• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.685-690
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• 2017

Ammonia is a useful substance which is widely used in various industries. It is generally released by the decomposition of agricultural wastes and known to have toxic effects on human beings. Due to the common usage, it is possible to cause water pollution through either direct or indirect leakage. Such cases, it is preferable to use the adsorption capacity of zeolite to rapidly remove ammonium ions, but it is not sufficiently removed by the adsorption only. In this paper, the removal efficiency of ammonium ion through both the adsorption capacities of commercial synthetic zeolites and the biological mechanism of microorganisms were compared. In addition, microorganisms were immobilized on the zeolite in order to enhance the removal efficiency by applying a chemo-biological process. As a result, the standard commercial zeolite showed 67~81% of the removal efficiency in 2~4 hours at a 100 ppm concentration of ammonium, whereas the selected microorganism Klebsiella pneumoniae subsp. Pneumoniae showed up to 97% within 8 hours. When the microorganism was immobilized on the zeolite, the highest removal efficiency of approximately 98.5% were observed within 8 hours.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.285-285
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• 2010

Zinc oxide (ZnO) is a direct band gap semiconductor with 3.37 eV, which has in a hexagonal wurtzite structure. ZnO is a good candidate for a photocatalyst because it has physical and chemical stability, high oxidative properties, and absorbs of ultraviolet light. During ZnO is irradiated by UV light, redox (reduction and oxidation) reactions will occur on the ZnO surface, generating the radicals O2- and OH. These two powerful oxidizing agents have been proven to be effective in decomposition of harmful organic materials, converting them into CO2 and H2O. Therefore, we assume that oxygen on the surface of ZnO is a very important factor in the photocatalytic activities of ZnO nanoparticles. Recently, ZnO nanoparticles are studied in various application fields by many researchers. Photocatalyst research is progressing much in various application fields. But the ZnO nanoparticles have disadvantage that is unstable in water in comparison titanium dioxide (TiO2). The Zn(OH)2 was formed at the ZnO surface and ZnO become inactive as a photocatalyst when ZnO is present in the solution. Therefore, we prepared synthesized ZnO nanoaprticles that were immersed in the water and dried in the oven. After that, we measured photocatalytic activities of prepared samples and find the cause of their phtocatalytic activity changes. The characterization of ZnO nanoparticles were analyzed by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and BET test. Also we defined the photocatalytic activity of ZnO nanoparticles using UV-VIS Spectroscopy. And we explained changing of photocatalytic activity after the water treatment using X-ray Photoelectron Spectroscopy (XPS).

• Journal of Korean Society on Water Environment
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• v.24 no.1
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• pp.63-68
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• 2008

This study was performed to assess the potential use of ozone or UV radiation for the treatment of water contaminated with sulfamethoxazole (SMX), which is frequently used antibiotic in human and veterinary medicines, especially focusing on the kinetic study and effect of pH. In a study using ozone alone, kinetic study was performed to determine second-order rate constant ($k_{O3,SMX}$) for the reactions of SMX with ozone, which was found to be $1.9{\times}10^6M^{-1}s^{-1}$ at pH 7. The removal efficiencies of SMX by ozone were decreased with increase of pH due to rapid decomposition of ozone under the condition of various pH (2.5, 5.3, 7, 8, 10). In a UV irradiation study at 254 nm, a kinetic model for direct photolysis of SMX was developed with determination of quantum yield ($0.08mol\;Einstein^{-1}$) and molar extinction coefficient ($15,872M^{-1}cm^{-1}$) values under the condition of quantum shielding due to the presence of reaction by-products formed during photolysis. For effect of pH on photolysis of SMX, SMX in the anionic state ($S^-$, pH > 5.6), most prevalent form at environmentally relevant pH values, degraded more slowly than in the neutral state (SH, 1.85 < pH < 5.6) by UV radiation at 254 nm.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.10
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• pp.894-898
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• 2016

Solution plasma is a unique method which provides a direct discharge in solutions. It is one of the promising techniques for various applications including the synthesis of metallic/non-metallic nanomaterials, decomposition of organic compounds, and the removal of microorganism. In the context of nanomaterial syntheses, solution plasma has been utilized to produce carbon nanoparticles and metallic-carbon nanoparticle systems. The main purpose of this study was to synthesize nickel nanoparticles embedded in a matrix of carbon particles by solution plasma in one-step using waste vegetable oil as the carbon source. The experimental setup was done by simply connecting a bipolar pulsed power generator to nickel electrodes, which were submerged in the waste vegetable oil. Black powders of the nickel nanoparticles-embedded carbon (NiNPs/Carbon) particles were successfully obtained after discharging for 90 min. The morphology of the synthesized NiNPs/Carbon was investigated by a scanning electron microscope, which revealed a good dispersion of NiNPs in the carbon-particle matrix. The X-ray diffraction of NiNPs/Carbon clearly showed the co-existence of crystalline Ni nanostructures and amorphous carbon. The crystallite size of NiNPs (through the Ni (111) diffraction plane), as calculated by the Scherrer equation was found to be 64 nm. In addition, the catalytic activity of NiNPs/Carbon was evaluated by cyclic voltammetry in an acid solution. It was found that NiNPs/Carbon did not show a significant catalytic activity in the acid solution. Although this work might not be helpful in enhancing the activity of the fuel cell catalysts, it is expected to find application in other processes such as the CO conversion (by oxidation) and cyclization of organic compounds.

