• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1087-1094
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• 2016

The responsibility of the vehicle holding device (VHD) is to hold the launch vehicle while it is stayed on launch pad and release the holding mechanism to allow a lift-off of launch vehicle at a moment of lift-off. During a release of the holding mechanism, in order to prevent the Ka doing a doing a doing mode which is vertical oscillation of entire liquid propellant and very severe for vehicle structure, gradual release of holding force is required. Also, a release operation of all 4 VHD should be synchronized very precisely. In this study, to comply the "gradual release and synchronized operation requirement", concept of VHD hydraulic system using an accumulator, pyro valve and orifice to control speed of hydraulic cylinder is proposed instead of using complicated hydraulic components. Then through multi-body dynamic analysis and computational hydraulic analysis, a size of orifice to meet a target speed of hydraulic cylinder is calculated. Through this study, simple and reliable VHD hydraulic system complying requirements is designed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.3
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• pp.157-165
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• 2000

A small hydraulic winch system with an automatic tension control unit was designed to improve the work efficiency of coastal small vessels and the dynamic response characteristics of the winch system operated in the open loop condition was investigated. The inlet and the outlet pressures in hydraulic motor, the torque and the rotating speed of winch drum were measured as a function of time, and the behaviour in autotension mode for stepped load changes was analyzed. The results obtained are summarized as follows : 1. The developed winch system for coastal small vessels will result in better fishing with improved efficiency and lower manpower consumption by remote control of winch system. 2. The rotating delay times of winch drum for on/off operations of solenoid valve were 0.09 see at CW mode and 0.04 sec at CCW mode, respectively. After the solenoid valve was controlled, response characteristics were unstable slightly but showed good tracking behaviour over short time. 3. The driving torque of winch system in autotension mode was kept almost constant of 55.9 kgf·m, and 11.1 then the rotating speed of winch drum was kept almost constant of 5.1 rpm in the larger torque than 55.9 kgf·m and 11.1 rpm in the lower torque than that. 4. The 5% settling times in the transient response characteristics of autotension mode under rapid increasing and decreasing conditions of load were 0.12 sec and 0.2 sec, respectively, and then the rotating speeds were 11 rpm and 5.3 rpm, respectively. 5. The tracking behaviour of torque and rotating speed by remote control operation were stable within 0.23 sec at CW mode and 0.37 sec at CCW mode, respectively.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.269-277
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• 1996

The vacuum systems of PLS linac provides average pressure of $2.6\times 10^{-6}$Pa under high power microwave of 54 MW peak with 4.1 $\mu \textrm s$ pulse width and 10 Hz repetition rates. The base pressure of system is$2.4\times 10^{-6}$Pa with 45$^{\circ}C$ cooling water. The outgassing rate of the system is decreased from $3.0\times 10^{-11}Torr-l/sec-\textrm{cm}^2$ at the initial stage after installation to $1\times 10^{-12}Torr-l/sec-\textrm{cm}^2$ at present. Total accumulated microwave energy dose is about 140 GJ per module. All ion pumps are working under saturated regime and effective pumping speeds of 60 I/s, 230 I/s ion pumps are 45 I/s, 65 I/s, 140 I/s under the operating range. Main problems occurred in recent year are troubles of ion pump controller and vacuum gauge controller, vacuum leak of energy doubler window and electron gun ceramic, and water leak in the dummy load of acceleraing columns. Total of 41 troubles with 140. 8 hours down time give good system availability of 98%. Down time can be reduced by high power waveguide valves and water dummy loads under development, and then availability is expected to be increased up to 99.5%.

