• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.533-542
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• 2016

We investigate fluidization characteristics of the mixture of rice husk, silica sand and rice husk ash as a preliminary study for valuable utilization of rice husk ash obtained from gasification of rice husk in a fluidized bed reactor. As experiment valuables, the blending ratio of rice husk and sand (rice husk: sand) is selected as 5:95, 10:90, 20:80 and 30:70 on a volume base. Rice husk ash was added with 6 vol% of rice husk for each experiment and air velocity to the reactor was 0~0.63 m/s. In both rice husk/sand and rice husk/sand/ash mixture, the minimum fluidization velocity (Umf) is observed as 0.19~0.21 m/s at feeding of 0~10 vol.% of rice husk and 0.30 m/s at feeding of 20 vol.% of rice husk. With increasing the amount of rice husk up to 30 vol.%, $U_{mf}$ can not measure due to segregation behavior. The mixing index for each experiment is determined using mixing index equation proposed by Brereton and Grace. The mixing index of the mixture of rice husk/sand and rice husk/sand/ash was 0.8~1 and 0.88~1, respectively. The optimum fluidization condition was found for the good mixing and separation of rice husk ash.

• Journal of the Korean GEO-environmental Society
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• v.14 no.8
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• pp.11-21
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• 2013

In-situ test to find the change of $Fe^{2+}$ and $Mn^{2+}$ concentrations and ion contents in groundwater was conducted during two pumping tests at the riverbank filtration site, where is the riverine area of the Nakdong River in Changnyeong-Gun. Groundwater was sampled at one pumping well and 10 monitoring wells during a 5 steps drawdown pumping test with the rates from $500m^3/day$ to $900m^3/day$ and a constant pumping test with $800m^3/day$. The change in ion concentration of groundwater was more remarkable during a step drawdown pumping test than a constant pumping test. Especially, the decrease in $Fe^{2+}$ and $Mn^{2+}$ concentrations was distinct in a step drawdown pumping test and it happens predominantly along the direction that the radius of pumping influence was small due to a good aquifer connectivity to a pumping position. The precipitation and the oxidation of iron and manganese were caused by an air inflow and a disturbance in groundwater flow due to an abrupt change in pumping rate. The pumping rate and spatial distribution of an aquifer around a pumping well need to be considered as an important factor for the development of in-situ iron and manganese treatment technology.

• Tuberculosis and Respiratory Diseases
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• v.39 no.2
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• pp.141-149
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• 1992

In order to establish predicted normal values of volume of isoflow($V_{iso}\dot{V}$), $V_{iso}\dot{V}$ were measured in a total 234 healthy adults, consisting of 78 male nonsmokers, 108 male smokers and 48 female nonsmokers. The volumes of isoflow were determined through analysis of maximal expiratory flow volume curves recorded with a mixture of 80% helium and 20% oxygen(He-$O_2$ gas) following one(1VC) and three vital capacity(3VC) maneuver and with room air. Based upon the correlation of the observed values of the parameters to age and physical characteristics, the following regression formulars for the prediction of the parameters, using age in year(A) as a variable, were obtained. 1VC method ($V_{iso}\dot{V}_1$) Male smoker : 0.614A+2.347 Male nonsmoker : 0.370A-2.792 Female nonsmoker : 0.588A-2.459 3VC method ($V_{iso}\dot{V}_3$) Male smoker : 0.467A+1.696 Male nonsmoker : 0.288A-1.538 Female nonsmoker : 0.367A-0.114.

• Ocean Systems Engineering
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• v.6 no.3
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• pp.245-264
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• 2016

