• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.327-332
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• 2000

The objective of this study was to improve the defects of lightweight cement concrete by treating with redispersible polymer powders. The statistical relationships of water-cement ratios, contents of lightweight aggregates and polymer powers and be used for predicting the concrete strength. It was found that the varieties and techniques adopted in this experiment were capable of identifying the influence of various tested for air contents, flow test, water absorption, specific gravity, flexural and compressive strength. This study showed that fundamental properties were very affected by cement- lightweight aggregate ratio, polymer-cement ratio and water-cement ratio.

• Korea-Australia Rheology Journal
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• v.13 no.1
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• pp.19-27
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• 2001

In this symposium paper, the migration and hydrodynamic diffusion of non-colloidal, spherical particles suspended in polymer solutions are considered under Poiseuille or torsional flows. The migration phenomena in polymer solutions are compared with those in Newtonian fluids and the effect of fluid elasticity is discussed. The experimental results on particle migration in dilute polymer solution reveal that even a slight change in the rheological property of the dispersing medium can induce drastic differences in flow behavior and migration of particles, especially in dilute and semi-concentrated suspensions.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.575-580
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• 2010

In this work, the electrophoretic motion of dsDNA molecule represented by a polymer through an artificial nano-pore in a membrane is simulated using the numerical method combining the lattice Boltzmann and Langevin molecular dynamic method. The polymer motion is represented by Langevin molecular dynamics technique while the fluid flow is taken into account by fluctuating lattice-Boltzmann method. The hydrodynamic interactions between the polymer and solvent in a confined space with a membrane having a hole are considered explicitly through the frictional and the random forces. The electric field intensity over the space is obtained from a finite difference method. Initially, the polymer is placed at one side of the space, and an electric field is applied to drive the polymer to the other side of the space through the nano-pore. In future, we plan to study the effect of the polymer size and the electric field on the electrophoretic velocity.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.11
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• pp.37-43
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• 2018

According to the evaluation of basic properties and mechanical characteristics of polymer cement mortars that contain re-dispersible type polymer, in the case of fresh mortars, flow and air content were increased due to the dispersion action of entrained air and surfactant with an increase of polymer addition ratio. In the case of mortars after hardening, flexural strength, bonding strength, absorption rate and carbonation resistance were improved due to the increased union and waterproof characteristics of internal structures as a result of the formation of polymer film.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.113-116
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• 2005

In this paper, a computational and experimental analysis about the flow behavior of thin polymer film in the spin coating process for stable cover layer coating of a blu-ray disc is described. The blu-ray disc, a next-generation optical disc format over 25GB, consists of a 1.1mm thick substrate and a 0.1mm tick cover layer. Generally, cover layer on the blu-ray disc is made by the polymer spin coating process. However, it is hard to secure sufficient coating uniformity around the rim on the cover layer. In order to get the uniform thickness deviation and to minimize the bead around the rim, the edge of the disc substrate can be modified into various shapes around the rim on the disc and analyzed with various parameters, such as surface tension, viscosity, and rotation speed, etc. The optimal shape of the rim was tried to get by 3 dimensional computer simulation of the polymer expulsion process.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.4
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• pp.78-83
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• 1998

A small size cartrideg for FET type electrolyte sensor is designed and faricated with much simplified process by using micromachining tenchiques such as silicon etching andglass bonding. Size of the whole cartideg is 2.4cm*2.5cm, and the dead volume of a micro flow-channel in the cartrideg is only 8.5.mu.l. The photosensitive polymer(THB 30) is used to define a micropool and to encapsulate the sensor surface for standardizationof electrolyte sensors. To miniaturize micro flow-channel conventional reference electrode(Ag/AgCl) a differential amplification is introduced using REFET and quasi reference electrode. Refet was fabricated using photosensitive polymer(OMR 83). The fabricated cartridge with built-in pH-ISFET showed good operational characteristics such as linearity and high sensitivity (55.4mV/pH) in a wide pH range(pH2-pH12).

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.192-197
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• 1998

Abrasive flow machining is useful to abrasive polish a internal or external surface of the free shape dimensional parts, which are used in many fields such as machine tool parts, semi-conductor, and medical component industries. The machining process is that two hydraulic cylinders, which are located surface to surface, are enforce media to the passage between workpiece and tooling part alternately, and then the abrasives included in the media pass the passage and polish the surface of workpiece. The media which is made of polymer and abrasive plays complex have workpiece by its viscoelastic characteristics. In this study, the media for AMF was made by mixing viscoelastic polymer with alumina and silicon carbide abrasive respectively. As a result, alumina include media is also the experiments of deburring the inside burr of in order to analyse the deburring machinability of abrasive flow machining according to various machining parameters which were media flow rate extrusion pressure, passage gap, media viscosity, abrasive content, and abrasive grain size.

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.875-881
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• 2000

We study the rheological properties of concentrated polymer solution and the melt under simple shear and elon-gational flow using Brownian dynamicssimulation. In order to describe the anisotropic molecular motion, we modifiedthe Giesekus' mobility tensor by incorporating the finitely extensible non-linear elastic (FENE) spring force into dumbbell model. To elucidate the nature of this model, our simulation results are compared with the data of FENE-P ("P"standsfor the Perterin) dumbbell model and experiments. While in steady state both original FENE and FENE-P models exhibit a similar viscosity response,the growthof viscosity becomes dissimilar as the anisotropy decreases and the flowrate increases. The steady state viscosity obtained from the simulation well describes the experiments including the shear-thinning behavior in shear flow and viscosity-thinning behavior in elongational flow. But the growth of viscosity oforiginal FENE dumbbell model cannot describe the experimental results in both flow fields.

• Journal of the Korea Safety Management & Science
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• v.20 no.4
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• pp.7-13
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• 2018

This study investigates the enhancement of the oxygen diffusion rate in the cathode channel of a proton exchange membrane fuel cell (PEMFC) by pure oscillating flow, which is the same as the mechanism of human breathe. Three-dimensional numerical simulation, which has the full model of the fuel cell including electrochemical reaction, ion and electronic conduction, mass transfer and thermal variation and so on, is performed to show the phenomena in the channel at the case of a steady state. This model could analysis the oscillating flow as a moving mesh calculation coupled with electrochemical reaction on the catalyst layer, however, it needs a lot of calculation time for each case. The two dimensional numerical simulation has carried on for the study of oscillating flow effect in the cathode channel of PEMFC in order to reduce the calculation time. This study shows the diffusion rate of the oxygen increased and the emission rate of the water vapor increased in the channel by oscillating flow without any forced flow.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.19-20
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• 2018

For this study, a test was conducted on the basic polymer property depending on the replacement amount of polymer. The result showed that the flow of slump was increased with the increase of polymer replacement amount and an amount of air entraining. In addition, with a decrease of unit W/B, an amount of bleeding was reduced, and the first and final time for 6% replacement amount was found to be the fastest. This implies that replacement of more than 6% may affect the hydration of cement.