Bi_{4-x}$La$_{x}$Ti$_3$O$_{12}$ (x=0.70)thin films were about 272.54, 0.059, 32.4 $\mu$C/cm$^2$, 2Ec=119.9kV/cm. Also the capacitor did not show any significant fatigue up to 4.8$\times$10$^{10}$ read/write switching cycles.hing cycles.s.