• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
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• pp.273-278
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• 1998

The phase stability of atomized U-10wt. ％Mo powder and the thermal compatibility of dispersed fuel meats at 40$0^{\circ}C$ and 50$0^{\circ}C$ have been characterized. Atomized U-10Mo powder has a good \ulcorner-U phase stability, and excellent thermal compatibility with aluminum matrix in a dispersion fuel. It is thought that the good phase stability is related to th large supersaturation of Mo atoms in the atomized particles. The reasons for the excellent thermal compatibility have been considered to be as follows. Before thermal decomposition of ${\gamma}$-U in particle, supersaturated Mo atoms at ${\gamma}$-U grain boundaries inhibit the diffusion of Al atoms. After thermal decomposition of ${\gamma}$-U into ${\gamma}$-U and U$_2$Mo, the intermetallic compound of U$_2$Mo seems to retard the penetration of Al atoms. The penetration mechanisms of aluminum atoms in the atomized particles are assumed be classified as (a) diffusion through the reacted layer between fuel particles and Al matrix leaving a kernel-like unreacted island and (b) diffusion along grain boundaries showing several unreacted islands and more reacted regions.

• 한국주조공학회지
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• 제20권1호
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• pp.13-20
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• 2000

In the present study,($10%Al_2O_3+5%Si$)/AZ91 Mg hybrid composite was fabricated using the squeeze casting method. During squeeze casting, Molten Mg was infiltrated into the preform of $10%Al_2O_3+5%Si$ and reaction product of $Mg_2Si$ intermetallic compound was formed by the reaction between molten Mg and Si Powder. Microstructure has been observed and mechanical properties were evaluated for the reaction squeeze cast(RSC) hybrid composite. It was found that Si powder totally reacted with molten Mg to form $Mg_2Si$. Reinforcement($Al_2O_3$) and the reaction product ($Mg_2Si$) are fairly uniformly distributed in Mg Matrix for the squeeze cast hybrid composite. Mechanical Properties were improved with hybridization of reinforcements, namely higher hardness and enhanced wear resistance comparing squeeze cast($15%Al_2O_3$)/AZ91 Mg composite.

• Journal of Power Electronics
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• 제13권6호
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• pp.1080-1089
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• 2013

In this paper, the superposition principle of a heat sink temperature rise is verified based on the mathematical model of a plate-fin heat sink with two mounted heat sources. According to this, the distributed coupling thermal impedance matrix for a heat sink with multiple devices is present, and the equations for calculating the device transient junction temperatures are given. Then methods to extract the heat sink thermal impedance matrix and to measure the Epoxy Molding Compound (EMC) surface temperature of the power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) instead of the junction temperature or device case temperature are proposed. The new thermal impedance model for the power converters in Switched Reluctance Motor (SRM) drivers is implemented in MATLAB/Simulink. The obtained simulation results are validated with experimental results. Compared with the Finite Element Method (FEM) thermal model and the traditional thermal impedance model, the proposed thermal model can provide a high simulation speed with a high accuracy. Finally, the temperature rise distributions of a power converter with two control strategies, the maximum junction temperature rise, the transient temperature rise characteristics, and the thermal coupling effect are discussed.

• 한국자기공명학회논문지
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• 제6권2호
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• pp.94-102
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• 2002

An interesting recent application of intermolecular NOE experiment is the saturation transfer difference NMR(STD-NMR) method that is useful in screening compound libraries to identify bio-active ligands. This technique also identifies the group epitopes of the bound ligand in a reversibly forming protein-ligand complex. We present here a complete relaxation and conformational exchange matrix (CORCEMA) theory (Moseley et al., J. Magn. Reson. B, 108, 243-261 (1995)) applicable for the STD-NMR experiment. Using some ideal model systems we have analyzed the factors that influence the STD intensity changes in the ligand proton NMR spectrum when the resonances from some protons on the receptor protein are saturated. These factors will be discussed and some examples of its application in some model systems will be presented. This CORCEMA theory for STD-NMR and the associated algorithm are useful in a quantitative interpretation of the STD-NMR effects, and are likely to be useful in structure-based drug design efforts. They are also useful in a quantitative characterization of protein-protein (or protein-nucleic acid) contact surfaces from an intermolecular cross-saturation NMR experiment.

