• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.424-429
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• 2018

In this study, an expansion joint that is susceptible to waterhammer was tested for its vibration durability. The operation data for the hydraulic actuator was the expansion length of the expansion joint when the waterhammer occurred. In the case of the vibration durability test, the internal temperature status of the expansion joint was assumed to be a stress factor and a lifespan prediction model was assumed to follow the Arrhenius model. A test was carried out by increasing the internal temperature status at $30^{\circ}C$, $50^{\circ}C$, and $65^{\circ}C$. By a linear transformation of the lifespan data for each temperature, a constant value and activation energy coefficient was induced for the Arrhenius equation and verified by comparing the value of a lifetime prediction model with the experimental value at $85^{\circ}C$. The failure modes of the ongoing or finished test were leakage, bellows separation, and internal deformation. In the future, a composite lifespan prediction model, including two more stress factors, will be developed.

• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.15-23
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• 2023

The grouting method is a method of construction for the purpose of waterproofing and reinforcing soft ground. When grout is injected into the ground, there are various types of penetration and diffusion of grout depending on the shape of the ground, the size of soil, the porosity, and the presence or absence of groundwater. the current situation. Therefore, in this study, to investigate the penetration performance of the grouting to conductive material, laboratory tests were performed on the addition of the conductive material. In the injection test, 0%, 3%, and 5% of the mixed water were added as conductive materials to the grout, and the original ground condition was composed of various types of ground composed of gravel and silica sand. Conductive grout is injected by pressure into the model ground using a dedicated injection device, and the injection time (t), pressure (p), flow rate (v) and injection amount (q) are measured, and the hardened body injected in the model ground is collected. Penetration performance was evaluated. In the results of the grout injection experiment, the amount of conductive material used and the grout injection rate showed an inverse relationship, and it was confirmed that the penetration pattern was changed according to the size of the soil particles in the model ground. The grout containing the conductive material has relatively good penetration into the ground and excellent strength and durability of the hardened body, so it was judged that it could be used as an additive for measuring the penetration range of the grout.

• Journal of the Korean Institute of Gas
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• v.4 no.1 s.9
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• pp.63-68
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• 2000

We have developed a new relief valve which is a safety device for the domestic gas-fired hot water boilers. The relief valve has been designed to expand the inner diameter of the inlet, the outlet and the seat of the valve considering the relief capacity, and also to separate the spring from the room heating water. Therefore, we could minimize the adhesion and/or obstruction of the inlet and the corrosion phenomena of the spring which used to be the problem of the conventional relief valves. Test results of the developed relief valve showed that the performance of the opening pressure, reseating pressure, tightness, endurance were excellent, and the operating boiler with developed relief valve was evaluated as very good. The standardization and application of the relief valve can provide the advantage of component exchange and easy maintenance and repair.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.444-449
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• 2004

The design modification of bottom guide structures of the instrumented capsule, which is used for the irradiation test in the HANARO reactor, was required because of the trouble of the bottom guide arm's pin during irradiation. The previous structure with 3-pin arms was changed into the cone shape of one body. The specimens of the bottom end cap ring with three different sizes (${\Phi}68/70/72mm$) were designed and manufactured. The out-pile tests for the capsule with previous and new three bottom guide structures were performed in the one-channel flow test facilities. In order to evaluate the compatibility with HANARO and the structural integrity of the capsule, a loading/unloading, a pressure drop, a thermal performance, a vibration, and an endurance test were conducted. From out-pile test results, the capsule with the cone shape bottom guide structures was found to be more stable than the previous structure and the optimized size of the bottom guide structure selected was 70mm in diameter. It is expected that the new bottom guide structures will be applicable to all material and special capsules which will be designed and manufactured for the irradiation tests in the future.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.21-29
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• 2016

