• Journal of the Korea Safety Management & Science
• /
• v.17 no.4
• /
• pp.297-304
• /
• 2015

This study concerns the integrated gas sensor system of wire and wireless communication by using IoT(Internet of Things) technology. First, communication part is that it delivers the detection information, which transferred by wire or wireless communication and required control procedure based on a wireless module that receives the gas leakage information from wired or wireless detector, to administrator or user's terminal. Second, receiver part is that it shows the location and information, which received from the wired detector formed by a detecting sensor's node as linking with the communication part, and transfers these to the communication part. Third, wireless detector formed as a communication module of a detecting sensor node is that it detects gas leakage and transfers the information through wireless as a packet.Fourth, wired detector communicated with the receiver part and formed as a communication module of a detecting sensor node is that it detects gas leakage, transfers and shows the information as a packet. Fifth, administrator's terminal is that it receives gas leakage information by the communication part, transfers the signal by remote-control, and shut off a gas valve as responding the information. Sixth, database is that it is connected with the communication part; it sets and stores the default values for detecting smoke, CO., and temperature; it transfers this information to the communication part or sends a gas detecting signal to user's terminal. Seventh, user's terminal is that it receives each location's default value which stored and set at the database; it manages emergency situation as shutting off a gas valve through remote control by corresponding each location's gas leakage information, which transferred from the detector to the communication part by wireless.It is possible to process a high quality data regarding flammable or toxic gas by transferring the data, which measured by a sensor module of detector, to the communication part through wire and wireless. And, it allows a user to find the location by a smart phone where gas leaks. Eventually, it minimizes human life or property loss by having stability on gas leakage as well as corresponding each location's information quickly.

• Journal of the Korean Society for Railway
• /
• v.20 no.5
• /
• pp.569-576
• /
• 2017

The electromagnetic valve of pneumatic doors of EMUs has a high failure rate due to air leakage because it supplies air on and off to operate the doors repeatedly. The electromagnetic valve is a very important safety component for which a very high reliability is required because failure makes it impossible to operate the passenger cars. However, domestic urban railway operators maintain electronic valves of the EMU door under a fixed cycle with a spare period according to the full overhaul cycle of the EMU. An improvement of the current maintenance cycle was suggested based on the reliability function and mission reliability. Using the statistical program MINITAB for the operational data of EMU line 6, we analyzed the characteristics of the fault distribution and derived the shape and scale parameters of the reliability function. If we limit the specific reliability probability to under a certain failure rate and calculate its statistical parameters, we can calculate the allowable inspection period with mission reliability. Through this study, we suggested a maintenance period based on RCM (reliability centered-maintenance) to improve the reliability of electromagnetic valves from 68% to 95%.

• Journal of Advanced Marine Engineering and Technology
• /
• v.33 no.8
• /
• pp.1129-1136
• /
• 2009

The paper presents the performance characteristics for a cooling system using EEV. The water cooler was used to reduce thermal deformation and contraction due to high speed of machine tools and the EEV was used for capacity control for water cooler. The apparatus was designed for hot-gas bypass system which a hot-gas can flows from outlet of compressor to the inlet of evaporator. This experiment is the intermediary study for precise temperature control through PID control. The results show that the evaporator pressure increased and refrigeration capacity decreased as the EEV opening step of hot-gas bypass increased. These results can be used as basic data for the design of effective water cooler.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.13 no.2
• /
• pp.89-99
• /
• 2001

In the present paper, Helmholtz resonator, which is widely used as a sound-amplification device, is applied to the development of seawater-exchanging breakwater. The incident waves can induce a large response in the resonator when incident wave frequency is close to one of natural modes of the resonator. Largely amplified potential energy due to the resonance supplies clean seawater into the harbor side throughout the channel. Flow supplied by the resonator circulates the seawater of harbor and helps to improve water quality. Within the framework of linear potential theory, matched asymptotic expansion method is employed to analyze the wave responses in a resonator. The semi-circular shape of the resonator has been chosen as an analytic model for mathematical simplicity. The wave responses of both single and arrays of Helmholtz resonator are investi¬gated. To validate an analytic solution, model test is conducted at 2-dimensional wave tanle Wave hcights in the resonator and velocity at the channel are measured for the state of valve-on and valve-off.

• Proceedings of the Korea Contents Association Conference
• /
• 2008.05a
• /
• pp.771-775
• /
• 2008

Concerns related to protecting, identifying, and isolating of subsystems of a water distribution network have led to the realization of the increased importance of valves in the system. The most important purpose of valves in water distribution systems is to isolate subsystems due to breakage, maintenance activities, or contamination. A subsystem called segment is isolated by the closure of adjacent valves and an efficient algorithm should identify the adjacent valves to minimize the pipe failure impact. In this paper, an algorithm to identify adjacent valves to be closed to isolate a subsystem from the remainder of a network in case of a pipe failure is presented. An application to the water distribution system in Ottawa, Canada demonstrates the developed algorithm efficiently locates the adjacent valves for the isolation of a broken pipe.

