• Journal of the Korean Ceramic Society
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• v.36 no.11
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• pp.1198-1204
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• 1999

The effect of sintering atmosphere on the grain sizes and phase distributions in 3Y-ZrO2 and 8Y-ZrO2 was investigated O2 and N2 were used as sintering atmospheres. In the case of 3Y-ZrO2 the sintered density was higher in N2 than in O2 while in the case of 8Y-ZrO2 contrary results were obtained. The observation can be explained by the nitrogen solubility into the zirconia lattice. That is nitrogen gas can behave as a diffusive gas contrary to the behavior in other oxides depending on the amount of Y2O3. In 3Y-ZrO2 tetragonal phase was retained at room temperature irrespective of sintering atmospheres. Grain sizes of two specimens were below 2㎛ and larger in O2 thin in N2 Under a given stress the transformability of tetragonal phase into monoclinic phase was higher in O2 than N2. The results are discussed on the basis of an effect of the grain size and non-transformable ttragonal(t') phase.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.4041-4046
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• 2010

Wholly aromatic polyesters having flexible alkoxy side chain were synthesized by direct polycondensation. The synthetic polymers have been characterized by $^1H$-NMR, FT-IR. DSC, TGA, optical polarizing microscope and X-ray diffractometer. The inherent viscosities (${\eta}_{inh}$) measured in 1,1,2,2-tetrachloroethane (TCE) were 0.46~2.41 dL/g. The polymers having side chain showed double melting transition, ie, solid-sanidic liquid crystalline (LC) phase transition ($T_{m1}$) and sanidic LC phase-nematic LC phase transition ($T_{m2}$). As incresing length of alkoxy side chain, phase transition temperatures decreased and solubilities in organic solvents incresed. The peaks of $2{\theta}\;{\simeq}5$ and $2{\theta}\;{\simeq}20$ in X-ray diffractograms are due to crystallization of polymer main chain and of long side chain, respectively.

• Journal of Powder Materials
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• v.22 no.6
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• pp.426-431
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• 2015

Microstructural examination of the Nb-Si-B alloys at Nb-rich compositions is performed. The Nb-rich corner of the Nb-Si-B system is favorable in that the constituent phases are Nb (ductile and tough phase with high melting temperature) and $T_2$ phase (very hard intermetallic compound with favorable oxidation resistance) which are good combination for high temperature structural materials. The samples containing compositions near Nb-rich corner of the Nb-Si-B ternary system are prepared by spark plasma sintering (SPS) process using $T_2$ and Nb powders. $T_2$ bulk phase is made in arc furnace by melting the Nb slug and the Si-B powder compact. The $T_2$ bulk phase was subsequently ball-milled to powders. SPS is performed at $1300^{\circ}C$ and $1400^{\circ}C$, depending on the composition, under 30 MPa for 600s, to produce disc-shaped specimen with 15 mm in diameter and 3 mm high. Hardness tests (Rockwell A-scale and micro Vickers) are carried out to estimate the mechanical property.

• Journal of the Korean institute of surface engineering
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• v.34 no.5
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• pp.486-493
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• 2001

Partially stabilized zirconia (PSZ) is an attractive material for thermal barrier coating. Zirconia exists in three crystallographic phases: cubic, tetragonal and monoclinic. Especially, the phase transformation of tetragonal phase to monoclinic phase accompanies significant volume expansion, so this transition generally results in cracking and contributes to the failure of the TBC system. Both the plasma sprayed ZrO$_2$-8Y$_2$O$_3$ (YSZ) coat and the ZrO$_2$,-25CeO$_2$,-2.5Y$_2$O$_3$ (CYSZ) coat are isothermally heat -treated at 130$0^{\circ}C$ and 150$0^{\circ}C$ for 100hr and cooled at different cooling rates. The monoclinic phase is not discovered in all the CYSZ annealed at 130$0^{\circ}C$ and 150$0^{\circ}C$. In the 150$0^{\circ}C$ heat-treated specimens, the YSZ contains some monoclinic phase while none exists in the 130$0^{\circ}C$ heat-treated YSZ coat. For the YSZ, the different phase transformation behaviors at the two temperatures are due to the stabilizer concentration of high temperature phases and grain growth. For the YSZ with 150$0^{\circ}C$-100hr annealing, the amount of monoclinic phase increased with the slower cooling rate. The extra oxygen vacancy, thermal stress, and c to t'phase transformation might suppress the t to m martensitic phase transformation.

