• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.50-57
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• 2004

For the application of structural health monitoring such as AE detection, a stabilized FBG sensor system with wide dynamic range was proposed. A tunable Fabry-Perot filter with narrow free spectral range(FSR) was used to simplify the multiplexing demodulator for FBG vibration sensors. Stabilization controlling system was also developed for the maintenance of maximum sensitivity of the sensors. In order to verify the performance of the proposed FBG vibration sensor system, we measured sensitivity, and the system showed the average sensitivity of 256 $n{\in}_{mas}/{\sqrt{Hz}}$. Finally, multi-points vibration tests using in-line FBG sensors were conducted to validate the multiplexing performance of the FBG system.

• Journal of Convergence for Information Technology
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• v.11 no.9
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• pp.124-129
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• 2021

A time-interpolation technique has been applied to the conventional FLASH analog-to-digital converter (ADC) to increase a number of quantization level, thus it reduces not only a power dissipation, but also minimize an active chip area. In this work, we demonstrated 5-bit ADC which has 31 quantization levels consisting of 16 conventional voltage-mode comparators and 15 time-mode comparators. As a result, we have achieved about 48.4% voltage-mode comparator reductions. The ADC is fabricated in a 14nm fin Field-effect transistor (FinFET) process with an active die area of 0.0024 mm2 while consuming 0.82 mW through a 0.8 V supply. At 400-MS/s conversion rate, the ADC performs 28.03 dB SNDR (4.36 ENOB) at 21MHz input frequency.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.6 s.52
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• pp.137-145
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• 2006

Recently, the interests in structural monitoring of civil infrastructures are increased. Especially, as the civil infrastructures such as bridges, tunnels and buildings become large-scale, it is necessary to monitor and maintain the safety state of the structures, which requires smart systems that can supply long-term monitoring during the service time of the structures. In this paper, we investigated the possibilities of fiber optic sensor application to the various structures. We investigate the possibility of using fiber optic Bragg grating sensors to joint structure. The sensors show good response to the structural behavior of the joint while electric gauges lack of sensitivity, durability and long term stability for continuous monitoring. We also apply fiber optic structural monitoring to the composite repaired concrete beam structure. Peel-out effects is detected with optical fiber Bragg grating sensors and the strain difference between main structure and repaired carbon sheets is observed when they separate each other. The real field test was performed to verify the behaviors of fiber Bragg grating sensors attached to the containment structure in Uljin nuclear power plant in Korea as a part of structural integrity test which demonstrates that the structural response of the non-prototype primary containment structures. The optical fiber Bragg grating sensor smart system which is the probable means for long term assessments can be applicable to monitoring of structural members in various civil infrastructures.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.11 s.353
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• pp.83-89
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• 2006

This paper describes the design of I/Q channel 12bit Digital-to-Analog Converter(DAC) which shows the conversion rate of 120MHz and the power supply of 3.3V with 0.35um CMOS n-well 1-poly 4-metal process for advanced wireless transceiver. The proposed DAC utilizes 4-bit thermometer decoder with 3 stages for minimum glitch energy and linearity error. Also, using a optimized 4bit thermometer decoder for the decrement of the chip area. Integral nonlinearity(INL) of ${\pm}1.6LSB$ and differential nonlinearity(DNL) of ${\pm}1.3LSB$ have been measured. In single tone test, the ENOB of the proposed 12bit DAC is 10.5bit and SFDR of 73dB(@ Fs=120MHz, Fin=1MHz) is measured, respectively. Dual-tone test SFDR is 61 dB (@ Fs=100MHz, Fin=1.5MHz, 2MHz). Glitch energy of 31 pV.s is measured. The converter consumes a total of 105mW from 3.3-V power supply.

• Journal of the Korean Geosynthetics Society
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• v.21 no.1
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• pp.1-10
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• 2022

In this study, a model parameter evaluation method using relative density was proposed to utilize applicable UBC3D-PLM for liquefaction behavior. In addition, dynamic effective stress analysis, that is, liquefaction analysis, was performed on the case of the liquefaction occurrence region where acceleration and pore water pressure were measured, and compared with the actual measurement and the existing Finn analysis results. Through this study, it was found that the proposed method can easily evaluate the necessary parameters required by the related model and predict the pore water pressure behavior in the region where liquefaction occurs. In addition, in the case of the study area, both measurements and numerical analysis showed that liquefaction occurred when a certain amount of time elapsed after the earthquake acceleration reached the maximum value. In the case of UBC3D-PLM applied in this study, the excess pore water pressure behavior similar to the actual measurement was predicted, and the occurrence of liquefaction was evaluated in the same way as the actual measurement. In particular, although the excess pore water pressure in the sand layer was greater, the phenomenon in which liquefaction occurred in the silt layer was accurately realized. It is expected that the proposed model parameter evaluation method and finite element analysis applying UBC3D-PLM can be used to select the liquefaction reinforcement region in the future seismic design and reinforcement by evaluating the liquefaction occurrence region similarly to the real one.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.386-395
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• 2010

