• Journal of the Korean Ceramic Society
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• v.43 no.3 s.286
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• pp.173-176
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• 2006

${Sr_{1-x}Ba_xNb_2O_6$(SBN) have been obtained in Pt crucible by melting and cooling in air atmosphere. Some SBNs being at the bottom of the crucible are black and transparent, and the other SBNs colorless. The black SBN became to be colorless by oxidation heat treatment $1,300^{\circ}C$ for 4 h, Curie temperature is changed by colorless change of black SBN. The reason seems to be $Nb^{5+}$ oxidation of some $Nb^{4+}$ ions in SBN or effect of unknown impurities. Diffused Phase Transition (DPT) was appeared during heating and cooling process. Various sintered SBN ceramics specimen showed relaxor characteristics.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.271-277
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• 2010

In this paper two aspects of the percolation and conductivity of carbon black-filled polyethylene matrix composites will be discussed. Firstly, the percolation behavior, the critical exponent of conductivity of these composites, are discussed based on studying the whole change of resistivity, the relationship between frequency and relative permittivity or ac conductivity. There are two transitions of resistivity for carbon black filling. Below the first transition, resistivity shows an ohmic behavior and its value is almost the same as that of the matrix. Between the first and second transition, the change in resistivity is very sharp, and a non-ohmic electric field dependence of current has been observed. Secondly, the electrical conduction property of the carbon black-filled polyethylene matrix composites below the percolation threshold is discussed with the hopping conduction model. This study investigates the electrical conduction property of the composites below the percolation threshold based on the frequency dependence of conductivity in the range of 20 Hz to 1 MHz. There are two components for the observed ac loss current. One is independent of frequency that becomes prevalent in low frequencies just below the percolation threshold and under a high electrical field. The other is proportional to the frequency of the applied ac voltage in high frequencies and its origin is not clear. These results support the conclusion that the electrical conduction mechanism below the percolation threshold is tunneling.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.5
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• pp.39-50
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• 2008

This study are decided the mix proportion method of latex modified concrete for agricultural concrete structures from the results of workability and strength test with mix proportion factor. For mix proportion factor, this study are selected the water-cement ratio, unit cement amount and latex content. Also, this study were performed the slump, compressive strength test and microstructure analysis using the scanning electron microscope(SEM). The strength and slump of LMC are dependent with unit cement amount, latex content, and water-cement ratio. Especially, the strength of LMC are not controlled by single mix proportion factor but effected by combined mix proportion factor. Microstructure investigation are showed the LMC are reduced the internal pore volume and enhanced the transition zone between cement paste and aggregate interface. This effect get by consist of latex films in the concrete. Also, this study were recommended the mix proportion method for LMC. These mix proportions method are estimated the mix design for satisfied the target performance which are applied the agricultural concrete structure.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.86-91
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• 2009

In this paper, we analyze the Transition of Isc by natural solar spectrum of c-Si and a-Si PV module. Commonly, performance of photovoltaic (PV) module is estimated under the standard test condition (STC). That is, solar irradiance $1kW/m^2$, solar spectrum distribution: AM1 5G, module temperature $25^{\circ}C$ This means it rarely meets actual outdoor conditions. The solar spectrum always changes. So it is rare to fit the standard solar spectrum AM1 5G defined in ASTM G173-03 or IEC 60904-3. Thus spectral response of PV module is different depending on the material. so we estimated the variation of Isc at every minutes by comparing c-Si PV module with a-si PV module for outdoor conditions.

• Journal of the Optical Society of Korea
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• v.17 no.6
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• pp.543-547
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• 2013

A temperature dependent (10K-290K) photoluminescence (PL) study for two differently prepared ZnO thin films (as-grown and O-plasma treated) is presented. Four characteristic peaks were identified for both samples: (i) neutral donor-bound excitons ($D^oX$), (ii) two electron satellites (TES), (iii) phonon replica of $D^oX$ ($D^oX$-1LO), and (iv) donor-acceptor pair transition (DAP). As the sample temperature increased, $D^oX$-1LO and DAP transitions became indistinct. This was accompanied by newly-rising emission of free electron-acceptor transitions (e, $A^o$). The spectral evolution with temperature for as-grown samples also showed the optical emission from free excitons, which became dominant at higher temperatures. Some features related to O-plasma were identified in PL spectra: (i) different positions of TES transitions (28meV lower than $D^oX$ for as-grown samples and 35meV for O-plasma treated samples), (ii) the decrease of spectral intensity in both emissions of $D^oX$ and DAP after O-plasma treatment, and (iii) no noticeable transition from free excitons after the O-plasma treatment.

• Genomics & Informatics
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• v.18 no.3
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• pp.30.1-30.7
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• 2020

The novel coronavirus pandemic that has originated from China and spread throughout the world in three months. Genome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) predecessor, severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) play an important role in understanding the concept of genetic variation. In this paper, the genomic data accessed from National Center for Biotechnology Information (NCBI) through Molecular Evolutionary Genetic Analysis (MEGA) for statistical analysis. Firstly, the Bayesian information criterion (BIC) and Akaike information criterion (AICc) are used to evaluate the best substitution pattern. Secondly, the maximum likelihood method used to estimate of transition/transversions (R) through Kimura-2, Tamura-3, Hasegawa-Kishino-Yano, and Tamura-Nei nucleotide substitutions model. Thirdly and finally nucleotide frequencies computed based on genomic data of NCBI. The results indicate that general times reversible model has the lowest BIC and AICc score 347,394 and 347,287, respectively. The transition/transversions bias for nucleotide substitutions models varies from 0.56 to 0.59 in MEGA output. The average nitrogenous bases frequency of U, C, A, and G are 31.74, 19.48, 28.04, and 20.74, respectively in percentages. Overall the genomic data analysis of SARS-CoV-2, SARS-CoV, and MERS-CoV highlights the close genetic relationship.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.763-767
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• 2008

