• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.6
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• pp.130-136
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• 2002

A novel ozonizer has been developed using a high frequency surface discharge and a high purity Ti-Si-Al ceramic catalyst as its dielectric component. A cylindrical thin compound ceramic catalyst in reactor is adhered to inside of the film-like outside electrode. And, when experiment condition are oxygen gas temperature of 20 ［$^{\circ}C$］, inner reactor pressure of 1.6 atm 600［Hz］ and flow late of 2［l/min］. the ozonizer can easily produce ozone concentration(50～60［g/㎥］for oxygen) and power efficiency(180［g/kWh］for oxygen) without using a special enrichment means. At 2［l/min］, 20［$^{\circ}C$］, 1.6［atm］, 600［Hz］and 40［W］, the result of simulation to gas temperature of reactor using general code Phoenics, the maximum temperature of reactor was 132［$^{\circ}C$］in reactor. Ant the result electric field simulation of Ti-Si-Al type reactor using general code Flux 2D, maximum electric field was 0.131E.08［V/m］.

• Journal of the Korea Institute of Building Construction
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• v.21 no.6
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• pp.593-604
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• 2021

In this study, a comparative test was conducted on a specially developed elastic waterproof paint and general water-based paint for the purpose of responding to cracks occurring on the outer wall of concrete structures and improving watertightness. Through the comparative experiment, it was confirmed that the watertightness could be improved by securing the crack shielding property, and it was also confirmed that about 10 times more crack responsiveness was secured compared to general water-based paint. In addition, it was confirmed that the adhesion performance of at least 1.3MPa and resistance to a water permeation pressure of 0.1MPa were possible, confirming that stability was secured from a waterproofing perspective.

• Membrane and Water Treatment
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• v.15 no.2
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• pp.59-66
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• 2024

This study evaluated the performance of a membrane aerated biofilm reactor (MABR) for nitrogen removal from a high-strength ammonia nitrogen-containing wastewater. The experimental setup consisted of four compartments that are sequentially anaerobic and aerobic to achieve complete nitrogen removal. The last compartment of the reactor setup contained a membrane bioreactor (MBR) to reduce sludge production in the system and to obtain a better-quality effluent. Continuous experiment over a period of 47 days showed that MABR exhibited excellent NH₄⁺-N removal efficiency (99.5%) compared to the control setup without MABR (56.5%). The final effluent NH₄⁺-N concentration obtained in the MABR was 2.99±1.56 mg/L. In contrast to NH₄⁺-N removal, comparable TOC removal values in the MABR and the control reactor (99.2% and 99.3%, respectively) showed that air supply through MABR is much more critical for denitrification than for organic removal. Further study to understand the effect of air supply rate and holding pressure on NH₄⁺-N removal in MABR revealed that an increase in both these parameters positively impacted reactor performance. These parameters are related to oxygen supply to the biofilm formed over the membrane surface, which in turn influenced NH₄⁺-N removal in MABR. Among the two different strategies to control biofilm over the membrane surface, results showed that scouring for a duration of 10 min on a weekly basis, along with mixing air supply, could be an effective method.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.17 no.2
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• pp.93-103
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• 1981

It is well-known that nowadays heat resisting and anti-corrosive materials have been widely used as the components materials of gas turbines, nuclear power plants and engines etc. In the fields of machine production industry. And materials for engine components, like as the exhaust valve of internal combustion engine, have been required to operate under the high temperature range of $700^{\circ}C$-$800^{\circ}C$ and high pressured gas with repeated mechanical load for the high performance of engines. For these components, friction welding for bonding of dissimilar steels can be applied for in order to obtain process shortening, production cost reduction and excellent bonding quality. And age hardening recently has been noticed to the heat resisting materials for further strengthening of high temperature strength, especially high temperature fatigue strength. However, it is difficult to find out any report concerning the effects of age hardening for strengthening high temperature fatigue strength to the Friction welded heat resisting and anti-corrosive materials. In this study the experiment was carried out as the high temperature rotary bending fatigue testing under the condition of $700^{\circ}C$ high temperature to the friction welded domestic heat resisting steels, SUH3-SUS303, which were 10hr., 100hr. aging heat treated at $700^{\circ}C$ after solution treatment 1hr. at $1, 060^{\circ}C$ for the purpose of observing the effects of the high temperature fatigue strength and fatigue fracture behaviors as well as with various mechanical properties of welded joints. The results obtained are summarized as follows: 1) Through mechanical tests and micro-structural examinations, the determined optimum welding conditions, rotating speed 2420 rpm, heating pressure 8kg/mm super(2), upsetting pressure 22kg/mm super(2), the amount of total upset 7mm (heating time 3 sec and upsetting time 2 sec) were satisfied. 2) The solution treated material SUH 3, SUS 303, have the highest inclination gradient on S-N curve due to the high temperature fatigue testing for long time at $700^{\circ}C$. 3) The optimum aging time of friction welded SUH3-SUS 303, has been recognized near the 10hr. at $700^{\circ}C$ after the solution treatment of 1hr. at $1, 060^{\circ}C$. 4) The high temperature fatigue limits of aging treated materials were compared with those of raw material according to the extender of aging time, on 10hr. aging, fatigue limits were increased by SUH 3 75.4%, SUS 303 28.5%, friction welded joints SUH 3-SUS 303 44.2% and 100hr. aging the rates were 64.9%, 30.4% and 36.6% respectively. 5) The fatigue fractures occurred at the side of the base matal SUS303 of the friction welded joints SUH 3-SUS 303 and it is difficult to find out fractures at the friction welding interfaces. 6) The cracking mode of SUS 303, SUH 3-303 is intergranular in any case, but SUH 3 is fractured by transgranular cracking.

