• Proceedings of the KIPE Conference
• /
• 2015.07a
• /
• pp.205-206
• /
• 2015

본 논문에서는 단일 전류 센서를 가진 IPMSM 구동 시스템의 고주파 신호 주입 센서리스 제어를 제안한다. 단일 전류 센서 시스템에서 3상 전류를 재구축하기 위해 DC link 전류를 검출한다. DC link 전류를 이용하여 3상 전류를 재구축하는 경우의 문제점은 1개 또는 2개의 유효벡터가 DC link 전류를 검출하는데 필요한 최소 시간보다 짧게 인가될 때 발생한다. 센서리스 제어시 이러한 경우가 발생하면, 재구축된 전류의 왜곡에 의해 제어 성능이 저하된다. 본 논문은 전압 벡터가 작은 경우, 전류 예측을 통하여 신뢰할 만한 3상 전류를 재구축하여 전류의 왜곡을 줄임으로써 센서리스 제어 성능을 향상시켰다. 시뮬레이션을 통하여 제안한 기법의 타당성을 검증하였다.

• Journal of the Korean Ceramic Society
• /
• v.37 no.9
• /
• pp.909-914
• /
• 2000

반응금속 침투법으로 제조한 $Al_2$O$_3$/Al 복합체의 파괴특성과 손상 내구성을 침투방향성에 따라 관찰하였으며, 복합체는 $Al_2$O$_3$단일상보다 향상된 파괴인성과 Al 단일상보다 높은 경도값을 나타내었다. Vickers 압입법을 사용한 복합체의 손상형태에서는 침투방향에 따른 각각의 미세구조에 의해 상이한 특성을 나타내었으며, 헤르찌안 압입법을 사용한 복합체의 손상거동은 $Al_2$O$_3$과 Al의 중간거동을 나타내었다. 헤르찌안 압입 후 강도저하시험으로 복합체가 갖는 우수한 결함저항성을 관찰할 수 있었으며, 높은 헤르찌안 하중에서는 복합체의 강도저하 특성이 복합체의 미세구조에 의존함을 관찰할 수 있었다. 이와 함께 복합체에서의 반응금속 침투방향성, 미세구조 그리고 손상 내구성 사이 상호연관성에 대해 논의하였다.

• Journal of the Korean Ceramic Society
• /
• v.38 no.5
• /
• pp.474-478
• /
• 2001

유기 화학 기상 증착법(MOCVD)을 이용하여 반응기체 $O_2$의 양 및 Y와 Mn의 운반기체 비(Y/Mn)를 변화시켜가며 Si(100) 기판 위에서 MFSFET(metal-ferroelectric-semiconductor field effect transistor) 구조의 YMnO$_3$박막을 증착하였다. 반응기체 $O_2$의 양이 150sccm일 때 Y/Mn=2와 3인 경우 단일상의 육방정계 YMnO$_3$박막이 형성되었다. YMnO$_3$박막의 전기적 특성은 사방정계 YMnO$_3$박막에서는 나타나지 않았으나, 육방정계 YMnO$_3$박막의 경우 결정립 크기에 영향을 받아 단일상의 육방정계 YMnO$_3$박막 중 결정립 크기가 150nm~200nm(Y/Mn=2)인 경우에는 잔류분극이 100nC/$ extrm{cm}^2$인 P-E 이력곡선의 특성을 나타내었다.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2007.11a
• /
• pp.103-104
• /
• 2007

$CuInO_2$ 단일상은 합성조건이 매우 까다롭기 때문에 일반적인 고상법으로 얻기 힘든 것으로 알려저 있다. 투명전도성 $CuInO_2$ 박막을 증착하기 위하여 일반적인 고상법으로 Cu와 In의 비율이 1:1인 $Cu_2O-In_2O_3$ composite target 및 In 대신 Ca, Mg, Ti가 각각 1mol% 도핑된 target을 제작하였다. 제작된 각각의 composite target을 이용하여 pulsed laser deposition(PLD) 공정으로 투명전도성 $CuInO_2$ 박막을 증착하였다. Cu와 In이 1:1 인 $Cu_2O-In_2O_3$ composite target을 사용한 경우, 증착된 박막이 Cu와 In의 비율이 1:1인 c-axis 배향된 단일상의 $CuInO_2$ 박막임을 확인하였다.