In this paper, we developed a flexible transparent capacitive pressure sensor which can recognize X and Y coordinates and the size of force simultaneously by sensing a change in electrical capacitance. The flexible transparent capacitive pressure sensor was composed of 3 layers which were top electrode, pressure sensing layer, and bottom electrode. Silver nanowire(Ag NW)/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) hybrid film was used for top and bottom flexible transparent electrode. The fabricated capacitive pressure sensor had a total size of 5 inch, and was composed of 11 driving line and 19 sensing line channels. The electrical, optical properties of the Ag NW/PEDOT:PSS and capacitive pressure sensor were investigated respectively. The mechanical flexibility was also investigated by bending tests. Ag NW/PEDOT:PSS exhibited the sheet resistance of $44.1{\Omega}/square$, transmittance of 91.1%, and haze of 1.35%. Notably, the Ag NW/PEDOT:PSS hybrid electrode had a constant resistance change within a bending radius of 3 mm. The bending fatigue tests showed that the Ag NW/PEDOT:PSS could withstand 200,000 bending cycles which indicated the superior flexibility and durability of the hybrid electrode. The flexible transparent capacitive pressure sensor showed the transmittance of 84.1%, and haze of 3.56%. When the capacitive pressure sensor was pressed with the multiple 2 mm-diameter tips, it can well detect the force depending on the applied pressure. This indicated that the capacitive pressure sensor is a promising scheme for next generation flexible transparent touch screens which can provide multi-tasking capabilities through simultaneous multi-touch and multi-force sensing.

• Journal of the Korean Institute of Gas
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• v.26 no.6
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• pp.9-15
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• 2022

In order to verify the durability of the high-pressure hydrogen tank in the operating pressure range, a hydraulic rupture test should be performed. However, if the bubbles generated by the initial injection process of water are attached to the inner wall of the tank and remain, a sudden pressure change of the bubbles during the rupture of the pressurized tank may cause shock and noise. Therefore, in this study, the flow velocity required to remove the bubbles remaining on the inner wall of the tank was predicted through simplified formulas, and the shape of the injection nozzle to maintain the flow velocity was determined based on the shape of the hydrogen tank for the hydrogen bus. In addition, a numerical model was developed to predict the change in flow velocity according to the inlet pressure, and an experiment was performed through a model tank to prove the validity of the prediction result. As a result of the experiment, the flow velocity near the tank wall was similar to the predicted value of the analysis model, and when the inlet pressure was 1.5 to 5.5 bar, the minimum size of the removable bubble was predicted to be about 2.2 to 4.6 mm.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.607-617
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• 2023

This study aims to analyze whether the performance of the fire extinguisher meets the criteria for the apparent specific gravity property test by calculating the change in internal pressure and the use period of the fire extinguisher as a new one with 5 years, recycled one with 5 years, a new one with 10 years, and a new one with 13 years, respectively. As a result of the experiment, when the internal pressure of the fire extinguisher was 0%, the first, second, and third arithmetic mean analysis of the dry chemical extinguisher according to the use period was found to be condemned. When the internal pressure of the fire extinguisher was 50%, it was measured as 130 ml in sample 12-08-new and analyzed as unsuitable. Also, sample 09-09-new of a new dry chemical extinguisher with 13 elapsed years measured 145ml, which was found inappropriate. All other dry chemical extinguishers were analyzed to be suitable. All were noted suitable when having normal internal pressure of the fire extinguisher, except for sample 09-06 of a new dry chemical extinguisher with 13 elapsed years, which was determined to be unsuitable caused by measuring as 131 ml for experimental value. As a result of experiments, some of the apparent specific gravity tests of dry chemical extinguishers from 10 years to 13 years have found that they are unsuitable for the performance of the fire extinguishers due to the massive phenomenon. Accordingly, it is necessary to reduce the endurance period of dry chemical extinguishers from 10 years to 7 years.

