• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.12
• /
• pp.1179-1183
• /
• 2007

Electro-Active paper(EAPap) is a new smart material that has a potential to be used in biomimetic actuator and sensor. It is made by cellulose that is abundant material in nature. EAPap is fascinating with its biodegradability, lightweight, large displacement, high mechanical strength and low actuation voltage. Actuating mechanism of EAPap is known to be the combined effects of ion migration and piezoelectricity. However, the electromechanical actuation mechanisms are not yet to be established. This paper presents the modeling of the actuation behavior of water infused cellulose samples and their composite dielectric constants calculated by Maxwell-Wagner theory. Electro-mechanical forces were calculated using Maxwell stress tensor method. Bending deflection was evaluated from simple beam model and compared with experimental observation, and which result in good correlation with each other.

• Korean Chemical Engineering Research
• /
• v.53 no.4
• /
• pp.503-508
• /
• 2015

The adsorption characteristics of ammonia on MSWI bottom ash were investigated. The effect of the variation of the landfill environmental parameters including pH, anions and organic matter on the adsorption process was discussed. Results showed that the adsorption could be well described by pseudo-second-order kinetics and Langmuir model, with a maximum adsorption capacity of 156.2 mg/g. The optimum adsorption of ammonia was observed when the pH was 6.0. High level of ion and organic matter could restrict the adsorption to a low level. The above results suggested that MSWI bottom ash could affect the migration of ammonia in the landfill, which is related to the variation of the landfill circumstance.

• Journal of the Korean Magnetics Society
• /
• v.14 no.6
• /
• pp.219-223
• /
• 2004

L $i_{0.5}$F $e_{2.5-{\chi}}$R $h_{\chi}$ $O_4$ ($\chi$ = 0.25, 0.50, 0.75, 1.00) has been prepared by solid state reaction. Crystallographic and magnetic properties were investigated by Mossbauer spectroscopy, SQUID magnetometry, and x-ray diffraction. The crystal structure is found to be a cubic spinel structure with space group Fd3m for all the samples. The lattice constant $a_{0}$ increases from 8.3365 $\AA$ to 8.3932 $\AA$ with increasing Rh concentration $\chi$. The migration of Li ion has been confirmed by x-ray patterns and the results of applied field Mossbauer analysis. The temperature dependence of the absorption area of each site was analyzed with the Debye model for the recoil-free fraction. The Debye temperature for the octahedral sites is almost as large as for the tetrahedral sites, thereby suggesting similar inter-atomic binding forces for the octahedral and the tetrahedral sites. The saturated magnetic moment and the Mossbauer spectra taken at 4.2 K under the applied field (6 T) show that the spin structure of L $i_{0.5}$F $e_{2.5-{\chi}}$R $h_{\chi}$ $O_4$ is compatible with the collinear Neel Model.

• Geomechanics and Engineering
• /
• v.12 no.3
• /
• pp.523-539
• /
• 2017

Clay soils are typical for their swelling properties upon absorption of water during rains and development of cracks during summer time owing to the profile desorption of water through the inter-connected soil pores by water vapour diffusion leading to evaporation. This type of unstable soil phenomenon by and large poses a serious threat to the strength and stability of structures when rest on such type of soils. Even as lime and cement are extensively used for stabilization of clay soils it has become imperative to find relatively cheaper alternative materials to bring out the desired properties within the clay soil domain. In the present era of catastrophic environmental degradation as a side effect to modernized manufacturing processes, industrialization and urbanization the creative idea would be treating the waste products in a beneficial way for reuse and recycling. Bottom ash and ecosand are construed as a waste product from cement industry. An optimal combination of bottom ash-eco sand can be thought of as a viable alternative to stabilize the clay soils by means of an effective dispersion dynamics associated with the inter connected network of pore spaces. A CATIA model was created and imported to ANSYS Fluent to study the dispersion dynamics. Ion migration from the bottom ash-ecosand pile was facilitated through natural formation of cracks in clay soil subjected to atmospheric conditions. Treated samples collected at different curing days from inner and outer zones at different depths were tested for, plasticity index, Unconfined Compressive Strength (UCS), free swell index, water content, Cation Exchange Capacity (CEC), pH and ion concentration to show the effectiveness of the method in improving the clay soil.

• Korea journal of population studies
• /
• v.11 no.1
• /
• pp.185-196
• /
• 1988

This study considers inter-jurisdictional fiscal externalities between a central city and suburbs, rigorously examines. and empirically tests the suburban-exploitation-of-central-cities hypothesis. Using micro-migra4ion data, house-holds 'intra-metropolitan migration between 1985 and 1990 Is examined based on a random utility model. It is found that efficient population distribution between a central city and suburbs can be achieved when local government stake into account inter-jurisdictional externalities. External aids from the federal and state governments should be given to public services such as education, welfare, health, and employee retirement services, if they intend to arrest central city decline. Regional tax sharifs can be another way of dealing with these externalities.

