• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2844-2853
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• 2023

A sophisticated Bayesian multilevel model for estimating group bias was developed to improve the utility of the ASTM E900-15 embrittlement trend curve (ETC) to assess the conditions of nuclear power plants (NPPs). For multilevel model development, the Baseline 22 surveillance dataset was basically classified into groups based on the NPP name, product form, and notch orientation. By including the notch direction in the grouping criteria, the developed model could account for TTS differences among NPP groups with different notch orientations, which have not been considered in previous ETCs. The parameters of the multilevel model and biases of the NPP groups were calculated using the Markov Chain Monte Carlo method. As the number of data points within a group increased, the group bias approached the mean residual, resulting in reduced credible intervals of the mean, and vice versa. Even when the number of surveillance test data points was less than three, the multilevel model could estimate appropriate biases without overfitting. The model also allowed for a quantitative estimate of the changes in the bias and prediction interval that occurred as a result of adding more surveillance test data. The biases estimated through the multilevel model significantly improved the performance of E900-15.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1913-1924
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• 2024

This paper presents the design and operation of an autonomous robot for pyroprocess automation, which requires unique approaches beyond those used in industrial applications to achieve the desired performance. Maintaining an extremely dry atmosphere is crucial to handle various materials, including chloride, and an autonomous system ensures this dry environment. The drying room dehumidifier was carefully selected and designed to generate dry air, and different types of dry air conditioning performance were evaluated, including assessing worker accessibility inside the mock-up to determine the system's feasibility. Containers used for process materials were modified to fit the gripper system of the gantry robot for automation. The loading and unloading of process materials in each equipment were automatically performed to connect the process equipment with the robotic system. The gantry robot primarily operated through macro motion to approach waypoints containing process materials, eliminating the need for precise approach motion. The robot's tapered jaw design allowed it to grasp the target object even with imperfect positioning. Robot motions were programmed using a robot simulator for initial positioning and motion planning, and real accuracy was tested in a mock-up facility using the OPC platform.

• Journal of Radiation Industry
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• v.7 no.2_3
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• pp.177-182
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• 2013

This study was conducted to evaluate the effect of gamma irradiation on the microbial populations of dried raw materials (9 products) and Saengsik powder. The samples were gammairradiated at doses of 2, 4, 6 and 8 kGy and the microbiological populations were evaluated. The total numbers of bacteria and Bacillus cereus in non-irradiated dried-raw materials for Saengsik powder was 1.3~3.4 and $1.7{\sim}2.4log\;CFU\;g^{-1}$. However, gamma irradiation reduced the microbiological populations in all samples, and Saengsik powder were sterilized at more than 6 kGy. Moreover, Clostridium perfringens were not observed in all samples within detection limit (<$1log\;CFU\;g^{-1}$). Therefore, the results of this study suggest that gamma irradiation at 6 kGy is sufficient to sterilize Saengsik powder, and thus, irradiated Saengsik powder at 6 kGy fulfills the microbiological requirements for sterilized food.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.6
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• pp.421-428
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• 2021

Lithium-ion secondary batteries exhibit advantageous characteristics such as high voltage, high energy density, and long life, allowing them to be widely used in both military and daily life. However, the lithium-ion secondary battery does have its limitation; for example, the output power and capacity are readily decreased due to the increased internal impedance during discharging at a lower temperature (-32℃, military requirement). Also, during charging at a lower temperature, lithium dendrite growth is accelerated at the anode, thereby decreasing the battery capacity and life as well. This paper describes a study that involves increasing the internal temperature of lithium-ion secondary battery by energy circulation operation in a low-temperature environment. The energy circulation operation allows the lithium-ion secondary battery to alternately charge and discharge, while the internal resistance of lithium-ion battery acts as a heating element to raise its own temperature. Therefore, the energy circulation operation method and device were newly designed based on the electrochemical impedance spectroscopy of the lithium-ion secondary battery to mediate the battery performance at a lower temperature. Through the energy circulation operation of lithium ion secondary battery, as a result of the heat generated from internal resistance in an extremely low-temperature environment, the temperature of the lithium-ion secondary battery increased by more than 20℃ within 10 minutes and showed a 75% discharging capacity compared with that at room temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.424-424
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• 2009

• ETRI Journal
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• v.34 no.6
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• pp.966-969
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• 2012

From a practical viewpoint, the topic of electrical stability in oxide thin-film transistors (TFTs) has attracted strong interest from researchers. Positive bias stress and constant current stress tests on indium-gallium-zinc-oxide (IGZO)-TFTs have revealed that an IGZO-TFT with a larger Ga portion has stronger stability, which is closely related with the strong binding of O atoms, as determined from an X-ray photoelectron spectroscopy analysis.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.04a
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• pp.43-43
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• 2006

• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.70-85
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• 2006

The supersonic flutter suppression of a cantilevered plate wing is studied with the finite element method and the quasi-steady aerodynamic theory. We suppress wing flutter by using piezoelectric materials and electric devices. Two approaches to flutter suppression using piezoelectric materials are presented; an energy-recycling semi-active approach and a negative capacitance approach. To assess their flutter suppression performances, we simulate flutter dynamics of the plate wing to which piezoelectric patches are attached. The critical dynamic pressure drastically increases with our flutter control using a negative capacitor.

• Solar Energy
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• v.2 no.2
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• pp.37-53
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• 1982

In general, glass has proven to be an effective glazing material, exhibiting extended service lifetime and high solar transmittance while remaining opaque to long wave thermal reradiation. Plastics, which possess higher solar transmittance than commercial glass, are lightweight and also cost competitive with glass. In this paper a survey of various glazing materials is presented, and the comparative analysis of their properties are perform ed in detail with special emphasis on double glazing materials, which can be adaptable to various passive solar systems.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.36-36
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• 2011