• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.75-81
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• 2016

Tendon corrosion reliability in KICT-ultra high performance concrete (K-UHPC) bridges is assessed and predicted considering uncertainties in flexural bending capacity and corrosion occurrence. In post-tensioning bridge systems, corrosion is a one of most critical failure mechanisms due to strength reduction by it. During the entire service life, those bridges may experience lifetime corrosion deterioration initiated and propagated in tendons which are embedded not only in normal concrete but also in K-UHPC. For this reason, the time-variant corrosion performance has to be assessed. In the absence of in-depth researches associated with K-UHPC tendon corrosion, a reliability-based prediction model is developed to evaluate lifetime corrosion performance of tendon in K-UHPC bridges. In 2015, KICT built a K-UHPC pilot bridge at 168/5~168/6 milestone on Yangon-Mandalay Expressway in Myanmar, by using locally produced tendons which post-tensioned in longitudinal and lateral ways of K-UHPC girders. For an illustrative purpose, this K-UHPC bridge is used to identify the time-variant corrosion performance.

• Journal of the Korean Geosynthetics Society
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• v.4 no.1
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• pp.3-6
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• 2005

The failure of geogrids can be defined as an excessive creep strain which causes the collapse of slopes and embankments. In this study, the lifetime of knitted polyester geogrids was predicted by using SIM(Stepped Isothermal Methods using TTS principal) and statistical data analysis techniques. The results indicate that the creep strain was 8.74, 8.79, 8.80% with 2.16~2.20% of CV% at 75, 100, 114 years, respectively and the creep strain reaches 9.3% after 100 years of usage at $27^{\circ}C$ which meets the required lifetime(creep strain less than 10% after 100 years of usage) in the fields. The SIM method is shown to be effective in reduction of uncertainty associated with inherent variability of multi-specimen tests and shorter test times than conventional TTS(Time-Temperature Superposition).

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.4
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• pp.173-179
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• 2023

This paper analyzes the time-dependent dielectric breakdown(TDDB) degradation mechanism for each stress region of Peri devices manufactured by 4th generation VNAND process, and presents a complementary lifetime prediction model that improves speed and accuracy in a wider reliability evaluation region compared to the conventional model presented. SiON dielectric nMOSFETs were measured 10 times each under 5 constant voltage stress(CVS) conditions. The analysis of stress-induced leakage current(SILC) confirmed the significance of the field-based degradation mechanism in the low electric field region and the current-based degradation mechanism in the high field region. Time-to-failure(TF) was extracted from Weibull distribution to ascertain the lifetime prediction limitations of the conventional E-model and 1/E-model, and a parallel complementary model including both electric field and current based degradation mechanisms was proposed by extracting and combining the thermal bond breakage rate constant(k) of each model. Finally, when predicting the lifetime of the measured TDDB data, the proposed complementary model predicts lifetime faster and more accurately, even in the wider electric field region, compared to the conventional E-model and 1/E-model.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.5
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• pp.408-413
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• 2004

An experimental study has been carried out to investigate overheating of oil and bearing housing during pump operation. This problem is of particular interest in the pre diction of lifetime and failure of pump. Transient variation of oil temperature as well as bearing housing temperature is measured to study the effect of oil viscosity, oil amount, and discharge flow rate of pump. It is found that optimal oil quantity as well as proper viscosity of oil is required to keep the safe temperature level of oil and bearing housing in a pump. The oil temperature at steady state is almost not affected by discharge flow rate in the range of discharge flow rates considered in the present study.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.9
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• pp.758-763
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• 2000

Dielectric strength of insulators made of epoxy composites rapidly decreases due to ageing to interfaces between the matric resin and filler particles. The adhesion variation of interfaces caused by moisture absorption also alters electrical properties that are the basic characteristics of insulators, particularly, in outdoor use. In this paper, electrical properties of epox/SiO$_2$composites were investigated at boiling absorption condition to observe the influences of moisture. In order to analyze the basic physical properties of samples, scanning electron microscopy and DC, AC and impulse voltage dielectric strength were measured. Also, the breakdown time of samples was measured under AC 6[kV] applied voltage, and the variation of lifetime was verified by using Weibull distribution function.

• Design & Manufacturing
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• v.13 no.2
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• pp.49-53
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• 2019

The temperature distribution and lifetime of molds were predicted by computer simulation analysis with various spraying and blowing process of high pressure die casting. After varying the spraying angle and time, the mold temperature, heat exchange and mold life were predicted. As the spraying angle increases, the maximum temperature of the mold decreases, which is because the spraying area increases and the heat exchange with the mold increases. Heat exchange occurs more actively in the blowing process than in the spraying process. This is because the cooling is not performed due to the steam generation. When the spraying angle is 50 degree, the minimum life of the mold is analyzed 200 times. After adjusting the blowing time from 5s to 3s, the minimum lifetime of the mold has been increased almost twice.

• Journal of Korea Multimedia Society
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• v.14 no.9
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• pp.1138-1151
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• 2011

Sensor network clustering scheme is an efficient method that prolongs network lifetime. However, when it is applied to an environment in which collected data of the sensor nodes easily overlap, sensor node unnecessarily consumes energy. Accordingly, we proposed a data prediction scheme that sensor node can predict current data to exclude redundant data transmission and to minimize data transmission among the cluster head node and member nodes. Our scheme excludes redundant data collection by neighbor nodes. Thus it is possible that energy efficient data transmission. Moreover, to alleviate unnecessary data transmission, we introduce data prediction graph whether transmit or not through analyze between prediction and current data. According to the result of performance analysis, our method consume less energy than the existing clustering method. Nevertheless, transmission efficiency and data accuracy is increased. Consequently, network lifetime is prolonged.

• Computers and Concrete
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• v.17 no.4
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• pp.499-521
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• 2016

In this paper, a probabilistic- and finite element-based approach to evaluate and predict the lifetime performance of reinforced concrete (RC) bridges undergoing various maintenance actions is proposed with the time-variant system reliability being utilized as a performance indicator. Depending on their structural state during the degradation process, the classical maintenance actions for RC bridges are firstly categorized into four types: Preventive type I, Preventive type II, Strengthening and Replacement. Preventive type I is used to delay the onset of steel corrosion, Preventive type II can suppress the corrosion process of reinforcing steel, Strengthening is the application of various maintenance materials to improve the structural performance and Replacement is performed to restore the individual components or overall structure to their original conditions. The quantitative influence of these maintenance types on structural performance is investigated and the respective analysis modules are written and inputted into the computer program. Accordingly, the time-variant system reliability can be calculated by the use of Monte Carlo simulations and the updated the program. Finally, an existing RC continuous bridge located in Shanghai, China, is used as an illustrative example and the lifetime structural performance with and without each of the maintenance types are discussed. It is felt that the proposed approach can be applied to various RC bridges with different structural configurations, construction methods and environmental conditions.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.25-29
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• 2011

Emerging demands for rechargeable battery for various applications needs more effective battery management system such as the prediction of the usable time about a battery. Many prediction methods have been suggested but none of them come into bounds of reliability. In this paper, we proposed a new prediction algorithm for the remaining capacity of a rechargeable battery by using the transformed curve based on its impedance. Hardware for monitoring a battery was designed and made. Through a series of experiment, we showed the effectiveness of the proposed prediction algorithm of a battery's remaining capacity.

• Proceedings of the Korean Fiber Society Conference
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• 2007.11a
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• pp.201-202
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• 2007