• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.2
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• pp.147-152
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• 2001

Corrosion damage of boiler, factory equipment and so forth occur quickly due to using of the polluted water, resulting in increasing leak accident. Especially, working life of hot water boiler using the polluted water becomes more short, and energy loss increases. The cathodic protection method is the most economical and reliable one to prevent corrosion damage of steel structures. Mg-base alloys galvanic anode protection of cathodic protection methode is suitable for the application of hot water boiler using water with high specific resistance such as tap water. This paper is studied on the cathodic protection characteristics of hot water boiler. In tap water solution, the measurement of cathodic protection potential according to the time elapsed is carried out, and behavior of cathodic polarization with current change is investigated. The main results obtained are as follows. In hot water boiler shell, the open circuit potential of base metal become less noble than that of weld Bone, and the current density of base metal becomes low than that of weld zone. The further distance from Mg-alloy galvanic anode, the higher cathodic protection potential of hot water boiler appears. And protective potential becomes high according to pass cathodic protection time and after 6∼10 days become stable.

• Journal of Digital Contents Society
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• v.18 no.8
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• pp.1661-1669
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• 2017

In 2017, Korea has reached 1.3 million elderly people living alone. The government is promoting the basic care service for the elderly by using care workers to check the security of the elderly living alone. However, due to lack of service personnel and service usage rate of elderly care workers, it is difficult to manage. To improve these environmental constraints, this study attempted to construct a monitoring system for elderly people living alone by using sensors such as temperature, humidity, motion detection, and gas leak detection. The sensor periodically collects the current status data of the elderly and sends them to the server, creates a real time graph based on the data, and monitors it through the web. In the monitoring process, when the sensor is out of the range of the specified value, it sends a warning text message to the guardian to inform the current situation, and is designed and implemented so as to support the safety life of the elderly living alone.

• Journal of the Korean Vacuum Society
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• v.16 no.2
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• pp.153-159
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• 2007

In-cryostat helium lines are under installation to transfer a cryogenic helium into cold components in KSTAR device. In KSTAR, three kinds of helium should be supplied into the cold components, which are supercritical helium Into superconduction(SC) magnet system, liquid helium into current lead system, and gas helium into thermal shields. Cryogenic helium lines consist of transfer lines outside the cryostat, in-cryostat helium lines, and electrical breaks. In-cryostat helium lines should be guaranteed of leak tightness for tong time operation at high internal helium pressure of 20 bar. We wrapped the helium line with multi-layer insulator(MLI) to reduce radiation heat and insulated the surface of the high potential part with prepreg tape. The electrical break was fabricated by brazing ceramic tube with stainless steel tube. To ensure the operation reliability at operation temperature, all the electrical break have been examined by the thermal cycle test at liquid nitrogen and by the hydraulic test at 30 bar. And additional surface insulation was prepared with prepreg tape to give structural safety. At present most of the in-cryostat helium lines have been installed and the final inspection test is progressing.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.1-5
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• 2003

In this project, the efficiency of localized heating for micro systems packaging is developed by using a forced potential scheme microheater. Less than 0.2 Mpa contact pressure was used for bonding with a 200 mA current input for $50{\mu}m$ width, $2{\mu}m$ height and $8mm{\times}8mm$, $5mm{\times}5mm$, $3mm{\times}3mm$ sized phosphorus-doped poly-silicon microheater. The temperature can be raised at the bonding region to $800^{\circ}C$, and it was enough to achieve a strong and reliable bonding in 3 minutes. The IR camera test results show improved uniformity in heat distribution compared with conventional microheaters. For performing the gross leak check, IPA (Isopropanol Alcohol) was used. Since IPA has better wetability than water, it can easily penetrate small openings, and is more suitable for conducting a gross leak check. The pass ratio of bonded dies was 67%, for conventional localized heating, and 85% for our newly developed FP scheme. The bonding strength was more than 25Mpa for FP scheme packaging, which shows that FP scheme can be a good candidate for micro-scale hermetic packaging.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.2
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• pp.145-150
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• 2020

