• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.6
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• pp.9-17
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• 2011

The high-power LED (Light Emitting Diode) which is recently gaining popularity as a digital light source has such advantages as low power consumption, long life, fast switching speed, and high efficiency. Thus, many efforts are being made to use the high-power LEDs for general lighting. This paper proposes LED driving circuit uses a DC/DC converter that can recover energy to compensate for the current variations caused by changes in LED equivalent resistance following a temperature change instead of serial resistance. The maximum input voltage of this DC/DC converter has low voltage variations by temperature change when the rated current is formed. In order to return current to the input side, we need a high boosting at low power. Thus, to improve the low efficiency of power converter, the power converter can be configured in such a way to gather the powers of low-capacity DC/DC converters and return the total power. Experiments showed that the proposed system improved efficiency compared to the conventional LED drive using the existing DC/DC converter.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.2
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• pp.172-177
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• 2022

The quench voltage of the second-generation superconducting wire is affected by the resistivity characteristics of the stabilization layer. The specific resistance of the stabilization layer can be changed by the deposition process using RF magnetron sputtering. In this paper, a thin film made of a homogeneous material (Ag) and a dissimilar material (Cu) was deposited on the stabilization layer of the second-generation superconducting wire through RF magnetron sputtering. We found that the specific resistance was reduced by increasing the thickness of the stabilization layer. The reduction in the resistivity of the stabilization layer led to a decrease in the quench voltage of the second-generation superconducting wire. We suggest that various characteristic changes of the second-generation superconducting wire can be expected through the successful change in the resistivity of the stabilization layer of the proposed deposition process.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.365-373
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• 2018

In this paper, inter-turn fault diagnosis of the interior permanent magnet synchronous motor (IPMSM) is performed in offline state by linking the finite element analysis (FEA) tool and control simulation tool. In order to diagnose the inter-turn fault, it is important to select the current value to determine the fault. First, the basic principles for inter-turn fault diagnosis of IPMSM are explained and co-analysis model for fault diagnosis is constructed. Further, in order to select the appropriate high frequency voltage, the change of the current value to be judged as failure was analyzed at various voltage and frequency conditions, and the change of the current value according to the number of the failed windings was analyzed. Finally, the current value to be judged as failure is selected.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.8
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• pp.1070-1074
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• 2014

With the development of the electronics industry and widespread supply of many different electrical appliances, the factors of the electrical fires are also diversified. For this reason, the fuse, safety-critical component, needs accurate and stable operating characteristics for preventing various fire factor, and also needs various operating characteristics. Especially when the all electrical resistance are dropped by internal short of circuit, high current inrushes and makes the fire. In order to prevent this, very fast acting fuses should be applied. However, existing very fast acting characteristics fuse has less wire dimension of element Ag100% metal than that of fast acting fuse, and it is made of plating with low melting point metals, so it satisfy very fast acting but it can't satisfy durability and safety. For this reason, in this study, through the analyzing fusing characteristics of Ag-Cu alloy composition, the new alloy composition, which implement to very fast acting fuse without decrease of fuse elements dimension, is suggested. And this study classify the operating characteristics changes, a resistance change, and the rated current of the fuse in the overall composition change of Ag-Cu alloying. and it can be utilized for designing fuse.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.9
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• pp.707-711
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• 2013

Carbon nanotubes(CNT) has strength and chemical stability, greatly conductivity characteristics. In particular, MWCNT (multi-walled carbon nanotubes) show rapidly resistance sensitive for changes in the ambient gas, and therefore they are ideal materials to gas sensor. So, we fabricated NOx gas sensors structured MOS-FET using MWCNT (multi-walled carbon nanotubes) material. We investigate the change resistance of NOx gas sensors based on MOS-FET with ultra lean NOx gas concentrations absorption. And NOx gas sensors show sensitivity on the change of gate-source voltage ($V_{gs}=0[V]$ or $V_{gs}=3.5[V]$). The gas sensors show the increase of sensitivity with increasing the temperature (largest value at $40^{\circ}C$). On the other hand, the sensitivity of sensors decreased with increasing of NOx gas concentration. In addition, We obtained the adsorption energy($U_a$), $U_a$ = 0.06714[eV] at the NOx gas concentration of 8[ppm], $U_a$ = 0.06769[eV] at 16[ppm], $U_a$ = 0.06847[eV] at 24[ppm] and $U_a$ = 0.06842[eV] at 32[ppm], of NOx gas molecules concentration on the MWCNT gas sensors surface with using the Arrhenius plots. As a result, the saturation phenomena is occurred by NOx gas injection of concentration for 32[ppm].

