• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.3
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• pp.100-107
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• 1984

농축산 배설물을 호기성 환기처리하여 토양에 환원이용을 목적으로 컴포스트(Compost)화 할 때에 공극률(Pore space)에 미치는 물리적인 자 성설의 상화관계를 공명하고져 실험을 수행하였다. 본 연구는 여러가지 수준의 압축력에 따른 첨가 재료의 공극률 변화 과정 측정하고 이와 동시에 서로 다른 5종류의 재료별 입자 크기에 대하여 영수률, 용적 중량, 용적 밀도 및 입자 대소가 공극률에 미치는 영향을 조사분석 하였으며 그 결과는 아래와 같다. 1. 세립자 재료의 용적 밀도는 세립자보다 더욱 크게 나타났다. 2. 염수률과 용적 중량이 증가하면 용적밀도는 커지나 공극률은 감소하였다. 3. 공극률은 영수률과 용적 중량보다 첨가재료의 입자크기와 대소분포에 더욱 커다란 영향을 받고 있었다. 4. 영수률이 55~65%이고, 용적중량이 0.25~0.38g/cm2이며 입자크기가 1.5~5cm인 범위내의 효율적인 콤포스트화에 있어서 공극률은 65~80%의 범위를 형성하고 있음을 알 수 있다.

• The Journal of Engineering Geology
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• v.14 no.2
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• pp.169-177
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• 2004

The permeation movements of groundwater recharge and contaminate materials receive a eat effect due to porosity and effective porosity of porous media which is composing underground consisted of saturation and unsaturated states. This study developed Frequency Domain Reflectometry(FDR) system and measurement sensor, and then carried out the laboratory experiments to measure effective porosity for unsaturated porous media. Also, I suggested dielectric mixing models(DMMs) which can calculate the effective porosity from relation of measured dielectric constants. In the experimental results the extent range of effective porosity of standard sand and river sand which are unsaturated soil sample were measured in about 65∼85 % for porosity. In relation of effective porosity and porosity, especially, effective porosity confirmed that displays decreasing a little tendency as porosity increases. This is because unsaturated soil did not reach in saturation enough by air of very small amount that exist in pore between soil particles.

• Journal of the Korean earth science society
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• v.38 no.2
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• pp.150-160
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• 2017

In order to determine the porosity of rock, the 'standard test method for porosity and density of rock' proposed by the Korean Society for Rock Mechanics is commonly used. However, the standard test method, which uses a drying oven, takes 8 to 24 hours to complete the test in taking samples out of the oven every four hours and measuring the weight of the specimen. To complement these disadvantages, we devised a method for measuring rock porosity by using a microwave oven. The devised method reduced the cause of errors and the inconvenience occurred in the process of weighing samples by constructing a weight monitoring system, which monitors the drying process. A suitable heating/pause time was set up to maintain the temperature of sample below $105{\pm}3^{\circ}C$ in drying process, and an alarm system was implemented in order to stop drying process when the weight change of the rock sample is within 0.1% of the initial weight. The porosity was determined from the dry weight of the sample, which was obtained by the curve fitting of weight monitoring data. Then, the porosities obtained by using the microwave oven were compared with those obtained by the standard test method. Test results using sandstone samples showed that the porosities obtained by a microwave oven was similar to those obtained by the standard method and the porosity difference between two methods was as large as 0.4%. In addition, repeated porosity measurement using the same specimen showed that the standard deviation of the porosity, which reflects the precision of the measurement was as good as 0.23%. Therefore, a microwave oven porosity measurement system can give the porosity of rock samples with high reliability.

• The Journal of Engineering Geology
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• v.13 no.4
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• pp.419-428
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• 2003

In order to evaluate groundwater movement and the infiltration of contaminants, such as petroleum products, the determination of porosity and effective porosity is very important. Porosity and effective porosity are important physical parameters that determine the transfer and movement of water and solutes in porous media. Various methods of determining these parameters have been developed, with varying degrees of accuracy and applicability. Most of the existing methods produce static results. They do not produce instantaneous and real time of porosity and effective porosity in a porous media. In this study, we used a new permittivity method called Frequency Domain Reflectometry with Vector analyzer (FDR-V) to determine the porosity and effective porosity of some sand samples in the laboratory. The advantage of the FDR-V method is that it instantaneously determines the temporal variation of dielectric constants of porous media. Then, the porosity and the effective porosity of porous media are computed using well established empirical equations. Results obtained from the FDR-V method compared favorably with results from other permittivity methods such as gravimetric, injection and replacement tests. The ratio of effective porosity to porosity was 85 - 92 %, when FDR-V was used. This value compared favourably with 90 %, which has been usually quoted in previous studies. Considering the convenience and its applicability, the EDR-V permittivity holds a great potential in porous media and contaminant transport studies.

