• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2001년도 추계학술강연 및 발표대회
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• pp.36-36
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• 2001

$BaTiO_3$는 현재 전기 전자 부속 산업엣 필수적인 재료로서, multilayer capacitor,positive temperature coefficient(PTC) resistor, grain-boundary battier layer capacitor(GBBLC)등에 쓰이고 있다. $BaTiO_3$의 전기적 특성을 최대화하기 위해서는 미세구조가 최적화 되어야만 하는데 일반적으로 수 마이트로 이내의 작고 균일한 크기의 입자크기가 바람직하다. 그러나 $BaTiO_3$계에서 화학양론의 조성이 정확하게 일치하지 않거나 $La^{3+}$나 $Nb^{5+}$같은 첨가제가 들어가지 않으면 비정상 입자 성장은 자발적으로 일어난다. 그러나 첨가제는 $BaTiO_3$의 강자성 특성에 영향을 주게 되므로 첨가제 없이 비정상 입자 성장을 억제할 수 있는 것이 바람직한 방법이며, 이 것이 본 실험의 목표이다. 본 실험에서는 0.4-mol%-$TiO_2$가 첨가된 $BaTiO_3$ 분말을 디스크 형태로 성형하여 $H_2$ 분위기, 1250에서 5시간동안 열처리한 후, 공기 중, 1300도에서 48시간까지 소결한 후 미세조직을 관찰하였다. 소결 전에 $H_2$ 분위기에서 열처리를 함으로서 초기 입자 크기는 증가하게 되고 이로 인한 계의 성장 구동력 감소로 비정상 입자 성장이 억제되었으며 균일하고 미세한 입자 크기를 가지는$BaTiO_3$ 소결체를 얻을 수 있었다. 또한 비정상이 억제되지 않은 $BaTiO_3$의 유전 특성보다 우수한 유전 특성을 나타내었다. 본 실험을 통해서 첨가제를 사용하지 않고 우수한 유전 특성을 가지는 미세한 균일한 입자의 $BaTiO_3$를 제조하는 새로운 기술을 개발하였다.

• 한국환경과학회지
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• 제20권1호
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• pp.119-126
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• 2011

In this study, reaction model and reactions rate accelerated by o-iodosobenzoate ion(IB$^{\ominus}$) on hydrolysis reaction of p-nitrophenyl valate(NPV) using ethyl tri-octyl ammonium mesylate(ETAMs) for quaternary ammonium salts, the phase transfer catalysis(PTC) reagent, were investigated. The effect of IB$^{\ominus}$ on hydrolysis reaction rate constant of NPV was weak without ETAMs solutions. Otherwise, in ETAMs solutions, the hydrolysis reactions exhibit higher first order kinetics with respect to the nucleophile, IB$^{\ominus}$, and ETAMs, suggesting that reactions are occurring in small aggregates of the three species including the substrate(NPV), whereas the reaction of NPV with OH$^{\ominus}$ is not catalyzed by ETAMs. Different concentrations of NPV were tested to measure the change of rate constants to investigate the effect of NPV as substrate and the results showed that the effect was weak. This means the reaction would be the first order kinetics with respect to the nucleophile. This behavior for the drastic rate-enhancement of the hydrolysis is referred as 'Aggregation complex model' for reaction of hydrophobic organic ester with o-iodosobenzoate ion(IB$^{\ominus}$) in hydrophobic quarternary ammonium salt(ETAMs) solutions.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.147-147
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• 2010

PTC Thermistors specimens were fabricated by added $MnO_2$ as donors, and $Nb_2O_5$ as acceptors and sintered $1250^{\circ}C$/2hrs. Average grain size decreased with increased in added $MnO_2$, and increased with added in $Nb_2O_5$. But, appeared liquid phase as $Bi_2O_3$ and $TiO_2$, affect to grain growth. XRD result, peak strength waslowed then crystallization not well, but, secondary phase were not showed all specimens. All specimens resistance were so high, about $40M{\Omega}$ over, couldn't measured to those resistance and doesn't appear PTCR effect.

• 한국전기전자재료학회논문지
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• 제26권2호
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• pp.119-125
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• 2013

In this paper, semiconducting shield specimens for a DC cable is fabricated and characterized by measurement of volume resistance, tensile strength, and the coefficient of expansion to show the electrical and mechanical characteristics of the semiconducting shield. Due to the PTC phenomenon, the volume resistance at $25^{\circ}C$ increases rapidly in comparison to the volume resistance at $90^{\circ}C$. Since the compounding ratio of carbon black is low, the tensile strength and density become lower and the coefficient of expansion is increased. As the general specification of the tensile strength and density is $0.8kgf/mm^2$ and 150%, respectively, the fabricated specimen in this paper has excellent mechanical characteristic.

