• Environmental Engineering Research
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• v.19 no.2
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• pp.123-130
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• 2014

Percolation is the important process of extracting the soluble constituents of a fine mesh, porous substance by passage of a liquid through it. In this study, bio-wastes were percolated under various conditions through continuous percolation processes, and the energy potential of percolate was evaluated. The representative bio-wastes from the K composting plant in Darmstadt, Germany were used as the sample for percolation. The central objective of this study was to determine the optimal amount of process water and the optimum duration of percolation through the bio-wastes. For economic reasons, the retention time of the percolation medium should be as long as necessary and as short as possible. For the percolation of the bio-wastes, the optimal percolation time was 2 hr and maximum percolation time was 4 hr. After 2 hr, more than two-thirds of the organic substances from the input material were percolated. In the first percolation process, the highest yields of organic substance were achieved. The best percolation of the bio-wastes was achieved when the process water of 2 L for the first percolation procedure and then the process water of 1.5 L for each further percolation procedure for a total 8 L for all five procedures were used on 1,000 g fresh bio-waste. The gas formation potentials of 0.83 and $0.96Nm^3/ton$ fresh matter (FM) were obtained based on the percolate from 1 hr percolation of 1,000 g bio-waste with the process water of 2 L according to the measurement of the gas formation in 21 days (GB21). This method can potentially contribute to reducing fossil fuel consumption and thus combating climate change.

• Journal of the Korean Electrochemical Society
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• v.7 no.3
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• pp.155-162
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• 2004

This article covers the fundamentals of percolation phenomenon giving emphasis to the percolation concept involved in disordered electrochemical systems. After a brief discourse on the basic concepts of percolation theory, the geometrical properties and fractality of percolation clusters were presented. Then, anomalous behaviours of diffusion in percolation clusters were explained in terms of the fractal structures of the infinite percolation clusters. Finally, the conductivity-related properties of composite ionic materials were shortly discussed on the basis of percolation theory from practical points of view.

• Computers and Concrete
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• v.22 no.6
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• pp.551-561
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• 2018

The percolation of interfacial transition zone (ITZ) in cementitious materials is of great importance to the transport properties and durability issues. This paper presents numerical simulation research on the ITZ percolation threshold of mortar specimens at meso-scale. To simulate the meso-scale model of mortar as realistically as possible, the aggregates are simplified as ellipsoids with arbitrary orientations. Major and minor aspect ratios are defined to represent the global shape characteristics of aggregates. Some algorithms such as the burning algorithm, Dijkstra's algorithm and Connected-Component Labeling (CCL) algorithm are adopted for identification of connected ITZ clusters and percolation detection. The effects of gradation and aspect ratios of aggregates on ITZ percolation threshold are quantitatively studied. The results show that (1) the ITZ percolation threshold is mainly affected by the specific surface area (SSA) of aggregates and shows a global decreasing tendency with an increasing SSA; (2) elongated ellipsoidal particles can effectively bridge isolated ITZ clusters and thus lower the ITZ percolation threshold; (3) as ITZ volume fraction increases, the bridging effect of elongated particles will be less significant, and has only a minor effect on ITZ percolation threshold; (4) it is the ITZ connectivity that is essentially responsible for ITZ percolation threshold, while other factors such as SSA and ITZ volume fraction are only the superficial reasons.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.6
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• pp.713-721
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• 1999

A composite plastic, where long metallic fibers are used as filling materials, is transformed from nonconducting to conducting medium as the volume fraction of filling metallic fibers is increased from zero : such drastic change in property is called the percolation. It is desired both for practical and theoretical purposes to understand the physics underlying the percolation and to estimate the percolation threshold that is defined by the minimum volume fraction of the metallic fibers for which the percolation occurs. In this study, percolation thresholds are calculated by Monte Carlo Computer simulation. Both lattice and continuum spaces are considered and detailed microstructures of metallic fibers are modelled as rigid and flexible bodies for both model spaces. Simulations are carried out for wide range of aspect ratios and discussions are given.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.271-277
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• 2010

In this paper two aspects of the percolation and conductivity of carbon black-filled polyethylene matrix composites will be discussed. Firstly, the percolation behavior, the critical exponent of conductivity of these composites, are discussed based on studying the whole change of resistivity, the relationship between frequency and relative permittivity or ac conductivity. There are two transitions of resistivity for carbon black filling. Below the first transition, resistivity shows an ohmic behavior and its value is almost the same as that of the matrix. Between the first and second transition, the change in resistivity is very sharp, and a non-ohmic electric field dependence of current has been observed. Secondly, the electrical conduction property of the carbon black-filled polyethylene matrix composites below the percolation threshold is discussed with the hopping conduction model. This study investigates the electrical conduction property of the composites below the percolation threshold based on the frequency dependence of conductivity in the range of 20 Hz to 1 MHz. There are two components for the observed ac loss current. One is independent of frequency that becomes prevalent in low frequencies just below the percolation threshold and under a high electrical field. The other is proportional to the frequency of the applied ac voltage in high frequencies and its origin is not clear. These results support the conclusion that the electrical conduction mechanism below the percolation threshold is tunneling.

