• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.70-71
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• 2021

The unit quantity that affects the workability, shrinkage cracking, and durability of concrete is an important factor. Methods for measuring the unit quantity include a high frequency heating method, a capacitance method, a unit volume mass method, and a simple method. However, these methods have the disadvantage of poor measurement method, time required, and precision. To solve this problem, a relatively simple and fast measurement method was adopted to compensate for the shortcomings through a Frequency Domain Reflection (FDR) sensor, and the unit quantity was used. In addition, the measurement data was analyzed by deep learning to evaluate the unit quantity of concrete.

• Ocean and Polar Research
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• v.24 no.4
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• pp.483-490
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• 2002

Detailed investigations on both submarine and subaerial volcaniclastic deposits around Dokdo were carried out to identify geomorphologic characteristics, stratigraphy, and associated depositional processes of Dokdo caldera. Dokdo volcano has a gently sloping summit (about 11km in diameter) and relatively steep slope (basal diameter is about 20-25 km) rising above sea level at about 2,270m. We found ragged, elliptical-form of Dokdo caldera with a diameter of about 2km estimated by Chirp (3-11 kHz) sub-bottom profile data and side scan sonar data for the central summit area of Dokdo volcano. We interpreted that the volcaniclastic deposits of Dokdo unconformably consist of the Seodo (west islet) and the Dongdo(east islet) formations based on internal structure, constituent mineral composition, and bedding morphology. The Seodo Formation mainly consisted of massive or inversely graded trachytic breccias (Unit S-I), overlain by fine-grained tuff (Unit S-II), which is probably supplied by mass-wasting processes resulting from Dokdo caldera collapse. The Dongdo Formation consists of alternated units of stratified lapilli tuff and inversely graded basaltic breccia (Unit D-I, Unit D-III, and Unit D-V), and massive to undulatory-bedded basaltic tuff breccias (Unit D-II and Unit D-IV) formed by a repetitive pyroclastic surge and reworking processes. Although, two islets of Dokdo are geographically near each other, they have different formations reflecting their different depositional processes and eruptive stages.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.5
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• pp.246-254
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• 2022

The high-temperature oxidation behavior of Cr-Mo steel AISI 4115 in air at different temperatures (600, 850, 950℃) for 120 min was studied by mass gain analysis, phase analysis (optical microscopy, electron probe micro-analysis, x-ray diffraction) and hardness measurement of each iron oxide-phase. The oxidation scales that formed on oxidation process consisted outer layer (Hematite), middle layer (Magnetite) and the inner layer (Chromite). In the case of 850 and 950℃, the oxidation mass gain per unit area of AISI 4115 steel increased according to the logarithmic rate as atmospheric pressure increased. Especially, It has been observed that with an increase in the atmospheric pressure at 600℃, the oxidation mass gain per unit area changed from a linear to logarithmic relationship.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.4
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• pp.389-394
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• 2010

This paper describes the conceptual design of mass memory unit for high speed data processing and mass memory management in the STSAT-3 compared to that of STSAT-2. The FPGA directly controls the data receiving from two payloads with the maximum 100Mbps speed and 32Gb mass memory management to satisfy these requirements. We used SRAM-based FPGA from XILINX having fast operating speed and large logic cells. Therefore, the Triple Modular Redundancy(TMR) and configuration memory scrubbing techniques will also be used to protect FPGA from Single Event Upset(SEU) in space.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.11
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• pp.115-120
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• 2005

This paper describes the design and implementation of engineering model(EM) of Mass Memory Unit(MMU) for Science and Technology Satellite 2(STSAT-2) and the results of integration test. The use of Field-Programmable Gate Array(FPGA) instead of using private electric parts makes a miniaturization and lightweight of MMU possible. 2Gbits Synchronous Dynamic Random Access Memory(SDRAM) module for mass memory is used to store payload and satellite status data. Moreover, file system is applied to manage them easily in the ground station. RS(207,187) code improves the tolerance with respect to Single Event Upset(SEU) induced in SDRAM. The simulator is manufactured to verify receiving performance of payload data.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.59-60
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• 2021

The unit-water content has a major problem in concrete structures which leads to micro cracks on the concrete during drying time. Thus, the compressive strength and durability of the concrete structures are significantly reduced. Several techniques have been developed to measure the unit-water content in concrete structures such as heating drying, unit volume mass, and capacitance measurements. However, these techniques have problems in during measurement such as longer time, expensive and difficult in analysis of data. Frequency Domain Reflectivity (FDR) is one of the sensors which used to measure the water content. This method has several advantages including easy to measure, inexpensive, and capable of measuring moisture in real time. In this study, an attempt has been made to evaluate the unit-water content in concrete using the FDR sensor and interpret the data with deep learning method.