• Korean Journal of Food Science and Technology
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• v.12 no.4
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• pp.272-277
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• 1980

The tolerance of useful bacterial spores to the conditions of tablet making, specifically, the destruction of bacterial spores upon compressional pressure was investigated. The damage of bacterial spores occurred mainly during the tabletting. The bacterial spores obeyed a logarithmic destruction rate upon compressional pressure. The spore destruction rate was dependent upon the strains of microorganism. The Decimal Reduction Pressure, designated as P-value, were $2.9\;ton/cm^2$, $2.6\;ton/cm^2$ and $2.1\;ton/cm^2$ for the spores of Bacillus subtilis, Bacilus coagulans and Clostridium butyricum, respectively, and $1.7\;ton/cm^2$ for the vegetative cell of Streptococcus faecalis. The spore destruction upon compressional pressure was influenced by the type of filler. The P-value of the spore of B. coagulans was $2.8\;ton/cm^2$ in the lactose filler, but $2.0\;ton/cm^2$ in the starch filler. The number of viable spores was inversely proportional to the hardness and density of tablet, in case that the same type of filler was used. The starch filler, which resulted in the lower hardness and lower density of tablet, caused higher spore destruction rate compared with the lactose filler.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.112-112
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• 2018

알루미늄 합금은 내구성과 내식성이 우수한 경량 재료이다. 그 중 Al-Mg계 5083 Al 합금은 가공성 및 용접성이 우수하여 선체 재료로 널리 이용되고 있다. 이는 선체 중량의 경량화로 인해, 연료비 절감과 빠른 선속 등 다양한 이점을 지니기 때문이다. 그러나 선박의 고속화에 따라 선체에 가해지는 유체충격이 증가하고, 압력 저하에 기인하여 캐비테이션-침식 손상이 증가할 뿐만 아니라, 염소이온이 존재하는 해수환경에서는 침식과 부식의 시너지효과로 인하여 재료의 손상이 더욱 가속화된다. 이에 대한 다양한 방지책들이 제안되고 있으나, 강한 충격압을 동반한 캐비테이션 침식-부식 복합 손상 환경에서는 다소 한계가 있다. 따라서 본 연구에서는 알루미늄 5083에 대하여 캐비테이션 환경 하에서 일정 전위를 인가하며 침식-부식 손상이 최소화 되는 전위 구간을 규명하고자 하였다. 먼저, 분극 실험을 선행하여 재료의 전기화학적 거동을 파악 한 후 적용 전위구간을 선정하여, 해당 전위를 인가한 상태에서 캐비테이션 실험을 실시하였다. 전기화학적 분극실험과 캐비테이션-전기화학 복합 실험은 $25^{\circ}C$의 해수 하에서 실시하였으며, 시험편의 노출면적은 $3.24cm^2$으로 하였다. 분극 실험은 개로전위로부터 +3 V까지 2 mV/s의 분극속도로 전위를 인가하였고, 기준전극으로 Ag/AgCl, 대극으로 백금전극을 사용하였다. 캐비테이션-전기화학 복합 실험은 정전위를 인가한 상태에서 대향형 진동법으로 진동수 20 kHz, 진폭 $30{\mu}m$ 진동을 20분간 가하였으며, 혼팁과 시험편 사이의 거리는 1 mm로 일정하게 유지하였다. 실험 후 표면 손상의 정량적 분석을 위해 인가된 전위별 전류밀도를 비교하고, 무게감소량을 측정하였으며, 손상경향 파악을 위하여 3D광학현미경과 주사전자현미경(SEM)을 통해 표면을 분석하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.209-214
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• 2017

Most of the present potential transformers of train vehicles are of the oil-type filled with insulating oil and are susceptible to problems such as explosion due to the increase in the internal pressure during train operation and poor reliability near the end of their life cycle. As a solution to this problem, it is necessary to develop a molded dry-type potential transformer with excellent pressure-resistance performance using insulating resin. In order to localize the product, the Korea Railroad Research Institute has been developing a molded dry-type potential transformer. As part of this research, it is necessary to analyze the vibration characteristics of the developed product and to check the transformer performance in a vibration environment. In this study, a resonance test and simulated long-term life test of the developed product were conducted according to the KS R 9144 and IEC 61373 standards, respectively, which are vibration test methods for railway vehicle parts. Their natural frequencies were analyzed by comparing the results of the numerical modal analysis and resonance test, in order to confirm their adherence to the standards. Also, the performance test after the simulated long-term life test confirmed that the operation of the developed transformer was not problematic even in a long-time vibration environment.