• Journal of the Korea Institute of Building Construction
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• v.9 no.2
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• pp.85-91
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• 2009

W/C and unit volume, which significantly affect quality of concrete related to strength and durability, are regulated at below $185kg/m^3$ for regular concrete generally used in standard specification for constructions. The aim of this research is to develop chemical admixture and find out its potential use by identifying characteristics of admixtures added to soft concrete and hardening concrete, of which content ratio of component for each type of admixtures is subject to change in accordance with unit volume within KS' allowable range. Sodium gluconate, polyoxyethylene nonylphenyl ether, poly carboxylic copolymer in slump, which is characteristic of soft concrete, are deemed highly sensitive while there is no air entrainment except for $10\sim70%$ in WE, WR component content ratio and NP. In hardening concrete, strength in general showed higher action in compressive strength and tensile strength than in plain strength. Use of proper AE agent and AE water reducing agent at the same time is deemed to be used as chemical admixtures capable of manufacturing high-quality, high-quantity concrete.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2130-2141
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• 2002

A unique technique to estimate the magnitude or contribution ratio of each stage backlash in a system with a two-stage gear reducer is proposed. The concept to estimate the magnitude or contribution ratio of each stage backlash is based on the change of frequency response characteristic, in particular, the change of anti-resonant frequency and resonant frequency, due to the change of each stage backlash magnitude, even though the total backlash magnitude of a system with a two-stage gear reducer is constant. The validity of the technique is verified in a seeker gimbal and satisfactory results are obtained. It is thought that the diagnosis and maintenance of the manufacturing machines and systems with two-stage gear reducers will become more efficient and economical by virtue of the proposed technique.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.258-262
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• 2011

The hybrid combustion experiments using non-combustible diaphragm were performed for characteristic of regression rate and combustion efficiency. Results of experiments using diaphragm were showed that the regression rate and efficiency were increased. In addition, the larger difference between fuel grain port and diaphragm port increase the regression rate and efficiency. The modified regression rate equation was proposed with the port area ratio of fuel and diaphragm.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.1
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• pp.33-39
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• 2018

This study performed experimental validation of the hysteretic steel slit damper's basic and dependent characteristics, which should be considered for the design. The basic characteristic of the steel slit damper is used for determining design properties of non-linear analysis, such as yielding strength, yielding displacement, elastic stiffness and post-yielding stiffness. In order to evaluate dependent characteristics of the hysteretic steel slit damper, repeated deformation capacity with respect to the displacement, velocity and aspect ratio of the damper was evaluated. In this study, steel slit damper, which is widely used in Korea, was considered. The slit dampers with 55kN and 240kN of yielding strength were produced and tested. It was concluded that the slit damper's hysteresis behavior was affected by the dependent characteristics: displacement, velocity and aspect ratio. In other words, the steel slit damper's behavior was stable within limit displacement, and aspect ratio of the strut affected repeated deformation capacity of the damper subjected to large deformation. In addition, it was observed that the repeated deformation capacity abruptly decreased at the high speed range (${\geq}60mm/sec$). Furthermore, the experimental results were evaluated with the criterion of the damping device specified in ASCE7-10.

• Journal of the Korean Geotechnical Society
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• v.25 no.8
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• pp.23-32
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• 2009

In this study, the reliable and simple analysis method was proposed to predict the settlement characteristic of composite ground in stage of design and construction of sand compaction pile (SCP). Model parameters could be obtained by the optimization process based on genetic algorithm. In order to examine the proposed method, laboratory consolidation tests on the settlement characteristic of SCP composite ground were performed for various replacement ratio of sand such as 0 (no replacement), 20, 36, and 56%. The proposed model showed very good agreements with measured data in the relation of void ratio-log scaled stress and time-compression far each replacement ratio.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.1
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• pp.65-73
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• 1986

