• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.183-194
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• 2013

Liquid urea based SCR has been used in the market to reduce NOx in the exhaust emission of the diesel engine vehicle. This system has several problems at low temperature, which are freezing below $-12^{\circ}C$, solid deposit formation in the exhaust, and difficulties in dosing system at exhaust temperature below $200^{\circ}C$. Also, it is required complicated exhaust packaging equipment and mixer due to supply uniform ammonia concentration. In order to solve these issues, solid urea, ammonium carbonate, and ammonium carbamate are selected as ammonia sources for the application of solid SCR. In this paper, basic research on reaction rate of three ammonia-transporting materials was performed. TGA (Thermogravimetric Analysis) and DTA (Differential Thermal Analysis) tests for these materials are carried out for various heating conditions. From the results, chemical kinetic parameters such as activation energy and frequency factor are obtained from the Arrhenius plot. Additionally, from test results of DSC (Differential Scanning Calorimeter) for these materials, chemical kinetic parameters using the Kissinger method are calculated. Activation energies of solid SCR from this experiment are compared with proper data of literature study, then obtained data of this experiment are used for the design of reactor and dosing system for candidate vehicle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.200-203
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• 2009

Ultrasonic techniques have the advantage of determining the burning rates with wide range of pressure in only a single test. However, ultrasonic techniques have a drawback, which is that they are using high frequency transducers and it is easily affected by noise. Therefore, ultrasonic measurement method needs noise reduction algorithm to improve or grantee accuracy of burning rate measurements of solid propellants using ultrasound. Thus, in the present study, we propose a noise reduction method of measured ultrasonic signals by applying wavelet shrinkage.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1195-1211
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• 2016

The emerging video coding standard High Efficiency Video Coding (HEVC) has shown almost 40% bit-rate reduction over the state-of-the-art Advanced Video Coding (AVC) standard but at about 40% computational complexity overhead. The main reason for HEVC computational complexity is the inter prediction that accounts for 60%-70% of the whole encoding time. In this paper, we propose several fast coding unit (CU) encoding schemes based on the Merge mode and motion estimation information to reduce the computational complexity caused by the HEVC inter prediction. Firstly, an early Merge mode decision method based on motion estimation (EMD) is proposed for each CU size. Then, a Merge mode based early termination method (MET) is developed to determine the CU size at an early stage. To provide a better balance between computational complexity and coding efficiency, several fast CU encoding schemes are surveyed according to the rate-distortion-complexity characteristics of EMD and MET methods as a function of CU sizes. These fast CU encoding schemes can be seamlessly incorporated in the existing control structures of the HEVC encoder without limiting its potential parallelization and hardware acceleration. Experimental results demonstrate that the proposed schemes achieve 19%-46% computational complexity reduction over the HEVC test model reference software, HM 16.4, at a cost of 0.2%-2.4% bit-rate increases under the random access coding configuration. The respective values under the low-delay B coding configuration are 17%-43% and 0.1%-1.2%.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.6
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• pp.529-537
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• 1992

Airlift pumps were tested to evaluate their pumping and aeration capacities. The pumps were 34.5 inch long made of 2, 3, 4 and 6 inch nominal diameter PVC pipes. An one hp air blower was used to supply the air. The air-flow rate was measured by an anemometer type air-flow meter and air pressure was level changes in a water tank from which water was pumped. Aeration by the pumps was tested by the standard aeration test method with the center of pump outlet positioned 3 inches above water surface. Oxygen concentrations in water were measured to determine aeration rate. As pumping head increased by water level draw-down in the tank water flow decreased while air flow increased. The reduction rate of water flow was higher with 4 and 6-inch pumps. Small pumps showed very minor changes in the reduction. Aeration rates were similar among 3, 4, and 6 inch pumps. With one hp air blower 6-inch pump at the minimum pumping head achieved the best performance in terms of water circulation.

• Journal of Family Resource Management and Policy Review
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• v.12 no.2
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• pp.15-30
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• 2008

According to the research taken by the National Statistical Office, the fertility rate of a Korean fertile female is 1.17. This figure is the lowest in the world, and the reduction in the fertility rate over the last 30 years was the biggest in the world. It can be seen as a warning alarm about the effects of a low birth rate and a silver society. Assuming that there are several factors involved in this phenomenon, this study inquired into the attitude towards children, attitude towards nourishing children, attitude towards sex roles and the harmony between the jobs and families of married females, and examined the factors that influence the willingness to give birth. Final 581 copies of the survey questionnaire were used for analysis and the collected data were analysed by SPSS, Pearson's correlation analysis, t-test, ANOVA, and Duncan's Multiple Range Test. Three main conclusions were reached: Firstly, the value variables, such as sex-role attitudes and the preference for work or home, affect the willingness to give birth. Therefore, it can be said that one's values have a significant effect on these variables and the willingness to give birth. Secondly, both working morns and housewives have a strong tendency to give a birth if they are supported on child rearing. Finally, the employment of the married women itself can be a variable that can affect childbirth. In other words, the working hours affect employed married women so as sex-role attitudes, the preference between work and home, ideal number of children, and the income to housewives. Also, even in whole married women, the employment itself can be a major factor of the willingness to have a baby. Therefore, unemployed married women have more of a tendency to have children than employed married women.

