• Journal of the Microelectronics and Packaging Society
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• v.25 no.1
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• pp.35-40
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• 2018

Nd:YAG laser was used to carbonize polyimide films to produce carbon films. This is a simple manufacturing process to fabricate low cost sensors. By applying this method, we studied characteristics of flexible and low-cost piezoresistive. Previously, many studies focused on carbonization of polyimide using $CO_2$ laser with wavelength of $10.6{\mu}m$. In this paper, carbonization (carbonization process) was performed on polyimide films using an Nd:YAG laser with a wavelength of $1.064{\mu}m$. In order to increase the resolution, we optimized the laser conditions of the power density ($W/cm^2$) and the beam scan rate. In previous studies using $CO_2$ laser, the minimum line width was $140{\sim}220{\mu}m$ but in this study, carbon line width was reduced to $35{\sim}40{\mu}m$. The initial sheet resistance of the carbon sensor was $100{\sim}300{\Omega}/{\square}$. The resistance decreased by 30% under stretched with a curvature radius of 21 R. The calculated gauge factor was 56.6. This work offers a simple, highly flexible, and low-cost process to fabricate piezoresistive sensors.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.2
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• pp.219-226
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• 2020

Nondestructive testing is one of the most commonly used quality inspection methods for evaluating ship structures. However, accurate evaluation is dif icult because various composite materials, such as reinforcements, resin, and fiber-reinforced plastics (FRPs), are used in hulls, and manufacturing quality differences are likely to exist owing to the fabrication environment and the skill level of workers. This possibility is especially true for FRP ships because they are significantly thicker than other structures, such as automobiles and aircraft, and are mainly manufactured using the hand lay-up method. Because the density of a material is a critical condition for ultrasonic inspection, in this study, a hull plate was selected from a vessel manufactured using e-glass fiber, which is widely used in the manufacture of FRP vessels with the weight fraction of the glass content generally considered. The most suitable ultrasonic testing conditions for the glass FRP hull plate were investigated using a pulse-echo ultrasonic gauge. A-scans were performed with three probes (1.00, 2.25, and 5.00 MHz), and the results were compared with those of the hull plate thickness measured using a Vernier caliper. It was found that when the probe frequency was higher, the eco-pulse velocity of the receiver had to be lowered to obtain accurate measurement results, whereas fewer errors occurred at a relatively low probe frequency.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.1
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• pp.45-56
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• 2013

This study was suggested as fundamental data to control medical materials remained in Nakdong range gauge. The level of Iopromide detected in Nakdong mainstream was $0.0015{\sim}0.37{\mu}g/L$, Mefenamic acid $0.0087{\sim}0.056{\mu}g/L$, Diclofenac $N.D.{\sim}0.01{\mu}g/L$, Atenolol $N.D.{\sim}0.024{\mu}g/L$, Propranolol $N.D.{\sim}0.0038{\mu}g/L$, Lincomycin $0.0005{\sim}0.038{\mu}g/L$, and Trimethoprim $N.D.{\sim}0.0083{\mu}g/L$. At sewage disposal plant in the region, most of them were detected high levels of density. Especially, the level of Iopromide was found the highest up to $5.38{\mu}g/L$. At livestock wasted water disposal plant, the level of lincomycin was detected the highest figure of $477{\mu}g/L$. As a result, medical materials from Nakdong River mainstream got increasing the concentration due to inflow from sewage disposal plant in Gumi and River Geumho in Daegu, which affects residential and industrial areas significantly. Therefore, to control medical materials remained in Nakdong River efficiently, Geumho River and sewage disposal plants shall be continuously monitored and managed, which is recommendable.