• Magazine of the Korean Society of Agricultural Engineers
• /
• v.42 no.2
• /
• pp.71-77
• /
• 2000

A multi-region model for solute transport through saturated soils has been developed to describe preferential flow. The model consists of numerous discrete pore groups, which are characterized by a discrete dispersion coefficient, flow velocity, and porosity . The hydraulic properties for each pore group are derived from a soil's hydraluic conductivity and soil water characteristic functions . Flow in pore group is described by the classical advection-disersion equation (ADE). An implict finite difference scheme was applied to the governing equation that results in a block-tridiagonal system of equations that is very efficient and allows the soil to be divided into any number of pore groups. The numerical technique is derived from methods used to solve coupled equations in fluid dynamics problems and can also be applied to the transport of interacting solutes. The results of the model are compared to the experimental data from published papers. This paper contributes on the characteristics of the method when applied to the parallel porosity model to describe preferential flow of solutes in soil.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.265.2-265.2
• /
• 2013

We fabricate poly(3,4-ethylenedioxythiopene patterns using liquid-bridge-mediated nanotransfer (LB-nTM) printing via vapor phase polymerization (VPP). LB-nTM printing method can simultaneously enable the synthesis, alignment and patterning of the nanowires from molecular ink solutions. Two- or three-dimensional complex structures of VPP-PEDOT were directly fabricated over a large area using many types of molecular inks. VPP method is a versatile technique that can be used to obtain highly conducting coatings of conjugated polymer on both conducting and non-conducting substrates. The PEDOT patterns has analyzed crystallinity from X-ray diffraction pattern and select-area diffraction patterns. In addition, the PEDOT pattern has high conductivity compared other conducting polymers.

• Transactions of Materials Processing
• /
• v.21 no.1
• /
• pp.5-12
• /
• 2012

The weight of the bipolar plate is one of the crucial aspects of improving power density in PEMFC stacks. Aluminum alloys have good mechanical properties such as density, electrical resistivity, and thermal conductivity. Furthermore, using aluminum in a bipolar plate instead of graphite reduces the bipolar plate cost and makes machining easier. Therefore in this study, an aluminum alloy was selected as the appropriate material for a bipolar plate. Results from feasibility experiments with the aim of developing fuel cells consisting of Al bipolar plates with multiple channels are presented. Dynamic loading was applied and the formability of micro channels was estimated as a function of punch pressure and die radius. Sheets of Al5052 with a thickness of 0.3mm were used. For a die radius of 0.1mm the formability was optimized with a sine wave dynamic load of 90kN at maximum pressure and 5 cycles of a sine wave punch travel. The experimental results demonstrate the feasibility of the proposed manufacturing technique for producing bipolar plates.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.4 s.235
• /
• pp.441-452
• /
• 2005

The physical model considered here is a horizontal layer of fluid heated below and cold above with heat-generating conducting body placed at the center of the layer. The dimensionless thermal conductivities of body considered in the present study are 0.01, 1 and 150. The dimensionless temperature difference ratios considered are 0.25, 2.5 and 25. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral methodology for variety of Rayleigh number from $10^{3}\;to\;10^{6}.$ Multi-domain technique is used to handle square- shaped heat-generating conducting body. The results for the case of conducting body with heat generation are also compared to those without heat generation.

• Steel and Composite Structures
• /
• v.34 no.2
• /
• pp.309-319
• /
• 2020

The objective is to study the deformation in a homogeneous isotropic modified couple stress thermoelastic medium with mass diffusion and with two temperatures due to a thermal source and mechanical force. Laplace and Fourier transform techniques are applied to obtain the solutions of the governing equations. The displacements, stress components, conductive temperature, mass concentration and couple stress are obtained in the transformed domain. Numerical inversion technique has been used to obtain the solutions in the physical domain. Isothermal boundary and insulated boundaryconditions are used to investigate the problem. Some special cases of interest are also deduced.

• Journal of Ceramic Processing Research
• /
• v.20 no.4
• /
• pp.388-394
• /
• 2019

In this study, high-purity single-walled carbon nanotubes (SWCNTs) were prepared by removing the unreacted metal constituents and amorphous carbon impurities using a post-annealing process. Unlike conventional thermal processing techniques, this technique involved different gas atmospheres for efficient removal of impurities. A heat treatment was conducted in the presence of chlorine, oxygen, and chlorine + oxygen gases. The nanotubes demonstrated the best characteristics, when the heat treatment was conducted in the presence of a mixture of chlorine and oxygen gases. The scanning electron microscopy, transmission electron microscopy, ultraviolet absorbance, and sheet resistance measurements showed that the heat treatment process efficiently removed the unreacted metal and amorphous carbon impurities from the as-synthesized SWCNTs. The high-purity SWCNTs exhibited improved electrical conductivities. Such high-purity SWCNTs can be used in various carbon composites for improving the sensitivity of gas sensors.

