• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.2
• /
• pp.128-134
• /
• 2013

A 2-way solenoid valve regulates to maintain the pressure of ullage volume of propellant tanks when the command is given by control system for the liquid-propellant feeding system of space launch vehicle. The simulation model of solenoid valve for pressurization is designed with AMESim to verify the designs and evaluate the dynamic characteristics and pneumatic behaviors of valve. To improve the accuracy of the model, numerical flow analysis by using FLUNET code. The simulation results of their operating durations of valve by AMESim analysis are matched up with the results of experiments and validate valve model. Using the model, we analyze performance of valve; opening/closing pressure, operating time on various design factors of basic valve and control valve; geometrical size of valve seat, ratio of basic valve and sealing area.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.5
• /
• pp.214-221
• /
• 2015

In this paper, we present robust estimation and detection algorithms for discrete-time switched linear systems whose output measurements are corrupted by noises. First, a mode estimation algorithm is proposed based on the minimum distance criterion. Then, state variables are also observed under the active mode estimate. Second, a detection algorithm is constructed to detect the mode switching of the switched system. With the boundedness of measurement noise, the proposed estimation algorithm returns the exact active mode and approximate state information of the switched system. In addition, the detection algorithm can detect the switching time within a pre-determined time interval after the actual switching occurred.

• Fire Science and Engineering
• /
• v.34 no.4
• /
• pp.36-44
• /
• 2020

It is necessary to predict the activation time of fire detectors accurately to improve the reliability for evaluating the required safe egress time (RSET) in performance-based fire safety design. In this study, problems of the plunge test, which is widely applied in assessing fire detectors, were examined through experiments and numerical simulations. In addition, a new shield-cup test method was proposed to address these problems. A fire detector evaluator (FDE) developed in a previous study was applied to ensure measurement accuracy and reproducibility. During the plunge tests, a significant measurement error was observed in the activation time of the smoke detector because of the rapid flow change when the detector was input. However, during the shield-cup tests, slight changes occurred in the flow inside the FDE when the detector as exposed to smoke. In conclusion, the proposed shield-cup test method is expected to be useful for evaluating the response characteristics of fire detectors more accurately in simulated fire environments.

• Journal of the Korean Society of Safety
• /
• v.9 no.1
• /
• pp.61-67
• /
• 1994

Rate of rise heat detectors that respond to the heat generated in fire plume and alarm when the temperature reaches a specified point, give a great influences to the loss of life and property according to their reaction sensitivity. In this study, simple equations were derived which can be predicted the response time and temperature of the rate of rise heat detector with the results of hot wind tunnel tests and compartment fire experiments.

• Journal of Korean Society of Transportation
• /
• v.33 no.5
• /
• pp.488-496
• /
• 2015

The main reason to install pedestrian pushbuttons is improving traffic operations. The current guideline for the installation of signal systems with pedestrian pushbuttons is car-oriented. It is difficult to clearly understand the guideline because there isn't an in-depth study to compare the pros and cons of the pedestrian- and vehicle-oriented methods in terms of waiting time. Thus, this study aims to estimate the waiting times of pedestrians and vehicles. The two delay times are compared considering the hypothetical circumstances such as geometry, pedestrian crossing time, pedestrian/vehicle counts and arrival distribution. The results show that when the pedestrian traffic volume exceeds 97 ped/h in the case of a two-lane road (one lane in each direction) the pushbutton system is effective and beneficial to pedestrians. It means that the total waiting time of pedestrians is less than the one of vehicles. Additional four scenarios are designed and tested by varying the number of lanes and design speeds. In conclusion, the pushbutton signal is more beneficial for pedestrians when the number of pedestrians is less than or equal to 85, 70, and 70 ped/h for the three-lane scenario, the four-lane with the design speed of 80km/h scenario, and the four-lane with the design speed of 100km/h, respectively.

