• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1998.06a
• /
• pp.23-26
• /
• 1998

The domain formation phenomena of {{{{ { LiLbO}_{ 3} }}}} crystals was investigated and the method for the periodic domain formation in {{{{ { LiLbO}_{ 3} }}}} single crystals during growth was proposed in this study. The strees-induced domain formation mechanism was proposed and explained. The strong piezoelectric effect of{{{{ { LiLbO}_{ 3} }}}} at elevated temperature would be the direct driving force for the inversion of the tensile component of the internal stresses can inverse the original direction of the spontaneous polarization.

• Journal of The Korean Astronomical Society
• /
• v.29 no.spc1
• /
• pp.71-72
• /
• 1996

We show that the star formation activity of spiral galaxies has a great variety. The star formation variation in a time scale of $10^8$ yr and the mechanism responsible for the variation are discussed.

• Journal of the Korean Geotechnical Society
• /
• v.32 no.12
• /
• pp.33-43
• /
• 2016

In order to analyze ground relaxation and cavity formation mechanism due to deteriorated sewer pipe, field test was carried out and a numerical assessments were compared with the field test results. An artificial underground cavity was intended using the ice block overlaying the buried pipe and confirmed that the cavity and relaxation of the surrounding ground were gradually formed as the ice block starts to melt down. Such mechanism was highly suspected to be involved with soil particle interlocking as a soil compaction was a typical process for the buried pipes. In exploring such mechanism numerically, commercially available DEM (Discrete Element Method) code PFC2D was used and the interlocking induced cavern behaviors were successfully simulated and compared with field test results by utilizing the clump logic imbedded in PFC code.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1995.03a
• /
• pp.211-223
• /
• 1995

The purpose of the present study is to examine shearing mechanism through rigidplastic finite element analysis. Difficulties arise in simulating shearing process due tothe narrow shear band formation andlackof proper fracture resolve these difficulties by using adaptive mesh generation crriterion. The simulation results are obtained for various punch clearances and these are compared with existing experimental results. It is shown that FEM simulation technique can be used to further understand the shearing mechanism.

• 한국연소학회:학술대회논문집
• /
• 1998.10a
• /
• pp.155-164
• /
• 1998

Numerical analysis was performed with multicomponent transport properties and detailed reaction mechanisms for axisymetric 2-D CH4 jet diffusion, partial premixed, premixed flame. Calculations were carried out twice with C2-Full Mechanism including prompt NO reaction in addition to the above C2-Thermal NO Mechanism. The role of thermal NO mechanism and prompt NO mechanism on each flame's NO production is investigated by using the numerical result. The NOx production of each flame were evaluated Quantitatively in terms of the NOx emission index

• Geomechanics and Engineering
• /
• v.20 no.1
• /
• pp.29-41
• /
• 2020

It is extremely important to obtain rock strength parameters for geological engineering. In this paper, the evolution of sandstone cohesion and internal friction angle with plastic shear strain was obtained by simulating the cyclic loading and unloading tests under different confining pressures using Particle Flow Code software. By which and combined with the micro-crack propagation process, the mesoscopic mechanism of parameter evolution was studied. The results show that with the increase of plastic shear strain, the sandstone cohesion decreases first and then tends to be stable, while the internal friction angle increases first, then decreases, and finally maintains unchanged. The evolution of sandstone shear strength parameters is closely related to the whole process of crack formation, propagation and coalescence. When the internal micro-cracks are less and distributed randomly and dispersedly, and the rock shear strength parameters (cohesion, internal friction angle) are considered to have not been fully mobilized. As the directional development of the internal micro-fractures as well as the gradual formation of macroscopic shear plane, the rock cohesion reduces continuously and the internal friction angle is in the rise stage. As the formation of the macroscopic shear plane, both the rock cohesion and internal friction angle continuously decrease to a certain residual level.

• Journal of the Korean Ceramic Society
• /
• v.38 no.10
• /
• pp.881-885
• /
• 2001

Kinetics and mechanisms of intermediate phases formation in $Ba(Mg_{1/3}Ta_{2/3})O_3$, obtained by a solid state reaction were studied. $Ba{Ta_2}{O_6}$ and ${Ba_4}{Ta_2}{O_9}$ as intermediate products were first formed at $700^{\circ}C$. $Ba(Mg_{1/3}Ta_{2/3})O_3$ was appeared at $800^{\circ}C$. Several reactions take place on heating process. $Ba{Ta_2}{O_6}$ is found at the first stage of the reaction, and then $Ba{Ta_2}{O_6}$ or ${Ba_4}{Ta_2}{O_9}$ react with MgO to form $Ba(Mg_{1/3}Ta_{2/3})O_3$. The reaction of $Ba(Mg_{1/3}Ta_{2/3})O_3$ formation does not complete until fired at $1350^{\circ}C$ for 60 min. The kinetics of solid-state reaction between powdered reactants was controlled by diffusion mechanism, and can be explained by the Jander's model for three-dimensional diffusion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.119-120
• /
• 2008

