• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.185-190
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• 2016

The high-power 6.6 kV XLPE (or CV) cables at Korean electric power stations have been in operation for the last 40 years. Most of the XLPE cables starts deteriorating in 6-8 years from the operating instant of time, some cables may be breakdown at any moment even though they were installed in recent years, causing, huge socioeconomic losses. In order to prevent unexpected cable accident, the operating status of power cables should be monitored in regularly, timely bases. We have invented a device in order to systematically monitor and prevent an abrupt accidents of high-power cables in operation at power station. It has been installed at Korean Western Power Co. Ltd. at Taean, and operating normally for the last 4 years. In this paper, we introduce the functions and operating principles of the measuring device, and present the relationship between humidity and insulation status of XLPE cables for the load of electric turbine generator.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.213-218
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• 2017

High-voltage power systems operate in order to generate and transmit electric power at power stations. Compared to low-power systems, high-power systems are complex in structure, large-scale, and expensive. When high-power cable accidents occur, most facilities are incapacitated-including low-power systems-causing huge economic losses. Great care must therefore be taken in designing, installing and managing power systems. Although dependent on installation circumstances and usage conditions, in some cases the cross-sectional areas of cables fall short of the critical area due to the expansion of and improper design and installation of power facilities. In this situation, the exceeded ampacity (allowable current) above the critical value caused by the operating current initiates the deterioration processes of power cables. In order to systematically monitor power cables operating at power stations, we have developed the first device of its kind in Korea. In this paper, we present the analyzed characteristics of expected temperatures of cables based on the load current of high-voltage cables operating at Korean Western Power Co. Ltd. We can predict the lifetime of cables by analyzing the temperature obtained from our device.

• Journal of Sensor Science and Technology
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• v.13 no.2
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• pp.128-132
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• 2004

Short wave infrared (SWIR) photovoltaic devices have been fabricated from metal organic vapour phase epitaxy (MOVPE) grown n- on p- HgCdTe films on GaAs substrates. The MOVPE grown films were processed into mesa type discrete devices with wet chemical etching employed for meas delineation and ZnS surface passivatlon. ZnS was thermally evaporated from effusion cell in an ultra high vacuum (UHV) chamber. The main features of the ZnS deposited from effusion cell in UHV chamber are low fixed surface charge density, and small hysteresis. It was found that a negative flat band voltage with -0.6 V has been obtained for Metal Insulator Semiconductor (MIS) capacitor which was evaporated at $910^{\circ}C$ for 90 min. Current-Voltage (I-V) and temperature dependence of the I-V characteristics were measured in the temperature range 80 - 300 K. The Zero bias dynamic resistance-area product ($R_{0}A$) was about $7500{\Omega}-cm^{2}$ at room temperature. The physical mechanisms that dominate dark current properties in the HgCdTe photodiodes are examined by the dependence of the $R_{0}A$ product upon reciprocal temperature. From theoretical considerations and known current expressions for thermal and tunnelling process, the device is shown to be diffusion limited up to 180 K and g-r limited at temperature below this.

• Journal of Sensor Science and Technology
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• v.6 no.2
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• pp.115-122
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• 1997

In this paper, on-chp atomatic tuning circuit, using proposed integration level approximation technique, is designed to tuning of the variation of RC time-constant due to aging or temperature variation, etc. This circuit reduces the error, the difference between code values and real outputs of integrator, which is drawback of presented dual-slope tuning circuit and eliminates modulations of processing signals in integrated circuit due to fixed tuning codes during ordinary operation. This system is made up of simple integrator, A/D converter and digital control circuit and all capacitors are replaced by programed capacitor arrays in this system. This tuning circuit with 4 bit resolution achieves $-9.74{\sim}+9.68%$ of RC time constant error for 50% resistance variation.

• Journal of Sensor Science and Technology
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• v.24 no.4
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• pp.264-269
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• 2015

An infrared (IR) bolometer measures the change of resistance by absorbing incident IR radiation and generates a signal as a function of the radiation intensity. Since a bolometer requires temperature stabilization and light filtering except for the infrared rays, it is essential for the device to be packaged meeting conditions that above mentioned. Minimization of heat loss is needed in order to stabilize temperature of bolometer. Heat loss by conduction or convection requires a medium, so the heat loss will be minimized if the medium is a vacuum. Therefore, vacuum packaging for bolometer is necessary. Another important element in bolometer packaging is germanium (Ge) window, which transmits IR radiation to heat the bolometer. To ensure a complete transmittance of IR light, anti-reflection (AR) coatings are deposited on both sides of the window. Although the transmittance of Ge window is high for IR rays, it is difficult to use frequently in low-price IR bolometer because of its high price. In this paper, we fabricated IR window by utilizing silicon (Si) substrate instead of Ge in order to reduce the cost of bolometer packaging. To enhance the IR transmittance through Si substrate, it is textured using Reactive Ion Etching (RIE). The texturing process of Si substrate is performed along with the change of experimental conditions such as gas ratio, pressure, etching time and RF power.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.215-219
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• 2020

