• Corrosion Science and Technology
• /
• v.14 no.6
• /
• pp.261-266
• /
• 2015

The capacity of passive metal to repassivate after film damage determines the development of local corrosion and the resistance to corrosion failures. In this work, the repassivation kinetics of 316L stainless steel (316L SS) was investigated in borate buffer solution (pH 9.1) using a novel abrading electrode technique. The repassivation kinetics was analyzed in terms of the current density flowing from freshly bare 316L SS surface as measured by a potentiostatic method. During the early phase of decay (t < 2 s), according to the Avrami kinetics-based film growth model, the transient current was separated into anodic dissolution ($i_{diss}$) and film formation ($i_{film}$) components and analyzed individually. The film reformation rate and thickness were compared according to applied potential. Anodic dissolution initially dominated the repassivation for a short time, and the amount of dissolution increased with increasing applied potential in the passive region. Film growth at higher potentials occurred more rapidly compared to at lower potentials. Increasing the applied potential from 0 $V_{SCE}$ to 0.8 $V_{SCE}$ resulted in a thicker passive film (0.12 to 0.52 nm). If the oxide monolayer covered the entire bare surface (${\theta}=1$), the electric field strength through the thin passive film reached $1.6{\times}10^7V/cm$.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.10
• /
• pp.245-251
• /
• 2013

An impedance of ground electrode for information and communication facilities has a significant relationship with the electrical characteristics of soil where the ground electrode is buried. Especially, the impedance of ground electrode is directly affected by the characteristics of permittivity and conductivity in soil as a function of a frequency of an applied electric field. The program based on the electromagnetic field model was developed in MATLAB. Because both permittivity and conductivity can not be modified in commercial programs. The permittivity of soil was applied with the Debye equation which is a model of dielectric relaxation. And the empirical equation of the conductivity in soil was quoted in other paper. In order to confirm the reliability of proposed program, the impedance measurement of ground electrode was carried out, which were compared with the results of simulation in commercial program. In result, it was confirmed that the impedance and phase different simulated by appling the characteristics of permittivity and conductivity in soil are in good agreement with the measured values than results of NEC.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.27 no.1
• /
• pp.47-58
• /
• 1994

Field observation and numerical experiments with a two-dimensional depth-integrated model were undertaken in order to investigate some of the effects on the flow structure resulting from the construction of a bridge connecting Kohung Peninsula and the Narodo Islands on the southern coast of Korea. Tidal currents passing through the straits between the Narodo Islands showed that, although the phase lagged one hour behind that passing through the strait between Kohung Peninsula and Naenarodo Island, it still kept strong flows of more than 80cm/sec near the bottom. The seawater temperature and salinity within the study area seemed to be higher southward but uniform vertically. The results of the drogue experiments in the straits between the Narodo Islands showed that the drogues moved northward of Sayangdo in the early part of the flood tide, but southward in the late part of the flood tide and finally stopped a mile from the east coast of Surakdo. On the other hand, the numerical computation showed that the flow structures after construction of the bridge piers were basically in line with those before construction of the bridge piers, except for the slight variations of velocities in the vicinity of the bridge piers. A large scale clockwise circulation has been confirmed in the south area of Namsungri of Kohung Peninsula from the computational results of tide-induced residual currents. Referring to these computational results, the impact category on the flow structures due to the bridge piers construction has been estimated to be within around 2km. The results were in good agreement with the field observations.

• Nuclear Engineering and Technology
• /
• v.40 no.3
• /
• pp.213-224
• /
• 2008

The pumping of coolant in a liquid metal fast reactor may be performed with an annular linear induction electro-magnetic (EM) pump. Linear induction pumps use a traveling magnetic field wave created by poly-phase currents, and the induced currents and their associated magnetic field generate a Lorentz force, whose effect can be the pumping of the liquid metal. The flow behaviors in the pump are very complex, including a time-varying Lorentz force and pressure pulsation, because an induction EM pump has time-varying magnetic fields and the induced convective currents that originate from the flow of the liquid metal. These phenomena lead to an instability problem in the pump arising from the changes of the generated Lorentz forces along the pump's geometry. Therefore, a magneto-hydro-dynamics (MHD) analysis is required for the design and operation of a linear induction EM pump. We have developed a time-harmonic 2-dimensional axisymmetry MHD analysis method based on the Maxwell equations. This paper describes the analysis and numerical method for obtaining solutions for some MHD parameters in an induction EM pump. Experimental test results obtained from an induction EM pump of CLIP-150 at the STC "Sintez," D.V. Efremov Institute of Electro-physical Apparatus in St. Petersburg were used to validate the method. In addition, we investigated some characteristics of a linear induction EM pump, such as the effect of the convective current and the double supply frequency (DSF) pressure pulsation. This simple model overestimated the convective eddy current generated from the sodium flow in the pump channel; however, it had a similar tendency for the measured data of the pump performance through a comparison with the experimental data. Considering its simplicity, it could be a base model for designing an EM pump and for evaluating the MHD flow in an EM pump.