The iterative boundary element method (IBEM) developed originally before for cavitating two-dimensional (2-D) and three-dimensional (3-D) hydrofoils moving under free surface is modified and applied to the case of 2-D (two-dimensional) airfoils and 3-D (three-dimensional) wings over water. The calculation of the steady-state flow characteristics of an inviscid, incompressible fluid past 2-D airfoils and 3-D wings above free water surface is of practical importance for air-assisted marine vehicles such as some racing boats including catamarans with hydrofoils and WIG (Wing-In-Ground) effect crafts. In the present paper, the effects of free surface both on 2-D airfoils and 3-D wings moving steadily over free water surface are investigated in detail. The iterative numerical method (IBEM) based on the Green's theorem allows separating the airfoil or wing problems and the free surface problem. Both the 2-D airfoil surface (or 3-D wing surface) and the free surface are modeled with constant strength dipole and constant strength source panels. While the kinematic boundary condition is applied on the airfoil surface or on the wing surface, the linearized kinematic-dynamic combined condition is applied on the free surface. The source strengths on the free surface are expressed in terms of perturbation potential by applying the linearized free surface conditions. No radiation condition is enforced for downstream boundary in 2-D airfoil and 3-D wing cases and transverse boundaries in only 3-D wing case. The method is first applied to 2-D NACA0004 airfoil with angle of attack of four degrees to validate the method. The effects of height of 2-D airfoil from free surface and Froude number on lift and drag coefficients are investigated. The method is also applied to NACA0015 airfoil for another validation with experiments in case of ground effect. The lift coefficient with different clearance values are compared with those of experiments. The numerical method is then applied to NACA0012 airfoil with the angle of attack of five degrees and the effects of Froude number and clearance on the lift and drag coefficients are discussed. The method is lastly applied to a rectangular 3-D wing and the effects of Froude number on wing performance have been investigated. The numerical results for wing moving under free surface have also been compared with those of the same wing moving above free surface. It has been found that the free surface can affect the wing performance significantly.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.120-126
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• 2009

As the information age grows rapidly, the amount of digital texts has been increasing as well. It has brought an increasing of visualization case in order to figure out lots of digital texts. Existing visualized design of digital text is merely concentrating on figuration of subject word through adoption of stemming algorithm and word frequency extraction, prominence of meaning of text, and connection in between sentences. So it is a fact that expression of rhythm that can visualize sentimental feeing of digital text was insufficient. Syllable is a phoneme unit that can express rhythm more efficiently. In sentences, syllable is a most basic pronunciation unit in pronouncing word, phase and sentence. On this basis, accent, intonation, length of rhythm factor and others are based on syllable. Sonority, which is most closely associated with definitions of syllable, is expressed through air flow of igniting lung and acoustic energy that is specified kinetic energy into sonority. Seen from this perspective, this study examines phonologic definition and characteristics based on syllable, which is properties of digital text, and research the way to visualize rhythm through diagram. After converting digital text into phonetic symbol by the experiment, rhythm information are visualized into images using degree of resonance, which was started from rhythm in all languages, and using syllable establishment of digital text. By visualizing syllable information, it provides syllable information of digital text and express sentiment of digital text through diagram to assist user's understanding by systematic formula. Therefore, this study is aimed at planning for easy understanding of text's rhythm and realizing visualization of digital text.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.10
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• pp.861-867
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• 2001

In this paper, in order to investigate the catalytic effect of the sludge exhausted from waterworks on NO$_{x}$ removal, we measure NO removal characteristics with and without sludge pellets in BaTiO$_3$-sludge packed-bed reactor of plate-plate geometry. NO initial concentration is 50 ppm balanced with air and a gas flow rate is 5ι/min. Gas temperature is changed from 25 to 10$0^{\circ}C$ to investigate the role of sludge pellet on removing active oxygen species and NO$_2$. BaTiO$_3$pellets is filled for coronal discharge at upstream of reactor and sludge pellets is filled for catalytic effect at downstream of reactor. The volume percent of sludge pellets to BaTiO$_3$pellets is changed from 0% to 100% and AC voltage is supplied to the reactor for discharging simulated gases. In the results, when sludge pellets is put at the downstream of plasma reactor, NO removal rate is slightly increased. However, NO$_2$and $O_3$ as by-products during NO removal is significantly decreased from 51ppm without sludge pellets to 5 ppm with sludge pellets and from 50 ppm without sludge pellets to 0.004ppm with sludge pellets, respectively. Therefore, NO$_{x}$(NO+NO$_2$) removal rate is increased up to 93%. It is thought that sludge pellet maybe react with active oxygen species and NO$_2$ generated by corona discharge in surface of BaTiO$_3$pellets, the then NO$_2$O$_3$as by-products are considerably decreased. When we increase gas temperature from room temperature to 10$0^{\circ}C$, NO removal rate is decreased, while NO$_2$ concentration is independent on gas temperature. These result suggest that the removal mechanism of active oxygen species and NO$_2$in sludge pellet is not absorption, but chemical reaction. Therefore we expect that sludge pellets exhausted for waterworks could be used as catalyst for NO$_{x}$ removal with high removal rate and low by-product.oduct.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.509-516
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• 2012

