• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.63-69
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• 2012

Recently, the cement industries brought very severe environment problems such as resource depletion and global warming with massive carbon dioxide during its production. The number of cases using industrial by-products such as the ground granulated blast furnace slag (GGBFS) in concrete mixtures is increasing to resolve the environmental issue. GGBFS is mainly used in the range between 20 to 50% to replace cement, but nowadays lots of researches are carried out to develop the alkali-activated slag (AAS) concrete with no cement. In this study, the early age properties of alkali activated slag (AAS) mortar are investigated to obtain the fundamental data for AAS concrete application to structural members. The experimental variables were the water-binder ratios of 0.3, 0.4, and 0.5 and NaOH as the alkali activator of 4%, 8%, and 12% by the mass of GGBFS, and compressive strength, flow, setting time, and ultrasonic pulse velocity of AAS mortars were measured and analyzed. It is found from the test results that as the normal concrete the lower W/B, the higher compressive strength. However, superplasticizer has to be used for producing high strength AAS concrete because the workability of AAS mortar are significantly lowered.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.3
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• pp.194-204
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• 2007

A numerical analysis and hydraulic experiments were undertaken to investigate the head loss occurring when a flow passes through vertical perforated walls. The numerical analysis applied continuity, momentum and energy equations to the control volumes that were set near the perforated wall. Non-dimensional equations were then derived to calculate both upstream depth and head loss for the given values of downstream depth and velocity. The hydraulic experiments were performed with several single and triple perforated plates varying their opening ratios and intervals. The numerical results with the single plates were compared with the experimental results, and it was shown that the contraction coefficient of the vertical line jet formed after the perforated plates relies on downstream Froude number as well as opening ratio. Based on the experimental results, empirical formulas were formulated. Finally, the formulas were applied to the triple plates sequentially from downstream side to upstream side, and it was found that in general the predicted values nicely agreed with the experimental results.

• Journal of the Korean Association of Geographic Information Studies
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• v.11 no.2
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• pp.85-92
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• 2008

This study, the one concerning the evaluation analysis of the function of the wind generation using KLAM_21, has examined closely how the wind really flows on the space of the city, working with the object of case location. In the first place, the cold air formed at upper stream of Sincheon river, a ravine of whole area of Gachang gully and an inclined plane of neighboring mountainous district, flows to the north and expands itself along the upper stream of the Sincheon river, and as the time passes, it is tending upwards in the change of the volume and height as well as of the velocity and direction, of the cold air. It was learned that this phenomenon has made it clear that the spatial features of this area give rise to very good condition in generating and flowing the cold air. Meanwhile, it has been shown that in the area of park in the Ap-mountain, the generation and flow of the cold air are much interrupted because of the overpass traversing the whole area of the park of Ap-mountain, the congested area of large-scaled apartments and the urban development activities constructing the building in the park, and the volume and height of the cold air has been grown very small. In conclusion, It has been learned that for maximization of the spatial effect of the wind corridor, the areas where the cold air is generated, flowed, accumulated, and maintained, have to be connected spatially, and this spatial connection has a close relation with spatial features of the area.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.9
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• pp.654-659
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• 2013

This study was conducted to identify an optimal ratio of carbon to nitrogen (C/N ratio) for denitrification of nitrate using molasses as an external carbon source. A series of batch and column tests was conducted using an indigenous bacterium Pseudomonas sp. KY1 isolated from a nitrate-contaminated soil. For the initial nitrate-nitrogen concentration of 100 mg-N/L, batch test results indicated that C/N ratio of 3/1 was the optimal ratio with a relatively high pseudo-first-order reaction constant of $0.0263hr^{-1}$. At C/N ratio of 3/1, more than 80% of nitrate-nitrogen concentration of 100 mg-N/L was removed in 100 hrs. Results of column tests with a flow velocity of 0.3 mL/min also indicated that the C/N ratio of 3/1 was optimal for denitrification with minimizing remaining molasses concentrations. After 172 hrs of column operation (35 pore volumes) with an influent nitrate-nitrogen concentration of 100 mg-N/L, the effluent met the drinking water standard (i.e., 10 mg $NO_3$-N/L).

