• Journal of the Society of Naval Architects of Korea
• /
• v.47 no.1
• /
• pp.11-19
• /
• 2010

A code is developed to simulate incompressible free surface flows using the Roe's flux-difference splitting scheme. An interface of two fluids is considered as a moving contact discontinuity. The continuities of pressure and normal velocity across the interface are enforced by the conservation law in the integral sense. The fluxes are computed using the Roe's flux-difference splitting scheme for two incompressible fluids. The interface can be identified based on the computed density distribution. However, no additional treatment is required along the interface during the whole computations. Complicated time evolution of the interface including topological change can be captured without any difficulties. The developed code is applied to simulate the Rayleigh-Taylor instability of two incompressible fluids in the density ratio of 7.2:1 and the broken dam problem of water-air. The present results are compared with other available results and good agreements are achieved for the both cases.

• Journal of the Semiconductor & Display Technology
• /
• v.17 no.4
• /
• pp.66-69
• /
• 2018

This study was researched the electrical properties of semiconductor devices such as ITO, $SiO_2$, $V_2O_5$ thin films. The films of ITO, $SiO_2$, $V_2O_5$ were deposited by the rf magnetron sputtering system with mixed gases of oxygen and argon to generate the plasma. All samples were cleaned before deposition and prepared the metal electrodes to research the current-voltage properties. The electrical characteristics of semiconductors depends on the interface's properties at the junction. There are two kinds of junctions such as ohmic and schottky contacts in the semiconductors. In this study, the ITO thin film was shown the ohmic contact properties as the linear current-voltage curves, and the electrical characteristics of $SiO_2$ and $V_2O_5$ films were shown the non-linear current-voltage curves as the schottky contacts. It was confirmed that the electronic system with schottky contacts enhanced the electronic flow owing to the increment of efficiency and increased the conductivity. The schottky contact was only defined special characteristics at the semiconductor and the interface depletion layer at the junction made the schottky contact which has the effect of leakage current cutoff. Consequently the semiconductor device with shottky contact increased the electronic current flow, in spite of depletion of carriers.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.8 s.227
• /
• pp.996-1003
• /
• 2004

The bubble motion during nucleate boiling in a microchannel is investigated by numerically solving the equations governing conservation of mass, momentum and energy in the liquid and vapor phases. The liquid-vapor interface is tracked by a level set method which is modified to include the effects of phase change at the interface and contact angle at the wall. Also, the evaporative heat flux from the thin liquid film that forms underneath a growing bubble attached to the wall is incorporated in the analysis. Based on the numerical results, the effects of channel size, contact angle, wall superheat and waiting period on the bubble growth and heat transfer in a microchannel are quantified.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1997.04a
• /
• pp.33-40
• /
• 1997

This study was undertaken to investigate tribology characteristics of the alumina ceramics($Al_2O_3$) for the vauiation of ambient condition such as air and distilled water. The results obtained were as follows. As the sliding speed increases, the friction coefficient in the air decreased due to the reduction of sheafing stress caused by the heat accumulation of contact interface. And the friction coefficient in the distilled water decreased due to an activation of the tribochemical reaction. As the contact load increases, the friction coefficient is small in the air due to temperature rise of the contact interface. However, at the low speed side in the distilled water, the friction coefficient holds a large value due to decrease of the tribochemical reaction. The friction surface of ceramics can be protected in the air by the influence of the oxides tansfered from STB2 and also in the distilled water by the influence of the corrosive productive hydroxides.

• Journal of the Korean Ceramic Society
• /
• v.35 no.12
• /
• pp.1257-1265
• /
• 1998

Hertzian contact tests were used to investigate the evolution of fracturedamage in the coating layer as functions of contact load and coating thickness by studying crack patterns in porcelain on glass-infiltrated alumina bilayer system conceived to simulate the crown structure of a tooth. Cone cracks initiated at the coating top surface without delamination at interface and crack propagation to substrate. Preferentially the cracks made multi-cracks at the coating top surface rather than proceeding to interface. The cracks were highly stabilized with wide ranges between the loads to initiate first cracking and to cause final failure im-plying damage-tolerant capability. Finite element modelling was used to evaluate the stress distribution. Maximum tensile stress were responsible for the cracking at the coating layer and had a profound influence on the crack pattern and fracture damage in the layered structure materials.

