• Bulletin of the Korean Chemical Society
• /
• v.27 no.10
• /
• pp.1572-1576
• /
• 2006

A dimeric precursor, $[Cu(dmae)(OCOCH_3)(H_2O)]_2$ for the CVD of copper metal films, (dmaeH = N,N-dimethylaminoethanol) was synthesized by the reaction of copper(II) acetate monohydrate ($Cu(OCOCH_3)_2{\cdot}H_2O$) and dmaeH in toluene. The product was characterized by m.p. determination, elemental analysis and X-ray crystallography. Molecular structure of $[Cu(dmae)(OCOCH_3)(H_2O)]_2$ shows that a dimeric unit $[Cu(dmae)(OCOCH_3)(H_2O)]_2$ is linked to another through hydrogen bond and it undergoes facile decomposition at 300 C to deposit granular copper metal film under nitrogen atmosphere. The decomposition temperature, thermal behaviour, kinetic parameters, evolved gas pattern of the complex, morphology, and the composition of the film were also investigated.

• Journal of the Korean Ceramic Society
• /
• v.38 no.7
• /
• pp.672-677
• /
• 2001

Ca$_{1-x}$Nd$_{2+x}$3/TiO$_3$계에 대하여 소결 온도 변화(120$0^{\circ}C$-140$0^{\circ}C$) 및 Nd$^{3+}$ 의 치환량 (0.15$\leq$x$\leq$0.51)에 따른 마이크로파 유전특성을 조사하였다. 동일 조성의 경우 소결 온도 변화에 따라 Qf(Q=1/tan$\delta$, f=frequency)는 밀도 증가에 의해 다소 증가되었으나, 유전상수(K)는 커다란 변화가 없었다. 소결 온도가 동일한 경우 Qf는 x=0.42 조성까지는 증가하였으나, x=0.51 조성에서는 상대 밀도와 결정립 크기의 감소로 인해 감소하였다. Nd$^{3+}$ 의 치환량이 증가함에 따라 A-자리의 평균 이온 반경의 세제곱에 비례하여 유전상수(K)는 감소하였고, 공진주파수의 온도계수(TCF)는 tolerance factor(t)와 A-자리 결합원자가의 감소로 급격히 감소하였으나, 이차상 TiO$_2$의 영향으로 x=0.3 이상에서는 증가하였다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.340-340
• /
• 2012

최근 MOS 소자들이 게이트 산화막을 Mono-layer가 아닌 Multi-Layer을 사용하는 추세이다. Bulk와 High-k물질간의 Dangling Bond를 줄이기 위해 Passivation 층을 만드는 것을 예로 들 수 있다. 이러한 Double Layer의 쓰임이 많아지면서 계면에서의 Interface State Density의 영향도 커지게 되면서 이를 측정하는 방법에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 $SiO_2$ Double Layer의 Interface State Density를 Conductance Method를 사용하여 구하는 연구를 진행하였다. Wet Oxidation과 Chemical Vapor Deposition (CVD) 공정을 이용하여 $SiO_2$ Double-layer로 증착한 후 Aluminium을 전극으로 하는 MOS-Cap 구조를 만들었다. 마지막 공정은 $450^{\circ}C$에서 30분 동안 Forming-Gas Annealing (FGA) 공정을 진행하였다. LCR meter를 이용하여 high frequency C-V를 측정한 후 North Carolina State University California Virtual Campus (NCSU CVC) 프로그램을 이용하여 Flatband Voltage를 구한 후에 Conductance Method를 측정하여 Dit를 측정하였다. 본 연구 결과 Double layer (Wet/CVD $SiO_2$)에 대해서 Conductance Method를 방법을 이용하여 Dit를 측정하는 것이 유효하다는 것을 확인 할 수 있었다. 본 실험은 앞으로 많이 쓰이고 측정될 Double layer (Wet/CVD $SiO_2$)에 대한 Interface State Density의 측정과 분석에 대한 방향을 제시하는데 도움이 될 것이라 판단된다.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.6
• /
• pp.941-946
• /
• 2007

Bacillus halodurans O-methyltransferase (BhOMT) is a S-adenosylmethionine (SAM or AdoMet) dependent methyltransferase. Three dimensional structure of the BhOMT bound to S-adenosyl-L-homocysteine (SAH or AdoHcy) has been determined by comparative homology modeling. BhOMT has 40% sequence identity with caffeoyl-CoA 3-O-methyltransferase (CCoAOMT) from alfalfa. Based on x-ray structure of CCoAOMT, three dimensional structure of BhOMT was determined using MODELLER. The substrate binding sites of these two proteins showed slight differences, but these differences were important to characterize the substrate of BhOMT. Automated docking study showed that four flavonoids, quercetin, fisetin, myricetin, and luteolin which have two hydroxyl groups simultaneously at 3'- and 4'-position in the B-ring and structural rigidity of Cring resulting from the double bond characters between C2 and C3, were well docked as ligands of BhOMT. These flavonoids form stable hydrogen bondings with K211, R170, and hydroxyl group at 3'-position in the Bring has stable electrostatic interaction with Ca2+ ion in BhOMT. This study will be helpful to understand the biochemical function of BhOMT as an O-methyltransferase for flavonoids.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.24 no.1
• /
• pp.112-124
• /
• 1997