• Journal of Korea Water Resources Association
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• v.37 no.1
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• pp.77-86
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• 2004

This paper presents a reservoir operation plan coupled with storage forecasting model to maintain a target storage and a critical storage. The observed storage data from 1990 to 2001 in the Geum-Gang agricultural reservoir in Korea have been applied to the low flow frequency analysis, which yields storage for each return period. Two year return period drought storage is then designated as the target storage and ten year return period drought storage as the critical storage. Storage in reservoir should be forecasted to perform reasonable reservoir operation. The predicted storage can be effectively utilized to establish a reservoir operation plan. In this study the autoregressive error (ARE) model and the ARIMA model are adopted to predict storage of reservoir. The ARIMA model poorly generated reservoir storage in series because only observed storage data were used, but the autoregressive error model made to enhance the reliability of the forecasted storage by applying the explanation variables to the model. Since storages of agricultural reservoir with respect to time have been affected by irrigation area, high or mean temperature, precipitation, previous storage and wind velocity, the autoregressive error model has been adopted to analyze the relationship between storage at a period and affecting factors for storage at the period. Since the equation for predicting storage at a period by the autoregressive error model is similar to the continuity equation, the predicting storage equation may be practical. The results from compared the actual storage in 2002 and the predicted storage in the Geum-Gang reservoir show that forecasted storage by the autoregressive error model is reasonable.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.82-82
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• 2009

Although leakage at a low carbon steel pipe made by electrical resistance welding(ERW) was reported due to grooving corrosion, the cause for the corrosion has not yet been cleared. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the corrosion test carried out using the ERW carbon steel pipe by changed the water speed and heat input in a month. The level of dissolved oxygen is maintained 5~5.5mg/l(amount of dissolved oxygen in tap water). The water speed for corrosion test is 1m/s, 2m/s, 3m/s. As the results, grooving corrosion rate is increased cause by water speed in the pipe. In the case of the ERW pipe with more heat input, grooving corrosion rate is decreased. It is therefore that welding heat input should be controlled based on the carbon content of the pipe in order to improve the corrosion reistance of the ERW pipe.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.730-738
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• 1992

Filtration characteristics according to membrane materials were studied In the ultrafiltration of anaerobic digestion broth as a post treatment method. A series of resistances for different membranes were quantitatively assessed on the basis of the resistance-in-series model. Flux behavior observed with the digestion broth was irrelevant to initial water permeabilities of each membrane. The fluoro polymer membrane showed the most significant improvement of flux with increase of cross-flow velocity, which suggests that the cake layer formed on this membrane is more weakly attached to the membrane surface than those on the other membranes. Flux reduction during longtime running was attrib-used to the polarization layer resistance ($R_p$) as well as the fouling layer resistance($R_f$). Continuous increase of $R_p$ may reflect the variation in the characteristics of cake layers, which could result from size, shape, and structure changes due to lysis and growth of biomass. Hydrophilic cellulosic membrane had a much lower fouling tendency than hydrophobic polysulfone membrane. The depressurization method induced a small increase in flux of $5-10L/m^2/h$. During washing and cleaning, filtrability of each membrane was rapidly recovered within 15 minutes until a stationary value was reached.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1576-1581
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• 2013

In the present study, the performance of a PF heat exchanger for heat pump dryer was investigated. Capacity and dehumidification amount of the PF heat exchangers(PF1, PF2, PF3) by different inclination angles($0^{\circ}$, $30^{\circ}$, $60^{\circ}$) were studied. Experimental conditions were an air velocity crossing to the heat exchanger(0.5m/s), an air dry-bulb temperature($60^{\circ}C$) and relative humidity(70%). The experimental results have shown that the performance of the inclined PF heat exchangers was better than that of the vertically installed one. PF3 showed better performance compared to PF1 and PF2 due to the large pin pitch which are leading to more draining for dehumidified water. But, capacity and dehumidification amount of the PF heat exchanger at the inclination angles of $60^{\circ}$ was decreased due to pressure drop. Also, to predict the experimental data of the PF heat exchanger, the performance program was developed for the inclination angles of $0^{\circ}$. PF heat exchanger performance between experiment data and calculation data was satisfied within the maximum 2% for capacity and 3% for dehumidification amount.