• Korean Chemical Engineering Research
• /
• v.50 no.2
• /
• pp.300-303
• /
• 2012

Phase change of calcium carbontae crystals in crystallization of precipitated calcium carbonate was researched by adding additives such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), citric acid (CIT) and pyromellitic amid (PMA). At low temperature $20^{\circ}C$, calcite crystal was made. At high temperature $80^{\circ}C$, aragonite crystal was made without additives. At middle temperature $40^{\circ}C$ and $60^{\circ}C$, Aragonite crystal also made by adding EDTA, DTPA. The crystal growth of Aragonite was retarded by the presence of CIT, PMA and the single phase of calcite was made. It was found that additives were important factors to make the single phase of calcium carbonate.

• Journal of the Korean Ceramic Society
• /
• v.33 no.1
• /
• pp.110-118
• /
• 1996

• Journal of the Korean Chemical Society
• /
• v.61 no.4
• /
• pp.191-196
• /
• 2017

One-phase method to prevent the initial formation of Ag(I) thiolate layered materal from the mixture of $AgNO_3$ and thiols was previously developed to generate TP (Thiolate-Protected)-nanosilver. In this modified method, $AgNO_3$ is added to the mixtures of $NaBH_4$ and thiols in ethanol. This method was so successful that it was applied to synthesize TP-nanogold and nanoplatinum. The synthesis and characterization of these nanoparticles by ultraviolet-visible (UV-vis) absorption spectra, transmission electron microscopy (TEM) pictures, X-ray powder differaction (XRD) patterns and infrared(IR) spectra are described. The results show that colloidal nanoparticles are spherical or oval shape and the mean sizes for TP-nanogold and nanoplatinum are about 3~7 nm and below 2 nm, respectively. The conformation of polymethylene [$-(CH_2)_7-$] sequence in octanethiolate attached to nanogold was elucidated as trans.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.10 no.2
• /
• pp.145-151
• /
• 2000

The sintering behaviour of monolithic zirconium diboride (ZrB$_{2 }$) and ZrB$_{2 }$-based composite ZrB$_{2 }$-ZrC were studied using a pressureless sintering technique. The specimens were prepared using commercially available ZrB$_{2 }$ and ZrC powder which were pressed and subjected to pressureless sintering. The effects of lanthanum and neodymium used as sintering aids in the sintering processes were investigated. The sintered specimens were characterized using X-ray diffraction analysis and scanning electron microscopy. The ZrB$_{2 }$ specimen prepared using and addition of 1 wt% lanthanum and pressurelessly sintered at $2200^{\circ}C$ showed the maximum relative density of 96%. The ZrB$_{2 }$-ZrC composite specimen without the addition of any sintering aids exhibits the maximum sintered density but contains significantly detectable amount of secondary phase.

• International Journal of Highway Engineering
• /
• v.7 no.2 s.24
• /
• pp.57-67
• /
• 2005

Almost most of literatures treat behaviors of asphalt binders as a homogeneous single-phase fluid, but this generalization turns out to be a serious mistake. This study introduces all the characteristic equations for asphalt binders, which are modified or unmodified. Especially, characteristic equations for a unhomogeneous multi-phase fluid for modified asphalts is first time proposed. Characteristics of each equations introduced are explained by employing dynamic shear testing data actually measured for specific asphalt binders. Differences of moving behaviors and characteristic equations between a homogeneous single-phase and a unhomogeneous multi-phase fluid are emphasized. These differences help us understand which characteristic equations must be used for a given asphalt fluid and what kinds of properties must be investigated for analysis of a specific asphalt binder. Results of this study provide how to analyse modified and unmodified asphalts, and informations necessary for binder grading.

• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.4
• /
• pp.83-88
• /
• 2019

LiBaPO₄:Eu²⁺ phosphors with stoichiometric and nonstoichiometric compositions were prepared using a solid state reaction followed by heat treatment in reduced atmosphere, and the crystal structures and photoluminescence(PL) properties of the powders were investigated by x-ray powder diffraction and luminescence spectrometer. At 900℃, the Ba₃(PO₄)₂ phase as the intermediate phase was observed with the LiBaPO₄ phase as the main crystalline phase. Samples with a low europium concentration at 1,000℃ belonged to the trigonal structure, whereas samples with Eu²⁺ content more than 4 mol% showed monoclinic structure. In the nonstoichiometric compositions of 4 mol% Eu²⁺ and above, a single phase of Eu²⁺-doped LiBaPO₄, showing bluish green emission, was formed.