• Journal of Soil and Groundwater Environment
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• v.8 no.2
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• pp.62-69
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• 2003

The aim of research is the evaluation of the $Cr^{6+}$ emission features of the liquid injection through emission experiments in varying conditions, based on a field-mixing ratio. The results showed that the content of $Cr^{6+}$ content in cement measured had an Ordinary Potland Cement (OPC) of 25.3 mg/kg, which constitute the largest portion among the other materials. Likewise, the emission experiment of homo-gel and sand-gel generally satisfied the standard of KSLT (Korea Standard Leaching Test) in waste of 1.5 mg/L, but in case of the standard of KSLT in soil the emission of OPC $Cr^{6+}$ of 4.85 mg/kg. These conditions is a little exceeded the criteria in the ‘Ga’ area in terms of Korea Soil Environmental Preservation Law. In addition, results generated by the mock-up injection facilities revealed that $Cr^{6+}$ emission increased as Water/Cement and injection pressure increased. At injection pressure higher than 4 kg/㎤, $Cr^{6+}$ emission exceeded the water preservation standard of 0.5 mg/L. Similarly, a pattern experiment of C $r^{6+}$ emission according to pH was conducted, in order to evaluate the $Cr^{6+}$ emission features of grout materials in leachate below pH 5 such as pH 4 acid rain or landfill. Results show that $Cr^{6+}$ emission dramatically increased in high acidic or basic state. It indicates that $Cr^{6+}$ emission will probably increase in an environment where grout materials are injected. On the other hand, concentration of leachate was determined in areas where grout materials are used. The results show that the concentration of emission in an ultra purity condition does not manifest intensity, and is affected in the OPC>MC>SC order. It means that the pollutants or $Cr^{6+}$ emission increases with decreasing concentration. As such, $Cr^{6+}$ emission will probably exceed the countermeasure criteria according to the types of gout materials. Similarly, high pressure or injection will cause increased $Cr^{6+}$ emission. Therefore, the selection of materials or mixing ratio should be considered in general as well as according to specific industries, based on the strength and pH of $Cr^{6+}$ emission.

• Polymer(Korea)
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• v.38 no.2
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• pp.144-149
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• 2014

Large residual stresses are remained in the conventional injection molded products because of the high cavity pressure in packing phase during injection molding process. Conventional injection molding (CIM) invokes distribution of cavity pressure and it has a limitation to obtain product with uniform physical property. Multi-cavity conventional injection molding contains quality deviation among the cavities since flow imbalance occurs during filling phase. Injection compression molding (ICM) is adopted to overcome these limitations of CIM. In this study, molding characteristics of CIM and ICM have been investigated using multi-cavity injection mold. Researches were performed by both experiment and computer simulation through observations of birefringence for transparent resins, polycarbonate and polystyrene in CIM and ICM. As a result, low and uniform birefringence and mold shrinkage were showed in the specimens by ICM that could give a uniform cavity pressure. Deviation of physical property among the specimens in multi-cavity mold shown in CIM was significantly reduced in the specimens by ICM. Through this study it was concluded that the ICM in multi-cavity molding was valid for molding products with uniform property in an individual cavity and also reduced property deviation among the cavities.