• 한국결정성장학회지
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• 제16권4호
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• pp.172-179
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• 2006

[ $Al_2O_3-MoO_3$ ]의 혼합물을 환원소성하면 $MoO_3$만 $900^{\circ}C$에서 Mo로 환원되고 $1300^{\circ}C$까지 $Al_2O_3$와 Mo간의 화합물은 형성되지 않았다. $Al_2O_3-MoO_3-MnO_2$, 혼합물의 경우, $900^{\circ}C$에서 먼저 $MnO_2$가 $MoO_3$와 반응하여 중간화합물 $Mn_2Mo_3O_8$를 형성하였다가. $1100^{\circ}C$와 $1300^{\circ}C$에서 $Mn_2Mo_3O_8$ 화합물은 사라지고 새로운 화합물 $MnAl_2O_4$가 생성되었다. $Al_2O_3$와 $MoO_3,\;MnO_2$의 혼합분말 중 Mo만이 선택적으로 환원되는 selective reduction process에 의해 $Al_2O_3/Mo/MnO_2$ 복합재를 제조하였다. $Al_2O_3/Mo$ 복합재의 경우 Mo의 함량이 증가함에도 불구하고 Mo입자가 $Al_2O_3$ matrix의 입성장을 억제하여 평균입경의 변화는 거의 없었다. 파괴강도는 $Al_2O_3$ matrix의 입성장 억제 현상 때문에 Mo의 함량이 증가함에 따라 증가하였다. 경도는 Mo의 낮은 경도값 때문에 약간 감소하였으나 반면에 파괴인성은 증가하였다. $Al_2O_3/Mo/MnO_2$ 복합재의 경우 $MnO_2$는 matrix의 입성장을 촉진시켰고, Mo와 $MnO_2$의 함량이 증가함에 따라 $MnO_2$의 입성장효과 때문에 오히려 낮은 파괴강도를 보였다. 경도는 입계에 존재하는 coalesced Mo 입자들과 matrix의 입성장 때문에 더욱 감소하였으나 반면에 파괴인성은 더욱 증가하는 경 향을 보였다.

• 한국재료학회지
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• 제9권11호
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• pp.1102-1107
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• 1999

FeAl 기지 복합재료는 hot-pressing에 의해서 성공적으로 제조할 수 있다. 이러한 FeAl 합금의 기계적 특성에 대한 연구는 많이 진행되었으나 플라즈마 질화에 의한 표면 경화특성에 관한 연구는 아직 미흡한 실정이다. 본 연구에서는 hot-pressing으로 제조된 소결 복합재료의 미세구조와 플라즈마 질화처리시 표면경화의 관계를 분석하였다. FeAl을 기지로 하는 합금은 플라즈마 질화처리에 의해서 표면경도가 상승하는 경향을 보였고, 이러한 경향은 질화처리 시간이 증가할수록 더욱 뚜렷하였다($\textrm{H}_{\textrm{v}}$ 100gf, 확산층 : 1100~1450kg/$\textrm{mm}^2$, matrix : 330~360kg/$\textrm{mm}^2$). FeAl 합금으로 플라즈마 질화처리에 의해서 매우 우수한 표면경화특성을 얻을 수 있었다. 확산층은 플라즈마 질화처리시간이 증가할수록 두꺼워졌으며, SiC(sub)p의 함유량이 증가함에 따라 확산층은 감소하였다.