• Bulletin of the Korean Space Science Society
• /
• 2010.04a
• /
• pp.33.2-33.2
• /
• 2010

옥루(玉漏)는 1438년(세종 20)에 장영실이 제작한 자동물시계이다. 종, 북, 징을 타격하여 시간을 알려주고 태양운행 장치가 있어 절기를 알 수 있도록 하였다. 옥루에 대한 관련 문헌을 연구하여 옥루 작동구조에 대하여 분석하였다. 옥루는 물의 흐름을 이용한 수력으로 운행하는 동력장치를 두고 있다. 옥루를 이루고 있는 가산의 형태는 빈풍도를 나타낸 것으로 백성들의 농사짓는 어려움을 볼 수 있게 하였다. 옥루의 구조는 산위, 산기슭, 평지로 구분할 수 있다. 산위에는 태양운행 장치, 옥녀(玉女)와 사신(四神), 산기슭에는 사신(司辰)과 무사(武士), 평지에는 12신(神), 옥녀(玉女), 관인(官人)이 위치해 있다. 각 층별로 구성되어 있는 시간을 알려주는 인형들의 기본적인 운행 메커니즘에 대하여 분석하고 작동 개념도로 제시하였다. 또한 태양운행장치의 작동 원리에 대해서 개념도로 제시하였다.

• Fire Science and Engineering
• /
• v.17 no.1
• /
• pp.1-7
• /
• 2003

In general, small buildings and residence housings rely on manual fire extinguishers instead of automatic fire suppression systems, which causes bigger disasters during the absence of human-beings or in the presence of children or the olders. For this reason, simple structured and low-cost automatic fire extinguisher using fusible metal detector was newly developed and patented. In this paper, some field tests were carried out to investigate its fire suppression performance. As a result, reaction time of the detection parts varied from 2 min 19s to 7 min 20s depending upon the room size and installation position. It was suggested that to reduce reaction time within 3 minutes, fusible metals with lower melting point should be adopted and the installation location should be moved to near ceiling instead of below 1.5 m.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2009.04a
• /
• pp.389-395
• /
• 2009

본 연구에서는 일체형방화셔터가 설치된 초등학교 재실자의 피난특성에 관한 연구를 위해 먼저 일체형방화셔터를 포함한 방화셔터 전반에 대한 기초 자료를 수집 검토하였으며, 초등학교에 설치된 일체형방화셔터 작동 유무에 따른 재실자 피난특성을 비교 분석하였다. 화재 모의실험 결과, 일체형방화셔터 미작동시 최종 대피완료 시간은 130초이며, 일체형 방화셔터 작동시 에는 190초가 소요되었다. 또한 일체형방화셔터 작동시 피난대피 상황에서 초등학생들이 셔터내의 출입문을 열지 못하는 상황이 발생되었다. 이러한 상황을 고려 한다면 일체형방화셔터 작동시 최종피난완료시간은 상당히 지연되었을 것이며 대다수의 대피자들이 화재위험에 노출되었을 것이다. 따라서 향후 일체형방화셔터 출입문 개폐력에 대한 연구가 반드시 진행되어야 할 것으로 판단된다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.725-730
• /
• 2011

A 2-way solenoid valve regulates to maintain the pressure of ullage volume of propellant tanks when the command is given by control system for the liquid-propellant feeding system of space launch vehicle. The simulation model of solenoid valve for pressurization is designed with AMESim to verify the designs and evaluate the dynamic characteristics and pneumatic behaviors of valve. To validate a valve simulation model, the simulation results of their operating durations of valve by AMESim analysis are compared with the results of experiments. Using the model, we analyze performance of valve; opening/closing pressure, operating time on various design factors; shape of control valve seat, basic valve seat, rate of sealing diameter. This study will serve as one of reference guides to enhance the developmental efficiency of ventilation-relief valves with the various operating conditions, which shall be used in Korea Space Launch Vehicle-II.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.3
• /
• pp.218-224
• /
• 2007

Although piezoelectric materials such as PZT have been widely used as actuators in the field of active vibration suppression, the use of bare PZT as an actuator may cause some drawbacks such as critical breaks in the installation process, short circuits in the host material and low fatigue performance. The LIPCA-C2 (lightweight piezocomposite actuator) was developed to alleviate these problems. We implemented the LIPCA as an actuator to suppress the vibration of an aluminum cantilever beam with a tip mass. In our test, we used positive position feedback control algorithm. The filter frequency for this type of feedback should be tuned to the natural frequency of the target mode. The first three experimental natural frequencies of the aluminum cantilever beam agree well with the results of finite element analysis. The effectiveness of using the LIPCA as an actuator in active vibration suppression was investigated with respect to the time and frequency domains, and the experimental results show that LIPCAs with PPF control can significantly reduce the amplitude of forced vibrations and the settling time of free vibrations. For a case study, the forced vibration control of several beams with different thicknesses were performed.