Water wall tube is one of the major factors consisting of a fluidized bed boiler and it plays very important role for the generation of electricity within the boiler. But these water wall tubes within the fluidized bed boiler are subject to the ware and corrosion caused by the high temperature gas and the flowing medium. If water leak is occurred, the secondary damage by the water leak will occur. As a result of that, the power generation efficiency decreases noticeably. Therefore, the maintenance of the water wall tube is very important. In this study, we designed a exciter sensor based on simulation and composed a remote field eddy current system for the defect evaluation of the outer water wall tube. Starting from the shape design of exciter, we conducted simulations for various design factors such as the water wall tube size, material, frequency, lift-off and so on. Based on the results, we designed the optimum exciter sensor for the water wall tube test within the fluidized bed boiler.

• Journal of the Korean Institute of Gas
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• v.25 no.5
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• pp.1-10
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• 2021

Semiconductor Photo Resist (PR) automation equipment uses a mixture of several flammable substances, and when it leaks during the process, it can lead to various accidents, therefore, risk assessment is necessary. This study analyzed the frequency of leakage of Acetone and PGMEA used in PR automation equipment and the frequency at which such leakage could lead to a fire accident through the frequency analysis method, and evaluated the need for additional risk reduction measures in the current facility. Based on the process leak data and ignition probability data of IOGP, leak frequency analysis and ignition probability were derived, and the frequency of actual fire accidents was analyzed by combining them. The frequency of material leakage in semiconductor PR process is 7.30E-03/year, and fire accidents can occur by acetone that exists above the flash point when the material is leaked, the frequency was calculated at the level of 1.24E-05/year. According to the UK HSE, for a major accident occurring with a frequency of 1.24E-05/year, it is defined as "Broadly Acceptable", a level that does not require additional measures for risk reduction when it causes 7 or less deaths, and due to the process operated by two people, no additional risk reduction are required.

• Journal of the Korean Society of Safety
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• v.35 no.6
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• pp.15-24
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• 2020

With the development of the chemical industry, the chemical accident is increasing every year, thereby increasing the risk of accidents caused by chemicals. The Ministry of Environment provides the criteria for determining shelter-in-place or outdoor evacuation by material, duration of accident, and distance from the toxic substance leak. However, it is hard to say that the criteria for determining the transition point are not clear. Transition point mean the time that evacuation method is switched from shelter-in-place to outdoor evacuation. So, the purpose of this study was to calculate appropriate transition point by comparing the cumulative toxic load. Namdong-gu in Incheon Metropolitan City was finally selected as the target area, considering the current status of the population of Incheon Metropolitan City in 2016 and the statistical survey of chemicals in 2016. The target materials were HCl, HF, and NH₃. Modeling was simulated by ALOHA and performed assuming that the entire amount would be leaked for 10 min. Residents' evacuation scenarios were assumed to be shelter-in-place, immediate outdoor evacuation, and outdoor evacuation at an appropriate time after shelter-in-place. Based on the above method, the appropriate transition point from residents located in A(800 m away), B(1,200 m away), C(1,400 m away) and D(2,200 m away) was identified. In HCl, appropriate transition point was after 15 min, after 16 min, after 17 min, after 20 min in order by A, B, C and D. In HF, appropriate transition point was before 1 min or after 16 min, before 4 min or after 19 min, before 5 min or after 20 min, before 14 min or after 26 min in order by A, B, C and D. In NH₃, appropriate transition point at A was before 4 min or after 16. Others are not in chemical cloud. This study confirmed the transition point to minimize the cumulative toxic load can be obtained by quantitative method. Through this, it might be possible to select evacuation method quantitatively that cumulative toxic load are minimal. In addition, if the shelter-in-place is maintained without transition to outdoor evacuation, the cumulative toxic load will increase more than outdoor evacuation. Therefore, it was confirmed that actions to reduce the concentration of chemicals in the room were necessary, such as conducting ventilation after the chemical cloud passed through the site.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.4
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• pp.169-176
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• 1998

