• Journal of the Korean Ceramic Society
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• v.44 no.5 s.300
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• pp.179-183
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• 2007

BCB $Resin-BaNd_2Ti_4O_{12}$(BNT) composites with BNT contents were prepared by tape casting method and epoxy resin-BNT composites were prepared by using heating press. Their dielectric properties and microstructures were investigated. The dielectric properties such as dielectric constant and dielectric loss at 1 MHz for epoxy resin-BNT composites and BCB resin-BNT composites are improved with an increase of BNT volume fraction. The dielectric constant of the Epoxy-BNT composite increased from 5.9 to 7.8 as the volume fraction of BNT increased from 15 to 25. The dielectric constant of the BCB-BNT composite increased from 9.1 to 15.5 as the volume fraction of BNT increased from 30 to 50. The dielectric behavior of BCB-BNT system can be explained by Lichtenecker's equation. The dielectric constant of epoxy resin-BNT composite is smaller than that of BCB resin-BNT composite. These results are considered to be related with the dispersion of BNT filler in polymer matrix from the result of SEM photograph.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1242_1243
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• 2009

The heterolayered BT-BNT thick films were fabricated by screen printing techniques on alumina substrates electrodes with Pt. We report the improved ferroelectric and dielectric properties in the heterolayered teteragonal/rhombohedral structure composed of the BT and the BNT thick films. We investigated the effects of deposition conditions on the structural and electrical properties of the heterolayered BT-BNT thick films. The dielectric properties of the heterolayered BT-BNT thick films were superior to those of single composition BNT, and those values for the heterolayered BT-BNT thick films were 1455, 0.025 and $12.63{\mu}C/cm^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.547-553
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• 2011

We investigated the dielectric and mechanical properties of ceramic polymer composite xBNT - (1-x)LCP (x= 0, 10, 20, 30, 40 vol.%). The disk shaped BNT ($BaNd_2Ti_4O_{12}$) - LCP (liquid crystal polymer) composite samples were prepared by compression molding method. With increasing the BNT content in composites from 10 to 40 vol.%, the dielectric constant increased but the dielectric loss as well as bending strength of composites reduced. These composites were well described with modified Lichtenecker's model having k = 0.392 and 0.303 for the first and second ball milled BNT filled composites, which means that the BNT filler in composites are well dispersed. The dielectric constant of the composite comprised of the second milled BNT ($D_{50}$ = 1.39 um) was higher that of the composite of the first milled BNT ($D_{50}$= 2.45 um), which seems to be related with the different particle size and dispersion of BNT fillers in LCP matrix. The bending strength of the composite containing the second milled BNT was superior to that of the composite of the first milled BNT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.298-298
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• 2010

In this study, both structural, dielectric properties of the NKN-0.94BNT-0.06BT ceramics were investigated. All samples of the NKN-0.94BNT-0.06BT ceramics were fabricated by conventional mixed oxide method with Pt electrodes. We report the improved electrical properties in the perovskite structure composed of the NKN, BNT and the BT ceramics. We investigated the effects of NKN, BT on the structural and electrical properties of the NKN-0.94BNT-0.06BT ceramics. The dielectric and structural properties of the NKN-0.94BNT-0.06BT ceramics were superior to those of single composition NKN, NKN-BNT and those values for the NKN-0.94BNT-0.06BT ceramics were 1455, 0.025 and $29.04{\mu}C/cm^2$.

• Phonetics and Speech Sciences
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• v.4 no.3
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• pp.137-142
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• 2012

The aim of this study is to investigate the usefulness of the multiple-choice name matching test (MC-NMT) in adults with aphasia by comparing the Korean version of the Boston Naming Test (K-BNT) and subsets of the Korean version of the Western Aphasia Battery (K-WAB). Thirty-nine patients who suffer from aphasia participated in the study. All patients were examined by the K-BNT, MC-NMT and K-WAB. The MC-NMT consisted of the 30 original BNT object stimuli which were presented with four response choices (written words) with similar frequency, including one correct and three incorrect responses. Cards containing the drawings were presented to the patient one at time. An item was passed if the patient chose the correct response within 10 seconds. We subdivided two groups into a total group and a low K-BNT group (at and below 15 points). We evaluated the correlation between the K-BNT, MC-NMT score and production, naming, repetition, comprehension, reading and writing scores in subsets of the K-WAB. There was a highly positive correlation between the K-BNT score and naming score of the K-WAB in total patients. However, the MC-NMT was highly correlated with reading scores in the K-WAB. In low score K-BNT patients, the K-BNT strongly correlated with production, naming and repetition scores of the K-WAB. These findings mean that K-BNT reflects motor language function. However, the MC-NMT was strong correlated comprehension, reading and writing of the K-WAB. This finding reflects sensory language function. We suggest that the combination of K-BNT and newly developed MC-NMT will be useful to evaluate speech functions in aphasic patients.

