• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.3
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• pp.59-67
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• 1984

This study was carried out to find physical and mechanical properties of soil in Yongsan project area to support basic data for tidalland reclamation. The main results are as follows. 1. Most of the soils in this area consist of clay and silt, and inorganic materials. 2. Natural moisture contents are ranged from 42.2% to 92.9% initial void ratio, from 1.4 to 2.3 Therefore it takes a longtime in Settlement of considerable depth. 3. Wet unit weights decrease with increasing of the nataral moistare contents as rt=2. 005-0. 0065wn.4. The relationships between compression index. and liquid limit, initial void ratio and natural moisture contents are found as follows respectively. Cc =0. 046+0. O12LL Cc=-0. 068+0.367eo Cc =0. 056+0. OO8Wn 5. Natural moisture content, plastic limit, plastic index, initial void ratio and liquid :limit are directly proportional to clay content ratio. The relationships are found as Wn=26. 083+0. 797Cy PL=14. 223+0. 128Cy P1=0. 457+0. 492Cy eo=0. 757+0. O2Ocy LL=14. 695+0. 620Cy. 6. Initial void ratio and liquid limit are directly proportional to natural moisture con-tent as follows. eo=0. 310+0.022wn LL=6. 275+0.592wn

• The International Journal of Costume Culture
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• v.5 no.2
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• pp.53-65
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• 2002

Morphology of polyester fiber was physically modified by solvent treatment. PET fiber was treated with N,N-dimethylformamide (DMF) at 100, 120, $140^{circ}C$ for 10 minutes without tension. The structural changes in the morphology of DMF-induced modified PET fiber were FTIR and SEM analysis. Also dyeing behavior of DMF-treated polyester fibers with various disperse dyes was studied to detect changes of amorphous area in fine structure. DMF treatment resulted in increases in total void content, degree of crystallinity, trans isomer content, chain folding, segmental mobility and molecular packing, but it resulted in decreases in amorphous orientation, intermolecular forces and individual void size through longitudinal shrinkage, lateral welling and removal of oligomers. Void-size distribution could be estimated from the dye uptake with various sizes of disperse dyes. In contrast to the large increases in dye uptake with small dye molecules, there is no and little dye uptake with the bulkiest dye, which means that void size is bigger or smaller than the volume of each dye. Diffusion rates of dye molecules showed increases. This dyeing study revealed that the disperse dyeing is very effective method for characterizing the internal morphology of polyester fiber.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.789-792
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• 2004

This study aims to detect only voids and estimate the cross-sectional size and thickness of voids using radar. A new method based on radar image processing is carried out with various void sizes and depths. The regression relationship between void size which has different depth and the amplitude characteristics of the radar return is considered in a new method of this research. For the purpose of examining; this regression relationship, experiments with change of void depth, surface area and thickness were carried out. Finally, the threshold value for image processing which aims to represent only voids to be fitted size (width) can be obtained. As the results, a proposed method in this study has a possibility of detecting only voids and estimating void size and thickness with good accuracy.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6A
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• pp.449-456
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• 2011

Spacing factor proposed by Power is a concept of averaging air void spacing composed of geometric models. Thus, there's a limitation on simulating actual air void characteristics in concrete. This study presents SDI(spacing distribution index) to overcome the limitation of spacing factor. SDI is also evaluated through comparing SDI with SF(spacing factor). In this study, it was confirmed that SF decreased due to increasing air-entrainer content but SDI increased. This occurs because SDI is the area of spacing distribution curve and SDI increases with increasing the frequency of spacing. SDI is evaluated to have better coverage below $300{\mu}m$ of SF so that determination of critical point of SDI above 80% of durability index can be easily obtained with more reliability. SDI is the area of spacing distribution curve and reflects actual air void characteristics in concrete. A comparative study of SDI and results of freeze-thaw test will be performed later.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2626-2631
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• 2007

