• Journal of the Korean Ceramic Society
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• v.42 no.7 s.278
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• pp.449-454
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• 2005

A waveguide method is developed to study the materials with relatively large dielectric constants at microwave range. Basically, the method is similar to the previous waveguide methods represented by short-circuit line and transmission/reflection measurement methods. However, the complex permittivity is not determined by the shift in resonance frequencies, but by numerical analysis of measured scattering parameters. In order to enhance microwave penetration into the specimen with relatively large permittivity, a dielectric plate with lower permittivity is employed for impedance matching. The influences of air gap between the specimen and waveguide wall are evaluated, and the corresponding errors are estimated. The propagation of higher order modes is also considered. Experimental results for several reference ceramics are presented.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.104-107
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• 2004

In this work, the blend of diglycidylether of bisphenol A (DGEBA) and modified polyurethane (PU) was prepared and characterized in the cure behaviors and mechanical interfacial properties. The N-benzylpyrazinium hexafluoroantimonate was used as a cationic initiator for cure, and the content of PU was varied within 0-20 phr. The cure behaviors and mechanical interfacial properties were studied by DSC, near­IR, and the critical stress intensity actor $(K_{IC})$ measurements. Also thermal stabilities were carried out by TMA and TGA analyses. As a result, the cure activation energy $(E_a)$ and the conversion $(\alpha)$ were slightly increased with increasing the PU content, and a maximum value was found at 10 phr PU. The mechanical interfacial properties measured from $K_{IC}$ showed a similar behaviors with the results of conversion. These results were probably due to the increase of the hydrogen bonding between the hydroxyl groups of DGEBA and isocyanate groups in PU.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.265-268
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• 2002

In this work, the blend system of epoxy and PMR-15 polyimide is investigated in terms of the cure behaviors and thermal stabilities. The cure behaviors are studied in DSC measurements and thermal stabilities are also carried out by TGA analysis. DDM (4, 4'-diamino diphenyl methane) is used as curing agent for EP and the content of PMR-15 is varied within 0, 5, 10, 35, and 20 phr to neat EP. As a result, the cure activation energy ($E_a$) is increased at 10 phr of PMR-15, compared with that of neat EP. From the TGA results of EP/PMR-15 blend system, the thermal stabilities based in the initial decomposed temperature (IDT) and integral procedural decomposition temperature (IPDT) are increased with increasing the PMR-15 content. The fracture toughness, measured in the context of critical stress intensity factor ($K_{IC}$) and critical strain energy release rate ($G_{IC}$), shows a similar behavior with $E_a$. This result is probably due to the crosslinking developed by the interactions between intermolecules in the polymer chains.

• Journal of Korean Society for Quality Management
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• v.20 no.2
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• pp.109-117
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• 1992

An inspection task largely can be seen as a job divided up into a series of visual search and classification subtasks. In these subtasks, an Inspector must performs to compare the standard references proposed in visual environments and recalled in his memory with the visual stimuli to be inspected. It means that the judgement of similarity should be demanded on inspection tasks. Therefore, the inspector's ability for the judgement of similarity and the difference similarity between inspection materials are important factors to effect on performances in inspection tasks. In this paper, to analysis the effect of these factors on inspection time, an inspection task is designed and suggested by means of computer simulator. Especially, the skin conductance responses(SCR) of subjects are measured to evaluate the complexity of tasks due to the difference of similarity between materials. In the results of experiment, the more similar or different the difference of similarity between materials is, the shorter the inspection time is because of the reduction of task complexity. And, When the inspector's cognition for similarity between materials is consistanct, the inpsection time is improved. Concludingly, the consistency of reponses for similarity judgement becomes a measurement to present the performance levels. And the information of inspection time that due to the difference of similarity between materials must be considered in planning and scheduling inspection tasks.

• Journal of the Korean Society of School Health
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• v.19 no.1
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• pp.31-43
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• 2006

Purpose: The purpose of this study was to identify the effects of sex education on middle school boys' perception about obscene materials and self identity. Methods: This study was employed, using pretest-posttest of nonequivalent control group design. Data were collected from April 1st to May 14th, 2005. The subjects were recruited from two middle boys' school in Incheon which have similar class accomplishments and financial statues. Sampling method was used 70 students were assigned to experimental group and 74 students to control group. The 45 minutes sex education was given 4 times within 3 weeks to the experimental group. Four weeks later after education has finished, post test was done. The data were analyzed using Chi test, Fisher's exact test and t -test by SPSS. Results: The 1st hypothesis 'The experimental group which received sex education will have a higher score of perception about obscene materials than control group' was supported(t = 3.370, p = .001). The 2nd hypothesis 'The experimental group which received sex education will have a higher score about self identity than the control group' was supported(t = 1.997, p = .048). Conclusion: This study showed that sex education effectively helps middle school boys to have right perception about obscene materials and to promote self identity.