• The Journal of the Korea Contents Association
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• v.13 no.12
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• pp.321-327
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• 2013

Impaired naming difficulty is common in normal elderly as well as in patients with neurological impairment. The 60-item Korean version-Boston Naming Test(K-BNT) is one of the most commonly used test for measuring confrontational naming ability. However, age-related cognitive decline may make the elderly difficult concentrating during the 60-item test, therefore, item reduction of the K-BNT would improve test validity and reliability. Thus, the purpose of this study was to develop a short form of the K-BNT based on Item Response Theory(IRT). Considering item-fit index, sex factor, and item difficulty through Rasch analysis, the 15-item K-BNT(i.e., K-BNT-15) was developed. Via administration of the K-BNT-15, we observed age-related decline in naming ability and significantly different performance between the normal elderly and patients with mild cognitive impairment. This study demonstrates the utility of IRT for developing a short-form language evaluation tool. The K-BNT-15 can be effective as a language screening tool to differentiate between normal aging and pathological diseases.

• Korean Journal of Cognitive Science
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• v.11 no.2
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• pp.59-68
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• 2000

An increase in senile dementia population has caused social concerns in Korea. The Korean-Boston Naming Test(K-BNT) has been used in assessing naming ability of patients with diffuse brain damage as well as senile dementia. This study was conducted to develop a short from of the K-BNT. to present normative data, and to demonstrate clinical utility of the shortform K-BNT. The participants were 142 healthy elderly adults, ages between 55 and 84, who were sampled in the Seoul-Kyungki area. Twenty patients with mild probable DAT participated in the study. We developed four norms based on education(0∼6 years and more than 6 years) and age(55∼64 and 65∼84 years). The study showed high internal consistency among the items. Further. DAT patients and normal controls showed significant difference in the K-BNT short form scores(F(1, 158) = 23,216, p < .0001). Normative data presented in this study will be useful in evaluating the naming ability of elderly patients in clinical setting.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.10
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• pp.771-775
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• 2010

In this study, piezoelectric and dielectric properties of the $(Na_{0.5}K_{0.5})NbO_3-(1-x)(Bi_{0.5}Na_{0.5})TiO_3-xBaTiO_3$ [NKN-(1-x)BNT-xBT] ceramics were investigated. The lead-free NKN-(1-x)BNT-xBT ceramics were fabricated by a conventional mixed oxide method. The results indicate that the addition of $BaTiO_3$ significantly influences the sintering, microstructure, phase transition and electrical properties of NKN-BNT ceramics. A gradual change in the piezoelectric and dielectric properties was observed with the increase of BT contents. The dielectric constant, piezoelectric constant ($d_{33}$) and electromechanical coupling factor ($k_p$) increased at the morphotropic phase boundary (MPB). The $d_{33}$=184 pC/N, $k_p$=0.38, dielectric constant=1455 with dielectric loss value of less than 1% were obtained for the NKN-0.95BNT-0.05BT ceramics sintered at $1150^{\circ}C$ for 2h. These results demonstrate that the NKN-(1-x)BNT-xBT ceramics is an attractive candidate for lead-free piezoelectric materials.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.6
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• pp.251-255
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• 2007

We made $(1-x)BCB-xBNT(BaNd_2Ti_4O_{12})$ (x=20, 30, 40, 50 vol%) composite thick film with a high dielectric constant and low loss by the hand casting method. Dielectric constant and dielectric loss of prepared thick film are measured at 1MHz and curing behavior of the film are observed through thermal analysis such as DSC. We investigated the effect of contents of BNT filler and curing behavior of film on dielectric properties of BCB-BNT composite. Dielectric constant increased with increasing BNT filler from 20 to 50 vol% and dielectric loss ($tan{\delta}$) decreased with increasing BNT filler. Dielectric constant and loss ($tan{\delta}$) of composite material was not nearly dependent on the curing behavior. But as a result of TCC (Temperature Characteristics of Coefficient) decreased with increasing the curing temperature, we confirmed that the curing of these composite system is most stable above $250^{\circ}C$.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1324_1325
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• 2009

The heterolayered $BaTiO_3/(Bi_{0.5}Na_{0.5})TiO_3$ thick films were fabricated by screen printing techniques on alumina substrates electrodes with Pt. We report the improved ferroelectric properties in the heterolayered teteragonal/rhombohedral structure composed of the $BaTiO_3$ and the $(Bi_{0.5}Na_{0.5})TiO_3$ thick films. We investigated the effects of deposition conditions on the structural and electrical properties of the heterolayered BNT/BT thick films. The structural and electrical properties of the heterolayered BNT/BT thick films were studied. All PZT heterolayered thin films show dense and homogeneous structure without the presence of the rosette structure. The dielectric constant, loss and remanent polarization oft heheterolayered BNT/BT thick films were superior to those of single composition $BaTiO_3$ and $(Bi_{1/2}Na_{1/2})TiO_3$, and those values for the heterolayered BNT/BT thick films sintered at $1100^{\circ}C$ were 916, 0.79 and $12.63{\mu}C/cm^2$.