• Geomechanics and Engineering
• /
• v.29 no.1
• /
• pp.91-97
• /
• 2022

The cohesive non-swelling soil (CNS) cushion technology has been widely applied in the subgrade and slope improvement at expansive soil regions. However, the mechanism of the inhibition effect of the CNS layer on expansive soil (ES) has not been fully understood. We performed four outdoor model tests to further understand the inhibition effect, including different kinds of upper layer and thickness, under the unidirectional seepage condition. The swelling deformation, soil pressure, and electrical resistivity were constantly monitored during the saturation process. It is found that when a CNS layer covered the ES layer, the swelling deformation and electrical resistivity of the ES layer decreased significantly, especially the upper part. The inhibition effect of the CNS layer increases with the increase of CNS thickness. The distribution of vertical and lateral soil pressure also changed with the covering of a CNS layer. The electrical resistivity can be an effective index to describe the swelling deformation of ES layer and analyze the inhibition effect of the CNS layer. Overall, the CNS deadweight and the ion migration are the major factors that inhibit the swelling deformation of expansive soil.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.17 no.6
• /
• pp.104-111
• /
• 2013

Deterioration is accelerated due to additional intrusion of chloride ion in crack width in cracked concrete. In this paper, modeling on equivalent diffusion coefficient in cracked concrete is performed for 1-D (Anisotropic) and 2-D (Isotropic) diffusion based on steady state condition. In the previous research, rectangular shape of crack was considered but the shape was modified to wedge shape with torturity. For verification of the proposed model, crack is induced in concrete sample and migration test in steady state is performed for 1-D diffusion. For 2-D diffusion, previous test results are adopted for verification. Through considering wedge shape of crack with torturity, diffusion coefficients in 1-D and 2-D diffusion are reduced, and the more reasonable prediction is obtained. The results from the proposed model with torturity of 0.10~0.15 are shown to be in the best agreement with the test results.

• Journal of Soil and Groundwater Environment
• /
• v.6 no.1
• /
• pp.13-21
• /
• 2001

The characteristics of $Co^{2+}$ removal in the kaolinite column were analyzed by electrokinetic remediation. Ethanoic buffer was injected in the kaolinite column and $CH_3$COOH was continuously added to the cathode reservoir to restrain the pH increase. The pH of the cathode of the kaolinite column was 4.0 at first. Since it was controlled to be under 6.5 after 43.6 hours due to ethanoic buffer, precipitation of ${Co(OH)}_2$ was not formed in the column. Effluent rate increased with time and $Co^{2+}$ removal in the column at initial time was mainly controlled by ion migration. 13.1% of total $Co^{2+}$ in the column was removed after 10 hours, the 46.8% of total $Co^{2+}$ after 20.8 hours, and the 71.7% of total $Co^{2+}$ after 30.1 hours, the 94.6% of total $Co^{2+}$ after 43.6 hours, Meanwhile, the residual concentrations in the column calculated by the developed model were similar to experiment results.

• Journal of Korea Soil Environment Society
• /
• v.4 no.1
• /
• pp.109-118
• /
• 1999

Recently, transport parameters of conservative solutes such as KCl in a porous medium have been successfully determined using time domain reflectometry (TDR) . This study was initiated to Investigate the applicability of TDR technique to monitoring the fate of a heavy metal ion in a sandy soil and the distribution of its concentration along travel distance with time. A column test was conducted in a laboratory that consists of monitoring both resident and flux concentrations of $ZnCl_2$in a sandy soil under a breakthrough condition. A tracer of $ZnCl_2$(10 g/L) was injected onto the top surface of the sample as pulse type as soon as a steady-state condition was achieved. Time-series measurements of resistance and electrical conductivity were performed at 10 cm and 20 cm of distances from the inlet boundary by horizontal-positioning of parallel TDR metallic rods and using an EC-meter for the effluent exiting the bottom boundary respectively. In addition. Zn ions of the effluent were analyzed by ICP-AES. Since the mode and position of concentration detected by TDR and effluent were different, comparison between ICP analysis and TDR-detected concentration was made by predicting flux concentration using CDE model accommodating a decay constant with the transport parameters obtained from the resident concentrations. The experimental results showed that the resident concentration resulted in earlier and higher peak than the flux concentration obtained by EC-meter, implying the homogeneity of the packed sandy soil. A close agreement was found between the predicted from the transport parameters obtained by TDR and the measured $ZnCl_2$concentration. This indicates that TDR technique can also be applied to monitoring heavy metal concentrations in the soil once that a decay constant is obtained for a given soil.