In a speech coding system using excitation source of voiced and unvoiced, it would be involved a distortion of speech qualify in case coexist with a voiced and an unvoiced consonants in a frame. So, We proposed TS(Transition Segment) including unvoiced consonant searching and extraction method in order to uncoexistent with a voiced and unvoiced consonants in a frame. This research present a new method of TS approximate-synthesis by using Least Mean Square and frequency band division. As a result, this method obtain a high quality approximation-synthesis waveforms within TS by using frequency information of 0.547kHz below and 2.813kHz above. The important thing is that the maximum error signal can be made with low distortion approximation-synthesis waveform within TS. This method has the capability of being applied to a new speech coding of Voiced/Silence/TS, speech analysis and speech synthesis.

• Korean Journal of Materials Research
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• v.23 no.7
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• pp.373-378
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• 2013

In order to clarify the effect of C/Ti atom ratios(${\chi}$) on the deformation behavior of $TiC_{\chi}$ at high temperature, single crystals having a wide range of ${\chi}$, from 0.56 to 0.96, were deformed by compression test in a temperature range of 1183~2273 K and in a strain rate range of $1.9{\times}10^{-4}{\sim}5.9{\times}10^{-3}s^{-1}$. Before testing, $TiC_{\chi}$ single crystals were grown by the FZ method in a He atmosphere of 0.3MPa. The concentrations of combined carbon were determined by chemical analysis and the lattice parameters by the X-ray powder diffraction technique. It was found that the high temperature deformation behavior observed is the ${\chi}$-less dependent type, including the work softening phenomenon, the critical resolved shear stress, the transition temperature where the deformation mechanism changes, the stress exponent of strain rate and activation energy for deformation. The shape of stress-strain curves of $TiC_{0.96}$, $TiC_{0.85}$ and $TiC_{0.56}$ is seen to be less dependent on ${\chi}$, the work hardening rate after the softening is slightly higher in $TiC_{0.96}$ than in $TiC_{0.85}$ and $TiC_{0.56}$. As ${\chi}$ decreases the work softening becomes less evident and the transition temperature where the work softening disappears, shifts to a lower temperature. The ${\tau}_c$ decreases monotonously with decreasing ${\chi}$ in a range of ${\chi}$ from 0.86 to 0.96. The transition temperature where the deformation mechanism changes shifts to a lower temperature as ${\chi}$ decreases. The activation energy for deformation in the low temperature region also decreased monotonously as ${\chi}$ decreased. The deformation in this temperature region is thought to be governed by the Peierls mechanism.

• Journal of Electrochemical Science and Technology
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• v.12 no.4
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• pp.377-386
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• 2021

The Li-rich oxides are promising cathode materials due to their high energy density. However, characteristics such as low rate capability, unstable cyclic performance, and rapid capacity fading during cycling prevent their commercialization. These characteristics are mainly attributed to the phase instability of the host structure and undesirable side reactions at the cathode/electrolyte interface. To suppress the phase transition during cycling and interfacial side reactions with the reactive electrolyte, K (potassium) doping and Nb oxide coating were simultaneously introduced to a Li-rich oxide (Li_1.2Ni_0.13Co_0.13Mn_0.54O₂). The capacity and rate capability of the Li-rich oxide were significantly enhanced by K doping. Considering the X-ray diffraction (XRD) analysis, the interslab thickness of LiO₂ increased and cation mixing decreased due to K doping, which facilitated Li migration during cycling and resulted in enhanced capacity and rate capability. The K-doped Li-rich oxide also exhibited considerably improved cyclic performance, probably because the large K⁺ ions disturb the migration of the transition metals causing the phase transition and act as a pillar stabilizing the host structure during cycling. The Nb oxide coating also considerably enhanced the capacity and rate capability of the samples, indicating that the undesirable interfacial layer formed from the side reaction was a major resistance factor that reduced the capacity of the cathode. This result confirms that the introduction of K doping and Nb oxide coating is an effective approach to enhance the electrochemical performance of Li-rich oxides.

• Journal of Integrative Natural Science
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• v.4 no.2
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• pp.113-120
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• 2011

Brassinosteroids (BRs) are plant steroid hormones that play essential roles in growth and development. Mutations in BR-signaling pathways cause defective in growth and development like dwarfism, male sterility, abnormal vascular development and photomorphogenesis. Transition from vegetative to reproductive growth is a critical phase change in the development of a flowering plant. In a screen of activation-tagged Arabidopsis, we identified a mutant named abz126 that displayed longer hypocotyls when grown in the dark on MS media containing brassinazole (Brz), an inhibitor of BRs biosynthesis. We have cloned the mutant locus using adapter ligation PCR walking and identified that a single T-DNA had been integrated into the ninth exon of the GIGANTEA (GI) gene, involved in controling flowering time. This insertion resulted in loss-of-function of the GI gene and caused the following phenotypes: long petioles, tall plant height, many rosette leaves and late flowering. RT-PCR assays on abz126 mutant showed that the T-DNA insertion in GIGANTEA led to the loss of mRNA expression of the GI gene. In the hormone dose response assay, abz126 mutant showed: 1) an insensitivity to paclobutrazole (PAC), 2) an altered response with 6-benzylaminopurine (BAP) and 3) insensitive to Brassinolide (BL). Based on these results, we propose that the late flowering and tall phenotypes displayed by the abz126 mutant are caused by a loss-of-function of the GI gene associated with brassinosteroid hormone signaling.