• The magazine of the Korean Society for Advanced Composite Structures
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• v.5 no.2
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• pp.26-31
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• 2014

This invention is purposed to provide an innovative solution for the inside of roof structures, which is cultural assets. The Asian old houses generally have several layered roofs on top of the structures. If a fire has started inside of the roof, it is hard to be extinguished before eliminating all the upper layers of the roof. This invention provides pre constructed embedded pipes, which is flammable and easy to be dissolved by the fire. The material of pipe is composed of rubbers, of which the combustion point is so low that the extinguishing of initial fire is possible without additional fire service. The inside of pipe is filled with halon gas. If the filled gas is consumed after ignited by fire, additional fire extinguishing water is supplied. If the flexible pipes are totally combusted by a big fire, the sprinkler at the end of inflexible pipe will work continuously, which is located between flexible and inflexible pipes. The extinguishing pipe network is suggested as dividing whole roof as multiple sections for a swift fire extinguishing in case of intentional or natural fire attack to our invaluable cultural assets.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.66-73
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• 2020

In the hydrogen compression cycle, which is currently being developed, hydrogen is compressed to a very high pressure using a compressor, and then stored and used in a high-pressure vessel. This shows that an increase in the temperature of hydrogen in the vessel due to a pressure rise during the filling process and the pressure fatigue due to the repeated cycle may cause problems in the reliability of the vessel. In this paper, for the entire processes in a 50 MPa hydrogen compression system, theoretical and numerical methods were conducted to analyze the following: the temperature increase of hydrogen in the vessel and the time required to reach thermal equilibrium with the surroundings, the change in temperature of hydrogen passing through the pressure reducing valve, and the required capacity of the heat exchanger for cooling the vessel. The results will be useful for the design and construction of hydrogen compression systems, such as hydrogen charging stations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.451-454
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• 2000

Invasive methode and Non-invasive methode are used in blood pressure measurement. The Invasive methode can Set the correct measured blood pressure but, it has patient feels uncomfortable. So most of cases use Non-invasive methode. The Oscillometric method is commonly apply to modem electric sphygmomanometer and using various algorithm. In this paper describe about a algorithm it control and to determinate the cuff pressure, and filtering that data for measure the blood pressure. The communicating with personal computer can pressure deflation is by Solenoid valve and it uses RS-232 system in packet communication. The main using algorithm for blood pressure measurements are maximum amplitude algorithm and oscillometric algorithm. MAA(maximum amplitude algorithm) has various measured oscillation it depend on patient's age, height, weight and arm circumference size. In this paper, 1 studied the various measured oscillation apply to characteristic ratio and can get the result of systolic blood pressure, diastolic blood pressure, mean blood pressure. It was not used same ratio to measuring oscillation. In the MAA(maximum amplitude algorithm), we hope for reduce the difference with the real blood pressure and the measured blood pressure, when it applied with various specific ratio.

• Journal of the Korean Institute of Gas
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• v.18 no.4
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• pp.13-20
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• 2014

In natural gas distribution system, gas pressure is regulated correspond to requirement using throttle valve which is releasing huge pressure energy as useless form. The waste pressure can be recovered by using turbo machinery devices such as a turbo expander. In this process, excessive temperature drop occurs due to Joule-Thompson effect during the expansion process. Installing natural gas boiler before or after the turbo expander prevents temperature drop. Fuel cell or gas engine hybrid system further improve the efficiency, but 1~2% of total transporting natural gas is used for operating the hybrid system. In this study, a heat pump system is proposed as a preheating device which can be operated without using transporting natural gas. Thermodynamic analysis on evaporating and condensing temperatures and refrigerants is conducted. Results show that R717 is proper refrigerant for the hybrid system with high COP and low turbine work within the defined operating conditions. In domestic usage in Korea, the heat pump system has more economic feasibility owing to natural gas being imported with a high price of LNG form.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5C
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• pp.429-436
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• 2012

In this paper, an RFID system for the automatic preparation system of positron emission tomography (PET) radiopharmaceuticals is developed. Since the preparation system uses radioactive isotope, the preparation system is generally placed in lead-shielded hot-cell. Disposable cassettes including tubes and valves are used in the preparation system, since they are easily contaminated by radioactivity during preparation of radiopharmaceuticals. Currently, a system for preventing re-use of the cassette and managing the information about the preparation precess and result independently from the PC which control the preparation system is highly required for preventing danger from the radiation accident. Since RFID can store and re-write relatively large amount of information, it is suitable for the purpose. However, it is hard to read multiple cassettes' information using antennas installed on the metallic surfaces with current RFID systems. For the problem, we improve RFID system in two directions. First, the interface of the RFID reader is changed then it is possible that multiple readers can be daisy-chained. Also, antenna is tuned while inserting in a metallic coated antenna case, then the effect from the metallic surface of the preparation system is minimized. The test result using the developed system shows that the developed RFID system can read multiple tags using the antennas which are attached on the metallic surface.

