• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.5
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• pp.356-367
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• 2001

A numerical analysis on branch type sparger in drain tank for depressurization is performed to investigate the flow characteristics due to the change of design factor. As the result of this study, sparger\\`s flow resistance coefficient(K) is 3.53 at the present design condition when engineering margin for surface roughness is considered as 20%, and flow ratio into branch pipe ($Q_s/Q_i$) is 0.41. The correlation for calculating flow resistance coefficients as design factor is presented. Flow resistance coefficient is increased as section area ratio of branch pipe for main pipe and outlet nozzle diameter of main pipe decreasing, but the effects of branch angle and inlet flow rate of main pipe are small. As the change rate of ($Q_s/Q_i$)becomes larger, the change rate of flow resistance coefficient increases. The rate of pressure loss has the largest change as section area ratio changing. The condition of maximum flow resistance in sparger is when the outlet nozzle diameter ratio of main pipe ($D_e/D_i$) is 0.167, the section area ratio ($A_s/A_i$) is 0.1 and the branch angle ($\alpha$) is 55^{\circ}$.

• Journal of the Korean Society of Visualization
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• v.18 no.1
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• pp.11-17
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• 2020

The reduction of CO2 emissions has been a key target in the marine industry since the IMO's MEPC published its findings in 2009. Air lubrication method is one of the mature technologies for commercialization to reduce the frictional resistance and enhance fuel efficiency of ships. Since the air lubrication pattern varies according to the ship's standing position and injection flow rate, in order to effectively control the air lubrication system, it is necessary to be able to judge the air layer development state based on the information collected from the monitoring sensor. In this study, we performed the air lubrication ship simulation experiment to measure the void fraction and the frictional resistance. The void fraction was measured to confirm the behavior of the air. Through the measurement of the frictional resistance, the change in frictional resistance reduction rate from the injection point to the longitudinal direction of the ship was confirmed. Based on the measurement results, correlation analysis was performed on void fraction and frictional resistance reduction rate.

• Journal of the Korean institute of surface engineering
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• v.53 no.6
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• pp.322-329
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• 2020

The utilization of aluminum scrap is a subject of great importance in terms of reducing energy consumption and environmental protection. However, aluminum scrap contains impurities, which can degrade the properties of aluminum alloy, especially corrosion resistance. This study examines the effect of scrap charge rate of aluminum alloys about microstructures and corrosion characteristics. According to the metallographic examinations, Mg2Si tended to become coarser and its uniformity was decreased by increasing aluminum scrap charge rate. The immersion test exhibited corrosion progressed through the eutectic areas due to micro-galvanic interactions. Electrochemical measurements revealed that excess aluminum scrap could reduce the intergranular corrosion resistance of aluminum alloys. Results showed that the scrap charge rate is important factor in the design of corrosion resistance of aluminum die casting alloys.

• Corrosion Science and Technology
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• v.8 no.5
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• pp.193-196
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• 2009

For the estimation of uncertainty in potentiodynamic polarization resistance measurement, the type A uncertainty was measured using type 316 stainless steel in an acidified NaCl solution. Sensitivity coefficients were determined for measurand such as scan rate of potential, temperature of solution, concentration of NaCl, concentration of HCl, surface roughness of specimen and flow rate of purging gas. Sensitivity coefficients were large for the measurand such as the scan rate of potential, temperature of solution and roughness of specimen. However, the sensitivity coefficients were not the major factors influencing the combined standard uncertainty of polarization resistance due to the low values of uncertainty in measurements of the measurands. A major influencing factor was the concentration of NaCl. The value of type A uncertainty was 1.1 times the value of type B uncertainty, and the combined standard uncertainty was 10.5 % of the average value of polarization resistance.

• Mycobiology
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• v.31 no.3
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• pp.173-178
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• 2003

India has maximum genetic materials in early cauliflower, which grow in subtropical conditions. Different disease parameters like linear growth, maximum growth rate per day, AUDPC, apparent infection rate and percent diseased area were calculated in artificially inoculated plants. Apparent infection rate is not co-related with the black rot disease incidence and should never be considered during characterization of disease resistance and varietal screening. Based on the above disease parameters Kunwari-18, Phool Gobhi Kunwari, Kataki-7 and BT-10-2 were selected as moderately resistance to black rot in early cauliflower. These lines can be used for black rot prone area and also for black rot disease improvement programme. Considering the qualitative and quantitative parameters, slow rotting resistance cauliflower lines are selected as such for cultivation and would be best suited in integrated disease programme.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.961-966
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• 2004

Lateral ballast resistance is one of track components that causes much effects in track buckling. Ballast work or tie renewal if is done the ballast original lateral resistance lose. Reduction of lateral ballast resistance may significantly reduce the stability of track. Lateral ballast resistance that is decreased by these work increases slowly according to the increase of train passing tonnage. We measured the ballast lateral resistance in Okchon station neighborhood in Seoul-Busan line to grasp fluctuation phenomenon of ballast resistance by ballast class-2 work. The rate of decrease of ballast lateral resistance shortly after ballast work and the rate of increase by increase of train passing tonnage were investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.94-97
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• 1997