• Clinical and Experimental Pediatrics
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• v.52 no.2
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• pp.234-241
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• 2009

Purpose : We investigated the relationship between thyroid hormone and serum tumor necrosis factor (TNF-${\alpha}$), interleukin (IL-6) and N-terminal fragment of pro-brain natriuretic peptide (NT-proBNP) in patients with Kawasaki disease (KD). Methods : Serum levels of thyroid hormone, TNF-${\alpha}$, IL-6, and NT-proBNP were measured in 52 KD patients in the acute and subacute phase and 10 patients with acute febrile illness (control group). TNF-${\alpha}$ and IL-6 were determined by sandwich enzyme-linked immunosorbent assay (ELISA). Echocardiography was performed to detect coronary artery lesions (CAL) in KD patients. Results : Low $T_3$ syndrome occurred in 63.5% of KD patients. $T_3$ in the acute phase of KD was lower than that in the control. In KD patients, $T_3$ was lowered in the acute phase and elevated in the subacute phase, whereas TNF-${\alpha}$, IL-6 and NT-proBNP were elevated in the acute phase and decreased in the subacute phase. NT-proBNP, and IL-6 were higher in patients with low $T_3$ than in those with normal $T_3$. In addition, $T_3$ inversely correlated with IL-6 and NT-proBNP. Of the 4 patients with CAL, 3 had very low $T_3$. Compared with intravenous immunoglobulin (IVIG)-responsive patients, IVIG-resistant patients had lower $T_3$ and higher IL-6 and NT-proBNP. Conclusion : $T_3$ decreases in the acute phase of KD and normalizes in the subacute phase without thyroid hormone replacement. Low $T_3$ may be partially induced by IL-6 rather than TNF-${\alpha}$, and is strongly associated with high NT-proBNP. $T_3$ in KD may be used for the differential diagnosis, monitoring the activity of the disease, and predicting the severity of inflammation.

• Investigative Magnetic Resonance Imaging
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• v.5 no.1
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• pp.57-65
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• 2001

Purpose : $T_2$-weighted half courier Echo Planar Imaging (T2HEPI) method is proposed to reduce measurement time of existing EPI by a factor of 2. In addition, high $T_2$ contrast is obtained for clinical applications. High resolution single-shot EPI images with $T_2$ contrast are obtained with $128{\times}128$ matrix size by the proposed method. Materials and methods : In order to reduce measurement time in EPI, half courier space is measured, and rest of half courier data is obtained by conjugate symmetric filling. Thus high resolution single shot EPI image with $128{\times}128$ matrix size is obtained with 64 echoes. By the arrangement of phase encoding gradients, high $T_2$ weighted images are obtained. The acquired data in k-space are shifted if there exists residual gradient field due to eddy current along phase encoding gradient, which results in a serious problem in the reconstructed image. The residual field is estimated by the correlation coefficient between the echo signal for dc and the corresponding reference data acquired during the pre-scan. Once the residual gradient field is properly estimated, it can be removed by the adjustment of initial phase encoding gradient field between $70^{\circ}$ and $180^{\circ}$ rf pulses. Results : The suggested T2EPl is implemented in a 1.0 Tela whole body MRI system. Experiments are done with the effective echo times of 72ms and 96ms with single shot acquisitions. High resolution($128{\times}128$) volunteer head images with high $T_2$ contrast are obtained in a single scan by the proposed method. Conclusion : Using the half courier technique, higher resolution EPI images are obtained with matrix size of $128{\times}128$ in a single scan. Furthermore $T_2$ contrast is controlled by the effective echo time. Since the suggested method can be implemented by software alone (pulse sequence and corresponding tuning and reconstruction algorithms) without addition of special hardware, it can be widely used in existing MRI systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.7
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• pp.571-575
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• 2017

This paper presents a C-band bi-directional T/R chipset in $0.13{\mu}m$ TSMC CMOS technology for phased array antenna. The T/R chipset, which is a key component of phased array antenna, consists of a 6 bit phase shifter, a 6 bit step attenuator, and three bi-directional gain amplifiers. The phase shifter is controlled up to $354^{\circ}$ with $5.625^{\circ}$ phase step for precise beam steering. The step attenuator is also controlled up to 31.5 dB with 0.5 dB attenuation step for the side lobe level rejection. The LDO(Low Drop Output) regulator for stable 1.2 V DC power and the SPI(Serial Peripheral Interface) for digital control are integrated in the chipset. The chip size is $2.5{\times}1.5mm^2$ including pads.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.2
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• pp.615-618
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• 2016

Ethyl acetate extracts obtained from culture of endophytic fungi Aspergillus sp isolated from Piper crocatum Ruiz & Pav, have been shown to possess cytotoxic activity against T47D breast cancer cells. Investigations were here conducted to determine bioactive compounds responsible for the activity. Bioassay guided fractionation was employed to obtain active compounds. Structure elucidation was performed based on analysis of LC-MS, $^1H$-NMR, $^{13}C$-NMR, COSY, DEPT, HMQC, HMBC data. Cytotoxity assays were conducted in 96 well plates against T47D and Vero cell lines. Bioassay guided isolation and chemical investigation led to the isolation of pyrophen, a 4-methoxy-6-(1'-acetamido-2'-phenylethyl)-2H-pyran-2-one. Further analysis of its activity against T47D and Vero cells showed an ability to inhibit the growth of T47D cells with IC50 values of $9.2{\mu}g/mL$ but less cytotoxicity to Vero cells with an $IC_{50}$ of $109{\mu}g/mL$. This compound at a concentration of 400 ng/mL induced S-phase arrest in T47D cells.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.24.1-24.1
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• 2009

