• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4C
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• pp.229-238
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• 2006

Observed field behaviors are frequently different from the behaviors predicted in the design state due to several uncertainties involved in soil properties, numerical modeling, and error of measuring system even though a sophisticated numerical analysis technique is applied to solve the consolidation behavior of drainage-installed soft deposits. In this study, genetic algorithms are applied to back-analyze the soil properties using the observed behavior of soft clay deposit composed of multi layers that shows complex consolidation characteristics. Utilizing the program, one might be able to appropriately predict the subsequent consolidation behavior from the measured data in an early stage of consolidation of multi layered soft deposits. Example analyses for drainage-installed multi-layered soft deposits are performed to examine the applicability of proposed back-analysis method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.597-604
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• 2006

Fiber Reinforced Polymer (FRP) is a relatively new material in the bridge construction. With high strength to weight ratios, excellent durability, and low life-cycle costs of FRP, FRP bridge decks can offer a low dead load, reduced maintenance, and long service life. Due to the lightweight of FRP, if existing concrete decks can be replaced with the FRP decks, the load carrying capacity of superstructure can be increased without strengthening of girders. In this study, we have conducted an experiment on 7 cases of connection conditions with steel girder by using bolts considering a rational and economical method of connection and compared with the results of FEM analysis. From the experimental result, if the bolts are strong enough to resist shear force between the FRP bridge deck and the steel girder, it will be structurally secure to use the zigzag method.

• The Journal of the Acoustical Society of Korea
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• v.26 no.1
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• pp.48-54
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• 2007

In this paper we have implemented a 3-D PL (Position Location) system to estimate the 3-dimensional position of a moving object in underwater environments. In this research, we let four sensors fixed in different Positions and moving sensorsto communicate with each other to find the 3-dementianal positions for both the fixed and moving objects. Using this we were also able to control the moving object remotely. When finding the position, we calculated the norm of the Jacobian matrix every iteration in the Newton algorithm. Also by using a different initial value for calculating the solution when the norm became higher than the critical value and the solution from the inverse matrix became unstable, we could find a more reliable position for the moving object. The proposed algorithm was used in implementing a DSP system capable of real-time position location. To verify the performance, experiments were done in a water tank. As a result we could see that our system could located the position of an object every 2 seconds with a error range of 5cm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.3
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• pp.69-76
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• 2024

This dissertation developed a five-story vertical livestock and fisheries farm (palm tower) model for sustainable food production in cities. It proposes to integrate marine farms, livestock raising, and pesticide-free automated crop farms to efficiently use resources and minimize environmental impact. Based on circular economy principles, the model can recycle the output of each part into resources from the other, increasing the efficiency of the system, utilizing idle space in the city, and promoting job creation and community participation. It can also contribute to reducing the carbon footprint of food production and improving food safety. In addition, the study explores how advanced agricultural technologies can be integrated into urban structures to address global food security challenges. This model presents potential solutions to the food crisis caused by climate change and population growth, and suggests a direction for the development of urban agriculture. Future research should address the technical and policy challenges for practical implementation.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.8
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• pp.554-560
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• 2014

To investigate the applicability of montmorillonite to capping material for the remediation of contaminated marine sediment, adsorption characteristics of $PO{_4}{^{3-}}$ onto montmorillonite were studied in a batch system with respect to changes in contact time, initial concentration, pH, adsorbent dose amount, competing anions, adsorbent mixture, and seawater. Sorption equilibrium reached in 1 h at 50 mg/L but 3 h was required to reach sorption equilibrium at 300 mg/L. Freundlich model was more suitable to describe equilibrium sorption data than Langmuir model. The $PO{_4}{^{3-}}$ adsorption decreased as pH increased, due to the $PO{_4}{^{3-}}$ competition for favorable adsorption site with OH- at higher pH. The presence of anions such as nitrate, sulfate, and bicarbonate had no significant effect on the $PO{_4}{^{3-}}$ adsorption onto the montmorillonite. The use of the montmorillonite alone was more effective for the removal of the $PO{_4}{^{3-}}$ than mixing the montmorillonite with red mud and steel slag. The $PO{_4}{^{3-}}$ adsorption capacity of the montmorillonite was higher in seawater than deionized water, resulting from the presence of calcium ion in seawater. The water tank elution experiments showed that montmorillonite capping blocked well the elution of $PO{_4}{^{3-}}$, which was not measured up to 14 days. It was concluded that the montmirillonite has a potential capping material for the removal of the $PO{_4}{^{3-}}$ from the aqueous solutions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.1
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• pp.25-33
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• 2015