The aims of this research is to develop a fire resistant admixture to enhance high-pressured pumping of high-strength concrete (HSC) with a compressive strength of 60~80 MPa. Generally, the efficiency of HSC high-pressured pumping is dramatically reduced due to entanglement of short fibers added to prevent fire spalling. Therefore, the fire resistant admixture that can facilitate pumping of fire resistant HSC is urgently needed presently. The fire resistant HSC mix is comprised of Polypropylene fiber, Nylon fiber and Polymer powder. The test results showed that the slump-flow was improved by approximately 70% of the HSC without fire resistant admixture. However, the air void content was increased slightly due to the addition. The standard design compressive strength at 28-days was satisfied, while its flexural strength was similar to the concrete without the admixture. Since the flexural strength was 12~15% of its compressive strength, the general trend of flexural to compressive strength ratio in normal concrete was maintained. Even though its elastic modulus was decreased by adding the admixture, the study results showed that the concrete can be used for construction since all of the test results exceeded the code requirements.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.27-36
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• 2018

A significant amount of studies were performed on evaporation heat transfer and pressure drop in microfin tubes. Most studies, however, focused on the refrigerants used in air-conditioners or heat pumps, and very limited information is available on R-404A, which is used in low temperature refrigeration. In this study, the evaporation heat transfer and pressure drop characteristics of R-404A in a 9.5 mm O.D. microfin tube were investigated for the mass flux range from $80kg/m^2s$ and $200kg/m^2s$. A smooth tube of the same outer dimeter was also tested for comparison. The results showed that the heat transfer enhancement ratio of the microfin tube increased with increasing mass flux and the heat flux decreased. The relative contribution of the convective heat transfer and the heat flux on total heat transfer was attributed to the observed trend. The pressure drops of the microfin tube were slightly (maximum 28%) larger than those of the smooth tube. Existing correlations do not adequately predict the measured heat transfer coefficients of pressure drops, probably due to the test range of the present study, which is outside of the existing correlations.

• Journal of Korea Soil Environment Society
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• v.3 no.2
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• pp.101-114
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• 1998

Soil vapor extraction (SVE) is known to be an effective process to remove the contaminants from the soils by enhancing the vaporization of organic compounds using forced vapor flows or applying vacuum through soils. Experiments are carried out to investigate the effects of the organic contaminants, types of soils, and water contents on the removal efficiency with operating time. In the study, simulated soils include the glass bead which has no micropore, sand and molecular sieve which has a large volume of micropores. As model organic pollutants, toluene, methyl ethyl ketone, and trichloroethylene are selected. Desorption experiments are conducted by flowing nitrogen gas. Under the experimental conditions, it is found that there are linear relationships between logarithm of removal efficiency and logarithm of number of pore volumes. The number of pore volumes are defined as the total amount of air flow through the soil column divided by the pore volume of soil column. For three organic compounds studied, the removal rate is slow for no water content, while the number of pore volumes for removal of organic compounds are notably reduced for water contents up to 37%. For the removal of dense organic compound, such as trichloroethylene, a large number of pore volumes are needed. Also, the effects of the characteristics of simulated soils on the removal efficiency of organic compounds are studied. After the characterization of soil surface, porosity of soil columns and types of contaminants, the results could provide a basis for the design of SVE process.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.404-406
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• 2009

This study note wished to introduce special-purpose ship for algae removal that is developed by core technology of our country. The ship is consisted of main frame and adjuvant that can attach and detach as cross (+) shape of a character. The characteristics of ship are super light weight and low draft. That is consisted of four devices as suction, collection, filtration and recovering units. Among these, filtration used screen filter (mesh size 30 ${\mu}m$). Also, can separate and remove water and algae by compression air participle notion. Percentage of moisture content of concentrated algal particle was 85%. Water parted with algae finally is exhausted to water area. Removal efficiency that compare by chlorophyll-$\alpha$ concentration was about 57% (inflow: 83.2 ${\mu}g\;L^{-1}$, outflow: 35.8 $[\mu}g\;L^{-1}$) without physical and chemical pretreatment. Forward, need to achieve effect test in various conditions (algal biomass, flow etc.) for efficiency and technological elevation of exclusion device. We wished to contribute in presuppression system construction of massive algal development that manage blue-green algae occurrence area effectively, and prevents spread as lower part of reservoir.