An experimental study on effect of vapor-cooled heat stations in a 5.5 liter cryogenic vessel has been performed. The cryogenic vessel is made of stainless steel of thickness of 1mm and insulated by the combined insulation of vacuum, MLI(multi-layer insulation) and vapor-cooled radiation shield. Vapor-cooled heat stations are also constructed based on the 1-dimensional thermal analysis to reduce the heat inleak through a filling tube. Thermal analysis indicates that the vapor-cooled heat stations can substantially enhance the performance of vessel for cryogenic fluids with high $C_p/h_{fg}$ where $C_p$ the specific heat and $h_{fg}$ the heat of vaporization, such as $LH_2$ and LHe. The experimental results for $LN_2$ shows that the total heat inleak into inner vessel consists of 14% radiation and 86% conduction through the filling tube. Therefore, it is expected that the conduction heat in leak of the vessel for high $C_p/h_{fg}$ cryogenic fluids can be significantly reduced. powders. The amount of copper coating was 20wt%. In order to examine corrosion behavior of the electrodes, the corrosion current and the current density, in 6M KOH aqueous solution after removal of oxygen in the solution, were measured by potentiodynamic and cyclic voltamo methods. The results showed that Co in the alloy increased corrosion resistance of the electrode whereas Ni decreased the stability of the electrode during the charge-discharge cycles. The electrode used Si sealant as a binder showed a lower corrosion current density than the electrode used PTFE and the electrode used Cu-coated alloy powders showed the best corrosion resistance.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.301-305
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• 2007

The performance of polymer electrolyte membrane fuel cell could be decreased due to coolant leaked from connection part. Micro pump was used to put small amount of coolant and investigate the effect on fuel cell. The stoichiometric ratio of hydrogen/air was 1.5/2.0, both side of gas was fully humidified, and current density of $400mA/cm^2$ was used as standard condition in this experiment. Constant current method was used to check performance recovery from coolant effect in 3 cell stack. The performance was recovered when coolant was injected in cathode side. On the other hand, the performance was not recovered when coolant was injected in anode side. Ethylene glycol could be converted to CO in oxidation process and cause poisoning effect on platinum catalyst or be adhered on GDL and cause gas diffusion block effect resulting performance decrease. Water with nitrogen gas was supplied in anode side to check performance recovery. Polarization curve, cyclic voltammetry, electrochemical impedance spectroscopy was used to check performance, and gas chromatography was used to check coolant concentration. Constant current method was not enough in full recovery of performance. However, water injection method was proved good method in full recovery of performance.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.92-94
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• 2003

The autotransformer currently used on the electric railway system is made of class A insulation material and uses the paper insulation method. As a power converter supplying power to the trolley wire, the autotransformer is one of critical equipment in the railway system. In the autotransformer, load irregularly changes and overload often occurs. These cause overheating of the autotransformer and facilitate deterioration of the autotransformer resulting in burnout accidents due to insulation breakdown. Also, the current autotransformer has poor insolation and short-circuit strength which often badly affect the service life of the transformer, and needs to improve its quality urgently. To overcome one of existing shortcomings of the mold transformer, manufacturers use epoxy resins that have superior flame retardancy to get rid of fro and explosion possibilities during accidents. Currently, new mold transformers are used in indoor distribution facilities with fire-fighting equipments. Coils molded in epoxy resins do not have their insulation performance compromised by humidity, dust, etc enabling easy inspection and maintenance. Comparing to the oil immersed transformer, the mold transformer does not have any concern about environmental pollutions by oil leak or replacement Therefore, to reduce breakdowns and improve reliability of the autotransformer, it is necessary to develop a new mold autotransformer with low loss suitable for our environment to suppress breakdowns of the autotransformer and improve the reliability. This study is about development of a low-loss mold autotransformer necessitated by reasons mentioned earlier.