• Journal of Korean Society of Environmental Engineers
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• v.29 no.4
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• pp.412-418
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• 2007

The purpose of this study was to determine the several factors for affecting chlorine disinfection by-products(DBPs) characteristics by reacting chlorine and organic matters in the aquatic phase. The results of this research yield the following specific conclusions: The concentration of trihalomethanes(THMs) was increased with increasing dissolved organic carbon(DOC), and a trend of THMs formation was parabolic with increasing organic matters. Formations of THMs increased straightly for the first 4 hours and the amounts of producted THMs for the 30 minutes were up to $25\sim43%$ in the entire experiment periods(168 hours). When keeping up the concentration of organic matters at constant and changing that of bromide, the quantity of formed THMs did not show distinguished difference with the reaction times. THMs were gradually increased at $4^{\circ}C$ even though a reaction phase was parabolic formation(PF) phase. However, THMs were increased rapidly in the instantaneous formation(IF) phase and then became slowdown in the PF phase between $20\sim35^{\circ}C$. THMs were gradually increased although entering in the PF phase at pH 5. However, THMswere increased rapidly in the IF phase and then became slowdown in the PF phase at pH 7 and pH 9, and these treads were much more clear at pH 9 than at pH 7.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.1 s.20
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• pp.49-58
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• 2006

Rainfall-runoff characteristics are analysed based on the geomorphological instantaneous unit hydrograph(GIUH) derived by geomorphological parameters using geographical information system in watershed ungaged or deficient of field data. Observed data of Seom river experiment watershed at upstream of Hoengseong dam and variable slope method for hydrograph separating of direct non are used. The 4th stream order of Seom river experimental watershed is developed with a regular correlation referred to the Horton-Strahler's law of stream order. The characteristic velocity to determine shape parameter of GIUH is 1.0m/s and its equation is modified for accurate results. Hydrograph at the outlet of 4th stream order of Maeil gage station and at the outlets of 3rd stream order of Sogun and Nonggeori gage stations show a little differences in falling limb of hydrograph but agree well to the observed data in general. The results by hydrological routing with HEC-HMS to the outlet of 4th stream order of Maeil gage station which the hydrograph by GIUH obtained at Sogun and Nonggeori gage stations of 3rd stream oder are applied as upstream inputs give better agreement with observed data than those by hydrograph by GIUH obtained at Maeil gage station of 4th stream order. In general, the rainfall-runoff by GIUH has applicability to the watershed routing of ungaged project regions.

• Korean Journal of Environment and Ecology
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• v.25 no.3
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• pp.318-326
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• 2011

The population ecological characteristics of the Crucian carp, Carassius auratus, were determined in order to estimate stock of the mid-upper system of the Seomjin River. The fish ranged in size from 95 to 288mm total length. The age was determined by counting the scale annulus. The scales displayed clear annulus that were used to estimate the age. The oldest fish observed in this study was 5 years old. Age-2 fishes were the most numerous in the sample(n=38), followed in frequency be age-3(n=22). Marginal index analysis validated the formation of a single annulus per year. The relationship between body length and body weight was BW = $0.0038BL^{3.73}$($R^2$=0.96) (p<0.01). The relationship between the scale radius and body length was BL = 2.362R+2.76($R^2$=0.89). The von Bertalanffy growth parameters estimated from a non-linear regression method were $L_{\infty}$=33.2 cm, $W_{\infty}$=1,798.4 g, $K=0.20year^{-1}$ and $t_0$=-0.51year. Therefore, Growth in length of the fish was expressed by the von Bertalanffy's growth equation as $L_t=33.23$($1-e^{-0.20(t+0.51)}$)($R^2$=0.98). The annual survival rate was estimated to be 0.427year$^{-1}$. The instantaneous coefficient of natural mortality of estimated from the Zhang and Megrey method was $0.784year^{-1}$, and instantaneous coefficient of fishing mortality was calculated $0.067year^{-1}$. From the estimates of survival rate, the instantaneous coefficient of total mortality was estimated to be $0.851year^{-1}$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.1
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• pp.95-103
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• 2015

This paper presents the effects of the tool shape on the geometrical characteristics of flat end-milled side walls. A tool shape is characterized by such parameters as helix angle, number of cutting edges, and diameter. The geometrical characteristics of the side walls are represented by the surface profiles in the feed and axial directions, which are orthogonal to each other. The geometrical defects in each direction are estimated based on the instantaneous apparent cutting areas, which are represented by the interference area between the tool and workpiece and that between the cutting edge and workpiece. It is confirmed that a geometrical defect in the feed direction is formed when the tool leaves the workpiece and the curvature of the tool path changes. Defects in the axial direction are also found in the side walls, except for the defect zone in the feed direction. An up-cut using an end-mill with a steeper helix angle, a greater number of cutting edges, and a smaller diameter are thus found to improve the geometrical accuracy of end-milled side walls.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.5
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• pp.694-699
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• 2012

This paper proposes a new sensorless speed control scheme of permanent magnet DC motor using a numerical model and hysteresis controller, which requires neither shaft encoder, speed estimator nor PI controllers. By supplying the identical instantaneous voltage to both model and motor in the direction of reducing torque difference, the rotor speed approaches to the model speed, namely setting value and the system can control motor speed precisely. As the numerical model whose electric parameters are the same as those of the actual motor is adopted, the armature rotating speed can be converged to the setting value by controlling torque on both sides to be equalized. And the hysteresis controller controls torque by restricting the torque errors within respective hysteresis bands, and motor torque are controlled by the armature voltage. The experiment results indicate good speed and load responses from the low speed range to the high, show accurate speed changing performance.