• Korean Journal of Veterinary Research
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• v.39 no.1
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• pp.230-239
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• 1999

Digital color doppler ultrasonographic system(DCDUS) has a lot of diagnostic functions. One of these is a detection of low velocity vessels in the organs of abdominal cavity. The purpose of study was to determine the clinical usefulness of DCDUS. Interlobar artery resistive index(RI), pulsatility index(PI) and systolic diastolic ratio(SDr) were measured for diagnosis of obstructed urinary tract. RI, PI and SDr were a measure of intrarenal blood flow impedance. This study was consisted of 2 groups. The normal group was studied in 16 normal adult dogs and the study group was studied 7 dogs with surgically induced, unilateral ureteral obstruction. In the study group, parameters were checked in normal condition and on 1, 2, 3, 5, 7 and 10th day after ligation. The result were summarized as follows. In the normal group, RI, PI and SDr of the left kidney was $0.65{\pm}0.04$, $1.25{\pm}0.12$ and $292.45{\pm}29.40$, respectively. RI, PI and SDr of the right kidney were $0.64{\pm}0.05$, $1.28{\pm}0.20$ and $282.25{\pm}37.26$, respectively. In the study group, RI of the left kidney induced ligation was increased significantly on 1, 2, 3, 5, 7 and 10th day. RI of the left kidney on 1, 2, 3, 5, 7 and 10th day were $0.75{\pm}0.05$, $0.71{\pm}0.03$, $0.74{\pm}0.04$, $0.74{\pm}0.02$, $0.73{\pm}0.02$ and $0.73{\pm}0.04$, respectively. PI of the left kidney was increased significantly on 1, 3, 5 and 7th day. PI of the left kidney on 1, 3, 5 and 7th day were $1.57{\pm}0.21$, $1.54{\pm}0.24$, $1.60{\pm}0.15$ and $1.60{\pm}0.26$, respectively. SDr of the left kidney increased significantly on 1, 2, 3, 5 and 7th day. SDr of the left kidney on 1, 2, 3, 5 and 7th day were $412.18{\pm}86.69$, $352.14{\pm}47.05$, $399.77{\pm}65.54$, $369.43{\pm}48.34$ and $365.57{\pm}22.46$, respectively(p<0.05). In the study group, RI of the left kidney was more increased than that of the right kidney on 1, 2, 3, 5, 7 and 10th day. PI of the left kidney was more increased than that of the right kidney on 1, 3, 5, and 7th day. SDr of the left kidney was more increased than that of the right kidney on 1, 2, 3, 5 and 7th day(p<0.05). RI was effective in the diagnosis of an acute unilateral ureteral obstruction. PI and SDr were insufficient in the diagnosis of an acute unilateral ureteral obstruction.

• Journal of Energy Engineering
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• v.28 no.4
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• pp.35-41
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• 2019

In order to overcome these disadvantages, the halogen light source, which was previously used as a vehicle fog light, has increased power consumption and a short lifetime, and thus, an automobile light source is gradually being replaced with an LED. However, when the vehicle LED fog light is turned on, there is a disadvantage in reducing the life of the fog lamp due to the high heat generated from the LED. The heat generated by the LED inside the fog lamp is mainly emitted by the heatsink, but most of the remaining heat is released to the outside through convection. When cooling efficiency decreases due to convection, thermal energy generates heat to lenses, reflectors, and bezels, which are the main parts of lamps, or generates high temperatures in LED, thereby shortening the life of LED fog lights. In this study, we tried to improve the heat dissipation performance by convection in addition to the heat dissipation method by heat sink, and to determine the installation location of vents that can discharge the internal air or intake the external air of LED fog lamp for vehicle. Thermal fluid analysis was performed to ensure that the optimal data were reflected in the design. The average velocity of air increased in the order of Case3 and Case2 compared to Case1, which is the existing prototype, and the increase rate of Case3 was relatively higher than that of other cases. This is because the vents installed above and below the fog lamps induce the convective phenomena generated according to the temperature difference, and the heat is efficiently discharged with the increase of the air speed.