• Geomechanics and Engineering
• /
• v.28 no.4
• /
• pp.347-358
• /
• 2022

The main concern of this article is to discuss the problem of a two-temperature fiber-reinforced micropolar thermoelastic medium with voids under the effect rotation, mechanical force in the context four different theories with memory-dependent derivative (MDD) and variable thermal conductivity. The three-phase-lag model (3PHL), dual-phase-lag model (DPL), Green-Naghdi theory (G-N II, G-N III), coupled theory, and the Lord-Shulman theory (L-S) are employed to solve the present problem. Analytical expressions of the physical quantities are obtained by using Laplace-Fourier transforms technique. Numerical results are shown graphically and the results obtained are analyzed. The most significant points are highlighted.

• International Journal of Computer Science & Network Security
• /
• v.22 no.3
• /
• pp.292-302
• /
• 2022

The radar tomographic imaging is based on the Radar Cross-Section "RCS" of the materials of a shape under examination and investigation. The RCS varies as the conductivity and permittivity of a target, where the target has a different material profile than other background objects in a scene. In this research paper, we use Hierarchical Performance Modeling "HPM" and a framework developed earlier to determine/spot bottleneck(s) for pattern recognition of materials using a combination of the Single Layer Perceptron (SLP) technique and tomographic images in radar systems. HPM provides mathematical equations which create Objective Functions "OFs" to find an average performance metric such as throughput or response time. Herein, response time is used as the performance metric and during the estimation of it, bottlenecks are found with the help of OFs. The obtained results indicate that processing images consumes around 90% of the execution time.

• Journal of the Korean Mathematical Society
• /
• v.61 no.4
• /
• pp.621-657
• /
• 2024

In this study, the numerical solution of a space-fractional Burgers' equation with initial and boundary conditions is considered. This equation is the simplest nonlinear model for diffusive waves in fluid dynamics. It occurs in a variety of physical phenomena, including viscous sound waves, waves in fluid-filled viscous elastic pipes, magneto-hydrodynamic waves in a medium with finite electrical conductivity, and one-dimensional turbulence. The proposed QBS/CNG technique consists of the Galerkin method with a function basis of quadratic B-splines for the spatial discretization of the space-fractional Burgers' equation. This is then followed by the Crank-Nicolson approach for time-stepping. A linearized scheme is fully constructed to reduce computational costs. Stability analysis, error estimates, and convergence rates are studied. Finally, some test problems are used to confirm the theoretical results and the proposed method's effectiveness, with the results displayed in tables, 2D, and 3D graphs.

• Journal of the Microelectronics and Packaging Society
• /
• v.31 no.2
• /
• pp.54-62
• /
• 2024

SICM (Scanning Ion Conductivity Microscopy) is a technique for measuring surface topography in an environment where electrochemical reactions occur, by detecting changes in ion conductivity as a nanopipette tip approaches the sample. This study includes an investigation of the current response curve, known as the approach curve, according to the distance between the tip and the sample. First, a simulation analysis was conducted on the approach curves. Based on the simulation results, then, several measuring experiments were conducted concurrently to analyze the difference between the simulated and measured approach curves. The simulation analysis confirms that the current squeezing effect occurs as the distance between the tip and the sample approaches half the inner radius of the tip. However, through the calculations, the decrease in current density due to the simple reduction in ion channels was found to be much smaller compared to the current squeezing effect measured through actual experiments. This suggests that ion conductivity in nano-scale narrow channels does not simply follow the Nernst-Einstein relationship based on the diffusion coefficients, but also takes into account the fluidic hydrodynamic resistance at the interface created by the tip and the sample. It is expected that SICM can be combined with SECM (Scanning Electrochemical Microscopy) to overcome the limitations of SECM through consecutive measurement of the two techniques, thereby to strengthen the analysis of electrochemical surface reactivity. This could potentially provide groundbreaking help in understanding the local catalytic reactions in electroless plating and the behaviors of organic additives in electroplating for various kinds of patterns used in semiconductor damascene processes and packaging processes.