• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.909-915
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• 2006

To predict autogenous shrinkage of concrete, unsaturated pore compensation factor could be calculated by experiments of autogenous shrinkage of cement paste on the assumption that the differences between degree of hydration and strain rate of autogenous shrinkage are unsaturated pore formation rate. Applying unsaturated pore compensation factor on modified Pickket model considering contribution factor and non-contribution factor to autogenous shrinkage of concrete, experimental data and existing model were compared. From the results modified Pickket model was verified to present similar tendency between Tazawa model and experimental data, but CEB-FIP model might be corrected because this model uses ultimate autogenous shrinkage underestimated and the same autogenous time function of concrete material properties considering only compressive strength.

• Proceedings of the Membrane Society of Korea Conference
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• 2001.10a
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• pp.39-50
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• 2001

The performance of membranes is governed their pore struture. Pore structures of porous materials can be determined by a number of techniques. However, The novel technique, capillary folw porometry has a number of advantages. In this technique, the sample is brought in contact with a liquid that fills the pores in the membrane spontaneously. Gas under pressure is used to force the liquid from the pores and increase gas flow. Gas flow rate measured as a function of gas pressure in wet and dry samples yield data on the largest pore size, the mean flow pore size, flow distribution and permeability. Pore characteristics of a number of membranes were measured using this technique. This technique did not require the use of any toxic material and the pressure employed was low. Capillary flow porometry is a suitable technique for measurement of the pore structure of many membranes.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.4
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• pp.137-143
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• 2003

The initial condition of $\Delta \sigma_3 \;=\; \Delta u$ is used for analyzing the time dependent behavior of ground. This is based on the concept that the coefficient of pore water B is the unity on the condition of saturation. but some measured consolidation data in the field showed that the pore water pressure was not dissipated as time elapsed but it was maintained constant value or it's dissipation rate was slower than that of the predicted. and so the measured data of pore water pressure was not consistent with that of settlement. In this study, the rheological model for the pore water pressure behavior on undrained condition was induced and compared with the experiment data of the literature. The result showed that the suggested model was consistent well with the result of experiment, but the suggested model could not explain the effect of the decrease of void ratio according to consolidation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.97.1-97.1
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• 2012

Porous ceramics are widely used for applications such as catalysis supports, gas distributors and filters such as DPF. For these purpose, it is important to have proper porosity controlling pore structure while maintaining mechanical and thermal properties. In this work, we have prepared the porous ceramic structures made of reaction bonded silicon nitride with hierarchical pore structures. Uni-directionally aligned pore channels, which are mostly filled with ${\beta}$-Si3N4 whiskers, were achieved by an ice-templating method. The structures of the pore channels and the walls are controllable by the processing conditions, such as solid concentration, freezing rate of the slurry, and additives. We have investigated and characterized the influences of the conditions on the microstructures and the properties, such as porosity, pore size distribution, lamellar thickness, wavelength, and orientations. The compressive strength test and flow test was performed to determine the structural integrity and air permeability.

• Geomechanics and Engineering
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• v.8 no.2
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• pp.187-220
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• 2015

Soil disturbance induced by installation of mandrel driven vertical drains decreases the in situ horizontal hydraulic conductivity of the soil in the vicinity of the drains, decelerating the consolidation rate. According to available literature, several different profiles for the hydraulic conductivity variation with the radial distance from the vertical drain, influencing the excess pore water pressure dissipation rate, have been identified. In addition, it is well known that the visco-plastic properties of the soil also influence the excess pore water pressure dissipation rate and consequently the settlement rate. In this study, a numerical solution adopting an elastic visco-plastic model with nonlinear creep function incorporated in the consolidation equations has been developed to investigate the effects of disturbed zone properties on the time dependent behaviour of soft soil deposits improved with vertical drains and preloading. The employed elastic visco-plastic model is based on the framework of the modified Cam-Clay model capturing soil creep during excess pore water pressure dissipation. Besides, nonlinear variations of creep coefficient with stress and time and permeability variations during the consolidation process are considered. The predicted results have been compared with V$\ddot{a}$sby test fill measurements. According to the results, different variations of the hydraulic conductivity profile in the disturbed zone result in varying excess pore water pressure dissipation rate and consequently varying the effective vertical stresses in the soil profile. Thus, the creep coefficient and the creep strain limit are notably influenced resulting in significant changes in the predicted settlement rate.