MnCo₂S₄/CoS₂ electrode with highly accessible electroactive sites is prepared using the hydrothermal method. The electrode exhibits an areal capacitance of 0.75 Fcm^-2 at 6 mAcm^-2 in 1 M KOH. The capacitance is further increased to 2.06 Fcm^-2 by adding K₃Fe(CN)₆ and K₄Fe(CN)₆ (a redox couple) to KOH. This increment is associated with the redox-active properties of cobalt and manganese transition metals, as well as the ion pair of [Fe(CN)₆]^-3/[Fe(CN)₆]^-4. The capacitance retention of the MnCo₂S₄/CoS₂ electrode is 87.5% for successive 4000 charge-discharge cycles at 10 mAcm^-2 in a composite electrolyte system of KOH and ferri/ferrocyanide. The capacitance enhancement is supported by the lowest equivalent series resistance (0.62 Ωcm^-2) of MnCo₂S₄/CoS₂ in the presence of redox additive couple compared with the bare KOH electrolyte.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.1
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• pp.8-13
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• 2014

As packing density in integrated circuits increases, multilevel metallization process has been widely used. But hillock formed in the bottom layers of aluminum are well known to make interlayer short in multilevel metallization. In this study, the effects of ion implantation to the metal film and deposition temperature on the hillock formation were investigated. The Al-1%Si thin film of $1{\mu}m$ thickness was DC sputtered with substrate ($SiO_2/Si$) temperature of $20^{\circ}C$, $200^{\circ}C$, and $400^{\circ}C$, respectively. Ar ions ($1{\times}10^{15}cm^{-2}$: 150 keV) and B ions ($1{\times}10^{15}cm^{-2}$, 30 keV, 150 keV) were implanted to the Al-Si thin film. The deposited films were evaluated by SEM, surface profiler and resistance measuring system. As a results, Ar implanting to Al-Si film is very effective to reduce hillock size in the metal deposition temperature below than $200^{\circ}C$, and B implanting to an Al-Si film is effective to reduce hillock density in the high temperature deposition conditions around $400^{\circ}C$. Line width less than $3{\mu}m$ was free of hillock after alloying.

• Fashion & Textile Research Journal
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• v.15 no.2
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• pp.309-315
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• 2013

This study examines the difference of surface properties according to napping characteristic of artificial suedes, measuring surface structure observation, the contact/non-contact method roughness, warm-cool feeling of touch, and subjective hand evaluation. Surface and cross-section observations showed a discernible difference in fineness, curl, length, mount of napping, and covering power of base fabric. The surface properties of artificial suede evaluated by KES-FB4 showed that the shorter napping length the more smooth surface and the roughness increased reciprocally with friction resistance and surface contour when the nap length reaches a high level. The surface roughness measuring system applied a laser displacement sensor by a non-contact method to assess napping characteristic and the base fabric and napping height. Surface roughness decreased when napping was uniformly covered with base fabric; however, the surface roughness increased specifically with the uneven covering power of the base fabric. For qmax of the suedes, those that had short and smaller amounts of napping increased; however, the napping of length and amount at some stage generated a low qmax value. The warm sensation in all suedes were strongly perceived, but the cool sensation of the perception was lower in the subjective evaluation. Smoothness and softness were perceived when the suede has a long and large amount napping; however, smoothness and hardness were perceived when the suede was short and with the uneven covering power.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.4
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• pp.255-262
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• 2016

There has been intense research on self-diagnosis systems in railway applications, since stability and reliability have become more and more significant issues. Wired sensors have been widely used in the railway vehicles, but because of the difficulty in their maintenance and accessibility, they ar not considered for self-diagnosis systems. To have a self-monitoring system, wireless data transmission and self-powered sensors are required. For this purpose, a thermoelectric energy harvesting module that can generate electricity from temperature gradient between the bogie axle box and ambient environment was introduced in this work. The temperature gradient was measured under actual operation conditions, and the behavior of the thermoelectric module with an external load resistance and booster circuits was studied. The proposed energy harvesting system can be applied for wireless sensor nodes in railroad vehicles with optimization of thermal management.

• Korean Journal of Materials Research
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• v.21 no.9
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• pp.486-490
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• 2011

Nano-indium-coated ZnO:In thick films were prepared by a hydrothermal method. ZnO:In gas sensors were fabricated by a screen printing method on alumina substrates. The gas sensing properties of the gas sensors were investigated for hydrocarbon gas. The effects of the indium concentration of the ZnO:In gas sensors on the structural and morphological properties were investigated by X-ray diffraction and scanning electron microscopy. XRD patterns revealed that the ZnO:In with wurtzite structure was grown with (1 0 0), (0 0 2), and (1 0 1) peaks. The quantity of In coating on the ZnO surface increased with increasing In concentration. The sensitivity of the ZnO:In sensors was measured for 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity to $CH_4$ gas and $CH_3CH_2CH_3$ gas of the ZnO:In sensors was observed at the In 6 wt%. The response and recovery times of the 6 wt% indiumcoated ZnO:In gas sensors were 19 s and 12 s, respectively.