• 생명과학회지
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• 제16권6호
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• pp.964-971
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• 2006

기질의 침윤과 전이를 특징으로 하는 악성종양 세포는 세포외 기질이나 기저막에 의존적으로 작용한다. 세포외 기질을 분해하는 효소인 matrix metalloproteinase (MMP) 계들의 발현 및 활성증가는 대부분의 악성종양세포에서 전이와 침윤을 촉진시킨다. MMP family 가운데 특히 type IV collagenase 활성을 지닌 MMP-2와 MMP-9은 세포외기질의 중요한 구성분인 collagen, fibronectin을 분해하는 특성을 가지며 암 전이를 용이하게 하는 주요한 효소로 잘 알려져 있다. 본 연구에서는 항암후보물질인 disulfiram이 골 육종 (U20S), 신장암 (Caki-1) 및 자궁암 (Caski) 세포에서 MMP-2와 MMP-9의 효소활성 및 발현억제에 대해 조사하였다. MTT assay를 이용하여 disulfiram에 대한 암세포 viability 실험에서는 disulfiram이 암세포의 viability를 저해하였다. 또한 zymography, western blot 및 RT-PCR 등을 이용한 type IV collagenase의 활성 및 발현 실험에서 disulfiram은 type IV collagenase의 활성을 비롯하여 단백질 및 mRNA 발현을 억제시키는 것을 확인하였다. 따라서 disulfiram이 MMP-2와 MMP-9의 활성 및 발현 억제 기전을 통하여 골 육종, 신장암 및 자궁경부암 세포의 작용을 억제한다는 연구 결과는 disulfiram이 각종 악성종양의 침윤과 전이를 억제 또는 방지하기 위한 치료물질로서 임상에서 활용할 수 있는 가능성을 보여준다.

• 한국재료학회지
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• 제15권10호
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• pp.662-666
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• 2005

Solid solutions of $(Zr/Ti)O_2$ were prepared in powder form by the coprecipitation technique. After mixing with carbon or exposing to nitrogen gas at elevated temperature, titanium cations selectively diffused out from the oxide compound to form titanium carbide (TiC) or titanium nitride (TiN), respectively. TiN formed strong interfacial contacts between the oxide grains. In contrast, TiC formed as small crystallites on oxide grains but did not bind the matrix grains together. TiN therefore played a role in strengthening the interparticle bonding, but TiC weakened the bonding between grains. Partial diffusion of titanium cations also led to nanolayered structure being formed between the oxide grains, which provided weak interfacial layers that fractured in a step-wise fashion.

• 한국염색가공학회:학술대회논문집
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• 한국염색가공학회 2008년도 제38차 학술발표대회
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• pp.190-191
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• 2008

In the presence of heat and oxygen, phosphorous compounds decompose to form water vapor and phosphorous oxides. The phosphorous oxides subsequently reat with the polymer matrix and dehydrate it, reforming phosphoric acids. These acids again decompose to reform water vapor and phosphorous oxides. Ultimately as the water available from normal combustion of hydrocarbons diminishes, the phosphorous oxide reat with hydrocarbon fragments to produce a very high melting point char at the interface between the polymer and the heat material. The chars, which contain phosphorous, rapidly dissipate heat energy and lose their glow. This antiglow property of phosphorous compound contributes to its availability as a flame retardant. In this study, the acrylated phosphorous compounds will be prepared and demonstrated as flame retardants.

• 반도체디스플레이기술학회지
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• 제14권1호
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• pp.67-71
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• 2015

Pulse electroplating was studied to form nanocrystal structure effectively by changing plating current density and duty cycle. When both of plating current density and duty cycle were decreased from $100mA/cm^2$ and 70% to $50mA/cm^2$ and 30%, the P content in the Ni matrix was increased almost up to the composition of $Ni_3P$ compound and the grain growth after annealing was retarded as well. The as-plated hardness values ranging from 660 to 753 HV are mainly based on the formation of nanocrystal structure. On the other hand, the post-anneal hardness values ranging from 898 to 1045 HV, which are comparable to the hardness of hard Cr, are coming from how competition worked between the precipitation of $Ni_3P$ and the grain coarsening. According to the ANOVA and regression analysis, the plating current density showed more strong effect on nanocrystal size and film hardness than the duty cycle.