• Wind and Structures
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• v.14 no.4
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• pp.301-319
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• 2011

The full-scale measurements are compared with the wind tunnel test results for the long-span roof latticed spatial structure of Shenzhen Citizen Center. A direct comparison of model testing results to full-scale measurements is always desirable, not only in validating the experimental data and methods but also in providing better understanding of the physics such as Reynolds numbers and scale effects. Since the quantity and location of full-scale measurements points are different from those of the wind tunnel tests taps, the weighted proper orthogonal decomposition technique is applied to the wind pressure data obtained from the wind tunnel tests to generate a time history of wind load vector, then loads acted on all the internal nodes are obtained by interpolation technique. The nodal mean wind pressure coefficients, root-mean-square of wind pressure coefficients and wind pressure power spectrum are also calculated. The time and frequency domain characteristics of full-scale measurements wind load are analyzed based on filtered data-acquisitions. In the analysis, special attention is paid to the distributions of the mean wind pressure coefficients of center part of Shenzhen Citizen Center long-span roof spatial latticed structure. Furthermore, a brief discussion about difference between the wind pressure power spectrum from the wind tunnel experiments and that from the full-scale in-site measurements is compared. The result is important fundament of wind-induced dynamic response of long-span spatial latticed structures.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.461-480
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• 2010

This paper analyses the data collected from the $2^{nd}$ Jindo Bridge, a cable-stayed bridge in Korea that is a structural health monitoring (SHM) international test bed for advanced wireless smart sensors network (WSSN) technology. The SHM system consists of a total of 70 wireless smart sensor nodes deployed underneath of the deck, on the pylons, and on the cables to capture the vibration of the bridge excited by traffic and environmental loadings. Analysis of the data is performed in both the time and frequency domains. Modal properties of the bridge are identified using the frequency domain decomposition and the stochastic subspace identification methods based on the output-only measurements, and the results are compared with those obtained from a detailed finite element model. Tension forces for the 10 instrumented stay cables are also estimated from the ambient acceleration data and compared both with those from the initial design and with those obtained during two previous regular inspections. The results of the data analyses demonstrate that the WSSN-based SHM system performs effectively for this cable-stayed bridge, giving direct access to the physical status of the bridge.

• International Area Studies Review
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• v.13 no.3
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• pp.145-161
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• 2009

Applying the shift-share analysis, this paper decomposes FDI inflow into Korea for the period of 2003-2006. The paper finds that Korea has been lagging behind the world average in absorbing inward FDI, thereby recording negative aggregate industry-mix effects and negative aggregate competitive effects as well. However, the following industries have recorded positive competitive effect: electrical and electronic equipment, motor vehicles and other transport equipment, hotels and restaurants, transport, storage and communications, finance, and business services. In a nutshell, Korea is revealed to have competitive advantage in absorbing inward FDI in a few manufacturing industries and most of service industries. Government policies should accordingly be focused on these industries to encourage more inward FDIs.

• Korea Trade Review
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• v.42 no.6
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• pp.131-154
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• 2017

In international trade, transportation generally has the largest and direct impact on freight costs. However, it is also sensitive to external factors such as global economic conditions, global trade volume and exchange rate. Therefore, it is necessary to examine the relationship and influence of international trade in terms of external factors that affect the change of imports and exports by marine and air transportation through empirical analysis. In particular, the analysis of the impact of these external factors on marine and air transportation is an important topic when recent exchange rate changes are significant, and it is also necessary to analyze what transportation means are more sensitive to exchange rate changes. In this study, we use the Vector Error Correction Model to analyze the dynamic effects of changes in exchange rate and domestic and international economic conditions on marine and air transportation from January 2000 to March 2017. Respectively. Alos, Impulse response function and variance decomposition were examined.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.497-512
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• 2006

In this paper, a simple but effective analysis procedure to estimate seismic capacities of multi-span continuous bridge structures is proposed on the basis of modal pushover analysis considering all the dynamic modes of structure. Unlike previous studies, the proposed method eliminates the coupling effects induced from the direct application of modal decomposition by introducing an identical stiffness ratio and an approximate elastic deformed shape. Moreover, in addition to these two introductions, the use of an appropriate distributed load {P} makes it possible to predict the dynamic responses for all kinds of bridge structures through a simpler analysis procedure. Finally, in order to establish the validity and applicability of the proposed method, correlation studies between rigorous nonlinear time history analysis and the proposed method are conducted for multi-span continuous bridges.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.1
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• pp.63-70
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• 2024

Lithium-ion batteries (LIB) are widely used in various sectors, such as transportation (e.g., electric vehicles (EV)) and energy (e.g., energy storage facilities) due to their high energy density, broad operating temperature (-20 ℃ ~ 60 ℃), and high capacities. LIBs are powerful but fragile on external factors, including pressure, physical damage, overheating, and overcharging, that cause thermal runaway causing fires and explosions. During a LIB fire, a large amount of oxygen is generated from the decomposition of ionogenic materials. A water fire extinguisher that helps with cooling and suffocating must be essentially required at the same time. In fact, however, it is difficult to suppress LIB fires in the case of EVs because a LIB is installed with a battery pack housing that interrupts direct extinguishing by water. Thus, this study aims to investigate effective fire extinguishing measurements for LIB fires by using an EV. Relevant documents, including research articles and reports, were reviewed to identify effective ways of LIBs fire extinguishing. A real-scale fire experiment generating thermal runaway was carried out to figure out the combustion characteristics of EVs. This study revealed that the most effective fire extinguishing measurements for LIB fires are applying fire blankets and water tanks. However, there is still a lack of adequate regulation and guidelines for LIB fire extinguishment. Taking this into account, developing functional fire extinguishment measurements and available regulatory instruments is an urgent issue to secure the safety of firefighters and citizens.