• Journal of Korean Society on Water Environment
• /
• v.23 no.2
• /
• pp.206-215
• /
• 2007

The objective of this study was to establish the optimal system operating strategies for nitrogen and phosphorus removal through model simulation system built for advanced wastewater treatment targeting on simultaneous temporal/special phase isolation BNR process. The simulation system was built with unit process modules using object modules in GPS-X code. The system was well verified by field experiment data. Simulation study was carried out to investigate performance response to design and operation parameters, i.e. hydraulic retention time (HRT), solids retention time (SRT), and cycle time. The process operated at HRTs of 10~15 hours, longer SRTs, and cycle time of 2 hours showed optimal removal of nitrogen. The HRTs of 10~15 hours, SRTs of 20~25 days, and longer cycle time was optimal for phosphorus removal. Both simulation and field studies showed that optimal operating strategies satisfying both the best nitrogen and phosphorus removals include HRTs ranged 10~15 hours, SRTs ranged 20~25 days, and cycle times of 4~8 hours. The simulation system with modularization of generalized components in BNR processes was, therefore, believed to be a powerful tool for establishing optimal strategies of advanced wastewater treatment.

• Cartoon and Animation Studies
• /
• s.35
• /
• pp.129-153
• /
• 2014

This study is a process of studying an alternative educational model and a preceding analysis process of the study where a teaching method considering the expertise of animation is applied with a perspective of effectively increasing the animation drawing ability. The animation field which is the image contents is a visual art that delivers the story through the movement of the subject, and when looking only at the education related to the drawing, the items required for expertise should be clarified and the development of a systematic curriculum and teaching method is required. Therefore in this study, it aims to review the necessity of education model development by analyzing the educational contents and domestic and foreign curriculums that corresponds to the categorization of motion drawing considered with expertise of animation. As a result, it will be used as a basis for planning the educational model of a subject in the category of motion drawing. This process corresponds to the analysis phase of ADDIE educational model development and in the future, as an attempt for integrated studies, will lead to a study of developing and applying the educational model based on the functions of brain and creative mechanism.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.417-423
• /
• 2007

Oxy-gasification or oxygen-blown gasification, enables a clean and efficient use of coal and opens a promising way to CO2 capture. The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. The purposes of this study are to develop an evaluation technique for design and performance optimization of coal gasifiers using a numerical simulation technique, and to confirm the validity of the model. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization, mixture fraction model and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The influence of turbulence on the gas properties was taken into account by the PDF (Probability Density Function) model. A numerical simulation with the coal gasification model is performed on the Conoco-Philips type gasifier for IGCC plant. Gas temperature distribution and product gas composition are also presented. Numerical computations were performed to assess the effect of variation in oxygen to coal ratio and steam to coal ratio on reactive flow field. The concentration of major products, CO and H2 were calculated with varying oxygen to coal ratio (0.2-1.5) and steam to coal ratio(0.3-0.7). To verify the validity of predictions, predicted values of CO and H2 concentrations at the exit of the gasifier were compared with previous work of the same geometry and operating points. Predictions showed that the CO and H2 concentration increased gradually to its maximum value with increasing oxygen-coal and hydrogen-coal ratio and decreased. When the oxygen-coal ratio was between 0.8 and 1.2, and the steam-coal ratio was between 0.4 and 0.5, high values of CO and H2 were obtained. This study also deals with the comparison of CFD (Computational Flow Dynamics) and STATNJAN results which consider the objective gasifier as chemical equilibrium to know the effect of flow on objective gasifier compared to equilibrium. This study makes objective gasifier divided into a few ranges to study the evolution of the gasification locally. By this method, we can find that there are characteristics in the each scope divided.

