• Korea-Australia Rheology Journal
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• v.19 no.2
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• pp.51-59
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• 2007

A polyelectrolyte chain confined in a slit nanochannel exhibits a structural transition from the one in free space. In this paper, the effect of the long-range electrostatic interactions between the xanthan polyelectrolyte and the slit wall on the confined xanthan conformation is investigated via the Brownian dynamics simulation. A neutral and two negatively charged surfaces of polydimethylsiloxane (PDMS) and glass are combined to make four kinds of slit channels with different charge characteristics: i) neutral-neutral, ii) glass-glass, iii) neutral-PDMS and iv) neutral-glass walls. Their walls are characterized by uniform surface charge densities determined from experimental data of zeta potential. Both the nonmonotonic chain size variation and the loss of long-range bond vector correlation, previously observed under confinement in the PDMS-PDMS slit, are also found in the neutral slit, demonstrating the nonelectrostatic origin of such crossover behaviors. As expected, the effect of wall charges is negligible at sufficiently high medium ionic strength of 100mM but it becomes significant in the opposite limit of 0.01mM. In the latter case, the high charge density of glass walls strengthens the effective confinement of a negatively charged polyelectrolyte and produces a xanthan structure comparable to that confined in a much narrower neutral slit. The obtained structural data suggest the possibility of controlling the structure of confined polyelectrolytes by the modification of surface charge characteristics of micro/nanofluidic devices in combination with the adjustment of the medium ionic strength.

• Bulletin of the Korean Chemical Society
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• v.7 no.3
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• pp.204-210
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• 1986

It is shown that the linear stability coincides with the thermodynamic stability in the case of stress tensor evolution for simple dense fluids even if the constitutive (evolution) equation for the stress tensor is nolinear. The domain of coincidence can be defined in the space of parameters appearing in the constitutive equation and we find the domain is confined in an elliptical cone in a three-dimensional parameter space. The corresponding state theory in rheology of simple dense fluids is also further examined. The validity of the idea is strengthened by the examination.

• 한국가스학회:학술대회논문집
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• 2000.09a
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• pp.22-26
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• 2000

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.8
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• pp.1310-1315
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• 1999

Air quality in confinement pig houses is important to production and health. Mechanical ventilation and confinement is known to be the most practical tool for maintaining adequate air quality in pig houses through extensive researches since Millier (1950) invented the 'slotted inlet' ventilation system. A variety of mechanical ventilation systems have been applied to confined nursery pig houses in Korea without scientific verification of their ventilation effectiveness. Ventilation systems with three feasible combinations (NA, NB, and NC) of inlets and outlets in a confined nursery pig house were tested to evaluate their ventilation efficiency, of which the one with the performance was supposed to be taken as a standard ventilation system for nursery pig houses in Korea. Field data of air velocity and temperature fields, and ammonia concentration with three ventilation systems were taken and compared to determine the best system. The air velocity and temperature fields predicted by the PHOENICS computer program were also validated against the available experimental data to investigate the feasibility of computer simulation of air and temperature distribution with an acceptable accuracy in a confined house. NC system with duct-induced in-coming air, performed best among the three different ventilation systems, which created higher velocity field and evener distribution ($2.5m/s{\pm}0.3m/s$) over the space with a Reynolds number of $10^4$. The experimental data obtained also fitted well with the simulated values using the modified PHOENICS, which suggested a viable tool for the prediction of air and temperature field with given calculation geometries.

• Journal of the Korean Society of Safety
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• v.33 no.5
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• pp.28-34
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• 2018

Recently, various engineering approaches have been widely used in the accident investigation field to identify the cause of the accident and to predict damage by accident. Computational analysis is the most commonly used method of accident investigation technique. This technique is mainly used to identify the mechanism of the accident generation and to determine the cause when it is difficult to reproduce the situation at the time of the accident or when it is impossible to perform a reproduction experiment. In this study, The computational fluid dynamics analysis for nitrogen asphyxiation accident generated by defect of building structural between diffusion outlet and cooling tower was performed to determine the inflow path of the suffocation gas, death possibility by concentration of suffocation gas and predicted the time of death due to the accident using 3D modeling and FLACS program. We can quantify diffusion concentration of asphyxiation gas and predict mechanism of death occurrence by accident and evaluate the consequence Analysis through this study. In the future, This method can be widely used in the field of gas safety by improving the reliability and validity of the analysis.

• Geomechanics and Engineering
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• v.32 no.2
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• pp.179-191
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• 2023

To study the influences of tunneling on the earth pressure and ground settlement when the tunnel passes through the adjacent underground retaining structure, 30 two-dimensional model tests were carried out taking into account the ratios of tunnel excavation depth (H) to lateral width (w), excavation width (B), and excavation distance using a custom-made test device and an analogical soil. Tunnel crossing adjacent existing retaining structure (TCE) and tunnel crossing adjacent newly-built retaining structure (TCN) were simulated and the earth pressure variations and ground settlement distribution during excavation were analyzed. For TCE condition, the earth pressure increments, maximum ground settlement and the curvature of the ground settlement curve are negatively related to H/B, but positively related to H/s and H/w. For TCN condition, most trends are consistent with TCE except that the earth pressure increments and the curvature of ground settlement curve are negatively related to H/w. The maximum ground settlement is larger than that observed in tunnel crossing the existing underground structure. This study provides an assessment basis for the design and construction under confined space conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.601-604
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• 1999

The objective of this study is to investigate the flexural behavior of reinforced concrete columns confined by lateral ties. This test was carried on the twelve reinforced concrete columns, 200$\times$200$\times$800mm size. objected to flexure and constant axial loads. The main variables are concrete strength, the configuration of lateral ties and the amount of lateral ties. Test results indicated that steel configuration plays an important role in column behavior, and a proper configuration of lateral ties can be more ductile than the reduce of the space of lateral ties. By this experiment, the ductility of high-strength concrete columns designed on A.C.I Code is not adequate, and are concluded that the design of high-strength concrete column is executed by more lateral ties under high axial loads.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.67-67
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• 2003

Filamentous actin (F-actin) is a two stranded long helix that performs structural function in eukaryotic cells. F-actin had been assembled from Alexa-labeled G-actin and had been confined in microchannel. The fluctuation of single filaments was observed by fluorescence optical microscopy. We measured Tangent-tangent Correlation Function G(s) (where s is the distance along the contour of the chain), which tells us the confining wall effect of wormlike semi-flexible polymers as well as the flexural rigidity, such as persistence length.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.305-308
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• 2008

The purpose of this study is to propose the confinement effectiveness of precast segmental concrete that binding by lateral confining steel in the method of precast segmental concrete pridge piers construction. Generally, the confinement effect of concrete that binding by lateral confining steel is defined by the confinement effectiveness coefficient and the confinement effectiveness coefficient is defined as the ratio of area of effectively confined concrete core to area of confined concrete core. The area of effectively confined concrete core is defined by Arching action occurred on a space of lateral confinement steel and The area of confined concrete core is defined by the ratio of area of longitudinal reinforcement to area of core of section. But in case of precast segmental concrete, concrete cover that exist on top and bottom of concrete segment should be considered.

• 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.