• Analytical Science and Technology
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• v.8 no.4
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• pp.493-498
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• 1995

PAZO-6 is a new combined type liquid crystalline polymers (LCP) which has two types of mesogens combined non linearly. Ordering of branch mesogen azo group, in PAZO-6 is an important parameter to observe as well as the substitution effect on the backbone. The related small molecules sllch as monomers as well as the polymer itself are studied by solid state NMR techniques. Preliminary $^{13}C$ CP/MAS (cross polarization/ magic angle spinning) spectral results suggest that the azo groups in the monomers are not aligned with themselves. Azo groups in the monomers seem to be poorly ordered between well ordered p-phenylene terephthalate moeities. Similar disordering tendency of the azo group in PAZO-6 is deduced from the overall aromatic carbon peak positions which are not much different from those of the monomer.

• Applied Microscopy
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• v.28 no.1
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• pp.121-126
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• 1998

Detailed studies of high resolution TEM inages on the modulated structure caused by Zn vacancy ordering along [110] direction in BZT sintered at $1400^{\circ}C$ for 90 hours had revealed that the images which had hexagonal patterns were similar to those obtained from the structure which had no modulation, These images had appeared over the wide ranges from -30 nm to -42 nm in defocus values and from 2 nm to 20 nm in thickness. The computer simulated images showed that the modulation due to Zn vacancy ordering had made a small change in contrast in the interior of hexagonal pattern, which was very difficult to differenciate in experiments. The image which demonstrated the modulated structure very well was the one which obtained at -52 nm in defocus value and 16 nm in thickness.

• Korean Journal of Materials Research
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• v.27 no.7
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• pp.364-368
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• 2017

We performed temperature dependent current-voltage (I-V) measurements to characterize the electrical properties of $Au/Al_2O_3/n-Ge$ metal-insulator-semiconductor (MIS) diodes prepared with and without $H_2O$ prepulse treatment by atomic layer deposition (ALD). By considering the thickness of the $Al_2O_3$ interlayer, the barrier height for the treated sample was found to be 0.61 eV, similar to those of Au/n-Ge Schottky diodes. The thermionic emission (TE) model with barrier inhomogeneity explained the final state of the treated sample well. Compared to the untreated sample, the treated sample was found to have improved diode characteristics for both forward and reverse bias conditions. These results were associated with the reduction of charge trapping and interface states near the $Ge/Al_2O_3$ interface.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.301-306
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• 2008

Surface composite layers of 1.9~2.9 mm in thickness were fabricated by depositing metamorphic powders on a carbon steel substrate and by irradiating with a high-energy electron beam. In the surface composite layers, 48~64 vol.% of $Cr_{2}B$ or $Cr_{1.65}Fe_{0.35}B_{0.96}$ borides were densely precipitated in the austenite or martensite matrix. These hard borides improved the hardness of the surface composite layer. According to the otentiodynamic polarization test results of the surface composites, coatings, STS304 stainless steel, and carbon steel substrate, the corrosion potential of the surface composite fabricated with 'C+' powders was highest, and its corrosion current density was lowest, while its pitting potential was similar to that of the STS304 steel. This indicated that the overall corrosion resistance of the surface composite fabricated with 'C+' powders was the best among the tested materials. Austenite and martensite phases of the surface composites and coatings was selectively corroded, while borides were retained inside pits. In the coating fabricated with 'C+' powders, the localized corrosion additionally occurred along splat boundaries, and thus the corrosion resistance of the coating was worse than that of the surface composite.

• Elastomers and Composites
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• v.54 no.4
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• pp.308-312
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• 2019

Polyphenylene sulfide (PPS) is a well-known super engineering plastic with a high melting temperature (above 290℃). It is generally insoluble under regular conditions. Therefore, it can be used for replacing metallic materials. Many researchers are looking at the possibility of replacing aluminum in the engine compartment of an automobile. However, studies on PPS are not common as compared to conventional engineering plastics because only a few companies produce super engineering plastics. In this research, the material properties of PPS composites containing two different kinds of glass fibers and produced under different processing temperatures were investigated. The tensile strength of the PPS composites increased as the processing temperature increased. Although glass fibers with similar aspect ratios were compounded under the same processing condition, one of them yielded a higher mechanical strength.