The Strait of Malacca is one of the most important fairways in the world and its traffic safety has direct effect on economic development of East Asian countries including China, Japan and Korea. Because of this reason, a safety analysis of the marine traffic in the strait has a great significance. In this paper, we analysed the statistic distribution of marine traffic in the Strait of Malacca based on the vessels' AIS data for 1 month by using the TOAIS and EasyFit programs. As the results of the analysis, it was found that the traffic distribution of this strait was different with normal distribution, which had been still widely used in marine traffic engineering field. Furthermore, with the traffic distribution analysis results, the traffic safety of the strait was also assessed by using the IWRAP model. The results showed that the highest level of risk were overtaking and crossing situations. Finally, we found that the highest risk of collision area in the Strait of Malacca was crossing area between the Strait of Malacca and the Port Klang fairway.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.7
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• pp.469-475
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• 2014

The study investigated the physicochemical characteristics and the ecological risk of the Northport sediment in B city and the releasing properties of heavy metals into seawater during the resuspension also studied. The major components of the sediment are fine silt and clay which contains high organic matter and AVS (Acid volatile sulfide) and the ecological risk of the heavy metals in sediment also very high. The release rate of heavy metals into seawater was in order of Pb>>Cu>Cr>>Zn>Cd during the resuspension in a batch experiment, and the heavy metal release mainly attributed to the oxidation of metal sulfides. Heavy metals which came from easily oxidisable metal sulfides rapidly contaminated seawater within about 1.0 h of the sediment resuspension. The sulfide oxidation during the resuspension increased the residual fraction of heavy metals in the sediment, decreased the organic bound fraction, and changed the other fractions of heavy metals in the sediment. The release of heavy metals from the sediment during resuspension was affected by the resuspension time, the oxidation rate of metal sulfides and resuspended concentration of the sediment particle.

• Journal of the Korean GEO-environmental Society
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• v.21 no.9
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• pp.25-32
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• 2020

The underground utilities installed under the ground is an important civil engineering structure, such as water supply and sewerage pipes, underground power lines, various communication lines, and city gas pipes. Such underground utilities can be exposed to risk due to external factors such as concentrated rainfall and vehicle load, and it is important to select and construct an appropriate backfill material. Currently, a method mainly used is to fill the soil around the underground utilities and compact it. But it is difficult to compact the lower part of the buried pipe and the compaction efficiency decreases, reducing the stability of the underground utilities and causing various damages. In addition, there are disadvantages such as a decrease in ground strength due to disturbance of the ground, a complicated construction process, and construction costs increase because the construction period becomes longer, and civil complaints due to traffic restrictions. One way to solve this problem is to use a liquid filler. The liquid filler has advantages such as self-leveling ability, self-compaction, fluidity, artificial strength control, and low strength that can be re-excavated for maintenance. In this study, uniaxial compression strength test and fluidity test were performed to characterize the mixed soil using marine clay, stabilizer, and in-situ soil as backfill material. A freezing-thawing test was performed to understand the strength characteristics of the liquid filler by freezing, and in order to examine the effect of the filling materials on the corrosion of the underground pipe, an electrical resistivity test and a pH test were performed.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.900-906
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• 2005

The responses of two luminescence-based biosensors were studied on various heavy metals in aqueous solutions. One was recombinant E. coli ($DH5{\alpha}$/pSB311), genetically modified luminescence-based bacteria, and the other was Vibrio fisheri used for the LumisTox system. The recombinant E. coli was marked with the lux CDABE gene from multicopy plasmid, pACYC184, originally isolated from Photorhabdus luminescens. The $DH5{\alpha}$/pSB311 had a characteristic of no organic substrate for its luminescence reaction. Among the tested heavy metals Zinc and cadmium were less toxic than copper and mercury. The recombinant E. coli was more sensitive to toxicity of heavy metals than the LumisTox. The order of toxicity of the heavy metals to the recombinant E. coli was $Hg^{2+}>Cu^{2+}>Zn^{2+}>Cd^{2+}$. In case of the LumisTox, the order of the toxicity of heavy metals was $Hg^{2+}>Cu^{2+}>Cd^{2+}>Zn^{2+}$. The genetically modified luminescence-based biosensor offers a range of sensitive, rapid, and easy to use methods for assessing the potential toxicity of heavy metals in aqueous samples.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.2
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• pp.75-83
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• 2014

The present study estimated nitrogen budget of South Korea including nitrogen oxides (NOx) in 2011. Emission sources of NOx were calculated with the higher contributors, such as vehicles, businesses, power plants, based on the IPCC and EPA reports. Moreover, nitrogen budget was separated for city, agriculture livestock and forest. Input and output were chemical fertilizer, crop uptake, fixation, irrigation, compost, leaching, volatilization, imported food, denitrification, runoff, and so on. Annual nitrogen input were 1,692,650 ton/yr and output were 837,739 ton/yr which were increased from 2010 budget. In 2011, NOx emissions by vehicles, power plants, and businesses were 308,207 ton/yr, 601,437 ton/yr, and 469,946 ton/yr, respectively. Including nitrogen oxide, total nitrogen input and output in 2011 was calculated as 5,652,366 ton/yr and 1,425,371 ton/yr, respectively.