• Journal of Soil and Groundwater Environment
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• v.18 no.4
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• pp.1-7
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• 2013

Subcritical water which acts as organic solvent with increasing temperature and pressure because dielectric constant and viscosity decrease can be used to remediate PAHs-contaminated soil. Factors influencing on extraction were studied with varying the water temperature $200{\sim}275^{\circ}C$, extraction time 0~90 min, flow rate 10~100 mL/min and pressure 3.9~10MPa. 300 g of soil sample which was contaminated with PAHs(naphthalene, phenanthrene, fluoranthene and pyrene; 423, 420, 539 and 428 mg/kg of initial concentration) was packed into the cell and placed to reactor and then the subcritical water was pumped through the cell for PAHs extraction. Naphthalene was removed almost 100% at relatively low temperature ($200^{\circ}C$). The removal rate of phenanthrene, fluoranthene, and pyrene increased by 8, 26, and 23% when the temperature increased from 200 to $275^{\circ}C$; and it was gradually increased as extraction time increased from 0 to 90 min. Decreasing removal rate when water flow rate increased from 10 to 30 mL/min, but there was no significant change after 30 mL/min. This is supposed due to channeling phenomenon. The pressure was not an effective factor for extraction of PAHs in this study. Based on the results, the importance of effective factor was in following sequence: temperature >> time > flow rate.

• Analytical Science and Technology
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• v.26 no.1
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• pp.34-41
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• 2013

Split-flow thin cell (SPLITT) fractionation (SF) is a rapid separation technique capable of separating colloidal particles or macromolecules into two or more fractions. SF allows fractionations in a preparative scale as sample is fed continuously. Generally SF uses a thin ribbon-like channel equipped with two flow stream splitters at the inlet and outlet of the channel. Thus there exist two flow inlets and two flow outlets at the top and bottom of the inlet and outlet of the channel, respectively. There are two operating modes in SF, conventional mode and full-feed mode (FFD). Although the resolution in the FFD mode is lower than that in the conventional mode, FFD mode has some merits. The design of the channel and operation are simpler in the FFD mode, as it does not require the feeding of the solvent. Thus there is no flow stream splitter at the channel inlet, and only one pump is needed, unlike the conventional mode, where two pumps are required for the feedings of the sample and the solvent separately. Also the sample is not diluted in the FFD mode as there is no solvent feeding, which is important for fractionation samples with low colloidal concentrations such as environmental samples. For some of environmental samples, pre-concentration is often required. In this study, a new large-scale splitter-less FFD-SF channel was implemented, where there is no splitter at the outlet as well as at the inlet of the channel. It was possible to build the channel in a much larger dimension than conventional ones, allowing much higher sample throughput (TP). The new channel was tested and optimized with polyurethane (PU) latex beads, and then applied to large-scale separation of Polyacrylate (PA).

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.2021-2026
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• 2011

AgNPs (silver nanoparticles) has been widely used for the commercial products, which have antimicrobial agent, medical devices, food industry and cosmetics. Despite, AgNPs have been reported as toxic to the mammalian cell, lung, liver, brain and other organs and many researchers have investigated the toxicity of AgNPs. In this study, we investigated toxicity of the AgNPs to the liver cell using metabolomics based on HRMAS NMR (High Resolution Magic Angle Spinning Nuclear Magnetic Resonance) technics, which could apply to the intact tissues or cells, to avoid the sample destruction. Target profiling and multivariative statistical analysis were performed to analyze the 1D $^1H$ spectrum. The results show that the concentrations of many metabolites were affected by the AgNPs in the liver cell. The concentrations of glutathione (GSH), lactate, taurine, and glycine were decreased and most of amino acids, choline analogues, and pyruvate were increased by the AgNPs. Moreover, the levels of the metabolites were recovered upto similar level of metabolites in the normal cell by the pre-treatment of NAC, external antioxidant. The results suggest that the depletion of the GSH by the AgNPs might induce the conversion of lactate and taurine to the pyruvate.

