• 대한기계학회논문집A
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• 제29권12권
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• pp.1645-1652
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• 2005

Pick-and-place systems using suction cups have been being widely used and continuously developed in production automation. There are, however, some drawbacks in constructing such systems. One of them is that it generates high level noise due to air compressors. And the system must have complex constitutions of mechanical component such as air compressors, air tubes, air valves, etc. Moreover, it needs continuous air supply to maintain vacuum in suction cups. If there is a failure in any suction cup, the total suction system may fail owing to air leakage. To overcome these drawbacks, we propose PMS (Permanent Magnet Suction) mechanism which has permanent magnets for vacuuming suction cups with no air compressor. The basic concept of PMS mechanism is to rotate permanent magnets with fixed angle. Simple rotation of permanent magnets changes the direction of the magnetic force applied at the suction cups. Since each suction cup has no direct connection with any of the others, the air leakage at one suction cup is not critical. The proposed suction mechanism was designed and fabricated. With some experiments, the feasibility and performance of the PMS mechanism was shown. The strong points of the PMS mechanism are in its simple structure, generating low noise, high energy efficiency, and no need of continuous energy supply.

• 조명전기설비학회논문지
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• 제28권9호
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• pp.14-19
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• 2014

Recently, many renewable energy generating businesses are ongoing progress due to the introduction of the RPS(Renewable Portfolio Standards) as well as the needs of environmentally friendly energy resources. Researches on photovoltaic system are actively being processed since the photovoltaic system is relatively easy to install and becomes commercialized in many domestic application areas. Furthermore, the floating photovoltaic system is likely to be installed more actively since the conventional photovoltaic system requires relatively large areas of land. Also, the floating photovoltaic system is more efficient than photovoltaic system installed in land due to the operation in lower temperature. However, safety problems such as electric shock could arise since the cable should be installed in the water. In this paper, the leakage current and the voltage rising are measured and analyzed for the case when the cables are damaged connecting the floating photovoltaic system to the grid.

• 동력기계공학회지
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• 제11권3호
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• pp.35-40
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• 2007

Leak would happen because of the damage of high temperature and high-pressure valve in nuclear power plant. condition based prevention maintenance is essential by using the suitable method based on local condition. Energy loss prevention can prevent from an accurate test, Local actually and ability. The methods of test for high energy fluid leak at present are analysis of ${\Delta}T$, AE(Acoustic Emission) analysis, and thermal image. The result for test of secondary system in nuclear power plant Unit reveals that the AE occurred clearly in leakage situation, but thermal image didn't occur. It is identified that leak is occurred when the orifice located front and back of valve operates. It shows that making a impatient judgment by using the single method if it is leakage is containing uncertainty. So we think that using the Multi-Measuring method is more sound judgment than single-measuring method.

• 대한기계학회논문집A
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• 제39권2호
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• pp.187-193
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• 2015

STS310S 는 열전달 능력이 우수하여, 열교환기용 열전달 튜브 재료로서 많이 사용된다. 튜브의 안쪽은 가스와 물의 혼합물이 흐르고, 튜브 바깥은 화염이 흐른다. 이와 같은 환경에서 튜브는 취화하였고, 누설이 발생하였다. 균열은 안쪽에서 바깥으로 전파하여 취성파괴 하였다. 본 연구는 취성파괴의 원인을 실험과 고찰을 통하여 규명하고, 해결 방법을 제안하였다.

• 한국세라믹학회지
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• 제51권3호
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• pp.190-196
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• 2014

Flexible $TiO_2$ films were deposited as dielectric materials for high-energy-density capacitors on polyethylene terephthalate (PET) substrates using a roll-to-roll sputtering method. Both the growth behavior and electrical properties of the flexible $TiO_2$ films were dependent on the sputtering pressure and $O_2$/Ar gas ratio during the sputtering process. All $TiO_2$ films had an amorphous structure regardless of the sputtering conditions due to the low substrate temperature. Microstructural characteristics such as the surface morphology and roughness of the films degraded with an increase in the sputtering pressure and $O_2$ gas concentration. The $TiO_2$ films deposited at a low pressure showed better electrical properties than those of films deposited at a high pressure. The $TiO_2$ films prepared at 10 mTorr exhibited a dielectric constant of approximately 90 at 1 kHz and a leakage current density of $5{\sim}6{\times}10^{-7}A/cm^2$ at 3 MV/cm.

