• Transactions of the Korean hydrogen and new energy society
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• v.31 no.1
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• pp.73-81
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• 2020

For the fault tree analysis (FTA) analysis of the packaged hydrogen filling station, the composition of the charging station was analyzed and the fault tree (FT) diagram was prepared. FT diagrams were created by dividing the causes of events into external factors and internal factors with the hydrogen event as the top event. The external factors include the effects of major disasters caused by natural disasters and external factors as OR gates. Internal factors are divided into tube tailer, compressor & storage tank, and dispenser, which are composed of mistakes in operation process and causes of accidents caused by parts leakage. In this study, the purpose was to improve the hydrogen station. The subjects of this study were domestic packaged hydrogen stations and FTA study was conducted based on the previous studies, failure mode & effect analysis (FMEA) and hazard & operability study (HAZOP). Top event as a hydrogen leaking event and constructed the flow of events based on the previous study. Refer to "Off shore and onshore reliability data 6th edition", "European Industry Reliability Data Bank", technique for human error rate prediction (THERP) for reliability data. We hope that this study will help to improve the safety and activation of the hydrogen station.

• Journal of Biosystems Engineering
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• v.23 no.4
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• pp.319-326
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• 1998

A herbicide applicator attached to a rice transplanter was developed to perform herbicide application and transplanting simultaneously. The prototype machine was composed of herbicide tank, discharge device, spinner, scattering plate and power drive. The application rate of the machine could be adjusted from 10 to 30 kg/㏊ and the application swath was 1.8m. According to the field test, application uniformity showed the range of 13.6~43.9％ in terms of CV(coefficient of variation) depending on the spinner speed, application height and shape of diffuser. The best uniformity could be achieved with the spinner speed of 30.8m/s and application height of 20cm. Field efficiency of the prototype was 4.7hr/㏊. Transplanting machine has field efficiency of 4.6hr/㏊ in Korea. By attaching the herbicide applicator, field efficiency became lowed only by 0.1hr/㏊, which was counted for filling time of herbicide. Simultaneous operation of transplanting and herbicide application had a of labor saying. The weed control efficacy was measured to be 96% in field when AC140 + Stomp and Londax + YRC was applied at the 65th day after transplanting. Nonanmae was treated by manual application to be compared to.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.89-95
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• 2003

Propulsion system of the current developing satellite is roughly composed of propellant tank and four major modules. Each module prevides the pulse momentum for spacecraft attitude control, filling/draining of propellant and pressurant, propellant filtering, and the change of flow passage in the spacecraft emergency situation, respectively. These modules will be fixed on the propulsion platform with their suitable mounting brackers, so the brackets shall be designed sufficiently to support a function of the modules under launch environment and on-orbit condition. The purpose of this article is to check if all the bracket designs satisfy the defined structural requirements through finite element analysis, and then to verify structural safety.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.6
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• pp.485-493
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• 2017

In this study, the collision analysis of SCP(Sandwich Concrete Panel) composing the outer tank of LNG storage was performed and its collision behavior was analyzed. For the same collision energy value proposed in BS7777 code, the collision conditions are composed by using two types of missiles and various collision speeds. Nonlinear dynamic analysis models were constructed to perform numerical analysis on the various collision conditions. Also, the collision behavior was analyzed assuming that the second collision with the same collision energy occurs at the same point after the first collision. As a result of the analysis, it was found that with smaller missile and low collision speed had caused larger deformation. The collision energy dissipated in ratio of about 6: 4 in the outer steel plate and the inner filling concrete. In the results of double collision analysis, the final collisional deformation was dominated by the size of the second missile, and the amount of deformation due to the second collision was smaller than that of the first collision because of the membrane behavior of the steel plates. In the offset double collision cases, the largest deformation occurs at the secondary collision point regardless of the offset distance.

• Journal of Sensor Science and Technology
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• v.6 no.3
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• pp.172-179
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• 1997

This paper describes a multiplexed-multivariate fiber-optic interferometric sensor system with remote sensing capability. Signal processor of the implemented sensor system is designed as a digital fringe counter that is well adapted to the signal processing of the remote fiber-optic Fabry-Perot interferometric sensor array. By summing up the reported optical data of the optical fiber, a guideline for choosing the optical effect suitable for a specific measurand is presented. As an example, a pressure sensing device that utilizes the strain-optic effect of the optical fiber by attaching it onto a stainless steel diaphragm of which diameter is 4.3 cm, is built and attached to the sensor system. The changes in optical phase difference of the fiber-optic Fabry-Perot interferometric press ure sensor while filling a water tank 2 meters high, was counted by the half-fringe counting signal processor. Test results showed that the measurement error is less than ${\pm}3.6\;cm$ over the measured range of 2 meters.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.2
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• pp.155-163
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• 2014