• Korea-Australia Rheology Journal
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• v.14 no.2
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• pp.63-70
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• 2002

Chemical mechanical planarization (CMP) is the polishing process enabled by both chemical and mechanical actions. CMP is used in the fabrication process of the integrated circuits to achieve adequate planarity necessary for stringent photolithography depth of focus requirements. And recently copper is preferred in the metallization process because of its low resistivity. We have studied the effects of chemical reaction on the polishing rate and surface planarity in copper CMP by means of numerical simulation solving Navier-Stokes equation and copper diffusion equation. We have performed pore-scale simulation and integrated the results over all the pores underneath the wafer surface to calculate the macroscopic material removal rate. The mechanical abrasion effect was not included in our study and we concentrated our focus on the transport phenomena occurring in a single pore. We have observed the effects of several parameters such as concentration of chemical additives, relative velocity of the wafer, slurry film thickness or ash)tract ratio of the pore on the copper removal rate and the surface planarity. We observed that when the chemical reaction was rate-limiting step, the results of simulation matched well with the experimental data.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.750-754
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• 2008

The artificial aggregates with dense surface layer (shell) was fabricated and the dependence of water emission rate upon the shell structures was studied. The EAF dust containing many flux components and waste white clay with ignition loss of above 48% were used as for liquid phase and gas forming agents during a sintering process respectively. In addition, the shell structure was modified with various processes and the modification effect on water emission rate was analyzed. The pores under $10{\mu}m$ were found in the sintered artificial light aggregates and disappeared by incorporating to a bigger pore during re-sintering. The water emission rate in an initial step depended on a void content of aggregates filled in a bottle rather than a shell structure. But, after 7 days where the water emission of the aggregate with a shell is above 40%, the shell of aggregates suppressed the water emission. The core of aggregates was exposed and most shell was lost when crushed to smaller size so, the ability for suppressing water emission of the crushed aggregates decreased. The activation energy for the water emission was $3.46{\pm}0.25{\times}10^{-1}$J/mol for the most specimens showing that the activation energy is irrelevant to the pore size distribution and shell structure.

• Science of Emotion and Sensibility
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• v.17 no.4
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• pp.71-78
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• 2014

Composite draw textured yarns(DTY) and air jet textured yarns(ATY) with hollow PET filament have been used for making high emotional fabrics including light weight sports wear garments. This study investigated effect of hollow composite yarns and fabric structural parameters to the comfort properties related to the moisture and thermal transport phenomena for the composite fabrics made of DTY and ATY with hollow PET filament. Wicking property of hollow composite fabric was superior at the high pore size fabric and was not influenced by fabric cover factor. Wicking property of the fabric with ATY was better than that of the fabric with DTY. On the other hand, drying rate of fine pore sized fabric was shorter than that of large pore sized fabric and drying rate of high multi yarn fabric with low cover factor and small pore size was superior than that of hollow composite fabric. The pore size of the fabric was dominant factor in the air permeability and thermal conductivity of hollow composite fabric. High pore sized fabric showed high air permeability and thermal conductivity of hollow composite fabric was nonlinearly inversely proportional to pore size of the fabric.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.557-563
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• 2022

In order to measure the allergen penetration of micropore fabrics, it is necessary to develop a convenient and appropriate experimental method for measuring a pore size of micropore fabrics. In this study, a simple and economical experimental apparatus was developed for the analysis of the pore size of micropore fabrics by measuring the weight reduction rate. In addition, the allergen blocking properties was evaluated by measuring the pore sizes of various fabrics. According to this study, the size of the pores of the microporous fabric could be obtained by measuring the weight reduction rates. In addition, higher weight reduction rate was obtained as the suction pressure passing through the particle permeation device decreased and the suction time was increased. It is expected that the developed experimental method and apparatus can be utilized as an experimental standard for quality control methods to verify the effectiveness of micropore fabrics used for house dust mite blocking bedding.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.77-84
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• 2007

One of the most sensitive design specifications to be considered is infiltration and external pore-water pressures on underground structure construction. Development of pore-water pressure may accelerate leakage and consequently cause deterioration of the lining. In this paper, the development of pore-water pressure due to malfunctioning of drainage system and its potential effect on the linings are investigated using physical model tests. The deterioration procedure was simulated by controlling both permeability and flow rate. Development of pore-water pressure was monitored on the lining using pore pressure measurement cells. Test results identified the mechanism of pore-water pressure development on the tunnel lining. In addition, they showed that controlling flow rate is more effective method fur simulating deterioration procedure than permeability control. The laboratory model tests were reproduced using coupled numerical method, and showed that the effect of deterioration of drainage system can be theoretically expected using coupled numerical modeling method.