ILD CMP process has been well accepted for the planarization of the dielectric oxide film and becomes a critical process in ULSI manufacturing due to the rapid shrinkage of the design rule for the device. In total manufacturing process steps for a device, the proportion of ILD CMP process has been gradually increased. Ever since ILD CMP has been introduced, the scratches have been a major defects on polished surfaces which cause the electrical shorts between vias or metal lines [1,2]. It was reported that micro-scratches are caused by large, irregularly shaped particles during CMP process. Therefore, most of the CMP users have used < 5 m POU filter to remove and reduce the scratch source from the slurry. However, the scratch has always been the biggest concern in ILD polishing whatever preventive actions are taken. Silica and ceria slurries are widely used for ILD CMP process. There are not much differences in generated scratches and their formation mechanism. In this study, the scratches were investigated as a function of polishing conditions with possible explanation on formation mechanism in ILD CMP.

• Journal of Welding and Joining
• /
• v.18 no.2
• /
• pp.86-94
• /
• 2000

This study was performed to investigate types and formation mechanism of cracks in two Al alloy welds, A5083 and A7N01 spot-welded by pulse Nd : YAG laser, using SEM, EPMA and Micro-XRD. In the weld zone, three types of crack were observed : center line crack({TEX}$C_{C}${/TEX}), diagonal crack({TEX}$C_{D}${/TEX}), and U shape crack({TEX}$C_{U}${/TEX}). Also, HAZ crack({TEX}$C_{H}${/TEX}) was observed in the HAZ region, furthermore, mixing crack({TEX}$C_{M}${/TEX}) consisting of diagonal crack and HAZ crack was observed. White film was formed at th hot crack region in the fractured surface after it was immersed to 10% NaOH water. In the case of A5083 alloy, white films in {TEX}$C_{C}${/TEX} crack and {TEX}$C_{D}${/TEX} crack region were composed of low melting phases, {TEX}$Fe_{2}SiAl_{8}${/TEX} and eutectic phases, $Mg_2$Al$_3$ and $Mg_2$Si. Such films observed $CuAl_2$, {TEX}$Mg_{32}(Al,Zn)_{3}${/TEX}, MgZn$_2$, $Al_2$CuMg and $Mg_2$Si were observed in the whitely etched films near {TEX}$C_{C}${/TEX} crack and {TEX}$C_{D}${/TEX} crack regions. The formation of liquid films was due to the segregation of Mg, Si, Fe in the case of A5083 alloy and Zn, Mg, Cu, Sim in the case of A7N01 alloy, respectively. The {TEX}$C_{C}${/TEX} and {TEX}$C_{D}${/TEX} cracks were regarded as a result of the occurrence of tensile strain during the welding process. The formation of {TEX}$C_{M}${/TEX} crack is likely to be due to the presence of liquid film at the grain boundary near the fusion line in the base metal as well as in the weld fusion zone during solidification. The {TEX}$C_{U}${/TEX} crack is considered a result of the collapsed keyhole through incomplete closure during rapid solidification.

• BMB Reports
• /
• v.45 no.3
• /
• pp.189-193
• /
• 2012

Cyst formation is a major characteristic of ADPKD and is caused by the abnormal proliferation of epithelial cells. Renal cyst formation disrupts renal function and induces diverse complications. The mechanism of cyst formation is unclear. mIMCD-3 cells were established to develop simple epithelial cell cysts in 3-D culture. We confirmed previously that Mxi1 plays a role in cyst formation in Mxi1-deficient mice. Cysts in Mxi1 transfectanted cells were showed by collagen or mebiol gels in 3-D cell culture system. Causative genes of ADPKD were measured by q RT-PCR. Herein, Mxi1 transfectants rarely formed a simple epithelial cyst and induced cell death. Overexpression of Mxi1 resulted in a decrease in the PKD1, PKD2 and c-myc mRNA relating to the pathway of cyst formation. These data indicate that Mxi1 influences cyst formation of mIMCD-3 cells in 3-D culture and that Mxi1 may control the mechanism of renal cyst formation.