• Korean Journal of Materials Research
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• v.19 no.12
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• pp.644-648
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• 2009

Temperature dependency of resistivity of the carbon black-polyethylene composites below and above percolation threshold is studied based on the electrical conduction mechanism. Temperature coefficient of resistance of the composites below percolation threshold changed from minus to plus, increasing volume fraction of carbon black; this trend decreased with increasing volume fraction of carbon black. The temperature dependence of resistivity of the composites below percolation threshold can be explained with a tunneling conduction model by incorporating the effect of thermal expansion of the composites into a tunneling gap. Temperature coefficient of resistance of the composites above percolation threshold was positive and its absolute value increased with increasing volume fraction of carbon black. By assuming that the electrical conduction through percolating paths is a thermally activated process and by incorporating the effect of thermal expansion into the volume fraction of carbon black, the temperature dependency of the resistivity above percolation threshold has been well explained without violating the universal law of conductivity. The apparent activation energy is estimated to be 0.14 eV.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.235-242
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• 2022

The percolation threshold of the CNT-reinforced cement paste is closely related to the optimal CNT amount to maximize the sensing ability of self-sensing concrete. However, the percolation threshold has various values depending on the cement, CNT, and water-to-cement ratio used. In this study, a percolation simulation model was proposed to predict the percolation threshold of the CNT-reinforced cement paste. The proposed model can simulate the percolation according to the amount of CNT using only the properties of CNT and cement, and for this, the concept of the number of aggregated CNT particles was used. The percolation simulation consists of forming a pre-hydrated cement paste model, random dispersion of CNTs, and percolation investigation. The simulation used CNT-reinforced cement paste with a water-cement ratio of 0.4 to 0.6, and the simulated percolation threshold point showed high accuracy with a simulation residual ratio of up to 7.5 % compared to the literature results.

• Korean Journal of Materials Research
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• v.25 no.12
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• pp.678-682
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• 2015

The electrical property of polymer matrix composites with added carbon powder is studied based on the temperature dependency of the conduction mechanism. The temperature coefficient of the resistance of the polymer matrix composites below the percolation threshold (x) changed from negative to positive at 0.20 < x < 0.21; this trend decreased with increasing of the percolation threshold. The temperature dependence of the electrical property(resistivity) of the polymer matrix composites below the percolation threshold can be explained by using a tunneling conduction model that incorporates the effect of the thermal expansion of the polymer matrix composites into the tunneling gap. The temperature coefficient of the resistance of the polymer matrix composites above the percolation threshold has a positive value; its absolute value increased with increasing volume fraction of carbon powder. By assuming that the electrical conduction through the percolating paths is a thermally activated process and by incorporating the effect of thermal expansion into the volume fraction of the carbon power, the temperature dependency of the resistivity above the percolation threshold can be well explained without violating the universal law of conductivity.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.4
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• pp.264-268
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• 1998

The experiment was conducted to clarify irrigation requirement and percolation rate in rice paddy. The four rice cultural system of no-tin, till, transplanting, and direct seeding condition were treated in the lysimeter filled with sandy loam soil. The amounts of irrigation and soil percolation were measured daily, and irrigation requirement was estimated. The daily percolation was 19.5 l/$\textrm{m}^2$ in no-till direct seeding on flooded paddy surface, 17.4 l/$\textrm{m}^2$ in both of till-direct seeding on flooded surface and no-till transplanting, and 15.2 l/$\textrm{m}^2$ in transplanting plot. This is equivalent to 19.5, 17.4, and 15.2 mm per day, respectively. Highest irrigation requirement was 3,770 l/$\textrm{m}^2$ in no-till direct seeding plots. Others were 3,249, 2,577, and 2,321 l/$\textrm{m}^2$ in till-direct seeding, no-till transplanting and transplanting plot, respectively. The estimated irrigation requirement of no-till transplanting, till-direct seeding and no-till direct seeding was increased by 11, 37, and 59% compared to till-transplanting plot. Percolation rate of no-till transplanting, till direct seeding and no-till direct seeding was increased by 12%, 40%, and 66%, respectively compared to the till-transplanting plot. The percolation rate in paddy soil was increased greatly after reproductive stage of rice.

• Journal of the Korean Applied Science and Technology
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• v.30 no.3
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• pp.472-479
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• 2013

The conductive polymer composites recently became increasingly to many fields of industry due to their electrical properties. To understand these properties of composites, electrical properties were measured and were studied relatively. Electrical conductivity measurements showed percolation phenomena. Percolation theories are frequently applied to describe the insulator-to-conductor transitions in composites made of a conductive filler and an insulating matrix. It has been showed both experimentally and theoretically that the percolation threshold strongly depends on the aspect ratio of filler particles. The critical concentration of percolation formed is defined as the percolation threshold. This paper was to study epoxy resin filled with copper. The experiment was made with vehicle such as epoxy resin replenished with copper powder and the study about their practical use was performed in order to apply to electric and electronic industry as well as general field. The volume specific resistance of epoxy resin composites was 3.065~13.325 in using copper powder. The weight loss of conductive composites happened from $350^{\circ}C{\sim}470^{\circ}C$.