The steam generator management program(SGMP) has recently defined the procedures for the qualification of eddy current hardware and technique. These procedures provide two basic methods for qualification. The first way is to qualify the equipment or the probe by using the flaw mechanism and method of the pulled tubes from the heat exchangers or the artificial flawed tubes. The second way is to verify the equivalency with the characteristics of the qualified equipment or probe. In this case, the qualified equipment or probe may be modified to substitute or replace instruments or probes without re-qualification provided that the range of essential variables defined in the examination technique specification sheet are met. This study is to describe the result of the comparative performance evaluation of bobbin coil eddy current probes manufactured by KEPCO Research Institute and probes manufactured by a foreign manufacturer. As a result of this study, although there were minor differences between the two kinds of probes, it was evaluated that the two kinds of probes were almost identical in the significant performance characteristics described in the KEPCO Research Institute guideline.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.6
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• pp.959-967
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• 2008

The body measurement ratios and indices used in this study are all 3D female measurement data of the two countries were obtained from Size Korea Project and SizeUSA Project. The purpose of the study is to compare and analyze body measurement data between two countries. The results of this research are helpful for the clothing manufacturer and company to trade with America. The samples were 1,988 Korean and 6,306 American females. Thirty-five body measurement ratios and indices were chosen as the principal measurements in making garments. The conclusion of this research was as follow; First, U.S. females have measurements that exceed Korean women, except for crotch length total and shoulder slope. Second, the correlation coefficients of height and weight are relatively higher than other measurements in the two countries' body measurements. Finally, American women's height ratios are significantly bigger than Korean women's in most height ratios. On the other hand, Korean are significantly bigger than American in weight ratios. The drop values of Korean females are also smaller than those of American. It was recognized that American women are much bigger, wider and more obese than Korean according to the results by utilizing the girth ratios. BMI, Rohrer and Vervaeck index.

• Journal of the Korean Society of Radiology
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• v.18 no.3
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• pp.257-265
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• 2024

In this study, we applied AEC(Auto Exposure Control), which is used in many chest examinations, to evaluate whether medical devices inserted into the body affect the dose and image quality of chest images. After attaching three HIMD(Human implantable medical devices) to the ion chamber, the Monte Carlo methodology-based program PCXMC(PC Program for X-ray Monte Carlo) 2.0 was applied to measure the effective dose by inputting the DAP(Dose Ares Product) value derived from the Pacemaker and CRT and Chemoport Additionally, to evaluate image quality, we set three regions of interest and one noise region on the chest and measured SNR and CNR. The final study results showed significant differences in DAP and Effective dose. There was a significant difference between Pacemaker and CRT when AEC was applied and not applied. (p<0.05) When applied, the dose increased by 37% for Pacemaekr and 52% for CRT. Chemoport showed a 10% increase in effective dose depending on whether AEC was applied, but there was no significant difference. (p>0.05) In the image quality evaluation, there was no significant difference in image quality between all HIMD insertions and AEC applied or not. (p>0.05) Therefore, when the HIMD was inserted into the chest during a chest x ray and overlapped with the ion chamber sensor, the effective dose increased, and there was no difference in image quality even at a low dose without AEC. Therefore, when performing a chest X-ray examination of a patient with a HIMD inserted, it is considered that performing the examination without applying AEC is a method that can be considered to reduce the patient's radiation exposure.

• Smart Media Journal
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• v.4 no.2
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• pp.68-76
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• 2015

Recently, research on indoor locating techniques using smart device sensors has been conducted actively, Owing to the exponential increase in the use of various smart devices. However, in order to develop indoor location techniques, there are limitations due to the requirement that the tracking system has to function without GPS. In this paper, we propose an accurate indoor locating system that does not require additional infrastructure. The proposed scheme is developed based on the idea that the advantages and disadvantages of "Wi-Fi Fingerprinting" and "Step Detection" techniques are complementary. In the proposed scheme, we track users with "Step Detection," and correct errors with "Wi-Fi Fingerprinting." In this paper, we demonstrate the effectiveness and feasibility of our proposed scheme through experiments.

• Applied Biological Chemistry
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• v.33 no.4
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• pp.315-318
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• 1990

After technical pesticides and dispersants were dissolved in a volatile organic solvent, the wettable powders(WP's) were formulated by adsorbing the pesticide-dispersant solution to finely powdered porous synthetic silica without milling process. The median sizes of 11 WP'S were smaller than $8{\mu}m$, 9 of which had more than 80% suspensibility after 2 hours. It was possible In formulate 50% WP for liquid of fly technical pesticides. The pesticidal efficacies of WP's tested were comparable In commercial formulations regardless of suspensibilities of WP's.