• Journal of Advanced Marine Engineering and Technology
• /
• v.29 no.2
• /
• pp.185-193
• /
• 2005

The present study composed a diesel-atkinson cycle of high expansion as a method of achieving high efficiency in diesel cycle engines. It also interpreted the cycle engine thermodynamically analysis to determine the possibility of the improvement of thermal efficiency and clarified the characteristics of several factors . According to the result of theoretical analysis, heat efficiency was highest when expansion-compression ratio Reど:1. In addition. diesel engines with high apparent compression ratio had higher expansion-compression ratio than otto engines and consequently their effect of high expansion was high. which in turn enhanced thermal efficiency. When the atkinson cycle was implemented in a real diesel engine by applying the miller cycle through the variation of the closing time of the intake valve, the effective compression ratio and the quantify of intake air decreased and as a result, the effect of high expansion was not observed. Accordingly. the atkinson cycle can be implemented when the quantity of intake air is compensated by supercharge and the effective compression ratio is maintained at its initial level through the reduction of the clearance volume. In this case. heat efficiency increased by $4.1\%$ at the same expansion-compression ratio when the apparent compression ratio was 20 and the fuel cut off ratio was 2. As explained above, when the atkinson cycle was used for diesel cycle. heat efficiency was improved. In order to realize high expansion through retarding the intake value closing time, the engine needs to be equipped with variable valve timing equipment, variable compression ratio equipment and supercharged Pressure equipment. Then a diesel-atkinson cycle engine is realized.

• Journal of Hydrogen and New Energy
• /
• v.35 no.3
• /
• pp.280-289
• /
• 2024

In this study, a cryogenic vessel was constructed to maintain and control the safe pressure of liquid hydrogen boil-off gas (BOG), and the numerical analysis was conducted on the development of computational fluid dynamics model inside the high-pressure vessel. An evaluation system was constructed using cryogenic inner and outer containers, pre-cooler, upper flange, and internal high-pressure container. We attempted to analyze the performance of the safety valve by injecting relatively high temperature hydrogen gas to generate BOG gas and quickly control the pressure of the high-pressure vessel up to 10 bar. As a results, the liquid volume fraction decreased with a rapid evaporation, and the pressure distribution increased monotonically inside a high pressure vessel. Additionally, it was found that the time to reach 10 bar was greatly affected by the filling rate of liquid hydrogen.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.48 no.3
• /
• pp.13-20
• /
• 2011

In this paper, we proposed a system to raise gas safety management by using the wireless communication module and intelligent gas safety appliances. Our designed systems configure a micom-gas meter, an automatic extinguisher, sensors, and a wallpad. A micom-gas-meter monitors gas flow, gas pressure, and earthquake. An automatic fire extinguisher checks gas(combustible) leaks and temperature of $100^{\circ}C$ and $130^{\circ}C$. Sensors measure smoke and CO gas. In our novel system, a micom-gas meter cut off inner valve with warnings, an automatic fire extinguisher cut off middle valve and spray extinguishing materials, and sensors generate signals for smoke and CO when occurring gas risk. Gas safety appliances and sensors takes safety measures, and transmit those signal to a wallpad. The wallpad again transmit signal like events to a control server. Users can connect web pages for gas safety through B-ISDN and control and manage them. We hereby devised scenarios for gas safety and risk management, and demonstrated their effectiveness through experiments.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.6
• /
• pp.70-75
• /
• 2010

Compressed air represents an energy source and an force-transmission medium for brake systems on medium-heavy and heavy-duty commercial vehicles. However, one disadvantage is the tendency of air to absorb moisture in the form of water vapor. This water vapor condenses once the air, which is heated during compression, cools back to ambient temperature upon emerging from the air compressor. The resulting condensation assumes the form of moisture in pneumatic lines, air tanks, cylinders and valve assemblies and can have negative consequences for the brake system and vehicle safety. The pneumatic systems on today's vehicles are equipped with air dryers, in which the supplied air is dried according to the adsorption principle. In the systems, the compressed air flows through a granular desiccant with molecular sieves which captures the water molecules.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.1384-1386
• /
• 2005

This paper focuses on development of load test simulator of a steam turbine-generator in a nuclear power plant. When load is taken off from electrical power network, it is very difficult to effectively control the steam flow to turbine of the nuclear turbine-generator, because of disturbances, such as electrical load and network unbalance on electrical network. Up to the present time, the conventional control system has been used for the load control on nuclear steam generator, owing to the easy control algorithms and the advantage which have been proven on the nuclear power plant. However, since there are problems with stability control during low power and start-up, only a highly experienced operator can operate during those procedures. Also, a great deal of time and an expensive simulator is needed for the training of an operator. The KEPRI is developed simulator for 600MW nuclear power plant to take a test of generator load rejection, throttle valve, and turbine load control. Total load test is implemented before start up.