Tantalum carbo-nitride($T_aC_xN_y$) films were deposited with chemical vapor deposition(CVD) using tert-butylimido tris-diethylamido tantalum (TBTDET, $^tBu-N=Ta-(NEt_2)_3$, $Et=C_2H_5$, $^tBu=C(CH_3)_3$) between $350^{\circ}C$ and $600^{\circ}C$ with argon as a carrier gas. Fourier transform infrared (FT-IR)spectroscopy was used to study the thermal decomposition behavior of TBTDET in the gas phase. When the temperature was increased, C-H and C-N bonding of TBTDET disappeared and the peaks of ethylene appeared above $450^{\circ}C$ in the gas phase. The growth rate and film density of $T_aC_xN_y$ film were in the range of 0.1nm/min to 1.30nm/min and of $8.92g/cm^3$ to $10.6g/cm^3$ depending on the deposition temperature. $T_aC_xN_y$ films deposited below $400^{\circ}C$ were amorphous and became polycrystal line above $500^{\circ}C$. It was confirmed that the $T_aC_xN_y$ film was a mixture of TaC, graphite, $Ta_3N_5$, TaN, and $Ta_2O_5$ phases and the oxide phase was formed from the post deposition oxygen uptake. With the increase of the deposition temperature, the TaN phase was increased over TaC and $Ta_3N_5$ and crystallinity, work function, conductivity and density of the film were increased. Also the oxygen uptake was decreased due to the increase of the film density. With the increase of the TaC phase in $T_aC_xN_y$ film, the work function was decreased to 4.25eV and with the increase of the TaN phase in $T_aC_xN_y$ film,it was increased to 4.48eV.

• Asian-Australasian Journal of Animal Sciences
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• v.24 no.9
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• pp.1256-1267
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• 2011

Two experiments were conducted to determine the effects of dietary lysine and energy level on performance and apparent total tract digestibility (ATTD) of nutrients in weanling pigs. In Exp. 1, a total of 288 weaned pigs (initial BW $5.77{\pm}0.85\;kg$) were randomly allotted to 4 treatments (4 replicates per treatment with 18 pigs in each replicate). Experimental diets were fed in the 3 phases: phase I (d 0 to 7), phase II (d 8 to 14) and phase III (d 15 to 28). Isocalorific diets (3,450 kcal/kg) with incremental lysine levels (Phase I: 1.51, 1.61, 1.71 and 1.81; Phase II: 1.35, 1.46, 1.56 and 1.66; Phase III: 1.18, 1.28, 1.39 and 1.49% lysine respectively for T1, T2, T3 and T4) were used as treatments. An increase in the dietary lysine levels linearly improved (p<0.05) the ADG and G:F during phases I, II and III as well as overall study period. The ATTD of DM (d 7 and 28) and CP (d 7, 14 and 28) were linearly improved (p<0.05) with increasing dietary lysine levels. ATTD of ash, Ca and P were not affected by dietary lysine level. In Exp. 2, 64 weanling pigs (initial BW $4.79{\pm}0.79\;kg$) were randomly allotted to 4 treatments (4 replicates per treatment with 4 pigs in each replicate) in a $2{\times}2$ factorial arrangement on the basis of BW. Effects of two levels of energy (high, 3,450 or low, 3,350 kcal/kg) and lysine (high or low; 1.70 or 1.50, 1.55 or 1.35 and 1.40 or 1.20% in phase I, II and III diets, respectively) on performance and ATTD of nutrients were investigated. High energy and lysine diets improved ADG (p<0.05) in pigs during phase I, II and III and overall period (p<0.001), while G:F increased (p<0.05) during phase I and overall period. Pigs fed high lysine diets consumed more (p<0.05) feed during phase III and overall period. Additionally, pigs fed high energy diets had greater (p<0.05) ATTD of GE (d 7 and 14), CP (d 7 and 28) and DM (d 28); whereas, pigs fed high lysine diets had greater (p<0.05) ATTD of GE and CP during d 7, 14 and 28. ATTD of ash, Ca and P remained unaffected (p>0.05) by dietary energy and lysine level. However, there was no energy${\times}$lysine interaction for any of the measured variables. Results obtained in present study suggested that high energy and lysine level improve the growth performance and ATTD of nutrients in weanling pigs.