• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.182-182
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• 2009

The effect of Re-oxidation on the PTCR properties of Sm-doped barium titanate ceramics was investigated by means of impedance spectroscopy. Electrical properties such as resistance vs. temperature, I-V curve were measured and microstructure was observed with SEM photography. Sample was fabricated with thick film process such as tape casting of green sheet, screen printing of electrode pattern, stacking, firing in reduced atmosphere and re-oxidation, etc. As the temperature of re-oxidation increases, resistance jump as a function of temperature enhances but resistance at room temperature increases. These behavior of resistance as a function of temperature, dependent on the re-oxidation condition, is analyzed with Cole-Cole impedance plot and is shown to be related with the degree of oxidation of grain boundary regardless of grain core during re-oxidation process of sample.

• The Korean Journal of Ceramics
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• 제2권4호
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• pp.238-241
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• 1996

New porous BaTiO$_3$ thermistors were fabricated using graphite powders (0 to 10 wt. %) and their porosities were in the range of 9.1% to 16.2%. As results of impedance analysis, it was confirmed that the pores affected the grain-boundary resistance and the bulk (grain interior) resistance was constant as about 25 $\Omega$ at room temperature. The magnitude of PTCR effect $(p_{max}/p)$ markedly increased from 3 orders to 7 orders without addition of any acceptor dopant such as Mn or Cr.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1994년도 춘계학술대회 and 제3회 신약개발 연구발표회
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• pp.299-299
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• 1994

펩타이드 약물의 일종인 LHRH 및 그의 analogue인 〔D-Ala$^{6}$)LHRH의 경점막 수송경로를 개발하기 위하여 이들 약물을 점막 균질액과 배양시 점막에 존재하는 효소에 의해 분해되는 것을 발견하였다. 이에 저자등은 LHRH 및 〔D-Ala$^{6}$〕 LHRH의 점막 균질액 중에서의 분해산물을 HPLC에 의해 정량하였다. 또한 PITC법에 따라 아미노산 분석을 실시하여 이들 분해산물의 아미노산 조성을 밝히고 아울러 분해위치를 규명하였다. 즉 LHRH또는 〔D-Ala$^{6}$〕 LHRH를 직장, 비강 및 질점막과 일정시간 배양 후 시료를 HPLC에 주입하여 각 분해산물의 peak time에 용리액을 분획 수집하였다. 이것을 6N-HCl로 가수분해하여 유리아미노산으로 만들고 phenylisothiocyanate 유도체화 하여 PTC 아미노산으로 한후 아미노산 분석용 컬럼을 사용하여 HPLC로 정량 하였다.

• Advanced Composite Materials
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• 제16권3호
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• pp.195-206
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• 2007

Carbon nanofiber (CNF)/unsaturated polyester resin (UPR) was prepared by a solvent evaporation method, and the temperature dependency of electrical conductivity was investigated. The CNF/UPR composites had quite a low percolation threshold due to CNF having a larger aspect ratio and being well dispersed in the UPR matrix. The positive temperature coefficient (PTC) was found in the CNF/UPR composites and it showed stronger effect around the percolation threshold. The electrical resistance of the CNF/UPR composites decreased and had lower temperature dependency with increasing numbers of thermal cycles.

• 한국세라믹학회지
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• 제32권1호
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• pp.140-144
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• 1995

The role of Mn on the PTCR characteristics of La-doped BaTiO3 ceramics was studied. The calculated Ns value was increased with Mn concentration and consequently pmax and pmin were increased. The behavior of pmin was explained by the Jonker's theory, and Ns value of 6.35×1017m-2 was well agreed with the theoretical estimate of Jonker's. The value state of Mn was measured by ESR, and changed around Tc from ＋3 in tetragonal phase to ＋2 in cubic phase. Therefore, the amount of electron trap increased at Tc led to the great improvement of PTC R characteristics.