• Journal of environmental and Sanitary engineering
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• v.23 no.4
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• pp.37-44
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• 2008

In this study we developed the analytical methods for the determination of three neurotoxin; anatoxin-a, saxitoxin and neosaxitoxin using HPLC/FLD system and this analytical methods were applied to real sample; algae culture and algae extracts. For the HPLC/FLD analysis of anatoxin-a samples were concentrated on WCX(Weak Cation Exchanger) SPE and then anatoxin-a in concentrate was derivatized with NBD-F solution. Supernatant was injected on HPLC system. For the HPLC/FLD analysis of saxitoxin and neosaxitoxin samples were separated on the column and then derivatizied by post column reactor for fluorescen detection. For post column reaction of saxitoxin we feed two kinds of reaction solution; Oxidizing Reagent of which composition was periodic acid(7mM) in 50mM potassium phosphate buffer, pH 9 and acidifying reagent of which Composition was 0.5M acetic acid. The LOD value for anatoxin-a, saxitoxin and neosaxitoxin in HPLC/FLD method was 24.3 ng. $35{\mu}g/L$, $27{\mu}g/L$ respectively. We determined the anatoxin-a content of lyophilized anabaena flos-aquae and $20{\mu}g/g$ d.w. of anatoxin-a was detected. We analyzed saxitoxin and neosaxitoxin in algae culture media and extracts of lypopyllized algal cell cultured and that of Deachung reservior. Saxitoxin and neosaxitoxin in real sample were below the limit of detection. Although there are various water treatment processes for removing neurotoxins were suggested no process give simultaneous and complete removal of neurotoxins. It was cocluded that nanofiltration which reject material by size can be a process for removal of neurotoxins.

• Journal of the Korean Geotechnical Society
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• v.31 no.8
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• pp.17-28
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• 2015

The purpose of this study is to measure the volumetric water content of unsaturated soils during drying and wetting process by using volumetric pressure plate extractor (VPPE) incorporated with time domain reflectometry (TDR). The VPPE consists of a pressure cell, a pressure regulator, a burette system and a TDR probe. Two samples with different initial void ratios were prepared in the pressure cell, and the air pressure at the range of 0.1 kPa - 50 kPa was applied to adjust the matric suction by the pressure regulator. The burette system was used to measure the volumetric water content change of the sample according to the matric suction. In addition, the TDR probe, installed in the cell, was used to evaluate the dielectric constant from the reflected signal of the electromagnetic wave at the probe. The volumetric water content of specimen was estimated by the empirical equation between the volumetric water content and dielectric constant, which was calibrated with the Jumunjin sand. The test results show that the volumetric water content calculated by TDR probe is strongly correlated to the measured value by burette system. The hysteresis occurs during drying and wetting process. Furthermore, the degree of hysteresis reduces in the repeated process. This study suggests that TDR may be effectively used to evaluate the water content soil for the determination of water characteristic curve of unsaturated soils.

• Korean Journal of Environmental Biology
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• v.34 no.3
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• pp.141-150
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• 2016

Most previous studies on dinoflagellates in Korean coastal areas were conducted without morphological descriptions and illustrations of the observed dinoflagellates. This indicates that the species and diversity of dinoflagellates may have been respectively misidentified and underestimated in the past, probably due to cell shrinkage, distortion and loss caused by sample fixation. This study provides information on the morphological observations of four dinoflagellate orders (Prorocentrales, Dinophysiales, Gonyaulacales and Gymnodiniales) from Jangmok Harbour in Jinhae Bay, Korea. The unfixed samples were collected weekly from December 2013 to February 2015. A total of 13 genera and 30 species were identified using light and scanning electron microscopy, although some samples were not clarified at the species level. Harmful dinoflagellates, Prorocentrum donghaiense, Tripos furca, Alexandrium affine, A. fundyense, Akashiwo sanguinea and Cochlodinium polykrikoides, were identified based on the morphological observations. The results also reflect the occurrence and identification of dinoflagellates that had not been previously recorded in Jangmok Harbour.