• Communications of the Korean Mathematical Society
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• v.35 no.1
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• pp.251-260
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• 2020

In this paper, we show that it is Chen surfaces that non-minimal pseudo-Hermitian mass-symmetric 2-type Legendre surfaces in S⁵. Moreover, we show that pseudo-Hermitian mass-symmetric 2-type Legendre surfaces in S⁵ are the locally product of two pseudo-Hermitian circles.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.2 s.25
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• pp.1-6
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• 2007

When the water content within concrete swells, diverse problems occur such as drop in durability. Due to this reason, a change is being managed in the unit water contents by using electric capacity measurements, high frequency heating methods, and unit-volume mass measurements, which are methods of measuring the unit water contents. Particularly, Japan is prescribing the guideline of management on a change in unit water content unit quantity $({\pm}10,\;15,\;20kg//m^3,\;etc.)$. However, the guideline of Japan dose not consider a fall in durability, and is decided on the value of pass-fail criteria by random fabrication errors and measurement errors. Consequently, this study was aimed to investigate the influence of a change In water content within concrete due to an addend caused by management error and to an artificial addend, upon drop in durability.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.553-556
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• 2008

We hereby report novel driving scheme to eliminate effect of "residual" image sticking (RRI) problem which arises due to hysteresis problem in Thin Film Transistor (TFT) in AMOLED Displays. The driving scheme applies "black" voltage after every data voltage period in order to drive AMOLED in uni-direction. The system can be easily implemented with 120 Hz driving scheme which is well matured in AMLCD industries. Our analyses show systematic evaluation of the problem and thereby solving it by simple methods which will be significantly effective of driving OLED towards mass manufacturing stage.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.1
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• pp.65-73
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• 2014

Objectives: The purposes of this study are to investigate workers' exposures to respirable particles generated in taconite mines and to compare two metric methods for mass concentrations using direct-reading instruments. Methods: Air monitorings were conducted at six mines where subjects have been exposed primarily to particulate matters in crushing, concentrating, and pelletizing processes. Air samples were collected during 4 hours of the entire work shift for similarly exposure groups(SEGs) of nine jobs(N=37). Following instruments were employed to evaluate the workplace: a nanoparticle aerosol monitor(particle size range; 10-1000 nm, unit: ${\mu}m^2/cc$, Model 9000, TSI Inc.); DustTrak air monitors($PM_{10}$, $PM_{2.5}$, unit: $mg/m^3$, Model 8520, TSI Inc.); a condensation particle counter(size range; 20-1000 nm, unit: #/cc, P-Trak 8525, TSI Inc.); and an optical particle counter(particle number by size range $0.3-25{\mu}m$, unit: #/cc, Aerotrak 9306, TSI Inc.). Results: The highest airborne concentration among SEGs was for furnace operator followed by pelletizing maintenance workers in number of particle and surface area, but not in mass concentrations. The geometric means of $PM_{2.5}$ by the DustTrak and the Ptrak/Aerotrak were $0.04{\mu}m$(GSD 2.52) and $0.07{\mu}m$(GSD 2.60), respectively. Also, the geometric means of RPM by the DustTrak and the Ptrak/Aerotrak were $0.16{\mu}m$(GSD 2.24) and $0.32{\mu}m$(GSD 3.24), respectively. The Pearson correlation coefficient for DustTrak $PM_{2.5}$ and Ptrak/Aerotrak $PM_{2.5}$ was 0.56, and that of DustTrak RPM and Ptrak/Aerotrak RPM was 0.65, indicating a moderate positive association between the two sampling methods. Surface area and number concentration were highly correlated($R^2$ = 0.80), while $PM_{2.5}$ and RPM were also statistically correlated each other($R^2$ = 0.79). Conclusions: The results suggest that it is possible to measure airborne particulates by mass concentrations or particle number concentrations using real-time instruments instead of using the DustTrak Aerosol monitor that monitor mass concentrations only.