• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.401-403
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• 2012

In this paper, we introduce a multipath congestion control algorithm for audio/video streaming, called MPSQRT. MPSQRT is derived from single-path Square-Root TCP (SQRT TCP) designed for multimedia streaming, where a lower variation of sending rate is important. Based on the fluid model of SQRT for single-path, we extend it towards spreading concurrently packets across multiple paths ensuring load-balancing and fairness to SQRT at shared bottleneck. Through simulations, we evaluate the proposed protocol under various network conditions.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.70.2-70
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• 2002

In the thermal power plant, it is difficult to maintain strict control of the steam temperature in order to avoid thermal stress, because of variation of the heating value according to the fuel source, the time delay of changes in main steam temperature versus changes in fuel flow rate, difficulty of control on the main steam temperature control and the reheater steam temperature control system owing to the dynamic response characteristics of changes in steam temperature and the reheater steam temperature, fluctuation of inner fluid water and steam flow rates widely during load-following operation. Up to the present time, the PID controller has been used to operate this system...

• Journal of Korean Society on Water Environment
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• v.36 no.6
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• pp.521-534
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• 2020

In this study, the variation of water quality was analyzed for six sites in major tributaries of the Nakdong River Basin. Standard-FDC (Flow Duration Curve) was developed using PM (Percentile Method), one of the statistical FDC estimation methods. The LDC (Load Duration Curve) was obtained using the developed FDC. The current method and the LDC evaluation method were compared and analyzed to evaluate the achievement of TWQ (Target Water Quality). Regarding the monthly flow rate variation, the five sites showed the distribution of the lowest flow rate between May and June, indicating a high probability of dry weathering of the streams. The variation of water quality confirmed the vulnerable timing of flow rate in each site, and it is therefore deemed necessary to plan to reduce T-P and TOC. A comparison and evaluation of TWQ showed that there was a difference between the TWQ values achieved by the two techniques. In addition, the margin ratio to the 50% excess ratio can be found in the LDC evaluation. The results of the LDC evaluation by section and by month showed whether or not the water quality was exceeded by flow conditions, along with the vulnerable sections and timing. Accordingly, it is judged that this method can be used for water quality management in TMDLs (Total Maximum Daily Loads).

• Journal of the Korean Institute of Gas
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• v.12 no.1
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• pp.1-6
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• 2008

The notched Charpy impact test is one of the most prevalent techniques used to characterize the effect of high impulse loads on polymeric materials. In this study, a method of analysis in nylon plastic materials is suggested to evaluate the critical strain energy release rate for variation of notch angles from the Charpy impact energy measurement. Instrumented Charpy impact tester was used to extract ancillary information concerning fracture parameters in addition to total fracture properties and maximum critical load. The dynamic stress intensity factor of nylon plastic material was calculated for the ASTM Charpy specimen from the obtained maximum critical load. Also, the finite element model was developed to figure out the stress distributions for Charpy specimen with different notch angles subject to 3 point bending load which is equivalent to the load applied in the experiment.

• Tunnel and Underground Space
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• v.15 no.1 s.54
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• pp.55-60
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• 2005

In this study, the 1/20 reduced-scale experiments using Froude scaling were conducted to investigate the effect of longitudinal ventilation on the variation of burning rate in tunnel fires. The methanol square pool fires with heat release rate ranging from 3.57 kW to 10.95 kW were used. The burning rate of fuel was obtained by measured mass using load cell and temperature distribution were measured by K-type theomocouples in order to investigate smoke movement. The wind tunnel was connected with one side of the tested tunnel, and logitudinal ventilation velocity in the tested tunnel was controlled by power of the wind tunnel. In methanol fire case, the increase in ventilation velocity decreased the turning rate due to the direct cooling of fire plume. For the same dimensionless velocity(V), homing rate decreased as the size of pool fire increased.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.109-117
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• 2005

In this study, the 1/20 reduced-scale experiments using Froude scaling were conducted to investigate the ventilation velocity of the variation of burning rate in tunnel fires. The heptane square pool fire with heat release rate ranging from 3.71~15.6 kW were used. The burning rate of fuel was obtained by measuring mass using load cell and temperature distributions were measured by K-type theomocouples in order to investigate smoke movement. The ventilation velocity in the tested tunnel was controlled by inverter of the wind tunnel. In heptane pool fire case, the increase in ventilation velocity incresed the burning rate due to the direct supply of oxygen to the fire plume. For the same dimensionless velocity($\bar{V}$), burning rate increased as the size of pool fire decreased.

• Journal of the Ergonomics Society of Korea
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• v.24 no.2
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• pp.9-15
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• 2005

The purpose of this study is to quantitatively investigate perceived discomfort of complex shoulder postures with external loads and to propose a preliminary evaluation scheme of shoulder postures. Twelve healthy male adults participated in an experiment to rate their perceived discomfort of shoulder postures. The independent variables were shoulder flexion angle(45, 90 and 150$^{\circ}$), adduction/abduction angle(-30, -10, 0, 30 and 60$^{\circ}$), and external load(0, 1.5 and 3.0kg). The results revealed that the flexion angle, external load and their interaction significantly affected the perceived discomfort(p$<$0.05) but the effect of adduction/abduction angle on the discomfort was not significant(p$>$0.05). The effect of external load was much larger than that of any other factor with explaining about 81% of the total variation of discomfort scores. Based on the experimental results a preliminary scheme was presented to evaluate the stress of shoulder postures with external loads.

• Journal of Power System Engineering
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• v.14 no.4
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• pp.50-55
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• 2010

In order to investigate tribological effects of nano copper particles impregnated(CuN) on surface polytetrafluoroethylene(PTFE) on sealing wear and an experimental study was carried out to determine the wear behavior of copper nano-particles impregnation two kind thickness in super critical $CO_2$ liquid. Experimental results showed that the friction coefficients of CuN PTFE at the low sliding speed(0.44m/s) and the oil temperature ($60^{\circ}C$) were higher than that of virgin PTFE. And a thin nano copper particles impreganated thickness was formed on the surface in the PTFE and the specimen with this treatment has much better friction properties than the original one. Fortunately, at the high load(80 N) and the oil temperature, the friction coefficient of CuN PTFE was lower than that of virgin PTFE. This evidenced the load carrying capacity of CuN PTFE was much better than that of virgin PTFE under the high load condition(80 N) specially. Therefore, it can be concluded that the friction coefficient variation of CuN PTFE is very small but its wear rate decreases greatly with increase in sliding speed.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.83-88
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• 2010

The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the wear resistance according to the change of apply load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and the wear test results exhibited as following ; The epoxy matrix composites showed lower coefficient of friction compared to the neat epoxy through the whole sliding distance. As increasing the sliding velocity the epoxy matrix composites indicated lower coefficient of friction, whereas the neat epoxy showed higher coefficient of friction as increasing the sliding velocity. The specific friction work of both materials were increased with apply load. In case of the epoxy matrix composites, the running in periods of friction were reduced as increase in apply load. The epoxy matrix composites were improved the wear resistance by adding the nano silica particles remarkably. It is expected that the load carrying capacity of the epoxy matrix composites will be improved by increase of Pv factor.

• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.527-529
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• 1997

In this paper, a system to control feeding rate by fuzzy controller was developed and tested in the various raw material of the powder gram state. The designed fuzzy controller for feeding rate control system is proved robust performance under parameter variation and load disturbance effect which is caused by the kind and quantity of various raw material.