• Journal of the Geological Society of Korea
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• v.54 no.6
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• pp.631-640
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• 2018

To understand the formation and evolution of a sedimentary basin in basin analysis and modelling studies, it is important to analyze the thickness and age range of sedimentary layers infilling a basin. Because the compaction effect reduces the thickness of sedimentary layers during burial, basin modelling studies typically restore the reduced thickness using the relation of porosity and depth (compaction trend). Based on the compilation plots of published compaction trends of representative sedimentary rocks (sandstone, shale and carbonate), this study estimates the compaction trend ranges with exponential curves and equations. Numerical analysis of sedimentary compaction is performed to evaluate the variation of porosity and layer thickness with depth at key curves within the compaction trend ranges. In sandstone, initial porosity lies in a narrow range and decreases steadily with increasing depth, which results in relatively constant thickness variations. For shale, the porosity variation shows two phases which are fast reduction until ~2,000 m in depth and slow reduction at deeper burial, which corresponds to the thickness variation pattern of shale layers. Carbonate compaction is characterized by widely distributed porosity values, which results in highly varying layer thickness with depth. This numerical compaction analysis presents quantitatively the characteristics of porosity and layer thickness variation of each lithology, which influence on layer thickness reconstruction, subsidence and thermal effect analyses to understand the basin formation and evolution. This work demonstrates that the compaction trend is an important factor in basin modelling and underlines the need for appropriate application of porosity data to produce accurate analysis outcomes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.124-133
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• 2012

Compressive strength in concrete increases with time. Regression analysis with time is conventionally performed for strength evaluation and prediction. In this study, hydrate amount is assumed as a function of hydration rate and porosity, and modeling on compressive strength is carried out considering decreasing porosity with time, which does not need the regression analysis with time. For twenty one mix proportions of HPC (High Performance Concrete), DUCOM (FE program) which can simulate the behavior in early aged concrete is utilized, and porosity from each mix proportions is obtained with time. For HPC with OPC (Ordinary Portland Cement) concrete, modeling on compressive strength is performed considering hydration rate, unit content of cement, and porosity with time. For HPC with mineral admixtures, a long-term parameter which can handle long-term strength development is additionally considered. From the comparison with the previous test results, the applicability of the proposed model is verified.

• International Journal of Highway Engineering
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• v.11 no.1
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• pp.95-104
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• 2009

This study was conducted to evaluate the relationship between the dielectric constant and air void of asphalt concrete. Standard specimens that have air voids of various range $(0%{\sim}20%)$ were used to measure the dielectric constant using parallel plate method that measures low frequency dielectric constant. From the tests, dielectric constant of asphalt concrete was tend to decrease as the frequency was increased, and the decrement slope was varied with the types of asphalt binders. Dielectric constant was decreased linearly as air void was increased from zero to twenty percent. Consequently, the effect of temperature and moisture content on dielectric constants of asphalt concrete was evaluated to develop the standard curve between dielectric constant and air void of asphalt concrete. The standard curve developed in this study can be used to calibrate or develop the algorithm of non-destructive density gauge.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.541-548
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• 2004

This study peformed an evaluation of the physical and mechanical properties and sound absorption characteristics of porous concrete according to the target void ratio and content of the recycled aggregate in order to reduce the noise generated in roads, railroads, residential areas and downtown areas and effectively utilize the recycled waste concrete aggregate generated as a byproduct of construction. The test results demonstrated that the difference between the target void ratio and the actual measured void ratio was less than 1.7% and that the tendency of the compression strength was to reduce rapidly when the target void ratio and the content of the recycled aggregate exceeded 25% and 50%, respectively. In addition, the sound absorption characteristics of the porous concrete using recycled waste concrete aggregate showed that the NRC was the highest at the target void ratio of 25% and the content of the recycled aggregate had very little influence on the NRC. Therefore, when considering the compression strength and the sound absorption characteristics of porous concrete, the proper target void ratio and the content of the recycled waste concrete aggregate are thought to be 25% and 50%, respectively

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.597-604
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• 2004

This work involves quantitatively investigating the correlation between reductions in strength and variations in pore structure under high temperature that can be utilized as estimation for predicting the inner temperature of member damaged by fire. The experimental results were remarkedly affected by micro-filling effect of silica fume and the different water-binder ratios. The increase of the exposure temperature caused the increase of porosity, which resulted from the reason that evaporable water in gel pore or capillary pores as well as chemically bound water was eliminated from hardened cement paste due to the dehydration of C-S-H and $Ca(OH)_2$. Thermal shrinkage of hardened cement paste gives rise to micro-crack, which cause the increase of porosity. Based on the experimental result that the increase of porosity is in charge of exposure temperature, how porosity is distributed can predict temperature-time history and assess the performance of concrete damaged by fire.

• Journal of the Korea Concrete Institute
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• v.28 no.6
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• pp.703-711
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• 2016

The present study is mainly aimed at securing adequate pores which are applicable to the aquatic environment and satisfying the required strength of porous concrete as a structure by substituting pumice for crushed stone which is usually used for the fabrication of porous concrete. Accordingly, in order to deduce the optimum mixing conditions applicable to the aquatic environment, we sought to evaluate the porosity, coefficient of permeability and compressive strength of porous concrete based on the target porosity and the mixing factors for pumice. By examining the porosity and coefficient of permeability of porous concrete and the physical properties of its compressive strength based on the target porosity and the mixing factors for pumice, it is judged that the optimum mixtures for porous concrete applicable to the aquatic environment which satisfy both the necessity of securing adequate pores and the required strength for porous concrete as a structure are PC I I-10-0, PC I I-10-5 and PC I I-10-10.