• Journal of the Semiconductor & Display Technology
• /
• v.16 no.2
• /
• pp.9-14
• /
• 2017

$ISnO_2$ thin films were prepared on p-type and n-type Si substrates to research the interface characteristics between $SnO_2$ and substrate. After the annealing processes, the amorphous structure was formed at the interface to make a Schottky contact. The O 1s spectra showed the bond of 530.4 eV as an amorphous structure, and the Schottky contact. The analysis by the deconvoluted spectra was observed the drastic variation of oxygen vacancies at the amorphous structure because of the depletion layer is directly related to the oxygen vacancy. $SnO_2$ thin film changed the electrical properties depending on the characteristics of substrates. It was confirmed that it is useful to observe the Schottky contact's properties by complementary using the XPS analysis and I-V measurement.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.1
• /
• pp.34-42
• /
• 1986

An interface of a circular arc formed by two isotropic, homogeneous elastic materials is investigated. It is shown that L integral satisfies the conservation law for the interface if it is perfectly bonded, in frictionless contact or separated such as in a crack with the origin of the coordinate system being located at the center of the circular arc. The property of path independence of the L integral is applied to an interfacial crack problem, to obtain the stress intensity factors, where the interfacial crack is located along the arc of the circular inclusion embedded in infinite matrix. It is assumed here that the contact zone exist as in the model proposed by Comninou, thus removing the overlapping of the materials along the interface. Another example is shown for case of a circular interfacial crack in the matrix of finite size, where the stress intensity factors are determined by computing a value of the L integral numerically along the path far from the crack tip.

• Journal of Adhesion and Interface
• /
• v.23 no.3
• /
• pp.87-93
• /
• 2022

To analyze the interfacial property between the fiber and the matrix, work of adhesion was used generally that was calculated by surface energies. In this paper, it was determined what types of contact angle measurement methods were more accurate between static and dynamic contact angle measurements. 4 types of glass fiber and epoxy resin were used each other to measure the contact angle. The contact angle was measured using two types, static and dynamic contact angle methods, and work of adhesion, W_a was calculated to compare interfacial properties. The interfacial property was evaluated using microdroplet pull-out test. Generally, the interfacial property was proportional to work of adhesion. In the case of static contact angle, however, work of adhesion was not consistent with interfacial property. It is because that dynamic contact angle measurement comparing to static contact angle could delete the error due to microdroplet size to minimize the surface area as well as the meniscus measuring error.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.491-494
• /
• 2002

To assess the electrostatic interaction of surfaces at the triple contact line, the electrostatic field is analyzed by using the finite element method. The Helmholtz free energy is used as a functional which should be minimized under an equilibrium condition. The numerical results are compared with the nonlinear analytical solution for a two-dimensional charged interface and linear solution for a wedge shaped geometry, which shows fairly good agreement. The method is applied to the analysis of electrostatic influence on the contact angle on a charged substrate. The excess free energy found to increase drastically as the contact angle approaches to zero. This excess free energy Plays an opposite role to the Primary electrocapillary effect, as the contact angle gets smaller. This enables an alternative explanation for the contact-angle saturation phenomenon occurring in electrical control of surface tension and contact angle.

• Korean Journal of Clinical Laboratory Science
• /
• v.37 no.1
• /
• pp.35-40
• /
• 2005

This paper reports the morphological nature of the remodelled interface process between implants and surrounding bone after 1, 4, 6, 8 and 12 weeks of implantation of smooth machined implants into rat tibias. After 4 weeks of implantation, histochemical analysis showed that the new bone was growing in direct contact with the implant. In the forming process, the activatived osteoblast cells migrated toward the interface and colonized the surface at the contact areas. This immature woven bone, rich in osteocyte lacunae, was deposited directly onto the implant surface. Osteoblast activity was found to continue ill 12 weeks of implantation The osteoblasts in lacunar areas developed numerous processes and synthesized bone matrix, after all, surrounded by secreting matrix. At the 12th week, the amount of newly formed bone matrix between bone and implant increased in mineralization. The mineralized mature bone contained well organized collagen fibers with characteristic banding pattern bone tissue formation around the implant.