• Journal of Power Electronics
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• 제16권2호
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• pp.436-446
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• 2016

A novel step-up DC-DC converter with a switched-coupled-inductor-capacitor (SCIC) which successfully integrates three-winding coupled inductors and switched-capacitor techniques is proposed in this paper. The primary side of the coupled inductors for the SCIC is charged by the input source, and the capacitors are charged in parallel and discharged in series by the secondary windings of the coupled inductor to achieve a high step-up voltage gain with an appropriate duty ratio. In addition, the passive lossless clamped circuits recycle the leakage energy and reduce the voltage stress on the main switch effectively, and the reverse-recovery problem of the diodes is alleviated by the leakage inductor. Thus, the efficiency can be improved. The operating principle and steady-state analyses of the converter are discussed in detail. Finally, a prototype circuit at a 50 kHz switching frequency with a 20-V input voltage, a 200-V output voltage, and a 200-W output power is built in the laboratory to verify the performance of the proposed converter.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 제5회 영호남 학술대회 논문집
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• pp.126-129
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• 2003

The electrical properties of a ZnO-based multilayered chip varistor (abbreviated as MLV) were studied as functions of firing condition and the degree of lamination. The fundamental varistor characteristics such as nonlinear coefficient and breakdown voltage were independent of the degree of lamination. As the number of the laminated ceramic sheets increased, however, not only the energy handling capability but also the capacitance and the leakage current which are relevant to delayed response to the voltage surge and the pre-breakdown energy loss, respectively, increased. With the increase of firing temperature between $950^{\circ}C$ and $1150^{\circ}C$, both the capacitance and the leakage current of the MLV increased due mainly to the grain growth of ZnO and the volatilization of $BiO_2O_3$. High performance MLVs with clear electrode pattern were obtained at the firing temperature range of $l000{\sim}1050^{\circ}C$ in this experiment.

• Corrosion Science and Technology
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• 제3권6호
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• pp.233-239
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• 2004

Primary water stress corrosion cracking of steam generator tubings occur on many tubes in pressurized water reactors(PWRs), and they are repaired using sleeves or plugs. In order to develop proper repair criteria, it is necessary to know the leak behavior of the tubes, which have stress corrosion cracks. Crack development tests were carried out on the tubes at room temperature, and leak rate and burst pressure were measured on the degraded tubes at room temperature and a high temperature. No leakage was detected on the tubes where 100 % through wall crack developed, at 1560 psi, which is an operating pressure difference of pressurized water reactors(PWRs). In some tests, leak rates of the tubes increased with time at a constant internal water pressure. A test tube showed a very small amount of leakage at 2700 psi in a high temperature pressure test at $282^{\circ}C$, but it disappeared after the pressure increased slightly. Even cracks are 100 % through wall, they need to open in order to reach a certain amount of leak rate at the operating pressure difference.

• 전기학회논문지
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• 제66권3호
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• pp.540-544
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• 2017

In this study, we analyzed the effects of TID(Total Ionizing Dese) and TREE(Transient Radiation Effects on Electronics) on nMOSFET and pMOSFET fabricated by 0.18um CMOS process. The size of nMOSFET and pMOSFET is 100um/1um(W/L). The TID test was conducted up to 1 Mrad(Si) with a gamma-ray(Co-60). During the TID test, the nMOSFET generated leakage current proportional to the applied dose, but that of the pMOSFET was remained in a steady state. The TREE test was conducted at TEST LINAC in Pohang Accelerator Laboratory with a maximum dose-rate of $3.16{\times}10^8rad(si)/s$. In that test nMOESFET generated a large amount of photocurrent at a maximum of $3.16{\times}10^8rad(si)/s$. Whereas, pMOSFETs showed high TREE immunity with a little amount of photocurrent at the same dose rate. Based on the results of this experiment, we will progress the research of the radiation hardening for CMOS unit devices.

• 한국수소및신에너지학회논문집
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• 제34권2호
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• pp.205-211
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• 2023

Hydrogen gas is light and diffuses very quickly. Therefore, when a leakage accident occurs, the damage is great, so a technology that can quickly measure the leakage in the air at a long distance is needed. In order to develop hydrogen gas leaked in the atmosphere in a non-contact manner, an experiment was performed to measure hydrogen gas using a lidar technology using the Raman effect. Hydrogen Raman signals were detected using a UV LED light source, which is a Raman light source, and a spectrometer in the ultraviolet region including an optical filter in the 400-430 nm band. To develop this, a Raman lidar optical structure was designed to measure the hydrogen Raman signal at a certain distance, and the hydrogen Raman spectrum was confirmed using a standard gas to evaluate the performance of this optical structure. The linearity was found to be 0.99 using hydrogen standard gas (10, 50, 100, 500, 1,000 ppm). Accordingly, a Raman lidar capable of measuring hydrogen gas rapidly diffusing in the air in an open state was developed to improve the limitations of existing hydrogen sensors.