We investigated the sheet resistance properties of tungsten nitride thin films deposited by RF and DC sputtering system. It deposited at various conditions that determine the sheet resistance. The properties of the sheet resistance of these films were measured under various conditions. Sheet resistance analysed under the flow rate of the argon gas and contents of nitrogen from nitrogen-argon gas mixtures. We found that these sheet resistance were largely depend on the temperature of substrate, gas flow rate and RF power. Very high and low sheet resistance of tungsten films obtained by DC sputtering. As the increase of contents of nitrogen gas obtained from nitrogen-argon gas mixture, tungsten nitride thin films deposited by the reactive DC sputtering and the sheet resistance of these films were increased.

• Journal of Biosystems Engineering
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• v.20 no.4
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• pp.351-359
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• 1995

In pressure cooling system, produce were packed in vented box and cooled rapidly by producing a difference in air pressure on opposite faces of stacks of vented box. So, energy requirements and performance of pressure cooling system depended upon the air flow rate and the static pressure drop through packed produce in vented box. The static pressure drop across packed produce in vented box normally depended upon air flow rate, vent area of box and conditions of produce bed (depth, porosity, stacking patterns, size and shape of products) in box. The objectives of this study were to investigate the effect of vent area and air flow rate on airflow resistance of empty box and packed produce in vented box, and to investigate the relationship between the air flow resistance of packed products in vented box and sum of air flow resistance of empty box only and products in bulk only. Mandarins and tomatoes were used in the experiment. The airflow rate were in the range of 0.02~1.0$m^3$/s.$m^2$, the opening ratio of vent hole were in the range of 2.5~20% of the side area. The results were summerized as follows. 1. The pressure drops across vented box increased in proportion to superficial air velocity and decreased in proportion to opening ratio of vent hole. A regression equation to calculate airflow resistance of vented box was derived as a function of superficial air velocity and opening ratio of vent hole. 2. The pressure drops across packed produce in vented box increased in proportion to superficial air velocity and decreased in proportion to opening ratio of vent hole. 3. Because of the air velocity increase in the vicinity of vent hole in box, the airflow resistances of packed products in vented box were always higher than sum of air flow resistance of empty box only and products in bulk only. 4. Based on the airflow resistance of empty box and products in bulk, a regression equation to calculate airflow resistance of packed products in vented box was derived.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.97-103
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• 2023

Recently, research on the lateral resistance of pile foundations has been actively conducted. In experimental studies on the lateral resistance of pile foundations, displacement control or load control methods are used. However, in the case of the displacement control method, the lateral resistance of the pile varies depending on the rate of the load applied to the pile. Therefore, this study seeks to determine the change in lateral resistance of pile foundations according to lateral loading rate through model experiments. The experimental results showed that the lateral resistance of the pile tended to decrease as the lateral loading rate applied to the pile head increased. In order to confirm this, a model experiment of the side change of the ground and pile according to the loading rate was additionally conducted. Through inverse analysis, the change in the depth of the rotation point according to the lateral loading rate was identified. Through the change in the lateral resistance of the pile foundation and the depth of the rotating point according to the lateral loading rate, it was proposed to test the loading rate within 1.5 mm/min during the lateral loading test of the pile.

• Tuberculosis and Respiratory Diseases
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• v.58 no.3
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• pp.243-247
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• 2005

Background : The prevalence of tuberculosis is slowly decreasing in Korea. However, the drug-resistance of pulmonary tuberculosis is a major risk factor of treatment failure. Moreover, the National Surveillance System has recently been discontinued. Therefore, a continuous survey is necessary for the exact detection of the rate of drug resistance. We studied the recent 4-year drug resistance rate of tuberculosis at a single University hospital in Seoul. Materials and Methods : The study included 239 pulmonary tuberculosis patients performed with a tuberculosis culture and a drug-sensitivity test at Hanyang University Medical Center from March 1999 to March 2003. Results : Of the 239 patients included in the study during the 4-year period, 52 patients showed resistance to one or more anti-tuberculosis drug (21.8%). The rate of multi-drug resistance was 12.6%. The resistance rates to isoniazid, rifampin, ethambutol, streptomycin and pyrazinamide were 18.4%, 13.8%, 11.7%, 6.7% and 8.4%, respectively. Ninety patients had a history of previous anti-tuberculosis treatment, and the rates of the overall drug resistance and multi-drug resistance of these patients were 36.7% and 25.6%, respectively. The patients with drug-resistance showed a higher rate of a previous tuberculosis treatment history (63.5%) than the drug-sensitive group patients (30.5%). Conclusion : The rate of drug resistant tuberculosis is 21.8%, and multi-drug resistant tuberculosis is 12.6%. The rate of drug resistance is higher in those previously treated for tuberculosis.