• Geomechanics and Engineering
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• v.3 no.2
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• pp.131-151
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• 2011

The electrical conductivity of a soil-water system is related to its engineering properties. By measuring the soil electrical conductivity, one may obtain quantitative, semi-quantitative, or qualitative information to estimate the in-situ soil behavior for site characterization. This paper presents the results of electrical conductivity measured on compacted kaolin clay samples using a circular two-electrode cell in conjunction with a specially designed compaction apparatus, which has the advantage of reducing errors due to sample handling and increasing measurement accuracy. The experimental results are analyzed to observe the effects of various parameters on soil electrical conductivity, i.e. porosity, unit weight, water content and pore water salinity. The performance of existing analytical models for predicting the electrical conductivity of saturated and unsaturated soils is evaluated by calculating empirical constants in these models. It is found that the Rhoades model gives the best fit for the kaolin clay investigated. Two general relationships between the formation factor and soil porosity are established based on the experimental data reported in the literature and measured from this study for saturated soils, which may provide insight for understanding electrical conduction characteristics of soils over a wide range of porosity.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.939-952
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• 2016

A compression to tensile load transforming (CTT) device was developed to determine indirect tensile strength of concrete material. Before CTT test, Particle flow code was used for the determination of the standard dimension of physical samples. Four numerical models with different dimensions were made and were subjected to tensile loading. The geometry of the model with ideal failure pattern was selected for physical sample preparation. A concrete slab with dimensions of $15{\times}19{\times}6cm$ and a hole at its center was prepared and subjected to tensile loading using this special loading device. The ratio of hole diameter to sample width was 0.5. The samples were made from a mixture of water, fine sand and cement with a ratio of 1-0.5-1, respectively. A 30-ton hydraulic jack with a load cell applied compressive loading to CTT with the compressive pressure rate of 0.02 MPa per second. The compressive loading was converted to tensile stress on the sample because of the overall test design. A numerical modeling was also done to analyze the effect of the hole diameter on stress concentrations of the hole side along its horizontal axis to provide a suitable criterion for determining the real tensile strength of concrete. Concurrent with indirect tensile test, the Brazilian test was performed to compare the results from two methods and also to perform numerical calibration. The numerical modeling shows that the models have tensile failure in the sides of the hole along the horizontal axis before any failure under shear loading. Also the stress concentration at the edge of the hole was 1.4 times more than the applied stress registered by the machine. Experimental Results showed that, the indirect tensile strength was clearly lower than the Brazilian test strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.107-113
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• 1989

The purpose of this study is to compare the results of shear-deformation of saturated sand under the 3 dimensional stress with the results of simple torque-shear test already reported, Japaness standard sand, Toyoura sand, was chosen as test sample and the equipments of the department of soil mechancis laboratory of Nihon University were used. The conclusions obtained are as follows. 1). The friction angle of sand (${\phi}$) is proportional to the density regardless of the condition of stress-strain. This is because of the reason that the lower the cell pressure becomes, the larger the volume changes in case of the same density. 2). The value of ${\varphi}$ are variable according to the condition of stress-strain in the same density, and ${\phi}_dTS$ is larger than ${\phi}_dPS$ and ${\phi}_dTC$ when cell pressure is low. 3). ${\phi}_dPS$ is larger then ${\phi}_dTS$, under the same denstiy and same cell pressure. Thus the shear strength of sand is decided according to the condition of stress-strain 4). the relationship between the stress ratio (q/p) and strain increment ration in the plane strain test is linear regardless of the density and the cell pressure of the test sample.

• Journal of the Korean GEO-environmental Society
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• v.9 no.6
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• pp.31-41
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• 2008

Consolidation characteristics of reclamated ground with dredged soil and methods of evaluating them are investigated in this paper. For a dredged and reclamated ground with a very high water content, self-weight consolidation being progressed, its consolidation characteristics are difficult to find since it is almost impossible to have a undisturbed sample. In order to overcome such a problem, methods of laboratory tests with disturbed sample were studied to obtain consolidation parameters required to analyze consolidation settlement in practices, using the conventional infinitesimal consolidation theory, were evaluated by carrying out various laboratory tests with disturbed soils such as oedometer test, constant rate of deformation test, Rowe-cell tests with ring diameters of 60 mm, 100 mm and 150 mm and the centrifuge model tests with 40 g-levels. Constitutive relations of void ratio - effective vertical stress - permeability were evaluated by using the inverse technique implemented with the finite strain consolidation theory and results of centrifuge model tests. Design soil parameters related to consolidation such as compression index, swelling index, coefficient of volume change and vertical and horizontal consolidation coefficients were proposed properly by analyzing the various test results comprehensively.