• Design & Manufacturing
• /
• v.14 no.2
• /
• pp.1-6
• /
• 2020

Recently, research and commercialization related to the field of cell-based therapeutic drug development has been actively conducted. In order to maintain cell viability and prevent contamination, refrigeration preservation devices, such as CRF (controlled rate freezer) or vapor type LN2 tanks have been developed. On the other hand, the storage container for liquid nitrogen tanks currently on sale minimizes the flow structure to prevent structural defects when stored in a liquid nitrogen tank having a high thermal conductivity than vapor nitrogen. If the cell-based treatment drug is stored in the gaseous LN2 tank as it is, the cell survival after thawing is greatly reduced. It was estimated that the existing storage container structure was a factor that prevented the rapid entry and circulation of gaseous nitrogen into the container. Therefore, this study intends to propose a new supercellular storage container model that can maintain the mechanical strength while maximizing the fluid flow structure. To this end, we estimated that the structural change of the storage container effects on the equivalent stress formed around the through-holes of them when exposed to a cryogenic environment using thermal-structural coupled field analysis. As a result of storage experiments in the gas phase tank of the cell-based therapeutic agent using the developed storage container, it was confirmed that the cell growth rate was improved from 66% to 77%, which satisfied the transportation standards of the FDA(Food and Drug Administration) cell-based therapeutic agent.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.13-13
• /
• 2010

Switching an elementary excitation by injecting a single carrier would offer the exciting opportunity for the ultra-high data storage technologies. However, there has been no methodology available to investigate the interaction of low energy discrete carriers with nano-structures. In order to map out the spatial dependency of such single carrier level interactions, we developed a pulse-and-probe algorithm, combining with low temperature scanning tunneling microscopy. The new tool, which we call single carrier spectroscopy, allows us to track the interaction with the target macrostructure with tunneling carriers on a single carrier basis. Using this tool, we demonstrate that it is possible not only to locally write and erase individual bi-solitons, reliably and reversibly, but also to track of creation yields of single and multiple bi-solitons. Bi-solitons are pairs of solitons that are elementary out-of-phase excitations on anti-ferromagnetically ordered pseudo-spin system of Si dimers on Si(001)-c(42) surfaces. We found that at low energy tunneling the single bisoliton creation mechanism is not correlated with the number of carriers tunneling, but with the production of a potential hole under the tip. An electric field at the surface determines the density of the local charge density under the tip, and band-bending. However a rapid, dynamic change of a field produces a potential hole that can be filled by energetic carriers, and the amount of energy released during filling process is responsible for the creation of bi-solitons. Our model based on the field-induced local hole gives excellent explanation for bi-soliton yield behaviors. Scanning tunneling spectroscopy data supports the existence of such a potential hole. The mechanism also explains the site-dependency of bi-soliton yields, which is highest at the trough, not on the dimer rows. Our study demonstrates that we can manipulate not just single atoms and molecules, but also single pseudo-spin excitations as well.

• Progress in Superconductivity and Cryogenics
• /
• v.15 no.2
• /
• pp.34-38
• /
• 2013

AC Losses for face to face stacks of four identical coated conductors (CCs) were numerically calculated using the H-formulation combined with the E-J power law and the Kim model. The motive sample was the face to face stack of four 2 mm-wide CC tapes with 2 ${\mu}m$ thick superconducting layer of which the critical current density, $J_c$, was $2.16{\times}10^6A/cm^2$ on IBAD-MgO template, which was suggested for the mitigation of ac loss as a round shaped wire by Korea Electrotechnology Research Institute. For the calculation the cross section of the stack was simply modeled as vertically aligned 4 rectangles of superconducting (SC) layers with $E=E_o(J(x,y,t)/J_c(B))^n$ in x-y plane where $E_o$ was $10^{-6}$ V/cm, $J_c$(B) was the field dependence of current density and n was 21. The field dependence of the critical current of the sample measured in four-probe method was employed for $J_c$(B) in the equation. The model was implemented in the finite element method program by commercial software. The ac loss properties for the stacks were compared with those of single 4 cm-wide SC layers with the same critical current density or the same critical current. The constraint for the simulation was imposed in two different ways that the total current of the stack obtained by integrating J(x,y,t) over the cross sections was the same as that of the applied transport current: one is that one fourth of the external current was enforced to flow through each SC. In this case, the ac loss values for the stacks were lower than those of single wide SC layer. This mitigation of the loss is attributed to the reduction of the normal component of the magnetic field near the SC layers due to the strong expulsion of the magnetic field by the enforced transport current. On the contrary, for the other case of no such enforcement, the ac loss values were greater than those of single 4cm-wide SC layer and. In this case, the phase difference of the current flowing through the inner and the outer SC layers of the stack was observed as the transport current was increased, which was a cause of the abrupt increase of ac loss for higher transport current.