Air-water two phase natural circulation flow in the T-HERMES (Thermo-Hydraulic Evaluation of Reactor cooling Mechanism by External Self-induced flow)-1D experiment has been evaluated to verify and evaluate the experimental results by using the RELAP5/MOD3 computer code. The RELAP5 results have shown that an increase in the coolant inlet area leads to an increase in the water circulation mass flow rate. However, the water outlet area does not effective on the water circulation mass flow rate. As the coolant outlet moves to a lower position, the water circulation mass flow rate decreases. The water level is not effective on the water circulation mass flow rate. As the height increases in the air injection part, the void fraction increases. However, the void fraction in the upper part of the air injector maintains a constant value. An increase in the air injection mass flow rate leads to an increase in the local void fraction, but it is not effective on the local pressure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1398-1406
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• 2004

The nonlinear signals from an impedance meter for the area average void fraction in two-phase flow have been analyzed to construct a phase space trajectory. The pseudo phase space was constructed with the time delay and proper dimensions. The time delay and the embedding dimension were chosen by the average mutual information and by the false nearest neighborhood, respectively. The attractor-density-map of projected states was used to produce the two dimensional probability distribution functions (2D-PDF). Since the developed 2D-PDF showed clear distinction of the flow patterns, the flow regime identification was made with three rules and with the 2D-PDF. Also, the transition criteria of Mishima-Ishii agree well with the present results.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.568-571
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• 2004

This research estimated the physical. mechanical characteristic and the character of sound absorption according to target void ratio of porous concrete and the mixing ratio of recycled aggregate for the valid utilization of recycled aggregate using waste concrete and sound reduction out of a road, a railway, a residential street, and a downtown area. As a result of the test, compressive strength tended to be a radical strength fall when target void ratio was $25\%$ and contents of recycled aggregate exceeded over $50\%$. Also, the character of sound absorption of porous concrete which used recycled aggregate using waste concrete was the most excellent when target void ratio was $25\%$, and the influence by contents of recycled aggregate was trivial. Therefore, when the strength and the character of sound absorption of porous concrete are considered, it is proved valid that proper target void ratio was $25\%$ and contents of recycled aggregate using waste concrete was $50\%$ or so.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.577-583
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• 2010

In this study, the effect of void formation resulting from gas hydrate dissociation or loss of some particles within soil structure on the strength of soil is examined. Beag-ma river sands with uniform gradation were used to simulate a gas hydrate bearing or washable soil structure. Empty capsules for medicine are used to mimic large voids, which are bigger than soil particle. Beag-ma river sand was miced with 8% cement ratio and 14% water content and compacted into a shear box. The number and direction embedded into a specimen. After 4 hours curing, a series of direct shear test is performed on the capsule embedded cemented sands. Shear strength of cemented sands with capsules depends on the volume and direction. The volume and direction formed by voids are most important factors in strength. A shear strength of a specimen with large voids decreases up to 39% of a specimen without void. The results of this study can be used to predict the strength degradation of gas hydrate bearing sediments after dissociation and loss of fine particles within soil structure.

• Journal of the Korean Society of Safety
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• v.28 no.1
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• pp.52-56
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• 2013

The purpose of this study is to evaluate the influence of form-oil on steam-cured concrete surface condition. Based, viscosity(high, medium, low) and flash point($26^{\circ}C$, $70^{\circ}C$) of form oil were considered as test variables. The digital image process method was applied for the extraction of air-void area from concrete surface. Test result showed that oil-based form oil reduced air-void by approximately 46% compared to water-based form oil, and the higher the viscosity was, the smaller air-void rate was. In addition, it was conformed that flash point of form oil had a considerable influence on the surface condition of steam-cured concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.649-652
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• 2006

This paper describe the performance of seawater purification, to which living organisms can adapt, and the physical properties of porous concrete with continuous void. Although conventional concrete has been regarded as a destroyer of nature, seawater and air can pass freely through concrete when it is made porous by forming continuous void. This not only enables plants to vegetables, but also makes it possible for microscopic animals and plants, including bacteria, to attach to and inhabit uneven surface as well as internal voids when the concrete is provided in a natural seawater area or seawater side area. As a result, porous concrete using recycled aggregate improved the performance of seawater purification. In this study, The performance of seawater purification of porous concrete using recycled aggregate analyzed by T-P, T-N.