• Journal of Energy Engineering
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• v.17 no.2
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• pp.67-76
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• 2008

A thermal-hydraulic integral effect test facility, ATLAS (Advanced Thermal-hydraulic Test Loop for Accident Simulation), has been constructed at KAERI (Korea Atomic Energy Research Institute). Recently several integral effect tests for the reflood period of a LBLOCA (Large Break LOss of Coolant Accident) of the APR1400 have been performed with the ATLAS. In the APR1400 a high flow condition is changed to a low flow condition due to an fluidic device during an operation of the SIT. As the self-controlled fluidic device was not installed in the ATLAS, a set of characterization tests was performed to simulate its injection capability from the SIT for the APR1400 simulation. In the ATLAS the required SIT flow rate in the high flow condition was acquired by installing orifices with an optimized flow area to throttle the SIT discharge line and the low flow condition was achieved by changing the opening of the flow control valve in the SIT injection line. The test results showed that the safety injection systems of the ATLAS could simulate the required high and low flow rates of the SIT for the APR1400 simulation efficiently.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.39-39
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• 2007

원자층 증착(Atomic Layer Deposition: ALD) 방법은 반응물질들을 펄스형태로 챔버에 공급하여 기판표면에 반응물질의 표면 포화반응에 의한 화학적 흡착과 탈착을 이용한 박막증착기술이다. ALD법은 기존의 화학적 기상증착(Chemical Vapor Deposition: CVD)과 달리 자기 제한적 반응(self-limiting reaction) 에 의하여 반응가스가 기판 표면에서만 반응하고 가스와 가스 간에는 반응하지 않는다. 따라서 박막의 조성 정밀제어가 쉽고, 파티클 발생이 없으며, 대면적의 박막 증착시 균일성이 우수하고, 박막 두께의 정밀 조절이 용이한 장점이 있다. 이러한 ALD 방식으로 3차원의 반도체 장치 구조물에 산화막 등을 형성하는 공정에서 중요한 요소 중의 하나는 전구체의 충분한 공급이다. 따라서 증기압이 높은 전구체를 선호하는 경향이 있다. 그러나 증기압이 낮은 전구체를 사용할 경우, 공급량이 부족하여 단차 도포성(step coverage)이 떨어지는 문제가 있다. 원자층 증착 공정에서 전구체를 충분히 공급하기 위해전구체 온도를 증가시키거나 전구체의 공급시간을 늘리는 방법을 사용한다. 그러나 전구체 온도를 상승시키는 경우, 전구체의 변질이나 수명을 단축시키는 문제점을 발생시킬 수 있으며. 전구체를 충분히 공급하기 위하여 전구체의 공급시간을 늘이는 방법을 사용하면, 원하는 박막을 형성하기 위하여 소요되는 공정시간과 전구체 사용량이 증가된다. 본 논문에서는 이러한 문제점을 해결하기 위해 반응기 안에서 전구체 노출 시간을 조절하는 새로운 ALD 공정을 소개한다. 특히 이러한 기술을 적용하면 나노튜브를 성장시키는데 매우 유리하다. 본 연구에서 전구체 노출 시간을 조절하기 위하여 사용된 ALD 장비는 Lucida-D200-PL (NCD Technology사)이며 (TEMA)Zr와 H2O를 사용하여 ZrO2 나노튜브를 폴리카보네이트 위에 성장시켰다. 전구체의 노출 시간은 반응기의 Stop 밸브를 이용하여 조절하였으며, SEM, TEM 등을 이용하여 나노튜브의 균일성과 단차피복성 등의 특성을 관찰하였다. 그 결과 전구체 노출시간을 조절함으로써 높은 종횡비를 갖는 나노튜브를 성장 시킬 수 있음을 확인하였다. 또한 낮은 증기압을 가지는 전구체를 이용하여도 우수한 특성의 나노튜브를 균일하게 성장시킬 수 있었다.