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.2
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• pp.115-123
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• 2007

For investigating self-diagnosis applicability, a method based on monitoring the changes in the electrical resistance of carbon fiber reinforced concrete has been tested. Then after examining change in the value of electrical resistance at each flexural weight-stage of carbon fiber in CFGFRP (carbon fiber and glass fiber reinforcing plastic) with new type rib and carbon sheet for concrete reinforcing, the correlations of electrical resistance and load as a function of strain, deflection were analyzed. As the results, it is clarified that when carbon fiber rod, rib and sheet fracture, the electrical resistance of it increase largely, and specially in case of CFGFRP, afterwards glass fiber tows can be resist the load due to the presence of the hybrid (carbon and glass) reinforced fiber. Therefore, it can be recognized that reinforcing bar and new type rib of CFGFRP and sheet of CF could be applied for self-diagnosis of fracture in reinforced FRP concrete.

• Journal of Biosystems Engineering
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• v.11 no.2
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• pp.14-22
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• 1986

This study was carried out to find a method which can be used to measure the soil moisture content of the soil bin exactly and quickly. And gypsum block is used as an instrument in measuring soil moisture content in the field of green house farming, etc.. However the characteristics of gypsum block, or the guide line of making gypsum block is not well introduced in Korea. So the information about gypsum block such as the density of gypsum, type of electrode, dimension of electrode, distance between electrodes, density of surrounding soil were included in this study and their effects on the relationship between soil moisture content and electrical resistance were investigated. The results of this study are as follows; 1. The grid type electrode was quicker in accessing the equilibrium condition and showed more sensitive response to the change of soil moisture content than the plate type electrode. 2. The longer the distance between the electrodes, the larger the electrical resistance, and the distance of 3 to 5 mm was recommended. 3. The larger the width of the electrode, the smaller the electrical resistance. However, there was no significance between the levels designed in this study. Considering the size of the gypsum block itself, the adaptible range of width may be 4 to 8 mm. 4. The higher the density of gypsum, the smaller the electrical resistance. And the block of lower density was broken down in the soil of higy moisture content. The optimum ratio of gypsum to water was 7:5. 5. The measuring system used in this study allowed simultaneous, multi-data acquisition. So this system using A/D converter can be applied to the measurement of soil moisture content of soil bin.

• Journal of Adhesion and Interface
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• v.18 no.1
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• pp.1-7
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• 2017

This study is about basic sensor experiment using PDPS by common pencil. 20 mm length, 3 mm thickness of line using 4B pencil is optimum condition. In order to be stable at point of contact between pencil line and copper wire, silver paste is needed. At using the PDPS, thermal detecting is able and thermal properties is inversely proportional to electrical resistance in the based on empirical formula. The sensor can be also used in the composites mold via the empirical formula by the relationship between thermal impact and electrical resistance. The change of electrical resistance relates the interfacial property of composites. It leads to expectation of properties.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.56-62
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• 2018

The bus bar is an electrical connection widely used for the power supply of skyscrapers and power distribution and industrial equipment electrical panels in industrial plants. There are various materials to be considered in the design of the bus bar, such as material based on the use environment, the sectional area according to the power capacity, the length of the surface circumference, and the tightening method. Even with a bus bar manufactured to a size of sufficient power capacity in the design, if the actual tightening is incorrect, it may lead to fire due to deterioration. For these reasons, a variety of research on the temperature rise of the electrical contact point has continued. However, the temperature rise of the contacts is a consequence of the result, not a direct cause. In this paper, the influence of contact resistance on the fastening force and the overlapping section of the bus bar are investigated by measuring the change in resistance from building the specimen. A total of eight bus bar specimens were manufactured and measured. Resistance was measured by varying the clamping force and the interval between overlapping sections when the specimens were crossed. We propose a safe power connection model by analyzing the contribution of these factors to the actual contact resistance change.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.67-68
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• 2009

In this study, we studied the nature of thin films formed by photodoping chalcogenide materials with for use in programmable metallization cell devices, a type of ReRAM. We investigated the resistance of Ag-doped chalcogenide thin films varied in the applied voltage bias direction from about $1\;M{\Omega}$ to several hundreds of $\Omega$. As a result of these resistance change effects, it was found that these effects agreed with PMC-RAM. The results imply that a Ag-rich phase separates owing to the reaction of Ag with free atoms from the chalcogenide materials.