According to extensive use of composite resin which have superior esthetic property, every effort on improving bonding strength between a tooth and composite resin has been continued. Acid etching technique is a method that micro-etches the tooth surface which provides bonding with composite resin possible. Recently, there were several reports that mechanical treatment obtained from air-abrasion can provide similar bonding strength with acid etching technique. So, this experimental study was designed to compare the shear bonding strength between using air-abrasion technique and using acid etching technique. Initially, bovine teeth were divided into enamel and dentin experimental groups. Respectively each group was categorized into three subgroups. One subgroup was acid etched with 35% phosphoric acid, then bonded with composite resin. The other subgroup was air-abraded with $50{\mu}m$ $Al_2O_3$ particles sprayed with 160psi air pressure using air abrasion unit(KCP-1000, A.D.T., U.SA), and composite resin was bonded. In another subgroup, composite resin was bonded after acid etching following air-abrasion. So, enamel experimental groups were made of E1 (acid etched only), E2(air-abraded only), E3(acid etched following air-abraded), and dentin experimental groups were made of D1(acid etched only), D2(air-abraded only), D3(acid etched following air-abraded). Each subgroup had 10 specimens. Dentin bonding system(Scotchbond Multi-purpose, 3M Co., U.S.A.) and composite resin(Z-100, 3M Co., U.S.A.) were applied on treated surface using 5mm diameter gelatin capsule as manufacturer's direction. After 1200 times thermocycling between $5^{\circ}C$ and $55^{\circ}C$, shear bond strength was measured in 5mm/min crosshead speed with Instron(Instron Co., U.S.A.), and also treated enamel and dentin were observed with SEM(JEOL Co., Japan). The following results were obtained: 1. In the enamel experimental groups, acid etched following air-abraded group had highest shear bond strength, but there was no significant difference compared to acid etched group. Air-abraded only group had lowest shear bond strength, and there was significant difference compared to the rest of groups. 2. In the dentin experimental groups, acid etched following air-abraded group had highest shear bond strength, but there was no significant difference compared to acid etched group. Air-abraded only group had lowest shear bond strength, and there was significant difference compared to the rest of groups. 3. In the SEM study, air-abraded enamel and dentin had irregular and rough surfaces.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.3
• /
• pp.848-858
• /
• 2014

In this paper the construction of a model that represents the behavior of an Electric Vehicle is described. Both the mechanical and the electric traction systems are represented using Multi-Bond Graph structural approach suited to model large scale physical systems. Then the model of the controllers, represented with a functional approach, is included giving rise to an integrated model which exploits the advantages of both approaches. Simulation and experimental results are aimed to illustrate the electromechanical interaction and to validate the proposal.

• Bulletin of the Korean Chemical Society
• /
• v.8 no.3
• /
• pp.193-196
• /
• 1987

The gas phase pyrolyses of eight esters have been studied by MNDO-MO method. In the ethylformate pyrolysis, ${\alpha}$-methylation had a steric releasing effect whereas ${\beta}$-methylation had a steric crowding in the transition state; the latter, however, is over-compensated by a greater electronic repulsion resulting in a net steric releasing effect. Considerations of formal charges and geometrical changes involved in the activation led us to propose a pyrolysis mechanism in which a preequilibrium of acidic proton transfer is followed by the rate-limiting bond polarization of $C_{\alpha}$-O bond in a cyclic transition state.

• Resources Recycling
• /
• v.13 no.3
• /
• pp.3-11
• /
• 2004

Basic studies have been conducted regarding the crystal formation of hydroxyapatite which was produced in the treatment process of phosphate-containing wastewater using calcium ions as the precipitating agent for its employment as the material for artificial bones. The precipitation of hydroxyapatite were conducted in the synthetic solution which simulating human body fluid for its increased applicability. Ca($NO_3$)$_2$$.$$4H_2$O and ($NH_4$)$_2$$HPO_4$ were employed for the precipitation of hydroxyapatite and its composition was analyzed after drying at 80oC. The thermal behavior of precipitate was investigated by examining the change in its crystalline structure according to the sintering temperature. DTA/TG analysis showed that the escape of moisture from the precipitate occurred at ca. $100^{\circ}C$ and the decomposition of ammonia and the evaporation of lattice water were brought about at around $250^{\circ}C$. X-ray diffraction analysis indicated that the thermally treated precipitate consisted mainly of hydroxyapatite. For dried precipitate, the bonds in the component materials which used for the precipitate formation were observed by FT-IR, and after thermal treatment the major bonds in the precipitate were shown to be $OH^{-}$, $PO_4^{3-}$ , and $CO_3^{ 2-}$ , which were main comprising bonds of hydroxyapatite.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.553-554
• /
• 2007

By sol-gel method, we have fabricated silica-titania hybrid film using silane treated colloidal $TiO_2$ and characterized the film through FT-IR, TGA, UV-VIS and AFM. The silica-titania hybrid film showed Ti-O-Si chemical bond at FT-IR peak of $910{\sim}940cm^{-1}$. The fabricated hybrid film showed thermal stability of around $350^{\circ}C$(5wt% loss temperature) and transparency more than 90%. In addition, the good surface smoothness was confirmed by AFM. Therefore, the silica-titania hybrid film with outstanding properties can be potential for application in electronics and displays.

• Korea-Australia Rheology Journal
• /
• v.15 no.1
• /
• pp.9-17
• /
• 2003

The rheological behaviour of anatase $TiO_2$ with organic coating has been investigated extensively in this study. The yield stress was measured over a wide range of solids concentration and pH using stress-controlled and speed-controlled rheometers. The organic treatment leads to a shift of the isoelectric point (IEP) from around pH 5.5 to pH 2.4. A maximum yield stress occurs in the vicinity of the isoelectric point determined by electrokinetic measurements. The transition of rheological behaviour between elastic solid and viscous liquid is represented by a stress plateau in a plot of stress against strain. It is hypothesised that the slope of the stress plateau reflects the uniformity of the structure, and hence the distribution of bond strength. Altering the concentration and the surface chemistry can vary the bond strength and its distribution. therefore, resulting in different type of failure: "ductile-type" or "brittle-type". pH and volume fraction dependence of yield stress could be described quantitatively using existing models with reasonable agreement.easonable agreement.