• Textile Coloration and Finishing
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• v.15 no.1
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• pp.8-14
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• 2003

The effect of pasting agent on the defibrillation of Tencel fabric was investigated. It was evaluated by the weigth loss of fabric when the fabric was treated with cellulase containing various kinds of pasting agents. The surface appearance of Tencel fabric was checked by SEM. Under the treatment condition without pasting agent, the weight loss of fabric was high at pH 5.0 and $60^\circ{C}$. This means that the cellulase activity was high at this condition. By increasing the concentration of carboxymethyl cellulose(CMC), the weight loss of fabric was decreased monotonously. This tendency was not appeared in other pasting agents. CMC is synthesized by the reaction of chloroacetic acid and cellulose. The glucose units may be remained after the reaction. So, it was considered that the degradation of glucose unit in Tencel was decreased, because cellulase had to attack both Tencel and CMC.

• Journal of the Korean Society of Visualization
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• v.4 no.1
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• pp.41-46
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• 2006

In this study, one-way fluid structure interaction analysis(FSI) on wind turbine blade was performed. Both a quantitative fluid analysis on 3-bladed wind turbine and a structural analysis using the surface pressure data resulting from fluid analysis were carried out. Streamlines and angle of attack was easily acquired from analysis results, we showed the inlet velocity that the stall begins to occur. In the structural analysis, structural displacement and maximum stress of the two comparative models was calculated. The location that has maximum stress was found. The pressure difference between back and front part of the blade increases as the inlet velocity increase. The torque and maximum with regard to inlet velocity was also presented.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.1
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• pp.130-143
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• 2007

Using steady state aerodynamic theories, it has been claimed that insects and birds cannot fly. To make matters worse, insects and birds fly at low Reynolds numbers. Therefore, a recurring theme in the literature is the importance of understanding unsteady aerodynamic effect and how the vortices behave when they separate from the moving surface that created them. In flapping flight, birds and insects can modify wing beat amplitude, stroke angle, wing planform area, angle of attack, and to a lesser extent flapping frequency to optimize the generation of lift force. Some birds are thought to employ two different gaits(a vortex ring gait and a continuous vortex gait) and unsteady aerodynamic effect(Clap and fling, Delayed stall, Wake capture and Rotational Circulation) in flapping flight. Leading edge vortices may produce an increase in lift. The trailing edge vortex could be an important component in gliding flight. Tip vortices in hovering support the body weight of the hummingbirds. Thus, this study investigated how insects and birds generate lift at low Reynolds numbers. This research is written to further that as yet incomplete understanding.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.771-776
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• 2001

Test results on the deterioration process of concrete under single and combined attacks of chloride penetration have been obtained. After test period of 52 weeks, it is found that the internally penetrated chloride ion contents are less in the single attacks of chloride than the combined attacks of chloride and sulfate. Both the diffusion coefficients and surface chloride concentration derived form the chloride profiles showed a time dependence. Also the performance of fly ash-blended cements was observed to be better than plain cements in retarding chloride attack. However it should be needed that improved chloride diffusion model for the combined deterioration process.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.479-482
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• 2007

This paper presents experimental analysis of a friction-driven wheel responsible for generating wheel squeal. Creep and squeal noise generating mechanism are influenced by friction conditions of attack angle, loading force, driving velocity and surface roughness. Squeal noise phenomena has been examined under the laboratory condition by the model rig. Creep characteristics and squeal noise were observed by varying relative velocity of the wheel with respect to the rail and friction coefficient.

• Journal of Aerospace System Engineering
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• v.10 no.3
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• pp.9-14
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• 2016

Using a multiple regression analysis, a total of 78 low-Reynolds-number airfoils are examined in this paper to clarify the systematic relationships between the geometrical parameters of the airfoils and experimentally-determined aerodynamic coefficients. The results show that the effects of the maximum camber and the maximum thickness regarding the maximum lift and the stalling angle of attack, respectively, are major. The lower-surface flatness of the airfoil is also a crucial geometrical parameter for aerodynamic performance. It is proven here that, generally, the application of the regression equations for an assessment of the aerodynamic performance is relatively acceptable, along with an expectation that the lift-curve slope violates the normality assumption.

• Tribology and Lubricants
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• v.29 no.1
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• pp.19-26
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• 2013

Cu-matrix sintered brake pads and low-alloy heat-resistant steel are commonly applied to basic brake systems in high-energy moving machines. In this research, we analyzed the tribological characteristics to determine the influence of the air velocity between the disk and pad. At a low brake pressure with airflow, the friction stability was decreased as a result of the lack of tribofilm formation at the disk surface. However, there were no significant changes in the friction coefficient under any of the test conditions. The wear rates of the friction materials were decreased with an increase in the airflow velocity. As a result, the airflow velocity influenced the friction stability, as well as the wear rate of the friction materials and disk, but not the friction coefficient.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.203-206
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• 1996

The purpose of this paper is to find how to determine the parameters of the basic control system design such as hinge moment coefficients and to display the controllability of the ChangCong-91. Since the estimation from the flight test of real aircraft is the most reliable, we performed the flight test of ChangGong-91 to get the various parameters such as velocity, height, control force, control surface deflection, 3 axis acceleration, 3 axis angular rate, pitch angle, angle of attack temperature and so on. We recorded the flight test data in VHS tapes and stored them to personal computer using A/D(analog to digital) converter. Flight test was done in various conditions, and the acquired data was processed with parameter identification method such as least square method. These data will be utilized for the development of Autopilot System design and Control Loading System design.

• Journal of Ocean Engineering and Technology
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• v.12 no.3 s.29
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• pp.75-85
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• 1998

A finite difference model for predicting time-dependent, wave-induced nearshore current is studied. The model includes wave refraction, wave-current interaction, bottom friction and wind effect. This model iteratively solved the linear the linear set of conservation of both mass and momentum, which were time averaged (over one wave period) and depth integrated, for mean velocities and free surface displacement. Numerical simulations of nearshore current under oblique wave attack, and for wave and wind induced current on a longshore periodic beach are carried out. Longshore velocities tend to zero in some distances outside the breaker line. And the peak velocity is shifted shoreward at the breaker line. The results represent the general characteristics of the nearshore current induced by wave.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.9
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• pp.656-661
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• 2013

In this study, the moisture content, charge discharge current, electrostatic capacity and dielectric loss tangent are measured for the specimen of bisphenol type epoxy resin which is mixed with squared amorphous silica filler and dipped in hot water of $50^{\circ}C$ for 169 days. The results of this study are listed below. The longer of deposition day, the charge and discharge current was increased. It is considered that the reason is because there was water attack through the squared silica surface. The longer of deposition day, the absorption rate of all specimens was increased. It found that the absorption rate reached saturated state after 100 days. The higher frequency and the longer of deposition day, the $tan{\delta}$ was decreased. Also, It found that the $tan{\delta}$ and electrostatic capacity of the specimen which is mixed with squared filler are greater.