• 한국세라믹학회지
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• 제26권1호
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• pp.7-12
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• 1989

The effects of composition ratios and sintering conditions in Co1-xMgxO ceramics on the sintering characteristics, electrical properties and oxygen sensing characteristics were investigated. In the same sintering conditions, porosity decreased with increase of MgO contents. The relationshiop of temperature and resistance in Co1-xMgxO ceramics showed NTC(negative temperature coefficient) characteristics at the temperature range from $700^{\circ}C$ to 1,10$0^{\circ}C$. In the case of pure CoO, however, the PTC(positive temperature coefficient) characteristics were shown over about 90$0^{\circ}C$. The electrical conductivity of Co1-xMgxO ceramics decreased proportionally with decrease of oxygen partial pressure at the range from 1 to 10-4(atm). Particularly, Co0.5Mg0.5O ceramics showed the highest sensitivity to oxygen gas.

• 한국환경과학회지
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• 제16권5호
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• pp.641-647
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• 2007

The phase transfer catalysis(PTC) reagent, ethyl tri-octyl ammonium bromide(ETABr), strongly catalyzes the reaction of p-nitrophenyi diphenyl phosphinate(p-NPDPIN) with benzimidazole(BI) and its anion($BI^{\theta}$). In ETABr solutions, the dephosphorylation reactions exhibit higher first order kinetics with respect to the nucleophile, BI, and ETABr, suggesting that reactions are occuring in small aggregates of the three species including the sub-strate(p-NPDPIN), whereas the reaction of p-NPDPIN with $OH^{\theta}$ is not catalyzed by ETABr. This behavior for the drastic rate-enhancement of the dephosphorylation is referred as 'aggregation complex model' for reaction of hydrophobic organic phosphinates with benzimidazole(BI) in hydrophobic quarternary ammonium salt(ETABr) solutions.

• 한국정밀공학회지
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• 제21권10호
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• pp.94-101
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• 2004

This paper presents the development of a keypad test system for the improvement of working environment and productivity using PTC 16F877 microprocessor. In order to detect the fault of keypad products, hardware and software design is performed in this system. Keypad fault detection system is controlled by the 8 bit one chip PIC microcontroller for the exactness and speed. Developed panel of the keypad test system is comprised of the sub-panel for selecting in the inspected keypad types and the main panel f3r displaying the working order and fault position. Furthermore, all data from keypad inspection are stored in main memory of personal computer for the database. All these functions lead to the improvement of working speed and environment.

• 열처리공학회지
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• 제23권6호
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• pp.323-330
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• 2010

The present study was motivated by increasing demands on quantitative measurements of the heat flux through the water cooling and quenching process of hot steel. The local heat flux measurements are employed by a novel experimental technique that has a function of high-temperature heat flux gauge in which test block assemblies are directly used to measure the heat flux variation during water cooling and quenching of hot steel. The heat flux can be directly achieved by Fourier's law and is also compared with numerical estimation which is solved by inverse heat conduction problem (IHCP). The high-temperature heat flux gauge developed in this study can be applicable to measure cooling rate and history during the actual cooling applications of steelmaking process. In addition, the measurement uncertainty of heat flux is calculated by a quantitative uncertainty analysis which is based on the ANSI/ASME PTC 19.1-2005 standard.

• 보험의학회지
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• 제3권1호
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• pp.90-102
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• 1986

The gallbladder is a pear-shaped, thin walled sac located on the inferior surface of the liver between the right and quadrate lobe, in a recess called fossa vesicae felleae. It is 7.5cm-12.5 cm in length, 3.5 cm in the largest width, and has a volume of about 45 ml with a remarkable capacity for expansion. There are many kinds of diagnostic methods to evaluate diseases of biliary tract including gallbladder-Plain abdomen, Oral cholecystography. Intravenous cholangiography, Percutaneous transhepatic cholangiography(PTC), Endoscopic retrograde cholangiography(ERCP), Operative or T-tube cholangiography, Ultrasonography, Radioisotope study, Computed tomography, and Angiography. Especially, ultrasonography is the most effective and noninvasive study in these days. Plain abdomen, oral cholecystography, intravenous cholangiography, and ultrasonography have been performed in our clinic. Methods and findings of above mentioned study are discussed with consideration of references.