• Journal of Korean Public Health Nursing
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• v.27 no.3
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• pp.513-526
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• 2013

Purpose: The purpose of this study was to determine the effects of the Traditional Play-centered Obesity Control Cooperative Learning Program based on the cooperative learning theory on obesity rate, physical fitness, self-esteem, and body image specifically in obese elementary school children. Methods: The research design for this study was based on a non- equivalent control group pretest-posttest design. The study was conducted from September, 5 to November 30, 2012. The subjects included 74 obese children ($Exp.=25^{(a)}$, $Com.=24^{(b)}$, $Cont.=25^{(c)}$) with an obesity rate above 20% at an elementary school in G City. Data analysis was performed using SPSS/WIN 18.0, using Chi-square test, one-way ANOVA, and Scheffe test. Results: The obesity rate (F=4.033, p<.022) in the experimental group was significantly lower than that in the group (Com, Cont), in which the Traditional Play-Centered Obesity Control Cooperative Learning Program was not implemented. Self-esteem (F=4.310, p<.017) also caused significant differences. However, physical fitness (Muscular endurance F=1.545, p=.220; Flexibility F=.671, p=.514; Agility F=1.594, p=.210; Speed F=5.386, p<.007, scheffe (a,b

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.31 no.2
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• pp.138-146
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• 2021

Objectives: This study aims to compare and evaluate the reduction efficiency of disinfectants used in the domestic meat processing industry to reduce bioaerosol exposure of meat industry workers and to use this as basic data for establishing work environment management measures. Methods: Thirteen disinfectants sold in South Korea were selected for evaluation and the bacterial reduction effect of the disinfectants was investigated. Bacterial suspension and surface disinfection tests were conducted to compare and analyze the antibacterial strength of the disinfectants. Pork carcasses, cutting boards, benches, and conveyor belts were selected for surface sterilization tests. Results: As a result of the bacterial suspension experiment test, all disinfectants had a bacterial reduction efficiency of more than 86%. Among them, the bacterial reduction efficiency of chlorine disinfectants was 99.93% on average. In the results of the pork carcass surface sterilization test, the rate of reduction of disinfectants made of quaternary ammonium compounds (QACs) was the highest. Tests of plastic cutting boards showed that chlorine disinfectants had the best sterilization effect. Experiments on stainless steel benches showed the best bacterial reduction efficiency for chlorine dioxide and QACs disinfectants. In the conveyor belt made of urethane, QACs disinfectants showed excellent sterilization effects. Conclusions: The study evaluated the disinfection power of disinfectants against bacteria occurring in domestic meat processing plants. All disinfectants were found to be effective in bacterial suspension experiments, and chlorine disinfectants were particularly effective. In surface sterilization experiments, sterilizing agents with QACs as the main ingredient were excellent.

• Journal of Soil and Groundwater Environment
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• v.9 no.2
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• pp.1-10
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• 2004

The purpose of this study is to evaluate a laboratory test on arsenic reduction efficiency for ARD (Acid Rock Drainage) using limestone and apatite, and to design an apatite drain system. As a result of the laboratory test, results of this study show that pH, arsenic removal ratio, and dissolution amount of limestone ＆ apatite are inversely proportional to flow rates, and apatite removes 100％ of arsenic at 0.6 ml/min/kg flow rate. It is supposed that dissolution rate of apatite is ten times higher than that of limestone. The arsenic compounds are assumed to be Johnbaumnite, and/or Ca-arsenic hydrate. According to the results of the laboratory test, apatite drain system is designed as follow; Sixty two tons of apatite will be needed per one year and six months, and the precipitates will be removed from the precipitation pond per 3 months.

• Tribology and Lubricants
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• v.36 no.2
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• pp.75-81
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• 2020

In this paper, we present an experimental investigation of the leakage and endurance performances of mechanical face seals in a 75-tonf turbopump for the Korea Space Launch Vehicle II first-stage engine. A mechanical face seal is used between the fuel pump and turbine to prevent mixing of the fuel and turbine gas. However, excessive leakage occurs through the carbon attached to the mechanical face seal bellows. To reduce this leakage, we redesign the mechanical face seal such that the contact area between the fuel and carbon is reduced, height of the carbon nose is reduced, and stiffness of the bellows is increased. Then, we conduct static and dynamic leakage tests and endurance tests to compare the performances of the original and modified mechanical face seals. The investigation of the leakage of the old and new mechanical face seals confirms that the leakage performance is significantly improved, by 80%, in the new design in comparison with the old design. The endurance tests demonstrate that the average wear rate of carbon in the new mechanical face seal is 0.1094 ㎛/s. The service lifetime is predicted to be 4,200 s, which is 28 times greater than the requirement. Finally, we present a new mechanical face seal in a 75-tonf turbopump, and perform a validation test in the real-propellant test facility at the NARO Space Center. Based on the test results, we can confirm that the modified mechanical face seal works well under real operating conditions.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.2
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• pp.25-36
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• 1999

The main objectives of this research are to experimently explain the drilling mechanism for the production of bad holes and good holes during the drilling operation, to investigate how a wide range of drilling parameter affect composite laminate strength reduction, and to find which type of test provides the greatest interrogation of notched composite laminates. To achieve these objectives, a bulk of test specimens have been drilled with 5 different drilling parameters and tested with compressive, tensile, and flexural loads. It was found that the drilling parameters had a measurable effect on specimen hole quality as measured by static strength. The specimens, which were well supported, which had the higher spindle speed and lower feed rate, and which were well clamped gave the best hole qualities. The flexural test results presented the most clear and consistent failure strengths relating to the drilling parameters and associated hole quality.