• 대한기계학회논문집B
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• 제26권11호
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• pp.1496-1502
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• 2002

An Altitude Engine Test Facility(AETF) was built at the Korea Aerospace Research Institute in October 1999 and has been being operated for altitude testing of gas turbine engines of 3,000 Ibf class or less. The AETF has been calibrated using several engines such as J69 of Teledyne Co. as a facility checkout engine. Uncertainty analyses on the air flow rate and thrust were performed using the test results, according to ASME PTC 19.1-1998. Several modifications on the facility and test method were made in order to improve the measurement uncertainty to a satisfactory level over the whole operating envelop. Spatial distributions of pressure and temperature were measured, sensors were substituted by more accurate ones, inlet duct was modified to refine the flow quality, and pressure control logic was revised to remove the cell pressure fluctuation. As a result, the uncertainty of the air flow measurement was improved by 0.1% over all the test conditions, and the net thrust measurement by up to 3%. The improved measurement uncertainties of air flow and thrust are 0.68～O.73% and 0.4～1.3%, respectively.

• 해양환경안전학회지
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• 제9권1호
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• pp.17-23
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• 2003

2001년 9.11 테러사건 이후 선박과 승무원의 안전과 보안문제가 해양산업에서 새로운 화제로 대두되고 있다. 고 위험 테러시대에 선주와 항만당국 뿐만 아니라, 선박 종사자들도 그들의 업무와 행동에 있어서 테러위협에 대한 경각심과 대응책이 요구되고 있다. 본 논문에서는 먼저 해양보안관리의 개념과 원칙에 입각하여 상선의 보안 취약성과 주요 요소를 분석하여 상선보안관리원칙을 도출하였다. 그리고 ISPS 규정에 입각하여 선내의 보안조직과 보안업무를 설정하고 승무원의 보안문화 정착을 위한 PTC 프로그램과 선박보안 시스템을 구성하였다.

• 한국전기전자재료학회논문지
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• 제21권3호
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• pp.217-221
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• 2008

In this study, We have been investigated the effect of calcination temperature and high-energy ball-milling of powder influences the $BaTiO_3$-based PTCR(Positive Temperature coefficient Resistance) characteristics and microstructure. The mixed powder was obtained from $BaCO_3$, $TiO_2$, $CeO_2$ ball-milled in attrition mill. The mixed powder was calcine from 1000 $^{\circ}C$ to 1200 $^{\circ}C$ in air and then it was sintered in reduction- re-oxidation atmosphere. As a result, The room-temperature electrical resistivity decreased and increased with increasing calcination temperature. specially, Attrition milled powder could have low room-temperature resistivity and high PTC jump order at 1100 $^{\circ}C$. attrition milling had lower room-temperature resistivity than ball milling. Particle size decreased by Attrition milling of powder influences in calcination temperature and room-temperature resistivity.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.17-22
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• 2014

Recently, the quick heating performance is an important issue in the car because engine power becomes so high. So car makers have been adapted the additional heating devices as like PTC(Positive Temperature Coefficient) heater. And the quick cooling performance is also important issue because its result is used in the IQS(Initial Quality Study). In this paper, control of the HVAC(Heating, Ventilation and Air Conditioning) intake door has been studied for the quick heating and cooling performance. Heating performance is improved $4.0^{\circ}C$ at $-20^{\circ}C$ ambient temperature after 20 minutes. And cooling performance is improved $1.5^{\circ}C$ at $35^{\circ}C$ ambient temperature after 10 minutes. In addition, intake door control system brings on the cost reduction because the flab door can be eliminated. This intake door control system has been adapted to the new developing cars.

• 대한화학회지
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• 제54권4호
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• pp.437-442
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• 2010

수용액 속에서 $NaHSO_4$, TBAB (phase transfer catalyst), ionic liquid (IL) (1-butyl-3-methyl imidazolium hydrogen sulphate [bmim]$HSO_4$)를 사용하여, formalin, ${\beta}$-naphthol, aromatic amines을 반응시켜서 대응하는 2,3-dihydro-2-phenyl-1Hnaphtho-[1,2-e] [1,3] oxazine 유도체를 합성할 수 있는 보다 친환경적이고, 수율이 좋고, 크로마토그래피 분리 방법을 사용하지 않는 합성 방법을 개발하였다.

• 한국유체기계학회 논문집
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• 제12권6호
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• pp.18-25
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• 2009

Venturi has long been an attractive method of measuring flow rate in a variety of engineering applications since pressure loss is relatively small compared with other measuring methods. The current study focuses on making detailed uncertainty estimations as the upstream flow disturbance affects uncertainty levels of the flow rate measurement. Upstream flow disturbance can be determined by 9 different swirl generators. Measurement uncertainty of flow rate has been estimated by a quantitative uncertainty analysis which is based on the ANSI/ASME PTC 19.1-2005 standard. The results of flow rate uncertainty analysis show that the case with systematic error has higher than that without systematic error. Especially the result with systematic error exhibits that the uncertainty of flow rate was gradually increased by swirl flow disturbance. The uncertainty of flow rate measurement can be mainly affected by differential pressure and discharge coefficient. Flow disturbance can be also reduced by increasing of the upstream straight length of Venturi.