At gas stations, liquid fuels expand and contract in volume owing to temperature variations. In Korea, the ambient temperature varies between $-15^{\circ}C$ in winter and $35^{\circ}C$ in summer. The volume expansion coefficients of liquid fuels are about $0.1%/^{\circ}C$. To investigate this issue, we measured daily changes in fuel temperature and the delivered fuel temperature at gas stations. In addition, we scrutinized the daily, monthly, and annual changes in temperature over past 50 years in Korea. The results show that the temperature of the fuel in the storage tank was maintained at a stable value(summer or winter). Many factors, such as the surrounding conditions, fuel filling frequency, and gas station location, influence the delivered fuel temperature. The results of this study can be applied for establishing a national regulation and will contribute to fair transactions.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.109-116
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• 2012

A vent-relief valve performs as a safety-valve assembly for liquid propellant feeding system of space launch vehicle, which relives pressurant propellant tanks during the filling and the flight. At vent mode, valve is opened and closed by driving pneumatic pressure, and at relief mode, valve is automatically operated to set relief pressure. In this study, we have analyzed a basic layout of vent-relief valve which is designed using foreign LVs(Saturn) to satisfy requirements of Korean Space Launch Vehicle. The simulation model of vent-relief valve is designed by using the AMESim code to verify design parameters and evaluate pneumatic behaviors of valve. In this study, we performed dynamic characteristic simulations on design parameters. And we could predict opening/closing time and pressures, operating performances on design parameters. Using this results, we could suggest detail design and boundary conditions of design.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.6
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• pp.70-77
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• 2011

A ventilation-relief valve performs as a safety-valve assembly for the liquid-propellant feeding system of space launch vehicle. This valve plays a role of relieving the vaporized propellants from propellant tanks during the filling and storing stages of propellants. Also it regulates to maintain the pressure of ullage volume of on-board propellant tanks within the safety-margin during the flight. The simulation model of ventilation-relief valve is designed with AMESim to predict and evaluate the dynamic characteristics and pneumatic behaviors of valve. To validate a valve simulation model, the simulation results of the opening and closing pressures and their operating durations of valve by AMESim analysis are compared with the results of mathematical methods. In addition, the results of internal flow simulation with FLUENT are utilized to improve the accuracy of valve-modeling. This study will serve as one of reference guides to enhance the developmental efficiency of ventilation-relief valves with the various operating conditionss, which shall be used in Korea Space Launch Vehicle-II.

• Journal of Environmental Health Sciences
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• v.38 no.6
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• pp.503-509
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• 2012

Objectives: This study was performed in order to evaluate the generation characteristics of airborne bacteria and fungi while operating a household humidifier, in consideration of user habits. Methods: Microbial samples were collected in a closed chamber with a total volume of 2.76 $m^3$, in which a humidifier was operated according to experimental strategies. A cultivation method based on the viable counts of mesophilic heterotrophic bacteria and fungi was performed. Experimental strategies were divided into three classes: the type of water in the water reservoir (tap water, cooled boiled water); the frequency of filling the reservoir (refill every day, no refill); and the sterilization method (sterilization function mode, humidifier disinfectants). Results: Significant increases in the concentration of airborne bacteria were observed while the humidifier was in operation. The concentration had increased to 2,407 $CFU/m^3$ by 120 hours when tap water filled the reservoir without any application of sterilization, while for cooled boiled water, it was merely 393 $CFU/m^3$ at a similar time point. Usages of disinfectant in the water tank were more effective in decreasing bioaerosol generation compared to sterilization function mode operation. Generation characteristics of airborne fungi were similar to those of bacteria, but the levels were not significant in all experiments. Calculated exposure factor can be used as an indicator to compare biorisk exposure. Conclusion: This study identified the potential for bioaerosol generation in indoor environments while operating a household humidifier. User practices were critical in the generation of bioaerosol, or more specifically, airborne bacteria. Proper usage of a humidifier ensures that any biorisks resulting from generated bioaerosol can be prevented.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.10
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• pp.711-718
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• 2014

Investigated the processing characteristics of the pollutants and runoff due to storm events in the actual application of the road fields and a Non-Point Sources (NPS) pilot scale equipment. This phenomenon has occurred in the influent bypass the blockage occurs after 90 min the expended polymeric media was filled with filtered column. When entering a treatment tank SS 200 mg/L or more high concentration of effluent treatment efficiency was reduced from the reaction time 60 min. Influent concentration less then SS 180 mg/L was stable handling. The $COD_{Cr}/SS$ ratio were analyzed with 0.67, median value. Showed 92.1% and 82.3% respectively with an average removal rate of the SS and the $COD_{Cr}$. If the influent concentration of TP is the 0.5 mg/L or less, the quality of the treated water is 0.1 mg/L levels were expressed in a stable process. And when entering the 1.0 mg/L or more of the treated water, had a greater than average 0.2 mg/L. If the influent concentration of TN is 4~10 mg/L, the treatment water quality level was kept a 1.5~3.0 mg/L. The average removal efficiency of TP and TN respectively 73.9%, 50.4%.