• Membrane Journal
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• v.27 no.2
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• pp.147-153
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• 2017

In this study, we investigated permeation properties of single gas ($N_2$, $O_2$, $CO_2$) through membranes composed of poly(ethylene oxide) (PEO) and poly(ethylene-co-vinyl acetate) (EVA) blend. The prepared membranes showed no new absorbance peaks, which indicate the physical blending of PEO and EVA by FT-IR analysis. SEM observation showed that the crystalline phase of PEO decreased with increasing EVA content in the PEO/EVA mixed matrix. DSC analysis showed that the crystallinity of the PEO/EVA blend membrane decreased with increasing EVA content. Gas permeation experiment was performed with various feed pressure (4~8 bar). The permeability increased in the following order: $N_2$ < $O_2$ < $CO_2$. The permeability of $CO_2$ in PEO/EVA blend membranes were increased with increasing feed pressure, However, the permeability of $N_2$ and $O_2$ were independent of feed pressure. On the other hand, the permeability of all the gases in PEO/EVA blend membranes increased with increasing amorphous EVA content in semi-crystalline PEO. In particular, the blend membrane with 40 wt% EVA showed $CO_2$ permeability of 64 Barrer and $CO_2/N_2$ ideal selectivity of 61.5. The high $CO_2$ permeability and $CO_2/N_2$ ideal selectivity are attributed to strong affinity between the polar ether groups of PEO or the polar ester groups of EVA and polar $CO_2$.

• The Journal of the Acoustical Society of Korea
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• v.33 no.2
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• pp.87-93
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• 2014

If one identifies the detailed distribution of pressure and axial velocity at a source plane, the position and strength of major noise sources can be known, and the propagation characteristics in axial direction can be well understood to be used for the low noise design. Conventional techniques are usually limited in considering the constant source characteristics specified on the whole source surface; then, the source activity cannot be known in detail. In this work, a method to estimate the pressure and velocity field distribution on the source surface with high spatial resolution is studied. The matrix formulation including the evanescent modes is given, and the nearfield measurement method is proposed. Validation experiment is conducted on a wide duct system, at which a part of the source plane is excited by an acoustic driver in the absence of airflow. Increasing the number of evanescent modes, the prediction of pressure spectrum becomes further precise, and it has less than -25 dB error with 26 converged evanescent modes within the Helmholtz number range of interest. By using the converged modal amplitudes, the source parameter distribution is restored, and the position of the driver is clearly identified at kR = 1. By applying the regularization technique to the restored result, the unphysical minor peaks at the source plane can be effectively suppressed with the filtering of the over-estimated pure radial modes.

• Tunnel and Underground Space
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• v.29 no.4
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• pp.262-279
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• 2019

In the engineering barriers of high-level radioactive waste disposal, gases could be generated through a number of processes. If the gas production rate exceeds the gas diffusion rate, the pressure of the gas increases and gases could migrate through the bentonite buffer. Because people and the environment can be exposed to radioactivity, it is very important to clarify gas migration in terms of long-term integrity of the engineered barrier system. In particular, it is necessary to identify the hydro-mechanical mechanism for the dilation flow, which is a very important gas flow phenomenon only in medium containing large amounts of clay materials such as bentonite buffer, and to develop and validate new numerical approach for the quantitative evaluation of the gas migration phenomenon. Therefore, in this study, we developed a two-phase flow model considering the mechanical damage model in order to simulate the gas migration in the engineered barrier system, and validated with 1D gas flow modelling through saturated bentonite under constant volume boundary conditions. As a result of numerical analysis, the rapid increase in pore water pressure, stress, and gas outflow could be simulated when the dilation flow was occurred.

• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.92-96
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• 2009

Nowadays, many research groups try to achieve the high Xe mole fraction discharge gas for high efficiency in AC-PDPs. However, the high Xe mole fraction discharge gas causes the high discharge voltage, which is a serious problem in AC-PDP's for high efficiency. In this study, the discharge gas with high Xe mole fraction and the low pressures has been applied and it's discharge voltage and vacuum ultraviolet emission characteristics have also been measured. It is shown that the discharge voltage is 354V and 389V at Ne+Xe (15%) with 400 Torr and Ne+Xe (30%) with 200 Torr, respectively. Their vacuum ultraviolet emission characteristics have similar characteristics to each other, in which their wavelengths are ranged from 140 nm to 200 nm. It is found in this experiment that the luminous efficiency for the discharge gas of Ne+Xe (30%) with 200 Torr is drastically increased by about 30%.