Experiment have been conducted about thin oxide characteristics according to O2/N2 ratio needed for EEPROM cell fabrication. As a result, we think that there is no problem even if we grow oxide layer with large O2/N2 ratio and short exidation time and when the water is implated by As before oxidation, the oxide breakdown field is about IMV/cm lower than that is not implanted. Especially, the thin oxide characteristic seems to be affected largely by wafer cleaning and oxidation in air. On the basis of these, tunnel type EEPROM cell is fabricated by 3um CMOS process and its characteristic is studied. Tunnel oxide thickness(100\ulcorner is chosen to allow Fowler-Nordheim tunneling to charge the floating gate at the desired programming voltage and tunnel area(2x2um\ulcorneris chosen to increase capacitive coupling ratio. For program operation, high voltage (20-22V) is applied to the control gate, while both drain and source are gdrounded. The drain voltage for erase is 16V. It is shown that charge retention characteristics is not limited by leakage in the oxide and program/erase endurance is over 10E4 cycles of program erase operation.

• Proceedings of the KWS Conference
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• 1997.05a
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• pp.91-98
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• 1997

This research is to evaluate of the J-R curve characteristic in 5083 aluminum alloy weldment by utilizing the load ratio analysis. This analysis method can be evaluated the J-R curve only with load-displacement curve without any particular precision instrument equipment in CT specimen. For validity, the results of the load ratio analysis are compared with the those of the J-R curve, which are obtained by the ASTM standard unloading compliance method. The calculated crack length of the load ratio analysis is well appropriate that the measured final crack length. And the J-R curve slope estimated by the load ratio analysis is slightly smaller than that by the ASTM unloading compliance method.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.57-64
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• 2002

This paper describes the results of a series of experiments executed by using two pilot-scale oxv-fuel burners are designed for maximum capacity of 50,000 kacl/hr, 300,000 kcal/hr and installed in the test furnace. The effects of turn-down ratio, excess oxygen ratio, nozzle exit velocity, injection angle, swirl vane angle and inlet oxygen temperature on the combustion characteristic are investigated. Temperature distributions are measured using R-type and Molybdenum sheathed C-type thermocouple. The results showed that maximum temperature and mean temperature increase with the increase of turn-down ratio and inlet oxygen temperature. The maximum flame temperature was increased about 35% compared to the case of equivalent air operated condition. In addition, Optimum excess oxygen ratio and nozzle characteristics are obtained for this oxy-fuel glass melting furnace.

• Textile Coloration and Finishing
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• v.20 no.1
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• pp.28-35
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• 2008

Texturing is the process of including a characteristic of a natural fiber in a synthetic fiber. The most common method of it the false twist texturing. Nylon textured yarn is primarily manufactured by the disk type. The major process parameters or the disk type false twist machine ratio, disk/yarn, and heater temperature. This study therefore investigated the effects of false twist texturing, especially speed and draw ratio, on the physical properties of nylon textured yarn. The increase of speed was proportional to the increase of unwinding tension, which could reduce the production efficiency by elevating the tension affecting to fiber during the process. In addition, the increase of speed was inversely proportional to the increase of crimp rigidity of nylon textured yarn. Draw ratio was proportionally increased with the increase of tenacity and the reductions of fineness and elongation, showing the influence or draw ratio to the ultimate physical properties of textured yarn.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.317-323
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• 2017

Due to the unique characteristic of auxetic material, negative poisson's ratio, it has a variety of distinctive properties compared to conventional materials. Numerous researches have been conducted on the auxetic material in order to find out how to make auxetics. In this study, we analyzed triangular and rectangular patterned rotating rigid units using finite element method. Our purpose is to investigate the mechanical properties of the rotating rigid units and to show their auxetic behaviors. We studied the Poisson's ratio and the bulk modulus of the rotating rigid units depending on their unit cell sizes. The Poisson's ratio and the bulk modulus decreased as the number of unit cells increased. Also, when the geometry of the unit cell was changed, the tendency of the Poisson's ratio and the bulk modulus was also different from the previous case. The results of the Poisson's ratio and the bulk modulus referred that they were critically affected by the number of unit cells and the shape of unit cell.