• Journal of Korea Water Resources Association
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• v.32 no.5
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• pp.565-577
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• 1999

The geometric patterns of a stream network in a drainage basin can be viewed as a "fractal" with fractal dimensions. Fractals provide a mathematical framework for treatment of irregular, ostensively complex shapes that show similar patterns or geometric characteristics over a range of scale. GIUH (Geomorphological Instantaneous Unit Hydrograph) is based on the hydrologic response of surface runoff in a catchment basin. This model incorporates geomorphologic parameters of a basin using Horton's order ratios. For an ordered drainage system, the fractal dimensions can be derived from Horton's laws of stream numbers, stream lengths and stream areas. In this paper, a fractal approach, which is leading to representation of a 2-parameter Gamma distribution type GIUH, has been carried out to incorporate the self similarity of the channel networks based on the high correlations between the Horton's order ratios. The shape and scale parameter of the GIUH-Nash model of IUH in terms of Horton's order ratios of a catchment proposed by Rosso(l984J are simplified by applying the fractal dimension of main stream length and channel network of a river basin. basin.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.2131-2137
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• 2008

In this paper, COP (center of pressure) during quiet standing and squat-and-stand movement was analyzed to compare the postural control of young and elderly subjects with special interest in the elderly females who were reported to have higher fall rate than the elderly males. Subjects include the young subjects (10 males: $21.8{\pm}2.6yrs$, 10 females: $20.4{\pm}0.3yrs$) and the elderly subjects (8 males: $75.5{\pm}4yrs$, 8 females: $72.3{\pm}3.5yrs$). Analysis parameters were the mean of the distance between the instantaneous COP and the average COP (COP distance) and the mean of the COP movement velocity (COP velocity) in both AP (anterio-posterior) and ML (media-lateral) directions. During quiet standing, the COP distance in ML direction of elderly females was significantly greater than that of elderly males and the COP velocity of elderly females in both ML and AP direction were significantly greater than those of all the other groups. During squat and stand movement, the COP distance of elderly females was not significantly different with that of the elderly males. However, the COP velocity of elderly females was significantly greater than that of all the other groups. The large lateral weight shift (COP distance) of elderly females during quiet standing may explain their greater fall rate. However, this does not apply to squat-and stand movement. In contrast, COP velocity results show that the elderly females' COP is rapidly trembling compared to that of elderly males during both quiet standing and squat and-stand movement. This results suggest that rapid trembling or postural sway may reflect the reduced postural control ability and the risk of falling.

• Journal of Advanced Navigation Technology
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• v.18 no.5
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• pp.461-467
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• 2014

Active queue management (AQM) algorithms run on routers and detect incipient congestion by typically monitoring the instantaneous or average queue size. When the average queue size exceeds a certain threshold, AQM algorithms infer congestion on the link and notify the end systems to back off by proactively dropping some of the packets arriving at a router or marking the packets to reduce transmission rate at the sender. Among the existing AQM algorithms, random early detection (RED) is well known as the representative queue-based management scheme by randomizing packet dropping. To reduce the number of timeouts in TCP and queuing delay, maintain high link utilization, and remove bursty traffic biases, the RED considers an average queue size as a degree of congestions. However, RED do not well in the specified networks conditions due to the fixed parameters($P_{max}$ and $TH_{min}$) of RED. This paper addresses a extended RED to be adapted in various networks conditions. By sensing network state, $P_{max}$ and $TH_{min}$ can be automatically changed to proper value and then RED do well in various networks conditions.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.265-269
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• 2006

Anti-Roll Tanks, also called Sloshing Tanks, is a rather common and sometimes an efficient method of limiting the roll angles. The important parameters, when considering using anti-roll tanks, are positioning, size, duct area, flow control device etc. Measurement by the PIV(Particle Image Velocimetry) was conducted to investigate the flow characteristics around control damper and inlet area of duct for three kind of inclined angle $(\alpha=0^*,\;10^*\;and\;20^*)$. Flow behaviors such as instantaneous and time-mean velocity vectors are investigated. Furthermore, to reveal boundaries between flowing and stagnant zones and to extract velocity profiles at any selected sections of the lower duct for passive anti-rolling tanks system.

• Structural Engineering and Mechanics
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• v.40 no.3
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• pp.431-451
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• 2011

Time delay inevitably exists in active control systems, and it may cause the degradation of control efficiency or instability of the systems. So time delay needs to be compensated in control design in order to eliminate its negative effect on control efficiency. Today time delay in linear systems has been more studied and some treating methods had been worked out. However, there are few treating methods for time delay in nonlinear systems. In this paper, an active controller for a nonlinear and hysteretic building structure with time delay is studied. The nonlinear and hysteretic behavior of the system is illustrated by the Bouc-Wen model. By specific transformation and augmentation of state parameters, the motion equation of the system with explicit time delay is transformed into the standard state space representation without any explicit time delay. Then the fourth-order Runge-Kutta method and instantaneous optimal control method are applied to the controller design with time delay. Finally, numerical simulations and comparisons of an eight-story building using the proposed time-delay controller are carried out. Simulation results indicate that the control performance will deteriorate if time delay is not taken into account in the control design. The simulations also prove the proposed time delay controller in this paper can not only effectively compensate time delay to get better control effectiveness, but also work well with both small and large time delay problems.